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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2306.15225 | Tanmoy Paul | Sergei D. Odintsov, Simone D'Onofrio, Tanmoy Paul | Holographic realization from inflation to reheating in generalized
entropic cosmology | "Physics of the Dark Universe" Accepted | null | 10.1016/j.dark.2023.101277 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The growing cosmological interest of different entropy functions (like the
Tsallis entropy, the R\'{e}nyi entropy, the Barrow entropy, the Sharma-Mittal
entropy, the Kaniadakis entropy and the Loop Quantum gravity entropy) naturally
raises an important question: "Does there exist a generalized entropy that can
bring all the known entropies proposed so far within a single umbrella?" In
spirit of this, recently a four parameter generalized entropy has been
formulated that reduces to different known entropies for suitable limits of the
parameters. Based on such four parameter generalized entropy (symbolized by
$S_\mathrm{g}$), in the present paper, we examine the universe's evolution
during its early phase, particularly from inflation to reheating, in the
context of entropic cosmology where the entropic energy density acts as the
inflaton. It turns out that the entropic energy successfully drives an early
inflationary phase with a graceful exit, and moreover, the theoretical
expectations of the observable indices get consistent with the recent Planck
data for suitable ranges of the entropic parameters. After the inflation ends,
the universe enters to a reheating stage when the entropic energy decays to
relativistic particles with a certain decay rate. Actually the presence of the
entropic parameters in the $S_\mathrm{g}$ ensures a continuous evolution of the
Hubble parameter from a quasi de-Sitter phase during the inflation to a power
law phase during the reheating stage dominated by a constant EoS parameter.
Consequently we investigate the reheating phenomenology, and scan the entropic
parameters from both the inflation and reheating requirements. We further
address the possibility of instantaneous reheating in the present context of
generalized entropy.
| [
{
"created": "Tue, 27 Jun 2023 05:58:04 GMT",
"version": "v1"
}
] | 2023-09-18 | [
[
"Odintsov",
"Sergei D.",
""
],
[
"D'Onofrio",
"Simone",
""
],
[
"Paul",
"Tanmoy",
""
]
] | The growing cosmological interest of different entropy functions (like the Tsallis entropy, the R\'{e}nyi entropy, the Barrow entropy, the Sharma-Mittal entropy, the Kaniadakis entropy and the Loop Quantum gravity entropy) naturally raises an important question: "Does there exist a generalized entropy that can bring all the known entropies proposed so far within a single umbrella?" In spirit of this, recently a four parameter generalized entropy has been formulated that reduces to different known entropies for suitable limits of the parameters. Based on such four parameter generalized entropy (symbolized by $S_\mathrm{g}$), in the present paper, we examine the universe's evolution during its early phase, particularly from inflation to reheating, in the context of entropic cosmology where the entropic energy density acts as the inflaton. It turns out that the entropic energy successfully drives an early inflationary phase with a graceful exit, and moreover, the theoretical expectations of the observable indices get consistent with the recent Planck data for suitable ranges of the entropic parameters. After the inflation ends, the universe enters to a reheating stage when the entropic energy decays to relativistic particles with a certain decay rate. Actually the presence of the entropic parameters in the $S_\mathrm{g}$ ensures a continuous evolution of the Hubble parameter from a quasi de-Sitter phase during the inflation to a power law phase during the reheating stage dominated by a constant EoS parameter. Consequently we investigate the reheating phenomenology, and scan the entropic parameters from both the inflation and reheating requirements. We further address the possibility of instantaneous reheating in the present context of generalized entropy. |
gr-qc/9804046 | David Wands | Karim A. Malik and David Wands | Gauge-Invariant Variables on Cosmological Hypersurfaces | 4 pages, Revtex, no figures | null | null | PU-RCG/98-5 | gr-qc astro-ph | null | We show how gauge-invariant cosmological perturbations may be constructed by
an unambiguous choice of hypersurface-orthogonal time-like vector field (i.e.,
time-slicing). This may be defined either in terms of the metric quantities
such as curvature or shear, or using some matter field. As an example, we show
how linear perturbations in the covariant fluid-flow approach can then be
presented in an explicitly gauge-invariant form in the coordinate based
formalism.
| [
{
"created": "Tue, 21 Apr 1998 10:35:15 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Malik",
"Karim A.",
""
],
[
"Wands",
"David",
""
]
] | We show how gauge-invariant cosmological perturbations may be constructed by an unambiguous choice of hypersurface-orthogonal time-like vector field (i.e., time-slicing). This may be defined either in terms of the metric quantities such as curvature or shear, or using some matter field. As an example, we show how linear perturbations in the covariant fluid-flow approach can then be presented in an explicitly gauge-invariant form in the coordinate based formalism. |
gr-qc/0201033 | Salvatore Capozziello | Salvatore Capozziello | Curvature Quintessence | 10 pages, LATEX files, to appear on IJMPD | Int.J.Mod.Phys.D11:483-492,2002 | 10.1142/S0218271802002025 | null | gr-qc | null | The issues of quintessence and cosmic acceleration can be discussed in the
framework of higher order theories of gravity. We can define effective pressure
and energy density directly connected to the Ricci scalar of curvature of a
generic fourth order theory and then ask for the conditions to get an
accelerated expansion. Exact accelerated expanding solutions can be achieved
for several fourth order theories so that we get an alternative scheme to the
standard quintessence scalar field, minimally coupled to gravity, usually
adopted. We discuss also conformal transformations in order to see the links of
quintessence between the Jordan and Einstein frames.
| [
{
"created": "Thu, 10 Jan 2002 17:42:19 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Capozziello",
"Salvatore",
""
]
] | The issues of quintessence and cosmic acceleration can be discussed in the framework of higher order theories of gravity. We can define effective pressure and energy density directly connected to the Ricci scalar of curvature of a generic fourth order theory and then ask for the conditions to get an accelerated expansion. Exact accelerated expanding solutions can be achieved for several fourth order theories so that we get an alternative scheme to the standard quintessence scalar field, minimally coupled to gravity, usually adopted. We discuss also conformal transformations in order to see the links of quintessence between the Jordan and Einstein frames. |
gr-qc/0602003 | Antonio F. Ranada | Antonio F. Ranada and Alfredo Tiemblo | Time, clocks, parametric invariance and the Pioneer Anomaly | 19 pages, one figure | null | null | null | gr-qc | null | In the context of a parametric theory (with the time being a dynamical
variable) we consider the coupling between the quantum vacuum and the
background gravitation that pervades the universe (unavoidable because of the
universality of gravity). In our model the fourth Heisenberg relation
introduces a possible source of discrepancy between the marches of atomic and
gravitational clocks, which accelerate with respect to one another. This
produces in its turn another discrepancy between the observations, performed
with atomic time, and the theoretical analysis, which uses parametric
astronomical time. Curiously, this approach turns out to be compatible with
current physics; lacking a unified theory of quantum physics and gravitation,
it cannot be discarded {\it a priori}. It happens that this phenomenon has the
same footprint as the Pioneer Anomaly, what suggests a solution to this riddle.
This is because the velocity of the Pioneer spaceship with respect to atomic
time turns out to be slightly smaller that with astronomical time, so that that
the apparent trajectory lags behind the real one. In 1998, after many
unsuccessful efforts to account for this phenomenon, the discoverers suggested
"the possibility that the origin of the anomalous signal is new physics".
| [
{
"created": "Wed, 1 Feb 2006 15:30:16 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Nov 2006 15:05:40 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Ranada",
"Antonio F.",
""
],
[
"Tiemblo",
"Alfredo",
""
]
] | In the context of a parametric theory (with the time being a dynamical variable) we consider the coupling between the quantum vacuum and the background gravitation that pervades the universe (unavoidable because of the universality of gravity). In our model the fourth Heisenberg relation introduces a possible source of discrepancy between the marches of atomic and gravitational clocks, which accelerate with respect to one another. This produces in its turn another discrepancy between the observations, performed with atomic time, and the theoretical analysis, which uses parametric astronomical time. Curiously, this approach turns out to be compatible with current physics; lacking a unified theory of quantum physics and gravitation, it cannot be discarded {\it a priori}. It happens that this phenomenon has the same footprint as the Pioneer Anomaly, what suggests a solution to this riddle. This is because the velocity of the Pioneer spaceship with respect to atomic time turns out to be slightly smaller that with astronomical time, so that that the apparent trajectory lags behind the real one. In 1998, after many unsuccessful efforts to account for this phenomenon, the discoverers suggested "the possibility that the origin of the anomalous signal is new physics". |
gr-qc/0112015 | A. R. Prasanna | A.R.Prasanna | Inertial forces - a la Newton in General Relativity | Lecture notes 18 pages including five figs | null | null | null | gr-qc | null | In this we briefly cover the covariant approach to describe inertial forces
in general relativity and in particular look at the behaviour of the cumulative
drag index for stationary Kerr geometry.
| [
{
"created": "Mon, 10 Dec 2001 09:28:28 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Prasanna",
"A. R.",
""
]
] | In this we briefly cover the covariant approach to describe inertial forces in general relativity and in particular look at the behaviour of the cumulative drag index for stationary Kerr geometry. |
2105.00744 | Albert Huber | Albert Huber | A remark on the quasilocal calculation of tidal heating: energy transfer
through the quasilocal surface | extended version; accepted for publication in PRD | Physical Review D 105(2) 2022 | 10.1103/PhysRevD.105.024011 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | In this note, using the quasilocal formalism of Brown and York, the flow of
energy through a closed surface containing a gravitating physical system is
calculated in a way that augments earlier results on the subject by Booth and
Creighton. To this end, by performing a variation of the total gravitational
Hamiltonian (bulk plus boundary part), it is shown that associated tidal
heating and deformation effects generally are larger than expected. This is
because this variation leads to previously unrecognized correction terms,
including a bulk-to-boundary inflow term that does not appear in the original
calculation of the time derivative of the Brown-York energy and leads to
corrective extensions of Einstein's quadrupole formula in the large sphere
limit.
| [
{
"created": "Mon, 3 May 2021 10:41:09 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Dec 2021 07:00:39 GMT",
"version": "v2"
}
] | 2022-01-05 | [
[
"Huber",
"Albert",
""
]
] | In this note, using the quasilocal formalism of Brown and York, the flow of energy through a closed surface containing a gravitating physical system is calculated in a way that augments earlier results on the subject by Booth and Creighton. To this end, by performing a variation of the total gravitational Hamiltonian (bulk plus boundary part), it is shown that associated tidal heating and deformation effects generally are larger than expected. This is because this variation leads to previously unrecognized correction terms, including a bulk-to-boundary inflow term that does not appear in the original calculation of the time derivative of the Brown-York energy and leads to corrective extensions of Einstein's quadrupole formula in the large sphere limit. |
2109.04238 | Shaoqi Hou | Shaoqi Hou, Tao Zhu, Zong-Hong Zhu | Gravitational memory effects in Chern-Simons modified gravity | 13 pages, 0 figure. To be published in PRD | Phys. Rev. D 105, 024025 (2022) | 10.1103/PhysRevD.105.024025 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational memory effects of Chern-Simons modified gravity are
considered in the asymptotically flat spacetime. If the Chern-Simons scalar
does not directly couple with the ordinary matter fields, there are also
displacement, spin and center-of-mass memory effects as in general relativity.
This is because the term of the action that violates the parity invariance is
linear in the scalar field but quadratic in the curvature tensor. This results
in the parity violation occuring at the higher orders in the inverse luminosity
radius. The scalar field does not induce any new memory effects that can be
detected by interferometers or pulsar timing arrays. The asymptotic symmetry is
group is also the extended Bondi-Metzner-Sachs group. The constraints on the
memory effects excited by the tensor modes are obtained.
| [
{
"created": "Thu, 9 Sep 2021 12:58:25 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Sep 2021 03:18:32 GMT",
"version": "v2"
},
{
"created": "Sun, 2 Jan 2022 13:02:58 GMT",
"version": "v3"
}
] | 2022-01-10 | [
[
"Hou",
"Shaoqi",
""
],
[
"Zhu",
"Tao",
""
],
[
"Zhu",
"Zong-Hong",
""
]
] | The gravitational memory effects of Chern-Simons modified gravity are considered in the asymptotically flat spacetime. If the Chern-Simons scalar does not directly couple with the ordinary matter fields, there are also displacement, spin and center-of-mass memory effects as in general relativity. This is because the term of the action that violates the parity invariance is linear in the scalar field but quadratic in the curvature tensor. This results in the parity violation occuring at the higher orders in the inverse luminosity radius. The scalar field does not induce any new memory effects that can be detected by interferometers or pulsar timing arrays. The asymptotic symmetry is group is also the extended Bondi-Metzner-Sachs group. The constraints on the memory effects excited by the tensor modes are obtained. |
0907.2186 | Michele Maggiore | Umberto Cannella, Stefano Foffa, Michele Maggiore, Hillary Sanctuary
and Riccardo Sturani | Extracting the three- and four-graviton vertices from binary pulsars and
coalescing binaries | 10 pages, 5 figures; v2: an error corrected; references added | null | 10.1103/PhysRevD.80.124035 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using a formulation of the post-Newtonian expansion in terms of Feynman
graphs, we discuss how various tests of General Relativity (GR) can be
translated into measurement of the three- and four-graviton vertices. In
problems involving only the conservative dynamics of a system, a deviation of
the three-graviton vertex from the GR prediction is equivalent, to lowest
order, to the introduction of the parameter beta_{PPN} in the parametrized
post-Newtonian formalism, and its strongest bound comes from lunar laser
ranging, which measures it at the 0.02% level. Deviation of the three-graviton
vertex from the GR prediction, however, also affects the radiative sector of
the theory. We show that the timing of the Hulse-Taylor binary pulsar provides
a bound on the deviation of the three-graviton vertex from the GR prediction at
the 0.1% level. For coalescing binaries at interferometers we find that,
because of degeneracies with other parameters in the template such as mass and
spin, the effects of modified three- and four-graviton vertices is just to
induce an error in the determination of these parameters and, at least in the
restricted PN approximation, it is not possible to use coalescing binaries for
constraining deviations of the vertices from the GR prediction.
| [
{
"created": "Mon, 13 Jul 2009 15:14:13 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Nov 2009 19:51:15 GMT",
"version": "v2"
}
] | 2015-05-13 | [
[
"Cannella",
"Umberto",
""
],
[
"Foffa",
"Stefano",
""
],
[
"Maggiore",
"Michele",
""
],
[
"Sanctuary",
"Hillary",
""
],
[
"Sturani",
"Riccardo",
""
]
] | Using a formulation of the post-Newtonian expansion in terms of Feynman graphs, we discuss how various tests of General Relativity (GR) can be translated into measurement of the three- and four-graviton vertices. In problems involving only the conservative dynamics of a system, a deviation of the three-graviton vertex from the GR prediction is equivalent, to lowest order, to the introduction of the parameter beta_{PPN} in the parametrized post-Newtonian formalism, and its strongest bound comes from lunar laser ranging, which measures it at the 0.02% level. Deviation of the three-graviton vertex from the GR prediction, however, also affects the radiative sector of the theory. We show that the timing of the Hulse-Taylor binary pulsar provides a bound on the deviation of the three-graviton vertex from the GR prediction at the 0.1% level. For coalescing binaries at interferometers we find that, because of degeneracies with other parameters in the template such as mass and spin, the effects of modified three- and four-graviton vertices is just to induce an error in the determination of these parameters and, at least in the restricted PN approximation, it is not possible to use coalescing binaries for constraining deviations of the vertices from the GR prediction. |
2003.08448 | Gabriel Andres Piovano | Gabriel Andres Piovano, Andrea Maselli, Paolo Pani | Model independent tests of the Kerr bound with extreme mass ratio
inspirals | Improvements in response to referee reports. Typos corrected. Data
and code available at https://web.uniroma1.it/gmunu | PLB 811 135860 (2020) | 10.1016/j.physletb.2020.135860 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An outstanding prediction of general relativity is the fact that the angular
momentum $S$ of an isolated black hole with mass $\mu$ is limited by the Kerr
bound, $S\leq G\mu^2/c$. Testing this cornerstone is challenging due to the
difficulty in modelling spinning compact objects that violate this bound. We
argue that precise, model-independent tests can be achieved by measuring
gravitational waves from an extreme mass ratio inspiral around a supermassive
object, one of the main targets of the future LISA mission. In the extreme mass
ratio limit, the dynamics of the small compact object depends only on its
multipole moments, which are free parameters. At variance with the
comparable-mass case, accurate waveforms are valid also when the spin of the
small object greatly exceeds the Kerr bound. By computing the orbital dephasing
and the gravitational-wave signal emitted by a spinning point particle in
circular, nonprecessing, equatorial motion around a Kerr black hole, we
estimate that LISA will be able to measure the spin of the small compact object
at the level of $10\%$. Together with mass measurements, this will allow for
theory-agnostic, unprecedented constraints on string-theory inspired objects
such as "superspinars", almost in their entire parameter space.
| [
{
"created": "Wed, 18 Mar 2020 19:25:48 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Jun 2020 21:55:42 GMT",
"version": "v2"
}
] | 2020-10-22 | [
[
"Piovano",
"Gabriel Andres",
""
],
[
"Maselli",
"Andrea",
""
],
[
"Pani",
"Paolo",
""
]
] | An outstanding prediction of general relativity is the fact that the angular momentum $S$ of an isolated black hole with mass $\mu$ is limited by the Kerr bound, $S\leq G\mu^2/c$. Testing this cornerstone is challenging due to the difficulty in modelling spinning compact objects that violate this bound. We argue that precise, model-independent tests can be achieved by measuring gravitational waves from an extreme mass ratio inspiral around a supermassive object, one of the main targets of the future LISA mission. In the extreme mass ratio limit, the dynamics of the small compact object depends only on its multipole moments, which are free parameters. At variance with the comparable-mass case, accurate waveforms are valid also when the spin of the small object greatly exceeds the Kerr bound. By computing the orbital dephasing and the gravitational-wave signal emitted by a spinning point particle in circular, nonprecessing, equatorial motion around a Kerr black hole, we estimate that LISA will be able to measure the spin of the small compact object at the level of $10\%$. Together with mass measurements, this will allow for theory-agnostic, unprecedented constraints on string-theory inspired objects such as "superspinars", almost in their entire parameter space. |
2201.02754 | Pardyumn Kumar Sahoo | Riasat Ali, Rimsha Babar, P.K. Sahoo | Quantum Gravity Evolution in the Hawking Radiation of a Rotating Regular
Hayward Black Hole | Physics of the Dark Universe accepted version | Physics of the Dark Universe, vol 35 (2022) 100948 | 10.1016/j.dark.2022.100948 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper, we study two different phenomena (the Newman-Janis algorithm
and the semiclassical Hamilton-Jacobi method) to analyze the Hawking
temperature ($T_H$) for massive $4$-dimensional regular Hayward BH with spin
parameter. First of all, we compute the rotating regular Hayward black hole
solution by taking the Newman-Janis algorithmic rule. We derive the $T_H$ for
rotating regular Hayward BH with the help of surface gravity. We have also
analyzed the effects of spin parameter $a$ and free parameter $l$ on $T_H$ with
the help of graphs. Moreover, we investigate the quantum corrected Hawking
temperature ($T'_H$) for rotating regular Hayward black hole. To do so, we
utilize the Lagrangian filed equation in the background of GUP within the
concept of WKB approximation and semiclassical Hamilton-Jacobi method. The
$T'_H$ of rotating regular Hayward BH depends upon correction parameter
$\beta$, BH mass $m$, spin parameter $a$, free parameter $l$ and BH radius
$r_+$. We also study the graphical behavior of $T'_H$ versus event horizon
$r_+$ for rotating regular Hayward BH and check the influences of quantum
gravity parameter $\beta$, spin parameter $a$ and free parameter $l$ on the
stability of corresponding black hole. Moreover, we study the significance's of
logarithmic entropy correction for regular rotating Hayward BH.
| [
{
"created": "Sat, 8 Jan 2022 04:03:04 GMT",
"version": "v1"
}
] | 2022-01-25 | [
[
"Ali",
"Riasat",
""
],
[
"Babar",
"Rimsha",
""
],
[
"Sahoo",
"P. K.",
""
]
] | In this paper, we study two different phenomena (the Newman-Janis algorithm and the semiclassical Hamilton-Jacobi method) to analyze the Hawking temperature ($T_H$) for massive $4$-dimensional regular Hayward BH with spin parameter. First of all, we compute the rotating regular Hayward black hole solution by taking the Newman-Janis algorithmic rule. We derive the $T_H$ for rotating regular Hayward BH with the help of surface gravity. We have also analyzed the effects of spin parameter $a$ and free parameter $l$ on $T_H$ with the help of graphs. Moreover, we investigate the quantum corrected Hawking temperature ($T'_H$) for rotating regular Hayward black hole. To do so, we utilize the Lagrangian filed equation in the background of GUP within the concept of WKB approximation and semiclassical Hamilton-Jacobi method. The $T'_H$ of rotating regular Hayward BH depends upon correction parameter $\beta$, BH mass $m$, spin parameter $a$, free parameter $l$ and BH radius $r_+$. We also study the graphical behavior of $T'_H$ versus event horizon $r_+$ for rotating regular Hayward BH and check the influences of quantum gravity parameter $\beta$, spin parameter $a$ and free parameter $l$ on the stability of corresponding black hole. Moreover, we study the significance's of logarithmic entropy correction for regular rotating Hayward BH. |
1308.2863 | Yu-Xiao Liu | Xiang-Nan Zhou, Xiao-Long Du, Ke Yang, Yu-Xiao Liu | Dirac dynamical resonance states around Schwarzschild black holes | v2: 23 pages, 8 figures, 3 tables, improved version to be published
in Phys. Rev. D | Phys. Rev. D 89, 043006 (2014) | 10.1103/PhysRevD.89.043006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, a novel kind of scalar wigs around Schwarzschild black
holes---scalar dynamical resonance states were introduced in [Phys. Rev. D 84,
083008 (2011)] and [Phys. Rev. Lett. 109, 081102 (2012)]. In this paper, we
investigate the existence and evolution of Dirac dynamical resonance states.
First we look for stationary resonance states of a Dirac field around a
Schwarzchild black hole by using the Schr\"{o}dinger-like equations reduced
from the Dirac equation in Schwarzschild spacetime. Then Dirac
pseudo-stationary configurations are constructed from the stationary resonance
states. We use these configurations as initial data and investigate their
numerical evolutions and energy decay. These dynamical solutions are the
so-called "Dirac dynamical resonance states". It is found that the energy of
the Dirac dynamical resonance states shows an exponential decay. The decay rate
of energy is affected by the resonant frequency, the mass of Dirac field, the
total angular momentum, and the spin-orbit interaction. In particular, for
ultra-light Dirac field, the corresponding particles can stay around a
Schwarzschild black hole for a very long time, even for cosmological
time-scales.
| [
{
"created": "Tue, 13 Aug 2013 13:30:57 GMT",
"version": "v1"
},
{
"created": "Sat, 24 Aug 2013 10:19:09 GMT",
"version": "v2"
},
{
"created": "Mon, 20 Jan 2014 08:22:12 GMT",
"version": "v3"
}
] | 2014-02-26 | [
[
"Zhou",
"Xiang-Nan",
""
],
[
"Du",
"Xiao-Long",
""
],
[
"Yang",
"Ke",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | Recently, a novel kind of scalar wigs around Schwarzschild black holes---scalar dynamical resonance states were introduced in [Phys. Rev. D 84, 083008 (2011)] and [Phys. Rev. Lett. 109, 081102 (2012)]. In this paper, we investigate the existence and evolution of Dirac dynamical resonance states. First we look for stationary resonance states of a Dirac field around a Schwarzchild black hole by using the Schr\"{o}dinger-like equations reduced from the Dirac equation in Schwarzschild spacetime. Then Dirac pseudo-stationary configurations are constructed from the stationary resonance states. We use these configurations as initial data and investigate their numerical evolutions and energy decay. These dynamical solutions are the so-called "Dirac dynamical resonance states". It is found that the energy of the Dirac dynamical resonance states shows an exponential decay. The decay rate of energy is affected by the resonant frequency, the mass of Dirac field, the total angular momentum, and the spin-orbit interaction. In particular, for ultra-light Dirac field, the corresponding particles can stay around a Schwarzschild black hole for a very long time, even for cosmological time-scales. |
1812.10076 | Leron Borsten | L. Borsten, M. J. Duff and A. Marrani | Freudenthal duality and conformal isometries of extremal black holes | null | null | null | DFPD/2018/TH/04, DIAS-STP-18-18, Imperial-TP-2018-MJD-02 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a conformal isometry for static extremal black hole solutions in
all four-dimensional Einstein-Maxwell-scalar theories with electromagnetic
duality groups `of type $E_7$'. This includes, but is not limited to, all
supergravity theories with $\mathcal{N}>2$ supersymmetry and all
$\mathcal{N}=2$ supergravity theories with symmetric scalar manifolds. The
conformal isometry is valid for arbitrary electromagnetic charge configurations
and relies crucially on the notion of Freudenthal duality.
| [
{
"created": "Tue, 25 Dec 2018 09:25:37 GMT",
"version": "v1"
}
] | 2018-12-27 | [
[
"Borsten",
"L.",
""
],
[
"Duff",
"M. J.",
""
],
[
"Marrani",
"A.",
""
]
] | We present a conformal isometry for static extremal black hole solutions in all four-dimensional Einstein-Maxwell-scalar theories with electromagnetic duality groups `of type $E_7$'. This includes, but is not limited to, all supergravity theories with $\mathcal{N}>2$ supersymmetry and all $\mathcal{N}=2$ supergravity theories with symmetric scalar manifolds. The conformal isometry is valid for arbitrary electromagnetic charge configurations and relies crucially on the notion of Freudenthal duality. |
0907.4322 | Tomasz Pawlowski | Wojciech Kaminski, Jerzy Lewandowski, Tomasz Pawlowski | Quantum constraints, Dirac observables and evolution: group averaging
versus Schroedinger picture in LQC | RevTex4, 32 pages | Class.Quant.Grav.26:245016,2009 | 10.1088/0264-9381/26/24/245016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A general quantum constraint of the form $C= - \partial_T^2 \otimes B -
I\otimes H$ (realized in particular in Loop Quantum Cosmology models) is
studied. Group Averaging is applied to define the Hilbert space of solutions
and the relational Dirac observables. Two cases are considered. In the first
case, the spectrum of the operator $(1/2)\pi^2 B - H$ is assumed to be
discrete. The quantum theory defined by the constraint takes the form of a
Schroedinger-like quantum mechanics with a generalized Hamiltonian
$\sqrt{B^{-1} H}$. In the second case, the spectrum is absolutely continuous
and some peculiar asymptotic properties of the eigenfunctions are assumed. The
resulting Hilbert space and the dynamics are characterized by a continuous
family of the Schroedinger-like quantum theories. However, the relational
observables mix different members of the family. Our assumptions are motivated
by new Loop Quantum Cosmology models of quantum FRW spacetime. The two cases
considered in the paper correspond to the negative and, respectively, positive
cosmological constant. Our results should be also applicable in many other
general relativistic contexts.
| [
{
"created": "Fri, 24 Jul 2009 16:03:50 GMT",
"version": "v1"
}
] | 2010-04-14 | [
[
"Kaminski",
"Wojciech",
""
],
[
"Lewandowski",
"Jerzy",
""
],
[
"Pawlowski",
"Tomasz",
""
]
] | A general quantum constraint of the form $C= - \partial_T^2 \otimes B - I\otimes H$ (realized in particular in Loop Quantum Cosmology models) is studied. Group Averaging is applied to define the Hilbert space of solutions and the relational Dirac observables. Two cases are considered. In the first case, the spectrum of the operator $(1/2)\pi^2 B - H$ is assumed to be discrete. The quantum theory defined by the constraint takes the form of a Schroedinger-like quantum mechanics with a generalized Hamiltonian $\sqrt{B^{-1} H}$. In the second case, the spectrum is absolutely continuous and some peculiar asymptotic properties of the eigenfunctions are assumed. The resulting Hilbert space and the dynamics are characterized by a continuous family of the Schroedinger-like quantum theories. However, the relational observables mix different members of the family. Our assumptions are motivated by new Loop Quantum Cosmology models of quantum FRW spacetime. The two cases considered in the paper correspond to the negative and, respectively, positive cosmological constant. Our results should be also applicable in many other general relativistic contexts. |
1603.01406 | Narayan Banerjee | Sachin Pandey and Narayan Banerjee | Unitary evolution for anisotropic quantum cosmologies: models with
variable spatial curvature | 10 pages, no figure | null | 10.1088/0031-8949/91/11/115001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Contrary to the general belief, there has recently been quite a few examples
of unitary evolution of quantum cosmological models. The present work gives
more examples, namely Bianchi type VI and type II. These examples are important
as they involve varying spatial curvature unlike the most talked about
homogeneous but anisotropic cosmological models like Bianchi I, V and IX. We
exhibit either explicit example of the unitary solutions of the Wheeler-DeWitt
equation, or at least show that a self-adjoint extension is possible.
| [
{
"created": "Fri, 4 Mar 2016 10:09:16 GMT",
"version": "v1"
}
] | 2016-11-03 | [
[
"Pandey",
"Sachin",
""
],
[
"Banerjee",
"Narayan",
""
]
] | Contrary to the general belief, there has recently been quite a few examples of unitary evolution of quantum cosmological models. The present work gives more examples, namely Bianchi type VI and type II. These examples are important as they involve varying spatial curvature unlike the most talked about homogeneous but anisotropic cosmological models like Bianchi I, V and IX. We exhibit either explicit example of the unitary solutions of the Wheeler-DeWitt equation, or at least show that a self-adjoint extension is possible. |
1712.07281 | Lu\'is Filipe Costa | L. Filipe O. Costa, Georgios Lukes-Gerakopoulos, Old\v{r}ich Semer\'ak | Spinning particles in general relativity: Momentum-velocity relation for
the Mathisson-Pirani spin condition | 18 pages, 7 Figures. Slightly improved version, references added,
Figure 4 rescaled. Supplemental material is provided in the ancillary files
"CircularOrbits.nb" and "AdditionalPlots.pdf". Matches the final published
version | Phys. Rev. D 97, 084023 (2018) | 10.1103/PhysRevD.97.084023 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Mathisson-Papapetrou-Dixon (MPD) equations, providing the "pole-dipole"
description of spinning test particles in general relativity, have to be
supplemented by a condition specifying the worldline that will represent the
history of the studied body. It has long been thought that the Mathisson-Pirani
(MP) spin condition -- unlike other major choices made in the literature --
does not yield an explicit momentum-velocity relation. We derive here the
desired (and very simple) relation and show that it is in fact equivalent to
the MP condition. We clarify the apparent paradox between the existence of such
a definite relation and the known fact that the MP condition is degenerate
(does not specify a unique worldline), thus shedding light on some conflicting
statements made in the literature. We then show how, for a given body, this
spin condition yields infinitely many possible representative worldlines, and
derive a detailed method how to switch between them in a curved spacetime. The
MP condition is a convenient choice in situations when it is easy to recognize
its "non-helical" solution, as exemplified here by bodies in circular orbits
and in radial fall in the Schwarzschild spacetime.
| [
{
"created": "Wed, 20 Dec 2017 00:57:20 GMT",
"version": "v1"
},
{
"created": "Wed, 30 May 2018 21:12:29 GMT",
"version": "v2"
}
] | 2018-06-01 | [
[
"Costa",
"L. Filipe O.",
""
],
[
"Lukes-Gerakopoulos",
"Georgios",
""
],
[
"Semerák",
"Oldřich",
""
]
] | The Mathisson-Papapetrou-Dixon (MPD) equations, providing the "pole-dipole" description of spinning test particles in general relativity, have to be supplemented by a condition specifying the worldline that will represent the history of the studied body. It has long been thought that the Mathisson-Pirani (MP) spin condition -- unlike other major choices made in the literature -- does not yield an explicit momentum-velocity relation. We derive here the desired (and very simple) relation and show that it is in fact equivalent to the MP condition. We clarify the apparent paradox between the existence of such a definite relation and the known fact that the MP condition is degenerate (does not specify a unique worldline), thus shedding light on some conflicting statements made in the literature. We then show how, for a given body, this spin condition yields infinitely many possible representative worldlines, and derive a detailed method how to switch between them in a curved spacetime. The MP condition is a convenient choice in situations when it is easy to recognize its "non-helical" solution, as exemplified here by bodies in circular orbits and in radial fall in the Schwarzschild spacetime. |
1211.6326 | Mauricio Bellini | Jes\'us Mart\'in Romero, Mauricio Bellini (IFIMAR - UNMdP & CONICET) | Induced Matter Theory of gravity from a Weitzenb\"ock 5D vacuum and
pre-big bang collapse of the universe | version accepted in European Physical Journal C (16 pages, no
figures) | null | 10.1140/epjc/s10052-013-2317-x | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend the Induced Matter Theory of gravity (IMT) to 5D curved spacetimes
by using the Weitzenb\"ock representation of connections on a 5D curved
spacetime. In this representation the 5D curvature tensor becomes null, so that
we can make a static foliation on the extra noncompact coordinate to induce in
the Weitzenb\"ock representation the Einstein equations. Once we have done it,
we can rewrite the effective 4D Einstein equations in the Levi-Civita
representation. This generalization of IMT opens a huge window of possible
applications for this theory. A pre-big bang collapsing scenario is explored as
an example.
| [
{
"created": "Tue, 27 Nov 2012 15:31:54 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Dec 2012 22:53:51 GMT",
"version": "v2"
},
{
"created": "Sat, 12 Jan 2013 14:13:47 GMT",
"version": "v3"
},
{
"created": "Thu, 14 Feb 2013 16:19:29 GMT",
"version": "v4"
}
] | 2022-06-29 | [
[
"Romero",
"Jesús Martín",
"",
"IFIMAR - UNMdP & CONICET"
],
[
"Bellini",
"Mauricio",
"",
"IFIMAR - UNMdP & CONICET"
]
] | We extend the Induced Matter Theory of gravity (IMT) to 5D curved spacetimes by using the Weitzenb\"ock representation of connections on a 5D curved spacetime. In this representation the 5D curvature tensor becomes null, so that we can make a static foliation on the extra noncompact coordinate to induce in the Weitzenb\"ock representation the Einstein equations. Once we have done it, we can rewrite the effective 4D Einstein equations in the Levi-Civita representation. This generalization of IMT opens a huge window of possible applications for this theory. A pre-big bang collapsing scenario is explored as an example. |
1611.06075 | Nabil Youssef L | M. I. Wanas, Nabil L. Youssef, W. El Hanafy and S. N. Osman | Einstein Geometrization Philosophy and Differential Identities in
PAP-Geometry | LaTeX file, 17 pages, comments and criticism are welcome | Advances in Mathematical Physics, vol. 2016, Article ID 1037849, 8
pages, 2016 | 10.1155/2016/1037849 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The importance of Einstein's geometrization philosophy, as an alternative to
the least action principle, in constructing general relativity (GR), is
illuminated. The role of differential identities in this philosophy is
clarified. The use of Bianchi identity to write the field equations of GR is
shown. Another similar identity in the absolute parallelism geometry is given.
A more general differential identity in the parameterized absolute parallelism
geometry is derived. Comparison and interrelationships between the above
mentioned identities and their role in constructing field theories are
discussed.
| [
{
"created": "Fri, 18 Nov 2016 13:53:43 GMT",
"version": "v1"
}
] | 2016-12-05 | [
[
"Wanas",
"M. I.",
""
],
[
"Youssef",
"Nabil L.",
""
],
[
"Hanafy",
"W. El",
""
],
[
"Osman",
"S. N.",
""
]
] | The importance of Einstein's geometrization philosophy, as an alternative to the least action principle, in constructing general relativity (GR), is illuminated. The role of differential identities in this philosophy is clarified. The use of Bianchi identity to write the field equations of GR is shown. Another similar identity in the absolute parallelism geometry is given. A more general differential identity in the parameterized absolute parallelism geometry is derived. Comparison and interrelationships between the above mentioned identities and their role in constructing field theories are discussed. |
1905.04299 | Nan Zhang | Nan Zhang, Ya-Bo Wu, Jia-Nan Chi, Zhe Yu, Dong-Fang Xu | Diagnosing Tsallis Holographic Dark Energy models with interactions | 10 pages,6 figures | Modern Physics Letters A Vol. 33, No. 1 (2020) 2050044 | 10.1142/S0217732320500443 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been found that the geometrical diagnostic methods can break the
degeneracy for dark energy models. In this paper, we investigate the $Om$
diagnostic, the statefinder hierarchy $S_{n}$ and the composite null diagnostic
$\{S_{n},\epsilon\}$ for the Tsallis holographic dark energy models with
interactions. We find that model parameters and the forms of interaction will
influence the values of diagnostic parameters or the trends of the evolutionary
trajectories for each model. Moreover, the statefinder hierarchy $S_{3}^{(1)}$
together with $\{S_{3}^{(1)},\epsilon\}$ could give good diagnostic results.
Furthermore, we also obtain some issues of cosmological structure by means of
the composite null diagnostic.
| [
{
"created": "Fri, 10 May 2019 07:45:17 GMT",
"version": "v1"
},
{
"created": "Fri, 24 May 2019 10:11:14 GMT",
"version": "v2"
},
{
"created": "Sun, 24 Nov 2019 14:30:53 GMT",
"version": "v3"
}
] | 2019-11-26 | [
[
"Zhang",
"Nan",
""
],
[
"Wu",
"Ya-Bo",
""
],
[
"Chi",
"Jia-Nan",
""
],
[
"Yu",
"Zhe",
""
],
[
"Xu",
"Dong-Fang",
""
]
] | It has been found that the geometrical diagnostic methods can break the degeneracy for dark energy models. In this paper, we investigate the $Om$ diagnostic, the statefinder hierarchy $S_{n}$ and the composite null diagnostic $\{S_{n},\epsilon\}$ for the Tsallis holographic dark energy models with interactions. We find that model parameters and the forms of interaction will influence the values of diagnostic parameters or the trends of the evolutionary trajectories for each model. Moreover, the statefinder hierarchy $S_{3}^{(1)}$ together with $\{S_{3}^{(1)},\epsilon\}$ could give good diagnostic results. Furthermore, we also obtain some issues of cosmological structure by means of the composite null diagnostic. |
gr-qc/9805029 | Sanjay Jhingan | I. H. Dwivedi | Photon redshift and the appearance of a naked singularity | Latex file, 14 pages, no figures, one change in the reference.
Accepted for publication in Phys. Rev. D | Phys.Rev. D58 (1998) 064004 | 10.1103/PhysRevD.58.064004 | null | gr-qc | null | In this paper we analyze the redshift as observed by an external observer
receiving photons which terminate in the past at the naked singularity formed
in a Tolman-Bondi dust collapse. Within the context of models considered here
it is shown that photons emitted from a weak curvature naked singularity are
always finitely redshifted to an external observer. Certain cases of strong
curvature naked singularities, including the self-similar one, where the
photons are infinitely redshifted are also pointed out.
| [
{
"created": "Sat, 9 May 1998 15:12:49 GMT",
"version": "v1"
},
{
"created": "Wed, 27 May 1998 06:12:52 GMT",
"version": "v2"
},
{
"created": "Thu, 28 May 1998 04:24:37 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Dwivedi",
"I. H.",
""
]
] | In this paper we analyze the redshift as observed by an external observer receiving photons which terminate in the past at the naked singularity formed in a Tolman-Bondi dust collapse. Within the context of models considered here it is shown that photons emitted from a weak curvature naked singularity are always finitely redshifted to an external observer. Certain cases of strong curvature naked singularities, including the self-similar one, where the photons are infinitely redshifted are also pointed out. |
1208.5399 | Christopher J. Fewster | Christopher J. Fewster | Lectures on quantum energy inequalities | 50pp, Lectures given at the Albert Einstein Institute, Golm | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum field theory violates all the classical energy conditions of general
relativity. Nonetheless, it turns out that quantum field theories satisfy
remnants of the classical energy conditions, known as Quantum Energy
Inequalities (QEIs), that have been developed by various authors since the
original pioneering work of Ford in 1978. These notes provide an introduction
to QEIs and also to some of the techniques of quantum field theory in curved
spacetime (particularly, the use of microlocal analysis together with the
algebraic formulation of QFT) that enable rigorous and general QEIs to be
derived. Specific examples are computed for the free scalar field and their
consequences are discussed. QEIs are also derived for the class of unitary,
positive energy conformal field theories in two spacetime dimensions. In that
setting it is also possible to determine the probability distribution for
individual measurements of certain smearings of the stress-energy tensor in the
vacuum state.
| [
{
"created": "Mon, 27 Aug 2012 13:53:07 GMT",
"version": "v1"
}
] | 2012-08-28 | [
[
"Fewster",
"Christopher J.",
""
]
] | Quantum field theory violates all the classical energy conditions of general relativity. Nonetheless, it turns out that quantum field theories satisfy remnants of the classical energy conditions, known as Quantum Energy Inequalities (QEIs), that have been developed by various authors since the original pioneering work of Ford in 1978. These notes provide an introduction to QEIs and also to some of the techniques of quantum field theory in curved spacetime (particularly, the use of microlocal analysis together with the algebraic formulation of QFT) that enable rigorous and general QEIs to be derived. Specific examples are computed for the free scalar field and their consequences are discussed. QEIs are also derived for the class of unitary, positive energy conformal field theories in two spacetime dimensions. In that setting it is also possible to determine the probability distribution for individual measurements of certain smearings of the stress-energy tensor in the vacuum state. |
1306.3231 | Michel Buck | Siavash Aslanbeigi, Michel Buck | A preferred ground state for the scalar field in de Sitter space | 35 pages, 9 figures | null | 10.1007/JHEP08(2013)039 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate a recent proposal for a distinguished vacuum state of a free
scalar quantum field in an arbitrarily curved spacetime, known as the
Sorkin-Johnston (SJ) vacuum, by applying it to de Sitter space. We derive the
associated two-point functions on both the global and Poincar\'e (cosmological)
patches in general d+1 dimensions. In all cases where it is defined, the SJ
vacuum belongs to the family of de Sitter invariant alpha-vacua. We obtain
different states depending on the spacetime dimension, mass of the scalar
field, and whether the state is evaluated on the global or Poincar\'e patch. We
find that the SJ vacuum agrees with the Euclidean/Bunch-Davies state for heavy
("principal series") fields on the global patch in even spacetime dimensions.
We also compute the SJ vacuum on a causal set corresponding to a causal diamond
in 1+1 dimensional de Sitter space. Our simulations show that the mean of the
SJ two-point function on the causal set agrees well with its expected continuum
counterpart.
| [
{
"created": "Thu, 13 Jun 2013 20:00:06 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Aslanbeigi",
"Siavash",
""
],
[
"Buck",
"Michel",
""
]
] | We investigate a recent proposal for a distinguished vacuum state of a free scalar quantum field in an arbitrarily curved spacetime, known as the Sorkin-Johnston (SJ) vacuum, by applying it to de Sitter space. We derive the associated two-point functions on both the global and Poincar\'e (cosmological) patches in general d+1 dimensions. In all cases where it is defined, the SJ vacuum belongs to the family of de Sitter invariant alpha-vacua. We obtain different states depending on the spacetime dimension, mass of the scalar field, and whether the state is evaluated on the global or Poincar\'e patch. We find that the SJ vacuum agrees with the Euclidean/Bunch-Davies state for heavy ("principal series") fields on the global patch in even spacetime dimensions. We also compute the SJ vacuum on a causal set corresponding to a causal diamond in 1+1 dimensional de Sitter space. Our simulations show that the mean of the SJ two-point function on the causal set agrees well with its expected continuum counterpart. |
gr-qc/0412021 | Mamdouh Wanas | M.I.Wanas | Quantum Properties of a General Path Deviation Equation in the
Pap-Geometry | LaTex File, 8 pages | null | null | null | gr-qc | null | A path deviation equation in the Parameterized Absolute Parallelism (PAP)
geometry is derived. This equation includes curvature and torsion terms. These
terms are found to be naturally quantized. The equation represents the
deviation from a general path equation, in the PAP-geometry, derived by the
author in a previous work. It is shown that, as the effect of the torsion, on
the deviation, increases, the effect of the curvature decreases. It is also
shown that the general path deviation equation can be reduced to the geodesic
deviation equation if PAP-geometry becomes Riemannian. The equation can be used
to study the deviation from the trajectories of spinning elementary particles.
| [
{
"created": "Sat, 4 Dec 2004 10:34:38 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Wanas",
"M. I.",
""
]
] | A path deviation equation in the Parameterized Absolute Parallelism (PAP) geometry is derived. This equation includes curvature and torsion terms. These terms are found to be naturally quantized. The equation represents the deviation from a general path equation, in the PAP-geometry, derived by the author in a previous work. It is shown that, as the effect of the torsion, on the deviation, increases, the effect of the curvature decreases. It is also shown that the general path deviation equation can be reduced to the geodesic deviation equation if PAP-geometry becomes Riemannian. The equation can be used to study the deviation from the trajectories of spinning elementary particles. |
1204.0794 | Barry Wardell | Anna Heffernan, Adrian Ottewill, Barry Wardell | High-order expansions of the Detweiler-Whiting singular field in
Schwarzschild spacetime | 38 pages, typos fixed, final published version | Phys. Rev. D 82, 104023 (2012) | 10.1103/PhysRevD.86.104023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The self field of a charged particle has a component that diverges at the
particle. We use both coordinate and covariant approaches to compute an
expansion of this singular field for generic geodesic orbits in Schwarzschild
spacetime for scalar, electromagnetic and graviational cases. We check
agreement of both approaches and give, as an application, the calculation of
previously unknown regularisation parameters. In this so-called "mode-sum
regularization" approach, each mode of the field is finite, while their sum
diverges. The sum may be rendered finite and convergent by the subtraction of
"regularization parameters". Higher order parameters lead to faster convergence
in the mode-sum. As a second example application, we compute high order
expressions for the effective source approach to self-force calculations.
| [
{
"created": "Tue, 3 Apr 2012 20:02:24 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jun 2012 19:25:28 GMT",
"version": "v2"
},
{
"created": "Sun, 1 Jul 2012 10:52:12 GMT",
"version": "v3"
},
{
"created": "Tue, 5 Nov 2013 16:02:40 GMT",
"version": "v4"
}
] | 2013-11-06 | [
[
"Heffernan",
"Anna",
""
],
[
"Ottewill",
"Adrian",
""
],
[
"Wardell",
"Barry",
""
]
] | The self field of a charged particle has a component that diverges at the particle. We use both coordinate and covariant approaches to compute an expansion of this singular field for generic geodesic orbits in Schwarzschild spacetime for scalar, electromagnetic and graviational cases. We check agreement of both approaches and give, as an application, the calculation of previously unknown regularisation parameters. In this so-called "mode-sum regularization" approach, each mode of the field is finite, while their sum diverges. The sum may be rendered finite and convergent by the subtraction of "regularization parameters". Higher order parameters lead to faster convergence in the mode-sum. As a second example application, we compute high order expressions for the effective source approach to self-force calculations. |
1706.03209 | Soumya Jana | Soumya Jana, Sayan Kar (IIT Kharagpur, India) | Born-Infeld gravity with a Brans-Dicke scalar | 25 pages, 7 figures. Published version | Phys. Rev. D 96, 024050 (2017) | 10.1103/PhysRevD.96.024050 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently proposed Born-Infeld (BI) theories of gravity assume a constant BI
parameter ($\kappa$). However, no clear consensus exists on the sign and value
of $\kappa$. Recalling the Brans-Dicke (BD) approach, where a scalar field was
used to generate the gravitational constant $G$, we suggest an extension of
Born-Infeld gravity with a similar Brans-Dicke flavor. Thus, a new action, with
$\kappa$ elevated to a spacetime dependent real scalar field, is proposed. We
illustrate this new theory in a cosmological setting with pressureless dust and
radiation as matter. Assuming a functional form of $\kappa(t)$, we numerically
obtain the scale factor evolution and other details of the background
cosmology. It is known that BI gravity differs from general relativity (GR) in
the strong-field regime but reduces to GR for intermediate and weak fields. Our
studies in cosmology demonstrate how, with this new, scalar-tensor BI gravity,
deviations from GR as well as usual BI gravity, may arise in the weak-field
regime too. For example, we note a late-time acceleration without any dark
energy contribution. Apart from such qualitative differences, we note that
fixing the sign and value of $\kappa$ is no longer a necessity in this theory,
though the origin of the BD scalar does remain an open question.
| [
{
"created": "Sat, 10 Jun 2017 09:32:24 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Jul 2017 14:18:07 GMT",
"version": "v2"
}
] | 2017-07-28 | [
[
"Jana",
"Soumya",
"",
"IIT Kharagpur, India"
],
[
"Kar",
"Sayan",
"",
"IIT Kharagpur, India"
]
] | Recently proposed Born-Infeld (BI) theories of gravity assume a constant BI parameter ($\kappa$). However, no clear consensus exists on the sign and value of $\kappa$. Recalling the Brans-Dicke (BD) approach, where a scalar field was used to generate the gravitational constant $G$, we suggest an extension of Born-Infeld gravity with a similar Brans-Dicke flavor. Thus, a new action, with $\kappa$ elevated to a spacetime dependent real scalar field, is proposed. We illustrate this new theory in a cosmological setting with pressureless dust and radiation as matter. Assuming a functional form of $\kappa(t)$, we numerically obtain the scale factor evolution and other details of the background cosmology. It is known that BI gravity differs from general relativity (GR) in the strong-field regime but reduces to GR for intermediate and weak fields. Our studies in cosmology demonstrate how, with this new, scalar-tensor BI gravity, deviations from GR as well as usual BI gravity, may arise in the weak-field regime too. For example, we note a late-time acceleration without any dark energy contribution. Apart from such qualitative differences, we note that fixing the sign and value of $\kappa$ is no longer a necessity in this theory, though the origin of the BD scalar does remain an open question. |
1105.6197 | Jose Natario | Jose Natario | Optimal time travel in the Godel universe | 16 pages, 2 figures; v2: lower bound in the velocity and reference
added | Gen. Rel. Grav. 44 (2012) 855-874 | 10.1007/s10714-011-1308-1 | null | gr-qc math.OC | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the theory of optimal rocket trajectories in general relativity,
recently developed in arXiv:1105.5235, we present a candidate for the minimum
total integrated acceleration closed timelike curve in the Godel universe, and
give evidence for its minimality. The total integrated acceleration of this
curve is lower than Malament's conjectured value (Malament, 1984), as was
already implicit in the work of Manchak (Manchak, 2011); however, Malament's
conjecture does seem to hold for periodic closed timelike curves.
| [
{
"created": "Tue, 31 May 2011 08:11:24 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Oct 2011 13:45:18 GMT",
"version": "v2"
}
] | 2015-05-28 | [
[
"Natario",
"Jose",
""
]
] | Using the theory of optimal rocket trajectories in general relativity, recently developed in arXiv:1105.5235, we present a candidate for the minimum total integrated acceleration closed timelike curve in the Godel universe, and give evidence for its minimality. The total integrated acceleration of this curve is lower than Malament's conjectured value (Malament, 1984), as was already implicit in the work of Manchak (Manchak, 2011); however, Malament's conjecture does seem to hold for periodic closed timelike curves. |
2303.14945 | Octavian Micu | Roberto Casadio and Octavian Micu | Quantum matter core of black holes (and quantum hair) | Invited chapter for the edited book New Frontiers in Gravitational
Collapse and Spacetime Singularities (Eds. P. Joshi and D. Malafarina,
Springer Singapore, expected in 2023) | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The idea that gravity can act as a regulator of ultraviolet divergences is
almost a century old and has inspired several approaches to quantum gravity. In
fact, a minimum Planckian length can be shown to emerge from the nonlinear
dynamics of gravity in the effective field theory approach to gravitational
scatterings at Planckian energies. A simple quantum description of the
gravitational collapse of a ball of dust supports the conclusion that such a
length scale is indeed dynamical and matter inside black holes forms extended
cores of macroscopic size. The geometry of these quantum black holes can be
described by coherent states which cannot contain modes of arbitrarily short
wavelength, compatibly with a matter core of finite size. Therefore, the
classical central singularity is not realised, yet the expected general
relativistic behaviour can be recovered in the weak-field region outside the
horizon with good approximation. Deviations from classical general relativistic
solutions are still present and form quantum hair which modify the
thermodynamical description of black holes. These quantum black holes also
avoid the presence of inner (Cauchy) horizons, since the effective energy
density and pressures are integrable, as required by quantum physics, and not
as regular as in classical physics.
| [
{
"created": "Mon, 27 Mar 2023 07:06:36 GMT",
"version": "v1"
}
] | 2023-03-28 | [
[
"Casadio",
"Roberto",
""
],
[
"Micu",
"Octavian",
""
]
] | The idea that gravity can act as a regulator of ultraviolet divergences is almost a century old and has inspired several approaches to quantum gravity. In fact, a minimum Planckian length can be shown to emerge from the nonlinear dynamics of gravity in the effective field theory approach to gravitational scatterings at Planckian energies. A simple quantum description of the gravitational collapse of a ball of dust supports the conclusion that such a length scale is indeed dynamical and matter inside black holes forms extended cores of macroscopic size. The geometry of these quantum black holes can be described by coherent states which cannot contain modes of arbitrarily short wavelength, compatibly with a matter core of finite size. Therefore, the classical central singularity is not realised, yet the expected general relativistic behaviour can be recovered in the weak-field region outside the horizon with good approximation. Deviations from classical general relativistic solutions are still present and form quantum hair which modify the thermodynamical description of black holes. These quantum black holes also avoid the presence of inner (Cauchy) horizons, since the effective energy density and pressures are integrable, as required by quantum physics, and not as regular as in classical physics. |
2304.12733 | Spiros Cotsakis | Spiros Cotsakis, Jose P. Mimoso, John Miritzis | The cosmological frame principle and cosmic acceleration | v2: 12 pages, 3 figures, some more discussion and references added,
matches published version | Eur. Phys. J. C 83, 735 (2023) | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss implications of the cosmological frame principle which states that
cosmological effects of modified gravity must be stable as solutions of each of
the corresponding sets of dynamical equations holding in the two
conformally-related frames. We show that there are such globally stable,
`frame-independent' solutions describing cosmic acceleration, suggesting that
they may represent a physically relevant effect. This result highlights the
importance of further investigation into the implications of the frame
principle for cosmological properties that rely on the use of conformal frames.
| [
{
"created": "Tue, 25 Apr 2023 11:25:01 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Aug 2023 16:58:48 GMT",
"version": "v2"
}
] | 2023-08-23 | [
[
"Cotsakis",
"Spiros",
""
],
[
"Mimoso",
"Jose P.",
""
],
[
"Miritzis",
"John",
""
]
] | We discuss implications of the cosmological frame principle which states that cosmological effects of modified gravity must be stable as solutions of each of the corresponding sets of dynamical equations holding in the two conformally-related frames. We show that there are such globally stable, `frame-independent' solutions describing cosmic acceleration, suggesting that they may represent a physically relevant effect. This result highlights the importance of further investigation into the implications of the frame principle for cosmological properties that rely on the use of conformal frames. |
1510.04784 | Prasobh C.B | Prasobh C.B., Jishnu Suresh, V.C. Kuriakose | Thermodynamics of Charged Lovelock - AdS Black Holes | 17 pages, 13 figures. arXiv admin note: text overlap with
arXiv:1312.0679 by other authors | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the thermodynamic behavior of maximally symmetric charged,
asymptotically AdS black hole solutions of Lovelock gravity. We explore the
thermodynamic stability of such solutions by the ordinary method of calculating
the specific heat of the black holes and investigating its divergences which
signal second order phase transitions between black hole states. We then
utilize the methods of thermodynamic geometry of black hole spacetimes in order
to explain the origin of these points of divergence. We calculate the curvature
scalar corresponding to a Legendre-invariant thermodynamic metric of these
spacetimes and find that the divergences in the black hole specific heat
correspond to singularities in the thermodynamic phase space. We also calculate
the area spectrum for large black holes in the model by applying the
Bohr-Sommerfeld quantization to the adiabatic invariant calculated for the
spacetime.
| [
{
"created": "Fri, 16 Oct 2015 05:40:15 GMT",
"version": "v1"
}
] | 2015-10-19 | [
[
"B.",
"Prasobh C.",
""
],
[
"Suresh",
"Jishnu",
""
],
[
"Kuriakose",
"V. C.",
""
]
] | We investigate the thermodynamic behavior of maximally symmetric charged, asymptotically AdS black hole solutions of Lovelock gravity. We explore the thermodynamic stability of such solutions by the ordinary method of calculating the specific heat of the black holes and investigating its divergences which signal second order phase transitions between black hole states. We then utilize the methods of thermodynamic geometry of black hole spacetimes in order to explain the origin of these points of divergence. We calculate the curvature scalar corresponding to a Legendre-invariant thermodynamic metric of these spacetimes and find that the divergences in the black hole specific heat correspond to singularities in the thermodynamic phase space. We also calculate the area spectrum for large black holes in the model by applying the Bohr-Sommerfeld quantization to the adiabatic invariant calculated for the spacetime. |
1807.10729 | Diego S\'aez-Chill\'on G\'omez | Norman Cruz, Esteban Gonzalez, Samuel Lepe and Diego Saez-Chillon
Gomez | Analysing dissipative effects in the $\Lambda$CDM model | 11 pages, 4 figures, analysis extended | JCAP 12 (2018) 017 | 10.1088/1475-7516/2018/12/017 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present paper, the effects of viscous dark matter are analysed within
the $\Lambda$CDM model. Here we consider bulk viscosity through the
Israel-Stewart theory approach, leading to an effective pressure term in the
continuity equation that accomplishes for the dissipative effects of the dark
matter fluid. Then, the corresponding equation for viscosity is solved and a
general equation for the Hubble parameter is obtained with the presence of a
cosmological constant. The existence of de Sitter solutions is discussed, where
a wider range of solutions is found in comparison to the $\Lambda$CDM model.
Also the conditions for the near thermodynamical equilibrium of the fluid is
analysed. Finally, a qualitative analysis provides some constraints on the
model by using Supernovae Ia data which reveals the possible importance of
causal thermodynamics in cosmology.
| [
{
"created": "Fri, 27 Jul 2018 16:56:26 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Oct 2018 12:14:35 GMT",
"version": "v2"
}
] | 2018-12-13 | [
[
"Cruz",
"Norman",
""
],
[
"Gonzalez",
"Esteban",
""
],
[
"Lepe",
"Samuel",
""
],
[
"Gomez",
"Diego Saez-Chillon",
""
]
] | In the present paper, the effects of viscous dark matter are analysed within the $\Lambda$CDM model. Here we consider bulk viscosity through the Israel-Stewart theory approach, leading to an effective pressure term in the continuity equation that accomplishes for the dissipative effects of the dark matter fluid. Then, the corresponding equation for viscosity is solved and a general equation for the Hubble parameter is obtained with the presence of a cosmological constant. The existence of de Sitter solutions is discussed, where a wider range of solutions is found in comparison to the $\Lambda$CDM model. Also the conditions for the near thermodynamical equilibrium of the fluid is analysed. Finally, a qualitative analysis provides some constraints on the model by using Supernovae Ia data which reveals the possible importance of causal thermodynamics in cosmology. |
1507.07100 | Tim Dietrich | Tim Dietrich, Niclas Moldenhauer, Nathan K. Johnson-McDaniel,
Sebastiano Bernuzzi, Charalampos M. Markakis, Bernd Bruegmann, Wolfgang Tichy | Binary Neutron Stars with Generic Spin, Eccentricity, Mass ratio, and
Compactness - Quasi-equilibrium Sequences and First Evolutions | (37pages, 26 figures) | Phys. Rev. D 92, 124007 (2015) | 10.1103/PhysRevD.92.124007 | ICTS/2015/5 | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Information about the last stages of a binary neutron star inspiral and the
final merger can be extracted from quasi-equilibrium configurations and
dynamical evolutions. In this article, we construct quasi-equilibrium
configurations for different spins, eccentricities, mass ratios, compactnesses,
and equations of state. For this purpose we employ the SGRID code, which allows
us to construct such data in previously inaccessible regions of the parameter
space. In particular, we consider spinning neutron stars in isolation and in
binary systems; we incorporate new methods to produce highly eccentric and
eccentricity reduced data; we present the possibility of computing data for
significantly unequal-mass binaries; and we create equal-mass binaries with
individual compactness up to 0.23. As a proof of principle, we explore the
dynamical evolution of three new configurations. First, we simulate a $q=2.06$
mass ratio which is the highest mass ratio for a binary neutron star evolved in
numerical relativity to date. We find that mass transfer from the companion
star sets in a few revolutions before merger and a rest mass of
$\sim10^{-2}M_\odot$ is transferred between the two stars. This configuration
also ejects a large amount of material during merger, imparting a substantial
kick to the remnant. Second, we simulate the first merger of a precessing
binary neutron star. We present the dominant modes of the gravitational waves
for the precessing simulation, where a clear imprint of the precession is
visible in the (2,1) mode. Finally, we quantify the effect of an eccentricity
reduction procedure on the gravitational waveform. The procedure improves the
waveform quality and should be employed in future precision studies, but also
other errors, notably truncation errors, need to be reduced in order for the
improvement due to eccentricity reduction to be effective. [abridged]
| [
{
"created": "Sat, 25 Jul 2015 13:24:10 GMT",
"version": "v1"
}
] | 2015-12-09 | [
[
"Dietrich",
"Tim",
""
],
[
"Moldenhauer",
"Niclas",
""
],
[
"Johnson-McDaniel",
"Nathan K.",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Markakis",
"Charalampos M.",
""
],
[
"Bruegmann",
"Bernd",
""
],
[
"Tichy",
"Wolfgang",
""
]
] | Information about the last stages of a binary neutron star inspiral and the final merger can be extracted from quasi-equilibrium configurations and dynamical evolutions. In this article, we construct quasi-equilibrium configurations for different spins, eccentricities, mass ratios, compactnesses, and equations of state. For this purpose we employ the SGRID code, which allows us to construct such data in previously inaccessible regions of the parameter space. In particular, we consider spinning neutron stars in isolation and in binary systems; we incorporate new methods to produce highly eccentric and eccentricity reduced data; we present the possibility of computing data for significantly unequal-mass binaries; and we create equal-mass binaries with individual compactness up to 0.23. As a proof of principle, we explore the dynamical evolution of three new configurations. First, we simulate a $q=2.06$ mass ratio which is the highest mass ratio for a binary neutron star evolved in numerical relativity to date. We find that mass transfer from the companion star sets in a few revolutions before merger and a rest mass of $\sim10^{-2}M_\odot$ is transferred between the two stars. This configuration also ejects a large amount of material during merger, imparting a substantial kick to the remnant. Second, we simulate the first merger of a precessing binary neutron star. We present the dominant modes of the gravitational waves for the precessing simulation, where a clear imprint of the precession is visible in the (2,1) mode. Finally, we quantify the effect of an eccentricity reduction procedure on the gravitational waveform. The procedure improves the waveform quality and should be employed in future precision studies, but also other errors, notably truncation errors, need to be reduced in order for the improvement due to eccentricity reduction to be effective. [abridged] |
1901.02202 | Gen Ye | Gen Ye, Yun-Song Piao | Implication of GW170817 for cosmological bounces | 17 pages, 4 figures; refs added, typos fixed | Commun. Theor. Phys. 71 no.4 (2019), 427 | 10.1088/0253-6102/71/4/427 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The detection of GW170817 and its electromagnetic counterpart has revealed
the speed of gravitational waves coincides with the speed of light, $c_T=1$.
Inspired by the possibility that the physics implied by GW170817 might be
related with that for the primordial universe, we construct the spatially flat
stable (throughout the whole evolution) nonsingular bounce models in the beyond
Horndeski theory with $c_T=1$ and in the degenerate higher-order scalar-tensor
(DHOST) theory with $c_T=1$, respectively. Though it constricts the space of
viable models, the constraint of $c_T=1$ makes the procedure of building models
simpler.
| [
{
"created": "Tue, 8 Jan 2019 08:24:08 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Mar 2019 09:37:24 GMT",
"version": "v2"
}
] | 2019-05-22 | [
[
"Ye",
"Gen",
""
],
[
"Piao",
"Yun-Song",
""
]
] | The detection of GW170817 and its electromagnetic counterpart has revealed the speed of gravitational waves coincides with the speed of light, $c_T=1$. Inspired by the possibility that the physics implied by GW170817 might be related with that for the primordial universe, we construct the spatially flat stable (throughout the whole evolution) nonsingular bounce models in the beyond Horndeski theory with $c_T=1$ and in the degenerate higher-order scalar-tensor (DHOST) theory with $c_T=1$, respectively. Though it constricts the space of viable models, the constraint of $c_T=1$ makes the procedure of building models simpler. |
2106.10644 | Tiberiu Harko | Zahra Haghani, Tiberiu Harko | Generalizing the coupling between geometry and matter: $f(R,L_m,T)$
gravity | 21 pages, 3 figures, accepted for publication in EPJC; references
added | null | 10.1140/epjc/s10052-021-09359-3 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We generalize and unify the $f(R,T)$ and $f(R,L_m)$ type gravity models by
assuming that the gravitational Lagrangian is given by an arbitrary function of
the Ricci scalar $R$, of the trace of the energy-momentum tensor $T$, and of
the matter Lagrangian $L_m$, so that $L_{grav}=f(R,L_m,T)$. We obtain the
gravitational field equations in the metric formalism, the equations of motion
for test particles, and the energy and momentum balance equations, which follow
from the covariant divergence of the energy-momentum tensor. Generally, the
motion is non-geodesic, and takes place in the presence of an extra force
orthogonal to the four-velocity. The Newtonian limit of the equations of motion
is also investigated, and the expression of the extra acceleration is obtained
for small velocities and weak gravitational fields. The generalized Poisson
equation is also obtained in the Newtonian limit, and the Dolgov-Kawasaki
instability is also investigated. The cosmological implications of the theory
are investigated for a homogeneous, isotropic and flat Universe for two
particular choices of the Lagrangian density $f(R,L_m,T)$ of the gravitational
field, with a multiplicative and additive algebraic structure in the matter
couplings, respectively, and for two choices of the matter Lagrangian, by using
both analytical and numerical methods.
| [
{
"created": "Sun, 20 Jun 2021 07:41:30 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Jun 2021 09:58:23 GMT",
"version": "v2"
}
] | 2021-07-28 | [
[
"Haghani",
"Zahra",
""
],
[
"Harko",
"Tiberiu",
""
]
] | We generalize and unify the $f(R,T)$ and $f(R,L_m)$ type gravity models by assuming that the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar $R$, of the trace of the energy-momentum tensor $T$, and of the matter Lagrangian $L_m$, so that $L_{grav}=f(R,L_m,T)$. We obtain the gravitational field equations in the metric formalism, the equations of motion for test particles, and the energy and momentum balance equations, which follow from the covariant divergence of the energy-momentum tensor. Generally, the motion is non-geodesic, and takes place in the presence of an extra force orthogonal to the four-velocity. The Newtonian limit of the equations of motion is also investigated, and the expression of the extra acceleration is obtained for small velocities and weak gravitational fields. The generalized Poisson equation is also obtained in the Newtonian limit, and the Dolgov-Kawasaki instability is also investigated. The cosmological implications of the theory are investigated for a homogeneous, isotropic and flat Universe for two particular choices of the Lagrangian density $f(R,L_m,T)$ of the gravitational field, with a multiplicative and additive algebraic structure in the matter couplings, respectively, and for two choices of the matter Lagrangian, by using both analytical and numerical methods. |
1410.7296 | Xuefei Gong | Xuefei Gong, Yun-Kau Lau, Shengnian Xu, Pau Amaro-Seoane, Shan Bai,
Xing Bian, Zhoujian Cao, Gerui Chen, Xian Chen, Yanwei Ding, Peng Dong, Wei
Gao, Gerhard Heinzel, Ming Li, Shuo Li, Fukun Liu, Ziren Luo, Mingxue Shao,
Rainer Spurzem, Baosan Sun, Wenlin Tang, Yan Wang, Peng Xu, Pin Yu, Yefei
Yuan, Xiaomin Zhang and Zebing Zhou | Descope of the ALIA mission | null | null | 10.1088/1742-6596/610/1/012011 | null | gr-qc astro-ph.CO astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present work reports on a feasibility study commissioned by the Chinese
Academy of Sciences of China to explore various possible mission options to
detect gravitational waves in space alternative to that of the eLISA/LISA
mission concept. Based on the relative merits assigned to science and
technological viability, a few representative mission options descoped from the
ALIA mission are considered. A semi-analytic Monte Carlo simulation is carried
out to understand the cosmic black hole merger histories starting from
intermediate mass black holes at high redshift as well as the possible
scientific merits of the mission options considered in probing the light seed
black holes and their coevolution with galaxies in early Universe. The study
indicates that, by choosing the armlength of the interferometer to be three
million kilometers and shifting the sensitivity floor to around one-hundredth
Hz, together with a very moderate improvement on the position noise budget,
there are certain mission options capable of exploring light seed, intermediate
mass black hole binaries at high redshift that are not readily accessible to
eLISA/LISA, and yet the technological requirements seem to within reach in the
next few decades for China.
| [
{
"created": "Wed, 22 Oct 2014 08:48:08 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Nov 2014 14:41:08 GMT",
"version": "v2"
}
] | 2015-06-11 | [
[
"Gong",
"Xuefei",
""
],
[
"Lau",
"Yun-Kau",
""
],
[
"Xu",
"Shengnian",
""
],
[
"Amaro-Seoane",
"Pau",
""
],
[
"Bai",
"Shan",
""
],
[
"Bian",
"Xing",
""
],
[
"Cao",
"Zhoujian",
""
],
[
"Chen",
"Gerui",
""
],
[
"Chen",
"Xian",
""
],
[
"Ding",
"Yanwei",
""
],
[
"Dong",
"Peng",
""
],
[
"Gao",
"Wei",
""
],
[
"Heinzel",
"Gerhard",
""
],
[
"Li",
"Ming",
""
],
[
"Li",
"Shuo",
""
],
[
"Liu",
"Fukun",
""
],
[
"Luo",
"Ziren",
""
],
[
"Shao",
"Mingxue",
""
],
[
"Spurzem",
"Rainer",
""
],
[
"Sun",
"Baosan",
""
],
[
"Tang",
"Wenlin",
""
],
[
"Wang",
"Yan",
""
],
[
"Xu",
"Peng",
""
],
[
"Yu",
"Pin",
""
],
[
"Yuan",
"Yefei",
""
],
[
"Zhang",
"Xiaomin",
""
],
[
"Zhou",
"Zebing",
""
]
] | The present work reports on a feasibility study commissioned by the Chinese Academy of Sciences of China to explore various possible mission options to detect gravitational waves in space alternative to that of the eLISA/LISA mission concept. Based on the relative merits assigned to science and technological viability, a few representative mission options descoped from the ALIA mission are considered. A semi-analytic Monte Carlo simulation is carried out to understand the cosmic black hole merger histories starting from intermediate mass black holes at high redshift as well as the possible scientific merits of the mission options considered in probing the light seed black holes and their coevolution with galaxies in early Universe. The study indicates that, by choosing the armlength of the interferometer to be three million kilometers and shifting the sensitivity floor to around one-hundredth Hz, together with a very moderate improvement on the position noise budget, there are certain mission options capable of exploring light seed, intermediate mass black hole binaries at high redshift that are not readily accessible to eLISA/LISA, and yet the technological requirements seem to within reach in the next few decades for China. |
1302.5079 | Masoud Allahverdizadeh | Masoud Allahverdizadeh, Jose P. S. Lemos and Ahmad Sheykhi | Extremal Myers-Perry black holes coupled to Born-Infeld electrodynamics
in five dimensions | null | Phys. Rev. D 87, 084002 (2013) | 10.1103/PhysRevD.87.084002 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/3.0/ | We construct a new class of perturbative extremal charged rotating black hole
solutions in five dimensions in the Einstein--Born-Infeld theory. We start with
an extremal five-dimensional Myers-Perry black hole seed in which the two
possible angular momenta have equal magnitude, and add Born-Infeld electrical
charge keeping the extremality condition as a constraint. The perturbative
parameter is assumed to be the electric charge $q$ and the perturbations are
performed up to 4th order. We also study some physical properties of these
black holes. It is shown that the perturbative parameter $q$ and the
Born-Infeld parameter $\beta$ modify the values of the physical quantities of
the black holes. The solution suggests that the magnetic moment and
gyromagnetic ratio of the black hole spacetime change sign when the Born-Infeld
character of the solution starts to depart strongly from the Maxwell limit. We
venture an interpretation for the effect.
| [
{
"created": "Tue, 19 Feb 2013 15:06:46 GMT",
"version": "v1"
}
] | 2014-08-18 | [
[
"Allahverdizadeh",
"Masoud",
""
],
[
"Lemos",
"Jose P. S.",
""
],
[
"Sheykhi",
"Ahmad",
""
]
] | We construct a new class of perturbative extremal charged rotating black hole solutions in five dimensions in the Einstein--Born-Infeld theory. We start with an extremal five-dimensional Myers-Perry black hole seed in which the two possible angular momenta have equal magnitude, and add Born-Infeld electrical charge keeping the extremality condition as a constraint. The perturbative parameter is assumed to be the electric charge $q$ and the perturbations are performed up to 4th order. We also study some physical properties of these black holes. It is shown that the perturbative parameter $q$ and the Born-Infeld parameter $\beta$ modify the values of the physical quantities of the black holes. The solution suggests that the magnetic moment and gyromagnetic ratio of the black hole spacetime change sign when the Born-Infeld character of the solution starts to depart strongly from the Maxwell limit. We venture an interpretation for the effect. |
1705.08585 | Jennie D'Ambroise | Jennie D'Ambroise, Floyd L. Williams | Elliptic function solutions in Jackiw-Teitelboim dilaton gravity | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new family of solutions for the Jackiw-Teitelboim model of
two-dimensional gravity with a negative cosmological constant. Here, a metric
of constant Ricci scalar curvature is constructed, and explicit linearly
independent solutions of the corresponding dilaton field equations are
determined. The metric is transformed to a black hole metric, and the dilaton
solutions are expressed in terms of Jacobi elliptic functions. Using these
solutions we compute, for example, Killing vectors for the metric.
| [
{
"created": "Wed, 24 May 2017 02:30:23 GMT",
"version": "v1"
}
] | 2017-05-25 | [
[
"D'Ambroise",
"Jennie",
""
],
[
"Williams",
"Floyd L.",
""
]
] | We present a new family of solutions for the Jackiw-Teitelboim model of two-dimensional gravity with a negative cosmological constant. Here, a metric of constant Ricci scalar curvature is constructed, and explicit linearly independent solutions of the corresponding dilaton field equations are determined. The metric is transformed to a black hole metric, and the dilaton solutions are expressed in terms of Jacobi elliptic functions. Using these solutions we compute, for example, Killing vectors for the metric. |
2112.10530 | Ezgi Canay | Maxim Eingorn, Andrew McLaughlin II, Ezgi Canay, Maksym Brilenkov,
Alexander Zhuk | Gravitational Interaction in the Chimney Lattice Universe | null | Universe 7, 101 (2021) | 10.3390/universe7040101 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | We investigate the influence of the chimney topology $T\times T\times R$ of
the Universe on the gravitational potential and force that are generated by
point-like massive bodies. We obtain three distinct expressions for the
solutions. One follows from Fourier expansion of delta functions into series
using periodicity in two toroidal dimensions. The second one is the summation
of solutions of the Helmholtz equation, for a source mass and its infinitely
many images, which are in the form of Yukawa potentials. The third alternative
solution for the potential is formulated via the Ewald sums method applied to
Yukawa-type potentials. We show that, for the present Universe, the formulas
involving plain summation of Yukawa potentials are preferable for computational
purposes, as they require a smaller number of terms in the series to reach
adequate precision.
| [
{
"created": "Mon, 20 Dec 2021 13:47:04 GMT",
"version": "v1"
}
] | 2021-12-21 | [
[
"Eingorn",
"Maxim",
""
],
[
"McLaughlin",
"Andrew",
"II"
],
[
"Canay",
"Ezgi",
""
],
[
"Brilenkov",
"Maksym",
""
],
[
"Zhuk",
"Alexander",
""
]
] | We investigate the influence of the chimney topology $T\times T\times R$ of the Universe on the gravitational potential and force that are generated by point-like massive bodies. We obtain three distinct expressions for the solutions. One follows from Fourier expansion of delta functions into series using periodicity in two toroidal dimensions. The second one is the summation of solutions of the Helmholtz equation, for a source mass and its infinitely many images, which are in the form of Yukawa potentials. The third alternative solution for the potential is formulated via the Ewald sums method applied to Yukawa-type potentials. We show that, for the present Universe, the formulas involving plain summation of Yukawa potentials are preferable for computational purposes, as they require a smaller number of terms in the series to reach adequate precision. |
1107.2882 | Miguel Oliveira | Miguel A. Oliveira | Velocity measurements in General Relativity revisited | 15 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we generalize an earlier treatment of the measurements of
velocities at the event horizon of a black hole. This is intended as a
pedagogical exercise as well as one more contribution to the resolution of some
unphysical interpretations related to velocity measurements by generalized
observers. We now use a more general metric and, non-geodesic observer sets to
show that the velocity of a test particle at the event horizon is less than the
speed of light.
| [
{
"created": "Thu, 14 Jul 2011 18:16:52 GMT",
"version": "v1"
}
] | 2011-07-15 | [
[
"Oliveira",
"Miguel A.",
""
]
] | In this work we generalize an earlier treatment of the measurements of velocities at the event horizon of a black hole. This is intended as a pedagogical exercise as well as one more contribution to the resolution of some unphysical interpretations related to velocity measurements by generalized observers. We now use a more general metric and, non-geodesic observer sets to show that the velocity of a test particle at the event horizon is less than the speed of light. |
gr-qc/0611078 | Christophe Le Poncin-Lafitte | Pierre Teyssandier (1), Christophe Le Poncin-Lafitte (2) ((1) SYRTE
Observatoire de Paris, (2) Lohrmann Observatory, Dresden Technical
University) | Angular distances in metric theories | 11 pages, no figure. Submitted to Physical Review D | null | null | null | gr-qc | null | The general expression of the angular distance between two point sources as
measured by an arbitrary observer is given. The modelling presented here is
rigorous, covariant and valid in any space-time. The sources of light may be
located at a finite distance from the observer. The aberration and the
gravitational deflection of light are treated in a unified way. Assuming the
gravitational field to be weak, an explicit expansion of the angular separation
within the post-post-Minkowskian approximation is carried out. The angular
separation within the post-Newtonian approximation truncated at the order
$1/c^3$ is straightforwardly derived.
| [
{
"created": "Tue, 14 Nov 2006 18:31:54 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Teyssandier",
"Pierre",
""
],
[
"Poncin-Lafitte",
"Christophe Le",
""
]
] | The general expression of the angular distance between two point sources as measured by an arbitrary observer is given. The modelling presented here is rigorous, covariant and valid in any space-time. The sources of light may be located at a finite distance from the observer. The aberration and the gravitational deflection of light are treated in a unified way. Assuming the gravitational field to be weak, an explicit expansion of the angular separation within the post-post-Minkowskian approximation is carried out. The angular separation within the post-Newtonian approximation truncated at the order $1/c^3$ is straightforwardly derived. |
2306.02023 | Majid Mohsenzadeh Ganji | Majid Mohsenzadeh | Quasi-de Sitter Solution, Negative Norm State and Krein Space in
Cosmology | 12 Pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent observational data have shown two important results about cosmic
inflation: First, the primordial power spectrum is approximately scale
invariant. Secondly, the space-time geometry during inflation is quasi-de
Sitter. In this paper, we study the background field method and the concept of
negative norm states in the framework of Krein space to use in early universe
cosmology. For the inflaton field equation, based on the observations and
taking into account our studies, we suggest an alternative proposal. We will
take the quasi-de Sitter solutions as the physical geometry with the positive
norm and the pure de Sitter solutions as the background geometry with the
negative norm. In the following, we review the consequences of applying the
proposal to calculate some cosmological quantities.
| [
{
"created": "Sat, 3 Jun 2023 06:48:18 GMT",
"version": "v1"
}
] | 2023-06-06 | [
[
"Mohsenzadeh",
"Majid",
""
]
] | Recent observational data have shown two important results about cosmic inflation: First, the primordial power spectrum is approximately scale invariant. Secondly, the space-time geometry during inflation is quasi-de Sitter. In this paper, we study the background field method and the concept of negative norm states in the framework of Krein space to use in early universe cosmology. For the inflaton field equation, based on the observations and taking into account our studies, we suggest an alternative proposal. We will take the quasi-de Sitter solutions as the physical geometry with the positive norm and the pure de Sitter solutions as the background geometry with the negative norm. In the following, we review the consequences of applying the proposal to calculate some cosmological quantities. |
2103.15549 | Abbas Sherif | Abbas M. Sherif, Peter K. S. Dunsby, Rituparno Goswami and Sunil D.
Maharaj | On homothetic Killing vectors in stationary axisymmetric vacuum
spacetimes | 24 pages | null | 10.1142/S0219887821501218 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper we consider homothetic Killing vectors in the class of
stationary axisymmetric vacuum (SAV) spacetimes, where the components of the
vectors are functions of the time and radial coordinates. In this case the
component of any homothetic Killing vector along the $z$ direction must be
constant. Firstly, it is shown that either the component along the radial
direction is constant or we have the proportionality $g_{\phi\phi}\propto
g_{\rho\rho}$, where $g_{\phi\phi}>0$. In both cases, complete analyses are
carried out and the general forms of the homothetic Killing vectors are
determined. The associated conformal factors are also obtained. The case of
vanishing twist in the metric, i.e., $\omega= 0$ is considered and the complete
forms of the homothetic Killing vectors are determined, as well as the
associated conformal factors.
| [
{
"created": "Mon, 29 Mar 2021 12:25:29 GMT",
"version": "v1"
},
{
"created": "Thu, 6 May 2021 18:30:03 GMT",
"version": "v2"
}
] | 2021-05-10 | [
[
"Sherif",
"Abbas M.",
""
],
[
"Dunsby",
"Peter K. S.",
""
],
[
"Goswami",
"Rituparno",
""
],
[
"Maharaj",
"Sunil D.",
""
]
] | In this paper we consider homothetic Killing vectors in the class of stationary axisymmetric vacuum (SAV) spacetimes, where the components of the vectors are functions of the time and radial coordinates. In this case the component of any homothetic Killing vector along the $z$ direction must be constant. Firstly, it is shown that either the component along the radial direction is constant or we have the proportionality $g_{\phi\phi}\propto g_{\rho\rho}$, where $g_{\phi\phi}>0$. In both cases, complete analyses are carried out and the general forms of the homothetic Killing vectors are determined. The associated conformal factors are also obtained. The case of vanishing twist in the metric, i.e., $\omega= 0$ is considered and the complete forms of the homothetic Killing vectors are determined, as well as the associated conformal factors. |
2008.10130 | Maciek Wielgus | Maciek Wielgus, Jiri Horak, Frederic Vincent, Marek Abramowicz | Reflection-asymmetric wormholes and their double shadows | 9 pages, accepted in Phys. Rev. D | Phys. Rev. D 102, 084044 (2020) | 10.1103/PhysRevD.102.084044 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss construction and observational properties of wormholes obtained by
connecting two Reissner-Nordstrom spacetimes with distinct mass and charge
parameters. These objects are spherically symmetric, but not
reflection-symmetric, as the connected spacetimes differ. The
reflection-asymmetric wormholes may reflect a significant fraction of the
infalling radiation back to the spacetime of its origin. We interpret this
effect in a simple framework of the effective photon potential. Depending on
the model parameters, image of such a wormhole seen by a distant observer (its
"shadow") may contain a photon ring formed on the observer's side, photon ring
formed on the other side of the wormhole, or both photon rings. These unique
topological features would allow us to firmly distinguish this class of objects
from Kerr black holes using radioastronomical observations.
| [
{
"created": "Sun, 23 Aug 2020 23:19:25 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Sep 2020 22:09:52 GMT",
"version": "v2"
}
] | 2020-10-28 | [
[
"Wielgus",
"Maciek",
""
],
[
"Horak",
"Jiri",
""
],
[
"Vincent",
"Frederic",
""
],
[
"Abramowicz",
"Marek",
""
]
] | We discuss construction and observational properties of wormholes obtained by connecting two Reissner-Nordstrom spacetimes with distinct mass and charge parameters. These objects are spherically symmetric, but not reflection-symmetric, as the connected spacetimes differ. The reflection-asymmetric wormholes may reflect a significant fraction of the infalling radiation back to the spacetime of its origin. We interpret this effect in a simple framework of the effective photon potential. Depending on the model parameters, image of such a wormhole seen by a distant observer (its "shadow") may contain a photon ring formed on the observer's side, photon ring formed on the other side of the wormhole, or both photon rings. These unique topological features would allow us to firmly distinguish this class of objects from Kerr black holes using radioastronomical observations. |
2302.14553 | Marcelo Schiffer | Marcelo Schiffer | Angular Momentum Fluctuations | 6 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we consider angular momentum fluctuations of a Schwartzschild
black hole in thermal equilibrium with radiation which, for the sake of
simplicity is here modeled by a scalar field. Important, we do not set the
black hole angular momentum $J$ identically to zero at the outset; we allow it
to have a small value (in the sense that $J/M<<1$) and then study the
conditions for thermodynamical equilibrium; only then take the $J\rightarrow 0$
limit. We calculate the black hole's angular momentum fluctuations which turn
out to have two independent contributions: one that comes from the black hole
itself, with no respect to the radiation, and another one that arises from the
radiation. The result is astonishingly simple: the radiation contribution
depends exclusively on the cut-off proper distance from the horizon (or
equivalently, the width of the brick wall), while the black hole contribution
is proportional to its event horizon area. Accordingly, there are no strictly
static black holes in nature, they randomly rotate in all possible directions.
Since a black hole is nothing but geometry, we are dealing with geometry
fluctuations -- our results are of quantum-gravitational nature (albeit at a
semi-classical level). Interestingly enough, if we apply to the black hole
fluctuations component the (quantum) rules of angular momentum we obtain an
event horizon area quantization rule, albeit with a different spectrum from an
equally spaced area spectrum which is widely accepted in the literature.
| [
{
"created": "Tue, 28 Feb 2023 13:18:36 GMT",
"version": "v1"
}
] | 2023-03-01 | [
[
"Schiffer",
"Marcelo",
""
]
] | In this paper, we consider angular momentum fluctuations of a Schwartzschild black hole in thermal equilibrium with radiation which, for the sake of simplicity is here modeled by a scalar field. Important, we do not set the black hole angular momentum $J$ identically to zero at the outset; we allow it to have a small value (in the sense that $J/M<<1$) and then study the conditions for thermodynamical equilibrium; only then take the $J\rightarrow 0$ limit. We calculate the black hole's angular momentum fluctuations which turn out to have two independent contributions: one that comes from the black hole itself, with no respect to the radiation, and another one that arises from the radiation. The result is astonishingly simple: the radiation contribution depends exclusively on the cut-off proper distance from the horizon (or equivalently, the width of the brick wall), while the black hole contribution is proportional to its event horizon area. Accordingly, there are no strictly static black holes in nature, they randomly rotate in all possible directions. Since a black hole is nothing but geometry, we are dealing with geometry fluctuations -- our results are of quantum-gravitational nature (albeit at a semi-classical level). Interestingly enough, if we apply to the black hole fluctuations component the (quantum) rules of angular momentum we obtain an event horizon area quantization rule, albeit with a different spectrum from an equally spaced area spectrum which is widely accepted in the literature. |
gr-qc/9507020 | Philip Carinhas | Philip A. Carinhas | Cauchy Problem for Gott Spacetime | 44 pages, 7 postscript figures. Latex version uses revtex.sty and
aps.sty. Complete downloadable postscript version with embeded figures
available from http://vlbi.matapl.uv.es/~carinhas/resume.html or
http://www.ph.utexas.edu/~carinhas/resume.html | null | null | WISC-MIL-94-TH-17 | gr-qc | null | Gott recently has constructed a spacetime modeled by two infinitely long,
parallel cosmic strings which pass and gravitationally interact with each
other. For large enough velocity, the spacetime will contain closed timelike
curves. An explicit construction of the solution for a scalar field is
presented in detail and a proof for the existence of such a solution is given
for initial data satisfying conditions on an asymptotically null partial Cauchy
surface.
Solutions to smooth operators on the covering space are invariant under the
isometry are shown to be pull back of solutions of the associated operator on
the base space.
Projection maps and translation operators for the covering space are
developed for the spacetime, and explicit expressions for the projection
operator and the isometry group of the covering space are given. It is shown
that the Gott spacetime defined is a quotient space of Minkowski space by the
discrete isometry subgroup of self-equivalences of the projection map.
| [
{
"created": "Mon, 10 Jul 1995 19:33:56 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Carinhas",
"Philip A.",
""
]
] | Gott recently has constructed a spacetime modeled by two infinitely long, parallel cosmic strings which pass and gravitationally interact with each other. For large enough velocity, the spacetime will contain closed timelike curves. An explicit construction of the solution for a scalar field is presented in detail and a proof for the existence of such a solution is given for initial data satisfying conditions on an asymptotically null partial Cauchy surface. Solutions to smooth operators on the covering space are invariant under the isometry are shown to be pull back of solutions of the associated operator on the base space. Projection maps and translation operators for the covering space are developed for the spacetime, and explicit expressions for the projection operator and the isometry group of the covering space are given. It is shown that the Gott spacetime defined is a quotient space of Minkowski space by the discrete isometry subgroup of self-equivalences of the projection map. |
2302.03710 | Molly Burkmar | Molly Burkmar and Marco Bruni | Bouncing cosmology from nonlinear dark energy with two cosmological
constants | 26 pages, 21 figures. Updated version to reflect changes made for
publication | null | 10.1103/PhysRevD.107.083533 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | We explore the dynamics of FLRW cosmologies which consist of dark matter,
radiation and dark energy with a quadratic equation of state. Standard
cosmological singularities arise due to energy conditions which are violated by
dark energy, therefore we focus our analysis on non-singular bouncing and
cyclic cosmologies, in particular focusing on the possibility of closed models
always having a bounce for any initial conditions. We analyse the range of
dynamical behaviour admitted by the system, and find a class of closed models
that admit a non-singular bounce, with early- and late-time accelerated
expansion connected by a decelerating phase. In all cases, we find the bouncing
models are only relevant when dark matter and radiation appear at a certain
energy scale, and so require a period such as reheating. We then investigate
imposing an upper bound on the dark matter and radiation, such that their
energy densities cannot become infinite. We find that bounces are always the
general closed model, and a class of models exist with early- and late-time
acceleration, connected by a decelerating phase. We also consider parameter
values for the dark energy component, such that the discrepancy between the
observed value of $\Lambda$ and the theoretical estimates of the contributions
to the effective cosmological constant expected from quantum field theory would
be explained. However, we find that the class of models left does not allow for
an early- and late-time accelerated expansion, connected by a decelerating
period where large-scale structure could form. Nonetheless, our qualitative
analysis serves as a basis for the construction of more realistic models with
realistic quantitative behaviour.
| [
{
"created": "Tue, 7 Feb 2023 19:01:00 GMT",
"version": "v1"
},
{
"created": "Thu, 18 May 2023 10:31:43 GMT",
"version": "v2"
}
] | 2023-05-19 | [
[
"Burkmar",
"Molly",
""
],
[
"Bruni",
"Marco",
""
]
] | We explore the dynamics of FLRW cosmologies which consist of dark matter, radiation and dark energy with a quadratic equation of state. Standard cosmological singularities arise due to energy conditions which are violated by dark energy, therefore we focus our analysis on non-singular bouncing and cyclic cosmologies, in particular focusing on the possibility of closed models always having a bounce for any initial conditions. We analyse the range of dynamical behaviour admitted by the system, and find a class of closed models that admit a non-singular bounce, with early- and late-time accelerated expansion connected by a decelerating phase. In all cases, we find the bouncing models are only relevant when dark matter and radiation appear at a certain energy scale, and so require a period such as reheating. We then investigate imposing an upper bound on the dark matter and radiation, such that their energy densities cannot become infinite. We find that bounces are always the general closed model, and a class of models exist with early- and late-time acceleration, connected by a decelerating phase. We also consider parameter values for the dark energy component, such that the discrepancy between the observed value of $\Lambda$ and the theoretical estimates of the contributions to the effective cosmological constant expected from quantum field theory would be explained. However, we find that the class of models left does not allow for an early- and late-time accelerated expansion, connected by a decelerating period where large-scale structure could form. Nonetheless, our qualitative analysis serves as a basis for the construction of more realistic models with realistic quantitative behaviour. |
2303.17640 | Ulrich Beckering Vinckers | Ulrich K. Beckering Vinckers, \'Alvaro de la Cruz-Dombriz and Anupam
Mazumdar | Quantum entanglement of masses with non-local gravitational interaction | 12 pages, 3 figures, version published in PRD | Phys. Rev. D 107, 124036 (2023) | 10.1103/PhysRevD.107.124036 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the quantum gravitational entanglement of two test masses in the
context of linearized General Relativity with specific non-local interaction
with matter. To accomplish this, we consider an energy-momentum tensor
describing two test particles of equal mass with each possessing some non-zero
momentum. After discussing the quantization of the linearized theory, we
compute the gravitational energy shift which is operator-valued in this case.
As compared to the local gravitational interaction, we find that the change in
the gravitational energy due to the self-interaction terms is finite. We then
move on to study the quantum gravity induced entanglement of masses for two
different scenarios. The first scenario involves treating the two test masses
as harmonic oscillators with an interaction Hamiltonian given by the aforesaid
gravitational energy shift. In the second scenario, each of the test masses is
placed in a quantum spatial superposition of two locations, based on their
respective spin states, and their entanglement being induced by the
gravitational interaction and the shift in the vacuum energy. For these two
scenarios, we compute both the concurrence and the von Neumann entropy; showing
that an increase in the non-locality of the gravitational interaction results
in a decrease in both of these quantities.
| [
{
"created": "Thu, 30 Mar 2023 18:14:28 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Jun 2023 15:16:13 GMT",
"version": "v2"
}
] | 2023-06-19 | [
[
"Vinckers",
"Ulrich K. Beckering",
""
],
[
"de la Cruz-Dombriz",
"Álvaro",
""
],
[
"Mazumdar",
"Anupam",
""
]
] | We examine the quantum gravitational entanglement of two test masses in the context of linearized General Relativity with specific non-local interaction with matter. To accomplish this, we consider an energy-momentum tensor describing two test particles of equal mass with each possessing some non-zero momentum. After discussing the quantization of the linearized theory, we compute the gravitational energy shift which is operator-valued in this case. As compared to the local gravitational interaction, we find that the change in the gravitational energy due to the self-interaction terms is finite. We then move on to study the quantum gravity induced entanglement of masses for two different scenarios. The first scenario involves treating the two test masses as harmonic oscillators with an interaction Hamiltonian given by the aforesaid gravitational energy shift. In the second scenario, each of the test masses is placed in a quantum spatial superposition of two locations, based on their respective spin states, and their entanglement being induced by the gravitational interaction and the shift in the vacuum energy. For these two scenarios, we compute both the concurrence and the von Neumann entropy; showing that an increase in the non-locality of the gravitational interaction results in a decrease in both of these quantities. |
2312.15666 | Xinliang An | Xinliang An, Taoran He | Dynamics of Apparent Horizon and a Null Comparison Principle | 42 pages | null | null | null | gr-qc math-ph math.AP math.DG math.MP | http://creativecommons.org/licenses/by/4.0/ | This paper investigates the global dynamics of the apparent horizon. We
present an approach to establish its existence and its long-term behaviors. Our
apparent horizon is constructed by solving the marginally outer trapped surface
(MOTS) along each incoming null hypersurface. Based on the nonlinear hyperbolic
estimates established in [24] by Klainerman-Szeftel under polarized axial
symmetry, we prove that the corresponding apparent horizon is smooth,
asymptotically null and converging to the event horizon eventually. To further
address the local achronality of the apparent horizon, a new concept, called
the null comparison principle, is introduced in this paper. For three typical
scenarios of gravitational collapse, our null comparison principle is tested
and verified, which guarantees that the apparent horizon must be piecewise
spacelike or piecewise null. In addition, we also validate and provide new
proofs for several physical laws along the apparent horizon.
| [
{
"created": "Mon, 25 Dec 2023 09:22:58 GMT",
"version": "v1"
}
] | 2023-12-27 | [
[
"An",
"Xinliang",
""
],
[
"He",
"Taoran",
""
]
] | This paper investigates the global dynamics of the apparent horizon. We present an approach to establish its existence and its long-term behaviors. Our apparent horizon is constructed by solving the marginally outer trapped surface (MOTS) along each incoming null hypersurface. Based on the nonlinear hyperbolic estimates established in [24] by Klainerman-Szeftel under polarized axial symmetry, we prove that the corresponding apparent horizon is smooth, asymptotically null and converging to the event horizon eventually. To further address the local achronality of the apparent horizon, a new concept, called the null comparison principle, is introduced in this paper. For three typical scenarios of gravitational collapse, our null comparison principle is tested and verified, which guarantees that the apparent horizon must be piecewise spacelike or piecewise null. In addition, we also validate and provide new proofs for several physical laws along the apparent horizon. |
gr-qc/0405072 | T. Padmanabhan | T. Padmanabhan | Entropy of Horizons, Complex Paths and Quantum Tunneling | published version | Mod.Phys.Lett. A19 (2004) 2637-2643 | 10.1142/S0217732304015257 | null | gr-qc astro-ph hep-th | null | In any spacetime, it is possible to have a family of observers following a
congruence of timelike curves such that they do not have access to part of the
spacetime. This lack of information suggests associating a (congruence
dependent) notion of entropy with the horizon that blocks the information from
these observers. While the blockage of information is absolute in classical
physics, quantum mechanics will allow tunneling across the horizon. This
process can be analysed in a simple, yet general, manner and we show that the
probability for a system with energy $E$ to tunnel across the horizon is
$P(E)\propto\exp[-(2\pi/\kappa)E)$ where $\kappa$ is the surface gravity of the
horizon. If the surface gravity changes due to the leakage of energy through
the horizon, then one can associate an entropy $S(M)$ with the horizon where
$dS = [ 2\pi / \kappa (M) ] dM$ and $M$ is the active gravitational mass of the
system. Using this result, we discuss the conditions under which, a small patch
of area $\Delta A$ of the horizon contributes an entropy $(\Delta A/4L_P^2)$,
where $L_P^2$ is the Planck area.
| [
{
"created": "Fri, 14 May 2004 05:56:37 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Jan 2005 13:56:42 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Padmanabhan",
"T.",
""
]
] | In any spacetime, it is possible to have a family of observers following a congruence of timelike curves such that they do not have access to part of the spacetime. This lack of information suggests associating a (congruence dependent) notion of entropy with the horizon that blocks the information from these observers. While the blockage of information is absolute in classical physics, quantum mechanics will allow tunneling across the horizon. This process can be analysed in a simple, yet general, manner and we show that the probability for a system with energy $E$ to tunnel across the horizon is $P(E)\propto\exp[-(2\pi/\kappa)E)$ where $\kappa$ is the surface gravity of the horizon. If the surface gravity changes due to the leakage of energy through the horizon, then one can associate an entropy $S(M)$ with the horizon where $dS = [ 2\pi / \kappa (M) ] dM$ and $M$ is the active gravitational mass of the system. Using this result, we discuss the conditions under which, a small patch of area $\Delta A$ of the horizon contributes an entropy $(\Delta A/4L_P^2)$, where $L_P^2$ is the Planck area. |
gr-qc/9512008 | Kenneth Dalton | Kenneth Dalton | Einstein's Energy-Free Gravitational Field | 5 pages, LaTeX. Note: Divergence formula (13) is clarified | null | null | null | gr-qc | null | We show that Einstein's gravitational field has zero energy, momentum, and
stress. This conclusion follows directly from the gravitational field
equations, in conjunction with the differential law of energy-momentum
conservation $ T^{\mu\nu}_{;\nu} = 0 $. Einstein rejected this conservation law
despite the fact that it is generally covariant. We trace his rejection to a
misapplication of Gauss' divergence formula. Finally, we derive the formula
which pertains to energy-momentum conservation.
| [
{
"created": "Mon, 4 Dec 1995 15:14:00 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Mar 1997 18:17:03 GMT",
"version": "v2"
},
{
"created": "Fri, 13 Mar 1998 21:29:34 GMT",
"version": "v3"
}
] | 2008-02-03 | [
[
"Dalton",
"Kenneth",
""
]
] | We show that Einstein's gravitational field has zero energy, momentum, and stress. This conclusion follows directly from the gravitational field equations, in conjunction with the differential law of energy-momentum conservation $ T^{\mu\nu}_{;\nu} = 0 $. Einstein rejected this conservation law despite the fact that it is generally covariant. We trace his rejection to a misapplication of Gauss' divergence formula. Finally, we derive the formula which pertains to energy-momentum conservation. |
gr-qc/9905055 | Kleidis Kostas | K. Kleidis and N. K. Spyrou | Geodesic motions versus hydrodynamic flows in a gravitating perfect
fluid: Dynamical equivalence and consequences | LaTeX file, 22 pages | Class.Quant.Grav. 17 (2000) 2965-2982 | 10.1088/0264-9381/17/15/308 | null | gr-qc | null | Stimulated by the methods applied for the observational determination of
masses in the central regions of the AGNs, we examine the conditions under
which, in the interior of a gravitating perfect fluid source, the geodesic
motions and the general relativistic hydrodynamic flows are dynamically
equivalent to each other. Dynamical equivalence rests on the functional
similarity between the corresponding (covariantly expressed) differential
equations of motion and is obtained by conformal transformations. In this case,
the spaces of the solutions of these two kinds of motion are isomorphic. In
other words, given a solution to the problem "hydrodynamic flow in a perfect
fluid", one can always construct a solution formally equivalent to the problem
"geodesic motion of a fluid element" and vice versa. Accordingly, we show that,
the observationally determined nuclear mass of the AGNs is being overestimated
with respect to the real, physical one. We evaluate the corresponding
mass-excess and show that it is not always negligible with respect to the mass
ofthe central dark object, while, under circumstances, can be even larger than
the rest-mass of the circumnuclear gas involved.
| [
{
"created": "Mon, 17 May 1999 08:20:50 GMT",
"version": "v1"
},
{
"created": "Tue, 18 May 1999 09:25:51 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Kleidis",
"K.",
""
],
[
"Spyrou",
"N. K.",
""
]
] | Stimulated by the methods applied for the observational determination of masses in the central regions of the AGNs, we examine the conditions under which, in the interior of a gravitating perfect fluid source, the geodesic motions and the general relativistic hydrodynamic flows are dynamically equivalent to each other. Dynamical equivalence rests on the functional similarity between the corresponding (covariantly expressed) differential equations of motion and is obtained by conformal transformations. In this case, the spaces of the solutions of these two kinds of motion are isomorphic. In other words, given a solution to the problem "hydrodynamic flow in a perfect fluid", one can always construct a solution formally equivalent to the problem "geodesic motion of a fluid element" and vice versa. Accordingly, we show that, the observationally determined nuclear mass of the AGNs is being overestimated with respect to the real, physical one. We evaluate the corresponding mass-excess and show that it is not always negligible with respect to the mass ofthe central dark object, while, under circumstances, can be even larger than the rest-mass of the circumnuclear gas involved. |
1804.04753 | Peter Zimmerman | Samuel E. Gralla and Peter Zimmerman | Scaling and Universality in Extremal Black Hole Perturbations | 31 pages. v3 matches published version | null | 10.1007/JHEP06(2018)061 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the emergent near-horizon conformal symmetry of extremal black
holes gives rise to universal behavior in perturbing fields, both near and far
from the black hole horizon. The scale-invariance of the near-horizon region
entails power law time-dependence with three universal features: (1) the decay
off the horizon is always precisely twice as fast as the decay on the horizon;
(2) the special rates of $1/t$ off the horizon and $1/\sqrt{v}$ on the horizon
commonly occur; and (3) sufficiently high-order transverse derivatives grow on
the horizon (Aretakis instability). The results are simply understood in terms
of near-horizon ($\mathrm{AdS}_2$) holography. We first show how the general
features follow from symmetry alone and then go on to present the detailed
universal behavior of scalar, electromagnetic, and gravitational perturbations
of $d$-dimensional electrovacuum black holes.
| [
{
"created": "Fri, 13 Apr 2018 00:32:20 GMT",
"version": "v1"
},
{
"created": "Sun, 29 Apr 2018 23:56:14 GMT",
"version": "v2"
},
{
"created": "Wed, 11 Jul 2018 15:52:47 GMT",
"version": "v3"
}
] | 2018-07-12 | [
[
"Gralla",
"Samuel E.",
""
],
[
"Zimmerman",
"Peter",
""
]
] | We show that the emergent near-horizon conformal symmetry of extremal black holes gives rise to universal behavior in perturbing fields, both near and far from the black hole horizon. The scale-invariance of the near-horizon region entails power law time-dependence with three universal features: (1) the decay off the horizon is always precisely twice as fast as the decay on the horizon; (2) the special rates of $1/t$ off the horizon and $1/\sqrt{v}$ on the horizon commonly occur; and (3) sufficiently high-order transverse derivatives grow on the horizon (Aretakis instability). The results are simply understood in terms of near-horizon ($\mathrm{AdS}_2$) holography. We first show how the general features follow from symmetry alone and then go on to present the detailed universal behavior of scalar, electromagnetic, and gravitational perturbations of $d$-dimensional electrovacuum black holes. |
gr-qc/0509041 | Stephen Fairhurst | F.Beauville, M.-A.Bizouard, L.Blackburn, L.Bosi, P.Brady, L.Brocco,
D.Brown, D.Buskulic, F.Cavalier, S.Chatterji, N.Christensen, A.-C.Clapson,
S.Fairhurst, D.Grosjean, G.Guidi, P.Hello, E.Katsavounidis, M.Knight,
A.Lazzarini, N.Leroy, F.Marion, B.Mours, F.Ricci, A.Vicere, M.Zanolin | Benefits of joint LIGO -- Virgo coincidence searches for burst and
inspiral signals | 11 pages 8 figures, Amaldi 6 proceedings | J.Phys.Conf.Ser. 32 (2006) 212 | 10.1088/1742-6596/32/1/032 | null | gr-qc | null | We examine the benefits of performing a joint LIGO--Virgo search for
transient signals. We do this by adding burst and inspiral signals to 24 hours
of simulated detector data. We find significant advantages to performing a
joint coincidence analysis, above either a LIGO only or Virgo only search.
These include an increased detection efficiency, at a fixed false alarm rate,
to both burst and inspiral events and an ability to reconstruct the sky
location of a signal.
| [
{
"created": "Mon, 12 Sep 2005 18:18:58 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Beauville",
"F.",
""
],
[
"Bizouard",
"M. -A.",
""
],
[
"Blackburn",
"L.",
""
],
[
"Bosi",
"L.",
""
],
[
"Brady",
"P.",
""
],
[
"Brocco",
"L.",
""
],
[
"Brown",
"D.",
""
],
[
"Buskulic",
"D.",
""
],
[
"Cavalier",
"F.",
""
],
[
"Chatterji",
"S.",
""
],
[
"Christensen",
"N.",
""
],
[
"Clapson",
"A. -C.",
""
],
[
"Fairhurst",
"S.",
""
],
[
"Grosjean",
"D.",
""
],
[
"Guidi",
"G.",
""
],
[
"Hello",
"P.",
""
],
[
"Katsavounidis",
"E.",
""
],
[
"Knight",
"M.",
""
],
[
"Lazzarini",
"A.",
""
],
[
"Leroy",
"N.",
""
],
[
"Marion",
"F.",
""
],
[
"Mours",
"B.",
""
],
[
"Ricci",
"F.",
""
],
[
"Vicere",
"A.",
""
],
[
"Zanolin",
"M.",
""
]
] | We examine the benefits of performing a joint LIGO--Virgo search for transient signals. We do this by adding burst and inspiral signals to 24 hours of simulated detector data. We find significant advantages to performing a joint coincidence analysis, above either a LIGO only or Virgo only search. These include an increased detection efficiency, at a fixed false alarm rate, to both burst and inspiral events and an ability to reconstruct the sky location of a signal. |
2002.02119 | Todd Oliynyk | David Fajman, Todd A. Oliynyk and Zoe Wyatt | Stabilizing relativistic fluids on spacetimes with non-accelerated
expansion | null | Commun. Math. Phys. 383, 401-426 (2021) | 10.1007/s00220-020-03924-9 | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We establish global regularity and stability for the irrotational
relativistic Euler equations with equation of state
$\overline{p}=K\overline{\rho}$, where $0<K<1/3$, for small initial data in the
expanding direction of FLRW spacetimes of the form $(\mathbb R\times\mathbb
T^3,-d\tb^2+\tb^2\delta_{ij} dx^i dx^j)$. This provides the first case of
non-dust fluid stabilization by spacetime expansion where the expansion rate is
of power law type but non-accelerated. In particular, the time integral of the
inverse scale factor diverges as $t\rightarrow\infty$.
| [
{
"created": "Thu, 6 Feb 2020 06:40:06 GMT",
"version": "v1"
}
] | 2021-03-30 | [
[
"Fajman",
"David",
""
],
[
"Oliynyk",
"Todd A.",
""
],
[
"Wyatt",
"Zoe",
""
]
] | We establish global regularity and stability for the irrotational relativistic Euler equations with equation of state $\overline{p}=K\overline{\rho}$, where $0<K<1/3$, for small initial data in the expanding direction of FLRW spacetimes of the form $(\mathbb R\times\mathbb T^3,-d\tb^2+\tb^2\delta_{ij} dx^i dx^j)$. This provides the first case of non-dust fluid stabilization by spacetime expansion where the expansion rate is of power law type but non-accelerated. In particular, the time integral of the inverse scale factor diverges as $t\rightarrow\infty$. |
2208.08877 | Mouhssine Koussour | M. Koussour, K. El Bourakadi, S. H. Shekh, S. K. J. Pacif and M.
Bennai | Late-time acceleration in $f\left( Q\right) $ gravity: Analysis and
constraints in an anisotropic background | Annals of Physics accepted version | null | 10.1016/j.aop.2022.169092 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is devoted to investigate the anisotropic locally rotationally
symmetric (LRS) Bianchi type-I space-time in the context of the recently
proposed $f(Q)$ gravity in which $Q$ is the non-metricity scalar. For this
purpose, we consider a linear form of $f\left( Q\right) $ gravity model,
specifically, $f\left( Q\right) =\alpha Q+\beta $, where $\alpha $ and $% \beta
$ are free parameters and we analyzed the exact solutions of LRS Bianchi type-I
space-time. The modified Friedmann equations are solved by presuming an
expansion scalar $\theta \left( t\right) $ is proportional to the shear scalar
$\sigma \left( t\right) $ which leads to the relation between the metric
potentials as $A=B^{n}$ where $n$ is an arbitrary constant. Then we constrain
our model parameters with the observational Hubble datasets of 57 data points.
Moreover, we discuss the physical behavior of cosmological parameters such as
energy density, pressure, EoS parameter, and deceleration parameter. The
behavior of the deceleration parameter predicts a transition from deceleration
to accelerated phases in an expanding Universe. Finally, the EoS parameter
indicates that the anisotropic fluid behaves like the standard $\Lambda $CDM
model.
| [
{
"created": "Tue, 16 Aug 2022 19:17:00 GMT",
"version": "v1"
}
] | 2022-08-26 | [
[
"Koussour",
"M.",
""
],
[
"Bourakadi",
"K. El",
""
],
[
"Shekh",
"S. H.",
""
],
[
"Pacif",
"S. K. J.",
""
],
[
"Bennai",
"M.",
""
]
] | This paper is devoted to investigate the anisotropic locally rotationally symmetric (LRS) Bianchi type-I space-time in the context of the recently proposed $f(Q)$ gravity in which $Q$ is the non-metricity scalar. For this purpose, we consider a linear form of $f\left( Q\right) $ gravity model, specifically, $f\left( Q\right) =\alpha Q+\beta $, where $\alpha $ and $% \beta $ are free parameters and we analyzed the exact solutions of LRS Bianchi type-I space-time. The modified Friedmann equations are solved by presuming an expansion scalar $\theta \left( t\right) $ is proportional to the shear scalar $\sigma \left( t\right) $ which leads to the relation between the metric potentials as $A=B^{n}$ where $n$ is an arbitrary constant. Then we constrain our model parameters with the observational Hubble datasets of 57 data points. Moreover, we discuss the physical behavior of cosmological parameters such as energy density, pressure, EoS parameter, and deceleration parameter. The behavior of the deceleration parameter predicts a transition from deceleration to accelerated phases in an expanding Universe. Finally, the EoS parameter indicates that the anisotropic fluid behaves like the standard $\Lambda $CDM model. |
1912.08295 | Kayll Lake | Kayll Lake | Spacetimes with a vanishing second Ricci invariant | 3 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spacetimes with a vanishing second Ricci invariant, but which are not
necessarily Ricci - flat, though common in general relativity, are seldom
studied in a coordinate and symmetry independent way by actually using their
Ricci invariants. Yet, and as an example, it can be shown by use of Ricci
invariants that no such spacetimes can actually represent a perfect fluid by
way of Einstein's equations. The widely studied Kiselev black hole is a
particularly simple example of such a spacetime. Yet it is frequently, and
erroneously, referred to as a perfect fluid. This paper gathers together
information relevant to the study of spacetimes with vanishing a second Ricci
invariant. It is shown that such spacetimes need not be stationary, a point
relevant to their possible physical significance.
| [
{
"created": "Tue, 17 Dec 2019 22:30:42 GMT",
"version": "v1"
}
] | 2019-12-19 | [
[
"Lake",
"Kayll",
""
]
] | Spacetimes with a vanishing second Ricci invariant, but which are not necessarily Ricci - flat, though common in general relativity, are seldom studied in a coordinate and symmetry independent way by actually using their Ricci invariants. Yet, and as an example, it can be shown by use of Ricci invariants that no such spacetimes can actually represent a perfect fluid by way of Einstein's equations. The widely studied Kiselev black hole is a particularly simple example of such a spacetime. Yet it is frequently, and erroneously, referred to as a perfect fluid. This paper gathers together information relevant to the study of spacetimes with vanishing a second Ricci invariant. It is shown that such spacetimes need not be stationary, a point relevant to their possible physical significance. |
gr-qc/0508052 | Richard Price | Richard H. Price and Joseph D. Romano | In an expanding universe, what doesn't expand? | 8 pages, 9 eps figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The expansion of the universe is often viewed as a uniform stretching of
space that would affect compact objects, atoms and stars, as well as the
separation of galaxies. One usually hears that bound systems do not take part
in the general expansion, but a much more subtle question is whether bound
systems expand partially. In this paper, a very definitive answer is given for
a very simple system: a classical "atom" bound by electrical attraction. With a
mathemical description appropriate for undergraduate physics majors, we show
that this bound system either completely follows the cosmological expansion, or
-- after initial transients -- completely ignores it. This "all or nothing"
behavior can be understood with techniques of junior-level mechanics. Lastly,
the simple description is shown to be a justifiable approximation of the
relativistically correct formulation of the problem.
| [
{
"created": "Fri, 12 Aug 2005 14:46:30 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Jan 2012 14:37:47 GMT",
"version": "v2"
}
] | 2012-01-10 | [
[
"Price",
"Richard H.",
""
],
[
"Romano",
"Joseph D.",
""
]
] | The expansion of the universe is often viewed as a uniform stretching of space that would affect compact objects, atoms and stars, as well as the separation of galaxies. One usually hears that bound systems do not take part in the general expansion, but a much more subtle question is whether bound systems expand partially. In this paper, a very definitive answer is given for a very simple system: a classical "atom" bound by electrical attraction. With a mathemical description appropriate for undergraduate physics majors, we show that this bound system either completely follows the cosmological expansion, or -- after initial transients -- completely ignores it. This "all or nothing" behavior can be understood with techniques of junior-level mechanics. Lastly, the simple description is shown to be a justifiable approximation of the relativistically correct formulation of the problem. |
1008.2125 | Massimiliano Rinaldi | Carlos Mayoral, Alessandro Fabbri and Massimiliano Rinaldi | Step-like discontinuities in Bose-Einstein condensates and Hawking
radiation: dispersion effects | One figure and few comments added. Version accepted for publication
in PRD | Phys.Rev.D83:124047,2011 | 10.1103/PhysRevD.83.124047 | null | gr-qc cond-mat.quant-gas hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we extend the hydrodynamic results of [1] and study,
analytically, the propagation of Bogoliubov phonons on top of Bose-Einstein
condensates with step-like discontinuities by taking into account dispersion
effects. We focus on the Hawking signal in the density-density correlations in
the formation of acoustic black hole-like configurations.
| [
{
"created": "Thu, 12 Aug 2010 15:02:24 GMT",
"version": "v1"
},
{
"created": "Fri, 27 May 2011 13:42:41 GMT",
"version": "v2"
}
] | 2011-07-28 | [
[
"Mayoral",
"Carlos",
""
],
[
"Fabbri",
"Alessandro",
""
],
[
"Rinaldi",
"Massimiliano",
""
]
] | In this paper we extend the hydrodynamic results of [1] and study, analytically, the propagation of Bogoliubov phonons on top of Bose-Einstein condensates with step-like discontinuities by taking into account dispersion effects. We focus on the Hawking signal in the density-density correlations in the formation of acoustic black hole-like configurations. |
2010.14518 | Francois Foucart | Francois Foucart, Alexander Chernoglazov, Michael Boyle, Tanja
Hinderer, Max Miller, Jordan Moxon, Mark A. Scheel, Nils Deppe, Matthew D.
Duez, Francois Hebert, Lawrence E. Kidder, William Throwe, Harald P. Pfeiffer | High-accuracy waveforms for black hole-neutron star systems with
spinning black holes | 16p, 14 figs, 2 tables; To be submitted to PRD | Phys. Rev. D 103, 064007 (2021) | 10.1103/PhysRevD.103.064007 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The availability of accurate numerical waveforms is an important requirement
for the creation and calibration of reliable waveform models for gravitational
wave astrophysics. For black hole-neutron star binaries, very few accurate
waveforms are however publicly available. Most recent models are calibrated to
a large number of older simulations with good parameter space coverage for
low-spin non-precessing binaries but limited accuracy, and a much smaller
number of longer, more recent simulations limited to non-spinning black holes.
In this paper, we present long, accurate numerical waveforms for three new
systems that include rapidly spinning black holes, and one precessing
configuration. We study in detail the accuracy of the simulations, and in
particular perform for the first time in the context of BHNS binaries a
detailed comparison of waveform extrapolation methods to the results of Cauchy
Characteristic Extraction. The new waveforms have $<0.1\,{\rm rad}$ phase
errors during inspiral, rising to $\sim (0.2-0.4)\,{\rm rad}$ errors at merger,
and $\lesssim 1\%$ error in their amplitude. We compute the faithfulness of
recent analytical models to these numerical results, and find that models
specifically designed for BHNS binaries perform well ($F>0.99$) for binaries
seen face-on. For edge-on observations, particularly for precessing systems,
disagreements between models and simulations increase, and models that include
precession and/or higher-order modes start to perform better than BHNS models
that currently lack these features.
| [
{
"created": "Tue, 27 Oct 2020 18:00:01 GMT",
"version": "v1"
}
] | 2021-03-10 | [
[
"Foucart",
"Francois",
""
],
[
"Chernoglazov",
"Alexander",
""
],
[
"Boyle",
"Michael",
""
],
[
"Hinderer",
"Tanja",
""
],
[
"Miller",
"Max",
""
],
[
"Moxon",
"Jordan",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Deppe",
"Nils",
""
],
[
"Duez",
"Matthew D.",
""
],
[
"Hebert",
"Francois",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Throwe",
"William",
""
],
[
"Pfeiffer",
"Harald P.",
""
]
] | The availability of accurate numerical waveforms is an important requirement for the creation and calibration of reliable waveform models for gravitational wave astrophysics. For black hole-neutron star binaries, very few accurate waveforms are however publicly available. Most recent models are calibrated to a large number of older simulations with good parameter space coverage for low-spin non-precessing binaries but limited accuracy, and a much smaller number of longer, more recent simulations limited to non-spinning black holes. In this paper, we present long, accurate numerical waveforms for three new systems that include rapidly spinning black holes, and one precessing configuration. We study in detail the accuracy of the simulations, and in particular perform for the first time in the context of BHNS binaries a detailed comparison of waveform extrapolation methods to the results of Cauchy Characteristic Extraction. The new waveforms have $<0.1\,{\rm rad}$ phase errors during inspiral, rising to $\sim (0.2-0.4)\,{\rm rad}$ errors at merger, and $\lesssim 1\%$ error in their amplitude. We compute the faithfulness of recent analytical models to these numerical results, and find that models specifically designed for BHNS binaries perform well ($F>0.99$) for binaries seen face-on. For edge-on observations, particularly for precessing systems, disagreements between models and simulations increase, and models that include precession and/or higher-order modes start to perform better than BHNS models that currently lack these features. |
gr-qc/0107073 | Giovanni Modanese | G. Modanese (Univ. of Bolzano and CIPA - Palo Alto) | Local contribution of a quantum condensate to the vacuum energy density | LaTeX, 8 pages. Final journal version | Mod.Phys.Lett. A18 (2003) 683-690 | 10.1142/S0217732303009812 | null | gr-qc | null | We evaluate the local contribution g_[mu nu]L of coherent matter with
lagrangian density L to the vacuum energy density. Focusing on the case of
superconductors obeying the Ginzburg-Landau equation, we express the
relativistic invariant density L in terms of low-energy quantities containing
the pairs density. We discuss under which physical conditions the sign of the
local contribution of the collective wave function to the vacuum energy density
is positive or negative. Effects of this kind can play an important role in
bringing about local changes in the amplitude of gravitational vacuum
fluctuations - a phenomenon reminiscent of the Casimir effect in QED.
| [
{
"created": "Mon, 23 Jul 2001 14:43:59 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Oct 2001 14:53:43 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Feb 2002 17:07:40 GMT",
"version": "v3"
},
{
"created": "Sat, 6 Jul 2002 13:09:55 GMT",
"version": "v4"
},
{
"created": "Tue, 22 Apr 2003 10:08:23 GMT",
"version": "v5"
}
] | 2009-11-07 | [
[
"Modanese",
"G.",
"",
"Univ. of Bolzano and CIPA - Palo Alto"
]
] | We evaluate the local contribution g_[mu nu]L of coherent matter with lagrangian density L to the vacuum energy density. Focusing on the case of superconductors obeying the Ginzburg-Landau equation, we express the relativistic invariant density L in terms of low-energy quantities containing the pairs density. We discuss under which physical conditions the sign of the local contribution of the collective wave function to the vacuum energy density is positive or negative. Effects of this kind can play an important role in bringing about local changes in the amplitude of gravitational vacuum fluctuations - a phenomenon reminiscent of the Casimir effect in QED. |
1709.01512 | Soumya Chakrabarti | Soumya Chakrabarti | Aspects of Gravitational Collapse and the formation of Spacetime
Singularities | 146 pages, PhD thesis, IISER Kolkata, Sep 2017. arXiv admin note:
text overlap with arXiv:1409.2371, arXiv:1305.1005, arXiv:0810.2602,
arXiv:1310.7167 by other authors | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Possibilities emerging out of the dynamical evolutions of collapsing systems
are addressed in this thesis through analytical investigations of the highly
non-linear Einstein Field Equations. Studies of exact solutions and their
properties, play a non-trivial role in general relativity, even in the current
context. Finding non-trivial solutions to the Einstein field equations requires
some reduction of the problem, which usually is done by exploiting symmetries
or other properties. Exact solutions of the Einsteins field equations
describing an unhindered gravitational collapse are studied which generally
predict an ultimate singular end-state. In the vicinity of such a spacetime
singularity, the energy densities, spacetime curvatures, and all other physical
quantities blow up. Despite exhaustive attempts over decades, the famous
conjecture that the formation of a singularity during stellar collapse
necessarily accompanies the formation of an event horizon, thereby covering the
central singularity, still remains without a proof. Moreover, there are
examples of stellar collapse models with reasonable matter contribution in
which an event horizon does not form at all, giving rise to a naked singularity
from which both matter and radiation can fall in and come out. These examples
suggest that the so-called cosmic censorship conjecture may not be a general
rule. Therefore one must embark upon analysis of realistic theoretical models
of gravitational collapse and gradually generalizing previous efforts.
| [
{
"created": "Tue, 5 Sep 2017 07:10:14 GMT",
"version": "v1"
}
] | 2017-09-07 | [
[
"Chakrabarti",
"Soumya",
""
]
] | Possibilities emerging out of the dynamical evolutions of collapsing systems are addressed in this thesis through analytical investigations of the highly non-linear Einstein Field Equations. Studies of exact solutions and their properties, play a non-trivial role in general relativity, even in the current context. Finding non-trivial solutions to the Einstein field equations requires some reduction of the problem, which usually is done by exploiting symmetries or other properties. Exact solutions of the Einsteins field equations describing an unhindered gravitational collapse are studied which generally predict an ultimate singular end-state. In the vicinity of such a spacetime singularity, the energy densities, spacetime curvatures, and all other physical quantities blow up. Despite exhaustive attempts over decades, the famous conjecture that the formation of a singularity during stellar collapse necessarily accompanies the formation of an event horizon, thereby covering the central singularity, still remains without a proof. Moreover, there are examples of stellar collapse models with reasonable matter contribution in which an event horizon does not form at all, giving rise to a naked singularity from which both matter and radiation can fall in and come out. These examples suggest that the so-called cosmic censorship conjecture may not be a general rule. Therefore one must embark upon analysis of realistic theoretical models of gravitational collapse and gradually generalizing previous efforts. |
2001.08690 | Hor\'acio Vieira | H. S. Vieira | Scalar fields in a five-dimensional Lovelock black hole spacetime | 19 pages, 4 figures, 4 tables | Annals of Physics 418 (2020) 168197 | 10.1016/j.aop.2020.168197 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the interaction between massive scalar fields and the gravitational
field produced by a higher dimensional Schwarzschild solution in a string cloud
model. Exact analytical solutions of both angular and radial parts of the
Klein--Gordon equation are obtained in terms of the three-dimensional spherical
harmonics and general Heun functions, respectively. From these solutions, we
examine the interesting physical phenomena related to the Hawking radiation and
resonant frequencies.
| [
{
"created": "Thu, 23 Jan 2020 17:34:40 GMT",
"version": "v1"
},
{
"created": "Sat, 16 May 2020 17:24:17 GMT",
"version": "v2"
}
] | 2020-05-19 | [
[
"Vieira",
"H. S.",
""
]
] | We study the interaction between massive scalar fields and the gravitational field produced by a higher dimensional Schwarzschild solution in a string cloud model. Exact analytical solutions of both angular and radial parts of the Klein--Gordon equation are obtained in terms of the three-dimensional spherical harmonics and general Heun functions, respectively. From these solutions, we examine the interesting physical phenomena related to the Hawking radiation and resonant frequencies. |
gr-qc/9506081 | Arkadiusz Blaut | Arkadiusz Blaut and Jerzy Kowalski-Glikman | Quantum Potential Approach to Quantum Cosmology | 17 pages,LaTeX. A newer version of this paper appears as
gr-qc/9509040 since the author didn't use the replace command. | null | null | null | gr-qc | null | In this paper we discuss the quantum potential approach of Bohm in the
context of quantum cosmological model. This approach makes it possible to
convert the wavefunction of the universe to a set of equations describing the
time evolution of the universe. Following Ashtekar et.\ al., we make use of
quantum canonical transformation to cast a class of quantum cosmological models
to a simple form in which they can be solved explicitly, and then we use the
solutions to recover the time evolution.
| [
{
"created": "Fri, 30 Jun 1995 12:25:06 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Jul 1995 13:41:01 GMT",
"version": "v2"
},
{
"created": "Wed, 5 Jul 1995 11:26:45 GMT",
"version": "v3"
}
] | 2008-02-03 | [
[
"Blaut",
"Arkadiusz",
""
],
[
"Kowalski-Glikman",
"Jerzy",
""
]
] | In this paper we discuss the quantum potential approach of Bohm in the context of quantum cosmological model. This approach makes it possible to convert the wavefunction of the universe to a set of equations describing the time evolution of the universe. Following Ashtekar et.\ al., we make use of quantum canonical transformation to cast a class of quantum cosmological models to a simple form in which they can be solved explicitly, and then we use the solutions to recover the time evolution. |
gr-qc/9905012 | Larry Ford | C.-H. Wu and L.H. Ford | Fluctuations of the Hawking Flux | 25 pages, LaTeX, with 3 figures, uses epsf | Phys. Rev. D 60, 104013 (1999) | 10.1103/PhysRevD.60.104013 | null | gr-qc hep-th quant-ph | null | The fluctuations of the flux radiated by an evaporating black hole will be
discussed. Two approaches to this problem will be adopted. In the first, the
squared flux operator is defined by normal ordering. In this case, both the
mean flux and the mean squared flux are well defined local quantites. It is
shown that the flux undergoes large fluctuations on a time scale of the order
of the black hole's mass. Thus the semiclassical theory of gravity, in which a
classical gravitational field is coupled to the expectation value of the stress
tensor, breaks down below this time scale. In the second approach, one does not
attempt to give meaning to the squared flux as a local quantity, but only as a
time-averaged quantity. In both approaches, the mean squared mass minus the
square of the mean mass grows linearly in time, but four times as fast in the
second approach as in the first.
| [
{
"created": "Tue, 4 May 1999 19:25:14 GMT",
"version": "v1"
}
] | 2016-08-25 | [
[
"Wu",
"C. -H.",
""
],
[
"Ford",
"L. H.",
""
]
] | The fluctuations of the flux radiated by an evaporating black hole will be discussed. Two approaches to this problem will be adopted. In the first, the squared flux operator is defined by normal ordering. In this case, both the mean flux and the mean squared flux are well defined local quantites. It is shown that the flux undergoes large fluctuations on a time scale of the order of the black hole's mass. Thus the semiclassical theory of gravity, in which a classical gravitational field is coupled to the expectation value of the stress tensor, breaks down below this time scale. In the second approach, one does not attempt to give meaning to the squared flux as a local quantity, but only as a time-averaged quantity. In both approaches, the mean squared mass minus the square of the mean mass grows linearly in time, but four times as fast in the second approach as in the first. |
gr-qc/0607005 | S. Mignemi | S. Mignemi | Black hole solutions of dimensionally reduced Einstein-Gauss-Bonnet
gravity | 11 pages, plain TeX. The paper has been completely rewritten using
new coordinates that give a more transparent picture of the phase space | Phys.Rev.D74:124008,2006 | 10.1103/PhysRevD.74.124008 | null | gr-qc | null | We study the phase space of the spherically symmetric solutions of the system
obtained from the dimensional reduction of the six-dimensional Einstein-Gauss-
Bonnet action. We show the existence of solutions with nonflat asymptotic
behavior.
| [
{
"created": "Mon, 3 Jul 2006 10:37:20 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Aug 2006 10:18:23 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Mignemi",
"S.",
""
]
] | We study the phase space of the spherically symmetric solutions of the system obtained from the dimensional reduction of the six-dimensional Einstein-Gauss- Bonnet action. We show the existence of solutions with nonflat asymptotic behavior. |
2206.08694 | Chen Lan | Chen Lan, Yan-Gang Miao and Yi-Xiong Zang | Regular black holes with improved energy conditions and their analogues
in fluids | 38 pages, 30 figures, published version in Chinese Physics C | Chin. Phys. C 47, no.5,052001 (2023) | 10.1088/1674-1137/acc1cd | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | On the premise of the importance of energy conditions for regular black
holes, we propose a method to remedy those models that break the dominant
energy condition, e.g., the Bardeen and Hayward black holes. We modify the
metrics but ensure their regularity at the same time, so that the weak, null,
and dominant energy conditions are satisfied, with the exception of the strong
energy condition. Likewise, we prove a no-go theorem for conformally related
regular black holes, which states that the four energy conditions can never be
met in this class of black holes. In order to seek evidences for distinguishing
regular black holes from singular black holes, we resort to analogue gravity
and regard it as a tool to mimic realistic regular black holes in a fluid. The
equations of state for the fluid are solved via an asymptotic analysis
associated with a numerical method, which provides a modus operandi for
experimental observations, in particular, the conditions under which one can
simulate realistic regular black holes in the fluid.
| [
{
"created": "Fri, 17 Jun 2022 11:26:24 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Apr 2023 10:54:35 GMT",
"version": "v2"
}
] | 2023-04-14 | [
[
"Lan",
"Chen",
""
],
[
"Miao",
"Yan-Gang",
""
],
[
"Zang",
"Yi-Xiong",
""
]
] | On the premise of the importance of energy conditions for regular black holes, we propose a method to remedy those models that break the dominant energy condition, e.g., the Bardeen and Hayward black holes. We modify the metrics but ensure their regularity at the same time, so that the weak, null, and dominant energy conditions are satisfied, with the exception of the strong energy condition. Likewise, we prove a no-go theorem for conformally related regular black holes, which states that the four energy conditions can never be met in this class of black holes. In order to seek evidences for distinguishing regular black holes from singular black holes, we resort to analogue gravity and regard it as a tool to mimic realistic regular black holes in a fluid. The equations of state for the fluid are solved via an asymptotic analysis associated with a numerical method, which provides a modus operandi for experimental observations, in particular, the conditions under which one can simulate realistic regular black holes in the fluid. |
1712.04267 | Francesco Zappa | Francesco Zappa, Sebastiano Bernuzzi, David Radice, Albino Perego, and
Tim Dietrich | Gravitational-wave luminosity of binary neutron stars mergers | 5 pages, 4 figures | Phys. Rev. Lett. 120, 111101 (2018) | 10.1103/PhysRevLett.120.111101 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the gravitational-wave peak luminosity and radiated energy of
quasicircular neutron star mergers using a large sample of numerical relativity
simulations with different binary parameters and input physics. The peak
luminosity for all the binaries can be described in terms of the mass ratio and
of the leading-order post-Newtonian tidal parameter solely. The mergers
resulting in a prompt collapse to black hole have largest peak luminosities.
However, the largest amount of energy per unit mass is radiated by mergers that
produce a hypermassive neutron star or a massive neutron star remnant. We
quantify the gravitational-wave luminosity of binary neutron star merger
events, and set upper limits on the radiated energy and the remnant angular
momentum from these events. We find that there is an empirical universal
relation connecting the total gravitational radiation and the angular momentum
of the remnant. Our results constrain the final spin of the remnant black-hole
and also indicate that stable neutron star remnant forms with super-Keplerian
angular momentum.
| [
{
"created": "Tue, 12 Dec 2017 12:41:25 GMT",
"version": "v1"
}
] | 2018-03-21 | [
[
"Zappa",
"Francesco",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Radice",
"David",
""
],
[
"Perego",
"Albino",
""
],
[
"Dietrich",
"Tim",
""
]
] | We study the gravitational-wave peak luminosity and radiated energy of quasicircular neutron star mergers using a large sample of numerical relativity simulations with different binary parameters and input physics. The peak luminosity for all the binaries can be described in terms of the mass ratio and of the leading-order post-Newtonian tidal parameter solely. The mergers resulting in a prompt collapse to black hole have largest peak luminosities. However, the largest amount of energy per unit mass is radiated by mergers that produce a hypermassive neutron star or a massive neutron star remnant. We quantify the gravitational-wave luminosity of binary neutron star merger events, and set upper limits on the radiated energy and the remnant angular momentum from these events. We find that there is an empirical universal relation connecting the total gravitational radiation and the angular momentum of the remnant. Our results constrain the final spin of the remnant black-hole and also indicate that stable neutron star remnant forms with super-Keplerian angular momentum. |
2104.13009 | Hernando Quevedo | Luis Aragon-Munoz and Hernando Quevedo | Symplectic structure of equilibrium thermodynamics | New sections, comments and references added. Final version to appear
in IJGMMP | null | 10.1142/S021988782250178X | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The contact geometric structure of the thermodynamic phase space is used to
introduce a novel symplectic structure on the tangent bundle of the equilibrium
space. Moreover, it turns out that the equilibrium space can be interpreted as
a Lagrange submanifold of the corresponding tangent bundle, if the fundamental
equation is known explicitly. As a consequence, Hamiltonians can be defined
that describe thermodynamic processes.
| [
{
"created": "Tue, 27 Apr 2021 07:11:43 GMT",
"version": "v1"
},
{
"created": "Wed, 5 May 2021 07:38:29 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Jun 2022 21:06:27 GMT",
"version": "v3"
}
] | 2022-10-05 | [
[
"Aragon-Munoz",
"Luis",
""
],
[
"Quevedo",
"Hernando",
""
]
] | The contact geometric structure of the thermodynamic phase space is used to introduce a novel symplectic structure on the tangent bundle of the equilibrium space. Moreover, it turns out that the equilibrium space can be interpreted as a Lagrange submanifold of the corresponding tangent bundle, if the fundamental equation is known explicitly. As a consequence, Hamiltonians can be defined that describe thermodynamic processes. |
gr-qc/9801003 | Hagen Kleinert | Hagen Kleinert | Nonholonomic Mapping Principle for Classical Mechanics in Spaces with
Curvature and Torsion. New Covariant Conservation Law for Energy-Momentum
Tensor | Corrected typos. Author Information under
http://www.physik.fu-berlin.de/~kleinert/institution.html . Paper also at
http://www.physik.fu-berlin.de/~kleinert/kleiner_re261/preprint.html | Gen.Rel.Grav. D32 (2000) 769 | 10.1023/A:1001962922592 | null | gr-qc | null | The lecture explains the geometric basis for the recently-discovered
nonholonomic mapping principle which specifies certain laws of nature in
spacetimes with curvature and torsion from those in flat spacetime, thus
replacing and extending Einstein's equivalence principle. An important
consequence is a new action principle for determining the equation of motion of
a free spinless point particle in such spacetimes. Surprisingly, this equation
contains a torsion force, although the action involves only the metric. This
force changes geodesic into autoparallel trajectories, which are a direct
manifestation of inertia. The geometric origin of the torsion force is a
closure failure of parallelograms. The torsion force changes the covariant
conservation law of the energy-momentum tensor whose new form is derived.
| [
{
"created": "Sat, 3 Jan 1998 07:41:44 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Jan 1998 10:04:36 GMT",
"version": "v2"
},
{
"created": "Thu, 15 Jan 1998 06:48:12 GMT",
"version": "v3"
}
] | 2015-06-25 | [
[
"Kleinert",
"Hagen",
""
]
] | The lecture explains the geometric basis for the recently-discovered nonholonomic mapping principle which specifies certain laws of nature in spacetimes with curvature and torsion from those in flat spacetime, thus replacing and extending Einstein's equivalence principle. An important consequence is a new action principle for determining the equation of motion of a free spinless point particle in such spacetimes. Surprisingly, this equation contains a torsion force, although the action involves only the metric. This force changes geodesic into autoparallel trajectories, which are a direct manifestation of inertia. The geometric origin of the torsion force is a closure failure of parallelograms. The torsion force changes the covariant conservation law of the energy-momentum tensor whose new form is derived. |
gr-qc/9902020 | Brien C. Nolan | Brien C. Nolan | A regular C^0 singularity is not necessarily weak | null | null | null | null | gr-qc | null | Examples of space-times are given which contain scalar curvature
singularities whereat the metric tensor is regular and continuous, but which
are gravitationally strong. Thus the argument that such singularities are
necessarily weak is incomplete; in particular the question of the gravitational
strength of the null Cauchy horizon singularity which occurs in gravitational
collapse remains open.
| [
{
"created": "Tue, 9 Feb 1999 14:51:49 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Nolan",
"Brien C.",
""
]
] | Examples of space-times are given which contain scalar curvature singularities whereat the metric tensor is regular and continuous, but which are gravitationally strong. Thus the argument that such singularities are necessarily weak is incomplete; in particular the question of the gravitational strength of the null Cauchy horizon singularity which occurs in gravitational collapse remains open. |
gr-qc/9809065 | Jiri Podolsky | J. Podolsky, K. Vesely | Chaotic motion in pp-wave spacetimes | 15 pages (latex),12 figures (gif), to appear in Class. Quantum Grav | Class.Quant.Grav. 15 (1998) 3505-3521 | 10.1088/0264-9381/15/11/015 | KTF MFF UK JP7 | gr-qc | null | We investigate geodesics in non-homogeneous vacuum pp-wave solutions and
demonstrate their chaotic behavior by rigorous analytic and numerical methods.
For the particular class of solutions considered, distinct "outcomes" (channels
to infinity) are identified, and it is shown that the boundary between
different outcomes has a fractal structure. This seems to be the first example
of chaos in exact radiative spacetimes.
| [
{
"created": "Wed, 23 Sep 1998 15:06:22 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Podolsky",
"J.",
""
],
[
"Vesely",
"K.",
""
]
] | We investigate geodesics in non-homogeneous vacuum pp-wave solutions and demonstrate their chaotic behavior by rigorous analytic and numerical methods. For the particular class of solutions considered, distinct "outcomes" (channels to infinity) are identified, and it is shown that the boundary between different outcomes has a fractal structure. This seems to be the first example of chaos in exact radiative spacetimes. |
gr-qc/9902083 | Valerio Faraoni | Valerio Faraoni (Universite' Libre de Bruxelles) | Illusions of general relativity in Brans-Dicke gravity | 16 pages, LaTeX, to appear in Physical Review D | Phys.Rev.D59:084021,1999 | 10.1103/PhysRevD.59.084021 | null | gr-qc astro-ph | null | Contrary to common belief, the standard tenet of Brans-Dicke theory reducing
to general relativity when omega tends to infinity is false if the trace of the
matter energy-momentum tensor vanishes. The issue is clarified in a new
approach using conformal transformations. The otherwise unaccountable limiting
behavior of Brans-Dicke gravity is easily understood in terms of the conformal
invariance of the theory when the sources of gravity have radiation-like
properties. The rigorous computation of the asymptotic behavior of the
Brans-Dicke scalar field is straightforward in this new approach.
| [
{
"created": "Fri, 26 Feb 1999 10:48:04 GMT",
"version": "v1"
}
] | 2011-08-17 | [
[
"Faraoni",
"Valerio",
"",
"Universite' Libre de Bruxelles"
]
] | Contrary to common belief, the standard tenet of Brans-Dicke theory reducing to general relativity when omega tends to infinity is false if the trace of the matter energy-momentum tensor vanishes. The issue is clarified in a new approach using conformal transformations. The otherwise unaccountable limiting behavior of Brans-Dicke gravity is easily understood in terms of the conformal invariance of the theory when the sources of gravity have radiation-like properties. The rigorous computation of the asymptotic behavior of the Brans-Dicke scalar field is straightforward in this new approach. |
1401.1366 | Stefano Bertone | Stefano Bertone, Alberto Vecchiato, Christophe Le Poncin-Lafitte,
Mariateresa Crosta and Luca Bianchi | Latest advances in an astrometric model based on the Time Transfer
Functions formalism | 4 pages, 2 figures, submitted to the Proceedings of the "Journ\'ees
Syst\`emes de R\'ef\'erence Spatio-Temporels 2013" | null | null | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Given the extreme accuracy of modern space astrometry, a precise relativistic
modeling of observations is required. Moreover, the availability of several
models formulated in different and independent ways is a security against the
presence of systematic errors in the analysis of future experimental results,
like in the case of the Gaia mission. In this work, we simulate a series of
observations using the two models to be used for the data analysis of Gaia, the
Gaia RElativistic Model (GREM) and the Relativistic Astrometric MODel (RAMOD),
and we compare them with the results of our astrometric model based on the Time
Transfer Functions.
| [
{
"created": "Tue, 7 Jan 2014 13:27:24 GMT",
"version": "v1"
}
] | 2014-01-08 | [
[
"Bertone",
"Stefano",
""
],
[
"Vecchiato",
"Alberto",
""
],
[
"Poncin-Lafitte",
"Christophe Le",
""
],
[
"Crosta",
"Mariateresa",
""
],
[
"Bianchi",
"Luca",
""
]
] | Given the extreme accuracy of modern space astrometry, a precise relativistic modeling of observations is required. Moreover, the availability of several models formulated in different and independent ways is a security against the presence of systematic errors in the analysis of future experimental results, like in the case of the Gaia mission. In this work, we simulate a series of observations using the two models to be used for the data analysis of Gaia, the Gaia RElativistic Model (GREM) and the Relativistic Astrometric MODel (RAMOD), and we compare them with the results of our astrometric model based on the Time Transfer Functions. |
2205.15329 | Lorenzo Rossi | Lorenzo Rossi | Numerical Cauchy evolution of asymptotically AdS spacetimes with no
symmetries | Ph.D. thesis - few typos removed and bibliography improved | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this thesis, I present the first numerical scheme able to perform Cauchy
evolutions of asymptotically AdS spacetimes with reflective boundary conditions
under no symmetry requirements on the solution. The scheme is based on the
generalised harmonic formulation of the Einstein equations. The main difficulty
in removing all symmetry assumptions can be phrased in terms of finding a set
of generalised harmonic source functions that are consistent with the AdS
boundary conditions. I detail a prescription to obtain the set of source
functions that achieves stable evolution in full generality. This prescription
leads to the first long-time stable 3+1 simulations of four dimensional
spacetimes with a negative cosmological constant in Cartesian coordinates. I
show results of gravitational collapse with no symmetry assumptions, and the
subsequent ringdown to a static black hole in the bulk, which corresponds to
evolution towards a homogeneous state on the boundary. Furthermore, it is
argued that this scheme is well-suited for the study of black hole
superradiance -- the amplification of waves scattering off a rotating black
hole -- in Kerr-AdS spacetime. This statement is supported by the results of a
preliminary simulation of perturbed Kerr-AdS.
| [
{
"created": "Mon, 30 May 2022 18:00:01 GMT",
"version": "v1"
},
{
"created": "Sat, 20 Aug 2022 11:29:54 GMT",
"version": "v2"
},
{
"created": "Thu, 23 Nov 2023 23:23:55 GMT",
"version": "v3"
}
] | 2023-11-27 | [
[
"Rossi",
"Lorenzo",
""
]
] | In this thesis, I present the first numerical scheme able to perform Cauchy evolutions of asymptotically AdS spacetimes with reflective boundary conditions under no symmetry requirements on the solution. The scheme is based on the generalised harmonic formulation of the Einstein equations. The main difficulty in removing all symmetry assumptions can be phrased in terms of finding a set of generalised harmonic source functions that are consistent with the AdS boundary conditions. I detail a prescription to obtain the set of source functions that achieves stable evolution in full generality. This prescription leads to the first long-time stable 3+1 simulations of four dimensional spacetimes with a negative cosmological constant in Cartesian coordinates. I show results of gravitational collapse with no symmetry assumptions, and the subsequent ringdown to a static black hole in the bulk, which corresponds to evolution towards a homogeneous state on the boundary. Furthermore, it is argued that this scheme is well-suited for the study of black hole superradiance -- the amplification of waves scattering off a rotating black hole -- in Kerr-AdS spacetime. This statement is supported by the results of a preliminary simulation of perturbed Kerr-AdS. |
gr-qc/0106035 | Hans-Juergen Schmidt | H.-J. Schmidt | Comparing selfinteracting scalar fields and R + R^3 cosmological models | 16 pages, LaTeX | Astron.Nachr.308:183,1987 | 10.1002/asna.2113080309 | Report UNIPO-MATH-01-Jun-04 | gr-qc | null | We generalize the well-known analogies between m^2 \phi^2 and R + R^2
theories to include the selfinteraction \lambda \phi^4-term for the scalar
field. It turns out to be the R + R^3 Lagrangian which gives an appropriate
model for it. Considering a spatially flat Friedman cosmological model, common
and different properties of these models are discussed, e.g., by linearizing
around a ground state the masses of the resp. spin 0-parts coincide. Finally,
we prove a general conformal equivalence theorem between a Lagrangian L = L(R),
L'L" \ne 0, and a minimally coupled scalar field in a general potential.
| [
{
"created": "Mon, 11 Jun 2001 14:23:56 GMT",
"version": "v1"
}
] | 2011-04-22 | [
[
"Schmidt",
"H. -J.",
""
]
] | We generalize the well-known analogies between m^2 \phi^2 and R + R^2 theories to include the selfinteraction \lambda \phi^4-term for the scalar field. It turns out to be the R + R^3 Lagrangian which gives an appropriate model for it. Considering a spatially flat Friedman cosmological model, common and different properties of these models are discussed, e.g., by linearizing around a ground state the masses of the resp. spin 0-parts coincide. Finally, we prove a general conformal equivalence theorem between a Lagrangian L = L(R), L'L" \ne 0, and a minimally coupled scalar field in a general potential. |
0805.3017 | Shahram Jalalzadeh | S. Jalalzadeh and A. M. Yazdani | Variation of mass in primordial nucleosynthesis as a test of Induced
Matter Brane Gravity | 11 pages, to appear in PLB | Phys.Lett.B664:229-234,2008 | 10.1016/j.physletb.2008.05.041 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The variation of mass in induced matter theory using Ceroch-Stewart-Walter
perturbations of submanifolds [1] is redefined. It is shown that the deviation
of primordial Helium production due to a variation on the difference between
the rest mass of the nucleus is in agrement with induced matter brane gravity.
| [
{
"created": "Tue, 20 May 2008 07:35:11 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Jalalzadeh",
"S.",
""
],
[
"Yazdani",
"A. M.",
""
]
] | The variation of mass in induced matter theory using Ceroch-Stewart-Walter perturbations of submanifolds [1] is redefined. It is shown that the deviation of primordial Helium production due to a variation on the difference between the rest mass of the nucleus is in agrement with induced matter brane gravity. |
gr-qc/0304004 | Guido Pizzella | P. Astone, D. Babusci, M. Bassan, P. Bonifazi, P. Carelli, G.
Cavallari, E. Coccia, C. Cosmelli, S. D'Antonio, V. Fafone, S. Frasca, G.
Giordano, A. Marini, Y. Minenkov, I. Modena, G. Modestino, A. Moleti, G. V.
Pallottino, G. Pizzella, L. Quintieri, A. Rocchi, F. Ronga, R. Terenzi, G.
Torrioli, M. Visco | Comments on the 2001 run of the EXPLORER/NAUTILUS gravitational wave
experiment | To appear in Classical and Quantum Gravity | null | 10.1088/0264-9381/20/17/321 | null | gr-qc | null | The recently published analysis of the coincidences between the EXPLORER and
NAUTILUS gravitational wave detectors in the year 2001 (Astone et al. 2002) has
drawn some criticism (Finn 2003). We do not hold with these objections, even if
we agree that no claim can be made with our data. The paper we published
reports data of unprecedented quality and sets a new procedure for the
coincidence search, which can be repeated again by us and by other groups in
order to search for signature of possible signals. About the reported
coincidence excess, we remark that it is not destined to remain an intriguing
observation for long: it will be confirmed or denied soon by interferometers
and bars operating at their expected sensitivity.
| [
{
"created": "Tue, 1 Apr 2003 09:43:29 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Apr 2003 07:08:34 GMT",
"version": "v2"
},
{
"created": "Fri, 1 Aug 2003 07:35:33 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Astone",
"P.",
""
],
[
"Babusci",
"D.",
""
],
[
"Bassan",
"M.",
""
],
[
"Bonifazi",
"P.",
""
],
[
"Carelli",
"P.",
""
],
[
"Cavallari",
"G.",
""
],
[
"Coccia",
"E.",
""
],
[
"Cosmelli",
"C.",
""
],
[
"D'Antonio",
"S.",
""
],
[
"Fafone",
"V.",
""
],
[
"Frasca",
"S.",
""
],
[
"Giordano",
"G.",
""
],
[
"Marini",
"A.",
""
],
[
"Minenkov",
"Y.",
""
],
[
"Modena",
"I.",
""
],
[
"Modestino",
"G.",
""
],
[
"Moleti",
"A.",
""
],
[
"Pallottino",
"G. V.",
""
],
[
"Pizzella",
"G.",
""
],
[
"Quintieri",
"L.",
""
],
[
"Rocchi",
"A.",
""
],
[
"Ronga",
"F.",
""
],
[
"Terenzi",
"R.",
""
],
[
"Torrioli",
"G.",
""
],
[
"Visco",
"M.",
""
]
] | The recently published analysis of the coincidences between the EXPLORER and NAUTILUS gravitational wave detectors in the year 2001 (Astone et al. 2002) has drawn some criticism (Finn 2003). We do not hold with these objections, even if we agree that no claim can be made with our data. The paper we published reports data of unprecedented quality and sets a new procedure for the coincidence search, which can be repeated again by us and by other groups in order to search for signature of possible signals. About the reported coincidence excess, we remark that it is not destined to remain an intriguing observation for long: it will be confirmed or denied soon by interferometers and bars operating at their expected sensitivity. |
1807.07323 | German Sharov | G. S. Sharov and V. O. Vasiliev | How predictions of cosmological models depend on Hubble parameter data
sets | 15 pages, 5 figures, published in Mathematical Modelling and
Geometry, http://mmg.tversu.ru | Mathematical Modelling and Geometry, V. 6, No 1, pp. 1 - 20 (2018) | 10.26456/mmg/2018-611 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore recent estimations of the Hubble parameter $H$ depending on
redshift $z$, which include 31 $H(z)$ data points measured from differential
ages of galaxies and 26 data points, obtained with other methods. We describe
these data together with Union 2.1 observations of Type Ia supernovae and
observed parameters of baryon acoustic oscillations with 2 cosmological models:
the standard cold dark matter model with the $\Lambda$ term ($\Lambda$CDM) and
the model with generalized Chaplygin gas (GCG). For these models with different
sets of $H(z)$ data we calculate two-parameter and one-parameter distributions
of $\chi^2$ functions for all observed effects, estimate optimal values of
model parameters and their $1\sigma$ errors. For both considered models the
results appeared to be strongly depending on a choice of Hubble parameter data
sets if we use all 57 $H(z)$ data points or only 31 data points from
differential ages. This strong dependence can be explained in connection with 4
$H(z)$ data points with high redshifts $z>2$.
| [
{
"created": "Thu, 19 Jul 2018 10:00:27 GMT",
"version": "v1"
}
] | 2018-07-20 | [
[
"Sharov",
"G. S.",
""
],
[
"Vasiliev",
"V. O.",
""
]
] | We explore recent estimations of the Hubble parameter $H$ depending on redshift $z$, which include 31 $H(z)$ data points measured from differential ages of galaxies and 26 data points, obtained with other methods. We describe these data together with Union 2.1 observations of Type Ia supernovae and observed parameters of baryon acoustic oscillations with 2 cosmological models: the standard cold dark matter model with the $\Lambda$ term ($\Lambda$CDM) and the model with generalized Chaplygin gas (GCG). For these models with different sets of $H(z)$ data we calculate two-parameter and one-parameter distributions of $\chi^2$ functions for all observed effects, estimate optimal values of model parameters and their $1\sigma$ errors. For both considered models the results appeared to be strongly depending on a choice of Hubble parameter data sets if we use all 57 $H(z)$ data points or only 31 data points from differential ages. This strong dependence can be explained in connection with 4 $H(z)$ data points with high redshifts $z>2$. |
gr-qc/0505003 | Alikram Aliev | A. N. Aliev | A Slowly Rotating Charged Black Hole in Five Dimensions | Talk given at GR17: 17th International Conference on General
Relativity and Gravitation, Dublin, 18-24 Jule,2004 ; Corrected typos, minor
changes, new formula added | Mod.Phys.Lett. A21 (2006) 751-758 | 10.1142/S0217732306019281 | null | gr-qc hep-th | null | Black hole solutions in higher dimensional Einstein and Einstein-Maxwell
gravity have been discussed by Tangherlini as well as Myers and Perry a long
time ago. These solutions are the generalizations of the familiar
Schwarzschild, Reissner-Nordstrom and Kerr solutions of four-dimensional
general relativity. However, higher dimensional generalization of the
Kerr-Newman solution in four dimensions has not been found yet. As a first step
in this direction I shall report on a new solution of the Einstein-Maxwell
system of equations that describes an electrically charged and slowly rotating
black hole in five dimensions.
| [
{
"created": "Sat, 30 Apr 2005 19:51:40 GMT",
"version": "v1"
},
{
"created": "Tue, 3 May 2005 06:17:03 GMT",
"version": "v2"
},
{
"created": "Tue, 31 May 2005 16:20:30 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Aliev",
"A. N.",
""
]
] | Black hole solutions in higher dimensional Einstein and Einstein-Maxwell gravity have been discussed by Tangherlini as well as Myers and Perry a long time ago. These solutions are the generalizations of the familiar Schwarzschild, Reissner-Nordstrom and Kerr solutions of four-dimensional general relativity. However, higher dimensional generalization of the Kerr-Newman solution in four dimensions has not been found yet. As a first step in this direction I shall report on a new solution of the Einstein-Maxwell system of equations that describes an electrically charged and slowly rotating black hole in five dimensions. |
2307.04459 | Yu Zhang | Qian Li, Yu Zhang, Qi-Quan Li, Qi Sun | Thermal fluctuation, deflection angle and greybody factor of a
high-dimensional Schwarzschild black hole in STVG | 13 pages, 11 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we study the thermal fluctuation, deflection angle and greybody
factor of the high-dimensional Schwarzschild black hole in scalar-tensor-vector
gravity (STVG). Based on the correction of black hole entropy due to thermal
fluctuation, we calculate some thermodynamic quantities associated with the
correction of black hole entropy. The influence of the first-order and
second-order corrections, spacetime dimensionality and STVG parameters on these
thermodynamics quantities are discussed in detail. Additionally, by utilizing
the Gauss-Bonnet theorem, the deflection angle is obtained in the weak field
limit and the effect of two parameters on the results is visualized. Finally,
we calculate the bounds on greybody factors of a massless scalar field.
| [
{
"created": "Mon, 10 Jul 2023 10:12:28 GMT",
"version": "v1"
}
] | 2023-07-11 | [
[
"Li",
"Qian",
""
],
[
"Zhang",
"Yu",
""
],
[
"Li",
"Qi-Quan",
""
],
[
"Sun",
"Qi",
""
]
] | In this work, we study the thermal fluctuation, deflection angle and greybody factor of the high-dimensional Schwarzschild black hole in scalar-tensor-vector gravity (STVG). Based on the correction of black hole entropy due to thermal fluctuation, we calculate some thermodynamic quantities associated with the correction of black hole entropy. The influence of the first-order and second-order corrections, spacetime dimensionality and STVG parameters on these thermodynamics quantities are discussed in detail. Additionally, by utilizing the Gauss-Bonnet theorem, the deflection angle is obtained in the weak field limit and the effect of two parameters on the results is visualized. Finally, we calculate the bounds on greybody factors of a massless scalar field. |
1011.3166 | Antonio C. Guti\'errez-Pi\~neres | Antonio C. Guti\'errez-Pi\~neres and Guillermo A. Gonz\'alez | An infinite family of magnetized Morgan-Morgan relativistic thin disks | Submitted to IJTP. This paper is a revised and extended version of a
paper that was presented at arXiv:1006.2032 | null | 10.1007/s10773-011-1051-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Applying the Horsk\'y-Mitskievitch conjecture to the empty space solutions of
Morgan and Morgan due to the gravitational field of a finite disk, we have
obtained the corresponding solutions of the Einstein-Maxwell equations. The
resulting expressions are simply written in terms of oblate spheroidal
coordinates and the solutions represent fields due to magnetized static thin
disk of finite extension. Now, although the solutions are not asymptotically
flat, the masses of the disks are finite and the energy-momentum tensor agrees
with the energy conditions. Furthermore, the magnetic field and the circular
velocity show an acceptable physical behavior.
| [
{
"created": "Sat, 13 Nov 2010 23:41:58 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Dec 2011 16:34:02 GMT",
"version": "v2"
}
] | 2015-05-20 | [
[
"Gutiérrez-Piñeres",
"Antonio C.",
""
],
[
"González",
"Guillermo A.",
""
]
] | Applying the Horsk\'y-Mitskievitch conjecture to the empty space solutions of Morgan and Morgan due to the gravitational field of a finite disk, we have obtained the corresponding solutions of the Einstein-Maxwell equations. The resulting expressions are simply written in terms of oblate spheroidal coordinates and the solutions represent fields due to magnetized static thin disk of finite extension. Now, although the solutions are not asymptotically flat, the masses of the disks are finite and the energy-momentum tensor agrees with the energy conditions. Furthermore, the magnetic field and the circular velocity show an acceptable physical behavior. |
1612.06292 | Nikodem Poplawski | Nikodem Pop{\l}awski | Primordial fluctuations of scale factor in closed Universe in
Einstein$-$Cartan gravity | 9 pages; published version | Mod. Phys. Lett. A 33, 1850236 (2018) | 10.1142/S021773231850236X | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a homogeneous and isotropic Universe, described by the
minisuperspace Lagrangian with the scale factor as a generalized coordinate. We
show that the energy of a closed Universe is zero. We apply the uncertainty
principle to this Lagrangian and propose that the quantum uncertainty of the
scale factor causes the primordial fluctuations of the matter density. We use
the dynamics of the early Universe in the Einstein$-$Cartan theory of gravity
with spin and torsion, which eliminates the big-bang singularity and replaces
it with a nonsingular bounce. Quantum particle production in highly curved
spacetime generates a finite period of cosmic inflation that is consistent with
the Planck satellite data. From the inflated primordial fluctuations, we
determine the magnitude of the temperature fluctuations in the cosmic microwave
background, as a function of the numbers of the thermal degrees of freedom of
elementary particles and the particle production coefficient, which is the only
unknown parameter.
| [
{
"created": "Mon, 19 Dec 2016 17:56:28 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Feb 2019 17:32:26 GMT",
"version": "v2"
}
] | 2019-02-26 | [
[
"Popławski",
"Nikodem",
""
]
] | We consider a homogeneous and isotropic Universe, described by the minisuperspace Lagrangian with the scale factor as a generalized coordinate. We show that the energy of a closed Universe is zero. We apply the uncertainty principle to this Lagrangian and propose that the quantum uncertainty of the scale factor causes the primordial fluctuations of the matter density. We use the dynamics of the early Universe in the Einstein$-$Cartan theory of gravity with spin and torsion, which eliminates the big-bang singularity and replaces it with a nonsingular bounce. Quantum particle production in highly curved spacetime generates a finite period of cosmic inflation that is consistent with the Planck satellite data. From the inflated primordial fluctuations, we determine the magnitude of the temperature fluctuations in the cosmic microwave background, as a function of the numbers of the thermal degrees of freedom of elementary particles and the particle production coefficient, which is the only unknown parameter. |
1810.07957 | Shinji Tsujikawa | Noemi Frusciante, Ryotaro Kase, Nelson J. Nunes, Shinji Tsujikawa | Most general cubic-order Horndeski Lagrangian allowing for scaling
solutions and the application to dark energy | 17 pages, 3 figures, version to appear in Physical Review D | Phys. Rev. D 98, 123517 (2018) | 10.1103/PhysRevD.98.123517 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In cubic-order Horndeski theories where a scalar field $\phi$ is coupled to
nonrelativistic matter with a field-dependent coupling $Q(\phi)$, we derive the
most general Lagrangian having scaling solutions on the isotropic and
homogenous cosmological background. For constant $Q$ including the case of
vanishing coupling, the corresponding Lagrangian reduces to the form
$L=Xg_2(Y)-g_3(Y)\square \phi$, where
$X=-\partial_{\mu}\phi\partial^{\mu}\phi/2$ and $g_2, g_3$ are arbitrary
functions of $Y=Xe^{\lambda \phi}$ with constant $\lambda$. We obtain the fixed
points of the scaling Lagrangian for constant $Q$ and show that the
$\phi$-matter-dominated-epoch ($\phi$MDE) is present for the cubic coupling
$g_3(Y)$ containing inverse power-law functions of $Y$. The stability analysis
around the fixed points indicates that the $\phi$MDE can be followed by a
stable critical point responsible for the cosmic acceleration. We propose a
concrete dark energy model allowing for such a cosmological sequence and show
that the ghost and Laplacian instabilities can be avoided even in the presence
of the cubic coupling.
| [
{
"created": "Thu, 18 Oct 2018 09:19:09 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Dec 2018 00:04:53 GMT",
"version": "v2"
}
] | 2018-12-27 | [
[
"Frusciante",
"Noemi",
""
],
[
"Kase",
"Ryotaro",
""
],
[
"Nunes",
"Nelson J.",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | In cubic-order Horndeski theories where a scalar field $\phi$ is coupled to nonrelativistic matter with a field-dependent coupling $Q(\phi)$, we derive the most general Lagrangian having scaling solutions on the isotropic and homogenous cosmological background. For constant $Q$ including the case of vanishing coupling, the corresponding Lagrangian reduces to the form $L=Xg_2(Y)-g_3(Y)\square \phi$, where $X=-\partial_{\mu}\phi\partial^{\mu}\phi/2$ and $g_2, g_3$ are arbitrary functions of $Y=Xe^{\lambda \phi}$ with constant $\lambda$. We obtain the fixed points of the scaling Lagrangian for constant $Q$ and show that the $\phi$-matter-dominated-epoch ($\phi$MDE) is present for the cubic coupling $g_3(Y)$ containing inverse power-law functions of $Y$. The stability analysis around the fixed points indicates that the $\phi$MDE can be followed by a stable critical point responsible for the cosmic acceleration. We propose a concrete dark energy model allowing for such a cosmological sequence and show that the ghost and Laplacian instabilities can be avoided even in the presence of the cubic coupling. |
gr-qc/0202044 | Jorge Pullin | Jorge Pullin | Matters of Gravity, the newsletter of the APS Topical Group on
Gravitation, Spring 2002 | 19 pages, LaTeX with html.sty. PDF and html versions in
http://www.phys.psu.edu/mog | null | null | MOG-19 | gr-qc | null | Community News:
- Center for Gravitational Wave Physics, by Sam Finn
- Perimeter Institute for Theoretical Physics, by Lee Smolin
Research Briefs:
- Detector and Data Developments within GEO 600, by Alicia Sintes
- The Virtual Data Grid and LIGO, by Pat Brady and Manuela Campanelli
- 1000 hours of data and first lock of the recycled TAMA300, by Seiji
Kawamura
- LIGO Takes Some Data!, by Stan Whitcomb
- Quantum gravity: progress from an unexpected direction, by Matt Visser
Conference report:
- Gravitational-wave phenomenology at PennState, by Nils Andersson
| [
{
"created": "Wed, 13 Feb 2002 02:54:44 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pullin",
"Jorge",
""
]
] | Community News: - Center for Gravitational Wave Physics, by Sam Finn - Perimeter Institute for Theoretical Physics, by Lee Smolin Research Briefs: - Detector and Data Developments within GEO 600, by Alicia Sintes - The Virtual Data Grid and LIGO, by Pat Brady and Manuela Campanelli - 1000 hours of data and first lock of the recycled TAMA300, by Seiji Kawamura - LIGO Takes Some Data!, by Stan Whitcomb - Quantum gravity: progress from an unexpected direction, by Matt Visser Conference report: - Gravitational-wave phenomenology at PennState, by Nils Andersson |
gr-qc/0407036 | Masaru Shibata | Masaru Shibata, Koji Uryu, and John L. Friedman | Deriving formulations for numerical computation of binary neutron stars
in quasicircular orbits | to be published in Phys. Rev. D | Phys.Rev.D70:044044,2004; Erratum-ibid.D70:129901,2004 | 10.1103/PhysRevD.70.044044 10.1103/PhysRevD.70.129901 | null | gr-qc | null | Two relations, the virial relation $M_{\rm ADM}=M_{\rm K}$ and the first law
in the form $\delta M_{\rm ADM}=\Omega \delta J$, should be satisfied by a
solution and a sequence of solutions describing binary compact objects in
quasiequilibrium circular orbits. Here, $M_{\rm ADM}$, $M_{\rm K}$, $J$, and
$\Omega$ are the ADM mass, Komar mass, angular momentum, and orbital angular
velocity, respectively. $\delta$ denotes an Eulerian variation. These two
conditions restrict the allowed formulations that we may adopt. First, we
derive relations between $M_{\rm ADM}$ and $M_{\rm K}$ and between $\delta
M_{\rm ADM}$ and $\Omega \delta J$ for general asymptotically flat spacetimes.
Then, to obtain solutions that satisfy the virial relation and sequences of
solutions that satisfy the first law at least approximately, we propose a
formulation for computation of quasiequilibrium binary neutron stars in general
relativity. In contrast to previous approaches in which a part of the Einstein
equation is solved, in the new formulation, the full Einstein equation is
solved with maximal slicing and in a transverse gauge for the conformal
three-metric. Helical symmetry is imposed in the near zone, while in the
distant zone, a waveless condition is assumed. We expect the solutions obtained
in this formulation to be excellent quasiequilibria as well as initial data for
numerical simulations of binary neutron star mergers.
| [
{
"created": "Fri, 9 Jul 2004 02:21:38 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Shibata",
"Masaru",
""
],
[
"Uryu",
"Koji",
""
],
[
"Friedman",
"John L.",
""
]
] | Two relations, the virial relation $M_{\rm ADM}=M_{\rm K}$ and the first law in the form $\delta M_{\rm ADM}=\Omega \delta J$, should be satisfied by a solution and a sequence of solutions describing binary compact objects in quasiequilibrium circular orbits. Here, $M_{\rm ADM}$, $M_{\rm K}$, $J$, and $\Omega$ are the ADM mass, Komar mass, angular momentum, and orbital angular velocity, respectively. $\delta$ denotes an Eulerian variation. These two conditions restrict the allowed formulations that we may adopt. First, we derive relations between $M_{\rm ADM}$ and $M_{\rm K}$ and between $\delta M_{\rm ADM}$ and $\Omega \delta J$ for general asymptotically flat spacetimes. Then, to obtain solutions that satisfy the virial relation and sequences of solutions that satisfy the first law at least approximately, we propose a formulation for computation of quasiequilibrium binary neutron stars in general relativity. In contrast to previous approaches in which a part of the Einstein equation is solved, in the new formulation, the full Einstein equation is solved with maximal slicing and in a transverse gauge for the conformal three-metric. Helical symmetry is imposed in the near zone, while in the distant zone, a waveless condition is assumed. We expect the solutions obtained in this formulation to be excellent quasiequilibria as well as initial data for numerical simulations of binary neutron star mergers. |
gr-qc/9810012 | WU Zhong Chao | Wu Zhong Chao (Beijing Normal University) | Pair Creation of Black Hole in Anti-de Sitter Space Background | null | Phys.Lett.B445:274,1999 | 10.1016/S0370-2693(98)01509-3 | Beijing Preprint 98-108 | gr-qc astro-ph hep-th | null | In the absence of a general no-boundary proposal for open creation, the
complex constrained instanton is used as the seed for the open pair creations
of black holes in the Kerr-Newman-anti-de Sitter family. The relative
probability of the chargeless and nonrotating black hole pair is the
exponential of the negative of the entropy, and that of the charged and (or)
rotating black hole pair is the exponential of the negative of one quarter of
the sum of the outer and inner black hole horizon areas.
| [
{
"created": "Mon, 5 Oct 1998 22:08:02 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Oct 1998 16:00:49 GMT",
"version": "v2"
},
{
"created": "Wed, 14 Oct 1998 19:44:35 GMT",
"version": "v3"
},
{
"created": "Thu, 28 Jan 1999 15:58:08 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Chao",
"Wu Zhong",
"",
"Beijing Normal University"
]
] | In the absence of a general no-boundary proposal for open creation, the complex constrained instanton is used as the seed for the open pair creations of black holes in the Kerr-Newman-anti-de Sitter family. The relative probability of the chargeless and nonrotating black hole pair is the exponential of the negative of the entropy, and that of the charged and (or) rotating black hole pair is the exponential of the negative of one quarter of the sum of the outer and inner black hole horizon areas. |
1808.06485 | Sunandan Gangopadhyay | Sukanta Bhattacharyya, Sunandan Gangopadhyay, Anirban Saha | Footprint of spatial noncommutativity in resonant detectors of
gravitational wave | 11 pages Latex, comments are welcome | Class. Quantum Grav. 36 (2019) 055006 | 10.1088/1361-6382/ab008a | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present day gravitational wave (GW) detectors strive to detect the length
variation $\delta L = h L$, which, owing to the smallness of the metric
perturbation $\sim h$, is an extremely small length $\mathcal{O} \sim 10^{-18}
- 10^{-21}$ meter. The recently proposed noncommutative structure of space has
a characteristic length-scale $\sqrt{\theta}$ which has an estimated
upper-bound in similar length-scale range. We therefore propose that GW data
can be used as an effective probe of noncommutative structure of space and
demonstrate how spatial noncommutativity modifies the responding frequency of
the resonant mass detectors of GW and also the corresponding probabilities of
GW induced transitions that the phonon modes of the resonant mass detectors
undergo. In this paper we present the complete perturbative calculation
involving both time-independent and time-dependent perturbation terms in the
Hamiltonian.
| [
{
"created": "Thu, 16 Aug 2018 13:23:49 GMT",
"version": "v1"
}
] | 2019-02-12 | [
[
"Bhattacharyya",
"Sukanta",
""
],
[
"Gangopadhyay",
"Sunandan",
""
],
[
"Saha",
"Anirban",
""
]
] | The present day gravitational wave (GW) detectors strive to detect the length variation $\delta L = h L$, which, owing to the smallness of the metric perturbation $\sim h$, is an extremely small length $\mathcal{O} \sim 10^{-18} - 10^{-21}$ meter. The recently proposed noncommutative structure of space has a characteristic length-scale $\sqrt{\theta}$ which has an estimated upper-bound in similar length-scale range. We therefore propose that GW data can be used as an effective probe of noncommutative structure of space and demonstrate how spatial noncommutativity modifies the responding frequency of the resonant mass detectors of GW and also the corresponding probabilities of GW induced transitions that the phonon modes of the resonant mass detectors undergo. In this paper we present the complete perturbative calculation involving both time-independent and time-dependent perturbation terms in the Hamiltonian. |
gr-qc/0210032 | Steve Drasco | Steve Drasco and Eanna E. Flanagan | Detection methods for non-Gaussian gravitational wave stochastic
backgrounds | 25 pages, 12 figures, submitted to physical review D, added revisions
in response to reviewers comments | Phys.Rev. D67 (2003) 082003 | 10.1103/PhysRevD.67.082003 | null | gr-qc astro-ph | null | We address the issue of finding an optimal detection method for a
discontinuous or intermittent gravitational wave stochastic background. Such a
signal might sound something like popcorn popping. We derive an appropriate
version of the maximum likelihood detection statistic, and compare its
performance to that of the standard cross-correlation statistic both
analytically and with Monte Carlo simulations. The maximum likelihood statistic
performs better than the cross-correlation statistic when the background is
sufficiently non-Gaussian. For both ground and space based detectors, this
results in a gain factor, ranging roughly from 1 to 3, in the minimum
gravitational-wave energy density necessary for detection, depending on the
duty cycle of the background. Our analysis is exploratory, as we assume that
the time structure of the events cannot be resolved, and we assume white,
Gaussian noise in two collocated, aligned detectors. Before this detection
method can be used in practice with real detector data, further work is
required to generalize our analysis to accommodate separated, misaligned
detectors with realistic, colored, non-Gaussian noise.
| [
{
"created": "Thu, 10 Oct 2002 17:44:44 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Feb 2003 20:55:23 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Drasco",
"Steve",
""
],
[
"Flanagan",
"Eanna E.",
""
]
] | We address the issue of finding an optimal detection method for a discontinuous or intermittent gravitational wave stochastic background. Such a signal might sound something like popcorn popping. We derive an appropriate version of the maximum likelihood detection statistic, and compare its performance to that of the standard cross-correlation statistic both analytically and with Monte Carlo simulations. The maximum likelihood statistic performs better than the cross-correlation statistic when the background is sufficiently non-Gaussian. For both ground and space based detectors, this results in a gain factor, ranging roughly from 1 to 3, in the minimum gravitational-wave energy density necessary for detection, depending on the duty cycle of the background. Our analysis is exploratory, as we assume that the time structure of the events cannot be resolved, and we assume white, Gaussian noise in two collocated, aligned detectors. Before this detection method can be used in practice with real detector data, further work is required to generalize our analysis to accommodate separated, misaligned detectors with realistic, colored, non-Gaussian noise. |
gr-qc/9803039 | Wang Anzhong | Jos\'e A.C. Nogales and Anzhong Wang | Instability of cosmological event horizons of nonstatic global cosmic
strings II: perturbations of gravitational waves and massless scalar field | No figures, Revtex | Phys.Rev.D57:6089-6093,1998 | 10.1103/PhysRevD.57.6089 | null | gr-qc | null | The stability of the cosmological event horizons (CEHs) of a class of
non-static global cosmic strings is studied against perturbations of
gravitational waves and massless scalar field. It is found that the
perturbations of gravitational waves always turn the CEHs into non-scalar weak
spacetime curvature singularities, while the ones of massless scalar field turn
the CEHs either into non-scalar weak singularities or into scalar ones
depending on the particular cases considered. The perturbations of test
massless scalar field is also studied, and it is found that they do not always
give the correct prediction.
| [
{
"created": "Wed, 11 Mar 1998 15:53:48 GMT",
"version": "v1"
}
] | 2009-07-07 | [
[
"Nogales",
"José A. C.",
""
],
[
"Wang",
"Anzhong",
""
]
] | The stability of the cosmological event horizons (CEHs) of a class of non-static global cosmic strings is studied against perturbations of gravitational waves and massless scalar field. It is found that the perturbations of gravitational waves always turn the CEHs into non-scalar weak spacetime curvature singularities, while the ones of massless scalar field turn the CEHs either into non-scalar weak singularities or into scalar ones depending on the particular cases considered. The perturbations of test massless scalar field is also studied, and it is found that they do not always give the correct prediction. |
2205.00270 | Sanjar Shaymatov | Sanjar Shaymatov, Mubasher Jamil, Kimet Jusufi, Kazuharu Bamba | Constraints on the magnetized Ernst black hole spacetime through
quasiperiodic oscillations | 11 pages, 10 captioned figures. Updated to match with the published
version | Eur. Phys. J. C (2022) 82:636 | 10.1140/epjc/s10052-022-10560-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the dynamics of test particles around a magnetized Ernst black hole
considering its magnetic field in the environment surrounding the black hole.
We show how its magnetic field can influence the dynamics of particles and
epicyclic motion around the black hole. Based on the analysis, we find that the
radius of the innermost stable circular orbit (ISCO) for both neutral and
charged test particles and epicyclic frequencies are strongly affected by the
influence of the magnetic field. We also show that the ISCO radius of charged
particles decreases rapidly. It turns out that the gravitational and Lorentz
forces of the magnetic field are combined, thus strongly shrinking the values
of the ISCO of charged test particles. Finally, we obtain the generic form for
the epicyclic frequencies and select three microquasars with known
astrophysical quasiperiodic oscillation (QPO) data to constrain the magnetic
field.We show that the magnetic field is of the order of magnitude $B\sim
10^{-7}$ Gauss, taking into account the motion of neutral particles in circular
orbit about the black hole.
| [
{
"created": "Sat, 30 Apr 2022 13:42:31 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Jun 2022 10:06:30 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Aug 2022 19:18:25 GMT",
"version": "v3"
}
] | 2022-08-10 | [
[
"Shaymatov",
"Sanjar",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Jusufi",
"Kimet",
""
],
[
"Bamba",
"Kazuharu",
""
]
] | We study the dynamics of test particles around a magnetized Ernst black hole considering its magnetic field in the environment surrounding the black hole. We show how its magnetic field can influence the dynamics of particles and epicyclic motion around the black hole. Based on the analysis, we find that the radius of the innermost stable circular orbit (ISCO) for both neutral and charged test particles and epicyclic frequencies are strongly affected by the influence of the magnetic field. We also show that the ISCO radius of charged particles decreases rapidly. It turns out that the gravitational and Lorentz forces of the magnetic field are combined, thus strongly shrinking the values of the ISCO of charged test particles. Finally, we obtain the generic form for the epicyclic frequencies and select three microquasars with known astrophysical quasiperiodic oscillation (QPO) data to constrain the magnetic field.We show that the magnetic field is of the order of magnitude $B\sim 10^{-7}$ Gauss, taking into account the motion of neutral particles in circular orbit about the black hole. |
2211.11708 | Manasse R. Mbonye | Manasse R. Mbonye | Is cosmic dynamics self-regulating? | Updated version submitted for review, 5 figures | Int. J. Mod. Phys. D 32 12 2350076-786 (2023) | 10.1142/S0218271823500761 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | In this paper we discuss a cosmological model for a universe with
self-regulating features. We set up the theoretical framework for the model and
determine the time evolution of the scale-factor $a(t)$. It is shown that such
a universe repeatedly goes through alternate periods of matter and dark energy
domination. The resulting dynamics oscillates about the would-be ideal
time-linear or coasting path, with monotonic expansion. When compared to
dynamics of the observed physical Universe, the model recovers the
observationally-established evolutionary features of the latter, from the big
bang to the current acceleration, and farther. It suggests a universe that
initially emerges from a non-singular state, associated with a non-inflationary
acceleration, and which acceleration it exits naturally with matter-energy
generation. The model does not have a horizon problem or a flatness problem. It
reproduces the observed current values of standard cosmic parameters, including
the age $t_{0}$, the current Hubble parameter $H_{0}$ and dark energy
$\Omega_{de}\ $and matter $\Omega_{m}$ density parameters. We find the dark
matter density-profile generated by the model naturally leads to flat rotation
curves in galaxy halos. The model is falsifiable. It makes predictions that can
be tested, as suggested. Finally, we discuss the dimensionless age
$(H_{0}t_{0}\simeq1)$ paradox as an example of the model's ability to address
standing puzzles. The findings suggest dynamics of the physical Universe may be
self-regulating and predictable.
| [
{
"created": "Mon, 14 Nov 2022 17:11:01 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Nov 2022 13:50:32 GMT",
"version": "v2"
}
] | 2024-01-15 | [
[
"Mbonye",
"Manasse R.",
""
]
] | In this paper we discuss a cosmological model for a universe with self-regulating features. We set up the theoretical framework for the model and determine the time evolution of the scale-factor $a(t)$. It is shown that such a universe repeatedly goes through alternate periods of matter and dark energy domination. The resulting dynamics oscillates about the would-be ideal time-linear or coasting path, with monotonic expansion. When compared to dynamics of the observed physical Universe, the model recovers the observationally-established evolutionary features of the latter, from the big bang to the current acceleration, and farther. It suggests a universe that initially emerges from a non-singular state, associated with a non-inflationary acceleration, and which acceleration it exits naturally with matter-energy generation. The model does not have a horizon problem or a flatness problem. It reproduces the observed current values of standard cosmic parameters, including the age $t_{0}$, the current Hubble parameter $H_{0}$ and dark energy $\Omega_{de}\ $and matter $\Omega_{m}$ density parameters. We find the dark matter density-profile generated by the model naturally leads to flat rotation curves in galaxy halos. The model is falsifiable. It makes predictions that can be tested, as suggested. Finally, we discuss the dimensionless age $(H_{0}t_{0}\simeq1)$ paradox as an example of the model's ability to address standing puzzles. The findings suggest dynamics of the physical Universe may be self-regulating and predictable. |
1904.06572 | Masato Minamitsuji | Masato Minamitsuji and Taishi Ikeda | Spontaneous scalarization of black holes in the Horndeski theory | 24 pages, 7 figures, references added, typos corrected, published
version | Phys. Rev. D 99, 104069 (2019) | 10.1103/PhysRevD.99.104069 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the possibility of spontaneous scalarization of static,
spherically symmetric, and asymptotically flat black holes (BHs) in the
Horndeski theory. Spontaneous scalarization of BHs is a phenomenon that the
scalar field spontaneously obtains a nontrivial profile in the vicinity of the
event horizon via the nonminimal couplings and eventually the BH possesses a
scalar charge. In the theory in which spontaneous scalarization takes place,
the Schwarzschild solution with a trivial profile of the scalar field exhibits
a tachyonic instability in the vicinity of the event horizon, and evolves into
a hairy BH solution. Our analysis will extend the previous studies about the
Einstein-scalar-Gauss-Bonnet (GB) theory to other classes of the Horndeski
theory. First, we clarify the conditions for the existence of the vanishing
scalar field solution $\phi=0$ on top of the Schwarzschild spacetime, and we
apply them to each individual generalized galileon coupling. For each coupling,
we choose the coupling function with minimal power of $\phi$ and
$X:=-(1/2)g^{\mu\nu}\partial_\mu\phi\partial_\nu\phi$ that satisfies the above
condition, which leaves nonzero and finite imprints in the radial perturbation
of the scalar field. Second, we investigate the radial perturbation of the
scalar field about the $\phi=0$ solution on top of the Schwarzschild spacetime.
While each individual generalized galileon coupling except for a generalized
quartic coupling does not satisfy the hyperbolicity condition or realize a
tachyonic instability of the Schwarzschild spacetime by itself, a generalized
quartic coupling can realize it in the intermediate length scales outside the
event horizon. Finally, we investigate a model with generalized quartic and
quintic galileon couplings, which includes the Einstein-scalar-GB theory as the
special case.
| [
{
"created": "Sat, 13 Apr 2019 17:13:14 GMT",
"version": "v1"
},
{
"created": "Thu, 30 May 2019 15:14:18 GMT",
"version": "v2"
}
] | 2019-05-31 | [
[
"Minamitsuji",
"Masato",
""
],
[
"Ikeda",
"Taishi",
""
]
] | We investigate the possibility of spontaneous scalarization of static, spherically symmetric, and asymptotically flat black holes (BHs) in the Horndeski theory. Spontaneous scalarization of BHs is a phenomenon that the scalar field spontaneously obtains a nontrivial profile in the vicinity of the event horizon via the nonminimal couplings and eventually the BH possesses a scalar charge. In the theory in which spontaneous scalarization takes place, the Schwarzschild solution with a trivial profile of the scalar field exhibits a tachyonic instability in the vicinity of the event horizon, and evolves into a hairy BH solution. Our analysis will extend the previous studies about the Einstein-scalar-Gauss-Bonnet (GB) theory to other classes of the Horndeski theory. First, we clarify the conditions for the existence of the vanishing scalar field solution $\phi=0$ on top of the Schwarzschild spacetime, and we apply them to each individual generalized galileon coupling. For each coupling, we choose the coupling function with minimal power of $\phi$ and $X:=-(1/2)g^{\mu\nu}\partial_\mu\phi\partial_\nu\phi$ that satisfies the above condition, which leaves nonzero and finite imprints in the radial perturbation of the scalar field. Second, we investigate the radial perturbation of the scalar field about the $\phi=0$ solution on top of the Schwarzschild spacetime. While each individual generalized galileon coupling except for a generalized quartic coupling does not satisfy the hyperbolicity condition or realize a tachyonic instability of the Schwarzschild spacetime by itself, a generalized quartic coupling can realize it in the intermediate length scales outside the event horizon. Finally, we investigate a model with generalized quartic and quintic galileon couplings, which includes the Einstein-scalar-GB theory as the special case. |
2004.09208 | Naqing Xie | Xiaokai He and Naqing Xie | Hayward Quasilocal Energy of Tori | 11 pages, 6 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is dedicated to the investigation of the positivity of the Hayward
quasilocal energy of tori. Marginally trapped tori have nonnegative Hayward
energy. We consider a scenario of a spherically symmetric constant density star
matched to an exterior Schwarzschild solution. We show that any generic tori
within the star, distorted or not, trapped or not, have strictly positive
Hayward energy. Surprisingly we find analytic examples of `thin' tori with
negative Hayward energy in the outer neighborhood of the Schwarzschild horizon.
These tori are swept out by rotating the standard round circles in the static
coordinates but they are distorted in the isotropic coordinates. Numerical
results also indicate that there exist horizontally dragged tori with strictly
negative Hayward energy in the region between the boundary of the star and the
Schwarzschild horizon.
| [
{
"created": "Mon, 20 Apr 2020 11:20:03 GMT",
"version": "v1"
}
] | 2020-04-21 | [
[
"He",
"Xiaokai",
""
],
[
"Xie",
"Naqing",
""
]
] | This paper is dedicated to the investigation of the positivity of the Hayward quasilocal energy of tori. Marginally trapped tori have nonnegative Hayward energy. We consider a scenario of a spherically symmetric constant density star matched to an exterior Schwarzschild solution. We show that any generic tori within the star, distorted or not, trapped or not, have strictly positive Hayward energy. Surprisingly we find analytic examples of `thin' tori with negative Hayward energy in the outer neighborhood of the Schwarzschild horizon. These tori are swept out by rotating the standard round circles in the static coordinates but they are distorted in the isotropic coordinates. Numerical results also indicate that there exist horizontally dragged tori with strictly negative Hayward energy in the region between the boundary of the star and the Schwarzschild horizon. |
gr-qc/9803002 | Max Banados | Maximo Banados | Higher Dimensional Chern-Simons Theories and Topological Black Holes | 13 pages, Latex. Talk given at the Conference "Quantum Mechanics of
Fundamental Systems VI", Santiago, Chile, Aug 1997 | null | null | null | gr-qc | null | It has been recently pointed out that black holes of constant curvature with
a "chronological singularity" can be constructed in any spacetime dimension.
These black holes share many common properties with the 2+1 black hole. In this
contribution we give a brief summary of these new black holes and consider them
as solutions of a Chern-Simons gravity theory. We also provide a brief
introduction to some aspects of higher dimensional Chern-Simons theories.
| [
{
"created": "Sat, 28 Feb 1998 23:30:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Banados",
"Maximo",
""
]
] | It has been recently pointed out that black holes of constant curvature with a "chronological singularity" can be constructed in any spacetime dimension. These black holes share many common properties with the 2+1 black hole. In this contribution we give a brief summary of these new black holes and consider them as solutions of a Chern-Simons gravity theory. We also provide a brief introduction to some aspects of higher dimensional Chern-Simons theories. |
gr-qc/0004049 | Grigori Volovik | G.E. Volovik | Links between gravity and dynamics of quantum liquids | RevTex file, 16 pages, no figures, prepared for Proceedings of IV
International Conference "Cosmology. Relativistic Astropohysics.
Cosmoparticle Physics" (COSMION-99) in the Honor of 80-th Birthday of Isaak
M. Khalatnikov | Grav.Cosmol.Suppl.6:187-203,2000 | null | null | gr-qc cond-mat hep-ph | null | We consider the Landau-Khalatnikov two-fluid hydrodynamics of superfluid
liquid as an effective theory, which provides a self-consistent analog of
Einstein equations for gravity and matter.
| [
{
"created": "Sun, 16 Apr 2000 11:55:03 GMT",
"version": "v1"
}
] | 2011-04-15 | [
[
"Volovik",
"G. E.",
""
]
] | We consider the Landau-Khalatnikov two-fluid hydrodynamics of superfluid liquid as an effective theory, which provides a self-consistent analog of Einstein equations for gravity and matter. |
2112.14166 | Adam Balcerzak | Adam Balcerzak and Mateusz Lisaj | Decaying universes and the emergence of Bell-type interuniversal
entanglement in varying fundamental constants cosmological model | 8 pages, 4 figures, revised, matches published version | Eur. Phys. J. C 82, 732 (2022) | 10.1140/epjc/s10052-022-10704-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we consider a high-curvature limit of the varying fundamental
constants toy model in which both the value of the speed of light and the value
of the gravitational constant are related to the values of the two
non-minimally coupled scalar fields. The high-curvature limit motivates the
application of the third quantization procedure to such a toy model which
results in a theory that describes bosonic massive particles that move freely
in the three-dimensional minisuperspace associated with the degrees of freedom
of the original model. Motivated by the idea that in the quantum cosmological
description the minisuperspace gets promoted to a real configurational space of
the system we supplement the third quantized action of the considered model
with an interaction term that allows for decay and scattering processes. We
show that such interaction term induces a scenario in which a parent universe
decays into two universes described by a maximally entangled Bell state. We
eventually asses the strength of the entanglement, in the created pair of
universes, by calculating the von Neumann entropy of entanglement.
| [
{
"created": "Tue, 28 Dec 2021 14:51:23 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Dec 2021 12:51:34 GMT",
"version": "v2"
},
{
"created": "Fri, 26 Aug 2022 10:48:06 GMT",
"version": "v3"
}
] | 2022-08-29 | [
[
"Balcerzak",
"Adam",
""
],
[
"Lisaj",
"Mateusz",
""
]
] | In this paper, we consider a high-curvature limit of the varying fundamental constants toy model in which both the value of the speed of light and the value of the gravitational constant are related to the values of the two non-minimally coupled scalar fields. The high-curvature limit motivates the application of the third quantization procedure to such a toy model which results in a theory that describes bosonic massive particles that move freely in the three-dimensional minisuperspace associated with the degrees of freedom of the original model. Motivated by the idea that in the quantum cosmological description the minisuperspace gets promoted to a real configurational space of the system we supplement the third quantized action of the considered model with an interaction term that allows for decay and scattering processes. We show that such interaction term induces a scenario in which a parent universe decays into two universes described by a maximally entangled Bell state. We eventually asses the strength of the entanglement, in the created pair of universes, by calculating the von Neumann entropy of entanglement. |
0902.4097 | Hakan Andreasson | Hakan Andreasson, Gerhard Rein | The asymptotic behaviour in Schwarzschild time of Vlasov matter in
spherically symmetric gravitational collapse | 22 pages | Math.Proc.Cambridge Phil.Soc.149:173-188,2010 | 10.1017/S0305004109990454 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Given a static Schwarzschild spacetime of ADM mass M, it is well-known that
no ingoing causal geodesic starting in the outer domain r>2M will cross the
event horizon r=2M in finite Schwarzschild time. In the present paper we show
that in gravitational collapse of Vlasov matter this behaviour can be very
different. We construct initial data for which a black hole forms and all
matter crosses the event horizon as Schwarzschild time goes to infinity, and we
show that this is a necessary condition for geodesic completeness of the event
horizon. In addition to a careful analysis of the asymptotic behaviour of the
matter characteristics our proof requires a new argument for global existence
of solutions to the spherically symmetric Einstein-Vlasov system in an outer
domain, since our initial data have non-compact support in the radial momentum
variable and previous methods break down.
| [
{
"created": "Tue, 24 Feb 2009 16:21:33 GMT",
"version": "v1"
}
] | 2011-02-01 | [
[
"Andreasson",
"Hakan",
""
],
[
"Rein",
"Gerhard",
""
]
] | Given a static Schwarzschild spacetime of ADM mass M, it is well-known that no ingoing causal geodesic starting in the outer domain r>2M will cross the event horizon r=2M in finite Schwarzschild time. In the present paper we show that in gravitational collapse of Vlasov matter this behaviour can be very different. We construct initial data for which a black hole forms and all matter crosses the event horizon as Schwarzschild time goes to infinity, and we show that this is a necessary condition for geodesic completeness of the event horizon. In addition to a careful analysis of the asymptotic behaviour of the matter characteristics our proof requires a new argument for global existence of solutions to the spherically symmetric Einstein-Vlasov system in an outer domain, since our initial data have non-compact support in the radial momentum variable and previous methods break down. |
0909.4998 | Xinlian Luo | Luo Xin-Lian | Neutrino Lensing | 8 pages, 2 figures, uses iopart | Chin.Phys.Lett.26:10980,2009 | 10.1088/0256-307X/26/10/109801 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Due to the intrinsic properties of neutrinos, the gravitational lens effect
for neutrino should be more colorful and meaningful than the normal lens effect
of photon. Other than the oscillation experiments operated at terrestrial
laboratory, in principle, we can propose a completely new astrophysical method
to determine not only the nature of gravity and spacetime of lens objects but
also the mixing parameters of neutrinos by analyzing neutrino trajectories near
the central objects. However, compared with the contemporaneous telescopes
through the observation of the electromagnetic radiation, the angular, energy
and time resolution of the neutrino telescopes are still comparatively poor, we
just concentrate on the two classical tests of general relativity, i.e. the
angular deflection and time delay of neutrino by a lens object as a preparative
work in this paper. In addition, some simple properties of neutrino lensing are
investigated.
| [
{
"created": "Mon, 28 Sep 2009 03:44:14 GMT",
"version": "v1"
}
] | 2010-04-30 | [
[
"Xin-Lian",
"Luo",
""
]
] | Due to the intrinsic properties of neutrinos, the gravitational lens effect for neutrino should be more colorful and meaningful than the normal lens effect of photon. Other than the oscillation experiments operated at terrestrial laboratory, in principle, we can propose a completely new astrophysical method to determine not only the nature of gravity and spacetime of lens objects but also the mixing parameters of neutrinos by analyzing neutrino trajectories near the central objects. However, compared with the contemporaneous telescopes through the observation of the electromagnetic radiation, the angular, energy and time resolution of the neutrino telescopes are still comparatively poor, we just concentrate on the two classical tests of general relativity, i.e. the angular deflection and time delay of neutrino by a lens object as a preparative work in this paper. In addition, some simple properties of neutrino lensing are investigated. |
2206.10055 | Yuchen Huang | Yuchen Huang, Jun Tao, Peng Wang and Shuxuan Ying | Phase transitions and thermodynamic geometry of a Kerr-Newman black hole
in a cavity | 25 pages, 8 figures | Eur.Phys.J.Plus 138 (2023) 3, 265 | 10.1140/epjp/s13360-023-03858-w | CTP-SCU/2022011 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Being placed in a cavity is an effective way of reaching thermodynamic
equilibrium for black holes. We investigate a Kerr-Newman black hole in a
cavity as well as compare it with two reduced cases, i.e., a RN black hole in a
cavity and a Kerr black hole in a cavity. We derive the quasi-local energy from
the Hamiltonian, and construct the first law of thermodynamics accordingly. In
a canonical ensemble, these black holes could undergo a van der Waals-like
phase transition, which is very similar to that in AdS space. We further
investigate the black holes' thermodynamic geometry, which is a powerful tool
to diagnose microscopic interactions of a thermodynamic system. Our results
show that in a cavity, although phase structures of these black holes are
similar, their thermodynamic geometry show strong dissimilarities, implying
that the microstructure of a black hole is sensitive to its states.
| [
{
"created": "Tue, 21 Jun 2022 00:38:37 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Jun 2022 07:46:06 GMT",
"version": "v2"
},
{
"created": "Wed, 31 Aug 2022 13:34:51 GMT",
"version": "v3"
},
{
"created": "Mon, 5 Sep 2022 15:40:02 GMT",
"version": "v4"
}
] | 2023-06-06 | [
[
"Huang",
"Yuchen",
""
],
[
"Tao",
"Jun",
""
],
[
"Wang",
"Peng",
""
],
[
"Ying",
"Shuxuan",
""
]
] | Being placed in a cavity is an effective way of reaching thermodynamic equilibrium for black holes. We investigate a Kerr-Newman black hole in a cavity as well as compare it with two reduced cases, i.e., a RN black hole in a cavity and a Kerr black hole in a cavity. We derive the quasi-local energy from the Hamiltonian, and construct the first law of thermodynamics accordingly. In a canonical ensemble, these black holes could undergo a van der Waals-like phase transition, which is very similar to that in AdS space. We further investigate the black holes' thermodynamic geometry, which is a powerful tool to diagnose microscopic interactions of a thermodynamic system. Our results show that in a cavity, although phase structures of these black holes are similar, their thermodynamic geometry show strong dissimilarities, implying that the microstructure of a black hole is sensitive to its states. |
0809.2474 | Farook Rahaman | M.Kalam, F.Rahaman, A.Ghosh and B. Raychaudhuri | Discussion on some characteristics of the Charged Brane-world Black
holes | 23 pages, 9 figures. To be appeared in Int.J.Mod.Phys.A | Int.J.Mod.Phys.A24:719-739,2009 | 10.1142/S0217751X09042542 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several physical natures of charged brane-world black holes have been
investigated. At first, time-like and null geodesics of the charged brane-world
black holes are presented. We also analyze all the possible motions by plotting
the effective potentials for various parameters for circular and radial
geodesics. Secondly, we investigate the motion of test particles in the
gravitational field of charged brane-world black holes using Hamilton-Jacobi
(H-J) formalism. We have considered charged and uncharged test particles and
examine its behavior both in static and non-static cases. Thirdly,
thermodynamics of the charged brane-world black holes are studied. Finally, it
has been also shown that there is no phenomenon of superradiance for an
incident massless scalar field for this black hole.
| [
{
"created": "Mon, 15 Sep 2008 10:09:52 GMT",
"version": "v1"
}
] | 2009-03-12 | [
[
"Kalam",
"M.",
""
],
[
"Rahaman",
"F.",
""
],
[
"Ghosh",
"A.",
""
],
[
"Raychaudhuri",
"B.",
""
]
] | Several physical natures of charged brane-world black holes have been investigated. At first, time-like and null geodesics of the charged brane-world black holes are presented. We also analyze all the possible motions by plotting the effective potentials for various parameters for circular and radial geodesics. Secondly, we investigate the motion of test particles in the gravitational field of charged brane-world black holes using Hamilton-Jacobi (H-J) formalism. We have considered charged and uncharged test particles and examine its behavior both in static and non-static cases. Thirdly, thermodynamics of the charged brane-world black holes are studied. Finally, it has been also shown that there is no phenomenon of superradiance for an incident massless scalar field for this black hole. |
1207.5863 | Dennis Bessada | Dennis Bessada, Nelson Pinto-Neto, Beatriz B. Siffert, Oswaldo D.
Miranda | Stochastic background of relic gravitons in a bouncing quantum
cosmological model | 10 pages, 3 figures, to appear in JCAP | null | 10.1088/1475-7516/2012/11/054 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The spectrum and amplitude of the stochastic background of relic gravitons
produced in a bouncing universe is calculated. The matter content of the model
consists of dust and radiation fluids, and the bounce occurs due to quantum
cosmological effects when the universe approaches the classical singularity in
the contracting phase. The resulting amplitude is very small and it cannot be
observed by any present and near future gravitational wave detector. Hence, as
in the ekpyrotic model, any observation of these relic gravitons will rule out
this type of quantum cosmological bouncing model.
| [
{
"created": "Wed, 25 Jul 2012 01:17:05 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Nov 2012 12:28:43 GMT",
"version": "v2"
}
] | 2015-06-05 | [
[
"Bessada",
"Dennis",
""
],
[
"Pinto-Neto",
"Nelson",
""
],
[
"Siffert",
"Beatriz B.",
""
],
[
"Miranda",
"Oswaldo D.",
""
]
] | The spectrum and amplitude of the stochastic background of relic gravitons produced in a bouncing universe is calculated. The matter content of the model consists of dust and radiation fluids, and the bounce occurs due to quantum cosmological effects when the universe approaches the classical singularity in the contracting phase. The resulting amplitude is very small and it cannot be observed by any present and near future gravitational wave detector. Hence, as in the ekpyrotic model, any observation of these relic gravitons will rule out this type of quantum cosmological bouncing model. |
1605.05928 | Ahmed Farag Ali | Ahmed Farag Ali, Saurya Das | Stringent theoretical and experimental bounds on graviton mass | 3 pages, revtex4, no figures. This essay received an Honorable
mention in the 2016 Essay Competition of the Gravity Research Foundation | Int.J.Mod.Phys. D25 (2016) 1644001 | 10.1142/S0218271816440016 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show from theoretical considerations, that if the graviton is massive, its
mass is constrained to be about $10^{-32}~eV/c^2$. This estimate is consistent
with those obtained from experiments, including the recent gravitational wave
detection in advanced LIGO.
| [
{
"created": "Sat, 14 May 2016 02:14:44 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jul 2016 15:01:48 GMT",
"version": "v2"
}
] | 2016-10-10 | [
[
"Ali",
"Ahmed Farag",
""
],
[
"Das",
"Saurya",
""
]
] | We show from theoretical considerations, that if the graviton is massive, its mass is constrained to be about $10^{-32}~eV/c^2$. This estimate is consistent with those obtained from experiments, including the recent gravitational wave detection in advanced LIGO. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.