id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1405.2803 | Bogeun Gwak | Bogeun Gwak and Bum-Hoon Lee | Instability of Rotating Anti-de Sitter Black Holes | 11 pages, 5 figures, published version in PRD | Phys. Rev. D 91, 064020 (2015) | 10.1103/PhysRevD.91.064020 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the instability of higher-dimensional rotating anti-de Sitter black
holes through fragmentation. Fragmentation occurs when black holes rotate too
fast to sustain their horizon, and then the black holes are broken into small
pieces. Using this process, we test the stability of AdS black holes and
discover the dynamical upper bounds of the angular momentum and the
cosmological constant. We show that AdS black holes can exist stably within
limited parameter ranges in the general dimensions. The parameter ranges are
obtained numerically in terms of angular momentum and cosmological constant.
| [
{
"created": "Mon, 12 May 2014 15:27:19 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Mar 2015 07:17:15 GMT",
"version": "v2"
}
] | 2015-03-18 | [
[
"Gwak",
"Bogeun",
""
],
[
"Lee",
"Bum-Hoon",
""
]
] | We study the instability of higher-dimensional rotating anti-de Sitter black holes through fragmentation. Fragmentation occurs when black holes rotate too fast to sustain their horizon, and then the black holes are broken into small pieces. Using this process, we test the stability of AdS black holes and discover the dynamical upper bounds of the angular momentum and the cosmological constant. We show that AdS black holes can exist stably within limited parameter ranges in the general dimensions. The parameter ranges are obtained numerically in terms of angular momentum and cosmological constant. |
2402.10501 | Jean-Luc Lehners | Jean-Luc Lehners | NUTs, Bolts and Stokes Phenomena in the No-Boundary Wave Function | 27 pages, 14 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note, we revisit and extend the analysis of the no-boundary wave
function for the minisuperspace model in which the universe is described by a
biaxial Bianchi IX metric. As matter content, we simply assume a positive
cosmological constant. We find that two Stokes phenomena occur, at large
squashing parameters of the spatial section of the universe. These Stokes
phenomena eliminate potentially dominant Taub-Bolt-de Sitter saddle point
geometries and are crucial for the consistency of the model. They also imply
that phase transitions occur at certain levels of squashing, where NUT and Bolt
saddle points exchange dominance.
| [
{
"created": "Fri, 16 Feb 2024 08:20:31 GMT",
"version": "v1"
}
] | 2024-02-19 | [
[
"Lehners",
"Jean-Luc",
""
]
] | In this note, we revisit and extend the analysis of the no-boundary wave function for the minisuperspace model in which the universe is described by a biaxial Bianchi IX metric. As matter content, we simply assume a positive cosmological constant. We find that two Stokes phenomena occur, at large squashing parameters of the spatial section of the universe. These Stokes phenomena eliminate potentially dominant Taub-Bolt-de Sitter saddle point geometries and are crucial for the consistency of the model. They also imply that phase transitions occur at certain levels of squashing, where NUT and Bolt saddle points exchange dominance. |
0910.3484 | Vitaly Melnikov Nikolaevich | V. N. Melnikov | Variations of constants as a test of gravity, cosmology and unified
models | 21 pages, Latex | Grav. Cosmol. 13, No. 2, 81-100 (2007) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitation as a fundamental interaction that governs all phenomena at large
and very small scales, but still not well understood at a quantum level, is a
cardinal missing link in unification of all physical interactions. Discovery of
the present acceleration of the Universe, the dark matter and dark energy
problems are also a great challenge to modern physics, which may lead to a new
revolution in it. Integrable multidimensional models of gravitation and
cosmology make up one of the proper approaches to studying basic issues and
strong field objects, the early and present Universe and black hole (BH)
physics in particular. Our main results within this approach are described for
both cosmology and BH physics. Problems of the absolute G measurements and its
possible time and range variations are reflections of the unification problem.
The choice, nature, classification and precision of determination of the
fundamental physical constants as well as their role in a transition, expected
in 2011, to new definitions of the main SI units, supposed to be based on
fundamental physical constants and stable quantum phenomena, are described. The
problem of temporal variations of constants is also discussed, temporal and
spatial variations of G in particular. A need for further absolute measurements
of G, its possible range and time variations is pointed out. The multipurpose
space project SEE is briefly described, aimed at measuring G and its stability
in space and time, with precision 3-4 orders better than at present. It may
answer many important questions posed by gravitation, cosmology and unified
theories. A project of a laboratory experiment for testing possible deviations
from the Newton law is also presented.
| [
{
"created": "Mon, 19 Oct 2009 09:01:44 GMT",
"version": "v1"
}
] | 2009-11-30 | [
[
"Melnikov",
"V. N.",
""
]
] | Gravitation as a fundamental interaction that governs all phenomena at large and very small scales, but still not well understood at a quantum level, is a cardinal missing link in unification of all physical interactions. Discovery of the present acceleration of the Universe, the dark matter and dark energy problems are also a great challenge to modern physics, which may lead to a new revolution in it. Integrable multidimensional models of gravitation and cosmology make up one of the proper approaches to studying basic issues and strong field objects, the early and present Universe and black hole (BH) physics in particular. Our main results within this approach are described for both cosmology and BH physics. Problems of the absolute G measurements and its possible time and range variations are reflections of the unification problem. The choice, nature, classification and precision of determination of the fundamental physical constants as well as their role in a transition, expected in 2011, to new definitions of the main SI units, supposed to be based on fundamental physical constants and stable quantum phenomena, are described. The problem of temporal variations of constants is also discussed, temporal and spatial variations of G in particular. A need for further absolute measurements of G, its possible range and time variations is pointed out. The multipurpose space project SEE is briefly described, aimed at measuring G and its stability in space and time, with precision 3-4 orders better than at present. It may answer many important questions posed by gravitation, cosmology and unified theories. A project of a laboratory experiment for testing possible deviations from the Newton law is also presented. |
0803.2003 | Stefan Hollands | S. Hollands and R. M. Wald | Axiomatic quantum field theory in curved spacetime | Latex, 44 pages, 2 figures | Commun.Math.Phys.293:85-125,2010 | 10.1007/s00220-009-0880-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The usual formulations of quantum field theory in Minkowski spacetime make
crucial use of features--such as Poincare invariance and the existence of a
preferred vacuum state--that are very special to Minkowski spacetime. In order
to generalize the formulation of quantum field theory to arbitrary globally
hyperbolic curved spacetimes, it is essential that the theory be formulated in
an entirely local and covariant manner, without assuming the presence of a
preferred state. We propose a new framework for quantum field theory, in which
the existence of an Operator Product Expansion (OPE) is elevated to a
fundamental status, and, in essence, all of the properties of the quantum field
theory are determined by its OPE. We provide general axioms for the OPE
coefficients of a quantum field theory. These include a local and covariance
assumption (implying that the quantum field theory is locally and covariantly
constructed from the spacetime metric), a microlocal spectrum condition, an
"associativity" condition, and the requirement that the coefficient of the
identity in the OPE of the product of a field with its adjoint have positive
scaling degree. We prove curved spacetime versions of the spin-statistics
theorem and the PCT theorem. Some potentially significant further implications
of our new viewpoint on quantum field theory are discussed.
| [
{
"created": "Thu, 13 Mar 2008 16:34:29 GMT",
"version": "v1"
}
] | 2009-12-15 | [
[
"Hollands",
"S.",
""
],
[
"Wald",
"R. M.",
""
]
] | The usual formulations of quantum field theory in Minkowski spacetime make crucial use of features--such as Poincare invariance and the existence of a preferred vacuum state--that are very special to Minkowski spacetime. In order to generalize the formulation of quantum field theory to arbitrary globally hyperbolic curved spacetimes, it is essential that the theory be formulated in an entirely local and covariant manner, without assuming the presence of a preferred state. We propose a new framework for quantum field theory, in which the existence of an Operator Product Expansion (OPE) is elevated to a fundamental status, and, in essence, all of the properties of the quantum field theory are determined by its OPE. We provide general axioms for the OPE coefficients of a quantum field theory. These include a local and covariance assumption (implying that the quantum field theory is locally and covariantly constructed from the spacetime metric), a microlocal spectrum condition, an "associativity" condition, and the requirement that the coefficient of the identity in the OPE of the product of a field with its adjoint have positive scaling degree. We prove curved spacetime versions of the spin-statistics theorem and the PCT theorem. Some potentially significant further implications of our new viewpoint on quantum field theory are discussed. |
2006.14153 | David Alejandro Tamayo Ram\'irez | David Tamayo | Thermodynamics of viscous dark energy for the late future time universe | 12 pages | Rev. Mex. Fis., 68, 2 (2022) | 10.31349/RevMexFis.68.020704 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we explore the thermodynamic aspects of dark energy for late
future time universe in two different scenarios: as a perfect fluid with
constant and variable equation of state parameter; and as dissipative fluid
described by a barotropic equation of state with bulk viscosity in the
framework of the Eckart theory and the full Israel-Stewart theory. We explore
cosmological solutions for a flat, homogeneous and isotropic universe; and we
assume the late future time behavior when the dark energy dominates the cosmic
evolution. When modeled as a perfect fluid with a dynamical equation of state,
$p=w(a)\rho$, the dark energy has an energy density, temperature and entropy
well defined and an interesting result is that there is no entropy production
even though been dynamical. For dissipative dark energy, in the Eckart theory
two cases are studied: $\xi=const.$ and $\xi =(\beta/\sqrt{3}) \rho^{1/2}$; it
is found that the entropy grows exponentially for the first case and as a
power-law for the second. In the Israel-Stewart theory we consider a $\xi
=\xi_0 \rho^{1/2}$ and a relaxation time $\tau = \xi/\rho$; an analytical Big
Rip solution is obtained with a power-law entropy. In all cases a power-law
relation between temperature and energy density is obtained. In order to
maintain the second law of thermodynamics theoretical constraints for the
equation of state are found in the different dark energy models studied. A
barotropic dark fluid with $w<-1$ is thermodynamically difficult to support,
but the overall effect of bulk viscosity in certain cases allows a phantom
regime without thermodynamic anomalies.
| [
{
"created": "Thu, 25 Jun 2020 03:22:13 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Mar 2022 21:26:57 GMT",
"version": "v2"
}
] | 2022-03-03 | [
[
"Tamayo",
"David",
""
]
] | In this work we explore the thermodynamic aspects of dark energy for late future time universe in two different scenarios: as a perfect fluid with constant and variable equation of state parameter; and as dissipative fluid described by a barotropic equation of state with bulk viscosity in the framework of the Eckart theory and the full Israel-Stewart theory. We explore cosmological solutions for a flat, homogeneous and isotropic universe; and we assume the late future time behavior when the dark energy dominates the cosmic evolution. When modeled as a perfect fluid with a dynamical equation of state, $p=w(a)\rho$, the dark energy has an energy density, temperature and entropy well defined and an interesting result is that there is no entropy production even though been dynamical. For dissipative dark energy, in the Eckart theory two cases are studied: $\xi=const.$ and $\xi =(\beta/\sqrt{3}) \rho^{1/2}$; it is found that the entropy grows exponentially for the first case and as a power-law for the second. In the Israel-Stewart theory we consider a $\xi =\xi_0 \rho^{1/2}$ and a relaxation time $\tau = \xi/\rho$; an analytical Big Rip solution is obtained with a power-law entropy. In all cases a power-law relation between temperature and energy density is obtained. In order to maintain the second law of thermodynamics theoretical constraints for the equation of state are found in the different dark energy models studied. A barotropic dark fluid with $w<-1$ is thermodynamically difficult to support, but the overall effect of bulk viscosity in certain cases allows a phantom regime without thermodynamic anomalies. |
gr-qc/0703080 | Thomas Sotiriou | Thomas P. Sotiriou, Stefano Liberati | Reply to "Can gravitational dynamics be obtained by diffeomorphism
invariance of action?" | Accepted for publication in PRD | Phys.Rev.D75:068502,2007 | 10.1103/PhysRevD.75.068502 | null | gr-qc | null | In a previous work we showed that, in a suitable setting, one can use
diffeomorphism invariance in order to derive gravitational field equations from
boundary terms of the gravitational action. Standing by our results we reply
here to a recent comment questioning their validity.
| [
{
"created": "Wed, 14 Mar 2007 15:48:49 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Sotiriou",
"Thomas P.",
""
],
[
"Liberati",
"Stefano",
""
]
] | In a previous work we showed that, in a suitable setting, one can use diffeomorphism invariance in order to derive gravitational field equations from boundary terms of the gravitational action. Standing by our results we reply here to a recent comment questioning their validity. |
1504.00286 | Yosef Zlochower | Yosef Zlochower, Hiroyuki Nakano, Bruno C. Mundim, Manuela Campanelli,
Scott Noble, Miguel Zilhao | Inspiraling black-hole binary spacetimes: Challenges in transitioning
from analytical to numerical techniques | Accepted for publication in PRD, 14 pages, 21 figures, revtex 4-1 | Phys. Rev. D 93, 124072 (2016) | 10.1103/PhysRevD.93.124072 | null | gr-qc astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore how a recently developed analytical black-hole binary spacetime
can be extended using numerical simulations to go beyond the slow-inspiral
phase. The analytic spacetime solves the Einstein field equations
approximately, with the approximation error becoming progressively smaller the
more separated the binary. To continue the spacetime beyond the slow-inspiral
phase, we need to transition. Such a transition was previously explored at
smaller separations. Here, we perform this transition at a separation of D=20M
(large enough that the analytical metric is expected to be accurate), and
evolve for six orbits. We find that small constraint violations can have large
dynamical effects, but these can be removed by using a constraint-damping
system like the conformal covariant formulation of the Z4 system. We find
agreement between the subsequent numerical spacetime and the predictions of
post-Newtonian theory for the waveform and inspiral rate that is within the
post-Newtonian truncation error.
| [
{
"created": "Wed, 1 Apr 2015 16:40:33 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jun 2016 15:08:41 GMT",
"version": "v2"
}
] | 2016-07-05 | [
[
"Zlochower",
"Yosef",
""
],
[
"Nakano",
"Hiroyuki",
""
],
[
"Mundim",
"Bruno C.",
""
],
[
"Campanelli",
"Manuela",
""
],
[
"Noble",
"Scott",
""
],
[
"Zilhao",
"Miguel",
""
]
] | We explore how a recently developed analytical black-hole binary spacetime can be extended using numerical simulations to go beyond the slow-inspiral phase. The analytic spacetime solves the Einstein field equations approximately, with the approximation error becoming progressively smaller the more separated the binary. To continue the spacetime beyond the slow-inspiral phase, we need to transition. Such a transition was previously explored at smaller separations. Here, we perform this transition at a separation of D=20M (large enough that the analytical metric is expected to be accurate), and evolve for six orbits. We find that small constraint violations can have large dynamical effects, but these can be removed by using a constraint-damping system like the conformal covariant formulation of the Z4 system. We find agreement between the subsequent numerical spacetime and the predictions of post-Newtonian theory for the waveform and inspiral rate that is within the post-Newtonian truncation error. |
gr-qc/9909007 | Fabio Finelli | F. Finelli (Ist. TeSRE & Bologna U. & INFN, Bologna), A. Gruppuso, G.
Venturi (Bologna U. & INFN, Bologna) | Quantum Fields in an Expanding Universe | 15 pp, no figures, accepted for publication in Class. Quantum Grav | Class.Quant.Grav.16:3923-3935,1999 | 10.1088/0264-9381/16/12/310 | null | gr-qc | null | We extend our analysis for scalar fields in a Robertson-Walker metric to the
electromagnetic field and Dirac fields by the method of invariants. The issue
of the relation between conformal properties and particle production is
re-examined and it is verified that the electromagnetic and massless spinor
actions are conformal invariant, while the massless conformally coupled scalar
field is not. For the scalar field case it is pointed out that the violation of
conformal simmetry due to surface terms, although ininfluential for the
equation of motion, does lead to effects in the quantized theory.
| [
{
"created": "Thu, 2 Sep 1999 10:25:08 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Finelli",
"F.",
"",
"Ist. TeSRE & Bologna U. & INFN, Bologna"
],
[
"Gruppuso",
"A.",
"",
"Bologna U. & INFN, Bologna"
],
[
"Venturi",
"G.",
"",
"Bologna U. & INFN, Bologna"
]
] | We extend our analysis for scalar fields in a Robertson-Walker metric to the electromagnetic field and Dirac fields by the method of invariants. The issue of the relation between conformal properties and particle production is re-examined and it is verified that the electromagnetic and massless spinor actions are conformal invariant, while the massless conformally coupled scalar field is not. For the scalar field case it is pointed out that the violation of conformal simmetry due to surface terms, although ininfluential for the equation of motion, does lead to effects in the quantized theory. |
gr-qc/0406001 | Timothy Clifton | T. Clifton, D. F. Mota and J. D. Barrow | Inhomogeneous Gravity | 15 pages, 15 figures. Submitted to MNRAS. References added | Mon.Not.Roy.Astron.Soc.358:601,2005 | 10.1111/j.1365-2966.2005.08831.x | DAMTP-2004-57 | gr-qc astro-ph | null | We study the inhomogeneous cosmological evolution of the Newtonian
gravitational 'constant' G in the framework of scalar-tensor theories. We
investigate the differences that arise between the evolution of G in the
background universes and in local inhomogeneities that have separated out from
the global expansion. Exact inhomogeneous solutions are found which describe
the effects of masses embedded in an expanding FRW Brans-Dicke universe. These
are used to discuss possible spatial variations of G in different regions. We
develop the technique of matching different scalar-tensor cosmologies of
different spatial curvature at a boundary. This provides a model for the linear
and non-linear evolution of spherical overdensities and inhomogeneities in G.
This allows us to compare the evolution of G and \dot{G} that occurs inside a
collapsing overdense cluster with that in the background universe. We develop a
simple virialisation criterion and apply the method to a realistic lambda-CDM
cosmology containing spherical overdensities. Typically, far slower evolution
of \dot{G} will be found in the bound virialised cluster than in the
cosmological background. We consider the behaviour that occurs in Brans-Dicke
theory and in some other representative scalar-tensor theories.
| [
{
"created": "Tue, 1 Jun 2004 17:49:30 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Jan 2005 11:19:52 GMT",
"version": "v2"
}
] | 2009-09-29 | [
[
"Clifton",
"T.",
""
],
[
"Mota",
"D. F.",
""
],
[
"Barrow",
"J. D.",
""
]
] | We study the inhomogeneous cosmological evolution of the Newtonian gravitational 'constant' G in the framework of scalar-tensor theories. We investigate the differences that arise between the evolution of G in the background universes and in local inhomogeneities that have separated out from the global expansion. Exact inhomogeneous solutions are found which describe the effects of masses embedded in an expanding FRW Brans-Dicke universe. These are used to discuss possible spatial variations of G in different regions. We develop the technique of matching different scalar-tensor cosmologies of different spatial curvature at a boundary. This provides a model for the linear and non-linear evolution of spherical overdensities and inhomogeneities in G. This allows us to compare the evolution of G and \dot{G} that occurs inside a collapsing overdense cluster with that in the background universe. We develop a simple virialisation criterion and apply the method to a realistic lambda-CDM cosmology containing spherical overdensities. Typically, far slower evolution of \dot{G} will be found in the bound virialised cluster than in the cosmological background. We consider the behaviour that occurs in Brans-Dicke theory and in some other representative scalar-tensor theories. |
gr-qc/0409078 | Burak Himmeto\u{g}lu | Burak Himmetoglu | Analysis of Dynamic Axial-Symmetric Shells | 11 pages, Revtex4; minor changes, added reference, typos added | null | null | null | gr-qc hep-th | null | The aim of this work is to analyze the dynamical behavior of relativistic
infinite axial-symmetric shells with flat interior and a radiation filled
curved exterior spacetimes. It will be proven, by the use of conservation
equations of Israel, that the given configuration does not let expansion or
collapse of the shell which was proposed before, but rather the shell stays at
constant radius. The case of null-collapse will also be considered in this work
and it will be shown that the shell collapses to zero radius, and moreover, if
cylindrical flatness is imposed a boundary layer is obtained still contrary to
previous works.
| [
{
"created": "Mon, 20 Sep 2004 19:24:20 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Sep 2004 10:17:13 GMT",
"version": "v2"
},
{
"created": "Fri, 1 Oct 2004 15:12:04 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Himmetoglu",
"Burak",
""
]
] | The aim of this work is to analyze the dynamical behavior of relativistic infinite axial-symmetric shells with flat interior and a radiation filled curved exterior spacetimes. It will be proven, by the use of conservation equations of Israel, that the given configuration does not let expansion or collapse of the shell which was proposed before, but rather the shell stays at constant radius. The case of null-collapse will also be considered in this work and it will be shown that the shell collapses to zero radius, and moreover, if cylindrical flatness is imposed a boundary layer is obtained still contrary to previous works. |
gr-qc/0612038 | Wu Ning | Ning Wu | Spin-Spin Interactions in Gauge Theory of Gravity, Violation of Weak
Equivalence Principle and New Classical Test of General Relativity | 17 pages, no figure | Commun.Theor.Phys.49:1533-1540,2008 | 10.1088/0253-6102/49/6/39 | null | gr-qc | null | For a long time, it is generally believed that spin-spin interactions can
only exist in a theory where Lorentz symmetry is gauged, and a theory with
spin-spin interactions is not perturbatively renormalizable. But this is not
true. By studying the motion of a spinning particle in gravitational field, it
is found that there exist spin-spin interactions in gauge theory of gravity.
Its mechanism is that a spinning particle will generate gravitomagnetic field
in space-time, and this gravitomagnetic field will interact with the spin of
another particle, which will cause spin-spin interactions. So, spin-spin
interactions are transmitted by gravitational field. The form of spin-spin
interactions in post Newtonian approximations is deduced. This result can also
be deduced from the Papapetrou equation. This kind of interactions will not
affect the renormalizability of the theory. The spin-spin interactions will
violate the weak equivalence principle, and the violation effects are
detectable. An experiment is proposed to detect the effects of the violation of
the weak equivalence principle.
| [
{
"created": "Wed, 6 Dec 2006 13:15:06 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Mar 2007 04:08:13 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Wu",
"Ning",
""
]
] | For a long time, it is generally believed that spin-spin interactions can only exist in a theory where Lorentz symmetry is gauged, and a theory with spin-spin interactions is not perturbatively renormalizable. But this is not true. By studying the motion of a spinning particle in gravitational field, it is found that there exist spin-spin interactions in gauge theory of gravity. Its mechanism is that a spinning particle will generate gravitomagnetic field in space-time, and this gravitomagnetic field will interact with the spin of another particle, which will cause spin-spin interactions. So, spin-spin interactions are transmitted by gravitational field. The form of spin-spin interactions in post Newtonian approximations is deduced. This result can also be deduced from the Papapetrou equation. This kind of interactions will not affect the renormalizability of the theory. The spin-spin interactions will violate the weak equivalence principle, and the violation effects are detectable. An experiment is proposed to detect the effects of the violation of the weak equivalence principle. |
gr-qc/0108070 | Koji Uryu | John L. Friedman, Koji Uryu and Masaru Shibata | Thermodynamics of binary black holes and neutron stars | 26 pages, revised version, modified appendix A, to appear in PRD | Phys.Rev.D65:064035,2002; Erratum-ibid.D70:129904,2004 | 10.1103/PhysRevD.65.064035 10.1103/PhysRevD.70.129904 | null | gr-qc astro-ph | null | We consider compact binary systems, modeled in general relativity as vacuum
or perfect-fluid spacetimes with a helical Killing vector k^\alpha,
heuristically, the generator of time-translations in a corotating frame.
Systems that are stationary in this sense are not asymptotically flat, but have
asymptotic behavior corresponding to equal amounts of ingoing and outgoing
radiation. For black-hole binaries, a rigidity theorem implies that the Killing
vector lies along the horizon's generators, and from this one can deduce the
zeroth law (constant surface gravity of the horizon). Remarkably, although the
mass and angular momentum of such a system are not defined, there is an exact
first law, relating the change in the asymptotic Noether charge to the changes
in the vorticity, baryon mass, and entropy of the fluid, and in the area of
black holes.
Binary systems with M\Omega small have an approximate asymptopia in which one
can write the first law in terms of the asymptotic mass and angular momentum.
Asymptotic flatness is precise in two classes of solutions used to model binary
systems: spacetimes satisfying the post-Newtonian equations, and solutions to a
modified set of field equations that have a spatially conformally flat metric.
(The spatial conformal flatness formalism with helical symmetry, however, is
consistent with maximal slicing only if replaces the extrinsic curvature in the
field equations by an artificially tracefree expression in terms of the shift
vector.) For these spacetimes, nearby equilibria whose stars have the same
vorticity obey the relation \delta M = \Omega \delta J, from which one can
obtain a turning point criterion that governs the stability of orbits.
| [
{
"created": "Tue, 28 Aug 2001 23:05:38 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Dec 2001 21:01:08 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Friedman",
"John L.",
""
],
[
"Uryu",
"Koji",
""
],
[
"Shibata",
"Masaru",
""
]
] | We consider compact binary systems, modeled in general relativity as vacuum or perfect-fluid spacetimes with a helical Killing vector k^\alpha, heuristically, the generator of time-translations in a corotating frame. Systems that are stationary in this sense are not asymptotically flat, but have asymptotic behavior corresponding to equal amounts of ingoing and outgoing radiation. For black-hole binaries, a rigidity theorem implies that the Killing vector lies along the horizon's generators, and from this one can deduce the zeroth law (constant surface gravity of the horizon). Remarkably, although the mass and angular momentum of such a system are not defined, there is an exact first law, relating the change in the asymptotic Noether charge to the changes in the vorticity, baryon mass, and entropy of the fluid, and in the area of black holes. Binary systems with M\Omega small have an approximate asymptopia in which one can write the first law in terms of the asymptotic mass and angular momentum. Asymptotic flatness is precise in two classes of solutions used to model binary systems: spacetimes satisfying the post-Newtonian equations, and solutions to a modified set of field equations that have a spatially conformally flat metric. (The spatial conformal flatness formalism with helical symmetry, however, is consistent with maximal slicing only if replaces the extrinsic curvature in the field equations by an artificially tracefree expression in terms of the shift vector.) For these spacetimes, nearby equilibria whose stars have the same vorticity obey the relation \delta M = \Omega \delta J, from which one can obtain a turning point criterion that governs the stability of orbits. |
2403.18533 | Ryotaku Suzuki | Eiki Kagohashi, Ryotaku Suzuki, Shinya Tomizawa | Innermost stable circular orbits around a spinning black hole binary | 20 pages, 11 figures | null | null | TTI-MATHPHYS-28 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the exact solution that describes multi-centered rotating black holes,
recently discovered by Teo and Wan, we investigate the innermost stable
circular orbit (ISCO) for massive particles and the circular orbit for massless
particles moving around a spinning black hole binary. We assume equal masses
$M_1 = M_2=m$ and equal spin angular momenta $|J_1| = |J_2|$ for both black
holes. Firstly, we examine the case where two black holes are spinning in the
same direction ($J_1=J_2$). We clarify that that for particles rotating in the
same direction as (opposite directions to) black holes' spin, the greater the
spin angular momenta of the black holes, the more the radii of the ISCO for
massive particles and the circular orbit for massless particles decrease
(increase). We show that distinct ISCO transitions occur for particles rotating
in the same direction as the black holes in three ranges of spin angular
momenta: $0<J_1/m^2=J_2/m^2< 0.395...$, $0.395...<J_1/m^2=J_2/m^2< 0.483...$,
and $0.483...<J_1/m^2=J_2/m^2<0.5$. Conversely, particles rotating in the
opposite direction to the black holes exhibit a consistent transition pattern
for the case $0<J_1/m^2=J_2/m^2<0.5$. Secondly, we study the situation where
binary black holes are spinning in opposite directions ($J_1=-J_2$). We clarify
that for large (small) separations between black holes, the ISCO appears near
the black hole that is spinning in the same (opposite) direction as particles'
rotation. Additionally, we show that different ISCO transitions occur in the
three angular momentum ranges: $0<J_1/m^2=-J_2/m^2< 0.160...$,
$0.160...<J_1/m^2=-J_2/m^2< 0.467...$, and $0.467...<J_1/m^2=-J_2/m^2<0.5$.
| [
{
"created": "Wed, 27 Mar 2024 13:11:09 GMT",
"version": "v1"
}
] | 2024-03-28 | [
[
"Kagohashi",
"Eiki",
""
],
[
"Suzuki",
"Ryotaku",
""
],
[
"Tomizawa",
"Shinya",
""
]
] | Using the exact solution that describes multi-centered rotating black holes, recently discovered by Teo and Wan, we investigate the innermost stable circular orbit (ISCO) for massive particles and the circular orbit for massless particles moving around a spinning black hole binary. We assume equal masses $M_1 = M_2=m$ and equal spin angular momenta $|J_1| = |J_2|$ for both black holes. Firstly, we examine the case where two black holes are spinning in the same direction ($J_1=J_2$). We clarify that that for particles rotating in the same direction as (opposite directions to) black holes' spin, the greater the spin angular momenta of the black holes, the more the radii of the ISCO for massive particles and the circular orbit for massless particles decrease (increase). We show that distinct ISCO transitions occur for particles rotating in the same direction as the black holes in three ranges of spin angular momenta: $0<J_1/m^2=J_2/m^2< 0.395...$, $0.395...<J_1/m^2=J_2/m^2< 0.483...$, and $0.483...<J_1/m^2=J_2/m^2<0.5$. Conversely, particles rotating in the opposite direction to the black holes exhibit a consistent transition pattern for the case $0<J_1/m^2=J_2/m^2<0.5$. Secondly, we study the situation where binary black holes are spinning in opposite directions ($J_1=-J_2$). We clarify that for large (small) separations between black holes, the ISCO appears near the black hole that is spinning in the same (opposite) direction as particles' rotation. Additionally, we show that different ISCO transitions occur in the three angular momentum ranges: $0<J_1/m^2=-J_2/m^2< 0.160...$, $0.160...<J_1/m^2=-J_2/m^2< 0.467...$, and $0.467...<J_1/m^2=-J_2/m^2<0.5$. |
1602.03844 | LVC Publications | The LIGO Scientific Collaboration, the Virgo Collaboration | Characterization of transient noise in Advanced LIGO relevant to
gravitational wave signal GW150914 | null | null | 10.1088/0264-9381/33/13/134001 | null | gr-qc astro-ph.HE astro-ph.IM physics.ins-det | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On September 14, 2015, a gravitational wave signal from a coalescing black
hole binary system was observed by the Advanced LIGO detectors. This paper
describes the transient noise backgrounds used to determine the significance of
the event (designated GW150914) and presents the results of investigations into
potential correlated or uncorrelated sources of transient noise in the
detectors around the time of the event. The detectors were operating nominally
at the time of GW150914. We have ruled out environmental influences and
non-Gaussian instrument noise at either LIGO detector as the cause of the
observed gravitational wave signal.
| [
{
"created": "Thu, 11 Feb 2016 19:26:51 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Feb 2016 00:02:23 GMT",
"version": "v2"
},
{
"created": "Sat, 4 Jun 2016 00:27:07 GMT",
"version": "v3"
}
] | 2016-06-22 | [
[
"The LIGO Scientific Collaboration",
"",
""
],
[
"the Virgo Collaboration",
"",
""
]
] | On September 14, 2015, a gravitational wave signal from a coalescing black hole binary system was observed by the Advanced LIGO detectors. This paper describes the transient noise backgrounds used to determine the significance of the event (designated GW150914) and presents the results of investigations into potential correlated or uncorrelated sources of transient noise in the detectors around the time of the event. The detectors were operating nominally at the time of GW150914. We have ruled out environmental influences and non-Gaussian instrument noise at either LIGO detector as the cause of the observed gravitational wave signal. |
1910.08688 | Rodrigo Avalos | Rodrigo Avalos and Jorge H. Lira | Einstein-type elliptic systems | null | Ann. Henri Poincar\'e, 2022 | 10.1007/s00023-022-01180-2 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we analyse semi-linear systems of partial differential
equations which are motivated by the conformal formulation of the Einstein
constraint equations coupled with realistic physical fields on asymptotically
Euclidean (AE) manifolds. In particular, electromagnetic fields give rise to
this kind of system. In this context, under suitable conditions, we prove a
general existence theorem for such systems, and, in particular, under smallness
assumptions on the free parameters of the problem, we prove existence of far
from CMC (near CMC) Yamabe positive (Yamabe non-positive) solutions for charged
dust coupled to the Einstein equations, satisfying a trapped surface condition
on the boundary. As a bypass, we prove a Helmholtz decomposition on AE
manifolds with boundary, which extends and clarifies previously known results.
| [
{
"created": "Sat, 19 Oct 2019 03:16:55 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Nov 2019 19:19:24 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Nov 2021 23:41:40 GMT",
"version": "v3"
}
] | 2022-04-18 | [
[
"Avalos",
"Rodrigo",
""
],
[
"Lira",
"Jorge H.",
""
]
] | In this paper we analyse semi-linear systems of partial differential equations which are motivated by the conformal formulation of the Einstein constraint equations coupled with realistic physical fields on asymptotically Euclidean (AE) manifolds. In particular, electromagnetic fields give rise to this kind of system. In this context, under suitable conditions, we prove a general existence theorem for such systems, and, in particular, under smallness assumptions on the free parameters of the problem, we prove existence of far from CMC (near CMC) Yamabe positive (Yamabe non-positive) solutions for charged dust coupled to the Einstein equations, satisfying a trapped surface condition on the boundary. As a bypass, we prove a Helmholtz decomposition on AE manifolds with boundary, which extends and clarifies previously known results. |
1311.5327 | Jian-Yang Zhu | Xiao-Min Zhang and Jian-Yang Zhu | Consistency of the tachyon warm inflationary universe models | 10 pages, 0 figures, accepted for publication in Journal of Cosmology
and Astroparticle Physics (JCAP) | JCAP 02(2014)005 | 10.1088/1475-7516/2014/02/005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This study concerns the consistency of the tachyon warm inflationary models.
A linear stability analysis is performed to find the slow-roll conditions,
characterized by the potential slow-roll (PSR) parameters, for the existence of
a tachyon warm inflationary attractor in the system. The PSR parameters in the
tachyon warm inflationary models are redefined. Two cases, an exponential
potential and an inverse power-law potential, are studied, when the dissipative
coefficient $\Gamma=\Gamma_0$ and $\Gamma=\Gamma(\phi)$, respectively. A
crucial condition is obtained for a tachyon warm inflationary model
characterized by the Hubble slow-roll (HSR) parameter $\epsilon_{_H}$, and the
condition is extendable to some other inflationary models as well. A proper
number of e-folds is obtained in both cases of the tachyon warm inflation, in
contrast to existing works. It is also found that a constant dissipative
coefficient $(\Gamma=\Gamma_0)$ is usually not a suitable assumption for a warm
inflationary model.
| [
{
"created": "Thu, 21 Nov 2013 08:04:07 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Jan 2014 17:29:35 GMT",
"version": "v2"
}
] | 2014-02-25 | [
[
"Zhang",
"Xiao-Min",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | This study concerns the consistency of the tachyon warm inflationary models. A linear stability analysis is performed to find the slow-roll conditions, characterized by the potential slow-roll (PSR) parameters, for the existence of a tachyon warm inflationary attractor in the system. The PSR parameters in the tachyon warm inflationary models are redefined. Two cases, an exponential potential and an inverse power-law potential, are studied, when the dissipative coefficient $\Gamma=\Gamma_0$ and $\Gamma=\Gamma(\phi)$, respectively. A crucial condition is obtained for a tachyon warm inflationary model characterized by the Hubble slow-roll (HSR) parameter $\epsilon_{_H}$, and the condition is extendable to some other inflationary models as well. A proper number of e-folds is obtained in both cases of the tachyon warm inflation, in contrast to existing works. It is also found that a constant dissipative coefficient $(\Gamma=\Gamma_0)$ is usually not a suitable assumption for a warm inflationary model. |
2012.03856 | Yungui Gong | Qing Gao, Yungui Gong, Zhu Yi | Primordial black holes and secondary gravitational waves from natural
inflation | mathced with the published version | Nucl. Phys. B 969 (2021) 115480 | 10.1016/j.nuclphysb.2021.115480 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The production of primordial black hole (PBH) dark matter (DM) and the
generation of scalar induced secondary gravitational waves by using the
enhancement mechanism with a peak function in the non-canonical kinetic term in
natural inflation is discussed. We show explicitly that the power spectrum for
the primordial curvature perturbation can be enhanced at $10^{12}$ Mpc$^{-1}$,
$10^{8}$ Mpc$^{-1}$ and $10^{5}$ Mpc$^{-1}$ by adjusting the model parameters.
With the enhanced primordial curvature perturbations, we show the production of
PBH DM with peak masses around $10^{-13}\ M_{\odot}$, the Earth's mass and the
stellar mass, and the generation of scalar induced gravitational waves (SIGWs)
with peak frequencies around mHz, $10^{-6}$ Hz and nHz, respectively. The PBHs
with the mass scale $10^{-13}\ M_{\odot}$ can make up almost all the DM and the
associated SIGWs is testable by spaced based gravitational wave observatory.
| [
{
"created": "Mon, 7 Dec 2020 17:06:25 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Apr 2022 12:31:35 GMT",
"version": "v2"
},
{
"created": "Sat, 7 May 2022 04:18:43 GMT",
"version": "v3"
}
] | 2022-05-10 | [
[
"Gao",
"Qing",
""
],
[
"Gong",
"Yungui",
""
],
[
"Yi",
"Zhu",
""
]
] | The production of primordial black hole (PBH) dark matter (DM) and the generation of scalar induced secondary gravitational waves by using the enhancement mechanism with a peak function in the non-canonical kinetic term in natural inflation is discussed. We show explicitly that the power spectrum for the primordial curvature perturbation can be enhanced at $10^{12}$ Mpc$^{-1}$, $10^{8}$ Mpc$^{-1}$ and $10^{5}$ Mpc$^{-1}$ by adjusting the model parameters. With the enhanced primordial curvature perturbations, we show the production of PBH DM with peak masses around $10^{-13}\ M_{\odot}$, the Earth's mass and the stellar mass, and the generation of scalar induced gravitational waves (SIGWs) with peak frequencies around mHz, $10^{-6}$ Hz and nHz, respectively. The PBHs with the mass scale $10^{-13}\ M_{\odot}$ can make up almost all the DM and the associated SIGWs is testable by spaced based gravitational wave observatory. |
2112.06856 | Karan Jani | Patrick Hu, Karan Jani, Kelly Holley-Bockelmann and Gregorio Carullo | Thermodynamics to infer the astrophysics of binary black hole mergers | 7 pages, 5 figures | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We introduce the Merger Entropy Index ($\mathcal{I}_\mathrm{BBH}$), a new
parameter to measure the efficiency of entropy transfer for any generic binary
black hole merger in General Relativity. We find that
$\mathcal{I}_\mathrm{BBH}$ is bounded between an asymptotic maximum and
minimum. For the observed population of mergers detected by LIGO and Virgo, we
find that $\mathcal{I}_\mathrm{BBH}$ is $\lesssim30\%$ of its theoretical
maximum. By imposing the thermodynamical consistency between the pre- and
post-merger states through $\mathcal{I}_\mathrm{BBH}$, we showcase BRAHMA -- a
novel framework to infer the properties and astrophysical implications of
gravitational-wave detections. For GW190521 -- the heaviest confirmed binary
black hole merger observed so far -- our framework rules out high mass-ratio,
negative effective inspiral spin, and electromagnetic counterpart claims.
Furthermore, our analysis provides an independent confirmation that GW190521
belongs to a separate population.
| [
{
"created": "Mon, 13 Dec 2021 18:12:19 GMT",
"version": "v1"
}
] | 2021-12-14 | [
[
"Hu",
"Patrick",
""
],
[
"Jani",
"Karan",
""
],
[
"Holley-Bockelmann",
"Kelly",
""
],
[
"Carullo",
"Gregorio",
""
]
] | We introduce the Merger Entropy Index ($\mathcal{I}_\mathrm{BBH}$), a new parameter to measure the efficiency of entropy transfer for any generic binary black hole merger in General Relativity. We find that $\mathcal{I}_\mathrm{BBH}$ is bounded between an asymptotic maximum and minimum. For the observed population of mergers detected by LIGO and Virgo, we find that $\mathcal{I}_\mathrm{BBH}$ is $\lesssim30\%$ of its theoretical maximum. By imposing the thermodynamical consistency between the pre- and post-merger states through $\mathcal{I}_\mathrm{BBH}$, we showcase BRAHMA -- a novel framework to infer the properties and astrophysical implications of gravitational-wave detections. For GW190521 -- the heaviest confirmed binary black hole merger observed so far -- our framework rules out high mass-ratio, negative effective inspiral spin, and electromagnetic counterpart claims. Furthermore, our analysis provides an independent confirmation that GW190521 belongs to a separate population. |
1606.03075 | Marc Casals | Marc Casals and Brien Nolan | Global Hadamard form for the Green Function in Schwarzschild space-time | 39 pages, 3 figures. In this version we have tidied up the paper
throughout and added the new part on relating the Green functions in
Schwarzschild and Pleba{\'n}ski-Hacyan spacetimes | Physical Review D 108, 044033, 2023 | 10.1103/PhysRevD.108.044033 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The retarded Green function of a wave equation on a 4-dimensional curved
background spacetime is a (generalized) function of two spacetime points and
diverges when these are connected by a null geodesic. The Hadamard form makes
explicit the form of this divergence but only when one of the points is in a
normal neighbourhood of the other point. In this paper we derive a
representation for the retarded Green function for a scalar field in
Schwarzschild spacetime which makes explicit its {\it complete} singularity
structure beyond the normal neighbourhood. We interpret this representation as
a sum of Hadamard forms, the summation being taken over the number of times the
null wavefront has passed through a caustic point: the sum of Hadamard forms
applies to the non-smooth contribution to the full Green function, not only the
singular contribution. (The term non-smooth applies modulo the
causality-generating step functions that must appear in the retarded Green
function.) The singularity structure is determined using two independent
approaches, one based on a Bessel function expansion of the Green function, and
another that exploits a link between the Green functions of Schwarzschild
spacetime and Pleba{\'n}ski-Hacyan spacetime (the latter approach also yields
another representation for the {\it full} Schwarzschild Green function, not
just for its non-smooth part). Our representation is not valid in a
neighbourhood of caustic points. We deal with these points by providing a
separate representation for the Green function in Schwarzschild spacetime which
makes explicit its (different) singularity structure at caustics of this
spacetime.
| [
{
"created": "Thu, 9 Jun 2016 19:30:25 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Jul 2016 20:13:46 GMT",
"version": "v2"
},
{
"created": "Fri, 21 Feb 2020 20:49:02 GMT",
"version": "v3"
},
{
"created": "Wed, 16 Aug 2023 15:48:30 GMT",
"version": "v4"
}
] | 2023-08-17 | [
[
"Casals",
"Marc",
""
],
[
"Nolan",
"Brien",
""
]
] | The retarded Green function of a wave equation on a 4-dimensional curved background spacetime is a (generalized) function of two spacetime points and diverges when these are connected by a null geodesic. The Hadamard form makes explicit the form of this divergence but only when one of the points is in a normal neighbourhood of the other point. In this paper we derive a representation for the retarded Green function for a scalar field in Schwarzschild spacetime which makes explicit its {\it complete} singularity structure beyond the normal neighbourhood. We interpret this representation as a sum of Hadamard forms, the summation being taken over the number of times the null wavefront has passed through a caustic point: the sum of Hadamard forms applies to the non-smooth contribution to the full Green function, not only the singular contribution. (The term non-smooth applies modulo the causality-generating step functions that must appear in the retarded Green function.) The singularity structure is determined using two independent approaches, one based on a Bessel function expansion of the Green function, and another that exploits a link between the Green functions of Schwarzschild spacetime and Pleba{\'n}ski-Hacyan spacetime (the latter approach also yields another representation for the {\it full} Schwarzschild Green function, not just for its non-smooth part). Our representation is not valid in a neighbourhood of caustic points. We deal with these points by providing a separate representation for the Green function in Schwarzschild spacetime which makes explicit its (different) singularity structure at caustics of this spacetime. |
1410.6785 | Douglas A. Singleton | Sujoy K. Modak and Douglas Singleton | Baryogenesis via Hawking-like Radiation in the FRW Space-time | 17 pages, 0 figures, added references, discussion/comparison of
PLANCK and BICEP2 results, added discussion of generation of anisotropies.
Published versions (EPJC) | Eur.Phys.J. C75 (2015) 5, 200 | 10.1140/epjc/s10052-015-3431-8 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a phenomenological model for baryogenesis based on particle
creation in the Friedman-Robertson-Walker (FRW) spacetime. This study is a
continuation of our proposal that Hawking-like radiation in FRW space-time
explains several physical aspects of the early Universe including inflation. In
this model we study a coupling between the FRW space-time, in the form of the
derivative of the Ricci scalar, and the $B-L$ current, $J^{\mu} _{B-L}$, which
leads to a different chemical potential between baryons and anti-baryons
resulting in an excess of baryons over anti-baryons with the right order of
magnitude. In this model the generation of baryon asymmetry, in principle,
occurs over the entire history of the Universe starting from the beginning of
the radiation phase. However, in practice, almost the entire contribution to
the baryon asymmetry only comes from the very beginning of the Universe and is
negligible thereafter. There is a free parameter in our model which can be
interpreted as defining the boundary between the unknown quantum gravity regime
and the inflation/baryogenesis regime covered by our model. When this parameter
is adjusted to give the observed value of baryon asymmetry we get a higher than
usual energy scale for our inflation model which however may be in line with
the GUT scale for inflation in view of the BICEP2 and Planck results. In
addition our model provides the correct temperature for the CMB photons at the
time of decoupling.
| [
{
"created": "Wed, 15 Oct 2014 20:08:32 GMT",
"version": "v1"
},
{
"created": "Thu, 7 May 2015 17:13:45 GMT",
"version": "v2"
}
] | 2015-05-11 | [
[
"Modak",
"Sujoy K.",
""
],
[
"Singleton",
"Douglas",
""
]
] | We present a phenomenological model for baryogenesis based on particle creation in the Friedman-Robertson-Walker (FRW) spacetime. This study is a continuation of our proposal that Hawking-like radiation in FRW space-time explains several physical aspects of the early Universe including inflation. In this model we study a coupling between the FRW space-time, in the form of the derivative of the Ricci scalar, and the $B-L$ current, $J^{\mu} _{B-L}$, which leads to a different chemical potential between baryons and anti-baryons resulting in an excess of baryons over anti-baryons with the right order of magnitude. In this model the generation of baryon asymmetry, in principle, occurs over the entire history of the Universe starting from the beginning of the radiation phase. However, in practice, almost the entire contribution to the baryon asymmetry only comes from the very beginning of the Universe and is negligible thereafter. There is a free parameter in our model which can be interpreted as defining the boundary between the unknown quantum gravity regime and the inflation/baryogenesis regime covered by our model. When this parameter is adjusted to give the observed value of baryon asymmetry we get a higher than usual energy scale for our inflation model which however may be in line with the GUT scale for inflation in view of the BICEP2 and Planck results. In addition our model provides the correct temperature for the CMB photons at the time of decoupling. |
1609.03189 | Eduardo Guendelman I | David Benisty and E.I. Guendelman | Radiation Like Scalar Field and Gauge Fields in Cosmology for a theory
with Dynamical Time | 7 pages, to appear in Mod. Phys. Lett. A | null | 10.1142/S0217732316501881 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmological solutions with a scalar field behaving as radiation are
obtained, in the context of gravitational theory with dynamical time. The
solution requires the spacial curvature of the universe k, to be zero, unlike
the standard radiation solutions, which do not impose any constraint on the
spacial curvature of the universe. This is because only such $ k=0 $ radiation
solutions poses a homothetic Killimg vector. This kind of theory can be used to
generalize electromagnetism and other gauge theories, in curved space time, and
there are no deviations from standard gauge filed equation (like Maxwell
equations) in the case there exist a conformal Killing vector. But there could
be departures from Maxwell and Yang Mills equations, for more general space
times.
| [
{
"created": "Sun, 11 Sep 2016 18:33:21 GMT",
"version": "v1"
}
] | 2016-10-19 | [
[
"Benisty",
"David",
""
],
[
"Guendelman",
"E. I.",
""
]
] | Cosmological solutions with a scalar field behaving as radiation are obtained, in the context of gravitational theory with dynamical time. The solution requires the spacial curvature of the universe k, to be zero, unlike the standard radiation solutions, which do not impose any constraint on the spacial curvature of the universe. This is because only such $ k=0 $ radiation solutions poses a homothetic Killimg vector. This kind of theory can be used to generalize electromagnetism and other gauge theories, in curved space time, and there are no deviations from standard gauge filed equation (like Maxwell equations) in the case there exist a conformal Killing vector. But there could be departures from Maxwell and Yang Mills equations, for more general space times. |
gr-qc/0205096 | Demetrios Papadopoulos | D.B. Papadopoulos | Plasma waves driven by gravitational waves in an expanding universe | 14 pages | Class.Quant.Grav.19:1-12,2002 | 10.1088/0264-9381/19/11/312 | null | gr-qc | null | In a Friedmann-Robertson-Walker (FRW) cosmological model with zero spatial
curvature, we consider the interaction of the gravitational waves with the
plasma in the presence of a weak magnetic field. Using the relativistic
hydromagnetic equations it is verified that large amplitude magnetosonic waves
are excited, assuming that both, the gravitational field and the weak magnetic
field do not break the homogeneity and isotropy of the considered FRW
spacetime.
| [
{
"created": "Wed, 22 May 2002 07:55:19 GMT",
"version": "v1"
}
] | 2010-04-30 | [
[
"Papadopoulos",
"D. B.",
""
]
] | In a Friedmann-Robertson-Walker (FRW) cosmological model with zero spatial curvature, we consider the interaction of the gravitational waves with the plasma in the presence of a weak magnetic field. Using the relativistic hydromagnetic equations it is verified that large amplitude magnetosonic waves are excited, assuming that both, the gravitational field and the weak magnetic field do not break the homogeneity and isotropy of the considered FRW spacetime. |
2110.10610 | Pankaj Sheoran | Sanjar Shaymatov, Pankaj Sheoran and Sanjay Siwach | Motion of charged and spinning particle influenced by dark matter field
surrounding a charged dyonic black hole | 24 pages, 12 captioned figures, 2 tables and 2 appendices, (A new
figure added, text modified, to match with the published version in PRD) | Phys. Rev. D 105, 104059 (2022) | 10.1103/PhysRevD.105.104059 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the motion of massive charged and spinning test particles
around a charged dyonic black hole spacetime surrounded by perfect fluid scalar
dark matter field. We obtain the equations of motion and find the expressions
for the four-velocity for the case of a charged particle, and four-momentum
components for the case of a spinning particle. The trajectories for various
values of electric $Q_{e}$ and magnetic $Q_{m}$ charges are investigated under
the influence of dark matter field $\lambda$. We find the equations of motion
of a spinning particle that follows a non-geodesic trajectory via Lagrangian
approach in addition to the charged and non-spinning particles that follow
geodesic motion in this set-up. We study in detail the properties of innermost
stable circular orbits (ISCOs) in the equatorial plane. The study of ISCOs of a
spinning massive particle is done by using the pole-dipole approximation. We
show that, in addition to the particle's spin, the dark matter field parameter
$\lambda$ and black hole charges ($Q_{m}\;\text{and}\;Q_{e}$) have a
significant influence on the ISCOs of spinning particles. It is observed that
if the spin is parallel to the total angular momentum $J$ (i.e.
$\mathcal{S}>0$), the ISCO parameters (i.e.$r_{ISCO}, L_{ISCO}\;\text{and}\;
E_{ISCO}$) of a spinning particle are smaller than those of a non-spinning
particle, whereas if the spin is anti-parallel to total angular momentum $J$
(i.e. $\mathcal{S}<0$), the value of the ISCO parameters is greater than that
of the non-spinning particle. We also show that for the corresponding values of
spin parameter S, the behaviour of Keplerian angular frequency of ISCO
$\Omega_{ISCO}$ is opposite to that of $r_{ISCO}, L_{ISCO}\; \text{and}\;
E_{ISCO}$.
| [
{
"created": "Wed, 20 Oct 2021 15:11:21 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Jun 2022 12:37:09 GMT",
"version": "v2"
}
] | 2022-06-07 | [
[
"Shaymatov",
"Sanjar",
""
],
[
"Sheoran",
"Pankaj",
""
],
[
"Siwach",
"Sanjay",
""
]
] | We investigate the motion of massive charged and spinning test particles around a charged dyonic black hole spacetime surrounded by perfect fluid scalar dark matter field. We obtain the equations of motion and find the expressions for the four-velocity for the case of a charged particle, and four-momentum components for the case of a spinning particle. The trajectories for various values of electric $Q_{e}$ and magnetic $Q_{m}$ charges are investigated under the influence of dark matter field $\lambda$. We find the equations of motion of a spinning particle that follows a non-geodesic trajectory via Lagrangian approach in addition to the charged and non-spinning particles that follow geodesic motion in this set-up. We study in detail the properties of innermost stable circular orbits (ISCOs) in the equatorial plane. The study of ISCOs of a spinning massive particle is done by using the pole-dipole approximation. We show that, in addition to the particle's spin, the dark matter field parameter $\lambda$ and black hole charges ($Q_{m}\;\text{and}\;Q_{e}$) have a significant influence on the ISCOs of spinning particles. It is observed that if the spin is parallel to the total angular momentum $J$ (i.e. $\mathcal{S}>0$), the ISCO parameters (i.e.$r_{ISCO}, L_{ISCO}\;\text{and}\; E_{ISCO}$) of a spinning particle are smaller than those of a non-spinning particle, whereas if the spin is anti-parallel to total angular momentum $J$ (i.e. $\mathcal{S}<0$), the value of the ISCO parameters is greater than that of the non-spinning particle. We also show that for the corresponding values of spin parameter S, the behaviour of Keplerian angular frequency of ISCO $\Omega_{ISCO}$ is opposite to that of $r_{ISCO}, L_{ISCO}\; \text{and}\; E_{ISCO}$. |
2304.02092 | Arvin Ravanpak | Arvin Ravanpak and Golnaz Farpour Fadakar | Logamediate inflation in DGP cosmology driven by a non-canonical scalar
field | null | Gravitation and Cosmology, Vol.29, No.1, pp 88-94, 2023 | 10.1134/S0202289323010085 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | The main properties of the logamediate inflation driven by a non-canonical
scalar field in the framework of DGP braneworld gravity are investigated.
Considering high energy conditions we calculate the slow-roll parameters,
analytically. Then, we deal with the perturbation theory and calculate the most
important respective parameters such as the scalar spectral index and the
tensor-to-scalar ratio. We find that the spectrum of scalar fluctuations is
always red-tilted. Also, we understand that the running in the scalar spectral
index is nearly zero. Finally, we compare this inflationary scenario with the
latest observational results from Planck 2018.
| [
{
"created": "Tue, 4 Apr 2023 19:40:28 GMT",
"version": "v1"
}
] | 2023-04-06 | [
[
"Ravanpak",
"Arvin",
""
],
[
"Fadakar",
"Golnaz Farpour",
""
]
] | The main properties of the logamediate inflation driven by a non-canonical scalar field in the framework of DGP braneworld gravity are investigated. Considering high energy conditions we calculate the slow-roll parameters, analytically. Then, we deal with the perturbation theory and calculate the most important respective parameters such as the scalar spectral index and the tensor-to-scalar ratio. We find that the spectrum of scalar fluctuations is always red-tilted. Also, we understand that the running in the scalar spectral index is nearly zero. Finally, we compare this inflationary scenario with the latest observational results from Planck 2018. |
1610.09960 | Rui Xu | Rui Xu | Looking for Lorentz Violation in Short-Range Gravity | 3 pages, Presented at the Seventh Meeting on CPT and Lorentz
Symmetry, Bloomington, Indiana, June 20-24, 2016 | null | null | IUHET 619 | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General violations of Lorentz symmetry can be described by the Standard-Model
Extension (SME) framework. The SME predicts modifications to existing physics
and can be tested in high-precision experiments. By looking for small
deviations from Newton gravity, short-range gravity experiments are expected to
be sensitive to possible gravitational Lorentz-violation signals. With two
group's short-range gravity data analyzed recently, no nonminimal Lorentz
violation signal is found at the micron distance scale, which gives stringent
constraints on nonminimal Lorentz-violation coefficients in the SME.
| [
{
"created": "Fri, 28 Oct 2016 19:41:14 GMT",
"version": "v1"
}
] | 2016-11-01 | [
[
"Xu",
"Rui",
""
]
] | General violations of Lorentz symmetry can be described by the Standard-Model Extension (SME) framework. The SME predicts modifications to existing physics and can be tested in high-precision experiments. By looking for small deviations from Newton gravity, short-range gravity experiments are expected to be sensitive to possible gravitational Lorentz-violation signals. With two group's short-range gravity data analyzed recently, no nonminimal Lorentz violation signal is found at the micron distance scale, which gives stringent constraints on nonminimal Lorentz-violation coefficients in the SME. |
1305.3363 | Meng-Sen Ma | Meng-Sen Ma, Hui-Hua Zhao | Quantized space-time and its influences on some physical problems | 5pages, 1 figure | Chinese Physics C , 2014 38 (4): 045102 | 10.1088/1674-1137/38/4/045102 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on the idea of quantized space-time of Snyder, we derive new
generalized uncertainty principle and new modified density of states.
Accordingly we discuss the influences of the modified density of states on some
physical quantities and laws. In addition we analyzed the exact solution of the
harmonic oscillator in Snyder's quantized space-time.
| [
{
"created": "Wed, 15 May 2013 06:20:20 GMT",
"version": "v1"
}
] | 2014-07-01 | [
[
"Ma",
"Meng-Sen",
""
],
[
"Zhao",
"Hui-Hua",
""
]
] | Based on the idea of quantized space-time of Snyder, we derive new generalized uncertainty principle and new modified density of states. Accordingly we discuss the influences of the modified density of states on some physical quantities and laws. In addition we analyzed the exact solution of the harmonic oscillator in Snyder's quantized space-time. |
1012.3165 | Alexandre Yale | Alexandre Yale | Exact Hawking Radiation of Scalars, Fermions, and Bosons Using the
Tunneling Method Without Back-Reaction | 8 pages, no figures. v3: Introduction updated. Version to appear in
PLB | Phys.Lett.B697:398-403,2011 | 10.1016/j.physletb.2011.02.023 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hawking radiation is studied for arbitrary scalars, fermions, and spin-1
bosons, using a tunneling approach, to every order in $\hbar$ but ignoring
back-reaction effects. It is shown that the additional quantum terms yield no
new contribution to the Hawking temperature. Indeed, it is found that the limit
of small $\hbar$ in the standard quantum WKB approximation is replaced by the
near-horizon limit in the gravitational WKB approach.
| [
{
"created": "Tue, 14 Dec 2010 21:00:01 GMT",
"version": "v1"
},
{
"created": "Sat, 18 Dec 2010 20:14:26 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Feb 2011 16:09:25 GMT",
"version": "v3"
}
] | 2011-05-19 | [
[
"Yale",
"Alexandre",
""
]
] | Hawking radiation is studied for arbitrary scalars, fermions, and spin-1 bosons, using a tunneling approach, to every order in $\hbar$ but ignoring back-reaction effects. It is shown that the additional quantum terms yield no new contribution to the Hawking temperature. Indeed, it is found that the limit of small $\hbar$ in the standard quantum WKB approximation is replaced by the near-horizon limit in the gravitational WKB approach. |
gr-qc/9701025 | Claude Barrabes | C. Barrabes, G.F. Bressange and P.A. Hogan | Some Physical Consequences of Abrupt Changes in the Multipole Moments of
a Gravitating Body | 26 pages, tex, no figures, to appear in Phys.Rev.D | Phys.Rev.D55:3477-3484,1997 | 10.1103/PhysRevD.55.3477 | null | gr-qc | null | The Barrab\`es-Israel theory of light-like shells in General Relativity is
used to show explicitly that in general a light-like shell is accompanied by an
impulsive gravitational wave. The gravitational wave is identified by its
Petrov Type N contribution to a Dirac delta-function term in the Weyl conformal
curvature tensor (with the delta-function singular on the null hypersurface
history of the wave and shell). An example is described in which an
asymptotically flat static vacuum Weyl space-time experiences a sudden change
across a null hypersurface in the multipole moments of its isolated axially
symmetric source. A light-like shell and an impulsive gravitational wave are
identified, both having the null hypersurface as history. The stress-energy in
the shell is dominated (at large distance from the source) by the jump in the
monopole moment (the mass) of the source with the jump in the quadrupole moment
mainly responsible for the stress being anisotropic. The gravitational wave
owes its existence principally to the jump in the quadrupole moment of the
source confirming what would be expected.
| [
{
"created": "Mon, 13 Jan 1997 15:11:21 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Barrabes",
"C.",
""
],
[
"Bressange",
"G. F.",
""
],
[
"Hogan",
"P. A.",
""
]
] | The Barrab\`es-Israel theory of light-like shells in General Relativity is used to show explicitly that in general a light-like shell is accompanied by an impulsive gravitational wave. The gravitational wave is identified by its Petrov Type N contribution to a Dirac delta-function term in the Weyl conformal curvature tensor (with the delta-function singular on the null hypersurface history of the wave and shell). An example is described in which an asymptotically flat static vacuum Weyl space-time experiences a sudden change across a null hypersurface in the multipole moments of its isolated axially symmetric source. A light-like shell and an impulsive gravitational wave are identified, both having the null hypersurface as history. The stress-energy in the shell is dominated (at large distance from the source) by the jump in the monopole moment (the mass) of the source with the jump in the quadrupole moment mainly responsible for the stress being anisotropic. The gravitational wave owes its existence principally to the jump in the quadrupole moment of the source confirming what would be expected. |
1610.08744 | Luca Buoninfante | L. Buoninfante | Ghost and singularity free theories of gravity | Master's thesis. Review. 139 pages. Supervisors: G. Lambiase and A.
Mazumdar. References added, changes to text | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Albert Einstein's General Relativity (GR) from 1916 has become the widely
accepted theory of gravity and been tested observationally to a very high
precision at different scales of energy and distance. At the same time, there
still remain important questions to resolve. At the classical level
cosmological and black hole singularities are examples of problems which let us
notice that GR is incomplete at short distances (high energy). Furthermore, at
the quantum level GR is not ultraviolet (UV) complete, namely it is not
perturbatively renormalizable. Most of the work try to solve these problems
modifying GR by considering finite higher order derivative terms. Fourth
Derivative Gravity, for example, turns out to be renormalizable, but at the
same time it introduces ghost. To avoid both UV divergence and presence of
ghost one could consider sets of infinite higher derivative terms that can be
expressed in the form of entire functions satisfying the special property do
not introduce new poles other than GR graviton one. By making a special choice
for these entire functions, one could show that such a theory describes a
gravity that, at least in the linear regime, can avoid both the presence of
ghost and classical singularities (both black hole and cosmological
singularities). In this master's thesis we review some of these aspects
regarding gravitational interaction, focusing more on the classical level. Most
of the calculations are done in detail and an extended treatment of the
formalism of the spin projector operators is presented.
| [
{
"created": "Thu, 27 Oct 2016 12:22:42 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Oct 2016 16:58:55 GMT",
"version": "v2"
},
{
"created": "Fri, 4 Nov 2016 16:21:39 GMT",
"version": "v3"
},
{
"created": "Thu, 8 Dec 2016 14:21:41 GMT",
"version": "v4"
}
] | 2016-12-09 | [
[
"Buoninfante",
"L.",
""
]
] | Albert Einstein's General Relativity (GR) from 1916 has become the widely accepted theory of gravity and been tested observationally to a very high precision at different scales of energy and distance. At the same time, there still remain important questions to resolve. At the classical level cosmological and black hole singularities are examples of problems which let us notice that GR is incomplete at short distances (high energy). Furthermore, at the quantum level GR is not ultraviolet (UV) complete, namely it is not perturbatively renormalizable. Most of the work try to solve these problems modifying GR by considering finite higher order derivative terms. Fourth Derivative Gravity, for example, turns out to be renormalizable, but at the same time it introduces ghost. To avoid both UV divergence and presence of ghost one could consider sets of infinite higher derivative terms that can be expressed in the form of entire functions satisfying the special property do not introduce new poles other than GR graviton one. By making a special choice for these entire functions, one could show that such a theory describes a gravity that, at least in the linear regime, can avoid both the presence of ghost and classical singularities (both black hole and cosmological singularities). In this master's thesis we review some of these aspects regarding gravitational interaction, focusing more on the classical level. Most of the calculations are done in detail and an extended treatment of the formalism of the spin projector operators is presented. |
1811.08503 | Carlos A. S. Almeida | D. A. Gomes, R. V. Maluf, C. A. S. Almeida | Thermodynamics of Schwarzschild-like black holes in modified gravity
models | Title changed, section VI suppressed. Other slight modifications in
order to match the accepted version to appears in Annals of Physics. 17
pages, no figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Over the last decades, many methods were developed to prove Hawking
radiation. Recently, a semiclassical method known as the tunneling method has
been proposed as a more straightforward way of derivating black hole
thermodynamical properties. This method has been widely applied to a vast sort
of spacetimes with satisfactory results. In this work, we obtain the black hole
thermodynamics in the presence of a Lorentz symmetry breaking (LSB). We apply
the Hamilton-Jacobi method to Schwarzschild-like black holes, and we
investigate whether the LSB affects their thermodynamics. The results found
show that the LSB not only changes the black hole thermodynamic quantities but
also makes it necessary to modify the standard first law of thermodynamics.
| [
{
"created": "Tue, 20 Nov 2018 21:58:30 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Apr 2020 23:49:56 GMT",
"version": "v2"
}
] | 2020-04-28 | [
[
"Gomes",
"D. A.",
""
],
[
"Maluf",
"R. V.",
""
],
[
"Almeida",
"C. A. S.",
""
]
] | Over the last decades, many methods were developed to prove Hawking radiation. Recently, a semiclassical method known as the tunneling method has been proposed as a more straightforward way of derivating black hole thermodynamical properties. This method has been widely applied to a vast sort of spacetimes with satisfactory results. In this work, we obtain the black hole thermodynamics in the presence of a Lorentz symmetry breaking (LSB). We apply the Hamilton-Jacobi method to Schwarzschild-like black holes, and we investigate whether the LSB affects their thermodynamics. The results found show that the LSB not only changes the black hole thermodynamic quantities but also makes it necessary to modify the standard first law of thermodynamics. |
2106.03203 | Sarbari Guha Dr. | Sucheta Datta and Sarbari Guha | Propagation of Axial and Polar Gravitational Waves in Kantowski-Sachs
Universe | 26 pages, 3 figures, accepted for publication in Physics of the Dark
Universe | Physics of the Dark Universe 34 (2021) 100890 | 10.1016/j.dark.2021.100890 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We apply the Regge-Wheeler formalism to study axial and polar gravitational
waves in Kantowski-Sachs universe. The background field equations and the
linearised perturbation equations for the modes are derived in presence of
matter. To find analytical solutions, we analyze the propagation of waves in
vacuum spacetime. The background field equations in absence of matter are
solved by assuming the expansion scalar to be proportional to the shear scalar.
Using the method of separation of variables, the axial perturbation parameter $
h_0(t, r) $ is obtained from its wave equation. The other perturbation $ h_1(t,
r) $ is then determined from $ h_0(t, r) $. The anisotropy of the background
spacetime is responsible for the damping of the axial waves. The polar
perturbation equations are much more involved compared to their FLRW
counterparts, as well as to the axial perturbations in Kantowski-Sachs
background. In both the axial and polar cases, the radial and temporal
solutions separate out as products. The temporal part of the polar perturbation
solutions are plotted against time to obtain an order of magnitude estimate of
the frequency of the propagating GWs and lies in the range 1000-2000 Hz. Using
standard observational data for the GW strain we have placed constraints on the
parameters in the polar perturbation solutions. The perturbation equations in
presence of matter show that the axial waves can cause perturbations only in
the azimuthal velocity of the fluid without deforming the matter field. But the
polar waves must perturb the energy density, the pressure and also the
non-azimuthal components of the fluid velocity.
| [
{
"created": "Sun, 6 Jun 2021 18:25:56 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Sep 2021 18:31:42 GMT",
"version": "v2"
}
] | 2021-10-15 | [
[
"Datta",
"Sucheta",
""
],
[
"Guha",
"Sarbari",
""
]
] | We apply the Regge-Wheeler formalism to study axial and polar gravitational waves in Kantowski-Sachs universe. The background field equations and the linearised perturbation equations for the modes are derived in presence of matter. To find analytical solutions, we analyze the propagation of waves in vacuum spacetime. The background field equations in absence of matter are solved by assuming the expansion scalar to be proportional to the shear scalar. Using the method of separation of variables, the axial perturbation parameter $ h_0(t, r) $ is obtained from its wave equation. The other perturbation $ h_1(t, r) $ is then determined from $ h_0(t, r) $. The anisotropy of the background spacetime is responsible for the damping of the axial waves. The polar perturbation equations are much more involved compared to their FLRW counterparts, as well as to the axial perturbations in Kantowski-Sachs background. In both the axial and polar cases, the radial and temporal solutions separate out as products. The temporal part of the polar perturbation solutions are plotted against time to obtain an order of magnitude estimate of the frequency of the propagating GWs and lies in the range 1000-2000 Hz. Using standard observational data for the GW strain we have placed constraints on the parameters in the polar perturbation solutions. The perturbation equations in presence of matter show that the axial waves can cause perturbations only in the azimuthal velocity of the fluid without deforming the matter field. But the polar waves must perturb the energy density, the pressure and also the non-azimuthal components of the fluid velocity. |
gr-qc/0507093 | E. Paul J. Haas de | E.P.J. de Haas | The combination of de Broglie's Harmony of the Phases and Mie's theory
of gravity results in a Principle of Equivalence for Quantum Gravity | 8 pages, 2 figures | Annales Fond.Broglie 29 (2004) 707-726 | null | null | gr-qc | null | Under a Lorentz-transformation, Mie's 1912 gravitational mass behaves
identical as de Broglie's 1923 clock-like frequency. The same goes for Mie's
inertial mass and de Broglie's wave-like frequency. This allows the
interpretation of de Broglie's "Harmony of the Phases" as a "Principle of
Equivalence" for Quantum Gravity. Thus, the particle-wave duality can be given
a realist interpretation. The "Mie-de Broglie" interpretation suggests a
correction of Hamilton's variational principle in the quantum domain. The
equivalence of the masses can be seen as the classical "limit" of the quantum
equivalence of the phases.
| [
{
"created": "Thu, 21 Jul 2005 16:35:52 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Haas",
"E. P. J.",
""
]
] | Under a Lorentz-transformation, Mie's 1912 gravitational mass behaves identical as de Broglie's 1923 clock-like frequency. The same goes for Mie's inertial mass and de Broglie's wave-like frequency. This allows the interpretation of de Broglie's "Harmony of the Phases" as a "Principle of Equivalence" for Quantum Gravity. Thus, the particle-wave duality can be given a realist interpretation. The "Mie-de Broglie" interpretation suggests a correction of Hamilton's variational principle in the quantum domain. The equivalence of the masses can be seen as the classical "limit" of the quantum equivalence of the phases. |
2406.16636 | Jorge Valencia | Jorge Valencia, Rodrigo Tenorio, Maria Rossell\'o-Sastre, Sascha Husa | Mind the step: On the frequency-domain analysis of gravitational-wave
memory waveforms | 13 pages, 13 figures | null | null | LIGO-P2400263 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Gravitational-wave memory is characterized by a signal component that
persists after a transient signal has decayed. Treating such signals in the
frequency domain is non-trivial, since discrete Fourier transforms assume
periodic signals on finite time intervals. In order to reduce artifacts in the
Fourier transform, it is common to use recipes that involve windowing and
padding with constant values. Here we discuss how to regularize the Fourier
transform in a straightforward way by splitting the signal into a given sigmoid
function that can be Fourier transformed in closed form, and a residual which
does depend on the details of the gravitational-wave signal and has to be
Fourier transformed numerically, but does not contain a persistent component.
We provide a detailed discussion of how to map between continuous and discrete
Fourier transforms of signals that contain a persistent component. We apply
this approach to discuss the frequency-domain phenomenology of the $(\ell=2,
m=0)$ spherical harmonic mode, which contains both a memory and an oscillatory
ringdown component.
| [
{
"created": "Mon, 24 Jun 2024 13:42:11 GMT",
"version": "v1"
}
] | 2024-06-25 | [
[
"Valencia",
"Jorge",
""
],
[
"Tenorio",
"Rodrigo",
""
],
[
"Rosselló-Sastre",
"Maria",
""
],
[
"Husa",
"Sascha",
""
]
] | Gravitational-wave memory is characterized by a signal component that persists after a transient signal has decayed. Treating such signals in the frequency domain is non-trivial, since discrete Fourier transforms assume periodic signals on finite time intervals. In order to reduce artifacts in the Fourier transform, it is common to use recipes that involve windowing and padding with constant values. Here we discuss how to regularize the Fourier transform in a straightforward way by splitting the signal into a given sigmoid function that can be Fourier transformed in closed form, and a residual which does depend on the details of the gravitational-wave signal and has to be Fourier transformed numerically, but does not contain a persistent component. We provide a detailed discussion of how to map between continuous and discrete Fourier transforms of signals that contain a persistent component. We apply this approach to discuss the frequency-domain phenomenology of the $(\ell=2, m=0)$ spherical harmonic mode, which contains both a memory and an oscillatory ringdown component. |
0705.2880 | Sam Dolan Dr | Sam R. Dolan | Instability of the massive Klein-Gordon field on the Kerr spacetime | Added references. 27 pages, 7 figures | Phys.Rev.D76:084001,2007 | 10.1103/PhysRevD.76.084001 | null | gr-qc hep-th | null | We investigate the instability of the massive scalar field in the vicinity of
a rotating black hole. The instability arises from amplification caused by the
classical superradiance effect. The instability affects bound states: solutions
to the massive Klein-Gordon equation which tend to zero at infinity. We
calculate the spectrum of bound state frequencies on the Kerr background using
a continued fraction method, adapted from studies of quasinormal modes. We
demonstrate that the instability is most significant for the $l = 1$, $m = 1$
state, for $M \mu \lesssim 0.5$. For a fast rotating hole ($a = 0.99$) we find
a maximum growth rate of $\tau^{-1} \approx 1.5 \times 10^{-7} (GM/c^3)^{-1}$,
at $M \mu \approx 0.42$. The physical implications are discussed.
| [
{
"created": "Sun, 20 May 2007 17:56:25 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jun 2007 09:26:12 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Dolan",
"Sam R.",
""
]
] | We investigate the instability of the massive scalar field in the vicinity of a rotating black hole. The instability arises from amplification caused by the classical superradiance effect. The instability affects bound states: solutions to the massive Klein-Gordon equation which tend to zero at infinity. We calculate the spectrum of bound state frequencies on the Kerr background using a continued fraction method, adapted from studies of quasinormal modes. We demonstrate that the instability is most significant for the $l = 1$, $m = 1$ state, for $M \mu \lesssim 0.5$. For a fast rotating hole ($a = 0.99$) we find a maximum growth rate of $\tau^{-1} \approx 1.5 \times 10^{-7} (GM/c^3)^{-1}$, at $M \mu \approx 0.42$. The physical implications are discussed. |
1108.3793 | Benjamin K Tippett | Benjamin K. Tippett | Gravitational Lensing as a Mechanism For Effective Cloaking | 5 pages, 6 figures | null | 10.1103/PhysRevD.84.104034 | null | gr-qc physics.optics physics.pop-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In light of the surge in popularity of electromagnetic cloaking devices, we
consider whether it is possible to use gravitational lensing to cloak a volume
of spacetime. A metric for such a spacetime geometry is presented, and its
geometric and physical implications are explained.
| [
{
"created": "Thu, 18 Aug 2011 16:54:09 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Sep 2011 16:38:59 GMT",
"version": "v2"
}
] | 2012-10-30 | [
[
"Tippett",
"Benjamin K.",
""
]
] | In light of the surge in popularity of electromagnetic cloaking devices, we consider whether it is possible to use gravitational lensing to cloak a volume of spacetime. A metric for such a spacetime geometry is presented, and its geometric and physical implications are explained. |
0712.0645 | Bin Wang | Xiaoping Rao, Bin Wang, Guohong Yang | Quasinormal modes and phase Transition of black holes | 6 pages | Phys.Lett.B649:472-477,2007 | 10.1016/j.physletb.2007.04.049 | null | gr-qc | null | We have studied the scalar field as well as the fermonic field perturbations
in the background of the massless BTZ black holes. Comparing with the
perturbation results in the generic nonrotating BTZ black hole background, we
found that the massless BTZ hole contains only normal modes in the
perturbations. We argued that this special property reflects that the massless
BTZ black hole is a different phase from that of the generic nonrotating BTZ
hole.
| [
{
"created": "Wed, 5 Dec 2007 03:20:48 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Rao",
"Xiaoping",
""
],
[
"Wang",
"Bin",
""
],
[
"Yang",
"Guohong",
""
]
] | We have studied the scalar field as well as the fermonic field perturbations in the background of the massless BTZ black holes. Comparing with the perturbation results in the generic nonrotating BTZ black hole background, we found that the massless BTZ hole contains only normal modes in the perturbations. We argued that this special property reflects that the massless BTZ black hole is a different phase from that of the generic nonrotating BTZ hole. |
1210.2046 | Oleg Zaslavskii | O. B. Zaslavskii | Acceleration of particles by quasiblack holes | 8 pages. Final version | Int. Journ. Mod. Phys. D. 22 6 (2013) 1350028 | 10.1142/S0218271813500284 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | If two particles collide near the black hole horizon, the energy in the
centre of mass (CM) frame can grow indefinitely (the so-called the BSW effect).
This requires fine-tuning the parameters (the energy, angular momentum or
electric charge) of one particle. We show that the CM energy can be unbound
also for collisions in the space-time of quasiblack holes - QBHs (the objects
on the threshold of forming the horizon which do not collapse). It does not
require special fine-tuning of parameters and occurs when any particle inside a
QBH having a finite energy collides with the particle that entered a QBH from
the outside region.
| [
{
"created": "Sun, 7 Oct 2012 12:01:30 GMT",
"version": "v1"
},
{
"created": "Sun, 3 Mar 2013 19:33:18 GMT",
"version": "v2"
},
{
"created": "Fri, 5 Apr 2013 23:20:32 GMT",
"version": "v3"
}
] | 2015-06-11 | [
[
"Zaslavskii",
"O. B.",
""
]
] | If two particles collide near the black hole horizon, the energy in the centre of mass (CM) frame can grow indefinitely (the so-called the BSW effect). This requires fine-tuning the parameters (the energy, angular momentum or electric charge) of one particle. We show that the CM energy can be unbound also for collisions in the space-time of quasiblack holes - QBHs (the objects on the threshold of forming the horizon which do not collapse). It does not require special fine-tuning of parameters and occurs when any particle inside a QBH having a finite energy collides with the particle that entered a QBH from the outside region. |
0801.1823 | Manuel Tiglio | Oleg Korobkin, Burak Aksoylu, Michael Holst, Enrique Pazos, Manuel
Tiglio | Solving the Einstein constraint equations on multi-block triangulations
using finite element methods | Changes made to match the version to appear in Classical and Quantum
Gravity | Class. Quantum Grav. 26, 145007 (2009) | 10.1088/0264-9381/26/14/145007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In order to generate initial data for nonlinear relativistic simulations, one
needs to solve the Einstein constraints, which can be cast into a coupled set
of nonlinear elliptic equations. Here we present an approach for solving these
equations on three-dimensional multi-block domains using finite element
methods. We illustrate our approach on a simple example of Brill wave initial
data, with the constraints reducing to a single linear elliptic equation for
the conformal factor $\psi$. We use quadratic Lagrange elements on
semi-structured simplicial meshes, obtained by triangulation of multi-block
grids. In the case of uniform refinement the scheme is superconvergent at most
mesh vertices, due to local symmetry of the finite element basis with respect
to local spatial inversions. We show that in the superconvergent case
subsequent unstructured mesh refinements do not improve the quality of our
initial data. As proof of concept that this approach is feasible for generating
multi-block initial data in three dimensions, after constructing the initial
data we evolve them in time using a high order finite-differencing multi-block
approach and extract the gravitational waves from the numerical solution.
| [
{
"created": "Fri, 11 Jan 2008 19:20:08 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jan 2008 21:33:19 GMT",
"version": "v2"
},
{
"created": "Wed, 3 Jun 2009 07:05:21 GMT",
"version": "v3"
}
] | 2015-05-13 | [
[
"Korobkin",
"Oleg",
""
],
[
"Aksoylu",
"Burak",
""
],
[
"Holst",
"Michael",
""
],
[
"Pazos",
"Enrique",
""
],
[
"Tiglio",
"Manuel",
""
]
] | In order to generate initial data for nonlinear relativistic simulations, one needs to solve the Einstein constraints, which can be cast into a coupled set of nonlinear elliptic equations. Here we present an approach for solving these equations on three-dimensional multi-block domains using finite element methods. We illustrate our approach on a simple example of Brill wave initial data, with the constraints reducing to a single linear elliptic equation for the conformal factor $\psi$. We use quadratic Lagrange elements on semi-structured simplicial meshes, obtained by triangulation of multi-block grids. In the case of uniform refinement the scheme is superconvergent at most mesh vertices, due to local symmetry of the finite element basis with respect to local spatial inversions. We show that in the superconvergent case subsequent unstructured mesh refinements do not improve the quality of our initial data. As proof of concept that this approach is feasible for generating multi-block initial data in three dimensions, after constructing the initial data we evolve them in time using a high order finite-differencing multi-block approach and extract the gravitational waves from the numerical solution. |
1506.05336 | Minas Tsoukalas | Gaston Giribet and Minas Tsoukalas | Warped-AdS3 black holes with scalar halo | v2, 7 pages, minor corrections, version accepted to PRD | Phys. Rev. D 92, 064027 (2015) | 10.1103/PhysRevD.92.064027 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a stretched (aka Warped) Anti-de Sitter black hole in 3
dimensions supported by a real scalar field configuration. The latter is
regular everywhere outside and on the horizon. No hair theorems in 3 dimensions
demand the matter to be coupled to the curvature in a non-minimal way; however,
this coupling can still be of the Horndeski type, i.e. yielding second order
field equations similar to those appearing in the context of Galileon theories.
These Warped-Anti-de Sitter black holes exhibit interesting thermodynamical
properties, such as finite Hawking temperature and entropy. We compute the
black hole entropy in the gravity theory and speculate with the possibility of
this to admit a microscopic description in terms of a dual (Warped) Conformal
Field Theory. We also discuss the inner and outer black hole mechanics.
| [
{
"created": "Wed, 17 Jun 2015 13:49:36 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Sep 2015 12:41:38 GMT",
"version": "v2"
}
] | 2015-09-25 | [
[
"Giribet",
"Gaston",
""
],
[
"Tsoukalas",
"Minas",
""
]
] | We construct a stretched (aka Warped) Anti-de Sitter black hole in 3 dimensions supported by a real scalar field configuration. The latter is regular everywhere outside and on the horizon. No hair theorems in 3 dimensions demand the matter to be coupled to the curvature in a non-minimal way; however, this coupling can still be of the Horndeski type, i.e. yielding second order field equations similar to those appearing in the context of Galileon theories. These Warped-Anti-de Sitter black holes exhibit interesting thermodynamical properties, such as finite Hawking temperature and entropy. We compute the black hole entropy in the gravity theory and speculate with the possibility of this to admit a microscopic description in terms of a dual (Warped) Conformal Field Theory. We also discuss the inner and outer black hole mechanics. |
1601.04506 | Helmut Friedrich | Helmut Friedrich | Sharp asymptotics for Einstein-$\lambda$-dust flows | 44 pages | null | 10.1007/s00220-016-2716-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the Einstein-dust equations with positive cosmological constant
$\lambda$ on manifolds with time slices diffeomorphic to an orientable, compact
3-manifold $S$. It is shown that the set of standard Cauchy data for the
Einstein-$\lambda$-dust equations on $S$ contains an open (in terms of suitable
Sobolev norms) subset of data that develop into solutions which admit at future
time-like infinity a space-like conformal boundary ${\cal J}^+$ that is
$C^{\infty}$ if the data are of class $C^{\infty}$ and of correspondingly lower
smoothness otherwise. As a particular case follows a strong stability result
for FLRW solutions. The solutions can conveniently be characterized in terms of
their asymptotic end data induced on ${\cal J}^+$, only a linear equation must
be solved to construct such data. In the case where the energy density
$\hat{\rho}$ is everywhere positive such data can be constructed without
solving any differential equation at all.
| [
{
"created": "Mon, 18 Jan 2016 13:33:48 GMT",
"version": "v1"
}
] | 2016-08-24 | [
[
"Friedrich",
"Helmut",
""
]
] | We consider the Einstein-dust equations with positive cosmological constant $\lambda$ on manifolds with time slices diffeomorphic to an orientable, compact 3-manifold $S$. It is shown that the set of standard Cauchy data for the Einstein-$\lambda$-dust equations on $S$ contains an open (in terms of suitable Sobolev norms) subset of data that develop into solutions which admit at future time-like infinity a space-like conformal boundary ${\cal J}^+$ that is $C^{\infty}$ if the data are of class $C^{\infty}$ and of correspondingly lower smoothness otherwise. As a particular case follows a strong stability result for FLRW solutions. The solutions can conveniently be characterized in terms of their asymptotic end data induced on ${\cal J}^+$, only a linear equation must be solved to construct such data. In the case where the energy density $\hat{\rho}$ is everywhere positive such data can be constructed without solving any differential equation at all. |
0901.0993 | Doreen M\"uller | Benny Walther, Bernd Bruegmann, Doreen Mueller | Numerical black hole initial data with low eccentricity based on
post-Newtonian orbital parameters | 20 pages, 11 figures, pdflatex; V2 with minor changes according to
published version | Phys.Rev.D79:124040,2009 | 10.1103/PhysRevD.79.124040 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black hole binaries on non-eccentric orbits form an important subclass of
gravitational wave sources, but it is a non-trivial issue to construct
numerical initial data with minimal initial eccentricity for numerical
simulations. We compute post-Newtonian orbital parameters for quasi-spherical
orbits using the method of Buonanno, Chen and Damour (2006) and examine the
resulting eccentricity in numerical simulations. Four different methods are
studied resulting from the choice of Taylor-expanded or effective-one-body
Hamiltonians, and from two choices for the energy flux. The eccentricity
increases for unequal masses and for spinning black holes, but remains smaller
than that obtained from previous post-Newtonian approaches. The
effective-one-body Hamiltonian offers advantages for decreasing initial
separation as expected, but in the context of this study also performs
significantly better than the Taylor-expanded Hamiltonian for binaries with
spin.
| [
{
"created": "Thu, 8 Jan 2009 09:15:52 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Sep 2009 15:35:48 GMT",
"version": "v2"
},
{
"created": "Fri, 26 Mar 2010 15:37:56 GMT",
"version": "v3"
}
] | 2010-03-29 | [
[
"Walther",
"Benny",
""
],
[
"Bruegmann",
"Bernd",
""
],
[
"Mueller",
"Doreen",
""
]
] | Black hole binaries on non-eccentric orbits form an important subclass of gravitational wave sources, but it is a non-trivial issue to construct numerical initial data with minimal initial eccentricity for numerical simulations. We compute post-Newtonian orbital parameters for quasi-spherical orbits using the method of Buonanno, Chen and Damour (2006) and examine the resulting eccentricity in numerical simulations. Four different methods are studied resulting from the choice of Taylor-expanded or effective-one-body Hamiltonians, and from two choices for the energy flux. The eccentricity increases for unequal masses and for spinning black holes, but remains smaller than that obtained from previous post-Newtonian approaches. The effective-one-body Hamiltonian offers advantages for decreasing initial separation as expected, but in the context of this study also performs significantly better than the Taylor-expanded Hamiltonian for binaries with spin. |
0712.2260 | Marcelo Salgado | Marcelo Salgado and David Martinez-del Rio | The initial value problem of scalar-tensor theories of gravity | 12 pages; RevTex; Published in the Proceedings of the VII Mexican
School on Gravitation and Mathematical Physics | J.Phys.Conf.Ser.91:012004,2007 | 10.1088/1742-6596/91/1/012004 | null | gr-qc | null | The initial value problem of scalar-tensor theories of gravity (STT) is
analyzed in the physical (Jordan) frame using a 3+1 decomposition of spacetime.
A first order strongly hyperbolic system is obtained for which the well
posedness of the Cauchy problem can be established. We provide two simple
applications of the 3+1 system of equations: one for static and spherically
symmetric spacetimes which allows the construction of unstable initial data
(compact objects) for which a further black hole formation and scalar
gravitational wave emission can be analyzed, and another application is for
homogeneous and isotropic spacetimes that permits to study the dynamics of the
Universe in the framework of STT.
| [
{
"created": "Thu, 13 Dec 2007 23:33:01 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Salgado",
"Marcelo",
""
],
[
"Rio",
"David Martinez-del",
""
]
] | The initial value problem of scalar-tensor theories of gravity (STT) is analyzed in the physical (Jordan) frame using a 3+1 decomposition of spacetime. A first order strongly hyperbolic system is obtained for which the well posedness of the Cauchy problem can be established. We provide two simple applications of the 3+1 system of equations: one for static and spherically symmetric spacetimes which allows the construction of unstable initial data (compact objects) for which a further black hole formation and scalar gravitational wave emission can be analyzed, and another application is for homogeneous and isotropic spacetimes that permits to study the dynamics of the Universe in the framework of STT. |
1701.00259 | Andrei Galiautdinov | Andrei Galiautdinov (University of Georgia) and Lewis H. Ryder
(University of Kent, Canterbury) | Neutron interference in the Earth's gravitational field | 7 pages, 1 figure | null | 10.1007/s10714-017-2241-8 | null | gr-qc physics.pop-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work relates to the famous experiments, performed in 1975 and 1979 by
Werner et al., measuring neutron interference and neutron Sagnac effects in the
earth's gravitational field. Employing the method of Stodolsky in its weak
field approximation, explicit expressions are derived for the two phase shifts,
which turn out to be in agreement with the experiments and with the previously
obtained expressions derived from semi-classical arguments: these expressions
are simply modified by relativistic correction factors.
| [
{
"created": "Sun, 1 Jan 2017 16:22:05 GMT",
"version": "v1"
}
] | 2017-06-28 | [
[
"Galiautdinov",
"Andrei",
"",
"University of Georgia"
],
[
"Ryder",
"Lewis H.",
"",
"University of Kent, Canterbury"
]
] | This work relates to the famous experiments, performed in 1975 and 1979 by Werner et al., measuring neutron interference and neutron Sagnac effects in the earth's gravitational field. Employing the method of Stodolsky in its weak field approximation, explicit expressions are derived for the two phase shifts, which turn out to be in agreement with the experiments and with the previously obtained expressions derived from semi-classical arguments: these expressions are simply modified by relativistic correction factors. |
2403.09489 | Wynn C. G. Ho | Oliver H. Wilson (Haverford), Wynn C.G. Ho (Haverford) | Gravitational waves from glitch-induced f-mode oscillations in quark and
neutron stars | 12 pages, 16 figures; accepted for publication in Physical Review D | Phys. Rev. D 109, 083006 (2024) | 10.1103/PhysRevD.109.083006 | null | gr-qc astro-ph.SR nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Matter in compact stars is dense enough that transient events within the star
could have sufficiently high energies to produce detectable gravitational waves
(GWs). These GWs could be used to constrain the equation of state (EoS) for
matter in the star and could reveal that there is more than one type of EoS at
play in the population, implying that multiple types of compact stars exist.
One of these types could be quark stars, composed almost entirely of stable
quark matter, and observing GWs is a way to test for the strange matter EoS.
Here we explore the possibility that, if fundamental (f-) mode oscillations in
pulsars are induced by a pulsar glitch, then these oscillations might produce
detectable GWs. We use the existing population of pulsars and their glitches,
as well as a much larger synthesized population, along with 15 EoSs (8 for
neutron stars and 7 for quark stars) to generate frequencies, damping times,
and GW strengths for each. We find that of the EoSs examined, all quark star
EoSs produce narrower distributions of f-mode frequency than neutron star EoSs.
This result, along with other elements of the data, could be used to
differentiate between GWs (or other signals from f-modes) originating from
neutron stars and quark stars and thus could confirm the existence of quark
stars. We also find that GW astronomy is a potentially viable method for
detecting a larger population of pulsars which are not observable
electromagnetically and that future GW observatories have the possibility to
greatly expand this capability.
| [
{
"created": "Thu, 14 Mar 2024 15:30:19 GMT",
"version": "v1"
}
] | 2024-04-08 | [
[
"Wilson",
"Oliver H.",
"",
"Haverford"
],
[
"Ho",
"Wynn C. G.",
"",
"Haverford"
]
] | Matter in compact stars is dense enough that transient events within the star could have sufficiently high energies to produce detectable gravitational waves (GWs). These GWs could be used to constrain the equation of state (EoS) for matter in the star and could reveal that there is more than one type of EoS at play in the population, implying that multiple types of compact stars exist. One of these types could be quark stars, composed almost entirely of stable quark matter, and observing GWs is a way to test for the strange matter EoS. Here we explore the possibility that, if fundamental (f-) mode oscillations in pulsars are induced by a pulsar glitch, then these oscillations might produce detectable GWs. We use the existing population of pulsars and their glitches, as well as a much larger synthesized population, along with 15 EoSs (8 for neutron stars and 7 for quark stars) to generate frequencies, damping times, and GW strengths for each. We find that of the EoSs examined, all quark star EoSs produce narrower distributions of f-mode frequency than neutron star EoSs. This result, along with other elements of the data, could be used to differentiate between GWs (or other signals from f-modes) originating from neutron stars and quark stars and thus could confirm the existence of quark stars. We also find that GW astronomy is a potentially viable method for detecting a larger population of pulsars which are not observable electromagnetically and that future GW observatories have the possibility to greatly expand this capability. |
1202.1846 | Alejandro Corichi | Alejandro Corichi and Tatjana Vukasinac | Effective constrained polymeric theories and their continuum limit | 20 pages, 5 figures. Typos corrected, discussion expanded, references
added. Version to be published in PRD | Phys.Rev. D86 (2012) 064019 | 10.1103/PhysRevD.86.064019 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The classical limit of polymer quantum theories yields a one parameter family
of `effective' theories labeled by \lambda. Here we consider such families for
constrained theories and pose the problem of taking the `continuum limit',
\lambda -> 0. We put forward criteria for such question to be well posed, and
propose a concrete strategy based in the definition of appropriately
constructed Dirac observables. We analyze two models in detail, namely a
constrained oscillator and a cosmological model arising from loop quantum
cosmology. For both these models we show that the program can indeed be
completed, provided one makes a particular choice of \lambda-dependent internal
time with respect to which the dynamics is described and compared. We show that
the limiting theories exist and discuss the corresponding limit. These results
might shed some light in the problem of defining a renormalization group
approach, and its associated continuum limit, for quantum constrained systems.
| [
{
"created": "Wed, 8 Feb 2012 22:06:56 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Aug 2012 20:59:18 GMT",
"version": "v2"
}
] | 2020-06-18 | [
[
"Corichi",
"Alejandro",
""
],
[
"Vukasinac",
"Tatjana",
""
]
] | The classical limit of polymer quantum theories yields a one parameter family of `effective' theories labeled by \lambda. Here we consider such families for constrained theories and pose the problem of taking the `continuum limit', \lambda -> 0. We put forward criteria for such question to be well posed, and propose a concrete strategy based in the definition of appropriately constructed Dirac observables. We analyze two models in detail, namely a constrained oscillator and a cosmological model arising from loop quantum cosmology. For both these models we show that the program can indeed be completed, provided one makes a particular choice of \lambda-dependent internal time with respect to which the dynamics is described and compared. We show that the limiting theories exist and discuss the corresponding limit. These results might shed some light in the problem of defining a renormalization group approach, and its associated continuum limit, for quantum constrained systems. |
2312.17662 | Gerard Clement | G\'erard Cl\'ement and Khireddine Nouicer | Cotton gravity is not predictive | 11 pages, revised augmented version, incorporates input from
arXiv:2401.16008 | Phys. Lett. B 856 (2024) 138947 | null | LAPTH-065/23 | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | It is well-known that the theory of Cotton gravity proposed by Harada is
trivially solved by all isotropic and homogeneous cosmologies. We show that
this under-determination is more general. More precisely, the degree of
arbitrariness in the solutions increases with the degree of symmetry. We give
two simple examples. The first is that of static spherically symmetric
solutions, which depend on an arbitrary function of the radial coordinate. The
second is that of anisotropic cosmologies, which depend on an arbitrary
function of time.
| [
{
"created": "Fri, 29 Dec 2023 16:03:08 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Jan 2024 10:59:31 GMT",
"version": "v2"
},
{
"created": "Tue, 13 Aug 2024 08:40:51 GMT",
"version": "v3"
}
] | 2024-08-14 | [
[
"Clément",
"Gérard",
""
],
[
"Nouicer",
"Khireddine",
""
]
] | It is well-known that the theory of Cotton gravity proposed by Harada is trivially solved by all isotropic and homogeneous cosmologies. We show that this under-determination is more general. More precisely, the degree of arbitrariness in the solutions increases with the degree of symmetry. We give two simple examples. The first is that of static spherically symmetric solutions, which depend on an arbitrary function of the radial coordinate. The second is that of anisotropic cosmologies, which depend on an arbitrary function of time. |
gr-qc/9708020 | Alicia Sintes Olives | A.M. Sintes, A.A. Coley, J. Carot | Lie groups of conformal motions acting on null orbits | 5 pages, Latex | Gen.Rel.Grav. 30 (1998) 151-157 | 10.1023/A:1018885203138 | null | gr-qc | null | Space-times admitting a 3-dimensional Lie group of conformal motions $C_3$
acting on null orbits are studied. Coordinate expressions for the metric and
the conformal Killing vectors (CKV) are provided (irrespectively of the matter
content) and then all possible perfect fluid solutions are found, although none
of these verify the weak and dominant energy conditions over the whole
space-time manifold.
| [
{
"created": "Mon, 11 Aug 1997 09:44:14 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Sintes",
"A. M.",
""
],
[
"Coley",
"A. A.",
""
],
[
"Carot",
"J.",
""
]
] | Space-times admitting a 3-dimensional Lie group of conformal motions $C_3$ acting on null orbits are studied. Coordinate expressions for the metric and the conformal Killing vectors (CKV) are provided (irrespectively of the matter content) and then all possible perfect fluid solutions are found, although none of these verify the weak and dominant energy conditions over the whole space-time manifold. |
1204.1691 | Celia Escamilla-Rivera | Celia Escamilla-Rivera, Maximo Banados and Pedro G. Ferreira | A tensor instability in the Eddington inspired Born-Infeld Theory of
Gravity | 5 pages, approved by Phys. Rev. D, additional references and minor
modifications | Phys. Rev. D 85, 087302 (2012) | 10.1103/PhysRevD.85.087302 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we consider an extension to Eddington's proposal for the
gravitational action. We study tensor perturbations of a homogeneous and
isotropic space-time in the Eddington regime, where modifications to Einstein
gravity are strong. We find that the tensor mode is linearly unstable deep in
the Eddington regime and discuss its cosmological implications.
| [
{
"created": "Sat, 7 Apr 2012 23:19:59 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Apr 2012 14:50:30 GMT",
"version": "v2"
}
] | 2012-05-08 | [
[
"Escamilla-Rivera",
"Celia",
""
],
[
"Banados",
"Maximo",
""
],
[
"Ferreira",
"Pedro G.",
""
]
] | In this paper we consider an extension to Eddington's proposal for the gravitational action. We study tensor perturbations of a homogeneous and isotropic space-time in the Eddington regime, where modifications to Einstein gravity are strong. We find that the tensor mode is linearly unstable deep in the Eddington regime and discuss its cosmological implications. |
0812.5081 | Sergei Maydanyuk | Sergei P. Maydanyuk | A fully quantum method of determination of penetrability and reflection
coefficients in quantum FRW model with radiation | 28 pages, 7 figures (20 files in eps format), 4 tables | Int.J.Mod.Phys.D19:395-435,2010 | 10.1142/S0218271810016464 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the paper the closed Friedmann--Robertson--Walker model with quantization
in the presence of the positive cosmological constant and radiation is studied.
For analysis of tunneling probability for birth of an asymptotically deSitter,
inflationary Universe as a function of the radiation energy a new definition of
a "free" wave propagating inside strong fields is proposed. On such a basis,
tunneling boundary condition is corrected, penetrability and reflection
concerning to the barrier are calculated in fully quantum stationary approach.
For the first time non-zero interference between the incident and reflected
waves has been taken into account which turns out to play important role inside
cosmological potentials and could be explained by non-locality of barriers in
quantum mechanics. Inside whole region of energy of radiation the tunneling
probability for the birth of the inflationary Universe is found to be close to
its value obtained in semiclassical approach. The reflection from the barrier
is determined for the first time (which is essentially differs on 1 at the
energy of radiation close to the barrier height). The proposed method could be
easily generalized on the cosmological models with the barriers of arbitrary
shape, that has been demonstrated for the FRW-model with included Chaplygin
gas. Result is stable for variations of the studied barriers, accuracy are
found to be 11--18 digits for all coefficients and energies below the barrier
height.
| [
{
"created": "Tue, 30 Dec 2008 15:16:22 GMT",
"version": "v1"
},
{
"created": "Sat, 9 Jan 2010 10:22:52 GMT",
"version": "v2"
}
] | 2010-05-07 | [
[
"Maydanyuk",
"Sergei P.",
""
]
] | In the paper the closed Friedmann--Robertson--Walker model with quantization in the presence of the positive cosmological constant and radiation is studied. For analysis of tunneling probability for birth of an asymptotically deSitter, inflationary Universe as a function of the radiation energy a new definition of a "free" wave propagating inside strong fields is proposed. On such a basis, tunneling boundary condition is corrected, penetrability and reflection concerning to the barrier are calculated in fully quantum stationary approach. For the first time non-zero interference between the incident and reflected waves has been taken into account which turns out to play important role inside cosmological potentials and could be explained by non-locality of barriers in quantum mechanics. Inside whole region of energy of radiation the tunneling probability for the birth of the inflationary Universe is found to be close to its value obtained in semiclassical approach. The reflection from the barrier is determined for the first time (which is essentially differs on 1 at the energy of radiation close to the barrier height). The proposed method could be easily generalized on the cosmological models with the barriers of arbitrary shape, that has been demonstrated for the FRW-model with included Chaplygin gas. Result is stable for variations of the studied barriers, accuracy are found to be 11--18 digits for all coefficients and energies below the barrier height. |
1505.00600 | Olivier Minazzoli | Olivier Minazzoli, Aur\'elien Hees | Basics of the pressuron | 4 pages, proceedings of the 50th Rencontres de Moriond, Gravitation
Session: "100 years after GR", 21-28 March 2015 | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The pressuron is a specific case of a dilaton-like field that leads to a
decoupling of the scalar-field in the field equation for pressureless fluids.
Hence, the pressuron recovers general relativity in the limit of weak pressure.
Here we review its basics.
| [
{
"created": "Mon, 4 May 2015 11:54:08 GMT",
"version": "v1"
},
{
"created": "Thu, 7 May 2015 15:42:53 GMT",
"version": "v2"
}
] | 2015-05-08 | [
[
"Minazzoli",
"Olivier",
""
],
[
"Hees",
"Aurélien",
""
]
] | The pressuron is a specific case of a dilaton-like field that leads to a decoupling of the scalar-field in the field equation for pressureless fluids. Hence, the pressuron recovers general relativity in the limit of weak pressure. Here we review its basics. |
gr-qc/9406023 | Chris. Fama | Christopher J. Fama and Susan M. Scott | Invariance properties of boundary sets of open embeddings of manifolds
and their application to the abstract boundary | about 30 pp. (LaTeX/AMS-LaTeX), 8 figures included, also available
via FTP or WWW - see paper. To appear in AMS Contemporary Math. volume 170
Bemm/Duggal, eds.; CMA preprint # MRR-036-94. (Revision corrects some TeX
problems, mainly occuring when using XY-Pic.) | null | null | null | gr-qc | null | The {\em abstract boundary\/} (or {\em {\em a\/}-boundary\/}) of Scott and
Szekeres \cite{Scott94} constitutes a ``boundary'' to any $n$-dimensional,
paracompact, connected, Hausdorff, $C^\infty$-manifold (without a boundary in
the usual sense). In general relativity one deals with a {\em space-% time\/}
$(\cM,g)$ (a 4-dimensional manifold $\cM$ with a Lorentzian metric $g$),
together with a chosen preferred class of curves in $\cM$. In this case the
{\em a\/}-boundary points may represent ``singularities'' or ``points at
infinity''. Since the {\em a\/}-boundary itself, however, does not depend on
the existence of further structure on the manifold such as a Lorentzian metric
or connection, it is possible for it to be used in many contexts.
In this paper we develop some purely topological properties of abstract
boundary sets and abstract boundary points ({\em a\/}-boundary points). We
prove, amongst other things, that compactness is invariant under boundary set
equivalence, and introduce another invariant concept ({\em isolation\/}), which
encapsulates the notion that a boundary set is ``separated'' from other
boundary points of the same embedding. .......
[The abstract continues in paper proper - truncated to fit here.]
| [
{
"created": "Thu, 16 Jun 1994 06:02:09 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Jun 1994 00:09:50 GMT",
"version": "v2"
},
{
"created": "Tue, 21 Jun 1994 02:11:06 GMT",
"version": "v3"
}
] | 2008-02-03 | [
[
"Fama",
"Christopher J.",
""
],
[
"Scott",
"Susan M.",
""
]
] | The {\em abstract boundary\/} (or {\em {\em a\/}-boundary\/}) of Scott and Szekeres \cite{Scott94} constitutes a ``boundary'' to any $n$-dimensional, paracompact, connected, Hausdorff, $C^\infty$-manifold (without a boundary in the usual sense). In general relativity one deals with a {\em space-% time\/} $(\cM,g)$ (a 4-dimensional manifold $\cM$ with a Lorentzian metric $g$), together with a chosen preferred class of curves in $\cM$. In this case the {\em a\/}-boundary points may represent ``singularities'' or ``points at infinity''. Since the {\em a\/}-boundary itself, however, does not depend on the existence of further structure on the manifold such as a Lorentzian metric or connection, it is possible for it to be used in many contexts. In this paper we develop some purely topological properties of abstract boundary sets and abstract boundary points ({\em a\/}-boundary points). We prove, amongst other things, that compactness is invariant under boundary set equivalence, and introduce another invariant concept ({\em isolation\/}), which encapsulates the notion that a boundary set is ``separated'' from other boundary points of the same embedding. ....... [The abstract continues in paper proper - truncated to fit here.] |
1509.09017 | Dao-Jun Liu | Yang Huang, Dao-Jun Liu | Charged scalar perturbations around a regular magnetic black hole | 7 pages, 4 figures, substantially revised, published in Phys. Rev. D | Physical Review D 93, 104011 (2016) | 10.1103/PhysRevD.93.104011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study charged scalar perturbations in the background of a regular magnetic
black hole. In this case, the charged scalar perturbation does not result in
superradiance. By using careful time-domain analysis, we show that the charge
of scalar field can change the real part of quasinormal frequency, but has
little impact on the imaginary part of quasinormal frequency and the behavior
of the late-time tail. Therefore, the regular magnetic black hole may be stable
under the perturbations of charged scalar field at the linear level.
| [
{
"created": "Wed, 30 Sep 2015 05:24:23 GMT",
"version": "v1"
},
{
"created": "Wed, 4 May 2016 01:21:57 GMT",
"version": "v2"
}
] | 2016-05-05 | [
[
"Huang",
"Yang",
""
],
[
"Liu",
"Dao-Jun",
""
]
] | We study charged scalar perturbations in the background of a regular magnetic black hole. In this case, the charged scalar perturbation does not result in superradiance. By using careful time-domain analysis, we show that the charge of scalar field can change the real part of quasinormal frequency, but has little impact on the imaginary part of quasinormal frequency and the behavior of the late-time tail. Therefore, the regular magnetic black hole may be stable under the perturbations of charged scalar field at the linear level. |
1101.1654 | Yurii Ignatyev | A.A. Agathonov and Yu.G. Ignatyev | Exact solution of the relativistic magnetohydrodynamic equations in the
background of a plane gravitational wave with combined polarization | 5 pages, 8 references | Grav. Cosmol. Vol. 17, No.1, 2011 | 10.1134/S0202289311010038 | null | gr-qc astro-ph.HE math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain an exact solution of the self-consistent relativistic
magnetohydrodynamic equations for an anisotropic magnetoactive plasma in the
background of a plane gravitational wave metric (PGW) with an arbitrary
polarization. It is shown that, in the linear approximation in the
gravitational wave amplitude, only the $\mathbf{e_+}$ polarization of the PGW
interacts with a magnetoactive plasma.
| [
{
"created": "Sun, 9 Jan 2011 16:46:38 GMT",
"version": "v1"
}
] | 2015-05-27 | [
[
"Agathonov",
"A. A.",
""
],
[
"Ignatyev",
"Yu. G.",
""
]
] | We obtain an exact solution of the self-consistent relativistic magnetohydrodynamic equations for an anisotropic magnetoactive plasma in the background of a plane gravitational wave metric (PGW) with an arbitrary polarization. It is shown that, in the linear approximation in the gravitational wave amplitude, only the $\mathbf{e_+}$ polarization of the PGW interacts with a magnetoactive plasma. |
gr-qc/0606048 | Michael Fil'chenkov Dr | Irina Dymnikova, Michael Fil'chenkov | Gauge-noninvariance of quantum cosmology and vacuum dark energy | 5 pages, 1 figure | Phys.Lett.B635:181-185,2006 | 10.1016/j.physletb.2006.02.060 | null | gr-qc | null | We address the question how to adapt cosmological constant $\Lambda$ for
description of a vacuum dark energy density jumping from the big initial value
to the small today value suggested by observations. We find such a possibility
in the gauge-noninvariance of quantum cosmology which leads to a connection
between a choice of the gauge and quantum spectrum for a certain physical
quantity which can be specified in the framework of the minisuperspace model.
We introduce a particular gauge in which the cosmological constant $\Lambda$ is
quantized and show that making a measurement of $\Lambda$ today one can find
its small value with the biggest probability, while at the beginning of the
evolution, the biggest probability corresponds to its biggest value.
Transitions between quantum levels of $\Lambda$ in the course of the Universe
evolution, could be related to several scales for symmetry breaking.
| [
{
"created": "Mon, 12 Jun 2006 14:09:50 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Dymnikova",
"Irina",
""
],
[
"Fil'chenkov",
"Michael",
""
]
] | We address the question how to adapt cosmological constant $\Lambda$ for description of a vacuum dark energy density jumping from the big initial value to the small today value suggested by observations. We find such a possibility in the gauge-noninvariance of quantum cosmology which leads to a connection between a choice of the gauge and quantum spectrum for a certain physical quantity which can be specified in the framework of the minisuperspace model. We introduce a particular gauge in which the cosmological constant $\Lambda$ is quantized and show that making a measurement of $\Lambda$ today one can find its small value with the biggest probability, while at the beginning of the evolution, the biggest probability corresponds to its biggest value. Transitions between quantum levels of $\Lambda$ in the course of the Universe evolution, could be related to several scales for symmetry breaking. |
2112.12149 | Christian Dioguardi | Christian Dioguardi, Antonio Racioppi, Eemeli Tomberg | Slow-roll inflation in Palatini $F(R)$ gravity | 20 pages, 5 figures, 1 table, matches the published version | JHEP 06 (2022) 106 | 10.1007/JHEP06(2022)106 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study single field slow-roll inflation in the presence of $F(R)$ gravity
in the Palatini formulation. In contrast to metric $F(R)$, when rewritten in
terms of an auxiliary field and moved to the Einstein frame, Palatini $F(R)$
does not develop a new dynamical degree of freedom. However, it is not possible
to solve analytically the constraint equation of the auxiliary field for a
general $F(R)$. We propose a method that allows us to circumvent this issue and
compute the inflationary observables. We apply this method to test scenarios of
the form $F(R) = R + \alpha R^n$ and find that, as in the previously known
$n=2$ case, a large $\alpha$ suppresses the tensor-to-scalar ratio $r$. We also
find that models with $F(R)$ increasing faster than $R^2$ for large $R$ suffer
from numerous problems.
| [
{
"created": "Wed, 22 Dec 2021 18:59:37 GMT",
"version": "v1"
},
{
"created": "Sat, 9 Jul 2022 12:09:33 GMT",
"version": "v2"
}
] | 2022-07-12 | [
[
"Dioguardi",
"Christian",
""
],
[
"Racioppi",
"Antonio",
""
],
[
"Tomberg",
"Eemeli",
""
]
] | We study single field slow-roll inflation in the presence of $F(R)$ gravity in the Palatini formulation. In contrast to metric $F(R)$, when rewritten in terms of an auxiliary field and moved to the Einstein frame, Palatini $F(R)$ does not develop a new dynamical degree of freedom. However, it is not possible to solve analytically the constraint equation of the auxiliary field for a general $F(R)$. We propose a method that allows us to circumvent this issue and compute the inflationary observables. We apply this method to test scenarios of the form $F(R) = R + \alpha R^n$ and find that, as in the previously known $n=2$ case, a large $\alpha$ suppresses the tensor-to-scalar ratio $r$. We also find that models with $F(R)$ increasing faster than $R^2$ for large $R$ suffer from numerous problems. |
0810.0064 | Roman Sverdlov | Roman Sverdlov | Quantum mechanics and gravity as preclusion principles of four
dimensional geometries | I have incorporated third law of thermodynamics into the decoherence
arguments | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The goal of this paper is to employ a "preclusion principle" originally
suggested by Rafael Sorkin in order to come up with a relativistically
covariant model of quantum mechanics and gravity. Space-time is viewed as
geometry as opposed to dynamics, and "unwanted" histories in that geometry are
precluded.
| [
{
"created": "Wed, 1 Oct 2008 02:33:05 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Oct 2008 21:09:35 GMT",
"version": "v2"
},
{
"created": "Sun, 12 Oct 2008 01:20:50 GMT",
"version": "v3"
},
{
"created": "Thu, 16 Oct 2008 17:57:51 GMT",
"version": "v4"
}
] | 2008-10-16 | [
[
"Sverdlov",
"Roman",
""
]
] | The goal of this paper is to employ a "preclusion principle" originally suggested by Rafael Sorkin in order to come up with a relativistically covariant model of quantum mechanics and gravity. Space-time is viewed as geometry as opposed to dynamics, and "unwanted" histories in that geometry are precluded. |
1708.03675 | Abolhassan Mohammadi | Kh. Saaidi, A. Mohammadi, T. Golanbari | Light of Planck-2015 on Non-Canonical Inflation | 12 pages, 6 figures, 2 tables, Advances in High Energy Physics, 2015 | null | 10.1155/2015/926807 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Slow-roll inflationary scenario is considered in non-canonical scalar field
model supposing a power-law function for kinetic term, and using two
formalisms. In the first approach, the potential is considered as a power-law
function, that is the most common approach in studying inflation.
Hamilton-Jacobi approach is selected as the second formalism, so that the
Hubble parameter is introduced as a function of scalar field instead of the
potential. Employing the last observational data, the free parameters of the
model are constrained, and the predicted form of the potential and attractor
behavior of the model are considered in detail.
| [
{
"created": "Thu, 10 Aug 2017 04:37:17 GMT",
"version": "v1"
}
] | 2017-08-15 | [
[
"Saaidi",
"Kh.",
""
],
[
"Mohammadi",
"A.",
""
],
[
"Golanbari",
"T.",
""
]
] | Slow-roll inflationary scenario is considered in non-canonical scalar field model supposing a power-law function for kinetic term, and using two formalisms. In the first approach, the potential is considered as a power-law function, that is the most common approach in studying inflation. Hamilton-Jacobi approach is selected as the second formalism, so that the Hubble parameter is introduced as a function of scalar field instead of the potential. Employing the last observational data, the free parameters of the model are constrained, and the predicted form of the potential and attractor behavior of the model are considered in detail. |
gr-qc/9605011 | Domenico Giulini | Domenico Giulini | Consistently Implementing the Fields Self-Energy in Newtonian Gravity | Plain-TeX, 12 pages, no figures | Phys.Lett. A232 (1997) 165-170 | 10.1016/S0375-9601(97)00369-1 | THEP-96/7 | gr-qc | null | We consider in a pedagogical fashion alterations to Newtonian gravity due to
the postulate that all energy corresponds to active gravitational mass when
applied to the self-energy of the gravitational field. We show why a simple
addition of ${1\over c^2}$ times the gravitational field energy to the matter
density in Newton's field equation is inconsistent. A consistent prescription
is shown and discussed. The connection to general relativity is pointed out.
| [
{
"created": "Mon, 6 May 1996 14:49:03 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Giulini",
"Domenico",
""
]
] | We consider in a pedagogical fashion alterations to Newtonian gravity due to the postulate that all energy corresponds to active gravitational mass when applied to the self-energy of the gravitational field. We show why a simple addition of ${1\over c^2}$ times the gravitational field energy to the matter density in Newton's field equation is inconsistent. A consistent prescription is shown and discussed. The connection to general relativity is pointed out. |
gr-qc/0610053 | Giorgio Longhi | G.Longhi | Locality hypothesis and the speed of light | 23 pages | Found.Phys. 19 (2006) 201-223 | 10.1007/s10702-006-0513-8 | null | gr-qc | null | The locality hypothesis is generally considered necessary for the study of
the kinematics of non-inertial systems in special relativity. In this paper we
discuss this hypothesis, showing the necessity of an improvement, in order to
get a more clear understanding of the various concepts involved, like
coordinate velocity and standard velocity of light. Concrete examples are
shown, where these concepts are discussed.
| [
{
"created": "Wed, 11 Oct 2006 10:49:15 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Longhi",
"G.",
""
]
] | The locality hypothesis is generally considered necessary for the study of the kinematics of non-inertial systems in special relativity. In this paper we discuss this hypothesis, showing the necessity of an improvement, in order to get a more clear understanding of the various concepts involved, like coordinate velocity and standard velocity of light. Concrete examples are shown, where these concepts are discussed. |
0803.2228 | Neil Russell | Neil Russell | Lorentz Violation and Torsion | 5 pp, talk given at 4th Meeting on Lorentz and CPT Violation,
Bloomington, Indiana, USA, 8-11 August 2007 | null | 10.1142/9789812779519_0044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this proceedings, similarities between the structure of theories with
Lorentz violation and theories with constant torsion in flat spacetime are
exploited to place bounds on torsion components. An example is given showing
the analysis leading to bounds on the axial-vector and mixed-symmetry
components of torsion, based on a dual-maser experiment.
| [
{
"created": "Fri, 14 Mar 2008 19:17:26 GMT",
"version": "v1"
}
] | 2016-11-09 | [
[
"Russell",
"Neil",
""
]
] | In this proceedings, similarities between the structure of theories with Lorentz violation and theories with constant torsion in flat spacetime are exploited to place bounds on torsion components. An example is given showing the analysis leading to bounds on the axial-vector and mixed-symmetry components of torsion, based on a dual-maser experiment. |
2306.12350 | Giulia Ventagli | Giulia Ventagli, Paolo Pani, Thomas P. Sotiriou | Incompatibility of gravity theories with auxiliary fields with the
Standard Model | 12 pages, added references, corrected typos, revised argument in
section IV, results unchanged | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Theories of gravity with auxiliary fields are of particular interest since
they are able to circumvent Lovelock's theorem while avoiding to introduce new
degrees of freedom. This type of theories introduces derivatives of the
stress-energy tensor in the modified Einstein equation. This peculiar structure
of the field equations was shown to lead to spacetime singularities on the
surface of stars. Here we focus on yet another problem afflicting gravity
theories with auxiliary field. We show that such theories introduce deviations
to the Standard Model unless one severely constrains the parameters of the
theory, preventing them to produce significant phenomenology at large scales.
We first consider the specific case of Palatini $f({\cal R})$ gravity, to
clarify the results previously obtained in arXiv:astro-ph/0308111. We show that
the matter fields satisfy the Standard Model field equations which reduce to
those predicted by General Relativity in the local frame only at tree level,
whereas at higher orders in perturbation theory they are affected by
corrections that percolate from the gravity sector regardless of the specific
$f({\cal R})$ model considered. Finally, we show that this is a more general
issue affecting theories with auxiliary fields connected to the same terms
responsible for the appearance of surface singularities.
| [
{
"created": "Wed, 21 Jun 2023 15:46:45 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Jan 2024 19:07:56 GMT",
"version": "v2"
}
] | 2024-01-17 | [
[
"Ventagli",
"Giulia",
""
],
[
"Pani",
"Paolo",
""
],
[
"Sotiriou",
"Thomas P.",
""
]
] | Theories of gravity with auxiliary fields are of particular interest since they are able to circumvent Lovelock's theorem while avoiding to introduce new degrees of freedom. This type of theories introduces derivatives of the stress-energy tensor in the modified Einstein equation. This peculiar structure of the field equations was shown to lead to spacetime singularities on the surface of stars. Here we focus on yet another problem afflicting gravity theories with auxiliary field. We show that such theories introduce deviations to the Standard Model unless one severely constrains the parameters of the theory, preventing them to produce significant phenomenology at large scales. We first consider the specific case of Palatini $f({\cal R})$ gravity, to clarify the results previously obtained in arXiv:astro-ph/0308111. We show that the matter fields satisfy the Standard Model field equations which reduce to those predicted by General Relativity in the local frame only at tree level, whereas at higher orders in perturbation theory they are affected by corrections that percolate from the gravity sector regardless of the specific $f({\cal R})$ model considered. Finally, we show that this is a more general issue affecting theories with auxiliary fields connected to the same terms responsible for the appearance of surface singularities. |
gr-qc/9902057 | Tekin Dereli | T. Dereli (METU, Ankara), R. W. Tucker (Lancaster U.) | Self-gravitating line sources of weak hypercharge | 4 pages, REVTeX file, no figures | Class.Quant.Grav.16:L45-L49,1999 | 10.1088/0264-9381/16/8/101 | null | gr-qc | null | We explore the role of the Cremmer-Scherk mechanism in the context of low
energy effective string theory by coupling the antisymmetric 3-form gauge
potential to an Abelian gauge potential carrying weak hypercharge. The theory
admits a class of exact self-gravitating solutions in the spontaneously broken
phase in which the dual fields acquire massive perturbative modes. Despite the
massive nature of these fields they admit non-perturbative progressive
longitudinal modes that together with pp-type gravitational waves travel in a
direction of a line source at the speed of light.
| [
{
"created": "Fri, 19 Feb 1999 12:24:52 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Dereli",
"T.",
"",
"METU, Ankara"
],
[
"Tucker",
"R. W.",
"",
"Lancaster U."
]
] | We explore the role of the Cremmer-Scherk mechanism in the context of low energy effective string theory by coupling the antisymmetric 3-form gauge potential to an Abelian gauge potential carrying weak hypercharge. The theory admits a class of exact self-gravitating solutions in the spontaneously broken phase in which the dual fields acquire massive perturbative modes. Despite the massive nature of these fields they admit non-perturbative progressive longitudinal modes that together with pp-type gravitational waves travel in a direction of a line source at the speed of light. |
1612.06515 | Yun Soo Myung | Yun Soo Myung, Young-Jai Park | Preheating in the nonminimal derivative coupling to gravity | 15 pages, 4 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the reheating mechanism after the end of inflation in the
non-minimal derivative coupling (NDC) to gravity with quadratic potential. This
is because the inflaton of the NDC should describe the slow-roll inflation as
well as the preheating stage after the end of inflation. We point out that the
non-periodic inflaton solution implies the absence of parametric resonance,
compared to the periodic oscillating inflaton for the canonical coupling (CC)
to gravity. Furthermore, it is demonstrated that narrow and broad parametric
resonances do not appear after the end of inflation in the NDC model by solving
the differential equation numerically for the quantum field, which differs from
the case of the the CC model obtained by solving Mathieu equation.
| [
{
"created": "Tue, 20 Dec 2016 06:07:45 GMT",
"version": "v1"
}
] | 2016-12-21 | [
[
"Myung",
"Yun Soo",
""
],
[
"Park",
"Young-Jai",
""
]
] | We revisit the reheating mechanism after the end of inflation in the non-minimal derivative coupling (NDC) to gravity with quadratic potential. This is because the inflaton of the NDC should describe the slow-roll inflation as well as the preheating stage after the end of inflation. We point out that the non-periodic inflaton solution implies the absence of parametric resonance, compared to the periodic oscillating inflaton for the canonical coupling (CC) to gravity. Furthermore, it is demonstrated that narrow and broad parametric resonances do not appear after the end of inflation in the NDC model by solving the differential equation numerically for the quantum field, which differs from the case of the the CC model obtained by solving Mathieu equation. |
2105.01702 | Banibrata Mukhopadhyay | Agrim Sharma and Banibrata Mukhopadhyay | Modified Newtonian Gravity: Explaining observations of sub- and
super-Chandrasekhar limiting mass white dwarfs | 9 pages including 4 figures; published in Scientific Voyage (ISSN:
2395-5546); http://scientificvoyage.net/index.php/sv/article/view/32/26 | Scientific Voyage 2 (No. 1) (2021) 20-28 | null | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The idea of possible modification to gravity theory, whether it is in the
Newtonian or general relativistic premises, is there for quite sometime. Based
on it, astrophysical and cosmological problems are targeted to solve. But none
of the Newtonian theories of modification has been performed from the first
principle. Here, we modify Poisson's equation and propose two possible ways to
modify the law gravitation which, however, reduces to Newton's law far away
from the center of source. Based on these modified Newton's laws, we attempt to
solve problems lying with white dwarfs. There are observational evidences for
possible violation of the Chandrasekhar mass-limit significantly: it could be
sub- as well as super-Chandrasekhar. We show that modified Newton's law, either
by modifying LHS or RHS of Poisson's equation, can explain them.
| [
{
"created": "Tue, 4 May 2021 18:52:34 GMT",
"version": "v1"
}
] | 2022-01-02 | [
[
"Sharma",
"Agrim",
""
],
[
"Mukhopadhyay",
"Banibrata",
""
]
] | The idea of possible modification to gravity theory, whether it is in the Newtonian or general relativistic premises, is there for quite sometime. Based on it, astrophysical and cosmological problems are targeted to solve. But none of the Newtonian theories of modification has been performed from the first principle. Here, we modify Poisson's equation and propose two possible ways to modify the law gravitation which, however, reduces to Newton's law far away from the center of source. Based on these modified Newton's laws, we attempt to solve problems lying with white dwarfs. There are observational evidences for possible violation of the Chandrasekhar mass-limit significantly: it could be sub- as well as super-Chandrasekhar. We show that modified Newton's law, either by modifying LHS or RHS of Poisson's equation, can explain them. |
1710.10438 | Vyacheslav Dokuchaev | Victor Berezin, Vyacheslav Dokuchaev and Yury Eroshenko | On the theory of spherically symmetric thin shells in conformal gravity | 11 pages, ICPPA-2017 conference report | Intern. J. Mod. Phys. D 27, 1841012 (2018) | 10.1142/S0218271818410122 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The spherically symmetric thin shells are the nearest generalizations of the
point-like particles. Moreover, they serve as the simple sources of the
gravitational fields both in General Relativity and much more complex quadratic
gravity theories. We are interested in the special and physically important
case when all the quadratic in curvature tensor (Riemann tensor) and its
contractions (Ricci tensor and scalar curvature) terms are present in the form
of the square of Weyl tensor. By definition, the energy-momentum tensor of the
thin shell is proportional to Dirac delta-function. We constructed the theory
of the spherically symmetric thin shells for three types of gravitational
theories with the shell: (1) General Relativity; (2) Pure conformal (Weyl)
gravity where the gravitational part of the total Lagrangian is just the square
of the Weyl tensor; (3) Weyl+Einstein gravity. The results are compared with
these in General Relativity (Israel equations). We considered in details the
shells immersed in the vacuum. Some peculiar properties of such shells are
found. In particular, for the traceless (= massless) shells it is shown that
their dynamics can not be derived from the matching conditions and, thus, is
completely arbitrary. On the contrary, in the case of the Weyl+Einstein gravity
the trajectory of the same type of shell is completely restored even without
knowledge of the outside solution.
| [
{
"created": "Sat, 28 Oct 2017 09:57:43 GMT",
"version": "v1"
}
] | 2018-12-17 | [
[
"Berezin",
"Victor",
""
],
[
"Dokuchaev",
"Vyacheslav",
""
],
[
"Eroshenko",
"Yury",
""
]
] | The spherically symmetric thin shells are the nearest generalizations of the point-like particles. Moreover, they serve as the simple sources of the gravitational fields both in General Relativity and much more complex quadratic gravity theories. We are interested in the special and physically important case when all the quadratic in curvature tensor (Riemann tensor) and its contractions (Ricci tensor and scalar curvature) terms are present in the form of the square of Weyl tensor. By definition, the energy-momentum tensor of the thin shell is proportional to Dirac delta-function. We constructed the theory of the spherically symmetric thin shells for three types of gravitational theories with the shell: (1) General Relativity; (2) Pure conformal (Weyl) gravity where the gravitational part of the total Lagrangian is just the square of the Weyl tensor; (3) Weyl+Einstein gravity. The results are compared with these in General Relativity (Israel equations). We considered in details the shells immersed in the vacuum. Some peculiar properties of such shells are found. In particular, for the traceless (= massless) shells it is shown that their dynamics can not be derived from the matching conditions and, thus, is completely arbitrary. On the contrary, in the case of the Weyl+Einstein gravity the trajectory of the same type of shell is completely restored even without knowledge of the outside solution. |
0710.1598 | Alan Coley | A. Coley | Classification of the Weyl Tensor in Higher Dimensions and Applications | Topical Review for Classical and Quantum Gravity. Final published
version | Class.Quant.Grav.25:033001,2008 | 10.1088/0264-9381/25/3/033001 | null | gr-qc hep-th | null | We review the theory of alignment in Lorentzian geometry and apply it to the
algebraic classification of the Weyl tensor in higher dimensions. This
classification reduces to the the well-known Petrov classification of the Weyl
tensor in four dimensions. We discuss the algebraic classification of a number
of known higher dimensional spacetimes. There are many applications of the Weyl
classification scheme, especially in conjunction with the higher dimensional
frame formalism that has been developed in order to generalize the four
dimensional Newman--Penrose formalism. For example, we discuss higher
dimensional generalizations of the Goldberg-Sachs theorem and the Peeling
theorem. We also discuss the higher dimensional Lorentzian spacetimes with
vanishing scalar curvature invariants and constant scalar curvature invariants,
which are of interest since they are solutions of supergravity theory.
| [
{
"created": "Mon, 8 Oct 2007 17:25:19 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Jan 2008 18:11:11 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Coley",
"A.",
""
]
] | We review the theory of alignment in Lorentzian geometry and apply it to the algebraic classification of the Weyl tensor in higher dimensions. This classification reduces to the the well-known Petrov classification of the Weyl tensor in four dimensions. We discuss the algebraic classification of a number of known higher dimensional spacetimes. There are many applications of the Weyl classification scheme, especially in conjunction with the higher dimensional frame formalism that has been developed in order to generalize the four dimensional Newman--Penrose formalism. For example, we discuss higher dimensional generalizations of the Goldberg-Sachs theorem and the Peeling theorem. We also discuss the higher dimensional Lorentzian spacetimes with vanishing scalar curvature invariants and constant scalar curvature invariants, which are of interest since they are solutions of supergravity theory. |
1811.09625 | Debottam Nandi | Debottam Nandi | Stable contraction in Brans-Dicke cosmology | 22 pages and 5 tables, accepted in JCAP | JCAP05(2019)040 | 10.1088/1475-7516/2019/05/040 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Contracting Universe (including bouncing models) solution generally depends
on the initial conditions and hence possesses an extreme fine-tuning problem.
In order to probe the stability of those solutions, in this work, we consider
the Brans-Dicke theory with the power law potential in the presence of an
additional barotropic matter in the homogeneous and isotropic background. We
study the phase space and obtain critical points. We find that the quadratic
potential is a special case where one of the solutions always gives rise to
de-Sitter solution in all conformally connected frame. We generalize the
condition for arbitrary power law potential and find that contracting Universe
solution can indeed lead to an attractor solution. In doing so, we also provide
an example of a matter contracting Universe that leads to near scale-invariant
spectra and study the behavior near the fixed point. In the vicinity of this
point, the system behaves as the Universe contains three different types of
matter. Amongst them, with time, energy densities of two effective fluids decay
down and only the leading order solution survives. Therefore, the non-minimal
coupling can address and solve the problem of fine-tuning of the contraction
models and may open a different outlook.
| [
{
"created": "Fri, 23 Nov 2018 10:08:28 GMT",
"version": "v1"
},
{
"created": "Fri, 24 May 2019 05:20:22 GMT",
"version": "v2"
}
] | 2019-05-27 | [
[
"Nandi",
"Debottam",
""
]
] | Contracting Universe (including bouncing models) solution generally depends on the initial conditions and hence possesses an extreme fine-tuning problem. In order to probe the stability of those solutions, in this work, we consider the Brans-Dicke theory with the power law potential in the presence of an additional barotropic matter in the homogeneous and isotropic background. We study the phase space and obtain critical points. We find that the quadratic potential is a special case where one of the solutions always gives rise to de-Sitter solution in all conformally connected frame. We generalize the condition for arbitrary power law potential and find that contracting Universe solution can indeed lead to an attractor solution. In doing so, we also provide an example of a matter contracting Universe that leads to near scale-invariant spectra and study the behavior near the fixed point. In the vicinity of this point, the system behaves as the Universe contains three different types of matter. Amongst them, with time, energy densities of two effective fluids decay down and only the leading order solution survives. Therefore, the non-minimal coupling can address and solve the problem of fine-tuning of the contraction models and may open a different outlook. |
gr-qc/9609030 | Dr John W. Barrett | John W. Barrett, Louis Crane | An algebraic interpretation of the Wheeler-DeWitt equation | 10 pages, amstex, uses epsf.tex. New version has improved
presentation | Class.Quant.Grav. 14 (1997) 2113-2121 | 10.1088/0264-9381/14/8/011 | null | gr-qc | null | We make a direct connection between the construction of three dimensional
topological state sums from tensor categories and three dimensional quantum
gravity by noting that the discrete version of the Wheeler-DeWitt equation is
exactly the pentagon for the associator of the tensor category, the
Biedenharn-Elliott identity. A crucial role is played by an asymptotic formula
relating 6j-symbols to rotation matrices given by Edmonds.
| [
{
"created": "Thu, 12 Sep 1996 11:31:24 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Apr 1997 22:31:02 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Barrett",
"John W.",
""
],
[
"Crane",
"Louis",
""
]
] | We make a direct connection between the construction of three dimensional topological state sums from tensor categories and three dimensional quantum gravity by noting that the discrete version of the Wheeler-DeWitt equation is exactly the pentagon for the associator of the tensor category, the Biedenharn-Elliott identity. A crucial role is played by an asymptotic formula relating 6j-symbols to rotation matrices given by Edmonds. |
1206.3067 | Gherardo Piacitelli | Sergio Doplicher, Gherardo Piacitelli, Luca Tomassini, Stefano Viaggiu | Comment on "Can we measure structures to a precision better than the
Planck length?"[arXiv:1205.3636], by Sabine Hossenfelder | LaTeX, 6 pages. A discussion about the meaning of localisation added
to the previous version, together with two new references | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | First principles do imply a non-zero minimal distance between events in
spacetime, but no positive lower bound to the precision of the measurement of a
single coordinate.
| [
{
"created": "Thu, 14 Jun 2012 10:34:10 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Sep 2012 06:01:57 GMT",
"version": "v2"
}
] | 2012-09-21 | [
[
"Doplicher",
"Sergio",
""
],
[
"Piacitelli",
"Gherardo",
""
],
[
"Tomassini",
"Luca",
""
],
[
"Viaggiu",
"Stefano",
""
]
] | First principles do imply a non-zero minimal distance between events in spacetime, but no positive lower bound to the precision of the measurement of a single coordinate. |
1207.6350 | Kayll Lake | Philippe Landry, Majd Abdelqader and Kayll Lake | The McVittie solution with a negative cosmological constant | 6 pages twocolumn revtex 4-1 8 figures updated references Final form
to appear in Phys Rev D | Physical Review D 86, 084002 (2012) | 10.1103/PhysRevD.86.084002 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Whereas current cosmological observations suggest that the universe is
dominated by a positive cosmological constant ($\Lambda > 0$), the AdS/CFT
correspondence tells us that the case $\Lambda<0$ is still worthy of
consideration. In this paper we study the McVittie solution with $\Lambda<0$.
Following a related study, the solution is understood here by way of a
systematic construction of conformal diagrams based on detailed numerical
integrations of the null geodesic equations. As in the pure Robertson - Walker
case, we find that $\Lambda<0$ ensures collapse to a Big Crunch, a feature
which completely dominates the global structure.
| [
{
"created": "Thu, 26 Jul 2012 17:51:44 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Jul 2012 18:16:27 GMT",
"version": "v2"
},
{
"created": "Tue, 4 Sep 2012 19:45:43 GMT",
"version": "v3"
}
] | 2013-05-30 | [
[
"Landry",
"Philippe",
""
],
[
"Abdelqader",
"Majd",
""
],
[
"Lake",
"Kayll",
""
]
] | Whereas current cosmological observations suggest that the universe is dominated by a positive cosmological constant ($\Lambda > 0$), the AdS/CFT correspondence tells us that the case $\Lambda<0$ is still worthy of consideration. In this paper we study the McVittie solution with $\Lambda<0$. Following a related study, the solution is understood here by way of a systematic construction of conformal diagrams based on detailed numerical integrations of the null geodesic equations. As in the pure Robertson - Walker case, we find that $\Lambda<0$ ensures collapse to a Big Crunch, a feature which completely dominates the global structure. |
gr-qc/0506020 | Martin Einhorn | Martin B Einhorn and Manavendra Mahato | Beyond the Horizon | 9 pages, 1 figure | Phys.Rev. D73 (2006) 104035 | 10.1103/PhysRevD.73.104035 | MCTP-05-80 & NSF-KITP-05-30 | gr-qc hep-th | null | Cosmic horizons arise in general relativity in the context of black holes and
in certain cosmologies. Classically, regions beyond a horizon are inaccessible
to causal observers. However, quantum mechanical correlations may exist across
horizons that may influence local observations. For the case of de Sitter
space, we show how a single particle excitation behind the horizon changes the
density matrix governing local observables. As compared to the vacuum state, we
calculate the change in the average energy and entropy per unit volume. This
illustrates what may be a generic property allowing some features of spacetime
beyond a horizon to be inferred.
| [
{
"created": "Fri, 3 Jun 2005 17:02:17 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Einhorn",
"Martin B",
""
],
[
"Mahato",
"Manavendra",
""
]
] | Cosmic horizons arise in general relativity in the context of black holes and in certain cosmologies. Classically, regions beyond a horizon are inaccessible to causal observers. However, quantum mechanical correlations may exist across horizons that may influence local observations. For the case of de Sitter space, we show how a single particle excitation behind the horizon changes the density matrix governing local observables. As compared to the vacuum state, we calculate the change in the average energy and entropy per unit volume. This illustrates what may be a generic property allowing some features of spacetime beyond a horizon to be inferred. |
1202.4097 | Khaled Saaidi | Khaled Saaidi | Stability of Ghost Dark Energy in CBD Model of Gravity | 17 pages, 7 figures, Latex | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the stability of the ghost dark energy model versus perturbation.
Since this kind of dark energy is instable in Einsteinian general relativity
theory, then we study a new type of Brans-Dicke theory which has non-minimal
coupling with matter which is called chameleon Brans-Dicke (CBD) model of
gravity. Due to this coupling the equation of conservation energy is modified.
For considering the stability of the model we use the adiabatic squared sound
speed, $c_s^2$, whose sign of it determines the stability of the model in which
for $c_s^2 >0 $ the model is stable and for $c_s^2 <0 $ the model is instable.
However, we study the interacting and non-interacting version of chameleon
Brans-Dicke ghost dark energy (CBDGDE) with cold dark matter in non flat FLRW
metric. We show that in all cases of investigation the model is stable with a
suitable choice of parameters.
| [
{
"created": "Sat, 18 Feb 2012 19:42:29 GMT",
"version": "v1"
}
] | 2012-02-21 | [
[
"Saaidi",
"Khaled",
""
]
] | We study the stability of the ghost dark energy model versus perturbation. Since this kind of dark energy is instable in Einsteinian general relativity theory, then we study a new type of Brans-Dicke theory which has non-minimal coupling with matter which is called chameleon Brans-Dicke (CBD) model of gravity. Due to this coupling the equation of conservation energy is modified. For considering the stability of the model we use the adiabatic squared sound speed, $c_s^2$, whose sign of it determines the stability of the model in which for $c_s^2 >0 $ the model is stable and for $c_s^2 <0 $ the model is instable. However, we study the interacting and non-interacting version of chameleon Brans-Dicke ghost dark energy (CBDGDE) with cold dark matter in non flat FLRW metric. We show that in all cases of investigation the model is stable with a suitable choice of parameters. |
2108.11795 | Jo\~ao Cavedagne Lobato | Jo\~ao C. Lobato, Isabela S. Matos, Lucas T. Santana, Ribamar R. R.
Reis, Maur\'icio O. Calv\~ao | Influence of gravitational waves upon light in the Minkowski background:
from null geodesics to interferometry | 25 pages, 6 figures, 1 table | Physical Review D 104, 024024 (2021) | 10.1103/PhysRevD.104.024024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have recently derived a manifestly covariant evolution law, under the
geometrical optics approximation of the vacuum Maxwell's equations, for the
electric field along null geodesics in a general spacetime, relative to an
arbitrary set of instantaneous observers [arXiv:2004.03496]. As one of its
applications, we derive here the final detected intensity signal arising from a
prototypical laser interferometric gravitational wave (GW) Michelson-Morley
detector, comoving with transverse traceless (TT) observers, valid for both
long and short GW wavelengths. One of our main results is the presentation of
the integrated null geodesic parametric equations exchanged between two TT
observers in terms of explicitly observable quantities and the profile of the
plane GW packet. This allows us to revisit the derivation of the consequential
radar distance and Doppler shift, taking the opportunity to discuss some
related subtle conceptual issues and how they might affect the interferometric
process. Another achievement is the calculation of the electric field in each
arm up to the detection event, for any relative orientations of the arms and
the GW direction. The main quantitative result is the new expression for the
final interference pattern, for normal GW incidence, which turns out to have
three contributions: (i) the well-known traditional one due to the difference
in optical paths, and two new ones due to (ii) the Doppler effect, and (iii)
the divergence of the laser beams. The quantitative relevance of the last two
contributions is compared to the traditional one and shown to be negligible
within the geometrical optics regime of light. Although in general further
contributions from the non-parallel transport of the polarization vector are
expected, again in the case of GW normal incidence, such a vector is indeed
parallel transported, and those contributions are absent.
| [
{
"created": "Sun, 11 Jul 2021 13:31:37 GMT",
"version": "v1"
}
] | 2021-08-27 | [
[
"Lobato",
"João C.",
""
],
[
"Matos",
"Isabela S.",
""
],
[
"Santana",
"Lucas T.",
""
],
[
"Reis",
"Ribamar R. R.",
""
],
[
"Calvão",
"Maurício O.",
""
]
] | We have recently derived a manifestly covariant evolution law, under the geometrical optics approximation of the vacuum Maxwell's equations, for the electric field along null geodesics in a general spacetime, relative to an arbitrary set of instantaneous observers [arXiv:2004.03496]. As one of its applications, we derive here the final detected intensity signal arising from a prototypical laser interferometric gravitational wave (GW) Michelson-Morley detector, comoving with transverse traceless (TT) observers, valid for both long and short GW wavelengths. One of our main results is the presentation of the integrated null geodesic parametric equations exchanged between two TT observers in terms of explicitly observable quantities and the profile of the plane GW packet. This allows us to revisit the derivation of the consequential radar distance and Doppler shift, taking the opportunity to discuss some related subtle conceptual issues and how they might affect the interferometric process. Another achievement is the calculation of the electric field in each arm up to the detection event, for any relative orientations of the arms and the GW direction. The main quantitative result is the new expression for the final interference pattern, for normal GW incidence, which turns out to have three contributions: (i) the well-known traditional one due to the difference in optical paths, and two new ones due to (ii) the Doppler effect, and (iii) the divergence of the laser beams. The quantitative relevance of the last two contributions is compared to the traditional one and shown to be negligible within the geometrical optics regime of light. Although in general further contributions from the non-parallel transport of the polarization vector are expected, again in the case of GW normal incidence, such a vector is indeed parallel transported, and those contributions are absent. |
1709.08020 | Lee Lindblom | Lee Lindblom, Nicholas W. Taylor, and Fan Zhang | Scalar, Vector and Tensor Harmonics on the Three-Sphere | 14 pages, 9 figures, to appear in General Relativity and Gravitation | null | 10.1007/s10714-017-2303-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scalar, vector and tensor harmonics on the three-sphere were introduced
originally to facilitate the study of various problems in gravitational
physics. These harmonics are defined as eigenfunctions of the covariant Laplace
operator which satisfy certain divergence and trace identities, and
ortho-normality conditions. This paper provides a summary of these properties,
along with a new notation that simplifies and clarifies some of the key
expressions. Practical methods are described for accurately and efficiently
computing these harmonics numerically, and test results are given that
illustrate how well the analytical identities are satisfied by the harmonics
computed numerically in this way.
| [
{
"created": "Sat, 23 Sep 2017 08:18:40 GMT",
"version": "v1"
}
] | 2017-11-01 | [
[
"Lindblom",
"Lee",
""
],
[
"Taylor",
"Nicholas W.",
""
],
[
"Zhang",
"Fan",
""
]
] | Scalar, vector and tensor harmonics on the three-sphere were introduced originally to facilitate the study of various problems in gravitational physics. These harmonics are defined as eigenfunctions of the covariant Laplace operator which satisfy certain divergence and trace identities, and ortho-normality conditions. This paper provides a summary of these properties, along with a new notation that simplifies and clarifies some of the key expressions. Practical methods are described for accurately and efficiently computing these harmonics numerically, and test results are given that illustrate how well the analytical identities are satisfied by the harmonics computed numerically in this way. |
gr-qc/0512098 | Wenbiao Liu | Wenbiao Liu | Hawking Radiation as Tunnelling in Static Black Holes | null | null | null | null | gr-qc | null | Hawking radiation can usefully be viewed as a semi-classical tunnelling
process that originates at the black hole horizon. The conservation of energy
implies the effect of self-gravitation. For a static black hole, a generalized
Painleve coordinate system is introduced, and Hawking radiation as tunnelling
under the effect of self-gravitation is investigated. The corrected radiation
is consistent with the underlying unitary theory.
| [
{
"created": "Fri, 16 Dec 2005 14:43:33 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Liu",
"Wenbiao",
""
]
] | Hawking radiation can usefully be viewed as a semi-classical tunnelling process that originates at the black hole horizon. The conservation of energy implies the effect of self-gravitation. For a static black hole, a generalized Painleve coordinate system is introduced, and Hawking radiation as tunnelling under the effect of self-gravitation is investigated. The corrected radiation is consistent with the underlying unitary theory. |
gr-qc/9711061 | null | Thibault Damour | Gravitation and Experiment | 23 pages, Latex, psfig, 2 figures, to appear in the Proceedings of
Princeton's 250th Anniversary Conference on Critical Problems in Physics
(October 31-November 2, 1996) to be published by Princeton University Press
(1997) | null | null | IHES/P/97/51 | gr-qc | null | The confrontation between Einstein's gravitation theory and experimental
results, notably binary pulsar data, is summarized and its significance
discussed. Experiment and theory agree at the 10^{-3} level. All the basic
structures of Einstein's theory (coupling of gravity to matter; propagation and
self-interaction of the gravitational field, including in strong-field
conditions) have been verified. However, some recent theoretical findings
(cosmological relaxation toward zero scalar couplings) suggest that the present
agreement between Einstein's theory and experiment might be naturally
compatible with the existence of a long-range scalar contribution to gravity
(such as the dilaton, or a moduli field of string theory). This provides a new
theoretical paradigm, and new motivations for improving the experimental tests
of gravity. Ultra-high precision tests of the Equivalence Principle appear as
the most sensitive way to look for possible long-range deviations from General
Relativity: they might open a low-energy window on string-scale physics.
| [
{
"created": "Thu, 20 Nov 1997 16:15:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Damour",
"Thibault",
""
]
] | The confrontation between Einstein's gravitation theory and experimental results, notably binary pulsar data, is summarized and its significance discussed. Experiment and theory agree at the 10^{-3} level. All the basic structures of Einstein's theory (coupling of gravity to matter; propagation and self-interaction of the gravitational field, including in strong-field conditions) have been verified. However, some recent theoretical findings (cosmological relaxation toward zero scalar couplings) suggest that the present agreement between Einstein's theory and experiment might be naturally compatible with the existence of a long-range scalar contribution to gravity (such as the dilaton, or a moduli field of string theory). This provides a new theoretical paradigm, and new motivations for improving the experimental tests of gravity. Ultra-high precision tests of the Equivalence Principle appear as the most sensitive way to look for possible long-range deviations from General Relativity: they might open a low-energy window on string-scale physics. |
1808.09643 | Tao Zhu | Wei-Jian Jin, Yongge Ma, and Tao Zhu | Pre-inflationary dynamics of Starobinsky inflation and its generization
in Loop Quantum Brans-Dicke Cosmology | 15 pages, 8 figures, 3 tables; v2: references and discussions added | JCAP 02(2019)010 | 10.1088/1475-7516/2019/02/010 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, the nonperturbative quantization scheme of loop quantum gravity has
been extended to the Brans-Dicke theory and the corresponding loop quantum
Brans-Dicke cosmology has been derived, which provides an essential platform to
explore inflationary models in this framework. In this paper, we consider two
inflation models, the Starobinsky and $\alpha$-attractor inflation whose
cosmological predictions are in excellent agreement with Planck data, and study
systematically their pre-inflationary dynamics as well as the slow-roll
inflation. We show that for both models, the background evolution of a flat
Friedmann-Lema\^{i}tre-Robertson-Walker universe in general can be divided into
three different phases: the pre-inflationary quantum phase,
quantum-to-classical transition, and the slow-roll inflation. The
pre-inflationary dynamics are dominated by the quantum geometry effects of loop
quantum Brans-Dicke cosmology and the corresponding Universe could be either
initially expanding or contracting, depending on the initial velocity of
inflaton field. It is shown that the detailed evolution of pre-inflationary
quantum phase also depend on specific inflation models. After the
pre-inflationary quantum phase, the universe gradually evolves into the
slow-roll inflation with some of initial conditions for Starobinsky and
$\alpha$-attractor potentials. In addition, to be consistent with observational
data, we also find the restricted parameter space of initial conditions that
could produce at least $60$ $e$-folds during the slow-roll inflation.
| [
{
"created": "Wed, 29 Aug 2018 05:30:23 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Jan 2019 03:10:22 GMT",
"version": "v2"
}
] | 2019-02-15 | [
[
"Jin",
"Wei-Jian",
""
],
[
"Ma",
"Yongge",
""
],
[
"Zhu",
"Tao",
""
]
] | Recently, the nonperturbative quantization scheme of loop quantum gravity has been extended to the Brans-Dicke theory and the corresponding loop quantum Brans-Dicke cosmology has been derived, which provides an essential platform to explore inflationary models in this framework. In this paper, we consider two inflation models, the Starobinsky and $\alpha$-attractor inflation whose cosmological predictions are in excellent agreement with Planck data, and study systematically their pre-inflationary dynamics as well as the slow-roll inflation. We show that for both models, the background evolution of a flat Friedmann-Lema\^{i}tre-Robertson-Walker universe in general can be divided into three different phases: the pre-inflationary quantum phase, quantum-to-classical transition, and the slow-roll inflation. The pre-inflationary dynamics are dominated by the quantum geometry effects of loop quantum Brans-Dicke cosmology and the corresponding Universe could be either initially expanding or contracting, depending on the initial velocity of inflaton field. It is shown that the detailed evolution of pre-inflationary quantum phase also depend on specific inflation models. After the pre-inflationary quantum phase, the universe gradually evolves into the slow-roll inflation with some of initial conditions for Starobinsky and $\alpha$-attractor potentials. In addition, to be consistent with observational data, we also find the restricted parameter space of initial conditions that could produce at least $60$ $e$-folds during the slow-roll inflation. |
2407.05270 | Handhika Ramadhan | Leonardus B. Putra and H. S. Ramadhan | Gravitational field and lensing of a circular chiral vorton | 31 pages, 11 captioned figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We derive the metric of a circular chiral vorton in the weak field limit. The
object is self-supporting by means of its chiral current. A conical singularity
with deficit angle, identical to that of straight string with the same linear
mass density, is present at the vorton's core. We find that the metric is akin
to the electromagnetic $4$-potential of a circular current wire loop,
illustrating the concept of gravito-electromagnetism. Surprisingly we find that
the solution asymptotically mimics a Kerr-like naked singularity with mass
$M_v=4\pi R\mu$ and spin parameter $a=R/2$. Finally, we also simulate the
gravitational lensing images by solving the corresponding null geodesic
equations. This reveals interesting properties of the images, such as the
simultaneous creation of a minimally distorted source image and its Einstein
ring, as well as the formation of double images of the back side of the ring.
| [
{
"created": "Sun, 7 Jul 2024 05:50:44 GMT",
"version": "v1"
}
] | 2024-07-09 | [
[
"Putra",
"Leonardus B.",
""
],
[
"Ramadhan",
"H. S.",
""
]
] | We derive the metric of a circular chiral vorton in the weak field limit. The object is self-supporting by means of its chiral current. A conical singularity with deficit angle, identical to that of straight string with the same linear mass density, is present at the vorton's core. We find that the metric is akin to the electromagnetic $4$-potential of a circular current wire loop, illustrating the concept of gravito-electromagnetism. Surprisingly we find that the solution asymptotically mimics a Kerr-like naked singularity with mass $M_v=4\pi R\mu$ and spin parameter $a=R/2$. Finally, we also simulate the gravitational lensing images by solving the corresponding null geodesic equations. This reveals interesting properties of the images, such as the simultaneous creation of a minimally distorted source image and its Einstein ring, as well as the formation of double images of the back side of the ring. |
2311.03160 | Yuri Obukhov | Yuri N. Obukhov, Friedrich W. Hehl | Nonmetricity and hypermomentum: on the possible violation of Lorentz
invariance | 15 pages, no figures, Revtex; Contributed paper to appear in the
volume "Tribute to Ruben Aldrovandi" (Editora Livraria da Fisica, Sao Paulo,
2024) | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We outline how the symmetry groups of spacetime are interpreted in a
gauge-theoretic approach. Specifically, we focus on the hypermomentum concept
and discuss the hyperfluid, that appropriately generalizes the perfect (Euler)
fluid of general relativity to the case of continuous media with
microstructure. We demonstrate that a possible violation of Lorentz invariance
is most adequately understood by means of non-vanishing nonmetricity of a
metric-affine geometry of spacetime.
| [
{
"created": "Mon, 6 Nov 2023 14:57:31 GMT",
"version": "v1"
}
] | 2023-11-07 | [
[
"Obukhov",
"Yuri N.",
""
],
[
"Hehl",
"Friedrich W.",
""
]
] | We outline how the symmetry groups of spacetime are interpreted in a gauge-theoretic approach. Specifically, we focus on the hypermomentum concept and discuss the hyperfluid, that appropriately generalizes the perfect (Euler) fluid of general relativity to the case of continuous media with microstructure. We demonstrate that a possible violation of Lorentz invariance is most adequately understood by means of non-vanishing nonmetricity of a metric-affine geometry of spacetime. |
1902.09452 | Marica Minucci | Marica Minucci | Hyperbolic Equations and General Relativity | 233 pages, 7 figures. arXiv admin note: text overlap with
arXiv:gr-qc/9506088, arXiv:gr-qc/0101076, arXiv:gr-qc/0607134,
arXiv:1801.01714, arXiv:1410.3971, arXiv:astro-ph/0504599 by other authors | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is the author Master's Thesis and its main purpose is to demonstrate
that it is possible to formulate Einstein's field equations as an initial value
problem. The first chapter concerns the hyperbolic equations theory. The
definition of hyperbolic equation is given and the concept of wavelike
propagation is presented. Hence, once Riemann kernel definition is given,
Riemann method to solve an hyperbolic equation in two variables is showed. The
second chapter is about the fundamental solution and its relation to Riemann
kernel. Therefore, the study of the fundamental solutions proceeds by showing
how to build them and by providing some examples of solution with odd and even
number of variables. In chapter four, by following Foures-Bruhat, the problem
of finding a solution to the Cauchy problem for Einstein field equations in
vacuum with non analytic initial data is presented by studying under which
assumptions second-order systems of partial differential equations, linear and
hyperbolic, with n functions and four variables admit a solution. Thus, in
chapter five, it is showed how to turn non-linear systems of partial
differential equations into linear systems of the same type for which the
previous results hold. Eventually, in chapter six, the existence and uniqueness
of the solution to the Cauchy problem for Einstein vacuum field equations is
proved. Another part of this work consists in the study of the causal structure
of space-time. The definitions of strong causality, stable causality and global
hyperbolicity are given and the relation between the property of global
hyperbolicity and the existence of Cauchy surfaces is stressed. The last
chapter concerns the study of gravitational radiation in axisymmetric black
hole collisions at the speed of light as an useful application of Riemann
kernel method to solve a second-order hyperbolic equation in two variables.
| [
{
"created": "Mon, 18 Feb 2019 16:13:23 GMT",
"version": "v1"
}
] | 2019-02-26 | [
[
"Minucci",
"Marica",
""
]
] | This is the author Master's Thesis and its main purpose is to demonstrate that it is possible to formulate Einstein's field equations as an initial value problem. The first chapter concerns the hyperbolic equations theory. The definition of hyperbolic equation is given and the concept of wavelike propagation is presented. Hence, once Riemann kernel definition is given, Riemann method to solve an hyperbolic equation in two variables is showed. The second chapter is about the fundamental solution and its relation to Riemann kernel. Therefore, the study of the fundamental solutions proceeds by showing how to build them and by providing some examples of solution with odd and even number of variables. In chapter four, by following Foures-Bruhat, the problem of finding a solution to the Cauchy problem for Einstein field equations in vacuum with non analytic initial data is presented by studying under which assumptions second-order systems of partial differential equations, linear and hyperbolic, with n functions and four variables admit a solution. Thus, in chapter five, it is showed how to turn non-linear systems of partial differential equations into linear systems of the same type for which the previous results hold. Eventually, in chapter six, the existence and uniqueness of the solution to the Cauchy problem for Einstein vacuum field equations is proved. Another part of this work consists in the study of the causal structure of space-time. The definitions of strong causality, stable causality and global hyperbolicity are given and the relation between the property of global hyperbolicity and the existence of Cauchy surfaces is stressed. The last chapter concerns the study of gravitational radiation in axisymmetric black hole collisions at the speed of light as an useful application of Riemann kernel method to solve a second-order hyperbolic equation in two variables. |
0812.4382 | Luca Antonio Forte Dr | Luca Antonio Forte | Arithmetical Chaos and Quantum Cosmology | 35 pages, 4 figures. to be published on Classical and Quantum Gravity
(scheduled for January 2009) | Class.Quant.Grav.26:045001,2009 | 10.1088/0264-9381/26/4/045001 | DSF/14/2008 | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note, we present the formalism to start a quantum analysis for the
recent billiard representation introduced by Damour, Henneaux and Nicolai in
the study of the cosmological singularity. In particular we use the theory of
Maass automorphic forms and recent mathematical results about arithmetical
dynamical systems. The predictions of the billiard model give precise
automorphic properties for the wave function (Maass-Hecke eigenform), the
asymptotic number of quantum states (Selberg asymptotics for PSL(2,Z)), the
distribution for the level spacing statistics (the Poissonian one) and the
absence of scarred states. The most interesting implication of this model is
perhaps that the discrete spectrum is fully embedded in the continuous one.
| [
{
"created": "Tue, 23 Dec 2008 12:27:14 GMT",
"version": "v1"
}
] | 2009-02-23 | [
[
"Forte",
"Luca Antonio",
""
]
] | In this note, we present the formalism to start a quantum analysis for the recent billiard representation introduced by Damour, Henneaux and Nicolai in the study of the cosmological singularity. In particular we use the theory of Maass automorphic forms and recent mathematical results about arithmetical dynamical systems. The predictions of the billiard model give precise automorphic properties for the wave function (Maass-Hecke eigenform), the asymptotic number of quantum states (Selberg asymptotics for PSL(2,Z)), the distribution for the level spacing statistics (the Poissonian one) and the absence of scarred states. The most interesting implication of this model is perhaps that the discrete spectrum is fully embedded in the continuous one. |
1510.06676 | Martin Kr\v{s}\v{s}\'ak | Martin Kr\v{s}\v{s}\'ak | Holographic Renormalization in Teleparallel Gravity | 9 pages, v3: Extended discussion on reference tetrads. Matches the
published version | Eur.Phys.J. C77 (2017) no.1, 44 | 10.1140/epjc/s10052-017-4621-3 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the problem of IR divergences of the action in the covariant
formulation of teleparallel gravity in asymptotically Minkowski spacetimes. We
show that divergences are caused by inertial effects and can be removed by
adding an appropriate surface term, leading to the renormalized action. This
process can be viewed as a teleparallel analogue of holographic
renormalization. Moreover, we explore the variational problem in teleparallel
gravity and explain how the variation with respect to the spin connection
should be performed.
| [
{
"created": "Thu, 22 Oct 2015 16:26:49 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jul 2016 18:37:51 GMT",
"version": "v2"
},
{
"created": "Thu, 25 May 2017 16:04:41 GMT",
"version": "v3"
}
] | 2017-05-26 | [
[
"Krššák",
"Martin",
""
]
] | We consider the problem of IR divergences of the action in the covariant formulation of teleparallel gravity in asymptotically Minkowski spacetimes. We show that divergences are caused by inertial effects and can be removed by adding an appropriate surface term, leading to the renormalized action. This process can be viewed as a teleparallel analogue of holographic renormalization. Moreover, we explore the variational problem in teleparallel gravity and explain how the variation with respect to the spin connection should be performed. |
1110.1720 | Debraj Roy | Rabin Banerjee and Debraj Roy | Poincar\'{e} gauge symmetries, hamiltonian symmetries and trivial gauge
transformations | 13 pages, LaTeX2e, no figures; (v2) 14 pages, LaTeX2e, no figures,
some comments added, journal version | Phys.Rev.D84:124034,2011 | 10.1103/PhysRevD.84.124034 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We resolve a problem of finding the Poincare symmetries from hamiltonian
gauge symmetries constructed through a canonical procedure of handling
constrained systems. Through the use of Noether identities corresponding to the
symmetries, we motivate a procedure of finding the map between the hamiltonian
and Poincare gauge parameters. Using this map, we show that the Poincare and
hamiltonian gauge symmetries are equivalent, modulo trivial gauge
transformations.
| [
{
"created": "Sat, 8 Oct 2011 10:52:49 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Dec 2011 08:10:43 GMT",
"version": "v2"
}
] | 2011-12-21 | [
[
"Banerjee",
"Rabin",
""
],
[
"Roy",
"Debraj",
""
]
] | We resolve a problem of finding the Poincare symmetries from hamiltonian gauge symmetries constructed through a canonical procedure of handling constrained systems. Through the use of Noether identities corresponding to the symmetries, we motivate a procedure of finding the map between the hamiltonian and Poincare gauge parameters. Using this map, we show that the Poincare and hamiltonian gauge symmetries are equivalent, modulo trivial gauge transformations. |
gr-qc/0306043 | Bartolome Coll | Bartolom\'e Coll | A principal positioning system for the Earth | null | null | null | null | gr-qc | null | The project SYPOR wishes to use the global navigation satellite system
GALILEO as an autonomous relativistic positioning system for the Earth.
Motivations and a sketch of the basic concepts underlying the project are
presented. For non geodetic (perturbed) satellites, a two-dimensional example
describes how the dynamics of the constellation of satellites and that of the
users may be deduced from the knowledge of the dynamics of only one of the
satellites during a partial interval.
| [
{
"created": "Tue, 10 Jun 2003 15:38:40 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Coll",
"Bartolomé",
""
]
] | The project SYPOR wishes to use the global navigation satellite system GALILEO as an autonomous relativistic positioning system for the Earth. Motivations and a sketch of the basic concepts underlying the project are presented. For non geodetic (perturbed) satellites, a two-dimensional example describes how the dynamics of the constellation of satellites and that of the users may be deduced from the knowledge of the dynamics of only one of the satellites during a partial interval. |
gr-qc/0611125 | Valter Moretti | Valter Moretti (Math. Dept. Trento University, INdAM, INFN) | Some recent results in scalar quantum field theory in globally
hyperbolic asymptotically flat spacetimes | 10 pages, 2 figures, invited plenary talk at the XVII SIGRAV
Conference held in Torino, September 4-7, 2006 | null | null | UTM-706 | gr-qc | null | Some recent results obtained by the author and collaborators about QFT in
asymptotically flat spacetimes at null infinity are summarized and reviewed. In
particular it is focused on the physical properties of ground states in the
bulk induced by the BMS-invariant state defined at null infinity.
| [
{
"created": "Thu, 23 Nov 2006 15:08:11 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Moretti",
"Valter",
"",
"Math. Dept. Trento University, INdAM, INFN"
]
] | Some recent results obtained by the author and collaborators about QFT in asymptotically flat spacetimes at null infinity are summarized and reviewed. In particular it is focused on the physical properties of ground states in the bulk induced by the BMS-invariant state defined at null infinity. |
gr-qc/0311013 | Ernesto F. Eiroa | Ernesto F. Eiroa, Diego F. Torres | Strong field limit analysis of gravitational retro-lensing | 11 pages, 1 figure; v2: minor changes. Accepted for publication in
Physical Review D | Phys.Rev. D69 (2004) 063004 | 10.1103/PhysRevD.69.063004 | null | gr-qc astro-ph | null | We present a complete treatment in the strong field limit of gravitational
retro-lensing by a static spherically symmetric compact object having a photon
sphere. The results are compared with those corresponding to ordinary lensing
in similar strong field situations. As examples of application of the
formalism, a supermassive black hole at the galactic center and a stellar mass
black hole in the galactic halo are studied as retro-lenses, in both cases
using the Schwarzschild and Reissner-Nordstrom geometries.
| [
{
"created": "Tue, 4 Nov 2003 22:58:40 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Dec 2003 16:11:12 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Eiroa",
"Ernesto F.",
""
],
[
"Torres",
"Diego F.",
""
]
] | We present a complete treatment in the strong field limit of gravitational retro-lensing by a static spherically symmetric compact object having a photon sphere. The results are compared with those corresponding to ordinary lensing in similar strong field situations. As examples of application of the formalism, a supermassive black hole at the galactic center and a stellar mass black hole in the galactic halo are studied as retro-lenses, in both cases using the Schwarzschild and Reissner-Nordstrom geometries. |
2312.06780 | Damianos Iosifidis | Damianos Iosifidis, Tomi S. Koivisto | Hyperhydrodynamics: Relativistic Viscous Fluids Emerging from
Hypermomentum | 38 pages, no figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore a new action formulation of hyperfluids, fluids with intrinsic
hypermomentum. Brown's Lagrangian for a relativistic perfect fluid is
generalised by incorporating the degrees of freedom encoded in the
hypermomentum tensor, namely by including connection-matter couplings. Quite
interestingly, generic hyperfluids are imperfect, since hypermomentum induces
such effects as bulk and shear viscosities as well as heat fluxes. The various
coefficients that appear in the first order expansion of hydrodynamics can now
be deduced from a Lagrangian formulation, given a geometrical interpretation
and a suggested microscopic description in terms of hypermomentum. This
connection between hypermomentum and dissipative fluids could shed new light on
the physics of relativistic hydrodynamics. The applicability of the new
formalism is demonstrated by exact cosmological solutions.
| [
{
"created": "Mon, 11 Dec 2023 19:00:32 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Apr 2024 08:02:52 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Apr 2024 11:56:07 GMT",
"version": "v3"
}
] | 2024-04-12 | [
[
"Iosifidis",
"Damianos",
""
],
[
"Koivisto",
"Tomi S.",
""
]
] | We explore a new action formulation of hyperfluids, fluids with intrinsic hypermomentum. Brown's Lagrangian for a relativistic perfect fluid is generalised by incorporating the degrees of freedom encoded in the hypermomentum tensor, namely by including connection-matter couplings. Quite interestingly, generic hyperfluids are imperfect, since hypermomentum induces such effects as bulk and shear viscosities as well as heat fluxes. The various coefficients that appear in the first order expansion of hydrodynamics can now be deduced from a Lagrangian formulation, given a geometrical interpretation and a suggested microscopic description in terms of hypermomentum. This connection between hypermomentum and dissipative fluids could shed new light on the physics of relativistic hydrodynamics. The applicability of the new formalism is demonstrated by exact cosmological solutions. |
gr-qc/0107048 | L. C. Garcia de Andrade | L.C.Garcia de Andrade | Detecting torsion from LISA and teleparallel gravity | Latex file | null | null | null | gr-qc | null | Torsion detection from totally skew symmetric torsion waves in the context of
teleparallel gravity is discussed. A gedanken experiment to detect Cartan's
contortion based on a circle of particles not necessarily spinning is proposed.
It is shown that by making use of previous value of contortion at the surface
of the Earth computed by Nitsch of $10^{-24} s^{-1}$ a relative displacement of
$10^{-21}$ is obtained which is of the order of the gravitational wave of
$10^{-3}Hz$. Since LISA has been designed to work in the mHz regime this GW
detector could be used for an indirect detection of torsion in $T_{4}$.
| [
{
"created": "Fri, 13 Jul 2001 03:27:06 GMT",
"version": "v1"
},
{
"created": "Wed, 22 May 2002 08:14:50 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"de Andrade",
"L. C. Garcia",
""
]
] | Torsion detection from totally skew symmetric torsion waves in the context of teleparallel gravity is discussed. A gedanken experiment to detect Cartan's contortion based on a circle of particles not necessarily spinning is proposed. It is shown that by making use of previous value of contortion at the surface of the Earth computed by Nitsch of $10^{-24} s^{-1}$ a relative displacement of $10^{-21}$ is obtained which is of the order of the gravitational wave of $10^{-3}Hz$. Since LISA has been designed to work in the mHz regime this GW detector could be used for an indirect detection of torsion in $T_{4}$. |
0705.3902 | Marco Spaans | M. Spaans | A Derivation of Einstein Gravity without the Axiom of Choice: Topology
Hidden in GR | final edits: more detail on derivation of equations of motion for q | null | null | null | gr-qc hep-th math-ph math.MP | null | A derivation of the equations of motion of general relativity is presented
that does not invoke the Axiom of Choice, but requires the explicit
construction of a choice function q for continuous three-space regions. The
motivation for this (seemingly academic) endeavour is to take the background
independence intrinsic to Einstein gravity one step further, and to assure that
both the equations of motion and the way in which those equations of motion are
derived are as self-consistent as possible. That is, solutions to the equations
of motion of general relativity endow a three-space region with a physical and
distinguishing geometry in four-dimensional space-time. However, in order to
derive these equations of motion one should first be able to choose a
three-space region without having any prior knowledge of its physically
appropriate geometry. The expression of this choice process requires a
three-dimensional topological manifold Q, to which all considered three-space
regions belong, and that generates an equation of motion whose solutions are q.
These solutions relate the effects of curvature to the source term through the
topology of Q and constitute Einstein gravity. Q is given by 2T^3+3S^1xS^2, and
is embedded in four dimensions. This points toward a hidden topological content
for general relativity, best phrased as: Q and q provide a structure for how to
choose a three-space region irrespective of what geometric properties it has,
while at the same time Q and q determine that only GR can endow a three-space
with those geometric properties. In this sense, avoiding the Axiom of Choice
allows one to gain physical insight into GR. Possible links with holography are
pointed out.
| [
{
"created": "Sat, 26 May 2007 17:30:42 GMT",
"version": "v1"
},
{
"created": "Tue, 29 May 2007 19:45:13 GMT",
"version": "v2"
},
{
"created": "Sun, 17 Jun 2007 19:57:11 GMT",
"version": "v3"
}
] | 2007-06-17 | [
[
"Spaans",
"M.",
""
]
] | A derivation of the equations of motion of general relativity is presented that does not invoke the Axiom of Choice, but requires the explicit construction of a choice function q for continuous three-space regions. The motivation for this (seemingly academic) endeavour is to take the background independence intrinsic to Einstein gravity one step further, and to assure that both the equations of motion and the way in which those equations of motion are derived are as self-consistent as possible. That is, solutions to the equations of motion of general relativity endow a three-space region with a physical and distinguishing geometry in four-dimensional space-time. However, in order to derive these equations of motion one should first be able to choose a three-space region without having any prior knowledge of its physically appropriate geometry. The expression of this choice process requires a three-dimensional topological manifold Q, to which all considered three-space regions belong, and that generates an equation of motion whose solutions are q. These solutions relate the effects of curvature to the source term through the topology of Q and constitute Einstein gravity. Q is given by 2T^3+3S^1xS^2, and is embedded in four dimensions. This points toward a hidden topological content for general relativity, best phrased as: Q and q provide a structure for how to choose a three-space region irrespective of what geometric properties it has, while at the same time Q and q determine that only GR can endow a three-space with those geometric properties. In this sense, avoiding the Axiom of Choice allows one to gain physical insight into GR. Possible links with holography are pointed out. |
2112.09978 | Gonzalo Olmo | Victor I. Afonso, Cecilia Bejarano, Rafael Ferraro, and Gonzalo J.
Olmo | Determinantal Born-Infeld Coupling of Gravity and Electromagnetism | 12 pages, 1 figure | Phys. Rev. D 105, 084067 (2022) | 10.1103/PhysRevD.105.084067 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a Born-Infeld inspired model of gravity and electromagnetism in
which both types of fields are treated on an equal footing via a determinantal
approach in a metric-affine formulation. Though this formulation is a priori in
conflict with the postulates of metric theories of gravity, we find that the
resulting equations can also be obtained from an action combining the
Einstein-Hilbert action with a minimally coupled nonlinear electrodynamics. As
an example, the dynamics is solved for the charged static black hole.
| [
{
"created": "Sat, 18 Dec 2021 17:52:19 GMT",
"version": "v1"
}
] | 2022-05-03 | [
[
"Afonso",
"Victor I.",
""
],
[
"Bejarano",
"Cecilia",
""
],
[
"Ferraro",
"Rafael",
""
],
[
"Olmo",
"Gonzalo J.",
""
]
] | We study a Born-Infeld inspired model of gravity and electromagnetism in which both types of fields are treated on an equal footing via a determinantal approach in a metric-affine formulation. Though this formulation is a priori in conflict with the postulates of metric theories of gravity, we find that the resulting equations can also be obtained from an action combining the Einstein-Hilbert action with a minimally coupled nonlinear electrodynamics. As an example, the dynamics is solved for the charged static black hole. |
1212.5848 | Cosimo Bambi | Zilong Li, Cosimo Bambi | Super-spinning compact objects generated by thick accretion disks | 1+16 pages, 4 figures. v2: refereed version. v3: indicated the
corresponding author | JCAP 1303:031,2013 | 10.1088/1475-7516/2013/03/031 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | If astrophysical black hole candidates are the Kerr black holes predicted by
General Relativity, the value of their spin parameter must be subject to the
theoretical bound $|a_*| \le 1$. In this work, we consider the possibility that
these objects are either non-Kerr black holes in an alternative theory of
gravity or exotic compact objects in General Relativity. We study the accretion
process when their accretion disk is geometrically thick with a simple version
of the Polish doughnut model. The picture of the accretion process may be
qualitatively different from the one around a Kerr black hole. The inner edge
of the disk may not have the typical cusp on the equatorial plane any more, but
there may be two cusps, respectively above and below the equatorial plane. We
extend previous work on the evolution of the spin parameter and we estimate the
maximum value of $a_*$ for the super-massive black hole candidates in galactic
nuclei. Since measurements of the mean radiative efficiency of AGNs require
$\eta > 0.15$, we infer the "observational" bound $|a_*| \lesssim 1.3$, which
seems to be quite independent of the exact nature of these objects. Such a
bound is only slightly weaker than $|a_*| \lesssim 1.2$ found in previous work
for thin disks.
| [
{
"created": "Mon, 24 Dec 2012 00:50:39 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Mar 2013 17:54:39 GMT",
"version": "v2"
},
{
"created": "Thu, 30 May 2013 08:38:05 GMT",
"version": "v3"
}
] | 2013-05-31 | [
[
"Li",
"Zilong",
""
],
[
"Bambi",
"Cosimo",
""
]
] | If astrophysical black hole candidates are the Kerr black holes predicted by General Relativity, the value of their spin parameter must be subject to the theoretical bound $|a_*| \le 1$. In this work, we consider the possibility that these objects are either non-Kerr black holes in an alternative theory of gravity or exotic compact objects in General Relativity. We study the accretion process when their accretion disk is geometrically thick with a simple version of the Polish doughnut model. The picture of the accretion process may be qualitatively different from the one around a Kerr black hole. The inner edge of the disk may not have the typical cusp on the equatorial plane any more, but there may be two cusps, respectively above and below the equatorial plane. We extend previous work on the evolution of the spin parameter and we estimate the maximum value of $a_*$ for the super-massive black hole candidates in galactic nuclei. Since measurements of the mean radiative efficiency of AGNs require $\eta > 0.15$, we infer the "observational" bound $|a_*| \lesssim 1.3$, which seems to be quite independent of the exact nature of these objects. Such a bound is only slightly weaker than $|a_*| \lesssim 1.2$ found in previous work for thin disks. |
gr-qc/0604019 | Edisom S. Moreira jr | E. S. Moreira, Jr. and E. S. Oliveira | Specific heat of a particle on the cone | 7 pages, 1 figure, REVTeX4 file. Version to appear in Physical Review
A | Phys.Rev. A73 (2006) 052105 | 10.1103/PhysRevA.73.052105 | null | gr-qc quant-ph | null | This work investigates how a conical singularity can affect the specific heat
of systems. A free nonrelativistic particle confined to the lateral surface of
a cone -- conical box -- is taken as a toy model. Its specific heat is
determined as a function of the deficit angle and the temperature. For a
vanishing deficit angle, the specific heat is that of a particle in a flat disk
where a characteristic temperature separates quantum and classical behaviors,
as usual. By increasing the deficit angle the characteristic temperature
increases also, and eventually another characteristic temperature (which does
not depend on the deficit angle) arises. When the cone gets sufficiently sharp,
at low and intermediate temperatures the azimuthal degree of freedom is
suppressed. At low temperatures the specific heat varies discontinuously with
the deficit angle. Connections between certain theorems regarding common zeros
of the Bessel functions and this discontinuity are reported.
| [
{
"created": "Wed, 5 Apr 2006 12:32:41 GMT",
"version": "v1"
}
] | 2012-08-27 | [
[
"Moreira,",
"E. S.",
"Jr."
],
[
"Oliveira",
"E. S.",
""
]
] | This work investigates how a conical singularity can affect the specific heat of systems. A free nonrelativistic particle confined to the lateral surface of a cone -- conical box -- is taken as a toy model. Its specific heat is determined as a function of the deficit angle and the temperature. For a vanishing deficit angle, the specific heat is that of a particle in a flat disk where a characteristic temperature separates quantum and classical behaviors, as usual. By increasing the deficit angle the characteristic temperature increases also, and eventually another characteristic temperature (which does not depend on the deficit angle) arises. When the cone gets sufficiently sharp, at low and intermediate temperatures the azimuthal degree of freedom is suppressed. At low temperatures the specific heat varies discontinuously with the deficit angle. Connections between certain theorems regarding common zeros of the Bessel functions and this discontinuity are reported. |
2210.17162 | Chandrachur Chakraborty | Chandrachur Chakraborty (MCNS-MAHE, India), Parthasarathi Majumdar
(IACS, India) | Gravitational Larmor precession | 9 pages including 2 figures, matches published version | Eur. Phys. J. C (Letter) 83, 714 (2023) | 10.1140/epjc/s10052-023-11858-4 | null | gr-qc astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspired by the reported existence of substantive magnetic fields in the
vicinity of the central supermassive black holes in Sagitarius A* and Messier
87*, we consider test particle motion in the spacetime close to a generic
spherical black hole in the presence of magnetic fields in its vicinity.
Modelling such a spacetime in terms of an axisymmetric, non-rotating
Ernst-Melvin-Schwarzschild black hole geometry with appropriate parameters, we
compute the geodesic nodal-plane precession frequency for a test particle with
mass, for such a spacetime, and obtain a non-vanishing result, surpassing
earlier folklore that only axisymmetric spacetimes with rotation (non-vanishing
Kerr parameter) can generate such a precession. We call this magnetic
field-generated phenomenon Gravitational Larmor Precession. What we present
here is a Proof of Concept incipient assay, rather than a detailed analysis of
supermassive black holes with magnetic fields in their neighbourhood. However,
for completeness, we briefly discuss observational prospects of this precession
in terms of available magnetic field strengths close to central black holes in
galaxies.
| [
{
"created": "Mon, 31 Oct 2022 09:18:48 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Jul 2023 03:19:28 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Aug 2023 09:05:53 GMT",
"version": "v3"
}
] | 2023-08-11 | [
[
"Chakraborty",
"Chandrachur",
"",
"MCNS-MAHE, India"
],
[
"Majumdar",
"Parthasarathi",
"",
"IACS, India"
]
] | Inspired by the reported existence of substantive magnetic fields in the vicinity of the central supermassive black holes in Sagitarius A* and Messier 87*, we consider test particle motion in the spacetime close to a generic spherical black hole in the presence of magnetic fields in its vicinity. Modelling such a spacetime in terms of an axisymmetric, non-rotating Ernst-Melvin-Schwarzschild black hole geometry with appropriate parameters, we compute the geodesic nodal-plane precession frequency for a test particle with mass, for such a spacetime, and obtain a non-vanishing result, surpassing earlier folklore that only axisymmetric spacetimes with rotation (non-vanishing Kerr parameter) can generate such a precession. We call this magnetic field-generated phenomenon Gravitational Larmor Precession. What we present here is a Proof of Concept incipient assay, rather than a detailed analysis of supermassive black holes with magnetic fields in their neighbourhood. However, for completeness, we briefly discuss observational prospects of this precession in terms of available magnetic field strengths close to central black holes in galaxies. |
1702.05908 | Alfred Molina | A. Molina and E. Ruiz | An approximate global solution of Einstein's equations for
differentially rotating compact body | 14 pages. arXiv admin note: text overlap with arXiv:gr-qc/0611013 | null | 10.1007/s10714-017-2297-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain an approximate global stationary and axisymmetric solution of
Einstein's equations which can be thought as a simple star model: a
self-gravitating perfect fluid ball with a differential rotation motion
pattern. Using the post--Minkowskian formalism (weak field approximation) and
considering rotation as a perturbation (slow rotation approximation), we find
approximate interior and exterior (asymptotically flat) solutions to this
problem in harmonic coordinates. Interior and exterior solutions are matched,
in the sense of Lichnerowicz, on the surface of zero pressure to get a global
solution. The resulting metric depends on four arbitrary constants: mass
density, rotational velocity at $r=0$, a parameter which takes into account of
the change in the rotational velocity through the star and the star radius in
the non-rotation limit. The mass, angular momentum, quadrupole moment and other
constants of the exterior metric are determined in terms of these four
parameters.
| [
{
"created": "Mon, 20 Feb 2017 09:37:47 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Jun 2017 08:23:34 GMT",
"version": "v2"
}
] | 2017-10-04 | [
[
"Molina",
"A.",
""
],
[
"Ruiz",
"E.",
""
]
] | We obtain an approximate global stationary and axisymmetric solution of Einstein's equations which can be thought as a simple star model: a self-gravitating perfect fluid ball with a differential rotation motion pattern. Using the post--Minkowskian formalism (weak field approximation) and considering rotation as a perturbation (slow rotation approximation), we find approximate interior and exterior (asymptotically flat) solutions to this problem in harmonic coordinates. Interior and exterior solutions are matched, in the sense of Lichnerowicz, on the surface of zero pressure to get a global solution. The resulting metric depends on four arbitrary constants: mass density, rotational velocity at $r=0$, a parameter which takes into account of the change in the rotational velocity through the star and the star radius in the non-rotation limit. The mass, angular momentum, quadrupole moment and other constants of the exterior metric are determined in terms of these four parameters. |
2203.10607 | Kaushik Bhattacharya | Saddam Hussain, Anirban Chatterjee, Kaushik Bhattacharya | Ghost condensates and pure kinetic $k$-essence condensates in presence
of field-fluid non-minimal coupling in the dark sector | Corrected and modified version. 25 pages, Accepted for publication in
Universe | Universe 2023, 9(2), 65 | 10.3390/universe9020065 | null | gr-qc astro-ph.CO hep-ph | http://creativecommons.org/licenses/by/4.0/ | In this article we try to find out the conditions when a ghost field in
conjunction with a barotropic fluid produces a stable accelerating expansion
phase of the universe. It is seen that in many cases the ghost field produces a
condensate and drives the fluid energy density to zero in the final
accelerating phase, but there can be other possibilities. We have shown that a
pure kinetic $k$-essence field (which is not a ghost field) interacting with a
fluid can also form an interaction induced condensate and produce a stable
accelerating phase of the universe. In the latter case the fluid energy density
does not vanish in the stable phase.
| [
{
"created": "Sun, 20 Mar 2022 17:42:48 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Dec 2022 10:40:58 GMT",
"version": "v2"
},
{
"created": "Sun, 22 Jan 2023 06:53:22 GMT",
"version": "v3"
}
] | 2023-02-08 | [
[
"Hussain",
"Saddam",
""
],
[
"Chatterjee",
"Anirban",
""
],
[
"Bhattacharya",
"Kaushik",
""
]
] | In this article we try to find out the conditions when a ghost field in conjunction with a barotropic fluid produces a stable accelerating expansion phase of the universe. It is seen that in many cases the ghost field produces a condensate and drives the fluid energy density to zero in the final accelerating phase, but there can be other possibilities. We have shown that a pure kinetic $k$-essence field (which is not a ghost field) interacting with a fluid can also form an interaction induced condensate and produce a stable accelerating phase of the universe. In the latter case the fluid energy density does not vanish in the stable phase. |
1801.05549 | Matt Visser | Sebastian Schuster (1) and Matt Visser (1) ((1) Victoria University of
Wellington) | Bespoke analogue space-times: Meta-material mimics | 22 pages | General Relativity and Gravitation 50 (2018) 55 | 10.1007/s10714-018-2376-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modern meta-materials allow one to construct electromagnetic media with
almost arbitrary bespoke permittivity, permeability, and magneto-electric
tensors. If (and only if) the permittivity, permeability, and magneto-electric
tensors satisfy certain stringent compatibility conditions, can the
meta-material be fully described (at the wave optics level) in terms of an
effective Lorentzian metric --- an analogue spacetime. We shall consider some
of the standard black-hole spacetimes of primary interest in general
relativity, in various coordinate systems, and determine the equivalent
meta-material susceptibility tensors in a laboratory setting. In static black
hole spacetimes (Schwarzschild and the like) certain eigenvalues of the
susceptibility tensors will be seen to diverge on the horizon. In stationary
black hole spacetimes (Kerr and the like) certain eigenvalues of the
susceptibility tensors will be seen to diverge on the ergo-surface.
| [
{
"created": "Wed, 17 Jan 2018 05:03:02 GMT",
"version": "v1"
}
] | 2018-08-16 | [
[
"Schuster",
"Sebastian",
""
],
[
"Visser",
"Matt",
""
]
] | Modern meta-materials allow one to construct electromagnetic media with almost arbitrary bespoke permittivity, permeability, and magneto-electric tensors. If (and only if) the permittivity, permeability, and magneto-electric tensors satisfy certain stringent compatibility conditions, can the meta-material be fully described (at the wave optics level) in terms of an effective Lorentzian metric --- an analogue spacetime. We shall consider some of the standard black-hole spacetimes of primary interest in general relativity, in various coordinate systems, and determine the equivalent meta-material susceptibility tensors in a laboratory setting. In static black hole spacetimes (Schwarzschild and the like) certain eigenvalues of the susceptibility tensors will be seen to diverge on the horizon. In stationary black hole spacetimes (Kerr and the like) certain eigenvalues of the susceptibility tensors will be seen to diverge on the ergo-surface. |
0706.2179 | Francisco Diego Mazzitelli | Diana L\'opez Nacir and Francisco D. Mazzitelli | Backreaction in trans-Planckian cosmology: renormalization, trace
anomaly and selfconsistent solutions | 19 pages, 3 figures | Phys.Rev.D76:024013,2007 | 10.1103/PhysRevD.76.024013 | null | gr-qc hep-th | null | We analyze the semiclassical Einstein equations for quantum scalar fields
satisfying modified dispersion relations. We first discuss in detail the
renormalization procedure based on adiabatic subtraction and dimensional
regularization. We show that, contrary to what expected from power counting
arguments, in 3+1 dimensions the subtraction involves up to the fourth
adiabatic order even for dispersion relations containing higher powers of the
momentum. Then we analyze the dependence of the trace of the renormalized
energy momentum tensor with the scale of new physics, and we recover the usual
trace anomaly in the appropriate limit. We also find selfconsistent de Sitter
solutions for dispersion relations that contain up to the fourth power of the
momentum. Using this particular example, we also discuss the possibility that
the modified dispersion relation can be mimicked at lower energies by an
effective initial state in a theory with the usual dispersion relation.
| [
{
"created": "Thu, 14 Jun 2007 19:34:07 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Nacir",
"Diana López",
""
],
[
"Mazzitelli",
"Francisco D.",
""
]
] | We analyze the semiclassical Einstein equations for quantum scalar fields satisfying modified dispersion relations. We first discuss in detail the renormalization procedure based on adiabatic subtraction and dimensional regularization. We show that, contrary to what expected from power counting arguments, in 3+1 dimensions the subtraction involves up to the fourth adiabatic order even for dispersion relations containing higher powers of the momentum. Then we analyze the dependence of the trace of the renormalized energy momentum tensor with the scale of new physics, and we recover the usual trace anomaly in the appropriate limit. We also find selfconsistent de Sitter solutions for dispersion relations that contain up to the fourth power of the momentum. Using this particular example, we also discuss the possibility that the modified dispersion relation can be mimicked at lower energies by an effective initial state in a theory with the usual dispersion relation. |
gr-qc/9510002 | null | Alpan Raval, B.L. Hu and James Anglin | Stochastic Theory of Accelerated Detectors in a Quantum Field | 32 pages, Latex | Phys.Rev. D53 (1996) 7003-7019 | 10.1103/PhysRevD.53.7003 | IASSNS-HEP-95/39, UMDPP 95-131, LA-UR-95-1736 | gr-qc atom-ph hep-th quant-ph | null | We analyze the statistical mechanical properties of n-detectors in arbitrary
states of motion interacting with each other via a quantum field. We use the
open system concept and the influence functional method to calculate the
influence of quantum fields on detectors in motion, and the mutual influence of
detectors via fields. We discuss the difference between self and mutual
impedance and advanced and retarded noise. The mutual effects of detectors on
each other can be studied from the Langevin equations derived from the
influence functional, as it contains the backreaction of the field on the
system self-consistently. We show the existence of general fluctuation-
dissipation relations, and for trajectories without event horizons,
correlation-propagation relations, which succinctly encapsulate these quantum
statistical phenomena. These findings serve to clarify some existing confusions
in the accelerated detector problem. The general methodology presented here
could also serve as a platform to explore the quantum statistical properties of
particles and fields, with practical applications in atomic and optical physics
problems.
| [
{
"created": "Tue, 3 Oct 1995 02:12:54 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Raval",
"Alpan",
""
],
[
"Hu",
"B. L.",
""
],
[
"Anglin",
"James",
""
]
] | We analyze the statistical mechanical properties of n-detectors in arbitrary states of motion interacting with each other via a quantum field. We use the open system concept and the influence functional method to calculate the influence of quantum fields on detectors in motion, and the mutual influence of detectors via fields. We discuss the difference between self and mutual impedance and advanced and retarded noise. The mutual effects of detectors on each other can be studied from the Langevin equations derived from the influence functional, as it contains the backreaction of the field on the system self-consistently. We show the existence of general fluctuation- dissipation relations, and for trajectories without event horizons, correlation-propagation relations, which succinctly encapsulate these quantum statistical phenomena. These findings serve to clarify some existing confusions in the accelerated detector problem. The general methodology presented here could also serve as a platform to explore the quantum statistical properties of particles and fields, with practical applications in atomic and optical physics problems. |
gr-qc/0205088 | Hernando Quevedo | Leonardo Pati\~no and Hernando Quevedo | Bosonic and fermionic behavior in gravitational configurations | 7 pages, revtex, no figures | Mod.Phys.Lett. A18 (2003) 1331 | 10.1142/S0217732303011083 | null | gr-qc | null | We extend Dirac's approach about the quantization of the electric charge to
the case of gravitational configurations. The spacetime curvature is used to
define a phase-like object which allows us to extract information about the
behavior of the corresponding spacetime. We show that all spacetimes that
satisfy certain simple symmetry condition and for which the Petrov type is the
same whitin a specific region, quantization conditions can be derived that
impose constraints on the possible values of the parameters entering the
respective metrics. As a general result we obtain that for the gravitational
configurations described by those metrics, the behavior under rotations can be
only of bosonic or fermionic nature.
| [
{
"created": "Mon, 20 May 2002 22:07:28 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Patiño",
"Leonardo",
""
],
[
"Quevedo",
"Hernando",
""
]
] | We extend Dirac's approach about the quantization of the electric charge to the case of gravitational configurations. The spacetime curvature is used to define a phase-like object which allows us to extract information about the behavior of the corresponding spacetime. We show that all spacetimes that satisfy certain simple symmetry condition and for which the Petrov type is the same whitin a specific region, quantization conditions can be derived that impose constraints on the possible values of the parameters entering the respective metrics. As a general result we obtain that for the gravitational configurations described by those metrics, the behavior under rotations can be only of bosonic or fermionic nature. |
0907.4064 | Kirill Krasnov | Kirill Krasnov | Gravity as BF theory plus potential | 7 pages, published in Proceedings of the Second Workshop on Quantum
Gravity and Noncommutative Geometry (Lisbon, Portugal) | Int.J.Mod.Phys.A24:2776-2782,2009 | 10.1142/S0217751X09046151 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spin foam models of quantum gravity are based on Plebanski's formulation of
general relativity as a constrained BF theory. We give an alternative
formulation of gravity as BF theory plus a certain potential term for the
B-field. When the potential is taken to be infinitely steep one recovers
general relativity. For a generic potential the theory still describes gravity
in that it propagates just two graviton polarizations. The arising class of
theories is of the type amenable to spin foam quantization methods, and, we
argue, may allow one to come to terms with renormalization in the spin foam
context.
| [
{
"created": "Thu, 23 Jul 2009 13:33:57 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Krasnov",
"Kirill",
""
]
] | Spin foam models of quantum gravity are based on Plebanski's formulation of general relativity as a constrained BF theory. We give an alternative formulation of gravity as BF theory plus a certain potential term for the B-field. When the potential is taken to be infinitely steep one recovers general relativity. For a generic potential the theory still describes gravity in that it propagates just two graviton polarizations. The arising class of theories is of the type amenable to spin foam quantization methods, and, we argue, may allow one to come to terms with renormalization in the spin foam context. |
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