id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2007.05064 | Fabio D'Ambrosio | Fabio D'Ambrosio and Lavinia Heisenberg | Classification of Primary Constraints of Quadratic Non-Metricity
Theories of Gravity | 8 pages, 3 tables, 1 figure | null | 10.1007/JHEP02(2021)170 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform the ADM decomposition of a five-parameter family of quadratic
non-metricity theories and study their conjugate momenta. After systematically
identifying all possible conditions which can be imposed on the parameters such
that different sets of primary constraints arise, we find that the
five-parametric theory space can be compartmentalized into nine different
sectors, based on the presence or absence of primary constraints. This
classification allows to dismiss certain classes of theories as unphysical and
invites further investigations into the remaining sectors, which may contain
phenomenologically interesting modifications of General Relativity.
| [
{
"created": "Thu, 9 Jul 2020 21:03:49 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Dec 2020 20:18:05 GMT",
"version": "v2"
}
] | 2021-03-17 | [
[
"D'Ambrosio",
"Fabio",
""
],
[
"Heisenberg",
"Lavinia",
""
]
] | We perform the ADM decomposition of a five-parameter family of quadratic non-metricity theories and study their conjugate momenta. After systematically identifying all possible conditions which can be imposed on the parameters such that different sets of primary constraints arise, we find that the five-parametric theory space can be compartmentalized into nine different sectors, based on the presence or absence of primary constraints. This classification allows to dismiss certain classes of theories as unphysical and invites further investigations into the remaining sectors, which may contain phenomenologically interesting modifications of General Relativity. |
2212.05564 | Dmitri Fursaev | D.V. Fursaev and I.G. Pirozhenko | Electrodynamics under Action of Null Cosmic Strings | 22 pages, 11 figures, new figure added | null | 10.1103/PhysRevD.107.025018 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A method to study electromagnetic (EM) effects generated by a straight null
cosmic string moving in classical EM fields is suggested. The string is shown
to induce an additional EM field which can be described as a solution to
homogeneous Maxwell equations with initial data set on a null surface, the
string event horizon, where the string world-sheet belongs to. The initial data
ensure the required holonomy of the string space-time caused by the gravity of
the string. This characteristic initial value problem is used to study
interaction of plane waves with null strings and perturbations by the strings
of the Coulomb fields of electric charges. It is shown that parts of an
incoming EM wave crossing the string horizon from different sides of the string
are refracted with respect to each other and leave behind the string a
wedge-like region of interference. A null string moving near an electric charge
results in two effects: it creates a self-force of the charge and induces a
pulse of EM radiation traveling away from the charge in the direction close to
trajectory of the string.
| [
{
"created": "Sun, 11 Dec 2022 18:11:51 GMT",
"version": "v1"
},
{
"created": "Sat, 17 Dec 2022 18:30:29 GMT",
"version": "v2"
}
] | 2023-02-15 | [
[
"Fursaev",
"D. V.",
""
],
[
"Pirozhenko",
"I. G.",
""
]
] | A method to study electromagnetic (EM) effects generated by a straight null cosmic string moving in classical EM fields is suggested. The string is shown to induce an additional EM field which can be described as a solution to homogeneous Maxwell equations with initial data set on a null surface, the string event horizon, where the string world-sheet belongs to. The initial data ensure the required holonomy of the string space-time caused by the gravity of the string. This characteristic initial value problem is used to study interaction of plane waves with null strings and perturbations by the strings of the Coulomb fields of electric charges. It is shown that parts of an incoming EM wave crossing the string horizon from different sides of the string are refracted with respect to each other and leave behind the string a wedge-like region of interference. A null string moving near an electric charge results in two effects: it creates a self-force of the charge and induces a pulse of EM radiation traveling away from the charge in the direction close to trajectory of the string. |
2205.09112 | Matteo Breschi | Matteo Breschi, Sebastiano Bernuzzi, Kabir Chakravarti, Alessandro
Camilletti, Aviral Prakash, Albino Perego | Kilohertz Gravitational Waves From Binary Neutron Star Mergers:
Numerical-relativity Informed Postmerger Model | null | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We present ${\tt NRPMw}$, an analytical model of gravitational-waves from
neutron star merger remnants informed using 618 numerical relativity (NR)
simulations. ${\tt NRPMw}$ is designed in the frequency domain using a
combination of complex Gaussian wavelets. The wavelet's parameters are
calibrated to equations of state (EOS) insensitive relations from NR data. The
NR simulations are computed with 21 EOS (7 of which are finite-temperature
microphysical models, and 3 of which contain quark phase transitions or
hyperonic degrees of freedom) and span total binary masses $M\in[2.4,3.4]~{\rm
M}_\odot$, mass ratios up to $q=2$, and (nonprecessing) dimensionless spins
magnitudes up to ${0.2}$. The theoretical uncertainties of the EOS-insensitive
relations are incorporated in ${\tt NRPMw}$ using recalibration parameters that
enhance the flexibility and accuracy of the model. ${\tt NRPMw}$ is NR-faithful
with fitting factors ${\gtrsim}0.9$ computed on an independent validation set
of 102 simulations.
| [
{
"created": "Wed, 18 May 2022 17:59:15 GMT",
"version": "v1"
}
] | 2022-05-19 | [
[
"Breschi",
"Matteo",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Chakravarti",
"Kabir",
""
],
[
"Camilletti",
"Alessandro",
""
],
[
"Prakash",
"Aviral",
""
],
[
"Perego",
"Albino",
""
]
] | We present ${\tt NRPMw}$, an analytical model of gravitational-waves from neutron star merger remnants informed using 618 numerical relativity (NR) simulations. ${\tt NRPMw}$ is designed in the frequency domain using a combination of complex Gaussian wavelets. The wavelet's parameters are calibrated to equations of state (EOS) insensitive relations from NR data. The NR simulations are computed with 21 EOS (7 of which are finite-temperature microphysical models, and 3 of which contain quark phase transitions or hyperonic degrees of freedom) and span total binary masses $M\in[2.4,3.4]~{\rm M}_\odot$, mass ratios up to $q=2$, and (nonprecessing) dimensionless spins magnitudes up to ${0.2}$. The theoretical uncertainties of the EOS-insensitive relations are incorporated in ${\tt NRPMw}$ using recalibration parameters that enhance the flexibility and accuracy of the model. ${\tt NRPMw}$ is NR-faithful with fitting factors ${\gtrsim}0.9$ computed on an independent validation set of 102 simulations. |
1801.08396 | Magd Elias Kahil | Magd E. Kahil | Dark Matter: The Problem of Motion | 17 LaTex pages | null | 10.1134/S020228931903006X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Equations of non-geodesic and non-geodesic deviations for different particles
are obtained, using a specific type of classes of the Bazanski Lagrangian. Such
type of paths has been found to describe the problem of variable mass in the
presence of Riemannian geometry. This may give rise to detect the effect of
dark matter which reveals the mystery of motion of celestial objects that are
not responding neither to Newtonian nor Einsteinian gravity. An important link
between non-geodesic equations and the dipolar particle or fluids has been
introduced to apply the concept of geometization of physics. This concept has
been already extended to represent the hydrodynamic equations in a geometric
way. Such an approach, demands to seek for an appropriate theory of gravity
able to describe different regions, eligible for detecting dark matter. Using
different versions of bi-metric theory of gravity, to examine their associate
non-geodesic paths. Due to implementing the geometrization concept, the
stability problem of non-geodesic equations are essential to be studied for
detecting the behavior of those objects in the presence of dark matter.
| [
{
"created": "Thu, 25 Jan 2018 13:34:27 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Feb 2018 00:54:47 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Apr 2019 08:26:29 GMT",
"version": "v3"
}
] | 2019-09-04 | [
[
"Kahil",
"Magd E.",
""
]
] | Equations of non-geodesic and non-geodesic deviations for different particles are obtained, using a specific type of classes of the Bazanski Lagrangian. Such type of paths has been found to describe the problem of variable mass in the presence of Riemannian geometry. This may give rise to detect the effect of dark matter which reveals the mystery of motion of celestial objects that are not responding neither to Newtonian nor Einsteinian gravity. An important link between non-geodesic equations and the dipolar particle or fluids has been introduced to apply the concept of geometization of physics. This concept has been already extended to represent the hydrodynamic equations in a geometric way. Such an approach, demands to seek for an appropriate theory of gravity able to describe different regions, eligible for detecting dark matter. Using different versions of bi-metric theory of gravity, to examine their associate non-geodesic paths. Due to implementing the geometrization concept, the stability problem of non-geodesic equations are essential to be studied for detecting the behavior of those objects in the presence of dark matter. |
2112.06312 | Branko Dragovich | Ivan Dimitrijevic, Branko Dragovich, Zoran Rakic and Jelena Stankovic | New Cosmological Solutions of a Nonlocal Gravity Model | 18 pages, submitted to the journal Symmetry | Symmetry 2022, 14, 3 | 10.3390/sym14010003 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A nonlocal gravity model (2.1) was introduced and considered recently [49],
and two exact cosmological solutions in flat space were presented. The first
solution is related to some radiation effects generated by nonlocal dynamics on
dark energy background, while the second one is a nonsingular time symmetric
bounce. In the present paper we investigate other possible exact cosmological
solutions and find some the new ones in nonflat space. Used nonlocal gravity
dynamics can change background topology. To solve the corresponding eqations of
motion, we first look for a solution of the eigenvalue problem $\Box (R
-4\Lambda) = q\ (R - 4\Lambda) .$ We also discuss possible extension of this
model with nonlocal operator symmetric under $\Box \longleftrightarrow
\Box^{-1}$ and its connection with another interesting nonlocal gravity model.
| [
{
"created": "Sun, 12 Dec 2021 20:05:12 GMT",
"version": "v1"
}
] | 2022-01-07 | [
[
"Dimitrijevic",
"Ivan",
""
],
[
"Dragovich",
"Branko",
""
],
[
"Rakic",
"Zoran",
""
],
[
"Stankovic",
"Jelena",
""
]
] | A nonlocal gravity model (2.1) was introduced and considered recently [49], and two exact cosmological solutions in flat space were presented. The first solution is related to some radiation effects generated by nonlocal dynamics on dark energy background, while the second one is a nonsingular time symmetric bounce. In the present paper we investigate other possible exact cosmological solutions and find some the new ones in nonflat space. Used nonlocal gravity dynamics can change background topology. To solve the corresponding eqations of motion, we first look for a solution of the eigenvalue problem $\Box (R -4\Lambda) = q\ (R - 4\Lambda) .$ We also discuss possible extension of this model with nonlocal operator symmetric under $\Box \longleftrightarrow \Box^{-1}$ and its connection with another interesting nonlocal gravity model. |
2212.11437 | Xuefeng Zhang | Lu Zheng, Shutao Yang, Xuefeng Zhang | Doppler effect in TianQin time-delay interferometry | 10 pages, 11 figures, revised to match the version accepted by Phys.
Rev. D | Phys. Rev. D 108, 022001 (2023) | 10.1103/PhysRevD.108.022001 | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | The current design of space-based gravitational wave detectors utilizes
heterodyne laser interferometry in inter-satellite science measurements.
Frequency variations of the heterodyne beatnotes are predominantly caused by
the Doppler effect from relative satellite motion along lines of sight.
Generally considered to be outside the measurement band, this Doppler frequency
shift appears to have been overlooked in numerical simulations of time-delay
interferometry (TDI). However, the potential impact on the implementation of
TDI should be assessed. The issue is particularly relevant to TianQin that
features geocentric orbits, because of strong gravity disturbances from the
Earth-Moon system at frequencies $<1\times 10^{-4}$ Hz. In this
proof-of-principle study, based on high-precision orbital data obtained from
detailed gravity field modeling, we incorporate the Doppler shift in the
generation of TianQin's beatnote phase signals. To remove the large-scale
Doppler phase drift at frequencies $<1\times 10^{-4}$ Hz, we develop a
high-performance high-pass filter and consider two possible processing
sequences, i.e., applying the filter before or after TDI combinations. Our
simulation results favor the former and demonstrate successful removal of the
low-frequency gravity disturbances for TianQin without degrading the TDI
performance, assuming 10 m pseudo-ranging uncertainty. The filtering scheme can
be used in developing the initial noise-reduction pipeline for TianQin.
| [
{
"created": "Thu, 22 Dec 2022 01:02:30 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Jul 2023 01:50:22 GMT",
"version": "v2"
}
] | 2023-07-19 | [
[
"Zheng",
"Lu",
""
],
[
"Yang",
"Shutao",
""
],
[
"Zhang",
"Xuefeng",
""
]
] | The current design of space-based gravitational wave detectors utilizes heterodyne laser interferometry in inter-satellite science measurements. Frequency variations of the heterodyne beatnotes are predominantly caused by the Doppler effect from relative satellite motion along lines of sight. Generally considered to be outside the measurement band, this Doppler frequency shift appears to have been overlooked in numerical simulations of time-delay interferometry (TDI). However, the potential impact on the implementation of TDI should be assessed. The issue is particularly relevant to TianQin that features geocentric orbits, because of strong gravity disturbances from the Earth-Moon system at frequencies $<1\times 10^{-4}$ Hz. In this proof-of-principle study, based on high-precision orbital data obtained from detailed gravity field modeling, we incorporate the Doppler shift in the generation of TianQin's beatnote phase signals. To remove the large-scale Doppler phase drift at frequencies $<1\times 10^{-4}$ Hz, we develop a high-performance high-pass filter and consider two possible processing sequences, i.e., applying the filter before or after TDI combinations. Our simulation results favor the former and demonstrate successful removal of the low-frequency gravity disturbances for TianQin without degrading the TDI performance, assuming 10 m pseudo-ranging uncertainty. The filtering scheme can be used in developing the initial noise-reduction pipeline for TianQin. |
1004.3937 | Fabio Dahia | F. Dahia and P. J. Felix da Silva | Static Observers in Curved Spaces and Non-inertial Frames in Minkowski
Spacetime | 28 pages, 4 figures. | null | 10.1007/s10714-010-1086-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Static observers in curved spacetimes may interpret their proper acceleration
as the opposite of a local gravitational field (in the Newtonian sense). Based
on this interpretation and motivated by the equivalence principle, we are led
to investigate congruences of timelike curves in Minkowski spacetime whose
acceleration field coincides with the acceleration field of static observers of
curved spaces. The congruences give rise to non-inertial frames that are
examined. Specifically we find, based on the locality principle, the embedding
of simultaneity hypersurfaces adapted to the non-inertial frame in an explicit
form for arbitrary acceleration fields. We also determine, from the Einstein
equations, a covariant field equation that regulates the behavior of the proper
acceleration of static observers in curved spacetimes. It corresponds to an
exact relativistic version of the Newtonian gravitational field equation. In
the specific case in which the level surfaces of the norm of the acceleration
field of the static observers are maximally symmetric two-dimensional spaces,
the energy-momentum tensor of the source is analyzed.
| [
{
"created": "Thu, 22 Apr 2010 14:52:41 GMT",
"version": "v1"
}
] | 2015-05-18 | [
[
"Dahia",
"F.",
""
],
[
"da Silva",
"P. J. Felix",
""
]
] | Static observers in curved spacetimes may interpret their proper acceleration as the opposite of a local gravitational field (in the Newtonian sense). Based on this interpretation and motivated by the equivalence principle, we are led to investigate congruences of timelike curves in Minkowski spacetime whose acceleration field coincides with the acceleration field of static observers of curved spaces. The congruences give rise to non-inertial frames that are examined. Specifically we find, based on the locality principle, the embedding of simultaneity hypersurfaces adapted to the non-inertial frame in an explicit form for arbitrary acceleration fields. We also determine, from the Einstein equations, a covariant field equation that regulates the behavior of the proper acceleration of static observers in curved spacetimes. It corresponds to an exact relativistic version of the Newtonian gravitational field equation. In the specific case in which the level surfaces of the norm of the acceleration field of the static observers are maximally symmetric two-dimensional spaces, the energy-momentum tensor of the source is analyzed. |
gr-qc/0304061 | Grigori Volovik | G.E. Volovik | Phenomenology of effective gravity | LaTeX file, 29 pages, no figures, prepared for proceedings of the
COSLAB school in Krakow, 2002; discussion on energy-momentum tensor is
extended, references are added | in: Patterns of Symmetry Breaking, H. Arodz et al. (eds.), Kluwer
Academic Publishers (2003), pp. 381--404 | null | null | gr-qc cond-mat hep-ph | null | The cosmological constant is not an absolute constant. The gravitating part
of the vacuum energy is adjusted to the energy density of matter and to other
types of the perturbations of the vacuum. We discuss how the vacuum energy
responds (i) to the curvature of space in the Einstein closed Universe; (ii) to
the expansion rate in the de Sitter Universe; and (iii) to the rotation in the
Goedel Universe. In all these steady state Universes, the gravitating vacuum
energy is zero in the absence of the perturbation, and is proportional to the
energy density of perturbation. This is in a full agreement with the
thermodynamic Gibbs-Duhem relation applicable to any quantum vacuum. It
demonstrates that (i) the cosmological constant is not huge, since according to
the Gibbs-Duhem relation the contribution of zero point fluctuations to the
vacuum energy is cancelled by the trans-Planckian degrees of freedom; (ii) the
cosmological constant is non-zero, since the perturbations of the vacuum state
induce the non-zero vacuum energy; and (iii) the gravitating vacuum energy is
on the order of the energy density of matter and/or of other perturbations. We
also consider the vacuum response to the non-steady-state perturbations. In
this case the Einstein equations are modified to include the non-covariant
corrections, which are responsible for the relaxation of the cosmological
constant. The connection to the quintessence is demonstrated. The problem of
the energy-momentum tensor for the gravitational field is discussed in terms of
effective gravity. The difference between the momentum and pseudo-momentum of
gravitational waves in general relativity is similar to that for sound waves in
hydrodynamics.
| [
{
"created": "Wed, 16 Apr 2003 13:13:41 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Apr 2003 12:11:21 GMT",
"version": "v2"
},
{
"created": "Wed, 7 May 2003 13:46:01 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Volovik",
"G. E.",
""
]
] | The cosmological constant is not an absolute constant. The gravitating part of the vacuum energy is adjusted to the energy density of matter and to other types of the perturbations of the vacuum. We discuss how the vacuum energy responds (i) to the curvature of space in the Einstein closed Universe; (ii) to the expansion rate in the de Sitter Universe; and (iii) to the rotation in the Goedel Universe. In all these steady state Universes, the gravitating vacuum energy is zero in the absence of the perturbation, and is proportional to the energy density of perturbation. This is in a full agreement with the thermodynamic Gibbs-Duhem relation applicable to any quantum vacuum. It demonstrates that (i) the cosmological constant is not huge, since according to the Gibbs-Duhem relation the contribution of zero point fluctuations to the vacuum energy is cancelled by the trans-Planckian degrees of freedom; (ii) the cosmological constant is non-zero, since the perturbations of the vacuum state induce the non-zero vacuum energy; and (iii) the gravitating vacuum energy is on the order of the energy density of matter and/or of other perturbations. We also consider the vacuum response to the non-steady-state perturbations. In this case the Einstein equations are modified to include the non-covariant corrections, which are responsible for the relaxation of the cosmological constant. The connection to the quintessence is demonstrated. The problem of the energy-momentum tensor for the gravitational field is discussed in terms of effective gravity. The difference between the momentum and pseudo-momentum of gravitational waves in general relativity is similar to that for sound waves in hydrodynamics. |
1111.0263 | Papantonopoulos Eleftherios | Theodoros Kolyvaris, George Koutsoumbas, Eleftherios Papantonopoulos
and George Siopsis | Scalar Hair from a Derivative Coupling of a Scalar Field to the Einstein
Tensor | 24 pages, 13 figures, title changed, improved discussion of the first
order perturbative analysis, reference added, published version | null | 10.1088/0264-9381/29/20/205011 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/3.0/ | We consider a gravitating system of vanishing cosmological constant
consisting of an electromagnetic field and a scalar field coupled to the
Einstein tensor. A Reissner-Nordstr\"om black hole undergoes a second-order
phase transition to a hairy black hole of generally anisotropic hair at a
certain critical temperature which we compute. The no-hair theorem is evaded
due to the coupling between the scalar field and the Einstein tensor. Within a
first order perturbative approach we calculate explicitly the properties of a
hairy black hole configuration near the critical temperature and show that it
is energetically favorable over the corresponding Reissner-Nordstr\"om black
hole.
| [
{
"created": "Tue, 1 Nov 2011 18:21:44 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Aug 2012 18:54:47 GMT",
"version": "v2"
}
] | 2015-06-03 | [
[
"Kolyvaris",
"Theodoros",
""
],
[
"Koutsoumbas",
"George",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
],
[
"Siopsis",
"George",
""
]
] | We consider a gravitating system of vanishing cosmological constant consisting of an electromagnetic field and a scalar field coupled to the Einstein tensor. A Reissner-Nordstr\"om black hole undergoes a second-order phase transition to a hairy black hole of generally anisotropic hair at a certain critical temperature which we compute. The no-hair theorem is evaded due to the coupling between the scalar field and the Einstein tensor. Within a first order perturbative approach we calculate explicitly the properties of a hairy black hole configuration near the critical temperature and show that it is energetically favorable over the corresponding Reissner-Nordstr\"om black hole. |
1306.4899 | Sante Carloni Dr | C. Garc\'ia-Meca, S. Carloni, C. Barcel\'o, G. Jannes, J.
S\'anchez-Dehesa, A. Mart\'inez | Spacetime transformation acoustics | 10 pages, 2 figures, published in Wave Motion 51, 785-797 (2014) | null | 10.1016/j.wavemoti.2014.01.008 | null | gr-qc cond-mat.mes-hall cond-mat.mtrl-sci | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A recently proposed analogue transformation method has allowed the extension
of transformation acoustics to general spacetime transformations. We analyze
here in detail the differences between this new analogue transformation
acoustics (ATA) method and the standard one (STA). We show explicitly that STA
is not suitable for transformations that mix space and time. ATA takes as
starting point the acoustic equation for the velocity potential, instead of
that for the pressure as in STA. This velocity-potential equation by itself
already allows for some transformations mixing space and time, but not all of
them. We explicitly obtain the entire set of transformations that do not leave
its form invariant. It is in these cases that ATA shows its true potential,
allowing for building a transformation acoustics method that enables the full
range of spacetime transformations. We provide an example of an important
transformation which cannot be achieved with STA. Using this transformation, we
design and simulate an acoustic frequency converter via the ATA approach.
Furthermore, in those cases in which one can apply both the STA and ATA
approaches, we study the different transformational properties of the
corresponding physical quantities.
| [
{
"created": "Thu, 20 Jun 2013 14:55:47 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Jul 2014 09:59:55 GMT",
"version": "v2"
}
] | 2014-07-09 | [
[
"García-Meca",
"C.",
""
],
[
"Carloni",
"S.",
""
],
[
"Barceló",
"C.",
""
],
[
"Jannes",
"G.",
""
],
[
"Sánchez-Dehesa",
"J.",
""
],
[
"Martínez",
"A.",
""
]
] | A recently proposed analogue transformation method has allowed the extension of transformation acoustics to general spacetime transformations. We analyze here in detail the differences between this new analogue transformation acoustics (ATA) method and the standard one (STA). We show explicitly that STA is not suitable for transformations that mix space and time. ATA takes as starting point the acoustic equation for the velocity potential, instead of that for the pressure as in STA. This velocity-potential equation by itself already allows for some transformations mixing space and time, but not all of them. We explicitly obtain the entire set of transformations that do not leave its form invariant. It is in these cases that ATA shows its true potential, allowing for building a transformation acoustics method that enables the full range of spacetime transformations. We provide an example of an important transformation which cannot be achieved with STA. Using this transformation, we design and simulate an acoustic frequency converter via the ATA approach. Furthermore, in those cases in which one can apply both the STA and ATA approaches, we study the different transformational properties of the corresponding physical quantities. |
1007.4213 | Richard O'Shaughnessy | Richard O'Shaughnessy (1,4), Birjoo Vaishnav (2), James Healy (3),
Deirdre Shoemaker (3) ((1) Center for Gravitational Wave Physics, Penn State
University, (2) Center for Gravitational Wave Astronomy, The University of
Texas at Brownsville, (3) Center for Relativistic Astrophysics, Georgia Tech,
(4) Center for Gravitation and Cosmology, University of Wisconsin-Milwaukee) | Intrinsic selection biases of ground-based gravitational wave searches
for high-mass BH-BH mergers | 18 pages, 15 figures, accepted by PRD. v2 is version accepted for
publication, including minor changes in response to referee feedback and
updated citations | Phys.Rev.D82:104006,2010 | 10.1103/PhysRevD.82.104006 | LIGO DCC P1000069; IGC-10/7-2 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The next generation of ground-based gravitational wave detectors may detect a
few mergers of comparable-mass M\simeq 100-1000 Msun ("intermediate-mass'', or
IMBH) spinning black holes. Black hole spin is known to have a significant
impact on the orbit, merger signal, and post-merger ringdown of any binary with
non-negligible spin. In particular, the detection volume for spinning binaries
depends significantly on the component black hole spins. We provide a fit to
the single-detector and isotropic-network detection volume versus (total) mass
and arbitrary spin for equal-mass binaries. Our analysis assumes matched
filtering to all significant available waveform power (up to l=6 available for
fitting, but only l<= 4 significant) estimated by an array of 64 numerical
simulations with component spins as large as S_{1,2}/M^2 <= 0.8. We provide a
spin-dependent estimate of our uncertainty, up to S_{1,2}/M^2 <= 1. For the
initial (advanced) LIGO detector, our fits are reliable for
$M\in[100,500]M_\odot$ ($M\in[100,1600]M_\odot$). In the online version of this
article, we also provide fits assuming incomplete information, such as the
neglect of higher-order harmonics. We briefly discuss how a strong selection
bias towards aligned spins influences the interpretation of future
gravitational wave detections of IMBH-IMBH mergers.
| [
{
"created": "Fri, 23 Jul 2010 20:45:02 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Oct 2010 17:02:15 GMT",
"version": "v2"
}
] | 2010-11-11 | [
[
"O'Shaughnessy",
"Richard",
""
],
[
"Vaishnav",
"Birjoo",
""
],
[
"Healy",
"James",
""
],
[
"Shoemaker",
"Deirdre",
""
]
] | The next generation of ground-based gravitational wave detectors may detect a few mergers of comparable-mass M\simeq 100-1000 Msun ("intermediate-mass'', or IMBH) spinning black holes. Black hole spin is known to have a significant impact on the orbit, merger signal, and post-merger ringdown of any binary with non-negligible spin. In particular, the detection volume for spinning binaries depends significantly on the component black hole spins. We provide a fit to the single-detector and isotropic-network detection volume versus (total) mass and arbitrary spin for equal-mass binaries. Our analysis assumes matched filtering to all significant available waveform power (up to l=6 available for fitting, but only l<= 4 significant) estimated by an array of 64 numerical simulations with component spins as large as S_{1,2}/M^2 <= 0.8. We provide a spin-dependent estimate of our uncertainty, up to S_{1,2}/M^2 <= 1. For the initial (advanced) LIGO detector, our fits are reliable for $M\in[100,500]M_\odot$ ($M\in[100,1600]M_\odot$). In the online version of this article, we also provide fits assuming incomplete information, such as the neglect of higher-order harmonics. We briefly discuss how a strong selection bias towards aligned spins influences the interpretation of future gravitational wave detections of IMBH-IMBH mergers. |
1809.09820 | Ernesto Contreras | Ernesto Contreras and Pedro Bargue\~no | Minimal Geometric Deformation in asymptotically (A-)dS space-times and
the isotropic sector for a polytropic black hole | 5 pages, typos corrected, references added | Eur. Phys. J. C 79, 985 (2018) | 10.1140/epjc/s10052-018-6472-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of the Minimal Geometric Deformation method, in this paper we
implement the inverse problem in a black hole scenario. In order to deal with
an anisotropic polytropic black hole solution of the Einstein field equations
with cosmological constant, the deformation method is slightly extended. After
obtaining the isotropic sector and the decoupler for an anisotropic (A-)dS
polytropic black hole solution, we emphasize a possible relation between
anisotropization/isotropization and the violation of the energy conditions.
| [
{
"created": "Wed, 26 Sep 2018 06:15:37 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Sep 2018 13:40:16 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Dec 2018 13:06:29 GMT",
"version": "v3"
}
] | 2018-12-04 | [
[
"Contreras",
"Ernesto",
""
],
[
"Bargueño",
"Pedro",
""
]
] | In the context of the Minimal Geometric Deformation method, in this paper we implement the inverse problem in a black hole scenario. In order to deal with an anisotropic polytropic black hole solution of the Einstein field equations with cosmological constant, the deformation method is slightly extended. After obtaining the isotropic sector and the decoupler for an anisotropic (A-)dS polytropic black hole solution, we emphasize a possible relation between anisotropization/isotropization and the violation of the energy conditions. |
1004.3559 | Andrei V. Frolov | Andrei V. Frolov | Non-linear Dynamics and Primordial Curvature Perturbations from
Preheating | 15 pages, 10 figures; review for CQG special issue | Class.Quant.Grav.27:124006,2010 | 10.1088/0264-9381/27/12/124006 | SCG-2010-04 | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper I review the theory and numerical simulations of non-linear
dynamics of preheating, a stage of dynamical instability at the end of
inflation during which homogeneous inflaton explosively decays and deposits its
energy into excitation of other matter fields. I focus on preheating in chaotic
inflation models, which proceeds via broad parametric resonance. I describe a
simple method to evaluate Floquet exponents, calculating stability diagrams of
Mathieu and Lame equations describing development of instability in $m^2\phi^2$
and $\lambda\phi^4$ preheating models. I discuss basic numerical methods and
issues, and present simulation results highlighting non-equilibrium
transitions, topological defect formation, late-time universality, turbulent
scaling and approach to thermalization. I explain how preheating can generate
large-scale primordial (non-Gaussian) curvature fluctuations manifest in cosmic
microwave background anisotropy and large scale structure, and discuss
potentially observable signatures of preheating.
| [
{
"created": "Tue, 20 Apr 2010 20:21:05 GMT",
"version": "v1"
},
{
"created": "Thu, 13 May 2010 19:56:58 GMT",
"version": "v2"
}
] | 2015-03-14 | [
[
"Frolov",
"Andrei V.",
""
]
] | In this paper I review the theory and numerical simulations of non-linear dynamics of preheating, a stage of dynamical instability at the end of inflation during which homogeneous inflaton explosively decays and deposits its energy into excitation of other matter fields. I focus on preheating in chaotic inflation models, which proceeds via broad parametric resonance. I describe a simple method to evaluate Floquet exponents, calculating stability diagrams of Mathieu and Lame equations describing development of instability in $m^2\phi^2$ and $\lambda\phi^4$ preheating models. I discuss basic numerical methods and issues, and present simulation results highlighting non-equilibrium transitions, topological defect formation, late-time universality, turbulent scaling and approach to thermalization. I explain how preheating can generate large-scale primordial (non-Gaussian) curvature fluctuations manifest in cosmic microwave background anisotropy and large scale structure, and discuss potentially observable signatures of preheating. |
2004.06276 | Daichi Tsuna | Naritaka Oshita, Daichi Tsuna, Niayesh Afshordi | Quantum Black Hole Seismology II: Applications to Astrophysical Black
Holes | 14 pages, 14 figures. NO and DT equally contributed to this work.
Accepted for publication in PRD | Phys. Rev. D 102, 024046 (2020) | 10.1103/PhysRevD.102.024046 | RESCEU-5/20 | gr-qc astro-ph.CO astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With the advent of gravitational wave astronomy, searching for gravitational
wave echoes from black holes (BHs) is becoming an interesting probe of their
quantum nature near their horizons. Newborn BHs may be strong emitters of
echoes, as they accompany large perturbations in the surrounding spacetime upon
formation. Utilizing the Quantum Black Hole Seismology framework (Oshita et al.
2020), we study the expected echoes upon BH formation resulting from neutron
star mergers and failed supernovae. For BH remnants from neutron star mergers,
we evaluate the consistency of these models with the recent claim on the
existence of echoes following the neutron star merger event GW170817. We find
that the claimed echoes in GW170817, if real, suggest that overtones contribute
a significant amount of energy in the ringdown of the remnant BH. We finally
discuss the detectability of echoes from failed supernovae by second and
third-generation gravitational wave detectors, and find that current (future)
detectors constrain physical reflectivity models for events occurring within a
few Mpc (a few x 10 Mpc). Detecting such echo signals may significantly
constrain the maximum mass and equation of state of neutron stars.
| [
{
"created": "Tue, 14 Apr 2020 02:42:15 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Jul 2020 01:28:45 GMT",
"version": "v2"
}
] | 2020-07-22 | [
[
"Oshita",
"Naritaka",
""
],
[
"Tsuna",
"Daichi",
""
],
[
"Afshordi",
"Niayesh",
""
]
] | With the advent of gravitational wave astronomy, searching for gravitational wave echoes from black holes (BHs) is becoming an interesting probe of their quantum nature near their horizons. Newborn BHs may be strong emitters of echoes, as they accompany large perturbations in the surrounding spacetime upon formation. Utilizing the Quantum Black Hole Seismology framework (Oshita et al. 2020), we study the expected echoes upon BH formation resulting from neutron star mergers and failed supernovae. For BH remnants from neutron star mergers, we evaluate the consistency of these models with the recent claim on the existence of echoes following the neutron star merger event GW170817. We find that the claimed echoes in GW170817, if real, suggest that overtones contribute a significant amount of energy in the ringdown of the remnant BH. We finally discuss the detectability of echoes from failed supernovae by second and third-generation gravitational wave detectors, and find that current (future) detectors constrain physical reflectivity models for events occurring within a few Mpc (a few x 10 Mpc). Detecting such echo signals may significantly constrain the maximum mass and equation of state of neutron stars. |
2405.06565 | Masroor C. Pookkillath | Masroor C. Pookkillath, Kazuya Koyama | Theory of interacting vector dark energy and fluid | 25 pages, 5 figures, revtex | null | null | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work, we study interaction between dark energy and dark matter, where
dark energy is described by a massive vector field, and dark matter is modelled
as a fluid. We present new interaction term, which affects only perturbations
and can give interesting phenomenology. Then we present a general Lagrangian
for the interacting vector dark energy with dark matter. For the dark energy,
we choose Proca theory with $G_{3}$ term to study its phenomenological
consequence. For this model, we explore both background and perturbation
dynamics. We also present the no-ghost condition for tensor modes and scalar
modes. Subsequently, we also study the evolution of the overdensities of both
baryon and cold dark matter in the high$-k$ limit. We show that the effective
gravitational coupling is modified for cold dark matter and baryon. We also
choose a simple concrete model and numerically show a suppression in the growth
of cold dark matter overdensity.
| [
{
"created": "Fri, 10 May 2024 16:09:55 GMT",
"version": "v1"
}
] | 2024-05-13 | [
[
"Pookkillath",
"Masroor C.",
""
],
[
"Koyama",
"Kazuya",
""
]
] | In this work, we study interaction between dark energy and dark matter, where dark energy is described by a massive vector field, and dark matter is modelled as a fluid. We present new interaction term, which affects only perturbations and can give interesting phenomenology. Then we present a general Lagrangian for the interacting vector dark energy with dark matter. For the dark energy, we choose Proca theory with $G_{3}$ term to study its phenomenological consequence. For this model, we explore both background and perturbation dynamics. We also present the no-ghost condition for tensor modes and scalar modes. Subsequently, we also study the evolution of the overdensities of both baryon and cold dark matter in the high$-k$ limit. We show that the effective gravitational coupling is modified for cold dark matter and baryon. We also choose a simple concrete model and numerically show a suppression in the growth of cold dark matter overdensity. |
2112.14273 | Puskar Mondal | Puskar Mondal | Local well-posedness of the Einstein-Yang-Mills system in CMCSHGC gauge | 32 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study the local well-posedness of the Einstein-Yang-Mills equations in
constant mean extrinsic curvature spatial harmonic generalized Coulomb gauge
(CMCSHGC). In this choice of gauge, the complete Einstein-Yang-Mills equations
reduce to a coupled elliptic-hyperbolic system. Utilizing the method developed
by Andersson and Moncrief \cite{andersson2003elliptic}, we establish the
existence of a unique, local, continuous-in-time solution of this coupled
system. This yields an `in time' continuation criteria of the solutions which
is to be used in the potential future proof of an improved continuation
criteria for this coupled system utilizing Moncrief's light cone estimate
technique.
| [
{
"created": "Tue, 28 Dec 2021 19:18:47 GMT",
"version": "v1"
}
] | 2021-12-30 | [
[
"Mondal",
"Puskar",
""
]
] | We study the local well-posedness of the Einstein-Yang-Mills equations in constant mean extrinsic curvature spatial harmonic generalized Coulomb gauge (CMCSHGC). In this choice of gauge, the complete Einstein-Yang-Mills equations reduce to a coupled elliptic-hyperbolic system. Utilizing the method developed by Andersson and Moncrief \cite{andersson2003elliptic}, we establish the existence of a unique, local, continuous-in-time solution of this coupled system. This yields an `in time' continuation criteria of the solutions which is to be used in the potential future proof of an improved continuation criteria for this coupled system utilizing Moncrief's light cone estimate technique. |
2405.09468 | Dimitrios Pesios | Dimitrios Pesios, Ioannis Koutalios, Dimitris Kugiumtzis, Nikolaos
Stergioulas | Predicting Binary Neutron Star Postmerger Spectra Using Artificial
Neural Networks | 20 pages, 12 figures, to be submitted to PRD | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves in the postmerger phase of binary neutron star mergers
may become detectable with planned upgrades of existing gravitational-wave
detectors or with more sensitive next-generation detectors. The construction of
template banks for the postmerger phase can facilitate signal detection and
parameter estimation. Here, we investigate the performance of an artificial
neural network in predicting simulation-based waveforms in the frequency domain
(restricted to the magnitude of the frequency spectrum and to equal-mass
models) that depend on three parameters that can be inferred through
observations, neutron star mass, tidal deformability, and the gradient of
radius versus mass. Compared to a baseline study using multiple linear
regression, we find that the artificial neural network can predict waveforms
with higher accuracy and more consistent performance in a cross-validation
study. We also demonstrate, through a recalibration procedure, that future
reduction of uncertainties in empirical relations that are used in our
hierarchical scheme will result in more accurate predicted postmerger spectra.
| [
{
"created": "Wed, 15 May 2024 16:03:51 GMT",
"version": "v1"
}
] | 2024-05-16 | [
[
"Pesios",
"Dimitrios",
""
],
[
"Koutalios",
"Ioannis",
""
],
[
"Kugiumtzis",
"Dimitris",
""
],
[
"Stergioulas",
"Nikolaos",
""
]
] | Gravitational waves in the postmerger phase of binary neutron star mergers may become detectable with planned upgrades of existing gravitational-wave detectors or with more sensitive next-generation detectors. The construction of template banks for the postmerger phase can facilitate signal detection and parameter estimation. Here, we investigate the performance of an artificial neural network in predicting simulation-based waveforms in the frequency domain (restricted to the magnitude of the frequency spectrum and to equal-mass models) that depend on three parameters that can be inferred through observations, neutron star mass, tidal deformability, and the gradient of radius versus mass. Compared to a baseline study using multiple linear regression, we find that the artificial neural network can predict waveforms with higher accuracy and more consistent performance in a cross-validation study. We also demonstrate, through a recalibration procedure, that future reduction of uncertainties in empirical relations that are used in our hierarchical scheme will result in more accurate predicted postmerger spectra. |
1902.01017 | Jian-Yang Zhu | Xi-Bin Li, Xiao-Gang Zheng and Jian-Yang Zhu | Spectra and entropy of multi-field warm inflation | 12 pages, 5 figures. Accepted for publication in Physical Review D | Phys.Rev.D99,043528(2019) | 10.1103/PhysRevD.99.043528 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the power spectra and entropy of two-field warm inflationary
scenario with canonical condition which is described by many-dimensional
stochastic differential equations. The field perturbations are analytically
calculated via a Volterra integral equation of the second kind, based on which
we obtain a spectra with leading order and first order of slow-roll parameters.
We also find the evolutions of background are not independent but relying on
dissipative coefficients, which is distinguished from that in cold inflation.
Then, we calculate the entropy on the basis of statistical physics theory by
introducing an entropy matrix. On super-horizon scale, the entropy matrix
follows the fluctuation-dissipation relation consistent with the
scale-invariance of spectra or the stationarity of field perturbations. The
entropy perturbation vanishes at both super-horizon and sub-horizon scale,
while narrow peaks generate at a specific scale which could be considered as
horizon. In addition, the second law of thermodynamics is followed as well.
| [
{
"created": "Mon, 4 Feb 2019 02:53:54 GMT",
"version": "v1"
}
] | 2019-03-12 | [
[
"Li",
"Xi-Bin",
""
],
[
"Zheng",
"Xiao-Gang",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | We study the power spectra and entropy of two-field warm inflationary scenario with canonical condition which is described by many-dimensional stochastic differential equations. The field perturbations are analytically calculated via a Volterra integral equation of the second kind, based on which we obtain a spectra with leading order and first order of slow-roll parameters. We also find the evolutions of background are not independent but relying on dissipative coefficients, which is distinguished from that in cold inflation. Then, we calculate the entropy on the basis of statistical physics theory by introducing an entropy matrix. On super-horizon scale, the entropy matrix follows the fluctuation-dissipation relation consistent with the scale-invariance of spectra or the stationarity of field perturbations. The entropy perturbation vanishes at both super-horizon and sub-horizon scale, while narrow peaks generate at a specific scale which could be considered as horizon. In addition, the second law of thermodynamics is followed as well. |
gr-qc/9909033 | Randall Guedes Teixeira | J. T. Lunardi, B. M. Pimentel, R. G. Teixeira (Sao Paulo, IFT) | Duffin-Kemmer-Petiau equation in Riemannian space-times | LaTex, 23 pages, no figures. Minor misprints in version 2 corrected.
Final version published | Published in Geometrical Aspects of Quantum Fields, ed. by, A.A.
Bytsenko, A.E. Golcalves and B.M. Pimentel, World Scientific, 2001. pp 111.
ISBN 9810245025 | 10.1142/9789812810366_fmatter | null | gr-qc hep-th | null | In this work we analyze the generalization of Duffin-Kemmer-Petiau equation
to the case of Riemannian space-times and show that the usual results for
Klein-Gordon and Proca equations in Riemannian space-times can be fully
recovered when one selects, respectively, the spin 0 and 1 sectors of
Duffin-Kemmer-Petiau theory.
| [
{
"created": "Fri, 10 Sep 1999 01:52:11 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Mar 2000 22:11:47 GMT",
"version": "v2"
},
{
"created": "Tue, 20 Mar 2001 20:27:35 GMT",
"version": "v3"
}
] | 2020-05-19 | [
[
"Lunardi",
"J. T.",
"",
"Sao Paulo, IFT"
],
[
"Pimentel",
"B. M.",
"",
"Sao Paulo, IFT"
],
[
"Teixeira",
"R. G.",
"",
"Sao Paulo, IFT"
]
] | In this work we analyze the generalization of Duffin-Kemmer-Petiau equation to the case of Riemannian space-times and show that the usual results for Klein-Gordon and Proca equations in Riemannian space-times can be fully recovered when one selects, respectively, the spin 0 and 1 sectors of Duffin-Kemmer-Petiau theory. |
gr-qc/0407112 | Dr. Anirudh Pradhan | Anirudh Pradhan and Purnima Pandey | Some Bianchi Type I Viscous Fluid Cosmological Models with a Variable
Cosmological Constant | 16 pages | Astrophys.Space Sci. 301 (2006) 127-134 | 10.1007/s10509-006-0141-6 | null | gr-qc | null | Some Bianchi type I viscous fluid cosmological models with a variable
cosmological constant are investigated in which the expansion is considered
only in two direction i.e. one of the Hubble parameter $(H_{1} =
\frac{A_{4}}{A})$ is zero. The viscosity coefficient of bulk viscous fluid is
assumed to be a power function of mass density whereas the coefficient of shear
viscosity is considered as constant in first case whereas in other case it is
taken as proportional to scale of expansion in the model. The cosmological
constant $\Lambda$ is found to be positive and is a decreasing function of time
which is supported by results from recent supernovae Ia observations. Some
physical and geometric properties of the models are also discussed.
| [
{
"created": "Thu, 29 Jul 2004 10:38:30 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Pradhan",
"Anirudh",
""
],
[
"Pandey",
"Purnima",
""
]
] | Some Bianchi type I viscous fluid cosmological models with a variable cosmological constant are investigated in which the expansion is considered only in two direction i.e. one of the Hubble parameter $(H_{1} = \frac{A_{4}}{A})$ is zero. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density whereas the coefficient of shear viscosity is considered as constant in first case whereas in other case it is taken as proportional to scale of expansion in the model. The cosmological constant $\Lambda$ is found to be positive and is a decreasing function of time which is supported by results from recent supernovae Ia observations. Some physical and geometric properties of the models are also discussed. |
2312.11620 | David Radice | Harshraj Bandyopadhyay and David Radice and Aviral Prakash and Arnab
Dhani and Domenico Logoteta and Albino Perego and Rahul Kashyap | Do black holes remember what they are made of? | 15 pages, 7 figures. Accepted version | null | 10.1088/1361-6382/ad56ed | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the ringdown signal of black holes formed in prompt-collapse binary
neutron star mergers. We analyze data from $47$ numerical relativity
simulations. We show that the $(\ell=2,m=2)$ and $(\ell=2,m=1)$ multipoles of
the gravitational wave signal are well fitted by decaying damped exponentials,
as predicted by black-hole perturbation theory. We show that the ratio of the
amplitude in the two modes depends on the progenitor binary mass ratio $q$ and
reduced tidal parameter $\tilde\Lambda$. Unfortunately, the numerical
uncertainty in our data is too large to fully quantify this dependency. If
confirmed, these results will enable novel tests of general relativity in the
presence of matter with next-generation gravitational-wave observatories.
| [
{
"created": "Mon, 18 Dec 2023 19:00:01 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jun 2024 16:40:44 GMT",
"version": "v2"
}
] | 2024-06-13 | [
[
"Bandyopadhyay",
"Harshraj",
""
],
[
"Radice",
"David",
""
],
[
"Prakash",
"Aviral",
""
],
[
"Dhani",
"Arnab",
""
],
[
"Logoteta",
"Domenico",
""
],
[
"Perego",
"Albino",
""
],
[
"Kashyap",
"Rahul",
""
]
... | We study the ringdown signal of black holes formed in prompt-collapse binary neutron star mergers. We analyze data from $47$ numerical relativity simulations. We show that the $(\ell=2,m=2)$ and $(\ell=2,m=1)$ multipoles of the gravitational wave signal are well fitted by decaying damped exponentials, as predicted by black-hole perturbation theory. We show that the ratio of the amplitude in the two modes depends on the progenitor binary mass ratio $q$ and reduced tidal parameter $\tilde\Lambda$. Unfortunately, the numerical uncertainty in our data is too large to fully quantify this dependency. If confirmed, these results will enable novel tests of general relativity in the presence of matter with next-generation gravitational-wave observatories. |
1503.01888 | Roberto Casadio | Roberto Casadio, Octavian Micu, Dejan Stojkovic | Inner Horizon of the Quantum Reissner-Nordstr\"om Black Holes | RevTeX4, 7 pages, 4 figures: new section about HWF added for clarity,
references updated, results unchanged. Version to appear in JHEP | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the nature of the inner Cauchy horizon of a Reissner-Nordstr\"om
black hole in a quantum context by means of the horizon wave-function obtained
from modelling the electrically charged source as a Gaussian wave-function. Our
main finding it that there is a significant range of black hole mass (around
the Planck scale) and specific charge for which the probability of realizing
the inner horizon is negligible. This result suggests that any semiclassical
instability one expects near the inner horizon may not be occur in quantum
black holes.
| [
{
"created": "Fri, 6 Mar 2015 09:35:08 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Apr 2015 10:11:37 GMT",
"version": "v2"
}
] | 2015-04-29 | [
[
"Casadio",
"Roberto",
""
],
[
"Micu",
"Octavian",
""
],
[
"Stojkovic",
"Dejan",
""
]
] | We study the nature of the inner Cauchy horizon of a Reissner-Nordstr\"om black hole in a quantum context by means of the horizon wave-function obtained from modelling the electrically charged source as a Gaussian wave-function. Our main finding it that there is a significant range of black hole mass (around the Planck scale) and specific charge for which the probability of realizing the inner horizon is negligible. This result suggests that any semiclassical instability one expects near the inner horizon may not be occur in quantum black holes. |
2403.01490 | Gang Wang | Gang Wang | Time delay interferometry with minimal null frequencies | 14 pages, 10 figures, accepted for publication in PRD | null | null | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Time delay interferometry (TDI) is a key technique employed in gravitational
wave (GW) space missions to mitigate laser frequency noise by combining
multiple laser links and establishing an equivalent equal arm interferometry.
The null frequencies will be introduced in noise spectra and GW response when
the periodical signal/noise is canceled in synthesized laser links. These
frequencies are characteristic frequencies (CFs) of a TDI which related to its
geometry of combination. In this work, we implement a second-generation TDI
configuration referred to as hybrid Relay to perform noise suppressions and
data analysis, whose CFs are only one-quarter that of the fiducial
second-generation Michelson observables. We examine the performance of TDI
configuration in laser noise cancellation and clock noise suppression and
justify its essential capabilities. To assess its robustness for signal
extraction, we simulate data containing GW signals from massive black hole
binaries and perform parameter inferences with comparisons against the fiducial
Michelson TDI configuration. The results demonstrate that the alternative TDI
solution could be more robust than Michelson in fulfilling data analysis.
| [
{
"created": "Sun, 3 Mar 2024 11:57:23 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jun 2024 02:57:57 GMT",
"version": "v2"
}
] | 2024-06-26 | [
[
"Wang",
"Gang",
""
]
] | Time delay interferometry (TDI) is a key technique employed in gravitational wave (GW) space missions to mitigate laser frequency noise by combining multiple laser links and establishing an equivalent equal arm interferometry. The null frequencies will be introduced in noise spectra and GW response when the periodical signal/noise is canceled in synthesized laser links. These frequencies are characteristic frequencies (CFs) of a TDI which related to its geometry of combination. In this work, we implement a second-generation TDI configuration referred to as hybrid Relay to perform noise suppressions and data analysis, whose CFs are only one-quarter that of the fiducial second-generation Michelson observables. We examine the performance of TDI configuration in laser noise cancellation and clock noise suppression and justify its essential capabilities. To assess its robustness for signal extraction, we simulate data containing GW signals from massive black hole binaries and perform parameter inferences with comparisons against the fiducial Michelson TDI configuration. The results demonstrate that the alternative TDI solution could be more robust than Michelson in fulfilling data analysis. |
0901.2362 | Sean Gryb B | Sean B. Gryb | Implementing Mach's Principle Using Gauge Theory | 31 pages, 3 figures. Clarifications added, figures and typos fixed,
journal-ref updated | Phys.Rev.D80:024018,2009 | 10.1103/PhysRevD.80.024018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reformulate an approach fist given by Barbour and Bertotti (BB) for
implementing Mach's principle for nonrelativistic particles. This reformulation
can deal with arbitrary symmetry groups and finite group elements. Applying
these techniques to U(1) and SU(N) invariant scalar field theories, we show
that BB's proposal is nearly equivalent to defining a covariant derivative
using a dynamical connection. We then propose a modified version of the BB
method which implements Mach's principle using gauge theory techniques and
argue that this modified method is equivalent to the original. Given this
connection between the particle models and Yang-Mills theories, we consider the
effect of dynamic curvature as a possible generalization of the BB scheme.
Since the BB method can be used as a novel way of deriving geometrodynamics,
the connection with gauge theory may shed new light on the gauge properties of
the gravitational field.
| [
{
"created": "Thu, 15 Jan 2009 22:26:03 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Jul 2009 15:30:37 GMT",
"version": "v2"
}
] | 2010-04-14 | [
[
"Gryb",
"Sean B.",
""
]
] | We reformulate an approach fist given by Barbour and Bertotti (BB) for implementing Mach's principle for nonrelativistic particles. This reformulation can deal with arbitrary symmetry groups and finite group elements. Applying these techniques to U(1) and SU(N) invariant scalar field theories, we show that BB's proposal is nearly equivalent to defining a covariant derivative using a dynamical connection. We then propose a modified version of the BB method which implements Mach's principle using gauge theory techniques and argue that this modified method is equivalent to the original. Given this connection between the particle models and Yang-Mills theories, we consider the effect of dynamic curvature as a possible generalization of the BB scheme. Since the BB method can be used as a novel way of deriving geometrodynamics, the connection with gauge theory may shed new light on the gauge properties of the gravitational field. |
1412.3424 | Rafael Ferraro | Rafael Ferraro and Franco Fiorini | Remnant group of local Lorentz transformations in f(T) theories | 10 pages. Minor changes. To appear in PRD | Phys. Rev. D 91, 064019 (2015) | 10.1103/PhysRevD.91.064019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the extended teleparallel gravitational theories, known as
f(T) theories, inherit some on shell local Lorentz invariance associated with
the tetrad field defining the spacetime structure. We discuss some enlightening
examples, such as Minkowski spacetime and cosmological
(Friedmann-Robertson-Walker and Bianchi type I) manifolds. In the first case,
we show that the absence of gravity reveals itself as an incapability in the
selection of a preferred parallelization at a local level, due to the fact that
the infinitesimal local Lorentz subgroup acts as a symmetry group of the frame
characterizing Minkowski spacetime. Finite transformations are also discussed
in these examples and, contrary to the common lore on the subject, we conclude
that the set of tetrads responsible for the parallelization of these manifolds
is quite vast and that the remnant group of local Lorentz transformations
includes one and two dimensional Abelian subgroups of the Lorentz group.
| [
{
"created": "Wed, 10 Dec 2014 19:38:24 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Dec 2014 19:49:01 GMT",
"version": "v2"
},
{
"created": "Wed, 18 Feb 2015 14:14:21 GMT",
"version": "v3"
}
] | 2015-03-18 | [
[
"Ferraro",
"Rafael",
""
],
[
"Fiorini",
"Franco",
""
]
] | It is shown that the extended teleparallel gravitational theories, known as f(T) theories, inherit some on shell local Lorentz invariance associated with the tetrad field defining the spacetime structure. We discuss some enlightening examples, such as Minkowski spacetime and cosmological (Friedmann-Robertson-Walker and Bianchi type I) manifolds. In the first case, we show that the absence of gravity reveals itself as an incapability in the selection of a preferred parallelization at a local level, due to the fact that the infinitesimal local Lorentz subgroup acts as a symmetry group of the frame characterizing Minkowski spacetime. Finite transformations are also discussed in these examples and, contrary to the common lore on the subject, we conclude that the set of tetrads responsible for the parallelization of these manifolds is quite vast and that the remnant group of local Lorentz transformations includes one and two dimensional Abelian subgroups of the Lorentz group. |
gr-qc/9902039 | Ishwaree Prasad Neupane | Ishwaree P.Neupane | Planetary Perturbation with Cosmological Constant | 6 pages, RevTex, some corrections on gr-qc/9812096 | null | null | null | gr-qc | null | A contribution of quantum vacuum to the energy momentum tensor is inevitably
experienced in the present universe. One requires the presence of non-zero
cosmological constant ($\Lambda$) to make the various observations consistent.
A case of $\Lambda$ in the Schwarzschild de Sitter space-time shows that
precession of perihelion orbit provides a sensative solar test for non-zero
$\Lambda$. Application of the relations involving $\Lambda$ to the planetery
perturbation indicates the values near to the present bound on $\Lambda$. Also
suggested are some relations in vacuum dominated flat universe with a positive
$\Lambda$.
| [
{
"created": "Fri, 12 Feb 1999 05:52:54 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Neupane",
"Ishwaree P.",
""
]
] | A contribution of quantum vacuum to the energy momentum tensor is inevitably experienced in the present universe. One requires the presence of non-zero cosmological constant ($\Lambda$) to make the various observations consistent. A case of $\Lambda$ in the Schwarzschild de Sitter space-time shows that precession of perihelion orbit provides a sensative solar test for non-zero $\Lambda$. Application of the relations involving $\Lambda$ to the planetery perturbation indicates the values near to the present bound on $\Lambda$. Also suggested are some relations in vacuum dominated flat universe with a positive $\Lambda$. |
1007.4820 | Neil J. Cornish | Neil J. Cornish | Fast Fisher Matrices and Lazy Likelihoods | 4 pages. Simpler Implementation | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Theoretical studies in gravitational wave astronomy often require the
calculation of Fisher Information Matrices and Likelihood functions, which in a
direct approach entail the costly step of computing gravitational waveforms.
Here I describe an alternative technique that sidesteps the need to compute
full waveforms, resulting in significant computational savings. I describe how
related techniques can be used to speed up Bayesian inference applied to real
gravitational wave data.
| [
{
"created": "Tue, 27 Jul 2010 20:43:25 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Aug 2010 19:51:54 GMT",
"version": "v2"
},
{
"created": "Wed, 6 Feb 2013 19:53:45 GMT",
"version": "v3"
}
] | 2013-02-07 | [
[
"Cornish",
"Neil J.",
""
]
] | Theoretical studies in gravitational wave astronomy often require the calculation of Fisher Information Matrices and Likelihood functions, which in a direct approach entail the costly step of computing gravitational waveforms. Here I describe an alternative technique that sidesteps the need to compute full waveforms, resulting in significant computational savings. I describe how related techniques can be used to speed up Bayesian inference applied to real gravitational wave data. |
2210.08718 | Chao Wang | Chao Wang, Bin Wu, Zhen Ming Xu, Wen Li Yang | Thermodynamic geometry of the RN-AdS black hole and non-local
observables | 13 oages, 7 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we show the relation between the thermodynamic geometry of a
four-dimensional Reissner-Nordstrom-AdS (RN-AdS) black hole and non-local
observables in boundary field theory. Instead of introducing the critical point
associating with the black hole charge to nondimensionalize the thermodynamics
parameters, we use the cosmological constant to rescale these variables, so
that a universal specific equation of state of the black hole is obtained.
Further, the correspondence between thermodynamic properties of the black hole
and the oscillating behaviors of the non-local observables has been studied
numerically. Our results indicate that the study of the dual field theory will
reveal to us the thermodynamic geometry of the AdS black hole.
| [
{
"created": "Mon, 17 Oct 2022 03:19:20 GMT",
"version": "v1"
}
] | 2022-10-18 | [
[
"Wang",
"Chao",
""
],
[
"Wu",
"Bin",
""
],
[
"Xu",
"Zhen Ming",
""
],
[
"Yang",
"Wen Li",
""
]
] | In this paper, we show the relation between the thermodynamic geometry of a four-dimensional Reissner-Nordstrom-AdS (RN-AdS) black hole and non-local observables in boundary field theory. Instead of introducing the critical point associating with the black hole charge to nondimensionalize the thermodynamics parameters, we use the cosmological constant to rescale these variables, so that a universal specific equation of state of the black hole is obtained. Further, the correspondence between thermodynamic properties of the black hole and the oscillating behaviors of the non-local observables has been studied numerically. Our results indicate that the study of the dual field theory will reveal to us the thermodynamic geometry of the AdS black hole. |
gr-qc/0512119 | Mihalis Dafermos | Mihalis Dafermos and Igor Rodnianski | The red-shift effect and radiation decay on black hole spacetimes | 43 pages, 8 figures | Comm. Pure Appl. Math. 62 (2009), 859-919 | null | null | gr-qc math.AP | null | We consider solutions to the linear wave equation on a (maximally extended)
Schwarzschild spacetime, assuming only that the solution decays suitably at
spatial infinity on a complete Cauchy hypersurface. (In particular, we allow
the support of the solution to contain the bifurcate event horizon.) We prove
uniform decay bounds for the solution in the exterior regions, including the
uniform bound Cv_+^{-1}, where v_+ denotes max{v,1} and v denotes
Eddington-Finkelstein advanced time. We also prove uniform decay bounds for the
flux of energy through the event horizon and null infinity. The estimates near
the event horizon exploit an integral energy identity normalized to local
observers. This estimate can be thought to quantify the celebrated red-shift
effect. The results in particular give an independent proof of the classical
uniform boundedness theorem of Kay and Wald, without recourse to the discrete
isometries of spacetime.
| [
{
"created": "Wed, 21 Dec 2005 00:02:40 GMT",
"version": "v1"
}
] | 2014-12-30 | [
[
"Dafermos",
"Mihalis",
""
],
[
"Rodnianski",
"Igor",
""
]
] | We consider solutions to the linear wave equation on a (maximally extended) Schwarzschild spacetime, assuming only that the solution decays suitably at spatial infinity on a complete Cauchy hypersurface. (In particular, we allow the support of the solution to contain the bifurcate event horizon.) We prove uniform decay bounds for the solution in the exterior regions, including the uniform bound Cv_+^{-1}, where v_+ denotes max{v,1} and v denotes Eddington-Finkelstein advanced time. We also prove uniform decay bounds for the flux of energy through the event horizon and null infinity. The estimates near the event horizon exploit an integral energy identity normalized to local observers. This estimate can be thought to quantify the celebrated red-shift effect. The results in particular give an independent proof of the classical uniform boundedness theorem of Kay and Wald, without recourse to the discrete isometries of spacetime. |
1406.5703 | Francisco Lobo | Mahdi Kord Zangeneh, Francisco S. N. Lobo, Nematollah Riazi | Higher-dimensional evolving wormholes satisfying the null energy
condition | 9 pages, 4 figures. V2: References added, minor corrections
(including in the Flamm discussion); to appear in PRD | Phys.Rev.D90:024072,2014 | 10.1103/PhysRevD.90.024072 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we consider the possibility of expanding wormholes in
higher-dimensions, which is an important ingredient of modern theories of
fundamental physics. An important motivation is that non-trivial topological
objects such as microscopic wormholes may have been enlarged to macroscopic
sizes in an expanding inflationary cosmological background. Since the Ricci
scalar is only a function of time in standard cosmological models, we use this
property as a simplifying assumption. More specifically, we consider a
particular class of wormhole solutions corresponding to the choice of a
spatially homogeneous Ricci scalar. The possibility of obtaining solutions with
normal and exotic matter is explored and we find a variety of solutions
including those in four dimensions that satisfy the null energy condition (NEC)
in specific time intervals. In particular, for five dimensions, we find
solutions that satisfy the NEC throughout the respective evolution.
| [
{
"created": "Sun, 22 Jun 2014 11:12:22 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Jul 2014 15:07:34 GMT",
"version": "v2"
}
] | 2014-07-30 | [
[
"Zangeneh",
"Mahdi Kord",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Riazi",
"Nematollah",
""
]
] | In this work, we consider the possibility of expanding wormholes in higher-dimensions, which is an important ingredient of modern theories of fundamental physics. An important motivation is that non-trivial topological objects such as microscopic wormholes may have been enlarged to macroscopic sizes in an expanding inflationary cosmological background. Since the Ricci scalar is only a function of time in standard cosmological models, we use this property as a simplifying assumption. More specifically, we consider a particular class of wormhole solutions corresponding to the choice of a spatially homogeneous Ricci scalar. The possibility of obtaining solutions with normal and exotic matter is explored and we find a variety of solutions including those in four dimensions that satisfy the null energy condition (NEC) in specific time intervals. In particular, for five dimensions, we find solutions that satisfy the NEC throughout the respective evolution. |
1910.00284 | Luis Herrera | L: Herrera | Causal heat conduction contravening the fading memory paradigm | 22 pages Latex. Published in the special issue of Entropy: Entropy
generation and heat transfer II | Entropy 21, 950, (2019) | null | null | gr-qc physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a causal heat conduction model based on a heat kernel violating
the fading memory paradigm. The resulting transport equation produces an
equation for the temperature. The model is applied to the discussion of two
important issues such as the thermohaline convection and the nuclear burning
(in)stability. In both cases the behaviour of the system appears to be strongly
dependent on the transport equation assumed, bringing out the effects of our
specific kernel on the final description of these problems. A possible
relativistic version of the obtained transport equation is presented.
| [
{
"created": "Tue, 1 Oct 2019 10:00:27 GMT",
"version": "v1"
}
] | 2019-10-02 | [
[
"L",
"",
""
],
[
":",
"",
""
],
[
"Herrera",
"",
""
]
] | We propose a causal heat conduction model based on a heat kernel violating the fading memory paradigm. The resulting transport equation produces an equation for the temperature. The model is applied to the discussion of two important issues such as the thermohaline convection and the nuclear burning (in)stability. In both cases the behaviour of the system appears to be strongly dependent on the transport equation assumed, bringing out the effects of our specific kernel on the final description of these problems. A possible relativistic version of the obtained transport equation is presented. |
2111.08407 | Jan Henryk Kwapisz | Jan Chojnacki, Jan Henryk Kwapisz | Finite Action Principle and wormholes | Contribution to the Proceedings of the Sixteenth Marcel Grossmann
Meeting (MG16), July 5-10, 2021 based on a invited parallel talk(s) in the
Horava-Lifshitz Gravity session | null | 10.1142/9789811269776_0082 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work, we elaborate on the finite action for wormholes in higher
derivative theories. Both non-traversable and traversable wormholes in theories
with higher curvature invariants posses finite action.
| [
{
"created": "Tue, 16 Nov 2021 12:13:44 GMT",
"version": "v1"
}
] | 2023-01-27 | [
[
"Chojnacki",
"Jan",
""
],
[
"Kwapisz",
"Jan Henryk",
""
]
] | In this work, we elaborate on the finite action for wormholes in higher derivative theories. Both non-traversable and traversable wormholes in theories with higher curvature invariants posses finite action. |
2003.00564 | Jeferson de Oliveira | B. Cuadros-Melgar, R. D. B. Fontana, Jeferson de Oliveira | Late-time tails, entropy aspects, and stability of black holes with
anisotropic fluids | 23 pages, 4 figures | The European Physical Journal C volume 80, Article number: 848
(2020) | 10.1140/epjc/s10052-020-8415-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we consider black holes surrounded by anisotropic fluids in four
dimensions. We first study the causal structure of these solutions showing some
similarities and differences with Reissner-Nordstr\"om-de Sitter black holes.
In addition, we consider scalar perturbations on this background geometry and
compute the corresponding quasinormal modes. Moreover, we discuss the late-time
behavior of the perturbations finding an interesting new feature, i.e., the
presence of a subdominant power-law tail term. Likewise, we compute the
Bekenstein entropy bound and the first semiclassical correction to the black
hole entropy using the brick wall method, showing their universality. Finally,
we also discuss the thermodynamical stability of the model.
| [
{
"created": "Sun, 1 Mar 2020 19:23:24 GMT",
"version": "v1"
}
] | 2020-11-20 | [
[
"Cuadros-Melgar",
"B.",
""
],
[
"Fontana",
"R. D. B.",
""
],
[
"de Oliveira",
"Jeferson",
""
]
] | In this work we consider black holes surrounded by anisotropic fluids in four dimensions. We first study the causal structure of these solutions showing some similarities and differences with Reissner-Nordstr\"om-de Sitter black holes. In addition, we consider scalar perturbations on this background geometry and compute the corresponding quasinormal modes. Moreover, we discuss the late-time behavior of the perturbations finding an interesting new feature, i.e., the presence of a subdominant power-law tail term. Likewise, we compute the Bekenstein entropy bound and the first semiclassical correction to the black hole entropy using the brick wall method, showing their universality. Finally, we also discuss the thermodynamical stability of the model. |
2206.04366 | Marica Minucci | Marica Minucci, Rodrigo Panosso Macedo and Juan Antonio Valiente Kroon | The Maxwell-scalar field system near spatial infinity | null | null | 10.1063/5.0104602 | null | gr-qc math.AP | http://creativecommons.org/licenses/by/4.0/ | We make use of Friedrich's representation of spatial infinity to study
asymptotic expansions of the Maxwell-scalar field system near spatial infinity.
The main objective of this analysis is to understand the effects of the
non-linearities of this system on the regularity of solutions and
polyhomogeneous expansions at null infinity and, in particular, at the critical
sets where null infinity touches spatial infinity. The main outcome from our
analysis is that the nonlinear interaction makes both fields more singular at
the conformal boundary than what is seen when the fields are non-interacting.
In particular, we find a whole new class of logarithmic terms in the asymptotic
expansions which depend on the coupling constant between the Maxwell and scalar
fields. We analyse the implications of these results on the peeling (or rather
lack thereof) of the fields at null infinity.
| [
{
"created": "Thu, 9 Jun 2022 09:22:16 GMT",
"version": "v1"
}
] | 2022-09-14 | [
[
"Minucci",
"Marica",
""
],
[
"Macedo",
"Rodrigo Panosso",
""
],
[
"Kroon",
"Juan Antonio Valiente",
""
]
] | We make use of Friedrich's representation of spatial infinity to study asymptotic expansions of the Maxwell-scalar field system near spatial infinity. The main objective of this analysis is to understand the effects of the non-linearities of this system on the regularity of solutions and polyhomogeneous expansions at null infinity and, in particular, at the critical sets where null infinity touches spatial infinity. The main outcome from our analysis is that the nonlinear interaction makes both fields more singular at the conformal boundary than what is seen when the fields are non-interacting. In particular, we find a whole new class of logarithmic terms in the asymptotic expansions which depend on the coupling constant between the Maxwell and scalar fields. We analyse the implications of these results on the peeling (or rather lack thereof) of the fields at null infinity. |
gr-qc/9608064 | Jorge Pullin | John Baker, Andrew Abrahams, Peter Anninos, Steve Brandt, Richard
Price, Jorge Pullin, Edward Seidel | The collision of boosted black holes | 8 pages, RevTeX, 3 figures included with epsf | Phys.Rev. D55 (1997) 829-834 | 10.1103/PhysRevD.55.829 | CGQG-96/8-3 | gr-qc | null | We study the radiation from a collision of black holes with equal and
opposite linear momenta. Results are presented from a full numerical relativity
treatment and are compared with the results from a ``close-slow''
approximation. The agreement is remarkable, and suggests several insights about
the generation of gravitational radiation in black hole collisions.
| [
{
"created": "Wed, 28 Aug 1996 01:44:51 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Baker",
"John",
""
],
[
"Abrahams",
"Andrew",
""
],
[
"Anninos",
"Peter",
""
],
[
"Brandt",
"Steve",
""
],
[
"Price",
"Richard",
""
],
[
"Pullin",
"Jorge",
""
],
[
"Seidel",
"Edward",
""
]
] | We study the radiation from a collision of black holes with equal and opposite linear momenta. Results are presented from a full numerical relativity treatment and are compared with the results from a ``close-slow'' approximation. The agreement is remarkable, and suggests several insights about the generation of gravitational radiation in black hole collisions. |
2109.06104 | Kristina Giesel | Kristina Giesel and Almut Vetter | Coherent states for fractional powers of the harmonic oscillator
Hamiltonian | 36 pages | Universe 2021, 7, 442 | 10.3390/universe7110442 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspired by special and general relativistic systems that can have
Hamiltonians involving square roots, or more general fractional powers, in this
article we address the question how a suitable set of coherent states for such
systems can be obtained. This becomes a relevant topic if the semiclassical
sector of a given quantum theory wants to be analysed. As a simple setup we
consider the toy model of a deparametrised system with one constraint that
involves a fractional power of the harmonic oscillator Hamiltonian operator and
we discuss two approaches for finding suitable coherent states for this system.
In the first approach we consider Dirac quantisation and group averaging that
have been used by Ashtekar et. al. but only for integer powers of operators.
Our generalisation to fractional powers yields in the case of the toy model a
suitable set of coherent states. The second approach is inspired by coherent
states based on a fractional Poisson distribution introduced by Laskin, which
however turn out not to satisfy all properties to yield good semiclassical
results for the operators considered here and in particular do not satisfy a
resolution of identity as claimed. Therefore, we present a generalisation of
the standard harmonic oscillator coherent states to states involving fractional
labels, which approximate the fractional operators in our toy model
semiclassically more accurately and satisfy a resolution of identity. In
addition, motivated by the way the proof of the resolution of identity is
performed, we consider these kind of coherent states also for the polymerised
harmonic oscillator and discuss their semiclassical properties
| [
{
"created": "Mon, 13 Sep 2021 16:25:49 GMT",
"version": "v1"
}
] | 2021-11-18 | [
[
"Giesel",
"Kristina",
""
],
[
"Vetter",
"Almut",
""
]
] | Inspired by special and general relativistic systems that can have Hamiltonians involving square roots, or more general fractional powers, in this article we address the question how a suitable set of coherent states for such systems can be obtained. This becomes a relevant topic if the semiclassical sector of a given quantum theory wants to be analysed. As a simple setup we consider the toy model of a deparametrised system with one constraint that involves a fractional power of the harmonic oscillator Hamiltonian operator and we discuss two approaches for finding suitable coherent states for this system. In the first approach we consider Dirac quantisation and group averaging that have been used by Ashtekar et. al. but only for integer powers of operators. Our generalisation to fractional powers yields in the case of the toy model a suitable set of coherent states. The second approach is inspired by coherent states based on a fractional Poisson distribution introduced by Laskin, which however turn out not to satisfy all properties to yield good semiclassical results for the operators considered here and in particular do not satisfy a resolution of identity as claimed. Therefore, we present a generalisation of the standard harmonic oscillator coherent states to states involving fractional labels, which approximate the fractional operators in our toy model semiclassically more accurately and satisfy a resolution of identity. In addition, motivated by the way the proof of the resolution of identity is performed, we consider these kind of coherent states also for the polymerised harmonic oscillator and discuss their semiclassical properties |
0709.4414 | Valerio Faraoni | Nicolas Lanahan-Tremblay and Valerio Faraoni (Bishop's University) | The Cauchy problem of f(R) gravity | 16 latex pages, to appear in Class. Quantum Grav; typographical
errors corrected, new references added | Class.Quant.Grav.24:5667-5680,2007 | 10.1088/0264-9381/24/22/024 | null | gr-qc astro-ph hep-th | null | The initial value problem of metric and Palatini f(R)gravity is studied by
using the dynamical equivalence between these theories and Brans-Dicke gravity.
The Cauchy problem is well-formulated for metric f(R)gravity in the presence of
matter and well-posed in vacuo. For Palatini f(R)gravity, instead, the Cauchy
problem is not well-formulated.
| [
{
"created": "Thu, 27 Sep 2007 14:56:46 GMT",
"version": "v1"
},
{
"created": "Sun, 7 Oct 2007 15:01:32 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Lanahan-Tremblay",
"Nicolas",
"",
"Bishop's University"
],
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
]
] | The initial value problem of metric and Palatini f(R)gravity is studied by using the dynamical equivalence between these theories and Brans-Dicke gravity. The Cauchy problem is well-formulated for metric f(R)gravity in the presence of matter and well-posed in vacuo. For Palatini f(R)gravity, instead, the Cauchy problem is not well-formulated. |
2311.03556 | Akash Kumar Mishra | Akash K Mishra, Gregorio Carullo, Sumanta Chakraborty | Bounds on tidal charges from gravitational-wave ringdown observations | 15 pages, 4 figures, 1 table, Matches published version | Phys. Rev. D 109, 024025 (2024) | 10.1103/PhysRevD.109.024025 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black hole solutions in the braneworld scenario are predicted to possess a
tidal charge parameter, leaving imprints in the quasinormal spectrum. We
conduct an extensive computation of such spectrum, and use it to construct a
waveform model for the ringdown relaxation regime of binary black hole mergers
observed by LIGO and Virgo. Applying a Bayesian time-domain analysis formalism,
we analyse a selected dataset from the GWTC-3 LIGO-Virgo-Kagra catalog of
binary coalescences, bounding the value of the tidal charge. With our analysis
we obtain the first robust constraints on such charges, highlighting the
importance of accounting for the previously ignored correlations with the other
black hole intrinsic parameters.
| [
{
"created": "Mon, 6 Nov 2023 21:48:46 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Apr 2024 11:14:55 GMT",
"version": "v2"
}
] | 2024-04-18 | [
[
"Mishra",
"Akash K",
""
],
[
"Carullo",
"Gregorio",
""
],
[
"Chakraborty",
"Sumanta",
""
]
] | Black hole solutions in the braneworld scenario are predicted to possess a tidal charge parameter, leaving imprints in the quasinormal spectrum. We conduct an extensive computation of such spectrum, and use it to construct a waveform model for the ringdown relaxation regime of binary black hole mergers observed by LIGO and Virgo. Applying a Bayesian time-domain analysis formalism, we analyse a selected dataset from the GWTC-3 LIGO-Virgo-Kagra catalog of binary coalescences, bounding the value of the tidal charge. With our analysis we obtain the first robust constraints on such charges, highlighting the importance of accounting for the previously ignored correlations with the other black hole intrinsic parameters. |
1611.08251 | Olga Babourova Valer'evna | O.V. Babourova, B.N. Frolov, P.E. Kudlaev | Approximate axially symmetric solution of the Weyl-Dirac theory of
gravitation and the spiral galactic rotation problem | 6 pages, no figures, typos added,added references for section 3 | null | null | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On the basis of the Poincare-Weyl gauge theory of gravitation, a new
conformal Weyl-Dirac theory of gravitation is proposed, which is a
gravitational theory in Cartan-Weyl spacetime with the Dirac scalar field
representing the dark matter model. A static approximate axially symmetric
solution of the field equations in vacuum is obtained. On the base of this
solution in the Newtonian approximation one considers the problem of rotation
velocities in spiral components of galaxies.
| [
{
"created": "Thu, 24 Nov 2016 16:54:57 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jul 2017 18:13:53 GMT",
"version": "v2"
}
] | 2017-07-17 | [
[
"Babourova",
"O. V.",
""
],
[
"Frolov",
"B. N.",
""
],
[
"Kudlaev",
"P. E.",
""
]
] | On the basis of the Poincare-Weyl gauge theory of gravitation, a new conformal Weyl-Dirac theory of gravitation is proposed, which is a gravitational theory in Cartan-Weyl spacetime with the Dirac scalar field representing the dark matter model. A static approximate axially symmetric solution of the field equations in vacuum is obtained. On the base of this solution in the Newtonian approximation one considers the problem of rotation velocities in spiral components of galaxies. |
1605.00820 | Soumya Jana | Soumya Jana, Sayan Kar (IIT Kharagpur, India) | Born-Infeld cosmology with scalar Born-Infeld matter | 24 pages, 8 figures. Published version | Phys. Rev. D 94, 064016 (2016) | 10.1103/PhysRevD.94.064016 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmology in Eddington-inspired Born-Infeld gravity is investigated using a
scalar Born-Infeld field (e.g. tachyon condensate) as matter. In this way, both
in the gravity and matter sectors we have Born-Infeld-like structures
characterized by their actions and via two separate constants, $\kappa$ and
$\alpha_T^2$ respectively. With a particular choice of the form of $\dot{\phi}$
(the time derivative of the Born-Infeld scalar), analytical cosmological
solutions are found. Thereafter, we explore some of the unique features of the
corresponding cosmological spacetimes. For $\kappa>0$, our solution has a de
Sitter-like expansion both at early and late times, with an intermediate
deceleration sandwiched between the accelerating phases. On the other hand,
when $\kappa<0$, the initial de Sitter phase is replaced by a bounce. Our
solutions, at late time, fit well with available supernova data-- a fact we
demonstrate explicitly. The estimated properties of the Universe obtained from
the fitting of the $\kappa>0$ solution, are as good as in $\Lambda$CDM
cosmology. However, the $\kappa<0$ solution has to be discarded due to the
occurrence of a bounce at an unacceptably low redshift.
| [
{
"created": "Tue, 3 May 2016 10:04:06 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Sep 2016 07:05:42 GMT",
"version": "v2"
}
] | 2016-09-27 | [
[
"Jana",
"Soumya",
"",
"IIT Kharagpur, India"
],
[
"Kar",
"Sayan",
"",
"IIT Kharagpur, India"
]
] | Cosmology in Eddington-inspired Born-Infeld gravity is investigated using a scalar Born-Infeld field (e.g. tachyon condensate) as matter. In this way, both in the gravity and matter sectors we have Born-Infeld-like structures characterized by their actions and via two separate constants, $\kappa$ and $\alpha_T^2$ respectively. With a particular choice of the form of $\dot{\phi}$ (the time derivative of the Born-Infeld scalar), analytical cosmological solutions are found. Thereafter, we explore some of the unique features of the corresponding cosmological spacetimes. For $\kappa>0$, our solution has a de Sitter-like expansion both at early and late times, with an intermediate deceleration sandwiched between the accelerating phases. On the other hand, when $\kappa<0$, the initial de Sitter phase is replaced by a bounce. Our solutions, at late time, fit well with available supernova data-- a fact we demonstrate explicitly. The estimated properties of the Universe obtained from the fitting of the $\kappa>0$ solution, are as good as in $\Lambda$CDM cosmology. However, the $\kappa<0$ solution has to be discarded due to the occurrence of a bounce at an unacceptably low redshift. |
0711.0686 | Saibal Ray | Saibal Ray, Maxim Khlopov, Utpal Mukhopadhyay and Partha Pratim Ghosh | Phenomenology of $\Lambda$-CDM model: a possibility of accelerating
Universe with positive pressure | 16 Latex pages, 11 figures, Considerable modifications in the text;
Accepted in IJTP | Int.J.Theor.Phys.50:939-951,2011 | 10.1007/s10773-010-0639-0 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Among various phenomenological $\Lambda$ models, a time-dependent model $\dot
\Lambda\sim H^3$ is selected here to investigate the $\Lambda$-CDM cosmology.
Using this model the expressions for the time-dependent equation of state
parameter $\omega$ and other physical parameters are derived. It is shown that
in $H^3$ model accelerated expansion of the Universe takes place at negative
energy density, but with a positive pressure. It has also been possible to
obtain the change of sign of the deceleration parameter $q$ during cosmic
evolution.
| [
{
"created": "Mon, 5 Nov 2007 16:42:51 GMT",
"version": "v1"
},
{
"created": "Sat, 17 Jul 2010 07:40:08 GMT",
"version": "v2"
},
{
"created": "Tue, 14 Dec 2010 07:00:31 GMT",
"version": "v3"
}
] | 2011-01-25 | [
[
"Ray",
"Saibal",
""
],
[
"Khlopov",
"Maxim",
""
],
[
"Mukhopadhyay",
"Utpal",
""
],
[
"Ghosh",
"Partha Pratim",
""
]
] | Among various phenomenological $\Lambda$ models, a time-dependent model $\dot \Lambda\sim H^3$ is selected here to investigate the $\Lambda$-CDM cosmology. Using this model the expressions for the time-dependent equation of state parameter $\omega$ and other physical parameters are derived. It is shown that in $H^3$ model accelerated expansion of the Universe takes place at negative energy density, but with a positive pressure. It has also been possible to obtain the change of sign of the deceleration parameter $q$ during cosmic evolution. |
1506.03814 | T. Padmanabhan | T. Padmanabhan | Momentum density of spacetime and the gravitational dynamics | six pages; no figures | null | 10.1007/s10714-015-1996-z | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I introduce a covariant four-vector $\mathcal{G}^a[v]$, which can be
interpreted as the momentum density attributed to the spacetime geometry by an
observer with velocity $v^a$, and describe its properties: (a) Demanding that
the total momentum of matter plus geometry is conserved for all observers,
leads to the gravitational field equations. Thus, how matter curves spacetime
is entirely determined by this principle of momentum conservation. (b) The
$\mathcal{G}^a[v]$ can be related to the gravitational Lagrangian in a manner
similar to the usual definition of Hamiltonian in, say, classical mechanics.
(c) Geodesic observers in a spacetime will find that the conserved total
momentum vanishes on-shell. (d) The on-shell, conserved, total energy in a
region of space, as measured by the comoving observers, will be equal to the
total heat energy of the boundary surface. (e) The off-shell gravitational
energy in a region will be the sum of the ADM energy in the bulk plus the
thermal energy of the boundary. These results suggest that $\mathcal{G}^a[v]$
can be a useful physical quantity to probe the gravitational theories.
| [
{
"created": "Thu, 11 Jun 2015 20:00:36 GMT",
"version": "v1"
}
] | 2015-12-09 | [
[
"Padmanabhan",
"T.",
""
]
] | I introduce a covariant four-vector $\mathcal{G}^a[v]$, which can be interpreted as the momentum density attributed to the spacetime geometry by an observer with velocity $v^a$, and describe its properties: (a) Demanding that the total momentum of matter plus geometry is conserved for all observers, leads to the gravitational field equations. Thus, how matter curves spacetime is entirely determined by this principle of momentum conservation. (b) The $\mathcal{G}^a[v]$ can be related to the gravitational Lagrangian in a manner similar to the usual definition of Hamiltonian in, say, classical mechanics. (c) Geodesic observers in a spacetime will find that the conserved total momentum vanishes on-shell. (d) The on-shell, conserved, total energy in a region of space, as measured by the comoving observers, will be equal to the total heat energy of the boundary surface. (e) The off-shell gravitational energy in a region will be the sum of the ADM energy in the bulk plus the thermal energy of the boundary. These results suggest that $\mathcal{G}^a[v]$ can be a useful physical quantity to probe the gravitational theories. |
gr-qc/9406039 | Jorge Griego | C. Di Bartolo, R. Gambini and J. Griego | The Extended Loop Representation of Quantum Gravity | 27 pages, report IFFC/94-13 | Phys.Rev. D51 (1995) 502-516 | 10.1103/PhysRevD.51.502 | null | gr-qc | null | A new representation of Quantum Gravity is developed. This formulation is
based on an extension of the group of loops. The enlarged group, that we call
the Extended Loop Group, behaves locally as an infinite dimensional Lie group.
Quantum Gravity can be realized on the state space of extended loop dependent
wavefunctions. The extended representation generalizes the loop representation
and contains this representation as a particular case. The resulting
diffeomorphism and hamiltonian constraints take a very simple form and allow to
apply functional methods and simplify the loop calculus. In particular we show
that the constraints are linear in the momenta. The nondegenerate solutions
known in the loop representation are also solutions of the constraints in the
new representation. The practical calculation advantages allows to find a new
solution to the Wheeler-DeWitt equation. Moreover, the extended representation
puts in a precise framework some of the regularization problems of the loop
representation. We show that the solutions are generalized knot invariants,
smooth in the extended variables, and any framing is unnecessary.
| [
{
"created": "Wed, 22 Jun 1994 19:26:27 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Di Bartolo",
"C.",
""
],
[
"Gambini",
"R.",
""
],
[
"Griego",
"J.",
""
]
] | A new representation of Quantum Gravity is developed. This formulation is based on an extension of the group of loops. The enlarged group, that we call the Extended Loop Group, behaves locally as an infinite dimensional Lie group. Quantum Gravity can be realized on the state space of extended loop dependent wavefunctions. The extended representation generalizes the loop representation and contains this representation as a particular case. The resulting diffeomorphism and hamiltonian constraints take a very simple form and allow to apply functional methods and simplify the loop calculus. In particular we show that the constraints are linear in the momenta. The nondegenerate solutions known in the loop representation are also solutions of the constraints in the new representation. The practical calculation advantages allows to find a new solution to the Wheeler-DeWitt equation. Moreover, the extended representation puts in a precise framework some of the regularization problems of the loop representation. We show that the solutions are generalized knot invariants, smooth in the extended variables, and any framing is unnecessary. |
1405.1922 | Miroslav Shaltev | Miroslav Shaltev, Paola Leaci, Maria Alessandra Papa, Reinhard Prix | Fully coherent follow-up of continuous gravitational-wave candidates: an
application to Einstein@Home results | 8 pages, 3 figures, 3 tables | Phys. Rev. D 89, 124030 (2014) | 10.1103/PhysRevD.89.124030 | LIGO-P1400057-v2 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We characterize and present the details of the follow-up method used on the
most significant outliers of the Hough Einstein@Home all-sky search for
continuous gravitational waves arXiv:1207.7176. This follow-up method is based
on the two-stage approach introduced in arXiv:1303.2471, consisting of a
semicoherent refinement followed by a fully coherent zoom. We quantify the
efficiency of the follow-up pipeline using simulated signals in Gaussian noise.
This pipeline does not search beyond first-order frequency spindown, and
therefore we also evaluate its robustness against second-order spindown. We
present the details of the Hough Einstein@Home follow-up (arXiv:1207.7176) on
three hardware-injected signals and on the 8 most significant outliers of
unknown origin.
| [
{
"created": "Thu, 8 May 2014 13:41:16 GMT",
"version": "v1"
}
] | 2014-07-02 | [
[
"Shaltev",
"Miroslav",
""
],
[
"Leaci",
"Paola",
""
],
[
"Papa",
"Maria Alessandra",
""
],
[
"Prix",
"Reinhard",
""
]
] | We characterize and present the details of the follow-up method used on the most significant outliers of the Hough Einstein@Home all-sky search for continuous gravitational waves arXiv:1207.7176. This follow-up method is based on the two-stage approach introduced in arXiv:1303.2471, consisting of a semicoherent refinement followed by a fully coherent zoom. We quantify the efficiency of the follow-up pipeline using simulated signals in Gaussian noise. This pipeline does not search beyond first-order frequency spindown, and therefore we also evaluate its robustness against second-order spindown. We present the details of the Hough Einstein@Home follow-up (arXiv:1207.7176) on three hardware-injected signals and on the 8 most significant outliers of unknown origin. |
1809.03879 | Giorgos Manolakos | D. Jurman, G. Manolakos, P. Manousselis, G. Zoupanos | Gravity as a Gauge Theory on Three-Dimensional Noncommutative spaces | arXiv admin note: text overlap with arXiv:1802.07550 | null | 10.22323/1.318.0162 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We plan to translate the successful description of three-dimensional gravity
as a gauge theory in the noncommutative framework, making use of the covariant
coordinates. We consider two specific three-dimensional fuzzy spaces based on
SU(2) and SU(1,1), which carry appropriate symmetry groups. These are the
groups we are going to gauge in order to result with the transformations of the
gauge fields (dreibein, spin connection and two extra Maxwell fields due to
noncommutativity), their corresponding curvatures and eventually determine the
action and the equations of motion. Finally, we verify their connection to
three-dimensional gravity.
| [
{
"created": "Sun, 9 Sep 2018 10:46:55 GMT",
"version": "v1"
}
] | 2018-09-12 | [
[
"Jurman",
"D.",
""
],
[
"Manolakos",
"G.",
""
],
[
"Manousselis",
"P.",
""
],
[
"Zoupanos",
"G.",
""
]
] | We plan to translate the successful description of three-dimensional gravity as a gauge theory in the noncommutative framework, making use of the covariant coordinates. We consider two specific three-dimensional fuzzy spaces based on SU(2) and SU(1,1), which carry appropriate symmetry groups. These are the groups we are going to gauge in order to result with the transformations of the gauge fields (dreibein, spin connection and two extra Maxwell fields due to noncommutativity), their corresponding curvatures and eventually determine the action and the equations of motion. Finally, we verify their connection to three-dimensional gravity. |
gr-qc/0601063 | Friedrich W. Hehl | Peter Baekler and Friedrich W. Hehl | Rotating Black Holes in Metric-Affine Gravity | 32 pages latex, 3 tables | Int.J.Mod.Phys.D15:635-668,2006 | 10.1142/S0218271806008589 | null | gr-qc hep-th | null | Within the framework of metric-affine gravity (MAG, metric and an independent
linear connection constitute spacetime), we find, for a specific gravitational
Lagrangian and by using {\it prolongation} techniques, a stationary axially
symmetric exact solution of the vacuum field equations. This black hole
solution embodies a Kerr-deSitter metric and the post-Riemannian structures of
torsion and nonmetricity. The solution is characterized by mass, angular
momentum, and shear charge, the latter of which is a measure for violating
Lorentz invariance.
| [
{
"created": "Mon, 16 Jan 2006 21:50:58 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Baekler",
"Peter",
""
],
[
"Hehl",
"Friedrich W.",
""
]
] | Within the framework of metric-affine gravity (MAG, metric and an independent linear connection constitute spacetime), we find, for a specific gravitational Lagrangian and by using {\it prolongation} techniques, a stationary axially symmetric exact solution of the vacuum field equations. This black hole solution embodies a Kerr-deSitter metric and the post-Riemannian structures of torsion and nonmetricity. The solution is characterized by mass, angular momentum, and shear charge, the latter of which is a measure for violating Lorentz invariance. |
0710.2568 | Yun Soo Myung | Yun Soo Myung | Phase transition between non-extremal and extremal Reissner-Nordstr\"om
black holes | 12 pages, 6 figures, version to appear in MPLA | Mod.Phys.Lett.A23:667-676,2008 | 10.1142/S0217732308026741 | INJE-TP-07-10 | gr-qc | null | We discuss the phase transition between non-extremal and extremal
Reissner-Nordstr\"om black holes. This transition is considered as the
$T \to 0$ limit of the transition between the non-extremal and near-extremal
black holes.
We show that an evaporating process from non-extremal black hole to extremal
one is possible to occur, but its reverse process is not possible to occur
because of the presence of the maximum temperature.
Furthermore, it is shown that the Hawking-Page phase transition between small
and large black holes unlikely occurs in the AdS Reissner-Nordstr\"om black
holes.
| [
{
"created": "Fri, 12 Oct 2007 23:46:43 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Oct 2007 07:38:13 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Mar 2008 23:47:42 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Myung",
"Yun Soo",
""
]
] | We discuss the phase transition between non-extremal and extremal Reissner-Nordstr\"om black holes. This transition is considered as the $T \to 0$ limit of the transition between the non-extremal and near-extremal black holes. We show that an evaporating process from non-extremal black hole to extremal one is possible to occur, but its reverse process is not possible to occur because of the presence of the maximum temperature. Furthermore, it is shown that the Hawking-Page phase transition between small and large black holes unlikely occurs in the AdS Reissner-Nordstr\"om black holes. |
gr-qc/9409012 | null | A. Lukas | The No-Boundary Wave Function and the Duration of the Inflationary
Period | 11 pages, TUM-HEP-206/94, 2 figures (added as uu-encoded postscript
file) | Phys.Lett.B347:13-20,1995 | 10.1016/0370-2693(94)01693-7 | null | gr-qc | null | For the simplest minisuperspace model based on a homogeneous, isotropic
metric and a minimally coupled scalar field we derive analytic expressions for
the caustic which separates Euklidean and Minkowskian region and its breakdown
value $\p_*$. This value represents the prediction of the no-boundary wave
function for the scalar field at the beginning of inflation. We use our results
to search for inflationary models which can render the no-boundary wave
function consistent with the requirement of a sufficiently long inflationary
period.
| [
{
"created": "Wed, 7 Sep 1994 14:13:22 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Lukas",
"A.",
""
]
] | For the simplest minisuperspace model based on a homogeneous, isotropic metric and a minimally coupled scalar field we derive analytic expressions for the caustic which separates Euklidean and Minkowskian region and its breakdown value $\p_*$. This value represents the prediction of the no-boundary wave function for the scalar field at the beginning of inflation. We use our results to search for inflationary models which can render the no-boundary wave function consistent with the requirement of a sufficiently long inflationary period. |
1408.4283 | Andrea Geralico | Donato Bini, Fernando de Felice, Andrea Geralico | Strains in General Relativity | 25 pages, 7 figures; published version | Class. Quantum Grav. 23, 7603 (2006) | 10.1088/0264-9381/23/24/028 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The definition of relative accelerations and strains among a set of comoving
particles is studied in connection with the geometric properties of the frame
adapted to a "fiducial observer." We find that a relativistically complete and
correct definition of strains must take into account the transport law of the
chosen spatial triad along the observer's congruence. We use special
congruences of (accelerated) test particles in some familiar spacetimes to
elucidate such a point. The celebrated idea of Szekeres' compass of inertia,
arising when studying geodesic deviation among a set of free-falling particles,
is here generalized to the case of accelerated particles. In doing so we have
naturally contributed to the theory of relativistic gravity gradiometer.
Moreover, our analysis was made in an observer-dependent form, a fact that
would be very useful when thinking about general relativistic tests on space
stations orbiting compact objects like black holes and also in other
interesting gravitational situations.
| [
{
"created": "Tue, 19 Aug 2014 10:30:02 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Bini",
"Donato",
""
],
[
"de Felice",
"Fernando",
""
],
[
"Geralico",
"Andrea",
""
]
] | The definition of relative accelerations and strains among a set of comoving particles is studied in connection with the geometric properties of the frame adapted to a "fiducial observer." We find that a relativistically complete and correct definition of strains must take into account the transport law of the chosen spatial triad along the observer's congruence. We use special congruences of (accelerated) test particles in some familiar spacetimes to elucidate such a point. The celebrated idea of Szekeres' compass of inertia, arising when studying geodesic deviation among a set of free-falling particles, is here generalized to the case of accelerated particles. In doing so we have naturally contributed to the theory of relativistic gravity gradiometer. Moreover, our analysis was made in an observer-dependent form, a fact that would be very useful when thinking about general relativistic tests on space stations orbiting compact objects like black holes and also in other interesting gravitational situations. |
1004.3291 | Dejan Stojkovic | De-Chang Dai and Dejan Stojkovic | Analytic solution for a static black hole in RSII model | extended discussion, appendix added, published in Phys. Lett. B | Phys.Lett. B704 (2011) 354-359 | 10.1016/j.physletb.2011.09.038 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present here a static solution for a large black hole (whose horizon
radius is larger than the AdS radius) located on the brane in RSII model.
According to some arguments based on the AdS/CFT conjecture, a solution for the
black hole located on the brane in RSII model must encode quantum gravitational
effects and therefore can not be static. We demonstrated that a static solution
can be found if the bulk is not empty. The stress energy tensor of the matter
distribution in the bulk for the solution we found is physical (i.e. it is
non-singular with the energy density and pressure not violating any energy
conditions). However, the solution can not be transformed into the
Schwarzschild-like form and does not reduce to the Schwarzschild solution on
the brane. We also present two other related static solutions. At the end, we
discuss why the numerical methods failed so far in finding static solutions in
this context, including the solutions we found analytically here.
| [
{
"created": "Mon, 19 Apr 2010 20:02:03 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Dec 2011 14:47:07 GMT",
"version": "v2"
}
] | 2015-05-18 | [
[
"Dai",
"De-Chang",
""
],
[
"Stojkovic",
"Dejan",
""
]
] | We present here a static solution for a large black hole (whose horizon radius is larger than the AdS radius) located on the brane in RSII model. According to some arguments based on the AdS/CFT conjecture, a solution for the black hole located on the brane in RSII model must encode quantum gravitational effects and therefore can not be static. We demonstrated that a static solution can be found if the bulk is not empty. The stress energy tensor of the matter distribution in the bulk for the solution we found is physical (i.e. it is non-singular with the energy density and pressure not violating any energy conditions). However, the solution can not be transformed into the Schwarzschild-like form and does not reduce to the Schwarzschild solution on the brane. We also present two other related static solutions. At the end, we discuss why the numerical methods failed so far in finding static solutions in this context, including the solutions we found analytically here. |
1104.3126 | Eric G. Brown | Eric G. Brown, Robert B. Mann, Leonardo Modesto | Mass Inflation in the Loop Black Hole | Latex 20 pages, 7 figures | null | 10.1103/PhysRevD.84.104041 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In classical general relativity the Cauchy horizon within a two-horizon black
hole is unstable via a phenomenon known as mass inflation, in which the mass
parameter (and the spacetime curvature) of the black hole diverges at the
Cauchy horizon. Here we study this effect for loop black holes -- quantum
gravitationally corrected black holes from loop quantum gravity -- whose
construction alleviates the $r=0$ singularity present in their classical
counterparts. We use a simplified model of mass inflation, which makes use of
the generalized DTR relation, to conclude that the Cauchy horizon of loop black
holes indeed results in a curvature singularity similar to that found in
classical black holes. The DTR relation is of particular utility in the loop
black hole because it does not directly rely upon Einstein's field equations.
We elucidate some of the interesting and counterintuitive properties of the
loop black hole, and corroborate our results using an alternate model of mass
inflation due to Ori.
| [
{
"created": "Fri, 15 Apr 2011 19:05:26 GMT",
"version": "v1"
}
] | 2013-05-29 | [
[
"Brown",
"Eric G.",
""
],
[
"Mann",
"Robert B.",
""
],
[
"Modesto",
"Leonardo",
""
]
] | In classical general relativity the Cauchy horizon within a two-horizon black hole is unstable via a phenomenon known as mass inflation, in which the mass parameter (and the spacetime curvature) of the black hole diverges at the Cauchy horizon. Here we study this effect for loop black holes -- quantum gravitationally corrected black holes from loop quantum gravity -- whose construction alleviates the $r=0$ singularity present in their classical counterparts. We use a simplified model of mass inflation, which makes use of the generalized DTR relation, to conclude that the Cauchy horizon of loop black holes indeed results in a curvature singularity similar to that found in classical black holes. The DTR relation is of particular utility in the loop black hole because it does not directly rely upon Einstein's field equations. We elucidate some of the interesting and counterintuitive properties of the loop black hole, and corroborate our results using an alternate model of mass inflation due to Ori. |
gr-qc/0506103 | Ishwaree Neupane | Benedict M.N. Carter and Ishwaree P Neupane | Thermodynamics and Stability of Higher Dimensional Rotating (Kerr) AdS
Black Holes | 15 pages, 23 eps figures, RevTex4 | Phys.Rev.D72:043534,2005 | 10.1103/PhysRevD.72.043534 | null | gr-qc hep-th | null | We study the thermodynamic and gravitational stability of Kerr anti-de Sitter
black holes in five and higher dimensions. We show, in the case of equal
rotation parameters, $a_i=a$, that the Kerr-AdS background metrics become
stable, both thermodynamically and gravitationally, when the rotation
parameters $a_i$ take values comparable to the AdS curvature radius. In turn, a
Kerr-AdS black hole can be in thermal equilibrium with the thermal radiation
around it only when the rotation parameters become not significantly smaller
than the AdS curvature radius. We also find with equal rotation parameters that
a Kerr-AdS black hole is thermodynamically favored against the existence of a
thermal AdS space, while the opposite behavior is observed in the case of a
single non-zero rotation parameter. The five dimensional case is however
different and also special in that there is no high temperature thermal AdS
phase regardless of the choice of rotation parameters. We also verify that at
fixed entropy, the temperature of a rotating black hole is always bounded above
by that of a non-rotating black hole, in four and five dimensions, but not in
six and more dimensions (especially, when the entropy approaches zero or the
minimum of entropy does not correspond to the minimum of temperature). In this
last context, the six dimensional case is marginal.
| [
{
"created": "Tue, 21 Jun 2005 07:04:48 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Jul 2005 07:34:44 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Jul 2005 12:04:22 GMT",
"version": "v3"
},
{
"created": "Fri, 2 Sep 2005 07:14:45 GMT",
"version": "v4"
}
] | 2010-11-19 | [
[
"Carter",
"Benedict M. N.",
""
],
[
"Neupane",
"Ishwaree P",
""
]
] | We study the thermodynamic and gravitational stability of Kerr anti-de Sitter black holes in five and higher dimensions. We show, in the case of equal rotation parameters, $a_i=a$, that the Kerr-AdS background metrics become stable, both thermodynamically and gravitationally, when the rotation parameters $a_i$ take values comparable to the AdS curvature radius. In turn, a Kerr-AdS black hole can be in thermal equilibrium with the thermal radiation around it only when the rotation parameters become not significantly smaller than the AdS curvature radius. We also find with equal rotation parameters that a Kerr-AdS black hole is thermodynamically favored against the existence of a thermal AdS space, while the opposite behavior is observed in the case of a single non-zero rotation parameter. The five dimensional case is however different and also special in that there is no high temperature thermal AdS phase regardless of the choice of rotation parameters. We also verify that at fixed entropy, the temperature of a rotating black hole is always bounded above by that of a non-rotating black hole, in four and five dimensions, but not in six and more dimensions (especially, when the entropy approaches zero or the minimum of entropy does not correspond to the minimum of temperature). In this last context, the six dimensional case is marginal. |
gr-qc/0406057 | Claudio Benedito Silva Furtado | L.C. Garcia de Andrade, A. M. de M. Carvalho and C. Furtado | Geometric Phase for Fermionic Quasiparticles Scattering by Disgyration
in Superfluids | 7 pages, to appear in Europhys. Lett | Europhys.Lett.67:538-544,2004 | 10.1209/epl/i2004-10096-6 | null | gr-qc | null | We consider a Volovik's analog model for description of a topological defects
in a superfluid and we investigate the scattering of quasiparticles in this
background. The analog of the gravitational Aharonov-Bohm in this system is
found. An analysis of this problem employing loop variables is considered and
corroborates for the existence of the Aharonov-Bohm effect in this system. The
results presented here may be used to study the Aharonov-Bohm effect in
superconductors.
| [
{
"created": "Mon, 14 Jun 2004 17:33:20 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"de Andrade",
"L. C. Garcia",
""
],
[
"Carvalho",
"A. M. de M.",
""
],
[
"Furtado",
"C.",
""
]
] | We consider a Volovik's analog model for description of a topological defects in a superfluid and we investigate the scattering of quasiparticles in this background. The analog of the gravitational Aharonov-Bohm in this system is found. An analysis of this problem employing loop variables is considered and corroborates for the existence of the Aharonov-Bohm effect in this system. The results presented here may be used to study the Aharonov-Bohm effect in superconductors. |
1210.5870 | David Kofro\v{n} | Ji\v{r}\'i Bi\v{c}\'ak and David Kofro\v{n} | Variations on spacetimes with boost-rotation symmetry | 4 pages, 3 figures; Contribution to the proceedings of "Relativity
and Gravitation - 100 years after Einstein in Prague" (Prague, June 25-29,
2012) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some new results on the boost-rotation symmetric spacetimes representing
pairs of rotating charged objects accelerated in opposite directions are
summarized. A particular attention is paid to (a) the Newtonian limit analyzed
using the Ehlers frame theory and (b) the special-relativistic limit of the
C-metric. Starting from the new, simpler form of the rotating charged C-metric
we also show how to remove nodal singularities and obtain a rotating charged
black hole freely falling in an external electromagnetic field.
| [
{
"created": "Mon, 22 Oct 2012 11:11:01 GMT",
"version": "v1"
}
] | 2012-10-23 | [
[
"Bičák",
"Jiří",
""
],
[
"Kofroň",
"David",
""
]
] | Some new results on the boost-rotation symmetric spacetimes representing pairs of rotating charged objects accelerated in opposite directions are summarized. A particular attention is paid to (a) the Newtonian limit analyzed using the Ehlers frame theory and (b) the special-relativistic limit of the C-metric. Starting from the new, simpler form of the rotating charged C-metric we also show how to remove nodal singularities and obtain a rotating charged black hole freely falling in an external electromagnetic field. |
1308.5403 | Brian Dolan | Brian P. Dolan | The compressibility of rotating black holes in D-dimensions | 14 pages, 2 figures; discussion of extensive/intensive thermodynamic
variables added, and minor typos corrected, in v2 | null | 10.1088/0264-9381/31/3/035022 | DIAS-STP-13-08 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Treating the cosmological constant as a pressure, in the context of black
hole thermodynamics, a thermodynamic volume for the black hole can be defined
as being the thermodynamic variable conjugate to the pressure, in the sense of
a Legendre transform. The thermodynamic volume is explicitly calculated, as the
Legendre transform of the pressure in the enthalpy for a rotating
asymptotically anti-de Sitter Myers-Perry black hole in D space-time
dimensions. The volume obtained is shown to agree with previous calculations
using the Smarr relation. The compressibility is calculated and shown to be
non-negative and bounded.
Taking the limit of zero cosmological constant, the compressibility of a
rotating black hole in asymptotically flat space-times is determined and the
corresponding speed of sound computed. The latter is bounded above and has an
elegant expression purely in terms of the angular momenta, in the form of
quartic and quadratic Casimirs of the rotation group, SO(D-1).
| [
{
"created": "Sun, 25 Aug 2013 12:54:55 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Dec 2013 15:16:58 GMT",
"version": "v2"
}
] | 2015-06-17 | [
[
"Dolan",
"Brian P.",
""
]
] | Treating the cosmological constant as a pressure, in the context of black hole thermodynamics, a thermodynamic volume for the black hole can be defined as being the thermodynamic variable conjugate to the pressure, in the sense of a Legendre transform. The thermodynamic volume is explicitly calculated, as the Legendre transform of the pressure in the enthalpy for a rotating asymptotically anti-de Sitter Myers-Perry black hole in D space-time dimensions. The volume obtained is shown to agree with previous calculations using the Smarr relation. The compressibility is calculated and shown to be non-negative and bounded. Taking the limit of zero cosmological constant, the compressibility of a rotating black hole in asymptotically flat space-times is determined and the corresponding speed of sound computed. The latter is bounded above and has an elegant expression purely in terms of the angular momenta, in the form of quartic and quadratic Casimirs of the rotation group, SO(D-1). |
0910.1181 | Nikodem Poplawski | Nikodem J. Poplawski | Nonsingular Dirac particles in spacetime with torsion | 8 pages; published version | Phys.Lett.B690:73-77,2010; Erratum-ibid.B727:575,2013 | 10.1016/j.physletb.2010.04.073 10.1016/j.physletb.2013.11.005 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the Papapetrou method of multipole expansion to show that a Dirac
field in the Einstein-Cartan-Kibble-Sciama (ECKS) theory of gravity cannot form
singular configurations concentrated on one- or two-dimensional surfaces in
spacetime. Instead, such a field describes a nonsingular particle whose spatial
dimension is at least on the order of its Cartan radius. In particular, torsion
modifies Burinskii's model of the Dirac electron as a Kerr-Newman singular ring
of the Compton size, by replacing the ring with a toroidal structure with the
outer radius of the Compton size and the inner radius of the Cartan size. We
conjecture that torsion produced by spin prevents the formation of
singularities from matter composed of quarks and leptons. We expect that the
Cartan radius of an electron, ~10^{-27} m, introduces an effective ultraviolet
cutoff in quantum field theory for fermions in the ECKS spacetime. We also
estimate a maximum density of matter to be on the order of the corresponding
Cartan density, ~10^{51} kg m^{-3}, which gives a lower limit for black-hole
masses ~10^{16} kg. This limit corresponds to energy ~10^{43} GeV which is 39
orders of magnitude larger than the maximum beam energy currently available at
the LHC. Thus, if torsion exists and the ECKS theory of gravity is correct, the
LHC cannot produce micro black holes.
| [
{
"created": "Wed, 7 Oct 2009 08:12:03 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Oct 2010 14:59:41 GMT",
"version": "v2"
}
] | 2013-12-03 | [
[
"Poplawski",
"Nikodem J.",
""
]
] | We use the Papapetrou method of multipole expansion to show that a Dirac field in the Einstein-Cartan-Kibble-Sciama (ECKS) theory of gravity cannot form singular configurations concentrated on one- or two-dimensional surfaces in spacetime. Instead, such a field describes a nonsingular particle whose spatial dimension is at least on the order of its Cartan radius. In particular, torsion modifies Burinskii's model of the Dirac electron as a Kerr-Newman singular ring of the Compton size, by replacing the ring with a toroidal structure with the outer radius of the Compton size and the inner radius of the Cartan size. We conjecture that torsion produced by spin prevents the formation of singularities from matter composed of quarks and leptons. We expect that the Cartan radius of an electron, ~10^{-27} m, introduces an effective ultraviolet cutoff in quantum field theory for fermions in the ECKS spacetime. We also estimate a maximum density of matter to be on the order of the corresponding Cartan density, ~10^{51} kg m^{-3}, which gives a lower limit for black-hole masses ~10^{16} kg. This limit corresponds to energy ~10^{43} GeV which is 39 orders of magnitude larger than the maximum beam energy currently available at the LHC. Thus, if torsion exists and the ECKS theory of gravity is correct, the LHC cannot produce micro black holes. |
2101.00665 | Vasilis Oikonomou | V.K. Oikonomou | Non-minimally Coupled Scalar $k$-Inflation Dynamics | Invited publication for the EPJP special issue Modified Gravity
Theories and Cosmology | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we shall study $k$-inflation theories with non-minimal coupling
of the scalar field to gravity, in the presence of only a higher order kinetic
term of the form $\sim \mathrm{const}\times X^{\mu}$, with
$X=\frac{1}{2}\partial_{\mu}\phi\partial^{\mu}\phi$. The study will be focused
in the cases where a scalar potential is included or is absent, and the
evolution of the scalar field will be assumed to satisfy the slow-roll or the
constant-roll condition. In the case of the slow-roll models with scalar
potential, we shall calculate the slow-roll indices, and the corresponding
observational indices of the theory, and we demonstrate that the resulting
theory is compatible with the latest Planck data. The same results are obtained
in the constant-roll case, at least in the presence of a scalar potential. In
the case that models without potential are considered, the results are less
appealing since these are strongly model dependent, and at least for a
power-law choice of the non-minimal coupling, the theory is non-viable.
Finally, due to the fact that the scalar and tensor power spectra are conformal
invariant quantities, we argue that the Einstein frame counterpart of the
non-minimal $k$-inflation models with scalar potential, can be a viable theory,
due to the conformal invariance of the observational indices. The Einstein
frame theory is more involved and thus more difficult to work with it
analytically, so one implication of our work is that we provide evidence for
the viability of another class of $k$-inflation models.
| [
{
"created": "Sun, 3 Jan 2021 16:44:45 GMT",
"version": "v1"
}
] | 2021-01-05 | [
[
"Oikonomou",
"V. K.",
""
]
] | In this work we shall study $k$-inflation theories with non-minimal coupling of the scalar field to gravity, in the presence of only a higher order kinetic term of the form $\sim \mathrm{const}\times X^{\mu}$, with $X=\frac{1}{2}\partial_{\mu}\phi\partial^{\mu}\phi$. The study will be focused in the cases where a scalar potential is included or is absent, and the evolution of the scalar field will be assumed to satisfy the slow-roll or the constant-roll condition. In the case of the slow-roll models with scalar potential, we shall calculate the slow-roll indices, and the corresponding observational indices of the theory, and we demonstrate that the resulting theory is compatible with the latest Planck data. The same results are obtained in the constant-roll case, at least in the presence of a scalar potential. In the case that models without potential are considered, the results are less appealing since these are strongly model dependent, and at least for a power-law choice of the non-minimal coupling, the theory is non-viable. Finally, due to the fact that the scalar and tensor power spectra are conformal invariant quantities, we argue that the Einstein frame counterpart of the non-minimal $k$-inflation models with scalar potential, can be a viable theory, due to the conformal invariance of the observational indices. The Einstein frame theory is more involved and thus more difficult to work with it analytically, so one implication of our work is that we provide evidence for the viability of another class of $k$-inflation models. |
gr-qc/0701108 | Plamen Fiziev | P P Fiziev | Static Fundamental Solutions of Einstein Equations and Superposition
Principle in Relativistic Gravityv | Talk, given at the Conference Gravity, Astrophysics and Strings at
Black Sea, Kiten, Bulgaria 2005. 40 pages, 6 figures, latex file | Gravity, Astrophysics and Strings'05, St. Kliment Ohridski
University Press, pp. 202-241, Sofia, 2006 | null | SU-TH0605 | gr-qc | null | We show that Einstein equations are compatible with the presence of massive
point particle idealization and find the corresponding two parameter family of
solutions. They are complete defined by the bare mechanical mass $M>0$ and the
Keplerian mass $m>0$ ($m < M$) of the point source of gravity. The global
analytical properties of these solutions in the complex plane define a unique
preferable radial variable of the one particle problem.
These new solutions are fundamental solutions of the quasi-linear Einstein
equations. We introduce and discuss a novel nonlinear superposition principle
for solutions of Einstein equations and discover the basic role of the
relativistic analog of the Newton gravitational potential. For the relativistic
potential we introduce a simple quasi-linear superposition principle as a new
physical requirement for the initial conditions for Einstein equations, thus
justifying the instant gravistatic case for N particle system.
This superposition principle allows us to sketch a new theory of the
gravitational mass defect. In it a specific Mach-like principle for the
Keplerian mass $m$ is valid, i.e. it depends on the mass distribution in the
universe, in contrast to the bare mass $M$, which remains a true constant.
Several basic examples both of discrete and of continuous mass distributions
are considered.
| [
{
"created": "Fri, 19 Jan 2007 13:11:30 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Fiziev",
"P P",
""
]
] | We show that Einstein equations are compatible with the presence of massive point particle idealization and find the corresponding two parameter family of solutions. They are complete defined by the bare mechanical mass $M>0$ and the Keplerian mass $m>0$ ($m < M$) of the point source of gravity. The global analytical properties of these solutions in the complex plane define a unique preferable radial variable of the one particle problem. These new solutions are fundamental solutions of the quasi-linear Einstein equations. We introduce and discuss a novel nonlinear superposition principle for solutions of Einstein equations and discover the basic role of the relativistic analog of the Newton gravitational potential. For the relativistic potential we introduce a simple quasi-linear superposition principle as a new physical requirement for the initial conditions for Einstein equations, thus justifying the instant gravistatic case for N particle system. This superposition principle allows us to sketch a new theory of the gravitational mass defect. In it a specific Mach-like principle for the Keplerian mass $m$ is valid, i.e. it depends on the mass distribution in the universe, in contrast to the bare mass $M$, which remains a true constant. Several basic examples both of discrete and of continuous mass distributions are considered. |
gr-qc/9712071 | Marcelo Jose Reboucas | M.J. Reboucas and A.F.F. Teixeira | Riemannian Space-times of G\"odel Type in Five Dimensions | 26 pages. LaTeX file. To appear in J. Math. Phys. (1998) | J.Math.Phys. 39 (1998) 2180-2192 | 10.1063/1.532281 | CBPF-NF-048/97 | gr-qc astro-ph | null | The five-dimensional (5D) Riemannian G\"odel-type manifolds are examined in
light of the equivalence problem techniques, as formulated by Cartan. The
necessary and sufficient conditions for local homogeneity of these 5D manifolds
are derived. The local equivalence of these homogeneous Riemannian manifolds is
studied. It is found that they are characterized by two essential parameters
$m^2$ and $\omega $: identical pairs $(m^2, \omega)$ correspond to locally
equivalent 5D manifolds. An irreducible set of isometrically nonequivalent 5D
locally homogeneous Riemannian G\"odel-type metrics are exhibited. A
classification of these manifolds based on the essential parameters is
presented, and the Killing vector fields as well as the corresponding Lie
algebra of each class are determined. It is shown that apart from the $(m^2= 4
\omega^2, \omega\not=0)$ and $(m^2\not=0, \omega = 0)$ classes the homogeneous
Riemannian G\"odel-type manifolds admit a seven-parameter maximal group of
isometry ($G_7$). The special class $(m^2= 4 \omega^2, \omega\not=0)$ and the
degenerated G\"odel-type class $(m^2\not=0, \omega=0)$ are shown to have a
$G_9$ as maximal group of motion. The breakdown of causality in these classes
of homogeneous G\"odel-type manifolds are also examined.
| [
{
"created": "Tue, 16 Dec 1997 22:31:48 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Reboucas",
"M. J.",
""
],
[
"Teixeira",
"A. F. F.",
""
]
] | The five-dimensional (5D) Riemannian G\"odel-type manifolds are examined in light of the equivalence problem techniques, as formulated by Cartan. The necessary and sufficient conditions for local homogeneity of these 5D manifolds are derived. The local equivalence of these homogeneous Riemannian manifolds is studied. It is found that they are characterized by two essential parameters $m^2$ and $\omega $: identical pairs $(m^2, \omega)$ correspond to locally equivalent 5D manifolds. An irreducible set of isometrically nonequivalent 5D locally homogeneous Riemannian G\"odel-type metrics are exhibited. A classification of these manifolds based on the essential parameters is presented, and the Killing vector fields as well as the corresponding Lie algebra of each class are determined. It is shown that apart from the $(m^2= 4 \omega^2, \omega\not=0)$ and $(m^2\not=0, \omega = 0)$ classes the homogeneous Riemannian G\"odel-type manifolds admit a seven-parameter maximal group of isometry ($G_7$). The special class $(m^2= 4 \omega^2, \omega\not=0)$ and the degenerated G\"odel-type class $(m^2\not=0, \omega=0)$ are shown to have a $G_9$ as maximal group of motion. The breakdown of causality in these classes of homogeneous G\"odel-type manifolds are also examined. |
2312.17724 | Jia-Hui Huang | Jing-Peng Ye, Zhi-Qing He, Ai-Xu Zhou, Zi-Yang Huang and Jia-Hui Huang | Shadows and photon rings of a quantum black hole | references added,one figure added | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Recently, a black hole model in loop quantum gravity has been proposed by
Lewandowski, Ma, Yang and Zhang (Phys. Rev. Lett. \textbf{130}, 101501 (2023)).
The metric tensor of the quantum black hole (QBH) is a suitably modified
Schwarzschild one. In this paper, we calculate the radius of light ring and
obtain the linear approximation of it with respect to the quantum correction
parameter $\alpha$: $r_{l} \simeq 3 M - \frac{\alpha}{9 M}$. We then assume the
QBH is backlit by a large, distant plane of uniform, isotropic emission and
calculate the radius of the black hole shadow and its linear approximation:
$r_{s} = 3 \sqrt{3} M - \frac{\alpha}{6 \left(\sqrt{3} M\right)}$. We also
consider the photon ring structures in the shadow when the impact parameter $b$
of the photon approaches to a critical impact parameter $b_{\textrm{c}}$, and
obtain a formula for estimating the deflection angle, which is
$\varphi_{\textrm{def}} = - \frac{\sqrt{2}}{\omega r_{l}^2}\log{\left(b -
b_c\right) + \widetilde{C}(b)}$. We also numerically plot the images of shadows
and photon rings of the QBH in three different illumination models and compare
them with that of a Schwarzschild in each model. It is found that we could
distinguish the quantum black hole with a Schwarzschild black hole by the
shadow images in certain specific illumination model.
| [
{
"created": "Fri, 29 Dec 2023 18:23:38 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Jan 2024 01:45:42 GMT",
"version": "v2"
}
] | 2024-01-30 | [
[
"Ye",
"Jing-Peng",
""
],
[
"He",
"Zhi-Qing",
""
],
[
"Zhou",
"Ai-Xu",
""
],
[
"Huang",
"Zi-Yang",
""
],
[
"Huang",
"Jia-Hui",
""
]
] | Recently, a black hole model in loop quantum gravity has been proposed by Lewandowski, Ma, Yang and Zhang (Phys. Rev. Lett. \textbf{130}, 101501 (2023)). The metric tensor of the quantum black hole (QBH) is a suitably modified Schwarzschild one. In this paper, we calculate the radius of light ring and obtain the linear approximation of it with respect to the quantum correction parameter $\alpha$: $r_{l} \simeq 3 M - \frac{\alpha}{9 M}$. We then assume the QBH is backlit by a large, distant plane of uniform, isotropic emission and calculate the radius of the black hole shadow and its linear approximation: $r_{s} = 3 \sqrt{3} M - \frac{\alpha}{6 \left(\sqrt{3} M\right)}$. We also consider the photon ring structures in the shadow when the impact parameter $b$ of the photon approaches to a critical impact parameter $b_{\textrm{c}}$, and obtain a formula for estimating the deflection angle, which is $\varphi_{\textrm{def}} = - \frac{\sqrt{2}}{\omega r_{l}^2}\log{\left(b - b_c\right) + \widetilde{C}(b)}$. We also numerically plot the images of shadows and photon rings of the QBH in three different illumination models and compare them with that of a Schwarzschild in each model. It is found that we could distinguish the quantum black hole with a Schwarzschild black hole by the shadow images in certain specific illumination model. |
1008.5006 | Emil Mottola | Emil Mottola | New Horizons in Gravity: The Trace Anomaly, Dark Energy and Condensate
Stars | Lectures given at the at the XLIX Krakow School. This review article
is pedagogical in style, and wide ranging in scope, collecting and presenting
a broad spectrum of results on black holes, the trace anomaly, and quantum
effects in cosmology. 127 pages, 13 figures. In press | Acta Physica Polonica B (2010) Vol.41, iss.9, p.2031-2162 | null | LA-UR 10-04531; CERN-PH-TH 2010-158 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General Relativity receives quantum corrections relevant at macroscopic
distance scales and near event horizons. These arise from the conformal scalar
degrees of freedom in the extended effective field theory of gravity generated
by the trace anomaly of massless quantum fields in curved space. The origin of
these conformal scalar degrees of freedom as massless poles in two-particle
intermediate states of anomalous amplitudes in flat space is exposed. At event
horizons the conformal anomaly scalar degrees of freedom can have
macroscopically large effects on the geometry, potentially removing the
classical event horizon of black hole and cosmological spacetimes, replacing
them with a quantum boundary layer where the effective value of the
gravitational vacuum energy density can change. In the effective theory, the
cosmological term becomes a dynamical condensate, whose value depends upon
boundary conditions near the horizon. In the conformal phase where the anomaly
induced fluctutations dominate, and the condensate dissolves, the effective
cosmological "constant" is a running coupling which has an infrared stable
fixed point at zero. By taking a positive value in the interior of a fully
collapsed star, the effective cosmological term removes any singularity,
replacing it with a smooth dark energy interior. The resulting gravitational
condensate star configuration resolves all black hole paradoxes, and provides a
testable alternative to black holes as the final state of complete
gravitational collapse. The observed dark energy of our universe likewise may
be a macroscopic finite size effect whose value depends not on microphysics but
on the cosmological horizon scale.
| [
{
"created": "Mon, 30 Aug 2010 05:23:49 GMT",
"version": "v1"
}
] | 2012-09-25 | [
[
"Mottola",
"Emil",
""
]
] | General Relativity receives quantum corrections relevant at macroscopic distance scales and near event horizons. These arise from the conformal scalar degrees of freedom in the extended effective field theory of gravity generated by the trace anomaly of massless quantum fields in curved space. The origin of these conformal scalar degrees of freedom as massless poles in two-particle intermediate states of anomalous amplitudes in flat space is exposed. At event horizons the conformal anomaly scalar degrees of freedom can have macroscopically large effects on the geometry, potentially removing the classical event horizon of black hole and cosmological spacetimes, replacing them with a quantum boundary layer where the effective value of the gravitational vacuum energy density can change. In the effective theory, the cosmological term becomes a dynamical condensate, whose value depends upon boundary conditions near the horizon. In the conformal phase where the anomaly induced fluctutations dominate, and the condensate dissolves, the effective cosmological "constant" is a running coupling which has an infrared stable fixed point at zero. By taking a positive value in the interior of a fully collapsed star, the effective cosmological term removes any singularity, replacing it with a smooth dark energy interior. The resulting gravitational condensate star configuration resolves all black hole paradoxes, and provides a testable alternative to black holes as the final state of complete gravitational collapse. The observed dark energy of our universe likewise may be a macroscopic finite size effect whose value depends not on microphysics but on the cosmological horizon scale. |
2104.14100 | Tuan Do | Tuan Q. Do, W. F. Kao | Anisotropic power-law inflation for a model of two scalar and two vector
fields | 13 pages, 2 figures. Updated version, in which several typos are
corrected and one reference is added. All results are not changed. Matches
the published version. Comments are welcome | Eur. Phys. J. C 81, 525 (2021) | 10.1140/epjc/s10052-021-09334-y | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspired by an interesting counterexample to the cosmic no-hair conjecture
found in a supergravity-motivated model recently, we propose a multi-field
extension, in which two scalar fields are allowed to non-minimally couple to
two vector fields, respectively. This model is shown to admit an exact Bianchi
type I power-law solution. Furthermore, stability analysis based on the
dynamical system method is performed to show that this anisotropic solution is
indeed stable and attractive if both scalar fields are canonical. Nevertheless,
if one of the two scalar fields is phantom then the corresponding anisotropic
power-law inflation turns unstable as expected.
| [
{
"created": "Thu, 29 Apr 2021 04:31:55 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Jun 2021 15:38:46 GMT",
"version": "v2"
}
] | 2021-06-22 | [
[
"Do",
"Tuan Q.",
""
],
[
"Kao",
"W. F.",
""
]
] | Inspired by an interesting counterexample to the cosmic no-hair conjecture found in a supergravity-motivated model recently, we propose a multi-field extension, in which two scalar fields are allowed to non-minimally couple to two vector fields, respectively. This model is shown to admit an exact Bianchi type I power-law solution. Furthermore, stability analysis based on the dynamical system method is performed to show that this anisotropic solution is indeed stable and attractive if both scalar fields are canonical. Nevertheless, if one of the two scalar fields is phantom then the corresponding anisotropic power-law inflation turns unstable as expected. |
2206.10398 | Roldao da Rocha | R. Casadio, R. da Rocha, P. Meert, L. Tabarroni, W. Barreto | Configurational entropy of black hole quantum cores | 14 pages, 4 figures, improved version | Class. Quantum Grav. 40 (2023) 075014 | 10.1088/1361-6382/acbe89 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Two types of information entropy are studied for the quantum states of a
model for the matter core inside a black hole geometry. A detailed description
is first given of the quantum mechanical picture leading to a spectrum of bound
states for a collapsing ball of dust in general relativity with a non-trivial
ground state. Information entropies are then computed, shedding new light on
the stability of the ground state and the spectrum of higher excited states.
| [
{
"created": "Tue, 21 Jun 2022 13:43:47 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Nov 2022 14:44:22 GMT",
"version": "v2"
}
] | 2023-03-15 | [
[
"Casadio",
"R.",
""
],
[
"da Rocha",
"R.",
""
],
[
"Meert",
"P.",
""
],
[
"Tabarroni",
"L.",
""
],
[
"Barreto",
"W.",
""
]
] | Two types of information entropy are studied for the quantum states of a model for the matter core inside a black hole geometry. A detailed description is first given of the quantum mechanical picture leading to a spectrum of bound states for a collapsing ball of dust in general relativity with a non-trivial ground state. Information entropies are then computed, shedding new light on the stability of the ground state and the spectrum of higher excited states. |
0708.0170 | Volker Perlick | Volker Perlick | On the radar method in general-relativistic spacetimes | Written version of talk given at 359th WE Heraeus Seminar ``Lasers,
Clocks, and Drag-Free. New Technologies for Testing Relativistic Gravity in
Space.'' Bremen, 2005; to appear in H. Dittus, C. L{\"a}mmerzahl, S. G.
Turyshev (eds.): ``Lasers, Clocks, and Drag-Free Control. Exploration of
Relativistic Gravity in Space.'' Springer, 2007 | null | 10.1007/978-3-540-34377-6_5 | null | gr-qc | null | If a clock, mathematically modeled by a parametrized timelike curve in a
general-relativistic spacetime, is given, the radar method assigns a time and a
distance to every event which is sufficiently close to the clock. Several
geometric aspects of this method are reviewed and their physical interpretation
is discussed.
| [
{
"created": "Wed, 1 Aug 2007 14:54:52 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Perlick",
"Volker",
""
]
] | If a clock, mathematically modeled by a parametrized timelike curve in a general-relativistic spacetime, is given, the radar method assigns a time and a distance to every event which is sufficiently close to the clock. Several geometric aspects of this method are reviewed and their physical interpretation is discussed. |
gr-qc/9605074 | Salman Habib | Tanmoy Bhattacharya, Salman Habib, and Emil Mottola (Los Alamos) | Comment on "Gravitationally Induced Neutrino-Oscillation Phases" | Plain LaTeX, 7 pages, no figures | Phys. Rev. D59 (1999) 067301 | 10.1103/PhysRevD.59.067301 | null | gr-qc astro-ph hep-ph quant-ph | null | We critically examine the recent claim (gr-qc/9603008) of a ``new effect'' of
gravitationally induced quantum mechanical phases in neutrino oscillations. A
straightforward exercise in the Schwarzschild coordinates appropriate to a
spherically symmetric non-rotating star shows that, although there is a general
relativistic effect of the star's gravity on neutrino oscillations, it is not
of the form claimed, and is too small to be measured.
| [
{
"created": "Mon, 3 Jun 1996 05:16:59 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bhattacharya",
"Tanmoy",
"",
"Los Alamos"
],
[
"Habib",
"Salman",
"",
"Los Alamos"
],
[
"Mottola",
"Emil",
"",
"Los Alamos"
]
] | We critically examine the recent claim (gr-qc/9603008) of a ``new effect'' of gravitationally induced quantum mechanical phases in neutrino oscillations. A straightforward exercise in the Schwarzschild coordinates appropriate to a spherically symmetric non-rotating star shows that, although there is a general relativistic effect of the star's gravity on neutrino oscillations, it is not of the form claimed, and is too small to be measured. |
gr-qc/9811028 | Leor Barack | Leor Barack | Late time dynamics of scalar perturbations outside black holes: II.
Schwarzschild geometry | 17 pages, 14 figures. Accepted for publication in Physical Review D | Phys.Rev. D59 (1999) 044017 | 10.1103/PhysRevD.59.044017 | null | gr-qc | null | We apply a new analytic scheme, developed in a preceding paper, in order to
calculate the late time behavior of scalar test fields evolving outside a
Schwarzschild black hole. The pattern of the late time decay at future null
infinity is found to be the same as in the shell toy-model studied in the
preceding paper. A simple late time expansion of the scalar field is then used,
relying on the results at null infinity, to construct a complete picture of the
late time wave behavior anywhere outside the black hole. This reproduces the
well known power-law tails at time-like infinity and along the event horizon.
The main motivation for the introduction of the new approach arises from its
applicability to rotating black holes, as shall be discussed in a forthcoming
paper.
| [
{
"created": "Tue, 10 Nov 1998 10:19:25 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Barack",
"Leor",
""
]
] | We apply a new analytic scheme, developed in a preceding paper, in order to calculate the late time behavior of scalar test fields evolving outside a Schwarzschild black hole. The pattern of the late time decay at future null infinity is found to be the same as in the shell toy-model studied in the preceding paper. A simple late time expansion of the scalar field is then used, relying on the results at null infinity, to construct a complete picture of the late time wave behavior anywhere outside the black hole. This reproduces the well known power-law tails at time-like infinity and along the event horizon. The main motivation for the introduction of the new approach arises from its applicability to rotating black holes, as shall be discussed in a forthcoming paper. |
gr-qc/9710139 | Robert Mann | H. Burton, R.B. Mann | Palatini Variational Principle for $N$-Dimensional Dilaton Gravity | 16 pages, LaTeX | Class.Quant.Grav. 15 (1998) 1375-1385 | 10.1088/0264-9381/15/5/019 | WATPHYS TH-97/16 | gr-qc | null | We consider a Palatini variation on a general $N$-Dimensional second order,
torsion-free dilaton gravity action and determine the resulting equations of
motion. Consistency is checked by considering the restraint imposed due to
invariance of the matter action under simple coordinate transformations, and
the special case of N=2 is examined. We also examine a sub-class of theories
whereby a Palatini variation dynamically coincides with that of the "ordinary"
Hilbert variational principle; in particular we examine a generalized
Brans-Dicke theory and the associated role of conformal transformations.
| [
{
"created": "Fri, 31 Oct 1997 21:22:56 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Burton",
"H.",
""
],
[
"Mann",
"R. B.",
""
]
] | We consider a Palatini variation on a general $N$-Dimensional second order, torsion-free dilaton gravity action and determine the resulting equations of motion. Consistency is checked by considering the restraint imposed due to invariance of the matter action under simple coordinate transformations, and the special case of N=2 is examined. We also examine a sub-class of theories whereby a Palatini variation dynamically coincides with that of the "ordinary" Hilbert variational principle; in particular we examine a generalized Brans-Dicke theory and the associated role of conformal transformations. |
gr-qc/0305019 | Yee J. Ng | Y. Jack Ng (University of North Carolina) | Selected topics in Planck-scale physics | 31 pages, 1 figure; minor changes; to appear in Mod. Phys. Lett. A as
a Brief Review | Mod.Phys.Lett.A18:1073-1098,2003 | 10.1142/S0217732303010934 | null | gr-qc astro-ph hep-ph hep-th | null | We review a few topics in Planck-scale physics, with emphasis on possible
manifestations in relatively low energy. The selected topics include quantum
fluctuations of spacetime, their cumulative effects, uncertainties in
energy-momentum measurements, and low energy quantum-gravity phenomenology. The
focus is on quantum-gravity-induced uncertainties in some observable
quantities. We consider four possible ways to probe Planck-scale physics
experimentally: 1. looking for energy-dependent spreads in the arrival time of
photons of the same energy from GRBs; 2. examining spacetime
fluctuation-induced phase incoherence of light from extragalactic sources; 3.
detecting spacetime foam with laser-based interferometry techniques; 4.
understanding the threshold anomalies in high energy cosmic ray and gamma ray
events. Some other experiments are briefly discussed. We show how some physics
behind black holes, simple clocks, simple computers, and the holographic
principle is related to Planck-scale physics. We also discuss a formulation of
the Dirac equation as a difference equation on a discrete Planck-scale
spacetime lattice, and a possible interplay between Planck-scale and
Hubble-scale physics encoded in the cosmological constant (dark energy).
| [
{
"created": "Sun, 4 May 2003 21:22:11 GMT",
"version": "v1"
},
{
"created": "Thu, 15 May 2003 19:00:08 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Ng",
"Y. Jack",
"",
"University of North Carolina"
]
] | We review a few topics in Planck-scale physics, with emphasis on possible manifestations in relatively low energy. The selected topics include quantum fluctuations of spacetime, their cumulative effects, uncertainties in energy-momentum measurements, and low energy quantum-gravity phenomenology. The focus is on quantum-gravity-induced uncertainties in some observable quantities. We consider four possible ways to probe Planck-scale physics experimentally: 1. looking for energy-dependent spreads in the arrival time of photons of the same energy from GRBs; 2. examining spacetime fluctuation-induced phase incoherence of light from extragalactic sources; 3. detecting spacetime foam with laser-based interferometry techniques; 4. understanding the threshold anomalies in high energy cosmic ray and gamma ray events. Some other experiments are briefly discussed. We show how some physics behind black holes, simple clocks, simple computers, and the holographic principle is related to Planck-scale physics. We also discuss a formulation of the Dirac equation as a difference equation on a discrete Planck-scale spacetime lattice, and a possible interplay between Planck-scale and Hubble-scale physics encoded in the cosmological constant (dark energy). |
1807.06509 | Lior M. Burko | Caroline Mallary, Gaurav Khanna, Lior M. Burko | Physical objects approaching the Cauchy horizon of a rapidly rotating
Kerr black hole | null | Phys. Rev. D 98, 104024 (2018) | 10.1103/PhysRevD.98.104024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We solve the 2+1-dimensional Teukolsky equation numerically for the Weyl
scalars $\psi_0$ and $\psi_4$ along a time-like geodesic approaching the Cauchy
horizon of a rapidly rotating perturbed Kerr black hole. We find that both the
amplitude and frequency of the Weyl scalars agree with the results of linear
perturbation analysis. We then model a physical object by a simple damped
harmonic oscillator, which is driven by an external force that mimics the tidal
force experienced by the infalling object. We use this model to find the total
deformation of the object at the Cauchy horizon, and the resonant effect when
the driving force's frequency matches the internal frequency of the oscillator
that models the object.
| [
{
"created": "Tue, 17 Jul 2018 15:46:37 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Dec 2018 19:26:02 GMT",
"version": "v2"
}
] | 2018-12-10 | [
[
"Mallary",
"Caroline",
""
],
[
"Khanna",
"Gaurav",
""
],
[
"Burko",
"Lior M.",
""
]
] | We solve the 2+1-dimensional Teukolsky equation numerically for the Weyl scalars $\psi_0$ and $\psi_4$ along a time-like geodesic approaching the Cauchy horizon of a rapidly rotating perturbed Kerr black hole. We find that both the amplitude and frequency of the Weyl scalars agree with the results of linear perturbation analysis. We then model a physical object by a simple damped harmonic oscillator, which is driven by an external force that mimics the tidal force experienced by the infalling object. We use this model to find the total deformation of the object at the Cauchy horizon, and the resonant effect when the driving force's frequency matches the internal frequency of the oscillator that models the object. |
2105.09294 | Lorenzo Gavassino | Lorenzo Gavassino | Proving the Lorentz invariance of the entropy and the covariance of
thermodynamics | 10 pages | Foundations of Physics volume 52, Article number: 11 (2022) | 10.1007/s10701-021-00518-w | null | gr-qc astro-ph.HE cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The standard argument for the Lorentz invariance of the thermodynamic entropy
in equilibrium is based on the assumption that it is possible to perform an
adiabatic transformation whose only outcome is to accelerate a macroscopic
body, keeping its rest mass unchanged. The validity of this assumption
constitutes the very foundation of relativistic thermodynamics and needs to be
tested in greater detail. We show that, indeed, such a transformation is always
possible, at least in principle. The only two assumptions invoked in the proof
are that there is at least one inertial reference frame in which the second law
of thermodynamics is valid and that the microscopic theory describing the
internal dynamics of the body is a field theory, with Lorentz invariant
Lagrangian density. The proof makes no reference to the connection between
entropy and probabilities and is valid both within classical and quantum
physics. To avoid any risk of circular reasoning, we do not postulate that the
laws of thermodynamics are the same in every reference frame, but we obtain
this fact as a direct consequence of the Lorentz invariance of the entropy.
| [
{
"created": "Wed, 19 May 2021 17:55:25 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Jun 2021 16:15:21 GMT",
"version": "v2"
}
] | 2021-12-15 | [
[
"Gavassino",
"Lorenzo",
""
]
] | The standard argument for the Lorentz invariance of the thermodynamic entropy in equilibrium is based on the assumption that it is possible to perform an adiabatic transformation whose only outcome is to accelerate a macroscopic body, keeping its rest mass unchanged. The validity of this assumption constitutes the very foundation of relativistic thermodynamics and needs to be tested in greater detail. We show that, indeed, such a transformation is always possible, at least in principle. The only two assumptions invoked in the proof are that there is at least one inertial reference frame in which the second law of thermodynamics is valid and that the microscopic theory describing the internal dynamics of the body is a field theory, with Lorentz invariant Lagrangian density. The proof makes no reference to the connection between entropy and probabilities and is valid both within classical and quantum physics. To avoid any risk of circular reasoning, we do not postulate that the laws of thermodynamics are the same in every reference frame, but we obtain this fact as a direct consequence of the Lorentz invariance of the entropy. |
2402.13665 | Nikolaos Dimakis | Homa Shababi, Theophanes Grammenos, Nikolaos Dimakis, Andronikos
Paliathanasis and Theodosios Christodoulakis | A five-dimensional Bianchi type V-like extension | 21 pages, 4 figures, Latex2e source file | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We uncover the solution space of a five dimensional geometry which we deem it
as the direct counterpart of the Bianchi Type V cosmological model. We
kinematically reduce the scale factor matrix and then, with an appropriate
scaling and choice of time, we cast the spatial equations into a simple
``Kasner'' like form; thus revealing linear integrals of motion. Their number
is enough so that, along with the quadratic constraint, it suffices to scan the
entire space of solutions. The latter is revealed to be quite rich, containing
cosmological solutions, some of which admit dimensional reduction
asymptotically to four dimensions, Kundt spacetimes with vanishing type I
(polynomial) curvature scalars and solutions describing periodic universes
which behave like cosmological time crystals.
| [
{
"created": "Wed, 21 Feb 2024 09:55:17 GMT",
"version": "v1"
}
] | 2024-02-22 | [
[
"Shababi",
"Homa",
""
],
[
"Grammenos",
"Theophanes",
""
],
[
"Dimakis",
"Nikolaos",
""
],
[
"Paliathanasis",
"Andronikos",
""
],
[
"Christodoulakis",
"Theodosios",
""
]
] | We uncover the solution space of a five dimensional geometry which we deem it as the direct counterpart of the Bianchi Type V cosmological model. We kinematically reduce the scale factor matrix and then, with an appropriate scaling and choice of time, we cast the spatial equations into a simple ``Kasner'' like form; thus revealing linear integrals of motion. Their number is enough so that, along with the quadratic constraint, it suffices to scan the entire space of solutions. The latter is revealed to be quite rich, containing cosmological solutions, some of which admit dimensional reduction asymptotically to four dimensions, Kundt spacetimes with vanishing type I (polynomial) curvature scalars and solutions describing periodic universes which behave like cosmological time crystals. |
0709.4391 | De-Chang Dai | De-Chang Dai, Irit Maor and Glenn Starkman | Modified Gravity: living without Birkhoff I. DGP | 5 pages, 3 figures | Phys.Rev.D77:064016,2008 | 10.1103/PhysRevD.77.064016 | null | gr-qc astro-ph | null | We consider the consequences of the absence of Birkhoff's theorem in theories
of modified gravity. As an example, we calculate the gravitational force on a
test particle due to a spherical mass shell in the Dvali-Gabadaze-Porrati model
(DGP). We show that unlike in General Relativity, the force depends on the mass
distribution. In particular, the gravitational force within a spherical mass
shell depends on the geometric structure of the bulk, and is likely non-zero.
| [
{
"created": "Thu, 27 Sep 2007 13:23:00 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Dec 2007 17:59:50 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Dai",
"De-Chang",
""
],
[
"Maor",
"Irit",
""
],
[
"Starkman",
"Glenn",
""
]
] | We consider the consequences of the absence of Birkhoff's theorem in theories of modified gravity. As an example, we calculate the gravitational force on a test particle due to a spherical mass shell in the Dvali-Gabadaze-Porrati model (DGP). We show that unlike in General Relativity, the force depends on the mass distribution. In particular, the gravitational force within a spherical mass shell depends on the geometric structure of the bulk, and is likely non-zero. |
1111.4187 | Roberto Chan | R. Chan, M. F. A. da Silva, P. Senna, J. F. Villas da Rocha | Gravastars with Dark Energy Evolving to Naked Singularity | 18 pages and 6 figures. arXiv admin note: substantial text overlap
with arXiv:1012.1233 and arXiv:0812.4924v2 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a gravastar model made of anisotropic dark energy with an
infinitely thin spherical shell of a perfect fluid with the equation of state
$p = (1-\gamma)\sigma$ with an external de Sitter-Schwarzschild region. It is
found that in some cases the models represent the "bounded excursion" stable
gravastars, where the thin shell is oscillating between two finite radii, while
in other cases they collapse until the formation of black holes or naked
singularities. An interesting result is that we can have black hole and stable
gravastar formation even with an interior and a shell constituted of dark and
repulsive dark energy, as also shown in previous work. Besides, in three cases
we have a dynamical evolution to a black hole (for $\Lambda=0$) or to a naked
singularity (for $\Lambda > 0$). This is the first time in the literature that
a naked singularity emerges from a gravastar model.
| [
{
"created": "Thu, 17 Nov 2011 19:20:21 GMT",
"version": "v1"
}
] | 2015-03-19 | [
[
"Chan",
"R.",
""
],
[
"da Silva",
"M. F. A.",
""
],
[
"Senna",
"P.",
""
],
[
"da Rocha",
"J. F. Villas",
""
]
] | We consider a gravastar model made of anisotropic dark energy with an infinitely thin spherical shell of a perfect fluid with the equation of state $p = (1-\gamma)\sigma$ with an external de Sitter-Schwarzschild region. It is found that in some cases the models represent the "bounded excursion" stable gravastars, where the thin shell is oscillating between two finite radii, while in other cases they collapse until the formation of black holes or naked singularities. An interesting result is that we can have black hole and stable gravastar formation even with an interior and a shell constituted of dark and repulsive dark energy, as also shown in previous work. Besides, in three cases we have a dynamical evolution to a black hole (for $\Lambda=0$) or to a naked singularity (for $\Lambda > 0$). This is the first time in the literature that a naked singularity emerges from a gravastar model. |
2010.00151 | Tianchi Ma | Tian-Chi Ma and He-Xu Zhang and Peng-Zhang He and Hao-Ran Zhang and
Yuan Chen and Jian-Bo Deng | Shadow cast by a rotating and nonlinear magnetic-charged black hole in
perfect fluid dark matter | null | null | 10.1142/S0217732321501121 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derived an exact solution of the spherically symmetric Hayward black hole
surrounded by perfect fluid dark matter (PFDM). By applying the Newman-Janis
algorithm, we generalized it to the corresponding rotating black hole. Then, we
studied the shadows of rotating Hayward black hole in PFDM. The apparent shape
of the shadow depends upon the black hole spin $a$, the magnetic charge $Q$ and
the PFDM intensity parameter $k$ ($k<0$). The shadow is a perfect circle in the
non-rotating case ($a=0$) and a deformed one in the rotating case ($a\neq{0}$).
For a fixed value of $a$, the size of the shadow increases with the increasing
$\vert{k}\vert$, but decreases with the increasing $Q$. We further investigated
the black hole emission rate. We found that the emission rate decreases with
the increasing $\vert{k}\vert$ (or $Q$) and the peak of the emission shifts to
lower frequency. Finally, we discussed the observational prospects
corresponding to the supermassive black hole $\mathrm{Sgr\ A^{*}}$ at the
center of the Milky Way.
| [
{
"created": "Thu, 1 Oct 2020 00:03:45 GMT",
"version": "v1"
},
{
"created": "Sun, 7 Mar 2021 14:22:42 GMT",
"version": "v2"
},
{
"created": "Sat, 18 Dec 2021 19:00:51 GMT",
"version": "v3"
}
] | 2021-12-21 | [
[
"Ma",
"Tian-Chi",
""
],
[
"Zhang",
"He-Xu",
""
],
[
"He",
"Peng-Zhang",
""
],
[
"Zhang",
"Hao-Ran",
""
],
[
"Chen",
"Yuan",
""
],
[
"Deng",
"Jian-Bo",
""
]
] | We derived an exact solution of the spherically symmetric Hayward black hole surrounded by perfect fluid dark matter (PFDM). By applying the Newman-Janis algorithm, we generalized it to the corresponding rotating black hole. Then, we studied the shadows of rotating Hayward black hole in PFDM. The apparent shape of the shadow depends upon the black hole spin $a$, the magnetic charge $Q$ and the PFDM intensity parameter $k$ ($k<0$). The shadow is a perfect circle in the non-rotating case ($a=0$) and a deformed one in the rotating case ($a\neq{0}$). For a fixed value of $a$, the size of the shadow increases with the increasing $\vert{k}\vert$, but decreases with the increasing $Q$. We further investigated the black hole emission rate. We found that the emission rate decreases with the increasing $\vert{k}\vert$ (or $Q$) and the peak of the emission shifts to lower frequency. Finally, we discussed the observational prospects corresponding to the supermassive black hole $\mathrm{Sgr\ A^{*}}$ at the center of the Milky Way. |
1102.2626 | A. Tawfik | A. Tawfik (Egyptian Ctr. Theor. Phys., Cairo) | The Hubble parameter in the early universe with viscous QCD matter and
finite cosmological constant | 9 pages, 4 eps figures, 5 eps graphs, revtex4-style. arXiv admin
note: text overlap with arXiv:gr-qc/0110119 and arXiv:1001.2814 | Ann. Phys. (Berlin) 523, No. 5, 423 - 434 (2011) | 10.1002/andp.201100038 | ECTP-2011-01 | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The evolution of a flat, isotropic and homogeneous universe is studied. The
background geometry in the early phases of the universe is conjectured to be
filled with causal bulk viscous cosmological fluid and dark energy. The energy
density relations obtained from the assumption of covariant conservation of
energy-momentum tensor of the background matter in the early universe are used
to derive the basic equation for the Hubble parameter $H$. The viscous
properties described by ultra-relativistic equations of state and bulk
viscosity taken from recent heavy-ion collisions and lattice QCD calculations
have been utilized to give an approximate solution of the field equations. The
cosmological constant is conjectured to be related to the energy density of the
vacuum. In this treatment, there is a clear evidence for singularity at
vanishing cosmic time $t$ indicating the dominant contribution from the dark
energy. The time evolution of $H$ seems to last for much longer time than the
ideal case, where both cosmological constant and viscosity coefficient are
entirely vanishing.
| [
{
"created": "Sun, 13 Feb 2011 19:25:31 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Apr 2012 20:31:36 GMT",
"version": "v2"
}
] | 2012-04-23 | [
[
"Tawfik",
"A.",
"",
"Egyptian Ctr. Theor. Phys., Cairo"
]
] | The evolution of a flat, isotropic and homogeneous universe is studied. The background geometry in the early phases of the universe is conjectured to be filled with causal bulk viscous cosmological fluid and dark energy. The energy density relations obtained from the assumption of covariant conservation of energy-momentum tensor of the background matter in the early universe are used to derive the basic equation for the Hubble parameter $H$. The viscous properties described by ultra-relativistic equations of state and bulk viscosity taken from recent heavy-ion collisions and lattice QCD calculations have been utilized to give an approximate solution of the field equations. The cosmological constant is conjectured to be related to the energy density of the vacuum. In this treatment, there is a clear evidence for singularity at vanishing cosmic time $t$ indicating the dominant contribution from the dark energy. The time evolution of $H$ seems to last for much longer time than the ideal case, where both cosmological constant and viscosity coefficient are entirely vanishing. |
gr-qc/9401031 | Biplab Bhawal | Biplab Bhawal and Vijay Chickarmane | Squeezing and Dual Recycling in Laser Interferometric Gravitational Wave
Detectors | Plain tex, 11 pages, 1 figure available on request from
biplab@iucaa.ernet.in | Phys.Lett. A190 (1994) 22; Erratum-ibid. A196 (1995) 377 | 10.1016/0375-9601(94)90360-3 | null | gr-qc | null | We calculate the response of an ideal Michelson interferometer incorporating
both dual recycling and squeezed light to gravitational waves. The photon
counting noise has contributions from the light which is sent in through the
input ports as well as the vacuum modes at sideband frequencies generated by
the gravitational waves. The minimum detectable gravity wave amplitude depends
on the frequency of the wave as well as the squeezing and recycling parameters.
Both squeezing and the broadband operation of dual recycling reduce the photon
counting noise and hence the two techniques can be used together to make more
accurate phase measurements. The variance of photon number is found to be
time-dependent, oscillating at the gravity wave frequency but of much lower
order than the constant part.
| [
{
"created": "Tue, 25 Jan 1994 15:00:42 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Bhawal",
"Biplab",
""
],
[
"Chickarmane",
"Vijay",
""
]
] | We calculate the response of an ideal Michelson interferometer incorporating both dual recycling and squeezed light to gravitational waves. The photon counting noise has contributions from the light which is sent in through the input ports as well as the vacuum modes at sideband frequencies generated by the gravitational waves. The minimum detectable gravity wave amplitude depends on the frequency of the wave as well as the squeezing and recycling parameters. Both squeezing and the broadband operation of dual recycling reduce the photon counting noise and hence the two techniques can be used together to make more accurate phase measurements. The variance of photon number is found to be time-dependent, oscillating at the gravity wave frequency but of much lower order than the constant part. |
1312.6425 | Abhay Ashtekar | Abhay Ashtekar | The Last 50 Years of General Relativity and Gravitation: From GR3 to
GR20 Warsaw Conferences | 15 pages, one figure. Minor typos corrected. A para on talks at GR3
on asymptotics added in the beginning of Section 2 | Gen. Relativ. Gravit. 46, 1706 (2014) | 10.1007/s10714-014-1706-2 | IGC-13/12-2 | gr-qc hep-th physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article has a dual purpose: i) to provide a flavor of the scientific
highlights of the landmark conference, GR3, held in July 1962 at Jablonna, near
Warsaw; and, ii) to present a bird's eye view of the tremendous advances that
have occurred over the half century that separates GR3 and GR20, which was
again held in Warsaw in July 2013.
| [
{
"created": "Sun, 22 Dec 2013 21:17:59 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Jan 2014 17:48:52 GMT",
"version": "v2"
}
] | 2014-04-17 | [
[
"Ashtekar",
"Abhay",
""
]
] | This article has a dual purpose: i) to provide a flavor of the scientific highlights of the landmark conference, GR3, held in July 1962 at Jablonna, near Warsaw; and, ii) to present a bird's eye view of the tremendous advances that have occurred over the half century that separates GR3 and GR20, which was again held in Warsaw in July 2013. |
gr-qc/9709016 | Joan Masso | Carles Bona, Joan Masso, Ed Seidel and Joan Stela | First order hyperbolic formalism for Numerical Relativity | To appear in Phys. Rev. D | Phys.Rev.D56:3405-3415,1997 | 10.1103/PhysRevD.56.3405 | null | gr-qc | null | The causal structure of Einstein's evolution equations is considered. We show
that in general they can be written as a first order system of balance laws for
any choice of slicing or shift. We also show how certain terms in the evolution
equations, that can lead to numerical inaccuracies, can be eliminated by using
the Hamiltonian constraint. Furthermore, we show that the entire system is
hyperbolic when the time coordinate is chosen in an invariant algebraic way,
and for any fixed choice of the shift. This is achieved by using the momentum
constraints in such as way that no additional space or time derivatives of the
equations need to be computed. The slicings that allow hyperbolicity in this
formulation belong to a large class, including harmonic, maximal, and many
others that have been commonly used in numerical relativity. We provide details
of some of the advanced numerical methods that this formulation of the
equations allows, and we also discuss certain advantages that a hyperbolic
formulation provides when treating boundary conditions.
| [
{
"created": "Sun, 7 Sep 1997 16:10:37 GMT",
"version": "v1"
}
] | 2011-04-21 | [
[
"Bona",
"Carles",
""
],
[
"Masso",
"Joan",
""
],
[
"Seidel",
"Ed",
""
],
[
"Stela",
"Joan",
""
]
] | The causal structure of Einstein's evolution equations is considered. We show that in general they can be written as a first order system of balance laws for any choice of slicing or shift. We also show how certain terms in the evolution equations, that can lead to numerical inaccuracies, can be eliminated by using the Hamiltonian constraint. Furthermore, we show that the entire system is hyperbolic when the time coordinate is chosen in an invariant algebraic way, and for any fixed choice of the shift. This is achieved by using the momentum constraints in such as way that no additional space or time derivatives of the equations need to be computed. The slicings that allow hyperbolicity in this formulation belong to a large class, including harmonic, maximal, and many others that have been commonly used in numerical relativity. We provide details of some of the advanced numerical methods that this formulation of the equations allows, and we also discuss certain advantages that a hyperbolic formulation provides when treating boundary conditions. |
1704.05639 | Edgar Gasperin | Alfonso Garc\'ia-Parrado G\'omez-Lobo, Edgar Gasperin, Juan A.
Valiente Kroon | Conformal geodesics in spherically symmetric vacuum spacetimes with
Cosmological constant | 51 pages, 12 figures. Minor changes. File updated. To appear in CQG | null | 10.1088/1361-6382/aa9f59 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An analysis of conformal geodesics in the Schwarzschild-de Sitter and
Schwarzschild-anti de Sitter families of spacetimes is given. For both families
of spacetimes we show that initial data on a spacelike hypersurface can be
given such that the congruence of conformal geodesics arising from this data
cover the whole maximal extension of canonical conformal representations of the
spacetimes without forming caustic points. For the Schwarzschild-de Sitter
family, the resulting congruence can be used to obtain global conformal
Gaussian systems of coordinates of the conformal representation. In the case of
the Schwarzschild-anti de Sitter family, the natural parameter of the curves
only covers a restricted time span so that these global conformal Gaussian
systems do not exist.
| [
{
"created": "Wed, 19 Apr 2017 07:49:27 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Dec 2017 21:02:35 GMT",
"version": "v2"
}
] | 2018-02-14 | [
[
"Gómez-Lobo",
"Alfonso García-Parrado",
""
],
[
"Gasperin",
"Edgar",
""
],
[
"Kroon",
"Juan A. Valiente",
""
]
] | An analysis of conformal geodesics in the Schwarzschild-de Sitter and Schwarzschild-anti de Sitter families of spacetimes is given. For both families of spacetimes we show that initial data on a spacelike hypersurface can be given such that the congruence of conformal geodesics arising from this data cover the whole maximal extension of canonical conformal representations of the spacetimes without forming caustic points. For the Schwarzschild-de Sitter family, the resulting congruence can be used to obtain global conformal Gaussian systems of coordinates of the conformal representation. In the case of the Schwarzschild-anti de Sitter family, the natural parameter of the curves only covers a restricted time span so that these global conformal Gaussian systems do not exist. |
1711.09430 | Lavinia Heisenberg | Lavinia Heisenberg and Shinji Tsujikawa | Dark energy survivals in massive gravity after GW170817: SO(3) invariant | 26 pages, 2 figues | null | 10.1088/1475-7516/2018/01/044 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent detection of the gravitational wave signal GW170817 together with
an electromagnetic counterpart GRB 170817A from the merger of two neutron stars
puts a stringent bound on the tensor propagation speed. This constraint can be
automatically satisfied in the framework of massive gravity. In this work we
consider a general $SO(3)$-invariant massive gravity with five propagating
degrees of freedom and derive the conditions for the absence of ghosts and
Laplacian instabilities in the presence of a matter perfect fluid on the flat
Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) cosmological background. The
graviton potential containing the dependence of three-dimensional metrics and a
fiducial metric coupled to a temporal scalar field gives rise to a scenario of
the late-time cosmic acceleration in which the dark energy equation of state
$w_{\rm DE}$ is equivalent to $-1$ or varies in time. We find that the
deviation from the value $w_{\rm DE}=-1$ provides important contributions to
the quantities associated with the stability conditions of tensor, vector, and
scalar perturbations. In concrete models, we study the dynamics of dark energy
arising from the graviton potential and show that there exist viable parameter
spaces in which neither ghosts nor Laplacian instabilities are present for both
$w_{\rm DE}>-1$ and $w_{\rm DE}<-1$. We also generally obtain the effective
gravitational coupling $G_{\rm eff}$ with non-relativistic matter as well as
the gravitational slip parameter $\eta_s$ associated with the observations of
large-scale structures and weak lensing. We show that, apart from a specific
case, the two quantities $G_{\rm eff}$ and $\eta_s$ are similar to those in
general relativity for scalar perturbations deep inside the sound horizon.
| [
{
"created": "Sun, 26 Nov 2017 17:36:57 GMT",
"version": "v1"
}
] | 2022-08-03 | [
[
"Heisenberg",
"Lavinia",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | The recent detection of the gravitational wave signal GW170817 together with an electromagnetic counterpart GRB 170817A from the merger of two neutron stars puts a stringent bound on the tensor propagation speed. This constraint can be automatically satisfied in the framework of massive gravity. In this work we consider a general $SO(3)$-invariant massive gravity with five propagating degrees of freedom and derive the conditions for the absence of ghosts and Laplacian instabilities in the presence of a matter perfect fluid on the flat Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) cosmological background. The graviton potential containing the dependence of three-dimensional metrics and a fiducial metric coupled to a temporal scalar field gives rise to a scenario of the late-time cosmic acceleration in which the dark energy equation of state $w_{\rm DE}$ is equivalent to $-1$ or varies in time. We find that the deviation from the value $w_{\rm DE}=-1$ provides important contributions to the quantities associated with the stability conditions of tensor, vector, and scalar perturbations. In concrete models, we study the dynamics of dark energy arising from the graviton potential and show that there exist viable parameter spaces in which neither ghosts nor Laplacian instabilities are present for both $w_{\rm DE}>-1$ and $w_{\rm DE}<-1$. We also generally obtain the effective gravitational coupling $G_{\rm eff}$ with non-relativistic matter as well as the gravitational slip parameter $\eta_s$ associated with the observations of large-scale structures and weak lensing. We show that, apart from a specific case, the two quantities $G_{\rm eff}$ and $\eta_s$ are similar to those in general relativity for scalar perturbations deep inside the sound horizon. |
2306.11588 | Andrea Pierfrancesco Sanna | M. Cadoni, A. P. Sanna, M. Pitzalis, B. Banerjee, R. Murgia, N. Hazra,
M. Branchesi | Cosmological coupling of nonsingular black holes | 12 pages, 2 figures, discussions/references added, matches the
version published in JCAP | JCAP 11 (2023), 007 | 10.1088/1475-7516/2023/11/007 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We show that -- in the framework of general relativity (GR) -- if black holes
(BHs) are singularity-free objects, they couple to the large-scale cosmological
dynamics. We find that the leading contribution to the resulting growth of the
BH mass ($M_{\rm BH}$) as a function of the scale factor $a$ stems from the
curvature term, yielding $M_{\rm BH} \propto a^k$, with $k=1$. We demonstrate
that such a linear scaling is universal for spherically-symmetric objects, and
it is the only contribution in the case of regular BHs. For nonsingular
horizonless compact objects we instead obtain an additional subleading
model-dependent term. We conclude that GR nonsingular BHs/horizonless compact
objects, although cosmologically coupled, are unlikely to be the source of dark
energy. We test our prediction with astrophysical data by analysing the
redshift dependence of the mass growth of supermassive BHs in a sample of
elliptical galaxies at redshift $z=0.8 -0.9$. We also compare our theoretical
prediction with higher redshift BH mass measurements obtained with the James
Webb Space Telescope (JWST). We find that, while $k=1$ is compatible within $1
\sigma$ with JWST results, the data from elliptical galaxies at $z=0.8 -0.9$
favour values of $k>1$. New samples of BHs covering larger mass and redshift
ranges and more precise BH mass measurements are required to settle the issue.
| [
{
"created": "Tue, 20 Jun 2023 15:05:08 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Dec 2023 10:00:03 GMT",
"version": "v2"
}
] | 2023-12-04 | [
[
"Cadoni",
"M.",
""
],
[
"Sanna",
"A. P.",
""
],
[
"Pitzalis",
"M.",
""
],
[
"Banerjee",
"B.",
""
],
[
"Murgia",
"R.",
""
],
[
"Hazra",
"N.",
""
],
[
"Branchesi",
"M.",
""
]
] | We show that -- in the framework of general relativity (GR) -- if black holes (BHs) are singularity-free objects, they couple to the large-scale cosmological dynamics. We find that the leading contribution to the resulting growth of the BH mass ($M_{\rm BH}$) as a function of the scale factor $a$ stems from the curvature term, yielding $M_{\rm BH} \propto a^k$, with $k=1$. We demonstrate that such a linear scaling is universal for spherically-symmetric objects, and it is the only contribution in the case of regular BHs. For nonsingular horizonless compact objects we instead obtain an additional subleading model-dependent term. We conclude that GR nonsingular BHs/horizonless compact objects, although cosmologically coupled, are unlikely to be the source of dark energy. We test our prediction with astrophysical data by analysing the redshift dependence of the mass growth of supermassive BHs in a sample of elliptical galaxies at redshift $z=0.8 -0.9$. We also compare our theoretical prediction with higher redshift BH mass measurements obtained with the James Webb Space Telescope (JWST). We find that, while $k=1$ is compatible within $1 \sigma$ with JWST results, the data from elliptical galaxies at $z=0.8 -0.9$ favour values of $k>1$. New samples of BHs covering larger mass and redshift ranges and more precise BH mass measurements are required to settle the issue. |
0812.4217 | Ran Li | Ran Li, Ji-Rong Ren and Dun-Fu Shi | Fermions Tunneling from Apparent Horizon of FRW Universe | 8 pages, no figures | Phys.Lett.B670:446-448,2009 | 10.1016/j.physletb.2008.11.029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the paper [arXiv:0809.1554], the scalar particles' Hawking radiation from
the apparent horizon of Friedmann-Robertson-Walker(FRW) universe was
investigated by using the tunneling formalism. They obtained the Hawking
temperature associated with the apparent horizon, which was extensively applied
in investigating the relationship between the first law of thermodynamics and
Friedmann equations. In this paper, we calculate Fermions' Hawking radiation
from the apparent horizon of FRW universe via tunneling formalism. Applying WKB
approximation to the general covariant Dirac equation in FRW spacetime
background, the radiation spectrum and Hawking temperature of apparent horizon
are correctly recovered, which supports the arguments presented in the paper
[arXiv:0809.1554].
| [
{
"created": "Mon, 22 Dec 2008 15:25:45 GMT",
"version": "v1"
}
] | 2014-11-18 | [
[
"Li",
"Ran",
""
],
[
"Ren",
"Ji-Rong",
""
],
[
"Shi",
"Dun-Fu",
""
]
] | In the paper [arXiv:0809.1554], the scalar particles' Hawking radiation from the apparent horizon of Friedmann-Robertson-Walker(FRW) universe was investigated by using the tunneling formalism. They obtained the Hawking temperature associated with the apparent horizon, which was extensively applied in investigating the relationship between the first law of thermodynamics and Friedmann equations. In this paper, we calculate Fermions' Hawking radiation from the apparent horizon of FRW universe via tunneling formalism. Applying WKB approximation to the general covariant Dirac equation in FRW spacetime background, the radiation spectrum and Hawking temperature of apparent horizon are correctly recovered, which supports the arguments presented in the paper [arXiv:0809.1554]. |
gr-qc/9212010 | null | A. Casher and F. Englert | Black Hole Tunneling Entropy and the Spectrum of Gravity | 26 pages + 3 figures, phyzzx macropackage, figures available from
Authors | Class.Quant.Grav.10:2479-2494,1993 | 10.1088/0264-9381/10/12/007 | ULB-TH 8/92 and TAUP 2017-92 | gr-qc hep-th | null | The tunneling approach for entropy generation in quantum gravity is applied
to black holes. The area entropy is recovered and shown to count only a tiny
fraction of the black hole degeneracy. The latter stems from the extension of
the wave function outside the barrier. In fact the semi-classical analysis
leads to infinite degeneracy. Evaporating black holes leave then infinitely
degenerate "planckons" remnants which can neither decay into, nor be formed
from, ordinary matter in a finite time. Quantum gravity opens up at the Planck
scale into an infinite Hilbert space which is expected to provide the
ultraviolet cutoff required to render the theory finite in the sector of large
scale physics.
| [
{
"created": "Tue, 15 Dec 1992 13:51:00 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Casher",
"A.",
""
],
[
"Englert",
"F.",
""
]
] | The tunneling approach for entropy generation in quantum gravity is applied to black holes. The area entropy is recovered and shown to count only a tiny fraction of the black hole degeneracy. The latter stems from the extension of the wave function outside the barrier. In fact the semi-classical analysis leads to infinite degeneracy. Evaporating black holes leave then infinitely degenerate "planckons" remnants which can neither decay into, nor be formed from, ordinary matter in a finite time. Quantum gravity opens up at the Planck scale into an infinite Hilbert space which is expected to provide the ultraviolet cutoff required to render the theory finite in the sector of large scale physics. |
2106.14188 | Mattia Villani Dr | Mattia Villani | Including topology change in Loop Quantum Gravity with topspin network
formalism with application to homogeneous and isotropic cosmology | Accepted for the pubblication on Class. Quantum Grav | null | 10.1088/1361-6382/ac0e1a | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply topspin network formalism to Loop Quantum Gravity in order to
include in the theory the possibility of changes in the topology of spacetime.
We apply this formalism to three toy models: with the first, we find that the
topology can actually change due to the action of the Hamiltonian constraint
and with the second we find that the final state might be a superposition of
states with different topologies. In the third and last application, we
consider an homogeneous and isotropic Universe, calculating the difference
equation that describes the evolution of the system and which are the final
topological states after the action of the Hamiltonian constraint. For this
last case, we also calculate the transition amplitudes and probabilities from
the initial to the final states.
| [
{
"created": "Sun, 27 Jun 2021 10:28:11 GMT",
"version": "v1"
}
] | 2021-06-29 | [
[
"Villani",
"Mattia",
""
]
] | We apply topspin network formalism to Loop Quantum Gravity in order to include in the theory the possibility of changes in the topology of spacetime. We apply this formalism to three toy models: with the first, we find that the topology can actually change due to the action of the Hamiltonian constraint and with the second we find that the final state might be a superposition of states with different topologies. In the third and last application, we consider an homogeneous and isotropic Universe, calculating the difference equation that describes the evolution of the system and which are the final topological states after the action of the Hamiltonian constraint. For this last case, we also calculate the transition amplitudes and probabilities from the initial to the final states. |
gr-qc/0505067 | Djordje Sijacki | Djordje Sijacki | Affine Particles and Fields | null | Int.J.Geom.Meth.Mod.Phys. 2 (2005) 189-201 | null | null | gr-qc | null | The covering of the affine symmetry group, a semidirect product of
translations and special linear transformations, in $D \geq 3$ dimensional
spacetime is considered. Infinite dimensional spinorial representations on
states and fields are presented. A Dirac-like affine equation, with infinite
matrices generalizing the $\gamma$ matrices, is constructed.
| [
{
"created": "Fri, 13 May 2005 12:01:52 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sijacki",
"Djordje",
""
]
] | The covering of the affine symmetry group, a semidirect product of translations and special linear transformations, in $D \geq 3$ dimensional spacetime is considered. Infinite dimensional spinorial representations on states and fields are presented. A Dirac-like affine equation, with infinite matrices generalizing the $\gamma$ matrices, is constructed. |
1803.11044 | Burkhard Kleihaus | Christian Hoffmann (Massachusetts U., Amherst & Oldenburg U.),
Theodora Ioannidou (Aristotle U., Thessaloniki), Sarah Kahlen, Burkhard
Kleihaus, and Jutta Kunz (Oldenburg U.) | Symmetric and Asymmetric Wormholes Immersed In Rotating Matter | 24 pages, 11 figures | Phys. Rev. D 97, 124019 (2018) | 10.1103/PhysRevD.97.124019 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider four-dimensional wormholes immersed in bosonic matter. While
their existence is based on the presence of a phantom field, many of their
interesting physical properties are bestowed upon them by an ordinary complex
scalar field, which carries only a mass term, but no self-interactions. For
instance, the rotation of the scalar field induces a rotation of the throat as
well. Moreover, the bosonic matter need not be symmetrically distributed in
both asymptotically flat regions, leading to symmetric and asymmetric rotating
wormhole spacetimes. The presence of the rotating matter also allows for
wormholes with a double throat.
| [
{
"created": "Thu, 29 Mar 2018 13:10:07 GMT",
"version": "v1"
}
] | 2018-06-20 | [
[
"Hoffmann",
"Christian",
"",
"Massachusetts U., Amherst & Oldenburg U."
],
[
"Ioannidou",
"Theodora",
"",
"Aristotle U., Thessaloniki"
],
[
"Kahlen",
"Sarah",
"",
"Oldenburg U."
],
[
"Kleihaus",
"Burkhard",
"",
"Oldenburg U."
],
[
... | We consider four-dimensional wormholes immersed in bosonic matter. While their existence is based on the presence of a phantom field, many of their interesting physical properties are bestowed upon them by an ordinary complex scalar field, which carries only a mass term, but no self-interactions. For instance, the rotation of the scalar field induces a rotation of the throat as well. Moreover, the bosonic matter need not be symmetrically distributed in both asymptotically flat regions, leading to symmetric and asymmetric rotating wormhole spacetimes. The presence of the rotating matter also allows for wormholes with a double throat. |
1409.2877 | Carlos A. R. Herdeiro | Carlos Herdeiro, Eugen Radu, Helgi Runarsson | Non-linear Q-clouds around Kerr black holes | 11 pages, 4 figures | null | 10.1016/j.physletb.2014.11.005 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Q-balls are regular extended `objects' that exist for some non-gravitating,
self-interacting, scalar field theories with a global, continuous, internal
symmetry, on Minkowski spacetime. Here, analogous objects are also shown to
exist around rotating (Kerr) black holes, as non-linear bound states of a test
scalar field. We dub such configurations Q-clouds. We focus on a complex
massive scalar field with quartic plus hexic self-interactions. Without the
self-interactions, linear clouds have been shown to exist, in synchronous
rotation with the black hole horizon, along 1-dimensional subspaces - existence
lines - of the Kerr 2-dimensional parameter space. They are zero modes of the
superradiant instability. Non-linear Q-clouds, on the other hand, are also in
synchronous rotation with the black hole horizon; but they exist on a
2-dimensional subspace, delimited by a minimal horizon angular velocity and by
an appropriate existence line, wherein the non-linear terms become irrelevant
and the Q-cloud reduces to a linear cloud. Thus, Q-clouds provide an example of
scalar bound states around Kerr black holes which, generically, are not zero
modes of the superradiant instability. We describe some physical properties of
Q-clouds, whose backreaction leads to a new family of hairy black holes,
continuously connected to the Kerr family.
| [
{
"created": "Tue, 9 Sep 2014 20:00:16 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Herdeiro",
"Carlos",
""
],
[
"Radu",
"Eugen",
""
],
[
"Runarsson",
"Helgi",
""
]
] | Q-balls are regular extended `objects' that exist for some non-gravitating, self-interacting, scalar field theories with a global, continuous, internal symmetry, on Minkowski spacetime. Here, analogous objects are also shown to exist around rotating (Kerr) black holes, as non-linear bound states of a test scalar field. We dub such configurations Q-clouds. We focus on a complex massive scalar field with quartic plus hexic self-interactions. Without the self-interactions, linear clouds have been shown to exist, in synchronous rotation with the black hole horizon, along 1-dimensional subspaces - existence lines - of the Kerr 2-dimensional parameter space. They are zero modes of the superradiant instability. Non-linear Q-clouds, on the other hand, are also in synchronous rotation with the black hole horizon; but they exist on a 2-dimensional subspace, delimited by a minimal horizon angular velocity and by an appropriate existence line, wherein the non-linear terms become irrelevant and the Q-cloud reduces to a linear cloud. Thus, Q-clouds provide an example of scalar bound states around Kerr black holes which, generically, are not zero modes of the superradiant instability. We describe some physical properties of Q-clouds, whose backreaction leads to a new family of hairy black holes, continuously connected to the Kerr family. |
gr-qc/0410052 | Kamal Nandi | K.K. Nandi and D.H. Xu | Unruh model for the Einstein-Rosen charge: Squealing Wormholes? | 10 pages | null | null | null | gr-qc | null | We present two kinds of acoustic models for the massless electric charge
conceived by Einstein and Rosen in the form of a bridge (wormhole throat). It
is found that the first kind of modelling requires a thin layer of exotic
matter at the bridge. We also derive an acoustic equation that exclusively
characterizes the model. Using a second kind of model, it is demonstrated that
the Einstein-Rosen charge has a sonic Hawking-Unruh temperature proportional to
+-1/$beta$, where $beta$ is the size of the charge. This suggests that
(squealing!) wormholes can also be formally accommodated into Unruh's fluid
model.
| [
{
"created": "Tue, 12 Oct 2004 14:04:49 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Oct 2004 09:07:50 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Nandi",
"K. K.",
""
],
[
"Xu",
"D. H.",
""
]
] | We present two kinds of acoustic models for the massless electric charge conceived by Einstein and Rosen in the form of a bridge (wormhole throat). It is found that the first kind of modelling requires a thin layer of exotic matter at the bridge. We also derive an acoustic equation that exclusively characterizes the model. Using a second kind of model, it is demonstrated that the Einstein-Rosen charge has a sonic Hawking-Unruh temperature proportional to +-1/$beta$, where $beta$ is the size of the charge. This suggests that (squealing!) wormholes can also be formally accommodated into Unruh's fluid model. |
2205.14635 | Handhika Ramadhan | A S. Habibina and H. S. Ramadhan | Bound orbits around charged black strings | 29 pages, 12 figures, 8 tables, accepted for publication in Annals of
Physics | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study the geodesics of $5d$ Reissner-Nordstrom and nonsingular black
strings, and establish a rational bound orbit taxonomy for both massive as well
as null test particles. For the timelike case, test particles with high energy
(that would have made them plunge into or scatter off a black hole) could still
form bound orbits around the black strings. We calculate the accumulated angles
of the corresponding radial periods and show that they are higher than their
$4d$ counterparts. For the null case, we found the existence of stable null
orbits outside their respective horizons, which do not exist in the four
dimensions except at their extremal limit.
| [
{
"created": "Sun, 29 May 2022 11:56:22 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Jun 2022 10:01:19 GMT",
"version": "v2"
},
{
"created": "Tue, 14 Jun 2022 09:00:56 GMT",
"version": "v3"
},
{
"created": "Thu, 16 Jun 2022 11:37:24 GMT",
"version": "v4"
},
{
"c... | 2022-11-22 | [
[
"Habibina",
"A S.",
""
],
[
"Ramadhan",
"H. S.",
""
]
] | We study the geodesics of $5d$ Reissner-Nordstrom and nonsingular black strings, and establish a rational bound orbit taxonomy for both massive as well as null test particles. For the timelike case, test particles with high energy (that would have made them plunge into or scatter off a black hole) could still form bound orbits around the black strings. We calculate the accumulated angles of the corresponding radial periods and show that they are higher than their $4d$ counterparts. For the null case, we found the existence of stable null orbits outside their respective horizons, which do not exist in the four dimensions except at their extremal limit. |
1501.05481 | Shahram Panahiyan | S. H. Hendi and S. Panahiyan | Thermodynamic instability of topological black holes in Gauss-Bonnet
gravity with a generalized electrodynamics | 16 pages, 6 figures | Phys. Rev. D 90, 124008 (2014) | 10.1103/PhysRevD.90.124008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the string corrections on the gravity and electrodynamics sides,
we consider a quadratic Maxwell invariant term as a correction of the Maxwell
Lagrangian to obtain exact solutions of higher dimensional topological black
holes in Gauss-Bonnet gravity. We first investigate the asymptotically flat
solutions and obtain conserved and thermodynamic quantities which satisfy the
first law of thermodynamics. We also analyze thermodynamic stability of the
solutions by calculating the heat capacity and the Hessian matrix. Then, we
focus on horizon-flat solutions with adS asymptote and produce a rotating
spacetime with a suitable transformation. In addition, we calculate the
conserved and thermodynamic quantities for asymptotically adS black branes
which satisfy the first law of thermodynamics. Finally, we perform
thermodynamic instability criterion to investigate the effects of nonlinear
electrodynamics in canonical and grand canonical ensembles.
| [
{
"created": "Thu, 22 Jan 2015 12:52:24 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Hendi",
"S. H.",
""
],
[
"Panahiyan",
"S.",
""
]
] | Motivated by the string corrections on the gravity and electrodynamics sides, we consider a quadratic Maxwell invariant term as a correction of the Maxwell Lagrangian to obtain exact solutions of higher dimensional topological black holes in Gauss-Bonnet gravity. We first investigate the asymptotically flat solutions and obtain conserved and thermodynamic quantities which satisfy the first law of thermodynamics. We also analyze thermodynamic stability of the solutions by calculating the heat capacity and the Hessian matrix. Then, we focus on horizon-flat solutions with adS asymptote and produce a rotating spacetime with a suitable transformation. In addition, we calculate the conserved and thermodynamic quantities for asymptotically adS black branes which satisfy the first law of thermodynamics. Finally, we perform thermodynamic instability criterion to investigate the effects of nonlinear electrodynamics in canonical and grand canonical ensembles. |
2309.16734 | Hassan Mehmood | Hassan Mehmood | Quantum Gravity as a Theory of Connections | Bachelor's thesis, Lahore University of Management Sciences, 158
pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Consider the interior of a black hole or the very early universe: matter is
so densely localized that neither the effects of gravity nor those of quantum
theory can be ignored. But this entails that neither general relativity nor
quantum theory on its own can fully describe such a situation, for some of the
most fundamental principles inhering in these two theories are haunted by the
specter of incompatibility. Quantum gravity is the name for the bewildering
penumbra of theories that seek to exorcise this demon. But it turns out that
the metrical variables of general relativity constitute a lamp too narrow to
bottle the phantom, and loop quantum gravity is a fascinating enterprise that
seeks the Aladdin who does possess the required lamp. This is achieved by
recasting general relativity as a theory of connections, rather than that of
metrics. This shift of emphasis allows one to use a number of mathematical
tools that make it possible to arrive at a fully consistent, almost
background-independent theory of quantum gravity. This thesis endeavours to
probe these ideas in detail.
| [
{
"created": "Wed, 27 Sep 2023 20:02:20 GMT",
"version": "v1"
}
] | 2023-10-02 | [
[
"Mehmood",
"Hassan",
""
]
] | Consider the interior of a black hole or the very early universe: matter is so densely localized that neither the effects of gravity nor those of quantum theory can be ignored. But this entails that neither general relativity nor quantum theory on its own can fully describe such a situation, for some of the most fundamental principles inhering in these two theories are haunted by the specter of incompatibility. Quantum gravity is the name for the bewildering penumbra of theories that seek to exorcise this demon. But it turns out that the metrical variables of general relativity constitute a lamp too narrow to bottle the phantom, and loop quantum gravity is a fascinating enterprise that seeks the Aladdin who does possess the required lamp. This is achieved by recasting general relativity as a theory of connections, rather than that of metrics. This shift of emphasis allows one to use a number of mathematical tools that make it possible to arrive at a fully consistent, almost background-independent theory of quantum gravity. This thesis endeavours to probe these ideas in detail. |
2110.11289 | Valerio Faraoni | Valerio Faraoni, Sonia Jose, and Alexandre Leblanc | The curious case of the Buchdahl-Land-Sultana-Wyman-Iba\~nez-Sanz
spacetime | 11 pages, 3 figures | null | 10.1103/PhysRevD.105.024030 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit Wyman's "other" scalar field solution of the Einstein equations
and its Sultana generalization to positive cosmological constant, which has a
finite 3-space and corresponds to a special case of a stiff fluid solution
proposed by Buchdahl and Land and, later, by Iba\~nez and Sanz to model
relativistic stars. However, there is a hidden cosmological constant and the
peculiar geometry prevents the use of this spacetime to model relativistic
stars.
| [
{
"created": "Thu, 21 Oct 2021 17:17:31 GMT",
"version": "v1"
}
] | 2022-01-26 | [
[
"Faraoni",
"Valerio",
""
],
[
"Jose",
"Sonia",
""
],
[
"Leblanc",
"Alexandre",
""
]
] | We revisit Wyman's "other" scalar field solution of the Einstein equations and its Sultana generalization to positive cosmological constant, which has a finite 3-space and corresponds to a special case of a stiff fluid solution proposed by Buchdahl and Land and, later, by Iba\~nez and Sanz to model relativistic stars. However, there is a hidden cosmological constant and the peculiar geometry prevents the use of this spacetime to model relativistic stars. |
1707.07674 | Abdul Jawad | Abdul Jawad and M. Umair Shahzad | Accreting Fluids onto Regular Black Holes Via Hamiltonian Approach | 25 pages; 10 Figures | null | 10.1140/epjc/s10052-017-5075-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the accretion of test fluids onto regular black holes such as
Kehagias-Sfetsos black hole and a regular black hole with Dagum Distribution
Function. We analyze the accretion process when different test fluids are
falling onto these regular black holes. The accreting fluid is being classified
through equation of state according to features of regular black holes. The
behavior of fluid flow and the existence of sonic points is being checked for
these regular black holes. It is noted that three velocity depends on critical
points and equation of state parameter on phase space.
| [
{
"created": "Mon, 24 Jul 2017 08:59:41 GMT",
"version": "v1"
}
] | 2017-09-13 | [
[
"Jawad",
"Abdul",
""
],
[
"Shahzad",
"M. Umair",
""
]
] | We investigate the accretion of test fluids onto regular black holes such as Kehagias-Sfetsos black hole and a regular black hole with Dagum Distribution Function. We analyze the accretion process when different test fluids are falling onto these regular black holes. The accreting fluid is being classified through equation of state according to features of regular black holes. The behavior of fluid flow and the existence of sonic points is being checked for these regular black holes. It is noted that three velocity depends on critical points and equation of state parameter on phase space. |
2112.13869 | Mostafizur Rahman | Mostafizur Rahman and Arpan Bhattacharyya | Prospects for determining the nature of the secondaries of extreme
mass-ratio inspirals using the spin-induced quadrupole deformation | 24 pages, 7 figures, 5 tables. Typos corrected. Accepted for
publication in PRD | Phys.Rev.D 107 (2023) 02 | 10.1103/PhysRevD.107.024006 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The measurement of multipole moments of astrophysical objects through
gravitational wave (GW) observations provides a novel way to distinguish black
holes from other astrophysical objects. This paper studies the gravitational
wave radiation from an extreme mass ratio inspiral (EMRI) system consisting of
a supermassive Kerr black hole (the primary object) and a spinning stellar-mass
compact object (the secondary object). The quadrupolar deformation induced by
the spin of the secondary is different for different astrophysical objects. We
compute the effect of the quadrupolar deformation on the GW phase and provide
an order of magnitude estimate of whether LISA can distinguish different
astrophysical objects through GW phase measurement. We find that although LISA
can not distinguish between a black hole and a neutron star, it can distinguish
black holes from a large variety of highly spinning astrophysical objects like
superspinars and highly deformable exotic compact objects like boson stars for
EMRI systems with relatively large mass ratio ($q\sim 10^{-4}$). Furthermore,
we show that the effect of spin-induced quadrupolar deformation on the GW phase
for white dwarf and brown dwarf-EMRI systems can be quite significant even for
small values of mass ratio ($q\lesssim 10^{-6}$).
| [
{
"created": "Mon, 27 Dec 2021 19:07:27 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Jul 2022 18:10:05 GMT",
"version": "v2"
},
{
"created": "Tue, 27 Dec 2022 10:53:23 GMT",
"version": "v3"
}
] | 2023-01-10 | [
[
"Rahman",
"Mostafizur",
""
],
[
"Bhattacharyya",
"Arpan",
""
]
] | The measurement of multipole moments of astrophysical objects through gravitational wave (GW) observations provides a novel way to distinguish black holes from other astrophysical objects. This paper studies the gravitational wave radiation from an extreme mass ratio inspiral (EMRI) system consisting of a supermassive Kerr black hole (the primary object) and a spinning stellar-mass compact object (the secondary object). The quadrupolar deformation induced by the spin of the secondary is different for different astrophysical objects. We compute the effect of the quadrupolar deformation on the GW phase and provide an order of magnitude estimate of whether LISA can distinguish different astrophysical objects through GW phase measurement. We find that although LISA can not distinguish between a black hole and a neutron star, it can distinguish black holes from a large variety of highly spinning astrophysical objects like superspinars and highly deformable exotic compact objects like boson stars for EMRI systems with relatively large mass ratio ($q\sim 10^{-4}$). Furthermore, we show that the effect of spin-induced quadrupolar deformation on the GW phase for white dwarf and brown dwarf-EMRI systems can be quite significant even for small values of mass ratio ($q\lesssim 10^{-6}$). |
gr-qc/9511081 | Thomas Kloesch | T. Kloesch and T. Strobl | Classical and Quantum Gravity in 1+1 Dimensions, Part II: The Universal
Coverings | 29 pages, 14 Postscript figures; one figure, some paragraphs, and
references added; to appear in Class. Quantum Grav | Class.Quant.Grav.13:2395-2422,1996 | 10.1088/0264-9381/13/9/007 | TUW-95-23, PITHA-95/24 | gr-qc hep-th | null | A set of simple rules for constructing the maximal (e.g. analytic) extensions
for any metric with a Killing field in an (effectively) two-dimensional
spacetime is formulated. The application of these rules is extremely
straightforward, as is demonstrated at various examples and illustrated with
numerous figures. Despite the resulting simplicity we also comment on some
subtleties concerning the concept of Penrose diagrams. Most noteworthy among
these, maybe, is that (smooth) spacetimes which have both degenerate and
non-degenerate (Killing) horizons do not allow for globally smooth Penrose
diagrams. Physically speaking this obstruction corresponds to an infinite
relative red/blueshift between observers moving across the two horizons. -- The
present work provides a further step in the classification of all global
solutions of the general class of two-dimensional gravity-Yang-Mills systems
introduced in Part I, comprising, e.g., all generalized (linear and nonlinear)
dilaton theories. In Part I we constructed the local solutions, which were
found to always have a Killing field; in this paper we provide all universal
covering solutions (the simply connected maximally extended spacetimes). A
subsequent Part III will treat the diffeomorphism inequivalent solutions for
all other spacetime topologies. -- Part II is kept entirely self-contained; a
prior reading of Part I is not necessary.
| [
{
"created": "Thu, 30 Nov 1995 13:26:42 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Apr 1996 09:25:34 GMT",
"version": "v2"
},
{
"created": "Fri, 26 Apr 1996 09:02:02 GMT",
"version": "v3"
}
] | 2010-04-06 | [
[
"Kloesch",
"T.",
""
],
[
"Strobl",
"T.",
""
]
] | A set of simple rules for constructing the maximal (e.g. analytic) extensions for any metric with a Killing field in an (effectively) two-dimensional spacetime is formulated. The application of these rules is extremely straightforward, as is demonstrated at various examples and illustrated with numerous figures. Despite the resulting simplicity we also comment on some subtleties concerning the concept of Penrose diagrams. Most noteworthy among these, maybe, is that (smooth) spacetimes which have both degenerate and non-degenerate (Killing) horizons do not allow for globally smooth Penrose diagrams. Physically speaking this obstruction corresponds to an infinite relative red/blueshift between observers moving across the two horizons. -- The present work provides a further step in the classification of all global solutions of the general class of two-dimensional gravity-Yang-Mills systems introduced in Part I, comprising, e.g., all generalized (linear and nonlinear) dilaton theories. In Part I we constructed the local solutions, which were found to always have a Killing field; in this paper we provide all universal covering solutions (the simply connected maximally extended spacetimes). A subsequent Part III will treat the diffeomorphism inequivalent solutions for all other spacetime topologies. -- Part II is kept entirely self-contained; a prior reading of Part I is not necessary. |
2109.12086 | Joan Sola | Joan Sola Peracaula | Running vacuum interacting with dark matter or with running
gravitational coupling. Phenomenological implications | 21 pages, slightly extended discussion. References added and others
updated. Invited talk in the 16th Marcel-Grossmann virtual Conference (MG16),
parallel session DM1: Interacting Dark Matter | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | The cosmological term, $\Lambda$, in Einstein's equations is an essential
ingredient of the `concordance' $\Lambda$CDM model of cosmology. In this
mini-review presentation, we assess the possibility that $\Lambda$ can be a
dynamical quantity, more specifically a `running quantity' in quantum field
theory in curved spacetime. A great deal of phenomenological works have shown
in the last few years that this option (sometimes accompanied with a running
gravitational coupling) may cure some of the tensions afflicting the
$\Lambda$CDM. The `running vacuum models' (RVM's) are characterized by the
vacuum energy density, $\rho_{\rm vac}$, being a series of (even) powers of the
Hubble rate and its time derivatives. Here we describe the technical quantum
field theoretical origin of the RVM structure in FLRW spacetime, which goes
well-beyond the original semi-qualitative renormalization group arguments. In
particular, we compute the renormalized energy-momentum tensor using the
adiabatic regularization procedure and show that it leads to the RVM form. In
other words, we find that the renormalized vacuum energy density,
$\rho_{vac}(H)$ evolves as a (constant) additive term plus a leading dynamical
components ${\cal O}(H^2)$. There are also ${\cal O}(H^4)$ contributions, which
can be relevant for the early universe. Remarkably enough, the renormalized
$\rho_{\rm vac}(H)$ does not exhibit dangerous terms proportional to the
quartic power of the masses ($\sim m^4$) of the fields. It is well-known that
these terms have been the main source of trouble since they are responsible for
the extreme fine tuning and ultimately for the cosmological constant problem.
In this context, the current $\rho_{vac}(H)$ is dominated by a constant term,
as it should be, but it acquires a mild dynamical component $\sim \nu H^2$
($|\nu|\ll1$) which makes the RVM to mimic quintessence.
| [
{
"created": "Fri, 24 Sep 2021 17:25:03 GMT",
"version": "v1"
},
{
"created": "Sun, 5 Dec 2021 10:34:24 GMT",
"version": "v2"
}
] | 2022-07-19 | [
[
"Peracaula",
"Joan Sola",
""
]
] | The cosmological term, $\Lambda$, in Einstein's equations is an essential ingredient of the `concordance' $\Lambda$CDM model of cosmology. In this mini-review presentation, we assess the possibility that $\Lambda$ can be a dynamical quantity, more specifically a `running quantity' in quantum field theory in curved spacetime. A great deal of phenomenological works have shown in the last few years that this option (sometimes accompanied with a running gravitational coupling) may cure some of the tensions afflicting the $\Lambda$CDM. The `running vacuum models' (RVM's) are characterized by the vacuum energy density, $\rho_{\rm vac}$, being a series of (even) powers of the Hubble rate and its time derivatives. Here we describe the technical quantum field theoretical origin of the RVM structure in FLRW spacetime, which goes well-beyond the original semi-qualitative renormalization group arguments. In particular, we compute the renormalized energy-momentum tensor using the adiabatic regularization procedure and show that it leads to the RVM form. In other words, we find that the renormalized vacuum energy density, $\rho_{vac}(H)$ evolves as a (constant) additive term plus a leading dynamical components ${\cal O}(H^2)$. There are also ${\cal O}(H^4)$ contributions, which can be relevant for the early universe. Remarkably enough, the renormalized $\rho_{\rm vac}(H)$ does not exhibit dangerous terms proportional to the quartic power of the masses ($\sim m^4$) of the fields. It is well-known that these terms have been the main source of trouble since they are responsible for the extreme fine tuning and ultimately for the cosmological constant problem. In this context, the current $\rho_{vac}(H)$ is dominated by a constant term, as it should be, but it acquires a mild dynamical component $\sim \nu H^2$ ($|\nu|\ll1$) which makes the RVM to mimic quintessence. |
1301.1480 | Javad Taghizadeh firouzjaee | Rahim Moradi, Javad T. Firouzjaee and Reza Mansouri | The spherical perfect fluid collapse with pressure in the cosmological
background | null | null | 10.1142/9789813226609_0593 | Proceedings of the MG14 Meeting on General Relativity, C15-07-12 | gr-qc astro-ph.GA | http://creativecommons.org/licenses/by/3.0/ | We have constructed a spherically symmetric structure model in a cosmological
background filled with perfect fluid with non-vanishing pressure and studied
its quasi-local characteristics. This is done by using the Lema\^{i}tre
solution of the Einstein equations and suggesting an algorithm to integrate it
numerically. The result shows intriguing effects of the pressure inside the
structure. The evolution of the central black hole within the FRW universe, its
decoupling from the expanding parts of the model, the structure of its
space-like apparent horizon, the limiting case of the dynamical horizon tending
to a slowly evolving horizon, and the decreasing mass in-fall to the black hole
is also studied. The quasi-local features of this cosmological black hole may
not be inferred from the weak field approximation although the gravity outside
the structure is very weak.
| [
{
"created": "Tue, 8 Jan 2013 10:41:49 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Aug 2013 14:12:11 GMT",
"version": "v2"
}
] | 2017-12-11 | [
[
"Moradi",
"Rahim",
""
],
[
"Firouzjaee",
"Javad T.",
""
],
[
"Mansouri",
"Reza",
""
]
] | We have constructed a spherically symmetric structure model in a cosmological background filled with perfect fluid with non-vanishing pressure and studied its quasi-local characteristics. This is done by using the Lema\^{i}tre solution of the Einstein equations and suggesting an algorithm to integrate it numerically. The result shows intriguing effects of the pressure inside the structure. The evolution of the central black hole within the FRW universe, its decoupling from the expanding parts of the model, the structure of its space-like apparent horizon, the limiting case of the dynamical horizon tending to a slowly evolving horizon, and the decreasing mass in-fall to the black hole is also studied. The quasi-local features of this cosmological black hole may not be inferred from the weak field approximation although the gravity outside the structure is very weak. |
0810.5038 | Margus Saal | Piret Kuusk, Laur Jarv, Margus Saal | Scalar-tensor cosmologies: general relativity as a fixed point of the
Jordan frame scalar field | 9 pages, talk at Seventh Alexander Friedmann International Seminar on
Gravitation and Cosmology | Int.J.Mod.Phys.A24:1631-1638,2009 | 10.1142/S0217751X09045133 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the evolution of homogeneous and isotropic, flat cosmological models
within the general scalar-tensor theory of gravity with arbitrary coupling
function and potential and scrutinize its limit to general relativity. Using
the methods of dynamical systems for the decoupled equation of the Jordan frame
scalar field we find the fixed points of flows in two cases: potential
domination and matter domination. We present the conditions on the mathematical
form of the coupling function and potential which determine the nature of the
fixed points (attractor or other). There are two types of fixed points, both
are characterized by cosmological evolution mimicking general relativity, but
only one of the types is compatible with the Solar System PPN constraints.
| [
{
"created": "Tue, 28 Oct 2008 14:31:22 GMT",
"version": "v1"
}
] | 2009-04-24 | [
[
"Kuusk",
"Piret",
""
],
[
"Jarv",
"Laur",
""
],
[
"Saal",
"Margus",
""
]
] | We study the evolution of homogeneous and isotropic, flat cosmological models within the general scalar-tensor theory of gravity with arbitrary coupling function and potential and scrutinize its limit to general relativity. Using the methods of dynamical systems for the decoupled equation of the Jordan frame scalar field we find the fixed points of flows in two cases: potential domination and matter domination. We present the conditions on the mathematical form of the coupling function and potential which determine the nature of the fixed points (attractor or other). There are two types of fixed points, both are characterized by cosmological evolution mimicking general relativity, but only one of the types is compatible with the Solar System PPN constraints. |
1809.04408 | Zacharias Roupas | Zacharias Roupas | Gravitational instability caused by the weight of heat | Typos corrected in last update | Symmetry 2019, 11(12), 1435 | 10.3390/sym11121435 | null | gr-qc astro-ph.HE cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Thermal energy points toward a disordered, completely uniform state acting
counter to gravity's tendency to generate order and structure through
gravitational collapse. It is, therefore, expected to contribute to the
stabilization of a self-gravitating, classical ideal gas over collapse.
However, I identified an instability that always occurs at sufficiently high
energies: the high-energy or relativistic gravothermal instability. I argue
here that this instability presents an analogous core--halo structure as its
Newtonian counterpart, the Antonov instability. The main difference is that in
the former case the core is dominated by the gravitation of thermal energy and
not rest mass energy. A relativistic generalization of Antonov's
instability---the low-energy gravothermal instability---also occurs. The two
turning points, which make themselves evident as a double spiral of the caloric
curve, approach each other as relativistic effects become more intense and
eventually merge in a single point. Thus, the high and low-energy cases may be
realized as two aspects of a single phenomenon---the gravothermal
instability---which involves a core--halo separation and an intrinsic heat
flow. Finally, I argue that the core formed during a core-collapse supernova is
subject to the relativistic gravothermal instability if it becomes sufficiently
hot and compactified at the time of the bounce. In this case, it will continue
to collapse towards the formation of a black hole.
| [
{
"created": "Wed, 12 Sep 2018 13:19:00 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Oct 2019 12:22:09 GMT",
"version": "v2"
},
{
"created": "Fri, 8 Nov 2019 10:31:41 GMT",
"version": "v3"
},
{
"created": "Tue, 26 Nov 2019 06:37:51 GMT",
"version": "v4"
},
{
"cr... | 2019-12-03 | [
[
"Roupas",
"Zacharias",
""
]
] | Thermal energy points toward a disordered, completely uniform state acting counter to gravity's tendency to generate order and structure through gravitational collapse. It is, therefore, expected to contribute to the stabilization of a self-gravitating, classical ideal gas over collapse. However, I identified an instability that always occurs at sufficiently high energies: the high-energy or relativistic gravothermal instability. I argue here that this instability presents an analogous core--halo structure as its Newtonian counterpart, the Antonov instability. The main difference is that in the former case the core is dominated by the gravitation of thermal energy and not rest mass energy. A relativistic generalization of Antonov's instability---the low-energy gravothermal instability---also occurs. The two turning points, which make themselves evident as a double spiral of the caloric curve, approach each other as relativistic effects become more intense and eventually merge in a single point. Thus, the high and low-energy cases may be realized as two aspects of a single phenomenon---the gravothermal instability---which involves a core--halo separation and an intrinsic heat flow. Finally, I argue that the core formed during a core-collapse supernova is subject to the relativistic gravothermal instability if it becomes sufficiently hot and compactified at the time of the bounce. In this case, it will continue to collapse towards the formation of a black hole. |
2203.13830 | Alex Davey | Alex Davey, Oscar J.C. Dias, Paul Rodgers, Jorge E. Santos | Strong Cosmic Censorship and Eigenvalue Repulsions for rotating de
Sitter black holes in higher-dimensions | 43 pages, 13 figures | null | 10.1007/JHEP07(2022)086 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been established that Christodoulou's formulation of Strong Cosmic
Censorship (SCC) is violated by Reissner-Nordstr\"om-de Sitter black holes, but
holds in four-dimensional Kerr-de Sitter black holes. We show that SCC is also
respected by equal angular momenta (cohomogeneity-1) Myers-Perry-de Sitter
(MP-dS) in odd $d \ge 5$ spacetime dimensions. This suggests that the
preservation of SCC in rotating backgrounds might be a universal property of
Einstein gravity and not limited to the d = 4 Kerr-dS background. As required
to discuss SCC in de Sitter spacetimes, we also study important aspects of the
scalar field quasinormal mode (QNM) spectra of MP-dS. In particular, we find
eigenvalue repulsions similar to those recently observed in the QNM spectra of
asymptotically flat Kerr-Newman black holes. For axisymmetric modes (i.e. with
azimuthal quantum number m = 0) there are three distinct families of QNM (de
Sitter, photon sphere and near-horizon). However, typically, for
non-axisymmetric ($m \ne 0$) QNMs, we find that the entire spectra can be
described by just two families of QNM (since several overtone sections of the
photon sphere and near-horizon families merge). For completeness, we also study
the full scalar field QNM spectra of higher-dimensional Schwarzschild-de Sitter
black holes.
| [
{
"created": "Fri, 25 Mar 2022 18:00:02 GMT",
"version": "v1"
}
] | 2022-08-10 | [
[
"Davey",
"Alex",
""
],
[
"Dias",
"Oscar J. C.",
""
],
[
"Rodgers",
"Paul",
""
],
[
"Santos",
"Jorge E.",
""
]
] | It has been established that Christodoulou's formulation of Strong Cosmic Censorship (SCC) is violated by Reissner-Nordstr\"om-de Sitter black holes, but holds in four-dimensional Kerr-de Sitter black holes. We show that SCC is also respected by equal angular momenta (cohomogeneity-1) Myers-Perry-de Sitter (MP-dS) in odd $d \ge 5$ spacetime dimensions. This suggests that the preservation of SCC in rotating backgrounds might be a universal property of Einstein gravity and not limited to the d = 4 Kerr-dS background. As required to discuss SCC in de Sitter spacetimes, we also study important aspects of the scalar field quasinormal mode (QNM) spectra of MP-dS. In particular, we find eigenvalue repulsions similar to those recently observed in the QNM spectra of asymptotically flat Kerr-Newman black holes. For axisymmetric modes (i.e. with azimuthal quantum number m = 0) there are three distinct families of QNM (de Sitter, photon sphere and near-horizon). However, typically, for non-axisymmetric ($m \ne 0$) QNMs, we find that the entire spectra can be described by just two families of QNM (since several overtone sections of the photon sphere and near-horizon families merge). For completeness, we also study the full scalar field QNM spectra of higher-dimensional Schwarzschild-de Sitter black holes. |
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