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2310.17479 | Suman Ghosh | Antariksha Mitra and Suman Ghosh | Signature quasinormal modes of Ellis-Bronnikov wormhole embedded in
warped braneworld background | One figure added, references updated, discussion improved, accepted
for publication in PRD | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We examine the quasi normal modes of Ellis-Bronnikov wormholes embedded in a
warped five dimensional braneworld background and compare with it's four
dimensional counterpart. These scalar quasi normal frequencies are obtained
using the WKB formula, Prony method and the direct integration method. The
signature of the warped extra dimension shows up as two distinct quasi normal
ringing era, characterised by two distinct dominant quasi normal modes.
Features of the latter region are similar to that observed earlier for massive
scalar field in black hole background. We also discuss the how steepness of the
neck of the wormhole effects the quasi normal frequencies.
| [
{
"created": "Thu, 26 Oct 2023 15:31:57 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Feb 2024 13:27:19 GMT",
"version": "v2"
}
] | 2024-02-13 | [
[
"Mitra",
"Antariksha",
""
],
[
"Ghosh",
"Suman",
""
]
] | We examine the quasi normal modes of Ellis-Bronnikov wormholes embedded in a warped five dimensional braneworld background and compare with it's four dimensional counterpart. These scalar quasi normal frequencies are obtained using the WKB formula, Prony method and the direct integration method. The signature of the warped extra dimension shows up as two distinct quasi normal ringing era, characterised by two distinct dominant quasi normal modes. Features of the latter region are similar to that observed earlier for massive scalar field in black hole background. We also discuss the how steepness of the neck of the wormhole effects the quasi normal frequencies. |
0709.4541 | Ujjal Debnath | Sanjukta Chakraborty, Subenoy Chakraborty and Ujjal Debnath | Quasi-Spherical Gravitational Collapse in higher dimension and the
effect of equation of state | 8 Latex pages, No figure, RevTex style | Grav.Cosmol.13:211-216,2007 | null | null | gr-qc | null | Gravitational collapse in (n+2) dimensional quasi-spherical space-time is
studied for a fluid with non vanishing radial pressure. An exact analytic
solution is obtained (ignoring the arbitrary integration function) for the
equation of state $p_{r}=(\gamma-1)\rho.$ The singularity is studied locally by
comparing the time of formation of apparent horizon and the central shell
focusing singularity while the global nature of the final fate of collapse is
characterized by the existence of radial null geodesic. It is revealed that the
end state of collapse for D dimension with equation of state $p=-\rho$, for
(D$-$1) dimensional dust and (D$-$2)dimension with equation of state $p=\rho$
are identical.
| [
{
"created": "Fri, 28 Sep 2007 07:09:34 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Chakraborty",
"Sanjukta",
""
],
[
"Chakraborty",
"Subenoy",
""
],
[
"Debnath",
"Ujjal",
""
]
] | Gravitational collapse in (n+2) dimensional quasi-spherical space-time is studied for a fluid with non vanishing radial pressure. An exact analytic solution is obtained (ignoring the arbitrary integration function) for the equation of state $p_{r}=(\gamma-1)\rho.$ The singularity is studied locally by comparing the time of formation of apparent horizon and the central shell focusing singularity while the global nature of the final fate of collapse is characterized by the existence of radial null geodesic. It is revealed that the end state of collapse for D dimension with equation of state $p=-\rho$, for (D$-$1) dimensional dust and (D$-$2)dimension with equation of state $p=\rho$ are identical. |
1910.12463 | Stefano Viaggiu | Stefano Viaggiu | The cosmological constant from Planckian fluctuations and the averaging
procedure | Accepted for publicationa in Foundations of Physics | Found Phys (2019) | 10.1007/s10701-019-00308-5 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper I continue the investigation in \cite{1,1b} concerning my
proposal on the nature of the cosmological constant. In particular, I study
both mathematically and physically the quantum Planckian context and I provide,
in order to depict quantum fluctuations and in absence of a complete quantum
gravity theory, a semiclassical solution where an effective inhomogeneous
metric at Planckian scales or above is averaged. In such a framework, a
generalization of the well known Buchert formalism \cite{2} is obtained with
the foliation in terms of the mean value $s(\hat{t})$ of the time operator
$\hat{t}$ in a maximally localizing state $\{s\}$ of a quantum spacetime
\cite{3,4,5,6} and in a cosmological context \cite{7}. As a result, after
introducing a decoherence length scale $L_D$ where quantum fluctuations are
averaged on, a classical de Sitter universe emerges with a small cosmological
constant depending on $L_D$ and frozen in a true vacuum state (lowest energy),
provided that the kinematical backreaction is negligible at that scale $L_D$.
Finally, I analyse the case with a non-vanishing initial spatial curvature
$\mathcal{R}$ showing that, for a reasonable large class of models, spatial
curvature and kinematical backreation $\mathcal{Q}$ are suppressed by the
dynamical evolution of the spacetime.
| [
{
"created": "Mon, 28 Oct 2019 06:47:31 GMT",
"version": "v1"
}
] | 2019-11-05 | [
[
"Viaggiu",
"Stefano",
""
]
] | In this paper I continue the investigation in \cite{1,1b} concerning my proposal on the nature of the cosmological constant. In particular, I study both mathematically and physically the quantum Planckian context and I provide, in order to depict quantum fluctuations and in absence of a complete quantum gravity theory, a semiclassical solution where an effective inhomogeneous metric at Planckian scales or above is averaged. In such a framework, a generalization of the well known Buchert formalism \cite{2} is obtained with the foliation in terms of the mean value $s(\hat{t})$ of the time operator $\hat{t}$ in a maximally localizing state $\{s\}$ of a quantum spacetime \cite{3,4,5,6} and in a cosmological context \cite{7}. As a result, after introducing a decoherence length scale $L_D$ where quantum fluctuations are averaged on, a classical de Sitter universe emerges with a small cosmological constant depending on $L_D$ and frozen in a true vacuum state (lowest energy), provided that the kinematical backreaction is negligible at that scale $L_D$. Finally, I analyse the case with a non-vanishing initial spatial curvature $\mathcal{R}$ showing that, for a reasonable large class of models, spatial curvature and kinematical backreation $\mathcal{Q}$ are suppressed by the dynamical evolution of the spacetime. |
1609.04428 | Claudio Cremaschini | Claudio Cremaschini and Massimo Tessarotto | Hamiltonian approach to GR - Part 2: covariant theory of quantum gravity | null | Eur. Phys. J. C (2017) 77:330 | 10.1140/epjc/s10052-017-4855-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A non-perturbative quantum field theory of General Relativity is presented
which leads to a new realization of the theory of Covariant Quantum-Gravity
(CQG-theory). The treatment is founded on the recently-identified Hamiltonian
structure associated with the classical space-time, i.e., the corresponding
manifestly-covariant Hamilton equations and the related Hamilton-Jacobi theory.
The quantum Hamiltonian operator and the CQG-wave equation for the
corresponding CQG-state and wave-function are realized in $% 4-$scalar form.
The new quantum wave equation is shown to be equivalent to a set of quantum
hydrodynamic equations which warrant the consistency with the classical GR
Hamilton-Jacobi equation in the semiclassical limit. A perturbative
approximation scheme is developed, which permits the adoption of the harmonic
oscillator approximation for the treatment of the Hamiltonian potential. As an
application of the theory, the stationary vacuum CQG-wave equation is studied,
yielding a stationary equation for the CQG-state in terms of the $4-$scalar
invariant-energy eigenvalue associated with the corresponding approximate
quantum Hamiltonian operator. The conditions for the existence of a discrete
invariant-energy spectrum are pointed out. This yields a possible estimate for
the graviton mass together with a new interpretation about the quantum origin
of the cosmological constant.
| [
{
"created": "Wed, 14 Sep 2016 20:13:48 GMT",
"version": "v1"
},
{
"created": "Mon, 22 May 2017 20:11:01 GMT",
"version": "v2"
}
] | 2017-05-24 | [
[
"Cremaschini",
"Claudio",
""
],
[
"Tessarotto",
"Massimo",
""
]
] | A non-perturbative quantum field theory of General Relativity is presented which leads to a new realization of the theory of Covariant Quantum-Gravity (CQG-theory). The treatment is founded on the recently-identified Hamiltonian structure associated with the classical space-time, i.e., the corresponding manifestly-covariant Hamilton equations and the related Hamilton-Jacobi theory. The quantum Hamiltonian operator and the CQG-wave equation for the corresponding CQG-state and wave-function are realized in $% 4-$scalar form. The new quantum wave equation is shown to be equivalent to a set of quantum hydrodynamic equations which warrant the consistency with the classical GR Hamilton-Jacobi equation in the semiclassical limit. A perturbative approximation scheme is developed, which permits the adoption of the harmonic oscillator approximation for the treatment of the Hamiltonian potential. As an application of the theory, the stationary vacuum CQG-wave equation is studied, yielding a stationary equation for the CQG-state in terms of the $4-$scalar invariant-energy eigenvalue associated with the corresponding approximate quantum Hamiltonian operator. The conditions for the existence of a discrete invariant-energy spectrum are pointed out. This yields a possible estimate for the graviton mass together with a new interpretation about the quantum origin of the cosmological constant. |
2012.01889 | Wolfgang Wieland | Wolfgang Wieland | Null infinity as an open Hamiltonian system | published version, typos removed | J. High Energ. Phys. 2021, 95 (2021) | 10.1007/JHEP04(2021)095 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When a system emits gravitational radiation, the Bondi mass decreases. If the
Bondi energy is Hamiltonian, it can thus only be a time dependent Hamiltonian.
In this paper, we show that the Bondi energy can be understood as a
time-dependent Hamiltonian on the covariant phase space. Our derivation starts
from the Hamiltonian formulation in domains with boundaries that are null. We
introduce the most general boundary conditions on a generic such null boundary,
and compute quasi-local charges for boosts, energy and angular momentum.
Initially, these domains are at finite distance, such that there is a natural
IR regulator. To remove the IR regulator, we introduce a double null foliation
together with an adapted Newman--Penrose null tetrad. Both null directions are
surface orthogonal. We study the falloff conditions for such specific null
foliations and take the limit to null infinity. At null infinity, we recover
the Bondi mass and the usual covariant phase space for the two radiative modes
at the full non-perturbative level. Apart from technical results, the framework
gives two important physical insights. First of all, it explains the physical
significance of the corner term that is added in the Wald--Zoupas framework to
render the quasi-conserved charges integrable. The term to be added is simply
the derivative of the Hamiltonian with respect to the background fields that
drive the time-dependence of the Hamiltonian. Secondly, we propose a new
interpretation of the Bondi mass as the thermodynamical free energy of
gravitational edge modes at future null infinity. The Bondi mass law is then
simply the statement that the free energy always decreases on its way towards
thermal equilibrium.
| [
{
"created": "Thu, 3 Dec 2020 13:12:13 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Apr 2021 19:18:55 GMT",
"version": "v2"
}
] | 2021-04-15 | [
[
"Wieland",
"Wolfgang",
""
]
] | When a system emits gravitational radiation, the Bondi mass decreases. If the Bondi energy is Hamiltonian, it can thus only be a time dependent Hamiltonian. In this paper, we show that the Bondi energy can be understood as a time-dependent Hamiltonian on the covariant phase space. Our derivation starts from the Hamiltonian formulation in domains with boundaries that are null. We introduce the most general boundary conditions on a generic such null boundary, and compute quasi-local charges for boosts, energy and angular momentum. Initially, these domains are at finite distance, such that there is a natural IR regulator. To remove the IR regulator, we introduce a double null foliation together with an adapted Newman--Penrose null tetrad. Both null directions are surface orthogonal. We study the falloff conditions for such specific null foliations and take the limit to null infinity. At null infinity, we recover the Bondi mass and the usual covariant phase space for the two radiative modes at the full non-perturbative level. Apart from technical results, the framework gives two important physical insights. First of all, it explains the physical significance of the corner term that is added in the Wald--Zoupas framework to render the quasi-conserved charges integrable. The term to be added is simply the derivative of the Hamiltonian with respect to the background fields that drive the time-dependence of the Hamiltonian. Secondly, we propose a new interpretation of the Bondi mass as the thermodynamical free energy of gravitational edge modes at future null infinity. The Bondi mass law is then simply the statement that the free energy always decreases on its way towards thermal equilibrium. |
0802.4077 | J. Fernando Barbero G. | Ivan Agullo, J. Fernando Barbero G., Jacobo Diaz-Polo, Enrique
Fernandez-Borja, Eduardo J. S. Villase\~nor | Black hole state counting in Loop Quantum Gravity: A number theoretical
approach | Accepted for publication in Physical Review Letters | Phys.Rev.Lett.100:211301,2008 | 10.1103/PhysRevLett.100.211301 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a practical method to exactly compute black hole entropy in the
framework of Loop Quantum Gravity. Along the way we provide a complete
characterization of the relevant sector of the spectrum of the area operator,
including degeneracies, and determine the number of solutions to the projection
constraint analytically. We use a computer implementation of the proposed
algorithm to confirm and extend previous results on the detailed structure of
the black hole degeneracy spectrum.
| [
{
"created": "Wed, 27 Feb 2008 20:41:27 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Apr 2008 14:22:18 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Agullo",
"Ivan",
""
],
[
"G.",
"J. Fernando Barbero",
""
],
[
"Diaz-Polo",
"Jacobo",
""
],
[
"Fernandez-Borja",
"Enrique",
""
],
[
"Villaseñor",
"Eduardo J. S.",
""
]
] | We give a practical method to exactly compute black hole entropy in the framework of Loop Quantum Gravity. Along the way we provide a complete characterization of the relevant sector of the spectrum of the area operator, including degeneracies, and determine the number of solutions to the projection constraint analytically. We use a computer implementation of the proposed algorithm to confirm and extend previous results on the detailed structure of the black hole degeneracy spectrum. |
gr-qc/0203036 | Fotini Markopoulou Kalamara | Fotini Markopoulou | Coarse graining in spin foam models | 38 pages, many eps figures | Class.Quant.Grav. 20 (2003) 777-800 | null | null | gr-qc hep-th | null | We formulate the problem of finding the low-energy limit of spin foam models
as a coarse-graining problem in the sense of statistical physics. This suggests
that renormalization group methods may be used to find that limit. However,
since spin foams are models of spacetime at Planck scale, novel issues arise:
these microscopic models are sums over irregular, background-independent
lattices. We show that all of these issues can be addressed by the recent
application of the Kreimer Hopf algebra for quantum field theory
renormalization to non-perturbative statistical physics. The main difference
from standard renormalization group is that the Hopf algebra executes block
transformations in parts of the lattice only but in a controlled manner so that
the end result is a fully block-transformed lattice.
| [
{
"created": "Tue, 12 Mar 2002 01:32:32 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Markopoulou",
"Fotini",
""
]
] | We formulate the problem of finding the low-energy limit of spin foam models as a coarse-graining problem in the sense of statistical physics. This suggests that renormalization group methods may be used to find that limit. However, since spin foams are models of spacetime at Planck scale, novel issues arise: these microscopic models are sums over irregular, background-independent lattices. We show that all of these issues can be addressed by the recent application of the Kreimer Hopf algebra for quantum field theory renormalization to non-perturbative statistical physics. The main difference from standard renormalization group is that the Hopf algebra executes block transformations in parts of the lattice only but in a controlled manner so that the end result is a fully block-transformed lattice. |
2307.10290 | Nils A. Nilsson | Nils A. Nilsson | Dynamical dark energy from spacetime-symmetry breaking -- late-time
behaviour and phantom crossing | Clarifications, analysis and references added, slight notation
change. Accepted for publication in Physics of the Dark Universe | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | We investigate the late-time cosmological dynamics in a simple case of
explicit spacetime-symmetry breaking. By expanding in a small symmetry-breaking
coefficient we are able to write the Friedmann equations as $\Lambda$CDM +
dynamical dark energy, which we show contains logarithmic dependence of the
scale factor. We find that the dark energy equation of state displays
divergencies and phantom behaviour for certain values of the symmetry-breaking
coefficient, where the NEC is also broken. We discuss the adiabatic sound speed
of dark energy and compare the model to current constraints using the
Chevallier-Polarski-Linder parametrisation. Remarkably, although the
constraints on the same symmetry-breaking coefficient from e.g.
gravitational-wave propagation are orders of magnitude stronger than what we
obtain in this paper, we are able to cut those constraints, which are more or
less symmetric around zero, in half by showing that same coefficient must be
negative (or zero) if one wishes to keep the NEC intact.
| [
{
"created": "Tue, 18 Jul 2023 14:26:48 GMT",
"version": "v1"
},
{
"created": "Thu, 2 May 2024 01:12:39 GMT",
"version": "v2"
}
] | 2024-05-03 | [
[
"Nilsson",
"Nils A.",
""
]
] | We investigate the late-time cosmological dynamics in a simple case of explicit spacetime-symmetry breaking. By expanding in a small symmetry-breaking coefficient we are able to write the Friedmann equations as $\Lambda$CDM + dynamical dark energy, which we show contains logarithmic dependence of the scale factor. We find that the dark energy equation of state displays divergencies and phantom behaviour for certain values of the symmetry-breaking coefficient, where the NEC is also broken. We discuss the adiabatic sound speed of dark energy and compare the model to current constraints using the Chevallier-Polarski-Linder parametrisation. Remarkably, although the constraints on the same symmetry-breaking coefficient from e.g. gravitational-wave propagation are orders of magnitude stronger than what we obtain in this paper, we are able to cut those constraints, which are more or less symmetric around zero, in half by showing that same coefficient must be negative (or zero) if one wishes to keep the NEC intact. |
gr-qc/9512043 | Roumen Borissov | Roumen Borissov (Temple University), Seth Major (CGPG), and Lee Smolin
(CGPG) | The geometry of quantum spin networks | 16 pages, 35 Postscript figures, uses epsfig.sty | Class.Quant.Grav. 13 (1996) 3183-3196 | 10.1088/0264-9381/13/12/009 | CGPG-95/12-4 | gr-qc | null | The discrete picture of geometry arising from the loop representation of
quantum gravity can be extended by a quantum deformation. The operators for
area and volume defined in the q-deformation of the theory are partly
diagonalized. The eigenstates are expressed in terms of q-deformed spin
networks. The q-deformation breaks some of the degeneracy of the volume
operator so that trivalent spin-networks have non-zero volume. These
computations are facilitated by use of a technique based on the recoupling
theory of SU(2)_q, which simplifies the construction of these and other
operators through diffeomorphism invariant regularization procedures.
| [
{
"created": "Wed, 27 Dec 1995 16:35:44 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Borissov",
"Roumen",
"",
"Temple University"
],
[
"Major",
"Seth",
"",
"CGPG"
],
[
"Smolin",
"Lee",
"",
"CGPG"
]
] | The discrete picture of geometry arising from the loop representation of quantum gravity can be extended by a quantum deformation. The operators for area and volume defined in the q-deformation of the theory are partly diagonalized. The eigenstates are expressed in terms of q-deformed spin networks. The q-deformation breaks some of the degeneracy of the volume operator so that trivalent spin-networks have non-zero volume. These computations are facilitated by use of a technique based on the recoupling theory of SU(2)_q, which simplifies the construction of these and other operators through diffeomorphism invariant regularization procedures. |
1909.07756 | Paul Tod | Paul Tod | Spacetimes with all Penrose limits diagonalisable | 13 pages, no figures; revised version as accepted in Class.Quant.Grav | null | 10.1088/1361-6382/ab738a | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the problem of finding all space-time metrics for which all
plane-wave Penrose limits are diagonalisable plane waves. This requirement
leads to a conformally invariant differential condition on the Weyl spinor
which we analyse for different algebraic types in the Petrov-Pirani-Penrose
classification. The only vacuum examples, apart from actual plane waves which
are their own Penrose limit, are some of the nonrotating type D metrics, but
some nonvacuum solutions are also identified. The condition requires the Weyl
spinor, whenever it is nonzero, to be proportional to a valence-4 Killing
spinor with a real function of proportionality.
| [
{
"created": "Tue, 17 Sep 2019 13:02:04 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Feb 2020 16:56:07 GMT",
"version": "v2"
}
] | 2020-04-08 | [
[
"Tod",
"Paul",
""
]
] | We consider the problem of finding all space-time metrics for which all plane-wave Penrose limits are diagonalisable plane waves. This requirement leads to a conformally invariant differential condition on the Weyl spinor which we analyse for different algebraic types in the Petrov-Pirani-Penrose classification. The only vacuum examples, apart from actual plane waves which are their own Penrose limit, are some of the nonrotating type D metrics, but some nonvacuum solutions are also identified. The condition requires the Weyl spinor, whenever it is nonzero, to be proportional to a valence-4 Killing spinor with a real function of proportionality. |
2207.12168 | Panagiotis Mavrogiannis | Panagiotis Mavrogiannis | Law of elasticity and fracture limit of magnetic forcelines under their
gravitational deformation | 18 pages, no figures, minor corrections | null | 10.1098/rspa.2023.0048 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Magnetic fields are a very special form of elastic medium. Within
astrophysical environments (magnetised stars and protogalaxies) they counteract
shear and rotational distortions as well as gravitational collapse. Their
vector nature allows for their extraordinary coupling with spacetime curvature
in the framework of general relativity. This particular coupling points out the
way to study magnetic elasticity under gravitational deformation. In this
context, we reveal their law of elasticity, calculate their fracture limit and
subsequently argue that they ultimately lose the battle against gravitational
contraction of magnetised matter. Two illustrative applications, in a neutron
star and a white dwarf, accompany the results.
| [
{
"created": "Mon, 25 Jul 2022 13:11:44 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Aug 2022 09:16:46 GMT",
"version": "v2"
},
{
"created": "Thu, 8 Dec 2022 19:35:11 GMT",
"version": "v3"
},
{
"created": "Thu, 19 Jan 2023 22:42:45 GMT",
"version": "v4"
},
{
"cre... | 2023-07-19 | [
[
"Mavrogiannis",
"Panagiotis",
""
]
] | Magnetic fields are a very special form of elastic medium. Within astrophysical environments (magnetised stars and protogalaxies) they counteract shear and rotational distortions as well as gravitational collapse. Their vector nature allows for their extraordinary coupling with spacetime curvature in the framework of general relativity. This particular coupling points out the way to study magnetic elasticity under gravitational deformation. In this context, we reveal their law of elasticity, calculate their fracture limit and subsequently argue that they ultimately lose the battle against gravitational contraction of magnetised matter. Two illustrative applications, in a neutron star and a white dwarf, accompany the results. |
1910.08451 | Karim Van Aelst | Karim Van Aelst, Eric Gourgoulhon, Philippe Grandcl\'ement, Christos
Charmousis | Hairy rotating black holes in cubic Galileon theory | 31 pages, 9 figures; v2 minor improvements, added references, minor
typos corrected, version published in Classical and Quantum Gravity | Class. Quantum Grav. 37 035007 (2020) | 10.1088/1361-6382/ab6391 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Numerical solutions for asymptotically flat rotating black holes in the cubic
Galileon theory are presented. These black holes are endowed with a nontrivial
scalar field and exhibit a non-Schwarzschild behaviour: faster than $1/r$
convergence to Minkowski spacetime at spatial infinity and hence vanishing of
the Komar mass. The metrics are compared with the Kerr metric for various
couplings and angular velocities. Their physical properties are extracted and
show significant deviations from the Kerr case.
| [
{
"created": "Fri, 18 Oct 2019 14:52:51 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jan 2020 15:18:44 GMT",
"version": "v2"
}
] | 2020-01-24 | [
[
"Van Aelst",
"Karim",
""
],
[
"Gourgoulhon",
"Eric",
""
],
[
"Grandclément",
"Philippe",
""
],
[
"Charmousis",
"Christos",
""
]
] | Numerical solutions for asymptotically flat rotating black holes in the cubic Galileon theory are presented. These black holes are endowed with a nontrivial scalar field and exhibit a non-Schwarzschild behaviour: faster than $1/r$ convergence to Minkowski spacetime at spatial infinity and hence vanishing of the Komar mass. The metrics are compared with the Kerr metric for various couplings and angular velocities. Their physical properties are extracted and show significant deviations from the Kerr case. |
1802.09663 | Diego Carranza | Diego A. Carranza and Juan A. Valiente Kroon | Killing boundary data for anti-de Sitter-like spacetimes | 15 pages | Class. Quantum Grav. 35, 155011 (2018) | 10.1088/1361-6382/aacdd2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Given an initial-boundary value problem for an anti-de Sitter-like spacetime,
we analyse conditions on the conformal boundary ensuring the existence of
Killing vectors in the spacetime arising from this problem. This analysis makes
use of a system of conformal wave equations describing the propagation of the
Killing equation first considered by Paetz. We identify an obstruction tensor
constructed from Killing vector candidate and the Cotton tensor of the
conformal boundary whose vanishing is a necessary condition for the existence
of Killing vectors in the spacetime. This obstruction tensor vanishes if the
conformal boundary is conformally flat.
| [
{
"created": "Tue, 27 Feb 2018 00:57:21 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Jul 2018 14:35:38 GMT",
"version": "v2"
}
] | 2018-12-19 | [
[
"Carranza",
"Diego A.",
""
],
[
"Kroon",
"Juan A. Valiente",
""
]
] | Given an initial-boundary value problem for an anti-de Sitter-like spacetime, we analyse conditions on the conformal boundary ensuring the existence of Killing vectors in the spacetime arising from this problem. This analysis makes use of a system of conformal wave equations describing the propagation of the Killing equation first considered by Paetz. We identify an obstruction tensor constructed from Killing vector candidate and the Cotton tensor of the conformal boundary whose vanishing is a necessary condition for the existence of Killing vectors in the spacetime. This obstruction tensor vanishes if the conformal boundary is conformally flat. |
1401.1759 | J. David Vergara | Marcos Rosenbaum, J. David Vergara, Rom\'an Ju\'arez and A.A. Minzoni | A Twisted ${\mathcal C}^{\star}$-algebra formulation of Quantum
Cosmology with application to the Bianchi I model | 31 pages, 10 figures, to appear in PRD | Phys. Rev. D 89, 085038 (2014) | 10.1103/PhysRevD.89.085038 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A twisted ${\mathcal C}^\star $- algebra of the extended (noncommutative)
Heisenberg-Weyl group has been constructed which takes into account the
Uncertainty Principle for coordinates in the Planck length regime. This general
construction is then used to generate an appropriate Hilbert space and
observables for the noncommutative theory which, when applied to the Bianchi I
Cosmology, leads to a new set of equations that describe the quantum evolution
of the universe. We find that this formulation matches theories based on a
reticular Heisenberg-Weyl algebra in the bouncing and expanding regions of a
collapsing Bianchi universe. There is, however, an additional effect introduced
by the dynamics generated by the noncommutativity. This is an oscillation in
the spectrum of the volume operator of the universe, within the bouncing region
of the commutative theories. We show that this effect is generic and produced
by the noncommutative momentum exchange between the degrees of freedom in the
cosmology. We give asymptotic and numerical solutions which show the above
mentioned effects of the noncommutativity.
| [
{
"created": "Wed, 8 Jan 2014 17:25:00 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Jan 2014 18:49:18 GMT",
"version": "v2"
},
{
"created": "Mon, 31 Mar 2014 23:29:48 GMT",
"version": "v3"
}
] | 2014-04-30 | [
[
"Rosenbaum",
"Marcos",
""
],
[
"Vergara",
"J. David",
""
],
[
"Juárez",
"Román",
""
],
[
"Minzoni",
"A. A.",
""
]
] | A twisted ${\mathcal C}^\star $- algebra of the extended (noncommutative) Heisenberg-Weyl group has been constructed which takes into account the Uncertainty Principle for coordinates in the Planck length regime. This general construction is then used to generate an appropriate Hilbert space and observables for the noncommutative theory which, when applied to the Bianchi I Cosmology, leads to a new set of equations that describe the quantum evolution of the universe. We find that this formulation matches theories based on a reticular Heisenberg-Weyl algebra in the bouncing and expanding regions of a collapsing Bianchi universe. There is, however, an additional effect introduced by the dynamics generated by the noncommutativity. This is an oscillation in the spectrum of the volume operator of the universe, within the bouncing region of the commutative theories. We show that this effect is generic and produced by the noncommutative momentum exchange between the degrees of freedom in the cosmology. We give asymptotic and numerical solutions which show the above mentioned effects of the noncommutativity. |
gr-qc/0310123 | Suresh Maran k | Suresh K. Maran | Spin Foam Models of Gravity and BF Theory as evolution of Spin Networks | This article has been replaced by gr-qc/0412011 | null | null | null | gr-qc | null | This article has been replaced by gr-qc/0412011
| [
{
"created": "Wed, 29 Oct 2003 21:16:38 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Oct 2003 18:17:36 GMT",
"version": "v2"
},
{
"created": "Tue, 4 Nov 2003 14:55:04 GMT",
"version": "v3"
},
{
"created": "Thu, 6 Nov 2003 06:59:11 GMT",
"version": "v4"
},
{
"cre... | 2007-05-23 | [
[
"Maran",
"Suresh K.",
""
]
] | This article has been replaced by gr-qc/0412011 |
1910.02924 | Klaountia Pasmatsiou | Yi-Zen Chu, Klaountia Pasmatsiou, Glenn D. Starkman | Finite-Size Effects On The Self-Force | null | Phys. Rev. D 101, 104020 (2020) | 10.1103/PhysRevD.101.104020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Electromagnetic and linear gravitational radiation do not solely propagate on
the null cone in 3+1 dimensions in curved spacetimes, contrary to their
well-known behavior in flat spacetime. Their additional propagation inside the
null cone is known as the tail effect. A compact body will produce a signal
whose tail will interact with its future worldline, thus producing a
tail-induced self-force. We present new results for the tail-induced scalar,
electromagnetic and gravitational self-force for a test mass in orbit around a
central mass, including effects from the internal structure of that body.
| [
{
"created": "Mon, 7 Oct 2019 17:27:23 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Mar 2020 19:23:42 GMT",
"version": "v2"
},
{
"created": "Sun, 29 Mar 2020 17:01:27 GMT",
"version": "v3"
},
{
"created": "Fri, 15 May 2020 07:14:13 GMT",
"version": "v4"
}
] | 2020-05-20 | [
[
"Chu",
"Yi-Zen",
""
],
[
"Pasmatsiou",
"Klaountia",
""
],
[
"Starkman",
"Glenn D.",
""
]
] | Electromagnetic and linear gravitational radiation do not solely propagate on the null cone in 3+1 dimensions in curved spacetimes, contrary to their well-known behavior in flat spacetime. Their additional propagation inside the null cone is known as the tail effect. A compact body will produce a signal whose tail will interact with its future worldline, thus producing a tail-induced self-force. We present new results for the tail-induced scalar, electromagnetic and gravitational self-force for a test mass in orbit around a central mass, including effects from the internal structure of that body. |
0808.1107 | Alejandro Satz | Eugenio Bianchi, Alejandro Satz | Semiclassical regime of Regge calculus and spin foams | 30 pages, no figures. Updated version with minor corrections, one
reference added | Nucl.Phys.B808:546-568,2009 | 10.1016/j.nuclphysb.2008.09.005 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent attempts to recover the graviton propagator from spin foam models
involve the use of a boundary quantum state peaked on a classical geometry. The
question arises whether beyond the case of a single simplex this suffices for
peaking the interior geometry in a semiclassical configuration. In this paper
we explore this issue in the context of quantum Regge calculus with a general
triangulation. Via a stationary phase approximation, we show that the boundary
state succeeds in peaking the interior in the appropriate configuration, and
that boundary correlations can be computed order by order in an asymptotic
expansion. Further, we show that if we replace at each simplex the exponential
of the Regge action by its cosine -- as expected from the semiclassical limit
of spin foam models -- then the contribution from the sign-reversed terms is
suppressed in the semiclassical regime and the results match those of
conventional Regge calculus.
| [
{
"created": "Thu, 7 Aug 2008 20:03:56 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Sep 2008 14:44:29 GMT",
"version": "v2"
}
] | 2008-12-18 | [
[
"Bianchi",
"Eugenio",
""
],
[
"Satz",
"Alejandro",
""
]
] | Recent attempts to recover the graviton propagator from spin foam models involve the use of a boundary quantum state peaked on a classical geometry. The question arises whether beyond the case of a single simplex this suffices for peaking the interior geometry in a semiclassical configuration. In this paper we explore this issue in the context of quantum Regge calculus with a general triangulation. Via a stationary phase approximation, we show that the boundary state succeeds in peaking the interior in the appropriate configuration, and that boundary correlations can be computed order by order in an asymptotic expansion. Further, we show that if we replace at each simplex the exponential of the Regge action by its cosine -- as expected from the semiclassical limit of spin foam models -- then the contribution from the sign-reversed terms is suppressed in the semiclassical regime and the results match those of conventional Regge calculus. |
1005.1387 | Khalid Saifullah | A. R. Kashif, K. Saifullah | Curvature and Weyl collineations of spacetimes | null | Proc. 12th Marcel Grossmann Meeting on General Relativity, World
Scientific, 2010 | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lie symmetries of various geometrical and physical quantities in general
relativity play an important role in understanding the curvature structure of
manifolds. The Riemann curvature and Weyl tensors are two fourth-rank tensors
in the theory. Interrelations between the symmetries of these two tensors
(known as collineations) are studied. Some illustrative examples are also
provided.
| [
{
"created": "Sun, 9 May 2010 11:37:32 GMT",
"version": "v1"
}
] | 2010-05-11 | [
[
"Kashif",
"A. R.",
""
],
[
"Saifullah",
"K.",
""
]
] | Lie symmetries of various geometrical and physical quantities in general relativity play an important role in understanding the curvature structure of manifolds. The Riemann curvature and Weyl tensors are two fourth-rank tensors in the theory. Interrelations between the symmetries of these two tensors (known as collineations) are studied. Some illustrative examples are also provided. |
2406.10821 | Amir Hadi Ziaie | Amir Hadi Ziaie and Mohammad Reza Mehdizadeh | Casimir Wormholes in Brans-Dicke Theory | 26 pages and 10 figures | Class. Quantum Grav. 41, 145001 (2024) | 10.1088/1361-6382/ad5136 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In recent years there has been a growing interest in the field of wormhole
physics in the presence of the Casimir effect. As this effect provides negative
energy density, it can be utilized as an ideal candidate for the exotic matter
required for creating a traversable wormhole. In the context of modified
theories of gravity such as Brans-Dicke (BD) theory \cite{BDTH}, wormhole
geometries {have} been vastly investigated{. However}, the scientific
literature is silent on the issue of BD wormholes in the presence of Casimir
energy. Our aim in the present study is to seek for static spherically
symmetric solutions representing wormhole configurations in BD theory with
Casimir energy as the supporting matter. The Casimir {setup} we assume
comprises two electrically neutral, infinitely large parallel planes placed in
a vacuum. We then consider the Casimir vacuum energy density of a scalar field
in such a configuration with Dirichlet {and} mixed boundary conditions. In the
former case, the corresponding Casimir force is attractive and in the latter
this force is repulsive. We present exact zero tidal force wormhole solutions
as well as those with non-vanishing redshift function for both types of Casimir
energies. The conditions on wormhole solutions along with the weak (WEC) and
null (NEC) energy conditions put constraints on the values of BD coupling
parameter. These constraints are also subject to the value of BD scalar field
at the throat and the throat radius. We therefore find that BD wormholes in the
presence of Casimir energy can exist without violating NEC and WEC (for the
repulsive Casimir force). Finally, we examine the equilibrium condition for the
stability of the obtained solutions using Tolman-Oppenheimer-Volkoff (TOV)
equation.
| [
{
"created": "Sun, 16 Jun 2024 07:07:45 GMT",
"version": "v1"
}
] | 2024-06-18 | [
[
"Ziaie",
"Amir Hadi",
""
],
[
"Mehdizadeh",
"Mohammad Reza",
""
]
] | In recent years there has been a growing interest in the field of wormhole physics in the presence of the Casimir effect. As this effect provides negative energy density, it can be utilized as an ideal candidate for the exotic matter required for creating a traversable wormhole. In the context of modified theories of gravity such as Brans-Dicke (BD) theory \cite{BDTH}, wormhole geometries {have} been vastly investigated{. However}, the scientific literature is silent on the issue of BD wormholes in the presence of Casimir energy. Our aim in the present study is to seek for static spherically symmetric solutions representing wormhole configurations in BD theory with Casimir energy as the supporting matter. The Casimir {setup} we assume comprises two electrically neutral, infinitely large parallel planes placed in a vacuum. We then consider the Casimir vacuum energy density of a scalar field in such a configuration with Dirichlet {and} mixed boundary conditions. In the former case, the corresponding Casimir force is attractive and in the latter this force is repulsive. We present exact zero tidal force wormhole solutions as well as those with non-vanishing redshift function for both types of Casimir energies. The conditions on wormhole solutions along with the weak (WEC) and null (NEC) energy conditions put constraints on the values of BD coupling parameter. These constraints are also subject to the value of BD scalar field at the throat and the throat radius. We therefore find that BD wormholes in the presence of Casimir energy can exist without violating NEC and WEC (for the repulsive Casimir force). Finally, we examine the equilibrium condition for the stability of the obtained solutions using Tolman-Oppenheimer-Volkoff (TOV) equation. |
1312.2580 | Sergiu I. Vacaru | Vyacheslav Ruchin, Olivia Vacaru and Sergiu I. Vacaru | On Relativistic Generalization of Perelman's W-entropy and Statistical
Thermodynamic Description of Gravitational Fields | latex2e, v4 is an accepted to EPJC substantial extension of a former
letter type paper on 10 pages to a research article on 41 pages; a new author
added, the paper's title and permanent and visiting affiliations were
correspondingly modified; and new results, conclusions and references are
provided | Eur. Phys. J. C 77 (2017) 184 | 10.1140/epjc/s10052-017-4712-1 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using double 2+2 and 3+1 nonholonomic fibrations on Lorentz manifolds, we
extend the concept of W-entropy for gravitational fields in the general
relativity, GR, theory. Such F- and W-functionals were introduced in the Ricci
flow theory of three dimensional, 3-d, Riemannian metrics by G. Perelman,
arXiv: math.DG/0211159. Nonrelativistic 3-d Ricci flows are characterized by
associated statistical thermodynamical values determined by W--entropy.
Generalizations for geometric flows of 4-d pseudo-Riemannian metrics are
considered for models with local thermodynamical equilibrium and separation of
dissipative and non-dissipative processes in relativistic hydrodynamics. The
approach is elaborated in the framework of classical filed theories
(relativistic continuum and hydrodynamic models) without an underlying kinetic
description which will be elaborated in other works. The 3+1 splitting allows
us to provide a general relativistic definition of gravitational entropy in the
Lyapunov-Perelman sense. It increases monotonically as structure forms in the
Universe. We can formulate a thermodynamic description of exact solutions in GR
depending, in general, on all spacetime coordinates. A corresponding 2+2
splitting with nonholonomic deformation of linear connection and frame
structures is necessary for generating in very general form various classes of
exact solutions of the Einstein and general relativistic geometric flow
equations. Finally, we speculate on physical macrostates and microstate
interpretations of the W-entropy in GR, geometric flow theories and possible
connections to string theory (a second unsolved problem also contained in
Perelman's works) in the Polyakov's approach.
| [
{
"created": "Sun, 8 Dec 2013 13:25:06 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Dec 2013 16:59:20 GMT",
"version": "v2"
},
{
"created": "Fri, 25 Sep 2015 07:53:10 GMT",
"version": "v3"
},
{
"created": "Mon, 27 Feb 2017 13:55:55 GMT",
"version": "v4"
}
] | 2017-03-28 | [
[
"Ruchin",
"Vyacheslav",
""
],
[
"Vacaru",
"Olivia",
""
],
[
"Vacaru",
"Sergiu I.",
""
]
] | Using double 2+2 and 3+1 nonholonomic fibrations on Lorentz manifolds, we extend the concept of W-entropy for gravitational fields in the general relativity, GR, theory. Such F- and W-functionals were introduced in the Ricci flow theory of three dimensional, 3-d, Riemannian metrics by G. Perelman, arXiv: math.DG/0211159. Nonrelativistic 3-d Ricci flows are characterized by associated statistical thermodynamical values determined by W--entropy. Generalizations for geometric flows of 4-d pseudo-Riemannian metrics are considered for models with local thermodynamical equilibrium and separation of dissipative and non-dissipative processes in relativistic hydrodynamics. The approach is elaborated in the framework of classical filed theories (relativistic continuum and hydrodynamic models) without an underlying kinetic description which will be elaborated in other works. The 3+1 splitting allows us to provide a general relativistic definition of gravitational entropy in the Lyapunov-Perelman sense. It increases monotonically as structure forms in the Universe. We can formulate a thermodynamic description of exact solutions in GR depending, in general, on all spacetime coordinates. A corresponding 2+2 splitting with nonholonomic deformation of linear connection and frame structures is necessary for generating in very general form various classes of exact solutions of the Einstein and general relativistic geometric flow equations. Finally, we speculate on physical macrostates and microstate interpretations of the W-entropy in GR, geometric flow theories and possible connections to string theory (a second unsolved problem also contained in Perelman's works) in the Polyakov's approach. |
1307.6241 | Betti Hartmann | Yves Brihaye, Betti Hartmann and Sardor Tojiev | AdS solitons with conformal scalar hair | 18 pages including 12 figures; v2: 19 pages including 12 figures,
definition of mass added, some figures replaced; v3: typos corrected, matches
version accepted for publication in Phys. Rev. D | Phys. Rev. D 88, 104006 (2013) | 10.1103/PhysRevD.88.104006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study spherically symmetric soliton solutions in a model with a
conformally coupled scalar field as well as in full conformal gravity. We
observe that a new type of limiting behaviour appears for particular choices of
the self-coupling of the scalar field, i.e. the solitons interpolate smoothly
between the Anti-de Sitter vacuum and an uncharged configuration. Furthermore,
within conformal gravity the qualitative approach of a limiting solution does
not change when varying the charge of the scalar field - contrary to the
Einstein-Hilbert case. However, it changes with the scalar self-coupling.
| [
{
"created": "Tue, 23 Jul 2013 20:34:01 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Aug 2013 20:17:35 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Nov 2013 17:31:39 GMT",
"version": "v3"
}
] | 2013-11-20 | [
[
"Brihaye",
"Yves",
""
],
[
"Hartmann",
"Betti",
""
],
[
"Tojiev",
"Sardor",
""
]
] | We study spherically symmetric soliton solutions in a model with a conformally coupled scalar field as well as in full conformal gravity. We observe that a new type of limiting behaviour appears for particular choices of the self-coupling of the scalar field, i.e. the solitons interpolate smoothly between the Anti-de Sitter vacuum and an uncharged configuration. Furthermore, within conformal gravity the qualitative approach of a limiting solution does not change when varying the charge of the scalar field - contrary to the Einstein-Hilbert case. However, it changes with the scalar self-coupling. |
gr-qc/9902034 | Valter Moretti | Valter Moretti (Math. Dept. Trento University) | Proof of the symmetry of the off-diagonal heat-kernel and Hadamard's
expansion coefficients in general $C^{\infty}$ Riemannian manifolds | 30 pages, latex, no figures, minor errors corrected, English
improved, shortened version accepted for publication in Commun. Math. Phys | Commun.Math.Phys. 208 (1999) 283-309 | 10.1007/s002200050759 | UTM 547 | gr-qc math-ph math.MP | null | We consider the problem of the symmetry of the off-diagonal heat-kernel
coefficients as well as the coefficients corresponding to the
short-distance-divergent part of the Hadamard expansion in general smooth
(analytic or not) manifolds. The requirement of such a symmetry played a
central r\^{o}le in the theory of the point-splitting one-loop renormalization
of the stress tensor in either Riemannian or Lorentzian manifolds. Actually,
the symmetry of these coefficients has been assumed as a hypothesis in several
papers concerning these issues without an explicit proof. The difficulty of a
direct proof is related to the fact that the considered off-diagonal
heat-kernel expansion, also in the Riemannian case, in principle, may be not a
proper asymptotic expansion. On the other hand, direct computations of the
off-diagonal heat-kernel coefficients are impossibly difficult in nontrivial
cases and thus no case is known in the literature where the symmetry does not
hold. By approximating $C^\infty$ metrics with analytic metrics in common
(totally normal) geodesically convex neighborhoods, it is rigorously proven
that, in general $C^\infty$ Riemannian manifolds, any point admits a
geodesically convex neighborhood where the off-diagonal heat-kernel
coefficients, as well as the relevant Hadamard's expansion coefficients, are
symmetric functions of the two arguments.
| [
{
"created": "Thu, 11 Feb 1999 15:06:13 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Jun 1999 08:35:08 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Moretti",
"Valter",
"",
"Math. Dept. Trento University"
]
] | We consider the problem of the symmetry of the off-diagonal heat-kernel coefficients as well as the coefficients corresponding to the short-distance-divergent part of the Hadamard expansion in general smooth (analytic or not) manifolds. The requirement of such a symmetry played a central r\^{o}le in the theory of the point-splitting one-loop renormalization of the stress tensor in either Riemannian or Lorentzian manifolds. Actually, the symmetry of these coefficients has been assumed as a hypothesis in several papers concerning these issues without an explicit proof. The difficulty of a direct proof is related to the fact that the considered off-diagonal heat-kernel expansion, also in the Riemannian case, in principle, may be not a proper asymptotic expansion. On the other hand, direct computations of the off-diagonal heat-kernel coefficients are impossibly difficult in nontrivial cases and thus no case is known in the literature where the symmetry does not hold. By approximating $C^\infty$ metrics with analytic metrics in common (totally normal) geodesically convex neighborhoods, it is rigorously proven that, in general $C^\infty$ Riemannian manifolds, any point admits a geodesically convex neighborhood where the off-diagonal heat-kernel coefficients, as well as the relevant Hadamard's expansion coefficients, are symmetric functions of the two arguments. |
0705.2656 | Xin Zhang | Xin Zhang, Yi Ling | Inflationary universe in loop quantum cosmology | 21 pages, 4 figures; accepted for publication in JCAP | JCAP0708:012,2007 | 10.1088/1475-7516/2007/08/012 | null | gr-qc astro-ph hep-ph hep-th | null | Loop quantum cosmology provides a nice solution of avoiding the big bang
singularity through a big bounce mechanism in the high energy region. In loop
quantum cosmology an inflationary universe is emergent after the big bounce, no
matter what matter component is filled in the universe. A super-inflation phase
without phantom matter will appear in a certain way in the initial stage after
the bounce; then the universe will undergo a normal inflation stage. We discuss
the condition of inflation in detail in this framework. Also, for slow-roll
inflation, we expect the imprint from the effects of the loop quantum cosmology
should be left in the primordial perturbation power spectrum. However, we show
that this imprint is too weak to be observed.
| [
{
"created": "Fri, 18 May 2007 08:48:10 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Jul 2007 08:49:17 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Zhang",
"Xin",
""
],
[
"Ling",
"Yi",
""
]
] | Loop quantum cosmology provides a nice solution of avoiding the big bang singularity through a big bounce mechanism in the high energy region. In loop quantum cosmology an inflationary universe is emergent after the big bounce, no matter what matter component is filled in the universe. A super-inflation phase without phantom matter will appear in a certain way in the initial stage after the bounce; then the universe will undergo a normal inflation stage. We discuss the condition of inflation in detail in this framework. Also, for slow-roll inflation, we expect the imprint from the effects of the loop quantum cosmology should be left in the primordial perturbation power spectrum. However, we show that this imprint is too weak to be observed. |
2211.13154 | Anish Agashe | Anish Agashe and Mustapha Ishak | An Almost-FLRW Universe as the Averaged Geometry in Macroscopic Gravity | Accepted for publication in Gravitation and Cosmology | null | 10.1134/S0202289323020020 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | It is well-known that spacetime averaging is an operation that does not
commute with building the Einstein tensor. In the framework of Macroscopic
gravity (MG), a covariant averaging procedure, this non-commutativity gives
averaged field equations with an additional correction term known as
back-reaction. It is important to explore whether such a term, even if known to
be small, may or may not cause any systematic effect for precision cosmology.
In this work, we explore the application of the MG formalism to an almost
Friedmann-Lema\^itre-Robertson-Walker (FLRW) model. Namely, we find solutions
to the field equations of MG taking the averaged universe to be almost-FLRW
modelled using a linearly perturbed FLRW metric. We study several solutions
with different functional forms of the metric perturbations including plane
waves ansatzes. We find that back-reaction terms are present not only at the
background level but also at perturbed level, reflecting the non-linear nature
of the averaging process. Thus, the averaging effect can extend to both the
expansion and the growth of structure in the universe.
| [
{
"created": "Wed, 23 Nov 2022 17:31:47 GMT",
"version": "v1"
}
] | 2023-06-28 | [
[
"Agashe",
"Anish",
""
],
[
"Ishak",
"Mustapha",
""
]
] | It is well-known that spacetime averaging is an operation that does not commute with building the Einstein tensor. In the framework of Macroscopic gravity (MG), a covariant averaging procedure, this non-commutativity gives averaged field equations with an additional correction term known as back-reaction. It is important to explore whether such a term, even if known to be small, may or may not cause any systematic effect for precision cosmology. In this work, we explore the application of the MG formalism to an almost Friedmann-Lema\^itre-Robertson-Walker (FLRW) model. Namely, we find solutions to the field equations of MG taking the averaged universe to be almost-FLRW modelled using a linearly perturbed FLRW metric. We study several solutions with different functional forms of the metric perturbations including plane waves ansatzes. We find that back-reaction terms are present not only at the background level but also at perturbed level, reflecting the non-linear nature of the averaging process. Thus, the averaging effect can extend to both the expansion and the growth of structure in the universe. |
1902.07287 | Pierre Fleury | Pierre Fleury | Gravitation: from Newton to Einstein | 107 pages, 23 figures, 77 exercises. Lectures given at the African
Institute for Mathematical Sciences of Cameroon (AIMS-Cameroon) in January
2018 and January 2019. V2: Added an introduction and a conclusion, corrected
a few typos. V3: sign issue corrected in eq. (II.135) | Springer Briefs in Physics 2019 | 10.1007/978-3-030-32001-0 | null | gr-qc physics.ed-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This document gathers the notes of a 30-hour review course on gravitation,
which I delivered in January 2018 and January 2019 at the African Institute for
Mathematical Sciences of Cameroon (AIMS-Cameroon). Its main goal is to propose
a big picture of gravitation, where Einstein's relativity arises as a natural
increment to Newton's theory. It is designed for bachelor/master students who
do not necessarily have prior knowledge about relativity. The students are
nevertheless expected to be familiar with the fundamentals of Newton's
mechanics and gravitation, for the first chapter to be a mere reformulation of
known concepts. The second chapter then introduces special and general
relativity at the same time, while the third chapter explores concrete
manifestations of relativistic gravitation, notably gravitational waves and
black holes. Each section corresponds, on average, to slightly more than a
2-hour black-board lecture. The numerous exercises must be considered part of
the course itself; they are intended to stimulate active reading.
| [
{
"created": "Tue, 19 Feb 2019 21:07:59 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Nov 2019 14:35:24 GMT",
"version": "v2"
},
{
"created": "Sat, 3 Aug 2024 10:18:55 GMT",
"version": "v3"
}
] | 2024-08-06 | [
[
"Fleury",
"Pierre",
""
]
] | This document gathers the notes of a 30-hour review course on gravitation, which I delivered in January 2018 and January 2019 at the African Institute for Mathematical Sciences of Cameroon (AIMS-Cameroon). Its main goal is to propose a big picture of gravitation, where Einstein's relativity arises as a natural increment to Newton's theory. It is designed for bachelor/master students who do not necessarily have prior knowledge about relativity. The students are nevertheless expected to be familiar with the fundamentals of Newton's mechanics and gravitation, for the first chapter to be a mere reformulation of known concepts. The second chapter then introduces special and general relativity at the same time, while the third chapter explores concrete manifestations of relativistic gravitation, notably gravitational waves and black holes. Each section corresponds, on average, to slightly more than a 2-hour black-board lecture. The numerous exercises must be considered part of the course itself; they are intended to stimulate active reading. |
2308.06318 | James Alvey | James Alvey, Uddipta Bhardwaj, Samaya Nissanke, Christoph Weniger | What to do when things get crowded? Scalable joint analysis of
overlapping gravitational wave signals | 6 pages. 3 figures. Codes: peregrine is publicly available at
https://github.com/PEREGRINE-GW/peregrine/tree/overlapping, swyft is
available at https://github.com/undark-lab/swyft | null | null | null | gr-qc astro-ph.CO astro-ph.HE astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | The gravitational wave sky is starting to become very crowded, with the
fourth science run (O4) at LIGO expected to detect $\mathcal{O}(100)$ compact
object coalescence signals. Data analysis issues start to arise as we look
further forwards, however. In particular, as the event rate increases in e.g.
next generation detectors, it will become increasingly likely that signals
arrive in the detector coincidentally, eventually becoming the dominant source
class. It is known that current analysis pipelines will struggle to deal with
this scenario, predominantly due to the scaling of traditional methods such as
Monte Carlo Markov Chains and nested sampling, where the time difference
between analysing a single signal and multiple can be as significant as days to
months. In this work, we argue that sequential simulation-based inference
methods can solve this problem by breaking the scaling behaviour. Specifically,
we apply an algorithm known as (truncated marginal) neural ratio estimation
(TMNRE), implemented in the code peregrine and based on swyft. To demonstrate
its applicability, we consider three case studies comprising two overlapping,
spinning, and precessing binary black hole systems with merger times separated
by 0.05 s, 0.2 s, and 0.5 s. We show for the first time that we can recover,
with full precision (as quantified by a comparison to the analysis of each
signal independently), the posterior distributions of all 30 model parameters
in a full joint analysis. Crucially, we achieve this with only $\sim 15\%$ of
the waveform evaluations that would be needed to analyse even a single signal
with traditional methods.
| [
{
"created": "Fri, 11 Aug 2023 18:00:01 GMT",
"version": "v1"
}
] | 2023-08-15 | [
[
"Alvey",
"James",
""
],
[
"Bhardwaj",
"Uddipta",
""
],
[
"Nissanke",
"Samaya",
""
],
[
"Weniger",
"Christoph",
""
]
] | The gravitational wave sky is starting to become very crowded, with the fourth science run (O4) at LIGO expected to detect $\mathcal{O}(100)$ compact object coalescence signals. Data analysis issues start to arise as we look further forwards, however. In particular, as the event rate increases in e.g. next generation detectors, it will become increasingly likely that signals arrive in the detector coincidentally, eventually becoming the dominant source class. It is known that current analysis pipelines will struggle to deal with this scenario, predominantly due to the scaling of traditional methods such as Monte Carlo Markov Chains and nested sampling, where the time difference between analysing a single signal and multiple can be as significant as days to months. In this work, we argue that sequential simulation-based inference methods can solve this problem by breaking the scaling behaviour. Specifically, we apply an algorithm known as (truncated marginal) neural ratio estimation (TMNRE), implemented in the code peregrine and based on swyft. To demonstrate its applicability, we consider three case studies comprising two overlapping, spinning, and precessing binary black hole systems with merger times separated by 0.05 s, 0.2 s, and 0.5 s. We show for the first time that we can recover, with full precision (as quantified by a comparison to the analysis of each signal independently), the posterior distributions of all 30 model parameters in a full joint analysis. Crucially, we achieve this with only $\sim 15\%$ of the waveform evaluations that would be needed to analyse even a single signal with traditional methods. |
1412.0605 | Letizia Sammut | The LIGO Scientific Collaboration, the Virgo Collaboration: J. Aasi,
B. P. Abbott, R. Abbott, T. Abbott, M. R. Abernathy, F. Acernese, K. Ackley,
C. Adams, T. Adams, T. Adams, P. Addesso, R. X. Adhikari, V. Adya, C.
Affeldt, M. Agathos, K. Agatsuma, N. Aggarwal, O. D. Aguiar, A. Ain, P.
Ajith, A. Alemic, B. Allen, A. Allocca, D. Amariutei, S. B. Anderson, W. G.
Anderson, K. Arai, M. C. Araya, C. Arceneaux, J. S. Areeda, G. Ashton, S.
Ast, S. M. Aston, P. Astone, P. Aufmuth, C. Aulbert, B. E. Aylott, S. Babak,
P. T. Baker, F. Baldaccini, G. Ballardin, S. W. Ballmer, J. C. Barayoga, M.
Barbet, S. Barclay, B. C. Barish, D. Barker, F. Barone, B. Barr, L. Barsotti,
M. Barsuglia, J. Bartlett, M. A. Barton, I. Bartos, R. Bassiri, A. Basti, J.
C. Batch, Th. S. Bauer, C. Baune, V. Bavigadda, B. Behnke, M. Bejger, C.
Belczynski, A. S. Bell, C. Bell, M. Benacquista, J. Bergman, G. Bergmann, C.
P. L. Berry, D. Bersanetti, A. Bertolini, J. Betzwieser, S. Bhagwat, R.
Bhandare, I. A. Bilenko, G. Billingsley, J. Birch, S. Biscans, M. Bitossi, C.
Biwer, M. A. Bizouard, J. K. Blackburn, L. Blackburn, C. D. Blair, D. Blair,
S. Bloemen, O. Bock, T. P. Bodiya, M. Boer, G. Bogaert, P. Bojtos, C. Bond,
F. Bondu, L. Bonelli, R. Bonnand, R. Bork, M. Born, V. Boschi, Sukanta Bose,
C. Bradaschia, P. R. Brady, V. B. Braginsky, M. Branchesi, J. E. Brau, T.
Briant, D. O. Bridges, A. Brillet, M. Brinkmann, V. Brisson, A. F. Brooks, D.
A. Brown, D. D. Brown, N. M. Brown, S. Buchman, A. Buikema, T. Bulik, H. J.
Bulten, A. Buonanno, D. Buskulic, C. Buy, L. Cadonati, G. Cagnoli, J.
Calder\'on Bustillo, E. Calloni, J. B. Camp, K. C. Cannon, J. Cao, C. D.
Capano, F. Carbognani, S. Caride, S. Caudill, M. Cavagli\`a, F. Cavalier, R.
Cavalieri, G. Cella, C. Cepeda, E. Cesarini, R. Chakraborty, T.
Chalermsongsak, S. J. Chamberlin, S. Chao, P. Charlton, E. Chassande-Mottin,
Y. Chen, A. Chincarini, A. Chiummo, H. S. Cho, M. Cho, J. H. Chow, N.
Christensen, Q. Chu, S. Chua, S. Chung, G. Ciani, F. Clara, J. A. Clark, F.
Cleva, E. Coccia, P.-F. Cohadon, A. Colla, C. Collette, M. Colombini, L.
Cominsky, M. Constancio, Jr., A. Conte, D. Cook, T. R. Corbitt, N. Cornish,
A. Corsi, C. A. Costa, M. W. Coughlin, J.-P. Coulon, S. Countryman, P.
Couvares, D. M. Coward, M. J. Cowart, D. C. Coyne, R. Coyne, K. Craig, J. D.
E. Creighton, T. D. Creighton, J. Cripe, S. G. Crowder, A. Cumming, L.
Cunningham, E. Cuoco, C. Cutler, K. Dahl, T. Dal Canton, M. Damjanic, S. L.
Danilishin, S. D'Antonio, K. Danzmann, L. Dartez, V. Dattilo, I. Dave, H.
Daveloza, M. Davier, G. S. Davies, E. J. Daw, R. Day, D. DeBra, G.
Debreczeni, J. Degallaix, M. De Laurentis, S. Del\'eglise, W. Del Pozzo, T.
Denker, T. Dent, H. Dereli, V. Dergachev, R. De Rosa, R. T. DeRosa, R.
DeSalvo, S. Dhurandhar, M. D\'iaz, L. Di Fiore, A. Di Lieto, I. Di Palma, A.
Di Virgilio, G. Dojcinoski, V. Dolique, E. Dominguez, F. Donovan, K. L.
Dooley, S. Doravari, R. Douglas, T. P. Downes, M. Drago, J. C. Driggers, Z.
Du, M. Ducrot, S. Dwyer, T. Eberle, T. Edo, M. Edwards, M. Edwards, A.
Effler, H.-B. Eggenstein, P. Ehrens, J. Eichholz, S. S. Eikenberry, R.
Essick, T. Etzel, M. Evans, T. Evans, M. Factourovich, V. Fafone, S.
Fairhurst, X. Fan, Q. Fang, S. Farinon, B. Farr, W. M. Farr, M. Favata, M.
Fays, H. Fehrmann, M. M. Fejer, D. Feldbaum, I. Ferrante, E. C. Ferreira, F.
Ferrini, F. Fidecaro, I. Fiori, R. P. Fisher, R. Flaminio, J.-D. Fournier, S.
Franco, S. Frasca, F. Frasconi, Z. Frei, A. Freise, R. Frey, T. T. Fricke, P.
Fritschel, V. V. Frolov, S. Fuentes-Tapia, P. Fulda, M. Fyffe, J. R. Gair, L.
Gammaitoni, S. Gaonkar, F. Garufi, A. Gatto, N. Gehrels, G. Gemme, B. Gendre,
E. Genin, A. Gennai, L. \'A. Gergely, S. Ghosh, J. A. Giaime, K. D. Giardina,
A. Giazotto, J. Gleason, E. Goetz, R. Goetz, L. Gondan, G. Gonz\'alez, N.
Gordon, M. L. Gorodetsky, S. Gossan, S. Go{\ss}ler, R. Gouaty, C. Gr\"af, P.
B. Graff, M. Granata, A. Grant, S. Gras, C. Gray, R. J. S. Greenhalgh, A. M.
Gretarsson, P. Groot, H. Grote, S. Grunewald, G. M. Guidi, C. J. Guido, X.
Guo, K. Gushwa, E. K. Gustafson, R. Gustafson, J. Hacker, E. D. Hall, G.
Hammond, M. Hanke, J. Hanks, C. Hanna, M. D. Hannam, J. Hanson, T. Hardwick,
J. Harms, G. M. Harry, I. W. Harry, M. Hart, M. T. Hartman, C.-J. Haster, K.
Haughian, S. Hee, A. Heidmann, M. Heintze, G. Heinzel, H. Heitmann, P. Hello,
G. Hemming, M. Hendry, I. S. Heng, A. W. Heptonstall, M. Heurs, M. Hewitson,
S. Hild, D. Hoak, K. A. Hodge, D. Hofman, S. E. Hollitt, K. Holt, P. Hopkins,
D. J. Hosken, J. Hough, E. Houston, E. J. Howell, Y. M. Hu, E. Huerta, B.
Hughey, S. Husa, S. H. Huttner, M. Huynh, T. Huynh-Dinh, A. Idrisy, N. Indik,
D. R. Ingram, R. Inta, G. Islas, J. C. Isler, T. Isogai, B. R. Iyer, K.
Izumi, M. Jacobson, H. Jang, P. Jaranowski, S. Jawahar, Y. Ji, F.
Jim\'enez-Forteza, W. W. Johnson, D. I. Jones, R. Jones, R.J.G. Jonker, L.
Ju, Haris K, V. Kalogera, S. Kandhasamy, G. Kang, J. B. Kanner, M. Kasprzack,
E. Katsavounidis, W. Katzman, H. Kaufer, S. Kaufer, T. Kaur, K. Kawabe, F.
Kawazoe, F. K\'ef\'elian, G. M. Keiser, D. Keitel, D. B. Kelley, W. Kells, D.
G. Keppel, J. S. Key, A. Khalaidovski, F. Y. Khalili, E. A. Khazanov, C. Kim,
K. Kim, N. G. Kim, N. Kim, Y.-M. Kim, E. J. King, P. J. King, D. L. Kinzel,
J. S. Kissel, S. Klimenko, J. Kline, S. Koehlenbeck, K. Kokeyama, V.
Kondrashov, M. Korobko, W. Z. Korth, I. Kowalska, D. B. Kozak, V. Kringel, B.
Krishnan, A. Kr\'olak, C. Krueger, G. Kuehn, A. Kumar, P. Kumar, L. Kuo, A.
Kutynia, M. Landry, B. Lantz, S. Larson, P. D. Lasky, A. Lazzarini, C.
Lazzaro, C. Lazzaro, J. Le, P. Leaci, S. Leavey, E. Lebigot, E. O. Lebigot,
C. H. Lee, H. K. Lee, H. M. Lee, M. Leonardi, J. R. Leong, N. Leroy, N.
Letendre, Y. Levin, B. Levine, J. Lewis, T. G. F. Li, K. Libbrecht, A.
Libson, A. C. Lin, T. B. Littenberg, N. A. Lockerbie, V. Lockett, J. Logue,
A. L. Lombardi, M. Lorenzini, V. Loriette, M. Lormand, G. Losurdo, J. Lough,
M. J. Lubinski, H. L\"uck, A. P. Lundgren, R. Lynch, Y. Ma, J. Macarthur, T.
MacDonald, B. Machenschalk, M. MacInnis, D. M. Macleod, F. Magana-Sandoval,
R. Magee, M. Mageswaran, C. Maglione, K. Mailand, E. Majorana, I. Maksimovic,
V. Malvezzi, N. Man, I. Mandel, V. Mandic, V. Mangano, V. Mangano, G. L.
Mansell, M. Mantovani, F. Marchesoni, F. Marion, S. M\'arka, Z. M\'arka, A.
Markosyan, E. Maros, F. Martelli, L. Martellini, I. W. Martin, R. M. Martin,
D. Martynov, J. N. Marx, K. Mason, A. Masserot, T. J. Massinger, F.
Matichard, L. Matone, N. Mavalvala, N. Mazumder, G. Mazzolo, R. McCarthy, D.
E. McClelland, S. McCormick, S. C. McGuire, G. McIntyre, J. McIver, K. McLin,
S. McWilliams, D. Meacher, G. D. Meadors, J. Meidam, M. Meinders, A. Melatos,
G. Mendell, R. A. Mercer, S. Meshkov, C. Messenger, P. M. Meyers, F. Mezzani,
H. Miao, C. Michel, H. Middleton, E. E. Mikhailov, L. Milano, A. Miller, J.
Miller, M. Millhouse, Y. Minenkov, J. Ming, S. Mirshekari, C. Mishra, S.
Mitra, V. P. Mitrofanov, G. Mitselmakher, R. Mittleman, B. Moe, A. Moggi, M.
Mohan, S. D. Mohanty, S. R. P. Mohapatra, B. Moore, D. Moraru, G. Moreno, S.
R. Morriss, K. Mossavi, B. Mours, C. M. Mow-Lowry, C. L. Mueller, G. Mueller,
S. Mukherjee, A. Mullavey, J. Munch, D. Murphy, P. G. Murray, A. Mytidis, M.
F. Nagy, I. Nardecchia, T. Nash, L. Naticchioni, R. K. Nayak, V. Necula, K.
Nedkova, G. Nelemans, I. Neri, M. Neri, G. Newton, T. Nguyen, A. B. Nielsen,
S. Nissanke, A. H. Nitz, F. Nocera, D. Nolting, M. E. N. Normandin, L. K.
Nuttall, E. Ochsner, J. O'Dell, E. Oelker, G. H. Ogin, J. J. Oh, S. H. Oh, F.
Ohme, P. Oppermann, R. Oram, B. O'Reilly, W. Ortega, R. O'Shaughnessy, C.
Osthelder, C. D. Ott, D. J. Ottaway, R. S. Ottens, H. Overmier, B. J. Owen,
C. Padilla, A. Pai, S. Pai, O. Palashov, C. Palomba, A. Pal-Singh, H. Pan, C.
Pankow, F. Pannarale, B. C. Pant, F. Paoletti, M. A. Papa, H. Paris, A.
Pasqualetti, R. Passaquieti, D. Passuello, Z. Patrick, M. Pedraza, L.
Pekowsky, A. Pele, S. Penn, A. Perreca, M. Phelps, M. Pichot, F.
Piergiovanni, V. Pierro, G. Pillant, L. Pinard, I. M. Pinto, M. Pitkin, J.
Poeld, R. Poggiani, A. Post, A. Poteomkin, J. Powell, J. Prasad, V. Predoi,
S. Premachandra, T. Prestegard, L. R. Price, M. Prijatelj, M. Principe, S.
Privitera, R. Prix, G. A. Prodi, L. Prokhorov, O. Puncken, M. Punturo, P.
Puppo, M. P\"urrer, J. Qin, V. Quetschke, E. Quintero, G. Quiroga, R.
Quitzow-James, F. J. Raab, D. S. Rabeling, I. R\'acz, H. Radkins, P. Raffai,
S. Raja, G. Rajalakshmi, M. Rakhmanov, K. Ramirez, P. Rapagnani, V. Raymond,
M. Razzano, V. Re, C. M. Reed, T. Regimbau, L. Rei, S. Reid, D. H. Reitze, O.
Reula, F. Ricci, K. Riles, N. A. Robertson, R. Robie, F. Robinet, A. Rocchi,
L. Rolland, J. G. Rollins, V. Roma, R. Romano, G. Romanov, J. H. Romie, D.
Rosi\'nska, S. Rowan, A. R\"udiger, P. Ruggi, K. Ryan, S. Sachdev, T.
Sadecki, L. Sadeghian, M. Saleem, F. Salemi, L. Sammut, V. Sandberg, J. R.
Sanders, V. Sannibale, I. Santiago-Prieto, B. Sassolas, B. S. Sathyaprakash,
P. R. Saulson, R. Savage, A. Sawadsky, J. Scheuer, R. Schilling, P. Schmidt,
R. Schnabel, R. M. S. Schofield, E. Schreiber, D. Schuette, B. F. Schutz, J.
Scott, S. M. Scott, D. Sellers, A. S. Sengupta, D. Sentenac, V. Sequino, R.
Serafinelli, A. Sergeev, G. Serna, A. Sevigny, D. A. Shaddock, S. Shah, M. S.
Shahriar, M. Shaltev, Z. Shao, B. Shapiro, P. Shawhan, D. H. Shoemaker, T. L.
Sidery, K. Siellez, X. Siemens, D. Sigg, A. D. Silva, D. Simakov, A. Singer,
L. Singer, R. Singh, A. M. Sintes, B. J. J. Slagmolen, J. R. Smith, M. R.
Smith, R. J. E. Smith, N. D. Smith-Lefebvre, E. J. Son, B. Sorazu, T.
Souradeep, A. Staley, J. Stebbins, M. Steinke, J. Steinlechner, S.
Steinlechner, D. Steinmeyer, B. C. Stephens, S. Steplewski, S. Stevenson, R.
Stone, K. A. Strain, N. Straniero, S. Strigin, R. Sturani, A. L. Stuver, T.
Z. Summerscales, P. J. Sutton, B. Swinkels, M. Szczepanczyk, G. Szeifert, M.
Tacca, D. Talukder, D. B. Tanner, M. T\'apai, S. P. Tarabrin, A. Taracchini,
R. Taylor, G. Tellez, T. Theeg, M. P. Thirugnanasambandam, M. Thomas, P.
Thomas, K. A. Thorne, K. S. Thorne, E. Thrane, V. Tiwari, C. Tomlinson, M.
Tonelli, C. V. Torres, C. I. Torrie, F. Travasso, G. Traylor, M. Tse, D.
Tshilumba, D. Ugolini, C. S. Unnikrishnan, A. L. Urban, S. A. Usman, H.
Vahlbruch, G. Vajente, G. Vajente, G. Valdes, M. Vallisneri, N. van Bakel, M.
van Beuzekom, J. F. J. van den Brand, C. van den Broeck, M. V. van der Sluys,
J. van Heijningen, A. A. van Veggel, S. Vass, M. Vas\'uth, R. Vaulin, A.
Vecchio, G. Vedovato, J. Veitch, J. Veitch, P. J. Veitch, K. Venkateswara, D.
Verkindt, F. Vetrano, A. Vicer\'e, R. Vincent-Finley, J.-Y. Vinet, S. Vitale,
T. Vo, H. Vocca, C. Vorvick, W. D. Vousden, S. P. Vyatchanin, A. R. Wade, L.
Wade, M. Wade, M. Walker, L. Wallace, S. Walsh, H. Wang, M. Wang, X. Wang, R.
L. Ward, J. Warner, M. Was, B. Weaver, L.-W. Wei, M. Weinert, A. J.
Weinstein, R. Weiss, T. Welborn, L. Wen, P. Wessels, T. Westphal, K. Wette,
J. T. Whelan, D. J. White, B. F. Whiting, C. Wilkinson, L. Williams, R.
Williams, A. R. Williamson, J. L. Willis, B. Willke, M. Wimmer, W. Winkler,
C. C. Wipf, H. Wittel, G. Woan, J. Worden, S. Xie, J. Yablon, I. Yakushin, W.
Yam, H. Yamamoto, C. C. Yancey, Q. Yang, M. Yvert, A. Zadro\.zny, M. Zanolin,
J.-P. Zendri, Fan Zhang, L. Zhang, M. Zhang, Y. Zhang, C. Zhao, M. Zhou, X.
J. Zhu, M. E. Zucker, S. Zuraw, J. Zweizig | A directed search for gravitational waves from Scorpius X-1 with initial
LIGO | 19 pages, 8 figures | Phys. Rev. D 91, 062008 (2015) | 10.1103/PhysRevD.91.062008 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present results of a search for continuously-emitted gravitational
radiation, directed at the brightest low-mass X-ray binary, Scorpius X-1. Our
semi-coherent analysis covers 10 days of LIGO S5 data ranging from 50-550 Hz,
and performs an incoherent sum of coherent $\mathcal{F}$-statistic power
distributed amongst frequency-modulated orbital sidebands. All candidates not
removed at the veto stage were found to be consistent with noise at a 1% false
alarm rate. We present Bayesian 95% confidence upper limits on
gravitational-wave strain amplitude using two different prior distributions: a
standard one, with no a priori assumptions about the orientation of Scorpius
X-1; and an angle-restricted one, using a prior derived from electromagnetic
observations. Median strain upper limits of 1.3e-24 and 8e-25 are reported at
150 Hz for the standard and angle-restricted searches respectively. This proof
of principle analysis was limited to a short observation time by unknown
effects of accretion on the intrinsic spin frequency of the neutron star, but
improves upon previous upper limits by factors of ~1.4 for the standard, and
2.3 for the angle-restricted search at the sensitive region of the detector.
| [
{
"created": "Mon, 1 Dec 2014 19:30:54 GMT",
"version": "v1"
}
] | 2015-04-01 | [
[
"The LIGO Scientific Collaboration",
"",
""
],
[
"the Virgo Collaboration",
"",
""
],
[
"Aasi",
"J.",
""
],
[
"Abbott",
"B. P.",
""
],
[
"Abbott",
"R.",
""
],
[
"Abbott",
"T.",
""
],
[
"Abernathy",
"M. R.",
... | We present results of a search for continuously-emitted gravitational radiation, directed at the brightest low-mass X-ray binary, Scorpius X-1. Our semi-coherent analysis covers 10 days of LIGO S5 data ranging from 50-550 Hz, and performs an incoherent sum of coherent $\mathcal{F}$-statistic power distributed amongst frequency-modulated orbital sidebands. All candidates not removed at the veto stage were found to be consistent with noise at a 1% false alarm rate. We present Bayesian 95% confidence upper limits on gravitational-wave strain amplitude using two different prior distributions: a standard one, with no a priori assumptions about the orientation of Scorpius X-1; and an angle-restricted one, using a prior derived from electromagnetic observations. Median strain upper limits of 1.3e-24 and 8e-25 are reported at 150 Hz for the standard and angle-restricted searches respectively. This proof of principle analysis was limited to a short observation time by unknown effects of accretion on the intrinsic spin frequency of the neutron star, but improves upon previous upper limits by factors of ~1.4 for the standard, and 2.3 for the angle-restricted search at the sensitive region of the detector. |
0707.2559 | Ernst Nils Dorband | Denis Pollney, Christian Reisswig, Luciano Rezzolla, Bela Szilagyi,
Marcus Ansorg, Barrett Deris, Peter Diener, Ernst Nils Dorband, Michael
Koppitz, Alessandro Nagar and Erik Schnetter | Recoil velocities from equal-mass binary black-hole mergers: a
systematic investigation of spin-orbit aligned configurations | 24 pages, 15 figures, 5 tables | Phys.Rev.D76:124002,2007 | 10.1103/PhysRevD.76.124002 | null | gr-qc astro-ph | null | Binary black-hole systems with spins aligned with the orbital angular
momentum are of special interest, as studies indicate that this configuration
is preferred in nature. If the spins of the two bodies differ, there can be a
prominent beaming of the gravitational radiation during the late plunge,
causing a recoil of the final merged black hole. We perform an accurate and
systematic study of recoil velocities from a sequence of equal-mass black holes
whose spins are aligned with the orbital angular momentum, and whose individual
spins range from a = +0.584 to -0.584. In this way we extend and refine the
results of a previous study and arrive at a consistent maximum recoil of 448 +-
5 km/s for anti-aligned models as well as to a phenomenological expression for
the recoil velocity as a function of spin ratio. This relation highlights a
nonlinear behavior, not predicted by the PN estimates, and can be readily
employed in astrophysical studies on the evolution of binary black holes in
massive galaxies. An essential result of our analysis is the identification of
different stages in the waveform, including a transient due to lack of an
initial linear momentum in the initial data. Furthermore we are able to
identify a pair of terms which are largely responsible for the kick, indicating
that an accurate computation can be obtained from modes up to l=3. Finally, we
provide accurate measures of the radiated energy and angular momentum, finding
these to increase linearly with the spin ratio, and derive simple expressions
for the final spin and the radiated angular momentum which can be easily
implemented in N-body simulations of compact stellar systems. Our code is
calibrated with strict convergence tests and we verify the correctness of our
measurements by using multiple independent methods whenever possible.
| [
{
"created": "Tue, 17 Jul 2007 16:16:30 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Pollney",
"Denis",
""
],
[
"Reisswig",
"Christian",
""
],
[
"Rezzolla",
"Luciano",
""
],
[
"Szilagyi",
"Bela",
""
],
[
"Ansorg",
"Marcus",
""
],
[
"Deris",
"Barrett",
""
],
[
"Diener",
"Peter",
""
],
[... | Binary black-hole systems with spins aligned with the orbital angular momentum are of special interest, as studies indicate that this configuration is preferred in nature. If the spins of the two bodies differ, there can be a prominent beaming of the gravitational radiation during the late plunge, causing a recoil of the final merged black hole. We perform an accurate and systematic study of recoil velocities from a sequence of equal-mass black holes whose spins are aligned with the orbital angular momentum, and whose individual spins range from a = +0.584 to -0.584. In this way we extend and refine the results of a previous study and arrive at a consistent maximum recoil of 448 +- 5 km/s for anti-aligned models as well as to a phenomenological expression for the recoil velocity as a function of spin ratio. This relation highlights a nonlinear behavior, not predicted by the PN estimates, and can be readily employed in astrophysical studies on the evolution of binary black holes in massive galaxies. An essential result of our analysis is the identification of different stages in the waveform, including a transient due to lack of an initial linear momentum in the initial data. Furthermore we are able to identify a pair of terms which are largely responsible for the kick, indicating that an accurate computation can be obtained from modes up to l=3. Finally, we provide accurate measures of the radiated energy and angular momentum, finding these to increase linearly with the spin ratio, and derive simple expressions for the final spin and the radiated angular momentum which can be easily implemented in N-body simulations of compact stellar systems. Our code is calibrated with strict convergence tests and we verify the correctness of our measurements by using multiple independent methods whenever possible. |
2109.04051 | Daiki Saito | Daiki Saito, Chul-Moon Yoo | False Vacuum Decay in Rotating BTZ Spacetimes | 23 pages, 15 figures, added the detailed information of the
reference, accepted version for publication | null | 10.1103/PhysRevD.104.124037 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse vacuum decay in rotating BTZ black hole spacetimes with the thin
wall approximation. Possible parameter regions for the vacuum decay are
clarified. We find that the nucleation rate is dominated by the bounce solution
with the static shell configuration. The nucleation rate of the static shell
decreases with the mass of the initial black hole. For a larger/smaller value
of the initial black hole, the nucleation rate can be smaller/larger than that
of the Coleman De Luccia vacuum decay in the pure AdS spacetime. Through the
vacuum decay, the black hole gains its mass and loses the horizon area. We also
find that the nucleation rate increases with increasing the angular momentum of
the spacetime.
| [
{
"created": "Thu, 9 Sep 2021 06:12:36 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Sep 2021 09:52:26 GMT",
"version": "v2"
},
{
"created": "Mon, 29 Nov 2021 01:15:41 GMT",
"version": "v3"
},
{
"created": "Tue, 30 Nov 2021 02:13:36 GMT",
"version": "v4"
}
] | 2021-12-22 | [
[
"Saito",
"Daiki",
""
],
[
"Yoo",
"Chul-Moon",
""
]
] | We analyse vacuum decay in rotating BTZ black hole spacetimes with the thin wall approximation. Possible parameter regions for the vacuum decay are clarified. We find that the nucleation rate is dominated by the bounce solution with the static shell configuration. The nucleation rate of the static shell decreases with the mass of the initial black hole. For a larger/smaller value of the initial black hole, the nucleation rate can be smaller/larger than that of the Coleman De Luccia vacuum decay in the pure AdS spacetime. Through the vacuum decay, the black hole gains its mass and loses the horizon area. We also find that the nucleation rate increases with increasing the angular momentum of the spacetime. |
gr-qc/0402021 | Babur Mirza Dr. | Babur M. Mirza | Travelling Magnetic Waves due to Plasma Surrounding a Slow Rotating
Compact Gravitational Source | null | null | null | null | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The magnetic field due to an axially symmetric, hot and highly conducting
plasma, taken as an ideal magnetohydrodynamic fluid, surrounding a slow
rotating compact gravitational object is studied within the context of
Einstein-Maxwell field equations. It is assumed that whereas the plasma is
effected by the background spacetime it does not effect the spacetime itself.
The Einstein-Maxwell equations are then solved for the magnetic field in a
comoving frame with the background spacetime described by the slow rotating
Kerr black hole spacetime. It is found that the solutions are magnetic waves
travelling along the azimuthal angle with velocity equal to the angular
velocity of a free falling intertial frame. These general solutions, when
applied to various particular cases of physical interest, show that for a fixed
value of the azimuthal angle the magnetic field is completely induced by the
dragging of the background spacetime.
| [
{
"created": "Wed, 4 Feb 2004 17:54:41 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Mar 2004 10:58:51 GMT",
"version": "v2"
},
{
"created": "Fri, 31 Mar 2017 13:49:56 GMT",
"version": "v3"
},
{
"created": "Fri, 29 Sep 2017 09:34:27 GMT",
"version": "v4"
}
] | 2017-10-02 | [
[
"Mirza",
"Babur M.",
""
]
] | The magnetic field due to an axially symmetric, hot and highly conducting plasma, taken as an ideal magnetohydrodynamic fluid, surrounding a slow rotating compact gravitational object is studied within the context of Einstein-Maxwell field equations. It is assumed that whereas the plasma is effected by the background spacetime it does not effect the spacetime itself. The Einstein-Maxwell equations are then solved for the magnetic field in a comoving frame with the background spacetime described by the slow rotating Kerr black hole spacetime. It is found that the solutions are magnetic waves travelling along the azimuthal angle with velocity equal to the angular velocity of a free falling intertial frame. These general solutions, when applied to various particular cases of physical interest, show that for a fixed value of the azimuthal angle the magnetic field is completely induced by the dragging of the background spacetime. |
gr-qc/0401012 | Sawa Manoff | Sawa Manoff | Doppler effect and Hubble effect in different models of space-time in
the case of auto-parallel motion of the observer | 12 pages, LaTex | null | null | null | gr-qc | null | Doppler effect and Hubble effect in different models of space-time in the
case of auto-parallel motion of the observer are considered. The Doppler effect
and shift frequency parameter are specialized for the case of auto-parallel
motion of the observer. The Hubble effect and shift frequency parameter are
considered for the same case. It is shown that by the use of the variation of
the shift frequency parameter during a time perod, considered locally in the
proper frame of reference of an observer, one can directly determine the
centrifugal (centripetal) relative velocity and acceleration as well as the
Coriolis relative velocity and acceleration of an astronomical object moving
relatively to the observer. All results are obtained on purely kinematic basis
without taking into account the dynamic reasons for the considered effect. PACS
numbers: 98.80.Jk; 98.62.Py; 04.90.+e; 04.80.Cc
| [
{
"created": "Sun, 4 Jan 2004 11:59:41 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Manoff",
"Sawa",
""
]
] | Doppler effect and Hubble effect in different models of space-time in the case of auto-parallel motion of the observer are considered. The Doppler effect and shift frequency parameter are specialized for the case of auto-parallel motion of the observer. The Hubble effect and shift frequency parameter are considered for the same case. It is shown that by the use of the variation of the shift frequency parameter during a time perod, considered locally in the proper frame of reference of an observer, one can directly determine the centrifugal (centripetal) relative velocity and acceleration as well as the Coriolis relative velocity and acceleration of an astronomical object moving relatively to the observer. All results are obtained on purely kinematic basis without taking into account the dynamic reasons for the considered effect. PACS numbers: 98.80.Jk; 98.62.Py; 04.90.+e; 04.80.Cc |
1705.05696 | Luca Giacomelli | Luca Giacomelli, Stefano Liberati | Rotating black hole solutions in relativistic analogue gravity | 15 pages, 4 figures | Phys. Rev. D 96, 064014 (2017) | 10.1103/PhysRevD.96.064014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Simulation and experimental realization of acoustic black holes in analogue
gravity systems have lead to a novel understanding of relevant phenomena such
as Hawking radiation or superradiance. We explore here the possibility to use
relativistic systems for simulating rotating black hole solutions and possibly
get an acoustic analogue of a Kerr black hole. In doing so we demonstrate a
precise relation between non-relativistic and relativistic solutions and
provide a new class of vortex solutions for relativistic systems. Such
solutions might be used in the future as a test bed in numerical simulations as
well as concrete experiments.
| [
{
"created": "Tue, 16 May 2017 13:13:19 GMT",
"version": "v1"
}
] | 2017-09-20 | [
[
"Giacomelli",
"Luca",
""
],
[
"Liberati",
"Stefano",
""
]
] | Simulation and experimental realization of acoustic black holes in analogue gravity systems have lead to a novel understanding of relevant phenomena such as Hawking radiation or superradiance. We explore here the possibility to use relativistic systems for simulating rotating black hole solutions and possibly get an acoustic analogue of a Kerr black hole. In doing so we demonstrate a precise relation between non-relativistic and relativistic solutions and provide a new class of vortex solutions for relativistic systems. Such solutions might be used in the future as a test bed in numerical simulations as well as concrete experiments. |
1809.04465 | Martin Bojowald | Jian-Pin Wu, Martin Bojowald, Yongge Ma | Anomaly freedom in perturbative models of Euclidean loop quantum gravity | 34 pages | Phys. Rev. D 98, 106009 (2018) | 10.1103/PhysRevD.98.106009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Euclidean gravity provides an interesting test system for an analysis of
cosmological perturbations in an effective Hamiltonian constraint with holonomy
modifications from loop quantum gravity. This paper presents a discussion of
scalar modes, with a specific form of the holonomy modification function
derived from a general expansion in a connection formulation. Compared with
some previous models, the constraint brackets are deformed in a different and
more restricted way. A general comparison of anomaly-free brackets in various
effective and operator versions shows overall consistency between different
approaches.
| [
{
"created": "Wed, 12 Sep 2018 14:01:37 GMT",
"version": "v1"
}
] | 2018-11-21 | [
[
"Wu",
"Jian-Pin",
""
],
[
"Bojowald",
"Martin",
""
],
[
"Ma",
"Yongge",
""
]
] | Euclidean gravity provides an interesting test system for an analysis of cosmological perturbations in an effective Hamiltonian constraint with holonomy modifications from loop quantum gravity. This paper presents a discussion of scalar modes, with a specific form of the holonomy modification function derived from a general expansion in a connection formulation. Compared with some previous models, the constraint brackets are deformed in a different and more restricted way. A general comparison of anomaly-free brackets in various effective and operator versions shows overall consistency between different approaches. |
2210.15634 | Virgo Publications | F. Acernese, M. Agathos, A. Ain, S. Albanesi, A. Allocca, A. Amato, T.
Andrade, N. Andres, M. Andr\'es-Carcasona, T. Andri\'c, S. Ansoldi, S.
Antier, T. Apostolatos, E. Z. Appavuravther, M. Ar\`ene, N. Arnaud, M.
Assiduo, S. Assis de Souza Melo, P. Astone, F. Aubin, S. Babak, F. Badaracco,
M. K. M. Bader, S. Bagnasco, J. Baird, T. Baka, G. Ballardin, G. Baltus, B.
Banerjee, C. Barbieri, P. Barneo, F. Barone, M. Barsuglia, D. Barta, A.
Basti, M. Bawaj, M. Bazzan, F. Beirnaert, M. Bejger, I. Belahcene, V.
Benedetto, M. Berbel, S. Bernuzzi, D. Bersanetti, A. Bertolini, U. Bhardwaj,
A. Bianchi, S. Bini, M. Bischi, M. Bitossi, M.-A. Bizouard, F. Bobba, M.
Bo\"er, G. Bogaert, M. Boldrini, L. D. Bonavena, F. Bondu, R. Bonnand, B. A.
Boom, V. Boschi, V. Boudart, Y. Bouffanais, A. Bozzi, C. Bradaschia, M.
Branchesi, M. Breschi, T. Briant, A. Brillet, J. Brooks, G. Bruno, F. Bucci,
T. Bulik, H. J. Bulten, D. Buskulic, C. Buy, G. S. Cabourn Davies, G. Cabras,
R. Cabrita, G. Cagnoli, E. Calloni, M. Canepa, S. Canevarolo, M.
Cannavacciuolo, E. Capocasa, G. Carapella, F. Carbognani, M. Carpinelli, G.
Carullo, J. Casanueva Diaz, C. Casentini, S. Caudill, F. Cavalier, R.
Cavalieri, G. Cella, P. Cerd\'a-Dur\'an, E. Cesarini, W. Chaibi, P. Chanial,
E. Chassande-Mottin, S. Chaty, F. Chiadini, G. Chiarini, R. Chierici, A.
Chincarini, M. L. Chiofalo, A. Chiummo, S. Choudhary, N. Christensen, G.
Ciani, P. Ciecielag, M. Cie\'slar, M. Cifaldi, R. Ciolfi, F. Cipriano, S.
Clesse, F. Cleva, E. Coccia, E. Codazzo, P.-F. Cohadon, D. E. Cohen, A.
Colombo, M. Colpi, L. Conti, I. Cordero-Carri\'on, S. Corezzi, D. Corre, S.
Cortese, J.-P. Coulon, M. Croquette, J. R. Cudell, E. Cuoco, M. Cury{\l}o, P.
Dabadie, T. Dal Canton, S. Dall'Osso, G. D\'alya, B. D'Angelo, S. Danilishin,
S. D'Antonio, V. Dattilo, M. Davier, D. Davis, J. Degallaix, M. De Laurentis,
S. Del\'eglise, F. De Lillo, D. Dell'Aquila, W. Del Pozzo, F. De Matteis, A.
Depasse, R. De Pietri, R. De Rosa, C. De Rossi, R. De Simone, L. Di Fiore, C.
Di Giorgio, F. Di Giovanni, M. Di Giovanni, T. Di Girolamo, A. Di Lieto, A.
Di Michele, S. Di Pace, I. Di Palma, F. Di Renzo, L. D'Onofrio, M. Drago,
J.-G. Ducoin, U. Dupletsa, O. Durante, D. D'Urso, P.-A. Duverne, M.
Eisenmann, L. Errico, D. Estevez, F. Fabrizi, F. Faedi, V. Fafone, S.
Farinon, G. Favaro, M. Fays, E. Fenyvesi, I. Ferrante, F. Fidecaro, P.
Figura, A. Fiori, I. Fiori, R. Fittipaldi, V. Fiumara, R. Flaminio, J. A.
Font, S. Frasca, F. Frasconi, A. Freise, O. Freitas, G. G. Fronz\'e, B. U.
Gadre, R. Gamba, B. Garaventa, F. Garufi, G. Gemme, A. Gennai, Archisman
Ghosh, B. Giacomazzo, L. Giacoppo, P. Giri, F. Gissi, S. Gkaitatzis, B.
Goncharov, M. Gosselin, R. Gouaty, A. Grado, M. Granata, V. Granata, G.
Greco, G. Grignani, A. Grimaldi, S. J. Grimm, P. Gruning, D. Guerra, G. M.
Guidi, G. Guix\'e, Y. Guo, P. Gupta, L. Haegel, O. Halim, O. Hannuksela, T.
Harder, K. Haris, J. Harms, B. Haskell, A. Heidmann, H. Heitmann, P. Hello,
G. Hemming, E. Hennes, S. Hild, D. Hofman, V. Hui, B. Idzkowski, A. Iess, P.
Iosif, T. Jacqmin, P.-E. Jacquet, S. P. Jadhav, J. Janquart, K. Janssens, P.
Jaranowski, V. Juste, C. Kalaghatgi, C. Karathanasis, S. Katsanevas, F.
K\'ef\'elian, N. Khetan, G. Koekoek, S. Koley, M. Kolstein, A. Kr\'olak, P.
Kuijer, P. Lagabbe, D. Laghi, M. Lalleman, A. Lamberts, I. La Rosa, A.
Lartaux-Vollard, C. Lazzaro, P. Leaci, A. Lema\^itre, M. Lenti, E. Leonova,
N. Leroy, N. Letendre, K. Leyde, F. Linde, L. London, A. Longo, M. Lopez
Portilla, M. Lorenzini, V. Loriette, G. Losurdo, D. Lumaca, A. Macquet, C.
Magazz\`u, M. Magnozzi, E. Majorana, I. Maksimovic, N. Man, V. Mangano, M.
Mantovani, M. Mapelli, F. Marchesoni, D. Mar\'in Pina, F. Marion, A.
Marquina, S. Marsat, F. Martelli, M. Martinez, V. Martinez, A. Masserot, S.
Mastrogiovanni, Q. Meijer, A. Menendez-Vazquez, L. Mereni, M. Merzougui, A.
Miani, C. Michel, L. Milano, A. Miller, B. Miller, E. Milotti, Y. Minenkov,
Ll. M. Mir, M. Miravet-Ten\'es, M. Montani, F. Morawski, B. Mours, C. M.
Mow-Lowry, S. Mozzon, F. Muciaccia, Suvodip Mukherjee, R. Musenich, A. Nagar,
V. Napolano, I. Nardecchia, H. Narola, L. Naticchioni, J. Neilson, C. Nguyen,
S. Nissanke, E. Nitoglia, F. Nocera, G. Oganesyan, C. Olivetto, G. Pagano, G.
Pagliaroli, C. Palomba, P. T. H. Pang, F. Pannarale, F. Paoletti, A. Paoli,
A. Paolone, G. Pappas, D. Pascucci, A. Pasqualetti, R. Passaquieti, D.
Passuello, B. Patricelli, R. Pedurand, M. Pegoraro, A. Perego, A. Pereira, C.
P\'erigois, A. Perreca, S. Perri\`es, D. Pesios, K. S. Phukon, O. J.
Piccinni, M. Pichot, M. Piendibene, F. Piergiovanni, L. Pierini, V. Pierro,
G. Pillant, M. Pillas, F. Pilo, L. Pinard, I. M. Pinto, M. Pinto, K.
Piotrzkowski, A. Placidi, E. Placidi, W. Plastino, R. Poggiani, E. Polini, E.
K. Porter, R. Poulton, M. Pracchia, T. Pradier, M. Principe, G. A. Prodi, P.
Prosposito, A. Puecher, M. Punturo, F. Puosi, P. Puppo, G. Raaijmakers, N.
Radulesco, P. Rapagnani, M. Razzano, T. Regimbau, L. Rei, P. Rettegno, B.
Revenu, A. Reza, F. Ricci, G. Riemenschneider, S. Rinaldi, F. Robinet, A.
Rocchi, L. Rolland, M. Romanelli, R. Romano, A. Romero, S. Ronchini, L. Rosa,
D. Rosi\'nska, S. Roy, D. Rozza, P. Ruggi, Jam. Sadiq, O. S. Salafia, L.
Salconi, F. Salemi, A. Samajdar, N. Sanchis-Gual, A. Sanuy, B. Sassolas, S.
Sayah, S. Schmidt, M. Seglar-Arroyo, D. Sentenac, V. Sequino, Y. Setyawati,
A. Sharma, N. S. Shcheblanov, M. Sieniawska, L. Silenzi, N. Singh, A. Singha,
V. Sipala, J. Soldateschi, K. Soni, V. Sordini, F. Sorrentino, N. Sorrentino,
R. Soulard, V. Spagnuolo, M. Spera, P. Spinicelli, C. Stachie, D. A. Steer,
J. Steinlechner, S. Steinlechner, N. Stergioulas, G. Stratta, M. Suchenek, A.
Sur, B. L. Swinkels, P. Szewczyk, M. Tacca, A. J. Tanasijczuk, E. N. Tapia
San Mart\'in, C. Taranto, A. E. Tolley, M. Tonelli, A. Torres-Forn\'e, I.
Tosta e Melo, A. Trapananti, F. Travasso, Max. Trevor, M. C. Tringali, L.
Troiano, A. Trovato, L. Trozzo, K. W. Tsang, K. Turbang, M. Turconi, A.
Utina, M. Valentini, N. van Bakel, M. van Beuzekom, M. van Dael, J. F. J. van
den Brand, C. Van Den Broeck, H. van Haevermaet, J. V. van Heijningen, N. van
Remortel, M. Vardaro, M. Vas\'uth, G. Vedovato, D. Verkindt, P. Verma, F.
Vetrano, A. Vicer\'e, V. Villa-Ortega, J.-Y. Vinet, A. Virtuoso, H. Vocca, R.
C. Walet, M. Was, A. R. Williamson, J. L. Willis, A. Zadro\.zny, T. Zelenova,
J.-P. Zendri | Virgo Detector Characterization and Data Quality: tools | 44 pages, 16 figures. New version, resubmitted to Class. and Quantum
Grav. This is the "Tools" part of preprint arXiv:2205.01555 [gr-qc] which has
been split into two companion articles: one about the tools and methods, the
other about the analyses of the O3 Virgo data | null | 10.1088/1361-6382/acdf36 | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | Detector characterization and data quality studies -- collectively referred
to as {\em DetChar} activities in this article -- are paramount to the
scientific exploitation of the joint dataset collected by the LIGO-Virgo-KAGRA
global network of ground-based gravitational-wave (GW) detectors. They take
place during each phase of the operation of the instruments (upgrade, tuning
and optimization, data taking), are required at all steps of the dataflow (from
data acquisition to the final list of GW events) and operate at various
latencies (from near real-time to vet the public alerts to offline analyses).
This work requires a wide set of tools which have been developed over the years
to fulfill the requirements of the various DetChar studies: data access and
bookkeeping; global monitoring of the instruments and of the different steps of
the data processing; studies of the global properties of the noise at the
detector outputs; identification and follow-up of noise peculiar features
(whether they be transient or continuously present in the data); quick
processing of the public alerts. The present article reviews all the tools used
by the Virgo DetChar group during the third LIGO-Virgo Observation Run (O3,
from April 2019 to March 2020), mainly to analyse the Virgo data acquired at
EGO. Concurrently, a companion article focuses on the results achieved by the
DetChar group during the O3 run using these tools.
| [
{
"created": "Fri, 14 Oct 2022 15:57:00 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Mar 2023 16:29:00 GMT",
"version": "v2"
}
] | 2023-08-16 | [
[
"Acernese",
"F.",
""
],
[
"Agathos",
"M.",
""
],
[
"Ain",
"A.",
""
],
[
"Albanesi",
"S.",
""
],
[
"Allocca",
"A.",
""
],
[
"Amato",
"A.",
""
],
[
"Andrade",
"T.",
""
],
[
"Andres",
"N.",
""
... | Detector characterization and data quality studies -- collectively referred to as {\em DetChar} activities in this article -- are paramount to the scientific exploitation of the joint dataset collected by the LIGO-Virgo-KAGRA global network of ground-based gravitational-wave (GW) detectors. They take place during each phase of the operation of the instruments (upgrade, tuning and optimization, data taking), are required at all steps of the dataflow (from data acquisition to the final list of GW events) and operate at various latencies (from near real-time to vet the public alerts to offline analyses). This work requires a wide set of tools which have been developed over the years to fulfill the requirements of the various DetChar studies: data access and bookkeeping; global monitoring of the instruments and of the different steps of the data processing; studies of the global properties of the noise at the detector outputs; identification and follow-up of noise peculiar features (whether they be transient or continuously present in the data); quick processing of the public alerts. The present article reviews all the tools used by the Virgo DetChar group during the third LIGO-Virgo Observation Run (O3, from April 2019 to March 2020), mainly to analyse the Virgo data acquired at EGO. Concurrently, a companion article focuses on the results achieved by the DetChar group during the O3 run using these tools. |
gr-qc/9604045 | Paulo Rodrigues Lima Vargas Moniz | P.V. Moniz | Quantization of a Friedmann-Robertson-Walker Model with Gauge Fields in
N=1 Supergravity | 19 pages, plain LaTeX file | null | null | DAMTP R95/36 | gr-qc | null | The purpose of this paper is to investigate a specific FRW model derived from
the theory of N=1 supergravity with gauged supermatter. The supermatter content
is restricted to a vector supermultiplet. This objective is particularly
worthwhile. In fact, it was pointed in ref. ({\em Class. Quantum Grav. {\bf 12}
{\rm (} {\rm 1995} {\rm )} {\rm 1343}}) that $\Psi = 0$ was the only allowed
quantum state for N=1 supergravity with {\em generic} gauged supermatter
subject to suitable FRW ans\"atze. The ans\"atze employed here for the physical
variables was presented in the above reference. The corresponding Lorentz and
supersymmetry quantum constraints are then derived. Non-trivial solutions are
subsquently found. A no-boundary solution is identified while another state may
be interpreted as a wormhole solution. In addition, the usefulness and
limitations of the ans\"atze are addressed. The implications of the ans\"atze
with respect to the allowed quantum states are also discussed.
| [
{
"created": "Wed, 24 Apr 1996 08:44:20 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Moniz",
"P. V.",
""
]
] | The purpose of this paper is to investigate a specific FRW model derived from the theory of N=1 supergravity with gauged supermatter. The supermatter content is restricted to a vector supermultiplet. This objective is particularly worthwhile. In fact, it was pointed in ref. ({\em Class. Quantum Grav. {\bf 12} {\rm (} {\rm 1995} {\rm )} {\rm 1343}}) that $\Psi = 0$ was the only allowed quantum state for N=1 supergravity with {\em generic} gauged supermatter subject to suitable FRW ans\"atze. The ans\"atze employed here for the physical variables was presented in the above reference. The corresponding Lorentz and supersymmetry quantum constraints are then derived. Non-trivial solutions are subsquently found. A no-boundary solution is identified while another state may be interpreted as a wormhole solution. In addition, the usefulness and limitations of the ans\"atze are addressed. The implications of the ans\"atze with respect to the allowed quantum states are also discussed. |
gr-qc/0005095 | Joseph Samuel | Joseph Samuel | Is Barbero's Hamiltonian formulation a Gauge Theory of Lorentzian
Gravity? | 12 pages, no figures, revised in the light of referee's comments,
accepted for publication in Classical and Quantum Gravity | Class.Quant.Grav.17:L141-L148,2000 | 10.1088/0264-9381/17/20/101 | null | gr-qc | null | This letter is a critique of Barbero's constrained Hamiltonian formulation of
General Relativity on which current work in Loop Quantum Gravity is based.
While we do not dispute the correctness of Barbero's formulation of general
relativity, we offer some criticisms of an aesthetic nature. We point out that
unlike Ashtekar's complex SU(2) connection, Barbero's real SO(3) connection
does not admit an interpretation as a space-time gauge field. We show that if
one tries to interpret Barbero's real SO(3) connection as a space-time gauge
field, the theory is not diffeomorphism invariant. We conclude that Barbero's
formulation is not a gauge theory of gravity in the sense that Ashtekar's
Hamiltonian formulation is. The advantages of Barbero's real connection
formulation have been bought at the price of giving up the description of
gravity as a gauge field.
| [
{
"created": "Mon, 22 May 2000 08:23:23 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Sep 2000 12:49:21 GMT",
"version": "v2"
},
{
"created": "Wed, 20 Sep 2000 10:18:02 GMT",
"version": "v3"
}
] | 2010-04-06 | [
[
"Samuel",
"Joseph",
""
]
] | This letter is a critique of Barbero's constrained Hamiltonian formulation of General Relativity on which current work in Loop Quantum Gravity is based. While we do not dispute the correctness of Barbero's formulation of general relativity, we offer some criticisms of an aesthetic nature. We point out that unlike Ashtekar's complex SU(2) connection, Barbero's real SO(3) connection does not admit an interpretation as a space-time gauge field. We show that if one tries to interpret Barbero's real SO(3) connection as a space-time gauge field, the theory is not diffeomorphism invariant. We conclude that Barbero's formulation is not a gauge theory of gravity in the sense that Ashtekar's Hamiltonian formulation is. The advantages of Barbero's real connection formulation have been bought at the price of giving up the description of gravity as a gauge field. |
0912.0107 | Janyce Franc | Janyce Franc, Nazario Morgado, Raffaele Flaminio, Ronny Nawrodt, Iain
Martin, Liam Cunningham, Alan Cumming, Sheila Rowan and James Hough | Mirror thermal noise in laser interferometer gravitational wave
detectors operating at room and cryogenic temperature | 28 pages, 6 figures, 4 tables | null | null | ET-02109 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Mirror thermal noise is and will remain one of the main limitations to the
sensitivity of gravitational wave detectors based on laser interferometers. We
report about projected mirror thermal noise due to losses in the mirror
coatings and substrates. The evaluation includes all kind of thermal noises
presently known. Several of the envisaged substrate and coating materials are
considered. The results for mirrors operated at room temperature and at
cryogenic temperature are reported.
| [
{
"created": "Tue, 1 Dec 2009 11:11:50 GMT",
"version": "v1"
}
] | 2009-12-02 | [
[
"Franc",
"Janyce",
""
],
[
"Morgado",
"Nazario",
""
],
[
"Flaminio",
"Raffaele",
""
],
[
"Nawrodt",
"Ronny",
""
],
[
"Martin",
"Iain",
""
],
[
"Cunningham",
"Liam",
""
],
[
"Cumming",
"Alan",
""
],
[
... | Mirror thermal noise is and will remain one of the main limitations to the sensitivity of gravitational wave detectors based on laser interferometers. We report about projected mirror thermal noise due to losses in the mirror coatings and substrates. The evaluation includes all kind of thermal noises presently known. Several of the envisaged substrate and coating materials are considered. The results for mirrors operated at room temperature and at cryogenic temperature are reported. |
gr-qc/9612056 | Luis Anchordoqui | Luis A. Anchordoqui | Wormholes in spacetime with torsion | 10 pages revtex | Mod.Phys.Lett. A13 (1998) 1095-1100 | 10.1142/S0217732398001169 | null | gr-qc | null | Analytical wormhole solutions in $U_4$ theory are presented. It is discussed
whether the extremely short range repulsive forces, related to the spin angular
momentum of matter, could be the ``carrier'' of the exoticity that threads the
wormhole throat.
| [
{
"created": "Thu, 19 Dec 1996 20:27:16 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Dec 1996 13:17:18 GMT",
"version": "v2"
},
{
"created": "Tue, 21 Oct 1997 15:07:13 GMT",
"version": "v3"
}
] | 2009-10-28 | [
[
"Anchordoqui",
"Luis A.",
""
]
] | Analytical wormhole solutions in $U_4$ theory are presented. It is discussed whether the extremely short range repulsive forces, related to the spin angular momentum of matter, could be the ``carrier'' of the exoticity that threads the wormhole throat. |
1506.08764 | Naresh Dadhich | Naresh Dadhich | A discerning gravitational property for gravitational equation in higher
dimensions | null | Euro. Phys. J. C 76, 104 (2016) | 10.1140/epjc/s10052-016-3933-z | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well-known that Einstein gravity is kinematic (no non-trivial vacuum
solution;i.e. Riemann vanishes whenever Ricci does so) in $3$ dimension because
Riemann is entirely given in terms of Ricci. Could this property be
universalized for all odd dimensions in a generalized theory? The answer is
yes, and this property uniquely singles out pure Lovelock (it has only one
$N$th order term in action) gravity for which $N$th order Lovelock Riemann
tensor is indeed given in terms of corresponding Ricci for all odd $d=2N+1$
dimensions. This feature of gravity is realized only in higher dimensions and
it uniquely picks out pure Lovelock gravity from all other generalizations of
Einstein gravity. It serves as a good discerning and guiding criterion for
gravitational equation in higher dimensions.
| [
{
"created": "Tue, 16 Jun 2015 12:58:23 GMT",
"version": "v1"
}
] | 2017-10-19 | [
[
"Dadhich",
"Naresh",
""
]
] | It is well-known that Einstein gravity is kinematic (no non-trivial vacuum solution;i.e. Riemann vanishes whenever Ricci does so) in $3$ dimension because Riemann is entirely given in terms of Ricci. Could this property be universalized for all odd dimensions in a generalized theory? The answer is yes, and this property uniquely singles out pure Lovelock (it has only one $N$th order term in action) gravity for which $N$th order Lovelock Riemann tensor is indeed given in terms of corresponding Ricci for all odd $d=2N+1$ dimensions. This feature of gravity is realized only in higher dimensions and it uniquely picks out pure Lovelock gravity from all other generalizations of Einstein gravity. It serves as a good discerning and guiding criterion for gravitational equation in higher dimensions. |
1301.0895 | Li-Ming Cao | Li-Ming Cao, Jianfei Xu and Zhe Zeng | Maximum Entropy Principle for Self-gravitating Perfect Fluid in Lovelock
Gravity | v1,revtex4, 9 pages, no figure; v2, two references added, typos
corrected | Phys. Rev. D. 87. 064005 (2013) | 10.1103/PhysRevD.87.064005 | USTC-ICTS-13-01 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a static self-gravitating system consisting of perfect fluid with
isometries of an $(n-2)$-dimensional maximally symmetric space in Lovelock
gravity theory. A straightforward analysis of the time-time component of the
equations of motion suggests a generalized mass function.
Tolman-Oppenheimer-Volkoff like equation is obtained by using this mass
function and gravitational equations. We investigate the maximum entropy
principle in Lovelock gravity, and find that this Tolman-Oppenheimer-Volkoff
equation can also be deduced from the so called "maximum entropy principle"
which is originally customized for Einstein gravity theory. This investigation
manifests a deep connection between gravity and thermodynamics in this
generalized gravity theory.
| [
{
"created": "Sat, 5 Jan 2013 11:35:59 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Jan 2013 08:53:16 GMT",
"version": "v2"
}
] | 2013-03-19 | [
[
"Cao",
"Li-Ming",
""
],
[
"Xu",
"Jianfei",
""
],
[
"Zeng",
"Zhe",
""
]
] | We consider a static self-gravitating system consisting of perfect fluid with isometries of an $(n-2)$-dimensional maximally symmetric space in Lovelock gravity theory. A straightforward analysis of the time-time component of the equations of motion suggests a generalized mass function. Tolman-Oppenheimer-Volkoff like equation is obtained by using this mass function and gravitational equations. We investigate the maximum entropy principle in Lovelock gravity, and find that this Tolman-Oppenheimer-Volkoff equation can also be deduced from the so called "maximum entropy principle" which is originally customized for Einstein gravity theory. This investigation manifests a deep connection between gravity and thermodynamics in this generalized gravity theory. |
2310.14241 | Ronni Amorim G. G. | Ronni Amorim and Vinicius Rispoli and S\'ergio Ulhoa and Kayo Ara\'ujo | Nonrelativistic Spinless Particle in Vicinity of Schwarzschild-like
Black Hole | 10 pages, no figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this article we analyze the behavior of a non-relativistic spinless
particle near the event horizon of a Schwarzschild-like black hole. In this
way, the Schr\"odinger covariant equation that describes the particle is
obtained from the Galilean covariance technique. The Schr\"odinger equation in
a Schwarzschild-like spacetime is solved analytically and its solutions are
given in terms of the confluent Heun function. As a relevant result, we
discovered that the energy levels of the particles are quantized and that the
particle does not escape to infinity. We obtain the existing transmission and
reflection coefficients for a particle and anti-particle pair at the event
horizon. We thus verify that there is no non-relativistic equivalent of Hawking
radiation.
| [
{
"created": "Sun, 22 Oct 2023 09:35:20 GMT",
"version": "v1"
},
{
"created": "Sun, 10 Dec 2023 21:17:24 GMT",
"version": "v2"
}
] | 2023-12-12 | [
[
"Amorim",
"Ronni",
""
],
[
"Rispoli",
"Vinicius",
""
],
[
"Ulhoa",
"Sérgio",
""
],
[
"Araújo",
"Kayo",
""
]
] | In this article we analyze the behavior of a non-relativistic spinless particle near the event horizon of a Schwarzschild-like black hole. In this way, the Schr\"odinger covariant equation that describes the particle is obtained from the Galilean covariance technique. The Schr\"odinger equation in a Schwarzschild-like spacetime is solved analytically and its solutions are given in terms of the confluent Heun function. As a relevant result, we discovered that the energy levels of the particles are quantized and that the particle does not escape to infinity. We obtain the existing transmission and reflection coefficients for a particle and anti-particle pair at the event horizon. We thus verify that there is no non-relativistic equivalent of Hawking radiation. |
gr-qc/9904049 | Yosef Verbin | M. Christensen, A.L. Larsen and Y. Verbin | Complete Classification of the String-like Solutions of the Gravitating
Abelian Higgs Model | 12 pages, 4 figures | Phys. Rev. D 60, 125012 (1999) | 10.1103/PhysRevD.60.125012 | null | gr-qc hep-th | null | The static cylindrically symmetric solutions of the gravitating Abelian Higgs
model form a two parameter family. In this paper we give a complete
classification of the string-like solutions of this system. We show that the
parameter plane is composed of two different regions with the following
characteristics: One region contains the standard asymptotically conic cosmic
string solutions together with a second kind of solutions with Melvin-like
asymptotic behavior. The other region contains two types of solutions with
bounded radial extension. The border between the two regions is the curve of
maximal angular deficit of $2\pi$.
| [
{
"created": "Tue, 20 Apr 1999 12:29:07 GMT",
"version": "v1"
}
] | 2016-08-25 | [
[
"Christensen",
"M.",
""
],
[
"Larsen",
"A. L.",
""
],
[
"Verbin",
"Y.",
""
]
] | The static cylindrically symmetric solutions of the gravitating Abelian Higgs model form a two parameter family. In this paper we give a complete classification of the string-like solutions of this system. We show that the parameter plane is composed of two different regions with the following characteristics: One region contains the standard asymptotically conic cosmic string solutions together with a second kind of solutions with Melvin-like asymptotic behavior. The other region contains two types of solutions with bounded radial extension. The border between the two regions is the curve of maximal angular deficit of $2\pi$. |
1603.09450 | Wen Zhao | Xing Zhang, Wen Zhao, He Huang, Yifu Cai | Post-Newtonian parameters and cosmological constant of screened modified
gravity | 15 pages, 1 figure, Phys. Rev. D accepted | Phys. Rev. D 93, 124003 (2016) | 10.1103/PhysRevD.93.124003 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Screened modified gravity (SMG) is a kind of scalar-tensor theories with
screening mechanisms, which can generate screening effect to suppress the fifth
force in high density environments and pass the solar system tests. Meanwhile,
the potential of scalar field in the theories can drive the acceleration of the
late universe. In this paper, we calculate the parameterized post-Newtonian
(PPN) parameters $\gamma$ and $\beta$, the effective gravitational constant
$G_{\rm eff}$ and the effective cosmological constant $\Lambda$ for SMG with a
general potential $V$ and coupling function $A$. The dependence of these
parameters on the model parameters of SMG and/or the physical properties of the
source object are clearly presented. As an application of these results, we
focus on three specific theories of SMG (chameleon, symmetron and dilaton
models). Using the formulae to calculate their PPN parameters and cosmological
constant, we derive the constraints on the model parameters by combining the
observations on solar system and cosmological scales.
| [
{
"created": "Thu, 31 Mar 2016 04:32:41 GMT",
"version": "v1"
},
{
"created": "Tue, 17 May 2016 01:12:19 GMT",
"version": "v2"
},
{
"created": "Wed, 18 May 2016 01:29:26 GMT",
"version": "v3"
}
] | 2016-06-14 | [
[
"Zhang",
"Xing",
""
],
[
"Zhao",
"Wen",
""
],
[
"Huang",
"He",
""
],
[
"Cai",
"Yifu",
""
]
] | Screened modified gravity (SMG) is a kind of scalar-tensor theories with screening mechanisms, which can generate screening effect to suppress the fifth force in high density environments and pass the solar system tests. Meanwhile, the potential of scalar field in the theories can drive the acceleration of the late universe. In this paper, we calculate the parameterized post-Newtonian (PPN) parameters $\gamma$ and $\beta$, the effective gravitational constant $G_{\rm eff}$ and the effective cosmological constant $\Lambda$ for SMG with a general potential $V$ and coupling function $A$. The dependence of these parameters on the model parameters of SMG and/or the physical properties of the source object are clearly presented. As an application of these results, we focus on three specific theories of SMG (chameleon, symmetron and dilaton models). Using the formulae to calculate their PPN parameters and cosmological constant, we derive the constraints on the model parameters by combining the observations on solar system and cosmological scales. |
2304.14129 | Shaun Fell | Shaun David Brocus Fell, Lavinia Heisenberg, Do\u{g}a Veske | Detecting Fundamental Vector Fields with LISA | 21 Pages, 8 Figures | null | 10.1103/PhysRevD.108.083010 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | The advent of gravitational wave astronomy has seen a huge influx of new
predictions for potential discoveries of beyond the Standard Model fields. The
coupling of all fundamental fields to gravity, together with its dominance on
large scales, makes gravitational physics a rich laboratory to study
fundamental physics. This holds especially true for the search for the elusive
dark photon, a promising dark matter candidate. The dark photon is predicted to
generate instabilities in a rotating black hole spacetime, birthing a
macroscopic Bose-Einstein condensate. These condensates can especially form
around super massive black holes, modifying the dynamical inspiralling process.
This then opens another window to leverage future space-borne gravitational
wave antennas to join the hunt for the elusive dark matter particle. This study
builds a preliminary model for the gravitational waveform emitted by such a
dressed extreme mass-ratio inspiral. Comparing these waveforms to the vacuum
scenario allows projections to the potential constrainability on the dark
photon mass by space-borne gravitational wave antennas. The superradiant
instability of a massive vector field on a Kerr background is calculated and,
under reasonable approximations, the backreaction on the orbit of an
inspiralling solar mass-scale compact object due to the secular evolution of
the resulting boson cloud is determined. The end result is the projection that
the LISA mission should be able to constrain the dark photon mass using extreme
mass ratio inspirals in the range $[1.8 \times 10^{-17}, 4.47 \times 10^{-16}]$
eV.
| [
{
"created": "Thu, 27 Apr 2023 12:24:19 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Sep 2023 13:56:56 GMT",
"version": "v2"
}
] | 2023-10-13 | [
[
"Fell",
"Shaun David Brocus",
""
],
[
"Heisenberg",
"Lavinia",
""
],
[
"Veske",
"Doğa",
""
]
] | The advent of gravitational wave astronomy has seen a huge influx of new predictions for potential discoveries of beyond the Standard Model fields. The coupling of all fundamental fields to gravity, together with its dominance on large scales, makes gravitational physics a rich laboratory to study fundamental physics. This holds especially true for the search for the elusive dark photon, a promising dark matter candidate. The dark photon is predicted to generate instabilities in a rotating black hole spacetime, birthing a macroscopic Bose-Einstein condensate. These condensates can especially form around super massive black holes, modifying the dynamical inspiralling process. This then opens another window to leverage future space-borne gravitational wave antennas to join the hunt for the elusive dark matter particle. This study builds a preliminary model for the gravitational waveform emitted by such a dressed extreme mass-ratio inspiral. Comparing these waveforms to the vacuum scenario allows projections to the potential constrainability on the dark photon mass by space-borne gravitational wave antennas. The superradiant instability of a massive vector field on a Kerr background is calculated and, under reasonable approximations, the backreaction on the orbit of an inspiralling solar mass-scale compact object due to the secular evolution of the resulting boson cloud is determined. The end result is the projection that the LISA mission should be able to constrain the dark photon mass using extreme mass ratio inspirals in the range $[1.8 \times 10^{-17}, 4.47 \times 10^{-16}]$ eV. |
2011.06154 | Jun-Qi Guo | Jun-Qi Guo, Pankaj S. Joshi, Ramesh Narayan, Lin Zhang | Accretion disks around naked singularities | 23 pages, 9 figures, 2 tables | Class. Quantum Grav. 38, 035012 (2021) | 10.1088/1361-6382/abce44 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate here the thermal properties of accretion disks in a spacetime
for some galactic density profiles in spherical symmetry. The matter
distributions have a finite outer radius with a naked central singularity. The
luminosities of the accretion disks for some density profile models are found
to be higher than those for a Schwarzschild black hole of the same mass. The
slopes for the luminosity distributions with respect to frequencies are
significantly different, especially at higher frequencies, from that in the
Schwarzschild black hole case. Such features may be used to distinguish black
holes from naked singularities. The efficiencies for the conversion of the mass
energy of the accreting gas into radiation and the strength of naked
singularities are analyzed. The novel feature that we find is, the strength of
the singularity is different depending on the profiles considered, and the
stronger the singularity is, the higher is the efficiency for the accretion
disk.
| [
{
"created": "Thu, 12 Nov 2020 01:40:38 GMT",
"version": "v1"
}
] | 2021-01-01 | [
[
"Guo",
"Jun-Qi",
""
],
[
"Joshi",
"Pankaj S.",
""
],
[
"Narayan",
"Ramesh",
""
],
[
"Zhang",
"Lin",
""
]
] | We investigate here the thermal properties of accretion disks in a spacetime for some galactic density profiles in spherical symmetry. The matter distributions have a finite outer radius with a naked central singularity. The luminosities of the accretion disks for some density profile models are found to be higher than those for a Schwarzschild black hole of the same mass. The slopes for the luminosity distributions with respect to frequencies are significantly different, especially at higher frequencies, from that in the Schwarzschild black hole case. Such features may be used to distinguish black holes from naked singularities. The efficiencies for the conversion of the mass energy of the accreting gas into radiation and the strength of naked singularities are analyzed. The novel feature that we find is, the strength of the singularity is different depending on the profiles considered, and the stronger the singularity is, the higher is the efficiency for the accretion disk. |
2310.03660 | Maria J. Rodriguez | Malcolm Perry and Maria J. Rodriguez | Dynamical Love Numbers for Kerr Black Holes | 35 pages, 1 figure | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | While static Love number vanish identically for Kerr black holes, we show
that the corresponding dynamical tidal coefficients are generically non-zero
and exhibit logarithmic behavior. The computational method employs a related
but simpler scheme consistent with CFT descriptions, low-frequency regimes and
post-Newtonian results. These coefficients are illustrated with a numerical
examples.
| [
{
"created": "Thu, 5 Oct 2023 16:38:03 GMT",
"version": "v1"
}
] | 2023-10-06 | [
[
"Perry",
"Malcolm",
""
],
[
"Rodriguez",
"Maria J.",
""
]
] | While static Love number vanish identically for Kerr black holes, we show that the corresponding dynamical tidal coefficients are generically non-zero and exhibit logarithmic behavior. The computational method employs a related but simpler scheme consistent with CFT descriptions, low-frequency regimes and post-Newtonian results. These coefficients are illustrated with a numerical examples. |
gr-qc/9406041 | null | Lajos Di\'osi | Comments on "Objectification of classical properties induced by quantum
vacuum fluctuations" | 4 pages Latex, 21-June-1994 | Phys.Lett.197A:183-184,1995 | 10.1016/0375-9601(94)00846-H | null | gr-qc | null | We argue that in standard quantum electrodynamics radiative corrections do
not lead to decoherence of unexcited atomic systems. The proposal of Santos
relies upon deliberate switching on and off the vacuum interactions.
| [
{
"created": "Thu, 23 Jun 1994 14:51:00 GMT",
"version": "v1"
}
] | 2011-08-04 | [
[
"Diósi",
"Lajos",
""
]
] | We argue that in standard quantum electrodynamics radiative corrections do not lead to decoherence of unexcited atomic systems. The proposal of Santos relies upon deliberate switching on and off the vacuum interactions. |
1402.3179 | Fernando Oscar Minotti | F. O. Minotti | Longitudinal forces in pinched electric currents | 3 pages, no figures | null | null | null | gr-qc physics.plasm-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the theory of Mbelek and Lachi\`eze-Rey predicts
longitudinal forces of gravitational origin in pinched current distributions,
with magnitudes large enough to have noticeable effects.
| [
{
"created": "Thu, 13 Feb 2014 15:36:11 GMT",
"version": "v1"
}
] | 2014-02-14 | [
[
"Minotti",
"F. O.",
""
]
] | It is shown that the theory of Mbelek and Lachi\`eze-Rey predicts longitudinal forces of gravitational origin in pinched current distributions, with magnitudes large enough to have noticeable effects. |
gr-qc/9802001 | Enrico Onofri | J. Maharana (CERN and Istitute of Physics, Bhubaneswar, India), E.
Onofri (INFN and Dipartimento di Fisica, Universita` di Parma, Italy) G.
Veneziano (CERN) | A numerical simulation of pre-big bang cosmology | 19 pages, revtex, matlab code available at
http://www.fis.unipr.it/~onofri | JHEP 9804:004,1998 | 10.1088/1126-6708/1998/04/004 | CERN-TH/98-24, UPRF-98-1 | gr-qc hep-th | null | We analyse numerically the onset of pre-big bang inflation in an
inhomogeneous, spherically symmetric Universe. Adding a small dilatonic
perturbation to a trivial (Milne) background, we find that suitable regions of
space undergo dilaton-driven inflation and quickly become spatially flat
($\Omega \to 1$). Numerical calculations are pushed close enough to the big
bang singularity to allow cross checks against previously proposed analytic
asymptotic solutions.
| [
{
"created": "Sat, 31 Jan 1998 10:42:15 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Feb 1998 17:43:12 GMT",
"version": "v2"
}
] | 2010-02-03 | [
[
"Maharana",
"J.",
"",
"CERN and Istitute of Physics, Bhubaneswar, India"
],
[
"Onofri",
"E.",
"",
"INFN and Dipartimento di Fisica, Universita` di Parma, Italy"
],
[
"Veneziano",
"G.",
"",
"CERN"
]
] | We analyse numerically the onset of pre-big bang inflation in an inhomogeneous, spherically symmetric Universe. Adding a small dilatonic perturbation to a trivial (Milne) background, we find that suitable regions of space undergo dilaton-driven inflation and quickly become spatially flat ($\Omega \to 1$). Numerical calculations are pushed close enough to the big bang singularity to allow cross checks against previously proposed analytic asymptotic solutions. |
2203.16449 | Medine Ildes | Medine Ildes and Metin Arik | Analytic Solutions of Scalar Field Cosmology, Mathematical Structures
for Early Inflation and Late Time Accelerated Expansion | 41 pages, 3 figures | null | 10.1140/epjc/s10052-023-11273-9 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study the most general cosmological model with real scalar field which is
minimally coupled to gravity. Our calculations are based on
Friedmann-Lemaitre-Robertson-Walker (FLRW) background metric. Field equations
consist of three differential equations. We switch independent variable from
time to scale factor by change of variable $\dot{a}/a=H(a)$. Thus a new set of
differential equations are analytically solvable with known methods. We
formulate Hubble function, the scalar field, potential and energy density when
one of them is given in the most general form. $a(t)$ can be explicitly found
as long as methods of integration techniques are available. We investigate the
dynamics of the universe at early times as well as at late times in light of
these formulas. We find mathematical machinery which turns on and turns off
early accelerated expansion. On the other hand late time accelerated expansion
is explained by cosmic domain walls. We have compared our results with recent
observations of type Ia supernovae by considering the Hubble tension and
absolute magnitude tension. Eighty-nine percent of present universe may consist
of domain walls while rest is matter.
| [
{
"created": "Wed, 30 Mar 2022 16:53:32 GMT",
"version": "v1"
}
] | 2023-03-22 | [
[
"Ildes",
"Medine",
""
],
[
"Arik",
"Metin",
""
]
] | We study the most general cosmological model with real scalar field which is minimally coupled to gravity. Our calculations are based on Friedmann-Lemaitre-Robertson-Walker (FLRW) background metric. Field equations consist of three differential equations. We switch independent variable from time to scale factor by change of variable $\dot{a}/a=H(a)$. Thus a new set of differential equations are analytically solvable with known methods. We formulate Hubble function, the scalar field, potential and energy density when one of them is given in the most general form. $a(t)$ can be explicitly found as long as methods of integration techniques are available. We investigate the dynamics of the universe at early times as well as at late times in light of these formulas. We find mathematical machinery which turns on and turns off early accelerated expansion. On the other hand late time accelerated expansion is explained by cosmic domain walls. We have compared our results with recent observations of type Ia supernovae by considering the Hubble tension and absolute magnitude tension. Eighty-nine percent of present universe may consist of domain walls while rest is matter. |
1309.5008 | David Hilditch | David Hilditch, Thomas W. Baumgarte, Andreas Weyhausen, Tim Dietrich,
Bernd Bruegmann, Pedro J. Montero and Ewald Mueller | Collapse of Nonlinear Gravitational Waves in Moving-Puncture Coordinates | null | Phys. Rev. D 88, 103009 (2013) | 10.1103/PhysRevD.88.103009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study numerical evolutions of nonlinear gravitational waves in
moving-puncture coordinates. We adopt two different types of initial data --
Brill and Teukolsky waves -- and evolve them with two independent codes
producing consistent results. We find that Brill data fail to produce long-term
evolutions for common choices of coordinates and parameters, unless the initial
amplitude is small, while Teukolsky wave initial data lead to stable
evolutions, at least for amplitudes sufficiently far from criticality. The
critical amplitude separates initial data whose evolutions leave behind flat
space from those that lead to a black hole. For the latter we follow the
interaction of the wave, the formation of a horizon, and the settling down into
a time-independent trumpet geometry. We explore the differences between Brill
and Teukolsky data and show that for less common choices of the parameters --
in particular negative amplitudes -- Brill data can be evolved with
moving-puncture coordinates, and behave similarly to Teukolsky waves.
| [
{
"created": "Thu, 19 Sep 2013 14:57:42 GMT",
"version": "v1"
}
] | 2013-11-27 | [
[
"Hilditch",
"David",
""
],
[
"Baumgarte",
"Thomas W.",
""
],
[
"Weyhausen",
"Andreas",
""
],
[
"Dietrich",
"Tim",
""
],
[
"Bruegmann",
"Bernd",
""
],
[
"Montero",
"Pedro J.",
""
],
[
"Mueller",
"Ewald",
""
... | We study numerical evolutions of nonlinear gravitational waves in moving-puncture coordinates. We adopt two different types of initial data -- Brill and Teukolsky waves -- and evolve them with two independent codes producing consistent results. We find that Brill data fail to produce long-term evolutions for common choices of coordinates and parameters, unless the initial amplitude is small, while Teukolsky wave initial data lead to stable evolutions, at least for amplitudes sufficiently far from criticality. The critical amplitude separates initial data whose evolutions leave behind flat space from those that lead to a black hole. For the latter we follow the interaction of the wave, the formation of a horizon, and the settling down into a time-independent trumpet geometry. We explore the differences between Brill and Teukolsky data and show that for less common choices of the parameters -- in particular negative amplitudes -- Brill data can be evolved with moving-puncture coordinates, and behave similarly to Teukolsky waves. |
0706.1534 | Simone Speziale | Simone Speziale | Coupling gauge theory to spinfoam 3d quantum gravity | 18 pages | Class.Quant.Grav.24:5139-5160,2007 | 10.1088/0264-9381/24/20/014 | pi-qg-46 | gr-qc hep-th | null | We construct a spinfoam model for Yang-Mills theory coupled to quantum
gravity in three dimensional riemannian spacetime. We define the partition
function of the coupled system as a power series in g_0^2 G that can be
evaluated order by order using grasping rules and the recoupling theory. With
respect to previous attempts in the literature, this model assigns the
dynamical variables of gravity and Yang-Mills theory to the same simplices of
the spinfoam, and it thus provides transition amplitudes for the spin network
states of the canonical theory. For SU(2) Yang-Mills theory we show explicitly
that the partition function has a semiclassical limit given by the Regge
discretization of the classical Yang-Mills action.
| [
{
"created": "Mon, 11 Jun 2007 19:51:04 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Oct 2007 19:17:13 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Speziale",
"Simone",
""
]
] | We construct a spinfoam model for Yang-Mills theory coupled to quantum gravity in three dimensional riemannian spacetime. We define the partition function of the coupled system as a power series in g_0^2 G that can be evaluated order by order using grasping rules and the recoupling theory. With respect to previous attempts in the literature, this model assigns the dynamical variables of gravity and Yang-Mills theory to the same simplices of the spinfoam, and it thus provides transition amplitudes for the spin network states of the canonical theory. For SU(2) Yang-Mills theory we show explicitly that the partition function has a semiclassical limit given by the Regge discretization of the classical Yang-Mills action. |
2007.04531 | Lijing Shao | Lijing Shao, Norbert Wex, Shuang-Yong Zhou | New Graviton Mass Bound from Binary Pulsars | 14 pages, 10 figures; accepted by PRD | Physical Review D 102 (2020) 024069 | 10.1103/PhysRevD.102.024069 | USTC-ICTS/PCFT-20-15 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Einstein's general relativity, gravity is mediated by a massless metric
field. The extension of general relativity to consistently include a mass for
the graviton has profound implications for gravitation and cosmology. Salient
features of various massive gravity theories can be captured by Galileon
models, the simplest of which is the cubic Galileon. The presence of the
Galileon field leads to additional gravitational radiation in binary pulsars
where the Vainshtein mechanism is less suppressed than its fifth-force
counterpart, which deserves a detailed confrontation with observations. We
prudently choose fourteen well-timed binary pulsars, and from their intrinsic
orbital decay rates we put a new bound on the graviton mass, $m_g \lesssim 2
\times 10^{-28}\,{\rm eV}/c^2$ at the 95% confidence level, assuming a flat
prior on $\ln m_g$. It is equivalent to a bound on the graviton Compton
wavelength $\lambda_g \gtrsim 7 \times 10^{21}\,{\rm m}$. Furthermore, we
extensively simulate times of arrival for pulsars in orbit around stellar-mass
black holes and the supermassive black hole at the Galactic center, and
investigate their prospects in probing the cubic Galileon theory in the near
future.
| [
{
"created": "Thu, 9 Jul 2020 03:17:29 GMT",
"version": "v1"
}
] | 2020-07-24 | [
[
"Shao",
"Lijing",
""
],
[
"Wex",
"Norbert",
""
],
[
"Zhou",
"Shuang-Yong",
""
]
] | In Einstein's general relativity, gravity is mediated by a massless metric field. The extension of general relativity to consistently include a mass for the graviton has profound implications for gravitation and cosmology. Salient features of various massive gravity theories can be captured by Galileon models, the simplest of which is the cubic Galileon. The presence of the Galileon field leads to additional gravitational radiation in binary pulsars where the Vainshtein mechanism is less suppressed than its fifth-force counterpart, which deserves a detailed confrontation with observations. We prudently choose fourteen well-timed binary pulsars, and from their intrinsic orbital decay rates we put a new bound on the graviton mass, $m_g \lesssim 2 \times 10^{-28}\,{\rm eV}/c^2$ at the 95% confidence level, assuming a flat prior on $\ln m_g$. It is equivalent to a bound on the graviton Compton wavelength $\lambda_g \gtrsim 7 \times 10^{21}\,{\rm m}$. Furthermore, we extensively simulate times of arrival for pulsars in orbit around stellar-mass black holes and the supermassive black hole at the Galactic center, and investigate their prospects in probing the cubic Galileon theory in the near future. |
gr-qc/9512025 | null | F.I. Cooperstock, V. Faraoni and G.P. Perry (University of Victoria) | Probing the gravitational geon | Replaced with revised version (substantial changes and additions,
conclusions unchanged), 36 pages, LaTex, 3 figures available from the authors | Int.J.Mod.Phys.D5:375-406,1996 | 10.1142/S0218271896000242 | null | gr-qc | null | The Brill-Hartle gravitational geon construct as a spherical shell of small
amplitude, high frequency gravitational waves is reviewed and critically
analyzed. The Regge-Wheeler formalism is used to represent gravitational wave
perturbations of the spherical background as a superposition of tensor
spherical harmonics and an attempt is made to build a non-singular solution to
meet the requirements of a gravitational geon. High-frequency waves are seen to
be a necessary condition for the geon and the field equations are decomposed
accordingly. It is shown that this leads to the impossibility of forming a
spherical gravitational geon. The attempted constructs of gravitational and
electromagnetic geons are contrasted. The spherical shell in the proposed
Brill-Hartle geon does not meet the regularity conditions required for a
non-singular source and hence cannot be regarded as an adequate geon construct.
Since it is the high frequency attribute which is the essential cause of the
geon non-viability, it is argued that a geon with less symmetry is an unlikely
prospect. The broader implications of the result are discussed with particular
reference to the problem of gravitational energy.
| [
{
"created": "Tue, 12 Dec 1995 00:32:14 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Oct 1996 22:09:12 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Cooperstock",
"F. I.",
"",
"University of Victoria"
],
[
"Faraoni",
"V.",
"",
"University of Victoria"
],
[
"Perry",
"G. P.",
"",
"University of Victoria"
]
] | The Brill-Hartle gravitational geon construct as a spherical shell of small amplitude, high frequency gravitational waves is reviewed and critically analyzed. The Regge-Wheeler formalism is used to represent gravitational wave perturbations of the spherical background as a superposition of tensor spherical harmonics and an attempt is made to build a non-singular solution to meet the requirements of a gravitational geon. High-frequency waves are seen to be a necessary condition for the geon and the field equations are decomposed accordingly. It is shown that this leads to the impossibility of forming a spherical gravitational geon. The attempted constructs of gravitational and electromagnetic geons are contrasted. The spherical shell in the proposed Brill-Hartle geon does not meet the regularity conditions required for a non-singular source and hence cannot be regarded as an adequate geon construct. Since it is the high frequency attribute which is the essential cause of the geon non-viability, it is argued that a geon with less symmetry is an unlikely prospect. The broader implications of the result are discussed with particular reference to the problem of gravitational energy. |
2301.04529 | Zhen Pan | Zhen Pan, Huan Yang | Improving the detection sensitivity to primordial stochastic
gravitational waves with reduced astrophysical foregrounds | 12 pages, 4 figs | Physical Review D 107 (12), 123036, 2023 | 10.1103/PhysRevD.107.123036 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | One of the primary targets of third-generation (3G) ground-based
gravitational wave (GW) detectors is detecting the stochastic GW background
(SGWB) from early universe processes. The astrophysical foreground from compact
binary mergers will be a major contamination to the background, which must be
reduced to high precision to enable the detection of primordial background. In
this work, we revisit the limit of foreground reduction computed in previous
studies, point out potential problems in previous foreground cleaning methods
and propose a novel cleaning method subtracting the approximate signal strain
and removing the average residual power. With this method, the binary black
hole foreground is reduced with fractional residual energy density below
$10^{-4}$ for frequency $f\in (10, 10^2)$ Hz, below $10^{-3}$ for frequency
$f\in (10^2, 10^3)$ Hz and below the detector sensitivity limit for all
relevant frequencies in our simulations. Similar precision is achieved to clean
the foreground from binary neutron stars (BNSs) that are above the detection
threshold, so that the residual foreground is dominated by sub-threshold BNSs,
which will be the next critical problem to solve for detecting the primordial
SGWB in the 3G era.
| [
{
"created": "Wed, 11 Jan 2023 15:47:05 GMT",
"version": "v1"
},
{
"created": "Tue, 2 May 2023 18:20:15 GMT",
"version": "v2"
},
{
"created": "Sat, 1 Jul 2023 03:14:41 GMT",
"version": "v3"
},
{
"created": "Tue, 11 Jul 2023 13:31:01 GMT",
"version": "v4"
}
] | 2023-07-12 | [
[
"Pan",
"Zhen",
""
],
[
"Yang",
"Huan",
""
]
] | One of the primary targets of third-generation (3G) ground-based gravitational wave (GW) detectors is detecting the stochastic GW background (SGWB) from early universe processes. The astrophysical foreground from compact binary mergers will be a major contamination to the background, which must be reduced to high precision to enable the detection of primordial background. In this work, we revisit the limit of foreground reduction computed in previous studies, point out potential problems in previous foreground cleaning methods and propose a novel cleaning method subtracting the approximate signal strain and removing the average residual power. With this method, the binary black hole foreground is reduced with fractional residual energy density below $10^{-4}$ for frequency $f\in (10, 10^2)$ Hz, below $10^{-3}$ for frequency $f\in (10^2, 10^3)$ Hz and below the detector sensitivity limit for all relevant frequencies in our simulations. Similar precision is achieved to clean the foreground from binary neutron stars (BNSs) that are above the detection threshold, so that the residual foreground is dominated by sub-threshold BNSs, which will be the next critical problem to solve for detecting the primordial SGWB in the 3G era. |
2008.12244 | Naoki Tsukamoto | Naoki Tsukamoto | Deflection angle of a light ray reflected by a general marginally
unstable photon sphere in a strong deflection limit | 10 pages, 5 figures, minor correction, title changed, accepted for
publication in Physical Review D | Phys. Rev. D 102, 104029 (2020) | 10.1103/PhysRevD.102.104029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the deflection angle in a strong deflection limit for a
marginally unstable photon sphere in a general asymptotically flat, static and
spherically symmetric spacetime under some assumptions to calculate
observables. The deflection angle of a light ray reflected by the marginally
unstable photon sphere diverges nonlogarithmically while the one reflected by a
photon sphere diverges logarithmically. We apply our formula to a
Reissner-Nordstrom spacetime and Hayward spacetime.
| [
{
"created": "Thu, 27 Aug 2020 16:39:21 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Oct 2020 14:41:09 GMT",
"version": "v2"
}
] | 2020-11-12 | [
[
"Tsukamoto",
"Naoki",
""
]
] | We investigate the deflection angle in a strong deflection limit for a marginally unstable photon sphere in a general asymptotically flat, static and spherically symmetric spacetime under some assumptions to calculate observables. The deflection angle of a light ray reflected by the marginally unstable photon sphere diverges nonlogarithmically while the one reflected by a photon sphere diverges logarithmically. We apply our formula to a Reissner-Nordstrom spacetime and Hayward spacetime. |
1006.3778 | Artur Alho | Artur Alho, Filipe C. Mena, Juan A. Valiente Kroon | The Einstein-Friedrich-nonlinear scalar field system and the stability
of scalar field Cosmologies | Version 4: Matches final published version | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A frame representation is used to derive a first order quasi-linear symmetric
hyperbolic system for a scalar field minimally coupled to gravity. This
procedure is inspired by similar evolution equations introduced by Friedrich to
study the Einstein-Euler system. The resulting evolution system is used to show
that small nonlinear perturbations of expanding
Friedman-Lema\^itre-Robertson-Walker backgrounds, with scalar field potentials
satisfying certain future asymptotic conditions, decay exponentially to zero,
in synchronous time.
| [
{
"created": "Fri, 18 Jun 2010 19:09:46 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Apr 2011 16:41:26 GMT",
"version": "v2"
},
{
"created": "Thu, 6 Aug 2015 12:28:20 GMT",
"version": "v3"
},
{
"created": "Sat, 14 Oct 2017 22:25:39 GMT",
"version": "v4"
}
] | 2017-10-17 | [
[
"Alho",
"Artur",
""
],
[
"Mena",
"Filipe C.",
""
],
[
"Kroon",
"Juan A. Valiente",
""
]
] | A frame representation is used to derive a first order quasi-linear symmetric hyperbolic system for a scalar field minimally coupled to gravity. This procedure is inspired by similar evolution equations introduced by Friedrich to study the Einstein-Euler system. The resulting evolution system is used to show that small nonlinear perturbations of expanding Friedman-Lema\^itre-Robertson-Walker backgrounds, with scalar field potentials satisfying certain future asymptotic conditions, decay exponentially to zero, in synchronous time. |
gr-qc/9306002 | Luis J. Garay | Luis J. Garay | Hilbert space of wormholes | 23 pages, 2 figures available upon request, REVTEX | Phys.Rev.D48:1710-1721,1993 | 10.1103/PhysRevD.48.1710 | null | gr-qc | null | Wormhole boundary conditions for the Wheeler--DeWitt equation can be derived
from the path integral formulation. It is proposed that the wormhole wave
function must be square integrable in the maximal analytic extension of
minisuperspace. Quantum wormholes can be invested with a Hilbert space
structure, the inner product being naturally induced by the minisuperspace
metric, in which the Wheeler--DeWitt operator is essentially self--adjoint.
This provides us with a kind of probabilistic interpretation. In particular,
giant wormholes will give extremely small contributions to any wormhole state.
We also study the whole spectrum of the Wheeler--DeWitt operator and its role
in the calculation of Green's functions and effective low energy interactions.
| [
{
"created": "Tue, 1 Jun 1993 14:43:00 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Garay",
"Luis J.",
""
]
] | Wormhole boundary conditions for the Wheeler--DeWitt equation can be derived from the path integral formulation. It is proposed that the wormhole wave function must be square integrable in the maximal analytic extension of minisuperspace. Quantum wormholes can be invested with a Hilbert space structure, the inner product being naturally induced by the minisuperspace metric, in which the Wheeler--DeWitt operator is essentially self--adjoint. This provides us with a kind of probabilistic interpretation. In particular, giant wormholes will give extremely small contributions to any wormhole state. We also study the whole spectrum of the Wheeler--DeWitt operator and its role in the calculation of Green's functions and effective low energy interactions. |
2101.06760 | Richard Woodard | S. Katuwal (Florida), S. P. Miao (NCKU) and R. P. Woodard (Florida) | Inflaton Effective Potential from Photons for General $\epsilon$ | 42 pages, 15 figures, uses LaTeX2e. Version 2 slightly revised for
publication, now 44 pages | Phys. Rev. D 103, 105007 (2021) | 10.1103/PhysRevD.103.105007 | UFIFT-QG-20-06 | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We accurately approximate the contribution that photons make to the effective
potential of a charged inflaton for inflationary geometries with an arbitrary
first slow roll parameter $\epsilon$. We find a small, nonlocal contribution
and a numerically larger, local part. The local part involves first and second
derivatives of $\epsilon$, coming exclusively from the constrained part of the
electromagnetic field which carries the long range interaction. This causes the
effective potential induced by electromagnetism to respond more strongly to
geometrical evolution than for either scalars, which have no derivatives, or
spin one half particles, which have only one derivative. For $\epsilon = 0$ our
final result agrees with that of Allen on de Sitter background, while the flat
space limit agrees with the classic result of Coleman and Weinberg.
| [
{
"created": "Sun, 17 Jan 2021 19:40:06 GMT",
"version": "v1"
},
{
"created": "Mon, 31 May 2021 05:53:50 GMT",
"version": "v2"
}
] | 2021-06-01 | [
[
"Katuwal",
"S.",
"",
"Florida"
],
[
"Miao",
"S. P.",
"",
"NCKU"
],
[
"Woodard",
"R. P.",
"",
"Florida"
]
] | We accurately approximate the contribution that photons make to the effective potential of a charged inflaton for inflationary geometries with an arbitrary first slow roll parameter $\epsilon$. We find a small, nonlocal contribution and a numerically larger, local part. The local part involves first and second derivatives of $\epsilon$, coming exclusively from the constrained part of the electromagnetic field which carries the long range interaction. This causes the effective potential induced by electromagnetism to respond more strongly to geometrical evolution than for either scalars, which have no derivatives, or spin one half particles, which have only one derivative. For $\epsilon = 0$ our final result agrees with that of Allen on de Sitter background, while the flat space limit agrees with the classic result of Coleman and Weinberg. |
1710.00938 | Steven Carlip | J. Abajian, S. Carlip | Dimensional reduction in manifold-like causal sets | 8 pages, 7 figures | Phys. Rev. D 97, 066007 (2018) | 10.1103/PhysRevD.97.066007 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the behavior of small subsets of causal sets that approximate
Minkowski space in three, four, and five dimensions, and show that their
effective dimension decreases smoothly at small distances. The details of the
short distance behavior depend on a choice of dimensional estimator, but for a
reasonable version of the Myrheim-Meyer dimension, the minimum dimension is $d
\approx 2$, reproducing results that have been seen in other approaches to
quantum gravity.
| [
{
"created": "Mon, 2 Oct 2017 23:21:17 GMT",
"version": "v1"
}
] | 2018-03-14 | [
[
"Abajian",
"J.",
""
],
[
"Carlip",
"S.",
""
]
] | We investigate the behavior of small subsets of causal sets that approximate Minkowski space in three, four, and five dimensions, and show that their effective dimension decreases smoothly at small distances. The details of the short distance behavior depend on a choice of dimensional estimator, but for a reasonable version of the Myrheim-Meyer dimension, the minimum dimension is $d \approx 2$, reproducing results that have been seen in other approaches to quantum gravity. |
1511.07501 | Oleg Zaslavskii | O. B. Zaslavskii | Is the super-Penrose process possible near black holes? | 16 pages. Presentation improved. To appear in PRD | Phys. Rev. D 93, 024056 (2016) | 10.1103/PhysRevD.93.024056 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider collisions of particles near generic axially symmetric extremal
black holes. We examine possibility of indefinitely large extraction of energy
(the so-called super-Penrose process) in the limit when the point of collision
approaches the horizon. Three potential options are considered (fractional
powers of the lapse function in the relations between the energies and the
angular momenta of particles in the point of collision), collision between
outgoing particles and ingoing ones, collision in the ergoregion far from the
horizon). It turns out in all three cases that states suitable for the
super-Penrose process cannot be obtained from the previous collision of
particles with finite masses and angular momenta.
| [
{
"created": "Mon, 23 Nov 2015 22:50:10 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Jan 2016 12:10:05 GMT",
"version": "v2"
}
] | 2016-02-03 | [
[
"Zaslavskii",
"O. B.",
""
]
] | We consider collisions of particles near generic axially symmetric extremal black holes. We examine possibility of indefinitely large extraction of energy (the so-called super-Penrose process) in the limit when the point of collision approaches the horizon. Three potential options are considered (fractional powers of the lapse function in the relations between the energies and the angular momenta of particles in the point of collision), collision between outgoing particles and ingoing ones, collision in the ergoregion far from the horizon). It turns out in all three cases that states suitable for the super-Penrose process cannot be obtained from the previous collision of particles with finite masses and angular momenta. |
2106.05034 | Alexander Zhidenko | R. A. Konoplya, A. Zhidenko | Traversable Wormholes in General Relativity | (title changed) | Phys. Rev. Lett. 128, 091104 (2022) | 10.1103/PhysRevLett.128.091104 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In [J. Blazquez-Salcedo, C. Knoll, E. Radu, Phys. Rev. Lett. 126 (2021)
no.10, 101102] asymptotically flat traversable wormhole solutions were obtained
in the Einstein-Dirac-Maxwell theory without using phantom matter. The
normalizable numerical solutions found therein require a peculiar behavior at
the throat: the mirror symmetry relatively the throat leads to the
nonsmoothness of gravitational and matter fields. In particular, one must
postulate changing of the sign of the fermionic charge density at the throat,
requiring coexistence of particle and antiparticles without annihilation and
posing a membrane of matter at the throat with specific properties. Apparently
this kind of configuration could not exist in nature. We show that there are
wormhole solutions, which are asymmetric relative the throat and endowed by
smooth gravitational and matter fields, thereby being free from all the above
problems. This indicates that such wormhole configurations could also be
supported in a realistic scenario.
| [
{
"created": "Wed, 9 Jun 2021 12:47:20 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Jun 2021 10:05:20 GMT",
"version": "v2"
},
{
"created": "Mon, 13 Sep 2021 22:04:21 GMT",
"version": "v3"
},
{
"created": "Fri, 4 Mar 2022 18:06:08 GMT",
"version": "v4"
}
] | 2022-03-07 | [
[
"Konoplya",
"R. A.",
""
],
[
"Zhidenko",
"A.",
""
]
] | In [J. Blazquez-Salcedo, C. Knoll, E. Radu, Phys. Rev. Lett. 126 (2021) no.10, 101102] asymptotically flat traversable wormhole solutions were obtained in the Einstein-Dirac-Maxwell theory without using phantom matter. The normalizable numerical solutions found therein require a peculiar behavior at the throat: the mirror symmetry relatively the throat leads to the nonsmoothness of gravitational and matter fields. In particular, one must postulate changing of the sign of the fermionic charge density at the throat, requiring coexistence of particle and antiparticles without annihilation and posing a membrane of matter at the throat with specific properties. Apparently this kind of configuration could not exist in nature. We show that there are wormhole solutions, which are asymmetric relative the throat and endowed by smooth gravitational and matter fields, thereby being free from all the above problems. This indicates that such wormhole configurations could also be supported in a realistic scenario. |
2104.12806 | Viktor T. Toth | J. W. Moffat and V. T. Toth | Scalar-Tensor-Vector modified gravity in light of the Planck 2018 data | 5 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent data release by the Planck satellite collaboration presents a
renewed challenge for modified theories of gravitation. Such theories must be
capable of reproducing the observed angular power spectrum of the cosmic
microwave background radiation. For modified theories of gravity, an added
challenge lies with the fact that standard computational tools do not readily
accommodate the features of a theory with a variable gravitational coupling
coefficient. An alternative is to use less accurate but more easily modifiable
semianalytical approximations to reproduce at least the qualitative features of
the angular power spectrum. We extend a calculation that was used previously to
demonstrate compatibility between the Scalar-Tensor-Vector-Gravity (STVG)
theory, also known by the acronym MOG, and data from the Wilkinson Microwave
Anisotropy Probe (WMAP) to show consistency between the theory and the newly
released Planck 2018 data. We find that within the limits of this
approximation, the theory accurately reproduces the features of the angular
power spectrum.
| [
{
"created": "Mon, 26 Apr 2021 18:06:39 GMT",
"version": "v1"
}
] | 2021-04-28 | [
[
"Moffat",
"J. W.",
""
],
[
"Toth",
"V. T.",
""
]
] | The recent data release by the Planck satellite collaboration presents a renewed challenge for modified theories of gravitation. Such theories must be capable of reproducing the observed angular power spectrum of the cosmic microwave background radiation. For modified theories of gravity, an added challenge lies with the fact that standard computational tools do not readily accommodate the features of a theory with a variable gravitational coupling coefficient. An alternative is to use less accurate but more easily modifiable semianalytical approximations to reproduce at least the qualitative features of the angular power spectrum. We extend a calculation that was used previously to demonstrate compatibility between the Scalar-Tensor-Vector-Gravity (STVG) theory, also known by the acronym MOG, and data from the Wilkinson Microwave Anisotropy Probe (WMAP) to show consistency between the theory and the newly released Planck 2018 data. We find that within the limits of this approximation, the theory accurately reproduces the features of the angular power spectrum. |
2105.15130 | Pramit Rej | Pramit Rej, Piyali Bhar, and Megan Govender | Charged compact star in $f(R,T)$ gravity in Tolman-Kuchowicz spacetime | 15 Pages | The European Physical Journal C, 81, 316 (2021) | 10.1140/epjc/s10052-021-09127-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this current study, our main focus is to model a specific charged compact
star SAX J 1808.4-3658 (M = 0.88 $M_{\odot}$,\, R = 8.9 km) within the realm of
$f(R,\,T)$ modified gravity theory using the metric potentials proposed by
Tolman-Kuchowicz (Tolman, Phys Rev 55:364, 1939; Kuchowicz Acta Phys Pol
33:541, 1968) and the interior spacetime is matched to the exterior
Reissner-Nordstr\"{o}m line element at the surface of the star.
Tolman-Kuchowicz metric potentials provide a singularity-free solution which
satisfies the stability criteria. Here we have used the simplified
phenomenological MIT bag model equation of state (EoS) to solve
Einstein-Maxwell field equations where the density profile ($\rho$) is related
to the radial pressure ($p_r$) as $p_r(r) = (\rho - 4B_g)/3$. Further, to
derive the values of unknown constants $a,\, b,\, B,\, C$ and the bag constant
$B_g$, we match our interior space-time to the exterior Reissner-Nordstr\"{o}m
line element at the surface of stellar system. In addition to this, to check
the physical validity and stability of our suggested model, we evaluate some
important properties such as effective energy density, effective pressures,
radial and transverse sound velocities, relativistic adiabatic index, all
energy conditions, compactness factor and surface redshift. It is depicted from
our current study that all our derived results lie within the physically
accepted regime which provides the viability of our present model in the
context of $f(R,\,T)$ modified gravity.
| [
{
"created": "Thu, 27 May 2021 04:45:13 GMT",
"version": "v1"
}
] | 2021-06-01 | [
[
"Rej",
"Pramit",
""
],
[
"Bhar",
"Piyali",
""
],
[
"Govender",
"Megan",
""
]
] | In this current study, our main focus is to model a specific charged compact star SAX J 1808.4-3658 (M = 0.88 $M_{\odot}$,\, R = 8.9 km) within the realm of $f(R,\,T)$ modified gravity theory using the metric potentials proposed by Tolman-Kuchowicz (Tolman, Phys Rev 55:364, 1939; Kuchowicz Acta Phys Pol 33:541, 1968) and the interior spacetime is matched to the exterior Reissner-Nordstr\"{o}m line element at the surface of the star. Tolman-Kuchowicz metric potentials provide a singularity-free solution which satisfies the stability criteria. Here we have used the simplified phenomenological MIT bag model equation of state (EoS) to solve Einstein-Maxwell field equations where the density profile ($\rho$) is related to the radial pressure ($p_r$) as $p_r(r) = (\rho - 4B_g)/3$. Further, to derive the values of unknown constants $a,\, b,\, B,\, C$ and the bag constant $B_g$, we match our interior space-time to the exterior Reissner-Nordstr\"{o}m line element at the surface of stellar system. In addition to this, to check the physical validity and stability of our suggested model, we evaluate some important properties such as effective energy density, effective pressures, radial and transverse sound velocities, relativistic adiabatic index, all energy conditions, compactness factor and surface redshift. It is depicted from our current study that all our derived results lie within the physically accepted regime which provides the viability of our present model in the context of $f(R,\,T)$ modified gravity. |
gr-qc/9403062 | Nail R. Khusnutdinov | N R Khusnutdinov | Self - Interaction Force for the Particle in the Cone Space - Time | 9, CQG-94-0324 | Class.Quant.Grav.11:1807-1814,1994 | 10.1088/0264-9381/11/7/017 | null | gr-qc astro-ph | null | The force acting on the charged particle moving along an arbitrary trajectory
near the straight cosmic string is calculated. This interaction leads to the
scattering of particles by the cosmic string. The scattering cross section is
considered.
| [
{
"created": "Wed, 30 Mar 1994 09:56:15 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Khusnutdinov",
"N R",
""
]
] | The force acting on the charged particle moving along an arbitrary trajectory near the straight cosmic string is calculated. This interaction leads to the scattering of particles by the cosmic string. The scattering cross section is considered. |
gr-qc/0308033 | Badri Krishnan | Abhay Ashtekar and Badri Krishnan | Dynamical Horizons and their Properties | 44 pages, 2 figures, RevTeX4. Minor typos corrected. Final PRD
version | Phys.Rev. D68 (2003) 104030 | 10.1103/PhysRevD.68.104030 | null | gr-qc hep-th | null | A detailed description of how black holes grow in full, non-linear general
relativity is presented. The starting point is the notion of dynamical
horizons. Expressions of fluxes of energy and angular momentum carried by
gravitational waves across these horizons are obtained. Fluxes are local and
the energy flux is positive. Change in the horizon area is related to these
fluxes. A notion of angular momentum and energy is associated with
cross-sections of the horizon and balance equations, analogous to those
obtained by Bondi and Sachs at null infinity, are derived. These in turn lead
to generalizations of the first and second laws of black hole mechanics. The
relation between dynamical horizons and their asymptotic states --the isolated
horizons-- is discussed briefly. The framework has potential applications to
numerical, mathematical, astrophysical and quantum general relativity.
| [
{
"created": "Mon, 11 Aug 2003 16:18:56 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Aug 2003 16:47:16 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Sep 2003 07:21:24 GMT",
"version": "v3"
},
{
"created": "Fri, 17 Oct 2003 12:33:11 GMT",
"version": "v4"
}
] | 2016-08-31 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Krishnan",
"Badri",
""
]
] | A detailed description of how black holes grow in full, non-linear general relativity is presented. The starting point is the notion of dynamical horizons. Expressions of fluxes of energy and angular momentum carried by gravitational waves across these horizons are obtained. Fluxes are local and the energy flux is positive. Change in the horizon area is related to these fluxes. A notion of angular momentum and energy is associated with cross-sections of the horizon and balance equations, analogous to those obtained by Bondi and Sachs at null infinity, are derived. These in turn lead to generalizations of the first and second laws of black hole mechanics. The relation between dynamical horizons and their asymptotic states --the isolated horizons-- is discussed briefly. The framework has potential applications to numerical, mathematical, astrophysical and quantum general relativity. |
1411.4316 | Edward Anderson | Edward Anderson | Where to Apply Relationalism | 24 pages including 9 figures. Comments and references updated. arXiv
admin note: substantial text overlap with arXiv:1409.4117 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Relationalism -- along the lines developed by Barbour and collaborators in
the past 3 decades -- can be considered an advance with 1/4 of the facets of
the canonical approach's Problem of Time as identified by Isham and Kuchar.
Indeed, almost all of the Problem of Time facets have classical counterparts,
since they arise from consequences of demanding background independence rather
than about combining GR and QM per se. Moreover the quantum version is harder,
while the classical counterpart provides some suggestions through being more
solvable. The suggestion then is to consider the effect of this advance on the
Problem of Time as a whole, as opposed to repeating the same classical portion
for a different redundancy group acting on the configuration space: shape
dynamics. There are indeed some knock-on effects because the facets are
notoriously not independent. The other facets do also however require distinct
insights. Finally, I comment on the above being `metric' background
independence, whereas quantum gravity usually assumes many other levels of
background structures. Whilst Isham already wrote about this over two decades
ago, it has largely not yet been incorporated into quantum gravity programs,
and could well be a good area to extend and re-envigour by use of relational
thinking.
| [
{
"created": "Sun, 16 Nov 2014 22:25:23 GMT",
"version": "v1"
},
{
"created": "Sun, 17 May 2015 19:50:35 GMT",
"version": "v2"
}
] | 2015-05-19 | [
[
"Anderson",
"Edward",
""
]
] | Relationalism -- along the lines developed by Barbour and collaborators in the past 3 decades -- can be considered an advance with 1/4 of the facets of the canonical approach's Problem of Time as identified by Isham and Kuchar. Indeed, almost all of the Problem of Time facets have classical counterparts, since they arise from consequences of demanding background independence rather than about combining GR and QM per se. Moreover the quantum version is harder, while the classical counterpart provides some suggestions through being more solvable. The suggestion then is to consider the effect of this advance on the Problem of Time as a whole, as opposed to repeating the same classical portion for a different redundancy group acting on the configuration space: shape dynamics. There are indeed some knock-on effects because the facets are notoriously not independent. The other facets do also however require distinct insights. Finally, I comment on the above being `metric' background independence, whereas quantum gravity usually assumes many other levels of background structures. Whilst Isham already wrote about this over two decades ago, it has largely not yet been incorporated into quantum gravity programs, and could well be a good area to extend and re-envigour by use of relational thinking. |
gr-qc/0212103 | Leor Barack | Leor Barack and Amos Ori | Gravitational self-force on a particle orbiting a Kerr black hole | 4 pages, Latex. Version to appear in Physical Review Letters | Phys.Rev.Lett. 90 (2003) 111101 | 10.1103/PhysRevLett.90.111101 | null | gr-qc | null | We present a practical method for calculating the gravitational self-force,
as well as the electromagnetic and scalar self forces, for a particle in a
generic orbit around a Kerr black hole. In particular, we provide the values of
all the regularization parameters needed for implementing the (previously
introduced) {\it mode-sum regularization} method. We also address the
gauge-regularization problem, as well as a few other issues involved in the
calculation of gravitational radiation-reaction in Kerr spacetime.
| [
{
"created": "Wed, 25 Dec 2002 17:59:47 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Mar 2003 20:18:26 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Barack",
"Leor",
""
],
[
"Ori",
"Amos",
""
]
] | We present a practical method for calculating the gravitational self-force, as well as the electromagnetic and scalar self forces, for a particle in a generic orbit around a Kerr black hole. In particular, we provide the values of all the regularization parameters needed for implementing the (previously introduced) {\it mode-sum regularization} method. We also address the gauge-regularization problem, as well as a few other issues involved in the calculation of gravitational radiation-reaction in Kerr spacetime. |
1910.00427 | Saibal Ray | Suparna Biswas, Dibyendu Shee, Saibal Ray, F. Rahaman and B.K. Guha | Relativistic strange stars in Tolman-Kuchowicz spacetime | 32 pages, 9 figures, 2 tables | Annals of Physics 409 (2019) 167905 | 10.1016/j.aop.2019.05.004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we propose a relativistic model of a static spherically
symmetric anisotropic strange star with the help of Tolman-Kuchowicz (TK)
metric potentials [Tolman, Phys. Rev. {\bf55}, 364 (1939) and Kuchowicz, Acta
Phys. Pol. {\bf33}, 541 (1968)]. The form of the potentials are
$\lambda(r)=\ln(1+ar^2+br^4)$ and $\nu(r)=Br^2+2\ln C$ where $a$, $b$, $B$ and
$C$ are constants which we have to evaluate using boundary conditions. We also
consider the simplest form of the phenomenological MIT bag equation of state
(EOS) to represent the strange quark matter (SQM) distribution inside the
stellar system. Here, the radial pressure $p_r$ relates with the density
profile $\rho$ as follows, $p_r(r)=\frac{1}{3}[\rho(r)-4B_g]$, where $B_g$ is
the Bag constant. To check the physical acceptability and stability of the
stellar system based on the obtained solutions, we have performed various
physical tests. It is shown that the model satisfies all the stability
criteria, including nonsingular nature of the density and pressure, implies
stable nature. Here, the Bag constant for different strange star candidates are
found to be $(68-70)$~MeV/{fm}$^3$ which satisfies all the acceptability
criteria and remains in the experimental range.
| [
{
"created": "Mon, 30 Sep 2019 07:31:49 GMT",
"version": "v1"
}
] | 2019-10-02 | [
[
"Biswas",
"Suparna",
""
],
[
"Shee",
"Dibyendu",
""
],
[
"Ray",
"Saibal",
""
],
[
"Rahaman",
"F.",
""
],
[
"Guha",
"B. K.",
""
]
] | In this article we propose a relativistic model of a static spherically symmetric anisotropic strange star with the help of Tolman-Kuchowicz (TK) metric potentials [Tolman, Phys. Rev. {\bf55}, 364 (1939) and Kuchowicz, Acta Phys. Pol. {\bf33}, 541 (1968)]. The form of the potentials are $\lambda(r)=\ln(1+ar^2+br^4)$ and $\nu(r)=Br^2+2\ln C$ where $a$, $b$, $B$ and $C$ are constants which we have to evaluate using boundary conditions. We also consider the simplest form of the phenomenological MIT bag equation of state (EOS) to represent the strange quark matter (SQM) distribution inside the stellar system. Here, the radial pressure $p_r$ relates with the density profile $\rho$ as follows, $p_r(r)=\frac{1}{3}[\rho(r)-4B_g]$, where $B_g$ is the Bag constant. To check the physical acceptability and stability of the stellar system based on the obtained solutions, we have performed various physical tests. It is shown that the model satisfies all the stability criteria, including nonsingular nature of the density and pressure, implies stable nature. Here, the Bag constant for different strange star candidates are found to be $(68-70)$~MeV/{fm}$^3$ which satisfies all the acceptability criteria and remains in the experimental range. |
0708.2673 | Yosef Verbin | Y. Verbin | Solitonic and Non-Solitonic Q-Stars | To appear in the proceedings of 11th Marcel Grossmann Meeting,
Berlin, July 2006 | null | 10.1142/9789812834300_0396 | null | gr-qc hep-th | null | The properties of several types of Q-stars are studied and compared with
their flat space analogues, i.e. Q-balls. The analysis is based on calculating
the mass, global U(1) charge and binding energy for families of solutions
parametrized by the central value of the scalar field. The two most frequently
used Q-star models (differing by their potential term) are studied. Although
there are general similarities between both Q-star types, there are important
differences as well as new features with respect to the non-gravitating
systems. We find non-solitonic solutions which do not have a flat space limit,
in the weak (scalar) field region as well as in the opposite region of strong
central scalar field for which there does not exist Q-ball solutions at all.
| [
{
"created": "Mon, 20 Aug 2007 14:36:28 GMT",
"version": "v1"
}
] | 2016-11-15 | [
[
"Verbin",
"Y.",
""
]
] | The properties of several types of Q-stars are studied and compared with their flat space analogues, i.e. Q-balls. The analysis is based on calculating the mass, global U(1) charge and binding energy for families of solutions parametrized by the central value of the scalar field. The two most frequently used Q-star models (differing by their potential term) are studied. Although there are general similarities between both Q-star types, there are important differences as well as new features with respect to the non-gravitating systems. We find non-solitonic solutions which do not have a flat space limit, in the weak (scalar) field region as well as in the opposite region of strong central scalar field for which there does not exist Q-ball solutions at all. |
1802.06977 | Soichiro Isoyama | Soichiro Isoyama, Hiroyuki Nakano, Takashi Nakamura | Multiband Gravitational-Wave Astronomy: Observing binary inspirals with
a decihertz detector, B-DECIGO | v3: 22 pages, 2 figures, matches the published version | Prog. Theor. Exp. Phys. (2018) 073E01 | 10.1093/ptep/pty078 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An evolving Japanese gravitational-wave (GW) mission in the deci-Hz band:
B-DECIGO (DECihertz laser Interferometer Gravitational wave Observatory) will
enable us to detect GW150914-like binary black holes, GW170817-like binary
neutron stars, and intermediate-mass binary black holes out to cosmological
distances. The B-DECIGO band slots in between the aLIGO-Virgo-KAGRA-IndIGO
(hecto-Hz) and LISA (milli-Hz) bands for broader bandwidth; the sources
described emit GWs for weeks to years across the multiband to accumulate high
signal-to-noise ratios. This suggests the possibility that joint detection
would greatly improve the parameter estimation of the binaries. We examine
B-DECIGO's ability to measure binary parameters and assess to what extent
multiband analysis could improve such measurement. Using non-precessing
post-Newtonian waveforms with the Fisher matrix approach, we find for systems
like GW150914 and GW170817 that B-DECIGO can measure the mass ratio to within
$< 0.1\%$, the individual black-hole spins to within $< 10\%$, and the
coalescence time to within $< 5\,$s about a week before alerting aLIGO and
electromagnetic facilities. Prior information from B-DECIGO for aLIGO can
further reduce the uncertainty in the measurement of, e.g., certain neutron
star tidally-induced deformations by factor of $\sim 6$, and potentially
determine the spin-induced neutron star quadrupole moment. Joint LISA and
B-DECIGO measurement will also be able to recover the masses and spins of
intermediate-mass binary black holes at percent-level precision. However, there
will be a large systematic bias in these results due to post-Newtonian
approximation of exact GW signals.
| [
{
"created": "Tue, 20 Feb 2018 06:18:00 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jun 2018 20:22:34 GMT",
"version": "v2"
},
{
"created": "Wed, 8 Aug 2018 19:10:39 GMT",
"version": "v3"
}
] | 2018-08-10 | [
[
"Isoyama",
"Soichiro",
""
],
[
"Nakano",
"Hiroyuki",
""
],
[
"Nakamura",
"Takashi",
""
]
] | An evolving Japanese gravitational-wave (GW) mission in the deci-Hz band: B-DECIGO (DECihertz laser Interferometer Gravitational wave Observatory) will enable us to detect GW150914-like binary black holes, GW170817-like binary neutron stars, and intermediate-mass binary black holes out to cosmological distances. The B-DECIGO band slots in between the aLIGO-Virgo-KAGRA-IndIGO (hecto-Hz) and LISA (milli-Hz) bands for broader bandwidth; the sources described emit GWs for weeks to years across the multiband to accumulate high signal-to-noise ratios. This suggests the possibility that joint detection would greatly improve the parameter estimation of the binaries. We examine B-DECIGO's ability to measure binary parameters and assess to what extent multiband analysis could improve such measurement. Using non-precessing post-Newtonian waveforms with the Fisher matrix approach, we find for systems like GW150914 and GW170817 that B-DECIGO can measure the mass ratio to within $< 0.1\%$, the individual black-hole spins to within $< 10\%$, and the coalescence time to within $< 5\,$s about a week before alerting aLIGO and electromagnetic facilities. Prior information from B-DECIGO for aLIGO can further reduce the uncertainty in the measurement of, e.g., certain neutron star tidally-induced deformations by factor of $\sim 6$, and potentially determine the spin-induced neutron star quadrupole moment. Joint LISA and B-DECIGO measurement will also be able to recover the masses and spins of intermediate-mass binary black holes at percent-level precision. However, there will be a large systematic bias in these results due to post-Newtonian approximation of exact GW signals. |
0911.5380 | Andrey Shoom A | Shohreh Abdolrahimi and Andrey A. Shoom | Analysis of the Fisher solution | 19 pages, 16 figures; Minor changes in the text | Phys.Rev.D81:024035,2010 | 10.1103/PhysRevD.81.024035 | Alberta-Thy-18-09 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the $d$-dimensional Fisher solution which represents a static,
spherically symmetric, asymptotically flat spacetime with a massless scalar
field. The solution has two parameters, the mass and the "scalar charge." The
Fisher solution has a naked curvature singularity which divides the spacetime
manifold into two disconnected parts. The part which is asymptotically flat we
call the {\em Fisher spacetime}, and another part we call the {\em Fisher
universe}. The Schwarzschild-Tangherlini (ST) solution and the Fisher solution
belong to the same theory and are dual to each other. The duality
transformation acting in the parameter space maps the exterior region of the ST
black hole into the Fisher spacetime which has a naked timelike singularity,
and interior region of the black hole into the Fisher universe, which is an
anisotropic expanding-contracting universe and which has two spacelike
singularities representing its "Big Bang" and "Big Crunch". The Big Bang
singularity and the singularity of the Fisher spacetime are {\em radially weak}
in the sense that a 1-dimensional object moving along a timelike radial
geodesic can arrive to the singularities intact. At the vicinity of the
singularity the Fisher spacetime of nonzero mass has a region where its
Misner-Sharp energy is negative. The Fisher universe has a marginally trapped
surface corresponding to the state of its maximal expansion in the angular
directions. These results and derived relations between geometric quantities of
the Fisher spacetime, the Fisher universe, and the ST black hole may suggest
that the massless scalar field transforms the black hole event horizon into the
naked radially weak disjoint singularities of the Fisher spacetime and the
Fisher universe which are "dual to the horizon."
| [
{
"created": "Sat, 28 Nov 2009 07:42:28 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Feb 2010 18:56:29 GMT",
"version": "v2"
}
] | 2010-05-12 | [
[
"Abdolrahimi",
"Shohreh",
""
],
[
"Shoom",
"Andrey A.",
""
]
] | We study the $d$-dimensional Fisher solution which represents a static, spherically symmetric, asymptotically flat spacetime with a massless scalar field. The solution has two parameters, the mass and the "scalar charge." The Fisher solution has a naked curvature singularity which divides the spacetime manifold into two disconnected parts. The part which is asymptotically flat we call the {\em Fisher spacetime}, and another part we call the {\em Fisher universe}. The Schwarzschild-Tangherlini (ST) solution and the Fisher solution belong to the same theory and are dual to each other. The duality transformation acting in the parameter space maps the exterior region of the ST black hole into the Fisher spacetime which has a naked timelike singularity, and interior region of the black hole into the Fisher universe, which is an anisotropic expanding-contracting universe and which has two spacelike singularities representing its "Big Bang" and "Big Crunch". The Big Bang singularity and the singularity of the Fisher spacetime are {\em radially weak} in the sense that a 1-dimensional object moving along a timelike radial geodesic can arrive to the singularities intact. At the vicinity of the singularity the Fisher spacetime of nonzero mass has a region where its Misner-Sharp energy is negative. The Fisher universe has a marginally trapped surface corresponding to the state of its maximal expansion in the angular directions. These results and derived relations between geometric quantities of the Fisher spacetime, the Fisher universe, and the ST black hole may suggest that the massless scalar field transforms the black hole event horizon into the naked radially weak disjoint singularities of the Fisher spacetime and the Fisher universe which are "dual to the horizon." |
2402.06739 | Ahmad Al-Badawi | Ahmad Al-Badawi, Sohan Kumar Jha and Anisur Rahaman | Hairy black hole, Fermionic greybody factors, Quasinormal modes, Hawking
radiation, Power spectrum and sparsity | null | Eur. Phys. J. C (2024) 84:145 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A hairy black hole (HBH) emerges due to matter surrounding the Schwarzschild
metric when using the Extended Gravitational Decoupling (GD) approach. The
fermionic greybody factors (GFs) and quasinormal modes (QNMs) as well as
Hawking spectra and sparsity of HBH solutions are investigated. We consider
massive and massless spin- 1/2 fermions, along with massless spin- 3/2
fermions. The equations of the effective potential for fermions with different
spins are derived in HBH spacetime. Then, the rigorous bound method is used to
calculate the fermionic spin- 1/2 and spin- 3/2 GFs. With the time domain
integration method at our disposal, we illustrate the impact of additional
parameters on the ringdown waveform of the massless fermionic spin -1/2 and
spin -3/2 fields and, in turn, on their quasinormal modes. We then delve into
investigating the Hawking spectra and sparsity of the radiation emitted by an
HBH. Hairy parameters significantly affect the sparsity of Hawking radiation as
well. We observe that the total power emitted by the BH increases both with
$\alpha$ and $Q$ but decreases with $l_{0}$. Our study conclusively shows the
significant impact of the additional parameters on important astrophysical
phenomena such as quasinormal modes, Hawking spectra, and sparsity.
| [
{
"created": "Fri, 9 Feb 2024 19:16:33 GMT",
"version": "v1"
}
] | 2024-02-13 | [
[
"Al-Badawi",
"Ahmad",
""
],
[
"Jha",
"Sohan Kumar",
""
],
[
"Rahaman",
"Anisur",
""
]
] | A hairy black hole (HBH) emerges due to matter surrounding the Schwarzschild metric when using the Extended Gravitational Decoupling (GD) approach. The fermionic greybody factors (GFs) and quasinormal modes (QNMs) as well as Hawking spectra and sparsity of HBH solutions are investigated. We consider massive and massless spin- 1/2 fermions, along with massless spin- 3/2 fermions. The equations of the effective potential for fermions with different spins are derived in HBH spacetime. Then, the rigorous bound method is used to calculate the fermionic spin- 1/2 and spin- 3/2 GFs. With the time domain integration method at our disposal, we illustrate the impact of additional parameters on the ringdown waveform of the massless fermionic spin -1/2 and spin -3/2 fields and, in turn, on their quasinormal modes. We then delve into investigating the Hawking spectra and sparsity of the radiation emitted by an HBH. Hairy parameters significantly affect the sparsity of Hawking radiation as well. We observe that the total power emitted by the BH increases both with $\alpha$ and $Q$ but decreases with $l_{0}$. Our study conclusively shows the significant impact of the additional parameters on important astrophysical phenomena such as quasinormal modes, Hawking spectra, and sparsity. |
1601.00746 | Antonio C. Guti\'errez-Pi\~neres | Antonio C. Guti\'errez-Pi\~neres, Abra\~ao J. S. Capistrano and
Hernando Quevedo | Test particles in a magnetized conformastatic spacetime | Updated version to match with the published version in Physical
Review D | Phys. Rev. D 93, 124009 (2016) | 10.1103/PhysRevD.93.124009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A class of exact conformastatic solutions of the Einstein-Maxwell field
equations is presented in which the gravitational and electromagnetic
potentials are completely determined by a harmonic function. We derive the
equations of motion for neutral and charged particles in a spacetime background
characterized by this class of solutions. As an example, we focus on the
analysis of a particular harmonic function, which generates a singularity-free
and asymptotically flat spacetime that describes the gravitational field of a
punctual mass endowed with a magnetic field. In this particular case, we
investigate the main physical properties of equatorial circular orbits. We show
that due to the electromagnetic interaction, it is possible to have charged
test particles which stay at rest with respect to a static observer located at
infinity. Additionally, we obtain an analytic expression for the perihelion
advance of test particles and the corresponding explicit value in the case of a
punctual magnetic mass. We show that the analytical expressions obtained from
our analysis are sufficient for being confronted with observations in order to
establish whether such objects can exist in nature.
| [
{
"created": "Tue, 5 Jan 2016 06:49:39 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Jan 2016 10:14:44 GMT",
"version": "v2"
},
{
"created": "Fri, 25 Mar 2016 04:13:38 GMT",
"version": "v3"
},
{
"created": "Sat, 4 Jun 2016 00:26:31 GMT",
"version": "v4"
}
] | 2016-06-08 | [
[
"Gutiérrez-Piñeres",
"Antonio C.",
""
],
[
"Capistrano",
"Abraão J. S.",
""
],
[
"Quevedo",
"Hernando",
""
]
] | A class of exact conformastatic solutions of the Einstein-Maxwell field equations is presented in which the gravitational and electromagnetic potentials are completely determined by a harmonic function. We derive the equations of motion for neutral and charged particles in a spacetime background characterized by this class of solutions. As an example, we focus on the analysis of a particular harmonic function, which generates a singularity-free and asymptotically flat spacetime that describes the gravitational field of a punctual mass endowed with a magnetic field. In this particular case, we investigate the main physical properties of equatorial circular orbits. We show that due to the electromagnetic interaction, it is possible to have charged test particles which stay at rest with respect to a static observer located at infinity. Additionally, we obtain an analytic expression for the perihelion advance of test particles and the corresponding explicit value in the case of a punctual magnetic mass. We show that the analytical expressions obtained from our analysis are sufficient for being confronted with observations in order to establish whether such objects can exist in nature. |
2402.11614 | S. Davood Sadatian | S. Davood Sadatian, S. Mohamad Reza Hosseini | Modified Gravity Model $f(Q,T)$ and Wormhole Solution | 14 pages, 8 figures, accepted for publication in Advances in High
Energy Physics journal | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We investigate wormhole solutions using the modified gravity model $f(Q,T)$
with viscosity and aim to find a solution for the existence of wormholes
mathematically without violating the energy conditions. We show that there is
no need to define a wormhole from exotic matter and analyze the equations with
numerical analysis to establish weak energy conditions. In the numerical
analysis, we found that the appropriate values of the parameters can maintain
the weak energy conditions without the need for exotic matter. Adjusting the
parameters of the model can increase or decrease the rate of positive energy
density or radial and tangential pressures. According to the numerical analysis
conducted in this paper, the weak energy conditions are established in the
whole space if $\alpha< 0$, $12.56 < \beta < 25.12$ or $\alpha > 0$, $\beta >
25.12$. The analysis also showed that the supporting matter of the wormhole is
near normal matter, indicating that the generalized $f(Q,T)$ model with
viscosity has an acceptable parameter space to describe a wormhole without the
need for exotic matter.
| [
{
"created": "Sun, 18 Feb 2024 15:08:06 GMT",
"version": "v1"
}
] | 2024-02-20 | [
[
"Sadatian",
"S. Davood",
""
],
[
"Hosseini",
"S. Mohamad Reza",
""
]
] | We investigate wormhole solutions using the modified gravity model $f(Q,T)$ with viscosity and aim to find a solution for the existence of wormholes mathematically without violating the energy conditions. We show that there is no need to define a wormhole from exotic matter and analyze the equations with numerical analysis to establish weak energy conditions. In the numerical analysis, we found that the appropriate values of the parameters can maintain the weak energy conditions without the need for exotic matter. Adjusting the parameters of the model can increase or decrease the rate of positive energy density or radial and tangential pressures. According to the numerical analysis conducted in this paper, the weak energy conditions are established in the whole space if $\alpha< 0$, $12.56 < \beta < 25.12$ or $\alpha > 0$, $\beta > 25.12$. The analysis also showed that the supporting matter of the wormhole is near normal matter, indicating that the generalized $f(Q,T)$ model with viscosity has an acceptable parameter space to describe a wormhole without the need for exotic matter. |
2112.01490 | Matteo Lulli Dr | Matteo Lulli, Antonino Marciano, Xiaowen Shan | Stochastic Quantization of General Relativity \`a la Ricci-Flow | 15 pages; all sections have been revised | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We follow a new pathway to the definition of the Stochastic Quantization
(SQ), first proposed by Parisi and Wu, of the action functional yielding the
Einstein equations. Hinging on the functional similarities between the
Ricci-Flow equation and the SQ Langevin equations proposed by Rumpf, we push
forward a novel approach with multiplicative noise and a stochastic time that
converges to the proper time of a space-like foliation in the equilibrium
limit. Furthermore, we express the starting system of equations using the
Arnowitt-Deser-Misner (ADM) variables and their conjugated Hamiltonian momenta.
Such a choice is instrumental in understanding the newly derived equations in
terms of the breakdown of the diffeomorphism invariance of the classical
theory, which instead will hold on average at the steady state. We comment on
the physical interpretation of the Ricci flow equations, and argue how they can
naturally provide, in a geometrical way, the renormalization group equation for
gravity theories. In the general setting, the equation associated to the shift
vector yields the Navier-Stokes equation with a stochastic source. Moreover, we
show that the fluctuations of the metric tensor components around the
equilibrium configurations, far away from the horizon of a Schwarzschild black
hole, are forced by the Ricci flow to follow the Kardar-Parisi-Zhang equation,
whose probabilistic distribution can yield an intermittent statistics. We
finally comment on the possible applications of this novel scenario to the
cosmological constant, arguing that the Ricci flow may provide a solution to
the Hubble tension, as a macroscopic effect of scale dependence of the quantum
fluctuations of the metric tensor.
| [
{
"created": "Thu, 2 Dec 2021 18:41:54 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Aug 2022 16:18:16 GMT",
"version": "v2"
}
] | 2022-08-09 | [
[
"Lulli",
"Matteo",
""
],
[
"Marciano",
"Antonino",
""
],
[
"Shan",
"Xiaowen",
""
]
] | We follow a new pathway to the definition of the Stochastic Quantization (SQ), first proposed by Parisi and Wu, of the action functional yielding the Einstein equations. Hinging on the functional similarities between the Ricci-Flow equation and the SQ Langevin equations proposed by Rumpf, we push forward a novel approach with multiplicative noise and a stochastic time that converges to the proper time of a space-like foliation in the equilibrium limit. Furthermore, we express the starting system of equations using the Arnowitt-Deser-Misner (ADM) variables and their conjugated Hamiltonian momenta. Such a choice is instrumental in understanding the newly derived equations in terms of the breakdown of the diffeomorphism invariance of the classical theory, which instead will hold on average at the steady state. We comment on the physical interpretation of the Ricci flow equations, and argue how they can naturally provide, in a geometrical way, the renormalization group equation for gravity theories. In the general setting, the equation associated to the shift vector yields the Navier-Stokes equation with a stochastic source. Moreover, we show that the fluctuations of the metric tensor components around the equilibrium configurations, far away from the horizon of a Schwarzschild black hole, are forced by the Ricci flow to follow the Kardar-Parisi-Zhang equation, whose probabilistic distribution can yield an intermittent statistics. We finally comment on the possible applications of this novel scenario to the cosmological constant, arguing that the Ricci flow may provide a solution to the Hubble tension, as a macroscopic effect of scale dependence of the quantum fluctuations of the metric tensor. |
2104.07931 | Shahab Shahidi | Shahab Shahidi | Non-minimal Energy-momentum squared gravity | 10 pages, 7 figures | Eur.Phys.J.C 81 (2021) 274 | 10.1140/epjc/s10052-021-09082-z | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider a gravitational theory with an additional non-minimal coupling
between baryonic matter fields and geometry. The coupling is second order in
the energy momentum tensor and can be seen as a generalization of the
energy-momentum squared gravity model. We will add a constraint through a
Lagrange multiplier to ensure the conservation of the energy-momentum tensor.
Background cosmological implications together with its dynamical system
analysis will be investigated in details. Also we will consider the growth of
matter perturbation at first order, and estimate the model parameter from
observations on $H$ and also $f\sigma_8$. We will show that the model parameter
should be small and positive in 2$\sigma$ confidence interval. The theory is
shown to be in a good agreement with observational data.
| [
{
"created": "Fri, 16 Apr 2021 07:28:51 GMT",
"version": "v1"
}
] | 2021-04-19 | [
[
"Shahidi",
"Shahab",
""
]
] | We consider a gravitational theory with an additional non-minimal coupling between baryonic matter fields and geometry. The coupling is second order in the energy momentum tensor and can be seen as a generalization of the energy-momentum squared gravity model. We will add a constraint through a Lagrange multiplier to ensure the conservation of the energy-momentum tensor. Background cosmological implications together with its dynamical system analysis will be investigated in details. Also we will consider the growth of matter perturbation at first order, and estimate the model parameter from observations on $H$ and also $f\sigma_8$. We will show that the model parameter should be small and positive in 2$\sigma$ confidence interval. The theory is shown to be in a good agreement with observational data. |
0709.0697 | H Mohseni Sadjadi | H. Mohseni Sadjadi | A Note on Gravitational Baryogenesis | 10 pages, accepted for publication in Physical Review D | Phys.Rev.D76:123507,2007 | 10.1103/PhysRevD.76.123507 | null | gr-qc hep-th | null | The coupling between Ricci scalar curvature and the baryon number current
dynamically breaks CPT in an expanding universe and leads to baryon asymmetry.
We study the effect of time dependence of equation of state parameter of the
FRW universe on this asymmetry.
| [
{
"created": "Wed, 5 Sep 2007 16:25:26 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Nov 2007 07:00:45 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Sadjadi",
"H. Mohseni",
""
]
] | The coupling between Ricci scalar curvature and the baryon number current dynamically breaks CPT in an expanding universe and leads to baryon asymmetry. We study the effect of time dependence of equation of state parameter of the FRW universe on this asymmetry. |
2407.05500 | Aliasghar Parvizi A. Parvizi | Aliasghar Parvizi, Tomasz Paw{\l}owski | Revisiting light propagation over (loop) quantum Universe | RevTex, 12 pages, 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the principal aspects through which the effects of quantum gravity are
hoped to manifest is the possible modification of the dispersion relation for
electromagnetic (e-m) waves. By combining (i) the symmetry reduced approaches
to spacetime quantization, including loop quantum cosmology or geometrodynamics
framework, and (ii) the (extension of the) Born-Oppenheimer approximation of
interacting fields, one can build a reliable though still
quasi-phenomenological model for a description of propagation of the e-m
radiation over a cosmological spacetime. The past works employing such approach
indicated a pathological behavior - superluminal propagation at low energies.
We reexamine the approach via systematic studies (using indicated method) of
e-m wave propagation over a flat quantum Friedmann-Lemaitre-Robertson-Walker
Universe using a synthesis of analytical and numerical methods. It turns out,
that (i) the e-m wave propagation agrees with the one predicted by general
relativity in the low energy limit, and (ii) loop quantum effects actually
suppress the modifications to the dispersion relation in comparison with those
predicted, where the geometry is quantized via geometrodynamics.
| [
{
"created": "Sun, 7 Jul 2024 21:19:59 GMT",
"version": "v1"
}
] | 2024-07-09 | [
[
"Parvizi",
"Aliasghar",
""
],
[
"Pawłowski",
"Tomasz",
""
]
] | One of the principal aspects through which the effects of quantum gravity are hoped to manifest is the possible modification of the dispersion relation for electromagnetic (e-m) waves. By combining (i) the symmetry reduced approaches to spacetime quantization, including loop quantum cosmology or geometrodynamics framework, and (ii) the (extension of the) Born-Oppenheimer approximation of interacting fields, one can build a reliable though still quasi-phenomenological model for a description of propagation of the e-m radiation over a cosmological spacetime. The past works employing such approach indicated a pathological behavior - superluminal propagation at low energies. We reexamine the approach via systematic studies (using indicated method) of e-m wave propagation over a flat quantum Friedmann-Lemaitre-Robertson-Walker Universe using a synthesis of analytical and numerical methods. It turns out, that (i) the e-m wave propagation agrees with the one predicted by general relativity in the low energy limit, and (ii) loop quantum effects actually suppress the modifications to the dispersion relation in comparison with those predicted, where the geometry is quantized via geometrodynamics. |
2109.10017 | Ram Brustein | Ram Brustein, A.J.M. Medved, Tamar Simhon | Black holes as frozen stars | null | null | 10.1103/PhysRevD.105.024019 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We have recently proposed a model for a regular black hole, or an
ultra-compact object, that is premised on having maximally negative radial
pressure throughout the entirety of the object's interior. This model can be
viewed as that of a highly entropic configuration of fundamental, closed
strings near the Hagedorn temperature, but from the perspective of an observer
who is ignorant about the role of quantum physics in counteracting against
gravitational collapse. The advantage of this classical perspective is that one
can use Einstein's equations to define a classical geometry and investigate its
stability. Here, we complete the model by studying an important aspect of this
framework that has so far been overlooked: The geometry and composition of the
outermost layer of the ultra-compact object, which interpolates between the
bulk geometry of the object and the standard Schwarzschild vacuum solution in
its exterior region. By imposing a well-defined set of matching conditions, we
find a metric that describes this transitional layer and show that it satisfies
all the basic requirements; including the stability of the object when
subjected to small perturbations about the background solution. In fact, we are
able to show that, at linearized order, all geometrical and matter fluctuations
are perfectly frozen in the transitional layer, just as they are known to be in
the bulk of the object's interior.
| [
{
"created": "Tue, 21 Sep 2021 08:07:59 GMT",
"version": "v1"
}
] | 2022-01-19 | [
[
"Brustein",
"Ram",
""
],
[
"Medved",
"A. J. M.",
""
],
[
"Simhon",
"Tamar",
""
]
] | We have recently proposed a model for a regular black hole, or an ultra-compact object, that is premised on having maximally negative radial pressure throughout the entirety of the object's interior. This model can be viewed as that of a highly entropic configuration of fundamental, closed strings near the Hagedorn temperature, but from the perspective of an observer who is ignorant about the role of quantum physics in counteracting against gravitational collapse. The advantage of this classical perspective is that one can use Einstein's equations to define a classical geometry and investigate its stability. Here, we complete the model by studying an important aspect of this framework that has so far been overlooked: The geometry and composition of the outermost layer of the ultra-compact object, which interpolates between the bulk geometry of the object and the standard Schwarzschild vacuum solution in its exterior region. By imposing a well-defined set of matching conditions, we find a metric that describes this transitional layer and show that it satisfies all the basic requirements; including the stability of the object when subjected to small perturbations about the background solution. In fact, we are able to show that, at linearized order, all geometrical and matter fluctuations are perfectly frozen in the transitional layer, just as they are known to be in the bulk of the object's interior. |
2211.17248 | Mary Letey | Mary I. Letey, Zakhar Shumaylov, Fruzsina J. Agocs, Will J. Handley,
Michael P. Hobson, Anthony N. Lasenby | Quantum initial conditions for curved inflating universes | 15 pages, 3 figures; v3: As published in PRD | Phys. Rev. D 109, 123502 (2024) | 10.1103/PhysRevD.109.123502 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the challenges of motivating, constructing, and quantizing a
canonically normalized inflationary perturbation in spatially curved universes.
We show that this has historically proved challenging due to the interaction of
nonadiabaticity with spatial curvature. We construct a novel curvature
perturbation that is canonically normalized in the sense of its equation of
motion and is unique up to a single scalar parameter. With this construction it
becomes possible to set initial conditions invariant under canonical
transformations, overcoming known ambiguities in the literature. This corrected
quantization has potentially observational consequences via modifications to
the primordial power spectrum at large angular scales, as well as theoretical
implications for quantization procedures in curved cosmologies filled with a
scalar field.
| [
{
"created": "Wed, 30 Nov 2022 18:48:07 GMT",
"version": "v1"
},
{
"created": "Sun, 7 May 2023 18:46:23 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Jul 2024 19:15:22 GMT",
"version": "v3"
}
] | 2024-07-10 | [
[
"Letey",
"Mary I.",
""
],
[
"Shumaylov",
"Zakhar",
""
],
[
"Agocs",
"Fruzsina J.",
""
],
[
"Handley",
"Will J.",
""
],
[
"Hobson",
"Michael P.",
""
],
[
"Lasenby",
"Anthony N.",
""
]
] | We discuss the challenges of motivating, constructing, and quantizing a canonically normalized inflationary perturbation in spatially curved universes. We show that this has historically proved challenging due to the interaction of nonadiabaticity with spatial curvature. We construct a novel curvature perturbation that is canonically normalized in the sense of its equation of motion and is unique up to a single scalar parameter. With this construction it becomes possible to set initial conditions invariant under canonical transformations, overcoming known ambiguities in the literature. This corrected quantization has potentially observational consequences via modifications to the primordial power spectrum at large angular scales, as well as theoretical implications for quantization procedures in curved cosmologies filled with a scalar field. |
2104.14158 | Sen Guo | Sen Guo and En-Wei Liang | Ehrenfest's scheme and microstructure for regular-AdS black hole in the
extended phase space | 14 pages, 5 figures | published in Classical and Quantum Gravity Vol:38; 125001 (2021) | 10.1088/1361-6382/abf9b6 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | The regular (Bardeen)-AdS (BAdS) black hole (BH) in the extended phase space
is taken as an example for investigating the BH phase transition grade from
both macroscopic and microscopic points of view. The equation of state and
thermodynamic quantities of this BH are obtained. It is found that the BAdS BH
phase space in the extended phase space should be a second-order phase
transition near the critical point by verifying the Ehrenfest's equation, and
the possibility of its first-order phase transition can be ruled out by the
entropy continuity and the heat capacity mutation. The critical exponents from
the microscopic structure are analytically and numerically presented with the
Landau continuous phase transition theory by introducing a microscopic
order-parameter.
| [
{
"created": "Thu, 29 Apr 2021 07:36:28 GMT",
"version": "v1"
},
{
"created": "Sun, 15 May 2022 09:39:57 GMT",
"version": "v2"
}
] | 2022-05-17 | [
[
"Guo",
"Sen",
""
],
[
"Liang",
"En-Wei",
""
]
] | The regular (Bardeen)-AdS (BAdS) black hole (BH) in the extended phase space is taken as an example for investigating the BH phase transition grade from both macroscopic and microscopic points of view. The equation of state and thermodynamic quantities of this BH are obtained. It is found that the BAdS BH phase space in the extended phase space should be a second-order phase transition near the critical point by verifying the Ehrenfest's equation, and the possibility of its first-order phase transition can be ruled out by the entropy continuity and the heat capacity mutation. The critical exponents from the microscopic structure are analytically and numerically presented with the Landau continuous phase transition theory by introducing a microscopic order-parameter. |
gr-qc/0502118 | J. E. Horvath | P. S. Cust\'odio and J.E.Horvath | Cosmological quintessence accretion onto primordial black holes :
conditions for their growth to the supermassive scale | 21 pp., 2 Figures, To appear in IJMPD | Int.J.Mod.Phys. D14 (2005) 257-274 | 10.1142/S0218271805006043 | null | gr-qc | null | In this work we revisit the growth of small primordial black holes (PBHs)
immersed in a quintessential field and/or radiation to the supermassive black
hole (SMBHs) scale. We show the difficulties of scenarios in which such huge
growth is possible. For that purpose we evaluated analytical solutions of the
differential equations (describing mass evolution) and point out the strong
fine tuning for that conclusions. The timescale for growth in a model with a
constant quintessence flux is calculated and we show that it is much bigger
than the Hubble time.The fractional gain of the mass is further evaluated in
other forms, including quintessence and/or radiation. We calculate the
cosmological density $\Omega$ due to quintessence necessary to grow BHs to the
supermassive range and show it to be much bigger than one. We also describe the
set of complete equations analyzing the evolution of the BH+quintessence
universe, showing some interesting effects such the quenching of the BH mass
growth due to the evolution of the background energy. Additional constraints
obtained by using the Holographic Bound are also described. The general
equilibrium conditions for evaporating/accreting black holes evolving in a
quintessence/radiation universe are discussed in the Appendix.
| [
{
"created": "Mon, 28 Feb 2005 12:53:22 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Custódio",
"P. S.",
""
],
[
"Horvath",
"J. E.",
""
]
] | In this work we revisit the growth of small primordial black holes (PBHs) immersed in a quintessential field and/or radiation to the supermassive black hole (SMBHs) scale. We show the difficulties of scenarios in which such huge growth is possible. For that purpose we evaluated analytical solutions of the differential equations (describing mass evolution) and point out the strong fine tuning for that conclusions. The timescale for growth in a model with a constant quintessence flux is calculated and we show that it is much bigger than the Hubble time.The fractional gain of the mass is further evaluated in other forms, including quintessence and/or radiation. We calculate the cosmological density $\Omega$ due to quintessence necessary to grow BHs to the supermassive range and show it to be much bigger than one. We also describe the set of complete equations analyzing the evolution of the BH+quintessence universe, showing some interesting effects such the quenching of the BH mass growth due to the evolution of the background energy. Additional constraints obtained by using the Holographic Bound are also described. The general equilibrium conditions for evaporating/accreting black holes evolving in a quintessence/radiation universe are discussed in the Appendix. |
2404.03815 | James T. Wheeler | James T. Wheeler | Geometry from geodesics: fine-tuning Ehlers, Pirani, and Schild | 24 pages plus references | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by-sa/4.0/ | Ehlers, Pirani, and Schild argued that measurements of timelike and null
geodesics yield projective and Weyl connections, respectively, with
compatibility giving an integrable Weyl geometry. We find greater freedom for
both connections, including either a 1-parameter class of projective
connections, or a conformal connection for timelike curves, and conformal
symmetry for null curves. Examining the effect of every member of both the
projective class and the conformal transformations on the curvature, torsion,
nonmetricity, and metric, we find the changes from the original geometry.
Forming invariant connections we compute both the projectively and conformally
invariant forms of the curvature, torsion, and nometricity, showing that the
projective and conformal tensors depend on the same gauge vector. We prove that
the conditions for projective and conformal Ricci flatness imply each other and
either reduces the geometry to the original form. The different transformations
depend on the same monotonic, twice differentiable function on a region of
spacetime. Existence of such a function requires a region foliated by order
isomorphic, totally ordered, twice differentiable timelike curves in a
necessarily Lorentzian geometry. To find a geometry consistent with the allowed
symmetry, we develop the real, linear, 6-dim representation of the conformal
connection. Taking the simplest form of the spacetime action using this
connection, we show that reductions of the system lead us back to an integrable
Weyl geometry.
| [
{
"created": "Thu, 4 Apr 2024 21:44:35 GMT",
"version": "v1"
}
] | 2024-04-08 | [
[
"Wheeler",
"James T.",
""
]
] | Ehlers, Pirani, and Schild argued that measurements of timelike and null geodesics yield projective and Weyl connections, respectively, with compatibility giving an integrable Weyl geometry. We find greater freedom for both connections, including either a 1-parameter class of projective connections, or a conformal connection for timelike curves, and conformal symmetry for null curves. Examining the effect of every member of both the projective class and the conformal transformations on the curvature, torsion, nonmetricity, and metric, we find the changes from the original geometry. Forming invariant connections we compute both the projectively and conformally invariant forms of the curvature, torsion, and nometricity, showing that the projective and conformal tensors depend on the same gauge vector. We prove that the conditions for projective and conformal Ricci flatness imply each other and either reduces the geometry to the original form. The different transformations depend on the same monotonic, twice differentiable function on a region of spacetime. Existence of such a function requires a region foliated by order isomorphic, totally ordered, twice differentiable timelike curves in a necessarily Lorentzian geometry. To find a geometry consistent with the allowed symmetry, we develop the real, linear, 6-dim representation of the conformal connection. Taking the simplest form of the spacetime action using this connection, we show that reductions of the system lead us back to an integrable Weyl geometry. |
gr-qc/0203023 | Yasusada Nambu | Yasusada Nambu | The back reaction and the effective Einstein's equation for the Universe
with ideal fluid cosmological perturbations | 16 pages, to appear in Phys. Rev. D | Phys.Rev. D65 (2002) 104013 | 10.1103/PhysRevD.65.104013 | null | gr-qc | null | We investigate the back reaction of cosmological perturbations on the
evolution of the Universe using the renormalization group method. Starting from
the second order perturbed Einstein's equation, we renormalize a scale factor
of the Universe and derive the evolution equation for the effective scale
factor which includes back reaction due to inhomogeneities of the Universe. The
resulting equation has the same form as the standard Friedman-Robertson-Walker
equation with the effective energy density and pressure which represent the
back reaction effect.
| [
{
"created": "Thu, 7 Mar 2002 04:17:01 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Nambu",
"Yasusada",
""
]
] | We investigate the back reaction of cosmological perturbations on the evolution of the Universe using the renormalization group method. Starting from the second order perturbed Einstein's equation, we renormalize a scale factor of the Universe and derive the evolution equation for the effective scale factor which includes back reaction due to inhomogeneities of the Universe. The resulting equation has the same form as the standard Friedman-Robertson-Walker equation with the effective energy density and pressure which represent the back reaction effect. |
gr-qc/0405117 | Ghazal Geshnizjani | Ghazal Geshnizjani, Niayesh Afshordi | Coarse-Grained Back Reaction in Single Scalar Field Driven Inflation | 6 pages, 1 figure | JCAP 0501 (2005) 011 | 10.1088/1475-7516/2005/01/011 | null | gr-qc astro-ph hep-ph hep-th | null | We introduce a self-consistent stochastic coarse-graining method, which
includes both metric and scalar field fluctuations, to investigate the back
reaction of long wavelength perturbations in single-scalar driven inflation, up
to the second (one loop) order. We demonstrate that, although back reaction
cannot be significant during the last 70 e-foldings of inflation with a smooth
potential, there exist non-smooth inflaton potentials which allow significant
back reaction, and are also consistent with cosmological observations. Such
non-smooth potentials may lead to the generation of massive primordial black
holes, which could be further used to constrain/verify these models.
| [
{
"created": "Fri, 21 May 2004 20:12:14 GMT",
"version": "v1"
}
] | 2009-08-29 | [
[
"Geshnizjani",
"Ghazal",
""
],
[
"Afshordi",
"Niayesh",
""
]
] | We introduce a self-consistent stochastic coarse-graining method, which includes both metric and scalar field fluctuations, to investigate the back reaction of long wavelength perturbations in single-scalar driven inflation, up to the second (one loop) order. We demonstrate that, although back reaction cannot be significant during the last 70 e-foldings of inflation with a smooth potential, there exist non-smooth inflaton potentials which allow significant back reaction, and are also consistent with cosmological observations. Such non-smooth potentials may lead to the generation of massive primordial black holes, which could be further used to constrain/verify these models. |
1701.04136 | Magd Elias Kahil | Magd E. Kahil | Spinning and Spinning Deviation Equations for Special Types of Gauge
Theories of Gravity | 15 pages, LaTeX file | null | 10.1134/S0202289318010103 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The problem of spinning and spin deviation equations for particles as defined
by their microscopic effect has led many authors to revisit non-Riemannian
geometry for being described torsion and its relation with the spin of
elementary particles. We obtain a new method to detect the existence of torsion
by deriving the equations of spin deviations in different classes of
non-Riemannian geometries, using a modified Bazanski method. We find that
translational gauge potentials and rotational gauge potentials regulate the
spin deviation equation in the presence of Poincare gauge field theory of
gravity.
| [
{
"created": "Mon, 16 Jan 2017 01:41:53 GMT",
"version": "v1"
}
] | 2018-04-04 | [
[
"Kahil",
"Magd E.",
""
]
] | The problem of spinning and spin deviation equations for particles as defined by their microscopic effect has led many authors to revisit non-Riemannian geometry for being described torsion and its relation with the spin of elementary particles. We obtain a new method to detect the existence of torsion by deriving the equations of spin deviations in different classes of non-Riemannian geometries, using a modified Bazanski method. We find that translational gauge potentials and rotational gauge potentials regulate the spin deviation equation in the presence of Poincare gauge field theory of gravity. |
gr-qc/0301067 | Jian Qi Shen | Jian Qi Shen | Gravitational Analogues, Geometric Effects and Gravitomagnetic Charge | 9 pages,0 figures, Latex | Gen.Rel.Grav. 34 (2002) 1423-1435 | 10.1023/A:1020082903104 | null | gr-qc | null | This essay discusses some geometric effects associated with gravitomagnetic
fields and gravitomagnetic charge as well as the gravity theory of the latter.
Gravitomagnetic charge is the duality of gravitoelectric charge (mass) and is
therefore also termed the dual mass which represents the topological property
of gravitation. The field equation of gravitomagnetic matter is suggested and a
static spherically symmetric solution of this equation is offered. A possible
explanation of the anomalous acceleration acting on Pioneer spacecrafts are
briefly proposed.
| [
{
"created": "Mon, 20 Jan 2003 06:00:04 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Feb 2003 08:05:08 GMT",
"version": "v2"
}
] | 2017-08-30 | [
[
"Shen",
"Jian Qi",
""
]
] | This essay discusses some geometric effects associated with gravitomagnetic fields and gravitomagnetic charge as well as the gravity theory of the latter. Gravitomagnetic charge is the duality of gravitoelectric charge (mass) and is therefore also termed the dual mass which represents the topological property of gravitation. The field equation of gravitomagnetic matter is suggested and a static spherically symmetric solution of this equation is offered. A possible explanation of the anomalous acceleration acting on Pioneer spacecrafts are briefly proposed. |
1211.5176 | Daniel Mart\'in-de Blas | Laura Castell\'o Gomar, Jer\'onimo Cortez, Daniel Mart\'in-de Blas,
Guillermo A. Mena Marug\'an and Jos\'e M. Velhinho | Uniqueness of the Fock quantization of scalar fields in spatially flat
cosmological spacetimes | 15 pages, version accepted for publication in JCAP | JCAP 1211:001, 2012 | 10.1088/1475-7516/2012/11/001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Fock quantization of scalar fields in (generically) time
dependent scenarios, focusing on the case in which the field propagation occurs
in --either a background or effective-- spacetime with spatial sections of flat
compact topology. The discussion finds important applications in cosmology,
like e.g. in the description of test Klein-Gordon fields and scalar
perturbations in Friedmann-Robertson-Walker spacetime in the observationally
favored flat case. Two types of ambiguities in the quantization are analyzed.
First, the infinite ambiguity existing in the choice of a Fock representation
for the canonical commutation relations, understandable as the freedom in the
choice of inequivalent vacua for a given field. Besides, in cosmological
situations, it is customary to scale the fields by time dependent functions,
which absorb part of the evolution arising from the spacetime, which is treated
classically. This leads to an additional ambiguity, this time in the choice of
a canonical pair of field variables. We show that both types of ambiguities are
removed by the requirements of (a) invariance of the vacuum under the
symmetries of the three-torus, and (b) unitary implementation of the dynamics
in the quantum theory. In this way, one arrives at a unique class of unitarily
equivalent Fock quantizations for the system. This result provides considerable
robustness to the quantum predictions and renders meaningful the confrontation
with observation.
| [
{
"created": "Thu, 22 Nov 2012 00:09:55 GMT",
"version": "v1"
}
] | 2012-11-26 | [
[
"Gomar",
"Laura Castelló",
""
],
[
"Cortez",
"Jerónimo",
""
],
[
"Blas",
"Daniel Martín-de",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
],
[
"Velhinho",
"José M.",
""
]
] | We study the Fock quantization of scalar fields in (generically) time dependent scenarios, focusing on the case in which the field propagation occurs in --either a background or effective-- spacetime with spatial sections of flat compact topology. The discussion finds important applications in cosmology, like e.g. in the description of test Klein-Gordon fields and scalar perturbations in Friedmann-Robertson-Walker spacetime in the observationally favored flat case. Two types of ambiguities in the quantization are analyzed. First, the infinite ambiguity existing in the choice of a Fock representation for the canonical commutation relations, understandable as the freedom in the choice of inequivalent vacua for a given field. Besides, in cosmological situations, it is customary to scale the fields by time dependent functions, which absorb part of the evolution arising from the spacetime, which is treated classically. This leads to an additional ambiguity, this time in the choice of a canonical pair of field variables. We show that both types of ambiguities are removed by the requirements of (a) invariance of the vacuum under the symmetries of the three-torus, and (b) unitary implementation of the dynamics in the quantum theory. In this way, one arrives at a unique class of unitarily equivalent Fock quantizations for the system. This result provides considerable robustness to the quantum predictions and renders meaningful the confrontation with observation. |
gr-qc/0312081 | Robert Oeckl | Robert Oeckl (CPT) | The general boundary approach to quantum gravity | 9 pages, LaTeX + AMS + XYpic, contribution to proceedings of ICP2004,
Tehran, Iran, January 2004 | Proceedings of the First International Conference on Physics
(ICP), Amirkabir University, Tehran, 2004, pp. 257-265 | null | CPT-2003/C.4619 | gr-qc hep-th | null | We present an approach to quantum gravity based on the general boundary
formulation of quantum mechanics, path integral quantization, spin foam models
and renormalization.
| [
{
"created": "Wed, 17 Dec 2003 18:59:16 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Oeckl",
"Robert",
"",
"CPT"
]
] | We present an approach to quantum gravity based on the general boundary formulation of quantum mechanics, path integral quantization, spin foam models and renormalization. |
gr-qc/9411032 | null | Norman Cruz and Jorge Zanelli | Stellar Equilibrium in 2+1 Dimensions | 11 pages, revtex, no figures | Class.Quant.Grav.12:975-982,1995 | 10.1088/0264-9381/12/4/008 | CECS/USACH-94/2 | gr-qc | null | The hydrostatic equilibrium of a $2+1$ dimensional perfect fluid star in
asymptotically anti-de Sitter space is discussed. The interior geometry matches
the exterior $2+1$ black-hole solution. An upper mass limit is found, analogous
to Buchdahl's theorem in 3+1, and the possibility of collapse is discussed. The
case of a uniform matter density is solved exactly and a new interior solution
is presented.
| [
{
"created": "Sat, 12 Nov 1994 23:19:17 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Cruz",
"Norman",
""
],
[
"Zanelli",
"Jorge",
""
]
] | The hydrostatic equilibrium of a $2+1$ dimensional perfect fluid star in asymptotically anti-de Sitter space is discussed. The interior geometry matches the exterior $2+1$ black-hole solution. An upper mass limit is found, analogous to Buchdahl's theorem in 3+1, and the possibility of collapse is discussed. The case of a uniform matter density is solved exactly and a new interior solution is presented. |
gr-qc/0506054 | Ding-Fang Zeng | Ding-fang Zeng and Yi-hong Gao | A Question About Standard Cosmology and Extremely Dense Stars'
Collapsing | 4 and half pages, 1 figures, two column styles | null | null | null | gr-qc | null | We ask if the conventional variable separation techniques in the studying of
standard cosmology and the collapsing of extremely dense stars introduce
Newton's absolute space-time concepts. If this is the case, then a completely
relative cosmology is needed. We build the basic frame-works for such a
cosmology and illustrate that, the observed luminosity-distance v.s. red-shift
relations of supernovaes can be explained naturally even without any conception
of dark energies.
| [
{
"created": "Thu, 9 Jun 2005 09:59:45 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Zeng",
"Ding-fang",
""
],
[
"Gao",
"Yi-hong",
""
]
] | We ask if the conventional variable separation techniques in the studying of standard cosmology and the collapsing of extremely dense stars introduce Newton's absolute space-time concepts. If this is the case, then a completely relative cosmology is needed. We build the basic frame-works for such a cosmology and illustrate that, the observed luminosity-distance v.s. red-shift relations of supernovaes can be explained naturally even without any conception of dark energies. |
2212.12466 | Behzad Tajahmad | Behzad Tajahmad | Formulating the fluctuations of space-time and a justification for
applying fractional gravity | null | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known that in quantum gravity, the very geometry of space and time
is subject to continual fluctuation. The mathematical formulation for this old
theory is still lacking. This article formulates this more than forty-year-old
theory of quantum gravity. On the other hand, recent attention has been paid to
fractional gravity. Although this type of gravity leads to brilliant results,
we have no deep reason for applying it other than that it works. In this paper,
it is demonstrated that quantum gravity equations become fractional when
space-time fluctuations are taken into account. Therefore, here a reasonable
root and argument for applying fractional gravity are found: ``Fractional
quantum gravity is generated by stochastic fluctuations of space-time''. For
clarification, Einstein-Hilbert theory along with a scalar field is
investigated in deformed and non-deformed minisuperspaces. The results
illustrate a transition from decelerated to accelerated expansion
(late-time-accelerated expansion).
| [
{
"created": "Fri, 23 Dec 2022 16:52:18 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Oct 2023 11:43:30 GMT",
"version": "v2"
},
{
"created": "Sat, 2 Dec 2023 15:56:06 GMT",
"version": "v3"
}
] | 2023-12-05 | [
[
"Tajahmad",
"Behzad",
""
]
] | It is well known that in quantum gravity, the very geometry of space and time is subject to continual fluctuation. The mathematical formulation for this old theory is still lacking. This article formulates this more than forty-year-old theory of quantum gravity. On the other hand, recent attention has been paid to fractional gravity. Although this type of gravity leads to brilliant results, we have no deep reason for applying it other than that it works. In this paper, it is demonstrated that quantum gravity equations become fractional when space-time fluctuations are taken into account. Therefore, here a reasonable root and argument for applying fractional gravity are found: ``Fractional quantum gravity is generated by stochastic fluctuations of space-time''. For clarification, Einstein-Hilbert theory along with a scalar field is investigated in deformed and non-deformed minisuperspaces. The results illustrate a transition from decelerated to accelerated expansion (late-time-accelerated expansion). |
1301.1159 | Anton Galajinsky | Anton Galajinsky | Near horizon geometry of extremal black holes and Banados-Silk-West
effect | V5:10 pages, major revision, title changed; the version published in
PRD | Phys.Rev. D88 (2013) 027505 | 10.1103/PhysRevD.88.027505 | LMP-TPU-01/13 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, Banados, Silk and West analyzed a collision of two particles near
the horizon of the extremal Kerr black hole and demonstrated that the energy in
the center-of-mass frame can be arbitrarily large provided the angular momentum
of one of the colliding particles takes a special value. As is known, the
vicinity of the extremal Kerr black hole horizon can be viewed as a complete
vacuum spacetime in its own right. In this work, we consider a collision of two
neutral particles within the context of the near horizon extremal Kerr geometry
and demonstrate that the energy in the center-of-mass frame is finite for any
admissible value of the particle parameters. An explanation of why the two
approaches disagree on the Banados-Silk-West effect is given.
| [
{
"created": "Mon, 7 Jan 2013 11:44:11 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Jan 2013 08:20:25 GMT",
"version": "v2"
},
{
"created": "Tue, 15 Jan 2013 08:53:57 GMT",
"version": "v3"
},
{
"created": "Wed, 20 Feb 2013 11:31:17 GMT",
"version": "v4"
},
{
"cr... | 2013-07-30 | [
[
"Galajinsky",
"Anton",
""
]
] | Recently, Banados, Silk and West analyzed a collision of two particles near the horizon of the extremal Kerr black hole and demonstrated that the energy in the center-of-mass frame can be arbitrarily large provided the angular momentum of one of the colliding particles takes a special value. As is known, the vicinity of the extremal Kerr black hole horizon can be viewed as a complete vacuum spacetime in its own right. In this work, we consider a collision of two neutral particles within the context of the near horizon extremal Kerr geometry and demonstrate that the energy in the center-of-mass frame is finite for any admissible value of the particle parameters. An explanation of why the two approaches disagree on the Banados-Silk-West effect is given. |
2404.07055 | Che-Yu Chen | Che-Yu Chen, Hung-Yi Pu | Observational features of reflection asymmetric black holes | 14 pages, 7 figures | null | null | RIKEN-iTHEMS-Report-24 | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Kerr spacetime is symmetric with respect to a well-defined equatorial
plane. When testing the equatorial reflection symmetry of an isolated black
hole, one is at the same time testing the Kerr hypothesis in General
Relativity. In this work, we investigate the possible observational features
when a Keplerian disk is surrounding a rotating black hole without reflection
symmetry. When such symmetry is broken, generically, the photon trajectories
around the black hole and the Keplerian orbits on the accretion disk are
distorted vertically away from the equatorial plane by an amount that depends
on their distance to the black hole. In the reflection asymmetric spacetime we
are considering, these two kinds of orbits are distorted in opposite
directions. Interestingly, while the size and shape of black hole shadows
closely resemble those of Kerr black holes, distinct observational
characteristics can emerge in the disk image and emission line profiles. When
observing the disk edge-on, a pronounced concave shape may appear along its
innermost edge on the incoming side. Furthermore, distinctive horn-like
features might be observed on the spectral line profile at the blue-shifted
side. These special features can serve as compelling indicators of the
reflection asymmetry present in rotating black holes.
| [
{
"created": "Wed, 10 Apr 2024 14:45:21 GMT",
"version": "v1"
}
] | 2024-04-11 | [
[
"Chen",
"Che-Yu",
""
],
[
"Pu",
"Hung-Yi",
""
]
] | The Kerr spacetime is symmetric with respect to a well-defined equatorial plane. When testing the equatorial reflection symmetry of an isolated black hole, one is at the same time testing the Kerr hypothesis in General Relativity. In this work, we investigate the possible observational features when a Keplerian disk is surrounding a rotating black hole without reflection symmetry. When such symmetry is broken, generically, the photon trajectories around the black hole and the Keplerian orbits on the accretion disk are distorted vertically away from the equatorial plane by an amount that depends on their distance to the black hole. In the reflection asymmetric spacetime we are considering, these two kinds of orbits are distorted in opposite directions. Interestingly, while the size and shape of black hole shadows closely resemble those of Kerr black holes, distinct observational characteristics can emerge in the disk image and emission line profiles. When observing the disk edge-on, a pronounced concave shape may appear along its innermost edge on the incoming side. Furthermore, distinctive horn-like features might be observed on the spectral line profile at the blue-shifted side. These special features can serve as compelling indicators of the reflection asymmetry present in rotating black holes. |
1204.1546 | Chih-Hung Wang | Yu-Huei Wu, Chih-Hung Wang | Local and global structure of domain wall space-times | 9 pages, no figure | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a general proof on the equivalence of the comoving-coordinate
approach, where the wall is fixed at a constant coordinate variable, and
moving-wall approach, where the wall is moving in a background static
space-time, in the domain wall space-times without reflection symmetry. We
further provide a general procedure to construct the comoving coordinates in
the domain wall space-times, where the two regions separated by an infinite
thin wall have different cosmological constant $\Lambda$ and Schwartzschild
mass $M$. By solving Israel's junction conditions in the thin-wall limit, the
gravitational fields of spherical, planar and hyperbolic domain wall
space-times with M=0 in the two different comoving coordinate systems are
obtained. We finally discuss the global structure of these domain wall
space-times.
| [
{
"created": "Fri, 6 Apr 2012 19:47:35 GMT",
"version": "v1"
}
] | 2012-04-09 | [
[
"Wu",
"Yu-Huei",
""
],
[
"Wang",
"Chih-Hung",
""
]
] | We present a general proof on the equivalence of the comoving-coordinate approach, where the wall is fixed at a constant coordinate variable, and moving-wall approach, where the wall is moving in a background static space-time, in the domain wall space-times without reflection symmetry. We further provide a general procedure to construct the comoving coordinates in the domain wall space-times, where the two regions separated by an infinite thin wall have different cosmological constant $\Lambda$ and Schwartzschild mass $M$. By solving Israel's junction conditions in the thin-wall limit, the gravitational fields of spherical, planar and hyperbolic domain wall space-times with M=0 in the two different comoving coordinate systems are obtained. We finally discuss the global structure of these domain wall space-times. |
2103.15832 | Paulo Luz | Jos\'e P. S. Lemos and Paulo Luz | All fundamental electrically charged thin shells in general relativity:
From star shells to tension shell black holes and regular black holes and
beyond | 56 pages including 31 figures, plus 2 appendices including 2 figures,
plus references; all together 67 pages and 33 figures | Phys. Rev. D 103, 104046 (2021) | 10.1103/PhysRevD.103.104046 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We classify all fundamental electrically charged thin shells in general
relativity, i.e., static spherically symmetric perfect fluid thin shells with a
Minkowski spacetime interior and a Reissner-Nordstr\"om spacetime exterior,
characterized by the spacetime mass and electric charge. The fundamental shell
can exist in three states, nonextremal, extremal, and overcharged. The
nonextremal state allows the shell to be located such that its radius can be
outside its own gravitational radius, or can be inside its own Cauchy radius.
The extremal state allows the shell to be located such that its radius can be
outside its own gravitational radius, or can be inside it. The overcharged
state allows the shell to be located anywhere. There is a further division, one
has to specify the orientation of the shell, i.e., whether the normal out of
the shell points toward increasing or decreasing radii. There is still a
subdivision in the extremal state when the shell is at the gravitational
radius, in that the shell can approach it from above or from below. The shell
is assumed to be composed of an electrically charged perfect fluid, and the
energy conditions are tested. Carter-Penrose diagrams are drawn for the shell
spacetimes. There are fourteen cases in the classification of the fundamental
shells, namely, nonextremal star shells, nonextremal tension shell black holes,
nonextremal tension shell regular and nonregular black holes, nonextremal
compact shell naked singularities, Majumdar-Papapetrou star shells, extremal
tension shell singularities, extremal tension shell regular and nonregular
black holes, Majumdar-Papapetrou compact shell naked singularities,
Majumdar-Papapetrou shell quasiblack holes, extremal null shell quasinonblack
holes, extremal null shell singularities, Majumdar-Papapetrou null shell
singularities, overcharged star shells, and overcharged compact shell naked
singularities.
| [
{
"created": "Mon, 29 Mar 2021 18:00:01 GMT",
"version": "v1"
}
] | 2021-05-26 | [
[
"Lemos",
"José P. S.",
""
],
[
"Luz",
"Paulo",
""
]
] | We classify all fundamental electrically charged thin shells in general relativity, i.e., static spherically symmetric perfect fluid thin shells with a Minkowski spacetime interior and a Reissner-Nordstr\"om spacetime exterior, characterized by the spacetime mass and electric charge. The fundamental shell can exist in three states, nonextremal, extremal, and overcharged. The nonextremal state allows the shell to be located such that its radius can be outside its own gravitational radius, or can be inside its own Cauchy radius. The extremal state allows the shell to be located such that its radius can be outside its own gravitational radius, or can be inside it. The overcharged state allows the shell to be located anywhere. There is a further division, one has to specify the orientation of the shell, i.e., whether the normal out of the shell points toward increasing or decreasing radii. There is still a subdivision in the extremal state when the shell is at the gravitational radius, in that the shell can approach it from above or from below. The shell is assumed to be composed of an electrically charged perfect fluid, and the energy conditions are tested. Carter-Penrose diagrams are drawn for the shell spacetimes. There are fourteen cases in the classification of the fundamental shells, namely, nonextremal star shells, nonextremal tension shell black holes, nonextremal tension shell regular and nonregular black holes, nonextremal compact shell naked singularities, Majumdar-Papapetrou star shells, extremal tension shell singularities, extremal tension shell regular and nonregular black holes, Majumdar-Papapetrou compact shell naked singularities, Majumdar-Papapetrou shell quasiblack holes, extremal null shell quasinonblack holes, extremal null shell singularities, Majumdar-Papapetrou null shell singularities, overcharged star shells, and overcharged compact shell naked singularities. |
2007.05875 | John Klauder | John R. Klauder | An Ultralocal Classical and Quantum Gravity Theory | 8 pages; an ultralocal gravity is quantized proving that full gravity
can be affine quantized: a minor equation or two errors fixed | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An ultralocal form of any classical field theory eliminates all spatial
derivatives in its action functional, e.g., in its Hamiltonian functional
density. It has been applied to covariant scalar field theories and even to
Einstein's general relativity, by Pilati, as an initial term in a perturbation
series that aimed to restore all omitted derivatives. Previously, the author
has quantized ultralocal scalar fields by affine quantization to show that
these non-renormalizanle theories can be correctly quantized by affine
quantization; the story of such scalar models is discussed in this paper. The
present paper will also show that ultralocal gravity can be successfully
quantized by affine quantization.
The purpose of this study is that a successful affine quantization of any
ultralocal field problem implies that, with properly restored derivatives, the
classical theory can, in principle, be guaranteed a successful result using
either a canonical quantization or an affine quantization. In particular,
Einstein's gravity requires an affine quantization, and it will be successful.
| [
{
"created": "Sat, 11 Jul 2020 23:54:32 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Aug 2020 02:26:26 GMT",
"version": "v2"
},
{
"created": "Wed, 2 Sep 2020 18:35:05 GMT",
"version": "v3"
}
] | 2020-09-04 | [
[
"Klauder",
"John R.",
""
]
] | An ultralocal form of any classical field theory eliminates all spatial derivatives in its action functional, e.g., in its Hamiltonian functional density. It has been applied to covariant scalar field theories and even to Einstein's general relativity, by Pilati, as an initial term in a perturbation series that aimed to restore all omitted derivatives. Previously, the author has quantized ultralocal scalar fields by affine quantization to show that these non-renormalizanle theories can be correctly quantized by affine quantization; the story of such scalar models is discussed in this paper. The present paper will also show that ultralocal gravity can be successfully quantized by affine quantization. The purpose of this study is that a successful affine quantization of any ultralocal field problem implies that, with properly restored derivatives, the classical theory can, in principle, be guaranteed a successful result using either a canonical quantization or an affine quantization. In particular, Einstein's gravity requires an affine quantization, and it will be successful. |
1212.3947 | Daniel Mart\'in-de Blas | Jer\'onimo Cortez, Luc\'ia Fonseca, Daniel Mart\'in-de Blas and
Guillermo A. Mena Marug\'an | Uniqueness of the Fock quantization of scalar fields under mode
preserving canonical transformations varying in time | 12 pages, submitted to Phys. Rev. D | Phys.Rev.D87:044013,2013 | 10.1103/PhysRevD.87.044013 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Fock quantization of scalar fields of Klein-Gordon type in
nonstationary scenarios propagating in spacetimes with compact spatial
sections, allowing for different field descriptions that are related by means
of certain nonlocal linear canonical transformations that depend on time. More
specifically, we consider transformations that do not mix eigenmodes of the
Laplace-Beltrami operator, which are supposed to be dynamically decoupled. In
addition, we assume that the canonical transformations admit an asymptotic
expansion for large eigenvalues (in norm) of the Laplace-Beltrami operator in
the form of a series of half integer powers. Canonical transformations of this
kind are found in the study of scalar perturbations in inflationary
cosmologies, relating for instance the physical degrees of freedom of these
perturbations after gauge fixing with gauge invariant canonical pairs of
Bardeen quantities. We characterize all possible transformations of this type
and show that, independently of the initial field description, the combined
criterion of requiring (i) invariance of the vacuum under the spatial
symmetries and (ii) a unitary implementation of the dynamics, leads to a unique
equivalence class of Fock quantizations, all of them related by unitary
transformations. This conclusion provides even further robustness to the
validity of the proposed criterion, completing the results that have already
appeared in the literature about the uniqueness of the Fock quantization under
changes of field description when one permits exclusively local time dependent
canonical transformations that scale the field configuration.
| [
{
"created": "Mon, 17 Dec 2012 09:58:18 GMT",
"version": "v1"
}
] | 2013-02-06 | [
[
"Cortez",
"Jerónimo",
""
],
[
"Fonseca",
"Lucía",
""
],
[
"Blas",
"Daniel Martín-de",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
]
] | We study the Fock quantization of scalar fields of Klein-Gordon type in nonstationary scenarios propagating in spacetimes with compact spatial sections, allowing for different field descriptions that are related by means of certain nonlocal linear canonical transformations that depend on time. More specifically, we consider transformations that do not mix eigenmodes of the Laplace-Beltrami operator, which are supposed to be dynamically decoupled. In addition, we assume that the canonical transformations admit an asymptotic expansion for large eigenvalues (in norm) of the Laplace-Beltrami operator in the form of a series of half integer powers. Canonical transformations of this kind are found in the study of scalar perturbations in inflationary cosmologies, relating for instance the physical degrees of freedom of these perturbations after gauge fixing with gauge invariant canonical pairs of Bardeen quantities. We characterize all possible transformations of this type and show that, independently of the initial field description, the combined criterion of requiring (i) invariance of the vacuum under the spatial symmetries and (ii) a unitary implementation of the dynamics, leads to a unique equivalence class of Fock quantizations, all of them related by unitary transformations. This conclusion provides even further robustness to the validity of the proposed criterion, completing the results that have already appeared in the literature about the uniqueness of the Fock quantization under changes of field description when one permits exclusively local time dependent canonical transformations that scale the field configuration. |
2303.13164 | Riasat Ali | Muhammad Asgher, Anosha Karamat, Rimsha Babar and Riasat Ali | Tunneling and entropy analysis of parameterized black hole with rotating
case | 13 Pages, 8 figures, Published in Physica Scripta | Phys. Scr. 98 (2023) 045023 | 10.1088/1402-4896/acc3c7 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this work, we study the parameterized black hole solution by applying the
Newman-Janis approach and also examine the Hawking temperature. We consider a
Lagrangian field equation associated with the generalized uncertainty principle
to study the motion of boson particles. By using semi-classical phenomenon, we
analyze the modified Hawking temperature and graphically check the effects of
deformation, rotation and correction parameter on black hole geometry.
Furthermore, we investigate the logarithmic corrected entropy and also analyze
the graphical behavior of deformation and quantum gravity parameter on the
logarithmic corrected entropy of black hole.
| [
{
"created": "Thu, 23 Mar 2023 10:30:16 GMT",
"version": "v1"
}
] | 2023-03-24 | [
[
"Asgher",
"Muhammad",
""
],
[
"Karamat",
"Anosha",
""
],
[
"Babar",
"Rimsha",
""
],
[
"Ali",
"Riasat",
""
]
] | In this work, we study the parameterized black hole solution by applying the Newman-Janis approach and also examine the Hawking temperature. We consider a Lagrangian field equation associated with the generalized uncertainty principle to study the motion of boson particles. By using semi-classical phenomenon, we analyze the modified Hawking temperature and graphically check the effects of deformation, rotation and correction parameter on black hole geometry. Furthermore, we investigate the logarithmic corrected entropy and also analyze the graphical behavior of deformation and quantum gravity parameter on the logarithmic corrected entropy of black hole. |
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