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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1104.5229 | Benjamin Shlaer | Jose J. Blanco-Pillado, Handhika S. Ramadhan, and Benjamin Shlaer | Bubbles from Nothing | 19 pages, 6 figures | null | 10.1088/1475-7516/2012/01/045 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the framework of flux compactifications, we construct an instanton
describing the quantum creation of an open universe from nothing. The solution
has many features in common with the smooth 6d bubble of nothing solutions
discussed recently, where the spacetime is described by a 4d compactification
of a 6d Einstein-Maxwell theory on S^2 stabilized by flux. The four-dimensional
description of this instanton reduces to that of Hawking and Turok. The choice
of parameters uniquely determines all future evolution, which we additionally
find to be stable against bubble of nothing instabilities.
| [
{
"created": "Wed, 27 Apr 2011 20:00:01 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Blanco-Pillado",
"Jose J.",
""
],
[
"Ramadhan",
"Handhika S.",
""
],
[
"Shlaer",
"Benjamin",
""
]
] | Within the framework of flux compactifications, we construct an instanton describing the quantum creation of an open universe from nothing. The solution has many features in common with the smooth 6d bubble of nothing solutions discussed recently, where the spacetime is described by a 4d compactification of a 6d Einstein-Maxwell theory on S^2 stabilized by flux. The four-dimensional description of this instanton reduces to that of Hawking and Turok. The choice of parameters uniquely determines all future evolution, which we additionally find to be stable against bubble of nothing instabilities. |
gr-qc/9804085 | Beverly K. Berger | Beverly K. Berger and Vincent Moncrief | Evidence for an oscillatory singularity in generic U(1) symmetric
cosmologies on $T^3 \times R$ | 15 pages, Revtex, includes 12 figures, psfig. High resolution
versions of figures 7, 8, 9, and 11 may be obtained from anonymous ftp to
ftp://vela.acs.oakland.edu/pub/berger/u1genfigs | Phys.Rev. D58 (1998) 064023 | 10.1103/PhysRevD.58.064023 | null | gr-qc | null | A longstanding conjecture by Belinskii, Lifshitz, and Khalatnikov that the
singularity in generic gravitational collapse is locally oscillatory is tested
numerically in vacuum, U(1) symmetric cosmological spacetimes on $T^3 \times
R$. If the velocity term dominated (VTD) solution to Einstein's equations is
substituted into the Hamiltonian for the full Einstein evolution equations, one
term is found to grow exponentially. This generates a prediction that
oscillatory behavior involving this term and another (which the VTD solution
causes to decay exponentially) should be observed in the approach to the
singularity. Numerical simulations strongly support this prediction.
| [
{
"created": "Thu, 30 Apr 1998 17:53:15 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Berger",
"Beverly K.",
""
],
[
"Moncrief",
"Vincent",
""
]
] | A longstanding conjecture by Belinskii, Lifshitz, and Khalatnikov that the singularity in generic gravitational collapse is locally oscillatory is tested numerically in vacuum, U(1) symmetric cosmological spacetimes on $T^3 \times R$. If the velocity term dominated (VTD) solution to Einstein's equations is substituted into the Hamiltonian for the full Einstein evolution equations, one term is found to grow exponentially. This generates a prediction that oscillatory behavior involving this term and another (which the VTD solution causes to decay exponentially) should be observed in the approach to the singularity. Numerical simulations strongly support this prediction. |
2110.13897 | Saqib Hussain | Sidra Shafiq, Saqib Hussain, Muhammad Ozair, Adnan Aslam, Takasar
Hussain | Charged particle dynamics in the surrounding of Schwarzschild anti-de
Sitter black hole with topological defect immersed in an external magnetic
field | 10 pages, 7 figures | Eur. Phys. J. C (2020) 80:744 | 10.1140/epjc/s10052-020-8314-y | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | In this paper, geodesic motion of the charged particles in the vicinity of
event horizon of Schwarzschild anti-de-Sitter black hole (BH) with topological
defects has been investigated. Weakly magnetized environment is considered in
the surrounding of BH which only effects the motion of the particles and
doesn't effect the geometry of the BH. Hence, particles are under the influence
of gravity and electromagnetic forces. We have explored the effect of magnetic
field on the trajectories of the particles and more importantly on the position
of the innermost stable circular orbit. It is observed that the trajectories of
the particles in the surrounding of BH are chaotic. Escape conditions of the
particles under the influence of gravitomagnetic force are also discussed.
Moreover, the escape velocity of particles and its different features have been
investigated in the presence and absence of magnetic field. Effect of dark
energy on the size of event horizon, mass of the BH and stability of the orbits
of the particles have also been explored in detail.
These studies can be used to estimate the power of relativistic jets
originated from the vicinity of BH.
| [
{
"created": "Tue, 26 Oct 2021 17:50:06 GMT",
"version": "v1"
}
] | 2021-11-03 | [
[
"Shafiq",
"Sidra",
""
],
[
"Hussain",
"Saqib",
""
],
[
"Ozair",
"Muhammad",
""
],
[
"Aslam",
"Adnan",
""
],
[
"Hussain",
"Takasar",
""
]
] | In this paper, geodesic motion of the charged particles in the vicinity of event horizon of Schwarzschild anti-de-Sitter black hole (BH) with topological defects has been investigated. Weakly magnetized environment is considered in the surrounding of BH which only effects the motion of the particles and doesn't effect the geometry of the BH. Hence, particles are under the influence of gravity and electromagnetic forces. We have explored the effect of magnetic field on the trajectories of the particles and more importantly on the position of the innermost stable circular orbit. It is observed that the trajectories of the particles in the surrounding of BH are chaotic. Escape conditions of the particles under the influence of gravitomagnetic force are also discussed. Moreover, the escape velocity of particles and its different features have been investigated in the presence and absence of magnetic field. Effect of dark energy on the size of event horizon, mass of the BH and stability of the orbits of the particles have also been explored in detail. These studies can be used to estimate the power of relativistic jets originated from the vicinity of BH. |
1204.1786 | XiaoXiong Zeng | Xian-Ming Liu, Xiao-Xiong Zeng, Wen-Biao Liu | Spectroscopy of the rotating BTZ black hole via adiabatic invariance | 6 pages, 0 figures, to appear in Sci China Ser G-Phys Mech Astron.
arXiv admin note: text overlap with arXiv:1106.2292 | Sci China-Phys Mech Astron, 2012, 55: 1--4 | 10.1007/s11433-012-4836-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | According to Bohr-Sommerfeld quantization rule, an equally spaced horizon
area spectrum of a static, spherically symmetric black hole was obtained under
an adiabatic invariant action. This method can be extended to the rotating
black holes. As an example, we apply this method to the rotating BTZ black hole
and obtain the quantized spectrum of the horizon area. It is shown that the
area spectrum of the rotating BTZ black hole is equally spaced and irrelevant
to the rotating parameter, which is consistent with the Bekenstein conjecture.
Specifically, the derivation do not need the quasinormal frequencies and the
small angular momentum limit.
| [
{
"created": "Mon, 9 Apr 2012 03:07:38 GMT",
"version": "v1"
}
] | 2012-07-25 | [
[
"Liu",
"Xian-Ming",
""
],
[
"Zeng",
"Xiao-Xiong",
""
],
[
"Liu",
"Wen-Biao",
""
]
] | According to Bohr-Sommerfeld quantization rule, an equally spaced horizon area spectrum of a static, spherically symmetric black hole was obtained under an adiabatic invariant action. This method can be extended to the rotating black holes. As an example, we apply this method to the rotating BTZ black hole and obtain the quantized spectrum of the horizon area. It is shown that the area spectrum of the rotating BTZ black hole is equally spaced and irrelevant to the rotating parameter, which is consistent with the Bekenstein conjecture. Specifically, the derivation do not need the quasinormal frequencies and the small angular momentum limit. |
1806.08850 | R. R. Cuzinatto | R. R. Cuzinatto, C. A. M. de Melo, L. G. Medeiros, and P. J. Pompeia | $f\left(R,\nabla_{\mu_{1}}R,\dots,\nabla_{\mu_{1}}\dots\nabla_{\mu_{n}}R\right)$
theories of gravity in Einstein frame: A higher order modified Starobinsky
inflation model in the Palatini approach | 13 pages; v2: references added; v3: extended to 23 pages, new section
with application to inflation, 4 figures, additional references, few
corrections; v4: matches the published version | Phys. Rev. D 99, 084053 (2019) | 10.1103/PhysRevD.99.084053 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Cuzinatto et al. [Phys. Rev. D 93, 124034 (2016)], it has been
demonstrated that theories of gravity in which the Lagrangian includes terms
depending on the scalar curvature $R$ and its derivatives up to order $n$, i.e.
$f\left(R,\nabla_{\mu}R,\nabla_{\mu_{1}}\nabla_{\mu_{2}}R,\dots,\nabla_{\mu_{1}}\dots\nabla_{\mu_{n}}R\right)$
theories of gravity, are equivalent to scalar-multitensorial theories in the
Jordan frame. In particular, in the metric and Palatini formalisms, this
scalar-multitensorial equivalent scenario shows a structure that resembles that
of the Brans-Dicke theories with a kinetic term for the scalar field with
$\omega_{0}=0$ or $\omega_{0}=-3/2$, respectively. In the present work, the
aforementioned analysis is extended to the Einstein frame. The conformal
transformation of the metric characterizing the transformation from Jordan's to
Einstein's frame is responsible for decoupling the scalar field from the scalar
curvature and also for introducing a usual kinetic term for the scalar field in
the metric formalism. In the Palatini approach, this kinetic term is absent in
the action. Concerning the other tensorial auxiliary fields, they appear in the
theory through a generalized potential. As an example, the analysis of an
extension of the Starobinsky model (with an extra term proportional to
$\nabla_{\mu}R\nabla^{\mu}R$) is performed and the fluid representation for the
energy-momentum tensor is considered. In the metric formalism, the presence of
the extra term causes the fluid to be an imperfect fluid with a heat flux
contribution; on the other hand, in the Palatini formalism the effective
energy-momentum tensor for the extended Starobinsky gravity is that of a
perfect fluid type. Finally, it is also shown that the extra term in the
Palatini formalism represents a dynamical field which is able to generate an
inflationary regime without a graceful exit.
| [
{
"created": "Fri, 22 Jun 2018 20:48:12 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Jul 2018 22:09:06 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Feb 2019 20:41:49 GMT",
"version": "v3"
},
{
"created": "Sun, 5 May 2019 20:50:20 GMT",
"version": "v4"
}
] | 2019-05-07 | [
[
"Cuzinatto",
"R. R.",
""
],
[
"de Melo",
"C. A. M.",
""
],
[
"Medeiros",
"L. G.",
""
],
[
"Pompeia",
"P. J.",
""
]
] | In Cuzinatto et al. [Phys. Rev. D 93, 124034 (2016)], it has been demonstrated that theories of gravity in which the Lagrangian includes terms depending on the scalar curvature $R$ and its derivatives up to order $n$, i.e. $f\left(R,\nabla_{\mu}R,\nabla_{\mu_{1}}\nabla_{\mu_{2}}R,\dots,\nabla_{\mu_{1}}\dots\nabla_{\mu_{n}}R\right)$ theories of gravity, are equivalent to scalar-multitensorial theories in the Jordan frame. In particular, in the metric and Palatini formalisms, this scalar-multitensorial equivalent scenario shows a structure that resembles that of the Brans-Dicke theories with a kinetic term for the scalar field with $\omega_{0}=0$ or $\omega_{0}=-3/2$, respectively. In the present work, the aforementioned analysis is extended to the Einstein frame. The conformal transformation of the metric characterizing the transformation from Jordan's to Einstein's frame is responsible for decoupling the scalar field from the scalar curvature and also for introducing a usual kinetic term for the scalar field in the metric formalism. In the Palatini approach, this kinetic term is absent in the action. Concerning the other tensorial auxiliary fields, they appear in the theory through a generalized potential. As an example, the analysis of an extension of the Starobinsky model (with an extra term proportional to $\nabla_{\mu}R\nabla^{\mu}R$) is performed and the fluid representation for the energy-momentum tensor is considered. In the metric formalism, the presence of the extra term causes the fluid to be an imperfect fluid with a heat flux contribution; on the other hand, in the Palatini formalism the effective energy-momentum tensor for the extended Starobinsky gravity is that of a perfect fluid type. Finally, it is also shown that the extra term in the Palatini formalism represents a dynamical field which is able to generate an inflationary regime without a graceful exit. |
1805.00005 | Ahmadjon Abdujabbarov | Bobur Turimov, Bobomurat Ahmedov, Ahmadjon Abdujabbarov, Cosimo Bambi | Electromagnetic fields of slowly rotating magnetized compact stars in
conformal gravity | 9 pages, 7 figures, accepted for publication in Phys. Rev. D | Phys. Rev. D 97, 124005 (2018) | 10.1103/PhysRevD.97.124005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The exact analytical solutions for vacuum electromagnetic fields of slowly
rotating magnetized compact stars in conformal gravity have been studied.
Taking the realistic dipolar magnetic field configuration for the star,
analytical solutions of the Maxwell equations for the near zone magnetic and
the electric fields exterior to a slowly rotating magnetized relativistic star
in conformal gravity are obtained. In addition, the dipolar electromagnetic
radiation and energy losses from the rotating magnetized compact star in
conformal gravity have been studied. With the aim to find observational
constraints on the $L$ parameter of conformal gravity, the theoretical results
for the electromagnetic radiation from the rotating magnetized relativistic
star in conformal gravity have been combined with the precise observational
data on the radio pulsars periods slow down and it is estimated that the upper
limit i.e. the maximum value of the parameter of conformal gravity is less than
$L \lesssim 9.5 \times 10^5\textrm{cm}$ ($L/M \lesssim 5$).
| [
{
"created": "Mon, 30 Apr 2018 01:55:12 GMT",
"version": "v1"
}
] | 2018-06-11 | [
[
"Turimov",
"Bobur",
""
],
[
"Ahmedov",
"Bobomurat",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
],
[
"Bambi",
"Cosimo",
""
]
] | The exact analytical solutions for vacuum electromagnetic fields of slowly rotating magnetized compact stars in conformal gravity have been studied. Taking the realistic dipolar magnetic field configuration for the star, analytical solutions of the Maxwell equations for the near zone magnetic and the electric fields exterior to a slowly rotating magnetized relativistic star in conformal gravity are obtained. In addition, the dipolar electromagnetic radiation and energy losses from the rotating magnetized compact star in conformal gravity have been studied. With the aim to find observational constraints on the $L$ parameter of conformal gravity, the theoretical results for the electromagnetic radiation from the rotating magnetized relativistic star in conformal gravity have been combined with the precise observational data on the radio pulsars periods slow down and it is estimated that the upper limit i.e. the maximum value of the parameter of conformal gravity is less than $L \lesssim 9.5 \times 10^5\textrm{cm}$ ($L/M \lesssim 5$). |
2309.02853 | Alexey Golovnev | Alexey Golovnev, A. N. Semenova, V.P. Vandeev | Gravitational Waves in New General Relativity | 14 pages; minor changes and additions | Journal of Cosmology and Astroparticle Physics JCAP01(2024)003 | 10.1088/1475-7516/2024/01/003 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The models of New General Relativity have recently got attention of research
community, and there are some works studying their dynamical properties. The
formal aspects of this investigation have been mostly restricted to the primary
constraints in the Hamiltonian analysis. However, it is by far not enough for
counting their degrees of freedom or judging whether they are any good and
viable. In this paper we study linearised equations in vacuum around the
trivial Minkowski tetrad. By taking the approach of cosmological perturbation
theory we show that the numbers of primary constraints are very easily seen
without any need of genuine Hamiltonian techniques, and give the full count of
linearised degrees of freedom in the weak field limit of each and every version
of New General Relativity without matter.
| [
{
"created": "Wed, 6 Sep 2023 09:30:06 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Nov 2023 15:26:43 GMT",
"version": "v2"
}
] | 2024-01-03 | [
[
"Golovnev",
"Alexey",
""
],
[
"Semenova",
"A. N.",
""
],
[
"Vandeev",
"V. P.",
""
]
] | The models of New General Relativity have recently got attention of research community, and there are some works studying their dynamical properties. The formal aspects of this investigation have been mostly restricted to the primary constraints in the Hamiltonian analysis. However, it is by far not enough for counting their degrees of freedom or judging whether they are any good and viable. In this paper we study linearised equations in vacuum around the trivial Minkowski tetrad. By taking the approach of cosmological perturbation theory we show that the numbers of primary constraints are very easily seen without any need of genuine Hamiltonian techniques, and give the full count of linearised degrees of freedom in the weak field limit of each and every version of New General Relativity without matter. |
2301.00319 | Rogerio Teixeira Cavalcanti | R. T. Cavalcanti and J. M. Hoff da Silva | Quantum Hairy Black Hole Formation and Horizon Quantum Mechanics | 10 pages, 5 figures | Universe 2023, 9(1), 23 | 10.3390/universe9010023 | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | After introducing the gravitational decoupling method and the hairy black
hole recently derived from it, we investigate the formation of quantum hairy
black holes by applying the horizon quantum mechanics formalism. It enables us
to determine how external fields, characterized by hairy parameters, affect the
probability of spherically symmetric black hole formation and the generalized
uncertainty principle.
| [
{
"created": "Sun, 1 Jan 2023 01:33:04 GMT",
"version": "v1"
}
] | 2023-01-03 | [
[
"Cavalcanti",
"R. T.",
""
],
[
"da Silva",
"J. M. Hoff",
""
]
] | After introducing the gravitational decoupling method and the hairy black hole recently derived from it, we investigate the formation of quantum hairy black holes by applying the horizon quantum mechanics formalism. It enables us to determine how external fields, characterized by hairy parameters, affect the probability of spherically symmetric black hole formation and the generalized uncertainty principle. |
gr-qc/9401008 | Domenico Seminara | P. Menotti and D. Seminara | Stationary Solutions in 2+1 Dimensional Gravity and Closed Time-Like
Curves | Talk presented at Europhysics Conference on High Energy Physics,
Marseille, France, July 22-28 1993, 5 pages, Latex, IFUP-49/93 | null | null | null | gr-qc | null | We apply the reduced radial gauge to give the general solution of the metric
in 2+1 dimensions in term of quadratures. It allows a complete controll on the
support of the source. We use the result to prove that for a general stationary
universe, conical at infinity, the weak energy condition and the absence of CTC
at space infinity prevent the occurrrence of any CTC.
| [
{
"created": "Sat, 8 Jan 1994 11:32:52 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Menotti",
"P.",
""
],
[
"Seminara",
"D.",
""
]
] | We apply the reduced radial gauge to give the general solution of the metric in 2+1 dimensions in term of quadratures. It allows a complete controll on the support of the source. We use the result to prove that for a general stationary universe, conical at infinity, the weak energy condition and the absence of CTC at space infinity prevent the occurrrence of any CTC. |
1709.06894 | Walberto Guzm\'an Ram\'irez | Walberto Guzm\'an Ram\'irez and Alexei A. Deriglazov | Relativistic effects due to gravimagnetic moment of a rotating body | 21 pages | Phys. Rev. D 96, 124013 (2017) | 10.1103/PhysRevD.96.124013 | null | gr-qc astro-ph.HE hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute exact Hamiltonian (and corresponding Dirac brackets) for spinning
particle with gravimagnetic moment $\kappa$ in an arbitrary gravitational
background. $\kappa=0$ corresponds to the Mathisson-Papapetrou-Tulczyjew-Dixon
(MPTD) equations. $\kappa=1$ leads to modified MPTD equations with reasonable
behavior in the ultrarelativistic limit. So we study the modified equations in
the leading post-Newtonian approximation. Rotating body with unit gravimagnetic
moment has qualitatively different behavior as compared with MPTD body: A) If a
number of gyroscopes with various rotation axes are freely traveling together,
the angles between the axes change with time. B) For specific binary systems,
gravimagnetic moment gives a contribution to frame-dragging effect with the
magnitude, that turns out to be comparable with that of Schiff frame dragging.
| [
{
"created": "Tue, 19 Sep 2017 16:36:32 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Oct 2017 16:50:37 GMT",
"version": "v2"
}
] | 2017-12-20 | [
[
"Ramírez",
"Walberto Guzmán",
""
],
[
"Deriglazov",
"Alexei A.",
""
]
] | We compute exact Hamiltonian (and corresponding Dirac brackets) for spinning particle with gravimagnetic moment $\kappa$ in an arbitrary gravitational background. $\kappa=0$ corresponds to the Mathisson-Papapetrou-Tulczyjew-Dixon (MPTD) equations. $\kappa=1$ leads to modified MPTD equations with reasonable behavior in the ultrarelativistic limit. So we study the modified equations in the leading post-Newtonian approximation. Rotating body with unit gravimagnetic moment has qualitatively different behavior as compared with MPTD body: A) If a number of gyroscopes with various rotation axes are freely traveling together, the angles between the axes change with time. B) For specific binary systems, gravimagnetic moment gives a contribution to frame-dragging effect with the magnitude, that turns out to be comparable with that of Schiff frame dragging. |
2402.02221 | Lamine Khodja | Houssam Eddine Trad and Lamine Khodja | New treatment of red/blue shifts of emitted photons in terms of
Kerr-Newman black hole parameters | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | This study presents a method for determining the mass, angular momentum, and
charge of Kerr-Newman black holes by analyzing the red/blue shifts of photons
emitted by geodesic neutral massive objects. We derive the equations of motion
for photons in the Kerr-Newman spacetime. We obtain explicit expressions for
redshift/blueshift photons emitted by an object orbiting a Kerr-Newman black
hole. Finally, using the Boyer-Lindquist coordinates, we express the red/blue
shifts in terms of the metric parameters.
| [
{
"created": "Sat, 3 Feb 2024 17:30:52 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Apr 2024 14:03:15 GMT",
"version": "v2"
}
] | 2024-04-08 | [
[
"Trad",
"Houssam Eddine",
""
],
[
"Khodja",
"Lamine",
""
]
] | This study presents a method for determining the mass, angular momentum, and charge of Kerr-Newman black holes by analyzing the red/blue shifts of photons emitted by geodesic neutral massive objects. We derive the equations of motion for photons in the Kerr-Newman spacetime. We obtain explicit expressions for redshift/blueshift photons emitted by an object orbiting a Kerr-Newman black hole. Finally, using the Boyer-Lindquist coordinates, we express the red/blue shifts in terms of the metric parameters. |
2006.14258 | Matt Visser | Joshua Baines, Thomas Berry, Alex Simpson, and Matt Visser (Victoria
University of Wellington) | Painleve-Gullstrand form of the Lense-Thirring spacetime | V1:19 pages. V2: now 30 pages. Significant additions: We now discuss
tetrads, orthonormal components, eigenvalues of the Weyl tensor, the Petrov
classification, ISCOs and circular photon orbits. Many small changes for
clarity. Two references updated, and one reference added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The standard Lense-Thirring metric is a century-old slow-rotation
large-distance approximation to the gravitational field outside a rotating
massive body, depending only on the total mass and angular momentum of the
source. Although it is not an exact solution to the vacuum Einstein equations,
asymptotically the Lense-Thirring metric approaches the Kerr metric at large
distances. Herein we shall discuss a specific variant of the standard
Lense-Thirring metric, carefully chosen for simplicity, clarity, and various
forms of "improved" behaviour, (to be more carefully defined in the body of the
article). In particular we shall construct an explicit unit-lapse
Painleve-Gullstrand variant of the Lense-Thirring spacetime, that has flat
spatial slices, a very simple and physically intuitive tetrad, and extremely
simple curvature tensors. We shall verify that this variant of the
Lense-Thirring spacetime is Petrov type I, (so it is not algebraically
special), but nevertheless possesses some very straightforward timelike
geodesics, (the "rain" geodesics). We shall also discuss on-axis and equatorial
geodesics, ISCOs and circular photon orbits. Finally, we wrap up by discussing
some astrophysically relevant estimates, and analyze what happens if we
extrapolate down to small values of r.
| [
{
"created": "Thu, 25 Jun 2020 09:04:11 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Oct 2020 06:14:37 GMT",
"version": "v2"
}
] | 2020-10-30 | [
[
"Baines",
"Joshua",
"",
"Victoria\n University of Wellington"
],
[
"Berry",
"Thomas",
"",
"Victoria\n University of Wellington"
],
[
"Simpson",
"Alex",
"",
"Victoria\n University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria\n University of Wellington"
]
] | The standard Lense-Thirring metric is a century-old slow-rotation large-distance approximation to the gravitational field outside a rotating massive body, depending only on the total mass and angular momentum of the source. Although it is not an exact solution to the vacuum Einstein equations, asymptotically the Lense-Thirring metric approaches the Kerr metric at large distances. Herein we shall discuss a specific variant of the standard Lense-Thirring metric, carefully chosen for simplicity, clarity, and various forms of "improved" behaviour, (to be more carefully defined in the body of the article). In particular we shall construct an explicit unit-lapse Painleve-Gullstrand variant of the Lense-Thirring spacetime, that has flat spatial slices, a very simple and physically intuitive tetrad, and extremely simple curvature tensors. We shall verify that this variant of the Lense-Thirring spacetime is Petrov type I, (so it is not algebraically special), but nevertheless possesses some very straightforward timelike geodesics, (the "rain" geodesics). We shall also discuss on-axis and equatorial geodesics, ISCOs and circular photon orbits. Finally, we wrap up by discussing some astrophysically relevant estimates, and analyze what happens if we extrapolate down to small values of r. |
1711.11380 | Jan Sbierski | Jan Sbierski | On the proof of the $C^0$-inextendibility of the Schwarzschild spacetime | Prepared for submission to the proceedings of the meeting
"Non-Regular Spacetime Geometry", Florence, 20.6.-22.6.2017. Based on
arXiv:1507.00601, v2: minor changes, version accepted for publication | null | 10.1088/1742-6596/968/1/012012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article presents a streamlined version of the author's original proof of
the $C^0$-inextendibility of the maximal analytic Schwarzschild spacetime.
Firstly, we deviate from the original proof by using the result, recently
established in collaboration with Galloway and Ling, that given a
$C^0$-extension of a globally hyperbolic spacetime, one can find a timelike
geodesic that leaves this spacetime. This result much simplifies the proof of
the inextendibility through the exterior region of the Schwarzschild spacetime.
Secondly, we give a more flexible and shorter argument for the inextendibility
through the interior region. Furthermore, we present a small new structural
result for the boundary of a globally hyperbolic spacetime within a
$C^0$-extension which serves as a new and simpler starting point for the proof.
| [
{
"created": "Thu, 30 Nov 2017 13:28:09 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Jan 2018 09:47:41 GMT",
"version": "v2"
}
] | 2018-03-14 | [
[
"Sbierski",
"Jan",
""
]
] | This article presents a streamlined version of the author's original proof of the $C^0$-inextendibility of the maximal analytic Schwarzschild spacetime. Firstly, we deviate from the original proof by using the result, recently established in collaboration with Galloway and Ling, that given a $C^0$-extension of a globally hyperbolic spacetime, one can find a timelike geodesic that leaves this spacetime. This result much simplifies the proof of the inextendibility through the exterior region of the Schwarzschild spacetime. Secondly, we give a more flexible and shorter argument for the inextendibility through the interior region. Furthermore, we present a small new structural result for the boundary of a globally hyperbolic spacetime within a $C^0$-extension which serves as a new and simpler starting point for the proof. |
1002.3836 | Mercedes Velazquez | Merced Montesinos, Mercedes Velazquez | BF gravity with Immirzi parameter and cosmological constant | 4 pages, no figures, LaTeX file | Phys.Rev.D81:044033,2010 | 10.1103/PhysRevD.81.044033 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The action principle of the BF type introduced by Capovilla, Montesinos,
Prieto, and Rojas (CMPR) which describes general relativity with Immirzi
parameter is modified in order to allow the inclusion of the cosmological
constant. The resulting action principle is on the same footing as the original
Plebanski action in the sense that the equations of motion coming from the new
action principle are equivalent to the Holst action principle plus a
cosmological constant without the need of imposing additional restrictions on
the fields. We consider this result a relevant step towards the coupling of
matter fields to gravity in the framework of the CMPR action principle.
| [
{
"created": "Fri, 19 Feb 2010 22:47:24 GMT",
"version": "v1"
}
] | 2010-04-21 | [
[
"Montesinos",
"Merced",
""
],
[
"Velazquez",
"Mercedes",
""
]
] | The action principle of the BF type introduced by Capovilla, Montesinos, Prieto, and Rojas (CMPR) which describes general relativity with Immirzi parameter is modified in order to allow the inclusion of the cosmological constant. The resulting action principle is on the same footing as the original Plebanski action in the sense that the equations of motion coming from the new action principle are equivalent to the Holst action principle plus a cosmological constant without the need of imposing additional restrictions on the fields. We consider this result a relevant step towards the coupling of matter fields to gravity in the framework of the CMPR action principle. |
2304.02027 | Diogo Bragan\c{c}a | Diogo P. L. Bragan\c{c}a | A viable relativistic scalar theory of gravitation | 15 pages, 4 figures. Accepted for publication in Classical and
Quantum Gravity | null | 10.1088/1361-6382/acd0ff | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We build a self-consistent relativistic scalar theory of gravitation on a
flat Minkowski spacetime from a general field Lagrangian. It is shown that, for
parameters that satisfy the Equivalence Principle, this theory predicts the
same outcome as general relativity for every classical solar-system test. This
theory also admits gravitational waves that propagate at the speed of light,
and the gravitational radiation energy loss in a binary system is shown to be
very similar to the GR prediction. We then analyze the strong gravity regime of
the theory for a spherically symmetric configuration and find that there is an
effective "singularity" near the Schwarzschild radius. The main goal of this
work is to show that, contrary to what is commonly believed, there are
relativistic scalar theories of gravitation defined on a Minkowski spacetime
that are not ruled out by the classical solar system tests of general
relativity.
| [
{
"created": "Tue, 4 Apr 2023 18:00:00 GMT",
"version": "v1"
}
] | 2023-05-15 | [
[
"Bragança",
"Diogo P. L.",
""
]
] | We build a self-consistent relativistic scalar theory of gravitation on a flat Minkowski spacetime from a general field Lagrangian. It is shown that, for parameters that satisfy the Equivalence Principle, this theory predicts the same outcome as general relativity for every classical solar-system test. This theory also admits gravitational waves that propagate at the speed of light, and the gravitational radiation energy loss in a binary system is shown to be very similar to the GR prediction. We then analyze the strong gravity regime of the theory for a spherically symmetric configuration and find that there is an effective "singularity" near the Schwarzschild radius. The main goal of this work is to show that, contrary to what is commonly believed, there are relativistic scalar theories of gravitation defined on a Minkowski spacetime that are not ruled out by the classical solar system tests of general relativity. |
1204.0054 | Yuri Bonder | Yuri Bonder | Quantum particles and an effective spacetime geometry | Presented at the IX Workshop of the Mexican Gravity Division | null | 10.1063/1.4748551 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spacetime geometry is supposed to be measured by identifying the trajectories
of free test particles with geodesics. In practice, this cannot be done
because, being described by Quantum Mechanics, particles do not follow
trajectories. As a first step to study how it is possible to read spacetime
geometry with quantum particles, we model these particles with classical
extended objects. We propose to represent such extended objects by its
covariant center of mass, which generically does not follow a geodesic of the
background metric. We present a scheme that allows to extract some of
components of an "effective" connection, namely, the connection that would be
obtained if the locus of the center of mass is regarded as a geodesic. We
discuss some issues that arise when trying to obtain all the components of the
effective connection and its possible implications.
| [
{
"created": "Sat, 31 Mar 2012 01:10:21 GMT",
"version": "v1"
}
] | 2015-06-04 | [
[
"Bonder",
"Yuri",
""
]
] | Spacetime geometry is supposed to be measured by identifying the trajectories of free test particles with geodesics. In practice, this cannot be done because, being described by Quantum Mechanics, particles do not follow trajectories. As a first step to study how it is possible to read spacetime geometry with quantum particles, we model these particles with classical extended objects. We propose to represent such extended objects by its covariant center of mass, which generically does not follow a geodesic of the background metric. We present a scheme that allows to extract some of components of an "effective" connection, namely, the connection that would be obtained if the locus of the center of mass is regarded as a geodesic. We discuss some issues that arise when trying to obtain all the components of the effective connection and its possible implications. |
1905.00012 | Nils Andersson | N. Andersson and P. Pnigouras | The phenomenology of dynamical neutron star tides | Revised version with added details. To appear in MNRAS | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a phenomenological, physically motivated, model for the
effective tidal deformability of a neutron star, adding the frequency
dependence (associated with the star's fundamental mode of oscillation) that
comes into play during the late stages of the binary inspiral. Testing the
model against alternative descriptions, we demonstrate that it provides an
accurate representation of the dynamical tide up to close to merger. The
simplicity of the prescription makes it an attractive alternative for a
gravitational-wave data analysis implementation, facilitating an inexpensive
construction of a large number of templates covering the relevant parameter
space.
| [
{
"created": "Tue, 30 Apr 2019 17:40:37 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Jun 2019 06:50:48 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Feb 2021 15:40:28 GMT",
"version": "v3"
}
] | 2021-02-09 | [
[
"Andersson",
"N.",
""
],
[
"Pnigouras",
"P.",
""
]
] | We introduce a phenomenological, physically motivated, model for the effective tidal deformability of a neutron star, adding the frequency dependence (associated with the star's fundamental mode of oscillation) that comes into play during the late stages of the binary inspiral. Testing the model against alternative descriptions, we demonstrate that it provides an accurate representation of the dynamical tide up to close to merger. The simplicity of the prescription makes it an attractive alternative for a gravitational-wave data analysis implementation, facilitating an inexpensive construction of a large number of templates covering the relevant parameter space. |
gr-qc/9909084 | Lee Lindblom | Lee Lindblom and Gregory Mendell | R-Modes in Superfluid Neutron Stars | 15 pages, 8 figures | Phys.Rev. D61 (2000) 104003 | 10.1103/PhysRevD.61.104003 | null | gr-qc astro-ph | null | The analogs of r-modes in superfluid neutron stars are studied here. These
modes, which are governed primarily by the Coriolis force, are identical to
their ordinary-fluid counterparts at the lowest order in the small
angular-velocity expansion used here. The equations that determine the next
order terms are derived and solved numerically for fairly realistic superfluid
neutron-star models. The damping of these modes by superfluid ``mutual
friction'' (which vanishes at the lowest order in this expansion) is found to
have a characteristic time-scale of about 10^4 s for the m=2 r-mode in a
``typical'' superfluid neutron-star model. This time-scale is far too long to
allow mutual friction to suppress the recently discovered gravitational
radiation driven instability in the r-modes. However, the strength of the
mutual friction damping depends very sensitively on the details of the
neutron-star core superfluid. A small fraction of the presently acceptable
range of superfluid models have characteristic mutual friction damping times
that are short enough (i.e. shorter than about 5 s) to suppress the
gravitational radiation driven instability completely.
| [
{
"created": "Mon, 27 Sep 1999 19:12:20 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Lindblom",
"Lee",
""
],
[
"Mendell",
"Gregory",
""
]
] | The analogs of r-modes in superfluid neutron stars are studied here. These modes, which are governed primarily by the Coriolis force, are identical to their ordinary-fluid counterparts at the lowest order in the small angular-velocity expansion used here. The equations that determine the next order terms are derived and solved numerically for fairly realistic superfluid neutron-star models. The damping of these modes by superfluid ``mutual friction'' (which vanishes at the lowest order in this expansion) is found to have a characteristic time-scale of about 10^4 s for the m=2 r-mode in a ``typical'' superfluid neutron-star model. This time-scale is far too long to allow mutual friction to suppress the recently discovered gravitational radiation driven instability in the r-modes. However, the strength of the mutual friction damping depends very sensitively on the details of the neutron-star core superfluid. A small fraction of the presently acceptable range of superfluid models have characteristic mutual friction damping times that are short enough (i.e. shorter than about 5 s) to suppress the gravitational radiation driven instability completely. |
gr-qc/9304032 | Henri Waelbrock | Jemal Guven | Covariant perturbations of domain walls in curved spacetime | 15 pages,ICN-UNAM-93-01 | Phys.Rev. D48 (1993) 4604-4608 | 10.1103/PhysRevD.48.4604 | null | gr-qc | null | A manifestly covariant equation is derived to describe the perturbations in a
domain wall on a given background spacetime. This generalizes recent work on
domain walls in Minkowski space and introduces a framework for examining the
stability of relativistic bubbles in curved spacetimes.
| [
{
"created": "Wed, 21 Apr 1993 21:20:04 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Guven",
"Jemal",
""
]
] | A manifestly covariant equation is derived to describe the perturbations in a domain wall on a given background spacetime. This generalizes recent work on domain walls in Minkowski space and introduces a framework for examining the stability of relativistic bubbles in curved spacetimes. |
0710.4919 | Martin Bojowald | Martin Bojowald | Harmonic cosmology: How much can we know about a universe before the big
bang? | 16 pages | Proc.Roy.Soc.Lond.A464:2135-2150,2008 | 10.1098/rspa.2008.0050 | null | gr-qc astro-ph hep-th | null | Quantum gravity may remove classical space-time singularities and thus reveal
what a universe at and before the big bang could be like. In loop quantum
cosmology, an exactly solvable model is available which allows one to address
precise dynamical coherent states and their evolution in such a setting. It is
shown here that quantum fluctuations before the big bang are generically
unrelated to those after the big bang. A reliable determination of pre-big bang
quantum fluctuations would require exceedingly precise observations.
| [
{
"created": "Thu, 25 Oct 2007 18:40:21 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Bojowald",
"Martin",
""
]
] | Quantum gravity may remove classical space-time singularities and thus reveal what a universe at and before the big bang could be like. In loop quantum cosmology, an exactly solvable model is available which allows one to address precise dynamical coherent states and their evolution in such a setting. It is shown here that quantum fluctuations before the big bang are generically unrelated to those after the big bang. A reliable determination of pre-big bang quantum fluctuations would require exceedingly precise observations. |
2111.08682 | Haidar Sheikhahmadi | Haidar Sheikhahmadi | Schwarzschild black hole perturbed by a force-free magnetic field | 12 Pages; Based on published version | Foundations of Physics 52, 93 (2022) | 10.1007/s10701-022-00612-7 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We envisage a black hole perturbed by a force-free magnetic field (FFMF)
outside and attempt to determine its structure. We suppose the metric that
describes this black hole is of the static spherical type, that is
Schwarzschild, and the energy-momentum tensor emanating from an FFMF source
perturbs this background metric, in this regard one can imagine a magnetic
accretion disk around the black hole. By solving the equations for such a
configuration, we will show that in addition to modifying the diagonal elements
of the background metric, we will also see the non-zeroing of the off-diagonal
elements of the general metric, one of the immediate consequences of which will
be a static to stationary transition.
"Space-time tells matter how to move; matter tells space-time how to curve"
-- John Archibald Wheeler
| [
{
"created": "Tue, 16 Nov 2021 18:35:01 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Nov 2022 07:26:38 GMT",
"version": "v2"
}
] | 2022-11-03 | [
[
"Sheikhahmadi",
"Haidar",
""
]
] | We envisage a black hole perturbed by a force-free magnetic field (FFMF) outside and attempt to determine its structure. We suppose the metric that describes this black hole is of the static spherical type, that is Schwarzschild, and the energy-momentum tensor emanating from an FFMF source perturbs this background metric, in this regard one can imagine a magnetic accretion disk around the black hole. By solving the equations for such a configuration, we will show that in addition to modifying the diagonal elements of the background metric, we will also see the non-zeroing of the off-diagonal elements of the general metric, one of the immediate consequences of which will be a static to stationary transition. "Space-time tells matter how to move; matter tells space-time how to curve" -- John Archibald Wheeler |
1803.03203 | Denis Dobkowski-Ry{\l}ko | Denis Dobkowski-Ry{\l}ko, Jerzy Lewandowski and Tomasz Paw{\l}owski | The Petrov type D isolated null surfaces | RevTex4, BibTex, 29 pages | null | 10.1088/1361-6382/aad209 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Generic black holes in vacuum-de Sitter / Anti-de Sitter spacetimes are
studied in quasi-local framework, where the relevant properties are captured in
the intrinsic geometry of the null surface (the horizon). Imposing the
quasi-local notion of stationarity (null symmetry of the metric up to second
order at the horizon only) we perform the complete classification of all the so
called special Petrov types of these surfaces defined by the properties
(structure of principal null direction) of the Weyl tensor at the surface. The
only possible types are: II, D and O. In particular all the geometries of type
O are identified. The condition distinguishing type D horizons, taking the form
of a second order differential equation on certain complex invariant
constructed from the Gaussian curvature and the rotation scalar, is shown to be
an integrability condition for the so called near horizon geometry equation.
The emergence of the near horizon geometry in this context is equivalent to the
hyper-suface orthogonality of both double principal null directions. We further
formulate a no-hair theorem for the Petrov type D axisymmetric null surfaces of
topologically spherical sections, showing that the space of solutions is
uniquely parametrized by the horizon area and angular momentum.
| [
{
"created": "Thu, 8 Mar 2018 17:08:19 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Jul 2018 10:42:06 GMT",
"version": "v2"
}
] | 2018-08-08 | [
[
"Dobkowski-Ryłko",
"Denis",
""
],
[
"Lewandowski",
"Jerzy",
""
],
[
"Pawłowski",
"Tomasz",
""
]
] | Generic black holes in vacuum-de Sitter / Anti-de Sitter spacetimes are studied in quasi-local framework, where the relevant properties are captured in the intrinsic geometry of the null surface (the horizon). Imposing the quasi-local notion of stationarity (null symmetry of the metric up to second order at the horizon only) we perform the complete classification of all the so called special Petrov types of these surfaces defined by the properties (structure of principal null direction) of the Weyl tensor at the surface. The only possible types are: II, D and O. In particular all the geometries of type O are identified. The condition distinguishing type D horizons, taking the form of a second order differential equation on certain complex invariant constructed from the Gaussian curvature and the rotation scalar, is shown to be an integrability condition for the so called near horizon geometry equation. The emergence of the near horizon geometry in this context is equivalent to the hyper-suface orthogonality of both double principal null directions. We further formulate a no-hair theorem for the Petrov type D axisymmetric null surfaces of topologically spherical sections, showing that the space of solutions is uniquely parametrized by the horizon area and angular momentum. |
1106.4911 | Jorge A. Rueda | M. Rotondo, Jorge A. Rueda, R. Ruffini, S.-S. Xue | The self-consistent general relativistic solution for a system of
degenerate neutrons, protons and electrons in beta-equilibrium | Letter in press, Physics Letters B (2011) | Physics Letters B, Volume 701, Issue 5, p. 667-671 (2011) | 10.1016/j.physletb.2011.06.041 | null | gr-qc astro-ph.SR nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the self-consistent treatment of the simplest, nontrivial,
self-gravitating system of degenerate neutrons, protons and electrons in
$\beta$-equilibrium within relativistic quantum statistics and the
Einstein-Maxwell equations. The impossibility of imposing the condition of
local charge neutrality on such systems is proved, consequently overcoming the
traditional Tolman-Oppenheimer-Volkoff treatment. We emphasize the crucial role
of imposing the constancy of the generalized Fermi energies. A new approach
based on the coupled system of the general relativistic
Thomas-Fermi-Einstein-Maxwell equations is presented and solved. We obtain an
explicit solution fulfilling global and not local charge neutrality by solving
a sophisticated eigenvalue problem of the general relativistic Thomas-Fermi
equation. The value of the Coulomb potential at the center of the configuration
is $eV(0)\simeq m_\pi c^2$ and the system is intrinsically stable against
Coulomb repulsion in the proton component. This approach is necessary, but not
sufficient, when strong interactions are introduced.
| [
{
"created": "Fri, 24 Jun 2011 08:54:15 GMT",
"version": "v1"
}
] | 2011-09-14 | [
[
"Rotondo",
"M.",
""
],
[
"Rueda",
"Jorge A.",
""
],
[
"Ruffini",
"R.",
""
],
[
"Xue",
"S. -S.",
""
]
] | We present the self-consistent treatment of the simplest, nontrivial, self-gravitating system of degenerate neutrons, protons and electrons in $\beta$-equilibrium within relativistic quantum statistics and the Einstein-Maxwell equations. The impossibility of imposing the condition of local charge neutrality on such systems is proved, consequently overcoming the traditional Tolman-Oppenheimer-Volkoff treatment. We emphasize the crucial role of imposing the constancy of the generalized Fermi energies. A new approach based on the coupled system of the general relativistic Thomas-Fermi-Einstein-Maxwell equations is presented and solved. We obtain an explicit solution fulfilling global and not local charge neutrality by solving a sophisticated eigenvalue problem of the general relativistic Thomas-Fermi equation. The value of the Coulomb potential at the center of the configuration is $eV(0)\simeq m_\pi c^2$ and the system is intrinsically stable against Coulomb repulsion in the proton component. This approach is necessary, but not sufficient, when strong interactions are introduced. |
1609.04013 | Ivica Smoli\'c | Ivica Smoli\'c | Constraints on the symmetry noninheriting scalar black hole hair | 10 pages | Phys. Rev. D 95, 024016 (2017) | 10.1103/PhysRevD.95.024016 | ZTF-EP-16-04 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Any recipe to grow black hole hair has to circumvent no-hair theorems by
violating some of their assumptions. Recently discovered hairy black hole
solutions exist due to the fact that their scalar fields don't inherit the
symmetries of the spacetime metric. We present here a general analysis of the
constraints which limit the possible forms of such a hair, for both the real
and the complex scalar fields. These results can be taken as a novel piece of
the black hole uniqueness theorems or simply as a symmetry noninheriting
Ans\"atze guide. In addition we introduce new classification of the
gravitational field equations which might prove useful for various
generalizations of the theorems about spacetimes with symmetries.
| [
{
"created": "Tue, 13 Sep 2016 20:00:01 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Jan 2017 19:00:05 GMT",
"version": "v2"
}
] | 2017-01-18 | [
[
"Smolić",
"Ivica",
""
]
] | Any recipe to grow black hole hair has to circumvent no-hair theorems by violating some of their assumptions. Recently discovered hairy black hole solutions exist due to the fact that their scalar fields don't inherit the symmetries of the spacetime metric. We present here a general analysis of the constraints which limit the possible forms of such a hair, for both the real and the complex scalar fields. These results can be taken as a novel piece of the black hole uniqueness theorems or simply as a symmetry noninheriting Ans\"atze guide. In addition we introduce new classification of the gravitational field equations which might prove useful for various generalizations of the theorems about spacetimes with symmetries. |
2105.06410 | Paolo Pani | Elisa Maggio, Paolo Pani, Guilherme Raposo | Testing the nature of dark compact objects with gravitational waves | 27 pages + references; 10 figures. Invited chapter for "Handbook of
Gravitational Wave Astronomy" (Eds. C. Bambi, S. Katsanevas and K. Kokkotas;
Springer Singapore, 2021) | null | 10.1007/978-981-15-4702-7_29-1 | null | gr-qc astro-ph.HE hep-ph | http://creativecommons.org/licenses/by/4.0/ | Within Einstein's theory of gravity, any compact object heavier than a few
solar masses must be a black hole. Any observation showing otherwise would
imply either new physics beyond General Relativity or new exotic matter fields
beyond the Standard Model, and might provide a portal to understand some
puzzling properties of a black hole. We give a short overview on tests of the
nature of dark compact objects with present and future gravitational-wave
observations, including inspiral tests of the multipolar structure of compact
objects and of their tidal deformability, ringdown tests, and searches for
near-horizon structures with gravitational-wave echoes.
| [
{
"created": "Thu, 13 May 2021 16:32:51 GMT",
"version": "v1"
}
] | 2022-07-20 | [
[
"Maggio",
"Elisa",
""
],
[
"Pani",
"Paolo",
""
],
[
"Raposo",
"Guilherme",
""
]
] | Within Einstein's theory of gravity, any compact object heavier than a few solar masses must be a black hole. Any observation showing otherwise would imply either new physics beyond General Relativity or new exotic matter fields beyond the Standard Model, and might provide a portal to understand some puzzling properties of a black hole. We give a short overview on tests of the nature of dark compact objects with present and future gravitational-wave observations, including inspiral tests of the multipolar structure of compact objects and of their tidal deformability, ringdown tests, and searches for near-horizon structures with gravitational-wave echoes. |
gr-qc/0703126 | Timothy Clifton | Timothy Clifton | Exact Friedmann Solutions in Higher-Order Gravity Theories | 24 pages, 6 figures | Class.Quant.Grav.24:5073-5091,2007 | 10.1088/0264-9381/24/20/010 | null | gr-qc astro-ph hep-th | null | We find the general behaviour of homogeneous and isotropic cosmological
models in some fourth-order theories of gravity. Explicit, exact, general
solutions are given for both empty universes and those filled with a perfect
fluid. For the vacuum case, solutions are found with closed, open and flat
geometries, whilst the perfect fluid solutions are all spatially flat. Both
early and late-time limits are studied, and attractor behaviour towards simple
power-law expansion is identified. Multiple solutions to the same theories,
with the same matter content and topology are found. It is shown that these
solutions exhibit great variety in their evolution.
| [
{
"created": "Mon, 26 Mar 2007 19:46:30 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Aug 2007 20:01:46 GMT",
"version": "v2"
}
] | 2010-10-27 | [
[
"Clifton",
"Timothy",
""
]
] | We find the general behaviour of homogeneous and isotropic cosmological models in some fourth-order theories of gravity. Explicit, exact, general solutions are given for both empty universes and those filled with a perfect fluid. For the vacuum case, solutions are found with closed, open and flat geometries, whilst the perfect fluid solutions are all spatially flat. Both early and late-time limits are studied, and attractor behaviour towards simple power-law expansion is identified. Multiple solutions to the same theories, with the same matter content and topology are found. It is shown that these solutions exhibit great variety in their evolution. |
1001.5147 | Abhay Ashtekar | Abhay Ashtekar, Miguel Campiglia, Adam Henderson | Casting Loop Quantum Cosmology in the Spin Foam Paradigm | 37 pages, no figures. 3 references and half a dozen clarifications
added. All changes are minor. | Class.Quant.Grav.27:135020,2010 | 10.1088/0264-9381/27/13/135020 | IGC-10/1-1 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The goal of spin foam models is to provide a viable path integral formulation
of quantum gravity. Because of background independence, their underlying
framework has certain novel features that are not shared by path integral
formulations of familiar field theories in Minkowski space. As a simple
viability test, these features were recently examined through the lens of loop
quantum cosmology (LQC). Results of that analysis, reported in a brief
communication [1], turned out to provide concrete arguments in support of the
spin foam paradigm. We now present detailed proofs of those results. Since the
quantum theory of LQC models is well understood, this analysis also serves to
shed new light on some long standing issues in the spin foam and group field
theory literature. In particular, it suggests an intriguing possibility for
addressing the question of why the cosmological constant is positive and small.
| [
{
"created": "Thu, 28 Jan 2010 17:16:39 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Apr 2010 02:11:35 GMT",
"version": "v2"
}
] | 2011-01-25 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Campiglia",
"Miguel",
""
],
[
"Henderson",
"Adam",
""
]
] | The goal of spin foam models is to provide a viable path integral formulation of quantum gravity. Because of background independence, their underlying framework has certain novel features that are not shared by path integral formulations of familiar field theories in Minkowski space. As a simple viability test, these features were recently examined through the lens of loop quantum cosmology (LQC). Results of that analysis, reported in a brief communication [1], turned out to provide concrete arguments in support of the spin foam paradigm. We now present detailed proofs of those results. Since the quantum theory of LQC models is well understood, this analysis also serves to shed new light on some long standing issues in the spin foam and group field theory literature. In particular, it suggests an intriguing possibility for addressing the question of why the cosmological constant is positive and small. |
2009.12839 | Daniele Malafarina | Daniele Malafarina and Sabina Sagynbayeva | What a difference a quadrupole makes? | 12 pages, 7 figures, published version | General Relativity and Gravitation, (2021) 53:11 | 10.1007/s10714-021-02881-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider some implications of the departure from spherical symmetry for
static solutions of the vacuum Einstein's equations describing black hole
mimickers. In particular, we investigate how the presence of mass quadrupole
moment affects the collision energy of test particles. We show that collision
processes in the vicinity of such exotic compact sources with non vanishing
mass quadrupole moment may be significantly different from those in the
vicinity of black holes.
| [
{
"created": "Sun, 27 Sep 2020 13:20:05 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Dec 2021 05:12:38 GMT",
"version": "v2"
}
] | 2021-12-14 | [
[
"Malafarina",
"Daniele",
""
],
[
"Sagynbayeva",
"Sabina",
""
]
] | We consider some implications of the departure from spherical symmetry for static solutions of the vacuum Einstein's equations describing black hole mimickers. In particular, we investigate how the presence of mass quadrupole moment affects the collision energy of test particles. We show that collision processes in the vicinity of such exotic compact sources with non vanishing mass quadrupole moment may be significantly different from those in the vicinity of black holes. |
gr-qc/0211067 | Gerold Betschart | Mattias Marklund, Peter K. S. Dunsby, Gerold Betschart, Martin Servin
and Christos Tsagas | Charged multifluids in general relativity | 14 pages (example added), to appear in Class. Quantum Grav | Class.Quant.Grav. 20 (2003) 1823-1834 | 10.1088/0264-9381/20/9/315 | null | gr-qc | null | The exact 1+3 covariant dynamical fluid equations for a multi-component
plasma, together with Maxwell's equations are presented in such a way as to
make them suitable for a gauge-invariant analysis of linear density and
velocity perturbations of the Friedmann-Robertson-Walker model. In the case
where the matter is described by a two component plasma where thermal effects
are neglected, a mode representing high-frequency plasma oscillations is found
in addition to the standard growing and decaying gravitational instability
picture. Further applications of these equations are also discussed.
| [
{
"created": "Wed, 20 Nov 2002 14:03:43 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Mar 2003 12:38:32 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Marklund",
"Mattias",
""
],
[
"Dunsby",
"Peter K. S.",
""
],
[
"Betschart",
"Gerold",
""
],
[
"Servin",
"Martin",
""
],
[
"Tsagas",
"Christos",
""
]
] | The exact 1+3 covariant dynamical fluid equations for a multi-component plasma, together with Maxwell's equations are presented in such a way as to make them suitable for a gauge-invariant analysis of linear density and velocity perturbations of the Friedmann-Robertson-Walker model. In the case where the matter is described by a two component plasma where thermal effects are neglected, a mode representing high-frequency plasma oscillations is found in addition to the standard growing and decaying gravitational instability picture. Further applications of these equations are also discussed. |
2404.09278 | Yen Chin Ong | Jiayi Xia, Yen Chin Ong | Upper Bound of Barrow Entropy Index from Black Hole Fragmentation | 3 pages; invited contribution | Universe 2024, 10(4), 177 | 10.3390/universe10040177 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Both classical and quantum arguments suggest that if Barrow entropy is
correct, its index $\delta$ must be energy dependent, which would affect the
very early universe. Based on thermodynamic stability that sufficiently large
black holes should not fragment, we argue that Barrow entropy correction must
be small except possibly at the Planckian regime. Furthermore, the fact that a
solar mass black hole does not fragment implies an upper bound $\delta \lesssim
O(10^{-3})$, which surprisingly lies in the same range as the bound obtained
from some cosmological considerations assuming fixed $\delta$. This indicates
that allowing $\delta$ to run does not raise its allowed value. We briefly
comment on the case of Kaniadakis entropy.
| [
{
"created": "Sun, 14 Apr 2024 15:01:34 GMT",
"version": "v1"
}
] | 2024-04-16 | [
[
"Xia",
"Jiayi",
""
],
[
"Ong",
"Yen Chin",
""
]
] | Both classical and quantum arguments suggest that if Barrow entropy is correct, its index $\delta$ must be energy dependent, which would affect the very early universe. Based on thermodynamic stability that sufficiently large black holes should not fragment, we argue that Barrow entropy correction must be small except possibly at the Planckian regime. Furthermore, the fact that a solar mass black hole does not fragment implies an upper bound $\delta \lesssim O(10^{-3})$, which surprisingly lies in the same range as the bound obtained from some cosmological considerations assuming fixed $\delta$. This indicates that allowing $\delta$ to run does not raise its allowed value. We briefly comment on the case of Kaniadakis entropy. |
1405.1977 | Savelova Elena P. Dr. | E.P. Savelova | On possible origin of an anisotropy in the speed of light in vacuum | arXiv admin note: text overlap with arXiv:1204.0351 | GRG (2016) 48:85 | 10.1007/s10714-016-2079-5 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We assume the spacetime foam picture in which vacuum is filled with virtual
wormholes. In the presence of an external field the distribution of wormholes
changes. We consider an anisotropic distribution of wormholes and analyze its
relation to the speed of light. We show that speed of light acquires an
anisotropic character and save the normal dispersion a gas of virtual wormholes
may possess also an anomalous dispersion, i.e., when the light velocity exceeds
that in the vacuum.
| [
{
"created": "Thu, 8 May 2014 15:41:35 GMT",
"version": "v1"
}
] | 2016-06-14 | [
[
"Savelova",
"E. P.",
""
]
] | We assume the spacetime foam picture in which vacuum is filled with virtual wormholes. In the presence of an external field the distribution of wormholes changes. We consider an anisotropic distribution of wormholes and analyze its relation to the speed of light. We show that speed of light acquires an anisotropic character and save the normal dispersion a gas of virtual wormholes may possess also an anomalous dispersion, i.e., when the light velocity exceeds that in the vacuum. |
2206.07616 | Bo-Qiang Ma | Jie Zhu, Bo-Qiang Ma | Lorentz-violation-induced arrival time delay of astroparticles in
Finsler spacetime | 7 latex pages, no figure, final version for journal publication | Phys.Rev.D 105 (2022) 124069 | 10.1103/PhysRevD.105.124069 | null | gr-qc astro-ph.HE hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Finsler geometry is a natural and fundamental generalization of Riemann
geometry. The Finsler structure depends on both coordinates and velocities. We
present the arrival time delay of astroparticles subject to Lorentz violation
in the framework of Finsler geometry, and the result corresponds to that
derived by Jacob and Piran in the standard model of cosmology.
| [
{
"created": "Wed, 15 Jun 2022 15:59:01 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Jun 2022 17:11:17 GMT",
"version": "v2"
}
] | 2022-06-28 | [
[
"Zhu",
"Jie",
""
],
[
"Ma",
"Bo-Qiang",
""
]
] | Finsler geometry is a natural and fundamental generalization of Riemann geometry. The Finsler structure depends on both coordinates and velocities. We present the arrival time delay of astroparticles subject to Lorentz violation in the framework of Finsler geometry, and the result corresponds to that derived by Jacob and Piran in the standard model of cosmology. |
2005.06817 | Baocheng Zhang | Feifan He and Baocheng Zhang | A protocol of potential advantage in the low frequency range to
gravitational wave detection with space based optical atomic clocks | null | Eur. Phys. J. D (2020) 74: 94 | 10.1140/epjd/e2020-100611-y | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A recent proposal describes space based gravitational wave (GW) detection
with optical lattice atomic clocks [Kolkowitz et. al., Phys. Rev. D 94, 124043
(2016)] [1]. Based on their setup, we propose a new measurement method for
gravitational wave detection in low frequency with optical lattice atomic
clocks. In our method, n successive Doppler signals are collected and the
summation for all these signals is made to improve the sensitivity of the
low-frequency GW detection. In particular, the improvement is adjustable by the
number of Doppler signals, which is equivalent to that the length between two
atomic clocks is increased. Thus, the same sensitivity can be reached but with
shorter distance, even though the acceleration noises lead to failing to
achieve the anticipated improvement below the inflection point of frequency
which is determined by the quantum projection noise. Our result is timely for
the ongoing development of space-born observatories aimed at studying physical
and astrophysical effects associated with low-frequency GW.
| [
{
"created": "Thu, 14 May 2020 08:56:58 GMT",
"version": "v1"
}
] | 2020-05-15 | [
[
"He",
"Feifan",
""
],
[
"Zhang",
"Baocheng",
""
]
] | A recent proposal describes space based gravitational wave (GW) detection with optical lattice atomic clocks [Kolkowitz et. al., Phys. Rev. D 94, 124043 (2016)] [1]. Based on their setup, we propose a new measurement method for gravitational wave detection in low frequency with optical lattice atomic clocks. In our method, n successive Doppler signals are collected and the summation for all these signals is made to improve the sensitivity of the low-frequency GW detection. In particular, the improvement is adjustable by the number of Doppler signals, which is equivalent to that the length between two atomic clocks is increased. Thus, the same sensitivity can be reached but with shorter distance, even though the acceleration noises lead to failing to achieve the anticipated improvement below the inflection point of frequency which is determined by the quantum projection noise. Our result is timely for the ongoing development of space-born observatories aimed at studying physical and astrophysical effects associated with low-frequency GW. |
gr-qc/9411002 | Eric Poisson | Dragoljub Markovic and Eric Poisson | Classical stability and quantum instability of black-hole Cauchy
horizons | 4 pages; uses ReVTeX; figure available upon request to
poisson@wurel.wustl.edu | Phys.Rev.Lett. 74 (1995) 1280-1283 | 10.1103/PhysRevLett.74.1280 | null | gr-qc | null | For a certain region of the parameter space $\{M,e,\Lambda\}$, the Cauchy
horizon of a (charged) black hole residing in de Sitter space is classically
stable to gravitational perturbations. This implies that, when left to its own
devices, classical theory is unable to retain full predictive power: the
evolution of physical fields beyond the Cauchy horizon is not uniquely
determined by the initial conditions. In this paper we argue that the Cauchy
horizon of a Reissner-Nordstr\"om-de Sitter black hole must always be unstable
quantum mechanically.
| [
{
"created": "Tue, 1 Nov 1994 18:09:25 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Markovic",
"Dragoljub",
""
],
[
"Poisson",
"Eric",
""
]
] | For a certain region of the parameter space $\{M,e,\Lambda\}$, the Cauchy horizon of a (charged) black hole residing in de Sitter space is classically stable to gravitational perturbations. This implies that, when left to its own devices, classical theory is unable to retain full predictive power: the evolution of physical fields beyond the Cauchy horizon is not uniquely determined by the initial conditions. In this paper we argue that the Cauchy horizon of a Reissner-Nordstr\"om-de Sitter black hole must always be unstable quantum mechanically. |
1301.5977 | Ali Alavi | S. A. Alavi, S. Nodeh | Neutrino spin oscillations in gravitational fields in non-commutative
Spaces | 17pages, 3 figures, replaced with the version accepted for
publication in Physica Scripta | Phys. Scr. 90 (2015) 035301 | 10.1088/0031-8949/90/3/035301 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study neutrino spin oscillations in gravitational fields in
non-commutative spaces. For the Schwarzschild metric the maximum frequency
decreases with increasing the noncommutativity parameter. In the case of
Reissner-Nordstrom (RN) metric, the maximum frequency of oscillation is a
monotonically increasing function of the noncommutativity parameter .In both
cases, the frequency of spin oscillations decreases as the distance from the
gravitational source grows. We present a phenomenological application of our
results. It is also shown that the noncommutativity parameter is bounded as 0.1
l_p.
| [
{
"created": "Fri, 25 Jan 2013 07:59:52 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Jul 2013 22:01:19 GMT",
"version": "v2"
},
{
"created": "Mon, 19 May 2014 11:03:19 GMT",
"version": "v3"
},
{
"created": "Fri, 19 Dec 2014 13:00:26 GMT",
"version": "v4"
}
] | 2015-03-19 | [
[
"Alavi",
"S. A.",
""
],
[
"Nodeh",
"S.",
""
]
] | We study neutrino spin oscillations in gravitational fields in non-commutative spaces. For the Schwarzschild metric the maximum frequency decreases with increasing the noncommutativity parameter. In the case of Reissner-Nordstrom (RN) metric, the maximum frequency of oscillation is a monotonically increasing function of the noncommutativity parameter .In both cases, the frequency of spin oscillations decreases as the distance from the gravitational source grows. We present a phenomenological application of our results. It is also shown that the noncommutativity parameter is bounded as 0.1 l_p. |
2302.06636 | Dejan Gajic | Dejan Gajic | Azimuthal instabilities on extremal Kerr | Version submitted for publication | null | null | null | gr-qc math.AP | http://creativecommons.org/licenses/by/4.0/ | We prove the existence of instabilities for the geometric linear wave
equation on extremal Kerr spacetime backgrounds, which describe stationary
black holes rotating at their maximally allowed angular velocity. These
instabilities can be associated to non-axisymmetric azimuthal modes and are
stronger than the axisymmetric instabilities discovered by Aretakis in [Are15].
The existence of non-axisymmetric instabilities follows from a derivation of
very precise stability properties of solutions: we determine therefore the
precise, global, leading-order, late-time behaviour of solutions supported on a
bounded set of azimuthal modes via energy estimates in both physical and
frequency space. In particular, we obtain sharp, uniform decay-in-time
estimates and we determine the coefficients and rates of inverse-polynomial
late-time tails everywhere in the exterior of extremal Kerr black holes. We
also demonstrate how non-axisymmetric instabilities leave an imprint on future
null infinity via the coefficients appearing in front of slowly decaying and
oscillating late-time tails.
| [
{
"created": "Mon, 13 Feb 2023 19:00:08 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Apr 2023 10:08:10 GMT",
"version": "v2"
}
] | 2023-04-18 | [
[
"Gajic",
"Dejan",
""
]
] | We prove the existence of instabilities for the geometric linear wave equation on extremal Kerr spacetime backgrounds, which describe stationary black holes rotating at their maximally allowed angular velocity. These instabilities can be associated to non-axisymmetric azimuthal modes and are stronger than the axisymmetric instabilities discovered by Aretakis in [Are15]. The existence of non-axisymmetric instabilities follows from a derivation of very precise stability properties of solutions: we determine therefore the precise, global, leading-order, late-time behaviour of solutions supported on a bounded set of azimuthal modes via energy estimates in both physical and frequency space. In particular, we obtain sharp, uniform decay-in-time estimates and we determine the coefficients and rates of inverse-polynomial late-time tails everywhere in the exterior of extremal Kerr black holes. We also demonstrate how non-axisymmetric instabilities leave an imprint on future null infinity via the coefficients appearing in front of slowly decaying and oscillating late-time tails. |
2207.07905 | Valerio Faraoni | Shin'ichi Nojiri, Sergei D. Odintsov, Valerio Faraoni | Alternative entropies and consistent black hole thermodynamics | 20 pages, LateX, to appear in Int. J. Geom. Meth. Mod. Phys | null | 10.1142/S0219887822502103 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | While the Bekenstein-Hawking entropy is the unique notion of entropy that
makes classical black hole thermodynamics consistent, alternative entropy
notions (R\'enyi, Tsallis, and generalized constructs) abound in the
literature. We explore conditions under which they are part of a consistent
horizon thermodynamics for certain classes of modified gravity black holes. We
provide examples in which black hole masses and temperatures going hand-in-hand
with these alternative entropies coincide with their usual counterparts
associated with the Bekenstein-Hawking entropy.
| [
{
"created": "Sat, 16 Jul 2022 11:24:12 GMT",
"version": "v1"
}
] | 2022-12-07 | [
[
"Nojiri",
"Shin'ichi",
""
],
[
"Odintsov",
"Sergei D.",
""
],
[
"Faraoni",
"Valerio",
""
]
] | While the Bekenstein-Hawking entropy is the unique notion of entropy that makes classical black hole thermodynamics consistent, alternative entropy notions (R\'enyi, Tsallis, and generalized constructs) abound in the literature. We explore conditions under which they are part of a consistent horizon thermodynamics for certain classes of modified gravity black holes. We provide examples in which black hole masses and temperatures going hand-in-hand with these alternative entropies coincide with their usual counterparts associated with the Bekenstein-Hawking entropy. |
1303.2109 | Muhammad Sharif | M. Sharif and Saira Waheed | Cosmic Acceleration and Brans-Dicke Theory | 29 pages, 13 figures | J. Exp. Theor. Phys. 115(2012)599-613 | 10.1134/S1063776112080158 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is devoted to study the accelerated expansion of the universe by
exploring the Brans-Dicke parameter in different eras. For this purpose, we
take FRW universe model with viscous fluid (without potential) and Bianchi type
I universe model with barotropic fluid (with and without potential). We
evaluate deceleration parameter as well as Brans-Dicke parameter to explore
cosmic acceleration. It is concluded that accelerated expansion of the universe
can also be achieved for higher values of the Brans-Dicke parameter in some
cases.
| [
{
"created": "Fri, 8 Mar 2013 02:45:26 GMT",
"version": "v1"
}
] | 2015-06-15 | [
[
"Sharif",
"M.",
""
],
[
"Waheed",
"Saira",
""
]
] | This paper is devoted to study the accelerated expansion of the universe by exploring the Brans-Dicke parameter in different eras. For this purpose, we take FRW universe model with viscous fluid (without potential) and Bianchi type I universe model with barotropic fluid (with and without potential). We evaluate deceleration parameter as well as Brans-Dicke parameter to explore cosmic acceleration. It is concluded that accelerated expansion of the universe can also be achieved for higher values of the Brans-Dicke parameter in some cases. |
1801.02555 | Ali \"Ovg\"un Dr. | Ali \"Ovg\"un, Kimet Jusufi | Quasinormal Modes and Greybody Factors of $f(R)$ gravity minimally
coupled to a cloud of strings in $2+1$ Dimensions | 9 pages, 3 figures, twocolumn. Accepted for publication in Annals of
Physics | Annals of Physics 395, 138-151 (2018) | 10.1016/j.aop.2018.05.013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we have studied the propagation of a massless scalar field
minimally coupled to a black hole with the source of cloud of strings in $2+1$
$f(R)$gravity theory. In particular we have found analytical results for the
decay rate, reflection coefficient, greybody factors, as well as the black hole
temperature. On the other hand, our quasinormal modes analyses reveals
stability in the propagation of a massless scalar field in the cloud of strings
black hole spacetime. However, under a suitable choose of parameters an
instability is found. Furthermore based on the Bekenstein conjecture on the
quantization of the surface area of the black hole we find the minimal surface
area associated to the black hole horizon which is in agreement with
Bekenstein's proposal.
| [
{
"created": "Mon, 8 Jan 2018 16:57:55 GMT",
"version": "v1"
},
{
"created": "Mon, 28 May 2018 01:53:30 GMT",
"version": "v2"
}
] | 2018-06-28 | [
[
"Övgün",
"Ali",
""
],
[
"Jusufi",
"Kimet",
""
]
] | In this paper we have studied the propagation of a massless scalar field minimally coupled to a black hole with the source of cloud of strings in $2+1$ $f(R)$gravity theory. In particular we have found analytical results for the decay rate, reflection coefficient, greybody factors, as well as the black hole temperature. On the other hand, our quasinormal modes analyses reveals stability in the propagation of a massless scalar field in the cloud of strings black hole spacetime. However, under a suitable choose of parameters an instability is found. Furthermore based on the Bekenstein conjecture on the quantization of the surface area of the black hole we find the minimal surface area associated to the black hole horizon which is in agreement with Bekenstein's proposal. |
1403.3356 | Maurice Dupre | Maurice J. Dupre | The structure of local gravity theories | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the structure of local gravity theories as resulting from the idea
that locally gravity must be physically characterized by tidal acceleration,
and show how this relates to both Newtonian gravity and Einstein's general
relativity.
| [
{
"created": "Wed, 12 Mar 2014 01:50:04 GMT",
"version": "v1"
}
] | 2014-03-14 | [
[
"Dupre",
"Maurice J.",
""
]
] | We discuss the structure of local gravity theories as resulting from the idea that locally gravity must be physically characterized by tidal acceleration, and show how this relates to both Newtonian gravity and Einstein's general relativity. |
2401.08758 | Lidia J. Gomes Da Silva Miss | Lidia J. Gomes Da Silva | DiscoTEX: Discontinuous collocation and implicit-turned-explicit (IMTEX)
integration symplectic, symmetric numerical algorithms with higher order
jumps for differential equations with numerical black hole perturbation
theory applications | 44 pages, 17 figures, 8 tables. Includes overview of previous
numerical methods implemented in the time-domain for the modelling of
Extreme-Mass-Ratio-Inspirals with suitability checks on Table 8. Comments are
welcome | null | null | null | gr-qc astro-ph.HE cs.NA math.NA physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dirac delta distributionally sourced differential equations emerge in many
dynamical physical systems from neuroscience to black hole perturbation theory.
Most of these lack exact analytical solutions and are thus best tackled
numerically. This work describes a generic numerical algorithm which constructs
discontinuous spatial and temporal discretisations by operating on
discontinuous Lagrange and Hermite interpolation formulae recovering higher
order accuracy. It is shown by solving the distributionally sourced wave
equation, which has analytical solutions, that numerical weak-form solutions
can be recovered to high order accuracy by solving a first-order reduced system
of ordinary differential equations. The method-of-lines framework is applied to
the DiscoTEX algorithm i.e through discontinuous collocation with
implicit-turned-explicit (IMTEX) integration methods which are symmetric and
conserve symplectic structure. Furthermore, the main application of the
algorithm is proved, for the first-time, by calculating the amplitude at any
desired location within the numerical grid, including at the position (and at
its right and left limit) where the wave- (or wave-like) equation is
discontinuous via interpolation using DiscoTEX. This is shown, firstly by
solving the wave- (or wave-like) equation and comparing the numerical weak-form
solution to the exact solution. Finally, one shows how to reconstruct the
scalar and gravitational metric perturbations from weak-form numerical
solutions of a non-rotating black hole, which do not have known exact
analytical solutions, and compare against state-of-the-art frequency domain
results. One concludes by motivating how DiscoTEX, and related algorithms, open
a promising new alternative Extreme-Mass-Ratio-Inspiral (EMRI)s waveform
generation route via a self-consistent evolution for the gravitational
self-force programme in the time-domain.
| [
{
"created": "Tue, 16 Jan 2024 19:00:02 GMT",
"version": "v1"
}
] | 2024-01-18 | [
[
"Da Silva",
"Lidia J. Gomes",
""
]
] | Dirac delta distributionally sourced differential equations emerge in many dynamical physical systems from neuroscience to black hole perturbation theory. Most of these lack exact analytical solutions and are thus best tackled numerically. This work describes a generic numerical algorithm which constructs discontinuous spatial and temporal discretisations by operating on discontinuous Lagrange and Hermite interpolation formulae recovering higher order accuracy. It is shown by solving the distributionally sourced wave equation, which has analytical solutions, that numerical weak-form solutions can be recovered to high order accuracy by solving a first-order reduced system of ordinary differential equations. The method-of-lines framework is applied to the DiscoTEX algorithm i.e through discontinuous collocation with implicit-turned-explicit (IMTEX) integration methods which are symmetric and conserve symplectic structure. Furthermore, the main application of the algorithm is proved, for the first-time, by calculating the amplitude at any desired location within the numerical grid, including at the position (and at its right and left limit) where the wave- (or wave-like) equation is discontinuous via interpolation using DiscoTEX. This is shown, firstly by solving the wave- (or wave-like) equation and comparing the numerical weak-form solution to the exact solution. Finally, one shows how to reconstruct the scalar and gravitational metric perturbations from weak-form numerical solutions of a non-rotating black hole, which do not have known exact analytical solutions, and compare against state-of-the-art frequency domain results. One concludes by motivating how DiscoTEX, and related algorithms, open a promising new alternative Extreme-Mass-Ratio-Inspiral (EMRI)s waveform generation route via a self-consistent evolution for the gravitational self-force programme in the time-domain. |
1711.01935 | Yeinzon Rodriguez Garcia | Yeinzon Rodriguez (1,2,3), Andres A. Navarro (2,4) ((1) Universidad
Antonio Narino, (2) Universidad Industrial de Santander, (3) The Abdus Salam
International Centre for Theoretical Physics, (4) Universidad Santo Tomas) | Non-Abelian $S$-term dark energy and inflation | LaTeX file in RevTeX 4.1 style, 8 pages, 20 figures. v2: several
changes here and there to improve the overall presentation of the paper.
Primordial inflation section clarified. The viability of the model after the
detection of the gravitational wave signal GW170817 and its electromagnetic
counterpart GRB 170817A is discussed. v4: version published in Physics of the
Dark Universe | Phys.Dark Univ. 19: 129-136, 2018 | 10.1016/j.dark.2018.01.003 | PI/UAN-2017-615FT | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the role that a cosmic triad in the generalized $SU(2)$ Proca
theory, specifically in one of the pieces of the Lagrangian that involves the
symmetric version $S_{\mu \nu}$ of the gauge field strength tensor $F_{\mu
\nu}$, has on dark energy and primordial inflation. Regarding dark energy, the
triad behaves asymptotically as a couple of radiation perfect fluids whose
energy densities are negative for the $S$ term but positive for the Yang-Mills
term. This leads to an interesting dynamical fine-tuning mechanism that gives
rise to a combined equation of state parameter $\omega \simeq -1$ and,
therefore, to an eternal period of accelerated isotropic expansion for an ample
spectrum of initial conditions. Regarding primordial inflation, one of the
critical points of the associated dynamical system can describe a prolonged
period of isotropic slow-roll inflation sustained by the $S$ term. This period
ends up when the Yang-Mills term dominates the energy density leading to the
radiation dominated epoch. Unfortunately, in contrast to the dark energy case,
the primordial inflation scenario is strongly sensitive to the coupling
constants and initial conditions. The whole model, including the other pieces
of the Lagrangian that involve $S_{\mu \nu}$, might evade the recent strong
constraints coming from the gravitational wave signal GW170817 and its
electromagnetic counterpart GRB 170817A.
| [
{
"created": "Fri, 3 Nov 2017 17:43:53 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Nov 2017 16:39:44 GMT",
"version": "v2"
},
{
"created": "Wed, 24 Jan 2018 13:17:43 GMT",
"version": "v3"
},
{
"created": "Tue, 20 Feb 2018 16:46:48 GMT",
"version": "v4"
}
] | 2018-02-21 | [
[
"Rodriguez",
"Yeinzon",
""
],
[
"Navarro",
"Andres A.",
""
]
] | We study the role that a cosmic triad in the generalized $SU(2)$ Proca theory, specifically in one of the pieces of the Lagrangian that involves the symmetric version $S_{\mu \nu}$ of the gauge field strength tensor $F_{\mu \nu}$, has on dark energy and primordial inflation. Regarding dark energy, the triad behaves asymptotically as a couple of radiation perfect fluids whose energy densities are negative for the $S$ term but positive for the Yang-Mills term. This leads to an interesting dynamical fine-tuning mechanism that gives rise to a combined equation of state parameter $\omega \simeq -1$ and, therefore, to an eternal period of accelerated isotropic expansion for an ample spectrum of initial conditions. Regarding primordial inflation, one of the critical points of the associated dynamical system can describe a prolonged period of isotropic slow-roll inflation sustained by the $S$ term. This period ends up when the Yang-Mills term dominates the energy density leading to the radiation dominated epoch. Unfortunately, in contrast to the dark energy case, the primordial inflation scenario is strongly sensitive to the coupling constants and initial conditions. The whole model, including the other pieces of the Lagrangian that involve $S_{\mu \nu}$, might evade the recent strong constraints coming from the gravitational wave signal GW170817 and its electromagnetic counterpart GRB 170817A. |
2006.10561 | Ranjan Sharma | Ranjan Sharma, Naresh Dadhich, Shyam Das and Sunil D. Maharaj | An electromagnetic extension of the Schwarzschild interior solution and
the corresponding Buchdahl limit | 12 pages, 8 figures | null | 10.1140/epjc/s10052-021-08894-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We wish to construct a model for charged star as a generalization of the
uniform density Schwarzschild interior solution. We employ the Vaidya and
Tikekar ansatz [{\it Astrophys. Astron.} {\bf 3} (1982) 325] for one of the
metric potentials and electric field is chosen in such a way that when it is
switched off the metric reduces to the Schwarzschild. This relates charge
distribution to the Vaidya-Tikekar parameter, $k$, indicating deviation form
sphericity of three dimensional space when embedded into four dimensional
Euclidean space. The model is examined against all the physical conditions
required for a relativistic charged fluid sphere as an interior to a charged
star. We also obtain and discuss charged analogue of the Buchdahl compactness
bound.
| [
{
"created": "Tue, 16 Jun 2020 18:45:13 GMT",
"version": "v1"
}
] | 2021-02-24 | [
[
"Sharma",
"Ranjan",
""
],
[
"Dadhich",
"Naresh",
""
],
[
"Das",
"Shyam",
""
],
[
"Maharaj",
"Sunil D.",
""
]
] | We wish to construct a model for charged star as a generalization of the uniform density Schwarzschild interior solution. We employ the Vaidya and Tikekar ansatz [{\it Astrophys. Astron.} {\bf 3} (1982) 325] for one of the metric potentials and electric field is chosen in such a way that when it is switched off the metric reduces to the Schwarzschild. This relates charge distribution to the Vaidya-Tikekar parameter, $k$, indicating deviation form sphericity of three dimensional space when embedded into four dimensional Euclidean space. The model is examined against all the physical conditions required for a relativistic charged fluid sphere as an interior to a charged star. We also obtain and discuss charged analogue of the Buchdahl compactness bound. |
gr-qc/9805024 | CJ Fewster | C.J. Fewster and S.P. Eveson (Department of Mathematics, University of
York) | Bounds on negative energy densities in flat spacetime | REVTeX, 13 pages and 2 figures. Minor typos corrected, one reference
added | Phys.Rev.D58:084010,1998 | 10.1103/PhysRevD.58.084010 | null | gr-qc hep-th | null | We generalise results of Ford and Roman which place lower bounds -- known as
quantum inequalities -- on the renormalised energy density of a quantum field
averaged against a choice of sampling function. Ford and Roman derived their
results for a specific non-compactly supported sampling function; here we use a
different argument to obtain quantum inequalities for a class of smooth, even
and non-negative sampling functions which are either compactly supported or
decay rapidly at infinity. Our results hold in $d$-dimensional Minkowski space
($d\ge 2$) for the free real scalar field of mass $m\ge 0$. We discuss various
features of our bounds in 2 and 4 dimensions. In particular, for massless field
theory in 2-dimensional Minkowski space, we show that our quantum inequality is
weaker than Flanagan's optimal bound by a factor of 3/2.
| [
{
"created": "Thu, 7 May 1998 17:28:57 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jul 1998 14:52:49 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Fewster",
"C. J.",
"",
"Department of Mathematics, University of\n York"
],
[
"Eveson",
"S. P.",
"",
"Department of Mathematics, University of\n York"
]
] | We generalise results of Ford and Roman which place lower bounds -- known as quantum inequalities -- on the renormalised energy density of a quantum field averaged against a choice of sampling function. Ford and Roman derived their results for a specific non-compactly supported sampling function; here we use a different argument to obtain quantum inequalities for a class of smooth, even and non-negative sampling functions which are either compactly supported or decay rapidly at infinity. Our results hold in $d$-dimensional Minkowski space ($d\ge 2$) for the free real scalar field of mass $m\ge 0$. We discuss various features of our bounds in 2 and 4 dimensions. In particular, for massless field theory in 2-dimensional Minkowski space, we show that our quantum inequality is weaker than Flanagan's optimal bound by a factor of 3/2. |
gr-qc/0402053 | Martin Bojowald | Martin Bojowald | Loop Quantum Cosmology: Recent Progress | 17 pages, 2 figures, Plenary talk at ICGC 04, Cochin, India | Pramana 63:765-776,2004 | 10.1007/BF02705198 | AEI-2004-017 | gr-qc | null | Aspects of the full theory of loop quantum gravity can be studied in a
simpler context by reducing to symmetric models like cosmological ones. This
leads to several applications where loop effects play a significant role when
one is sensitive to the quantum regime. As a consequence, the structure of and
the approach to classical singularities are very different from general
relativity: The quantum theory is free of singularities, and there are new
phenomenological scenarios for the evolution of the very early universe
including inflation. We give an overview of the main effects, focussing on
recent results obtained by several different groups.
| [
{
"created": "Thu, 12 Feb 2004 10:13:47 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Bojowald",
"Martin",
""
]
] | Aspects of the full theory of loop quantum gravity can be studied in a simpler context by reducing to symmetric models like cosmological ones. This leads to several applications where loop effects play a significant role when one is sensitive to the quantum regime. As a consequence, the structure of and the approach to classical singularities are very different from general relativity: The quantum theory is free of singularities, and there are new phenomenological scenarios for the evolution of the very early universe including inflation. We give an overview of the main effects, focussing on recent results obtained by several different groups. |
2311.04672 | Parthapratim Mahapatra | Parthapratim Mahapatra and Shilpa Kastha | Parametrized multipolar gravitational waveform for testing general
relativity: Amplitude corrections upto 2PN order | 15 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A parametrized multipolar gravitational wave phasing within multipolar
post-Minkowskian and post-Newtonian formalism was developed in earlier works
[S. Kastha et al., PRD 98, 124033 (2018) & S. Kastha et al., PRD 100, 044007
(2019)]. This facilitates the model-agnostic tests for the multipolar structure
of compact binaries using gravitational wave observations. In this paper, we
derive a parametrized multipolar amplitude of the gravitational wave signal in
terms of mass and current-type radiative multipole moments within the
post-Newtonian approximation to general relativity. We assume the compact
binary to be moving in quasi-circular orbits, with component spins (anti-)
aligned with respect to the binary's orbital angular momentum. We report a
closed-form expression for the parameterized multipolar amplitude of the
waveform at second post-Newtonian order both in time and frequency domains.
This includes the contribution from the leading five mass-type and the leading
four current-type radiative moments. This framework of constructing a
parametrized waveform accomplishes a generic parametrization of both
gravitational wave phase and amplitude with the same set of phenomenological
parameters. Hence, it should significantly enhance the precision of the
multipole tests in the context of present and future gravitational wave
detectors.
| [
{
"created": "Wed, 8 Nov 2023 13:27:23 GMT",
"version": "v1"
}
] | 2023-11-09 | [
[
"Mahapatra",
"Parthapratim",
""
],
[
"Kastha",
"Shilpa",
""
]
] | A parametrized multipolar gravitational wave phasing within multipolar post-Minkowskian and post-Newtonian formalism was developed in earlier works [S. Kastha et al., PRD 98, 124033 (2018) & S. Kastha et al., PRD 100, 044007 (2019)]. This facilitates the model-agnostic tests for the multipolar structure of compact binaries using gravitational wave observations. In this paper, we derive a parametrized multipolar amplitude of the gravitational wave signal in terms of mass and current-type radiative multipole moments within the post-Newtonian approximation to general relativity. We assume the compact binary to be moving in quasi-circular orbits, with component spins (anti-) aligned with respect to the binary's orbital angular momentum. We report a closed-form expression for the parameterized multipolar amplitude of the waveform at second post-Newtonian order both in time and frequency domains. This includes the contribution from the leading five mass-type and the leading four current-type radiative moments. This framework of constructing a parametrized waveform accomplishes a generic parametrization of both gravitational wave phase and amplitude with the same set of phenomenological parameters. Hence, it should significantly enhance the precision of the multipole tests in the context of present and future gravitational wave detectors. |
1906.07624 | Saulo Pereira H | S. H. Pereira, R. de C. Lima, J. F. Jesus and R. F. L. Holanda | Acceleration in Friedmann cosmology with torsion | 17 pages, 6 figures | Eur. Phys. J. C (2019) 79: 950 | 10.1140/epjc/s10052-019-7462-4 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A Friedmann like cosmological model in Einstein-Cartan framework is studied
when the torsion function is assumed to be proportional to a single $\phi(t)$
function coming just from the spin vector contribution of ordinary matter. By
analysing four different types of torsion function written in terms of one, two
and three free parameters, we found that a model with $\phi(t)=- \alpha H(t)
\big({\rho_{m}(t)}/{\rho_{0c}}\big)^n$ is totally compatible with recent
cosmological data, where $\alpha$ and $n$ are free parameters to be constrained
from observations, $\rho_m$ is the matter energy density and $\rho_{0c}$ the
critical density. The recent accelerated phase of expansion of the universe is
correctly reproduced by the contribution coming from torsion function, with a
deceleration parameter indicating a transition redshift of about $0.65$.
| [
{
"created": "Tue, 18 Jun 2019 14:58:39 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Nov 2019 14:42:17 GMT",
"version": "v2"
}
] | 2019-11-21 | [
[
"Pereira",
"S. H.",
""
],
[
"Lima",
"R. de C.",
""
],
[
"Jesus",
"J. F.",
""
],
[
"Holanda",
"R. F. L.",
""
]
] | A Friedmann like cosmological model in Einstein-Cartan framework is studied when the torsion function is assumed to be proportional to a single $\phi(t)$ function coming just from the spin vector contribution of ordinary matter. By analysing four different types of torsion function written in terms of one, two and three free parameters, we found that a model with $\phi(t)=- \alpha H(t) \big({\rho_{m}(t)}/{\rho_{0c}}\big)^n$ is totally compatible with recent cosmological data, where $\alpha$ and $n$ are free parameters to be constrained from observations, $\rho_m$ is the matter energy density and $\rho_{0c}$ the critical density. The recent accelerated phase of expansion of the universe is correctly reproduced by the contribution coming from torsion function, with a deceleration parameter indicating a transition redshift of about $0.65$. |
1409.3101 | H.-J. Schmidt | H.-J. Schmidt | Motion of a thin spherically symmetric Shell of Dust in the
Schwarzschild field | Reprinted from: 10th International Conference on General Relativity
and Gravitation, Padova (Italy) July 4 - 9, 1983. Eds.: B. Bertotti, F. de
Felice, A. Pascolini, Contributed papers Vol. 1, Roma (1983) page 339-341 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The equation of motion announced in the title was already deduced for the
cases the inner metric being flat and the shell being negligibly small (test
matter), using surface layers and geodesic trajectories resp. Here we derive
the general equation of motion and solve it in closed form for the case of
parabolic motion. Especially the motion near the horizon and near the
singularity are examined.
| [
{
"created": "Wed, 10 Sep 2014 14:56:12 GMT",
"version": "v1"
}
] | 2014-09-11 | [
[
"Schmidt",
"H. -J.",
""
]
] | The equation of motion announced in the title was already deduced for the cases the inner metric being flat and the shell being negligibly small (test matter), using surface layers and geodesic trajectories resp. Here we derive the general equation of motion and solve it in closed form for the case of parabolic motion. Especially the motion near the horizon and near the singularity are examined. |
2007.04733 | Imre Ferenc Barna Dr. | Imre F. Barna, Mih\'aly A. Pocsai and Gergely G\'abor Barnaf\"oldi | Scaling Hydrodynamical Evolution of a Gravitating Dark-fluid Universe | 8 pages and 5 figures | Mathematics 2022 (10) 3220 | 10.3390/math10183220 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a dark fluid model which contains the general linear equation of
state including the gravitation term. The obtained spherical symmetric Euler
equation and the continuity equation was investigated with the Sedov-type
time-dependent self-similar {\it ansatz} which is capable to describe
physically relevant diffusive and dispersive solutions. %The role of the
parameter in the equation of state is investigated. As results the space and
time dependent fluid density and radial velocity fields are presented and
analyzed. Additionally, the role of the initial velocity on the kinetic and
total energy densities of the fluid is discussed.
| [
{
"created": "Thu, 9 Jul 2020 12:12:11 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Nov 2020 13:54:54 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Sep 2021 15:03:30 GMT",
"version": "v3"
}
] | 2022-09-08 | [
[
"Barna",
"Imre F.",
""
],
[
"Pocsai",
"Mihály A.",
""
],
[
"Barnaföldi",
"Gergely Gábor",
""
]
] | We present a dark fluid model which contains the general linear equation of state including the gravitation term. The obtained spherical symmetric Euler equation and the continuity equation was investigated with the Sedov-type time-dependent self-similar {\it ansatz} which is capable to describe physically relevant diffusive and dispersive solutions. %The role of the parameter in the equation of state is investigated. As results the space and time dependent fluid density and radial velocity fields are presented and analyzed. Additionally, the role of the initial velocity on the kinetic and total energy densities of the fluid is discussed. |
2106.12273 | Shoichiro Miyashita | Shoichiro Miyashita | Gravitational and Gravitoscalar Thermodynamics | 41 pages, many figures; v2: footnotes added, type corrected | JHEP 09 (2021) 121 | 10.1007/JHEP09(2021)121 | WUCG-21-08 | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Gravitational thermodynamics and gravitoscalar thermodynamics with $S^2
\times \mathbb{R}$ boundary geometry are investigated through the partition
function, assuming that all Euclidean saddle point geometries contribute to the
path integral and dominant ones are in the $B^3 \times S^1$ or $S^2 \times
Disc$ topology sector. In the first part, I concentrate on the purely
gravitational case with or without a cosmological constant and show there
exists a new type of saddle point geometry, which I call the "bag of gold(BG)
instanton," only for the $\Lambda>0$ case. Because of this existence,
thermodynamical stability of the system and the entropy bound are absent for
$\Lambda>0$, these being universal properties for $\Lambda \leq 0$. In the
second part, I investigate the thermodynamical properties of a gravity-scalar
system with a $\varphi^2$ potential. I show that when $\Lambda \leq 0$ and the
boundary value of scalar field $J_{\varphi}$ is below some value, then the
entropy bound and thermodynamical stability do exist. When either condition on
the parameters does not hold, however, thermodynamical stability is (partially)
broken. The properties of the system and the relation between BG instantons and
the breakdown are discussed in detail.
| [
{
"created": "Wed, 23 Jun 2021 09:50:27 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Aug 2021 14:52:22 GMT",
"version": "v2"
}
] | 2021-09-28 | [
[
"Miyashita",
"Shoichiro",
""
]
] | Gravitational thermodynamics and gravitoscalar thermodynamics with $S^2 \times \mathbb{R}$ boundary geometry are investigated through the partition function, assuming that all Euclidean saddle point geometries contribute to the path integral and dominant ones are in the $B^3 \times S^1$ or $S^2 \times Disc$ topology sector. In the first part, I concentrate on the purely gravitational case with or without a cosmological constant and show there exists a new type of saddle point geometry, which I call the "bag of gold(BG) instanton," only for the $\Lambda>0$ case. Because of this existence, thermodynamical stability of the system and the entropy bound are absent for $\Lambda>0$, these being universal properties for $\Lambda \leq 0$. In the second part, I investigate the thermodynamical properties of a gravity-scalar system with a $\varphi^2$ potential. I show that when $\Lambda \leq 0$ and the boundary value of scalar field $J_{\varphi}$ is below some value, then the entropy bound and thermodynamical stability do exist. When either condition on the parameters does not hold, however, thermodynamical stability is (partially) broken. The properties of the system and the relation between BG instantons and the breakdown are discussed in detail. |
2311.04075 | Eric Poisson | Tristan Pitre and Eric Poisson | General relativistic dynamical tides in binary inspirals, without modes | 33 pages, 4 figures, 4 tables, matches published version | Phys. Rev. D 109, 064004 (2024) | 10.1103/PhysRevD.109.064004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A neutron star in an inspiraling binary system is tidally deformed by its
companion, and the effect leaves a measurable imprint on the emitted
gravitational waves. While the tidal interaction falls within the regime of
static tides during the early stages of inspiral, a regime of dynamical tides
takes over in the later stages. The description of dynamical tides found in the
literature makes integral use of a spectral representation of the tidal
deformation, in which it is expressed as a sum over the star's normal modes of
vibration. This description is deeply rooted in Newtonian fluid mechanics and
gravitation, and we point out that considerable obstacles manifest themselves
in an extension to general relativity. To remedy this we propose an
alternative, mode-less description of dynamical tides that can be formulated in
both Newtonian and relativistic mechanics. Our description is based on a
time-derivative expansion of the tidal dynamics. The tidal deformation is
characterized by two sets of Love numbers: the static Love numbers $k_\ell$ and
the dynamic Love numbers $\ddot{k}_\ell$. These are computed here for
polytropic stellar models in both Newtonian gravity and general relativity. The
time-derivative expansion of the tidal dynamics seems to preclude any attempt
to capture an approach to resonance, which occurs when the frequency of the
tidal field becomes equal to a normal-mode frequency. To overcome this
limitation we propose a pragmatic extension of the time-derivative expansion
which does capture an approach to resonance. We demonstrate that with this
extension, our formulation of dynamical tides should be just as accurate as the
$f$-mode truncation of the mode representation, in which the sum over modes is
truncated to a single term involving the star's fundamental mode of vibration.
| [
{
"created": "Tue, 7 Nov 2023 15:40:36 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Mar 2024 12:38:30 GMT",
"version": "v2"
}
] | 2024-03-07 | [
[
"Pitre",
"Tristan",
""
],
[
"Poisson",
"Eric",
""
]
] | A neutron star in an inspiraling binary system is tidally deformed by its companion, and the effect leaves a measurable imprint on the emitted gravitational waves. While the tidal interaction falls within the regime of static tides during the early stages of inspiral, a regime of dynamical tides takes over in the later stages. The description of dynamical tides found in the literature makes integral use of a spectral representation of the tidal deformation, in which it is expressed as a sum over the star's normal modes of vibration. This description is deeply rooted in Newtonian fluid mechanics and gravitation, and we point out that considerable obstacles manifest themselves in an extension to general relativity. To remedy this we propose an alternative, mode-less description of dynamical tides that can be formulated in both Newtonian and relativistic mechanics. Our description is based on a time-derivative expansion of the tidal dynamics. The tidal deformation is characterized by two sets of Love numbers: the static Love numbers $k_\ell$ and the dynamic Love numbers $\ddot{k}_\ell$. These are computed here for polytropic stellar models in both Newtonian gravity and general relativity. The time-derivative expansion of the tidal dynamics seems to preclude any attempt to capture an approach to resonance, which occurs when the frequency of the tidal field becomes equal to a normal-mode frequency. To overcome this limitation we propose a pragmatic extension of the time-derivative expansion which does capture an approach to resonance. We demonstrate that with this extension, our formulation of dynamical tides should be just as accurate as the $f$-mode truncation of the mode representation, in which the sum over modes is truncated to a single term involving the star's fundamental mode of vibration. |
gr-qc/0301063 | Nikolai V. Mitskievich | Vladimir N. Efremov and Nikolai V. Mitskievich | Discrete model of spacetime in terms of inverse spectra of the $T_0$
Alexandroff topological spaces | LaTeX, 39 pages, no figures | null | null | null | gr-qc | null | The theory of inverse spectra of $T_0$ Alexandroff topological spaces is used
to construct a model of $T_0$-discrete four-dimensional spacetime. The universe
evolution is interpreted in terms of a sequence of topology changes in the set
of $T_0$-discrete spaces realized as nerves of the canonical partitions of
three-dimensional compact manifolds. The cosmological time arrow arises being
connected with the refinement of the canonical partitions, and it is defined by
the action of homomorphisms in the proper inverse spectrum of three-dimensional
$T_0$-discrete spaces. A new causal order relation in this spectrum is
postulated having the basic properties of the causal order in the
pseudo-Riemannian spacetime however also bearing certain quasi-quantum
features. An attempt is made to describe topological changes between compact
manifolds in terms of bifurcations of proper inverse spectra; this led us to
the concept of bispectrum. As a generalization of this concept, inverse
multispectra and superspectrum are introduced. The last one enables us to
introduce the discrete superspace, a discrete counterpart of the
Wheeler--DeWitt superspace.
| [
{
"created": "Fri, 17 Jan 2003 05:00:50 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Efremov",
"Vladimir N.",
""
],
[
"Mitskievich",
"Nikolai V.",
""
]
] | The theory of inverse spectra of $T_0$ Alexandroff topological spaces is used to construct a model of $T_0$-discrete four-dimensional spacetime. The universe evolution is interpreted in terms of a sequence of topology changes in the set of $T_0$-discrete spaces realized as nerves of the canonical partitions of three-dimensional compact manifolds. The cosmological time arrow arises being connected with the refinement of the canonical partitions, and it is defined by the action of homomorphisms in the proper inverse spectrum of three-dimensional $T_0$-discrete spaces. A new causal order relation in this spectrum is postulated having the basic properties of the causal order in the pseudo-Riemannian spacetime however also bearing certain quasi-quantum features. An attempt is made to describe topological changes between compact manifolds in terms of bifurcations of proper inverse spectra; this led us to the concept of bispectrum. As a generalization of this concept, inverse multispectra and superspectrum are introduced. The last one enables us to introduce the discrete superspace, a discrete counterpart of the Wheeler--DeWitt superspace. |
1401.2810 | Alexey Golovnev | Alexey Golovnev | Smooth horizons and quantum ripples | 4 pages; minor changes, a few references added | The European Physical Journal C 75 (2015) 185 | 10.1140/epjc/s10052-015-3395-8 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black Holes are unique objects which allow for meaningful theoretical studies
of strong gravity and even quantum gravity effects. An infalling and a distant
observer would have very different views on the structure of the world.
However, a careful analysis has shown that it entails no genuine contradictions
for physics, and the paradigm of observer complementarity has been coined.
Recently this picture was put into doubt. In particular, it was argued that in
old Black Holes a firewall must form in order to protect the basic principles
of quantum mechanics. This AMPS paradox has already been discussed in a vast
number of papers with different attitudes and conclusions. Here we want to
argue that a possible source of confusion is neglection of quantum gravity
effects. Contrary to widespread perception, it does not necessarily mean that
effective field theory is inapplicable in rather smooth neighbourhoods of large
Black Hole horizons. The real offender might be an attempt to consistently use
it over the huge distances from the near-horizon zone of old Black Holes to the
early radiation. We give simple estimates to support this viewpoint and show
how the Page time and (somewhat more speculative) scrambling time do appear.
| [
{
"created": "Mon, 13 Jan 2014 12:24:39 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jan 2014 18:02:42 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Feb 2014 17:03:11 GMT",
"version": "v3"
}
] | 2015-05-06 | [
[
"Golovnev",
"Alexey",
""
]
] | Black Holes are unique objects which allow for meaningful theoretical studies of strong gravity and even quantum gravity effects. An infalling and a distant observer would have very different views on the structure of the world. However, a careful analysis has shown that it entails no genuine contradictions for physics, and the paradigm of observer complementarity has been coined. Recently this picture was put into doubt. In particular, it was argued that in old Black Holes a firewall must form in order to protect the basic principles of quantum mechanics. This AMPS paradox has already been discussed in a vast number of papers with different attitudes and conclusions. Here we want to argue that a possible source of confusion is neglection of quantum gravity effects. Contrary to widespread perception, it does not necessarily mean that effective field theory is inapplicable in rather smooth neighbourhoods of large Black Hole horizons. The real offender might be an attempt to consistently use it over the huge distances from the near-horizon zone of old Black Holes to the early radiation. We give simple estimates to support this viewpoint and show how the Page time and (somewhat more speculative) scrambling time do appear. |
2109.01525 | Manuel Hohmann | Manuel Hohmann | General covariant symmetric teleparallel cosmology | 18 pages, no figures | Phys. Rev. D 104 (2021) 124077 | 10.1103/PhysRevD.104.124077 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Symmetric teleparallel gravity theories, in which the gravitational
interaction is attributed to the nonmetricity of a flat, symmetric, but not
metric-compatible affine connection, have been a topic of growing interest in
recent studies. Numerous works study the cosmology of symmetric teleparallel
gravity assuming a flat Friedmann-Lema\^itre-Robertson-Walker metric, while
working in the so-called "coincident gauge", further assuming that the
connection coefficients vanish. However, little attention has been paid to the
fact that both of these assumptions rely on the freedom to choose a particular
coordinate system in order to simplify the metric or the connection, and that
they may, in general, not be achieved simultaneously. Here we construct the
most general symmetric teleparallel geometry obeying the conditions of
homogeneity and isotropy, without making any assumptions on the properties of
the coordinates, and present our results in both the usual cosmological
coordinates and in the coincident gauge. We find that in general these
coordinates do not agree, and that assuming both to hold simultaneously allows
only for a very restricted class of geometries. For the general case, we derive
the energy-momentum-hypermomentum conservation relations and the cosmological
dynamics of selected symmetric teleparallel gravity theories. Our results show
that the symmetric teleparallel connection in general contributes another
scalar quantity into the cosmological dynamics, which decouples only for a
specific class of theories from the dynamics of the metric, and only if the
most simple geometry is chosen, in which both assumed coordinate systems agree.
Most notably, the $f(Q)$ class of theories falls into this class.
| [
{
"created": "Thu, 2 Sep 2021 17:10:09 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Dec 2021 19:01:30 GMT",
"version": "v2"
}
] | 2022-01-03 | [
[
"Hohmann",
"Manuel",
""
]
] | Symmetric teleparallel gravity theories, in which the gravitational interaction is attributed to the nonmetricity of a flat, symmetric, but not metric-compatible affine connection, have been a topic of growing interest in recent studies. Numerous works study the cosmology of symmetric teleparallel gravity assuming a flat Friedmann-Lema\^itre-Robertson-Walker metric, while working in the so-called "coincident gauge", further assuming that the connection coefficients vanish. However, little attention has been paid to the fact that both of these assumptions rely on the freedom to choose a particular coordinate system in order to simplify the metric or the connection, and that they may, in general, not be achieved simultaneously. Here we construct the most general symmetric teleparallel geometry obeying the conditions of homogeneity and isotropy, without making any assumptions on the properties of the coordinates, and present our results in both the usual cosmological coordinates and in the coincident gauge. We find that in general these coordinates do not agree, and that assuming both to hold simultaneously allows only for a very restricted class of geometries. For the general case, we derive the energy-momentum-hypermomentum conservation relations and the cosmological dynamics of selected symmetric teleparallel gravity theories. Our results show that the symmetric teleparallel connection in general contributes another scalar quantity into the cosmological dynamics, which decouples only for a specific class of theories from the dynamics of the metric, and only if the most simple geometry is chosen, in which both assumed coordinate systems agree. Most notably, the $f(Q)$ class of theories falls into this class. |
gr-qc/9301014 | null | James D.E. Grant | On Self-Dual Gravity I | 17 pages, Latex, DAMTP-R92/47 | Phys.Rev. D48 (1993) 2606-2612 | 10.1103/PhysRevD.48.2606 | null | gr-qc hep-th | null | (One typo corrected and one incorrect statement removed. Extra details on
conserved quantities and symmetry algebras added).
| [
{
"created": "Thu, 14 Jan 1993 15:13:15 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Feb 1993 15:36:24 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Grant",
"James D. E.",
""
]
] | (One typo corrected and one incorrect statement removed. Extra details on conserved quantities and symmetry algebras added). |
0908.2874 | Francisco Lobo | Tiberiu Harko, Zoltan Kov\'acs, Francisco S. N. Lobo | Solar system tests of Ho\v{r}ava-Lifshitz gravity | 9 pages, 4 figures. V2: minor changes; accepted for publication in
Proceedings of the Royal Society A | Proc.Roy.Soc.Lond.A Math.Phys.Eng.Sci.467:1390-1407,2011 | 10.1098/rspa.2010.0477 | null | gr-qc astro-ph.SR hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, a renormalizable gravity theory with higher spatial derivatives in
four dimensions was proposed by Ho\v{r}ava. The theory reduces to Einstein
gravity with a non-vanishing cosmological constant in IR, but it has improved
UV behaviors. The spherically symmetric black hole solutions for an arbitrary
cosmological constant, which represent the generalization of the standard
Schwarzschild-(A)dS solution, has also been obtained for the
Ho\v{r}ava-Lifshitz theory. The exact asymptotically flat Schwarzschild type
solution of the gravitational field equations in Ho\v{r}ava gravity contains a
quadratic increasing term, as well as the square root of a fourth order
polynomial in the radial coordinate, and it depends on one arbitrary
integration constant. The IR modified Ho\v{r}ava gravity seems to be consistent
with the current observational data, but in order to test its viability more
observational constraints are necessary. In the present paper we consider the
possibility of observationally testing Ho\v{r}ava gravity at the scale of the
Solar System, by considering the classical tests of general relativity
(perihelion precession of the planet Mercury, deflection of light by the Sun
and the radar echo delay) for the spherically symmetric black hole solution of
Ho\v{r}ava-Lifshitz gravity. All these gravitational effects can be fully
explained in the framework of the vacuum solution of the gravity. Moreover, the
study of the classical general relativistic tests also constrain the free
parameter of the solution.
| [
{
"created": "Thu, 20 Aug 2009 08:31:17 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Oct 2010 21:26:22 GMT",
"version": "v2"
}
] | 2011-04-20 | [
[
"Harko",
"Tiberiu",
""
],
[
"Kovács",
"Zoltan",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | Recently, a renormalizable gravity theory with higher spatial derivatives in four dimensions was proposed by Ho\v{r}ava. The theory reduces to Einstein gravity with a non-vanishing cosmological constant in IR, but it has improved UV behaviors. The spherically symmetric black hole solutions for an arbitrary cosmological constant, which represent the generalization of the standard Schwarzschild-(A)dS solution, has also been obtained for the Ho\v{r}ava-Lifshitz theory. The exact asymptotically flat Schwarzschild type solution of the gravitational field equations in Ho\v{r}ava gravity contains a quadratic increasing term, as well as the square root of a fourth order polynomial in the radial coordinate, and it depends on one arbitrary integration constant. The IR modified Ho\v{r}ava gravity seems to be consistent with the current observational data, but in order to test its viability more observational constraints are necessary. In the present paper we consider the possibility of observationally testing Ho\v{r}ava gravity at the scale of the Solar System, by considering the classical tests of general relativity (perihelion precession of the planet Mercury, deflection of light by the Sun and the radar echo delay) for the spherically symmetric black hole solution of Ho\v{r}ava-Lifshitz gravity. All these gravitational effects can be fully explained in the framework of the vacuum solution of the gravity. Moreover, the study of the classical general relativistic tests also constrain the free parameter of the solution. |
0901.4000 | Alan D. Rendall | Ernesto Nungesser, Alan D. Rendall | Strong cosmic censorship for solutions of the Einstein-Maxwell field
equations with polarized Gowdy symmetry | Some references have been changed | Class.Quant.Grav.26:105019,2009 | 10.1088/0264-9381/26/10/105019 | AEI-2009-006 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A proof of strong cosmic censorship is presented for a class of solutions of
the Einstein-Maxwell equations, those with polarized Gowdy symmetry. A key
element of the argument is the observation that by means of a suitable choice
of variables the central equations in this problem can be written in a form
where they are identical to the central equations for general (i.e.
non-polarized) vacuum Gowdy spacetimes. Using this it is seen that the deep
results of Ringstr\"om on strong cosmic censorship in the vacuum case have
implications for the Einstein-Maxwell case. Working out the geometrical meaning
of these analytical results leads to the main conclusion.
| [
{
"created": "Mon, 26 Jan 2009 13:17:05 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Mar 2009 14:28:39 GMT",
"version": "v2"
}
] | 2010-08-03 | [
[
"Nungesser",
"Ernesto",
""
],
[
"Rendall",
"Alan D.",
""
]
] | A proof of strong cosmic censorship is presented for a class of solutions of the Einstein-Maxwell equations, those with polarized Gowdy symmetry. A key element of the argument is the observation that by means of a suitable choice of variables the central equations in this problem can be written in a form where they are identical to the central equations for general (i.e. non-polarized) vacuum Gowdy spacetimes. Using this it is seen that the deep results of Ringstr\"om on strong cosmic censorship in the vacuum case have implications for the Einstein-Maxwell case. Working out the geometrical meaning of these analytical results leads to the main conclusion. |
gr-qc/9509025 | Herbert Balasin | P.C.Aichelburg and H.Balasin | Symmetries of pp-Waves with Distributional Profile | 10 pages, latex2e, no figures, statement about the combination of
symmetry classes of impulsive waves corrected | Class.Quant.Grav. 13 (1996) 723-730 | 10.1088/0264-9381/13/4/012 | UWThPh-1995-30, TUW95-20 | gr-qc | null | We generalize the classification of (non-vacuum) pp-waves \cite{JEK} based on
the Killing-algebra of the space-time by admitting distribution-valued profile
functions. Our approach is based on the analysis of the (infinite-dimensional)
group of ``normal-form-preserving'' diffeomorphisms.
| [
{
"created": "Thu, 14 Sep 1995 12:07:39 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Dec 1995 09:45:59 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Aichelburg",
"P. C.",
""
],
[
"Balasin",
"H.",
""
]
] | We generalize the classification of (non-vacuum) pp-waves \cite{JEK} based on the Killing-algebra of the space-time by admitting distribution-valued profile functions. Our approach is based on the analysis of the (infinite-dimensional) group of ``normal-form-preserving'' diffeomorphisms. |
1608.04543 | Ioannis Dalianis | Ioannis Dalianis, George Koutsoumbas, Konstantinos Ntrekis,
Eleftherios Papantonopoulos | Reheating predictions in Gravity Theories with Derivative Coupling | JCAP version; minor corrections, results unchanged, figures and refs
added compared to v1; 28 pages, 30 plots, plain text | null | 10.1088/1475-7516/2017/02/027 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the inflationary predictions of a simple Horndeski theory
where the inflaton scalar field has a non-minimal derivative coupling (NMDC) to
the Einstein tensor. The NMDC is very motivated for the construction of
successful models for inflation, nevertheless its inflationary predictions are
not observationally distinct. We show that it is possible to probe the effects
of the NMDC on the CMB observables by taking into account both the dynamics of
the inflationary slow-roll phase and the subsequent reheating. We perform a
comparative study between representative inflationary models with canonical
fields minimally coupled to gravity and models with NMDC. We find that the
inflation models with dominant NMDC generically predict a higher reheating
temperature and a different range for the tilt of the scalar perturbation
spectrum $n_s$ and scalar-to-tensor ratio $r$, potentially testable by current
and future CMB experiments.
| [
{
"created": "Tue, 16 Aug 2016 10:25:13 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Feb 2017 22:58:54 GMT",
"version": "v2"
}
] | 2017-02-22 | [
[
"Dalianis",
"Ioannis",
""
],
[
"Koutsoumbas",
"George",
""
],
[
"Ntrekis",
"Konstantinos",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
]
] | We investigate the inflationary predictions of a simple Horndeski theory where the inflaton scalar field has a non-minimal derivative coupling (NMDC) to the Einstein tensor. The NMDC is very motivated for the construction of successful models for inflation, nevertheless its inflationary predictions are not observationally distinct. We show that it is possible to probe the effects of the NMDC on the CMB observables by taking into account both the dynamics of the inflationary slow-roll phase and the subsequent reheating. We perform a comparative study between representative inflationary models with canonical fields minimally coupled to gravity and models with NMDC. We find that the inflation models with dominant NMDC generically predict a higher reheating temperature and a different range for the tilt of the scalar perturbation spectrum $n_s$ and scalar-to-tensor ratio $r$, potentially testable by current and future CMB experiments. |
2305.08909 | Alexandre Toubiana | Alexandre Toubiana and Michael L. Katz and Jonathan R. Gair | Is there an excess of black holes around $20 M_{\odot}$? Optimising the
complexity of population models with the use of reversible jump MCMC | correct typo in equation 5 | null | 10.1093/mnras/stad2215 | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some analyses of the third gravitational wave catalogue released by the
LIGO-Virgo-KAGRA collaboration (LVK) suggest an excess of black holes around
$15-20 M_{\odot}$. In order to investigate this feature, we introduce two
flexible population models, a semi-parametric one and a non-parametric one.
Both make use of reversible jump Markov chain Monte-Carlo to optimise their
complexity. We also illustrate how the latter can be used to efficiently
perform model selection. Our parametric model broadly agrees with the fiducial
analysis of the LVK, but finds a peak of events at slightly larger masses. Our
non-parametric model shows this same displacement. Moreover, it also suggests
the existence of an excess of black holes around $20 M_{\odot}$. We assess the
robustness of this prediction by performing mock injections and running
hierarchical analyses on those. We find that such a feature might be due to
statistical fluctuations, given the small number of events observed so far,
with a $5\%$ probability. We estimate that with a few hundreds of observations,
as expected for O4, our non-parametric model will, be able to robustly
determine the presence of this excess. It will then allow for an efficient
agnostic inference of the properties of black holes.
| [
{
"created": "Mon, 15 May 2023 18:00:02 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Jul 2023 18:30:08 GMT",
"version": "v2"
},
{
"created": "Fri, 29 Sep 2023 10:00:47 GMT",
"version": "v3"
}
] | 2023-10-02 | [
[
"Toubiana",
"Alexandre",
""
],
[
"Katz",
"Michael L.",
""
],
[
"Gair",
"Jonathan R.",
""
]
] | Some analyses of the third gravitational wave catalogue released by the LIGO-Virgo-KAGRA collaboration (LVK) suggest an excess of black holes around $15-20 M_{\odot}$. In order to investigate this feature, we introduce two flexible population models, a semi-parametric one and a non-parametric one. Both make use of reversible jump Markov chain Monte-Carlo to optimise their complexity. We also illustrate how the latter can be used to efficiently perform model selection. Our parametric model broadly agrees with the fiducial analysis of the LVK, but finds a peak of events at slightly larger masses. Our non-parametric model shows this same displacement. Moreover, it also suggests the existence of an excess of black holes around $20 M_{\odot}$. We assess the robustness of this prediction by performing mock injections and running hierarchical analyses on those. We find that such a feature might be due to statistical fluctuations, given the small number of events observed so far, with a $5\%$ probability. We estimate that with a few hundreds of observations, as expected for O4, our non-parametric model will, be able to robustly determine the presence of this excess. It will then allow for an efficient agnostic inference of the properties of black holes. |
1111.0327 | Emanuel Gallo | Emanuel Gallo and Osvaldo Moreschi | Peculiar anisotropic stationary spherically symmetric solution of
Einstein equations | 6 pages, 5 figures. To appear in Modern Physics Letters A | Mod. Phys.Lett. A 1250044 (2012) | 10.1142/S0217732312500447 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by studies on gravitational lenses, we present an exact solution of
the field equations of general relativity, which is static and spherically
symmetric, has no mass but has a non-vanishing spacelike components of the
stress-energy-momentum tensor. In spite of its strange nature, this solution
provides with non-trivial descriptions of gravitational effects. We show that
the main aspects found in the \emph{dark matter phenomena} can be
satisfactorily described by this geometry. We comment on the relevance it could
have to consider non-vanishing spacelike components of the
stress-energy-momentum tensor ascribed to dark matter.
| [
{
"created": "Tue, 1 Nov 2011 21:51:08 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Mar 2012 14:42:14 GMT",
"version": "v2"
}
] | 2012-03-15 | [
[
"Gallo",
"Emanuel",
""
],
[
"Moreschi",
"Osvaldo",
""
]
] | Motivated by studies on gravitational lenses, we present an exact solution of the field equations of general relativity, which is static and spherically symmetric, has no mass but has a non-vanishing spacelike components of the stress-energy-momentum tensor. In spite of its strange nature, this solution provides with non-trivial descriptions of gravitational effects. We show that the main aspects found in the \emph{dark matter phenomena} can be satisfactorily described by this geometry. We comment on the relevance it could have to consider non-vanishing spacelike components of the stress-energy-momentum tensor ascribed to dark matter. |
1710.07838 | Vasilis Oikonomou | S. Nojiri, S.D. Odintsov, V.K. Oikonomou | Ghost-Free $F(R)$ Gravity with Lagrange Multiplier Constraint | PLB Accepted | null | 10.1016/j.physletb.2017.10.045 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose two new versions of ghost-free generalized $F(R)$ gravity with
Lagrange multiplier constraint. The first version of such theory for a
particular degenerate choice of the Lagrange multiplier, corresponds to mimetic
$F(R)$ gravity. The second version of such theory is just the Jordan frame
description of mimetic gravity with potential. As we demonstrate, it is
possible to realize several cosmological scenarios in such theory. In
particulary, de Sitter solutions may also be found.
| [
{
"created": "Sat, 21 Oct 2017 18:27:23 GMT",
"version": "v1"
}
] | 2017-11-22 | [
[
"Nojiri",
"S.",
""
],
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | We propose two new versions of ghost-free generalized $F(R)$ gravity with Lagrange multiplier constraint. The first version of such theory for a particular degenerate choice of the Lagrange multiplier, corresponds to mimetic $F(R)$ gravity. The second version of such theory is just the Jordan frame description of mimetic gravity with potential. As we demonstrate, it is possible to realize several cosmological scenarios in such theory. In particulary, de Sitter solutions may also be found. |
1808.05134 | Anzhong Wang | Manabendra Sharma, M. Shahalam, Wu Qiang, and Anzhong Wang | Preinflationary dynamics in loop quantum cosmology: Monodromy Potential | revtex4, seven figures and five tables. Version to appear in JCAP | JCAP11(2018)003 | 10.1088/1475-7516/2018/11/003 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we explore the pre-inflationary background dynamics of an
FLRW universe sourced by a scalar field with monodromy potential in LQC
framework. In particular we calculate the number of e-folds, $N_{inf}$,
produced during the slowly rolling phase of the inflation and find out the
critical value of the ratio of the kinetic to potential energy, $r_w^c$, at the
quantum bounce that is required to produce $N_{inf}\simeq 60.$ Two different
monodromy potentials, namely, linear and quadratic with a modulation term are
investigated to this effect. The effects on the value of $N_{inf}$ due to
parameters associated with the strength, decay constant and the phase factor of
the modulation term are calculated. In addition to this we present the
qualitative picture of the background dynamics by carrying out a dynamical
system analysis. We produce the phase portraits and carry out a detailed linear
stability analysis of the finite fixed points, if any, for each of the
potentials.
| [
{
"created": "Mon, 13 Aug 2018 08:35:02 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Oct 2018 10:01:49 GMT",
"version": "v2"
}
] | 2018-11-15 | [
[
"Sharma",
"Manabendra",
""
],
[
"Shahalam",
"M.",
""
],
[
"Qiang",
"Wu",
""
],
[
"Wang",
"Anzhong",
""
]
] | In this article we explore the pre-inflationary background dynamics of an FLRW universe sourced by a scalar field with monodromy potential in LQC framework. In particular we calculate the number of e-folds, $N_{inf}$, produced during the slowly rolling phase of the inflation and find out the critical value of the ratio of the kinetic to potential energy, $r_w^c$, at the quantum bounce that is required to produce $N_{inf}\simeq 60.$ Two different monodromy potentials, namely, linear and quadratic with a modulation term are investigated to this effect. The effects on the value of $N_{inf}$ due to parameters associated with the strength, decay constant and the phase factor of the modulation term are calculated. In addition to this we present the qualitative picture of the background dynamics by carrying out a dynamical system analysis. We produce the phase portraits and carry out a detailed linear stability analysis of the finite fixed points, if any, for each of the potentials. |
1603.08263 | Carlos Coimbra-Araujo | C. H. Coimbra-Araujo and R. C. Anjos | Stability of perturbed geodesics in $nD$ axisymmetric spacetimes | 21 pages, 7 figures, published in Classical and Quantum Gravity | Classical and Quantum Gravity, Volume 33, Number 18, 185010, 2016 | 10.1088/0264-9381/33/18/185010 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | The effect of self-gravity of a disk matter is evaluated by the simplest
modes of oscillation frequencies for perturbed circular geodesics. It is
plotted the radial profiles of free oscillations of an equatorial circular
geodesic perturbed within the orbital plane or in the vertical direction. The
calculation is carried out to geodesics of an axisymmetric $n$-dimensional
spacetime. The profiles are computed by examples of disks embeded in
five-dimensional or six-dimensional spacetime, where it is studied the motion
of free test particles for three axisymmetric cases: (i) the Newtonian limit of
a general proposed $5D$ and $6D$ axisymmetric spacetime; (ii) a simple
Randall-Sundrum $5D$ spacetime; (iii) general $5D$ and $6D$ Randall-Sundrum
spacetime. The equation of motion of such particles is derived and the
stability study is computed for both horizontal and vertical directions, to see
how extra dimensions could affect the system. In particular, we investigate a
disk constructed from Schwarzschild and Chazy-Curzon solutions with a simple
extension for extra dimensions in the case (i), and by solving vacuum Einstein
field equations for a kind of Randall-Sundrum-Weyl metric in cases (ii) and
(iii). We find that it is possible to compute a range of possible solutions
where such perturbed geodesics are stable. Basicaly, the stable solutions
appear, for the radial direction, in special cases when the system has $5D$ and
in all cases when the system has $6D$; and, for the axial direction, in all
cases when the system has both $5D$ or $6D$.
| [
{
"created": "Sun, 27 Mar 2016 22:26:01 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Sep 2016 23:14:06 GMT",
"version": "v2"
}
] | 2016-09-06 | [
[
"Coimbra-Araujo",
"C. H.",
""
],
[
"Anjos",
"R. C.",
""
]
] | The effect of self-gravity of a disk matter is evaluated by the simplest modes of oscillation frequencies for perturbed circular geodesics. It is plotted the radial profiles of free oscillations of an equatorial circular geodesic perturbed within the orbital plane or in the vertical direction. The calculation is carried out to geodesics of an axisymmetric $n$-dimensional spacetime. The profiles are computed by examples of disks embeded in five-dimensional or six-dimensional spacetime, where it is studied the motion of free test particles for three axisymmetric cases: (i) the Newtonian limit of a general proposed $5D$ and $6D$ axisymmetric spacetime; (ii) a simple Randall-Sundrum $5D$ spacetime; (iii) general $5D$ and $6D$ Randall-Sundrum spacetime. The equation of motion of such particles is derived and the stability study is computed for both horizontal and vertical directions, to see how extra dimensions could affect the system. In particular, we investigate a disk constructed from Schwarzschild and Chazy-Curzon solutions with a simple extension for extra dimensions in the case (i), and by solving vacuum Einstein field equations for a kind of Randall-Sundrum-Weyl metric in cases (ii) and (iii). We find that it is possible to compute a range of possible solutions where such perturbed geodesics are stable. Basicaly, the stable solutions appear, for the radial direction, in special cases when the system has $5D$ and in all cases when the system has $6D$; and, for the axial direction, in all cases when the system has both $5D$ or $6D$. |
2310.06899 | Sumanta Chakraborty | Sumanta Chakraborty, Anupam Mazumdar and Ritapriya Pradhan | Distinguishing Jordan and Einstein frames in gravity through
entanglement | v2, published version, 10 pages, 2 figures | Phy. Rev. D 108, L121505 (2023) | 10.1103/PhysRevD.108.L121505 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In general relativity, the use of conformal transformation is ubiquitous and
leads to two different frames of reference, known as the Jordan and the
Einstein frames. Typically, the transformation from the Jordan frame to the
Einstein frame involves introducing an additional scalar degree of freedom,
often already present in the theory. We will show that at the quantum level,
owing to this extra scalar degree of freedom these two frames exhibit subtle
differences that the entanglement between two massive objects can probe.
| [
{
"created": "Tue, 10 Oct 2023 18:00:26 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Jan 2024 02:11:43 GMT",
"version": "v2"
}
] | 2024-01-25 | [
[
"Chakraborty",
"Sumanta",
""
],
[
"Mazumdar",
"Anupam",
""
],
[
"Pradhan",
"Ritapriya",
""
]
] | In general relativity, the use of conformal transformation is ubiquitous and leads to two different frames of reference, known as the Jordan and the Einstein frames. Typically, the transformation from the Jordan frame to the Einstein frame involves introducing an additional scalar degree of freedom, often already present in the theory. We will show that at the quantum level, owing to this extra scalar degree of freedom these two frames exhibit subtle differences that the entanglement between two massive objects can probe. |
gr-qc/0107074 | M. Raiteri | M. Francaviglia, M. Raiteri | Hamiltonian, Energy and Entropy in General Relativity with
Non-Orthogonal Boundaries | 29 pages with 1 figure | Class.Quant.Grav.19:237-258,2002 | 10.1088/0264-9381/19/2/305 | null | gr-qc | null | A general recipe to define, via Noether theorem, the Hamiltonian in any
natural field theory is suggested. It is based on a Regge-Teitelboim-like
approach applied to the variation of Noether conserved quantities. The
Hamiltonian for General Relativity in presence of non-orthogonal boundaries is
analysed and the energy is defined as the on-shell value of the Hamiltonian.
The role played by boundary conditions in the formalism is outlined and the
quasilocal internal energy is defined by imposing metric Dirichlet boundary
conditions. A (conditioned) agreement with previous definitions is proved. A
correspondence with Brown-York original formulation of the first principle of
black hole thermodynamics is finally established.
| [
{
"created": "Mon, 23 Jul 2001 11:56:58 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Francaviglia",
"M.",
""
],
[
"Raiteri",
"M.",
""
]
] | A general recipe to define, via Noether theorem, the Hamiltonian in any natural field theory is suggested. It is based on a Regge-Teitelboim-like approach applied to the variation of Noether conserved quantities. The Hamiltonian for General Relativity in presence of non-orthogonal boundaries is analysed and the energy is defined as the on-shell value of the Hamiltonian. The role played by boundary conditions in the formalism is outlined and the quasilocal internal energy is defined by imposing metric Dirichlet boundary conditions. A (conditioned) agreement with previous definitions is proved. A correspondence with Brown-York original formulation of the first principle of black hole thermodynamics is finally established. |
1408.2788 | Alexander Graham | Alexander A. H. Graham | Varying-Alpha and K-Essence | 14 pages, 3 figures. v2: typos corrected, references added and some
additional comments. Matches published version | Class. Quantum Grav. 32, 015019 (2015) | 10.1088/0264-9381/32/1/015019 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a model which allows the fine structure constant (alpha) to vary
throughout space and time due to a coupling to a scalar field with a
non-canonical kinetic structure. This provided a new extension of the
Bekenstein-Sandvik-Barrow-Magueijo model of alpha variations. The background
cosmology is studied in detail using dynamical systems techniques for a scalar
field of ghost condensate type. We show generically that if the kinetic terms
are chosen to allow an accelerated late-time attractor for the expansion scale
factor then alpha will not asymptote to a constant at late times.
| [
{
"created": "Tue, 12 Aug 2014 17:54:11 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Jan 2015 17:33:22 GMT",
"version": "v2"
}
] | 2015-01-20 | [
[
"Graham",
"Alexander A. H.",
""
]
] | We introduce a model which allows the fine structure constant (alpha) to vary throughout space and time due to a coupling to a scalar field with a non-canonical kinetic structure. This provided a new extension of the Bekenstein-Sandvik-Barrow-Magueijo model of alpha variations. The background cosmology is studied in detail using dynamical systems techniques for a scalar field of ghost condensate type. We show generically that if the kinetic terms are chosen to allow an accelerated late-time attractor for the expansion scale factor then alpha will not asymptote to a constant at late times. |
1607.02476 | Luis L\'opez | N. Breton and L. A. Lopez | Quasinormal modes of nonlinear electromagnetic black holes from unstable
null geodesics | null | Phys. Rev. D 94, 104008 (2016) | 10.1103/PhysRevD.94.104008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The expressions for the quasinormal modes (QNMs) of black holes with
nonlinear electrodynamics, calculated in the eikonal approximation, are
presented. In the eikonal limit QNMs of black holes are determined by the
parameters of the circular null geodesics. The unstable circular null orbits
are derived from the effective metric that is the one obeyed by light rays
under the influence of a nonlinear electromagnetic field. As an illustration we
calculate the QNMs of four nonlinear electromagnetic black holes, two singular
and two regular, namely from Euler-Heisenberg and Born-Infeld theories, for
singular, and the magnetic Bardeen black hole and the one derived by Bronnikov
for regular ones. Comparison is shown with the QNMs of the linear
electromagnetic counterpart, their Reissner-Nordstr\"{o}m black hole.
| [
{
"created": "Fri, 8 Jul 2016 18:05:19 GMT",
"version": "v1"
}
] | 2016-11-09 | [
[
"Breton",
"N.",
""
],
[
"Lopez",
"L. A.",
""
]
] | The expressions for the quasinormal modes (QNMs) of black holes with nonlinear electrodynamics, calculated in the eikonal approximation, are presented. In the eikonal limit QNMs of black holes are determined by the parameters of the circular null geodesics. The unstable circular null orbits are derived from the effective metric that is the one obeyed by light rays under the influence of a nonlinear electromagnetic field. As an illustration we calculate the QNMs of four nonlinear electromagnetic black holes, two singular and two regular, namely from Euler-Heisenberg and Born-Infeld theories, for singular, and the magnetic Bardeen black hole and the one derived by Bronnikov for regular ones. Comparison is shown with the QNMs of the linear electromagnetic counterpart, their Reissner-Nordstr\"{o}m black hole. |
1702.04916 | Abdulla Al Mamon | Abdulla Al Mamon | Constraints on a generalized deceleration parameter from cosmic
chronometers | 9 pages, 5 figures, minor change in title, new references added,
revised version accepted for publication in MPLA | null | 10.1142/S0217732318500566 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have proposed a generalized parametrization for the
deceleration parameter $q$ in order to study the evolutionary history of the
universe. We have shown that the proposed model can reproduce three well known
$q$-parametrized models for some specific values of the model parameter
$\alpha$. We have used the latest compilation of the Hubble parameter
measurements obtained from the cosmic chronometer (CC) method (in combination
with the local value of the Hubble constant $H_{0}$) and the Type Ia supernova
(SNIa) data to place constraints on the parameters of the model for different
values of $\alpha$. We have found that the resulting constraints on the
deceleration parameter and the dark energy equation of state support the
$\Lambda$CDM model within $1\sigma$ confidence level at the present epoch.
| [
{
"created": "Thu, 16 Feb 2017 10:34:17 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Mar 2018 19:36:04 GMT",
"version": "v2"
}
] | 2018-04-25 | [
[
"Mamon",
"Abdulla Al",
""
]
] | In this paper, we have proposed a generalized parametrization for the deceleration parameter $q$ in order to study the evolutionary history of the universe. We have shown that the proposed model can reproduce three well known $q$-parametrized models for some specific values of the model parameter $\alpha$. We have used the latest compilation of the Hubble parameter measurements obtained from the cosmic chronometer (CC) method (in combination with the local value of the Hubble constant $H_{0}$) and the Type Ia supernova (SNIa) data to place constraints on the parameters of the model for different values of $\alpha$. We have found that the resulting constraints on the deceleration parameter and the dark energy equation of state support the $\Lambda$CDM model within $1\sigma$ confidence level at the present epoch. |
1510.03131 | Sergei Kopeikin | Sergei Kopeikin (University of Missouri, USA), Wenbiao Han (Shanghai
Astronomical Observatory), Elena Mazurova (Siberian State University of
Geosystems and Technologies, Russia) | Post-Newtonian reference-ellipsoid for relativistic geodesy | 32 pages, 2 figures, 71 references. Text improved and extended, one
more figure included | Phys. Rev. D 93, 044069 (2016) | 10.1103/PhysRevD.93.044069 | null | gr-qc math-ph math.MP physics.geo-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply general relativity to construct the post-Newtonian background
manifold that serves as a reference spacetime in relativistic geodesy for
conducting relativistic calculation of the geoid's undulation and the
deflection of the plumb line from the vertical. We chose an axisymmetric
ellipsoidal body made up of perfect homogeneous fluid uniformly rotating around
a fixed axis, as a source generating the reference geometry. We, then,
reformulate and extend hydrodynamic calculations of rotating fluids done by
previous researchers to the realm of relativistic geodesy to set up algebraic
equations defining the shape of the post-Newtonian reference ellipsoid. To
complete this task, we explicitly perform all integrals characterizing
gravitational field inside the fluid body and represent them in terms of the
elementary functions depending on its eccentricity. We fully explore the
coordinate freedom of the equations describing the post-Newtonian ellipsoid and
demonstrate that the fractional deviation of the post-Newtonian level surface
from the Maclaurin ellipsoid can be made much smaller than the previously
anticipated estimate based on the coordinate gauge advocated by Bardeen and
Chandrasekhar. We also derive the gauge-invariant relations of the
post-Newtonian mass and the angular velocity of the rotating fluid with the
parameters characterizing the shape of the post-Newtonian ellipsoid. We
formulate the post-Newtonian theorems of Pizzetti and Clairaut that are used in
geodesy to connect the geometric parameters of the reference ellipsoid to the
physically measurable force of gravity at the pole and equator. Finally, we
expand the post-Newtonian geodetic equations to the Taylor series with respect
to the eccentricity of the ellipsoid and discuss their practical applications.
| [
{
"created": "Mon, 12 Oct 2015 03:55:16 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Jan 2016 23:36:32 GMT",
"version": "v2"
}
] | 2016-03-02 | [
[
"Kopeikin",
"Sergei",
"",
"University of Missouri, USA"
],
[
"Han",
"Wenbiao",
"",
"Shanghai\n Astronomical Observatory"
],
[
"Mazurova",
"Elena",
"",
"Siberian State University of\n Geosystems and Technologies, Russia"
]
] | We apply general relativity to construct the post-Newtonian background manifold that serves as a reference spacetime in relativistic geodesy for conducting relativistic calculation of the geoid's undulation and the deflection of the plumb line from the vertical. We chose an axisymmetric ellipsoidal body made up of perfect homogeneous fluid uniformly rotating around a fixed axis, as a source generating the reference geometry. We, then, reformulate and extend hydrodynamic calculations of rotating fluids done by previous researchers to the realm of relativistic geodesy to set up algebraic equations defining the shape of the post-Newtonian reference ellipsoid. To complete this task, we explicitly perform all integrals characterizing gravitational field inside the fluid body and represent them in terms of the elementary functions depending on its eccentricity. We fully explore the coordinate freedom of the equations describing the post-Newtonian ellipsoid and demonstrate that the fractional deviation of the post-Newtonian level surface from the Maclaurin ellipsoid can be made much smaller than the previously anticipated estimate based on the coordinate gauge advocated by Bardeen and Chandrasekhar. We also derive the gauge-invariant relations of the post-Newtonian mass and the angular velocity of the rotating fluid with the parameters characterizing the shape of the post-Newtonian ellipsoid. We formulate the post-Newtonian theorems of Pizzetti and Clairaut that are used in geodesy to connect the geometric parameters of the reference ellipsoid to the physically measurable force of gravity at the pole and equator. Finally, we expand the post-Newtonian geodetic equations to the Taylor series with respect to the eccentricity of the ellipsoid and discuss their practical applications. |
1003.1014 | Isabel Cordero-Carri\'on | Isabel Cordero-Carri\'on, Jos\'e Mar\'ia Ib\'a\~nez and Juan Antonio
Morales-Lladosa | On the local existence of maximal slicings in spherically symmetric
spacetimes | 4 pages. Accepted for publication in Journal of Physics: Conference
Series, Proceedings of the Spanish Relativity Meeting ERE2009 | null | 10.1088/1742-6596/229/1/012029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this talk we show that any spherically symmetric spacetime admits locally
a maximal spacelike slicing. The above condition is reduced to solve a
decoupled system of first order quasi-linear partial differential equations.
The solution may be accomplished analytical or numerically. We provide a
general procedure to construct such maximal slicings.
| [
{
"created": "Thu, 4 Mar 2010 10:56:00 GMT",
"version": "v1"
}
] | 2015-05-18 | [
[
"Cordero-Carrión",
"Isabel",
""
],
[
"Ibáñez",
"José María",
""
],
[
"Morales-Lladosa",
"Juan Antonio",
""
]
] | In this talk we show that any spherically symmetric spacetime admits locally a maximal spacelike slicing. The above condition is reduced to solve a decoupled system of first order quasi-linear partial differential equations. The solution may be accomplished analytical or numerically. We provide a general procedure to construct such maximal slicings. |
1502.04953 | Bela Szilagyi | Bela Szilagyi, Jonathan Blackman, Alessandra Buonanno, Andrea
Taracchini, Harald P. Pfeiffer, Mark A. Scheel, Tony Chu, Lawrence E. Kidder
and Yi Pan | Numerical relativity reaching into post-Newtonian territory: a
compact-object binary simulation spanning 350 gravitational-wave cycles | null | Phys. Rev. Lett. 115, 031102 (2015) | 10.1103/PhysRevLett.115.031102 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first numerical-relativity simulation of a compact-object
binary whose gravitational waveform is long enough to cover the entire
frequency band of advanced gravitational-wave detectors, such as LIGO, Virgo
and KAGRA, for mass ratio 7 and total mass as low as $45.5\,M_\odot$. We find
that effective-one-body models, either uncalibrated or calibrated against
substantially shorter numerical-relativity waveforms at smaller mass ratios,
reproduce our new waveform remarkably well, with a negligible loss in detection
rate due to modeling error. In contrast, post-Newtonian inspiral waveforms and
existing calibrated phenomenological inspiral-merger-ringdown waveforms display
greater disagreement with our new simulation. The disagreement varies
substantially depending on the specific post-Newtonian approximant used.
| [
{
"created": "Tue, 17 Feb 2015 16:32:34 GMT",
"version": "v1"
}
] | 2015-07-22 | [
[
"Szilagyi",
"Bela",
""
],
[
"Blackman",
"Jonathan",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Taracchini",
"Andrea",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Chu",
"Tony",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Pan",
"Yi",
""
]
] | We present the first numerical-relativity simulation of a compact-object binary whose gravitational waveform is long enough to cover the entire frequency band of advanced gravitational-wave detectors, such as LIGO, Virgo and KAGRA, for mass ratio 7 and total mass as low as $45.5\,M_\odot$. We find that effective-one-body models, either uncalibrated or calibrated against substantially shorter numerical-relativity waveforms at smaller mass ratios, reproduce our new waveform remarkably well, with a negligible loss in detection rate due to modeling error. In contrast, post-Newtonian inspiral waveforms and existing calibrated phenomenological inspiral-merger-ringdown waveforms display greater disagreement with our new simulation. The disagreement varies substantially depending on the specific post-Newtonian approximant used. |
gr-qc/0503004 | Arunava Bhadra Dr. | Arunava Bhadra and Kabita Sarkar | Wormholes in vacuum Brans-Dicke theory | 13 pages, accepted by Mod. Phys. Letts. A, typos in references
corrected | Mod.Phys.Lett.A20:1831-1844,2005 | 10.1142/S0217732305016889 | null | gr-qc | null | It is shown that among the different classes of claimed static wormhole
solutions of the vacuum Brans-Dicke theory only Brans Class I solution with
coupling constant $\omega$ less than -1.5 (excluding the point $\omega =2$)
gives rise to physically viable traversable wormhole geometry. Usability of
this wormhole geometry for interstellar travel has been examined.
| [
{
"created": "Tue, 1 Mar 2005 17:32:14 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Feb 2006 08:06:06 GMT",
"version": "v2"
}
] | 2011-07-19 | [
[
"Bhadra",
"Arunava",
""
],
[
"Sarkar",
"Kabita",
""
]
] | It is shown that among the different classes of claimed static wormhole solutions of the vacuum Brans-Dicke theory only Brans Class I solution with coupling constant $\omega$ less than -1.5 (excluding the point $\omega =2$) gives rise to physically viable traversable wormhole geometry. Usability of this wormhole geometry for interstellar travel has been examined. |
gr-qc/0006049 | Fredrik Stahl | Fredrik St{\aa}hl | The Geometry of the Frame Bundle over Spacetime | 14 pages, no figures, LaTeX 2e with AMSLaTeX 1.2 and AMSFonts,
submitted to J. Math. Phys | null | null | null | gr-qc | null | One of the known mathematical descriptions of singularities in General
Relativity is the b-boundary, which is a way of attaching endpoints to
inextendible endless curves in a spacetime. The b-boundary of a manifold M with
connection is constructed by forming the Cauchy completion of the frame bundle
LM equipped with a certain Riemannian metric, the b-metric G. We study the
geometry of (LM,G) as a Riemannian manifold in the case when the connection is
the Levi-Civita connection of a Lorentzian metric g on M. In particular, we
give expressions for the curvature and discuss the isometries and the geodesics
of (LM,G) in relation to the geometry of (M,g).
| [
{
"created": "Tue, 13 Jun 2000 21:09:35 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ståhl",
"Fredrik",
""
]
] | One of the known mathematical descriptions of singularities in General Relativity is the b-boundary, which is a way of attaching endpoints to inextendible endless curves in a spacetime. The b-boundary of a manifold M with connection is constructed by forming the Cauchy completion of the frame bundle LM equipped with a certain Riemannian metric, the b-metric G. We study the geometry of (LM,G) as a Riemannian manifold in the case when the connection is the Levi-Civita connection of a Lorentzian metric g on M. In particular, we give expressions for the curvature and discuss the isometries and the geodesics of (LM,G) in relation to the geometry of (M,g). |
2301.08743 | Shibesh Kumar Jas Pacif | Keshav Ram Mishra, Shibesh Kumar Jas Pacif, Rajesh Kumar, Kazuharu
Bamba | Cosmological implications of an interacting model of dark matter \& dark
energy | arXiv admin note: text overlap with arXiv:1903.08562 by other authors | Physics of the Dark Universe Volume 40, 101211, May 2023 | 10.1016/j.dark.2023.101211 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have studied an interacting dark energy model. We have
assumed the gravitational interaction between the matter fields i.e. between
barotropic fluid and the dark energy. The dark energy evolution within the
framework of spatially homogeneous and isotropic Friedmann-Robertson-Walker
space-time. Therefore, we examine the cosmic evolution from the perspective of
interacting scenario by selecting a suitable ansatz for the scale factor
resulting from a parametrization of Hubble parameter. The evolution of the
cosmological parameters are discussed in some details in the considered
interacting scenario by calculating parameters and quantities such as
deceleration parameter, energy density, pressure, equation of state (EoS) etc.
Also, we have performed some cosmological tests and analysis in support of our
obtained interacting model. Finally, we reconstruct the potential of the scalar
field and refute the refined swampland conjecture using the equation of state
of dark energy and the relationship between energy density and pressure with
the scalar field and potential, and then thoroughly describe the findings.
| [
{
"created": "Thu, 19 Jan 2023 21:19:03 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Mar 2023 18:39:09 GMT",
"version": "v2"
},
{
"created": "Thu, 30 Mar 2023 18:35:09 GMT",
"version": "v3"
}
] | 2023-04-03 | [
[
"Mishra",
"Keshav Ram",
""
],
[
"Pacif",
"Shibesh Kumar Jas",
""
],
[
"Kumar",
"Rajesh",
""
],
[
"Bamba",
"Kazuharu",
""
]
] | In this paper, we have studied an interacting dark energy model. We have assumed the gravitational interaction between the matter fields i.e. between barotropic fluid and the dark energy. The dark energy evolution within the framework of spatially homogeneous and isotropic Friedmann-Robertson-Walker space-time. Therefore, we examine the cosmic evolution from the perspective of interacting scenario by selecting a suitable ansatz for the scale factor resulting from a parametrization of Hubble parameter. The evolution of the cosmological parameters are discussed in some details in the considered interacting scenario by calculating parameters and quantities such as deceleration parameter, energy density, pressure, equation of state (EoS) etc. Also, we have performed some cosmological tests and analysis in support of our obtained interacting model. Finally, we reconstruct the potential of the scalar field and refute the refined swampland conjecture using the equation of state of dark energy and the relationship between energy density and pressure with the scalar field and potential, and then thoroughly describe the findings. |
gr-qc/0508059 | Thomas Buchert | Thomas Buchert | An exact Lagrangian integral for the Newtonian gravitational field
strength | 15 pages, section on applications added; matches published version in
Phys.Lett.A | Phys.Lett. A354 (2006) 8-14 | 10.1016/j.physleta.2006.01.045 | null | gr-qc astro-ph math-ph math.MP | null | An exact expression for the gravitational field strength in a
self-gravitating dust continuum is derived within the Lagrangian picture of
continuum mechanics. From the Euler-Newton system a transport equation for the
gravitational field strength is formulated and then integrated along
trajectories of continuum elements. The resulting integral solves one of the
Lagrangian equations of the corresponding Lagrange-Newton system in general.
Relations to known exact solutions without symmetry in Newtonian gravity are
discussed. The presented integral may be employed to access the
non-perturbative regime of structure formation in Newtonian cosmology, and to
apply iterative Lagrangian schemes to solve the Lagrange-Newton system.
| [
{
"created": "Mon, 15 Aug 2005 12:50:40 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Dec 2005 17:35:26 GMT",
"version": "v2"
},
{
"created": "Mon, 23 Jan 2006 18:49:32 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Buchert",
"Thomas",
""
]
] | An exact expression for the gravitational field strength in a self-gravitating dust continuum is derived within the Lagrangian picture of continuum mechanics. From the Euler-Newton system a transport equation for the gravitational field strength is formulated and then integrated along trajectories of continuum elements. The resulting integral solves one of the Lagrangian equations of the corresponding Lagrange-Newton system in general. Relations to known exact solutions without symmetry in Newtonian gravity are discussed. The presented integral may be employed to access the non-perturbative regime of structure formation in Newtonian cosmology, and to apply iterative Lagrangian schemes to solve the Lagrange-Newton system. |
0904.3377 | M Hossain Ali | M. Hossain Ali and M. Khayrul Hasan | Dispersion Relations for Cold Plasmas around Reissner-Nordstr\"om Black
Holes | 25 pages, 9 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the general relativistic magnetohydrodynamic (GRMHD) equations
for cold plasma around the Reissner-Nordstr\"om black hole. Applying 3+1
spacetime split we linearize the perturbed equations for
non-magnetized/magnetized plasma in both rotating and non-rotating background.
By Fourier analyze we then derive dispersion relations and investigate the
existence of waves with positive angular frequency in the vicinity of the black
hole horizon. The analysis finds propagation of negative phase and group
velocities for rotating magnetized surroundings.
| [
{
"created": "Wed, 22 Apr 2009 03:06:24 GMT",
"version": "v1"
}
] | 2009-04-23 | [
[
"Ali",
"M. Hossain",
""
],
[
"Hasan",
"M. Khayrul",
""
]
] | We investigate the general relativistic magnetohydrodynamic (GRMHD) equations for cold plasma around the Reissner-Nordstr\"om black hole. Applying 3+1 spacetime split we linearize the perturbed equations for non-magnetized/magnetized plasma in both rotating and non-rotating background. By Fourier analyze we then derive dispersion relations and investigate the existence of waves with positive angular frequency in the vicinity of the black hole horizon. The analysis finds propagation of negative phase and group velocities for rotating magnetized surroundings. |
1711.07966 | Daniel George | Daniel George and E. A. Huerta | Deep Learning for Real-time Gravitational Wave Detection and Parameter
Estimation with LIGO Data | Camera-ready (final) version accepted to NIPS 2017 conference
workshop on Deep Learning for Physical Sciences and selected for contributed
talk. Also awarded 1st place at ACM SRC at SC17. Extended article:
arXiv:1711.03121 | null | null | null | gr-qc astro-ph.HE astro-ph.IM cs.LG cs.NE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent Nobel-prize-winning detections of gravitational waves from merging
black holes and the subsequent detection of the collision of two neutron stars
in coincidence with electromagnetic observations have inaugurated a new era of
multimessenger astrophysics. To enhance the scope of this emergent science, we
proposed the use of deep convolutional neural networks for the detection and
characterization of gravitational wave signals in real-time. This method, Deep
Filtering, was initially demonstrated using simulated LIGO noise. In this
article, we present the extension of Deep Filtering using real data from the
first observing run of LIGO, for both detection and parameter estimation of
gravitational waves from binary black hole mergers with continuous data streams
from multiple LIGO detectors. We show for the first time that machine learning
can detect and estimate the true parameters of a real GW event observed by
LIGO. Our comparisons show that Deep Filtering is far more computationally
efficient than matched-filtering, while retaining similar sensitivity and lower
errors, allowing real-time processing of weak time-series signals in
non-stationary non-Gaussian noise, with minimal resources, and also enables the
detection of new classes of gravitational wave sources that may go unnoticed
with existing detection algorithms. This approach is uniquely suited to enable
coincident detection campaigns of gravitational waves and their multimessenger
counterparts in real-time.
| [
{
"created": "Tue, 21 Nov 2017 18:45:01 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Dec 2017 19:36:44 GMT",
"version": "v2"
}
] | 2017-12-13 | [
[
"George",
"Daniel",
""
],
[
"Huerta",
"E. A.",
""
]
] | The recent Nobel-prize-winning detections of gravitational waves from merging black holes and the subsequent detection of the collision of two neutron stars in coincidence with electromagnetic observations have inaugurated a new era of multimessenger astrophysics. To enhance the scope of this emergent science, we proposed the use of deep convolutional neural networks for the detection and characterization of gravitational wave signals in real-time. This method, Deep Filtering, was initially demonstrated using simulated LIGO noise. In this article, we present the extension of Deep Filtering using real data from the first observing run of LIGO, for both detection and parameter estimation of gravitational waves from binary black hole mergers with continuous data streams from multiple LIGO detectors. We show for the first time that machine learning can detect and estimate the true parameters of a real GW event observed by LIGO. Our comparisons show that Deep Filtering is far more computationally efficient than matched-filtering, while retaining similar sensitivity and lower errors, allowing real-time processing of weak time-series signals in non-stationary non-Gaussian noise, with minimal resources, and also enables the detection of new classes of gravitational wave sources that may go unnoticed with existing detection algorithms. This approach is uniquely suited to enable coincident detection campaigns of gravitational waves and their multimessenger counterparts in real-time. |
2105.06090 | Hwajin Eom | Hwajin Eom, Wontae Kim | Quantum radiation of a collapsing shell in three-dimensional AdS
spacetime revisited | 15 pages, 1 figure, references and comments are added, published
version in JHEP | null | 10.1007/JHEP07(2021)108 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In three-dimensional AdS space, we consider the gravitational collapse of
dust shell and then investigate the quantum radiation from the collapsing shell
by employing the functional Schr\"odinger formalism. In the formation of the
BTZ black hole, the interior geometry of the shell can be chosen as either the
massless black hole or the global AdS space. In the incipient black hole limit,
we obtain the wave function exactly from the time-dependent Schr\"odinger
equation for a massless scalar field. Then, we show that the occupation number
of excited states can be written by analytic expressions, and the radiation
temperature is in agreement with the Hawking temperature, irrespective of the
specific choice of the interior geometries.
| [
{
"created": "Thu, 13 May 2021 05:39:18 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Jul 2021 08:32:23 GMT",
"version": "v2"
}
] | 2021-07-21 | [
[
"Eom",
"Hwajin",
""
],
[
"Kim",
"Wontae",
""
]
] | In three-dimensional AdS space, we consider the gravitational collapse of dust shell and then investigate the quantum radiation from the collapsing shell by employing the functional Schr\"odinger formalism. In the formation of the BTZ black hole, the interior geometry of the shell can be chosen as either the massless black hole or the global AdS space. In the incipient black hole limit, we obtain the wave function exactly from the time-dependent Schr\"odinger equation for a massless scalar field. Then, we show that the occupation number of excited states can be written by analytic expressions, and the radiation temperature is in agreement with the Hawking temperature, irrespective of the specific choice of the interior geometries. |
gr-qc/0209069 | Dilek Ciftci | Metin Arik, Dilek Ciftci | A Finslerian Cosmological Metric and its Riemannian Kaluza-Klein
Extension | 5 pages | Grav.Cosmol.9:259-261,2003 | null | null | gr-qc | null | In this study a rotationally and translationally invariant metric in Finsler
space is investigated. We choose to rewrite the metric in Riemanian space by
increasing the dimension of space-time and introducing additional coordinates
such that for specific values of these coordinates, the geodesics of the four
dimensional Finslerian space-time and six dimensional Riemanian space-time are
identical. Cosmological solutions described by this metric give rise to an
equation of state corresponding to a space dominated by domain walls and an
internal space dominated by strings.
| [
{
"created": "Fri, 20 Sep 2002 12:30:51 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Arik",
"Metin",
""
],
[
"Ciftci",
"Dilek",
""
]
] | In this study a rotationally and translationally invariant metric in Finsler space is investigated. We choose to rewrite the metric in Riemanian space by increasing the dimension of space-time and introducing additional coordinates such that for specific values of these coordinates, the geodesics of the four dimensional Finslerian space-time and six dimensional Riemanian space-time are identical. Cosmological solutions described by this metric give rise to an equation of state corresponding to a space dominated by domain walls and an internal space dominated by strings. |
1312.0254 | Piotr T. Chru\'sciel | Piotr T. Chrusciel | Boundary conditions at spatial infinity from a Hamiltonian point of view | Published in "Topological Properties and Global Structure of
Space-Time", ed. by P. Bergmann, V. de Sabbata, pp. 49-59, Plenum Press, New
York 1986 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the ADM mass and momentum are geometric invariants of
asymptotically flat initial data sets
| [
{
"created": "Sun, 1 Dec 2013 17:54:12 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Dec 2013 16:25:43 GMT",
"version": "v2"
}
] | 2013-12-09 | [
[
"Chrusciel",
"Piotr T.",
""
]
] | We show that the ADM mass and momentum are geometric invariants of asymptotically flat initial data sets |
gr-qc/0611002 | Paul Lasky | P. D. Lasky and A. W. C. Lun | Spherically Symmetric Gravitational Collapse of Perfect Fluids | 3 pages, To appear in the proceedings of the eleventh Marcel
Grossmann meeting on general relativity (MGXI), 23-29 July, 2006, Berlin | null | null | null | gr-qc | null | Formulating a perfect fluid filled spherically symmetric metric utilizing the
3+1 formalism for general relativity, we show that the metric coefficients are
completely determined by the mass-energy distribution, and its time rate of
change on an initial spacelike hypersurface. Rather than specifying
Schwarzschild coordinates for the exterior of the collapsing region, we let the
interior dictate the form of the solution in the exterior, and thus both
regions are found to be written in one coordinate patch. This not only
alleviates the need for complicated matching schemes at the interface, but also
finds a new coordinate system for the Schwarzschild spacetime expressed in
generalized Painleve-Gullstrand coordinates.
| [
{
"created": "Tue, 31 Oct 2006 22:36:43 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Lasky",
"P. D.",
""
],
[
"Lun",
"A. W. C.",
""
]
] | Formulating a perfect fluid filled spherically symmetric metric utilizing the 3+1 formalism for general relativity, we show that the metric coefficients are completely determined by the mass-energy distribution, and its time rate of change on an initial spacelike hypersurface. Rather than specifying Schwarzschild coordinates for the exterior of the collapsing region, we let the interior dictate the form of the solution in the exterior, and thus both regions are found to be written in one coordinate patch. This not only alleviates the need for complicated matching schemes at the interface, but also finds a new coordinate system for the Schwarzschild spacetime expressed in generalized Painleve-Gullstrand coordinates. |
0910.4677 | Federico Piazza | Federico Piazza | New views on the low-energy side of gravity | Review based on talks given at DICE (Castiglioncello) 2008, Emergent
gravity III (Boston 2008) and IV (Vancouver 2009), New Prospects for Solving
the Cosmological Constant Problem (Perimeter Institute 2009) and several
other more or less informal discussions. 51 pages, 2 figures. References
added | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Common wisdom associates all the unraveled and theoretically challenging
aspects of gravity with its UV-completion. However, there appear to be few
difficulties afflicting the effective framework for gravity already at low
energy, that are likely to be detached from the high-energy structure. Those
include the black hole information paradox, the cosmological constant problem
and the rather involved and fine tuned model building required to explain our
cosmological observations. I review some on-going research that aims to
generalize and extend the low-energy framework for gravity. In a quantum
informational fashion, regions of space at a given time are treated and
described as quantum subsystems, rather than submanifolds. The idea is to
define a region of space through the quantum degrees of freedom of the matter
fields "living therein". I show how the correspondence sub-system/sub-manifold
is realized in standard semi-classical gravity ("standard localization") and
discuss the implications of alternative localization schemes. By exploiting
further the subsystem description, I then consider the possibility that the
usual GR metric manifold description might break down in the infra-red. This
has implications on the description of the Universe on the largest scales and
on dark energy.
| [
{
"created": "Mon, 26 Oct 2009 19:59:48 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Oct 2009 21:36:35 GMT",
"version": "v2"
},
{
"created": "Wed, 20 Jan 2010 18:35:12 GMT",
"version": "v3"
}
] | 2010-01-20 | [
[
"Piazza",
"Federico",
""
]
] | Common wisdom associates all the unraveled and theoretically challenging aspects of gravity with its UV-completion. However, there appear to be few difficulties afflicting the effective framework for gravity already at low energy, that are likely to be detached from the high-energy structure. Those include the black hole information paradox, the cosmological constant problem and the rather involved and fine tuned model building required to explain our cosmological observations. I review some on-going research that aims to generalize and extend the low-energy framework for gravity. In a quantum informational fashion, regions of space at a given time are treated and described as quantum subsystems, rather than submanifolds. The idea is to define a region of space through the quantum degrees of freedom of the matter fields "living therein". I show how the correspondence sub-system/sub-manifold is realized in standard semi-classical gravity ("standard localization") and discuss the implications of alternative localization schemes. By exploiting further the subsystem description, I then consider the possibility that the usual GR metric manifold description might break down in the infra-red. This has implications on the description of the Universe on the largest scales and on dark energy. |
1905.02967 | Tomi Koivisto | Tomi Koivisto, Manuel Hohmann, Tom Z{\l}o\'snik | The General Linear Cartan Khronon | 6 pages, no figures. Contribution to the proceedings of the
conference "Teleparallel Universes in Salamanca" | Universe 2019, 5(7), 168 | 10.3390/universe5070168 | NORDITA 2019-045 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A Cartan geometry of the General Linear symmetry is formulated by dividing
out the displacements from the group. The resulting action is quadratic in
curvature, polynomial in all the (minimal) variables, and describes an observer
space that, in the symmetry-broken phase, reproduces the predictions of General
Relativity in the presence of dark matter.
| [
{
"created": "Wed, 8 May 2019 09:12:03 GMT",
"version": "v1"
}
] | 2021-04-02 | [
[
"Koivisto",
"Tomi",
""
],
[
"Hohmann",
"Manuel",
""
],
[
"Złośnik",
"Tom",
""
]
] | A Cartan geometry of the General Linear symmetry is formulated by dividing out the displacements from the group. The resulting action is quadratic in curvature, polynomial in all the (minimal) variables, and describes an observer space that, in the symmetry-broken phase, reproduces the predictions of General Relativity in the presence of dark matter. |
1307.4122 | Mauricio Cataldo MC | Mauricio Cataldo, Sebastian Bahamonde and Fernanda Arostica | (N+1)-dimensional Lorentzian evolving wormholes supported by polytropic
matter | 6 pages, 2 figures, accepted for publication in European Physical
Journal C | Eur. Phys. J. C 73, 2517 (2013) | 10.1140/epjc/s10052-013-2517-4 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study $(N+1)$-dimensional evolving wormholes supported by
energy satisfying a polytropic equation of state. The considered evolving
wormhole models are described by a constant redshift function and generalizes
the standard flat Friedmann-Robertson-Walker spacetime. The polytropic equation
of state allows us to consider in $(3+1)$-dimensions generalizations of the
phantom energy and the generalized Chaplygin gas sources.
| [
{
"created": "Mon, 15 Jul 2013 22:42:46 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Cataldo",
"Mauricio",
""
],
[
"Bahamonde",
"Sebastian",
""
],
[
"Arostica",
"Fernanda",
""
]
] | In this paper we study $(N+1)$-dimensional evolving wormholes supported by energy satisfying a polytropic equation of state. The considered evolving wormhole models are described by a constant redshift function and generalizes the standard flat Friedmann-Robertson-Walker spacetime. The polytropic equation of state allows us to consider in $(3+1)$-dimensions generalizations of the phantom energy and the generalized Chaplygin gas sources. |
gr-qc/0310125 | Leor Barack | Leor Barack and Curt Cutler | LISA Capture Sources: Approximate Waveforms, Signal-to-Noise Ratios, and
Parameter Estimation Accuracy | 34 pages, 27 eps figures; corrected factor 3/4 error in some formulae
for S_h | Phys.Rev. D69 (2004) 082005 | 10.1103/PhysRevD.69.082005 | null | gr-qc astro-ph | null | Captures of stellar-mass compact objects (COs) by massive ($\sim 10^6
M_\odot$) black holes (MBHs) are potentially an important source for LISA, the
proposed space-based gravitational-wave (GW) detector. The orbits of the
inspiraling COs are highly complicated; they can remain rather eccentric up
until the final plunge, and display extreme versions of relativistic perihelion
precession and Lense-Thirring precession of the orbital plane. The strongest
capture signals will be ~10 times weaker than LISA's instrumental noise, but in
principle (with sufficient computing power) they can be disentangled from the
noise by matched filtering. The associated template waveforms are not yet in
hand, but theorists will very likely be able to provide them before LISA
launches. Here we introduce a family of approximate (post-Newtonian) capture
waveforms, given in (nearly) analytic form, for use in advancing LISA studies
until more accurate versions are available. Our model waveforms include most of
the key qualitative features of true waveforms, and cover the full space of
capture-event parameters (including orbital eccentricity and the MBH's spin).
Here we use our approximate waveforms to (i) estimate the relative
contributions of different harmonics (of the orbital frequency) to the total
signal-to-noise ratio, and (ii) estimate the accuracy with which LISA will be
able to extract the physical parameters of the capture event from the measured
waveform. For a typical source (a $10 M_\odot$ CO captured by a $10^6 M_\odot$
MBH at a signal-to-noise ratio of 30), we find that LISA can determine the MBH
and CO masses to within a fractional error of $\sim 10^{-4}$, measure $S/M^2$
(where $S$ and $M$ are the MBH's mass and spin) to within $\sim 10^{-4}$, and
determine the sky location of the source to within $\sim 10^{-3}$ stradians.
| [
{
"created": "Thu, 30 Oct 2003 01:27:41 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Jan 2004 20:38:53 GMT",
"version": "v2"
},
{
"created": "Thu, 2 Sep 2004 09:29:13 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Barack",
"Leor",
""
],
[
"Cutler",
"Curt",
""
]
] | Captures of stellar-mass compact objects (COs) by massive ($\sim 10^6 M_\odot$) black holes (MBHs) are potentially an important source for LISA, the proposed space-based gravitational-wave (GW) detector. The orbits of the inspiraling COs are highly complicated; they can remain rather eccentric up until the final plunge, and display extreme versions of relativistic perihelion precession and Lense-Thirring precession of the orbital plane. The strongest capture signals will be ~10 times weaker than LISA's instrumental noise, but in principle (with sufficient computing power) they can be disentangled from the noise by matched filtering. The associated template waveforms are not yet in hand, but theorists will very likely be able to provide them before LISA launches. Here we introduce a family of approximate (post-Newtonian) capture waveforms, given in (nearly) analytic form, for use in advancing LISA studies until more accurate versions are available. Our model waveforms include most of the key qualitative features of true waveforms, and cover the full space of capture-event parameters (including orbital eccentricity and the MBH's spin). Here we use our approximate waveforms to (i) estimate the relative contributions of different harmonics (of the orbital frequency) to the total signal-to-noise ratio, and (ii) estimate the accuracy with which LISA will be able to extract the physical parameters of the capture event from the measured waveform. For a typical source (a $10 M_\odot$ CO captured by a $10^6 M_\odot$ MBH at a signal-to-noise ratio of 30), we find that LISA can determine the MBH and CO masses to within a fractional error of $\sim 10^{-4}$, measure $S/M^2$ (where $S$ and $M$ are the MBH's mass and spin) to within $\sim 10^{-4}$, and determine the sky location of the source to within $\sim 10^{-3}$ stradians. |
1402.4161 | Jorge Rocha | Jorge V. Rocha, Raphael Santarelli and T\'erence Delsate | Collapsing rotating shells in Myers-Perry-AdS$_5$ spacetime: A
perturbative approach | 13 pages, 1 figure, uses revtex4; v2: typos corrected, minor addition
regarding the one-point function of boundary stress-energy tensor, matches
published version | Phys. Rev. D 89, 104006 (2014) | 10.1103/PhysRevD.89.104006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study gravitational perturbations sourced by a rotating test shell
collapsing into five-dimensional Myers-Perry black holes in anti-de Sitter
(AdS). Our attention is restricted to the case in which the two possible
angular momenta of the geometry are set equal. In this situation the background
is cohomogeneity-1, which amounts to a crucial technical simplification. It is
found that the linearized Einstein equations are consistent only when the test
shell is corotating with the spacetime. However, it is argued that this is a
consequence of the matter on the shell being described by dust or, more
precisely, noninteracting test particles. We compute the mass and angular
momenta of the perturbed spacetime using a counterterm subtraction method, for
which we provide an explicit formula that has not appeared previously in the
literature. The results are in agreement with the expected expressions for
energy and angular momenta of geodesic particles in AdS$_5$.
| [
{
"created": "Mon, 17 Feb 2014 22:00:08 GMT",
"version": "v1"
},
{
"created": "Fri, 23 May 2014 10:28:53 GMT",
"version": "v2"
}
] | 2014-05-26 | [
[
"Rocha",
"Jorge V.",
""
],
[
"Santarelli",
"Raphael",
""
],
[
"Delsate",
"Térence",
""
]
] | We study gravitational perturbations sourced by a rotating test shell collapsing into five-dimensional Myers-Perry black holes in anti-de Sitter (AdS). Our attention is restricted to the case in which the two possible angular momenta of the geometry are set equal. In this situation the background is cohomogeneity-1, which amounts to a crucial technical simplification. It is found that the linearized Einstein equations are consistent only when the test shell is corotating with the spacetime. However, it is argued that this is a consequence of the matter on the shell being described by dust or, more precisely, noninteracting test particles. We compute the mass and angular momenta of the perturbed spacetime using a counterterm subtraction method, for which we provide an explicit formula that has not appeared previously in the literature. The results are in agreement with the expected expressions for energy and angular momenta of geodesic particles in AdS$_5$. |
gr-qc/9605006 | Anders H\vglund | S. Brian Edgar (Department of Mathematics, Link\"oping University) and
Garry Ludwig (Department of Mathematical Sciences, University of Alberta) | Integration in the GHP formalism II: An operator approach for spacetimes
with killing vectors, with applications to twisting type n spaces | 41 pages, plain TeX | null | 10.1023/A:1010200113770 | null | gr-qc | null | Held has proposed a coordinate- and gauge-free integration procedure within
the GHP formalism built around four functionally independent zero-weighted
scalars constructed from the spin coefficients and the Riemann tensor
components. Unfortunately, a spacetime with Killing vectors will be unable to
supply the full quota of four scalars of this type. However, for such a
spacetime additional scalars are supplied by the components of the Killing
vectors; by using these alongside the spin coefficients and the Riemann tensor
components we have the possibility of constructing the full quota of four
functionally independent zero-weighted scalars, and of exploiting Held's
procedure.
As an illustration we investigate the vacuum Type N spaces admitting a
Killing vector and a homothetic Killing vector. In a direct manner, we reduce
the problem to a pair of ordinary differential operator `master equations',
making use of a new zero-weighted GHP operator. By first rewriting the master
equations as a closed set of complex first order equations, we reduce the
problem to one real third order operator differential equation for a complex
function of a real variable --- but with still the freedom to choose explicitly
our fourth coordinate. An alternative, more algorithmic approach, using a
closed chain of real first order equations for real functions, reduces the
problem to the same order, but in a more natural and much more concise form. It
is also outlined how the various other third order differential equations,
which have been derived previously by other workers on this problem, can be
deduced from our master equations.
| [
{
"created": "Thu, 2 May 1996 11:39:39 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Edgar",
"S. Brian",
"",
"Department of Mathematics, Linköping University"
],
[
"Ludwig",
"Garry",
"",
"Department of Mathematical Sciences, University of Alberta"
]
] | Held has proposed a coordinate- and gauge-free integration procedure within the GHP formalism built around four functionally independent zero-weighted scalars constructed from the spin coefficients and the Riemann tensor components. Unfortunately, a spacetime with Killing vectors will be unable to supply the full quota of four scalars of this type. However, for such a spacetime additional scalars are supplied by the components of the Killing vectors; by using these alongside the spin coefficients and the Riemann tensor components we have the possibility of constructing the full quota of four functionally independent zero-weighted scalars, and of exploiting Held's procedure. As an illustration we investigate the vacuum Type N spaces admitting a Killing vector and a homothetic Killing vector. In a direct manner, we reduce the problem to a pair of ordinary differential operator `master equations', making use of a new zero-weighted GHP operator. By first rewriting the master equations as a closed set of complex first order equations, we reduce the problem to one real third order operator differential equation for a complex function of a real variable --- but with still the freedom to choose explicitly our fourth coordinate. An alternative, more algorithmic approach, using a closed chain of real first order equations for real functions, reduces the problem to the same order, but in a more natural and much more concise form. It is also outlined how the various other third order differential equations, which have been derived previously by other workers on this problem, can be deduced from our master equations. |
2112.05788 | Patrick Peter | Claus Kiefer and Patrick Peter | Time in quantum cosmology | 18 pages, 3 figures | Universe 2022, 8, 36 | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Time in quantum gravity is not a well-defined notion, despite its central
role in the very definition of dynamics. Using the formalism of quantum
geometrodynamics, we shortly review the problem and illustrate it with two
proposed solutions. Our main application is quantum cosmology -- the
application of quantum gravity to the Universe as a whole.
| [
{
"created": "Fri, 10 Dec 2021 19:16:25 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jan 2022 19:16:45 GMT",
"version": "v2"
}
] | 2022-01-12 | [
[
"Kiefer",
"Claus",
""
],
[
"Peter",
"Patrick",
""
]
] | Time in quantum gravity is not a well-defined notion, despite its central role in the very definition of dynamics. Using the formalism of quantum geometrodynamics, we shortly review the problem and illustrate it with two proposed solutions. Our main application is quantum cosmology -- the application of quantum gravity to the Universe as a whole. |
1205.3404 | Douglas A. Singleton | Sujoy Kumar Modak and Douglas Singleton | Hawking Radiation as a Mechanism for Inflation | 6 pages. Published version -- Awarded "Honorable Mention" for the
2012 Gravity Research Foundation Essay Contest | Int.J.Mod.Phys.D21,1242020(2012) | 10.1142/S0218271812420205 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Friedman-Robertson-Walker (FRW) space-time exhibits particle creation
similar to Hawking radiation of a black hole. In this essay we show that this
FRW Hawking radiation leads to an effective negative pressure fluid which can
drive an inflationary period of exponential expansion in the early Universe.
Since the Hawking temperature of the FRW space-time decreases as the Universe
expands this mechanism naturally turns off and the inflationary stage
transitions to a power law expansion associated with an ordinary radiation
dominated Universe.
| [
{
"created": "Tue, 15 May 2012 15:03:20 GMT",
"version": "v1"
},
{
"created": "Sun, 18 Nov 2012 09:49:33 GMT",
"version": "v2"
}
] | 2012-11-20 | [
[
"Modak",
"Sujoy Kumar",
""
],
[
"Singleton",
"Douglas",
""
]
] | The Friedman-Robertson-Walker (FRW) space-time exhibits particle creation similar to Hawking radiation of a black hole. In this essay we show that this FRW Hawking radiation leads to an effective negative pressure fluid which can drive an inflationary period of exponential expansion in the early Universe. Since the Hawking temperature of the FRW space-time decreases as the Universe expands this mechanism naturally turns off and the inflationary stage transitions to a power law expansion associated with an ordinary radiation dominated Universe. |
gr-qc/9811036 | Clifford M. Will | Clifford M. Will (Washington University, St. Louis) | The Confrontation between General Relativity and Experiment: A 1998
Update | Lecture notes from the 1998 Slac Summer Institute on Particle
Physics; 76 pages, 10 figures | ECONFC9808031:02,1998 | null | null | gr-qc | null | The status of experimental tests of general relativity and of theoretical
frameworks for analysing them are reviewed. Einstein's equivalence principle
(EEP) is well supported by experiments such as the E\"otv\"os experiment, tests
of special relativity, and the gravitational redshift experiment. Future tests
of EEP will search for new interactions arising from unification or quantum
gravity. Tests of general relativity have reached high precision, including the
light deflection, the Shapiro time delay, the perihelion advance of Mercury,
and the Nordtvedt effect in lunar motion. Gravitational wave damping has been
detected to half a percent using the binary pulsar, and new binary pulsar
systems promise further improvements. When direct observation of gravitational
radiation from astrophysical sources begins, new tests of general relativity
will be possible.
| [
{
"created": "Wed, 11 Nov 1998 19:48:42 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Will",
"Clifford M.",
"",
"Washington University, St. Louis"
]
] | The status of experimental tests of general relativity and of theoretical frameworks for analysing them are reviewed. Einstein's equivalence principle (EEP) is well supported by experiments such as the E\"otv\"os experiment, tests of special relativity, and the gravitational redshift experiment. Future tests of EEP will search for new interactions arising from unification or quantum gravity. Tests of general relativity have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, and the Nordtvedt effect in lunar motion. Gravitational wave damping has been detected to half a percent using the binary pulsar, and new binary pulsar systems promise further improvements. When direct observation of gravitational radiation from astrophysical sources begins, new tests of general relativity will be possible. |
2008.02921 | Atsushi Nishizawa | KAGRA Collaboration: T. Akutsu, M. Ando, K. Arai, Y. Arai, S. Araki,
A. Araya, N. Aritomi, H. Asada, Y. Aso, S. Bae, Y. Bae, L. Baiotti, R.
Bajpai, M. A. Barton, K. Cannon, Z. Cao, E. Capocasa, M. Chan, C. Chen, K.
Chen, Y. Chen, C-Y. Chiang, H. Chu, Y-K. Chu, S. Eguchi, Y. Enomoto, R.
Flaminio, Y. Fujii, F. Fujikawa, M. Fukunaga, M. Fukushima, D. Gao, G. Ge, S.
Ha, A. Hagiwara, S. Haino, W.-B. Han, K. Hasegawa, K. Hattori, H. Hayakawa,
K. Hayama, Y. Himemoto, Y. Hiranuma, N. Hirata, E. Hirose, Z. Hong, B. H.
Hsieh, C-Z. Huang, H-Y Huang, P. Huang, Y-C. Huang, Y. Huang, D. C. Y. Hui,
S. Ide, B. Ikenoue, S. Imam, K. Inayoshi, Y. Inoue, K. Ioka, K. Ito, Y. Itoh,
K. Izumi, C. Jeon, H-B. Jin, K. Jung, P. Jung, K. Kaihotsu, T. Kajita, M.
Kakizaki, M. Kamiizumi, N. Kanda, G. Kang, K. Kashiyama, K. Kawaguchi, N.
Kawai, T. Kawasaki, C. Kim, J. Kim, J. C. Kim, W. S. Kim, Y.-M. Kim, N.
Kimura, N. Kita, H. Kitazawa, Y. Kojima, K. Kokeyama, K. Komori, A. K. H.
Kong, K. Kotake, C. Kozakai, R. Kozu, R. Kumar, J. Kume, C. Kuo, H-S. Kuo, Y.
Kuromiya, S. Kuroyanagi, K. Kusayanagi, K. Kwak, H. K. Lee, H. W. Lee, R.
Lee, M. Leonardi, T. G. F. Li, K. L. Li, L. C.-C. Lin, C-Y. Lin, F-K. Lin,
F-L. Lin, H. L. Lin, G. C. Liu, L.-W. Luo, E. Majorana, M. Marchio, Y.
Michimura, N. Mio, O. Miyakawa, A. Miyamoto, Y. Miyazaki, K. Miyo, S. Miyoki,
Y. Mori, S. Morisaki, Y. Moriwaki, K. Nagano, S. Nagano, K. Nakamura, H.
Nakano, M. Nakano, R. Nakashima, Y. Nakayama, T. Narikawa, L. Naticchioni, R.
Negishi, L. Nguyen Quynh, W.-T. Ni, A. Nishizawa, S. Nozaki, Y. Obuchi, W.
Ogaki, J. J. Oh, K. Oh, S. H. Oh, M. Ohashi, N. Ohishi, M. Ohkawa, H. Ohta,
Y. Okutani, K. Okutomi, K. Oohara, C. P. Ooi, S. Oshino, S. Otabe, K. Pan, H.
Pang, A. Parisi, J. Park, F. E. Pena Arellano, I. Pinto, N. Sago, S. Saito,
Y. Saito, K. Sakai, Y. Sakai, Y. Sakuno, S. Sato, T. Sato, T. Sawada, T.
Sekiguchi, Y. Sekiguchi, L. Shao, S. Shibagaki, R. Shimizu, T. Shimoda, K.
Shimode, H. Shinkai, T. Shishido, A. Shoda, K. Somiya, E. J. Son, H. Sotani,
R. Sugimoto, J. Suresh, T. Suzuki, T. Suzuki, H. Tagoshi, H. Takahashi, R.
Takahashi, A. Takamori, S. Takano, H. Takeda, M. Takeda, H. Tanaka, K.
Tanaka, K. Tanaka, T. Tanaka, T. Tanaka, S. Tanioka, E. N. Tapia San Martin,
S. Telada, T. Tomaru, Y. Tomigami, T. Tomura, F. Travasso, L. Trozzo, T.
Tsang, J-S. Tsao, K. Tsubono, S. Tsuchida, D. Tsuna, T. Tsutsui, T. Tsuzuki,
D. Tuyenbayev, N. Uchikata, T. Uchiyama, A. Ueda, T. Uehara, K. Ueno, G.
Ueshima, F. Uraguchi, T. Ushiba, M. H. P. M. van Putten, H. Vocca, J. Wang,
T. Washimi, C. Wu, H. Wu, S. Wu, W-R. Xu, T. Yamada, K. Yamamoto, K.
Yamamoto, T. Yamamoto, K. Yamashita, R. Yamazaki, Y. Yang, K. Yokogawa, J.
Yokoyama, T. Yokozawa, T. Yoshioka, H. Yuzurihara, S. Zeidler, M. Zhan, H.
Zhang, Y. Zhao, and Z.-H. Zhu | Overview of KAGRA : KAGRA science | 73 pages, 11 figures, accepted by Progress of Theoretical and
Experimental Physics, in the series of KAGRA-featured articles | null | null | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | KAGRA is a newly build gravitational-wave observatory, a laser interferometer
with 3 km arm length, located in Kamioka, Gifu, Japan. In this paper in the
series of KAGRA-featured articles, we discuss the science targets of KAGRA
projects, considering not only the baseline KAGRA (current design) but also its
future upgrade candidates (KAGRA+) for the near to middle term (~5 years).
| [
{
"created": "Fri, 7 Aug 2020 01:01:36 GMT",
"version": "v1"
}
] | 2020-08-10 | [
[
"KAGRA Collaboration",
"",
""
],
[
"Akutsu",
"T.",
""
],
[
"Ando",
"M.",
""
],
[
"Arai",
"K.",
""
],
[
"Arai",
"Y.",
""
],
[
"Araki",
"S.",
""
],
[
"Araya",
"A.",
""
],
[
"Aritomi",
"N.",
""
],
[
"Asada",
"H.",
""
],
[
"Aso",
"Y.",
""
],
[
"Bae",
"S.",
""
],
[
"Bae",
"Y.",
""
],
[
"Baiotti",
"L.",
""
],
[
"Bajpai",
"R.",
""
],
[
"Barton",
"M. A.",
""
],
[
"Cannon",
"K.",
""
],
[
"Cao",
"Z.",
""
],
[
"Capocasa",
"E.",
""
],
[
"Chan",
"M.",
""
],
[
"Chen",
"C.",
""
],
[
"Chen",
"K.",
""
],
[
"Chen",
"Y.",
""
],
[
"Chiang",
"C-Y.",
""
],
[
"Chu",
"H.",
""
],
[
"Chu",
"Y-K.",
""
],
[
"Eguchi",
"S.",
""
],
[
"Enomoto",
"Y.",
""
],
[
"Flaminio",
"R.",
""
],
[
"Fujii",
"Y.",
""
],
[
"Fujikawa",
"F.",
""
],
[
"Fukunaga",
"M.",
""
],
[
"Fukushima",
"M.",
""
],
[
"Gao",
"D.",
""
],
[
"Ge",
"G.",
""
],
[
"Ha",
"S.",
""
],
[
"Hagiwara",
"A.",
""
],
[
"Haino",
"S.",
""
],
[
"Han",
"W. -B.",
""
],
[
"Hasegawa",
"K.",
""
],
[
"Hattori",
"K.",
""
],
[
"Hayakawa",
"H.",
""
],
[
"Hayama",
"K.",
""
],
[
"Himemoto",
"Y.",
""
],
[
"Hiranuma",
"Y.",
""
],
[
"Hirata",
"N.",
""
],
[
"Hirose",
"E.",
""
],
[
"Hong",
"Z.",
""
],
[
"Hsieh",
"B. H.",
""
],
[
"Huang",
"C-Z.",
""
],
[
"Huang",
"H-Y",
""
],
[
"Huang",
"P.",
""
],
[
"Huang",
"Y-C.",
""
],
[
"Huang",
"Y.",
""
],
[
"Hui",
"D. C. Y.",
""
],
[
"Ide",
"S.",
""
],
[
"Ikenoue",
"B.",
""
],
[
"Imam",
"S.",
""
],
[
"Inayoshi",
"K.",
""
],
[
"Inoue",
"Y.",
""
],
[
"Ioka",
"K.",
""
],
[
"Ito",
"K.",
""
],
[
"Itoh",
"Y.",
""
],
[
"Izumi",
"K.",
""
],
[
"Jeon",
"C.",
""
],
[
"Jin",
"H-B.",
""
],
[
"Jung",
"K.",
""
],
[
"Jung",
"P.",
""
],
[
"Kaihotsu",
"K.",
""
],
[
"Kajita",
"T.",
""
],
[
"Kakizaki",
"M.",
""
],
[
"Kamiizumi",
"M.",
""
],
[
"Kanda",
"N.",
""
],
[
"Kang",
"G.",
""
],
[
"Kashiyama",
"K.",
""
],
[
"Kawaguchi",
"K.",
""
],
[
"Kawai",
"N.",
""
],
[
"Kawasaki",
"T.",
""
],
[
"Kim",
"C.",
""
],
[
"Kim",
"J.",
""
],
[
"Kim",
"J. C.",
""
],
[
"Kim",
"W. S.",
""
],
[
"Kim",
"Y. -M.",
""
],
[
"Kimura",
"N.",
""
],
[
"Kita",
"N.",
""
],
[
"Kitazawa",
"H.",
""
],
[
"Kojima",
"Y.",
""
],
[
"Kokeyama",
"K.",
""
],
[
"Komori",
"K.",
""
],
[
"Kong",
"A. K. H.",
""
],
[
"Kotake",
"K.",
""
],
[
"Kozakai",
"C.",
""
],
[
"Kozu",
"R.",
""
],
[
"Kumar",
"R.",
""
],
[
"Kume",
"J.",
""
],
[
"Kuo",
"C.",
""
],
[
"Kuo",
"H-S.",
""
],
[
"Kuromiya",
"Y.",
""
],
[
"Kuroyanagi",
"S.",
""
],
[
"Kusayanagi",
"K.",
""
],
[
"Kwak",
"K.",
""
],
[
"Lee",
"H. K.",
""
],
[
"Lee",
"H. W.",
""
],
[
"Lee",
"R.",
""
],
[
"Leonardi",
"M.",
""
],
[
"Li",
"T. G. F.",
""
],
[
"Li",
"K. L.",
""
],
[
"Lin",
"L. C. -C.",
""
],
[
"Lin",
"C-Y.",
""
],
[
"Lin",
"F-K.",
""
],
[
"Lin",
"F-L.",
""
],
[
"Lin",
"H. L.",
""
],
[
"Liu",
"G. C.",
""
],
[
"Luo",
"L. -W.",
""
],
[
"Majorana",
"E.",
""
],
[
"Marchio",
"M.",
""
],
[
"Michimura",
"Y.",
""
],
[
"Mio",
"N.",
""
],
[
"Miyakawa",
"O.",
""
],
[
"Miyamoto",
"A.",
""
],
[
"Miyazaki",
"Y.",
""
],
[
"Miyo",
"K.",
""
],
[
"Miyoki",
"S.",
""
],
[
"Mori",
"Y.",
""
],
[
"Morisaki",
"S.",
""
],
[
"Moriwaki",
"Y.",
""
],
[
"Nagano",
"K.",
""
],
[
"Nagano",
"S.",
""
],
[
"Nakamura",
"K.",
""
],
[
"Nakano",
"H.",
""
],
[
"Nakano",
"M.",
""
],
[
"Nakashima",
"R.",
""
],
[
"Nakayama",
"Y.",
""
],
[
"Narikawa",
"T.",
""
],
[
"Naticchioni",
"L.",
""
],
[
"Negishi",
"R.",
""
],
[
"Quynh",
"L. Nguyen",
""
],
[
"Ni",
"W. -T.",
""
],
[
"Nishizawa",
"A.",
""
],
[
"Nozaki",
"S.",
""
],
[
"Obuchi",
"Y.",
""
],
[
"Ogaki",
"W.",
""
],
[
"Oh",
"J. J.",
""
],
[
"Oh",
"K.",
""
],
[
"Oh",
"S. H.",
""
],
[
"Ohashi",
"M.",
""
],
[
"Ohishi",
"N.",
""
],
[
"Ohkawa",
"M.",
""
],
[
"Ohta",
"H.",
""
],
[
"Okutani",
"Y.",
""
],
[
"Okutomi",
"K.",
""
],
[
"Oohara",
"K.",
""
],
[
"Ooi",
"C. P.",
""
],
[
"Oshino",
"S.",
""
],
[
"Otabe",
"S.",
""
],
[
"Pan",
"K.",
""
],
[
"Pang",
"H.",
""
],
[
"Parisi",
"A.",
""
],
[
"Park",
"J.",
""
],
[
"Arellano",
"F. E. Pena",
""
],
[
"Pinto",
"I.",
""
],
[
"Sago",
"N.",
""
],
[
"Saito",
"S.",
""
],
[
"Saito",
"Y.",
""
],
[
"Sakai",
"K.",
""
],
[
"Sakai",
"Y.",
""
],
[
"Sakuno",
"Y.",
""
],
[
"Sato",
"S.",
""
],
[
"Sato",
"T.",
""
],
[
"Sawada",
"T.",
""
],
[
"Sekiguchi",
"T.",
""
],
[
"Sekiguchi",
"Y.",
""
],
[
"Shao",
"L.",
""
],
[
"Shibagaki",
"S.",
""
],
[
"Shimizu",
"R.",
""
],
[
"Shimoda",
"T.",
""
],
[
"Shimode",
"K.",
""
],
[
"Shinkai",
"H.",
""
],
[
"Shishido",
"T.",
""
],
[
"Shoda",
"A.",
""
],
[
"Somiya",
"K.",
""
],
[
"Son",
"E. J.",
""
],
[
"Sotani",
"H.",
""
],
[
"Sugimoto",
"R.",
""
],
[
"Suresh",
"J.",
""
],
[
"Suzuki",
"T.",
""
],
[
"Suzuki",
"T.",
""
],
[
"Tagoshi",
"H.",
""
],
[
"Takahashi",
"H.",
""
],
[
"Takahashi",
"R.",
""
],
[
"Takamori",
"A.",
""
],
[
"Takano",
"S.",
""
],
[
"Takeda",
"H.",
""
],
[
"Takeda",
"M.",
""
],
[
"Tanaka",
"H.",
""
],
[
"Tanaka",
"K.",
""
],
[
"Tanaka",
"K.",
""
],
[
"Tanaka",
"T.",
""
],
[
"Tanaka",
"T.",
""
],
[
"Tanioka",
"S.",
""
],
[
"Martin",
"E. N. Tapia San",
""
],
[
"Telada",
"S.",
""
],
[
"Tomaru",
"T.",
""
],
[
"Tomigami",
"Y.",
""
],
[
"Tomura",
"T.",
""
],
[
"Travasso",
"F.",
""
],
[
"Trozzo",
"L.",
""
],
[
"Tsang",
"T.",
""
],
[
"Tsao",
"J-S.",
""
],
[
"Tsubono",
"K.",
""
],
[
"Tsuchida",
"S.",
""
],
[
"Tsuna",
"D.",
""
],
[
"Tsutsui",
"T.",
""
],
[
"Tsuzuki",
"T.",
""
],
[
"Tuyenbayev",
"D.",
""
],
[
"Uchikata",
"N.",
""
],
[
"Uchiyama",
"T.",
""
],
[
"Ueda",
"A.",
""
],
[
"Uehara",
"T.",
""
],
[
"Ueno",
"K.",
""
],
[
"Ueshima",
"G.",
""
],
[
"Uraguchi",
"F.",
""
],
[
"Ushiba",
"T.",
""
],
[
"van Putten",
"M. H. P. M.",
""
],
[
"Vocca",
"H.",
""
],
[
"Wang",
"J.",
""
],
[
"Washimi",
"T.",
""
],
[
"Wu",
"C.",
""
],
[
"Wu",
"H.",
""
],
[
"Wu",
"S.",
""
],
[
"Xu",
"W-R.",
""
],
[
"Yamada",
"T.",
""
],
[
"Yamamoto",
"K.",
""
],
[
"Yamamoto",
"K.",
""
],
[
"Yamamoto",
"T.",
""
],
[
"Yamashita",
"K.",
""
],
[
"Yamazaki",
"R.",
""
],
[
"Yang",
"Y.",
""
],
[
"Yokogawa",
"K.",
""
],
[
"Yokoyama",
"J.",
""
],
[
"Yokozawa",
"T.",
""
],
[
"Yoshioka",
"T.",
""
],
[
"Yuzurihara",
"H.",
""
],
[
"Zeidler",
"S.",
""
],
[
"Zhan",
"M.",
""
],
[
"Zhang",
"H.",
""
],
[
"Zhao",
"Y.",
""
],
[
"Zhu",
"Z. -H.",
""
]
] | KAGRA is a newly build gravitational-wave observatory, a laser interferometer with 3 km arm length, located in Kamioka, Gifu, Japan. In this paper in the series of KAGRA-featured articles, we discuss the science targets of KAGRA projects, considering not only the baseline KAGRA (current design) but also its future upgrade candidates (KAGRA+) for the near to middle term (~5 years). |
2002.05481 | Saskia Grunau | Jens-Christian Drawer and Saskia Grunau | Geodesic motion around a supersymmetric AdS5 black hole | 15 pages, 13 figures | Eur. Phys. J. C 80, no.6, 536 (2020) | 10.1140/epjc/s10052-020-8101-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article the geodesic motion of test particles in the spacetime of a
supersymmetric AdS$_5$ black hole is studied. The equations of motion are
derived and solved in terms of the Weierstrass $\wp$, $\sigma$ and $\zeta$
functions. Effective potentials and parametric diagrams are used to analyze and
characterize timelike, lightlike and spacelike particle motion and a list of
possible orbit types is given. Furthermore, various plots of orbits are
presented.
| [
{
"created": "Thu, 13 Feb 2020 12:42:09 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Jun 2020 11:27:27 GMT",
"version": "v2"
}
] | 2020-06-29 | [
[
"Drawer",
"Jens-Christian",
""
],
[
"Grunau",
"Saskia",
""
]
] | In this article the geodesic motion of test particles in the spacetime of a supersymmetric AdS$_5$ black hole is studied. The equations of motion are derived and solved in terms of the Weierstrass $\wp$, $\sigma$ and $\zeta$ functions. Effective potentials and parametric diagrams are used to analyze and characterize timelike, lightlike and spacelike particle motion and a list of possible orbit types is given. Furthermore, various plots of orbits are presented. |
gr-qc/0506081 | Mamdouh Wanas | M.I.Wanas | Quantum Roots in Geometry: I | 20 pages, 1 figure, talk at XXV-International Workshop on Fundamental
Problems of High Energy Physics and Field Theory, held 25-28 June 2002,
Protvino, Russia | Published in the proceedings of the above mentioned conference
entitled "Geometrical and Topological Ideas in Modern Physics", (2003) p.
315-331 | null | null | gr-qc | null | In the present work, it is shown that the geometerization philosophy has not
been exhausted. Some quantum roots are already built in non-symmetric
geometries. Path equations in such geometries give rise to spin-gravity
interaction. Some experimental evidences (the results of the COW-experiment)
indicate the existence of this interaction. It is shown that the new quantum
path equations could account for the results of the COW-experiment. Large scale
applications, of the new path equations, admitted by such geometries, give rise
to tests for the existence of this interaction on the astrophysical and
cosmological scales. As a byproduct, it is shown that the quantum roots
appeared explicitly, in the path equations, can be diffused in the whole
geometry using a parameterization scheme.
| [
{
"created": "Tue, 14 Jun 2005 13:29:53 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Wanas",
"M. I.",
""
]
] | In the present work, it is shown that the geometerization philosophy has not been exhausted. Some quantum roots are already built in non-symmetric geometries. Path equations in such geometries give rise to spin-gravity interaction. Some experimental evidences (the results of the COW-experiment) indicate the existence of this interaction. It is shown that the new quantum path equations could account for the results of the COW-experiment. Large scale applications, of the new path equations, admitted by such geometries, give rise to tests for the existence of this interaction on the astrophysical and cosmological scales. As a byproduct, it is shown that the quantum roots appeared explicitly, in the path equations, can be diffused in the whole geometry using a parameterization scheme. |
1506.04056 | Vassilios Mewes | Vassilios Mewes, Jos\'e A. Font, Filippo Galeazzi, Pedro J. Montero,
Nikolaos Stergioulas | Numerical relativity simulations of thick accretion disks around tilted
Kerr black holes | 35 pages, 33 figures, accepted for publication in PRD | Phys. Rev. D 93, 064055 (2016) | 10.1103/PhysRevD.93.064055 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we present 3D numerical relativity simulations of thick
accretion disks around tilted Kerr BH. We investigate the evolution of three
different initial disk models with a range of initial black hole spin
magnitudes and tilt angles. For all the disk-to-black hole mass ratios
considered (0.044-0.16) we observe significant black hole precession and
nutation during the evolution. This indicates that for such mass ratios,
neglecting the self-gravity of the disks by evolving them in a fixed background
black hole spacetime is not justified. We find that the two more massive models
are unstable against the Papaloizou-Pringle (PP) instability and that those
PP-unstable models remain unstable for all initial spins and tilt angles
considered, showing that the development of the instability is a very robust
feature of such PP-unstable disks. Our lightest model, which is the most
astrophysically favorable outcome of mergers of binary compact objects, is
stable. The tilt between the black hole spin and the disk is strongly modulated
during the growth of the PP instability, causing a partial global realignment
of black hole spin and disk angular momentum in the most massive model with
constant specific angular momentum l. For the model with non-constant l-profile
we observe a long-lived m=1 non-axisymmetric structure which shows strong
oscillations of the tilt angle in the inner regions of the disk. This effect
might be connected to the development of Kozai-Lidov oscillations. Our
simulations also confirm earlier findings that the development of the PP
instability causes the long-term emission of large amplitude gravitational
waves, predominantly for the l=m=2 multipole mode. The imprint of the BH
precession on the gravitational waves from tilted BH-torus systems remains an
interesting open issue that would require significantly longer simulations than
those presented in this work.
| [
{
"created": "Fri, 12 Jun 2015 16:06:46 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Feb 2016 11:27:41 GMT",
"version": "v2"
}
] | 2016-07-20 | [
[
"Mewes",
"Vassilios",
""
],
[
"Font",
"José A.",
""
],
[
"Galeazzi",
"Filippo",
""
],
[
"Montero",
"Pedro J.",
""
],
[
"Stergioulas",
"Nikolaos",
""
]
] | In this work we present 3D numerical relativity simulations of thick accretion disks around tilted Kerr BH. We investigate the evolution of three different initial disk models with a range of initial black hole spin magnitudes and tilt angles. For all the disk-to-black hole mass ratios considered (0.044-0.16) we observe significant black hole precession and nutation during the evolution. This indicates that for such mass ratios, neglecting the self-gravity of the disks by evolving them in a fixed background black hole spacetime is not justified. We find that the two more massive models are unstable against the Papaloizou-Pringle (PP) instability and that those PP-unstable models remain unstable for all initial spins and tilt angles considered, showing that the development of the instability is a very robust feature of such PP-unstable disks. Our lightest model, which is the most astrophysically favorable outcome of mergers of binary compact objects, is stable. The tilt between the black hole spin and the disk is strongly modulated during the growth of the PP instability, causing a partial global realignment of black hole spin and disk angular momentum in the most massive model with constant specific angular momentum l. For the model with non-constant l-profile we observe a long-lived m=1 non-axisymmetric structure which shows strong oscillations of the tilt angle in the inner regions of the disk. This effect might be connected to the development of Kozai-Lidov oscillations. Our simulations also confirm earlier findings that the development of the PP instability causes the long-term emission of large amplitude gravitational waves, predominantly for the l=m=2 multipole mode. The imprint of the BH precession on the gravitational waves from tilted BH-torus systems remains an interesting open issue that would require significantly longer simulations than those presented in this work. |
1801.01993 | Rajibul Shaikh | Rajibul Shaikh, Pankaj S. Joshi (TIFR Mumbai, India) | Gravitational collapse in $(2+1)$-dimensional Eddington-inspired
Born-Infeld gravity | 16 pages, 3 figures, revised version, published in Phys. Rev. D | Phys. Rev. D 98, 024033 (2018) | 10.1103/PhysRevD.98.024033 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study here the gravitational collapse of dust in $(2+1)$-dimensional
spacetimes for the formation of black holes (BH) and naked singularities (NS)
as final states in a modified theory of gravity, with vanishing cosmological
constant. From the perspective of cosmic censorship, we investigate the
collapse of a dust cloud in Eddington-inspired Born-Infeld gravity (EiBI) and
compare the results with those of general relativity (GR). It turns out that,
as opposed to the general relativistic situation, where the outcome of dust
collapse in $(2+1)$ dimensions is always a naked singularity, the EiBI theory
has a certain range of parameter values that avoid the naked singularity. This
indicates that a $(3+1)$-dimensional generalization of these results could be
useful and worth examining. Finally, using the results here, we show that the
singularity avoidance through homogeneous bounce in cosmology in this modified
gravity is not stable.
| [
{
"created": "Sat, 6 Jan 2018 09:36:06 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Jul 2018 15:22:16 GMT",
"version": "v2"
}
] | 2018-07-31 | [
[
"Shaikh",
"Rajibul",
"",
"TIFR Mumbai, India"
],
[
"Joshi",
"Pankaj S.",
"",
"TIFR Mumbai, India"
]
] | We study here the gravitational collapse of dust in $(2+1)$-dimensional spacetimes for the formation of black holes (BH) and naked singularities (NS) as final states in a modified theory of gravity, with vanishing cosmological constant. From the perspective of cosmic censorship, we investigate the collapse of a dust cloud in Eddington-inspired Born-Infeld gravity (EiBI) and compare the results with those of general relativity (GR). It turns out that, as opposed to the general relativistic situation, where the outcome of dust collapse in $(2+1)$ dimensions is always a naked singularity, the EiBI theory has a certain range of parameter values that avoid the naked singularity. This indicates that a $(3+1)$-dimensional generalization of these results could be useful and worth examining. Finally, using the results here, we show that the singularity avoidance through homogeneous bounce in cosmology in this modified gravity is not stable. |
1807.06047 | Aurelien Barrau | Aur\'elien Barrau, Pierre Jamet, Killian Martineau, Flora Moulin | Scalar spectra of primordial perturbations in loop quantum cosmology | null | Phys. Rev. D 98, 086003 (2018) | 10.1103/PhysRevD.98.086003 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article is devoted to the study of scalar perturbations in loop quantum
cosmology. It aims at clarifying the situation with respect to the way initial
conditions are set and to the specific choice of an inflaton potential. Several
monomial potentials are studied. Both the dressed metric and deformed algebra
approaches are considered. We show that the calculation of the ultraviolet part
of the spectrum, which is the physically relevant region for most background
trajectories, is reliable, whereas the infrared and intermediate parts do
depend on some specific choices that are made explicit.
| [
{
"created": "Mon, 16 Jul 2018 18:20:40 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Sep 2018 08:12:51 GMT",
"version": "v2"
}
] | 2018-10-10 | [
[
"Barrau",
"Aurélien",
""
],
[
"Jamet",
"Pierre",
""
],
[
"Martineau",
"Killian",
""
],
[
"Moulin",
"Flora",
""
]
] | This article is devoted to the study of scalar perturbations in loop quantum cosmology. It aims at clarifying the situation with respect to the way initial conditions are set and to the specific choice of an inflaton potential. Several monomial potentials are studied. Both the dressed metric and deformed algebra approaches are considered. We show that the calculation of the ultraviolet part of the spectrum, which is the physically relevant region for most background trajectories, is reliable, whereas the infrared and intermediate parts do depend on some specific choices that are made explicit. |
1407.1716 | Willians Barreto | W. Barreto (ULA) | Extended two-dimensional characteristic framework to study nonrotating
black holes | 13 pages, 11 figures; to appear in Physical Review D. arXiv admin
note: text overlap with arXiv:0711.0564 | Physical Review D 90, 024055 (2014) | 10.1103/PhysRevD.90.024055 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a numerical solver, that extends the computational framework
considered in [Phys. Rev. D 65, 084016 (2002)], to include scalar perturbations
of nonrotating black holes. The nonlinear Einstein-Klein-Gordon equations for a
massless scalar field minimally coupled to gravity are solved in two spatial
dimensions (2D). The numerical procedure is based on the ingoing light cone
formulation for an axially and reflection symmetric spacetime. The solver is
second order accurate and was validated in different ways. We use for
calibration an auxiliary 1D solver with the same initial and boundary
conditions and the same evolution algorithm. We reproduce the quasinormal modes
for the massless scalar field harmonics $\ell = 0$, $1$ and $2$. For these same
harmonics, in the linear approximation, we calculate the balance of energy
between the black hole and the world tube. As an example of nonlinear harmonic
generation, we show the distortion of a marginally trapped two-surface
approximated as a q-boundary and based upon the harmonic $\ell=2$.
Additionally, we study the evolution of the $\ell = 8$ harmonic in order to
test the solver in a spacetime with a complex angular structure. Further
applications and extensions are briefly discussed.
| [
{
"created": "Mon, 7 Jul 2014 13:56:16 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Barreto",
"W.",
"",
"ULA"
]
] | We develop a numerical solver, that extends the computational framework considered in [Phys. Rev. D 65, 084016 (2002)], to include scalar perturbations of nonrotating black holes. The nonlinear Einstein-Klein-Gordon equations for a massless scalar field minimally coupled to gravity are solved in two spatial dimensions (2D). The numerical procedure is based on the ingoing light cone formulation for an axially and reflection symmetric spacetime. The solver is second order accurate and was validated in different ways. We use for calibration an auxiliary 1D solver with the same initial and boundary conditions and the same evolution algorithm. We reproduce the quasinormal modes for the massless scalar field harmonics $\ell = 0$, $1$ and $2$. For these same harmonics, in the linear approximation, we calculate the balance of energy between the black hole and the world tube. As an example of nonlinear harmonic generation, we show the distortion of a marginally trapped two-surface approximated as a q-boundary and based upon the harmonic $\ell=2$. Additionally, we study the evolution of the $\ell = 8$ harmonic in order to test the solver in a spacetime with a complex angular structure. Further applications and extensions are briefly discussed. |
1908.07505 | Henk Bart | Henk Bart | Gravitational memory in the bulk | null | null | 10.1007/JHEP05(2020)106 | MPP-2019-180 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A method for detecting gravitational memory is proposed. It makes use of
ingoing null geodesics instead of timelike geodesics in the original
formulation by Christodoulou. It is argued that the method is applicable in the
bulk of a spacetime. In addition, it is shown that BMS symmetry generators in
Newman-Unti gauge have an interpretation in terms of the memory effect. This
generalises the connection between BMS supertranslations and gravitational
memory, discovered by Strominger and Zhiboedov at null infinity, to the bulk.
| [
{
"created": "Tue, 20 Aug 2019 17:28:45 GMT",
"version": "v1"
}
] | 2020-05-26 | [
[
"Bart",
"Henk",
""
]
] | A method for detecting gravitational memory is proposed. It makes use of ingoing null geodesics instead of timelike geodesics in the original formulation by Christodoulou. It is argued that the method is applicable in the bulk of a spacetime. In addition, it is shown that BMS symmetry generators in Newman-Unti gauge have an interpretation in terms of the memory effect. This generalises the connection between BMS supertranslations and gravitational memory, discovered by Strominger and Zhiboedov at null infinity, to the bulk. |
0706.1057 | Martin Bojowald | Martin Bojowald, Hector Hernandez, Aureliano Skirzewski | Effective equations for isotropic quantum cosmology including matter | 42 pages | Phys.Rev.D76:063511,2007 | 10.1103/PhysRevD.76.063511 | IGPG-07/6-2 | gr-qc astro-ph hep-th | null | Effective equations often provide powerful tools to develop a systematic
understanding of detailed properties of a quantum system. This is especially
helpful in quantum cosmology where several conceptual and technical
difficulties associated with the full quantum equations can be avoided in this
way. Here, effective equations for Wheeler-DeWitt and loop quantizations of
spatially flat, isotropic cosmological models sourced by a massive or
interacting scalar are derived and studied. The resulting systems are
remarkably different from that given for a free, massless scalar. This has
implications for the coherence of evolving states and the realization of a
bounce in loop quantum cosmology.
| [
{
"created": "Thu, 7 Jun 2007 18:58:32 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Bojowald",
"Martin",
""
],
[
"Hernandez",
"Hector",
""
],
[
"Skirzewski",
"Aureliano",
""
]
] | Effective equations often provide powerful tools to develop a systematic understanding of detailed properties of a quantum system. This is especially helpful in quantum cosmology where several conceptual and technical difficulties associated with the full quantum equations can be avoided in this way. Here, effective equations for Wheeler-DeWitt and loop quantizations of spatially flat, isotropic cosmological models sourced by a massive or interacting scalar are derived and studied. The resulting systems are remarkably different from that given for a free, massless scalar. This has implications for the coherence of evolving states and the realization of a bounce in loop quantum cosmology. |
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