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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1911.00414 | Georgios Lukes-Gerakopoulos | Ond\v{r}ej Zelenka, Georgios Lukes-Gerakopoulos, Vojt\v{e}ch Witzany
and Ond\v{r}ej Kop\'a\v{c}ek | Growth of resonances and chaos for a spinning test particle in the
Schwarzschild background | 18 pages, 14 figures | Phys. Rev. D 101, 024037 (2020) | 10.1103/PhysRevD.101.024037 | null | gr-qc nlin.CD | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspirals of stellar mass compact objects into supermassive black holes are
known as extreme mass ratio inspirals. In the simplest approximation, the
motion of the compact object is modeled as a geodesic in the space-time of the
massive black hole with the orbit decaying due to radiated energy and angular
momentum, thus yielding a highly regular inspiral. However, once the spin of
the secondary compact body is taken into account, integrability is broken and
prolonged resonances along with chaotic motion appear.
We numerically integrate the motion of a spinning test body in the field of a
non-spinning black hole and analyse it using various methods. We show for the
first time that resonances and chaos can be found even for astrophysical values
of spin. On the other hand, we devise a method to analyse the growth of the
resonances, and we conclude that the resonances we observe are only caused by
terms quadratic in spin and will generally stay very small in the
small-mass-ratio limit. Last but not least, we compute gravitational waveforms
by solving numerically the Teukolsky equations in the time-domain and establish
that they carry information on the motion's dynamics. In particular, we show
that the time series of the gravitational wave strain can be used to discern
regular from chaotic motion of the source.
| [
{
"created": "Fri, 1 Nov 2019 14:45:27 GMT",
"version": "v1"
}
] | 2020-01-22 | [
[
"Zelenka",
"Ondřej",
""
],
[
"Lukes-Gerakopoulos",
"Georgios",
""
],
[
"Witzany",
"Vojtěch",
""
],
[
"Kopáček",
"Ondřej",
""
]
] | Inspirals of stellar mass compact objects into supermassive black holes are known as extreme mass ratio inspirals. In the simplest approximation, the motion of the compact object is modeled as a geodesic in the space-time of the massive black hole with the orbit decaying due to radiated energy and angular momentum, thus yielding a highly regular inspiral. However, once the spin of the secondary compact body is taken into account, integrability is broken and prolonged resonances along with chaotic motion appear. We numerically integrate the motion of a spinning test body in the field of a non-spinning black hole and analyse it using various methods. We show for the first time that resonances and chaos can be found even for astrophysical values of spin. On the other hand, we devise a method to analyse the growth of the resonances, and we conclude that the resonances we observe are only caused by terms quadratic in spin and will generally stay very small in the small-mass-ratio limit. Last but not least, we compute gravitational waveforms by solving numerically the Teukolsky equations in the time-domain and establish that they carry information on the motion's dynamics. In particular, we show that the time series of the gravitational wave strain can be used to discern regular from chaotic motion of the source. |
1010.6175 | Spiros Cotsakis | I. Antoniadis, S. Cotsakis, I. klaoudatou | Brane singularities and their avoidance | 37 pages, latex, merged version of arXiv:1005.3221 and
arXiv:1004.3379, to appear in Class.Quant.Grav | Class.Quant.Grav.27:235018,2010 | 10.1088/0264-9381/27/23/235018 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The singularity structure and the corresponding asymptotic behavior of a
3-brane coupled to a scalar field or to a perfect fluid in a five-dimensional
bulk is analyzed in full generality using the method of asymptotic splittings.
In the case of the scalar field, it is shown that the collapse singularity at a
finite distance from the brane can be avoided only at the expense of making the
brane world-volume positively or negatively curved. In the case where the bulk
field content is parametrized by an analogue of perfect fluid with an arbitrary
equation of state P=\gamma\rho between the `pressure' P and the `density' \rho,
our results depend crucially on the constant fluid parameter \gamma: (i) For
\gamma>-1/2, the flat brane solution suffers from a collapse singularity at
finite distance, that disappears in the curved case. (ii) For \gamma<-1, the
singularity cannot be avoided and it becomes of the big rip type for a flat
brane. (iii) For -1<\gamma< or = -1/2, the surprising result is found that
while the curved brane solution is singular, the flat brane is not, opening the
possibility for a revival of the self-tuning proposal.
| [
{
"created": "Fri, 29 Oct 2010 10:30:40 GMT",
"version": "v1"
}
] | 2010-12-01 | [
[
"Antoniadis",
"I.",
""
],
[
"Cotsakis",
"S.",
""
],
[
"klaoudatou",
"I.",
""
]
] | The singularity structure and the corresponding asymptotic behavior of a 3-brane coupled to a scalar field or to a perfect fluid in a five-dimensional bulk is analyzed in full generality using the method of asymptotic splittings. In the case of the scalar field, it is shown that the collapse singularity at a finite distance from the brane can be avoided only at the expense of making the brane world-volume positively or negatively curved. In the case where the bulk field content is parametrized by an analogue of perfect fluid with an arbitrary equation of state P=\gamma\rho between the `pressure' P and the `density' \rho, our results depend crucially on the constant fluid parameter \gamma: (i) For \gamma>-1/2, the flat brane solution suffers from a collapse singularity at finite distance, that disappears in the curved case. (ii) For \gamma<-1, the singularity cannot be avoided and it becomes of the big rip type for a flat brane. (iii) For -1<\gamma< or = -1/2, the surprising result is found that while the curved brane solution is singular, the flat brane is not, opening the possibility for a revival of the self-tuning proposal. |
1702.08768 | Oleg Tsupko | Volker Perlick and Oleg Yu. Tsupko | Light propagation in a plasma on Kerr spacetime: Separation of the
Hamilton-Jacobi equation and calculation of the shadow | 19 pages, 6 figures; minor reformulations | Phys. Rev. D 95, 104003 (2017) | 10.1103/PhysRevD.95.104003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider light propagation in a non-magnetized pressureless plasma around
a Kerr black hole. We find the necessary and sufficient condition the plasma
electron density has to satisfy to guarantee that the Hamilton-Jacobi equation
for the light rays is separable, i.e., that a generalized Carter constant
exists. For all cases where this condition is satisfied we determine the photon
region, i.e., the region in the spacetime where spherical light rays exist. A
spherical light ray is a light ray that stays on a sphere $r =
\mathrm{constant}$ (in Boyer-Lindquist coordinates). Based on these results, we
calculate the shadow of a Kerr black hole under the influence of a plasma that
satisfies the separability condition. More precisely, we derive an analytical
formula for the boundary curve of the shadow on the sky of an observer that is
located anywhere in the domain of outer communication. Several examples are
worked out.
| [
{
"created": "Tue, 28 Feb 2017 12:48:52 GMT",
"version": "v1"
},
{
"created": "Mon, 15 May 2017 14:40:39 GMT",
"version": "v2"
}
] | 2017-05-16 | [
[
"Perlick",
"Volker",
""
],
[
"Tsupko",
"Oleg Yu.",
""
]
] | We consider light propagation in a non-magnetized pressureless plasma around a Kerr black hole. We find the necessary and sufficient condition the plasma electron density has to satisfy to guarantee that the Hamilton-Jacobi equation for the light rays is separable, i.e., that a generalized Carter constant exists. For all cases where this condition is satisfied we determine the photon region, i.e., the region in the spacetime where spherical light rays exist. A spherical light ray is a light ray that stays on a sphere $r = \mathrm{constant}$ (in Boyer-Lindquist coordinates). Based on these results, we calculate the shadow of a Kerr black hole under the influence of a plasma that satisfies the separability condition. More precisely, we derive an analytical formula for the boundary curve of the shadow on the sky of an observer that is located anywhere in the domain of outer communication. Several examples are worked out. |
2304.02378 | Ra\'ul Mart\'inez-Boh\'orquez | Ra\'ul Mart\'inez-Boh\'orquez | On the existence of the electromagnetic energy tensor in second order
Lovelock gravities | null | International Journal of Geometric Methods in Modern Physics
(2023) | 10.1142/S021988782450035X | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we prove that there are no electromagnetic energy tensors in
second order Lovelock gravities that verify properties equivalent to those of
the Maxwell electromagnetic energy tensor in General Relativity.
| [
{
"created": "Wed, 5 Apr 2023 11:32:47 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Aug 2023 10:27:03 GMT",
"version": "v2"
}
] | 2023-09-12 | [
[
"Martínez-Bohórquez",
"Raúl",
""
]
] | In this work we prove that there are no electromagnetic energy tensors in second order Lovelock gravities that verify properties equivalent to those of the Maxwell electromagnetic energy tensor in General Relativity. |
2210.17259 | Pan Li | Pan Li, Yi Ling, Zhangping Yu | The generation rate of quantum gravity induced entanglement with
multiple massive particles | minor changes, references added | null | 10.1103/PhysRevD.107.064054 | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | We investigate the generation rate of quantum gravity induced entanglement of
masses(QGEM) in setup with multiple quantum massive particles, among of which
only the gravity interaction due to the Newton potential is taken into account.
When the distance between any two adjacent Stern-Gerlach (SG) devices is fixed,
we consider all the possible configurations of the setup with the same number
of particles. In particular, we systemically analyze the case of particle
number n=4 and find that the prism setup with a massive particle at the center
is the most efficient setup for the entanglement generation. This result can be
extended to a system with multiple particles up to seven, where the
entanglement efficiency is also enhanced in comparison with the setup with
fewer particles. This work provides the strategy to construct the QGEM setup
with the best generation rate of entanglement.
| [
{
"created": "Mon, 31 Oct 2022 12:30:56 GMT",
"version": "v1"
},
{
"created": "Sun, 6 Nov 2022 12:05:52 GMT",
"version": "v2"
}
] | 2023-03-27 | [
[
"Li",
"Pan",
""
],
[
"Ling",
"Yi",
""
],
[
"Yu",
"Zhangping",
""
]
] | We investigate the generation rate of quantum gravity induced entanglement of masses(QGEM) in setup with multiple quantum massive particles, among of which only the gravity interaction due to the Newton potential is taken into account. When the distance between any two adjacent Stern-Gerlach (SG) devices is fixed, we consider all the possible configurations of the setup with the same number of particles. In particular, we systemically analyze the case of particle number n=4 and find that the prism setup with a massive particle at the center is the most efficient setup for the entanglement generation. This result can be extended to a system with multiple particles up to seven, where the entanglement efficiency is also enhanced in comparison with the setup with fewer particles. This work provides the strategy to construct the QGEM setup with the best generation rate of entanglement. |
2301.04950 | Alireza Amani | E. Mahichi and Alireza Amani | The interaction of extended Bose-Einstein condensate dark matter with
viscous $f(T, B)$ gravity | 20 pages, 5 figures. arXiv admin note: text overlap with
arXiv:2107.11827 | Physics of the Dark Universe 39 (2023) 101167 | 10.1016/j.dark.2023.101167 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-nd/4.0/ | In this paper, we study the viscous $f(T, B)$ gravity model as a source of
dark energy, and the Extended Bose-Einstein Condensate (EBEC) as a source of
dark matter, in a flat-FRW metric. In the presence of bulk viscosity, we obtain
Friedmann equations and write two continuity equations of dark energy and dark
matter by interacting them. Using the generalized Gross-Pitaeveskii equation,
we earn Equation of State (EoS) of dark matter by EBEC regime as $p_m = \alpha
\rho_{m} + \beta \rho_{m}^2$ in which the both of terms are respectively
introduced as normal dark matter and dark matter halo. The innovation of the
work is that we can simultaneously describe the nature of the dark parts of the
universe with the viscous $f(T, B)$ gravity and the EBEC regime, which leads to
a deep understanding of the different epochs of the universe from early to late
times. In what follows, the energy density and the pressure of dark energy are
reconstructed in terms of the redshift parameter, and then we fit the obtained
results with 53 supernova data from the Hubble data constraints. Next, we plot
the cosmological parameters in terms of the redshift parameter and conclude
that the current universe is in an accelerated phase. Finally, we analyze the
stability and instability of the current model with the sound speed parameter
as well as we draw the density parameter values for dark energy in terms of the
redshift parameter.
| [
{
"created": "Thu, 12 Jan 2023 11:44:06 GMT",
"version": "v1"
}
] | 2023-01-13 | [
[
"Mahichi",
"E.",
""
],
[
"Amani",
"Alireza",
""
]
] | In this paper, we study the viscous $f(T, B)$ gravity model as a source of dark energy, and the Extended Bose-Einstein Condensate (EBEC) as a source of dark matter, in a flat-FRW metric. In the presence of bulk viscosity, we obtain Friedmann equations and write two continuity equations of dark energy and dark matter by interacting them. Using the generalized Gross-Pitaeveskii equation, we earn Equation of State (EoS) of dark matter by EBEC regime as $p_m = \alpha \rho_{m} + \beta \rho_{m}^2$ in which the both of terms are respectively introduced as normal dark matter and dark matter halo. The innovation of the work is that we can simultaneously describe the nature of the dark parts of the universe with the viscous $f(T, B)$ gravity and the EBEC regime, which leads to a deep understanding of the different epochs of the universe from early to late times. In what follows, the energy density and the pressure of dark energy are reconstructed in terms of the redshift parameter, and then we fit the obtained results with 53 supernova data from the Hubble data constraints. Next, we plot the cosmological parameters in terms of the redshift parameter and conclude that the current universe is in an accelerated phase. Finally, we analyze the stability and instability of the current model with the sound speed parameter as well as we draw the density parameter values for dark energy in terms of the redshift parameter. |
2109.13667 | Zhongwen Feng | Zhong-Wen Feng, Xia Zhou, Shi-Qi Zhou, Shu-Zheng Yang | Quantum corrections to the thermodynamics and phase transition of a
black hole surrounded by a cavity in the extended phase space | 9 pages, 7 figures | Commun.Theor.Phys. 2022, 74: 085403 | 10.1088/1572-9494/ac770d | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | In the extended phase space, we investigate the rainbow gravity-corrected
thermodynamic phenomena and phase structure of the Schwarzschild black hole
surrounded by a spherical cavity. The results show that rainbow gravity has a
very significant effect on the thermodynamic phenomena and phase structure of
the black hole. It prevents the black hole from total evaporation and leads to
a remnant with a limited temperature but no mass. Additionally, we restore the
$P-V$ criticality and obtaine the critical quantities of the canonical
ensemble. When the temperature or pressure is smaller than the critical
quantities, the system undergoes two Hawking-Page-like phase transitions and
one first-order phase transition, which never occurs in the original case.
Remarkably, our findings demonstrate that the thermodynamic behavior and phase
transition of the rainbow SC black hole surrounded by a cavity in the extended
phase space are analogous to those of the Reissner-Nordstr\"{o}m anti-de Sitter
black hole. Therefore, rainbow gravity activates the effect of electric charge
and cutoff factor in the evolution of the black hole.
| [
{
"created": "Mon, 27 Sep 2021 13:34:21 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Sep 2021 09:17:46 GMT",
"version": "v2"
},
{
"created": "Sat, 25 Dec 2021 02:55:01 GMT",
"version": "v3"
},
{
"created": "Thu, 9 Jun 2022 13:39:00 GMT",
"version": "v4"
}
] | 2022-08-30 | [
[
"Feng",
"Zhong-Wen",
""
],
[
"Zhou",
"Xia",
""
],
[
"Zhou",
"Shi-Qi",
""
],
[
"Yang",
"Shu-Zheng",
""
]
] | In the extended phase space, we investigate the rainbow gravity-corrected thermodynamic phenomena and phase structure of the Schwarzschild black hole surrounded by a spherical cavity. The results show that rainbow gravity has a very significant effect on the thermodynamic phenomena and phase structure of the black hole. It prevents the black hole from total evaporation and leads to a remnant with a limited temperature but no mass. Additionally, we restore the $P-V$ criticality and obtaine the critical quantities of the canonical ensemble. When the temperature or pressure is smaller than the critical quantities, the system undergoes two Hawking-Page-like phase transitions and one first-order phase transition, which never occurs in the original case. Remarkably, our findings demonstrate that the thermodynamic behavior and phase transition of the rainbow SC black hole surrounded by a cavity in the extended phase space are analogous to those of the Reissner-Nordstr\"{o}m anti-de Sitter black hole. Therefore, rainbow gravity activates the effect of electric charge and cutoff factor in the evolution of the black hole. |
1812.07865 | Vijay Varma | Vijay Varma, Scott E. Field, Mark A. Scheel, Jonathan Blackman,
Lawrence E. Kidder, and Harald P. Pfeiffer | Surrogate model of hybridized numerical relativity binary black hole
waveforms | Matches PRD version. Model publicly available at
https://zenodo.org/record/2549618#.XJvMrutKii4. 18 pages, 12 figures | Phys. Rev. D 99, 064045 (2019) | 10.1103/PhysRevD.99.064045 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Numerical relativity (NR) simulations provide the most accurate binary black
hole gravitational waveforms, but are prohibitively expensive for applications
such as parameter estimation. Surrogate models of NR waveforms have been shown
to be both fast and accurate. However, NR-based surrogate models are limited by
the training waveforms' length, which is typically about 20 orbits before
merger. We remedy this by hybridizing the NR waveforms using both
post-Newtonian and effective one body waveforms for the early inspiral. We
present NRHybSur3dq8, a surrogate model for hybridized nonprecessing numerical
relativity waveforms, that is valid for the entire LIGO band (starting at
$20~\text{Hz}$) for stellar mass binaries with total masses as low as
$2.25\,M_{\odot}$. We include the $\ell \leq 4$ and $(5,5)$ spin-weighted
spherical harmonic modes but not the $(4,1)$ or $(4,0)$ modes. This model has
been trained against hybridized waveforms based on 104 NR waveforms with mass
ratios $q\leq8$, and $|\chi_{1z}|,|\chi_{2z}| \leq 0.8$, where $\chi_{1z}$
($\chi_{2z}$) is the spin of the heavier (lighter) BH in the direction of
orbital angular momentum. The surrogate reproduces the hybrid waveforms
accurately, with mismatches $\lesssim 3\times10^{-4}$ over the mass range
$2.25M_{\odot} \leq M \leq 300 M_{\odot}$. At high masses
($M\gtrsim40M_{\odot}$), where the merger and ringdown are more prominent, we
show roughly two orders of magnitude improvement over existing waveform models.
We also show that the surrogate works well even when extrapolated outside its
training parameter space range, including at spins as large as 0.998. Finally,
we show that this model accurately reproduces the spheroidal-spherical mode
mixing present in the NR ringdown signal.
| [
{
"created": "Wed, 19 Dec 2018 10:39:07 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Jan 2019 01:50:19 GMT",
"version": "v2"
},
{
"created": "Wed, 27 Mar 2019 19:24:14 GMT",
"version": "v3"
}
] | 2019-04-03 | [
[
"Varma",
"Vijay",
""
],
[
"Field",
"Scott E.",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Blackman",
"Jonathan",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Pfeiffer",
"Harald P.",
""
]
] | Numerical relativity (NR) simulations provide the most accurate binary black hole gravitational waveforms, but are prohibitively expensive for applications such as parameter estimation. Surrogate models of NR waveforms have been shown to be both fast and accurate. However, NR-based surrogate models are limited by the training waveforms' length, which is typically about 20 orbits before merger. We remedy this by hybridizing the NR waveforms using both post-Newtonian and effective one body waveforms for the early inspiral. We present NRHybSur3dq8, a surrogate model for hybridized nonprecessing numerical relativity waveforms, that is valid for the entire LIGO band (starting at $20~\text{Hz}$) for stellar mass binaries with total masses as low as $2.25\,M_{\odot}$. We include the $\ell \leq 4$ and $(5,5)$ spin-weighted spherical harmonic modes but not the $(4,1)$ or $(4,0)$ modes. This model has been trained against hybridized waveforms based on 104 NR waveforms with mass ratios $q\leq8$, and $|\chi_{1z}|,|\chi_{2z}| \leq 0.8$, where $\chi_{1z}$ ($\chi_{2z}$) is the spin of the heavier (lighter) BH in the direction of orbital angular momentum. The surrogate reproduces the hybrid waveforms accurately, with mismatches $\lesssim 3\times10^{-4}$ over the mass range $2.25M_{\odot} \leq M \leq 300 M_{\odot}$. At high masses ($M\gtrsim40M_{\odot}$), where the merger and ringdown are more prominent, we show roughly two orders of magnitude improvement over existing waveform models. We also show that the surrogate works well even when extrapolated outside its training parameter space range, including at spins as large as 0.998. Finally, we show that this model accurately reproduces the spheroidal-spherical mode mixing present in the NR ringdown signal. |
1112.2695 | Marc Casals | Marc Casals and Adrian C. Ottewill | The Branch Cut and Quasi-normal Modes at Large Imaginary Frequency in
Schwarzschild Space-time | 26 pages, 14 figures. Modifications in version 2: inclusion of spin=1
as well as expressions for the QNM sum and some corrections, all in Sec.V.
Minor corrections in the rest of the paper | null | 10.1103/PhysRevD.86.024021 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The 'retarded' Green function for fields propagating on a Schwarzschild black
hole spacetime possesses a branch cut on the complex frequency plane.
Classically, the branch cut is important, for example, in order to fully
determine the response of the black hole to a linear field perturbation. The
branch cut is also useful for the calculation of the self-force on a point
particle moving in the Schwarzschild background. In this paper we use
techniques of analytic-continuation to the complex plane of the radial
coordinate in order to calculate the branch cut contribution to the Green
function in the limit of large imaginary frequency. It is expected that the
contribution of this frequency regime to the perturbation response and to the
self-force will be mostly for short time intervals. We also determine the
highly-damped quasinormal mode frequencies for electromagnetic perturbations in
Schwarzschild for the first time (previously only the leading imaginary part
was known), which seem to have a 'deep connection' with the branch cut. We find
that these frequencies behave like $\omega_{\ell,n}=
-\dfrac{in}{2}-\dfrac{i[\ell(\ell+1)]^2}{2n}+\dfrac{\pi^{1/2}(1-i)[\ell(\ell+1)]^3}{2^{3/2}n^{3/2}}+O(n^{-2})$.
The highly-damped quasinormal modes are particularly interesting for theories
of quantum gravity in that they are believed to probe the small scale structure
of the spacetime.
| [
{
"created": "Mon, 12 Dec 2011 20:58:05 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Feb 2012 20:10:57 GMT",
"version": "v2"
}
] | 2013-05-30 | [
[
"Casals",
"Marc",
""
],
[
"Ottewill",
"Adrian C.",
""
]
] | The 'retarded' Green function for fields propagating on a Schwarzschild black hole spacetime possesses a branch cut on the complex frequency plane. Classically, the branch cut is important, for example, in order to fully determine the response of the black hole to a linear field perturbation. The branch cut is also useful for the calculation of the self-force on a point particle moving in the Schwarzschild background. In this paper we use techniques of analytic-continuation to the complex plane of the radial coordinate in order to calculate the branch cut contribution to the Green function in the limit of large imaginary frequency. It is expected that the contribution of this frequency regime to the perturbation response and to the self-force will be mostly for short time intervals. We also determine the highly-damped quasinormal mode frequencies for electromagnetic perturbations in Schwarzschild for the first time (previously only the leading imaginary part was known), which seem to have a 'deep connection' with the branch cut. We find that these frequencies behave like $\omega_{\ell,n}= -\dfrac{in}{2}-\dfrac{i[\ell(\ell+1)]^2}{2n}+\dfrac{\pi^{1/2}(1-i)[\ell(\ell+1)]^3}{2^{3/2}n^{3/2}}+O(n^{-2})$. The highly-damped quasinormal modes are particularly interesting for theories of quantum gravity in that they are believed to probe the small scale structure of the spacetime. |
2010.15544 | Gang Wang | Gang Wang, Wei-Tou Ni, Wen-Biao Han, Cong-Feng Qiao | Algorithm for TDI numerical simulation and sensitivity investigation | 13 pages, 8 figures | Phys. Rev. D 103, 122006 (2021) | 10.1103/PhysRevD.103.122006 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a generic algorithm to determine the time delays and spacecraft
(S/C) positions to compose any time-delay interferometry (TDI) channel in the
dynamical case and evaluate its sensitivity by using a full numerical method.
We select 11 second-generation TDI channels constructed from four approaches
and investigate their gravitational wave responses, noise levels, and averaged
sensitivities under a numerical LISA orbit. The sensitivities of selected
channels are various especially for frequencies lower than 20 mHz. The optimal
channel A$_2$ (or equivalently E$_2$) combined from second-generation Michelson
TDI channels (X$_1$, X$_2$, and X$_3$) achieves the best sensitivity among the
channels, while the Sagnac $\alpha_1$ channel shows the worse sensitivity.
Multiple channels show better sensitivities at some characteristic frequencies
compared to the fiducial X$_1$ channel. The joint $\mathrm{A_2+E_2+T_2}$
observation not only enhances the sensitivity of the X$_1$ channel by a factor
of $\sqrt{2}$ to 2 but also improves the capacity of sky coverage.
| [
{
"created": "Thu, 29 Oct 2020 13:24:04 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Feb 2021 03:08:16 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Jun 2021 13:13:07 GMT",
"version": "v3"
}
] | 2021-06-30 | [
[
"Wang",
"Gang",
""
],
[
"Ni",
"Wei-Tou",
""
],
[
"Han",
"Wen-Biao",
""
],
[
"Qiao",
"Cong-Feng",
""
]
] | We introduce a generic algorithm to determine the time delays and spacecraft (S/C) positions to compose any time-delay interferometry (TDI) channel in the dynamical case and evaluate its sensitivity by using a full numerical method. We select 11 second-generation TDI channels constructed from four approaches and investigate their gravitational wave responses, noise levels, and averaged sensitivities under a numerical LISA orbit. The sensitivities of selected channels are various especially for frequencies lower than 20 mHz. The optimal channel A$_2$ (or equivalently E$_2$) combined from second-generation Michelson TDI channels (X$_1$, X$_2$, and X$_3$) achieves the best sensitivity among the channels, while the Sagnac $\alpha_1$ channel shows the worse sensitivity. Multiple channels show better sensitivities at some characteristic frequencies compared to the fiducial X$_1$ channel. The joint $\mathrm{A_2+E_2+T_2}$ observation not only enhances the sensitivity of the X$_1$ channel by a factor of $\sqrt{2}$ to 2 but also improves the capacity of sky coverage. |
1511.08969 | Mehdi Saravani | Michael Meiers, Mehdi Saravani and Niayesh Afshordi | Cosmic Censorship in Lorentz Violating Theories of Gravity | null | Phys. Rev. D 93, 104008 (2016) | 10.1103/PhysRevD.93.104008 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Is Cosmic Censorship special to General Relativity, or can it survive a
violation of equivalence principle? Recent studies have shown that
singularities in Lorentz violating Einstein-Aether (or Horava-Lifhsitz)
theories can lie behind a universal horizon in simple black hole spacetimes.
Even infinitely fast signals cannot escape these universal horizons. We extend
this result, for an incompressible aether, to 3+1d dynamical or spinning
spacetimes which possess inner killing horizons, and show that a universal
horizon always forms in between the outer and (would-be) inner horizons. This
finding suggests a notion of Cosmic Censorship, given that geometry in these
theories never evolves beyond the universal horizon (avoiding potentially
singular inner killing horizons). A surprising result is that there are 3
distinct possible stationary universal horizons for a spinning black hole, only
one of which matches the dynamical spherical solution. This motivates dynamical
studies of collapse in Einstein-Aether theories beyond spherical symmetry,
which may reveal instabilities around the spherical solution.
| [
{
"created": "Sun, 29 Nov 2015 05:20:38 GMT",
"version": "v1"
}
] | 2016-05-11 | [
[
"Meiers",
"Michael",
""
],
[
"Saravani",
"Mehdi",
""
],
[
"Afshordi",
"Niayesh",
""
]
] | Is Cosmic Censorship special to General Relativity, or can it survive a violation of equivalence principle? Recent studies have shown that singularities in Lorentz violating Einstein-Aether (or Horava-Lifhsitz) theories can lie behind a universal horizon in simple black hole spacetimes. Even infinitely fast signals cannot escape these universal horizons. We extend this result, for an incompressible aether, to 3+1d dynamical or spinning spacetimes which possess inner killing horizons, and show that a universal horizon always forms in between the outer and (would-be) inner horizons. This finding suggests a notion of Cosmic Censorship, given that geometry in these theories never evolves beyond the universal horizon (avoiding potentially singular inner killing horizons). A surprising result is that there are 3 distinct possible stationary universal horizons for a spinning black hole, only one of which matches the dynamical spherical solution. This motivates dynamical studies of collapse in Einstein-Aether theories beyond spherical symmetry, which may reveal instabilities around the spherical solution. |
0902.4787 | Gian Luigi Alberghi | G.L.Alberghi | CMB: A Look Inside the Inflaton | 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that if the field seeding the formation of the cosmic structures is a
dynamically arising bosonic condensate, the features we observe in the CMB
might be interpreted as a manifestation of its compositeness.
| [
{
"created": "Fri, 27 Feb 2009 10:02:55 GMT",
"version": "v1"
}
] | 2009-03-02 | [
[
"Alberghi",
"G. L.",
""
]
] | We show that if the field seeding the formation of the cosmic structures is a dynamically arising bosonic condensate, the features we observe in the CMB might be interpreted as a manifestation of its compositeness. |
2408.06829 | Salomeh Khoeini-Moghaddam | Salomeh Khoeini-Moghaddam | Tachyon Inflation in $R+R^2$ Background | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The presence of a tachyon field in $R+\mu R^2$ is considered. Our analysis
shows that the contribution of the tachyon field in energy density is
suppressed, but it affects cosmological parameters.
| [
{
"created": "Tue, 13 Aug 2024 11:39:30 GMT",
"version": "v1"
}
] | 2024-08-14 | [
[
"Khoeini-Moghaddam",
"Salomeh",
""
]
] | The presence of a tachyon field in $R+\mu R^2$ is considered. Our analysis shows that the contribution of the tachyon field in energy density is suppressed, but it affects cosmological parameters. |
gr-qc/9903019 | Kostas Kokkotas | H.R. Beyer and K.D. Kokkotas | On the r-mode spectrum of relativistic stars | 6 pages, no figures | Mon.Not.Roy.Astron.Soc. 308 (1999) 745-750 | 10.1046/j.1365-8711.1999.02739.x | null | gr-qc | null | We present a mathematically rigorous proof that the r-mode spectrum of
relativistic stars to the rotational lowest order has a continuous part. A
rigorous definition of this spectrum is given in terms of the spectrum of a
continuous linear operator. This study verifies earlier results by Kojima
(1998) about the nature of the r-mode spectrum.
| [
{
"created": "Fri, 5 Mar 1999 12:37:41 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Beyer",
"H. R.",
""
],
[
"Kokkotas",
"K. D.",
""
]
] | We present a mathematically rigorous proof that the r-mode spectrum of relativistic stars to the rotational lowest order has a continuous part. A rigorous definition of this spectrum is given in terms of the spectrum of a continuous linear operator. This study verifies earlier results by Kojima (1998) about the nature of the r-mode spectrum. |
1209.3726 | Valerio Faraoni | Valerio Faraoni and Charles S. Protheroe (Bishop's University) | Scalar field cosmology in phase space | 24 pages, 3 figures, to appear in General Relativity and Gravitation | null | 10.1007/s10714-012-1462-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using dynamical systems methods, we describe the evolution of a minimally
coupled scalar field and a Friedmann-Lemaitre-Robertson-Walker universe in the
context of general relativity, which is relevant for inflation and late-time
quintessence eras. Focussing on the spatially flat case, we examine the
geometrical structure of the phase space, locate the equilibrium points of the
system (de Sitter spaces with a constant scalar field), study their stability
through both a third-order perturbation analysis and Lyapunov functions, and
discuss the late-time asymptotics. As we do not specify the scalar field's
origin or its potential, the results are independent of the high-energy model.
| [
{
"created": "Mon, 17 Sep 2012 17:18:59 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
],
[
"Protheroe",
"Charles S.",
"",
"Bishop's University"
]
] | Using dynamical systems methods, we describe the evolution of a minimally coupled scalar field and a Friedmann-Lemaitre-Robertson-Walker universe in the context of general relativity, which is relevant for inflation and late-time quintessence eras. Focussing on the spatially flat case, we examine the geometrical structure of the phase space, locate the equilibrium points of the system (de Sitter spaces with a constant scalar field), study their stability through both a third-order perturbation analysis and Lyapunov functions, and discuss the late-time asymptotics. As we do not specify the scalar field's origin or its potential, the results are independent of the high-energy model. |
1309.2036 | Olivier Sarbach | Olivier Sarbach and Thomas Zannias | The geometry of the tangent bundle and the relativistic kinetic theory
of gases | 30 pages, 2 figures (including one new figure illustrating the
connection map). References have been added along with a new section briefly
discussing the Newtonian limit | Class.Quant.Grav. 31 (2014) 085013 | 10.1088/0264-9381/31/8/085013 | null | gr-qc cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article discusses the relativistic kinetic theory for a simple
collisionless gas from a geometric perspective. We start by reviewing the rich
geometrical structure of the tangent bundle TM of a given spacetime manifold,
including the splitting of the tangent spaces of TM into horizontal and
vertical subspaces and the natural metric and symplectic structure it induces
on TM. Based on these structures we introduce the Liouville vector field L and
a suitable Hamiltonian function H on TM. The Liouville vector field turns out
to be the Hamiltonian vector field associated to H. On the other hand, H also
defines the mass shells as Lorentzian submanifolds of the tangent bundle. A
simple collisionless gas is described by a distribution function on a
particular mass shell, satisfying the Liouville equation. Together with the
Liouville vector field the distribution function can be thought of as defining
a fictitious incompressible fluid on the mass shells, with associated conserved
current density. Flux integrals of this current density provide the averaged
properties of the gas, while suitable fibre integrals of the distribution
function define divergence-free tensor fields on the spacetime manifold such as
the current density and stress-energy tensor. Finally, we discuss the
relationship between symmetries of the spacetime manifold and symmetries of the
distribution function.
As a first application of our formalism we derive the most general
spherically symmetric distribution function on any spherically symmetric
spacetime and write the Einstein-Liouville equations as effective field
equations on the two-dimensional radial manifold. As a second application we
derive the most general collisionless distribution function on a Kerr black
hole spacetime background.
| [
{
"created": "Mon, 9 Sep 2013 03:36:53 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Apr 2014 20:52:04 GMT",
"version": "v2"
}
] | 2014-06-17 | [
[
"Sarbach",
"Olivier",
""
],
[
"Zannias",
"Thomas",
""
]
] | This article discusses the relativistic kinetic theory for a simple collisionless gas from a geometric perspective. We start by reviewing the rich geometrical structure of the tangent bundle TM of a given spacetime manifold, including the splitting of the tangent spaces of TM into horizontal and vertical subspaces and the natural metric and symplectic structure it induces on TM. Based on these structures we introduce the Liouville vector field L and a suitable Hamiltonian function H on TM. The Liouville vector field turns out to be the Hamiltonian vector field associated to H. On the other hand, H also defines the mass shells as Lorentzian submanifolds of the tangent bundle. A simple collisionless gas is described by a distribution function on a particular mass shell, satisfying the Liouville equation. Together with the Liouville vector field the distribution function can be thought of as defining a fictitious incompressible fluid on the mass shells, with associated conserved current density. Flux integrals of this current density provide the averaged properties of the gas, while suitable fibre integrals of the distribution function define divergence-free tensor fields on the spacetime manifold such as the current density and stress-energy tensor. Finally, we discuss the relationship between symmetries of the spacetime manifold and symmetries of the distribution function. As a first application of our formalism we derive the most general spherically symmetric distribution function on any spherically symmetric spacetime and write the Einstein-Liouville equations as effective field equations on the two-dimensional radial manifold. As a second application we derive the most general collisionless distribution function on a Kerr black hole spacetime background. |
1204.4319 | Deyou Chen | Deyou Chen and Haitang Yang | Spectroscopy of the Einstein-Maxwell-Dilaton-Axion black hole | 9 pages | General Relativity and Gravitation, Volume 44, 2012, Issue 10,
pp.2529-2536 | 10.1007/s10714-012-1410-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The entropy spectrum of a spherically symmetric black hole was derived via
the Bohr-Sommerfeld quantization rule in Majhi and Vagenas's work. Extending
this work to charged and rotating black holes, we quantize the horizon area and
the entropy of an Einstein-Maxwell-Dilaton-Axion (EMDA) black hole via the
Bohr-Sommerfeld quantization rule and the adiabatic invariance. The result
shows the area spectrum and the entropy spectrum are respectively equally
spaced and independent on the parameters of the black hole.
| [
{
"created": "Thu, 19 Apr 2012 11:39:18 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Oct 2012 13:52:00 GMT",
"version": "v2"
}
] | 2015-06-04 | [
[
"Chen",
"Deyou",
""
],
[
"Yang",
"Haitang",
""
]
] | The entropy spectrum of a spherically symmetric black hole was derived via the Bohr-Sommerfeld quantization rule in Majhi and Vagenas's work. Extending this work to charged and rotating black holes, we quantize the horizon area and the entropy of an Einstein-Maxwell-Dilaton-Axion (EMDA) black hole via the Bohr-Sommerfeld quantization rule and the adiabatic invariance. The result shows the area spectrum and the entropy spectrum are respectively equally spaced and independent on the parameters of the black hole. |
1405.6396 | David Garfinkle | Alexander Tolish, Lydia Bieri, David Garfinkle, and Robert M. Wald | Examination of a simple example of gravitational wave memory | null | Phys. Rev. D 90, 044060 (2014) | 10.1103/PhysRevD.90.044060 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine a simple example of gravitational wave memory due to the decay of
a point particle into two point particles. In the case where one of the decay
products is null, there are two types of memory: a null memory due to the null
particle and an ordinary memory due to the recoiling timelike particle. In the
case where both decay products are timelike, there is only ordinary memory.
However, this ordinary memory can mimic the null memory in the limit where one
of the decay products has a large velocity.
| [
{
"created": "Sun, 25 May 2014 15:31:35 GMT",
"version": "v1"
}
] | 2014-09-05 | [
[
"Tolish",
"Alexander",
""
],
[
"Bieri",
"Lydia",
""
],
[
"Garfinkle",
"David",
""
],
[
"Wald",
"Robert M.",
""
]
] | We examine a simple example of gravitational wave memory due to the decay of a point particle into two point particles. In the case where one of the decay products is null, there are two types of memory: a null memory due to the null particle and an ordinary memory due to the recoiling timelike particle. In the case where both decay products are timelike, there is only ordinary memory. However, this ordinary memory can mimic the null memory in the limit where one of the decay products has a large velocity. |
1911.08624 | Iarley P. Lobo Dr | I. P. Lobo, V. B. Bezerra, J. P. Morais Gra\c{c}a, Luis C. N. Santos,
M. Ronco | Effects of Planck-scale-modified dispersion relations on the
thermodynamics of charged black holes | 16 pages, 8 figures | Phys. Rev. D 101, 084004 (2020) | 10.1103/PhysRevD.101.084004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Considering corrections produced by modified dispersion relations on the
equation of state parameter of radiation, we study the induced black hole
metric inspired by Kiselev's ansatz, thus defining a deformed
Reissner-Nordstr\"{o}m metric. In particular, we consider thermodynamic
properties of such a black hole from the combined viewpoints of the modified
equation of state parameter and the phenomenological approach to the quantum
gravity problem called rainbow gravity.
| [
{
"created": "Tue, 19 Nov 2019 23:12:13 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Apr 2020 14:37:38 GMT",
"version": "v2"
}
] | 2020-04-03 | [
[
"Lobo",
"I. P.",
""
],
[
"Bezerra",
"V. B.",
""
],
[
"Graça",
"J. P. Morais",
""
],
[
"Santos",
"Luis C. N.",
""
],
[
"Ronco",
"M.",
""
]
] | Considering corrections produced by modified dispersion relations on the equation of state parameter of radiation, we study the induced black hole metric inspired by Kiselev's ansatz, thus defining a deformed Reissner-Nordstr\"{o}m metric. In particular, we consider thermodynamic properties of such a black hole from the combined viewpoints of the modified equation of state parameter and the phenomenological approach to the quantum gravity problem called rainbow gravity. |
gr-qc/9806025 | Claude Barrabes | C. Barrab\`es and P.A. Hogan | Light-like Signals in General relativity and Cosmology | 21 pages, latex, no figures | Phys.Rev. D58 (1998) 044013 | 10.1103/PhysRevD.58.044013 | null | gr-qc | null | The modelling of light-like signals in General Relativity taking the form of
impulsive gravitational waves and light-like shells of matter is examined.
Systematic deductions from the Bianchi identities are made. These are based
upon Penrose's hierarchical classification of the geometry induced on the null
hypersurface history of the surface by its imbedding in the space-times to the
future and to the past of it. The signals are not confined to propagate in a
vacuum and thus their interaction with matter (a burst of radiation propagating
through a cosmic fluid, for example) is also studied. Results are accompanied
by illustrative examples using cosmological models, vacuum space-times, the de
sitter univers and Minkowskian space-time.
| [
{
"created": "Thu, 4 Jun 1998 14:50:15 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Barrabès",
"C.",
""
],
[
"Hogan",
"P. A.",
""
]
] | The modelling of light-like signals in General Relativity taking the form of impulsive gravitational waves and light-like shells of matter is examined. Systematic deductions from the Bianchi identities are made. These are based upon Penrose's hierarchical classification of the geometry induced on the null hypersurface history of the surface by its imbedding in the space-times to the future and to the past of it. The signals are not confined to propagate in a vacuum and thus their interaction with matter (a burst of radiation propagating through a cosmic fluid, for example) is also studied. Results are accompanied by illustrative examples using cosmological models, vacuum space-times, the de sitter univers and Minkowskian space-time. |
gr-qc/0109085 | Emilio Elizalde | Alexander Burinskii, Emilio Elizalde, Sergi R. Hildebrandt, Giulio
Magli | Regular Sources of the Kerr-Schild class for Rotating and Nonrotating
Black Hole Solutions | LaTeX, 26 pages, 6 figures | Phys.Rev.D65:064039,2002 | 10.1103/PhysRevD.65.064039 | null | gr-qc astro-ph hep-th math-ph math.MP | null | A unified approach to regular interiors of black holes with smooth matter
distributions in the core region is given. The approach is based on a class of
Kerr-Schild metrics representing minimal deformations of the Kerr-Newman
solution, and allows us to give a common treatment for (charged and uncharged)
rotating and nonrotating black holes. It is shown that the requirement of
smoothness of the source constraints the structure of the core region in many
respects: in particular, for Schwarzschild holes a de Sitter core can be
selected, which is surrounded by a smooth shell giving a leading contribution
to the total mass of the source. In the rotating, noncharged case the source
has a similar structure, taking the form of a (anisotropic and rotating) de
Sitter-like core surrounded by a rotating elliptic shell. The Kerr singular
ring is regularized by anisotropic matter rotating in the equatorial plane, so
that the negative sheet of the Kerr geometry is absent. In the charged case the
sources take the form of ``bags'', which can have de Sitter or anti de Sitter
interiors and a smooth domain wall boundary, with a tangential stress providing
charge confinement. The ADM and Tolman relations are used to calculate the
total mass of the sources.
| [
{
"created": "Tue, 25 Sep 2001 16:40:49 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Mar 2002 10:04:21 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Burinskii",
"Alexander",
""
],
[
"Elizalde",
"Emilio",
""
],
[
"Hildebrandt",
"Sergi R.",
""
],
[
"Magli",
"Giulio",
""
]
] | A unified approach to regular interiors of black holes with smooth matter distributions in the core region is given. The approach is based on a class of Kerr-Schild metrics representing minimal deformations of the Kerr-Newman solution, and allows us to give a common treatment for (charged and uncharged) rotating and nonrotating black holes. It is shown that the requirement of smoothness of the source constraints the structure of the core region in many respects: in particular, for Schwarzschild holes a de Sitter core can be selected, which is surrounded by a smooth shell giving a leading contribution to the total mass of the source. In the rotating, noncharged case the source has a similar structure, taking the form of a (anisotropic and rotating) de Sitter-like core surrounded by a rotating elliptic shell. The Kerr singular ring is regularized by anisotropic matter rotating in the equatorial plane, so that the negative sheet of the Kerr geometry is absent. In the charged case the sources take the form of ``bags'', which can have de Sitter or anti de Sitter interiors and a smooth domain wall boundary, with a tangential stress providing charge confinement. The ADM and Tolman relations are used to calculate the total mass of the sources. |
1806.08897 | Dominik \v{S}afr\'anek | Joshua M. Deutsch, Dominik \v{S}afr\'anek, and Anthony Aguirre | Probabilistic bound on extreme fluctuations in isolated quantum systems | 11+5 pages, 4 figures. v2: extended figures and discussions of
probability of a particle collapse into a small region of space. Title
changed | Phys. Rev. E 101, 032112 (2020) | 10.1103/PhysRevE.101.032112 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We ask to what extent an isolated quantum system can eventually "contract" to
be contained within a given Hilbert subspace. We do this by starting with an
initial random state, considering the probability that all the particles will
be measured in a fixed subspace, and maximizing this probability over all time.
This is relevant, for example, in a cosmological context, which may have access
to indefinite timescales. We find that when the subspace is much smaller than
the entire space, this maximal probability goes to $1/2$ for real initial wave
functions, and to $\pi^2/16$ when the initial wave function has been drawn from
a complex ensemble. For example when starting in a real generic state, the
chances of collapsing all particles into a small box will be less than but come
arbitrarily close to $50\%$. This contraction corresponds to an entropy
reduction by a factor of approximately two, thus bounding large downward
fluctuations in entropy from generic initial states.
| [
{
"created": "Sat, 23 Jun 2018 02:53:07 GMT",
"version": "v1"
},
{
"created": "Wed, 13 May 2020 04:30:09 GMT",
"version": "v2"
}
] | 2020-05-14 | [
[
"Deutsch",
"Joshua M.",
""
],
[
"Šafránek",
"Dominik",
""
],
[
"Aguirre",
"Anthony",
""
]
] | We ask to what extent an isolated quantum system can eventually "contract" to be contained within a given Hilbert subspace. We do this by starting with an initial random state, considering the probability that all the particles will be measured in a fixed subspace, and maximizing this probability over all time. This is relevant, for example, in a cosmological context, which may have access to indefinite timescales. We find that when the subspace is much smaller than the entire space, this maximal probability goes to $1/2$ for real initial wave functions, and to $\pi^2/16$ when the initial wave function has been drawn from a complex ensemble. For example when starting in a real generic state, the chances of collapsing all particles into a small box will be less than but come arbitrarily close to $50\%$. This contraction corresponds to an entropy reduction by a factor of approximately two, thus bounding large downward fluctuations in entropy from generic initial states. |
0901.1017 | Mariano Cadoni | M. Cadoni, M. Casula | General models of Einstein gravity with a non-Newtonian weak-field limit | 9 pages | Gen.Rel.Grav.42:103-112,2010 | 10.1007/s10714-009-0820-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate Einstein theories of gravity, coupled to a scalar field \vphi
and point-like matter, which are characterized by a scalar field-dependent
matter coupling function e^{H(\vphi)}. We show that under mild constraints on
the form of the potential for the scalar field, there are a broad class of
Einstein-like gravity models -characterized by the asymptotic behavior of H-
which allow for a non-Newtonian weak-field limit with the gravitational
potential behaving for large distances as ln r. The Newtonian term GM/r appears
only as sub-leading. We point out that this behavior is also shared by gravity
models described by f(R) Lagrangians. The relevance of our results for the
building of infrared modified theories of gravity and for modified Newtonian
dynamics is also discussed.
| [
{
"created": "Thu, 8 Jan 2009 11:06:10 GMT",
"version": "v1"
}
] | 2014-11-18 | [
[
"Cadoni",
"M.",
""
],
[
"Casula",
"M.",
""
]
] | We investigate Einstein theories of gravity, coupled to a scalar field \vphi and point-like matter, which are characterized by a scalar field-dependent matter coupling function e^{H(\vphi)}. We show that under mild constraints on the form of the potential for the scalar field, there are a broad class of Einstein-like gravity models -characterized by the asymptotic behavior of H- which allow for a non-Newtonian weak-field limit with the gravitational potential behaving for large distances as ln r. The Newtonian term GM/r appears only as sub-leading. We point out that this behavior is also shared by gravity models described by f(R) Lagrangians. The relevance of our results for the building of infrared modified theories of gravity and for modified Newtonian dynamics is also discussed. |
1504.02069 | Lars Andersson | Lars Andersson, Thomas B\"ackdahl and Pieter Blue | Spin geometry and conservation laws in the Kerr spacetime | 30 pages. To appear in the volume "The Centenary of General
Relativity" in "Surveys in Differential Geometry", edited by Lydia Bieri and
Shing-Tung Yau, in the series "Surveys in Differential Geometry" | null | 10.4310/SDG.2015.v20.n1.a8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we will review some facts, both classical and recent,
concerning the geometry and analysis of the Kerr and related black hole
spacetimes. This includes the analysis of test fields on these spacetimes.
Central to our analysis is the existence of a valence $(2,0)$ Killing spinor,
which we use to construct symmetry operators and conserved currents as well as
a new energy momentum tensor for the Maxwell test fields on a class of
spacetimes containing the Kerr spacetime. We then outline how this new energy
momentum tensor can be used to obtain decay estimated for Maxwell test fields.
An important motivation for this work is the black hole stability problem,
where fields with non-zero spin present interesting new challenges. The main
tool in the analysis is the 2-spinor calculus, and for completeness we
introduce its main features.
| [
{
"created": "Wed, 8 Apr 2015 18:31:06 GMT",
"version": "v1"
}
] | 2015-11-30 | [
[
"Andersson",
"Lars",
""
],
[
"Bäckdahl",
"Thomas",
""
],
[
"Blue",
"Pieter",
""
]
] | In this paper we will review some facts, both classical and recent, concerning the geometry and analysis of the Kerr and related black hole spacetimes. This includes the analysis of test fields on these spacetimes. Central to our analysis is the existence of a valence $(2,0)$ Killing spinor, which we use to construct symmetry operators and conserved currents as well as a new energy momentum tensor for the Maxwell test fields on a class of spacetimes containing the Kerr spacetime. We then outline how this new energy momentum tensor can be used to obtain decay estimated for Maxwell test fields. An important motivation for this work is the black hole stability problem, where fields with non-zero spin present interesting new challenges. The main tool in the analysis is the 2-spinor calculus, and for completeness we introduce its main features. |
0910.5755 | Morgan Le Delliou | Jos\'e Pedro Mimoso (DFUL, CAAUL, CFTC), Morgan Le Delliou (CFTC,
IFT), Filipe C. Mena (CMAT) | Separating expansion from contraction in spherically symmetric models
with a perfect-fluid: Generalization of the Tolman-Oppenheimer-Volkoff
condition and application to models with a cosmological constant | 17pp, 9 figures, accepted by PRD | Phys.Rev.D81:123514,2010 | 10.1103/PhysRevD.81.123514 | IFT-UAM/CSIC-08-14 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate spherically symmetric perfect-fluid spacetimes and discuss the
existence and stability of a dividing shell separating expanding and collapsing
regions. We perform a 3+1 splitting and obtain gauge invariant conditions
relating the intrinsic spatial curvature of the shells to the Misner-Sharp mass
and to a function of the pressure that we introduce and that generalizes the
Tolman-Oppenheimer-Volkoff equilibrium condition. We find that surfaces
fulfilling those two conditions fit, locally, the requirements of a dividing
shell and we argue that cosmological initial conditions should allow its global
validity. We analyze the particular cases of the Lema\^itre-Tolman-Bondi dust
models with a cosmological constant as an example of a cold dark matter model
with a cosmological constant (\Lambda-CDM) and its generalization to contain a
central perfect-fluid core. These models provide simple, but physically
interesting illustrations of our results.
| [
{
"created": "Fri, 30 Oct 2009 15:18:08 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Oct 2009 20:44:41 GMT",
"version": "v2"
},
{
"created": "Mon, 14 Jun 2010 12:40:54 GMT",
"version": "v3"
}
] | 2014-11-20 | [
[
"Mimoso",
"José Pedro",
"",
"DFUL, CAAUL, CFTC"
],
[
"Delliou",
"Morgan Le",
"",
"CFTC,\n IFT"
],
[
"Mena",
"Filipe C.",
"",
"CMAT"
]
] | We investigate spherically symmetric perfect-fluid spacetimes and discuss the existence and stability of a dividing shell separating expanding and collapsing regions. We perform a 3+1 splitting and obtain gauge invariant conditions relating the intrinsic spatial curvature of the shells to the Misner-Sharp mass and to a function of the pressure that we introduce and that generalizes the Tolman-Oppenheimer-Volkoff equilibrium condition. We find that surfaces fulfilling those two conditions fit, locally, the requirements of a dividing shell and we argue that cosmological initial conditions should allow its global validity. We analyze the particular cases of the Lema\^itre-Tolman-Bondi dust models with a cosmological constant as an example of a cold dark matter model with a cosmological constant (\Lambda-CDM) and its generalization to contain a central perfect-fluid core. These models provide simple, but physically interesting illustrations of our results. |
1007.2589 | Nikolai V. Mitskievich | Nikolai V. Mitskievich | Gravitational interaction for light-like motion in classical and quantum
theory | LaTeX with babel(English and Russian), 8 pages, no figures | Published in the Works of the Institute of Physics of Estonian
Academy of Sciences, Tartu, 1989 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On the basis of an exact vacuum solution of Einstein's equations, {\it vis}.
the pencil-of-light field, we study the light-like motion of test and non-test
objects. We also consider the quantum theoretical interaction of massless
scalar particles through virtual gravitons. The dragging phenomenon is
manifested and its agreement with astronomical observations established.
This paper submitted to {\bf arXiv} is a somewhat reedited copy of my article
dedicated to Dr. Ivar Piir in a volume published on the occasion of his 60th
birthday in 1989 in Tartu by the Estonian Academy of Sciences.
| [
{
"created": "Thu, 15 Jul 2010 15:35:26 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Jul 2010 04:20:21 GMT",
"version": "v2"
}
] | 2010-07-19 | [
[
"Mitskievich",
"Nikolai V.",
""
]
] | On the basis of an exact vacuum solution of Einstein's equations, {\it vis}. the pencil-of-light field, we study the light-like motion of test and non-test objects. We also consider the quantum theoretical interaction of massless scalar particles through virtual gravitons. The dragging phenomenon is manifested and its agreement with astronomical observations established. This paper submitted to {\bf arXiv} is a somewhat reedited copy of my article dedicated to Dr. Ivar Piir in a volume published on the occasion of his 60th birthday in 1989 in Tartu by the Estonian Academy of Sciences. |
2011.05947 | Benito A. Ju\'arez-Aubry | Benito A. Ju\'arez-Aubry | Semiclassical gravity in static spacetimes as a constrained initial
value problem | The previous version has been reorganised and expanded and minor
errors have been fixed. 25 pages | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the semiclassical Einstein field equations with a Klein-Gordon field
in ultrastatic and static spacetimes. In both cases, the equations for the
spacetime metric become constraint equations. In the ultrastatic case, the
Hadamard singular structure can be characterised explicitly, which allows one
to in principle give initial data for the Wightman function that has correct
distributional singularities, such that the expectation value of the
renormalised stress-energy tensor of the solution can be defined, and that
hence the semiclassical Einstein equations make sense. Assuming a "positive
energy" condition for the Klein-Gordon operator, we characterise the states for
which, if the constraints hold for initial data, they hold everywhere in
spacetime. These turn out to be time-translation invariant states. The static
case is analysed by conformal techniques, effectively reducing the problem to
an ultrastatic one.
| [
{
"created": "Wed, 11 Nov 2020 18:05:03 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Oct 2021 02:18:07 GMT",
"version": "v2"
}
] | 2021-11-01 | [
[
"Juárez-Aubry",
"Benito A.",
""
]
] | We study the semiclassical Einstein field equations with a Klein-Gordon field in ultrastatic and static spacetimes. In both cases, the equations for the spacetime metric become constraint equations. In the ultrastatic case, the Hadamard singular structure can be characterised explicitly, which allows one to in principle give initial data for the Wightman function that has correct distributional singularities, such that the expectation value of the renormalised stress-energy tensor of the solution can be defined, and that hence the semiclassical Einstein equations make sense. Assuming a "positive energy" condition for the Klein-Gordon operator, we characterise the states for which, if the constraints hold for initial data, they hold everywhere in spacetime. These turn out to be time-translation invariant states. The static case is analysed by conformal techniques, effectively reducing the problem to an ultrastatic one. |
1606.07733 | Guzel Garipova | Alexander A. Potapov, Guzel M. Garipova, Kamal K. Nandi | Revisiting perfect fluid dark matter: Observational constraints from our
galaxy | null | Phys. Lett. B 753 (2016) 140-146 | 10.1016/j.physletb.2015.11.057 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit certain features of an assumed spherically symmetric perfect fluid
dark matter halo in the light of the observed data of our galaxy
| [
{
"created": "Thu, 23 Jun 2016 05:07:31 GMT",
"version": "v1"
}
] | 2016-06-30 | [
[
"Potapov",
"Alexander A.",
""
],
[
"Garipova",
"Guzel M.",
""
],
[
"Nandi",
"Kamal K.",
""
]
] | We revisit certain features of an assumed spherically symmetric perfect fluid dark matter halo in the light of the observed data of our galaxy |
gr-qc/9701005 | Elias Kiritsis | E. Kiritsis, C. Kounnas | Dynamical Topology Change, Compactification and Waves in String
Cosmology | 29pp. LateX, no figures. | Nucl.Phys.Proc.Suppl.41:311,1995 | 10.1016/0920-5632(95)00440-K | null | gr-qc | null | Exact string solutions are presented, where moduli fields are varying with
time. They provide examples where a dynamical change of the topology of space
is occurring. Some other solutions give cosmological examples where some
dimensions are compactified dynamically or simulate pre-big bang type
scenarios. Some lessons are drawn concerning the region of validity of
effective theories and how they can be glued together, using stringy
information in the region where the geometry and topology are not well defined
from the low energy point of view. Other time dependent solutions are presented
where a hierarchy of scales is absent. Such solutions have dynamics which is
qualitatively different and resemble plane gravitational waves. (Talk given at
the Trieste Spring School and Workshop, 1994.)
| [
{
"created": "Sun, 5 Jan 1997 16:04:19 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Kiritsis",
"E.",
""
],
[
"Kounnas",
"C.",
""
]
] | Exact string solutions are presented, where moduli fields are varying with time. They provide examples where a dynamical change of the topology of space is occurring. Some other solutions give cosmological examples where some dimensions are compactified dynamically or simulate pre-big bang type scenarios. Some lessons are drawn concerning the region of validity of effective theories and how they can be glued together, using stringy information in the region where the geometry and topology are not well defined from the low energy point of view. Other time dependent solutions are presented where a hierarchy of scales is absent. Such solutions have dynamics which is qualitatively different and resemble plane gravitational waves. (Talk given at the Trieste Spring School and Workshop, 1994.) |
2405.13607 | Yurii Ignat'ev | Yu. G. Ignat'ev, I. A. Kokh | Cosmological models based on an asymmetric scalar doublet with kinetic
coupling of components. I. General properties of the cosmological model | 18 pages, 19 figures, 23 references | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A mathematical model of the Universe evolution, based on asymmetric doublet
of classical and phantom dcalar Higgs fields with a kinetic connection between
the components, has been constructed and studied. A detailed qualitative
analysis was carried out, the properties of the model's symmetry and invarience
with respect to the similariry transformations of fundamental constants were
proven. The principles of numerical modeling are formulated and an example of
numerical modeling of the evolution of the model for a specific set of
fundamental constants and initial conditions is given. the asymptotic behavior
of the model near cosmological singularities is studied. It is shown that
cosmological model near singularities manifests itself as an ideal fluid with
an extremelly ripid equation of state. Keywords: cosmological model, phantom
and classical scalar fields, kinetic interection, quality analysis, asymptotic
behavior, numerrical modeling.
| [
{
"created": "Wed, 22 May 2024 12:58:49 GMT",
"version": "v1"
}
] | 2024-05-24 | [
[
"Ignat'ev",
"Yu. G.",
""
],
[
"Kokh",
"I. A.",
""
]
] | A mathematical model of the Universe evolution, based on asymmetric doublet of classical and phantom dcalar Higgs fields with a kinetic connection between the components, has been constructed and studied. A detailed qualitative analysis was carried out, the properties of the model's symmetry and invarience with respect to the similariry transformations of fundamental constants were proven. The principles of numerical modeling are formulated and an example of numerical modeling of the evolution of the model for a specific set of fundamental constants and initial conditions is given. the asymptotic behavior of the model near cosmological singularities is studied. It is shown that cosmological model near singularities manifests itself as an ideal fluid with an extremelly ripid equation of state. Keywords: cosmological model, phantom and classical scalar fields, kinetic interection, quality analysis, asymptotic behavior, numerrical modeling. |
1904.04842 | Charles Woodford | Charles J. Woodford, Michael Boyle, Harald P. Pfeiffer | Compact Binary Waveform Center-of-Mass Corrections | 20 pages, 15 figures | Phys. Rev. D 100, 124010 (2019) | 10.1103/PhysRevD.100.124010 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a detailed study of the center-of-mass (c.m.) motion seen in
simulations produced by the Simulating eXtreme Spacetimes (SXS) collaboration.
We investigate potential physical sources for the large c.m. motion in binary
black hole simulations and find that a significant fraction of the c.m. motion
cannot be explained physically, thus concluding that it is largely a gauge
effect. These large c.m. displacements cause mode mixing in the gravitational
waveform, most easily recognized as amplitude oscillations caused by the
dominant (2,$\pm$2) modes mixing into subdominant modes. This mixing does not
diminish with increasing distance from the source; it is present even in
asymptotic waveforms, regardless of the method of data extraction. We describe
the current c.m.-correction method used by the SXS collaboration, which is
based on counteracting the motion of the c.m. as measured by the trajectories
of the apparent horizons in the simulations, and investigate potential methods
to improve that correction to the waveform. We also present a complementary
method for computing an optimal c.m. correction or evaluating any other c.m.
transformation based solely on the asymptotic waveform data.
| [
{
"created": "Tue, 9 Apr 2019 18:00:06 GMT",
"version": "v1"
},
{
"created": "Wed, 1 May 2019 16:51:27 GMT",
"version": "v2"
},
{
"created": "Tue, 10 Dec 2019 20:20:22 GMT",
"version": "v3"
}
] | 2019-12-12 | [
[
"Woodford",
"Charles J.",
""
],
[
"Boyle",
"Michael",
""
],
[
"Pfeiffer",
"Harald P.",
""
]
] | We present a detailed study of the center-of-mass (c.m.) motion seen in simulations produced by the Simulating eXtreme Spacetimes (SXS) collaboration. We investigate potential physical sources for the large c.m. motion in binary black hole simulations and find that a significant fraction of the c.m. motion cannot be explained physically, thus concluding that it is largely a gauge effect. These large c.m. displacements cause mode mixing in the gravitational waveform, most easily recognized as amplitude oscillations caused by the dominant (2,$\pm$2) modes mixing into subdominant modes. This mixing does not diminish with increasing distance from the source; it is present even in asymptotic waveforms, regardless of the method of data extraction. We describe the current c.m.-correction method used by the SXS collaboration, which is based on counteracting the motion of the c.m. as measured by the trajectories of the apparent horizons in the simulations, and investigate potential methods to improve that correction to the waveform. We also present a complementary method for computing an optimal c.m. correction or evaluating any other c.m. transformation based solely on the asymptotic waveform data. |
1706.00895 | Svetlana Jorstad | Dmitrij Nagirner and Svetlana Jorstad | Basic geometric and kinematic features of the Standard Cosmological
Model | Submitted to Journal of Cosmology and Astrophysical Particles | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we calculate quantitative characteristics of basic geometric
and kinematic properties of the Standard Cosmological Model ($\Lambda$CDM).
Using equations of Friedman uniform cosmological models we derive equations
characterizing a $\Lambda$CDM, which describes the most appropriate real
universe. The equations take into account the effects of radiation and
ultra-relativistic neutrinos. We show that the universe at very early and late
stages can be described to sufficient accuracy by simple formulas. We derive
moments when densities of gravitational components of the universe become
equal, when they contribute equally to the gravitational force, when the
accelerating expansion of space starts, and several others. The distance to the
expanding spherical horizon and its acceleration are determined. Terms of the
horizon, second inflation, and second horizon are explained. The remote future
of the universe and the opportunity in principle of connection with
extraterrestrial civilizations are discussed.
| [
{
"created": "Sat, 3 Jun 2017 03:48:22 GMT",
"version": "v1"
}
] | 2017-06-06 | [
[
"Nagirner",
"Dmitrij",
""
],
[
"Jorstad",
"Svetlana",
""
]
] | In this paper we calculate quantitative characteristics of basic geometric and kinematic properties of the Standard Cosmological Model ($\Lambda$CDM). Using equations of Friedman uniform cosmological models we derive equations characterizing a $\Lambda$CDM, which describes the most appropriate real universe. The equations take into account the effects of radiation and ultra-relativistic neutrinos. We show that the universe at very early and late stages can be described to sufficient accuracy by simple formulas. We derive moments when densities of gravitational components of the universe become equal, when they contribute equally to the gravitational force, when the accelerating expansion of space starts, and several others. The distance to the expanding spherical horizon and its acceleration are determined. Terms of the horizon, second inflation, and second horizon are explained. The remote future of the universe and the opportunity in principle of connection with extraterrestrial civilizations are discussed. |
2009.01484 | Guglielmo M. Tino | Guglielmo M. Tino | Testing gravity with cold atom interferometry: Results and prospects | null | 2021 Quantum Science and Technology - Focus Issue on "Quantum
sensors for new-physics discoveries", Special Issue Guest Editors: Marianna
Safronova and Dmitry Budker | 10.1088/2058-9565/abd83e | null | gr-qc physics.atom-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Atom interferometers have been developed in the last three decades as new
powerful tools to investigate gravity. They were used for measuring the gravity
acceleration, the gravity gradient, and the gravity-field curvature, for the
determination of the gravitational constant, for the investigation of gravity
at microscopic distances, to test the equivalence principle of general
relativity and the theories of modified gravity, to probe the interplay between
gravitational and quantum physics and to test quantum gravity models, to search
for dark matter and dark energy, and they were proposed as new detectors for
the observation of gravitational waves. Here I describe past and ongoing
experiments with an outlook on what I think are the main prospects in this
field and the potential to search for new physics.
| [
{
"created": "Thu, 3 Sep 2020 06:51:26 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Sep 2020 21:00:44 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Jan 2021 11:06:44 GMT",
"version": "v3"
}
] | 2021-01-06 | [
[
"Tino",
"Guglielmo M.",
""
]
] | Atom interferometers have been developed in the last three decades as new powerful tools to investigate gravity. They were used for measuring the gravity acceleration, the gravity gradient, and the gravity-field curvature, for the determination of the gravitational constant, for the investigation of gravity at microscopic distances, to test the equivalence principle of general relativity and the theories of modified gravity, to probe the interplay between gravitational and quantum physics and to test quantum gravity models, to search for dark matter and dark energy, and they were proposed as new detectors for the observation of gravitational waves. Here I describe past and ongoing experiments with an outlook on what I think are the main prospects in this field and the potential to search for new physics. |
2405.02455 | Dhruba Jyoti Gogoi Dr. | Dhruba Jyoti Gogoi | Violation of Hod's Conjecture and Probing it with Optical properties of
a 5-D black hole in Einstein Gauss-Bonnet Bumblebee theory of gravity | 16 pages, 8 figures (published version). arXiv admin note: text
overlap with arXiv:2102.13335, arXiv:2302.01580, arXiv:2005.09761 by other
authors | Phys.Dark Univ. 45 (2024) 101535 | 10.1016/j.dark.2024.101535 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work, the quasinormal modes of a $5$-D black hole in Einstein
Gauss-Bonnet Bumblebee theory of gravity have been investigated with the help
of the Pad\'e averaged higher order WKB approximation method and the validity
of Hod's conjecture has been studied. It is found that the presence of Lorentz
symmetry breaking due to the Bumblebee field favours Hod's conjecture. But in
the case of the Gauss-Bonnet term, an increase in the coupling parameter
increases the chances of violation of Hod's conjecture. We further investigated
the optical properties of the black hole {\it viz.}, shadow and emission rate.
It is found that a black hole with a lower lifetime favours Hod's conjecture.
| [
{
"created": "Fri, 3 May 2024 19:42:46 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Jul 2024 17:52:05 GMT",
"version": "v2"
}
] | 2024-07-16 | [
[
"Gogoi",
"Dhruba Jyoti",
""
]
] | In this work, the quasinormal modes of a $5$-D black hole in Einstein Gauss-Bonnet Bumblebee theory of gravity have been investigated with the help of the Pad\'e averaged higher order WKB approximation method and the validity of Hod's conjecture has been studied. It is found that the presence of Lorentz symmetry breaking due to the Bumblebee field favours Hod's conjecture. But in the case of the Gauss-Bonnet term, an increase in the coupling parameter increases the chances of violation of Hod's conjecture. We further investigated the optical properties of the black hole {\it viz.}, shadow and emission rate. It is found that a black hole with a lower lifetime favours Hod's conjecture. |
2011.09923 | Zhi-Wei Wang | Zhi-Wei Wang and Samuel L. Braunstein | Could dark matter be a natural consequence of a dynamical universe? | 8 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct the gravitating mass of an isolated composite system on
asymptotically-flat spacetimes within conventional general relativity and
investigate when this quantity is well defined. For stationary spacetimes, this
quantity is known to exactly equal the physical (ADM) mass. However, it remains
an open question whether these two masses are equal in the absence of a
timelike Killing vector. This is especially apropos since our universe has an
`origin' and hence no such Killing vector. Further, if these masses failed to
agree then composite systems could behave as if they had a `dark component,'
whose gravitating mass would not equal the physical mass-energy present. The
existence of such an apparent discrepancy is indeed ubiquitous in galaxies and
galaxy clusters, though currently it is attributed to the presence of dark
matter. We conclude that the theoretical question of the relation between these
masses for dynamical spacetimes is ripe for attention.
| [
{
"created": "Thu, 19 Nov 2020 16:06:47 GMT",
"version": "v1"
}
] | 2020-11-20 | [
[
"Wang",
"Zhi-Wei",
""
],
[
"Braunstein",
"Samuel L.",
""
]
] | We construct the gravitating mass of an isolated composite system on asymptotically-flat spacetimes within conventional general relativity and investigate when this quantity is well defined. For stationary spacetimes, this quantity is known to exactly equal the physical (ADM) mass. However, it remains an open question whether these two masses are equal in the absence of a timelike Killing vector. This is especially apropos since our universe has an `origin' and hence no such Killing vector. Further, if these masses failed to agree then composite systems could behave as if they had a `dark component,' whose gravitating mass would not equal the physical mass-energy present. The existence of such an apparent discrepancy is indeed ubiquitous in galaxies and galaxy clusters, though currently it is attributed to the presence of dark matter. We conclude that the theoretical question of the relation between these masses for dynamical spacetimes is ripe for attention. |
2308.10419 | Ryo Kato | Ryo Kato, Keitaro Takahashi | Precision of localization of single gravitational-wave source with
pulsar timing array | 13 pages, 7 figures | Phys. Rev. D 108, 123535, 2023 | 10.1103/PhysRevD.108.123535 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Pulsar Timing Arrays (PTAs) are expected to be able to detect gravitational
waves (GWs) from individual supermassive black hole binaries in the near
future. In order to identify the host galaxy of a gravitational wave source,
the angular resolution of PTAs should be much better than that expected from
the conventional methodology of PTAs. We study the potential usefulness of
precise pulsar-distance measurements in the determination of the sky location
of a single GW source. Precise distance information from external observations
such as astrometry by Very Long Baseline Interferometry is incorporated as
priors in the PTA analysis and we evaluate the precision of the sky location of
a GW source by simulating PTA data of 12 milli-second pulsars with only the GW
signal and the Gaussian white noise in the timing residuals. We show that only
a few pulsars with a distance precision of 1 pc will improve the precision of
the source location by more than 1 order in the presence of white noise of 10
ns.
| [
{
"created": "Mon, 21 Aug 2023 02:07:53 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Dec 2023 11:38:35 GMT",
"version": "v2"
}
] | 2023-12-20 | [
[
"Kato",
"Ryo",
""
],
[
"Takahashi",
"Keitaro",
""
]
] | Pulsar Timing Arrays (PTAs) are expected to be able to detect gravitational waves (GWs) from individual supermassive black hole binaries in the near future. In order to identify the host galaxy of a gravitational wave source, the angular resolution of PTAs should be much better than that expected from the conventional methodology of PTAs. We study the potential usefulness of precise pulsar-distance measurements in the determination of the sky location of a single GW source. Precise distance information from external observations such as astrometry by Very Long Baseline Interferometry is incorporated as priors in the PTA analysis and we evaluate the precision of the sky location of a GW source by simulating PTA data of 12 milli-second pulsars with only the GW signal and the Gaussian white noise in the timing residuals. We show that only a few pulsars with a distance precision of 1 pc will improve the precision of the source location by more than 1 order in the presence of white noise of 10 ns. |
gr-qc/0005093 | Takashi Tamaki | Takashi Tamaki, Kei-ichi Maeda | Estimating Hawking radiation for exotic black holes | 4 pages, 7 figures | Phys.Rev. D62 (2000) 107503 | 10.1103/PhysRevD.62.107503 | null | gr-qc | null | We study about an approximation method of the Hawking radiation. We analyze
an massless scalar field in exotic black hole backgrounds models which have
peculiar properties in black hole thermodynamics (monopole black hole in SO(3)
Einstein-Yang-Mills-Higgs system and dilatoic black hole in
Einstein-Maxwell-dilaton system). A scalar field is assumed not to be couple to
matter fields consisting of a black hole background. Except for extreme black
holes, we can well approximate the Hawking radiaition by `black body' one with
Hawking temperature estimated at a radius of a critical impact parameter.
| [
{
"created": "Mon, 22 May 2000 06:48:29 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Jun 2000 07:11:35 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Tamaki",
"Takashi",
""
],
[
"Maeda",
"Kei-ichi",
""
]
] | We study about an approximation method of the Hawking radiation. We analyze an massless scalar field in exotic black hole backgrounds models which have peculiar properties in black hole thermodynamics (monopole black hole in SO(3) Einstein-Yang-Mills-Higgs system and dilatoic black hole in Einstein-Maxwell-dilaton system). A scalar field is assumed not to be couple to matter fields consisting of a black hole background. Except for extreme black holes, we can well approximate the Hawking radiaition by `black body' one with Hawking temperature estimated at a radius of a critical impact parameter. |
1903.03835 | Leandros Perivolaropoulos | I. Antoniou, D. Papadopoulos and L. Perivolaropoulos | Spinning particle orbits around a black hole in an expanding background | 12 pages, 4 figures. Accepted in 'Classical and Quantum Gravity'. To
appear | null | 10.1088/1361-6382/ab0fc1 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate analytically and numerically the orbits of spinning particles
around black holes in the post Newtonian limit and in the presence of cosmic
expansion. We show that orbits that are circular in the absence of spin, get
deformed when the orbiting particle has spin. We show that the origin of this
deformation is twofold: a. the background expansion rate which induces an
attractive (repulsive) interaction due to the cosmic background fluid when the
expansion is decelerating (accelerating) and b. a spin-orbit interaction which
can be attractive or repulsive depending on the relative orientation between
spin and orbital angular momentum and on the expansion rate.
| [
{
"created": "Sat, 9 Mar 2019 17:45:24 GMT",
"version": "v1"
}
] | 2019-05-22 | [
[
"Antoniou",
"I.",
""
],
[
"Papadopoulos",
"D.",
""
],
[
"Perivolaropoulos",
"L.",
""
]
] | We investigate analytically and numerically the orbits of spinning particles around black holes in the post Newtonian limit and in the presence of cosmic expansion. We show that orbits that are circular in the absence of spin, get deformed when the orbiting particle has spin. We show that the origin of this deformation is twofold: a. the background expansion rate which induces an attractive (repulsive) interaction due to the cosmic background fluid when the expansion is decelerating (accelerating) and b. a spin-orbit interaction which can be attractive or repulsive depending on the relative orientation between spin and orbital angular momentum and on the expansion rate. |
2109.12938 | Meng-He Wu | Yi Ling, Meng-He Wu | Modified regular black holes with time delay and 1-loop quantum
correction | 11 pages, 12 figures | Chin.Phys.C 46 (2022) 2, 025102 | 10.1088/1674-1137/ac3643 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop the regular black hole solutions recently proposed in
arXiv:2109.05974 by incorporating the 1-loop quantum correction to the Newton
potential as well as a time delay between an observer at the regular center and
that at infinity. We define the maximal time delay between the center and the
infinity by scanning the mass of black holes such that the sub-Planckian
feature of Kretschmann scalar curvature is preserved during the whole process
of evaporation. We also compare the distinct behavior of Kretschmann curvature
for black holes with an asymptotically Minkowski core and those with an
asymptotically de-Sitter core, including Bardeen and Hayward black holes. We
expect that this sort of regular black holes may provide more information about
the construction of effective metric for Planck stars.
| [
{
"created": "Mon, 27 Sep 2021 10:45:51 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Mar 2022 11:58:26 GMT",
"version": "v2"
}
] | 2022-05-03 | [
[
"Ling",
"Yi",
""
],
[
"Wu",
"Meng-He",
""
]
] | We develop the regular black hole solutions recently proposed in arXiv:2109.05974 by incorporating the 1-loop quantum correction to the Newton potential as well as a time delay between an observer at the regular center and that at infinity. We define the maximal time delay between the center and the infinity by scanning the mass of black holes such that the sub-Planckian feature of Kretschmann scalar curvature is preserved during the whole process of evaporation. We also compare the distinct behavior of Kretschmann curvature for black holes with an asymptotically Minkowski core and those with an asymptotically de-Sitter core, including Bardeen and Hayward black holes. We expect that this sort of regular black holes may provide more information about the construction of effective metric for Planck stars. |
2010.05183 | Masato Nozawa | Cristian Martinez and Masato Nozawa | Static spacetimes haunted by a phantom scalar field: classification and
global structure in the massless case | 46 pages, 2 figures, 4 tables; v2 minor modifications, accepted
version in PRD | Phys. Rev. D 103, 024003 (2021) | 10.1103/PhysRevD.103.024003 | YITP-20-127 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss various novel features of $n(\ge 4)$-dimensional spacetimes
sourced by a massless (non-)phantom scalar field in general relativity.
Assuming that the metric is a warped product of static two-dimensional
Lorentzian spacetime and an $(n-2)$-dimensional Einstein space $K^{n-2}$ with
curvature $k=0, \pm 1$, and that the scalar field depends only on the radial
variable, we present a complete classification of static solutions for both
signs of kinetic term. Contrary to the case with a non-phantom scalar field,
the Fisher solution is not unique, and there exist two additional metrics
corresponding to the generalizations of the Ellis-Gibbons solution and the
Ellis-Bronnikov solution. We explore the maximal extension of these solutions
in detail by the analysis of null/spacelike geodesics and singularity. For the
phantom Fisher and Ellis-Gibbons solutions, we find that there inevitably
appear parallelly propagated (p.p) curvature singularities in the parameter
region where there are no scalar curvature singularities. Interestingly, the
areal radius blows up at these p.p curvature singularities, which are
nevertheless accessible within a finite affine time along the radial null
geodesics. It follows that only the Ellis-Bronnikov solution describes a
regular wormhole in the two-sided asymptotically flat spacetime. Using the
general transformation relating the Einstein and Jordan frames, we also present
a complete classification of solutions with the same symmetry coupled to a
conformal scalar field. Additionally, by solving the field equations in the
Jordan frame, we prove that this classification is genuinely complete.
| [
{
"created": "Sun, 11 Oct 2020 07:27:14 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Jan 2021 14:46:25 GMT",
"version": "v2"
}
] | 2021-01-19 | [
[
"Martinez",
"Cristian",
""
],
[
"Nozawa",
"Masato",
""
]
] | We discuss various novel features of $n(\ge 4)$-dimensional spacetimes sourced by a massless (non-)phantom scalar field in general relativity. Assuming that the metric is a warped product of static two-dimensional Lorentzian spacetime and an $(n-2)$-dimensional Einstein space $K^{n-2}$ with curvature $k=0, \pm 1$, and that the scalar field depends only on the radial variable, we present a complete classification of static solutions for both signs of kinetic term. Contrary to the case with a non-phantom scalar field, the Fisher solution is not unique, and there exist two additional metrics corresponding to the generalizations of the Ellis-Gibbons solution and the Ellis-Bronnikov solution. We explore the maximal extension of these solutions in detail by the analysis of null/spacelike geodesics and singularity. For the phantom Fisher and Ellis-Gibbons solutions, we find that there inevitably appear parallelly propagated (p.p) curvature singularities in the parameter region where there are no scalar curvature singularities. Interestingly, the areal radius blows up at these p.p curvature singularities, which are nevertheless accessible within a finite affine time along the radial null geodesics. It follows that only the Ellis-Bronnikov solution describes a regular wormhole in the two-sided asymptotically flat spacetime. Using the general transformation relating the Einstein and Jordan frames, we also present a complete classification of solutions with the same symmetry coupled to a conformal scalar field. Additionally, by solving the field equations in the Jordan frame, we prove that this classification is genuinely complete. |
1203.2140 | Ovidiu Cristinel Stoica | Ovidiu-Cristinel Stoica | Einstein equation at singularities | 12 pages. Ovidiu-Cristinel Stoica, Cent. Eur. J. Phys., 2014,
10.2478/s11534-014-0427-1 | Central European Journal of Physics, 12 (2014), 123-131 | 10.2478/s11534-014-0427-1 | null | gr-qc astro-ph.CO math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Einstein's equation is rewritten in an equivalent form, which remains valid
at the singularities in some major cases. These cases include the Schwarzschild
singularity, the Friedmann-Lema\^itre-Robertson-Walker Big Bang singularity,
isotropic singularities, and a class of warped product singularities. This
equation is constructed in terms of the Ricci part of the Riemann curvature (as
the Kulkarni-Nomizu product between Einstein's equation and the metric tensor).
| [
{
"created": "Fri, 9 Mar 2012 17:11:17 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Mar 2012 14:29:55 GMT",
"version": "v2"
},
{
"created": "Fri, 24 Jan 2014 10:31:32 GMT",
"version": "v3"
}
] | 2014-05-05 | [
[
"Stoica",
"Ovidiu-Cristinel",
""
]
] | Einstein's equation is rewritten in an equivalent form, which remains valid at the singularities in some major cases. These cases include the Schwarzschild singularity, the Friedmann-Lema\^itre-Robertson-Walker Big Bang singularity, isotropic singularities, and a class of warped product singularities. This equation is constructed in terms of the Ricci part of the Riemann curvature (as the Kulkarni-Nomizu product between Einstein's equation and the metric tensor). |
2205.11471 | Amare Abebe PhD | Amare Abebe | Dark-fluid constraints of shear-free universes | 4+2 pages, no figures. Accepted for publication in Proceedings of the
African Conference on Fundamental and Applied Physics (ACP2021) | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Integrability conditions arising from general irrotational fluid-flow
considerations of a universe dominated by cosmic dark fluids will be
investigated under special assumptions on the nature of the spacetime shear.
Special emphasis will be placed on linearized perturbations of quasi-Newtonian
and anti-Newtonian spacetimes, whereby the conditions for the existence and
consistent evolution of such spacetimes in the presence of the Chaplygin gas
fluid model will be derived and discussed.
| [
{
"created": "Mon, 23 May 2022 17:14:13 GMT",
"version": "v1"
}
] | 2022-05-24 | [
[
"Abebe",
"Amare",
""
]
] | Integrability conditions arising from general irrotational fluid-flow considerations of a universe dominated by cosmic dark fluids will be investigated under special assumptions on the nature of the spacetime shear. Special emphasis will be placed on linearized perturbations of quasi-Newtonian and anti-Newtonian spacetimes, whereby the conditions for the existence and consistent evolution of such spacetimes in the presence of the Chaplygin gas fluid model will be derived and discussed. |
2212.13546 | Lau Loi So | Lau Loi So | The Bel-Robinson tensor and the classical pseudotensors | 7 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Describing the gravitational energy and momentum, the Bel-Robinson tensor is
the best tensor. However, the classical pseudotensors can also manage the the
same job. As Deser mentioned in 1999, a certain linear combination between
Einstein pseudotensor and Landau-Lifshitz pseudoetnsor give a pure Bel-Robinson
tensor. Here we used the same idea but adapted the harmonic gauge, we found
that all the classical pseudotensor alone cannot give a multiple of the
Bel-Robinson tensor. But under a modification, all of them contribute the same
energy-momentum and stress as the Bel-Robinson tensor does.
| [
{
"created": "Tue, 27 Dec 2022 16:39:15 GMT",
"version": "v1"
}
] | 2022-12-29 | [
[
"So",
"Lau Loi",
""
]
] | Describing the gravitational energy and momentum, the Bel-Robinson tensor is the best tensor. However, the classical pseudotensors can also manage the the same job. As Deser mentioned in 1999, a certain linear combination between Einstein pseudotensor and Landau-Lifshitz pseudoetnsor give a pure Bel-Robinson tensor. Here we used the same idea but adapted the harmonic gauge, we found that all the classical pseudotensor alone cannot give a multiple of the Bel-Robinson tensor. But under a modification, all of them contribute the same energy-momentum and stress as the Bel-Robinson tensor does. |
2406.07722 | Anish Agashe | Anish Agashe and Sai Madhav Modumudi | On the Effects of Non-metricity in an Averaged Universe | Accepted for publication in Universe. Invited article for the topical
collection, 'Modified Theories of Gravity and Cosmological Applications' | Universe 2024, 10(6), 261 | 10.3390/universe10060261 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | In the covariant averaging scheme of macroscopic gravity, the process of
averaging breaks the metricity of geometry. We reinterpret the back-reaction
within macroscopic gravity in terms of the non-metricity of averaged geometry.
This interpretation extends the effect of back-reaction beyond mere dynamics to
kinematics of geodesic bundles. With a 1+3 decomposition of the spacetime, we
analyse how geometric flows are modified by deriving the Raychaudhuri and Sachs
equations. We also present the modified forms of Gauss and Codazzi equations.
Finally, we derive an expression for the angular diameter distance in Friedmann
Lema\^itre Robertson Walker universe and show that non-metricity modifies it
only through the Hubble parameter. Thus, we caution against overestimating the
influence of back-reaction on the distances.
| [
{
"created": "Tue, 11 Jun 2024 21:03:09 GMT",
"version": "v1"
}
] | 2024-06-18 | [
[
"Agashe",
"Anish",
""
],
[
"Modumudi",
"Sai Madhav",
""
]
] | In the covariant averaging scheme of macroscopic gravity, the process of averaging breaks the metricity of geometry. We reinterpret the back-reaction within macroscopic gravity in terms of the non-metricity of averaged geometry. This interpretation extends the effect of back-reaction beyond mere dynamics to kinematics of geodesic bundles. With a 1+3 decomposition of the spacetime, we analyse how geometric flows are modified by deriving the Raychaudhuri and Sachs equations. We also present the modified forms of Gauss and Codazzi equations. Finally, we derive an expression for the angular diameter distance in Friedmann Lema\^itre Robertson Walker universe and show that non-metricity modifies it only through the Hubble parameter. Thus, we caution against overestimating the influence of back-reaction on the distances. |
1901.00231 | Ernesto Contreras | Ernesto Contreras | Gravitational decoupling in $2+1$ dimensional space--times with
cosmological term | null | Class. Quantum. Grav 36, 095004, 2019 | 10.1088/1361-6382/ab11e6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we implement the Minimal Geometric Deformation method to obtain
the isotropic sector and the decoupler matter content of any anisotropic
solution of the Einstein field equations with cosmological constant in $2+1$
dimensional space--times. We obtain that the solutions of both sectors can be
expressed analytically in terms of the metric functions of the original
anisotropic solutions instead of formal integral as in its $3+1$ counterpart.
As a particular example we study a regular black hole solution and we show
that, depending on the sign of the cosmological constant, the solutions
correspond to regular black holes violating the null energy condition or to a
non--regular black hole without exotic hair. The exotic/non--exotic and the
regular/non--regular black hole dualities are discussed.
| [
{
"created": "Wed, 2 Jan 2019 01:37:01 GMT",
"version": "v1"
}
] | 2019-06-28 | [
[
"Contreras",
"Ernesto",
""
]
] | In this work we implement the Minimal Geometric Deformation method to obtain the isotropic sector and the decoupler matter content of any anisotropic solution of the Einstein field equations with cosmological constant in $2+1$ dimensional space--times. We obtain that the solutions of both sectors can be expressed analytically in terms of the metric functions of the original anisotropic solutions instead of formal integral as in its $3+1$ counterpart. As a particular example we study a regular black hole solution and we show that, depending on the sign of the cosmological constant, the solutions correspond to regular black holes violating the null energy condition or to a non--regular black hole without exotic hair. The exotic/non--exotic and the regular/non--regular black hole dualities are discussed. |
gr-qc/0201022 | Yee J. Ng | Y. Jack Ng (University of North Carolina) | Spacetime foam | 7 pages, LaTeX; will appear in the Dec. 2002 special issue of Int. J.
Mod. Phys. D (this essay received an honorable mention in the GRF essay
contest) | Int.J.Mod.Phys.D11:1585-1590,2002 | 10.1142/S0218271802002931 | null | gr-qc astro-ph hep-th quant-ph | null | Spacetime is composed of a fluctuating arrangement of bubbles or loops called
spacetime foam, or quantum foam. We use the holographic principle to deduce its
structure, and show that the result is consistent with gedanken experiments
involving spacetime measurements. We propose to use laser-based atom
interferometry techniques to look for spacetime fluctuations. Our analysis
makes it clear that the physics of quantum foam is inextricably linked to that
of black holes. A negative experimental result, therefore, might have
non-trivial ramifications for semiclassical gravity and black hole physics.
| [
{
"created": "Mon, 7 Jan 2002 17:45:40 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Oct 2002 22:54:00 GMT",
"version": "v2"
}
] | 2011-09-01 | [
[
"Ng",
"Y. Jack",
"",
"University of North Carolina"
]
] | Spacetime is composed of a fluctuating arrangement of bubbles or loops called spacetime foam, or quantum foam. We use the holographic principle to deduce its structure, and show that the result is consistent with gedanken experiments involving spacetime measurements. We propose to use laser-based atom interferometry techniques to look for spacetime fluctuations. Our analysis makes it clear that the physics of quantum foam is inextricably linked to that of black holes. A negative experimental result, therefore, might have non-trivial ramifications for semiclassical gravity and black hole physics. |
gr-qc/0101083 | Takashi Tamaki | Takashi Tamaki (Waseda University), Takashi Torii (University of
Tokyo) | Dyonic BIon black hole in string inspired model | 13 pages, 15 figures, Final version in PRD | Phys.Rev.D64:024027,2001 | 10.1103/PhysRevD.64.024027 | null | gr-qc hep-th | null | We construct static and spherically symmetric particle-like and black hole
solutions with magnetic and/or electric charge in the
Einstein-Born-Infeld-dilaton-axion system, which is a generalization of the
Einstein-Maxwell-dilaton-axion (EMDA) system and of the Einstein-Born-Infeld
(EBI) system. They have remarkable properties which are not seen for the
corresponding solutions in the EMDA and the EBI system.
| [
{
"created": "Mon, 22 Jan 2001 05:14:27 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Jul 2001 02:43:57 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Tamaki",
"Takashi",
"",
"Waseda University"
],
[
"Torii",
"Takashi",
"",
"University of\n Tokyo"
]
] | We construct static and spherically symmetric particle-like and black hole solutions with magnetic and/or electric charge in the Einstein-Born-Infeld-dilaton-axion system, which is a generalization of the Einstein-Maxwell-dilaton-axion (EMDA) system and of the Einstein-Born-Infeld (EBI) system. They have remarkable properties which are not seen for the corresponding solutions in the EMDA and the EBI system. |
1804.02560 | Marko Vojinovic | Aleksandar Mikovic, Marko Vojinovic | Quantum gravity for piecewise flat spacetimes | 14 pages. To appear as a contribution to the MPHYS9 2017 conference
proceedings | SFIN XXXI, 267 (2018) | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a theory of quantum gravity which is based on the assumption that
the spacetime structure at small distances is given by a piecewise linear (PL)
4-manifold corresponding to a triangulation of a smooth 4-manifold. The
fundamental degrees of freedom are the edge lengths of the triangulation. One
can work with finitely many edge lengths, so that the corresponding Regge path
integral can be made finite by using an appropriate path-integral measure. The
semi-classical limit is computed by using the effective action formalism, and
the existence of a semi-classical effective action restricts the choice of the
path-integral measure. The classical limit is given by the Regge action, so
that one has a quantum gravity theory for a piecewise-flat general relativity.
By using the effective action formalism we show that the observed value of the
cosmological constant can be recovered from the effective cosmological
constant. When the number of 4-simplices in the spacetime triangulation is
large, then the PL effective action is well approximated by a quantum field
theory effective action with a physical cutoff determined by the smallest edge
length.
| [
{
"created": "Sat, 7 Apr 2018 13:40:23 GMT",
"version": "v1"
}
] | 2018-07-18 | [
[
"Mikovic",
"Aleksandar",
""
],
[
"Vojinovic",
"Marko",
""
]
] | We describe a theory of quantum gravity which is based on the assumption that the spacetime structure at small distances is given by a piecewise linear (PL) 4-manifold corresponding to a triangulation of a smooth 4-manifold. The fundamental degrees of freedom are the edge lengths of the triangulation. One can work with finitely many edge lengths, so that the corresponding Regge path integral can be made finite by using an appropriate path-integral measure. The semi-classical limit is computed by using the effective action formalism, and the existence of a semi-classical effective action restricts the choice of the path-integral measure. The classical limit is given by the Regge action, so that one has a quantum gravity theory for a piecewise-flat general relativity. By using the effective action formalism we show that the observed value of the cosmological constant can be recovered from the effective cosmological constant. When the number of 4-simplices in the spacetime triangulation is large, then the PL effective action is well approximated by a quantum field theory effective action with a physical cutoff determined by the smallest edge length. |
1309.3977 | Eoin Condron Mr. | Eoin Condron and Brien C. Nolan | Collapse of a self-similar cylindrical scalar field with non-minimal
coupling II: strong cosmic censorship | 27 pages, 3 figures. To appear in CQG. Proofs in Section 5 corrected | null | 10.1088/0264-9381/31/16/165018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate self-similar scalar field solutions to the Einstein equations
in whole cylinder symmetry. Imposing self-similarity on the spacetime gives
rise to a set of single variable functions describing the metric. Furthermore,
it is shown that the scalar field is dependent on a single unknown function of
the same variable and that the scalar field potential has exponential form. The
Einstein equations then take the form of a set of ODEs. Self-similarity also
gives rise to a singularity at the scaling origin. We extend the work of [1],
which determined the global structure of all solutions in the causal past of
the singularity. We identified a class of solutions that evolves through the
past null cone of the singularity. We give the global structure of these
solutions and show that the singularity is censored in all cases.
| [
{
"created": "Mon, 16 Sep 2013 14:30:55 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Oct 2013 19:14:42 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Jul 2014 16:09:30 GMT",
"version": "v3"
}
] | 2015-06-30 | [
[
"Condron",
"Eoin",
""
],
[
"Nolan",
"Brien C.",
""
]
] | We investigate self-similar scalar field solutions to the Einstein equations in whole cylinder symmetry. Imposing self-similarity on the spacetime gives rise to a set of single variable functions describing the metric. Furthermore, it is shown that the scalar field is dependent on a single unknown function of the same variable and that the scalar field potential has exponential form. The Einstein equations then take the form of a set of ODEs. Self-similarity also gives rise to a singularity at the scaling origin. We extend the work of [1], which determined the global structure of all solutions in the causal past of the singularity. We identified a class of solutions that evolves through the past null cone of the singularity. We give the global structure of these solutions and show that the singularity is censored in all cases. |
0901.2931 | Mark Hannam | Mark Hannam | Status of black-hole-binary simulations for gravitational-wave detection | 22 pages, 6 figures, Version to be published in CQG, NRDA 2008
Special Issue | Class.Quant.Grav.26:114001,2009 | 10.1088/0264-9381/26/11/114001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is now possible to theoretically calculate the gravitational-wave signal
from the inspiral, merger and ringdown of a black-hole-binary system. The late
inspiral, merger and ringdown can be calculated in full general relativity
using numerical methods. The numerical waveforms can then be either stitched to
inspiral waveforms predicted by approximation techniques (in particular
post-Newtonian calculations) that start at an arbitrarily low frequency, or
used to calibrate free parameters in analytic models of the full waveforms. In
this review I summarize the status of numerical-relativity (NR) waveforms that
include at least ten cycles of the dominant mode of the GW signal before
merger, which should be long enough to produce accurate, complete waveforms for
GW observations.
| [
{
"created": "Mon, 19 Jan 2009 21:02:09 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Mar 2009 15:07:43 GMT",
"version": "v2"
}
] | 2009-06-10 | [
[
"Hannam",
"Mark",
""
]
] | It is now possible to theoretically calculate the gravitational-wave signal from the inspiral, merger and ringdown of a black-hole-binary system. The late inspiral, merger and ringdown can be calculated in full general relativity using numerical methods. The numerical waveforms can then be either stitched to inspiral waveforms predicted by approximation techniques (in particular post-Newtonian calculations) that start at an arbitrarily low frequency, or used to calibrate free parameters in analytic models of the full waveforms. In this review I summarize the status of numerical-relativity (NR) waveforms that include at least ten cycles of the dominant mode of the GW signal before merger, which should be long enough to produce accurate, complete waveforms for GW observations. |
1907.11083 | Andrea Geralico | Donato Bini, Andrea Geralico | Analytical determination of the periastron advance in spinning binaries
from self-force computations | 6 pages, 1 figure, revtex macros | Phys. Rev. D 100, 121502 (2019) | 10.1103/PhysRevD.100.121502 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first analytical computation of the (conservative)
gravitational self-force correction to the periastron advance around a spinning
black hole. Our result is accurate to the second order in the rotational
parameter and through the 9.5 post-Newtonian level. It has been obtained as the
circular limit of the correction to the gyroscope precession invariant along
slightly eccentric equatorial orbits in the Kerr spacetime. The latter result
is also new and we anticipate here the first few terms only of the
corresponding post-Newtonian expansion.
| [
{
"created": "Tue, 23 Jul 2019 20:35:37 GMT",
"version": "v1"
}
] | 2019-12-25 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
]
] | We present the first analytical computation of the (conservative) gravitational self-force correction to the periastron advance around a spinning black hole. Our result is accurate to the second order in the rotational parameter and through the 9.5 post-Newtonian level. It has been obtained as the circular limit of the correction to the gyroscope precession invariant along slightly eccentric equatorial orbits in the Kerr spacetime. The latter result is also new and we anticipate here the first few terms only of the corresponding post-Newtonian expansion. |
2304.10245 | Pardyumn Kumar Sahoo | Gaurav N. Gadbail, Ameya Kolhatkar, Sanjay Mandal, and P.K. Sahoo | Correction to Lagrangian for Bouncing Cosmologies in $f(Q)$ Gravity | EPJ C revised version | Eur. Phys. J. C 83, 595 (2023) | 10.1140/epjc/s10052-023-11798-z | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Symmetric teleparallel gravity offers to reformulate the gravitational
formalism without the presence of curvature and torsion with the help of
non-metricity tensors. Interestingly, Symmetric teleparallel gravity can be
formulated equivalently to teleparallel gravity or general relativity for an
appropriate setup. In this study, our aim lies in exploring the bouncing
cosmologies as an alternative to the initial singularity of the Universe in the
background of modified symmetric teleparallel gravity. To explore this, we
adopt the reconstruction technique to present the possible reconstructed
Lagrangian for various cosmological bouncing solutions in a flat
Friedmann-Lema\^itre-Robertson-Walker spacetime with a perfect fluid matter
distribution. We study the reconstructed gravitational Lagrangians, which are
capable of reproducing analytical solutions for \textit{symmetric bounce},
\textit{super-bounce}, \textit{oscillatory bounce}, \textit{matter bounce}, and
\textit{exponential bouncing} model settings. Further, we examine the dark
energy profiles of the models using reconstructed Lagrangians. In addition, we
found that an additional term arises in each reconstructed Lagrangian compared
to general relativity (GR). That extra term corrected the background GR to
present bouncing cosmology in modified gravity. These newly motivated
cosmological models may have an effect on gravitational phenomena at other
cosmological scales.
| [
{
"created": "Thu, 20 Apr 2023 12:05:30 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Jun 2023 16:08:32 GMT",
"version": "v2"
},
{
"created": "Wed, 28 Jun 2023 11:44:27 GMT",
"version": "v3"
}
] | 2023-07-12 | [
[
"Gadbail",
"Gaurav N.",
""
],
[
"Kolhatkar",
"Ameya",
""
],
[
"Mandal",
"Sanjay",
""
],
[
"Sahoo",
"P. K.",
""
]
] | Symmetric teleparallel gravity offers to reformulate the gravitational formalism without the presence of curvature and torsion with the help of non-metricity tensors. Interestingly, Symmetric teleparallel gravity can be formulated equivalently to teleparallel gravity or general relativity for an appropriate setup. In this study, our aim lies in exploring the bouncing cosmologies as an alternative to the initial singularity of the Universe in the background of modified symmetric teleparallel gravity. To explore this, we adopt the reconstruction technique to present the possible reconstructed Lagrangian for various cosmological bouncing solutions in a flat Friedmann-Lema\^itre-Robertson-Walker spacetime with a perfect fluid matter distribution. We study the reconstructed gravitational Lagrangians, which are capable of reproducing analytical solutions for \textit{symmetric bounce}, \textit{super-bounce}, \textit{oscillatory bounce}, \textit{matter bounce}, and \textit{exponential bouncing} model settings. Further, we examine the dark energy profiles of the models using reconstructed Lagrangians. In addition, we found that an additional term arises in each reconstructed Lagrangian compared to general relativity (GR). That extra term corrected the background GR to present bouncing cosmology in modified gravity. These newly motivated cosmological models may have an effect on gravitational phenomena at other cosmological scales. |
1808.01532 | Simone Mastrogiovanni | S. Mastrogiovanni, P. Astone, S. D Antonio, S. Frasca, G. Intini, I.
La Rosa, P. Leaci, A. Miller, F. Muciaccia, C. Palomba, O.J. Piccinni, A.
Singhal | Phase decomposition of the template metric for continuous
gravitational-wave searches | 17 pages, 16 figures | Phys. Rev. D 98, 102003 (2018) | 10.1103/PhysRevD.98.102003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A type of gravitational-wave signals in the LIGO-Virgo sensitivity band are
expected to be emitted by spinning asymmetric neutron stars, with rotational
frequencies that could plausibly emit continuous gravitational radiation in the
most sensitive band of the LIGO-Virgo detectors. The most important feature of
such kind of signals is in their phase evolution, which is stable over a long
observation run. When using analysis based on matched filtering, the phase
evolution of long-coherent signals is needed to define how to build a proper
template grid in order to gain the best signal-to-noise ratio possible. This
information is encoded in a matrix called \textit{phase metric}, which
characterizes the geometry for the likelihood given by the matched filtering.
Most of the times, the metric for long-coherent signals cannot be computed
anlaytically and even its numerical computation is not possible due to
numerical precision. In this paper we show a general phase decomposition
technique able to make the template metric analytically computable. We will
also show how this variables can be employed to distinguish in a robust way
among astrophysical signals and non-stationary noise artifacts that may affect
analysis pipelines.
| [
{
"created": "Sat, 4 Aug 2018 20:52:31 GMT",
"version": "v1"
}
] | 2018-11-14 | [
[
"Mastrogiovanni",
"S.",
""
],
[
"Astone",
"P.",
""
],
[
"Antonio",
"S. D",
""
],
[
"Frasca",
"S.",
""
],
[
"Intini",
"G.",
""
],
[
"La Rosa",
"I.",
""
],
[
"Leaci",
"P.",
""
],
[
"Miller",
"A.",... | A type of gravitational-wave signals in the LIGO-Virgo sensitivity band are expected to be emitted by spinning asymmetric neutron stars, with rotational frequencies that could plausibly emit continuous gravitational radiation in the most sensitive band of the LIGO-Virgo detectors. The most important feature of such kind of signals is in their phase evolution, which is stable over a long observation run. When using analysis based on matched filtering, the phase evolution of long-coherent signals is needed to define how to build a proper template grid in order to gain the best signal-to-noise ratio possible. This information is encoded in a matrix called \textit{phase metric}, which characterizes the geometry for the likelihood given by the matched filtering. Most of the times, the metric for long-coherent signals cannot be computed anlaytically and even its numerical computation is not possible due to numerical precision. In this paper we show a general phase decomposition technique able to make the template metric analytically computable. We will also show how this variables can be employed to distinguish in a robust way among astrophysical signals and non-stationary noise artifacts that may affect analysis pipelines. |
2111.00492 | Yurii Ignat'ev | Yu. G. Ignat'ev, D. Yu. Ignatyev | Cosmological Models Based on a Statistical System of Scalar Charged
Degenerate Fermions and an Asymmetric Higgs Scalar Doublet | 31 pages, 70 references | Theoret. and Math. Phys., 209:1 (2021), 1437 | 10.1134/S0040577921100081 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On the basis of the general relativistic statistical and kinetic theory, a
consistent closed cosmological model is formulated. It is based on a
statistical system of scalar charged fermions interacting by means of classical
and phantom scalar fields. Based on the study of the microscopic dynamics of
scalar charged particles, within the framework of the Lagrangian as well as
Hamiltonian formalism, a function of the dynamic mass of scalar charged
particles was constructed and it was shown that for the consistency of the
theory, it is necessary to remove the nonnegativity condition for this
function. On the basis of the Lagrangian formalism, equations of gravitational
and scalar fields with singular sources are formulated and microscopic
conservation laws are obtained. Within the framework of the general
relativistic kinetic theory, macroscopic equations of gravitational and scalar
fields are formulated and macroscopic conservation laws are obtained. These
equations' full correspondence to microscopic equations with singular sources
is shown. Further, on the basis of the obtained equations, a cosmological model
for a degenerate system of scalarly charged fermions is formulated. An exact
solution of the constitutive equations for a degenerate scalar-charged plasma
in the cosmological model is obtained, which made it possible to significantly
simplify the original system of equations. On the basis of the obtained
solution of the constitutive equations, two fundamentally different
cosmological models are formulated, one of which has two types of singly
scalarly charged fermions, while the second has one kind of fermions charged
with two charges of various nature. A qualitative analysis of the obtained
6-dimensional dynamic system for a two-component model is carried out.
| [
{
"created": "Sun, 31 Oct 2021 13:20:25 GMT",
"version": "v1"
}
] | 2021-11-02 | [
[
"Ignat'ev",
"Yu. G.",
""
],
[
"Ignatyev",
"D. Yu.",
""
]
] | On the basis of the general relativistic statistical and kinetic theory, a consistent closed cosmological model is formulated. It is based on a statistical system of scalar charged fermions interacting by means of classical and phantom scalar fields. Based on the study of the microscopic dynamics of scalar charged particles, within the framework of the Lagrangian as well as Hamiltonian formalism, a function of the dynamic mass of scalar charged particles was constructed and it was shown that for the consistency of the theory, it is necessary to remove the nonnegativity condition for this function. On the basis of the Lagrangian formalism, equations of gravitational and scalar fields with singular sources are formulated and microscopic conservation laws are obtained. Within the framework of the general relativistic kinetic theory, macroscopic equations of gravitational and scalar fields are formulated and macroscopic conservation laws are obtained. These equations' full correspondence to microscopic equations with singular sources is shown. Further, on the basis of the obtained equations, a cosmological model for a degenerate system of scalarly charged fermions is formulated. An exact solution of the constitutive equations for a degenerate scalar-charged plasma in the cosmological model is obtained, which made it possible to significantly simplify the original system of equations. On the basis of the obtained solution of the constitutive equations, two fundamentally different cosmological models are formulated, one of which has two types of singly scalarly charged fermions, while the second has one kind of fermions charged with two charges of various nature. A qualitative analysis of the obtained 6-dimensional dynamic system for a two-component model is carried out. |
1312.7721 | Kirill Bronnikov | K.A. Bronnikov, M.V. Skvortsova | Variations of $\alpha$ and $G$ from nonlinear multidimensional gravity | 11 pages, 2 figures. arXiv admin note: substantial text overlap with
arXiv:1301.3098 | Grav. Cosmol. 19 (2), 114-123 (2013) | 10.1134/S0202289313020035 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To explain the recently reported large-scale spatial variations of the fine
structure constant $\alpha$, we apply some models of curvature-nonlinear
multidimensional gravity. Under the reasonable assumption of slow changes of
all quantities as compared with the Planck scale, the original theory reduces
to a multi-scalar field theory in four dimensions. On this basis, we consider
different variants of isotropic cosmological models in both Einstein and Jordan
conformal frames. One of the models turns out to be equally viable in both
frames, but in the Jordan frame the model predicts simultaneous variations of
$\alpha$ and the gravitational constant $G$, equal in magnitude. Large-scale
small inhomogeneous perturbations of these models allow for explaining the
observed spatial distribution of $\alpha$ values.
| [
{
"created": "Mon, 30 Dec 2013 14:10:34 GMT",
"version": "v1"
}
] | 2013-12-31 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Skvortsova",
"M. V.",
""
]
] | To explain the recently reported large-scale spatial variations of the fine structure constant $\alpha$, we apply some models of curvature-nonlinear multidimensional gravity. Under the reasonable assumption of slow changes of all quantities as compared with the Planck scale, the original theory reduces to a multi-scalar field theory in four dimensions. On this basis, we consider different variants of isotropic cosmological models in both Einstein and Jordan conformal frames. One of the models turns out to be equally viable in both frames, but in the Jordan frame the model predicts simultaneous variations of $\alpha$ and the gravitational constant $G$, equal in magnitude. Large-scale small inhomogeneous perturbations of these models allow for explaining the observed spatial distribution of $\alpha$ values. |
2210.04063 | Konstantin Osetrin | Konstantin Osetrin and Evgeny Osetrin and Elena Osetrina | Gravitational Waves of Type III Shapovalov Spacetimes: Particle
Trajectories, Geodesic Deviation and Tidal Accelerations | 27 pages | Symmetry, 2023, 15(7), 1455 | 10.3390/sym15071455 | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by-nc-nd/4.0/ | For gravitational-wave spacetimes of Shapovalov type III, exact general
solutions of geodesic deviation equations and equations of motion of test
particles are obtained. Solutions are found in a privileged coordinate system,
where the metric of the considered spacetime models depends on the wave
variable. The exact form of tidal accelerations of the gravitational wave is
obtained. In the considered wave models of spacetime, the complete integral of
the Hamilton-Jacobi equations of test particles can be constructed. An explicit
form of the equations for the transition to a synchronous coordinate system is
found, where the proper time of a test particle on the base geodesic is chosen
as the time variable, and the time and space variables are separated. In the
synchronous coordinate system, the form of the metric of the considered wave
spacetime is presented, the form of the geodesic deviation vector and the tidal
acceleration vector are obtained. The methods used in the paper and the results
obtained are applicable to gravitational waves both in the general theory of
relativity and in modified theories of gravity. The proposed approaches are
applied to the case of Einstein's vacuum equations.
| [
{
"created": "Sat, 8 Oct 2022 17:15:58 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Oct 2022 07:37:49 GMT",
"version": "v2"
}
] | 2023-08-02 | [
[
"Osetrin",
"Konstantin",
""
],
[
"Osetrin",
"Evgeny",
""
],
[
"Osetrina",
"Elena",
""
]
] | For gravitational-wave spacetimes of Shapovalov type III, exact general solutions of geodesic deviation equations and equations of motion of test particles are obtained. Solutions are found in a privileged coordinate system, where the metric of the considered spacetime models depends on the wave variable. The exact form of tidal accelerations of the gravitational wave is obtained. In the considered wave models of spacetime, the complete integral of the Hamilton-Jacobi equations of test particles can be constructed. An explicit form of the equations for the transition to a synchronous coordinate system is found, where the proper time of a test particle on the base geodesic is chosen as the time variable, and the time and space variables are separated. In the synchronous coordinate system, the form of the metric of the considered wave spacetime is presented, the form of the geodesic deviation vector and the tidal acceleration vector are obtained. The methods used in the paper and the results obtained are applicable to gravitational waves both in the general theory of relativity and in modified theories of gravity. The proposed approaches are applied to the case of Einstein's vacuum equations. |
1704.04971 | Ezra Newman | Ezra T. Newman | Light-Cones, Almost Light-Cones and Almost-Complex Light-Cones | null | null | 10.1007/s10714-017-2264-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We point out an unusual relationship among a variety of null geodesic
congruences; (a) the generators of ordinary light-cones and (b) certain
(related) shear-free but twisting congruences in Minkowski Space-time as well
as (c) asymptotically shear-free null geodesic congruences that exist in the
neighborhood of Penrose's Scri in Einstein or Einstein-Maxwell asymptotically
flat-space-times. We refer to these geodesic congruences respectively as:
Lignt-Cones (LCs), as Almost-Complex- Light-Cones, (ACLCs), [though they are
real they resemble complex light-cones in complex Minkowski space] and finally
to a family of congruences in asymptotically flat-spaces as `Almost
Light-Cones', (ALC). The two essential points of resemblance among the three
families are: (1) they are all either shear-free or asymptotically shear-free
and (2) in each family the individual members of the family can be labeled by
the points in a real or complex four-dimensional manifold. As an example, the
Minkowski space LCs are labeled by the (real) coordinate value of their apex.
In the case of (ACLCs) (complex coordinate values), the congruences will have
non-vanishing twist whose magnitude is determined by the imaginary part of the
complex coordinate values.
In studies of gravitational radiation, Bondi-type of null surfaces and their
associated Bondi coordinates have been almost exclusively used for
calculations. Some surprising relations arise if, instead of the Bondi
coordinates, one uses ALCs and their associated coordinate systems in the
analysis of the Einstein-Maxwell equations near Scri. More explicitly and
surprisingly, the asymptotic Bianchi Identities expressed in the coordinates of
the ALCs, turn directly into many of the standard definitions and relations of
classical mechanics.
| [
{
"created": "Mon, 17 Apr 2017 14:16:52 GMT",
"version": "v1"
}
] | 2017-07-26 | [
[
"Newman",
"Ezra T.",
""
]
] | We point out an unusual relationship among a variety of null geodesic congruences; (a) the generators of ordinary light-cones and (b) certain (related) shear-free but twisting congruences in Minkowski Space-time as well as (c) asymptotically shear-free null geodesic congruences that exist in the neighborhood of Penrose's Scri in Einstein or Einstein-Maxwell asymptotically flat-space-times. We refer to these geodesic congruences respectively as: Lignt-Cones (LCs), as Almost-Complex- Light-Cones, (ACLCs), [though they are real they resemble complex light-cones in complex Minkowski space] and finally to a family of congruences in asymptotically flat-spaces as `Almost Light-Cones', (ALC). The two essential points of resemblance among the three families are: (1) they are all either shear-free or asymptotically shear-free and (2) in each family the individual members of the family can be labeled by the points in a real or complex four-dimensional manifold. As an example, the Minkowski space LCs are labeled by the (real) coordinate value of their apex. In the case of (ACLCs) (complex coordinate values), the congruences will have non-vanishing twist whose magnitude is determined by the imaginary part of the complex coordinate values. In studies of gravitational radiation, Bondi-type of null surfaces and their associated Bondi coordinates have been almost exclusively used for calculations. Some surprising relations arise if, instead of the Bondi coordinates, one uses ALCs and their associated coordinate systems in the analysis of the Einstein-Maxwell equations near Scri. More explicitly and surprisingly, the asymptotic Bianchi Identities expressed in the coordinates of the ALCs, turn directly into many of the standard definitions and relations of classical mechanics. |
1412.8117 | Sunil Maharaj | G. Z. Abebe, S. D. Maharaj, K. S. Govinder | Generalized Euclidean stars with equation of state | 15 pages, Submitted for publication | Gen. Relativ. Gravit. 46, 1733 (2014) | 10.1007/s10714-014-1733-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the general case of an accelerating, expanding and shearing model
of a radiating relativistic star using Lie symmetries. We obtain the Lie
symmetry generators that leave the equation for the junction condition
invariant, and find the Lie algebra corresponding to the optimal system of the
symmetries. The symmetries in the optimal system allow us to transform the
boundary condition to ordinary differential equations. The various cases for
which the resulting systems of equations can be solved are identified. For each
of these cases the boundary condition is integrated and the gravitational
potentials are found explicitly. A particular group invariant solution produces
a class of models which contains Euclidean stars as a special case. Our
generalized model satisfies a linear equation of state in general. We thus
establish a group theoretic basis for our generalized model with an equation of
state. By considering a particular example we show that the weak, dominant and
strong energy conditions are satisfied.
| [
{
"created": "Sun, 28 Dec 2014 06:04:34 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Abebe",
"G. Z.",
""
],
[
"Maharaj",
"S. D.",
""
],
[
"Govinder",
"K. S.",
""
]
] | We consider the general case of an accelerating, expanding and shearing model of a radiating relativistic star using Lie symmetries. We obtain the Lie symmetry generators that leave the equation for the junction condition invariant, and find the Lie algebra corresponding to the optimal system of the symmetries. The symmetries in the optimal system allow us to transform the boundary condition to ordinary differential equations. The various cases for which the resulting systems of equations can be solved are identified. For each of these cases the boundary condition is integrated and the gravitational potentials are found explicitly. A particular group invariant solution produces a class of models which contains Euclidean stars as a special case. Our generalized model satisfies a linear equation of state in general. We thus establish a group theoretic basis for our generalized model with an equation of state. By considering a particular example we show that the weak, dominant and strong energy conditions are satisfied. |
1102.0241 | H.-J. Schmidt | H.-J. Schmidt | Gauss-Bonnet lagrangian G ln G and cosmological exact solutions | 18 pages, amended version, accepted by Phys. Rev. D | Phys.Rev.D83:083513,2011 | 10.1103/PhysRevD.83.083513 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For the lagrangian L = G ln G where G is the Gauss-Bonnet curvature scalar we
deduce the field equation and solve it in closed form for 3-flat Friedman
models using a statefinder parametrization. Further we show, that among all
lagrangians F(G) this L is the only one not having the form G^r with a real
constant r but possessing a scale-invariant field equation. This turns out to
be one of its analogies to f(R)-theories in 2-dimensional space-time. In the
appendix, we systematically list several formulas for the decomposition of the
Riemann tensor in arbitrary dimensions n, which are applied in the main
deduction for n=4.
| [
{
"created": "Tue, 1 Feb 2011 18:22:06 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Mar 2011 16:54:46 GMT",
"version": "v2"
}
] | 2011-05-05 | [
[
"Schmidt",
"H. -J.",
""
]
] | For the lagrangian L = G ln G where G is the Gauss-Bonnet curvature scalar we deduce the field equation and solve it in closed form for 3-flat Friedman models using a statefinder parametrization. Further we show, that among all lagrangians F(G) this L is the only one not having the form G^r with a real constant r but possessing a scale-invariant field equation. This turns out to be one of its analogies to f(R)-theories in 2-dimensional space-time. In the appendix, we systematically list several formulas for the decomposition of the Riemann tensor in arbitrary dimensions n, which are applied in the main deduction for n=4. |
1508.01416 | Jeff Hnybida | Jeff Hnybida | Spin Foams Without Spins | 21 pages, 2 figures | null | 10.1088/0264-9381/33/20/205003 | null | gr-qc hep-lat math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We formulate the spin foam representation of discrete SU(2) gauge theory as a
product of vertex amplitudes each of which is the spin network generating
function of the boundary graph dual to the vertex. In doing so the sums over
spins have been carried out. The boundary data of each n-valent node is
explicitly reduced with respect to the local gauge invariance and has a
manifest geometrical interpretation as a framed polyhedron of fixed total area.
Ultimately, sums over spins are traded for contour integrals over simple poles
and recoupling theory is avoided using generating functions.
| [
{
"created": "Thu, 6 Aug 2015 14:22:58 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Aug 2016 12:27:25 GMT",
"version": "v2"
}
] | 2016-10-05 | [
[
"Hnybida",
"Jeff",
""
]
] | We formulate the spin foam representation of discrete SU(2) gauge theory as a product of vertex amplitudes each of which is the spin network generating function of the boundary graph dual to the vertex. In doing so the sums over spins have been carried out. The boundary data of each n-valent node is explicitly reduced with respect to the local gauge invariance and has a manifest geometrical interpretation as a framed polyhedron of fixed total area. Ultimately, sums over spins are traded for contour integrals over simple poles and recoupling theory is avoided using generating functions. |
1809.06753 | Alfonso Garc\'ia-Parrado G\'omez-Lobo Dr. | Alfonso Garc\'ia-Parrado | Type D conformal initial data | 22 pages, 2 figures. New section added and reference list enlarged.
To appear in General Relativity and Gravitation | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a vacuum initial data set of the Einstein field equations it is possible
to carry out a conformal rescaling or conformal compactification of the data
giving rise to an initial data set for the Friedrich vacuum conformal
equations. When will the data development with respect to the conformal
equations of this set be a conformal extension of a type D solution? In this
work we provide a set of necessary and sufficient conditions on a set of
initial data for the conformal equations that guarantees that the data
development of the conformal equations has a subset that is conformal to a
vacuum type D solution of the Einstein's equations. In particular we find the
conditions under which this vacuum solution corresponds to the Kerr solution.
Using our results we are able to show that there are no obstructions to extend
the Petrov type of the physical spacetime to the unphysical spacetime if the
conformal data are hyperboloidal.
| [
{
"created": "Tue, 18 Sep 2018 14:08:05 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Apr 2020 15:51:14 GMT",
"version": "v2"
}
] | 2020-04-22 | [
[
"García-Parrado",
"Alfonso",
""
]
] | For a vacuum initial data set of the Einstein field equations it is possible to carry out a conformal rescaling or conformal compactification of the data giving rise to an initial data set for the Friedrich vacuum conformal equations. When will the data development with respect to the conformal equations of this set be a conformal extension of a type D solution? In this work we provide a set of necessary and sufficient conditions on a set of initial data for the conformal equations that guarantees that the data development of the conformal equations has a subset that is conformal to a vacuum type D solution of the Einstein's equations. In particular we find the conditions under which this vacuum solution corresponds to the Kerr solution. Using our results we are able to show that there are no obstructions to extend the Petrov type of the physical spacetime to the unphysical spacetime if the conformal data are hyperboloidal. |
2405.10354 | Bivudutta Mishra Dr. | S.A. Kadam, Ananya Sahu, S.K. Tripathy, B.Mishra | Dynamical System Analysis for Scalar Field Potential in Teleparallel
Gravity | 17 pages, 8 figures, constructive comments appreciated | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have presented a power law cosmological model and its
dynamical system analysis in $f(T,\phi)$ gravity, where $T$ is the torsion
scalar and $\phi$ is the canonical scalar field. The two well-motivated forms
of the non-minimal coupling function $F(\phi)$, the exponential form and the
power law form, with exponential potential function, are investigated. The
dynamical system analysis is performed by establishing the dimensionless
dynamical variables, and the critical points were obtained. The evolution of
standard density parameters is analysed for each case. The behaviour of the
equation of state (EoS) and deceleration parameter show agreement with the
result of cosmological observations. The model parameters are constrained using
the existence and the stability conditions of the critical points describing
different epochs of the evolution of the Universe.
| [
{
"created": "Thu, 16 May 2024 16:03:11 GMT",
"version": "v1"
}
] | 2024-05-20 | [
[
"Kadam",
"S. A.",
""
],
[
"Sahu",
"Ananya",
""
],
[
"Tripathy",
"S. K.",
""
],
[
"Mishra",
"B.",
""
]
] | In this paper, we have presented a power law cosmological model and its dynamical system analysis in $f(T,\phi)$ gravity, where $T$ is the torsion scalar and $\phi$ is the canonical scalar field. The two well-motivated forms of the non-minimal coupling function $F(\phi)$, the exponential form and the power law form, with exponential potential function, are investigated. The dynamical system analysis is performed by establishing the dimensionless dynamical variables, and the critical points were obtained. The evolution of standard density parameters is analysed for each case. The behaviour of the equation of state (EoS) and deceleration parameter show agreement with the result of cosmological observations. The model parameters are constrained using the existence and the stability conditions of the critical points describing different epochs of the evolution of the Universe. |
2108.12210 | Clifford M. Will | Alexandria Tucker and Clifford M. Will | Residual eccentricity of inspiralling orbits at the gravitational-wave
detection threshold: Accurate estimates using post-Newtonian theory | 13 pages, 9 figures, version aligned with published paper | Phys. Rev. D 104, 104023 (2021) | 10.1103/PhysRevD.104.104023 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We use equations of motion containing gravitational radiation-reaction terms
through 4.5 post-Newtonian order to calculate the late-time eccentricities of
inspiraling binary systems of non-spinning compact bodies as they cross the
detection threshold of ground-based gravitational-wave interferometers. The
initial eccentricities can be as large as 0.999. We find that the final
eccentricities are systematically smaller than those predicted by the leading
quadrupole approximation, by as much as 30 percent for a 300 solar mass binary
crossing the LIGO/Virgo detection threshold at 10 Hz, or eight percent smaller
for a 60 solar mass binary. We find an analytic formula for the late-time
eccentricity that accurately accounts for the higher-order post-Newtonian
effects, generalizing a formula derived by Peters and Mathews in the 1960s. We
also find that the final eccentricities are independent of the ratio of the
masses of the two compact bodies to better than two percent.
| [
{
"created": "Fri, 27 Aug 2021 10:15:50 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Nov 2021 03:06:45 GMT",
"version": "v2"
}
] | 2021-11-16 | [
[
"Tucker",
"Alexandria",
""
],
[
"Will",
"Clifford M.",
""
]
] | We use equations of motion containing gravitational radiation-reaction terms through 4.5 post-Newtonian order to calculate the late-time eccentricities of inspiraling binary systems of non-spinning compact bodies as they cross the detection threshold of ground-based gravitational-wave interferometers. The initial eccentricities can be as large as 0.999. We find that the final eccentricities are systematically smaller than those predicted by the leading quadrupole approximation, by as much as 30 percent for a 300 solar mass binary crossing the LIGO/Virgo detection threshold at 10 Hz, or eight percent smaller for a 60 solar mass binary. We find an analytic formula for the late-time eccentricity that accurately accounts for the higher-order post-Newtonian effects, generalizing a formula derived by Peters and Mathews in the 1960s. We also find that the final eccentricities are independent of the ratio of the masses of the two compact bodies to better than two percent. |
gr-qc/9803074 | Kirill Krasnov | Kirill Krasnov | The Area Spectrum in Quantum Gravity | 8 pages, Revtex, no figures | Class.Quant.Grav.15:L47-L53,1998 | 10.1088/0264-9381/15/6/001 | CGPG-98/3-2 | gr-qc | null | We show that, apart from the usual area operator of non-perturbative quantum
gravity, there exists another, closely related, operator that measures areas of
surfaces. Both corresponding classical expressions yield the area. Quantum
mechanically, however, the spectra of the two operators are different,
coinciding only in the limit when the spins labelling the state are large. We
argue that both operators are legitimate quantum operators, and which one to
use depends on the context of a physical problem of interest. Thus, for
example, we argue that it is the operator proposed here that is relevant in the
black hole context to measure the area of black hole horizon. We show that the
difference between the two operators is due to non-commutativity that is known
to arise in the quantum theory. We give a heuristic picture explaining the
difference between the two area spectra in terms of quantum fluctuations of the
surface whose area is being measured.
| [
{
"created": "Sun, 22 Mar 1998 17:40:07 GMT",
"version": "v1"
},
{
"created": "Mon, 4 May 1998 01:58:28 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Krasnov",
"Kirill",
""
]
] | We show that, apart from the usual area operator of non-perturbative quantum gravity, there exists another, closely related, operator that measures areas of surfaces. Both corresponding classical expressions yield the area. Quantum mechanically, however, the spectra of the two operators are different, coinciding only in the limit when the spins labelling the state are large. We argue that both operators are legitimate quantum operators, and which one to use depends on the context of a physical problem of interest. Thus, for example, we argue that it is the operator proposed here that is relevant in the black hole context to measure the area of black hole horizon. We show that the difference between the two operators is due to non-commutativity that is known to arise in the quantum theory. We give a heuristic picture explaining the difference between the two area spectra in terms of quantum fluctuations of the surface whose area is being measured. |
1406.2307 | Davood Momeni Dr | Surajit Chattopadhyay, Abdul Jawad, Davood Momeni, Ratbay Myrzakulov | Pilgrim Dark Energy in $f(T, T_G)$ cosmology | Revised version accepted for publication in "Astrophysics and Space
Science", 23 pages, 20 figures | Astrophys.Space Sci. 353 (2014) no.1, 279-292 | 10.1007/s10509-014-2029-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We work on the reconstruction scenario of pilgrim dark energy" (PDE) in $f(T,
T_G)$. In PDE model it is assumed that a repulsive force that is accelerating
the Universe is phantom type with $(w_{DE}<-1)$ and it so strong that prevents
formation of the black hole. We construct the $f(T, T_G)$ models and
correspondingly evaluate equation of state parameter for various choices of
scale factor. Also, we assume polynomial form of $f(T, T_G)$ in terms of cosmic
time and reconstruct $H$ and $w_{DE}$ in this manner. Through discussion, it is
concluded that PDE shows aggressive phantom-like behaviour for$s=-2$ in $f(T,
T_G)$ gravity.
| [
{
"created": "Sat, 7 Jun 2014 07:18:41 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Jun 2014 09:32:46 GMT",
"version": "v2"
}
] | 2018-10-09 | [
[
"Chattopadhyay",
"Surajit",
""
],
[
"Jawad",
"Abdul",
""
],
[
"Momeni",
"Davood",
""
],
[
"Myrzakulov",
"Ratbay",
""
]
] | We work on the reconstruction scenario of pilgrim dark energy" (PDE) in $f(T, T_G)$. In PDE model it is assumed that a repulsive force that is accelerating the Universe is phantom type with $(w_{DE}<-1)$ and it so strong that prevents formation of the black hole. We construct the $f(T, T_G)$ models and correspondingly evaluate equation of state parameter for various choices of scale factor. Also, we assume polynomial form of $f(T, T_G)$ in terms of cosmic time and reconstruct $H$ and $w_{DE}$ in this manner. Through discussion, it is concluded that PDE shows aggressive phantom-like behaviour for$s=-2$ in $f(T, T_G)$ gravity. |
gr-qc/0402045 | Jose A. Gonzalez | Miguel Alcubierre, Jose A. Gonzalez, Marcelo Salgado and Daniel
Sudarsky | The cosmic censor conjecture: Is it generically violated? | 4 pages, 4 figures | null | null | null | gr-qc hep-th | null | It has been recently argued by Hertog, Horowitz and Maeda, that generic
reasonable initial data in asymptotically anti deSitter, spherically symmetric,
space-times within an Einstein-Higgs theory, will evolve toward a naked
singularity, in clear violation of the cosmic censor conjecture. We will argue
that there is a logical and physically plausible loophole in the argument and
that the numerical evidence in a related problem suggests that this loophole is
in fact employed by physics.
| [
{
"created": "Tue, 10 Feb 2004 16:50:42 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Alcubierre",
"Miguel",
""
],
[
"Gonzalez",
"Jose A.",
""
],
[
"Salgado",
"Marcelo",
""
],
[
"Sudarsky",
"Daniel",
""
]
] | It has been recently argued by Hertog, Horowitz and Maeda, that generic reasonable initial data in asymptotically anti deSitter, spherically symmetric, space-times within an Einstein-Higgs theory, will evolve toward a naked singularity, in clear violation of the cosmic censor conjecture. We will argue that there is a logical and physically plausible loophole in the argument and that the numerical evidence in a related problem suggests that this loophole is in fact employed by physics. |
2107.12968 | Muhammad Sharif | M. Sharif and Mariyah Aslam | Compact Objects by Gravitational Decoupling in f(R) Gravity | 30 pages, 10 figures | Eur. Phys. J. C (2021) 81:641 | 10.1140/epjc/s10052-021-09436-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The objective of this paper is to discuss anisotropic solutions representing
static spherical self-gravitating systems in $f(R)$ theory. We employ the
extended gravitational decoupling approach and transform temporal as well as
radial metric potentials which decomposes the system of non-linear field
equations into two arrays: one set corresponding to seed source and the other
one involves additional source terms. The domain of the isotropic solution is
extended in the background of $f(R)$ Starobinsky model by employing the metric
potentials of Krori-Barua spacetime. We determine two anisotropic solutions by
employing some physical constraints on the extra source. The values of unknown
constants are computed by matching the interior and exterior spacetimes. We
inspect the physical viability, equilibrium and stability of the obtained
solutions corresponding to the star Her X-I. It is observed that one of the two
extensions satisfies all the necessary physical requirements for particular
values of the decoupling parameter.
| [
{
"created": "Fri, 9 Jul 2021 09:13:47 GMT",
"version": "v1"
}
] | 2021-07-28 | [
[
"Sharif",
"M.",
""
],
[
"Aslam",
"Mariyah",
""
]
] | The objective of this paper is to discuss anisotropic solutions representing static spherical self-gravitating systems in $f(R)$ theory. We employ the extended gravitational decoupling approach and transform temporal as well as radial metric potentials which decomposes the system of non-linear field equations into two arrays: one set corresponding to seed source and the other one involves additional source terms. The domain of the isotropic solution is extended in the background of $f(R)$ Starobinsky model by employing the metric potentials of Krori-Barua spacetime. We determine two anisotropic solutions by employing some physical constraints on the extra source. The values of unknown constants are computed by matching the interior and exterior spacetimes. We inspect the physical viability, equilibrium and stability of the obtained solutions corresponding to the star Her X-I. It is observed that one of the two extensions satisfies all the necessary physical requirements for particular values of the decoupling parameter. |
2208.12566 | Harish Chandra Das | H. C. Das | $I-$Love$-C$ relation for an anisotropic neutron star | 12 pages, 15 figures, 4 tables, Published in Phys. rev. D | Phys. Rev. D 106, 103518 (2022) | 10.1103/PhysRevD.106.103518 | null | gr-qc astro-ph.HE nucl-th | http://creativecommons.org/licenses/by/4.0/ | One of the most common assumptions has been made that the pressure inside the
star is isotropic in nature. However, the pressure is locally anisotropic in
nature which is a more realistic case. In this study, we investigate certain
properties of anisotropic neutron stars with the scalar pressure anisotropy
model. Different perfect fluid conditions are tested within the star with the
relativistic mean-field model equation of states (EOSs). The anisotropic
neutron star properties such as mass ($M$), radius ($R$), compactness ($C$),
Love number ($k_2$), dimensionless tidal deformability ($\Lambda$), and the
moment of inertia ($I$) are calculated. The magnitude of the quantities as
mentioned above increases (decreases) with the positive (negative) value of
anisotropy except $k_2$ and $\Lambda$. The Universal relation $I-$Love$-C$ is
calculated with almost 58 EOSs spans from relativistic to non-relativistic
cases. We observed that the relations between them get weaker when we include
anisotropicity. With the help of the GW170817 tidal deformability limit and
radii constraints from different approaches, we find that the anisotropic
parameter is less than 1.0 if one uses the BL model. Using the universal
relation and the tidal deformability bound given by the GW170817, we put a
theoretical limit for the canonical radius, $R_{1.4}=10.74_{-1.36}^{+1.84}$ km,
and the moment of inertia, $I_{1.4} = 1.77_{-0.09}^{+0.17}\times10^{45}$ g
cm$^2$ with 90\% confidence limit for isotropic stars. Similarly, for
anisotropic stars with $\lambda_{\rm BL}=1.0$, the values are
$R_{1.4}=11.74_{-1.54}^{+2.11}$ km, $I_{1.4} = 2.40_{-0.08}^{+0.17}
\times10^{45}$ g cm$^2$ respectively.
| [
{
"created": "Fri, 26 Aug 2022 10:17:52 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Nov 2022 06:33:24 GMT",
"version": "v2"
}
] | 2022-11-18 | [
[
"Das",
"H. C.",
""
]
] | One of the most common assumptions has been made that the pressure inside the star is isotropic in nature. However, the pressure is locally anisotropic in nature which is a more realistic case. In this study, we investigate certain properties of anisotropic neutron stars with the scalar pressure anisotropy model. Different perfect fluid conditions are tested within the star with the relativistic mean-field model equation of states (EOSs). The anisotropic neutron star properties such as mass ($M$), radius ($R$), compactness ($C$), Love number ($k_2$), dimensionless tidal deformability ($\Lambda$), and the moment of inertia ($I$) are calculated. The magnitude of the quantities as mentioned above increases (decreases) with the positive (negative) value of anisotropy except $k_2$ and $\Lambda$. The Universal relation $I-$Love$-C$ is calculated with almost 58 EOSs spans from relativistic to non-relativistic cases. We observed that the relations between them get weaker when we include anisotropicity. With the help of the GW170817 tidal deformability limit and radii constraints from different approaches, we find that the anisotropic parameter is less than 1.0 if one uses the BL model. Using the universal relation and the tidal deformability bound given by the GW170817, we put a theoretical limit for the canonical radius, $R_{1.4}=10.74_{-1.36}^{+1.84}$ km, and the moment of inertia, $I_{1.4} = 1.77_{-0.09}^{+0.17}\times10^{45}$ g cm$^2$ with 90\% confidence limit for isotropic stars. Similarly, for anisotropic stars with $\lambda_{\rm BL}=1.0$, the values are $R_{1.4}=11.74_{-1.54}^{+2.11}$ km, $I_{1.4} = 2.40_{-0.08}^{+0.17} \times10^{45}$ g cm$^2$ respectively. |
2106.05558 | Akash Kumar Mishra | Akash K Mishra, Abhirup Ghosh, Sumanta Chakraborty | Constraining extra dimensions using observations of black hole
quasi-normal modes | 11 pages, 2 figures, 1 table, Revised version accepted in EPJC | Eur. Phys. J. C 82, 820 (2022) | 10.1140/epjc/s10052-022-10788-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The presence of extra dimensions generically modify the spacetime geometry of
a rotating black hole, by adding an additional hair, besides the mass $M$ and
the angular momentum $J$, known as the `tidal charge' parameter, $\beta$. In a
braneworld scenario with one extra spatial dimension, the extra dimension is
expected to manifest itself through -- (a) negative values of $\beta$, and (b)
modified gravitational perturbations. This in turn would affect the
quasi-normal modes of rotating black holes. We numerically solve the perturbed
gravitational field equations using the continued fractions method and
determine the quasi-normal mode spectra for the braneworld black hole. We find
that increasingly negative values of $\beta$ correspond to a diminishing
imaginary part of the quasi-normal mode, or equivalently, an increasing damping
time. Using the publicly available data of the properties of the remnant black
hole in the gravitational wave signal GW150914, we check for consistency
between the predicted values (for a given $\beta$) of the frequency and damping
time of the least-damped $\ell=2,m=2$ quasi-normal mode and measurements of
these quantities using other independent techniques. We find that it is highly
unlikely for the tidal charge, $\beta \lesssim -0.05$, providing a conservative
limit on the tidal charge parameter. Implications and future directions are
discussed.
| [
{
"created": "Thu, 10 Jun 2021 07:36:33 GMT",
"version": "v1"
},
{
"created": "Sat, 17 Sep 2022 21:58:50 GMT",
"version": "v2"
}
] | 2022-09-20 | [
[
"Mishra",
"Akash K",
""
],
[
"Ghosh",
"Abhirup",
""
],
[
"Chakraborty",
"Sumanta",
""
]
] | The presence of extra dimensions generically modify the spacetime geometry of a rotating black hole, by adding an additional hair, besides the mass $M$ and the angular momentum $J$, known as the `tidal charge' parameter, $\beta$. In a braneworld scenario with one extra spatial dimension, the extra dimension is expected to manifest itself through -- (a) negative values of $\beta$, and (b) modified gravitational perturbations. This in turn would affect the quasi-normal modes of rotating black holes. We numerically solve the perturbed gravitational field equations using the continued fractions method and determine the quasi-normal mode spectra for the braneworld black hole. We find that increasingly negative values of $\beta$ correspond to a diminishing imaginary part of the quasi-normal mode, or equivalently, an increasing damping time. Using the publicly available data of the properties of the remnant black hole in the gravitational wave signal GW150914, we check for consistency between the predicted values (for a given $\beta$) of the frequency and damping time of the least-damped $\ell=2,m=2$ quasi-normal mode and measurements of these quantities using other independent techniques. We find that it is highly unlikely for the tidal charge, $\beta \lesssim -0.05$, providing a conservative limit on the tidal charge parameter. Implications and future directions are discussed. |
1303.3215 | Pedro Fraz\~ao | Orfeu Bertolami, Pedro Fraz\~ao, Jorge P\'aramos | Cosmological perturbations in theories with non-minimal coupling between
curvature and matter | 20 pages, 1 figure | JCAP 05 (2013) 029 | 10.1088/1475-7516/2013/05/029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, one examines how the presence of a non-minimal coupling between
the spacetime curvature and matter affects the evolution of cosmological
perturbations around a homogeneous and isotropic Universe and hence the
formation of large-scale structure. This framework places constraints on the
terms which arise due to the coupling with matter and, in particular, on the
modification in the growth of matter density perturbations. One obtains
approximate analytical solutions for the evolution of matter overdensities
during the matter dominated era and shows that these favor the presence of a
coupling function that is compatible with the late-time cosmic acceleration.
| [
{
"created": "Wed, 13 Mar 2013 17:15:15 GMT",
"version": "v1"
},
{
"created": "Fri, 24 May 2013 12:51:06 GMT",
"version": "v2"
}
] | 2013-05-27 | [
[
"Bertolami",
"Orfeu",
""
],
[
"Frazão",
"Pedro",
""
],
[
"Páramos",
"Jorge",
""
]
] | In this work, one examines how the presence of a non-minimal coupling between the spacetime curvature and matter affects the evolution of cosmological perturbations around a homogeneous and isotropic Universe and hence the formation of large-scale structure. This framework places constraints on the terms which arise due to the coupling with matter and, in particular, on the modification in the growth of matter density perturbations. One obtains approximate analytical solutions for the evolution of matter overdensities during the matter dominated era and shows that these favor the presence of a coupling function that is compatible with the late-time cosmic acceleration. |
2304.03914 | Subhayan Maity | Subhayan Maity and Sujayita Bakra | Is emergent scenario in the early Universe a consequence of the dynamics
of real scalar field particle ? | null | Journal of Physics and Astronomy,2023 | 10.37532/2320-6756.2023.11(7).360 | tspa-23-110616 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Emergent scenario of cosmic evolution is a topic of great interest in recent
cosmology, especially because it describes a non-singular origin of the
Universe unlike the Big-Bang models. This types of cosmic evolution pattern
have already been established through the non-equilibrium thermodynamic
prescription. But those models are phenomenological and requires physical
interpretation from the perspective of quantum field theory. This work is an
effort to search a quantum field theoretical reason to justify the emergent
nature of the Universe and the nature of cosmic evolution at the early phase of
the cosmic expansion. Keywords : Non-singular evolution of the Universe,
Quantum field theory, Cosmology.
| [
{
"created": "Sat, 8 Apr 2023 05:15:13 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Apr 2023 08:15:26 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Apr 2023 15:53:48 GMT",
"version": "v3"
},
{
"created": "Thu, 13 Apr 2023 04:40:44 GMT",
"version": "v4"
},
{
"cr... | 2023-09-01 | [
[
"Maity",
"Subhayan",
""
],
[
"Bakra",
"Sujayita",
""
]
] | Emergent scenario of cosmic evolution is a topic of great interest in recent cosmology, especially because it describes a non-singular origin of the Universe unlike the Big-Bang models. This types of cosmic evolution pattern have already been established through the non-equilibrium thermodynamic prescription. But those models are phenomenological and requires physical interpretation from the perspective of quantum field theory. This work is an effort to search a quantum field theoretical reason to justify the emergent nature of the Universe and the nature of cosmic evolution at the early phase of the cosmic expansion. Keywords : Non-singular evolution of the Universe, Quantum field theory, Cosmology. |
1911.07341 | Gregory Horndeski | Gregory W. Horndeski | Reformulating Scalar-Tensor Field Theories as Scalar-Scalar Field
Theories Using Lorentzian Cofinsler Spaces | 83 pages, 4 figures. In this version of the paper I correct typos
that appeared previously, remove superfluous verbiage, and add more
references, along with additional material to section 3. I have also added
two appendices which deal with solutions to the field equations and the
structure of the multiverse | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper I shall show how notions of Finsler geometry can be used to
construct a new type of geometry using a scalar field, f, on the cotangent
bundle of a differentiable manifold, M. This new geometry will be called
Lorentzian Cofinsler geometry. This geometry will enable me to use the second
vertical derivatives of f, along with the differential of the scalar field, phi
on M, to construct a Lorentzian metric tensor on M, that depends upon phi. f
will be chosen so that the resultant metric on M has the form of a FLRW metric,
with the t equal constant slices being flat. When the Horndeski Lagrangians are
evaluated for this choice of geometry the quartic and quintic Lagrangians are
of third order, but reduce to non-degenerate second-order Lagrangians plus a
divergence. Upon varying phi in these "scalarized" Horndeski Lagrangians,
equations will be obtained which admit self-inflating universe solutions,
provided that the coefficient functions appearing in the Horndeski Lagrangians
are chosen suitably. This approach is also used to study solutions of the most
general conformally invariant scalar-tensor field theory which is flat space
compatible (i.e., such that the Lagrangians of the field theory are
well-defined when either the space is flat or the scalar field is constant).
There too the coefficient functions can be chosen to give self-inflating
universes. Arguments will be presented to show that it is possible to construct
model universes that begin explosively, and then settle down to a period of
much quieter acceleration which either continues forever, or stops and
collapses to the models original, pre-expansion, state.
| [
{
"created": "Sun, 17 Nov 2019 21:12:43 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Apr 2020 02:31:14 GMT",
"version": "v2"
},
{
"created": "Sat, 5 Sep 2020 20:54:04 GMT",
"version": "v3"
}
] | 2020-09-08 | [
[
"Horndeski",
"Gregory W.",
""
]
] | In this paper I shall show how notions of Finsler geometry can be used to construct a new type of geometry using a scalar field, f, on the cotangent bundle of a differentiable manifold, M. This new geometry will be called Lorentzian Cofinsler geometry. This geometry will enable me to use the second vertical derivatives of f, along with the differential of the scalar field, phi on M, to construct a Lorentzian metric tensor on M, that depends upon phi. f will be chosen so that the resultant metric on M has the form of a FLRW metric, with the t equal constant slices being flat. When the Horndeski Lagrangians are evaluated for this choice of geometry the quartic and quintic Lagrangians are of third order, but reduce to non-degenerate second-order Lagrangians plus a divergence. Upon varying phi in these "scalarized" Horndeski Lagrangians, equations will be obtained which admit self-inflating universe solutions, provided that the coefficient functions appearing in the Horndeski Lagrangians are chosen suitably. This approach is also used to study solutions of the most general conformally invariant scalar-tensor field theory which is flat space compatible (i.e., such that the Lagrangians of the field theory are well-defined when either the space is flat or the scalar field is constant). There too the coefficient functions can be chosen to give self-inflating universes. Arguments will be presented to show that it is possible to construct model universes that begin explosively, and then settle down to a period of much quieter acceleration which either continues forever, or stops and collapses to the models original, pre-expansion, state. |
0708.0250 | Jorge Pullin | Rodolfo Gambini and Jorge Pullin | Holography from loop quantum gravity | 6 pages, RevTex, no figures, Honorable Mention Gravity Research
Foundation 2007, to appear in special issue of IJMPD | Int.J.Mod.Phys.D17:545-549,2008 | 10.1142/S0218271808012231 | LSU-REL-080107 | gr-qc hep-th | null | We show that holography arises naturally in the context of spherically
symmetric loop quantum gravity. The result is not dependent on detailed
assumptions about the dynamics of the theory being considered. It ties strongly
the amount of information contained in a region of space to the tight
mathematical underpinnings of loop quantum geometry, at least in this
particular context.
| [
{
"created": "Thu, 2 Aug 2007 12:30:15 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Feb 2008 21:46:39 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | We show that holography arises naturally in the context of spherically symmetric loop quantum gravity. The result is not dependent on detailed assumptions about the dynamics of the theory being considered. It ties strongly the amount of information contained in a region of space to the tight mathematical underpinnings of loop quantum geometry, at least in this particular context. |
1410.8473 | Pierre Fleury | Pierre Fleury, Cyril Pitrou, Jean-Philippe Uzan | Light propagation in a homogeneous and anisotropic universe | 12 pages, no figure; v3 matches published version, except a minor
typo in Eqs. (4.8), (4.10), now corrected | Phys. Rev. D 91, 043511 (2015) | 10.1103/PhysRevD.91.043511 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article proposes a comprehensive analysis of light propagation in an
anisotropic and spatially homogeneous Bianchi I universe. After recalling that
null geodesics are easily determined in such a spacetime, we derive the
expressions of the redshift and direction drifts of light sources; by solving
analytically the Sachs equation, we then obtain an explicit expression of the
Jacobi matrix describing the propagation of narrow light beams. As a byproduct,
we recover the old formula by Saunders for the angular diameter distance in a
Bianchi I spacetime, but our derivation goes further since it also provides the
optical shear and rotation. These results pave the way to the analysis of both
supernovae data and weak lensing by the large-scale structure in Bianchi
universes.
| [
{
"created": "Wed, 29 Oct 2014 19:51:52 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Nov 2014 01:20:27 GMT",
"version": "v2"
},
{
"created": "Wed, 11 Mar 2015 09:59:24 GMT",
"version": "v3"
}
] | 2015-03-12 | [
[
"Fleury",
"Pierre",
""
],
[
"Pitrou",
"Cyril",
""
],
[
"Uzan",
"Jean-Philippe",
""
]
] | This article proposes a comprehensive analysis of light propagation in an anisotropic and spatially homogeneous Bianchi I universe. After recalling that null geodesics are easily determined in such a spacetime, we derive the expressions of the redshift and direction drifts of light sources; by solving analytically the Sachs equation, we then obtain an explicit expression of the Jacobi matrix describing the propagation of narrow light beams. As a byproduct, we recover the old formula by Saunders for the angular diameter distance in a Bianchi I spacetime, but our derivation goes further since it also provides the optical shear and rotation. These results pave the way to the analysis of both supernovae data and weak lensing by the large-scale structure in Bianchi universes. |
1505.06189 | Ivano Dami\~ao Soares | Rodrigo Maier, Ivano Dami\~ao Soares and Eduardo Valentino Tonini | General Bianchi IX dynamics in bouncing braneworld cosmology: homoclinic
chaos and the BKL conjecture | 41 pages, 17 figures | null | 10.1088/0264-9381/32/23/235001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the dynamics of a Bianchi IX model on a 4-dim brane embedded in a
5-dim conformally flat empty bulk with a timelike extra dimension. Einstein's
equations on the brane reduces to a 6-dim Hamiltonian dynamical system with
additional terms that implement nonsingular bounces in the model. The phase
space of the model has two critical points (a saddle-center-center and a
center-center-center) in a finite region of phase space, and two asymptotic de
Sitter critical points, one acting as an attractor to late-time dynamics. The
saddle-center-center engenders in the phase space the topology of stable and
unstable 4-dim cylinders $R \times S^3$, where $R$ is a saddle direction and
$S^3$ is the center manifold of unstable periodic orbits (the nonlinear
extension of the center-center sector). By a proper canonical transformation we
separate the degrees of freedom of the dynamics into one degree connected with
the expansion/contraction of the scales of the model, and two rotational
degrees of freedom connected to the $S^3$. The typical dynamical flow is then
an oscillatory mode about a neighborhood of the cylinders. For the stable and
unstable cylinders the oscillatory motion about the separatrix towards the
bounce leads to the homoclinic transversal intersection of the cylinders, as
shown numerically in two distinct experiments. We show that the homoclinic
intersection manifold has the topology of $R \times S^2$ consisting of
homoclinic orbits biasymptotic to the center manifold $S^3$. This behavior
defines a {\it chaotic saddle} associated with $S^3$, indicating that the
intersection points of the cylinders have the nature of a Cantor set with a
compact support $S^2$, characterizing chaos in the model. We discuss the
oscillatory approach to the bounce together with its chaotic behavior, and
analogous features present in the BKL conjecture in general relativity.
| [
{
"created": "Fri, 22 May 2015 19:36:17 GMT",
"version": "v1"
}
] | 2015-11-18 | [
[
"Maier",
"Rodrigo",
""
],
[
"Soares",
"Ivano Damião",
""
],
[
"Tonini",
"Eduardo Valentino",
""
]
] | We examine the dynamics of a Bianchi IX model on a 4-dim brane embedded in a 5-dim conformally flat empty bulk with a timelike extra dimension. Einstein's equations on the brane reduces to a 6-dim Hamiltonian dynamical system with additional terms that implement nonsingular bounces in the model. The phase space of the model has two critical points (a saddle-center-center and a center-center-center) in a finite region of phase space, and two asymptotic de Sitter critical points, one acting as an attractor to late-time dynamics. The saddle-center-center engenders in the phase space the topology of stable and unstable 4-dim cylinders $R \times S^3$, where $R$ is a saddle direction and $S^3$ is the center manifold of unstable periodic orbits (the nonlinear extension of the center-center sector). By a proper canonical transformation we separate the degrees of freedom of the dynamics into one degree connected with the expansion/contraction of the scales of the model, and two rotational degrees of freedom connected to the $S^3$. The typical dynamical flow is then an oscillatory mode about a neighborhood of the cylinders. For the stable and unstable cylinders the oscillatory motion about the separatrix towards the bounce leads to the homoclinic transversal intersection of the cylinders, as shown numerically in two distinct experiments. We show that the homoclinic intersection manifold has the topology of $R \times S^2$ consisting of homoclinic orbits biasymptotic to the center manifold $S^3$. This behavior defines a {\it chaotic saddle} associated with $S^3$, indicating that the intersection points of the cylinders have the nature of a Cantor set with a compact support $S^2$, characterizing chaos in the model. We discuss the oscillatory approach to the bounce together with its chaotic behavior, and analogous features present in the BKL conjecture in general relativity. |
1611.00085 | Seyed Meraj Mousavi Rasouli | S. M. M. Rasouli and Paulo Vargas Moniz | Gravity-Driven Acceleration and Kinetic Inflation in Noncommutative
Brans-Dicke Setting | 6 pages, 2 figures. arXiv admin note: substantial text overlap with
arXiv:1411.1346 | null | 10.18524/1810-4215.2016.29.84956 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By assuming the spatially flat~FLRW line-element and employing the
Hamiltonian formalism, a noncommutative (NC) setting of the Brans-Dicke (BD)
theory is introduced. We investigate gravity-driven acceleration and kinetic
inflation in this NC BD cosmology. Despite to the commutative case, in which
both the scale factor and BD scalar field are obtained in power-law forms (in
terms of the cosmic time), in our herein NC model, we see that the power-law
scalar factor is multiplied by a dynamical exponential warp factor. This warp
factor depends on not only the NC parameter but also the momentum conjugate
associated to the BD scalar field. For very small values of this parameter, we
obtain an appropriate inflationary solution, which can overcome the problems
within the standard BD cosmology in a more efficient manner. Moreover, we see
that a graceful exit from an early acceleration epoch towards a decelerating
radiation epoch is provided. For late times, due to the presence of the NC
parameter, we obtain a zero acceleration epoch, which can be interpreted as the
coarse-grained explanation.
| [
{
"created": "Mon, 31 Oct 2016 23:59:48 GMT",
"version": "v1"
}
] | 2017-01-18 | [
[
"Rasouli",
"S. M. M.",
""
],
[
"Moniz",
"Paulo Vargas",
""
]
] | By assuming the spatially flat~FLRW line-element and employing the Hamiltonian formalism, a noncommutative (NC) setting of the Brans-Dicke (BD) theory is introduced. We investigate gravity-driven acceleration and kinetic inflation in this NC BD cosmology. Despite to the commutative case, in which both the scale factor and BD scalar field are obtained in power-law forms (in terms of the cosmic time), in our herein NC model, we see that the power-law scalar factor is multiplied by a dynamical exponential warp factor. This warp factor depends on not only the NC parameter but also the momentum conjugate associated to the BD scalar field. For very small values of this parameter, we obtain an appropriate inflationary solution, which can overcome the problems within the standard BD cosmology in a more efficient manner. Moreover, we see that a graceful exit from an early acceleration epoch towards a decelerating radiation epoch is provided. For late times, due to the presence of the NC parameter, we obtain a zero acceleration epoch, which can be interpreted as the coarse-grained explanation. |
1304.6385 | Ivan Jardim Carneiro | I. C. Jardim, R. R. Landim | Deviation of Large Scale Gravitoelectromagnetic Field in Post-Newtonian
Approximation | 20 pages, 1 figure, corrected typos | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work a study of the gravity is made using Einstein's equation in the
post-Newtonian approach. This is a method to linearise the General Relativity
indicated to treat non-relativistic objects. It enables us to construct, from
metric-independent elements, fields that are governed by equations similar to
the Maxwell's ones in Lorentz gauge. We promediate these equations for matter
distributed in local systems, like solar systems or galaxies. Finally we define
the large scale fields for this distribution, which includes terms analogous to
electromagnetic case, like polarization, magnetization and superiors terms.
| [
{
"created": "Tue, 23 Apr 2013 19:27:42 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Apr 2013 18:37:44 GMT",
"version": "v2"
}
] | 2013-04-29 | [
[
"Jardim",
"I. C.",
""
],
[
"Landim",
"R. R.",
""
]
] | In this work a study of the gravity is made using Einstein's equation in the post-Newtonian approach. This is a method to linearise the General Relativity indicated to treat non-relativistic objects. It enables us to construct, from metric-independent elements, fields that are governed by equations similar to the Maxwell's ones in Lorentz gauge. We promediate these equations for matter distributed in local systems, like solar systems or galaxies. Finally we define the large scale fields for this distribution, which includes terms analogous to electromagnetic case, like polarization, magnetization and superiors terms. |
1404.6537 | Lorenzo Iorio | Lorenzo Iorio | The lingering anomalous secular increase of the eccentricity of the
orbit of the Moon: further attempts of explanation of cosmological origin | LaTex2e, 4 pages, no figures, no tables. Accepted for publication in
Galaxies | Galaxies: 2(2), pp. 259-262, 2014 | 10.3390/galaxies2020259 | null | gr-qc astro-ph.EP physics.geo-ph physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new analysis of extended data records collected with the Lunar Laser
Ranging (LLR) technique performed with improved tidal models was not able to
resolve the issue of the anomalous rate $\dot e$ of the eccentricity $e$ of the
orbit of the Moon, which is still in place with a magnitude of $\dot e=(5\pm
2)\times 10^{-12}$ yr$^{-1}$. Some possible cosmological explanations are
offered in terms of the post-Newtonian effects of the cosmological expansion,
and of the slow temporal variation of the relative acceleration rate $\ddot{S}
S^{-1}$ of the cosmic scale factor $S$. None of them is successful since their
predicted secular rates of the lunar eccentricity are too small by several
orders of magnitude.
| [
{
"created": "Sat, 26 Apr 2014 11:37:24 GMT",
"version": "v1"
}
] | 2014-05-05 | [
[
"Iorio",
"Lorenzo",
""
]
] | A new analysis of extended data records collected with the Lunar Laser Ranging (LLR) technique performed with improved tidal models was not able to resolve the issue of the anomalous rate $\dot e$ of the eccentricity $e$ of the orbit of the Moon, which is still in place with a magnitude of $\dot e=(5\pm 2)\times 10^{-12}$ yr$^{-1}$. Some possible cosmological explanations are offered in terms of the post-Newtonian effects of the cosmological expansion, and of the slow temporal variation of the relative acceleration rate $\ddot{S} S^{-1}$ of the cosmic scale factor $S$. None of them is successful since their predicted secular rates of the lunar eccentricity are too small by several orders of magnitude. |
1703.07400 | Elena Giorgi | Elena Giorgi | On the local extension of Killing vector fields in electrovacuum
spacetimes | 20 pages. Version accepted for publication in Ann. Henri Poincar\'e.
arXiv admin note: text overlap with arXiv:1108.3575 by other authors | null | 10.1007/s00023-019-00811-5 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the problem of extension of a Killing vector field in a spacetime
which is solution to the Einstein-Maxwell equation. This extension has been
proved to be unique in the case of a Killing vector field which is normal to a
bifurcate horizon by Yu. Here we generalize the extension of the vector field
to a strong null convex domain in an electrovacuum spacetime, inspired by the
same technique used by Ionescu-Klainerman in the setting of Ricci flat
manifolds. We also prove a result concerning non-extendibility: we show that
one can find local, stationary electrovacuum extension of a Kerr-Newman
solution in a full neighborhood of a point of the horizon (that is not on the
bifurcation sphere) which admits no extension of the Hawking vector field. This
generalizes the construction by Ionescu-Klainerman to the electrovacuum case.
| [
{
"created": "Tue, 21 Mar 2017 19:38:00 GMT",
"version": "v1"
},
{
"created": "Thu, 23 May 2019 23:01:18 GMT",
"version": "v2"
}
] | 2019-05-28 | [
[
"Giorgi",
"Elena",
""
]
] | We revisit the problem of extension of a Killing vector field in a spacetime which is solution to the Einstein-Maxwell equation. This extension has been proved to be unique in the case of a Killing vector field which is normal to a bifurcate horizon by Yu. Here we generalize the extension of the vector field to a strong null convex domain in an electrovacuum spacetime, inspired by the same technique used by Ionescu-Klainerman in the setting of Ricci flat manifolds. We also prove a result concerning non-extendibility: we show that one can find local, stationary electrovacuum extension of a Kerr-Newman solution in a full neighborhood of a point of the horizon (that is not on the bifurcation sphere) which admits no extension of the Hawking vector field. This generalizes the construction by Ionescu-Klainerman to the electrovacuum case. |
gr-qc/0509084 | Yasufumi Kojima | Yasufumi Kojima and Kentaro Takami | Tidal effects on magnetic gyration of a charged particle in Fermi
coordinates | 10 pages, 12 figures | Class.Quant.Grav. 23 (2006) 609-616 | 10.1088/0264-9381/23/3/004 | null | gr-qc | null | We examine the gyration motion of a charged particle, viewed from a reference
observer falling along the Z axis into a Schwarzschild black hole. It is
assumed that the magnetic field is constant and uniform along the Z axis, and
that the particle has a circular orbit in the X-Y plane far from the
gravitational source. When the particle as well as the reference observer
approaches the black hole, its orbit is disrupted by the tidal force. The final
plunging velocity increases in the non-relativistic case, but decreases if the
initial circular velocity exceeds a critical value, which is approximately
0.7c. This toy model suggests that disruption of a rapidly rotating star due to
a velocity-dependent tidal force may be quite different from that of a
non-relativistic star. The model also suggested that collapse of the orbit
after the disruption is slow in general, so that the particle subsequently
escapes outside the valid Fermi coordinates.
| [
{
"created": "Wed, 21 Sep 2005 06:23:38 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Sep 2005 09:16:17 GMT",
"version": "v2"
},
{
"created": "Thu, 12 Jan 2006 00:27:56 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Kojima",
"Yasufumi",
""
],
[
"Takami",
"Kentaro",
""
]
] | We examine the gyration motion of a charged particle, viewed from a reference observer falling along the Z axis into a Schwarzschild black hole. It is assumed that the magnetic field is constant and uniform along the Z axis, and that the particle has a circular orbit in the X-Y plane far from the gravitational source. When the particle as well as the reference observer approaches the black hole, its orbit is disrupted by the tidal force. The final plunging velocity increases in the non-relativistic case, but decreases if the initial circular velocity exceeds a critical value, which is approximately 0.7c. This toy model suggests that disruption of a rapidly rotating star due to a velocity-dependent tidal force may be quite different from that of a non-relativistic star. The model also suggested that collapse of the orbit after the disruption is slow in general, so that the particle subsequently escapes outside the valid Fermi coordinates. |
2205.04217 | Kuantay Boshkayev | Gulnara Sulieva, Kuantay Boshkayev, Gulmira Nurbakyt, Hernando
Quevedo, Aliya Taukenova, Abylaikhan Tlemissov, Zhanerke Tlemissova and Ainur
Urazalina | Adiabatic theory of motion of bodies in the Hartle-Thorne spacetime | 8 pages, 1 figure | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the motion of test particles in the gravitational field of a
rotating and deformed object within the framework of the adiabatic theory. For
this purpose, the Hartle-Thorne metric written in harmonic coordinates is
employed in the post-Newtonian approximation where the adiabatic theory is
valid. As a result, we obtain the perihelion shift formula for test particles
orbiting on the equatorial plane of a rotating and deformed object. Based on
the perihelion shift expression, we show that the principle of superposition is
valid for the individual effects of the gravitational source mass, angular
momentum and quadrupole moment. The resulting formula was applied to the inner
planets of the Solar system. The outcomes are in a good agreement with
observational data. It was also shown that the corrections related to the Sun's
angular moment and quadrupole moment have little impact on the perihelion
shift. On the whole, it was demonstrated that the adiabatic theory, along with
its simplicity, leads to correct results, which in the limiting cases
correspond to the ones reported in the literature.
| [
{
"created": "Mon, 9 May 2022 12:14:13 GMT",
"version": "v1"
}
] | 2022-05-10 | [
[
"Sulieva",
"Gulnara",
""
],
[
"Boshkayev",
"Kuantay",
""
],
[
"Nurbakyt",
"Gulmira",
""
],
[
"Quevedo",
"Hernando",
""
],
[
"Taukenova",
"Aliya",
""
],
[
"Tlemissov",
"Abylaikhan",
""
],
[
"Tlemissova",
"Zhaner... | We study the motion of test particles in the gravitational field of a rotating and deformed object within the framework of the adiabatic theory. For this purpose, the Hartle-Thorne metric written in harmonic coordinates is employed in the post-Newtonian approximation where the adiabatic theory is valid. As a result, we obtain the perihelion shift formula for test particles orbiting on the equatorial plane of a rotating and deformed object. Based on the perihelion shift expression, we show that the principle of superposition is valid for the individual effects of the gravitational source mass, angular momentum and quadrupole moment. The resulting formula was applied to the inner planets of the Solar system. The outcomes are in a good agreement with observational data. It was also shown that the corrections related to the Sun's angular moment and quadrupole moment have little impact on the perihelion shift. On the whole, it was demonstrated that the adiabatic theory, along with its simplicity, leads to correct results, which in the limiting cases correspond to the ones reported in the literature. |
1805.07534 | Siamak Akhshabi | Siamak Akhshabi | Light propagation and optical scalars in torsion theories of gravity | 7 pages, 1 figure | Modern Physics Letters A 2 Vol. 34 (2019) 1950029 | 10.1142/S0217732319500299 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the propagation of light rays and evolution of optical scalars
in gauge theories of gravity where torsion is present. Recently the modified
Raychaudhuri equation in the presence of torsion has been derived. We use this
result to derive the basic equations of geometric optics for several different
interesting solutions of the Poincar{\'e} gauge theory of gravity. The results
show that the focusing effects for neighboring light rays will be different
than general relativity. This in turn has practical consequences in the study
of gravitational lensing effects and also determining the angular diameter
distance for cosmological objects.
| [
{
"created": "Sat, 19 May 2018 07:38:02 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jun 2018 06:50:46 GMT",
"version": "v2"
}
] | 2019-01-09 | [
[
"Akhshabi",
"Siamak",
""
]
] | We investigate the propagation of light rays and evolution of optical scalars in gauge theories of gravity where torsion is present. Recently the modified Raychaudhuri equation in the presence of torsion has been derived. We use this result to derive the basic equations of geometric optics for several different interesting solutions of the Poincar{\'e} gauge theory of gravity. The results show that the focusing effects for neighboring light rays will be different than general relativity. This in turn has practical consequences in the study of gravitational lensing effects and also determining the angular diameter distance for cosmological objects. |
1803.08809 | Graham Weir J | Graham Weir | Removing classical singularities by use of quantum mechanical sources | 13 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For distances large relative to the electron Compton wavelength, the Maxwell
and gravitational fields from a bound electron in its groundstate are
essentially those from a rotating, charged, massive point particle. For
distances small relative to the electron Compton wavelength, the corresponding
Maxwell fields and General Relativity metric, Riemann and Einstein tensors
become bounded, showing that, for this example, quantum effects remove the
corresponding classical singularities in electromagnetism and General
Relativity. The asymptotic magnetic dipole field from the bound electron
produces a constant magnetic field of several Tesla, aligned along the spin
axis of the electron, at the singularity position. The corresponding apparent
mass density from the gravitational field from the bound electron is about
2kgm$^{-3}$, at the singularity position.
| [
{
"created": "Thu, 22 Mar 2018 01:51:26 GMT",
"version": "v1"
}
] | 2018-03-26 | [
[
"Weir",
"Graham",
""
]
] | For distances large relative to the electron Compton wavelength, the Maxwell and gravitational fields from a bound electron in its groundstate are essentially those from a rotating, charged, massive point particle. For distances small relative to the electron Compton wavelength, the corresponding Maxwell fields and General Relativity metric, Riemann and Einstein tensors become bounded, showing that, for this example, quantum effects remove the corresponding classical singularities in electromagnetism and General Relativity. The asymptotic magnetic dipole field from the bound electron produces a constant magnetic field of several Tesla, aligned along the spin axis of the electron, at the singularity position. The corresponding apparent mass density from the gravitational field from the bound electron is about 2kgm$^{-3}$, at the singularity position. |
gr-qc/9901007 | Maureen Meyer | S. Deser (Brandeis University) | The Immortal Bel-Robinson Tensor | 7 pages. Lecture at Iberian Gravity Symposium to appear in
"Gravitation and Relativity in General", World Publishing (1999) | Gravitation and Relativity in general (World Pub 1999) | null | null | gr-qc | null | We present some generalizations, and novel properties, of the Bel-Robinson
tensor, in the context of constructing local invariants in D=11 supergravity.
| [
{
"created": "Tue, 5 Jan 1999 14:29:24 GMT",
"version": "v1"
}
] | 2009-11-19 | [
[
"Deser",
"S.",
"",
"Brandeis University"
]
] | We present some generalizations, and novel properties, of the Bel-Robinson tensor, in the context of constructing local invariants in D=11 supergravity. |
0904.4379 | Jinsong Yang | Jinsong Yang, You Ding, Yongge Ma | Alternative quantization of the Hamiltonian in loop quantum cosmology
II: Including the Lorentz term | 8 pages, 2 figures | Phys.Lett.B682:1-7,2009 | 10.1016/j.physletb.2009.10.072 | AEI-2009-042 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Since there are quantization ambiguities in constructing the Hamiltonian
constraint operator in isotropic loop quantum cosmology, it is crucial to check
whether the key features of loop quantum cosmology are robust against the
ambiguities. In this paper, we quantize the Lorentz term of the gravitational
Hamiltonian constraint in the spatially flat FRW model by two approaches
different from that of the Euclidean term. One of the approaches is very
similar to the treatment of the Lorentz part of Hamiltonian in loop quantum
gravity and hence inherits more features from the full theory. Two symmetric
Hamiltonian constraint operators are constructed respectively in the improved
scheme. Both of them are shown to have the correct classical limit by the
semiclassical analysis. In the loop quantum cosmological model with a massless
scalar field, the effective Hamiltonians and Friedmann equations are derived.
It turns out that the classical big bang is again replaced by a quantum bounce
in both cases. Moreover, there are still great possibilities for the expanding
universe to recollapse due to the quantum gravity effect.
| [
{
"created": "Tue, 28 Apr 2009 12:33:55 GMT",
"version": "v1"
}
] | 2010-04-14 | [
[
"Yang",
"Jinsong",
""
],
[
"Ding",
"You",
""
],
[
"Ma",
"Yongge",
""
]
] | Since there are quantization ambiguities in constructing the Hamiltonian constraint operator in isotropic loop quantum cosmology, it is crucial to check whether the key features of loop quantum cosmology are robust against the ambiguities. In this paper, we quantize the Lorentz term of the gravitational Hamiltonian constraint in the spatially flat FRW model by two approaches different from that of the Euclidean term. One of the approaches is very similar to the treatment of the Lorentz part of Hamiltonian in loop quantum gravity and hence inherits more features from the full theory. Two symmetric Hamiltonian constraint operators are constructed respectively in the improved scheme. Both of them are shown to have the correct classical limit by the semiclassical analysis. In the loop quantum cosmological model with a massless scalar field, the effective Hamiltonians and Friedmann equations are derived. It turns out that the classical big bang is again replaced by a quantum bounce in both cases. Moreover, there are still great possibilities for the expanding universe to recollapse due to the quantum gravity effect. |
1212.0831 | Alexander Belikov V | Alexander V. Belikov, Wayne Hu | Equivalence Principle Violation in Weakly Vainshtein-Screened Systems | 7 pages, 4 figures | null | 10.1103/PhysRevD.87.084042 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Massive gravity, galileon and braneworld models that modify gravity to
explain cosmic acceleration utilize the nonlinear field interactions of the
Vainshtein mechanism to screen fifth forces in high density regimes. These
source-dependent interactions cause apparent equivalence principle violations.
In the weakly-screened regime violations can be especially prominent since the
fifth forces are at near full strength. Since they can also be calculated
perturbatively, we derive analytic solutions for illustrative cases: the motion
of massive objects in compensated shells and voids and infall toward halos that
are spherically symmetric. Using numerical techniques we show that these
solutions are valid until the characteristic scale becomes comparable to the
Vainshtein radius. We find a relative acceleration of more massive objects
toward the center of a void and a reduction of the infall acceleration that
increases with the mass ratio of the halos which can in principle be used to
test the Vainshtein screening mechanism.
| [
{
"created": "Tue, 4 Dec 2012 19:16:21 GMT",
"version": "v1"
}
] | 2013-04-24 | [
[
"Belikov",
"Alexander V.",
""
],
[
"Hu",
"Wayne",
""
]
] | Massive gravity, galileon and braneworld models that modify gravity to explain cosmic acceleration utilize the nonlinear field interactions of the Vainshtein mechanism to screen fifth forces in high density regimes. These source-dependent interactions cause apparent equivalence principle violations. In the weakly-screened regime violations can be especially prominent since the fifth forces are at near full strength. Since they can also be calculated perturbatively, we derive analytic solutions for illustrative cases: the motion of massive objects in compensated shells and voids and infall toward halos that are spherically symmetric. Using numerical techniques we show that these solutions are valid until the characteristic scale becomes comparable to the Vainshtein radius. We find a relative acceleration of more massive objects toward the center of a void and a reduction of the infall acceleration that increases with the mass ratio of the halos which can in principle be used to test the Vainshtein screening mechanism. |
1903.09786 | Shahar Hod | Shahar Hod | On the status of the hoop conjecture in charged curved spacetimes | 4 pages | The European Physical Journal C 78, 1013 (2018) | 10.1140/epjc/s10052-018-6496-3 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The status and regime of validity of the famous Thorne hoop conjecture in
spatially regular {\it charged} curved spacetimes are clarified.
| [
{
"created": "Sat, 23 Mar 2019 09:30:35 GMT",
"version": "v1"
}
] | 2019-04-03 | [
[
"Hod",
"Shahar",
""
]
] | The status and regime of validity of the famous Thorne hoop conjecture in spatially regular {\it charged} curved spacetimes are clarified. |
1904.02300 | Hideki Asada | Yuki Hagihara, Naoya Era, Daisuke Iikawa, Atsushi Nishizawa, Hideki
Asada | Constraining extra gravitational wave polarizations with Advanced LIGO,
Advanced Virgo and KAGRA and upper bounds from GW170817 | 22 pages, 9 figures | Phys. Rev. D 100, 064010 (2019) | 10.1103/PhysRevD.100.064010 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General metric theories of gravity in four-dimensional spacetimes can contain
at most six polarization modes (two spin-0, two spin-1 and two spin-2) of
gravitational waves (GWs). It has been recently shown that, with using four GW
non-coaligned detectors, a direct test of the spin-1 modes can be done in
principle separately from the spin-0 and spin-2 modes for a GW source in
particular sky positions [Hagihara et al., Phys. Rev. D 98, 064035 (2018)].
They have found particular sky positions that satisfy a condition of killing
completely the spin-0 modes in a so-called null stream which is a linear
combination of the signal outputs to kill the spin-2 modes. The present paper
expands the method to discuss a possibility that the spin-0 modes are not
completely but effectively suppressed in the null streams to test the spin-1
modes separately from the other modes, especially with an expected network of
Advanced LIGO, Advanced Virgo and KAGRA. We study also a possibility that the
spin-1 modes are substantially suppressed in the null streams to test the
spin-0 modes separately from the other modes, though the spin-1 modes for any
sky position cannot be completely killed in the null streams. Moreover, we find
that the coefficient of the spin-0 modes in the null stream is significantly
small for the GW170817 event, so that an upper bound can be placed on the
amplitude of the spin-1 modes as $< 6 \times 10^{-23}$.
| [
{
"created": "Thu, 4 Apr 2019 01:34:09 GMT",
"version": "v1"
}
] | 2019-09-11 | [
[
"Hagihara",
"Yuki",
""
],
[
"Era",
"Naoya",
""
],
[
"Iikawa",
"Daisuke",
""
],
[
"Nishizawa",
"Atsushi",
""
],
[
"Asada",
"Hideki",
""
]
] | General metric theories of gravity in four-dimensional spacetimes can contain at most six polarization modes (two spin-0, two spin-1 and two spin-2) of gravitational waves (GWs). It has been recently shown that, with using four GW non-coaligned detectors, a direct test of the spin-1 modes can be done in principle separately from the spin-0 and spin-2 modes for a GW source in particular sky positions [Hagihara et al., Phys. Rev. D 98, 064035 (2018)]. They have found particular sky positions that satisfy a condition of killing completely the spin-0 modes in a so-called null stream which is a linear combination of the signal outputs to kill the spin-2 modes. The present paper expands the method to discuss a possibility that the spin-0 modes are not completely but effectively suppressed in the null streams to test the spin-1 modes separately from the other modes, especially with an expected network of Advanced LIGO, Advanced Virgo and KAGRA. We study also a possibility that the spin-1 modes are substantially suppressed in the null streams to test the spin-0 modes separately from the other modes, though the spin-1 modes for any sky position cannot be completely killed in the null streams. Moreover, we find that the coefficient of the spin-0 modes in the null stream is significantly small for the GW170817 event, so that an upper bound can be placed on the amplitude of the spin-1 modes as $< 6 \times 10^{-23}$. |
1708.04349 | Yurii Ignat'ev | Yu.G. Ignat'ev | A qualitative and numerical analysis of cosmological models based on
assymetric scalar doublet: classical + phantom scalar field. I. A case of
minimally interacting scalar fields: the qualitative analysis | 15 pages, 13 figures, 40 references | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The paper provides a qualitative and numerical analysis-based investigation
of cosmological models founded on an asymmetrical scalar doublet comprising of
a classical and a phantom scalar fields. Presence of a phantom scalar field
allows one to consider also classical scalar fields with attraction of
like-charged particles which significantly extends a diversity of cosmological
models' behaviours. It is shown that a cosmological model based on an
asymmetric scalar doublet in the case of minimal interaction has 9 singular
points 2 of which are attractive and the rest are non-stable saddle ones. It is
also shown that a presence of even essentially weak phantom field significantly
changes the dynamics of a cosmological model.
| [
{
"created": "Mon, 14 Aug 2017 22:41:01 GMT",
"version": "v1"
}
] | 2017-08-16 | [
[
"Ignat'ev",
"Yu. G.",
""
]
] | The paper provides a qualitative and numerical analysis-based investigation of cosmological models founded on an asymmetrical scalar doublet comprising of a classical and a phantom scalar fields. Presence of a phantom scalar field allows one to consider also classical scalar fields with attraction of like-charged particles which significantly extends a diversity of cosmological models' behaviours. It is shown that a cosmological model based on an asymmetric scalar doublet in the case of minimal interaction has 9 singular points 2 of which are attractive and the rest are non-stable saddle ones. It is also shown that a presence of even essentially weak phantom field significantly changes the dynamics of a cosmological model. |
1712.03107 | Christian Boehmer | Sebastian Bahamonde, Christian G. Boehmer, Sante Carloni, Edmund J.
Copeland, Wei Fang, Nicola Tamanini | Dynamical systems applied to cosmology: dark energy and modified gravity | 181 pages, 35 figures, 29 tables. Comments and suggestions for
references are welcome, please note Section 1.4 `Note to the arXiv reader';
v2: revised version to take into account feedback by readers, references
updated; v3: final version matches published version | Physics Reports Vol. 775-777 (2018) 1-122 | 10.1016/j.physrep.2018.09.001 | null | gr-qc astro-ph.CO hep-th math.DS | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Nobel Prize winning confirmation in 1998 of the accelerated expansion of
our Universe put into sharp focus the need of a consistent theoretical model to
explain the origin of this acceleration. As a result over the past two decades
there has been a huge theoretical and observational effort into improving our
understanding of the Universe. The cosmological equations describing the
dynamics of a homogeneous and isotropic Universe are systems of ordinary
differential equations, and one of the most elegant ways these can be
investigated is by casting them into the form of dynamical systems. This allows
the use of powerful analytical and numerical methods to gain a quantitative
understanding of the cosmological dynamics derived by the models under study.
In this review we apply these techniques to cosmology. We begin with a brief
introduction to dynamical systems, fixed points, linear stability theory,
Lyapunov stability, centre manifold theory and more advanced topics relating to
the global structure of the solutions. Using this machinery we then analyse a
large number of cosmological models and show how the stability conditions allow
them to be tightly constrained and even ruled out on purely theoretical
grounds. We are also able to identify those models which deserve further in
depth investigation through comparison with observational data. This review is
a comprehensive and detailed study of dynamical systems applications to
cosmological models focusing on the late-time behaviour of our Universe, and in
particular on its accelerated expansion. In self contained sections we present
a large number of models ranging from canonical and non-canonical scalar
fields, interacting models and non-scalar field models through to modified
gravity scenarios. Selected models are discussed in detail and interpreted in
the context of late-time cosmology.
| [
{
"created": "Fri, 8 Dec 2017 14:55:27 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jan 2018 19:43:22 GMT",
"version": "v2"
},
{
"created": "Thu, 6 Dec 2018 11:03:43 GMT",
"version": "v3"
}
] | 2018-12-07 | [
[
"Bahamonde",
"Sebastian",
""
],
[
"Boehmer",
"Christian G.",
""
],
[
"Carloni",
"Sante",
""
],
[
"Copeland",
"Edmund J.",
""
],
[
"Fang",
"Wei",
""
],
[
"Tamanini",
"Nicola",
""
]
] | The Nobel Prize winning confirmation in 1998 of the accelerated expansion of our Universe put into sharp focus the need of a consistent theoretical model to explain the origin of this acceleration. As a result over the past two decades there has been a huge theoretical and observational effort into improving our understanding of the Universe. The cosmological equations describing the dynamics of a homogeneous and isotropic Universe are systems of ordinary differential equations, and one of the most elegant ways these can be investigated is by casting them into the form of dynamical systems. This allows the use of powerful analytical and numerical methods to gain a quantitative understanding of the cosmological dynamics derived by the models under study. In this review we apply these techniques to cosmology. We begin with a brief introduction to dynamical systems, fixed points, linear stability theory, Lyapunov stability, centre manifold theory and more advanced topics relating to the global structure of the solutions. Using this machinery we then analyse a large number of cosmological models and show how the stability conditions allow them to be tightly constrained and even ruled out on purely theoretical grounds. We are also able to identify those models which deserve further in depth investigation through comparison with observational data. This review is a comprehensive and detailed study of dynamical systems applications to cosmological models focusing on the late-time behaviour of our Universe, and in particular on its accelerated expansion. In self contained sections we present a large number of models ranging from canonical and non-canonical scalar fields, interacting models and non-scalar field models through to modified gravity scenarios. Selected models are discussed in detail and interpreted in the context of late-time cosmology. |
gr-qc/0406058 | Sawa Manoff | Sawa Manoff | Variation of the velocity and the frequency of a periodic signal along
the world line of the emitter | LaTeX, 15 pages | null | null | null | gr-qc astro-ph | null | The variation of the velocity of a periodic signal and its frequency along
the world line of a standard emitter (at rest with an observer) are considered
in a space with affine connections and metrics. It is shown that the frequency
of the emitted periodic signal is depending on the kinematic characteristics of
the motion of the emitter in space-time related to its shear and expansion
velocities. The same conclusions are valid for a standard clock moving with an
observer.
| [
{
"created": "Mon, 14 Jun 2004 07:46:42 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Manoff",
"Sawa",
""
]
] | The variation of the velocity of a periodic signal and its frequency along the world line of a standard emitter (at rest with an observer) are considered in a space with affine connections and metrics. It is shown that the frequency of the emitted periodic signal is depending on the kinematic characteristics of the motion of the emitter in space-time related to its shear and expansion velocities. The same conclusions are valid for a standard clock moving with an observer. |
gr-qc/0309055 | Jose M. M. Senovilla | Marc Mars and Jos\'e M. M. Senovilla | Trapped surfaces and symmetries | 9 pages, no figures. Final corrected version to appear in Class.
Quantum Grav | Class.Quant.Grav. 20 (2003) L293-L300 | 10.1088/0264-9381/20/24/L03 | null | gr-qc | null | We prove that strictly stationary spacetimes cannot contain closed trapped
nor marginally trapped surfaces. The result is purely geometric and holds in
arbitrary dimension. Other results concerning the interplay between
(generalized) symmetries and trapped submanifolds are also presented.
| [
{
"created": "Tue, 9 Sep 2003 18:34:34 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Sep 2003 13:39:46 GMT",
"version": "v2"
},
{
"created": "Thu, 16 Oct 2003 11:17:13 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Mars",
"Marc",
""
],
[
"Senovilla",
"José M. M.",
""
]
] | We prove that strictly stationary spacetimes cannot contain closed trapped nor marginally trapped surfaces. The result is purely geometric and holds in arbitrary dimension. Other results concerning the interplay between (generalized) symmetries and trapped submanifolds are also presented. |
gr-qc/9810054 | Redouane Fakir | Redouane Fakir | General relativistic cosmology with no beginning of time | Plain Latex, 3 figures | null | null | null | gr-qc astro-ph hep-ph hep-th | null | We find that general relativity can be naturally free of cosmological
singularities. Several nonsingular models are currently available that either
assume ad hoc matter contents, or are nonsingular only over a sector of
solution space of zero measure, or depart drastically from general relativity
at high energies. After much uncertainty over whether cosmological inflation
could help solve the initial-singularity problem, the prevailing belief today
is that general relativistic cosmology, with inflation or without, is
endemically singular. This belief was reinforced by recent singularity theorems
that take account specifically of inflation. Here, a viable inflationary
cosmology is worked out that is naturally free of singularities despite the
fact that 1) it uses only classical general relativity, 2) it assumes only the
most generic inflationary matter contents, and 3) it is a theory of the
chaotic-inflation type. That type of inflation is the most widely accepted
today, as it demands the least fine-tuning of initial conditions. It is also
shown how, by dropping the usual simplification of minimal coupling between
matter and geometry, the null energy condition can be violated and the relevant
singularity theorems circumvented.
| [
{
"created": "Sat, 17 Oct 1998 02:17:27 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Fakir",
"Redouane",
""
]
] | We find that general relativity can be naturally free of cosmological singularities. Several nonsingular models are currently available that either assume ad hoc matter contents, or are nonsingular only over a sector of solution space of zero measure, or depart drastically from general relativity at high energies. After much uncertainty over whether cosmological inflation could help solve the initial-singularity problem, the prevailing belief today is that general relativistic cosmology, with inflation or without, is endemically singular. This belief was reinforced by recent singularity theorems that take account specifically of inflation. Here, a viable inflationary cosmology is worked out that is naturally free of singularities despite the fact that 1) it uses only classical general relativity, 2) it assumes only the most generic inflationary matter contents, and 3) it is a theory of the chaotic-inflation type. That type of inflation is the most widely accepted today, as it demands the least fine-tuning of initial conditions. It is also shown how, by dropping the usual simplification of minimal coupling between matter and geometry, the null energy condition can be violated and the relevant singularity theorems circumvented. |
2301.04023 | Salvatore Capozziello | Salvatore Capozziello, Maurizio Capriolo, and Gaetano Lambiase | The energy-momentum complex in non-local gravity | 17 pages | null | 10.1142/S0219887823501773 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In General Relativity, the issue of defining the gravitational energy
contained in a given spatial region is still unresolved, except for particular
cases of localized objects where the asymptotic flatness holds for a given
spacetime. In principle, a theory of gravity is not self-consistent, if the
whole energy content is not uniquely defined in a specific volume. Here we
generalize the Einstein gravitational energy-momentum pseudotensor to non-local
theories of gravity where analytic functions of the non-local integral operator
$\Box^{-1}$ are taken into account. We apply the Noether theorem to a
gravitational Lagrangian, supposed invariant under the one-parameter group of
diffeomorphisms, that is, the infinitesimal rigid translations. The invariance
of non-local gravitational action under global translations leads to a locally
conserved Noether current, and thus, to the definition of a gravitational
energy-momentum pseudotensor, which is an affine object transforming like a
tensor under affine transformations. Furthermore, the energy-momentum complex
remains locally conserved, thanks to the non-local contracted Bianchi
identities. The continuity equations for the gravitational pseudotensor and the
energy-momentum complex, taking into account both gravitational and matter
components, can be derived. Finally, the weak field limit of pseudotensor is
performed to lowest order in metric perturbation in view of astrophysical
applications.
| [
{
"created": "Tue, 10 Jan 2023 15:09:49 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Apr 2023 06:29:55 GMT",
"version": "v2"
}
] | 2023-06-06 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Capriolo",
"Maurizio",
""
],
[
"Lambiase",
"Gaetano",
""
]
] | In General Relativity, the issue of defining the gravitational energy contained in a given spatial region is still unresolved, except for particular cases of localized objects where the asymptotic flatness holds for a given spacetime. In principle, a theory of gravity is not self-consistent, if the whole energy content is not uniquely defined in a specific volume. Here we generalize the Einstein gravitational energy-momentum pseudotensor to non-local theories of gravity where analytic functions of the non-local integral operator $\Box^{-1}$ are taken into account. We apply the Noether theorem to a gravitational Lagrangian, supposed invariant under the one-parameter group of diffeomorphisms, that is, the infinitesimal rigid translations. The invariance of non-local gravitational action under global translations leads to a locally conserved Noether current, and thus, to the definition of a gravitational energy-momentum pseudotensor, which is an affine object transforming like a tensor under affine transformations. Furthermore, the energy-momentum complex remains locally conserved, thanks to the non-local contracted Bianchi identities. The continuity equations for the gravitational pseudotensor and the energy-momentum complex, taking into account both gravitational and matter components, can be derived. Finally, the weak field limit of pseudotensor is performed to lowest order in metric perturbation in view of astrophysical applications. |
1110.5085 | S Habib Mazharimousavi | S. Habib Mazharimousavi, M. Halilsoy and T. Tahamtan | Solutions for f(R) gravity coupled with electromagnetic field | 7 pages no figure, final version for publication in European Physical
Journal C | Eur. Phys. J. C. 72, 1851 (2012) | 10.1140/epjc/s10052-011-1851-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the presence of external, linear / nonlinear electromagnetic fields we
integrate f(R) \sim R+2{\alpha}\surd(R+const.) gravity equations. In contrast
to their Einsteinian cousins the obtained black holes are non-asymptotically
flat with a deficit angle. In proper limits we obtain from our general solution
the global monopole solution in f(R) gravity. The scale symmetry breaking term
adopted as the nonlinear electromagnetic source adjusts the sign of the mass of
the resulting black hole to be physical.
| [
{
"created": "Sun, 23 Oct 2011 20:41:45 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Dec 2011 17:26:11 GMT",
"version": "v2"
}
] | 2012-01-05 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"M.",
""
],
[
"Tahamtan",
"T.",
""
]
] | In the presence of external, linear / nonlinear electromagnetic fields we integrate f(R) \sim R+2{\alpha}\surd(R+const.) gravity equations. In contrast to their Einsteinian cousins the obtained black holes are non-asymptotically flat with a deficit angle. In proper limits we obtain from our general solution the global monopole solution in f(R) gravity. The scale symmetry breaking term adopted as the nonlinear electromagnetic source adjusts the sign of the mass of the resulting black hole to be physical. |
gr-qc/0412061 | Badri Krishnan | Sergio Dain, Jose Luis Jaramillo, and Badri Krishnan | On the existence of initial data containing isolated black holes | 11 pages, 2 figures, RevTeX4 | Phys.Rev. D71 (2005) 064003 | 10.1103/PhysRevD.71.064003 | null | gr-qc | null | We present a general construction of initial data for Einstein's equations
containing an arbitrary number of black holes, each of which is instantaneously
in equilibrium. Each black hole is taken to be a marginally trapped surface and
plays the role of the inner boundary of the Cauchy surface. The black hole is
taken to be instantaneously isolated if its outgoing null rays are shear-free.
Starting from the choice of a conformal metric and the freely specifiable part
of the extrinsic curvature in the bulk, we give a prescription for choosing the
shape of the inner boundaries and the boundary conditions that must be imposed
there. We show rigorously that with these choices, the resulting non-linear
elliptic system always admits solutions.
| [
{
"created": "Mon, 13 Dec 2004 18:11:47 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Dain",
"Sergio",
""
],
[
"Jaramillo",
"Jose Luis",
""
],
[
"Krishnan",
"Badri",
""
]
] | We present a general construction of initial data for Einstein's equations containing an arbitrary number of black holes, each of which is instantaneously in equilibrium. Each black hole is taken to be a marginally trapped surface and plays the role of the inner boundary of the Cauchy surface. The black hole is taken to be instantaneously isolated if its outgoing null rays are shear-free. Starting from the choice of a conformal metric and the freely specifiable part of the extrinsic curvature in the bulk, we give a prescription for choosing the shape of the inner boundaries and the boundary conditions that must be imposed there. We show rigorously that with these choices, the resulting non-linear elliptic system always admits solutions. |
0811.2778 | Jose' P. S. Lemos | Jos\'e P. S. Lemos, Oleg B. Zaslavskii | The mass formula for quasi-black holes | 22 pages | Phys.Rev.D78:124013,2008 | 10.1103/PhysRevD.78.124013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A quasi-black hole, either non-extremal or extremal, can be broadly defined
as the limiting configuration of a body when its boundary approaches the body's
quasihorizon. We consider the mass contributions and the mass formula for a
static quasi-black hole. The analysis involves careful scrutiny of the surface
stresses when the limiting configuration is reached. It is shown that there
exists a strict correspondence between the mass formulas for quasi-black holes
and pure black holes. This perfect parallelism exists in spite of the
difference in derivation and meaning of the formulas in both cases. For
extremal quasi-black holes the finite surface stresses give zero contribution
to the total mass. This leads to a very special version of Abraham-Lorentz
electron in general relativity in which the total mass has pure electromagnetic
origin in spite of the presence of bare stresses.
| [
{
"created": "Mon, 17 Nov 2008 19:32:30 GMT",
"version": "v1"
}
] | 2008-12-30 | [
[
"Lemos",
"José P. S.",
""
],
[
"Zaslavskii",
"Oleg B.",
""
]
] | A quasi-black hole, either non-extremal or extremal, can be broadly defined as the limiting configuration of a body when its boundary approaches the body's quasihorizon. We consider the mass contributions and the mass formula for a static quasi-black hole. The analysis involves careful scrutiny of the surface stresses when the limiting configuration is reached. It is shown that there exists a strict correspondence between the mass formulas for quasi-black holes and pure black holes. This perfect parallelism exists in spite of the difference in derivation and meaning of the formulas in both cases. For extremal quasi-black holes the finite surface stresses give zero contribution to the total mass. This leads to a very special version of Abraham-Lorentz electron in general relativity in which the total mass has pure electromagnetic origin in spite of the presence of bare stresses. |
1508.07961 | Benjamin Bahr | Benjamin Bahr, Sebastian Steinhaus | Investigation of the Spinfoam Path integral with Quantum Cuboid
Intertwiners | 17 pages, 14 figures, changed to match published version, title
changed to match journal specifications | Phys. Rev. D 93, 104029 (2016) | 10.1103/PhysRevD.93.104029 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we investigate the 4d path integral for Euclidean quantum
gravity on a hypercubic lattice, as given by the Spin Foam model by Engle,
Pereira, Rovelli, Livine, Freidel and Krasnov (EPRL-FK). To tackle the problem,
we restrict to a set of quantum geometries that reflects the large amount of
lattice symmetries. In particular, the sum over intertwiners is restricted to
quantum cuboids, i.e. coherent intertwiners which describe a cuboidal geometry
in the large-$j$ limit.
Using asymptotic expressions for the vertex amplitude, we find several
interesting properties of the state sum. First of all, the value of coupling
constants in the amplitude functions determines whether geometric or
non-geometric configurations dominate the path integral. Secondly, there is a
critical value of the coupling constant $\alpha$, which separates two phases.
In both phases, the diffeomorphism symmetry appears to be broken. In one, the
dominant contribution comes from highly irregular, in the other from highly
regular configurations, both describing flat Euclidean space with small quantum
fluctuations around them, viewed in different coordinate systems. On the
critical point diffeomorphism symmetry is nearly restored, however.
Thirdly, we use the state sum to compute the physical norm of kinematical
states, i.e. their norm in the physical Hilbert space. We find that states
which describe boundary geometry with high torsion have exponentially
suppressed physical norm. We argue that this allows one to exclude them from
the state sum in calculations.
| [
{
"created": "Mon, 31 Aug 2015 18:59:49 GMT",
"version": "v1"
},
{
"created": "Tue, 17 May 2016 14:30:11 GMT",
"version": "v2"
}
] | 2016-05-25 | [
[
"Bahr",
"Benjamin",
""
],
[
"Steinhaus",
"Sebastian",
""
]
] | In this work, we investigate the 4d path integral for Euclidean quantum gravity on a hypercubic lattice, as given by the Spin Foam model by Engle, Pereira, Rovelli, Livine, Freidel and Krasnov (EPRL-FK). To tackle the problem, we restrict to a set of quantum geometries that reflects the large amount of lattice symmetries. In particular, the sum over intertwiners is restricted to quantum cuboids, i.e. coherent intertwiners which describe a cuboidal geometry in the large-$j$ limit. Using asymptotic expressions for the vertex amplitude, we find several interesting properties of the state sum. First of all, the value of coupling constants in the amplitude functions determines whether geometric or non-geometric configurations dominate the path integral. Secondly, there is a critical value of the coupling constant $\alpha$, which separates two phases. In both phases, the diffeomorphism symmetry appears to be broken. In one, the dominant contribution comes from highly irregular, in the other from highly regular configurations, both describing flat Euclidean space with small quantum fluctuations around them, viewed in different coordinate systems. On the critical point diffeomorphism symmetry is nearly restored, however. Thirdly, we use the state sum to compute the physical norm of kinematical states, i.e. their norm in the physical Hilbert space. We find that states which describe boundary geometry with high torsion have exponentially suppressed physical norm. We argue that this allows one to exclude them from the state sum in calculations. |
gr-qc/9505006 | Karen Brewster | Carlo Rovelli and Lee Smolin | Spin Networks and Quantum Gravity | 42 pages | Phys.Rev. D52 (1995) 5743-5759 | 10.1103/PhysRevD.52.5743 | CGPG-95/4-4, IASSNS-HEP-95/27 | gr-qc | null | We introduce a new basis on the state space of non-perturbative quantum
gravity. The states of this basis are linearly independent, are well defined in
both the loop representation and the connection representation, and are labeled
by a generalization of Penrose's spin netoworks. The new basis fully reduces
the spinor identities (SU(2) Mandelstam identities) and simplifies calculations
in non-perturbative quantum gravity. In particular, it allows a simple
expression for the exact solutions of the Hamiltonian constraint
(Wheeler-DeWitt equation) that have been discovered in the loop representation.
Since the states in this basis diagnolize operators that represent the three
geometry of space, such as the area and volumes of arbitrary surfaces and
regions, these states provide a discrete picture of quantum geometry at the
Planck scale.
| [
{
"created": "Thu, 4 May 1995 18:13:58 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Rovelli",
"Carlo",
""
],
[
"Smolin",
"Lee",
""
]
] | We introduce a new basis on the state space of non-perturbative quantum gravity. The states of this basis are linearly independent, are well defined in both the loop representation and the connection representation, and are labeled by a generalization of Penrose's spin netoworks. The new basis fully reduces the spinor identities (SU(2) Mandelstam identities) and simplifies calculations in non-perturbative quantum gravity. In particular, it allows a simple expression for the exact solutions of the Hamiltonian constraint (Wheeler-DeWitt equation) that have been discovered in the loop representation. Since the states in this basis diagnolize operators that represent the three geometry of space, such as the area and volumes of arbitrary surfaces and regions, these states provide a discrete picture of quantum geometry at the Planck scale. |
1608.06353 | Carlos Vega | Gregory J. Galloway and Carlos Vega | Hausdorff closed limits and rigidity in Lorentzian geometry | 29 pages, 5 figures | null | 10.1007/s00023-017-0594-x | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We begin with a basic exploration of the (point-set topological) notion of
Hausdorff closed limits in the spacetime setting. Specifically, we show that
this notion of limit is well suited to sequences of achronal sets, and use this
to generalize the `achronal limits' introduced in [12]. This, in turn, allows
for a broad generalization of the notion of Lorentzian horosphere introduced in
[12]. We prove a new rigidity result for such horospheres, which in a sense
encodes various spacetime splitting results, including the basic Lorentzian
splitting theorem. We use this to give a partial proof of the Bartnik splitting
conjecture, under a new condition involving past and future Cauchy horospheres,
which is weaker than those considered in [10] and [12]. We close with some
observations on spacetimes with spacelike causal boundary, including a rigidity
result in the positive cosmological constant case.
| [
{
"created": "Tue, 23 Aug 2016 01:28:19 GMT",
"version": "v1"
}
] | 2018-03-28 | [
[
"Galloway",
"Gregory J.",
""
],
[
"Vega",
"Carlos",
""
]
] | We begin with a basic exploration of the (point-set topological) notion of Hausdorff closed limits in the spacetime setting. Specifically, we show that this notion of limit is well suited to sequences of achronal sets, and use this to generalize the `achronal limits' introduced in [12]. This, in turn, allows for a broad generalization of the notion of Lorentzian horosphere introduced in [12]. We prove a new rigidity result for such horospheres, which in a sense encodes various spacetime splitting results, including the basic Lorentzian splitting theorem. We use this to give a partial proof of the Bartnik splitting conjecture, under a new condition involving past and future Cauchy horospheres, which is weaker than those considered in [10] and [12]. We close with some observations on spacetimes with spacelike causal boundary, including a rigidity result in the positive cosmological constant case. |
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