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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9701024 | Vitorio Alberto De Lorenci | Vitorio A. De Lorenci, Jerome Martin, Nelson Pinto-Neto and Ivano
Damiao Soares | Topology Change in Canonical Quantum Cosmology | 23 pages, LaTex file. We added in the conclusion some comments about
path integral formalism and corrected litle misprintings | Phys.Rev. D56 (1997) 3329-3340 | 10.1103/PhysRevD.56.3329 | Notas de Fisica CBPF-NF 002/97 | gr-qc | null | We develop the canonical quantization of a midisuperspace model which
contains, as a subspace, a minisuperspace constituted of a
Friedman-Lema\^{\i}tre-Robertson-Walker Universe filled with homogeneous scalar
and dust fields, where the sign of the intrinsic curvature of the spacelike
hypersurfaces of homogeneity is not specified, allowing the study of topology
change in these hypersurfaces. We solve the Wheeler-DeWitt equation of the
midisuperspace model restricted to this minisuperspace subspace in the
semi-classical approximation. Adopting the conditional probability
interpretation, we find that some of the solutions present change of topology
of the homogeneous hypersurfaces. However, this result depends crucially on the
interpretation we adopt: using the usual probabilistic interpretation, we find
selection rules which forbid some of these topology changes.
| [
{
"created": "Sun, 12 Jan 1997 19:14:00 GMT",
"version": "v1"
},
{
"created": "Mon, 5 May 1997 20:51:44 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"De Lorenci",
"Vitorio A.",
""
],
[
"Martin",
"Jerome",
""
],
[
"Pinto-Neto",
"Nelson",
""
],
[
"Soares",
"Ivano Damiao",
""
]
] | We develop the canonical quantization of a midisuperspace model which contains, as a subspace, a minisuperspace constituted of a Friedman-Lema\^{\i}tre-Robertson-Walker Universe filled with homogeneous scalar and dust fields, where the sign of the intrinsic curvature of the spacelike hypersurfaces of homogeneity is not specified, allowing the study of topology change in these hypersurfaces. We solve the Wheeler-DeWitt equation of the midisuperspace model restricted to this minisuperspace subspace in the semi-classical approximation. Adopting the conditional probability interpretation, we find that some of the solutions present change of topology of the homogeneous hypersurfaces. However, this result depends crucially on the interpretation we adopt: using the usual probabilistic interpretation, we find selection rules which forbid some of these topology changes. |
gr-qc/9803005 | Jorge Pullin | Jorge Pullin | Colliding black holes: analytic insights | 19 pages, crckapb.sty, 7 figures included with psfig, talk given at
GR15, Poona, India, to appear in the proceedings | null | null | CGPG-98/2-4 | gr-qc | null | We summarize the state of the art of the ``close approximation'' to black
hole collisions. We discuss results to first and second order in perturbation
theory for head-on collisions of momentarily-stationary and non-stationary
black holes and discuss the near-future prospect of non-axisymmetric
collisions.
| [
{
"created": "Mon, 2 Mar 1998 03:35:24 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pullin",
"Jorge",
""
]
] | We summarize the state of the art of the ``close approximation'' to black hole collisions. We discuss results to first and second order in perturbation theory for head-on collisions of momentarily-stationary and non-stationary black holes and discuss the near-future prospect of non-axisymmetric collisions. |
gr-qc/0609008 | Sean A. Hayward | Sean A. Hayward | Angular momentum conservation for dynamical black holes | 12 revtex4 pages, 3 eps figures. Version to be published, with minor
improvements | Phys.Rev.D74:104013,2006 | 10.1103/PhysRevD.74.104013 | null | gr-qc | null | Angular momentum can be defined by rearranging the Komar surface integral in
terms of a twist form, encoding the twisting around of space-time due to a
rotating mass, and an axial vector. If the axial vector is a coordinate vector
and has vanishing transverse divergence, it can be uniquely specified under
certain generic conditions. Along a trapping horizon, a conservation law
expresses the rate of change of angular momentum of a general black hole in
terms of angular momentum densities of matter and gravitational radiation. This
identifies the transverse-normal block of an effective gravitational-radiation
energy tensor, whose normal-normal block was recently identified in a
corresponding energy conservation law. Angular momentum and energy are dual
respectively to the axial vector and a previously identified vector, the
conservation equations taking the same form. Including charge conservation, the
three conserved quantities yield definitions of an effective energy, electric
potential, angular velocity and surface gravity, satisfying a dynamical version
of the so-called first law of black-hole mechanics. A corresponding zeroth law
holds for null trapping horizons, resolving an ambiguity in taking the null
limit.
| [
{
"created": "Mon, 4 Sep 2006 11:06:19 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Nov 2006 04:57:41 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Hayward",
"Sean A.",
""
]
] | Angular momentum can be defined by rearranging the Komar surface integral in terms of a twist form, encoding the twisting around of space-time due to a rotating mass, and an axial vector. If the axial vector is a coordinate vector and has vanishing transverse divergence, it can be uniquely specified under certain generic conditions. Along a trapping horizon, a conservation law expresses the rate of change of angular momentum of a general black hole in terms of angular momentum densities of matter and gravitational radiation. This identifies the transverse-normal block of an effective gravitational-radiation energy tensor, whose normal-normal block was recently identified in a corresponding energy conservation law. Angular momentum and energy are dual respectively to the axial vector and a previously identified vector, the conservation equations taking the same form. Including charge conservation, the three conserved quantities yield definitions of an effective energy, electric potential, angular velocity and surface gravity, satisfying a dynamical version of the so-called first law of black-hole mechanics. A corresponding zeroth law holds for null trapping horizons, resolving an ambiguity in taking the null limit. |
gr-qc/0112013 | Andrea Vicere | Andrea Vicer\'e | Optimal detection of burst events in gravitational wave interferometric
observatories | 21 pages, 5 figures in 3 groups. Submitted for publication to
Phys.Rev.D. A Mathematica notebook is available at
http://www.ligo.caltech.edu/~avicere/nda/burst/Burst.nb which allows to
reproduce the numerical results of the paper | Phys.Rev. D66 (2002) 062002 | 10.1103/PhysRevD.66.062002 | LIGO-P010019-01-E | gr-qc | null | We consider the problem of detecting a burst signal of unknown shape. We
introduce a statistic which generalizes the excess power statistic proposed by
Flanagan and Hughes and extended by Anderson et al. The statistic we propose is
shown to be optimal for arbitrary noise spectral characteristic, under the two
hypotheses that the noise is Gaussian, and that the prior for the signal is
uniform. The statistic derivation is based on the assumption that a signal
affects only affects N samples in the data stream, but that no other
information is a priori available, and that the value of the signal at each
sample can be arbitrary. We show that the proposed statistic can be implemented
combining standard time-series analysis tools which can be efficiently
implemented, and the resulting computational cost is still compatible with an
on-line analysis of interferometric data. We generalize this version of an
excess power statistic to the multiple detector case, also including the effect
of correlated noise. We give full details about the implementation of the
algorithm, both for the single and the multiple detector case, and we discuss
exact and approximate forms, depending on the specific characteristics of the
noise and on the assumed length of the burst event. As a example, we show what
would be the sensitivity of the network of interferometers to a delta-function
burst.
| [
{
"created": "Sat, 8 Dec 2001 07:48:26 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Viceré",
"Andrea",
""
]
] | We consider the problem of detecting a burst signal of unknown shape. We introduce a statistic which generalizes the excess power statistic proposed by Flanagan and Hughes and extended by Anderson et al. The statistic we propose is shown to be optimal for arbitrary noise spectral characteristic, under the two hypotheses that the noise is Gaussian, and that the prior for the signal is uniform. The statistic derivation is based on the assumption that a signal affects only affects N samples in the data stream, but that no other information is a priori available, and that the value of the signal at each sample can be arbitrary. We show that the proposed statistic can be implemented combining standard time-series analysis tools which can be efficiently implemented, and the resulting computational cost is still compatible with an on-line analysis of interferometric data. We generalize this version of an excess power statistic to the multiple detector case, also including the effect of correlated noise. We give full details about the implementation of the algorithm, both for the single and the multiple detector case, and we discuss exact and approximate forms, depending on the specific characteristics of the noise and on the assumed length of the burst event. As a example, we show what would be the sensitivity of the network of interferometers to a delta-function burst. |
1805.03035 | Sandipan Sengupta | Sandipan Sengupta | Time travel in vacuum spacetimes | null | Phys. Rev. D 97, 124038 (2018) | 10.1103/PhysRevD.97.124038 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The possibility of time travel through the geodesics of vacuum solutions in
first order gravity is explored. We present explicit examples of such
geometries, which contain degenerate as well as nondegenerate tetrad fields
that are sewn together continuously over different regions of the spacetime.
These classical solutions to the field equations satisfy the energy conditions.
| [
{
"created": "Fri, 4 May 2018 08:29:24 GMT",
"version": "v1"
}
] | 2018-06-29 | [
[
"Sengupta",
"Sandipan",
""
]
] | The possibility of time travel through the geodesics of vacuum solutions in first order gravity is explored. We present explicit examples of such geometries, which contain degenerate as well as nondegenerate tetrad fields that are sewn together continuously over different regions of the spacetime. These classical solutions to the field equations satisfy the energy conditions. |
2311.15252 | Daoqiang Liu | Daoqiang Liu | Tilted spacetime positive mass theorem with arbitrary ends | 19 pages, 3 figures. Comments are welcome! | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we prove the spacetime positive mass theorem for
asymptotically flat spin initial data sets with arbitrary ends and a
non-compact boundary. Moreover, we demonstrate a quantitative shielding
theorem, subject to the tilted boundary dominant energy condition. Our results
are established by solving a mixed boundary value problem for the Dirac-Witten
operator with a Callias potential.
| [
{
"created": "Sun, 26 Nov 2023 09:53:43 GMT",
"version": "v1"
}
] | 2023-11-28 | [
[
"Liu",
"Daoqiang",
""
]
] | In this paper, we prove the spacetime positive mass theorem for asymptotically flat spin initial data sets with arbitrary ends and a non-compact boundary. Moreover, we demonstrate a quantitative shielding theorem, subject to the tilted boundary dominant energy condition. Our results are established by solving a mixed boundary value problem for the Dirac-Witten operator with a Callias potential. |
2403.13308 | Luciano Combi | Luciano Combi and Sean M. Ressler | A binary black hole metric approximation from inspiral to merger | Version to be submitted to PRD. Comments are welcome | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We present a semi-analytic binary black hole (BBH) metric approximation that
models the entire evolution of the system from inspiral to merger. The metric
is constructed as a boosted Kerr-Schild superposition following post-Newtonian
(PN) trajectories at the fourth PN order in the inspiral phase. During merger,
we interpolate the binary metric in time to a single black hole remnant with
properties obtained from numerical relativity (NR) fittings. Different from
previous approaches, the new metric can model binary black holes with arbitrary
spin direction, mass ratio, and eccentricity at any stage of their evolution in
a fast and computationally efficient way. We analyze the properties of our new
metric and we compare it with a full numerical relativity evolution. We show
that Hamiltonian constraints are well-behaved even at merger and that the mass
and spin of the black holes deviate in average only $\sim 5 \%$ compared to the
full numerical evolution. We perform a General Relativistic
magneto-hydrodynamical (GRMHD) simulation of uniform gas evolving on top of our
approximate metric. We compare it with a full numerical relativity evolution of
the fluid and Einstein's equations. We show that the properties of the gas such
as the accretion rate are remarkably similar between the two approaches,
exhibiting only $\sim 10 \%$ differences in average. The approximate metric is
five times more efficient among other computational advantages. The numerical
implementation of the metric is now open-source and optimized for numerical
work. We have also implemented this spacetime in the widely used GRMHD codes
Athena++ and EinsteinToolkit.
| [
{
"created": "Wed, 20 Mar 2024 05:16:43 GMT",
"version": "v1"
}
] | 2024-03-21 | [
[
"Combi",
"Luciano",
""
],
[
"Ressler",
"Sean M.",
""
]
] | We present a semi-analytic binary black hole (BBH) metric approximation that models the entire evolution of the system from inspiral to merger. The metric is constructed as a boosted Kerr-Schild superposition following post-Newtonian (PN) trajectories at the fourth PN order in the inspiral phase. During merger, we interpolate the binary metric in time to a single black hole remnant with properties obtained from numerical relativity (NR) fittings. Different from previous approaches, the new metric can model binary black holes with arbitrary spin direction, mass ratio, and eccentricity at any stage of their evolution in a fast and computationally efficient way. We analyze the properties of our new metric and we compare it with a full numerical relativity evolution. We show that Hamiltonian constraints are well-behaved even at merger and that the mass and spin of the black holes deviate in average only $\sim 5 \%$ compared to the full numerical evolution. We perform a General Relativistic magneto-hydrodynamical (GRMHD) simulation of uniform gas evolving on top of our approximate metric. We compare it with a full numerical relativity evolution of the fluid and Einstein's equations. We show that the properties of the gas such as the accretion rate are remarkably similar between the two approaches, exhibiting only $\sim 10 \%$ differences in average. The approximate metric is five times more efficient among other computational advantages. The numerical implementation of the metric is now open-source and optimized for numerical work. We have also implemented this spacetime in the widely used GRMHD codes Athena++ and EinsteinToolkit. |
0704.1871 | Andres Balaguera | A. Balaguera-Antolinez, M. Nowakowski | From Global to Local Dynamics: Effects of the Expansion on Astrophysical
Structures | References added To be published in CQG | Class.Quant.Grav.24:2677-2688,2007 | 10.1088/0264-9381/24/10/013 | null | gr-qc | null | We explore the effects of background cosmology on large scale structures with
non-spherical symmetry by using the concept of quasi-equilibrium which allows
certain internal properties (e.g. angular velocity) of the bodies to change
with time. In accordance with the discovery of the accelerated phase of the
universe we model the cosmological background by two representative models: the
$\Lambda$CDM Model and the Chaplygin Gas Model. We compare the effects of the
two models on various properties of large astrophysical objects. Different
equations of state are also invoked in the investigation.
| [
{
"created": "Sat, 14 Apr 2007 16:49:41 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Apr 2007 16:37:47 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Balaguera-Antolinez",
"A.",
""
],
[
"Nowakowski",
"M.",
""
]
] | We explore the effects of background cosmology on large scale structures with non-spherical symmetry by using the concept of quasi-equilibrium which allows certain internal properties (e.g. angular velocity) of the bodies to change with time. In accordance with the discovery of the accelerated phase of the universe we model the cosmological background by two representative models: the $\Lambda$CDM Model and the Chaplygin Gas Model. We compare the effects of the two models on various properties of large astrophysical objects. Different equations of state are also invoked in the investigation. |
0704.1035 | Hamid Reza Sepangi | M. Heydari-Fard and H. R. Sepangi | Anisotropic brane gravity with a confining potential | 14 pages, 3 figures, to appear in PLB | Phys.Lett.B649:1-11,2007 | 10.1016/j.physletb.2007.04.008 | null | gr-qc hep-th | null | We consider an anisotropic brane world with Bianchi type I and V geometries
where the mechanism of confining the matter on the brane is through the use of
a confining potential. The resulting equations on the anisotropic brane are
modified by an extra term that may be interpreted as the x-matter, providing a
possible phenomenological explanation for the accelerated expansion of the
universe. We obtain the general solution of the field equations in an exact
parametric form for both Bianchi type I and V space-times. In the special case
of a Bianchi type I the solutions of the field equations are obtained in an
exact analytic form. Finally, we study the behavior of the observationally
important parameters.
| [
{
"created": "Sun, 8 Apr 2007 17:01:50 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Heydari-Fard",
"M.",
""
],
[
"Sepangi",
"H. R.",
""
]
] | We consider an anisotropic brane world with Bianchi type I and V geometries where the mechanism of confining the matter on the brane is through the use of a confining potential. The resulting equations on the anisotropic brane are modified by an extra term that may be interpreted as the x-matter, providing a possible phenomenological explanation for the accelerated expansion of the universe. We obtain the general solution of the field equations in an exact parametric form for both Bianchi type I and V space-times. In the special case of a Bianchi type I the solutions of the field equations are obtained in an exact analytic form. Finally, we study the behavior of the observationally important parameters. |
1104.1384 | Aleksandar Mikovic | A. Mikovic and M. Vojinovic | Effective action and semiclassical limit of spin foam models | Improved presentation, 2 references added. 15 pages, no figures | Class. Quant. Grav. 28, 225004 (2011) | 10.1088/0264-9381/28/22/225004 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We define an effective action for spin foam models of quantum gravity by
adapting the background field method from quantum field theory. We show that
the Regge action is the leading term in the semi-classical expansion of the
spin foam effective action if the vertex amplitude has the large-spin
asymptotics which is proportional to an exponential function of the vertex
Regge action. In the case of the known three-dimensional and four-dimensional
spin foam models this amounts to modifying the vertex amplitude such that the
exponential asymptotics is obtained. In particular, we show that the ELPR/FK
model vertex amplitude can be modified such that the new model is finite and
has the Einstein-Hilbert action as its classical limit. We also calculate the
first-order and some of the second-order quantum corrections in the
semi-classical expansion of the effective action.
| [
{
"created": "Thu, 7 Apr 2011 17:12:43 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Aug 2011 09:19:23 GMT",
"version": "v2"
}
] | 2011-11-01 | [
[
"Mikovic",
"A.",
""
],
[
"Vojinovic",
"M.",
""
]
] | We define an effective action for spin foam models of quantum gravity by adapting the background field method from quantum field theory. We show that the Regge action is the leading term in the semi-classical expansion of the spin foam effective action if the vertex amplitude has the large-spin asymptotics which is proportional to an exponential function of the vertex Regge action. In the case of the known three-dimensional and four-dimensional spin foam models this amounts to modifying the vertex amplitude such that the exponential asymptotics is obtained. In particular, we show that the ELPR/FK model vertex amplitude can be modified such that the new model is finite and has the Einstein-Hilbert action as its classical limit. We also calculate the first-order and some of the second-order quantum corrections in the semi-classical expansion of the effective action. |
1809.00555 | Branislav Cvetkovi\'c | B. Cvetkovi\'c and D. Simi\'c | Near-horizon geometry with torsion | LaTeX, 14 pages; v2: section 3 extended | Phys. Rev. D 99, 024032 (2019) | 10.1103/PhysRevD.99.024032 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate near-horizon geometry of the rotating Ba\~nados Teiteilboim
Zanelli (BTZ) black hole with torsion. Our main motivation is to gain insight
into the role of torsion in the near-horizon geometry, which is well understood
in the Riemannian case. We obtain that near-horizon geometry represents a
generalization of AdS self-dual orbifold with non-trivial torsion. We analyze
its asymptotic structure and derive the corresponding algebra of asymptotic
symmetries, which consists of chiral Virasoro and centrally extended $u(1)$
Kac-Moody algebra.
| [
{
"created": "Mon, 3 Sep 2018 11:21:07 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Feb 2019 11:32:53 GMT",
"version": "v2"
}
] | 2019-02-21 | [
[
"Cvetković",
"B.",
""
],
[
"Simić",
"D.",
""
]
] | We investigate near-horizon geometry of the rotating Ba\~nados Teiteilboim Zanelli (BTZ) black hole with torsion. Our main motivation is to gain insight into the role of torsion in the near-horizon geometry, which is well understood in the Riemannian case. We obtain that near-horizon geometry represents a generalization of AdS self-dual orbifold with non-trivial torsion. We analyze its asymptotic structure and derive the corresponding algebra of asymptotic symmetries, which consists of chiral Virasoro and centrally extended $u(1)$ Kac-Moody algebra. |
1209.4871 | Eduardo Bittencourt | M. Novello and E. Bittencourt | What is the origin of the mass of the Higgs boson? | 7 pages. arXiv admin note: substantial text overlap with
arXiv:1111.4228, arXiv:1008.2371 | Phys Rev D., vol. 86 063510 (2012) | 10.1103/PhysRevD.86.063510 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The purpose of this paper is to present a unified description of mass
generation mechanisms that have been investigated so far and that are called
the Mach and Higgs proposals. In our mechanism, gravity acts merely as a
catalyst and the final expression of the mass depends neither on the intensity
nor on the particular properties of the gravitational field. We shall see that
these two strategies to provide mass for all bodies that operate independently
and competitively can be combined into a single unified theoretical framework.
As a consequence of this new formulation we are able to present an answer to
the question: what is the origin of the mass of the Higgs boson?
| [
{
"created": "Fri, 21 Sep 2012 17:46:36 GMT",
"version": "v1"
}
] | 2013-09-24 | [
[
"Novello",
"M.",
""
],
[
"Bittencourt",
"E.",
""
]
] | The purpose of this paper is to present a unified description of mass generation mechanisms that have been investigated so far and that are called the Mach and Higgs proposals. In our mechanism, gravity acts merely as a catalyst and the final expression of the mass depends neither on the intensity nor on the particular properties of the gravitational field. We shall see that these two strategies to provide mass for all bodies that operate independently and competitively can be combined into a single unified theoretical framework. As a consequence of this new formulation we are able to present an answer to the question: what is the origin of the mass of the Higgs boson? |
1507.08651 | Saeed Rastgoo | Hugo A. Morales-T\'ecotl, Daniel H. Orozco-Borunda, Saeed Rastgoo | Polymer quantization and the saddle point approximation of partition
functions | 18 pages, 2 figures. Minor corrections based on PRD referee report.
Final version matching the one published in PRD | Phys. Rev. D 92, 104029 (2015) | 10.1103/PhysRevD.92.104029 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The saddle point approximation of the path integral partition functions is an
important way of deriving the thermodynamical properties of black holes.
However, there are certain black hole models and some mathematically analog
mechanical models for which this method cannot be applied directly. This is due
to the fact that their action evaluated on a classical solution is not finite
and its first variation does not vanish for all consistent boundary conditions.
These problems can be dealt with by adding a counterterm to the classical
action, which is a solution of the corresponding Hamilton-Jacobi equation.
In this work we study the effects of polymer quantization on a mechanical
model presenting the aforementioned difficulties and contrast it with the above
counterterm method. This type of quantization for mechanical models is
motivated by the loop quantization of gravity which is known to play a role in
the thermodynamics of black hole systems.
The model we consider is a nonrelativistic particle in an inverse square
potential, and analyze two polarizations of the polymer quantization in which
either the position or the momentum is discrete. In the former case, Thiemann's
regularization is applied to represent the inverse power potential but we still
need to incorporate the Hamilton-Jacobi counterterm which is now modified by
polymer corrections. In the latter, momentum discrete case however, such
regularization could not be implemented. Yet, remarkably, owing to the fact
that the position is bounded, we do not need a Hamilton-Jacobi counterterm in
order to have a well-defined saddle point approximation. Further developments
and extensions are commented upon in the discussion.
| [
{
"created": "Thu, 30 Jul 2015 19:55:44 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Jul 2015 20:22:10 GMT",
"version": "v2"
},
{
"created": "Tue, 10 Nov 2015 03:42:05 GMT",
"version": "v3"
}
] | 2015-11-11 | [
[
"Morales-Técotl",
"Hugo A.",
""
],
[
"Orozco-Borunda",
"Daniel H.",
""
],
[
"Rastgoo",
"Saeed",
""
]
] | The saddle point approximation of the path integral partition functions is an important way of deriving the thermodynamical properties of black holes. However, there are certain black hole models and some mathematically analog mechanical models for which this method cannot be applied directly. This is due to the fact that their action evaluated on a classical solution is not finite and its first variation does not vanish for all consistent boundary conditions. These problems can be dealt with by adding a counterterm to the classical action, which is a solution of the corresponding Hamilton-Jacobi equation. In this work we study the effects of polymer quantization on a mechanical model presenting the aforementioned difficulties and contrast it with the above counterterm method. This type of quantization for mechanical models is motivated by the loop quantization of gravity which is known to play a role in the thermodynamics of black hole systems. The model we consider is a nonrelativistic particle in an inverse square potential, and analyze two polarizations of the polymer quantization in which either the position or the momentum is discrete. In the former case, Thiemann's regularization is applied to represent the inverse power potential but we still need to incorporate the Hamilton-Jacobi counterterm which is now modified by polymer corrections. In the latter, momentum discrete case however, such regularization could not be implemented. Yet, remarkably, owing to the fact that the position is bounded, we do not need a Hamilton-Jacobi counterterm in order to have a well-defined saddle point approximation. Further developments and extensions are commented upon in the discussion. |
1606.02417 | Richard Woodard | S. Basu and R. P. Woodard | Testing an Ansatz for the Leading Secular Loop Corrections from Quantum
Gravity during Inflation | 24 pages, 2 figures, uses LaTeX2e, version 2 corrects some typos and
adds some references | Class. Quant. Grav. 33 (2016) no. 20, 205007 | 10.1088/0264-9381/33/20/205007 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is widely believed that the leading secular loop corrections from quantum
gravity can be subsumed into a coordinate redefinition. Hence the apparent
infrared logarithm corrections to any quantity would be just the result of
taking the expectation value of the tree order quantity at the transformed
coordinates in the graviton vacuum. We term this the Transformation Ansatz and
we compare its predictions against explicit one loop computations in Maxwell +
Einstein and Dirac + Einstein on de Sitter background. In each case the ansatz
fails.
| [
{
"created": "Wed, 8 Jun 2016 06:37:53 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Sep 2016 16:35:00 GMT",
"version": "v2"
}
] | 2016-10-03 | [
[
"Basu",
"S.",
""
],
[
"Woodard",
"R. P.",
""
]
] | It is widely believed that the leading secular loop corrections from quantum gravity can be subsumed into a coordinate redefinition. Hence the apparent infrared logarithm corrections to any quantity would be just the result of taking the expectation value of the tree order quantity at the transformed coordinates in the graviton vacuum. We term this the Transformation Ansatz and we compare its predictions against explicit one loop computations in Maxwell + Einstein and Dirac + Einstein on de Sitter background. In each case the ansatz fails. |
2103.10405 | Yannick Herfray | Yannick Herfray | Tractor geometry of asymptotically flat spacetimes | This match the version published in Annales Henri Poincar\'e (2022) | null | 10.1007/s00023-022-01174-0 | null | gr-qc math-ph math.DG math.MP | http://creativecommons.org/licenses/by-nc-sa/4.0/ | In a recent work it was shown that conformal Carroll geometries are
canonically equipped with a null-tractor bundle generalizing the tractor bundle
of conformal geometry. We here show that in the case of the conformal boundary
of an asymptotically flat spacetime of any dimension d>=3, this null-tractor
bundle over null infinity can be canonically derived from the interior
spacetime geometry. As was previously discussed, compatible normal connections
on the null-tractor bundle are not unique: We prove that they are in fact in
one-to-one correspondence with the germ of the asymptotically flat spacetimes
to leading order. In dimension d=3 the tractor connection invariantly encodes a
choice of mass and angular momentum aspect, in dimension d>=4 a choice of
asymptotic shear. In dimension d=4 the presence of tractor curvature correspond
to gravitational radiation. Even thought these results are by construction
geometrical and coordinate invariant, we give explicit expressions in BMS
coordinates for concreteness.
| [
{
"created": "Thu, 18 Mar 2021 17:40:54 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Mar 2021 16:21:05 GMT",
"version": "v2"
},
{
"created": "Thu, 18 Nov 2021 17:35:52 GMT",
"version": "v3"
},
{
"created": "Sat, 11 Jun 2022 12:26:36 GMT",
"version": "v4"
}
] | 2022-06-14 | [
[
"Herfray",
"Yannick",
""
]
] | In a recent work it was shown that conformal Carroll geometries are canonically equipped with a null-tractor bundle generalizing the tractor bundle of conformal geometry. We here show that in the case of the conformal boundary of an asymptotically flat spacetime of any dimension d>=3, this null-tractor bundle over null infinity can be canonically derived from the interior spacetime geometry. As was previously discussed, compatible normal connections on the null-tractor bundle are not unique: We prove that they are in fact in one-to-one correspondence with the germ of the asymptotically flat spacetimes to leading order. In dimension d=3 the tractor connection invariantly encodes a choice of mass and angular momentum aspect, in dimension d>=4 a choice of asymptotic shear. In dimension d=4 the presence of tractor curvature correspond to gravitational radiation. Even thought these results are by construction geometrical and coordinate invariant, we give explicit expressions in BMS coordinates for concreteness. |
2310.19183 | Andres Vargas-Sanchez Mr | Andr\'es F. Vargas and Andrew Melatos | Search for gravitational waves from Scorpius X-1 with a hidden Markov
model in O3 LIGO data with a corrected orbital ephemeris | 8 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Results are presented for a semi-coherent search for gravitational waves from
the low-mass X-ray binary Scorpius X-1 in Observing Run 3 (O3) data from the
Laser Interferometer Gravitational Wave Observatory, using an updated orbital
parameter ephemeris and a hidden Markov model (HMM) to allow for spin
wandering. The new orbital ephemeris corrects errors in previously published
orbital measurements and implies a new search domain. This search domain does
not overlap with the one used in the original Scorpius X-1 HMM O3 search. The
corrected domain is approximately three times smaller by area in the $T_{\rm
asc}$--$P$ plane than the original domain, where $T_{\rm asc}$ and $P$ denote
the time of passage through the ascending node and the orbital period
respectively, reducing the trials factor and computing time. No evidence is
found for gravitational radiation in the search band from 60 Hz to 500 Hz.
Upper limits are computed for the characteristic gravitational wave strain.
They are consistent with the values from the original Scorpius X-1 HMM O3
search.
| [
{
"created": "Sun, 29 Oct 2023 22:56:07 GMT",
"version": "v1"
}
] | 2023-10-31 | [
[
"Vargas",
"Andrés F.",
""
],
[
"Melatos",
"Andrew",
""
]
] | Results are presented for a semi-coherent search for gravitational waves from the low-mass X-ray binary Scorpius X-1 in Observing Run 3 (O3) data from the Laser Interferometer Gravitational Wave Observatory, using an updated orbital parameter ephemeris and a hidden Markov model (HMM) to allow for spin wandering. The new orbital ephemeris corrects errors in previously published orbital measurements and implies a new search domain. This search domain does not overlap with the one used in the original Scorpius X-1 HMM O3 search. The corrected domain is approximately three times smaller by area in the $T_{\rm asc}$--$P$ plane than the original domain, where $T_{\rm asc}$ and $P$ denote the time of passage through the ascending node and the orbital period respectively, reducing the trials factor and computing time. No evidence is found for gravitational radiation in the search band from 60 Hz to 500 Hz. Upper limits are computed for the characteristic gravitational wave strain. They are consistent with the values from the original Scorpius X-1 HMM O3 search. |
2010.01720 | Haret Rosu | H.C. Rosu, S.C. Mancas, C.-C. Hsieh | Superfluid Rayleigh-Plesset extension of FLRW cosmology | 13 pages, 11 figures with subfigures, new section with 2 figures and
new subsection added, published version | Annals of Physics 429 (2021) 168490 | 10.1016/j.aop.2021.168490 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Guided by the analogy with the Rayleigh-Plesset dynamics of multielectron
bubbles in superfluid He-4, we consider the cosmological FLRW evolution
equation with additional cubic and sixth powers of the inverse of the scale
factor of the universe. For the barotropic parameter w=2/3 (coasting universe),
along with zero cosmological constant in the absence of viscous terms, by using
the Sundman time as evolution parameter, we present parametric solutions for
the scale factor of the universe in terms of rational expressions of
Weierstrass elliptic functions and their particular cases thereof. For other
values of the equation of state parameter w, such as w=-1, but also the same
coasting case, we present a more standard discussion in the conformal time
variable using solutions obtained by numerical integration.
| [
{
"created": "Sun, 4 Oct 2020 23:47:12 GMT",
"version": "v1"
},
{
"created": "Sat, 24 Oct 2020 22:23:26 GMT",
"version": "v2"
},
{
"created": "Sun, 31 Jan 2021 03:53:29 GMT",
"version": "v3"
},
{
"created": "Tue, 18 May 2021 18:53:16 GMT",
"version": "v4"
}
] | 2021-05-20 | [
[
"Rosu",
"H. C.",
""
],
[
"Mancas",
"S. C.",
""
],
[
"Hsieh",
"C. -C.",
""
]
] | Guided by the analogy with the Rayleigh-Plesset dynamics of multielectron bubbles in superfluid He-4, we consider the cosmological FLRW evolution equation with additional cubic and sixth powers of the inverse of the scale factor of the universe. For the barotropic parameter w=2/3 (coasting universe), along with zero cosmological constant in the absence of viscous terms, by using the Sundman time as evolution parameter, we present parametric solutions for the scale factor of the universe in terms of rational expressions of Weierstrass elliptic functions and their particular cases thereof. For other values of the equation of state parameter w, such as w=-1, but also the same coasting case, we present a more standard discussion in the conformal time variable using solutions obtained by numerical integration. |
1609.02747 | Maciej Dunajski | Maciej Dunajski, Paul Tod | Non-diagonal four-dimensional cohomogeneity-one Einstein metrics in
various signatures | null | null | null | DAMTP-2016-67 | gr-qc hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Most known four-dimensional cohomogeneity-one Einstein metrics are diagonal
in the basis defined by the left-invariant one-forms, though some essentially
non-diagonal ones are known. We consider the problem of explicitly seeking
non-diagonal Einstein metrics, and we find solutions which in some cases
exhaust the possibilities. In particular we construct new examples of neutral
signature non--diagonal Bianchi type VIII Einstein metrics with self--dual Weyl
tensor.
| [
{
"created": "Fri, 9 Sep 2016 11:20:13 GMT",
"version": "v1"
}
] | 2016-09-15 | [
[
"Dunajski",
"Maciej",
""
],
[
"Tod",
"Paul",
""
]
] | Most known four-dimensional cohomogeneity-one Einstein metrics are diagonal in the basis defined by the left-invariant one-forms, though some essentially non-diagonal ones are known. We consider the problem of explicitly seeking non-diagonal Einstein metrics, and we find solutions which in some cases exhaust the possibilities. In particular we construct new examples of neutral signature non--diagonal Bianchi type VIII Einstein metrics with self--dual Weyl tensor. |
1907.07135 | Dinesh Chandra Maurya | Dinesh Chandra Maurya, Rashid Zia | Brans-Dicke Scalar Field Cosmological Model in Lyra's Geometry | 20 pages, 6 figures. arXiv admin note: substantial text overlap with
arXiv:1406.7636, arXiv:1710.09269, arXiv:1710.07281, arXiv:1203.0917 by other
authors | Phys. Rev. D, 100, 023503 (2019) | 10.1103/PhysRevD.100.023503 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have developed a new cosmological model in Einstein's
modified gravity theory using two types of modification.(i) Geometrical
modification, in which we have used Lyra's geometry in the left hand side of
the Einstein field equations (EFE) and (ii) Modification in gravity (energy
momentum tensor) on right hand side of EFE, as per Brans-Dicke (BD) model. With
these two modifications, we have investigated a spatially homogeneous and
anisotropic Bianchi type-I cosmological models of Einstein's Brans-Dicke theory
of gravitation in Lyra geometry. The model represents accelerating universe at
present and decelerating in past and is considered to be dominated by dark
energy. Gauge function $\beta$ and BD-scalar field $\phi$ are considered as a
candidate for the dark energy and is responsible for the present acceleration.
The derived model agrees at par with the recent supernovae (SN Ia)
observations. We have set BD-coupling constant $\omega$ to be greater than
40000, seeing the solar system tests and evidences. We have discussed the
various physical and geometrical properties of the models and have compared
them with the corresponding relativistic models.
| [
{
"created": "Sun, 14 Jul 2019 17:07:27 GMT",
"version": "v1"
}
] | 2019-07-17 | [
[
"Maurya",
"Dinesh Chandra",
""
],
[
"Zia",
"Rashid",
""
]
] | In this paper, we have developed a new cosmological model in Einstein's modified gravity theory using two types of modification.(i) Geometrical modification, in which we have used Lyra's geometry in the left hand side of the Einstein field equations (EFE) and (ii) Modification in gravity (energy momentum tensor) on right hand side of EFE, as per Brans-Dicke (BD) model. With these two modifications, we have investigated a spatially homogeneous and anisotropic Bianchi type-I cosmological models of Einstein's Brans-Dicke theory of gravitation in Lyra geometry. The model represents accelerating universe at present and decelerating in past and is considered to be dominated by dark energy. Gauge function $\beta$ and BD-scalar field $\phi$ are considered as a candidate for the dark energy and is responsible for the present acceleration. The derived model agrees at par with the recent supernovae (SN Ia) observations. We have set BD-coupling constant $\omega$ to be greater than 40000, seeing the solar system tests and evidences. We have discussed the various physical and geometrical properties of the models and have compared them with the corresponding relativistic models. |
2103.02389 | Mariem Magdy Ali Mohamed | Mariem M. Ali Mohamed, Juan A. Valiente Kroon | A comparison of Ashtekar's and Friedrich's formalisms of spatial
infinity | 33 pages, 4 figures | null | 10.1088/1361-6382/ac1208 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Penrose's idea of asymptotic flatness provides a framework for understanding
the asymptotic structure of gravitational fields of isolated systems at null
infinity. However, the studies of the asymptotic behaviour of fields near
spatial infinity are more challenging due to the singular nature of spatial
infinity in a regular point compactification for spacetimes with non-vanishing
ADM mass. Two different frameworks that address this challenge are Friedrich's
cylinder at spatial infinity and Ashtekar's definition of asymptotically
Minkowskian spacetimes at spatial infinity that give rise to the 3-dimensional
asymptote at spatial infinity $\mathcal{H}$. Both frameworks address the
singularity at spatial infinity although the link between the two approaches
had not been investigated in the literature. This article aims to show the
relation between Friedrich's cylinder and the asymptote as spatial infinity. To
do so, we initially consider this relation for Minkowski spacetime. It can be
shown that the solution to the conformal geodesic equations provides a
conformal factor that links the cylinder and the asymptote. For general
spacetimes satisfying Ashtekar's definition, the conformal factor cannot be
determined explicitly. However, proof of the existence of this conformal factor
is provided in this article. Additionally, the conditions satisfied by physical
fields on the asymptote $\mathcal{H}$ are derived systematically using the
conformal constraint equations. Finally, it is shown that a solution to the
conformal geodesic equations on the asymptote can be extended to a small
neighbourhood of spatial infinity by making use of the stability theorem for
ordinary differential equations. This solution can be used to construct a
conformal Gaussian system in a neighbourhood of $\mathcal{H}$.
| [
{
"created": "Wed, 3 Mar 2021 13:28:39 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Jun 2021 15:53:43 GMT",
"version": "v2"
},
{
"created": "Sat, 19 Aug 2023 10:50:26 GMT",
"version": "v3"
}
] | 2023-08-22 | [
[
"Mohamed",
"Mariem M. Ali",
""
],
[
"Kroon",
"Juan A. Valiente",
""
]
] | Penrose's idea of asymptotic flatness provides a framework for understanding the asymptotic structure of gravitational fields of isolated systems at null infinity. However, the studies of the asymptotic behaviour of fields near spatial infinity are more challenging due to the singular nature of spatial infinity in a regular point compactification for spacetimes with non-vanishing ADM mass. Two different frameworks that address this challenge are Friedrich's cylinder at spatial infinity and Ashtekar's definition of asymptotically Minkowskian spacetimes at spatial infinity that give rise to the 3-dimensional asymptote at spatial infinity $\mathcal{H}$. Both frameworks address the singularity at spatial infinity although the link between the two approaches had not been investigated in the literature. This article aims to show the relation between Friedrich's cylinder and the asymptote as spatial infinity. To do so, we initially consider this relation for Minkowski spacetime. It can be shown that the solution to the conformal geodesic equations provides a conformal factor that links the cylinder and the asymptote. For general spacetimes satisfying Ashtekar's definition, the conformal factor cannot be determined explicitly. However, proof of the existence of this conformal factor is provided in this article. Additionally, the conditions satisfied by physical fields on the asymptote $\mathcal{H}$ are derived systematically using the conformal constraint equations. Finally, it is shown that a solution to the conformal geodesic equations on the asymptote can be extended to a small neighbourhood of spatial infinity by making use of the stability theorem for ordinary differential equations. This solution can be used to construct a conformal Gaussian system in a neighbourhood of $\mathcal{H}$. |
gr-qc/0008050 | Christodoulakis Theodosios | T. Christodoulakis, G. Kofinas, E. Korfiatis, G.O. Papadopoulos and A.
Paschos | Time-Dependent Automorphism Inducing Diffeomorphisms In Vacuum Bianchi
Cosmologies And The Complete Closed Form Solutions For Type II & V | 60 pages, Typeset using Latex2e, no figures, 1 table | J.Math.Phys.42:3580-3608,2001 | 10.1063/1.1386637 | null | gr-qc math-ph math.DG math.MP | null | We investigate the set of spacetime general coordinate transformations
(G.C.T.) which leave the line element of a generic Bianchi Type Geometry,
quasi-form invariant; i.e. preserve manifest spatial Homogeneity. We find that
these G.C.T.'s, induce special time-dependent automorphic changes, on the
spatial scale factor matrix $\gamma_{\alpha\beta}(t)$ -along with corresponding
changes on the lapse function $N(t)$ and the shift vector $N^{\alpha}(t)$.
These changes, which are Bianchi Type dependent, form a group and are, in
general, different from those induced by the group SAut(G) -advocated in
earlier investigations as the relevant symmetry group-, they are used to
simplify the form of the line element -and thus simplify Einstein's equations
as well-, without losing generality.
As far as this simplification procedure is concerned, the transformations
found, are proved to be essentialy unique. For the case of Bianchi Types II and
V, where the most general solutions are known -Taub's and Joseph's,
respectively-, it is explicitly verified that our transformations and only
those, suffice to reduce the generic line element, to the previously known
forms. It becomes thus possible, -for these Types- to give in closed form, the
most general solution, containing all the necessary ``gauge'' freedom.
| [
{
"created": "Mon, 21 Aug 2000 10:53:08 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Aug 2000 07:59:12 GMT",
"version": "v2"
},
{
"created": "Thu, 1 Mar 2001 14:45:10 GMT",
"version": "v3"
},
{
"created": "Mon, 5 Mar 2001 12:05:30 GMT",
"version": "v4"
},
{
"created": "Tue, 22 May 2001 12:57:55 GMT",
"version": "v5"
}
] | 2009-10-09 | [
[
"Christodoulakis",
"T.",
""
],
[
"Kofinas",
"G.",
""
],
[
"Korfiatis",
"E.",
""
],
[
"Papadopoulos",
"G. O.",
""
],
[
"Paschos",
"A.",
""
]
] | We investigate the set of spacetime general coordinate transformations (G.C.T.) which leave the line element of a generic Bianchi Type Geometry, quasi-form invariant; i.e. preserve manifest spatial Homogeneity. We find that these G.C.T.'s, induce special time-dependent automorphic changes, on the spatial scale factor matrix $\gamma_{\alpha\beta}(t)$ -along with corresponding changes on the lapse function $N(t)$ and the shift vector $N^{\alpha}(t)$. These changes, which are Bianchi Type dependent, form a group and are, in general, different from those induced by the group SAut(G) -advocated in earlier investigations as the relevant symmetry group-, they are used to simplify the form of the line element -and thus simplify Einstein's equations as well-, without losing generality. As far as this simplification procedure is concerned, the transformations found, are proved to be essentialy unique. For the case of Bianchi Types II and V, where the most general solutions are known -Taub's and Joseph's, respectively-, it is explicitly verified that our transformations and only those, suffice to reduce the generic line element, to the previously known forms. It becomes thus possible, -for these Types- to give in closed form, the most general solution, containing all the necessary ``gauge'' freedom. |
2010.09064 | Alexander Zhidenko | R. A. Konoplya and A. Zhidenko | Massive particles in the Einstein-Lovelock-anti-de Sitter black hole
spacetime | 6 pages (revtex), 1 figure | Class. Quantum Grav. 38: 045015 (2021) | 10.1088/1361-6382/abd302 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An interpretation to the physics of stable geodesics of massive particles in
black hole backgrounds has been recently proposed in the context of the AdS/CFT
correspondence. It was argued that the existence of stable orbits indicates
that the dual state does not thermalize on a thermal time scale and the bulk
excitations can be interpreted as metastable states in the dual field theory.
Here we study motion of massive particles in the background of the
D-dimensional asymptotically anti-de Sitter (AdS) black holes in the
Einstein-Lovelock theory. We show that, unlike the asymptotically flat case,
for any kind of higher curvature Lovelock corrections there appear a stable
circular orbit at a distance from the black hole. We find the general
analytical expressions for the frequencies of distant circular orbits and
radial oscillation frequencies. We show that the corresponding correction has
the same power as in the Schwarzschild-AdS case, implying a universal scaling
with the temperature for any Lovelock theory.
| [
{
"created": "Sun, 18 Oct 2020 18:51:37 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Dec 2020 22:47:13 GMT",
"version": "v2"
}
] | 2020-12-29 | [
[
"Konoplya",
"R. A.",
""
],
[
"Zhidenko",
"A.",
""
]
] | An interpretation to the physics of stable geodesics of massive particles in black hole backgrounds has been recently proposed in the context of the AdS/CFT correspondence. It was argued that the existence of stable orbits indicates that the dual state does not thermalize on a thermal time scale and the bulk excitations can be interpreted as metastable states in the dual field theory. Here we study motion of massive particles in the background of the D-dimensional asymptotically anti-de Sitter (AdS) black holes in the Einstein-Lovelock theory. We show that, unlike the asymptotically flat case, for any kind of higher curvature Lovelock corrections there appear a stable circular orbit at a distance from the black hole. We find the general analytical expressions for the frequencies of distant circular orbits and radial oscillation frequencies. We show that the corresponding correction has the same power as in the Schwarzschild-AdS case, implying a universal scaling with the temperature for any Lovelock theory. |
gr-qc/0111053 | Pankaj S. Joshi | S. S. Deshingkar, P. S. Joshi and I. H. Dwivedi | Appearance of the central singularity in spherical collapse | 25 pages, 6 figures | Phys.Rev. D65 (2002) 084009 | 10.1103/PhysRevD.65.084009 | null | gr-qc | null | We analyze here the structure of non-radial nonspacelike geodesics
terminating in the past at a naked singularity formed as the end state of
inhomogeneous dust collapse. The spectrum of outgoing nonspacelike null
geodesics is examined analytically. The local and global visibility of the
singularity is also examined by integrating numerically the null geodesics
equations. The possible implications of existence of such families towards the
appearance of the star in late stages of gravitational collapse are considered.
It is seen that the outgoing non-radial geodesics give an appearance to the
naked central singularity as that of an expanding ball whose radius reaches a
maximum before the star goes within its apparent horizon. The radiated energy
(along the null geodesics) is shown to decay very sharply in the neighbourhood
of the singularity. Thus the total energy escaping via non-radial null
geodesics from the naked central singularity vanishes in the scenario
considered here.
| [
{
"created": "Fri, 16 Nov 2001 17:36:37 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Deshingkar",
"S. S.",
""
],
[
"Joshi",
"P. S.",
""
],
[
"Dwivedi",
"I. H.",
""
]
] | We analyze here the structure of non-radial nonspacelike geodesics terminating in the past at a naked singularity formed as the end state of inhomogeneous dust collapse. The spectrum of outgoing nonspacelike null geodesics is examined analytically. The local and global visibility of the singularity is also examined by integrating numerically the null geodesics equations. The possible implications of existence of such families towards the appearance of the star in late stages of gravitational collapse are considered. It is seen that the outgoing non-radial geodesics give an appearance to the naked central singularity as that of an expanding ball whose radius reaches a maximum before the star goes within its apparent horizon. The radiated energy (along the null geodesics) is shown to decay very sharply in the neighbourhood of the singularity. Thus the total energy escaping via non-radial null geodesics from the naked central singularity vanishes in the scenario considered here. |
gr-qc/0406086 | Valery Kiselev | V.V.Kiselev | Ghost condensate model of flat rotation curves | 4 pages, RevTeX4 file, references and clarifying footnotes added | null | null | null | gr-qc astro-ph hep-ph | null | An effective action of ghost condensate with higher derivatives creates a
source of gravity and mimics a dark matter in spiral galaxies. We present a
spherically symmetric static solution of Einstein--Hilbert equations with the
ghost condensate at large distances, where flat rotation curves are reproduced
in leading order over small ratio of two energy scales characterizing constant
temporal and spatial derivatives of ghost field: mu_*^2 and mu_\star^2,
respectively, with a hierarchy mu_\star\ll \mu_*. We assume that a mechanism of
hierarchy is provided by a global monopole in the center of galaxy. An estimate
based on the solution and observed velocities of rotations in the asymptotic
region of flatness, gives mu_* ~ 10^{19} GeV and the monopole scale in a GUT
range mu_\star ~ 10^{16} GeV, while a velocity of rotation v_0 is determined by
the ratio: sqrt{2} v_0^2= mu_\star^2/mu_*^2. A critical acceleration is
introduced and naturally evaluated of the order of Hubble rate, that represents
the Milgrom's acceleration.
| [
{
"created": "Tue, 22 Jun 2004 07:11:29 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Jul 2004 12:16:31 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Kiselev",
"V. V.",
""
]
] | An effective action of ghost condensate with higher derivatives creates a source of gravity and mimics a dark matter in spiral galaxies. We present a spherically symmetric static solution of Einstein--Hilbert equations with the ghost condensate at large distances, where flat rotation curves are reproduced in leading order over small ratio of two energy scales characterizing constant temporal and spatial derivatives of ghost field: mu_*^2 and mu_\star^2, respectively, with a hierarchy mu_\star\ll \mu_*. We assume that a mechanism of hierarchy is provided by a global monopole in the center of galaxy. An estimate based on the solution and observed velocities of rotations in the asymptotic region of flatness, gives mu_* ~ 10^{19} GeV and the monopole scale in a GUT range mu_\star ~ 10^{16} GeV, while a velocity of rotation v_0 is determined by the ratio: sqrt{2} v_0^2= mu_\star^2/mu_*^2. A critical acceleration is introduced and naturally evaluated of the order of Hubble rate, that represents the Milgrom's acceleration. |
gr-qc/0506140 | Albert V. Minkevich | A. V. Minkevich | Gauge Approach to Gravitation and Regular Big Bang Theory | 11 pages, 8 figures. Some misprints are corrected, minor addition is
made | Grav.Cosmol. 12 (2006) 11-20 | null | null | gr-qc | null | Field theoretical scheme of regular Big Bang in 4-dimensional physical
space-time, built in the framework of gauge approach to gravitation, is
discussed. Regular bouncing character of homogeneous isotropic cosmological
models is ensured by gravitational repulsion effect at extreme conditions
without quantum gravitational corrections. The most general properties of
regular inflationary cosmological models are examined. Developing theory is
valid, if energy density of gravitating matter is positive and energy dominance
condition is fulfilled.
| [
{
"created": "Thu, 30 Jun 2005 07:44:55 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Aug 2005 08:56:19 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Minkevich",
"A. V.",
""
]
] | Field theoretical scheme of regular Big Bang in 4-dimensional physical space-time, built in the framework of gauge approach to gravitation, is discussed. Regular bouncing character of homogeneous isotropic cosmological models is ensured by gravitational repulsion effect at extreme conditions without quantum gravitational corrections. The most general properties of regular inflationary cosmological models are examined. Developing theory is valid, if energy density of gravitating matter is positive and energy dominance condition is fulfilled. |
0710.5542 | Carlos O. Lousto | Carlos O. Lousto and Hiroyuki Nakano (RIT) | Three-body equations of motion in successive post-Newtonian
approximations | 8 pages, 9 figures | Class.Quant.Grav.25:195019,2008 | 10.1088/0264-9381/25/19/195019 | null | gr-qc astro-ph | null | There are periodic solutions to the equal-mass three-body (and N-body)
problem in Newtonian gravity. The figure-eight solution is one of them. In this
paper, we discuss its solution in the first and second post-Newtonian
approximations to General Relativity. To do so we derive the canonical
equations of motion in the ADM gauge from the three-body Hamiltonian. We then
integrate those equations numerically, showing that quantities such as the
energy, linear and angular momenta are conserved down to numerical error. We
also study the scaling of the initial parameters with the physical size of the
triple system. In this way we can assess when general relativistic results are
important and we determine that this occur for distances of the order of 100M,
with M the total mass of the system. For distances much closer than those,
presumably the system would completely collapse due to gravitational radiation.
This sets up a natural cut-off to Newtonian N-body simulations. The method can
also be used to dynamically provide initial parameters for subsequent full
nonlinear numerical simulations.
| [
{
"created": "Mon, 29 Oct 2007 21:51:52 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Lousto",
"Carlos O.",
"",
"RIT"
],
[
"Nakano",
"Hiroyuki",
"",
"RIT"
]
] | There are periodic solutions to the equal-mass three-body (and N-body) problem in Newtonian gravity. The figure-eight solution is one of them. In this paper, we discuss its solution in the first and second post-Newtonian approximations to General Relativity. To do so we derive the canonical equations of motion in the ADM gauge from the three-body Hamiltonian. We then integrate those equations numerically, showing that quantities such as the energy, linear and angular momenta are conserved down to numerical error. We also study the scaling of the initial parameters with the physical size of the triple system. In this way we can assess when general relativistic results are important and we determine that this occur for distances of the order of 100M, with M the total mass of the system. For distances much closer than those, presumably the system would completely collapse due to gravitational radiation. This sets up a natural cut-off to Newtonian N-body simulations. The method can also be used to dynamically provide initial parameters for subsequent full nonlinear numerical simulations. |
1812.10996 | Pietro Don\`a | Eugenio Bianchi, Pietro Dona, Ilya Vilensky | Entanglement entropy of Bell-network states in LQG: Analytical and
numerical results | 26 pages, 5 figures. The code is available at the link
https://bitbucket.org/pietrodona/bellnetworkentropy. Updated to match the
published version | Phys. Rev. D 99, 086013 (2019) | 10.1103/PhysRevD.99.086013 | IGC-18/12-1 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Bell-network states are loop-quantum-gravity states that glue quantum
polyhedra with entanglement. We present an algorithm and a code that evaluates
the reduced density matrix of a Bell-network state and computes its
entanglement entropy. In particular, we use our code for simple graphs to study
properties of Bell-network states and to show that they are non-typical in the
Hilbert space. Moreover, we investigate analytically Bell-network states on
arbitrary finite graphs. We develop methods to compute the R\'enyi entropy of
order p for a restriction of the state to an arbitrary region. In the uniform
large-spin regime, we determine bounds on the entanglement entropy and show
that it obeys an area law. Finally, we discuss the implications of our results
for correlations of geometric observables.
| [
{
"created": "Fri, 28 Dec 2018 14:04:41 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Apr 2019 18:51:34 GMT",
"version": "v2"
}
] | 2019-04-24 | [
[
"Bianchi",
"Eugenio",
""
],
[
"Dona",
"Pietro",
""
],
[
"Vilensky",
"Ilya",
""
]
] | Bell-network states are loop-quantum-gravity states that glue quantum polyhedra with entanglement. We present an algorithm and a code that evaluates the reduced density matrix of a Bell-network state and computes its entanglement entropy. In particular, we use our code for simple graphs to study properties of Bell-network states and to show that they are non-typical in the Hilbert space. Moreover, we investigate analytically Bell-network states on arbitrary finite graphs. We develop methods to compute the R\'enyi entropy of order p for a restriction of the state to an arbitrary region. In the uniform large-spin regime, we determine bounds on the entanglement entropy and show that it obeys an area law. Finally, we discuss the implications of our results for correlations of geometric observables. |
2003.02281 | Matthew Mould | Matthew Mould, Davide Gerosa | Endpoint of the up-down instability in precessing binary black holes | Animated versions of Figs. 2, 7 and 13 are available at
https://davidegerosa.com/spinprecession | Phys. Rev. D 101, 124037 (2020) | 10.1103/PhysRevD.101.124037 | null | gr-qc astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Binary black holes in which both spins are aligned with the binary's orbital
angular momentum do not precess. However, the up-down configuration, in which
the spin of the heavier (lighter) black hole is aligned (anti-aligned) with the
orbital angular momentum, is unstable to spin precession at small orbital
separations. We first cast the spin precession problem in terms of a simple
harmonic oscillator and provide a cleaner derivation of the instability onset.
Surprisingly, we find that following the instability, up-down binaries do not
disperse in the available parameter space but evolve toward precise endpoints.
We then present an analytic scheme to locate these final configurations and
confirm them with numerical integrations. Namely, unstable up-down binaries
approach mergers with the two spins coaligned with each other and equally
misaligned with the orbital angular momentum. Merging up-down binaries relevant
to LIGO/Virgo and LISA may be detected in these endpoint configurations if the
instability onset occurs prior to the sensitivity threshold of the detector. As
a by-product, we obtain new generic results on binary black hole spin-orbit
resonances at 2nd~post-Newtonian order. We finally apply these findings to a
simple astrophysical population of binary black holes where a formation
mechanism aligns the spins without preference for co- or counteralignment, as
might be the case for stellar-mass black holes embedded in the accretion disk
of a supermassive black hole.
| [
{
"created": "Wed, 4 Mar 2020 19:00:06 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Jun 2020 10:48:28 GMT",
"version": "v2"
}
] | 2020-06-22 | [
[
"Mould",
"Matthew",
""
],
[
"Gerosa",
"Davide",
""
]
] | Binary black holes in which both spins are aligned with the binary's orbital angular momentum do not precess. However, the up-down configuration, in which the spin of the heavier (lighter) black hole is aligned (anti-aligned) with the orbital angular momentum, is unstable to spin precession at small orbital separations. We first cast the spin precession problem in terms of a simple harmonic oscillator and provide a cleaner derivation of the instability onset. Surprisingly, we find that following the instability, up-down binaries do not disperse in the available parameter space but evolve toward precise endpoints. We then present an analytic scheme to locate these final configurations and confirm them with numerical integrations. Namely, unstable up-down binaries approach mergers with the two spins coaligned with each other and equally misaligned with the orbital angular momentum. Merging up-down binaries relevant to LIGO/Virgo and LISA may be detected in these endpoint configurations if the instability onset occurs prior to the sensitivity threshold of the detector. As a by-product, we obtain new generic results on binary black hole spin-orbit resonances at 2nd~post-Newtonian order. We finally apply these findings to a simple astrophysical population of binary black holes where a formation mechanism aligns the spins without preference for co- or counteralignment, as might be the case for stellar-mass black holes embedded in the accretion disk of a supermassive black hole. |
2106.00558 | Samuele Marco Silveravalle | Alfio Bonanno and Samuele Silveravalle | The gravitational field of a star in quadratic gravity | 18 pages, 7 figures, 1 table | JCAP 08 (2021) 050 | 10.1088/1475-7516/2021/08/050 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The characterization of the gravitational field of isolated objects is still
an open question in quadratic theories of gravity. We study static equilibrium
solutions for a self-gravitating fluid in extensions of General Relativity
including terms quadratic in the Weyl tensor $C_{\mu\nu\rho\sigma}$ and in the
Ricci scalar $R$, as suggested by one-loop corrections to classical gravity. By
the means of a shooting method procedure we link the total gravitational mass
and the strength of the Yukawa corrections associated with the quadratic terms
with the fluid properties at the center. It is shown that the inclusion of the
$C_{\mu\nu\rho\sigma}C^{\mu\nu\rho\sigma}$ coupling in the lagrangian has a
much stronger impact than the $R^2$ correction in the determination of the
radius and of the maximum mass of a compact object. We also suggest that the
ambiguity in the definition of mass in quadratic gravity theories can
conveniently be exploited to detect deviations from standard General
Relativity.
| [
{
"created": "Tue, 1 Jun 2021 15:18:09 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Jul 2021 12:29:40 GMT",
"version": "v2"
}
] | 2021-08-26 | [
[
"Bonanno",
"Alfio",
""
],
[
"Silveravalle",
"Samuele",
""
]
] | The characterization of the gravitational field of isolated objects is still an open question in quadratic theories of gravity. We study static equilibrium solutions for a self-gravitating fluid in extensions of General Relativity including terms quadratic in the Weyl tensor $C_{\mu\nu\rho\sigma}$ and in the Ricci scalar $R$, as suggested by one-loop corrections to classical gravity. By the means of a shooting method procedure we link the total gravitational mass and the strength of the Yukawa corrections associated with the quadratic terms with the fluid properties at the center. It is shown that the inclusion of the $C_{\mu\nu\rho\sigma}C^{\mu\nu\rho\sigma}$ coupling in the lagrangian has a much stronger impact than the $R^2$ correction in the determination of the radius and of the maximum mass of a compact object. We also suggest that the ambiguity in the definition of mass in quadratic gravity theories can conveniently be exploited to detect deviations from standard General Relativity. |
2307.12541 | Carla Cederbaum | Carla Cederbaum and Melanie Graf | Coordinates are messy -- not only in General Relativity | This article will appear in Gravity, Cosmology, and Astrophysics -- A
Journey of Exploration and Discovery with Female Pioneers (editors Betti
Hartmann, Jutta Kunz), Springer 2023,
https://link.springer.com/book/9783031420979 | null | null | null | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The coordinate freedom of General Relativity makes it challenging to find
mathematically rigorous and physically sound definitions for physical
quantities such as the center of mass of an isolated gravitating system. We
will argue that a similar phenomenon occurs in Newtonian Gravity once one
ahistorically drops the restriction that one should only work in Cartesian
coordinates when studying Newtonian Gravity. This will also shed light on the
nature of the challenge of defining the center of mass in General Relativity.
Relatedly, we will give explicit examples of asymptotically Euclidean
relativistic initial data sets which do not satisfy the Regge--Teitelboim
parity conditions often used to achieve a satisfactory definition of center of
mass. These originate in our joint work with Jan Metzger. This will require
appealing to Bartnik's asymptotic harmonic coordinates.
| [
{
"created": "Mon, 24 Jul 2023 06:09:27 GMT",
"version": "v1"
}
] | 2023-07-25 | [
[
"Cederbaum",
"Carla",
""
],
[
"Graf",
"Melanie",
""
]
] | The coordinate freedom of General Relativity makes it challenging to find mathematically rigorous and physically sound definitions for physical quantities such as the center of mass of an isolated gravitating system. We will argue that a similar phenomenon occurs in Newtonian Gravity once one ahistorically drops the restriction that one should only work in Cartesian coordinates when studying Newtonian Gravity. This will also shed light on the nature of the challenge of defining the center of mass in General Relativity. Relatedly, we will give explicit examples of asymptotically Euclidean relativistic initial data sets which do not satisfy the Regge--Teitelboim parity conditions often used to achieve a satisfactory definition of center of mass. These originate in our joint work with Jan Metzger. This will require appealing to Bartnik's asymptotic harmonic coordinates. |
1801.08473 | Maur\'icio Richartz | Sam Patrick, Antonin Coutant, Mauricio Richartz, Silke Weinfurtner | Black hole quasibound states from a draining bathtub vortex flow | Published as Editors' Suggestion in Physical Review Letters. v2: 10
pages, 4 figures, 1 table | Phys. Rev. Lett. 121, 061101 (2018) | 10.1103/PhysRevLett.121.061101 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quasinormal modes are a set of damped resonances that describe how an excited
open system is driven back to equilibrium. In gravitational physics these modes
characterise the ringdown of a perturbed black hole, e.g. following a binary
black hole merger. A careful analysis of the ringdown spectrum reveals the
properties of the black hole, such as its angular momentum and mass. In more
complex gravitational systems the spectrum might depend on more parameters, and
hence allows us to search for new physics. In this letter we present a
hydrodynamic analogue of a rotating black hole, that illustrates how the
presence of extra structure affects the quasinormal mode spectrum. The analogy
is obtained by considering wave scattering on a draining bathtub vortex flow.
We show that due to vorticity of the background flow, the resulting field
theory corresponds to a scalar field on an effective curved spacetime which
acquires a local mass in the vortex core. The obtained quasinormal mode
spectrum exhibits long-lived trapped modes, commonly known as quasibound
states. Our findings can be tested in future experiments, building up on recent
successful implementations of analogue rotating black holes.
| [
{
"created": "Thu, 25 Jan 2018 16:25:55 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Aug 2018 19:12:05 GMT",
"version": "v2"
}
] | 2018-08-09 | [
[
"Patrick",
"Sam",
""
],
[
"Coutant",
"Antonin",
""
],
[
"Richartz",
"Mauricio",
""
],
[
"Weinfurtner",
"Silke",
""
]
] | Quasinormal modes are a set of damped resonances that describe how an excited open system is driven back to equilibrium. In gravitational physics these modes characterise the ringdown of a perturbed black hole, e.g. following a binary black hole merger. A careful analysis of the ringdown spectrum reveals the properties of the black hole, such as its angular momentum and mass. In more complex gravitational systems the spectrum might depend on more parameters, and hence allows us to search for new physics. In this letter we present a hydrodynamic analogue of a rotating black hole, that illustrates how the presence of extra structure affects the quasinormal mode spectrum. The analogy is obtained by considering wave scattering on a draining bathtub vortex flow. We show that due to vorticity of the background flow, the resulting field theory corresponds to a scalar field on an effective curved spacetime which acquires a local mass in the vortex core. The obtained quasinormal mode spectrum exhibits long-lived trapped modes, commonly known as quasibound states. Our findings can be tested in future experiments, building up on recent successful implementations of analogue rotating black holes. |
1204.4593 | Nicola Tamanini | Nicola Tamanini and Christian G. Boehmer | Good and bad tetrads in f(T) gravity | 25 pages | Physical Review D86 (2012) 044009 | 10.1103/PhysRevD.86.044009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the importance of choosing good tetrads for the study of the
field equations of $f(T)$ gravity. It is well known that this theory is not
invariant under local Lorentz transformations, and therefore the choice of
tetrad plays a crucial role in such models. Different tetrads will lead to
different field equations which in turn have different solutions. We suggest to
speak of a good tetrad if it imposes no restrictions on the form of $f(T)$.
Employing local rotations, we construct good tetrads in the context of
homogeneity and isotropy, and spherical symmetry, where we show how to find
Schwarzschild-de Sitter solutions in vacuum. Our principal approach should be
applicable to other symmetries as well.
| [
{
"created": "Fri, 20 Apr 2012 11:59:38 GMT",
"version": "v1"
}
] | 2012-11-13 | [
[
"Tamanini",
"Nicola",
""
],
[
"Boehmer",
"Christian G.",
""
]
] | We investigate the importance of choosing good tetrads for the study of the field equations of $f(T)$ gravity. It is well known that this theory is not invariant under local Lorentz transformations, and therefore the choice of tetrad plays a crucial role in such models. Different tetrads will lead to different field equations which in turn have different solutions. We suggest to speak of a good tetrad if it imposes no restrictions on the form of $f(T)$. Employing local rotations, we construct good tetrads in the context of homogeneity and isotropy, and spherical symmetry, where we show how to find Schwarzschild-de Sitter solutions in vacuum. Our principal approach should be applicable to other symmetries as well. |
2207.01467 | Benrong Mu | Siyuan Hui, Benrong Mu and Jun Tao | Joule-Thomson expansion of the lower-dimensional black hole in rainbow
gravity | 14 pages, 7 figures, 2 tables | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we extend Joule-Thomson expansion to the low-dimensional
regime in rainbow gravity by considering the rainbow rotating BTZ metric in the
(2+1)-dimensional spacetime. After the metric of the black hole is obtained, we
get the Joule-Thomson expansion of the black hole, including the Joule-Thomson
coefficient, inversion curves, and isenthalpic curves. We find that a rainbow
rotating BTZ black hole does not have $P-V$ critical behavior. The effects of
rainbow gravity are to slow down the trend of the increase of the Joule-Thomson
coefficient and make its zero point larger. Moreover, the rainbow gravity slows
down the inverse temperature of the black hole, meaning that a rainbow rotating
BTZ black hole tends to change its heating or cooling action at a lower
temperature, which can be attributed to the topology of the black hole.
| [
{
"created": "Mon, 4 Jul 2022 14:55:18 GMT",
"version": "v1"
}
] | 2022-07-05 | [
[
"Hui",
"Siyuan",
""
],
[
"Mu",
"Benrong",
""
],
[
"Tao",
"Jun",
""
]
] | In this paper, we extend Joule-Thomson expansion to the low-dimensional regime in rainbow gravity by considering the rainbow rotating BTZ metric in the (2+1)-dimensional spacetime. After the metric of the black hole is obtained, we get the Joule-Thomson expansion of the black hole, including the Joule-Thomson coefficient, inversion curves, and isenthalpic curves. We find that a rainbow rotating BTZ black hole does not have $P-V$ critical behavior. The effects of rainbow gravity are to slow down the trend of the increase of the Joule-Thomson coefficient and make its zero point larger. Moreover, the rainbow gravity slows down the inverse temperature of the black hole, meaning that a rainbow rotating BTZ black hole tends to change its heating or cooling action at a lower temperature, which can be attributed to the topology of the black hole. |
2208.13956 | Abdallah Al Zahrani M. | A. M. Al Zahrani | Circular orbits of Charged Particles around a Weakly Charged and
Magnetized Schwarzschild Black Hole | null | null | 10.1103/PhysRevD.103.084008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the circular orbits of charged particles around a weakly charged
Schwarzschild black hole immersed in a weak, axisymmetric magnetic field. We
start by reviewing the circular orbits of neutral particles and charged
particles around only weakly charged and only weakly magnetized black holes.
The case of a weakly magnetized and charged black hole is investigated then. In
particular, we study the effect of the electromagnetic forces on the charged
particles innermost stable circular orbits. We show that negative energy stable
circular orbits are possible and that two bands of charged particles circular
orbits, separated by a gap of no stable circular orbits can exist. The
astrophysical aspects of our findings are discussed too.
| [
{
"created": "Tue, 30 Aug 2022 02:12:34 GMT",
"version": "v1"
}
] | 2022-08-31 | [
[
"Zahrani",
"A. M. Al",
""
]
] | We study the circular orbits of charged particles around a weakly charged Schwarzschild black hole immersed in a weak, axisymmetric magnetic field. We start by reviewing the circular orbits of neutral particles and charged particles around only weakly charged and only weakly magnetized black holes. The case of a weakly magnetized and charged black hole is investigated then. In particular, we study the effect of the electromagnetic forces on the charged particles innermost stable circular orbits. We show that negative energy stable circular orbits are possible and that two bands of charged particles circular orbits, separated by a gap of no stable circular orbits can exist. The astrophysical aspects of our findings are discussed too. |
0707.0635 | E. Canessa | E. Canessa | Possible Connection between Probability, Spacetime Geometry and Quantum
Mechanics | in press | PhysicaA385:185-190,2007 | 10.1016/j.physa.2007.06.006 | null | gr-qc cond-mat.other quant-ph | null | Following our discussion [Physica A, 375 (2007) 123] to associate an
analogous probabilistic description with spacetime geometry in the
Schwarzschild metric from the macro- to the micro-domain, we argue that there
is a possible connection among normalized probabilities, spacetime geometry (in
the form of Schwarzschild radii) and quantum mechanics (in the form of complex
wave functions). We show how this association along different (n)-nested
surfaces --representing curve space due to an inhomogeneous density of matter--
preserves the postulates of quantum mechanics at different geometrical scales.
| [
{
"created": "Wed, 4 Jul 2007 15:26:17 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Canessa",
"E.",
""
]
] | Following our discussion [Physica A, 375 (2007) 123] to associate an analogous probabilistic description with spacetime geometry in the Schwarzschild metric from the macro- to the micro-domain, we argue that there is a possible connection among normalized probabilities, spacetime geometry (in the form of Schwarzschild radii) and quantum mechanics (in the form of complex wave functions). We show how this association along different (n)-nested surfaces --representing curve space due to an inhomogeneous density of matter-- preserves the postulates of quantum mechanics at different geometrical scales. |
1801.03208 | Emanuele Berti | Emanuele Berti, Kent Yagi, Nicol\'as Yunes | Extreme Gravity Tests with Gravitational Waves from Compact Binary
Coalescences: (I) Inspiral-Merger | 46 pages, 4 figures, 4 tables. Review paper to appear in the General
Relativity and Gravitation (GRG) Topical Collection "Testing the Kerr
spacetime with gravitational-wave and electromagnetic observations" (Guest
Editor: Emanuele Berti). Added two figures and some references. Matches
version published in GRG and selected as "Editor's Choice" | null | 10.1007/s10714-018-2362-8 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The observation of the inspiral and merger of compact binaries by the
LIGO/Virgo collaboration ushered in a new era in the study of strong-field
gravity. We review current and future tests of strong gravity and of the Kerr
paradigm with gravitational-wave interferometers, both within a theory-agnostic
framework (the parametrized post-Einsteinian formalism) and in the context of
specific modified theories of gravity (scalar-tensor,
Einstein-dilaton-Gauss-Bonnet, dynamical Chern-Simons, Lorentz-violating, and
extra dimensional theories). In this contribution we focus on (i) the
information carried by the inspiral radiation, and (ii) recent progress in
numerical simulations of compact binary mergers in modified gravity.
| [
{
"created": "Wed, 10 Jan 2018 01:23:14 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Apr 2018 21:09:49 GMT",
"version": "v2"
}
] | 2018-04-06 | [
[
"Berti",
"Emanuele",
""
],
[
"Yagi",
"Kent",
""
],
[
"Yunes",
"Nicolás",
""
]
] | The observation of the inspiral and merger of compact binaries by the LIGO/Virgo collaboration ushered in a new era in the study of strong-field gravity. We review current and future tests of strong gravity and of the Kerr paradigm with gravitational-wave interferometers, both within a theory-agnostic framework (the parametrized post-Einsteinian formalism) and in the context of specific modified theories of gravity (scalar-tensor, Einstein-dilaton-Gauss-Bonnet, dynamical Chern-Simons, Lorentz-violating, and extra dimensional theories). In this contribution we focus on (i) the information carried by the inspiral radiation, and (ii) recent progress in numerical simulations of compact binary mergers in modified gravity. |
gr-qc/0609072 | Michael Edmund Tobar | Paul L. Stanwix, Michael E. Tobar, Peter Wolf, Clayton R. Locke,
Eugene N. Ivanov | Improved test of Lorentz Invariance in Electrodynamics using Rotating
Cryogenic Sapphire Oscillators | Accepted for publication in Phys. Rev. D | Phys.Rev.D74:081101,2006 | 10.1103/PhysRevD.74.081101 | null | gr-qc astro-ph hep-ph physics.ins-det | null | We present new results from our test of Lorentz invariance, which compares
two orthogonal cryogenic sapphire microwave oscillators rotating in the lab. We
have now acquired over 1 year of data, allowing us to avoid the short data set
approximation (less than 1 year) that assumes no cancelation occurs between the
$\tilde{\kappa}_{e-}$ and $\tilde{\kappa}_{o+}$ parameters from the photon
sector of the standard model extension. Thus, we are able to place independent
limits on all eight $\tilde{\kappa}_{e-}$ and $\tilde{\kappa}_{o+}$ parameters.
Our results represents up to a factor of 10 improvement over previous non
rotating measurements (which independently constrained 7 parameters), and is a
slight improvement (except for $\tilde{\kappa}_{e-}^{ZZ}$) over results from
previous rotating experiments that assumed the short data set approximation.
Also, an analysis in the Robertson-Mansouri-Sexl framework allows us to place a
new limit on the isotropy parameter $P_{MM}=\delta-\beta+{1/2}$ of
$9.4(8.1)\times10^{-11}$, an improvement of a factor of 2.
| [
{
"created": "Tue, 19 Sep 2006 16:15:46 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Oct 2006 05:42:25 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Stanwix",
"Paul L.",
""
],
[
"Tobar",
"Michael E.",
""
],
[
"Wolf",
"Peter",
""
],
[
"Locke",
"Clayton R.",
""
],
[
"Ivanov",
"Eugene N.",
""
]
] | We present new results from our test of Lorentz invariance, which compares two orthogonal cryogenic sapphire microwave oscillators rotating in the lab. We have now acquired over 1 year of data, allowing us to avoid the short data set approximation (less than 1 year) that assumes no cancelation occurs between the $\tilde{\kappa}_{e-}$ and $\tilde{\kappa}_{o+}$ parameters from the photon sector of the standard model extension. Thus, we are able to place independent limits on all eight $\tilde{\kappa}_{e-}$ and $\tilde{\kappa}_{o+}$ parameters. Our results represents up to a factor of 10 improvement over previous non rotating measurements (which independently constrained 7 parameters), and is a slight improvement (except for $\tilde{\kappa}_{e-}^{ZZ}$) over results from previous rotating experiments that assumed the short data set approximation. Also, an analysis in the Robertson-Mansouri-Sexl framework allows us to place a new limit on the isotropy parameter $P_{MM}=\delta-\beta+{1/2}$ of $9.4(8.1)\times10^{-11}$, an improvement of a factor of 2. |
0811.1573 | Guglielmo Fucci | Ivan G. Avramidi and Guglielmo Fucci | A Model for the Pioneer Anomaly | LaTeX, 12 pages | Can. J. Phys. 87: 1089-1093 (2009) | 10.1139/P09-076 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a previous work we showed that massive test particles exhibit a
non-geodesic acceleration in a modified theory of gravity obtained by a
non-commutative deformation of General Relativity (so-called Matrix Gravity).
We propose that this non-geodesic acceleration might be the origin of the
anomalous acceleration experienced by the Pioneer 10 and Pioneer 11
spacecrafts.
| [
{
"created": "Mon, 10 Nov 2008 20:56:57 GMT",
"version": "v1"
}
] | 2009-12-10 | [
[
"Avramidi",
"Ivan G.",
""
],
[
"Fucci",
"Guglielmo",
""
]
] | In a previous work we showed that massive test particles exhibit a non-geodesic acceleration in a modified theory of gravity obtained by a non-commutative deformation of General Relativity (so-called Matrix Gravity). We propose that this non-geodesic acceleration might be the origin of the anomalous acceleration experienced by the Pioneer 10 and Pioneer 11 spacecrafts. |
2208.02768 | Konstantin Eder | Konstantin Eder, Hanno Sahlmann | Chiral loop quantum supergravity and black hole entropy | 7 pages. arXiv admin note: substantial text overlap with
arXiv:2204.01661 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent work has shown that local supersymmetry on a spacetime boundary in
$\mathcal{N}$-extended AdS supergravity in chiral variables implies coupling to
a boundary $\mathrm{OSp}(\mathcal{N}|2)_{\mathbb{C}}$ super Chern-Simons
theory. We propose a way to calculate the entropy $S$ for the boundary, in the
supersymmetric version of loop quantum gravity, for the minimal case
$\mathcal{N}=1$. We calculate the dimensions of the quantum state spaces of
$\mathrm{UOSp}(1|2)$ super Chern-Simons theory with punctures, and analytically
continue, for fixed quantum super area of the surface, to
$\mathrm{OSp}(1|2)_{\mathbb{C}}$. We find $S = a_H/4$ for large areas and
determine the subleading correction.
| [
{
"created": "Thu, 4 Aug 2022 16:58:30 GMT",
"version": "v1"
}
] | 2022-08-05 | [
[
"Eder",
"Konstantin",
""
],
[
"Sahlmann",
"Hanno",
""
]
] | Recent work has shown that local supersymmetry on a spacetime boundary in $\mathcal{N}$-extended AdS supergravity in chiral variables implies coupling to a boundary $\mathrm{OSp}(\mathcal{N}|2)_{\mathbb{C}}$ super Chern-Simons theory. We propose a way to calculate the entropy $S$ for the boundary, in the supersymmetric version of loop quantum gravity, for the minimal case $\mathcal{N}=1$. We calculate the dimensions of the quantum state spaces of $\mathrm{UOSp}(1|2)$ super Chern-Simons theory with punctures, and analytically continue, for fixed quantum super area of the surface, to $\mathrm{OSp}(1|2)_{\mathbb{C}}$. We find $S = a_H/4$ for large areas and determine the subleading correction. |
1907.07622 | Matthew Fox | Matthew S. Fox | Multipole Hair of Schwarzschild-Tangherlini Black Holes | 11 pages; v2/v3: small revisions; accepted to JMP | J. Math. Phys. 60, 102502 (2019) | 10.1063/1.5124502 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the field of an electric point charge that is slowly lowered into an
$n + 1$ dimensional Schwarzschild-Tangherlini black hole. We find that if $n >
3$, then countably infinite nonzero multipole moments manifest to observers
outside the event horizon as the charge falls in. This suggests the final state
of the black hole is not characterized by a Reissner-Nordstr\"om-Tangherlini
geometry. Instead, for odd $n$, the final state either possesses a degenerate
horizon, undergoes a discontinuous topological transformation during the infall
of the charge, or both. For even $n$, the final state is not guaranteed to be
asymptotically-flat.
| [
{
"created": "Wed, 17 Jul 2019 16:24:52 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jul 2019 16:49:11 GMT",
"version": "v2"
},
{
"created": "Tue, 24 Sep 2019 03:01:49 GMT",
"version": "v3"
}
] | 2020-03-30 | [
[
"Fox",
"Matthew S.",
""
]
] | We study the field of an electric point charge that is slowly lowered into an $n + 1$ dimensional Schwarzschild-Tangherlini black hole. We find that if $n > 3$, then countably infinite nonzero multipole moments manifest to observers outside the event horizon as the charge falls in. This suggests the final state of the black hole is not characterized by a Reissner-Nordstr\"om-Tangherlini geometry. Instead, for odd $n$, the final state either possesses a degenerate horizon, undergoes a discontinuous topological transformation during the infall of the charge, or both. For even $n$, the final state is not guaranteed to be asymptotically-flat. |
1907.09473 | J. Brian Pitts | J. Brian Pitts | What Are Observables in Hamiltonian Einstein-Maxwell Theory? | Forthcoming in _Foundations of Physics_ | Foundations of Physics 49 (2019) pp. 786-796 | 10.1007/s10701-019-00284-w | null | gr-qc hep-th physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Is change missing in Hamiltonian Einstein-Maxwell theory? Given the most
common definition of observables (having weakly vanishing Poisson bracket with
each first-class constraint), observables are constants of the motion and
nonlocal. Unfortunately this definition also implies that the observables for
massive electromagnetism with gauge freedom (Stueckelberg) are inequivalent to
those of massive electromagnetism without gauge freedom (Proca). The
alternative Pons-Salisbury-Sundermeyer definition of observables, aiming for
Hamiltonian-Lagrangian equivalence, uses the gauge generator G, a tuned sum of
first-class constraints, rather than each first-class constraint separately,
and implies equivalent observables for equivalent massive electromagnetisms.
For General Relativity, G generates 4-dimensional Lie derivatives for
solutions. The Lie derivative compares different space-time points with the
same coordinate value in different coordinate systems, like 1 a.m. summer time
vs. 1 a.m. standard time, so a vanishing Lie derivative implies constancy
rather than covariance. Requiring equivalent observables for equivalent
formulations of massive gravity confirms that $G$ must generate the
$4$-dimensional Lie derivative (not $0$) for observables. These separate
results indicate that observables are invariant under internal gauge symmetries
but covariant under external gauge symmetries, but can this bifurcated
definition work for mixed theories such as Einstein-Maxwell theory? Pons,
Salisbury and Shepley have studied $G$ for Einstein-Yang-Mills. For
Einstein-Maxwell, both $F_{\mu\nu}$ and $g_{\mu\nu}$ are invariant under
electromagnetic gauge transformations and covariant (changing by a Lie
derivative) under $4$-dimensional coordinate transformations. Using the
bifurcated definition, these quantities count as observables, as one would
expect on non-Hamiltonian grounds.
| [
{
"created": "Mon, 22 Jul 2019 09:45:51 GMT",
"version": "v1"
}
] | 2019-09-16 | [
[
"Pitts",
"J. Brian",
""
]
] | Is change missing in Hamiltonian Einstein-Maxwell theory? Given the most common definition of observables (having weakly vanishing Poisson bracket with each first-class constraint), observables are constants of the motion and nonlocal. Unfortunately this definition also implies that the observables for massive electromagnetism with gauge freedom (Stueckelberg) are inequivalent to those of massive electromagnetism without gauge freedom (Proca). The alternative Pons-Salisbury-Sundermeyer definition of observables, aiming for Hamiltonian-Lagrangian equivalence, uses the gauge generator G, a tuned sum of first-class constraints, rather than each first-class constraint separately, and implies equivalent observables for equivalent massive electromagnetisms. For General Relativity, G generates 4-dimensional Lie derivatives for solutions. The Lie derivative compares different space-time points with the same coordinate value in different coordinate systems, like 1 a.m. summer time vs. 1 a.m. standard time, so a vanishing Lie derivative implies constancy rather than covariance. Requiring equivalent observables for equivalent formulations of massive gravity confirms that $G$ must generate the $4$-dimensional Lie derivative (not $0$) for observables. These separate results indicate that observables are invariant under internal gauge symmetries but covariant under external gauge symmetries, but can this bifurcated definition work for mixed theories such as Einstein-Maxwell theory? Pons, Salisbury and Shepley have studied $G$ for Einstein-Yang-Mills. For Einstein-Maxwell, both $F_{\mu\nu}$ and $g_{\mu\nu}$ are invariant under electromagnetic gauge transformations and covariant (changing by a Lie derivative) under $4$-dimensional coordinate transformations. Using the bifurcated definition, these quantities count as observables, as one would expect on non-Hamiltonian grounds. |
2204.10299 | Alessandro Nagar | Seth Hopper, Alessandro Nagar, and Piero Rettegno | Strong-field scattering of two spinning black holes: Numerics versus
Analytics | 9 pages, 4 figures. Submitted to Phys. Rev. D | null | 10.1103/PhysRevD.107.124034 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present new Numerical Relativity calculations of the scattering angle
$\chi$ between two, equal-mass, black holes on hyperbolic-like orbits. We build
upon previous work considering, for the first time, spinning black holes, with
equal spins either aligned or antialigned with the orbital angular momentum. We
detail the numerical techniques used in the computation of $\chi$. Special care
is taken in estimating error uncertainties on the quantities computed. The
numerical values are compared with analytical predictions obtained using a new,
state-of-the-art, effective one body model valid on generic orbits that
incorporates post-Newtonian analytic information up to 5PN in the nonspinning,
conservative sector and that has been additionally informed by Numerical
Relativity simulations of quasi-circular coalescing black hole binaries. Our
results indicate that the spin sector of the analytic model should be improved
further in order to achieve satisfactory consistency with the most relativistic
spinning configurations.
| [
{
"created": "Thu, 21 Apr 2022 17:33:34 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Apr 2022 11:13:47 GMT",
"version": "v2"
}
] | 2023-06-28 | [
[
"Hopper",
"Seth",
""
],
[
"Nagar",
"Alessandro",
""
],
[
"Rettegno",
"Piero",
""
]
] | We present new Numerical Relativity calculations of the scattering angle $\chi$ between two, equal-mass, black holes on hyperbolic-like orbits. We build upon previous work considering, for the first time, spinning black holes, with equal spins either aligned or antialigned with the orbital angular momentum. We detail the numerical techniques used in the computation of $\chi$. Special care is taken in estimating error uncertainties on the quantities computed. The numerical values are compared with analytical predictions obtained using a new, state-of-the-art, effective one body model valid on generic orbits that incorporates post-Newtonian analytic information up to 5PN in the nonspinning, conservative sector and that has been additionally informed by Numerical Relativity simulations of quasi-circular coalescing black hole binaries. Our results indicate that the spin sector of the analytic model should be improved further in order to achieve satisfactory consistency with the most relativistic spinning configurations. |
gr-qc/0404005 | Martin Tajmar | M. Tajmar, K. Hense, K. Marhold, C.J. de Matos | Weight Measurements of High-Temperature Superconductors during Phase
Transition in Stationary, Non-Stationary Condition and under ELF Radiation | Version as appeared in the STAIF conference proceedings. Received
Best Paper Award | Edited by El-Genk, M.S., "Proceedings of the Space Technology and
Applications International Forum (STAIF-2005)", AIP Conference Proceedings
746, Issue 1, American Institute of Physics, New York, 2005, pp. 1290-1297 | 10.1063/1.1867257 | null | gr-qc | null | There have been a number of claims in the literature about gravity shielding
effects of superconductors and more recently on the weight reduction of
superconductors passing through their critical temperature. We report several
experiments to test the weight of superconductors under various conditions.
First, we report tests on the weight of YBCO and BSCCO high temperature
superconductors passing through their critical temperature. No anomaly was
found within the equipment accuracy ruling out claimed anomalies by Rounds and
Reiss. Our experiments extend the accuracy of previous measurements by two
orders of magnitude. In addition, for the first time, the weight of a rotating
YBCO superconductor was measured. Also in this case, no weight anomaly could be
seen within the accuracy of the equipment used. In addition, also weight
measurements of a BSCCO superconductor subjected to extremely-low-frequency
(ELF) radiation have been done to test a claim of weight reduction under these
conditions by De Aquino, and again, no unusual behavior was found. These
measurements put new important boundaries on any inertial effect connected with
superconductivity - and consequently on possible space related applications.
| [
{
"created": "Thu, 1 Apr 2004 10:26:36 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Apr 2004 07:54:00 GMT",
"version": "v2"
},
{
"created": "Thu, 20 Jul 2006 22:51:55 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Tajmar",
"M.",
""
],
[
"Hense",
"K.",
""
],
[
"Marhold",
"K.",
""
],
[
"de Matos",
"C. J.",
""
]
] | There have been a number of claims in the literature about gravity shielding effects of superconductors and more recently on the weight reduction of superconductors passing through their critical temperature. We report several experiments to test the weight of superconductors under various conditions. First, we report tests on the weight of YBCO and BSCCO high temperature superconductors passing through their critical temperature. No anomaly was found within the equipment accuracy ruling out claimed anomalies by Rounds and Reiss. Our experiments extend the accuracy of previous measurements by two orders of magnitude. In addition, for the first time, the weight of a rotating YBCO superconductor was measured. Also in this case, no weight anomaly could be seen within the accuracy of the equipment used. In addition, also weight measurements of a BSCCO superconductor subjected to extremely-low-frequency (ELF) radiation have been done to test a claim of weight reduction under these conditions by De Aquino, and again, no unusual behavior was found. These measurements put new important boundaries on any inertial effect connected with superconductivity - and consequently on possible space related applications. |
2312.16866 | Allah Ditta | G. Mustafa, Allah Ditta, Saadia Mumtaz, S.K. Maurya, De\u{g}er
Sofuo\u{g}lu | Study on physical properties and maximum mass limit of Finch-Skea
anisotropic model under Karmarkar condition in $f(Q)$-gravity | 16 pages, 9 figures, 5 tables | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The primary objective of this work is to study the dynamical characteristics
of an anisotropic compact star model with spherical symmetry. This
investigation is conducted in the framework of $f(Q)$ modified gravity. To
simplify the calculations, we employ the Karmarkar condition and derive a
differential equation that establishes a relationship between two crucial
components of the spacetime namely $e^\nu$ and $e^\lambda$. Additionally, we
incorporate the well-known Finch-Skea structure as the component representing
$g_{rr}$ and subsequently find the resulting form of the component $g_{tt}$
from the relation of metric functions to formulate the precise solutions for
the stellar structure. To assess the behavior of the anisotropic fluid and
stability of the compact star, we use the observed values of mass and radius
for the compact star model $PSR J0437-4715$. The graphical analysis depicts
that the stellar structure possesses physical viability and exhibits intriguing
properties. Furthermore, we predicted the mass-radius relation along with the
maximum mass limit of several objects for different parameter values by
assuming two different surface densities. It is discovered that the compactness
rises when density increases.
| [
{
"created": "Thu, 28 Dec 2023 07:26:58 GMT",
"version": "v1"
}
] | 2023-12-29 | [
[
"Mustafa",
"G.",
""
],
[
"Ditta",
"Allah",
""
],
[
"Mumtaz",
"Saadia",
""
],
[
"Maurya",
"S. K.",
""
],
[
"Sofuoğlu",
"Değer",
""
]
] | The primary objective of this work is to study the dynamical characteristics of an anisotropic compact star model with spherical symmetry. This investigation is conducted in the framework of $f(Q)$ modified gravity. To simplify the calculations, we employ the Karmarkar condition and derive a differential equation that establishes a relationship between two crucial components of the spacetime namely $e^\nu$ and $e^\lambda$. Additionally, we incorporate the well-known Finch-Skea structure as the component representing $g_{rr}$ and subsequently find the resulting form of the component $g_{tt}$ from the relation of metric functions to formulate the precise solutions for the stellar structure. To assess the behavior of the anisotropic fluid and stability of the compact star, we use the observed values of mass and radius for the compact star model $PSR J0437-4715$. The graphical analysis depicts that the stellar structure possesses physical viability and exhibits intriguing properties. Furthermore, we predicted the mass-radius relation along with the maximum mass limit of several objects for different parameter values by assuming two different surface densities. It is discovered that the compactness rises when density increases. |
2308.15776 | Orlando Luongo | Peter K. S. Dunsby, Orlando Luongo, Marco Muccino | Unifying the dark sector through a single matter fluid with non-zero
pressure | 15 pages, 3 figures, 1 table | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore a generalised unified dark energy model that incorporates a
non-minimal interaction between a tachyonic fluid and an additional scalar
field. Specifically, we require that the second field possesses a vacuum
energy, introducing an ineliminable offset due to a symmetry-breaking
mechanism. After the transition (occurring as due to the symmetry-breaking
mechanism of the second field), the corresponding equation of state (EoS) takes
the form of a combination between a generalised Chaplygin gas (GCG) component
and a cosmological constant contribution. We reinterpret this outcome by
drawing parallels to the so-called Murnaghan EoS, widely-employed in the realm
of solid-state physics to characterise fluids that, under external pressure,
counteract the pressure's effect. We examine the dynamic behaviour of this
model and highlight its key distinctions compared to the GCG model. We
establish parameter bounds that clarifies the model's evolution across cosmic
expansion history, showing that it, precisely, exhibits behaviour akin to a
logotropic fluid that eventually converges to the $\Lambda$CDM model in the
early universe, while behaving as a logotropic or Chaplygin gas at intermediate
and late times respectively. We explain our findings from a thermodynamic
perspective, and determine the small perturbations in the linear regime. At
very early times, the growth factor flattens as expected while the main
departures occur at late times, where the Murnagham EoS results in a more
efficient growth of perturbations. We discuss this deviation in view of current
observations and conclude that our model is a suitable alternative to the
standard cosmological paradigm, introducing the concept of a matter-like field
with non-zero pressure.
| [
{
"created": "Wed, 30 Aug 2023 06:07:45 GMT",
"version": "v1"
}
] | 2023-08-31 | [
[
"Dunsby",
"Peter K. S.",
""
],
[
"Luongo",
"Orlando",
""
],
[
"Muccino",
"Marco",
""
]
] | We explore a generalised unified dark energy model that incorporates a non-minimal interaction between a tachyonic fluid and an additional scalar field. Specifically, we require that the second field possesses a vacuum energy, introducing an ineliminable offset due to a symmetry-breaking mechanism. After the transition (occurring as due to the symmetry-breaking mechanism of the second field), the corresponding equation of state (EoS) takes the form of a combination between a generalised Chaplygin gas (GCG) component and a cosmological constant contribution. We reinterpret this outcome by drawing parallels to the so-called Murnaghan EoS, widely-employed in the realm of solid-state physics to characterise fluids that, under external pressure, counteract the pressure's effect. We examine the dynamic behaviour of this model and highlight its key distinctions compared to the GCG model. We establish parameter bounds that clarifies the model's evolution across cosmic expansion history, showing that it, precisely, exhibits behaviour akin to a logotropic fluid that eventually converges to the $\Lambda$CDM model in the early universe, while behaving as a logotropic or Chaplygin gas at intermediate and late times respectively. We explain our findings from a thermodynamic perspective, and determine the small perturbations in the linear regime. At very early times, the growth factor flattens as expected while the main departures occur at late times, where the Murnagham EoS results in a more efficient growth of perturbations. We discuss this deviation in view of current observations and conclude that our model is a suitable alternative to the standard cosmological paradigm, introducing the concept of a matter-like field with non-zero pressure. |
1103.0543 | Abraham Harte | Abraham I. Harte | Mechanics of extended masses in general relativity | 39 pages, 2 figures; fixed equation satisfied by the Green function
used to construct the effective metric | Class. Quantum Grav. 29, 055012 (2012) | 10.1088/0264-9381/29/5/055012 | AEI-2011-010 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The "external" or "bulk" motion of extended bodies is studied in general
relativity. Compact material objects of essentially arbitrary shape, spin,
internal composition, and velocity are allowed as long as there is no direct
(non-gravitational) contact with other sources of stress-energy. Physically
reasonable linear and angular momenta are proposed for such bodies and exact
equations describing their evolution are derived. Changes in the momenta depend
on a certain "effective metric" that is closely related to a non-perturbative
generalization of the Detweiler-Whiting R-field originally introduced in the
self-force literature. If the effective metric inside a self-gravitating body
can be adequately approximated by an appropriate power series, the
instantaneous gravitational force and torque exerted on it is shown to be
identical to the force and torque exerted on an appropriate test body moving in
the effective metric. This result holds to all multipole orders. The only
instantaneous effect of a body's self-field is to finitely renormalize the
"bare" multipole moments of its stress-energy tensor. The MiSaTaQuWa expression
for the gravitational self-force is recovered as a simple application. A
gravitational self-torque is obtained as well. Lastly, it is shown that the
effective metric in which objects appear to move is approximately a solution to
the vacuum Einstein equation if the physical metric is an approximate solution
to Einstein's equation linearized about a vacuum background.
| [
{
"created": "Wed, 2 Mar 2011 20:58:05 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Mar 2011 17:19:04 GMT",
"version": "v2"
},
{
"created": "Mon, 19 Sep 2011 15:51:59 GMT",
"version": "v3"
},
{
"created": "Wed, 6 Jun 2012 13:54:05 GMT",
"version": "v4"
}
] | 2012-06-07 | [
[
"Harte",
"Abraham I.",
""
]
] | The "external" or "bulk" motion of extended bodies is studied in general relativity. Compact material objects of essentially arbitrary shape, spin, internal composition, and velocity are allowed as long as there is no direct (non-gravitational) contact with other sources of stress-energy. Physically reasonable linear and angular momenta are proposed for such bodies and exact equations describing their evolution are derived. Changes in the momenta depend on a certain "effective metric" that is closely related to a non-perturbative generalization of the Detweiler-Whiting R-field originally introduced in the self-force literature. If the effective metric inside a self-gravitating body can be adequately approximated by an appropriate power series, the instantaneous gravitational force and torque exerted on it is shown to be identical to the force and torque exerted on an appropriate test body moving in the effective metric. This result holds to all multipole orders. The only instantaneous effect of a body's self-field is to finitely renormalize the "bare" multipole moments of its stress-energy tensor. The MiSaTaQuWa expression for the gravitational self-force is recovered as a simple application. A gravitational self-torque is obtained as well. Lastly, it is shown that the effective metric in which objects appear to move is approximately a solution to the vacuum Einstein equation if the physical metric is an approximate solution to Einstein's equation linearized about a vacuum background. |
0902.1170 | John W. Barrett | John W. Barrett, R.J. Dowdall, Winston J. Fairbairn, Henrique Gomes,
Frank Hellmann | Asymptotic analysis of the EPRL four-simplex amplitude | v2: improved presentation, typos corrected, refs added; results
unchanged | J.Math.Phys.50:112504,2009 | 10.1063/1.3244218 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The semiclassical limit of a 4-simplex amplitude for a spin foam quantum
gravity model with an Immirzi parameter is studied. If the boundary state
represents a non-degenerate 4-simplex geometry, the asymptotic formula contains
the Regge action for general relativity. A canonical choice of phase for the
boundary state is introduced and is shown to be necessary to obtain the
results.
| [
{
"created": "Fri, 6 Feb 2009 20:57:06 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Apr 2009 23:42:54 GMT",
"version": "v2"
}
] | 2010-01-15 | [
[
"Barrett",
"John W.",
""
],
[
"Dowdall",
"R. J.",
""
],
[
"Fairbairn",
"Winston J.",
""
],
[
"Gomes",
"Henrique",
""
],
[
"Hellmann",
"Frank",
""
]
] | The semiclassical limit of a 4-simplex amplitude for a spin foam quantum gravity model with an Immirzi parameter is studied. If the boundary state represents a non-degenerate 4-simplex geometry, the asymptotic formula contains the Regge action for general relativity. A canonical choice of phase for the boundary state is introduced and is shown to be necessary to obtain the results. |
1709.07275 | Baocheng Zhang | Baocheng Zhang | On the entropy associated with the interior of a black hole | null | Physics Letters B 773 (2017) 644-646 | 10.1016/j.physletb.2017.09.035 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The investigation about the volume of a black hole is closely related to the
quantum nature of the black hole. The entropy is a significant concept for
this. A recent work by Majhi and Samanta [Phys. Lett. B 770 (2017) 314] after
us presented a similar conclusion that the entropy associated with the volume
is proportional to the surface area of the black hole, but the proportionality
coefficient is different from our earlier result. In this paper, we clarify the
difference and show that their calculation is unrelated to the interior of the
black hole.
| [
{
"created": "Thu, 21 Sep 2017 12:05:43 GMT",
"version": "v1"
}
] | 2017-09-22 | [
[
"Zhang",
"Baocheng",
""
]
] | The investigation about the volume of a black hole is closely related to the quantum nature of the black hole. The entropy is a significant concept for this. A recent work by Majhi and Samanta [Phys. Lett. B 770 (2017) 314] after us presented a similar conclusion that the entropy associated with the volume is proportional to the surface area of the black hole, but the proportionality coefficient is different from our earlier result. In this paper, we clarify the difference and show that their calculation is unrelated to the interior of the black hole. |
2307.00044 | Nuno M. Santos | Pedro Ildefonso, Miguel Zilh\~ao, Carlos Herdeiro, Eugen Radu, Nuno M.
Santos | Self-interacting dipolar boson stars and their dynamics | 13 pages, 14 figures; movies of the numerical simulations reported
can be found in http://gravitation.web.ua.pt/index.php/node/4488 | null | 10.1103/PhysRevD.108.064011 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct and dynamically evolve dipolar, self-interacting scalar boson
stars in a model with sextic (+ quartic) self-interactions. The domain of
existence of such dipolar $Q$-stars has a similar structure to that of the
fundamental monopolar stars of the same model. For the latter it is structured
in a Newtonian plus a relativistic branch, wherein perturbatively stable
solutions exist, connected by a middle unstable branch. Our evolutions support
similar dynamical properties of the dipolar $Q$-stars that: 1) in the Newtonian
and relativistic branches are dynamically robust over time scales longer than
those for which dipolar stars without self-interactions are seen to decay; 2)
in the middle branch migrate to either the Newtonian or the relativistic
branch; 3) beyond the relativistic branch decay to black holes. Overall, these
results strengthen the observation, seen in other contexts, that
self-interactions can mitigate dynamical instabilities of scalar boson star
models.
| [
{
"created": "Fri, 30 Jun 2023 18:00:00 GMT",
"version": "v1"
}
] | 2023-09-26 | [
[
"Ildefonso",
"Pedro",
""
],
[
"Zilhão",
"Miguel",
""
],
[
"Herdeiro",
"Carlos",
""
],
[
"Radu",
"Eugen",
""
],
[
"Santos",
"Nuno M.",
""
]
] | We construct and dynamically evolve dipolar, self-interacting scalar boson stars in a model with sextic (+ quartic) self-interactions. The domain of existence of such dipolar $Q$-stars has a similar structure to that of the fundamental monopolar stars of the same model. For the latter it is structured in a Newtonian plus a relativistic branch, wherein perturbatively stable solutions exist, connected by a middle unstable branch. Our evolutions support similar dynamical properties of the dipolar $Q$-stars that: 1) in the Newtonian and relativistic branches are dynamically robust over time scales longer than those for which dipolar stars without self-interactions are seen to decay; 2) in the middle branch migrate to either the Newtonian or the relativistic branch; 3) beyond the relativistic branch decay to black holes. Overall, these results strengthen the observation, seen in other contexts, that self-interactions can mitigate dynamical instabilities of scalar boson star models. |
1405.1248 | Philip D. Mannheim | Luca Fabbri and Philip D. Mannheim | Continuity of the torsionless limit as a selection rule for gravity
theories with torsion | 6 pages, revtex4. Final version, to appear in Phys. Rev. D | Phys. Rev. D 90, 024042 (2014) | 10.1103/PhysRevD.90.024042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | While one can in principle augment gravity theory with torsion, it is
generally thought that any such torsion affects would be too small to be of
consequence. Here we show that this cannot in general be the case. We show that
the limit of vanishing torsion is not necessarily a continuous one, with the
theory obtained in the limit not necessarily coinciding with the theory in
which torsion had never been present at all. However, for a standard torsion
tensor that is antisymmetric in two of its indices we have found two cases in
which the vanishing torsion limit is in fact continuous, namely Einstein
gravity and conformal gravity. For other gravity theories of common interest to
possess a continuous limit the torsion tensor would need to be antisymmetric in
all three of its indices.
| [
{
"created": "Tue, 6 May 2014 12:42:19 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Jun 2014 18:19:18 GMT",
"version": "v2"
}
] | 2014-07-23 | [
[
"Fabbri",
"Luca",
""
],
[
"Mannheim",
"Philip D.",
""
]
] | While one can in principle augment gravity theory with torsion, it is generally thought that any such torsion affects would be too small to be of consequence. Here we show that this cannot in general be the case. We show that the limit of vanishing torsion is not necessarily a continuous one, with the theory obtained in the limit not necessarily coinciding with the theory in which torsion had never been present at all. However, for a standard torsion tensor that is antisymmetric in two of its indices we have found two cases in which the vanishing torsion limit is in fact continuous, namely Einstein gravity and conformal gravity. For other gravity theories of common interest to possess a continuous limit the torsion tensor would need to be antisymmetric in all three of its indices. |
1608.04811 | Sarp Akcay | Sarp Akcay, David Dempsey, Sam Dolan | Spin-orbit precession for eccentric black hole binaries at first order
in the mass ratio | Matches the published version in CQG | Classical and Quantum Gravity, Volume 34, Number 8, 084001, 2017 | 10.1088/1361-6382/aa61d6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider spin-orbit ("geodetic") precession for a compact binary in
strong-field gravity. Specifically, we compute $\psi$, the ratio of the
accumulated spin-precession and orbital angles over one radial period, for a
spinning compact body of mass $m_1$ and spin $s_1$, with $s_1 \ll G m_1^2/c$,
orbiting a non-rotating black hole. We show that $\psi$ can be computed for
eccentric orbits in both the gravitational self-force and post-Newtonian
frameworks, and that the results appear to be consistent. We present a
post-Newtonian expansion for $\psi$ at next-to-next-to-leading order, and a
Lorenz-gauge gravitational self-force calculation for $\psi$ at first order in
the mass ratio. The latter provides new numerical data in the strong-field
regime to inform the Effective One-Body model of the gravitational two-body
problem. We conclude that $\psi$ complements the Detweiler redshift $z$ as a
key invariant quantity characterizing eccentric orbits in the gravitational
two-body problem.
| [
{
"created": "Tue, 16 Aug 2016 23:47:34 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Oct 2016 14:06:30 GMT",
"version": "v2"
},
{
"created": "Thu, 30 Mar 2017 15:50:35 GMT",
"version": "v3"
}
] | 2017-03-31 | [
[
"Akcay",
"Sarp",
""
],
[
"Dempsey",
"David",
""
],
[
"Dolan",
"Sam",
""
]
] | We consider spin-orbit ("geodetic") precession for a compact binary in strong-field gravity. Specifically, we compute $\psi$, the ratio of the accumulated spin-precession and orbital angles over one radial period, for a spinning compact body of mass $m_1$ and spin $s_1$, with $s_1 \ll G m_1^2/c$, orbiting a non-rotating black hole. We show that $\psi$ can be computed for eccentric orbits in both the gravitational self-force and post-Newtonian frameworks, and that the results appear to be consistent. We present a post-Newtonian expansion for $\psi$ at next-to-next-to-leading order, and a Lorenz-gauge gravitational self-force calculation for $\psi$ at first order in the mass ratio. The latter provides new numerical data in the strong-field regime to inform the Effective One-Body model of the gravitational two-body problem. We conclude that $\psi$ complements the Detweiler redshift $z$ as a key invariant quantity characterizing eccentric orbits in the gravitational two-body problem. |
0710.0722 | Francesco Cianfrani dr | F. Cianfrani, G. Montani | Boost symmetry in the Quantum Gravity sector | 8 pages, to appear in the proceedings of'' 4th Italian-Sino Workshop
on Relativistic Astrophysics'', AIP Conference Series | AIPConf.Proc.966:249-256,2008 | 10.1063/1.2837003 | null | gr-qc | null | We perform a canonical quantization of gravity in a second-order formulation,
taking as configuration variables those describing a 4-bein, not adapted to the
space-time splitting. We outline how, neither if we fix the Lorentz frame
before quantizing, nor if we perform no gauge fixing at all, is invariance
under boost transformations affected by the quantization.
| [
{
"created": "Wed, 3 Oct 2007 07:48:04 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Cianfrani",
"F.",
""
],
[
"Montani",
"G.",
""
]
] | We perform a canonical quantization of gravity in a second-order formulation, taking as configuration variables those describing a 4-bein, not adapted to the space-time splitting. We outline how, neither if we fix the Lorentz frame before quantizing, nor if we perform no gauge fixing at all, is invariance under boost transformations affected by the quantization. |
2407.20285 | Martiros Khurshudyan | Emilio Elizalde, Martiros Khurshudyan, Sergei D. Odintsov | Can we learn from matter creation to solve the $H_{0}$ tension problem? | To appear in EPJC | null | null | null | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | The $H_{0}$ tension problem is studied in the light of a matter creation
mechanism (an effective approach to replacing dark energy), the way to define
the matter creation rate being of pure phenomenological nature. Bayesian
(probabilistic) Machine Learning is used to learn the constraints on the free
parameters of the models, with the learning being based on the generated
expansion rate, $H(z)$. Taking advantage of the method, the constraints for
three redshift ranges are learned. Namely, for the two redshift ranges: $z\in
[0,2]$~(cosmic chronometers) and $z\in [0,2.5]$~(cosmic chronometers + BAO),
covering already available $H(z)$ data, to validate the learned results; and
for a third redshift interval, $z\in[0,5]$, for forecasting purposes. It is
learned that the $3\alpha H_{0}$ term in the creation rate provides options
that have the potential to solve the $H_{0}$ tension problem.
| [
{
"created": "Fri, 26 Jul 2024 08:58:07 GMT",
"version": "v1"
}
] | 2024-07-31 | [
[
"Elizalde",
"Emilio",
""
],
[
"Khurshudyan",
"Martiros",
""
],
[
"Odintsov",
"Sergei D.",
""
]
] | The $H_{0}$ tension problem is studied in the light of a matter creation mechanism (an effective approach to replacing dark energy), the way to define the matter creation rate being of pure phenomenological nature. Bayesian (probabilistic) Machine Learning is used to learn the constraints on the free parameters of the models, with the learning being based on the generated expansion rate, $H(z)$. Taking advantage of the method, the constraints for three redshift ranges are learned. Namely, for the two redshift ranges: $z\in [0,2]$~(cosmic chronometers) and $z\in [0,2.5]$~(cosmic chronometers + BAO), covering already available $H(z)$ data, to validate the learned results; and for a third redshift interval, $z\in[0,5]$, for forecasting purposes. It is learned that the $3\alpha H_{0}$ term in the creation rate provides options that have the potential to solve the $H_{0}$ tension problem. |
2001.05999 | Camilo Posada | Jan Hlad\'ik, Camilo Posada, Zden\v{e}k Stuchl\'ik | Radial instability of trapping polytropic spheres | 20 pages, 18 figures. Accepted manuscript to appear in IJMPD | Int. J. Mod. Phys. D29, 2050030 (2020) | 10.1142/S0218271820500303 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We complete the stability study of general relativistic spherically symmetric
polytropic perfect fluid spheres, concentrating attention to the newly
discovered polytropes containing region of trapped null geodesics. We compare
the methods of treating the dynamical stability based on the equation governing
infinitesimal radial pulsations of the polytropes and the related
Sturm-Liouville eigenvalue equation for the eigenmodes governing the
pulsations, to the methods of stability analysis based on the energetic
considerations. Both methods are applied to determine the stability of the
polytropes governed by the polytropic index n in the whole range 0 < n < 5, and
the relativistic parameter {\sigma} given by the ratio of the central pressure
and energy density, restricted by the causality limit. The critical values of
the adiabatic index for stability are determined, together with the critical
values of the relativistic parameter {\sigma}. For the dynamical approach we
implemented a numerical method which is independent on the choice of the trial
function, and compare its results with the standard trial function approach. We
found that the energetic and dynamic method give nearly the same critical
values of {\sigma}. We found that all the configurations having trapped null
geodesics are unstable according to both methods.
| [
{
"created": "Thu, 16 Jan 2020 18:59:40 GMT",
"version": "v1"
}
] | 2020-05-14 | [
[
"Hladík",
"Jan",
""
],
[
"Posada",
"Camilo",
""
],
[
"Stuchlík",
"Zdeněk",
""
]
] | We complete the stability study of general relativistic spherically symmetric polytropic perfect fluid spheres, concentrating attention to the newly discovered polytropes containing region of trapped null geodesics. We compare the methods of treating the dynamical stability based on the equation governing infinitesimal radial pulsations of the polytropes and the related Sturm-Liouville eigenvalue equation for the eigenmodes governing the pulsations, to the methods of stability analysis based on the energetic considerations. Both methods are applied to determine the stability of the polytropes governed by the polytropic index n in the whole range 0 < n < 5, and the relativistic parameter {\sigma} given by the ratio of the central pressure and energy density, restricted by the causality limit. The critical values of the adiabatic index for stability are determined, together with the critical values of the relativistic parameter {\sigma}. For the dynamical approach we implemented a numerical method which is independent on the choice of the trial function, and compare its results with the standard trial function approach. We found that the energetic and dynamic method give nearly the same critical values of {\sigma}. We found that all the configurations having trapped null geodesics are unstable according to both methods. |
2403.12840 | Lei You | Lei You and Rui-bo Wang and Shi-Jie Ma and Jian-Bo Deng and Xian-Ru Hu | Optical properties of Euler-Heisenberg black hole in the Cold Dark
Matter Halo | 42 pages,16 figures,4 tables | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The optical properties of Euler-Heisenberg (EH) black hole (BH) surrounded by
Cold Dark Matter (CDM) halo are investigated. By changing BH's parameters, we
found that the radius of horizon r_{h} and radius of photon sphere r_{ph} will
transparently increase as CDM halo parameters R and \rho increase. To show the
influence of CDM halo on the BH's optical characteristics, we took two sets of
R and \rho with prominent differences and plot the first four orders of images
for thin accretion disk with different angle of inclination \theta of observer.
The images with light intensity distributions using Novikov-Thorne (N-T) model
are also derived, as well as the effective potential, photon orbits.
Especially, analysis of intersection behaviors between photon trajectories with
different impact parameters and circular time-like orbits in accretion disk
will help better understand the image of thin accretion disk. Our results
showed that CDM halo will make BH become more larger and dimmer distinctly.
| [
{
"created": "Tue, 19 Mar 2024 15:46:18 GMT",
"version": "v1"
}
] | 2024-03-20 | [
[
"You",
"Lei",
""
],
[
"Wang",
"Rui-bo",
""
],
[
"Ma",
"Shi-Jie",
""
],
[
"Deng",
"Jian-Bo",
""
],
[
"Hu",
"Xian-Ru",
""
]
] | The optical properties of Euler-Heisenberg (EH) black hole (BH) surrounded by Cold Dark Matter (CDM) halo are investigated. By changing BH's parameters, we found that the radius of horizon r_{h} and radius of photon sphere r_{ph} will transparently increase as CDM halo parameters R and \rho increase. To show the influence of CDM halo on the BH's optical characteristics, we took two sets of R and \rho with prominent differences and plot the first four orders of images for thin accretion disk with different angle of inclination \theta of observer. The images with light intensity distributions using Novikov-Thorne (N-T) model are also derived, as well as the effective potential, photon orbits. Especially, analysis of intersection behaviors between photon trajectories with different impact parameters and circular time-like orbits in accretion disk will help better understand the image of thin accretion disk. Our results showed that CDM halo will make BH become more larger and dimmer distinctly. |
1704.06031 | Shin'ichi Hirano | Shin'ichi Hirano, Sakine Nishi, Tsutomu Kobayashi | Healthy imperfect dark matter from effective theory of mimetic
cosmological perturbations | 9 pages | null | 10.1088/1475-7516/2017/07/009 | RUP-17-6 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the stability of a recently proposed model of scalar-field matter
called mimetic dark matter or imperfect dark matter. It has been known that
mimetic matter with higher derivative terms suffers from gradient instabilities
in scalar perturbations. To seek for an instability-free extension of imperfect
dark matter, we develop an effective theory of cosmological perturbations
subject to the constraint on the scalar field's kinetic term. This is done by
using the unifying framework of general scalar-tensor theories based on the ADM
formalism. We demonstrate that it is indeed possible to construct a model of
imperfect dark matter which is free from ghost and gradient instabilities. As a
side remark, we also show that mimetic $F({\cal R})$ theory is plagued with the
Ostrogradsky instability.
| [
{
"created": "Thu, 20 Apr 2017 07:14:07 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jul 2017 04:53:15 GMT",
"version": "v2"
}
] | 2017-07-19 | [
[
"Hirano",
"Shin'ichi",
""
],
[
"Nishi",
"Sakine",
""
],
[
"Kobayashi",
"Tsutomu",
""
]
] | We study the stability of a recently proposed model of scalar-field matter called mimetic dark matter or imperfect dark matter. It has been known that mimetic matter with higher derivative terms suffers from gradient instabilities in scalar perturbations. To seek for an instability-free extension of imperfect dark matter, we develop an effective theory of cosmological perturbations subject to the constraint on the scalar field's kinetic term. This is done by using the unifying framework of general scalar-tensor theories based on the ADM formalism. We demonstrate that it is indeed possible to construct a model of imperfect dark matter which is free from ghost and gradient instabilities. As a side remark, we also show that mimetic $F({\cal R})$ theory is plagued with the Ostrogradsky instability. |
gr-qc/0402098 | Jerzy Matyjasek | Jerzy Matyjasek and Dariusz Tryniecki | Charged black holes in quadratic gravity | null | Phys.Rev. D69 (2004) 124016 | 10.1103/PhysRevD.69.124016 | null | gr-qc | null | Iterative solutions to fourth-order gravity describing static and
electrically charged black holes are constructed. Obtained solutions are
parametrized by two integration constants which are related to the electric
charge and the exact location of the event horizon. Special emphasis is put on
the extremal black holes. It is explicitly demonstrated that in the extremal
limit, the exact location of the (degenerate) event horizon is given by $\rp =
|e|.$ Similarly to the classical Reissner-Nordstr\"om solution, the
near-horizon geometry of the charged black holes in quadratic gravity, when
expanded into the whole manifold, is simply that of Bertotti and Robinson.
Similar considerations have been carried out for the boundary conditions of
second type which employ the electric charge and the mass of the system as seen
by a distant observer. The relations between results obtained within the
framework of each method are briefly discussed.
| [
{
"created": "Tue, 24 Feb 2004 09:07:24 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Matyjasek",
"Jerzy",
""
],
[
"Tryniecki",
"Dariusz",
""
]
] | Iterative solutions to fourth-order gravity describing static and electrically charged black holes are constructed. Obtained solutions are parametrized by two integration constants which are related to the electric charge and the exact location of the event horizon. Special emphasis is put on the extremal black holes. It is explicitly demonstrated that in the extremal limit, the exact location of the (degenerate) event horizon is given by $\rp = |e|.$ Similarly to the classical Reissner-Nordstr\"om solution, the near-horizon geometry of the charged black holes in quadratic gravity, when expanded into the whole manifold, is simply that of Bertotti and Robinson. Similar considerations have been carried out for the boundary conditions of second type which employ the electric charge and the mass of the system as seen by a distant observer. The relations between results obtained within the framework of each method are briefly discussed. |
1308.1455 | Yun Soo Myung | Yun Soo Myung | Instability of Schwarzschild-AdS black hole in Einstein-Weyl gravity | 1+13 pages, 1 figure, a version to appear in PLB | null | 10.1016/j.physletb.2013.12.019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the classical stability of Schwarzschild-AdS black hole in a
massive theory of the Einstein-Weyl gravity. It turns out that the linearized
Einstein tensor perturbations exhibit unstable modes featuring the
Gregory-Laflamme instability of five-dimensional AdS black string, in contrast
to the stable Schwarzschild-AdS black hole in the Einstein-Weyl gravity. We
confirm that the instability of the black hole in the Einstein-Weyl gravity
arises from the massiveness but not a feature of fourth-order derivative theory
giving ghost states.
| [
{
"created": "Wed, 7 Aug 2013 00:56:10 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Aug 2013 00:34:55 GMT",
"version": "v2"
},
{
"created": "Mon, 9 Dec 2013 04:03:48 GMT",
"version": "v3"
}
] | 2015-06-16 | [
[
"Myung",
"Yun Soo",
""
]
] | We investigate the classical stability of Schwarzschild-AdS black hole in a massive theory of the Einstein-Weyl gravity. It turns out that the linearized Einstein tensor perturbations exhibit unstable modes featuring the Gregory-Laflamme instability of five-dimensional AdS black string, in contrast to the stable Schwarzschild-AdS black hole in the Einstein-Weyl gravity. We confirm that the instability of the black hole in the Einstein-Weyl gravity arises from the massiveness but not a feature of fourth-order derivative theory giving ghost states. |
2203.01267 | Felipe Ferreira De Freitas | Felipe F. Freitas, Carlos A. R. Herdeiro, Ant\'onio P. Morais,
Ant\'onio Onofre, Roman Pasechnik, Eugen Radu, Nicolas Sanchis-Gual, Rui
Santos | Generating gravitational waveform libraries of exotic compact binaries
with deep learning | 20 pages, 13 figures, 4 tables | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Current gravitational wave (GW) detections rely on the existence of libraries
of theoretical waveforms. Consequently, finding new physics with GWs requires
libraries of non-standard models, which are computationally demanding. We
discuss how deep learning frameworks can be used to generate new waveforms
"learned" from a simulation dataset obtained, say, from numerical relativity
simulations. Concretely, we use the WaveGAN architecture of a generative
adversarial network (GAN). As a proof of concept we provide this neural network
(NN) with a sample of ($>500$) waveforms from the collisions of exotic compact
objects (Proca stars), obtained from numerical relativity simulations. Dividing
the sample into a training and a validation set, we show that after a
sufficiently large number of training epochs the NN can produce from 12\% to
25\% of the synthetic waveforms with an overlapping match of at least 95\% with
the ones from the validation set. We also demonstrate that a NN can be used to
predict the overlapping match score, with 90\% of accuracy, of new synthetic
samples. These are encouraging results for using GANs for data augmentation and
interpolation in the context of GWs, to cover the full parameter space of, say,
exotic compact binaries, without the need of intensive numerical relativity
simulations.
| [
{
"created": "Wed, 2 Mar 2022 17:54:40 GMT",
"version": "v1"
}
] | 2022-03-03 | [
[
"Freitas",
"Felipe F.",
""
],
[
"Herdeiro",
"Carlos A. R.",
""
],
[
"Morais",
"António P.",
""
],
[
"Onofre",
"António",
""
],
[
"Pasechnik",
"Roman",
""
],
[
"Radu",
"Eugen",
""
],
[
"Sanchis-Gual",
"Nicolas",
""
],
[
"Santos",
"Rui",
""
]
] | Current gravitational wave (GW) detections rely on the existence of libraries of theoretical waveforms. Consequently, finding new physics with GWs requires libraries of non-standard models, which are computationally demanding. We discuss how deep learning frameworks can be used to generate new waveforms "learned" from a simulation dataset obtained, say, from numerical relativity simulations. Concretely, we use the WaveGAN architecture of a generative adversarial network (GAN). As a proof of concept we provide this neural network (NN) with a sample of ($>500$) waveforms from the collisions of exotic compact objects (Proca stars), obtained from numerical relativity simulations. Dividing the sample into a training and a validation set, we show that after a sufficiently large number of training epochs the NN can produce from 12\% to 25\% of the synthetic waveforms with an overlapping match of at least 95\% with the ones from the validation set. We also demonstrate that a NN can be used to predict the overlapping match score, with 90\% of accuracy, of new synthetic samples. These are encouraging results for using GANs for data augmentation and interpolation in the context of GWs, to cover the full parameter space of, say, exotic compact binaries, without the need of intensive numerical relativity simulations. |
2303.06814 | Shao-Wen Wei | Shao-Wen Wei, Yu-Peng Zhang, Yu-Xiao Liu, Robert B. Mann | Static spheres around spherically symmetric black hole spacetime | 7 pages, 4 figures. Published version | Phys. Rev. Res. 5, 043050 (2023) | 10.1103/PhysRevResearch.5.043050 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Unique features of particle orbits produce novel signatures of gravitational
observable phenomena, and are quite useful in testing compact astrophysical
objects in general relativity or modified theories of gravity. Here we observe
a representative example that a static, spherically symmetric black hole
solution with nonlinear electrodynamics admits static points at finite radial
distance. Each static point thus produces a static sphere, on which a massive
test particle can remain at rest at arbitrary latitudes with respect to an
asymptotic static observer. As a result, the well-known static Dyson spheres
can be implemented by such orbits. More interestingly, employing a topological
argument, we disclose that stable and unstable static spheres (if they exist)
always come in pairs in an asymptotically flat spacetime. In contrast to this,
the counterpart naked singularity has one more stable static sphere than the
unstable one. Our results have potential applications in testing black holes in
standard Maxwell and nonlinear electrodynamics, as well as in uncovering the
underlying astronomical observation effects in other gravitational theories
beyond general relativity.
| [
{
"created": "Mon, 13 Mar 2023 02:14:33 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Oct 2023 08:15:35 GMT",
"version": "v2"
}
] | 2023-10-24 | [
[
"Wei",
"Shao-Wen",
""
],
[
"Zhang",
"Yu-Peng",
""
],
[
"Liu",
"Yu-Xiao",
""
],
[
"Mann",
"Robert B.",
""
]
] | Unique features of particle orbits produce novel signatures of gravitational observable phenomena, and are quite useful in testing compact astrophysical objects in general relativity or modified theories of gravity. Here we observe a representative example that a static, spherically symmetric black hole solution with nonlinear electrodynamics admits static points at finite radial distance. Each static point thus produces a static sphere, on which a massive test particle can remain at rest at arbitrary latitudes with respect to an asymptotic static observer. As a result, the well-known static Dyson spheres can be implemented by such orbits. More interestingly, employing a topological argument, we disclose that stable and unstable static spheres (if they exist) always come in pairs in an asymptotically flat spacetime. In contrast to this, the counterpart naked singularity has one more stable static sphere than the unstable one. Our results have potential applications in testing black holes in standard Maxwell and nonlinear electrodynamics, as well as in uncovering the underlying astronomical observation effects in other gravitational theories beyond general relativity. |
2405.01360 | Jos\'e Diogo Sim\~ao | Jos\'e Diogo Sim\~ao | Investigations on Lorentzian Spin-foams and Semiclassical Space-times | PhD Dissertation, 210 pages; v2: implemented minor corrections and
added additional references | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This thesis is developed in the context of the spin-foam approach to quantum
gravity; all results are concerned with the Lorentzian theory and with
semiclassical methods. A correspondence is given between Majorana 2-spinors and
time-like hypersurfaces in Minkowski 3-space based on complexified quaternions.
It is shown that the former suggest a symplectic structure on the spinor phase
space which, together with an area-matching constraint, yields a
symplectomorphism to $T^*\mathrm{SU}(1,1)$. A complete 3-dimensional Lorentzian
spin-foam amplitude for both space- and time-like triangles is proposed. It is
shown to asymptote to Regge theory in the semiclassical regime. The asymptotic
limit of the 4-dimensional Conrady-Hnybida model for general polytopes is
scrutinized. Minkowski's theorem on convex polyhedra is generalized to
Lorentzian signature, and new boundary states for time-like polygons are
introduced. It is found that the semiclassical amplitude for such polygons is
insufficiently constrained. A method for the asymptotic evaluation of integrals
subject to external parameters is discussed. The method is developed in detail
for the special problem of spin-foam gluing constraints away from their
dominant critical points. A relation to the gluing constraints of effective
spin-foams is suggested.
| [
{
"created": "Thu, 2 May 2024 15:07:58 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jun 2024 19:03:18 GMT",
"version": "v2"
}
] | 2024-06-12 | [
[
"Simão",
"José Diogo",
""
]
] | This thesis is developed in the context of the spin-foam approach to quantum gravity; all results are concerned with the Lorentzian theory and with semiclassical methods. A correspondence is given between Majorana 2-spinors and time-like hypersurfaces in Minkowski 3-space based on complexified quaternions. It is shown that the former suggest a symplectic structure on the spinor phase space which, together with an area-matching constraint, yields a symplectomorphism to $T^*\mathrm{SU}(1,1)$. A complete 3-dimensional Lorentzian spin-foam amplitude for both space- and time-like triangles is proposed. It is shown to asymptote to Regge theory in the semiclassical regime. The asymptotic limit of the 4-dimensional Conrady-Hnybida model for general polytopes is scrutinized. Minkowski's theorem on convex polyhedra is generalized to Lorentzian signature, and new boundary states for time-like polygons are introduced. It is found that the semiclassical amplitude for such polygons is insufficiently constrained. A method for the asymptotic evaluation of integrals subject to external parameters is discussed. The method is developed in detail for the special problem of spin-foam gluing constraints away from their dominant critical points. A relation to the gluing constraints of effective spin-foams is suggested. |
2304.14754 | Sanjay Siwach | Bijendra Kumar Vishvakarma, Dharm Veer Singh and Sanjay Siwach | Shadows and quasinormal modes of the Bardeen black hole in cloud of
strings | 15 pages, 3 figures, reference added, statement about singularity at
the origin changed | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the black hole (BH) solution of the Einstein's gravity coupled
with non-linear electrodynamics (NED) source in the background of a cloud of
strings. We analyze the horizon structure of the obtained BH solution. The
optical features of the BH are explored. The photon radius and shadows of the
BH are obtained as a function of black hole parameters. We observe that the
size of the shadow image is bigger than its horizon radius and photon sphere.
We also study the Quasinormal modes (QNM) using WKB formula for this black
hole. The dependence of shadow radius and QN modes on black hole parameters
reflects that they are mimicker to each other.
| [
{
"created": "Fri, 28 Apr 2023 10:51:04 GMT",
"version": "v1"
},
{
"created": "Tue, 2 May 2023 11:25:41 GMT",
"version": "v2"
}
] | 2023-05-03 | [
[
"Vishvakarma",
"Bijendra Kumar",
""
],
[
"Singh",
"Dharm Veer",
""
],
[
"Siwach",
"Sanjay",
""
]
] | We investigate the black hole (BH) solution of the Einstein's gravity coupled with non-linear electrodynamics (NED) source in the background of a cloud of strings. We analyze the horizon structure of the obtained BH solution. The optical features of the BH are explored. The photon radius and shadows of the BH are obtained as a function of black hole parameters. We observe that the size of the shadow image is bigger than its horizon radius and photon sphere. We also study the Quasinormal modes (QNM) using WKB formula for this black hole. The dependence of shadow radius and QN modes on black hole parameters reflects that they are mimicker to each other. |
1508.04602 | Ben Whale | Ben E. Whale and Mike J. S. L. Ashley and Susan M. Scott | Generalizations of the Abstract Boundary singularity theorem | 24 pages | Class. Quantum Grav. 32 135001 (2015) | 10.1088/0264-9381/32/13/135001 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Abstract Boundary singularity theorem was first proven by Ashley and
Scott. It links the existence of incomplete causal geodesics in strongly
causal, maximally extended spacetimes to the existence of Abstract Boundary
essential singularities, i.e., non-removable singular boundary points. We give
two generalizations of this theorem: the first to continuous causal curves and
the distinguishing condition, the second to locally Lipschitz curves in
manifolds such that no inextendible locally Lipschitz curve is totally
imprisoned. To do this we extend generalized affine parameters from $C^1$
curves to locally Lipschitz curves.
| [
{
"created": "Wed, 19 Aug 2015 11:29:55 GMT",
"version": "v1"
}
] | 2015-08-20 | [
[
"Whale",
"Ben E.",
""
],
[
"Ashley",
"Mike J. S. L.",
""
],
[
"Scott",
"Susan M.",
""
]
] | The Abstract Boundary singularity theorem was first proven by Ashley and Scott. It links the existence of incomplete causal geodesics in strongly causal, maximally extended spacetimes to the existence of Abstract Boundary essential singularities, i.e., non-removable singular boundary points. We give two generalizations of this theorem: the first to continuous causal curves and the distinguishing condition, the second to locally Lipschitz curves in manifolds such that no inextendible locally Lipschitz curve is totally imprisoned. To do this we extend generalized affine parameters from $C^1$ curves to locally Lipschitz curves. |
2003.01252 | Petya Nedkova | Efthimia Deligianni, Jutta Kunz, Petya Nedkova | Quasi-periodic oscillations from the accretion disk around distorted
black holes | 24 pages, 8 figures | Phys. Rev. D 102, 064023 (2020) | 10.1103/PhysRevD.102.064023 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the quasi-periodic oscillations from the accretion disk around the
distorted Schwarzschild black hole in the framework of the resonant models. We
confine ourselves to the case of a quadrupole distortion which can be caused
for example by the accreting matter flow in the vicinity of the compact object.
For the purpose we examine the linear stability of the circular geodesic orbits
in the equatorial plane and derive analytical expressions for the radial and
vertical epicyclic frequencies. We investigate their properties in comparison
with the isolated Schwarzschild black hole. Due to the influence of the
external matter the vertical epicyclic frequency is not always positive
anymore, and the stability of the circular orbits is determined by the
interplay between both of the frequencies. As a result, the stable circular
orbits do not extend to infinity, but are confined to a finite annular region
between an inner and an outer marginally stable orbit. In addition, the
degeneracy between the vertical epicyclic and the orbital frequency, which is
characteristic for the Schwarzschild solution, is broken, and there are regions
in the parametric space where the radial epicyclic frequency is larger than the
vertical one. All these properties allow for much more diverse types of
non-linear resonances to be excited than for the isolated Schwarzschild black
hole, which can provide an explanation for the observed 3:2 ratio between the
twin-peak frequencies of the quasi-periodic oscillations from the accretion
disk.
| [
{
"created": "Mon, 2 Mar 2020 23:47:16 GMT",
"version": "v1"
}
] | 2020-09-16 | [
[
"Deligianni",
"Efthimia",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Nedkova",
"Petya",
""
]
] | We study the quasi-periodic oscillations from the accretion disk around the distorted Schwarzschild black hole in the framework of the resonant models. We confine ourselves to the case of a quadrupole distortion which can be caused for example by the accreting matter flow in the vicinity of the compact object. For the purpose we examine the linear stability of the circular geodesic orbits in the equatorial plane and derive analytical expressions for the radial and vertical epicyclic frequencies. We investigate their properties in comparison with the isolated Schwarzschild black hole. Due to the influence of the external matter the vertical epicyclic frequency is not always positive anymore, and the stability of the circular orbits is determined by the interplay between both of the frequencies. As a result, the stable circular orbits do not extend to infinity, but are confined to a finite annular region between an inner and an outer marginally stable orbit. In addition, the degeneracy between the vertical epicyclic and the orbital frequency, which is characteristic for the Schwarzschild solution, is broken, and there are regions in the parametric space where the radial epicyclic frequency is larger than the vertical one. All these properties allow for much more diverse types of non-linear resonances to be excited than for the isolated Schwarzschild black hole, which can provide an explanation for the observed 3:2 ratio between the twin-peak frequencies of the quasi-periodic oscillations from the accretion disk. |
1204.6036 | Timothy H. Boyer | Timothy H. Boyer | Contrasting Classical and Quantum Vacuum States in Non-Inertial Frames | 29 pages | Found. Phys. 43, 923-947 (2013) | 10.1007/s10701-013-9726-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Classical electron theory with classical electromagnetic zero-point radiation
(stochastic electrodynamics) is the classical theory which most closely
approximates quantum electrodynamics. Indeed, in inertial frames, there is a
general connection between classical field theories with classical zero-point
radiation and quantum field theories. However, this connection does not extend
to noninertial frames where the time parameter is not a geodesic coordinate.
Quantum field theory applies the canonical quantization procedure (depending on
the local time coordinate) to a mirror-walled box, and, in general, each
non-inertial coordinate frame has its own vacuum state. In complete contrast,
the spectrum of random classical zero-point radiation is based upon symmetry
principles of relativistic spacetime; in empty space, the correlation functions
depend upon only the geodesic separations (and their coordinate derivatives)
between the spacetime points. It makes no difference whether a box of classical
zero-point radiation is gradually or suddenly set into uniform acceleration;
the radiation in the interior retains the same correlation function except for
small end-point (Casimir) corrections. Thus in classical theory where
zero-point radiation is defined in terms of geodesic separations, there is
nothing physically comparable to the quantum distinction between the Minkowski
and Rindler vacuum states. It is also noted that relativistic classical systems
with internal potential energy must be spatially extended and can not be point
systems. Based upon the classical analysis, it is suggested that the claimed
heating effects of acceleration through the vacuum may not exist in nature.
| [
{
"created": "Thu, 26 Apr 2012 17:36:58 GMT",
"version": "v1"
}
] | 2013-08-13 | [
[
"Boyer",
"Timothy H.",
""
]
] | Classical electron theory with classical electromagnetic zero-point radiation (stochastic electrodynamics) is the classical theory which most closely approximates quantum electrodynamics. Indeed, in inertial frames, there is a general connection between classical field theories with classical zero-point radiation and quantum field theories. However, this connection does not extend to noninertial frames where the time parameter is not a geodesic coordinate. Quantum field theory applies the canonical quantization procedure (depending on the local time coordinate) to a mirror-walled box, and, in general, each non-inertial coordinate frame has its own vacuum state. In complete contrast, the spectrum of random classical zero-point radiation is based upon symmetry principles of relativistic spacetime; in empty space, the correlation functions depend upon only the geodesic separations (and their coordinate derivatives) between the spacetime points. It makes no difference whether a box of classical zero-point radiation is gradually or suddenly set into uniform acceleration; the radiation in the interior retains the same correlation function except for small end-point (Casimir) corrections. Thus in classical theory where zero-point radiation is defined in terms of geodesic separations, there is nothing physically comparable to the quantum distinction between the Minkowski and Rindler vacuum states. It is also noted that relativistic classical systems with internal potential energy must be spatially extended and can not be point systems. Based upon the classical analysis, it is suggested that the claimed heating effects of acceleration through the vacuum may not exist in nature. |
2308.06469 | Kyosuke Tomonari | Kyosuke Tomonari and Sebastian Bahamonde | Dirac-Bergmann analysis and Degrees of Freedom of Coincident
$f(Q)$-gravity | 26 pages. v2: Added references and footnotes, revised overall, for
submission. 26 pages. v3: Added new Sec. V-A and references, revised overall.
31 pages. v4: Published in EPJC (Single column version) | Eur. Phys. J. C (2024) 84:349 | 10.1140/epjc/s10052-024-12677-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the propagating degrees of freedom of $f(Q)$-gravity in a
$4$-dimensional space-time under the imposition of the coincident gauge by
performing the Dirac-Bergmann analysis. In this work, we start with a top-down
reconstruction of the metric-affine gauge theory of gravity based only on the
concept of a vector bundle. Then, the so-called geometrical trinity of gravity
is introduced and the role of the coincident GR is clarified. After that, we
reveal relationships between the boundary terms in the variational principle
and the symplectic structure of the theory in order to confirm the validity of
the analysis for our studied theories. Then, as examples, we revisit the
analysis of GR and its $f(\lc{R})$-extensions. Finally, after reviewing the
Dirac-Bergmann analysis of the coincident GR and that of $f(T)$-gravity, we
perform the analysis of coincident $f(Q)$-gravity. Under the imposition of
appropriate spatial boundary conditions, we find that, as a generic case, the
theory has five primary, three secondary, and two tertiary constraint densities
and all these constraint densities are classified into second-class constraint
density; the number six is the propagating degrees of freedom of the theory and
there are no longer any remaining gauge degrees of freedom. We also discuss the
condition of providing seven pDoF as a generic case. The violation of
diffeomorphism invariance of coincident $f(Q)$-gravity make it possible to
emerge such several sectors.
| [
{
"created": "Sat, 12 Aug 2023 05:24:17 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Aug 2023 07:44:33 GMT",
"version": "v2"
},
{
"created": "Tue, 9 Jan 2024 08:18:10 GMT",
"version": "v3"
},
{
"created": "Wed, 24 Apr 2024 12:03:29 GMT",
"version": "v4"
}
] | 2024-04-25 | [
[
"Tomonari",
"Kyosuke",
""
],
[
"Bahamonde",
"Sebastian",
""
]
] | We investigate the propagating degrees of freedom of $f(Q)$-gravity in a $4$-dimensional space-time under the imposition of the coincident gauge by performing the Dirac-Bergmann analysis. In this work, we start with a top-down reconstruction of the metric-affine gauge theory of gravity based only on the concept of a vector bundle. Then, the so-called geometrical trinity of gravity is introduced and the role of the coincident GR is clarified. After that, we reveal relationships between the boundary terms in the variational principle and the symplectic structure of the theory in order to confirm the validity of the analysis for our studied theories. Then, as examples, we revisit the analysis of GR and its $f(\lc{R})$-extensions. Finally, after reviewing the Dirac-Bergmann analysis of the coincident GR and that of $f(T)$-gravity, we perform the analysis of coincident $f(Q)$-gravity. Under the imposition of appropriate spatial boundary conditions, we find that, as a generic case, the theory has five primary, three secondary, and two tertiary constraint densities and all these constraint densities are classified into second-class constraint density; the number six is the propagating degrees of freedom of the theory and there are no longer any remaining gauge degrees of freedom. We also discuss the condition of providing seven pDoF as a generic case. The violation of diffeomorphism invariance of coincident $f(Q)$-gravity make it possible to emerge such several sectors. |
gr-qc/9606066 | David Langlois | David Langlois | Cosmic Microwave Background Dipole induced by double inflation | Latex, 9 pages, no figure, to appear in Phys. Rev. D | Phys.Rev.D54:2447-2450,1996 | 10.1103/PhysRevD.54.2447 | null | gr-qc astro-ph | null | The observed CMBR dipole is generally interpreted as the consequence of the
peculiar motion of the Sun with respect to the reference frame of the CMBR.
This article proposes an alternative interpretation in which the observed
dipole is the result of isocurvature perturbations on scales larger than the
present Hubble radius. These perturbations are produced in the simplest model
of double inflation, depending on three parameters. The observed dipole and
quadrupole can be explained in this model, while severely constraining its
parameters.
| [
{
"created": "Sun, 23 Jun 1996 11:18:31 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Langlois",
"David",
""
]
] | The observed CMBR dipole is generally interpreted as the consequence of the peculiar motion of the Sun with respect to the reference frame of the CMBR. This article proposes an alternative interpretation in which the observed dipole is the result of isocurvature perturbations on scales larger than the present Hubble radius. These perturbations are produced in the simplest model of double inflation, depending on three parameters. The observed dipole and quadrupole can be explained in this model, while severely constraining its parameters. |
1809.00698 | Joel Berg\'e | Joel Berg\'e | The Inverse Square Law And Newtonian Dynamics space explorer (ISLAND) | Moriond Gravitation session 2017 proceeding + COSPAR meeting 2018 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The ISLAND (Inverse Square Law And Newtonian Dynamics) Space Explorer is a
new concept to test the gravitational Inverse Square Law at: (1) submillimeter
scale and (2) at the largest Solar System scales (dozens of Astronomical Units
--AU). The main idea is to embark a torsion pendulum at the center of gravity
of a dedicated, possibly drag-free and attitude-controlled, interplanetary
probe whose gravitational environment is accurately probed by, and corrected
for thanks to six ultrasensitive accelerometers arranged as a cross around the
torsion pendulum.
| [
{
"created": "Mon, 3 Sep 2018 19:35:07 GMT",
"version": "v1"
}
] | 2018-09-05 | [
[
"Bergé",
"Joel",
""
]
] | The ISLAND (Inverse Square Law And Newtonian Dynamics) Space Explorer is a new concept to test the gravitational Inverse Square Law at: (1) submillimeter scale and (2) at the largest Solar System scales (dozens of Astronomical Units --AU). The main idea is to embark a torsion pendulum at the center of gravity of a dedicated, possibly drag-free and attitude-controlled, interplanetary probe whose gravitational environment is accurately probed by, and corrected for thanks to six ultrasensitive accelerometers arranged as a cross around the torsion pendulum. |
1012.0886 | Bruno Coutinho Mundim | Bruno C. Mundim, Bernard J. Kelly, Yosef Zlochower, Hiroyuki Nakano,
Manuela Campanelli | Hybrid black-hole binary initial data | Proceedings of Theory Meets Data Analysis at Comparable and Extreme
Mass Ratios (NRDA/Capra 2010), Perimeter Institute, June 2010 - 19 pages | Class. Quantum Grav. 28 134003 (2011) | 10.1088/0264-9381/28/13/134003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Traditional black-hole binary puncture initial data is conformally flat. This
unphysical assumption is coupled with a lack of radiation signature from the
binary's past life. As a result, waveforms extracted from evolutions of this
data display an abrupt jump. In Kelly et al. [Class.Quant.Grav.27:114005,2010],
a new binary black-hole initial data with radiation contents derived in the
post-Newtonian (PN) calculation was adapted to puncture evolutions in numerical
relativity. This data satisfies the constraint equations to the 2.5PN order,
and contains a transverse-traceless "wavy" metric contribution, violating the
standard assumption of conformal flatness. Although the evolution contained
less spurious radiation, there were undesired features; the unphysical horizon
mass loss and the large initial orbital eccentricity. Introducing a hybrid
approach to the initial data evaluation, we significantly reduce these
undesired features.
| [
{
"created": "Sat, 4 Dec 2010 07:28:21 GMT",
"version": "v1"
}
] | 2015-03-17 | [
[
"Mundim",
"Bruno C.",
""
],
[
"Kelly",
"Bernard J.",
""
],
[
"Zlochower",
"Yosef",
""
],
[
"Nakano",
"Hiroyuki",
""
],
[
"Campanelli",
"Manuela",
""
]
] | Traditional black-hole binary puncture initial data is conformally flat. This unphysical assumption is coupled with a lack of radiation signature from the binary's past life. As a result, waveforms extracted from evolutions of this data display an abrupt jump. In Kelly et al. [Class.Quant.Grav.27:114005,2010], a new binary black-hole initial data with radiation contents derived in the post-Newtonian (PN) calculation was adapted to puncture evolutions in numerical relativity. This data satisfies the constraint equations to the 2.5PN order, and contains a transverse-traceless "wavy" metric contribution, violating the standard assumption of conformal flatness. Although the evolution contained less spurious radiation, there were undesired features; the unphysical horizon mass loss and the large initial orbital eccentricity. Introducing a hybrid approach to the initial data evaluation, we significantly reduce these undesired features. |
gr-qc/0004076 | Reinhard Prix | Reinhard Prix | Covariant Vortex In Superconducting-Superfluid-Normal Fluid Mixtures
with Stiff Equation of State | 14 pages, uses RevTeX and amssymb, submitted | Phys.Rev. D62 (2000) 103005 | 10.1103/PhysRevD.62.103005 | null | gr-qc astro-ph cond-mat.supr-con | null | The integrals of motion for a cylindrically symmetric stationary vortex are
obtained in a covariant description of a mixture of interacting
superconductors, superfluids and normal fluids. The relevant integrated
stress-energy coefficients for the vortex with respect to a vortex-free
reference state are calculated in the approximation of a ``stiff'', i.e. least
compressible, relativistic equation of state for the fluid mixture. As an
illustration of the foregoing general results, we discuss their application to
some of the well known examples of ``real'' superfluid and superconducting
systems that are contained as special cases. These include Landau's two-fluid
model, uncharged binary superfluid mixtures, rotating conventional
superconductors and the superfluid neutron-proton-electron plasma in the outer
core of neutron stars.
| [
{
"created": "Wed, 26 Apr 2000 15:55:49 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Prix",
"Reinhard",
""
]
] | The integrals of motion for a cylindrically symmetric stationary vortex are obtained in a covariant description of a mixture of interacting superconductors, superfluids and normal fluids. The relevant integrated stress-energy coefficients for the vortex with respect to a vortex-free reference state are calculated in the approximation of a ``stiff'', i.e. least compressible, relativistic equation of state for the fluid mixture. As an illustration of the foregoing general results, we discuss their application to some of the well known examples of ``real'' superfluid and superconducting systems that are contained as special cases. These include Landau's two-fluid model, uncharged binary superfluid mixtures, rotating conventional superconductors and the superfluid neutron-proton-electron plasma in the outer core of neutron stars. |
1305.7104 | Houwen Wu | Deyou Chen, Houwen Wu, Haitang Yang | Fermion's tunnelling with effects of quantum gravity | V2, 14 pages, references added, typos corrected | Advances in High Energy Physics, vol. 2013, Article ID 432412, 6
pages, 2013 | 10.1155/2013/432412 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, using Hamilton-Jacobi method, we address the tunnelling of
fermions in a 4-dimensional Schwarzschild spacetime. Base on the generalized
uncertainty principle, we introduce the influence of quantum gravity. After
solving the equation of motion of the spin 1/2 field, we derive the corrected
Hawking temperature. It turns out that the correction depends not only on the
black hole's mass but also on the mass (energy) of emitted fermions. It is of
interest that, in our calculation, the quantum gravity correction decelerates
the temperature increase during the radiation explicitly. This observation then
naturally leads to the remnants in black hole evaporation. Our calculation
shows that the residue mass is $\gtrsim M_p/\beta_0$, where $M_p$ is the Planck
mass and $\beta_0$ is a dimensionless parameter accounting for quantum gravity
effects. The evaporation singularity is then avoided.
| [
{
"created": "Thu, 30 May 2013 13:40:24 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Jun 2013 17:24:21 GMT",
"version": "v2"
}
] | 2013-11-14 | [
[
"Chen",
"Deyou",
""
],
[
"Wu",
"Houwen",
""
],
[
"Yang",
"Haitang",
""
]
] | In this paper, using Hamilton-Jacobi method, we address the tunnelling of fermions in a 4-dimensional Schwarzschild spacetime. Base on the generalized uncertainty principle, we introduce the influence of quantum gravity. After solving the equation of motion of the spin 1/2 field, we derive the corrected Hawking temperature. It turns out that the correction depends not only on the black hole's mass but also on the mass (energy) of emitted fermions. It is of interest that, in our calculation, the quantum gravity correction decelerates the temperature increase during the radiation explicitly. This observation then naturally leads to the remnants in black hole evaporation. Our calculation shows that the residue mass is $\gtrsim M_p/\beta_0$, where $M_p$ is the Planck mass and $\beta_0$ is a dimensionless parameter accounting for quantum gravity effects. The evaporation singularity is then avoided. |
2001.00772 | Shuxun Tian | S. X. Tian and Zong-Hong Zhu | Revisiting scalar and tensor perturbations in a nonlocal gravity | 5 pages, PRD in press | Phys. Rev. D 100, 124059 (2019) | 10.1103/PhysRevD.100.124059 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Nonlocal RT gravity is a successful modified gravity theory, which not only
explains the late-time cosmic acceleration but also behaves well in the solar
system. Previous analysis generally assumes the auxiliary field $S_i$ vanishes
at the cosmic background. However, we find the background $S_i$ is proportional
to $a^2$ with the expansion of the universe. Then we discuss the influence of
the nonzero background $S_i$ on the cosmic background evolution, the scalar and
tensor perturbations. We find the cosmic background evolution is independent of
$S_i$, and the influence of the nonzero background $S_i$ on the weak field
limit at solar system scales is negligible. For the tensor perturbation, we
find the only possible observable effect is the influence of nonzero background
$S_i$ on the LIGO gravitational wave amplitude and also luminosity distance.
Future high redshift gravitational wave observations could be used to constrain
the background value of $S_i$.
| [
{
"created": "Fri, 3 Jan 2020 09:58:16 GMT",
"version": "v1"
}
] | 2020-01-06 | [
[
"Tian",
"S. X.",
""
],
[
"Zhu",
"Zong-Hong",
""
]
] | Nonlocal RT gravity is a successful modified gravity theory, which not only explains the late-time cosmic acceleration but also behaves well in the solar system. Previous analysis generally assumes the auxiliary field $S_i$ vanishes at the cosmic background. However, we find the background $S_i$ is proportional to $a^2$ with the expansion of the universe. Then we discuss the influence of the nonzero background $S_i$ on the cosmic background evolution, the scalar and tensor perturbations. We find the cosmic background evolution is independent of $S_i$, and the influence of the nonzero background $S_i$ on the weak field limit at solar system scales is negligible. For the tensor perturbation, we find the only possible observable effect is the influence of nonzero background $S_i$ on the LIGO gravitational wave amplitude and also luminosity distance. Future high redshift gravitational wave observations could be used to constrain the background value of $S_i$. |
2003.00388 | Angel Garcia-Chung | Angel Garcia-Chung | The symplectic group in Polymer Quantum Mechanics | 20 pages | Phys. Rev. D 101, 106004 (2020) | 10.1103/PhysRevD.101.106004 | null | gr-qc math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we provide the representation of the symplectic group $Sp(2n,
\mathbb{R})$ in polymer quantum mechanics. We derive the propagator of the
polymer free particle and the polymer harmonic oscillator without considering a
polymer scale. The polymer scale is then introduced to reconcile our results
with those expressions for the polymer free particle. The propagator for the
polymer harmonic oscillator implies non-unitary evolution.
| [
{
"created": "Sun, 1 Mar 2020 03:35:41 GMT",
"version": "v1"
}
] | 2020-05-13 | [
[
"Garcia-Chung",
"Angel",
""
]
] | In this paper we provide the representation of the symplectic group $Sp(2n, \mathbb{R})$ in polymer quantum mechanics. We derive the propagator of the polymer free particle and the polymer harmonic oscillator without considering a polymer scale. The polymer scale is then introduced to reconcile our results with those expressions for the polymer free particle. The propagator for the polymer harmonic oscillator implies non-unitary evolution. |
2311.05652 | Ivan Arraut Dr. | Ivan Arraut | The Tully-Fisher's law and Dark Matter effects derived via modified
symmetries | 4 pages, Editor's choice at EPL | 2023 EPL 144 29003 | 10.1209/0295-5075/ad05f7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In any physical system, when we move from short to large scales, new
spacetime symmetries emerge which help us to simplify the dynamics of the
system. In this letter we demonstrate that certain variations on the symmetries
of General Relativity at large scales, generate the effects equivalent to Dark
Matter. In particular, we reproduce the Tully-Fisher law, consistent with the
predictions proposed by MOND. Additionally, we demonstrate that the dark matter
effects derived in this way, are consistent with the predictions suggested by
MOND, without modifying gravity.
| [
{
"created": "Wed, 8 Nov 2023 14:18:11 GMT",
"version": "v1"
}
] | 2023-11-13 | [
[
"Arraut",
"Ivan",
""
]
] | In any physical system, when we move from short to large scales, new spacetime symmetries emerge which help us to simplify the dynamics of the system. In this letter we demonstrate that certain variations on the symmetries of General Relativity at large scales, generate the effects equivalent to Dark Matter. In particular, we reproduce the Tully-Fisher law, consistent with the predictions proposed by MOND. Additionally, we demonstrate that the dark matter effects derived in this way, are consistent with the predictions suggested by MOND, without modifying gravity. |
2407.21522 | Albachiara Cogo | Carla Cederbaum, Albachiara Cogo and Axel Fehrenbach | Uniqueness of equipotential photon surfaces in 4-dimensional static
vacuum asymptotically flat spacetimes for positive, negative, and zero mass
-- and a new partial proof of the Willmore inequality | null | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present different proofs of the uniqueness of 4-dimensional static vacuum
asymptotically flat spacetimes containing a connected equipotential photon
surface or in particular a connected photon sphere. We do not assume that the
equipotential photon surface is outward directed or non-degenerate and hence
cover not only the positive but also the negative and the zero mass case which
has not yet been treated in the literature. Our results partially reproduce and
extend beyond results by Cederbaum and by Cederbaum and Galloway. In the
positive and negative mass cases, we give three proofs which are based on the
approaches to proving black hole uniqueness by Israel, Robinson, and
Agostiniani--Mazzieri, respectively. In the zero mass case, we give four
proofs. One is based on the positive mass theorem, the second one is inspired
by Israel's approach and in particular leads to a new proof of the Willmore
inequality in $(\mathbb{R}^3, \delta)$, under a technical assumption. The
remaining two proofs are inspired by proofs of the Willmore inequality by
Cederbaum and Miehe and by Agostiniani and Mazzieri, respectively. In
particular, this suggests to view the Willmore inequality and its rigidity case
as a zero mass version of equipotential photon surface uniqueness.
| [
{
"created": "Wed, 31 Jul 2024 10:49:21 GMT",
"version": "v1"
}
] | 2024-08-01 | [
[
"Cederbaum",
"Carla",
""
],
[
"Cogo",
"Albachiara",
""
],
[
"Fehrenbach",
"Axel",
""
]
] | We present different proofs of the uniqueness of 4-dimensional static vacuum asymptotically flat spacetimes containing a connected equipotential photon surface or in particular a connected photon sphere. We do not assume that the equipotential photon surface is outward directed or non-degenerate and hence cover not only the positive but also the negative and the zero mass case which has not yet been treated in the literature. Our results partially reproduce and extend beyond results by Cederbaum and by Cederbaum and Galloway. In the positive and negative mass cases, we give three proofs which are based on the approaches to proving black hole uniqueness by Israel, Robinson, and Agostiniani--Mazzieri, respectively. In the zero mass case, we give four proofs. One is based on the positive mass theorem, the second one is inspired by Israel's approach and in particular leads to a new proof of the Willmore inequality in $(\mathbb{R}^3, \delta)$, under a technical assumption. The remaining two proofs are inspired by proofs of the Willmore inequality by Cederbaum and Miehe and by Agostiniani and Mazzieri, respectively. In particular, this suggests to view the Willmore inequality and its rigidity case as a zero mass version of equipotential photon surface uniqueness. |
2002.11471 | Kazuharu Bamba | G.G.L. Nashed, Amare Abebe and Kazuharu Bamba | Neutral compact spherically symmetric stars in teleparallel gravity | 13 pages, 9 figures | Eur. Phys. J. C (2020) 80:1109 | 10.1140/epjc/s10052-020-08671-8 | FU-PCG-72 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present novel neutral and uncharged solutions that describe the cluster of
Einstein in the teleparallel equivalent of general relativity (TEGR). To this
end, we use a tetrad field with non-diagonal spherical symmetry which gives the
vanishing of the off-diagonal components for the gravitational field equations
in the TEGR theory. The clusters are calculated by using an anisotropic
energy-momentum tensor. We solve the field equations of TEGR theory, using two
assumptions: the first one is by using an equation of state that relates
density with tangential pressure while the second postulate is to assume a
specific form of one of the two unknown functions that appear in the
non-diagonal tetrad field. Among many things presented in this study, we
investigate the static stability specification. We also study the
Tolman-Oppenheimer-Volkoff equation of these solutions in addition to the
conditions of energy. The causality constraints with the adiabatic index in
terms of the limit of stability are discussed.
| [
{
"created": "Wed, 5 Feb 2020 09:53:25 GMT",
"version": "v1"
}
] | 2023-11-22 | [
[
"Nashed",
"G. G. L.",
""
],
[
"Abebe",
"Amare",
""
],
[
"Bamba",
"Kazuharu",
""
]
] | We present novel neutral and uncharged solutions that describe the cluster of Einstein in the teleparallel equivalent of general relativity (TEGR). To this end, we use a tetrad field with non-diagonal spherical symmetry which gives the vanishing of the off-diagonal components for the gravitational field equations in the TEGR theory. The clusters are calculated by using an anisotropic energy-momentum tensor. We solve the field equations of TEGR theory, using two assumptions: the first one is by using an equation of state that relates density with tangential pressure while the second postulate is to assume a specific form of one of the two unknown functions that appear in the non-diagonal tetrad field. Among many things presented in this study, we investigate the static stability specification. We also study the Tolman-Oppenheimer-Volkoff equation of these solutions in addition to the conditions of energy. The causality constraints with the adiabatic index in terms of the limit of stability are discussed. |
1401.7312 | Swastik Bhattacharya | Swastik Bhattacharya | A new proposal regarding the heat generated by gravity in locally
accelerating frames | 27 pages, 1 Figure | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For Rindler observers accelerating close to the horizon in local patches
around a spacetime point, the matter-energy passing through the horizon
increases the entropy and heat energy. Jacobson has showed that the Einstein
equation can be derived from the consideration of this thermodynamic process.
This, however, works only if the acceleration $a$ is much larger than the scale
set by the curvature of the spacetime. It is explored here whether an extension
is possible to the case with no lower bound on $a$. We show that this is
possible if one assumes that in a locally accelerating frame, the matter-energy
passing through null hypersurfaces could result in an increase in the heat
energy and the entropy. Such a generalisation extends the thermodynamic
derivation of gravity to include any non-freely falling observer. A new method
of determining the temperature detected by such locally accelerating observers
is also presented. By considering only the quantisation of sufficiently
localised wave modes of a field, it is shown that the observer finds himself in
a thermal environment.
| [
{
"created": "Tue, 28 Jan 2014 20:12:11 GMT",
"version": "v1"
}
] | 2014-01-29 | [
[
"Bhattacharya",
"Swastik",
""
]
] | For Rindler observers accelerating close to the horizon in local patches around a spacetime point, the matter-energy passing through the horizon increases the entropy and heat energy. Jacobson has showed that the Einstein equation can be derived from the consideration of this thermodynamic process. This, however, works only if the acceleration $a$ is much larger than the scale set by the curvature of the spacetime. It is explored here whether an extension is possible to the case with no lower bound on $a$. We show that this is possible if one assumes that in a locally accelerating frame, the matter-energy passing through null hypersurfaces could result in an increase in the heat energy and the entropy. Such a generalisation extends the thermodynamic derivation of gravity to include any non-freely falling observer. A new method of determining the temperature detected by such locally accelerating observers is also presented. By considering only the quantisation of sufficiently localised wave modes of a field, it is shown that the observer finds himself in a thermal environment. |
gr-qc/0609051 | Mayeul Arminjon | Mayeul Arminjon | On the extension of Newton's second law to theories of gravitation in
curved space-time | 32 pages | Arch.Mech. 48 (1996) 551-576 | null | null | gr-qc | null | We investigate the possibility of extending Newton's second law to the
general framework of theories in which special relativity is locally valid, and
in which gravitation changes the flat Galilean space-time metric into a curved
metric. This framework is first recalled, underlining the possibility to
uniquely define a space metric and a local time in any given reference frame,
hence to define velocity and momentum in terms of the local space and time
standards. It is shown that a unique consistent definition can be given for the
derivative of a vector (the momentum) along a trajectory. Then the possible
form of the gravitation force is investigated. It is shown that, if the motion
of free particles has to follow space-time geodesics, then the expression for
the gravity acceleration is determined uniquely. It depends on the variation of
the metric with space and time, and it involves the velocity of the particle.
| [
{
"created": "Thu, 14 Sep 2006 12:16:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Arminjon",
"Mayeul",
""
]
] | We investigate the possibility of extending Newton's second law to the general framework of theories in which special relativity is locally valid, and in which gravitation changes the flat Galilean space-time metric into a curved metric. This framework is first recalled, underlining the possibility to uniquely define a space metric and a local time in any given reference frame, hence to define velocity and momentum in terms of the local space and time standards. It is shown that a unique consistent definition can be given for the derivative of a vector (the momentum) along a trajectory. Then the possible form of the gravitation force is investigated. It is shown that, if the motion of free particles has to follow space-time geodesics, then the expression for the gravity acceleration is determined uniquely. It depends on the variation of the metric with space and time, and it involves the velocity of the particle. |
2212.06205 | Riasat Ali | Zunaira Akhtar, Rimsha Babar, Riasat Ali | Thermal Fluctuations Evolution of the New Schwarzschild Black Hole | 11 pages, 14 figures, version accepted for publication in Annals of
Physics | null | 10.1016/j.aop.2022.169190 | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | We study the thermodynamic analysis and logarithm corrections of the new
Schwarzschild black hole. We compute the thermodynamic quantities like entropy,
Hawking temperature and heat capacity. The area of black holes never decreases
because they absorb everything from their surroundings due to high gravity. In
this regard, the area-entropy relation proposed by Bekenstein needs to be
corrected, leading to the concept of logarithmic corrections. To do so, we
obtain the corrected entropy for new Schwarzschild black hole to analyze the
effects of thermal fluctuations and we evaluate the thermodynamic quantities
like specific heat, internal energy, Helmholtz free energy, Gibbs free energy,
enthalpy and pressure in the presence of correction parameter $\eta$.
Furthermore, we check the stability of the system with the help of heat
capacity and well known Hessian matrix technique. By our graphical analysis, we
observe that the thermal fluctuations effects the stability of small radii
black holes (e.g., New Schwarzchild black hole) and therefore, small black
holes get unstable regions due to these first order corrections.
| [
{
"created": "Mon, 12 Dec 2022 19:28:28 GMT",
"version": "v1"
}
] | 2022-12-14 | [
[
"Akhtar",
"Zunaira",
""
],
[
"Babar",
"Rimsha",
""
],
[
"Ali",
"Riasat",
""
]
] | We study the thermodynamic analysis and logarithm corrections of the new Schwarzschild black hole. We compute the thermodynamic quantities like entropy, Hawking temperature and heat capacity. The area of black holes never decreases because they absorb everything from their surroundings due to high gravity. In this regard, the area-entropy relation proposed by Bekenstein needs to be corrected, leading to the concept of logarithmic corrections. To do so, we obtain the corrected entropy for new Schwarzschild black hole to analyze the effects of thermal fluctuations and we evaluate the thermodynamic quantities like specific heat, internal energy, Helmholtz free energy, Gibbs free energy, enthalpy and pressure in the presence of correction parameter $\eta$. Furthermore, we check the stability of the system with the help of heat capacity and well known Hessian matrix technique. By our graphical analysis, we observe that the thermal fluctuations effects the stability of small radii black holes (e.g., New Schwarzchild black hole) and therefore, small black holes get unstable regions due to these first order corrections. |
gr-qc/0612089 | Rong-Gen Cai | M. Akbar and Rong-Gen Cai | Thermodynamic Behavior of Field Equations for f(R) Gravity | Latex 16 pages, v2: one reference added | Phys.Lett.B648:243-248,2007 | 10.1016/j.physletb.2007.03.005 | null | gr-qc hep-th | null | Recently it has shown that Einstein's field equations can be rewritten into a
form of the first law of thermodynamics both at event horizon of static
spherically symmetric black holes and apparent horizon of
Friedmann-Robertson-Walker (FRW) universe, which indicates intrinsic
thermodynamic properties of spacetime horizon. In the present paper we deal
with the so-called $f(R)$ gravity, whose action is a function of the curvature
scalar $R$. In the setup of static spherically symmetric black hole spacetime,
we find that at the event horizon, the field equations of $f(R)$ gravity can be
written into a form $dE = TdS - PdV + Td\bar{S}$, where $T$ is the Hawking
temperature and $S=Af'(R)/4G$ is the horizon entropy of the black hole, $E$ is
the horizon energy of the black hole, $P$ is the radial pressure of matter, $V$
is the volume of black hole horizon, and $d\bar S$ can be interpreted as the
entropy production term due to nonequilibrium thermodynamics of spacetime. In
the setup of FRW universe, the field equations can also be cast to a similar
form, $dE=TdS +WdV +Td\bar S$, at the apparent horizon, where $W=(\rho-P)/2$,
$E$ is the energy of perfect fluid with energy density $\rho$ and pressure $P$
inside the apparent horizon. Compared to the case of Einstein's general
relativity, an additional term $d\bar S$ also appears here. The appearance of
the additional term is consistent with the argument recently given by Eling
{\it et al.} (gr-qc/0602001) that the horizon thermodynamics is non-equilibrium
one for the $f(R)$ gravity.
| [
{
"created": "Thu, 14 Dec 2006 06:55:45 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Jan 2007 06:19:05 GMT",
"version": "v2"
}
] | 2010-10-27 | [
[
"Akbar",
"M.",
""
],
[
"Cai",
"Rong-Gen",
""
]
] | Recently it has shown that Einstein's field equations can be rewritten into a form of the first law of thermodynamics both at event horizon of static spherically symmetric black holes and apparent horizon of Friedmann-Robertson-Walker (FRW) universe, which indicates intrinsic thermodynamic properties of spacetime horizon. In the present paper we deal with the so-called $f(R)$ gravity, whose action is a function of the curvature scalar $R$. In the setup of static spherically symmetric black hole spacetime, we find that at the event horizon, the field equations of $f(R)$ gravity can be written into a form $dE = TdS - PdV + Td\bar{S}$, where $T$ is the Hawking temperature and $S=Af'(R)/4G$ is the horizon entropy of the black hole, $E$ is the horizon energy of the black hole, $P$ is the radial pressure of matter, $V$ is the volume of black hole horizon, and $d\bar S$ can be interpreted as the entropy production term due to nonequilibrium thermodynamics of spacetime. In the setup of FRW universe, the field equations can also be cast to a similar form, $dE=TdS +WdV +Td\bar S$, at the apparent horizon, where $W=(\rho-P)/2$, $E$ is the energy of perfect fluid with energy density $\rho$ and pressure $P$ inside the apparent horizon. Compared to the case of Einstein's general relativity, an additional term $d\bar S$ also appears here. The appearance of the additional term is consistent with the argument recently given by Eling {\it et al.} (gr-qc/0602001) that the horizon thermodynamics is non-equilibrium one for the $f(R)$ gravity. |
2106.11771 | Marie-No\"elle C\'el\'erier | Marie-No\"elle C\'el\'erier (Laboratoire Univers et TH\'eories,
Observatoire de Paris) | New classes of exact interior nonvacuum solutions to the GR field
equations for spacetimes sourced by a rigidly rotating stationary cylindrical
anisotropic fluid | 10 pages, 0 figure. arXiv admin note: text overlap with
arXiv:2004.02636, significant additions, final text complying with the
published version | Phys. Rev. D 104, 064040 (2021) | 10.1103/PhysRevD.104.064040 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A double new class of solutions to the general relativity field equations
describing interior spacetimes sourced by stationary cylindrical anisotropic
fluids with principal stress directed along the symmetry axis is displayed.
These solutions are required to satisfy regularity and junction conditions so
that they can be possibly used to represent rotating astrophysical objects.
Mathematical and physical properties are analyzed. The spacetime two
independent parameters are physically interpreted, and they are shown to define
two different solution classes together with stating the latters' properties.
| [
{
"created": "Sun, 20 Jun 2021 13:37:57 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Jul 2021 09:08:26 GMT",
"version": "v2"
},
{
"created": "Sat, 4 Sep 2021 07:10:51 GMT",
"version": "v3"
}
] | 2021-09-22 | [
[
"Célérier",
"Marie-Noëlle",
"",
"Laboratoire Univers et THéories,\n Observatoire de Paris"
]
] | A double new class of solutions to the general relativity field equations describing interior spacetimes sourced by stationary cylindrical anisotropic fluids with principal stress directed along the symmetry axis is displayed. These solutions are required to satisfy regularity and junction conditions so that they can be possibly used to represent rotating astrophysical objects. Mathematical and physical properties are analyzed. The spacetime two independent parameters are physically interpreted, and they are shown to define two different solution classes together with stating the latters' properties. |
2111.01779 | Thiago Barbosa Guerreiro | Thiago Guerreiro, Francesco Coradeschi, Antonia Micol Frassino,
Jennifer Rittenhouse West, Enrico Junior Schioppa | Quantum signatures in nonlinear gravitational waves | 16 pages, 2 figures; accepted final version, expanded work, added
quantum state reconstruction and more detailed calculations and information,
comments welcome | Quantum 6, 879 (2022) | 10.22331/q-2022-12-19-879 | null | gr-qc hep-ph quant-ph | http://creativecommons.org/licenses/by/4.0/ | The effective quantum field theory description of gravity, despite its
non-renormalizability, allows for predictions beyond classical general
relativity. As we enter the age of gravitational wave astronomy, an important
and timely question is whether measurable quantum predictions that depart from
classical gravity, analogous to quantum optics effects which cannot be
explained by classical electrodynamics, can be found. In this work, we
investigate quantum signatures in gravitational waves using tools from quantum
optics. Squeezed-coherent gravitational waves, which can exhibit sub-Poissonian
graviton statistics, can enhance or suppress the signal measured by an
interferometer, a characteristic effect of quantum squeezing. Moreover, we show
that Gaussian gravitational wave quantum states can be reconstructed from
measurements over an ensemble of optical fields interacting with a single copy
of the gravitational wave, thus opening the possibility of detecting quantum
features of gravity beyond classical general relativity.
| [
{
"created": "Tue, 2 Nov 2021 17:55:53 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Feb 2022 20:07:51 GMT",
"version": "v2"
},
{
"created": "Thu, 8 Sep 2022 19:29:05 GMT",
"version": "v3"
},
{
"created": "Wed, 14 Dec 2022 23:52:31 GMT",
"version": "v4"
}
] | 2022-12-21 | [
[
"Guerreiro",
"Thiago",
""
],
[
"Coradeschi",
"Francesco",
""
],
[
"Frassino",
"Antonia Micol",
""
],
[
"West",
"Jennifer Rittenhouse",
""
],
[
"Schioppa",
"Enrico Junior",
""
]
] | The effective quantum field theory description of gravity, despite its non-renormalizability, allows for predictions beyond classical general relativity. As we enter the age of gravitational wave astronomy, an important and timely question is whether measurable quantum predictions that depart from classical gravity, analogous to quantum optics effects which cannot be explained by classical electrodynamics, can be found. In this work, we investigate quantum signatures in gravitational waves using tools from quantum optics. Squeezed-coherent gravitational waves, which can exhibit sub-Poissonian graviton statistics, can enhance or suppress the signal measured by an interferometer, a characteristic effect of quantum squeezing. Moreover, we show that Gaussian gravitational wave quantum states can be reconstructed from measurements over an ensemble of optical fields interacting with a single copy of the gravitational wave, thus opening the possibility of detecting quantum features of gravity beyond classical general relativity. |
0806.2683 | Mariusz Dabrowski P. | Mariusz P. Dabrowski, Janusz Garecki and David B. Blaschke | Conformal transformations and conformal invariance in gravitation | REVTEX 4, 28 pages, no figures, version to match a published paper | Annalen Phys. (Berlin) 18 (2009), 13-32. | null | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Conformal transformations are frequently used tools in order to study
relations between various theories of gravity and the Einstein relativity. In
this paper we discuss the rules of these transformations for geometric
quantities as well as for the matter energy-momentum tensor. We show the
subtlety of the matter energy-momentum conservation law which refers to the
fact that the conformal transformation "creates" an extra matter term composed
of the conformal factor which enters the conservation law. In an extreme case
of the flat original spacetime the matter is "created" due to work done by the
conformal transformation to bend the spacetime which was originally flat. We
discuss how to construct the conformally invariant gravity theories and also
find the conformal transformation rules for the curvature invariants $R^2$,
$R_{ab}R^{ab}$, $R_{abcd}R^{abcd}$ and the Gauss-Bonnet invariant in a
spacetime of an arbitrary dimension. Finally, we present the conformal
transformation rules in the fashion of the duality transformations of the
superstring theory. In such a case the transitions between conformal frames
reduce to a simple change of the sign of a redefined conformal factor.
| [
{
"created": "Mon, 16 Jun 2008 22:13:42 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Jul 2008 21:13:59 GMT",
"version": "v2"
},
{
"created": "Mon, 5 Jan 2009 16:47:02 GMT",
"version": "v3"
}
] | 2009-02-20 | [
[
"Dabrowski",
"Mariusz P.",
""
],
[
"Garecki",
"Janusz",
""
],
[
"Blaschke",
"David B.",
""
]
] | Conformal transformations are frequently used tools in order to study relations between various theories of gravity and the Einstein relativity. In this paper we discuss the rules of these transformations for geometric quantities as well as for the matter energy-momentum tensor. We show the subtlety of the matter energy-momentum conservation law which refers to the fact that the conformal transformation "creates" an extra matter term composed of the conformal factor which enters the conservation law. In an extreme case of the flat original spacetime the matter is "created" due to work done by the conformal transformation to bend the spacetime which was originally flat. We discuss how to construct the conformally invariant gravity theories and also find the conformal transformation rules for the curvature invariants $R^2$, $R_{ab}R^{ab}$, $R_{abcd}R^{abcd}$ and the Gauss-Bonnet invariant in a spacetime of an arbitrary dimension. Finally, we present the conformal transformation rules in the fashion of the duality transformations of the superstring theory. In such a case the transitions between conformal frames reduce to a simple change of the sign of a redefined conformal factor. |
2003.02741 | Andrzej Borowiec | Andrzej Borowiec, Aleksander Kozak | New class of hybrid metric-Palatini scalar-tensor theories of gravity | 34 pages in LaTeX, comments and references added, final version
published in JCAP | JCAP07(2020)003 | 10.1088/1475-7516/2020/07/003 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A class of scalar-tensor theories (STT) including a non-metricity that
unifies metric, Palatini and hybrid metric-Palatini gravitational actions with
non-minimal interaction is proposed and investigated from the point of view of
their consistency with generalized conformal transformations. It is shown that
every such theory can be represented on-shell by a purely metric STT possessing
the same solutions for a metric and a scalar field. A set of generalized
invariants is also proposed. This extends the formalism previously introduced
in \cite{kozak2019}. We then apply the formalism to Starobinsky model, write
down the Friedmann equations for three possible cases: metric, Palatini and
hybrid metric-Palatini, and compare some inflationary observables.
| [
{
"created": "Thu, 5 Mar 2020 16:12:54 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Apr 2020 17:22:06 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Jul 2020 20:58:39 GMT",
"version": "v3"
}
] | 2020-07-03 | [
[
"Borowiec",
"Andrzej",
""
],
[
"Kozak",
"Aleksander",
""
]
] | A class of scalar-tensor theories (STT) including a non-metricity that unifies metric, Palatini and hybrid metric-Palatini gravitational actions with non-minimal interaction is proposed and investigated from the point of view of their consistency with generalized conformal transformations. It is shown that every such theory can be represented on-shell by a purely metric STT possessing the same solutions for a metric and a scalar field. A set of generalized invariants is also proposed. This extends the formalism previously introduced in \cite{kozak2019}. We then apply the formalism to Starobinsky model, write down the Friedmann equations for three possible cases: metric, Palatini and hybrid metric-Palatini, and compare some inflationary observables. |
1312.1322 | Farhad Darabi | F. Darabi, A. Parsiya | Cosmology with non-minimal coupled gravity: inflation and perturbation
analysis | Reference added | Class. Quantum Grav. 32 (2015) 155005 | 10.1088/0264-9381/32/15/155005 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a scalar-tensor cosmological model where the Einstein tensor is
non-minimally coupled to the free scalar field dynamics. Using FRW metric, we
investigate the behavior of scale factor for vacuum, matter and dark energy
dominated eras. Especially, we focus on the inflationary behavior at early
universe. Moreover, we study the perturbation analysis of this model in order
to confront the inflation under consideration with the observational results.
| [
{
"created": "Wed, 4 Dec 2013 20:42:55 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Jul 2014 08:44:55 GMT",
"version": "v2"
},
{
"created": "Fri, 10 Jul 2015 04:44:16 GMT",
"version": "v3"
},
{
"created": "Mon, 20 Jul 2015 12:50:16 GMT",
"version": "v4"
}
] | 2015-08-06 | [
[
"Darabi",
"F.",
""
],
[
"Parsiya",
"A.",
""
]
] | We study a scalar-tensor cosmological model where the Einstein tensor is non-minimally coupled to the free scalar field dynamics. Using FRW metric, we investigate the behavior of scale factor for vacuum, matter and dark energy dominated eras. Especially, we focus on the inflationary behavior at early universe. Moreover, we study the perturbation analysis of this model in order to confront the inflation under consideration with the observational results. |
2012.14518 | Marcus Reitz | Joren Brunekreef, Marcus Reitz | Approximate Killing symmetries in non-perturbative quantum gravity | 39 pages, 15 figures | null | 10.1088/1361-6382/abf412 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | It is an open question whether fluctuations at the Planck scale in a
non-perturbative theory of quantum gravity behave in such a way that the
resulting semi-classical geometry can be modelled by a space that admits
(approximate) Killing symmetries. We have investigated whether the notion of
approximate Killing vector fields is suitable to address this question in
lattice theories of quantum gravity, such as (Causal) Dynamical Triangulations.
We show that it is possible to construct quantum observables related to
approximate Killing vector fields using the framework of Discrete Exterior
Calculus. We have evaluated the expectation value of one particular choice of
observable on three toy models of two-dimensional quantum gravity.
| [
{
"created": "Mon, 28 Dec 2020 22:56:29 GMT",
"version": "v1"
}
] | 2021-07-07 | [
[
"Brunekreef",
"Joren",
""
],
[
"Reitz",
"Marcus",
""
]
] | It is an open question whether fluctuations at the Planck scale in a non-perturbative theory of quantum gravity behave in such a way that the resulting semi-classical geometry can be modelled by a space that admits (approximate) Killing symmetries. We have investigated whether the notion of approximate Killing vector fields is suitable to address this question in lattice theories of quantum gravity, such as (Causal) Dynamical Triangulations. We show that it is possible to construct quantum observables related to approximate Killing vector fields using the framework of Discrete Exterior Calculus. We have evaluated the expectation value of one particular choice of observable on three toy models of two-dimensional quantum gravity. |
gr-qc/9902080 | Fredrik Andersson | F. Andersson and S. B. Edgar | Local Existence of Spinor- and Tensor Potentials | 28 pages, LaTeX; paper expanded with additional results | null | null | null | gr-qc | null | We give new simple direct proofs in all spacetimes for the existence of
asymmetric $(n,m+1)$-spinor potentials for completely symmetric
$(n+1,m)$-spinors and for the existence of symmetric $(n,1)$-spinor potentials
for symmetric $(n+1,0)$-spinors. These proofs introduce a `superpotential',
i.e., a potential of the potential, which also enables us to get explicit
statements of the gauge freedom of the original potentials. The main
application for these results is the Lanczos potential $L_{ABCA'}$, of the Weyl
spinor and the electromagnetic vector potential $A_{AA'}$. We also investigate
the possibility of existence of a {\em symmetric} potential $H_{ABA'B'}$ for
the Lanczos potential, and prove that in {\em all Einstein spacetimes} any
symmetric (3,1)-spinor $L_{ABCA'}$ possesses a symmetric potential
$H_{ABA'B'}$. Potentials of this type have been found earlier in investigations
of some very special spinors in restricted classes of spacetimes. All of the
new spinor results are translated into tensor notation, and where possible
given also for four dimensional spaces of arbitrary signature.
| [
{
"created": "Thu, 25 Feb 1999 09:32:20 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jan 2000 10:46:46 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Andersson",
"F.",
""
],
[
"Edgar",
"S. B.",
""
]
] | We give new simple direct proofs in all spacetimes for the existence of asymmetric $(n,m+1)$-spinor potentials for completely symmetric $(n+1,m)$-spinors and for the existence of symmetric $(n,1)$-spinor potentials for symmetric $(n+1,0)$-spinors. These proofs introduce a `superpotential', i.e., a potential of the potential, which also enables us to get explicit statements of the gauge freedom of the original potentials. The main application for these results is the Lanczos potential $L_{ABCA'}$, of the Weyl spinor and the electromagnetic vector potential $A_{AA'}$. We also investigate the possibility of existence of a {\em symmetric} potential $H_{ABA'B'}$ for the Lanczos potential, and prove that in {\em all Einstein spacetimes} any symmetric (3,1)-spinor $L_{ABCA'}$ possesses a symmetric potential $H_{ABA'B'}$. Potentials of this type have been found earlier in investigations of some very special spinors in restricted classes of spacetimes. All of the new spinor results are translated into tensor notation, and where possible given also for four dimensional spaces of arbitrary signature. |
2207.12226 | Everett Patterson | Everett Patterson, Robert B. Mann | Fisher Information of a Black Hole Spacetime | 23 pages, 8 figures | null | 10.1007/JHEP06(2023)214 | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | Relativistic quantum metrology is the study of optimal measurement procedures
within systems that have both quantum and relativistic components. Here we use
Unruh-DeWitt detectors coupled to a massless scalar field as probes of thermal
parameters in different spacetimes via a relativistic quantum metrology
analysis. We consider both (2+1)-dimensional anti-de Sitter and BTZ black hole
spacetimes. We compute the Fisher information to identify characteristics of
the black hole spacetime and to compare it to a uniformly accelerating detector
in anti-de Sitter space. We find the dependence of the Fisher information on
temperature, detector energy gap, black hole mass, interaction time, and the
initial state of the detector. We identify strategies that maximize the Fisher
information and therefore the precision of estimation.
| [
{
"created": "Mon, 25 Jul 2022 14:27:01 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Mar 2023 01:34:26 GMT",
"version": "v2"
}
] | 2023-07-26 | [
[
"Patterson",
"Everett",
""
],
[
"Mann",
"Robert B.",
""
]
] | Relativistic quantum metrology is the study of optimal measurement procedures within systems that have both quantum and relativistic components. Here we use Unruh-DeWitt detectors coupled to a massless scalar field as probes of thermal parameters in different spacetimes via a relativistic quantum metrology analysis. We consider both (2+1)-dimensional anti-de Sitter and BTZ black hole spacetimes. We compute the Fisher information to identify characteristics of the black hole spacetime and to compare it to a uniformly accelerating detector in anti-de Sitter space. We find the dependence of the Fisher information on temperature, detector energy gap, black hole mass, interaction time, and the initial state of the detector. We identify strategies that maximize the Fisher information and therefore the precision of estimation. |
gr-qc/9912098 | Folomeev V. N. | V.N. Folomeev, V.Ts. Gurovich and I.V. Tokareva | Generation of the Scalar Field and Anisotropy at Quantum Creation of the
Closed Universe | 12 pages, Latex, 1 figure | Nuovo Cim. B115 (2000) 1091-1100 | null | null | gr-qc | null | The behaviour of the wave function of the Universe under the barrier for
anisotropic cosmological Bianchi type IX model with account of influence of the
scalar field is explored. In view of known difficulties with interpretation of
multidimensional wave functions the method of reduction of such problems to
one-dimensional is offered. For this purpose in frameworks of semiclassical
approach the system of characteristics equations relative to one variable is
written out. This system describe a bundle of the characteristics along which
the multidimensional problem is reduced to one-dimensional one that allows to
utillize the standard interpretation of the wave function as well as for usual
Schrodinger equation. The obtained results for Bianchi type IX model are
reduced to the following statement: the Universe tunnels through the barrier
from an isotropic state with zero initial value of the scalar field and appear
in classically allowed region with small anisotropy that is necessary for
providing of long-lived inflation for deriving the Universe such as ours.
| [
{
"created": "Thu, 23 Dec 1999 04:21:18 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Folomeev",
"V. N.",
""
],
[
"Gurovich",
"V. Ts.",
""
],
[
"Tokareva",
"I. V.",
""
]
] | The behaviour of the wave function of the Universe under the barrier for anisotropic cosmological Bianchi type IX model with account of influence of the scalar field is explored. In view of known difficulties with interpretation of multidimensional wave functions the method of reduction of such problems to one-dimensional is offered. For this purpose in frameworks of semiclassical approach the system of characteristics equations relative to one variable is written out. This system describe a bundle of the characteristics along which the multidimensional problem is reduced to one-dimensional one that allows to utillize the standard interpretation of the wave function as well as for usual Schrodinger equation. The obtained results for Bianchi type IX model are reduced to the following statement: the Universe tunnels through the barrier from an isotropic state with zero initial value of the scalar field and appear in classically allowed region with small anisotropy that is necessary for providing of long-lived inflation for deriving the Universe such as ours. |
1805.12304 | Bo Wang | Yang Zhang, Bo Wang | Adiabatic regularization of power spectrum and stress tensor of relic
gravitational wave without low-frequency distortion | 39 pages, 20 figures. Fix a typo in eq.(2.8) | JCAP 11(2018)006 | 10.1088/1475-7516/2018/11/006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Adiabatic regularization is a method to remove UV divergences in quantum
fields in curved spacetime. For relic gravitational wave generated during
inflation, regularization on all $k$-modes of the power spectrum to 2nd
adiabatic order, and of the energy density and pressure to 4th order,
respectively, causes low-frequency distortions. To avoid these, we regularize
only the short modes inside the horizon during inflation (corresponding to the
present frequencies $f \gtrsim 10^{9}$Hz), and keep the long modes intact.
Doing this does not violate the energy conservation since the $k$-modes of RGW
are independent of each other during inflation. The resulting spectra are UV
convergent and simultaneously free of low-frequency distortion, and these
properties remain in the present spectra after evolution, in contrast to
regularization at the present time which has some distortion or irregularities.
The spectra generally exhibit quick oscillations in frequency domain, even if
the initial spectra during inflation have no oscillations. This pattern is due
to the interference between the positive and negative frequency modes developed
during cosmic expansion, and may be probed by future RGW detections.
| [
{
"created": "Thu, 31 May 2018 03:23:17 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Jun 2019 13:22:04 GMT",
"version": "v10"
},
{
"created": "Wed, 25 Jul 2018 01:30:13 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Sep 2018 13:29:32 GMT",
"version": "v3"
},
{
"created": "Thu, 13 Sep 2018 00:47:16 GMT",
"version": "v4"
},
{
"created": "Mon, 15 Oct 2018 01:49:57 GMT",
"version": "v5"
},
{
"created": "Sun, 21 Oct 2018 12:43:33 GMT",
"version": "v6"
},
{
"created": "Thu, 1 Nov 2018 02:42:08 GMT",
"version": "v7"
},
{
"created": "Thu, 15 Nov 2018 00:42:22 GMT",
"version": "v8"
},
{
"created": "Tue, 19 Feb 2019 02:36:38 GMT",
"version": "v9"
}
] | 2019-06-27 | [
[
"Zhang",
"Yang",
""
],
[
"Wang",
"Bo",
""
]
] | Adiabatic regularization is a method to remove UV divergences in quantum fields in curved spacetime. For relic gravitational wave generated during inflation, regularization on all $k$-modes of the power spectrum to 2nd adiabatic order, and of the energy density and pressure to 4th order, respectively, causes low-frequency distortions. To avoid these, we regularize only the short modes inside the horizon during inflation (corresponding to the present frequencies $f \gtrsim 10^{9}$Hz), and keep the long modes intact. Doing this does not violate the energy conservation since the $k$-modes of RGW are independent of each other during inflation. The resulting spectra are UV convergent and simultaneously free of low-frequency distortion, and these properties remain in the present spectra after evolution, in contrast to regularization at the present time which has some distortion or irregularities. The spectra generally exhibit quick oscillations in frequency domain, even if the initial spectra during inflation have no oscillations. This pattern is due to the interference between the positive and negative frequency modes developed during cosmic expansion, and may be probed by future RGW detections. |
gr-qc/0001039 | Tonatiuh Matos | Tonatiuh Matos, Dario Nu\~nez, Gabino Estevez and Maribel Rios | Rotating 5D-Kaluza-Klein Space-Times from Invariant Transformations | 24 pages, latex, no figures. To appear in Gen. Rel. Grav., 32,
(2000), in press | Gen.Rel.Grav.32:1499-1525,2000 | 10.1023/A:1001982001694 | CINVESTAV-00/Fis-8 | gr-qc | null | Using invariant transformations of the five-dimensional Kaluza-Klein (KK)
field equations, we find a series of formulae to derive axial symmetric
stationary exact solutions of the KK theory starting from static ones. The
procedure presented in this work allows to derive new exact solutions up to
very simple integrations. Among other results, we find exact rotating solutions
containing magnetic monopoles, dipoles, quadripoles, etc., coupled to scalar
and to gravitational multipole fields.
| [
{
"created": "Fri, 14 Jan 2000 18:03:40 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Matos",
"Tonatiuh",
""
],
[
"Nuñez",
"Dario",
""
],
[
"Estevez",
"Gabino",
""
],
[
"Rios",
"Maribel",
""
]
] | Using invariant transformations of the five-dimensional Kaluza-Klein (KK) field equations, we find a series of formulae to derive axial symmetric stationary exact solutions of the KK theory starting from static ones. The procedure presented in this work allows to derive new exact solutions up to very simple integrations. Among other results, we find exact rotating solutions containing magnetic monopoles, dipoles, quadripoles, etc., coupled to scalar and to gravitational multipole fields. |
2206.07925 | Nils A. Nilsson | Nils A. Nilsson | SME Gravity in the Early Universe | Presented at the Ninth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, May 17-26, 2022 | null | null | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | In this talk, we give a short overview of recent work on cosmological
solutions within the SME gravitational sector under the assumption of explicit
spacetime-symmetry breaking. We show that for the special case of timelike
diffeomorphism breaking, the resulting Friedmann equations can be written as
standard FLRW cosmology with added dynamical dark energy, and we discuss
primordial gravitational waves in the context of this model.
| [
{
"created": "Thu, 16 Jun 2022 05:03:13 GMT",
"version": "v1"
}
] | 2022-06-17 | [
[
"Nilsson",
"Nils A.",
""
]
] | In this talk, we give a short overview of recent work on cosmological solutions within the SME gravitational sector under the assumption of explicit spacetime-symmetry breaking. We show that for the special case of timelike diffeomorphism breaking, the resulting Friedmann equations can be written as standard FLRW cosmology with added dynamical dark energy, and we discuss primordial gravitational waves in the context of this model. |
gr-qc/0303114 | V. Suneeta | V. Suneeta | Quasinormal modes for the SdS black hole : an analytical approximation
scheme | 12 pages, revtex, refs added and discussion expanded, version to
appear in Phys. Rev. D | Phys.Rev. D68 (2003) 024020 | 10.1103/PhysRevD.68.024020 | null | gr-qc hep-th | null | Quasinormal modes for scalar field perturbations of a Schwarzschild-de Sitter
(SdS) black hole are investigated. An analytical approximation is proposed for
the problem. The quasinormal modes are evaluated for this approximate model in
the limit when black hole mass is much smaller than the radius of curvature of
the spacetime. The model mirrors some striking features observed in numerical
studies of time behaviour of scalar perturbations of the SdS black hole. In
particular, it shows the presence of two sets of modes relevant at two
different time scales, proportional to the surface gravities of the black hole
and cosmological horizons respectively. These quasinormal modes are not
complete - another feature observed in numerical studies. Refinements of this
model to yield more accurate quantitative agreement with numerical studies are
discussed. Further investigations of this model are outlined, which would
provide a valuable insight into time behaviour of perturbations in the SdS
spacetime.
| [
{
"created": "Mon, 31 Mar 2003 16:08:03 GMT",
"version": "v1"
},
{
"created": "Mon, 26 May 2003 09:51:17 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Suneeta",
"V.",
""
]
] | Quasinormal modes for scalar field perturbations of a Schwarzschild-de Sitter (SdS) black hole are investigated. An analytical approximation is proposed for the problem. The quasinormal modes are evaluated for this approximate model in the limit when black hole mass is much smaller than the radius of curvature of the spacetime. The model mirrors some striking features observed in numerical studies of time behaviour of scalar perturbations of the SdS black hole. In particular, it shows the presence of two sets of modes relevant at two different time scales, proportional to the surface gravities of the black hole and cosmological horizons respectively. These quasinormal modes are not complete - another feature observed in numerical studies. Refinements of this model to yield more accurate quantitative agreement with numerical studies are discussed. Further investigations of this model are outlined, which would provide a valuable insight into time behaviour of perturbations in the SdS spacetime. |
1101.4890 | Hongwei Xiong | Hongwei Xiong | Abnormal Quantum Gravity Effect: Experimental Scheme with Superfluid
Helium Sphere and Applications to Accelerating Universe | Much better presentation has been given in my published paper
"Repulsive gravitational effect of a quantum wave packet and experimental
scheme with superfluid helium" (Front. Phys. 10, 100401 (2015)) [See
arXiv:1101.1270] and another paper "On the quantitative calculation of the
cosmological constant of the quantum vacuum"[See arXiv:1805.10440] | null | null | null | gr-qc astro-ph.CO cond-mat.quant-gas hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | From the general assumption that gravity originates from the coupling and
thermal equilibrium between matter and vacuum, after a derivation of Newton's
law of gravitation and an interpretation of the attractive gravity force
between two classical objects, we consider the macroscopic quantum gravity
effect for particles whose wave packets are delocalized at macroscopic scale.
We predict an abnormal repulsive gravity effect in this work. For a sphere full
of superfluid helium, it is shown that with a gravimeter placed in this sphere,
the sensitivities of the gravity acceleration $\Delta g/g$ below $10^{-8}$
could be used to test the abnormal quantum gravity effect, which satisfies the
present experimental technique of atom interferometer, free-fall absolute
gravimeters and superconducting gravimeters. We further propose a
self-consistent field equation including the quantum effect of gravity. As an
application of this field equation, we give a simple interpretation of the
accelerating universe due to dark energy. Based on the idea that the dark
energy originates from the quantum gravity effect of vacuum excitations due to
the coupling between matter and vacuum, without any fitting parameter, the
ratio between dark energy density and matter density (including dark matter) is
calculated as 2.2, which agrees quantitatively with the result 7/3 obtained
from various astronomical observations.
| [
{
"created": "Tue, 25 Jan 2011 18:31:52 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Feb 2011 11:15:04 GMT",
"version": "v2"
},
{
"created": "Wed, 25 May 2011 07:46:38 GMT",
"version": "v3"
},
{
"created": "Tue, 4 Dec 2018 12:05:57 GMT",
"version": "v4"
}
] | 2018-12-05 | [
[
"Xiong",
"Hongwei",
""
]
] | From the general assumption that gravity originates from the coupling and thermal equilibrium between matter and vacuum, after a derivation of Newton's law of gravitation and an interpretation of the attractive gravity force between two classical objects, we consider the macroscopic quantum gravity effect for particles whose wave packets are delocalized at macroscopic scale. We predict an abnormal repulsive gravity effect in this work. For a sphere full of superfluid helium, it is shown that with a gravimeter placed in this sphere, the sensitivities of the gravity acceleration $\Delta g/g$ below $10^{-8}$ could be used to test the abnormal quantum gravity effect, which satisfies the present experimental technique of atom interferometer, free-fall absolute gravimeters and superconducting gravimeters. We further propose a self-consistent field equation including the quantum effect of gravity. As an application of this field equation, we give a simple interpretation of the accelerating universe due to dark energy. Based on the idea that the dark energy originates from the quantum gravity effect of vacuum excitations due to the coupling between matter and vacuum, without any fitting parameter, the ratio between dark energy density and matter density (including dark matter) is calculated as 2.2, which agrees quantitatively with the result 7/3 obtained from various astronomical observations. |
2202.09543 | Rahul Nigam | Suraj Maurya, Sashideep Gutti, Rahul Nigam | Volume of a rotating black hole in 2+1 dimensions | null | Phys. Lett. B 833, 137381 (2022) | 10.1016/j.physletb.2022.137381 | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | In this article we apply the technique for maximal volume estimation of a
black hole developed by Christodoulou and Rovelli for Schwarzchild blackhole
and by Zhang et al for non rotating BTZ black hole, to the case of a rotating
black hole in 2+1 dimensions. We derive the equation of the maximal
hypersurface for the rotating BTZ blackhole using the Lagrangian formulation
demonstrated by Christodoulou and Rovelli . Further we use maximization
technique illustrated earlier by Bengtsson et al for Kerr black hole to arrive
at the similar result for our case. We argue that the maximum contribution to
the volume of the hypersurface comes from what we call the steady state radius,
which we show depends on mass M and the AdS length scale. We demonstrate that
this steady state radius can be arrived at using independent considerations of
vanishing extrinsic curvature. We show that the volume of this segment of the
maximal hypersurface, the CR volume, depends on mass, AdS length scale and
angular momentum J. We further compute the entropy of a scalar field living on
the maximal hypersurface for a near extremal black hole and show that it is
proportional to the horizon entropy of the black hole.
| [
{
"created": "Sat, 19 Feb 2022 07:38:41 GMT",
"version": "v1"
}
] | 2024-07-02 | [
[
"Maurya",
"Suraj",
""
],
[
"Gutti",
"Sashideep",
""
],
[
"Nigam",
"Rahul",
""
]
] | In this article we apply the technique for maximal volume estimation of a black hole developed by Christodoulou and Rovelli for Schwarzchild blackhole and by Zhang et al for non rotating BTZ black hole, to the case of a rotating black hole in 2+1 dimensions. We derive the equation of the maximal hypersurface for the rotating BTZ blackhole using the Lagrangian formulation demonstrated by Christodoulou and Rovelli . Further we use maximization technique illustrated earlier by Bengtsson et al for Kerr black hole to arrive at the similar result for our case. We argue that the maximum contribution to the volume of the hypersurface comes from what we call the steady state radius, which we show depends on mass M and the AdS length scale. We demonstrate that this steady state radius can be arrived at using independent considerations of vanishing extrinsic curvature. We show that the volume of this segment of the maximal hypersurface, the CR volume, depends on mass, AdS length scale and angular momentum J. We further compute the entropy of a scalar field living on the maximal hypersurface for a near extremal black hole and show that it is proportional to the horizon entropy of the black hole. |
1208.0941 | Luis P. Chimento | Luis P. Chimento, Adriana E. Cossarini and Alejandro S. Jakubi | Exact self-interacting scalar field cosmologies | 5 pages | Proceedings of the conference in celebration of the 65 th Birthday
of Professor Jerzy Plebanski. M\'exico DF, M\'exico, 2-4 June 1993. (World
Scientific, Singapore, 1994) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We solve isotropic, homogeneous cosmological models containing a
self-interacting scalar field. Calculations are performed in four and
two-dimensional spacetimes. We find several exact solutions that have an
inflationary regime or has a final Friedmann stage. Also their asymptotically
stability is studied.
| [
{
"created": "Sat, 4 Aug 2012 15:27:30 GMT",
"version": "v1"
}
] | 2012-08-07 | [
[
"Chimento",
"Luis P.",
""
],
[
"Cossarini",
"Adriana E.",
""
],
[
"Jakubi",
"Alejandro S.",
""
]
] | We solve isotropic, homogeneous cosmological models containing a self-interacting scalar field. Calculations are performed in four and two-dimensional spacetimes. We find several exact solutions that have an inflationary regime or has a final Friedmann stage. Also their asymptotically stability is studied. |
gr-qc/0308066 | Stefan Haesen | Stefan Haesen, Leopold Verstraelen | Ideally embedded space-times | layout changed and typos corrected; uses revtex4 | J.Math.Phys. 45 (2004) 1497-1510 | 10.1063/1.1668333 | null | gr-qc | null | Due to the growing interest in embeddings of space-time in higher-dimensional
spaces we consider a specific type of embedding. After proving an inequality
between intrinsically defined curvature invariants and the squared mean
curvature, we extend the notion of ideal embeddings from Riemannian geometry to
the indefinite case. Ideal embeddings are such that the embedded manifold
receives the least amount of tension from the surrounding space. Then it is
shown that the de Sitter spaces, a Robertson-Walker space-time and some
anisotropic perfect fluid metrics can be ideally embedded in a five-dimensional
pseudo-Euclidean space.
| [
{
"created": "Thu, 21 Aug 2003 11:48:53 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Apr 2004 11:37:43 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Haesen",
"Stefan",
""
],
[
"Verstraelen",
"Leopold",
""
]
] | Due to the growing interest in embeddings of space-time in higher-dimensional spaces we consider a specific type of embedding. After proving an inequality between intrinsically defined curvature invariants and the squared mean curvature, we extend the notion of ideal embeddings from Riemannian geometry to the indefinite case. Ideal embeddings are such that the embedded manifold receives the least amount of tension from the surrounding space. Then it is shown that the de Sitter spaces, a Robertson-Walker space-time and some anisotropic perfect fluid metrics can be ideally embedded in a five-dimensional pseudo-Euclidean space. |
gr-qc/0401007 | Sung Won Kim | Sung-Won Kim | Gravitational perturbation of traversable wormhole | 7 pages, Revtex4, 4 figures | null | null | null | gr-qc | null | In this paper, we study the perturbation problem of the scalar,
electromagnetic, and gravitational waves under the traversable Lorentzian
wormhole geometry. The unified form of the potential for the Schr\"odinger type
one-dimensional wave equation is found.
| [
{
"created": "Sat, 3 Jan 2004 06:58:17 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kim",
"Sung-Won",
""
]
] | In this paper, we study the perturbation problem of the scalar, electromagnetic, and gravitational waves under the traversable Lorentzian wormhole geometry. The unified form of the potential for the Schr\"odinger type one-dimensional wave equation is found. |
1808.09081 | Brian Dolan | Brian P Dolan | The definition of mass in asymptotically de Sitter space-times | 12 pages plus one 5 page appendix | null | 10.1088/1361-6382/ab0bdb | DIAS-STP-18-10 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An invariant definition of mass in asymptotically de-Sitter space-times is
given that relies on the existence of a time-like Killing vector on a sphere
surrounding the mass but does not require going to an asymptotic region. In
particular the mass can be calculated exactly on a sphere inside the
cosmological horizon. The formalism requires varying the background metric
solution by a perturbation that satisfies the linearized equations of motion
but need not share the Killing symmetry of the solution and is therefore
ideally suited to calculating masses in stationary space-times perturbed by a
gravitational wave without going beyond the cosmological horizon.
| [
{
"created": "Tue, 28 Aug 2018 01:25:20 GMT",
"version": "v1"
}
] | 2019-03-27 | [
[
"Dolan",
"Brian P",
""
]
] | An invariant definition of mass in asymptotically de-Sitter space-times is given that relies on the existence of a time-like Killing vector on a sphere surrounding the mass but does not require going to an asymptotic region. In particular the mass can be calculated exactly on a sphere inside the cosmological horizon. The formalism requires varying the background metric solution by a perturbation that satisfies the linearized equations of motion but need not share the Killing symmetry of the solution and is therefore ideally suited to calculating masses in stationary space-times perturbed by a gravitational wave without going beyond the cosmological horizon. |
0903.0100 | Thomas Prince | Bernard F. Schutz, Joan Centrella, Curt Cutler, Scott A. Hughes | Will Einstein Have the Last Word on Gravity? | Science White Paper submitted to the Astro2010 Decadal Survey | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is a whitepaper submitted to the 2010 Astronomy Decadal Review process,
addressing the potential tests of gravity theory that could be made by
observations of gravitational waves in the milliHertz frequency band by the
proposed ESA-NASA gravitational wave observatory LISA. A key issue is that
observations in this band of binary systems consisting of black holes offer
very clean tests with high signal-to-noise ratios. Gravitational waves would
probe nonlinear gravity and could reveal small corrections, such as extra
long-range fields that arise in unified theories, deviations of the metric
around massive black holes from the Kerr solution, massive gravitons, chiral
effects, and effects of extra dimensions. The availability of strong signals
from massive black hole binaries as well as complex signals from extreme
mass-ratio binaries is unique to the milliHertz waveband and makes LISA a
particularly sensitive probe of the validity of general relativity.
| [
{
"created": "Sat, 28 Feb 2009 19:44:21 GMT",
"version": "v1"
}
] | 2009-03-03 | [
[
"Schutz",
"Bernard F.",
""
],
[
"Centrella",
"Joan",
""
],
[
"Cutler",
"Curt",
""
],
[
"Hughes",
"Scott A.",
""
]
] | This is a whitepaper submitted to the 2010 Astronomy Decadal Review process, addressing the potential tests of gravity theory that could be made by observations of gravitational waves in the milliHertz frequency band by the proposed ESA-NASA gravitational wave observatory LISA. A key issue is that observations in this band of binary systems consisting of black holes offer very clean tests with high signal-to-noise ratios. Gravitational waves would probe nonlinear gravity and could reveal small corrections, such as extra long-range fields that arise in unified theories, deviations of the metric around massive black holes from the Kerr solution, massive gravitons, chiral effects, and effects of extra dimensions. The availability of strong signals from massive black hole binaries as well as complex signals from extreme mass-ratio binaries is unique to the milliHertz waveband and makes LISA a particularly sensitive probe of the validity of general relativity. |
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