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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1606.05879 | Richard Woodard | D. J. Brooker (Florida), S. D. Odintsov (Barcelona) and R. P. Woodard
(Florida) | Precision Predictions for the Primordial Power Spectra from f(R) Models
of Inflation | 27 pages, 8 figures, uses LaTeX2e Version 2 slightly revised for
publication | Nucl. Phys. B911 (2016) 318-337 | 10.1016/j.nuclphysb.2016.08.010 | UFIFT-QG-16-03 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the power spectra of f(R) inflation using a new technique in which
the norm-squared of the mode functions is evolved. Our technique results in
excellent analytic approximations for how the spectra depend upon the function
$f(R)$. Although the spectra are numerically the same in the Jordan and
Einstein frames for the same wave number $k$, they depend upon the geometries
of these frames in quite different ways. For example, the power spectra in the
two frames are different functions of the number of e-foldings until end of
inflation. We discuss how future data on reheating can be used to distinguish
f(R) inflation from scalar-driven inflation.
| [
{
"created": "Sun, 19 Jun 2016 15:07:13 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Sep 2016 17:34:05 GMT",
"version": "v2"
}
] | 2016-09-08 | [
[
"Brooker",
"D. J.",
"",
"Florida"
],
[
"Odintsov",
"S. D.",
"",
"Barcelona"
],
[
"Woodard",
"R. P.",
"",
"Florida"
]
] | We study the power spectra of f(R) inflation using a new technique in which the norm-squared of the mode functions is evolved. Our technique results in excellent analytic approximations for how the spectra depend upon the function $f(R)$. Although the spectra are numerically the same in the Jordan and Einstein frames for the same wave number $k$, they depend upon the geometries of these frames in quite different ways. For example, the power spectra in the two frames are different functions of the number of e-foldings until end of inflation. We discuss how future data on reheating can be used to distinguish f(R) inflation from scalar-driven inflation. |
gr-qc/0408003 | Matthew Anderson | Richard A. Matzner | Hyperbolicity and Constrained Evolution in Linearized Gravity | 18 pages | Phys.Rev. D71 (2005) 024011 | 10.1103/PhysRevD.71.024011 | null | gr-qc | null | Solving the 4-d Einstein equations as evolution in time requires solving
equations of two types: the four elliptic initial data (constraint) equations,
followed by the six second order evolution equations. Analytically the
constraint equations remain solved under the action of the evolution, and one
approach is to simply monitor them ({\it unconstrained} evolution). Since
computational solution of differential equations introduces almost inevitable
errors, it is clearly "more correct" to introduce a scheme which actively
maintains the constraints by solution ({\it constrained} evolution). This has
shown promise in computational settings, but the analysis of the resulting
mixed elliptic hyperbolic method has not been completely carried out. We
present such an analysis for one method of constrained evolution, applied to a
simple vacuum system, linearized gravitational waves.
We begin with a study of the hyperbolicity of the unconstrained Einstein
equations. (Because the study of hyperbolicity deals only with the highest
derivative order in the equations, linearization loses no essential details.)
We then give explicit analytical construction of the effect of initial data
setting and constrained evolution for linearized gravitational waves. While
this is clearly a toy model with regard to constrained evolution, certain
interesting features are found which have relevance to the full nonlinear
Einstein equations.
| [
{
"created": "Sat, 31 Jul 2004 19:10:36 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Matzner",
"Richard A.",
""
]
] | Solving the 4-d Einstein equations as evolution in time requires solving equations of two types: the four elliptic initial data (constraint) equations, followed by the six second order evolution equations. Analytically the constraint equations remain solved under the action of the evolution, and one approach is to simply monitor them ({\it unconstrained} evolution). Since computational solution of differential equations introduces almost inevitable errors, it is clearly "more correct" to introduce a scheme which actively maintains the constraints by solution ({\it constrained} evolution). This has shown promise in computational settings, but the analysis of the resulting mixed elliptic hyperbolic method has not been completely carried out. We present such an analysis for one method of constrained evolution, applied to a simple vacuum system, linearized gravitational waves. We begin with a study of the hyperbolicity of the unconstrained Einstein equations. (Because the study of hyperbolicity deals only with the highest derivative order in the equations, linearization loses no essential details.) We then give explicit analytical construction of the effect of initial data setting and constrained evolution for linearized gravitational waves. While this is clearly a toy model with regard to constrained evolution, certain interesting features are found which have relevance to the full nonlinear Einstein equations. |
2405.13354 | Subhra Bhattacharya | Subhra Bhattacharya | Some Classes of Interacting Two-Fluid Model of the Expanding Universe | null | Physica Scripta (2024) | 10.1088/1402-4896/ad4ea7 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider interacting dark matter-dark energy models arising out of a
general interaction term
$Q=f(\rho_{m},\rho_{d},\dot{\rho}_{m},\dot{\rho}_{d}).$ Here $f$ is a
functional relation connecting the energy densities $\rho_{m}$ and $\rho_{d}$
and their derivatives w.r.t. time $t.$ In our model we consider two interacting
barotropic fluid with constant equation of state $\omega_{m}$ and $\omega_{d}.$
By considering a dynamical interaction between them we trace out the
cosmological evolution dynamics of the universe. We analytically solve the
model by considering a constant ratio between the two fluids and then track the
corresponding analytical results using observational data from the baryon
acoustic oscillation measurements, Type Ia supernovae measurements and the
local Hubble constant measurements. From this general setting we introduce
three different models and nine different interaction function. Our final aim
is to set up a comparative analysis of the various class of models under the
different interaction function using common theoretical and numerical analysis.
| [
{
"created": "Wed, 22 May 2024 05:16:39 GMT",
"version": "v1"
}
] | 2024-05-24 | [
[
"Bhattacharya",
"Subhra",
""
]
] | We consider interacting dark matter-dark energy models arising out of a general interaction term $Q=f(\rho_{m},\rho_{d},\dot{\rho}_{m},\dot{\rho}_{d}).$ Here $f$ is a functional relation connecting the energy densities $\rho_{m}$ and $\rho_{d}$ and their derivatives w.r.t. time $t.$ In our model we consider two interacting barotropic fluid with constant equation of state $\omega_{m}$ and $\omega_{d}.$ By considering a dynamical interaction between them we trace out the cosmological evolution dynamics of the universe. We analytically solve the model by considering a constant ratio between the two fluids and then track the corresponding analytical results using observational data from the baryon acoustic oscillation measurements, Type Ia supernovae measurements and the local Hubble constant measurements. From this general setting we introduce three different models and nine different interaction function. Our final aim is to set up a comparative analysis of the various class of models under the different interaction function using common theoretical and numerical analysis. |
gr-qc/0609029 | Dah-Wei Chiou | Dah-Wei Chiou | Loop Quantum Cosmology in Bianchi Type I Models: Analytical
Investigation | 53 pages, 2 figures; more typos corrected; HyperTeX enabled | Phys.Rev.D75:024029,2007 | 10.1103/PhysRevD.75.024029 | null | gr-qc | null | The comprehensive formulation for loop quantum cosmology in the spatially
flat, isotropic model was recently constructed. In this paper, the methods are
extended to the anisotropic Bianchi I cosmology. Both the precursor and the
improved strategies are applied and the expected results are established: (i)
the scalar field again serves as an internal clock and is treated as emergent
time; (ii) the total Hamiltonian constraint is derived by imposing the
fundamental discreteness and gives the evolution as a difference equation; and
(iii) the physical Hilbert space, Dirac observables and semi-classical states
are constructed rigorously. It is also shown that the state in the kinematical
Hilbert space associated with the classical singularity is decoupled in the
difference evolution equation, indicating that the big bounce may take place
when any of the area scales undergoes the vanishing behavior. The investigation
affirms the robustness of the framework used in the isotropic model by
enlarging its domain of validity and provides foundations to conduct the
detailed numerical analysis.
| [
{
"created": "Thu, 7 Sep 2006 20:39:34 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Sep 2006 16:03:17 GMT",
"version": "v2"
},
{
"created": "Wed, 8 Nov 2006 00:34:48 GMT",
"version": "v3"
},
{
"created": "Tue, 2 Jan 2007 22:45:16 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Chiou",
"Dah-Wei",
""
]
] | The comprehensive formulation for loop quantum cosmology in the spatially flat, isotropic model was recently constructed. In this paper, the methods are extended to the anisotropic Bianchi I cosmology. Both the precursor and the improved strategies are applied and the expected results are established: (i) the scalar field again serves as an internal clock and is treated as emergent time; (ii) the total Hamiltonian constraint is derived by imposing the fundamental discreteness and gives the evolution as a difference equation; and (iii) the physical Hilbert space, Dirac observables and semi-classical states are constructed rigorously. It is also shown that the state in the kinematical Hilbert space associated with the classical singularity is decoupled in the difference evolution equation, indicating that the big bounce may take place when any of the area scales undergoes the vanishing behavior. The investigation affirms the robustness of the framework used in the isotropic model by enlarging its domain of validity and provides foundations to conduct the detailed numerical analysis. |
1510.04060 | Alan Pavan Bendasoli | A. B. Pavan, Rodrigo Silva Lima and Lu\'is Filipe de Almeida Roque | Comment on "Quasinormal modes of Schwarzschild anti de Sitter black
holes: Electromagnetic and gravitational perturbations" | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The quasinormal modes of the electromagnetic and gravitational perturbation
on Schwarzschild-AdS black hole calculated by Cardoso and Lemos has been
revisited. Although the equations of motion are correct some frequencies
calculated previously by the authors are not. We present the new values of
quasinormal modes and discuss the possible sources of problems and implications
on the conclusions presented.
| [
{
"created": "Wed, 14 Oct 2015 12:16:09 GMT",
"version": "v1"
}
] | 2015-10-15 | [
[
"Pavan",
"A. B.",
""
],
[
"Lima",
"Rodrigo Silva",
""
],
[
"Roque",
"Luís Filipe de Almeida",
""
]
] | The quasinormal modes of the electromagnetic and gravitational perturbation on Schwarzschild-AdS black hole calculated by Cardoso and Lemos has been revisited. Although the equations of motion are correct some frequencies calculated previously by the authors are not. We present the new values of quasinormal modes and discuss the possible sources of problems and implications on the conclusions presented. |
1010.5227 | Elena Magliaro | Elena Magliaro and Claudio Perini | Local spin foams | 9 pages, 8 figures, published version | Int.J.Mod.Phys. D21 (2012) 1250090 | 10.1142/S0218271812500903 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The central object of this paper is a holonomy formulation for spin foams.
Within this new represen- tation, we analyze three general requirements:
locality, composition law, cylindrical consistency. In particular, cylindrical
consistency is shown to fix the arbitrary normalization of the vertex amplitude
in the case of Euclidean signature.
| [
{
"created": "Mon, 25 Oct 2010 19:27:23 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Jan 2013 17:46:33 GMT",
"version": "v2"
}
] | 2013-01-09 | [
[
"Magliaro",
"Elena",
""
],
[
"Perini",
"Claudio",
""
]
] | The central object of this paper is a holonomy formulation for spin foams. Within this new represen- tation, we analyze three general requirements: locality, composition law, cylindrical consistency. In particular, cylindrical consistency is shown to fix the arbitrary normalization of the vertex amplitude in the case of Euclidean signature. |
2203.08567 | Maciej Dunajski | Maciej Dunajski, Roger Penrose | Quantum state reduction, and Newtonian twistor theory | 14 pages, one figure. Final version, published in the Annals of
Physics | Annals of Physics. Volume 451, April 2023, 169243 | 10.1016/j.aop.2023.169243 | null | gr-qc hep-th math.DG quant-ph | http://creativecommons.org/licenses/by/4.0/ | We discuss the equivalence principle in quantum mechanics in the context of
Newton--Cartan geometry, and non--relativistic twistor theory.
| [
{
"created": "Wed, 16 Mar 2022 11:58:20 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Feb 2023 14:27:04 GMT",
"version": "v2"
}
] | 2023-03-01 | [
[
"Dunajski",
"Maciej",
""
],
[
"Penrose",
"Roger",
""
]
] | We discuss the equivalence principle in quantum mechanics in the context of Newton--Cartan geometry, and non--relativistic twistor theory. |
1107.2669 | W. G. Unruh | W. G. Unruh | Quantum Noise in Amplifiers and Hawking/Dumb-Hole Radiation as Amplifier
Noise | 13 pages, 4 figures | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The quantum noise in a linear amplifier is shown to be thermal noise. The
theory of linear amplifiers is applied first to the simplest, single or double
oscillator model of an amplifier, and then to linear model of an amplifier with
continuous fields and input and outputs. Finally it is shown that the thermal
noise emitted by black holes first demonstrated by Hawking, and of dumb holes
(sonic and other analogs to black holes), arises from the same analysis as for
linear amplifiers. The amplifier noise of black holes acting as amplifiers on
the quantum fields living in the spacetime surrounding the black hole is the
radiation discovered by Hawking. For any amplifier, that quantum noise is
completely characterized by the attributes of the system regarded as a
classical amplifier, and arises out of those classical amplification factors
and the commutation relations of quantum mechanics.
| [
{
"created": "Wed, 13 Jul 2011 20:32:09 GMT",
"version": "v1"
}
] | 2011-07-15 | [
[
"Unruh",
"W. G.",
""
]
] | The quantum noise in a linear amplifier is shown to be thermal noise. The theory of linear amplifiers is applied first to the simplest, single or double oscillator model of an amplifier, and then to linear model of an amplifier with continuous fields and input and outputs. Finally it is shown that the thermal noise emitted by black holes first demonstrated by Hawking, and of dumb holes (sonic and other analogs to black holes), arises from the same analysis as for linear amplifiers. The amplifier noise of black holes acting as amplifiers on the quantum fields living in the spacetime surrounding the black hole is the radiation discovered by Hawking. For any amplifier, that quantum noise is completely characterized by the attributes of the system regarded as a classical amplifier, and arises out of those classical amplification factors and the commutation relations of quantum mechanics. |
2110.14310 | Mingzhe Li | Mingzhe Li, Yicen Mou, Haomin Rao, and Dehao Zhao | Gravitational leptogenesis in teleparallel and symmetric teleparallel
gravities | 7 pages, to be published in Chinese Physics C | null | 10.1088/1674-1137/ac3411 | USTC-ICTS/PCFT-21-38 | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we consider the possibilities of generating baryon number
asymmetry in thermal equilibrium within the frameworks of teleparallel and
symmetric teleparallel gravities. Through the derivative couplings of the
torsion scalar or the non-metricity scalar to baryons, the baryon number
asymmetry is indeed produced in the radiation dominated epoch. For
gravitational baryogenesis mechanisms in these two frameworks, the produced
baryon-to-entropy ratio is too small to be consistent with observations. But
the gravitational leptogenesis models within both frameworks have the
possibilities to interpret the observed baryon-antibaryon asymmetry.
| [
{
"created": "Wed, 27 Oct 2021 09:45:14 GMT",
"version": "v1"
}
] | 2022-11-09 | [
[
"Li",
"Mingzhe",
""
],
[
"Mou",
"Yicen",
""
],
[
"Rao",
"Haomin",
""
],
[
"Zhao",
"Dehao",
""
]
] | In this paper, we consider the possibilities of generating baryon number asymmetry in thermal equilibrium within the frameworks of teleparallel and symmetric teleparallel gravities. Through the derivative couplings of the torsion scalar or the non-metricity scalar to baryons, the baryon number asymmetry is indeed produced in the radiation dominated epoch. For gravitational baryogenesis mechanisms in these two frameworks, the produced baryon-to-entropy ratio is too small to be consistent with observations. But the gravitational leptogenesis models within both frameworks have the possibilities to interpret the observed baryon-antibaryon asymmetry. |
1511.01869 | Vakhid Gani | Vakhid A. Gani, Alexander E. Dmitriev, Sergey G. Rubin | Two-dimensional manifold with point-like defects | 4 pages, 2 figures; Proceedings of the Conference of Fundamental
Research and Particle Physics, 18-20 February 2015, Moscow, Russian
Federation | Physics Procedia 74 (2015) 32-35 | 10.1016/j.phpro.2015.09.186 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a class of two-dimensional compact extra spaces isomorphic to the
sphere $S^2$ in the framework of multidimensional gravitation. We show that
there exists a family of stationary metrics that depend on the initial
(boundary) conditions. All these geometries have a singular point. We also
discuss the possibility for these deformed extra spaces to be considered as
dark matter candidates.
| [
{
"created": "Thu, 5 Nov 2015 19:48:23 GMT",
"version": "v1"
}
] | 2015-11-06 | [
[
"Gani",
"Vakhid A.",
""
],
[
"Dmitriev",
"Alexander E.",
""
],
[
"Rubin",
"Sergey G.",
""
]
] | We study a class of two-dimensional compact extra spaces isomorphic to the sphere $S^2$ in the framework of multidimensional gravitation. We show that there exists a family of stationary metrics that depend on the initial (boundary) conditions. All these geometries have a singular point. We also discuss the possibility for these deformed extra spaces to be considered as dark matter candidates. |
gr-qc/9404005 | Piotr T. Chru\'sciel | B.Berger, P.T. Chrusciel, V.Moncrief | On "asymptotically flat" space-times with $G_{2}$-invariant Cauchy
surfaces | 33 pages, Latex (with amssymbols), Garching preprint MPA 797; texing
problems corrected | Ann.Phys.237:322-354,1995 | 10.1006/aphy.1995.1012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study space-times which evolve out of Cauchy data
$(\Sigma,{}^3g,K)$ invariant under the action of a two-dimensional commutative
Lie group. Moreover $(\Sigma,{}^3g,K)$ are assumed to satisfy certain
completeness and asymptotic flatness conditions in spacelike directions. We
show that asymptotic flatness and energy conditions exclude all topologies and
group actions except for a cylindrically symmetric $R^3$, or a periodic
identification thereof along the $z$-axis. We prove that asymptotic flatness,
energy conditions and cylindrical symmetry exclude the existence of compact
trapped surfaces. Finally we show that the recent results of Christodoulou and
Tahvildar-Zadeh concerning global existence of a class of wave-maps imply that
strong cosmic censorship holds in the class of asymptotically flat
cylindrically symmetric electro-vacuum space-times.
| [
{
"created": "Wed, 6 Apr 1994 14:24:29 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Dec 2013 05:03:56 GMT",
"version": "v2"
}
] | 2013-12-19 | [
[
"Berger",
"B.",
""
],
[
"Chrusciel",
"P. T.",
""
],
[
"Moncrief",
"V.",
""
]
] | In this paper we study space-times which evolve out of Cauchy data $(\Sigma,{}^3g,K)$ invariant under the action of a two-dimensional commutative Lie group. Moreover $(\Sigma,{}^3g,K)$ are assumed to satisfy certain completeness and asymptotic flatness conditions in spacelike directions. We show that asymptotic flatness and energy conditions exclude all topologies and group actions except for a cylindrically symmetric $R^3$, or a periodic identification thereof along the $z$-axis. We prove that asymptotic flatness, energy conditions and cylindrical symmetry exclude the existence of compact trapped surfaces. Finally we show that the recent results of Christodoulou and Tahvildar-Zadeh concerning global existence of a class of wave-maps imply that strong cosmic censorship holds in the class of asymptotically flat cylindrically symmetric electro-vacuum space-times. |
1210.0519 | Marc Casals | Marc Casals and Adrian C. Ottewill | Analytic Investigation of the Branch Cut of the Green Function in
Schwarzschild Space-time | 26 pages, 18 figures | null | 10.1103/PhysRevD.87.064010 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The retarded Green function for linear field perturbations in Schwarzschild
black hole space-time possesses a branch cut in the complex-frequency plane.
This branch cut has remained largely unexplored: only asymptotic analyses
either for small-frequency (yielding the known tail decay at late times of an
initial perturbation of the black hole) or for large-frequency (quasinormal
modes close to the branch cut in this regime have been linked to quantum
properties of black holes) have been carried out in the literature. The regime
along the cut inaccessible to these asymptotic analyses has so far remained
essentially unreachable. We present a new method for the analytic calculation
of the branch cut directly on the cut for general-spin fields in Schwarzschild
space-time. This method is valid for any values of the frequency on the cut and
so it provides analytic access to the whole branch cut for the first time. We
calculate the modes along the cut and investigate their properties and
connection with quasinormal modes. We also investigate the contribution from
these branch cut modes to the self-force acting on a point particle on a
Schwarzschild background space-time.
| [
{
"created": "Mon, 1 Oct 2012 19:37:49 GMT",
"version": "v1"
}
] | 2013-03-14 | [
[
"Casals",
"Marc",
""
],
[
"Ottewill",
"Adrian C.",
""
]
] | The retarded Green function for linear field perturbations in Schwarzschild black hole space-time possesses a branch cut in the complex-frequency plane. This branch cut has remained largely unexplored: only asymptotic analyses either for small-frequency (yielding the known tail decay at late times of an initial perturbation of the black hole) or for large-frequency (quasinormal modes close to the branch cut in this regime have been linked to quantum properties of black holes) have been carried out in the literature. The regime along the cut inaccessible to these asymptotic analyses has so far remained essentially unreachable. We present a new method for the analytic calculation of the branch cut directly on the cut for general-spin fields in Schwarzschild space-time. This method is valid for any values of the frequency on the cut and so it provides analytic access to the whole branch cut for the first time. We calculate the modes along the cut and investigate their properties and connection with quasinormal modes. We also investigate the contribution from these branch cut modes to the self-force acting on a point particle on a Schwarzschild background space-time. |
gr-qc/9901015 | Jerzy Lewandowski | Jerzy Lewandowski and Thomas Thiemann | Diffeomorphism invariant Quantum Field Theories of Connections in terms
of webs | 21 pages, 3 figurs | Class.Quant.Grav.16:2299-2322,1999 | 10.1088/0264-9381/16/7/311 | null | gr-qc | null | In the canonical quantization of gravity in terms of the Ashtekar variables
one uses paths in the 3-space to construct the quantum states. Usually, one
restricts oneself to families of paths admitting only finite number of isolated
intersections. This assumption implies a limitation on the diffeomorphisms
invariance of the introduced structures. In this work, using the previous
results of Baez and Sawin, we extend the existing results to a theory admitting
all the possible piecewise smooth finite paths and loops. In particular, we
$(i)$ characterize the spectrum of the Ashtekar-Isham configuration space,
$(ii)$ introduce spin-web states, a generalization of the spin-network states,
$(iii)$ extend the diffeomorphism averaging to the spin-web states and derive a
large class of diffeomorphism invariant states and finally $(iv)$ extend the
3-geometry operators and the Hamiltonian operator.
| [
{
"created": "Thu, 7 Jan 1999 11:19:58 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Lewandowski",
"Jerzy",
""
],
[
"Thiemann",
"Thomas",
""
]
] | In the canonical quantization of gravity in terms of the Ashtekar variables one uses paths in the 3-space to construct the quantum states. Usually, one restricts oneself to families of paths admitting only finite number of isolated intersections. This assumption implies a limitation on the diffeomorphisms invariance of the introduced structures. In this work, using the previous results of Baez and Sawin, we extend the existing results to a theory admitting all the possible piecewise smooth finite paths and loops. In particular, we $(i)$ characterize the spectrum of the Ashtekar-Isham configuration space, $(ii)$ introduce spin-web states, a generalization of the spin-network states, $(iii)$ extend the diffeomorphism averaging to the spin-web states and derive a large class of diffeomorphism invariant states and finally $(iv)$ extend the 3-geometry operators and the Hamiltonian operator. |
2203.10740 | Hiroki Asami | Hiroki Asami and Chul-Moon Yoo | Gravothermal catastrophe and critical dimension in a $D$-dimensional
asymptotically AdS spacetime | 23 pages | null | 10.1103/PhysRevD.106.044065 | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | We investigate the structure and stability of the thermal equilibrium states
of a spherically symmetric self-gravitating system in a $D$-dimensional
asymptotically Anti-de Sitter(AdS) spacetime. The system satisfies the
Einstein-Vlasov equations with a negative cosmological constant. Due to the
confined structure of the AdS potential, we can construct thermal equilibrium
states without any artificial wall in the asymptotically AdS spacetime.
Accordingly, the AdS radius can be regarded as the typical size of the system.
Then the system can be characterized by the gravothermal energy and AdS radius
normalized by the total particle number. We investigate the catastrophic
instability of the system in a $D$-dimensional spacetime by using the turning
point method. As a result, we find that the curve has a double spiral structure
for $4\le D\le 10$ while it does not have any spiral structures for $D\ge11$ as
in the asymptotically flat case confined by an adiabatic wall. Irrespective of
the existence of the spiral structure, there exist upper and lower bounds for
the value of the gravothermal energy. This fact indicates that there is no
thermal equilibrium solution outside the allowed region of the gravothermal
energy. This property is also similar to the asymptotically flat case.
| [
{
"created": "Mon, 21 Mar 2022 05:19:36 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Mar 2022 05:40:44 GMT",
"version": "v2"
},
{
"created": "Mon, 15 Aug 2022 07:47:44 GMT",
"version": "v3"
}
] | 2022-09-07 | [
[
"Asami",
"Hiroki",
""
],
[
"Yoo",
"Chul-Moon",
""
]
] | We investigate the structure and stability of the thermal equilibrium states of a spherically symmetric self-gravitating system in a $D$-dimensional asymptotically Anti-de Sitter(AdS) spacetime. The system satisfies the Einstein-Vlasov equations with a negative cosmological constant. Due to the confined structure of the AdS potential, we can construct thermal equilibrium states without any artificial wall in the asymptotically AdS spacetime. Accordingly, the AdS radius can be regarded as the typical size of the system. Then the system can be characterized by the gravothermal energy and AdS radius normalized by the total particle number. We investigate the catastrophic instability of the system in a $D$-dimensional spacetime by using the turning point method. As a result, we find that the curve has a double spiral structure for $4\le D\le 10$ while it does not have any spiral structures for $D\ge11$ as in the asymptotically flat case confined by an adiabatic wall. Irrespective of the existence of the spiral structure, there exist upper and lower bounds for the value of the gravothermal energy. This fact indicates that there is no thermal equilibrium solution outside the allowed region of the gravothermal energy. This property is also similar to the asymptotically flat case. |
gr-qc/9606017 | L. Sriramkumar | K. Srinivasan, L. Sriramkumar, T. Padmanabhan | `Thermal' ambience and fluctuations in classical field theory | LATEX document, 15 pages | null | null | IUCAA-18/96 | gr-qc | null | A plane monochromatic wave will not appear monochromatic to a noninertial
observer. We show that this feature leads to a `thermal' ambience in an
accelerated frame {\it even in classical field theory}. When a real,
monochromatic, mode of a scalar field is Fourier analyzed with respect to the
proper time of a uniformly accelerating observer, the resulting power spectrum
consists of three terms: (i)~a factor $(1/2)$ that is typical of the ground
state energy of a quantum oscillator, (ii)~a Planckian distribution $N(\Omega)$
and---most importantly---(iii)~a term $\sqrt{N(N+1)}$, which is the root mean
square fluctuations about the Planckian distribution. It is the appearance of
the root mean square fluctuations that motivates us to attribute a `thermal'
nature to the power spectrum. This result shows that some of the `purely'
quantum mechanical results might have a classical analogue. The `thermal'
ambience that we report here also proves to be a feature of observers stationed
at a constant radius in the Schwarzschild and de-Sitter spacetimes.
| [
{
"created": "Mon, 10 Jun 1996 09:54:46 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Srinivasan",
"K.",
""
],
[
"Sriramkumar",
"L.",
""
],
[
"Padmanabhan",
"T.",
""
]
] | A plane monochromatic wave will not appear monochromatic to a noninertial observer. We show that this feature leads to a `thermal' ambience in an accelerated frame {\it even in classical field theory}. When a real, monochromatic, mode of a scalar field is Fourier analyzed with respect to the proper time of a uniformly accelerating observer, the resulting power spectrum consists of three terms: (i)~a factor $(1/2)$ that is typical of the ground state energy of a quantum oscillator, (ii)~a Planckian distribution $N(\Omega)$ and---most importantly---(iii)~a term $\sqrt{N(N+1)}$, which is the root mean square fluctuations about the Planckian distribution. It is the appearance of the root mean square fluctuations that motivates us to attribute a `thermal' nature to the power spectrum. This result shows that some of the `purely' quantum mechanical results might have a classical analogue. The `thermal' ambience that we report here also proves to be a feature of observers stationed at a constant radius in the Schwarzschild and de-Sitter spacetimes. |
gr-qc/9805025 | Valery Rupasov | Igor Bulyzhenkov | Gravitational light bending in Euclidean space | 2 pages, Latex | null | null | null | gr-qc | null | Both the non-homogeneous slowness of electromagnetic waves in gravitational
fields and the frequency red shift contribute to the gravitational light
bending. This twofold contribution explains the measured deflection of light
rays by the Sun under Euclidean geometry of space.
| [
{
"created": "Fri, 8 May 1998 20:59:54 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Mar 2000 06:23:35 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Bulyzhenkov",
"Igor",
""
]
] | Both the non-homogeneous slowness of electromagnetic waves in gravitational fields and the frequency red shift contribute to the gravitational light bending. This twofold contribution explains the measured deflection of light rays by the Sun under Euclidean geometry of space. |
2308.12155 | Anjan Kar | Anjan Kar and Sayan Kar (Indian Institute of Technology Kharagpur,
India) | Novel regular black holes: geometry, source and shadow | Matches the published version | General Relativity and Gravitation 56, 52 (2024) | 10.1007/s10714-024-03238-4 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We propose a two-parameter, static and spherically symmetric regular
geometry, which, for specific parameter values represents a regular black hole.
The matter required to support such spacetimes within the framework of General
Relativity (GR), is found to violate the energy conditions, though not in the
entire domain of the radial coordinate. A particular choice of the parameters
reduces the regular black hole to a singular, mutated Reissner-Nordstrom
geometry. It also turns out that our regular black hole is geodesically
complete. Fortunately, despite energy condition violation, we are able to
construct a viable source, within the framework of GR coupled to matter, for
our regular geometry. The source term involves a nonlinear magnetic monopole in
a chosen version of nonlinear electrodynamics. We also suggest an alternative
approach towards constructing a source, using the effective Einstein equations
which arise in the context of braneworld gravity. Finally, we obtain the
circular shadow profile of our regular black hole and provide a preliminary
estimate of the metric parameters using recent observational results from the
EHT collaboration.
| [
{
"created": "Wed, 23 Aug 2023 14:17:40 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Sep 2023 17:55:09 GMT",
"version": "v2"
},
{
"created": "Wed, 1 May 2024 10:55:23 GMT",
"version": "v3"
}
] | 2024-05-02 | [
[
"Kar",
"Anjan",
"",
"Indian Institute of Technology Kharagpur,\n India"
],
[
"Kar",
"Sayan",
"",
"Indian Institute of Technology Kharagpur,\n India"
]
] | We propose a two-parameter, static and spherically symmetric regular geometry, which, for specific parameter values represents a regular black hole. The matter required to support such spacetimes within the framework of General Relativity (GR), is found to violate the energy conditions, though not in the entire domain of the radial coordinate. A particular choice of the parameters reduces the regular black hole to a singular, mutated Reissner-Nordstrom geometry. It also turns out that our regular black hole is geodesically complete. Fortunately, despite energy condition violation, we are able to construct a viable source, within the framework of GR coupled to matter, for our regular geometry. The source term involves a nonlinear magnetic monopole in a chosen version of nonlinear electrodynamics. We also suggest an alternative approach towards constructing a source, using the effective Einstein equations which arise in the context of braneworld gravity. Finally, we obtain the circular shadow profile of our regular black hole and provide a preliminary estimate of the metric parameters using recent observational results from the EHT collaboration. |
1707.03726 | Ernst A. Pashitskii | E.A. Pashitskii and V.I. Pentegov | On the nature of the Newton's gravitational constant and the possible
quantum-field theory of gravitation | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On the basis of the coincidence of the physical dimensions (in natural units
$\hbar = c = 1$) of the Newton's gravitational constant $G_{N} $ and the
phenomenological Fermi constant $G_{F} $ for weak interaction, it is suggested
that there is a certain similarity between weak forces, which are caused by the
exchange of massive intermediate vector bosons with spin $S=1$, and "superweak"
gravitational forces that can be caused by the exchange of "supermassive"
hypothetical tensor bosons with spin $S=2$. By analogy with how the masses of
intermediate bosons in the theory of electroweak interaction arise as a result
of spontaneous breaking of the gauge symmetry of the electromagnetic field due
to its interaction with the nonlinear scalar Higgs field, the masses of
hypothetical tensor bosons carrying gravitational interaction can also arise as
a result of spontaneous breaking of gauge symmetry of the massless gravitons
when they interact with a fundamental nonlinear scalar field in a flat
4-dimensional space-time.
| [
{
"created": "Wed, 12 Jul 2017 14:07:46 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Jul 2017 12:04:52 GMT",
"version": "v2"
},
{
"created": "Wed, 26 Jul 2017 12:06:45 GMT",
"version": "v3"
}
] | 2017-07-27 | [
[
"Pashitskii",
"E. A.",
""
],
[
"Pentegov",
"V. I.",
""
]
] | On the basis of the coincidence of the physical dimensions (in natural units $\hbar = c = 1$) of the Newton's gravitational constant $G_{N} $ and the phenomenological Fermi constant $G_{F} $ for weak interaction, it is suggested that there is a certain similarity between weak forces, which are caused by the exchange of massive intermediate vector bosons with spin $S=1$, and "superweak" gravitational forces that can be caused by the exchange of "supermassive" hypothetical tensor bosons with spin $S=2$. By analogy with how the masses of intermediate bosons in the theory of electroweak interaction arise as a result of spontaneous breaking of the gauge symmetry of the electromagnetic field due to its interaction with the nonlinear scalar Higgs field, the masses of hypothetical tensor bosons carrying gravitational interaction can also arise as a result of spontaneous breaking of gauge symmetry of the massless gravitons when they interact with a fundamental nonlinear scalar field in a flat 4-dimensional space-time. |
2009.05358 | James Lucietti | James Lucietti | All higher-dimensional Majumdar-Papapetrou black holes | 10 pages. v2: minor correction, assumption added, references added.
v3: main result stated as a theorem, published version | Ann. Henri Poincare (2021) | 10.1007/s00023-021-01037-0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that the only asymptotically flat spacetimes with a suitably regular
event horizon, in a generalised Majumdar-Papapetrou class of solutions to
higher-dimensional Einstein-Maxwell theory, are the standard multi-black holes.
The proof involves a careful analysis of the near-horizon geometry and an
extension of the positive mass theorem to Riemannian manifolds with conical
singularities. This completes the classification of asymptotically flat,
static, extreme black hole solutions in this theory.
| [
{
"created": "Fri, 11 Sep 2020 11:54:05 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Sep 2020 12:57:47 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Mar 2021 10:31:29 GMT",
"version": "v3"
}
] | 2021-03-09 | [
[
"Lucietti",
"James",
""
]
] | We prove that the only asymptotically flat spacetimes with a suitably regular event horizon, in a generalised Majumdar-Papapetrou class of solutions to higher-dimensional Einstein-Maxwell theory, are the standard multi-black holes. The proof involves a careful analysis of the near-horizon geometry and an extension of the positive mass theorem to Riemannian manifolds with conical singularities. This completes the classification of asymptotically flat, static, extreme black hole solutions in this theory. |
2112.03307 | Seth Asante | Seth K. Asante, Bianca Dittrich | Perfect discretizations as a gateway to one-loop partition functions for
4D gravity | 22 pages | null | 10.1007/JHEP05(2022)172 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lattice actions and amplitudes that perfectly mirror continuum physics are
known as perfect discretizations. Such perfect discretizations naturally
preserve the symmetries of the continuum. This is a key concern for general
relativity, where diffeomorphism symmetry and dynamics are deeply connected,
and diffeomorphisms play a crucial role in quantization. In this work we
construct for the first time a perfect discretizations for four-dimensional
linearized gravity. We show how the perfect discretizations do lead to a
straightforward construction of the one-loop quantum corrections for manifolds
with boundary. This will also illustrate, that for manifolds with boundaries,
gauge modes that affect the boundary, need to be taken into account for the
computation of the one-loop correction. This work provides therefore an
evaluation of the boundary action for the diffeomorphism modes for a general
class of backgrounds.
| [
{
"created": "Mon, 6 Dec 2021 19:02:07 GMT",
"version": "v1"
}
] | 2022-06-15 | [
[
"Asante",
"Seth K.",
""
],
[
"Dittrich",
"Bianca",
""
]
] | Lattice actions and amplitudes that perfectly mirror continuum physics are known as perfect discretizations. Such perfect discretizations naturally preserve the symmetries of the continuum. This is a key concern for general relativity, where diffeomorphism symmetry and dynamics are deeply connected, and diffeomorphisms play a crucial role in quantization. In this work we construct for the first time a perfect discretizations for four-dimensional linearized gravity. We show how the perfect discretizations do lead to a straightforward construction of the one-loop quantum corrections for manifolds with boundary. This will also illustrate, that for manifolds with boundaries, gauge modes that affect the boundary, need to be taken into account for the computation of the one-loop correction. This work provides therefore an evaluation of the boundary action for the diffeomorphism modes for a general class of backgrounds. |
gr-qc/9207001 | null | Riccardo Capovilla | Non-Minimally Coupled Scalar Field and Ashtekar Variables | 6 pages | Phys.Rev.D46:1450-1452,1992 | 10.1103/PhysRevD.46.1450 | null | gr-qc | null | The non-minimal coupling of a scalar field is considered in the framework of
Ashtekar's new variables formulation of gravity. A first order action
functional for this system is derived in which the field variables are a tetrad
field, and an SL(2,C) connection, together with the scalar field. The tetrad
field and the SL(2,C) connection are related to the Ashtekar variables for the
vacuum case by a conformal transformation. A canonical analysis shows that for
this coupling the equations of Ashtekar's formulation of canonical gravity are
non-polynomial in the scalar field. (to be published in Phys. Rev. D)
| [
{
"created": "Mon, 20 Jul 1992 22:50:00 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Capovilla",
"Riccardo",
""
]
] | The non-minimal coupling of a scalar field is considered in the framework of Ashtekar's new variables formulation of gravity. A first order action functional for this system is derived in which the field variables are a tetrad field, and an SL(2,C) connection, together with the scalar field. The tetrad field and the SL(2,C) connection are related to the Ashtekar variables for the vacuum case by a conformal transformation. A canonical analysis shows that for this coupling the equations of Ashtekar's formulation of canonical gravity are non-polynomial in the scalar field. (to be published in Phys. Rev. D) |
gr-qc/0203064 | Sergio Dain | Sergio Dain and Osvaldo M. Moreschi and Reinaldo J. Gleiser | Photon rockets and the Robinson-Trautman geometries | 7 pages, no figures, LaTeX2e | Class.Quant.Grav. 13 (1996) 1155-1160 | 10.1088/0264-9381/13/5/026 | null | gr-qc | null | We point out the relation between the photon rocket spacetimes and the
Robinson Trautman geometries. This allows a discussion of the issues related to
the distinction between the gravitational and matter energy radiation that
appear in these metrics in a more geometrical way, taking full advantage of
their asymptotic properties at null infinity to separate the Weyl and Ricci
radiations, and to clearly establish their gravitational energy content. We
also give the exact solution for the generalized photon rockets.
| [
{
"created": "Tue, 19 Mar 2002 15:48:50 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Dain",
"Sergio",
""
],
[
"Moreschi",
"Osvaldo M.",
""
],
[
"Gleiser",
"Reinaldo J.",
""
]
] | We point out the relation between the photon rocket spacetimes and the Robinson Trautman geometries. This allows a discussion of the issues related to the distinction between the gravitational and matter energy radiation that appear in these metrics in a more geometrical way, taking full advantage of their asymptotic properties at null infinity to separate the Weyl and Ricci radiations, and to clearly establish their gravitational energy content. We also give the exact solution for the generalized photon rockets. |
0905.4492 | Philip Fellman | Philip V. Fellman, Jonathan Vos Post, Christine Carmichael, Alexandru
Manus, and Dawna Lee Attig | Time, Incompleteness and Singularity in Quantum Cosmology | 14 Pages. Complex 2009. The First International Conference on Complex
Sciences: Theory and Applications, Shanghai China, February 23-25, 2009 | null | 10.1007/978-3-642-02466-5_73 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/3.0/ | In this paper we extend our 2007 paper, Comparative Quantum Cosmology:
Causality, Singularity, and Boundary Conditions, arXiv:0710.5046 to include
consideration of universal expansion, various implications of extendibility and
incompleteness in spacetime metrics and, absent the treatment of Feynman
diagrams, the use of Penning trap dynamics as explained by Ferdandez and
Velazquez to describe the Hamiltonians of space-times with no characteristic
upper or lower bound and to compare the above with Peter Lynds' conjecture on
the specialness of initial conditions in inflationary theory in quantum
cosmology.
| [
{
"created": "Wed, 27 May 2009 19:36:37 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Fellman",
"Philip V.",
""
],
[
"Post",
"Jonathan Vos",
""
],
[
"Carmichael",
"Christine",
""
],
[
"Manus",
"Alexandru",
""
],
[
"Attig",
"Dawna Lee",
""
]
] | In this paper we extend our 2007 paper, Comparative Quantum Cosmology: Causality, Singularity, and Boundary Conditions, arXiv:0710.5046 to include consideration of universal expansion, various implications of extendibility and incompleteness in spacetime metrics and, absent the treatment of Feynman diagrams, the use of Penning trap dynamics as explained by Ferdandez and Velazquez to describe the Hamiltonians of space-times with no characteristic upper or lower bound and to compare the above with Peter Lynds' conjecture on the specialness of initial conditions in inflationary theory in quantum cosmology. |
2201.09588 | Christian Boehmer | Christian G. Boehmer, Erik Jensko, Ruth Lazkoz | Cosmological dynamical systems in modified gravity | 19 pages, 6 figures; v2 minor changes, updated references | Eur. Phys. J. C 82, 500 (2022) | 10.1140/epjc/s10052-022-10412-y | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The field equations of modified gravity theories, when considering a
homogeneous and isotropic cosmological model, always become autonomous
differential equations. This relies on the fact that in such models all
variables only depend on cosmological time, or another suitably chosen time
parameter. Consequently, the field equations can always be cast into the form
of a dynamical system, a successful approach to study such models. We propose a
perspective that is applicable to many different modified gravity models and
relies on the standard cosmological density parameters only, making our choice
of variables model independent. The drawback of our approach is a more
complicated constraint equation. We demonstrate our procedure studying various
modified gravity models and show how much generic information can be extracted
before a specific model is considered.
| [
{
"created": "Mon, 24 Jan 2022 10:54:52 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Feb 2022 10:30:23 GMT",
"version": "v2"
}
] | 2023-02-03 | [
[
"Boehmer",
"Christian G.",
""
],
[
"Jensko",
"Erik",
""
],
[
"Lazkoz",
"Ruth",
""
]
] | The field equations of modified gravity theories, when considering a homogeneous and isotropic cosmological model, always become autonomous differential equations. This relies on the fact that in such models all variables only depend on cosmological time, or another suitably chosen time parameter. Consequently, the field equations can always be cast into the form of a dynamical system, a successful approach to study such models. We propose a perspective that is applicable to many different modified gravity models and relies on the standard cosmological density parameters only, making our choice of variables model independent. The drawback of our approach is a more complicated constraint equation. We demonstrate our procedure studying various modified gravity models and show how much generic information can be extracted before a specific model is considered. |
1305.6947 | J. A. Preciado Ph.D. | O. Obreg\'on, J. A. Preciado (Guanajuato U.) | A quantum cosmological model in Ho\v{r}ava-Lifshitz gravity | 5 pages, 2 figures. This work was presented at the 8th Workshop of
the Gravitation and Mathematical Physics Division of the Mexican Physical
Society, Tuxtla Gutierrez, Chiapas, Mexico, November 22-26, 2010 | AIP Conf. Proc. 1396, 151 (2011) | 10.1063/1.3647539 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A Wheeler-DeWitt equation for the Kantowski-Sachs model is derived within the
framework of the minimal quantum gravity theory proposed by Ho\v{r}ava. We
study the solution to this equation in the ultraviolet limit for the specific
case where the {\lambda} parameter of the theory takes its relativistic value
{\lambda} = 1. It is observed that the minisuperspace variables switch their
role compared with their usual infrared (General Relativity) behavior.
| [
{
"created": "Wed, 29 May 2013 20:50:32 GMT",
"version": "v1"
}
] | 2013-05-31 | [
[
"Obregón",
"O.",
"",
"Guanajuato U."
],
[
"Preciado",
"J. A.",
"",
"Guanajuato U."
]
] | A Wheeler-DeWitt equation for the Kantowski-Sachs model is derived within the framework of the minimal quantum gravity theory proposed by Ho\v{r}ava. We study the solution to this equation in the ultraviolet limit for the specific case where the {\lambda} parameter of the theory takes its relativistic value {\lambda} = 1. It is observed that the minisuperspace variables switch their role compared with their usual infrared (General Relativity) behavior. |
2205.08448 | Qian Hu | Qian Hu and John Veitch | Assessing the model waveform accuracy of gravitational waves | 17 pages, 6 figures. Accepted by PRD | Phys. Rev. D 106, 044042 (2022) | 10.1103/PhysRevD.106.044042 | LIGO-P2200107 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With the improvement in sensitivity of gravitational wave (GW) detectors and
the increasing diversity of GW sources, there is a strong need for accurate GW
waveform models for data analysis. While the current model accuracy assessments
require waveforms generated by numerical relativity (NR) simulations as the
"true waveforms", in this paper we propose an assessment approach that does not
require NR simulations, which enables us to assess model accuracy everywhere in
the parameter space. By measuring the difference between two waveform models,
we derive a necessary condition for a pair of waveform models to both be
accurate, for a particular set of parameters. We then apply this method to the
parameter estimation samples of the Gravitational-Wave Transient Catalogs
GWTC-3 and GWTC-2.1, and find that the waveform accuracy for high
signal-to-noise ratio events in some cases fails our assessment criterion.
Based on analysis of real events' posterior samples, we discuss the correlation
between our quantified accuracy assessments and systematic errors in parameter
estimation. We find waveform models that perform worse in our assessment are
more likely to give inconsistent estimations. We also investigate waveform
accuracy in different parameter regions, and find the accuracy degrades as the
spin effects go up, the mass ratio deviates from one, or the orbital plane is
near-aligned to the line of sight. Furthermore, we make predictions of waveform
accuracy requirements for future detectors and find the accuracy of current
waveform models should be improved by at least 3 orders of magnitude, which is
consistent with previous works.
| [
{
"created": "Tue, 17 May 2022 15:49:54 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Aug 2022 16:59:19 GMT",
"version": "v2"
},
{
"created": "Wed, 17 Aug 2022 09:25:40 GMT",
"version": "v3"
}
] | 2022-08-22 | [
[
"Hu",
"Qian",
""
],
[
"Veitch",
"John",
""
]
] | With the improvement in sensitivity of gravitational wave (GW) detectors and the increasing diversity of GW sources, there is a strong need for accurate GW waveform models for data analysis. While the current model accuracy assessments require waveforms generated by numerical relativity (NR) simulations as the "true waveforms", in this paper we propose an assessment approach that does not require NR simulations, which enables us to assess model accuracy everywhere in the parameter space. By measuring the difference between two waveform models, we derive a necessary condition for a pair of waveform models to both be accurate, for a particular set of parameters. We then apply this method to the parameter estimation samples of the Gravitational-Wave Transient Catalogs GWTC-3 and GWTC-2.1, and find that the waveform accuracy for high signal-to-noise ratio events in some cases fails our assessment criterion. Based on analysis of real events' posterior samples, we discuss the correlation between our quantified accuracy assessments and systematic errors in parameter estimation. We find waveform models that perform worse in our assessment are more likely to give inconsistent estimations. We also investigate waveform accuracy in different parameter regions, and find the accuracy degrades as the spin effects go up, the mass ratio deviates from one, or the orbital plane is near-aligned to the line of sight. Furthermore, we make predictions of waveform accuracy requirements for future detectors and find the accuracy of current waveform models should be improved by at least 3 orders of magnitude, which is consistent with previous works. |
1408.6316 | Andrei V. Frolov | Andrei V. Frolov and Valeri P. Frolov | Rigidly rotating ZAMO surfaces in the Kerr spacetime | REVTeX 4.0; 11 pages, 9 figures | Phys. Rev. D 90, 124010 (2014) | 10.1103/PhysRevD.90.124010 | Alberta-Thy-15-14, SCG-2014-02 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A stationary observer in the Kerr spacetime has zero angular momentum if
his/her angular velocity $\omega$ has a particular value, which depends on the
position of the observer. Worldlines of such zero angular momentum observers
(ZAMOs) with the same value of the angular velocity $\omega$ form a three
dimensional surface, which has the property that the Killing vectors generating
time translation and rotation are tangent to it. We call such a surface a
rigidly rotating ZAMO surface. This definition allows a natural generalization
to the surfaces inside the black hole, where ZAMO's trajectories formally
become spacelike. A general property of such a surface is that there exist
linear combinations of the Killing vectors with constant coefficients which
make them orthogonal on it. In this paper we discuss properties of the rigidly
rotating ZAMO surfaces both outside and inside the black hole and relevance of
these objects to a couple of interesting physical problems.
| [
{
"created": "Wed, 27 Aug 2014 05:50:26 GMT",
"version": "v1"
}
] | 2014-12-10 | [
[
"Frolov",
"Andrei V.",
""
],
[
"Frolov",
"Valeri P.",
""
]
] | A stationary observer in the Kerr spacetime has zero angular momentum if his/her angular velocity $\omega$ has a particular value, which depends on the position of the observer. Worldlines of such zero angular momentum observers (ZAMOs) with the same value of the angular velocity $\omega$ form a three dimensional surface, which has the property that the Killing vectors generating time translation and rotation are tangent to it. We call such a surface a rigidly rotating ZAMO surface. This definition allows a natural generalization to the surfaces inside the black hole, where ZAMO's trajectories formally become spacelike. A general property of such a surface is that there exist linear combinations of the Killing vectors with constant coefficients which make them orthogonal on it. In this paper we discuss properties of the rigidly rotating ZAMO surfaces both outside and inside the black hole and relevance of these objects to a couple of interesting physical problems. |
1401.6555 | Mariafelicia De Laurentis PhD | Salvatore Capozziello, Diego Julio Cirilo-Lombardo, Mariafelicia De
Laurentis | The Affine Structure of Gravitational Theories: Symplectic Groups and
Geometry | 21 pages. arXiv admin note: text overlap with arXiv:0910.2881,
arXiv:0705.4609 | Int. J. Geom. Methods Mod. Phys. 11, 1450081 (2014) | 10.1142/S0219887814500819 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a geometrical description of gravitational theories from the
viewpoint of symmetries and affine structure. We show how gravity, considered
as a gauge theory, can be consistently achieved by the nonlinear realization of
the conformal-affine group in an indirect manner: due the partial isomorphism
between $CA\left( 3,1\right) $ and the centrally extended $Sp\left( 8\right) $,
we perform a nonlinear realization of the centrally extended (CE)$Sp\left(
8\right) $ in its semi-simple version. In particular, starting from the bundle
structure of gravity, we derive the conformal-affine Lie algebra and then, by
the non-linear realization, we define the coset field transformations, the
Cartan forms and the inverse Higgs constraints. Finally we discuss the
geometrical Lagrangians where all the information on matter fields and their
interactions can be contained.
| [
{
"created": "Sat, 25 Jan 2014 16:20:38 GMT",
"version": "v1"
}
] | 2014-11-13 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Cirilo-Lombardo",
"Diego Julio",
""
],
[
"De Laurentis",
"Mariafelicia",
""
]
] | We give a geometrical description of gravitational theories from the viewpoint of symmetries and affine structure. We show how gravity, considered as a gauge theory, can be consistently achieved by the nonlinear realization of the conformal-affine group in an indirect manner: due the partial isomorphism between $CA\left( 3,1\right) $ and the centrally extended $Sp\left( 8\right) $, we perform a nonlinear realization of the centrally extended (CE)$Sp\left( 8\right) $ in its semi-simple version. In particular, starting from the bundle structure of gravity, we derive the conformal-affine Lie algebra and then, by the non-linear realization, we define the coset field transformations, the Cartan forms and the inverse Higgs constraints. Finally we discuss the geometrical Lagrangians where all the information on matter fields and their interactions can be contained. |
2201.05092 | Paolo Cappuccio | Paolo Cappuccio, Ivan di Stefano, Gael Cascioli, Luciano Iess | Comparison of light-time formulations in the post-Newtonian framework
for the BepiColombo MORE experiment | null | null | 10.1088/1361-6382/ac2b0a | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The ESA/JAXA BepiColombo mission, launched on 20 October 2018, is currently
in cruise toward Mercury. The Mercury Orbiter Radio-science Experiment (MORE),
one of the 16 experiments of the mission, will exploit range and range-rate
measurements collected during superior solar conjunctions to better constrain
the post-Newtonian parameter ${\gamma}$. The MORE radio tracking system is
capable of establishing a 5-leg link in X- and Ka-band to obtain 2-way
range-rate measurements with an accuracy of $0.01 mm/s^-1$ @ 60 s sampling time
and 2-way range measurements at centimeter level after a few seconds of
integration time, at almost all solar elongation angles. In this paper, we
investigate if the light-time formulation derived by Moyer, implemented in
JPL's orbit determination code MONTE, is still a valid approximation, in light
of the recent advancements in radiometric measurement performance. Several
formulations of the gravitational time delay, expressed as an expansion in
powers of $GM/c^2r$, are considered in this work. We quantified the
contribution of each term of the light-time expansion for the first superior
solar conjunction experiment of BepiColombo. The maximum 2-way error caused by
Moyer approximation with respect to a complete second order expansion amounts
to 17 mm. This is at the level of accuracy of the novel pseudo-noise (PN)
ranging system at 24 Mcps used by MORE. A complete second order expansion is
then recommended for present and future superior solar conjunction experiments.
The perturbation caused by the planets in the Solar System is considered as
well, resulting in significant effects due to the Jupiter, the Earth and the
Saturn systems. For these bodies the classical Shapiro time delay is
sufficient. The corrections due to the Sun oblateness and angular momentum are
negligible.
| [
{
"created": "Thu, 13 Jan 2022 17:22:06 GMT",
"version": "v1"
}
] | 2022-01-14 | [
[
"Cappuccio",
"Paolo",
""
],
[
"di Stefano",
"Ivan",
""
],
[
"Cascioli",
"Gael",
""
],
[
"Iess",
"Luciano",
""
]
] | The ESA/JAXA BepiColombo mission, launched on 20 October 2018, is currently in cruise toward Mercury. The Mercury Orbiter Radio-science Experiment (MORE), one of the 16 experiments of the mission, will exploit range and range-rate measurements collected during superior solar conjunctions to better constrain the post-Newtonian parameter ${\gamma}$. The MORE radio tracking system is capable of establishing a 5-leg link in X- and Ka-band to obtain 2-way range-rate measurements with an accuracy of $0.01 mm/s^-1$ @ 60 s sampling time and 2-way range measurements at centimeter level after a few seconds of integration time, at almost all solar elongation angles. In this paper, we investigate if the light-time formulation derived by Moyer, implemented in JPL's orbit determination code MONTE, is still a valid approximation, in light of the recent advancements in radiometric measurement performance. Several formulations of the gravitational time delay, expressed as an expansion in powers of $GM/c^2r$, are considered in this work. We quantified the contribution of each term of the light-time expansion for the first superior solar conjunction experiment of BepiColombo. The maximum 2-way error caused by Moyer approximation with respect to a complete second order expansion amounts to 17 mm. This is at the level of accuracy of the novel pseudo-noise (PN) ranging system at 24 Mcps used by MORE. A complete second order expansion is then recommended for present and future superior solar conjunction experiments. The perturbation caused by the planets in the Solar System is considered as well, resulting in significant effects due to the Jupiter, the Earth and the Saturn systems. For these bodies the classical Shapiro time delay is sufficient. The corrections due to the Sun oblateness and angular momentum are negligible. |
0908.0784 | Lars Andersson | Lars Andersson and Vincent Moncrief | Einstein spaces as attractors for the Einstein flow | 50 pages | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we prove a global existence theorem, in the direction of
cosmological expansion, for sufficiently small perturbations of a family of
$n+1$-dimensional, $n \geq 3$, spatially compact spacetimes which generalizes
the $k=-1$ Friedmann--Robertson--Walker vacuum spacetime.
Our results demonstrate causal geodesic completeness of the perturbed
spacetimes, in the expanding direction, and show that the scale-free geometry
converges towards an element in the moduli space of Einstein geometries, with a
rate of decay depending on the stability properties of the Einstein geometry.
| [
{
"created": "Thu, 6 Aug 2009 17:23:17 GMT",
"version": "v1"
}
] | 2009-08-20 | [
[
"Andersson",
"Lars",
""
],
[
"Moncrief",
"Vincent",
""
]
] | In this paper we prove a global existence theorem, in the direction of cosmological expansion, for sufficiently small perturbations of a family of $n+1$-dimensional, $n \geq 3$, spatially compact spacetimes which generalizes the $k=-1$ Friedmann--Robertson--Walker vacuum spacetime. Our results demonstrate causal geodesic completeness of the perturbed spacetimes, in the expanding direction, and show that the scale-free geometry converges towards an element in the moduli space of Einstein geometries, with a rate of decay depending on the stability properties of the Einstein geometry. |
gr-qc/0505129 | Kazuyasu Shigemoto | M.Kenmoku, K.K.Nandi and K.Shigemoto | Solution Independent Analysis of Black Hole Entropy in Brick Wall Model | 19 pages | Class.Quant.Grav.22:3923-3934,2005 | 10.1088/0264-9381/22/19/008 | null | gr-qc | null | Using the brick wall regularization of 't Hooft, the entropy of non-extreme
and extreme black holes is investigated in a general static, spherically
symmetric spacetime. We classify the singularity in the entropy by introducing
a {\it new} index $\delta $ with respect to the brick wall cut-off $\epsilon $.
The leading contribution to entropy for non-extreme case $(\delta \neq 0)$ is
shown to satisfy the area law with quadratic divergence with respect to the
invariant cut-off $\epsilon_{{\rm inv}}$ while the extreme case $(\delta =0)$
exhibits logarithmic divergence or constant value with respect to $\epsilon $.
The general formula is applied to Reissner-Nordstr\"{o}m, dilaton and
brane-world black holes and we obtain consistent results.
| [
{
"created": "Thu, 26 May 2005 05:51:30 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Jun 2007 04:30:53 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Kenmoku",
"M.",
""
],
[
"Nandi",
"K. K.",
""
],
[
"Shigemoto",
"K.",
""
]
] | Using the brick wall regularization of 't Hooft, the entropy of non-extreme and extreme black holes is investigated in a general static, spherically symmetric spacetime. We classify the singularity in the entropy by introducing a {\it new} index $\delta $ with respect to the brick wall cut-off $\epsilon $. The leading contribution to entropy for non-extreme case $(\delta \neq 0)$ is shown to satisfy the area law with quadratic divergence with respect to the invariant cut-off $\epsilon_{{\rm inv}}$ while the extreme case $(\delta =0)$ exhibits logarithmic divergence or constant value with respect to $\epsilon $. The general formula is applied to Reissner-Nordstr\"{o}m, dilaton and brane-world black holes and we obtain consistent results. |
0707.3919 | Tomas Janssen | Tomas Janssen and Tomislav Prokopec | A graviton propagator for inflation | 23 pages | Class.Quant.Grav.25:055007,2008 | 10.1088/0264-9381/25/5/055007 | ITP-UU-07/37, SPIN-07/25 | gr-qc | null | We construct the scalar and graviton propagator in quasi de Sitter space up
to first order in the slow roll parameter $\epsilon\equiv -\dot{H}/H^2$. After
a rescaling, the propagators are similar to those in de Sitter space with an
$\epsilon$ correction to the effective mass. The limit $\epsilon\to 0$
corresponds to the E(3) vacuum that breaks de Sitter symmetry, but does not
break spatial isotropy and homogeneity. The new propagators allow for a
self-consistent, dynamical study of quantum back-reaction effects during
inflation.
| [
{
"created": "Thu, 26 Jul 2007 14:52:36 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Janssen",
"Tomas",
""
],
[
"Prokopec",
"Tomislav",
""
]
] | We construct the scalar and graviton propagator in quasi de Sitter space up to first order in the slow roll parameter $\epsilon\equiv -\dot{H}/H^2$. After a rescaling, the propagators are similar to those in de Sitter space with an $\epsilon$ correction to the effective mass. The limit $\epsilon\to 0$ corresponds to the E(3) vacuum that breaks de Sitter symmetry, but does not break spatial isotropy and homogeneity. The new propagators allow for a self-consistent, dynamical study of quantum back-reaction effects during inflation. |
gr-qc/9706002 | Rafael D. Sorkin | Rafael D. Sorkin (ICN-UNAM and Syracuse University) | Forks in the Road, on the Way to Quantum Gravity | 29 pages, plainTeX, no figures | Int.J.Theor.Phys.36:2759-2781,1997 | 10.1007/BF02435709 | SU-GP-93-12-2 | gr-qc hep-th quant-ph | null | In seeking to arrive at a theory of ``quantum gravity'', one faces several
choices among alternative approaches. I list some of these ``forks in the
road'' and offer reasons for taking one alternative over the other. In
particular, I advocate the following: the sum-over-histories framework for
quantum dynamics over the ``observable and state-vector'' framework; relative
probabilities over absolute ones; spacetime over space as the gravitational
``substance'' (4 over 3+1); a Lorentzian metric over a Riemannian
(``Euclidean'') one; a dynamical topology over an absolute one; degenerate
metrics over closed timelike curves to mediate topology-change; ``unimodular
gravity'' over the unrestricted functional integral; and taking a discrete
underlying structure (the causal set) rather than the differentiable manifold
as the basis of the theory.
In connection with these choices, I also mention some results from unimodular
quantum cosmology, sketch an account of the origin of black hole entropy,
summarize an argument that the quantum mechanical measurement scheme breaks
down for quantum field theory, and offer a reason why the cosmological constant
of the present epoch might have a magnitude of around $10^{-120}$ in natural
units.
| [
{
"created": "Sun, 1 Jun 1997 13:55:19 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Sorkin",
"Rafael D.",
"",
"ICN-UNAM and Syracuse University"
]
] | In seeking to arrive at a theory of ``quantum gravity'', one faces several choices among alternative approaches. I list some of these ``forks in the road'' and offer reasons for taking one alternative over the other. In particular, I advocate the following: the sum-over-histories framework for quantum dynamics over the ``observable and state-vector'' framework; relative probabilities over absolute ones; spacetime over space as the gravitational ``substance'' (4 over 3+1); a Lorentzian metric over a Riemannian (``Euclidean'') one; a dynamical topology over an absolute one; degenerate metrics over closed timelike curves to mediate topology-change; ``unimodular gravity'' over the unrestricted functional integral; and taking a discrete underlying structure (the causal set) rather than the differentiable manifold as the basis of the theory. In connection with these choices, I also mention some results from unimodular quantum cosmology, sketch an account of the origin of black hole entropy, summarize an argument that the quantum mechanical measurement scheme breaks down for quantum field theory, and offer a reason why the cosmological constant of the present epoch might have a magnitude of around $10^{-120}$ in natural units. |
2303.05366 | M Blagojevi\'c | Friedrich W. Hehl | Four Lectures on Poincar\'e Gauge Field Theory | Latex, 3 figures, 51 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Poincar\'e (inhomogeneous Lorentz) group underlies special relativity. In
these lectures a consistent formalism is developed allowing an appropriate
gauging of the Poincar\'e group. The physical laws are formulated in terms of
points, orthonormal tetrad frames, and components of the matter fields with
respect to these frames. The laws are postulated to be gauge invariant under
local Poincar\'e transformations. This implies the existence of 4 translational
gauge potentials ${e}^\alpha$ (``gravitons") and 6 Lorentz gauge potentials
${\Gamma}^{\alpha\beta}$ (``rotons") and the coupling of the momentum current
and the spin current of matter to these potentials, respectively. In this way
one is led to a Riemann-Cartan spacetime carrying torsion and curvature, richer
in structure than the spacetime of general relativity. The Riemann-Cartan
spacetime is controlled by the two general gauge field equations (3.44) and
(3.45), in which material momentum and spin act as sources. The general
framework of the theory is summarized in a table in Section 3.6. -- Options for
picking a gauge field lagrangian are discussed (teleparallelism, ECSK). We
propose a lagrangian quadratic in torsion and curvature governing the
propagation of gravitons and rotons. A suppression of the rotons leads back to
general relativity.
| [
{
"created": "Thu, 9 Mar 2023 16:13:03 GMT",
"version": "v1"
}
] | 2023-03-10 | [
[
"Hehl",
"Friedrich W.",
""
]
] | The Poincar\'e (inhomogeneous Lorentz) group underlies special relativity. In these lectures a consistent formalism is developed allowing an appropriate gauging of the Poincar\'e group. The physical laws are formulated in terms of points, orthonormal tetrad frames, and components of the matter fields with respect to these frames. The laws are postulated to be gauge invariant under local Poincar\'e transformations. This implies the existence of 4 translational gauge potentials ${e}^\alpha$ (``gravitons") and 6 Lorentz gauge potentials ${\Gamma}^{\alpha\beta}$ (``rotons") and the coupling of the momentum current and the spin current of matter to these potentials, respectively. In this way one is led to a Riemann-Cartan spacetime carrying torsion and curvature, richer in structure than the spacetime of general relativity. The Riemann-Cartan spacetime is controlled by the two general gauge field equations (3.44) and (3.45), in which material momentum and spin act as sources. The general framework of the theory is summarized in a table in Section 3.6. -- Options for picking a gauge field lagrangian are discussed (teleparallelism, ECSK). We propose a lagrangian quadratic in torsion and curvature governing the propagation of gravitons and rotons. A suppression of the rotons leads back to general relativity. |
1811.11021 | Francisco Jos\'e Maldonado Torralba | \'Alvaro de la Cruz-Dombriz, Francisco J. Maldonado Torralba | Birkhoff's theorem for stable torsion theories | 39 pages, 5 figures, minor corrections, conclusions unchanged. It
matches the version published in JCAP | JCAP 1903 (2019) 002 | 10.1088/1475-7516/2019/03/002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a novel approach to establish the Birkhoff's theorem validity in
the so-called quadratic Poincar\'e Gauge theories of gravity. By obtaining the
field equations via the Palatini formalism, we find paradigmatic scenarios
where the theorem applies neatly. For more general and physically relevant
situations, a suitable decomposition of the torsion tensor also allows us to
establish the validity of the theorem. Our analysis shows rigorously how for
all stable cases under consideration, the only solution of the vacuum field
equations is a torsionless Schwarzschild spacetime, although it is possible to
find non-Schwarzschild metrics in the realm of unstable Lagrangians. Finally,
we study the weakened formulation of the Birkhoff's theorem where an
asymptotically flat metric is assumed, showing that the theorem also holds.
| [
{
"created": "Tue, 27 Nov 2018 14:28:39 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Mar 2019 15:28:01 GMT",
"version": "v2"
}
] | 2019-03-05 | [
[
"de la Cruz-Dombriz",
"Álvaro",
""
],
[
"Torralba",
"Francisco J. Maldonado",
""
]
] | We present a novel approach to establish the Birkhoff's theorem validity in the so-called quadratic Poincar\'e Gauge theories of gravity. By obtaining the field equations via the Palatini formalism, we find paradigmatic scenarios where the theorem applies neatly. For more general and physically relevant situations, a suitable decomposition of the torsion tensor also allows us to establish the validity of the theorem. Our analysis shows rigorously how for all stable cases under consideration, the only solution of the vacuum field equations is a torsionless Schwarzschild spacetime, although it is possible to find non-Schwarzschild metrics in the realm of unstable Lagrangians. Finally, we study the weakened formulation of the Birkhoff's theorem where an asymptotically flat metric is assumed, showing that the theorem also holds. |
gr-qc/0410079 | Carles Bona | C. Bona, T. Ledvinka, C. Palenzuela-Luque, J.A. Pons and M. Zajeck | Gauge pathologies in singularity-avoidant spacetime foliations | 8 pages, 9 figures | null | null | null | gr-qc | null | The family of generalized-harmonic gauge conditions, which is currently used
in Numerical Relativity for its singularity-avoidant behavior, is analyzed by
looking for pathologies of the corresponding spacetime foliation. The
appearance of genuine shocks, arising from the crossing of characteristic
lines, is completely discarded. Runaway solutions, meaning that the lapse
function can grow without bound at an accelerated rate, are instead predicted.
Black Hole simulations are presented, showing spurious oscillations due to the
well known slice stretching phenomenon. These oscillations are made to
disappear by switching the numerical algorithm to a high-resolution
shock-capturing one, of the kind currently used in Computational Fluid
Dynamics. Even with these shock-capturing algorithms, runaway solutions are
seen to appear and the resulting lapse blow-up is causing the simulations to
crash. As a side result, a new method is proposed for obtaining regular initial
data for Black Hole spacetimes, even inside the horizons.
| [
{
"created": "Mon, 18 Oct 2004 09:15:32 GMT",
"version": "v1"
}
] | 2009-09-29 | [
[
"Bona",
"C.",
""
],
[
"Ledvinka",
"T.",
""
],
[
"Palenzuela-Luque",
"C.",
""
],
[
"Pons",
"J. A.",
""
],
[
"Zajeck",
"M.",
""
]
] | The family of generalized-harmonic gauge conditions, which is currently used in Numerical Relativity for its singularity-avoidant behavior, is analyzed by looking for pathologies of the corresponding spacetime foliation. The appearance of genuine shocks, arising from the crossing of characteristic lines, is completely discarded. Runaway solutions, meaning that the lapse function can grow without bound at an accelerated rate, are instead predicted. Black Hole simulations are presented, showing spurious oscillations due to the well known slice stretching phenomenon. These oscillations are made to disappear by switching the numerical algorithm to a high-resolution shock-capturing one, of the kind currently used in Computational Fluid Dynamics. Even with these shock-capturing algorithms, runaway solutions are seen to appear and the resulting lapse blow-up is causing the simulations to crash. As a side result, a new method is proposed for obtaining regular initial data for Black Hole spacetimes, even inside the horizons. |
2303.02726 | Heling Deng | Heling Deng, Andrei Gruzinov, Yuri Levin and Alexander Vilenkin | Simulating cosmic string loop captured by a rotating black hole | 28 pages, 10 figures | null | 10.1103/PhysRevD.107.123016 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the dynamics of a cosmic string loop captured by a rotating black
hole, ignoring string reconnections. A loop is numerically evolved in Kerr
spacetime, with the result that it turns into one or more growing or
contracting double-lines rotating around the black hole in the equatorial
plane. This is in good agreement with the approximate analytical treatment of
the problem investigated by Xing et al., who studied the evolution of the
auxiliary curve associated with the string loop. We confirm that the auxiliary
curve deformation can indeed describe the string motion in realistic physical
scenarios to a reasonable accuracy, and can thus be used to further study other
phenomena such as superradiance and reconnections of the captured loop.
| [
{
"created": "Sun, 5 Mar 2023 17:46:47 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Apr 2023 21:03:12 GMT",
"version": "v2"
}
] | 2023-06-28 | [
[
"Deng",
"Heling",
""
],
[
"Gruzinov",
"Andrei",
""
],
[
"Levin",
"Yuri",
""
],
[
"Vilenkin",
"Alexander",
""
]
] | We study the dynamics of a cosmic string loop captured by a rotating black hole, ignoring string reconnections. A loop is numerically evolved in Kerr spacetime, with the result that it turns into one or more growing or contracting double-lines rotating around the black hole in the equatorial plane. This is in good agreement with the approximate analytical treatment of the problem investigated by Xing et al., who studied the evolution of the auxiliary curve associated with the string loop. We confirm that the auxiliary curve deformation can indeed describe the string motion in realistic physical scenarios to a reasonable accuracy, and can thus be used to further study other phenomena such as superradiance and reconnections of the captured loop. |
0811.4235 | David P. Rideout | Song He and David Rideout | A Causal Set Black Hole | 22 pages, 9 figures, LaTeX; response to referee comments | Class.Quant.Grav. 26:125015, 2009. | 10.1088/0264-9381/26/12/125015 | pi-qg-105 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explicitly compute the causal structure of the Schwarzschild black hole
spacetime, by providing an algorithm to decide if any pair of events is
causally related. The primary motivation for this study comes from discrete
quantum gravity, in particular the causal set approach, in which the
fundamental variables can be thought of as the causal ordering of randomly
selected events in spacetime. This work opens the way to simulating
non-conformally flat spacetimes within the causal set approach, which may allow
one to study important questions such as black hole entropy and Hawking
radiation on a full four dimensional causal set black hole.
| [
{
"created": "Wed, 26 Nov 2008 07:11:12 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Apr 2009 20:48:34 GMT",
"version": "v2"
}
] | 2015-05-13 | [
[
"He",
"Song",
""
],
[
"Rideout",
"David",
""
]
] | We explicitly compute the causal structure of the Schwarzschild black hole spacetime, by providing an algorithm to decide if any pair of events is causally related. The primary motivation for this study comes from discrete quantum gravity, in particular the causal set approach, in which the fundamental variables can be thought of as the causal ordering of randomly selected events in spacetime. This work opens the way to simulating non-conformally flat spacetimes within the causal set approach, which may allow one to study important questions such as black hole entropy and Hawking radiation on a full four dimensional causal set black hole. |
1410.4481 | Emanuele Berti | Emanuele Berti | A Black-Hole Primer: Particles, Waves, Critical Phenomena and
Superradiant Instabilities | 46 pages, 10 figures. Fixed some typos and references. The other
lectures delivered at the school can be found at
http://www.dpg-physik.de/dpg/pbh/aktuelles/S214.html | null | null | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | These notes were prepared for a lecture on black holes delivered at the DPG
Physics School "General Relativity @ 99" (Physikzentrum Bad Honnef, Germany,
September 2014). The common thread of the lecture is the relation between
geodesic stability and black-hole perturbations in the geometric optics limit.
Chapter 1 establishes notation and discusses a common misconception on
Michell's "Newtonian black holes". Chapters 2 and 3 deal with particle dynamics
and wave dynamics in black-hole spacetimes, respectively. All calculations
should be simple enough that they can be done with pen and paper. Chapter 4
builds on this introduction to discuss two exciting topics in current research:
critical phenomena in black-hole mergers and the black-hole bomb instability.
| [
{
"created": "Thu, 16 Oct 2014 16:08:55 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Oct 2014 00:39:28 GMT",
"version": "v2"
}
] | 2014-10-23 | [
[
"Berti",
"Emanuele",
""
]
] | These notes were prepared for a lecture on black holes delivered at the DPG Physics School "General Relativity @ 99" (Physikzentrum Bad Honnef, Germany, September 2014). The common thread of the lecture is the relation between geodesic stability and black-hole perturbations in the geometric optics limit. Chapter 1 establishes notation and discusses a common misconception on Michell's "Newtonian black holes". Chapters 2 and 3 deal with particle dynamics and wave dynamics in black-hole spacetimes, respectively. All calculations should be simple enough that they can be done with pen and paper. Chapter 4 builds on this introduction to discuss two exciting topics in current research: critical phenomena in black-hole mergers and the black-hole bomb instability. |
1601.04177 | Andrea Geralico | Donato Bini, Giampiero Esposito, Andrea Geralico | Late-time evolution of cosmological models with fluids obeying a
Shan-Chen-like equation of state | 18 pages, 6 figures, revtex4 macros; to appear in PRD | null | 10.1103/PhysRevD.93.023511 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Classical as well as quantum features of the late-time evolution of
cosmological models with fluids obeying a Shan-Chen-like equation of state are
studied. The latter is of the type $p=w_{\rm eff}(\rho)\,\rho$, and has been
used in previous works to describe, e.g., a possible scenario for the growth of
the dark-energy content of the present Universe. At the classical level the
fluid dynamics in a spatially flat Friedmann-Robertson-Walker background
implies the existence of two possible equilibrium solutions depending on the
model parameters, associated with (asymptotic) finite pressure and energy
density. We show that no future cosmological singularity is developed during
the evolution for this specific model. The corresponding quantum effects in the
late-time behavior of the system are also investigated within the framework of
quantum geometrodynamics, i.e., by solving the (minisuperspace) Wheeler-DeWitt
equation in the Born-Oppenheimer approximation, constructing wave-packets and
analyzing their behavior.
| [
{
"created": "Sat, 16 Jan 2016 16:03:11 GMT",
"version": "v1"
}
] | 2016-02-17 | [
[
"Bini",
"Donato",
""
],
[
"Esposito",
"Giampiero",
""
],
[
"Geralico",
"Andrea",
""
]
] | Classical as well as quantum features of the late-time evolution of cosmological models with fluids obeying a Shan-Chen-like equation of state are studied. The latter is of the type $p=w_{\rm eff}(\rho)\,\rho$, and has been used in previous works to describe, e.g., a possible scenario for the growth of the dark-energy content of the present Universe. At the classical level the fluid dynamics in a spatially flat Friedmann-Robertson-Walker background implies the existence of two possible equilibrium solutions depending on the model parameters, associated with (asymptotic) finite pressure and energy density. We show that no future cosmological singularity is developed during the evolution for this specific model. The corresponding quantum effects in the late-time behavior of the system are also investigated within the framework of quantum geometrodynamics, i.e., by solving the (minisuperspace) Wheeler-DeWitt equation in the Born-Oppenheimer approximation, constructing wave-packets and analyzing their behavior. |
1510.03693 | Valery Kiselev | Ja.V.Balitsky, V.V.Kiselev | Global shift symmetry and vacuum energy of matter fields | 8 pages, 1 figure, revtex4 | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct the model incorporating both an arbitrary shift of cosmological
constant and Goldstone boson corresponding to the spontaneous breaking down the
global shift symmetry in the matter action. The gravity breaks down the
symmetry explicitly and transforms the Goldstone boson to the inflaton field.
| [
{
"created": "Thu, 8 Oct 2015 08:17:26 GMT",
"version": "v1"
}
] | 2015-10-14 | [
[
"Balitsky",
"Ja. V.",
""
],
[
"Kiselev",
"V. V.",
""
]
] | We construct the model incorporating both an arbitrary shift of cosmological constant and Goldstone boson corresponding to the spontaneous breaking down the global shift symmetry in the matter action. The gravity breaks down the symmetry explicitly and transforms the Goldstone boson to the inflaton field. |
1407.7896 | Alessio Belenchia | Alessio Belenchia, Stefano Liberati, Arif Mohd | Emergent gravitational dynamics in relativistic Bose--Einstein
condensate | 23 pages, no figures, new references added and minor modifications on
the anonymous referee's feedback, this version accepted for publication in
Phys. Rev. D | Phys.Rev. D90 (2014) no.10, 104015 | 10.1103/PhysRevD.90.104015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Analogue models of gravity have played a pivotal role in the past years by
providing a test bench for many open issues in quantum field theory in curved
spacetime such as the robustness of Hawking radiation and cosmological particle
production. More recently, the same models have offered a valuable framework
within which current ideas about the emergence of spacetime and its dynamics
could be discussed via convenient toy models. In this context, we study here an
analogue gravity system based on a relativistic Bose--Einstein condensate. We
show that in a suitable limit this system provides not only an example of an
emergent spacetime (with a massive and a massless relativistic fields
propagating on it) but also that such spacetime is governed by an equation with
geometric meaning that takes the familiar form of Nordstr{\"o}m theory of
gravitation. In this equation the gravitational field is sourced by the
expectation value of the trace of the effective stress energy tensor of the
quasiparticles while the Newton and cosmological constants are functions of the
fundamental scales of the microscopic system. This is the first example of
analogue gravity in which a Lorentz invariant, geometric theory of
semiclassical gravity emerges from an underlying quantum theory of matter in
flat spacetime.
| [
{
"created": "Tue, 29 Jul 2014 21:45:20 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Oct 2014 09:51:46 GMT",
"version": "v2"
}
] | 2018-07-19 | [
[
"Belenchia",
"Alessio",
""
],
[
"Liberati",
"Stefano",
""
],
[
"Mohd",
"Arif",
""
]
] | Analogue models of gravity have played a pivotal role in the past years by providing a test bench for many open issues in quantum field theory in curved spacetime such as the robustness of Hawking radiation and cosmological particle production. More recently, the same models have offered a valuable framework within which current ideas about the emergence of spacetime and its dynamics could be discussed via convenient toy models. In this context, we study here an analogue gravity system based on a relativistic Bose--Einstein condensate. We show that in a suitable limit this system provides not only an example of an emergent spacetime (with a massive and a massless relativistic fields propagating on it) but also that such spacetime is governed by an equation with geometric meaning that takes the familiar form of Nordstr{\"o}m theory of gravitation. In this equation the gravitational field is sourced by the expectation value of the trace of the effective stress energy tensor of the quasiparticles while the Newton and cosmological constants are functions of the fundamental scales of the microscopic system. This is the first example of analogue gravity in which a Lorentz invariant, geometric theory of semiclassical gravity emerges from an underlying quantum theory of matter in flat spacetime. |
2205.11445 | Fotios Anagnostopoulos | Fotios K. Anagnostopoulos, Viktor Gakis, Emmanuel N. Saridakis, Spyros
Basilakos | New models and Big Bang Nucleosynthesis constraints in $f(Q)$ gravity | 10 pages, 2 figures. To be submitted at PRD. Comments are welcome | null | 10.1140/epjc/s10052-023-11190-x | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by-sa/4.0/ | The $f(Q)$ theories of modified gravity arise from the consideration of
non-metricity as the basic geometric quantity, and have been proven to be very
efficient in describing the late-time Universe. We use the Big Bang
Nucleosynthesis (BBN) formalism and observations in order to extract
constraints on various classes of f(Q) models. In particular, we calculate the
deviations that f(Q) terms bring on the freeze-out temperature in comparison to
that of the standard $\Lambda CDM$ evolution, and then we impose the
observational bound on $ |\frac{\delta {T}_f}{{T}_f}|$ to extract constraints
on the involved parameters of the considered models. Concerning the polynomial
model, we show that the exponent parameter should be negative, while for the
power-exponential model and the new hyperbolic tangent - power model we find
that they pass the BBN constraints trivially. Finally, we examine two DGP-like
$f(Q)$ models, and we extract the bounds on their model parameters. Since many
gravitational modifications, although able to describe the late-time evolution
of the Universe, produce too-much modification at early times and thus fall to
pass the BBN confrontation, the fact that $f(Q)$ gravity can safely pass the
BBN constraints is an important advantage of this modified gravity class.
| [
{
"created": "Mon, 23 May 2022 16:35:44 GMT",
"version": "v1"
}
] | 2023-02-08 | [
[
"Anagnostopoulos",
"Fotios K.",
""
],
[
"Gakis",
"Viktor",
""
],
[
"Saridakis",
"Emmanuel N.",
""
],
[
"Basilakos",
"Spyros",
""
]
] | The $f(Q)$ theories of modified gravity arise from the consideration of non-metricity as the basic geometric quantity, and have been proven to be very efficient in describing the late-time Universe. We use the Big Bang Nucleosynthesis (BBN) formalism and observations in order to extract constraints on various classes of f(Q) models. In particular, we calculate the deviations that f(Q) terms bring on the freeze-out temperature in comparison to that of the standard $\Lambda CDM$ evolution, and then we impose the observational bound on $ |\frac{\delta {T}_f}{{T}_f}|$ to extract constraints on the involved parameters of the considered models. Concerning the polynomial model, we show that the exponent parameter should be negative, while for the power-exponential model and the new hyperbolic tangent - power model we find that they pass the BBN constraints trivially. Finally, we examine two DGP-like $f(Q)$ models, and we extract the bounds on their model parameters. Since many gravitational modifications, although able to describe the late-time evolution of the Universe, produce too-much modification at early times and thus fall to pass the BBN confrontation, the fact that $f(Q)$ gravity can safely pass the BBN constraints is an important advantage of this modified gravity class. |
2203.01725 | Nicholas Loutrel | Nicholas Loutrel, Richard Brito, Andrea Maselli, Paolo Pani | Inspiralling compact objects with generic deformations | 21 pages, 4 figures, journal version | Phys. Rev. D 105, 12, 124050 (2022) | 10.1103/PhysRevD.105.124050 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Self-gravitating bodies can have an arbitrarily complex shape, which implies
a much richer multipolar structure than that of a black hole in General
Relativity. With this motivation, we study the corrections to the dynamics of a
binary system due to generic, nonaxisymmetric mass quadrupole moments to
leading post-Newtonian (PN) order. Utilizing the method of osculating orbits
and a multiple scale analysis, we find analytic solutions to the precession and
orbital dynamics of a (generically eccentric) binary in terms of the
dimensionless modulus parameters $\epsilon_{m}$, corresponding to axial $m=1$
and polar $m=2$ corrections from oblateness/prolateness. The solutions to the
precession dynamics are exact for $0 \le \epsilon_{2} < 1$, and perturbative in
$\epsilon_{1} \ll 1$. We further compute the leading order corrections to the
gravitational wave amplitude and phase for a quasi-circular binary due to mass
quadrupole effects. Making use of the stationary phase approximation and
shifted uniform asymptotics (SUA), the corrections to the phase enter at
relative 2PN order, while the amplitude modulations enter at -0.5PN order with
a SUA amplitude correction at 3.25PN order, relative 2PN order to the leading
order SUA correction. By investigating the dephasing due to generic quadrupole
moments, we find that a phase difference $\gtrsim 0.1$~radians is achievable
for $\epsilon_{m} \gtrsim 10^{-3}$, which suggests that constraints with
current and future ground-based gravitational wave detectors are possible. Our
results can be implemented in parameter estimation studies to constrain generic
multipolar deformations of the Kerr geometry and of neutron stars.
| [
{
"created": "Thu, 3 Mar 2022 14:15:27 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Jun 2022 10:22:12 GMT",
"version": "v2"
}
] | 2022-06-28 | [
[
"Loutrel",
"Nicholas",
""
],
[
"Brito",
"Richard",
""
],
[
"Maselli",
"Andrea",
""
],
[
"Pani",
"Paolo",
""
]
] | Self-gravitating bodies can have an arbitrarily complex shape, which implies a much richer multipolar structure than that of a black hole in General Relativity. With this motivation, we study the corrections to the dynamics of a binary system due to generic, nonaxisymmetric mass quadrupole moments to leading post-Newtonian (PN) order. Utilizing the method of osculating orbits and a multiple scale analysis, we find analytic solutions to the precession and orbital dynamics of a (generically eccentric) binary in terms of the dimensionless modulus parameters $\epsilon_{m}$, corresponding to axial $m=1$ and polar $m=2$ corrections from oblateness/prolateness. The solutions to the precession dynamics are exact for $0 \le \epsilon_{2} < 1$, and perturbative in $\epsilon_{1} \ll 1$. We further compute the leading order corrections to the gravitational wave amplitude and phase for a quasi-circular binary due to mass quadrupole effects. Making use of the stationary phase approximation and shifted uniform asymptotics (SUA), the corrections to the phase enter at relative 2PN order, while the amplitude modulations enter at -0.5PN order with a SUA amplitude correction at 3.25PN order, relative 2PN order to the leading order SUA correction. By investigating the dephasing due to generic quadrupole moments, we find that a phase difference $\gtrsim 0.1$~radians is achievable for $\epsilon_{m} \gtrsim 10^{-3}$, which suggests that constraints with current and future ground-based gravitational wave detectors are possible. Our results can be implemented in parameter estimation studies to constrain generic multipolar deformations of the Kerr geometry and of neutron stars. |
2006.00685 | Qing-Hua Zhu | Zhe Chang and Qing-Hua Zhu | Does the shape of the shadow of a black hole depend on motional status
of an observer? | 20 pages, 10 figures; v2: published in PRD | Phys. Rev. D 102, 044012 (2020) | 10.1103/PhysRevD.102.044012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent work on rotating black hole shadows [Phys. Rev. D{\bf 101},
084029 (2020)], we proposed a new approach for calculating size and shape of
the shadows in terms of astrometrical observables with respect to
finite-distance observers. In this paper, we introduce a distortion parameter
for the shadow shapes and discuss the appearance of the shadows of static
spherical black holes and Kerr black holes in a uniform framework. We show that
the shape of the shadow of a spherical black hole is circular in the view of
arbitrary observers, and the size of the shadows tends to be shrunk in the view
of a moving observer. The diameter of the shadows is contracted even in the
direction perpendicular to the observers' motion. This seems not to be
understood as length contraction effect in special relativity. The shape of
Kerr black holes is dependent on motional status of observers located at finite
distance. In spite of this, it is found that there is not a surrounding
observer who could view the shape of the Kerr black hole shadows as
circularity. These results could be helpful for observation of the Sagittarius
A* in the centre of the Milky Way, as our solar system is moving around the
centre black hole.
| [
{
"created": "Mon, 1 Jun 2020 03:16:46 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Aug 2020 06:31:23 GMT",
"version": "v2"
}
] | 2020-08-11 | [
[
"Chang",
"Zhe",
""
],
[
"Zhu",
"Qing-Hua",
""
]
] | In a recent work on rotating black hole shadows [Phys. Rev. D{\bf 101}, 084029 (2020)], we proposed a new approach for calculating size and shape of the shadows in terms of astrometrical observables with respect to finite-distance observers. In this paper, we introduce a distortion parameter for the shadow shapes and discuss the appearance of the shadows of static spherical black holes and Kerr black holes in a uniform framework. We show that the shape of the shadow of a spherical black hole is circular in the view of arbitrary observers, and the size of the shadows tends to be shrunk in the view of a moving observer. The diameter of the shadows is contracted even in the direction perpendicular to the observers' motion. This seems not to be understood as length contraction effect in special relativity. The shape of Kerr black holes is dependent on motional status of observers located at finite distance. In spite of this, it is found that there is not a surrounding observer who could view the shape of the Kerr black hole shadows as circularity. These results could be helpful for observation of the Sagittarius A* in the centre of the Milky Way, as our solar system is moving around the centre black hole. |
gr-qc/9912068 | Michael Bachmann | Michael Bachmann and Hans-Jurgen Schmidt | Period-doubling bifurcation in strongly anisotropic Bianchi I quantum
cosmology | Latest update of the paper at
http://www.physik.fu-berlin.de/~mbach/publics.html#6 | Phys.Rev. D62 (2000) 043515 | 10.1103/PhysRevD.62.043515 | null | gr-qc | null | We solve the Wheeler-DeWitt equation for the minisuperspace of a cosmological
model of Bianchi type I with a minimally coupled massive scalar field $\phi$ as
source by generalizing the calculation of Lukash and Schmidt [1]. Contrarily to
other approaches we allow strong anisotropy. Combining analytical and numerical
methods, we apply an adiabatic approximation for $\phi$, and as new feature we
find a period-doubling bifurcation. This bifurcation takes place near the
cosmological quantum boundary, i.e., the boundary of the quasiclassical region
with oscillating $\psi$-function where the WKB-approximation is good. The
numerical calculations suggest that such a notion of a ``cosmological quantum
boundary'' is well-defined, because sharply beyond that boundary, the
WKB-approximation is no more applicable at all. This result confirms the
adequateness of the introduction of a cosmological quantum boundary in quantum
cosmology.
| [
{
"created": "Thu, 16 Dec 1999 11:31:16 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Bachmann",
"Michael",
""
],
[
"Schmidt",
"Hans-Jurgen",
""
]
] | We solve the Wheeler-DeWitt equation for the minisuperspace of a cosmological model of Bianchi type I with a minimally coupled massive scalar field $\phi$ as source by generalizing the calculation of Lukash and Schmidt [1]. Contrarily to other approaches we allow strong anisotropy. Combining analytical and numerical methods, we apply an adiabatic approximation for $\phi$, and as new feature we find a period-doubling bifurcation. This bifurcation takes place near the cosmological quantum boundary, i.e., the boundary of the quasiclassical region with oscillating $\psi$-function where the WKB-approximation is good. The numerical calculations suggest that such a notion of a ``cosmological quantum boundary'' is well-defined, because sharply beyond that boundary, the WKB-approximation is no more applicable at all. This result confirms the adequateness of the introduction of a cosmological quantum boundary in quantum cosmology. |
1210.3004 | Yuri Bonder | Mario A. Acero and Yuri Bonder | Phenomenology of Quantum Gravity and its Possible Role in Neutrino
Anomalies | For the proceedings of "Relativity and Gravitation: 100 Years after
Einstein in Prague" (June 2012, Prague) | null | null | IUHET 570 | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | New phenomenological models of Quantum Gravity have suggested that a
Lorentz-Invariant discrete spacetime structure may become manifest through a
nonstandard coupling of matter fields and spacetime curvature. On the other
hand, there is strong experimental evidence suggesting that neutrino
oscillations cannot be described by simply considering neutrinos as massive
particles. In this manuscript we motivate and construct one particular
phenomenological model of Quantum Gravity that could account for the so-called
neutrino anomalies.
| [
{
"created": "Wed, 10 Oct 2012 18:54:26 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Feb 2013 17:59:56 GMT",
"version": "v2"
}
] | 2013-02-13 | [
[
"Acero",
"Mario A.",
""
],
[
"Bonder",
"Yuri",
""
]
] | New phenomenological models of Quantum Gravity have suggested that a Lorentz-Invariant discrete spacetime structure may become manifest through a nonstandard coupling of matter fields and spacetime curvature. On the other hand, there is strong experimental evidence suggesting that neutrino oscillations cannot be described by simply considering neutrinos as massive particles. In this manuscript we motivate and construct one particular phenomenological model of Quantum Gravity that could account for the so-called neutrino anomalies. |
gr-qc/0210025 | Mihalis Dafermos | Mihalis Dafermos | On "time-periodic" black-hole solutions to certain spherically symmetric
Einstein-matter systems | 17 pages, 5 figures | Commun.Math.Phys.238:411-427,2003 | 10.1007/s00220-003-0870-0 | null | gr-qc | null | This paper explores ``black hole'' solutions of various Einstein-wave matter
systems admitting an isometry of their domain of outer communications taking
every point to its future. In the first two parts, it is shown that such
solutions, assuming in addition that they are spherically symmetric and the
matter has a certain structure, must be Schwarzschild or Reissner-Nordstrom.
Non-trivial examples of matter for which the result applies are a wave map and
a massive charged scalar field interacting with an electromagnetic field. The
results thus generalize work of Bekenstein [1] and Heusler [12] from the static
to the periodic case. In the third part, which is independent of the first two,
it is shown that Dirac fields preserved by an isometry of a spherically
symmetric domain of outer communications of the type described above must
vanish. It can be applied in particular to the Einstein-Dirac-Maxwell equations
or the Einstein-Dirac-Yang/Mills equations, generalizing work of Finster,
Smoller, and Yau [9], [7], [8], and also [6].
| [
{
"created": "Tue, 8 Oct 2002 13:59:59 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Dafermos",
"Mihalis",
""
]
] | This paper explores ``black hole'' solutions of various Einstein-wave matter systems admitting an isometry of their domain of outer communications taking every point to its future. In the first two parts, it is shown that such solutions, assuming in addition that they are spherically symmetric and the matter has a certain structure, must be Schwarzschild or Reissner-Nordstrom. Non-trivial examples of matter for which the result applies are a wave map and a massive charged scalar field interacting with an electromagnetic field. The results thus generalize work of Bekenstein [1] and Heusler [12] from the static to the periodic case. In the third part, which is independent of the first two, it is shown that Dirac fields preserved by an isometry of a spherically symmetric domain of outer communications of the type described above must vanish. It can be applied in particular to the Einstein-Dirac-Maxwell equations or the Einstein-Dirac-Yang/Mills equations, generalizing work of Finster, Smoller, and Yau [9], [7], [8], and also [6]. |
1403.2366 | Donato Bini | Donato Bini and Thibault Damour | Analytic determination of the eight-and-a-half post-Newtonian self-force
contributions to the two-body gravitational interaction potential | 13 pages; 1 eps figure. Revtex latex macros used | null | 10.1103/PhysRevD.89.104047 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We {\it analytically} compute, to the eight-and-a-half post-Newtonian order,
and to linear order in the mass ratio, the radial potential describing (within
the effective one-body formalism) the gravitational interaction of two bodies,
thereby extending previous analytic results. These results are obtained by
applying analytical gravitational self-force theory (for a particle in circular
orbit around a Schwarzschild black hole) to Detweiler's gauge-invariant
redshift variable. We emphasize the increase in \lq\lq transcendentality" of
the numbers entering the post-Newtonian expansion coefficients as the order
increases, in particular we note the appearance of $\zeta(3)$ (as well as the
square of Euler's constant $\gamma$) starting at the seventh post-Newtonian
order. We study the convergence of the post-Newtonian expansion as the
expansion parameter $u=GM/(c^2r)$ leaves the weak-field domain $u\ll 1$ to
enter the strong field domain $u=O(1)$.
| [
{
"created": "Mon, 10 Mar 2014 19:48:51 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Bini",
"Donato",
""
],
[
"Damour",
"Thibault",
""
]
] | We {\it analytically} compute, to the eight-and-a-half post-Newtonian order, and to linear order in the mass ratio, the radial potential describing (within the effective one-body formalism) the gravitational interaction of two bodies, thereby extending previous analytic results. These results are obtained by applying analytical gravitational self-force theory (for a particle in circular orbit around a Schwarzschild black hole) to Detweiler's gauge-invariant redshift variable. We emphasize the increase in \lq\lq transcendentality" of the numbers entering the post-Newtonian expansion coefficients as the order increases, in particular we note the appearance of $\zeta(3)$ (as well as the square of Euler's constant $\gamma$) starting at the seventh post-Newtonian order. We study the convergence of the post-Newtonian expansion as the expansion parameter $u=GM/(c^2r)$ leaves the weak-field domain $u\ll 1$ to enter the strong field domain $u=O(1)$. |
2011.05837 | Uwe R. Fischer | Satadal Datta, Uwe R. Fischer | Inherent nonlinearity of fluid motion and acoustic gravitational wave
memory | 10 pages, 3 figures; as published in Physical Review D | Phys. Rev. D 105, 022003 (2022) | 10.1103/PhysRevD.105.022003 | null | gr-qc cond-mat.quant-gas | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the propagation of nonlinear sound waves in a perfect fluid at
rest. By employing the Riemann wave equation of nonlinear acoustics in one
spatial dimension, it is shown that waves carrying a constant density
perturbation at their tails produce an acoustic analogue of gravitational wave
memory. For the acoustic memory, which is in general $nonlinear$, the
nonlinearity of the effective spacetime dynamics is not due to the Einstein
equations, but due to the nonlinearity of the perfect fluid equations. For
concreteness, we employ a box-trapped Bose-Einstein condensate, and suggest an
experimental protocol to observe acoustic gravitational wave memory.
| [
{
"created": "Wed, 11 Nov 2020 15:01:15 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Oct 2021 16:39:06 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Jan 2022 17:19:34 GMT",
"version": "v3"
}
] | 2022-01-25 | [
[
"Datta",
"Satadal",
""
],
[
"Fischer",
"Uwe R.",
""
]
] | We consider the propagation of nonlinear sound waves in a perfect fluid at rest. By employing the Riemann wave equation of nonlinear acoustics in one spatial dimension, it is shown that waves carrying a constant density perturbation at their tails produce an acoustic analogue of gravitational wave memory. For the acoustic memory, which is in general $nonlinear$, the nonlinearity of the effective spacetime dynamics is not due to the Einstein equations, but due to the nonlinearity of the perfect fluid equations. For concreteness, we employ a box-trapped Bose-Einstein condensate, and suggest an experimental protocol to observe acoustic gravitational wave memory. |
gr-qc/9805010 | Luis J. Garay | Luis J. Garay and Guillermo A. Mena Marugan | Thiemann transform for gravity with matter fields | LaTeX 2.09, 14 pages, no figures | Class.Quant.Grav. 15 (1998) 3763-3775 | 10.1088/0264-9381/15/12/007 | null | gr-qc | null | The generalised Wick transform discovered by Thiemann provides a
well-established relation between the Euclidean and Lorentzian theories of
general relativity. We extend this Thiemann transform to the Ashtekar
formulation for gravity coupled with spin-1/2 fermions, a non-Abelian
Yang-Mills field, and a scalar field. It is proved that, on functions of the
gravitational and matter phase space variables, the Thiemann transform is
equivalent to the composition of an inverse Wick rotation and a constant
complex scale transformation of all fields. This result holds as well for
functions that depend on the shift vector, the lapse function, and the Lagrange
multipliers of the Yang-Mills and gravitational Gauss constraints, provided
that the Wick rotation is implemented by means of an analytic continuation of
the lapse. In this way, the Thiemann transform is furnished with a geometric
interpretation. Finally, we confirm the expectation that the generator of the
Thiemann transform can be determined just from the spin of the fields and give
a simple explanation for this fact.
| [
{
"created": "Tue, 5 May 1998 10:47:40 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Dec 1998 09:07:33 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Garay",
"Luis J.",
""
],
[
"Marugan",
"Guillermo A. Mena",
""
]
] | The generalised Wick transform discovered by Thiemann provides a well-established relation between the Euclidean and Lorentzian theories of general relativity. We extend this Thiemann transform to the Ashtekar formulation for gravity coupled with spin-1/2 fermions, a non-Abelian Yang-Mills field, and a scalar field. It is proved that, on functions of the gravitational and matter phase space variables, the Thiemann transform is equivalent to the composition of an inverse Wick rotation and a constant complex scale transformation of all fields. This result holds as well for functions that depend on the shift vector, the lapse function, and the Lagrange multipliers of the Yang-Mills and gravitational Gauss constraints, provided that the Wick rotation is implemented by means of an analytic continuation of the lapse. In this way, the Thiemann transform is furnished with a geometric interpretation. Finally, we confirm the expectation that the generator of the Thiemann transform can be determined just from the spin of the fields and give a simple explanation for this fact. |
1208.5251 | Laszlo Arpad Gergely | L\'aszl\'o \'A. Gergely, Peter L. Biermann | The typical mass ratio and typical final spin in supermassive black hole
mergers | 12 pages, 6 figures | null | null | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that merging supermassive black holes (SMBHs) typically have neither
equal masses, nor is their mass ratio too extreme. The majority of such mergers
fall into the mass ratio range of 1:30 to 1:3, implying a spin flip during the
inspiral. We also present a simple expression for the final spin $\chi_{f}$ of
the emerging SMBH, as function of the mass ratio, initial spin magnitudes, and
orientation of the spins with respect to the orbital plane and each other. This
formula approximates well more cumbersome expressions obtained from the fit
with numerical simulations. By integrating over all equally likely orientations
for precessing mergers we determine a lower approximant to the final spin
distribution as function of the mass ratio alone. By folding this with the
derived mass ratio dependent merger rate we derive a lower bound to the typical
final spin value after mergers. We repeat the procedure deriving an upper bound
for the typical spin in the case when the spins are aligned to the orbital
angular momentum, such that there is no precession in the system. Both slopes
of $\chi_{f}$ as function of the initial spins being smaller than one lead to
two attractors at $\chi_{f}^{prec}=0.2$ and $\chi_{f}^{align}=0.45$,
respectively. Real mergers, biased toward partial alignment by interactions
with the environment (accretion, host galaxy, etc.) would generate a typical
final spin lying between these two limiting values. These are the typical
values of the spin after the merger, starting from which the spin can built up
by further gaseous accretion.
| [
{
"created": "Sun, 26 Aug 2012 20:38:39 GMT",
"version": "v1"
}
] | 2012-08-28 | [
[
"Gergely",
"László Á.",
""
],
[
"Biermann",
"Peter L.",
""
]
] | We prove that merging supermassive black holes (SMBHs) typically have neither equal masses, nor is their mass ratio too extreme. The majority of such mergers fall into the mass ratio range of 1:30 to 1:3, implying a spin flip during the inspiral. We also present a simple expression for the final spin $\chi_{f}$ of the emerging SMBH, as function of the mass ratio, initial spin magnitudes, and orientation of the spins with respect to the orbital plane and each other. This formula approximates well more cumbersome expressions obtained from the fit with numerical simulations. By integrating over all equally likely orientations for precessing mergers we determine a lower approximant to the final spin distribution as function of the mass ratio alone. By folding this with the derived mass ratio dependent merger rate we derive a lower bound to the typical final spin value after mergers. We repeat the procedure deriving an upper bound for the typical spin in the case when the spins are aligned to the orbital angular momentum, such that there is no precession in the system. Both slopes of $\chi_{f}$ as function of the initial spins being smaller than one lead to two attractors at $\chi_{f}^{prec}=0.2$ and $\chi_{f}^{align}=0.45$, respectively. Real mergers, biased toward partial alignment by interactions with the environment (accretion, host galaxy, etc.) would generate a typical final spin lying between these two limiting values. These are the typical values of the spin after the merger, starting from which the spin can built up by further gaseous accretion. |
1907.03622 | Remo Garattini | Remo Garattini | Traversable Wormholes and Yukawa Potentials | 6 pages. Contribution to the proceedings of "The Fifteenth Marcel
Grossmann Meeting on General Relativity", University of Rome "La Sapienza",
Rome, July 1-7, 2018, based on a talk delivered at the AT3 parallel session | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Traversable Wormhole are amazing astrophysical objects predicted by General
Relativity which are able to connect remote region of space-time. Even if their
existence has not been proved yet they are object of continuous investigation.
From the theoretically point of view, to exist, traversable wormholes need a
special form of energy density termed exotic. Since this exotic source must be
concentrated on the throat of the wormhole, we discuss the implications of
assuming Yukawa-like profiles which could be realize such a configuration.
| [
{
"created": "Fri, 5 Jul 2019 15:17:16 GMT",
"version": "v1"
}
] | 2019-07-09 | [
[
"Garattini",
"Remo",
""
]
] | Traversable Wormhole are amazing astrophysical objects predicted by General Relativity which are able to connect remote region of space-time. Even if their existence has not been proved yet they are object of continuous investigation. From the theoretically point of view, to exist, traversable wormholes need a special form of energy density termed exotic. Since this exotic source must be concentrated on the throat of the wormhole, we discuss the implications of assuming Yukawa-like profiles which could be realize such a configuration. |
gr-qc/0702046 | Sunil Maharaj | R. Sharma, S. D. Maharaj | A class of relativistic stars with a linear equation of state | 5 pages, 3 figures, to appear in Mon. Not. R. Astron. Soc | Mon.Not.Roy.Astron.Soc.375:1265-1268,2007 | 10.1111/j.1365-2966.2006.11355.x | null | gr-qc | null | By assuming a particular mass function we find new exact solutions to the
Einstein field equations with an anisotropic matter distribution. The solutions
are shown to be relevant for the description of compact stars. A distinguishing
feature of this class of solutions is that they admit a linear equation of
state which can be applied to strange stars with quark matter.
| [
{
"created": "Thu, 8 Feb 2007 08:16:33 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Sharma",
"R.",
""
],
[
"Maharaj",
"S. D.",
""
]
] | By assuming a particular mass function we find new exact solutions to the Einstein field equations with an anisotropic matter distribution. The solutions are shown to be relevant for the description of compact stars. A distinguishing feature of this class of solutions is that they admit a linear equation of state which can be applied to strange stars with quark matter. |
0802.1660 | James Lindesay | Beth A. Brown, James Lindesay | Radial Photon Trajectories Near an Evaporating Black Hole | 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The radial motion of photons emitted near the horizon of a black hole that
evaporates at a steady rate is examined. The space-time of the black hole is
generated using non-orthogonal coordinates. It is shown that some photons that
are initially drawn towards the singularity can escape falling into the
horizon. The behaviors of various outgoing and ingoing photons are clearly
demonstrated through the use of a Penrose diagram.
| [
{
"created": "Tue, 12 Feb 2008 16:10:05 GMT",
"version": "v1"
}
] | 2008-02-13 | [
[
"Brown",
"Beth A.",
""
],
[
"Lindesay",
"James",
""
]
] | The radial motion of photons emitted near the horizon of a black hole that evaporates at a steady rate is examined. The space-time of the black hole is generated using non-orthogonal coordinates. It is shown that some photons that are initially drawn towards the singularity can escape falling into the horizon. The behaviors of various outgoing and ingoing photons are clearly demonstrated through the use of a Penrose diagram. |
2312.08458 | Vasileios Mpisketzis | Vasilis Mpisketzis, Rapha\"el Duqu\'e, Antonios Nathanail, Alejandro
Cruz-Osorio, Luciano Rezzolla | Impact of anisotropic ejecta on jet dynamics and afterglow emission in
binary neutron-star mergers | 19 pages, 9 figures. Accepted for publication in MNRAS | null | 10.1093/mnras/stad3774 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Binary neutron stars mergers widely accepted as potential progenitors of
short gamma-ray bursts. After the remnant of the merger has collapsed to a
black hole, a jet is powered and may breakout from the the matter expelled
during the collision and the subsequent wind emission. The interaction of the
jet with the ejecta may affect its dynamics and the resulting electromagnetic
counterparts. We here examine how an inhomogeneous and anisotropic distribution
of ejecta affects such dynamics, dictating the properties of the jet-ejecta
cocoon and of the afterglow radiated by the jet upon deceleration. More
specifically, we carry out general-relativistic hydrodynamical simulations of
relativistic jets launched within a variety of geometrically inhomogeneous and
anisotropic distributions of ejected matter. We find that different
anisotropies impact the variance of the afterglow light-curves as a function of
the jet luminosity and ejected mass. A considerable amount of the jet energy is
deposited in the cocoon through the jet-ejecta interaction with a small but
important dependence on the properties of the ejecta. Furthermore, all
configurations show a two-component behaviour for the polar structure of the
jet, with a narrow core at large energies and Lorentz factors and a shallow
segment at high latitudes from the jet axis. Hence, afterglows measured on
off-axis lines of sight could be used to deduce the properties of the ejected
matter, but also that the latter need to be properly accounted for when
modelling the afterglow signal and the jet-launching mechanisms.
| [
{
"created": "Wed, 13 Dec 2023 19:01:02 GMT",
"version": "v1"
}
] | 2023-12-15 | [
[
"Mpisketzis",
"Vasilis",
""
],
[
"Duqué",
"Raphaël",
""
],
[
"Nathanail",
"Antonios",
""
],
[
"Cruz-Osorio",
"Alejandro",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | Binary neutron stars mergers widely accepted as potential progenitors of short gamma-ray bursts. After the remnant of the merger has collapsed to a black hole, a jet is powered and may breakout from the the matter expelled during the collision and the subsequent wind emission. The interaction of the jet with the ejecta may affect its dynamics and the resulting electromagnetic counterparts. We here examine how an inhomogeneous and anisotropic distribution of ejecta affects such dynamics, dictating the properties of the jet-ejecta cocoon and of the afterglow radiated by the jet upon deceleration. More specifically, we carry out general-relativistic hydrodynamical simulations of relativistic jets launched within a variety of geometrically inhomogeneous and anisotropic distributions of ejected matter. We find that different anisotropies impact the variance of the afterglow light-curves as a function of the jet luminosity and ejected mass. A considerable amount of the jet energy is deposited in the cocoon through the jet-ejecta interaction with a small but important dependence on the properties of the ejecta. Furthermore, all configurations show a two-component behaviour for the polar structure of the jet, with a narrow core at large energies and Lorentz factors and a shallow segment at high latitudes from the jet axis. Hence, afterglows measured on off-axis lines of sight could be used to deduce the properties of the ejected matter, but also that the latter need to be properly accounted for when modelling the afterglow signal and the jet-launching mechanisms. |
0710.3137 | Victor Stenger | Victor J. Stenger | A Scenario for a Natural Origin of Our Universe | 9 pages, 4 figures. Published in slightly longer form in Philo 9, no.
2 (2006): 93-102. This paper is written at about the senior physics major
level in order to reach the widest possible audience | Philo 9N2:93-102,2006 | null | null | gr-qc physics.pop-ph | null | A mathematical model of the natural origin of our universe is presented. The
model is based only on well-established physics. No claim is made that this
model uniquely represents exactly how the universe came about. But the
viability of a single model serves to refute any assertions that the universe
cannot have come about by natural means.
| [
{
"created": "Tue, 16 Oct 2007 17:42:59 GMT",
"version": "v1"
}
] | 2009-04-08 | [
[
"Stenger",
"Victor J.",
""
]
] | A mathematical model of the natural origin of our universe is presented. The model is based only on well-established physics. No claim is made that this model uniquely represents exactly how the universe came about. But the viability of a single model serves to refute any assertions that the universe cannot have come about by natural means. |
1006.4139 | Michele Levi | Michele Levi | Next-to-leading order gravitational spin-orbit coupling in an effective
field theory approach | 27 pages, revtex4-1, 4 figures; v2: minor editing made; v3: published | Phys.Rev.D82:104004,2010 | 10.1103/PhysRevD.82.104004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use an effective field theory (EFT) approach to calculate the next to
leading order (NLO) gravitational spin-orbit interaction between two spinning
compact objects. The NLO spin-orbit interaction provides the most
computationally complex sector of the NLO spin effects, previously derived
within the EFT approach. In particular, it requires the inclusion of
non-stationary cubic self-gravitational interaction, as well as the
implementation of a spin supplementary condition (SSC) at higher orders. The
EFT calculation is carried out in terms of the non-relativistic gravitational
field parametrization, making the calculation more efficient with no need to
rely on automated computations, and illustrating the coupling hierarchy of the
different gravitational field components to the spin and mass sources. Finally,
we show explicitly how to relate the EFT derived spin results to the canonical
results obtained with the ADM Hamiltonian formalism. This is done using
non-canonical transformations, required due to the implementation of covariant
SSC, as well as canonical transformations at the level of the Hamiltonian, with
no need to resort to the equations of motion or the Dirac brackets.
| [
{
"created": "Mon, 21 Jun 2010 19:11:31 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Jul 2010 13:55:35 GMT",
"version": "v2"
},
{
"created": "Wed, 3 Nov 2010 16:48:33 GMT",
"version": "v3"
}
] | 2010-12-03 | [
[
"Levi",
"Michele",
""
]
] | We use an effective field theory (EFT) approach to calculate the next to leading order (NLO) gravitational spin-orbit interaction between two spinning compact objects. The NLO spin-orbit interaction provides the most computationally complex sector of the NLO spin effects, previously derived within the EFT approach. In particular, it requires the inclusion of non-stationary cubic self-gravitational interaction, as well as the implementation of a spin supplementary condition (SSC) at higher orders. The EFT calculation is carried out in terms of the non-relativistic gravitational field parametrization, making the calculation more efficient with no need to rely on automated computations, and illustrating the coupling hierarchy of the different gravitational field components to the spin and mass sources. Finally, we show explicitly how to relate the EFT derived spin results to the canonical results obtained with the ADM Hamiltonian formalism. This is done using non-canonical transformations, required due to the implementation of covariant SSC, as well as canonical transformations at the level of the Hamiltonian, with no need to resort to the equations of motion or the Dirac brackets. |
1211.6619 | Vladimir Strokov N. | V. N. Lukash, E. V. Mikheeva, and V. N. Strokov | Generation of Cosmological Flows in General Relativity (Features and
Properties of Integrable Singularities) | 21 pages, 3 figures, extended Introduction and minor changes as
compared to the published version | Phys. Usp. 55 831-837 (2012) | 10.3367/UFNe.0182.201208k.0894 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss status of the singularity problem in General Relativity and argue
that the requirement that a physical solution must be completely free of
singularities may be too strong. As an example, we consider properties of the
integrable singularities and show that they represent light horizons separating
T-regions of black and white holes. Connecting an astrophysical black hole to a
white hole, they lead to a natural mechanism of generating new universes. Under
favorable conditions the new universes will also contain black holes which, in
their turn, will give rise to another generation of universes. In this case the
cosmological evolutionary tree will continue to grow to form the "hyperverse".
This scenario essentially differs from other known mechanisms, such as bounce,
birth from "nothing", baby-universe scenario, etc.
| [
{
"created": "Wed, 28 Nov 2012 14:55:04 GMT",
"version": "v1"
}
] | 2012-11-29 | [
[
"Lukash",
"V. N.",
""
],
[
"Mikheeva",
"E. V.",
""
],
[
"Strokov",
"V. N.",
""
]
] | We discuss status of the singularity problem in General Relativity and argue that the requirement that a physical solution must be completely free of singularities may be too strong. As an example, we consider properties of the integrable singularities and show that they represent light horizons separating T-regions of black and white holes. Connecting an astrophysical black hole to a white hole, they lead to a natural mechanism of generating new universes. Under favorable conditions the new universes will also contain black holes which, in their turn, will give rise to another generation of universes. In this case the cosmological evolutionary tree will continue to grow to form the "hyperverse". This scenario essentially differs from other known mechanisms, such as bounce, birth from "nothing", baby-universe scenario, etc. |
2207.05030 | Oleksandr Sobol Dr. | R. Durrer, O. Sobol, S. Vilchinskii | Magnetogenesis in Higgs-Starobinsky inflation | 20 pages, 7 figures | Physical Review D 106 (12), 123520 (2022) | 10.1103/PhysRevD.106.123520 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of mixed Higgs-Starobinsky inflation, we consider the
generation of Abelian gauge fields due to their nonminimal coupling to gravity
(in two different formulations of gravity -- metric and Palatini). We couple
the gauge-field invariants $F_{\mu\nu}F^{\mu\nu}$ and
$F_{\mu\nu}\tilde{F}^{\mu\nu}$ to an integer power of the scalar curvature
$R^n$ in Jordan frame and, treating these interactions perturbatively, switch
to the Einstein frame where they lead to effective kinetic and axial couplings
between gauge fields and inflaton. We determine the power spectra, energy
densities, correlation length, and helicality of the generated gauge fields for
different values of the nonminimal coupling constants and parameter $n$. We
analytically estimate the spectral index $n_{B}$ of the magnetic power spectrum
and show that for $n>1$ it is possible to get the scale-invariant or even
red-tilted spectrum for a wide range of modes that implies larger correlation
length of the generated fields. On the other hand, the magnitude of these
fields typically decreases in time becoming very small in the end of inflation.
Thus, it is difficult to obtain both large magnitude and correlation length of
the gauge field in the frame of this model.
| [
{
"created": "Mon, 11 Jul 2022 17:33:41 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Jul 2022 22:11:58 GMT",
"version": "v2"
},
{
"created": "Wed, 28 Dec 2022 01:23:15 GMT",
"version": "v3"
}
] | 2022-12-29 | [
[
"Durrer",
"R.",
""
],
[
"Sobol",
"O.",
""
],
[
"Vilchinskii",
"S.",
""
]
] | In the framework of mixed Higgs-Starobinsky inflation, we consider the generation of Abelian gauge fields due to their nonminimal coupling to gravity (in two different formulations of gravity -- metric and Palatini). We couple the gauge-field invariants $F_{\mu\nu}F^{\mu\nu}$ and $F_{\mu\nu}\tilde{F}^{\mu\nu}$ to an integer power of the scalar curvature $R^n$ in Jordan frame and, treating these interactions perturbatively, switch to the Einstein frame where they lead to effective kinetic and axial couplings between gauge fields and inflaton. We determine the power spectra, energy densities, correlation length, and helicality of the generated gauge fields for different values of the nonminimal coupling constants and parameter $n$. We analytically estimate the spectral index $n_{B}$ of the magnetic power spectrum and show that for $n>1$ it is possible to get the scale-invariant or even red-tilted spectrum for a wide range of modes that implies larger correlation length of the generated fields. On the other hand, the magnitude of these fields typically decreases in time becoming very small in the end of inflation. Thus, it is difficult to obtain both large magnitude and correlation length of the gauge field in the frame of this model. |
gr-qc/0611147 | Malcolm MacCallum | L. Herrera, M.A.H. MacCallum and N.O. Santos | On the Matching Conditions for the Collapsing Cylinder | Submitted to Class. Quant. Grav. as a comment | Class.Quant.Grav.24:1033,2007 | 10.1088/0264-9381/24/4/C01 | null | gr-qc | null | We review the matching conditions for a collapsing anisotropic cylindrical
perfect fluid, recently discussed in the literature (2005 {\it Class. Quantum
Grav.} {\bf 22} 2407). It is shown that radial pressure vanishes on the surface
of the cylinder, contrary to what is asserted in that reference. The origin of
this discrepancy is to be found in a mistake made in one step of the
calculations. Some comments about the relevance of this result in relation to
the momentum of Einstein--Rosen waves are presented.
| [
{
"created": "Tue, 28 Nov 2006 15:54:46 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Herrera",
"L.",
""
],
[
"MacCallum",
"M. A. H.",
""
],
[
"Santos",
"N. O.",
""
]
] | We review the matching conditions for a collapsing anisotropic cylindrical perfect fluid, recently discussed in the literature (2005 {\it Class. Quantum Grav.} {\bf 22} 2407). It is shown that radial pressure vanishes on the surface of the cylinder, contrary to what is asserted in that reference. The origin of this discrepancy is to be found in a mistake made in one step of the calculations. Some comments about the relevance of this result in relation to the momentum of Einstein--Rosen waves are presented. |
2102.12573 | Nelson Falcon Veloz | Nelson Falcon | A large-scale heuristic modification of Newtonian gravity as alternative
approach to the dark energy and dark matter | 16 pages, 7 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | The peculiarities of the inverse square law of Newtonian gravity in standard
Big Bang Cosmology are discussed. It is shown that the incorporation of an
additive term to Newtonian gravitation, as the inverse Yukawa-like field,
allows remove the incompatibility between the flatness of the Universe and the
density of matter in the Friedmann equation, provides a new approach for dark
energy, and enable theoretical deduce the Hubble-Lemaitre's law. The source of
this inverse Yukawa-like field is the ordinary baryonic matter and represents
the large-scale contribution of gravity in accordance with the Mach's
principle. It's heuristically build from a specular reflection of the Yukawa
potential, in agreement with astronomical and laboratory observables, result
null in the inner solar system, weakly attractive in ranges of interstellar
distances, very attractive in distance ranges comparable to the clusters of
galaxies and repulsive in cosmic scales. Its implications in the missing mass
of Zwicky, Virial Theorem, Kepler's Third Law in Globular Clusters, rotations
curves of galaxies, gravitational redshift and the Jean's mass are discussed.
The inclusion of the inverse Yukawa-like field in Newtonian gravitation
predicts a graviton mass of at least 10-64 kg and could be an alternative to
the paradigm of non-baryonic dark matter concomitant with the observables of
the Big Bang.
| [
{
"created": "Tue, 23 Feb 2021 16:26:57 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Dec 2021 08:45:34 GMT",
"version": "v2"
}
] | 2021-12-28 | [
[
"Falcon",
"Nelson",
""
]
] | The peculiarities of the inverse square law of Newtonian gravity in standard Big Bang Cosmology are discussed. It is shown that the incorporation of an additive term to Newtonian gravitation, as the inverse Yukawa-like field, allows remove the incompatibility between the flatness of the Universe and the density of matter in the Friedmann equation, provides a new approach for dark energy, and enable theoretical deduce the Hubble-Lemaitre's law. The source of this inverse Yukawa-like field is the ordinary baryonic matter and represents the large-scale contribution of gravity in accordance with the Mach's principle. It's heuristically build from a specular reflection of the Yukawa potential, in agreement with astronomical and laboratory observables, result null in the inner solar system, weakly attractive in ranges of interstellar distances, very attractive in distance ranges comparable to the clusters of galaxies and repulsive in cosmic scales. Its implications in the missing mass of Zwicky, Virial Theorem, Kepler's Third Law in Globular Clusters, rotations curves of galaxies, gravitational redshift and the Jean's mass are discussed. The inclusion of the inverse Yukawa-like field in Newtonian gravitation predicts a graviton mass of at least 10-64 kg and could be an alternative to the paradigm of non-baryonic dark matter concomitant with the observables of the Big Bang. |
gr-qc/0607062 | Ren\'e Meyer | Rene Meyer | Classical and Quantum Dilaton Gravity in Two Dimensions with Fermions | Diploma Thesis presented to the University of Leipzig (Advisor: Dr.
Daniel Grumiller), 85 pages, 1 figure | null | null | null | gr-qc hep-th | null | In this thesis the first order formulation of generalized dilaton gravities
in two dimensions coupled to a Dirac fermion is considered. After a Hamiltonian
analysis of the gauge symmetries and constraints of the theory and fixing
Eddington-Finkelstein gauge by use of the Batalin-Vilkovisky-Fradkin method,
the system is quantized in the Feynman path integral approach. It turns out
that the path integral over the dilaton gravity sector can be evaluated
exactly, while in the matter sector perturbative methods are applied. The
gravitationally induced four-fermi scattering vertices as well as asymptotic
states are calculated, and -- as for dilaton gravities coupled to scalar fields
-- a ``virtual black hole'' is found to form as an intermediary geometric state
in scattering processes. The results are compared to the well-known scalar case
and evidence for bosonization in this context is found.
| [
{
"created": "Mon, 17 Jul 2006 12:49:32 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Meyer",
"Rene",
""
]
] | In this thesis the first order formulation of generalized dilaton gravities in two dimensions coupled to a Dirac fermion is considered. After a Hamiltonian analysis of the gauge symmetries and constraints of the theory and fixing Eddington-Finkelstein gauge by use of the Batalin-Vilkovisky-Fradkin method, the system is quantized in the Feynman path integral approach. It turns out that the path integral over the dilaton gravity sector can be evaluated exactly, while in the matter sector perturbative methods are applied. The gravitationally induced four-fermi scattering vertices as well as asymptotic states are calculated, and -- as for dilaton gravities coupled to scalar fields -- a ``virtual black hole'' is found to form as an intermediary geometric state in scattering processes. The results are compared to the well-known scalar case and evidence for bosonization in this context is found. |
1810.08220 | Jackson Levi Said | Ismail Soudi, Gabriel Farrugia, Viktor Gakis, Jackson Levi Said,
Emmanuel N. Saridakis | Polarization of gravitational waves in symmetric teleparallel theories
of gravity and their modifications | 11 pages | Phys. Rev. D 100, 044008 (2019) | 10.1103/PhysRevD.100.044008 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Symmetric teleparallel gravity (STG) offers an interesting avenue to
formulate a theory of gravitation that relies neither on curvature nor torsion
but only on non-metricity Q. Given the growing number of observations of
gravitational waves (GWs) and their use to explore gravitational theories, in
this work we investigate the GWs in various extensions of STG, focusing on
their speed and polarization. For the simple STG, for theories that arise from
the generalized irreducible decomposition of STG, and for f(Q) gravity, we
obtain the same speed and polarizations with general relativity. For scalar -
non-metricity theories, where a scalar field is nonminimally coupled to f(Q),
we find that GWs propagate in general with a speed different than the one of
light. Finally, for the case of f(Q,B) gravity we find that new polarizations
do appear.
| [
{
"created": "Thu, 18 Oct 2018 18:06:25 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Aug 2019 08:25:15 GMT",
"version": "v2"
}
] | 2020-09-08 | [
[
"Soudi",
"Ismail",
""
],
[
"Farrugia",
"Gabriel",
""
],
[
"Gakis",
"Viktor",
""
],
[
"Said",
"Jackson Levi",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | Symmetric teleparallel gravity (STG) offers an interesting avenue to formulate a theory of gravitation that relies neither on curvature nor torsion but only on non-metricity Q. Given the growing number of observations of gravitational waves (GWs) and their use to explore gravitational theories, in this work we investigate the GWs in various extensions of STG, focusing on their speed and polarization. For the simple STG, for theories that arise from the generalized irreducible decomposition of STG, and for f(Q) gravity, we obtain the same speed and polarizations with general relativity. For scalar - non-metricity theories, where a scalar field is nonminimally coupled to f(Q), we find that GWs propagate in general with a speed different than the one of light. Finally, for the case of f(Q,B) gravity we find that new polarizations do appear. |
1805.00807 | Alexander E. Shalyt-Margolin | Alexander Shalyt-Margolin | Minimal Length, Minimal Inverse Temperature, Measurability and Black
Holes | 27 pages. arXiv admin note: text overlap with arXiv:1709.03875 | Electronic Journal of Theoretical Physics 14, No. 37 (2018) 35--54 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The measurability notion introduced previously in a quantum theory on the
basis of a minimal length in this paper is defined in thermodynamics on the
basis of a minimal inverse temperature. Based on this notion, some inferences
are made for gravitational thermodynamics of horizon spaces and, specifically,
for black holes with the Schwarzschild metric.
| [
{
"created": "Mon, 30 Apr 2018 06:29:29 GMT",
"version": "v1"
}
] | 2018-05-03 | [
[
"Shalyt-Margolin",
"Alexander",
""
]
] | The measurability notion introduced previously in a quantum theory on the basis of a minimal length in this paper is defined in thermodynamics on the basis of a minimal inverse temperature. Based on this notion, some inferences are made for gravitational thermodynamics of horizon spaces and, specifically, for black holes with the Schwarzschild metric. |
1408.4272 | Andrea Geralico | Donato Bini, Fernando de Felice, Andrea Geralico | Charged spinning particles on circular orbits in the
Reissner-Nordstr\"om spacetime | 19 pages, 4 figures; published version. arXiv admin note: text
overlap with arXiv:gr-qc/0410082 | IJMPD 14, 1793 (2005) | 10.1142/S0218271805007358 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The behaviour of charged spinning test particles moving along circular orbits
in the equatorial plane of the Reissner-Nordstr\"om spacetime is studied in the
framework of the Dixon-Souriau model completed with standard choices of
supplementary conditions. The gravitomagnetic " clock effect", i.e. the delay
in the arrival times of two oppositely circulating particles as measured by a
static observer, is derived and discussed in the cases in which the particles
have equal/opposite charge and spin, the latter being directed along the
$z$-axis.
| [
{
"created": "Tue, 19 Aug 2014 09:57:55 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Bini",
"Donato",
""
],
[
"de Felice",
"Fernando",
""
],
[
"Geralico",
"Andrea",
""
]
] | The behaviour of charged spinning test particles moving along circular orbits in the equatorial plane of the Reissner-Nordstr\"om spacetime is studied in the framework of the Dixon-Souriau model completed with standard choices of supplementary conditions. The gravitomagnetic " clock effect", i.e. the delay in the arrival times of two oppositely circulating particles as measured by a static observer, is derived and discussed in the cases in which the particles have equal/opposite charge and spin, the latter being directed along the $z$-axis. |
2011.13764 | Suman Kulkarni | Suman Kulkarni and Collin D. Capano | On the reliability of parameter estimates in the first observing run of
Advanced LIGO | 11 pages, 5 figures | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Accurate parameter estimation is key to maximizing the scientific impact of
gravitational-wave astronomy. Parameters of a binary merger are typically
estimated using Bayesian inference. It is necessary to make several assumptions
when doing so, one of which is that the the detectors output stationary
Gaussian noise. We test the validity of these assumptions by performing
percentile-percentile tests in both simulated Gaussian noise and real detector
data in the first observing run of Advanced LIGO (O1). We add simulated signals
to 512s of data centered on each of the three events detected in O1 --
GW150914, GW151012, and GW151226 -- and check that the recovered credible
intervals match statistical expectations. We find that we are able to recover
unbiased parameter estimates in the real detector data, indicating that the
assumption of Gaussian noise does not adversely effect parameter estimates.
However, we also find that both the parallel-tempered sampler emcee_pt and the
nested sampler dynesty struggle to produced unbiased parameter estimates for
GW151226-like signals, even in simulated Gaussian noise. The emcee_pt sampler
does produce unbiased estimates for GW150914-like signals. This highlights the
importance of performing percentile-percentile tests in different targeted
areas of parameter space.
| [
{
"created": "Fri, 27 Nov 2020 14:52:24 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Jun 2021 12:14:24 GMT",
"version": "v2"
}
] | 2021-06-11 | [
[
"Kulkarni",
"Suman",
""
],
[
"Capano",
"Collin D.",
""
]
] | Accurate parameter estimation is key to maximizing the scientific impact of gravitational-wave astronomy. Parameters of a binary merger are typically estimated using Bayesian inference. It is necessary to make several assumptions when doing so, one of which is that the the detectors output stationary Gaussian noise. We test the validity of these assumptions by performing percentile-percentile tests in both simulated Gaussian noise and real detector data in the first observing run of Advanced LIGO (O1). We add simulated signals to 512s of data centered on each of the three events detected in O1 -- GW150914, GW151012, and GW151226 -- and check that the recovered credible intervals match statistical expectations. We find that we are able to recover unbiased parameter estimates in the real detector data, indicating that the assumption of Gaussian noise does not adversely effect parameter estimates. However, we also find that both the parallel-tempered sampler emcee_pt and the nested sampler dynesty struggle to produced unbiased parameter estimates for GW151226-like signals, even in simulated Gaussian noise. The emcee_pt sampler does produce unbiased estimates for GW150914-like signals. This highlights the importance of performing percentile-percentile tests in different targeted areas of parameter space. |
gr-qc/9310027 | David Politzer | H. David Politzer | Path Integrals, Density Matrices, and Information Flow with Closed
Timelike Curves | 25 pages, phyzzx, CALT-68-1886 | Phys.Rev. D49 (1994) 3981-3989 | 10.1103/PhysRevD.49.3981 | null | gr-qc hep-th | null | Two formulations of quantum mechanics, inequivalent in the presence of closed
timelike curves, are studied in the context of a soluable system. It
illustrates how quantum field nonlinearities lead to a breakdown of unitarity,
causality, and superposition using a path integral. Deutsch's density matrix
approach is causal but typically destroys coherence. For each of these
formulations I demonstrate that there are yet further alternatives in
prescribing the handling of information flow (inequivalent to previous
analyses) that have implications for any system in which unitarity or coherence
are not preserved.
| [
{
"created": "Tue, 19 Oct 1993 22:53:44 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Politzer",
"H. David",
""
]
] | Two formulations of quantum mechanics, inequivalent in the presence of closed timelike curves, are studied in the context of a soluable system. It illustrates how quantum field nonlinearities lead to a breakdown of unitarity, causality, and superposition using a path integral. Deutsch's density matrix approach is causal but typically destroys coherence. For each of these formulations I demonstrate that there are yet further alternatives in prescribing the handling of information flow (inequivalent to previous analyses) that have implications for any system in which unitarity or coherence are not preserved. |
gr-qc/0312070 | Marek Abramowicz A. | M.A. Abramowicz, G.J.E. Almergren, W. Kluzniak, A.V. Thampan | The Hartle-Thorne circular geodesics | 9 pages | null | null | null | gr-qc | null | The Hartle-Thorne metric is an exact solution of vacuum Einstein field
equations that describes the exterior of any slowly and rigidly rotating,
stationary and axially symmetric body. The metric is given with accuracy up to
the second order terms in the body's angular momentum, and first order in its
quadrupole moment. We give, with the same accuracy, analytic formulae for
circular geodesics in the Hartle-Thorne metrics. They describe angular
velocity, angular momentum, energy, epicyclic frequencies, shear, vorticity and
Fermi-Walker precession. These quantities are relevant to several astrophysical
phenomena, in particular to the observed high frequency, kilohertz Quasi
Periodic Oscillations (kHz QPOs) in the X-ray luminosity from black hole and
neutron star sources. It is believed that kHz QPO data may be used to test the
strong field regime of Einstein's general relativity, and the physics of
super-dense matter of which neutron stars are made of.
| [
{
"created": "Mon, 15 Dec 2003 22:47:05 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Abramowicz",
"M. A.",
""
],
[
"Almergren",
"G. J. E.",
""
],
[
"Kluzniak",
"W.",
""
],
[
"Thampan",
"A. V.",
""
]
] | The Hartle-Thorne metric is an exact solution of vacuum Einstein field equations that describes the exterior of any slowly and rigidly rotating, stationary and axially symmetric body. The metric is given with accuracy up to the second order terms in the body's angular momentum, and first order in its quadrupole moment. We give, with the same accuracy, analytic formulae for circular geodesics in the Hartle-Thorne metrics. They describe angular velocity, angular momentum, energy, epicyclic frequencies, shear, vorticity and Fermi-Walker precession. These quantities are relevant to several astrophysical phenomena, in particular to the observed high frequency, kilohertz Quasi Periodic Oscillations (kHz QPOs) in the X-ray luminosity from black hole and neutron star sources. It is believed that kHz QPO data may be used to test the strong field regime of Einstein's general relativity, and the physics of super-dense matter of which neutron stars are made of. |
gr-qc/9705036 | Palii Yurii | S. A. Gogilidze, A. M. Khvedelidze, V. V. Papoyan, Yu.G.Palii, V. N.
Pervushin | Dirac and Friedmann Observables in Quantum Universe with Radiation | 18 pages, LaTex | Grav.Cosmol. 3 (1997) 17-23 | null | null | gr-qc | null | Relations between the Friedmann observables of the expanding Universe and the
Dirac observables in the generalized Hamiltonian approach are established for
the Friedmann cosmological model of the Universe with the field excitations
imitating radiation. A full separation of the physical sector from the gauge
one is fulfilled by the method of the gaugeless reduction in which the
gravitational part of the energy constraint is considered as a new momentum. We
show that this reduction removes an infinite factor from the Hartle -- Hawking
functional integral, provides the normalizability of the Wheeler -- DeWitt wave
function, clarifies its relation to the observational cosmology, and picks out
a conformal frame of Narlikar.
| [
{
"created": "Wed, 14 May 1997 08:56:30 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gogilidze",
"S. A.",
""
],
[
"Khvedelidze",
"A. M.",
""
],
[
"Papoyan",
"V. V.",
""
],
[
"Palii",
"Yu. G.",
""
],
[
"Pervushin",
"V. N.",
""
]
] | Relations between the Friedmann observables of the expanding Universe and the Dirac observables in the generalized Hamiltonian approach are established for the Friedmann cosmological model of the Universe with the field excitations imitating radiation. A full separation of the physical sector from the gauge one is fulfilled by the method of the gaugeless reduction in which the gravitational part of the energy constraint is considered as a new momentum. We show that this reduction removes an infinite factor from the Hartle -- Hawking functional integral, provides the normalizability of the Wheeler -- DeWitt wave function, clarifies its relation to the observational cosmology, and picks out a conformal frame of Narlikar. |
2406.04392 | Naman Kumar | Naman Kumar | On the Accelerated Expansion of the Universe | published version, comments are welcome, covered in phys.org:
https://phys.org/news/2024-06-partner-anti-universe-expansion-dark.html | Gravit. Cosmol. 30, 85-88 (2024) | 10.1134/S0202289324010080 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | If we look at from a quantum perspective, the most natural way in which the
universe can be created is in entangled pairs whose time flow is oppositely
related. This suggests the idea of the creation of a universe-antiuniverse
pair. Assuming the validity of this hypothesis, in this paper, we show that the
universe expands in an accelerated manner. The same reasoning holds for the
anti-universe as well. This idea does not require any form of dark energy as
used in the standard cosmological model of ${\Lambda}$CDM or in the modified
theories of gravity.
| [
{
"created": "Thu, 6 Jun 2024 17:59:08 GMT",
"version": "v1"
}
] | 2024-06-10 | [
[
"Kumar",
"Naman",
""
]
] | If we look at from a quantum perspective, the most natural way in which the universe can be created is in entangled pairs whose time flow is oppositely related. This suggests the idea of the creation of a universe-antiuniverse pair. Assuming the validity of this hypothesis, in this paper, we show that the universe expands in an accelerated manner. The same reasoning holds for the anti-universe as well. This idea does not require any form of dark energy as used in the standard cosmological model of ${\Lambda}$CDM or in the modified theories of gravity. |
1205.7063 | Henric Krawczynski | Henric Krawczynski (Washington University in St. Louis) | Tests of General Relativity in the Strong Gravity Regime Based on X-Ray
Spectropolarimetric Observations of Black Holes in X-Ray Binaries | 27 pages, 8 figures, accepted for publication in the Astrophysical
Journal | null | 10.1088/0004-637X/754/2/133 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Although General Relativity (GR) has been tested extensively in the weak
gravity regime, similar tests in the strong gravity regime are still missing.
In this paper we explore the possibility to use X-ray spectropolarimetric
observations of black holes in X-ray binaries to distinguish between the Kerr
metric and the phenomenological metrics introduced by Johannsen and Psaltis
(2011) (which are not vacuum solutions of Einstein's equation) and thus to test
the no-hair theorem of GR. To this end, we have developed a numerical code that
calculates the radial brightness profiles of accretion disks and parallel
transports the wave vector and polarization vector of photons through the Kerr
and non-GR spacetimes. We used the code to predict the observational appearance
of GR and non-GR accreting black hole systems. We find that the predicted
energy spectra and energy dependent polarization degree and polarization
direction do depend strongly on the underlying spacetime. However, for large
regions of the parameter space, the GR and non-GR metrics lead to very similar
observational signatures, making it difficult to observationally distinguish
between the two types of models.
| [
{
"created": "Thu, 31 May 2012 18:36:12 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Krawczynski",
"Henric",
"",
"Washington University in St. Louis"
]
] | Although General Relativity (GR) has been tested extensively in the weak gravity regime, similar tests in the strong gravity regime are still missing. In this paper we explore the possibility to use X-ray spectropolarimetric observations of black holes in X-ray binaries to distinguish between the Kerr metric and the phenomenological metrics introduced by Johannsen and Psaltis (2011) (which are not vacuum solutions of Einstein's equation) and thus to test the no-hair theorem of GR. To this end, we have developed a numerical code that calculates the radial brightness profiles of accretion disks and parallel transports the wave vector and polarization vector of photons through the Kerr and non-GR spacetimes. We used the code to predict the observational appearance of GR and non-GR accreting black hole systems. We find that the predicted energy spectra and energy dependent polarization degree and polarization direction do depend strongly on the underlying spacetime. However, for large regions of the parameter space, the GR and non-GR metrics lead to very similar observational signatures, making it difficult to observationally distinguish between the two types of models. |
2204.13948 | Guangzhou Guo | Guangzhou Guo, Xin Jiang, Peng Wang, Houwen Wu | Gravitational Lensing by Black Holes with Multiple Photon Spheres | 21 pages, 6 figures, references added | null | 10.1103/PhysRevD.105.124064 | CTP-SCU/2022007 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study gravitational lensing of light by hairy black holes, which, in a
certain parameter regime, can possess two photon spheres of different size
outside the event horizon. In particular, we focus on higher-order images of a
point-like light source and a luminous celestial sphere produced by strong
gravitational lensing near photon spheres. Two photon spheres usually triple
the number of high-order images of a point-like light source. When a hairy
black hole is illuminated by a celestial sphere, two photon spheres would give
rise to two critical curves in the black hole image, and the smaller critical
curve coincides with the shadow edge. In addition to a set of higher-order
images of the celestial sphere outside the shadow edge, two more sets of
higher-order images are observed inside and outside the larger critical curve,
respectively.
| [
{
"created": "Fri, 29 Apr 2022 08:47:56 GMT",
"version": "v1"
},
{
"created": "Sat, 7 May 2022 15:06:32 GMT",
"version": "v2"
}
] | 2022-07-13 | [
[
"Guo",
"Guangzhou",
""
],
[
"Jiang",
"Xin",
""
],
[
"Wang",
"Peng",
""
],
[
"Wu",
"Houwen",
""
]
] | We study gravitational lensing of light by hairy black holes, which, in a certain parameter regime, can possess two photon spheres of different size outside the event horizon. In particular, we focus on higher-order images of a point-like light source and a luminous celestial sphere produced by strong gravitational lensing near photon spheres. Two photon spheres usually triple the number of high-order images of a point-like light source. When a hairy black hole is illuminated by a celestial sphere, two photon spheres would give rise to two critical curves in the black hole image, and the smaller critical curve coincides with the shadow edge. In addition to a set of higher-order images of the celestial sphere outside the shadow edge, two more sets of higher-order images are observed inside and outside the larger critical curve, respectively. |
1203.4210 | Alexander Burinskii | Alexander Burinskii | Complex structure of Kerr-Schild geometry: Calabi-Yau twofold from the
Kerr theorem | 9 pages, 3 figures. Essay written for the Gravity Research Foundation
2012 Awards for Essays on Gravitation | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider Newman's representation of the Kerr geometry as a complex
retarded-time construction generated by a source propagating along a complex
world-line. We notice that the complex world-line forms really an open complex
string, endpoints of which should have independent dynamics by the string
excitations. The adjoined to complex Kerr string twistorial structure is
determined by the Kerr theorem, and we obtain that the resulting Kerr's
equation describes a quartic in projective twistor $CP^3 ,$ which is known as
Calabi-Yau twofold of superstring theory. Along with other remarkable
similarities with superstring theory, the Kerr geometry has principal
distinctions being the four-dimensional theory consistent with gravity at the
Compton scale, contrary to the Planck scale of the superstring theory.
| [
{
"created": "Mon, 19 Mar 2012 19:26:15 GMT",
"version": "v1"
}
] | 2012-03-20 | [
[
"Burinskii",
"Alexander",
""
]
] | We consider Newman's representation of the Kerr geometry as a complex retarded-time construction generated by a source propagating along a complex world-line. We notice that the complex world-line forms really an open complex string, endpoints of which should have independent dynamics by the string excitations. The adjoined to complex Kerr string twistorial structure is determined by the Kerr theorem, and we obtain that the resulting Kerr's equation describes a quartic in projective twistor $CP^3 ,$ which is known as Calabi-Yau twofold of superstring theory. Along with other remarkable similarities with superstring theory, the Kerr geometry has principal distinctions being the four-dimensional theory consistent with gravity at the Compton scale, contrary to the Planck scale of the superstring theory. |
1503.02981 | Steven Carlip | S. Carlip | Four-Dimensional Entropy from Three-Dimensional Gravity | 8 pages; v2: more references, typos fixed, minor rewording; v3: some
clearer explanations in response to referees, more references | Phys. Rev. Lett. 115, 071302 (2015) | 10.1103/PhysRevLett.115.071302 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | At the horizon of a black hole, the action of (3+1)-dimensional loop quantum
gravity acquires a boundary term that is formally identical to an action for
three-dimensional gravity. I show how to use this correspondence to obtain the
entropy of the (3+1)-dimensional black hole from well-understood conformal
field theory computations of the entropy in (2+1)-dimensional de Sitter space.
| [
{
"created": "Tue, 10 Mar 2015 16:32:44 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Mar 2015 20:23:52 GMT",
"version": "v2"
},
{
"created": "Fri, 3 Jul 2015 22:38:04 GMT",
"version": "v3"
}
] | 2015-08-19 | [
[
"Carlip",
"S.",
""
]
] | At the horizon of a black hole, the action of (3+1)-dimensional loop quantum gravity acquires a boundary term that is formally identical to an action for three-dimensional gravity. I show how to use this correspondence to obtain the entropy of the (3+1)-dimensional black hole from well-understood conformal field theory computations of the entropy in (2+1)-dimensional de Sitter space. |
1810.02115 | Kunihiko Hasegawa | Kunihiko Hasegawa, Tomotada Akutsu, Nobuhiro Kimura, Yoshio Saito,
Toshikazu Suzuki, Takayuki Tomaru, Ayako Ueda, and Shinji Miyoki | Molecular adsorbed layer formation on cooled mirrors and its impacts on
cryogenic gravitational wave telescopes | 11 pages, 13 figures | Phys. Rev. D 99, 022003 (2019) | 10.1103/PhysRevD.99.022003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cryogenic mirrors have been introduced to the KAGRA gravitational wave
telescope in Japan, and are also planned to be used in next-generation
gravitational wave telescopes to further improve their sensitivity. Molecular
gases inside vacuum chambers adhere to cold mirror surfaces because they lose
their kinetic energy when they hit cryogenic surfaces. Finally, a number of
adsorbed molecules form an adlayer, which will grow with time. The growing
adlayer functions as an optical coating and changes the properties of the
underlying mirror, such as reflectance, transmittance, and absorption, which
are carefully chosen to maximize the detector sensitivity. The adlayer possibly
affects the gravitational wave detector sensitivity. In order to characterize
these changes, a high-finesse Fabry--Perot cavity was introduced to a KAGRA
cryostat and the finesse of the cavity was monitored for 35 days under
cryogenic conditions. We confirmed that the molecular adlayer was formed on a
cold mirror and caused an oscillation in the finesse. The real and imaginary
parts of the refractive index of the adlayer were $1.26 \pm 0.073$ and $2.2
\times 10^{-7} \pm 1.3 \times 10^{-7} $, respectively. These are considered to
be that of $\mathrm{H_2O}$ molecules. The formation rate of the molecular
adlayer was 27 $\pm$ 1.9 $\mathrm{nm/day}$. In this paper, we describe
theoretical and experimental studies of the formation of a molecular adlayer on
cryogenic mirrors. Furthermore, the effects of a molecular adlayer on the
quantum noise and the input heat to the test mass are also discussed.
| [
{
"created": "Thu, 4 Oct 2018 09:20:57 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Dec 2018 04:59:01 GMT",
"version": "v2"
}
] | 2019-02-06 | [
[
"Hasegawa",
"Kunihiko",
""
],
[
"Akutsu",
"Tomotada",
""
],
[
"Kimura",
"Nobuhiro",
""
],
[
"Saito",
"Yoshio",
""
],
[
"Suzuki",
"Toshikazu",
""
],
[
"Tomaru",
"Takayuki",
""
],
[
"Ueda",
"Ayako",
""
],
... | Cryogenic mirrors have been introduced to the KAGRA gravitational wave telescope in Japan, and are also planned to be used in next-generation gravitational wave telescopes to further improve their sensitivity. Molecular gases inside vacuum chambers adhere to cold mirror surfaces because they lose their kinetic energy when they hit cryogenic surfaces. Finally, a number of adsorbed molecules form an adlayer, which will grow with time. The growing adlayer functions as an optical coating and changes the properties of the underlying mirror, such as reflectance, transmittance, and absorption, which are carefully chosen to maximize the detector sensitivity. The adlayer possibly affects the gravitational wave detector sensitivity. In order to characterize these changes, a high-finesse Fabry--Perot cavity was introduced to a KAGRA cryostat and the finesse of the cavity was monitored for 35 days under cryogenic conditions. We confirmed that the molecular adlayer was formed on a cold mirror and caused an oscillation in the finesse. The real and imaginary parts of the refractive index of the adlayer were $1.26 \pm 0.073$ and $2.2 \times 10^{-7} \pm 1.3 \times 10^{-7} $, respectively. These are considered to be that of $\mathrm{H_2O}$ molecules. The formation rate of the molecular adlayer was 27 $\pm$ 1.9 $\mathrm{nm/day}$. In this paper, we describe theoretical and experimental studies of the formation of a molecular adlayer on cryogenic mirrors. Furthermore, the effects of a molecular adlayer on the quantum noise and the input heat to the test mass are also discussed. |
gr-qc/0310036 | Robert Spero | Robert Spero, Andreas Kuhnert | The ST7 Interferometer | 11 pages, 5 figures including 1 photo, for special issue of
"Classical and Quantum Gravity," proceedings of Amaldi 5 | Class.Quant.Grav. 21 (2004) S589-S596 | 10.1088/0264-9381/21/5/030 | null | gr-qc | null | Two homodyne Michelson interferferometers aboard the LISA Pathfinder
spacecraft will measure the the positions of two free-floating test masses, as
part of the NASA ST7 mission. The interferometer is required to measure the
separation between the test masses with sensitivity of 30 pm/sqrt(Hz) at 10
mHz. The readout scheme is described, error sources are analyzed, and
experimental results are presented.
| [
{
"created": "Tue, 7 Oct 2003 01:28:16 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Spero",
"Robert",
""
],
[
"Kuhnert",
"Andreas",
""
]
] | Two homodyne Michelson interferferometers aboard the LISA Pathfinder spacecraft will measure the the positions of two free-floating test masses, as part of the NASA ST7 mission. The interferometer is required to measure the separation between the test masses with sensitivity of 30 pm/sqrt(Hz) at 10 mHz. The readout scheme is described, error sources are analyzed, and experimental results are presented. |
gr-qc/0108040 | Steven Carlip | S. Carlip | Quantum Gravity: a Progress Report | 72 pages, 5 figures; review solicited by Reports on Progress in
Physics, http://www.iop.org/Journals/RoPP | Rept.Prog.Phys.64:885,2001 | 10.1088/0034-4885/64/8/301 | UCD-2001-04 | gr-qc hep-th | null | The problem of reconciling general relativity and quantum theory has
fascinated and bedeviled physicists for more than 70 years. Despite recent
progress in string theory and loop quantum gravity, a complete solution remains
out of reach. I review the status of the continuing effort to quantize gravity,
emphasizing the underlying conceptual issues and the various attempts to come
to grips with them.
| [
{
"created": "Tue, 14 Aug 2001 18:01:55 GMT",
"version": "v1"
}
] | 2010-04-28 | [
[
"Carlip",
"S.",
""
]
] | The problem of reconciling general relativity and quantum theory has fascinated and bedeviled physicists for more than 70 years. Despite recent progress in string theory and loop quantum gravity, a complete solution remains out of reach. I review the status of the continuing effort to quantize gravity, emphasizing the underlying conceptual issues and the various attempts to come to grips with them. |
1408.5232 | Ahmet Baykal | Ahmet Baykal | An alternative derivation of the Minimal massive 3D gravity | 12 pages in IOP article format, improved presentation with minor
corrections, an appendix added | Class. Quantum Grav. 32 (2015) 025013 | 10.1088/0264-9381/32/2/025013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By using the algebra of exterior forms and the first order formalism with
constraints, an alternative derivation of the field equations for the Minimal
massive 3D gravity model is presented.
| [
{
"created": "Fri, 22 Aug 2014 09:05:04 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Dec 2014 08:11:58 GMT",
"version": "v2"
}
] | 2014-12-24 | [
[
"Baykal",
"Ahmet",
""
]
] | By using the algebra of exterior forms and the first order formalism with constraints, an alternative derivation of the field equations for the Minimal massive 3D gravity model is presented. |
2306.06937 | Riccardo Della Monica | Rebeca Fern\'andez Fern\'andez, Riccardo Della Monica, Ivan de Martino | Constraining an Einstein-Maxwell-dilaton-axion black hole at the
Galactic Center with the orbit of the S2 star | 17 pages, 5 figures, 2 tables. Comments are welcome | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive new constraints on the dilaton parameter appearing in the
spherically-symmetric black hole solution of Einstein-Maxwell-dilaton-axion
gravity, by studying the geodesic motion of the S2 star in the Galactic Center.
Einstein-Maxwell-dilaton-axion black holes represent a compelling alternative
to the standard black hole paradigm in General Relativity. This theory emerges
from the low energy effective action of the heterotic string theory and has
been proven to predict peculiar observational features from the direct imaging
of black hole shadows. At a fundamental level, Einstein-Maxwell-dilaton-axion
includes additional electromagnetic, dilatonic and axionic fields coupled to
the space-time metric. When considering charged non-rotating black hole
solutions, the additional fields endow the metric with one extra parameter $b$,
called dilaton parameter, that is theoretically bound to $0<b<M$. Using
publicly available astrometric data for S2 we derive an upper bound on
$b\lesssim 12M$ at 95% confidence level and we demonstrate that only including
the measurement of the relativistic orbital precession for S2 is sufficient to
reduce this bound to $b\lesssim 1.4M$ at the same confidence level.
Additionally, using a mock data mimicking future observations of S2 with the
GRAVITY interferometer, we show that improved astrometric precision can help
further narrow down the allowed dilaton parameter range to $b\lesssim0.033M$
after monitoring the S2 orbit for one and a half period.
| [
{
"created": "Mon, 12 Jun 2023 08:14:42 GMT",
"version": "v1"
}
] | 2023-06-13 | [
[
"Fernández",
"Rebeca Fernández",
""
],
[
"Della Monica",
"Riccardo",
""
],
[
"de Martino",
"Ivan",
""
]
] | We derive new constraints on the dilaton parameter appearing in the spherically-symmetric black hole solution of Einstein-Maxwell-dilaton-axion gravity, by studying the geodesic motion of the S2 star in the Galactic Center. Einstein-Maxwell-dilaton-axion black holes represent a compelling alternative to the standard black hole paradigm in General Relativity. This theory emerges from the low energy effective action of the heterotic string theory and has been proven to predict peculiar observational features from the direct imaging of black hole shadows. At a fundamental level, Einstein-Maxwell-dilaton-axion includes additional electromagnetic, dilatonic and axionic fields coupled to the space-time metric. When considering charged non-rotating black hole solutions, the additional fields endow the metric with one extra parameter $b$, called dilaton parameter, that is theoretically bound to $0<b<M$. Using publicly available astrometric data for S2 we derive an upper bound on $b\lesssim 12M$ at 95% confidence level and we demonstrate that only including the measurement of the relativistic orbital precession for S2 is sufficient to reduce this bound to $b\lesssim 1.4M$ at the same confidence level. Additionally, using a mock data mimicking future observations of S2 with the GRAVITY interferometer, we show that improved astrometric precision can help further narrow down the allowed dilaton parameter range to $b\lesssim0.033M$ after monitoring the S2 orbit for one and a half period. |
gr-qc/0312033 | Dieter Brill | Dieter R. Brill | Lattice Universes in 2+1-dimensional gravity | 14 pages 7 figures, to appear in Festschrift for Vince Moncrief (CQG) | Class.Quant.Grav. 21 (2004) S97-S108 | 10.1088/0264-9381/21/3/007 | null | gr-qc | null | Lattice universes are spatially closed space-times of spherical topology in
the large, containing masses or black holes arranged in the symmetry of a
regular polygon or polytope. Exact solutions for such spacetimes are found in
2+1 dimensions for Einstein gravity with a non-positive cosmological constant.
By means of a mapping that preserves the essential nature of geodesics we
establish analogies between the flat and the negative curvature cases. This map
also allows treatment of point particles and black holes on a similar footing.
| [
{
"created": "Thu, 4 Dec 2003 23:20:55 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Brill",
"Dieter R.",
""
]
] | Lattice universes are spatially closed space-times of spherical topology in the large, containing masses or black holes arranged in the symmetry of a regular polygon or polytope. Exact solutions for such spacetimes are found in 2+1 dimensions for Einstein gravity with a non-positive cosmological constant. By means of a mapping that preserves the essential nature of geodesics we establish analogies between the flat and the negative curvature cases. This map also allows treatment of point particles and black holes on a similar footing. |
gr-qc/0604045 | Carlo Rovelli | Carlo Rovelli | Unfinished revolution | 8 pages. Version 2: minor corrections | null | null | null | gr-qc hep-th | null | Introductive chapter of a book on Quantum Gravity, edited by Daniele Oriti,
to appear with Cambridge University Press.
| [
{
"created": "Mon, 10 Apr 2006 13:06:39 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Apr 2006 07:55:42 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Rovelli",
"Carlo",
""
]
] | Introductive chapter of a book on Quantum Gravity, edited by Daniele Oriti, to appear with Cambridge University Press. |
gr-qc/0110121 | Duncan Noltingk | D. Noltingk | BRST Quantisation of Histories Electrodynamics | Introductory material on BRST methods expanded and mistake corrected
in final section. To appear in Journ Math Phys | J.Math.Phys. 43 (2002) 4801-4818 | 10.1063/1.1503867 | null | gr-qc | null | This paper is a continuation of earlier work where a classical history theory
of pure electrodynamics was developed in which the the history fields have
\emph{five} components. The extra component is associated with an extra
constraint, thus enlarging the gauge group of histories electrodynamics. In
this paper we quantise the classical theory developed previously by two
methods. Firstly we quantise the reduced classical history space, to obtain a
reduced quantum history theory. Secondly we quantise the classical
BRST-extended history space, and use the BRST charge to define a
`cohomological' quantum history theory. Finally we show that the reduced
history theory is isomorphic, as a history theory, to the cohomological history
theory.
| [
{
"created": "Mon, 29 Oct 2001 13:32:55 GMT",
"version": "v1"
},
{
"created": "Sun, 19 May 2002 16:36:44 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Noltingk",
"D.",
""
]
] | This paper is a continuation of earlier work where a classical history theory of pure electrodynamics was developed in which the the history fields have \emph{five} components. The extra component is associated with an extra constraint, thus enlarging the gauge group of histories electrodynamics. In this paper we quantise the classical theory developed previously by two methods. Firstly we quantise the reduced classical history space, to obtain a reduced quantum history theory. Secondly we quantise the classical BRST-extended history space, and use the BRST charge to define a `cohomological' quantum history theory. Finally we show that the reduced history theory is isomorphic, as a history theory, to the cohomological history theory. |
2012.12158 | Daniel Hartwig | Daniel Hartwig, Jan Petermann, Roman Schnabel | Mechanical parametric feedback-cooling for pendulum-based gravity
experiments | 5 pages, 4 figures, submitted to Physical Review Letters, replaced
original version to include missing acknowledgment | null | null | null | gr-qc physics.ins-det | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational forces that oscillate at audio-band frequencies are measured
with masses suspended as pendulums that have resonance frequencies even lower.
If the pendulum is excited by thermal energy or by seismic motion of the
environment, the measurement sensitivity is reduced. Conventionally, this
problem is mitigated by seismic isolation and linear damping, potentially
combined with cryogenic cooling. Here, we propose mechanical parametric cooling
of the pendulum motion during the gravitational field measurement. We report a
proof of principle demonstration in the seismic noise dominated regime and
achieve a damping factor of the pendulum motion of 5.7. We find a model system
for which mechanical parametric feedback cooling reaches the quantum mechanical
regime near the ground state. More feasible applications we anticipate in
gravitational-wave detectors.
| [
{
"created": "Tue, 22 Dec 2020 16:47:44 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Feb 2021 17:31:24 GMT",
"version": "v2"
}
] | 2021-02-18 | [
[
"Hartwig",
"Daniel",
""
],
[
"Petermann",
"Jan",
""
],
[
"Schnabel",
"Roman",
""
]
] | Gravitational forces that oscillate at audio-band frequencies are measured with masses suspended as pendulums that have resonance frequencies even lower. If the pendulum is excited by thermal energy or by seismic motion of the environment, the measurement sensitivity is reduced. Conventionally, this problem is mitigated by seismic isolation and linear damping, potentially combined with cryogenic cooling. Here, we propose mechanical parametric cooling of the pendulum motion during the gravitational field measurement. We report a proof of principle demonstration in the seismic noise dominated regime and achieve a damping factor of the pendulum motion of 5.7. We find a model system for which mechanical parametric feedback cooling reaches the quantum mechanical regime near the ground state. More feasible applications we anticipate in gravitational-wave detectors. |
1903.08312 | Yun Soo Myung | Yun Soo Myung, De-Cheng Zou | Black holes in Gauss-Bonnet and Chern-Simons-scalar theory | 18 pages, 2 figures, version to appear in IJMPD | null | 10.1142/S0218271819501141 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We carry out the stability analysis of the Schwarzschild black hole in
Gauss-Bonnet and Chern-Simons-scalar theory. Here, we introduce two quadratic
scalar couplings ($\phi_1^2,\phi_2^2$) to Gauss-Bonnet and Chern-Simons terms,
where the former term is parity-even, while the latter one is parity-odd. The
perturbation equation for the scalar $\phi_1$ is the Klein-Gordon equation with
an effective mass, while the perturbation equation for $\phi_2$ is coupled to
the parity-odd metric perturbation, providing a system of two coupled
equations. It turns out that the Schwarzschild black hole is unstable against
$\phi_1$ perturbation, leading to scalarized black holes, while the black hole
is stable against $\phi_2$ and metric perturbations, implying no scalarized
black holes.
| [
{
"created": "Wed, 20 Mar 2019 01:59:13 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Mar 2019 00:39:35 GMT",
"version": "v2"
}
] | 2019-07-24 | [
[
"Myung",
"Yun Soo",
""
],
[
"Zou",
"De-Cheng",
""
]
] | We carry out the stability analysis of the Schwarzschild black hole in Gauss-Bonnet and Chern-Simons-scalar theory. Here, we introduce two quadratic scalar couplings ($\phi_1^2,\phi_2^2$) to Gauss-Bonnet and Chern-Simons terms, where the former term is parity-even, while the latter one is parity-odd. The perturbation equation for the scalar $\phi_1$ is the Klein-Gordon equation with an effective mass, while the perturbation equation for $\phi_2$ is coupled to the parity-odd metric perturbation, providing a system of two coupled equations. It turns out that the Schwarzschild black hole is unstable against $\phi_1$ perturbation, leading to scalarized black holes, while the black hole is stable against $\phi_2$ and metric perturbations, implying no scalarized black holes. |
2108.00494 | James B. Hartle | James B. Hartle (University of California, Santa Barbara) | Prediction in Quantum Cosmology | 34 pages, 5 figures | null | null | null | gr-qc astro-ph.CO hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lectures by the author at the 1986 Cargese summer school modestly corrected
and uploaded for greater accessibility. Some of the author's views on the
quantum mechanics of cosmology have changed from those presented here but may
still be of historical interest. The material on the Born-Oppenheimer
approximation for solving the Wheeler-DeWitt equation and the work on the
classical geometry limit and the approximation of quantum field theory in
curved spacetime are still of interest and of use.
| [
{
"created": "Sun, 1 Aug 2021 17:07:46 GMT",
"version": "v1"
}
] | 2021-08-03 | [
[
"Hartle",
"James B.",
"",
"University of California, Santa Barbara"
]
] | Lectures by the author at the 1986 Cargese summer school modestly corrected and uploaded for greater accessibility. Some of the author's views on the quantum mechanics of cosmology have changed from those presented here but may still be of historical interest. The material on the Born-Oppenheimer approximation for solving the Wheeler-DeWitt equation and the work on the classical geometry limit and the approximation of quantum field theory in curved spacetime are still of interest and of use. |
2104.09209 | Felix Spengler | Felix Spengler, Dennis R\"atzel and Daniel Braun | Perspectives of measuring gravitational effects of laser light and
particle beams | Main Text: 23 pages, 1 figure. Appendix: 7 pages, 2 figures | New J. Phys. 24 053021 (2022) | 10.1088/1367-2630/ac5372 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study possibilities of creation and detection of oscillating gravitational
fields from lab-scale high energy, relativistic sources. The sources considered
are high energy laser beams in an optical cavity and the ultra-relativistic
proton bunches circulating in the beam of the Large Hadron Collider (LHC) at
CERN. These sources allow for signal frequencies much higher and far narrower
in bandwidth than what most celestial sources produce. In addition, by
modulating the beams, one can adjust the source frequency over a very broad
range, from Hz to GHz. The gravitational field of these sources and responses
of a variety of detectors are analyzed. We optimize a mechanical oscillator
such as a pendulum or torsion balance as detector and find parameter regimes
such that -- combined with the planned high-luminosity upgrade of the LHC as a
source -- a signal-to-noise ratio substantially larger than 1 should be
achievable at least in principle, neglecting all sources of technical noise.
This opens new perspectives of studying general relativistic effects and
possibly quantum-gravitational effects with ultra-relativistic, well-controlled
terrestrial sources.
| [
{
"created": "Mon, 19 Apr 2021 11:11:13 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Apr 2021 17:46:24 GMT",
"version": "v2"
},
{
"created": "Thu, 1 Jul 2021 15:54:15 GMT",
"version": "v3"
},
{
"created": "Sun, 15 May 2022 15:17:52 GMT",
"version": "v4"
},
{
"cr... | 2022-05-25 | [
[
"Spengler",
"Felix",
""
],
[
"Rätzel",
"Dennis",
""
],
[
"Braun",
"Daniel",
""
]
] | We study possibilities of creation and detection of oscillating gravitational fields from lab-scale high energy, relativistic sources. The sources considered are high energy laser beams in an optical cavity and the ultra-relativistic proton bunches circulating in the beam of the Large Hadron Collider (LHC) at CERN. These sources allow for signal frequencies much higher and far narrower in bandwidth than what most celestial sources produce. In addition, by modulating the beams, one can adjust the source frequency over a very broad range, from Hz to GHz. The gravitational field of these sources and responses of a variety of detectors are analyzed. We optimize a mechanical oscillator such as a pendulum or torsion balance as detector and find parameter regimes such that -- combined with the planned high-luminosity upgrade of the LHC as a source -- a signal-to-noise ratio substantially larger than 1 should be achievable at least in principle, neglecting all sources of technical noise. This opens new perspectives of studying general relativistic effects and possibly quantum-gravitational effects with ultra-relativistic, well-controlled terrestrial sources. |
0910.2054 | Roberto Chan | R. Chan, M.F.A. da Silva and P. Rocha | How the Cosmological Constant Affects Gravastar Formation | 36 pages and 23 figures, correcting some typos and clarifying some
points, accepted for publication in JCAP | JCAP 0912:017,2009 | 10.1088/1475-7516/2009/12/017 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Here we generalized a previous model of gravastar consisted of an internal de
Sitter spacetime, a dynamical infinitely thin shell with an equation of state,
but now we consider an external de Sitter-Schwarzschild spacetime. We have
shown explicitly that the final output can be a black hole, a "bounded
excursion" stable gravastar, a stable gravastar, or a de Sitter spacetime,
depending on the total mass of the system, the cosmological constants, the
equation of state of the thin shell and the initial position of the dynamical
shell. We have found that the exterior cosmological constant imposes a limit to
the gravastar formation, i.e., the exterior cosmological constant must be
smaller than the interior cosmological constant. Besides, we have also shown
that, in the particular case where the Schwarzschild mass vanishes, no stable
gravastar can be formed, but we still have formation of black hole.
| [
{
"created": "Sun, 11 Oct 2009 21:59:57 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Dec 2009 18:20:57 GMT",
"version": "v2"
}
] | 2012-10-25 | [
[
"Chan",
"R.",
""
],
[
"da Silva",
"M. F. A.",
""
],
[
"Rocha",
"P.",
""
]
] | Here we generalized a previous model of gravastar consisted of an internal de Sitter spacetime, a dynamical infinitely thin shell with an equation of state, but now we consider an external de Sitter-Schwarzschild spacetime. We have shown explicitly that the final output can be a black hole, a "bounded excursion" stable gravastar, a stable gravastar, or a de Sitter spacetime, depending on the total mass of the system, the cosmological constants, the equation of state of the thin shell and the initial position of the dynamical shell. We have found that the exterior cosmological constant imposes a limit to the gravastar formation, i.e., the exterior cosmological constant must be smaller than the interior cosmological constant. Besides, we have also shown that, in the particular case where the Schwarzschild mass vanishes, no stable gravastar can be formed, but we still have formation of black hole. |
1707.09180 | Gabor Etesi | Gabor Etesi | Exotica and the status of the strong cosmic censor conjecture in four
dimensions | 24 pages, 2 figures, LaTeX; published version with an extra "Footnote
3" on p. 10. This work is partly based on arXiv:1503.04945 [gr-qc] | Class. Quantum Grav. 34, No. 24, 245010-1-245010-26 (2017) | 10.1088/1361-6382/aa945b | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An immense class of physical counterexamples to the four dimensional strong
cosmic censor conjecture---in its usual broad formulation---is exhibited. More
precisely, out of any closed and simply connected 4-manifold an open Ricci-flat
Lorentzian 4-manifold is constructed which is not globally hyperbolic and no
perturbation of it, in any sense, can be globally hyperbolic. This very stable
non-global-hyperbolicity is the consequence of our open spaces having a
"creased end" i.e., an end diffeomorphic to an exotic ${\mathbb R}^4$. Open
manifolds having an end like this is a typical phenomenon in four dimensions.
The construction is based on a collection of results of Gompf and Taubes on
exotic and self-dual spaces, respectively, as well as applying Penrose'
non-linear graviton construction (i.e., twistor theory) to solve the Riemannian
Einstein's equation. These solutions then are converted into stably
non-globally-hyperbolic Lorentzian vacuum solutions. It follows that the
plethora of vacuum solutions we found cannot be obtained via the initial value
formulation of the Einstein's equation because they are "too long" in a certain
sense (explained in the text). This different (i.e., not based on the initial
value formulation but twistorial) technical background might partially explain
why the existence of vacuum solutions of this kind have not been realized so
far in spite of the fact that, apparently, their superabundance compared to the
well-known globally hyperbolic vacuum solutions is overwhelming.
| [
{
"created": "Fri, 28 Jul 2017 10:34:40 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Nov 2017 10:12:43 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Sep 2018 10:57:43 GMT",
"version": "v3"
}
] | 2018-10-01 | [
[
"Etesi",
"Gabor",
""
]
] | An immense class of physical counterexamples to the four dimensional strong cosmic censor conjecture---in its usual broad formulation---is exhibited. More precisely, out of any closed and simply connected 4-manifold an open Ricci-flat Lorentzian 4-manifold is constructed which is not globally hyperbolic and no perturbation of it, in any sense, can be globally hyperbolic. This very stable non-global-hyperbolicity is the consequence of our open spaces having a "creased end" i.e., an end diffeomorphic to an exotic ${\mathbb R}^4$. Open manifolds having an end like this is a typical phenomenon in four dimensions. The construction is based on a collection of results of Gompf and Taubes on exotic and self-dual spaces, respectively, as well as applying Penrose' non-linear graviton construction (i.e., twistor theory) to solve the Riemannian Einstein's equation. These solutions then are converted into stably non-globally-hyperbolic Lorentzian vacuum solutions. It follows that the plethora of vacuum solutions we found cannot be obtained via the initial value formulation of the Einstein's equation because they are "too long" in a certain sense (explained in the text). This different (i.e., not based on the initial value formulation but twistorial) technical background might partially explain why the existence of vacuum solutions of this kind have not been realized so far in spite of the fact that, apparently, their superabundance compared to the well-known globally hyperbolic vacuum solutions is overwhelming. |
1310.1322 | Roland Steinbauer | Alexander Lecke, Roland Steinbauer, Robert Svarc | The regularity of geodesics in impulsive pp-waves | final version, minor changes, reference added | Gen. Relativ. Gravit. 46, 1648, 8p, 2014 | 10.1007/s10714-013-1648-0 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the geodesic equation in impulsive pp-wave space-times in Rosen
form, where the metric is of Lipschitz regularity. We prove that the geodesics
(in the sense of Caratheodory) are actually continuously differentiable,
thereby rigorously justifying the $C^1$-matching procedure which has been used
in the literature to explicitly derive the geodesics in space-times of this
form.
| [
{
"created": "Fri, 4 Oct 2013 15:38:34 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Feb 2014 19:28:04 GMT",
"version": "v2"
}
] | 2014-02-24 | [
[
"Lecke",
"Alexander",
""
],
[
"Steinbauer",
"Roland",
""
],
[
"Svarc",
"Robert",
""
]
] | We consider the geodesic equation in impulsive pp-wave space-times in Rosen form, where the metric is of Lipschitz regularity. We prove that the geodesics (in the sense of Caratheodory) are actually continuously differentiable, thereby rigorously justifying the $C^1$-matching procedure which has been used in the literature to explicitly derive the geodesics in space-times of this form. |
gr-qc/0410067 | Sugumi Kanno | Sugumi Kanno, Jiro Soda | On The Higher Codimension Braneworld | Talk given at Gamov Memorial International Conference, Odessa,
Ukraine, August 8-14, 2004; 4 pages | null | null | null | gr-qc | null | We study a codimension 2 braneworld in the Einstein-Gauss-Bonnet gravity. In
the linear regime, we show the conventional Einstein gravity can be recovered
on the brane. While, in the nonlinear regime, we find corrections due to the
thickness and the bulk geometry.
| [
{
"created": "Fri, 15 Oct 2004 09:41:55 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kanno",
"Sugumi",
""
],
[
"Soda",
"Jiro",
""
]
] | We study a codimension 2 braneworld in the Einstein-Gauss-Bonnet gravity. In the linear regime, we show the conventional Einstein gravity can be recovered on the brane. While, in the nonlinear regime, we find corrections due to the thickness and the bulk geometry. |
1305.0653 | Przemyslaw Malkiewicz | Herve Bergeron, Andrea Dapor, Jean Pierre Gazeau and Przemyslaw
Malkiewicz | Smooth Big Bounce from Affine Quantization | 22+9 pages, 3 figures | Phys. Rev. D 89, 083522 (2014) | 10.1103/PhysRevD.89.083522 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the possibility of dealing with gravitational singularities on a
quantum level through the use of coherent state or wavelet quantization instead
of canonical quantization. We consider the Robertson-Walker metric coupled to a
perfect fluid. It is the simplest model of a gravitational collapse and the
results obtained here may serve as a useful starting point for more complex
investigations in future. We follow a quantization procedure based on affine
coherent states or wavelets built from the unitary irreducible representation
of the affine group of the real line with positive dilation. The main issue of
our approach is the appearance of a quantum centrifugal potential allowing for
regularization of the singularity, essential self-adjointness of the
Hamiltonian, and unambiguous quantum dynamical evolution.
| [
{
"created": "Fri, 3 May 2013 09:40:53 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jun 2013 07:30:21 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Jun 2013 19:41:17 GMT",
"version": "v3"
},
{
"created": "Tue, 28 Jan 2014 13:42:55 GMT",
"version": "v4"
}
] | 2015-06-15 | [
[
"Bergeron",
"Herve",
""
],
[
"Dapor",
"Andrea",
""
],
[
"Gazeau",
"Jean Pierre",
""
],
[
"Malkiewicz",
"Przemyslaw",
""
]
] | We examine the possibility of dealing with gravitational singularities on a quantum level through the use of coherent state or wavelet quantization instead of canonical quantization. We consider the Robertson-Walker metric coupled to a perfect fluid. It is the simplest model of a gravitational collapse and the results obtained here may serve as a useful starting point for more complex investigations in future. We follow a quantization procedure based on affine coherent states or wavelets built from the unitary irreducible representation of the affine group of the real line with positive dilation. The main issue of our approach is the appearance of a quantum centrifugal potential allowing for regularization of the singularity, essential self-adjointness of the Hamiltonian, and unambiguous quantum dynamical evolution. |
2405.10585 | Omar Mustafa | Omar Mustafa | KG-oscillators in Som-Raychaudhuri rotating cosmic string spacetime in a
mixed magnetic field | 10 pages, 2 figures | Nucl. Phys. B 1006 (2024) 116629 | 10.1016/j.nuclphysb.2024.116629 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We investigate Klein-Gordon (KG) oscillators in a G\"{o}% del-type
Som-Raychaudhuri spacetime in a mixed magnetic field (given by the vector
potential $A_{\mu }=\left( 0,0,A_{\varphi },0\right) $, with $% A_{\varphi
}=B_{1}r^{2}/2+B_{2}r$). The resulting KG equation takes a Schr%
\"{o}dinger-like form (with an oscillator plus a linear plus a Coulomb-like
interactions potential) that admits a solution in the form of biconfluent Heun
functions/series $H_{B}\left( \alpha ,\beta ,\gamma ,\delta ,z\right) $% . The
usual power series expansion of which is truncated to a polynomial of \ order
$n_{r}+1=n\geq 1$ through the usual condition $\gamma =2\left( n_{r}+1\right)
+\alpha $. However, we use the very recent recipe suggested by Mustafa
\cite{1.29} as an alternative parametric condition/correlation. i.e., $\delta
=-\beta \left( 2n_{r}+\alpha +3\right) $, to facilitate conditional exact
solvability of the problem. We discuss and report the effects of the mixed
magnetic field as well as the effects of the G\"{o}del-type SR-spacetime
background on the KG-oscillators' spectroscopic structure.
| [
{
"created": "Fri, 17 May 2024 07:19:46 GMT",
"version": "v1"
}
] | 2024-08-01 | [
[
"Mustafa",
"Omar",
""
]
] | We investigate Klein-Gordon (KG) oscillators in a G\"{o}% del-type Som-Raychaudhuri spacetime in a mixed magnetic field (given by the vector potential $A_{\mu }=\left( 0,0,A_{\varphi },0\right) $, with $% A_{\varphi }=B_{1}r^{2}/2+B_{2}r$). The resulting KG equation takes a Schr% \"{o}dinger-like form (with an oscillator plus a linear plus a Coulomb-like interactions potential) that admits a solution in the form of biconfluent Heun functions/series $H_{B}\left( \alpha ,\beta ,\gamma ,\delta ,z\right) $% . The usual power series expansion of which is truncated to a polynomial of \ order $n_{r}+1=n\geq 1$ through the usual condition $\gamma =2\left( n_{r}+1\right) +\alpha $. However, we use the very recent recipe suggested by Mustafa \cite{1.29} as an alternative parametric condition/correlation. i.e., $\delta =-\beta \left( 2n_{r}+\alpha +3\right) $, to facilitate conditional exact solvability of the problem. We discuss and report the effects of the mixed magnetic field as well as the effects of the G\"{o}del-type SR-spacetime background on the KG-oscillators' spectroscopic structure. |
1404.0778 | Davood Momeni Dr | Davood Momeni, Ratbay Myrzakulov | Conformal Invariant Teleparallel Cosmology | Revised version; References added,Accepted for publication in The
"European Physical Journal - Plus" | Eur. Phys. J. Plus (2014) 129: 137 | 10.1140/epjp/i2014-14137-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study teleparallel gravitational theories with are invariant under the
conformal transformations. Wide family of the gravitational Lagrangians that
are invariant under conformal transformations have investigated. Cosmological
solutions inspired by the observational data for a flat Universe in the vacuum
has been found. To add matter fields to the cosmological models by preserving
the conformal symmetry there are significant limitations.
Friedmann-Robertson-Walker (FRW) equations based on the effective terms of
energy density and pressure have been rewriting and continuity equation for the
effective quantities are derived. In the vacuum and in the absence of any
matter field,the FRW equation has an exact solution for Hubble parameter which
is consistent with the cosmological data,specially given analytical solution is
in good agreement with $\Lambda$CDM model in the present time. Then the scalar
field-Torsion models in the cosmological FRW background investigated. Massless
scalar field equations are very complex with an exact analytical solution in
special limits. We have shown that the Lagrangian scalar field with self
interaction $V(\phi)=\frac{1}{4!}\mu\phi^4$ can be written that the conformal
symmetry is preserved.
| [
{
"created": "Thu, 3 Apr 2014 06:49:46 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jun 2014 15:47:03 GMT",
"version": "v2"
}
] | 2014-06-24 | [
[
"Momeni",
"Davood",
""
],
[
"Myrzakulov",
"Ratbay",
""
]
] | We study teleparallel gravitational theories with are invariant under the conformal transformations. Wide family of the gravitational Lagrangians that are invariant under conformal transformations have investigated. Cosmological solutions inspired by the observational data for a flat Universe in the vacuum has been found. To add matter fields to the cosmological models by preserving the conformal symmetry there are significant limitations. Friedmann-Robertson-Walker (FRW) equations based on the effective terms of energy density and pressure have been rewriting and continuity equation for the effective quantities are derived. In the vacuum and in the absence of any matter field,the FRW equation has an exact solution for Hubble parameter which is consistent with the cosmological data,specially given analytical solution is in good agreement with $\Lambda$CDM model in the present time. Then the scalar field-Torsion models in the cosmological FRW background investigated. Massless scalar field equations are very complex with an exact analytical solution in special limits. We have shown that the Lagrangian scalar field with self interaction $V(\phi)=\frac{1}{4!}\mu\phi^4$ can be written that the conformal symmetry is preserved. |
1504.06941 | Edwin J. Son | Edwin J. Son and Wontae Kim | Note on uncertainty relations in doubly special relativity and rainbow
gravity | 7 pages | Mod. Phys. Lett. A, Vol. 30, No. 33 (2015) 1550178 | 10.1142/S0217732315501783 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present commutation relations depending on the rainbow functions which are
slightly different from the well-known results. However, the advantage of these
new commutation relations are compatible with the calculation of the Hawking
temperature in the rainbow Schwarzschild black hole.
| [
{
"created": "Mon, 27 Apr 2015 06:11:18 GMT",
"version": "v1"
}
] | 2015-09-30 | [
[
"Son",
"Edwin J.",
""
],
[
"Kim",
"Wontae",
""
]
] | We present commutation relations depending on the rainbow functions which are slightly different from the well-known results. However, the advantage of these new commutation relations are compatible with the calculation of the Hawking temperature in the rainbow Schwarzschild black hole. |
gr-qc/0003053 | Gorbatsievich Alexander K. | A.K.Gorbatsievich | On the Axiomatics of the 5-dimensional Projective Unified Field Theory
of Schmutzer | 32 pages, 1 figure, LaTeX 2e, will be submitted to Genaral Relativity
and Gravitation | Gen.Rel.Grav. 33 (2001) 965-998 | 10.1023/A:1010220113388 | null | gr-qc | null | For more than 40 years E.Schmutzer has developed a new approach to the
(5-dimensional) projective relativistic theory which he later called Projective
Unified Field Theory (PUFT). In the present paper we introduce a new axiomatics
for Schmutzer's theory. By means of this axiomatics we can give a new
geometrical interpretation of the physical concept of the PUFT.
| [
{
"created": "Tue, 14 Mar 2000 09:12:40 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Gorbatsievich",
"A. K.",
""
]
] | For more than 40 years E.Schmutzer has developed a new approach to the (5-dimensional) projective relativistic theory which he later called Projective Unified Field Theory (PUFT). In the present paper we introduce a new axiomatics for Schmutzer's theory. By means of this axiomatics we can give a new geometrical interpretation of the physical concept of the PUFT. |
2208.08702 | Siyuan Ma | Siyuan Ma and Lin Zhang | Precise late-time asymptotics of scalar field in the interior of a
subextreme Kerr black hole and its application in Strong Cosmic Censorship
conjecture | Compatible with the version that will appear in Transaction of the
AMS | Transaction of the AMS, 2023 | null | null | gr-qc math.AP | http://creativecommons.org/publicdomain/zero/1.0/ | In this work, we compute the precise late-time asymptotics for the scalar
field in the interior of a non-static subextreme Kerr black hole, based on
recent progress on deriving its precise asymptotics in the Kerr exterior
region. This provides a new proof of the generic
$H^1_{\text{loc}}$-inextendibility of the Kerr Cauchy horizon against scalar
perturbations that is first shown by Luk--Sbierski (J. Func. Anal., 2016). The
analogous results in Reissner--Nordstr\"{o}m spacetimes are also discussed.
| [
{
"created": "Thu, 18 Aug 2022 08:26:49 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Jul 2023 02:50:24 GMT",
"version": "v2"
}
] | 2023-07-06 | [
[
"Ma",
"Siyuan",
""
],
[
"Zhang",
"Lin",
""
]
] | In this work, we compute the precise late-time asymptotics for the scalar field in the interior of a non-static subextreme Kerr black hole, based on recent progress on deriving its precise asymptotics in the Kerr exterior region. This provides a new proof of the generic $H^1_{\text{loc}}$-inextendibility of the Kerr Cauchy horizon against scalar perturbations that is first shown by Luk--Sbierski (J. Func. Anal., 2016). The analogous results in Reissner--Nordstr\"{o}m spacetimes are also discussed. |
1702.00472 | Aida Ahmadzadegan | Aida Ahmadzadegan, Achim Kempf | On the Unruh effect, trajectories and information | 12 pages, 3 figures | Class. Quantum Grav. 1361-6382 (2018) | 10.1088/1361-6382/aad13a | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the trajectories which maximize the Unruh effect, mode by mode,
when given a fixed energy budget for acceleration. We find that Unruh processes
are most likely to occur, and therefore potentially best observable, for
certain trajectories whose acceleration is not uniform. In practice, the
precise form of optimal trajectories depends on experimental bounds on how fast
the acceleration can be changed. We also show that the Unruh spectra of
arbitrarily accelerated observers contain the complete information to
reconstruct the observers' trajectories.
| [
{
"created": "Wed, 1 Feb 2017 22:06:22 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Feb 2017 00:27:03 GMT",
"version": "v2"
},
{
"created": "Sat, 17 Nov 2018 18:56:51 GMT",
"version": "v3"
}
] | 2018-11-20 | [
[
"Ahmadzadegan",
"Aida",
""
],
[
"Kempf",
"Achim",
""
]
] | We calculate the trajectories which maximize the Unruh effect, mode by mode, when given a fixed energy budget for acceleration. We find that Unruh processes are most likely to occur, and therefore potentially best observable, for certain trajectories whose acceleration is not uniform. In practice, the precise form of optimal trajectories depends on experimental bounds on how fast the acceleration can be changed. We also show that the Unruh spectra of arbitrarily accelerated observers contain the complete information to reconstruct the observers' trajectories. |
1209.3950 | Stefano Ansoldi | Stefano Ansoldi and Lorenzo Sindoni | Multihorizon regular black holes | To appear in the proceedings of the 13th Marcel Grossmann Meeting,
Stockholm 1-7 July 2012 (3 pages, 1 figure); references added | null | null | AEI-2012-083 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a general procedure to generate a class of (everywhere regular)
solutions of Einstein equations that can have an (a-priori fixed) arbitrary
number of horizons. We then report on work currently in progress i) to find a
suitable classification scheme for the maximal extension of these solutions and
ii) to interpret the source term in Einstein equations as an effective
contribution arising from higher dimensional and/or modified gravity.
| [
{
"created": "Tue, 18 Sep 2012 13:19:40 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Sep 2012 12:20:33 GMT",
"version": "v2"
}
] | 2012-09-24 | [
[
"Ansoldi",
"Stefano",
""
],
[
"Sindoni",
"Lorenzo",
""
]
] | We discuss a general procedure to generate a class of (everywhere regular) solutions of Einstein equations that can have an (a-priori fixed) arbitrary number of horizons. We then report on work currently in progress i) to find a suitable classification scheme for the maximal extension of these solutions and ii) to interpret the source term in Einstein equations as an effective contribution arising from higher dimensional and/or modified gravity. |
2106.08925 | Kanchan Soni | Kanchan Soni, Bhooshan Uday Gadre, Sanjit Mitra, Sanjeev Dhurandhar | Hierarchical search for compact binary coalescences in the Advanced
LIGO's first two observing runs | 15 pages, 11 figures | null | 10.1103/PhysRevD.105.064005 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Detection of many compact binary coalescences (CBCs) is one of the primary
goals of the present and future ground-based gravitational-wave (GW) detectors.
While increasing the detectors' sensitivities will be crucial in achieving
this, efficient data analysis strategies can play a vital role. With given
computational power in hand, efficient data analysis techniques can expand the
size and dimensionality of the parameter space to search for a variety of GW
sources. Matched filtering based analyses that depend on modeled signals to
produce adequate signal-to-noise ratios for signal detection may miss them if
the parameter space is too restrained. Specifically, the CBC search is
currently limited to non-precessing binaries only, where the spins of the
components are either aligned or anti-aligned to the orbital angular momentum.
A hierarchical search for CBCs is thus well motivated. The first stage of this
search is performed by matched filtering coarsely sampled data with a coarse
template bank to look for candidate events. These candidates are then followed
up for a finer search around the vicinity of an event's parameter space.
Performing such a search leads to enormous savings in computational cost. Here
we report the first successful implementation of the hierarchical search as a
PyCBC-based production pipeline to perform a complete analysis of LIGO
observing runs. With this, we analyze Advanced LIGO's first and second
observing run data. We recover all the events detected by the PyCBC (flat)
search in the first GW catalog, GWTC-1, published by the LIGO-Virgo
collaboration, with nearly the same significance using a scaled background. In
the analysis, we get an impressive factor of 20 reduction in computation
compared to the flat search. With a standard injection study, we show that the
sensitivity of the hierarchical search remains comparable to the flat search
within the error bars.
| [
{
"created": "Wed, 16 Jun 2021 16:30:46 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Jun 2021 13:29:02 GMT",
"version": "v2"
},
{
"created": "Mon, 7 Mar 2022 05:42:09 GMT",
"version": "v3"
}
] | 2022-03-08 | [
[
"Soni",
"Kanchan",
""
],
[
"Gadre",
"Bhooshan Uday",
""
],
[
"Mitra",
"Sanjit",
""
],
[
"Dhurandhar",
"Sanjeev",
""
]
] | Detection of many compact binary coalescences (CBCs) is one of the primary goals of the present and future ground-based gravitational-wave (GW) detectors. While increasing the detectors' sensitivities will be crucial in achieving this, efficient data analysis strategies can play a vital role. With given computational power in hand, efficient data analysis techniques can expand the size and dimensionality of the parameter space to search for a variety of GW sources. Matched filtering based analyses that depend on modeled signals to produce adequate signal-to-noise ratios for signal detection may miss them if the parameter space is too restrained. Specifically, the CBC search is currently limited to non-precessing binaries only, where the spins of the components are either aligned or anti-aligned to the orbital angular momentum. A hierarchical search for CBCs is thus well motivated. The first stage of this search is performed by matched filtering coarsely sampled data with a coarse template bank to look for candidate events. These candidates are then followed up for a finer search around the vicinity of an event's parameter space. Performing such a search leads to enormous savings in computational cost. Here we report the first successful implementation of the hierarchical search as a PyCBC-based production pipeline to perform a complete analysis of LIGO observing runs. With this, we analyze Advanced LIGO's first and second observing run data. We recover all the events detected by the PyCBC (flat) search in the first GW catalog, GWTC-1, published by the LIGO-Virgo collaboration, with nearly the same significance using a scaled background. In the analysis, we get an impressive factor of 20 reduction in computation compared to the flat search. With a standard injection study, we show that the sensitivity of the hierarchical search remains comparable to the flat search within the error bars. |
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