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2106.01971 | Praveen Negi | P S Negi | A Core-envelope Analytic Model for the Vela Pulsar | 13 pages, 7 figures. arXiv admin note: substantial text overlap with
arXiv:2105.14324 | INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME
9, ISSUE 02, FEBRUARY 2020 | null | null | gr-qc astro-ph.HE | http://creativecommons.org/publicdomain/zero/1.0/ | The core-envelope models presented in {Ref1}; {Ref2}, corresponding to the
values of compactness parameter, $u \equiv M/a$ = 0.30 and 0.25 (mass to size
ratio in geometrized units) have been studied under slow rotation. It is seen
that these models are capable of explaining all the observational values of
glitch healing parameter, $G_h = I_{\rm core}/I_{\rm total} < 0.55$ {Ref3} for
the Vela pulsar. The models yield the maximum values of mass, $M$, surface
redshift, $z_a$, and the moment of inertia, $I_{\rm Vela}$ for the Vela pulsar
in the range $M = 3.079M_\odot - 2.263M_\odot$; $z_a = 0.581 - 0.414$ and
$I_{\rm Vela,45} =6.9 - 3.5$ (where $I_{45}=I/10^{45}\rm g{cm}^2$) respectively
for the values of $u = $ 0.30 and 0.25 and for an assigned value of the surface
density, $E_a = 2\times 10^{14}\rm g{cm}^{-3}$ {Ref4}. The values of masses
lower than the above mentioned values ( so called the realistic mass range, $M
= 1.4\pm0.2 M_\odot$, in the literature) but significantly higher than that of
the unrealistic mass range $M \leq 0.5M_\odot$ (obtained for the Vela pulsar in
the literature on the basis of parametrized neutron star (NS) models based on
equations of state (EOSs) of dense nuclear matter {Ref3}) and other parameters
may be obtained likewise for the above mentioned range of the values of $G_h$
corresponding to the values of $u < 0.25$. The models are found to be causally
consistent, gravitational bound and pulsationally stable. The upper bound on
neutron star (NS) mass obtained in this study which is applicable for the Vela
pulsar, in fact, corresponds to the mean value of the upper bound on NS mass
obtained in the classical result {Ref5} and that obtained on the basis of
modern EOSs for neutron star matter {Ref6} and is in a good agreement with the
most recent theoretical estimate {Ref7}.
| [
{
"created": "Thu, 3 Jun 2021 16:18:13 GMT",
"version": "v1"
}
] | 2021-06-04 | [
[
"Negi",
"P S",
""
]
] | The core-envelope models presented in {Ref1}; {Ref2}, corresponding to the values of compactness parameter, $u \equiv M/a$ = 0.30 and 0.25 (mass to size ratio in geometrized units) have been studied under slow rotation. It is seen that these models are capable of explaining all the observational values of glitch healing parameter, $G_h = I_{\rm core}/I_{\rm total} < 0.55$ {Ref3} for the Vela pulsar. The models yield the maximum values of mass, $M$, surface redshift, $z_a$, and the moment of inertia, $I_{\rm Vela}$ for the Vela pulsar in the range $M = 3.079M_\odot - 2.263M_\odot$; $z_a = 0.581 - 0.414$ and $I_{\rm Vela,45} =6.9 - 3.5$ (where $I_{45}=I/10^{45}\rm g{cm}^2$) respectively for the values of $u = $ 0.30 and 0.25 and for an assigned value of the surface density, $E_a = 2\times 10^{14}\rm g{cm}^{-3}$ {Ref4}. The values of masses lower than the above mentioned values ( so called the realistic mass range, $M = 1.4\pm0.2 M_\odot$, in the literature) but significantly higher than that of the unrealistic mass range $M \leq 0.5M_\odot$ (obtained for the Vela pulsar in the literature on the basis of parametrized neutron star (NS) models based on equations of state (EOSs) of dense nuclear matter {Ref3}) and other parameters may be obtained likewise for the above mentioned range of the values of $G_h$ corresponding to the values of $u < 0.25$. The models are found to be causally consistent, gravitational bound and pulsationally stable. The upper bound on neutron star (NS) mass obtained in this study which is applicable for the Vela pulsar, in fact, corresponds to the mean value of the upper bound on NS mass obtained in the classical result {Ref5} and that obtained on the basis of modern EOSs for neutron star matter {Ref6} and is in a good agreement with the most recent theoretical estimate {Ref7}. |
gr-qc/9705083 | Madore | J. Madore | On Poisson Structure and Curvature | 8 pages, Latex | Rept.Math.Phys. 43 (1999) 231-238 | 10.1016/S0034-4877(99)80030-5 | null | gr-qc hep-th | null | We consider a curved space-time whose algebra of functions is the commutative
limit of a noncommutative algebra and which has therefore an induced Poisson
structure. In a simple example we determine a relation between this structure
and the Riemann tensor.
| [
{
"created": "Fri, 30 May 1997 14:05:30 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Madore",
"J.",
""
]
] | We consider a curved space-time whose algebra of functions is the commutative limit of a noncommutative algebra and which has therefore an induced Poisson structure. In a simple example we determine a relation between this structure and the Riemann tensor. |
1604.00541 | Gianluca Calcagni | Michele Arzano, Gianluca Calcagni | What gravity waves are telling about quantum spacetime | 5 pages. v2: one paragraph, one note, and references added; v3:
publication data added | Phys. Rev. D 93, 124065 (2016) | 10.1103/PhysRevD.93.124065 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss various modified dispersion relations motivated by quantum gravity
which might affect the propagation of the recently observed gravitational-wave
signal of the event GW150914. We find that the bounds set by the data on the
characteristic quantum-gravity mass scale $M$ are too weak to constrain these
scenarios and, in general, much weaker than the expected $M> 10^4\,\text{eV}$
for a correction to the dispersion relation linear in $1/M$. We illustrate this
issue by giving lower bounds on $M$, plus an upper bound coming from
constraints on the size of a quantum ergosphere. We also show that a
phenomenological dispersion relation $\omega^2 = k^2(1+\alpha k^n/M^n)$ is
compatible with observations and, at the same time, has a phenomenologically
viable mass $M>10\,\text{TeV}$ only in the quite restrictive range $0<n<0.68$.
Remarkably, this is the domain of multiscale spacetimes but not of known
quantum-gravity models.
| [
{
"created": "Sat, 2 Apr 2016 18:20:21 GMT",
"version": "v1"
},
{
"created": "Mon, 16 May 2016 15:16:13 GMT",
"version": "v2"
},
{
"created": "Tue, 28 Jun 2016 10:19:01 GMT",
"version": "v3"
}
] | 2016-06-29 | [
[
"Arzano",
"Michele",
""
],
[
"Calcagni",
"Gianluca",
""
]
] | We discuss various modified dispersion relations motivated by quantum gravity which might affect the propagation of the recently observed gravitational-wave signal of the event GW150914. We find that the bounds set by the data on the characteristic quantum-gravity mass scale $M$ are too weak to constrain these scenarios and, in general, much weaker than the expected $M> 10^4\,\text{eV}$ for a correction to the dispersion relation linear in $1/M$. We illustrate this issue by giving lower bounds on $M$, plus an upper bound coming from constraints on the size of a quantum ergosphere. We also show that a phenomenological dispersion relation $\omega^2 = k^2(1+\alpha k^n/M^n)$ is compatible with observations and, at the same time, has a phenomenologically viable mass $M>10\,\text{TeV}$ only in the quite restrictive range $0<n<0.68$. Remarkably, this is the domain of multiscale spacetimes but not of known quantum-gravity models. |
gr-qc/0006106 | Fabrizio Tamburini | Fabrizio Tamburini, Bruce A. Bassett, Carlo Ungarelli (Portsmouth) | Detection of gravitational waves with quantum encryption technology | 10 pages, Revtex, 2 colour JPEG figures, high resolution versions of
the figures and additional material available at
http://sun1.sms.port.ac.uk/cosmos/users/bruce/mousetrap/ | null | null | null | gr-qc astro-ph physics.ins-det quant-ph | null | We propose a new technique for detecting gravitational waves using Quantum
Entangled STate (QUEST) technology. Gravitational waves reduce the non-locality
of correlated quanta controlled by Bell's inequalities, distorting quantum
encryption key statistics away from a pure white noise. Gravitational waves
therefore act as shadow eavesdroppers. The resulting colour distortions can, at
least in principle, be separated from noise and can differentiate both
deterministic and stochastic sources.
| [
{
"created": "Thu, 29 Jun 2000 17:01:36 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Tamburini",
"Fabrizio",
"",
"Portsmouth"
],
[
"Bassett",
"Bruce A.",
"",
"Portsmouth"
],
[
"Ungarelli",
"Carlo",
"",
"Portsmouth"
]
] | We propose a new technique for detecting gravitational waves using Quantum Entangled STate (QUEST) technology. Gravitational waves reduce the non-locality of correlated quanta controlled by Bell's inequalities, distorting quantum encryption key statistics away from a pure white noise. Gravitational waves therefore act as shadow eavesdroppers. The resulting colour distortions can, at least in principle, be separated from noise and can differentiate both deterministic and stochastic sources. |
2006.03095 | Alexandru Dima | Alexandru Dima, Enrico Barausse, Nicola Franchini, Thomas P. Sotiriou | Spin-induced black hole spontaneous scalarization | Typos corrected in proof to match version published in PRL | Phys. Rev. Lett. 125, 231101 (2020) | 10.1103/PhysRevLett.125.231101 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study scalar fields in a black hole background and show that, when the
scalar is suitably coupled to curvature, rapid rotation can induce a tachyonic
instability. This instability, which is the hallmark of spontaneous
scalarization in the linearized regime, is expected to be quenched by
nonlinearities and endow the black hole with scalar hair. Hence, our results
demonstrate the existence of a broad class of theories that share the same
stationary black hole solutions with general relativity at low spins, but which
exhibit black hole hair at sufficiently high spins ($a/M\gtrsim 0.5$). This
result has clear implications for tests of general relativity and the nature of
black holes with gravitational and electromagnetic observations.
| [
{
"created": "Thu, 4 Jun 2020 18:40:41 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Jul 2020 11:03:14 GMT",
"version": "v2"
},
{
"created": "Fri, 30 Oct 2020 09:32:00 GMT",
"version": "v3"
},
{
"created": "Tue, 17 Nov 2020 08:45:57 GMT",
"version": "v4"
}
] | 2020-12-07 | [
[
"Dima",
"Alexandru",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Franchini",
"Nicola",
""
],
[
"Sotiriou",
"Thomas P.",
""
]
] | We study scalar fields in a black hole background and show that, when the scalar is suitably coupled to curvature, rapid rotation can induce a tachyonic instability. This instability, which is the hallmark of spontaneous scalarization in the linearized regime, is expected to be quenched by nonlinearities and endow the black hole with scalar hair. Hence, our results demonstrate the existence of a broad class of theories that share the same stationary black hole solutions with general relativity at low spins, but which exhibit black hole hair at sufficiently high spins ($a/M\gtrsim 0.5$). This result has clear implications for tests of general relativity and the nature of black holes with gravitational and electromagnetic observations. |
gr-qc/0512121 | Slava G. Turyshev | Slava G. Turyshev, Viktor T. Toth, Larry R. Kellogg, Eunice. L. Lau,
and Kyong J. Lee | The Study of the Pioneer Anomaly: New Data and Objectives for New
Investigation | 43 pages, 40 figures, 3 tables, minor changes before publication | Int.J.Mod.Phys.D15:1-56,2006 | 10.1142/S0218271806008218 | null | gr-qc | null | Radiometric tracking data from Pioneer 10 and 11 spacecraft has consistently
indicated the presence of a small, anomalous, Doppler frequency drift,
uniformly changing with a rate of ~6 x 10^{-9} Hz/s; the drift can be
interpreted as a constant sunward acceleration of each particular spacecraft of
a_P = (8.74 \pm 1.33) x 10^{-10} m/s^2. This signal is known as the Pioneer
anomaly; the nature of this anomaly remains unexplained. We discuss the efforts
to retrieve the entire data sets of the Pioneer 10/11 radiometric Doppler data.
We also report on the recently recovered telemetry files that may be used to
reconstruct the engineering history of both spacecraft using original project
documentation and newly developed software tools. We discuss possible ways to
further investigate the discovered effect using these telemetry files in
conjunction with the analysis of the much extended Doppler data. We present the
main objectives of new upcoming study of the Pioneer anomaly, namely i)
analysis of the early data that could yield the direction of the anomaly, ii)
analysis of planetary encounters, that should tell more about the onset of the
anomaly, iii) analysis of the entire dataset, to better determine the anomaly's
temporal behavior, iv) comparative analysis of individual anomalous
accelerations for the two Pioneers, v) the detailed study of on-board
systematics, and vi) development of a thermal-electric-dynamical model using
on-board telemetry. The outlined strategy may allow for a higher accuracy
solution for a_P and, possibly, will lead to an unambiguous determination of
the origin of the Pioneer anomaly.
| [
{
"created": "Wed, 21 Dec 2005 21:49:36 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Mar 2006 21:43:03 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Turyshev",
"Slava G.",
""
],
[
"Toth",
"Viktor T.",
""
],
[
"Kellogg",
"Larry R.",
""
],
[
"Lau",
"Eunice. L.",
""
],
[
"Lee",
"Kyong J.",
""
]
] | Radiometric tracking data from Pioneer 10 and 11 spacecraft has consistently indicated the presence of a small, anomalous, Doppler frequency drift, uniformly changing with a rate of ~6 x 10^{-9} Hz/s; the drift can be interpreted as a constant sunward acceleration of each particular spacecraft of a_P = (8.74 \pm 1.33) x 10^{-10} m/s^2. This signal is known as the Pioneer anomaly; the nature of this anomaly remains unexplained. We discuss the efforts to retrieve the entire data sets of the Pioneer 10/11 radiometric Doppler data. We also report on the recently recovered telemetry files that may be used to reconstruct the engineering history of both spacecraft using original project documentation and newly developed software tools. We discuss possible ways to further investigate the discovered effect using these telemetry files in conjunction with the analysis of the much extended Doppler data. We present the main objectives of new upcoming study of the Pioneer anomaly, namely i) analysis of the early data that could yield the direction of the anomaly, ii) analysis of planetary encounters, that should tell more about the onset of the anomaly, iii) analysis of the entire dataset, to better determine the anomaly's temporal behavior, iv) comparative analysis of individual anomalous accelerations for the two Pioneers, v) the detailed study of on-board systematics, and vi) development of a thermal-electric-dynamical model using on-board telemetry. The outlined strategy may allow for a higher accuracy solution for a_P and, possibly, will lead to an unambiguous determination of the origin of the Pioneer anomaly. |
1806.05944 | Octavian Micu | Roberto Casadio, Octavian Micu | Horizon Quantum Mechanics of collapsing shells | 21 pages, 11 figures | null | 10.1140/epjc/s10052-018-6326-7 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the probability that a horizon appears when concentric shells of
matter collide, by computing the horizon wave-function of the system. We mostly
consider the collision of two ultra-relativistic shells, both shrinking and
expanding, at the moment their radii are equal, and find a probability that the
system is a black hole which is in qualitative agreement with what one would
expect according to the hoop conjecture and the uncertainty principle of
quantum physics, and parallels the results obtained for simpler sources. One
new feature however emerges, in that this probability shows a modulation with
the momenta of the shells and the radius at which the shells collide, as a
manifestation of quantum mechanical interference. Finally, we also consider the
case of one light shell collapsing into a larger central mass.
| [
{
"created": "Fri, 15 Jun 2018 13:16:28 GMT",
"version": "v1"
}
] | 2018-11-14 | [
[
"Casadio",
"Roberto",
""
],
[
"Micu",
"Octavian",
""
]
] | We study the probability that a horizon appears when concentric shells of matter collide, by computing the horizon wave-function of the system. We mostly consider the collision of two ultra-relativistic shells, both shrinking and expanding, at the moment their radii are equal, and find a probability that the system is a black hole which is in qualitative agreement with what one would expect according to the hoop conjecture and the uncertainty principle of quantum physics, and parallels the results obtained for simpler sources. One new feature however emerges, in that this probability shows a modulation with the momenta of the shells and the radius at which the shells collide, as a manifestation of quantum mechanical interference. Finally, we also consider the case of one light shell collapsing into a larger central mass. |
1403.7452 | Sergey Chervon | S.V. Chervon | Chiral Cosmological Models: Dark Sector Fields Description | 17 pages; to appear in Quantum Matter | Quantum Matter (ISSN: 2164-7615) v.2, 71-82, 2013 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present review is devoted to a Chiral Cosmological Model as the
self-gravitating nonlinear sigma model with the potential of (self)interactions
employed in cosmology. The chiral cosmological model has successive
applications in descriptions of the inflationary epoch of the Universe
evolution; the present accelerated expansion of the Universe also can be
described by the chiral fields multiplet as the dark energy in wide sense.
To be more illustrative we are often addressed to the two-component chiral
cosmological model. Namely, the two-component chiral cosmological model
describing the phantom field with interaction to a canonical scalar field is
analyzed in details. New generalized model of quintom character is proposed and
exact solutions are founded out.
In the review we represented the perturbation theory for chiral cosmological
model with the aim to describe the structure formation using the progress
achieved in the inflation theory. It was shown that cosmological perturbations
from chiral fields can be decomposed for inflaton and the dark sector
perturbations. The two-component model is investigated in details, the general
solution for shortwave approximation is obtained and analyzed for power law
Universe expansion.
New issue for understanding the features of Universe evolution is proposed by
consideration of the dark sector fields on the inflaton background. The results
are illustrated for the solutions in the long-wave approximation.
| [
{
"created": "Fri, 28 Mar 2014 17:23:28 GMT",
"version": "v1"
}
] | 2014-03-31 | [
[
"Chervon",
"S. V.",
""
]
] | The present review is devoted to a Chiral Cosmological Model as the self-gravitating nonlinear sigma model with the potential of (self)interactions employed in cosmology. The chiral cosmological model has successive applications in descriptions of the inflationary epoch of the Universe evolution; the present accelerated expansion of the Universe also can be described by the chiral fields multiplet as the dark energy in wide sense. To be more illustrative we are often addressed to the two-component chiral cosmological model. Namely, the two-component chiral cosmological model describing the phantom field with interaction to a canonical scalar field is analyzed in details. New generalized model of quintom character is proposed and exact solutions are founded out. In the review we represented the perturbation theory for chiral cosmological model with the aim to describe the structure formation using the progress achieved in the inflation theory. It was shown that cosmological perturbations from chiral fields can be decomposed for inflaton and the dark sector perturbations. The two-component model is investigated in details, the general solution for shortwave approximation is obtained and analyzed for power law Universe expansion. New issue for understanding the features of Universe evolution is proposed by consideration of the dark sector fields on the inflaton background. The results are illustrated for the solutions in the long-wave approximation. |
1507.06299 | Eleni-Alexandra Kontou | Eleni-Alexandra Kontou | Averaged null energy condition and quantum inequalities in curved
spacetime | PhD Thesis, Tufts University, Advisor: Ken D. Olum, 85 Pages, 6
Figures | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Averaged Null Energy Condition (ANEC) states that the integral along a
complete null geodesic of the projection of the stress-energy tensor onto the
tangent vector to the geodesic cannot be negative. ANEC can be used to rule out
spacetimes with exotic phenomena, such as closed timelike curves, superluminal
travel and wormholes. We prove that ANEC is obeyed by a minimally-coupled, free
quantum scalar field on any achronal null geodesic (not two points can be
connected with a timelike curve) surrounded by a tubular neighborhood whose
curvature is produced by a classical source. To prove ANEC we use a
null-projected quantum inequality, which provides constraints on how negative
the weighted average of the renormalized stress-energy tensor of a quantum
field can be. Starting with a general result of Fewster and Smith, we first
derive a timelike projected quantum inequality for a minimally-coupled scalar
field on flat spacetime with a background potential. Using that result we
proceed to find the bound of a quantum inequality on a geodesic in a spacetime
with small curvature, working to first order in the Ricci tensor and its
derivatives. The last step is to derive a bound for the null-projected quantum
inequality on a general timelike path. Finally we use that result to prove
achronal ANEC in spacetimes with small curvature.
| [
{
"created": "Wed, 22 Jul 2015 19:58:26 GMT",
"version": "v1"
}
] | 2015-07-23 | [
[
"Kontou",
"Eleni-Alexandra",
""
]
] | The Averaged Null Energy Condition (ANEC) states that the integral along a complete null geodesic of the projection of the stress-energy tensor onto the tangent vector to the geodesic cannot be negative. ANEC can be used to rule out spacetimes with exotic phenomena, such as closed timelike curves, superluminal travel and wormholes. We prove that ANEC is obeyed by a minimally-coupled, free quantum scalar field on any achronal null geodesic (not two points can be connected with a timelike curve) surrounded by a tubular neighborhood whose curvature is produced by a classical source. To prove ANEC we use a null-projected quantum inequality, which provides constraints on how negative the weighted average of the renormalized stress-energy tensor of a quantum field can be. Starting with a general result of Fewster and Smith, we first derive a timelike projected quantum inequality for a minimally-coupled scalar field on flat spacetime with a background potential. Using that result we proceed to find the bound of a quantum inequality on a geodesic in a spacetime with small curvature, working to first order in the Ricci tensor and its derivatives. The last step is to derive a bound for the null-projected quantum inequality on a general timelike path. Finally we use that result to prove achronal ANEC in spacetimes with small curvature. |
1602.00391 | Yuta Michimura | Yuta Michimura, Jake Guscott, Matthew Mewes, Nobuyuki Matsumoto,
Noriaki Ohmae, Wataru Kokuyama, Yoichi Aso, Masaki Ando | Higher order test of Lorentz invariance with an optical ring cavity | 6 pages, 3 figures. Proceedings for the Fourteenth Marcel Grossmann
Meeting, Rome, July 12-18, 2015 | null | null | null | gr-qc physics.optics | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have developed an apparatus to search for the higher-order Lorentz
violation in photons by measuring the resonant frequency difference between two
counterpropagating directions of an asymmetric optical ring cavity. From the
year-long data taken between 2012 and 2013, we found no evidence for the light
speed anisotropy at the level of $\delta c/c \lesssim 10^{-15}$. Limits on the
dipole components of the anisotropy are improved by more than an order of
magnitude, and limits on the hexapole components are obtained for the first
time. An overview of our apparatus and the data analysis in the framework of
the spherical harmonics decomposition of anisotropy are presented. We also
present the status of the recent upgrade of the apparatus.
| [
{
"created": "Mon, 1 Feb 2016 04:46:04 GMT",
"version": "v1"
}
] | 2016-02-02 | [
[
"Michimura",
"Yuta",
""
],
[
"Guscott",
"Jake",
""
],
[
"Mewes",
"Matthew",
""
],
[
"Matsumoto",
"Nobuyuki",
""
],
[
"Ohmae",
"Noriaki",
""
],
[
"Kokuyama",
"Wataru",
""
],
[
"Aso",
"Yoichi",
""
],
[
... | We have developed an apparatus to search for the higher-order Lorentz violation in photons by measuring the resonant frequency difference between two counterpropagating directions of an asymmetric optical ring cavity. From the year-long data taken between 2012 and 2013, we found no evidence for the light speed anisotropy at the level of $\delta c/c \lesssim 10^{-15}$. Limits on the dipole components of the anisotropy are improved by more than an order of magnitude, and limits on the hexapole components are obtained for the first time. An overview of our apparatus and the data analysis in the framework of the spherical harmonics decomposition of anisotropy are presented. We also present the status of the recent upgrade of the apparatus. |
2007.01703 | Pardyumn Kumar Sahoo | Simran Arora, S. K. J. Pacif, Snehasish Bhattacharjee, P.K. Sahoo | $f(Q,T)$ gravity models with observational constraints | Physics of the Dark Universe accepted version | Physics of the Dark Universe, 30(2020) 100664 | 10.1016/j.dark.2020.100664 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The paper presents late time cosmology in $f(Q,T)$ gravity where the dark
energy is purely geometric in nature. We start by employing a well motivated
$f(Q,T)$ gravity model, $f(Q,T)=mQ^{n}+bT$ where $m,n$ and $b$ are model
parameters. Additionally we also assume the universe to be dominated by
pressure-less matter which yields a power law type scale factor of the form $%
a(t)=c_{2}(At+c_{1})^{\frac{1}{A}}$, where $A=\dfrac{3(8\pi +b)}{n(16\pi +3b)%
}$ and $c_{1}$ \& $c_{2}$ are just integration constants. To investigate the
cosmological viability of the model, constraints on the model parameters were
imposed from the updated 57 points of Hubble data sets and 580 points of union
2.1 compilation supernovae data sets. We have thoroughly investigated the
nature of geometrical dark energy mimicked by the parametrization of
$f(Q,T)=mQ^{n}+bT$ with the assistance of statefinder diagnostic in $\{s,r\}$
and $\{q,r\}$ planes and also performed the $Om$ -diagnostic analysis. The
present analysis makes it clear-cut that $f(Q,T)$ gravity can be promising in
addressing the current cosmic acceleration and therefore a suitable alternative
to the dark energy problem. Further studies in other cosmological areas are
therefore encouraging to further investigate the viability of $f(Q,T)$ gravity.
| [
{
"created": "Fri, 3 Jul 2020 17:01:48 GMT",
"version": "v1"
}
] | 2020-07-06 | [
[
"Arora",
"Simran",
""
],
[
"Pacif",
"S. K. J.",
""
],
[
"Bhattacharjee",
"Snehasish",
""
],
[
"Sahoo",
"P. K.",
""
]
] | The paper presents late time cosmology in $f(Q,T)$ gravity where the dark energy is purely geometric in nature. We start by employing a well motivated $f(Q,T)$ gravity model, $f(Q,T)=mQ^{n}+bT$ where $m,n$ and $b$ are model parameters. Additionally we also assume the universe to be dominated by pressure-less matter which yields a power law type scale factor of the form $% a(t)=c_{2}(At+c_{1})^{\frac{1}{A}}$, where $A=\dfrac{3(8\pi +b)}{n(16\pi +3b)% }$ and $c_{1}$ \& $c_{2}$ are just integration constants. To investigate the cosmological viability of the model, constraints on the model parameters were imposed from the updated 57 points of Hubble data sets and 580 points of union 2.1 compilation supernovae data sets. We have thoroughly investigated the nature of geometrical dark energy mimicked by the parametrization of $f(Q,T)=mQ^{n}+bT$ with the assistance of statefinder diagnostic in $\{s,r\}$ and $\{q,r\}$ planes and also performed the $Om$ -diagnostic analysis. The present analysis makes it clear-cut that $f(Q,T)$ gravity can be promising in addressing the current cosmic acceleration and therefore a suitable alternative to the dark energy problem. Further studies in other cosmological areas are therefore encouraging to further investigate the viability of $f(Q,T)$ gravity. |
1805.10523 | Clifford M. Will | Clifford M. Will | Solar system vs. gravitational-wave bounds on the graviton mass | 8 pages, aligned with published version | Class Quantum Grav Letters, 17, 17LT01 (2018) | 10.1088/1361-6382/aad13c | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | TThe detection of gravitational waves from merging binary black holes has led
to a bound on the mass of a hypothetical massive carrier of the gravitational
interaction predicted by some modified gravity theories (a massive graviton,
for short), corresponding to a bound on the Compton wavelength $\lambda_g > 1.6
\times 10^{13}$ km. This bound is six times more stringent than a 1988 bound
inferred from solar-system dynamics. Using 30 years of improvements in solar
system data, chiefly from missions involving orbiters and probes of planets
from Mercury to Saturn, we revisit this bound. We show that data on the
perihelion advance of Mars obtained from the Mars Reconnaissance Orbiter leads
to a credible lower bound on $\lambda_g$ between $1.2$ and $2.2 \times 10^{14}$
km, surpassing the gravitational-wave bound by an order of magnitude. We
discuss ways in which each of these competing bounds may improve in the future.
| [
{
"created": "Sat, 26 May 2018 19:01:35 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Aug 2018 13:46:51 GMT",
"version": "v2"
}
] | 2018-08-07 | [
[
"Will",
"Clifford M.",
""
]
] | TThe detection of gravitational waves from merging binary black holes has led to a bound on the mass of a hypothetical massive carrier of the gravitational interaction predicted by some modified gravity theories (a massive graviton, for short), corresponding to a bound on the Compton wavelength $\lambda_g > 1.6 \times 10^{13}$ km. This bound is six times more stringent than a 1988 bound inferred from solar-system dynamics. Using 30 years of improvements in solar system data, chiefly from missions involving orbiters and probes of planets from Mercury to Saturn, we revisit this bound. We show that data on the perihelion advance of Mars obtained from the Mars Reconnaissance Orbiter leads to a credible lower bound on $\lambda_g$ between $1.2$ and $2.2 \times 10^{14}$ km, surpassing the gravitational-wave bound by an order of magnitude. We discuss ways in which each of these competing bounds may improve in the future. |
1210.4696 | S Habib Mazharimousavi | S. Habib Mazharimousavi, M. Kerachian and M. Halilsoy | Existence of Reissner-Nordstrom type black holes in f(R) gravity | 8 pages, no figure, after minor revision is accepted for publication
in Int. J. Modern Physics D | Int. J. Modern Physics D 22, 1350057 (2013) | 10.1142/S0218271813500570 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the existence of Reissner-Nordstr\"om (RN) type black holes in
f(R) gravity. Our emphasis is to derive, in the presence of electrostatic
source, the necessary conditions which provide such static, spherically
symmetric (SSS) black holes available in f(R) gravity. We also study the
thermodynamics of the black hole solution.
| [
{
"created": "Wed, 17 Oct 2012 11:16:02 GMT",
"version": "v1"
},
{
"created": "Mon, 13 May 2013 17:07:00 GMT",
"version": "v2"
}
] | 2013-09-19 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Kerachian",
"M.",
""
],
[
"Halilsoy",
"M.",
""
]
] | We investigate the existence of Reissner-Nordstr\"om (RN) type black holes in f(R) gravity. Our emphasis is to derive, in the presence of electrostatic source, the necessary conditions which provide such static, spherically symmetric (SSS) black holes available in f(R) gravity. We also study the thermodynamics of the black hole solution. |
1002.1710 | Ippocratis Saltas | Ippocratis D. Saltas, Mark Hindmarsh | The dynamical equivalence of modified gravity revisited | 17 pages; v3: Revised version. New comments added in Sections 3 & 5.
New results added in Section 6. Version to appear in Class. Quantum Gravity | null | 10.1088/0264-9381/28/3/035002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the dynamical equivalence between different representations of
vacuum modified gravity models in view of Legendre transformations. The
equivalence is discussed for both bulk and boundary space, by including in our
analysis the relevant Gibbons-Hawking terms. In the f(R) case, the Legendre
transformed action coincides with the usual Einstein frame one. We then
re-express the R+f(G) action, where G is the Gauss-Bonnet term, as a second
order theory with a new set of field variables, four tensor fields and one
scalar and study its dynamics. For completeness, we also calculate the
conformal transformation of the full Jordan frame R+f(G) action. All the
appropriate Gibbons-Hawking terms are calculated explicitly.
| [
{
"created": "Mon, 8 Feb 2010 21:17:55 GMT",
"version": "v1"
},
{
"created": "Thu, 6 May 2010 14:43:32 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Jan 2011 13:37:23 GMT",
"version": "v3"
}
] | 2015-05-18 | [
[
"Saltas",
"Ippocratis D.",
""
],
[
"Hindmarsh",
"Mark",
""
]
] | We revisit the dynamical equivalence between different representations of vacuum modified gravity models in view of Legendre transformations. The equivalence is discussed for both bulk and boundary space, by including in our analysis the relevant Gibbons-Hawking terms. In the f(R) case, the Legendre transformed action coincides with the usual Einstein frame one. We then re-express the R+f(G) action, where G is the Gauss-Bonnet term, as a second order theory with a new set of field variables, four tensor fields and one scalar and study its dynamics. For completeness, we also calculate the conformal transformation of the full Jordan frame R+f(G) action. All the appropriate Gibbons-Hawking terms are calculated explicitly. |
1406.1309 | Philippe Spindel | Thibault Damour, Philippe Spindel | Quantum Supersymmetric Bianchi IX Cosmology | 94 pages, 3 figures | Phys. Rev. D 90, 103509 (2014) | 10.1103/PhysRevD.90.103509 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the quantum dynamics of a supersymmetric squashed three-sphere by
dimensionally reducing to one timelike dimension the action of D=4 simple
supergravity for a Bianchi IX cosmological model. After imposition of the
diffeomorphism constraints, the wave function of the Universe becomes a spinor
of Spin(8,4) depending on the three squashing parameters, which satisfies
Dirac, and Klein-Gordon-like, wave equations describing the propagation of a
quantum spinning particle reflecting off spin-dependent potential walls. The
algebra of the susy constraints and of the Hamiltonian one is found to close.
One finds that the quantum Hamiltonian is built from operators that generate a
64-dimensional representation of the maximally compact sub-algebra of the
rank-3 hyperbolic Kac-Moody algebra AE3. The (quartic-in-fermions) squared-mass
term entering the Klein-Gordon-like equation has several remarkable properties:
1)it commutes with all the other (Kac-Moody-related) building blocks of the
Hamiltonian; 2)it is a quadratic function of the fermion number NF; 3)it is
negative in most of the Hilbert space. The latter property leads to a possible
quantum avoidance of the singularity ("cosmological bounce"), and suggests
imposing the boundary condition that the wavefunction of the Universe vanish
when the volume of space tends to zero. The space of solutions is a mixture of
"discrete-spectrum states" (explicitely given) and of continuous-spectrum
states (parametrized by arbitrary functions entering some initial-value
problem). The predominantly negative values of the squared-mass term lead to a
"bottle effect" between small and large volume-Universes and to a possible
reduction of the continuous spectrum to a discrete spectrum of quantum states
looking like excited versions of the Planckian-size Universes described by the
discrete states at fermionic levels NF=0 and 1.
| [
{
"created": "Thu, 5 Jun 2014 09:29:55 GMT",
"version": "v1"
}
] | 2014-11-11 | [
[
"Damour",
"Thibault",
""
],
[
"Spindel",
"Philippe",
""
]
] | We study the quantum dynamics of a supersymmetric squashed three-sphere by dimensionally reducing to one timelike dimension the action of D=4 simple supergravity for a Bianchi IX cosmological model. After imposition of the diffeomorphism constraints, the wave function of the Universe becomes a spinor of Spin(8,4) depending on the three squashing parameters, which satisfies Dirac, and Klein-Gordon-like, wave equations describing the propagation of a quantum spinning particle reflecting off spin-dependent potential walls. The algebra of the susy constraints and of the Hamiltonian one is found to close. One finds that the quantum Hamiltonian is built from operators that generate a 64-dimensional representation of the maximally compact sub-algebra of the rank-3 hyperbolic Kac-Moody algebra AE3. The (quartic-in-fermions) squared-mass term entering the Klein-Gordon-like equation has several remarkable properties: 1)it commutes with all the other (Kac-Moody-related) building blocks of the Hamiltonian; 2)it is a quadratic function of the fermion number NF; 3)it is negative in most of the Hilbert space. The latter property leads to a possible quantum avoidance of the singularity ("cosmological bounce"), and suggests imposing the boundary condition that the wavefunction of the Universe vanish when the volume of space tends to zero. The space of solutions is a mixture of "discrete-spectrum states" (explicitely given) and of continuous-spectrum states (parametrized by arbitrary functions entering some initial-value problem). The predominantly negative values of the squared-mass term lead to a "bottle effect" between small and large volume-Universes and to a possible reduction of the continuous spectrum to a discrete spectrum of quantum states looking like excited versions of the Planckian-size Universes described by the discrete states at fermionic levels NF=0 and 1. |
1711.01759 | Alexander Zhuk | Maxim Eingorn, Claus Kiefer and Alexander Zhuk | Cosmic screening of the gravitational interaction | This essay received an Honorable Mention in the 2017 Essay
Competition of the Gravity Research Foundation | Int. J. Mod. Phys. D 26, 1743012 (2017) | 10.1142/S021827181743012X | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a universe filled with cold dark matter in the form of discrete
inhomogeneities (e.g., galaxies) and dark energy in the form of a continuous
perfect fluid. We develop a first-order scalar perturbation theory in the weak
gravity limit around a spatially flat Friedmann universe. Our approach works at
all cosmic scales and incorporates linear and nonlinear effects with respect to
energy density fluctuations. The gravitational potential can be split into
individual contributions from each matter source. Each potential is
characterized by a Yukawa interaction with the same range, which is of the
order of 3700 Mpc at the present time. The derived equations can form the
theoretical basis for numerical simulations for a wide class of modern
cosmological models.
| [
{
"created": "Mon, 6 Nov 2017 07:46:43 GMT",
"version": "v1"
}
] | 2017-11-07 | [
[
"Eingorn",
"Maxim",
""
],
[
"Kiefer",
"Claus",
""
],
[
"Zhuk",
"Alexander",
""
]
] | We study a universe filled with cold dark matter in the form of discrete inhomogeneities (e.g., galaxies) and dark energy in the form of a continuous perfect fluid. We develop a first-order scalar perturbation theory in the weak gravity limit around a spatially flat Friedmann universe. Our approach works at all cosmic scales and incorporates linear and nonlinear effects with respect to energy density fluctuations. The gravitational potential can be split into individual contributions from each matter source. Each potential is characterized by a Yukawa interaction with the same range, which is of the order of 3700 Mpc at the present time. The derived equations can form the theoretical basis for numerical simulations for a wide class of modern cosmological models. |
2310.01178 | Yu-Peng Zhang | Yu-Peng Zhang, Shi-Xian Sun, Yong-Qiang Wang, Shao-Wen Wei, Pablo
Laguna, Yu-Xiao Liu | Geodesic tracking of gravitational collapse and migration of boson stars | 6 pages, 5 figures, comments are welcome | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Boson stars are potential sources of gravitational radiation. To improve our
comprehension of these exotic objects, we present the study of geodesics within
the space-times of stable, collapsing, and migrating boson stars. We focus on
timelike geodesics that are initially circular or reciprocating. We verify that
orbits initially bound within a stable boson stars persist in their bound
states. For a collapsing boson star, we show that orbits initially bound and
reciprocating finally either become unbound or plunge into the newly formed
black hole, depending on their initial maximal radii. For initially circular
geodesics, orbits with small radii plunge into the black hole; orbits with
intermediate radii become unbound; and large radii orbits linger around the
black hole with nonvanishing eccentricities. For the migrating case, a black
hole does not form. In this case, the reciprocating orbits span a wider radial
range. For initially circular geodesics, orbits with small radii become
unbound, and orbits with large radii remain bound with nonvanishing
eccentricities. This geodesic study provides a novel approach to investigate
the gravitational collapse and migration of boson stars.
| [
{
"created": "Mon, 2 Oct 2023 13:15:37 GMT",
"version": "v1"
}
] | 2023-10-03 | [
[
"Zhang",
"Yu-Peng",
""
],
[
"Sun",
"Shi-Xian",
""
],
[
"Wang",
"Yong-Qiang",
""
],
[
"Wei",
"Shao-Wen",
""
],
[
"Laguna",
"Pablo",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | Boson stars are potential sources of gravitational radiation. To improve our comprehension of these exotic objects, we present the study of geodesics within the space-times of stable, collapsing, and migrating boson stars. We focus on timelike geodesics that are initially circular or reciprocating. We verify that orbits initially bound within a stable boson stars persist in their bound states. For a collapsing boson star, we show that orbits initially bound and reciprocating finally either become unbound or plunge into the newly formed black hole, depending on their initial maximal radii. For initially circular geodesics, orbits with small radii plunge into the black hole; orbits with intermediate radii become unbound; and large radii orbits linger around the black hole with nonvanishing eccentricities. For the migrating case, a black hole does not form. In this case, the reciprocating orbits span a wider radial range. For initially circular geodesics, orbits with small radii become unbound, and orbits with large radii remain bound with nonvanishing eccentricities. This geodesic study provides a novel approach to investigate the gravitational collapse and migration of boson stars. |
2008.06681 | Elham Nazari | Elham Nazari, Farahnaz Sarvi, Mahmood Roshan | Generalized Energy-Momentum-Squared Gravity in the Palatini Formalism | 20 pages, 6 figures, Accepted for publication in PRD | Phys. Rev. D 102, 064016, 2020 | 10.1103/PhysRevD.102.064016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the generalized version of energy-momentum squared gravity (EMSG) in
the Palatini formalism. This theory allows the existence of a scalar
constructed with energy-momentum tensor as $T_{\alpha\beta}T^{\alpha\beta}$ in
the generic action of the theory. We study the most general form of this theory
in the Palatini framework and present the underlying field equations. The
equations of motion of a massive test particle have been derived. The weak
field limit of the theory is explored and the generalized version of the
Poisson equation is obtained. Moreover, we explore the cosmological behavior of
the theory with emphasis on bouncing solutions. Some new bouncing solutions for
the specific Palatini EMSG model given by the Lagrangian density
$\mathcal{L}=R+\beta R^2+\eta T_{\mu\nu}T^{\mu\nu}$ are introduced. We show
that only the case $\eta>0$ can lead to viable cosmic bounce.
| [
{
"created": "Sat, 15 Aug 2020 08:50:11 GMT",
"version": "v1"
}
] | 2020-09-28 | [
[
"Nazari",
"Elham",
""
],
[
"Sarvi",
"Farahnaz",
""
],
[
"Roshan",
"Mahmood",
""
]
] | We study the generalized version of energy-momentum squared gravity (EMSG) in the Palatini formalism. This theory allows the existence of a scalar constructed with energy-momentum tensor as $T_{\alpha\beta}T^{\alpha\beta}$ in the generic action of the theory. We study the most general form of this theory in the Palatini framework and present the underlying field equations. The equations of motion of a massive test particle have been derived. The weak field limit of the theory is explored and the generalized version of the Poisson equation is obtained. Moreover, we explore the cosmological behavior of the theory with emphasis on bouncing solutions. Some new bouncing solutions for the specific Palatini EMSG model given by the Lagrangian density $\mathcal{L}=R+\beta R^2+\eta T_{\mu\nu}T^{\mu\nu}$ are introduced. We show that only the case $\eta>0$ can lead to viable cosmic bounce. |
1606.06525 | Luis Cort\'es Barbado | Luis C. Barbado, Carlos Barcel\'o, Luis J. Garay and Gil Jannes | A tensorial description of particle perception in black-hole physics | Minor corrections to match the published version. 11 pages, 5 figures | Phys. Rev. D 94, 064004 (2016) | 10.1103/PhysRevD.94.064004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In quantum field theory in curved backgrounds, one typically distinguishes
between objective, tensorial, quantities such as the Renormalized Stress-Energy
Tensor (RSET) and subjective, non-tensorial, quantities such as Bogoliubov
coefficients which encode perception effects associated with the specific
trajectory of a detector. In this work we propose a way to treat both objective
and subjective notions on an equal tensorial footing. For that purpose, we
define a new tensor which we will call the Perception Renormalized
Stress-Energy Tensor (PeRSET). The PeRSET is defined as the subtraction of the
RSET corresponding to two different vacuum states. Based on this tensor we can
define perceived energy densities and fluxes. The PeRSET helps to have a more
organized and systematic understanding of various results in the literature
regarding quantum field theory in black hole spacetimes. We illustrate the
physics encoded in this tensor by working out various examples of special
relevance.
| [
{
"created": "Tue, 21 Jun 2016 11:55:05 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Sep 2016 15:09:15 GMT",
"version": "v2"
}
] | 2016-09-19 | [
[
"Barbado",
"Luis C.",
""
],
[
"Barceló",
"Carlos",
""
],
[
"Garay",
"Luis J.",
""
],
[
"Jannes",
"Gil",
""
]
] | In quantum field theory in curved backgrounds, one typically distinguishes between objective, tensorial, quantities such as the Renormalized Stress-Energy Tensor (RSET) and subjective, non-tensorial, quantities such as Bogoliubov coefficients which encode perception effects associated with the specific trajectory of a detector. In this work we propose a way to treat both objective and subjective notions on an equal tensorial footing. For that purpose, we define a new tensor which we will call the Perception Renormalized Stress-Energy Tensor (PeRSET). The PeRSET is defined as the subtraction of the RSET corresponding to two different vacuum states. Based on this tensor we can define perceived energy densities and fluxes. The PeRSET helps to have a more organized and systematic understanding of various results in the literature regarding quantum field theory in black hole spacetimes. We illustrate the physics encoded in this tensor by working out various examples of special relevance. |
1104.4802 | Oleg Zaslavskii | O. B. Zaslavskii | Acceleration of particles by black holes: kinematic explanation | 14 pages. New version includes also contents of arXiv:1105.0303, so
both massive and massless cases are considered. Combined version to appear in
PRD | Phys.Rev.D84:024007,2011 | 10.1103/PhysRevD.84.024007 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new simple and general explanation of the effect of acceleration of
particles by black holes to infinite energies in the centre of mass frame is
suggested. It is based on kinematics of particles moving near the horizon. This
effect arises when particles of two kinds collide near the horizon. For massive
particles, the first kind represents a particle with the generic energy and
angular momentum (I call them "usual"). Near the horizon, such a particle has a
velocity almost equal to that of light in the frame that corotates with a black
hole (the frame is static if a black hole is static). The second kind (called
"critical") consists of particles with the velocity v<c near the horizon due to
special relationship between the energy and angular momentum (or charge). As a
result, the relative velocity approaches the speed of light c, the Lorentz
factor grows unbound. This explanation applies both to generic rotating black
holes and charged ones (even for radial motion of particles). If one of
colliding particles is massless (photon), the critical particle is
distinguished by the fact that its frequency is finite near the horizon. The
existence (or absence) of the effect is determined depending on competition of
two factors - gravitational blue shift for a photon propagating towards a black
hole and the Doppler effect due to transformation from the locally nonrotating
frame to a comoving one. Classification of all possible types of collisions is
suggested depending on whether massive or massless particle is critical or
usual.
| [
{
"created": "Mon, 25 Apr 2011 20:33:51 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Jun 2011 19:14:43 GMT",
"version": "v2"
}
] | 2011-08-12 | [
[
"Zaslavskii",
"O. B.",
""
]
] | A new simple and general explanation of the effect of acceleration of particles by black holes to infinite energies in the centre of mass frame is suggested. It is based on kinematics of particles moving near the horizon. This effect arises when particles of two kinds collide near the horizon. For massive particles, the first kind represents a particle with the generic energy and angular momentum (I call them "usual"). Near the horizon, such a particle has a velocity almost equal to that of light in the frame that corotates with a black hole (the frame is static if a black hole is static). The second kind (called "critical") consists of particles with the velocity v<c near the horizon due to special relationship between the energy and angular momentum (or charge). As a result, the relative velocity approaches the speed of light c, the Lorentz factor grows unbound. This explanation applies both to generic rotating black holes and charged ones (even for radial motion of particles). If one of colliding particles is massless (photon), the critical particle is distinguished by the fact that its frequency is finite near the horizon. The existence (or absence) of the effect is determined depending on competition of two factors - gravitational blue shift for a photon propagating towards a black hole and the Doppler effect due to transformation from the locally nonrotating frame to a comoving one. Classification of all possible types of collisions is suggested depending on whether massive or massless particle is critical or usual. |
1111.4275 | Stephane Houndjo Dr | M. J. S. Houndjo and Oliver F. Piattella | Reconstructing $f(R,T)$ gravity from holographic dark energy | 16 pages, 6 figures, accepted for publication in IJMPD | IJMPD 2, 1250024 (2012) | 10.1142/S0218271812500241 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider cosmological scenarios based on $f(R,T)$ theories of gravity ($R$
is the Ricci scalar and $T$ is the trace of the energy-momentum tensor) and
numerically reconstruct the function $f(R,T)$ which is able to reproduce the
same expansion history generated, in the standard General Relativity theory, by
dark matter and holographic dark energy. We consider two special $f(R,T)$
models: in the first instance, we investigate the modification $R + 2f(T)$,
i.e. the usual Einstein-Hilbert term plus a $f(T)$ correction. In the second
instance, we consider a $f(R)+\lambda T$ theory, i.e. a $T$ correction to the
renown $f(R)$ theory of gravity.
| [
{
"created": "Fri, 18 Nov 2011 04:08:17 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jan 2012 14:40:45 GMT",
"version": "v2"
}
] | 2015-03-19 | [
[
"Houndjo",
"M. J. S.",
""
],
[
"Piattella",
"Oliver F.",
""
]
] | We consider cosmological scenarios based on $f(R,T)$ theories of gravity ($R$ is the Ricci scalar and $T$ is the trace of the energy-momentum tensor) and numerically reconstruct the function $f(R,T)$ which is able to reproduce the same expansion history generated, in the standard General Relativity theory, by dark matter and holographic dark energy. We consider two special $f(R,T)$ models: in the first instance, we investigate the modification $R + 2f(T)$, i.e. the usual Einstein-Hilbert term plus a $f(T)$ correction. In the second instance, we consider a $f(R)+\lambda T$ theory, i.e. a $T$ correction to the renown $f(R)$ theory of gravity. |
0812.1087 | Norbert Van den Bergh | Liselotte De Groote and Norbert Van den Bergh | New results for Petrov type D pure radiation fields | 4 pages; changed the appearance of some v's and nu's | null | 10.1063/1.3141278 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new family of Petrov type D pure radiation spacetimes with a
shear-free, non-diverging geodesic principal null congruence.
| [
{
"created": "Fri, 5 Dec 2008 08:15:54 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Feb 2009 10:36:52 GMT",
"version": "v2"
}
] | 2015-05-13 | [
[
"De Groote",
"Liselotte",
""
],
[
"Bergh",
"Norbert Van den",
""
]
] | We present a new family of Petrov type D pure radiation spacetimes with a shear-free, non-diverging geodesic principal null congruence. |
2101.00866 | Jan Henryk Kwapisz | Jan Chojnacki, Julia Krajecka, Jan H. Kwapisz, Oskar S{\l}owik, Artur
Str\k{a}g | Is asymptotically safe inflation eternal? | 23 p., 8 fig, minor corrections in typography, accepted in JCAP | JCAP04(2021)076 | 10.1088/1475-7516/2021/04/076 | null | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Recently, based on swampland considerations in string theory, the (no)
eternal inflation principle has been put forward. The natural question arises
whether similar conditions hold in other approaches to quantum gravity. In this
article, the asymptotic safety hypothesis is considered in the context of
eternal inflation. As exemplary inflationary models the SU(N) Yang-Mills in the
Veneziano limit and various RG-improvements of the gravitational action are
studied. The existence of UV fixed point generically flattens the potential and
our findings suggest no tension between eternal inflation and asymptotic
safety, both in the matter and gravitational sector in contradistinction to
string theory. Moreover, the eternal inflation cannot take place in the range
of applicability of effective field quantum gravity theory. We employ the
analytical relations for eternal inflation to some of the models with single
minima, such as Starobinsky inflation, alpha-attractors, or the RG-improved
models and verify them with the massive numerical simulations. The validity of
these constraints is also discussed for a multi-minima model.
| [
{
"created": "Mon, 4 Jan 2021 10:26:36 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jan 2021 08:21:44 GMT",
"version": "v2"
},
{
"created": "Thu, 28 Jan 2021 11:55:37 GMT",
"version": "v3"
},
{
"created": "Mon, 22 Mar 2021 13:27:10 GMT",
"version": "v4"
},
{
"cr... | 2021-05-03 | [
[
"Chojnacki",
"Jan",
""
],
[
"Krajecka",
"Julia",
""
],
[
"Kwapisz",
"Jan H.",
""
],
[
"Słowik",
"Oskar",
""
],
[
"Strąg",
"Artur",
""
]
] | Recently, based on swampland considerations in string theory, the (no) eternal inflation principle has been put forward. The natural question arises whether similar conditions hold in other approaches to quantum gravity. In this article, the asymptotic safety hypothesis is considered in the context of eternal inflation. As exemplary inflationary models the SU(N) Yang-Mills in the Veneziano limit and various RG-improvements of the gravitational action are studied. The existence of UV fixed point generically flattens the potential and our findings suggest no tension between eternal inflation and asymptotic safety, both in the matter and gravitational sector in contradistinction to string theory. Moreover, the eternal inflation cannot take place in the range of applicability of effective field quantum gravity theory. We employ the analytical relations for eternal inflation to some of the models with single minima, such as Starobinsky inflation, alpha-attractors, or the RG-improved models and verify them with the massive numerical simulations. The validity of these constraints is also discussed for a multi-minima model. |
2208.00704 | Ra\'ul Carballo-Rubio | Ra\'ul Carballo-Rubio, Vitor Cardoso and Ziri Younsi | Towards VLBI Observations of Black Hole Structure | 12 pages, 10 figures | null | 10.1103/PhysRevD.106.084038 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes hold a tremendous discovery potential. In this paper the extent
to which the Event Horizon Telescope and its next generation upgrade can
resolve their structure is quantified. Black holes are characterized by a
perfectly absorptive boundary, with a specific area determined by intrinsic
parameters of the black hole. We use a general parametrization of spherically
symmetric spacetimes describing deviations from this behavior, with parameters
controlling the size of the central object and its interaction with light, in
particular through a specular reflection coefficient $\Gamma$ and an intrinsic
luminosity measured as a fraction $\eta$ of that of the accretion disc. This
enables us to study exotic compact objects and compare them with black holes in
a model-independent manner. We determine the image features associated with the
existence of a surface in the presence of a geometrically thin and optically
thick accretion disc, identifying requirements for VLBI observations to be able
to cast meaningful constraints on these parameters, in particular regarding
angular resolution and image dynamic range. For face-on observations,
constraints of order $\eta\lesssim 10^{-4}, \Gamma\lesssim 10^{-1}$ are
possible with an enhanced EHT array, imposing strong constraints on the nature
of the central object.
| [
{
"created": "Mon, 1 Aug 2022 09:23:04 GMT",
"version": "v1"
}
] | 2022-11-16 | [
[
"Carballo-Rubio",
"Raúl",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Younsi",
"Ziri",
""
]
] | Black holes hold a tremendous discovery potential. In this paper the extent to which the Event Horizon Telescope and its next generation upgrade can resolve their structure is quantified. Black holes are characterized by a perfectly absorptive boundary, with a specific area determined by intrinsic parameters of the black hole. We use a general parametrization of spherically symmetric spacetimes describing deviations from this behavior, with parameters controlling the size of the central object and its interaction with light, in particular through a specular reflection coefficient $\Gamma$ and an intrinsic luminosity measured as a fraction $\eta$ of that of the accretion disc. This enables us to study exotic compact objects and compare them with black holes in a model-independent manner. We determine the image features associated with the existence of a surface in the presence of a geometrically thin and optically thick accretion disc, identifying requirements for VLBI observations to be able to cast meaningful constraints on these parameters, in particular regarding angular resolution and image dynamic range. For face-on observations, constraints of order $\eta\lesssim 10^{-4}, \Gamma\lesssim 10^{-1}$ are possible with an enhanced EHT array, imposing strong constraints on the nature of the central object. |
1507.03184 | TaeHun Kim | TaeHun Kim and Hyunbyuk Kim | Geometrical Interpretation of Electromagnetism in a 5-Dimensional
Manifold | 23 pages, Latex, grammatical errors in text and a few index errors in
equations were corrected to be consistent with the published version | Class. Quantum Grav. 34 155006, 2017 | 10.1088/1361-6382/aa733d | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, Kaluza-Klein theory is revisited and its implications are
elaborated. We show that electromagnetic 4-potential can be considered as a
shearing-like deformation of a 5-dimensional (5D) manifold along the fifth
(5th) axis. The charge-to-mass ratio has a physical meaning of the ratio
between the movement along the direction of the 5th axis and the movement in
the 4D space-time. In order to have a 5D matter which is consistent with the
construction of the 5D manifold, a notion of particle-thread is suggested.
Examinations on the compatibility of reference frames reveal a covariance
breaking of the 5th dimension. The field equations which extend Einstein's
field equations give the total energy-momentum tensor as a sum of that of
matter, electromagnetic field, and the interaction between electric current and
electromagnetic potential. Finally, the experimental implications are
calculated for the weak potential case.
| [
{
"created": "Sun, 12 Jul 2015 04:18:05 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Sep 2016 11:59:10 GMT",
"version": "v2"
},
{
"created": "Fri, 19 May 2017 17:21:12 GMT",
"version": "v3"
},
{
"created": "Sun, 13 Aug 2017 07:06:21 GMT",
"version": "v4"
}
] | 2017-08-15 | [
[
"Kim",
"TaeHun",
""
],
[
"Kim",
"Hyunbyuk",
""
]
] | In this paper, Kaluza-Klein theory is revisited and its implications are elaborated. We show that electromagnetic 4-potential can be considered as a shearing-like deformation of a 5-dimensional (5D) manifold along the fifth (5th) axis. The charge-to-mass ratio has a physical meaning of the ratio between the movement along the direction of the 5th axis and the movement in the 4D space-time. In order to have a 5D matter which is consistent with the construction of the 5D manifold, a notion of particle-thread is suggested. Examinations on the compatibility of reference frames reveal a covariance breaking of the 5th dimension. The field equations which extend Einstein's field equations give the total energy-momentum tensor as a sum of that of matter, electromagnetic field, and the interaction between electric current and electromagnetic potential. Finally, the experimental implications are calculated for the weak potential case. |
2112.03890 | Mariem Magdy Ali Mohamed | Mariem Magdy Ali Mohamed, Juan A. Valiente Kroon | Asymptotic charges for spin-1 and spin-2 fields at the critical sets of
null infinity | Minor improvements and typos corrected throughout. Correction of typo
in Lemma 3 | null | 10.1063/5.0081834 | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | The asymptotic charges of spin-1 and spin-2 fields are studied near spatial
infinity. We evaluate the charges at the critical sets where spatial infinity
meets null infinity with the aim of finding the relation between the charges at
future and past null infinity. To this end, we make use of Friedrich's
framework of the cylinder at spatial infinity to obtain asymptotic expansions
of the Maxwell and spin-2 fields near spatial infinity, which are fully
determined in terms of initial data on a Cauchy hypersurface. Expanding the
initial data in terms of spin-weighted spherical harmonics, it is shown that
only a subset of the initial data, that satisfies certain regularity
conditions, gives rise to well-defined charges at the point where future (past)
infinity meets spatial infinity. Given such initial data, the charges are shown
to be fully expressed in terms of the freely specifiable part of the data.
Moreover, it is shown that there exists a natural correspondence between the
charges defined at future and past null infinity.
| [
{
"created": "Tue, 7 Dec 2021 18:38:19 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Jun 2022 09:49:54 GMT",
"version": "v2"
},
{
"created": "Thu, 31 Aug 2023 13:30:11 GMT",
"version": "v3"
}
] | 2023-09-01 | [
[
"Mohamed",
"Mariem Magdy Ali",
""
],
[
"Kroon",
"Juan A. Valiente",
""
]
] | The asymptotic charges of spin-1 and spin-2 fields are studied near spatial infinity. We evaluate the charges at the critical sets where spatial infinity meets null infinity with the aim of finding the relation between the charges at future and past null infinity. To this end, we make use of Friedrich's framework of the cylinder at spatial infinity to obtain asymptotic expansions of the Maxwell and spin-2 fields near spatial infinity, which are fully determined in terms of initial data on a Cauchy hypersurface. Expanding the initial data in terms of spin-weighted spherical harmonics, it is shown that only a subset of the initial data, that satisfies certain regularity conditions, gives rise to well-defined charges at the point where future (past) infinity meets spatial infinity. Given such initial data, the charges are shown to be fully expressed in terms of the freely specifiable part of the data. Moreover, it is shown that there exists a natural correspondence between the charges defined at future and past null infinity. |
2303.15523 | Konstantinos Dimopoulos | Lucy Brissenden, Konstantinos Dimopoulos and Samuel S\'anchez L\'opez | Explaining the Hubble tension and dark energy from alpha-attractors | 12 pages, 4 figures, contribution to proceedings of: Corfu Summer
Institute 2022 "School and Workshops on Elementary Particle Physics and
Gravity", 28 August - 1 October, 2022, Corfu, Greece | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | A compelling unified model of dark energy and early dark energy (EDE) is
presented, using a scalar field with an exponential runaway potential, in the
context of alpha-attractors. The field is originally trapped at an enhanced
symmetry point, subsequently thaws to become successful EDE and eventually
slow-rolls to become dark energy. EDE ameliorates the observed Hubble tension.
| [
{
"created": "Mon, 27 Mar 2023 18:05:08 GMT",
"version": "v1"
}
] | 2023-03-29 | [
[
"Brissenden",
"Lucy",
""
],
[
"Dimopoulos",
"Konstantinos",
""
],
[
"López",
"Samuel Sánchez",
""
]
] | A compelling unified model of dark energy and early dark energy (EDE) is presented, using a scalar field with an exponential runaway potential, in the context of alpha-attractors. The field is originally trapped at an enhanced symmetry point, subsequently thaws to become successful EDE and eventually slow-rolls to become dark energy. EDE ameliorates the observed Hubble tension. |
gr-qc/0302029 | Dr. Kirill Bronnikov | K.A. Bronnikov (Moscow), A. Dobosz and I.G. Dymnikova (Olsztyn) | Nonsingular vacuum cosmologies with a variable cosmological term | revtex, 10 pages, 8 eps figures | Class.Quant.Grav. 20 (2003) 3797-3814 | 10.1088/0264-9381/20/16/317 | null | gr-qc | null | We present nonsingular cosmological models with a variable cosmological term
described by the second-rank symmetric tensor $\Lambda_{mn}$ evolving from
$\Lambda g_{mn}$ to $\lambda g_{mn}$ with $\lambda < \Lambda$. All
$\Lambda_{mn}$ dominated cosmologies belong to Lemaitre type models for an
anisotropic perfect fluid. The expansion starts from a nonsingular
nonsimultaneous de Sitter bang, with $\Lambda$ on the scale responsible for the
earliest accelerated expansion, which is followed by an anisotropic Kasner type
stage. For a certain class of observers these models can be also identified as
Kantowski-Sachs models with regular R regions. For Kantowski-Sachs observers
the cosmological evolution starts from horizons with a highly anisotropic
``null bang'' where the volume of the spatial section vanishes. We study in
detail the spherically symmetric case and consider the general features of
cosmologies with planar and pseudospherical symmetries. Nonsingular
$\Lambda_{mn}$ dominated cosmologies are Bianchi type I in the planar case and
hyperbolic analogs of the Kantowski-Sachs models in the pseudospherical case.
At late times all models approach a de Sitter asymptotic with small $\lambda$.
| [
{
"created": "Mon, 10 Feb 2003 10:35:52 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Bronnikov",
"K. A.",
"",
"Moscow"
],
[
"Dobosz",
"A.",
"",
"Olsztyn"
],
[
"Dymnikova",
"I. G.",
"",
"Olsztyn"
]
] | We present nonsingular cosmological models with a variable cosmological term described by the second-rank symmetric tensor $\Lambda_{mn}$ evolving from $\Lambda g_{mn}$ to $\lambda g_{mn}$ with $\lambda < \Lambda$. All $\Lambda_{mn}$ dominated cosmologies belong to Lemaitre type models for an anisotropic perfect fluid. The expansion starts from a nonsingular nonsimultaneous de Sitter bang, with $\Lambda$ on the scale responsible for the earliest accelerated expansion, which is followed by an anisotropic Kasner type stage. For a certain class of observers these models can be also identified as Kantowski-Sachs models with regular R regions. For Kantowski-Sachs observers the cosmological evolution starts from horizons with a highly anisotropic ``null bang'' where the volume of the spatial section vanishes. We study in detail the spherically symmetric case and consider the general features of cosmologies with planar and pseudospherical symmetries. Nonsingular $\Lambda_{mn}$ dominated cosmologies are Bianchi type I in the planar case and hyperbolic analogs of the Kantowski-Sachs models in the pseudospherical case. At late times all models approach a de Sitter asymptotic with small $\lambda$. |
1212.0155 | Daniel Guariento | Alan M. da Silva, Michele Fontanini, Daniel C. Guariento | How the expansion of the universe determines the causal structure of
McVittie spacetimes | 9 pages, 5 figures. Corrections and updates to match published
version | Phys. Rev. D 87, 064030 (2013) | 10.1103/PhysRevD.87.064030 | null | gr-qc astro-ph.CO math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a theorem which allows one to recognize and classify the
asymptotic behavior and causal structure of McVittie metrics for different
choices of scale factor, establishing whether a black hole or a pair
black-white hole appears in the appropriate limit. Incidentally, the theorem
also solves an apparent contradiction present in the literature over the causal
structure analysis of the McVittie solution. Although the classification we
present is not fully complete, we argue that this result covers most if not all
physically relevant scenarios.
| [
{
"created": "Sat, 1 Dec 2012 20:31:37 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Mar 2013 13:05:40 GMT",
"version": "v2"
}
] | 2013-03-28 | [
[
"da Silva",
"Alan M.",
""
],
[
"Fontanini",
"Michele",
""
],
[
"Guariento",
"Daniel C.",
""
]
] | We present a theorem which allows one to recognize and classify the asymptotic behavior and causal structure of McVittie metrics for different choices of scale factor, establishing whether a black hole or a pair black-white hole appears in the appropriate limit. Incidentally, the theorem also solves an apparent contradiction present in the literature over the causal structure analysis of the McVittie solution. Although the classification we present is not fully complete, we argue that this result covers most if not all physically relevant scenarios. |
2201.10593 | Jonathan R. Gair | Jonathan R Gair, Martin Hewitson, Antoine Petiteau, Guido Mueller | Space-based Gravitational Wave Observatories | 74 pages, 17 figures, contribution to Handbook of Gravitational Wave
Astronomy | null | 10.1007/978-981-15-4702-7_3-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, which will appear as a chapter in the Handbook of
Gravitational Wave Astronomy, we will describe the detection of gravitational
waves with space-based interferometric gravitational wave observatories. We
will provide an overview of the key technologies underlying their operation,
illustrated using the specific example of the Laser Interferometer Space
Antenna (LISA). We will then give an overview of data analysis strategies for
space-based detectors, including a description of time-delay interferometry,
which is required to suppress laser frequency noise to the necessary level. We
will describe the main sources of gravitational waves in the millihertz
frequency range targeted by space-based detectors and then discuss some of the
key science investigations that these observations will facilitate. Once again,
quantitative statements given here will make reference to the capabilities of
LISA, as that is the best studied mission concept. Finally, we will describe
some of the proposals for even more sensitive space-based detectors that could
be launched further in the future.
| [
{
"created": "Tue, 25 Jan 2022 19:23:50 GMT",
"version": "v1"
}
] | 2022-01-27 | [
[
"Gair",
"Jonathan R",
""
],
[
"Hewitson",
"Martin",
""
],
[
"Petiteau",
"Antoine",
""
],
[
"Mueller",
"Guido",
""
]
] | In this article, which will appear as a chapter in the Handbook of Gravitational Wave Astronomy, we will describe the detection of gravitational waves with space-based interferometric gravitational wave observatories. We will provide an overview of the key technologies underlying their operation, illustrated using the specific example of the Laser Interferometer Space Antenna (LISA). We will then give an overview of data analysis strategies for space-based detectors, including a description of time-delay interferometry, which is required to suppress laser frequency noise to the necessary level. We will describe the main sources of gravitational waves in the millihertz frequency range targeted by space-based detectors and then discuss some of the key science investigations that these observations will facilitate. Once again, quantitative statements given here will make reference to the capabilities of LISA, as that is the best studied mission concept. Finally, we will describe some of the proposals for even more sensitive space-based detectors that could be launched further in the future. |
1005.3254 | Y. Jack Ng | Vishnu Jejjala, Djordje Minic, Y. Jack Ng, and Chia-Hsiung Tze | Quantum Gravity and Turbulence | 8 pages, LaTeX; Honorable Mention in the 2010 Gravity Research
Foundation Essay Contest | Int.J.Mod.Phys.D19:2311-2317,2010 | 10.1142/S021827181001830X | null | gr-qc hep-th nlin.CD physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply recent advances in quantum gravity to the problem of turbulence.
Adopting the AdS/CFT approach we propose a string theory of turbulence that
explains the Kolmogorov scaling in 3+1 dimensions and the Kraichnan and
Kolmogorov scalings in 2+1 dimensions. In the gravitational context, turbulence
is intimately related to the properties of spacetime, or quantum, foam.
| [
{
"created": "Tue, 18 May 2010 17:09:47 GMT",
"version": "v1"
}
] | 2011-01-17 | [
[
"Jejjala",
"Vishnu",
""
],
[
"Minic",
"Djordje",
""
],
[
"Ng",
"Y. Jack",
""
],
[
"Tze",
"Chia-Hsiung",
""
]
] | We apply recent advances in quantum gravity to the problem of turbulence. Adopting the AdS/CFT approach we propose a string theory of turbulence that explains the Kolmogorov scaling in 3+1 dimensions and the Kraichnan and Kolmogorov scalings in 2+1 dimensions. In the gravitational context, turbulence is intimately related to the properties of spacetime, or quantum, foam. |
2204.12832 | Javier Relancio | J.J. Relancio, S. Liberati | Exploring black hole mechanics in cotangent bundle geometries | 12 pages | International Journal of Geometric Methods in Modern Physics
Vol.19 No. 6 (2022), 2250089 | 10.1142/S021988782250089X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The classical and continuum limit of a quantum gravitational setting could
lead, at mesoscopic regimes, to a very different notion of geometry w.r.t. the
pseudo-Riemannian one of special and general relativity. A possible way to
characterize this modified space-time notion is by a momentum dependent metric,
in such a way that particles with different energies could probe different
spacetimes. Indeed, doubly special relativity theories, deforming the special
relativistic kinematics while maintaining a relativity principle, have been
understood within a geometrical context, by considering a curved momentum
space. The extension of these momentum spaces to curved spacetimes and its
possible phenomenological implications have been recently investigated.
Following this line of research, we address here the first two laws of black
holes thermodynamics in the context of a cotangent bundle metric, depending on
both momentum and space-time coordinates, compatible with the relativistic
deformed kinematics of doubly special relativity.
| [
{
"created": "Wed, 27 Apr 2022 10:35:54 GMT",
"version": "v1"
}
] | 2022-04-28 | [
[
"Relancio",
"J. J.",
""
],
[
"Liberati",
"S.",
""
]
] | The classical and continuum limit of a quantum gravitational setting could lead, at mesoscopic regimes, to a very different notion of geometry w.r.t. the pseudo-Riemannian one of special and general relativity. A possible way to characterize this modified space-time notion is by a momentum dependent metric, in such a way that particles with different energies could probe different spacetimes. Indeed, doubly special relativity theories, deforming the special relativistic kinematics while maintaining a relativity principle, have been understood within a geometrical context, by considering a curved momentum space. The extension of these momentum spaces to curved spacetimes and its possible phenomenological implications have been recently investigated. Following this line of research, we address here the first two laws of black holes thermodynamics in the context of a cotangent bundle metric, depending on both momentum and space-time coordinates, compatible with the relativistic deformed kinematics of doubly special relativity. |
1910.08960 | Elena Emtsova | Elena Emtsova, Alexander Petrov, Aleksey Toporensky | Conserved Currents and Superpotentials in Teleparallel Equivalent of
General Relativity | null | Class. Quantum Grav. 37 (2020) 095006 (34pp) | 10.1088/1361-6382/ab7715 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Teleparallel Equivalent of General Relativity (TEGR) with
Lagrangian that includes the flat (inertial) spin connection and that is
evidently invariant with respect to local Lorentz rotations. Applying directly
the Noether theorem, we construct new expressions for conserved currents and
related superpotentials. They are covariant both under coordinate
transformations and local Lorentz rotations, and allow us to construct well
defined conserved charges, unlike earlier approaches. The advantage is achieved
by an explicit presence of a displacement vector in the new expressions that
can be interpreted as a Killing vector, as a proper vector of an observer, etc.
The new expressions are used to introduce a principle for definition of an
inertial spin connection that is undetermined one in the TEGR from the start.
Theoretical results are applied to calculate mass for the Schwarzschild black
hole and densities of conserved quantities for freely falling observers both in
Friedmann-Lemaitre-Robertson-Walker world of all the three signs of curvature
and in (anti-)de Sitter space.
| [
{
"created": "Sun, 20 Oct 2019 12:14:57 GMT",
"version": "v1"
},
{
"created": "Sun, 18 Apr 2021 01:12:08 GMT",
"version": "v2"
}
] | 2021-04-20 | [
[
"Emtsova",
"Elena",
""
],
[
"Petrov",
"Alexander",
""
],
[
"Toporensky",
"Aleksey",
""
]
] | We study the Teleparallel Equivalent of General Relativity (TEGR) with Lagrangian that includes the flat (inertial) spin connection and that is evidently invariant with respect to local Lorentz rotations. Applying directly the Noether theorem, we construct new expressions for conserved currents and related superpotentials. They are covariant both under coordinate transformations and local Lorentz rotations, and allow us to construct well defined conserved charges, unlike earlier approaches. The advantage is achieved by an explicit presence of a displacement vector in the new expressions that can be interpreted as a Killing vector, as a proper vector of an observer, etc. The new expressions are used to introduce a principle for definition of an inertial spin connection that is undetermined one in the TEGR from the start. Theoretical results are applied to calculate mass for the Schwarzschild black hole and densities of conserved quantities for freely falling observers both in Friedmann-Lemaitre-Robertson-Walker world of all the three signs of curvature and in (anti-)de Sitter space. |
1407.0998 | Javier Olmedo | Laura Castell\'o Gomar, Mikel Fern\'andez-M\'endez, Guillermo A. Mena
Marug\'an, Javier Olmedo | Cosmological perturbations in Hybrid Loop Quantum Cosmology:
Mukhanov-Sasaki variables | 45 pages. Minor corrections and typos. Bibliography updated | Phys. Rev. D 90, 064015 (2014) | 10.1103/PhysRevD.90.064015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study cosmological perturbations in the framework of Loop Quantum
Cosmology, using a hybrid quantization approach and Mukhanov-Sasaki variables.
The formulation in terms of these gauge invariants allows one to clarify the
independence of the results on choices of gauge and facilitates the comparison
with other approaches proposed to deal with cosmological perturbations in the
context of Loop Quantum Theory. A kind of Born-Oppenheimer ansatz is employed
to extract the dynamics of the inhomogeneous perturbations, separating them
from the degrees of freedom of the Friedmann-Robertson-Walker geometry. With
this ansatz, we derive an approximate Schr\"odinger equation for the
cosmological perturbations and study its range of validity. We also prove that,
with an alternate factor ordering, the dynamics deduced for the perturbations
is similar to the one found in the so-called "dressed metric approach", apart
from a possible scaling of the matter field in order to preserve its unitary
evolution in the regime of Quantum Field Theory in a curved background and some
quantization prescription issues. Finally, we obtain the effective equations
that are naturally associated with the Mukhanov-Sasaki variables, both with and
without introducing the Born-Oppenheimer ansatz, and with the different factor
orderings that we have studied.
| [
{
"created": "Thu, 3 Jul 2014 18:04:48 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Sep 2014 23:33:47 GMT",
"version": "v2"
}
] | 2014-09-17 | [
[
"Gomar",
"Laura Castelló",
""
],
[
"Fernández-Méndez",
"Mikel",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
],
[
"Olmedo",
"Javier",
""
]
] | We study cosmological perturbations in the framework of Loop Quantum Cosmology, using a hybrid quantization approach and Mukhanov-Sasaki variables. The formulation in terms of these gauge invariants allows one to clarify the independence of the results on choices of gauge and facilitates the comparison with other approaches proposed to deal with cosmological perturbations in the context of Loop Quantum Theory. A kind of Born-Oppenheimer ansatz is employed to extract the dynamics of the inhomogeneous perturbations, separating them from the degrees of freedom of the Friedmann-Robertson-Walker geometry. With this ansatz, we derive an approximate Schr\"odinger equation for the cosmological perturbations and study its range of validity. We also prove that, with an alternate factor ordering, the dynamics deduced for the perturbations is similar to the one found in the so-called "dressed metric approach", apart from a possible scaling of the matter field in order to preserve its unitary evolution in the regime of Quantum Field Theory in a curved background and some quantization prescription issues. Finally, we obtain the effective equations that are naturally associated with the Mukhanov-Sasaki variables, both with and without introducing the Born-Oppenheimer ansatz, and with the different factor orderings that we have studied. |
1412.1112 | Mubasher Jamil | Ibrar Hussain, Mubasher Jamil, Bushra Majeed | A Slowly Rotating Black Hole in Horava-Lifshitz Gravity and a 3+1
Dimensional Topological Black Hole: Motion of Particles and BSW Mechanism | 14 pages, 2 figures, published in IJTP | Int. J. Theor. Phys. 54, 1567-1577 (2015) | 10.1007/s10773-014-2355-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The motion of a neutral particle in the vicinity of a slowly rotating black
hole in the Horava-Lifshitz theory of gravity and 3+1 dimensional topological
Lifshitz black hole is investigated. Geodesics for radial motion of the
particles are also plotted. Some different cases of the orbital motion of the
particle are discussed where maximum and minimum values of the effective
potential are calculated. Further the Ba\~{n}ados, Silk and West (BSW)
mechanism is studied for these black holes. It is shown that the centre-of-mass
energy (CME) of two colliding uncharged particles at the horizon of these black
holes remains finite. Thus the BSW effect cannot be seen in these cases.
| [
{
"created": "Tue, 18 Nov 2014 11:31:46 GMT",
"version": "v1"
}
] | 2015-04-16 | [
[
"Hussain",
"Ibrar",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Majeed",
"Bushra",
""
]
] | The motion of a neutral particle in the vicinity of a slowly rotating black hole in the Horava-Lifshitz theory of gravity and 3+1 dimensional topological Lifshitz black hole is investigated. Geodesics for radial motion of the particles are also plotted. Some different cases of the orbital motion of the particle are discussed where maximum and minimum values of the effective potential are calculated. Further the Ba\~{n}ados, Silk and West (BSW) mechanism is studied for these black holes. It is shown that the centre-of-mass energy (CME) of two colliding uncharged particles at the horizon of these black holes remains finite. Thus the BSW effect cannot be seen in these cases. |
1204.0866 | Antonio Enea Romano | Antonio Enea Romano | A discrete estimation of the uncertainty of the background redshift and
its effects on cosmological parameters | 17 pages, 5 figures, new sections and figure added, analytical
calculation of the redshift dispersion added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a discrete model to account for the effects of inhomogeneities on
the redshift of photons. Using this model we compute the probability
distribution of the observed redshift respect to the background value,
obtaining that its dispersion around the central value is proportional the
square root of the comoving distance. This implies that data analysis should
include a contribution to the total error budget which depends on the distance
of the source. Assuming large scale inhomogeneities with a power spectrum given
by primordial curvature perturbations the effect is expected to be small at low
red-shift, and to become important only at very high redshift. We then consider
what are the general implications for the estimation of background cosmological
parameters, giving some example for the case of quantities related to the
luminosity distance such as the Hubble parameter and the cosmological constant.
The model correctly reproduces the expected stochastic properties of the
propagation of photons in inhomogeneous media and due to its computational
simplicity it could be particularly suitable for the numerical estimation of
the effects of inhomogeneities on cosmological observables using Montecarlo
methods.
| [
{
"created": "Wed, 4 Apr 2012 05:26:13 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Jul 2012 01:48:56 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Jul 2017 12:42:32 GMT",
"version": "v3"
},
{
"created": "Sun, 29 Oct 2017 09:42:38 GMT",
"version": "v4"
}
] | 2017-10-31 | [
[
"Romano",
"Antonio Enea",
""
]
] | We develop a discrete model to account for the effects of inhomogeneities on the redshift of photons. Using this model we compute the probability distribution of the observed redshift respect to the background value, obtaining that its dispersion around the central value is proportional the square root of the comoving distance. This implies that data analysis should include a contribution to the total error budget which depends on the distance of the source. Assuming large scale inhomogeneities with a power spectrum given by primordial curvature perturbations the effect is expected to be small at low red-shift, and to become important only at very high redshift. We then consider what are the general implications for the estimation of background cosmological parameters, giving some example for the case of quantities related to the luminosity distance such as the Hubble parameter and the cosmological constant. The model correctly reproduces the expected stochastic properties of the propagation of photons in inhomogeneous media and due to its computational simplicity it could be particularly suitable for the numerical estimation of the effects of inhomogeneities on cosmological observables using Montecarlo methods. |
gr-qc/9811027 | Leor Barack | Leor Barack | Late time dynamics of scalar perturbations outside black holes: I. A
shell toy-model | 21 pages, 19 figures. Accepted for publication in Physical Review D | Phys.Rev. D59 (1999) 044016 | 10.1103/PhysRevD.59.044016 | null | gr-qc | null | We present a new analytic approach for the study of late time evolution of
linear test-fields, propagating on the exterior of black holes. This method
provides a calculation scheme applicable to Kerr black holes (for which case no
analytic calculation of the late time tails has been presented so far). In this
paper we develop the new technique and apply it to the case of massless scalar
waves evolving on the background geometry of a static spherically-symmetric
thin shell with a Schwarzschild exterior. The late time behavior of the scalar
field at null infinity is calculated, and is explicitly related to the form of
(quite arbitrary) initial data. This reproduces the well-known late time
power-law decaying tails. In an accompanying paper we apply our approach to the
complete Schwarzschild black hole geometry, where we obtain the familiar
inverse-power late time tails at null infinity, as well as at time-like
infinity and along the event horizon. A calculation of the late time power-law
tails in the Kerr geometry, based on the same approach, will be presented in a
forthcoming paper.
| [
{
"created": "Tue, 10 Nov 1998 09:50:24 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Barack",
"Leor",
""
]
] | We present a new analytic approach for the study of late time evolution of linear test-fields, propagating on the exterior of black holes. This method provides a calculation scheme applicable to Kerr black holes (for which case no analytic calculation of the late time tails has been presented so far). In this paper we develop the new technique and apply it to the case of massless scalar waves evolving on the background geometry of a static spherically-symmetric thin shell with a Schwarzschild exterior. The late time behavior of the scalar field at null infinity is calculated, and is explicitly related to the form of (quite arbitrary) initial data. This reproduces the well-known late time power-law decaying tails. In an accompanying paper we apply our approach to the complete Schwarzschild black hole geometry, where we obtain the familiar inverse-power late time tails at null infinity, as well as at time-like infinity and along the event horizon. A calculation of the late time power-law tails in the Kerr geometry, based on the same approach, will be presented in a forthcoming paper. |
2005.11163 | Pardyumn Kumar Sahoo | Snehasish Bhattacharjee, P.K. Sahoo | Redshift Drift in $f(R,T)$ Gravity | To appear in New Astronomy | New Astronomy, 81 (2020) 101425 | 10.1016/j.newast.2020.101425 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Redshift drift refers to the phenomena that redshift of cosmic objects is a
function of time. Measurement of redshift drift is of fundamental importance in
physical cosmology and can be utilized to distinguish different cosmological
models. Redshift drift can be expressed in two distinct methods. The first
method is related to cosmography, where the Redshift drift is given as a series
expansion of cosmological parameters, while the second method is written as a
function of Hubble parameter and its time derivatives which ultimately involve
field equations of a chosen theory of gravity. By equating corresponding terms
from both the series, the model parameter(s) of any modified theory of gravity
can be constrained. The present note aims at constraining the model parameter
$\zeta$ of $f(R,T)$ gravity theory where $f(R,T)= R + \zeta T$. By equating
linear terms in redshift $z$ from both the series, we constrain $\zeta$ in the
range $-0.51 \kappa^{2} \lesssim \zeta \lesssim -0.47 \kappa^{2}$, where
$\kappa^{2}=\frac{8 \pi G}{c^{4}}$.
| [
{
"created": "Thu, 21 May 2020 11:11:15 GMT",
"version": "v1"
}
] | 2020-06-16 | [
[
"Bhattacharjee",
"Snehasish",
""
],
[
"Sahoo",
"P. K.",
""
]
] | Redshift drift refers to the phenomena that redshift of cosmic objects is a function of time. Measurement of redshift drift is of fundamental importance in physical cosmology and can be utilized to distinguish different cosmological models. Redshift drift can be expressed in two distinct methods. The first method is related to cosmography, where the Redshift drift is given as a series expansion of cosmological parameters, while the second method is written as a function of Hubble parameter and its time derivatives which ultimately involve field equations of a chosen theory of gravity. By equating corresponding terms from both the series, the model parameter(s) of any modified theory of gravity can be constrained. The present note aims at constraining the model parameter $\zeta$ of $f(R,T)$ gravity theory where $f(R,T)= R + \zeta T$. By equating linear terms in redshift $z$ from both the series, we constrain $\zeta$ in the range $-0.51 \kappa^{2} \lesssim \zeta \lesssim -0.47 \kappa^{2}$, where $\kappa^{2}=\frac{8 \pi G}{c^{4}}$. |
2301.08736 | Andrew L. Miller | Andrew L. Miller and Luis Mendes | First search for ultralight dark matter with a space-based
gravitational-wave antenna: LISA Pathfinder | 9 pages, 5 figures | Phys. Rev. D 107, 063015 (2023) | 10.1103/PhysRevD.107.063015 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present here results from the first-ever search for dark photon dark
matter that could have coupled to baryons in LISA Pathfinder, the technology
demonstrator for a space-based gravitational-wave antenna. After analyzing
approximately three months of data taken by LISA Pathfinder in the frequency
range $[2\times 10^{-5},5]$ Hz, corresponding to dark photon masses of
$[8\times 10^{-20},2\times 10^{-14}]$ eV/$c^2$, we find no evidence of a
dark-matter signal, and set upper limits on the strength of the dark
photon/baryon coupling. To perform this search, we leveraged methods that
search for quasi-monochromatic gravitational-wave signals in ground-based
interferometers, and are robust against non-Gaussianities and gaps in the data.
Our work therefore represents a proof-of-concept test of search methods in LISA
to find persistent, quasi-monochromatic signals, and shows our ability to
handle non-Guassian artifacts and gaps while maintaining good sensitivity
compared to the optimal matched filter. The results also indicate that these
methods can be powerful tools in LISA to not only find dark matter, but also
look for other persistent signals from e.g. intermediate-mass black hole
inspirals and galactic white dwarf binaries.
| [
{
"created": "Fri, 20 Jan 2023 18:58:29 GMT",
"version": "v1"
}
] | 2023-03-15 | [
[
"Miller",
"Andrew L.",
""
],
[
"Mendes",
"Luis",
""
]
] | We present here results from the first-ever search for dark photon dark matter that could have coupled to baryons in LISA Pathfinder, the technology demonstrator for a space-based gravitational-wave antenna. After analyzing approximately three months of data taken by LISA Pathfinder in the frequency range $[2\times 10^{-5},5]$ Hz, corresponding to dark photon masses of $[8\times 10^{-20},2\times 10^{-14}]$ eV/$c^2$, we find no evidence of a dark-matter signal, and set upper limits on the strength of the dark photon/baryon coupling. To perform this search, we leveraged methods that search for quasi-monochromatic gravitational-wave signals in ground-based interferometers, and are robust against non-Gaussianities and gaps in the data. Our work therefore represents a proof-of-concept test of search methods in LISA to find persistent, quasi-monochromatic signals, and shows our ability to handle non-Guassian artifacts and gaps while maintaining good sensitivity compared to the optimal matched filter. The results also indicate that these methods can be powerful tools in LISA to not only find dark matter, but also look for other persistent signals from e.g. intermediate-mass black hole inspirals and galactic white dwarf binaries. |
1604.00624 | Julio Cesar Fabris | C.R. Almeida, J.C. Fabris, F. Sbis\'a, Y. Tavakoli | Quantum cosmology with k-Essence theory | Latex file, 7 pages. Version to appear in the proceedings of the 31st
International Colloquium on Group Theoretical Methods in Physics. Rio de
Janeiro, Brazil, 19-25 june 2016 | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A class of $k$-Essence cosmological models, with a power law kinetic term, is
quantised in the mini-superspace. It is shown that for a specific
configuration, corresponding to a pressureless fluid, a Schr\"odinger-type
equation is obtained with the scalar field playing the r\^ole of time. The
resulting quantum scenario reveals a bounce, the classical behaviour being
recovered asymptotically.
| [
{
"created": "Sun, 3 Apr 2016 11:54:50 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Dec 2016 12:29:28 GMT",
"version": "v2"
}
] | 2016-12-28 | [
[
"Almeida",
"C. R.",
""
],
[
"Fabris",
"J. C.",
""
],
[
"Sbisá",
"F.",
""
],
[
"Tavakoli",
"Y.",
""
]
] | A class of $k$-Essence cosmological models, with a power law kinetic term, is quantised in the mini-superspace. It is shown that for a specific configuration, corresponding to a pressureless fluid, a Schr\"odinger-type equation is obtained with the scalar field playing the r\^ole of time. The resulting quantum scenario reveals a bounce, the classical behaviour being recovered asymptotically. |
2408.07667 | Abdelghani Errehymy Ph.D. | Abdelghani Errehymy, Youssef Khedif, Orhan Donmez, Mohammed Daoud,
Kairat Myrzakulov, Sabit Bekov | Possible wormholes in $f(R)$ gravity sourced by solitonic quantum wave
and cold dark matter halos and their repulsive gravity effect | Accepted for publication in the European Physical Journal C, 15
pages, 18 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we present new generalized wormhole (WH) solutions within the
context of $f(R)$ gravity. Specifically, we focus on $f(R)$ gravitational
theories formulated in the metric formalism, with our investigation centered on
a power-law form represented by $f(R) = \epsilon R^{\chi}$. Here, $\epsilon$ is
an arbitrary constant, and $\chi$ is a real number. Notably, this form
possesses the advantageous property of reducing to Einstein gravity when
$\epsilon=1$ and $\chi=1$. To obtain these novel WH solutions, we establish the
general field equations for any $f(R)$ theory within the framework of
Morris-Thorne spacetime, assuming metric coefficients that are independent of
time. By utilizing an anisotropic matter source and a specific type of energy
density associated with solitonic quantum wave (SQW) and cold dark matter (CDM)
halos, we calculate two distinct WH solutions. We thoroughly investigate the
properties of the exotic matter (ExoM) residing within the WH geometry and
analyze the matter contents through energy conditions (ECs). Both analytical
and graphical methods are employed in this analysis to examine the validity of
different regions. Notably, the calculated shape functions for the WH geometry
satisfy the necessary conditions in both scenarios, emphasizing their
reliability. This ExoM is characterized by an energy-momentum tensor that
violates the null energy condition (NEC) and, consequently, the weak energy
condition as well, in the vicinity of the WH throats. Furthermore, we
investigated the repulsive effect of gravity and discovered that its presence
results in a negative deflection angle for photons following null geodesics.
Importantly, we observed that the deflection angle consistently exhibits
negative values across all $r_0$ values in both scenarios, indicating the
manifestation of the repulsive gravity effect.
| [
{
"created": "Wed, 14 Aug 2024 17:03:16 GMT",
"version": "v1"
}
] | 2024-08-15 | [
[
"Errehymy",
"Abdelghani",
""
],
[
"Khedif",
"Youssef",
""
],
[
"Donmez",
"Orhan",
""
],
[
"Daoud",
"Mohammed",
""
],
[
"Myrzakulov",
"Kairat",
""
],
[
"Bekov",
"Sabit",
""
]
] | In this paper, we present new generalized wormhole (WH) solutions within the context of $f(R)$ gravity. Specifically, we focus on $f(R)$ gravitational theories formulated in the metric formalism, with our investigation centered on a power-law form represented by $f(R) = \epsilon R^{\chi}$. Here, $\epsilon$ is an arbitrary constant, and $\chi$ is a real number. Notably, this form possesses the advantageous property of reducing to Einstein gravity when $\epsilon=1$ and $\chi=1$. To obtain these novel WH solutions, we establish the general field equations for any $f(R)$ theory within the framework of Morris-Thorne spacetime, assuming metric coefficients that are independent of time. By utilizing an anisotropic matter source and a specific type of energy density associated with solitonic quantum wave (SQW) and cold dark matter (CDM) halos, we calculate two distinct WH solutions. We thoroughly investigate the properties of the exotic matter (ExoM) residing within the WH geometry and analyze the matter contents through energy conditions (ECs). Both analytical and graphical methods are employed in this analysis to examine the validity of different regions. Notably, the calculated shape functions for the WH geometry satisfy the necessary conditions in both scenarios, emphasizing their reliability. This ExoM is characterized by an energy-momentum tensor that violates the null energy condition (NEC) and, consequently, the weak energy condition as well, in the vicinity of the WH throats. Furthermore, we investigated the repulsive effect of gravity and discovered that its presence results in a negative deflection angle for photons following null geodesics. Importantly, we observed that the deflection angle consistently exhibits negative values across all $r_0$ values in both scenarios, indicating the manifestation of the repulsive gravity effect. |
1008.1231 | Argelia Bernal | L. Arturo Ure\~na-L\'opez and Argelia Bernal | Bosonic gas as a Galactic Dark Matter Halo | 14 pages, 22 figures | Phys.Rev.D82:123535,2010 | 10.1103/PhysRevD.82.123535 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study in detail the properties of gravitationally-bounded multi-state
configurations, made of spin-zero bosons, in the Newtonian regime. We show that
the properties of such configurations, in particular their stability, depend
upon how the particles are distributed in the different states they are
composed of. Numerical techniques are used to distinguish between stable and
unstable solutions, and to determine the final configurations they evolve
towards to. Multi-state equilibrium configurations can be used as models of
galactic halos made of scalar field dark matter, whose rotation curves appear
more realistic than in the case of single-state configurations.
| [
{
"created": "Fri, 6 Aug 2010 16:43:14 GMT",
"version": "v1"
}
] | 2011-03-07 | [
[
"Ureña-López",
"L. Arturo",
""
],
[
"Bernal",
"Argelia",
""
]
] | We study in detail the properties of gravitationally-bounded multi-state configurations, made of spin-zero bosons, in the Newtonian regime. We show that the properties of such configurations, in particular their stability, depend upon how the particles are distributed in the different states they are composed of. Numerical techniques are used to distinguish between stable and unstable solutions, and to determine the final configurations they evolve towards to. Multi-state equilibrium configurations can be used as models of galactic halos made of scalar field dark matter, whose rotation curves appear more realistic than in the case of single-state configurations. |
1302.1918 | Kent Yagi | Kent Yagi, Leo C. Stein, Nicolas Yunes, Takahiro Tanaka | Isolated and Binary Neutron Stars in Dynamical Chern-Simons Gravity | 28 pages, 7 figures, 3 tables; erratum added, main results unchanged | Phys. Rev. D 87, 084058 (2013) | 10.1103/PhysRevD.87.084058 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study isolated and binary neutron stars in dynamical Chern-Simons gravity.
This theory modifies the Einstein-Hilbert action through the introduction of a
dynamical scalar field coupled to the Pontryagin density. We here treat this
theory as an effective model, working to leading order in the Chern-Simons
coupling. We first construct isolated neutron star solutions in the
slow-rotation expansion to quadratic order in spin. We find that isolated
neutron stars acquire a scalar dipole charge that corrects its spin angular
momentum to linear order in spin and corrects its mass and quadrupole moment to
quadratic order in spin, as measured by an observer at spatial infinity. We
then consider neutron stars binaries that are widely separated and solve for
their orbital evolution in this modified theory. We find that the evolution of
post-Keplerian parameters is modified, with the rate of periastron advance
being the dominant correction at first post-Newtonian order. We conclude by
applying these results to observed pulsars with the aim to place constraints on
dynamical Chern-Simons gravity. We find that the modifications to the observed
mass are degenerate with the neutron star equation of state, which prevents us
from testing the theory with the inferred mass of the millisecond pulsar
J1614-2230. We also find that the corrections to the post-Keplerian parameters
are too small to be observable today even with data from the double binary
pulsar J0737-3039. Our results suggest that pulsar observations are not
currently capable of constraining dynamical Chern-Simons gravity, and thus,
gravitational-wave observations may be the only path to a stringent constraint
of this theory in the imminent future.
| [
{
"created": "Fri, 8 Feb 2013 00:33:43 GMT",
"version": "v1"
},
{
"created": "Thu, 2 May 2013 23:10:33 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Apr 2016 19:56:27 GMT",
"version": "v3"
}
] | 2016-04-13 | [
[
"Yagi",
"Kent",
""
],
[
"Stein",
"Leo C.",
""
],
[
"Yunes",
"Nicolas",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | We study isolated and binary neutron stars in dynamical Chern-Simons gravity. This theory modifies the Einstein-Hilbert action through the introduction of a dynamical scalar field coupled to the Pontryagin density. We here treat this theory as an effective model, working to leading order in the Chern-Simons coupling. We first construct isolated neutron star solutions in the slow-rotation expansion to quadratic order in spin. We find that isolated neutron stars acquire a scalar dipole charge that corrects its spin angular momentum to linear order in spin and corrects its mass and quadrupole moment to quadratic order in spin, as measured by an observer at spatial infinity. We then consider neutron stars binaries that are widely separated and solve for their orbital evolution in this modified theory. We find that the evolution of post-Keplerian parameters is modified, with the rate of periastron advance being the dominant correction at first post-Newtonian order. We conclude by applying these results to observed pulsars with the aim to place constraints on dynamical Chern-Simons gravity. We find that the modifications to the observed mass are degenerate with the neutron star equation of state, which prevents us from testing the theory with the inferred mass of the millisecond pulsar J1614-2230. We also find that the corrections to the post-Keplerian parameters are too small to be observable today even with data from the double binary pulsar J0737-3039. Our results suggest that pulsar observations are not currently capable of constraining dynamical Chern-Simons gravity, and thus, gravitational-wave observations may be the only path to a stringent constraint of this theory in the imminent future. |
2401.10477 | Chi-Sing Lam | C.S. Lam | Dynamical Property of Black Hole Matter | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Matter loses its original characteristics after entering a black hole, thus
becoming a new kind of (black hole) matter. The property of this new matter
cannot be measured experimentally, but some of it can be deduced theoretically
from the Einstein equations and the conservation laws which it must still
satisfy. In a previous paper, this matter is modelled by an ideal fluid, with
an equation of state $p(r)=-\xi\r(r)$ between the pressure $p(r)$ and the
density $\rho(r)$. In order for this matter to fill the inside of a black hole
so that its property can be teased out from the Einstein and conservation
equations, it must possess a negative pressure ($\xi>0$) to counter the
gravitation attraction which draws all matter to the center. In that case a
solution of the Einstein and conservation equations exists if and only if the
constant $\xi$ is confined within a narrow range, between 0.1429 and 0.1716. In
the present paper, we try to find out its dynamical response by injecting
additional matter into the black hole over a period of time. The resulting
solutions of the six time-dependent Einstein equations and conservation laws
are presented in perturbation theory, valid if the total amount of injection is
small. Even in perturbation, the solutions can be obtained only with a special
trick. The result shows that the equation of state $p(r,t)=-\xi\r(r,t)$ remains
unchanged with the same $\xi$ when the injection rate is constant. When the
rate changes with time, $\xi$ requires a correction, $\xi\to\xi+\xi_1(r,t)$,
where $\xi_1(r,t)$ appears to be correlated with the acceleration of the
injected matter in a way to be shown in the text.
| [
{
"created": "Fri, 19 Jan 2024 04:01:59 GMT",
"version": "v1"
}
] | 2024-01-22 | [
[
"Lam",
"C. S.",
""
]
] | Matter loses its original characteristics after entering a black hole, thus becoming a new kind of (black hole) matter. The property of this new matter cannot be measured experimentally, but some of it can be deduced theoretically from the Einstein equations and the conservation laws which it must still satisfy. In a previous paper, this matter is modelled by an ideal fluid, with an equation of state $p(r)=-\xi\r(r)$ between the pressure $p(r)$ and the density $\rho(r)$. In order for this matter to fill the inside of a black hole so that its property can be teased out from the Einstein and conservation equations, it must possess a negative pressure ($\xi>0$) to counter the gravitation attraction which draws all matter to the center. In that case a solution of the Einstein and conservation equations exists if and only if the constant $\xi$ is confined within a narrow range, between 0.1429 and 0.1716. In the present paper, we try to find out its dynamical response by injecting additional matter into the black hole over a period of time. The resulting solutions of the six time-dependent Einstein equations and conservation laws are presented in perturbation theory, valid if the total amount of injection is small. Even in perturbation, the solutions can be obtained only with a special trick. The result shows that the equation of state $p(r,t)=-\xi\r(r,t)$ remains unchanged with the same $\xi$ when the injection rate is constant. When the rate changes with time, $\xi$ requires a correction, $\xi\to\xi+\xi_1(r,t)$, where $\xi_1(r,t)$ appears to be correlated with the acceleration of the injected matter in a way to be shown in the text. |
1208.3749 | Gunter Scharf | G\"unter Scharf | Against geometry: Nonstandard general relativity | 14 pages, no figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the Schwarzschild solution can be embedded in a class of
nonstandard solutions of the vacuum Einstein's equations with arbitrary
rotation curves. These nonstandard solutions have to be taken as physical if
dark matter as needed in the standard theory cannot be found. As a consequence
general relativity is considered as a classical field theory in Minkowski space
and not as a geometric theory in the sense of Einstein.
| [
{
"created": "Sat, 18 Aug 2012 14:37:11 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Nov 2012 16:49:43 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Jan 2013 16:33:00 GMT",
"version": "v3"
},
{
"created": "Wed, 8 May 2013 07:39:06 GMT",
"version": "v4"
},
{
"crea... | 2015-04-28 | [
[
"Scharf",
"Günter",
""
]
] | We show that the Schwarzschild solution can be embedded in a class of nonstandard solutions of the vacuum Einstein's equations with arbitrary rotation curves. These nonstandard solutions have to be taken as physical if dark matter as needed in the standard theory cannot be found. As a consequence general relativity is considered as a classical field theory in Minkowski space and not as a geometric theory in the sense of Einstein. |
0712.1575 | Badri Krishnan | Badri Krishnan | Fundamental properties and applications of quasi-local black hole
horizons | 14 pages, 2 figures. Based on a talk presented at the 18th
International Conference on General Relativity and Gravitation, 8-13 July
2007, Sydney, Australia | Class.Quant.Grav.25:114005,2008 | 10.1088/0264-9381/25/11/114005 | AEI-2007-170 | gr-qc | null | The traditional description of black holes in terms of event horizons is
inadequate for many physical applications, especially when studying black holes
in non-stationary spacetimes. In these cases, it is often more useful to use
the quasi-local notions of trapped and marginally trapped surfaces, which lead
naturally to the framework of trapping, isolated, and dynamical horizons. This
framework allows us to analyze diverse facets of black holes in a unified
manner and to significantly generalize several results in black hole physics.
It also leads to a number of applications in mathematical general relativity,
numerical relativity, astrophysics, and quantum gravity. In this review, I will
discuss the basic ideas and recent developments in this framework, and
summarize some of its applications with an emphasis on numerical relativity.
| [
{
"created": "Mon, 10 Dec 2007 19:29:00 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Krishnan",
"Badri",
""
]
] | The traditional description of black holes in terms of event horizons is inadequate for many physical applications, especially when studying black holes in non-stationary spacetimes. In these cases, it is often more useful to use the quasi-local notions of trapped and marginally trapped surfaces, which lead naturally to the framework of trapping, isolated, and dynamical horizons. This framework allows us to analyze diverse facets of black holes in a unified manner and to significantly generalize several results in black hole physics. It also leads to a number of applications in mathematical general relativity, numerical relativity, astrophysics, and quantum gravity. In this review, I will discuss the basic ideas and recent developments in this framework, and summarize some of its applications with an emphasis on numerical relativity. |
1911.03327 | Antonio Enea Romano | Sergio Andres Vallejo-Pena, Antonio Enea Romano | Effects of the modification of gravity on the production of primordial
black holes | Version published in PLB | null | 10.1016/j.physletb.2021.136289 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The enhancement of the spectrum of primordial comoving curvature perturbation
$\R$ can induce the production of primordial black holes (PBH) which could
account for part of present day dark matter. As an example of the effects of
the modification of gravity on the production of PBHs, we investigate the
effects on the spectrum of $\R$ produced by the modification of gravity in the
case of G-inflation, deriving the relation between the unitary gauge curvature
perturbation $\zeta$ and the comoving curvature perturbation $\R$, and
identifying a background dependent enhancement function $\E$ which can induce
large differences between the two gauge invariant variables. We use this
relation to derive an equation for $\R$, showing for the presence of a momentum
dependent effective sound speed (MESS), associated to the intrinsic entropy
which can arise in modified gravity theories, in agreement with the model
independent MESS approach to cosmological perturbations.
When $\zeta$ is not constant in time it is different from $\R$, for example
on sub-horizon scales, or in models exhibiting an anomalous super-horizon
growth of $\zeta$, but since this growth cannot last indefinitely, eventually
they will coincide. We derive the general condition for super-horizon growth of
$\zeta$, showing that slow-roll violation is not necessary. Since the abundance
of PBHs depends on the statistics of the peaks of the comoving density
contrast, which is related to the spectrum of $\R$, it is important to take
into account these effects on the PBHs abundance in modified gravity theories.
| [
{
"created": "Fri, 8 Nov 2019 15:31:45 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Apr 2021 23:01:34 GMT",
"version": "v2"
}
] | 2021-04-29 | [
[
"Vallejo-Pena",
"Sergio Andres",
""
],
[
"Romano",
"Antonio Enea",
""
]
] | The enhancement of the spectrum of primordial comoving curvature perturbation $\R$ can induce the production of primordial black holes (PBH) which could account for part of present day dark matter. As an example of the effects of the modification of gravity on the production of PBHs, we investigate the effects on the spectrum of $\R$ produced by the modification of gravity in the case of G-inflation, deriving the relation between the unitary gauge curvature perturbation $\zeta$ and the comoving curvature perturbation $\R$, and identifying a background dependent enhancement function $\E$ which can induce large differences between the two gauge invariant variables. We use this relation to derive an equation for $\R$, showing for the presence of a momentum dependent effective sound speed (MESS), associated to the intrinsic entropy which can arise in modified gravity theories, in agreement with the model independent MESS approach to cosmological perturbations. When $\zeta$ is not constant in time it is different from $\R$, for example on sub-horizon scales, or in models exhibiting an anomalous super-horizon growth of $\zeta$, but since this growth cannot last indefinitely, eventually they will coincide. We derive the general condition for super-horizon growth of $\zeta$, showing that slow-roll violation is not necessary. Since the abundance of PBHs depends on the statistics of the peaks of the comoving density contrast, which is related to the spectrum of $\R$, it is important to take into account these effects on the PBHs abundance in modified gravity theories. |
1903.02886 | LSC P&P Committee | The LIGO Scientific Collaboration and the Virgo Collaboration: B. P.
Abbott, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, K. Ackley, C.
Adams, V. B. Adya, C. Affeldt, M. Agathos, K. Agatsuma, N. Aggarwal, O. D.
Aguiar, L. Aiello, A. Ain, P. Ajith, G. Allen, A. Allocca, M. A. Aloy, P. A.
Altin, A. Amato, A. Ananyeva, S. B. Anderson, W. G. Anderson, S. V. Angelova,
S. Antier, S. Appert, K. Arai, M. C. Araya, J. S. Areeda, M. Ar\`ene, N.
Arnaud, K. G. Arun, S. Ascenzi, G. Ashton, S. M. Aston, P. Astone, F. Aubin,
P. Aufmuth, K. AultONeal, C. Austin, V. Avendano, A. Avila-Alvarez, S. Babak,
P. Bacon, F. Badaracco, M. K. M. Bader, S. Bae, P. T. Baker, F. Baldaccini,
G. Ballardin, S. W. Ballmer, S. Banagiri, J. C. Barayoga, S. E. Barclay, B.
C. Barish, D. Barker, K. Barkett, S. Barnum, F. Barone, B. Barr, L. Barsotti,
M. Barsuglia, D. Barta, J. Bartlett, I. Bartos, R. Bassiri, A. Basti, M.
Bawaj, J. C. Bayley, M. Bazzan, B. B\'ecsy, M. Bejger, I. Belahcene, A. S.
Bell, D. Beniwal, B. K. Berger, G. Bergmann, S. Bernuzzi, J. J. Bero, C. P.
L. Berry, D. Bersanetti, A. Bertolini, J. Betzwieser, R. Bhandare, J. Bidler,
I. A. Bilenko, S. A. Bilgili, G. Billingsley, J. Birch, R. Birney, O.
Birnholtz, S. Biscans, S. Biscoveanu, A. Bisht, M. Bitossi, M. A. Bizouard,
J. K. Blackburn, C. D. Blair, D. G. Blair, R. M. Blair, S. Bloemen, N. Bode,
M. Boer, Y. Boetzel, G. Bogaert, F. Bondu, E. Bonilla, R. Bonnand, P. Booker,
B. A. Boom, C. D. Booth, R. Bork, V. Boschi, S. Bose, K. Bossie, V.
Bossilkov, J. Bosveld, Y. Bouffanais, A. Bozzi, C. Bradaschia, P. R. Brady,
A. Bramley, M. Branchesi, J. E. Brau, T. Briant, J. H. Briggs, F. Brighenti,
A. Brillet, M. Brinkmann, V. Brisson, P. Brockill, A. F. Brooks, D. D. Brown,
S. Brunett, A. Buikema, T. Bulik, H. J. Bulten, A. Buonanno, D. Buskulic, C.
Buy, R. L. Byer, M. Cabero, L. Cadonati, G. Cagnoli, C. Cahillane, J.
Calder\'on Bustillo, T. A. Callister, E. Calloni, J. B. Camp, W. A. Campbell,
M. Canepa, K. C. Cannon, H. Cao, J. Cao, E. Capocasa, F. Carbognani, S.
Caride, M. F. Carney, G. Carullo, J. Casanueva Diaz, C. Casentini, S.
Caudill, M. Cavagli\`a, F. Cavalier, R. Cavalieri, G. Cella, P.
Cerd\'a-Dur\'an, G. Cerretani, E. Cesarini, O. Chaibi, K. Chakravarti, S. J.
Chamberlin, M. Chan, S. Chao, P. Charlton, E. A. Chase, E. Chassande-Mottin,
D. Chatterjee, M. Chaturvedi, B. D. Cheeseboro, H. Y. Chen, X. Chen, Y. Chen,
H.-P. Cheng, C. K. Cheong, H. Y. Chia, A. Chincarini, A. Chiummo, G. Cho, H.
S. Cho, M. Cho, N. Christensen, Q. Chu, S. Chua, K. W. Chung, S. Chung, G.
Ciani, A. A. Ciobanu, R. Ciolfi, F. Cipriano, A. Cirone, F. Clara, J. A.
Clark, P. Clearwater, F. Cleva, C. Cocchieri, E. Coccia, P.-F. Cohadon, D.
Cohen, R. Colgan, M. Colleoni, C. G. Collette, C. Collins, L. R. Cominsky, M.
Constancio Jr., L. Conti, S. J. Cooper, P. Corban, T. R. Corbitt, I.
Cordero-Carri\'on, K. R. Corley, N. Cornish, A. Corsi, S. Cortese, C. A.
Costa, R. Cotesta, M. W. Coughlin, S. B. Coughlin, J.-P. Coulon, S. T.
Countryman, P. Couvares, P. B. Covas, E. E. Cowan, D. M. Coward, M. J.
Cowart, D. C. Coyne, R. Coyne, J. D. E. Creighton, T. D. Creighton, J. Cripe,
M. Croquette, S. G. Crowder, T. J. Cullen, A. Cumming, L. Cunningham, E.
Cuoco, T. Dal Canton, G. D\'alya, S. L. Danilishin, S. D'Antonio, K.
Danzmann, A. Dasgupta, C. F. Da Silva Costa, L. E. H. Datrier, V. Dattilo, I.
Dave, M. Davier, D. Davis, E. J. Daw, D. DeBra, M. Deenadayalan, J.
Degallaix, M. De Laurentis, S. Del\'eglise, W. Del Pozzo, L. M. DeMarchi, N.
Demos, T. Dent, R. De Pietri, J. Derby, R. De Rosa, C. De Rossi, R. DeSalvo,
O. de Varona, S. Dhurandhar, M. C. D\'iaz, T. Dietrich, L. Di Fiore, M. Di
Giovanni, T. Di Girolamo, A. Di Lieto, B. Ding, S. Di Pace, I. Di Palma, F.
Di Renzo, A. Dmitriev, Z. Doctor, F. Donovan, K. L. Dooley, S. Doravari, I.
Dorrington, T. P. Downes, M. Drago, J. C. Driggers, Z. Du, J.-G. Ducoin, P.
Dupej, I. Dvorkin, S. E. Dwyer, P. J. Easter, T. B. Edo, M. C. Edwards, A.
Effler, P. Ehrens, J. Eichholz, S. S. Eikenberry, M. Eisenmann, R. A.
Eisenstein, R. C. Essick, H. Estelles, D. Estevez, Z. B. Etienne, T. Etzel,
M. Evans, T. M. Evans, V. Fafone, H. Fair, S. Fairhurst, X. Fan, S. Farinon,
B. Farr, W. M. Farr, E. J. Fauchon-Jones, M. Favata, M. Fays, M. Fazio, C.
Fee, J. Feicht, M. M. Fejer, F. Feng, A. Fernandez-Galiana, I. Ferrante, E.
C. Ferreira, T. A. Ferreira, F. Ferrini, F. Fidecaro, I. Fiori, D. Fiorucci,
M. Fishbach, R. P. Fisher, J. M. Fishner, M. Fitz-Axen, R. Flaminio, M.
Fletcher, E. Flynn, H. Fong, J. A. Font, P. W. F. Forsyth, J.-D. Fournier, S.
Frasca, F. Frasconi, Z. Frei, A. Freise, R. Frey, V. Frey, P. Fritschel, V.
V. Frolov, P. Fulda, M. Fyffe, H. A. Gabbard, B. U. Gadre, S. M. Gaebel, J.
R. Gair, L. Gammaitoni, M. R. Ganija, S. G. Gaonkar, A. Garcia, C.
Garc\'ia-Quir\'os, F. Garufi, B. Gateley, S. Gaudio, G. Gaur, V. Gayathri, G.
Gemme, E. Genin, A. Gennai, D. George, J. George, L. Gergely, V. Germain, S.
Ghonge, Abhirup Ghosh, Archisman Ghosh, S. Ghosh, B. Giacomazzo, J. A.
Giaime, K. D. Giardina, A. Giazotto, K. Gill, G. Giordano, L. Glover, P.
Godwin, E. Goetz, R. Goetz, B. Goncharov, G. Gonz\'alez, J. M. Gonzalez
Castro, A. Gopakumar, M. L. Gorodetsky, S. E. Gossan, M. Gosselin, R. Gouaty,
A. Grado, C. Graef, M. Granata, A. Grant, S. Gras, P. Grassia, C. Gray, R.
Gray, G. Greco, A. C. Green, R. Green, E. M. Gretarsson, P. Groot, H. Grote,
S. Grunewald, P. Gruning, G. M. Guidi, H. K. Gulati, Y. Guo, A. Gupta, M. K.
Gupta, E. K. Gustafson, R. Gustafson, L. Haegel, O. Halim, B. R. Hall, E. D.
Hall, E. Z. Hamilton, G. Hammond, M. Haney, M. M. Hanke, J. Hanks, C. Hanna,
O. A. Hannuksela, J. Hanson, T. Hardwick, K. Haris, J. Harms, G. M. Harry, I.
W. Harry, C.-J. Haster, K. Haughian, F. J. Hayes, J. Healy, A. Heidmann, M.
C. Heintze, H. Heitmann, P. Hello, G. Hemming, M. Hendry, I. S. Heng, J.
Hennig, A. W. Heptonstall, Francisco Hernandez Vivanco, M. Heurs, S. Hild, T.
Hinderer, D. Hoak, S. Hochheim, D. Hofman, A. M. Holgado, N. A. Holland, K.
Holt, D. E. Holz, P. Hopkins, C. Horst, J. Hough, E. J. Howell, C. G. Hoy, A.
Hreibi, E. A. Huerta, D. Huet, B. Hughey, M. Hulko, S. Husa, S. H. Huttner,
T. Huynh-Dinh, B. Idzkowski, A. Iess, C. Ingram, R. Inta, G. Intini, B.
Irwin, H. N. Isa, J.-M. Isac, M. Isi, B. R. Iyer, K. Izumi, T. Jacqmin, S. J.
Jadhav, K. Jani, N. N. Janthalur, P. Jaranowski, A. C. Jenkins, J. Jiang, D.
S. Johnson, A. W. Jones, D. I. Jones, R. Jones, R. J. G. Jonker, L. Ju, J.
Junker, C. V. Kalaghatgi, V. Kalogera, B. Kamai, S. Kandhasamy, G. Kang, J.
B. Kanner, S. J. Kapadia, S. Karki, K. S. Karvinen, R. Kashyap, M. Kasprzack,
S. Katsanevas, E. Katsavounidis, W. Katzman, S. Kaufer, K. Kawabe, N. V.
Keerthana, F. K\'ef\'elian, D. Keitel, R. Kennedy, J. S. Key, F. Y. Khalili,
H. Khan, I. Khan, S. Khan, Z. Khan, E. A. Khazanov, M. Khursheed, N.
Kijbunchoo, Chunglee Kim, J. C. Kim, K. Kim, W. Kim, W. S. Kim, Y.-M. Kim, C.
Kimball, E. J. King, P. J. King, M. Kinley-Hanlon, R. Kirchhoff, J. S.
Kissel, L. Kleybolte, J. H. Klika, S. Klimenko, T. D. Knowles, P. Koch, S. M.
Koehlenbeck, G. Koekoek, S. Koley, V. Kondrashov, A. Kontos, N. Koper, M.
Korobko, W. Z. Korth, I. Kowalska, D. B. Kozak, V. Kringel, N. Krishnendu, A.
Kr\'olak, G. Kuehn, A. Kumar, P. Kumar, R. Kumar, S. Kumar, L. Kuo, A.
Kutynia, S. Kwang, B. D. Lackey, K. H. Lai, T. L. Lam, M. Landry, B. B. Lane,
R. N. Lang, J. Lange, B. Lantz, R. K. Lanza, A. Lartaux-Vollard, P. D. Lasky,
M. Laxen, A. Lazzarini, C. Lazzaro, P. Leaci, S. Leavey, Y. K. Lecoeuche, C.
H. Lee, H. K. Lee, H. M. Lee, H. W. Lee, J. Lee, K. Lee, J. Lehmann, A.
Lenon, N. Leroy, N. Letendre, Y. Levin, J. Li, K. J. L. Li, T. G. F. Li, X.
Li, F. Lin, F. Linde, S. D. Linker, T. B. Littenberg, J. Liu, X. Liu, R. K.
L. Lo, N. A. Lockerbie, L. T. London, A. Longo, M. Lorenzini, V. Loriette, M.
Lormand, G. Losurdo, J. D. Lough, C. O. Lousto, G. Lovelace, M. E. Lower, H.
L\"uck, D. Lumaca, A. P. Lundgren, R. Lynch, Y. Ma, R. Macas, S. Macfoy, M.
MacInnis, D. M. Macleod, A. Macquet, F. Maga\~na-Sandoval, L. Maga\~na
Zertuche, R. M. Magee, E. Majorana, I. Maksimovic, A. Malik, N. Man, V.
Mandic, V. Mangano, G. L. Mansell, M. Manske, M. Mantovani, F. Marchesoni, F.
Marion, S. M\'arka, Z. M\'arka, C. Markakis, A. S. Markosyan, A. Markowitz,
E. Maros, A. Marquina, S. Marsat, F. Martelli, I. W. Martin, R. M. Martin, D.
V. Martynov, K. Mason, E. Massera, A. Masserot, T. J. Massinger, M.
Masso-Reid, S. Mastrogiovanni, A. Matas, F. Matichard, L. Matone, N.
Mavalvala, N. Mazumder, J. J. McCann, R. McCarthy, D. E. McClelland, S.
McCormick, L. McCuller, S. C. McGuire, J. McIver, D. J. McManus, T. McRae, S.
T. McWilliams, D. Meacher, G. D. Meadors, M. Mehmet, A. K. Mehta, J. Meidam,
A. Melatos, G. Mendell, R. A. Mercer, L. Mereni, E. L. Merilh, M. Merzougui,
S. Meshkov, C. Messenger, C. Messick, R. Metzdorff, P. M. Meyers, H. Miao, C.
Michel, H. Middleton, E. E. Mikhailov, L. Milano, A. L. Miller, A. Miller, M.
Millhouse, J. C. Mills, M. C. Milovich-Goff, O. Minazzoli, Y. Minenkov, A.
Mishkin, C. Mishra, T. Mistry, S. Mitra, V. P. Mitrofanov, G. Mitselmakher,
R. Mittleman, G. Mo, D. Moffa, K. Mogushi, S. R. P. Mohapatra, M. Montani, C.
J. Moore, D. Moraru, G. Moreno, S. Morisaki, B. Mours, C. M. Mow-Lowry,
Arunava Mukherjee, D. Mukherjee, S. Mukherjee, N. Mukund, A. Mullavey, J.
Munch, E. A. Mu\~niz, M. Muratore, P. G. Murray, A. Nagar, I. Nardecchia, L.
Naticchioni, R. K. Nayak, J. Neilson, G. Nelemans, T. J. N. Nelson, M. Nery,
A. Neunzert, K. Y. Ng, S. Ng, P. Nguyen, D. Nichols, S. Nissanke, F. Nocera,
C. North, L. K. Nuttall, M. Obergaulinger, J. Oberling, B. D. O'Brien, G. D.
O'Dea, G. H. Ogin, J. J. Oh, S. H. Oh, F. Ohme, H. Ohta, M. A. Okada, M.
Oliver, P. Oppermann, Richard J. Oram, B. O'Reilly, R. G. Ormiston, L. F.
Ortega, R. O'Shaughnessy, S. Ossokine, D. J. Ottaway, H. Overmier, B. J.
Owen, A. E. Pace, G. Pagano, M. A. Page, A. Pai, S. A. Pai, J. R. Palamos, O.
Palashov, C. Palomba, A. Pal-Singh, Huang-Wei Pan, B. Pang, P. T. H. Pang, C.
Pankow, F. Pannarale, B. C. Pant, F. Paoletti, A. Paoli, A. Parida, W.
Parker, D. Pascucci, A. Pasqualetti, R. Passaquieti, D. Passuello, M. Patil,
B. Patricelli, B. L. Pearlstone, C. Pedersen, M. Pedraza, R. Pedurand, A.
Pele, S. Penn, C. J. Perez, A. Perreca, H. P. Pfeiffer, M. Phelps, K. S.
Phukon, O. J. Piccinni, M. Pichot, F. Piergiovanni, G. Pillant, L. Pinard, M.
Pirello, M. Pitkin, R. Poggiani, D. Y. T. Pong, S. Ponrathnam, P. Popolizio,
E. K. Porter, J. Powell, A. K. Prajapati, J. Prasad, K. Prasai, R. Prasanna,
G. Pratten, T. Prestegard, S. Privitera, G. A. Prodi, L. G. Prokhorov, O.
Puncken, M. Punturo, P. Puppo, M. P\"urrer, H. Qi, V. Quetschke, P. J.
Quinonez, E. A. Quintero, R. Quitzow-James, F. J. Raab, H. Radkins, N.
Radulescu, P. Raffai, S. Raja, C. Rajan, B. Rajbhandari, M. Rakhmanov, K. E.
Ramirez, A. Ramos-Buades, Javed Rana, K. Rao, P. Rapagnani, V. Raymond, M.
Razzano, J. Read, T. Regimbau, L. Rei, S. Reid, D. H. Reitze, W. Ren, F.
Ricci, C. J. Richardson, J. W. Richardson, P. M. Ricker, K. Riles, M. Rizzo,
N. A. Robertson, R. Robie, F. Robinet, A. Rocchi, L. Rolland, J. G. Rollins,
V. J. Roma, M. Romanelli, J. D. Romano, R. Romano, C. L. Romel, J. H. Romie,
K. Rose, D. Rosi\'nska, S. G. Rosofsky, M. P. Ross, S. Rowan, A. R\"udiger,
P. Ruggi, G. Rutins, K. Ryan, S. Sachdev, T. Sadecki, M. Sakellariadou, L.
Salconi, M. Saleem, A. Samajdar, L. Sammut, E. J. Sanchez, L. E. Sanchez, N.
Sanchis-Gual, V. Sandberg, J. R. Sanders, K. A. Santiago, N. Sarin, B.
Sassolas, B. S. Sathyaprakash, P. R. Saulson, O. Sauter, R. L. Savage, P.
Schale, M. Scheel, J. Scheuer, P. Schmidt, R. Schnabel, R. M. S. Schofield,
A. Sch\"onbeck, E. Schreiber, B. W. Schulte, B. F. Schutz, S. G. Schwalbe, J.
Scott, S. M. Scott, E. Seidel, D. Sellers, A. S. Sengupta, N. Sennett, D.
Sentenac, V. Sequino, A. Sergeev, Y. Setyawati, D. A. Shaddock, T. Shaffer,
M. S. Shahriar, M. B. Shaner, L. Shao, P. Sharma, P. Shawhan, H. Shen, R.
Shink, D. H. Shoemaker, D. M. Shoemaker, S. ShyamSundar, K. Siellez, M.
Sieniawska, D. Sigg, A. D. Silva, L. P. Singer, N. Singh, A. Singhal, A. M.
Sintes, S. Sitmukhambetov, V. Skliris, B. J. J. Slagmolen, T. J.
Slaven-Blair, J. R. Smith, R. J. E. Smith, S. Somala, E. J. Son, B. Sorazu,
F. Sorrentino, T. Souradeep, E. Sowell, A. P. Spencer, A. K. Srivastava, V.
Srivastava, K. Staats, C. Stachie, M. Standke, D. A. Steer, M. Steinke, J.
Steinlechner, S. Steinlechner, D. Steinmeyer, S. P. Stevenson, D. Stocks, R.
Stone, D. J. Stops, K. A. Strain, G. Stratta, S. E. Strigin, A. Strunk, R.
Sturani, A. L. Stuver, V. Sudhir, T. Z. Summerscales, L. Sun, S. Sunil, J.
Suresh, P. J. Sutton, B. L. Swinkels, M. J. Szczepa\'nczyk, M. Tacca, S. C.
Tait, C. Talbot, D. Talukder, D. B. Tanner, M. T\'apai, A. Taracchini, J. D.
Tasson, R. Taylor, F. Thies, M. Thomas, P. Thomas, S. R. Thondapu, K. A.
Thorne, E. Thrane, Shubhanshu Tiwari, Srishti Tiwari, V. Tiwari, K. Toland,
M. Tonelli, Z. Tornasi, A. Torres-Forn\'e, C. I. Torrie, D. T\"oyr\"a, F.
Travasso, G. Traylor, M. C. Tringali, A. Trovato, L. Trozzo, R. Trudeau, K.
W. Tsang, M. Tse, R. Tso, L. Tsukada, D. Tsuna, D. Tuyenbayev, K. Ueno, D.
Ugolini, C. S. Unnikrishnan, A. L. Urban, S. A. Usman, H. Vahlbruch, G.
Vajente, G. Valdes, N. van Bakel, M. van Beuzekom, J. F. J. van den Brand, C.
Van Den Broeck, D. C. Vander-Hyde, J. V. van Heijningen, L. van der Schaaf,
A. A. van Veggel, M. Vardaro, V. Varma, S. Vass, M. Vas\'uth, A. Vecchio, G.
Vedovato, J. Veitch, P. J. Veitch, K. Venkateswara, G. Venugopalan, D.
Verkindt, F. Vetrano, A. Vicer\'e, A. D. Viets, D. J. Vine, J.-Y. Vinet, S.
Vitale, T. Vo, H. Vocca, C. Vorvick, S. P. Vyatchanin, A. R. Wade, L. E.
Wade, M. Wade, R. Walet, M. Walker, L. Wallace, S. Walsh, G. Wang, H. Wang,
J. Z. Wang, W. H. Wang, Y. F. Wang, R. L. Ward, Z. A. Warden, J. Warner, M.
Was, J. Watchi, B. Weaver, L.-W. Wei, M. Weinert, A. J. Weinstein, R. Weiss,
F. Wellmann, L. Wen, E. K. Wessel, P. We{\ss}els, J. W. Westhouse, K. Wette,
J. T. Whelan, B. F. Whiting, C. Whittle, D. M. Wilken, D. Williams, A. R.
Williamson, J. L. Willis, B. Willke, M. H. Wimmer, W. Winkler, C. C. Wipf, H.
Wittel, G. Woan, J. Woehler, J. K. Wofford, J. Worden, J. L. Wright, D. S.
Wu, D. M. Wysocki, L. Xiao, R. Xu, H. Yamamoto, C. C. Yancey, L. Yang, M. J.
Yap, M. Yazback, D. W. Yeeles, Hang Yu, Haocun Yu, S. H. R. Yuen, M. Yvert,
A. K. Zadro\.zny, M. Zanolin, T. Zelenova, J.-P. Zendri, M. Zevin, J. Zhang,
L. Zhang, T. Zhang, C. Zhao, M. Zhou, Z. Zhou, X. J. Zhu, M. E. Zucker, J.
Zweizig | Search for the isotropic stochastic background using data from Advanced
LIGO's second observing run | 20 pages, 8 figures | Phys. Rev. D 100, 061101 (2019) | 10.1103/PhysRevD.100.061101 | LIGO-P1800248 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The stochastic gravitational-wave background is a superposition of sources
that are either too weak or too numerous to detect individually. In this study
we present the results from a cross-correlation analysis on data from Advanced
LIGO's second observing run (O2), which we combine with the results of the
first observing run (O1). We do not find evidence for a stochastic background,
so we place upper limits on the normalized energy density in gravitational
waves at the 95% credible level of $\Omega_{\rm GW}<6.0\times 10^{-8}$ for a
frequency-independent (flat) background and $\Omega_{\rm GW}<4.8\times 10^{-8}$
at 25 Hz for a background of compact binary coalescences. The upper limit
improves over the O1 result by a factor of 2.8. Additionally, we place upper
limits on the energy density in an isotropic background of scalar- and
vector-polarized gravitational waves, and we discuss the implication of these
results for models of compact binaries and cosmic string backgrounds. Finally,
we present a conservative estimate of the correlated broadband noise due to the
magnetic Schumann resonances in O2, based on magnetometer measurements at both
the LIGO Hanford and LIGO Livingston observatories. We find that correlated
noise is well below the O2 sensitivity.
| [
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"version": "v3"
}
] | 2019-09-11 | [
[
"The LIGO Scientific Collaboration",
"",
""
],
[
"the Virgo Collaboration",
"",
""
],
[
"Abbott",
"B. P.",
""
],
[
"Abbott",
"R.",
""
],
[
"Abbott",
"T. D.",
""
],
[
"Abraham",
"S.",
""
],
[
"Acernese",
"F.",
... | The stochastic gravitational-wave background is a superposition of sources that are either too weak or too numerous to detect individually. In this study we present the results from a cross-correlation analysis on data from Advanced LIGO's second observing run (O2), which we combine with the results of the first observing run (O1). We do not find evidence for a stochastic background, so we place upper limits on the normalized energy density in gravitational waves at the 95% credible level of $\Omega_{\rm GW}<6.0\times 10^{-8}$ for a frequency-independent (flat) background and $\Omega_{\rm GW}<4.8\times 10^{-8}$ at 25 Hz for a background of compact binary coalescences. The upper limit improves over the O1 result by a factor of 2.8. Additionally, we place upper limits on the energy density in an isotropic background of scalar- and vector-polarized gravitational waves, and we discuss the implication of these results for models of compact binaries and cosmic string backgrounds. Finally, we present a conservative estimate of the correlated broadband noise due to the magnetic Schumann resonances in O2, based on magnetometer measurements at both the LIGO Hanford and LIGO Livingston observatories. We find that correlated noise is well below the O2 sensitivity. |
1412.8140 | Sunil Maharaj | Jefta M. Sunzu, Sunil D. Maharaj, Subharthi Ray | Charged anisotropic models for quark stars | 11 pages, Submitted for publication | Astrophys. Space Sci. 352: 719-727 (2014) | 10.1007/s10509-014-1918-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a detailed physical analysis for a class of exact solutions for
the Einstein-Maxwell equations. The linear equation of state consistent with
quark stars has been incorporated in the model. The physical analysis of the
exact solutions is performed by considering the charged anisotropic stars for
the particular nonsingular exact model obtained by Maharaj, Sunzu and Ray. In
performing such an analysis we regain masses obtained by previous researchers
for isotropic and anisotropic matter. It is also indicated that other masses
and radii may be generated which are in acceptable ranges consistent with
observed values of stellar objects. A study of the mass-radius relation
indicates the effect of the electromagnetic field and anisotropy on the mass of
the relativistic star.
| [
{
"created": "Sun, 28 Dec 2014 10:07:13 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Sunzu",
"Jefta M.",
""
],
[
"Maharaj",
"Sunil D.",
""
],
[
"Ray",
"Subharthi",
""
]
] | We perform a detailed physical analysis for a class of exact solutions for the Einstein-Maxwell equations. The linear equation of state consistent with quark stars has been incorporated in the model. The physical analysis of the exact solutions is performed by considering the charged anisotropic stars for the particular nonsingular exact model obtained by Maharaj, Sunzu and Ray. In performing such an analysis we regain masses obtained by previous researchers for isotropic and anisotropic matter. It is also indicated that other masses and radii may be generated which are in acceptable ranges consistent with observed values of stellar objects. A study of the mass-radius relation indicates the effect of the electromagnetic field and anisotropy on the mass of the relativistic star. |
1810.05393 | Nikolaos Mavromatos | John Ellis, Nick E. Mavromatos, Dimitri V. Nanopoulos | Constraining D-foam via the 21-cm Line | 15 pages revetex; possible minor text overlap with arXiv:1706.04080
[gr-qc] and arXiv:1712.03395 [hep-ph] | Phys. Rev. D 99, 015031 (2019) | 10.1103/PhysRevD.99.015031 | CERN-TH-2018-217,KCL-PH-TH/2018-45,ACT-03-18, MI-TH-18-183 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have suggested earlier that D-particles, which are stringy space-time
defects predicted in brane-inspired models of the Universe, might constitute a
component of dark matter, and that they might contribute to the masses of
singlet fermions that could provide another component. Interactions of the
quantum-fluctuating D-particles with matter induce vector forces that are
mediated by a massless effective U(1) gauge field, the "D-photon", which is
distinct from the ordinary photon and has different properties from dark
photons. We discuss the form of interactions of D-matter with conventional
matter induced by D-photon exchange and calculate their strength, which depends
on the density of D-particles. Observations of the hydrogen 21~cm line at
redshifts >= 15 can constrain these interactions and the density of D-matter in
the early Universe.
| [
{
"created": "Fri, 12 Oct 2018 08:09:59 GMT",
"version": "v1"
}
] | 2019-01-30 | [
[
"Ellis",
"John",
""
],
[
"Mavromatos",
"Nick E.",
""
],
[
"Nanopoulos",
"Dimitri V.",
""
]
] | We have suggested earlier that D-particles, which are stringy space-time defects predicted in brane-inspired models of the Universe, might constitute a component of dark matter, and that they might contribute to the masses of singlet fermions that could provide another component. Interactions of the quantum-fluctuating D-particles with matter induce vector forces that are mediated by a massless effective U(1) gauge field, the "D-photon", which is distinct from the ordinary photon and has different properties from dark photons. We discuss the form of interactions of D-matter with conventional matter induced by D-photon exchange and calculate their strength, which depends on the density of D-particles. Observations of the hydrogen 21~cm line at redshifts >= 15 can constrain these interactions and the density of D-matter in the early Universe. |
1408.5769 | Christian Friedrich Steinwachs | Alexander Yu. Kamenshchik and Christian F. Steinwachs | Question of quantum equivalence between Jordan frame and Einstein frame | 18 pages, 1 figure, revised version accepted for publication in
Physical Review D, new title, section V, VI and VIII of previous arXiv
version removed, references updated | Phys. Rev. D 91, 084033 (2015) | 10.1103/PhysRevD.91.084033 | FR-PHENO-2014-011 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of a general scalar-tensor theory, we investigate the
equivalence between two different parametrizations of fields that are commonly
used in cosmology - the so-called Jordan frame and Einstein frame. While it is
clear that both parametrizations are mathematically equivalent at the level of
the classical action, the question about their mathematical equivalence at the
quantum level as well as their physical equivalence is still a matter of debate
in cosmology. We analyze whether the mathematical equivalence still holds when
the first quantum corrections are taken into account. We explicitly calculate
the one-loop divergences in both parametrizations by using the generalized
Schwinger-DeWitt algorithm and compare both results. We find that the quantum
corrections do not coincide off shell and hence induce an off shell dependence
on the parametrization. According to the equivalence theorem, the one-loop
divergences should however coincide on shell. For a cosmological background, we
show explicitly that the on shell equivalence is indeed realized by a
nontrivial cancellation.
| [
{
"created": "Mon, 25 Aug 2014 14:21:46 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Oct 2014 16:58:55 GMT",
"version": "v2"
},
{
"created": "Sat, 18 Jul 2015 16:43:26 GMT",
"version": "v3"
}
] | 2015-07-21 | [
[
"Kamenshchik",
"Alexander Yu.",
""
],
[
"Steinwachs",
"Christian F.",
""
]
] | In the framework of a general scalar-tensor theory, we investigate the equivalence between two different parametrizations of fields that are commonly used in cosmology - the so-called Jordan frame and Einstein frame. While it is clear that both parametrizations are mathematically equivalent at the level of the classical action, the question about their mathematical equivalence at the quantum level as well as their physical equivalence is still a matter of debate in cosmology. We analyze whether the mathematical equivalence still holds when the first quantum corrections are taken into account. We explicitly calculate the one-loop divergences in both parametrizations by using the generalized Schwinger-DeWitt algorithm and compare both results. We find that the quantum corrections do not coincide off shell and hence induce an off shell dependence on the parametrization. According to the equivalence theorem, the one-loop divergences should however coincide on shell. For a cosmological background, we show explicitly that the on shell equivalence is indeed realized by a nontrivial cancellation. |
gr-qc/0503028 | Gordon McCabe | Gordon McCabe | The Structure and Interpretation of Cosmology: Part I - General
Relativistic Cosmology | null | Stud.Hist.Philos.Mod.Phys. 35 (2004) 549-595 | 10.1016/j.shpsb.2004.05.002 | null | gr-qc | null | The purpose of this work is to review, clarify, and critically analyse modern
mathematical cosmology. The emphasis is upon mathematical objects and
structures, rather than numerical computations. This paper concentrates on
general relativistic cosmology. The opening section reviews and clarifies the
Friedmann-Robertson-Walker models of general relativistic cosmology, while
Section 2 deals with the spatially homogeneous models. Particular attention is
paid in these opening sections to the topological and geometrical aspects of
cosmological models. Section 3 explains how the mathematical formalism can be
linked with astronomical observation. In particular, the informal,
observational notion of the celestial sphere is given a rigorous mathematical
implementation. Part II of this work will concentrate on inflationary cosmology
and quantum cosmology.
| [
{
"created": "Mon, 7 Mar 2005 21:25:35 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"McCabe",
"Gordon",
""
]
] | The purpose of this work is to review, clarify, and critically analyse modern mathematical cosmology. The emphasis is upon mathematical objects and structures, rather than numerical computations. This paper concentrates on general relativistic cosmology. The opening section reviews and clarifies the Friedmann-Robertson-Walker models of general relativistic cosmology, while Section 2 deals with the spatially homogeneous models. Particular attention is paid in these opening sections to the topological and geometrical aspects of cosmological models. Section 3 explains how the mathematical formalism can be linked with astronomical observation. In particular, the informal, observational notion of the celestial sphere is given a rigorous mathematical implementation. Part II of this work will concentrate on inflationary cosmology and quantum cosmology. |
1806.02564 | Shaoqi Hou | Shaoqi Hou, Yungui Gong | Gravitational waves in Einstein-{\AE}ther theory and generalized TeVeS
theory after GW170817 | 9 pages, 3 figures. Talk given in International Conference on Quantum
Gravity held in SUSTech, Shenzhen, China. Matches the published version | Universe 2018, 4, 84 | 10.3390/universe4080084 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, the polarization contents of Einstein-\ae ther theory and the
generalized TeVeS theory are studied. The Einstein-\ae ther theory has five
polarizations, while the generalized TeVeS theory has six. In particular,
transverse and longitudinal breathing polarization are mixed. The~possibility
of using pulsar timing arrays to detect the extra polarizations in
Einstein-\ae{}ther theory was also investigated. The analysis showed that
different polarizations cannot be easily distinguished by using pulsar timing
arrays in this theory. For generalized TeVeS theory, one of the propagating
modes travels much faster than the speed of light due to the speed bound set by
GW170817. In some parameter subspaces, the strong coupling does not take place,
so this theory is excluded.
| [
{
"created": "Thu, 7 Jun 2018 08:49:45 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Aug 2018 01:31:49 GMT",
"version": "v2"
}
] | 2018-08-10 | [
[
"Hou",
"Shaoqi",
""
],
[
"Gong",
"Yungui",
""
]
] | In this paper, the polarization contents of Einstein-\ae ther theory and the generalized TeVeS theory are studied. The Einstein-\ae ther theory has five polarizations, while the generalized TeVeS theory has six. In particular, transverse and longitudinal breathing polarization are mixed. The~possibility of using pulsar timing arrays to detect the extra polarizations in Einstein-\ae{}ther theory was also investigated. The analysis showed that different polarizations cannot be easily distinguished by using pulsar timing arrays in this theory. For generalized TeVeS theory, one of the propagating modes travels much faster than the speed of light due to the speed bound set by GW170817. In some parameter subspaces, the strong coupling does not take place, so this theory is excluded. |
2002.08449 | Carlos A. Batista da S. Filho | Carlos Batista and Jo\'as Ven\^ancio | Spin 2 Quasinormal Modes in Generalized Nariai Spacetimes | 13 pages, 1 figure | Phys. Rev. D 101, 084037 (2020) | 10.1103/PhysRevD.101.084037 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we analytically obtain the quasinormal spectrum for the
gravitational perturbation on a higher-dimensional generalization of the Nariai
spacetime that is comprised of the direct product of the two-dimensional de
Sitter space with several two-spheres. A key step in order to attain this
result is to use a suitable basis for the angular functions depending on the
rank of the tensorial degree of freedom that one needs to describe. Here we
define such a basis, which is a generalization of the tensor spherical
harmonics that is suited for spaces that are the product of several spaces of
constant curvature.
| [
{
"created": "Wed, 19 Feb 2020 21:16:28 GMT",
"version": "v1"
}
] | 2020-04-22 | [
[
"Batista",
"Carlos",
""
],
[
"Venâncio",
"Joás",
""
]
] | In this work we analytically obtain the quasinormal spectrum for the gravitational perturbation on a higher-dimensional generalization of the Nariai spacetime that is comprised of the direct product of the two-dimensional de Sitter space with several two-spheres. A key step in order to attain this result is to use a suitable basis for the angular functions depending on the rank of the tensorial degree of freedom that one needs to describe. Here we define such a basis, which is a generalization of the tensor spherical harmonics that is suited for spaces that are the product of several spaces of constant curvature. |
gr-qc/9810046 | Carey Carpenter Briggs | C. C. Briggs | Simple Formulas for Generating Chern-Simons Basic Invariant Polynomials
by Repeated Exterior Differentiation | 2 pages, PostScript file | null | null | null | gr-qc | null | Simple formulas are given for generating Chern-Simons basic invariant
polynomials by repeated exterior differentiation for n-dimensional
differentiable manifolds having a general linear connection.
| [
{
"created": "Wed, 14 Oct 1998 19:55:02 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Briggs",
"C. C.",
""
]
] | Simple formulas are given for generating Chern-Simons basic invariant polynomials by repeated exterior differentiation for n-dimensional differentiable manifolds having a general linear connection. |
2201.05543 | David Garfinkle | David Garfinkle | Gravitational wave memory and the wave equation | figure and references added. Discussion expanded and clarified | null | 10.1088/1361-6382/ac7203 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave memory and its electromagnetic analog are shown to be
straightforward consequences of the wave equation. From Maxwell's equations one
can derive a wave equation for the electric field, while from the Bianchi
identity one can derive a wave equation for the Riemann tensor in linearized
gravity. Memory in both cases is derived from the structure of the source of
those wave equations.
| [
{
"created": "Fri, 14 Jan 2022 16:29:16 GMT",
"version": "v1"
},
{
"created": "Mon, 16 May 2022 20:20:59 GMT",
"version": "v2"
}
] | 2022-06-22 | [
[
"Garfinkle",
"David",
""
]
] | Gravitational wave memory and its electromagnetic analog are shown to be straightforward consequences of the wave equation. From Maxwell's equations one can derive a wave equation for the electric field, while from the Bianchi identity one can derive a wave equation for the Riemann tensor in linearized gravity. Memory in both cases is derived from the structure of the source of those wave equations. |
gr-qc/0111060 | Masafumi Seriu | Masafumi Seriu | Evolution of the discrepancy between a universe and its model | To be published in Classical and Quantum Gravity | Class.Quant.Grav. 18 (2001) 5329-5352 | 10.1088/0264-9381/18/24/301 | null | gr-qc | null | We study a fundamental issue in cosmology: Whether we can rely on a
cosmological model to understand the real history of the Universe. This
fundamental, still unresolved issue is often called the ``model-fitting problem
(or averaging problem) in cosmology''. Here we analyze this issue with the help
of the spectral scheme prepared in the preceding studies.
Choosing two specific spatial geometries that are very close to each other,
we investigate explicitly the time evolution of the spectral distance between
them; as two spatial geometries, we choose a flat 3-torus and a perturbed
geometry around it, mimicking the relation of a ``model universe'' and the
``real Universe''. Then we estimate the spectral distance between them and
investigate its time evolution explicitly. This analysis is done efficiently by
making use of the basic results of the standard linear structure-formation
theory.
We observe that, as far as the linear perturbation of geometry is valid, the
spectral distance does not increase with time prominently,rather it shows the
tendency to decrease. This result is compatible with the general belief in the
reliability of describing the Universe by means of a model, and calls for more
detailed studies along the same line including the investigation of wider class
of spacetimes and the analysis beyond the linear regime.
| [
{
"created": "Tue, 20 Nov 2001 07:01:20 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Seriu",
"Masafumi",
""
]
] | We study a fundamental issue in cosmology: Whether we can rely on a cosmological model to understand the real history of the Universe. This fundamental, still unresolved issue is often called the ``model-fitting problem (or averaging problem) in cosmology''. Here we analyze this issue with the help of the spectral scheme prepared in the preceding studies. Choosing two specific spatial geometries that are very close to each other, we investigate explicitly the time evolution of the spectral distance between them; as two spatial geometries, we choose a flat 3-torus and a perturbed geometry around it, mimicking the relation of a ``model universe'' and the ``real Universe''. Then we estimate the spectral distance between them and investigate its time evolution explicitly. This analysis is done efficiently by making use of the basic results of the standard linear structure-formation theory. We observe that, as far as the linear perturbation of geometry is valid, the spectral distance does not increase with time prominently,rather it shows the tendency to decrease. This result is compatible with the general belief in the reliability of describing the Universe by means of a model, and calls for more detailed studies along the same line including the investigation of wider class of spacetimes and the analysis beyond the linear regime. |
2306.07095 | Alejandro Jim\'enez-Cano | Jose Beltr\'an Jim\'enez and Alejandro Jim\'enez-Cano | On the physical viability of black hole solutions in Einsteinian Cubic
Gravity and its generalisations | 17 pages, no figures, no tables | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note, we discuss the pathological nature of black holes in
Einsteinian Cubic gravity and its extensions. We compute the equations for the
odd perturbations and show how spherically symmetric solutions that
asymptotically approach a maximally symmetric space (Minkowski, de Sitter or
anti-de Sitter) are associated to having an asymptotically degenerate principal
part of the equations. We use these results to argue that the encountered
problems will be generic for any other cubic or higher-order with a reduced
linear spectrum around maximally symmetric spaces except the well-known healthy
case of $f(R)$. We highlight that these pathologies are only alarming when the
theory is regarded as a complete theory, but not when considered as a
perturbative correction to GR (as in e.g. the effective field theory framework)
since the the low-energy physics remains safe from them. Our results thus cast
doubts on possible resolutions of the singularities or non-perturbative effects
on horizons based on these theories.
| [
{
"created": "Mon, 12 Jun 2023 13:19:47 GMT",
"version": "v1"
}
] | 2023-06-13 | [
[
"Jiménez",
"Jose Beltrán",
""
],
[
"Jiménez-Cano",
"Alejandro",
""
]
] | In this note, we discuss the pathological nature of black holes in Einsteinian Cubic gravity and its extensions. We compute the equations for the odd perturbations and show how spherically symmetric solutions that asymptotically approach a maximally symmetric space (Minkowski, de Sitter or anti-de Sitter) are associated to having an asymptotically degenerate principal part of the equations. We use these results to argue that the encountered problems will be generic for any other cubic or higher-order with a reduced linear spectrum around maximally symmetric spaces except the well-known healthy case of $f(R)$. We highlight that these pathologies are only alarming when the theory is regarded as a complete theory, but not when considered as a perturbative correction to GR (as in e.g. the effective field theory framework) since the the low-energy physics remains safe from them. Our results thus cast doubts on possible resolutions of the singularities or non-perturbative effects on horizons based on these theories. |
gr-qc/0101054 | Marsha Weaver | M. Weaver, B. K. Berger and J. Isenberg | Oscillatory approach to the singularity in vacuum $T^2$ symmetric
spacetimes | 2 pages submitted to the Ninth Marcel Grossmann Proceedings; v2, "all
known cases" changed to "various known cases" in the first paragraph | null | 10.1142/9789812777386_0140 | null | gr-qc | null | A combination of qualitative analysis and numerical study indicates that
vacuum $T^2$ symmetric spacetimes are, generically, oscillatory.
| [
{
"created": "Sun, 14 Jan 2001 09:28:39 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Jan 2001 07:31:28 GMT",
"version": "v2"
}
] | 2017-08-23 | [
[
"Weaver",
"M.",
""
],
[
"Berger",
"B. K.",
""
],
[
"Isenberg",
"J.",
""
]
] | A combination of qualitative analysis and numerical study indicates that vacuum $T^2$ symmetric spacetimes are, generically, oscillatory. |
gr-qc/0408016 | Jose Ricardo Villanueva | Norman Cruz, Marco Olivares, Jose R. Villanueva | The geodesic structure of the Schwarzschild Anti-de Sitter black hole | 17 pages, 11 figures | Class.Quant.Grav. 22 (2005) 1167-1190 | 10.1088/0264-9381/22/6/016 | GACG-04/11 | gr-qc | null | In the present work we found the geodesic structure of an AdS black hole. By
means of a detailed analyze of the corresponding effective potentials for
particles and photon, we found all the possible motions which are allowed by
the energy levels. Radial and non radial trajectories were exactly evaluated
for both geodesics. The founded orbits were plotted in order to have a direct
visualization of the allowed motions. We show that the geodesic structure of
this black hole presents new type of motions not allowed by the Schwarzschild
spacetime.
| [
{
"created": "Thu, 5 Aug 2004 20:44:38 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Cruz",
"Norman",
""
],
[
"Olivares",
"Marco",
""
],
[
"Villanueva",
"Jose R.",
""
]
] | In the present work we found the geodesic structure of an AdS black hole. By means of a detailed analyze of the corresponding effective potentials for particles and photon, we found all the possible motions which are allowed by the energy levels. Radial and non radial trajectories were exactly evaluated for both geodesics. The founded orbits were plotted in order to have a direct visualization of the allowed motions. We show that the geodesic structure of this black hole presents new type of motions not allowed by the Schwarzschild spacetime. |
gr-qc/0207104 | Matteo Luca Ruggiero | Guido Rizzi, Matteo Luca Ruggiero | Space geometry of rotating platforms: an operational approach | 31 pages, LaTeX, 1 eps figure, accepted for publication in
Foundations of Physics, revised version with minor changes | Found.Phys.32:1525-1556,2002 | 10.1023/A:1020427318877 | null | gr-qc | null | We study the space geometry of a rotating disk both from a theoretical and
operational approach, in particular we give a precise definition of the space
of the disk, which is not clearly defined in the literature. To this end we
define an extended 3-space, which we call relative space: it is recognized as
the only space having an actual physical meaning from an operational point of
view, and it is identified as the 'physical space of the rotating platform'.
Then, the geometry of the space of the disk turns out to be non Euclidean,
according to the early Einstein's intuition; in particular the Born metric is
recovered, in a clear and self consistent context. Furthermore, the
relativistic kinematics reveals to be self consistent, and able to solve the
Ehrenfest's paradox without any need of dynamical considerations or ad hoc
assumptions.
| [
{
"created": "Fri, 26 Jul 2002 13:27:32 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Sep 2002 15:26:59 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Rizzi",
"Guido",
""
],
[
"Ruggiero",
"Matteo Luca",
""
]
] | We study the space geometry of a rotating disk both from a theoretical and operational approach, in particular we give a precise definition of the space of the disk, which is not clearly defined in the literature. To this end we define an extended 3-space, which we call relative space: it is recognized as the only space having an actual physical meaning from an operational point of view, and it is identified as the 'physical space of the rotating platform'. Then, the geometry of the space of the disk turns out to be non Euclidean, according to the early Einstein's intuition; in particular the Born metric is recovered, in a clear and self consistent context. Furthermore, the relativistic kinematics reveals to be self consistent, and able to solve the Ehrenfest's paradox without any need of dynamical considerations or ad hoc assumptions. |
1904.05185 | Koray D\"uzta\c{s} | Koray D\"uzta\c{s} | Kerr-Newman black holes can be generically overspun | 6 pages no figures | European Physical Journal C, Vol.(76), 316 (2019) | 10.1140/epjc/s10052-019-6851-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct thought experiments involving the perturbations of Kerr-Newman
black holes by neutral test fields to evaluate the validity of the weak form of
the cosmic censorship conjecture. We first show that neglecting backreaction
effects, extremal Kerr-Newman black holes which satisfy the condition
$(J^2/M^4)<(1/3)$ can be overspun by scalar fields. This result, which could
not be discerned in the previous analyses to first order, is prone to be fixed
by employing backreaction effects. However the perturbation of Kerr-Newman
black holes by neutrino fields leads to a generic overspinning of the black
hole due to the absence of a lower limit for the frequency of the incident wave
to ensure that it is absorbed by the black hole. For this case, the destruction
of the event horizon cannot be fixed by any form of backreaction effects. This
result should not be interpreted as a counter-example to any of the previous
results which were based on the assumption that the null energy condition is
satisfied. We clarify and justify our arguments with numerical examples.
| [
{
"created": "Tue, 9 Apr 2019 12:17:04 GMT",
"version": "v1"
}
] | 2019-04-11 | [
[
"Düztaş",
"Koray",
""
]
] | We construct thought experiments involving the perturbations of Kerr-Newman black holes by neutral test fields to evaluate the validity of the weak form of the cosmic censorship conjecture. We first show that neglecting backreaction effects, extremal Kerr-Newman black holes which satisfy the condition $(J^2/M^4)<(1/3)$ can be overspun by scalar fields. This result, which could not be discerned in the previous analyses to first order, is prone to be fixed by employing backreaction effects. However the perturbation of Kerr-Newman black holes by neutrino fields leads to a generic overspinning of the black hole due to the absence of a lower limit for the frequency of the incident wave to ensure that it is absorbed by the black hole. For this case, the destruction of the event horizon cannot be fixed by any form of backreaction effects. This result should not be interpreted as a counter-example to any of the previous results which were based on the assumption that the null energy condition is satisfied. We clarify and justify our arguments with numerical examples. |
0711.4013 | Raul Horvat | R. Horvat | Holographic dark energy: quantum correlations against thermodynamical
description | 8 pages, references added, to appear in Physics Letters B | Phys.Lett.B664:201-203,2008 | 10.1016/j.physletb.2008.05.030 | null | gr-qc astro-ph hep-th | null | Classical and quantum entropic properties of holographic dark energy (HDE)
are considered in view of the fact that its entropy is far more restrictive
than the entropy of a black hole of the same size. In cosmological settings (in
which HDE is promoted to a plausible candidate for being the dark energy of the
universe), HDE should be viewed as a combined state composed of the event
horizon and the stuff inside the horizon. By any interaction of the subsystems,
the horizon and the interior become entangled, raising thereby a possibility
that their quantum correlations be responsible for the almost purity of the
combined state. Under this circumstances, the entanglement entropy is almost
the same for both subsystems, being also of the same order as the thermal
(coarse grained) entropy of the interior or the horizon. In the context of
thermodynamics, however, only additive coarse grained entropies matter, so we
use these entropies to test the generalized second law (GSL) of gravitational
thermodynamics in this framework. While we find that the original Li's model
passes the GSL test for a special choice of parameters, in a saturated model
with the choice for the IR cutoff in the form of the Hubble parameter, the GSL
always breaks down.
| [
{
"created": "Mon, 26 Nov 2007 14:23:52 GMT",
"version": "v1"
},
{
"created": "Tue, 13 May 2008 09:05:29 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Horvat",
"R.",
""
]
] | Classical and quantum entropic properties of holographic dark energy (HDE) are considered in view of the fact that its entropy is far more restrictive than the entropy of a black hole of the same size. In cosmological settings (in which HDE is promoted to a plausible candidate for being the dark energy of the universe), HDE should be viewed as a combined state composed of the event horizon and the stuff inside the horizon. By any interaction of the subsystems, the horizon and the interior become entangled, raising thereby a possibility that their quantum correlations be responsible for the almost purity of the combined state. Under this circumstances, the entanglement entropy is almost the same for both subsystems, being also of the same order as the thermal (coarse grained) entropy of the interior or the horizon. In the context of thermodynamics, however, only additive coarse grained entropies matter, so we use these entropies to test the generalized second law (GSL) of gravitational thermodynamics in this framework. While we find that the original Li's model passes the GSL test for a special choice of parameters, in a saturated model with the choice for the IR cutoff in the form of the Hubble parameter, the GSL always breaks down. |
1403.1921 | Kun Meng | Kun Meng, Zhan-Ning Hu and Liu Zhao | Near horizon symmetry and entropy of black holes in the presence of a
conformally coupled scalar | to appear in CQG | Class. Quantum Grav. 31 085017 (2014) | 10.1088/0264-9381/31/8/085017 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the near horizon conformal symmetry for black hole solutions in
gravity with a conformally coupled scalar field using the method proposed by
Majhi and Padmanabhan recently. It is shown that the entropy of the black holes
of the form $\mathrm{d}s^2 = - f(r)\mathrm{d}t^2 + \mathrm{d}r^2/f(r)+...$
agrees with Wald entropy. This result is different from previous result
obtained by M. Natsuume, T. Okamura and M. Sato using the canonical Hamiltonian
formalism, which claims a discrepancy from Wald entropy.
| [
{
"created": "Sat, 8 Mar 2014 02:29:19 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Meng",
"Kun",
""
],
[
"Hu",
"Zhan-Ning",
""
],
[
"Zhao",
"Liu",
""
]
] | We analyze the near horizon conformal symmetry for black hole solutions in gravity with a conformally coupled scalar field using the method proposed by Majhi and Padmanabhan recently. It is shown that the entropy of the black holes of the form $\mathrm{d}s^2 = - f(r)\mathrm{d}t^2 + \mathrm{d}r^2/f(r)+...$ agrees with Wald entropy. This result is different from previous result obtained by M. Natsuume, T. Okamura and M. Sato using the canonical Hamiltonian formalism, which claims a discrepancy from Wald entropy. |
2307.15174 | Junji Jia | Tingyuan Jiang, Xiaoge Xu, Junji Jia | Off-equatorial deflections and gravitational lensing. I. In Kerr
spacetime and effect of spin | revised version, references added; language improved; 20 pages; 10
figures, 1 table | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper investigates the off-equatorial plane deflections and
gravitational lensing of both null and timeline signals in Kerr spacetime in
the weak deflection limit, with the finite distance effect of the source and
detector taken into account. The deflection in both the Boyer-Linquidist
coordinates $\phi$ and $\theta$ directions are computed as power series of
$M/r_0$ and $r_0/r_{\mathrm{s,d}}$, where $M,\,r_{\mathrm{s,d}}$ are the
spacetime mass and source and detector radii respectively, and $r_0$ is the
minimal radius of the trajectory. The coefficients of these series are simple
trigonometric functions of $\theta_\mathrm{e}$, the extreme value of $\theta$
coordinate of the trajectory. A set of exact gravitational lensing equations is
used to solve $r_0$ and $\theta_\mathrm{e}$ for given deviation angles
$\delta\theta$ and $\delta\phi$ of the source, and two lensed images are always
obtained. The apparent angles and their magnifications of these images, and the
time delay between them are solved and their dependence on various parameters,
especially spacetime spin $\hat{a}$ are analyzed in great detail. It is found
that generally there exist two critical spacetime spin values that separate the
case of signals reaching the detector from different sides of the $z$ axis and
the cases in which the images appear from the same side in the celestial plane.
Three potential applications of these results are discussed.
| [
{
"created": "Thu, 27 Jul 2023 20:06:47 GMT",
"version": "v1"
},
{
"created": "Tue, 14 May 2024 14:45:24 GMT",
"version": "v2"
}
] | 2024-05-15 | [
[
"Jiang",
"Tingyuan",
""
],
[
"Xu",
"Xiaoge",
""
],
[
"Jia",
"Junji",
""
]
] | This paper investigates the off-equatorial plane deflections and gravitational lensing of both null and timeline signals in Kerr spacetime in the weak deflection limit, with the finite distance effect of the source and detector taken into account. The deflection in both the Boyer-Linquidist coordinates $\phi$ and $\theta$ directions are computed as power series of $M/r_0$ and $r_0/r_{\mathrm{s,d}}$, where $M,\,r_{\mathrm{s,d}}$ are the spacetime mass and source and detector radii respectively, and $r_0$ is the minimal radius of the trajectory. The coefficients of these series are simple trigonometric functions of $\theta_\mathrm{e}$, the extreme value of $\theta$ coordinate of the trajectory. A set of exact gravitational lensing equations is used to solve $r_0$ and $\theta_\mathrm{e}$ for given deviation angles $\delta\theta$ and $\delta\phi$ of the source, and two lensed images are always obtained. The apparent angles and their magnifications of these images, and the time delay between them are solved and their dependence on various parameters, especially spacetime spin $\hat{a}$ are analyzed in great detail. It is found that generally there exist two critical spacetime spin values that separate the case of signals reaching the detector from different sides of the $z$ axis and the cases in which the images appear from the same side in the celestial plane. Three potential applications of these results are discussed. |
1008.0692 | Muhammad Sharif | M. Sharif and M. Zubair | Effects of Electromagnetic Field on the Dynamics of Bianchi type $VI_0$
Universe with Anisotropic Dark Energy | 21 pages, 10 figures, accepted for publication in Int. J. Mod. Phys.
D | Int.J.Mod.Phys.D19:1957-1972,2010 | 10.1142/S0218271810018165 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spatially homogeneous and anisotropic Bianchi type $VI_0$ cosmological models
with cosmological constant are investigated in the presence of anisotropic dark
energy. We examine the effects of electromagnetic field on the dynamics of the
universe and anisotropic behavior of dark energy. The law of variation of the
mean Hubble parameter is used to find exact solutions of the Einstein field
equations. We find that electromagnetic field promotes anisotropic behavior of
dark energy which becomes isotropic for future evolution. It is concluded that
the isotropic behavior of the universe model is seen even in the presence of
electromagnetic field and anisotropic fluid.
| [
{
"created": "Wed, 4 Aug 2010 04:48:16 GMT",
"version": "v1"
}
] | 2010-11-24 | [
[
"Sharif",
"M.",
""
],
[
"Zubair",
"M.",
""
]
] | Spatially homogeneous and anisotropic Bianchi type $VI_0$ cosmological models with cosmological constant are investigated in the presence of anisotropic dark energy. We examine the effects of electromagnetic field on the dynamics of the universe and anisotropic behavior of dark energy. The law of variation of the mean Hubble parameter is used to find exact solutions of the Einstein field equations. We find that electromagnetic field promotes anisotropic behavior of dark energy which becomes isotropic for future evolution. It is concluded that the isotropic behavior of the universe model is seen even in the presence of electromagnetic field and anisotropic fluid. |
gr-qc/0009072 | Andrew DeBenedictis | A. DeBenedictis, A. Das | On a General Class of Wormhole Geometries | 28 pages, 4 figures, AMS. Updated version contains more analysis at
the throat junction, corrected typos, added references. Accepted for
publication in Classical and Quantum Gravity | Class.Quant.Grav. 18 (2001) 1187-1204 | 10.1088/0264-9381/18/7/304 | null | gr-qc astro-ph | null | A general class of solutions is obtained which describe a spherically
symmetric wormhole system. The presence of arbitrary functions allows one to
describe infinitely many wormhole systems of this type. The source of the
stress-energy supporting the structure consists of an anisotropic brown dwarf
``star'' which smoothly joins the vacuum and may possess an arbitrary
cosmological constant. It is demonstrated how this set of solutions allows for
a non-zero energy density and therefore allows positive stellar mass as well as
how violations of energy conditions may be minimized. Unlike examples
considered thus far, emphasis here is placed on construction by manipulating
the matter field as opposed to the metric. This scheme is generally more
physical than the purely geometric method. Finally, explicit examples are
constructed including an example which demonstrates how multiple closed
universes may be connected by such wormholes. The number of connected universes
may be finite or infinite.
| [
{
"created": "Wed, 20 Sep 2000 21:02:00 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jan 2001 19:22:45 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"DeBenedictis",
"A.",
""
],
[
"Das",
"A.",
""
]
] | A general class of solutions is obtained which describe a spherically symmetric wormhole system. The presence of arbitrary functions allows one to describe infinitely many wormhole systems of this type. The source of the stress-energy supporting the structure consists of an anisotropic brown dwarf ``star'' which smoothly joins the vacuum and may possess an arbitrary cosmological constant. It is demonstrated how this set of solutions allows for a non-zero energy density and therefore allows positive stellar mass as well as how violations of energy conditions may be minimized. Unlike examples considered thus far, emphasis here is placed on construction by manipulating the matter field as opposed to the metric. This scheme is generally more physical than the purely geometric method. Finally, explicit examples are constructed including an example which demonstrates how multiple closed universes may be connected by such wormholes. The number of connected universes may be finite or infinite. |
2307.05917 | H. B. Benaoum | H. B. Benaoum, Luz \'Angela Garc\'ia and Leonardo Casta\~neda | Early dark energy induced by non-linear electrodynamics | 11 pages, 8 figures | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work, we introduce a parametrization of early dark energy that mimics
radiation at early times and governs the present acceleration of the Universe.
We show that such parametrization models non-linear electrodynamics in the
early Universe and investigate the cosmological viability of the model. In our
scenario, the early dark energy is encoded in the non-linearity of the
electromagnetic fields through a parameter $\beta$ that changes the Lagrangian
of the system, and the parameters $\gamma_s$ and $\alpha$, that define the
departure from the standard model constant equation of state. We use a Bayesian
method and the modular software \textsc{CosmoSIS} to find the best values for
the model's free parameters with precomputed likelihoods from Planck 2018,
primordial nucleosynthesis data, inferred distances from different wide galaxy
surveys and luminosity distances of SNIa from Pantheon and SH0ES, such that
$\gamma_s =$ 0.468 $\pm$ 0.026 and $\alpha =$ -0.947 $\pm$ 0.032, as opposed to
$\Lambda$CDM where $\gamma_s = \beta =$ 0 and there is no equivalence for the
$\alpha$ parameter. Our results predict an earlier formation of the structure
and a shorter age of the Universe compared with the canonical cosmological
model. One of the main findings of our work is that this kind of dark energy
alleviates the ongoing tensions in cosmology, the Hubble tension and the
so-called $\sigma_8$ tension, which predicted values by our model are H$_o =$
70.2 $\pm$ 0.9 km/s/Mpc and $\sigma_8 =$ 0.798 $\pm$ 0.007. The reported values
lie between the inferred values inferred from early and late (local) Universe
observations. Future observations will shed light on the nature of the dark
energy, its impact on the structure formation, and its dynamics.
| [
{
"created": "Wed, 12 Jul 2023 05:05:41 GMT",
"version": "v1"
}
] | 2023-07-13 | [
[
"Benaoum",
"H. B.",
""
],
[
"García",
"Luz Ángela",
""
],
[
"Castañeda",
"Leonardo",
""
]
] | In this work, we introduce a parametrization of early dark energy that mimics radiation at early times and governs the present acceleration of the Universe. We show that such parametrization models non-linear electrodynamics in the early Universe and investigate the cosmological viability of the model. In our scenario, the early dark energy is encoded in the non-linearity of the electromagnetic fields through a parameter $\beta$ that changes the Lagrangian of the system, and the parameters $\gamma_s$ and $\alpha$, that define the departure from the standard model constant equation of state. We use a Bayesian method and the modular software \textsc{CosmoSIS} to find the best values for the model's free parameters with precomputed likelihoods from Planck 2018, primordial nucleosynthesis data, inferred distances from different wide galaxy surveys and luminosity distances of SNIa from Pantheon and SH0ES, such that $\gamma_s =$ 0.468 $\pm$ 0.026 and $\alpha =$ -0.947 $\pm$ 0.032, as opposed to $\Lambda$CDM where $\gamma_s = \beta =$ 0 and there is no equivalence for the $\alpha$ parameter. Our results predict an earlier formation of the structure and a shorter age of the Universe compared with the canonical cosmological model. One of the main findings of our work is that this kind of dark energy alleviates the ongoing tensions in cosmology, the Hubble tension and the so-called $\sigma_8$ tension, which predicted values by our model are H$_o =$ 70.2 $\pm$ 0.9 km/s/Mpc and $\sigma_8 =$ 0.798 $\pm$ 0.007. The reported values lie between the inferred values inferred from early and late (local) Universe observations. Future observations will shed light on the nature of the dark energy, its impact on the structure formation, and its dynamics. |
2111.09715 | Wei-Tou Ni | Dongfeng Gao, Wei-Tou Ni, Jin Wang, Ming-Sheng Zhan, Lin Zhou | Mid-Frequency Gravitational Waves (0.1-10 Hz): Sources and Detection
Methods Summary of the parallel session GW2 of MG16 Meeting | 16 pages, 3 figures, 1 table | null | null | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article summarizes the talks in the session GW2 of the Sixteenth Marcel
Grossmann Meeting on Recent Developments in Theoretical and Experimental
General Relativity, Gravitation, and Relativistic Field Theories, 5-10 July,
2021, on Mid-frequency (0.1-10 Hz) gravitational waves: Sources and detection
methods with a review on strain power spectral density amplitude of various
mid-frequency gravitational wave projects/concepts and with extended summaries
on the progress of ZAIGA project and on the conceptual study of AMIGO.
| [
{
"created": "Thu, 18 Nov 2021 14:25:12 GMT",
"version": "v1"
}
] | 2021-11-19 | [
[
"Gao",
"Dongfeng",
""
],
[
"Ni",
"Wei-Tou",
""
],
[
"Wang",
"Jin",
""
],
[
"Zhan",
"Ming-Sheng",
""
],
[
"Zhou",
"Lin",
""
]
] | This article summarizes the talks in the session GW2 of the Sixteenth Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Gravitation, and Relativistic Field Theories, 5-10 July, 2021, on Mid-frequency (0.1-10 Hz) gravitational waves: Sources and detection methods with a review on strain power spectral density amplitude of various mid-frequency gravitational wave projects/concepts and with extended summaries on the progress of ZAIGA project and on the conceptual study of AMIGO. |
2107.14640 | Feiyu Yao | Peng Wang, Feiyu Yao | Thermodynamic Geometry of Black Holes Enclosed by a Cavity in Extended
Phase Space | null | null | 10.1016/j.nuclphysb.2022.115715 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, the phase space of black holes in a spherical cavity of radius
$r_{B}$ has been extended by introducing a thermodynamic volume $V\equiv4\pi
r_{B}^{3}/3$. In the extended phase space, we consider the thermodynamic
geometry, which provides a powerful tool to understand the microscopic
structure of black holes, of Reissner-Nordstr\"{o}m (RN) black holes in a
cavity, as well as that of Reissner-Nordstr\"{o}m-AdS black holes. Although the
phase structures of the cavity and AdS cases show striking resemblance, we find
that there exist significant differences between the thermodynamic geometries
of these two cases. In particular, a reentrant transition of the type of the
microstructure interactions, i.e., repulsive $\rightarrow$ attractive
$\rightarrow$ repulsive with increasing temperature in an isobaric process, is
observed for RN black holes in a cavity.
| [
{
"created": "Fri, 30 Jul 2021 14:04:55 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Aug 2021 01:10:55 GMT",
"version": "v2"
},
{
"created": "Sat, 29 Jan 2022 14:42:50 GMT",
"version": "v3"
}
] | 2022-03-14 | [
[
"Wang",
"Peng",
""
],
[
"Yao",
"Feiyu",
""
]
] | Recently, the phase space of black holes in a spherical cavity of radius $r_{B}$ has been extended by introducing a thermodynamic volume $V\equiv4\pi r_{B}^{3}/3$. In the extended phase space, we consider the thermodynamic geometry, which provides a powerful tool to understand the microscopic structure of black holes, of Reissner-Nordstr\"{o}m (RN) black holes in a cavity, as well as that of Reissner-Nordstr\"{o}m-AdS black holes. Although the phase structures of the cavity and AdS cases show striking resemblance, we find that there exist significant differences between the thermodynamic geometries of these two cases. In particular, a reentrant transition of the type of the microstructure interactions, i.e., repulsive $\rightarrow$ attractive $\rightarrow$ repulsive with increasing temperature in an isobaric process, is observed for RN black holes in a cavity. |
0912.2740 | Wade Naylor | H.T. Cho (Tamkang U.), A.S. Cornell (Witwatersrand U.), Jason Doukas
(Kyoto U., Yukawa Inst., Kyoto) and Wade Naylor (Doshisha U. & Osaka U.) | Black hole quasinormal modes using the asymptotic iteration method | 10 pages, LaTeX; references added; substantially expanded version | Class.Quant.Grav.27:155004,2010 | 10.1088/0264-9381/27/15/155004 | YITP-09-110, WITS-CTP-049 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we show that the asymptotic iteration method (AIM) allows one
to numerically find the quasinormal modes of Schwarzschild and Schwarzschild de
Sitter (SdS) black holes. An added benefit of the method is that it can also be
used to calculate the Schwarzschild anti-de Sitter (SAdS) quasinormal modes for
the case of spin zero perturbations. We also discuss an improved version of the
AIM, more suitable for numerical implementation.
| [
{
"created": "Tue, 15 Dec 2009 06:58:26 GMT",
"version": "v1"
},
{
"created": "Sat, 2 Jan 2010 15:20:56 GMT",
"version": "v2"
},
{
"created": "Mon, 3 May 2010 10:31:52 GMT",
"version": "v3"
}
] | 2011-04-11 | [
[
"Cho",
"H. T.",
"",
"Tamkang U."
],
[
"Cornell",
"A. S.",
"",
"Witwatersrand U."
],
[
"Doukas",
"Jason",
"",
"Kyoto U., Yukawa Inst., Kyoto"
],
[
"Naylor",
"Wade",
"",
"Doshisha U. & Osaka U."
]
] | In this article we show that the asymptotic iteration method (AIM) allows one to numerically find the quasinormal modes of Schwarzschild and Schwarzschild de Sitter (SdS) black holes. An added benefit of the method is that it can also be used to calculate the Schwarzschild anti-de Sitter (SAdS) quasinormal modes for the case of spin zero perturbations. We also discuss an improved version of the AIM, more suitable for numerical implementation. |
1203.1530 | Marcin Kisielowski M.Sc. | Marcin Kisielowski, Jerzy Lewandowski, Jacek Puchta | One vertex spin-foams with the Dipole Cosmology boundary | 23 pages, 30 figures | null | 10.1088/0264-9381/30/2/025007 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find all the spin-foams contributing in the first order of the vertex
expansion to the transition amplitude of the Bianchi-Rovelli-Vidotto Dipole
Cosmology model. Our algorithm is general and provides spin-foams of
arbitrarily given, fixed: boundary and, respectively, a number of internal
vertices. We use the recently introduced Operator Spin-Network Diagrams
framework.
| [
{
"created": "Wed, 7 Mar 2012 16:38:19 GMT",
"version": "v1"
}
] | 2015-06-04 | [
[
"Kisielowski",
"Marcin",
""
],
[
"Lewandowski",
"Jerzy",
""
],
[
"Puchta",
"Jacek",
""
]
] | We find all the spin-foams contributing in the first order of the vertex expansion to the transition amplitude of the Bianchi-Rovelli-Vidotto Dipole Cosmology model. Our algorithm is general and provides spin-foams of arbitrarily given, fixed: boundary and, respectively, a number of internal vertices. We use the recently introduced Operator Spin-Network Diagrams framework. |
1704.06824 | Slava G. Turyshev | Slava G. Turyshev, Viktor T. Toth | Diffraction of electromagnetic waves in the gravitational field of the
Sun | 43 pages, 9 figures, updated to match published version | Phys. Rev. D 96, 024008 (2017) | 10.1103/PhysRevD.96.024008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the propagation of electromagnetic (EM) waves in the
gravitational field of the Sun within the first post-Newtonian approximation of
the general theory of relativity. We solve Maxwell's equations for the EM field
propagating on the background of a static mass monopole and find an exact
closed form solution for the Debye potentials, which, in turn, yield a solution
to the problem of diffraction of EM waves in the gravitational field of the
Sun. The solution is given in terms of the confluent hypergeometric function
and, as such, it is valid for all distances and angles. Using this solution, we
develop a wave-theoretical description of the solar gravitational lens (SGL)
and derive expressions for the EM field and energy flux in the immediate
vicinity of the focal line of the SGL. Aiming at the potential practical
applications of the SGL, we study its optical properties and discuss its
suitability for direct high-resolution imaging of a distant exoplanet.
| [
{
"created": "Sat, 22 Apr 2017 17:44:05 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jul 2017 05:01:40 GMT",
"version": "v2"
},
{
"created": "Sun, 27 May 2018 05:39:55 GMT",
"version": "v3"
}
] | 2018-05-29 | [
[
"Turyshev",
"Slava G.",
""
],
[
"Toth",
"Viktor T.",
""
]
] | We consider the propagation of electromagnetic (EM) waves in the gravitational field of the Sun within the first post-Newtonian approximation of the general theory of relativity. We solve Maxwell's equations for the EM field propagating on the background of a static mass monopole and find an exact closed form solution for the Debye potentials, which, in turn, yield a solution to the problem of diffraction of EM waves in the gravitational field of the Sun. The solution is given in terms of the confluent hypergeometric function and, as such, it is valid for all distances and angles. Using this solution, we develop a wave-theoretical description of the solar gravitational lens (SGL) and derive expressions for the EM field and energy flux in the immediate vicinity of the focal line of the SGL. Aiming at the potential practical applications of the SGL, we study its optical properties and discuss its suitability for direct high-resolution imaging of a distant exoplanet. |
1406.2223 | Claudio Dappiaggi | Claudio Dappiaggi and Alberto Melati | Curvature fluctuations on asymptotically de Sitter spacetimes via the
semiclassical Einstein's equations | 23 pages | null | 10.1088/0264-9381/31/23/235006 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been proposed recently to consider in the framework of cosmology an
extension of the semiclassical Einstein's equations in which the Einstein
tensor is considered as a random function. This paradigm yields a hierarchy of
equations between the $n$-point functions of the quantum, normal ordered,
stress energy-tensor and those associated to the stochastic Einstein tensor.
Assuming that the matter content is a conformally coupled massive scalar field
on de Sitter spacetime, this framework has been applied to compute the power
spectrum of the quantum fluctuations and to show that it is almost
scale-invariant. We test the robustness and the range of applicability of this
proposal by applying it to a less idealized, but physically motivated,
scenario, namely we consider Friedmann-Robertson-Walker spacetimes which behave
only asymptotically in the past as a de Sitter spacetime. We show in particular
that, under this new assumption and independently from any renormalization
freedom, the power spectrum associated to scalar perturbations of the metric
behaves consistently with an almost scale-invariant power spectrum.
| [
{
"created": "Mon, 9 Jun 2014 15:44:53 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Dappiaggi",
"Claudio",
""
],
[
"Melati",
"Alberto",
""
]
] | It has been proposed recently to consider in the framework of cosmology an extension of the semiclassical Einstein's equations in which the Einstein tensor is considered as a random function. This paradigm yields a hierarchy of equations between the $n$-point functions of the quantum, normal ordered, stress energy-tensor and those associated to the stochastic Einstein tensor. Assuming that the matter content is a conformally coupled massive scalar field on de Sitter spacetime, this framework has been applied to compute the power spectrum of the quantum fluctuations and to show that it is almost scale-invariant. We test the robustness and the range of applicability of this proposal by applying it to a less idealized, but physically motivated, scenario, namely we consider Friedmann-Robertson-Walker spacetimes which behave only asymptotically in the past as a de Sitter spacetime. We show in particular that, under this new assumption and independently from any renormalization freedom, the power spectrum associated to scalar perturbations of the metric behaves consistently with an almost scale-invariant power spectrum. |
1209.3724 | Daniel Puigdomenech | Dom\`enec Espriu and Daniel Puigdom\`enech | Local measurement of {\Lambda} using pulsar timing arrays | null | ApJ 764 163, 2013 | 10.1088/0004-637X/764/2/163 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have considered the propagation of gravitational waves (GW) in de Sitter
space time and how a non-zero value of the cosmological constant might affect
their detection in pulsar timing arrays (PTA). If {\Lambda} is different from
zero waves are non-linear in Friedmann-Robertson-Walker coordinates and
although the amount of non-linearity is very small it gives noticeable effects
for GW originating in extragalactic sources such as spiraling black hole
binaries. The results indicate that the timing residuals induced by
gravitational waves from such sources in PTA would show a peculiar angular
dependence with a marked enhancement around a particular value of the angle
subtended by the source and the pulsars, depending mainly on the actual value
of the cosmological constant and the distance to the source. The position of
the peak could represent a gauge of the value of \Lambda. The enhancement that
the new effect brings about could facilitate the first direct detection of
gravitational waves while representing a local measurement of \Lambda.
| [
{
"created": "Mon, 17 Sep 2012 17:08:31 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Nov 2012 08:19:39 GMT",
"version": "v2"
}
] | 2013-02-28 | [
[
"Espriu",
"Domènec",
""
],
[
"Puigdomènech",
"Daniel",
""
]
] | We have considered the propagation of gravitational waves (GW) in de Sitter space time and how a non-zero value of the cosmological constant might affect their detection in pulsar timing arrays (PTA). If {\Lambda} is different from zero waves are non-linear in Friedmann-Robertson-Walker coordinates and although the amount of non-linearity is very small it gives noticeable effects for GW originating in extragalactic sources such as spiraling black hole binaries. The results indicate that the timing residuals induced by gravitational waves from such sources in PTA would show a peculiar angular dependence with a marked enhancement around a particular value of the angle subtended by the source and the pulsars, depending mainly on the actual value of the cosmological constant and the distance to the source. The position of the peak could represent a gauge of the value of \Lambda. The enhancement that the new effect brings about could facilitate the first direct detection of gravitational waves while representing a local measurement of \Lambda. |
0805.1117 | Mohammad Reza Setare | M. R. Setare, and J. Sadeghi | First-order formalism for the quintom model of dark energy | 9 pages, 3 figures. To appear in IJTP (2008) | Int.J.Theor.Phys.47:3219-3225,2008 | 10.1007/s10773-008-9757-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present paper deals to the quintom model of dark energy. We introduce a
first-order formalism, which shows how to relate the potential that specifies
the scalar field model to Hubble parameter. Reviewing briefly the quintom
scenario of dark energy, we present a general procedure to solve the equations
of motion for quintom model driven by a couple scalar fields with first-order
differential equations.
| [
{
"created": "Thu, 8 May 2008 07:42:58 GMT",
"version": "v1"
}
] | 2008-12-18 | [
[
"Setare",
"M. R.",
""
],
[
"Sadeghi",
"J.",
""
]
] | The present paper deals to the quintom model of dark energy. We introduce a first-order formalism, which shows how to relate the potential that specifies the scalar field model to Hubble parameter. Reviewing briefly the quintom scenario of dark energy, we present a general procedure to solve the equations of motion for quintom model driven by a couple scalar fields with first-order differential equations. |
gr-qc/0209014 | Steven Carlip | S. Carlip | Varying Constants, Black Holes, and Quantum Gravity | 10 pages, LaTeX; v4: substantially rewritten to emphasize assumptions
and ``loopholes,'' but basic conclusions unchanged; to appear in Phys. Rev. D | Phys.Rev.D67:023507,2003 | 10.1103/PhysRevD.67.023507 | UCD-02-12 | gr-qc astro-ph hep-th | null | Tentative observations and theoretical considerations have recently led to
renewed interest in models of fundamental physics in which certain
``constants'' vary in time. Assuming fixed black hole mass and the standard
form of the Bekenstein-Hawking entropy, Davies, Davis and Lineweaver have
argued that the laws of black hole thermodynamics disfavor models in which the
fundamental electric charge $e$ changes. I show that with these assumptions,
similar considerations severely constrain ``varying speed of light'' models,
unless we are prepared to abandon cherished assumptions about quantum gravity.
Relaxation of these assumptions permits sensible theories of quantum gravity
with ``varying constants,'' but also eliminates the thermodynamic constraints,
though the black hole mass spectrum may still provide some restrictions on the
range of allowable models.
| [
{
"created": "Wed, 4 Sep 2002 20:15:16 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Sep 2002 01:11:23 GMT",
"version": "v2"
},
{
"created": "Fri, 13 Sep 2002 18:19:26 GMT",
"version": "v3"
},
{
"created": "Thu, 14 Nov 2002 19:34:10 GMT",
"version": "v4"
}
] | 2010-04-28 | [
[
"Carlip",
"S.",
""
]
] | Tentative observations and theoretical considerations have recently led to renewed interest in models of fundamental physics in which certain ``constants'' vary in time. Assuming fixed black hole mass and the standard form of the Bekenstein-Hawking entropy, Davies, Davis and Lineweaver have argued that the laws of black hole thermodynamics disfavor models in which the fundamental electric charge $e$ changes. I show that with these assumptions, similar considerations severely constrain ``varying speed of light'' models, unless we are prepared to abandon cherished assumptions about quantum gravity. Relaxation of these assumptions permits sensible theories of quantum gravity with ``varying constants,'' but also eliminates the thermodynamic constraints, though the black hole mass spectrum may still provide some restrictions on the range of allowable models. |
1701.01489 | Amir Masoud Ghezelbash | A. M. Ghezelbash | A New Class of Exact Solutions in Einstein-Maxwell-dilaton Theory | 22 pages, 12 figures | Phys. Rev. D95, 064030 (2017) | 10.1103/PhysRevD.95.064030 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find new solutions to the five-dimensional Einstein-Maxwell-dilaton theory
with cosmological constant where the dilaton field couples to the
electromagnetic field as well as to the cosmological term with two different
coupling constants. The five-dimensional spacetime is non-stationary and is a
conformally regular spacetime, everywhere. Both the dilaton field and the
electromagnetic field depends on time and two spatial directions. The
cosmological constant takes positive, negative or zero value, depending on the
value of coupling constant. We study the physical properties of the spacetime
and show that the solutions are unique in five dimensions and can't be uplifted
to higher-dimensional Einstein-Maxwell theory or Einstein gravity in presence
of cosmological constant. Moreover, we construct new solutions to the theory
where both coupling constants are equal.
| [
{
"created": "Thu, 5 Jan 2017 21:47:50 GMT",
"version": "v1"
},
{
"created": "Sun, 12 Aug 2018 23:12:21 GMT",
"version": "v2"
}
] | 2018-08-14 | [
[
"Ghezelbash",
"A. M.",
""
]
] | We find new solutions to the five-dimensional Einstein-Maxwell-dilaton theory with cosmological constant where the dilaton field couples to the electromagnetic field as well as to the cosmological term with two different coupling constants. The five-dimensional spacetime is non-stationary and is a conformally regular spacetime, everywhere. Both the dilaton field and the electromagnetic field depends on time and two spatial directions. The cosmological constant takes positive, negative or zero value, depending on the value of coupling constant. We study the physical properties of the spacetime and show that the solutions are unique in five dimensions and can't be uplifted to higher-dimensional Einstein-Maxwell theory or Einstein gravity in presence of cosmological constant. Moreover, we construct new solutions to the theory where both coupling constants are equal. |
gr-qc/9803051 | Robert Mann | R.B. Mann | Summary of Session A6: Alternative Theories of Gravity | 4 pages, ReVTeX | null | null | WATPHYS-TH98/01 | gr-qc | null | This is a summary of the workshop A.6 on Alternative Theories of Gravity,
prepared for the proceedings for the GR15 conference.
| [
{
"created": "Fri, 13 Mar 1998 18:53:41 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mann",
"R. B.",
""
]
] | This is a summary of the workshop A.6 on Alternative Theories of Gravity, prepared for the proceedings for the GR15 conference. |
gr-qc/0206076 | Ramon Torres | Francesc Fayos, Jose M.M. Senovilla and Ramon Torres | Spherically symmetric models for charged radiating stars and voids:
Theoretical approach | 33 pages | Class.Quant.Grav.20:2579-2594,2003 | 10.1088/0264-9381/20/13/309 | null | gr-qc | null | We study the matching of a general spherically symmetric spacetime with a
Vaidya-Reissner-Nordstrom solution. To that end, we study the properties of
spherically symmetric electromagnetic fields and develop the proper
gravitational and electromagnetic junction conditions. We prove that generic
spacetimes can be matched to a Vaidya-Reissner-Nordstrom solution or one of its
specializations, and that these matchings have clear physical interpretations.
Furthermore, the non-spacelike nature of the matching hypersurface is proved
under very general hypotheses. We obtain the fundamental result that any
spherically symmetric body, be it in evolution or not, has un upper limit for
the total net electric charge that carries.
| [
{
"created": "Wed, 26 Jun 2002 00:13:44 GMT",
"version": "v1"
}
] | 2010-05-12 | [
[
"Fayos",
"Francesc",
""
],
[
"Senovilla",
"Jose M. M.",
""
],
[
"Torres",
"Ramon",
""
]
] | We study the matching of a general spherically symmetric spacetime with a Vaidya-Reissner-Nordstrom solution. To that end, we study the properties of spherically symmetric electromagnetic fields and develop the proper gravitational and electromagnetic junction conditions. We prove that generic spacetimes can be matched to a Vaidya-Reissner-Nordstrom solution or one of its specializations, and that these matchings have clear physical interpretations. Furthermore, the non-spacelike nature of the matching hypersurface is proved under very general hypotheses. We obtain the fundamental result that any spherically symmetric body, be it in evolution or not, has un upper limit for the total net electric charge that carries. |
1302.1705 | Valeria Kagramanova | V. Diemer (born Kagramanova) and E. Smolarek | Dynamics of test particles in thin-shell wormhole spacetimes | 14 pages, 9 Figs | null | 10.1088/0264-9381/30/17/175014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Geodesic motion in traversable Schwarzschild and Kerr thin-shell wormholes
constructed by the cut-and-paste method introduced by Visser (1989 Nucl. Phys.
B 328 203; 1995 Wormholes: from Einstein to Hawking (Woodbury, MN: American
Institute of Physics)) is studied. The orbits are calculated exactly in terms
of elliptic functions and visualized with the help of embedding diagrams.
| [
{
"created": "Thu, 7 Feb 2013 10:47:40 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Aug 2013 10:51:54 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Diemer",
"V.",
"",
"born Kagramanova"
],
[
"Smolarek",
"E.",
""
]
] | Geodesic motion in traversable Schwarzschild and Kerr thin-shell wormholes constructed by the cut-and-paste method introduced by Visser (1989 Nucl. Phys. B 328 203; 1995 Wormholes: from Einstein to Hawking (Woodbury, MN: American Institute of Physics)) is studied. The orbits are calculated exactly in terms of elliptic functions and visualized with the help of embedding diagrams. |
0804.3765 | Jose Manuel Velhinho | J. M. Velhinho | Groups of generalized flux transformations in the space of generalized
connections | 8 pages, title changed, new Conclusions section; to appear in IJGMMP | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a group of transformations in the space of generalized connections
that contains the set of transformations generated by the flux variables of
loop quantum gravity. This group is labelled by certain SU(2)-valued functions
on the bundle of directions in the spatial manifold. A further generalization
is obtained by considering functions that depend on germs of analytic curves,
rather than just on directions.
| [
{
"created": "Wed, 23 Apr 2008 17:21:21 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Jan 2009 08:35:19 GMT",
"version": "v2"
}
] | 2009-01-05 | [
[
"Velhinho",
"J. M.",
""
]
] | We present a group of transformations in the space of generalized connections that contains the set of transformations generated by the flux variables of loop quantum gravity. This group is labelled by certain SU(2)-valued functions on the bundle of directions in the spatial manifold. A further generalization is obtained by considering functions that depend on germs of analytic curves, rather than just on directions. |
1408.5787 | Canan Nurhan Karahan | Durmus Ali Demir, Canan Nurhan Karahan | Relativistic MOND from Modified Energetics | 7pp | Eur. Phys. J. C, 74 (2014) 3204 | 10.1140/epjc/s10052-014-3204-9 | IZTECH/PHYS-2014-06 | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We begin to investigate the question of what modifications in energy-momentum
tensor can yield correct MOND regime. As a starting study, we refrain from
insisting on an action principle and focus exclusively on the equations of
motion. The present work, despite the absence of an explicit action functional,
can be regarded to extend Milgrom's modified inertia approach to relativistic
domain. Our results show that a proper MOND limit arises if energy-momentum
tensor is modified to involve determinant of the metric tensor in reference to
the flat metric, where the latter is dynamically generated as in gravitational
Higgs mechanism. This modified energy-momentum tensor is conserved in both
Newtonian and MONDian regimes.
| [
{
"created": "Fri, 22 Aug 2014 18:03:49 GMT",
"version": "v1"
}
] | 2014-12-17 | [
[
"Demir",
"Durmus Ali",
""
],
[
"Karahan",
"Canan Nurhan",
""
]
] | We begin to investigate the question of what modifications in energy-momentum tensor can yield correct MOND regime. As a starting study, we refrain from insisting on an action principle and focus exclusively on the equations of motion. The present work, despite the absence of an explicit action functional, can be regarded to extend Milgrom's modified inertia approach to relativistic domain. Our results show that a proper MOND limit arises if energy-momentum tensor is modified to involve determinant of the metric tensor in reference to the flat metric, where the latter is dynamically generated as in gravitational Higgs mechanism. This modified energy-momentum tensor is conserved in both Newtonian and MONDian regimes. |
2107.12039 | Feiyu Yao | Feiyu Yao | Scalarized Einstein-Maxwell-scalar Black Holes in a Cavity | arXiv admin note: text overlap with arXiv:2012.01066,
arXiv:2102.04015 by other authors | null | 10.1140/epjc/s10052-021-09793-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the spontaneous scalarization of
Reissner-Nordstr{\"o}% m (RN) black holes enclosed by a cavity in an
Einstein-Maxwell-scalar (EMS) model with non-minimal couplings between the
scalar and Maxwell fields. In this model, scalar-free RN black holes in a
cavity may induce scalarized black holes due to the presence of a tachyonic
instability of the scalar field near the event horizon. We calculate
numerically the black hole solutions, and investigate the domain of existence,
perturbative stability against spherical perturbations and phase structure. The
scalarized solutions in a cavity are always thermodynamically preferred over
scalar-free solutions. In addition, a reentrant phase transition, composed of a
zeroth-order phase transition and a second-order one, occurs for large enough
electric charge $Q$.
| [
{
"created": "Mon, 26 Jul 2021 08:53:53 GMT",
"version": "v1"
},
{
"created": "Sun, 1 Aug 2021 15:31:34 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Oct 2021 03:32:57 GMT",
"version": "v3"
}
] | 2021-12-01 | [
[
"Yao",
"Feiyu",
""
]
] | In this paper, we study the spontaneous scalarization of Reissner-Nordstr{\"o}% m (RN) black holes enclosed by a cavity in an Einstein-Maxwell-scalar (EMS) model with non-minimal couplings between the scalar and Maxwell fields. In this model, scalar-free RN black holes in a cavity may induce scalarized black holes due to the presence of a tachyonic instability of the scalar field near the event horizon. We calculate numerically the black hole solutions, and investigate the domain of existence, perturbative stability against spherical perturbations and phase structure. The scalarized solutions in a cavity are always thermodynamically preferred over scalar-free solutions. In addition, a reentrant phase transition, composed of a zeroth-order phase transition and a second-order one, occurs for large enough electric charge $Q$. |
gr-qc/0309047 | C\'esar Augusto Costa | C\'esar A. Costa, Odylio D. Aguiar and Nadja S. Magalh\~aes | Response of the Brazilian gravitational wave detector to signals from a
black hole ringdown | 5 pages, 4 figures, Amaldi 5 Conference Proceedings contribution.
Submitted to Class. Quantum Grav | Class.Quant.Grav. 21 (2004) S827-S832 | 10.1088/0264-9381/21/5/066 | null | gr-qc | null | It is assumed that a black hole can be disturbed in such a way that a
ringdown gravitational wave would be generated. This ringdown waveform is well
understood and is modelled as an exponentially damped sinusoid. In this work we
use this kind of waveform to study the performance of the SCHENBERG
gravitational wave detector. This first realistic simulation will help us to
develop strategies for the signal analysis of this Brazilian detector. We
calculated the signal-to-noise ratio as a function of frequency for the
simulated signals and obtained results that show that SCHENBERG is expected to
be sensitive enough to detect this kind of signal up to a distance of $\sim
20\mathrm{kpc}$.
| [
{
"created": "Mon, 8 Sep 2003 20:25:04 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Costa",
"César A.",
""
],
[
"Aguiar",
"Odylio D.",
""
],
[
"Magalhães",
"Nadja S.",
""
]
] | It is assumed that a black hole can be disturbed in such a way that a ringdown gravitational wave would be generated. This ringdown waveform is well understood and is modelled as an exponentially damped sinusoid. In this work we use this kind of waveform to study the performance of the SCHENBERG gravitational wave detector. This first realistic simulation will help us to develop strategies for the signal analysis of this Brazilian detector. We calculated the signal-to-noise ratio as a function of frequency for the simulated signals and obtained results that show that SCHENBERG is expected to be sensitive enough to detect this kind of signal up to a distance of $\sim 20\mathrm{kpc}$. |
2207.05063 | Philip Tee | Philip Tee, Nosratollah Jafari | Fundamental length scale and the bending of light in a gravitational
field | null | Eur. Phys. J. C 82, 571 (2022) | 10.1140/epjc/s10052-022-10516-5 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The canonical approach to quantizing quantum gravity is understood to suffer
from pathological non-renomalizability. Nevertheless in the context of
effective field theory, a viable perturbative approach to calculating
elementary processes is possible. Some non-perturbative approaches, most
notably loop quantum gravity and combinatorial quantum gravity imply the
existence of a minimal length. To circumvent the seeming contradiction between
the existence of a minimum length and the principle of special relativity,
Double Special Relativity introduces modified dispersion relationships that
reconcile the conflict. In this work, we combine these dispersion relationships
with an effective field theory approach to compute the first post Newtonian
correction to the bending of light by a massive object. The calculation offers
the prospect of a directly measurable effect that rests upon both the existence
of a quantized gravitational field and a minimal length. Experimental
verification would provide evidence of the existence of a quantum theory of
gravity, and the fundamental quantization of spacetime with a bound on the
minimal distance.
| [
{
"created": "Sat, 9 Jul 2022 17:57:51 GMT",
"version": "v1"
}
] | 2022-07-13 | [
[
"Tee",
"Philip",
""
],
[
"Jafari",
"Nosratollah",
""
]
] | The canonical approach to quantizing quantum gravity is understood to suffer from pathological non-renomalizability. Nevertheless in the context of effective field theory, a viable perturbative approach to calculating elementary processes is possible. Some non-perturbative approaches, most notably loop quantum gravity and combinatorial quantum gravity imply the existence of a minimal length. To circumvent the seeming contradiction between the existence of a minimum length and the principle of special relativity, Double Special Relativity introduces modified dispersion relationships that reconcile the conflict. In this work, we combine these dispersion relationships with an effective field theory approach to compute the first post Newtonian correction to the bending of light by a massive object. The calculation offers the prospect of a directly measurable effect that rests upon both the existence of a quantized gravitational field and a minimal length. Experimental verification would provide evidence of the existence of a quantum theory of gravity, and the fundamental quantization of spacetime with a bound on the minimal distance. |
gr-qc/0104008 | J. Ponce de Leon | J. Ponce de Leon | Equations of Motion in Kaluza-Klein Gravity Revisited | Effects from an extra dimension are discussed in a separated section
(Sec. 7). References added. To appear in Gravitation & Cosmology | Grav.Cosmol. 8 (2002) 272-284 | null | null | gr-qc | null | We discuss the equations of motion of test particles for a version of
Kaluza-Klein theory where the cylinder condition is not imposed. The metric
tensor of the five-dimensional manifold is allowed to depend on the fifth
coordinate. This is the usual working scenario in brane-world, induced-matter
theory and other Kaluza-Klein theories with large extra dimensions. We present
a new version for the fully covariant splitting of the 5D equations. We show
how to change the usual definition of various physical quantities in order to
make physics in 4D invariant under transformations in 5D. These include the
redefinition of the electromagnetic tensor, force and Christoffel symbols. With
our definitions, each of the force terms in the equation of motion is gauge
invariant and orthogonal to the four-velocity of the particle. The "hidden"
parameter associated with the rate of motion along the extra dimension is
identified with the electric charge, regardless of whether there is an
electromagnetic field or not. In addition, for charged particles, the
charge-to-mass ratio should vary. Therefore, the motion of a charged particle
should differ from the motion of a neutral particle, with the same initial mass
and energy, even in the absence of electromagnetic field. These predictions
have important implications and could in principle be experimentally detected.
| [
{
"created": "Tue, 3 Apr 2001 05:45:12 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Dec 2002 14:26:58 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"de Leon",
"J. Ponce",
""
]
] | We discuss the equations of motion of test particles for a version of Kaluza-Klein theory where the cylinder condition is not imposed. The metric tensor of the five-dimensional manifold is allowed to depend on the fifth coordinate. This is the usual working scenario in brane-world, induced-matter theory and other Kaluza-Klein theories with large extra dimensions. We present a new version for the fully covariant splitting of the 5D equations. We show how to change the usual definition of various physical quantities in order to make physics in 4D invariant under transformations in 5D. These include the redefinition of the electromagnetic tensor, force and Christoffel symbols. With our definitions, each of the force terms in the equation of motion is gauge invariant and orthogonal to the four-velocity of the particle. The "hidden" parameter associated with the rate of motion along the extra dimension is identified with the electric charge, regardless of whether there is an electromagnetic field or not. In addition, for charged particles, the charge-to-mass ratio should vary. Therefore, the motion of a charged particle should differ from the motion of a neutral particle, with the same initial mass and energy, even in the absence of electromagnetic field. These predictions have important implications and could in principle be experimentally detected. |
2004.12664 | Oleksandr Sobol Dr. | O.O. Sobol, E.V. Gorbar, A.I. Momot, and S.I. Vilchinskii | Schwinger production of scalar particles during and after inflation from
the first principles | 22 pages, 4 figures | Phys. Rev. D 102, 023506 (2020) | 10.1103/PhysRevD.102.023506 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By using the first-principles approach, we derive a system of three quantum
kinetic equations governing the production and evolution of charged scalar
particles by an electric field in an expanding universe. Analyzing the
ultraviolet asymptotic behavior of the kinetic functions, we found the
divergent parts of the electric current and the energy-momentum tensor of the
produced particles and determined the corresponding counterterms. The
renormalized system of equations is used to study the generation of
electromagnetic fields during and after inflation in the kinetic coupling model
$\mathcal{L}_{\rm EM}=-(1/4)f^{2}(\phi)F_{\mu\nu}F^{\mu\nu}$ with the Ratra
coupling function $f=\exp(\beta\phi/M_{p})$. It is found that the electric
current of created particles is retarded with respect to the electric field.
This leads to an oscillatory behavior of both quantities in agreement with the
results obtained previously in phenomenological kinetic and hydrodynamical
approaches.
| [
{
"created": "Mon, 27 Apr 2020 09:24:56 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Apr 2020 21:02:56 GMT",
"version": "v2"
},
{
"created": "Sat, 1 Aug 2020 23:35:10 GMT",
"version": "v3"
}
] | 2020-08-04 | [
[
"Sobol",
"O. O.",
""
],
[
"Gorbar",
"E. V.",
""
],
[
"Momot",
"A. I.",
""
],
[
"Vilchinskii",
"S. I.",
""
]
] | By using the first-principles approach, we derive a system of three quantum kinetic equations governing the production and evolution of charged scalar particles by an electric field in an expanding universe. Analyzing the ultraviolet asymptotic behavior of the kinetic functions, we found the divergent parts of the electric current and the energy-momentum tensor of the produced particles and determined the corresponding counterterms. The renormalized system of equations is used to study the generation of electromagnetic fields during and after inflation in the kinetic coupling model $\mathcal{L}_{\rm EM}=-(1/4)f^{2}(\phi)F_{\mu\nu}F^{\mu\nu}$ with the Ratra coupling function $f=\exp(\beta\phi/M_{p})$. It is found that the electric current of created particles is retarded with respect to the electric field. This leads to an oscillatory behavior of both quantities in agreement with the results obtained previously in phenomenological kinetic and hydrodynamical approaches. |
2404.13037 | Mark Hertzberg | Mark P. Hertzberg, Abraham Loeb | Critical Analysis of Replacing Dark Matter and Dark Energy with a Model
of Stochastic Spacetime | 10 pages in double column format, 1 figure. V2: More details
including analysis of fluctuations. V3: Further details. V4: Analysis of
temporal correlations | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze consequences of trying to replace dark matter and dark energy with
models of stochastic spacetime. In particular, we analyze the model put forth
by Ref. [1], in which it is claimed that ``post-quantum classical gravity"
(PQCG), a stochastic theory of gravity, leads to modified Newtonian dynamics
(MOND) behavior on galactic scales that reproduces galactic rotation curves. We
show that this analysis has three basic problems: (i) the equations of PQCG do
not lead to a new large scale force of the form claimed in the paper, (ii) the
form claimed is not of the MONDian form anyhow and so does not correspond to
observed galactic dynamics, and (iii) the spectrum of fluctuations is very
different from observations.
| [
{
"created": "Fri, 19 Apr 2024 17:49:33 GMT",
"version": "v1"
},
{
"created": "Tue, 7 May 2024 17:03:23 GMT",
"version": "v2"
},
{
"created": "Wed, 15 May 2024 16:51:21 GMT",
"version": "v3"
},
{
"created": "Thu, 23 May 2024 17:56:14 GMT",
"version": "v4"
}
] | 2024-05-24 | [
[
"Hertzberg",
"Mark P.",
""
],
[
"Loeb",
"Abraham",
""
]
] | We analyze consequences of trying to replace dark matter and dark energy with models of stochastic spacetime. In particular, we analyze the model put forth by Ref. [1], in which it is claimed that ``post-quantum classical gravity" (PQCG), a stochastic theory of gravity, leads to modified Newtonian dynamics (MOND) behavior on galactic scales that reproduces galactic rotation curves. We show that this analysis has three basic problems: (i) the equations of PQCG do not lead to a new large scale force of the form claimed in the paper, (ii) the form claimed is not of the MONDian form anyhow and so does not correspond to observed galactic dynamics, and (iii) the spectrum of fluctuations is very different from observations. |
0711.0115 | Kristina Giesel | K. Giesel, S. Hofmann, T. Thiemann, O. Winkler | Manifestly Gauge-Invariant General Relativistic Perturbation Theory: I.
Foundations | 77 pages, no figures | Class.Quant.Grav.27:055005,2010 | 10.1088/0264-9381/27/5/055005 | AEI-2007-150 | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Linear cosmological perturbation theory is pivotal to a theoretical
understanding of current cosmological experimental data provided e.g. by cosmic
microwave anisotropy probes. A key issue in that theory is to extract the gauge
invariant degrees of freedom which allow unambiguous comparison between theory
and experiment. When one goes beyond first (linear) order, the task of writing
the Einstein equations expanded to n'th order in terms of quantities that are
gauge invariant up to terms of higher orders becomes highly non-trivial and
cumbersome. This fact has prevented progress for instance on the issue of the
stability of linear perturbation theory and is a subject of current debate in
the literature. In this series of papers we circumvent these difficulties by
passing to a manifestly gauge invariant framework. In other words, we only
perturb gauge invariant, i.e. measurable quantities, rather than gauge variant
ones. Thus, gauge invariance is preserved non perturbatively while we construct
the perturbation theory for the equations of motion for the gauge invariant
observables to all orders. In this first paper we develop the general framework
which is based on a seminal paper due to Brown and Kuchar as well as the
realtional formalism due to Rovelli. In the second, companion, paper we apply
our general theory to FRW cosmologies and derive the deviations from the
standard treatment in linear order. As it turns out, these deviations are
negligible in the late universe, thus our theory is in agreement with the
standard treatment. However, the real strength of our formalism is that it
admits a straightforward and unambiguous, gauge invariant generalisation to
higher orders. This will also allow us to settle the stability issue in a
future publication.
| [
{
"created": "Thu, 1 Nov 2007 18:02:51 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Nov 2009 11:59:34 GMT",
"version": "v2"
}
] | 2010-02-17 | [
[
"Giesel",
"K.",
""
],
[
"Hofmann",
"S.",
""
],
[
"Thiemann",
"T.",
""
],
[
"Winkler",
"O.",
""
]
] | Linear cosmological perturbation theory is pivotal to a theoretical understanding of current cosmological experimental data provided e.g. by cosmic microwave anisotropy probes. A key issue in that theory is to extract the gauge invariant degrees of freedom which allow unambiguous comparison between theory and experiment. When one goes beyond first (linear) order, the task of writing the Einstein equations expanded to n'th order in terms of quantities that are gauge invariant up to terms of higher orders becomes highly non-trivial and cumbersome. This fact has prevented progress for instance on the issue of the stability of linear perturbation theory and is a subject of current debate in the literature. In this series of papers we circumvent these difficulties by passing to a manifestly gauge invariant framework. In other words, we only perturb gauge invariant, i.e. measurable quantities, rather than gauge variant ones. Thus, gauge invariance is preserved non perturbatively while we construct the perturbation theory for the equations of motion for the gauge invariant observables to all orders. In this first paper we develop the general framework which is based on a seminal paper due to Brown and Kuchar as well as the realtional formalism due to Rovelli. In the second, companion, paper we apply our general theory to FRW cosmologies and derive the deviations from the standard treatment in linear order. As it turns out, these deviations are negligible in the late universe, thus our theory is in agreement with the standard treatment. However, the real strength of our formalism is that it admits a straightforward and unambiguous, gauge invariant generalisation to higher orders. This will also allow us to settle the stability issue in a future publication. |
1501.01397 | Sajid Ali | Sajid Ali | Revisiting Noether gauge symmetry approach in quintom cosmology | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Noether gauge symmetry approach is revisited to study various quintom
scenarios (those that arise by the presence of two dynamical scalar fields) to
comprehend the role of dark energy in our universe. For such models, we obtain
smooth parameterizations of the equation of state of dark energy across the
boundary of cosmological constant $w_{\Lambda}=-1$. This study gives rise to
two new cases of the potential $V(\phi, \sigma)$, due to a quintom field in
which nonlinear coupling of the scalar fields arise. Besides we report that a
few cases of Noether gauge symmetries and their invariants in [Adnan Aslam, et.
al., Astrophys Space Sci (2013), 348:533-540] are incorrect. Consequently, the
given cosmological model in their paper is not a feasible quintom model.
| [
{
"created": "Wed, 7 Jan 2015 08:57:33 GMT",
"version": "v1"
}
] | 2015-01-08 | [
[
"Ali",
"Sajid",
""
]
] | The Noether gauge symmetry approach is revisited to study various quintom scenarios (those that arise by the presence of two dynamical scalar fields) to comprehend the role of dark energy in our universe. For such models, we obtain smooth parameterizations of the equation of state of dark energy across the boundary of cosmological constant $w_{\Lambda}=-1$. This study gives rise to two new cases of the potential $V(\phi, \sigma)$, due to a quintom field in which nonlinear coupling of the scalar fields arise. Besides we report that a few cases of Noether gauge symmetries and their invariants in [Adnan Aslam, et. al., Astrophys Space Sci (2013), 348:533-540] are incorrect. Consequently, the given cosmological model in their paper is not a feasible quintom model. |
gr-qc/0702134 | Lorenzo Fatibene | L. Fatibene, M. Francaviglia, C. Rovelli | On a Covariant Formulation of the Barbero-Immirzi Connection | 13 pages | Class.Quant.Grav.24:3055-3066,2007 | 10.1088/0264-9381/24/11/017 | null | gr-qc | null | The Barbero-Immirzi (BI) connection, as usually introduced out of a spin
connection, is a global object though it does not transform properly as a
genuine connection with respect to generic spin transformations, unless quite
specific and suitable gauges are imposed. We shall here investigate whether and
under which global conditions a (properly transforming and hence global)
SU(2)-connection can be canonically defined in a gauge covariant way. Such
SU(2)-connection locally agrees with the usual BI connection and it can be
defined on pretty general bundles; in particular triviality is not assumed. As
a by-product we shall also introduce a global covariant SU(2)-connection over
the whole spacetime (while for technical reasons the BI connection in the
standard formulation is just introduced on a space slice) which restricts to
the usual BI connection on a space slice.
| [
{
"created": "Mon, 26 Feb 2007 08:25:26 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Fatibene",
"L.",
""
],
[
"Francaviglia",
"M.",
""
],
[
"Rovelli",
"C.",
""
]
] | The Barbero-Immirzi (BI) connection, as usually introduced out of a spin connection, is a global object though it does not transform properly as a genuine connection with respect to generic spin transformations, unless quite specific and suitable gauges are imposed. We shall here investigate whether and under which global conditions a (properly transforming and hence global) SU(2)-connection can be canonically defined in a gauge covariant way. Such SU(2)-connection locally agrees with the usual BI connection and it can be defined on pretty general bundles; in particular triviality is not assumed. As a by-product we shall also introduce a global covariant SU(2)-connection over the whole spacetime (while for technical reasons the BI connection in the standard formulation is just introduced on a space slice) which restricts to the usual BI connection on a space slice. |
1707.04424 | Giampiero Esposito Dr. | Emmanuele Battista, Giampiero Esposito, Simone Dell'Agnello | On the foundations of general relativistic celestial mechanics | 26 pages, 1 figure | null | 10.1142/S0217751X17300228 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Towards the end of nineteenth century, Celestial Mechanics provided the most
powerful tools to test Newtonian gravity in the solar system, and led also to
the discovery of chaos in modern science. Nowadays, in light of general
relativity, Celestial Mechanics leads to a new perspective on the motion of
satellites and planets. The reader is here introduced to the modern formulation
of the problem of motion, following what the leaders in the field have been
teaching since the nineties. In particular, the use of a global chart for the
overall dynamics of N bodies and N local charts describing the internal
dynamics of each body. The next logical step studies in detail how to split the
N-body problem into two sub-problems concerning the internal and external
dynamics, how to achieve the effacement properties that would allow a
decoupling of the two sub-problems, how to define external-potential-effacing
coordinates and how to generalize the Newtonian multipole and tidal moments.
The review paper ends with an assessment of the nonlocal equations of motion
obtained within such a framework, a description of the modifications induced by
general relativity of the theoretical analysis of the Newtonian three-body
problem, and a mention of the potentialities of the analysis of solar-system
metric data carried out with the Planetary Ephemeris Program.
| [
{
"created": "Fri, 14 Jul 2017 09:12:11 GMT",
"version": "v1"
}
] | 2017-09-18 | [
[
"Battista",
"Emmanuele",
""
],
[
"Esposito",
"Giampiero",
""
],
[
"Dell'Agnello",
"Simone",
""
]
] | Towards the end of nineteenth century, Celestial Mechanics provided the most powerful tools to test Newtonian gravity in the solar system, and led also to the discovery of chaos in modern science. Nowadays, in light of general relativity, Celestial Mechanics leads to a new perspective on the motion of satellites and planets. The reader is here introduced to the modern formulation of the problem of motion, following what the leaders in the field have been teaching since the nineties. In particular, the use of a global chart for the overall dynamics of N bodies and N local charts describing the internal dynamics of each body. The next logical step studies in detail how to split the N-body problem into two sub-problems concerning the internal and external dynamics, how to achieve the effacement properties that would allow a decoupling of the two sub-problems, how to define external-potential-effacing coordinates and how to generalize the Newtonian multipole and tidal moments. The review paper ends with an assessment of the nonlocal equations of motion obtained within such a framework, a description of the modifications induced by general relativity of the theoretical analysis of the Newtonian three-body problem, and a mention of the potentialities of the analysis of solar-system metric data carried out with the Planetary Ephemeris Program. |
0912.5048 | Israel Quiros | Ricardo Garc\'ia-Salcedo, Tame Gonzalez, Claudia Moreno, Yunelsy
Napoles, Yoelsy Leyva, Israel Quiros | Asymptotic Properties of a Supposedly Regular (Dirac-Born-Infeld)
Modification of General Relativity | 12 pages, Revtex, 12 eps figures. Several new references added. Minor
changes in the main text. Discussion improved | JCAP 1002:027,2010 | 10.1088/1475-7516/2010/02/027 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the dynamical systems tools to study the asymptotic properties of a
cosmological model based on a non-linear modification of General Relativity in
which the standard Einstein-Hilbert action is replaced by one of
Dirac-Born-Infeld type. It is shown that the dynamics of this model is
extremely rich: there are found equilibrium points in the phase space that can
be associated with matter-dominated, matter-curvature scaling, de Sitter, and
even phantom-like solutions. Depending on the value of the overall parameters
the dynamics in phase space can show multi-attractor structure into the future
(multiple future attractors may co-exist). This is a consequence of
bifurcations in control parameter space, showing strong dependence of the
model's dynamical properties on the free parameters. Contrary to what is
expected from non-linear modifications of general relativity of this kind,
removal of the initial spacetime singularity is not a generic feature of the
corresponding cosmological model. Instead, the starting point of the cosmic
dynamics -- the past attractor in the phase space -- is a state of infinitely
large value of the Hubble rate squared, usually associated with the big bang
singularity.
| [
{
"created": "Sun, 27 Dec 2009 02:03:22 GMT",
"version": "v1"
},
{
"created": "Sat, 2 Jan 2010 19:16:07 GMT",
"version": "v2"
},
{
"created": "Sat, 9 Jan 2010 19:11:28 GMT",
"version": "v3"
},
{
"created": "Mon, 25 Jan 2010 21:03:52 GMT",
"version": "v4"
}
] | 2010-05-12 | [
[
"García-Salcedo",
"Ricardo",
""
],
[
"Gonzalez",
"Tame",
""
],
[
"Moreno",
"Claudia",
""
],
[
"Napoles",
"Yunelsy",
""
],
[
"Leyva",
"Yoelsy",
""
],
[
"Quiros",
"Israel",
""
]
] | We apply the dynamical systems tools to study the asymptotic properties of a cosmological model based on a non-linear modification of General Relativity in which the standard Einstein-Hilbert action is replaced by one of Dirac-Born-Infeld type. It is shown that the dynamics of this model is extremely rich: there are found equilibrium points in the phase space that can be associated with matter-dominated, matter-curvature scaling, de Sitter, and even phantom-like solutions. Depending on the value of the overall parameters the dynamics in phase space can show multi-attractor structure into the future (multiple future attractors may co-exist). This is a consequence of bifurcations in control parameter space, showing strong dependence of the model's dynamical properties on the free parameters. Contrary to what is expected from non-linear modifications of general relativity of this kind, removal of the initial spacetime singularity is not a generic feature of the corresponding cosmological model. Instead, the starting point of the cosmic dynamics -- the past attractor in the phase space -- is a state of infinitely large value of the Hubble rate squared, usually associated with the big bang singularity. |
1510.06628 | Sandro D. P. Vitenti | Patrick Peter and Nelson Pinto-Neto and Sandro Dias Pinto Vitenti | Quantum Cosmological Perturbations of Multiple Fluids | 20 pages, matches PRD published version | Phys. Rev. D 93, 023520 (2016) | 10.1103/PhysRevD.93.023520 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The formalism to treat quantization and evolution of cosmological
perturbations of multiple fluids is described. We first construct the
Lagrangian for both the gravitational and matter parts, providing the necessary
relevant variables and momenta leading to the quadratic Hamiltonian describing
linear perturbations. The final Hamiltonian is obtained without assuming any
equations of motions for the background variables. This general formalism is
applied to the special case of two fluids, having in mind the usual radiation
and matter mix which made most of our current Universe history. Quantization is
achieved using an adiabatic expansion of the basis functions. This allows for
an unambiguous definition of a vacuum state up to the given adiabatic order.
Using this basis, we show that particle creation is well defined for a suitable
choice of vacuum and canonical variables, so that the time evolution of the
corresponding quantum fields is unitary. This provides constraints for setting
initial conditions for an arbitrary number of fluids and background time
evolution. We also show that the common choice of variables for quantization
can lead to an ill-defined vacuum definition. Our formalism is not restricted
to the case where the coupling between fields is small, but is only required to
vary adiabatically with respect to the ultraviolet modes, thus paving the way
to consistent descriptions of general models not restricted to single-field (or
fluid).
| [
{
"created": "Thu, 22 Oct 2015 13:55:46 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Jan 2016 12:36:10 GMT",
"version": "v2"
}
] | 2016-02-01 | [
[
"Peter",
"Patrick",
""
],
[
"Pinto-Neto",
"Nelson",
""
],
[
"Vitenti",
"Sandro Dias Pinto",
""
]
] | The formalism to treat quantization and evolution of cosmological perturbations of multiple fluids is described. We first construct the Lagrangian for both the gravitational and matter parts, providing the necessary relevant variables and momenta leading to the quadratic Hamiltonian describing linear perturbations. The final Hamiltonian is obtained without assuming any equations of motions for the background variables. This general formalism is applied to the special case of two fluids, having in mind the usual radiation and matter mix which made most of our current Universe history. Quantization is achieved using an adiabatic expansion of the basis functions. This allows for an unambiguous definition of a vacuum state up to the given adiabatic order. Using this basis, we show that particle creation is well defined for a suitable choice of vacuum and canonical variables, so that the time evolution of the corresponding quantum fields is unitary. This provides constraints for setting initial conditions for an arbitrary number of fluids and background time evolution. We also show that the common choice of variables for quantization can lead to an ill-defined vacuum definition. Our formalism is not restricted to the case where the coupling between fields is small, but is only required to vary adiabatically with respect to the ultraviolet modes, thus paving the way to consistent descriptions of general models not restricted to single-field (or fluid). |
1701.05998 | Yungui Gong | Dicong Liang, Yungui Gong, Shaoqi Hou, Yunqi Liu | Polarizations of gravitational waves in $f(R)$ gravity | no figure, comments are welcome, PRD in press | Phys. Rev. D 95, 104034 (2017) | 10.1103/PhysRevD.95.104034 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We point out that there are only three polarizations for gravitational waves
in $f(R)$ gravity, and the polarization due to the massive scalar mode is a mix
of the pure longitudinal and transverse breathing polarization. The
classification of the six polarizations by the Newman-Penrose quantities is
based on weak, plane and null gravitational waves, so it is not applicable to
the massive mode.
| [
{
"created": "Sat, 21 Jan 2017 08:49:58 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Jan 2017 13:30:06 GMT",
"version": "v2"
},
{
"created": "Sun, 14 May 2017 03:09:29 GMT",
"version": "v3"
}
] | 2017-05-31 | [
[
"Liang",
"Dicong",
""
],
[
"Gong",
"Yungui",
""
],
[
"Hou",
"Shaoqi",
""
],
[
"Liu",
"Yunqi",
""
]
] | We point out that there are only three polarizations for gravitational waves in $f(R)$ gravity, and the polarization due to the massive scalar mode is a mix of the pure longitudinal and transverse breathing polarization. The classification of the six polarizations by the Newman-Penrose quantities is based on weak, plane and null gravitational waves, so it is not applicable to the massive mode. |
2110.11011 | Areeba Merriam | Areeba Merriam, M. Zain Sarwar | Thermodynamics of Bardeen regular black hole with generalized
uncertainty principle | 13 pages, 4 figures | null | 10.1142/S0218271821501285 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This study explores the emission of massive charged spin-1 particles from the
background of Bardeen regular spacetime by the semi-classical method used to
study the Hawking radiation spectrum. We employed the Hamilton-Jacobi method
and WKB approximation technique with the suitable form of the wave function to
solve the Proca field equation. We calculated the tunneling probability of
outgoing spin-1 particles and the corresponding thermodynamic temperature.
Furthermore, we obtained the modified thermodynamic quantities like
temperature, entropy as well as heat capacity by utilizing the quadratic form
of generalized uncertainty principle (GUP) and minimal length. In the end, we
investigated the local stability as well as phase transitions of the Bardeen
black hole in the context of GUP-modified heat capacity.
| [
{
"created": "Thu, 21 Oct 2021 09:30:36 GMT",
"version": "v1"
}
] | 2021-10-22 | [
[
"Merriam",
"Areeba",
""
],
[
"Sarwar",
"M. Zain",
""
]
] | This study explores the emission of massive charged spin-1 particles from the background of Bardeen regular spacetime by the semi-classical method used to study the Hawking radiation spectrum. We employed the Hamilton-Jacobi method and WKB approximation technique with the suitable form of the wave function to solve the Proca field equation. We calculated the tunneling probability of outgoing spin-1 particles and the corresponding thermodynamic temperature. Furthermore, we obtained the modified thermodynamic quantities like temperature, entropy as well as heat capacity by utilizing the quadratic form of generalized uncertainty principle (GUP) and minimal length. In the end, we investigated the local stability as well as phase transitions of the Bardeen black hole in the context of GUP-modified heat capacity. |
gr-qc/0102050 | Bogdan Nita | Bogdan Nita and Ivor Robinson | Note on Invariants of the Weyl Tensor | 3 pages, no figures, corrected expression (12) | Gen.Rel.Grav. 35 (2003) 1865-1868 | 10.1023/A:1026074400196 | null | gr-qc | null | Algebraically special gravitational fields are described using algebraic and
differential invariants of the Weyl tensor. A type III invariant is also given
and calculated for Robinson-Trautman spaces.
| [
{
"created": "Mon, 12 Feb 2001 18:21:57 GMT",
"version": "v1"
},
{
"created": "Tue, 1 May 2001 13:05:47 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Nita",
"Bogdan",
""
],
[
"Robinson",
"Ivor",
""
]
] | Algebraically special gravitational fields are described using algebraic and differential invariants of the Weyl tensor. A type III invariant is also given and calculated for Robinson-Trautman spaces. |
gr-qc/0203060 | S. Shankaranarayanan | S. Shankaranarayanan (IUCAA) | Is there an imprint of Planck scale physics on inflationary cosmology? | 6 pages, uses RevTex4; References added; Final version | Class.Quant.Grav.20:75-84,2003 | 10.1088/0264-9381/20/1/305 | null | gr-qc astro-ph hep-th | null | We study the effects of the trans-Planckian dispersion relation on the
spectrum of the primordial density perturbations during inflation. In contrast
to the earlier analyses, we do not assume any specific form of the dispersion
relation and allow the initial state of the field to be arbitrary. We obtain
the spectrum of vacuum fluctuations of the quantum field by considering a
scalar field satisfying the linear wave equation with higher spatial derivative
terms propagating in the de Sitter space-time. We show that the power spectrum
does not strongly depend on the dispersion relation and that the form of the
dispersion relation does not play a significant role in obtaining the
corrections to the scale invariant spectrum. We also show that the signatures
of the deviations from the flat scale-invariant spectrum from the CMBR
observations due to quantum gravitational effects cannot be differentiated from
the standard inflationary scenario with an arbitrary initial state.
| [
{
"created": "Sun, 17 Mar 2002 17:05:52 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jan 2003 15:09:02 GMT",
"version": "v2"
}
] | 2011-07-19 | [
[
"Shankaranarayanan",
"S.",
"",
"IUCAA"
]
] | We study the effects of the trans-Planckian dispersion relation on the spectrum of the primordial density perturbations during inflation. In contrast to the earlier analyses, we do not assume any specific form of the dispersion relation and allow the initial state of the field to be arbitrary. We obtain the spectrum of vacuum fluctuations of the quantum field by considering a scalar field satisfying the linear wave equation with higher spatial derivative terms propagating in the de Sitter space-time. We show that the power spectrum does not strongly depend on the dispersion relation and that the form of the dispersion relation does not play a significant role in obtaining the corrections to the scale invariant spectrum. We also show that the signatures of the deviations from the flat scale-invariant spectrum from the CMBR observations due to quantum gravitational effects cannot be differentiated from the standard inflationary scenario with an arbitrary initial state. |
1609.09784 | Christian Corda Prof. | B. Nadiri Niri, A. Jahan, C. Corda | Gravitational luminosity of a hot plasma in R^2 gravity | 17 pages, final version accepted for publication in European Physical
Journal C. A discussion in arXiv:1211.1373 has been partially reviewed | EPJC 76, 692 (2016) | 10.1140/epjc/s10052-016-4545-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The R^{2}-gravity contribution to energy loss of a hot plasma due to the
gravitational bremsstrahlung is calculated in the linearized theory on the
basis of classical Coulomb scattering of plasma constituents in small-angle
scattering approximation. The explicit dependence of the gravitational
luminosity on the plasma temperature is derived and its relevance to the
Einstein gravity is demonstrated. The result when applied to the Sun as a hot
plasma, shows very good agreement with available data.
| [
{
"created": "Tue, 27 Sep 2016 07:24:21 GMT",
"version": "v1"
},
{
"created": "Sun, 27 Nov 2016 10:28:57 GMT",
"version": "v2"
}
] | 2016-12-20 | [
[
"Niri",
"B. Nadiri",
""
],
[
"Jahan",
"A.",
""
],
[
"Corda",
"C.",
""
]
] | The R^{2}-gravity contribution to energy loss of a hot plasma due to the gravitational bremsstrahlung is calculated in the linearized theory on the basis of classical Coulomb scattering of plasma constituents in small-angle scattering approximation. The explicit dependence of the gravitational luminosity on the plasma temperature is derived and its relevance to the Einstein gravity is demonstrated. The result when applied to the Sun as a hot plasma, shows very good agreement with available data. |
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