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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1512.01556 | Seth Hopper | Seth Hopper, Chris Kavanagh, Adrian C. Ottewill | Analytic self-force calculations in the post-Newtonian regime: eccentric
orbits on a Schwarzschild background | 20 pages, 2 figures, Updated with minor changes, mostly to references | Phys. Rev. D 93, 044010 (2016) | 10.1103/PhysRevD.93.044010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a method for solving the first-order field equations in a
post-Newtonian (PN) expansion. Our calculations generalize work of Bini and
Damour and subsequently Kavanagh et al., to consider eccentric orbits on a
Schwarzschild background. We derive expressions for the retarded metric
perturbation at the location of the particle for all $\ell$-modes. We find
that, despite first appearances, the Regge-Wheeler gauge metric perturbation is
$C^0$ at the particle for all $\ell$. As a first use of our solutions, we
compute the gauge-invariant quantity $\langle U \rangle$ through 4PN while
simultaneously expanding in eccentricity through $e^{10}$. By anticipating the
$e\to 1$ singular behavior at each PN order, we greatly improve the accuracy of
our results for large $e$. We use $\langle U \rangle$ to find 4PN contributions
to the effective one body potential $\hat Q$ through $e^{10}$ and at linear
order in the mass-ratio.
| [
{
"created": "Fri, 4 Dec 2015 21:00:11 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Dec 2015 19:34:16 GMT",
"version": "v2"
}
] | 2016-02-10 | [
[
"Hopper",
"Seth",
""
],
[
"Kavanagh",
"Chris",
""
],
[
"Ottewill",
"Adrian C.",
""
]
] | We present a method for solving the first-order field equations in a post-Newtonian (PN) expansion. Our calculations generalize work of Bini and Damour and subsequently Kavanagh et al., to consider eccentric orbits on a Schwarzschild background. We derive expressions for the retarded metric perturbation at the location of the particle for all $\ell$-modes. We find that, despite first appearances, the Regge-Wheeler gauge metric perturbation is $C^0$ at the particle for all $\ell$. As a first use of our solutions, we compute the gauge-invariant quantity $\langle U \rangle$ through 4PN while simultaneously expanding in eccentricity through $e^{10}$. By anticipating the $e\to 1$ singular behavior at each PN order, we greatly improve the accuracy of our results for large $e$. We use $\langle U \rangle$ to find 4PN contributions to the effective one body potential $\hat Q$ through $e^{10}$ and at linear order in the mass-ratio. |
0805.4268 | Rajeev Bhalerao | Budh Ram | Primordial matter density contrast and the size of the very early
universe in the Quantum Big Bang theory of the cosmological constant | 7 pages, no figs. v2: 8 pages, title changed, abstract and text
enlarged. Refs added | null | null | null | gr-qc astro-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the amount of primordial matter density contrast and the size of
the very early universe in the recent Quantum Big Bang theory [arXiv:0705.4549
[gr-qc](2007)] of the cosmological constant. We obtain $(\delta\rho/\rho)_M =
1.75 \times 10^{-5}$, {\it without} the introduction of an adjustable free
parameter. Harrison-Zel'dovich $k$-dependence with $A = 64/9\pi^2 = 0.72$ and
$n = 1$ in $|\delta_k|^2 = Ak^n$ arises inherently. The size of the universe
with which it enters the classical Friedmann-Robertson-Walker (FRW) phase comes
out to be 0.2 cm. We conclude that the hypothesis of classical inflation at an
early stage of cosmic evolution is {\bf not} needed.
| [
{
"created": "Wed, 28 May 2008 06:53:49 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Nov 2009 11:09:26 GMT",
"version": "v2"
}
] | 2009-11-13 | [
[
"Ram",
"Budh",
""
]
] | We calculate the amount of primordial matter density contrast and the size of the very early universe in the recent Quantum Big Bang theory [arXiv:0705.4549 [gr-qc](2007)] of the cosmological constant. We obtain $(\delta\rho/\rho)_M = 1.75 \times 10^{-5}$, {\it without} the introduction of an adjustable free parameter. Harrison-Zel'dovich $k$-dependence with $A = 64/9\pi^2 = 0.72$ and $n = 1$ in $|\delta_k|^2 = Ak^n$ arises inherently. The size of the universe with which it enters the classical Friedmann-Robertson-Walker (FRW) phase comes out to be 0.2 cm. We conclude that the hypothesis of classical inflation at an early stage of cosmic evolution is {\bf not} needed. |
1812.10115 | Ming Zhang | Ming Zhang, Wen-Biao Liu | Innermost stable circular orbits of charged spinning test particles | 6 pages | null | 10.1016/j.physletb.2018.12.051 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | The effects of a paritcle's spin and electric charge on its angular momentum,
energy and radius on the innermost stable circular orbit are investigated based
on the particle's equations of motion in a background of the Kerr-Newmann
spacetime. It is found that the particle's angular momentum and energy have
monotonous relationships with not only its spin but also its charge; it is also
discovered that the spinning particle's radius may change non-monotonously with
its charge. Hence, our result remarkably indicates that particles owning
identical spin but different charge may degenerate into a same last stable
circular orbit.
| [
{
"created": "Tue, 25 Dec 2018 15:01:50 GMT",
"version": "v1"
}
] | 2019-01-07 | [
[
"Zhang",
"Ming",
""
],
[
"Liu",
"Wen-Biao",
""
]
] | The effects of a paritcle's spin and electric charge on its angular momentum, energy and radius on the innermost stable circular orbit are investigated based on the particle's equations of motion in a background of the Kerr-Newmann spacetime. It is found that the particle's angular momentum and energy have monotonous relationships with not only its spin but also its charge; it is also discovered that the spinning particle's radius may change non-monotonously with its charge. Hence, our result remarkably indicates that particles owning identical spin but different charge may degenerate into a same last stable circular orbit. |
1612.05625 | Ofek Birnholtz | Gregory Ashton, Ofek Birnholtz, Miriam Cabero, Collin Capano, Thomas
Dent, Badri Krishnan, Grant David Meadors, Alex B. Nielsen, Alex Nitz, Julian
Westerweck | Comments on: "Echoes from the abyss: Evidence for Planck-scale structure
at black hole horizons" | null | null | null | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, Abedi, Dykaar and Afshordi claimed evidence for a repeating damped
echo signal following the binary black hole merger gravitational-wave events
recorded in the first observational period of the Advanced LIGO
interferometers. We discuss the methods of data analysis and significance
estimation leading to this claim, and identify several important shortcomings.
We conclude that their analysis does not provide significant observational
evidence for the existence of Planck-scale structure at black hole horizons,
and suggest renewed analysis correcting for these shortcomings.
| [
{
"created": "Fri, 16 Dec 2016 20:43:59 GMT",
"version": "v1"
}
] | 2016-12-19 | [
[
"Ashton",
"Gregory",
""
],
[
"Birnholtz",
"Ofek",
""
],
[
"Cabero",
"Miriam",
""
],
[
"Capano",
"Collin",
""
],
[
"Dent",
"Thomas",
""
],
[
"Krishnan",
"Badri",
""
],
[
"Meadors",
"Grant David",
""
],
[... | Recently, Abedi, Dykaar and Afshordi claimed evidence for a repeating damped echo signal following the binary black hole merger gravitational-wave events recorded in the first observational period of the Advanced LIGO interferometers. We discuss the methods of data analysis and significance estimation leading to this claim, and identify several important shortcomings. We conclude that their analysis does not provide significant observational evidence for the existence of Planck-scale structure at black hole horizons, and suggest renewed analysis correcting for these shortcomings. |
1109.6247 | Luc Blanchet | Peter Wolf, Luc Blanchet, Christian J. Bord\'e, Serge Reynaud,
Christophe Salomon and Clande Cohen-Tannoudji | Atom interferometry and the Einstein equivalence principle | 5 pages, to appear in the proceedings of the "46th Rencontres de
Moriond and GPhyS Colloquium on Gravitational Waves and Experimental
Gravity", la Thuile, March 20-27, 2011 | Experimental Gravity and Gravitational Waves, (Th\'e Gioi, 2011)
p.327-331 | null | null | gr-qc physics.atom-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The computation of the phase shift in a symmetric atom interferometer in the
presence of a gravitational field is reviewed. The difference of action-phase
integrals between the two paths of the interferometer is zero for any
Lagrangian which is at most quadratic in position and velocity. We emphasize
that in a large class of theories of gravity the atom interferometer permits a
test of the weak version of the equivalence principle (or universality of free
fall) by comparing the acceleration of atoms with that of ordinary bodies, but
is insensitive to that aspect of the equivalence principle known as the
gravitational redshift or universality of clock rates.
| [
{
"created": "Wed, 28 Sep 2011 15:44:23 GMT",
"version": "v1"
}
] | 2014-09-16 | [
[
"Wolf",
"Peter",
""
],
[
"Blanchet",
"Luc",
""
],
[
"Bordé",
"Christian J.",
""
],
[
"Reynaud",
"Serge",
""
],
[
"Salomon",
"Christophe",
""
],
[
"Cohen-Tannoudji",
"Clande",
""
]
] | The computation of the phase shift in a symmetric atom interferometer in the presence of a gravitational field is reviewed. The difference of action-phase integrals between the two paths of the interferometer is zero for any Lagrangian which is at most quadratic in position and velocity. We emphasize that in a large class of theories of gravity the atom interferometer permits a test of the weak version of the equivalence principle (or universality of free fall) by comparing the acceleration of atoms with that of ordinary bodies, but is insensitive to that aspect of the equivalence principle known as the gravitational redshift or universality of clock rates. |
1702.08455 | Abdel Nasser Tawfik | A. Tawfik (Egyptian Ctr. Theor. Phys., Cairo, WLCAPP, Cairo) and E.
Abou El Dahab (Egyptian Ctr. Theor. Phys., Cairo, MUTI, Cairo) | FLRW Cosmology with Horava-Lifshitz Gravity: Impacts of Equations of
State | 20 pages, 3 figures, accepted for publication in Int. J. Theor. Phys | Int. J. Theor. Phys. 56, 2122-2139 (2017) | 10.1007/s10773-017-3355-1 | ECTP-2014-09, WLCAPP-2014-09 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspired by Lifshitz theory for quantum critical phenomena in condensed
matter, Horava proposed a theory for quantum gravity with an anisotropic
scaling in ultraviolet. In Horava-Lifshitz gravity (HLG), we have studied the
impacts of six types of equations of state on the evolution of various
cosmological parameters such as Hubble parameters and scale factor. From the
comparison of the general relativity gravity with the HLG with detailed and
without with non-detailed balance conditions, remarkable differences are found.
Also, a noticeable dependence of singular and non-singular Big Bang on the
equations of state is observed. We conclude that HLG explains various epochs in
the early universe and might be able to reproduce the entire cosmic history
with and without singular Big Bang.
| [
{
"created": "Mon, 27 Feb 2017 17:41:50 GMT",
"version": "v1"
}
] | 2017-06-06 | [
[
"Tawfik",
"A.",
"",
"Egyptian Ctr. Theor. Phys., Cairo, WLCAPP, Cairo"
],
[
"Dahab",
"E. Abou El",
"",
"Egyptian Ctr. Theor. Phys., Cairo, MUTI, Cairo"
]
] | Inspired by Lifshitz theory for quantum critical phenomena in condensed matter, Horava proposed a theory for quantum gravity with an anisotropic scaling in ultraviolet. In Horava-Lifshitz gravity (HLG), we have studied the impacts of six types of equations of state on the evolution of various cosmological parameters such as Hubble parameters and scale factor. From the comparison of the general relativity gravity with the HLG with detailed and without with non-detailed balance conditions, remarkable differences are found. Also, a noticeable dependence of singular and non-singular Big Bang on the equations of state is observed. We conclude that HLG explains various epochs in the early universe and might be able to reproduce the entire cosmic history with and without singular Big Bang. |
1709.08099 | Dennis R\"atzel | Dennis R\"atzel, Ivette Fuentes | Testing small scale gravitational wave detectors with dynamical mass
distributions | 5 pages, 1 figure | null | null | null | gr-qc physics.ins-det quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent discovery of gravitational waves by the LIGO-Virgo collaboration
created renewed interest in the investigation of alternative gravitational
detector designs, such as small scale resonant detectors. In this article, it
is shown how proposed small scale detectors can be tested by generating
dynamical gravitational fields with appropriate distributions of moving masses.
A series of interesting experiments will be possible with this setup. In
particular, small scale detectors can be tested very early in the development
phase and tests can be used to progress quickly in their development. This
could contribute to the emerging field of gravitational wave astronomy.
| [
{
"created": "Sat, 23 Sep 2017 18:48:46 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Apr 2018 20:54:30 GMT",
"version": "v2"
}
] | 2018-05-02 | [
[
"Rätzel",
"Dennis",
""
],
[
"Fuentes",
"Ivette",
""
]
] | The recent discovery of gravitational waves by the LIGO-Virgo collaboration created renewed interest in the investigation of alternative gravitational detector designs, such as small scale resonant detectors. In this article, it is shown how proposed small scale detectors can be tested by generating dynamical gravitational fields with appropriate distributions of moving masses. A series of interesting experiments will be possible with this setup. In particular, small scale detectors can be tested very early in the development phase and tests can be used to progress quickly in their development. This could contribute to the emerging field of gravitational wave astronomy. |
1908.04102 | Jibitesh Dutta | Binod Chetry, Jibitesh Dutta and Wompherdeiki Khyllep | Thermodynamics of scalar field models with kinetic corrections | 20 pages, 9 figures, Accepted in IJMPD | null | 10.1142/S0218271819501633 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work, we compare the thermodynamical viability of two types of
non-canonical scalar field models with kinetic corrections: the square kinetic
and square root kinetic corrections. In modern cosmology, the generalised
second law of thermodynamics (GSLT) plays an important role in deciding
thermodynamical compliance of a model as one cannot consider a model to be
viable if it fails to respect GSLT. Hence, for comparing thermodynamical
viability, we examine the validity of GSLT for these two models. For this
purpose, by employing the Unified first law (UFL), we calculate the total
entropy of these two models in apparent and event horizons. The validity of
GSLT is then examined from the autonomous systems as the original expressions
of total entropy are very complicated. Although, at the background level, both
models give interesting cosmological dynamics, however, thermodynamically we
found that the square kinetic correction is more realistic as compared to the
square root kinetic correction. More precisely, the GSLT holds for the square
kinetic correction throughout the evolutionary history except only during the
radiation epoch where the scalar field may not represent a true description of
the matter content. On the other hand, the square root kinetic model fails to
satisfy the GSLT in major cosmological eras.
| [
{
"created": "Mon, 12 Aug 2019 11:54:12 GMT",
"version": "v1"
}
] | 2020-01-29 | [
[
"Chetry",
"Binod",
""
],
[
"Dutta",
"Jibitesh",
""
],
[
"Khyllep",
"Wompherdeiki",
""
]
] | In the present work, we compare the thermodynamical viability of two types of non-canonical scalar field models with kinetic corrections: the square kinetic and square root kinetic corrections. In modern cosmology, the generalised second law of thermodynamics (GSLT) plays an important role in deciding thermodynamical compliance of a model as one cannot consider a model to be viable if it fails to respect GSLT. Hence, for comparing thermodynamical viability, we examine the validity of GSLT for these two models. For this purpose, by employing the Unified first law (UFL), we calculate the total entropy of these two models in apparent and event horizons. The validity of GSLT is then examined from the autonomous systems as the original expressions of total entropy are very complicated. Although, at the background level, both models give interesting cosmological dynamics, however, thermodynamically we found that the square kinetic correction is more realistic as compared to the square root kinetic correction. More precisely, the GSLT holds for the square kinetic correction throughout the evolutionary history except only during the radiation epoch where the scalar field may not represent a true description of the matter content. On the other hand, the square root kinetic model fails to satisfy the GSLT in major cosmological eras. |
2010.03119 | Riccardo Sturani | Hebertt Leandro, Riccardo Sturani | A Gravitational non-Radiative Memory Effect | 13 pages, 1 figure. Appendix added in v2 with details of the
derivation of scalar potentials, as well as few references changed. Version
accepted for publication in GRG | null | 10.1007/s10714-021-02801-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the issue of memory effects, i.e. effects giving rise to a net
cumulative change of the configuration of test particles, using a toy model
describing the emission of radiation by a compact source and focusing on the
scalar, hence non-radiative, part of the Riemann curvature. Motivated by the
well known fact that gravitational radiation is accompanied by a memory effect,
i.e. a permanent displacement of the relative separation of test particles,
present after radiation has passed, we investigate the existence of an analog
effect in the non-radiative part of the gravitational field. While quadrupole
and higher multipoles undergo oscillations responsible for gravitational
radiation, energy, momentum and angular momentum are conserved charges
undergoing non-oscillatory change due to radiation emission. We show how the
source re-arrangement due to radiation emission produce time-dependent scalar
potentials which induce a time variation in the scalar part of the Riemann
curvature tensor. As a result, on general grounds a velocity memory effect
appears, depending on the inverse of the square of the distance of the observer
from the source, thus making it almost impossible to observe, as shown by
comparison to the planned gravitational detector noise spectral densities.
| [
{
"created": "Wed, 7 Oct 2020 02:34:53 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Mar 2021 00:27:51 GMT",
"version": "v2"
}
] | 2021-03-10 | [
[
"Leandro",
"Hebertt",
""
],
[
"Sturani",
"Riccardo",
""
]
] | We revisit the issue of memory effects, i.e. effects giving rise to a net cumulative change of the configuration of test particles, using a toy model describing the emission of radiation by a compact source and focusing on the scalar, hence non-radiative, part of the Riemann curvature. Motivated by the well known fact that gravitational radiation is accompanied by a memory effect, i.e. a permanent displacement of the relative separation of test particles, present after radiation has passed, we investigate the existence of an analog effect in the non-radiative part of the gravitational field. While quadrupole and higher multipoles undergo oscillations responsible for gravitational radiation, energy, momentum and angular momentum are conserved charges undergoing non-oscillatory change due to radiation emission. We show how the source re-arrangement due to radiation emission produce time-dependent scalar potentials which induce a time variation in the scalar part of the Riemann curvature tensor. As a result, on general grounds a velocity memory effect appears, depending on the inverse of the square of the distance of the observer from the source, thus making it almost impossible to observe, as shown by comparison to the planned gravitational detector noise spectral densities. |
gr-qc/0010032 | Brien C. Nolan | Brien C. Nolan (Dublin City University) | Sectors of spherical homothetic collapse | Now 40pp. plain latex including 11 of figures (using pstricks.tex).
Some proofs omitted for brevity (these are available in V1). To appear in
Classical and Quantum Gravity | Class.Quant.Grav. 18 (2001) 1651-1676 | 10.1088/0264-9381/18/9/304 | null | gr-qc | null | A study is undertaken of the gravitational collapse of spherically symmetric
thick shells admitting a homothetic Killing vector field under the assumption
that the energy momentum tensor corresponds to the absence of a pure outgoing
component of field. The energy-momentum tensor is not specified beyond this,
but is assumed to satisfy the strong and dominant energy conditions. The metric
tensor depends on only one function of the similarity variable and the energy
conditions identify a class of functions ${\cal F}$ to which the metric
function may belong. The possible global structure of such space-times is
determined, with particular attention being paid to singularities and their
temporal nature (naked or censored). It is shown that there are open subsets of
${\cal F}$ which correspond to naked singularities; in this sense, such
singularities are stable. Furthermore, it is shown that these singularities can
arise from regular (continuous), asymptotically flat initial data which deviate
from the trivial data by an arbitrarily small amount.
| [
{
"created": "Mon, 9 Oct 2000 16:52:42 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Mar 2001 14:43:35 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Nolan",
"Brien C.",
"",
"Dublin City University"
]
] | A study is undertaken of the gravitational collapse of spherically symmetric thick shells admitting a homothetic Killing vector field under the assumption that the energy momentum tensor corresponds to the absence of a pure outgoing component of field. The energy-momentum tensor is not specified beyond this, but is assumed to satisfy the strong and dominant energy conditions. The metric tensor depends on only one function of the similarity variable and the energy conditions identify a class of functions ${\cal F}$ to which the metric function may belong. The possible global structure of such space-times is determined, with particular attention being paid to singularities and their temporal nature (naked or censored). It is shown that there are open subsets of ${\cal F}$ which correspond to naked singularities; in this sense, such singularities are stable. Furthermore, it is shown that these singularities can arise from regular (continuous), asymptotically flat initial data which deviate from the trivial data by an arbitrarily small amount. |
2207.00435 | Gustavo Vicente dos Santos | Gustavo S. Vicente, Rudnei O. Ramos, Leila L. Graef | Gravitational Particle Production and the Validity of Effective
Descriptions in Loop Quantum Cosmology | Replaced with version matching the one published in the Physical
Review D | Physical Review D, Vol. 106, No. 4 (2022) | 10.1103/PhysRevD.106.043518 | null | gr-qc astro-ph.HE hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | The effective approach in Loop Quantum Cosmology (LQC) has provided means to
obtain predictions for observable quantities in LQC models. While an effective
dynamics in LQC has been extensively considered in different scenarios, a
robust demonstration of the validity of effective descriptions for the
perturbative level still requires further attention. The consistency of the
description adopted in most approaches requires the assumption of a test field
approximation, which is limited to the cases in which the backreaction of the
particles gravitationally produced can be safely neglected. Within the
framework of LQC, some of the main approaches to quantize the linear
perturbations are the dressed metric, the hybrid approaches and the
closed/deformed algebra approach. Here, we analyze the consistency of the test
field assumption in these frameworks by computing the energy density stored in
the particles gravitationally produced compared to the background energy
density. This analysis ultimately provides us with a consistency test of the
effective descriptions of LQC.
| [
{
"created": "Fri, 1 Jul 2022 13:55:47 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Jul 2022 22:10:55 GMT",
"version": "v2"
},
{
"created": "Wed, 13 Jul 2022 16:33:45 GMT",
"version": "v3"
},
{
"created": "Wed, 10 Aug 2022 14:55:52 GMT",
"version": "v4"
}
] | 2022-08-11 | [
[
"Vicente",
"Gustavo S.",
""
],
[
"Ramos",
"Rudnei O.",
""
],
[
"Graef",
"Leila L.",
""
]
] | The effective approach in Loop Quantum Cosmology (LQC) has provided means to obtain predictions for observable quantities in LQC models. While an effective dynamics in LQC has been extensively considered in different scenarios, a robust demonstration of the validity of effective descriptions for the perturbative level still requires further attention. The consistency of the description adopted in most approaches requires the assumption of a test field approximation, which is limited to the cases in which the backreaction of the particles gravitationally produced can be safely neglected. Within the framework of LQC, some of the main approaches to quantize the linear perturbations are the dressed metric, the hybrid approaches and the closed/deformed algebra approach. Here, we analyze the consistency of the test field assumption in these frameworks by computing the energy density stored in the particles gravitationally produced compared to the background energy density. This analysis ultimately provides us with a consistency test of the effective descriptions of LQC. |
1806.10364 | Flavio Bombacigno | Giovanni Montani, Claudia Mantero, Flavio Bombacigno, Francesco
Cianfrani, Gabriele Barca | Semi-classical and quantum analysis of the isotropic Universe in the
polymer paradigm | 11 pages, 11 figures, Accepted for publication in Physical Review D | Phys. Rev. D 99, 063534 (2019) | 10.1103/PhysRevD.99.063534 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We analyse the semi-classical and quantum dynamics of the isotropic Universe
in the framework of the Polymer Quantum mechanics, in order to implement a
cut-off physics on the initial singularity. We first identify in the Universe
cubed scale factor (i.e. the spatial volume) the suitable configuration
variable, providing a constant critical energy density, such that the Bounce
arises as intrinsic geometric feature. We then investigate the obtained
semi-classical Bounce dynamics for the primordial Universe, and we outline its
impact on the resolution of cosmological paradoxes, as soon as the
semi-classical evolution is extended (in the spirit of the Ehrenfest theorem)
to the collapsing pre-Bounce Universe. Finally, we validate the use of the
semi-classical effective dynamics by investigating the behaviour of the
expectation values of a proper semiclassical states. The present analysis has
the merit to enforce the equivalence between the Polymer quantization paradigm
in the Minisuperspace and the Loop Quantum Cosmology approach. In fact, our
study allows to define a precise correspondence between the Polymer cut-off
scale and the discrete geometric structure of LQG.
| [
{
"created": "Wed, 27 Jun 2018 09:27:55 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Nov 2018 15:59:44 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Mar 2019 22:21:04 GMT",
"version": "v3"
}
] | 2019-03-29 | [
[
"Montani",
"Giovanni",
""
],
[
"Mantero",
"Claudia",
""
],
[
"Bombacigno",
"Flavio",
""
],
[
"Cianfrani",
"Francesco",
""
],
[
"Barca",
"Gabriele",
""
]
] | We analyse the semi-classical and quantum dynamics of the isotropic Universe in the framework of the Polymer Quantum mechanics, in order to implement a cut-off physics on the initial singularity. We first identify in the Universe cubed scale factor (i.e. the spatial volume) the suitable configuration variable, providing a constant critical energy density, such that the Bounce arises as intrinsic geometric feature. We then investigate the obtained semi-classical Bounce dynamics for the primordial Universe, and we outline its impact on the resolution of cosmological paradoxes, as soon as the semi-classical evolution is extended (in the spirit of the Ehrenfest theorem) to the collapsing pre-Bounce Universe. Finally, we validate the use of the semi-classical effective dynamics by investigating the behaviour of the expectation values of a proper semiclassical states. The present analysis has the merit to enforce the equivalence between the Polymer quantization paradigm in the Minisuperspace and the Loop Quantum Cosmology approach. In fact, our study allows to define a precise correspondence between the Polymer cut-off scale and the discrete geometric structure of LQG. |
gr-qc/9805097 | Soker Noam | Amso Harpaz and Noam Soker (Univ. of Haifa) | Radiation from a Uniformly Accelerated Charge | Latex, uses aasms4.sty, 14 pages, Accepted for publication in General
Relativity and Gravitation. For a postscript file please contact Noam Soker:
soker@physics.technion.ac.il | Gen.Rel.Grav. 30 (1998) 1217-1227 | 10.1023/A:1026646928717 | null | gr-qc | null | The emission of radiation by a uniformly accelerated charge is analyzed.
According to the standard approach, a radiation is observed whenever there is a
relative acceleraion between the charge and the observer. Analyzing
difficulties that arose in the standard approach, we propose that a radaition
is created whenever a relative acceleration between the charge and its own
electric field exists. The electric field induced by a charge accelerated by an
external (nongravitational) force, is not accelerated with the charge. Hence
the electric field is curved in the instantanous rest frame of the accelerated
charge. This curvature gives rise to a stress force, and the work done to
overcome the stress force is the source of the energy carried by the radiation.
In this way, the "energy balance paradox" finds its solution.
| [
{
"created": "Thu, 28 May 1998 05:57:36 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Harpaz",
"Amso",
"",
"Univ. of Haifa"
],
[
"Soker",
"Noam",
"",
"Univ. of Haifa"
]
] | The emission of radiation by a uniformly accelerated charge is analyzed. According to the standard approach, a radiation is observed whenever there is a relative acceleraion between the charge and the observer. Analyzing difficulties that arose in the standard approach, we propose that a radaition is created whenever a relative acceleration between the charge and its own electric field exists. The electric field induced by a charge accelerated by an external (nongravitational) force, is not accelerated with the charge. Hence the electric field is curved in the instantanous rest frame of the accelerated charge. This curvature gives rise to a stress force, and the work done to overcome the stress force is the source of the energy carried by the radiation. In this way, the "energy balance paradox" finds its solution. |
2107.02456 | Stefan Czimek | Stefanos Aretakis, Stefan Czimek, Igor Rodnianski | Characteristic gluing to the Kerr family and application to spacelike
gluing | 88 pages, 10 figures | null | null | null | gr-qc math-ph math.AP math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is the third paper in a series of papers adressing the characteristic
gluing problem for the Einstein vacuum equations. We provide full details of
our characteristic gluing (including the $10$ charges) of strongly
asymptotically flat data to the data of a suitably chosen Kerr spacetime. The
choice of the Kerr spacetime crucially relies on relating the $10$ charges to
the ADM energy, linear momentum, angular momentum and the center-of-mass. As a
corollary, we obtain an alternative proof of the Corvino-Schoen spacelike
gluing construction for strongly asymptotically flat spacelike initial data.
| [
{
"created": "Tue, 6 Jul 2021 08:04:59 GMT",
"version": "v1"
}
] | 2021-07-07 | [
[
"Aretakis",
"Stefanos",
""
],
[
"Czimek",
"Stefan",
""
],
[
"Rodnianski",
"Igor",
""
]
] | This is the third paper in a series of papers adressing the characteristic gluing problem for the Einstein vacuum equations. We provide full details of our characteristic gluing (including the $10$ charges) of strongly asymptotically flat data to the data of a suitably chosen Kerr spacetime. The choice of the Kerr spacetime crucially relies on relating the $10$ charges to the ADM energy, linear momentum, angular momentum and the center-of-mass. As a corollary, we obtain an alternative proof of the Corvino-Schoen spacelike gluing construction for strongly asymptotically flat spacelike initial data. |
gr-qc/0702049 | Fabien Besnard | Fabien Besnard (CPL) | Canonical quantization and the spectral action, a nice example | A footnote on p 10 added wrt published version | J.Geom.Phys.57:1757-1770,2007 | 10.1016/j.geomphys.2007.02.007 | null | gr-qc math.OA | null | We study the canonical quantization of the theory given by Chamseddine-Connes
spectral action on a particular finite spectral triple with algebra
$M_2(\Cset)\oplus\Cset$. We define a quantization of the natural distance
associated with this noncommutative space and show that the quantum distance
operator has a discrete spectrum. We also show that it would be the same for
any other geometric quantity. Finally we propose a physical Hilbert space for
the quantum theory. This spectral triple had been previously considered by
Rovelli as a toy model, but with a different action which was not
gauge-invariant. The results are similar in both cases, but the
gauge-invariance of the spectral action manifests itself by the presence of a
non-trivial degeneracy structure for our distance operator.
| [
{
"created": "Thu, 8 Feb 2007 13:08:50 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Jun 2007 07:02:24 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Besnard",
"Fabien",
"",
"CPL"
]
] | We study the canonical quantization of the theory given by Chamseddine-Connes spectral action on a particular finite spectral triple with algebra $M_2(\Cset)\oplus\Cset$. We define a quantization of the natural distance associated with this noncommutative space and show that the quantum distance operator has a discrete spectrum. We also show that it would be the same for any other geometric quantity. Finally we propose a physical Hilbert space for the quantum theory. This spectral triple had been previously considered by Rovelli as a toy model, but with a different action which was not gauge-invariant. The results are similar in both cases, but the gauge-invariance of the spectral action manifests itself by the presence of a non-trivial degeneracy structure for our distance operator. |
gr-qc/9506003 | Anzhong Wang | Anzhong Wang and Patricio S. Letelier | Dynamic wormholes and Energy Conditions | To appear in Prog. Theor. Phys | Prog.Theor.Phys.94:137-142,1995 | 10.1143/PTP.94.137 | null | gr-qc | null | A class of exact solutions of the Einstein field equations representing
non-static wormholes that obey the {\em weak and dominant energy conditions }
is presented. Hence, in principle, these wormholes can be built with less
exotic matter than the static ones.
| [
{
"created": "Wed, 31 May 1995 12:38:11 GMT",
"version": "v1"
}
] | 2009-07-07 | [
[
"Wang",
"Anzhong",
""
],
[
"Letelier",
"Patricio S.",
""
]
] | A class of exact solutions of the Einstein field equations representing non-static wormholes that obey the {\em weak and dominant energy conditions } is presented. Hence, in principle, these wormholes can be built with less exotic matter than the static ones. |
2307.12670 | Andrea Geralico | Donato Bini, Andrea Geralico, Piero Rettegno | Spin-orbit contribution to radiative losses for spinning binaries with
aligned spins | 10 pages, no figures, revtex macros; v2 minimal text modifications | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the leading order contribution to radiative losses in the case of
spinning binaries with aligned spins due to their spin-orbit interaction. The
orbital average along hyperboliclike orbits is taken through an appropriate
spin-orbit modification to the quasi-Keplerian parametrization for nonspinning
bodies, which maintains the same functional form, but with spin-dependent
orbital elements. We perform consistency checks with existing PN-based and
PM-based results. In the former case, we compare our expressions for both
radiated energy and angular momentum with those obtained in [JHEP \textbf{04},
154 (2022)] by applying the boundary-to-bound correspondence to known results
for ellipticlike orbits, finding agreement. The linear momentum loss is instead
newly computed here. In the latter case, we also find agreement with the
low-velocity limit of recent calculations of the total radiated energy, angular
momentum and linear momentum in the framework of an extension of the worldline
quantum field theory approach to the classical scattering of spinning bodies at
the leading post-Minkowskian order [Phys. Rev. Lett. \textbf{128}, no.1, 011101
(2022), Phys. Rev. D \textbf{106}, no.4, 044013 (2022)]. We get exact
expressions of the radiative losses in terms of the orbital elements, even if
they are at the leading post-Newtonian order, so that their expansion for large
values of the eccentricity parameter (or equivalently of the impact parameter)
provides higher-order terms in the corresponding post-Minkowskian expansion,
which can be useful for future crosschecks of other approaches.
| [
{
"created": "Mon, 24 Jul 2023 10:20:09 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Sep 2023 14:07:33 GMT",
"version": "v2"
}
] | 2023-09-04 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
],
[
"Rettegno",
"Piero",
""
]
] | We compute the leading order contribution to radiative losses in the case of spinning binaries with aligned spins due to their spin-orbit interaction. The orbital average along hyperboliclike orbits is taken through an appropriate spin-orbit modification to the quasi-Keplerian parametrization for nonspinning bodies, which maintains the same functional form, but with spin-dependent orbital elements. We perform consistency checks with existing PN-based and PM-based results. In the former case, we compare our expressions for both radiated energy and angular momentum with those obtained in [JHEP \textbf{04}, 154 (2022)] by applying the boundary-to-bound correspondence to known results for ellipticlike orbits, finding agreement. The linear momentum loss is instead newly computed here. In the latter case, we also find agreement with the low-velocity limit of recent calculations of the total radiated energy, angular momentum and linear momentum in the framework of an extension of the worldline quantum field theory approach to the classical scattering of spinning bodies at the leading post-Minkowskian order [Phys. Rev. Lett. \textbf{128}, no.1, 011101 (2022), Phys. Rev. D \textbf{106}, no.4, 044013 (2022)]. We get exact expressions of the radiative losses in terms of the orbital elements, even if they are at the leading post-Newtonian order, so that their expansion for large values of the eccentricity parameter (or equivalently of the impact parameter) provides higher-order terms in the corresponding post-Minkowskian expansion, which can be useful for future crosschecks of other approaches. |
gr-qc/9901073 | Carlo Rovelli | Merced Montesinos, Carlo Rovelli and Thomas Thiemann | SL(2,R) model with two Hamiltonian constraints | 9 pages, 1 figure, revised version, to appear in Phys. Rev. D | Phys.Rev.D60:044009,1999 | 10.1103/PhysRevD.60.044009 | null | gr-qc hep-th quant-ph | null | We describe a simple dynamical model characterized by the presence of two
noncommuting Hamiltonian constraints. This feature mimics the constraint
structure of general relativity, where there is one Hamiltonian constraint
associated with each space point. We solve the classical and quantum dynamics
of the model, which turns out to be governed by an SL(2,R) gauge symmetry,
local in time. In classical theory, we solve the equations of motion, find a
SO(2,2) algebra of Dirac observables, find the gauge transformations for the
Lagrangian and canonical variables and for the Lagrange multipliers. In quantum
theory, we find the physical states, the quantum observables, and the physical
inner product, which is determined by the reality conditions. In addition, we
construct the classical and quantum evolving constants of the system. The model
illustrates how to describe physical gauge-invariant relative evolution when
coordinate time evolution is a gauge.
| [
{
"created": "Tue, 26 Jan 1999 09:57:32 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Jul 1999 16:44:06 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Montesinos",
"Merced",
""
],
[
"Rovelli",
"Carlo",
""
],
[
"Thiemann",
"Thomas",
""
]
] | We describe a simple dynamical model characterized by the presence of two noncommuting Hamiltonian constraints. This feature mimics the constraint structure of general relativity, where there is one Hamiltonian constraint associated with each space point. We solve the classical and quantum dynamics of the model, which turns out to be governed by an SL(2,R) gauge symmetry, local in time. In classical theory, we solve the equations of motion, find a SO(2,2) algebra of Dirac observables, find the gauge transformations for the Lagrangian and canonical variables and for the Lagrange multipliers. In quantum theory, we find the physical states, the quantum observables, and the physical inner product, which is determined by the reality conditions. In addition, we construct the classical and quantum evolving constants of the system. The model illustrates how to describe physical gauge-invariant relative evolution when coordinate time evolution is a gauge. |
2112.11333 | Omar Mustafa | Omar Mustafa | PDM Klein-Gordon oscillators in cosmic string spacetime in magnetic and
Aharonov-Bohm flux fields within the Kaluza-Klein theory | 14 pages, 5 figures | Annals of Physics 440 (2022) 168857 | 10.1016/j.aop.2022.168857 | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | In the cosmic string spacetime and within Kaluza-Klein theory (KKT)
backgrounds (indulging magnetic and Aharonov-Bohm flux fields), we introduce
and study position-dependent mass (PDM) Klein-Gordon (KG) oscillators. The
effective PDM is introduced as a deformation/defect in the momentum operator.
We show that there are four different ways to obtain KG-oscillator. Two of
which are readily known and the other two are obtained as byproducts of PDM
settings. Next, we provide a thorough analysis on the corresponding spectra
under different parametric effects, including the curvature parameter's effect.
Such analysis is used as a reference/lead model which is used in the discussion
of different PDM KG-oscillators models: a mixed power-law and exponential type
PDM model that yields a pseudo-confined PDM KG-oscillator in cosmic string
spacetime within KKT (i.e., the PDM KG-oscillators are confined in their own
PDM manifested Cornell-type confinement), and a PDM KG-oscillator confined in a
Cornell-type potential. Moreover, we extend our study and discuss a
non-Hermitian $\mathcal{PT}$-symmetric PDM-Coulombic-type KG-particle model in
cosmic string spacetime within KKT14
| [
{
"created": "Sat, 18 Dec 2021 17:39:42 GMT",
"version": "v1"
}
] | 2022-04-29 | [
[
"Mustafa",
"Omar",
""
]
] | In the cosmic string spacetime and within Kaluza-Klein theory (KKT) backgrounds (indulging magnetic and Aharonov-Bohm flux fields), we introduce and study position-dependent mass (PDM) Klein-Gordon (KG) oscillators. The effective PDM is introduced as a deformation/defect in the momentum operator. We show that there are four different ways to obtain KG-oscillator. Two of which are readily known and the other two are obtained as byproducts of PDM settings. Next, we provide a thorough analysis on the corresponding spectra under different parametric effects, including the curvature parameter's effect. Such analysis is used as a reference/lead model which is used in the discussion of different PDM KG-oscillators models: a mixed power-law and exponential type PDM model that yields a pseudo-confined PDM KG-oscillator in cosmic string spacetime within KKT (i.e., the PDM KG-oscillators are confined in their own PDM manifested Cornell-type confinement), and a PDM KG-oscillator confined in a Cornell-type potential. Moreover, we extend our study and discuss a non-Hermitian $\mathcal{PT}$-symmetric PDM-Coulombic-type KG-particle model in cosmic string spacetime within KKT14 |
0710.5721 | Martin Bojowald | Martin Bojowald and Rupam Das | The radiation equation of state and loop quantum gravity corrections | 11 pages, 1 figure | Phys.Rev.D75:123521,2007 | 10.1103/PhysRevD.75.123521 | IGPG-07/6-3 | gr-qc astro-ph | null | The equation of state for radiation is derived in a canonical formulation of
the electromagnetic field. This allows one to include correction terms expected
from canonical quantum gravity and to infer implications to the universe
evolution in radiation dominated epochs. Corrections implied by quantum
geometry can be interpreted in physically appealing ways, relating to the
conformal invariance of the classical equations.
| [
{
"created": "Tue, 30 Oct 2007 18:09:56 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Bojowald",
"Martin",
""
],
[
"Das",
"Rupam",
""
]
] | The equation of state for radiation is derived in a canonical formulation of the electromagnetic field. This allows one to include correction terms expected from canonical quantum gravity and to infer implications to the universe evolution in radiation dominated epochs. Corrections implied by quantum geometry can be interpreted in physically appealing ways, relating to the conformal invariance of the classical equations. |
2012.08542 | Sumanta Chakraborty | Sumanta Chakraborty and T. Padmanabhan | Eddington gravity with matter: An emergent perspective | 20 pages, no figures | Phys. Rev. D 103, 064033 (2021) | 10.1103/PhysRevD.103.064033 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe an action principle, within the framework of the Eddington
gravity, which incorporates the matter fields in a simple manner.
Interestingly, the gravitational field equations derived from this action is
identical to the Einstein's equations, in contrast with the earlier attempts in
the literature. The cosmological constant arises as an integration constant in
this approach. In fact, the derivation of the field equations demands the
existence of a non-zero cosmological constant, thereby providing the raison
d'\^{e}tre for a non-zero cosmological constant, implied by the current
observations. Several features of our approach strongly support the paradigm
that gravity is an emergent phenomenon and, in this perspective, our action
principle could have a possible origin in the microstructure of the spacetime.
We also discuss several extensions of the action principle, including the one
which can incorporate torsion in the spacetime. We also show that an
Eddington-like action can be constructed to obtain the field equations of the
Lanczos-Lovelock gravity.
| [
{
"created": "Tue, 15 Dec 2020 19:00:19 GMT",
"version": "v1"
}
] | 2021-03-24 | [
[
"Chakraborty",
"Sumanta",
""
],
[
"Padmanabhan",
"T.",
""
]
] | We describe an action principle, within the framework of the Eddington gravity, which incorporates the matter fields in a simple manner. Interestingly, the gravitational field equations derived from this action is identical to the Einstein's equations, in contrast with the earlier attempts in the literature. The cosmological constant arises as an integration constant in this approach. In fact, the derivation of the field equations demands the existence of a non-zero cosmological constant, thereby providing the raison d'\^{e}tre for a non-zero cosmological constant, implied by the current observations. Several features of our approach strongly support the paradigm that gravity is an emergent phenomenon and, in this perspective, our action principle could have a possible origin in the microstructure of the spacetime. We also discuss several extensions of the action principle, including the one which can incorporate torsion in the spacetime. We also show that an Eddington-like action can be constructed to obtain the field equations of the Lanczos-Lovelock gravity. |
2009.09833 | Bo Wang | Yi-Fu Cai, Chunshan Lin, Bo Wang, Sheng-Feng Yan | Sound speed resonance of the stochastic gravitational wave background | 6 pages, 2 figures | Phys. Rev. Lett. 126, 071303 (2021) | 10.1103/PhysRevLett.126.071303 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a novel mechanism to test time variation of the propagation speed
of gravitational waves (GWs) in light of GWs astronomy. As the stochastic GWs
experience the whole history of cosmic expansion, they encode potential
observational evidence of such variation. We report that, one feature of a
varying GWs speed is that the energy spectrum of GWs will present
resonantly-enhanced peaks if the GWs speed oscillates in time at high-energy
scales. Such oscillatory behaviour arises in a wide class of modified gravity
theories. The amplitude of these peaks can be at reach by current and
forthcoming GWs instruments, hence making the underlying theories falsifiable.
This mechanism reveals that probing the variation of GWs speed can be a
promising way to search for new physics beyond general relativity.
| [
{
"created": "Mon, 21 Sep 2020 13:11:52 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Sep 2020 13:30:30 GMT",
"version": "v2"
},
{
"created": "Sat, 20 Feb 2021 07:58:07 GMT",
"version": "v3"
}
] | 2021-02-23 | [
[
"Cai",
"Yi-Fu",
""
],
[
"Lin",
"Chunshan",
""
],
[
"Wang",
"Bo",
""
],
[
"Yan",
"Sheng-Feng",
""
]
] | We propose a novel mechanism to test time variation of the propagation speed of gravitational waves (GWs) in light of GWs astronomy. As the stochastic GWs experience the whole history of cosmic expansion, they encode potential observational evidence of such variation. We report that, one feature of a varying GWs speed is that the energy spectrum of GWs will present resonantly-enhanced peaks if the GWs speed oscillates in time at high-energy scales. Such oscillatory behaviour arises in a wide class of modified gravity theories. The amplitude of these peaks can be at reach by current and forthcoming GWs instruments, hence making the underlying theories falsifiable. This mechanism reveals that probing the variation of GWs speed can be a promising way to search for new physics beyond general relativity. |
1509.04665 | Kirill Bronnikov | K.A. Bronnikov, V.G. Krechet | Rotating cylindrical wormholes and energy conditions | 10 pages, no figures. Submitted to Proc. of the 9th Alexander
Friedmann International Seminar on Gravitation and Cosmology | Int. J. Mod. Phys. A 31, 1641022 (2016) | 10.1142/S0217751X16410220 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We seek wormholes among rotating cylindrically symmetric configurations in
general relativity. Exact wormhole solutions are presented with such sources of
gravity as a massless scalar field, a cosmological constant, and a scalar field
with an exponential potential. However, none of these solutions are
asymptotically flat, which excludes the existence of wormhole entrances as
local objects in our Universe. To overcome this difficulty, we try to build
configurations with flat asymptotic regions using the cut-and-paste procedure:
on both sides of the throat, a wormhole solution is matched to a properly
chosen region of flat space-time at some surfaces $\Sigma_-$ and $\Sigma_+$. It
is shown, however, that if the source of gravity in the throat region is a
scalar field with an arbitrary potential, then one or both thin shells
appearing on $\Sigma_-$ and $\Sigma_+$ inevitably violate the null energy
condition. Thus, although rotating wormhole solutions are easily found without
exotic matter, such matter is still necessary for obtaining asymptotic
flatness.
| [
{
"created": "Tue, 15 Sep 2015 18:19:54 GMT",
"version": "v1"
}
] | 2016-03-30 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Krechet",
"V. G.",
""
]
] | We seek wormholes among rotating cylindrically symmetric configurations in general relativity. Exact wormhole solutions are presented with such sources of gravity as a massless scalar field, a cosmological constant, and a scalar field with an exponential potential. However, none of these solutions are asymptotically flat, which excludes the existence of wormhole entrances as local objects in our Universe. To overcome this difficulty, we try to build configurations with flat asymptotic regions using the cut-and-paste procedure: on both sides of the throat, a wormhole solution is matched to a properly chosen region of flat space-time at some surfaces $\Sigma_-$ and $\Sigma_+$. It is shown, however, that if the source of gravity in the throat region is a scalar field with an arbitrary potential, then one or both thin shells appearing on $\Sigma_-$ and $\Sigma_+$ inevitably violate the null energy condition. Thus, although rotating wormhole solutions are easily found without exotic matter, such matter is still necessary for obtaining asymptotic flatness. |
1512.05192 | Behzad Eslam Panah | S. H. Hendi, S. Panahiyan, B. Eslam Panah and M. Momennia | Thermodynamic instability of nonlinearly charged black holes in
gravity's rainbow | 13 pages, 5 figures | Eur. Phys. J. C 76, 150 (2016) | 10.1140/epjc/s10052-016-3994-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the violation of Lorentz invariancy in quantum gravity, we study
black hole solutions in gravity's rainbow in context of Einstein gravity
coupled with various models of nonlinear electrodynamics. We regard an energy
dependent spacetime and obtain related metric functions and electric fields. We
show that there is an essential singularity at the origin which is covered with
an event horizon. We also compute the conserved and thermodynamical quantities
and examine the validity of the first law of thermodynamics in the presence of
rainbow functions. Finally, we investigate thermal stability conditions for
these black hole solutions in context of canonical ensemble. We show that
thermodynamical structure of the solutions depends on the choices of
nonlinearity parameters, charge and energy functions.
| [
{
"created": "Mon, 30 Nov 2015 14:10:04 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Mar 2016 16:25:39 GMT",
"version": "v2"
}
] | 2018-10-22 | [
[
"Hendi",
"S. H.",
""
],
[
"Panahiyan",
"S.",
""
],
[
"Panah",
"B. Eslam",
""
],
[
"Momennia",
"M.",
""
]
] | Motivated by the violation of Lorentz invariancy in quantum gravity, we study black hole solutions in gravity's rainbow in context of Einstein gravity coupled with various models of nonlinear electrodynamics. We regard an energy dependent spacetime and obtain related metric functions and electric fields. We show that there is an essential singularity at the origin which is covered with an event horizon. We also compute the conserved and thermodynamical quantities and examine the validity of the first law of thermodynamics in the presence of rainbow functions. Finally, we investigate thermal stability conditions for these black hole solutions in context of canonical ensemble. We show that thermodynamical structure of the solutions depends on the choices of nonlinearity parameters, charge and energy functions. |
2301.11364 | Konstantinos Pallikaris | Damianos Iosifidis and Konstantinos Pallikaris | Describing metric-affine theories anew: alternative frameworks, examples
and solutions | 35 pages, no figures | JCAP05(2023)037 | 10.1088/1475-7516/2023/05/037 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work we describe metric-affine theories anew by making a change of
field variables. A series of equivalent frameworks is presented and
identifications are worked out in detail. The advantage of applying the new
frameworks is that any MAG theory can be handled as a Riemannian theory with
additional fields. We study the Hilbert-Palatini action using the new field
variables and disclose interesting symmetries under $SO$ transformations in
field space. Then, we use solvable and suitable Riemannian theories as seed
models for solvable MAG theories, restricting ourselves to three examples. We
present a black hole solution with torsion and non-metricity which under a
certain tuning acquires a regular core. A de Sitter universe with the expansion
powered by 3-form torsion, is also reported.
| [
{
"created": "Thu, 26 Jan 2023 19:18:58 GMT",
"version": "v1"
},
{
"created": "Sat, 20 May 2023 09:53:04 GMT",
"version": "v2"
}
] | 2023-05-23 | [
[
"Iosifidis",
"Damianos",
""
],
[
"Pallikaris",
"Konstantinos",
""
]
] | In this work we describe metric-affine theories anew by making a change of field variables. A series of equivalent frameworks is presented and identifications are worked out in detail. The advantage of applying the new frameworks is that any MAG theory can be handled as a Riemannian theory with additional fields. We study the Hilbert-Palatini action using the new field variables and disclose interesting symmetries under $SO$ transformations in field space. Then, we use solvable and suitable Riemannian theories as seed models for solvable MAG theories, restricting ourselves to three examples. We present a black hole solution with torsion and non-metricity which under a certain tuning acquires a regular core. A de Sitter universe with the expansion powered by 3-form torsion, is also reported. |
2102.06063 | Nolene Naidu | Nolene F. Naidu, Robert S. Bogadi, Anand Kaisavelu and Megan Govender | Stability and Horizon Formation during Dissipative Collapse | 17 pages, 3 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the role played by density inhomogeneities and dissipation on
the final outcome of collapse of a self-gravitating sphere. By imposing a
perturbative scheme on the thermodynamical variables and gravitational
potentials we track the evolution of the collapse process starting off with an
initially static perfect fluid sphere which is shear-free. The collapsing core
dissipates energy in the form of a radial heat flux with the exterior spacetime
being filled with a superposition of null energy and an anisotropic string
distribution. The ensuing dynamical process slowly evolves into a shear-like
regime with contributions from the heat flux and density fluctuations. We show
that the anisotropy due to the presence of the strings drives the stellar fluid
towards instability with this effect being enhanced by the density
inhomogeneity. An interesting and novel consequence of this collapse scenario
is the delay in the formation of the horizon.
| [
{
"created": "Thu, 11 Feb 2021 15:09:52 GMT",
"version": "v1"
}
] | 2021-02-12 | [
[
"Naidu",
"Nolene F.",
""
],
[
"Bogadi",
"Robert S.",
""
],
[
"Kaisavelu",
"Anand",
""
],
[
"Govender",
"Megan",
""
]
] | We investigate the role played by density inhomogeneities and dissipation on the final outcome of collapse of a self-gravitating sphere. By imposing a perturbative scheme on the thermodynamical variables and gravitational potentials we track the evolution of the collapse process starting off with an initially static perfect fluid sphere which is shear-free. The collapsing core dissipates energy in the form of a radial heat flux with the exterior spacetime being filled with a superposition of null energy and an anisotropic string distribution. The ensuing dynamical process slowly evolves into a shear-like regime with contributions from the heat flux and density fluctuations. We show that the anisotropy due to the presence of the strings drives the stellar fluid towards instability with this effect being enhanced by the density inhomogeneity. An interesting and novel consequence of this collapse scenario is the delay in the formation of the horizon. |
1212.6661 | Michal Szczachor | A. Borowiec, J. Kowalski-Glikman and M. Szczachor | AdS-Maxwell Bf Theory As A Model Of Gravity And Bi-Gravity | 3 pages. Based on a talk given at the 13th Marcel Grossmann Meeting | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article presents an extended model of gravity obtained by gauging the
AdS-Mawell algebra. It involves additional fields that shift the spin
connection, leading effectively to theory of two independent connections.
Extension of algebraic structure by another tetrad gives rise to the model
described by a pair of Einstein equations.
| [
{
"created": "Sat, 29 Dec 2012 21:07:19 GMT",
"version": "v1"
}
] | 2013-01-01 | [
[
"Borowiec",
"A.",
""
],
[
"Kowalski-Glikman",
"J.",
""
],
[
"Szczachor",
"M.",
""
]
] | This article presents an extended model of gravity obtained by gauging the AdS-Mawell algebra. It involves additional fields that shift the spin connection, leading effectively to theory of two independent connections. Extension of algebraic structure by another tetrad gives rise to the model described by a pair of Einstein equations. |
1104.5192 | Lorenzo Iorio | Lorenzo Iorio | Orbital effects of spatial variations of fundamental coupling constants | Latex2e, 20 pages, 1 figure, 7 tables. Version accepted by Monthly
Notices of the Royal Astronomical Society (MNRAS). Error in the caption of
Table 5 corrected. References updated | Mon.Not.Roy.Astron.Soc.417:2392--2400,2011 | 10.1111/j.1365-2966.2011.19421.x | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We deal with the effects induced on the orbit of a test particle revolving
around a central body by putative spatial variations of fundamental coupling
constants $\zeta$. In particular, we assume a dipole gradient for $\zeta(\bds
r)/\bar{\zeta}$ along a generic direction $\bds{\hat{k}}$ in space. We
analytically work out the long-term variations of all the six standard
Keplerian orbital elements parameterizing the orbit of a test particle in a
gravitationally bound two-body system. It turns out that, apart from the
semi-major axis $a$, the eccentricity $e$, the inclination $I$, the longitude
of the ascending node $\Omega$, the longitude of pericenter $\pi$ and the mean
anomaly $\mathcal{M}$ undergo non-zero long-term changes. By using the usual
decomposition along the radial ($R$), transverse ($T$) and normal ($N$)
directions, we also analytically work out the long-term changes $\Delta
R,\Delta T,\Delta N$ and $\Delta v_R,\Delta v_T,\Delta v_N$ experienced by the
position and the velocity vectors $\bds r$ and $\bds v$ of the test particle.
It turns out that, apart from $\Delta N$, all the other five shifts do not
vanish over one full orbital revolution. In the calculation we do not use
\textit{a-priori} simplifying assumptions concerning $e$ and $I$. Thus, our
results are valid for a generic orbital geometry; moreover, they hold for any
gradient direction (abridged).
| [
{
"created": "Wed, 27 Apr 2011 17:09:17 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Apr 2011 17:17:47 GMT",
"version": "v2"
},
{
"created": "Sat, 30 Apr 2011 22:27:16 GMT",
"version": "v3"
},
{
"created": "Mon, 11 Jul 2011 16:16:54 GMT",
"version": "v4"
},
{
"c... | 2011-10-24 | [
[
"Iorio",
"Lorenzo",
""
]
] | We deal with the effects induced on the orbit of a test particle revolving around a central body by putative spatial variations of fundamental coupling constants $\zeta$. In particular, we assume a dipole gradient for $\zeta(\bds r)/\bar{\zeta}$ along a generic direction $\bds{\hat{k}}$ in space. We analytically work out the long-term variations of all the six standard Keplerian orbital elements parameterizing the orbit of a test particle in a gravitationally bound two-body system. It turns out that, apart from the semi-major axis $a$, the eccentricity $e$, the inclination $I$, the longitude of the ascending node $\Omega$, the longitude of pericenter $\pi$ and the mean anomaly $\mathcal{M}$ undergo non-zero long-term changes. By using the usual decomposition along the radial ($R$), transverse ($T$) and normal ($N$) directions, we also analytically work out the long-term changes $\Delta R,\Delta T,\Delta N$ and $\Delta v_R,\Delta v_T,\Delta v_N$ experienced by the position and the velocity vectors $\bds r$ and $\bds v$ of the test particle. It turns out that, apart from $\Delta N$, all the other five shifts do not vanish over one full orbital revolution. In the calculation we do not use \textit{a-priori} simplifying assumptions concerning $e$ and $I$. Thus, our results are valid for a generic orbital geometry; moreover, they hold for any gradient direction (abridged). |
gr-qc/9803008 | Piotr Chrusciel | Piotr T. Chrusciel | GR15 Workshop A3 --- Mathematical Studies of Field Equations --- A
report | 25 pages, Latex | null | null | Tours preprint 162/98 | gr-qc | null | This is a report of the A3 workshop ("Mathematical Studies of Field
Equations"), which was held in Poone during the GR15 Conference in December
1997.
| [
{
"created": "Mon, 2 Mar 1998 12:35:33 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Chrusciel",
"Piotr T.",
""
]
] | This is a report of the A3 workshop ("Mathematical Studies of Field Equations"), which was held in Poone during the GR15 Conference in December 1997. |
2205.06052 | Anisur Rahaman | Sohan Kumar Jha, Anisur Rahaman | Gravitational lensing by the hairy Schwarzschild black hole | 13 pages with fig. and tables. arXiv admin note: text overlap with
arXiv:gr-qc/0208075, arXiv:1910.02030 by other authors | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this manuscript, we consider the hairy Schwarzschild black hole that
evades the no-hair theorem. The hair is induced by an additional source from
surroundings, such as dark matter, that has a constant energy-momentum
tensor(EMT). We study the strong gravitational lensing of light in the
background of the hairy Schwarzschild black hole. We observe that the lensing
coefficient $\overline{a}$ increases with $\alpha$ but decreases with $\ell_0$.
The opposite effect is observed for the lensing coefficient $\overline{b}$ and
the impact parameter $b_m$. We also notice that the angular position
$\theta_\infty$ decreases with $\alpha$ but increases with $\ell_0$, whereas
the angular separation $s$ increases with $\alpha$ and decreases with $\ell_0$.
For all parameters mentioned, we regain their values for the Schwarzschild
black hole whenever we put either $\alpha=0$ or $\ell_0=1$. With the help of
the Gauss-Bonnet theorem, we briefly describe the weak gravitational lensing in
the background of the hairy Schwarzschild black hole.
| [
{
"created": "Thu, 12 May 2022 12:41:05 GMT",
"version": "v1"
}
] | 2022-05-13 | [
[
"Jha",
"Sohan Kumar",
""
],
[
"Rahaman",
"Anisur",
""
]
] | In this manuscript, we consider the hairy Schwarzschild black hole that evades the no-hair theorem. The hair is induced by an additional source from surroundings, such as dark matter, that has a constant energy-momentum tensor(EMT). We study the strong gravitational lensing of light in the background of the hairy Schwarzschild black hole. We observe that the lensing coefficient $\overline{a}$ increases with $\alpha$ but decreases with $\ell_0$. The opposite effect is observed for the lensing coefficient $\overline{b}$ and the impact parameter $b_m$. We also notice that the angular position $\theta_\infty$ decreases with $\alpha$ but increases with $\ell_0$, whereas the angular separation $s$ increases with $\alpha$ and decreases with $\ell_0$. For all parameters mentioned, we regain their values for the Schwarzschild black hole whenever we put either $\alpha=0$ or $\ell_0=1$. With the help of the Gauss-Bonnet theorem, we briefly describe the weak gravitational lensing in the background of the hairy Schwarzschild black hole. |
2011.03932 | Naoki Tsukamoto | Naoki Tsukamoto | Gravitational lensing in the Simpson-Visser black-bounce spacetime in a
strong deflection limit | 13 pages, 6 figures, minor correction, references added, accepted for
publication in Physical Review D | Phys. Rev. D 103, 024033 (2021) | 10.1103/PhysRevD.103.024033 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A Simpson-Visser spacetime has two nonnegative parameters $a$ and $m$ and its
metric is correspond with (i) a Schwarzschild metric for $a=0$ and $m\neq0$,
(ii) a regular black hole metric for $a<2m$, (iii) a one-way traversable
wormhole metric for $a=2m$, (vi) a two-way traversable wormhole metric for
$a>2m$, and (v) an Ellis-Bronnikov wormhole metric for $a\neq0$ and $m=0$. The
spacetime is one of the most useful spacetimes for the purpose of
comprehensively understanding gravitational lensing of light rays reflected by
a photon sphere of black holes and wormholes. We have investigated
gravitational lensing in the Simpson-Visser spacetime in a strong deflection
limit in all the nonnegative parameters of $a$ and $m$. In a case of $a=3m$,
two photon spheres and an antiphoton sphere at the throat degenerate into a
marginally unstable photon sphere. The deflection angle of the light rays
reflected by the marginally unstable photon sphere at the throat diverges
nonlogarithmically in the strong deflection limit.
| [
{
"created": "Sun, 8 Nov 2020 09:14:04 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Jan 2021 04:44:29 GMT",
"version": "v2"
}
] | 2021-01-27 | [
[
"Tsukamoto",
"Naoki",
""
]
] | A Simpson-Visser spacetime has two nonnegative parameters $a$ and $m$ and its metric is correspond with (i) a Schwarzschild metric for $a=0$ and $m\neq0$, (ii) a regular black hole metric for $a<2m$, (iii) a one-way traversable wormhole metric for $a=2m$, (vi) a two-way traversable wormhole metric for $a>2m$, and (v) an Ellis-Bronnikov wormhole metric for $a\neq0$ and $m=0$. The spacetime is one of the most useful spacetimes for the purpose of comprehensively understanding gravitational lensing of light rays reflected by a photon sphere of black holes and wormholes. We have investigated gravitational lensing in the Simpson-Visser spacetime in a strong deflection limit in all the nonnegative parameters of $a$ and $m$. In a case of $a=3m$, two photon spheres and an antiphoton sphere at the throat degenerate into a marginally unstable photon sphere. The deflection angle of the light rays reflected by the marginally unstable photon sphere at the throat diverges nonlogarithmically in the strong deflection limit. |
2110.05546 | Marco Antonelli | Lorenzo Gavassino, Marco Antonelli, Brynmor Haskell | Extending Israel and Stewart hydrodynamics to relativistic superfluids
via Carter's multifluid approach | 34 pages, 1 figure | Phys. Rev. D 105, 045011 - February 2022 | 10.1103/PhysRevD.105.045011 | null | gr-qc astro-ph.HE nucl-th physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a relativistic model for bulk viscosity and heat conduction in a
superfluid. Building on the principles of Unified Extended Irreversible
Thermodynamics, the model is derived from Carter's multifluid approach for a
theory with 3 four-currents: particles, entropy, and quasi-particles.
Dissipation arises directly from the fact that the quasi-particle four-current
is an independent degree of freedom that does not necessarily comove with the
entropy. For small deviations from local thermodynamic equilibrium, the model
provides an extension of the Israel-Stewart theory to superfluid systems. It
can, therefore, be made hyperbolic, causal and stable if the microscopic input
is accurate. The non-dissipative limit of the model is the relativistic
two-fluid model of Carter, Khalatnikov and Gusakov. The Newtonian limit of the
model is an Extended-Irreversible-Thermodynamic extension of Landau's two-fluid
model. The model predicts the existence of four bulk viscosity coefficients and
accounts for their microscopic origin, providing their exact formulas in terms
of the quasi-particle creation rate. Furthermore, when fast oscillations of
small amplitude around the equilibrium are considered, the relaxation-time term
in the telegraph-type equations for the bulk viscosities accounts directly for
their expected dependence on the frequency.
| [
{
"created": "Mon, 11 Oct 2021 18:31:57 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Feb 2022 15:26:44 GMT",
"version": "v2"
}
] | 2022-02-23 | [
[
"Gavassino",
"Lorenzo",
""
],
[
"Antonelli",
"Marco",
""
],
[
"Haskell",
"Brynmor",
""
]
] | We construct a relativistic model for bulk viscosity and heat conduction in a superfluid. Building on the principles of Unified Extended Irreversible Thermodynamics, the model is derived from Carter's multifluid approach for a theory with 3 four-currents: particles, entropy, and quasi-particles. Dissipation arises directly from the fact that the quasi-particle four-current is an independent degree of freedom that does not necessarily comove with the entropy. For small deviations from local thermodynamic equilibrium, the model provides an extension of the Israel-Stewart theory to superfluid systems. It can, therefore, be made hyperbolic, causal and stable if the microscopic input is accurate. The non-dissipative limit of the model is the relativistic two-fluid model of Carter, Khalatnikov and Gusakov. The Newtonian limit of the model is an Extended-Irreversible-Thermodynamic extension of Landau's two-fluid model. The model predicts the existence of four bulk viscosity coefficients and accounts for their microscopic origin, providing their exact formulas in terms of the quasi-particle creation rate. Furthermore, when fast oscillations of small amplitude around the equilibrium are considered, the relaxation-time term in the telegraph-type equations for the bulk viscosities accounts directly for their expected dependence on the frequency. |
1907.00683 | Badri Krishnan | Daniel Pook-Kolb, Ofek Birnholtz, Badri Krishnan and Erik Schnetter | Self-intersecting marginally outer trapped surfaces | 17 pages, 13 figures | Phys. Rev. D 100, 084044 (2019) | 10.1103/PhysRevD.100.084044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have shown previously that a merger of marginally outer trapped surfaces
(MOTSs) occurs in a binary black hole merger and that there is a continuous
sequence of MOTSs which connects the initial two black holes to the final one.
In this paper, we confirm this scenario numerically and we detail further
improvements in the numerical methods for locating MOTSs. With these
improvements, we confirm the merger scenario and demonstrate the existence of
self-intersecting MOTSs formed in the immediate aftermath of the merger. These
results will allow us to track physical quantities across the non-linear merger
process and to potentially infer properties of the merger from gravitational
wave observations.
| [
{
"created": "Mon, 1 Jul 2019 12:10:21 GMT",
"version": "v1"
}
] | 2019-10-23 | [
[
"Pook-Kolb",
"Daniel",
""
],
[
"Birnholtz",
"Ofek",
""
],
[
"Krishnan",
"Badri",
""
],
[
"Schnetter",
"Erik",
""
]
] | We have shown previously that a merger of marginally outer trapped surfaces (MOTSs) occurs in a binary black hole merger and that there is a continuous sequence of MOTSs which connects the initial two black holes to the final one. In this paper, we confirm this scenario numerically and we detail further improvements in the numerical methods for locating MOTSs. With these improvements, we confirm the merger scenario and demonstrate the existence of self-intersecting MOTSs formed in the immediate aftermath of the merger. These results will allow us to track physical quantities across the non-linear merger process and to potentially infer properties of the merger from gravitational wave observations. |
2204.12405 | Oleg Zaslavskii | O. B. Zaslavskii | Confined Penrose process and black-hole bomb | 16 pages. Presentation improved and slightly expanded, typos
corrected. Matches published version | Phys. Rev. D 106, 024037 (2022) | 10.1103/PhysRevD.106.024037 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | We consider the decay of a particle with some energy $E_{0}>0$ inside the
ergosphere of a black hole. After the first decay one of particles with the
energy $E_{1}<0$ falls towards a black hole while the second one with $%
E_{2}>E_{0}\,\ $moves in the outward direction. It bounces back from a
reflecting shell and, afterwards, the process repeats. For radial motion of
charged particles in the Reissner-Nordst\"{o}m metric, the result depends
strongly on a concrete scenario. In particular, an indefinitely large growth of
energy inside a shell is possible that gives rise to a black-hole bomb. We also
consider a similar multiple process with neutral particles in the background of
a rotating axially symmetric stationary black hole. We demonstrate that, if
particle decay occurs in the turning point, a black-hole bomb in this case is
impossible at all. For a generic point inside the ergoregion, there is a
condition for a black-hole bomb to exist. It relates the ratio of masses before
and after decay and the velocity of a fragment in the center of mass frame.
| [
{
"created": "Tue, 26 Apr 2022 16:02:27 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Jul 2022 09:05:35 GMT",
"version": "v2"
}
] | 2022-08-31 | [
[
"Zaslavskii",
"O. B.",
""
]
] | We consider the decay of a particle with some energy $E_{0}>0$ inside the ergosphere of a black hole. After the first decay one of particles with the energy $E_{1}<0$ falls towards a black hole while the second one with $% E_{2}>E_{0}\,\ $moves in the outward direction. It bounces back from a reflecting shell and, afterwards, the process repeats. For radial motion of charged particles in the Reissner-Nordst\"{o}m metric, the result depends strongly on a concrete scenario. In particular, an indefinitely large growth of energy inside a shell is possible that gives rise to a black-hole bomb. We also consider a similar multiple process with neutral particles in the background of a rotating axially symmetric stationary black hole. We demonstrate that, if particle decay occurs in the turning point, a black-hole bomb in this case is impossible at all. For a generic point inside the ergoregion, there is a condition for a black-hole bomb to exist. It relates the ratio of masses before and after decay and the velocity of a fragment in the center of mass frame. |
1301.7201 | Maksym Teslyk | Maksym Teslyk and Olena Teslyk | Scalar field entanglement entropy for small Schwarzschild black hole | 10 pages | Class. Quantum Grav. 30 (2013) 125013 | 10.1088/0264-9381/30/12/125013 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider scalar field entanglement entropy generated with black hole of
(sub)planck mass scale thus implying the unitary evolution of gravity. The
dependence on the dimension of the Hilbert space for degrees of freedom located
behind the horizon is taken into account. The obtained results contain
polylogarithmic terms.
| [
{
"created": "Wed, 30 Jan 2013 11:26:52 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Feb 2013 15:04:12 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Apr 2013 11:40:14 GMT",
"version": "v3"
}
] | 2013-05-20 | [
[
"Teslyk",
"Maksym",
""
],
[
"Teslyk",
"Olena",
""
]
] | We consider scalar field entanglement entropy generated with black hole of (sub)planck mass scale thus implying the unitary evolution of gravity. The dependence on the dimension of the Hilbert space for degrees of freedom located behind the horizon is taken into account. The obtained results contain polylogarithmic terms. |
2011.03571 | Aasim Jan | A. Z. Jan (1), A. B. Yelikar (1), J. Lange (2 and 1) and R.
O'Shaughnessy (1) ((1) Rochester Institute of Technology, (2) Brown
University) | Assessing and marginalizing over compact binary coalescence waveform
systematics with RIFT | 8 pages, 7 figures | Phys. Rev. D 102, 124069 (2020) | 10.1103/PhysRevD.102.124069 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As Einstein's equations for binary compact object inspiral have only been
approximately or intermittently solved by analytic or numerical methods, the
models used to infer parameters of gravitational wave (GW) sources are subject
to waveform modeling uncertainty. Using a simple scenario, we illustrate these
differences, then introduce a very efficient technique to marginalize over
waveform uncertainties, relative to a pre-specified sequence of waveform
models. Being based on RIFT, a very efficient parameter inference engine, our
technique can directly account for any available models, including very
accurate but computationally costly waveforms. Our evidence and
likelihood-based method works robustly on a point-by-point basis, enabling
accurate marginalization for models with strongly disjoint posteriors while
simultaneously increasing the reusability and efficiency of our intermediate
calculations.
| [
{
"created": "Fri, 6 Nov 2020 19:47:34 GMT",
"version": "v1"
}
] | 2021-01-04 | [
[
"Jan",
"A. Z.",
"",
"2 and 1"
],
[
"Yelikar",
"A. B.",
"",
"2 and 1"
],
[
"Lange",
"J.",
"",
"2 and 1"
],
[
"O'Shaughnessy",
"R.",
""
]
] | As Einstein's equations for binary compact object inspiral have only been approximately or intermittently solved by analytic or numerical methods, the models used to infer parameters of gravitational wave (GW) sources are subject to waveform modeling uncertainty. Using a simple scenario, we illustrate these differences, then introduce a very efficient technique to marginalize over waveform uncertainties, relative to a pre-specified sequence of waveform models. Being based on RIFT, a very efficient parameter inference engine, our technique can directly account for any available models, including very accurate but computationally costly waveforms. Our evidence and likelihood-based method works robustly on a point-by-point basis, enabling accurate marginalization for models with strongly disjoint posteriors while simultaneously increasing the reusability and efficiency of our intermediate calculations. |
gr-qc/9710138 | Luis Lehner | R. Gomez, L. Lehner, R.L. Marsa and J. Winicour | Moving Black Holes in 3D | 11 pages + 6 figures | Phys.Rev. D57 (1998) 4778-4788 | 10.1103/PhysRevD.57.4778 | null | gr-qc | null | We model a radiating, moving black hole in terms of a worldtube-nullcone
boundary value problem. We evolve this data in the region interior to the
worldtube but exterior to a trapped surface by means of a characteristic
evolution based upon a family of ingoing null hypersurfaces. Data on the
worldtube is induced from a Schwarzschild spacetime but the worldtube is
allowed to move relative to the static Schwarzschild trajectories. When the
worldtube is stationary (static or rotating in place), a distorted black hole
inside it evolves to equilibrium with the Schwarzschild boundary. A boost of
the worldtube with respect to the Schwarzschild black hole does not affect
these results. The code also stably tracks an unlimited number of orbits when
the worldtube wobbles periodically. The work establishes that characteristic
evolution can evolve a spacetime with a distorted black hole moving on a
3-dimensional grid with the controlled accuracy and long term stability
necessary to investigate new facets of black hole physics.
| [
{
"created": "Fri, 31 Oct 1997 19:40:55 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Gomez",
"R.",
""
],
[
"Lehner",
"L.",
""
],
[
"Marsa",
"R. L.",
""
],
[
"Winicour",
"J.",
""
]
] | We model a radiating, moving black hole in terms of a worldtube-nullcone boundary value problem. We evolve this data in the region interior to the worldtube but exterior to a trapped surface by means of a characteristic evolution based upon a family of ingoing null hypersurfaces. Data on the worldtube is induced from a Schwarzschild spacetime but the worldtube is allowed to move relative to the static Schwarzschild trajectories. When the worldtube is stationary (static or rotating in place), a distorted black hole inside it evolves to equilibrium with the Schwarzschild boundary. A boost of the worldtube with respect to the Schwarzschild black hole does not affect these results. The code also stably tracks an unlimited number of orbits when the worldtube wobbles periodically. The work establishes that characteristic evolution can evolve a spacetime with a distorted black hole moving on a 3-dimensional grid with the controlled accuracy and long term stability necessary to investigate new facets of black hole physics. |
1702.02694 | Florian Beyer | Florian Beyer, Leon Escobar, J\"org Frauendiener | Criticality of inhomogeneous Nariai-like cosmological models | 34 pages, 17 figures | Phys. Rev. D 95, 084030 (2017) | 10.1103/PhysRevD.95.084030 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we construct and study solutions of Einstein's equations in
vacuum with a positive cosmological constant which can be considered as
inhomogeneous generalizations of the Nariai cosmological model. Similar to this
Nariai spacetime, our solutions are at the borderline between gravitational
collapse and de-Sitter-like exponential expansion. Our studies focus in
particular on the intriguing oscillatory dynamics which we discover. Our
investigations are carried out both analytically (using heuristic mode analysis
arguments) and numerically (using the numerical infrastructure recently
introduced by us).
| [
{
"created": "Thu, 9 Feb 2017 03:58:24 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Apr 2017 23:21:07 GMT",
"version": "v2"
}
] | 2017-07-12 | [
[
"Beyer",
"Florian",
""
],
[
"Escobar",
"Leon",
""
],
[
"Frauendiener",
"Jörg",
""
]
] | In this paper, we construct and study solutions of Einstein's equations in vacuum with a positive cosmological constant which can be considered as inhomogeneous generalizations of the Nariai cosmological model. Similar to this Nariai spacetime, our solutions are at the borderline between gravitational collapse and de-Sitter-like exponential expansion. Our studies focus in particular on the intriguing oscillatory dynamics which we discover. Our investigations are carried out both analytically (using heuristic mode analysis arguments) and numerically (using the numerical infrastructure recently introduced by us). |
2408.03217 | Adriano Rocha Soares | A. R. Soares, R. L. L. Vit\'oria, C. F. S. Pereira | Topologically Charged Holonomy corrected Schwarzschild black hole
lensing | arXiv admin note: text overlap with arXiv:2309.05106 | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we theoretically investigate the deflection of light produced
by a topologically charged Holonomy corrected Schwarzschild black hole. The
study is carried out both in the weak field limit and in the strong field
limit. We analytically deduced the expansions for light deflection in the two
limits and, from them, we determined the observables in order to provide
elements so that observational tools are able to identify these solutions. We
model possible gravitational scenarios in order to verify the possible
gravitational characteristics of the solution.
| [
{
"created": "Tue, 6 Aug 2024 14:23:53 GMT",
"version": "v1"
}
] | 2024-08-07 | [
[
"Soares",
"A. R.",
""
],
[
"Vitória",
"R. L. L.",
""
],
[
"Pereira",
"C. F. S.",
""
]
] | In this paper, we theoretically investigate the deflection of light produced by a topologically charged Holonomy corrected Schwarzschild black hole. The study is carried out both in the weak field limit and in the strong field limit. We analytically deduced the expansions for light deflection in the two limits and, from them, we determined the observables in order to provide elements so that observational tools are able to identify these solutions. We model possible gravitational scenarios in order to verify the possible gravitational characteristics of the solution. |
gr-qc/0201089 | Artem Starodubtsev | Artem Starodubtsev | String theory in a vertex operator representation: a simple model for
testing loop quantum gravity | 23 pages 5 figures | null | null | null | gr-qc hep-th | null | The loop quantum gravity technique is applied to the free bosonic string. A
Hilbert space similar to loop space in loop quantum gravity as well as
representations of diffeomorphism and hamiltonian constraints on it are
constructed. The string in this representation can be viewed as a set of
interacting relativistic particles each carrying a certain momentum. Two
different regularizations of the hamiltonian constraint are proposed. The first
of them is anomaly-free and give rise to interaction very similar to that of
two dimensional $\phi^4$-model. The second version of hamiltonian constraint is
similar to $\phi^3$-model and contains an anomaly. A possible relation of these
two models to the conventional quantization of the string based on Fock space
representation is discussed.
| [
{
"created": "Mon, 28 Jan 2002 22:41:22 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Starodubtsev",
"Artem",
""
]
] | The loop quantum gravity technique is applied to the free bosonic string. A Hilbert space similar to loop space in loop quantum gravity as well as representations of diffeomorphism and hamiltonian constraints on it are constructed. The string in this representation can be viewed as a set of interacting relativistic particles each carrying a certain momentum. Two different regularizations of the hamiltonian constraint are proposed. The first of them is anomaly-free and give rise to interaction very similar to that of two dimensional $\phi^4$-model. The second version of hamiltonian constraint is similar to $\phi^3$-model and contains an anomaly. A possible relation of these two models to the conventional quantization of the string based on Fock space representation is discussed. |
1301.2077 | Alessandro Fabbri | Roberto Balbinot, Alessandro Fabbri and Carlos Mayoral | Hawking effect in BECs acoustic white holes | 29 pages, 32 figures | null | null | null | gr-qc cond-mat.quant-gas hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Bogoliubov pseudoparticle creation in a BEC undergoing a WH like flow is
investigated analytically in the case of a one dimensional geometry with
stepwise homogeneous regions. Comparison of the results with those
corresponding to a BH flow is performed. The implications for the analogous
gravitational problem is discussed.
| [
{
"created": "Thu, 10 Jan 2013 10:40:56 GMT",
"version": "v1"
}
] | 2013-01-11 | [
[
"Balbinot",
"Roberto",
""
],
[
"Fabbri",
"Alessandro",
""
],
[
"Mayoral",
"Carlos",
""
]
] | Bogoliubov pseudoparticle creation in a BEC undergoing a WH like flow is investigated analytically in the case of a one dimensional geometry with stepwise homogeneous regions. Comparison of the results with those corresponding to a BH flow is performed. The implications for the analogous gravitational problem is discussed. |
1912.09750 | Alejandro Perez | Lautaro Amadei, Hongguang Liu, Alejandro Perez | Unitarity and information in quantum gravity: a simple example | null | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In approaches to quantum gravity, where smooth spacetime is an emergent
approximation of a discrete Planckian fundamental structure, any effective
smooth field theoretical description would miss part of the fundamental degrees
of freedom and thus break unitarity. This is applicable also to trivial
gravitational field (low energy) idealizations realized by the use of the
Minkowski background geometry which, as any other spacetime geometry,
corresponds, in the fundamental description, to infinitely many different and
closely degenerate discrete microstates. The existence of such microstates
provides a large reservoir for information to be coded at the end of black hole
evaporation and thus opens the way to a natural resolution of the black hole
evaporation information puzzle.
In this paper we show that these expectations can be made precise in a simple
quantum gravity model for cosmology motivated by loop quantum gravity.
Concretely, even when the model is fundamentally unitary, when microscopic
degrees of freedom irrelevant to low-energy cosmological observers are suitably
ignored, pure states in the effective description evolve into mixed states due
to decoherence with the Planckian microscopic structure. Moreover, in the
relevant physical regime these hidden degrees freedom do not carry any `energy'
and thus realize in a fully quantum gravitational context the idea (emphasized
before by Unruh and Wald) that decoherence can take place without dissipation,
now in a concrete gravitational model strongly motivated by quantum gravity.
All this strengthen the perspective of a quite conservative and natural
resolution of the black hole evaporation puzzle where information is not
destroyed but simply degraded (made unavailable to low energy observers) into
correlations with the microscopic structure of the quantum geometry at the
Planck scale.
| [
{
"created": "Fri, 20 Dec 2019 10:47:39 GMT",
"version": "v1"
}
] | 2019-12-23 | [
[
"Amadei",
"Lautaro",
""
],
[
"Liu",
"Hongguang",
""
],
[
"Perez",
"Alejandro",
""
]
] | In approaches to quantum gravity, where smooth spacetime is an emergent approximation of a discrete Planckian fundamental structure, any effective smooth field theoretical description would miss part of the fundamental degrees of freedom and thus break unitarity. This is applicable also to trivial gravitational field (low energy) idealizations realized by the use of the Minkowski background geometry which, as any other spacetime geometry, corresponds, in the fundamental description, to infinitely many different and closely degenerate discrete microstates. The existence of such microstates provides a large reservoir for information to be coded at the end of black hole evaporation and thus opens the way to a natural resolution of the black hole evaporation information puzzle. In this paper we show that these expectations can be made precise in a simple quantum gravity model for cosmology motivated by loop quantum gravity. Concretely, even when the model is fundamentally unitary, when microscopic degrees of freedom irrelevant to low-energy cosmological observers are suitably ignored, pure states in the effective description evolve into mixed states due to decoherence with the Planckian microscopic structure. Moreover, in the relevant physical regime these hidden degrees freedom do not carry any `energy' and thus realize in a fully quantum gravitational context the idea (emphasized before by Unruh and Wald) that decoherence can take place without dissipation, now in a concrete gravitational model strongly motivated by quantum gravity. All this strengthen the perspective of a quite conservative and natural resolution of the black hole evaporation puzzle where information is not destroyed but simply degraded (made unavailable to low energy observers) into correlations with the microscopic structure of the quantum geometry at the Planck scale. |
0906.4191 | Valery Kiselev | V.V. Kiselev, S.A. Timofeev | Decoupling of Higgs boson from the inflationary stage of Universe
evolution | 6 pages, svjour class, comments and reference added | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The constraint on the mass of Higgs field in the Standard Model at the
minimal interaction with the gravity is derived in the form of lower bound
$m_H> 150$ GeV by the strict requirement of decoupling the Higgs boson from the
inflation of early Universe: the inflation produced by the Higgs scalar could
crucially destroy visible properties of large scale structure of Universe,
while the large mass makes the Higgs particle not able to produce the inflation
and shifts its cosmological role into the region of quantum gravity.
| [
{
"created": "Tue, 23 Jun 2009 08:45:35 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Jul 2009 11:46:38 GMT",
"version": "v2"
},
{
"created": "Fri, 31 Jul 2009 08:05:02 GMT",
"version": "v3"
},
{
"created": "Mon, 24 Aug 2009 11:36:52 GMT",
"version": "v4"
},
{
"cr... | 2010-05-10 | [
[
"Kiselev",
"V. V.",
""
],
[
"Timofeev",
"S. A.",
""
]
] | The constraint on the mass of Higgs field in the Standard Model at the minimal interaction with the gravity is derived in the form of lower bound $m_H> 150$ GeV by the strict requirement of decoupling the Higgs boson from the inflation of early Universe: the inflation produced by the Higgs scalar could crucially destroy visible properties of large scale structure of Universe, while the large mass makes the Higgs particle not able to produce the inflation and shifts its cosmological role into the region of quantum gravity. |
gr-qc/0007017 | Pawel Nurowski | Pawe{\l}~Nurowski, Jerzy F. Pleba\'nski | Non-vacuum twisting type N metrics | null | Class.Quant.Grav. 18 (2001) 341-351 | null | null | gr-qc | null | A maximally reduced system of equations corresponding to the twisting type N
Einstein metrics is given. When the cosmological constant $\lambda\to 0$ they
reduce to the standard equations for the vacuum twisting type N's. All the
metrics which are conformally equivalent to the twisting type N metrics and
which admit 3-dimensional conformal group of symmetries are presented. In the
Feferman class of metrics an example is given of a twisting type N metric which
satisfies Bach's equations but is not Einstein.
| [
{
"created": "Mon, 10 Jul 2000 15:45:11 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Paweł~Nurowski",
"",
""
],
[
"Plebański",
"Jerzy F.",
""
]
] | A maximally reduced system of equations corresponding to the twisting type N Einstein metrics is given. When the cosmological constant $\lambda\to 0$ they reduce to the standard equations for the vacuum twisting type N's. All the metrics which are conformally equivalent to the twisting type N metrics and which admit 3-dimensional conformal group of symmetries are presented. In the Feferman class of metrics an example is given of a twisting type N metric which satisfies Bach's equations but is not Einstein. |
1902.04411 | Ali \"Ovg\"un Dr. | A. \"Ovg\"un | Weak gravitational lensing of regular black holes with cosmic strings
using the Gauss-Bonnet theorem | Accepted for publication in Physical Review D
(https://journals.aps.org/prd/accepted/05075Qd6Pc511124453d5b89128d261ab2470a01f) | Phys. Rev. D 99, 104075 (2019) | 10.1103/PhysRevD.99.104075 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate light bending in the spacetime of regular black
holes with cosmic strings in weak field limits. To do so, we apply the
Gauss-Bonnet theorem to the optical geometry of the black hole; and, using the
Gibbons-Werner method, we obtain the deflection angle of light in the weak
field limits which shows that the bending of light is a global and topological
effect. Afterwards, we demonstrate the effect of a plasma medium on the
deflection of light by RBCS. We discuss that increasing cosmic string parameter
$\mu$ and mass $M_0$ will increase the bending angle.
| [
{
"created": "Sun, 10 Feb 2019 01:57:04 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Mar 2019 14:13:51 GMT",
"version": "v2"
},
{
"created": "Wed, 15 May 2019 06:37:56 GMT",
"version": "v3"
}
] | 2019-05-29 | [
[
"Övgün",
"A.",
""
]
] | In this paper, we investigate light bending in the spacetime of regular black holes with cosmic strings in weak field limits. To do so, we apply the Gauss-Bonnet theorem to the optical geometry of the black hole; and, using the Gibbons-Werner method, we obtain the deflection angle of light in the weak field limits which shows that the bending of light is a global and topological effect. Afterwards, we demonstrate the effect of a plasma medium on the deflection of light by RBCS. We discuss that increasing cosmic string parameter $\mu$ and mass $M_0$ will increase the bending angle. |
1604.00782 | Roland Haas | Roland Haas, Christian D. Ott, Bela Szilagyi, Jeffrey D. Kaplan, Jonas
Lippuner, Mark A. Scheel, Kevin Barkett, Curran D. Muhlberger, Tim Dietrich,
Matthew D. Duez, Francois Foucart, Harald P. Pfeiffer, Lawrence E. Kidder,
Saul A. Teukolsky | Simulations of inspiraling and merging double neutron stars using the
Spectral Einstein Code | 23 pages, 15 figures, published version | Phys. Rev. D 93, 124062 (2016) | 10.1103/PhysRevD.93.124062 | YITP-16-39 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present results on the inspiral, merger, and post-merger evolution of a
neutron star - neutron star (NSNS) system. Our results are obtained using the
hybrid pseudospectral-finite volume Spectral Einstein Code (SpEC). To test our
numerical methods, we evolve an equal-mass system for $\approx 22$ orbits
before merger. This waveform is the longest waveform obtained from fully
general-relativistic simulations for NSNSs to date. Such long (and accurate)
numerical waveforms are required to further improve semi-analytical models used
in gravitational wave data analysis, for example the effective one body models.
We discuss in detail the improvements to SpEC's ability to simulate NSNS
mergers, in particular mesh refined grids to better resolve the merger and
post-merger phases. We provide a set of consistency checks and compare our
results to NSNS merger simulations with the independent BAM code. We find
agreement between them, which increases confidence in results obtained with
either code. This work paves the way for future studies using long waveforms
and more complex microphysical descriptions of neutron star matter in SpEC.
| [
{
"created": "Mon, 4 Apr 2016 09:22:40 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Jun 2016 18:55:01 GMT",
"version": "v2"
}
] | 2016-06-29 | [
[
"Haas",
"Roland",
""
],
[
"Ott",
"Christian D.",
""
],
[
"Szilagyi",
"Bela",
""
],
[
"Kaplan",
"Jeffrey D.",
""
],
[
"Lippuner",
"Jonas",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Barkett",
"Kevin",
""
],
[... | We present results on the inspiral, merger, and post-merger evolution of a neutron star - neutron star (NSNS) system. Our results are obtained using the hybrid pseudospectral-finite volume Spectral Einstein Code (SpEC). To test our numerical methods, we evolve an equal-mass system for $\approx 22$ orbits before merger. This waveform is the longest waveform obtained from fully general-relativistic simulations for NSNSs to date. Such long (and accurate) numerical waveforms are required to further improve semi-analytical models used in gravitational wave data analysis, for example the effective one body models. We discuss in detail the improvements to SpEC's ability to simulate NSNS mergers, in particular mesh refined grids to better resolve the merger and post-merger phases. We provide a set of consistency checks and compare our results to NSNS merger simulations with the independent BAM code. We find agreement between them, which increases confidence in results obtained with either code. This work paves the way for future studies using long waveforms and more complex microphysical descriptions of neutron star matter in SpEC. |
1311.3146 | Remo Garattini | Remo Garattini | Self Sustained Traversable Wormholes and Topology Change Induced by
Gravity's Rainbow | 6 pages. Prepared for the Proceedings of the Karl Schwarzschild
meeting 2013 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the effects of Gravity's Rainbow on the self-sustained equation
which is responsible to find new traversable wormholes configurations which are
sustained by their own gravitational quantum fluctuations. The same
self-sustained equation is also used to discover if topology change is
possible. In this contribution, we will show that in both uses, the
self-sustained equation will produce a Wheeler wormhole, namely a wormhole of
Planckian size. This means that, from the point of view of traversability, the
wormhole will be traversable in principle, but not in practice. From the
topology change point of view, the background metric will be fixed to be
Minkowskian in the equation governing the quantum fluctuations, which behaves
essentially as a backreaction equation, and the quantum fluctuations are let to
evolve. Analyzing this procedure, we will show that the self-sustained
equation, endowed with a Gravity's Rainbow distortion, will be responsible of a
topology change with the appearance of a Planckian wormhole.
| [
{
"created": "Wed, 13 Nov 2013 14:41:21 GMT",
"version": "v1"
}
] | 2013-11-14 | [
[
"Garattini",
"Remo",
""
]
] | We consider the effects of Gravity's Rainbow on the self-sustained equation which is responsible to find new traversable wormholes configurations which are sustained by their own gravitational quantum fluctuations. The same self-sustained equation is also used to discover if topology change is possible. In this contribution, we will show that in both uses, the self-sustained equation will produce a Wheeler wormhole, namely a wormhole of Planckian size. This means that, from the point of view of traversability, the wormhole will be traversable in principle, but not in practice. From the topology change point of view, the background metric will be fixed to be Minkowskian in the equation governing the quantum fluctuations, which behaves essentially as a backreaction equation, and the quantum fluctuations are let to evolve. Analyzing this procedure, we will show that the self-sustained equation, endowed with a Gravity's Rainbow distortion, will be responsible of a topology change with the appearance of a Planckian wormhole. |
2012.02240 | J\"org Hennig | J\"org Hennig and Rodrigo Panosso Macedo | Fully pseudospectral solution of the conformally invariant wave equation
on a Kerr background | 31 pages, 14 figures | Class. Quantum Grav. 38, 135006 (2021) | 10.1088/1361-6382/abfd86 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study axisymmetric solution to the conformally invariant wave equation on
a Kerr background by means of numerical and analytical methods. Our main focus
is on the behaviour of the solutions near spacelike infinity, which is
appropriately represented as a cylinder. Earlier studies of the wave equation
on a Schwarzschild background have revealed important details about the
regularity of the corresponding solutions. It was found that, on the cylinder,
the solutions generically develop logarithmic singularities at infinitely many
orders. Moreover, these singularities also `spread' to future null infinity.
However, by imposing certain regularity conditions on the initial data, the
lowest-order singularities can be removed. Here we are interested in a
generalisation of these results to a rotating black hole background and study
the influence of the rotation rate on the properties of the solutions. To this
aim, we first construct a conformal compactification of the Kerr solution which
yields a suitable representation of the cylinder at spatial infinity. Besides
analytical investigations on the cylinder, we numerically solve the wave
equation with a fully pseudospectral method, which allows us to obtain highly
accurate numerical solutions. This is crucial for a detailed analysis of the
regularity of the solutions. In the Schwarzschild case, the numerical problem
could effectively be reduced to solving $(1+1)$-dimensional equations. Here we
present a code that can perform the full $2+1$ evolution as required for
axisymmetric waves on a Kerr background.
| [
{
"created": "Thu, 3 Dec 2020 20:12:03 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Jun 2021 21:03:20 GMT",
"version": "v2"
}
] | 2021-06-07 | [
[
"Hennig",
"Jörg",
""
],
[
"Macedo",
"Rodrigo Panosso",
""
]
] | We study axisymmetric solution to the conformally invariant wave equation on a Kerr background by means of numerical and analytical methods. Our main focus is on the behaviour of the solutions near spacelike infinity, which is appropriately represented as a cylinder. Earlier studies of the wave equation on a Schwarzschild background have revealed important details about the regularity of the corresponding solutions. It was found that, on the cylinder, the solutions generically develop logarithmic singularities at infinitely many orders. Moreover, these singularities also `spread' to future null infinity. However, by imposing certain regularity conditions on the initial data, the lowest-order singularities can be removed. Here we are interested in a generalisation of these results to a rotating black hole background and study the influence of the rotation rate on the properties of the solutions. To this aim, we first construct a conformal compactification of the Kerr solution which yields a suitable representation of the cylinder at spatial infinity. Besides analytical investigations on the cylinder, we numerically solve the wave equation with a fully pseudospectral method, which allows us to obtain highly accurate numerical solutions. This is crucial for a detailed analysis of the regularity of the solutions. In the Schwarzschild case, the numerical problem could effectively be reduced to solving $(1+1)$-dimensional equations. Here we present a code that can perform the full $2+1$ evolution as required for axisymmetric waves on a Kerr background. |
1208.3388 | Frank Hellmann | Benjamin Bahr, Bianca Dittrich, Frank Hellmann, Wojciech Kaminski | Holonomy Spin Foam Models: Definition and Coarse Graining | 36 pages, 12 figures | null | 10.1103/PhysRevD.87.044048 | null | gr-qc hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new holonomy formulation for spin foams, which naturally extends
the theory space of lattice gauge theories. This allows current spin foam
models to be defined on arbitrary two-complexes as well as to generalize
current spin foam models to arbitrary, in particular finite groups. The
similarity with standard lattice gauge theories allows to apply standard coarse
graining methods, which for finite groups can now be easily considered
numerically. We will summarize other holonomy and spin network formulations of
spin foams and group field theories and explain how the different
representations arise through variable transformations in the partition
function. A companion paper will provide a description of boundary Hilbert
spaces as well as a canonical dynamic encoded in transfer operators.
| [
{
"created": "Thu, 16 Aug 2012 14:55:08 GMT",
"version": "v1"
}
] | 2013-03-14 | [
[
"Bahr",
"Benjamin",
""
],
[
"Dittrich",
"Bianca",
""
],
[
"Hellmann",
"Frank",
""
],
[
"Kaminski",
"Wojciech",
""
]
] | We propose a new holonomy formulation for spin foams, which naturally extends the theory space of lattice gauge theories. This allows current spin foam models to be defined on arbitrary two-complexes as well as to generalize current spin foam models to arbitrary, in particular finite groups. The similarity with standard lattice gauge theories allows to apply standard coarse graining methods, which for finite groups can now be easily considered numerically. We will summarize other holonomy and spin network formulations of spin foams and group field theories and explain how the different representations arise through variable transformations in the partition function. A companion paper will provide a description of boundary Hilbert spaces as well as a canonical dynamic encoded in transfer operators. |
2310.02017 | Reed Essick | Reed Essick, Maya Fishbach | DAGnabbit! Ensuring Consistency between Noise and Detection in
Hierarchical Bayesian Inference | 12 pages (+8 pages of appendix). 6 Figures | null | null | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hierarchical Bayesian inference can simultaneously account for both
measurement uncertainty and selection effects within astronomical catalogs. In
particular, the hierarchy imposed encodes beliefs about the interdependence of
the physical processes that generate the observed data. We show that several
proposed approximations within the literature actually correspond to inferences
that are incompatible with any physical detection process, which can be
described by a directed acyclic graph (DAG). This generically leads to biases
and is associated with the assumption that detectability is independent of the
observed data given the true source parameters. We show several examples of how
this error can affect astrophysical inferences based on catalogs of coalescing
binaries observed through gravitational waves, including misestimating the
redshift evolution of the merger rate as well as incorrectly inferring that
General Relativity is the correct theory of gravity when it is not. In general,
one cannot directly fit for the ``detected distribution'' and ``divide out''
the selection effects in post-processing. Similarly, when comparing theoretical
predictions to observations, it is better to simulate detected data (including
both measurement noise and selection effects) rather than comparing estimates
of the detected distributions of event parameters (which include only selection
effects). While the biases introduced by model misspecification from incorrect
assumptions may be smaller than statistical uncertainty for moderate catalog
sizes (O(100) events), they will nevertheless pose a significant barrier to
precision measurements of astrophysical populations.
| [
{
"created": "Tue, 3 Oct 2023 12:46:07 GMT",
"version": "v1"
}
] | 2023-10-04 | [
[
"Essick",
"Reed",
""
],
[
"Fishbach",
"Maya",
""
]
] | Hierarchical Bayesian inference can simultaneously account for both measurement uncertainty and selection effects within astronomical catalogs. In particular, the hierarchy imposed encodes beliefs about the interdependence of the physical processes that generate the observed data. We show that several proposed approximations within the literature actually correspond to inferences that are incompatible with any physical detection process, which can be described by a directed acyclic graph (DAG). This generically leads to biases and is associated with the assumption that detectability is independent of the observed data given the true source parameters. We show several examples of how this error can affect astrophysical inferences based on catalogs of coalescing binaries observed through gravitational waves, including misestimating the redshift evolution of the merger rate as well as incorrectly inferring that General Relativity is the correct theory of gravity when it is not. In general, one cannot directly fit for the ``detected distribution'' and ``divide out'' the selection effects in post-processing. Similarly, when comparing theoretical predictions to observations, it is better to simulate detected data (including both measurement noise and selection effects) rather than comparing estimates of the detected distributions of event parameters (which include only selection effects). While the biases introduced by model misspecification from incorrect assumptions may be smaller than statistical uncertainty for moderate catalog sizes (O(100) events), they will nevertheless pose a significant barrier to precision measurements of astrophysical populations. |
gr-qc/0609064 | Celine Cattoen | Celine Cattoen, Matt Visser | Cosmological milestones and energy conditions | 8 pages, 1 table, conference proceedings for NEB XII conference in
Nafplio, Greece | J.Phys.Conf.Ser.68:012011,2007 | 10.1088/1742-6596/68/1/012011 | null | gr-qc | null | Until recently, the physically relevant singularities occurring in FRW
cosmologies had traditionally been thought to be limited to the "big bang", and
possibly a "big crunch". However, over the last few years, the zoo of
cosmological singularities considered in the literature has become considerably
more extensive, with "big rips" and "sudden singularities" added to the mix, as
well as renewed interest in non-singular cosmological events such as "bounces"
and "turnarounds". In this talk, we present an extensive catalogue of such
cosmological milestones, both at the kinematical and dynamical level. First,
using generalized power series, purely kinematical definitions of these
cosmological events are provided in terms of the behaviour of the scale factor
a(t). The notion of a "scale-factor singularity" is defined, and its relation
to curvature singularities (polynomial and differential) is explored. Second,
dynamical information is extracted by using the Friedmann equations (without
assuming even the existence of any equation of state) to place constraints on
whether or not the classical energy conditions are satisfied at the
cosmological milestones. Since the classification is extremely general, and
modulo certain technical assumptions complete, the corresponding results are to
a high degree model-independent.
| [
{
"created": "Mon, 18 Sep 2006 03:31:01 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Cattoen",
"Celine",
""
],
[
"Visser",
"Matt",
""
]
] | Until recently, the physically relevant singularities occurring in FRW cosmologies had traditionally been thought to be limited to the "big bang", and possibly a "big crunch". However, over the last few years, the zoo of cosmological singularities considered in the literature has become considerably more extensive, with "big rips" and "sudden singularities" added to the mix, as well as renewed interest in non-singular cosmological events such as "bounces" and "turnarounds". In this talk, we present an extensive catalogue of such cosmological milestones, both at the kinematical and dynamical level. First, using generalized power series, purely kinematical definitions of these cosmological events are provided in terms of the behaviour of the scale factor a(t). The notion of a "scale-factor singularity" is defined, and its relation to curvature singularities (polynomial and differential) is explored. Second, dynamical information is extracted by using the Friedmann equations (without assuming even the existence of any equation of state) to place constraints on whether or not the classical energy conditions are satisfied at the cosmological milestones. Since the classification is extremely general, and modulo certain technical assumptions complete, the corresponding results are to a high degree model-independent. |
gr-qc/9610058 | Eric Poisson | L.E. Simone, S.W. Leonard, E. Poisson, and C.M. Will | Gravitational waves from binary systems in circular orbits: Does the
post-Newtonian expansion converge? | 20 pages, IOP macros, 4 postscript figures, to appear in Classical
and Quantum Gravity | Class.Quant.Grav. 14 (1997) 237-256 | 10.1088/0264-9381/14/1/021 | null | gr-qc | null | Gravitational radiation can be expressed in terms of an infinite series of
radiative, symmetric trace-free (STF) multipole moments which can be connected
to the behavior of the source. We consider a truncated model for gravitational
radiation from binary systems in which each STF mass and current moment of
order l is given by the lowest-order, Newtonian-like l-pole moment of the
orbiting masses; we neglect post-Newtonian corrections to each STF moment.
Specializing to orbits which are circular (apart from the radiation-induced
inspiral), we find an explicit infinite series for the energy flux in powers of
$v/c$, where v is the orbital velocity. We show that the series converges for
all values $v/c < 2/e$ when one mass is much smaller than the other, and $v/c <
4/e$ for equal masses,where e is the base of natural logarithms. These values
include all physically relevant values for compact binary inspiral. This
convergence cannot indicate whether or not the full series (obtained from the
exact moments) will converge. But if the full series does not converge, our
analysis shows that this failure to converge does not originate from summing
over the Newtonian part of the multipole moments.
| [
{
"created": "Fri, 25 Oct 1996 00:45:51 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Simone",
"L. E.",
""
],
[
"Leonard",
"S. W.",
""
],
[
"Poisson",
"E.",
""
],
[
"Will",
"C. M.",
""
]
] | Gravitational radiation can be expressed in terms of an infinite series of radiative, symmetric trace-free (STF) multipole moments which can be connected to the behavior of the source. We consider a truncated model for gravitational radiation from binary systems in which each STF mass and current moment of order l is given by the lowest-order, Newtonian-like l-pole moment of the orbiting masses; we neglect post-Newtonian corrections to each STF moment. Specializing to orbits which are circular (apart from the radiation-induced inspiral), we find an explicit infinite series for the energy flux in powers of $v/c$, where v is the orbital velocity. We show that the series converges for all values $v/c < 2/e$ when one mass is much smaller than the other, and $v/c < 4/e$ for equal masses,where e is the base of natural logarithms. These values include all physically relevant values for compact binary inspiral. This convergence cannot indicate whether or not the full series (obtained from the exact moments) will converge. But if the full series does not converge, our analysis shows that this failure to converge does not originate from summing over the Newtonian part of the multipole moments. |
2007.13192 | Ludovico Machet | Ludovico Machet, Jinzhao Wang | On the continuum limit of Benincasa-Dowker-Glaser causal set action | 26 pages (including cover page), 2 figures. We expect an independent
work on the same topic by Fay Dowker to be submitted to the ArXiv at the same
time of this work. Cross reference to this work added in version 2 | 2021 Class. Quantum Grav. 38 015010 | 10.1088/1361-6382/abc274 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the continuum limit of the Benincasa-Dowker-Glaser causal set action
on a causally convex compact region. In particular, we compute the action of a
causal set randomly sprinkled on a small causal diamond in the presence of
arbitrary curvature in various spacetime dimensions. In the continuum limit, we
show that the action admits a finite limit. More importantly, the limit is
composed by an Einstein-Hilbert bulk term as predicted by the
Benincasa-Dowker-Glaser action, and a boundary term exactly proportional to the
codimension-two joint volume. Our calculation provides strong evidence in
support of the conjecture that the Benincasa-Dowker-Glaser action naturally
includes codimension-two boundary terms when evaluated on causally convex
regions.
| [
{
"created": "Sun, 26 Jul 2020 18:09:30 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Jul 2020 09:57:13 GMT",
"version": "v2"
}
] | 2020-12-14 | [
[
"Machet",
"Ludovico",
""
],
[
"Wang",
"Jinzhao",
""
]
] | We study the continuum limit of the Benincasa-Dowker-Glaser causal set action on a causally convex compact region. In particular, we compute the action of a causal set randomly sprinkled on a small causal diamond in the presence of arbitrary curvature in various spacetime dimensions. In the continuum limit, we show that the action admits a finite limit. More importantly, the limit is composed by an Einstein-Hilbert bulk term as predicted by the Benincasa-Dowker-Glaser action, and a boundary term exactly proportional to the codimension-two joint volume. Our calculation provides strong evidence in support of the conjecture that the Benincasa-Dowker-Glaser action naturally includes codimension-two boundary terms when evaluated on causally convex regions. |
gr-qc/9505036 | Shingo Suzuki | Y.Sota, S.Suzuki and K.Maeda | Chaos in Static Axisymmetric Spacetimes I : Vacuum Case | More comments for the quantitative estimation of chaos are added, and
some inappropriate terms are changed. This will appear on Class. Quant. Grav | Class.Quant.Grav. 13 (1996) 1241-1260 | 10.1088/0264-9381/13/5/034 | null | gr-qc astro-ph chao-dyn nlin.CD | null | We study the motion of test particle in static axisymmetric vacuum spacetimes
and discuss two criteria for strong chaos to occur: (1) a local instability
measured by the Weyl curvature, and (2) a tangle of a homoclinic orbit, which
is closely related to an unstable periodic orbit in general relativity. We
analyze several static axisymmetric spacetimes and find that the first
criterion is a sufficient condition for chaos, at least qualitatively. Although
some test particles which do not satisfy the first criterion show chaotic
behavior in some spacetimes, these can be accounted for the second criterion.
| [
{
"created": "Sat, 20 May 1995 05:55:20 GMT",
"version": "v1"
},
{
"created": "Mon, 22 May 1995 07:26:30 GMT",
"version": "v2"
},
{
"created": "Tue, 27 Feb 1996 23:12:31 GMT",
"version": "v3"
}
] | 2009-10-28 | [
[
"Sota",
"Y.",
""
],
[
"Suzuki",
"S.",
""
],
[
"Maeda",
"K.",
""
]
] | We study the motion of test particle in static axisymmetric vacuum spacetimes and discuss two criteria for strong chaos to occur: (1) a local instability measured by the Weyl curvature, and (2) a tangle of a homoclinic orbit, which is closely related to an unstable periodic orbit in general relativity. We analyze several static axisymmetric spacetimes and find that the first criterion is a sufficient condition for chaos, at least qualitatively. Although some test particles which do not satisfy the first criterion show chaotic behavior in some spacetimes, these can be accounted for the second criterion. |
2001.05500 | William C. C. Lima | Atsushi Higuchi, William C. C. Lima | Equivalence between the in-in perturbation theories for quantum fields
in Minkowski spacetime and in the Rindler wedge | 12 pages, 3 figures. Minor corrections; matches the published version | Phys. Rev. D 101, 065009 (2020) | 10.1103/PhysRevD.101.065009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the relation between the time-ordered vacuum correlation
functions for interacting real scalar fields in Minkowski spacetime and in the
Rindler wedge. The correlation functions are constructed perturbatively within
the in-in formalism, often employed in calculations in more general spacetimes.
We prove to all orders in perturbation theory that the time-ordered vacuum
correlation functions can be calculated in the in-in formalism with internal
vertices restricted to any Rindler wedge containing the external points. This
implies that the Minkowski in-in (or in-out) perturbative expansion of the
vacuum correlation functions is reproduced by the Rindler in-in perturbative
expansion of these correlators in a thermal state at the Unruh temperature.
| [
{
"created": "Wed, 15 Jan 2020 19:00:01 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Mar 2020 13:59:35 GMT",
"version": "v2"
}
] | 2020-03-18 | [
[
"Higuchi",
"Atsushi",
""
],
[
"Lima",
"William C. C.",
""
]
] | We investigate the relation between the time-ordered vacuum correlation functions for interacting real scalar fields in Minkowski spacetime and in the Rindler wedge. The correlation functions are constructed perturbatively within the in-in formalism, often employed in calculations in more general spacetimes. We prove to all orders in perturbation theory that the time-ordered vacuum correlation functions can be calculated in the in-in formalism with internal vertices restricted to any Rindler wedge containing the external points. This implies that the Minkowski in-in (or in-out) perturbative expansion of the vacuum correlation functions is reproduced by the Rindler in-in perturbative expansion of these correlators in a thermal state at the Unruh temperature. |
1009.1506 | Ming-Hua Li | Zhe Chang, Ming-Hua Li, and Xin Li | Unification of Dark Matter and Dark Energy in a Modified Entropic Force
Model | 23 pages, 6 figures | Commun.Theor.Phys. 56: 184-192,2011 | 10.1088/0253-6102/56/1/32 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/3.0/ | In Verlinde's entropic force scenario of gravity, Newton's laws and Einstein
equations can be obtained from the first pinciples and general assumptions.
However, the equipartition law of energy is invalid at very low temperatures.
We show clearly that the threshold of the equipartition law of energy is
related with horizon of the universe. Thus, a one-dimension Debye (ODD) model
in the direction of radius of the modified entropic force (MEF) maybe suitable
in description of the accelerated expanding universe. We present a Friedmann
cosmic dynamical model in the ODD-MEF framework. We examine carefully
constraints on the ODD-MEF model from the Union2 compilation of the Supernova
Cosmology Project (SCP) collaboration, the data from the observation of the
large-scale structure (LSS) and the cosmic microwave background (CMB), i.e. SNe
Ia+LSS+CMB. The combined numerical analysis gives the best-fit value of the
model parameters $\zeta\simeq10^{-9}$ and $\Omega_{m0}=0.224$, with
$\chi_{min}^2=591.156$. The corresponding age of the universe agrees with the
result of D. Spergel {\it et al.}\cite{Spergel2003} at 95% confidence level.
The numerical result also yields an accelerated expanding universe without
invoking any kind of dark energy. Taking $\zeta(\equiv 2\pi \omega_D/H_0)$ as a
running parameter associated with the structure scale $r$, we obtain a possible
unified scenario of the asymptotic flatness of the radial velocity dispersion
of spiral galaxies, the accelerated expanding universe and the Pioneer 10/11
anomaly in the entropic force framework of Verlinde.
| [
{
"created": "Wed, 8 Sep 2010 11:31:21 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Oct 2010 09:12:57 GMT",
"version": "v2"
},
{
"created": "Mon, 27 Jun 2011 06:36:33 GMT",
"version": "v3"
}
] | 2011-08-04 | [
[
"Chang",
"Zhe",
""
],
[
"Li",
"Ming-Hua",
""
],
[
"Li",
"Xin",
""
]
] | In Verlinde's entropic force scenario of gravity, Newton's laws and Einstein equations can be obtained from the first pinciples and general assumptions. However, the equipartition law of energy is invalid at very low temperatures. We show clearly that the threshold of the equipartition law of energy is related with horizon of the universe. Thus, a one-dimension Debye (ODD) model in the direction of radius of the modified entropic force (MEF) maybe suitable in description of the accelerated expanding universe. We present a Friedmann cosmic dynamical model in the ODD-MEF framework. We examine carefully constraints on the ODD-MEF model from the Union2 compilation of the Supernova Cosmology Project (SCP) collaboration, the data from the observation of the large-scale structure (LSS) and the cosmic microwave background (CMB), i.e. SNe Ia+LSS+CMB. The combined numerical analysis gives the best-fit value of the model parameters $\zeta\simeq10^{-9}$ and $\Omega_{m0}=0.224$, with $\chi_{min}^2=591.156$. The corresponding age of the universe agrees with the result of D. Spergel {\it et al.}\cite{Spergel2003} at 95% confidence level. The numerical result also yields an accelerated expanding universe without invoking any kind of dark energy. Taking $\zeta(\equiv 2\pi \omega_D/H_0)$ as a running parameter associated with the structure scale $r$, we obtain a possible unified scenario of the asymptotic flatness of the radial velocity dispersion of spiral galaxies, the accelerated expanding universe and the Pioneer 10/11 anomaly in the entropic force framework of Verlinde. |
1405.3640 | Mauricio Bellini | Mariano Anabitarte, Mauricio Bellini (IFIMAR - CONICET & UNMDP) | Inflation as a White Hole explosion from a 5D vacuum | improved version | null | 10.1139/cjp-2014-0588 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using a new kind of 5D Ricci-flat canonical metric, we obtain by a static
foliation an effective 4D Schwarzschild-de Sitter hypersurface. We examine some
particular initial conditions which could be responsible for the inflationary
expansion of the early universe, which could be driven by the explosion of a
White Hole (WH). The zeroth order spectrum outside the WH describes quantum
fluctuations, which for a scale invariant power spectrum, can be expressed in
terms of the cosmological constant, or the square mass of the WH.
| [
{
"created": "Wed, 14 May 2014 19:41:14 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Aug 2014 14:21:41 GMT",
"version": "v2"
}
] | 2023-07-19 | [
[
"Anabitarte",
"Mariano",
"",
"IFIMAR - CONICET & UNMDP"
],
[
"Bellini",
"Mauricio",
"",
"IFIMAR - CONICET & UNMDP"
]
] | Using a new kind of 5D Ricci-flat canonical metric, we obtain by a static foliation an effective 4D Schwarzschild-de Sitter hypersurface. We examine some particular initial conditions which could be responsible for the inflationary expansion of the early universe, which could be driven by the explosion of a White Hole (WH). The zeroth order spectrum outside the WH describes quantum fluctuations, which for a scale invariant power spectrum, can be expressed in terms of the cosmological constant, or the square mass of the WH. |
2004.09296 | Z. Yousaf | M. Z. Bhatti, Z. Yousaf, A. Rehman | Gravastars in $f(R,G)$ Gravity | 21 pages, 4 figures | Phys. Dark Universe 29, 100561 (2020) | 10.1016/j.dark.2020.100561 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we discuss some feasible features of gravastar that were
firstly demonstrated by Mazur and Mottola. It is already established that
gravastar associates the de-Sitter spacetime in its inner sector with the
Schwarzschild geometry at its exterior through the thin shell possessing the
ultra-relativistic matter. We have explored the singularity free spherical
model with a particular equation of state under the influence of $f(R,G)$
gravity, where $R$ is the Ricci scalar and $G$ is the Gauss-Bonnet term. The
interior geometry is matched with a suitable exterior using Israel formalism.
Also, we discussed a feasible solution of gravastar which describes the other
physically sustainable factors under the influence of $f(R,G)$ gravity.
Different realistic characteristics of the gravastar model are discussed, in
particular, shell's length, entropy, and energy. A significant role of this
particular gravity is examined for the sustainability of gravastar model.
| [
{
"created": "Fri, 17 Apr 2020 12:45:35 GMT",
"version": "v1"
}
] | 2020-05-05 | [
[
"Bhatti",
"M. Z.",
""
],
[
"Yousaf",
"Z.",
""
],
[
"Rehman",
"A.",
""
]
] | In this paper, we discuss some feasible features of gravastar that were firstly demonstrated by Mazur and Mottola. It is already established that gravastar associates the de-Sitter spacetime in its inner sector with the Schwarzschild geometry at its exterior through the thin shell possessing the ultra-relativistic matter. We have explored the singularity free spherical model with a particular equation of state under the influence of $f(R,G)$ gravity, where $R$ is the Ricci scalar and $G$ is the Gauss-Bonnet term. The interior geometry is matched with a suitable exterior using Israel formalism. Also, we discussed a feasible solution of gravastar which describes the other physically sustainable factors under the influence of $f(R,G)$ gravity. Different realistic characteristics of the gravastar model are discussed, in particular, shell's length, entropy, and energy. A significant role of this particular gravity is examined for the sustainability of gravastar model. |
gr-qc/0606014 | Diego Pavon | German Izquierdo and Diego Pavon | The generalized second law in phantom dominated universes in the
presence of black holes | 8 pages, one eps figure, to be published by Physics Letters B | Phys.Lett.B639:1-4,2006 | 10.1016/j.physletb.2006.05.082 | null | gr-qc astro-ph hep-ph hep-th | null | This Letter considers the generalized second law of gravitational
thermodynamics in two scenarios featuring a phantom dominated expansion plus a
black hole. The law is violated in both scenarios.
| [
{
"created": "Fri, 2 Jun 2006 13:17:12 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Izquierdo",
"German",
""
],
[
"Pavon",
"Diego",
""
]
] | This Letter considers the generalized second law of gravitational thermodynamics in two scenarios featuring a phantom dominated expansion plus a black hole. The law is violated in both scenarios. |
2407.17528 | Chia-Li Hsieh | Chia-Li Hsieh | Interacting Null Sources in Different Geometries | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We introduce basic mathematical techniques, followed by an exploration of
three distinct topics: the Callan-Giddings-Harvey-Strominger (CGHS) model in
1+1-dimensional spacetime, the formation of astrophysical jets in
Schwarzschild-like black holes, and collisions and confinement phenomena in the
third-order Lovelock gravity.
In the CGHS model, we investigate the collision of ghost fields within the
dilaton background geometry, observing the formation and dissolution of
wormholes by inserting and removing the ghost fields, respectively. This
process mimics a cosmological-scale analogue of Feynman diagrams.
Next, we study the non-zero expectation values of bumblebee fields due to
Lorentz symmetry breaking. This alteration in the energy-momentum tensor
necessitates the inclusion of a potential vacuum, resulting in a shift of the
vacuum solution towards Schwarzchild-like black holes with a scaling factor
$l$. This scaling factor facilitates discussions on the collision of null
sources, leading to the formation of impulsive null shells and satisfying the
type-D condition. When $l$ approaches zero, jet-like formations vanish,
transforming the problem into one involving colliding gravitational waves,
which is isometric to the Schwarzschild geometry. Moreover, our method can be
applied to any resembling Schwarzschild-like metrics. We aim to enhance our
model by incorporating additional physical factors such as extra polarizations
or EM fields.
Finally, our examination extends to the 4-dimensional third-order Lovelock
gravity, observing that particles possess finite energy and be confined within
the metric time interval extending from - to + infinity. Moreover, this finding
does not admit flat rotation curves. Additionally, when collisions occur within
the background of this metric, intriguingly, we observe impulsive Weyl
curvatures along the null boundaries subsequent to the collision.
| [
{
"created": "Tue, 23 Jul 2024 17:31:01 GMT",
"version": "v1"
}
] | 2024-07-26 | [
[
"Hsieh",
"Chia-Li",
""
]
] | We introduce basic mathematical techniques, followed by an exploration of three distinct topics: the Callan-Giddings-Harvey-Strominger (CGHS) model in 1+1-dimensional spacetime, the formation of astrophysical jets in Schwarzschild-like black holes, and collisions and confinement phenomena in the third-order Lovelock gravity. In the CGHS model, we investigate the collision of ghost fields within the dilaton background geometry, observing the formation and dissolution of wormholes by inserting and removing the ghost fields, respectively. This process mimics a cosmological-scale analogue of Feynman diagrams. Next, we study the non-zero expectation values of bumblebee fields due to Lorentz symmetry breaking. This alteration in the energy-momentum tensor necessitates the inclusion of a potential vacuum, resulting in a shift of the vacuum solution towards Schwarzchild-like black holes with a scaling factor $l$. This scaling factor facilitates discussions on the collision of null sources, leading to the formation of impulsive null shells and satisfying the type-D condition. When $l$ approaches zero, jet-like formations vanish, transforming the problem into one involving colliding gravitational waves, which is isometric to the Schwarzschild geometry. Moreover, our method can be applied to any resembling Schwarzschild-like metrics. We aim to enhance our model by incorporating additional physical factors such as extra polarizations or EM fields. Finally, our examination extends to the 4-dimensional third-order Lovelock gravity, observing that particles possess finite energy and be confined within the metric time interval extending from - to + infinity. Moreover, this finding does not admit flat rotation curves. Additionally, when collisions occur within the background of this metric, intriguingly, we observe impulsive Weyl curvatures along the null boundaries subsequent to the collision. |
1702.04687 | Luca Fabbri | Luca Fabbri | A geometrical assessment of spinorial energy conditions | 4 pages | Eur.Phys.J.Plus132:156(2017) | 10.1140/epjp/i2017-11444-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the problem of energy for spinor fields coupled to their
surrounding curved-twisted space-time, and we show that when treated
geometrically we cannot even be certain that there is a problem for the energy
in the first place.
| [
{
"created": "Wed, 15 Feb 2017 17:13:14 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Apr 2017 09:01:50 GMT",
"version": "v2"
},
{
"created": "Wed, 20 Dec 2017 23:44:04 GMT",
"version": "v3"
}
] | 2018-01-04 | [
[
"Fabbri",
"Luca",
""
]
] | We consider the problem of energy for spinor fields coupled to their surrounding curved-twisted space-time, and we show that when treated geometrically we cannot even be certain that there is a problem for the energy in the first place. |
gr-qc/0004058 | Masayasu Hosonuma | Yasufumi Kojima and Masayasu Hosonuma | Approximate equation relevant to axial oscillations on slowly rotating
relativistic stars | 13pages, no figures, accepted for publication in Physical Review D | Phys.Rev. D62 (2000) 044006 | 10.1103/PhysRevD.62.044006 | null | gr-qc astro-ph | null | Axial oscillations relevant to the r-mode instability are studied with slow
rotation formalism in general relativity. The approximate equation governing
the oscillations is derived with second-order rotational corrections. The
equation contains an effective 'viscosity-like' term, which originates from
coupling to the polar g-mode displacements. The term plays a crucial role on
the resonance point, where the disturbance on the rotating stars satisfies a
certain condition at the lowest order equation. The effect is significant for
newly born hot neutron stars, which are expected to be subject to the
gravitational radiation driven instability of the r-mode.
| [
{
"created": "Tue, 18 Apr 2000 12:13:28 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Kojima",
"Yasufumi",
""
],
[
"Hosonuma",
"Masayasu",
""
]
] | Axial oscillations relevant to the r-mode instability are studied with slow rotation formalism in general relativity. The approximate equation governing the oscillations is derived with second-order rotational corrections. The equation contains an effective 'viscosity-like' term, which originates from coupling to the polar g-mode displacements. The term plays a crucial role on the resonance point, where the disturbance on the rotating stars satisfies a certain condition at the lowest order equation. The effect is significant for newly born hot neutron stars, which are expected to be subject to the gravitational radiation driven instability of the r-mode. |
2204.04885 | Natalia Konobeeva | M.B. Belonenko and N.N. Konobeeva | Zitterbewegung of Klein-Gordon particles and Landau levels | 5 pages, 3 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we consider the Zitterbewegung (ZB) effect for Klein-Gordon
particles induced by a cosmic string, near which curvature effects play a
dominant role. An analytical expression for the current is obtained and
analyzed.
| [
{
"created": "Mon, 11 Apr 2022 06:06:51 GMT",
"version": "v1"
}
] | 2022-04-12 | [
[
"Belonenko",
"M. B.",
""
],
[
"Konobeeva",
"N. N.",
""
]
] | In this paper, we consider the Zitterbewegung (ZB) effect for Klein-Gordon particles induced by a cosmic string, near which curvature effects play a dominant role. An analytical expression for the current is obtained and analyzed. |
2107.02536 | Anil Yadav dr | Nishant Singla, M. K. Gupta, Anil Kumar Yadav, G. K. Goswami | Accelerating Universe with binary mixture of bulk viscous fluid and dark
energy | 10 Pages, 7 Figures, Accepted in Int. J. Mod. Phys. A | International Journal of Modern Physics A 36, 2150148 (2021) | 10.1142/S0217751X21501487 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have proposed a model of accelerating Universe with binary
mixture of bulk viscous fluid and dark energy. and probed the model parameters:
present values of Hubble's constant $H_{0}$, Equation of state paper of dark
energy $\omega_{de}$ and density parameter of dark energy $(\Omega_{de})_{0}$
with recent OHD as well as joint Pantheon compilation of SN Ia data and OHD.
Using cosmic chronometric technique, we obtain $H_{0} = 69.80 \pm
1.64~km~s^{-1}Mpc^{-1}$ and $70.0258 \pm 1.72~km~s^{-1}Mpc^{-1}$ by restricting
our derived model with recent OHD and joint Pantheon compilation SN Ia data and
OHD respectively. The age of the Universe in derived model is estimated as
$t_{0} = 13.82 \pm 0.33\; Gyrs$. Also, we observe that derived model represents
a model of transitioning Universe with transition redshift $z_{t} = 0.7286$. We
have constrained the present value of jerk parameter as $j_{0} = 0.969 \pm
0.0075$ with joint OHD and Pantheon data. From this analysis, we observed that
the model of the Universe, presented in this paper shows a marginal departure
from $\Lambda$CDM model.
| [
{
"created": "Tue, 6 Jul 2021 11:03:28 GMT",
"version": "v1"
}
] | 2021-08-18 | [
[
"Singla",
"Nishant",
""
],
[
"Gupta",
"M. K.",
""
],
[
"Yadav",
"Anil Kumar",
""
],
[
"Goswami",
"G. K.",
""
]
] | In this paper, we have proposed a model of accelerating Universe with binary mixture of bulk viscous fluid and dark energy. and probed the model parameters: present values of Hubble's constant $H_{0}$, Equation of state paper of dark energy $\omega_{de}$ and density parameter of dark energy $(\Omega_{de})_{0}$ with recent OHD as well as joint Pantheon compilation of SN Ia data and OHD. Using cosmic chronometric technique, we obtain $H_{0} = 69.80 \pm 1.64~km~s^{-1}Mpc^{-1}$ and $70.0258 \pm 1.72~km~s^{-1}Mpc^{-1}$ by restricting our derived model with recent OHD and joint Pantheon compilation SN Ia data and OHD respectively. The age of the Universe in derived model is estimated as $t_{0} = 13.82 \pm 0.33\; Gyrs$. Also, we observe that derived model represents a model of transitioning Universe with transition redshift $z_{t} = 0.7286$. We have constrained the present value of jerk parameter as $j_{0} = 0.969 \pm 0.0075$ with joint OHD and Pantheon data. From this analysis, we observed that the model of the Universe, presented in this paper shows a marginal departure from $\Lambda$CDM model. |
0705.0232 | Kotub Uddin | Kotub Uddin, James E Lidsey and Reza Tavakol | Cosmological perturbations in Palatini modified gravity | null | Class.Quant.Grav.24:3951-3962,2007 | 10.1088/0264-9381/24/15/012 | null | gr-qc astro-ph | null | Two approaches to the study of cosmological density perturbations in modified
theories of Palatini gravity have recently been discussed. These utilise,
respectively, a generalisation of Birkhoff's theorem and a direct linearization
of the gravitational field equations. In this paper these approaches are
compared and contrasted. The general form of the gravitational lagrangian for
which the two frameworks yield identical results in the long-wavelength limit
is derived. This class of models includes the case where the lagrangian is a
power-law of the Ricci curvature scalar. The evolution of density perturbations
in theories of the type $f(R)=R-c /R^ b$ is investigated numerically. It is
found that the results obtained by the two methods are in good agreement on
sufficiently large scales when the values of the parameters (b,c) are
consistent with current observational constraints. However, this agreement
becomes progressively poorer for models that differ significantly from the
standard concordance model and as smaller scales are considered.
| [
{
"created": "Wed, 2 May 2007 09:10:33 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Jul 2007 13:07:56 GMT",
"version": "v2"
}
] | 2010-10-27 | [
[
"Uddin",
"Kotub",
""
],
[
"Lidsey",
"James E",
""
],
[
"Tavakol",
"Reza",
""
]
] | Two approaches to the study of cosmological density perturbations in modified theories of Palatini gravity have recently been discussed. These utilise, respectively, a generalisation of Birkhoff's theorem and a direct linearization of the gravitational field equations. In this paper these approaches are compared and contrasted. The general form of the gravitational lagrangian for which the two frameworks yield identical results in the long-wavelength limit is derived. This class of models includes the case where the lagrangian is a power-law of the Ricci curvature scalar. The evolution of density perturbations in theories of the type $f(R)=R-c /R^ b$ is investigated numerically. It is found that the results obtained by the two methods are in good agreement on sufficiently large scales when the values of the parameters (b,c) are consistent with current observational constraints. However, this agreement becomes progressively poorer for models that differ significantly from the standard concordance model and as smaller scales are considered. |
gr-qc/0604109 | Fangyu Li | Fangyu Li, R. M. L. Baker, Jr., and Zhenya Chen | Perturbative photon flux generated by high-frequency relic gravitational
waves and utilization of them for their detection | 26 pages, 4 figures, 3 tables. submitted to Classical and Quantum
Gravity | null | null | null | gr-qc | null | There exist corresponding metric perturbations of the relic gravitational
waves (GWs) in the region of approximately h~10^(-30)-10^(-32)in the GHz band.
A detector for these GWs is described in which we measure the perturbative
photon flux (PPF) or signal generated by such high-frequency relic GWs (HFRGWs)
via a coupling system of fractal membranes and a Gaussian beam (GB) passing
through a static magnetic field. It is found that under the synchro-resonance
condition in which the frequency of the GB is set equal to the frequency of the
expected HFRGWs (h~2.00*10^(-31), v_g=10^10Hz in the quintessential
inflationary models (QIM) and h~6.32*10^(-31), v_g=10^10Hz in the pre-big bang
scenario (PBBS) may produce the PPFs of ~4.04*10^2/s and ~1.27*10^3/s in a
surface of 100cm^2 area at the waist of the GB, respectively. The relatively
weak first-order PPF, directed at right angles to the expected HFRGWs, is
reflected by fractal membrane and the resulting reflected PPF (signal) exhibits
a very small decay in transit to the detector (tunable microwave receiver)
compared with the much stronger background photon flux, which allows for
detection of the reflected PPF with signal to background noise ratios greater
than one at the distance of the detector. We also discuss the selection
capability of system and directional sensitivity for the resonance components
from the stochastic relic GW background. The resolution of tiny difference
between the PPFs generated by the relic GWs in the QIM and in the PBBS may be
established and will be of cosmological significance. PACS numbers: 04.30.Nk,
04.30.Db, and 98.80.Cq.
| [
{
"created": "Wed, 26 Apr 2006 03:17:02 GMT",
"version": "v1"
}
] | 2012-08-27 | [
[
"Li",
"Fangyu",
""
],
[
"Baker,",
"R. M. L.",
"Jr."
],
[
"Chen",
"Zhenya",
""
]
] | There exist corresponding metric perturbations of the relic gravitational waves (GWs) in the region of approximately h~10^(-30)-10^(-32)in the GHz band. A detector for these GWs is described in which we measure the perturbative photon flux (PPF) or signal generated by such high-frequency relic GWs (HFRGWs) via a coupling system of fractal membranes and a Gaussian beam (GB) passing through a static magnetic field. It is found that under the synchro-resonance condition in which the frequency of the GB is set equal to the frequency of the expected HFRGWs (h~2.00*10^(-31), v_g=10^10Hz in the quintessential inflationary models (QIM) and h~6.32*10^(-31), v_g=10^10Hz in the pre-big bang scenario (PBBS) may produce the PPFs of ~4.04*10^2/s and ~1.27*10^3/s in a surface of 100cm^2 area at the waist of the GB, respectively. The relatively weak first-order PPF, directed at right angles to the expected HFRGWs, is reflected by fractal membrane and the resulting reflected PPF (signal) exhibits a very small decay in transit to the detector (tunable microwave receiver) compared with the much stronger background photon flux, which allows for detection of the reflected PPF with signal to background noise ratios greater than one at the distance of the detector. We also discuss the selection capability of system and directional sensitivity for the resonance components from the stochastic relic GW background. The resolution of tiny difference between the PPFs generated by the relic GWs in the QIM and in the PBBS may be established and will be of cosmological significance. PACS numbers: 04.30.Nk, 04.30.Db, and 98.80.Cq. |
2408.05018 | Sanjay Siwach | Bijendra Kumar Vishvakarma, Shubham Kala and Sanjay Siwach | Strong Gravitational Lensing by Bardeen Black Hole in Cloud of Strings | 20 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the gravitational lensing by Bardeen black hole in cloud of
strings (CoS) in strong field limit. The effect of CoS parameter $b$ has been
outlined in comparison with Bardeen black hole lens. The impact parameter
increases as we increase the CoS parameter consequently more photons approach
towards lens. We also obtain magnification of relativistic images and determine
relativistic Einstein rings by using the parameters of two astrophysical black
hole lenses $SgrA^{*}$ and $M87^{*}$. We constrain CoS parameter of black hole
using EHT observations for these black holes. We also consider the time delay
of signals in the presence of CoS parameter. It is significantly measurable for
supermassive black hole $M87^{*}$ than $SgrA^{*}$. This analysis would
constrain the Bardeen black hole in CoS as one of the candidates of primordial
gravitational lens.
| [
{
"created": "Fri, 9 Aug 2024 12:12:55 GMT",
"version": "v1"
}
] | 2024-08-12 | [
[
"Vishvakarma",
"Bijendra Kumar",
""
],
[
"Kala",
"Shubham",
""
],
[
"Siwach",
"Sanjay",
""
]
] | We investigate the gravitational lensing by Bardeen black hole in cloud of strings (CoS) in strong field limit. The effect of CoS parameter $b$ has been outlined in comparison with Bardeen black hole lens. The impact parameter increases as we increase the CoS parameter consequently more photons approach towards lens. We also obtain magnification of relativistic images and determine relativistic Einstein rings by using the parameters of two astrophysical black hole lenses $SgrA^{*}$ and $M87^{*}$. We constrain CoS parameter of black hole using EHT observations for these black holes. We also consider the time delay of signals in the presence of CoS parameter. It is significantly measurable for supermassive black hole $M87^{*}$ than $SgrA^{*}$. This analysis would constrain the Bardeen black hole in CoS as one of the candidates of primordial gravitational lens. |
gr-qc/0608136 | Rituparno Goswami | Rituparno Goswami and Pankaj S Joshi | Spherical gravitational collapse in N-dimensions | Revtex4, The replaced version matches the published one | Phys.Rev.D76:084026,2007 | 10.1103/PhysRevD.76.084026 | null | gr-qc | null | We investigate here spherically symmetric gravitational collapse in a
spacetime with an arbitrary number of dimensions and with a general {\it type
I} matter field, which is a broad class that includes most of the physically
reasonable matter forms. We show that given the initial data for matter in
terms of the initial density and pressure profiles at an initial surface
$t=t_i$ from which the collapse evolves, there exist rest of the initial data
functions and classes of solutions of Einstein equations which we construct
here, such that the spacetime evolution goes to a final state which is either a
black hole or a naked singularity, depending on the nature of initial data and
evolutions chosen, and subject to validity of the weak energy condition. The
results are discussed and analyzed in the light of the cosmic censorship
hypothesis in black hole physics. The formalism here combines the earlier
results on gravitational collapse in four dimensions in a unified treatment.
Also the earlier work is generalized to higher dimensional spacetimes to allow
a study of the effect of number of dimensions on the possible final outcome of
the collapse in terms of either a black hole or naked singularity. No
restriction is adopted on the number of dimensions, and other limiting
assumptions such as self-similarity of spacetime are avoided, in order to keep
the treatment general. Our methodology allows to consider to an extent the
genericity and stability aspects related to the occurrence of naked
singularities in gravitational collapse.
| [
{
"created": "Wed, 30 Aug 2006 22:16:17 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Jan 2008 12:34:12 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Goswami",
"Rituparno",
""
],
[
"Joshi",
"Pankaj S",
""
]
] | We investigate here spherically symmetric gravitational collapse in a spacetime with an arbitrary number of dimensions and with a general {\it type I} matter field, which is a broad class that includes most of the physically reasonable matter forms. We show that given the initial data for matter in terms of the initial density and pressure profiles at an initial surface $t=t_i$ from which the collapse evolves, there exist rest of the initial data functions and classes of solutions of Einstein equations which we construct here, such that the spacetime evolution goes to a final state which is either a black hole or a naked singularity, depending on the nature of initial data and evolutions chosen, and subject to validity of the weak energy condition. The results are discussed and analyzed in the light of the cosmic censorship hypothesis in black hole physics. The formalism here combines the earlier results on gravitational collapse in four dimensions in a unified treatment. Also the earlier work is generalized to higher dimensional spacetimes to allow a study of the effect of number of dimensions on the possible final outcome of the collapse in terms of either a black hole or naked singularity. No restriction is adopted on the number of dimensions, and other limiting assumptions such as self-similarity of spacetime are avoided, in order to keep the treatment general. Our methodology allows to consider to an extent the genericity and stability aspects related to the occurrence of naked singularities in gravitational collapse. |
1509.05693 | Ivan Agullo | Ivan Agullo and Noah A. Morris | Detailed analysis of the predictions of loop quantum cosmology for the
primordial power spectra | 24 pages, 5 figures | Phys. Rev. D 92, 124040 (2015) | 10.1103/PhysRevD.92.124040 | LSU-REL-091815 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide an exhaustive numerical exploration of the predictions of loop
quantum cosmology (LQC) with a post-bounce phase of inflation for the
primordial power spectrum of scalar and tensor perturbations. We extend
previous analysis by characterizing the phenomenologically relevant parameter
space and by constraining it using observations. Furthermore, we characterize
the shape of LQC-corrections to observable quantities across this parameter
space. Our analysis provides a framework to contrast more accurately the theory
with forthcoming polarization data, and it also paves the road for the
computation of other observables beyond the power spectra, such as
non-Gaussianity.
| [
{
"created": "Fri, 18 Sep 2015 16:38:55 GMT",
"version": "v1"
}
] | 2015-12-30 | [
[
"Agullo",
"Ivan",
""
],
[
"Morris",
"Noah A.",
""
]
] | We provide an exhaustive numerical exploration of the predictions of loop quantum cosmology (LQC) with a post-bounce phase of inflation for the primordial power spectrum of scalar and tensor perturbations. We extend previous analysis by characterizing the phenomenologically relevant parameter space and by constraining it using observations. Furthermore, we characterize the shape of LQC-corrections to observable quantities across this parameter space. Our analysis provides a framework to contrast more accurately the theory with forthcoming polarization data, and it also paves the road for the computation of other observables beyond the power spectra, such as non-Gaussianity. |
gr-qc/9211021 | null | M.Gasperini and M.Giovannini | Dilaton Contributions to the Cosmic Gravitational Wave Background | 26 pages, plain tex (to appear in Phys.Rev.D, 1 fig available from
the authors upon req.) | Phys.Rev. D47 (1993) 1519-1528 | 10.1103/PhysRevD.47.1519 | DFTT-58/92 | gr-qc hep-th | null | We consider the cosmological amplification of a metric perturbation
propagating in a higher-dimensional Brans-Dicke background, including a non
trivial dilaton evolution. We discuss the properties of the spectral energy
density of the produced gravitons (as well as of the associated squeezing
parameter), and we show that the present observational bounds on the graviton
spectrum provide significant information on the dynamical evolution of the
early universe.
| [
{
"created": "Tue, 17 Nov 1992 21:57:00 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Gasperini",
"M.",
""
],
[
"Giovannini",
"M.",
""
]
] | We consider the cosmological amplification of a metric perturbation propagating in a higher-dimensional Brans-Dicke background, including a non trivial dilaton evolution. We discuss the properties of the spectral energy density of the produced gravitons (as well as of the associated squeezing parameter), and we show that the present observational bounds on the graviton spectrum provide significant information on the dynamical evolution of the early universe. |
1001.0079 | Bin Wang | Jian-Hua He, Bin Wang, Elcio Abdalla, Diego Pavon | The imprint of the interaction between dark sectors in galaxy clusters | revised version. New treatment has been provided on studying the
structure formation in the spherical collapsing system where DE does not
cluster together with DM. Accepted for publication in JCAP | JCAP 1012:022,2010 | 10.1088/1475-7516/2010/12/022 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on perturbation theory, we study the dynamics of how dark matter and
dark energy in the collapsing system approach dynamical equilibrium while
interacting. We find that the interaction between dark sectors cannot ensure
the dark energy to fully cluster along with dark, leading to the energy
non-conservation problem in the collapsing system We examine the cluster number
counts dependence on the interaction between dark sectors. Furthermore, we
analyze how dark energy inhomogeneities affect cluster abundances. It is shown
that cluster number counts can provide specific signature of dark sectors
interaction and dark energy inhomogeneities.
| [
{
"created": "Thu, 31 Dec 2009 03:38:30 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Dec 2010 10:26:27 GMT",
"version": "v2"
}
] | 2015-03-13 | [
[
"He",
"Jian-Hua",
""
],
[
"Wang",
"Bin",
""
],
[
"Abdalla",
"Elcio",
""
],
[
"Pavon",
"Diego",
""
]
] | Based on perturbation theory, we study the dynamics of how dark matter and dark energy in the collapsing system approach dynamical equilibrium while interacting. We find that the interaction between dark sectors cannot ensure the dark energy to fully cluster along with dark, leading to the energy non-conservation problem in the collapsing system We examine the cluster number counts dependence on the interaction between dark sectors. Furthermore, we analyze how dark energy inhomogeneities affect cluster abundances. It is shown that cluster number counts can provide specific signature of dark sectors interaction and dark energy inhomogeneities. |
2011.00805 | Zhi-Bang Yao | Zhi-Bang Yao, Michele Oliosi, Xian Gao, Shinji Mukohyama | Minimally modified gravity with an auxiliary constraint: a Hamiltonian
construction | 11 pages | Phys. Rev. D 103, 024032 (2021) | 10.1103/PhysRevD.103.024032 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Working directly with a general Hamiltonian for the spacetime metric with the
$3+1$ decomposition and keeping only the spatial covariance, we investigate the
possibility of reducing the number of degrees of freedom by introducing an
auxiliary constraint. The auxiliary constraint is considered as part of the
definition of the theory. Through a general Hamiltonian analysis, we find the
conditions for the Hamiltonian as well as for the auxiliary constraint, under
which the theory propagates two tensorial degrees of freedom only. The class of
theories satisfying these conditions can be viewed as a new construction for
the type-II minimally modified gravity theories, which propagate the same
degrees of freedom of but are not equivalent to general relativity in the
vacuum. We also illustrate our formalism by a concrete example, and derive the
dispersion relation for the gravitational waves, which can be constrained by
observations.
| [
{
"created": "Mon, 2 Nov 2020 08:11:22 GMT",
"version": "v1"
}
] | 2021-01-20 | [
[
"Yao",
"Zhi-Bang",
""
],
[
"Oliosi",
"Michele",
""
],
[
"Gao",
"Xian",
""
],
[
"Mukohyama",
"Shinji",
""
]
] | Working directly with a general Hamiltonian for the spacetime metric with the $3+1$ decomposition and keeping only the spatial covariance, we investigate the possibility of reducing the number of degrees of freedom by introducing an auxiliary constraint. The auxiliary constraint is considered as part of the definition of the theory. Through a general Hamiltonian analysis, we find the conditions for the Hamiltonian as well as for the auxiliary constraint, under which the theory propagates two tensorial degrees of freedom only. The class of theories satisfying these conditions can be viewed as a new construction for the type-II minimally modified gravity theories, which propagate the same degrees of freedom of but are not equivalent to general relativity in the vacuum. We also illustrate our formalism by a concrete example, and derive the dispersion relation for the gravitational waves, which can be constrained by observations. |
0710.3823 | Ulrich Sperhake | U. Sperhake, E. Berti, V. Cardoso, J. A. Gonzalez, B. Bruegmann and M.
Ansorg | Eccentric binary black-hole mergers: The transition from inspiral to
plunge in general relativity | Added sequence of long inspirals to the study. To match published
version | Phys.Rev.D78:064069,2008 | 10.1103/PhysRevD.78.064069 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the transition from inspiral to plunge in general relativity by
computing gravitational waveforms of non-spinning, equal-mass black-hole
binaries. We consider three sequences of simulations, starting with a
quasi-circular inspiral completing 1.5, 2.3 and 9.6 orbits, respectively, prior
to coalescence of the holes. For each sequence, the binding energy of the
system is kept constant and the orbital angular momentum is progressively
reduced, producing orbits of increasing eccentricity and eventually a head-on
collision. We analyze in detail the radiation of energy and angular momentum in
gravitational waves, the contribution of different multipolar components and
the final spin of the remnant. We find that the motion transitions from
inspiral to plunge when the orbital angular momentum L=L_crit is about 0.8M^2.
For L<L_crit the radiated energy drops very rapidly. Orbits with L of about
L_crit produce our largest dimensionless Kerr parameter for the remnant,
j=J/M^2=0.724. Generalizing a model recently proposed by Buonanno, Kidder and
Lehner to eccentric binaries, we conjecture that (1) j=0.724 is the maximal
Kerr parameter that can be obtained by any merger of non-spinning holes, and
(2) no binary merger (even if the binary members are extremal Kerr black holes
with spins aligned to the orbital angular momentum, and the inspiral is highly
eccentric) can violate the cosmic censorship conjecture.
| [
{
"created": "Sun, 21 Oct 2007 04:15:29 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Sep 2008 23:40:49 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Sperhake",
"U.",
""
],
[
"Berti",
"E.",
""
],
[
"Cardoso",
"V.",
""
],
[
"Gonzalez",
"J. A.",
""
],
[
"Bruegmann",
"B.",
""
],
[
"Ansorg",
"M.",
""
]
] | We study the transition from inspiral to plunge in general relativity by computing gravitational waveforms of non-spinning, equal-mass black-hole binaries. We consider three sequences of simulations, starting with a quasi-circular inspiral completing 1.5, 2.3 and 9.6 orbits, respectively, prior to coalescence of the holes. For each sequence, the binding energy of the system is kept constant and the orbital angular momentum is progressively reduced, producing orbits of increasing eccentricity and eventually a head-on collision. We analyze in detail the radiation of energy and angular momentum in gravitational waves, the contribution of different multipolar components and the final spin of the remnant. We find that the motion transitions from inspiral to plunge when the orbital angular momentum L=L_crit is about 0.8M^2. For L<L_crit the radiated energy drops very rapidly. Orbits with L of about L_crit produce our largest dimensionless Kerr parameter for the remnant, j=J/M^2=0.724. Generalizing a model recently proposed by Buonanno, Kidder and Lehner to eccentric binaries, we conjecture that (1) j=0.724 is the maximal Kerr parameter that can be obtained by any merger of non-spinning holes, and (2) no binary merger (even if the binary members are extremal Kerr black holes with spins aligned to the orbital angular momentum, and the inspiral is highly eccentric) can violate the cosmic censorship conjecture. |
2002.07918 | Anuradha Samajdar | Anuradha Samajdar and Tim Dietrich | Constructing Love-Q-Relations with Gravitational Wave Detections | 5 pages, 3 figures | Phys. Rev. D 101, 124014 (2020) | 10.1103/PhysRevD.101.124014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quasi-universal relations connecting the tidal deformability and the
quadrupole moment of individual neutron stars are predicted by theoretical
computations, but have not been measured experimentally. However, such
relations are employed during the interpretation of gravitational waves and,
therefore, have a direct impact on the interpretation of real data. In this
work, we study how quasi-universal relations can be tested and measured from
gravitational wave signals connected to binary neutron star coalescences. We
study a population of $120$ binary neutron star systems and find that Advanced
LIGO and Advanced Virgo at design sensitivity could find possible deviations of
predicted relations if the observed neutron stars are highly spinning. In the
future, a network of third generation (3G) detectors will be able to even allow
a measurement of quasi-universal relations. Thus, the outlined approach
provides a new test of general relativity and nuclear physics predictions.
| [
{
"created": "Tue, 18 Feb 2020 23:10:03 GMT",
"version": "v1"
}
] | 2020-07-01 | [
[
"Samajdar",
"Anuradha",
""
],
[
"Dietrich",
"Tim",
""
]
] | Quasi-universal relations connecting the tidal deformability and the quadrupole moment of individual neutron stars are predicted by theoretical computations, but have not been measured experimentally. However, such relations are employed during the interpretation of gravitational waves and, therefore, have a direct impact on the interpretation of real data. In this work, we study how quasi-universal relations can be tested and measured from gravitational wave signals connected to binary neutron star coalescences. We study a population of $120$ binary neutron star systems and find that Advanced LIGO and Advanced Virgo at design sensitivity could find possible deviations of predicted relations if the observed neutron stars are highly spinning. In the future, a network of third generation (3G) detectors will be able to even allow a measurement of quasi-universal relations. Thus, the outlined approach provides a new test of general relativity and nuclear physics predictions. |
1610.08225 | Hedvika Kadlecova | Hedvika Kadlecov\'a and Pavel Krtou\v{s} | The gyraton solutions on generalized Melvin universe with cosmological
constant | 16 pages, 7 figures, Workshop proceeding RAGtime 2010-14 on black
holes and neutron stars | Workshops on black holes and neutron stars 2008/2009/2010/2011
Silesian University in Opava, 2014, pp. 61-74 | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present and analyze new exact gyraton solutions of algebraic type II on
generalized Melvin universe of type D which admit non-vanishing cosmological
constant $\Lambda$. We show that it generalizes both, gyraton solutions on
Melvin and on direct product spacetimes. When we set $\Lambda = 0$ we get
solutions on Melvin spacetime and for $\Sigma = 1$ we obtain solutions on
direct product spacetimes. We demonstrate that the solutions are member of the
Kundt family of spacetimes as its subcases. We show that the Einstein equations
reduce to a set of equations on the transverse 2-space. We also discuss the
polynomial scalar invariants which are non-constant in general but constant for
sub-solutions on direct product spacetimes.
| [
{
"created": "Wed, 26 Oct 2016 08:23:28 GMT",
"version": "v1"
}
] | 2016-10-27 | [
[
"Kadlecová",
"Hedvika",
""
],
[
"Krtouš",
"Pavel",
""
]
] | We present and analyze new exact gyraton solutions of algebraic type II on generalized Melvin universe of type D which admit non-vanishing cosmological constant $\Lambda$. We show that it generalizes both, gyraton solutions on Melvin and on direct product spacetimes. When we set $\Lambda = 0$ we get solutions on Melvin spacetime and for $\Sigma = 1$ we obtain solutions on direct product spacetimes. We demonstrate that the solutions are member of the Kundt family of spacetimes as its subcases. We show that the Einstein equations reduce to a set of equations on the transverse 2-space. We also discuss the polynomial scalar invariants which are non-constant in general but constant for sub-solutions on direct product spacetimes. |
2004.10772 | Adrien Kuntz | Adrien Kuntz, Riccardo Penco and Federico Piazza | Extreme Mass Ratio Inspirals with Scalar Hair | 37 pages; version accepted for publication in JCAP | null | 10.1088/1475-7516/2020/08/023 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Stellar mass objects orbiting around supermassive black holes are primary
targets for future gravitational wave detectors like LISA. However, in theories
beyond general relativity, the corresponding waveform templates are still
relatively poorly known. We propose a universal description for these systems
which applies to any black hole with a non trivial scalar profile, or scalar
hair. To this aim, we use the effective field theory recently introduced by
Franciolini et al. to write the most general action for the perturbations of a
spherically symmetric solution up to some given order in derivatives and/or
number of fields. At any post-Newtonian order, the background metric and the
relevant operators can be encoded in a limited number of parameters which are
readily calculated in some given scalar tensor model, as we show with a couple
of examples. In terms of such parameters, we obtain an analytic expression for
the dissipated power in the odd sector by solving perturbatively the
Regge-Wheeler equation in the presence of a point-particle source.
| [
{
"created": "Wed, 22 Apr 2020 18:01:02 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Sep 2020 07:07:58 GMT",
"version": "v2"
}
] | 2020-09-16 | [
[
"Kuntz",
"Adrien",
""
],
[
"Penco",
"Riccardo",
""
],
[
"Piazza",
"Federico",
""
]
] | Stellar mass objects orbiting around supermassive black holes are primary targets for future gravitational wave detectors like LISA. However, in theories beyond general relativity, the corresponding waveform templates are still relatively poorly known. We propose a universal description for these systems which applies to any black hole with a non trivial scalar profile, or scalar hair. To this aim, we use the effective field theory recently introduced by Franciolini et al. to write the most general action for the perturbations of a spherically symmetric solution up to some given order in derivatives and/or number of fields. At any post-Newtonian order, the background metric and the relevant operators can be encoded in a limited number of parameters which are readily calculated in some given scalar tensor model, as we show with a couple of examples. In terms of such parameters, we obtain an analytic expression for the dissipated power in the odd sector by solving perturbatively the Regge-Wheeler equation in the presence of a point-particle source. |
0707.3073 | Belinch\'on Jos\'e Antonio | Jos\'e Antonio Belinch\'on | About Bianchi I with time varying constants | 30 pages. Revtex4 | Gravitation and Cosmology, 15, 306-316. (2009) | null | null | gr-qc | null | In this paper we study how to attack through different techniques a perfect
fluid Bianchi I model with variable G, and $\Lambda.$ These tactics are: Lie
groups method (LM), imposing a particular symmetry, self-similarity (SS),
matter collineations (MC). and kinematical self-similarity (KSS). We compare
both tactics since they are quite similar (symmetry principles). We arrive to
the conclusion that the LM is too restrictive and brings us to get only the
flat FRW solution with G=const. and $\Lambda=0$. The SS, MC and KSS approaches
bring us to obtain the following solution: G is a decreasing time function and
$\Lambda\thickapprox t^{-2}$, with $\Lambda<0$, while the exponents of the
scale factor must satisfy the conditions $\sum_{i=1}% ^{3}\alpha_{i}=1$ and
$\sum_{i=1}^{3}\alpha_{i}^{2}<1,$ $\forall\omega \in(-1,1)$, relaxing in this
way the Kasner conditions.
| [
{
"created": "Fri, 20 Jul 2007 13:55:11 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Jul 2007 13:37:02 GMT",
"version": "v2"
}
] | 2009-10-12 | [
[
"Belinchón",
"José Antonio",
""
]
] | In this paper we study how to attack through different techniques a perfect fluid Bianchi I model with variable G, and $\Lambda.$ These tactics are: Lie groups method (LM), imposing a particular symmetry, self-similarity (SS), matter collineations (MC). and kinematical self-similarity (KSS). We compare both tactics since they are quite similar (symmetry principles). We arrive to the conclusion that the LM is too restrictive and brings us to get only the flat FRW solution with G=const. and $\Lambda=0$. The SS, MC and KSS approaches bring us to obtain the following solution: G is a decreasing time function and $\Lambda\thickapprox t^{-2}$, with $\Lambda<0$, while the exponents of the scale factor must satisfy the conditions $\sum_{i=1}% ^{3}\alpha_{i}=1$ and $\sum_{i=1}^{3}\alpha_{i}^{2}<1,$ $\forall\omega \in(-1,1)$, relaxing in this way the Kasner conditions. |
2308.03501 | Georgios Antoniou | Georgios Antoniou | New perspectives on scalar fields in strong gravity | 132 pages, Ph.D. thesis | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent developments in the field of gravitational physics, including the
emergence of gravitational wave astronomy, black hole images, and more accurate
telescopes, have allowed us to probe the strong-field character of gravity in a
novel and revolutionary manner. This accessibility related to strong gravity
brings into the foreground discussions about potential modifications to General
Relativity (GR) that are particularly relevant in high curvature regimes. The
most straightforward way to generalise GR is to consider an additional degree
of freedom, in the form of a scalar field. In this thesis, we study generalised
scalar tensor theories that predict interesting strong-gravity phenomenology.
First, we review scalar no-hair theorems and the conditions under which they
can be evaded. Next, we study solutions of black holes with scalar hair and the
way in which higher derivative terms alter their properties. We then move our
discussion to the spontaneously scalarized solutions, which only deviate from
GR in the strong-field regime. We propose a model consistent with compact
object scalarization, that allows for a GR attractor at late times, without
fine-tuning (EsRGB model). Then, we proceed to study properties of black holes
and neutron stars in this theory, revealing the interesting phenomenology of
the solutions. We also study the radial stability of black holes in EsRGB and
perform a preliminary analysis of the hyperbolicity of the problem. Finally, we
take a look at the shadows of black holes and wormholes in theories with scalar
fields, in light of recent observations of black hole shadows.
| [
{
"created": "Mon, 7 Aug 2023 11:53:47 GMT",
"version": "v1"
}
] | 2023-08-08 | [
[
"Antoniou",
"Georgios",
""
]
] | Recent developments in the field of gravitational physics, including the emergence of gravitational wave astronomy, black hole images, and more accurate telescopes, have allowed us to probe the strong-field character of gravity in a novel and revolutionary manner. This accessibility related to strong gravity brings into the foreground discussions about potential modifications to General Relativity (GR) that are particularly relevant in high curvature regimes. The most straightforward way to generalise GR is to consider an additional degree of freedom, in the form of a scalar field. In this thesis, we study generalised scalar tensor theories that predict interesting strong-gravity phenomenology. First, we review scalar no-hair theorems and the conditions under which they can be evaded. Next, we study solutions of black holes with scalar hair and the way in which higher derivative terms alter their properties. We then move our discussion to the spontaneously scalarized solutions, which only deviate from GR in the strong-field regime. We propose a model consistent with compact object scalarization, that allows for a GR attractor at late times, without fine-tuning (EsRGB model). Then, we proceed to study properties of black holes and neutron stars in this theory, revealing the interesting phenomenology of the solutions. We also study the radial stability of black holes in EsRGB and perform a preliminary analysis of the hyperbolicity of the problem. Finally, we take a look at the shadows of black holes and wormholes in theories with scalar fields, in light of recent observations of black hole shadows. |
gr-qc/9511069 | {\O}ystein Lund B{\o} | B.L.Altshuler, A.M.Boyarsky and A.Yu.Neronov | The Problem of Classical Limit in Quantum Cosmology: The effective
action language | 16 pages, Latex, Report at the seminar ``Quantum Gravity. In Memory
of Academician Moisei Markov'', Moscow, June 12-19, 1995. To be published in
World Scientific | Int.J.Mod.Phys. D5 (1996) 869-884 | 10.1142/S0218271896000527 | null | gr-qc | null | The tool of functional averaging over some ``large'' diffeomorphisms is used
to describe quantum systems with constraints, in particular quantum cosmology,
in the language of quantum Effective Action. Simple toy models demonstrate a
supposedly general phenomenon: the presence of a constraint results in
``quantum repel'' from the classical mass shell.
| [
{
"created": "Mon, 27 Nov 1995 09:26:02 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Altshuler",
"B. L.",
""
],
[
"Boyarsky",
"A. M.",
""
],
[
"Neronov",
"A. Yu.",
""
]
] | The tool of functional averaging over some ``large'' diffeomorphisms is used to describe quantum systems with constraints, in particular quantum cosmology, in the language of quantum Effective Action. Simple toy models demonstrate a supposedly general phenomenon: the presence of a constraint results in ``quantum repel'' from the classical mass shell. |
1408.5253 | Andrea Geralico | Donato Bini and Andrea Geralico | Observer-dependent tidal indicators in the Kerr spacetime | 15 pages, 4 figures. Note that there is a misprint in Eq. (4.5) of
the published version: the plus sign in front of the last term in the sum (at
the beginning of the last line) should be a minus sign. The resulting Eq.
(4.6) should be corrected too. However, these misprinted equations are only a
re-writing of previous equations, so that the analysis of the tidal
indicators is not affected. arXiv admin note: text overlap with
arXiv:1306.4803 | Class. Quantum Grav. 29, 055005 (2012) | 10.1088/0264-9381/29/5/055005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The observer-dependent tidal effects associated with the electric and
magnetic parts of the Riemann tensor with respect to an arbitrary family of
observers are discussed in a general spacetime in terms of certain "tidal
indicators." The features of such indicators are then explored by specializing
our considerations to the family of stationary circularly rotating observers in
the equatorial plane of the Kerr spacetime. There exist a number of observer
families which are special for several reasons and for each of them such
indicators are evaluated. The transformation laws of tidal indicators when
passing from one observer to another are also discussed, clarifying the
interplay among them. Our analysis shows that no equatorial plane circularly
rotating observer in the Kerr spacetime can ever measure a vanishing tidal
electric indicator, whereas the family of Carter's observers measures zero
tidal magnetic indicator.
| [
{
"created": "Fri, 22 Aug 2014 10:34:23 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
]
] | The observer-dependent tidal effects associated with the electric and magnetic parts of the Riemann tensor with respect to an arbitrary family of observers are discussed in a general spacetime in terms of certain "tidal indicators." The features of such indicators are then explored by specializing our considerations to the family of stationary circularly rotating observers in the equatorial plane of the Kerr spacetime. There exist a number of observer families which are special for several reasons and for each of them such indicators are evaluated. The transformation laws of tidal indicators when passing from one observer to another are also discussed, clarifying the interplay among them. Our analysis shows that no equatorial plane circularly rotating observer in the Kerr spacetime can ever measure a vanishing tidal electric indicator, whereas the family of Carter's observers measures zero tidal magnetic indicator. |
1711.05514 | Ohkyung Kwon | Craig Hogan and Ohkyung Kwon | Models of Exotic Interferometer Cross-Correlations in Emergent
Space-Time | 26 pages, 14 figures. This is an author-created, un-copyedited
version of an article published in Classical and Quantum Gravity. IOP
Publishing Ltd is not responsible for any errors or omissions in this version
of the manuscript or any version derived from it. The Version of Record is
available online at the DOI link below. Includes quotes from arXiv:1109.2435
by T. Banks | Class. Quantum Grav. 35 204001 (2018) -- Focus Issue on Gravity in
the Lab | 10.1088/1361-6382/aadea4 | FERMILAB-PUB-17-481-A | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A Lorentz invariant framework is developed to model the cross spectrum of two
interferometers in a space-time that emerges from a Planck scale quantum system
with exact causal symmetry and holographic spacelike rotational correlations.
Space-time relationships between world lines are generated by entanglement of
geometrical states on causal diamonds. The entanglement is tied to a unique
observable signature: an exotic imaginary broad band cross spectrum, with a
frequency structure determined by the layout of the interferometers. The models
will be used to interpret data from the reconfigured Fermilab Holometer, and
for conceptual design of future experiments.
| [
{
"created": "Wed, 15 Nov 2017 12:14:09 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Nov 2017 03:12:48 GMT",
"version": "v2"
},
{
"created": "Tue, 28 Nov 2017 16:25:54 GMT",
"version": "v3"
},
{
"created": "Sun, 17 Dec 2017 07:57:17 GMT",
"version": "v4"
},
{
"c... | 2018-09-21 | [
[
"Hogan",
"Craig",
""
],
[
"Kwon",
"Ohkyung",
""
]
] | A Lorentz invariant framework is developed to model the cross spectrum of two interferometers in a space-time that emerges from a Planck scale quantum system with exact causal symmetry and holographic spacelike rotational correlations. Space-time relationships between world lines are generated by entanglement of geometrical states on causal diamonds. The entanglement is tied to a unique observable signature: an exotic imaginary broad band cross spectrum, with a frequency structure determined by the layout of the interferometers. The models will be used to interpret data from the reconfigured Fermilab Holometer, and for conceptual design of future experiments. |
gr-qc/0402078 | Suresh Paingalil Kunjan | K. K. Venkataratnam and P. K. Suresh | Particle Production of Coherently Oscillating Nonclassical Inflaton in
FRW Universe | 15 pages, 1 figure, to appear in IJMPD | Int.J.Mod.Phys. D13 (2004) 239-252 | 10.1142/S0218271804004578 | null | gr-qc | null | We study particle production of coherently oscillating inflaton in the
semiclassical theory of gravity by representing inflaton in coherent and
squeezed state formalisms. A comparative study of the inflaton in classical
gravity with coherent state inflaton in semiclassical gravity is also
presented.
| [
{
"created": "Wed, 18 Feb 2004 06:29:08 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Venkataratnam",
"K. K.",
""
],
[
"Suresh",
"P. K.",
""
]
] | We study particle production of coherently oscillating inflaton in the semiclassical theory of gravity by representing inflaton in coherent and squeezed state formalisms. A comparative study of the inflaton in classical gravity with coherent state inflaton in semiclassical gravity is also presented. |
2203.08831 | Carlos O. Lousto | Carlos O. Lousto and James Healy | Study of the Intermediate Mass Ratio Black Hole Binary Merger up to
1000:1 with Numerical Relativity | 7 pages, 5 figures, 2 tables | null | 10.1088/1361-6382/acc7ef | null | gr-qc astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explicitly demonstrate that current numerical relativity techniques are
able to accurately evolve black hole binaries with mass ratios of the order of
1000:1. This proof of principle is relevant for future third generation (3G)
gravitational wave detectors and space mission LISA, as by purely numerical
methods we would be able to accurately compute gravitational waves from the
last stages of black hole mergers, as directly predicted by general relativity.
We perform a sequence of simulations in the intermediate to small mass ratio
regime, $m_1^p/m_2^p = 1/7, 1/16, 1/32, 1/64, 1/128, 1/256, 1/512, 1/1024$,
with the small hole starting from rest at a proper distance $D\approx13M$. We
compare these headon full numerical evolutions with the corresponding
semianalytic point particle perturbative results finding an impressive
agreement for the total gravitational radiated energy and linear momentum as
well as for the waveform spectra. We display numerical convergence of the
results and identify the minimal numerical resolutions required to accurately
solve for these very low amplitude gravitational waves. This work represents a
first step towards the considerable challenge of applying numerical-relativity
waveforms to interpreting gravitational-wave observations by LISA and
next-generation ground-based gravitational-wave detectors.
| [
{
"created": "Wed, 16 Mar 2022 18:00:01 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Sep 2022 12:30:53 GMT",
"version": "v2"
},
{
"created": "Fri, 24 Mar 2023 20:11:32 GMT",
"version": "v3"
}
] | 2023-04-19 | [
[
"Lousto",
"Carlos O.",
""
],
[
"Healy",
"James",
""
]
] | We explicitly demonstrate that current numerical relativity techniques are able to accurately evolve black hole binaries with mass ratios of the order of 1000:1. This proof of principle is relevant for future third generation (3G) gravitational wave detectors and space mission LISA, as by purely numerical methods we would be able to accurately compute gravitational waves from the last stages of black hole mergers, as directly predicted by general relativity. We perform a sequence of simulations in the intermediate to small mass ratio regime, $m_1^p/m_2^p = 1/7, 1/16, 1/32, 1/64, 1/128, 1/256, 1/512, 1/1024$, with the small hole starting from rest at a proper distance $D\approx13M$. We compare these headon full numerical evolutions with the corresponding semianalytic point particle perturbative results finding an impressive agreement for the total gravitational radiated energy and linear momentum as well as for the waveform spectra. We display numerical convergence of the results and identify the minimal numerical resolutions required to accurately solve for these very low amplitude gravitational waves. This work represents a first step towards the considerable challenge of applying numerical-relativity waveforms to interpreting gravitational-wave observations by LISA and next-generation ground-based gravitational-wave detectors. |
1811.12283 | Ram Brustein | Ram Brustein, A.J.M. Medved, K. Yagi | Lower limit on the entropy of black holes as inferred from gravitational
wave observations | Corrected error in estimation of current bounds on the entropy.
Improved discussion of energy stored in echoes, V3 replaced to match
published version, clarifications and explanations added | Phys. Rev. D 100, 104009 (2019) | 10.1103/PhysRevD.100.104009 | CERN-TH-2018-261 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black hole (BH) thermodynamics was established by Bekenstein and Hawking, who
made abstract theoretical arguments about the second law of thermodynamics and
quantum theory in curved spacetime respectively. Testing these ideas
experimentally has, so far, been impractical because the putative flux of
Hawking radiation from astrophysical BHs is too small to be distinguished from
the rest of the hot environment. Here, it is proposed that the spectrum of
emitted gravitational waves (GWs) after the merger of two BHs, in particular
the spectrum of GW150914, can be used to infer a lower limit on the magnitude
of the entropy of the post-merger BH. This lower bound is potentially
significant as it could be of the same order as the Bekenstein-Hawking entropy.
To infer this limit, we first assume that the result of the merger is an
ultracompact object with an external geometry which is Schwarzschild or Kerr,
but with an outer surface which is capable of reflecting in-falling GWs rather
than fully absorbing them. If the absence of deviations from the predictions of
general relativity in detected GW signals will be verified, we will then obtain
a bound on the minimal redshift factor of GWs that emerge from the vicinity of
the object's surface. This lack of deviations would also mean that the remnant
of the merger has to have a strongly absorbing surface and must then be a BH
for all practical purposes. We conclude that a relationship between the minimal
redshift factor and the BH entropy, which was first proposed by 't Hooft, could
then be used to set a lower bound on the entropy of the post-merger BH.
| [
{
"created": "Thu, 29 Nov 2018 16:16:10 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Mar 2019 21:16:38 GMT",
"version": "v2"
},
{
"created": "Sat, 2 Nov 2019 08:03:59 GMT",
"version": "v3"
}
] | 2019-11-13 | [
[
"Brustein",
"Ram",
""
],
[
"Medved",
"A. J. M.",
""
],
[
"Yagi",
"K.",
""
]
] | Black hole (BH) thermodynamics was established by Bekenstein and Hawking, who made abstract theoretical arguments about the second law of thermodynamics and quantum theory in curved spacetime respectively. Testing these ideas experimentally has, so far, been impractical because the putative flux of Hawking radiation from astrophysical BHs is too small to be distinguished from the rest of the hot environment. Here, it is proposed that the spectrum of emitted gravitational waves (GWs) after the merger of two BHs, in particular the spectrum of GW150914, can be used to infer a lower limit on the magnitude of the entropy of the post-merger BH. This lower bound is potentially significant as it could be of the same order as the Bekenstein-Hawking entropy. To infer this limit, we first assume that the result of the merger is an ultracompact object with an external geometry which is Schwarzschild or Kerr, but with an outer surface which is capable of reflecting in-falling GWs rather than fully absorbing them. If the absence of deviations from the predictions of general relativity in detected GW signals will be verified, we will then obtain a bound on the minimal redshift factor of GWs that emerge from the vicinity of the object's surface. This lack of deviations would also mean that the remnant of the merger has to have a strongly absorbing surface and must then be a BH for all practical purposes. We conclude that a relationship between the minimal redshift factor and the BH entropy, which was first proposed by 't Hooft, could then be used to set a lower bound on the entropy of the post-merger BH. |
gr-qc/0412081 | Ivan L. Zhogin | I.L.Zhogin | Absolute Parallelism: Spherical Symmetry and Singularities | v.2: 7 pages, in Latex; a bit expanded version, with more detailed
derivations and explanations; typos corrected; v.3: minor corrections, one
reference is added [quite a number of mistypes, e.g. in eqs (5),(9),(15)] | Sov.Phys.J. 34 (1992) 781 | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by-nc-sa/4.0/ | Observing the list of compatible second order equations of Absolute
Parallelism (AP) found by Einstein and Mayer (they used D=4), we choose the
one-parameter class of equations which take on a 3-linear form (when
contra-frame density of some weight is in use). Spherically symmetric solutions
to these equations are considered, and we try not to add any delta-sources (ie,
$\delta(x)$-sources of unknown nature) during integrations allowed due to this
high symmetry.
Using two different ways to fix the radius and time, we have found that only
non-static solutions (except for trivial one, of course) are possible. If D=5,
such solutions, looking like a single wave moving along the radius, could serve
as an expanding cosmological model (with a simple Hubble diagram).
With one coordinate choice (gauge), a single second order equation remains
and there exist spherically symmetric solutions with arising singularities. On
the other hand, a more reasonable (covariant) choice of the radius and time
reduces the problem to a system of two first order equations looking like
Chaplygin gas dynamics, where solutions are seemingly free of emerging
singularities and gradient catastrophe.
| [
{
"created": "Fri, 17 Dec 2004 09:34:21 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Jul 2022 14:22:12 GMT",
"version": "v2"
},
{
"created": "Sun, 21 Aug 2022 20:55:30 GMT",
"version": "v3"
}
] | 2022-09-08 | [
[
"Zhogin",
"I. L.",
""
]
] | Observing the list of compatible second order equations of Absolute Parallelism (AP) found by Einstein and Mayer (they used D=4), we choose the one-parameter class of equations which take on a 3-linear form (when contra-frame density of some weight is in use). Spherically symmetric solutions to these equations are considered, and we try not to add any delta-sources (ie, $\delta(x)$-sources of unknown nature) during integrations allowed due to this high symmetry. Using two different ways to fix the radius and time, we have found that only non-static solutions (except for trivial one, of course) are possible. If D=5, such solutions, looking like a single wave moving along the radius, could serve as an expanding cosmological model (with a simple Hubble diagram). With one coordinate choice (gauge), a single second order equation remains and there exist spherically symmetric solutions with arising singularities. On the other hand, a more reasonable (covariant) choice of the radius and time reduces the problem to a system of two first order equations looking like Chaplygin gas dynamics, where solutions are seemingly free of emerging singularities and gradient catastrophe. |
gr-qc/9910113 | Kenji Sakamoto | Kenji Sakamoto, Kiyoshi Shiraishi (Yamaguchi University) | Rotating Boson Star with Large Self-interaction in (2+1) dimensions | 14 pages, 6 figures, RevTeX | Phys.Rev. D62 (2000) 124014 | 10.1103/PhysRevD.62.124014 | null | gr-qc | null | Solutions for rotating boson stars in (2+1) dimensional gravity with a
negative cosmological constant are obtained numerically. The mass, particle
number, and radius of the (2+1) dimensional rotating boson star are shown.
Consequently we find the region where the stable boson star can exist.
| [
{
"created": "Mon, 1 Nov 1999 05:41:52 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Dec 1999 16:56:07 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Sakamoto",
"Kenji",
"",
"Yamaguchi University"
],
[
"Shiraishi",
"Kiyoshi",
"",
"Yamaguchi University"
]
] | Solutions for rotating boson stars in (2+1) dimensional gravity with a negative cosmological constant are obtained numerically. The mass, particle number, and radius of the (2+1) dimensional rotating boson star are shown. Consequently we find the region where the stable boson star can exist. |
1909.02997 | Ulrich Sperhake | Ulrich Sperhake, William Cook, Diandian Wang | The high-energy collision of black holes in higher dimensions | minor corrections to references; 10 pages, 5 figures, in print in
Physical Review D | Phys. Rev. D 100, 104046 (2019) | 10.1103/PhysRevD.100.104046 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the gravitational wave energy $E_{\rm rad}$ radiated in head-on
collisions of equal-mass, nonspinning black holes in up to $D=8$ dimensional
asymptotically flat spacetimes for boost velocities $v$ up to about $90\,\%$ of
the speed of light. We identify two main regimes: Weak radiation at velocities
up to about $40\,\%$ of the speed of light, and exponential growth of $E_{\rm
rad}$ with $v$ at larger velocities. Extrapolation to the speed of light
predicts a limit of $12.9\,\%$ $(10.1,~7.7,~5.5,~4.5)\,\%$. of the total mass
that is lost in gravitational waves in $D=4$ $(5,\,6,\,7,\,8)$ spacetime
dimensions. In agreement with perturbative calculations, we observe that the
radiation is minimal for small but finite velocities, rather than for
collisions starting from rest. Our computations support the identification of
regimes with super Planckian curvature outside the black-hole horizons reported
by Okawa, Nakao, and Shibata [Phys.~Rev.~D {\bf 83} 121501(R) (2011)].
| [
{
"created": "Fri, 6 Sep 2019 16:24:19 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Oct 2019 20:08:53 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Nov 2019 16:08:14 GMT",
"version": "v3"
}
] | 2019-11-27 | [
[
"Sperhake",
"Ulrich",
""
],
[
"Cook",
"William",
""
],
[
"Wang",
"Diandian",
""
]
] | We compute the gravitational wave energy $E_{\rm rad}$ radiated in head-on collisions of equal-mass, nonspinning black holes in up to $D=8$ dimensional asymptotically flat spacetimes for boost velocities $v$ up to about $90\,\%$ of the speed of light. We identify two main regimes: Weak radiation at velocities up to about $40\,\%$ of the speed of light, and exponential growth of $E_{\rm rad}$ with $v$ at larger velocities. Extrapolation to the speed of light predicts a limit of $12.9\,\%$ $(10.1,~7.7,~5.5,~4.5)\,\%$. of the total mass that is lost in gravitational waves in $D=4$ $(5,\,6,\,7,\,8)$ spacetime dimensions. In agreement with perturbative calculations, we observe that the radiation is minimal for small but finite velocities, rather than for collisions starting from rest. Our computations support the identification of regimes with super Planckian curvature outside the black-hole horizons reported by Okawa, Nakao, and Shibata [Phys.~Rev.~D {\bf 83} 121501(R) (2011)]. |
2302.04654 | Supakchai Ponglertsakul | Chatchai Promsiri and Takol Tangphati and Ekapong Hirunsirisawat and
Supakchai Ponglertsakul | Scalarization of planar anti de Sitter charged black holes in
Einstein-Maxwell-Scalar theory | 31 pages, 13 figures, to match Physical Review D version | Phys. Rev. D 108, 024015 (2023) | 10.1103/PhysRevD.108.024015 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We construct scalarized planar charged black holes in Einstein-Maxwell-scalar
(EMS) theory with the presence of a negative cosmological constant. Domains of
existence of black hole solutions are given in term of nonminimally coupling
constant $\alpha$. Perturbative stability of a scalarized black hole is
investigated by calculating its quasinormal modes. Thermodynamic properties of
the scalarized planar solution are also discussed. We observe no evidence of
instability of the scalarized black holes. Moreover, we find that scalarized
planar charged AdS black holes are thermodynamically preferred over scalar-free
solutions in grand canonical and canonical ensembles. The transition between
scalar-free solutions and scalarized solutions is found to be the thermal
second order phase transition. The transition of these solutions shares some
similar features with conductor-superconductor phase transition.
| [
{
"created": "Thu, 9 Feb 2023 14:09:11 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Jul 2023 08:03:42 GMT",
"version": "v2"
}
] | 2023-07-19 | [
[
"Promsiri",
"Chatchai",
""
],
[
"Tangphati",
"Takol",
""
],
[
"Hirunsirisawat",
"Ekapong",
""
],
[
"Ponglertsakul",
"Supakchai",
""
]
] | We construct scalarized planar charged black holes in Einstein-Maxwell-scalar (EMS) theory with the presence of a negative cosmological constant. Domains of existence of black hole solutions are given in term of nonminimally coupling constant $\alpha$. Perturbative stability of a scalarized black hole is investigated by calculating its quasinormal modes. Thermodynamic properties of the scalarized planar solution are also discussed. We observe no evidence of instability of the scalarized black holes. Moreover, we find that scalarized planar charged AdS black holes are thermodynamically preferred over scalar-free solutions in grand canonical and canonical ensembles. The transition between scalar-free solutions and scalarized solutions is found to be the thermal second order phase transition. The transition of these solutions shares some similar features with conductor-superconductor phase transition. |
1005.2838 | Allan Joseph Michael Medved | A.J.M. Medved | Yet More on the Universal Quantum Area Spectrum | 6 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We briefly comment on the quantum area spectra of black holes, paying
particular attention to the size of the spacing between adjacent spectral
levels. It has previously been conjectured that this spacing is uniform with a
universal value of $8\pi$ in Planck units. In spite of a recent claim to the
contrary, we argue that this particular value remains, by far, the most
qualified candidate for a universal area gap.
| [
{
"created": "Mon, 17 May 2010 08:38:23 GMT",
"version": "v1"
}
] | 2010-05-18 | [
[
"Medved",
"A. J. M.",
""
]
] | We briefly comment on the quantum area spectra of black holes, paying particular attention to the size of the spacing between adjacent spectral levels. It has previously been conjectured that this spacing is uniform with a universal value of $8\pi$ in Planck units. In spite of a recent claim to the contrary, we argue that this particular value remains, by far, the most qualified candidate for a universal area gap. |
2404.11801 | Jo\~ao Paulo Bessa Brito | Jo\~ao P. B. Brito, Rafael P. Bernar, Atsushi Higuchi, Lu\'is C. B.
Crispino | Semiclassical bremsstrahlung from a charge radially falling into a
Schwarzschild black hole | 17 pages, 15 figures, published version | Phys. Rev. D 109, 084041, 2024 | 10.1103/PhysRevD.109.084041 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | A semiclassical investigation of the electromagnetic radiation emitted by a
charged particle in a radially freely falling motion in Schwarzschild spacetime
is carried out. We use quantum field theory at tree level to obtain the
one-particle-emission amplitudes. We analyze and compare the energy spectrum
and total energy released, which are calculated from these amplitudes, for
particles with varying initial positions and for particles originating from
infinity with varying kinetic energy. We also compare the results with those
due to a falling charged "string" extended in the radial direction.
| [
{
"created": "Wed, 17 Apr 2024 23:42:11 GMT",
"version": "v1"
}
] | 2024-04-19 | [
[
"Brito",
"João P. B.",
""
],
[
"Bernar",
"Rafael P.",
""
],
[
"Higuchi",
"Atsushi",
""
],
[
"Crispino",
"Luís C. B.",
""
]
] | A semiclassical investigation of the electromagnetic radiation emitted by a charged particle in a radially freely falling motion in Schwarzschild spacetime is carried out. We use quantum field theory at tree level to obtain the one-particle-emission amplitudes. We analyze and compare the energy spectrum and total energy released, which are calculated from these amplitudes, for particles with varying initial positions and for particles originating from infinity with varying kinetic energy. We also compare the results with those due to a falling charged "string" extended in the radial direction. |
gr-qc/0411129 | Emanuele Berti | Emanuele Berti, Alessandra Buonanno, Clifford M. Will | Estimating spinning binary parameters and testing alternative theories
of gravity with LISA | 29 pages, 9 figures. Matches version accepted in Physical Review D.
More stringent checks in the inversion of the Fisher matrix | Phys.Rev. D71 (2005) 084025 | 10.1103/PhysRevD.71.084025 | null | gr-qc astro-ph hep-th | null | We investigate the effect of spin-orbit and spin-spin couplings on the
estimation of parameters for inspiralling compact binaries of massive black
holes, and for neutron stars inspiralling into intermediate-mass black holes,
using hypothetical data from the proposed Laser Interferometer Space Antenna
(LISA). We work both in Einstein's theory and in alternative theories of
gravity of the scalar-tensor and massive-graviton types. We restrict the
analysis to non-precessing spinning binaries, i.e. to cases where the spins are
aligned normal to the orbital plane. We find that the accuracy with which
intrinsic binary parameters such as chirp mass and reduced mass can be
estimated within general relativity is degraded by between one and two orders
of magnitude. We find that the bound on the coupling parameter omega_BD of
scalar-tensor gravity is significantly reduced by the presence of spin
couplings, while the reduction in the graviton-mass bound is milder. Using fast
Monte-Carlo simulations of 10^4 binaries, we show that inclusion of spin terms
in massive black-hole binaries has little effect on the angular resolution or
on distance determination accuracy. For stellar mass inspirals into
intermediate-mass black holes, the angular resolution and the distance are
determined only poorly, in all cases considered. We also show that, if LISA's
low-frequency noise sensitivity can be extrapolated from 10^-4 Hz to as low as
10^-5 Hz, the accuracy of determining both extrinsic parameters (distance, sky
location) and intrinsic parameters (chirp mass, reduced mass) of massive
binaries may be greatly improved.
| [
{
"created": "Sat, 27 Nov 2004 17:35:24 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Apr 2005 13:41:10 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Berti",
"Emanuele",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Will",
"Clifford M.",
""
]
] | We investigate the effect of spin-orbit and spin-spin couplings on the estimation of parameters for inspiralling compact binaries of massive black holes, and for neutron stars inspiralling into intermediate-mass black holes, using hypothetical data from the proposed Laser Interferometer Space Antenna (LISA). We work both in Einstein's theory and in alternative theories of gravity of the scalar-tensor and massive-graviton types. We restrict the analysis to non-precessing spinning binaries, i.e. to cases where the spins are aligned normal to the orbital plane. We find that the accuracy with which intrinsic binary parameters such as chirp mass and reduced mass can be estimated within general relativity is degraded by between one and two orders of magnitude. We find that the bound on the coupling parameter omega_BD of scalar-tensor gravity is significantly reduced by the presence of spin couplings, while the reduction in the graviton-mass bound is milder. Using fast Monte-Carlo simulations of 10^4 binaries, we show that inclusion of spin terms in massive black-hole binaries has little effect on the angular resolution or on distance determination accuracy. For stellar mass inspirals into intermediate-mass black holes, the angular resolution and the distance are determined only poorly, in all cases considered. We also show that, if LISA's low-frequency noise sensitivity can be extrapolated from 10^-4 Hz to as low as 10^-5 Hz, the accuracy of determining both extrinsic parameters (distance, sky location) and intrinsic parameters (chirp mass, reduced mass) of massive binaries may be greatly improved. |
1211.0823 | Ghanashyam Date | Ghanashyam Date and Nirmalya Kajuri | Polymer quantization and Symmetries | 20 pages, version 2, added further explanations and references.
Results and conclusions unchanged. Version to appear in CQG | Class. Quantum Grav. 30 (2013) 075010 | 10.1088/0264-9381/30/7/075010 | IMSc/2012/11/17 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Polymer quantization was discovered during the construction of Loop Quantum
Cosmology. For the simplest quantum theory of one degree of freedom, the
implications for dynamics were studied for the harmonic oscillator as well as
some other potentials. For more degrees of freedom, the possibility of
continuous, kinematic symmetries arises. While these are realised on the
Hilbert space of polymer quantum mechanics, their infinitesimal versions are
not supported. For an invariant Hamiltonian, these symmetry realizations imply
infinite degeneracy suggesting that the symmetry should be spontaneously or
explicitly broken. The estimation of symmetry violations in some cases have
been analysed before. Here we explore the alternative of shifting the arena to
the distributional states. We discuss both the polymer quantum mechanics case
as well as polymer quantized scalar field.
| [
{
"created": "Mon, 5 Nov 2012 10:47:27 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Feb 2013 08:02:06 GMT",
"version": "v2"
}
] | 2013-03-19 | [
[
"Date",
"Ghanashyam",
""
],
[
"Kajuri",
"Nirmalya",
""
]
] | Polymer quantization was discovered during the construction of Loop Quantum Cosmology. For the simplest quantum theory of one degree of freedom, the implications for dynamics were studied for the harmonic oscillator as well as some other potentials. For more degrees of freedom, the possibility of continuous, kinematic symmetries arises. While these are realised on the Hilbert space of polymer quantum mechanics, their infinitesimal versions are not supported. For an invariant Hamiltonian, these symmetry realizations imply infinite degeneracy suggesting that the symmetry should be spontaneously or explicitly broken. The estimation of symmetry violations in some cases have been analysed before. Here we explore the alternative of shifting the arena to the distributional states. We discuss both the polymer quantum mechanics case as well as polymer quantized scalar field. |
0704.0753 | Dr. Anirudh Pradhan | Raj Bali, Umesh Kumar Pareek and Anirudh Pradhan | Bianchi Type I Massive String Magnetized Barotropic Perfect Fluid
Cosmological Model in General Relativity | 10 pages, no figure. Chin. Phys. Lett., Vol. 24, No. 8 (2007), to
appear | Chin.Phys.Lett.24:2455-2458,2007 | 10.1088/0256-307X/24/8/082 | null | gr-qc | null | Bianchi type I massive string cosmological model with magnetic field of
barotropic perfect fluid distribution through the techniques used by Latelier
and Stachel, is investigated. To get the deterministic model of the universe,
it is assumed that the universe is filled with barotropic perfect fluid
distribution. The magnetic field is due to electric current produced along
x-axis with infinite electrical conductivity. The behaviour of the model in
presence and absence of magnetic field together with other physical aspects is
further discussed.
| [
{
"created": "Thu, 5 Apr 2007 16:07:36 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Jun 2007 11:40:50 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bali",
"Raj",
""
],
[
"Pareek",
"Umesh Kumar",
""
],
[
"Pradhan",
"Anirudh",
""
]
] | Bianchi type I massive string cosmological model with magnetic field of barotropic perfect fluid distribution through the techniques used by Latelier and Stachel, is investigated. To get the deterministic model of the universe, it is assumed that the universe is filled with barotropic perfect fluid distribution. The magnetic field is due to electric current produced along x-axis with infinite electrical conductivity. The behaviour of the model in presence and absence of magnetic field together with other physical aspects is further discussed. |
1205.1071 | Ivica Smoli\'c | Ivica Smoli\'c | Killing Horizons as Equipotential Hypersurfaces | 8 pages; revised, published version; several assumptions removed from
the final theorem | Class. Quantum Grav. 29 (2012) 207002 | 10.1088/0264-9381/29/20/207002 | ZTF-12-03 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note we present a new proof that Killing horizons are equipotential
hypersurfaces for the electric and the magnetic scalar potential, that makes no
use of gravitational field equations or the assumption about the existence of
bifurcation surface.
| [
{
"created": "Fri, 4 May 2012 20:44:23 GMT",
"version": "v1"
},
{
"created": "Thu, 10 May 2012 13:42:59 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Sep 2012 20:00:17 GMT",
"version": "v3"
}
] | 2015-03-20 | [
[
"Smolić",
"Ivica",
""
]
] | In this note we present a new proof that Killing horizons are equipotential hypersurfaces for the electric and the magnetic scalar potential, that makes no use of gravitational field equations or the assumption about the existence of bifurcation surface. |
2005.08828 | Diego Rubiera-Garcia | Merce Guerrero, Diego Rubiera-Garcia | Nonsingular black holes in nonlinear gravity coupled to Euler-Heisenberg
electrodynamics | 14 pages, 8 figures, revtex4-1 style. v2: some new discussion and
minor corrections. Version to appear in Phys. Rev. D | Phys. Rev. D 102, 024005 (2020) | 10.1103/PhysRevD.102.024005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study static, spherically symmetric black holes supported by
Euler-Heisenberg theory of electrodynamics and coupled to two different
modified theories of gravity. Such theories are the quadratic $f(R)$ model and
Eddington-inspired Born-Infeld gravity, both formulated in metric-affine
spaces, where metric and affine connection are independent fields. We find
exact solutions of the corresponding field equations in both cases,
characterized by mass, charge, the Euler-Heisenberg coupling parameter and the
modified gravity one. For each such family of solutions, we characterize its
horizon structure and the modifications in the innermost region, finding that
some subclasses are geodesically complete. The singularity regularization is
achieved under two different mechanisms: either the boundary of the manifold is
pushed to an infinite affine distance, not being able to be reached in finite
time by any geodesic, or the presence of a wormhole structure allows for the
smooth extension of all geodesics overcoming the maximum of the potential
barrier.
| [
{
"created": "Mon, 18 May 2020 15:59:03 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Jun 2020 06:24:34 GMT",
"version": "v2"
}
] | 2020-07-08 | [
[
"Guerrero",
"Merce",
""
],
[
"Rubiera-Garcia",
"Diego",
""
]
] | We study static, spherically symmetric black holes supported by Euler-Heisenberg theory of electrodynamics and coupled to two different modified theories of gravity. Such theories are the quadratic $f(R)$ model and Eddington-inspired Born-Infeld gravity, both formulated in metric-affine spaces, where metric and affine connection are independent fields. We find exact solutions of the corresponding field equations in both cases, characterized by mass, charge, the Euler-Heisenberg coupling parameter and the modified gravity one. For each such family of solutions, we characterize its horizon structure and the modifications in the innermost region, finding that some subclasses are geodesically complete. The singularity regularization is achieved under two different mechanisms: either the boundary of the manifold is pushed to an infinite affine distance, not being able to be reached in finite time by any geodesic, or the presence of a wormhole structure allows for the smooth extension of all geodesics overcoming the maximum of the potential barrier. |
2307.11933 | Krishnanand K Nair | Krishnanand K. Nair and Mathew Thomas Arun | Constraint on cosmological constant in generalized Skryme-teleparallel
system | 19 pages, 10 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The Einstein-Skyrme system is understood to defy the "no hair" conjecture by
possessing black-hole solutions with fractional baryon number outside the event
horizon. In this article, we extend the study of the Skyrme system to
teleparallel gravity framework. We consider two scenarios, the Teleparallel
Equivalent of General Relativity (TEGR) and generalized teleparallel gravity
$f(T)$. In our analysis, we compute the fractional baryon number beyond the
black-hole horizon and its correlation with the cosmological constant
($\Lambda$). In the TEGR context, where $f(T) = -T - 2\Lambda$, the results
match with the Einstein-Skyrme model, assuming a positive $\Lambda$. More
interestingly, in generalized teleparallel gravity scenario, defined by $f(T) =
-T - \tau T^2 - 2\Lambda$, we show that the existence of a solution demands
that not only must $\Lambda$ be positive but has to lie in a range,
$\Lambda_{min} < \Lambda < \Lambda_{max}$. While the upper bound depends
inversely on $\tau$, the lower bound is a linear function of it. Hence, in the
limiting case with generalized teleparallel gravity converging towards TEGR
($\tau \rightarrow 0$), the constraints on the cosmological constant relax to
the Einstein Skryme system ($\Lambda_{min}$ approaches zero and $\Lambda_{max}$
becomes unbounded). On the other hand, in f(T) gravity, vanishing cosmological
constant solution is found only if the lower bound on the energy of the soliton
is very large.
| [
{
"created": "Fri, 21 Jul 2023 22:53:52 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Apr 2024 14:34:17 GMT",
"version": "v2"
}
] | 2024-04-02 | [
[
"Nair",
"Krishnanand K.",
""
],
[
"Arun",
"Mathew Thomas",
""
]
] | The Einstein-Skyrme system is understood to defy the "no hair" conjecture by possessing black-hole solutions with fractional baryon number outside the event horizon. In this article, we extend the study of the Skyrme system to teleparallel gravity framework. We consider two scenarios, the Teleparallel Equivalent of General Relativity (TEGR) and generalized teleparallel gravity $f(T)$. In our analysis, we compute the fractional baryon number beyond the black-hole horizon and its correlation with the cosmological constant ($\Lambda$). In the TEGR context, where $f(T) = -T - 2\Lambda$, the results match with the Einstein-Skyrme model, assuming a positive $\Lambda$. More interestingly, in generalized teleparallel gravity scenario, defined by $f(T) = -T - \tau T^2 - 2\Lambda$, we show that the existence of a solution demands that not only must $\Lambda$ be positive but has to lie in a range, $\Lambda_{min} < \Lambda < \Lambda_{max}$. While the upper bound depends inversely on $\tau$, the lower bound is a linear function of it. Hence, in the limiting case with generalized teleparallel gravity converging towards TEGR ($\tau \rightarrow 0$), the constraints on the cosmological constant relax to the Einstein Skryme system ($\Lambda_{min}$ approaches zero and $\Lambda_{max}$ becomes unbounded). On the other hand, in f(T) gravity, vanishing cosmological constant solution is found only if the lower bound on the energy of the soliton is very large. |
gr-qc/0102062 | Daniel Sforza | Rafael Ferraro and Daniel M. Sforza | Quantization of a generally covariant gauge system with two super
Hamiltonian constraints | 17 pages. Latex file. Minor changes, two references added | Phys.Rev. D64 (2001) 024020 | 10.1103/PhysRevD.64.024020 | null | gr-qc | null | The Becci-Rouet-Stora-Tyutin (BRST) operator quantization of a
finite-dimensional gauge system featuring two quadratic super Hamiltonian and m
linear supermomentum constraints is studied as a model for quantizing generally
covariant gauge theories. The proposed model ``completely'' mimics the
constraint algebra of General Relativity. The Dirac constraint operators are
identified by realizing the BRST generator of the system as a Hermitian
nilpotent operator, and a physical inner product is introduced to complete a
consistent quantization procedure.
| [
{
"created": "Tue, 13 Feb 2001 20:02:29 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Jul 2001 20:51:19 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Ferraro",
"Rafael",
""
],
[
"Sforza",
"Daniel M.",
""
]
] | The Becci-Rouet-Stora-Tyutin (BRST) operator quantization of a finite-dimensional gauge system featuring two quadratic super Hamiltonian and m linear supermomentum constraints is studied as a model for quantizing generally covariant gauge theories. The proposed model ``completely'' mimics the constraint algebra of General Relativity. The Dirac constraint operators are identified by realizing the BRST generator of the system as a Hermitian nilpotent operator, and a physical inner product is introduced to complete a consistent quantization procedure. |
1807.03795 | Ludwig Jens Papenfort | L. Jens Papenfort, Roman Gold, Luciano Rezzolla | Dynamical ejecta and nucleosynthetic yields from eccentric binary
neutron-star mergers | 24 pages, 14 figures, matches version accepted by PRD | Phys. Rev. D 98, 104028 (2018) | 10.1103/PhysRevD.98.104028 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With the recent advent of multi-messenger gravitational-wave astronomy and in
anticipation of more sensitive, next-generation gravitational-wave detectors,
we investigate the dynamics, gravitational-wave emission, and nucleosynthetic
yields of numerous eccentric binary neutron-star mergers having different
equations of state. For each equation of state we vary the orbital properties
around the threshold of immediate merger, as well as the binary mass ratio. In
addition to a study of the gravitational-wave emission including $f$-mode
oscillations before and after merger, we couple the dynamical ejecta output
from the simulations to the nuclear-reaction network code \texttt{SkyNet} to
compute nucleosynthetic yields and compare to the corresponding results in the
case of a quasi-circular merger. We find that the amount and velocity of
dynamically ejected material is always much larger than in the quasi-circular
case, reaching maximal values of $M_{\rm ej, max} \sim 0.1 \, M_{\odot}$ and
$v_{\rm max}/c \sim 0.75$. At the same time, the properties of this material
are rather insensitive to the details of the orbit, such as pericenter distance
or post-encounter apoastron distance. Furthermore, while the composition of the
ejected matter depends on the orbital parameters and on the equation of state,
the relative nucleosynthetic yields do not, thus indicating that kilonova
signatures could provide information on the orbital properties of dynamically
captured neutron-star binaries.
| [
{
"created": "Tue, 10 Jul 2018 18:00:06 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Dec 2018 21:58:17 GMT",
"version": "v2"
}
] | 2018-12-07 | [
[
"Papenfort",
"L. Jens",
""
],
[
"Gold",
"Roman",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | With the recent advent of multi-messenger gravitational-wave astronomy and in anticipation of more sensitive, next-generation gravitational-wave detectors, we investigate the dynamics, gravitational-wave emission, and nucleosynthetic yields of numerous eccentric binary neutron-star mergers having different equations of state. For each equation of state we vary the orbital properties around the threshold of immediate merger, as well as the binary mass ratio. In addition to a study of the gravitational-wave emission including $f$-mode oscillations before and after merger, we couple the dynamical ejecta output from the simulations to the nuclear-reaction network code \texttt{SkyNet} to compute nucleosynthetic yields and compare to the corresponding results in the case of a quasi-circular merger. We find that the amount and velocity of dynamically ejected material is always much larger than in the quasi-circular case, reaching maximal values of $M_{\rm ej, max} \sim 0.1 \, M_{\odot}$ and $v_{\rm max}/c \sim 0.75$. At the same time, the properties of this material are rather insensitive to the details of the orbit, such as pericenter distance or post-encounter apoastron distance. Furthermore, while the composition of the ejected matter depends on the orbital parameters and on the equation of state, the relative nucleosynthetic yields do not, thus indicating that kilonova signatures could provide information on the orbital properties of dynamically captured neutron-star binaries. |
1702.03285 | Muxin Han | Muxin Han, Zichang Huang | Loop-Quantum-Gravity Simplicity Constraint as Surface Defect in Complex
Chern-Simons Theory | 16 pages, 3 figures, presentation improved | Phys. Rev. D 95, 104031 (2017) | 10.1103/PhysRevD.95.104031 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The simplicity constraint is studied in the context of 4d spinfoam models
with cosmological constant. We find that the quantum simplicity constraint is
realized as the 2d surface defect in SL(2,$\mathbb{C}$) Chern-Simons theory in
the construction of spinfoam amplitudes. By this realization of simplicity
constraint in Chern-Simons theory, we are able to construct the new spinfoam
amplitude with cosmological constant for arbitrary simplicial complex (with
many 4-simplices). The semiclassical asymptotics of the amplitude is shown to
reproduce correctly the 4-dimensional Einstein-Regge action with cosmological
constant term.
| [
{
"created": "Fri, 10 Feb 2017 18:57:00 GMT",
"version": "v1"
},
{
"created": "Fri, 5 May 2017 01:53:01 GMT",
"version": "v2"
}
] | 2017-05-25 | [
[
"Han",
"Muxin",
""
],
[
"Huang",
"Zichang",
""
]
] | The simplicity constraint is studied in the context of 4d spinfoam models with cosmological constant. We find that the quantum simplicity constraint is realized as the 2d surface defect in SL(2,$\mathbb{C}$) Chern-Simons theory in the construction of spinfoam amplitudes. By this realization of simplicity constraint in Chern-Simons theory, we are able to construct the new spinfoam amplitude with cosmological constant for arbitrary simplicial complex (with many 4-simplices). The semiclassical asymptotics of the amplitude is shown to reproduce correctly the 4-dimensional Einstein-Regge action with cosmological constant term. |
1801.09711 | Paul Chesler | Paul M. Chesler and David A. Lowe | Nonlinear evolution of the AdS$_4$ black hole bomb | 5 pages + 2 pages supplemental materials. v2: added ref and minor
clarifications in discussion | Phys. Rev. Lett. 122, 181101 (2019) | 10.1103/PhysRevLett.122.181101 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The superradiant instability of rotating black holes with negative
cosmological constant is studied by numerically solving the full
3+1-dimensional Einstein equations. We find evidence for an epoch dominated by
a solution with a single helical Killing vector and a multi-stage process with
distinct superradiant instabilities.
| [
{
"created": "Mon, 29 Jan 2018 19:12:17 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Feb 2018 03:20:53 GMT",
"version": "v2"
}
] | 2019-05-15 | [
[
"Chesler",
"Paul M.",
""
],
[
"Lowe",
"David A.",
""
]
] | The superradiant instability of rotating black holes with negative cosmological constant is studied by numerically solving the full 3+1-dimensional Einstein equations. We find evidence for an epoch dominated by a solution with a single helical Killing vector and a multi-stage process with distinct superradiant instabilities. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.