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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2112.06952 | Antoni Ramos-Buades | Antoni Ramos-Buades, Alessandra Buonanno, Mohammed Khalil, Serguei
Ossokine | Effective-one-body multipolar waveforms for eccentric binary black holes
with non-precessing spins | Version accepted for publication in PRD | null | 10.1103/PhysRevD.105.044035 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct an inspiral-merger-ringdown eccentric gravitational-wave (GW)
model for binary black holes with non-precessing spins within the
effective-one-body formalism. This waveform model, SEOBNRv4EHM, extends the
accurate quasi-circular SEOBNRv4HM model to eccentric binaries by including
recently computed eccentric corrections up to 2PN order in the gravitational
waveform modes, notably the $(l,|m|)=(2,2),(2,1),(3,3),(4,4),(5,5)$ multipoles.
The waveform model reproduces the zero eccentricity limit with an accuracy
comparable to the underlying quasi-circular model, with the unfaithfulness of
$\lesssim1\%$ against quasi-circular numerical-relativity (NR) simulations.
When compared against 28 public eccentric NR simulations from the Simulating
eXtreme Spacetimes catalog with initial orbital eccentricities up to
$e\simeq0.3$ and dimensionless spin magnitudes up to $+0.7$, the model provides
unfaithfulness $<1\%$, showing that both the $(2,|2|)$-modes and the
higher-order modes are reliably described without calibration to NR datasets in
the eccentric sector. The waveform model SEOBNRv4EHM is able to qualitatively
reproduce the phenomenology of dynamical captures, and can be extended to
include spin-precession effects. It can be employed for upcoming observing runs
with the LIGO-Virgo-KAGRA detectors and used to re-analyze existing GW catalogs
to infer the eccentricity parameters for binaries with $e\lesssim0.3$ (at 20 Hz
or lower) and spins up to $\lesssim 0.9-0.95$. The latter is a promising region
of the parameter space where some astrophysical formation scenarios of binaries
predict mild eccentricity in the ground-based detectors' bandwidth. Assessing
the accuracy and robustness of the eccentric waveform model SEOBNRv4EHM for
larger eccentricities and spins will require comparisons with, and, likely,
calibration to eccentric NR waveforms in a larger region of the parameter
space.
| [
{
"created": "Mon, 13 Dec 2021 19:00:11 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Feb 2022 07:54:06 GMT",
"version": "v2"
}
] | 2022-03-02 | [
[
"Ramos-Buades",
"Antoni",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Khalil",
"Mohammed",
""
],
[
"Ossokine",
"Serguei",
""
]
] | We construct an inspiral-merger-ringdown eccentric gravitational-wave (GW) model for binary black holes with non-precessing spins within the effective-one-body formalism. This waveform model, SEOBNRv4EHM, extends the accurate quasi-circular SEOBNRv4HM model to eccentric binaries by including recently computed eccentric corrections up to 2PN order in the gravitational waveform modes, notably the $(l,|m|)=(2,2),(2,1),(3,3),(4,4),(5,5)$ multipoles. The waveform model reproduces the zero eccentricity limit with an accuracy comparable to the underlying quasi-circular model, with the unfaithfulness of $\lesssim1\%$ against quasi-circular numerical-relativity (NR) simulations. When compared against 28 public eccentric NR simulations from the Simulating eXtreme Spacetimes catalog with initial orbital eccentricities up to $e\simeq0.3$ and dimensionless spin magnitudes up to $+0.7$, the model provides unfaithfulness $<1\%$, showing that both the $(2,|2|)$-modes and the higher-order modes are reliably described without calibration to NR datasets in the eccentric sector. The waveform model SEOBNRv4EHM is able to qualitatively reproduce the phenomenology of dynamical captures, and can be extended to include spin-precession effects. It can be employed for upcoming observing runs with the LIGO-Virgo-KAGRA detectors and used to re-analyze existing GW catalogs to infer the eccentricity parameters for binaries with $e\lesssim0.3$ (at 20 Hz or lower) and spins up to $\lesssim 0.9-0.95$. The latter is a promising region of the parameter space where some astrophysical formation scenarios of binaries predict mild eccentricity in the ground-based detectors' bandwidth. Assessing the accuracy and robustness of the eccentric waveform model SEOBNRv4EHM for larger eccentricities and spins will require comparisons with, and, likely, calibration to eccentric NR waveforms in a larger region of the parameter space. |
1811.01728 | Valerio Faraoni | Valerio Faraoni and Jeremy C\^ot\'e | Two new approaches to the anomalous limit of Brans-Dicke to Einstein
gravity | Explanation and bibliography expanded, matches version published in
Phys. Rev. D | Phys. Rev. D 99, 064013 (2019) | 10.1103/PhysRevD.99.064013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Contrary to common belief, (electro)vacuum Brans-Dicke gravity does not
reduce to general relativity for large Brans-Dicke coupling $\omega$, a problem
which has never been fully solved. Two new approaches, independent from each
other, shed light on this issue producing the same result: in the limit $\omega
\rightarrow \infty $ an (electro)vacuum Brans-Dicke spacetime reduces to a
solution of the Einstein equations sourced, not by (electro)vacuum, but by a
minimally coupled scalar field. The latter is shown to coincide with the
Einstein frame scalar field. The first method employs a direct analysis of the
Einstein frame, while the second (complementary and independent) method uses an
imperfect fluid representation of Brans-Dicke gravity together with a little
known 1-parameter symmetry group of this theory.
| [
{
"created": "Mon, 5 Nov 2018 14:32:24 GMT",
"version": "v1"
},
{
"created": "Sat, 16 Mar 2019 20:35:46 GMT",
"version": "v2"
}
] | 2019-03-27 | [
[
"Faraoni",
"Valerio",
""
],
[
"Côté",
"Jeremy",
""
]
] | Contrary to common belief, (electro)vacuum Brans-Dicke gravity does not reduce to general relativity for large Brans-Dicke coupling $\omega$, a problem which has never been fully solved. Two new approaches, independent from each other, shed light on this issue producing the same result: in the limit $\omega \rightarrow \infty $ an (electro)vacuum Brans-Dicke spacetime reduces to a solution of the Einstein equations sourced, not by (electro)vacuum, but by a minimally coupled scalar field. The latter is shown to coincide with the Einstein frame scalar field. The first method employs a direct analysis of the Einstein frame, while the second (complementary and independent) method uses an imperfect fluid representation of Brans-Dicke gravity together with a little known 1-parameter symmetry group of this theory. |
gr-qc/9502001 | null | Sean A. Hayward | COMMENT ON ``BOUNDARY CONDITIONS FOR THE SCALAR FIELD IN THE PRESENCE OF
SIGNATURE CHANGE'' | 4 pages. TeX. | null | null | null | gr-qc | null | Fundamental errors exist in the above-mentioned article, which attempts to
justify previous erroneous claims concerning signature change. In the simplest
example, the authors' proposed ``solutions'' do not satisfy the relevant
equation, as may be checked by substitution. These ``solutions'' are also
different to the authors' originally proposed ``solutions'', which also do not
satisfy the equation. The variational equations obtained from the authors'
``actions'' are singular at the change of signature. The authors'
``distributional field equations'' are manifestly ill defined.
| [
{
"created": "Wed, 1 Feb 1995 08:24:13 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Hayward",
"Sean A.",
""
]
] | Fundamental errors exist in the above-mentioned article, which attempts to justify previous erroneous claims concerning signature change. In the simplest example, the authors' proposed ``solutions'' do not satisfy the relevant equation, as may be checked by substitution. These ``solutions'' are also different to the authors' originally proposed ``solutions'', which also do not satisfy the equation. The variational equations obtained from the authors' ``actions'' are singular at the change of signature. The authors' ``distributional field equations'' are manifestly ill defined. |
gr-qc/0309035 | Seth A. Major | Franz Hinterleitner and Seth Major | Isotropic Loop Quantum Cosmology with Matter II: The Lorentzian
Constraint | 19 pages, 4 figures | Phys.Rev. D68 (2003) 124023 | 10.1103/PhysRevD.68.124023 | null | gr-qc | null | The Lorentzian Hamiltonian constraint is solved for isotropic loop quantum
cosmology coupled to a massless scalar field. As in the Euclidean case, the
discreteness of quantum geometry removes the classical singularity from the
quantum Friedmann models. In spite of the absence of the classical singularity,
a modified DeWitt initial condition is incompatible with a late-time smooth
behavior. Further, the smooth behavior is recovered only for positive or
negatives times but not both. An important feature, which is shared with the
Euclidean case, is a minimal initial energy of the order of the Planck energy
required for the system to evolve dynamically. By forming wave packets of the
matter field an explicit evolution in terms of an internal time is obtained.
| [
{
"created": "Fri, 5 Sep 2003 20:29:04 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Hinterleitner",
"Franz",
""
],
[
"Major",
"Seth",
""
]
] | The Lorentzian Hamiltonian constraint is solved for isotropic loop quantum cosmology coupled to a massless scalar field. As in the Euclidean case, the discreteness of quantum geometry removes the classical singularity from the quantum Friedmann models. In spite of the absence of the classical singularity, a modified DeWitt initial condition is incompatible with a late-time smooth behavior. Further, the smooth behavior is recovered only for positive or negatives times but not both. An important feature, which is shared with the Euclidean case, is a minimal initial energy of the order of the Planck energy required for the system to evolve dynamically. By forming wave packets of the matter field an explicit evolution in terms of an internal time is obtained. |
gr-qc/0512077 | Nathalie Deruelle | Nathalie Deruelle and Joseph Katz | Comments on conformal masses, asymptotics backgrounds and conservation
laws | accepted for publication by Class. and Quant. Grav Note added in
Proof | Class.Quant.Grav. 23 (2006) 753-760 | 10.1088/0264-9381/23/3/013 | null | gr-qc hep-th | null | The "conformal mass prescriptions" were used recently to calculate the mass
of spacetimes in higher dimensional and higher curvature theories of gravity.
These definitions are closely related to Komar integrals for spacetimes that
are conformally flat at great distances from the sources. We derive these
relations without using the conformal infinity formalism.
| [
{
"created": "Tue, 13 Dec 2005 16:16:45 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Jan 2006 14:54:54 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Deruelle",
"Nathalie",
""
],
[
"Katz",
"Joseph",
""
]
] | The "conformal mass prescriptions" were used recently to calculate the mass of spacetimes in higher dimensional and higher curvature theories of gravity. These definitions are closely related to Komar integrals for spacetimes that are conformally flat at great distances from the sources. We derive these relations without using the conformal infinity formalism. |
2012.02583 | Matteo Galaverni | Matteo Galaverni, Gabriele Gionti S.J. | Photon helicity and quantum anomalies in curved spacetimes | Accepted for publication in General Relativity and Gravitation:
changed to correspond to the proof-read version | Gen Relativ Gravit 53, 46 (2021) | 10.1007/s10714-021-02817-z | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compare several definitions of photon helicity (magnetic, electric,
electromagnetic) present in literature. In curved spacetime quantum anomalies
can spoil helicity conservation inducing, according to these definitions,
different effects on photons: either rotation of linear polarization or
production of circular polarization. We derive the Noether current associated
with duality transformations starting from manifestly invariant Lagrangians.
| [
{
"created": "Wed, 2 Dec 2020 10:15:31 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Dec 2020 15:38:51 GMT",
"version": "v2"
},
{
"created": "Thu, 29 Apr 2021 17:10:22 GMT",
"version": "v3"
}
] | 2023-06-02 | [
[
"Galaverni",
"Matteo",
""
],
[
"J.",
"Gabriele Gionti S.",
""
]
] | We compare several definitions of photon helicity (magnetic, electric, electromagnetic) present in literature. In curved spacetime quantum anomalies can spoil helicity conservation inducing, according to these definitions, different effects on photons: either rotation of linear polarization or production of circular polarization. We derive the Noether current associated with duality transformations starting from manifestly invariant Lagrangians. |
gr-qc/9403041 | Jorma Louko | Jorma Louko and Donald Marolf | Global structure of Witten's 2+1 gravity on ${\bf R}\times T^2$ | 3 pages, LaTeX. CGPG-94/3-2, WISC-MILW-94-TH-12 | null | null | null | gr-qc hep-th | null | We investigate the space ${\cal M}$ of classical solutions to Witten's
formulation of 2+1 gravity on the manifold ${\bf R} \times T^2$. ${\cal M}$ is
connected, but neither Hausdorff nor a manifold. However, removing from ${\cal
M}$ a set of measure zero yields a connected manifold which is naturally viewed
as the cotangent bundle over a non-Hausdorff base space. Avenues towards
quantizing the theory are discussed in view of the relation between spacetime
metrics and the various parts of~${\cal M}$. (Contribution to the proceedings
of the Lanczos Centenary Conference, Raleigh, NC, December 12--17, 1993.)
| [
{
"created": "Mon, 21 Mar 1994 15:39:52 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Louko",
"Jorma",
""
],
[
"Marolf",
"Donald",
""
]
] | We investigate the space ${\cal M}$ of classical solutions to Witten's formulation of 2+1 gravity on the manifold ${\bf R} \times T^2$. ${\cal M}$ is connected, but neither Hausdorff nor a manifold. However, removing from ${\cal M}$ a set of measure zero yields a connected manifold which is naturally viewed as the cotangent bundle over a non-Hausdorff base space. Avenues towards quantizing the theory are discussed in view of the relation between spacetime metrics and the various parts of~${\cal M}$. (Contribution to the proceedings of the Lanczos Centenary Conference, Raleigh, NC, December 12--17, 1993.) |
gr-qc/0004057 | Waseem Kamleh | Waseem Kamleh | Signature Changing Space-times and the New Generalised Functions | 19 pages; Section on point-values has been changed, other related and
minor changes; Conclusion and focus are essentially the same | null | null | null | gr-qc | null | A signature changing spacetime is one where an initially Riemannian manifold
with Euclidean signature evolves into the Lorentzian universe we see today.
This concept is motivated by problems in causality implied by the isotropy and
homogeneity of the universe. As initially time and space are indistinguishable
in signature change, these problems are removed. There has been some dispute as
to the nature of the junction conditions across the signature change, and in
particular, whether or not the metric is continuous there. We determine to what
extent the Colombeau algebra of new generalised functions resolves this dispute
by analysing both types of signature change within its framework. A covariant
formulation of the Colombeau algebra is used, in which the usual properties of
the new generalised functions are extended. We find that the Colombeau algebra
is insufficient to preclude either continuous or discontinuous signature
change, and is also unable to settle the dispute over the nature of the
junction conditions.
| [
{
"created": "Tue, 18 Apr 2000 05:10:14 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Sep 2000 04:12:54 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Kamleh",
"Waseem",
""
]
] | A signature changing spacetime is one where an initially Riemannian manifold with Euclidean signature evolves into the Lorentzian universe we see today. This concept is motivated by problems in causality implied by the isotropy and homogeneity of the universe. As initially time and space are indistinguishable in signature change, these problems are removed. There has been some dispute as to the nature of the junction conditions across the signature change, and in particular, whether or not the metric is continuous there. We determine to what extent the Colombeau algebra of new generalised functions resolves this dispute by analysing both types of signature change within its framework. A covariant formulation of the Colombeau algebra is used, in which the usual properties of the new generalised functions are extended. We find that the Colombeau algebra is insufficient to preclude either continuous or discontinuous signature change, and is also unable to settle the dispute over the nature of the junction conditions. |
1909.08751 | Stanley Deser | S. Deser | Why does D=4, rather than more (or less)? An Orwellian explanation | For Mike Duff, friend, collaborator, eminent theoretician, peerless
Defender of the Faith, on his 70th. Minor clarifications for published
version. Final typos corrected | Proc Roy Soc A 476 20190632(2020) | 10.1098/rspa.2019.0632 | BRX-TH 6656, Calt-TH 2019-037 CALT-TH 2019-037 | gr-qc hep-th physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Two simple, if Draconian, assumptions about classical gravity fix
space-time's dimension at D=4
| [
{
"created": "Thu, 19 Sep 2019 00:46:45 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Sep 2019 05:14:02 GMT",
"version": "v2"
},
{
"created": "Thu, 26 Dec 2019 23:27:04 GMT",
"version": "v3"
},
{
"created": "Sun, 29 Mar 2020 19:55:28 GMT",
"version": "v4"
}
] | 2022-12-08 | [
[
"Deser",
"S.",
""
]
] | Two simple, if Draconian, assumptions about classical gravity fix space-time's dimension at D=4 |
1111.2740 | Jorge Paramos | J. P\'aramos | Testing a non-minimal coupling between matter and curvature | 11 pages, 3 figures. To appear in the Proceedings of the "QSO
Astrophysics, Fundamental physics, and Astrometric Cosmology in the Gaia era"
GREAT-ESF Workshop, 6-9 June 2011, Faculdade de Ci\^encias da Universidade do
Porto, Portugal | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the most interesting and current phenomenological extensions of
General Relativity is the so-called $f (R)$ class of theories; a natural
generalization of this includes an explicit non-minimal coupling between matter
and curvature. The purpose of this work is to present a unified view of the
applicability of the latter to various contexts, ranging from astrophysical
matter distributions to a cosmological setting. Various results are discussed,
including the impact of this non-minimal coupling in the choice of Lagrangian
density, a mechanism to mimic galactic dark matter and a Cosmological Constant
at a astrophysical scale, the possibility of accounting for the accelerated
expansion of the Universe and modifications to post-inflationary reheating. The
equivalence between a model exhibiting a non-minimal coupling and
multi-scalar-theories is also discussed.
| [
{
"created": "Fri, 11 Nov 2011 13:45:02 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Nov 2011 21:37:40 GMT",
"version": "v2"
}
] | 2011-11-16 | [
[
"Páramos",
"J.",
""
]
] | One of the most interesting and current phenomenological extensions of General Relativity is the so-called $f (R)$ class of theories; a natural generalization of this includes an explicit non-minimal coupling between matter and curvature. The purpose of this work is to present a unified view of the applicability of the latter to various contexts, ranging from astrophysical matter distributions to a cosmological setting. Various results are discussed, including the impact of this non-minimal coupling in the choice of Lagrangian density, a mechanism to mimic galactic dark matter and a Cosmological Constant at a astrophysical scale, the possibility of accounting for the accelerated expansion of the Universe and modifications to post-inflationary reheating. The equivalence between a model exhibiting a non-minimal coupling and multi-scalar-theories is also discussed. |
0804.1161 | Antony Searle | Antony C. Searle | Monte-Carlo and Bayesian techniques in gravitational wave burst data
analysis | 9 pages, submitted to GWDAW12 proceedings | null | null | LIGO-P080034-00-Z | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Monte-Carlo simulations are used in the gravitational wave burst detection
community to demonstrate and compare the properties of different search
techniques. We note that every Monte-Carlo simulation has a corresponding
optimal search technique according to both the non-Bayesian Neyman-Pearson
criterion and the Bayesian approach, and that this optimal search technique is
the Bayesian statistic. When practical, we recommend deriving the optimal
statistic for a credible Monte-Carlo simulation, rather than testing ad hoc
statistics against that simulation.
| [
{
"created": "Mon, 7 Apr 2008 23:44:06 GMT",
"version": "v1"
}
] | 2008-04-09 | [
[
"Searle",
"Antony C.",
""
]
] | Monte-Carlo simulations are used in the gravitational wave burst detection community to demonstrate and compare the properties of different search techniques. We note that every Monte-Carlo simulation has a corresponding optimal search technique according to both the non-Bayesian Neyman-Pearson criterion and the Bayesian approach, and that this optimal search technique is the Bayesian statistic. When practical, we recommend deriving the optimal statistic for a credible Monte-Carlo simulation, rather than testing ad hoc statistics against that simulation. |
0904.4811 | Richard Woodard | E. O. Kahya (Koc University), V. K. Onemli (Koc University), R. P.
Woodard (University of Florida) | A Completely Regular Quantum Stress Tensor with $w < -1$ | 23 pages, 1 figure | Phys.Rev.D81:023508,2010 | 10.1103/PhysRevD.81.023508 | UFIFT-QG-09-04 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For many quantum field theory computations in cosmology it is not possible to
use the flat space trick of obtaining full, interacting states by evolving free
states over infinite times. State wave functionals must be specified at finite
times and, although the free states suffice to obtain the lowest order effects,
higher order corrections necessarily involve changes of the initial state.
Failing to correctly change the initial state can result in effective field
equations which diverge on the initial value surface, or which contain tedious
sums of terms that redshift like inverse powers of the scale factor. In this
paper we verify a conjecture from 2004 that the lowest order initial state
correction can indeed absorb the initial value divergences and all the
redshifting terms of the two loop expectation value of the stress tensor of a
massless, minimally coupled scalar with a quartic self interaction on
nondynamical de Sitter background.
| [
{
"created": "Thu, 30 Apr 2009 12:56:48 GMT",
"version": "v1"
}
] | 2010-01-22 | [
[
"Kahya",
"E. O.",
"",
"Koc University"
],
[
"Onemli",
"V. K.",
"",
"Koc University"
],
[
"Woodard",
"R. P.",
"",
"University of Florida"
]
] | For many quantum field theory computations in cosmology it is not possible to use the flat space trick of obtaining full, interacting states by evolving free states over infinite times. State wave functionals must be specified at finite times and, although the free states suffice to obtain the lowest order effects, higher order corrections necessarily involve changes of the initial state. Failing to correctly change the initial state can result in effective field equations which diverge on the initial value surface, or which contain tedious sums of terms that redshift like inverse powers of the scale factor. In this paper we verify a conjecture from 2004 that the lowest order initial state correction can indeed absorb the initial value divergences and all the redshifting terms of the two loop expectation value of the stress tensor of a massless, minimally coupled scalar with a quartic self interaction on nondynamical de Sitter background. |
2309.15138 | Albert Huber | Albert Huber | Quasilocal Corrections to Bondi's Mass-Loss Formula and Dynamical
Horizons | 26 pages, 1 Figure, to be published in PRD | PRD 2023 | 10.1103/PhysRevD.108.084056 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work, a null geometric approach to the Brown-York quasilocal
formalism is used to derive an integral law that describes the rate of change
of mass and/or radiative energy escaping through a dynamical horizon of a
non-stationary spacetime. The result thus obtained shows - in accordance with
previous results from the theory of dynamical horizons of Ashtekar et al. -
that the rate at which energy is transferred from the bulk to the boundary of
spacetime through the dynamical horizon becomes zero at equilibrium, where said
horizon becomes non-expanding and null. Moreover, it reveals previously
unrecognized quasilocal corrections to the Bondi mass-loss formula arising from
the combined variation of bulk and boundary components of the Brown-York
Hamiltonian, given in terms of a bulk-to-boundary inflow term akin to an
expression derived in an earlier paper by the author [#huber2022remark]. For
clarity, this is discussed with reference to the Generalized Vaidya family of
spacetimes, for which derived integral expressions take a particularly simple
form.
| [
{
"created": "Tue, 26 Sep 2023 15:21:09 GMT",
"version": "v1"
}
] | 2023-10-26 | [
[
"Huber",
"Albert",
""
]
] | In this work, a null geometric approach to the Brown-York quasilocal formalism is used to derive an integral law that describes the rate of change of mass and/or radiative energy escaping through a dynamical horizon of a non-stationary spacetime. The result thus obtained shows - in accordance with previous results from the theory of dynamical horizons of Ashtekar et al. - that the rate at which energy is transferred from the bulk to the boundary of spacetime through the dynamical horizon becomes zero at equilibrium, where said horizon becomes non-expanding and null. Moreover, it reveals previously unrecognized quasilocal corrections to the Bondi mass-loss formula arising from the combined variation of bulk and boundary components of the Brown-York Hamiltonian, given in terms of a bulk-to-boundary inflow term akin to an expression derived in an earlier paper by the author [#huber2022remark]. For clarity, this is discussed with reference to the Generalized Vaidya family of spacetimes, for which derived integral expressions take a particularly simple form. |
1212.6655 | Sunil Maharaj | A. M. Msomi, K. S. Govinder, S. D. Maharaj | New shear-free relativistic models with heat flow | 10 pages, To appear in Gen. Relativ. Gravit | Gen. Relativ. Gravit. 43: 1685-1696, 2011 | 10.1007/s10714-011-1150-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study shear-free spherically symmetric relativistic models with heat flow.
Our analysis is based on Lie's theory of extended groups applied to the
governing field equations. In particular, we generate a five-parameter family
of transformations which enables us to map existing solutions to new solutions.
All known solutions of Einstein equations with heat flow can therefore produce
infinite families of new solutions. In addition, we provide two new classes of
solutions utilising the Lie infinitesimal generators. These solutions generate
an infinite class of solutions given any one of the two unknown metric
functions.
| [
{
"created": "Sat, 29 Dec 2012 19:05:53 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Msomi",
"A. M.",
""
],
[
"Govinder",
"K. S.",
""
],
[
"Maharaj",
"S. D.",
""
]
] | We study shear-free spherically symmetric relativistic models with heat flow. Our analysis is based on Lie's theory of extended groups applied to the governing field equations. In particular, we generate a five-parameter family of transformations which enables us to map existing solutions to new solutions. All known solutions of Einstein equations with heat flow can therefore produce infinite families of new solutions. In addition, we provide two new classes of solutions utilising the Lie infinitesimal generators. These solutions generate an infinite class of solutions given any one of the two unknown metric functions. |
1111.7082 | Ovidiu Cristinel Stoica | Ovidiu-Cristinel Stoica | Kerr-Newman Solutions with Analytic Singularity and no Closed Timelike
Curves | null | U.P.B. Sci Bull. Series A, 77(1) (2015) | null | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the Kerr-Newman solution, representing charged and rotating
stationary black holes, admits analytic extension at the singularity. This
extension is obtained by using new coordinates, in which the metric tensor
becomes smooth on the singularity ring. On the singularity, the metric is
degenerale - its determinant cancels. The analytic extension can be naturally
chosen so that the region with negative r no longer exists, eliminating by this
the closed timelike curves normally present in the Kerr and Kerr-Newman
solutions. On the extension proposed here the electromagnetic potential is
smooth, being thus able to provide non-singular models of charged spinning
particles. The maximal analytic extension of this solution can be restrained to
a globally hyperbolic region containing the exterior universe, having the same
topology as the Minkowski spacetime. This admits a spacelike foliation in
Cauchy hypersurfaces, on which the information contained in the initial data is
preserved.
| [
{
"created": "Wed, 30 Nov 2011 08:53:33 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Mar 2012 16:11:25 GMT",
"version": "v2"
}
] | 2017-01-31 | [
[
"Stoica",
"Ovidiu-Cristinel",
""
]
] | It is shown that the Kerr-Newman solution, representing charged and rotating stationary black holes, admits analytic extension at the singularity. This extension is obtained by using new coordinates, in which the metric tensor becomes smooth on the singularity ring. On the singularity, the metric is degenerale - its determinant cancels. The analytic extension can be naturally chosen so that the region with negative r no longer exists, eliminating by this the closed timelike curves normally present in the Kerr and Kerr-Newman solutions. On the extension proposed here the electromagnetic potential is smooth, being thus able to provide non-singular models of charged spinning particles. The maximal analytic extension of this solution can be restrained to a globally hyperbolic region containing the exterior universe, having the same topology as the Minkowski spacetime. This admits a spacelike foliation in Cauchy hypersurfaces, on which the information contained in the initial data is preserved. |
0901.3640 | Richard Obousy Dr. | Richard K. Obousy | Investigation into Compactified Dimensions: Casimir Energies and
Phenomenological Aspects | Ph.D dissertation. 147 pages, 16 figures, 3 tables, accepted December
2008 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The primary focus of this dissertation is the study of the Casimir effect and
the possibility that this phenomenon may serve as a mechanism to mediate higher
dimensional stability, and also as a possible mechanism for creating a small
but non-zero vacuum energy density. In chapter one we review the nature of the
quantum vacuum and discuss the different contributions to the vacuum energy
density arising from different sectors of the standard model. Next, in chapter
two, we discuss cosmology and the introduction of the cosmological constant
into Einstein's field equations. In chapter three we explore the Casimir effect
and study a number of mathematical techniques used to obtain a finite physical
result for the Casimir energy. We also review the experiments that have
verified the Casimir force. In chapter four we discuss the introduction of
extra dimensions into physics. We begin by reviewing Kaluza Klein theory, and
then discuss three popular higher dimensional models: bosonic string theory,
large extra dimensions and warped extra dimensions. Chapter five is devoted to
an original derivation of the Casimir energy we derived for the scenario of a
higher dimensional vector field coupled to a scalar field in the fifth
dimension. In chapter six we explore a range of vacuum scenarios and discuss
research we have performed regarding moduli stability. Chapter seven explores a
novel approach to spacecraft propulsion we have proposed based on the idea of
manipulating the extra dimensions of string/M theory. Finally, in chapter 8, we
discuss some issues in heterotic string phenomenology derived from the free
fermionic approach.
| [
{
"created": "Fri, 23 Jan 2009 20:11:24 GMT",
"version": "v1"
}
] | 2009-01-26 | [
[
"Obousy",
"Richard K.",
""
]
] | The primary focus of this dissertation is the study of the Casimir effect and the possibility that this phenomenon may serve as a mechanism to mediate higher dimensional stability, and also as a possible mechanism for creating a small but non-zero vacuum energy density. In chapter one we review the nature of the quantum vacuum and discuss the different contributions to the vacuum energy density arising from different sectors of the standard model. Next, in chapter two, we discuss cosmology and the introduction of the cosmological constant into Einstein's field equations. In chapter three we explore the Casimir effect and study a number of mathematical techniques used to obtain a finite physical result for the Casimir energy. We also review the experiments that have verified the Casimir force. In chapter four we discuss the introduction of extra dimensions into physics. We begin by reviewing Kaluza Klein theory, and then discuss three popular higher dimensional models: bosonic string theory, large extra dimensions and warped extra dimensions. Chapter five is devoted to an original derivation of the Casimir energy we derived for the scenario of a higher dimensional vector field coupled to a scalar field in the fifth dimension. In chapter six we explore a range of vacuum scenarios and discuss research we have performed regarding moduli stability. Chapter seven explores a novel approach to spacecraft propulsion we have proposed based on the idea of manipulating the extra dimensions of string/M theory. Finally, in chapter 8, we discuss some issues in heterotic string phenomenology derived from the free fermionic approach. |
2310.00312 | Bayram Tekin | Metin Gurses, Bayram Tekin | Kerr-Vaidya type radiating black holes in semi-classical gravity with
conformal anomaly | 12 pages,matches the published version | Phys.Rev.D 109 (2024) 2, 024001 | 10.1103/PhysRevD.109.024001 | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | Static black holes in the conformal anomaly-sourced semi-classical General
Relativity in four dimensions were extended to rotating, stationary solutions,
recently. These quantum-corrected black holes show different features compared
to the Kerr black hole and need for further extensions. Here we remove the
condition of stationarity and find radiating (Kerr-Vaidya-type) solutions in
the same theory augmented with a cosmological constant. As long as the coupling
constant $\alpha$ of the $A$-type trace anomaly is non-zero, we show that $i)$
the cosmological constant is bounded from above, i.e $\Lambda \le \frac{3}{4
\alpha}$; $ii)$ static black holes exist but they may not be unique; $iii)$
static black holes do not satisfy the second law of black hole thermodynamics;
$iv)$ static black holes may have unstable inner horizons; $v)$ In the
nonstationary and axially symmetric case, stability of the event horizon and
the second law of thermodynamics black holes are problematic.
| [
{
"created": "Sat, 30 Sep 2023 08:53:31 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Jan 2024 08:29:41 GMT",
"version": "v2"
}
] | 2024-01-17 | [
[
"Gurses",
"Metin",
""
],
[
"Tekin",
"Bayram",
""
]
] | Static black holes in the conformal anomaly-sourced semi-classical General Relativity in four dimensions were extended to rotating, stationary solutions, recently. These quantum-corrected black holes show different features compared to the Kerr black hole and need for further extensions. Here we remove the condition of stationarity and find radiating (Kerr-Vaidya-type) solutions in the same theory augmented with a cosmological constant. As long as the coupling constant $\alpha$ of the $A$-type trace anomaly is non-zero, we show that $i)$ the cosmological constant is bounded from above, i.e $\Lambda \le \frac{3}{4 \alpha}$; $ii)$ static black holes exist but they may not be unique; $iii)$ static black holes do not satisfy the second law of black hole thermodynamics; $iv)$ static black holes may have unstable inner horizons; $v)$ In the nonstationary and axially symmetric case, stability of the event horizon and the second law of thermodynamics black holes are problematic. |
gr-qc/9710106 | Zerbini Sergio | A.A. Bytsenko, L. Vanzo and S. Zerbini | Quantum Correction to the Entropy of the (2+1)-Dimensional Black Hole | 14 pages, Latex, one new reference added | Phys.Rev. D57 (1998) 4917-4924 | 10.1103/PhysRevD.57.4917 | null | gr-qc hep-th | null | The thermodynamic properties of the (2+1)-dimensional non-rotating black hole
of Ba\~nados, Teitelboim and Zanelli are discussed. The first quantum
correction to the Bekenstein-Hawking entropy is evaluated within the on-shell
Euclidean formalism, making use of the related Chern-Simons representation of
the 3-dimensional gravity. Horizon and ultraviolet divergences in the quantum
correction are dealt with a renormalization of the Newton constant. It is
argued that the quantum correction due to the gravitational field shrinks the
effective radius of a hole and becomes more and more important as soon as the
evaporation process goes on, while the area law is not violated.
| [
{
"created": "Wed, 22 Oct 1997 14:40:50 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Oct 1997 13:44:20 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Bytsenko",
"A. A.",
""
],
[
"Vanzo",
"L.",
""
],
[
"Zerbini",
"S.",
""
]
] | The thermodynamic properties of the (2+1)-dimensional non-rotating black hole of Ba\~nados, Teitelboim and Zanelli are discussed. The first quantum correction to the Bekenstein-Hawking entropy is evaluated within the on-shell Euclidean formalism, making use of the related Chern-Simons representation of the 3-dimensional gravity. Horizon and ultraviolet divergences in the quantum correction are dealt with a renormalization of the Newton constant. It is argued that the quantum correction due to the gravitational field shrinks the effective radius of a hole and becomes more and more important as soon as the evaporation process goes on, while the area law is not violated. |
gr-qc/9306005 | null | Mirjam Cveti\v{c}, Stephen Griffies, and Harald H. Soleng | Local and global gravitational aspects of domain wall space-times | UPR-565-T, 26 REVTEX pages, 10 figures available upon request | Phys.Rev.D48:2613-2634,1993 | 10.1103/PhysRevD.48.2613 | null | gr-qc hep-th | null | Local and global gravitational effects induced by eternal vacuum domain walls
are studied. We concentrate on thin walls between non-equal and non-positive
cosmological constants on each side of the wall. These vacuum domain walls fall
in three classes depending on the value of their energy density $\sigma$: (1)\
extreme walls with $\sigma = \sigma_{{\text{ext}}}$ are planar, static walls
corresponding to supersymmetric configurations, (2)\ non-extreme walls with
$\sigma = \sigma_{{\text{non}}} > \sigma_{{\text{ext}}}$ correspond to
expanding bubbles with observers on either side of the wall being {\em
inside\/} the bubble, and (3)\ ultra-extreme walls with $\sigma =
\sigma_{{\text{ultra}}} < \sigma_{{\text{ext}}}$ represent the bubbles of false
vacuum decay. On the sides with less negative cosmological constant, the
extreme, non-extreme, and ultra-extreme walls exhibit no, repulsive, and
attractive effective ``gravitational forces,'' respectively. These
``gravitational forces'' are global effects not caused by local curvature.
Since the non-extreme wall encloses observers on both sides, the supersymmetric
system has the lowest gravitational mass accessable to outside observers. It is
conjectured that similar positive mass protection occurs in all physical
systems and that no finite negative mass object can exist inside the universe.
We also discuss the global space-time structure of these singularity free
space-times and point out intriguing analogies with the causal structure of
black holes.
| [
{
"created": "Wed, 2 Jun 1993 15:07:24 GMT",
"version": "v1"
}
] | 2009-09-17 | [
[
"Cvetič",
"Mirjam",
""
],
[
"Griffies",
"Stephen",
""
],
[
"Soleng",
"Harald H.",
""
]
] | Local and global gravitational effects induced by eternal vacuum domain walls are studied. We concentrate on thin walls between non-equal and non-positive cosmological constants on each side of the wall. These vacuum domain walls fall in three classes depending on the value of their energy density $\sigma$: (1)\ extreme walls with $\sigma = \sigma_{{\text{ext}}}$ are planar, static walls corresponding to supersymmetric configurations, (2)\ non-extreme walls with $\sigma = \sigma_{{\text{non}}} > \sigma_{{\text{ext}}}$ correspond to expanding bubbles with observers on either side of the wall being {\em inside\/} the bubble, and (3)\ ultra-extreme walls with $\sigma = \sigma_{{\text{ultra}}} < \sigma_{{\text{ext}}}$ represent the bubbles of false vacuum decay. On the sides with less negative cosmological constant, the extreme, non-extreme, and ultra-extreme walls exhibit no, repulsive, and attractive effective ``gravitational forces,'' respectively. These ``gravitational forces'' are global effects not caused by local curvature. Since the non-extreme wall encloses observers on both sides, the supersymmetric system has the lowest gravitational mass accessable to outside observers. It is conjectured that similar positive mass protection occurs in all physical systems and that no finite negative mass object can exist inside the universe. We also discuss the global space-time structure of these singularity free space-times and point out intriguing analogies with the causal structure of black holes. |
0704.0007 | Alejandro Corichi | Alejandro Corichi, Tatjana Vukasinac and Jose A. Zapata | Polymer Quantum Mechanics and its Continuum Limit | 16 pages, no figures. Typos corrected to match published version | Phys.Rev.D76:044016,2007 | 10.1103/PhysRevD.76.044016 | IGPG-07/03-2 | gr-qc | null | A rather non-standard quantum representation of the canonical commutation
relations of quantum mechanics systems, known as the polymer representation has
gained some attention in recent years, due to its possible relation with Planck
scale physics. In particular, this approach has been followed in a symmetric
sector of loop quantum gravity known as loop quantum cosmology. Here we explore
different aspects of the relation between the ordinary Schroedinger theory and
the polymer description. The paper has two parts. In the first one, we derive
the polymer quantum mechanics starting from the ordinary Schroedinger theory
and show that the polymer description arises as an appropriate limit. In the
second part we consider the continuum limit of this theory, namely, the reverse
process in which one starts from the discrete theory and tries to recover back
the ordinary Schroedinger quantum mechanics. We consider several examples of
interest, including the harmonic oscillator, the free particle and a simple
cosmological model.
| [
{
"created": "Sat, 31 Mar 2007 04:27:22 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Aug 2007 22:42:11 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Corichi",
"Alejandro",
""
],
[
"Vukasinac",
"Tatjana",
""
],
[
"Zapata",
"Jose A.",
""
]
] | A rather non-standard quantum representation of the canonical commutation relations of quantum mechanics systems, known as the polymer representation has gained some attention in recent years, due to its possible relation with Planck scale physics. In particular, this approach has been followed in a symmetric sector of loop quantum gravity known as loop quantum cosmology. Here we explore different aspects of the relation between the ordinary Schroedinger theory and the polymer description. The paper has two parts. In the first one, we derive the polymer quantum mechanics starting from the ordinary Schroedinger theory and show that the polymer description arises as an appropriate limit. In the second part we consider the continuum limit of this theory, namely, the reverse process in which one starts from the discrete theory and tries to recover back the ordinary Schroedinger quantum mechanics. We consider several examples of interest, including the harmonic oscillator, the free particle and a simple cosmological model. |
2107.12531 | Takuya Tsutsui | Takuya Tsutsui, Atsushi Nishizawa, Soichiro Morisaki | Early warning of precessing neutron-star black-hole binary mergers with
the near-future gravitational-wave detectors | MNRAS version (change author names) | null | 10.1093/mnras/stac715 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Since gravitational and electromagnetic waves from a compact binary
coalescence carry independent information about the source, the joint
observation is important for understanding the physical mechanisms of the
emissions. Rapid detection and source localization of a gravitational wave
signal are crucial for the joint observation to be successful. For a signal
with a high signal-to-noise ratio, it is even possible to detect it before the
merger, which is called early warning. In this letter, we estimate the
performances of the early warning for neutron-star black-hole binaries,
considering the precession effect of a binary orbit, with the near-future
detectors such as A+, AdV+, KAGRA+, and Voyager. We find that a gravitational
wave source can be localized in $100 \,\mathrm{deg^2}$ on the sky before $\sim
10$--$40 \,\mathrm{s}$ of time to merger once per year.
| [
{
"created": "Tue, 27 Jul 2021 00:46:27 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Apr 2022 06:40:39 GMT",
"version": "v2"
},
{
"created": "Fri, 6 May 2022 00:42:20 GMT",
"version": "v3"
}
] | 2022-05-09 | [
[
"Tsutsui",
"Takuya",
""
],
[
"Nishizawa",
"Atsushi",
""
],
[
"Morisaki",
"Soichiro",
""
]
] | Since gravitational and electromagnetic waves from a compact binary coalescence carry independent information about the source, the joint observation is important for understanding the physical mechanisms of the emissions. Rapid detection and source localization of a gravitational wave signal are crucial for the joint observation to be successful. For a signal with a high signal-to-noise ratio, it is even possible to detect it before the merger, which is called early warning. In this letter, we estimate the performances of the early warning for neutron-star black-hole binaries, considering the precession effect of a binary orbit, with the near-future detectors such as A+, AdV+, KAGRA+, and Voyager. We find that a gravitational wave source can be localized in $100 \,\mathrm{deg^2}$ on the sky before $\sim 10$--$40 \,\mathrm{s}$ of time to merger once per year. |
1901.04308 | Z. Yousaf | M. Ilyas, Z. Yousaf, M. Z. Bhatti | Bounds on Higher Derivative $f(R,\square R,T)$ Models from Energy
Conditions | 11 pages, 8 figures, version accepted for publication in the Modern
Physics Letters A | Mod. Phys. Lett. A 34, 1950082 (2019) | 10.1142/S0217732319500822 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper studies the viable regions of some cosmic models in a higher
derivative $f(R,\square R, T)$ theory with the help of energy conditions (where
$R$ and $T$ are the Ricci scalar, and trace of energy momentum tensor,
respectively). For this purpose, we assume a flat
Friedmann-Lema\^{i}tre-Robertson-Walker metric which is assumed to be filled
with perfect fluid configurations. We take two distinct realistic models, that
might be helpful to explore stable regimes of cosmological solutions. After
taking some numerical values of cosmic parameters, like crackle, snap, jerk
(etc) as well as viable constraints from energy conditions, the viable zones
for the under observed $f(R,\square R, T)$ models are examined.
| [
{
"created": "Wed, 9 Jan 2019 03:22:14 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Jan 2019 03:06:16 GMT",
"version": "v2"
}
] | 2020-03-03 | [
[
"Ilyas",
"M.",
""
],
[
"Yousaf",
"Z.",
""
],
[
"Bhatti",
"M. Z.",
""
]
] | This paper studies the viable regions of some cosmic models in a higher derivative $f(R,\square R, T)$ theory with the help of energy conditions (where $R$ and $T$ are the Ricci scalar, and trace of energy momentum tensor, respectively). For this purpose, we assume a flat Friedmann-Lema\^{i}tre-Robertson-Walker metric which is assumed to be filled with perfect fluid configurations. We take two distinct realistic models, that might be helpful to explore stable regimes of cosmological solutions. After taking some numerical values of cosmic parameters, like crackle, snap, jerk (etc) as well as viable constraints from energy conditions, the viable zones for the under observed $f(R,\square R, T)$ models are examined. |
2402.18785 | Wagno Cesar E Silva | Wagno Cesar e Silva and Ilya L. Shapiro | On the semiclassical bounce with strong minimal assumptions | 14 pages, 3 figures. Added discussion related to the energy
conditions and some references | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We explore the possibility of avoiding cosmological singularity with a bounce
solution in the early Universe. The main finding is that simple and well-known
semiclassical correction, which describes the mixing of radiation and gravity
in the effective action, may provide an analytic solution with a bounce. The
solution requires a positive beta function for the total radiation term and the
contraction of the Universe at the initial instant. The numerical estimate
shows that the bounce may occur in an acceptable range of energies, but only
under strong assumptions about the particle physics beyond the Standard Model.
| [
{
"created": "Thu, 29 Feb 2024 01:18:43 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Apr 2024 15:14:35 GMT",
"version": "v2"
}
] | 2024-04-29 | [
[
"Silva",
"Wagno Cesar e",
""
],
[
"Shapiro",
"Ilya L.",
""
]
] | We explore the possibility of avoiding cosmological singularity with a bounce solution in the early Universe. The main finding is that simple and well-known semiclassical correction, which describes the mixing of radiation and gravity in the effective action, may provide an analytic solution with a bounce. The solution requires a positive beta function for the total radiation term and the contraction of the Universe at the initial instant. The numerical estimate shows that the bounce may occur in an acceptable range of energies, but only under strong assumptions about the particle physics beyond the Standard Model. |
2110.10424 | Horacio Vieira | H. S. Vieira | On the Schwarzschild-Anti-de Sitter black hole with an f(R) global
monopole | 13 pages, 7 figures | Eur. Phys. J. C (2021) 81:1143 | 10.1140/epjc/s10052-021-09961-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we follow the recently revisited f(R) theory of gravity for
studying the interaction between quantum scalar particles and the gravitational
field of a generalized black hole with an f(R) global monopole. This background
has a term playing the role of an effective cosmological constant, which
permits us to call it as Schwarzschild-Anti-de Sitter (SAdS) black hole with an
f(R) global monopole. We examine the separability of the Klein-Gordon equation
with a non-minimal coupling and then we discuss both the massless and massive
cases for a conformal coupling. We investigate some physical phenomena related
to the asymptotic behavior of the radial function, namely, the black hole
radiation, the quasibound states, and the wave eigenfunctions.
| [
{
"created": "Wed, 20 Oct 2021 08:21:24 GMT",
"version": "v1"
}
] | 2022-01-04 | [
[
"Vieira",
"H. S.",
""
]
] | In this work, we follow the recently revisited f(R) theory of gravity for studying the interaction between quantum scalar particles and the gravitational field of a generalized black hole with an f(R) global monopole. This background has a term playing the role of an effective cosmological constant, which permits us to call it as Schwarzschild-Anti-de Sitter (SAdS) black hole with an f(R) global monopole. We examine the separability of the Klein-Gordon equation with a non-minimal coupling and then we discuss both the massless and massive cases for a conformal coupling. We investigate some physical phenomena related to the asymptotic behavior of the radial function, namely, the black hole radiation, the quasibound states, and the wave eigenfunctions. |
1004.3240 | Benjamin Koch | Benjamin Koch | Geometrizing the Quantum - A Toy Model | Talk given the XXV Max Born Symposium, 6 pages, no figure | AIP Conf. Proc. 1196, 161 (2009) | 10.1063/1.3284379 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the equations of relativistic Bohmian mechanics for multiple
bosonic particles have a dual description in terms of a classical theory of
conformally "curved" space-time. This shows that it is possible to formulate
quantum mechanics as a purely classical geometrical theory. The results are
further generalized to interactions with an external electromagnetic field.
| [
{
"created": "Mon, 19 Apr 2010 16:13:03 GMT",
"version": "v1"
}
] | 2015-05-18 | [
[
"Koch",
"Benjamin",
""
]
] | It is shown that the equations of relativistic Bohmian mechanics for multiple bosonic particles have a dual description in terms of a classical theory of conformally "curved" space-time. This shows that it is possible to formulate quantum mechanics as a purely classical geometrical theory. The results are further generalized to interactions with an external electromagnetic field. |
2003.08665 | Vijay Singh Dr. | Vijay Singh and Aroonkumar Beesham | Plane symmetric model in $f(R,T)$ gravity | 11 pages | Eur. Phys. J. Plus 135, 319 (2020) | 10.1140/epjp/s13360-020-00314-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A plane symmetric Bianchi-I model is explored in $f(R,T)$ gravity, where $R$
is the Ricci scalar and $T$ is the trace of energy-momentum tensor. The
solutions are obtained with the consideration of a specific Hubble parameter
which yields a constant deceleration parameter. The various evolutionary phases
are identified under the constraints obtained for physically viable
cosmological scenarios. Although a single (primary) matter source is taken, due
to the coupling between matter and $f(R,T)$ gravity, an additional matter
source appears, which mimics a perfect fluid or exotic matter. The solutions
are also extended to the case of a scalar field model. The kinematical behavior
of the model remains independent of $f(R,T)$ gravity. The physical behavior of
the effective matter also remains the same as in general relativity. It is
found that $f(R,T)$ gravity can be a good alternative to the hypothetical
candidates of dark energy to describe the present accelerating expansion of the
universe.
| [
{
"created": "Thu, 19 Mar 2020 10:31:26 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Mar 2020 07:30:51 GMT",
"version": "v2"
}
] | 2020-03-23 | [
[
"Singh",
"Vijay",
""
],
[
"Beesham",
"Aroonkumar",
""
]
] | A plane symmetric Bianchi-I model is explored in $f(R,T)$ gravity, where $R$ is the Ricci scalar and $T$ is the trace of energy-momentum tensor. The solutions are obtained with the consideration of a specific Hubble parameter which yields a constant deceleration parameter. The various evolutionary phases are identified under the constraints obtained for physically viable cosmological scenarios. Although a single (primary) matter source is taken, due to the coupling between matter and $f(R,T)$ gravity, an additional matter source appears, which mimics a perfect fluid or exotic matter. The solutions are also extended to the case of a scalar field model. The kinematical behavior of the model remains independent of $f(R,T)$ gravity. The physical behavior of the effective matter also remains the same as in general relativity. It is found that $f(R,T)$ gravity can be a good alternative to the hypothetical candidates of dark energy to describe the present accelerating expansion of the universe. |
gr-qc/9301008 | Gary Horowitz | Gary T. Horowitz | What is the True Description of Charged Black Holes? | 15 pages, harvmac, UCSBTH-92-52 | null | null | null | gr-qc hep-th | null | If string theory describes nature, then charged black holes are not described
by the Reissner-Nordstrom solution. This solution must be modified to include a
massive dilaton. In the limit of vanishing dilaton mass, the new solution can
be found by a generalization of the Harrison transformation for the
Einstein-Maxwell equations. These two solution generating transformations and
the resulting black holes are compared. It is shown that the extremal black
hole with massless dilaton can be viewed as the ``square root" of the extremal
Reissner-Nordstrom solution. When the dilaton mass is included, extremal black
holes are repulsive, and it is energetically favorable for them to bifurcate
into smaller holes. (To appear in the Festschrift for Dieter Brill)
| [
{
"created": "Tue, 12 Jan 1993 01:18:20 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Horowitz",
"Gary T.",
""
]
] | If string theory describes nature, then charged black holes are not described by the Reissner-Nordstrom solution. This solution must be modified to include a massive dilaton. In the limit of vanishing dilaton mass, the new solution can be found by a generalization of the Harrison transformation for the Einstein-Maxwell equations. These two solution generating transformations and the resulting black holes are compared. It is shown that the extremal black hole with massless dilaton can be viewed as the ``square root" of the extremal Reissner-Nordstrom solution. When the dilaton mass is included, extremal black holes are repulsive, and it is energetically favorable for them to bifurcate into smaller holes. (To appear in the Festschrift for Dieter Brill) |
1812.01590 | Christos Karathanasis | Christos Karathanasis, Theocharis Apostolatos | Gravitational solitons on Kasner background revisited: The simplest
solitons with physical context | null | null | 10.1088/1361-6382/ab23c2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revise the one-pair complex poles soliton solutions on a Kasner
background. In the literature, these were rejected as solutions with no
cosmological interest due to singularities that supposedly show up at
space-like infinity. The only accepted solutions of this kind were those with
background metric parameter $d=\pm 1$. By computing the scalars $I, J$ we find
that there are no scalar singularities at all, for a wide range of the
background parameter $d$. This means that there are actually an enormous number
of acceptable simple complex-poles solutions, besides the $d=\pm1$ cases. These
solutions are interesting, because they are much simpler than the two-pairs
complex poles solutions and, consequently, it is easier to draw conclusions and
relate physical phenomena to them.
| [
{
"created": "Tue, 4 Dec 2018 18:46:40 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Apr 2019 16:26:58 GMT",
"version": "v2"
}
] | 2019-07-17 | [
[
"Karathanasis",
"Christos",
""
],
[
"Apostolatos",
"Theocharis",
""
]
] | We revise the one-pair complex poles soliton solutions on a Kasner background. In the literature, these were rejected as solutions with no cosmological interest due to singularities that supposedly show up at space-like infinity. The only accepted solutions of this kind were those with background metric parameter $d=\pm 1$. By computing the scalars $I, J$ we find that there are no scalar singularities at all, for a wide range of the background parameter $d$. This means that there are actually an enormous number of acceptable simple complex-poles solutions, besides the $d=\pm1$ cases. These solutions are interesting, because they are much simpler than the two-pairs complex poles solutions and, consequently, it is easier to draw conclusions and relate physical phenomena to them. |
2401.00098 | Adailton Ara\'ujo Filho | A. A. Ara\'ujo Filho, J. A. A. S. Reis, L. Lisboa-Santos | An anisotropic rotating cosmic string with Lorentz violation:
thermodynamics and Landau levels | 19 pages and 2 figures | The European Physical Journal Plus, 139, 438 (2024) | 10.1140/epjp/s13360-024-05232-w | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we generalize the spacetime induced by a rotating cosmic
string, taking into account anisotropic effects due the breaking of the Lorentz
violation. In particular, we explore the energy levels of a massive spinless
particle that is covariantly coupled to a uniform magnetic field aligned with
the string. Subsequently, we introduce a scalar potential featuring both a
Coulomb-type and a linear confining term and comprehensively solve the
Klein-Gordon equations for each configuration. Finally, by imposing rigid-wall
boundary conditions, we determine the Landau levels when the linear defect
itself possesses magnetization. Notably, our analysis reveals the occurrence of
Landau quantization even in the absence of gauge fields, provided the string
possesses spin. Finally, the thermodynamic properties are computed as well in
these scenarios.
| [
{
"created": "Fri, 29 Dec 2023 23:33:56 GMT",
"version": "v1"
}
] | 2024-05-27 | [
[
"Filho",
"A. A. Araújo",
""
],
[
"Reis",
"J. A. A. S.",
""
],
[
"Lisboa-Santos",
"L.",
""
]
] | In this work, we generalize the spacetime induced by a rotating cosmic string, taking into account anisotropic effects due the breaking of the Lorentz violation. In particular, we explore the energy levels of a massive spinless particle that is covariantly coupled to a uniform magnetic field aligned with the string. Subsequently, we introduce a scalar potential featuring both a Coulomb-type and a linear confining term and comprehensively solve the Klein-Gordon equations for each configuration. Finally, by imposing rigid-wall boundary conditions, we determine the Landau levels when the linear defect itself possesses magnetization. Notably, our analysis reveals the occurrence of Landau quantization even in the absence of gauge fields, provided the string possesses spin. Finally, the thermodynamic properties are computed as well in these scenarios. |
1512.05233 | Aur\'elien Hees | A. Hees and O. Minazzoli | Post-Newtonian phenomenology of a massless dilaton | 27 pages, comments welcome | null | null | null | gr-qc astro-ph.EP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we present extensively the observational consequences of
massless dilaton theories at the post-Newtonian level. We extend previous work
by considering a general model including a dilaton-Ricci coupling as well as a
general dilaton kinetic term while using the microphysical dilaton-matter
coupling model proposed in [Damour and Donoghue, PRD 2010].
We derive all the expressions needed to analyze local gravitational
observations in a dilaton framework, which is useful to derive constraints on
the dilaton theories. In particular, we present the equations of motion of
celestial bodies (in barycentric and planetocentric reference frames), the
equation of propagation of light and the evolution of proper time as measured
by specific clocks. Particular care is taken in order to derive properly the
observables. The resulting equations can be used to analyse a large numbers of
observations: universality of free fall tests, planetary ephemerides analysis,
analysis of satellites motion, Very Long Baseline Interferometry, tracking of
spacecraft, gravitational redshift tests, ...
| [
{
"created": "Wed, 16 Dec 2015 16:26:34 GMT",
"version": "v1"
}
] | 2015-12-17 | [
[
"Hees",
"A.",
""
],
[
"Minazzoli",
"O.",
""
]
] | In this paper, we present extensively the observational consequences of massless dilaton theories at the post-Newtonian level. We extend previous work by considering a general model including a dilaton-Ricci coupling as well as a general dilaton kinetic term while using the microphysical dilaton-matter coupling model proposed in [Damour and Donoghue, PRD 2010]. We derive all the expressions needed to analyze local gravitational observations in a dilaton framework, which is useful to derive constraints on the dilaton theories. In particular, we present the equations of motion of celestial bodies (in barycentric and planetocentric reference frames), the equation of propagation of light and the evolution of proper time as measured by specific clocks. Particular care is taken in order to derive properly the observables. The resulting equations can be used to analyse a large numbers of observations: universality of free fall tests, planetary ephemerides analysis, analysis of satellites motion, Very Long Baseline Interferometry, tracking of spacecraft, gravitational redshift tests, ... |
2203.15035 | Che-Yu Chen | Che-Yu Chen, Yakefu Reyimuaji, Xinyi Zhang | Slow-roll inflation in $f(R,T)$ gravity with a $RT$ mixing term | 17 pages, 4 figures, updated to match the published version | null | 10.1016/j.dark.2022.101130 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider slow-roll inflationary models in a class of modified theories of
gravity which contains non-minimal curvature-inflaton couplings, i.e., the
$f(R,T)$ gravity, where $R$ is the Ricci scalar and $T$ is the trace of the
inflaton energy-momentum tensor. On top of the minimally coupled $T$ that has
been widely investigated in the literature, we further include a $RT$ mixing
term in the theory. This mixing term introduces non-minimal derivative
couplings and plays an important role in inflationary dynamics. Taking chaotic
and natural inflation as examples, we find that the predictions for spectral
tilt and the tensor-to-scalar ratio are sensitive to the existence of the $RT$
mixing term. In particular, by turning on this mixing term, it is possible to
bring chaotic and natural inflation into better agreement with observational
data.
| [
{
"created": "Mon, 28 Mar 2022 18:59:14 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Nov 2022 06:27:42 GMT",
"version": "v2"
}
] | 2022-11-07 | [
[
"Chen",
"Che-Yu",
""
],
[
"Reyimuaji",
"Yakefu",
""
],
[
"Zhang",
"Xinyi",
""
]
] | We consider slow-roll inflationary models in a class of modified theories of gravity which contains non-minimal curvature-inflaton couplings, i.e., the $f(R,T)$ gravity, where $R$ is the Ricci scalar and $T$ is the trace of the inflaton energy-momentum tensor. On top of the minimally coupled $T$ that has been widely investigated in the literature, we further include a $RT$ mixing term in the theory. This mixing term introduces non-minimal derivative couplings and plays an important role in inflationary dynamics. Taking chaotic and natural inflation as examples, we find that the predictions for spectral tilt and the tensor-to-scalar ratio are sensitive to the existence of the $RT$ mixing term. In particular, by turning on this mixing term, it is possible to bring chaotic and natural inflation into better agreement with observational data. |
1906.05090 | Maarten van de Meent | Maarten van de Meent | Analytic solutions for parallel transport along generic bound geodesics
in Kerr spacetime | null | null | 10.1088/1361-6382/ab79d5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide analytical closed form solutions for the parallel transport along
a bound geodesic in Kerr spacetime. This can be considered the lowest order
approximation for the motion a spinning black hole in an extreme mass-ratio
inspiral. As an illustration of the usefulness of our new found expressions we
scope out the locations of spin-spin resonances in quasi-circular EMRIs. All
solutions are given as functions of Mino time, which facilitates the decoupling
of the equations of motion. To help physical interpretation, we also provide an
analytical expression for the proper time along a geodesic as a function of
Mino time.
| [
{
"created": "Wed, 12 Jun 2019 12:40:28 GMT",
"version": "v1"
}
] | 2020-08-26 | [
[
"van de Meent",
"Maarten",
""
]
] | We provide analytical closed form solutions for the parallel transport along a bound geodesic in Kerr spacetime. This can be considered the lowest order approximation for the motion a spinning black hole in an extreme mass-ratio inspiral. As an illustration of the usefulness of our new found expressions we scope out the locations of spin-spin resonances in quasi-circular EMRIs. All solutions are given as functions of Mino time, which facilitates the decoupling of the equations of motion. To help physical interpretation, we also provide an analytical expression for the proper time along a geodesic as a function of Mino time. |
1712.02458 | Betti Hartmann | Yves Brihaye, Betti Hartmann, Jon Urrestilla | Solitons and black hole in shift symmetric scalar-tensor gravity with
cosmological constant | null | null | 10.1007/JHEP06(2018)074 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate the existence of static, spherically symmetric globally
regular, i.e. solitonic solutions of a shift-symmetric scalar-tensor gravity
model with negative cosmological constant. The norm of the Noether current
associated to the shift symmetry is finite in the full space-time. We also
discuss the corresponding black hole solutions and demonstrate that the
interplay between the scalar-tensor coupling and the cosmological constant
leads to the existence of new branches of solutions. To linear order in the
scalar-tensor coupling, the asymptotic space-time corresponds to an Anti-de
Sitter space-time with a non-trivial scalar field on its conformal boundary.
This allows the interpretation of our solutions in the context of the AdS/CFT
correspondence. Finally, we demonstrate that - for physically relevant, small
values of the scalar-tensor coupling - solutions with positive cosmological
constant do not exist in our model.
| [
{
"created": "Thu, 7 Dec 2017 00:48:06 GMT",
"version": "v1"
}
] | 2018-08-01 | [
[
"Brihaye",
"Yves",
""
],
[
"Hartmann",
"Betti",
""
],
[
"Urrestilla",
"Jon",
""
]
] | We demonstrate the existence of static, spherically symmetric globally regular, i.e. solitonic solutions of a shift-symmetric scalar-tensor gravity model with negative cosmological constant. The norm of the Noether current associated to the shift symmetry is finite in the full space-time. We also discuss the corresponding black hole solutions and demonstrate that the interplay between the scalar-tensor coupling and the cosmological constant leads to the existence of new branches of solutions. To linear order in the scalar-tensor coupling, the asymptotic space-time corresponds to an Anti-de Sitter space-time with a non-trivial scalar field on its conformal boundary. This allows the interpretation of our solutions in the context of the AdS/CFT correspondence. Finally, we demonstrate that - for physically relevant, small values of the scalar-tensor coupling - solutions with positive cosmological constant do not exist in our model. |
2310.11039 | Diego Rubiera-Garcia | I. De Martino, R. Della Monica, D. Rubiera-Garcia | The optical appearance of a nonsingular de Sitter core black hole
geometry under several thin disk emissions | 12 pages, 5 figures | null | null | IPARCOS-UCM-23-122 | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We consider the optical appearance under a thin accretion disk of a regular
black hole with a central de Sitter core implementing $\mathcal{O}(l^2/r^2)$
far-corrections to the Schwarzschild black hole. We use the choice $l=0.25M$,
which satisfies recently found constraints from the motion of the S2 star
around Sgr A$^*$ in this model, and which leads to thermodynamically stable
black holes. As the emission model, we suitably adapt ten samples of the
Standard Unbound emission profile for a monochromatic intensity in the disk's
frame, which have been previously employed in the literature within the context
of reproducing General Relativistic Magneto-Hydrodynamic simulations of the
accretion flow. We find the usual central brightness depression surrounded by
the bright ring cast by the disk's direct emission as well as two
non-negligible photon ring contributions. As compared to the usual
Schwarzschild solution, the relative luminosities of the latter are
significantly boosted, while the size of the former is strongly decreased. We
discuss the entanglement of the background geometry and the choice of emission
model in generating these black hole images, as well as the capability of these
modifications of Schwarzschild solution to pass present and future tests based
on their optical appearance when illuminated by an accretion disk.
| [
{
"created": "Tue, 17 Oct 2023 07:10:44 GMT",
"version": "v1"
}
] | 2023-10-19 | [
[
"De Martino",
"I.",
""
],
[
"Della Monica",
"R.",
""
],
[
"Rubiera-Garcia",
"D.",
""
]
] | We consider the optical appearance under a thin accretion disk of a regular black hole with a central de Sitter core implementing $\mathcal{O}(l^2/r^2)$ far-corrections to the Schwarzschild black hole. We use the choice $l=0.25M$, which satisfies recently found constraints from the motion of the S2 star around Sgr A$^*$ in this model, and which leads to thermodynamically stable black holes. As the emission model, we suitably adapt ten samples of the Standard Unbound emission profile for a monochromatic intensity in the disk's frame, which have been previously employed in the literature within the context of reproducing General Relativistic Magneto-Hydrodynamic simulations of the accretion flow. We find the usual central brightness depression surrounded by the bright ring cast by the disk's direct emission as well as two non-negligible photon ring contributions. As compared to the usual Schwarzschild solution, the relative luminosities of the latter are significantly boosted, while the size of the former is strongly decreased. We discuss the entanglement of the background geometry and the choice of emission model in generating these black hole images, as well as the capability of these modifications of Schwarzschild solution to pass present and future tests based on their optical appearance when illuminated by an accretion disk. |
1208.2604 | Andrzej Krasi\'nski | Andrzej Krasi\'nski and Krzysztof Bolejko | Geometry of the quasi-hyperbolic Szekeres models | 19 pages, 13 figures. This version matches the published text | Phys. Rev. D86, 104036 (2012) | 10.1103/PhysRevD.86.104036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Geometric properties of the quasi-hyperbolic Szekeres models are discussed
and related to the quasi-spherical Szekeres models. Typical examples of shapes
of various classes of 2-dimensional coordinate surfaces are shown in graphs;
for the hyperbolically symmetric subcase and for the general quasi-hyperbolic
case. An analysis of the mass function $M(z)$ is carried out in parallel to an
analogous analysis for the quasi-spherical models. This leads to the conclusion
that $M(z)$ determines the density of rest mass averaged over the whole space
of constant time.
| [
{
"created": "Mon, 13 Aug 2012 14:51:31 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Aug 2012 11:52:56 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Dec 2012 16:01:02 GMT",
"version": "v3"
}
] | 2013-05-30 | [
[
"Krasiński",
"Andrzej",
""
],
[
"Bolejko",
"Krzysztof",
""
]
] | Geometric properties of the quasi-hyperbolic Szekeres models are discussed and related to the quasi-spherical Szekeres models. Typical examples of shapes of various classes of 2-dimensional coordinate surfaces are shown in graphs; for the hyperbolically symmetric subcase and for the general quasi-hyperbolic case. An analysis of the mass function $M(z)$ is carried out in parallel to an analogous analysis for the quasi-spherical models. This leads to the conclusion that $M(z)$ determines the density of rest mass averaged over the whole space of constant time. |
1905.05085 | Sergey Yu. Vernov | Ekaterina O. Pozdeeva, Mohammad Sami, Alexey V. Toporensky, Sergey Yu.
Vernov | Stability analysis of de Sitter solutions in models with the
Gauss-Bonnet term | 9 pages, 5 figures, some references and comments are added, revised
version to appear in Phys. Rev. D | Phys. Rev. D 100, 083527 (2019) | 10.1103/PhysRevD.100.083527 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the scalar field dynamics of models with nonminimally coupled
scalar fields in the presence of the Gauss-Bonnet term and derive the structure
of the effective potential and conditions for stable de Sitter solutions in
general. Specializing to specific couplings, we explore the possibility of
realizing the stable de Sitter configurations which may have implications for
both the early Universe and late time evolution.
| [
{
"created": "Mon, 13 May 2019 15:27:20 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Oct 2019 20:27:12 GMT",
"version": "v2"
}
] | 2019-10-21 | [
[
"Pozdeeva",
"Ekaterina O.",
""
],
[
"Sami",
"Mohammad",
""
],
[
"Toporensky",
"Alexey V.",
""
],
[
"Vernov",
"Sergey Yu.",
""
]
] | We investigate the scalar field dynamics of models with nonminimally coupled scalar fields in the presence of the Gauss-Bonnet term and derive the structure of the effective potential and conditions for stable de Sitter solutions in general. Specializing to specific couplings, we explore the possibility of realizing the stable de Sitter configurations which may have implications for both the early Universe and late time evolution. |
2009.12897 | Vasilis Oikonomou | V.K. Oikonomou, F.P. Fronimos, N. Th. Chatzarakis | $f(R)$ Gravity Phase Space in the Presence of Thermal Effects | Abstract reduced due to arXiv limitations | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we shall consider $f(R)$ gravity and its cosmological
implications, when an extra matter term generated by thermal effects is added
by hand in the Lagrangian. We formulate the equations of motion of the theory
as a dynamical system, that can be treated as an autonomous one only for
specific solutions for the Hubble rate, which are of cosmological interest.
Particularly, we focus our analysis on subspaces of the total phase space,
corresponding to (quasi-)de Sitter accelerating expansion, matter-dominated and
radiation-dominated solutions. In all the aforementioned cases, the dynamical
system is an autonomous dynamical system. With regard to the thermal term
effects, these are expected to significantly affect the evolution near a Big
Rip singularity, and we also consider this case in terms of the corresponding
dynamical system, in which case the system is non-autonomous, and we attempt to
extract analytical and numerical solutions that can assess the specific cases.
This course is taken twice: the first for the vacuum theory and the second when
two perfect fluids (dust and radiation) are included as matter sources in the
field equations. In both cases, we reach similar conclusions. The results of
this theory do not differ significantly from the results of the pure $f(R)$ in
the de Sitter and quasi-de Sitter phases, as the same fixed points are
attained, so for sure the late-time era de Sitter is not affected. However, in
the matter-dominated and radiation-dominated phases, the fixed points attained
are affected by the presence of the thermal term, so surely the thermal effects
would destroy the matter and radiation domination eras.
| [
{
"created": "Sun, 27 Sep 2020 16:59:43 GMT",
"version": "v1"
}
] | 2020-09-29 | [
[
"Oikonomou",
"V. K.",
""
],
[
"Fronimos",
"F. P.",
""
],
[
"Chatzarakis",
"N. Th.",
""
]
] | In this paper, we shall consider $f(R)$ gravity and its cosmological implications, when an extra matter term generated by thermal effects is added by hand in the Lagrangian. We formulate the equations of motion of the theory as a dynamical system, that can be treated as an autonomous one only for specific solutions for the Hubble rate, which are of cosmological interest. Particularly, we focus our analysis on subspaces of the total phase space, corresponding to (quasi-)de Sitter accelerating expansion, matter-dominated and radiation-dominated solutions. In all the aforementioned cases, the dynamical system is an autonomous dynamical system. With regard to the thermal term effects, these are expected to significantly affect the evolution near a Big Rip singularity, and we also consider this case in terms of the corresponding dynamical system, in which case the system is non-autonomous, and we attempt to extract analytical and numerical solutions that can assess the specific cases. This course is taken twice: the first for the vacuum theory and the second when two perfect fluids (dust and radiation) are included as matter sources in the field equations. In both cases, we reach similar conclusions. The results of this theory do not differ significantly from the results of the pure $f(R)$ in the de Sitter and quasi-de Sitter phases, as the same fixed points are attained, so for sure the late-time era de Sitter is not affected. However, in the matter-dominated and radiation-dominated phases, the fixed points attained are affected by the presence of the thermal term, so surely the thermal effects would destroy the matter and radiation domination eras. |
1604.08002 | Diego S\'aez-G\'omez | Diego Saez-Gomez (IA, U. of Lisbon) | Testing the concordance model in cosmology with model-independent
methods: some issues | 6 pages, 2 figures; Contribution to the proceedings of "The
Fourteenth Marcel Grossmann Meeting", University of Rome "La Sapienza", Rome,
July 12-18, 2015 | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Since the number of dark energy models have rapidly increased over the last
years, some model-independent methods have been developed in order to analyse
the cosmological evolution in a phenomenological way. In this manuscript, we
analyse some of these approaches and their shortcomings to provide reliable
information.
| [
{
"created": "Wed, 27 Apr 2016 10:00:43 GMT",
"version": "v1"
}
] | 2016-04-28 | [
[
"Saez-Gomez",
"Diego",
"",
"IA, U. of Lisbon"
]
] | Since the number of dark energy models have rapidly increased over the last years, some model-independent methods have been developed in order to analyse the cosmological evolution in a phenomenological way. In this manuscript, we analyse some of these approaches and their shortcomings to provide reliable information. |
1902.00701 | Vahid Kamali | Vahid Kamali | Reheating After Swampland Conjecture | The abstract was changed, Motivation was added, Typos were corrected,
5 pages, 4 figures. In press Journal of High Energy Physics | null | 10.1007/JHEP01(2020)092 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The evolution of the universe started from a hot and dense Big Bang point.
Temperature fluctuation map of cosmic microwave background (CMB) radiation and
initial seeds of large scale structures (LSS) are explained by an inflationary
period in a very early time. Inflaton as quanta of inflation field is
responsible for the accelerated expansion of the universe. Potentials of the
self-interacting single field models are constrained by observational data as
well as quantum gravity. Some forms of the potential are rolled out by data of
Planck satellite and some of them by quantum gravity constraints. In the
standard model of inflation or cold inflation firstly universe expands where
the inflaton rolls the nearly flat part of the potential and in the second
part, the universe reheats where the inflaton oscillates around the minimum of
the potential which leads to thermalized radiation dominated universe. String
theory as the best model of quantum gravity forbids the oscillation around the
minimum of the potential during the thermalized epoch of the reheating. But in
the warm model of inflation thermalization happens during the expansion of the
universe where the inflaton rolls nearly steep potential and the universe will
be radiation dominated without any separated reheating epoch.
| [
{
"created": "Sat, 2 Feb 2019 11:47:30 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Dec 2019 19:16:41 GMT",
"version": "v2"
}
] | 2020-02-19 | [
[
"Kamali",
"Vahid",
""
]
] | The evolution of the universe started from a hot and dense Big Bang point. Temperature fluctuation map of cosmic microwave background (CMB) radiation and initial seeds of large scale structures (LSS) are explained by an inflationary period in a very early time. Inflaton as quanta of inflation field is responsible for the accelerated expansion of the universe. Potentials of the self-interacting single field models are constrained by observational data as well as quantum gravity. Some forms of the potential are rolled out by data of Planck satellite and some of them by quantum gravity constraints. In the standard model of inflation or cold inflation firstly universe expands where the inflaton rolls the nearly flat part of the potential and in the second part, the universe reheats where the inflaton oscillates around the minimum of the potential which leads to thermalized radiation dominated universe. String theory as the best model of quantum gravity forbids the oscillation around the minimum of the potential during the thermalized epoch of the reheating. But in the warm model of inflation thermalization happens during the expansion of the universe where the inflaton rolls nearly steep potential and the universe will be radiation dominated without any separated reheating epoch. |
2402.15575 | Yerko V\'asquez | Sebasti\'an Alfaro, P. A. Gonz\'alez, Diego Olmos, Eleftherios
Papantonopoulos and Yerko V\'asquez | Quasinormal modes and bound states of massive scalar fields in wormhole
spacetimes | Version accepted for publication in PRD. arXiv admin note: text
overlap with arXiv:2205.06079 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we explore the propagation of massive scalar fields on some
wormhole backgrounds. On one side, we consider the Bronnikov-Ellis wormhole
solution and wormhole geometries with a non-constant redshift function by
introducing a gravitational mass $M$, which goes over into the Bronnikov-Ellis
wormhole when the gravitational mass parameter vanishes. We employ the
continued fraction method to calculate accurately the quasinormal frequencies
of massive scalar fields, particularly focusing on low values of the angular
number, and we show an anomalous behaviour of the decay rate of the quasinormal
frequencies, for $n \geq \ell$. Also, we show that for a massive scalar field
and $M \neq 0$ the effective potential allows potential wells for some values
of the parameters which support bound states, which are obtained using the
continued fraction method and they are characterized by having only a frequency
of oscillation and they do not decay; however, for the Bronnikov-Ellis wormhole
the effective potential do not support bound states. On the other side, we
consider a wormhole geometry which is an exact solution of $f(R)$ modified
gravity. For this geometry the quasinormal frequencies can be obtained
analytically, being the longest-lived modes the ones with lowest angular number
$\ell$. So, in this wormhole background the anomalous behaviour is avoided.
| [
{
"created": "Fri, 23 Feb 2024 19:24:01 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Mar 2024 02:03:13 GMT",
"version": "v2"
},
{
"created": "Wed, 10 Apr 2024 02:17:32 GMT",
"version": "v3"
}
] | 2024-04-11 | [
[
"Alfaro",
"Sebastián",
""
],
[
"González",
"P. A.",
""
],
[
"Olmos",
"Diego",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
],
[
"Vásquez",
"Yerko",
""
]
] | In this work we explore the propagation of massive scalar fields on some wormhole backgrounds. On one side, we consider the Bronnikov-Ellis wormhole solution and wormhole geometries with a non-constant redshift function by introducing a gravitational mass $M$, which goes over into the Bronnikov-Ellis wormhole when the gravitational mass parameter vanishes. We employ the continued fraction method to calculate accurately the quasinormal frequencies of massive scalar fields, particularly focusing on low values of the angular number, and we show an anomalous behaviour of the decay rate of the quasinormal frequencies, for $n \geq \ell$. Also, we show that for a massive scalar field and $M \neq 0$ the effective potential allows potential wells for some values of the parameters which support bound states, which are obtained using the continued fraction method and they are characterized by having only a frequency of oscillation and they do not decay; however, for the Bronnikov-Ellis wormhole the effective potential do not support bound states. On the other side, we consider a wormhole geometry which is an exact solution of $f(R)$ modified gravity. For this geometry the quasinormal frequencies can be obtained analytically, being the longest-lived modes the ones with lowest angular number $\ell$. So, in this wormhole background the anomalous behaviour is avoided. |
gr-qc/0504020 | Liang Gang Liu | De-hua Wen, Wei Chen, Jian-xun Hu, Liang-gang Liu | Frame Dragging Effect on Moment of Inertia and Radius of Gyration of
Neutron Star | 6 pages, 5 figures | Mod.Phys.Lett.A22:631-636,2007 | 10.1142/S0217732307023225 | null | gr-qc | null | Accurate to the first order in the uniform angular velocity, the general
relativity frame dragging effect of the moments of inertia and radii of
gyration of two kinds of neutron stars are calculated in a relativistic
$\sigma-\omega$ model. The calculation shows that the dragging effect will
diminish the moments of inertia and radii of gyration.
| [
{
"created": "Wed, 6 Apr 2005 02:11:24 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Wen",
"De-hua",
""
],
[
"Chen",
"Wei",
""
],
[
"Hu",
"Jian-xun",
""
],
[
"Liu",
"Liang-gang",
""
]
] | Accurate to the first order in the uniform angular velocity, the general relativity frame dragging effect of the moments of inertia and radii of gyration of two kinds of neutron stars are calculated in a relativistic $\sigma-\omega$ model. The calculation shows that the dragging effect will diminish the moments of inertia and radii of gyration. |
gr-qc/0410136 | Muhammad Sharif | M. Sharif | Addendum: Symmetries of the energy-momentum tensor | 7 pages, no figure, LaTex | J.Math.and Phys. 45 (2004) 4193 | 10.1063/1.1777404 | null | gr-qc | null | In recent papers [1-3], we have discussed matter symmetries of non-static
spherically symmetric spacetimes, static plane symmetric spacetimes and
cylindrically symmetric static spacetimes. These have been classified for both
cases when the energy-momentum tensor is non-degenerate and also when it is
degenerate. Here we add up some consequences and the missing references about
the Ricci tensor.
| [
{
"created": "Thu, 28 Oct 2004 04:25:02 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Sharif",
"M.",
""
]
] | In recent papers [1-3], we have discussed matter symmetries of non-static spherically symmetric spacetimes, static plane symmetric spacetimes and cylindrically symmetric static spacetimes. These have been classified for both cases when the energy-momentum tensor is non-degenerate and also when it is degenerate. Here we add up some consequences and the missing references about the Ricci tensor. |
1004.0508 | Mohammad Malekjani | M. Malekjani and A. Khodam-Mohammadi | Agegraphic Dark Energy Model in Non-Flat Universe: Statefinder
Diagnostic and $w-w^{\prime}$ Analysis | 20 pages, 4 figures, 2 tables, International Journal of Modern
Physics D accepted | Int. J. Mod. Phys. D19:1857-1871,2010 | 10.1142/S0218271810018086 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the interacting agegraphic dark energy (ADE) model in non-flat
universe by means of statefinder diagnostic and $w-w^{\prime}$ analysis. First,
the evolution of EoS parameter ($w_d$) and deceleration parameter ($q$) in
terms of scale factor for interacting ADE model in non-flat universe are
calculated. Dependence of $w_d$ on the ADE model parameters $n$ and $\alpha$ in
different spatial curvatures is investigated. We show that the evolution of $q$
is dependent on the type of spatial curvature, beside of dependence on
parameters $n$ and $\alpha$. The accelerated expansion takes place sooner in
open universe and later in closed universe compare with flat universe. Then, we
plot the evolutionary trajectories of the interacting ADE model for different
values of the parameters $n$ and $\alpha$ as well as for different
contributions of spatial curvature, in the statefinder parameters plane. In
addition to statefinder, we also investigate the ADE model in non-flat universe
with $w-w^{\prime}$ analysis.
| [
{
"created": "Sun, 4 Apr 2010 13:34:20 GMT",
"version": "v1"
},
{
"created": "Sun, 6 Jun 2010 13:54:25 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"Malekjani",
"M.",
""
],
[
"Khodam-Mohammadi",
"A.",
""
]
] | We study the interacting agegraphic dark energy (ADE) model in non-flat universe by means of statefinder diagnostic and $w-w^{\prime}$ analysis. First, the evolution of EoS parameter ($w_d$) and deceleration parameter ($q$) in terms of scale factor for interacting ADE model in non-flat universe are calculated. Dependence of $w_d$ on the ADE model parameters $n$ and $\alpha$ in different spatial curvatures is investigated. We show that the evolution of $q$ is dependent on the type of spatial curvature, beside of dependence on parameters $n$ and $\alpha$. The accelerated expansion takes place sooner in open universe and later in closed universe compare with flat universe. Then, we plot the evolutionary trajectories of the interacting ADE model for different values of the parameters $n$ and $\alpha$ as well as for different contributions of spatial curvature, in the statefinder parameters plane. In addition to statefinder, we also investigate the ADE model in non-flat universe with $w-w^{\prime}$ analysis. |
gr-qc/0512149 | Carsten Gundlach | Gioel Calabrese, Carsten Gundlach and David Hilditch | Asymptotically null slices in numerical relativity: mathematical
analysis and spherical wave equation tests | Numerical tests improved, conclusions extended | Class.Quant.Grav. 23 (2006) 4829-4846 | 10.1088/0264-9381/23/15/004 | null | gr-qc | null | We investigate the use of asymptotically null slices combined with stretching
or compactification of the radial coordinate for the numerical simulation of
asymptotically flat spacetimes. We consider a 1-parameter family of coordinates
characterised by the asymptotic relation $r\sim R^{1-n}$ between the physical
radius $R$ and coordinate radius $r$, and the asymptotic relation $K\sim
R^{n/2-1}$ for the extrinsic curvature of the slices. These slices are
asymptotically null in the sense that their Lorentz factor relative to
stationary observers diverges as $\Gamma\sim R^{n/2}$. While $1<n\le 2$ slices
intersect $\scri$, $0< n\le 1$ slices end at $i^0$. We carry out numerical
tests with the spherical wave equation on Minkowski and Schwarzschild
spacetime. Simulations using our coordinates with $0<n\le 2$ achieve higher
accuracy at lower computational cost in following outgoing waves to very large
radius than using standard $n=0$ slices without compactification. Power-law
tails in Schwarzschild are also correctly represented.
| [
{
"created": "Sat, 24 Dec 2005 16:29:15 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Jun 2006 18:47:25 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Calabrese",
"Gioel",
""
],
[
"Gundlach",
"Carsten",
""
],
[
"Hilditch",
"David",
""
]
] | We investigate the use of asymptotically null slices combined with stretching or compactification of the radial coordinate for the numerical simulation of asymptotically flat spacetimes. We consider a 1-parameter family of coordinates characterised by the asymptotic relation $r\sim R^{1-n}$ between the physical radius $R$ and coordinate radius $r$, and the asymptotic relation $K\sim R^{n/2-1}$ for the extrinsic curvature of the slices. These slices are asymptotically null in the sense that their Lorentz factor relative to stationary observers diverges as $\Gamma\sim R^{n/2}$. While $1<n\le 2$ slices intersect $\scri$, $0< n\le 1$ slices end at $i^0$. We carry out numerical tests with the spherical wave equation on Minkowski and Schwarzschild spacetime. Simulations using our coordinates with $0<n\le 2$ achieve higher accuracy at lower computational cost in following outgoing waves to very large radius than using standard $n=0$ slices without compactification. Power-law tails in Schwarzschild are also correctly represented. |
2405.08846 | Hristu Culetu | Hristu Culetu | Semiclassical corrections to a regularized Schwarzschild metric | Acta Phys.Pol.B 10, 431 (2017) | null | 10.5506/APhysPolBSupp.10.431 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A regular form of the Schwarzschild geometry is proposed. It is more suitable
for application in microphysics because the source mass comes out both as a
Schwarzschild radius and the Compton wavelength of the mass $m$. The Komar
energy equals $mc^{2}$ in the classical situation ($\hbar = 0$).
| [
{
"created": "Tue, 14 May 2024 11:23:24 GMT",
"version": "v1"
}
] | 2024-05-16 | [
[
"Culetu",
"Hristu",
""
]
] | A regular form of the Schwarzschild geometry is proposed. It is more suitable for application in microphysics because the source mass comes out both as a Schwarzschild radius and the Compton wavelength of the mass $m$. The Komar energy equals $mc^{2}$ in the classical situation ($\hbar = 0$). |
gr-qc/0609113 | Peter Beyersdorf | Peter T. Beyersdorf | Input spectrum for heterodyne detection in advanced gravitational wave
detectors without non-stationary shot-noise | 10 pages with 6 figures | null | null | null | gr-qc | null | Future interferometric gravitational wave detectors will make use of the
coupling between shot noise and radiation pressure noise that produces a
squeezed output for the quantum noise at the dark-port of the interferometer
allowing these interferometers to operate with a sensitivity that exceeds the
standard quantum limit at certain frequencies. The ability of the detector to
take advantage of this squeezed output state depends in part on the readout
system used. With the phase modulated laser input planned for these
interferometers the quantum-noise limited sensitivity is slightly better when
homodyne (rather than heterodyne) detection is used. We show that by modifying
the laser input spectrum for these interferometers, readout with heterodyne
detection can be made to have the same quantum-noise limited sensitivity as
readout with homodyne detection.
| [
{
"created": "Mon, 25 Sep 2006 18:27:06 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Beyersdorf",
"Peter T.",
""
]
] | Future interferometric gravitational wave detectors will make use of the coupling between shot noise and radiation pressure noise that produces a squeezed output for the quantum noise at the dark-port of the interferometer allowing these interferometers to operate with a sensitivity that exceeds the standard quantum limit at certain frequencies. The ability of the detector to take advantage of this squeezed output state depends in part on the readout system used. With the phase modulated laser input planned for these interferometers the quantum-noise limited sensitivity is slightly better when homodyne (rather than heterodyne) detection is used. We show that by modifying the laser input spectrum for these interferometers, readout with heterodyne detection can be made to have the same quantum-noise limited sensitivity as readout with homodyne detection. |
gr-qc/0511164 | Ashutosh Mahajan | Ashutosh Mahajan and Pankaj S. Joshi | Rebounce and Black hole formation in a Gravitational Collapse Model with
Vanishing Radial Pressure | 15 pages, To be published in Gen.Rel.Grav | Gen.Rel.Grav.39:825-838,2007 | 10.1007/s10714-007-0424-4 | null | gr-qc | null | We examine spherical gravitational collapse of a matter model with vanishing
radial pressure and non-zero tangential pressure. It is seen analytically that
the collapsing cloud either forms a black hole or disperses depending on values
of the initial parameters which are initial density, tangential pressure and
velocity profile of the cloud. A threshold of black hole formation is observed
near which a scaling relation is obtained for the mass of black hole, assuming
initial profiles to be smooth. The similarities in the behaviour of this model
at the onset of black hole formation with that of numerical critical behaviour
in other collapse models are indicated.
| [
{
"created": "Wed, 30 Nov 2005 14:50:55 GMT",
"version": "v1"
},
{
"created": "Sat, 12 May 2007 15:08:22 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Mahajan",
"Ashutosh",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | We examine spherical gravitational collapse of a matter model with vanishing radial pressure and non-zero tangential pressure. It is seen analytically that the collapsing cloud either forms a black hole or disperses depending on values of the initial parameters which are initial density, tangential pressure and velocity profile of the cloud. A threshold of black hole formation is observed near which a scaling relation is obtained for the mass of black hole, assuming initial profiles to be smooth. The similarities in the behaviour of this model at the onset of black hole formation with that of numerical critical behaviour in other collapse models are indicated. |
2206.03980 | Riccardo Della Monica | Riccardo Della Monica, Ivan de Martino | Narrowing the allowed mass range of ultralight bosons with the S2 star | 5 pages, 2 figures, 1 table, 5 appendices. Accepted for publication
in A&A Letters. Publication title changed with respect to previous versions
during the editorial process | A&A 670, L4 (2023) | 10.1051/0004-6361/202245150 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known that N-body simulations of ultralight bosons show the
formation of a solitonic dark matter core in the innermost part of the halo.
The scale length of such a soliton depends on the inverse of the mass of the
boson. On the other hand, the orbital motion of stars in the Galactic Center
depends on the distribution of matter whether be it baryonic or dark, providing
an excellent probe for the gravitational field of the region. In this Letter we
propose the S-stars in the Galactic Center as a new observational tool,
complementary to other astrophysical systems, to narrow down the range of
allowed values for an ultralight dark matter candidate boson mass. We built
mock catalogs mirroring the forthcoming astrometric and spectroscopic
observations of S2, and we used a MCMC analysis to predict the accuracy down to
which the mass of an ultralight boson may be bounded, and we showed that, once
complementary constraints are considered, this analysis will help to restrict
the allowed range of the boson mass. Our analysis forecasts the bound on the
mass of an ultralight boson to be $< 10^{-19}$ eV at the 95% of confidence
level.
| [
{
"created": "Wed, 8 Jun 2022 15:57:48 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Dec 2022 15:36:29 GMT",
"version": "v2"
},
{
"created": "Mon, 16 Jan 2023 09:21:54 GMT",
"version": "v3"
}
] | 2023-02-01 | [
[
"Della Monica",
"Riccardo",
""
],
[
"de Martino",
"Ivan",
""
]
] | It is well known that N-body simulations of ultralight bosons show the formation of a solitonic dark matter core in the innermost part of the halo. The scale length of such a soliton depends on the inverse of the mass of the boson. On the other hand, the orbital motion of stars in the Galactic Center depends on the distribution of matter whether be it baryonic or dark, providing an excellent probe for the gravitational field of the region. In this Letter we propose the S-stars in the Galactic Center as a new observational tool, complementary to other astrophysical systems, to narrow down the range of allowed values for an ultralight dark matter candidate boson mass. We built mock catalogs mirroring the forthcoming astrometric and spectroscopic observations of S2, and we used a MCMC analysis to predict the accuracy down to which the mass of an ultralight boson may be bounded, and we showed that, once complementary constraints are considered, this analysis will help to restrict the allowed range of the boson mass. Our analysis forecasts the bound on the mass of an ultralight boson to be $< 10^{-19}$ eV at the 95% of confidence level. |
2208.08461 | Bob Holdom | Bob Holdom | Towards rotating 2-2-holes | 14 pages, no figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Static 2-2-hole solutions of quadratic gravity have been investigated to be a
possible horizonless replacement for black holes as the endpoint of
gravitational collapse. Realistically such objects will form with spin, but
rotating 2-2-hole solutions are currently not known. We take some steps here to
explore the existence and properties of such solutions. We employ an expansion
of the field equations where the expansion parameter is inversely related to
the size of the object. This expansion parameter appears explicitly in the
trial metrics, and we are able to find solutions of the leading order field
equations. These vacuum solutions are candidates to describe most of the
interior of a rotating 2-2-hole.
| [
{
"created": "Wed, 17 Aug 2022 18:03:22 GMT",
"version": "v1"
}
] | 2022-08-19 | [
[
"Holdom",
"Bob",
""
]
] | Static 2-2-hole solutions of quadratic gravity have been investigated to be a possible horizonless replacement for black holes as the endpoint of gravitational collapse. Realistically such objects will form with spin, but rotating 2-2-hole solutions are currently not known. We take some steps here to explore the existence and properties of such solutions. We employ an expansion of the field equations where the expansion parameter is inversely related to the size of the object. This expansion parameter appears explicitly in the trial metrics, and we are able to find solutions of the leading order field equations. These vacuum solutions are candidates to describe most of the interior of a rotating 2-2-hole. |
2405.13373 | Andrei V. Frolov | Jonathan Barenboim, Andrei V. Frolov, Gabor Kunstatter | No Drama in 2D Black Hole Evaporation | 4 pages, 5 figures, REVTex 4.2 | null | null | SCG-2024-01 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We numerically calculate the spacetime describing the formation and
evaporation of a regular black hole in 2D dilaton gravity. The apparent
horizons evaporate smoothly in finite time to form a compact trapped region. We
nevertheless see rich dynamics; an anti-trapped region forms alongside the
black hole, and additional compact trapped and anti-trapped regions are formed
by backreaction effects as the mass radiates away. The spacetime is
asymptotically flat at future null infinity and is free of singularities and
Cauchy horizons. These results suggest that the evaporation of regular 2D black
holes is unitary.
| [
{
"created": "Wed, 22 May 2024 06:16:16 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jul 2024 20:18:02 GMT",
"version": "v2"
}
] | 2024-07-29 | [
[
"Barenboim",
"Jonathan",
""
],
[
"Frolov",
"Andrei V.",
""
],
[
"Kunstatter",
"Gabor",
""
]
] | We numerically calculate the spacetime describing the formation and evaporation of a regular black hole in 2D dilaton gravity. The apparent horizons evaporate smoothly in finite time to form a compact trapped region. We nevertheless see rich dynamics; an anti-trapped region forms alongside the black hole, and additional compact trapped and anti-trapped regions are formed by backreaction effects as the mass radiates away. The spacetime is asymptotically flat at future null infinity and is free of singularities and Cauchy horizons. These results suggest that the evaporation of regular 2D black holes is unitary. |
gr-qc/0606019 | Yuri Laptev | Yu.P. Laptev, M.L. Fil'chenkov | Electromagnetic and Gravitational Radiation of Graviatoms | 7 pages, 1 figure, 3 tables; accepted in "Astronomical and
Astrophysical Transactions" | null | 10.1080/10556790600804424 | null | gr-qc | null | Graviatom existence conditions have been found. The graviatoms (quantum
systems around mini-black-holes) satisfying these conditions contain the
following charged particles: the electron, muon, tau lepton, wino, pion and
kaon. Electric dipole and quadrupole and gravitational radiations are
calculated for the graviatoms and compared with Hawking's mini-hole radiation.
| [
{
"created": "Sat, 3 Jun 2006 15:14:07 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Laptev",
"Yu. P.",
""
],
[
"Fil'chenkov",
"M. L.",
""
]
] | Graviatom existence conditions have been found. The graviatoms (quantum systems around mini-black-holes) satisfying these conditions contain the following charged particles: the electron, muon, tau lepton, wino, pion and kaon. Electric dipole and quadrupole and gravitational radiations are calculated for the graviatoms and compared with Hawking's mini-hole radiation. |
2209.08589 | Konstantin Osetrin | Konstantin Osetrin and Evgeny Osetrin and Elena Osetrina | Deviation of geodesics and particle trajectories in a gravitational wave
of the Bianchi type VI universe | 26 pages | Journal of Physics A: Mathematical and Theoretical, 2023, 56(32),
325205 | 10.1088/1751-8121/ace6e3 | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by-nc-sa/4.0/ | For the Bianchi type VI universe, exact solutions of the equation of geodesic
deviation in a strong primordial gravitational wave in a privileged coordinate
system are obtained. The solutions refer to Shapovalov's gravitational-wave
models of spacetime and allow the existence of complete integrals of the
Hamilton-Jacobi equation for test particles. For all the solutions obtained,
the analytical form of the tidal acceleration vector in a strong primordial
gravitational wave is obtained. An explicit form of the coordinate
transformation, an explicit form of the metric of the primordial gravitational
wave of the Bianchi type VI universe, and the form of the tidal acceleration
vector in the laboratory synchronous coordinate system are obtained. The
synchronous coordinate system is associated with a freely falling observer and
allows the observer to separate time and spatial coordinates, as well as to
synchronize time at different points in space. The presented mathematical
approach can be applied both in the general theory of relativity and in
modified theories of gravity.
| [
{
"created": "Sun, 18 Sep 2022 15:59:35 GMT",
"version": "v1"
}
] | 2023-08-02 | [
[
"Osetrin",
"Konstantin",
""
],
[
"Osetrin",
"Evgeny",
""
],
[
"Osetrina",
"Elena",
""
]
] | For the Bianchi type VI universe, exact solutions of the equation of geodesic deviation in a strong primordial gravitational wave in a privileged coordinate system are obtained. The solutions refer to Shapovalov's gravitational-wave models of spacetime and allow the existence of complete integrals of the Hamilton-Jacobi equation for test particles. For all the solutions obtained, the analytical form of the tidal acceleration vector in a strong primordial gravitational wave is obtained. An explicit form of the coordinate transformation, an explicit form of the metric of the primordial gravitational wave of the Bianchi type VI universe, and the form of the tidal acceleration vector in the laboratory synchronous coordinate system are obtained. The synchronous coordinate system is associated with a freely falling observer and allows the observer to separate time and spatial coordinates, as well as to synchronize time at different points in space. The presented mathematical approach can be applied both in the general theory of relativity and in modified theories of gravity. |
gr-qc/0101116 | D. H. Santamore | D. H. Santamore and Yuri Levin | Eliminating Thermal Violin Spikes from LIGO Noise | 15 pages, 3 figures | Phys.Rev.D64:042002,2001 | 10.1103/PhysRevD.64.042002 | null | gr-qc cond-mat.stat-mech | null | We have developed a scheme for reducing LIGO suspension thermal noise close
to violin-mode resonances. The idea is to monitor directly the
thermally-induced motion of a small portion of (a ``point'' on) each suspension
fiber, thereby recording the random forces driving the test-mass motion close
to each violin-mode frequency. One can then suppress the thermal noise by
optimally subtracting the recorded fiber motions from the measured motion of
the test mass, i.e., from the LIGO output. The proposed method is a
modification of an analogous but more technically difficult scheme by
Braginsky, Levin and Vyatchanin for reducing broad-band suspension thermal
noise. The efficiency of our method is limited by the sensitivity of the sensor
used to monitor the fiber motion. If the sensor has no intrinsic noise (i.e.
has unlimited sensitivity), then our method allows, in principle, a complete
removal of violin spikes from the thermal-noise spectrum. We find that in
LIGO-II interferometers, in order to suppress violin spikes below the
shot-noise level, the intrinsic noise of the sensor must be less than
\~2*10^{-13}cm/sqrt(Hz). This sensitivity is two orders of magnitude greater
than that of currently available sensors.
| [
{
"created": "Tue, 30 Jan 2001 11:12:49 GMT",
"version": "v1"
}
] | 2009-12-31 | [
[
"Santamore",
"D. H.",
""
],
[
"Levin",
"Yuri",
""
]
] | We have developed a scheme for reducing LIGO suspension thermal noise close to violin-mode resonances. The idea is to monitor directly the thermally-induced motion of a small portion of (a ``point'' on) each suspension fiber, thereby recording the random forces driving the test-mass motion close to each violin-mode frequency. One can then suppress the thermal noise by optimally subtracting the recorded fiber motions from the measured motion of the test mass, i.e., from the LIGO output. The proposed method is a modification of an analogous but more technically difficult scheme by Braginsky, Levin and Vyatchanin for reducing broad-band suspension thermal noise. The efficiency of our method is limited by the sensitivity of the sensor used to monitor the fiber motion. If the sensor has no intrinsic noise (i.e. has unlimited sensitivity), then our method allows, in principle, a complete removal of violin spikes from the thermal-noise spectrum. We find that in LIGO-II interferometers, in order to suppress violin spikes below the shot-noise level, the intrinsic noise of the sensor must be less than \~2*10^{-13}cm/sqrt(Hz). This sensitivity is two orders of magnitude greater than that of currently available sensors. |
1711.02583 | Griselda Figueroa Aguirre | Ernesto F. Eiroa, Griselda Figueroa-Aguirre | Spherical thin shells in F(R) gravity: construction and stability | 13 pages, 2 figures; v2: improved version, new references added | Eur. Phys. J. C (2018) 78:54 | 10.1140/epjc/s10052-018-5518-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a broad class of spherical thin shells of matter in F(R) gravity.
We show that the corresponding junction conditions determine the equation of
state between the energy density and the pressure/tension at the surface. We
analyze the stability of the static configurations under perturbations
preserving the symmetry. We apply the formalism to the construction of charged
bubbles and we find that there exist stable static configurations for a
suitable set of the parameters of the model.
| [
{
"created": "Tue, 7 Nov 2017 16:16:08 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jan 2018 14:23:19 GMT",
"version": "v2"
}
] | 2020-07-22 | [
[
"Eiroa",
"Ernesto F.",
""
],
[
"Figueroa-Aguirre",
"Griselda",
""
]
] | We present a broad class of spherical thin shells of matter in F(R) gravity. We show that the corresponding junction conditions determine the equation of state between the energy density and the pressure/tension at the surface. We analyze the stability of the static configurations under perturbations preserving the symmetry. We apply the formalism to the construction of charged bubbles and we find that there exist stable static configurations for a suitable set of the parameters of the model. |
gr-qc/0311037 | Hirotaka Takahashi | Hirotaka Takahashi, Hideyuki Tagoshi, the TAMA Collaboration | Toward the search for gravitational waves from inspiralling compact
binaries in TAMA300 data during 2003: data quality and stability | 6 pages, 4 figures,accepted for publication in Class. Quant. Grav. as
Special issue article (Proceedings of the 5th Edoardo Amaldi Conference on
Gravitational Waves, Tirrenia, Pisa, Italy, 6-11 July 2003) | Class.Quant.Grav. 21 (2004) S697-S702 | 10.1088/0264-9381/21/5/046 | null | gr-qc | null | We present the preliminary results of the analysis to search for inspiraling
compact binaries using TAMA300 DT8 data which was taken during 2003. We compare
the quality and the stability of the data with that taken during DT6 in 2001.
We find that the DT8 data has better quality and stability than the DT6 data.
| [
{
"created": "Wed, 12 Nov 2003 03:30:47 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Takahashi",
"Hirotaka",
""
],
[
"Tagoshi",
"Hideyuki",
""
],
[
"Collaboration",
"the TAMA",
""
]
] | We present the preliminary results of the analysis to search for inspiraling compact binaries using TAMA300 DT8 data which was taken during 2003. We compare the quality and the stability of the data with that taken during DT6 in 2001. We find that the DT8 data has better quality and stability than the DT6 data. |
1707.05017 | Michele Arzano | Giovanni Amelino-Camelia, Michele Arzano, Mal\'u Maira Da Silva and
Daniel H. Orozco-Borunda | Relativistic Planck-scale polymer | 5 pages, no figures. v2: minor changes in Section II | null | 10.1016/j.physletb.2017.10.071 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Polymer quantum mechanics has been studied as a simplified picture that
reflects some of the key properties of Loop Quantum Gravity; however, while the
fate of relativistic symmetries in Loop Quantum Gravity is still not
established, it is usually assumed that the discrete polymer structure should
lead to a breakdown of relativistic symmetries. We here focus for simplicity on
a one-spatial-dimension polymer model and show that relativistic symmetries are
deformed, rather than being broken. The specific type of deformed relativistic
symmetries which we uncover appears to be closely related to analogous
descriptions of relativistic symmetries in some noncommutative spacetimes. This
also contributes to an ongoing effort attempting to establish whether the
"quantum-Minkowski limit" of Loop Quantum Gravity is a noncommutative
spacetime.
| [
{
"created": "Mon, 17 Jul 2017 06:59:23 GMT",
"version": "v1"
},
{
"created": "Sat, 16 Sep 2017 14:20:59 GMT",
"version": "v2"
}
] | 2017-12-06 | [
[
"Amelino-Camelia",
"Giovanni",
""
],
[
"Arzano",
"Michele",
""
],
[
"Da Silva",
"Malú Maira",
""
],
[
"Orozco-Borunda",
"Daniel H.",
""
]
] | Polymer quantum mechanics has been studied as a simplified picture that reflects some of the key properties of Loop Quantum Gravity; however, while the fate of relativistic symmetries in Loop Quantum Gravity is still not established, it is usually assumed that the discrete polymer structure should lead to a breakdown of relativistic symmetries. We here focus for simplicity on a one-spatial-dimension polymer model and show that relativistic symmetries are deformed, rather than being broken. The specific type of deformed relativistic symmetries which we uncover appears to be closely related to analogous descriptions of relativistic symmetries in some noncommutative spacetimes. This also contributes to an ongoing effort attempting to establish whether the "quantum-Minkowski limit" of Loop Quantum Gravity is a noncommutative spacetime. |
2308.03603 | Dipanjan Dey | Dipanjan Dey, Koushiki, Pankaj S. Joshi | Equilibrium states from gravitational collapse of minimally coupled
scalar field with non-zero potential | 8 pages, 1 figure | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study the model of spherically symmetric and spatially homogeneous
gravitational collapse of a minimally coupled scalar field. Our study focuses
on obtaining the scalar field potential that leads to a final equilibrium state
in the gravitational collapse. We demonstrate the existence of a class of
scalar field solutions that can indeed result in such an end equilibrium state.
| [
{
"created": "Mon, 7 Aug 2023 14:06:57 GMT",
"version": "v1"
}
] | 2023-08-08 | [
[
"Dey",
"Dipanjan",
""
],
[
"Koushiki",
"",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | We study the model of spherically symmetric and spatially homogeneous gravitational collapse of a minimally coupled scalar field. Our study focuses on obtaining the scalar field potential that leads to a final equilibrium state in the gravitational collapse. We demonstrate the existence of a class of scalar field solutions that can indeed result in such an end equilibrium state. |
0804.3787 | Francois Foucart | Francois Foucart, Lawrence E. Kidder, Harald P. Pfeiffer, Saul A.
Teukolsky | Initial data for black hole-neutron star binaries: a flexible,
high-accuracy spectral method | 19 pages, 11 figures, Modified to match final PRD version | Phys.Rev.D77:124051,2008 | 10.1103/PhysRevD.77.124051 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new numerical scheme to solve the initial value problem for
black hole-neutron star binaries. This method takes advantage of the
flexibility and fast convergence of a multidomain spectral representation of
the initial data to construct high-accuracy solutions at a relatively low
computational cost. We provide convergence tests of the method for both
isolated neutron stars and irrotational binaries. In the second case, we show
that we can resolve the small inconsistencies that are part of the
quasi-equilibrium formulation, and that these inconsistencies are significantly
smaller than observed in previous works. The possibility of generating a wide
variety of initial data is also demonstrated through two new configurations
inspired by results from binary black holes. First, we show that choosing a
modified Kerr-Schild conformal metric instead of a flat conformal metric allows
for the construction of quasi-equilibrium binaries with a spinning black hole.
Second, we construct binaries in low-eccentricity orbits, which are a better
approximation to astrophysical binaries than quasi-equilibrium systems.
| [
{
"created": "Wed, 23 Apr 2008 19:11:20 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Apr 2008 14:56:58 GMT",
"version": "v2"
},
{
"created": "Mon, 30 Jun 2008 15:48:06 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Foucart",
"Francois",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Teukolsky",
"Saul A.",
""
]
] | We present a new numerical scheme to solve the initial value problem for black hole-neutron star binaries. This method takes advantage of the flexibility and fast convergence of a multidomain spectral representation of the initial data to construct high-accuracy solutions at a relatively low computational cost. We provide convergence tests of the method for both isolated neutron stars and irrotational binaries. In the second case, we show that we can resolve the small inconsistencies that are part of the quasi-equilibrium formulation, and that these inconsistencies are significantly smaller than observed in previous works. The possibility of generating a wide variety of initial data is also demonstrated through two new configurations inspired by results from binary black holes. First, we show that choosing a modified Kerr-Schild conformal metric instead of a flat conformal metric allows for the construction of quasi-equilibrium binaries with a spinning black hole. Second, we construct binaries in low-eccentricity orbits, which are a better approximation to astrophysical binaries than quasi-equilibrium systems. |
gr-qc/9707040 | Carlos Augusto Romero | A.Barros and C.Romero | Global Monopoles in Brans-Dicke Theory of Gravity | 10 pages, LaTeX; replaced with revised version Wed, 24 Sep 1997 | Phys.Rev.D56:6688-6691,1997 | 10.1103/PhysRevD.56.6688 | null | gr-qc | null | The gravitational field of a global monopole in the context of Brans-Dicke
theory of gravity is investigated. The space-time and the scalar field
generated by the monopole are obtained by solving the field equations in the
weak field approximation. A comparison is made with the corresponding results
predicted by General Relativity.
| [
{
"created": "Tue, 16 Jul 1996 18:50:24 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Sep 1997 18:20:46 GMT",
"version": "v2"
}
] | 2011-09-09 | [
[
"Barros",
"A.",
""
],
[
"Romero",
"C.",
""
]
] | The gravitational field of a global monopole in the context of Brans-Dicke theory of gravity is investigated. The space-time and the scalar field generated by the monopole are obtained by solving the field equations in the weak field approximation. A comparison is made with the corresponding results predicted by General Relativity. |
2009.09901 | David Kofro\v{n} | David Kofro\v{n} | On the nature of cosmic strings in black hole spacetimes | arXiv admin note: substantial text overlap with arXiv:1705.01138 | Gen Relativ Gravit 52, 91 (2020) | 10.1007/s10714-020-02741-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new model for cosmic strings (i.e. conical singularities) attached to black
holes is proposed. These string are obtained by a explicit construction via
limiting process from the so-called Bonnor rocket. This reveals quite
surprising nature of their stress-energy tensor which contains first derivative
of Dirac $\delta$ distribution. Starting from the Bonnor rocket we explicitly
construct the Schwarzschild solution witch conical singularity and the
C-metric. In the latter case we show that there is a momentum flux through the
cosmic string, causing the acceleration of the black hole and the amount of
this momentum is in agreement with the momentum taken away by gravitational
radiation.
| [
{
"created": "Mon, 14 Sep 2020 13:28:46 GMT",
"version": "v1"
}
] | 2020-09-22 | [
[
"Kofroň",
"David",
""
]
] | A new model for cosmic strings (i.e. conical singularities) attached to black holes is proposed. These string are obtained by a explicit construction via limiting process from the so-called Bonnor rocket. This reveals quite surprising nature of their stress-energy tensor which contains first derivative of Dirac $\delta$ distribution. Starting from the Bonnor rocket we explicitly construct the Schwarzschild solution witch conical singularity and the C-metric. In the latter case we show that there is a momentum flux through the cosmic string, causing the acceleration of the black hole and the amount of this momentum is in agreement with the momentum taken away by gravitational radiation. |
gr-qc/0111093 | Florian Siebel | Florian Siebel, Jose A. Font, Ewald Mueller, Philippos Papadopoulos | Simulating the dynamics of relativistic stars via a light-cone approach | 15 pages, 10 figures, submitted to Phys. Rev. D | Phys.Rev. D65 (2002) 064038 | 10.1103/PhysRevD.65.064038 | null | gr-qc astro-ph | null | We present new numerical algorithms for the coupled Einstein-perfect fluid
system in axisymmetry. Our framework uses a foliation based on a family of
light cones, emanating from a regular center, and terminating at future null
infinity. This coordinate system is well adapted to the study of the dynamical
spacetimes associated with isolated relativistic compact objects such as
neutron stars. In particular, the approach allows the unambiguous extraction of
gravitational waves at future null infinity and avoids spurious outer boundary
reflections. The code can accurately maintain long-term stability of polytropic
equilibrium models of relativistic stars. We demonstrate global energy
conservation in a strongly perturbed neutron star spacetime, for which the
total energy radiated away by gravitational waves corresponds to a significant
fraction of the Bondi mass. As a first application we present results in the
study of pulsations of axisymmetric relativistic stars, extracting the
frequencies of the different fluid modes in fully relativistic evolutions of
the Einstein-perfect fluid system and making a first comparison between the
gravitational news function and the predicted wave using the approximations of
the quadrupole formula.
| [
{
"created": "Tue, 27 Nov 2001 11:10:30 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Siebel",
"Florian",
""
],
[
"Font",
"Jose A.",
""
],
[
"Mueller",
"Ewald",
""
],
[
"Papadopoulos",
"Philippos",
""
]
] | We present new numerical algorithms for the coupled Einstein-perfect fluid system in axisymmetry. Our framework uses a foliation based on a family of light cones, emanating from a regular center, and terminating at future null infinity. This coordinate system is well adapted to the study of the dynamical spacetimes associated with isolated relativistic compact objects such as neutron stars. In particular, the approach allows the unambiguous extraction of gravitational waves at future null infinity and avoids spurious outer boundary reflections. The code can accurately maintain long-term stability of polytropic equilibrium models of relativistic stars. We demonstrate global energy conservation in a strongly perturbed neutron star spacetime, for which the total energy radiated away by gravitational waves corresponds to a significant fraction of the Bondi mass. As a first application we present results in the study of pulsations of axisymmetric relativistic stars, extracting the frequencies of the different fluid modes in fully relativistic evolutions of the Einstein-perfect fluid system and making a first comparison between the gravitational news function and the predicted wave using the approximations of the quadrupole formula. |
gr-qc/0304030 | Nils Andersson | K. Glampedakis and N. Andersson | Quick and dirty methods for studying black-hole resonances | 18 pages, RevTeX, 7 ps figs | Class.Quant.Grav. 20 (2003) 3441-3464 | 10.1088/0264-9381/20/15/312 | null | gr-qc | null | We discuss simple integration methods for the calculation of rotating black
hole scattering resonances both in the complex frequency plane (quasinormal
modes) and the complex angular momentum plane (Regge poles). Our numerical
schemes are based on variations of "phase-amplitude" methods. In particular, we
discuss the Pruefer transformation, where the original (frequency domain)
Teukolsky wave equation is replaced by a pair of first-order non-linear
equations governing the introduced phase functions. Numerical integration of
these equations, performed along the real coordinate axis, or along rotated
contours in the complex coordinate plane, provides the required S-matrix
element (the ratio of amplitudes of the outgoing and ingoing waves at
infinity). Mueller's algorithm is then employed to conduct searches in the
complex plane for the poles of this quantity (which are, by definition, the
desired resonances). We have tested this method by verifying known results for
Schwarzschild quasinormal modes and Regge poles, and provide new results for
the Kerr black hole problem. We also describe a new method for estimating the
"excitation coefficients" for quasinormal modes. The method is applied to
scalar waves moving in the Kerr geometry, and the obtained results shed light
on the long-lived quasinormal modes that exist for black holes rotating near
the extreme Kerr limit.
| [
{
"created": "Mon, 7 Apr 2003 09:49:09 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Glampedakis",
"K.",
""
],
[
"Andersson",
"N.",
""
]
] | We discuss simple integration methods for the calculation of rotating black hole scattering resonances both in the complex frequency plane (quasinormal modes) and the complex angular momentum plane (Regge poles). Our numerical schemes are based on variations of "phase-amplitude" methods. In particular, we discuss the Pruefer transformation, where the original (frequency domain) Teukolsky wave equation is replaced by a pair of first-order non-linear equations governing the introduced phase functions. Numerical integration of these equations, performed along the real coordinate axis, or along rotated contours in the complex coordinate plane, provides the required S-matrix element (the ratio of amplitudes of the outgoing and ingoing waves at infinity). Mueller's algorithm is then employed to conduct searches in the complex plane for the poles of this quantity (which are, by definition, the desired resonances). We have tested this method by verifying known results for Schwarzschild quasinormal modes and Regge poles, and provide new results for the Kerr black hole problem. We also describe a new method for estimating the "excitation coefficients" for quasinormal modes. The method is applied to scalar waves moving in the Kerr geometry, and the obtained results shed light on the long-lived quasinormal modes that exist for black holes rotating near the extreme Kerr limit. |
2408.03967 | Sanjay Mandal | Sneha Pradhan, Piyali Bhar, Sanjay Mandal, P.K. Sahoo, Kazuharu Bamba | The Stability of Anisotropic Compact Stars Influenced by Dark Matter
under Teleparallel Gravity: An Extended Gravitational Deformation Approach | 22 pages, 10 figures. Comments are welcome | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In our investigation, we pioneer the development of geometrically deformed
strange stars within the framework of $f(\mathcal{T})$ gravity theory through
gravitational decoupling via the complete geometric deformation (CGD)
technique. The significant finding is the precise solution for deformed strange
star (SS) models achieved through the vanishing complexity factor scenario.
Further, we introduce the concept of space-time deformation caused by dark
matter (DM) content in DM haloes, leading to perturbations in the metric
potentials $g_{tt}$ and $g_{rr}$ components. Mathematically, this DM-induced
deformation is achieved through the CGD method, where the decoupling parameter
$\alpha$ governs the extent of DM influence. To validate our findings, we
compare our model predictions with observational constraints, including
GW190814 (with a mass range of $2.5-2.67 M_{\odot}$) and neutron stars (NSTRs)
such as EXO 1785-248 [mass=$1.3_{-0.2}^{+0.2}~M_{\odot}$], 4U 1608-52
[mass=$1.74_{-0.14}^{+0.14}~M_{\odot}$], and PSR J0952-0607
[mass=$2.35_{-0.17}^{+0.17}~M_{\odot}$]. Our investigation delves into the
stability of the model by considering causality conditions, Herrera's Cracking
Method, the adiabatic index, and the Harrison-Zeldovich-Novikov criterion. We
demonstrate that the developed model mimics a wide range of recently observed
pulsars. To emphasize its compatibility, we highlight the predicted mass and
radius in tabular form by varying both the parameters $\alpha$ and $\zeta_1$.
Notably, our findings are consistent with the observation of gravitational
waves from the first binary merger event. Furthermore, we compare our results
with those obtained for a slow-rotating configuration. In addition to this, we
discuss the moment of inertia using the Bejger-Haensel approach in this
formulation.
| [
{
"created": "Tue, 6 Aug 2024 14:04:05 GMT",
"version": "v1"
}
] | 2024-08-09 | [
[
"Pradhan",
"Sneha",
""
],
[
"Bhar",
"Piyali",
""
],
[
"Mandal",
"Sanjay",
""
],
[
"Sahoo",
"P. K.",
""
],
[
"Bamba",
"Kazuharu",
""
]
] | In our investigation, we pioneer the development of geometrically deformed strange stars within the framework of $f(\mathcal{T})$ gravity theory through gravitational decoupling via the complete geometric deformation (CGD) technique. The significant finding is the precise solution for deformed strange star (SS) models achieved through the vanishing complexity factor scenario. Further, we introduce the concept of space-time deformation caused by dark matter (DM) content in DM haloes, leading to perturbations in the metric potentials $g_{tt}$ and $g_{rr}$ components. Mathematically, this DM-induced deformation is achieved through the CGD method, where the decoupling parameter $\alpha$ governs the extent of DM influence. To validate our findings, we compare our model predictions with observational constraints, including GW190814 (with a mass range of $2.5-2.67 M_{\odot}$) and neutron stars (NSTRs) such as EXO 1785-248 [mass=$1.3_{-0.2}^{+0.2}~M_{\odot}$], 4U 1608-52 [mass=$1.74_{-0.14}^{+0.14}~M_{\odot}$], and PSR J0952-0607 [mass=$2.35_{-0.17}^{+0.17}~M_{\odot}$]. Our investigation delves into the stability of the model by considering causality conditions, Herrera's Cracking Method, the adiabatic index, and the Harrison-Zeldovich-Novikov criterion. We demonstrate that the developed model mimics a wide range of recently observed pulsars. To emphasize its compatibility, we highlight the predicted mass and radius in tabular form by varying both the parameters $\alpha$ and $\zeta_1$. Notably, our findings are consistent with the observation of gravitational waves from the first binary merger event. Furthermore, we compare our results with those obtained for a slow-rotating configuration. In addition to this, we discuss the moment of inertia using the Bejger-Haensel approach in this formulation. |
1011.3641 | Kirill Krasnov | Alexander Torres-Gomez, Kirill Krasnov and Carlos Scarinci | A Unified Theory of Non-Linear Electrodynamics and Gravity | 31 page, no figures | Phys.Rev.D83:025023,2011 | 10.1103/PhysRevD.83.025023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a class of unified theories of electromagnetism and gravity. The
Lagrangian is of the BF type, with a potential for the B-field, the gauge group
is U(2) (complexified). Given a choice of the potential function the theory is
a deformation of (complex) general relativity and electromagnetism, and
describes just two propagating polarisations of the graviton and two of the
photon. When gravity is switched off the theory becomes the usual non-linear
electrodynamics with a general structure function. The Einstein-Maxwell theory
can be recovered by sending some of the parameters of the defining potential to
zero, but for any generic choice of the potential the theory is
indistinguishable from Einstein-Maxwell at low energies. A real theory is
obtained by imposing suitable reality conditions. We also study the
spherically-symmetric solution and show how the usual Reissner-Nordstrom
solution is recovered.
| [
{
"created": "Tue, 16 Nov 2010 10:36:58 GMT",
"version": "v1"
}
] | 2011-02-28 | [
[
"Torres-Gomez",
"Alexander",
""
],
[
"Krasnov",
"Kirill",
""
],
[
"Scarinci",
"Carlos",
""
]
] | We describe a class of unified theories of electromagnetism and gravity. The Lagrangian is of the BF type, with a potential for the B-field, the gauge group is U(2) (complexified). Given a choice of the potential function the theory is a deformation of (complex) general relativity and electromagnetism, and describes just two propagating polarisations of the graviton and two of the photon. When gravity is switched off the theory becomes the usual non-linear electrodynamics with a general structure function. The Einstein-Maxwell theory can be recovered by sending some of the parameters of the defining potential to zero, but for any generic choice of the potential the theory is indistinguishable from Einstein-Maxwell at low energies. A real theory is obtained by imposing suitable reality conditions. We also study the spherically-symmetric solution and show how the usual Reissner-Nordstrom solution is recovered. |
2208.10969 | Richard Petti | Richard James Petti | Conformal Structure of Quantum Wave Mechanics | 17 pages, 2 figures, 30 lines of computer algebra code, 2 Appendices | International Journal of Geometric Methods in Modern Physics
2250174, August 15, 2022 | 10.1142/S0219887822501742 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work interprets the quantum terms in a Lagrangian, and consequently of
the wave equation and momentum tensor, in terms of a modified spacetime metric.
Part I interprets the quantum terms in the Lagrangian of a Klein Gordon field
as scalar curvature of conformal dilation covector nm that is proportional to
hbar times the gradient of wave amplitude R. Part II replaces conformal
dilation with a conformal factor rho that defines a modified spacetime metric
gc = exp(rho) g, where g is the gravitational metric. Quantum terms appear only
in metric gc and its metric connection coefficients. Metric gc preserves
lengths and angles in classical physics and in the domain of the quantum field
itself. gc combines concepts of quantum theory and spacetime geometry in one
structure. The conformal factor can be interpreted as the limit of a
distribution of inclusions and voids in a lattice that cause the metric to
bulge or contract. All components of all free quantum fields satisfy the Klein
Gordon equation, so this interpretation extends to all quantum fields.
Measurement operations, and elements of quantum field theory are not
considered.
| [
{
"created": "Sun, 21 Aug 2022 18:24:48 GMT",
"version": "v1"
}
] | 2022-08-24 | [
[
"Petti",
"Richard James",
""
]
] | This work interprets the quantum terms in a Lagrangian, and consequently of the wave equation and momentum tensor, in terms of a modified spacetime metric. Part I interprets the quantum terms in the Lagrangian of a Klein Gordon field as scalar curvature of conformal dilation covector nm that is proportional to hbar times the gradient of wave amplitude R. Part II replaces conformal dilation with a conformal factor rho that defines a modified spacetime metric gc = exp(rho) g, where g is the gravitational metric. Quantum terms appear only in metric gc and its metric connection coefficients. Metric gc preserves lengths and angles in classical physics and in the domain of the quantum field itself. gc combines concepts of quantum theory and spacetime geometry in one structure. The conformal factor can be interpreted as the limit of a distribution of inclusions and voids in a lattice that cause the metric to bulge or contract. All components of all free quantum fields satisfy the Klein Gordon equation, so this interpretation extends to all quantum fields. Measurement operations, and elements of quantum field theory are not considered. |
0806.4765 | Scott Pollack | Scott E Pollack and Stephan Schlamminger and Jens Gundlach | Temporal Extent of Surface Potentials between Closely Spaced Metals | null | Phys.Rev.Lett.101:071101,2008 | 10.1103/PhysRevLett.101.071101 | null | gr-qc physics.ins-det | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Variations in the electrostatic surface potential between the proof mass and
electrode housing in the space-based gravitational wave mission LISA is one of
the largest contributors of noise at frequencies below a few mHz. Torsion
balances provide an ideal testbed for investigating these effects in conditions
emulative of LISA. Our apparatus consists of a Au coated Cu plate brought near
a Au coated Si plate pendulum suspended from a thin W wire. We have measured a
white noise level of $30, \uVhz$ above approximately 0.1, mHz, rising at lower
frequencies, for the surface potential variations between these two closely
spaced metals.
| [
{
"created": "Sun, 29 Jun 2008 15:28:18 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Pollack",
"Scott E",
""
],
[
"Schlamminger",
"Stephan",
""
],
[
"Gundlach",
"Jens",
""
]
] | Variations in the electrostatic surface potential between the proof mass and electrode housing in the space-based gravitational wave mission LISA is one of the largest contributors of noise at frequencies below a few mHz. Torsion balances provide an ideal testbed for investigating these effects in conditions emulative of LISA. Our apparatus consists of a Au coated Cu plate brought near a Au coated Si plate pendulum suspended from a thin W wire. We have measured a white noise level of $30, \uVhz$ above approximately 0.1, mHz, rising at lower frequencies, for the surface potential variations between these two closely spaced metals. |
0806.3132 | Molin Liu | Molin Liu, Hongya Liu, Jingfei Zhang, Fei Yu | Real Scalar Field Scattering with Polynomial Approximation around
Schwarzschild-de Sitter Black-hole | revtex4 source file, 11 pages, 8 figures | Chin.Phys.B17:1633-1639, 2008 | 10.1088/1674-1056/17/5/018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As one of the fitting methods, the polynomial approximation is effective to
process sophisticated problem. In this paper, we employ this approach to handle
the scattering of scalar field around the Schwarzschild-de Sitter black-hole.
The complex relationship between tortoise coordinate and radial coordinate is
replaced by the approximate polynomial. The Schr$\ddot{o}$dinger-like equation,
the real boundary conditions and the polynomial approximation construct a full
Sturm-Liouville type problem. Then this boundary value problem can be solved
numerically according to two limiting cases: the first one is the Nariai
black-hole whose horizons are close to each other, the second one is when the
horizons are widely separated. Compared with previous results (Brevik and
Tian), the field near the event horizon and cosmological horizon can have a
better description.
| [
{
"created": "Thu, 19 Jun 2008 05:43:15 GMT",
"version": "v1"
}
] | 2009-09-01 | [
[
"Liu",
"Molin",
""
],
[
"Liu",
"Hongya",
""
],
[
"Zhang",
"Jingfei",
""
],
[
"Yu",
"Fei",
""
]
] | As one of the fitting methods, the polynomial approximation is effective to process sophisticated problem. In this paper, we employ this approach to handle the scattering of scalar field around the Schwarzschild-de Sitter black-hole. The complex relationship between tortoise coordinate and radial coordinate is replaced by the approximate polynomial. The Schr$\ddot{o}$dinger-like equation, the real boundary conditions and the polynomial approximation construct a full Sturm-Liouville type problem. Then this boundary value problem can be solved numerically according to two limiting cases: the first one is the Nariai black-hole whose horizons are close to each other, the second one is when the horizons are widely separated. Compared with previous results (Brevik and Tian), the field near the event horizon and cosmological horizon can have a better description. |
2408.05484 | Saddam Hussain | Saddam Hussain, Simran Arora, Yamuna Rana, Benjamin Rose, and Anzhong
Wang | Interacting Models of Dark Energy and Dark Matter in Einstein scalar
Gauss Bonnet Gravity | 31 pages, 21 figures, and 3 tables | null | null | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | We study the dynamics of the interacting models between the Gauss-Bonnet (GB)
coupled scalar field and the dark matter fluid in a homogeneous and isotropic
background. A key feature of GB coupling models is the varying speed of
gravitational waves (GWs). We utilize recent constraints on the GW speed and
conduct our analysis in two primary scenarios: model-dependent and
model-independent. In the model-dependent scenario, where determining the GW
speed requires a specific GB coupling functional form, we choose an exponential
GB coupling. We adopt a dynamical system analysis to obtain the necessary
constraints on the model parameters that describe different phases of the
universe and produce a stable late-time accelerating solution following the GW
constraint, and find that to satisfy all these constraints, fine-tuning of the
free parameters involved in the models is often needed. In the
model-independent scenario, the GW speed is fixed to one, and we construct the
autonomous system to identify the late-time stable accelerating critical
points. Furthermore, we adopt a Bayesian inference method using late-time
observational data sets, including 31 data points from cosmic chronometer data
(Hubble data) and 1701 data points from Pantheon+ and find that all the
observational constraints can be satisfied without fine-tuning. In addition, we
also utilize simulated binned Roman and LSST data to study the evolution of the
universe in the model-independent scenario. We find that the model shows
significant deviation at higher redshifts from $\Lambda$CDM and fits the
current data much better than $\Lambda$CDM within the error bars.
| [
{
"created": "Sat, 10 Aug 2024 08:25:52 GMT",
"version": "v1"
}
] | 2024-08-13 | [
[
"Hussain",
"Saddam",
""
],
[
"Arora",
"Simran",
""
],
[
"Rana",
"Yamuna",
""
],
[
"Rose",
"Benjamin",
""
],
[
"Wang",
"Anzhong",
""
]
] | We study the dynamics of the interacting models between the Gauss-Bonnet (GB) coupled scalar field and the dark matter fluid in a homogeneous and isotropic background. A key feature of GB coupling models is the varying speed of gravitational waves (GWs). We utilize recent constraints on the GW speed and conduct our analysis in two primary scenarios: model-dependent and model-independent. In the model-dependent scenario, where determining the GW speed requires a specific GB coupling functional form, we choose an exponential GB coupling. We adopt a dynamical system analysis to obtain the necessary constraints on the model parameters that describe different phases of the universe and produce a stable late-time accelerating solution following the GW constraint, and find that to satisfy all these constraints, fine-tuning of the free parameters involved in the models is often needed. In the model-independent scenario, the GW speed is fixed to one, and we construct the autonomous system to identify the late-time stable accelerating critical points. Furthermore, we adopt a Bayesian inference method using late-time observational data sets, including 31 data points from cosmic chronometer data (Hubble data) and 1701 data points from Pantheon+ and find that all the observational constraints can be satisfied without fine-tuning. In addition, we also utilize simulated binned Roman and LSST data to study the evolution of the universe in the model-independent scenario. We find that the model shows significant deviation at higher redshifts from $\Lambda$CDM and fits the current data much better than $\Lambda$CDM within the error bars. |
1704.02120 | Jose Geraldo Pereira | A. Araujo, D. F. Lopez, J. G. Pereira | de Sitter-invariant special relativity and the dark energy problem | 14 pages. Accepted for publication in Class. Quantum Grav. V2: a few
corrections and small presentation changes | Class. Quantum Grav. 34 (2017) 115014 | 10.1088/1361-6382/aa6bbb | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The replacement of the Poincar\'e-invariant Einstein special relativity by a
de Sitter-invariant special relativity produces concomitant changes in all
relativistic theories, including general relativity. A crucial change in the
latter is that both the background de Sitter curvature and the gravitational
dynamical curvature turns out to be included in a single curvature tensor. This
means that the cosmological term no longer explicitly appears in Einstein
equation, and is consequently not restricted to be constant. In this paper, the
Newtonian limit of such theory is obtained, and the ensuing Newtonian Friedmann
equations are show to provide a good account of the dark energy content of the
present-day universe.
| [
{
"created": "Fri, 7 Apr 2017 08:04:45 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Apr 2017 16:42:05 GMT",
"version": "v2"
}
] | 2017-05-23 | [
[
"Araujo",
"A.",
""
],
[
"Lopez",
"D. F.",
""
],
[
"Pereira",
"J. G.",
""
]
] | The replacement of the Poincar\'e-invariant Einstein special relativity by a de Sitter-invariant special relativity produces concomitant changes in all relativistic theories, including general relativity. A crucial change in the latter is that both the background de Sitter curvature and the gravitational dynamical curvature turns out to be included in a single curvature tensor. This means that the cosmological term no longer explicitly appears in Einstein equation, and is consequently not restricted to be constant. In this paper, the Newtonian limit of such theory is obtained, and the ensuing Newtonian Friedmann equations are show to provide a good account of the dark energy content of the present-day universe. |
1307.4828 | James M. Overduin | Paul S. Wesson and James M. Overduin | The Scalar Field Source in Kaluza-Klein Theory | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To better understand the scalar field typical of higher-dimensional
extensions of general relativity, we analyse three classes of solutions. In
all, the field equation for the extra dimension resembles the Klein-Gordon
equation, and we evaluate the strength of the source. Our results show that the
scalar field is coupled to matter, and may be regarded as generating it.
| [
{
"created": "Thu, 18 Jul 2013 04:19:55 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Oct 2013 03:22:49 GMT",
"version": "v2"
}
] | 2013-10-25 | [
[
"Wesson",
"Paul S.",
""
],
[
"Overduin",
"James M.",
""
]
] | To better understand the scalar field typical of higher-dimensional extensions of general relativity, we analyse three classes of solutions. In all, the field equation for the extra dimension resembles the Klein-Gordon equation, and we evaluate the strength of the source. Our results show that the scalar field is coupled to matter, and may be regarded as generating it. |
gr-qc/9606049 | Alan Rendall | Alan D. Rendall | Constant mean curvature foliations in cosmological spacetimes | 11 pages. Contribution to the Journees Relativistes | Helv.Phys.Acta 69:490-500,1996 | null | null | gr-qc | null | Foliations by constant mean curvature hypersurfaces provide a possibility of
defining a preferred time coordinate in general relativity. In the following
various conjectures are made about the existence of foliations of this kind in
spacetimes satisfying the strong energy condition and possessing compact Cauchy
hypersurfaces. Recent progress on proving these conjectures under supplementary
assumptions is reviewed. The method of proof used is explained and the
prospects for generalizing it discussed. The relations of these questions to
cosmic censorship and the closed universe recollapse conjecture are pointed
out.
| [
{
"created": "Mon, 17 Jun 1996 12:27:40 GMT",
"version": "v1"
}
] | 2011-04-15 | [
[
"Rendall",
"Alan D.",
""
]
] | Foliations by constant mean curvature hypersurfaces provide a possibility of defining a preferred time coordinate in general relativity. In the following various conjectures are made about the existence of foliations of this kind in spacetimes satisfying the strong energy condition and possessing compact Cauchy hypersurfaces. Recent progress on proving these conjectures under supplementary assumptions is reviewed. The method of proof used is explained and the prospects for generalizing it discussed. The relations of these questions to cosmic censorship and the closed universe recollapse conjecture are pointed out. |
2106.09520 | Manuel D. Malaver | M.Malaver, H.D.Kasmaei, R.Iyer, S.Sadhukhan, A.Kar | A theoretical model of Dark Energy Stars in Einstein-Gauss-Bonnet
Gravity | 26 pages, 10 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Dark energy stars research is an issue of great interest since recent
astronomical observations with respect to measurements in distant supernovas,
cosmic microwave background and weak gravitational lensing confirm that the
universe is undergoing a phase of accelerated expansion and this cosmological
behavior is caused by the presence of a cosmic fluid which has a strong
negative pressure that allows to explain the expanding universe. In this paper,
we obtained new relativistic stellar configurations within the framework of
Einstein-Gauss-Bonnet (EGB) gravity considering negative anisotropic pressures
and the equation of state pr={\omega}\r{ho} where pr is the radial pressure,
{\omega} is the dark energy parameter, and \r{ho} is the dark energy density.
We have chosen a modified version of metric potential proposed by
Korkina-Orlyanskii (1991). For the new solutions we checked that the radial
pressure, metric coefficients, energy density and anisotropy are well defined
and are regular in the interior of the star and are dependent of the values of
the Gauss-Bonnet coupling constant. The solutions found can be used in the
development of dark energy stars models satisfying all physical acceptability
conditions, but the causality condition and strong energy condition cannot be
satisfied.
| [
{
"created": "Wed, 16 Jun 2021 12:46:16 GMT",
"version": "v1"
}
] | 2021-06-18 | [
[
"Malaver",
"M.",
""
],
[
"Kasmaei",
"H. D.",
""
],
[
"Iyer",
"R.",
""
],
[
"Sadhukhan",
"S.",
""
],
[
"Kar",
"A.",
""
]
] | Dark energy stars research is an issue of great interest since recent astronomical observations with respect to measurements in distant supernovas, cosmic microwave background and weak gravitational lensing confirm that the universe is undergoing a phase of accelerated expansion and this cosmological behavior is caused by the presence of a cosmic fluid which has a strong negative pressure that allows to explain the expanding universe. In this paper, we obtained new relativistic stellar configurations within the framework of Einstein-Gauss-Bonnet (EGB) gravity considering negative anisotropic pressures and the equation of state pr={\omega}\r{ho} where pr is the radial pressure, {\omega} is the dark energy parameter, and \r{ho} is the dark energy density. We have chosen a modified version of metric potential proposed by Korkina-Orlyanskii (1991). For the new solutions we checked that the radial pressure, metric coefficients, energy density and anisotropy are well defined and are regular in the interior of the star and are dependent of the values of the Gauss-Bonnet coupling constant. The solutions found can be used in the development of dark energy stars models satisfying all physical acceptability conditions, but the causality condition and strong energy condition cannot be satisfied. |
1603.04576 | Sergio Cacciatori | F. Belgiorno and S. L. Cacciatori | Stimulated emission and Hawking radiation in black hole analogues | 14 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Stimulated emission by black holes is discussed in light of the analogue
gravity program. We first consider initial quantum states containing a definite
number of particles, and then we take into account the case where the initial
state is a coherent state. The latter case is particularly significant in the
case where Hawking radiation is studied in dielectric black holes, and the
emission is stimulated by a laser probe. We are particularly interested in the
case of the electromagnetic field, for which stimulated radiation is calculated
too.
| [
{
"created": "Tue, 15 Mar 2016 07:21:28 GMT",
"version": "v1"
}
] | 2016-03-16 | [
[
"Belgiorno",
"F.",
""
],
[
"Cacciatori",
"S. L.",
""
]
] | Stimulated emission by black holes is discussed in light of the analogue gravity program. We first consider initial quantum states containing a definite number of particles, and then we take into account the case where the initial state is a coherent state. The latter case is particularly significant in the case where Hawking radiation is studied in dielectric black holes, and the emission is stimulated by a laser probe. We are particularly interested in the case of the electromagnetic field, for which stimulated radiation is calculated too. |
2212.06340 | Wolfgang Tichy | Wolfgang Tichy, Liwei Ji, Ananya Adhikari, Alireza Rashti, Michal
Pirog | The new discontinuous Galerkin methods based numerical relativity
program Nmesh | 44 pages, 17 figures | null | 10.1088/1361-6382/acaae7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Interpreting gravitational wave observations and understanding the physics of
astrophysical compact objects such as black holes or neutron stars requires
accurate theoretical models. Here, we present a new numerical relativity
computer program, called Nmesh, that has the design goal to become a next
generation program for the simulation of challenging relativistic astrophysics
problems such as binary black hole or neutron star mergers. In order to
efficiently run on large supercomputers, Nmesh uses a discontinuous Galerkin
method together with a domain decomposition and mesh refinement that
parallelizes and scales well. In this work, we discuss the various numerical
methods we use. We also present results of test problems such as the evolution
of scalar waves, single black holes and neutron stars, as well as shock tubes.
In addition, we introduce a new positivity limiter that allows us to stably
evolve single neutron stars without an additional artificial atmosphere, or
other more traditional limiters.
| [
{
"created": "Tue, 13 Dec 2022 02:46:55 GMT",
"version": "v1"
}
] | 2023-01-04 | [
[
"Tichy",
"Wolfgang",
""
],
[
"Ji",
"Liwei",
""
],
[
"Adhikari",
"Ananya",
""
],
[
"Rashti",
"Alireza",
""
],
[
"Pirog",
"Michal",
""
]
] | Interpreting gravitational wave observations and understanding the physics of astrophysical compact objects such as black holes or neutron stars requires accurate theoretical models. Here, we present a new numerical relativity computer program, called Nmesh, that has the design goal to become a next generation program for the simulation of challenging relativistic astrophysics problems such as binary black hole or neutron star mergers. In order to efficiently run on large supercomputers, Nmesh uses a discontinuous Galerkin method together with a domain decomposition and mesh refinement that parallelizes and scales well. In this work, we discuss the various numerical methods we use. We also present results of test problems such as the evolution of scalar waves, single black holes and neutron stars, as well as shock tubes. In addition, we introduce a new positivity limiter that allows us to stably evolve single neutron stars without an additional artificial atmosphere, or other more traditional limiters. |
gr-qc/0306036 | Konstantina Savvidou | Ntina Savvidou | General relativity histories theory II: Invariance groups | 24 pages, submitted to Class. Quant. Grav | Class.Quant.Grav. 21 (2004) 631 | 10.1088/0264-9381/21/2/021 | Imperial/TP/2-03/17 | gr-qc hep-th math-ph math.MP quant-ph | null | We show in detail how the histories description of general relativity carries
representations of both the spacetime diffeomorphisms group and the Dirac
algebra of constraints. We show that the introduction of metric-dependent
equivariant foliations leads to the crucial result that the canonical
constraints are invariant under the action of spacetime diffeomorphisms.
Furthermore, there exists a representation of the group of generalised
spacetime mappings that are functionals of the four-metric: this is a spacetime
analogue of the group originally defined by Bergmann and Komar in the context
of the canonical formulation of general relativity. Finally, we discuss the
possible directions for the quantization of gravity in histories theory.
| [
{
"created": "Mon, 9 Jun 2003 15:39:34 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Savvidou",
"Ntina",
""
]
] | We show in detail how the histories description of general relativity carries representations of both the spacetime diffeomorphisms group and the Dirac algebra of constraints. We show that the introduction of metric-dependent equivariant foliations leads to the crucial result that the canonical constraints are invariant under the action of spacetime diffeomorphisms. Furthermore, there exists a representation of the group of generalised spacetime mappings that are functionals of the four-metric: this is a spacetime analogue of the group originally defined by Bergmann and Komar in the context of the canonical formulation of general relativity. Finally, we discuss the possible directions for the quantization of gravity in histories theory. |
1511.00594 | E M Howard Dr. | E M Howard | Geometric aspects of Extremal Kerr black hole entropy | 10 pages, published in Journal of Modern Physics, 2013, 4, 357-363.
arXiv admin note: text overlap with arXiv:hep-th/9608162, arXiv:1201.4017 by
other authors | Journal of Modern Physics, 2013, vol. 4, issue 03, pp. 357-363 | 10.4236/jmp.2013.43050 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Extreme Black holes are an important theoretical laboratory for exploring the
nature of entropy. We suggest that this unusual nature of the extremal limit
could explain the entropy of extremal Kerr black holes. The time-independence
of the extremal black hole, the zero surface gravity, the zero entropy and the
absence of a bifurcate Killing horizon are all related properties that define
and reduce to one single unique feature of the extremal Kerr spacetime. We
suggest the presence of a true geometric discontinuity as the underlying cause
of a vanishing entropy.
| [
{
"created": "Tue, 20 Oct 2015 10:31:57 GMT",
"version": "v1"
}
] | 2016-09-23 | [
[
"Howard",
"E M",
""
]
] | Extreme Black holes are an important theoretical laboratory for exploring the nature of entropy. We suggest that this unusual nature of the extremal limit could explain the entropy of extremal Kerr black holes. The time-independence of the extremal black hole, the zero surface gravity, the zero entropy and the absence of a bifurcate Killing horizon are all related properties that define and reduce to one single unique feature of the extremal Kerr spacetime. We suggest the presence of a true geometric discontinuity as the underlying cause of a vanishing entropy. |
1603.09559 | Luigi Seveso | Luigi Seveso, Valerio Peri, Matteo G. A. Paris | Quantum limits to mass sensing in a gravitational field | null | null | 10.1088/1751-8121/aa6cc5 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We address the problem of estimating the mass of a quantum particle in a
gravitational field and seek the ultimate bounds to precision of
quantum-limited detection schemes. In particular, we study the effect of the
field on the achievable sensitivity and address the question of whether
quantumness of the probe state may provide a precision enhancement. The
ultimate bounds to precision are quantified in terms of the corresponding
Quantum Fisher Information. Our results show that states with no classical
limit perform better than semiclassical ones and that a non-trivial interplay
exists between the external field and the statistical model. More intense
fields generally lead to a better precision, with the exception of position
measurements in the case of freely-falling systems.
| [
{
"created": "Thu, 31 Mar 2016 12:44:25 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Jul 2016 14:14:04 GMT",
"version": "v2"
},
{
"created": "Mon, 26 Sep 2016 09:50:40 GMT",
"version": "v3"
},
{
"created": "Mon, 19 Dec 2016 16:00:33 GMT",
"version": "v4"
}
] | 2017-05-24 | [
[
"Seveso",
"Luigi",
""
],
[
"Peri",
"Valerio",
""
],
[
"Paris",
"Matteo G. A.",
""
]
] | We address the problem of estimating the mass of a quantum particle in a gravitational field and seek the ultimate bounds to precision of quantum-limited detection schemes. In particular, we study the effect of the field on the achievable sensitivity and address the question of whether quantumness of the probe state may provide a precision enhancement. The ultimate bounds to precision are quantified in terms of the corresponding Quantum Fisher Information. Our results show that states with no classical limit perform better than semiclassical ones and that a non-trivial interplay exists between the external field and the statistical model. More intense fields generally lead to a better precision, with the exception of position measurements in the case of freely-falling systems. |
1309.5707 | Kerson Huang | Kerson Huang | Dark Energy and Dark Matter in a Superfluid Universe | Invited talk at the Conference in Honor of 90th Birthday of Freeman
Dyson, Institute of Advanced Studies, Nanyang Technological University,
Singapore, 26-29 August, 2013 | Int. J. Mod. Phys. A, 28 (2013) 1330049 | 10.1142/S021775X13300494 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The vacuum is filled with complex scalar fields, such as the Higgs field.
These fields serve as order parameters for superfluidity (quantum phase
coherence over macroscopic distances), making the entire universe a superfluid.
We review a mathematical model consisting of two aspects: (a) emergence of the
superfluid during the big bang; (b) observable manifestations of superfluidity
in the present universe. The creation aspect requires a self-interacting scalar
field that is asymptotically free, i.e., the interaction must grow from zero
during the big bang, and this singles out the Halpern-Huang potential, which
has exponential behavior for large fields. It leads to an equivalent
cosmological constant that decays like a power law, and this gives dark energy
without "fine-tuning". Quantum turbulence (chaotic vorticity) in the early
universe was able to create all the matter in the universe, fulfilling the
inflation scenario. In the present universe, the superfluid can be
phenomenologically described by a nonlinear Klein-Gordon equation. It predicts
halos around galaxies with higher superfluid density, which is perceived as
dark matter through gravitational lensing. In short, dark energy is the energy
density of the cosmic superfluid, and dark matter arises from local
fluctuations of the superfluid density.
| [
{
"created": "Mon, 23 Sep 2013 06:51:36 GMT",
"version": "v1"
}
] | 2013-11-18 | [
[
"Huang",
"Kerson",
""
]
] | The vacuum is filled with complex scalar fields, such as the Higgs field. These fields serve as order parameters for superfluidity (quantum phase coherence over macroscopic distances), making the entire universe a superfluid. We review a mathematical model consisting of two aspects: (a) emergence of the superfluid during the big bang; (b) observable manifestations of superfluidity in the present universe. The creation aspect requires a self-interacting scalar field that is asymptotically free, i.e., the interaction must grow from zero during the big bang, and this singles out the Halpern-Huang potential, which has exponential behavior for large fields. It leads to an equivalent cosmological constant that decays like a power law, and this gives dark energy without "fine-tuning". Quantum turbulence (chaotic vorticity) in the early universe was able to create all the matter in the universe, fulfilling the inflation scenario. In the present universe, the superfluid can be phenomenologically described by a nonlinear Klein-Gordon equation. It predicts halos around galaxies with higher superfluid density, which is perceived as dark matter through gravitational lensing. In short, dark energy is the energy density of the cosmic superfluid, and dark matter arises from local fluctuations of the superfluid density. |
1501.07089 | Amir H. Abbassi | A.A. Asgari and A.H. Abbassi | Slow-roll inflationary senario in the maximally extended background | 21 pages,n o figures | null | 10.1140/epjc/s10052-015-3792-z | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | During the inflationary epoch,geometry of the universe may be described by
quasi-de Sitter space. On the other hand,maximally extended de Sitter metric in
the comoving coordinates accords with a special FLRW model with positive
spatial curvature,so in this article we focus on the positively curved
inflationary paradigm.For this purpose,first we derive the power spectra of
comoving curvature perturbation and primordial gravitational waves in a
positively curved FLRW universe according to the slowly rolling inflationary
senario. It can be shown that the curvature spectral index in this model
automatically has a small negative running parameter which is compatible with
observational measurements.Then,by taking into account the curvature factor,we
investigate the relative amplitude of the scalar and tensor perturbations.It
would be clarified that the tensor-scalar ratio for this model against the
spatially flat one,depends on the waelength of the perturbative models
directly.
| [
{
"created": "Wed, 28 Jan 2015 12:50:30 GMT",
"version": "v1"
}
] | 2016-01-20 | [
[
"Asgari",
"A. A.",
""
],
[
"Abbassi",
"A. H.",
""
]
] | During the inflationary epoch,geometry of the universe may be described by quasi-de Sitter space. On the other hand,maximally extended de Sitter metric in the comoving coordinates accords with a special FLRW model with positive spatial curvature,so in this article we focus on the positively curved inflationary paradigm.For this purpose,first we derive the power spectra of comoving curvature perturbation and primordial gravitational waves in a positively curved FLRW universe according to the slowly rolling inflationary senario. It can be shown that the curvature spectral index in this model automatically has a small negative running parameter which is compatible with observational measurements.Then,by taking into account the curvature factor,we investigate the relative amplitude of the scalar and tensor perturbations.It would be clarified that the tensor-scalar ratio for this model against the spatially flat one,depends on the waelength of the perturbative models directly. |
2206.06384 | Gianluca Calcagni | Leonardo Modesto, Gianluca Calcagni | Early universe in quantum gravity | 1+43 pages, 7 figures. v2: nature of beta coefficients and solution
of flatness problem clarified, discussion on spontaneous symmetry breaking
expanded. v3: discussions on background metrics and on singularity problem
resolution substantially clarified, derivation of cosmological spectra moved
to companion paper arXiv:2206.07066, typos corrected, references added. Main
results unchanged | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new picture of the early universe in finite nonlocal quantum
gravity, which is conformally invariant at the classical and quantum levels.
The high-energy regime of the theory consists of two phases, a conformally
invariant trans-Planckian phase and a post-Planckian or Higgs phase described
by an action quadratic in the Ricci tensor and where the cosmos evolves
according to the standard radiation-dominated model. In the first phase, all
the issues of the hot big bang such as the singularity, flatness, and horizon
problems find a universal and simple non-inflationary solution by means of Weyl
(or scale, or conformal) invariance, regardless of the microscopic details of
the theory. In the second phase, once conformal symmetry is spontaneously
broken, primordial perturbations are generated around a background that
asymptotically evolves as a radiation-dominated flat
Friedmann--Lema\^{i}tre--Robertson--Walker universe.
| [
{
"created": "Mon, 13 Jun 2022 18:00:02 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jul 2022 02:57:11 GMT",
"version": "v2"
},
{
"created": "Wed, 29 May 2024 10:56:37 GMT",
"version": "v3"
}
] | 2024-05-30 | [
[
"Modesto",
"Leonardo",
""
],
[
"Calcagni",
"Gianluca",
""
]
] | We present a new picture of the early universe in finite nonlocal quantum gravity, which is conformally invariant at the classical and quantum levels. The high-energy regime of the theory consists of two phases, a conformally invariant trans-Planckian phase and a post-Planckian or Higgs phase described by an action quadratic in the Ricci tensor and where the cosmos evolves according to the standard radiation-dominated model. In the first phase, all the issues of the hot big bang such as the singularity, flatness, and horizon problems find a universal and simple non-inflationary solution by means of Weyl (or scale, or conformal) invariance, regardless of the microscopic details of the theory. In the second phase, once conformal symmetry is spontaneously broken, primordial perturbations are generated around a background that asymptotically evolves as a radiation-dominated flat Friedmann--Lema\^{i}tre--Robertson--Walker universe. |
1402.4672 | Aleksandar Mikovic | Aleksandar Mikovic | Effective Actions for Regge State-Sum Models of Quantum Gravity | 22 pages, improved presentation, 4 references added | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the semiclassical expansion of the effective action for a Regge
state-sum model and its dependence on the choice of the path-integral measure
and the spectrum of the edge lengths. If the positivity of the edge lengths is
imposed in the effective action equation, we find that the semiclassical
expansion is not possible for the power-law measures, while the exponential
measures allow the semiclassical expansion. Furthermore, a slightly generalized
exponential measure can generate the cosmological term in the effective action
as a quantum correction, with a naturally small value of the cosmological
constant. We also find that in the case of a discrete length spectrum, the
semiclassical expansion is allowed only if the spectrum gap is much smaller
than the Planck length.
| [
{
"created": "Wed, 19 Feb 2014 14:22:38 GMT",
"version": "v1"
},
{
"created": "Wed, 14 May 2014 13:09:48 GMT",
"version": "v2"
}
] | 2014-05-15 | [
[
"Mikovic",
"Aleksandar",
""
]
] | We study the semiclassical expansion of the effective action for a Regge state-sum model and its dependence on the choice of the path-integral measure and the spectrum of the edge lengths. If the positivity of the edge lengths is imposed in the effective action equation, we find that the semiclassical expansion is not possible for the power-law measures, while the exponential measures allow the semiclassical expansion. Furthermore, a slightly generalized exponential measure can generate the cosmological term in the effective action as a quantum correction, with a naturally small value of the cosmological constant. We also find that in the case of a discrete length spectrum, the semiclassical expansion is allowed only if the spectrum gap is much smaller than the Planck length. |
0904.2904 | Mohammad Nouri-Zonoz | M. Nouri-Zonoz | Vacuum energy and the spacetime index of refraction: A new synthesis | 10 pages, RevTex, more typos corrected (combined with arXiv:1003.0614
published in PRD) | Phys.Rev.D82:044047,2010 | 10.1103/PhysRevD.82.044047 | IPM/A-2009/004 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In 1+3 (threading) formulation of general relativity spacetime behaves
analogous to a medium with a specific index of refraction with respect to the
light propagation. Accepting the reality of zero point energy, through the
equivalence principle, we elevate this analogy to the case of virtual photon
propagation in a quantum vacuum in a curved background spacetime. Employing
this new idea one could examine the response of vacuum energy to the presence
of a stationary gravitational field in its different quantum field theoretic
manifestations such as Casimir effect and Lamb shift. The results are given
explicitly for a Casimir apparatus in the weak field limit of a Kerr hole.
| [
{
"created": "Sun, 19 Apr 2009 10:13:06 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jun 2009 13:34:10 GMT",
"version": "v2"
},
{
"created": "Wed, 6 Oct 2010 09:15:59 GMT",
"version": "v3"
}
] | 2010-10-07 | [
[
"Nouri-Zonoz",
"M.",
""
]
] | In 1+3 (threading) formulation of general relativity spacetime behaves analogous to a medium with a specific index of refraction with respect to the light propagation. Accepting the reality of zero point energy, through the equivalence principle, we elevate this analogy to the case of virtual photon propagation in a quantum vacuum in a curved background spacetime. Employing this new idea one could examine the response of vacuum energy to the presence of a stationary gravitational field in its different quantum field theoretic manifestations such as Casimir effect and Lamb shift. The results are given explicitly for a Casimir apparatus in the weak field limit of a Kerr hole. |
1505.06917 | Marco Frasca | Marco Frasca | Einstein-Maxwell equations for asymmetric resonant cavities | 17 pages, no figure. Added computation of the scalar field in a
Brans-Dicke-Maxwell theory and proper references | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the behavior of electromagnetic fields inside a resonant cavity by
solving Einstein--Maxwell field equations. It is shown that the modified
geometry of space-time inside the cavity due to a propagating mode can affect
the propagation of a laser beam. It is seen that components of laser light with
a shifted frequency appear originating from the coupling between the laser
field and the mode cavity due to gravity. The analysis is extended to the case
of an asymmetric resonant cavity taken to be a truncated cone. It is shown that
a proper choice of the geometrical parameters of the cavity and dielectric can
make the gravitational effects significant for an interferometric setup. This
could make possible to realize table-top experiments involving gravitational
effects.
| [
{
"created": "Tue, 26 May 2015 12:14:48 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Sep 2016 06:33:06 GMT",
"version": "v2"
}
] | 2016-09-06 | [
[
"Frasca",
"Marco",
""
]
] | We analyze the behavior of electromagnetic fields inside a resonant cavity by solving Einstein--Maxwell field equations. It is shown that the modified geometry of space-time inside the cavity due to a propagating mode can affect the propagation of a laser beam. It is seen that components of laser light with a shifted frequency appear originating from the coupling between the laser field and the mode cavity due to gravity. The analysis is extended to the case of an asymmetric resonant cavity taken to be a truncated cone. It is shown that a proper choice of the geometrical parameters of the cavity and dielectric can make the gravitational effects significant for an interferometric setup. This could make possible to realize table-top experiments involving gravitational effects. |
1803.09094 | Sergey Cherkas L | S.L. Cherkas and V.L. Kalashnikov | Plasma Perturbations and Cosmic Microwave Background Anisotropy in the
Linearly Expanding Milne-like Universe | 20 pages | Chapter 9 in Fractional Dynamics, Anomalous Transport and Plasma
Science, ed. by Ch. H. Skiadas, Springer, Berlin, (2018) | 10.1007/978-3-030-04483-1 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We expose the scenarios of primordial baryon-photon plasma evolution within
the framework of the Milne-like universe models. Recently, such models find a
second wind and promise an inflation-free solution of a lot of cosmological
puzzles including the cosmological constant one. Metric tensor perturbations
are considered using the five-vectors theory of gravity admitting the Friedmann
equation satisfied up to some constant. The Cosmic Microwave Background (CMB)
spectrum is calculated qualitatively.
| [
{
"created": "Sat, 24 Mar 2018 11:22:25 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Oct 2018 11:04:05 GMT",
"version": "v2"
}
] | 2019-01-09 | [
[
"Cherkas",
"S. L.",
""
],
[
"Kalashnikov",
"V. L.",
""
]
] | We expose the scenarios of primordial baryon-photon plasma evolution within the framework of the Milne-like universe models. Recently, such models find a second wind and promise an inflation-free solution of a lot of cosmological puzzles including the cosmological constant one. Metric tensor perturbations are considered using the five-vectors theory of gravity admitting the Friedmann equation satisfied up to some constant. The Cosmic Microwave Background (CMB) spectrum is calculated qualitatively. |
gr-qc/0506059 | Neil J. Cornish | Neil J. Cornish and Jeff Crowder | LISA Data Analysis using MCMC methods | 14 pages, 7 figures | Phys.Rev. D72 (2005) 043005 | 10.1103/PhysRevD.72.043005 | null | gr-qc astro-ph | null | The Laser Interferometer Space Antenna (LISA) is expected to simultaneously
detect many thousands of low frequency gravitational wave signals. This
presents a data analysis challenge that is very different to the one
encountered in ground based gravitational wave astronomy. LISA data analysis
requires the identification of individual signals from a data stream containing
an unknown number of overlapping signals. Because of the signal overlaps, a
global fit to all the signals has to be performed in order to avoid biasing the
solution. However, performing such a global fit requires the exploration of an
enormous parameter space with a dimension upwards of 50,000. Markov Chain Monte
Carlo (MCMC) methods offer a very promising solution to the LISA data analysis
problem. MCMC algorithms are able to efficiently explore large parameter
spaces, simultaneously providing parameter estimates, error analyses and even
model selection. Here we present the first application of MCMC methods to
simulated LISA data and demonstrate the great potential of the MCMC approach.
Our implementation uses a generalized F-statistic to evaluate the likelihoods,
and simulated annealing to speed convergence of the Markov chains. As a final
step we super-cool the chains to extract maximum likelihood estimates, and
estimates of the Bayes factors for competing models. We find that the MCMC
approach is able to correctly identify the number of signals present, extract
the source parameters, and return error estimates consistent with Fisher
information matrix predictions.
| [
{
"created": "Fri, 10 Jun 2005 19:51:28 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Cornish",
"Neil J.",
""
],
[
"Crowder",
"Jeff",
""
]
] | The Laser Interferometer Space Antenna (LISA) is expected to simultaneously detect many thousands of low frequency gravitational wave signals. This presents a data analysis challenge that is very different to the one encountered in ground based gravitational wave astronomy. LISA data analysis requires the identification of individual signals from a data stream containing an unknown number of overlapping signals. Because of the signal overlaps, a global fit to all the signals has to be performed in order to avoid biasing the solution. However, performing such a global fit requires the exploration of an enormous parameter space with a dimension upwards of 50,000. Markov Chain Monte Carlo (MCMC) methods offer a very promising solution to the LISA data analysis problem. MCMC algorithms are able to efficiently explore large parameter spaces, simultaneously providing parameter estimates, error analyses and even model selection. Here we present the first application of MCMC methods to simulated LISA data and demonstrate the great potential of the MCMC approach. Our implementation uses a generalized F-statistic to evaluate the likelihoods, and simulated annealing to speed convergence of the Markov chains. As a final step we super-cool the chains to extract maximum likelihood estimates, and estimates of the Bayes factors for competing models. We find that the MCMC approach is able to correctly identify the number of signals present, extract the source parameters, and return error estimates consistent with Fisher information matrix predictions. |
gr-qc/0107004 | Tiberiu Harko | M. K. Mak, T. Harko | Exact Dissipative Cosmologies with Stiff Fluid | 7 pages, 6 figures | Europhys.Lett.56:762-767,2001 | 10.1209/epl/i2001-00114-3 | null | gr-qc | null | The general solution of the gravitational field equations in the flat
Friedmann-Robertson-Walker geometry is obtained in the framework of the full
Israel-Stewart-Hiscock theory for a bulk viscous stiff cosmological fluid, with
bulk viscosity coefficient proportional to the energy density.
| [
{
"created": "Mon, 2 Jul 2001 04:53:04 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Mak",
"M. K.",
""
],
[
"Harko",
"T.",
""
]
] | The general solution of the gravitational field equations in the flat Friedmann-Robertson-Walker geometry is obtained in the framework of the full Israel-Stewart-Hiscock theory for a bulk viscous stiff cosmological fluid, with bulk viscosity coefficient proportional to the energy density. |
2309.04157 | Yiqian Chen | Yiqian Chen, Peng Wang, and Haitang Yang | Observations of Orbiting Hot Spots around Naked Singularities | 24 pages, 6 figures, and 3 animated images of intensity for
ancillary. References added and typo corrected | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, it has been reported that photons can traverse naked singularities
in the Janis-Newman-Winicour and Born-Infeld spacetimes when these
singularities are appropriately regularized. In this paper, we investigate
observational signatures of hot spots orbiting these naked singularities, with
a focus on discerning them from black holes. In contrast to Schwarzschild black
holes, we unveil the presence of multiple additional image tracks within
critical curves in time integrated images capturing a complete orbit of hot
spots. Moreover, these new images manifest as a more pronounced second-highest
peak in temporal magnitudes when observed at low inclinations.
| [
{
"created": "Fri, 8 Sep 2023 06:50:36 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Oct 2023 08:14:20 GMT",
"version": "v2"
}
] | 2023-10-11 | [
[
"Chen",
"Yiqian",
""
],
[
"Wang",
"Peng",
""
],
[
"Yang",
"Haitang",
""
]
] | Recently, it has been reported that photons can traverse naked singularities in the Janis-Newman-Winicour and Born-Infeld spacetimes when these singularities are appropriately regularized. In this paper, we investigate observational signatures of hot spots orbiting these naked singularities, with a focus on discerning them from black holes. In contrast to Schwarzschild black holes, we unveil the presence of multiple additional image tracks within critical curves in time integrated images capturing a complete orbit of hot spots. Moreover, these new images manifest as a more pronounced second-highest peak in temporal magnitudes when observed at low inclinations. |
1709.04031 | Daniele Pranzetti | Ramit Dey, Stefano Liberati, Daniele Pranzetti | Spacetime thermodynamics in the presence of torsion | 18 pages | Phys. Rev. D 96, 124032 (2017) | 10.1103/PhysRevD.96.124032 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was shown by Jacobson in 1995 that the Einstein equation can be derived as
a local constitutive equation for an equilibrium spacetime thermodynamics. With
the aim to understand if such thermodynamical description is an intrinsic
property of gravitation, many attempts have been done so far to generalise this
treatment to a broader class of gravitational theories. Here we consider the
case of the Einstein-Cartan theory as a prototype of theories with
non-propagating torsion. In doing so, we study the properties of Killing
horizons in the presence of torsion, establish the notion of local causal
horizon in Riemann-Cartan spacetimes, and derive the generalised Raychaudhuri
equation for this kind of geometries. Then, starting with the entropy that can
be associated to these local causal horizons, we derive the Einstein-Cartan
equation by implementing the Clausius equation. We outline two ways of
proceeding with the derivation depending on whether we take torsion as a
geometric field or as a matter field. In both cases we need to add internal
entropy production terms to the Clausius equation as the shear and twist cannot
be taken to be zero a priori for our setup. This fact implies the necessity of
a non-equilibrium thermodynamics treatment for the local causal horizon.
Furthermore, it implies that a non-zero twist at the horizon will in general
contribute to the Hartle-Hawking tidal heating for black holes with possible
implications for future observations.
| [
{
"created": "Tue, 12 Sep 2017 19:22:07 GMT",
"version": "v1"
}
] | 2017-12-27 | [
[
"Dey",
"Ramit",
""
],
[
"Liberati",
"Stefano",
""
],
[
"Pranzetti",
"Daniele",
""
]
] | It was shown by Jacobson in 1995 that the Einstein equation can be derived as a local constitutive equation for an equilibrium spacetime thermodynamics. With the aim to understand if such thermodynamical description is an intrinsic property of gravitation, many attempts have been done so far to generalise this treatment to a broader class of gravitational theories. Here we consider the case of the Einstein-Cartan theory as a prototype of theories with non-propagating torsion. In doing so, we study the properties of Killing horizons in the presence of torsion, establish the notion of local causal horizon in Riemann-Cartan spacetimes, and derive the generalised Raychaudhuri equation for this kind of geometries. Then, starting with the entropy that can be associated to these local causal horizons, we derive the Einstein-Cartan equation by implementing the Clausius equation. We outline two ways of proceeding with the derivation depending on whether we take torsion as a geometric field or as a matter field. In both cases we need to add internal entropy production terms to the Clausius equation as the shear and twist cannot be taken to be zero a priori for our setup. This fact implies the necessity of a non-equilibrium thermodynamics treatment for the local causal horizon. Furthermore, it implies that a non-zero twist at the horizon will in general contribute to the Hartle-Hawking tidal heating for black holes with possible implications for future observations. |
0911.3431 | Muxin Han | Muxin Han, Thomas Thiemann | On the Relation between Rigging Inner Product and Master Constraint
Direct Integral Decomposition | 25 pages | J.Math.Phys.51:092501,2010 | 10.1063/1.3486359 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Canonical quantisation of constrained systems with first class constraints
via Dirac's operator constraint method proceeds by the thory of Rigged Hilbert
spaces, sometimes also called Refined Algebraic Quantisation (RAQ). This method
can work when the constraints form a Lie algebra. When the constraints only
close with nontrivial structure functions, the Rigging map can no longer be
defined.
To overcome this obstacle, the Master Constraint Method has been proposed
which replaces the individual constraints by a weighted sum of absolute squares
of the constraints. Now the direct integral decomposition methods (DID), which
are closely related to Rigged Hilbert spaces, become available and have been
successfully tested in various situations.
It is relatively straightforward to relate the Rigging Inner Product to the
path integral that one obtains via reduced phase space methods. However, for
the Master Constraint this is not at all obvious. In this paper we find
sufficient conditions under which such a relation can be established. Key to
our analysis is the possibility to pass to equivalent, Abelian constraints, at
least locally in phase space. Then the Master Constraint DID for those Abelian
constraints can be directly related to the Rigging Map and therefore has a path
integral formulation.
| [
{
"created": "Tue, 17 Nov 2009 23:53:42 GMT",
"version": "v1"
}
] | 2011-04-07 | [
[
"Han",
"Muxin",
""
],
[
"Thiemann",
"Thomas",
""
]
] | Canonical quantisation of constrained systems with first class constraints via Dirac's operator constraint method proceeds by the thory of Rigged Hilbert spaces, sometimes also called Refined Algebraic Quantisation (RAQ). This method can work when the constraints form a Lie algebra. When the constraints only close with nontrivial structure functions, the Rigging map can no longer be defined. To overcome this obstacle, the Master Constraint Method has been proposed which replaces the individual constraints by a weighted sum of absolute squares of the constraints. Now the direct integral decomposition methods (DID), which are closely related to Rigged Hilbert spaces, become available and have been successfully tested in various situations. It is relatively straightforward to relate the Rigging Inner Product to the path integral that one obtains via reduced phase space methods. However, for the Master Constraint this is not at all obvious. In this paper we find sufficient conditions under which such a relation can be established. Key to our analysis is the possibility to pass to equivalent, Abelian constraints, at least locally in phase space. Then the Master Constraint DID for those Abelian constraints can be directly related to the Rigging Map and therefore has a path integral formulation. |
gr-qc/9511012 | Robert Mann | J.D.E. Creighton and R.B. Mann | Thermodynamics of Dilatonic Black Holes in $n$ Dimensions | 27 pages, latex, uses amstex | null | null | WATPHYS TH-95/08 | gr-qc hep-th | null | We present a formalism for studying the thermodynamics of black holes in
dilaton gravity. The thermodynamic variables are defined on a quasilocal
surface surrounding the black hole system and are obtained from a general class
of Lagrangians involving a dilaton. The formalism thus accommodates a large
number of possible theories and black hole spacetimes. Many of the
thermodynamic quantities are identified from the contribution of the action on
the quasilocal boundary. The entropy is found using path integral techniques,
and a first law of thermodynamics is obtained. As an illustration, we calculate
the thermodynamic quantities for two black hole solutions in $(1+1)$
dimensions: one obtained from a string inspired theory and the other being a
Liouville black hole in the ``$R=\kappa T$'' theory with a Liouville field.
| [
{
"created": "Fri, 3 Nov 1995 00:48:54 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Creighton",
"J. D. E.",
""
],
[
"Mann",
"R. B.",
""
]
] | We present a formalism for studying the thermodynamics of black holes in dilaton gravity. The thermodynamic variables are defined on a quasilocal surface surrounding the black hole system and are obtained from a general class of Lagrangians involving a dilaton. The formalism thus accommodates a large number of possible theories and black hole spacetimes. Many of the thermodynamic quantities are identified from the contribution of the action on the quasilocal boundary. The entropy is found using path integral techniques, and a first law of thermodynamics is obtained. As an illustration, we calculate the thermodynamic quantities for two black hole solutions in $(1+1)$ dimensions: one obtained from a string inspired theory and the other being a Liouville black hole in the ``$R=\kappa T$'' theory with a Liouville field. |
1311.5188 | Yi-Cheng Huang | Yi-Cheng Huang | Thermalized Vacuum and Vacuum Effects | 18 pages, 0 figure | null | null | null | gr-qc hep-ph hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some of the well-known effects regarding the vacuum are revisited under the
formalism of the imaginary-time field theory. From these effects, they could
imply the existence of one thermal vacuum in different circumstances. The
imaginary-time hamiltonian of the vacuum is found to provide not only exact
distribution functions in the calculations of the Casimir effect and the Van
der Waals force but also cutoff functions. The thermal bath for the Unruh
effect is constructed from the imaginary-time Green function. From the field
theory in the curved space-time, field quantizations are defined according to
different vacuum states and lead to the Hawking radiation; the introduced
conformal invariance agree with the formalism of the imaginary-time field
theory. The induced Green functions in the curved space-time are in accordance
with those from the picture given from the thermal vacuum.
| [
{
"created": "Thu, 14 Nov 2013 18:18:30 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Dec 2013 02:49:37 GMT",
"version": "v2"
}
] | 2013-12-03 | [
[
"Huang",
"Yi-Cheng",
""
]
] | Some of the well-known effects regarding the vacuum are revisited under the formalism of the imaginary-time field theory. From these effects, they could imply the existence of one thermal vacuum in different circumstances. The imaginary-time hamiltonian of the vacuum is found to provide not only exact distribution functions in the calculations of the Casimir effect and the Van der Waals force but also cutoff functions. The thermal bath for the Unruh effect is constructed from the imaginary-time Green function. From the field theory in the curved space-time, field quantizations are defined according to different vacuum states and lead to the Hawking radiation; the introduced conformal invariance agree with the formalism of the imaginary-time field theory. The induced Green functions in the curved space-time are in accordance with those from the picture given from the thermal vacuum. |
1107.5077 | Ronald Adler | Ronald J. Adler | Genesis and the tipping pencil; why the Universe is flat | 8 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a room with five cosmologists there there may easily be ten theories of
cosmogenesis. Cosmogenesis is a popular topic for speculation because it is
philosophically deep and because such speculations are unlikely to be proven
wrong in the near future. The scenario we present here was intended mainly as a
pedagogical illustration or toy model, but it turns out to possibly have a more
serious and interesting result - a rationale for the spatial flatness of the
Universe. Our basic assumptions are that the cosmological scale factor obeys
the standard Friedman equation of general relativistic cosmology and that the
equation is dominated by a cosmological constant term and a curvature term; the
dynamics of the Universe is then (approximately) the same as that of a tipping
pencil. The scale factor cannot remain at an unstable initial value of zero and
must increase (i.e. the Universe must come into existence) according to the
uncertainty principle, that is due to quantum fluctuations; in other words we
propose in a precise but limited context an answer to Heidegger's famous
question "Why is there something rather than nothing." The mechanism is the
same as that whereby an idealized pencil balanced on its point cannot remain so
and must tip over. If it is moreover assumed that the Universe expands at the
minimum asymptotic rate consistent with the uncertainty principle then the
result is spatial flatness.
| [
{
"created": "Thu, 21 Jul 2011 22:23:25 GMT",
"version": "v1"
}
] | 2011-07-27 | [
[
"Adler",
"Ronald J.",
""
]
] | In a room with five cosmologists there there may easily be ten theories of cosmogenesis. Cosmogenesis is a popular topic for speculation because it is philosophically deep and because such speculations are unlikely to be proven wrong in the near future. The scenario we present here was intended mainly as a pedagogical illustration or toy model, but it turns out to possibly have a more serious and interesting result - a rationale for the spatial flatness of the Universe. Our basic assumptions are that the cosmological scale factor obeys the standard Friedman equation of general relativistic cosmology and that the equation is dominated by a cosmological constant term and a curvature term; the dynamics of the Universe is then (approximately) the same as that of a tipping pencil. The scale factor cannot remain at an unstable initial value of zero and must increase (i.e. the Universe must come into existence) according to the uncertainty principle, that is due to quantum fluctuations; in other words we propose in a precise but limited context an answer to Heidegger's famous question "Why is there something rather than nothing." The mechanism is the same as that whereby an idealized pencil balanced on its point cannot remain so and must tip over. If it is moreover assumed that the Universe expands at the minimum asymptotic rate consistent with the uncertainty principle then the result is spatial flatness. |
2402.10984 | Muhammad Sharif | M. Sharif and M. Sallah | Decoupled Charged Anisotropic Spherical Solutions in Rastall Gravity | 38 pages, 16 figures | New Astronomy 109(2024)102198 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper uses the gravitational decoupling through the minimal geometric
deformation approach and extends a known isotropic solution for a
self-gravitating interior to two types of anisotropic spherical solutions in
Rastall gravity in the presence of electromagnetic field. By deforming only the
radial metric component, the field equations are decoupled into two sets, the
first of which corresponds to an isotropic distribution of matter while the
second set contains the anisotropic source. We obtain a solution of the first
set by employing the charged isotropic Finch-Skea ansatz, whereas a solution
for the second set is obtained by adopting two mimic constraints on the
pressure and density. The matching conditions at the stellar surface are
explored with the exterior geometry given by the deformed
Reissner-Nordstr$\ddot{o}$m spacetime. For the two fixed values of the Rastall
and charge parameters, we investigate physical features of both solutions
through graphical analysis of the energy conditions, equation of state
parameters, surface redshift and compactness function. The stability of both
solutions is also studied through the Herrera cracking approach and causality
condition. We deduce that while both solutions are physically viable, only the
solution corresponding to the pressure-like constraint is stable.
| [
{
"created": "Fri, 16 Feb 2024 02:30:32 GMT",
"version": "v1"
}
] | 2024-02-20 | [
[
"Sharif",
"M.",
""
],
[
"Sallah",
"M.",
""
]
] | This paper uses the gravitational decoupling through the minimal geometric deformation approach and extends a known isotropic solution for a self-gravitating interior to two types of anisotropic spherical solutions in Rastall gravity in the presence of electromagnetic field. By deforming only the radial metric component, the field equations are decoupled into two sets, the first of which corresponds to an isotropic distribution of matter while the second set contains the anisotropic source. We obtain a solution of the first set by employing the charged isotropic Finch-Skea ansatz, whereas a solution for the second set is obtained by adopting two mimic constraints on the pressure and density. The matching conditions at the stellar surface are explored with the exterior geometry given by the deformed Reissner-Nordstr$\ddot{o}$m spacetime. For the two fixed values of the Rastall and charge parameters, we investigate physical features of both solutions through graphical analysis of the energy conditions, equation of state parameters, surface redshift and compactness function. The stability of both solutions is also studied through the Herrera cracking approach and causality condition. We deduce that while both solutions are physically viable, only the solution corresponding to the pressure-like constraint is stable. |
2308.12182 | Hoi Tim Cheung | Damon H. T. Cheung, Stefano Rinaldi, Martina Toscani and Otto A.
Hannuksela | Mitigating the effect of population model uncertainty on strong lensing
Bayes factor using nonparametric methods | 15 pages, 8 figures | null | null | null | gr-qc astro-ph.CO hep-ph | http://creativecommons.org/licenses/by/4.0/ | Strong lensing of gravitational waves can produce several detectable images
as repeated events in the upcoming observing runs, which can be detected with
the posterior overlap analysis (Bayes factor). The choice of the binary black
hole population plays an important role in the analysis as two
gravitational-wave events could be similar either because of lensing or
astrophysical coincidence. In this study, we investigate the biases induced by
different population models on the Bayes factor. We build up a mock catalogue
of gravitational-wave events following a benchmark population and reconstruct
it using both non-parametric and parametric methods. Using these
reconstructions, we compute the Bayes factor for lensed pair events by
utilizing both models and compare the results with a benchmark model. We show
that the use of a non-parametric population model gives a smaller bias than
parametric population models. Therefore, our study demonstrates the importance
of choosing a sufficiently agnostic population model for strong lensing
analyses.
| [
{
"created": "Wed, 23 Aug 2023 15:12:32 GMT",
"version": "v1"
}
] | 2023-08-24 | [
[
"Cheung",
"Damon H. T.",
""
],
[
"Rinaldi",
"Stefano",
""
],
[
"Toscani",
"Martina",
""
],
[
"Hannuksela",
"Otto A.",
""
]
] | Strong lensing of gravitational waves can produce several detectable images as repeated events in the upcoming observing runs, which can be detected with the posterior overlap analysis (Bayes factor). The choice of the binary black hole population plays an important role in the analysis as two gravitational-wave events could be similar either because of lensing or astrophysical coincidence. In this study, we investigate the biases induced by different population models on the Bayes factor. We build up a mock catalogue of gravitational-wave events following a benchmark population and reconstruct it using both non-parametric and parametric methods. Using these reconstructions, we compute the Bayes factor for lensed pair events by utilizing both models and compare the results with a benchmark model. We show that the use of a non-parametric population model gives a smaller bias than parametric population models. Therefore, our study demonstrates the importance of choosing a sufficiently agnostic population model for strong lensing analyses. |
2307.00603 | Arunoday Sarkar | Arunoday Sarkar and Buddhadeb Ghosh | Constraining an Early Dark Energy Motivated Quintessential
$\alpha$-Attractor Inflaton Potential | 54 pages, 25 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We construct a new model of quintessential $\alpha$ attractor inflation in
conjunction with the features of non-oscillating early dark energy (EDE).
Slow-roll plateau of this model is obtained, and analyzed in $k$-space, through
the inflaton field and its first-order perturbation over a quasi de-Sitter
metric fluctuation in the range $k=0.001-0.009$ Mpc$^{-1}$. The estimated
cosmological parameters are found to obey Planck+BICEP2/Keck bounds with $68\%$
CL with the required trend of spectral tilts in the $n_s-r$ parametric space.
We verify that, the inclusion of the EDE does not significantly affect the
observed parameters. Its presence manifests in obtaining \textit{improved
values} of the energy scale of inflation ($M$) and the present-day vacuum
density ($V_{\Lambda}$). They are found to be $M=5.58\times 10^{-4}-4.57\times
10^{-3} M_P$ and $V_{\Lambda}=1.042\times 10^{-119}-4.688\times 10^{-116}
M_P^4$.
However, the $\alpha$-parameter is drastically constrained in two ways. Its
lower end is fixed by the consistency analysis of the $k$-mode equations, while
the upper end is evaluated as a derived expression of $\alpha$-cut-off through
the aspects of EDE \textit{viz.,} the effects of \textit{Enhanced Symmetry
Point} (ESP) in the potential during inflation. Improvised range of $\alpha$ is
found to be $0.001\leq\alpha<0.1$ for the model parameters $\gamma$ and $n$
lying within $0.01\leq\gamma\leq 0.09$ and $8\leq n\leq 10$ respectively. These
ranges are shown to be essential for satisfying the COBE/Planck normalized
energy scale of inflation and the Planck-value of present-day vacuum density.
If we choose $\gamma=0.0818$ and $n=8$, then we get $0.001\leq\alpha\leq
0.0186$. Thus, the lower and upper limits of $\alpha$ are diminished
substantially, compared with those in the earlier studies.
| [
{
"created": "Sun, 2 Jul 2023 16:04:14 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Apr 2024 15:40:39 GMT",
"version": "v2"
}
] | 2024-04-15 | [
[
"Sarkar",
"Arunoday",
""
],
[
"Ghosh",
"Buddhadeb",
""
]
] | We construct a new model of quintessential $\alpha$ attractor inflation in conjunction with the features of non-oscillating early dark energy (EDE). Slow-roll plateau of this model is obtained, and analyzed in $k$-space, through the inflaton field and its first-order perturbation over a quasi de-Sitter metric fluctuation in the range $k=0.001-0.009$ Mpc$^{-1}$. The estimated cosmological parameters are found to obey Planck+BICEP2/Keck bounds with $68\%$ CL with the required trend of spectral tilts in the $n_s-r$ parametric space. We verify that, the inclusion of the EDE does not significantly affect the observed parameters. Its presence manifests in obtaining \textit{improved values} of the energy scale of inflation ($M$) and the present-day vacuum density ($V_{\Lambda}$). They are found to be $M=5.58\times 10^{-4}-4.57\times 10^{-3} M_P$ and $V_{\Lambda}=1.042\times 10^{-119}-4.688\times 10^{-116} M_P^4$. However, the $\alpha$-parameter is drastically constrained in two ways. Its lower end is fixed by the consistency analysis of the $k$-mode equations, while the upper end is evaluated as a derived expression of $\alpha$-cut-off through the aspects of EDE \textit{viz.,} the effects of \textit{Enhanced Symmetry Point} (ESP) in the potential during inflation. Improvised range of $\alpha$ is found to be $0.001\leq\alpha<0.1$ for the model parameters $\gamma$ and $n$ lying within $0.01\leq\gamma\leq 0.09$ and $8\leq n\leq 10$ respectively. These ranges are shown to be essential for satisfying the COBE/Planck normalized energy scale of inflation and the Planck-value of present-day vacuum density. If we choose $\gamma=0.0818$ and $n=8$, then we get $0.001\leq\alpha\leq 0.0186$. Thus, the lower and upper limits of $\alpha$ are diminished substantially, compared with those in the earlier studies. |
gr-qc/9412053 | Harald Soleng | Harald H. Soleng | Dark matter and non-Newtonian gravity from General Relativity coupled to
a fluid of strings | 12 pages, REVTeX, no figures | Gen.Rel.Grav.27:367-378,1995 | 10.1007/BF02107935 | NORDITA 94/69 | gr-qc | null | An exact solution of Einstein's field equations for a point mass surrounded
by a static, spherically symmetric fluid of strings is presented. The solution
is singular at the origin. Near the string cloud limit there is a $1/r$
correction to Newton's force law. It is noted that at large distances and small
accelerations, this law coincides with the phenomenological force law invented
by Milgrom in order to explain the flat rotation curves of galaxies without
introducing dark matter. When interpreted in the context of a cosmological
model with a string fluid, the new solution naturally explains why the critical
acceleration of Milgrom is of the same order of magnitude as the Hubble
parameter.
| [
{
"created": "Tue, 20 Dec 1994 13:29:07 GMT",
"version": "v1"
}
] | 2010-11-30 | [
[
"Soleng",
"Harald H.",
""
]
] | An exact solution of Einstein's field equations for a point mass surrounded by a static, spherically symmetric fluid of strings is presented. The solution is singular at the origin. Near the string cloud limit there is a $1/r$ correction to Newton's force law. It is noted that at large distances and small accelerations, this law coincides with the phenomenological force law invented by Milgrom in order to explain the flat rotation curves of galaxies without introducing dark matter. When interpreted in the context of a cosmological model with a string fluid, the new solution naturally explains why the critical acceleration of Milgrom is of the same order of magnitude as the Hubble parameter. |
1904.11338 | Danilo Artigas | Danilo Artigas Guimarey, Jakub Mielczarek, Carlo Rovelli | Minisuperspace model of compact phase space gravity | 13 pages, 5 figures | Phys. Rev. D 100, 043533 (2019) | 10.1103/PhysRevD.100.043533 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The kinematical phase space of classical gravitational field is flat (affine)
and unbounded. Because of this, field variables may tend to infinity leading to
appearance of singularities, which plague Einstein's theory of gravity. The
purpose of this article is to study the idea of generalizing the theory of
gravity by compactification of the phase space. We investigate the procedure of
compactification of the phase space on a minisuperspace gravitational model
with two dimensional phase space. In the affine limit, the model reduces to the
flat de Sitter cosmology. The phase space is generalized to the spherical case,
and the case of loop quantum cosmology is recovered in the cylindrical phase
space limit. Analysis of the dynamics reveals that the compactness of the phase
space leads to both UV and IR effects. In particular, the phase of re-collapse
appears, preventing the universe from expanding to infinite volume.
Furthermore, the quantum version of the model is investigated and the quantum
constraint is solved. As an example, we analyze the case with the spin quantum
number $s=2$, for which we determine transition amplitude between initial and
final state of the classical trajectory. The probability of the transition is
peaked at $\Lambda=0$.
| [
{
"created": "Thu, 25 Apr 2019 13:49:43 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Aug 2019 21:49:32 GMT",
"version": "v2"
}
] | 2019-08-28 | [
[
"Guimarey",
"Danilo Artigas",
""
],
[
"Mielczarek",
"Jakub",
""
],
[
"Rovelli",
"Carlo",
""
]
] | The kinematical phase space of classical gravitational field is flat (affine) and unbounded. Because of this, field variables may tend to infinity leading to appearance of singularities, which plague Einstein's theory of gravity. The purpose of this article is to study the idea of generalizing the theory of gravity by compactification of the phase space. We investigate the procedure of compactification of the phase space on a minisuperspace gravitational model with two dimensional phase space. In the affine limit, the model reduces to the flat de Sitter cosmology. The phase space is generalized to the spherical case, and the case of loop quantum cosmology is recovered in the cylindrical phase space limit. Analysis of the dynamics reveals that the compactness of the phase space leads to both UV and IR effects. In particular, the phase of re-collapse appears, preventing the universe from expanding to infinite volume. Furthermore, the quantum version of the model is investigated and the quantum constraint is solved. As an example, we analyze the case with the spin quantum number $s=2$, for which we determine transition amplitude between initial and final state of the classical trajectory. The probability of the transition is peaked at $\Lambda=0$. |
2303.14235 | Marc Schneider | M. Schneider, F. Del Porro, M. Herrero-Valea, S. Liberati | On the Resilience of Black Hole Evaporation: Gravitational Tunneling
through Universal Horizons | 16 pages, 4 figures, contribution to the proceedings of the
conference: "Avenues of Quantum Field Theory in Curved Space-time", Genova,
14-16. September 2022 | null | 10.1088/1742-6596/2531/1/012013 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using a quantum tunneling derivation, we show the resilience of Hawking
radiation in Lorentz violating gravity. In particular, we show that the
standard derivation of the Hawking effect in relativistic quantum field theory
can be extended to Lorentz breaking situations thanks to the presence of
universal horizons (causal boundaries for infinite speed signals) inside black
hole solutions. Correcting previous studies, we find that such boundaries are
characterized by a universal temperature governed by their surface gravity. We
also show that within the tunneling framework, given the pole structure and the
tunneling path, only a vacuum state set in the preferred frame provides a
consistent picture. Our results strongly suggest that the robustness of black
hole thermodynamics is ultimately linked to the consistency of quantum field
theories across causal boundaries.
| [
{
"created": "Fri, 24 Mar 2023 19:00:01 GMT",
"version": "v1"
}
] | 2023-06-27 | [
[
"Schneider",
"M.",
""
],
[
"Del Porro",
"F.",
""
],
[
"Herrero-Valea",
"M.",
""
],
[
"Liberati",
"S.",
""
]
] | Using a quantum tunneling derivation, we show the resilience of Hawking radiation in Lorentz violating gravity. In particular, we show that the standard derivation of the Hawking effect in relativistic quantum field theory can be extended to Lorentz breaking situations thanks to the presence of universal horizons (causal boundaries for infinite speed signals) inside black hole solutions. Correcting previous studies, we find that such boundaries are characterized by a universal temperature governed by their surface gravity. We also show that within the tunneling framework, given the pole structure and the tunneling path, only a vacuum state set in the preferred frame provides a consistent picture. Our results strongly suggest that the robustness of black hole thermodynamics is ultimately linked to the consistency of quantum field theories across causal boundaries. |
gr-qc/9307022 | Stephen Lau | James. W. York, Jr | Energy, Temperature, and Entropy of Black Holes Dressed with Quantum
Fields | (In the revised version some problematic fonts have been removed and
some carriage returns added. There are no changes to the text.), 11 pages,
IFP-469 | null | null | null | gr-qc | null | A deeper understanding of the thermal properties of black holes than we
presently have depends to a large degree on obtaining a firmer grasp of the
properties of the entropy. For such an understanding we must at least know the
basic relations among entropy, energy, and temperature of a black hole in
thermal equilibrium with quantized matter fields. Limiting attention to
spherical, uncharged (``Schwarzschild") holes, we will find that the basic
Bekenstein-Hawking relations have to be generalized when the hole is dressed by
quantum fields. Though this fact is not surprising, the corrections contain
surprises and are very instructive. My purpose here is to discuss several
aspects of this problem and to display some concrete results within the
framework of the semi-classical theory of quantum fields in curved spacetime.
| [
{
"created": "Mon, 19 Jul 1993 11:10:43 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jul 1993 18:52:43 GMT",
"version": "v2"
}
] | 2012-08-27 | [
[
"York,",
"James. W.",
"Jr"
]
] | A deeper understanding of the thermal properties of black holes than we presently have depends to a large degree on obtaining a firmer grasp of the properties of the entropy. For such an understanding we must at least know the basic relations among entropy, energy, and temperature of a black hole in thermal equilibrium with quantized matter fields. Limiting attention to spherical, uncharged (``Schwarzschild") holes, we will find that the basic Bekenstein-Hawking relations have to be generalized when the hole is dressed by quantum fields. Though this fact is not surprising, the corrections contain surprises and are very instructive. My purpose here is to discuss several aspects of this problem and to display some concrete results within the framework of the semi-classical theory of quantum fields in curved spacetime. |
2112.14063 | James Read | Niels Linnemann and James Read | Constructive Axiomatics in Spacetime Physics Part I: Walkthrough to the
Ehlers-Pirani-Schild Axiomatisation | 38 pages; compiled on LuaLaTeX; critical feedback welcome | null | null | null | gr-qc physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Ehlers-Pirani-Schild (EPS) constructive axiomatisation of general
relativity, published in 1972, purports to build up the kinematical structure
of that theory from only axioms which have indubitable empirical content. It
is, therefore, of profound significance both to the epistemology and to the
metaphysics of spacetime theories. This axiomatisation is, however,
self-consciously terse, rendering it difficult to ascertain whether it
succeeds. In this article, we provide a pedagogical walkthrough to the EPS
axiomatisation, filling relevant conceptual and mathematical gaps and rendering
explicit controversial assumptions. There are two companion papers, in which we
discuss the significance of constructive approaches to spacetime structure more
generally (Part II), and (with Emily Adlam) consider extensions of the EPS
axiomatisation towards quantum general relativity based upon quantum mechanical
inputs (Part III).
| [
{
"created": "Tue, 28 Dec 2021 09:19:55 GMT",
"version": "v1"
}
] | 2021-12-30 | [
[
"Linnemann",
"Niels",
""
],
[
"Read",
"James",
""
]
] | The Ehlers-Pirani-Schild (EPS) constructive axiomatisation of general relativity, published in 1972, purports to build up the kinematical structure of that theory from only axioms which have indubitable empirical content. It is, therefore, of profound significance both to the epistemology and to the metaphysics of spacetime theories. This axiomatisation is, however, self-consciously terse, rendering it difficult to ascertain whether it succeeds. In this article, we provide a pedagogical walkthrough to the EPS axiomatisation, filling relevant conceptual and mathematical gaps and rendering explicit controversial assumptions. There are two companion papers, in which we discuss the significance of constructive approaches to spacetime structure more generally (Part II), and (with Emily Adlam) consider extensions of the EPS axiomatisation towards quantum general relativity based upon quantum mechanical inputs (Part III). |
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