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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1206.5029 | Gil de Oliveira-Neto | G. Oliveira-Neto, G. A. Monerat, E. V. Corr\^ea Silva, C. Neves and L.
G. Ferreira Filho | Quantum noncomutativity in quantum cosmology | 7 pages and no figures. Modifications in the introduction and
references | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work, we study the noncommutative version of a quantum
cosmology model. The model has a Friedmann-Robertson-Walker geometry, the
matter content is a radiative perfect fluid and the spatial sections have
positive constant curvatures. We work in the Schutz's variational formalism. We
quantize the model and obtain the appropriate Wheeler-DeWitt equation. In this
model the states are bounded. Therefore, we compute the discrete energy
spectrum and the corresponding eigenfunctions. The energies depend on a
noncommutative parameter ($\theta$). The solutions to the Wheeler-DeWitt
equation are function of the scale factor ($a$) and a time variable ($\tau$),
associated to the fluid. They also depend on an integer ($n$) and $\theta$. The
most general solution ($\Psi(a,\tau)$) to the Wheeler-DeWitt equation is a sum,
in the integer $n$, of the solutions mentioned above. We observe that, there is
no $\Psi(a,\tau)$ satisfying the appropriate boundary conditions. Therefore, we
conclude that it is not possible to obtain a wavefunction satisfying the
appropriate boundary conditions for the present model with the considered
noncommutativity.
| [
{
"created": "Thu, 21 Jun 2012 22:40:58 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Oct 2014 18:21:33 GMT",
"version": "v2"
},
{
"created": "Tue, 3 May 2016 21:52:28 GMT",
"version": "v3"
}
] | 2016-05-05 | [
[
"Oliveira-Neto",
"G.",
""
],
[
"Monerat",
"G. A.",
""
],
[
"Silva",
"E. V. Corrêa",
""
],
[
"Neves",
"C.",
""
],
[
"Filho",
"L. G. Ferreira",
""
]
] | In the present work, we study the noncommutative version of a quantum cosmology model. The model has a Friedmann-Robertson-Walker geometry, the matter content is a radiative perfect fluid and the spatial sections have positive constant curvatures. We work in the Schutz's variational formalism. We quantize the model and obtain the appropriate Wheeler-DeWitt equation. In this model the states are bounded. Therefore, we compute the discrete energy spectrum and the corresponding eigenfunctions. The energies depend on a noncommutative parameter ($\theta$). The solutions to the Wheeler-DeWitt equation are function of the scale factor ($a$) and a time variable ($\tau$), associated to the fluid. They also depend on an integer ($n$) and $\theta$. The most general solution ($\Psi(a,\tau)$) to the Wheeler-DeWitt equation is a sum, in the integer $n$, of the solutions mentioned above. We observe that, there is no $\Psi(a,\tau)$ satisfying the appropriate boundary conditions. Therefore, we conclude that it is not possible to obtain a wavefunction satisfying the appropriate boundary conditions for the present model with the considered noncommutativity. |
gr-qc/0211001 | Matt Visser | Nicolas Yunes (Washington University in Saint Louis) and Matt Visser
(Victoria University of Wellington) | Power laws, scale invariance, and generalized Frobenius series:
Applications to Newtonian and TOV stars near criticality | 35 pages; IJMPA style file | Int.J.Mod.Phys. A18 (2003) 3433-3468 | 10.1142/S0217751X03013892 | null | gr-qc | null | We present a self-contained formalism for analyzing scale invariant
differential equations. We first cast the scale invariant model into its
equidimensional and autonomous forms, find its fixed points, and then obtain
power-law background solutions. After linearizing about these fixed points, we
find a second linearized solution, which provides a distinct collection of
power laws characterizing the deviations from the fixed point. We prove that
generically there will be a region surrounding the fixed point in which the
complete general solution can be represented as a generalized Frobenius-like
power series with exponents that are integer multiples of the exponents arising
in the linearized problem. This Frobenius-like series can be viewed as a
variant of Liapunov's expansion theorem. As specific examples we apply these
ideas to Newtonian and relativistic isothermal stars and demonstrate (both
numerically and analytically) that the solution exhibits oscillatory power-law
behaviour as the star approaches the point of collapse. These series solutions
extend classical results. (Lane, Emden, and Chandrasekhar in the Newtonian
case; Harrison, Thorne, Wakano, and Wheeler in the relativistic case.) We also
indicate how to extend these ideas to situations where fixed points may not
exist -- either due to ``monotone'' flow or due to the presence of limit
cycles. Monotone flow generically leads to logarithmic deviations from scaling,
while limit cycles generally lead to discrete self-similar solutions.
| [
{
"created": "Thu, 31 Oct 2002 23:18:35 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Yunes",
"Nicolas",
"",
"Washington University in Saint Louis"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | We present a self-contained formalism for analyzing scale invariant differential equations. We first cast the scale invariant model into its equidimensional and autonomous forms, find its fixed points, and then obtain power-law background solutions. After linearizing about these fixed points, we find a second linearized solution, which provides a distinct collection of power laws characterizing the deviations from the fixed point. We prove that generically there will be a region surrounding the fixed point in which the complete general solution can be represented as a generalized Frobenius-like power series with exponents that are integer multiples of the exponents arising in the linearized problem. This Frobenius-like series can be viewed as a variant of Liapunov's expansion theorem. As specific examples we apply these ideas to Newtonian and relativistic isothermal stars and demonstrate (both numerically and analytically) that the solution exhibits oscillatory power-law behaviour as the star approaches the point of collapse. These series solutions extend classical results. (Lane, Emden, and Chandrasekhar in the Newtonian case; Harrison, Thorne, Wakano, and Wheeler in the relativistic case.) We also indicate how to extend these ideas to situations where fixed points may not exist -- either due to ``monotone'' flow or due to the presence of limit cycles. Monotone flow generically leads to logarithmic deviations from scaling, while limit cycles generally lead to discrete self-similar solutions. |
1609.05636 | Tiberiu Harko | Bogdan D\u{a}nil\u{a}, Tiberiu Harko, Man Kwong Mak, Praiboon
Pantaragphong, Sorin Sabau | Jacobi stability analysis of scalar field models with minimal coupling
to gravity in a cosmological background | 24 pages, 14 figures, accepted for publication in Advances in High
Energy Physics, special issue "Dark Physics in the Early Universe" | Advances in High Energy Physics, 2016, 7521464 (2016) | 10.1155/2016/7521464 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform the study of the stability of the cosmological scalar field
models, by using the Jacobi stability analysis, or the Kosambi-Cartan-Chern
(KCC) theory. In the KCC approach we describe the time evolution of the scalar
field cosmologies in geometric terms, by performing a "second geometrization",
by considering them as paths of a semispray. By introducing a non-linear
connection and a Berwald type connection associated to the Friedmann and
Klein-Gordon equations, five geometrical invariants can be constructed, with
the second invariant giving the Jacobi stability of the cosmological model. We
obtain all the relevant geometric quantities, and we formulate the condition of
the Jacobi stability for scalar field cosmologies in the second order
formalism. As an application of the developed methods we consider the Jacobi
stability properties of the scalar fields with exponential and Higgs type
potential. We find that the Universe dominated by a scalar field exponential
potential is in Jacobi unstable state, while the cosmological evolution in the
presence of Higgs fields has alternating stable and unstable phases. By using
the standard first order formulation of the cosmological models as dynamical
systems we have investigated the stability of the phantom quintessence and
tachyonic scalar fields, by lifting the first order system to the tangent
bundle. It turns out that in the presence of a power law potential both these
models are Jacobi unstable during the entire cosmological evolution.
| [
{
"created": "Mon, 19 Sep 2016 08:46:17 GMT",
"version": "v1"
}
] | 2016-10-31 | [
[
"Dănilă",
"Bogdan",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Mak",
"Man Kwong",
""
],
[
"Pantaragphong",
"Praiboon",
""
],
[
"Sabau",
"Sorin",
""
]
] | We perform the study of the stability of the cosmological scalar field models, by using the Jacobi stability analysis, or the Kosambi-Cartan-Chern (KCC) theory. In the KCC approach we describe the time evolution of the scalar field cosmologies in geometric terms, by performing a "second geometrization", by considering them as paths of a semispray. By introducing a non-linear connection and a Berwald type connection associated to the Friedmann and Klein-Gordon equations, five geometrical invariants can be constructed, with the second invariant giving the Jacobi stability of the cosmological model. We obtain all the relevant geometric quantities, and we formulate the condition of the Jacobi stability for scalar field cosmologies in the second order formalism. As an application of the developed methods we consider the Jacobi stability properties of the scalar fields with exponential and Higgs type potential. We find that the Universe dominated by a scalar field exponential potential is in Jacobi unstable state, while the cosmological evolution in the presence of Higgs fields has alternating stable and unstable phases. By using the standard first order formulation of the cosmological models as dynamical systems we have investigated the stability of the phantom quintessence and tachyonic scalar fields, by lifting the first order system to the tangent bundle. It turns out that in the presence of a power law potential both these models are Jacobi unstable during the entire cosmological evolution. |
2305.15503 | Jiangtao Wang | B. Q. Wang, S. R. Wu | Echoes of the regularized dilatonic black hole | Lack of graphical analysis | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In present work, the evolution of scalar field and electromagnetic field
under the background of the regularized dilatonic black bounces spacetimes are
investigated, we obtain an obvious echoes signal which appropriately reports
the properties of regularized dilatonic black bounces spacetimes and disclose
the physical reasons behind such phenomena. By studying the quasinormal
ringdown of the three states of regularized dilatonic black bounces spacetimes,
it shows that the echoes signal only appears when $b>2k$.
| [
{
"created": "Wed, 24 May 2023 18:44:45 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jan 2024 12:26:47 GMT",
"version": "v2"
}
] | 2024-01-30 | [
[
"Wang",
"B. Q.",
""
],
[
"Wu",
"S. R.",
""
]
] | In present work, the evolution of scalar field and electromagnetic field under the background of the regularized dilatonic black bounces spacetimes are investigated, we obtain an obvious echoes signal which appropriately reports the properties of regularized dilatonic black bounces spacetimes and disclose the physical reasons behind such phenomena. By studying the quasinormal ringdown of the three states of regularized dilatonic black bounces spacetimes, it shows that the echoes signal only appears when $b>2k$. |
2310.19706 | Zachary Nasipak | Zachary Nasipak | BHPWAVE: An adiabatic gravitational waveform model for compact objects
undergoing quasi-circular inspirals into rotating massive black holes | 24 pages, 17 figures, 2 tables | Phys. Rev. D 109, 044020 (2024) | 10.1103/PhysRevD.109.044020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present {bhpwave}: a new Python-based, open-source tool for generating the
gravitational waveforms of stellar-mass compact objects undergoing
quasi-circular inspirals into rotating massive black holes. These binaries,
known as extreme-mass-ratio inspirals (EMRIs), are exciting mHz gravitational
wave sources for future space-based detectors such as the Laser Interferometer
Space Antenna (LISA). Relativistic models of EMRI gravitational wave signals
are necessary to unlock the full scientific potential of mHz detectors, yet few
open-source EMRI waveform models exist. Thus we built {bhpwave}, which uses the
adiabatic approximation from black hole perturbation theory to rapidly
construct gravitational waveforms based on the leading-order inspiral dynamics
of the binary. In this work, we present the theoretical and numerical
foundations underpinning {bhpwave}. We also demonstrate how {bhpwave} can be
used to assess the impact of EMRI modeling errors on LISA gravitational wave
data analysis. In particular, we find that for retrograde orbits and
slowly-spinning black holes we can mismodel the gravitational wave phasing by
as much as $\sim 10$ radians without significantly biasing EMRI parameter
estimation.
| [
{
"created": "Mon, 30 Oct 2023 16:33:36 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Mar 2024 01:45:23 GMT",
"version": "v2"
}
] | 2024-03-08 | [
[
"Nasipak",
"Zachary",
""
]
] | We present {bhpwave}: a new Python-based, open-source tool for generating the gravitational waveforms of stellar-mass compact objects undergoing quasi-circular inspirals into rotating massive black holes. These binaries, known as extreme-mass-ratio inspirals (EMRIs), are exciting mHz gravitational wave sources for future space-based detectors such as the Laser Interferometer Space Antenna (LISA). Relativistic models of EMRI gravitational wave signals are necessary to unlock the full scientific potential of mHz detectors, yet few open-source EMRI waveform models exist. Thus we built {bhpwave}, which uses the adiabatic approximation from black hole perturbation theory to rapidly construct gravitational waveforms based on the leading-order inspiral dynamics of the binary. In this work, we present the theoretical and numerical foundations underpinning {bhpwave}. We also demonstrate how {bhpwave} can be used to assess the impact of EMRI modeling errors on LISA gravitational wave data analysis. In particular, we find that for retrograde orbits and slowly-spinning black holes we can mismodel the gravitational wave phasing by as much as $\sim 10$ radians without significantly biasing EMRI parameter estimation. |
gr-qc/9609009 | Kim Sang Pyo | Sang Pyo Kim | Coherent State Representation of Semiclassical Quantum Gravity | 10 Pages, ReVTeX, No figures | J.Korean Phys.Soc.30:349,1997 | null | SNUTP 96-089, KNUTH-34 | gr-qc | null | We elaborate the recently introduced asymptotically exact semiclassical
quantum gravity derived from the Wheeler-DeWitt equation by finding a
particular coherent state representation of a quantum scalar field in which the
back-reaction of the scalar field Hamiltonian exactly gives rise to the
classical one. In this coherent state representation classical spacetime
emerges naturally from semiclassical quantum gravity.
| [
{
"created": "Mon, 2 Sep 1996 07:46:01 GMT",
"version": "v1"
}
] | 2011-08-17 | [
[
"Kim",
"Sang Pyo",
""
]
] | We elaborate the recently introduced asymptotically exact semiclassical quantum gravity derived from the Wheeler-DeWitt equation by finding a particular coherent state representation of a quantum scalar field in which the back-reaction of the scalar field Hamiltonian exactly gives rise to the classical one. In this coherent state representation classical spacetime emerges naturally from semiclassical quantum gravity. |
1004.4885 | Philippe G. LeFloch | Florian Beyer and Philippe G. LeFloch | Second-order hyperbolic Fuchsian systems. General theory | 32 pages. A shortened version of the material presented in this
preprint is published in: F. Beyer and P.G. LeFloch, Second-order hyperbolic
Fuchsian systems and applications, Class. Quantum Grav. 27 (2010), 245012 | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a class of singular partial differential equations, the
second-order hyperbolic Fuchsian systems, and we investigate the associated
initial value problem when data are imposed on the singularity. First of all,
we analyze a class of equations in which hyperbolicity is not assumed and we
construct asymptotic solutions of arbitrary order. Second, for the proposed
class of second-order hyperbolic Fuchsian systems, we establish the existence
of solutions with prescribed asymptotic behavior on the singularity. Our proof
is based on a new scheme which is also suitable to design numerical
approximations. Furthermore, as shown in a follow-up paper, the second-order
Fuchsian framework is appropriate to handle Einstein's field equations for
Gowdy symmetric spacetimes and allows us to recover (and slightly generalize)
earlier results by Rendall and collaborators, while providing a direct approach
leading to accurate numerical solutions. The proposed framework is also robust
enough to encompass matter models arising in general relativity.
| [
{
"created": "Tue, 27 Apr 2010 18:58:35 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jan 2011 20:46:26 GMT",
"version": "v2"
}
] | 2015-03-17 | [
[
"Beyer",
"Florian",
""
],
[
"LeFloch",
"Philippe G.",
""
]
] | We introduce a class of singular partial differential equations, the second-order hyperbolic Fuchsian systems, and we investigate the associated initial value problem when data are imposed on the singularity. First of all, we analyze a class of equations in which hyperbolicity is not assumed and we construct asymptotic solutions of arbitrary order. Second, for the proposed class of second-order hyperbolic Fuchsian systems, we establish the existence of solutions with prescribed asymptotic behavior on the singularity. Our proof is based on a new scheme which is also suitable to design numerical approximations. Furthermore, as shown in a follow-up paper, the second-order Fuchsian framework is appropriate to handle Einstein's field equations for Gowdy symmetric spacetimes and allows us to recover (and slightly generalize) earlier results by Rendall and collaborators, while providing a direct approach leading to accurate numerical solutions. The proposed framework is also robust enough to encompass matter models arising in general relativity. |
1204.0872 | Wei-Tou Ni | Wei-Tou Ni, Hsien-Hao Mei and Shan-Jyun Wu | Foundations of Classical Electrodynamics, Equivalence Principle and
Cosmic Interactions: A Short Exposition and an Update | 15 pages, 2 figures, 2 tables. Plenary talk at First LeCosPA
Symposium: Towards Ultimate Understanding of the Universe(LeCosPA2012),
National Taiwan University, Taipei, ROC, February 6-9, 2012 | Modern Physics Letters A, Vol. 28, No. 3 (2013) 1340013 | 10.1142/S0217732313400130 | null | gr-qc hep-ph physics.class-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We look at the foundations of electromagnetism in this 1st LeCosPA Symposium.
For doing this, after some review (constraints on photon mass etc.), we use two
approaches. The first one is to formulate a Parametrized Post-Maxwellian (PPM)
framework to include QED corrections and a pseudoscalar photon interaction. PPM
framework includes lowest corrections to unified electromagnetism-gravity
theories based on connection approach. It may also overlap with corrections
implemented from generalized uncertainty principle (GUP) when
electromagnetism-gravity coupling is considered. We discuss various vacuum
birefringence experiments - ongoing and proposed - to measure these parameters.
The second approach - the chi-g framework is to look at electromagnetism in
gravity and various experiments and observations to determine its empirical
foundation. The SME (Standard Model Extension) and SMS (Standard Model
Supplement) overlap with the chi-g framework in their photon sector. We found
that the foundation is solid with the only exception of a potentially possible
pseudoscalar-photon interaction. We discussed its experimental constraints and
look forward to more future experiments.
| [
{
"created": "Wed, 4 Apr 2012 06:22:46 GMT",
"version": "v1"
}
] | 2013-01-11 | [
[
"Ni",
"Wei-Tou",
""
],
[
"Mei",
"Hsien-Hao",
""
],
[
"Wu",
"Shan-Jyun",
""
]
] | We look at the foundations of electromagnetism in this 1st LeCosPA Symposium. For doing this, after some review (constraints on photon mass etc.), we use two approaches. The first one is to formulate a Parametrized Post-Maxwellian (PPM) framework to include QED corrections and a pseudoscalar photon interaction. PPM framework includes lowest corrections to unified electromagnetism-gravity theories based on connection approach. It may also overlap with corrections implemented from generalized uncertainty principle (GUP) when electromagnetism-gravity coupling is considered. We discuss various vacuum birefringence experiments - ongoing and proposed - to measure these parameters. The second approach - the chi-g framework is to look at electromagnetism in gravity and various experiments and observations to determine its empirical foundation. The SME (Standard Model Extension) and SMS (Standard Model Supplement) overlap with the chi-g framework in their photon sector. We found that the foundation is solid with the only exception of a potentially possible pseudoscalar-photon interaction. We discussed its experimental constraints and look forward to more future experiments. |
2301.07250 | Rodrigo Gonzalez Quaglia | R. Gonzalez Quaglia | An early and late times dynamical analysis of a scale invariant
gravitational model with a vector scalar interaction: the isotropic case | 26 pages, 8 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scalar fields are widely and popularly used in cosmology in order to explain
different phenomena among which, inflation and dark energy are two of the most
popular ones. Specifically, in recent years, scale invariance in the
gravitational sector has gained interest due to its simplicity, ability to
model inflation and the dynamical generation of the Planck scale. In this
paper, motivated by a non minimally coupled scale invariant $R^{2}$
gravitational model originally proposed by M.Rinaldi and L. Vanzo, we
investigate how the inclusion of a vector scalar interaction that respects the
scale invariance of the original model may affect the early and late time
dynamics. We employ dynamical analysis tools in order to find the fixed points
of the system and the local solutions for each variable around each fixed point
finding out that the early universe solution of the extended model is
compatible with that found in the original model with the exception of a new
unstable fixed point appearing in the extended model. This new fixed point
however has the same linealized solutions as the unstable fixed point found for
the original model. We later employ numerical calculations in order to check
that the analytical approach holds. Furthermore we show how the dynamical
generation of the Planck mass is unaffected by the new field content of the
model. Finally, we motivate and investigate a reduced version of the extended
model finding out that, at late times, the extended model has only stable de
Sitter fixed points where the scalar field becomes constant taking the role of
the cosmological constant and the vector field is washed out.
| [
{
"created": "Wed, 18 Jan 2023 01:23:58 GMT",
"version": "v1"
}
] | 2023-01-19 | [
[
"Quaglia",
"R. Gonzalez",
""
]
] | Scalar fields are widely and popularly used in cosmology in order to explain different phenomena among which, inflation and dark energy are two of the most popular ones. Specifically, in recent years, scale invariance in the gravitational sector has gained interest due to its simplicity, ability to model inflation and the dynamical generation of the Planck scale. In this paper, motivated by a non minimally coupled scale invariant $R^{2}$ gravitational model originally proposed by M.Rinaldi and L. Vanzo, we investigate how the inclusion of a vector scalar interaction that respects the scale invariance of the original model may affect the early and late time dynamics. We employ dynamical analysis tools in order to find the fixed points of the system and the local solutions for each variable around each fixed point finding out that the early universe solution of the extended model is compatible with that found in the original model with the exception of a new unstable fixed point appearing in the extended model. This new fixed point however has the same linealized solutions as the unstable fixed point found for the original model. We later employ numerical calculations in order to check that the analytical approach holds. Furthermore we show how the dynamical generation of the Planck mass is unaffected by the new field content of the model. Finally, we motivate and investigate a reduced version of the extended model finding out that, at late times, the extended model has only stable de Sitter fixed points where the scalar field becomes constant taking the role of the cosmological constant and the vector field is washed out. |
gr-qc/9711016 | Steve Brandt | S. R. Brandt, K. Camarda, E. Seidel | Three Dimensional Distorted Black Holes: Initial Data and Evolution | 3 pages, 2 postscript figures, LaTeX, uses mprocl.sty (available at
http://shemesh.fiz.huji.ac.il/MG8/submission.html) To appear in the
proceedings of the Marcel Grossmann 8 (Jerusalem, 1997) | null | null | null | gr-qc | null | We present a new class of 3D black hole initial data sets for numerical
relativity. These data sets go beyond the axisymmetric, ``gravity wave plus
rotating black hole'' single black hole data sets by creating a dynamic,
distorted hole with adjustable distortion parameters in 3D. These data sets
extend our existing test beds for 3D numerical relativity, representing the
late stages of binary black hole collisions resulting from on-axis collision or
3D spiralling coalescence, and should provide insight into the physics of such
systems. We describe the construction of these sets, the properties for a
number of example cases, and report on progress evolving them.
| [
{
"created": "Thu, 6 Nov 1997 07:40:05 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Mar 1998 08:25:44 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Brandt",
"S. R.",
""
],
[
"Camarda",
"K.",
""
],
[
"Seidel",
"E.",
""
]
] | We present a new class of 3D black hole initial data sets for numerical relativity. These data sets go beyond the axisymmetric, ``gravity wave plus rotating black hole'' single black hole data sets by creating a dynamic, distorted hole with adjustable distortion parameters in 3D. These data sets extend our existing test beds for 3D numerical relativity, representing the late stages of binary black hole collisions resulting from on-axis collision or 3D spiralling coalescence, and should provide insight into the physics of such systems. We describe the construction of these sets, the properties for a number of example cases, and report on progress evolving them. |
1212.4847 | Istvan Racz | Andr\'as L\'aszl\'o, Istv\'an R\'acz | Superradiance or total reflection? | 8 pages, 6 figures, contribution to the proceedings of the conference
on Relativity and Gravitation: 100 Years after Einstein in Prague | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Numerical evolution of massless scalar fields on Kerr background is studied.
The initial data specifications are chosen to have compact support separated
from the ergoregion and to yield nearly monochromatic incident wave packets.
The initial data is also tuned to maximize the effect of superradiance.
Evidences are shown indicating that instead of the anticipated energy
extraction from black hole the incident radiation fail to reach the ergoregion
rather it suffers a nearly perfect reflection.
| [
{
"created": "Wed, 19 Dec 2012 21:01:07 GMT",
"version": "v1"
}
] | 2012-12-21 | [
[
"László",
"András",
""
],
[
"Rácz",
"István",
""
]
] | Numerical evolution of massless scalar fields on Kerr background is studied. The initial data specifications are chosen to have compact support separated from the ergoregion and to yield nearly monochromatic incident wave packets. The initial data is also tuned to maximize the effect of superradiance. Evidences are shown indicating that instead of the anticipated energy extraction from black hole the incident radiation fail to reach the ergoregion rather it suffers a nearly perfect reflection. |
2011.14760 | Maryam Roushan | M. Roushan and K. Nozari | Thermostatistics with an Invariant Infrared Cutoff | null | The European Physical Journal C (2020) 1-12 | 10.1140/epjc/s10052-020-8378-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum gravitational effects may affect the large scale dynamics of the
universe. Phenomenologically, quantum gravitational effect at large distances
can be encoded in an extended uncertainty principle that admits a minimal
measurable momentum/energy or a maximal length. This maximal length can be
considered as the size of the cosmological horizon today. In this paper we
study thermostatistics of an expanding universe as a gaseous system and in the
presence of an invariant infrared cutoff. We also compare the thermostatistics
of different eras of the evolution of the universe in two classes, Fermions and
Bosons.
| [
{
"created": "Mon, 30 Nov 2020 13:15:43 GMT",
"version": "v1"
}
] | 2020-12-01 | [
[
"Roushan",
"M.",
""
],
[
"Nozari",
"K.",
""
]
] | Quantum gravitational effects may affect the large scale dynamics of the universe. Phenomenologically, quantum gravitational effect at large distances can be encoded in an extended uncertainty principle that admits a minimal measurable momentum/energy or a maximal length. This maximal length can be considered as the size of the cosmological horizon today. In this paper we study thermostatistics of an expanding universe as a gaseous system and in the presence of an invariant infrared cutoff. We also compare the thermostatistics of different eras of the evolution of the universe in two classes, Fermions and Bosons. |
1404.4025 | Dipongkar Talukder | Dipongkar Talukder, Eric Thrane, Sukanta Bose, and Tania Regimbau | Measuring neutron-star ellipticity with measurements of the stochastic
gravitational-wave background | null | Phys. Rev. D 89, 123008 (2014) | 10.1103/PhysRevD.89.123008 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Galactic neutron stars are a promising source of gravitational waves in the
analysis band of detectors such as LIGO and Virgo. Previous searches for
gravitational waves from neutron stars have focused on the detection of
individual neutron stars, which are either nearby or highly non-spherical. Here
we consider the stochastic gravitational-wave signal arising from the ensemble
of Galactic neutron stars. Using a population synthesis model, we estimate the
single-sigma sensitivity of current and planned gravitational-wave
observatories to average neutron star ellipticity $\epsilon$ as a function of
the number of in-band Galactic neutron stars $N_\text{tot}$. For the plausible
case of $N_\text{tot}\approx 53000$, and assuming one year of observation time
with colocated initial LIGO detectors, we find it to be
$\sigma_\epsilon=2.1\times10^{-7}$, which is comparable to current bounds on
some nearby neutron stars. (The current best $95\%$ upper limits are
$\epsilon\lesssim7\times10^{-8}.$) It is unclear if Advanced LIGO can
significantly improve on this sensitivity using spatially separated detectors.
For the proposed Einstein Telescope, we estimate that
$\sigma\epsilon=5.6\times10^{-10}$. Finally, we show that stochastic
measurements can be combined with measurements of individual neutron stars in
order to estimate the number of in-band Galactic neutron stars. In this way,
measurements of stochastic gravitational waves provide a complementary tool for
studying Galactic neutron stars.
| [
{
"created": "Tue, 15 Apr 2014 19:25:34 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Jun 2014 21:07:24 GMT",
"version": "v2"
},
{
"created": "Thu, 12 Jun 2014 17:46:40 GMT",
"version": "v3"
}
] | 2014-06-25 | [
[
"Talukder",
"Dipongkar",
""
],
[
"Thrane",
"Eric",
""
],
[
"Bose",
"Sukanta",
""
],
[
"Regimbau",
"Tania",
""
]
] | Galactic neutron stars are a promising source of gravitational waves in the analysis band of detectors such as LIGO and Virgo. Previous searches for gravitational waves from neutron stars have focused on the detection of individual neutron stars, which are either nearby or highly non-spherical. Here we consider the stochastic gravitational-wave signal arising from the ensemble of Galactic neutron stars. Using a population synthesis model, we estimate the single-sigma sensitivity of current and planned gravitational-wave observatories to average neutron star ellipticity $\epsilon$ as a function of the number of in-band Galactic neutron stars $N_\text{tot}$. For the plausible case of $N_\text{tot}\approx 53000$, and assuming one year of observation time with colocated initial LIGO detectors, we find it to be $\sigma_\epsilon=2.1\times10^{-7}$, which is comparable to current bounds on some nearby neutron stars. (The current best $95\%$ upper limits are $\epsilon\lesssim7\times10^{-8}.$) It is unclear if Advanced LIGO can significantly improve on this sensitivity using spatially separated detectors. For the proposed Einstein Telescope, we estimate that $\sigma\epsilon=5.6\times10^{-10}$. Finally, we show that stochastic measurements can be combined with measurements of individual neutron stars in order to estimate the number of in-band Galactic neutron stars. In this way, measurements of stochastic gravitational waves provide a complementary tool for studying Galactic neutron stars. |
1505.06058 | Sanjeev S. Seahra | Jack Gegenberg, Shohreh Rahmati, Sanjeev S. Seahra | Infrared modification of gravity from conformal symmetry | 7 pages. Expanded presentation and some changes of notation. Matches
version published in PRD | Phys. Rev. D 93, 064025 (2016) | 10.1103/PhysRevD.93.064025 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reconsider a gauge theory of gravity in which the gauge group is the
conformal group SO(4,2) and the action is of the Yang-Mills form, quadratic in
the curvature. The resulting gravitational theory exhibits local conformal
symmetry and reduces to Weyl-squared gravity under certain conditions. When the
theory is linearized about flat spacetime, we find that matter which couples to
the generators of special conformal transformations reproduces Newton's inverse
square law. Conversely, matter which couples to generators of translations
induces a constant and possibly repulsive force far from the source, which may
be relevant for explaining the late time acceleration of the universe. The
coupling constant of theory is dimensionless, which means that it is
potentially renormalizable.
| [
{
"created": "Fri, 22 May 2015 13:04:55 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Apr 2016 17:24:03 GMT",
"version": "v2"
}
] | 2016-04-07 | [
[
"Gegenberg",
"Jack",
""
],
[
"Rahmati",
"Shohreh",
""
],
[
"Seahra",
"Sanjeev S.",
""
]
] | We reconsider a gauge theory of gravity in which the gauge group is the conformal group SO(4,2) and the action is of the Yang-Mills form, quadratic in the curvature. The resulting gravitational theory exhibits local conformal symmetry and reduces to Weyl-squared gravity under certain conditions. When the theory is linearized about flat spacetime, we find that matter which couples to the generators of special conformal transformations reproduces Newton's inverse square law. Conversely, matter which couples to generators of translations induces a constant and possibly repulsive force far from the source, which may be relevant for explaining the late time acceleration of the universe. The coupling constant of theory is dimensionless, which means that it is potentially renormalizable. |
1606.00214 | Bijan Saha Dr. | Bijan Saha | Nonlinear Spinor field in isotropic space-time and dark energy models | 21 pages, 20 figures | The European Phys. J Plus 131: 242 (2016) | 10.1140/epjp/i2016-16242-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the scope of isotropic FRW cosmological model the role of nonlinear
spinor field in the evolution of the Universe is studied. It is found that
unlike in anisotropic cosmological models in the present case the spinor field
does not possess nontrivial non-diagonal components of energy-momentum tensor,
consequently does not impose any additional restrictions on the components of
the spinor field or metric function. The spinor description of different matter
was given and evolution of the Universe corresponding to these sources is
illustrated. In the framework of a three fluid system the utility of spinor
description of matter is established.
| [
{
"created": "Wed, 1 Jun 2016 10:51:07 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Jul 2016 12:26:58 GMT",
"version": "v2"
}
] | 2016-07-27 | [
[
"Saha",
"Bijan",
""
]
] | Within the scope of isotropic FRW cosmological model the role of nonlinear spinor field in the evolution of the Universe is studied. It is found that unlike in anisotropic cosmological models in the present case the spinor field does not possess nontrivial non-diagonal components of energy-momentum tensor, consequently does not impose any additional restrictions on the components of the spinor field or metric function. The spinor description of different matter was given and evolution of the Universe corresponding to these sources is illustrated. In the framework of a three fluid system the utility of spinor description of matter is established. |
2405.20193 | Martin Bojowald | Kallan Berglund, Martin Bojowald, Aurora Colter, Manuel Diaz | Space-time superpositions as fluctuating geometries | 33 pages | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Superpositions of black holes can be described geometrically using a combined
canonical formulation for space-time and quantum states. A previously
introduced black-hole model that includes quantum fluctuations of metric
components is shown here to give full access to the corresponding space-time
geometry of weak-field gravity in terms of suitable line elements with quantum
corrections. These results can be interpreted as providing covariant
formulations of the gravitational force implied by a distribution of black
holes in superposition. They can also be understood as a distribution of
quantum matter constituents in superposition for a single black hole. A
detailed analysis in the weak-field limit reveals quantum corrections to
Newton's potential in generic semiclassical states, as well as new bounds on
quantum fluctuations, implied by the covariance condition, rather than the
usual uncertainty principle. These results provide additional control on
quantum effects in Newton's potential that can be used in a broad range of
predictions to be compared with observations.
| [
{
"created": "Thu, 30 May 2024 15:58:00 GMT",
"version": "v1"
}
] | 2024-05-31 | [
[
"Berglund",
"Kallan",
""
],
[
"Bojowald",
"Martin",
""
],
[
"Colter",
"Aurora",
""
],
[
"Diaz",
"Manuel",
""
]
] | Superpositions of black holes can be described geometrically using a combined canonical formulation for space-time and quantum states. A previously introduced black-hole model that includes quantum fluctuations of metric components is shown here to give full access to the corresponding space-time geometry of weak-field gravity in terms of suitable line elements with quantum corrections. These results can be interpreted as providing covariant formulations of the gravitational force implied by a distribution of black holes in superposition. They can also be understood as a distribution of quantum matter constituents in superposition for a single black hole. A detailed analysis in the weak-field limit reveals quantum corrections to Newton's potential in generic semiclassical states, as well as new bounds on quantum fluctuations, implied by the covariance condition, rather than the usual uncertainty principle. These results provide additional control on quantum effects in Newton's potential that can be used in a broad range of predictions to be compared with observations. |
2406.09006 | Dhanvarsh Annamalai S. R. | Dhanvarsh Annamalai and Akshat Pandey | Tunneling of Hawking Radiation in Starobinsky-Bel-Robinson gravity | This work is accepted for publication in Gravitation and Cosmology,
Vol. 30 , Issue 4 | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | We examine Hawking radiation for a Schwarszchild-type black hole in
Starobinsky Bel Robinson (SBR) gravity and calculate the corrected Hawking
Temperature using the tunnelling method. We then discuss the deviation of our
Hawking temperature from the standard Schwarszchild result. We relate the
corrections to the Hawking temperature beyond the semi-classical approximation.
We highlight that starting with a modification of the classical black hole
geometry and calculating the semi-classical Hawking temperature, yields
temperature corrections comparable to those obtained when the classical
background is kept unchanged and beyond semi-classical terms in the temperature
are included.
| [
{
"created": "Thu, 13 Jun 2024 11:19:35 GMT",
"version": "v1"
}
] | 2024-06-14 | [
[
"Annamalai",
"Dhanvarsh",
""
],
[
"Pandey",
"Akshat",
""
]
] | We examine Hawking radiation for a Schwarszchild-type black hole in Starobinsky Bel Robinson (SBR) gravity and calculate the corrected Hawking Temperature using the tunnelling method. We then discuss the deviation of our Hawking temperature from the standard Schwarszchild result. We relate the corrections to the Hawking temperature beyond the semi-classical approximation. We highlight that starting with a modification of the classical black hole geometry and calculating the semi-classical Hawking temperature, yields temperature corrections comparable to those obtained when the classical background is kept unchanged and beyond semi-classical terms in the temperature are included. |
1809.07623 | Sebastien Galtier | S\'ebastien Galtier, Sergey V. Nazarenko, \'Eric Buchlin, Simon
Thalabard | Nonlinear Diffusion Models for Gravitational Wave Turbulence | 5 figures | null | 10.1016/j.physd.2019.01.007 | null | gr-qc physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A fourth-order and a second-order nonlinear diffusion models in spectral
space are proposed to describe gravitational wave turbulence in the
approximation of strongly local interactions. We show analytically that the
model equations satisfy the conservation of energy and wave action, and
reproduce the power law solutions previously derived from the kinetic equations
with a direct cascade of energy and an explosive inverse cascade of wave
action. In the latter case, we show numerically by computing the second-order
diffusion model that the non-stationary regime exhibits an anomalous scaling
which is understood as a self-similar solution of the second kind with a front
propagation following the law $k_f \sim (t_*-t)^{3.296}$, with $t<t_*$. These
results are relevant to better understand the dynamics of the primordial
universe where potent sources of gravitational waves may produce space-time
turbulence.
| [
{
"created": "Tue, 18 Sep 2018 15:34:56 GMT",
"version": "v1"
}
] | 2019-03-27 | [
[
"Galtier",
"Sébastien",
""
],
[
"Nazarenko",
"Sergey V.",
""
],
[
"Buchlin",
"Éric",
""
],
[
"Thalabard",
"Simon",
""
]
] | A fourth-order and a second-order nonlinear diffusion models in spectral space are proposed to describe gravitational wave turbulence in the approximation of strongly local interactions. We show analytically that the model equations satisfy the conservation of energy and wave action, and reproduce the power law solutions previously derived from the kinetic equations with a direct cascade of energy and an explosive inverse cascade of wave action. In the latter case, we show numerically by computing the second-order diffusion model that the non-stationary regime exhibits an anomalous scaling which is understood as a self-similar solution of the second kind with a front propagation following the law $k_f \sim (t_*-t)^{3.296}$, with $t<t_*$. These results are relevant to better understand the dynamics of the primordial universe where potent sources of gravitational waves may produce space-time turbulence. |
0902.2844 | Rajesh R. Parwani | Le-Huy Nguyen and Rajesh R. Parwani | Singularity Avoidance in Nonlinear Quantum Cosmology | 6 pages. Presented at the DSU conference in Cairo, Egypt 2008. Typos
in eq. 22 and 29 of the proceedings version corrected here | AIP Conf.Proc.1115:180-185,2009 | 10.1063/1.3131494 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend our previous study on the effects of an information-theoretically
motivated nonlinear correction to the Wheeler-deWitt equation in the
minisuperspace scheme for FRW universes. Firstly we show that even when the
geometry is hyperbolic, and matter given by a cosmological constant, the
nonlinearity can still provide a barrier to screen the initial singularity,
just as in the case for flat universes. Secondly, in the flat case we show that
singularity avoidance in the presence of a free massless scalar field is
perturbatively possible for a very large class of initially unperturbed quantum
states, generalising our previous discussion using Gaussian states.
| [
{
"created": "Tue, 17 Feb 2009 07:24:19 GMT",
"version": "v1"
}
] | 2009-05-01 | [
[
"Nguyen",
"Le-Huy",
""
],
[
"Parwani",
"Rajesh R.",
""
]
] | We extend our previous study on the effects of an information-theoretically motivated nonlinear correction to the Wheeler-deWitt equation in the minisuperspace scheme for FRW universes. Firstly we show that even when the geometry is hyperbolic, and matter given by a cosmological constant, the nonlinearity can still provide a barrier to screen the initial singularity, just as in the case for flat universes. Secondly, in the flat case we show that singularity avoidance in the presence of a free massless scalar field is perturbatively possible for a very large class of initially unperturbed quantum states, generalising our previous discussion using Gaussian states. |
0811.1266 | Philippe G. LeFloch | Paulo Amorim, Christine Bernardi, and Philippe G. LeFloch | Computing Gowdy spacetimes via spectral evolution in future and past
directions | 19 pages, 12 figures | Class.Quant.Grav.26:025007,2009 | 10.1088/0264-9381/26/2/025007 | null | gr-qc math.NA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a system of nonlinear wave equations with constraints that arises
from the Einstein equations of general relativity and describes the geometry of
the so-called Gowdy symmetric spacetimes on T3. We introduce two numerical
methods, which are based on pseudo-spectral approximation. The first approach
relies on marching in the future time-like direction and toward the coordinate
singularity t=0. The second approach is designed from asymptotic formulas that
are available near this singularity; it evolves the solutions in the past
timelike direction from "final" data given at t=0. This backward method relies
a novel nonlinear transformation, which allows us to reduce the nonlinear
source terms to simple quadratic products of the unknown variables. Numerical
experiments are presented in various regimes, including cases where "spiky"
structures are observed as the coordinate singularity is approached. The
proposed backward strategy leads to a robust numerical method which allows us
to accurately simulate the long-time behavior of a large class of Gowdy
spacetimes.
| [
{
"created": "Sat, 8 Nov 2008 15:11:33 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Nov 2008 22:03:53 GMT",
"version": "v2"
}
] | 2009-01-08 | [
[
"Amorim",
"Paulo",
""
],
[
"Bernardi",
"Christine",
""
],
[
"LeFloch",
"Philippe G.",
""
]
] | We consider a system of nonlinear wave equations with constraints that arises from the Einstein equations of general relativity and describes the geometry of the so-called Gowdy symmetric spacetimes on T3. We introduce two numerical methods, which are based on pseudo-spectral approximation. The first approach relies on marching in the future time-like direction and toward the coordinate singularity t=0. The second approach is designed from asymptotic formulas that are available near this singularity; it evolves the solutions in the past timelike direction from "final" data given at t=0. This backward method relies a novel nonlinear transformation, which allows us to reduce the nonlinear source terms to simple quadratic products of the unknown variables. Numerical experiments are presented in various regimes, including cases where "spiky" structures are observed as the coordinate singularity is approached. The proposed backward strategy leads to a robust numerical method which allows us to accurately simulate the long-time behavior of a large class of Gowdy spacetimes. |
1207.3673 | Javad Taghizadeh firouzjaee | Pouria Dadras, J. T. Firouzjaee and Reza Mansouri | A concrete anti-de Sitter black hole with dynamical horizon having
toroidal cross-sections and its characteristics | improved version. arXiv admin note: text overlap with
arXiv:gr-qc/0308033 by other authors | Europhys. Lett. 100 (2012) 39001 | 10.1209/0295-5075/100/39001 | IPM/P-2012/027 | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/3.0/ | We propose a special solution of Einstein equations in the general Vaidya
form representing a dynamical black hole having horizon cross-sections with
toroidal topology. The concrete model enables us to study for the first time
dynamical horizons with toroidal topology, its area law, and the question of
matter flux inside the horizon, without using a cut-and-paste technology to
construct the solution.
| [
{
"created": "Mon, 16 Jul 2012 13:27:08 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Nov 2012 12:08:45 GMT",
"version": "v2"
}
] | 2015-06-05 | [
[
"Dadras",
"Pouria",
""
],
[
"Firouzjaee",
"J. T.",
""
],
[
"Mansouri",
"Reza",
""
]
] | We propose a special solution of Einstein equations in the general Vaidya form representing a dynamical black hole having horizon cross-sections with toroidal topology. The concrete model enables us to study for the first time dynamical horizons with toroidal topology, its area law, and the question of matter flux inside the horizon, without using a cut-and-paste technology to construct the solution. |
0907.3081 | Jean-Philippe Uzan | Jean-Philippe Uzan | Fundamental constants and tests of general relativity - Theoretical and
cosmological considerations | Proceedings of the workshop ``The nature of gravity, confronting
theory and experiment in space'', ISSI, Bern, october 2008 | null | 10.1007/s11214-009-9503-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The tests of the constancy of the fundamental constants are tests of the
local position invariance and thus of the equivalence principle. We summarize
the various constraints that have been obtained and then describe the
connection between varying constants and extensions of general relativity. To
finish, we discuss the link with cosmology, and more particularly with the
acceleration of the Universe. We take the opportunity to summarize various
possibilities to test general relativity (but also the Copernican principle) on
cosmological scales.
| [
{
"created": "Fri, 17 Jul 2009 14:13:55 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Uzan",
"Jean-Philippe",
""
]
] | The tests of the constancy of the fundamental constants are tests of the local position invariance and thus of the equivalence principle. We summarize the various constraints that have been obtained and then describe the connection between varying constants and extensions of general relativity. To finish, we discuss the link with cosmology, and more particularly with the acceleration of the Universe. We take the opportunity to summarize various possibilities to test general relativity (but also the Copernican principle) on cosmological scales. |
0705.3620 | Darren Golbourn | Leor Barack and Darren A Golbourn | Scalar-field perturbations from a particle orbiting a black hole using
numerical evolution in 2+1 dimensions | Accepted for publication in PRD, minor typographical corrections,
references updated, 25 pages, 22 eps figures | Phys.Rev.D76:044020,2007 | 10.1103/PhysRevD.76.044020 | null | gr-qc | null | We present a new technique for time-domain numerical evolution of the scalar
field generated by a pointlike scalar charge orbiting a black hole. Time-domain
evolution offers an efficient way for calculating black hole perturbations,
especially as input for computations of the local self force acting on orbiting
particles. In Kerr geometry, the field equations are not fully separable in the
time domain, and one has to tackle them in 2+1 dimensions (two spatial
dimensions and time; the azimuthal dependence is still separable). A technical
difficulty arises when the source of the field is a pointlike particle, as the
2+1-dimensional perturbation is then singular: Each of the azimuthal modes
diverges logarithmically at the particle. To deal with this problem we split
the numerical domain into two regions: Inside a thin worldtube surrounding the
particle's worldline we solve for a regularized variable, obtained from the
full field by subtracting out a suitable ``puncture'' function, given
analytically. Outside this worldtube we solve for the full, original field. The
value of the evolution variable is adjusted across the boundary of the
worldtube. In this work we demonstrate the applicability of this method in the
example of circular orbits around a Schwarzschild black hole (refraining from
exploiting the spherical symmetry of the background, and working in 2+1
dimensions).
| [
{
"created": "Thu, 24 May 2007 16:51:44 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Aug 2007 15:03:36 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Barack",
"Leor",
""
],
[
"Golbourn",
"Darren A",
""
]
] | We present a new technique for time-domain numerical evolution of the scalar field generated by a pointlike scalar charge orbiting a black hole. Time-domain evolution offers an efficient way for calculating black hole perturbations, especially as input for computations of the local self force acting on orbiting particles. In Kerr geometry, the field equations are not fully separable in the time domain, and one has to tackle them in 2+1 dimensions (two spatial dimensions and time; the azimuthal dependence is still separable). A technical difficulty arises when the source of the field is a pointlike particle, as the 2+1-dimensional perturbation is then singular: Each of the azimuthal modes diverges logarithmically at the particle. To deal with this problem we split the numerical domain into two regions: Inside a thin worldtube surrounding the particle's worldline we solve for a regularized variable, obtained from the full field by subtracting out a suitable ``puncture'' function, given analytically. Outside this worldtube we solve for the full, original field. The value of the evolution variable is adjusted across the boundary of the worldtube. In this work we demonstrate the applicability of this method in the example of circular orbits around a Schwarzschild black hole (refraining from exploiting the spherical symmetry of the background, and working in 2+1 dimensions). |
gr-qc/9707054 | Zloshchastiev Konstantin | Konstantin G. Zloshchastiev | Radiation fluid singular hypersurfaces with de Sitter interior as models
of charged extended particles in general relativity | LaTeX (IOPP style); final version | Class.Quant.Grav. 16 (1999) 1737-1744 | 10.1088/0264-9381/16/6/308 | null | gr-qc | null | In present paper we construct the classical and minisuperspace quantum models
of an extended charged particle. The modelling is based on the radiation fluid
singular hypersurface filled with physical vacuum. We demonstrate that both at
classical and quantum levels such a model can have equilibrium states at the
radius equal to the classical radius of a charged particle. In the cosmological
context the model could be considered also as the primary stationary state,
having the huge internal energy being nonobservable for an external observer,
from which the Universe was born by virtue of the quantum tunnelling.
| [
{
"created": "Fri, 25 Jul 1997 13:26:05 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Aug 1997 09:13:08 GMT",
"version": "v2"
},
{
"created": "Fri, 3 Jul 1998 05:32:56 GMT",
"version": "v3"
},
{
"created": "Sat, 29 May 1999 14:32:31 GMT",
"version": "v4"
}
] | 2009-10-30 | [
[
"Zloshchastiev",
"Konstantin G.",
""
]
] | In present paper we construct the classical and minisuperspace quantum models of an extended charged particle. The modelling is based on the radiation fluid singular hypersurface filled with physical vacuum. We demonstrate that both at classical and quantum levels such a model can have equilibrium states at the radius equal to the classical radius of a charged particle. In the cosmological context the model could be considered also as the primary stationary state, having the huge internal energy being nonobservable for an external observer, from which the Universe was born by virtue of the quantum tunnelling. |
1001.1112 | Edward Anderson | Edward Anderson | Relational mechanics of shape and scale | Just a few minor changes/references added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Relational particle mechanics models (RPM's) are useful models for the
problem of time in quantum gravity and other foundational issues in quantum
cosmology. Some concrete examples of scalefree RPM's have already been studied,
but it is the case with scale that is needed for the semiclassical and
dilational internal time approaches to the problem of time. In this paper, I
show that the scaled RPM's configuration spaces are the cones over the
scalefree RPM's configuration spaces, which are spheres in 1-d and complex
projective spaces in 2-d for plain shapes, and these quotiented by Z_2 for
oriented shapes. I extend the method of physical interpretation by tessellation
of the configuration space and the description in terms of geometrical
quantities to the cases with scale and/or orientation. I show that there is an
absence of monopole issues for RPM's and point out a difference between quantum
cosmological operator ordering and that used in molecular physics. I use up
RPM's freedom of the form of the potential to more closely parallel various
well-known cosmologies, and begin the investigation of the semiclassical
approach to the problem of time for such models.
| [
{
"created": "Thu, 7 Jan 2010 17:01:52 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Feb 2010 11:55:03 GMT",
"version": "v2"
}
] | 2010-02-15 | [
[
"Anderson",
"Edward",
""
]
] | Relational particle mechanics models (RPM's) are useful models for the problem of time in quantum gravity and other foundational issues in quantum cosmology. Some concrete examples of scalefree RPM's have already been studied, but it is the case with scale that is needed for the semiclassical and dilational internal time approaches to the problem of time. In this paper, I show that the scaled RPM's configuration spaces are the cones over the scalefree RPM's configuration spaces, which are spheres in 1-d and complex projective spaces in 2-d for plain shapes, and these quotiented by Z_2 for oriented shapes. I extend the method of physical interpretation by tessellation of the configuration space and the description in terms of geometrical quantities to the cases with scale and/or orientation. I show that there is an absence of monopole issues for RPM's and point out a difference between quantum cosmological operator ordering and that used in molecular physics. I use up RPM's freedom of the form of the potential to more closely parallel various well-known cosmologies, and begin the investigation of the semiclassical approach to the problem of time for such models. |
gr-qc/0701086 | Emanuele Berti | Emanuele Berti, Vitor Cardoso, Jose A. Gonzalez, Ulrich Sperhake | Mining information from binary black hole mergers: a comparison of
estimation methods for complex exponentials in noise | 20 pages, 7 figures, minor changes to match version in press in PRD | Phys.Rev.D75:124017,2007 | 10.1103/PhysRevD.75.124017 | null | gr-qc astro-ph | null | The ringdown phase following a binary black hole merger is usually assumed to
be well described by a linear superposition of complex exponentials
(quasinormal modes). In the strong-field conditions typical of a binary black
hole merger, non-linear effects may produce mode coupling. Artificial mode
coupling can also be induced by the black hole's rotation, if the radiation
field is expanded in terms of spin-weighted spherical (rather than spheroidal)
harmonics. Observing deviations from linear black hole perturbation theory
requires optimal fitting techniques to extract ringdown parameters from
numerical waveforms, which are inevitably affected by errors. So far,
non-linear least-squares fitting methods have been used as the standard
workhorse to extract frequencies from ringdown waveforms. These methods are
known not to be optimal for estimating parameters of complex exponentials.
Furthermore, different fitting methods have different performance in the
presence of noise. The main purpose of this paper is to introduce the
gravitational wave community to modern variations of a linear parameter
estimation technique first devised in 1795 by Prony: the Kumaresan-Tufts and
matrix pencil methods. Using "test" damped sinusoidal signals in Gaussian white
noise we illustrate the advantages of these methods, showing that they have
variance and bias at least comparable to standard non-linear least-squares
techniques. Then we compare the performance of different methods on
unequal-mass binary black hole merger waveforms. The methods we discuss should
be useful both theoretically (to monitor errors and search for non-linearities
in numerical relativity simulations) and experimentally (for parameter
estimation from ringdown signals after a gravitational wave detection).
| [
{
"created": "Tue, 16 Jan 2007 19:56:35 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Jun 2007 14:46:53 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Berti",
"Emanuele",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Gonzalez",
"Jose A.",
""
],
[
"Sperhake",
"Ulrich",
""
]
] | The ringdown phase following a binary black hole merger is usually assumed to be well described by a linear superposition of complex exponentials (quasinormal modes). In the strong-field conditions typical of a binary black hole merger, non-linear effects may produce mode coupling. Artificial mode coupling can also be induced by the black hole's rotation, if the radiation field is expanded in terms of spin-weighted spherical (rather than spheroidal) harmonics. Observing deviations from linear black hole perturbation theory requires optimal fitting techniques to extract ringdown parameters from numerical waveforms, which are inevitably affected by errors. So far, non-linear least-squares fitting methods have been used as the standard workhorse to extract frequencies from ringdown waveforms. These methods are known not to be optimal for estimating parameters of complex exponentials. Furthermore, different fitting methods have different performance in the presence of noise. The main purpose of this paper is to introduce the gravitational wave community to modern variations of a linear parameter estimation technique first devised in 1795 by Prony: the Kumaresan-Tufts and matrix pencil methods. Using "test" damped sinusoidal signals in Gaussian white noise we illustrate the advantages of these methods, showing that they have variance and bias at least comparable to standard non-linear least-squares techniques. Then we compare the performance of different methods on unequal-mass binary black hole merger waveforms. The methods we discuss should be useful both theoretically (to monitor errors and search for non-linearities in numerical relativity simulations) and experimentally (for parameter estimation from ringdown signals after a gravitational wave detection). |
1904.11917 | Tommi Markkanen | Tommi Markkanen, Arttu Rajantie, Stephen Stopyra and Tommi Tenkanen | Scalar correlation functions in de Sitter space from the stochastic
spectral expansion | 21 pages, 4 figures, 2 tables. v2: minor revision, version published
in JCAP | null | 10.1088/1475-7516/2019/08/001 | IMPERIAL/TP/2019/TM/03 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider light scalar fields during inflation and show how the stochastic
spectral expansion method can be used to calculate two-point correlation
functions of an arbitrary local function of the field in de Sitter space. In
particular, we use this approach for a massive scalar field with quartic
self-interactions to calculate the fluctuation spectrum of the density contrast
and compare it to other approximations. We find that neither Gaussian nor
linear approximations accurately reproduce the power spectrum, and in fact
always overestimate it. For example, for a scalar field with only a quartic
term in the potential, $V=\lambda\phi^4/4$, we find a blue spectrum with
spectral index $n-1=0.579\sqrt{\lambda}$.
| [
{
"created": "Fri, 26 Apr 2019 16:18:57 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Aug 2019 16:27:29 GMT",
"version": "v2"
}
] | 2019-08-02 | [
[
"Markkanen",
"Tommi",
""
],
[
"Rajantie",
"Arttu",
""
],
[
"Stopyra",
"Stephen",
""
],
[
"Tenkanen",
"Tommi",
""
]
] | We consider light scalar fields during inflation and show how the stochastic spectral expansion method can be used to calculate two-point correlation functions of an arbitrary local function of the field in de Sitter space. In particular, we use this approach for a massive scalar field with quartic self-interactions to calculate the fluctuation spectrum of the density contrast and compare it to other approximations. We find that neither Gaussian nor linear approximations accurately reproduce the power spectrum, and in fact always overestimate it. For example, for a scalar field with only a quartic term in the potential, $V=\lambda\phi^4/4$, we find a blue spectrum with spectral index $n-1=0.579\sqrt{\lambda}$. |
0804.1674 | Bernard Lavenda | B. H. Lavenda | Hyperbolic nature of uniformly rotating systems and their relation to
gravity | 8 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Special relativity corresponds to hyperbolic geometry at constant velocity
while the so-called general relativity corresponds to hyperbolic geometry of
uniformly accelerated systems. Generalized expressions for angular momentum,
centrifugal and Coriolis forces are found in hyperbolic space, which reduce to
the usual expressions of Euclidean space when the absolute constant tends to
infinity. Gravity enters only in the specification of the absolute constant. A
uniformly rotating disc corresponds exactly to hyperbolic geometry with a
constant negative Gaussian curvature. The angle defect is related to Lorentz
contraction of objects normal to the radial direction. Lobachevsky's angle of
parallelism accounts for the apparent relativistic distortion of moving objects
and would provide a testing ground to measure a positive defect by replacing
large distances by high speeds that are comparable with that of light.
| [
{
"created": "Thu, 10 Apr 2008 11:25:03 GMT",
"version": "v1"
}
] | 2008-04-11 | [
[
"Lavenda",
"B. H.",
""
]
] | Special relativity corresponds to hyperbolic geometry at constant velocity while the so-called general relativity corresponds to hyperbolic geometry of uniformly accelerated systems. Generalized expressions for angular momentum, centrifugal and Coriolis forces are found in hyperbolic space, which reduce to the usual expressions of Euclidean space when the absolute constant tends to infinity. Gravity enters only in the specification of the absolute constant. A uniformly rotating disc corresponds exactly to hyperbolic geometry with a constant negative Gaussian curvature. The angle defect is related to Lorentz contraction of objects normal to the radial direction. Lobachevsky's angle of parallelism accounts for the apparent relativistic distortion of moving objects and would provide a testing ground to measure a positive defect by replacing large distances by high speeds that are comparable with that of light. |
2308.07475 | Todd Oliynyk | Florian Beyer and Todd A. Oliynyk | Past stability of FLRW solutions to the Einstein-Euler-scalar field
equations and their big bang singularites | arXiv admin note: substantial text overlap with arXiv:2112.07730 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We establish, in spacetime dimensions $n\geq 3$, the nonlinear stability in
the contracting direction of Friedmann-Lema\^itre-Robertson-Walker (FLRW)
solutions to the Einstein-Euler-scalar field equations with linear equations of
state $P=c_s^2 \rho$ for sounds speeds $c_s$ satisfying $1/(n-1)<c_s^2 < 1$. We
further show that nonlinear perturbations of the FLRW solutions are
asymptotically pointwise Kasner and terminate in crushing, asymptotically
velocity term dominated (AVTD) big bang singularities characterised by
curvature blow-up.
| [
{
"created": "Mon, 14 Aug 2023 22:01:53 GMT",
"version": "v1"
}
] | 2023-08-16 | [
[
"Beyer",
"Florian",
""
],
[
"Oliynyk",
"Todd A.",
""
]
] | We establish, in spacetime dimensions $n\geq 3$, the nonlinear stability in the contracting direction of Friedmann-Lema\^itre-Robertson-Walker (FLRW) solutions to the Einstein-Euler-scalar field equations with linear equations of state $P=c_s^2 \rho$ for sounds speeds $c_s$ satisfying $1/(n-1)<c_s^2 < 1$. We further show that nonlinear perturbations of the FLRW solutions are asymptotically pointwise Kasner and terminate in crushing, asymptotically velocity term dominated (AVTD) big bang singularities characterised by curvature blow-up. |
gr-qc/9506056 | null | Giampiero Esposito and Giuseppe Pollifrone | Spin-Raising Operators and Spin-3/2 Potentials in Quantum Cosmology | 13 pages, plain-tex, recently appearing in Classical and Quantum
Gravity, volume 11, April 1994, pages 897-903. Apologies for the delay in
circulating the file, due to technical problems now fixed | Class.Quant.Grav.11:897-904,1994 | 10.1088/0264-9381/11/4/009 | DSF report 95/32 (see SLAC for previous data) | gr-qc | null | Local boundary conditions involving field strengths and the normal to the
boundary, originally studied in anti-de Sitter space-time, have been recently
considered in one-loop quantum cosmology. This paper derives the conditions
under which spin-raising operators preserve these local boundary conditions on
a 3-sphere for fields of spin 0,1/2,1,3/2 and 2. Moreover, the two-component
spinor analysis of the four potentials of the totally symmetric and independent
field strengths for spin 3/2 is applied to the case of a 3-sphere boundary. It
is shown that such boundary conditions can only be imposed in a flat Euclidean
background, for which the gauge freedom in the choice of the potentials
remains.
| [
{
"created": "Tue, 27 Jun 1995 06:52:20 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Esposito",
"Giampiero",
""
],
[
"Pollifrone",
"Giuseppe",
""
]
] | Local boundary conditions involving field strengths and the normal to the boundary, originally studied in anti-de Sitter space-time, have been recently considered in one-loop quantum cosmology. This paper derives the conditions under which spin-raising operators preserve these local boundary conditions on a 3-sphere for fields of spin 0,1/2,1,3/2 and 2. Moreover, the two-component spinor analysis of the four potentials of the totally symmetric and independent field strengths for spin 3/2 is applied to the case of a 3-sphere boundary. It is shown that such boundary conditions can only be imposed in a flat Euclidean background, for which the gauge freedom in the choice of the potentials remains. |
1705.06647 | John Barrow | John D. Barrow and Chandrima Ganguly | The Shape of Bouncing Universes | Awarded Honorable Mention in the 2017 Gravity Research Foundation
Essay competition; 4 pages, 6 figures | Int. J. Mod. Phys. D 26, 1743016 (2017) | 10.1142/S0218271817430167 | null | gr-qc astro-ph.CO hep-th physics.pop-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | What happens to the most general closed oscillating universes in general
relativity? We sketch the development of interest in cyclic universes from the
early work of Friedmann and Tolman to modern variations introduced by the
presence of a cosmological constant. Then we show what happens in the cyclic
evolution of the most general closed anisotropic universes provided by the
Mixmaster universe. We show that in the presence of entropy increase its cycles
grow in size and age, increasingly approaching flatness. But these cycles also
grow increasingly anisotropic at their expansion maxima. If there is a positive
cosmological constant, or dark energy, present then these oscillations always
end and the last cycle evolves from an anisotropic inflexion point towards a de
Sitter future of everlasting expansion.
| [
{
"created": "Thu, 18 May 2017 15:21:53 GMT",
"version": "v1"
}
] | 2018-01-08 | [
[
"Barrow",
"John D.",
""
],
[
"Ganguly",
"Chandrima",
""
]
] | What happens to the most general closed oscillating universes in general relativity? We sketch the development of interest in cyclic universes from the early work of Friedmann and Tolman to modern variations introduced by the presence of a cosmological constant. Then we show what happens in the cyclic evolution of the most general closed anisotropic universes provided by the Mixmaster universe. We show that in the presence of entropy increase its cycles grow in size and age, increasingly approaching flatness. But these cycles also grow increasingly anisotropic at their expansion maxima. If there is a positive cosmological constant, or dark energy, present then these oscillations always end and the last cycle evolves from an anisotropic inflexion point towards a de Sitter future of everlasting expansion. |
2304.00348 | Sohrab Rahvar | Sohrab Rahvar | Primordial black hole collision with neutron stars and astrophysical
black holes and the observational signatures | 12 pages, 2 figures, accepted in Int. J. Mod. Phys. D | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | In this paper, we examine whether low-mass Primordial Black Holes (PBHs) can
be considered a plausible dark matter candidate in galactic halos. We derive
the relativistic dynamics of PBHs around the heavy compact objects and evaluate
their collision rate, as well as the likelihood of PBH capture in neutron stars
and black holes. Although the rate of these collisions in the Milky Way is
lower than our lifetime (i.e. almost one collision per hundred years), it may
still be observable on cosmological scales. Additionally, we investigate the
gravitational wave emission as an important observable window for
PBH-astrophysical black hole merging. For the allowed range of PBH mass,
gravitational wave signal is smaller than the sensitivity of present
gravitational wave detectors. We provide observational prospect for detection
of these events in future.
| [
{
"created": "Sat, 1 Apr 2023 16:08:11 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Jun 2023 10:22:29 GMT",
"version": "v2"
},
{
"created": "Tue, 21 Nov 2023 11:10:43 GMT",
"version": "v3"
}
] | 2023-11-22 | [
[
"Rahvar",
"Sohrab",
""
]
] | In this paper, we examine whether low-mass Primordial Black Holes (PBHs) can be considered a plausible dark matter candidate in galactic halos. We derive the relativistic dynamics of PBHs around the heavy compact objects and evaluate their collision rate, as well as the likelihood of PBH capture in neutron stars and black holes. Although the rate of these collisions in the Milky Way is lower than our lifetime (i.e. almost one collision per hundred years), it may still be observable on cosmological scales. Additionally, we investigate the gravitational wave emission as an important observable window for PBH-astrophysical black hole merging. For the allowed range of PBH mass, gravitational wave signal is smaller than the sensitivity of present gravitational wave detectors. We provide observational prospect for detection of these events in future. |
1012.5172 | Riccardo Sturani | R. Sturani, S. Fischetti, L. Cadonati, G. M. Guidi, J. Healy, D.
Shoemaker, A. Vicere' | Phenomenological gravitational waveforms from spinning coalescing
binaries | 9 pages, 2 figures. Results updated in v2 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An accurate knowledge of the coalescing binary gravitational waveform is
crucial for experimental searches as the ones performed by the LIGO-Virgo
collaboration. Following an earlier paper by the same authors we refine the
construction of analytical phenomenological waveforms describing the signal
sourced by generically spinning binary systems. The gap between the initial
inspiral part of the waveform, described by spin-Taylor approximants, and its
final ring-down part, described by damped exponentials, is bridged by a
phenomenological phase calibrated by comparison with the dominant spherical
harmonic mode of a set of waveforms including both numerical and
phenomenological waveforms of different type. All waveforms considered describe
equal mass systems. The Advanced LIGO noise-weighted overlap integral between
the numerical and phenomenological waveforms presented here ranges between 0.95
and 0.99 for a wide span of mass values.
| [
{
"created": "Thu, 23 Dec 2010 10:41:45 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jun 2011 10:37:57 GMT",
"version": "v2"
}
] | 2011-06-24 | [
[
"Sturani",
"R.",
""
],
[
"Fischetti",
"S.",
""
],
[
"Cadonati",
"L.",
""
],
[
"Guidi",
"G. M.",
""
],
[
"Healy",
"J.",
""
],
[
"Shoemaker",
"D.",
""
],
[
"Vicere'",
"A.",
""
]
] | An accurate knowledge of the coalescing binary gravitational waveform is crucial for experimental searches as the ones performed by the LIGO-Virgo collaboration. Following an earlier paper by the same authors we refine the construction of analytical phenomenological waveforms describing the signal sourced by generically spinning binary systems. The gap between the initial inspiral part of the waveform, described by spin-Taylor approximants, and its final ring-down part, described by damped exponentials, is bridged by a phenomenological phase calibrated by comparison with the dominant spherical harmonic mode of a set of waveforms including both numerical and phenomenological waveforms of different type. All waveforms considered describe equal mass systems. The Advanced LIGO noise-weighted overlap integral between the numerical and phenomenological waveforms presented here ranges between 0.95 and 0.99 for a wide span of mass values. |
1511.02164 | Lunchakorn Tannukij | Lunchakorn Tannukij and Pitayuth Wongjun | Mass-Varying Massive Gravity with k-essence | 23 pages, 6 figures. Typos correction | null | 10.1140/epjc/s10052-015-3872-0 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a large class of mass-varying massive gravity models, the graviton mass
cannot provide the late-time cosmic expansion of the universe due to its
vanishing at late time. In this work, we propose a new class of mass-varying
massive gravity in which the graviton mass varies according to a kinetic term
of a k-essence field. By using a more general form of the fiducial metric, we
found a solution such that a non-vanishing graviton mass can drive the
accelerated expansion of the universe at late time. We also perform dynamical
analyses of such model and found that without introducing the k-essence
Lagrangian, the graviton mass can be responsible for both dark contents of the
universe, namely dark energy that drives the accelerated expansion of the
universe and non-relativistic matter that plays the role of dark matter.
Moreover, by including the k-essence Lagrangian, we found that it is possible
to alleviate the so-called cosmic coincidence problem.
| [
{
"created": "Thu, 5 Nov 2015 07:49:36 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Jan 2016 09:10:11 GMT",
"version": "v2"
}
] | 2016-02-17 | [
[
"Tannukij",
"Lunchakorn",
""
],
[
"Wongjun",
"Pitayuth",
""
]
] | For a large class of mass-varying massive gravity models, the graviton mass cannot provide the late-time cosmic expansion of the universe due to its vanishing at late time. In this work, we propose a new class of mass-varying massive gravity in which the graviton mass varies according to a kinetic term of a k-essence field. By using a more general form of the fiducial metric, we found a solution such that a non-vanishing graviton mass can drive the accelerated expansion of the universe at late time. We also perform dynamical analyses of such model and found that without introducing the k-essence Lagrangian, the graviton mass can be responsible for both dark contents of the universe, namely dark energy that drives the accelerated expansion of the universe and non-relativistic matter that plays the role of dark matter. Moreover, by including the k-essence Lagrangian, we found that it is possible to alleviate the so-called cosmic coincidence problem. |
2207.03966 | Griselda Figueroa Aguirre | Griselda Figueroa-Aguirre | Thin-shell wormholes in N-dimensional F(R) gravity | 18 pages, 6 figures; v3: minor changes, new references added | Int. J. Mod. Phys. D 32 (2023) 2350052 | 10.1142/S0218271823500529 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, spherically symmetric thin-shell wormholes with a conformally
invariant Maxwell field for $N$-dimensional $F(R)$ gravity and constant scalar
curvature $R$ are built. Two cases are considered: symmetric wormholes and
asymmetric ones in the scalar curvature. Their stability under radial
perturbations is analyzed, finding stable solutions made of exotic matter for a
given range of the parameters.
| [
{
"created": "Fri, 8 Jul 2022 15:32:19 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Feb 2023 15:13:59 GMT",
"version": "v2"
},
{
"created": "Thu, 1 Jun 2023 11:29:43 GMT",
"version": "v3"
}
] | 2023-07-13 | [
[
"Figueroa-Aguirre",
"Griselda",
""
]
] | In this work, spherically symmetric thin-shell wormholes with a conformally invariant Maxwell field for $N$-dimensional $F(R)$ gravity and constant scalar curvature $R$ are built. Two cases are considered: symmetric wormholes and asymmetric ones in the scalar curvature. Their stability under radial perturbations is analyzed, finding stable solutions made of exotic matter for a given range of the parameters. |
0707.4654 | Milton Ruiz | Milton Ruiz, Miguel Alcubierre, Dario Nunez, Ryoji Takahashi | Multipole expansions for energy and momenta carried by gravitational
waves | 12 pages. Typo fixed in equation (2.25) | Gen.Rel.Grav.40:2467,2008 | 10.1007/s10714-007-0570-8 | null | gr-qc | null | We present expressions for the energy, linear momentum and angular momentum
carried away from an isolated system by gravitational radiation based on
spin-weighted spherical harmonics decomposition of the Weyl scalar $\Psi_4$. We
also show that the expressions derived are equivalent to the common expressions
obtained when using a framework based on perturbations of a Schwazschild
background. The main idea is to collect together all the different expressions
in a uniform and consistent way. The formulae presented here are directly
applicable to the calculation of the radiated energy, linear momentum and
angular momentum starting from the gravitational waveforms which are typically
extracted from numerical simulations.
| [
{
"created": "Tue, 31 Jul 2007 16:41:06 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Dec 2007 17:17:51 GMT",
"version": "v2"
},
{
"created": "Mon, 25 Feb 2008 15:55:56 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Ruiz",
"Milton",
""
],
[
"Alcubierre",
"Miguel",
""
],
[
"Nunez",
"Dario",
""
],
[
"Takahashi",
"Ryoji",
""
]
] | We present expressions for the energy, linear momentum and angular momentum carried away from an isolated system by gravitational radiation based on spin-weighted spherical harmonics decomposition of the Weyl scalar $\Psi_4$. We also show that the expressions derived are equivalent to the common expressions obtained when using a framework based on perturbations of a Schwazschild background. The main idea is to collect together all the different expressions in a uniform and consistent way. The formulae presented here are directly applicable to the calculation of the radiated energy, linear momentum and angular momentum starting from the gravitational waveforms which are typically extracted from numerical simulations. |
gr-qc/9402005 | null | L.B. Szabados | Two dimensional Sen connections and quasi-local energy-momentum | 20 pages, Plain Tex, II | Class.Quant.Grav.11:1847-1866,1994 | 10.1088/0264-9381/11/7/020 | null | gr-qc | null | The recently constructed two dimensional Sen connection is applied in the
problem of quasi-local energy-momentum in general relativity. First it is shown
that, because of one of the two 2 dimensional Sen--Witten identities, Penrose's
quasi-local charge integral can be expressed as a Nester--Witten integral.Then,
to find the appropriate spinor propagation laws to the Nester--Witten integral,
all the possible first order linear differential operators that can be
constructed only from the irreducible chiral parts of the Sen operator alone
are determined and examined. It is only the holomorphy or anti-holomorphy
operator that can define acceptable propagation laws. The 2 dimensional Sen
connection thus naturally defines a quasi-local energy-momentum, which is
precisely that of Dougan and Mason. Then provided the dominant energy condition
holds and the 2-sphere S is convex we show that the next statements are
equivalent: i. the quasi-local mass (energy-momentum) associated with S is
zero; ii.the Cauchy development $D(\Sigma)$ is a pp-wave geometry with pure
radiation ($D(\Sigma)$ is flat), where $\Sigma$ is a spacelike hypersurface
whose boundary is S; iii. there exist a Sen--constant spinor field (two spinor
fields) on S. Thus the pp-wave Cauchy developments can be characterized by the
geometry of a two rather than a three dimensional submanifold.
| [
{
"created": "Wed, 2 Feb 1994 16:06:00 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Szabados",
"L. B.",
""
]
] | The recently constructed two dimensional Sen connection is applied in the problem of quasi-local energy-momentum in general relativity. First it is shown that, because of one of the two 2 dimensional Sen--Witten identities, Penrose's quasi-local charge integral can be expressed as a Nester--Witten integral.Then, to find the appropriate spinor propagation laws to the Nester--Witten integral, all the possible first order linear differential operators that can be constructed only from the irreducible chiral parts of the Sen operator alone are determined and examined. It is only the holomorphy or anti-holomorphy operator that can define acceptable propagation laws. The 2 dimensional Sen connection thus naturally defines a quasi-local energy-momentum, which is precisely that of Dougan and Mason. Then provided the dominant energy condition holds and the 2-sphere S is convex we show that the next statements are equivalent: i. the quasi-local mass (energy-momentum) associated with S is zero; ii.the Cauchy development $D(\Sigma)$ is a pp-wave geometry with pure radiation ($D(\Sigma)$ is flat), where $\Sigma$ is a spacelike hypersurface whose boundary is S; iii. there exist a Sen--constant spinor field (two spinor fields) on S. Thus the pp-wave Cauchy developments can be characterized by the geometry of a two rather than a three dimensional submanifold. |
1304.4973 | Orchidea Maria Lecian | Orchidea Maria Lecian | BKL maps and Poincar\'e sections | 21 pages, 2 tables, 2 figures; comparison with Farey maps and
relation with scars in the quantum regime added; accepted for publication on
Phys. Rev. D; matches published version | Phys. Rev. D 88, 104014 (2013) | 10.1103/PhysRevD.88.104014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmological billiards arise as a map of the solution to the Einstein
equations, when the most general symmetry of the metric tensor is implemented,
under the BKL (named after Belinskii, Khalatnikov and Lifshitz) paradigm, for
which points are spatially decoupled in the asymptotical limit close to the
cosmological singularity. Cosmological billiards in $4=3+1$ dimensions for the
case of pure gravity are analyzed for those features, for which the content of
Weyl reflections in the BKL maps requires definition of a 3-dimensional
restricted phase space. The role of Poincar\'e sections in these processes is
outlined. The quantum regime is investigated within this framework: as a
result, 1-epoch BKL eras are found to be the most probable configuration at
which the wavefunctions have to be evaluated; furthermore, BKL eras containing
$n>>1$ epochs are shown to be a less probable configuration for the
wavefunctions. This description of the dynamics allows one to gain information
about the connections between the statistical characterization of the maps
which imply the different symmetry-quotienting mechanisms and the
characterization of the semiclassical limit of the wavefunctions for the
classical trajectories, for which the phenomenon of 'scars' on the wavefunction
is found for other kinds of billiards.
| [
{
"created": "Wed, 17 Apr 2013 21:27:26 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Oct 2013 13:28:08 GMT",
"version": "v2"
}
] | 2013-11-20 | [
[
"Lecian",
"Orchidea Maria",
""
]
] | Cosmological billiards arise as a map of the solution to the Einstein equations, when the most general symmetry of the metric tensor is implemented, under the BKL (named after Belinskii, Khalatnikov and Lifshitz) paradigm, for which points are spatially decoupled in the asymptotical limit close to the cosmological singularity. Cosmological billiards in $4=3+1$ dimensions for the case of pure gravity are analyzed for those features, for which the content of Weyl reflections in the BKL maps requires definition of a 3-dimensional restricted phase space. The role of Poincar\'e sections in these processes is outlined. The quantum regime is investigated within this framework: as a result, 1-epoch BKL eras are found to be the most probable configuration at which the wavefunctions have to be evaluated; furthermore, BKL eras containing $n>>1$ epochs are shown to be a less probable configuration for the wavefunctions. This description of the dynamics allows one to gain information about the connections between the statistical characterization of the maps which imply the different symmetry-quotienting mechanisms and the characterization of the semiclassical limit of the wavefunctions for the classical trajectories, for which the phenomenon of 'scars' on the wavefunction is found for other kinds of billiards. |
0808.2561 | J. Fernando Barbero G. | J. Fernando Barbero G., I\~naki Garay, Eduardo J. S. Villase\~nor | Quantum Einstein-Rosen waves: Coherent states and n-point functions | 24 pages | Class.Quant.Grav.25:205013,2008 | 10.1088/0264-9381/25/20/205013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss two different types of issues concerning the quantization of
Einstein-Rosen waves. First of all we study in detail the possibility of using
the coherent states corresponding to the dynamics of the auxiliary, free
Hamiltonian appearing in the description of the model to study the full
dynamics of the system. For time periods of arbitrary length we show that this
is only possible for states that are close, in a precise mathematical sense, to
the vacuum. We do this by comparing the quantum evolutions defined by the
auxiliary and physical Hamiltonians on the class of coherent states. In the
second part of the paper we study the structure of n-point functions. As we
will show their detailed behavior differs from the one corresponding to
standard perturbative quantum field theories. We take this as a manifestation
of the fact that the correct approximation scheme for physically interesting
objects in these models does not lead to a power series expansion in the
relevant coupling constant but to a more complicated asymptotic behavior.
| [
{
"created": "Tue, 19 Aug 2008 09:51:42 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"G.",
"J. Fernando Barbero",
""
],
[
"Garay",
"Iñaki",
""
],
[
"Villaseñor",
"Eduardo J. S.",
""
]
] | We discuss two different types of issues concerning the quantization of Einstein-Rosen waves. First of all we study in detail the possibility of using the coherent states corresponding to the dynamics of the auxiliary, free Hamiltonian appearing in the description of the model to study the full dynamics of the system. For time periods of arbitrary length we show that this is only possible for states that are close, in a precise mathematical sense, to the vacuum. We do this by comparing the quantum evolutions defined by the auxiliary and physical Hamiltonians on the class of coherent states. In the second part of the paper we study the structure of n-point functions. As we will show their detailed behavior differs from the one corresponding to standard perturbative quantum field theories. We take this as a manifestation of the fact that the correct approximation scheme for physically interesting objects in these models does not lead to a power series expansion in the relevant coupling constant but to a more complicated asymptotic behavior. |
gr-qc/0001098 | Rosario Martin | Rosario Martin and Enric Verdaguer | Stochastic semiclassical fluctuations in Minkowski spacetime | 28 pages, RevTeX, no figures | Phys.Rev. D61 (2000) 124024 | 10.1103/PhysRevD.61.124024 | null | gr-qc hep-th | null | The semiclassical Einstein-Langevin equations which describe the dynamics of
stochastic perturbations of the metric induced by quantum stress-energy
fluctuations of matter fields in a given state are considered on the background
of the ground state of semiclassical gravity, namely, Minkowski spacetime and a
scalar field in its vacuum state. The relevant equations are explicitly derived
for massless and massive fields arbitrarily coupled to the curvature. In doing
so, some semiclassical results, such as the expectation value of the
stress-energy tensor to linear order in the metric perturbations and particle
creation effects, are obtained. We then solve the equations and compute the
two-point correlation functions for the linearized Einstein tensor and for the
metric perturbations. In the conformal field case, explicit results are
obtained. These results hint that gravitational fluctuations in stochastic
semiclassical gravity have a ``non-perturbative'' behavior in some
characteristic correlation lengths.
| [
{
"created": "Fri, 28 Jan 2000 16:16:13 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Martin",
"Rosario",
""
],
[
"Verdaguer",
"Enric",
""
]
] | The semiclassical Einstein-Langevin equations which describe the dynamics of stochastic perturbations of the metric induced by quantum stress-energy fluctuations of matter fields in a given state are considered on the background of the ground state of semiclassical gravity, namely, Minkowski spacetime and a scalar field in its vacuum state. The relevant equations are explicitly derived for massless and massive fields arbitrarily coupled to the curvature. In doing so, some semiclassical results, such as the expectation value of the stress-energy tensor to linear order in the metric perturbations and particle creation effects, are obtained. We then solve the equations and compute the two-point correlation functions for the linearized Einstein tensor and for the metric perturbations. In the conformal field case, explicit results are obtained. These results hint that gravitational fluctuations in stochastic semiclassical gravity have a ``non-perturbative'' behavior in some characteristic correlation lengths. |
gr-qc/0010026 | Francisco Navarro | F. J. Chinea (Univ. Complutense, Madrid (Spain)), F. Navarro-Lerida
(Univ. Complutense, Madrid (Spain)) | Twisting type-N vacuum fields with a group $H_2$ | LaTeX, 11 pages. To be published in Classical and Quantum Gravity | Class.Quant.Grav. 17 (2000) 4587-4596 | 10.1088/0264-9381/17/21/314 | null | gr-qc | null | We derive the equations corresponding to twisting type-N vacuum gravitational
fields with one Killing vector and one homothetic Killing vector by using the
same approach as that developed by one of us in order to treat the case with
two non-commuting Killing vectors. We study the case when the homothetic
parameter $\phi$ takes the value -1, which is shown to admit a reduction to a
third-order real ordinary differential equation for this problem, similar to
that previously obtained by one of us when two Killing vectors are present.
| [
{
"created": "Sat, 7 Oct 2000 21:28:27 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Chinea",
"F. J.",
"",
"Univ. Complutense, Madrid"
],
[
"Navarro-Lerida",
"F.",
"",
"Univ. Complutense, Madrid"
]
] | We derive the equations corresponding to twisting type-N vacuum gravitational fields with one Killing vector and one homothetic Killing vector by using the same approach as that developed by one of us in order to treat the case with two non-commuting Killing vectors. We study the case when the homothetic parameter $\phi$ takes the value -1, which is shown to admit a reduction to a third-order real ordinary differential equation for this problem, similar to that previously obtained by one of us when two Killing vectors are present. |
0710.0614 | Lawrence E. Kidder | Lawrence E. Kidder | Using Full Information When Computing Modes of Post-Newtonian Waveforms
From Inspiralling Compact Binaries in Circular Orbit | 15 pages | Phys.Rev.D77:044016,2008 | 10.1103/PhysRevD.77.044016 | null | gr-qc | null | The increasing sophistication and accuracy of numerical simulations of
compact binaries (especially binary black holes) presents the opportunity to
test the regime in which post-Newtonian (PN) predictions for the emitted
gravitational waves are accurate. In order to confront numerical results with
those of post-Newtonian theory, it is convenient to compare multipolar
decompositions of the two waveforms. It is pointed out here that the individual
modes can be computed to higher post-Newtonian order by examining the radiative
multipole moments of the system, rather than by decomposing the 2.5PN
polarization waveforms. In particular, the dominant (l = 2, m = 2) mode can be
computed to 3PN order. Individual modes are computed to as high a
post-Newtonian order as possible given previous post-Newtonian results.
| [
{
"created": "Tue, 2 Oct 2007 19:46:57 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kidder",
"Lawrence E.",
""
]
] | The increasing sophistication and accuracy of numerical simulations of compact binaries (especially binary black holes) presents the opportunity to test the regime in which post-Newtonian (PN) predictions for the emitted gravitational waves are accurate. In order to confront numerical results with those of post-Newtonian theory, it is convenient to compare multipolar decompositions of the two waveforms. It is pointed out here that the individual modes can be computed to higher post-Newtonian order by examining the radiative multipole moments of the system, rather than by decomposing the 2.5PN polarization waveforms. In particular, the dominant (l = 2, m = 2) mode can be computed to 3PN order. Individual modes are computed to as high a post-Newtonian order as possible given previous post-Newtonian results. |
2012.12606 | David Senjaya | David Senjaya and Alejandro Saiz Rivera | Canonical Quantization of Neutral and Charged Static Black Hole as a
Gravitational Atom | Presented in Siam Physics Conference 2020 | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The gravitational field is usually neglected in the calculation of atomic
energy levels as its effect is much weaker than the electromagnetic field, but
that is not the case for a particle orbiting a black hole. In this work, the
canonical quantization of a massive and massless particles under gravitational
field exerted by this tiny but very massive object, both neutral and charged,
is carried out. By using this method, a very rare exact result of the
particle's quantized energy can be discovered. The presence of a very strong
attractive field and also the horizon make the energy complex valued and force
the corresponding wave function to be a quasibound state. Moreover, by taking
the small scale limit, the system becomes a gravitational atom in the sense of
Hydrogenic atoms energy levels and its wave function can be rediscovered.
Moreover, analogous to electronic transitions, the transition of the particle
in this case emits a graviton which carries a unique fingerprint of the black
hole such as black hole's mass and charge.
| [
{
"created": "Wed, 23 Dec 2020 11:17:17 GMT",
"version": "v1"
}
] | 2020-12-24 | [
[
"Senjaya",
"David",
""
],
[
"Rivera",
"Alejandro Saiz",
""
]
] | The gravitational field is usually neglected in the calculation of atomic energy levels as its effect is much weaker than the electromagnetic field, but that is not the case for a particle orbiting a black hole. In this work, the canonical quantization of a massive and massless particles under gravitational field exerted by this tiny but very massive object, both neutral and charged, is carried out. By using this method, a very rare exact result of the particle's quantized energy can be discovered. The presence of a very strong attractive field and also the horizon make the energy complex valued and force the corresponding wave function to be a quasibound state. Moreover, by taking the small scale limit, the system becomes a gravitational atom in the sense of Hydrogenic atoms energy levels and its wave function can be rediscovered. Moreover, analogous to electronic transitions, the transition of the particle in this case emits a graviton which carries a unique fingerprint of the black hole such as black hole's mass and charge. |
gr-qc/9911043 | Simon Davis | Simon Davis and Hugh Luckock | The Effect of Higher-Order Curvature Terms on String Quantum Cosmology | 24 pages, TeX. Several remarks on operator ordering, the complete
computation of $H_1\psi_0$, and approximate solutions of the $a$ and $\Phi$
equations of motion, which are stable and exponentially expanding, have been
included. Substantial revision of equations (5)-(7), (10)-(20) from version 2 | Phys.Lett. B485 (2000) 408-421 | 10.1016/S0370-2693(00)00610-9 | Report 99-23 | gr-qc | null | Several new results regarding the quantum cosmology of the quadratic gravity
theory derived from the heterotic string effective action are presented. After
describing techniques for solving the Wheeler-De Witt equation with appropriate
boundary conditions, it is shown that this quantum cosmological model may be
compared with semiclassical theories of inflationary cosmology. In particular,
it should be possible to compute corrections to the standard inflationary model
perturbatively about a stable exponentially expanding classical background.
| [
{
"created": "Wed, 10 Nov 1999 23:04:20 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Feb 2000 08:06:11 GMT",
"version": "v2"
},
{
"created": "Wed, 9 Aug 2000 14:31:11 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Davis",
"Simon",
""
],
[
"Luckock",
"Hugh",
""
]
] | Several new results regarding the quantum cosmology of the quadratic gravity theory derived from the heterotic string effective action are presented. After describing techniques for solving the Wheeler-De Witt equation with appropriate boundary conditions, it is shown that this quantum cosmological model may be compared with semiclassical theories of inflationary cosmology. In particular, it should be possible to compute corrections to the standard inflationary model perturbatively about a stable exponentially expanding classical background. |
1212.2709 | Yousef Bisabr | Yousef Bisabr (Farzan-Nahad) | On the Chameleon Brans-Dicke Cosmology | 9 pages, no figure | Phys. Rev. D 86, 127503 (2012) | 10.1103/PhysRevD.86.127503 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a generalized Brans-Dicke model in which the scalar field has a
potential function and is also allowed to couple non-minimally with the matter
sector. We assume a power law form for the potential and the coupling functions
as the inputs of the model and show that acceleration of the universe can be
realized for a constrained range of exponent of the potential function. We also
argue that this accelerating phase is consistent with a large and positive
Brans-Dicke parameter. In our analysis, the potential plays a more important
role with respect to the coupling function in dynamics of the universe as the
latter does not contribute to any of the relations characterizing evolution of
scale factor of the universe and the scalar field. However, we will show that
the coupling function is closely related to magnitude and direction of the
energy transfer between matter and the scale field. We use this fact and some
thermodynamic aspects of the model to put some constraints on the coupling
function. In particular, we argue that the second law of thermodynamics
constrains direction of the overall energy transfer.
| [
{
"created": "Wed, 12 Dec 2012 05:41:14 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Dec 2012 05:50:17 GMT",
"version": "v2"
}
] | 2012-12-14 | [
[
"Bisabr",
"Yousef",
"",
"Farzan-Nahad"
]
] | We consider a generalized Brans-Dicke model in which the scalar field has a potential function and is also allowed to couple non-minimally with the matter sector. We assume a power law form for the potential and the coupling functions as the inputs of the model and show that acceleration of the universe can be realized for a constrained range of exponent of the potential function. We also argue that this accelerating phase is consistent with a large and positive Brans-Dicke parameter. In our analysis, the potential plays a more important role with respect to the coupling function in dynamics of the universe as the latter does not contribute to any of the relations characterizing evolution of scale factor of the universe and the scalar field. However, we will show that the coupling function is closely related to magnitude and direction of the energy transfer between matter and the scale field. We use this fact and some thermodynamic aspects of the model to put some constraints on the coupling function. In particular, we argue that the second law of thermodynamics constrains direction of the overall energy transfer. |
1301.5508 | Radu Slobodeanu Al. | Radu Slobodeanu | Shear-free perfect fluids with linear equation of state | 24 pages. Expanded Sections 1, 7 and 8; minor change in the end of
Section 4; added references. Mathematica files available at
http://unibuc.ro/prof/slobodeanu_r_a/resurse.php | null | 10.1088/0264-9381/31/12/125012 | null | gr-qc hep-th math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that shear-free perfect fluid solutions of Einstein's field
equations must be either expansion-free or non-rotating (as conjectured by
Treciokas and Ellis) for all linear equations of state $p = w \rho$ except for
six values of $w$.
| [
{
"created": "Wed, 23 Jan 2013 14:14:52 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Mar 2013 11:21:27 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Slobodeanu",
"Radu",
""
]
] | We prove that shear-free perfect fluid solutions of Einstein's field equations must be either expansion-free or non-rotating (as conjectured by Treciokas and Ellis) for all linear equations of state $p = w \rho$ except for six values of $w$. |
gr-qc/0401063 | Slava G. Turyshev | Slava G. Turyshev, Michael Shao and Kenneth L. Nordtvedt Jr | The Laser Astrometric Test of Relativity Mission | 8 pages, 2 figures, invited talk given at the Second International
Conference on Particle and Fundamental Physics in Space (SpacePart'03), 10-12
December 2003, Washington, DC | Nucl.Phys.Proc.Suppl. 134 (2004) 171-178 | 10.1088/0264-9381/21/12/001 | null | gr-qc | null | This paper discusses new fundamental physics experiment to test relativistic
gravity at the accuracy better than the effects of the 2nd order in the
gravitational field strength. The Laser Astrometric Test Of Relativity (LATOR)
mission uses laser interferometry between two micro-spacecraft whose lines of
sight pass close by the Sun to accurately measure deflection of light in the
solar gravity. The key element of the experimental design is a redundant
geometry optical truss provided by a long-baseline (100 m) multi-channel
stellar optical interferometer placed on the International Space Station. The
geometric redundancy enables LATOR to measure the departure from Euclidean
geometry caused by the solar gravity field to a very high accuracy. LATOR will
not only improve the value of the parameterized post-Newtonian (PPN) parameter
gamma to unprecedented levels of accuracy of 1 part in 1e8, it will also reach
ability to measure effects of the next post-Newtonian order (1/c^4) of light
deflection resulting from gravity's intrinsic non-linearity. The solar
quadrupole moment parameter, J2, will be measured with high precision, as well
as a variety of other relativistic. LATOR will lead to very robust advances in
the tests of fundamental physics: this mission could discover a violation or
extension of general relativity, or reveal the presence of an additional long
range interaction in the physical law. There are no analogs to the LATOR
experiment; it is unique and is a natural culmination of solar system gravity
experiments.
| [
{
"created": "Thu, 15 Jan 2004 07:57:07 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Turyshev",
"Slava G.",
""
],
[
"Shao",
"Michael",
""
],
[
"Nordtvedt",
"Kenneth L.",
"Jr"
]
] | This paper discusses new fundamental physics experiment to test relativistic gravity at the accuracy better than the effects of the 2nd order in the gravitational field strength. The Laser Astrometric Test Of Relativity (LATOR) mission uses laser interferometry between two micro-spacecraft whose lines of sight pass close by the Sun to accurately measure deflection of light in the solar gravity. The key element of the experimental design is a redundant geometry optical truss provided by a long-baseline (100 m) multi-channel stellar optical interferometer placed on the International Space Station. The geometric redundancy enables LATOR to measure the departure from Euclidean geometry caused by the solar gravity field to a very high accuracy. LATOR will not only improve the value of the parameterized post-Newtonian (PPN) parameter gamma to unprecedented levels of accuracy of 1 part in 1e8, it will also reach ability to measure effects of the next post-Newtonian order (1/c^4) of light deflection resulting from gravity's intrinsic non-linearity. The solar quadrupole moment parameter, J2, will be measured with high precision, as well as a variety of other relativistic. LATOR will lead to very robust advances in the tests of fundamental physics: this mission could discover a violation or extension of general relativity, or reveal the presence of an additional long range interaction in the physical law. There are no analogs to the LATOR experiment; it is unique and is a natural culmination of solar system gravity experiments. |
2008.04404 | John W. Moffat | J. W. Moffat | Modified Gravity (MOG) and Heavy Neutron Star in Mass Gap | 4 pages, no figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The modified gravity (MOG) theory is applied to the gravitational wave binary
merger GW190814 to demonstrate that the modified Tolman-Oppenheimer-Volkoff
equation for a neutron star can produce a mass $M=2.6 -2.7 M_\odot$, allowing
for the binary secondary component to be identified as a heavy neutron star in
the hypothesized mass gap $2.5 - 5 M_\odot$.
| [
{
"created": "Mon, 10 Aug 2020 20:27:30 GMT",
"version": "v1"
}
] | 2020-08-17 | [
[
"Moffat",
"J. W.",
""
]
] | The modified gravity (MOG) theory is applied to the gravitational wave binary merger GW190814 to demonstrate that the modified Tolman-Oppenheimer-Volkoff equation for a neutron star can produce a mass $M=2.6 -2.7 M_\odot$, allowing for the binary secondary component to be identified as a heavy neutron star in the hypothesized mass gap $2.5 - 5 M_\odot$. |
gr-qc/0111097 | Daniel Grumiller | Daniel Grumiller | Virtual black hole phenomenology from 2d dilaton theories | 17 pages, 13 figures | Class.Quant.Grav. 19 (2002) 997-1009 | 10.1088/0264-9381/19/5/311 | TUW-01-31 | gr-qc hep-th | null | Equipped with the tools of (spherically reduced) dilaton gravity in first
order formulation and with the results for the lowest order S-matrix for s-wave
gravitational scattering (P. Fischer, D. Grumiller, W. Kummer, and D.
Vassilevich, gr-qc/0105034) new properties of the ensuing cross-section are
discussed. We find CPT invariance, despite of the non-local nature of our
effective theory and discover pseudo-self-similarity in its kinematic sector.
After presenting the Carter-Penrose diagram for the corresponding virtual
black hole geometry we encounter distributional contributions to its
Ricci-scalar and a vanishing Einstein-Hilbert action for that configuration.
Finally, a comparison is done between our (Minkowskian) virtual black hole and
Hawking's (Euclidean) virtual black hole bubbles.
| [
{
"created": "Wed, 28 Nov 2001 16:13:47 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Feb 2002 12:51:47 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Grumiller",
"Daniel",
""
]
] | Equipped with the tools of (spherically reduced) dilaton gravity in first order formulation and with the results for the lowest order S-matrix for s-wave gravitational scattering (P. Fischer, D. Grumiller, W. Kummer, and D. Vassilevich, gr-qc/0105034) new properties of the ensuing cross-section are discussed. We find CPT invariance, despite of the non-local nature of our effective theory and discover pseudo-self-similarity in its kinematic sector. After presenting the Carter-Penrose diagram for the corresponding virtual black hole geometry we encounter distributional contributions to its Ricci-scalar and a vanishing Einstein-Hilbert action for that configuration. Finally, a comparison is done between our (Minkowskian) virtual black hole and Hawking's (Euclidean) virtual black hole bubbles. |
2407.07043 | Ethan Payne | Ethan Payne, Maximiliano Isi, Katerina Chatziioannou, Luis Lehner,
Yanbei Chen, Will M. Farr | The curvature dependence of gravitational-wave tests of General
Relativity | 8 pages, 3 figures | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | High-energy extensions to General Relativity modify the Einstein-Hilbert
action with higher-order curvature corrections and theory-specific coupling
constants. The order of these corrections imprints a universal curvature
dependence on observations while the coupling constant controls the deviation
strength. In this Letter, we leverage the theory-independent expectation that
modifications to the action of a given order in spacetime curvature (Riemann
tensor and contractions) lead to observational deviations that scale with the
system length-scale to a corresponding power. Focusing on gravitational wave
observations, the relevant scale is the binary total mass, and deviations scale
as a power of mass $p$ related to the action order. For example, $p=4,6$ arise
in effective field theory for cubic and quartic theories respectively. We
incorporate this universal scaling into theory-agnostic tests of General
Relativity with current gravitational-wave observations, thus enabling
constraints on the curvature scaling without compromising the agnostic nature
of these tests. This introduces a flexible yet highly interpretable new
paradigm for tests of General Relativity with gravitational-wave catalogs.
| [
{
"created": "Tue, 9 Jul 2024 17:04:10 GMT",
"version": "v1"
}
] | 2024-07-10 | [
[
"Payne",
"Ethan",
""
],
[
"Isi",
"Maximiliano",
""
],
[
"Chatziioannou",
"Katerina",
""
],
[
"Lehner",
"Luis",
""
],
[
"Chen",
"Yanbei",
""
],
[
"Farr",
"Will M.",
""
]
] | High-energy extensions to General Relativity modify the Einstein-Hilbert action with higher-order curvature corrections and theory-specific coupling constants. The order of these corrections imprints a universal curvature dependence on observations while the coupling constant controls the deviation strength. In this Letter, we leverage the theory-independent expectation that modifications to the action of a given order in spacetime curvature (Riemann tensor and contractions) lead to observational deviations that scale with the system length-scale to a corresponding power. Focusing on gravitational wave observations, the relevant scale is the binary total mass, and deviations scale as a power of mass $p$ related to the action order. For example, $p=4,6$ arise in effective field theory for cubic and quartic theories respectively. We incorporate this universal scaling into theory-agnostic tests of General Relativity with current gravitational-wave observations, thus enabling constraints on the curvature scaling without compromising the agnostic nature of these tests. This introduces a flexible yet highly interpretable new paradigm for tests of General Relativity with gravitational-wave catalogs. |
2110.02704 | Lorenzo Annulli | Lorenzo Annulli | Challenging theories of gravitation: dark matter, compact objects and
gravitational waves | 224 pages, PhD Thesis | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The most accurate model to describe the gravitational interaction is the
well-known theory of General Relativity. Several observational evidences
corroborate the legitimacy of the theory compared to the older Newtonian
gravity. General Relativity furthermore predicts the existence of gravitational
waves, i.e. spacetime ripples produced by accelerated masses. Thanks to a
connected network of interferometers called LIGO/Virgo, gravitational waves
from the coalescence of massive and compact astrophysical bodies have been
measured directly. These recent observations paved the way to a completely new
route to test the gravitational interaction. The possibility of using
gravitational waves to obtain a deeper understanding of open problems within
General Relativity motivates the work developed in this thesis. Each part is
essentially devoted to challenging the current model of gravitation, sometimes
including yet undiscovered new matter fields, and other times modifying the
theoretical framework of General Relativity.
In the first part of this manuscript, I discuss the astrophysical
consequences of the presence of scalar fields permeating galaxies. A detailed
picture of the interaction of massive black holes and scalar dark matter
structures is provided. The second part is dedicated to the analysis of the
generation and propagation of gravitational waves. As an example, I examine the
close limit approximation as a promising tool to investigate the collision of
extreme compact objects. The last part of this thesis instead focuses on
unstable mechanisms around black holes and stars (scalarization and
vectorization), in two alternative models of gravitation.
| [
{
"created": "Wed, 6 Oct 2021 12:44:12 GMT",
"version": "v1"
}
] | 2021-10-07 | [
[
"Annulli",
"Lorenzo",
""
]
] | The most accurate model to describe the gravitational interaction is the well-known theory of General Relativity. Several observational evidences corroborate the legitimacy of the theory compared to the older Newtonian gravity. General Relativity furthermore predicts the existence of gravitational waves, i.e. spacetime ripples produced by accelerated masses. Thanks to a connected network of interferometers called LIGO/Virgo, gravitational waves from the coalescence of massive and compact astrophysical bodies have been measured directly. These recent observations paved the way to a completely new route to test the gravitational interaction. The possibility of using gravitational waves to obtain a deeper understanding of open problems within General Relativity motivates the work developed in this thesis. Each part is essentially devoted to challenging the current model of gravitation, sometimes including yet undiscovered new matter fields, and other times modifying the theoretical framework of General Relativity. In the first part of this manuscript, I discuss the astrophysical consequences of the presence of scalar fields permeating galaxies. A detailed picture of the interaction of massive black holes and scalar dark matter structures is provided. The second part is dedicated to the analysis of the generation and propagation of gravitational waves. As an example, I examine the close limit approximation as a promising tool to investigate the collision of extreme compact objects. The last part of this thesis instead focuses on unstable mechanisms around black holes and stars (scalarization and vectorization), in two alternative models of gravitation. |
gr-qc/0108047 | Michael D. Seifert | M. Seifert | Angle and Volume Studies in Quantized Space | Undergraduate thesis. 85 pp. (incl. TOC & appendices), 21 figures
(not incl. diagrams in eqns.) | null | null | null | gr-qc | null | The search for a quantum theory of gravity is one of the major challenges
facing theoretical physics today. While no complete theory exists, a promising
avenue of research is the loop quantum gravity approach. In this approach,
quantum states are represented by spin networks, essentially graphs with
weighted edges. Since general relativity predicts the structure of space, any
quantum theory of gravity must do so as well; thus, "spatial observables" such
as area, volume, and angle are given by the eigenvalues of Hermitian operators
on the spin network states. We present results obtained in our investigations
of the angle and volume operators, two operators which act on the vertices of
spin networks. We find that the minimum observable angle is inversely
proportional to the square root of the total spin of the vertex, a fairly slow
decrease to zero. We also present numerical results indicating that the angle
operator can reproduce the classical angle distribution. The volume operator is
significantly harder to investigate analytically; however, we present
analytical and numerical results indicating that the volume of a region scales
as the 3/2 power of its bounding surface, which corresponds to the classical
model of space.
| [
{
"created": "Sun, 19 Aug 2001 15:27:58 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Seifert",
"M.",
""
]
] | The search for a quantum theory of gravity is one of the major challenges facing theoretical physics today. While no complete theory exists, a promising avenue of research is the loop quantum gravity approach. In this approach, quantum states are represented by spin networks, essentially graphs with weighted edges. Since general relativity predicts the structure of space, any quantum theory of gravity must do so as well; thus, "spatial observables" such as area, volume, and angle are given by the eigenvalues of Hermitian operators on the spin network states. We present results obtained in our investigations of the angle and volume operators, two operators which act on the vertices of spin networks. We find that the minimum observable angle is inversely proportional to the square root of the total spin of the vertex, a fairly slow decrease to zero. We also present numerical results indicating that the angle operator can reproduce the classical angle distribution. The volume operator is significantly harder to investigate analytically; however, we present analytical and numerical results indicating that the volume of a region scales as the 3/2 power of its bounding surface, which corresponds to the classical model of space. |
gr-qc/0401113 | Jose A. Gonzalez | Miguel Alcubierre and Jose A. Gonzalez | Regularization of spherically symmetric evolution codes in numerical
relativity | 7 pages, 4 figures, submitted to Computer Physics Communications | Comput.Phys.Commun. 167 (2005) 76-84 | 10.1016/j.cpc.2005.01.008 | null | gr-qc | null | The lack of regularity of geometric variables at the origin is often a source
of serious problem for spherically symmetric evolution codes in numerical
relativity. One usually deals with this by restricting the gauge and solving
the hamiltonian constraint for the metric. Here we present a generic algorithm
for dealing with the regularization of the origin that can be used directly on
the evolution equations and that allows very general gauge choices. Our
approach is similar in spirit to the one introduced by Arbona and Bona for the
particular case of the Bona-Masso formulation. However, our algorithm is more
general and can be used with a wide variety of evolution systems.
| [
{
"created": "Wed, 28 Jan 2004 19:25:50 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Alcubierre",
"Miguel",
""
],
[
"Gonzalez",
"Jose A.",
""
]
] | The lack of regularity of geometric variables at the origin is often a source of serious problem for spherically symmetric evolution codes in numerical relativity. One usually deals with this by restricting the gauge and solving the hamiltonian constraint for the metric. Here we present a generic algorithm for dealing with the regularization of the origin that can be used directly on the evolution equations and that allows very general gauge choices. Our approach is similar in spirit to the one introduced by Arbona and Bona for the particular case of the Bona-Masso formulation. However, our algorithm is more general and can be used with a wide variety of evolution systems. |
1004.2470 | Mauro Cattani | M.Cattani | Gravitational Waves III: Detecting Systems | 12 pages 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent paper we have deduced the basic equations that predict the
emission of gravitational waves (GW) according to the Einstein gravitation
theory. In a subsequent paper these equations have been used to calculate the
luminosities and the amplitudes of the waves generated by binary stars,
pulsations of neutron stars, wobbling of deformed neutron stars, oscillating
quadrupoles, rotating bars and collapsing and bouncing cores of supernovas. We
show here how the GW could be detected in our laboratories. This paper, like
the preceding ones, was written to graduate and postgraduate students of
Physics.
| [
{
"created": "Wed, 14 Apr 2010 18:43:23 GMT",
"version": "v1"
}
] | 2010-04-15 | [
[
"Cattani",
"M.",
""
]
] | In a recent paper we have deduced the basic equations that predict the emission of gravitational waves (GW) according to the Einstein gravitation theory. In a subsequent paper these equations have been used to calculate the luminosities and the amplitudes of the waves generated by binary stars, pulsations of neutron stars, wobbling of deformed neutron stars, oscillating quadrupoles, rotating bars and collapsing and bouncing cores of supernovas. We show here how the GW could be detected in our laboratories. This paper, like the preceding ones, was written to graduate and postgraduate students of Physics. |
gr-qc/0205016 | Simonetta Frittelli | Simonetta Frittelli and Ezra T. Newman | Dynamics of Fermat potentials in non-perturbative gravitational lensing | Accepted for publication in Phys. Rev. D | Phys.Rev. D65 (2002) 123006 | 10.1103/PhysRevD.65.123006 | null | gr-qc astro-ph | null | We present a framework, based on the null-surface formulation of general
relativity, for discussing the dynamics of Fermat potentials for gravitational
lensing in a generic situation without approximations of any kind.
Additionally, we derive two lens equations: one for the case of thick compact
lenses and the other one for lensing by gravitational waves. These equations in
principle generalize the astrophysical scheme for lensing by removing the
thin-lens approximation while retaining the weak fields.
| [
{
"created": "Fri, 3 May 2002 20:35:13 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Frittelli",
"Simonetta",
""
],
[
"Newman",
"Ezra T.",
""
]
] | We present a framework, based on the null-surface formulation of general relativity, for discussing the dynamics of Fermat potentials for gravitational lensing in a generic situation without approximations of any kind. Additionally, we derive two lens equations: one for the case of thick compact lenses and the other one for lensing by gravitational waves. These equations in principle generalize the astrophysical scheme for lensing by removing the thin-lens approximation while retaining the weak fields. |
2304.10367 | Daniel Harlow | Daniel Harlow | Black holes in quantum gravity | 36 pages. This chapter is the pre-print of the version currently in
production. Please cite this chapter as the following: D.Harlow. "Black holes
in quantum gravity" in The Encyclopedia of Cosmology (Set 2): Black Holes,
edited by Z. Haiman (World Scientific, New Jersey, 2023) | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This chapter gives an overview of the quantum aspects of black holes,
focusing on the black hole information problem, the counting of black hole
entropy in string theory, and the emergence of spacetime in holography. It is
aimed at a broad physics audience, and does not presuppose knowledge of string
theory or holography.
| [
{
"created": "Wed, 19 Apr 2023 14:44:35 GMT",
"version": "v1"
}
] | 2023-04-21 | [
[
"Harlow",
"Daniel",
""
]
] | This chapter gives an overview of the quantum aspects of black holes, focusing on the black hole information problem, the counting of black hole entropy in string theory, and the emergence of spacetime in holography. It is aimed at a broad physics audience, and does not presuppose knowledge of string theory or holography. |
1202.3864 | Amare Abebe Mr | Amare Abebe, Rituparno Goswami and Peter K.S. Dunsby | Simultaneous expansion and rotation of shear-free universes in modified
gravity | 4 pages, no figures. Contribution submitted to the proceedings of the
Spanish Relativity Meeting ERE2011, September 2011, Madrid, Spain | null | 10.1063/1.4734421 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show in a fully covariant way that, there exist a class of $f(R)$ models
for which a shear-free, almost FLRW universe can expand and rotate at the same
time .
| [
{
"created": "Fri, 17 Feb 2012 10:17:43 GMT",
"version": "v1"
}
] | 2015-06-04 | [
[
"Abebe",
"Amare",
""
],
[
"Goswami",
"Rituparno",
""
],
[
"Dunsby",
"Peter K. S.",
""
]
] | We show in a fully covariant way that, there exist a class of $f(R)$ models for which a shear-free, almost FLRW universe can expand and rotate at the same time . |
gr-qc/0411049 | Charles Hoyle | L. Carbone, A. Cavalleri, R. Dolesi, C.D. Hoyle, M. Hueller, S.
Vitale, and W.J. Weber | Improved Torsion Pendulum for Ground Testing of LISA Displacement
Sensors | 4 pages 1 figure, to appear in the Proceedings of the 10th Marcel
Grossmann Meeting on General Relativity | null | 10.1142/9789812704030_0258 | null | gr-qc | null | We discuss a new torsion pendulum design for ground testing of prototype LISA
(Laser Interferometer Space Antenna) displacement sensors. This new design is
directly sensitive to net forces and therefore provides a more representative
test of the noisy forces and parasitic stiffnesses acting on the test mass as
compared to previous ground-based experiments. We also discuss a specific
application to the measurement of thermal gradient effects.
| [
{
"created": "Tue, 9 Nov 2004 23:44:45 GMT",
"version": "v1"
}
] | 2016-11-09 | [
[
"Carbone",
"L.",
""
],
[
"Cavalleri",
"A.",
""
],
[
"Dolesi",
"R.",
""
],
[
"Hoyle",
"C. D.",
""
],
[
"Hueller",
"M.",
""
],
[
"Vitale",
"S.",
""
],
[
"Weber",
"W. J.",
""
]
] | We discuss a new torsion pendulum design for ground testing of prototype LISA (Laser Interferometer Space Antenna) displacement sensors. This new design is directly sensitive to net forces and therefore provides a more representative test of the noisy forces and parasitic stiffnesses acting on the test mass as compared to previous ground-based experiments. We also discuss a specific application to the measurement of thermal gradient effects. |
gr-qc/0610029 | Firmin Oliveira | Firmin J. Oliveira | Is the pioneer anomaly a counter example to the dark matter hypothesis? | Ver. 1: 4 pages. Submitted for publication. Ver. 2: 7 pages. The
extension of the Hubble law to massive particles is the same as in version 1,
but the rest is a total re-write. Intended to be submitted for publication.
Ver. 3: 8 pages. Ver. 4: 10 pages. Theoretical support added (JL Anderson)
Ver. 5: 9 pages. Title changed. Accepted by Int. J. Theor. Phys | null | 10.1007/s10773-007-9434-y | null | gr-qc | null | The Hubble law is extended to massive particles based on the de Broglie
wavelength. Due to the expansion of the universe the wavelength of an unbound
particle would increase according to its cosmological redshift. Based on the
navigation anomalies of the Pioneer 10 & 11 spacecraft it is postulated that an
unbound massive particle has a cosmological redshift z = (c / v_0) H_0 t, where
c is the speed of light in vacuum, v_0 is the initial velocity of the particle,
H_0 is Hubble's constant and t is the duration of time that the particle has
been unbound. The increase in wavelength of the particle corresponds to a
decrease in its speed by delta_v = - c H_0 t. Furthermore, it is hypothesized
that the solar system has escaped the gravity of the Galaxy as evidenced by its
orbital speed and radial distance and by the visible mass within the solar
system radius. This means that spacecraft which become unbound to the solar
system would also be galactically unbound and subject to the Hubble law. This
hypothesis and the extended Hubble law may explain the anomalous acceleration
found to be acting upon the unbound Pioneer 10 & 11 spacecraft. Thus, the
Pioneer anomaly may be a counter example to the dark matter hypothesis.
Because photons have a speed which make them unbound to the Galaxy, it is
predicted that the navigation beam in open space would undergo a cosmological
redshift in its frequency which would be detectable with modern clocks.
| [
{
"created": "Sun, 8 Oct 2006 03:18:57 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Nov 2006 00:00:33 GMT",
"version": "v2"
},
{
"created": "Sat, 2 Dec 2006 01:38:07 GMT",
"version": "v3"
},
{
"created": "Sat, 6 Jan 2007 00:16:00 GMT",
"version": "v4"
},
{
"created": "Wed, 6 Jun 2007 03:18:47 GMT",
"version": "v5"
}
] | 2009-11-11 | [
[
"Oliveira",
"Firmin J.",
""
]
] | The Hubble law is extended to massive particles based on the de Broglie wavelength. Due to the expansion of the universe the wavelength of an unbound particle would increase according to its cosmological redshift. Based on the navigation anomalies of the Pioneer 10 & 11 spacecraft it is postulated that an unbound massive particle has a cosmological redshift z = (c / v_0) H_0 t, where c is the speed of light in vacuum, v_0 is the initial velocity of the particle, H_0 is Hubble's constant and t is the duration of time that the particle has been unbound. The increase in wavelength of the particle corresponds to a decrease in its speed by delta_v = - c H_0 t. Furthermore, it is hypothesized that the solar system has escaped the gravity of the Galaxy as evidenced by its orbital speed and radial distance and by the visible mass within the solar system radius. This means that spacecraft which become unbound to the solar system would also be galactically unbound and subject to the Hubble law. This hypothesis and the extended Hubble law may explain the anomalous acceleration found to be acting upon the unbound Pioneer 10 & 11 spacecraft. Thus, the Pioneer anomaly may be a counter example to the dark matter hypothesis. Because photons have a speed which make them unbound to the Galaxy, it is predicted that the navigation beam in open space would undergo a cosmological redshift in its frequency which would be detectable with modern clocks. |
1201.2071 | Salvatore Capozziello | S. Capozziello, M. De Laurentis, G. Lambiase | Cosmic relic abundance and f(R) gravity | 9 pages, 2 figures | null | 10.1016/j.physletb.2012.07.007 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmological consequences of $f(R)$ gravity are reviewed in the framework
of recent data obtained by PAMELA (Payload for Antimatter Matter Exploration
and Light-nuclei Astrophysics) experiment. This collaboration has reported an
excess of positron events that cannot be explained by conventional cosmology
and particle physics, and are usually ascribed to the dark matter presence (in
particular, weak interacting massive particles). The dark matter interpretation
of PAMELA data has motivated the study of alternative cosmological models (with
respect to the standard cosmology) owing to the fact that they predict an
enhancement of the Hubble expansion rate, giving rise, in such a way, to
thermal relics with a larger relic abundance. Our analysis shows that $f(R)$
cosmology allows to explain the PAMELA puzzle for dark matter relic particles
with masses of the order or lesser than $10^2$ GeV in the regime $\rho^c
\lesssim \rho^m $ where $\rho^c$ is the curvature density and $\rho^m$ the
radiation density. For the model $f(R)=R+\alpha R^n$, it then follows that
$n\simeq 1$ and small corrections with respect to General Relativity could lead
indeed to address the experimental results. However other interesting
cosmological models can be considered during the pre-BBN epoch as soon as the
BBN constraints are relaxed. In such a case, the PAMELA data can be fitted for
a larger class of $f(R)$-models.
| [
{
"created": "Tue, 10 Jan 2012 15:15:50 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Jul 2012 07:13:55 GMT",
"version": "v2"
}
] | 2012-07-20 | [
[
"Capozziello",
"S.",
""
],
[
"De Laurentis",
"M.",
""
],
[
"Lambiase",
"G.",
""
]
] | The cosmological consequences of $f(R)$ gravity are reviewed in the framework of recent data obtained by PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) experiment. This collaboration has reported an excess of positron events that cannot be explained by conventional cosmology and particle physics, and are usually ascribed to the dark matter presence (in particular, weak interacting massive particles). The dark matter interpretation of PAMELA data has motivated the study of alternative cosmological models (with respect to the standard cosmology) owing to the fact that they predict an enhancement of the Hubble expansion rate, giving rise, in such a way, to thermal relics with a larger relic abundance. Our analysis shows that $f(R)$ cosmology allows to explain the PAMELA puzzle for dark matter relic particles with masses of the order or lesser than $10^2$ GeV in the regime $\rho^c \lesssim \rho^m $ where $\rho^c$ is the curvature density and $\rho^m$ the radiation density. For the model $f(R)=R+\alpha R^n$, it then follows that $n\simeq 1$ and small corrections with respect to General Relativity could lead indeed to address the experimental results. However other interesting cosmological models can be considered during the pre-BBN epoch as soon as the BBN constraints are relaxed. In such a case, the PAMELA data can be fitted for a larger class of $f(R)$-models. |
1712.07658 | Ian Ruchlin | Ian Ruchlin and Zachariah B. Etienne and Thomas W. Baumgarte | SENR/NRPy+: Numerical Relativity in Singular Curvilinear Coordinate
Systems | 23 pages, 7 figures, matches published version | Phys. Rev. D 97, 064036 (2018) | 10.1103/PhysRevD.97.064036 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report on a new open-source, user-friendly numerical relativity code
package called SENR/NRPy+. Our code extends previous implementations of the
BSSN reference-metric formulation to a much broader class of curvilinear
coordinate systems, making it ideally-suited to modeling physical
configurations with approximate or exact symmetries. In the context of modeling
black hole dynamics, it is orders of magnitude more efficient than other widely
used open-source numerical relativity codes. NRPy+ provides a Python-based
interface in which equations are written in natural tensorial form and output
at arbitrary finite difference order as highly efficient C code, putting
complex tensorial equations at the scientist's fingertips without the need for
an expensive software license. SENR provides the algorithmic framework that
combines the C codes generated by NRPy+ into a functioning numerical relativity
code. We validate against two other established, state-of-the-art codes, and
achieve excellent agreement. For the first time we demonstrate--in the context
of puncture, trumpet, and dual black hole evolutions--nearly exponential
convergence of constraint violation and gravitational waveform errors to zero
as the order of spatial finite difference derivatives is increased, while
holding the spherical-like coordinate grids fixed at moderate resolution. Such
behavior outside the horizons is remarkable, as numerical errors do not
converge to zero inside horizons, and all points along the polar axis are
coordinate singularities. The formulation addresses such coordinate
singularities via cell-centered grids and a simple change of basis that
analytically regularizes tensor components with respect to the coordinates.
Future plans include extending this formulation to allow dynamical coordinate
grids and bispherical-like distribution of points to efficiently capture
orbiting compact binary dynamics.
| [
{
"created": "Wed, 20 Dec 2017 19:00:01 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Mar 2018 14:16:23 GMT",
"version": "v2"
}
] | 2018-03-30 | [
[
"Ruchlin",
"Ian",
""
],
[
"Etienne",
"Zachariah B.",
""
],
[
"Baumgarte",
"Thomas W.",
""
]
] | We report on a new open-source, user-friendly numerical relativity code package called SENR/NRPy+. Our code extends previous implementations of the BSSN reference-metric formulation to a much broader class of curvilinear coordinate systems, making it ideally-suited to modeling physical configurations with approximate or exact symmetries. In the context of modeling black hole dynamics, it is orders of magnitude more efficient than other widely used open-source numerical relativity codes. NRPy+ provides a Python-based interface in which equations are written in natural tensorial form and output at arbitrary finite difference order as highly efficient C code, putting complex tensorial equations at the scientist's fingertips without the need for an expensive software license. SENR provides the algorithmic framework that combines the C codes generated by NRPy+ into a functioning numerical relativity code. We validate against two other established, state-of-the-art codes, and achieve excellent agreement. For the first time we demonstrate--in the context of puncture, trumpet, and dual black hole evolutions--nearly exponential convergence of constraint violation and gravitational waveform errors to zero as the order of spatial finite difference derivatives is increased, while holding the spherical-like coordinate grids fixed at moderate resolution. Such behavior outside the horizons is remarkable, as numerical errors do not converge to zero inside horizons, and all points along the polar axis are coordinate singularities. The formulation addresses such coordinate singularities via cell-centered grids and a simple change of basis that analytically regularizes tensor components with respect to the coordinates. Future plans include extending this formulation to allow dynamical coordinate grids and bispherical-like distribution of points to efficiently capture orbiting compact binary dynamics. |
gr-qc/0608020 | Andrea Geralico | Donato Bini, Christian Cherubini, Geralico Andrea, Robert T. Jantzen | Massless spinning test particles in vacuum algebraically special
spacetimes | Slightly modified version with respect to the published one [
International Journal of Modern Physics D, Vol. 15 pp. 737-758 (2006)] which
unfortunately contains few (unespected) misprints | Int.J.Mod.Phys.D15:737-758,2006 | 10.1142/S0218271806008498 | null | gr-qc | null | The motion of massless spinning test particles is investigated using the
Newman-Penrose formalism within the Mathisson-Papapetrou model extended to
massless particles by Mashhoon and supplemented by the Pirani condition. When
the "multipole reduction world line" lies along a principal null direction of
an algebraically special vacuum spacetime, the equations of motion can be
explicitly integrated. Examples are given for some familiar spacetimes of this
type in the interest of shedding some light on the consequences of this model.
| [
{
"created": "Fri, 4 Aug 2006 08:53:21 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Bini",
"Donato",
""
],
[
"Cherubini",
"Christian",
""
],
[
"Andrea",
"Geralico",
""
],
[
"Jantzen",
"Robert T.",
""
]
] | The motion of massless spinning test particles is investigated using the Newman-Penrose formalism within the Mathisson-Papapetrou model extended to massless particles by Mashhoon and supplemented by the Pirani condition. When the "multipole reduction world line" lies along a principal null direction of an algebraically special vacuum spacetime, the equations of motion can be explicitly integrated. Examples are given for some familiar spacetimes of this type in the interest of shedding some light on the consequences of this model. |
gr-qc/0412006 | Nigel Bishop | Nigel T. Bishop | Linearized solutions of the Einstein equations within a Bondi-Sachs
framework, and implications for boundary conditions in numerical simulations | Revised following referee comments | Class.Quant.Grav. 22 (2005) 2393-2406 | 10.1088/0264-9381/22/12/006 | null | gr-qc | null | We linearize the Einstein equations when the metric is Bondi-Sachs, when the
background is Schwarzschild or Minkowski, and when there is a matter source in
the form of a thin shell whose density varies with time and angular position.
By performing an eigenfunction decomposition, we reduce the problem to a system
of linear ordinary differential equations which we are able to solve. The
solutions are relevant to the characteristic formulation of numerical
relativity: (a) as exact solutions against which computations of gravitational
radiation can be compared; and (b) in formulating boundary conditions on the
$r=2M$ Schwarzschild horizon.
| [
{
"created": "Thu, 2 Dec 2004 09:42:23 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Jun 2005 11:34:09 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Bishop",
"Nigel T.",
""
]
] | We linearize the Einstein equations when the metric is Bondi-Sachs, when the background is Schwarzschild or Minkowski, and when there is a matter source in the form of a thin shell whose density varies with time and angular position. By performing an eigenfunction decomposition, we reduce the problem to a system of linear ordinary differential equations which we are able to solve. The solutions are relevant to the characteristic formulation of numerical relativity: (a) as exact solutions against which computations of gravitational radiation can be compared; and (b) in formulating boundary conditions on the $r=2M$ Schwarzschild horizon. |
1306.6887 | Robert Lompay | Robert R. Lompay and Alexander N. Petrov | Covariant Differential Identities and Conservation Laws in
Metric-Torsion Theories of Gravitation. I. General Consideration | 23 pages, 0 figures, revtex 4.1 | J. Math. Phys. 54, 062504 (2013) | 10.1063/1.4810017 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Arbitrary diffeomorphically invariant metric-torsion theories of gravity are
considered. It is assumed that Lagrangians of such theories contain derivatives
of field variables (tensor densities of arbitrary ranks and weights) up to a
second order only. The generalized Klein-Noether methods for constructing
manifestly covariant identities and conserved quantities are developed.
Manifestly covariant expressions are constructed without including auxiliary
structures like a background metric. In the Riemann-Cartan space, the following
\emph{manifestly generally covariant results} are presented: (a) The complete
generalized system of differential identities (the Klein-Noether identities) is
obtained. (b) The generalized currents of three types depending on an arbitrary
vector field displacements are constructed: they are the canonical Noether
current, symmetrized Belinfante current and identically conserved
Hilbert-Bergmann current. In particular, it is stated that the symmetrized
Belinfante current does not depend on divergences in the Lagrangian. (c) The
generalized boundary Klein theorem (third Noether theorem) is proved. (d) The
construction of the generalized superpotential is presented in details, and
questions related to its ambiguities are analyzed.
| [
{
"created": "Fri, 28 Jun 2013 16:21:33 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Jul 2013 18:37:03 GMT",
"version": "v2"
}
] | 2013-07-02 | [
[
"Lompay",
"Robert R.",
""
],
[
"Petrov",
"Alexander N.",
""
]
] | Arbitrary diffeomorphically invariant metric-torsion theories of gravity are considered. It is assumed that Lagrangians of such theories contain derivatives of field variables (tensor densities of arbitrary ranks and weights) up to a second order only. The generalized Klein-Noether methods for constructing manifestly covariant identities and conserved quantities are developed. Manifestly covariant expressions are constructed without including auxiliary structures like a background metric. In the Riemann-Cartan space, the following \emph{manifestly generally covariant results} are presented: (a) The complete generalized system of differential identities (the Klein-Noether identities) is obtained. (b) The generalized currents of three types depending on an arbitrary vector field displacements are constructed: they are the canonical Noether current, symmetrized Belinfante current and identically conserved Hilbert-Bergmann current. In particular, it is stated that the symmetrized Belinfante current does not depend on divergences in the Lagrangian. (c) The generalized boundary Klein theorem (third Noether theorem) is proved. (d) The construction of the generalized superpotential is presented in details, and questions related to its ambiguities are analyzed. |
gr-qc/9701004 | Bill Hiscock | William A. Hiscock, Shane L. Larson (Montana State University), and
Paul R. Anderson (Wake Forest University) | Semiclassical effects in black hole interiors | 29 pages, ReVTeX; 4 ps figures | Phys.Rev.D56:3571-3581,1997 | 10.1103/PhysRevD.56.3571 | MSUPHY97.01 | gr-qc | null | First-order semiclassical perturbations to the Schwarzschild black hole
geometry are studied within the black hole interior. The source of the
perturbations is taken to be the vacuum stress-energy of quantized scalar,
spinor, and vector fields, evaluated using analytic approximations developed by
Page and others (for massless fields) and the DeWitt-Schwinger approximation
(for massive fields). Viewing the interior as an anisotropic collapsing
cosmology, we find that minimally or conformally coupled scalar fields, and
spinor fields, decrease the anisotropy as the singularity is approached, while
vector fields increase the anisotropy. In addition, we find that massless
fields of all spins, and massive vector fields, strengthen the singularity,
while massive scalar and spinor fields tend to slow the growth of curvature.
| [
{
"created": "Fri, 3 Jan 1997 00:34:12 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Hiscock",
"William A.",
"",
"Montana State University"
],
[
"Larson",
"Shane L.",
"",
"Montana State University"
],
[
"Anderson",
"Paul R.",
"",
"Wake Forest University"
]
] | First-order semiclassical perturbations to the Schwarzschild black hole geometry are studied within the black hole interior. The source of the perturbations is taken to be the vacuum stress-energy of quantized scalar, spinor, and vector fields, evaluated using analytic approximations developed by Page and others (for massless fields) and the DeWitt-Schwinger approximation (for massive fields). Viewing the interior as an anisotropic collapsing cosmology, we find that minimally or conformally coupled scalar fields, and spinor fields, decrease the anisotropy as the singularity is approached, while vector fields increase the anisotropy. In addition, we find that massless fields of all spins, and massive vector fields, strengthen the singularity, while massive scalar and spinor fields tend to slow the growth of curvature. |
2201.12299 | Orlando Luongo | Alessio Belfiglio, Orlando Luongo, Stefano Mancini | Geometric corrections to cosmological entanglement | 8 pages, 3 figures | Phys. Rev. D, 105, 123523 (2022) | 10.1103/PhysRevD.105.123523 | null | gr-qc astro-ph.CO quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate entanglement production by inhomogeneous perturbations over a
homogeneous and isotropic cosmic background, demonstrating that the interplay
between quantum and geometric effects can have relevant consequences on
entanglement entropy, with respect to homogeneous scenarios. To do so, we focus
on a conformally coupled scalar field and discuss how geometric production of
scalar particles leads to entanglement. Perturbatively, at first order we find
oscillations in entropy correction, whereas at second order the underlying
geometry induces mode-mixing on entanglement production. We thus quantify
entanglement solely due to geometrical contribution and compare our outcomes
with previous findings. We characterize the geometric contribution through
geometric (quasi)-particles, interpreted as dark matter candidates.
| [
{
"created": "Fri, 28 Jan 2022 18:06:04 GMT",
"version": "v1"
}
] | 2022-10-17 | [
[
"Belfiglio",
"Alessio",
""
],
[
"Luongo",
"Orlando",
""
],
[
"Mancini",
"Stefano",
""
]
] | We investigate entanglement production by inhomogeneous perturbations over a homogeneous and isotropic cosmic background, demonstrating that the interplay between quantum and geometric effects can have relevant consequences on entanglement entropy, with respect to homogeneous scenarios. To do so, we focus on a conformally coupled scalar field and discuss how geometric production of scalar particles leads to entanglement. Perturbatively, at first order we find oscillations in entropy correction, whereas at second order the underlying geometry induces mode-mixing on entanglement production. We thus quantify entanglement solely due to geometrical contribution and compare our outcomes with previous findings. We characterize the geometric contribution through geometric (quasi)-particles, interpreted as dark matter candidates. |
1511.06600 | Hemza Azri | Hemza Azri | Separate Einstein-Eddington Spaces and the Cosmological Constant | Accepted in Annalen der Physik journal. 7 pages, typos corrected | Annalen Phys. 528, 404 (2016) | 10.1002/andp.201500270 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on Eddington affine variational principle on a locally product
manifold, we derive the separate Einstein space described by its Ricci tensor.
The derived field equations split into two field equations of motion that
describe two maximally symmetric spaces with two cosmological constants. We
argue that the invariance of the bi-field equations under projections on the
separate spaces, may render one of the cosmological constants to zero. We also
formulate the model in the presence of a scalar field. The resulted separate
Einstein-Eddington spaces maybe considered as two states that describe the
universe before and after inflation. A possibly interesting affine action for a
general perfect fluid is also proposed. It turns out that the condition which
leads to zero cosmological constant in the vacuum case, eliminates here the
effects of the gravitational mass density of the perfect fluid, and the dynamic
of the universe in its final state is governed by only the inertial mass
density of the fluid.
| [
{
"created": "Fri, 20 Nov 2015 13:56:41 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Dec 2015 18:45:07 GMT",
"version": "v2"
}
] | 2016-05-31 | [
[
"Azri",
"Hemza",
""
]
] | Based on Eddington affine variational principle on a locally product manifold, we derive the separate Einstein space described by its Ricci tensor. The derived field equations split into two field equations of motion that describe two maximally symmetric spaces with two cosmological constants. We argue that the invariance of the bi-field equations under projections on the separate spaces, may render one of the cosmological constants to zero. We also formulate the model in the presence of a scalar field. The resulted separate Einstein-Eddington spaces maybe considered as two states that describe the universe before and after inflation. A possibly interesting affine action for a general perfect fluid is also proposed. It turns out that the condition which leads to zero cosmological constant in the vacuum case, eliminates here the effects of the gravitational mass density of the perfect fluid, and the dynamic of the universe in its final state is governed by only the inertial mass density of the fluid. |
1605.05774 | Yen Chin Ong | Fech Scen Khoo, Yen Chin Ong | Lux in obscuro: Photon Orbits of Extremal Black Holes Revisited | Some technical errors in Sec.4.2 are now fixed. Main conclusions
unchanged | Class. Quantum Grav. 33 (2016) 235002 | 10.1088/0264-9381/33/23/235002 | NORDITA-2016-40 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been shown in the literature that the event horizon of an extremal
asymptotically flat Reissner-Nordstrom black hole is also a stable photon
sphere. We further clarify this statement and give a general proof that this
holds for a large class of static spherically symmetric black hole spacetimes
with an extremal horizon. In contrast, in the Doran frame, an extremal
asymptotically flat Kerr black hole has an unstable photon orbit on the
equatorial plane of its horizon. In addition, we show that an extremal
asymptotically flat Kerr-Newman black hole exhibits two equatorial photon
orbits if a < M/2, one of which is on the extremal horizon in the Doran frame
and is stable, whereas the second one outside the horizon is unstable. For a >
M/2, there is only one equatorial photon orbit, located on the extremal
horizon, and it is unstable. There can be no photon orbit on the horizon of a
non-extremal Kerr-Newman black hole.
| [
{
"created": "Wed, 18 May 2016 22:13:57 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Oct 2016 13:31:22 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Jul 2017 14:48:49 GMT",
"version": "v3"
}
] | 2017-07-31 | [
[
"Khoo",
"Fech Scen",
""
],
[
"Ong",
"Yen Chin",
""
]
] | It has been shown in the literature that the event horizon of an extremal asymptotically flat Reissner-Nordstrom black hole is also a stable photon sphere. We further clarify this statement and give a general proof that this holds for a large class of static spherically symmetric black hole spacetimes with an extremal horizon. In contrast, in the Doran frame, an extremal asymptotically flat Kerr black hole has an unstable photon orbit on the equatorial plane of its horizon. In addition, we show that an extremal asymptotically flat Kerr-Newman black hole exhibits two equatorial photon orbits if a < M/2, one of which is on the extremal horizon in the Doran frame and is stable, whereas the second one outside the horizon is unstable. For a > M/2, there is only one equatorial photon orbit, located on the extremal horizon, and it is unstable. There can be no photon orbit on the horizon of a non-extremal Kerr-Newman black hole. |
1611.09032 | KaiXi Feng | Kaixi Feng | Gravitational waves induced by massless vector fields with non-minimal
coupling to gravity | 13 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we calculate the contribution of the late time mode of a
massless vector field to the power spectrum of the primordial gravitational
wave using retarded Green's propagator. We consider a non-trivial coupling
between gravity and the vector field. We find that the correction is
scale-invariant and of order $\frac{H^4}{M_P^4}$. The non-minimal coupling
leads to a dependence of $\frac{H^2}{M^2}$, which can amplify the correlation
function up to the level of $\frac{H^2}{M^2_P}$.
| [
{
"created": "Mon, 28 Nov 2016 09:16:11 GMT",
"version": "v1"
}
] | 2016-11-29 | [
[
"Feng",
"Kaixi",
""
]
] | In this paper, we calculate the contribution of the late time mode of a massless vector field to the power spectrum of the primordial gravitational wave using retarded Green's propagator. We consider a non-trivial coupling between gravity and the vector field. We find that the correction is scale-invariant and of order $\frac{H^4}{M_P^4}$. The non-minimal coupling leads to a dependence of $\frac{H^2}{M^2}$, which can amplify the correlation function up to the level of $\frac{H^2}{M^2_P}$. |
1508.03330 | Pedro Labra\~na | Sergio del Campo, Eduardo I. Guendelman, Ramon Herrera, Pedro Labrana | Classically and Quantum stable Emergent Universe from Conservation Laws | 18 pages, 10 figures, typos corrected, some improvements in the text
and comments added in conclusions. Two new appendices, references added.
Accepted for publication in JCAP. arXiv admin note: text overlap with
arXiv:1105.0651 | null | 10.1088/1475-7516/2016/08/049 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been recently pointed out by Mithani-Vilenkin that certain emergent
universe scenarios which are classically stable are nevertheless unstable
semiclassically to collapse. Here, we show that there is a class of emergent
universes derived from scale invariant two measures theories with spontaneous
symmetry breaking (s.s.b) of the scale invariance, which can have both
classical stability and do not suffer the instability pointed out by
Mithani-Vilenkin towards collapse. We find that this stability is due to the
presence of a symmetry in the "emergent phase", which together with the non
linearities of the theory, does not allow that the FLRW scale factor to be
smaller that a certain minimum value $a_0$ in a certain protected region.
| [
{
"created": "Wed, 12 Aug 2015 21:16:16 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Aug 2016 22:25:52 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"del Campo",
"Sergio",
""
],
[
"Guendelman",
"Eduardo I.",
""
],
[
"Herrera",
"Ramon",
""
],
[
"Labrana",
"Pedro",
""
]
] | It has been recently pointed out by Mithani-Vilenkin that certain emergent universe scenarios which are classically stable are nevertheless unstable semiclassically to collapse. Here, we show that there is a class of emergent universes derived from scale invariant two measures theories with spontaneous symmetry breaking (s.s.b) of the scale invariance, which can have both classical stability and do not suffer the instability pointed out by Mithani-Vilenkin towards collapse. We find that this stability is due to the presence of a symmetry in the "emergent phase", which together with the non linearities of the theory, does not allow that the FLRW scale factor to be smaller that a certain minimum value $a_0$ in a certain protected region. |
1111.2755 | Joan Josep Ferrando | Joan Josep Ferrando and Juan Antonio S\'aez | On the Bel radiative gravitational fields | 15 pages; no figures; v2: minor changes | Class. Quantum Grav. 29:075012, 2012 | 10.1088/0264-9381/29/7/075012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the concept of intrinsic radiative gravitational fields defined by
Bel and we show that the three radiative types, N, III and II, correspond with
the three following different physical situations: {\it pure radiation}, {\it
asymptotic pure radiation} and {\it generic} (non pure, non asymptotic pure)
{\it radiation}. We introduce the concept of {\em observer at rest} with
respect to the gravitational field and that of {\em proper super-energy} of the
gravitational field and we show that, for non radiative fields, the minimum
value of the relative super-energy density is the proper super-energy density,
which is acquired by the observers at rest with respect to the field. Several
{\it super-energy inequalities} are also examined.
| [
{
"created": "Fri, 11 Nov 2011 14:35:22 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Apr 2012 10:41:50 GMT",
"version": "v2"
}
] | 2015-06-03 | [
[
"Ferrando",
"Joan Josep",
""
],
[
"Sáez",
"Juan Antonio",
""
]
] | We analyze the concept of intrinsic radiative gravitational fields defined by Bel and we show that the three radiative types, N, III and II, correspond with the three following different physical situations: {\it pure radiation}, {\it asymptotic pure radiation} and {\it generic} (non pure, non asymptotic pure) {\it radiation}. We introduce the concept of {\em observer at rest} with respect to the gravitational field and that of {\em proper super-energy} of the gravitational field and we show that, for non radiative fields, the minimum value of the relative super-energy density is the proper super-energy density, which is acquired by the observers at rest with respect to the field. Several {\it super-energy inequalities} are also examined. |
2004.14849 | Vittorio De Falco Dr | Vittorio De Falco, Emmanuele Battista, Salvatore Capozziello,
Mariafelicia De Laurentis | General relativistic Poynting-Robertson effect to diagnose wormholes
existence: static and spherically symmetric case | 17 pages, 11 figures, 1 Table. Paper accepted on April 30, 2020 on
Physical Review D | Phys. Rev. D 101, 104037, Published 20 May 2020 | 10.1103/PhysRevD.101.104037 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the equations of motion of a test particle in the equatorial plane
around a static and spherically symmetric wormhole influenced by a radiation
field including the general relativistic Poynting-Robertson effect. From the
analysis of this dynamical system, we develop a diagnostic to distinguish a
black hole from a wormhole, which can be timely supported by several and
different observational data. This procedure is based on the possibility of
having some wormhole metrics, which smoothly connect to the Schwarzschild
metric in a small transition surface layer very close to the black hole event
horizon. To detect such a metric-change, we analyse the emission proprieties
from the critical hypersurface (stable region where radiation and gravitational
fields balance) together with those from an accretion disk in the Schwarzschild
spacetime toward a distant observer. Indeed, if the observational data are well
fitted within such model, it immediately implies the existence of a black hole;
while in case of strong departures from such description it means that a
wormhole could be present. Finally, we discuss our results and draw the
conclusions.
| [
{
"created": "Thu, 30 Apr 2020 15:01:54 GMT",
"version": "v1"
},
{
"created": "Fri, 1 May 2020 09:55:20 GMT",
"version": "v2"
},
{
"created": "Wed, 20 May 2020 14:37:26 GMT",
"version": "v3"
}
] | 2020-05-21 | [
[
"De Falco",
"Vittorio",
""
],
[
"Battista",
"Emmanuele",
""
],
[
"Capozziello",
"Salvatore",
""
],
[
"De Laurentis",
"Mariafelicia",
""
]
] | We derive the equations of motion of a test particle in the equatorial plane around a static and spherically symmetric wormhole influenced by a radiation field including the general relativistic Poynting-Robertson effect. From the analysis of this dynamical system, we develop a diagnostic to distinguish a black hole from a wormhole, which can be timely supported by several and different observational data. This procedure is based on the possibility of having some wormhole metrics, which smoothly connect to the Schwarzschild metric in a small transition surface layer very close to the black hole event horizon. To detect such a metric-change, we analyse the emission proprieties from the critical hypersurface (stable region where radiation and gravitational fields balance) together with those from an accretion disk in the Schwarzschild spacetime toward a distant observer. Indeed, if the observational data are well fitted within such model, it immediately implies the existence of a black hole; while in case of strong departures from such description it means that a wormhole could be present. Finally, we discuss our results and draw the conclusions. |
2102.04728 | Tiberiu Harko | Tiberiu Harko, Haidar Sheikhahmadi | Warm inflation with non-comoving scalar field and radiation fluid | 25 pages, 8 figures, accepted for publication in EPJC | Eur. Phys. J. C (2021) 81: 165 | 10.1140/epjc/s10052-021-08964-6 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a warm inflationary scenario in which the two dominant matter
components present in the early Universe, the scalar field, and the radiation
fluid, evolve with different four-velocities. This cosmological system is
mathematically equivalent to a single anisotropic fluid, evolving with a
four-velocity that is a function of the two independent fluid four-velocities.
Due to the presence of the anisotropic physical parameters, the overall
cosmological evolution is also anisotropic. We derive the gravitational field
equations of the noncomoving scalar field-radiation mixture for a Bianchi type
I geometry. By considering that the decay of the scalar field is accompanied by
a corresponding radiation generation, we formulate the basic equations of the
warm inflationary model in the presence of two noncomoving components. By
adopting the slow roll approximation, we perform a detailed comparison of the
theoretical predictions of the warm inflationary scenario with noncomoving
scalar field and radiation fluid with the observational data obtained by the
Planck satellite, by investigating both the weak dissipation and strong
dissipation limits. Constraints on the free parameters of the model are
obtained in both cases. The functional forms of the scalar field potentials
compatible with the noncomoving nature of warm inflation are also derived.
| [
{
"created": "Tue, 9 Feb 2021 09:45:54 GMT",
"version": "v1"
}
] | 2021-03-15 | [
[
"Harko",
"Tiberiu",
""
],
[
"Sheikhahmadi",
"Haidar",
""
]
] | We consider a warm inflationary scenario in which the two dominant matter components present in the early Universe, the scalar field, and the radiation fluid, evolve with different four-velocities. This cosmological system is mathematically equivalent to a single anisotropic fluid, evolving with a four-velocity that is a function of the two independent fluid four-velocities. Due to the presence of the anisotropic physical parameters, the overall cosmological evolution is also anisotropic. We derive the gravitational field equations of the noncomoving scalar field-radiation mixture for a Bianchi type I geometry. By considering that the decay of the scalar field is accompanied by a corresponding radiation generation, we formulate the basic equations of the warm inflationary model in the presence of two noncomoving components. By adopting the slow roll approximation, we perform a detailed comparison of the theoretical predictions of the warm inflationary scenario with noncomoving scalar field and radiation fluid with the observational data obtained by the Planck satellite, by investigating both the weak dissipation and strong dissipation limits. Constraints on the free parameters of the model are obtained in both cases. The functional forms of the scalar field potentials compatible with the noncomoving nature of warm inflation are also derived. |
1904.08776 | Ahmadjon Abdujabbarov | Sudipta Hensh, Ahmadjon Abdujabbarov, Jan Schee, Zden\v{e}k Stuchl\'ik | Gravitational lensing around Kehagias-Sfetsos compact objects surrounded
by plasma | 15 pages, 10 figures | null | 10.1140/epjc/s10052-019-7034-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the optical properties of the Kehagias-Sfetsos (KS) compact objects,
characterized by the "Ho\v{r}ava" parameter $\omega_{_{KS}}$, in the presence
of plasma, considering its homogeneous or power-law density distribution. The
strong effects of both "Ho\v{r}ava" parameter $\omega_{_{KS}}$ and plasma on
the shadow cast by the KS compact objects are demonstrated. Using the weak
field approximation, we investigate the gravitational lensing effect. Strong
dependence of the deflection angle of the light on both the "Ho\v{r}ava" and
plasma parameter is explicitly shown. The magnification of image source due to
the weak gravitational lensing is given for both the homogeneous and
inhomogeneous plasma.
| [
{
"created": "Wed, 17 Apr 2019 06:56:20 GMT",
"version": "v1"
}
] | 2022-10-19 | [
[
"Hensh",
"Sudipta",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
],
[
"Schee",
"Jan",
""
],
[
"Stuchlík",
"Zdeněk",
""
]
] | We study the optical properties of the Kehagias-Sfetsos (KS) compact objects, characterized by the "Ho\v{r}ava" parameter $\omega_{_{KS}}$, in the presence of plasma, considering its homogeneous or power-law density distribution. The strong effects of both "Ho\v{r}ava" parameter $\omega_{_{KS}}$ and plasma on the shadow cast by the KS compact objects are demonstrated. Using the weak field approximation, we investigate the gravitational lensing effect. Strong dependence of the deflection angle of the light on both the "Ho\v{r}ava" and plasma parameter is explicitly shown. The magnification of image source due to the weak gravitational lensing is given for both the homogeneous and inhomogeneous plasma. |
2404.03872 | Abdelrahman Yasser | Nader Inan, Ahmed Farag Ali, Kimet Jusufi, Abdelrahman Yasser | Graviton mass due to dark energy as a superconducting medium:
theoretical and phenomenological aspects | Accepted for publication in JCAP | null | 10.1088/1475-7516/2024/08/012 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known that the cosmological constant term in the Einstein field
equations can be interpreted as a stress tensor for dark energy. This stress
tensor is formally analogous to an elastic constitutive equation in continuum
mechanics. As a result, the cosmological constant leads to a "shear modulus"
and "bulk modulus" affecting all gravitational fields in the universe. The form
of the constitutive equation is also analogous to the London constitutive
equation for a superconductor. Treating dark energy as a type of
superconducting medium for gravitational waves leads to a Yukawa-like
gravitational potential and a massive graviton within standard General
Relativity. We discuss a number of resulting phenomenological aspects such as a
screening length scale that can also be used to describe the effects generally
attributed to dark matter. In addition, we find a gravitational wave plasma
frequency, index of refraction, and impedance. The expansion of the universe is
interpreted as a Meissner-like effect as dark energy causes an outward
"expulsion" of space-time similar to a superconductor expelling a magnetic
field. The fundamental cause of these effects is interpreted as a type of
spontaneous symmetry breaking of a scalar field. There is an associated
chemical potential, critical temperature, and an Unruh-Hawking effect
associated with the formulation.
| [
{
"created": "Fri, 5 Apr 2024 03:22:00 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Jul 2024 15:18:00 GMT",
"version": "v2"
},
{
"created": "Fri, 9 Aug 2024 22:05:30 GMT",
"version": "v3"
}
] | 2024-08-13 | [
[
"Inan",
"Nader",
""
],
[
"Ali",
"Ahmed Farag",
""
],
[
"Jusufi",
"Kimet",
""
],
[
"Yasser",
"Abdelrahman",
""
]
] | It is well known that the cosmological constant term in the Einstein field equations can be interpreted as a stress tensor for dark energy. This stress tensor is formally analogous to an elastic constitutive equation in continuum mechanics. As a result, the cosmological constant leads to a "shear modulus" and "bulk modulus" affecting all gravitational fields in the universe. The form of the constitutive equation is also analogous to the London constitutive equation for a superconductor. Treating dark energy as a type of superconducting medium for gravitational waves leads to a Yukawa-like gravitational potential and a massive graviton within standard General Relativity. We discuss a number of resulting phenomenological aspects such as a screening length scale that can also be used to describe the effects generally attributed to dark matter. In addition, we find a gravitational wave plasma frequency, index of refraction, and impedance. The expansion of the universe is interpreted as a Meissner-like effect as dark energy causes an outward "expulsion" of space-time similar to a superconductor expelling a magnetic field. The fundamental cause of these effects is interpreted as a type of spontaneous symmetry breaking of a scalar field. There is an associated chemical potential, critical temperature, and an Unruh-Hawking effect associated with the formulation. |
1407.5022 | Lorenzo Iorio | Lorenzo Iorio | Revisiting the gravitomagnetic clock effect | LaTex2e, 17 pages, 7 figures, 1 table. Figures of the
counter-revolving particles replaced. Some other changes made | Eur. Phys. J. C 84, 280 (2024) | 10.1140/epjc/s10052-024-12603-1 | null | gr-qc astro-ph.EP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To the first post-Newtonian order, if two test particles revolve in opposite
directions about a massive, spinning body along two circular and equatorial
orbits with the same radius, they take different times to return to the
reference direction relative to which their motion is measured: it is the
so-called gravitomagnetic clock effect. The satellite moving in the same sense
of the rotation of the primary is slower, and experiences a retardation with
respect to the case when the latter does not spin, while the one circling in
the opposite sense of the rotation of the source is faster, and its orbital
period is shorter than it would be in the static case. The resulting time
difference due to the stationary gravitomagnetic field of the central spinning
body is proportional to the angular momentum per unit mass of the latter
through a numerical factor which so far has been found to be $4\pi$. A
numerical integration of the equations of motion of a fictitious test particle
moving along a circular path lying in the equatorial plane of a hypothetical
rotating object by including the gravitomagnetic acceleration to the first
post-Newtonian order shows that, actually, the gravitomagnetic corrections to
the orbital periods are larger by a factor of $4$ in both the prograde and
retrograde cases. Such an outcome, which makes the proportionality coefficient
of the gravitomagnetic difference in the orbital periods of the two
counter-revolving orbiters equal to $16\pi$, confirms an analytical calculation
recently published in the literature by the present author.
| [
{
"created": "Thu, 17 Jul 2014 15:09:36 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Nov 2023 20:20:25 GMT",
"version": "v2"
},
{
"created": "Thu, 16 Nov 2023 09:19:27 GMT",
"version": "v3"
},
{
"created": "Sat, 2 Dec 2023 22:56:36 GMT",
"version": "v4"
},
{
"created": "Thu, 14 Dec 2023 21:11:48 GMT",
"version": "v5"
}
] | 2024-03-19 | [
[
"Iorio",
"Lorenzo",
""
]
] | To the first post-Newtonian order, if two test particles revolve in opposite directions about a massive, spinning body along two circular and equatorial orbits with the same radius, they take different times to return to the reference direction relative to which their motion is measured: it is the so-called gravitomagnetic clock effect. The satellite moving in the same sense of the rotation of the primary is slower, and experiences a retardation with respect to the case when the latter does not spin, while the one circling in the opposite sense of the rotation of the source is faster, and its orbital period is shorter than it would be in the static case. The resulting time difference due to the stationary gravitomagnetic field of the central spinning body is proportional to the angular momentum per unit mass of the latter through a numerical factor which so far has been found to be $4\pi$. A numerical integration of the equations of motion of a fictitious test particle moving along a circular path lying in the equatorial plane of a hypothetical rotating object by including the gravitomagnetic acceleration to the first post-Newtonian order shows that, actually, the gravitomagnetic corrections to the orbital periods are larger by a factor of $4$ in both the prograde and retrograde cases. Such an outcome, which makes the proportionality coefficient of the gravitomagnetic difference in the orbital periods of the two counter-revolving orbiters equal to $16\pi$, confirms an analytical calculation recently published in the literature by the present author. |
1906.10531 | Xiao-Xiong Zeng | Ke-Jian He, Xin-Yun Hu, Xiao-Xiong Zeng | The weak cosmic censorship conjecture and thermodynamics in the
quintessence AdS black hole under charge particle absorption | Accepted by Chin. Phys. C | Chinese Physics C 43 (2019) 125101 | 10.1088/1674-1137/43/12/125101 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | Considering the cosmological constant as the pressure, we mainly study the
laws of thermodynamics and weak cosmic censorship conjecture in the
Reissner-Nordstr\"{o}m-AdS black hole surrounded by quintessence dark energy
under charged particle absorption. The first law of thermodynamics is found to
be valid as a particle is absorbed by the black hole. The second law however is
found to be violated for the extremal and near-extremal black holes since the
entropy of these black hole decrease. Moreover, we find that the extremal black
hole do not change it configuration in the extended phase space, implying that
the weak cosmic censorship conjecture is valid. Remarkably, the near-extremal
black hole can be overcharged beyond the extremal condition under charged
particle absorption. That is, the cosmic censorship conjecture could be
violated for the near-extremal black hole in the extended phase space. To make
a comparison, we also discuss the first law, second law as well as the weak
cosmic censorship conjecture in the normal phase space, and find that all of
them are valid in this case.
| [
{
"created": "Mon, 24 Jun 2019 07:25:37 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Aug 2019 02:22:39 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Oct 2019 03:33:00 GMT",
"version": "v3"
}
] | 2019-12-19 | [
[
"He",
"Ke-Jian",
""
],
[
"Hu",
"Xin-Yun",
""
],
[
"Zeng",
"Xiao-Xiong",
""
]
] | Considering the cosmological constant as the pressure, we mainly study the laws of thermodynamics and weak cosmic censorship conjecture in the Reissner-Nordstr\"{o}m-AdS black hole surrounded by quintessence dark energy under charged particle absorption. The first law of thermodynamics is found to be valid as a particle is absorbed by the black hole. The second law however is found to be violated for the extremal and near-extremal black holes since the entropy of these black hole decrease. Moreover, we find that the extremal black hole do not change it configuration in the extended phase space, implying that the weak cosmic censorship conjecture is valid. Remarkably, the near-extremal black hole can be overcharged beyond the extremal condition under charged particle absorption. That is, the cosmic censorship conjecture could be violated for the near-extremal black hole in the extended phase space. To make a comparison, we also discuss the first law, second law as well as the weak cosmic censorship conjecture in the normal phase space, and find that all of them are valid in this case. |
1506.05793 | Joan Sola | Joan Sola, Adria Gomez-Valent, Javier de Cruz Perez | Hints of dynamical vacuum energy in the expanding Universe | Accepted for publication in Astrophysical Journal Letters. Extended
discussion including BBN and CMB bounds, one more table and figure.
References added | Astrophys.J. 811 (2015) L14 | 10.1088/2041-8205/811/1/L14 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently there have been claims on model-independent evidence of dynamical
dark energy. Herein we consider a fairly general class of cosmological models
with a time-evolving cosmological term of the form $\Lambda(H)=C_0+C_H
H^2+C_{\dot{H}} \dot{H}$, where $H$ is the Hubble rate. These models are well
motivated from the theoretical point of view since they can be related to the
general form of the effective action of quantum field theory in curved
spacetime. Consistency with matter conservation can be achieved by letting the
Newtonian coupling $G$ change very slowly with the expansion. We solve these
dynamical vacuum models and fit them to the wealth of expansion history and
linear structure formation data. The results of our analysis show a
significantly better agreement as compared to the concordance $\Lambda$CDM
model, thus supporting the possibility of a dynamical cosmic vacuum.
| [
{
"created": "Thu, 18 Jun 2015 19:57:19 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Sep 2015 20:26:18 GMT",
"version": "v2"
}
] | 2015-10-08 | [
[
"Sola",
"Joan",
""
],
[
"Gomez-Valent",
"Adria",
""
],
[
"Perez",
"Javier de Cruz",
""
]
] | Recently there have been claims on model-independent evidence of dynamical dark energy. Herein we consider a fairly general class of cosmological models with a time-evolving cosmological term of the form $\Lambda(H)=C_0+C_H H^2+C_{\dot{H}} \dot{H}$, where $H$ is the Hubble rate. These models are well motivated from the theoretical point of view since they can be related to the general form of the effective action of quantum field theory in curved spacetime. Consistency with matter conservation can be achieved by letting the Newtonian coupling $G$ change very slowly with the expansion. We solve these dynamical vacuum models and fit them to the wealth of expansion history and linear structure formation data. The results of our analysis show a significantly better agreement as compared to the concordance $\Lambda$CDM model, thus supporting the possibility of a dynamical cosmic vacuum. |
1510.04795 | Safia Ahmad | Safia Ahmad, Nurgissa Myrzakulov, R. Myrzakulov | Tachyon field non-minimally coupled to massive neutrino matter | 15 pages, 6 figures, Published version | JCAP 07 (2016) 032 | 10.1088/1475-7516/2016/07/032 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we consider rolling tachyon, with steep run-away type of
potentials non-minimally coupled to massive neutrino matter. The coupling
dynamically builds up at late times as neutrino matter turns non-relativistic.
In case of scaling and string inspired potentials, we have shown that
non-minimal coupling leads to minimum in the field potential. Given a suitable
choice of model parameters, it is shown to give rise to late-time acceleration
with the desired equation of state.
| [
{
"created": "Fri, 16 Oct 2015 06:50:23 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Aug 2016 09:10:22 GMT",
"version": "v2"
}
] | 2016-08-05 | [
[
"Ahmad",
"Safia",
""
],
[
"Myrzakulov",
"Nurgissa",
""
],
[
"Myrzakulov",
"R.",
""
]
] | In this paper, we consider rolling tachyon, with steep run-away type of potentials non-minimally coupled to massive neutrino matter. The coupling dynamically builds up at late times as neutrino matter turns non-relativistic. In case of scaling and string inspired potentials, we have shown that non-minimal coupling leads to minimum in the field potential. Given a suitable choice of model parameters, it is shown to give rise to late-time acceleration with the desired equation of state. |
0910.2125 | S. Mignemi | S. Mignemi | Lifetime of flying particles in canonical Doubly Special Relativity | The previous submission was wrong: it contained the file of a
differnt paper | Phys.Lett.A373:4401-4404,2009 | 10.1016/j.physleta.2009.09.068 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the corrections to the lifetime of unstable elementary particles
in some models of doubly special relativity. We assume that the speed of light
is invariant and that the position coordinates transform in such a way to
ensure the invariance of the deformed symplectic structure of phase space.
| [
{
"created": "Mon, 12 Oct 2009 10:14:13 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Oct 2009 09:13:06 GMT",
"version": "v2"
}
] | 2010-01-11 | [
[
"Mignemi",
"S.",
""
]
] | We discuss the corrections to the lifetime of unstable elementary particles in some models of doubly special relativity. We assume that the speed of light is invariant and that the position coordinates transform in such a way to ensure the invariance of the deformed symplectic structure of phase space. |
1905.07251 | Pierre Martin-Dussaud | Pierre Martin-Dussaud and Carlo Rovelli | Evaporating black-to-white hole | null | Class. Quantum Grav. 36, 245002 (2019) | 10.1088/1361-6382/ab5097 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct and discuss the form of the (effective) spacetime geometry
inside a black hole undergoing a quantum transition to a white hole, taking
into account the back-reaction of the component of the Hawking radiation
falling into the hole.
| [
{
"created": "Fri, 17 May 2019 13:20:52 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Sep 2019 15:05:48 GMT",
"version": "v2"
}
] | 2022-08-03 | [
[
"Martin-Dussaud",
"Pierre",
""
],
[
"Rovelli",
"Carlo",
""
]
] | We construct and discuss the form of the (effective) spacetime geometry inside a black hole undergoing a quantum transition to a white hole, taking into account the back-reaction of the component of the Hawking radiation falling into the hole. |
2209.13387 | Hui-Min Fan | Hui-Min Fan, Shiyan Zhong, Zheng-Cheng Liang, Zheng Wu, Jian-dong
Zhang, Yi-Ming Hu | Extreme-mass-ratio burst detection with TianQin | null | null | 10.1103/PhysRevD.106.124028 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The capture of compact objects by massive black holes in galaxies or dwarf
galaxies will generate short gravitational wave signals, called
extreme-mass-ratio bursts (EMRBs), before evolving into extreme-mass-ratio
inspirals. Their detection will provide an investigation of the black hole
properties and shed light on astronomy and astrophysics. In this work, we
investigate the detection number of the TianQin observatory on EMRBs. Our
result shows that TianQin can detect tens of EMRBs events during its mission
lifetime. For those detected events, we use the Fisher information matrix to
quantify these uncertainties in the inference of their parameters. We consider
the possible network of TianQin+LISA and study how a network can improve
parameter estimation. The result shows that, for most sources, the CO mass, the
MBH mass, and the MBH spin can be determined with an accuracy of the order
$10^{-1}$ and the sky localization can be determined with an accuracy of 10
square degrees. We further explore the gravitational wave background generated
by those unsolved EMRBs and conclude that it is about $10^6$ times weaker than
TianQin's sensitivity and thus it can be ignored.
| [
{
"created": "Tue, 27 Sep 2022 13:45:12 GMT",
"version": "v1"
}
] | 2023-01-04 | [
[
"Fan",
"Hui-Min",
""
],
[
"Zhong",
"Shiyan",
""
],
[
"Liang",
"Zheng-Cheng",
""
],
[
"Wu",
"Zheng",
""
],
[
"Zhang",
"Jian-dong",
""
],
[
"Hu",
"Yi-Ming",
""
]
] | The capture of compact objects by massive black holes in galaxies or dwarf galaxies will generate short gravitational wave signals, called extreme-mass-ratio bursts (EMRBs), before evolving into extreme-mass-ratio inspirals. Their detection will provide an investigation of the black hole properties and shed light on astronomy and astrophysics. In this work, we investigate the detection number of the TianQin observatory on EMRBs. Our result shows that TianQin can detect tens of EMRBs events during its mission lifetime. For those detected events, we use the Fisher information matrix to quantify these uncertainties in the inference of their parameters. We consider the possible network of TianQin+LISA and study how a network can improve parameter estimation. The result shows that, for most sources, the CO mass, the MBH mass, and the MBH spin can be determined with an accuracy of the order $10^{-1}$ and the sky localization can be determined with an accuracy of 10 square degrees. We further explore the gravitational wave background generated by those unsolved EMRBs and conclude that it is about $10^6$ times weaker than TianQin's sensitivity and thus it can be ignored. |
2006.09088 | Adam Szereszewski | Eryk Buk, Jerzy Lewandowski, Adam Szereszewski | Lie point symmetries of near-horizon geometry equation | null | Phys. Rev. D 102, 124064 (2020) | 10.1103/PhysRevD.102.124064 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | All the Lie point symmetries of the near extremal horizon geometry equation,
in the case of 4-dimensional Einstein vacuum spacetime with cosmological
constant, are the diffeomorphisms of the space of the null generators of the
horizon. This result is also generalised to the Maxwell-Einstein spacetime.
| [
{
"created": "Tue, 16 Jun 2020 11:47:20 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Jul 2020 14:09:21 GMT",
"version": "v2"
}
] | 2021-01-04 | [
[
"Buk",
"Eryk",
""
],
[
"Lewandowski",
"Jerzy",
""
],
[
"Szereszewski",
"Adam",
""
]
] | All the Lie point symmetries of the near extremal horizon geometry equation, in the case of 4-dimensional Einstein vacuum spacetime with cosmological constant, are the diffeomorphisms of the space of the null generators of the horizon. This result is also generalised to the Maxwell-Einstein spacetime. |
1804.01439 | Pedro Bargueno | Ernesto Contreras, Pedro Bargueno, Gretel Quintero, Aurora
Perez-Martinez, Diana Alvear | Exact solutions of Einstein equations for anisotropic magnetic sources | 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we have obtained exact solutions of Einstein equations for
static and axially symmetric magnetized matter, specifically in plane-symmetric
and almost-plane symmetric cases. Although these solutions impose constraints
on the components of the energy-momentum tensor, some physically interesting
situations, like the magnetized vacuum, might be described. Plane-symmetric
solutions in presence of a non-vanishing cosmological constant have remarkable
features. In particular, the system can be driven continuously to the isotropic
case by an appropriate tuning of the cosmological constant, sweeping the
magnetic field from weak to strong magnetic field regimes. The role of the
cosmological constant in magnetic collapse is discussed with an emphasis in the
description of jets from compact objects. For illustrative purposes, specific
calculations for a magnetized electron gas have been developed.
| [
{
"created": "Wed, 4 Apr 2018 14:36:53 GMT",
"version": "v1"
}
] | 2018-04-05 | [
[
"Contreras",
"Ernesto",
""
],
[
"Bargueno",
"Pedro",
""
],
[
"Quintero",
"Gretel",
""
],
[
"Perez-Martinez",
"Aurora",
""
],
[
"Alvear",
"Diana",
""
]
] | In this work, we have obtained exact solutions of Einstein equations for static and axially symmetric magnetized matter, specifically in plane-symmetric and almost-plane symmetric cases. Although these solutions impose constraints on the components of the energy-momentum tensor, some physically interesting situations, like the magnetized vacuum, might be described. Plane-symmetric solutions in presence of a non-vanishing cosmological constant have remarkable features. In particular, the system can be driven continuously to the isotropic case by an appropriate tuning of the cosmological constant, sweeping the magnetic field from weak to strong magnetic field regimes. The role of the cosmological constant in magnetic collapse is discussed with an emphasis in the description of jets from compact objects. For illustrative purposes, specific calculations for a magnetized electron gas have been developed. |
2405.09590 | Gamal G.L. Nashed | G.G.L. Nashed and Salvatore Capozziello | Constraining $f({\cal R})$ gravity by Pulsar {\textit SAX J1748.9-2021}
observations | 28 pages, 8 figures, Will appear in EPJC | null | null | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | We discuss spherically symmetric dynamical systems in the framework of a
general model of $f({\cal R})$ gravity, i.e. $f({\cal R})={\cal R}e^{\zeta
{\cal R}}$, where $\zeta$ is a dimensional quantity in squared length units
[L$^2$]. We initially assume that the internal structure of such systems is
governed by the Krori-Barua ansatz, alongside the presence of fluid anisotropy.
By employing astrophysical observations obtained from the pulsar {\textit SAX
J1748.9-2021}, derived from bursting X-ray binaries located within globular
clusters, we determine that $\zeta$ is approximately equal to $\pm 5$ km$^2$.
In particular, the model can create a stable configuration for {\textit SAX
J1748.9-2021}, encompassing its geometric and physical characteristics. In
$f({\cal R})$ gravity, the Krori-Barua approach links $p_r$ and $p_t$, which
represent the components of the pressures, to ($\rho$), representing the
density, semi-analytically. These relations are described as $p_r\approx v_r^2
(\rho-\rho_{I})$ and $p_t\approx v_t^2 (\rho-\rho_{II})$. Here, the expression
$v_r$ and $v_t$ represent the radial and tangential sound speeds, respectively.
Meanwhile, $\rho_I$ pertains to the surface density and $\rho_{II}$ is derived
using the parameters of the model. Notably, within the frame of $f({\cal R})$
gravity where $\zeta$ is negative, the maximum compactness, denoted as $C$, is
inherently limited to values that do not exceed the Buchdahl limit. This
contrasts with general relativity or with $f({\cal R})$ with positive $\zeta$,
where $C$ has the potential to reach the limit of the black hole
asymptotically. The predictions of such model suggest a central energy density
which largely exceeds the saturation of nuclear density, which has the value
$\rho_{\text{nuc}} = 3\times 10^{14}$ g/cm$^3$. Also, the density at the
surface $\rho_I$ surpasses $\rho_{\text{nuc}}$.
| [
{
"created": "Wed, 15 May 2024 10:54:46 GMT",
"version": "v1"
}
] | 2024-05-17 | [
[
"Nashed",
"G. G. L.",
""
],
[
"Capozziello",
"Salvatore",
""
]
] | We discuss spherically symmetric dynamical systems in the framework of a general model of $f({\cal R})$ gravity, i.e. $f({\cal R})={\cal R}e^{\zeta {\cal R}}$, where $\zeta$ is a dimensional quantity in squared length units [L$^2$]. We initially assume that the internal structure of such systems is governed by the Krori-Barua ansatz, alongside the presence of fluid anisotropy. By employing astrophysical observations obtained from the pulsar {\textit SAX J1748.9-2021}, derived from bursting X-ray binaries located within globular clusters, we determine that $\zeta$ is approximately equal to $\pm 5$ km$^2$. In particular, the model can create a stable configuration for {\textit SAX J1748.9-2021}, encompassing its geometric and physical characteristics. In $f({\cal R})$ gravity, the Krori-Barua approach links $p_r$ and $p_t$, which represent the components of the pressures, to ($\rho$), representing the density, semi-analytically. These relations are described as $p_r\approx v_r^2 (\rho-\rho_{I})$ and $p_t\approx v_t^2 (\rho-\rho_{II})$. Here, the expression $v_r$ and $v_t$ represent the radial and tangential sound speeds, respectively. Meanwhile, $\rho_I$ pertains to the surface density and $\rho_{II}$ is derived using the parameters of the model. Notably, within the frame of $f({\cal R})$ gravity where $\zeta$ is negative, the maximum compactness, denoted as $C$, is inherently limited to values that do not exceed the Buchdahl limit. This contrasts with general relativity or with $f({\cal R})$ with positive $\zeta$, where $C$ has the potential to reach the limit of the black hole asymptotically. The predictions of such model suggest a central energy density which largely exceeds the saturation of nuclear density, which has the value $\rho_{\text{nuc}} = 3\times 10^{14}$ g/cm$^3$. Also, the density at the surface $\rho_I$ surpasses $\rho_{\text{nuc}}$. |
1805.10455 | Thomas Buchert | Thomas Buchert, Pierre Mourier, Xavier Roy | Cosmological backreaction and its dependence on spacetime foliation | 9 pages, Letter, matches published version in CQG | Class. Quantum Grav. 35 (2018) 24LT02 | 10.1088/1361-6382/aaebce | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The subject of cosmological backreaction in General Relativity is often
approached by coordinate-dependent and metric-based analyses. We present in
this letter an averaging formalism for the scalar parts of Einstein's equations
that is coordinate-independent and only functionally depends on a metric. This
formalism is applicable to general 3+1 foliations of spacetime for an arbitrary
fluid with tilted flow. We clarify the dependence on spacetime foliation and
argue that this dependence is weak in cosmological settings. We also introduce
a new set of averaged equations that feature a global cosmological time despite
the generality of the setting, and we put the statistical nature of effective
cosmologies into perspective.
| [
{
"created": "Sat, 26 May 2018 10:04:25 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Nov 2018 11:08:29 GMT",
"version": "v2"
}
] | 2018-12-04 | [
[
"Buchert",
"Thomas",
""
],
[
"Mourier",
"Pierre",
""
],
[
"Roy",
"Xavier",
""
]
] | The subject of cosmological backreaction in General Relativity is often approached by coordinate-dependent and metric-based analyses. We present in this letter an averaging formalism for the scalar parts of Einstein's equations that is coordinate-independent and only functionally depends on a metric. This formalism is applicable to general 3+1 foliations of spacetime for an arbitrary fluid with tilted flow. We clarify the dependence on spacetime foliation and argue that this dependence is weak in cosmological settings. We also introduce a new set of averaged equations that feature a global cosmological time despite the generality of the setting, and we put the statistical nature of effective cosmologies into perspective. |
1803.10767 | Christian Corda Prof. | S. H. Hendi, Z. S. Taghadomi and C. Corda | New aspect of critical nonlinearly charged black hole | 10 pages, 2 tables, 4 figures. Accepted for publication in Physical
Review D | Phys. Rev. D 97, 084039 (2018) | 10.1103/PhysRevD.97.084039 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The motion of a point charged particle moving in the background of the
critical power Maxwell charged AdS black holes, in a probe approximation is
studied. The extended phase space, where the cosmological constant appears as a
pressure, is regarded and the effective potential is investigated. At last, the
mass-to-charge ratio and the large q limit are studied.
| [
{
"created": "Wed, 28 Mar 2018 09:53:07 GMT",
"version": "v1"
}
] | 2018-05-09 | [
[
"Hendi",
"S. H.",
""
],
[
"Taghadomi",
"Z. S.",
""
],
[
"Corda",
"C.",
""
]
] | The motion of a point charged particle moving in the background of the critical power Maxwell charged AdS black holes, in a probe approximation is studied. The extended phase space, where the cosmological constant appears as a pressure, is regarded and the effective potential is investigated. At last, the mass-to-charge ratio and the large q limit are studied. |
2401.13857 | Kristian Gjorgjieski | Kristian Gjorgjieski, Jutta Kunz and Petya Nedkova | Comparison of Magnetized Thick Disks around Black Holes and Boson Stars | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Boson stars are considered as promising candidates for black hole mimickers.
Similar to other compact objects they can form accretion disks around them. The
properties of these disks could possibly distinguish them from other compact
objects like black holes in future observations. Retrograde thick disks around
boson stars and the influence of strong magnetic fields on them were already
studied and it was shown that they can harbor very distinct features compared
to black hole disks. However, the case of prograde thick disks is mostly
unexplored, since they may appear much more similar to black hole disks. In
this work we will investigate similarities and differences regarding prograde
thick disks around non-selfinteracting rotating boson stars and rotating black
holes. We assume thereby a polytropic equation of state and a constant specific
angular momentum distribution of the disks. We classify the various conceivable
boson star and black hole solutions by a dimensionless spin parameter $a$ and
compare their corresponding disk solutions. The influence of toroidal magnetic
fields on the disks is analyzed by selected disk properties, as the rest-mass
density distribution and the Bernoulli parameter. Disk solutions are
characterized by their degree of magnetization represented by the magnetization
parameter $\beta_{mc}$. We found that strong magnetic fields can strengthen the
differences of disk solutions or oppositely even lead to a correlation in disk
properties, depending on the spin parameter of the boson star and black hole
solutions. We identify the vertical thickness of the boson star disks as the
main differentiating factor, since for most solutions the vertical density
distribution is far more outreaching for boson star disks compared to black
hole disks.
| [
{
"created": "Wed, 24 Jan 2024 23:42:50 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Feb 2024 15:48:12 GMT",
"version": "v2"
}
] | 2024-02-06 | [
[
"Gjorgjieski",
"Kristian",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Nedkova",
"Petya",
""
]
] | Boson stars are considered as promising candidates for black hole mimickers. Similar to other compact objects they can form accretion disks around them. The properties of these disks could possibly distinguish them from other compact objects like black holes in future observations. Retrograde thick disks around boson stars and the influence of strong magnetic fields on them were already studied and it was shown that they can harbor very distinct features compared to black hole disks. However, the case of prograde thick disks is mostly unexplored, since they may appear much more similar to black hole disks. In this work we will investigate similarities and differences regarding prograde thick disks around non-selfinteracting rotating boson stars and rotating black holes. We assume thereby a polytropic equation of state and a constant specific angular momentum distribution of the disks. We classify the various conceivable boson star and black hole solutions by a dimensionless spin parameter $a$ and compare their corresponding disk solutions. The influence of toroidal magnetic fields on the disks is analyzed by selected disk properties, as the rest-mass density distribution and the Bernoulli parameter. Disk solutions are characterized by their degree of magnetization represented by the magnetization parameter $\beta_{mc}$. We found that strong magnetic fields can strengthen the differences of disk solutions or oppositely even lead to a correlation in disk properties, depending on the spin parameter of the boson star and black hole solutions. We identify the vertical thickness of the boson star disks as the main differentiating factor, since for most solutions the vertical density distribution is far more outreaching for boson star disks compared to black hole disks. |
1808.10278 | Herwig Dejonghe | Herwig Dejonghe | Spherical cosmological models: an alternative cosmology | null | null | null | null | gr-qc astro-ph.CO astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The properties of universes are explored that are entirely in the interior of
black holes in another universe, a `mother universe'. It is argued that these
models offer a paradigm that may shed a new light on old cosmological problems.
The geometry of such a universe is discussed including how it would appear to
the observer. The Hubble parameter is direction dependent, but it is argued
that the interpretation of any such dependence will be hard to separate from
local inhomogeneities. The models do not originate from a big bang, but rather
from an initial collapse and subsequent infall, that started probably a very
long time ago, presumably much earlier than the accepted age of the universe.
The relation to the concordance model is discussed and it is shown that a lot
of the existing theory can be taken over into the proposed models. The universe
has an edge, which is an ordinary spherical surface in 3 dimensions. That
sphere acts as a gravitational mirror as seen from inside the universe, but it
does not mirror redshift. The same object can thus be seen in direct sight and
in reflection, although with different redshifts, different ages and different
aspect angles. The models do not need dark energy, but they need dark matter,
of course. Since the models are closed and neutrino's are nowadays believed to
have mass, neutrino's can be reconsidered as candidates for the dark matter. As
a bonus result from this paradigm, mass ejection from black holes is shown to
be possible, which links that process to the controversial anomalous galaxy
redshifts. Finally, we show that gravitational mass and inertial mass are
proportional, and that the inertial acceleration scales as $c^2/M$, with $M$ a
characteristic length scale of the universe.
| [
{
"created": "Tue, 28 Aug 2018 09:17:03 GMT",
"version": "v1"
},
{
"created": "Tue, 21 May 2019 14:26:36 GMT",
"version": "v2"
},
{
"created": "Thu, 13 Oct 2022 19:32:56 GMT",
"version": "v3"
}
] | 2022-10-17 | [
[
"Dejonghe",
"Herwig",
""
]
] | The properties of universes are explored that are entirely in the interior of black holes in another universe, a `mother universe'. It is argued that these models offer a paradigm that may shed a new light on old cosmological problems. The geometry of such a universe is discussed including how it would appear to the observer. The Hubble parameter is direction dependent, but it is argued that the interpretation of any such dependence will be hard to separate from local inhomogeneities. The models do not originate from a big bang, but rather from an initial collapse and subsequent infall, that started probably a very long time ago, presumably much earlier than the accepted age of the universe. The relation to the concordance model is discussed and it is shown that a lot of the existing theory can be taken over into the proposed models. The universe has an edge, which is an ordinary spherical surface in 3 dimensions. That sphere acts as a gravitational mirror as seen from inside the universe, but it does not mirror redshift. The same object can thus be seen in direct sight and in reflection, although with different redshifts, different ages and different aspect angles. The models do not need dark energy, but they need dark matter, of course. Since the models are closed and neutrino's are nowadays believed to have mass, neutrino's can be reconsidered as candidates for the dark matter. As a bonus result from this paradigm, mass ejection from black holes is shown to be possible, which links that process to the controversial anomalous galaxy redshifts. Finally, we show that gravitational mass and inertial mass are proportional, and that the inertial acceleration scales as $c^2/M$, with $M$ a characteristic length scale of the universe. |
2403.19315 | Bogeun Gwak | Hyewon Han, Bogeun Gwak | Mass fluctuations in non-rotating BTZ black holes | 17 pages, 1 figure | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the impact of oscillations of a black-hole mass around its
average value on the three-dimensional black hole geometry. Drawing on a
classical framework that conceptualizes fluctuations near an event horizon as
mass variations, we introduce a model where the metric of a black hole, formed
from the collapse of a massive null shell, exhibits oscillatory behavior in
spherical modes. This dynamic is encapsulated by a non-rotating BTZ-Vaidya
solution, characterized by the black hole mass fluctuating at a resonant
frequency $\omega$ and a small amplitude parameter $\mu_0$. Using a
perturbative approach, solutions to the null geodesic equation are determined
up to the second order in $\mu_0$. The temporal fluctuations of the event
horizon's location induce alterations in the thermodynamic variables' values.
Upon calculating the time-averaged values, it is observed that the mean Hawking
temperature experiences a slight decrease due to these fluctuations, while the
mean entropy exhibits an increase, deviating from trends observed in four- and
higher-dimensional spacetimes. Further, the study delves into the influence of
these fluctuations on the trajectories of null rays near the horizon,
ultimately reaching the anti-de Sitter boundary at late times. The analytical
computation of the general solution for the perturbed rays up to the second
order underscores the novel approach of this study in examining the effects of
mass oscillations on black hole thermodynamics and geometry, contributing a
unique perspective to the field.
| [
{
"created": "Thu, 28 Mar 2024 11:15:39 GMT",
"version": "v1"
}
] | 2024-03-29 | [
[
"Han",
"Hyewon",
""
],
[
"Gwak",
"Bogeun",
""
]
] | We investigate the impact of oscillations of a black-hole mass around its average value on the three-dimensional black hole geometry. Drawing on a classical framework that conceptualizes fluctuations near an event horizon as mass variations, we introduce a model where the metric of a black hole, formed from the collapse of a massive null shell, exhibits oscillatory behavior in spherical modes. This dynamic is encapsulated by a non-rotating BTZ-Vaidya solution, characterized by the black hole mass fluctuating at a resonant frequency $\omega$ and a small amplitude parameter $\mu_0$. Using a perturbative approach, solutions to the null geodesic equation are determined up to the second order in $\mu_0$. The temporal fluctuations of the event horizon's location induce alterations in the thermodynamic variables' values. Upon calculating the time-averaged values, it is observed that the mean Hawking temperature experiences a slight decrease due to these fluctuations, while the mean entropy exhibits an increase, deviating from trends observed in four- and higher-dimensional spacetimes. Further, the study delves into the influence of these fluctuations on the trajectories of null rays near the horizon, ultimately reaching the anti-de Sitter boundary at late times. The analytical computation of the general solution for the perturbed rays up to the second order underscores the novel approach of this study in examining the effects of mass oscillations on black hole thermodynamics and geometry, contributing a unique perspective to the field. |
1804.10793 | Jakub Mielczarek Ph.D. | Michal Mandrysz, Jakub Mielczarek | Ultralocal nature of geometrogenesis | 23 pages, 9 figures | null | 10.1088/1361-6382/aaef71 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we show that the ultralocal state of gravity can be
associated with the so-called crumpled phase of gravity, observed e.g. in
Causal Dynamical Triangulations. By considering anisotropic scaling present in
the Ho\v{r}ava-Lifshitz theory, we prove that in the ultralocal scaling limit
($z \rightarrow 0$) the graph representing connectivity structure of space is
becoming complete. In consequence, transition from the ultralocal phase ($z=0$)
to the standard relativistic scaling ($z=1$) is implemented by the
geometrogensis, similar to the one considered in Quantum Graphity approach.
However, the relation holds only for the finite number of nodes $N$ and in the
continuous limit ($N\rightarrow \infty$) the complete graph reduces to the set
of disconnected points due to the weights $w=1/N$ associated with the links. By
coupling Ising spin matter to the considered graph we show that the process of
geometrogensis can be associated with critical behavior. Based on both
analytical and numerical analysis phase diagram of the system is reconstructed
showing that (for a ring graph) symmetry broken phase occurs at $z\in [0,
0.5)$. Finally, cosmological consequences of the considered process of
geometrogenesis as well as similarities with the so-called synaptic pruning are
briefly discussed.
| [
{
"created": "Sat, 28 Apr 2018 12:19:47 GMT",
"version": "v1"
}
] | 2018-12-26 | [
[
"Mandrysz",
"Michal",
""
],
[
"Mielczarek",
"Jakub",
""
]
] | In this article we show that the ultralocal state of gravity can be associated with the so-called crumpled phase of gravity, observed e.g. in Causal Dynamical Triangulations. By considering anisotropic scaling present in the Ho\v{r}ava-Lifshitz theory, we prove that in the ultralocal scaling limit ($z \rightarrow 0$) the graph representing connectivity structure of space is becoming complete. In consequence, transition from the ultralocal phase ($z=0$) to the standard relativistic scaling ($z=1$) is implemented by the geometrogensis, similar to the one considered in Quantum Graphity approach. However, the relation holds only for the finite number of nodes $N$ and in the continuous limit ($N\rightarrow \infty$) the complete graph reduces to the set of disconnected points due to the weights $w=1/N$ associated with the links. By coupling Ising spin matter to the considered graph we show that the process of geometrogensis can be associated with critical behavior. Based on both analytical and numerical analysis phase diagram of the system is reconstructed showing that (for a ring graph) symmetry broken phase occurs at $z\in [0, 0.5)$. Finally, cosmological consequences of the considered process of geometrogenesis as well as similarities with the so-called synaptic pruning are briefly discussed. |
2103.08872 | Zhigang Bu | Zhigang Bu, Liangliang Ji and Baifei Shen | Unruh effect and angular momentum correlation of Rindler particles | 23 pages, 1 figure | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | It is well known that the rotational motion does not induce Unruh effect,
because the Minkowski vacuum coincides with the vacuum state defined by the
pure rotating observers. However, are there Rindler particles carrying orbital
angular momentum (OAM), and do they produce observable effect? To answer these
questions, we need an accelerated observer having a vortex structure in the
transverse dimensions and carrying well-defined OAM. Here we consider the
angular momentum characteristics of Unruh effect in the theory of scalar field
and electromagnetic field for the first time. We find that the rotation and
vortex structure of a uniformly accelerated observer lead to the definite
angular momentum correlation between Rindler particles and their counterparts
in Minkowski vacuum. When interacting with the Unruh thermal bath, the
accelerated vortex observer carrying the OAM of l can absorb and emit Rindler
particles with the same OAM, and the particle energy is determined by the
angular velocity of the rotation. The absorption rate is not equal to the
emission rate in general. Both the absorption and emission processes in the
thermal bath are correlated with the emission process of particles with OAM of
+l or -1 in Minkowski vacuum. This effect may promote a potential scheme to
detect the Unruh effect. The OAM provides a potential approach to filter out
the background noise so that the signal particles could be extracted
sufficiently.
| [
{
"created": "Tue, 16 Mar 2021 06:47:07 GMT",
"version": "v1"
}
] | 2021-03-17 | [
[
"Bu",
"Zhigang",
""
],
[
"Ji",
"Liangliang",
""
],
[
"Shen",
"Baifei",
""
]
] | It is well known that the rotational motion does not induce Unruh effect, because the Minkowski vacuum coincides with the vacuum state defined by the pure rotating observers. However, are there Rindler particles carrying orbital angular momentum (OAM), and do they produce observable effect? To answer these questions, we need an accelerated observer having a vortex structure in the transverse dimensions and carrying well-defined OAM. Here we consider the angular momentum characteristics of Unruh effect in the theory of scalar field and electromagnetic field for the first time. We find that the rotation and vortex structure of a uniformly accelerated observer lead to the definite angular momentum correlation between Rindler particles and their counterparts in Minkowski vacuum. When interacting with the Unruh thermal bath, the accelerated vortex observer carrying the OAM of l can absorb and emit Rindler particles with the same OAM, and the particle energy is determined by the angular velocity of the rotation. The absorption rate is not equal to the emission rate in general. Both the absorption and emission processes in the thermal bath are correlated with the emission process of particles with OAM of +l or -1 in Minkowski vacuum. This effect may promote a potential scheme to detect the Unruh effect. The OAM provides a potential approach to filter out the background noise so that the signal particles could be extracted sufficiently. |
0902.3199 | Laszlo B. Szabados | Laszlo B Szabados | Towards the quasi-localization of canonical GR | 28 pages, typos corrected, a reference is changed, the text is
improved at several points, appearing in Class. Quantum Grav | null | 10.1088/0264-9381/26/12/125013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A general framework for a systematic quasi-localization of canonical general
relativity and a new ingredient, the requirement of the gauge invariance of the
boundary terms appearing in the calculation of Poisson brackets, are given. As
a consequence of this it is shown, in particular, that the generator vector
fields (built from the lapse and shift) of the quasi-local quantities must be
divergence free with respect to a Sen-type connection; and the volume form
induced from the spatial metric on the boundary surface must be fixed.
| [
{
"created": "Wed, 18 Feb 2009 17:27:59 GMT",
"version": "v1"
},
{
"created": "Tue, 19 May 2009 12:09:10 GMT",
"version": "v2"
}
] | 2015-05-13 | [
[
"Szabados",
"Laszlo B",
""
]
] | A general framework for a systematic quasi-localization of canonical general relativity and a new ingredient, the requirement of the gauge invariance of the boundary terms appearing in the calculation of Poisson brackets, are given. As a consequence of this it is shown, in particular, that the generator vector fields (built from the lapse and shift) of the quasi-local quantities must be divergence free with respect to a Sen-type connection; and the volume form induced from the spatial metric on the boundary surface must be fixed. |
gr-qc/0509049 | Krzysztof A. Meissner | Krzysztof A. Meissner | Eigenvalues of the volume operator in loop quantum gravity | 12 pages, version accepted in Class. Quantum Grav | Class.Quant.Grav. 23 (2006) 617-626 | 10.1088/0264-9381/23/3/005 | null | gr-qc | null | We present a simple method to calculate certain sums of the eigenvalues of
the volume operator in loop quantum gravity. We derive the asymptotic
distribution of the eigenvalues in the classical limit of very large spins
which turns out to be of a very simple form. The results can be useful for
example in the statistical approach to quantum gravity.
| [
{
"created": "Wed, 14 Sep 2005 13:59:38 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Jan 2006 10:59:25 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Meissner",
"Krzysztof A.",
""
]
] | We present a simple method to calculate certain sums of the eigenvalues of the volume operator in loop quantum gravity. We derive the asymptotic distribution of the eigenvalues in the classical limit of very large spins which turns out to be of a very simple form. The results can be useful for example in the statistical approach to quantum gravity. |
2305.14186 | Jessica Page | Jessica Page, Tyson Littenberg | Bayesian Time Delay Interferometry for Orbiting LISA: Accounting for the
Time Dependence of Spacecraft Separations | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Previous work demonstrated effective laser frequency noise (LFN) suppression
for Laser Interferometer Space Antenna (LISA) data from raw phasemeter
measurements using a Markov Chain Monte Carlo (MCMC) algorithm with fractional
delay interpolation (FDI) techniques to estimate the spacecraft separation
parameters required for time-delay interferometry (TDI) under the assumption of
a rigidly rotating LISA configuration. Including TDI parameters in the LISA
data model as part of a global fit analysis pipeline enables gravitational wave
inferences to be marginalized over uncertainty in the spacecraft separations.
Here we extend the algorithm's capability to perform data-driven TDI on LISA in
Keplerian orbits, which introduce a time-dependence in the arm-length
parameters and at least $\mathcal{O}$(M) times greater computational cost since
the filter must be applied for every sample in the time series of sample size
M. We find feasibility of arm-length estimation on $\sim$day-long time scales
by using a novel Taylor-expanded version of the fractional delay interpolation
filter that allows half of the filter computation to be calculated and stored
before MCMC iterations and requires shorter filter lengths than previously
reported. We demonstrate LFN suppression for orbiting LISA using accurate
arm-length estimates parameterized by Keplerian orbital parameters under the
assumption of unperturbed analytical Keplerian orbits, and explore the
potential extension of these methods to arbitrary numerical orbits.
| [
{
"created": "Tue, 23 May 2023 16:07:30 GMT",
"version": "v1"
},
{
"created": "Fri, 26 May 2023 15:00:11 GMT",
"version": "v2"
}
] | 2023-05-29 | [
[
"Page",
"Jessica",
""
],
[
"Littenberg",
"Tyson",
""
]
] | Previous work demonstrated effective laser frequency noise (LFN) suppression for Laser Interferometer Space Antenna (LISA) data from raw phasemeter measurements using a Markov Chain Monte Carlo (MCMC) algorithm with fractional delay interpolation (FDI) techniques to estimate the spacecraft separation parameters required for time-delay interferometry (TDI) under the assumption of a rigidly rotating LISA configuration. Including TDI parameters in the LISA data model as part of a global fit analysis pipeline enables gravitational wave inferences to be marginalized over uncertainty in the spacecraft separations. Here we extend the algorithm's capability to perform data-driven TDI on LISA in Keplerian orbits, which introduce a time-dependence in the arm-length parameters and at least $\mathcal{O}$(M) times greater computational cost since the filter must be applied for every sample in the time series of sample size M. We find feasibility of arm-length estimation on $\sim$day-long time scales by using a novel Taylor-expanded version of the fractional delay interpolation filter that allows half of the filter computation to be calculated and stored before MCMC iterations and requires shorter filter lengths than previously reported. We demonstrate LFN suppression for orbiting LISA using accurate arm-length estimates parameterized by Keplerian orbital parameters under the assumption of unperturbed analytical Keplerian orbits, and explore the potential extension of these methods to arbitrary numerical orbits. |
2202.13935 | Marcony Silva Cunha | C. R. Muniz, H. R. Christiansen, M. S. Cunha, J. Furtado | Four-dimensional regular black strings in bilocal gravity | 12 pages, 5 figures, text improved, final version to be published in
the Annals of Physics | Annals of Physics 443, 168980 (2022) | 10.1016/j.aop.2022.168980 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we obtain a static black string solution for a bilocal
gravitational source in 3+1 dimensions. The solution is regular at the origin
and tends asymptotically to the ordinary static uncharged black string solution
of general relativity. It allows an event horizon and an internal horizon
depending on the value of the mass density. A mass remnant associated with a
vanishing Hawking temperature is also found. In order to stabilize the
solution, a perfect cosmological fluid with state parameter $\omega>-1$ should
be present throughout space. However, energy conditions do not exclude an
exotic substance nearby the black string. Finally, we find the stationary
counterpart of the solution and analyze the behavior of the horizons according
to the mass and angular momentum of the spinning object.
| [
{
"created": "Mon, 28 Feb 2022 16:34:12 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Mar 2022 02:23:52 GMT",
"version": "v2"
},
{
"created": "Thu, 30 Jun 2022 13:39:43 GMT",
"version": "v3"
}
] | 2022-08-08 | [
[
"Muniz",
"C. R.",
""
],
[
"Christiansen",
"H. R.",
""
],
[
"Cunha",
"M. S.",
""
],
[
"Furtado",
"J.",
""
]
] | In this paper, we obtain a static black string solution for a bilocal gravitational source in 3+1 dimensions. The solution is regular at the origin and tends asymptotically to the ordinary static uncharged black string solution of general relativity. It allows an event horizon and an internal horizon depending on the value of the mass density. A mass remnant associated with a vanishing Hawking temperature is also found. In order to stabilize the solution, a perfect cosmological fluid with state parameter $\omega>-1$ should be present throughout space. However, energy conditions do not exclude an exotic substance nearby the black string. Finally, we find the stationary counterpart of the solution and analyze the behavior of the horizons according to the mass and angular momentum of the spinning object. |
1601.05965 | Pouria Pedram | Hossein Ardehali and Pouria Pedram | Chaplygin Gas Ho\v{r}ava-Lifshitz Quantum Cosmology | 11 pages, 2 figures, to appear in Physical Review D | Phys. Rev. D 93, 043532 (2016) | 10.1103/PhysRevD.93.043532 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the Chaplygin gas Ho\v{r}ava-Lifshitz quantum
cosmology. Using Schutz formalism and Arnowitt-Deser-Misner decomposition, we
obtain the corresponding Schr\"{o}dinger-Wheeler-DeWitt equation. We obtain
exact classical and quantum mechanical solutions and construct wave packets to
study the time evolution of the expectation value of the scale factor for two
cases. We show that unlike classical solutions and upon choosing appropriate
initial conditions, the expectation value of the scale factor never tends to
the singular point which exhibits the singularity-free behavior of the
solutions in the quantum domain.
| [
{
"created": "Fri, 22 Jan 2016 11:43:55 GMT",
"version": "v1"
}
] | 2016-02-24 | [
[
"Ardehali",
"Hossein",
""
],
[
"Pedram",
"Pouria",
""
]
] | In this paper, we study the Chaplygin gas Ho\v{r}ava-Lifshitz quantum cosmology. Using Schutz formalism and Arnowitt-Deser-Misner decomposition, we obtain the corresponding Schr\"{o}dinger-Wheeler-DeWitt equation. We obtain exact classical and quantum mechanical solutions and construct wave packets to study the time evolution of the expectation value of the scale factor for two cases. We show that unlike classical solutions and upon choosing appropriate initial conditions, the expectation value of the scale factor never tends to the singular point which exhibits the singularity-free behavior of the solutions in the quantum domain. |
2006.03339 | Tayyaba Naz | M. Farasat Shamir, Tayyaba Naz | Stellar Structures in $f(\mathcal{G})$ Gravity Admitting Noether
Symmetries | 11 pages, 5 figures | Phys. Lett. B 806 (2020) 135519 | 10.1016/j.physletb.2020.135519 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work aims to investigate some possible emergence of relativistic compact
stellar objects in modified $f(\mathcal{G})$ gravity using Noether symmetry
approach. For this purpose, we assume static spherically symmetric spacetime in
the presence of isotropic matter distribution. We construct Noether symmetry
generators along with associated conserved quantities by considering the
standard choice of viable $f(\mathcal{G})$ gravity model i.e. $f(\mathcal{G})=
\alpha\mathcal{G}^{n}$, where $\alpha$ is the model parameter. In particular,
we use conservation relation acquired from the classical Noether approach by
imposing some appropriate initial conditions to construct the metric
potentials. The obtained conserved quantity play vital role in describing the
stellar structure of compact stars. Moreover, by considering an appropriate
numerical solution, some salient features of compact stellar structures like
effective energy density, pressure, energy conditions, stability against
equilibrium of the forces and speed of sound are discussed by assigning the
suitable values of model parameter involved. Our study reveals that the compact
objects in $f(\mathcal{G})$ gravity from Noether symmetry approach depend on
the conserved quantity obtained and the model parameter $\alpha$. In nutshell,
Noether symmetries are quite helpful to generate solutions that follow
physically accepted phenomena. Moreover, we observed that these obtained
solutions are consistent with the astrophysical observational data, which
depicts the viability of our proposed Noether symmetry scheme.
| [
{
"created": "Fri, 5 Jun 2020 09:46:33 GMT",
"version": "v1"
}
] | 2020-06-08 | [
[
"Shamir",
"M. Farasat",
""
],
[
"Naz",
"Tayyaba",
""
]
] | This work aims to investigate some possible emergence of relativistic compact stellar objects in modified $f(\mathcal{G})$ gravity using Noether symmetry approach. For this purpose, we assume static spherically symmetric spacetime in the presence of isotropic matter distribution. We construct Noether symmetry generators along with associated conserved quantities by considering the standard choice of viable $f(\mathcal{G})$ gravity model i.e. $f(\mathcal{G})= \alpha\mathcal{G}^{n}$, where $\alpha$ is the model parameter. In particular, we use conservation relation acquired from the classical Noether approach by imposing some appropriate initial conditions to construct the metric potentials. The obtained conserved quantity play vital role in describing the stellar structure of compact stars. Moreover, by considering an appropriate numerical solution, some salient features of compact stellar structures like effective energy density, pressure, energy conditions, stability against equilibrium of the forces and speed of sound are discussed by assigning the suitable values of model parameter involved. Our study reveals that the compact objects in $f(\mathcal{G})$ gravity from Noether symmetry approach depend on the conserved quantity obtained and the model parameter $\alpha$. In nutshell, Noether symmetries are quite helpful to generate solutions that follow physically accepted phenomena. Moreover, we observed that these obtained solutions are consistent with the astrophysical observational data, which depicts the viability of our proposed Noether symmetry scheme. |
1206.7093 | Lu\'is Filipe de Pinho Oliveira e Costa | L. Filipe O. Costa, Jos\'e Nat\'ario, Miguel Zilh\~ao | Mathisson's helical motions demystified | To appear in the Proceedings of the Spanish Relativity Meeting 2011
(ERE2011), "Towards new paradigms", Madrid 29 August - 2 September 2011 | AIP Conf.Proc. 1458 (2011) 367-370 | 10.1063/1.4734436 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The motion of spinning test particles in general relativity is described by
Mathisson-Papapetrou-Dixon equations, which are undetermined up to a spin
supplementary condition, the latter being today still an open question. The
Mathisson-Pirani (MP) condition is known to lead to rather mysterious helical
motions which have been deemed unphysical, and for this reason discarded. We
show that these assessments are unfounded and originate from a subtle (but
crucial) misconception. We discuss the kinematical explanation of the helical
motions, and dynamically interpret them through the concept of hidden momentum,
which has an electromagnetic analogue. We also show that, contrary to previous
claims, the frequency of the helical motions coincides exactly with the
zitterbewegung frequency of the Dirac equation for the electron.
| [
{
"created": "Fri, 29 Jun 2012 18:27:09 GMT",
"version": "v1"
}
] | 2012-08-07 | [
[
"Costa",
"L. Filipe O.",
""
],
[
"Natário",
"José",
""
],
[
"Zilhão",
"Miguel",
""
]
] | The motion of spinning test particles in general relativity is described by Mathisson-Papapetrou-Dixon equations, which are undetermined up to a spin supplementary condition, the latter being today still an open question. The Mathisson-Pirani (MP) condition is known to lead to rather mysterious helical motions which have been deemed unphysical, and for this reason discarded. We show that these assessments are unfounded and originate from a subtle (but crucial) misconception. We discuss the kinematical explanation of the helical motions, and dynamically interpret them through the concept of hidden momentum, which has an electromagnetic analogue. We also show that, contrary to previous claims, the frequency of the helical motions coincides exactly with the zitterbewegung frequency of the Dirac equation for the electron. |
2204.12097 | Titus K Mathew | Sarath N, Jerin Mohan N D and Titus K Mathew | Running vacuum cosmology with bulk viscous matter | 25 pages and 11 figures | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | We study the late acceleration of the universe by incorporating bulk viscous
matter with the running vacuum. The vacuum energy density varies as the squares
of the Hubble parameter ($\rho_{\Lambda}\propto H^2$), and the coefficient of
bulk viscosity of matter is proportional to the velocity of expansion ($\xi
\propto H$). We obtained an analytical solution to the Friedmann equations and
estimated the model parameters using the combined data set SN1a+CMB+BAO+OHD. We
have evaluated the universe's age as 14 Gyr, which is slightly higher than the
age-predicted by the $\Lambda$CDM model. However, it is an improved result
compared to the age-predicted by a class of bulk viscous matter-dominated
models. Interestingly, we have obtained the coefficient of bulk viscosity of
the matter component as $1.316\times 10^5$ kg $\textnormal m^{-1}$ $\textnormal
s^{-1}$ which is one to two orders of magnitude less than the value predicted
by most of the bulk viscous matter-dominated models and it falls in the range
of highly viscous materials found on the earth. The Hubble parameter is a
decreasing function of the scale factor, and it attains a constant value in the
far future that corresponds to an end deSitter phase of evolution. The
deceleration parameter shows a transition from matter-dominated decelerated
phase to vacuum energy-dominated accelerating phase, and the transition
redshift is obtained as $z_T = 0.73$. The statefinder analysis distinguishes
our model from the $\Lambda$CDM model at present, and the $r-s$ trajectory
reveals the quintessence behaviour of the vacuum energy. The phase space
analysis shows that the universe is evolving towards a mechanically stable
state in the far future. The entropy evolution satisfies the generalised second
law of thermodynamics, and the entropy is maximised in the far future
evolution.
| [
{
"created": "Tue, 26 Apr 2022 06:23:06 GMT",
"version": "v1"
}
] | 2022-04-27 | [
[
"N",
"Sarath",
""
],
[
"D",
"Jerin Mohan N",
""
],
[
"Mathew",
"Titus K",
""
]
] | We study the late acceleration of the universe by incorporating bulk viscous matter with the running vacuum. The vacuum energy density varies as the squares of the Hubble parameter ($\rho_{\Lambda}\propto H^2$), and the coefficient of bulk viscosity of matter is proportional to the velocity of expansion ($\xi \propto H$). We obtained an analytical solution to the Friedmann equations and estimated the model parameters using the combined data set SN1a+CMB+BAO+OHD. We have evaluated the universe's age as 14 Gyr, which is slightly higher than the age-predicted by the $\Lambda$CDM model. However, it is an improved result compared to the age-predicted by a class of bulk viscous matter-dominated models. Interestingly, we have obtained the coefficient of bulk viscosity of the matter component as $1.316\times 10^5$ kg $\textnormal m^{-1}$ $\textnormal s^{-1}$ which is one to two orders of magnitude less than the value predicted by most of the bulk viscous matter-dominated models and it falls in the range of highly viscous materials found on the earth. The Hubble parameter is a decreasing function of the scale factor, and it attains a constant value in the far future that corresponds to an end deSitter phase of evolution. The deceleration parameter shows a transition from matter-dominated decelerated phase to vacuum energy-dominated accelerating phase, and the transition redshift is obtained as $z_T = 0.73$. The statefinder analysis distinguishes our model from the $\Lambda$CDM model at present, and the $r-s$ trajectory reveals the quintessence behaviour of the vacuum energy. The phase space analysis shows that the universe is evolving towards a mechanically stable state in the far future. The entropy evolution satisfies the generalised second law of thermodynamics, and the entropy is maximised in the far future evolution. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.