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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0405099 | Mustapha Ishak | Mustapha Ishak (Princeton University) | On perfect fluid models in non-comoving observational spherical
coordinates | 8 pages, 1 figure. To appear in Phys.Rev.D | Phys.Rev. D69 (2004) 124027 | 10.1103/PhysRevD.69.124027 | null | gr-qc astro-ph | null | We use null spherical (observational) coordinates to describe a class of
inhomogeneous cosmological models. The proposed cosmological construction is
based on the observer past null cone. A known difficulty in using inhomogeneous
models is that the null geodesic equation is not integrable in general. Our
choice of null coordinates solves the radial ingoing null geodesic by
construction. Furthermore, we use an approach where the velocity field is
uniquely calculated from the metric rather than put in by hand. Conveniently,
this allows us to explore models in a non-comoving frame of reference. In this
frame, we find that the velocity field has shear, acceleration and expansion
rate in general. We show that a comoving frame is not compatible with expanding
perfect fluid models in the coordinates proposed and dust models are simply not
possible. We describe the models in a non-comoving frame. We use the dust
models in a non-comoving frame to outline a fitting procedure.
| [
{
"created": "Tue, 18 May 2004 17:54:03 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Ishak",
"Mustapha",
"",
"Princeton University"
]
] | We use null spherical (observational) coordinates to describe a class of inhomogeneous cosmological models. The proposed cosmological construction is based on the observer past null cone. A known difficulty in using inhomogeneous models is that the null geodesic equation is not integrable in general. Our choice of null coordinates solves the radial ingoing null geodesic by construction. Furthermore, we use an approach where the velocity field is uniquely calculated from the metric rather than put in by hand. Conveniently, this allows us to explore models in a non-comoving frame of reference. In this frame, we find that the velocity field has shear, acceleration and expansion rate in general. We show that a comoving frame is not compatible with expanding perfect fluid models in the coordinates proposed and dust models are simply not possible. We describe the models in a non-comoving frame. We use the dust models in a non-comoving frame to outline a fitting procedure. |
1312.0705 | Hyeong-Chan Kim | Hyeong-Chan Kim | Physics at the surface of a star in Eddington-inspired Born-Infeld
gravity | 7 pages, Comments are added for negative curvatures | Phys. Rev. D 89, 064001 (2014) | 10.1103/PhysRevD.89.064001 | null | gr-qc astro-ph.SR hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study phenomena happening at the surface of a star in Eddington-inspired
Born-Infeld (EiBI) gravity. The star is made of particles, which are
effectively described by a polytropic fluid. The EiBI theory was known to have
a pathology that singularities happen at a star surface. We suggest that the
gravitational back-reaction on the particles cures the problem. Strong tidal
forces near the (surface) singularity modify the effective equation of state of
the particles or make the surface be unstable depending on its matter contents.
The geodesic deviation equations take after the Hooke's law, where its
frequency-squared is proportional to the scalar curvature at the surface. For a
positive curvature, a particle collides with a probing wall more often and
increases the pressure. With the increased pressure, the surface is no longer
singular. For a negative curvature, the matters around the surface experience
repulsions with infinite accelerations. Therefore, the EiBI gravity is saved
from the pathology of surface singularity.
| [
{
"created": "Tue, 3 Dec 2013 05:55:02 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Jan 2014 03:00:55 GMT",
"version": "v2"
}
] | 2014-06-17 | [
[
"Kim",
"Hyeong-Chan",
""
]
] | We study phenomena happening at the surface of a star in Eddington-inspired Born-Infeld (EiBI) gravity. The star is made of particles, which are effectively described by a polytropic fluid. The EiBI theory was known to have a pathology that singularities happen at a star surface. We suggest that the gravitational back-reaction on the particles cures the problem. Strong tidal forces near the (surface) singularity modify the effective equation of state of the particles or make the surface be unstable depending on its matter contents. The geodesic deviation equations take after the Hooke's law, where its frequency-squared is proportional to the scalar curvature at the surface. For a positive curvature, a particle collides with a probing wall more often and increases the pressure. With the increased pressure, the surface is no longer singular. For a negative curvature, the matters around the surface experience repulsions with infinite accelerations. Therefore, the EiBI gravity is saved from the pathology of surface singularity. |
2301.13008 | Marco Schreck MS | M. Schreck | New Developments in the Hamiltonian Formulation of the Gravitational
Standard-Model Extension | Presented at the Ninth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, May 17-26, 2022; 4 pages | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This chapter of the proceedings for the Ninth Meeting on CPT and Lorentz
Symmetry is dedicated to the Hamiltonian formulation of the minimal
gravitational Standard-Model Extension. Some theoretical questions associated
with the latter shall be reviewed. First, we recall the properties of the
Hamiltonian, which was computed elsewhere, and discuss how it is linked to the
modified Einstein equations. Second, we describe how the covariant and
Hamiltonian formulations are shown to be consistent with each other.
| [
{
"created": "Mon, 30 Jan 2023 15:48:07 GMT",
"version": "v1"
}
] | 2023-01-31 | [
[
"Schreck",
"M.",
""
]
] | This chapter of the proceedings for the Ninth Meeting on CPT and Lorentz Symmetry is dedicated to the Hamiltonian formulation of the minimal gravitational Standard-Model Extension. Some theoretical questions associated with the latter shall be reviewed. First, we recall the properties of the Hamiltonian, which was computed elsewhere, and discuss how it is linked to the modified Einstein equations. Second, we describe how the covariant and Hamiltonian formulations are shown to be consistent with each other. |
2305.14925 | Dnyaneshwar Tadas | S. D. Katore, S. P. Hatkar, D. P. Tadas | Accelerating Kaluza-Klein Universe in Modified Theory of Gravitation | 20 Pages, 08 Figures | Astrophysics 66 98-113 (2023) | 10.1007/s10511-023-09773-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The purpose of this paper is to study the Kaluza-Klein universe in the
context of the $f(R,T)$ gravity theory using magnetized strange quark matter
(MSQM). To obtain exact solutions of field equations, we assume two types of
volumetric expansion: power law and exponential law volumetric expansions. The
violation of energy conditions has been studied. The physical and geometrical
properties of the examined model have also been investigated thoroughly.
Keywords: Kaluza-Klein metric, Magnetized Strange Quark Matter, Power and
Exponential law, $f(R,T)$ gravity.
| [
{
"created": "Wed, 24 May 2023 09:09:44 GMT",
"version": "v1"
}
] | 2023-05-25 | [
[
"Katore",
"S. D.",
""
],
[
"Hatkar",
"S. P.",
""
],
[
"Tadas",
"D. P.",
""
]
] | The purpose of this paper is to study the Kaluza-Klein universe in the context of the $f(R,T)$ gravity theory using magnetized strange quark matter (MSQM). To obtain exact solutions of field equations, we assume two types of volumetric expansion: power law and exponential law volumetric expansions. The violation of energy conditions has been studied. The physical and geometrical properties of the examined model have also been investigated thoroughly. Keywords: Kaluza-Klein metric, Magnetized Strange Quark Matter, Power and Exponential law, $f(R,T)$ gravity. |
gr-qc/0307120 | Massimo Bassan | P. Astone, D. Babusci, M. Bassan, P. Carelli, G. Cavallari, E. Coccia,
C. Cosmelli, S. D'Antonio, V. Fafone, A.C. Fauth, G. Federici, G. Giordano,
A. Marini, Y. Minenkov, I. Modena, G. Modestino, A. Moleti, G.V. Pallottino,
G. Pizzella, L. Quintieri, A. Rocchi, F. Ronga, R. Terenzi, G. Torrioli, M.
Visco | Increasing the bandwidth of resonant gravitational antennas: The case of
Explorer | 4 pages- 4 figures Acceted for publication on Physical Review Letters | Phys.Rev.Lett. 91 (2003) 111101 | 10.1103/PhysRevLett.91.111101 | null | gr-qc | null | Resonant gravitational wave detectors with an observation bandwidth of tens
of hertz are a reality: the antenna Explorer, operated at CERN by the ROG
collaboration, has been upgraded with a new read-out. In this new
configuration, it exhibits an unprecedented useful bandwidth: in over 55 Hz
about its frequency of operation of 919 Hz the spectral sensitivity is better
than 10^{-20} /sqrt(Hz) . We describe the detector and its sensitivity and
discuss the foreseable upgrades to even larger bandwidths.
| [
{
"created": "Wed, 30 Jul 2003 17:32:27 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Astone",
"P.",
""
],
[
"Babusci",
"D.",
""
],
[
"Bassan",
"M.",
""
],
[
"Carelli",
"P.",
""
],
[
"Cavallari",
"G.",
""
],
[
"Coccia",
"E.",
""
],
[
"Cosmelli",
"C.",
""
],
[
"D'Antonio",
"S.",
... | Resonant gravitational wave detectors with an observation bandwidth of tens of hertz are a reality: the antenna Explorer, operated at CERN by the ROG collaboration, has been upgraded with a new read-out. In this new configuration, it exhibits an unprecedented useful bandwidth: in over 55 Hz about its frequency of operation of 919 Hz the spectral sensitivity is better than 10^{-20} /sqrt(Hz) . We describe the detector and its sensitivity and discuss the foreseable upgrades to even larger bandwidths. |
2401.02201 | Allan Ranieri Pereira Moreira | A. R. P. Moreira and Shi-Hai Dong | Probabilistic configurations for thick braneworld in modified symmetric
teleparallel gravity | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this research, we delve into the localization patterns of fermionic fields
within a braneworld setting, employing a modified gravity model denoted as
$f(Q)$. Our investigation revolves around two specific models, $f_1(Q)=Q+kQ^n$
and $f_2(Q)=Q+k_1Q^2+k_2Q^3$, where we systematically vary the parameters $n$
and $k_{1,2}$. Through an in-depth analysis encompassing the effective
potential, massless, and massive modes, we elucidate how deviations from the
conventional symmetric teleparallel equivalent of general relativity (STEGR)
gravity impact the localization of fermionic fields. To ensure greater
precision, our methodology integrates probabilistic measures such as Shannon
entropy and relative probability. Moreover, we gauge the stability of these
models employing differential configurational entropy (DCE), revealing a
compelling correlation between the most stable configurations and the emergence
of novel structures within the background scalar field. This work significantly
contributes to our understanding of the gravitational modifications' intricate
influence on fermionic field localization within braneworld scenarios. By
shedding light on these dynamics, it advances the broader comprehension of the
interplay between gravity modifications and fermionic field behaviors in these
theoretical frameworks.
| [
{
"created": "Thu, 4 Jan 2024 11:10:55 GMT",
"version": "v1"
}
] | 2024-01-05 | [
[
"Moreira",
"A. R. P.",
""
],
[
"Dong",
"Shi-Hai",
""
]
] | In this research, we delve into the localization patterns of fermionic fields within a braneworld setting, employing a modified gravity model denoted as $f(Q)$. Our investigation revolves around two specific models, $f_1(Q)=Q+kQ^n$ and $f_2(Q)=Q+k_1Q^2+k_2Q^3$, where we systematically vary the parameters $n$ and $k_{1,2}$. Through an in-depth analysis encompassing the effective potential, massless, and massive modes, we elucidate how deviations from the conventional symmetric teleparallel equivalent of general relativity (STEGR) gravity impact the localization of fermionic fields. To ensure greater precision, our methodology integrates probabilistic measures such as Shannon entropy and relative probability. Moreover, we gauge the stability of these models employing differential configurational entropy (DCE), revealing a compelling correlation between the most stable configurations and the emergence of novel structures within the background scalar field. This work significantly contributes to our understanding of the gravitational modifications' intricate influence on fermionic field localization within braneworld scenarios. By shedding light on these dynamics, it advances the broader comprehension of the interplay between gravity modifications and fermionic field behaviors in these theoretical frameworks. |
1101.2980 | Hristu Culetu | Hristu Culetu | Anisotropic fluid inside a relativistic star | 9 pages, refs added, new chapter added, no figures | null | 10.1142/S2010194511000973 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An anisotropic fluid with variable energy density and negative pressure is
proposed, both outside and inside stars. The gravitational field is constant
everywhere in free space (if we neglect the local contributions) and its value
is of the order of $g = 10^{-8} cm/s^{2}$, in accordance with MOND model. With
$\rho,~ p \propto 1/r$, the acceleration is also constant inside stars but the
value is different from one star to another and depends on their mass $M$ and
radius $R$. In spite of the fact that the spacetime is of Rindler type and
curved even far from a local mass, the active gravitational energy on the
horizon is $-1/4g$, as for the flat Rindler space, excepting the negative sign.
| [
{
"created": "Sat, 15 Jan 2011 12:32:13 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Feb 2011 14:14:35 GMT",
"version": "v2"
}
] | 2015-05-27 | [
[
"Culetu",
"Hristu",
""
]
] | An anisotropic fluid with variable energy density and negative pressure is proposed, both outside and inside stars. The gravitational field is constant everywhere in free space (if we neglect the local contributions) and its value is of the order of $g = 10^{-8} cm/s^{2}$, in accordance with MOND model. With $\rho,~ p \propto 1/r$, the acceleration is also constant inside stars but the value is different from one star to another and depends on their mass $M$ and radius $R$. In spite of the fact that the spacetime is of Rindler type and curved even far from a local mass, the active gravitational energy on the horizon is $-1/4g$, as for the flat Rindler space, excepting the negative sign. |
0905.2222 | Alexander Zhuk | Maxim Eingorn and Alexander Zhuk | The shape of multidimensional gravity | 4 pages of Revtex4, 2 eps figures | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the case of one extra dimension, well known Newton's potential $\phi
(r_3)=-G_N m/r_3$ is generalized to compact and elegant formula
$\phi(r_3,\xi)=-(G_N m/r_3)\sinh(2\pi r_3/a)[\cosh(2\pi
r_3/a)-\cos(2\pi\xi/a)]^{-1}$ if four-dimensional space has topology
$\mathbb{R}^3\times T$. Here, $r_3$ is magnitude of three-dimensional radius
vector, $\xi$ is extra dimension and $a$ is a period of a torus $T$. This
formula is valid for full range of variables $r_3 \in [0,+\infty)$ and $\xi\in
[0,a]$ and has known asymptotic behavior: $\phi \sim 1/r_3$ for $r_3>>a$ and
$\phi \sim 1/r_4^2$ for $r_4=\sqrt{r_3^2+\xi^2}<<a$. Obtained formula is
applied to an infinitesimally thin shell, a shell, a sphere and two spheres to
show deviations from the newtonian expressions. Usually, these corrections are
very small to observe at experiments. Nevertheless, in the case of spatial
topology $\mathbb{R}^3\times T^{d}$, experimental data can provide us with a
limitation on maximal number of extra dimensions.
| [
{
"created": "Wed, 13 May 2009 23:47:06 GMT",
"version": "v1"
}
] | 2009-05-18 | [
[
"Eingorn",
"Maxim",
""
],
[
"Zhuk",
"Alexander",
""
]
] | In the case of one extra dimension, well known Newton's potential $\phi (r_3)=-G_N m/r_3$ is generalized to compact and elegant formula $\phi(r_3,\xi)=-(G_N m/r_3)\sinh(2\pi r_3/a)[\cosh(2\pi r_3/a)-\cos(2\pi\xi/a)]^{-1}$ if four-dimensional space has topology $\mathbb{R}^3\times T$. Here, $r_3$ is magnitude of three-dimensional radius vector, $\xi$ is extra dimension and $a$ is a period of a torus $T$. This formula is valid for full range of variables $r_3 \in [0,+\infty)$ and $\xi\in [0,a]$ and has known asymptotic behavior: $\phi \sim 1/r_3$ for $r_3>>a$ and $\phi \sim 1/r_4^2$ for $r_4=\sqrt{r_3^2+\xi^2}<<a$. Obtained formula is applied to an infinitesimally thin shell, a shell, a sphere and two spheres to show deviations from the newtonian expressions. Usually, these corrections are very small to observe at experiments. Nevertheless, in the case of spatial topology $\mathbb{R}^3\times T^{d}$, experimental data can provide us with a limitation on maximal number of extra dimensions. |
2011.08351 | Yong-Wan Kim | Soon-Tae Hong, Yong-Wan Kim, Young-Jai Park | GEMS embeddings of Schwarzschild and RN black holes in
Painlev\'e-Gullstrand spacetimes | 18 pages, 3 figures, version to appear in Universe | Universe 2022, 8(1), 15 | 10.3390/universe8010015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Making use of the higher dimensional global embedding Minkowski spacetime
(GEMS), we embed (3+1)-dimensional Schwarzschild and Reissner-Nordstr\"om (RN)
black holes written by the Painlev\'e-Gullstrand (PG) spacetimes, which have
off-diagonal components in metrics, into (5+1)- and (5+2)-dimensional flat
ones, respectively. As a result, we have shown the equivalence of the GEMS
embeddings of the spacetimes with the diagonal and off-diagonal terms in
metrics. Moreover, with the aid of their geodesic equations satisfying various
boundary conditions in the flat embedded spacetimes, we directly obtain freely
falling temperatures. We also show that freely falling temperatures in the PG
spacetimes are well-defined beyond the event horizons, while they are
equivalent to the Hawking temperatures, which are obtained in the original
curved ones in the ranges between the horizon and the infinity. These will be
helpful to study GEMS embeddings of more realistic Kerr, or rotating BTZ black
holes.
| [
{
"created": "Tue, 17 Nov 2020 00:36:42 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Dec 2021 09:06:22 GMT",
"version": "v2"
}
] | 2021-12-30 | [
[
"Hong",
"Soon-Tae",
""
],
[
"Kim",
"Yong-Wan",
""
],
[
"Park",
"Young-Jai",
""
]
] | Making use of the higher dimensional global embedding Minkowski spacetime (GEMS), we embed (3+1)-dimensional Schwarzschild and Reissner-Nordstr\"om (RN) black holes written by the Painlev\'e-Gullstrand (PG) spacetimes, which have off-diagonal components in metrics, into (5+1)- and (5+2)-dimensional flat ones, respectively. As a result, we have shown the equivalence of the GEMS embeddings of the spacetimes with the diagonal and off-diagonal terms in metrics. Moreover, with the aid of their geodesic equations satisfying various boundary conditions in the flat embedded spacetimes, we directly obtain freely falling temperatures. We also show that freely falling temperatures in the PG spacetimes are well-defined beyond the event horizons, while they are equivalent to the Hawking temperatures, which are obtained in the original curved ones in the ranges between the horizon and the infinity. These will be helpful to study GEMS embeddings of more realistic Kerr, or rotating BTZ black holes. |
1907.09118 | Zhan-Feng Mai | Jia-Hui Huang, Wen-Xiang Chen, Zi-Yang Huang, Zhan-Feng Mai | Superradiant stability of the Kerr black holes | null | null | 10.1016/j.physletb.2019.135026 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the superradiant stability of the system of a Kerr black hole and a
massive scalar perturbation. It was proved previously that this system is
superradiantly stable when $\mu\geq \sqrt{2}m\Omega_H$, where $\mu$ is the
proper mass of the scalar, $m$ is the azimuthal number of the scalar mode, and
$\Omega_H$ is the angular velocity of the Kerr black hole horizon. Our study is
a complementary work of this result. We analytically prove that in the
complementary parameter region $\mu<\sqrt{2}m\Omega_H$, when the parameters of
scalar perturbation and Kerr black hole satisfy two simple inequalities,
$\omega<\frac{\mu}{\sqrt{2}}$,~ $\frac{r_-}{r_+}<0.802$, the system is also
superradiantly stable.
| [
{
"created": "Mon, 22 Jul 2019 03:32:51 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Jul 2019 02:24:28 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Oct 2019 11:37:21 GMT",
"version": "v3"
}
] | 2019-10-16 | [
[
"Huang",
"Jia-Hui",
""
],
[
"Chen",
"Wen-Xiang",
""
],
[
"Huang",
"Zi-Yang",
""
],
[
"Mai",
"Zhan-Feng",
""
]
] | We study the superradiant stability of the system of a Kerr black hole and a massive scalar perturbation. It was proved previously that this system is superradiantly stable when $\mu\geq \sqrt{2}m\Omega_H$, where $\mu$ is the proper mass of the scalar, $m$ is the azimuthal number of the scalar mode, and $\Omega_H$ is the angular velocity of the Kerr black hole horizon. Our study is a complementary work of this result. We analytically prove that in the complementary parameter region $\mu<\sqrt{2}m\Omega_H$, when the parameters of scalar perturbation and Kerr black hole satisfy two simple inequalities, $\omega<\frac{\mu}{\sqrt{2}}$,~ $\frac{r_-}{r_+}<0.802$, the system is also superradiantly stable. |
1404.2126 | David Kubiznak | David Kubiznak and Robert B. Mann | Black Hole Chemistry | 12 pages, Essay written for the Gravity Research Foundation 2014
Awards for Essays on Gravitation | null | 10.1139/cjp-2014-0465 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The mass of a black hole has traditionally been identified with its energy.
We describe a new perspective on black hole thermodynamics, one that identifies
the mass of a black hole with chemical enthalpy, and the cosmological constant
as thermodynamic pressure. This leads to an understanding of black holes from
the viewpoint of chemistry, in terms of concepts such as Van der Waals fluids,
reentrant phase transitions, and triple points. Both charged and rotating black
holes exhibit novel chemical-type phase behaviour, hitherto unseen.
| [
{
"created": "Tue, 8 Apr 2014 13:43:59 GMT",
"version": "v1"
}
] | 2023-07-19 | [
[
"Kubiznak",
"David",
""
],
[
"Mann",
"Robert B.",
""
]
] | The mass of a black hole has traditionally been identified with its energy. We describe a new perspective on black hole thermodynamics, one that identifies the mass of a black hole with chemical enthalpy, and the cosmological constant as thermodynamic pressure. This leads to an understanding of black holes from the viewpoint of chemistry, in terms of concepts such as Van der Waals fluids, reentrant phase transitions, and triple points. Both charged and rotating black holes exhibit novel chemical-type phase behaviour, hitherto unseen. |
1410.4434 | Tatyana P. Shestakova | T. P. Shestakova | The role of BRST charge as a generator of gauge transformations in
quantization of gauge theories and Gravity | 6 pages, the paper is based on the talks presented at the
International Symposium "Frontiers of Fundamental Physics" (Marseille,
France, 15 - 18 July 2014) and the International Conference "Quantum Field
Theory and Gravity" (Tomsk, Russia, 28 July - 3 August 2014) | Tomsk State Pedagogical University Bulletin 153 (2014) P. 224 -
227 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the Batalin - Fradkin - Vilkovisky approach to quantization of gauge
theories a principal role is given to the BRST charge which can be constructed
as a series in Grassmannian (ghost) variables with coefficients given by
generalized structure functions of constraints algebra. Alternatively, the BRST
charge can be derived making use of the Noether theorem and global BRST
invariance of the effective action. In the case of Yang - Mills fields the both
methods lead to the same expression for the BRST charge, but it is not valid in
the case of General Relativity. It is illustrated by examples of an isotropic
cosmological model as well as by spherically-symmetric gravitational model
which imitates the full theory of gravity much better. The consideration is
based on Hamiltonian formulation of General Relativity in extended phase space.
At the quantum level the structure of the BRST charge is of great importance
since BRST invariant quantum states are believed to be physical states. Thus,
the definition of the BRST charge at the classical level is inseparably related
to our attempts to find a true way to quantize Gravity.
| [
{
"created": "Thu, 16 Oct 2014 14:08:52 GMT",
"version": "v1"
}
] | 2015-04-09 | [
[
"Shestakova",
"T. P.",
""
]
] | In the Batalin - Fradkin - Vilkovisky approach to quantization of gauge theories a principal role is given to the BRST charge which can be constructed as a series in Grassmannian (ghost) variables with coefficients given by generalized structure functions of constraints algebra. Alternatively, the BRST charge can be derived making use of the Noether theorem and global BRST invariance of the effective action. In the case of Yang - Mills fields the both methods lead to the same expression for the BRST charge, but it is not valid in the case of General Relativity. It is illustrated by examples of an isotropic cosmological model as well as by spherically-symmetric gravitational model which imitates the full theory of gravity much better. The consideration is based on Hamiltonian formulation of General Relativity in extended phase space. At the quantum level the structure of the BRST charge is of great importance since BRST invariant quantum states are believed to be physical states. Thus, the definition of the BRST charge at the classical level is inseparably related to our attempts to find a true way to quantize Gravity. |
2111.05856 | Zhen-Ming Xu | Zhen-Ming Xu | Fokker-Planck equation for black holes in thermal potential | 10 pages, published in Phys. Rev. D | Phys. Rev. D 104 (2021) 104022 | 10.1103/PhysRevD.104.104022 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a kind of thermal potential and then put the black hole
thermodynamic system in it. In this regard, some thermodynamic properties of
the black hole are related to the geometric characteristics of the thermal
potential. Driven by the intrinsic thermodynamic fluctuations, the behavior of
the black hole in the thermal potential is stochastic. With the help of solving
the Fokker-Planck equation analytically, we obtain the discrete energy spectrum
of Schwarzschild and Banados-Teitelboim-Zanelli (BTZ) black holes in the
thermal potential. For Schwarzschild black hole, the energy spectrum is
proportional to the temperature of the ensemble, which is an external
parameter, and the ground state is non-zero. For BTZ black hole, the energy
spectrum only depends on the AdS radius, which is the intrinsic parameter.
Moreover, the ground state of BTZ black hole in thermal potential is zero. This
also reflects the difference between three-dimensional gravity and
four-dimensional gravity.
| [
{
"created": "Wed, 10 Nov 2021 10:21:38 GMT",
"version": "v1"
}
] | 2021-11-12 | [
[
"Xu",
"Zhen-Ming",
""
]
] | We construct a kind of thermal potential and then put the black hole thermodynamic system in it. In this regard, some thermodynamic properties of the black hole are related to the geometric characteristics of the thermal potential. Driven by the intrinsic thermodynamic fluctuations, the behavior of the black hole in the thermal potential is stochastic. With the help of solving the Fokker-Planck equation analytically, we obtain the discrete energy spectrum of Schwarzschild and Banados-Teitelboim-Zanelli (BTZ) black holes in the thermal potential. For Schwarzschild black hole, the energy spectrum is proportional to the temperature of the ensemble, which is an external parameter, and the ground state is non-zero. For BTZ black hole, the energy spectrum only depends on the AdS radius, which is the intrinsic parameter. Moreover, the ground state of BTZ black hole in thermal potential is zero. This also reflects the difference between three-dimensional gravity and four-dimensional gravity. |
2303.00572 | Phongpichit Channuie | Thammarong Eadkhong (Walailak U.), Punsiri Dam-O (Walailak U.),
Phongpichit Channuie (Walailak U.), Davood Momeni (Northern Virginia
Community College) | Nonminimally-coupled warm Higgs inflation: Metric vs. Palatini
Formulations | v2: 18 pages, many figures. version accepted for publication in
Nuclear Physics Section B. arXiv admin note: text overlap with
arXiv:1812.03107, arXiv:2110.03925 by other authors | Nuclear Physics B 994 (2023) 116289 | 10.1016/j.nuclphysb.2023.116289 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this work, we study the non-minimally-coupled Higgs model in the context
of warm inflation scenario on both metric and Palatini approaches. We
particularly consider a dissipation parameter of the form $\Gamma=C_{T}T$ with
$C_{T}$ being a coupling parameter and focus only on the strong regime of the
interaction between inflaton and radiation fluid. We compute all relevant
cosmological parameters and constrain the models using the observational Planck
2018 data. We discover that the $n_s$ and $r$ values are consistent with the
observational bounds. Having used the observational data, we constrain a
relation between $\xi$ and $\lambda$ for the non-minimally-coupled warm Higgs
inflation in both metric and Palatini cases. To produce $n_s$ and $r$ in
agreement with observation, we find that their values are two orders of
magnitude higher than those of the usual (cold) non-minimally-coupled Higgs
inflation.
| [
{
"created": "Wed, 1 Mar 2023 15:16:23 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Jul 2023 04:04:12 GMT",
"version": "v2"
}
] | 2023-07-20 | [
[
"Eadkhong",
"Thammarong",
"",
"Walailak U."
],
[
"Dam-O",
"Punsiri",
"",
"Walailak U."
],
[
"Channuie",
"Phongpichit",
"",
"Walailak U."
],
[
"Momeni",
"Davood",
"",
"Northern Virginia\n Community College"
]
] | In this work, we study the non-minimally-coupled Higgs model in the context of warm inflation scenario on both metric and Palatini approaches. We particularly consider a dissipation parameter of the form $\Gamma=C_{T}T$ with $C_{T}$ being a coupling parameter and focus only on the strong regime of the interaction between inflaton and radiation fluid. We compute all relevant cosmological parameters and constrain the models using the observational Planck 2018 data. We discover that the $n_s$ and $r$ values are consistent with the observational bounds. Having used the observational data, we constrain a relation between $\xi$ and $\lambda$ for the non-minimally-coupled warm Higgs inflation in both metric and Palatini cases. To produce $n_s$ and $r$ in agreement with observation, we find that their values are two orders of magnitude higher than those of the usual (cold) non-minimally-coupled Higgs inflation. |
1312.6741 | Xu Wei | Bin Wu and Wei Xu | New class of rotating perfect fluid black holes in three dimensional
gravity | 12 pages, no figures; a few references added and typos corrected;
published version | Eur. Phys. J. C (2014) 74:3007 | 10.1140/epjc/s10052-014-3007-z | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain a new class of rotating black holes for Einstein theory with
perfect fluid source in (2+1) dimensions. We conclude that these black hole
solutions only depend on variable angular velocity $m(r)$. Some examples of
these black holes are given explicitly. In particular, the unknown static black
hole in this special background is obtained. In addition, the general
properties including the horizon structure, energy conditions and equation of
state, mass and angular momentum are explained in detail.
| [
{
"created": "Tue, 24 Dec 2013 02:19:56 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Dec 2013 10:26:34 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Aug 2014 12:52:04 GMT",
"version": "v3"
}
] | 2014-08-19 | [
[
"Wu",
"Bin",
""
],
[
"Xu",
"Wei",
""
]
] | We obtain a new class of rotating black holes for Einstein theory with perfect fluid source in (2+1) dimensions. We conclude that these black hole solutions only depend on variable angular velocity $m(r)$. Some examples of these black holes are given explicitly. In particular, the unknown static black hole in this special background is obtained. In addition, the general properties including the horizon structure, energy conditions and equation of state, mass and angular momentum are explained in detail. |
1509.06366 | Shasvath Kapadia | Shasvath J. Kapadia, Nathan K. Johnson-McDaniel, Parameswaran Ajith | Estimating effective higher order terms in the post-Newtonian binding
energy and gravitational-wave flux: Non-spinning compact binary inspiral | 11 pages, 5 figures | Phys. Rev. D 93, 024006 (2016) | 10.1103/PhysRevD.93.024006 | ICTS/2015/8 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the adiabatic post-Newtonian (PN) approximation, the phase evolution of
gravitational waves (GWs) from inspiralling compact binaries in quasicircular
orbits is computed by equating the change in binding energy with the GW flux.
This energy balance equation can be solved in different ways, which result in
multiple approximants of the PN waveforms. Due to the poor convergence of the
PN expansion, these approximants tend to differ from each other during the late
inspiral. Which of these approximants should be chosen as templates for
detection and parameter estimation of GWs from inspiraling compact binaries is
not obvious. In this paper, we present estimates of the effective higher order
(beyond the currently available 4PN and 3.5PN) non-spinning terms in the PN
expansion of the binding energy and the GW flux that minimize the difference of
multiple PN approximants (TaylorT1, TaylorT2, TaylorT4, TaylorF2) with
effective one body waveforms calibrated to numerical relativity (EOBNR). We
show that PN approximants constructed using the effective higher order terms
show significantly better agreement (as compared to 3.5PN) with the inspiral
part of the EOBNR. For non-spinning binaries with component masses $m_{1,2} \in
[1.4 M_\odot, 15 M_\odot]$, most of the approximants have a match
(faithfulness) of better than 99% with both EOBNR and each other.
| [
{
"created": "Mon, 21 Sep 2015 20:02:31 GMT",
"version": "v1"
}
] | 2016-01-13 | [
[
"Kapadia",
"Shasvath J.",
""
],
[
"Johnson-McDaniel",
"Nathan K.",
""
],
[
"Ajith",
"Parameswaran",
""
]
] | In the adiabatic post-Newtonian (PN) approximation, the phase evolution of gravitational waves (GWs) from inspiralling compact binaries in quasicircular orbits is computed by equating the change in binding energy with the GW flux. This energy balance equation can be solved in different ways, which result in multiple approximants of the PN waveforms. Due to the poor convergence of the PN expansion, these approximants tend to differ from each other during the late inspiral. Which of these approximants should be chosen as templates for detection and parameter estimation of GWs from inspiraling compact binaries is not obvious. In this paper, we present estimates of the effective higher order (beyond the currently available 4PN and 3.5PN) non-spinning terms in the PN expansion of the binding energy and the GW flux that minimize the difference of multiple PN approximants (TaylorT1, TaylorT2, TaylorT4, TaylorF2) with effective one body waveforms calibrated to numerical relativity (EOBNR). We show that PN approximants constructed using the effective higher order terms show significantly better agreement (as compared to 3.5PN) with the inspiral part of the EOBNR. For non-spinning binaries with component masses $m_{1,2} \in [1.4 M_\odot, 15 M_\odot]$, most of the approximants have a match (faithfulness) of better than 99% with both EOBNR and each other. |
1301.4483 | Roldao da Rocha | Roldao da Rocha, A. Piloyan, A. M. Kuerten, C. H. Coimbra-Araujo | Casadio-Fabbri-Mazzacurati Black Strings and Braneworld-induced Quasars
Luminosity Corrections | 13 pages, 4 figures (to appear in Class. Quant. Grav.) | Class. Quantum Grav. 30 (2013) 045014 | 10.1088/0264-9381/30/4/045014 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper aims to evince the corrections on the black string warped horizon
in the braneworld paradigm, and their drastic physical consequences, as well as
to provide subsequent applications in astrophysics. Our analysis concerning
black holes on the brane departs from the Schwarzschild case, where the black
string is unstable to large-scale perturbation. The cognizable measurability of
the black string horizon corrections due to braneworld effects is investigated,
as well as their applications in the variation of quasars luminosity. We delve
into the case wherein two solutions of Einstein's equations proposed by
Casadio, Fabbri, and Mazzacurati, regarding black hole metrics presenting a
post-Newtonian parameter measured on the brane. In this scenario, it is
possible to analyze purely the braneworld corrected variation in quasars
luminosity, by an appropriate choice of the post-Newtonian parameter that
precludes Hawking radiation on the brane: the variation in quasars luminosity
is uniquely provided by pure braneworld effects, as the Hawking radiation on
the brane is suppressed.
| [
{
"created": "Fri, 18 Jan 2013 20:22:34 GMT",
"version": "v1"
}
] | 2013-01-31 | [
[
"da Rocha",
"Roldao",
""
],
[
"Piloyan",
"A.",
""
],
[
"Kuerten",
"A. M.",
""
],
[
"Coimbra-Araujo",
"C. H.",
""
]
] | This paper aims to evince the corrections on the black string warped horizon in the braneworld paradigm, and their drastic physical consequences, as well as to provide subsequent applications in astrophysics. Our analysis concerning black holes on the brane departs from the Schwarzschild case, where the black string is unstable to large-scale perturbation. The cognizable measurability of the black string horizon corrections due to braneworld effects is investigated, as well as their applications in the variation of quasars luminosity. We delve into the case wherein two solutions of Einstein's equations proposed by Casadio, Fabbri, and Mazzacurati, regarding black hole metrics presenting a post-Newtonian parameter measured on the brane. In this scenario, it is possible to analyze purely the braneworld corrected variation in quasars luminosity, by an appropriate choice of the post-Newtonian parameter that precludes Hawking radiation on the brane: the variation in quasars luminosity is uniquely provided by pure braneworld effects, as the Hawking radiation on the brane is suppressed. |
1106.3542 | Laura Mersini-Houghton | Laura Mersini-Houghton | Is Eternal Inflation Eternal? | 7 pages, 2 figs | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we explore the relationship between the existence of eternal
inflation and the initial conditions leading to inflation. We demonstrate that
past and future completion of inflation is related, in that past-incomplete
inflation can not be future eternal. Bubble universes nucleating close to the
initial conditions hypersurface have the largest Lorentz boosts and experience
the highest anisotropy. Consequently, their probability to collide upon
formation is one. Thus instead of continuing eternally inflation ends soon
after it starts. The difficulty in actualizing eternal inflation originates
from the breaking of two underlying symmetries: Lorentz invariance and the
general covariance of the theory which lead to an inconsistency of Einstein
equations. Eternal inflation may not be eternal.
| [
{
"created": "Fri, 17 Jun 2011 18:15:31 GMT",
"version": "v1"
}
] | 2011-06-20 | [
[
"Mersini-Houghton",
"Laura",
""
]
] | In this paper we explore the relationship between the existence of eternal inflation and the initial conditions leading to inflation. We demonstrate that past and future completion of inflation is related, in that past-incomplete inflation can not be future eternal. Bubble universes nucleating close to the initial conditions hypersurface have the largest Lorentz boosts and experience the highest anisotropy. Consequently, their probability to collide upon formation is one. Thus instead of continuing eternally inflation ends soon after it starts. The difficulty in actualizing eternal inflation originates from the breaking of two underlying symmetries: Lorentz invariance and the general covariance of the theory which lead to an inconsistency of Einstein equations. Eternal inflation may not be eternal. |
1704.00038 | Antonios Tsokaros A. | Antonios Tsokaros, Milton Ruiz, Vasileios Paschalidis, Stuart L.
Shapiro, Luca Baiotti, K\=oji Ury\=u | Gravitational wave content and stability of uniformly, rotating,
triaxial neutron stars in general relativity | 12 pages, 5 figures | Phys. Rev. D 95, 124057 (2017) | 10.1103/PhysRevD.95.124057 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Targets for ground-based gravitational wave interferometers include
continuous, quasiperiodic sources of gravitational radiation, such as isolated,
spinning neutron stars. In this work we perform evolution simulations of
uniformly rotating, triaxially deformed stars, the compressible analogues in
general relativity of incompressible, Newtonian Jacobi ellipsoids. We
investigate their stability and gravitational wave emission. We employ five
models, both normal and supramassive, and track their evolution with different
grid setups and resolutions, as well as with two different evolution codes. We
find that all models are dynamically stable and produce a strain that is
approximately one-tenth the average value of a merging binary system. We track
their secular evolution and find that all our stars evolve towards axisymmetry,
maintaining their uniform rotation, kinetic energy, and angular momentum
profiles while losing their triaxiality.
| [
{
"created": "Fri, 31 Mar 2017 20:00:03 GMT",
"version": "v1"
}
] | 2017-07-05 | [
[
"Tsokaros",
"Antonios",
""
],
[
"Ruiz",
"Milton",
""
],
[
"Paschalidis",
"Vasileios",
""
],
[
"Shapiro",
"Stuart L.",
""
],
[
"Baiotti",
"Luca",
""
],
[
"Uryū",
"Kōji",
""
]
] | Targets for ground-based gravitational wave interferometers include continuous, quasiperiodic sources of gravitational radiation, such as isolated, spinning neutron stars. In this work we perform evolution simulations of uniformly rotating, triaxially deformed stars, the compressible analogues in general relativity of incompressible, Newtonian Jacobi ellipsoids. We investigate their stability and gravitational wave emission. We employ five models, both normal and supramassive, and track their evolution with different grid setups and resolutions, as well as with two different evolution codes. We find that all models are dynamically stable and produce a strain that is approximately one-tenth the average value of a merging binary system. We track their secular evolution and find that all our stars evolve towards axisymmetry, maintaining their uniform rotation, kinetic energy, and angular momentum profiles while losing their triaxiality. |
0902.3107 | Mariusz Dabrowski P. | Mariusz P. Dabrowski and Tomasz Denkiewicz | Barotropic index w-singularities in cosmology | REVTEX4, 4 pages, 4 figures, version to match a published paper,
title expanded | Phys. Rev. D 79, 063521 (2009) | 10.1103/PhysRevD.79.063521 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find an explicit cosmological model which allows a special type of
cosmological singularity which we call a $w$-singularity. This singularity has
the scale factor finite, the energy density and pressure vanishing, and the
only singular behaviour appears in a time-dependent barotropic index $w(t)$. It
is different from the type IV cosmological singularity in that it does not
exhibit the divergence of the higher derivatives of the Hubble parameter and
from the big-brake since it does not fulfill the anti-Chaplygin gas equation of
state. We also find an interesting duality between the $w$-singularities and
the big-bang singularities. Physical examples of $w$-singularities appear in
$f(R)$, scalar field and brane cosmologies.
| [
{
"created": "Wed, 18 Feb 2009 11:46:21 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Feb 2009 11:58:53 GMT",
"version": "v2"
},
{
"created": "Fri, 17 Apr 2009 10:07:23 GMT",
"version": "v3"
}
] | 2009-11-13 | [
[
"Dabrowski",
"Mariusz P.",
""
],
[
"Denkiewicz",
"Tomasz",
""
]
] | We find an explicit cosmological model which allows a special type of cosmological singularity which we call a $w$-singularity. This singularity has the scale factor finite, the energy density and pressure vanishing, and the only singular behaviour appears in a time-dependent barotropic index $w(t)$. It is different from the type IV cosmological singularity in that it does not exhibit the divergence of the higher derivatives of the Hubble parameter and from the big-brake since it does not fulfill the anti-Chaplygin gas equation of state. We also find an interesting duality between the $w$-singularities and the big-bang singularities. Physical examples of $w$-singularities appear in $f(R)$, scalar field and brane cosmologies. |
2305.12345 | Jie Jiang | Jie Jiang and Ming Zhang | Overspinning a rotating black hole in semiclassical gravity with type-A
trace anomaly | 10 pages and 7 figures | null | 10.1140/epjc/s10052-023-11868-2 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | Recently, Fernandes discovered an analytic solution for rotating black holes
in semiclassical gravity induced by the trace anomaly. These solutions exhibit
some distinctive characteristics, including a non-spherically symmetric event
horizon and violations of the Kerr bound. As a crucial assumption to uphold
causality in spacetime, we investigate the validity of the weak cosmic
censorship conjecture (WCCC) within this class of solutions with type-A trace
anomaly by introducing a test particle on the equatorial plane. Our study
reveals three distinct mechanisms that can potentially destroy the event
horizon, leading to a violation of the WCCC. Our findings indicate that, with
the exception of extremal Kerr, static extremal, and static singular black
holes, the WCCC may be violated under the first-order perturbation of the test
particle. These results suggest the need for further exploration of
modifications to the behavior of the test particle under quantum effects in
order to address the violation of the WCCC in this system.
| [
{
"created": "Sun, 21 May 2023 04:43:55 GMT",
"version": "v1"
}
] | 2023-08-16 | [
[
"Jiang",
"Jie",
""
],
[
"Zhang",
"Ming",
""
]
] | Recently, Fernandes discovered an analytic solution for rotating black holes in semiclassical gravity induced by the trace anomaly. These solutions exhibit some distinctive characteristics, including a non-spherically symmetric event horizon and violations of the Kerr bound. As a crucial assumption to uphold causality in spacetime, we investigate the validity of the weak cosmic censorship conjecture (WCCC) within this class of solutions with type-A trace anomaly by introducing a test particle on the equatorial plane. Our study reveals three distinct mechanisms that can potentially destroy the event horizon, leading to a violation of the WCCC. Our findings indicate that, with the exception of extremal Kerr, static extremal, and static singular black holes, the WCCC may be violated under the first-order perturbation of the test particle. These results suggest the need for further exploration of modifications to the behavior of the test particle under quantum effects in order to address the violation of the WCCC in this system. |
2305.06719 | Marko Sossich | Petar Pavlovi\'c and Marko Sossich | Geodesically complete cyclic cosmologies and entropy | 18 pages, 2 figures, the major revision has been done and some
dubious analysis with entropy free models have been omitted, also the article
in this form has been accepted in EPJC | Eur. Phys. J. C 84, 242 (2024) | 10.1140/epjc/s10052-024-12621-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate that there exists a class of cyclic cosmological models, such
that these models can in principle solve the problem of the entropy growth, and
are at the same time geodesically complete. We thus show that some recently
stated conclusions, according to which cyclic cosmologies solving the problem
of entropy growth can not be geodesically complete due to the
Borde-Guth-Vilenkin (BGV) theorem, are not justified. We also add a short
conceptual discussion on entropy and cyclic cosmology, and present a detailed
analysis of entropy density growth during periodic and non-periodic evolution
for cyclic cosmologies.
| [
{
"created": "Thu, 11 May 2023 10:54:17 GMT",
"version": "v1"
},
{
"created": "Fri, 26 May 2023 09:01:07 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Sep 2023 11:33:34 GMT",
"version": "v3"
},
{
"created": "Thu, 29 Feb 2024 11:45:25 GMT",
"version": "v4"
}
] | 2024-03-12 | [
[
"Pavlović",
"Petar",
""
],
[
"Sossich",
"Marko",
""
]
] | We demonstrate that there exists a class of cyclic cosmological models, such that these models can in principle solve the problem of the entropy growth, and are at the same time geodesically complete. We thus show that some recently stated conclusions, according to which cyclic cosmologies solving the problem of entropy growth can not be geodesically complete due to the Borde-Guth-Vilenkin (BGV) theorem, are not justified. We also add a short conceptual discussion on entropy and cyclic cosmology, and present a detailed analysis of entropy density growth during periodic and non-periodic evolution for cyclic cosmologies. |
0706.1513 | Cecilia Chirenti | Cecilia B. M. H. Chirenti and Luciano Rezzolla | How to tell a gravastar from a black hole | 16 pages, 13 figures, minor improvement | Class.Quant.Grav.24:4191-4206,2007 | 10.1088/0264-9381/24/16/013 | null | gr-qc astro-ph | null | Gravastars have been recently proposed as potential alternatives to explain
the astrophysical phenomenology traditionally associated to black holes,
raising the question of whether the two objects can be distinguished at all.
Leaving aside the debate about the processes that would lead to the formation
of a gravastar and the astronomical evidence in their support, we here address
two basic questions: Is a gravastar stable against generic perturbations? If
stable, can an observer distinguish it from a black hole of the same mass? To
answer these questions we construct a general class of gravastars and determine
the conditions they must satisfy in order to exist as equilibrium solutions of
the Einstein equations. For such models we perform a systematic stability
analysis against axial-perturbations, computing the real and imaginary parts of
the eigenfrequencies. Overall, we find that gravastars are stable to axial
perturbations, but also that their quasi-normal modes differ from those of a
black hole of the same mass and thus can be used to discern, beyond dispute, a
gravastar from a black hole.
| [
{
"created": "Mon, 11 Jun 2007 16:35:46 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Jun 2007 17:43:53 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Chirenti",
"Cecilia B. M. H.",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | Gravastars have been recently proposed as potential alternatives to explain the astrophysical phenomenology traditionally associated to black holes, raising the question of whether the two objects can be distinguished at all. Leaving aside the debate about the processes that would lead to the formation of a gravastar and the astronomical evidence in their support, we here address two basic questions: Is a gravastar stable against generic perturbations? If stable, can an observer distinguish it from a black hole of the same mass? To answer these questions we construct a general class of gravastars and determine the conditions they must satisfy in order to exist as equilibrium solutions of the Einstein equations. For such models we perform a systematic stability analysis against axial-perturbations, computing the real and imaginary parts of the eigenfrequencies. Overall, we find that gravastars are stable to axial perturbations, but also that their quasi-normal modes differ from those of a black hole of the same mass and thus can be used to discern, beyond dispute, a gravastar from a black hole. |
1602.07189 | Hao Wei | Ya-Nan Zhou, De-Zi Liu, Xiao-Bo Zou, Hao Wei | New Generalizations of Cosmography Inspired by the Pade Approximant | 16 pages, 3 tables, 5 figures, revtex4; v2: discussions added, Eur.
Phys. J. C in press; v3: published version | Eur. Phys. J. C76 (2016) 281 | 10.1140/epjc/s10052-016-4091-z | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The current accelerated expansion of the universe has been one of the most
important fields in physics and astronomy since 1998. Many cosmological models
have been proposed in the literature to explain this mysterious phenomenon.
Since the nature and cause of the cosmic acceleration are still unknown,
model-independent approaches to study the evolution of the universe are
welcome. One of the powerful model-independent approaches is the so-called
cosmography. It only relies on the cosmological principle, without postulating
any underlying theoretical model. However, there are several shortcomings in
the usual cosmography. For instance, it is plagued with the problem of
divergence (or an unacceptably large error), and it fails to predict the future
evolution of the universe. In the present work, we try to overcome or at least
alleviate these problems, and we propose two new generalizations of cosmography
inspired by the Pad\'e approximant. One is to directly parameterize the
luminosity distance based on the Pad\'e approximant, while the other is to
generalize cosmography with respect to a so-called $y_\beta$-shift
$y_\beta=z/(1+\beta z)$, which is also inspired by the Pad\'e approximant.
Then, we confront them with the observational data with the help of the Markov
chain Monte Carlo (MCMC) code emcee, and find that they work fairly well.
| [
{
"created": "Tue, 23 Feb 2016 15:19:00 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Apr 2016 01:00:00 GMT",
"version": "v2"
},
{
"created": "Mon, 23 May 2016 18:36:00 GMT",
"version": "v3"
}
] | 2016-05-24 | [
[
"Zhou",
"Ya-Nan",
""
],
[
"Liu",
"De-Zi",
""
],
[
"Zou",
"Xiao-Bo",
""
],
[
"Wei",
"Hao",
""
]
] | The current accelerated expansion of the universe has been one of the most important fields in physics and astronomy since 1998. Many cosmological models have been proposed in the literature to explain this mysterious phenomenon. Since the nature and cause of the cosmic acceleration are still unknown, model-independent approaches to study the evolution of the universe are welcome. One of the powerful model-independent approaches is the so-called cosmography. It only relies on the cosmological principle, without postulating any underlying theoretical model. However, there are several shortcomings in the usual cosmography. For instance, it is plagued with the problem of divergence (or an unacceptably large error), and it fails to predict the future evolution of the universe. In the present work, we try to overcome or at least alleviate these problems, and we propose two new generalizations of cosmography inspired by the Pad\'e approximant. One is to directly parameterize the luminosity distance based on the Pad\'e approximant, while the other is to generalize cosmography with respect to a so-called $y_\beta$-shift $y_\beta=z/(1+\beta z)$, which is also inspired by the Pad\'e approximant. Then, we confront them with the observational data with the help of the Markov chain Monte Carlo (MCMC) code emcee, and find that they work fairly well. |
2202.02205 | Roman Konoplya | R. A. Konoplya and A. Zhidenko | Solutions of the Einstein equations for a black hole surrounded by a
galactic halo | 6 pages, 3 figures, 1 ancillary Mathematica file, the version to
match published in the journal | Astrophys. J. 933 (2022) 166 | 10.3847/1538-4357/ac76bc | null | gr-qc astro-ph.GA hep-th | http://creativecommons.org/licenses/by/4.0/ | Various profiles of matter distribution in galactic halos (such as
Navarro-Frenk-White, Burkert, Hernquist, Moore, Taylor-Silk and others) are
considered here as the source term for the Einstein equations. We solve these
equations and find exact solutions which represent the metric of a central
black hole immersed in a galactic halo. Even though in the general case the
solution is numerical, very accurate general analytical metric, which includes
all the particular models, are found in the astrophysically relevant regime,
when the mass of the galaxy is much smaller than the characteristic scale in
the halo.
| [
{
"created": "Fri, 4 Feb 2022 15:52:56 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Feb 2022 20:36:53 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Jul 2022 13:54:50 GMT",
"version": "v3"
}
] | 2022-07-13 | [
[
"Konoplya",
"R. A.",
""
],
[
"Zhidenko",
"A.",
""
]
] | Various profiles of matter distribution in galactic halos (such as Navarro-Frenk-White, Burkert, Hernquist, Moore, Taylor-Silk and others) are considered here as the source term for the Einstein equations. We solve these equations and find exact solutions which represent the metric of a central black hole immersed in a galactic halo. Even though in the general case the solution is numerical, very accurate general analytical metric, which includes all the particular models, are found in the astrophysically relevant regime, when the mass of the galaxy is much smaller than the characteristic scale in the halo. |
1207.3481 | Katanaev | M. O. Katanaev | Point massive particle in General Relativity | 15 pages, references added, 1 figure | Gen. Rel. Grav. 45 (2013) 1861-1875 | 10.1007/s10714-013-1564-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known that the Schwarzschild solution describes the gravitational
field outside compact spherically symmetric mass distribution in General
Relativity. In particular, it describes the gravitational field outside a point
particle. Nevertheless, what is the exact solution of Einstein's equations with
$\delta$-type source corresponding to a point particle is not known. In the
present paper, we prove that the Schwarzschild solution in isotropic
coordinates is the asymptotically flat static spherically symmetric solution of
Einstein's equations with $\delta$-type energy-momentum tensor corresponding to
a point particle. Solution of Einstein's equations is understood in the
generalized sense after integration with a test function. Metric components are
locally integrable functions for which nonlinear Einstein's equations are
mathematically defined. The Schwarzschild solution in isotropic coordinates is
locally isometric to the Schwarzschild solution in Schwarzschild coordinates
but differs essentially globally. It is topologically trivial neglecting the
world line of a point particle. Gravity attraction at large distances is
replaced by repulsion at the particle neighbourhood.
| [
{
"created": "Sun, 15 Jul 2012 07:49:42 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Aug 2012 16:43:43 GMT",
"version": "v2"
},
{
"created": "Fri, 7 Dec 2012 12:18:31 GMT",
"version": "v3"
},
{
"created": "Tue, 3 Sep 2013 06:54:56 GMT",
"version": "v4"
}
] | 2013-09-04 | [
[
"Katanaev",
"M. O.",
""
]
] | It is well known that the Schwarzschild solution describes the gravitational field outside compact spherically symmetric mass distribution in General Relativity. In particular, it describes the gravitational field outside a point particle. Nevertheless, what is the exact solution of Einstein's equations with $\delta$-type source corresponding to a point particle is not known. In the present paper, we prove that the Schwarzschild solution in isotropic coordinates is the asymptotically flat static spherically symmetric solution of Einstein's equations with $\delta$-type energy-momentum tensor corresponding to a point particle. Solution of Einstein's equations is understood in the generalized sense after integration with a test function. Metric components are locally integrable functions for which nonlinear Einstein's equations are mathematically defined. The Schwarzschild solution in isotropic coordinates is locally isometric to the Schwarzschild solution in Schwarzschild coordinates but differs essentially globally. It is topologically trivial neglecting the world line of a point particle. Gravity attraction at large distances is replaced by repulsion at the particle neighbourhood. |
1509.03298 | Joan Sola | Adria Gomez-Valent, Elahe Karimkhani, and Joan Sola | Background history and cosmic perturbations for a general system of
self-conserved dynamical dark energy and matter | Accepted in JCAP, extended discussion and references added | null | 10.1088/1475-7516/2015/12/048 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We determine the Hubble expansion and the general cosmic perturbations
equations for a general system consisting of self-conserved matter and
self-conserved dark energy (DE). While at the background level the two
components are non-interacting, they do interact at the perturbations level. We
show that the coupled system of matter and DE perturbations can be transformed
into a single, third order, matter perturbation equation, which reduces to the
(derivative of the) standard one in the case that the DE is just a cosmological
constant. As a nontrivial application we analyze a class of dynamical models
whose DE density $\rho_D$ consists of a constant term, $C_0$, and a series of
powers of the Hubble rate. These models were previously analyzed from the point
of view of dynamical vacuum models, but here we treat them as self-conserved DE
models with a dynamical equation of state. We fit them to the wealth of
expansion history and linear structure formation data and compare the obtained
fit quality with that of the concordance $\Lambda$CDM model. Those with $C_0=0$
include the so-called "entropic-force" and "QCD-ghost" DE models, as well as
the pure linear model $\rho_D\sim H$, all of which appear strongly disfavored.
The models with $C_0\neq 0$, in contrast, emerge as promising dynamical DE
candidates whose phenomenological performance is highly competitive with the
rigid $\Lambda$-term inherent to the $\Lambda$CDM.
| [
{
"created": "Thu, 10 Sep 2015 19:53:02 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Sep 2015 19:57:27 GMT",
"version": "v2"
},
{
"created": "Sat, 14 Nov 2015 19:34:13 GMT",
"version": "v3"
}
] | 2016-01-13 | [
[
"Gomez-Valent",
"Adria",
""
],
[
"Karimkhani",
"Elahe",
""
],
[
"Sola",
"Joan",
""
]
] | We determine the Hubble expansion and the general cosmic perturbations equations for a general system consisting of self-conserved matter and self-conserved dark energy (DE). While at the background level the two components are non-interacting, they do interact at the perturbations level. We show that the coupled system of matter and DE perturbations can be transformed into a single, third order, matter perturbation equation, which reduces to the (derivative of the) standard one in the case that the DE is just a cosmological constant. As a nontrivial application we analyze a class of dynamical models whose DE density $\rho_D$ consists of a constant term, $C_0$, and a series of powers of the Hubble rate. These models were previously analyzed from the point of view of dynamical vacuum models, but here we treat them as self-conserved DE models with a dynamical equation of state. We fit them to the wealth of expansion history and linear structure formation data and compare the obtained fit quality with that of the concordance $\Lambda$CDM model. Those with $C_0=0$ include the so-called "entropic-force" and "QCD-ghost" DE models, as well as the pure linear model $\rho_D\sim H$, all of which appear strongly disfavored. The models with $C_0\neq 0$, in contrast, emerge as promising dynamical DE candidates whose phenomenological performance is highly competitive with the rigid $\Lambda$-term inherent to the $\Lambda$CDM. |
gr-qc/9705073 | Misao Sasaki | Yasushi Mino, Misao Sasaki and Takahiro Tanaka | Gravitational Radiation Reaction to a Particle Motion II: Spinning
Particle | 10 pages, revtex | null | null | OU-TAP 46 and KUNS 1419 | gr-qc | null | We discuss the leading order correction to the equation of motion of a
particle with spin on an arbitrary spacetime. A particle traveling in a curved
spacetime is known to trace a geodesic of the background spacetime if the mass
of the particle is negligibly small. For a spinning particle, it is known that
there appears a term due to the coupling of the spin and the Riemann tensor of
the background spacetime. Recently we have found the equation of motion of a
non-spinning particle which includes the effect of gravitational radiation
reaction. This paper is devoted to discussion of a consistent derivation of the
equation of motion which is corrected both by the spin-Riemann coupling and the
gravitational radiation reaction.
| [
{
"created": "Tue, 27 May 1997 11:47:05 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mino",
"Yasushi",
""
],
[
"Sasaki",
"Misao",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | We discuss the leading order correction to the equation of motion of a particle with spin on an arbitrary spacetime. A particle traveling in a curved spacetime is known to trace a geodesic of the background spacetime if the mass of the particle is negligibly small. For a spinning particle, it is known that there appears a term due to the coupling of the spin and the Riemann tensor of the background spacetime. Recently we have found the equation of motion of a non-spinning particle which includes the effect of gravitational radiation reaction. This paper is devoted to discussion of a consistent derivation of the equation of motion which is corrected both by the spin-Riemann coupling and the gravitational radiation reaction. |
2005.03850 | Michael Good | Michael R.R. Good, Abay Zhakenuly, and Eric V. Linder | The mirror at the edge of the universe: Reflections on an accelerated
boundary correspondence with de Sitter cosmology | 4 pages, 5 figures | Phys. Rev. D 102, 045020 (2020) | 10.1103/PhysRevD.102.045020 | null | gr-qc astro-ph.CO hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An accelerated boundary correspondence (ABC) is solved for the de Sitter
moving mirror cosmology. The beta Bogoliubov coefficients reveal the particle
spectrum is a Planck distribution with temperature inversely proportional to
horizon radius. The quantum stress-tensor indicates a constant emission of
energy flux consistent with eternal equilibrium, while the total energy carried
by the particles remains finite. The curved spacetime transformation to flat
spacetime with an accelerated boundary is illustrated, and also shown for
Anti-de Sitter (AdS) spacetime.
| [
{
"created": "Fri, 8 May 2020 04:34:36 GMT",
"version": "v1"
}
] | 2020-09-01 | [
[
"Good",
"Michael R. R.",
""
],
[
"Zhakenuly",
"Abay",
""
],
[
"Linder",
"Eric V.",
""
]
] | An accelerated boundary correspondence (ABC) is solved for the de Sitter moving mirror cosmology. The beta Bogoliubov coefficients reveal the particle spectrum is a Planck distribution with temperature inversely proportional to horizon radius. The quantum stress-tensor indicates a constant emission of energy flux consistent with eternal equilibrium, while the total energy carried by the particles remains finite. The curved spacetime transformation to flat spacetime with an accelerated boundary is illustrated, and also shown for Anti-de Sitter (AdS) spacetime. |
gr-qc/9903056 | The Mammouth | Tamath Rainsford and Peter Szekeres | Post-Newtonian Cosmology | 12 pages, Latex | Gen.Rel.Grav.32:479-490,2000 | 10.1023/A:1001976317159 | The University of Adelaide preprint 9913M79 | gr-qc | null | Newtonian Cosmology is commonly used in astrophysical problems, because of
its obvious simplicity when compared with general relativity. However it has
inherent difficulties, the most obvious of which is the non-existence of a
well-posed initial value problem. In this paper we investigate how far these
problems are met by using the post-Newtonian approximation in cosmology.
| [
{
"created": "Mon, 15 Mar 1999 07:32:48 GMT",
"version": "v1"
}
] | 2010-12-03 | [
[
"Rainsford",
"Tamath",
""
],
[
"Szekeres",
"Peter",
""
]
] | Newtonian Cosmology is commonly used in astrophysical problems, because of its obvious simplicity when compared with general relativity. However it has inherent difficulties, the most obvious of which is the non-existence of a well-posed initial value problem. In this paper we investigate how far these problems are met by using the post-Newtonian approximation in cosmology. |
1204.2507 | Slava G. Turyshev | Slava G. Turyshev, Viktor T. Toth, Gary Kinsella, Siu-Chun Lee, Shing
M. Lok, and Jordan Ellis | Support for the thermal origin of the Pioneer anomaly | 5 pages, 4 figures, 3 tables, accepted to Phys. Rev. Letters | Phys. Rev. Lett. 108, 241101 (2012) | 10.1103/PhysRevLett.108.241101 | null | gr-qc astro-ph.IM physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the possibility that the anomalous acceleration of the Pioneer
10 and 11 spacecraft is due to the recoil force associated with an anisotropic
emission of thermal radiation off the vehicles. To this end, relying on the
project and spacecraft design documentation, we constructed a comprehensive
finite-element thermal model of the two spacecraft. Then, we numerically solve
thermal conduction and radiation equations using the actual flight telemetry as
boundary conditions. We use the results of this model to evaluate the effect of
the thermal recoil force on the Pioneer 10 spacecraft at various heliocentric
distances. We found that the magnitude, temporal behavior, and direction of the
resulting thermal acceleration are all similar to the properties of the
observed anomaly. As a novel element of our investigation, we develop a
parameterized model for the thermal recoil force and estimate the coefficients
of this model independently from navigational Doppler data. We find no
statistically significant difference between the two estimates and conclude
that once the thermal recoil force is properly accounted for, no anomalous
acceleration remains.
| [
{
"created": "Wed, 11 Apr 2012 17:46:02 GMT",
"version": "v1"
}
] | 2012-06-13 | [
[
"Turyshev",
"Slava G.",
""
],
[
"Toth",
"Viktor T.",
""
],
[
"Kinsella",
"Gary",
""
],
[
"Lee",
"Siu-Chun",
""
],
[
"Lok",
"Shing M.",
""
],
[
"Ellis",
"Jordan",
""
]
] | We investigate the possibility that the anomalous acceleration of the Pioneer 10 and 11 spacecraft is due to the recoil force associated with an anisotropic emission of thermal radiation off the vehicles. To this end, relying on the project and spacecraft design documentation, we constructed a comprehensive finite-element thermal model of the two spacecraft. Then, we numerically solve thermal conduction and radiation equations using the actual flight telemetry as boundary conditions. We use the results of this model to evaluate the effect of the thermal recoil force on the Pioneer 10 spacecraft at various heliocentric distances. We found that the magnitude, temporal behavior, and direction of the resulting thermal acceleration are all similar to the properties of the observed anomaly. As a novel element of our investigation, we develop a parameterized model for the thermal recoil force and estimate the coefficients of this model independently from navigational Doppler data. We find no statistically significant difference between the two estimates and conclude that once the thermal recoil force is properly accounted for, no anomalous acceleration remains. |
gr-qc/0307071 | Anzhong Wang | Anzhong Wang | Critical Collapse of Cylindrically Symmetric Scalar Field in
Four-Dimensional Einstein's Theory of Gravity | Some typos are corrected. The final version to appear in Phys. Rev. D | Phys.Rev.D68:064006,2003 | 10.1103/PhysRevD.68.064006 | null | gr-qc | null | Four-dimensional cylindrically symmetric spacetimes with homothetic
self-similarity are studied in the context of Einstein's Theory of Gravity, and
a class of exact solutions to the Einstein-massless scalar field equations is
found. Their local and global properties are investigated and found that they
represent gravitational collapse of a massless scalar field. In some cases the
collapse forms black holes with cylindrical symmetry, while in the other cases
it does not. The linear perturbations of these solutions are also studied and
given in closed form. From the spectra of the unstable eigen-modes, it is found
that there exists one solution that has precisely one unstable mode, which may
represent a critical solution, sitting on a boundary that separates two
different basins of attraction in the phase space.
| [
{
"created": "Tue, 15 Jul 2003 20:00:53 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Jul 2003 15:22:57 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Sep 2003 22:05:35 GMT",
"version": "v3"
}
] | 2009-07-07 | [
[
"Wang",
"Anzhong",
""
]
] | Four-dimensional cylindrically symmetric spacetimes with homothetic self-similarity are studied in the context of Einstein's Theory of Gravity, and a class of exact solutions to the Einstein-massless scalar field equations is found. Their local and global properties are investigated and found that they represent gravitational collapse of a massless scalar field. In some cases the collapse forms black holes with cylindrical symmetry, while in the other cases it does not. The linear perturbations of these solutions are also studied and given in closed form. From the spectra of the unstable eigen-modes, it is found that there exists one solution that has precisely one unstable mode, which may represent a critical solution, sitting on a boundary that separates two different basins of attraction in the phase space. |
1205.6637 | Atanu Kumar | Atanu Kumar | Growth of covariant perturbations in the contracting phase of a bouncing
universe | 9 pages, final version | Phys. Rev. D 86, 123522 (2012) | 10.1103/PhysRevD.86.123522 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we examine the validity of the linear perturbation theory near
a bounce in the covariant analysis. Some linearity parameters are defined to
set up conditions for a linear theory. Linear evolution of density perturbation
and gravitational waves have been computed previously. We have calculated the
vector and scalar induced parts of the shear tensor. For radiationlike and
dustlike single fluid dominated collapsing Friedmann-Lemaitre-Robertson-Walker
background it is shown that the linearity conditions are not satisfied near a
bounce.
| [
{
"created": "Wed, 30 May 2012 11:42:43 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Dec 2012 06:21:55 GMT",
"version": "v2"
}
] | 2012-12-21 | [
[
"Kumar",
"Atanu",
""
]
] | In this paper we examine the validity of the linear perturbation theory near a bounce in the covariant analysis. Some linearity parameters are defined to set up conditions for a linear theory. Linear evolution of density perturbation and gravitational waves have been computed previously. We have calculated the vector and scalar induced parts of the shear tensor. For radiationlike and dustlike single fluid dominated collapsing Friedmann-Lemaitre-Robertson-Walker background it is shown that the linearity conditions are not satisfied near a bounce. |
gr-qc/0206081 | William A. Hiscock | Shane L. Larson, Ronald W. Hellings, and William A. Hiscock | Unequal arm space-borne gravitational wave detectors | 14 pages, 7 figures, REVTeX 4 | Phys.Rev. D66 (2002) 062001 | 10.1103/PhysRevD.66.062001 | null | gr-qc | null | Unlike ground-based interferometric gravitational wave detectors, large
space-based systems will not be rigid structures. When the end-stations of the
laser interferometer are freely flying spacecraft, the armlengths will change
due to variations in the spacecraft positions along their orbital trajectories,
so the precise equality of the arms that is required in a laboratory
interferometer to cancel laser phase noise is not possible. However, using a
method discovered by Tinto and Armstrong, a signal can be constructed in which
laser phase noise exactly cancels out, even in an unequal arm interferometer.
We examine the case where the ratio of the armlengths is a variable parameter,
and compute the averaged gravitational wave transfer function as a function of
that parameter. Example sensitivity curve calculations are presented for the
expected design parameters of the proposed LISA interferometer, comparing it to
a similar instrument with one arm shortened by a factor of 100, showing how the
ratio of the armlengths will affect the overall sensitivity of the instrument.
| [
{
"created": "Wed, 26 Jun 2002 23:07:20 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Larson",
"Shane L.",
""
],
[
"Hellings",
"Ronald W.",
""
],
[
"Hiscock",
"William A.",
""
]
] | Unlike ground-based interferometric gravitational wave detectors, large space-based systems will not be rigid structures. When the end-stations of the laser interferometer are freely flying spacecraft, the armlengths will change due to variations in the spacecraft positions along their orbital trajectories, so the precise equality of the arms that is required in a laboratory interferometer to cancel laser phase noise is not possible. However, using a method discovered by Tinto and Armstrong, a signal can be constructed in which laser phase noise exactly cancels out, even in an unequal arm interferometer. We examine the case where the ratio of the armlengths is a variable parameter, and compute the averaged gravitational wave transfer function as a function of that parameter. Example sensitivity curve calculations are presented for the expected design parameters of the proposed LISA interferometer, comparing it to a similar instrument with one arm shortened by a factor of 100, showing how the ratio of the armlengths will affect the overall sensitivity of the instrument. |
gr-qc/0411134 | William A. Hiscock | Hector Calderon and William A. Hiscock (Montana State University) | Quantum fields and "Big Rip" expansion singularities | 7 pages; REVTeX 4 | Class.Quant.Grav. 22 (2005) L23-L26 | 10.1088/0264-9381/22/4/L01 | null | gr-qc | null | The effects of quantized conformally invariant massless fields on the
evolution of cosmological models containing a ``Big Rip'' future expansion
singularity are examined. Quantized scalar, spinor, and vector fields are found
to strengthen the accelerating expansion of such models as they approach the
expansion singularity.
| [
{
"created": "Mon, 29 Nov 2004 00:36:35 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Calderon",
"Hector",
"",
"Montana State University"
],
[
"Hiscock",
"William A.",
"",
"Montana State University"
]
] | The effects of quantized conformally invariant massless fields on the evolution of cosmological models containing a ``Big Rip'' future expansion singularity are examined. Quantized scalar, spinor, and vector fields are found to strengthen the accelerating expansion of such models as they approach the expansion singularity. |
gr-qc/0112067 | Ken-ichi Nakao | Ken-ichi Nakao, Kouji Nakamura and Takashi Mishima | Hoop Conjecture and Cosmic Censorship in the Brane-World | 5 pages, 1 figure, to be published in Physics Letters B | Phys.Lett. B564 (2003) 143-148 | 10.1016/S0370-2693(03)00588-4 | OCU-PHYS-183, APGR-2, NAOJ-Th-Ap 2001, No.72 | gr-qc hep-th | null | The initial data of gravity for a cylindrical matter distribution confined on
the brane is studied in the framework of the single brane Randall-Sundrum
scenario. In this scenario, 5-dimensional aspect of gravity appears in the
short range gravitational interaction. We found that the sufficiently thin
configuration of matter leads to the formation of the marginal surface even if
the configuration is infinitely long. This means that the hoop conjecture
proposed by Thorne does not hold in the Randall-Sundrum scenario; Even if a
mass $M$ does not get compacted into a region whose circumference in every
direction is ${\cal C}\le 4\pi GM$, black holes with horizons can form in the
Randall-Sundrum scenario.
| [
{
"created": "Wed, 26 Dec 2001 01:45:50 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Apr 2003 07:01:50 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Nakao",
"Ken-ichi",
""
],
[
"Nakamura",
"Kouji",
""
],
[
"Mishima",
"Takashi",
""
]
] | The initial data of gravity for a cylindrical matter distribution confined on the brane is studied in the framework of the single brane Randall-Sundrum scenario. In this scenario, 5-dimensional aspect of gravity appears in the short range gravitational interaction. We found that the sufficiently thin configuration of matter leads to the formation of the marginal surface even if the configuration is infinitely long. This means that the hoop conjecture proposed by Thorne does not hold in the Randall-Sundrum scenario; Even if a mass $M$ does not get compacted into a region whose circumference in every direction is ${\cal C}\le 4\pi GM$, black holes with horizons can form in the Randall-Sundrum scenario. |
gr-qc/9807079 | Thomas Kloesch | M. O. Katanaev (Steklov Math. Inst.), T. Kloesch (Tech. U. Vienna), W.
Kummer (Tech. U. Vienna) | Global properties of warped solutions in General Relativity | 35 pages, 5 eps figures, minor changes | Annals Phys. 276 (1999) 191-222 | 10.1006/aphy.1999.5923 | null | gr-qc | null | Assuming the four-dimensional space-time to be a general warped product of
two surfaces we reduce the four-dimensional Einstein equations to a
two-dimensional problem which can be solved. All global vacuum solutions are
explicitly constructed and analysed. The classification of the solutions
includes the Schwarzschild, the (anti-)de Sitter, and other well-known
solutions but also many exact ones whose detailed global properties to our
knowledge have not been discussed before. They have a natural physical
interpretation describing single or several wormholes, domain walls of
curvature singularities, cosmic strings, cosmic strings surrounded by domain
walls, solutions with closed timelike curves, etc.
| [
{
"created": "Wed, 29 Jul 1998 09:42:20 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Oct 1999 07:03:32 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Katanaev",
"M. O.",
"",
"Steklov Math. Inst."
],
[
"Kloesch",
"T.",
"",
"Tech. U. Vienna"
],
[
"Kummer",
"W.",
"",
"Tech. U. Vienna"
]
] | Assuming the four-dimensional space-time to be a general warped product of two surfaces we reduce the four-dimensional Einstein equations to a two-dimensional problem which can be solved. All global vacuum solutions are explicitly constructed and analysed. The classification of the solutions includes the Schwarzschild, the (anti-)de Sitter, and other well-known solutions but also many exact ones whose detailed global properties to our knowledge have not been discussed before. They have a natural physical interpretation describing single or several wormholes, domain walls of curvature singularities, cosmic strings, cosmic strings surrounded by domain walls, solutions with closed timelike curves, etc. |
1207.0504 | Richard Brito | Richard Brito, Vitor Cardoso, Paolo Pani | Tidal effects around higher-dimensional black holes | 10 pages, 3 figures, RevTex 4; To be published in Phys.Rev.D; v2:
typos and references corrected | Phys.Rev.D86:024032,2012 | 10.1103/PhysRevD.86.024032 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In four-dimensional spacetime, moons around black holes generate
low-amplitude tides, and the energy extracted from the hole's rotation is
always smaller than the gravitational radiation lost to infinity. Thus, moons
orbiting a black hole inspiral and eventually merge. However, it has been
conjectured that in higher-dimensional spacetimes orbiting bodies generate much
stronger tides, which backreact by tidally accelerating the body outwards. This
effect, analogous to the tidal acceleration experienced by the Earth-Moon
system, would determine the evolution of the binary. Here, we put this
conjecture to the test, by studying matter coupled to a massless scalar field
in orbit around a singly-spinning rotating black hole in higher dimensions. We
show that in dimensions larger than five the energy extracted from the black
hole through superradiance is larger than the energy carried out to infinity.
Our numerical results are in excellent agreement with analytic approximations
and lend strong support to the conjecture that tidal acceleration is the rule,
rather than the exception, in higher dimensions. Superradiance dominates the
energy budget and moons "outspiral"; for some particular orbital frequency, the
energy extracted at the horizon equals the energy emitted to infinity and
"floating orbits" generically occur. We give an interpretation of this
phenomenon in terms of the membrane paradigm and of tidal acceleration due to
energy dissipation across the horizon.
| [
{
"created": "Mon, 2 Jul 2012 20:00:07 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Jul 2012 12:20:24 GMT",
"version": "v2"
}
] | 2012-07-31 | [
[
"Brito",
"Richard",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Pani",
"Paolo",
""
]
] | In four-dimensional spacetime, moons around black holes generate low-amplitude tides, and the energy extracted from the hole's rotation is always smaller than the gravitational radiation lost to infinity. Thus, moons orbiting a black hole inspiral and eventually merge. However, it has been conjectured that in higher-dimensional spacetimes orbiting bodies generate much stronger tides, which backreact by tidally accelerating the body outwards. This effect, analogous to the tidal acceleration experienced by the Earth-Moon system, would determine the evolution of the binary. Here, we put this conjecture to the test, by studying matter coupled to a massless scalar field in orbit around a singly-spinning rotating black hole in higher dimensions. We show that in dimensions larger than five the energy extracted from the black hole through superradiance is larger than the energy carried out to infinity. Our numerical results are in excellent agreement with analytic approximations and lend strong support to the conjecture that tidal acceleration is the rule, rather than the exception, in higher dimensions. Superradiance dominates the energy budget and moons "outspiral"; for some particular orbital frequency, the energy extracted at the horizon equals the energy emitted to infinity and "floating orbits" generically occur. We give an interpretation of this phenomenon in terms of the membrane paradigm and of tidal acceleration due to energy dissipation across the horizon. |
gr-qc/0306048 | M. Meyer | S. Deser | Novel Properties of Massive Higher Spin Fields | 9 pages, 1 figure. Invited talk at "Renormalization Group and
Anomalies in Gravity and Cosmology", Ouro Preto, Brazil, March 17-23, 2003 | Nucl.Phys.Proc.Suppl.127:36-44,2004 | 10.1016/S0920-5632(03)02398-3 | BRX TH-518 | gr-qc hep-th | null | I outline a series of results obtained in collaboration with A. Waldron on
the properties of massive higher (s>1) spin fields in cosmological, constant
curvature, backgrounds and the resulting unexpected qualitative effects on
their degrees of freedom and unitarity properties. The dimensional parameter
$\L$ extends the flat space m-line to a $(m^2,\L)$ "phase" plane in which these
novel phenomena unfold. In this light, I discuss a possible partial
resurrection of deSitter supergravity. I will also exhibit the well-known
causality problems of coupling these systems to gravity and, for complex
fields, to electromagnetism, systematizing some of the occasionally
misunderstood obstacles to interactions, particularly for s = 3/2 and 2.
| [
{
"created": "Wed, 11 Jun 2003 21:54:20 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Deser",
"S.",
""
]
] | I outline a series of results obtained in collaboration with A. Waldron on the properties of massive higher (s>1) spin fields in cosmological, constant curvature, backgrounds and the resulting unexpected qualitative effects on their degrees of freedom and unitarity properties. The dimensional parameter $\L$ extends the flat space m-line to a $(m^2,\L)$ "phase" plane in which these novel phenomena unfold. In this light, I discuss a possible partial resurrection of deSitter supergravity. I will also exhibit the well-known causality problems of coupling these systems to gravity and, for complex fields, to electromagnetism, systematizing some of the occasionally misunderstood obstacles to interactions, particularly for s = 3/2 and 2. |
1008.0910 | Hossein Farajollahi | Hossein Farajollahi, Mehrdad Farhoudi, Hossein Shojaie | On Dynamics of Brans--Dicke Theory of Gravitation | 15 pages | Int.J.Theor.Phys.49:2558-2568,2010 | 10.1007/s10773-010-0447-6 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study longstanding problem of cosmological clock in the context of
Brans-Dicke theory of gravitation. We present the Hamiltonian formulation of
the theory for a class of spatially homogenous cosmological models. Then, we
show that formulation of the Brans-Dicke theory in the Einstein frame allows
how an identification of an appropriate cosmological time variable, as a
function of the scalar field in the theory, can be emerged in quantum
cosmology. The classical and quantum results are applied to the
Friedmann-Robertson-Walker cosmological models.
| [
{
"created": "Thu, 5 Aug 2010 04:10:10 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jun 2011 07:07:32 GMT",
"version": "v2"
}
] | 2011-06-09 | [
[
"Farajollahi",
"Hossein",
""
],
[
"Farhoudi",
"Mehrdad",
""
],
[
"Shojaie",
"Hossein",
""
]
] | We study longstanding problem of cosmological clock in the context of Brans-Dicke theory of gravitation. We present the Hamiltonian formulation of the theory for a class of spatially homogenous cosmological models. Then, we show that formulation of the Brans-Dicke theory in the Einstein frame allows how an identification of an appropriate cosmological time variable, as a function of the scalar field in the theory, can be emerged in quantum cosmology. The classical and quantum results are applied to the Friedmann-Robertson-Walker cosmological models. |
1512.02120 | Andre Landulfo | Jessica Santiago, Andre G. S. Landulfo, William C. C. Lima, George E.
A. Matsas, Raissa F. P. Mendes, Daniel A. T. Vanzella | Instability of nonminimally coupled scalar fields in the spacetime of
thin charged shells | 9 pages, 5 figures. Minor changes to match the published version | Phys. Rev. D 93, 024043 (2016) | 10.1103/PhysRevD.93.024043 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the stability of a free scalar field nonminimally coupled to
gravity under linear perturbations in the spacetime of a charged spherical
shell. Our analysis is performed in the context of quantum field theory in
curved spacetimes. This paper completes previous analyses which considered the
exponential enhancement of vacuum fluctuations in the spacetime of massive
shells.
| [
{
"created": "Mon, 7 Dec 2015 17:06:29 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Feb 2016 12:35:03 GMT",
"version": "v2"
}
] | 2016-02-24 | [
[
"Santiago",
"Jessica",
""
],
[
"Landulfo",
"Andre G. S.",
""
],
[
"Lima",
"William C. C.",
""
],
[
"Matsas",
"George E. A.",
""
],
[
"Mendes",
"Raissa F. P.",
""
],
[
"Vanzella",
"Daniel A. T.",
""
]
] | We investigate the stability of a free scalar field nonminimally coupled to gravity under linear perturbations in the spacetime of a charged spherical shell. Our analysis is performed in the context of quantum field theory in curved spacetimes. This paper completes previous analyses which considered the exponential enhancement of vacuum fluctuations in the spacetime of massive shells. |
gr-qc/9305009 | Herbert Balasin | Herbert Balasin, Herbert Nachbagauer | On the Distributional Nature of the Energy Momentum Tensor of a Black
Hole or What Curves the Schwarzschild Geometry ? | 12 pages, latex, TUW-93-12 | Phys. Lett. B315 (1993) 93-97 | 10.1088/0264-9381/10/11/010 | null | gr-qc | null | Using distributional techniques we calculate the energy--momentum tensor of
the Schwarzschild geometry. It turns out to be a well--defined
tensor--distribution concentrated on the $r=0$ region which is usually excluded
from space--time. This provides a physical interpretation for the curvature of
this geometry.
| [
{
"created": "Mon, 10 May 1993 12:43:12 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Balasin",
"Herbert",
""
],
[
"Nachbagauer",
"Herbert",
""
]
] | Using distributional techniques we calculate the energy--momentum tensor of the Schwarzschild geometry. It turns out to be a well--defined tensor--distribution concentrated on the $r=0$ region which is usually excluded from space--time. This provides a physical interpretation for the curvature of this geometry. |
1606.06867 | A. N. Ivanov | A. N. Ivanov, G. Cronenberg, R. H\"ollwieser, T. Jenke, M. Pitschmann,
M. Wellenzohn, H. Abele | Exact Solution for Chameleon Field, Self-Coupled Through the
Ratra-Peebles Potential with n = 1 and Confined Between Two Parallel Plates | 1 figure, 8 pages, the incorrect value rho = 1.188x10^(-8)g/cm^3 is
replaced by the correct one rho =1.188x10^(-10)g/cm^3 | Phys. Rev. D 94, 085005 (2016) | 10.1103/PhysRevD.94.085005 | null | gr-qc astro-ph.CO hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the chameleon field profile, confined between two parallel
plates, filled with air at pressure $P = 10^{-4}\,{\rm mbar}$ and room
temperature and separated by the distance $L$, in the chameleon field theory
with Ratra--Peebles self--interaction potential with index $n = 1$. We give the
exact analytical solution in terms of Jacobian elliptic functions, depending on
the mass density of the ambient matter. The obtained analytical solution can be
used in qBounce experiments, measuring transition frequencies between quantum
gravitational states of ultracold neutrons and also for the calculation of the
chameleon field induced Casimir force for the CANNEX experiment. We show that
the chameleon--matter interactions with coupling constants $\beta \le 10^4$ can
be probed by qBounce experiments with sensitivities $\Delta E \le
10^{-18}\,{\rm eV}$. At $L = 30.1\,{\rm \mu m}$ we reproduce the result $\beta
< 5.8\times 10^8$, obtained by Jenke {\it et al.} Phys. Rev. Lett. {\bf 112},
151105 (2014)) at sensitivity $\Delta E \sim 10^{-14}\,{\rm eV}$. In the
vicinity of one of the plates our solution coincides with the solution,
obtained by Brax and Pignol (Phys. Rev. Lett. {\bf 107}, 111301 (2011)) (see
also Ivanov {\it et al.} Phys. Rev. D {\bf 87}, 105013 (2013)) above a plate at
zero density of the ambient matter.
| [
{
"created": "Wed, 22 Jun 2016 09:51:15 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jul 2016 18:12:46 GMT",
"version": "v2"
},
{
"created": "Sun, 28 Aug 2016 06:17:26 GMT",
"version": "v3"
}
] | 2016-10-12 | [
[
"Ivanov",
"A. N.",
""
],
[
"Cronenberg",
"G.",
""
],
[
"Höllwieser",
"R.",
""
],
[
"Jenke",
"T.",
""
],
[
"Pitschmann",
"M.",
""
],
[
"Wellenzohn",
"M.",
""
],
[
"Abele",
"H.",
""
]
] | We calculate the chameleon field profile, confined between two parallel plates, filled with air at pressure $P = 10^{-4}\,{\rm mbar}$ and room temperature and separated by the distance $L$, in the chameleon field theory with Ratra--Peebles self--interaction potential with index $n = 1$. We give the exact analytical solution in terms of Jacobian elliptic functions, depending on the mass density of the ambient matter. The obtained analytical solution can be used in qBounce experiments, measuring transition frequencies between quantum gravitational states of ultracold neutrons and also for the calculation of the chameleon field induced Casimir force for the CANNEX experiment. We show that the chameleon--matter interactions with coupling constants $\beta \le 10^4$ can be probed by qBounce experiments with sensitivities $\Delta E \le 10^{-18}\,{\rm eV}$. At $L = 30.1\,{\rm \mu m}$ we reproduce the result $\beta < 5.8\times 10^8$, obtained by Jenke {\it et al.} Phys. Rev. Lett. {\bf 112}, 151105 (2014)) at sensitivity $\Delta E \sim 10^{-14}\,{\rm eV}$. In the vicinity of one of the plates our solution coincides with the solution, obtained by Brax and Pignol (Phys. Rev. Lett. {\bf 107}, 111301 (2011)) (see also Ivanov {\it et al.} Phys. Rev. D {\bf 87}, 105013 (2013)) above a plate at zero density of the ambient matter. |
1902.11051 | Georgios Lukes-Gerakopoulos | Georgios Lukes-Gerakopoulos, Giovanni Acquaviva and Charalampos
Markakis | Probing Dark Energy through Perfect Fluid Thermodynamics | 10 pages, 1 figure, to appear in the RAGtime20 conference proceedings
(Opava, October 15-19 2018) | Proceedings of RAGtime 20-22, 15-19 Oct., 16-20 Sept., 19-23 Oct.,
2018-2020, Opava, Czech Republic Z. Stuchlik, G. Torook and V. Karas,
editors, Silesian University in Opava, 2020, pp. 375-382 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate that the thermodynamics of a perfect fluid describing baryonic
matter can, in certain limits, lead to an equation of state similar to that of
dark energy. We keep the cosmic fluid equation of state quite general by just
demanding that the speed of sound is positive and less than the speed of light.
In this framework, we discuss some propositions by looking at the asymptotic
behavior of the cosmic fluid.
| [
{
"created": "Thu, 28 Feb 2019 12:34:55 GMT",
"version": "v1"
}
] | 2021-01-26 | [
[
"Lukes-Gerakopoulos",
"Georgios",
""
],
[
"Acquaviva",
"Giovanni",
""
],
[
"Markakis",
"Charalampos",
""
]
] | We demonstrate that the thermodynamics of a perfect fluid describing baryonic matter can, in certain limits, lead to an equation of state similar to that of dark energy. We keep the cosmic fluid equation of state quite general by just demanding that the speed of sound is positive and less than the speed of light. In this framework, we discuss some propositions by looking at the asymptotic behavior of the cosmic fluid. |
2308.02850 | Roman Konoplya | R. A. Konoplya | Hawking radiation of renormalization group improved regular black holes | 17 pages, 10 captioned figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a renormalization group approach based on the idea that the
primary contribution to the Schwarzschild-like black hole spacetime arises from
the value of the gravitational coupling. The latter depends on the distance
from the origin and approaches its classical value in the far zone. However, at
some stage, this approach introduces an arbitrariness in choosing an
identification parameter. There are three approaches to the identification: the
modified proper length (the Bonanno-Reuter metric), the Kretschmann scalar (the
Hayward metric), and an iterative, and, in a sense, coordinate-independent
procedure (Dymnikova solution). Using the WKB method, we calculated grey-body
factors for the Standard Model massless test fields and their corresponding
energy emission rates. For all of these solutions, we found that the intensity
of Hawking radiation of massless fields is significantly suppressed by several
or more orders once the quantum correction is taken into consideration. This
indicates that the effect of suppression of the Hawking radiation may be
appropriate to the quantum corrected black holes in asymptotically safe gravity
in general and is independent on the particular choice of the identification
parameter.
| [
{
"created": "Sat, 5 Aug 2023 11:35:35 GMT",
"version": "v1"
}
] | 2023-08-08 | [
[
"Konoplya",
"R. A.",
""
]
] | We consider a renormalization group approach based on the idea that the primary contribution to the Schwarzschild-like black hole spacetime arises from the value of the gravitational coupling. The latter depends on the distance from the origin and approaches its classical value in the far zone. However, at some stage, this approach introduces an arbitrariness in choosing an identification parameter. There are three approaches to the identification: the modified proper length (the Bonanno-Reuter metric), the Kretschmann scalar (the Hayward metric), and an iterative, and, in a sense, coordinate-independent procedure (Dymnikova solution). Using the WKB method, we calculated grey-body factors for the Standard Model massless test fields and their corresponding energy emission rates. For all of these solutions, we found that the intensity of Hawking radiation of massless fields is significantly suppressed by several or more orders once the quantum correction is taken into consideration. This indicates that the effect of suppression of the Hawking radiation may be appropriate to the quantum corrected black holes in asymptotically safe gravity in general and is independent on the particular choice of the identification parameter. |
2405.09702 | Francisco Lobo | Jos\'e Tarciso S. S. Junior, Francisco S. N. Lobo, Manuel E. Rodrigues | Black bounces in conformal Killing gravity | 13 pages, 12 figures. Accepted for publication in EPJC | Eur. Phys. J. C 84, 557 (2024) | 10.1140/epjc/s10052-024-12922-3 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we analyse black bounce solutions in the recently proposed
``Conformal Killing gravity'' (CKG), by coupling the theory to nonlinear
electrodynamics (NLED) and scalar fields. The original motivation of the theory
was essentially to fulfil specific criteria that are absent in existing
gravitational theories, namely, to obtain the cosmological constant as an
integration constant, derive the energy-momentum conservation law as a
consequence of the gravitational field equations, rather than assuming it, and
not necessarily considering conformally flat metrics as vacuum solutions. In
this work, we extend the static and spherically symmetric solutions obtained in
the literature, and explore the possibility of black bounces in CKG, coupled to
NLED and scalar fields. We find novel NLED Lagrangian densities and scalar
potentials, and extend the class of black bounce solutions found in the
literature. Furthermore, within black bounce geometries, we find
generalizations of the Bardeen-type and Simpson-Visser geometries and explore
the regularity conditions of the solutions.
| [
{
"created": "Wed, 15 May 2024 20:58:28 GMT",
"version": "v1"
}
] | 2024-06-05 | [
[
"Junior",
"José Tarciso S. S.",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Rodrigues",
"Manuel E.",
""
]
] | In this work, we analyse black bounce solutions in the recently proposed ``Conformal Killing gravity'' (CKG), by coupling the theory to nonlinear electrodynamics (NLED) and scalar fields. The original motivation of the theory was essentially to fulfil specific criteria that are absent in existing gravitational theories, namely, to obtain the cosmological constant as an integration constant, derive the energy-momentum conservation law as a consequence of the gravitational field equations, rather than assuming it, and not necessarily considering conformally flat metrics as vacuum solutions. In this work, we extend the static and spherically symmetric solutions obtained in the literature, and explore the possibility of black bounces in CKG, coupled to NLED and scalar fields. We find novel NLED Lagrangian densities and scalar potentials, and extend the class of black bounce solutions found in the literature. Furthermore, within black bounce geometries, we find generalizations of the Bardeen-type and Simpson-Visser geometries and explore the regularity conditions of the solutions. |
1301.3772 | Ulrich Sperhake | Ulrich Sperhake | Numerical relativity in higher dimensions | 24 pages, Rapporteur article for the 13th Marcel Grossmann Meeting,
submitted to IJMPD | null | 10.1142/S021827181330005X | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an overview of recent developments in numerical relativity studies
of higher dimensional spacetimes with a focus on time evolutions of black-hole
systems. After a brief review of the numerical techniques employed for these
studies, we summarize results grouped into the following three areas: (i)
Numerical studies of fundamental properties of black holes, (ii) Applications
of black-hole collisions to the modeling of Trans-Planckian scattering, (iii)
Numerical studies of asymptotically anti-de Sitter spacetimes in the context of
the gauge-gravity duality.
| [
{
"created": "Wed, 16 Jan 2013 18:03:22 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Jan 2013 09:21:13 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Sperhake",
"Ulrich",
""
]
] | We present an overview of recent developments in numerical relativity studies of higher dimensional spacetimes with a focus on time evolutions of black-hole systems. After a brief review of the numerical techniques employed for these studies, we summarize results grouped into the following three areas: (i) Numerical studies of fundamental properties of black holes, (ii) Applications of black-hole collisions to the modeling of Trans-Planckian scattering, (iii) Numerical studies of asymptotically anti-de Sitter spacetimes in the context of the gauge-gravity duality. |
1311.4255 | Jozef Skakala | Jozef Skakala (IISER-TVM), S. Shankaranarayanan (IISER-TVM) | Horizon spectroscopy in and beyond general relativity | 10 pages, v2: final version accepted for publication in Phys.Rev.D,
(v2 with respect to v1: one reference and two sentences added) | Phys. Rev. D 89, 044019 (2014) | 10.1103/PhysRevD.89.044019 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we generalize the results for the entropy spectra typically
derived for black holes in general relativity to a generic horizon within the
spherically symmetric (asymptotically flat and non-flat) space-times of more
general theories of gravity. We use all the standard --- Bekenstein's universal
lower bound on the entropy transition, the highly damped quasi-normal modes and
reduced phase-space quantization --- approaches to derive the spectra. In
particular, the three approaches show that the Bekenstein-like spectra for the
horizon entropy is a robust result. Our results confirm the suggestion made
relatively recently by an independent fourth argument by Kothawala et al [1].
| [
{
"created": "Mon, 18 Nov 2013 03:38:38 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Dec 2013 07:53:21 GMT",
"version": "v2"
}
] | 2014-02-19 | [
[
"Skakala",
"Jozef",
"",
"IISER-TVM"
],
[
"Shankaranarayanan",
"S.",
"",
"IISER-TVM"
]
] | In this work we generalize the results for the entropy spectra typically derived for black holes in general relativity to a generic horizon within the spherically symmetric (asymptotically flat and non-flat) space-times of more general theories of gravity. We use all the standard --- Bekenstein's universal lower bound on the entropy transition, the highly damped quasi-normal modes and reduced phase-space quantization --- approaches to derive the spectra. In particular, the three approaches show that the Bekenstein-like spectra for the horizon entropy is a robust result. Our results confirm the suggestion made relatively recently by an independent fourth argument by Kothawala et al [1]. |
gr-qc/9612004 | Barvinski | A.O. Barvinsky, A.Yu. Kamenshchik and I.V. Mishakov | Quantum origin of the early inflationary Universe | 43 pages, LaTeX, figures not included | Nucl.Phys.B491:387-426,1997 | 10.1016/S0550-3213(97)00118-1 | null | gr-qc | null | We give a detailed presentation of a recently proposed mechanism of
generating the energy scale of inflation by loop effects in quantum cosmology.
We discuss the quantum origin of the early inflationary Universe from the
no-boundary and tunneling quantum states and present a universal effective
action algorithm for the distribution function of chaotic inflationary
cosmologies in both of these states. The energy scale of inflation is
calculated by finding a sharp probability peak in this distribution function
for a tunneling model driven by the inflaton field with large negative constant
$\xi$ of non-minimal interaction. The sub-Planckian parameters of this peak
(the mean value of the corresponding Hubble constant $H\simeq 10^{-5}m_P$, its
quantum width $\Delta H/H\simeq 10^{-5}$ and the number of inflationary
e-foldings $N\geq 60$) are found to be in good correspondence with the
observational status of inflation theory, provided the coupling constants of
the theory are constrained by a condition which is likely to be enforced by the
(quasi) supersymmetric nature of the sub-Planckian particle physics model.
| [
{
"created": "Mon, 2 Dec 1996 10:09:14 GMT",
"version": "v1"
}
] | 2011-08-17 | [
[
"Barvinsky",
"A. O.",
""
],
[
"Kamenshchik",
"A. Yu.",
""
],
[
"Mishakov",
"I. V.",
""
]
] | We give a detailed presentation of a recently proposed mechanism of generating the energy scale of inflation by loop effects in quantum cosmology. We discuss the quantum origin of the early inflationary Universe from the no-boundary and tunneling quantum states and present a universal effective action algorithm for the distribution function of chaotic inflationary cosmologies in both of these states. The energy scale of inflation is calculated by finding a sharp probability peak in this distribution function for a tunneling model driven by the inflaton field with large negative constant $\xi$ of non-minimal interaction. The sub-Planckian parameters of this peak (the mean value of the corresponding Hubble constant $H\simeq 10^{-5}m_P$, its quantum width $\Delta H/H\simeq 10^{-5}$ and the number of inflationary e-foldings $N\geq 60$) are found to be in good correspondence with the observational status of inflation theory, provided the coupling constants of the theory are constrained by a condition which is likely to be enforced by the (quasi) supersymmetric nature of the sub-Planckian particle physics model. |
gr-qc/0403069 | Hiroyuki Nakano | Hiroyuki Nakano, Hirotaka Takahashi, Hideyuki Tagoshi, Misao Sasaki | An Improved Search Method for Gravitational Ringing of Black Holes | 19 pages, 9 figures | Prog.Theor.Phys.111:781-805,2004 | 10.1143/PTP.111.781 | OCU-PHYS-209, AP-GR-14, OU-TAP-228, YITP-04-14 | gr-qc astro-ph | null | A black hole has characteristic quasi-normal modes that will be excited when
it is formed or when the geometry is perturbed. The state of a black hole when
the quasi-normal modes are excited is called the gravitational ringing, and
detections of it will be a direct confirmation of the existence of black holes.
To detect it, a method based on matched filtering needs to be developed.
Generically, matched filtering requires a large number of templates, because
one has to ensure a proper match of a real gravitational wave with one of
template waveforms to keep the detection efficiency as high as possible. On the
other hand, the number of templates must be kept as small as possible under
limited computational costs. In our previous paper, assuming that the
gravitational ringing is dominated by the least-damped (fundamental) mode with
the least imaginary part of frequency, we constructed an efficient method for
tiling the template space. However, the dependence of the template space metric
on the initial phase of a wave was not taken into account. This dependence
arises because of an unavoidable mismatch between the parameters of a signal
waveform and those given discretely in the template space. In this paper, we
properly take this dependence into account and present an improved, efficient
search method for gravitational ringing of black holes.
| [
{
"created": "Tue, 16 Mar 2004 07:06:46 GMT",
"version": "v1"
}
] | 2009-10-09 | [
[
"Nakano",
"Hiroyuki",
""
],
[
"Takahashi",
"Hirotaka",
""
],
[
"Tagoshi",
"Hideyuki",
""
],
[
"Sasaki",
"Misao",
""
]
] | A black hole has characteristic quasi-normal modes that will be excited when it is formed or when the geometry is perturbed. The state of a black hole when the quasi-normal modes are excited is called the gravitational ringing, and detections of it will be a direct confirmation of the existence of black holes. To detect it, a method based on matched filtering needs to be developed. Generically, matched filtering requires a large number of templates, because one has to ensure a proper match of a real gravitational wave with one of template waveforms to keep the detection efficiency as high as possible. On the other hand, the number of templates must be kept as small as possible under limited computational costs. In our previous paper, assuming that the gravitational ringing is dominated by the least-damped (fundamental) mode with the least imaginary part of frequency, we constructed an efficient method for tiling the template space. However, the dependence of the template space metric on the initial phase of a wave was not taken into account. This dependence arises because of an unavoidable mismatch between the parameters of a signal waveform and those given discretely in the template space. In this paper, we properly take this dependence into account and present an improved, efficient search method for gravitational ringing of black holes. |
2007.06601 | Laur J\"arv | Jibitesh Dutta, Laur Jarv, Wompherdeiki Khyllep, Sulev Tokke | From inflation to dark energy in scalar-tensor cosmology | 25 pages, 22 plots | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The methods of dynamical systems have found wide applications in cosmology,
with focus either upon inflation or upon the passage into dark energy era. In
this paper, we endeavor to capture the whole history of the universe into a
dynamical system by considering generic scalar tensor gravity with radiation
and dust matter fluids in flat Friedmann-Lemaitre-Robertson-Walker spacetime.
We construct the dynamical variables in such a way that the main stages of the
cosmic evolution, viz. inflation, radiation domination, matter domination, and
dark energy domination can be represented by the respective fixed points in the
phase space. As the evolution of solutions is ruled by the sequence of these
fixed points with appropriate properties, we can determine the conditions that
the scalar potential and nonminimal coupling must satisfy for the model to
deliver viable cosmic history in a generic manner. We illustrate the
construction by a scalar field with quartic potential, with and without
quadratic nonminimal coupling to curvature.
| [
{
"created": "Mon, 13 Jul 2020 18:06:53 GMT",
"version": "v1"
}
] | 2020-07-15 | [
[
"Dutta",
"Jibitesh",
""
],
[
"Jarv",
"Laur",
""
],
[
"Khyllep",
"Wompherdeiki",
""
],
[
"Tokke",
"Sulev",
""
]
] | The methods of dynamical systems have found wide applications in cosmology, with focus either upon inflation or upon the passage into dark energy era. In this paper, we endeavor to capture the whole history of the universe into a dynamical system by considering generic scalar tensor gravity with radiation and dust matter fluids in flat Friedmann-Lemaitre-Robertson-Walker spacetime. We construct the dynamical variables in such a way that the main stages of the cosmic evolution, viz. inflation, radiation domination, matter domination, and dark energy domination can be represented by the respective fixed points in the phase space. As the evolution of solutions is ruled by the sequence of these fixed points with appropriate properties, we can determine the conditions that the scalar potential and nonminimal coupling must satisfy for the model to deliver viable cosmic history in a generic manner. We illustrate the construction by a scalar field with quartic potential, with and without quadratic nonminimal coupling to curvature. |
1407.6992 | Justin Vines | Justin Vines | Geodesic deviation at higher orders via covariant bitensors | 15 pages, 4 figures | null | 10.1007/s10714-015-1901-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review a simple but instructive application of the formalism of covariant
bitensors, to use a deviation vector field along a fiducial geodesic to
describe a neighboring worldline, in an exact and manifestly covariant manner,
via the exponential map. Requiring the neighboring worldline to be a geodesic
leads to the usual linear geodesic deviation equation for the deviation vector,
plus corrections at higher order in the deviation and relative velocity. We
show how these corrections can be efficiently computed to arbitrary orders via
covariant bitensor expansions, deriving a form of the geodesic deviation
equation valid to all orders, and producing its explicit expanded form through
fourth order. We also discuss the generalized Jacobi equation, action
principles for the higher-order geodesic deviation equations, results useful
for describing accelerated neighboring worldlines, and the formal general
solution to the geodesic deviation equation through second order.
| [
{
"created": "Fri, 25 Jul 2014 18:06:53 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Vines",
"Justin",
""
]
] | We review a simple but instructive application of the formalism of covariant bitensors, to use a deviation vector field along a fiducial geodesic to describe a neighboring worldline, in an exact and manifestly covariant manner, via the exponential map. Requiring the neighboring worldline to be a geodesic leads to the usual linear geodesic deviation equation for the deviation vector, plus corrections at higher order in the deviation and relative velocity. We show how these corrections can be efficiently computed to arbitrary orders via covariant bitensor expansions, deriving a form of the geodesic deviation equation valid to all orders, and producing its explicit expanded form through fourth order. We also discuss the generalized Jacobi equation, action principles for the higher-order geodesic deviation equations, results useful for describing accelerated neighboring worldlines, and the formal general solution to the geodesic deviation equation through second order. |
1705.03867 | Diego S\'aez-G\'omez | Alvaro de la Cruz-Dombriz (Cape Town U.), Gabriel Farrugia (U. of
Malta), Jackson Levi Said (U. of Malta) and Diego Saez-Chillon Gomez
(Institute of Space Sciences, CSIC/IEEC) | Cosmological reconstructed solutions in extended teleparallel gravity
theories with a teleparallel Gauss-Bonnet term | 40 pages, 3 tables, 2 appendices. For a quick view: see Tables 1,2,3.
Extended analysis and conclusions. Version published in CQG | Class. Quantum Grav. 34, 235011 (2017) | 10.1088/1361-6382/aa93c8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of extended Teleparallel gravity theories with a 3+1
dimensions Gauss-Bonnet analog term, we address the possibility of these
theories reproducing several well-known cosmological solutions. In particular
when applied to a Friedmann-Lema\^itre-Robertson-Walker geometry in
four-dimensional spacetime with standard fluids exclusively. We study different
types of gravitational Lagrangians and reconstruct solutions provided by
analytical expressions for either the cosmological scale factor or the Hubble
parameter. We also show that it is possible to find Lagrangians of this type
without a cosmological constant such that the behaviour of the LCDM model is
precisely mimicked. The new Lagrangians may also lead to other phenomenological
consequences opening up the possibility for new theories to compete directly
with other extensions of General Relativity.
| [
{
"created": "Wed, 10 May 2017 17:34:37 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Nov 2017 16:40:59 GMT",
"version": "v2"
}
] | 2017-12-06 | [
[
"de la Cruz-Dombriz",
"Alvaro",
"",
"Cape Town U."
],
[
"Farrugia",
"Gabriel",
"",
"U. of\n Malta"
],
[
"Said",
"Jackson Levi",
"",
"U. of Malta"
],
[
"Gomez",
"Diego Saez-Chillon",
"",
"Institute of Space Sciences, CSIC/IEEC"
]
] | In the context of extended Teleparallel gravity theories with a 3+1 dimensions Gauss-Bonnet analog term, we address the possibility of these theories reproducing several well-known cosmological solutions. In particular when applied to a Friedmann-Lema\^itre-Robertson-Walker geometry in four-dimensional spacetime with standard fluids exclusively. We study different types of gravitational Lagrangians and reconstruct solutions provided by analytical expressions for either the cosmological scale factor or the Hubble parameter. We also show that it is possible to find Lagrangians of this type without a cosmological constant such that the behaviour of the LCDM model is precisely mimicked. The new Lagrangians may also lead to other phenomenological consequences opening up the possibility for new theories to compete directly with other extensions of General Relativity. |
2105.00876 | Pardyumn Kumar Sahoo | Raja Solanki, S. K. J. Pacif, Abhishek Parida, P.K. Sahoo | Cosmic acceleration with bulk viscosity in modified $f(Q)$ gravity | Physics of Dark Universe published version | Physics of the Dark Universe, 32, 100820 (2021) | 10.1016/j.dark.2021.100820 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this article, we have investigated the role of bulk viscosity to study the
accelerated expansion of the universe in the framework of modified $f(Q)$
gravity. The gravitational action in this modified gravity theory has the form
$f(Q)$, where $Q$ denote the non-metricity scalar. In the present manuscript,
we have considered a bulk viscous matter-dominated cosmological model with the
bulk viscosity coefficient of the form $\xi =\xi _{0}+\xi _{1}H+\xi _{2}\left(
\frac{\dot{H}}{H}+H\right) $ which is proportional to the velocity and
acceleration of the expanding universe. Two sets of limiting conditions on the
bulk viscous parameters $\xi _{0},$ $\xi _{1},$ $% \xi _{2}$ and model
parameter $\alpha $ arose here out of which one condition favours the present
scenario of cosmic acceleration with a phase transition and corresponds to the
universe with a Big Bang origin. Moreover, we have discussed the cosmological
behaviour of some geometrical parameters. Then, we have obtained the best
fitting values of the model parameters $\xi _{0},$ $\xi _{1},$ $\xi _{2}$ and
$\alpha $ by constraining our model with updated Hubble datasets consisting of
$57$ data points and recently released Pantheon datasets consisting of $1048$
data points which show that our obtained model has good compatibility with
observations. Further, we have also included the Baryon Acoustic Oscillation
(BAO) datasets of six data points with the Hubble \& Pantheon datasets and
obtained slightly different values of the model parameters. Finally, we have
analyzed our model with the statefinder diagnostic analysis and found some
interesting results and are discussed in details.
| [
{
"created": "Fri, 30 Apr 2021 05:24:01 GMT",
"version": "v1"
}
] | 2022-07-20 | [
[
"Solanki",
"Raja",
""
],
[
"Pacif",
"S. K. J.",
""
],
[
"Parida",
"Abhishek",
""
],
[
"Sahoo",
"P. K.",
""
]
] | In this article, we have investigated the role of bulk viscosity to study the accelerated expansion of the universe in the framework of modified $f(Q)$ gravity. The gravitational action in this modified gravity theory has the form $f(Q)$, where $Q$ denote the non-metricity scalar. In the present manuscript, we have considered a bulk viscous matter-dominated cosmological model with the bulk viscosity coefficient of the form $\xi =\xi _{0}+\xi _{1}H+\xi _{2}\left( \frac{\dot{H}}{H}+H\right) $ which is proportional to the velocity and acceleration of the expanding universe. Two sets of limiting conditions on the bulk viscous parameters $\xi _{0},$ $\xi _{1},$ $% \xi _{2}$ and model parameter $\alpha $ arose here out of which one condition favours the present scenario of cosmic acceleration with a phase transition and corresponds to the universe with a Big Bang origin. Moreover, we have discussed the cosmological behaviour of some geometrical parameters. Then, we have obtained the best fitting values of the model parameters $\xi _{0},$ $\xi _{1},$ $\xi _{2}$ and $\alpha $ by constraining our model with updated Hubble datasets consisting of $57$ data points and recently released Pantheon datasets consisting of $1048$ data points which show that our obtained model has good compatibility with observations. Further, we have also included the Baryon Acoustic Oscillation (BAO) datasets of six data points with the Hubble \& Pantheon datasets and obtained slightly different values of the model parameters. Finally, we have analyzed our model with the statefinder diagnostic analysis and found some interesting results and are discussed in details. |
gr-qc/0506072 | Vladimir Khatsymovsky | V.M. Khatsymovsky | On the area expectation values in area tensor Regge calculus in the
Lorentzian domain | LaTeX, 7 pages, introduction and discussion given in more detail,
references added | Phys.Lett.B633:653-656,2006 | 10.1016/j.physletb.2005.12.033 | null | gr-qc | null | Wick rotation in area tensor Regge calculus is considered. The heuristical
expectation is confirmed that the Lorentzian quantum measure on a spacelike
area should coincide with the Euclidean measure at the same argument. The
consequence is validity of probabilistic interpretation of the Lorentzian
measure as well (on the real, i.e. spacelike areas).
| [
{
"created": "Sun, 12 Jun 2005 10:12:48 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Dec 2005 12:20:44 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Khatsymovsky",
"V. M.",
""
]
] | Wick rotation in area tensor Regge calculus is considered. The heuristical expectation is confirmed that the Lorentzian quantum measure on a spacelike area should coincide with the Euclidean measure at the same argument. The consequence is validity of probabilistic interpretation of the Lorentzian measure as well (on the real, i.e. spacelike areas). |
gr-qc/9608013 | null | Y.B.Grinkevich ( Omsk State University, Russia ) | Synthetic Differential Geometry: A Way to Intuitionistic Models of
General Relativity in Toposes | 19 pages | null | null | null | gr-qc | null | W.Lawvere suggested a approach to differential geometry and to others
mathematical disciplines closed to physics, which allows to give definitions of
derivatives, tangent vectors and tangent bundles without passages to the
limits. This approach is based on a idea of consideration of all settings not
in sets but in some cartesian closed category E, particular in some elementary
topos.
The synthetic differential geometry (SDG) is the theory developed by A.Kock
in a context of Lawvere's ideas. In a base of the theory is an assumption of
that a geometric line is not a filed of real numbers, but a some nondegenerate
commutative ring R of a line type in E.
In this work we shall show that SDG allows to develop a Riemannian geometry
and write the Einstein's equations of a field on pseudo-Riemannian formal
manifold. This give a way for constructing a intuitionistic models of general
relativity in suitable toposes.
| [
{
"created": "Tue, 6 Aug 1996 15:35:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Grinkevich",
"Y. B.",
"",
"Omsk State University, Russia"
]
] | W.Lawvere suggested a approach to differential geometry and to others mathematical disciplines closed to physics, which allows to give definitions of derivatives, tangent vectors and tangent bundles without passages to the limits. This approach is based on a idea of consideration of all settings not in sets but in some cartesian closed category E, particular in some elementary topos. The synthetic differential geometry (SDG) is the theory developed by A.Kock in a context of Lawvere's ideas. In a base of the theory is an assumption of that a geometric line is not a filed of real numbers, but a some nondegenerate commutative ring R of a line type in E. In this work we shall show that SDG allows to develop a Riemannian geometry and write the Einstein's equations of a field on pseudo-Riemannian formal manifold. This give a way for constructing a intuitionistic models of general relativity in suitable toposes. |
2004.14935 | Rittick Roy | Saraswati Devi, Rittick Roy and Sayan Chakrabarti | Quasinormal modes and greybody factors of the novel four dimensional
Gauss-Bonnet black holes in asymptotically de Sitter space time: Scalar,
Electromagnetic and Dirac perturbations | New tables added summarizing primary results, version published in
EPJC | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find the low lying quasinormal mode frequencies of the recently proposed
novel four dimensional Gauss-Bonnet de Sitter black holes for scalar,
electromagnetic and Dirac field perturbations using the third order WKB
approximation as well as Pad\'{e} approximation, as an improvement over WKB. We
figure out the effect of the Gauss-Bonnet coupling $\alpha$ and the
cosmological constant $\Lambda$ on the real and imaginary parts of the QNM
frequencies. We also study the greybody factors and eikonal limits in the above
background for all three different types of perturbations.
| [
{
"created": "Thu, 30 Apr 2020 16:38:00 GMT",
"version": "v1"
},
{
"created": "Sun, 23 Aug 2020 16:08:29 GMT",
"version": "v2"
}
] | 2020-08-25 | [
[
"Devi",
"Saraswati",
""
],
[
"Roy",
"Rittick",
""
],
[
"Chakrabarti",
"Sayan",
""
]
] | We find the low lying quasinormal mode frequencies of the recently proposed novel four dimensional Gauss-Bonnet de Sitter black holes for scalar, electromagnetic and Dirac field perturbations using the third order WKB approximation as well as Pad\'{e} approximation, as an improvement over WKB. We figure out the effect of the Gauss-Bonnet coupling $\alpha$ and the cosmological constant $\Lambda$ on the real and imaginary parts of the QNM frequencies. We also study the greybody factors and eikonal limits in the above background for all three different types of perturbations. |
gr-qc/9505025 | Serge Droz | C. Barrabes, B. Boisseau and W. Israel | Orbits, forces and accretion dynamics near spinning black holes | 14 pages, latex, no figures | null | 10.1093/mnras/276.2.432 | null | gr-qc astro-ph | null | We analyze the relativistic dynamical properties of Keplerian and
non-Keplerian circular orbits in a general axisymmetric and stationary
gravitational field, and discuss the implications for the stability of co- and
counter-rotating accretion disks and tori surrounding a spinning black hole.
Close to the horizon there are orbital peculiarities which can seem
counterintuitive, but are elucidated by formulating the dynamics in terms of
the orbital velocity actually measured by a local, zero-angular-momentum
observer.
| [
{
"created": "Tue, 16 May 1995 20:47:28 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Barrabes",
"C.",
""
],
[
"Boisseau",
"B.",
""
],
[
"Israel",
"W.",
""
]
] | We analyze the relativistic dynamical properties of Keplerian and non-Keplerian circular orbits in a general axisymmetric and stationary gravitational field, and discuss the implications for the stability of co- and counter-rotating accretion disks and tori surrounding a spinning black hole. Close to the horizon there are orbital peculiarities which can seem counterintuitive, but are elucidated by formulating the dynamics in terms of the orbital velocity actually measured by a local, zero-angular-momentum observer. |
1706.07854 | Dejan Stojkovic | De-Chang Dai, Dejan Stojkovic | A note on a covariant version of Verlinde's emergent gravity | accepted for publication in Phys. Rev. D | Phys. Rev. D 96, 108501 (2017) | 10.1103/PhysRevD.96.108501 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following recent Verlinde's heuristic construction or emergent gravity,
Hossenfelder wrote down the Lagrangian capturing some aspects of this theory.
We point out that there is an error in calculations whose consequence is that a
cosmological de Sitter space solution is not recovered from this Lagrangian. We
correct this error in order to obtain the desired solution. We also show that
small perturbations around de Sitter space grow, which implies that this state
is not stable. However, the presence of matter and radiation might in principle
provide stability.
| [
{
"created": "Fri, 23 Jun 2017 20:37:27 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Oct 2017 19:44:34 GMT",
"version": "v2"
}
] | 2017-11-22 | [
[
"Dai",
"De-Chang",
""
],
[
"Stojkovic",
"Dejan",
""
]
] | Following recent Verlinde's heuristic construction or emergent gravity, Hossenfelder wrote down the Lagrangian capturing some aspects of this theory. We point out that there is an error in calculations whose consequence is that a cosmological de Sitter space solution is not recovered from this Lagrangian. We correct this error in order to obtain the desired solution. We also show that small perturbations around de Sitter space grow, which implies that this state is not stable. However, the presence of matter and radiation might in principle provide stability. |
gr-qc/9405017 | Kenmoku | Masakatsu Kenmoku, Kaori Otsuki and Rieko Sakai | Gravitational Force by Point Particle in Static Einstein Universe | 10 pages, latex, NWU-4/94 | null | null | null | gr-qc | null | The gravitaional force produced by a point particle, like the sun, in the
background of the static Einstein universe is studied. Both the approximate
solution in the weak field limit and exact solution are obtained. The main
properties of the solution are {\it i}) near the point particle, the metric
approaches the Schwarzschild one and the radius of its singularity becomes
larger than that of the Schwarzschild singularity, {\it ii}) far from the point
particle, the metric approaches the static Einstein closed universe. The
maximum length of the equator of the universe becomes smaller than that of the
static Einstein universe due to the existence of the point particle. These
properties show the strong correlation betweem the particle and the universe.
| [
{
"created": "Mon, 9 May 1994 05:09:28 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kenmoku",
"Masakatsu",
""
],
[
"Otsuki",
"Kaori",
""
],
[
"Sakai",
"Rieko",
""
]
] | The gravitaional force produced by a point particle, like the sun, in the background of the static Einstein universe is studied. Both the approximate solution in the weak field limit and exact solution are obtained. The main properties of the solution are {\it i}) near the point particle, the metric approaches the Schwarzschild one and the radius of its singularity becomes larger than that of the Schwarzschild singularity, {\it ii}) far from the point particle, the metric approaches the static Einstein closed universe. The maximum length of the equator of the universe becomes smaller than that of the static Einstein universe due to the existence of the point particle. These properties show the strong correlation betweem the particle and the universe. |
gr-qc/0504102 | Muhammad Sharif | M. Sharif and Sehar Aziz | On Physical Properties of Cylindrically Symmetric Self-Similar Solutions | 16 pages, accepted for publication in Int. J. of Mod. Phys. A | Int.J.Mod.Phys. A20 (2005) 7579-7591 | 10.1142/S0217751X05023906 | null | gr-qc | null | This paper is devoted to discuss some of the features of self-similar
solutions of the first kind. We consider the cylindrically symmetric solutions
with different homotheties. We are interested in evaluating the quantities
acceleration, rotation, expansion, shear, shear invariant and expansion rate.
These kinematical quantities are discussed both in co-moving as well as in
non-co-moving coordinates (only in radial direction). Finally, we would discuss
the singularity feature of these solutions. It is expected that these
properties would help in exploring some interesting features of the
self-similar solutions.
| [
{
"created": "Thu, 21 Apr 2005 09:27:15 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Sharif",
"M.",
""
],
[
"Aziz",
"Sehar",
""
]
] | This paper is devoted to discuss some of the features of self-similar solutions of the first kind. We consider the cylindrically symmetric solutions with different homotheties. We are interested in evaluating the quantities acceleration, rotation, expansion, shear, shear invariant and expansion rate. These kinematical quantities are discussed both in co-moving as well as in non-co-moving coordinates (only in radial direction). Finally, we would discuss the singularity feature of these solutions. It is expected that these properties would help in exploring some interesting features of the self-similar solutions. |
2108.07101 | Paul Steinhardt | Anna Ijjas and Paul J. Steinhardt | Entropy, Black holes, and the New Cyclic Universe | v2: minor amendments | null | 10.1016/j.physletb.2021.136823 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We track the evolution of entropy and black holes in a cyclic universe that
undergoes repeated intervals of expansion followed by slow contraction and a
smooth (non-singular) bounce. In this kind of cyclic scenario, there is no big
crunch and no chaotic mixmaster behavior. We explain why the entropy following
each bounce is naturally partitioned into near-maximal entropy in the
matter-radiation sector and near-minimal in the gravitational sector,
satisfying the Weyl curvature conditions conjectured to be essential for a
cosmology consistent with observations. As a result, this kind of cyclic
universe can undergo an unbounded number of cycles in the past and/or the
future.
| [
{
"created": "Mon, 16 Aug 2021 14:12:36 GMT",
"version": "v1"
},
{
"created": "Fri, 6 May 2022 14:01:14 GMT",
"version": "v2"
}
] | 2022-05-09 | [
[
"Ijjas",
"Anna",
""
],
[
"Steinhardt",
"Paul J.",
""
]
] | We track the evolution of entropy and black holes in a cyclic universe that undergoes repeated intervals of expansion followed by slow contraction and a smooth (non-singular) bounce. In this kind of cyclic scenario, there is no big crunch and no chaotic mixmaster behavior. We explain why the entropy following each bounce is naturally partitioned into near-maximal entropy in the matter-radiation sector and near-minimal in the gravitational sector, satisfying the Weyl curvature conditions conjectured to be essential for a cosmology consistent with observations. As a result, this kind of cyclic universe can undergo an unbounded number of cycles in the past and/or the future. |
1002.2992 | Muhammad Sharif | M. Sharif and M. Jamil Amir | Kinematic Self-Similar Solutions of Locally Rotationally Symmetric
Spacetimes | 17 pages, accepted for publication Brazilian J. Physics | Brazilian J. Physics 40(2010)210-216 | 10.1590/S0103-97332010000200015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper contains locally rotationally symmetric kinematic self-similar
perfect fluid and dust solutions. We consider three families of metrics which
admit kinematic self-similar vectors of the first, second, zeroth and infinite
kinds, not only for the tilted fluid case but also for the parallel and
orthogonal cases. It is found that the orthogonal case gives contradiction both
in perfect fluid and dust cases for all the three metrics while the tilted case
reduces to the parallel case in both perfect fluid and dust cases for the
second metric. The remaining cases give self-similar solutions of different
kinds. We obtain a total of seventeen independent solutions out of which two
are vacuum. The third metric yields contradiction in all the cases.
| [
{
"created": "Tue, 16 Feb 2010 02:42:54 GMT",
"version": "v1"
}
] | 2015-05-18 | [
[
"Sharif",
"M.",
""
],
[
"Amir",
"M. Jamil",
""
]
] | This paper contains locally rotationally symmetric kinematic self-similar perfect fluid and dust solutions. We consider three families of metrics which admit kinematic self-similar vectors of the first, second, zeroth and infinite kinds, not only for the tilted fluid case but also for the parallel and orthogonal cases. It is found that the orthogonal case gives contradiction both in perfect fluid and dust cases for all the three metrics while the tilted case reduces to the parallel case in both perfect fluid and dust cases for the second metric. The remaining cases give self-similar solutions of different kinds. We obtain a total of seventeen independent solutions out of which two are vacuum. The third metric yields contradiction in all the cases. |
1906.06654 | P. A. Gonzalez | Ram\'on B\'ecar, P. A. Gonz\'alez, Eleftherios Papantonopoulos and
Yerko V\'asquez | Quasinormal modes of three-dimensional rotating Ho\v{r}ava AdS black
hole and the approach to thermal equilibrium | 17 pages, 14 figures. arXiv admin note: text overlap with
arXiv:hep-th/0112055 by other authors | null | 10.1140/epjc/s10052-020-8169-2 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the quasinormal modes (QNMs) of a massive scalar field in the
background of a rotating three-dimensional Ho\v{r}ava AdS black hole, and we
analyze the effect of the breaking of the Lorentz invariance on the QNMs.
Imposing on the horizon that there are only ingoing waves and at infinity the
Dirichlet boundary conditions and the Neumann boundary condition, we calculate
the oscillatory and the decay modes of the QNMs. We find that the propagation
of the scalar field is stable in this background and employing the holographic
principle we find the different times of the perturbed system to reach thermal
equilibrium for the various branches of solutions.
| [
{
"created": "Sun, 16 Jun 2019 06:55:18 GMT",
"version": "v1"
}
] | 2020-08-26 | [
[
"Bécar",
"Ramón",
""
],
[
"González",
"P. A.",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
],
[
"Vásquez",
"Yerko",
""
]
] | We compute the quasinormal modes (QNMs) of a massive scalar field in the background of a rotating three-dimensional Ho\v{r}ava AdS black hole, and we analyze the effect of the breaking of the Lorentz invariance on the QNMs. Imposing on the horizon that there are only ingoing waves and at infinity the Dirichlet boundary conditions and the Neumann boundary condition, we calculate the oscillatory and the decay modes of the QNMs. We find that the propagation of the scalar field is stable in this background and employing the holographic principle we find the different times of the perturbed system to reach thermal equilibrium for the various branches of solutions. |
1111.0814 | Hristu Culetu | Hristu Culetu | Hyperbolic motion generated by inversion | 4 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An inversion transformation applied to an inertial observer is used to
generate a nonstatic conformally flat geometry in spherical coordinates. A
static observer in the new geometry is uniformly accelerating with respect to
the inertial one and vice versa, but its acceleration $g$ undergoes the
transformation $g \rightarrow 1/b^{2}g$, where $b$ is a constant. A nongeodesic
congruence of a static observer has a scalar expansion which grows linearly
with time but the acceleration is proportional to $r$, as for the classical
rotation.
| [
{
"created": "Thu, 3 Nov 2011 12:38:47 GMT",
"version": "v1"
}
] | 2011-11-04 | [
[
"Culetu",
"Hristu",
""
]
] | An inversion transformation applied to an inertial observer is used to generate a nonstatic conformally flat geometry in spherical coordinates. A static observer in the new geometry is uniformly accelerating with respect to the inertial one and vice versa, but its acceleration $g$ undergoes the transformation $g \rightarrow 1/b^{2}g$, where $b$ is a constant. A nongeodesic congruence of a static observer has a scalar expansion which grows linearly with time but the acceleration is proportional to $r$, as for the classical rotation. |
1710.09205 | Arpita Mitra | Karan Fernandes, Arpita Mitra | Electrovacuum solutions in non-local gravity | 25 pages, 6 figures, new subsection and new references added | Phys. Rev. D 97, 105003 (2018) | 10.1103/PhysRevD.97.105003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the coupling of the electromagnetic field to a non-local gravity
theory comprising of the Einstein-Hilbert action in addition to a non-local
$R\, {\Box}^{-2} R$ term associated with a mass scale $m$. We demonstrate that
in the case of the minimally coupled electromagnetic field, real corrections
about the Reissner-Nordstr\"om background only exist between the inner Cauchy
horizon and the event horizon of the black hole. This motivates us to consider
the modified coupling of electromagnetism to this theory via the Kaluza ansatz.
The Kaluza reduction introduces non-local terms involving the electromagnetic
field to the pure gravitational non-local theory. An iterative approach is
provided to perturbatively solve the equations of motion to arbitrary order in
$m^2$ about any known solution of General Relativity. We derive the first-order
corrections and demonstrate that the higher order corrections are real and
perturbative about the external background of a Reissner-Nordstr\"om black
hole. We also discuss how the Kaluza reduced action, through the inclusion of
non-local electromagnetic fields, could also be relevant in quantum effects on
curved backgrounds with horizons.
| [
{
"created": "Wed, 25 Oct 2017 12:54:26 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Jan 2018 17:39:36 GMT",
"version": "v2"
}
] | 2018-05-09 | [
[
"Fernandes",
"Karan",
""
],
[
"Mitra",
"Arpita",
""
]
] | We consider the coupling of the electromagnetic field to a non-local gravity theory comprising of the Einstein-Hilbert action in addition to a non-local $R\, {\Box}^{-2} R$ term associated with a mass scale $m$. We demonstrate that in the case of the minimally coupled electromagnetic field, real corrections about the Reissner-Nordstr\"om background only exist between the inner Cauchy horizon and the event horizon of the black hole. This motivates us to consider the modified coupling of electromagnetism to this theory via the Kaluza ansatz. The Kaluza reduction introduces non-local terms involving the electromagnetic field to the pure gravitational non-local theory. An iterative approach is provided to perturbatively solve the equations of motion to arbitrary order in $m^2$ about any known solution of General Relativity. We derive the first-order corrections and demonstrate that the higher order corrections are real and perturbative about the external background of a Reissner-Nordstr\"om black hole. We also discuss how the Kaluza reduced action, through the inclusion of non-local electromagnetic fields, could also be relevant in quantum effects on curved backgrounds with horizons. |
2108.01409 | Umananda Dev Goswami | Dhruba Jyoti Gogoi and Umananda Dev Goswami | Cosmology with a new f(R) gravity model in Palatini formalism | 19 pages, 15 figures | IJMP D 31, 2250048 (2022) | 10.1142/S0218271822500481 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the most favourable extensions of General Relativity is the $f(R)$
gravity. $f(R)$ gravity in Palatini formalism can be a realistic alternative to
the dark energy problem. In this work we study a recently introduced dark
energy $f(R)$ gravity model along with two other models in cosmological
perspectives under the Palatini formalism. First, we study the cosmic expansion
history of these models with the help of the important cosmographic parameters,
such as the Hubble parameter, luminosity distance, effective equation of state
etc. This study shows that the new model behaves similarly with the other two
models as well as with the $\Lambda$CDM model in some respects in the early or
very early phases of the universe. It could predict the present accelerated
expansion of the universe somewhat differently from the other models with a
peculiar future history of the universe. Within a constrained range of
parameters all models show a good agreement with the Union2.1 luminosity
distance data. However, the new model shows a quite satisfactory agreement in
the whole range of its allowed parameters than that of the other two models. We
also obtain cosmological constraints on these models from the Observed Hubble
Data. Further, models have been tested by using $Om(z)$ test and statefinder
diagnostics. These diagnostics especially, the statefinder diagnostic shows
that the evolutionary differences between these models are distinct. The
evolutionary trajectories of the new model are completely different from the
other two models we have considered.
| [
{
"created": "Tue, 3 Aug 2021 10:52:59 GMT",
"version": "v1"
},
{
"created": "Thu, 19 May 2022 14:05:43 GMT",
"version": "v2"
}
] | 2022-05-20 | [
[
"Gogoi",
"Dhruba Jyoti",
""
],
[
"Goswami",
"Umananda Dev",
""
]
] | One of the most favourable extensions of General Relativity is the $f(R)$ gravity. $f(R)$ gravity in Palatini formalism can be a realistic alternative to the dark energy problem. In this work we study a recently introduced dark energy $f(R)$ gravity model along with two other models in cosmological perspectives under the Palatini formalism. First, we study the cosmic expansion history of these models with the help of the important cosmographic parameters, such as the Hubble parameter, luminosity distance, effective equation of state etc. This study shows that the new model behaves similarly with the other two models as well as with the $\Lambda$CDM model in some respects in the early or very early phases of the universe. It could predict the present accelerated expansion of the universe somewhat differently from the other models with a peculiar future history of the universe. Within a constrained range of parameters all models show a good agreement with the Union2.1 luminosity distance data. However, the new model shows a quite satisfactory agreement in the whole range of its allowed parameters than that of the other two models. We also obtain cosmological constraints on these models from the Observed Hubble Data. Further, models have been tested by using $Om(z)$ test and statefinder diagnostics. These diagnostics especially, the statefinder diagnostic shows that the evolutionary differences between these models are distinct. The evolutionary trajectories of the new model are completely different from the other two models we have considered. |
1510.07701 | Kimet Jusufi | Kimet Jusufi | Hawking radiation via tunneling from the spacetime of a spinning cosmic
string black holes | null | Gen. Rel. Grav. 47, 124 (2015) | 10.1007/s10714-015-1969-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study Hawking radiation as a massless particles tunneling
process across the event horizon from the Schwarzschild and
Reissner-Nordstr\"om black holes pierced by an infinitely long spinning cosmic
string and a global monopole. Applying the WKB approximation and using a
generalized Painlev\'e line element for stationary axisymmetric spacetimes,
also by taking into account that the ADM mass of the black hole decreases due
to the presence of topological defects, it is shown that the Hawking
temperature remains unchanged for these black holes. The tunneling of charged
massive particles from Reissner-Nordstr\"om black holes is also studied, in
both cases the tunneling rate is related to the change of the
Bekenstein-Hawking entropy. The results extend the work of Parikh and Wilczek
and are consistent with an underlying unitary theory.
| [
{
"created": "Mon, 26 Oct 2015 21:56:25 GMT",
"version": "v1"
}
] | 2015-10-28 | [
[
"Jusufi",
"Kimet",
""
]
] | In this paper, we study Hawking radiation as a massless particles tunneling process across the event horizon from the Schwarzschild and Reissner-Nordstr\"om black holes pierced by an infinitely long spinning cosmic string and a global monopole. Applying the WKB approximation and using a generalized Painlev\'e line element for stationary axisymmetric spacetimes, also by taking into account that the ADM mass of the black hole decreases due to the presence of topological defects, it is shown that the Hawking temperature remains unchanged for these black holes. The tunneling of charged massive particles from Reissner-Nordstr\"om black holes is also studied, in both cases the tunneling rate is related to the change of the Bekenstein-Hawking entropy. The results extend the work of Parikh and Wilczek and are consistent with an underlying unitary theory. |
1806.01772 | Alessandro Nagar | Alessandro Nagar, Sebastiano Bernuzzi, Walter Del Pozzo, Gunnar
Riemenschneider, Sarp Akcay, Gregorio Carullo, Philipp Fleig, Stanislav
Babak, Ka Wa Tsang, Marta Colleoni, Francesco Messina, Geraint Pratten, David
Radice, Piero Rettegno, Michalis Agathos, Edward Fauchon-Jones, Mark Hannam,
Sascha Husa, Tim Dietrich, Pablo Cerda-Duran, Jose A. Font, Francesco
Pannarale, Patricia Schmidt and Thibault Damour | Time-domain effective-one-body gravitational waveforms for coalescing
compact binaries with nonprecessing spins, tides and self-spin effects | 39 pages, 36 figures. Extended appendix with discussion of the
postmerger fits. Version accepted for publication in Phys. Rev. D | Phys. Rev. D 98, 104052 (2018) | 10.1103/PhysRevD.98.104052 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present TEOBResumS, a new effective-one-body (EOB) waveform model for
nonprecessing (spin-aligned) and tidally interacting compact
binaries.Spin-orbit and spin-spin effects are blended together by making use of
the concept of centrifugal EOB radius. The point-mass sector through merger and
ringdown is informed by numerical relativity (NR) simulations of binary black
holes (BBH) computed with the SpEC and BAM codes. An improved, NR-based
phenomenological description of the postmerger waveform is developed.The tidal
sector of TEOBResumS describes the dynamics of neutron star binaries up to
merger and incorporates a resummed attractive potential motivated by recent
advances in the post-Newtonian and gravitational self-force description of
relativistic tidal interactions. Equation-of-state dependent self-spin
interactions (monopole-quadrupole effects) are incorporated in the model using
leading-order post-Newtonian results in a new expression of the centrifugal
radius. TEOBResumS is compared to 135 SpEC and 19 BAM BBH waveforms. The
maximum unfaithfulness to SpEC data $\bar{F}$ -- at design Advanced-LIGO
sensitivity and evaluated with total mass $M$ varying between $10M_\odot \leq M
\leq 200 M_\odot$ --is always below $2.5 \times 10^{-3}$ except for a single
outlier that grazes the $7.1 \times 10^{-3}$ level. When compared to BAM data,
$\bar{F}$ is smaller than $0.01$ except for a single outlier in one of the
corners of the NR-covered parameter space, that reaches the $0.052$
level.TEOBResumS is also compatible, up to merger, to high end NR waveforms
from binary neutron stars with spin effects and reduced initial eccentricity
computed with the BAM and THC codes. The model is designed to generate accurate
templates for the analysis of LIGO-Virgo data through merger and ringdown. We
demonstrate its use by analyzing the publicly available data for GW150914.
| [
{
"created": "Tue, 5 Jun 2018 16:10:39 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Oct 2018 18:57:38 GMT",
"version": "v2"
}
] | 2018-12-05 | [
[
"Nagar",
"Alessandro",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Del Pozzo",
"Walter",
""
],
[
"Riemenschneider",
"Gunnar",
""
],
[
"Akcay",
"Sarp",
""
],
[
"Carullo",
"Gregorio",
""
],
[
"Fleig",
"Philipp",
... | We present TEOBResumS, a new effective-one-body (EOB) waveform model for nonprecessing (spin-aligned) and tidally interacting compact binaries.Spin-orbit and spin-spin effects are blended together by making use of the concept of centrifugal EOB radius. The point-mass sector through merger and ringdown is informed by numerical relativity (NR) simulations of binary black holes (BBH) computed with the SpEC and BAM codes. An improved, NR-based phenomenological description of the postmerger waveform is developed.The tidal sector of TEOBResumS describes the dynamics of neutron star binaries up to merger and incorporates a resummed attractive potential motivated by recent advances in the post-Newtonian and gravitational self-force description of relativistic tidal interactions. Equation-of-state dependent self-spin interactions (monopole-quadrupole effects) are incorporated in the model using leading-order post-Newtonian results in a new expression of the centrifugal radius. TEOBResumS is compared to 135 SpEC and 19 BAM BBH waveforms. The maximum unfaithfulness to SpEC data $\bar{F}$ -- at design Advanced-LIGO sensitivity and evaluated with total mass $M$ varying between $10M_\odot \leq M \leq 200 M_\odot$ --is always below $2.5 \times 10^{-3}$ except for a single outlier that grazes the $7.1 \times 10^{-3}$ level. When compared to BAM data, $\bar{F}$ is smaller than $0.01$ except for a single outlier in one of the corners of the NR-covered parameter space, that reaches the $0.052$ level.TEOBResumS is also compatible, up to merger, to high end NR waveforms from binary neutron stars with spin effects and reduced initial eccentricity computed with the BAM and THC codes. The model is designed to generate accurate templates for the analysis of LIGO-Virgo data through merger and ringdown. We demonstrate its use by analyzing the publicly available data for GW150914. |
gr-qc/0002086 | Alexei Zakharov | Alexei V. Zakharov | Macroscopic Einstein-Maxwell equations for a system of interacting
particles to second-order accuracy in the interaction constant | 31 pages, LaTeX 2.09 | null | null | KSU-GRG-00-az01 | gr-qc | null | In this paper the macroscopic Einstein and Maxwell equations for system, in
which the electromagnetic interactions are dominating (for instance, the
cosmological plasma before the moment of recombination), are derived. Ensemble
averaging of the microscopic Einstein - Maxwell equations and the iouville
equations for the random functions leads to a closed system of macroscopic
Einstein - Maxwell equations and kinetic equations for one-particle
distribution functions. The macroscopic Einstein equations for a relativistic
plasma differ from the classical Einstein equations in that their left-hand
sides contain additional terms due to particle interaction. The terms are
traceless tensors with zero divergence. An explicit covariant expression for
these terms is given in the form of momentum-space integrals of expressions
depending on one-particles distribution functions of the interacting particles
of the medium. The macroscopic Maxwell equations alsow differ from the
classical macroscopic Maxwell equations in that their left-hand sides contain
additional terms due to particle interaction as well the effects of general
relativity.
| [
{
"created": "Fri, 25 Feb 2000 06:58:27 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Zakharov",
"Alexei V.",
""
]
] | In this paper the macroscopic Einstein and Maxwell equations for system, in which the electromagnetic interactions are dominating (for instance, the cosmological plasma before the moment of recombination), are derived. Ensemble averaging of the microscopic Einstein - Maxwell equations and the iouville equations for the random functions leads to a closed system of macroscopic Einstein - Maxwell equations and kinetic equations for one-particle distribution functions. The macroscopic Einstein equations for a relativistic plasma differ from the classical Einstein equations in that their left-hand sides contain additional terms due to particle interaction. The terms are traceless tensors with zero divergence. An explicit covariant expression for these terms is given in the form of momentum-space integrals of expressions depending on one-particles distribution functions of the interacting particles of the medium. The macroscopic Maxwell equations alsow differ from the classical macroscopic Maxwell equations in that their left-hand sides contain additional terms due to particle interaction as well the effects of general relativity. |
2306.05282 | Stefano Savastano | Stefano Savastano, Giovanni Tambalo, Hector Villarrubia-Rojo and
Miguel Zumalacarregui | Weakly Lensed Gravitational Waves: Probing Cosmic Structures with
Wave-Optics Features | 26 pages, 12 figures | Phys. Rev. D 108 (2023) 103532 | 10.1103/PhysRevD.108.103532 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | Every signal propagating through the universe is at least weakly lensed by
the intervening gravitational field. In some situations, wave-optics phenomena
(diffraction, interference) can be observed as frequency-dependent modulations
of the waveform of gravitational waves (GWs). We will denote these signatures
as Wave-Optics Features (WOFs) and analyze them in detail. Our framework can
efficiently and accurately compute WOF in the single-image regime, of which
weak lensing is a limit. The phenomenology of WOF is rich and offers valuable
information: the dense cusps of individual halos appear as peaks in Green's
function for lensing. If resolved, these features probe the number, effective
masses, spatial distribution and inner profiles of substructures. High
signal-to-noise GW signals reveal WOFs well beyond the Einstein radius, leading
to a fair probability of observation by upcoming detectors such as LISA.
Potential applications of WOF include reconstruction of the lens' projected
density, delensing standard sirens and inferring large-scale structure
morphology and the halo mass function. Because WOF are sourced by light halos
with negligible baryonic content, their detection (or lack thereof) holds
promise to test dark matter scenarios.
| [
{
"created": "Thu, 8 Jun 2023 15:30:45 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Nov 2023 11:05:32 GMT",
"version": "v2"
}
] | 2023-11-30 | [
[
"Savastano",
"Stefano",
""
],
[
"Tambalo",
"Giovanni",
""
],
[
"Villarrubia-Rojo",
"Hector",
""
],
[
"Zumalacarregui",
"Miguel",
""
]
] | Every signal propagating through the universe is at least weakly lensed by the intervening gravitational field. In some situations, wave-optics phenomena (diffraction, interference) can be observed as frequency-dependent modulations of the waveform of gravitational waves (GWs). We will denote these signatures as Wave-Optics Features (WOFs) and analyze them in detail. Our framework can efficiently and accurately compute WOF in the single-image regime, of which weak lensing is a limit. The phenomenology of WOF is rich and offers valuable information: the dense cusps of individual halos appear as peaks in Green's function for lensing. If resolved, these features probe the number, effective masses, spatial distribution and inner profiles of substructures. High signal-to-noise GW signals reveal WOFs well beyond the Einstein radius, leading to a fair probability of observation by upcoming detectors such as LISA. Potential applications of WOF include reconstruction of the lens' projected density, delensing standard sirens and inferring large-scale structure morphology and the halo mass function. Because WOF are sourced by light halos with negligible baryonic content, their detection (or lack thereof) holds promise to test dark matter scenarios. |
2103.03121 | Z. Yousaf | Z. Yousaf | Stable Charged Radiating Systems Associated with Tilted Observers | 26 pages, 2 figures | Eur. Phys. J. Plus 136, 281 (2021) | 10.1140/epjp/s13360-021-01278-2 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This paper is aimed to study the influence of electromagnetic field and
tilted congruences on the dynamical features of self-gravitating system. We
shall explore the stability of homogeneous energy density in the background of
Maxwell-Palatini $f(R)$ gravity. In this respect, we have considered an
irrotational non-static planar geometry which is assumed to have two different
types of gravitating sources. The role of tilted congruences and the geodesic
motion of an evolving system is studied through the divergence of the entropy
vector field. The condition for the emergence of Minskoskian cavity is also
explored. In order to connect tilted and non-tilted reference frames with
inflationary and inverse Ricci scalar corrections in the charged medium, few
well-consistent relations are presented. It is concluded that effective
electric charge is trying to increase the stability of regular energy density
of the planar system.
| [
{
"created": "Wed, 3 Mar 2021 11:57:58 GMT",
"version": "v1"
}
] | 2021-03-05 | [
[
"Yousaf",
"Z.",
""
]
] | This paper is aimed to study the influence of electromagnetic field and tilted congruences on the dynamical features of self-gravitating system. We shall explore the stability of homogeneous energy density in the background of Maxwell-Palatini $f(R)$ gravity. In this respect, we have considered an irrotational non-static planar geometry which is assumed to have two different types of gravitating sources. The role of tilted congruences and the geodesic motion of an evolving system is studied through the divergence of the entropy vector field. The condition for the emergence of Minskoskian cavity is also explored. In order to connect tilted and non-tilted reference frames with inflationary and inverse Ricci scalar corrections in the charged medium, few well-consistent relations are presented. It is concluded that effective electric charge is trying to increase the stability of regular energy density of the planar system. |
1008.3669 | Puxun Wu | Puxun Wu and Hongwei Yu | $f(T)$ models with phantom divide line crossing | 12 pages, 4 figures, equations corrected | Eur.Phys.J.C71:1552,2011 | 10.1140/epjc/s10052-011-1552-2 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we propose two new models in $f(T)$ gravity to realize the
crossing of the phantom divide line for the effective equation of state, and we
then study the observational constraints on the model parameters. The best fit
results suggest that the observations favor a crossing of the phantom divide
line.
| [
{
"created": "Sat, 21 Aug 2010 23:31:01 GMT",
"version": "v1"
},
{
"created": "Sun, 10 Oct 2010 03:28:19 GMT",
"version": "v2"
},
{
"created": "Sun, 20 Feb 2011 03:39:59 GMT",
"version": "v3"
}
] | 2011-03-03 | [
[
"Wu",
"Puxun",
""
],
[
"Yu",
"Hongwei",
""
]
] | In this paper, we propose two new models in $f(T)$ gravity to realize the crossing of the phantom divide line for the effective equation of state, and we then study the observational constraints on the model parameters. The best fit results suggest that the observations favor a crossing of the phantom divide line. |
1806.07696 | Donato Bini | Donato Bini and Andrea Geralico | Tidal invariants along the world line of an extended body in the Kerr
spacetime | 17 pages, 4 figures; revised version: sign misprints in Eqs.
(4.39)--(4.43) fixed; Eqs. (4.44)--(4.46) corrected | Phys.Rev. D 91, 084012 (2015) | 10.1103/PhysRevD.91.084012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An extended body orbiting a compact object undergoes tidal deformations by
the background gravitational field. Tidal invariants built up with the Riemann
tensor and their derivatives evaluated along the world line of the body are
essential tools to investigate both geometrical and physical properties of the
tidal interaction. For example, one can determine the tidal potential in the
neighborhood of the body by constructing a body-fixed frame, which requires
Fermi-type coordinates attached to the body itself, the latter being in turn
related to the spacetime metric and curvature along the considered world line.
Similarly, in an effective field theory description of extended bodies finite
size effects are taken into account by adding to the point mass action certain
non-minimal couplings which involve integrals of tidal invariants along the
orbit of the body. In both cases such a computation of tidal tensors is
required. Here we consider the case of a spinning body also endowed with a
non-vanishing quadrupole moment in a Kerr spacetime. The structure of the body
is modeled by a multipolar expansion around the "center of mass line" according
to the Mathisson-Papapetrou-Dixon model truncated at the quadrupolar order. The
quadrupole tensor is assumed to be quadratic in spin, accounting for rotational
deformations. The behavior of tidal invariants of both electric and magnetic
type is discussed in terms of gauge-invariant quantities when the body is
moving along a circular orbit as well as in the case of an arbitrary
(equatorial) motion. The analysis is completed by examining the associated
eigenvalues and eigenvectors of the tidal tensors. The limiting situation of
the Schwarzschild solution is also explored both in the strong field regime and
in the weak field limit.
| [
{
"created": "Wed, 20 Jun 2018 12:46:19 GMT",
"version": "v1"
}
] | 2018-06-21 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
]
] | An extended body orbiting a compact object undergoes tidal deformations by the background gravitational field. Tidal invariants built up with the Riemann tensor and their derivatives evaluated along the world line of the body are essential tools to investigate both geometrical and physical properties of the tidal interaction. For example, one can determine the tidal potential in the neighborhood of the body by constructing a body-fixed frame, which requires Fermi-type coordinates attached to the body itself, the latter being in turn related to the spacetime metric and curvature along the considered world line. Similarly, in an effective field theory description of extended bodies finite size effects are taken into account by adding to the point mass action certain non-minimal couplings which involve integrals of tidal invariants along the orbit of the body. In both cases such a computation of tidal tensors is required. Here we consider the case of a spinning body also endowed with a non-vanishing quadrupole moment in a Kerr spacetime. The structure of the body is modeled by a multipolar expansion around the "center of mass line" according to the Mathisson-Papapetrou-Dixon model truncated at the quadrupolar order. The quadrupole tensor is assumed to be quadratic in spin, accounting for rotational deformations. The behavior of tidal invariants of both electric and magnetic type is discussed in terms of gauge-invariant quantities when the body is moving along a circular orbit as well as in the case of an arbitrary (equatorial) motion. The analysis is completed by examining the associated eigenvalues and eigenvectors of the tidal tensors. The limiting situation of the Schwarzschild solution is also explored both in the strong field regime and in the weak field limit. |
1908.00504 | Ozgur Delice | M. Haluk Se\c{c}uk, \"Ozg\"ur Delice | Superradiance of a Global Monopole in Reissner-Nordstr\"{o}m(-AdS)
Space-time | V3: 19 pages, 3 figures, references added, introduction is extended,
Revtex, Published version | Eur. Phys. J. C (2020) 80: 396 | 10.1140/epjc/s10052-020-7988-5 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, the behaviour of a charged and massive scalar field around a
global monopole swallowed by a Reissner-Nordstr\"{o}m-Anti-de Sitter (RN-AdS)
black hole is investigated by considering the Klein-Gordon equation in this
geometry. The superradiance phenomenon and instability behaviour of the black
hole against charged scalar perturbations are studied for both an RN-AdS case
and also for an RN black hole surrounded by a reflective mirror, i.e., the
black hole bomb case. The effects of the monopole on these cases are discussed
analytically and also with the help of several graphs in detail. The monopole
charge affects the superradiance threshold frequency and also effects the
instability time scale for both cases. The existence of global monopole makes
these black holes more stable against superradiance instability.
| [
{
"created": "Thu, 1 Aug 2019 16:56:13 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Jan 2020 17:02:09 GMT",
"version": "v2"
},
{
"created": "Sat, 16 May 2020 22:46:42 GMT",
"version": "v3"
}
] | 2020-05-19 | [
[
"Seçuk",
"M. Haluk",
""
],
[
"Delice",
"Özgür",
""
]
] | In this article, the behaviour of a charged and massive scalar field around a global monopole swallowed by a Reissner-Nordstr\"{o}m-Anti-de Sitter (RN-AdS) black hole is investigated by considering the Klein-Gordon equation in this geometry. The superradiance phenomenon and instability behaviour of the black hole against charged scalar perturbations are studied for both an RN-AdS case and also for an RN black hole surrounded by a reflective mirror, i.e., the black hole bomb case. The effects of the monopole on these cases are discussed analytically and also with the help of several graphs in detail. The monopole charge affects the superradiance threshold frequency and also effects the instability time scale for both cases. The existence of global monopole makes these black holes more stable against superradiance instability. |
gr-qc/0005109 | null | Andrzej Krasinski (N. Copernicus Astronomical Center and College of
Science, Polish Academy of Sciences, Warszawa, Poland) | Rotating Bianchi type V dust models generalizing the k = -1 Friedmann
model | 23 pages, LaTeX, no figures, to be submitted for publication.
Subjects: General relativity; exact solutions; cosmology | J.Math.Phys. 42 (2001) 355-367 | 10.1063/1.1330197 | null | gr-qc | null | The Einstein equations for one of the hypersurface-homogeneous rotating dust
models are investigated. It is a Bianchi type V model in which one of the
Killing fields is spanned on velocity and rotation (case 1.2.2.2 in the
classification scheme of the earlier papers). A first integral of the field
equations is found, and with a special value of this integral coordinate
transformations are used to eliminate two components of the metric. The k = -1
Friedmann model is shown to be contained among the solutions in the limit of
zero rotation. The field equations for the simplified metric are reduced to 3
second-order ordinary differential equations that determine 3 metric components
plus a first integral that algebraically determines the fourth component. First
derivatives of the metric components are subject to a constraint (a
second-degree polynomial with coefficients depending on the functions). It is
shown that the set does not follow from a Lagrangian of the Hilbert type. The
group of Lie point-symmetries of the set is found, it is two-dimensional
noncommutative. Finally, a method of searching for first integrals (for sets of
differential equations) that are polynomials of degree 1 or 2 in the first
derivatives is applied. No such first integrals exist. The method is used to
find a constraint (of degree 1 in first derivatives) that could be imposed on
the metric, but it leads to a vacuum solution, and so is of no interest for
cosmology.
| [
{
"created": "Wed, 24 May 2000 15:26:02 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Krasinski",
"Andrzej",
"",
"N. Copernicus Astronomical Center and College of\n Science, Polish Academy of Sciences, Warszawa, Poland"
]
] | The Einstein equations for one of the hypersurface-homogeneous rotating dust models are investigated. It is a Bianchi type V model in which one of the Killing fields is spanned on velocity and rotation (case 1.2.2.2 in the classification scheme of the earlier papers). A first integral of the field equations is found, and with a special value of this integral coordinate transformations are used to eliminate two components of the metric. The k = -1 Friedmann model is shown to be contained among the solutions in the limit of zero rotation. The field equations for the simplified metric are reduced to 3 second-order ordinary differential equations that determine 3 metric components plus a first integral that algebraically determines the fourth component. First derivatives of the metric components are subject to a constraint (a second-degree polynomial with coefficients depending on the functions). It is shown that the set does not follow from a Lagrangian of the Hilbert type. The group of Lie point-symmetries of the set is found, it is two-dimensional noncommutative. Finally, a method of searching for first integrals (for sets of differential equations) that are polynomials of degree 1 or 2 in the first derivatives is applied. No such first integrals exist. The method is used to find a constraint (of degree 1 in first derivatives) that could be imposed on the metric, but it leads to a vacuum solution, and so is of no interest for cosmology. |
1002.1291 | Neil J. Cornish | Matthew R. Adams and Neil J. Cornish | Discriminating between a Stochastic Gravitational Wave Background and
Instrument Noise | 10 Pages, 10 Figures | Phys.Rev.D82:022002,2010 | 10.1103/PhysRevD.82.022002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The detection of a stochastic background of gravitational waves could
significantly impact our understanding of the physical processes that shaped
the early Universe. The challenge lies in separating the cosmological signal
from other stochastic processes such as instrument noise and astrophysical
foregrounds. One approach is to build two or more detectors and cross correlate
their output, thereby enhancing the common gravitational wave signal relative
to the uncorrelated instrument noise. When only one detector is available, as
will likely be the case with the Laser Interferometer Space Antenna (LISA),
alternative analysis techniques must be developed. Here we show that models of
the noise and signal transfer functions can be used to tease apart the
gravitational and instrument noise contributions. We discuss the role of
gravitational wave insensitive "null channels" formed from particular
combinations of the time delay interferometry, and derive a new combination
that maintains this insensitivity for unequal arm length detectors. We show
that, in the absence of astrophysical foregrounds, LISA could detect signals
with energy densities as low as $\Omega_{\rm gw} = 6 \times 10^{-13}$ with just
one month of data. We describe an end-to-end Bayesian analysis pipeline that is
able to search for, characterize and assign confidence levels for the detection
of a stochastic gravitational wave background, and demonstrate the
effectiveness of this approach using simulated data from the third round of
Mock LISA Data Challenges.
| [
{
"created": "Fri, 5 Feb 2010 18:13:44 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Adams",
"Matthew R.",
""
],
[
"Cornish",
"Neil J.",
""
]
] | The detection of a stochastic background of gravitational waves could significantly impact our understanding of the physical processes that shaped the early Universe. The challenge lies in separating the cosmological signal from other stochastic processes such as instrument noise and astrophysical foregrounds. One approach is to build two or more detectors and cross correlate their output, thereby enhancing the common gravitational wave signal relative to the uncorrelated instrument noise. When only one detector is available, as will likely be the case with the Laser Interferometer Space Antenna (LISA), alternative analysis techniques must be developed. Here we show that models of the noise and signal transfer functions can be used to tease apart the gravitational and instrument noise contributions. We discuss the role of gravitational wave insensitive "null channels" formed from particular combinations of the time delay interferometry, and derive a new combination that maintains this insensitivity for unequal arm length detectors. We show that, in the absence of astrophysical foregrounds, LISA could detect signals with energy densities as low as $\Omega_{\rm gw} = 6 \times 10^{-13}$ with just one month of data. We describe an end-to-end Bayesian analysis pipeline that is able to search for, characterize and assign confidence levels for the detection of a stochastic gravitational wave background, and demonstrate the effectiveness of this approach using simulated data from the third round of Mock LISA Data Challenges. |
1001.1205 | Pisin Chen | Ronald J. Adler | Six easy roads to the Planck scale | 22 pages and 6 figures | Am.J.Phys.78:925-932,2010 | 10.1119/1.3439650 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give six arguments that the Planck scale should be viewed as a fundamental
minimum or boundary for the classical concept of spacetime, beyond which
quantum effects cannot be neglected and the basic nature of spacetime must be
reconsidered. The arguments are elementary, heuristic, and plausible, and as
much as possible rely on only general principles of quantum theory and gravity
theory. The paper is primarily pedagogical, and its main goal is to give
physics students, non-specialists, engineers etc. an awareness and appreciation
of the Planck scale and the role it should play in present and future theories
of quantum spacetime and quantum gravity.
| [
{
"created": "Fri, 8 Jan 2010 07:07:03 GMT",
"version": "v1"
}
] | 2011-03-28 | [
[
"Adler",
"Ronald J.",
""
]
] | We give six arguments that the Planck scale should be viewed as a fundamental minimum or boundary for the classical concept of spacetime, beyond which quantum effects cannot be neglected and the basic nature of spacetime must be reconsidered. The arguments are elementary, heuristic, and plausible, and as much as possible rely on only general principles of quantum theory and gravity theory. The paper is primarily pedagogical, and its main goal is to give physics students, non-specialists, engineers etc. an awareness and appreciation of the Planck scale and the role it should play in present and future theories of quantum spacetime and quantum gravity. |
gr-qc/0606110 | Andrzej Rostworowski | Andrzej Rostworowski | Quasinormal frequencies of D-dimensional Schwarzschild black holes:
evaluation via continued fraction method | 6 pages, no figures, freely available from
http://th-www.if.uj.edu.pl/acta/ | ActaPhys.Polon.B38:81-89,2007 | null | null | gr-qc | null | We adopt Leaver's method to determine quasi normal frequencies of the
Schwarzschild black hole in higher (D >= 10) dimensions. In D-dimensional
Schwarzschild metric, when D increases, more and more singularities, spaced
uniformly on the unit circle |r|=1, approach the horizon at r = r_h = 1. Thus,
a solution satisfying the outgoing wave boundary condition at the horizon must
be continued to some mid point and only then the continued fraction condition
can be applied. This prescription is general and applies to all cases for
which, due to regular singularities on the way from the point of interest to
the irregular singularity, Leaver's method in its original setting breaks down.
We illustrate the method calculating gravitational vector and tensor
quasinormal frequencies of the Schwarzschild black hole in D=11 and D=10
dimensions. We also give the details for the D=9 case, considered in
gr-qc/0511064.
| [
{
"created": "Mon, 26 Jun 2006 15:44:41 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Rostworowski",
"Andrzej",
""
]
] | We adopt Leaver's method to determine quasi normal frequencies of the Schwarzschild black hole in higher (D >= 10) dimensions. In D-dimensional Schwarzschild metric, when D increases, more and more singularities, spaced uniformly on the unit circle |r|=1, approach the horizon at r = r_h = 1. Thus, a solution satisfying the outgoing wave boundary condition at the horizon must be continued to some mid point and only then the continued fraction condition can be applied. This prescription is general and applies to all cases for which, due to regular singularities on the way from the point of interest to the irregular singularity, Leaver's method in its original setting breaks down. We illustrate the method calculating gravitational vector and tensor quasinormal frequencies of the Schwarzschild black hole in D=11 and D=10 dimensions. We also give the details for the D=9 case, considered in gr-qc/0511064. |
gr-qc/0005043 | Robert Beig | Robert Beig | Generalized Bowen--York Initial Data | 15 pages, LaTeX, uses Springer cl2emult style | pp.55-69 in Spiros Cotsakis and Gary Gibbons, Eds., "Mathematical
and Quantum Aspects of Relativity and Cosmology", Springer Lecture Notes in
Physics v.537 | null | UWThPh1999-3 | gr-qc | null | A class of vacuum initial-data sets is described which are based on certain
expressions for the extrinsic curvature first studied and employed by Bowen and
York. These expressions play a role for the momentum constraint of general
relativity which is analogous to the role played by the Coulomb solution for
the Gauss-law constraint of electromagnetism.
| [
{
"created": "Fri, 12 May 2000 15:26:25 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Beig",
"Robert",
""
]
] | A class of vacuum initial-data sets is described which are based on certain expressions for the extrinsic curvature first studied and employed by Bowen and York. These expressions play a role for the momentum constraint of general relativity which is analogous to the role played by the Coulomb solution for the Gauss-law constraint of electromagnetism. |
1401.0931 | Alok Laddha | Alok Laddha | Hamiltonian constraint in Euclidean LQG revisited: First hints of
off-shell Closure | 68 pages, 6 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We initiate the hunt for a definition of Hamiltonian constraint in Euclidean
Loop Quantum Gravity (LQG) which faithfully represents quantum Dirac algebra.
Borrowing key ideas from previous works on Hamiltonian constraint in LQG and
several toy models, we present some evidence that there exists such a continuum
Hamiltonian constraint operator which is well defined on a suitable
generalization of the Lewandowski-Marolf Habitat and is anomaly free off-shell.
| [
{
"created": "Sun, 5 Jan 2014 19:27:28 GMT",
"version": "v1"
}
] | 2014-01-07 | [
[
"Laddha",
"Alok",
""
]
] | We initiate the hunt for a definition of Hamiltonian constraint in Euclidean Loop Quantum Gravity (LQG) which faithfully represents quantum Dirac algebra. Borrowing key ideas from previous works on Hamiltonian constraint in LQG and several toy models, we present some evidence that there exists such a continuum Hamiltonian constraint operator which is well defined on a suitable generalization of the Lewandowski-Marolf Habitat and is anomaly free off-shell. |
2212.08784 | Yu-Xiao Liu | Wen-Di Guo, Qin Tan, and Yu-Xiao Liu | Gravitoelectromagnetic coupled perturbations and quasinormal modes of a
charged black hole with scalar hair | 10 pages, 3 figures, 2 tables, some mistakes have been corrected | Phys. Rev. D 107 (2023) 12, 124046 | 10.1103/PhysRevD.107.124046 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | From the quantum point of view, singularity should not exist. Recently, Bah
and Heidmann constructed a five-dimensional singularity free topology
star/black hole [Phys. Rev. Lett. 126, 151101 (2021)]. By integrating the extra
dimension, a four-dimensional static spherical black hole with a magnetic
charge and scalar hair can be obtained. In this paper, we study the quasinormal
modes (QNMs) of the magnetic field and gravitational field on the background of
this four-dimensional charged black hole with scalar hair. The odd parity of
the gravitational perturbations couples with the even parity of the magnetic
field perturbations. Two coupled second-order derivative equations are
obtained. Using the matrix-valued direct integration method, we obtain the
fundamental QNM frequencies numerically. The effect of the magnetic charge on
the QNMs is studied. The differences of the frequencies of the fundamental QNMs
between the charged black hole with scalar hair and the Reissner-Norstr\"{o}m
black hole are very small for the angular number $l=2$. However, some new
interesting results are found for higher angular number.
| [
{
"created": "Sat, 17 Dec 2022 02:52:32 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Dec 2022 12:12:30 GMT",
"version": "v2"
},
{
"created": "Sun, 1 Jan 2023 13:57:25 GMT",
"version": "v3"
},
{
"created": "Thu, 22 Feb 2024 03:46:33 GMT",
"version": "v4"
}
] | 2024-02-23 | [
[
"Guo",
"Wen-Di",
""
],
[
"Tan",
"Qin",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | From the quantum point of view, singularity should not exist. Recently, Bah and Heidmann constructed a five-dimensional singularity free topology star/black hole [Phys. Rev. Lett. 126, 151101 (2021)]. By integrating the extra dimension, a four-dimensional static spherical black hole with a magnetic charge and scalar hair can be obtained. In this paper, we study the quasinormal modes (QNMs) of the magnetic field and gravitational field on the background of this four-dimensional charged black hole with scalar hair. The odd parity of the gravitational perturbations couples with the even parity of the magnetic field perturbations. Two coupled second-order derivative equations are obtained. Using the matrix-valued direct integration method, we obtain the fundamental QNM frequencies numerically. The effect of the magnetic charge on the QNMs is studied. The differences of the frequencies of the fundamental QNMs between the charged black hole with scalar hair and the Reissner-Norstr\"{o}m black hole are very small for the angular number $l=2$. However, some new interesting results are found for higher angular number. |
2209.07226 | Hugo L\'evy | Hugo L\'evy, Jo\"el Berg\'e and Jean-Philippe Uzan | Solving nonlinear Klein-Gordon equations on unbounded domains via the
Finite Element Method | 35 pages, 20 figures, 2 tables. Accepted for publication in PRD | null | 10.1103/PhysRevD.106.124021 | null | gr-qc astro-ph.IM cs.NA math.NA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A large class of scalar-tensor theories of gravity exhibit a screening
mechanism that dynamically suppresses fifth forces in the Solar system and
local laboratory experiments. Technically, at the scalar field equation level,
this usually translates into nonlinearities which strongly limit the scope of
analytical approaches. This article presents $femtoscope$ $-$ a Python
numerical tool based on the Finite Element Method (FEM) and Newton method for
solving Klein-Gordon-like equations that arise in particular in the symmetron
or chameleon models. Regarding the latter, the scalar field behavior is
generally only known infinitely far away from the its sources. We thus
investigate existing and new FEM-based techniques for dealing with asymptotic
boundary conditions on finite-memory computers, whose convergence are assessed.
Finally, $femtoscope$ is showcased with a study of the chameleon fifth force in
Earth orbit.
| [
{
"created": "Thu, 15 Sep 2022 11:40:37 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Sep 2022 08:04:47 GMT",
"version": "v2"
},
{
"created": "Tue, 20 Dec 2022 12:39:41 GMT",
"version": "v3"
}
] | 2022-12-21 | [
[
"Lévy",
"Hugo",
""
],
[
"Bergé",
"Joël",
""
],
[
"Uzan",
"Jean-Philippe",
""
]
] | A large class of scalar-tensor theories of gravity exhibit a screening mechanism that dynamically suppresses fifth forces in the Solar system and local laboratory experiments. Technically, at the scalar field equation level, this usually translates into nonlinearities which strongly limit the scope of analytical approaches. This article presents $femtoscope$ $-$ a Python numerical tool based on the Finite Element Method (FEM) and Newton method for solving Klein-Gordon-like equations that arise in particular in the symmetron or chameleon models. Regarding the latter, the scalar field behavior is generally only known infinitely far away from the its sources. We thus investigate existing and new FEM-based techniques for dealing with asymptotic boundary conditions on finite-memory computers, whose convergence are assessed. Finally, $femtoscope$ is showcased with a study of the chameleon fifth force in Earth orbit. |
1904.02915 | Lunchakorn Tannukij | Sirachak Panpanich, Supakchai Ponglertsakul, Lunchakorn Tannukij | Particle motions and Gravitational Lensing in de Rham-Gabadadze-Tolley
Massive Gravity Theory | 12 pages, 2 tables, 9 figures, matched with the PRD version | Phys. Rev. D 100, 044031 (2019) | 10.1103/PhysRevD.100.044031 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate gravitational lensing and particle motions around
non-asymptotically flat black hole spacetime in non-linear, ghost-free massive
gravity theory, called de Rham-Gabadadze-Tolley (dRGT) massive gravity.
Deflection angle formulae are derived in terms of perihelion parameter. The
deflection angle can be positive, zero or even negative with various perihelion
distance. The negative angle reveals repulsive behaviour of gravity from a
linear term $\gamma$ in the dRGT black hole solution. We also find an
analytically approximated formula of deflection angle in two regimes: large and
small $\gamma$ term regimes which are shown to be consistent with direct
numerical integration. Null and timelike geodesic motions on equatorial plane
are explored. Particle trajectories around the dRGT black hole are plotted and
discussed in details.
| [
{
"created": "Fri, 5 Apr 2019 07:48:44 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Aug 2019 09:05:31 GMT",
"version": "v2"
}
] | 2019-08-23 | [
[
"Panpanich",
"Sirachak",
""
],
[
"Ponglertsakul",
"Supakchai",
""
],
[
"Tannukij",
"Lunchakorn",
""
]
] | We investigate gravitational lensing and particle motions around non-asymptotically flat black hole spacetime in non-linear, ghost-free massive gravity theory, called de Rham-Gabadadze-Tolley (dRGT) massive gravity. Deflection angle formulae are derived in terms of perihelion parameter. The deflection angle can be positive, zero or even negative with various perihelion distance. The negative angle reveals repulsive behaviour of gravity from a linear term $\gamma$ in the dRGT black hole solution. We also find an analytically approximated formula of deflection angle in two regimes: large and small $\gamma$ term regimes which are shown to be consistent with direct numerical integration. Null and timelike geodesic motions on equatorial plane are explored. Particle trajectories around the dRGT black hole are plotted and discussed in details. |
1212.2195 | Jay Tasson | Jay D. Tasson | Lorentz Symmetry, the SME, and Gravitational Experiments | 9 pages, presented at the XLVIth Rencontres de Moriond and GPhyS
Colloquium, La Thuile, Aosta Valley, Italy, March 2011 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This proceedings contribution summarizes the implications of recent SME-based
investigations of Lorentz violation for gravitational experiments.
| [
{
"created": "Mon, 10 Dec 2012 20:43:43 GMT",
"version": "v1"
}
] | 2012-12-11 | [
[
"Tasson",
"Jay D.",
""
]
] | This proceedings contribution summarizes the implications of recent SME-based investigations of Lorentz violation for gravitational experiments. |
2407.09663 | Vicente Antunes | Mario Novello and Vicente Antunes | Rotation in the Geometric Scalar Theory of Gravity | null | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | We present solutions corresponding to rotational configurations in the
recently proposed Geometric Scalar Gravity (GSG) theory. The solutions obtained
here have the important property that the associated closed time-like curves
are always restricted to a compact domain of space-time. We compare this
property with those of analogous solutions in General Relativity (GR).
| [
{
"created": "Fri, 12 Jul 2024 19:56:56 GMT",
"version": "v1"
}
] | 2024-07-16 | [
[
"Novello",
"Mario",
""
],
[
"Antunes",
"Vicente",
""
]
] | We present solutions corresponding to rotational configurations in the recently proposed Geometric Scalar Gravity (GSG) theory. The solutions obtained here have the important property that the associated closed time-like curves are always restricted to a compact domain of space-time. We compare this property with those of analogous solutions in General Relativity (GR). |
1912.03701 | John Westernacher-Schneider | John Ryan Westernacher-Schneider, Charalampos Markakis, Bing Jyun Tsao | Hamilton-Jacobi hydrodynamics of pulsating relativistic stars | 24 pgs, 3 figs. Typo fixed. v3: published version.
https://doi.org/10.1088/1361-6382/ab93e9 | null | 10.1088/1361-6382/ab93e9 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamics of self-gravitating fluid bodies is described by the
Euler-Einstein system of partial differential equations. The break-down of
well-posedness on the fluid-vacuum interface remains a challenging open
problem, which is manifested in simulations of oscillating or inspiraling
binary neutron-stars. We formulate and implement a well-posed canonical
hydrodynamic scheme, suitable for neutron-star simulations in numerical general
relativity. The scheme uses a variational principle by Carter-Lichnerowicz
stating that barotropic fluid motions are conformally geodesic and Helmholtz's
third theorem stating that initially irrotational flows remain irrotational. We
apply this scheme in 3+1 numerical general relativity to evolve the canonical
momentum of a fluid element via the Hamilton-Jacobi equation. We explore a
regularization scheme for the Euler equations, that uses a fiducial atmosphere
in hydrostatic equilibrium and allows the pressure to vanish, while preserving
strong hyperbolicity on the vacuum boundary. The new regularization scheme
resolves a larger number of radial oscillation modes compared to standard,
non-equilibrium atmosphere treatments.
| [
{
"created": "Sun, 8 Dec 2019 15:38:01 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Dec 2019 17:50:49 GMT",
"version": "v2"
},
{
"created": "Thu, 16 Jul 2020 16:55:04 GMT",
"version": "v3"
}
] | 2020-07-17 | [
[
"Westernacher-Schneider",
"John Ryan",
""
],
[
"Markakis",
"Charalampos",
""
],
[
"Tsao",
"Bing Jyun",
""
]
] | The dynamics of self-gravitating fluid bodies is described by the Euler-Einstein system of partial differential equations. The break-down of well-posedness on the fluid-vacuum interface remains a challenging open problem, which is manifested in simulations of oscillating or inspiraling binary neutron-stars. We formulate and implement a well-posed canonical hydrodynamic scheme, suitable for neutron-star simulations in numerical general relativity. The scheme uses a variational principle by Carter-Lichnerowicz stating that barotropic fluid motions are conformally geodesic and Helmholtz's third theorem stating that initially irrotational flows remain irrotational. We apply this scheme in 3+1 numerical general relativity to evolve the canonical momentum of a fluid element via the Hamilton-Jacobi equation. We explore a regularization scheme for the Euler equations, that uses a fiducial atmosphere in hydrostatic equilibrium and allows the pressure to vanish, while preserving strong hyperbolicity on the vacuum boundary. The new regularization scheme resolves a larger number of radial oscillation modes compared to standard, non-equilibrium atmosphere treatments. |
1001.1068 | Matteo Luca Ruggiero | Angelo Tartaglia, Matteo Luca Ruggiero, Emiliano Capolongo | A null frame for spacetime positioning by means of pulsating sources | 19 pages, revised to match the version accepted for publication in
Advances in Space Research | Adv.Space Res.47:645-653,2011 | 10.1016/j.asr.2010.10.023 | null | gr-qc astro-ph.IM physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce an operational approach to the use of pulsating sources, located
at spatial infinity, for defining a relativistic positioning and navigation
system, based on the use of four-dimensional bases of null four-vectors, in
flat spacetime. As a prototypical case, we show how pulsars can be used to
define such a positioning system. The reception of the pulses for a set of
different sources whose positions in the sky and periods are assumed to be
known allows the determination of the user's coordinates and spacetime
trajectory, in the reference frame where the sources are at rest. We describe
our approach in flat Minkowski spacetime, and discuss the validity of this and
other approximations we have considered.
| [
{
"created": "Thu, 7 Jan 2010 13:25:36 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jun 2010 11:16:12 GMT",
"version": "v2"
},
{
"created": "Sat, 30 Oct 2010 11:17:53 GMT",
"version": "v3"
}
] | 2011-03-04 | [
[
"Tartaglia",
"Angelo",
""
],
[
"Ruggiero",
"Matteo Luca",
""
],
[
"Capolongo",
"Emiliano",
""
]
] | We introduce an operational approach to the use of pulsating sources, located at spatial infinity, for defining a relativistic positioning and navigation system, based on the use of four-dimensional bases of null four-vectors, in flat spacetime. As a prototypical case, we show how pulsars can be used to define such a positioning system. The reception of the pulses for a set of different sources whose positions in the sky and periods are assumed to be known allows the determination of the user's coordinates and spacetime trajectory, in the reference frame where the sources are at rest. We describe our approach in flat Minkowski spacetime, and discuss the validity of this and other approximations we have considered. |
gr-qc/9910014 | Marcelo B. Ribeiro | Marcelo B. Ribeiro (1 and 2) ((1) Vatican Group, Steward Observatory,
U. Arizona, (2) Physics Institute, U. Brazil - UFRJ, Rio de Janeiro) | Limited Frequency Range Observations of Cosmological Point Sources | 11 pages, LaTeX. Improved text, typos corrected, references added.
Accepted for publication in "The Observatory" | Observatory 122 (2002) 201-210 | null | null | gr-qc astro-ph | null | This paper advances a general proposal for testing non-standard cosmological
models by means of observational relations of cosmological point sources in
some specific waveband, and their use in the context of the data provided by
the galaxy redshift surveys, but for any cosmological metric. By starting from
the general theory for observations in relativistic cosmology the equations for
colour, K-correction, and number counts of cosmological point sources are
discussed in the context of curved spacetimes. The number counts equation is
also written in terms of the selection and luminosity functions, which provides
a relativistic generalization of its Euclidean version. Since these observables
were not derived in the framework of any specific cosmology, they are valid for
any cosmological model. The hypotheses used in such derivation are reviewed,
together with some difficulties for the practical use of those observables.
| [
{
"created": "Mon, 4 Oct 1999 23:49:51 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jun 2002 00:37:11 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Ribeiro",
"Marcelo B.",
"",
"1 and 2"
]
] | This paper advances a general proposal for testing non-standard cosmological models by means of observational relations of cosmological point sources in some specific waveband, and their use in the context of the data provided by the galaxy redshift surveys, but for any cosmological metric. By starting from the general theory for observations in relativistic cosmology the equations for colour, K-correction, and number counts of cosmological point sources are discussed in the context of curved spacetimes. The number counts equation is also written in terms of the selection and luminosity functions, which provides a relativistic generalization of its Euclidean version. Since these observables were not derived in the framework of any specific cosmology, they are valid for any cosmological model. The hypotheses used in such derivation are reviewed, together with some difficulties for the practical use of those observables. |
gr-qc/9905029 | Alex Kaganovich | E. I. Guendelman and A. B. Kaganovich | Dynamical measure and field theory models free of the cosmological
constant problem | Extended version of the contribution to the fourth Alexander
Friedmann International Seminar on Gravitation and Cosmology; accepted for
publication in Phys. Rev. D; 31 pages | Phys.Rev.D60:065004,1999 | 10.1103/PhysRevD.60.065004 | null | gr-qc hep-th | null | Summary of abstract Field theory models including gauge theories with SSB are
presented where the energy density of the true vacuum state (TVS) is zero
without fine tuning. The above models are constructed in the gravitational
theory where a measure of integration \Phi in the action is not necessarily
\sqrt{-g} but it is determined dynamically through additional degrees of
freedom. The ratio \Phi/\sqrt{-g} is a scalar field which can be solved in
terms of the matter degrees of freedom due to the existence of a constraint. We
study a few explicit field theory models where it is possible to combine the
solution of the cosmological constant problem with: 1) possibility for
inflationary scenario for the early universe; 2) spontaneously broken gauge
unified theories (including fermions). The models are free from the well known
problem of the usual scalar-tensor theories in what is concerned with the
classical GR tests. The only difference of the field equations in the Einstein
frame from the canonical equations of the selfconsistent system of Einstein's
gravity and matter fields, is the appearance of the effective scalar field
potential which vanishes in TVS without fine tuning.
| [
{
"created": "Mon, 10 May 1999 09:32:47 GMT",
"version": "v1"
}
] | 2011-04-20 | [
[
"Guendelman",
"E. I.",
""
],
[
"Kaganovich",
"A. B.",
""
]
] | Summary of abstract Field theory models including gauge theories with SSB are presented where the energy density of the true vacuum state (TVS) is zero without fine tuning. The above models are constructed in the gravitational theory where a measure of integration \Phi in the action is not necessarily \sqrt{-g} but it is determined dynamically through additional degrees of freedom. The ratio \Phi/\sqrt{-g} is a scalar field which can be solved in terms of the matter degrees of freedom due to the existence of a constraint. We study a few explicit field theory models where it is possible to combine the solution of the cosmological constant problem with: 1) possibility for inflationary scenario for the early universe; 2) spontaneously broken gauge unified theories (including fermions). The models are free from the well known problem of the usual scalar-tensor theories in what is concerned with the classical GR tests. The only difference of the field equations in the Einstein frame from the canonical equations of the selfconsistent system of Einstein's gravity and matter fields, is the appearance of the effective scalar field potential which vanishes in TVS without fine tuning. |
2208.02690 | Igor Bogush M.Sc. | Kirill Kobialko, Igor Bogush, Dmitri Gal'tsov | The geometry of massive particle surfaces | 30 pages, revtex4, 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a generalization of Claudel, Virbhadra, and Ellis photon surfaces
to the case of massive charged particles, considering a timelike hypersurface
such that any worldline of a particle with mass $m$, electric charge $q$ and
fixed total energy $\mathcal{E}$, initially touching it, will remain in this
hypersurface forever. This definition does not directly appeal to the equations
of motion, but instead make use of partially umbilic nature of the surface
geometry. Such an approach should be especially useful in the case of
non-integrable equations of motion. It may be applied in the theory of non-thin
accretion discs, and also may serve a new tool for some general problems, such
as uniqueness theorems, Penrose inequalities and hidden symmetries. The
condition for the stability of the worldlines is derived, which reduces to
differentiation along the flow of surfaces of a certain energy. We consider a
number of examples of electrovacuum and dilaton solutions, find conditions for
marginally stable orbits, regions of stable or unstable spherical orbits,
stable and unstable photon surfaces, and solutions satisfying the no-force
condition.
| [
{
"created": "Thu, 4 Aug 2022 14:42:27 GMT",
"version": "v1"
}
] | 2022-08-05 | [
[
"Kobialko",
"Kirill",
""
],
[
"Bogush",
"Igor",
""
],
[
"Gal'tsov",
"Dmitri",
""
]
] | We propose a generalization of Claudel, Virbhadra, and Ellis photon surfaces to the case of massive charged particles, considering a timelike hypersurface such that any worldline of a particle with mass $m$, electric charge $q$ and fixed total energy $\mathcal{E}$, initially touching it, will remain in this hypersurface forever. This definition does not directly appeal to the equations of motion, but instead make use of partially umbilic nature of the surface geometry. Such an approach should be especially useful in the case of non-integrable equations of motion. It may be applied in the theory of non-thin accretion discs, and also may serve a new tool for some general problems, such as uniqueness theorems, Penrose inequalities and hidden symmetries. The condition for the stability of the worldlines is derived, which reduces to differentiation along the flow of surfaces of a certain energy. We consider a number of examples of electrovacuum and dilaton solutions, find conditions for marginally stable orbits, regions of stable or unstable spherical orbits, stable and unstable photon surfaces, and solutions satisfying the no-force condition. |
0810.0079 | Shahar Hod | Shahar Hod | Return of the quantum cosmic censor | 5 pages | Phys.Lett.B668:346-349,2008 | 10.1016/j.physletb.2008.08.059 | null | gr-qc astro-ph hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The influential theorems of Hawking and Penrose demonstrate that spacetime
singularities are ubiquitous features of general relativity, Einstein's theory
of gravity. The utility of classical general relativity in describing
gravitational phenomena is maintained by the cosmic censorship principle. This
conjecture, whose validity is still one of the most important open questions in
general relativity, asserts that the undesirable spacetime singularities are
always hidden inside of black holes. In this Letter we reanalyze extreme
situations which have been considered as counterexamples to the cosmic
censorship hypothesis. In particular, we consider the absorption of fermion
particles by a spinning black hole. Ignoring quantum effects may lead one to
conclude that an incident fermion wave may over spin the black hole, thereby
exposing its inner singularity to distant observers. However, we show that when
quantum effects are properly taken into account, the integrity of the
black-hole event horizon is irrefutable. This observation suggests that the
cosmic censorship principle is intrinsically a quantum phenomena.
| [
{
"created": "Wed, 1 Oct 2008 06:35:50 GMT",
"version": "v1"
}
] | 2009-01-09 | [
[
"Hod",
"Shahar",
""
]
] | The influential theorems of Hawking and Penrose demonstrate that spacetime singularities are ubiquitous features of general relativity, Einstein's theory of gravity. The utility of classical general relativity in describing gravitational phenomena is maintained by the cosmic censorship principle. This conjecture, whose validity is still one of the most important open questions in general relativity, asserts that the undesirable spacetime singularities are always hidden inside of black holes. In this Letter we reanalyze extreme situations which have been considered as counterexamples to the cosmic censorship hypothesis. In particular, we consider the absorption of fermion particles by a spinning black hole. Ignoring quantum effects may lead one to conclude that an incident fermion wave may over spin the black hole, thereby exposing its inner singularity to distant observers. However, we show that when quantum effects are properly taken into account, the integrity of the black-hole event horizon is irrefutable. This observation suggests that the cosmic censorship principle is intrinsically a quantum phenomena. |
gr-qc/9811093 | Mark D. Roberts | Mark D. Roberts | Spacetime Exterior to a Star: Against Asymptotic Flatness | Five references added, some small changes | null | null | uct-cosmology-99/08 | gr-qc astro-ph | null | In many circumstances the perfect fluid conservation equations can be
directly integrated to give a Geometric-Thermodynamic equation: typically that
the lapse $N$ is the reciprocal of the enthalphy $h$, ($ N=1/h$). This result
is aesthetically appealing as it depends only on the fluid conservation
equations and does not depend on specific field equations such as Einstein's.
Here the form of the Geometric-Thermodynamic equation is derived subject to
spherical symmetry and also for the shift-free ADM formalism. There at least
three applications of the Geometric-Thermodynamic equation, the most important
being to the notion of asympotic flatness and hence to spacetime exterior to a
star. For asymptotic flatness one wants $h\to 0$ and $N\to 1$ simultaneously,
but this is incompatible with the Geometric-Thermodynamic equation.
Observational data and asymptotic flatness are discussed. It is argued that a
version of Mach's principle does not allow asymptotic flatness.
| [
{
"created": "Sat, 28 Nov 1998 13:43:08 GMT",
"version": "v1"
},
{
"created": "Sat, 13 Nov 1999 12:19:10 GMT",
"version": "v2"
},
{
"created": "Sat, 11 Mar 2000 16:47:04 GMT",
"version": "v3"
},
{
"created": "Tue, 4 Jul 2000 17:38:24 GMT",
"version": "v4"
},
{
"cr... | 2007-05-23 | [
[
"Roberts",
"Mark D.",
""
]
] | In many circumstances the perfect fluid conservation equations can be directly integrated to give a Geometric-Thermodynamic equation: typically that the lapse $N$ is the reciprocal of the enthalphy $h$, ($ N=1/h$). This result is aesthetically appealing as it depends only on the fluid conservation equations and does not depend on specific field equations such as Einstein's. Here the form of the Geometric-Thermodynamic equation is derived subject to spherical symmetry and also for the shift-free ADM formalism. There at least three applications of the Geometric-Thermodynamic equation, the most important being to the notion of asympotic flatness and hence to spacetime exterior to a star. For asymptotic flatness one wants $h\to 0$ and $N\to 1$ simultaneously, but this is incompatible with the Geometric-Thermodynamic equation. Observational data and asymptotic flatness are discussed. It is argued that a version of Mach's principle does not allow asymptotic flatness. |
1202.3445 | Claude Warnick | C. M. Warnick | The massive wave equation in asymptotically AdS spacetimes | Minor changes, 26 pages | Commun.Math.Phys. 321 (2013) 85-111 | 10.1007/s00220-013-1720-3 | ALBERTA THY 3-12 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the massive wave equation on asymptotically AdS spaces. We show
that the timelike scri behaves like a finite timelike boundary, on which one
may impose the equivalent of Dirichlet, Neumann or Robin conditions for a range
of (negative) mass parameter which includes the conformally coupled case. We
demonstrate well posedness for the associated initial-boundary value problems
at the $H^1$ level of regularity. We also prove that higher regularity may be
obtained, together with an asymptotic expansion for the field near scri. The
proofs rely on energy methods, tailored to the modified energy introduced by
Breitenlohner and Freedman. We do not assume the spacetime is stationary, nor
that the wave equation separates.
| [
{
"created": "Wed, 15 Feb 2012 21:08:28 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Mar 2012 18:52:23 GMT",
"version": "v2"
},
{
"created": "Mon, 28 Jul 2014 09:43:27 GMT",
"version": "v3"
}
] | 2014-07-29 | [
[
"Warnick",
"C. M.",
""
]
] | We consider the massive wave equation on asymptotically AdS spaces. We show that the timelike scri behaves like a finite timelike boundary, on which one may impose the equivalent of Dirichlet, Neumann or Robin conditions for a range of (negative) mass parameter which includes the conformally coupled case. We demonstrate well posedness for the associated initial-boundary value problems at the $H^1$ level of regularity. We also prove that higher regularity may be obtained, together with an asymptotic expansion for the field near scri. The proofs rely on energy methods, tailored to the modified energy introduced by Breitenlohner and Freedman. We do not assume the spacetime is stationary, nor that the wave equation separates. |
1801.02249 | Sarah Geller | Sarah R. Geller, Jolyon K. Bloomfield, Alan H. Guth | Mass of a Patch of an FRW Universe | 9 figures, 12 pages | null | null | MIT-CTP/4971 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In 1963, Zel'dovich devised a method to define the mass of a closed
Friedmann-Robertson-Walker (FRW) universe, showing that by this definition it
is exactly zero. Rounding out this result, we show that the masses of flat and
open universes are (unsurprisingly) divergent. We also present closed-form
solutions for the trajectory of the boundary of a finite spherical patch of
homogeneous pressureless dust for each class of curvature, exploring the
dynamics of the boundary in detail. In all cases, the FRW patch emerges from a
white hole. In the closed case, the patch expands to a maximum radius before
contracting and entering a black hole, while flat and open FRW patches expand
without bound. We compare our results to the classical expectations of
Newtonian cosmology, showing that for small radii the Newtonian energy gives
the leading correction to the rest mass energy.
| [
{
"created": "Sun, 7 Jan 2018 20:55:07 GMT",
"version": "v1"
}
] | 2018-01-09 | [
[
"Geller",
"Sarah R.",
""
],
[
"Bloomfield",
"Jolyon K.",
""
],
[
"Guth",
"Alan H.",
""
]
] | In 1963, Zel'dovich devised a method to define the mass of a closed Friedmann-Robertson-Walker (FRW) universe, showing that by this definition it is exactly zero. Rounding out this result, we show that the masses of flat and open universes are (unsurprisingly) divergent. We also present closed-form solutions for the trajectory of the boundary of a finite spherical patch of homogeneous pressureless dust for each class of curvature, exploring the dynamics of the boundary in detail. In all cases, the FRW patch emerges from a white hole. In the closed case, the patch expands to a maximum radius before contracting and entering a black hole, while flat and open FRW patches expand without bound. We compare our results to the classical expectations of Newtonian cosmology, showing that for small radii the Newtonian energy gives the leading correction to the rest mass energy. |
gr-qc/0108050 | Taylan Yetkin | Ali Havare, Taylan Yetkin | Exact Solution of Photon Equation in Stationary G\"{o}del-type and
G\"{o}del Space-Times | 9 pages,RevTeX, no figure, revised for publication | Class.Quant.Grav.19:2783-2792,2002 | 10.1088/0264-9381/19/11/303 | null | gr-qc | null | In this work the photon equation (massless Duffin-Kemmer-Petiau equation) is
written expilicitly for general type of stationary G\"{o}del space-times and is
solved exactly for G\"{o}del-type and G\"{o}del space-times. Harmonic
oscillator behaviour of the solutions is discussed and energy spectrum of
photon is obtained.
| [
{
"created": "Mon, 20 Aug 2001 10:31:36 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Nov 2001 22:30:49 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Havare",
"Ali",
""
],
[
"Yetkin",
"Taylan",
""
]
] | In this work the photon equation (massless Duffin-Kemmer-Petiau equation) is written expilicitly for general type of stationary G\"{o}del space-times and is solved exactly for G\"{o}del-type and G\"{o}del space-times. Harmonic oscillator behaviour of the solutions is discussed and energy spectrum of photon is obtained. |
gr-qc/0612054 | Roldao da Rocha | Julio M. Hoff da Silva and Roldao da Rocha | Shortcuts in particle production in a toroidal compactified spacetime | 5 pages, RevTeX, to be published in Int.J.Mod.Phys.D 11 (2007) | Int.J.Mod.Phys.D16:1853-1861,2007 | 10.1142/S0218271807011140 | null | gr-qc | null | We investigate the particle production in a toroidal compactified spacetime
due to the expansion of a Friedmann cosmological model in R3 x S1 outside a
U(1) local cosmic string. The case of a Friedmann spacetime is also
investigated when torsion is incorporated in the connection. We present a
generalization to toroidal compactification of p extra dimensions, where the
topology is given by R3 x T^p. Some implications are presented and discussed.
Besides the dynamics of spacetime, we also investigate in details the physical
consequences of the topological transformations.
| [
{
"created": "Fri, 8 Dec 2006 20:56:19 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Dec 2006 21:25:54 GMT",
"version": "v2"
},
{
"created": "Tue, 6 Mar 2007 18:37:29 GMT",
"version": "v3"
},
{
"created": "Fri, 9 Nov 2007 19:23:59 GMT",
"version": "v4"
}
] | 2009-02-18 | [
[
"da Silva",
"Julio M. Hoff",
""
],
[
"da Rocha",
"Roldao",
""
]
] | We investigate the particle production in a toroidal compactified spacetime due to the expansion of a Friedmann cosmological model in R3 x S1 outside a U(1) local cosmic string. The case of a Friedmann spacetime is also investigated when torsion is incorporated in the connection. We present a generalization to toroidal compactification of p extra dimensions, where the topology is given by R3 x T^p. Some implications are presented and discussed. Besides the dynamics of spacetime, we also investigate in details the physical consequences of the topological transformations. |
gr-qc/9709033 | Eric Poisson | William G. Laarakkers and Eric Poisson | Quadrupole moments of rotating neutron stars | ReVTeX, 7 pages, 5 figures, additional material, and references added | null | 10.1086/306732 | null | gr-qc | null | Numerical models of rotating neutron stars are constructed for four equations
of state using the computer code RNS written by Stergioulas. For five selected
values of the star's gravitational mass (in the interval between 1.0 and 1.8
solar masses) and for each equation of state, the star's angular momentum is
varied from J=0 to the Keplerian limit J=J_{max}. For each neutron-star
configuration we compute Q, the quadrupole moment of the mass distribution. We
show that for given values of M and J, |Q| increases with the stiffness of the
equation of state. For fixed mass and equation of state, the dependence on J is
well reproduced with a simple quadratic fit, Q \simeq - aJ^2/M c^2, where c is
the speed of light, and a is a parameter of order unity depending on the mass
and the equation of state.
| [
{
"created": "Fri, 12 Sep 1997 20:33:10 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Mar 1998 00:28:00 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Laarakkers",
"William G.",
""
],
[
"Poisson",
"Eric",
""
]
] | Numerical models of rotating neutron stars are constructed for four equations of state using the computer code RNS written by Stergioulas. For five selected values of the star's gravitational mass (in the interval between 1.0 and 1.8 solar masses) and for each equation of state, the star's angular momentum is varied from J=0 to the Keplerian limit J=J_{max}. For each neutron-star configuration we compute Q, the quadrupole moment of the mass distribution. We show that for given values of M and J, |Q| increases with the stiffness of the equation of state. For fixed mass and equation of state, the dependence on J is well reproduced with a simple quadratic fit, Q \simeq - aJ^2/M c^2, where c is the speed of light, and a is a parameter of order unity depending on the mass and the equation of state. |
2209.00952 | Mohammed Alzain | Mohammed Alzain | General Relativity and the Ricci Flow | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Riemannian geometry, the Ricci flow is the analogue of heat diffusion; a
deformation of the metric tensor driven by its Ricci curvature. As a step
towards resolving the problem of time in quantum gravity, we attempt to merge
the Ricci flow equation with the Hamilton-Jacobi equation for general
relativity.
| [
{
"created": "Fri, 2 Sep 2022 11:17:20 GMT",
"version": "v1"
}
] | 2022-09-05 | [
[
"Alzain",
"Mohammed",
""
]
] | In Riemannian geometry, the Ricci flow is the analogue of heat diffusion; a deformation of the metric tensor driven by its Ricci curvature. As a step towards resolving the problem of time in quantum gravity, we attempt to merge the Ricci flow equation with the Hamilton-Jacobi equation for general relativity. |
1502.04693 | Maxim Eingorn | Ozgur Akarsu, Mariam Bouhmadi-L\'opez, Maxim Brilenkov, Ruslan
Brilenkov, Maxim Eingorn, Alexander Zhuk | Are dark energy models with variable EoS parameter $w$ compatible with
the late inhomogeneous Universe? | 14 pages, no figures | JCAP 07 (2015) 038 | 10.1088/1475-7516/2015/07/038 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the late-time evolution of the Universe where dark energy (DE) is
presented by a barotropic fluid on top of cold dark matter (CDM). We also take
into account the radiation content of the Universe. Here by the late stage of
the evolution we refer to the epoch where CDM is already clustered into
inhomogeneously distributed discrete structures (galaxies, groups and clusters
of galaxies). Under this condition the mechanical approach is an adequate tool
to study the Universe deep inside the cell of uniformity. More precisely, we
study scalar perturbations of the FLRW metric due to inhomogeneities of CDM as
well as fluctuations of radiation and DE. For an arbitrary equation of state
for DE we obtain a system of equations for the scalar perturbations within the
mechanical approach. First, in the case of a constant DE equation of state
parameter $w$, we demonstrate that our method singles out the cosmological
constant as the only viable dark energy candidate. Then, we apply our approach
to variable equation of state parameters in the form of three different linear
parametrizations of $w$, e.g., the Chevallier-Polarski-Linder perfect fluid
model. We conclude that all these models are incompatible with the theory of
scalar perturbations in the late Universe.
| [
{
"created": "Mon, 16 Feb 2015 20:56:55 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jul 2015 19:44:30 GMT",
"version": "v2"
}
] | 2015-07-24 | [
[
"Akarsu",
"Ozgur",
""
],
[
"Bouhmadi-López",
"Mariam",
""
],
[
"Brilenkov",
"Maxim",
""
],
[
"Brilenkov",
"Ruslan",
""
],
[
"Eingorn",
"Maxim",
""
],
[
"Zhuk",
"Alexander",
""
]
] | We study the late-time evolution of the Universe where dark energy (DE) is presented by a barotropic fluid on top of cold dark matter (CDM). We also take into account the radiation content of the Universe. Here by the late stage of the evolution we refer to the epoch where CDM is already clustered into inhomogeneously distributed discrete structures (galaxies, groups and clusters of galaxies). Under this condition the mechanical approach is an adequate tool to study the Universe deep inside the cell of uniformity. More precisely, we study scalar perturbations of the FLRW metric due to inhomogeneities of CDM as well as fluctuations of radiation and DE. For an arbitrary equation of state for DE we obtain a system of equations for the scalar perturbations within the mechanical approach. First, in the case of a constant DE equation of state parameter $w$, we demonstrate that our method singles out the cosmological constant as the only viable dark energy candidate. Then, we apply our approach to variable equation of state parameters in the form of three different linear parametrizations of $w$, e.g., the Chevallier-Polarski-Linder perfect fluid model. We conclude that all these models are incompatible with the theory of scalar perturbations in the late Universe. |
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