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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1602.03869 | Andrea Zanzi | Andrea Zanzi | Chameleonic Theories: A Short Review | Invited contribution to the special issue "Modified Gravity
Cosmology: from Inflation to Dark Energy", published in Universe. 30 pages. 2
figures. arXiv admin note: substantial text overlap with
arXiv:hep-ph/0608078, arXiv:astro-ph/0611816 by other authors | Universe 2015, 1(3), 446-475 | 10.3390/universe1030446 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In the chameleon mechanism, a field (typically scalar) has a mass that
depends on the matter density of the environment: the larger is the matter
density, the larger is the mass of the chameleon. We briefly review some
aspects of chameleonic theories. In particular, in a typical class of these
theories, we discuss the lagrangian, the role of conformal transformations, the
equation of motion and the thin-shell effect. We also discuss $f(R)$ theories
and chameleonic quantum gravity.
| [
{
"created": "Wed, 30 Dec 2015 12:19:23 GMT",
"version": "v1"
}
] | 2016-02-12 | [
[
"Zanzi",
"Andrea",
""
]
] | In the chameleon mechanism, a field (typically scalar) has a mass that depends on the matter density of the environment: the larger is the matter density, the larger is the mass of the chameleon. We briefly review some aspects of chameleonic theories. In particular, in a typical class of these theories, we discuss the lagrangian, the role of conformal transformations, the equation of motion and the thin-shell effect. We also discuss $f(R)$ theories and chameleonic quantum gravity. |
1008.4622 | Marc Favata | Marc Favata | Conservative self-force correction to the innermost stable circular
orbit: comparison with multiple post-Newtonian-based methods | 27 pages, 2 figures, 2 tables. v2: some changes to Sec. VI in
response to referee comments; references added; other minor changes to match
published version | Phys.Rev.D83:024027,2011 | 10.1103/PhysRevD.83.024027 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | [abridged] Barack & Sago have recently computed the shift of the innermost
stable circular orbit (ISCO) due to the conservative self-force that arises
from the finite-mass of an orbiting test-particle. This is one of the first
concrete results of the self-force program, and provides an exact point of
comparison with approximate post-Newtonian (PN) computations of the ISCO. Here
this exact ISCO shift is compared with nearly all known PN-based methods. These
include both "nonresummed" and "resummed" approaches (the latter reproduce the
test-particle limit by construction). The best agreement with the exact result
is found from effective-one-body (EOB) calculations that are fit to numerical
relativity simulations. However, if one considers uncalibrated methods based
only on the currently known 3PN-order conservative dynamics, the best agreement
is found from the gauge-invariant ISCO condition of Blanchet and Iyer (2003).
This method reproduces the exact test-particle limit without any resummation. A
comparison of PN methods with the equal-mass ISCO is also performed. The
results of this study suggest that the EOB approach---while exactly
incorporating the conservative test-particle dynamics---does not (in the
absence of calibration) incorporate conservative self-force effects more
accurately than standard PN methods. I also consider how the conservative
self-force ISCO shift, combined with numerical relativity computations of the
ISCO, can be used to constrain our knowledge of (1) the EOB effective metric,
(2) phenomenological inspiral-merger-ringdown templates, and (3) 4PN and 5PN
order terms in the PN orbital energy. These constraints could help in
constructing better gravitational-wave templates. Lastly, I suggest a new
method to calibrate unknown PN-terms in inspiral templates using
numerical-relativity calculations.
| [
{
"created": "Fri, 27 Aug 2010 00:10:31 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Jan 2011 05:52:53 GMT",
"version": "v2"
}
] | 2011-01-25 | [
[
"Favata",
"Marc",
""
]
] | [abridged] Barack & Sago have recently computed the shift of the innermost stable circular orbit (ISCO) due to the conservative self-force that arises from the finite-mass of an orbiting test-particle. This is one of the first concrete results of the self-force program, and provides an exact point of comparison with approximate post-Newtonian (PN) computations of the ISCO. Here this exact ISCO shift is compared with nearly all known PN-based methods. These include both "nonresummed" and "resummed" approaches (the latter reproduce the test-particle limit by construction). The best agreement with the exact result is found from effective-one-body (EOB) calculations that are fit to numerical relativity simulations. However, if one considers uncalibrated methods based only on the currently known 3PN-order conservative dynamics, the best agreement is found from the gauge-invariant ISCO condition of Blanchet and Iyer (2003). This method reproduces the exact test-particle limit without any resummation. A comparison of PN methods with the equal-mass ISCO is also performed. The results of this study suggest that the EOB approach---while exactly incorporating the conservative test-particle dynamics---does not (in the absence of calibration) incorporate conservative self-force effects more accurately than standard PN methods. I also consider how the conservative self-force ISCO shift, combined with numerical relativity computations of the ISCO, can be used to constrain our knowledge of (1) the EOB effective metric, (2) phenomenological inspiral-merger-ringdown templates, and (3) 4PN and 5PN order terms in the PN orbital energy. These constraints could help in constructing better gravitational-wave templates. Lastly, I suggest a new method to calibrate unknown PN-terms in inspiral templates using numerical-relativity calculations. |
0803.2194 | Chih-Hung Wang | Yu-Huei Wu and Chih-Hung Wang | Quasi-local mass in the covariant Newtonian space-time | Submit to Class. Quantum Grav | Class.Quant.Grav.25:135007,2008 | 10.1088/0264-9381/25/13/135007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In general relativity, quasi-local energy-momentum expressions have been
constructed from various formulae. However, Newtonian theory of gravity gives a
well known and an unique quasi-local mass expression (surface integration).
Since geometrical formulation of Newtonian gravity has been established in the
covariant Newtonian space-time, it provides a covariant approximation from
relativistic to Newtonian theories. By using this approximation, we calculate
Komar integral, Brown-York quasi-local energy and Dougan-Mason quasi-local mass
in the covariant Newtonian space-time. It turns out that Komar integral
naturally gives the Newtonian quasi-local mass expression, however, further
conditions (spherical symmetry) need to be made for Brown-York and Dougan-Mason
expressions.
| [
{
"created": "Fri, 14 Mar 2008 16:10:15 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Wu",
"Yu-Huei",
""
],
[
"Wang",
"Chih-Hung",
""
]
] | In general relativity, quasi-local energy-momentum expressions have been constructed from various formulae. However, Newtonian theory of gravity gives a well known and an unique quasi-local mass expression (surface integration). Since geometrical formulation of Newtonian gravity has been established in the covariant Newtonian space-time, it provides a covariant approximation from relativistic to Newtonian theories. By using this approximation, we calculate Komar integral, Brown-York quasi-local energy and Dougan-Mason quasi-local mass in the covariant Newtonian space-time. It turns out that Komar integral naturally gives the Newtonian quasi-local mass expression, however, further conditions (spherical symmetry) need to be made for Brown-York and Dougan-Mason expressions. |
2002.01892 | Yan Peng | Yan Peng | Analytical investigations on formations of hairy neutral reflecting
shells in the scalar-Gauss-Bonnet gravity | 10 pages, 2 figures | Eur. Phys. J. C 80(2020)202 | 10.1140/epjc/s10052-020-7778-0 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study scalarization of spherically symmetric neutral reflecting shells in
the scalar-tensor gravity. We consider neutral static massless scalar fields
non-minimally coupled to the Gauss-Bonnet invariant. We obtain a relation
representing the existence regime of hairy neutral reflecting shells. For
parameters unsatisfying this relation, the massless scalar field cannot exist
outside the neutral reflecting shell. In the parameter region where this
relation holds, we get analytical solutions of scalar field hairs outside
neutral reflecting shells.
| [
{
"created": "Thu, 30 Jan 2020 13:25:00 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Mar 2020 07:49:07 GMT",
"version": "v2"
}
] | 2020-03-09 | [
[
"Peng",
"Yan",
""
]
] | We study scalarization of spherically symmetric neutral reflecting shells in the scalar-tensor gravity. We consider neutral static massless scalar fields non-minimally coupled to the Gauss-Bonnet invariant. We obtain a relation representing the existence regime of hairy neutral reflecting shells. For parameters unsatisfying this relation, the massless scalar field cannot exist outside the neutral reflecting shell. In the parameter region where this relation holds, we get analytical solutions of scalar field hairs outside neutral reflecting shells. |
2209.08439 | Hongxing Zhang | Hongxing Zhang, Naying Zhou, Wenfang Liu and Xin Wu | Equivalence between two charged black holes in dynamics of orbits
outside the event horizons | 18 pages, 12 figures | General Relativity and Gravitation (2022) 54:110 | 10.1007/s10714-022-02998-1 | null | gr-qc physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the FermiDirac distribution function, Balart and Vagenas gave a charged
spherically symmetric regular black hole, which is a solution of Einstein field
equations coupled to a nonlinear electrodynamics. In fact, the regular black
hole is a Reissner-Nordstrom (RN) black hole when a metric function is given a
Taylor expansion to first order approximations. It does not have a curvature
singularity at the origin,but the RN black hole does. Both black hole metrics
have horizons and similar asymptotic behaviors, and satisfy the weak energy
conditions everywhere. They are almost the same in photon effective potentials,
photon circular orbits and photon spheres outside the event horizons. There are
relatively minor differences between effective potentials, stable circular
orbits and innermost stable circular orbits of charged particles outside the
event horizons of the two black holes immersed in external magnetic fields.
Although the twomagnetized black holes allow different construction methods of
explicit symplectic integrators, they exhibit approximately consistent results
in the regular and chaotic dynamics of charged particles outside the event
horizons. Chaos gets strong as the magnetic field parameter or the magnitude of
negative Coulomb parameter increases, but becomes weak when the black hole
charge or the positive Coulomb parameter increases. A variation of dynamical
properties is not sensitive dependence on an appropriate increase of the black
hole charge. The basic equivalence between the two black hole gravitational
systems in the dynamics of orbits outside the event horizons is due to the two
metric functions having an extremely small difference. This implies that the RN
black hole is reasonably replaced by the regular black hole without curvature
singularity in many situations.
| [
{
"created": "Sun, 18 Sep 2022 01:31:00 GMT",
"version": "v1"
}
] | 2022-09-20 | [
[
"Zhang",
"Hongxing",
""
],
[
"Zhou",
"Naying",
""
],
[
"Liu",
"Wenfang",
""
],
[
"Wu",
"Xin",
""
]
] | Using the FermiDirac distribution function, Balart and Vagenas gave a charged spherically symmetric regular black hole, which is a solution of Einstein field equations coupled to a nonlinear electrodynamics. In fact, the regular black hole is a Reissner-Nordstrom (RN) black hole when a metric function is given a Taylor expansion to first order approximations. It does not have a curvature singularity at the origin,but the RN black hole does. Both black hole metrics have horizons and similar asymptotic behaviors, and satisfy the weak energy conditions everywhere. They are almost the same in photon effective potentials, photon circular orbits and photon spheres outside the event horizons. There are relatively minor differences between effective potentials, stable circular orbits and innermost stable circular orbits of charged particles outside the event horizons of the two black holes immersed in external magnetic fields. Although the twomagnetized black holes allow different construction methods of explicit symplectic integrators, they exhibit approximately consistent results in the regular and chaotic dynamics of charged particles outside the event horizons. Chaos gets strong as the magnetic field parameter or the magnitude of negative Coulomb parameter increases, but becomes weak when the black hole charge or the positive Coulomb parameter increases. A variation of dynamical properties is not sensitive dependence on an appropriate increase of the black hole charge. The basic equivalence between the two black hole gravitational systems in the dynamics of orbits outside the event horizons is due to the two metric functions having an extremely small difference. This implies that the RN black hole is reasonably replaced by the regular black hole without curvature singularity in many situations. |
2009.04353 | Ulrich Beckering Vinckers | U. K. Beckering Vinckers, A. de la Cruz-Dombriz, F. J. Maldonado
Torralba | Focusing conditions for extended teleparallel gravity theories | 31 pages, 9 figures, JCAP format, minor changes, matches published
version in JCAP | JCAP12(2020)020 | 10.1088/1475-7516/2020/12/020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of extended theories of teleparallel gravity $f(T)$ we derive
the focusing conditions for a one-parameter dependent congruence of timelike
auto-parallels of the Levi-Civita connection. We also consider the $f(T)$ field
equations for a general metric tensor before moving on to consider a spatially
flat Robertson-Walker space-time. Following this, we study the expansion rate
for a one-parameter dependent congruence of timelike auto-parallel curves of
the Levi-Civita connection. Given the fact that test particles follow
auto-parallels of the Levi-Civita connection, the torsion-free Raychaudhuri
equation is used in order to determine the desired focusing conditions. Finally
we study the obtained focusing conditions for three $f(T)$ paradigmatic
cosmological models and discuss the satisfaction or violation of these
conditions. Through this, we find $f(T)$ models that allow for the weak and
strong focusing conditions to be satisfied or violated. It is mentioned that
this behaviour can also be found in the so-called $f(R)$ and $f(Q)$ theories.
| [
{
"created": "Wed, 9 Sep 2020 15:21:18 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Dec 2020 12:05:52 GMT",
"version": "v2"
}
] | 2020-12-14 | [
[
"Vinckers",
"U. K. Beckering",
""
],
[
"de la Cruz-Dombriz",
"A.",
""
],
[
"Torralba",
"F. J. Maldonado",
""
]
] | In the context of extended theories of teleparallel gravity $f(T)$ we derive the focusing conditions for a one-parameter dependent congruence of timelike auto-parallels of the Levi-Civita connection. We also consider the $f(T)$ field equations for a general metric tensor before moving on to consider a spatially flat Robertson-Walker space-time. Following this, we study the expansion rate for a one-parameter dependent congruence of timelike auto-parallel curves of the Levi-Civita connection. Given the fact that test particles follow auto-parallels of the Levi-Civita connection, the torsion-free Raychaudhuri equation is used in order to determine the desired focusing conditions. Finally we study the obtained focusing conditions for three $f(T)$ paradigmatic cosmological models and discuss the satisfaction or violation of these conditions. Through this, we find $f(T)$ models that allow for the weak and strong focusing conditions to be satisfied or violated. It is mentioned that this behaviour can also be found in the so-called $f(R)$ and $f(Q)$ theories. |
1510.07311 | Peter K.F. Kuhfittig | Peter K.F. Kuhfittig and Vance D. Gladney | The no-boundary proposal via the five-dimensional
Friedmann-Lemaitre-Robertson-Walker model | 5 pages, no figures | Adv. Studies Theor. Phys., vol. 9, pp. 821-826 (2015) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hawking's proposal that the Universe has no temporal boundary and hence no
beginning depends on the notion of imaginary time and is usually referred to as
the "no-boundary proposal." This paper discusses a simple alternative approach
by means of the five-dimensional Friedmann-Lemaitre-Robertson-Walker model.
| [
{
"created": "Sun, 25 Oct 2015 21:37:27 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Jan 2016 16:09:44 GMT",
"version": "v2"
}
] | 2016-01-08 | [
[
"Kuhfittig",
"Peter K. F.",
""
],
[
"Gladney",
"Vance D.",
""
]
] | Hawking's proposal that the Universe has no temporal boundary and hence no beginning depends on the notion of imaginary time and is usually referred to as the "no-boundary proposal." This paper discusses a simple alternative approach by means of the five-dimensional Friedmann-Lemaitre-Robertson-Walker model. |
1208.4201 | Franco Albareti | F. D. Albareti (Madrid Complutense University), J. A. R. Cembranos
(Madrid Complutense University) and A. de la Cruz-Dombriz (ACGC and
University of Cape Town) | Focusing of geodesic congruences in an accelerated expanding Universe | 11 pages, 2 figures. Final version changed to match published version
in JCAP. References updated. Conclusions unchanged | JCAP 1212 (2012) 020 | 10.1088/1475-7516/2012/12/020 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the accelerated expansion of the Universe through its consequences
on a congruence of geodesics. We make use of the Raychaudhuri equation which
describes the evolution of the expansion rate for a congruence of timelike or
null geodesics. In particular, we focus on the space-time geometry contribution
to this equation. By straightforward calculation from the metric of a
Robertson-Walker cosmological model, it follows that in an accelerated
expanding Universe the space-time contribution to the Raychaudhuri equation is
positive for the fundamental congruence, favoring a non-focusing of the
congruence of geodesics. However, the accelerated expansion of the present
Universe does not imply a tendency of the fundamental congruence to diverge. It
is shown that this is in fact the case for certain congruences of timelike
geodesics without vorticity. Therefore, the focusing of geodesics remains
feasible in an accelerated expanding Universe. Furthermore, a negative
contribution to the Raychaudhuri equation from space-time geometry which is
usually interpreted as the manifestation of the attractive character of gravity
is restored in an accelerated expanding Robertson-Walker space-time at high
speeds.
| [
{
"created": "Tue, 21 Aug 2012 06:51:57 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Jan 2013 17:05:23 GMT",
"version": "v2"
}
] | 2013-01-09 | [
[
"Albareti",
"F. D.",
"",
"Madrid Complutense University"
],
[
"Cembranos",
"J. A. R.",
"",
"Madrid Complutense University"
],
[
"de la Cruz-Dombriz",
"A.",
"",
"ACGC and\n University of Cape Town"
]
] | We study the accelerated expansion of the Universe through its consequences on a congruence of geodesics. We make use of the Raychaudhuri equation which describes the evolution of the expansion rate for a congruence of timelike or null geodesics. In particular, we focus on the space-time geometry contribution to this equation. By straightforward calculation from the metric of a Robertson-Walker cosmological model, it follows that in an accelerated expanding Universe the space-time contribution to the Raychaudhuri equation is positive for the fundamental congruence, favoring a non-focusing of the congruence of geodesics. However, the accelerated expansion of the present Universe does not imply a tendency of the fundamental congruence to diverge. It is shown that this is in fact the case for certain congruences of timelike geodesics without vorticity. Therefore, the focusing of geodesics remains feasible in an accelerated expanding Universe. Furthermore, a negative contribution to the Raychaudhuri equation from space-time geometry which is usually interpreted as the manifestation of the attractive character of gravity is restored in an accelerated expanding Robertson-Walker space-time at high speeds. |
1502.01676 | Mubasher Jamil | Azka Younas, Mubasher Jamil, Sebastian Bahamonde, Saqib Hussain | Strong Gravitational Lensing by Kiselev Black Hole | null | Phys. Rev. D 92, 084042 (2015) | 10.1103/PhysRevD.92.084042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the gravitational lensing scenario due to Schwarzschild-like
black hole surrounded by quintessence (Kiselev black hole). We work for the
special case of Kiselev black hole where we take the state parameter
$w_{q}=-\frac{2}{3}$. For the detailed derivation and analysis of the bending
angle involved in the deflection of light, we discuss three special cases of
Kiselev black hole: non-extreme, extreme and naked singularity. We also
calculate the approximate bending angle and compare it with exact bending
angle. We found the relation of bending angles in the decreasing order as:
naked singularity, extreme Kiselev black hole, non-extreme Kiselev black hole
and Schwarzschild black hole. In the weak field approximation, we compute the
position and total magnification of relativistic images as well.
| [
{
"created": "Wed, 4 Feb 2015 10:54:39 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Feb 2015 09:25:42 GMT",
"version": "v2"
},
{
"created": "Mon, 13 Apr 2015 19:07:45 GMT",
"version": "v3"
},
{
"created": "Wed, 16 Sep 2015 15:43:29 GMT",
"version": "v4"
},
{
"cr... | 2015-10-21 | [
[
"Younas",
"Azka",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Bahamonde",
"Sebastian",
""
],
[
"Hussain",
"Saqib",
""
]
] | We investigate the gravitational lensing scenario due to Schwarzschild-like black hole surrounded by quintessence (Kiselev black hole). We work for the special case of Kiselev black hole where we take the state parameter $w_{q}=-\frac{2}{3}$. For the detailed derivation and analysis of the bending angle involved in the deflection of light, we discuss three special cases of Kiselev black hole: non-extreme, extreme and naked singularity. We also calculate the approximate bending angle and compare it with exact bending angle. We found the relation of bending angles in the decreasing order as: naked singularity, extreme Kiselev black hole, non-extreme Kiselev black hole and Schwarzschild black hole. In the weak field approximation, we compute the position and total magnification of relativistic images as well. |
0709.2131 | L\'aszl\'o \'A Gergely | Zolt\'an Kov\'acs, L\'aszl\'o \'A. Gergely | Gravitational dynamics in s+1+1 dimensions II. Hamiltonian theory | 13 pages | Phys.Rev.D77:024003,2008 | 10.1103/PhysRevD.77.024003 | null | gr-qc astro-ph hep-th | null | We develop a Hamiltonian formalism of brane-world gravity, which singles out
two preferred, mutually orthogonal directions. One is a unit twist-free field
of spatial vectors with integral lines intersecting perpendicularly the brane.
The other is a temporal vector field with respect to which we perform the
Arnowitt-Deser-Misner decomposition of the Einstein-Hilbert Lagrangian. The
gravitational variables arise from the projections of the spatial metric and
their canonically conjugated momenta as tensorial, vectorial and scalar
quantities defined on the family of hypersurfaces containing the brane. They
represent the gravitons, a gravi-photon and a gravi-scalar, respectively. From
the action we derive the canonical evolution equations and the constraints for
these gravitational degrees of freedom both on the brane and outside it. By
integrating across the brane, the dynamics also generates the tensorial and
scalar projection of the Lanczos equation. The vectorial projection of the
Lanczos equation arises in a similar way from the diffeomorphism constraint.
Both the graviton and the gravi-scalar are continuous across the brane, however
the momentum of the gravi-vector has a jump, related to the energy transport
(heat flow) on the brane.
| [
{
"created": "Thu, 13 Sep 2007 17:11:50 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kovács",
"Zoltán",
""
],
[
"Gergely",
"László Á.",
""
]
] | We develop a Hamiltonian formalism of brane-world gravity, which singles out two preferred, mutually orthogonal directions. One is a unit twist-free field of spatial vectors with integral lines intersecting perpendicularly the brane. The other is a temporal vector field with respect to which we perform the Arnowitt-Deser-Misner decomposition of the Einstein-Hilbert Lagrangian. The gravitational variables arise from the projections of the spatial metric and their canonically conjugated momenta as tensorial, vectorial and scalar quantities defined on the family of hypersurfaces containing the brane. They represent the gravitons, a gravi-photon and a gravi-scalar, respectively. From the action we derive the canonical evolution equations and the constraints for these gravitational degrees of freedom both on the brane and outside it. By integrating across the brane, the dynamics also generates the tensorial and scalar projection of the Lanczos equation. The vectorial projection of the Lanczos equation arises in a similar way from the diffeomorphism constraint. Both the graviton and the gravi-scalar are continuous across the brane, however the momentum of the gravi-vector has a jump, related to the energy transport (heat flow) on the brane. |
1805.02240 | Bayram Tekin | Ercan Kilicarslan and Bayram Tekin | Graviton Mass and Memory | 6 pages, matches the published version | Eur. Phys. J. C (2019) 79: 114 | 10.1140/epjc/s10052-019-6636-4 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational memory, a residual change, arises after a finite gravitational
wave pulse interacts with free masses. We calculate the memory effect in
massive gravity as a function of the graviton mass $(m_g)$ and show that it is
discretely different from the result of general relativity: the memory is
reduced not just via the usual expected Yukawa decay but by a numerical factor
which survives even in the massless limit. For the strongest existing bounds on
the graviton mass, the memory is essentially wiped out for the sources located
at distances above 10 Mpc. On the other hand, for the weaker bounds found in
the LIGO observations, the memory is reduced to zero for distances above 0.1
Pc. Hence, we suggest that careful observations of the gravitational wave
memory effect can rule out the graviton mass or significantly bound it. We also
show that adding higher curvature terms reduces the memory effect.
| [
{
"created": "Sun, 6 May 2018 16:21:35 GMT",
"version": "v1"
},
{
"created": "Wed, 16 May 2018 16:46:24 GMT",
"version": "v2"
},
{
"created": "Wed, 6 Feb 2019 13:37:32 GMT",
"version": "v3"
}
] | 2019-02-07 | [
[
"Kilicarslan",
"Ercan",
""
],
[
"Tekin",
"Bayram",
""
]
] | Gravitational memory, a residual change, arises after a finite gravitational wave pulse interacts with free masses. We calculate the memory effect in massive gravity as a function of the graviton mass $(m_g)$ and show that it is discretely different from the result of general relativity: the memory is reduced not just via the usual expected Yukawa decay but by a numerical factor which survives even in the massless limit. For the strongest existing bounds on the graviton mass, the memory is essentially wiped out for the sources located at distances above 10 Mpc. On the other hand, for the weaker bounds found in the LIGO observations, the memory is reduced to zero for distances above 0.1 Pc. Hence, we suggest that careful observations of the gravitational wave memory effect can rule out the graviton mass or significantly bound it. We also show that adding higher curvature terms reduces the memory effect. |
gr-qc/0203018 | John W. Barrett | John W. Barrett | Geometrical measurements in three-dimensional quantum gravity | This is the first of three lectures given at the Xth Oporto Meeting
on Geometry, Topology and Physics, September 2001. v2: one typo corrected | Int.J.Mod.Phys. A18S2 (2003) 97-113 | 10.1142/S0217751X03017981 | null | gr-qc hep-th | null | A set of observables is described for the topological quantum field theory
which describes quantum gravity in three space-time dimensions with positive
signature and positive cosmological constant. The simplest examples measure the
distances between points, giving spectra and probabilities which have a
geometrical interpretation. The observables are related to the evaluation of
relativistic spin networks by a Fourier transform.
| [
{
"created": "Wed, 6 Mar 2002 11:01:16 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Feb 2005 11:41:11 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Barrett",
"John W.",
""
]
] | A set of observables is described for the topological quantum field theory which describes quantum gravity in three space-time dimensions with positive signature and positive cosmological constant. The simplest examples measure the distances between points, giving spectra and probabilities which have a geometrical interpretation. The observables are related to the evaluation of relativistic spin networks by a Fourier transform. |
1210.0837 | Luke Butcher | Luke M. Butcher, Michael Hobson, Anthony Lasenby | Localized Energetics of Linear Gravity: Theoretical Development | null | Phys. Rev. D 86, 084013 (2012) | 10.1103/PhysRevD.86.084013 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We recently developed a local description of the energy, momentum and angular
momentum carried by the linearized gravitational field, wherein the
gravitational energy-momentum tensor displays positive energy-density and
causal energy-flux, and the gravitational spin-tensor describes purely spatial
spin. We now investigate the role these tensors play in a broader theoretical
context, demonstrating for the first time that (a) they do indeed constitute
Noether currents associated with the symmetry of the linearized gravitational
field under translation and rotation, and (b) they are themselves a source of
gravity, analogous to the energy-momentum and spin of matter. To prove (a) we
construct a Lagrangian for linearized gravity (a covariantized Fierz-Pauli
Lagrangian for a massless spin-2 field) and show that our tensors can be
obtained from this Lagrangian using a standard variational technique for
calculating Noether currents. This approach generates formulae that uniquely
generalize our gravitational energy-momentum tensor and spin tensor beyond
harmonic gauge: we show that no other generalization can be obtained from a
covariantized Fierz-Pauli Lagrangian without introducing second derivatives in
the energy-momentum tensor. We then construct the Belinfante energy-momentum
tensor associated with our framework (combining spin and energy-momentum into a
single object) and as our first demonstration of (b) we establish that this
Belinfante tensor appears as the second-order contribution to a perturbative
expansion of the Einstein field equations. By considering a perturbative
expansion of the Einstein-Cartan field equations, we then demonstrate that (b)
can be realized without forming the Belinfante tensor: our energy-momentum
tensor and spin tensor appear as the quadratic terms in separate field
equations, generating gravity as distinct entities. Finally, we examine the
role of...
| [
{
"created": "Tue, 2 Oct 2012 16:43:02 GMT",
"version": "v1"
}
] | 2012-10-03 | [
[
"Butcher",
"Luke M.",
""
],
[
"Hobson",
"Michael",
""
],
[
"Lasenby",
"Anthony",
""
]
] | We recently developed a local description of the energy, momentum and angular momentum carried by the linearized gravitational field, wherein the gravitational energy-momentum tensor displays positive energy-density and causal energy-flux, and the gravitational spin-tensor describes purely spatial spin. We now investigate the role these tensors play in a broader theoretical context, demonstrating for the first time that (a) they do indeed constitute Noether currents associated with the symmetry of the linearized gravitational field under translation and rotation, and (b) they are themselves a source of gravity, analogous to the energy-momentum and spin of matter. To prove (a) we construct a Lagrangian for linearized gravity (a covariantized Fierz-Pauli Lagrangian for a massless spin-2 field) and show that our tensors can be obtained from this Lagrangian using a standard variational technique for calculating Noether currents. This approach generates formulae that uniquely generalize our gravitational energy-momentum tensor and spin tensor beyond harmonic gauge: we show that no other generalization can be obtained from a covariantized Fierz-Pauli Lagrangian without introducing second derivatives in the energy-momentum tensor. We then construct the Belinfante energy-momentum tensor associated with our framework (combining spin and energy-momentum into a single object) and as our first demonstration of (b) we establish that this Belinfante tensor appears as the second-order contribution to a perturbative expansion of the Einstein field equations. By considering a perturbative expansion of the Einstein-Cartan field equations, we then demonstrate that (b) can be realized without forming the Belinfante tensor: our energy-momentum tensor and spin tensor appear as the quadratic terms in separate field equations, generating gravity as distinct entities. Finally, we examine the role of... |
gr-qc/0011056 | Israel Quiroz | Israel Quiros (Universidad Central de Las Villas. Santa Clara. Cuba) | The Weyl anomaly and the nature of the background geometry | 11 pages, RevTex, no figures | null | null | null | gr-qc hep-th | null | The Weyl anomaly problem is treated within a purely geometrical context.
Arguments are given that hint at a possible classical origin of the conformal
anomaly in the Riemannian nature of the background geometry where the matter
fields play out their dynamics. Some considerations allowing for a possible
resolution of the Weyl anomaly problem are briefly outlined. Following the
spirit of the standard model of the fundamental interactions, it is argued that
the Weyl anomaly should be a consequence of the breaking of the gauge symmetry
at some stage during the evolution of the universe.
| [
{
"created": "Wed, 15 Nov 2000 20:02:25 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Quiros",
"Israel",
"",
"Universidad Central de Las Villas. Santa Clara. Cuba"
]
] | The Weyl anomaly problem is treated within a purely geometrical context. Arguments are given that hint at a possible classical origin of the conformal anomaly in the Riemannian nature of the background geometry where the matter fields play out their dynamics. Some considerations allowing for a possible resolution of the Weyl anomaly problem are briefly outlined. Following the spirit of the standard model of the fundamental interactions, it is argued that the Weyl anomaly should be a consequence of the breaking of the gauge symmetry at some stage during the evolution of the universe. |
2403.11301 | Salvatore Capozziello | Salvatore Capozziello, Anupam Mazumdar, Giuseppe Meluccio | Can nonlocal gravity really explain dark energy? | 16 pages, 2 figures, accepted for publication in Physics of the Dark
Universe | null | null | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | In view to scrutinize the idea that nonlocal modifications of General
Relativity could dynamically address the dark energy problem, we investigate
the evolution of the Universe at infrared scales as an Infinite Derivative
Gravity model of the Ricci scalar, without introducing the cosmological
constant $\Lambda$ or any scalar field. The accelerated expansion of the late
Universe is shown to be compatible with the emergence of nonlocal gravitational
effects at sufficiently low energies. A technique for circumventing the
mathematical complexity of the nonlocal cosmological equations is developed
and, after drawing a connection with the Starobinsky gravity, verifiable
predictions are considered, like a possible decreasing in the strength of the
effective gravitational constant. In conclusion, the emergence of nonlocal
gravity corrections at given scales could be an efficient mechanism to address
the dark energy problem.
| [
{
"created": "Sun, 17 Mar 2024 18:46:13 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Mar 2024 12:36:32 GMT",
"version": "v2"
},
{
"created": "Wed, 20 Mar 2024 09:50:15 GMT",
"version": "v3"
},
{
"created": "Thu, 2 May 2024 09:01:21 GMT",
"version": "v4"
}
] | 2024-05-03 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Mazumdar",
"Anupam",
""
],
[
"Meluccio",
"Giuseppe",
""
]
] | In view to scrutinize the idea that nonlocal modifications of General Relativity could dynamically address the dark energy problem, we investigate the evolution of the Universe at infrared scales as an Infinite Derivative Gravity model of the Ricci scalar, without introducing the cosmological constant $\Lambda$ or any scalar field. The accelerated expansion of the late Universe is shown to be compatible with the emergence of nonlocal gravitational effects at sufficiently low energies. A technique for circumventing the mathematical complexity of the nonlocal cosmological equations is developed and, after drawing a connection with the Starobinsky gravity, verifiable predictions are considered, like a possible decreasing in the strength of the effective gravitational constant. In conclusion, the emergence of nonlocal gravity corrections at given scales could be an efficient mechanism to address the dark energy problem. |
2306.00839 | Orlando Luongo | Orlando Luongo, Hernando Quevedo | Geometrothermodynamic cosmology | Invited review, 33 pages, 1 figure | null | 10.3390/e25071037 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the main aspects of geometrothermodynamics, a formalism that uses
contact geometry and Riemannian geometry to describe the properties of
thermodynamic systems. We show how to handle in a geometric way the invariance
of classical thermodynamics with respect to Legendre transformations, which
means that the properties of the systems do not depend on the choice of the
thermodynamic potential. Moreover, we show that in geometrothermodynamics it is
possible to apply a variational principle to generate thermodynamic fundamental
equations, which can be used in the context of relativistic cosmology to
generate cosmological models. As a particular example, we consider a
fundamental equation that relates the entropy with the internal energy and the
volume of the Universe, and construct cosmological models with arbitrary
parameters, which can be fixed to reproduce the main aspects of the
inflationary era and the standard cosmological paradigm.
| [
{
"created": "Thu, 1 Jun 2023 16:00:58 GMT",
"version": "v1"
}
] | 2023-07-26 | [
[
"Luongo",
"Orlando",
""
],
[
"Quevedo",
"Hernando",
""
]
] | We review the main aspects of geometrothermodynamics, a formalism that uses contact geometry and Riemannian geometry to describe the properties of thermodynamic systems. We show how to handle in a geometric way the invariance of classical thermodynamics with respect to Legendre transformations, which means that the properties of the systems do not depend on the choice of the thermodynamic potential. Moreover, we show that in geometrothermodynamics it is possible to apply a variational principle to generate thermodynamic fundamental equations, which can be used in the context of relativistic cosmology to generate cosmological models. As a particular example, we consider a fundamental equation that relates the entropy with the internal energy and the volume of the Universe, and construct cosmological models with arbitrary parameters, which can be fixed to reproduce the main aspects of the inflationary era and the standard cosmological paradigm. |
2404.06934 | Rajibul Shaikh | Inyong Cho and Rajibul Shaikh | Homogeneous spacetime with shear viscosity | 26 pages, 7 captioned figures, abstract modified, studies on
deceleration and anisotropy parameters added, published in JCAP | JCAP 07 (2024) 025 | 10.1088/1475-7516/2024/07/025 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the homogeneous and anisotropic evolution of Bianchi type-I
spacetime driven by perfect fluid with shear viscosity. We obtain exact
solutions by considering the simplest form of the equation of state wherein the
pressure and the shear stress are proportional to the energy density
individually. A special case of our general solutions represent Bianchi
type-VII cosmology. We analyse the singularity structure of the solutions and
its connection with various energy conditions. We find that the initial
singularity can be removed only for the Bianchi type-VII. We also analyse the
late-time behaviour of the solutions and find that, compared to the usual
Friedmann universe, the spacetime expands less rapidly and the energy density
drops faster.
| [
{
"created": "Wed, 10 Apr 2024 11:35:39 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Jul 2024 08:18:40 GMT",
"version": "v2"
}
] | 2024-07-22 | [
[
"Cho",
"Inyong",
""
],
[
"Shaikh",
"Rajibul",
""
]
] | We study the homogeneous and anisotropic evolution of Bianchi type-I spacetime driven by perfect fluid with shear viscosity. We obtain exact solutions by considering the simplest form of the equation of state wherein the pressure and the shear stress are proportional to the energy density individually. A special case of our general solutions represent Bianchi type-VII cosmology. We analyse the singularity structure of the solutions and its connection with various energy conditions. We find that the initial singularity can be removed only for the Bianchi type-VII. We also analyse the late-time behaviour of the solutions and find that, compared to the usual Friedmann universe, the spacetime expands less rapidly and the energy density drops faster. |
1504.07660 | Netta Engelhardt | Raphael Bousso and Netta Engelhardt | Proof of a New Area Law in General Relativity | 15 pages, 10 figures; v4: conclusion of Theorem IV.2 strengthened | Phys. Rev. D 92, 044031 (2015) | 10.1103/PhysRevD.92.044031 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A future holographic screen is a hypersurface of indefinite signature,
foliated by marginally trapped surfaces with area $A(r)$. We prove that $A(r)$
grows strictly monotonically. Future holographic screens arise in gravitational
collapse. Past holographic screens exist in our own universe; they obey an
analogous area law. Both exist more broadly than event horizons or dynamical
horizons. Working within classical General Relativity, we assume the null
curvature condition and certain generiticity conditions. We establish several
nontrivial intermediate results. If a surface $\sigma$ divides a Cauchy surface
into two disjoint regions, then a null hypersurface $N$ that contains $\sigma$
splits the entire spacetime into two disjoint portions: the
future-and-interior, $K^+$; and the past-and-exterior, $K^-$. If a family of
surfaces $\sigma(r)$ foliate a hypersurface, while flowing everywhere to the
past or exterior, then the future-and-interior $K^+(r)$ grows monotonically
under inclusion. If the surfaces $\sigma(r)$ are marginally trapped, we prove
that the evolution must be everywhere to the past or exterior, and the area
theorem follows. A thermodynamic interpretation as a Second Law is suggested by
the Bousso bound, which relates $A(r)$ to the entropy on the null slices $N(r)$
foliating the spacetime. In a companion letter, we summarize the proof and
discuss further implications.
| [
{
"created": "Tue, 28 Apr 2015 21:11:29 GMT",
"version": "v1"
},
{
"created": "Fri, 8 May 2015 20:14:40 GMT",
"version": "v2"
},
{
"created": "Sun, 24 May 2015 20:13:14 GMT",
"version": "v3"
},
{
"created": "Thu, 27 Aug 2015 02:31:18 GMT",
"version": "v4"
}
] | 2015-08-28 | [
[
"Bousso",
"Raphael",
""
],
[
"Engelhardt",
"Netta",
""
]
] | A future holographic screen is a hypersurface of indefinite signature, foliated by marginally trapped surfaces with area $A(r)$. We prove that $A(r)$ grows strictly monotonically. Future holographic screens arise in gravitational collapse. Past holographic screens exist in our own universe; they obey an analogous area law. Both exist more broadly than event horizons or dynamical horizons. Working within classical General Relativity, we assume the null curvature condition and certain generiticity conditions. We establish several nontrivial intermediate results. If a surface $\sigma$ divides a Cauchy surface into two disjoint regions, then a null hypersurface $N$ that contains $\sigma$ splits the entire spacetime into two disjoint portions: the future-and-interior, $K^+$; and the past-and-exterior, $K^-$. If a family of surfaces $\sigma(r)$ foliate a hypersurface, while flowing everywhere to the past or exterior, then the future-and-interior $K^+(r)$ grows monotonically under inclusion. If the surfaces $\sigma(r)$ are marginally trapped, we prove that the evolution must be everywhere to the past or exterior, and the area theorem follows. A thermodynamic interpretation as a Second Law is suggested by the Bousso bound, which relates $A(r)$ to the entropy on the null slices $N(r)$ foliating the spacetime. In a companion letter, we summarize the proof and discuss further implications. |
1405.3696 | Carlos A. R. Herdeiro | Carlos A. R. Herdeiro and Eugen Radu | A new spin on black hole hair | 9 pages, 1 figure, Essay written for the Gravity Research Foundation
2014 Awards for Essays on Gravitation and selected for Honorable Mention | null | 10.1142/S0218271814420140 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that scalar hair can be added to rotating, vacuum black holes of
general relativity. These hairy black holes (HBHs) clarify a lingering question
concerning gravitational solitons: if a black hole can be added at the centre
of a boson star, as it typically can for other solitons. We argue that it can,
but only if it is spinning. The existence of such HBHs is related to the Kerr
superradiant instability triggered by a massive scalar field. This connection
leads to the following conjecture: a (hairless) black hole which is afflicted
by the superradiant instability of a given field must allow hairy
generalizations with that field.
| [
{
"created": "Wed, 14 May 2014 21:33:40 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Herdeiro",
"Carlos A. R.",
""
],
[
"Radu",
"Eugen",
""
]
] | We show that scalar hair can be added to rotating, vacuum black holes of general relativity. These hairy black holes (HBHs) clarify a lingering question concerning gravitational solitons: if a black hole can be added at the centre of a boson star, as it typically can for other solitons. We argue that it can, but only if it is spinning. The existence of such HBHs is related to the Kerr superradiant instability triggered by a massive scalar field. This connection leads to the following conjecture: a (hairless) black hole which is afflicted by the superradiant instability of a given field must allow hairy generalizations with that field. |
0903.5030 | Kentaro Takami | Kentaro Takami and Yasufumi Kojima | Collimation of a spherical collisionless particles stream in Kerr
space-time | 11 pages, 8 figures; accepted for publication in CQG | Class.Quant.Grav.26:085013,2009 | 10.1088/0264-9381/26/8/085013 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the propagation of collisionless particles emitted from a
spherical shell to infinity. The number distribution at infinity, calculated as
a function of the polar angle, exhibits a small deviation from uniformity. The
number of particles moving from the polar region toward the equatorial plane is
slightly larger than that of particles in the opposite direction, for an
emission radius $ > 4.5M$ in extreme Kerr space-time. This means that the black
hole spin exerts an anti-collimation effect on the particles stream propagating
along the rotation axis. We also confirm this property in the weak field limit.
The quadrupole moment of the central object produces a force toward the
equatorial plane. For a smaller emission radius $r<4.5M$, the absorption of
particles into the black hole, the non-uniformity and/or the anisotropy of the
emission distribution become much more important.
| [
{
"created": "Sun, 29 Mar 2009 08:39:59 GMT",
"version": "v1"
}
] | 2009-05-20 | [
[
"Takami",
"Kentaro",
""
],
[
"Kojima",
"Yasufumi",
""
]
] | We examine the propagation of collisionless particles emitted from a spherical shell to infinity. The number distribution at infinity, calculated as a function of the polar angle, exhibits a small deviation from uniformity. The number of particles moving from the polar region toward the equatorial plane is slightly larger than that of particles in the opposite direction, for an emission radius $ > 4.5M$ in extreme Kerr space-time. This means that the black hole spin exerts an anti-collimation effect on the particles stream propagating along the rotation axis. We also confirm this property in the weak field limit. The quadrupole moment of the central object produces a force toward the equatorial plane. For a smaller emission radius $r<4.5M$, the absorption of particles into the black hole, the non-uniformity and/or the anisotropy of the emission distribution become much more important. |
2107.10841 | Leong Khim Wong | Philippe Brax, Anne-Christine Davis, Scott Melville, Leong Khim Wong | Spin-orbit effects for compact binaries in scalar-tensor gravity | 57 pages + appendices, 8 figures, 5 tables. v2: Version accepted for
publication. Some minor clarifications added compared to v1 | JCAP 10 (2021) 075 | 10.1088/1475-7516/2021/10/075 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves provide us with a new window into our Universe, and have
already been used to place strong constrains on the existence of light scalar
fields, which are a common feature in many alternative theories of gravity.
However, spin effects are still relatively unexplored in this context. In this
work, we construct an effective point-particle action for a generic spinning
body that can couple both conformally and disformally to a real scalar field,
and we show that requiring the existence of a self-consistent solution
automatically implies that if a scalar couples to the mass of a body, then it
must also couple to its spin. We then use well-established effective field
theory techniques to conduct a comprehensive study of spin-orbit effects in
binary systems to leading order in the post-Newtonian (PN) expansion. Focusing
on quasicircular nonprecessing binaries for simplicity, we systematically
compute all key quantities, including the conservative potential, the orbital
binding energy, the radiated power, and the gravitational-wave phase. We show
that depending on how strongly each member of the binary couples to the scalar,
the spin-orbit effects that are due to a conformal coupling first enter into
the phase at either 0.5PN or 1.5PN order, while those that arise from a
disformal coupling start at either 3.5PN or 4.5PN order. This suppression by
additional PN orders notwithstanding, we find that the disformal spin-orbit
terms can actually dominate over their conformal counterparts due to an
enhancement by a large prefactor. Accordingly, our results suggest that
upcoming gravitational-wave detectors could be sensitive to disformal
spin-orbit effects in double neutron star binaries if at least one of the two
bodies is sufficiently scalarised.
| [
{
"created": "Thu, 22 Jul 2021 17:54:45 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Oct 2021 17:27:36 GMT",
"version": "v2"
}
] | 2021-10-28 | [
[
"Brax",
"Philippe",
""
],
[
"Davis",
"Anne-Christine",
""
],
[
"Melville",
"Scott",
""
],
[
"Wong",
"Leong Khim",
""
]
] | Gravitational waves provide us with a new window into our Universe, and have already been used to place strong constrains on the existence of light scalar fields, which are a common feature in many alternative theories of gravity. However, spin effects are still relatively unexplored in this context. In this work, we construct an effective point-particle action for a generic spinning body that can couple both conformally and disformally to a real scalar field, and we show that requiring the existence of a self-consistent solution automatically implies that if a scalar couples to the mass of a body, then it must also couple to its spin. We then use well-established effective field theory techniques to conduct a comprehensive study of spin-orbit effects in binary systems to leading order in the post-Newtonian (PN) expansion. Focusing on quasicircular nonprecessing binaries for simplicity, we systematically compute all key quantities, including the conservative potential, the orbital binding energy, the radiated power, and the gravitational-wave phase. We show that depending on how strongly each member of the binary couples to the scalar, the spin-orbit effects that are due to a conformal coupling first enter into the phase at either 0.5PN or 1.5PN order, while those that arise from a disformal coupling start at either 3.5PN or 4.5PN order. This suppression by additional PN orders notwithstanding, we find that the disformal spin-orbit terms can actually dominate over their conformal counterparts due to an enhancement by a large prefactor. Accordingly, our results suggest that upcoming gravitational-wave detectors could be sensitive to disformal spin-orbit effects in double neutron star binaries if at least one of the two bodies is sufficiently scalarised. |
2106.12818 | Davide Astesiano | Davide Astesiano, Sergio L. Cacciatori, Federico Re | Towards a full general relativistic approach to galaxies | 13 pages | null | 10.1140/epjc/s10052-022-10506-7 | null | gr-qc astro-ph.GA | http://creativecommons.org/licenses/by/4.0/ | We analyze the dynamics of a single spiral galaxy from a general relativistic
viewpoint. We employ the known family of stationary axially-symmetric solutions
to Einstein gravity coupled with dust in order to model the halo external to
the bulge. In particular, we generalize the known results of Balasin and
Grumiller, relaxing the condition of co-rotation, thus including non
co-rotating dust. This further highlights the discrepancy between Newtonian
theory of gravity and general relativity at low velocities and energy
densities. We investigate the role of dragging in simulating dark matter
effects. In particular, we show that non co-rotance further reduce the amount
of energy density required to explain the rotation curves for spiral galaxies.
| [
{
"created": "Thu, 24 Jun 2021 08:18:26 GMT",
"version": "v1"
}
] | 2022-07-13 | [
[
"Astesiano",
"Davide",
""
],
[
"Cacciatori",
"Sergio L.",
""
],
[
"Re",
"Federico",
""
]
] | We analyze the dynamics of a single spiral galaxy from a general relativistic viewpoint. We employ the known family of stationary axially-symmetric solutions to Einstein gravity coupled with dust in order to model the halo external to the bulge. In particular, we generalize the known results of Balasin and Grumiller, relaxing the condition of co-rotation, thus including non co-rotating dust. This further highlights the discrepancy between Newtonian theory of gravity and general relativity at low velocities and energy densities. We investigate the role of dragging in simulating dark matter effects. In particular, we show that non co-rotance further reduce the amount of energy density required to explain the rotation curves for spiral galaxies. |
1707.09194 | Shintaro Nakamura | Shintaro Nakamura, Ryotaro Kase, and Shinji Tsujikawa | Suppression of matter couplings with a vector field in generalized Proca
theories | 20 pages, 2 figures | Phys. Rev. D 96, 084005 (2017) | 10.1103/PhysRevD.96.084005 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the profile of a vector field coupled to matter on a static and
spherically symmetric background in the context of generalized Proca theories.
The cubic Galileon self-interaction leads to the suppression of a longitudinal
vector component due to the operation of the Vainshtein mechanism. For quartic
and sixth-order derivative interactions, the solutions consistent with those in
the continuous limit of small derivative couplings correspond to the branch
with the vanishing longitudinal mode. We compute the corrections to
gravitational potentials outside a compact body induced by the vector field in
the presence of cubic, quartic, and sixth-order derivative couplings, and show
that the models can be consistent with local gravity constraints under mild
bounds on the temporal vector component. The quintic Galileon interaction does
not allow regular solutions of the longitudinal mode for a rapidly decreasing
matter density outside the body.
| [
{
"created": "Fri, 28 Jul 2017 11:16:17 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Oct 2017 22:33:26 GMT",
"version": "v2"
}
] | 2017-10-11 | [
[
"Nakamura",
"Shintaro",
""
],
[
"Kase",
"Ryotaro",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | We derive the profile of a vector field coupled to matter on a static and spherically symmetric background in the context of generalized Proca theories. The cubic Galileon self-interaction leads to the suppression of a longitudinal vector component due to the operation of the Vainshtein mechanism. For quartic and sixth-order derivative interactions, the solutions consistent with those in the continuous limit of small derivative couplings correspond to the branch with the vanishing longitudinal mode. We compute the corrections to gravitational potentials outside a compact body induced by the vector field in the presence of cubic, quartic, and sixth-order derivative couplings, and show that the models can be consistent with local gravity constraints under mild bounds on the temporal vector component. The quintic Galileon interaction does not allow regular solutions of the longitudinal mode for a rapidly decreasing matter density outside the body. |
gr-qc/9510017 | James E. Lidsey | James E. Lidsey | Scale Factor Duality and Hidden Supersymmetry in Scalar--Tensor
Cosmology | 10 pages, latex, To appear in Phys. Rev. D15 Rapid Communications | Phys.Rev. D52 (1995) 5407-5411 | 10.1103/PhysRevD.52.R5407 | null | gr-qc astro-ph hep-th | null | It is shown that spatially flat, isotropic cosmologies derived from the
Brans--Dicke gravity action exhibit a scale factor duality invariance. This
classical duality is then associated with a hidden $N=2$ supersymmetry at the
quantum level and the supersymmetric quantum constraints are solved exactly.
These symmetries also apply to a dimensionally reduced version of vacuum
Einstein gravity.
| [
{
"created": "Tue, 10 Oct 1995 13:49:01 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Lidsey",
"James E.",
""
]
] | It is shown that spatially flat, isotropic cosmologies derived from the Brans--Dicke gravity action exhibit a scale factor duality invariance. This classical duality is then associated with a hidden $N=2$ supersymmetry at the quantum level and the supersymmetric quantum constraints are solved exactly. These symmetries also apply to a dimensionally reduced version of vacuum Einstein gravity. |
2011.04559 | Beatriz Elizaga Navascu\'es | Beatriz Elizaga Navascu\'es and Guillermo A. Mena Marug\'an | Hybrid Loop Quantum Cosmology: An Overview | 39 pages | Front. Astron. Space Sci. 8, 624824 (2021) | 10.3389/fspas.2021.624824 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Loop Quantum Gravity is a nonperturbative and background independent program
for the quantization of General Relativity. Its underlying formalism has been
applied successfully to the study of cosmological spacetimes, both to test the
principles and techniques of the theory and to discuss its physical
consequences. These applications have opened a new area of research known as
Loop Quantum Cosmology. The hybrid approach addresses the quantization of
cosmological systems that include fields. This proposal combines the
description of a finite number of degrees of freedom using Loop Quantum
Cosmology, typically corresponding to a homogeneous background, and a Fock
quantization of the field content of the model. In this review we first present
a summary of the foundations of homogeneous Loop Quantum Cosmology and we then
revisit the hybrid quantization approach, applying it to the study of Gowdy
spacetimes with linearly polarized gravitational waves on toroidal spatial
sections, and to the analysis of cosmological perturbations in preinflationary
and inflationary stages of the Universe. The main challenge is to extract
predictions about quantum geometry effects that eventually might be confronted
with cosmological observations. This is the first extensive review of the
hybrid approach in the literature on Loop Quantum Cosmology.
| [
{
"created": "Mon, 9 Nov 2020 16:56:19 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Nov 2020 10:00:25 GMT",
"version": "v2"
},
{
"created": "Fri, 10 Sep 2021 04:42:56 GMT",
"version": "v3"
}
] | 2021-09-13 | [
[
"Navascués",
"Beatriz Elizaga",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
]
] | Loop Quantum Gravity is a nonperturbative and background independent program for the quantization of General Relativity. Its underlying formalism has been applied successfully to the study of cosmological spacetimes, both to test the principles and techniques of the theory and to discuss its physical consequences. These applications have opened a new area of research known as Loop Quantum Cosmology. The hybrid approach addresses the quantization of cosmological systems that include fields. This proposal combines the description of a finite number of degrees of freedom using Loop Quantum Cosmology, typically corresponding to a homogeneous background, and a Fock quantization of the field content of the model. In this review we first present a summary of the foundations of homogeneous Loop Quantum Cosmology and we then revisit the hybrid quantization approach, applying it to the study of Gowdy spacetimes with linearly polarized gravitational waves on toroidal spatial sections, and to the analysis of cosmological perturbations in preinflationary and inflationary stages of the Universe. The main challenge is to extract predictions about quantum geometry effects that eventually might be confronted with cosmological observations. This is the first extensive review of the hybrid approach in the literature on Loop Quantum Cosmology. |
1912.02556 | Maciej Kolanowski | Wojciech Kami\'nski, Maciej Kolanowski, Jerzy Lewandowski | Dressed metric predictions revisited | 9 pages | null | 10.1088/1361-6382/ab7ee0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was recently shown that the volume operator of loop quantum cosmology
(LQC) and all its positive powers are ill-defined on physical states. In this
paper, we investigate how it effects predictions of cosmic microwave background
(CMB) power spectra obtained within dressed metric approach for which
expectations values of $\hat{a}$ are the key element. We find that almost every
step in the procedure is ill-defined and relies heavily upon a (seemingly
premature) numerical truncation. Thus, it suggests that more care is needed in
making predictions regarding pre-inflationary physics. We propose a new scheme
which contains only well-defined quantities. The surprising agreement of the
hitherto models with observational data, especially at low angular momenta $l$
is explained.
| [
{
"created": "Thu, 5 Dec 2019 13:13:12 GMT",
"version": "v1"
}
] | 2020-06-17 | [
[
"Kamiński",
"Wojciech",
""
],
[
"Kolanowski",
"Maciej",
""
],
[
"Lewandowski",
"Jerzy",
""
]
] | It was recently shown that the volume operator of loop quantum cosmology (LQC) and all its positive powers are ill-defined on physical states. In this paper, we investigate how it effects predictions of cosmic microwave background (CMB) power spectra obtained within dressed metric approach for which expectations values of $\hat{a}$ are the key element. We find that almost every step in the procedure is ill-defined and relies heavily upon a (seemingly premature) numerical truncation. Thus, it suggests that more care is needed in making predictions regarding pre-inflationary physics. We propose a new scheme which contains only well-defined quantities. The surprising agreement of the hitherto models with observational data, especially at low angular momenta $l$ is explained. |
2202.08563 | Jochen Zahn | Christoph Giese and Jochen Zahn | Dynamics of spherical charged dust shells in de Sitter space | 16 page2; v2 final version | Physical Review D 106 (2022) 064005 | 10.1103/PhysRevD.106.064005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the dynamics of charged, spherically symmetric dust shells in the
presence of a positive cosmological constant. We find generalizations of the
well-known solutions in asymptotically flat spacetime, in particular orbits
into "parallel universes", but also new solutions corresponding to a "bounce"
of the shell before an event horizon has formed. We also discuss "bubble"
solutions, in which a charged shell and an oppositely charged singularity are
spontaneously created and annihilated.
| [
{
"created": "Thu, 17 Feb 2022 10:14:19 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Sep 2022 07:43:59 GMT",
"version": "v2"
}
] | 2022-09-07 | [
[
"Giese",
"Christoph",
""
],
[
"Zahn",
"Jochen",
""
]
] | We study the dynamics of charged, spherically symmetric dust shells in the presence of a positive cosmological constant. We find generalizations of the well-known solutions in asymptotically flat spacetime, in particular orbits into "parallel universes", but also new solutions corresponding to a "bounce" of the shell before an event horizon has formed. We also discuss "bubble" solutions, in which a charged shell and an oppositely charged singularity are spontaneously created and annihilated. |
gr-qc/0312060 | Hendryk Pfeiffer | Hendryk Pfeiffer | Diffeomorphisms from finite triangulations and absence of 'local'
degrees of freedom | 4 pages, RevTeX with combined PicTeX/postscript figures; v2:
presentation improved, typos corrected | Phys.Lett.B591:197-201,2004 | 10.1016/j.physletb.2004.04.026 | DAMTP-2003-132 | gr-qc | null | If the diffeomorphism symmetry of general relativity is fully implemented
into a path integral quantum theory, the path integral leads to a partition
function which is an invariant of smooth manifolds. We comment on the physical
implications of results on the classification of smooth and piecewise-linear
4-manifolds which show that the partition function can already be computed from
a triangulation of space-time. Such a triangulation characterizes the topology
and the differentiable structure, but is completely unrelated to any physical
cut-off. It can be arbitrarily refined without affecting the physical
predictions and without increasing the number of degrees of freedom
proportionally to the volume. Only refinements at the boundary have a physical
significance as long as the experimenters who observe through this boundary,
can increase the resolution of their measurements. All these are consequences
of the symmetries. The Planck scale cut-off expected in quantum gravity is
rather a dynamical effect.
| [
{
"created": "Wed, 10 Dec 2003 17:24:35 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Apr 2004 15:50:56 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Pfeiffer",
"Hendryk",
""
]
] | If the diffeomorphism symmetry of general relativity is fully implemented into a path integral quantum theory, the path integral leads to a partition function which is an invariant of smooth manifolds. We comment on the physical implications of results on the classification of smooth and piecewise-linear 4-manifolds which show that the partition function can already be computed from a triangulation of space-time. Such a triangulation characterizes the topology and the differentiable structure, but is completely unrelated to any physical cut-off. It can be arbitrarily refined without affecting the physical predictions and without increasing the number of degrees of freedom proportionally to the volume. Only refinements at the boundary have a physical significance as long as the experimenters who observe through this boundary, can increase the resolution of their measurements. All these are consequences of the symmetries. The Planck scale cut-off expected in quantum gravity is rather a dynamical effect. |
0812.2210 | Diego Pavon | Sergio del Campo (Valparaiso), Ramon Herrera (Valparaiso), and Diego
Pavon (Bellaterra, Barcelona) | Interacting models may be key to solve the cosmic coincidence problem | 25 pages, 11 figures; accepted for publication in JCAP | JCAP 0901:020,2009 | 10.1088/1475-7516/2009/01/020 | null | gr-qc astro-ph hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is argued that cosmological models that feature a flow of energy from dark
energy to dark matter may solve the coincidence problem of late acceleration
(i.e., "why the energy densities of both components are of the same order
precisely today?"). However, much refined and abundant observational data of
the redshift evolution of the Hubble factor are needed to ascertain whether
they can do the job.
| [
{
"created": "Thu, 11 Dec 2008 18:12:13 GMT",
"version": "v1"
}
] | 2009-02-06 | [
[
"del Campo",
"Sergio",
"",
"Valparaiso"
],
[
"Herrera",
"Ramon",
"",
"Valparaiso"
],
[
"Pavon",
"Diego",
"",
"Bellaterra, Barcelona"
]
] | It is argued that cosmological models that feature a flow of energy from dark energy to dark matter may solve the coincidence problem of late acceleration (i.e., "why the energy densities of both components are of the same order precisely today?"). However, much refined and abundant observational data of the redshift evolution of the Hubble factor are needed to ascertain whether they can do the job. |
0911.2981 | Lorenzo Fatibene | L. Fatibene, M. Francaviglia, S. Mercadante | Matter Lagrangians Coupled with Connections | Refs added | Int.J.Geom.Meth.Mod.Phys.7:1185-1189,2010 | 10.1142/S0219887810004798 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We shall here consider extended theories of gravitation in the metric-affine
formalism with matter coupled directly to the connection. A sufficiently
general procedure will be exhibited to solve the resulting field equation
associated to the connection. As special cases one has the no-coupling case
(which is standard in f(R) literature) as well as the cases already analyzed in
ref.[1].
| [
{
"created": "Mon, 16 Nov 2009 09:09:17 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jan 2010 11:25:12 GMT",
"version": "v2"
}
] | 2011-01-05 | [
[
"Fatibene",
"L.",
""
],
[
"Francaviglia",
"M.",
""
],
[
"Mercadante",
"S.",
""
]
] | We shall here consider extended theories of gravitation in the metric-affine formalism with matter coupled directly to the connection. A sufficiently general procedure will be exhibited to solve the resulting field equation associated to the connection. As special cases one has the no-coupling case (which is standard in f(R) literature) as well as the cases already analyzed in ref.[1]. |
0710.1887 | Celine Cattoen | Celine Cattoen (Victoria University of Wellington), Matt Visser
(Victoria University of Wellington) | The Hubble series: Convergence properties and redshift variables | 15 pages, 2 figures, accepted for publication in Classical and
Quantum Gravity | Class.Quant.Grav.24:5985-5998,2007 | 10.1088/0264-9381/24/23/018 | null | gr-qc | null | In cosmography, cosmokinetics, and cosmology it is quite common to encounter
physical quantities expanded as a Taylor series in the cosmological redshift z.
Perhaps the most well-known exemplar of this phenomenon is the Hubble relation
between distance and redshift. However, we now have considerable high-z data
available, for instance we have supernova data at least back to redshift
z=1.75. This opens up the theoretical question as to whether or not the Hubble
series (or more generally any series expansion based on the z-redshift)
actually converges for large redshift? Based on a combination of mathematical
and physical reasoning, we argue that the radius of convergence of any series
expansion in z is less than or equal to 1, and that z-based expansions must
break down for z>1, corresponding to a universe less than half its current
size.
Furthermore, we shall argue on theoretical grounds for the utility of an
improved parameterization y=z/(1+z). In terms of the y-redshift we again argue
that the radius of convergence of any series expansion in y is less than or
equal to 1, so that y-based expansions are likely to be good all the way back
to the big bang y=1, but that y-based expansions must break down for y<-1, now
corresponding to a universe more than twice its current size.
| [
{
"created": "Wed, 10 Oct 2007 00:00:19 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Cattoen",
"Celine",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | In cosmography, cosmokinetics, and cosmology it is quite common to encounter physical quantities expanded as a Taylor series in the cosmological redshift z. Perhaps the most well-known exemplar of this phenomenon is the Hubble relation between distance and redshift. However, we now have considerable high-z data available, for instance we have supernova data at least back to redshift z=1.75. This opens up the theoretical question as to whether or not the Hubble series (or more generally any series expansion based on the z-redshift) actually converges for large redshift? Based on a combination of mathematical and physical reasoning, we argue that the radius of convergence of any series expansion in z is less than or equal to 1, and that z-based expansions must break down for z>1, corresponding to a universe less than half its current size. Furthermore, we shall argue on theoretical grounds for the utility of an improved parameterization y=z/(1+z). In terms of the y-redshift we again argue that the radius of convergence of any series expansion in y is less than or equal to 1, so that y-based expansions are likely to be good all the way back to the big bang y=1, but that y-based expansions must break down for y<-1, now corresponding to a universe more than twice its current size. |
1612.07178 | Vladimir Ivashchuk | V. D. Ivashchuk | On stable exponential solutions in Einstein-Gauss-Bonnet cosmology with
zero variation of G | 4 pages, Latex, corrected version of the paper published in Grav.
Cosmol. Three typos for Lambda corresponding to (m,l) = (6,7), (7,5), (7,6)
are eliminated | Gravitation and Cosmology 22(4), 329-332 (2016) | 10.1134/S0202289316040095 | IGC-RUDN-2016-12-1 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A D-dimensional gravitational model with a Gauss-Bonnet term and the
cosmological term Lambda is considered. Assuming diagonal cosmological metrics,
we find, for certain non-zero Lambda new examples of solutions with an
exponential time dependence of two scale factors, governed by two Hubble-like
parameters H > 0 and h < 0, corresponding to submanifolds of dimensions m and
l, respectively, with (m,l) = (4,2), (5,2), (5,3), (6,7), (7,5), (7,6) and D =
1 + m + l. Any of these solutions describes an exponential expansion of "our"
3-dimensional factor-space with Hubble parameter H and zero variation of the
effective gravitational constant G. We also prove the stability of these
solutions in the class of cosmological solutions with diagonal metrics.
| [
{
"created": "Wed, 21 Dec 2016 15:21:26 GMT",
"version": "v1"
}
] | 2016-12-28 | [
[
"Ivashchuk",
"V. D.",
""
]
] | A D-dimensional gravitational model with a Gauss-Bonnet term and the cosmological term Lambda is considered. Assuming diagonal cosmological metrics, we find, for certain non-zero Lambda new examples of solutions with an exponential time dependence of two scale factors, governed by two Hubble-like parameters H > 0 and h < 0, corresponding to submanifolds of dimensions m and l, respectively, with (m,l) = (4,2), (5,2), (5,3), (6,7), (7,5), (7,6) and D = 1 + m + l. Any of these solutions describes an exponential expansion of "our" 3-dimensional factor-space with Hubble parameter H and zero variation of the effective gravitational constant G. We also prove the stability of these solutions in the class of cosmological solutions with diagonal metrics. |
2111.02963 | Patrick Peter | Jaime de Cabo Martin, Przemys{\l}aw Ma{\l}kiewicz and Patrick Peter | Unitarily inequivalent quantum cosmological bouncing models | 13 pages, 7 figures | Phys.Rev.D 105 (2022) 2, 023522 | 10.1103/PhysRevD.105.023522 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By quantising the background as well as the perturbations in a simple one
fluid model, we show that there exists an ambiguity in the choice of relevant
variables, potentially leading to incompatible observational physical
predictions. In a classical or quantum inflationary background, the exact same
canonical transformations lead to unique predictions, so the ambiguity we put
forward demands a semiclassical background with a sufficiently strong departure
from classical evolution. The latter condition happens to be satisfied in
bouncing scenarios, which may thus be having predictability issues.
Inflationary models could evade such a problem because of the monotonic
behavior of their scale factor; they do, however, initiate from a singular
state which bouncing scenarios aim at solving.
| [
{
"created": "Thu, 4 Nov 2021 15:45:40 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Nov 2021 22:35:46 GMT",
"version": "v2"
}
] | 2023-10-25 | [
[
"Martin",
"Jaime de Cabo",
""
],
[
"Małkiewicz",
"Przemysław",
""
],
[
"Peter",
"Patrick",
""
]
] | By quantising the background as well as the perturbations in a simple one fluid model, we show that there exists an ambiguity in the choice of relevant variables, potentially leading to incompatible observational physical predictions. In a classical or quantum inflationary background, the exact same canonical transformations lead to unique predictions, so the ambiguity we put forward demands a semiclassical background with a sufficiently strong departure from classical evolution. The latter condition happens to be satisfied in bouncing scenarios, which may thus be having predictability issues. Inflationary models could evade such a problem because of the monotonic behavior of their scale factor; they do, however, initiate from a singular state which bouncing scenarios aim at solving. |
2102.00553 | Oleg Tsupko | Oleg Yu. Tsupko | Deflection of light rays by spherically symmetric black hole in
dispersive medium | 10 pages, 3 figures | Phys. Rev. D 103, 104019 (2021) | 10.1103/PhysRevD.103.104019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The influence of the medium on the gravitational deflection of light rays is
widely discussed in literature for the simplest non-trivial case: cold
non-magnetized plasma. In this article, we generalize these studies to the case
of an arbitrary transparent dispersive medium with a given refractive index. We
calculate the deflection angle of light ray moving in a general spherically
symmetric metric in the presence of medium with the spherically symmetric
refractive index. The equation for the radius of circular light orbits is also
derived. We discuss in detail the properties of these results and various
special cases. In particular, we show that multiplying the refractive index by
a constant does not affect the deflection angle and radius of circular orbits.
At the same time, the presence of dispersion makes the trajectories different
from the case of vacuum even in spatially homogeneous medium. As one of the
applications of our results, we calculate the correction to the angle of vacuum
gravitational deflection for the case when a massive object is surrounded by
homogeneous but dispersive medium. As another application, we present the
calculation of the shadow of a black hole surrounded by medium with arbitrary
refractive index. Our results can serve as a basis for studies of various
plasma models beyond the cold plasma case.
| [
{
"created": "Sun, 31 Jan 2021 22:47:58 GMT",
"version": "v1"
}
] | 2021-05-19 | [
[
"Tsupko",
"Oleg Yu.",
""
]
] | The influence of the medium on the gravitational deflection of light rays is widely discussed in literature for the simplest non-trivial case: cold non-magnetized plasma. In this article, we generalize these studies to the case of an arbitrary transparent dispersive medium with a given refractive index. We calculate the deflection angle of light ray moving in a general spherically symmetric metric in the presence of medium with the spherically symmetric refractive index. The equation for the radius of circular light orbits is also derived. We discuss in detail the properties of these results and various special cases. In particular, we show that multiplying the refractive index by a constant does not affect the deflection angle and radius of circular orbits. At the same time, the presence of dispersion makes the trajectories different from the case of vacuum even in spatially homogeneous medium. As one of the applications of our results, we calculate the correction to the angle of vacuum gravitational deflection for the case when a massive object is surrounded by homogeneous but dispersive medium. As another application, we present the calculation of the shadow of a black hole surrounded by medium with arbitrary refractive index. Our results can serve as a basis for studies of various plasma models beyond the cold plasma case. |
gr-qc/9904009 | Jose A. Font | N. Stergioulas (1,2), J.A. Font (1), K.D. Kokkotas (2) ((1)
AEI-Potsdam, (2) Thessaloniki) | Non-linear Evolution of Rotating Relativistic Stars | 12 pages, 4 figures, Contribution to the 19th Texas Symposium | null | null | null | gr-qc astro-ph | null | We present first results of the non-linear evolution of rotating relativistic
stars obtained with an axisymmetric relativistic hydrodynamics code in a fixed
spacetime. As initial data we use stationary axisymmetric and perturbed
configurations. We find that, in order to prevent (numerical) angular momentum
loss at the surface layers of the star a high-resolution grid (or a numerical
scheme that retains high order at local extrema) is needed. For non-rotating
stars, we compute frequencies of radial and non-radial small-amplitude
oscillations, which are in excellent agreement with linear normal mode
frequencies computed in the Cowling approximation. As a first application of
our code, quasi-radial modes of rapidly rotating relativistic stars are
computed. By generalizing our numerical code to 3-D, we plan to study the
evolution and non-linear dynamics of toroidal oscillations (r-modes) of rapidly
rotating neutron stars, which are a promising source of gravitational waves.
| [
{
"created": "Mon, 5 Apr 1999 07:20:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Stergioulas",
"N.",
""
],
[
"Font",
"J. A.",
""
],
[
"Kokkotas",
"K. D.",
""
]
] | We present first results of the non-linear evolution of rotating relativistic stars obtained with an axisymmetric relativistic hydrodynamics code in a fixed spacetime. As initial data we use stationary axisymmetric and perturbed configurations. We find that, in order to prevent (numerical) angular momentum loss at the surface layers of the star a high-resolution grid (or a numerical scheme that retains high order at local extrema) is needed. For non-rotating stars, we compute frequencies of radial and non-radial small-amplitude oscillations, which are in excellent agreement with linear normal mode frequencies computed in the Cowling approximation. As a first application of our code, quasi-radial modes of rapidly rotating relativistic stars are computed. By generalizing our numerical code to 3-D, we plan to study the evolution and non-linear dynamics of toroidal oscillations (r-modes) of rapidly rotating neutron stars, which are a promising source of gravitational waves. |
1212.4928 | Jun Wang | Jun Wang, Ya-Bo Wu, Yong-Xin Guo, Fang Qi, Yue-Yue Zhao, Xiao-Yu Sun | Conditions and instability in $f(R)$ gravity with non-minimal coupling
between matter and geometry | 9 pages | Eur. Phys. J. C, Volume 69, Numbers 3-4, 541-546, 2010 | 10.1140/epjc/s10052-010-1419-y | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper on the basis of the generalized $f(R)$ gravity model with
arbitrary coupling between geometry and matter, four classes of $f(R)$ gravity
models with non minimal coupling between geometry and matter will be studied.
By means of conditions of power law expansion and the equation of state of
matter less than -1/3, the relationship among p, w and n, the conditions and
the candidate for late time cosmic accelerated expansion will be discussed in
the four classes of $f(R)$ gravity models with non minimal coupling.
Furthermore, in order to keep considering models to be realistic ones, the
Dolgov Kawasaki instability will be investigated in each of them.
| [
{
"created": "Thu, 20 Dec 2012 05:47:10 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Wang",
"Jun",
""
],
[
"Wu",
"Ya-Bo",
""
],
[
"Guo",
"Yong-Xin",
""
],
[
"Qi",
"Fang",
""
],
[
"Zhao",
"Yue-Yue",
""
],
[
"Sun",
"Xiao-Yu",
""
]
] | In this paper on the basis of the generalized $f(R)$ gravity model with arbitrary coupling between geometry and matter, four classes of $f(R)$ gravity models with non minimal coupling between geometry and matter will be studied. By means of conditions of power law expansion and the equation of state of matter less than -1/3, the relationship among p, w and n, the conditions and the candidate for late time cosmic accelerated expansion will be discussed in the four classes of $f(R)$ gravity models with non minimal coupling. Furthermore, in order to keep considering models to be realistic ones, the Dolgov Kawasaki instability will be investigated in each of them. |
2001.02414 | Andronikos Paliathanasis | Alex Giacomini, Genly Leon, Andronikos Paliathanasis and Supriya Pan | Cosmological Evolution of Two-Scalar fields Cosmology in the Jordan
frame | 38 pages, 13 figures, no tables | null | 10.1140/epjc/s10052-020-7730-3 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present article we study the cosmological evolution of a two-scalar
field gravitational theory defined in the Jordan frame. Specifically, we assume
one of the scalar fields to be minimally coupled to gravity, while the second
field which is the Brans-Dicke scalar field is nonminimally coupled to gravity
and also coupled to the other scalar field. In the Einstein frame this theory
reduces to a two-scalar field theory where the two fields can interact only in
the potential term, which means that the quintom theory is recovered. The
cosmological evolution is studied by analyzing the equilibrium points of the
field equations in the Jordan frame. We find that the theory can describe the
cosmological evolution in large scales, while inflationary solutions are also
provided.
| [
{
"created": "Wed, 8 Jan 2020 08:47:47 GMT",
"version": "v1"
}
] | 2020-03-18 | [
[
"Giacomini",
"Alex",
""
],
[
"Leon",
"Genly",
""
],
[
"Paliathanasis",
"Andronikos",
""
],
[
"Pan",
"Supriya",
""
]
] | In the present article we study the cosmological evolution of a two-scalar field gravitational theory defined in the Jordan frame. Specifically, we assume one of the scalar fields to be minimally coupled to gravity, while the second field which is the Brans-Dicke scalar field is nonminimally coupled to gravity and also coupled to the other scalar field. In the Einstein frame this theory reduces to a two-scalar field theory where the two fields can interact only in the potential term, which means that the quintom theory is recovered. The cosmological evolution is studied by analyzing the equilibrium points of the field equations in the Jordan frame. We find that the theory can describe the cosmological evolution in large scales, while inflationary solutions are also provided. |
gr-qc/9502006 | Renate Loll | R. Loll (INFN, Florence) | NON-PERTURBATIVE SOLUTIONS FOR LATTICE QUANTUM GRAVITY | 26 pages, 2 figures (postscript, compressed and uuencoded), TeX, Jan
95 | Nucl.Phys.B444:619-640,1995 | 10.1016/0550-3213(95)00184-T | DFF 220/01/95 | gr-qc hep-th | null | We propose a new, discretized model for the study of 3+1-dimensional
canonical quantum gravity, based on the classical $SL(2,\C)$-connection
formulation. The discretization takes place on a topological $N^3$- lattice
with periodic boundary conditions. All operators and wave functions are
constructed from one-dimensional link variables, which are regarded as the
fundamental building blocks of the theory. The kinematical Hilbert space is
spanned by polynomials of certain Wilson loops on the lattice and is manifestly
gauge- and diffeomorphism- invariant. The discretized quantum Hamiltonian $\hat
H$ maps this space into itself. We find a large sector of solutions to the
discretized Wheeler-DeWitt equation $\hat H\psi=0$, which are labelled by
single and multiple Polyakov loops. These states have a finite norm with
respect to a natural scalar product on the space of holomorphic
$SL(2,\C)$-Wilson loops. We also investigate the existence of further solutions
for the case of the $1^3$-lattice. - Our results provide for the first time a
rigorous, regularized framework for studying non-perturbative quantum gravity.
| [
{
"created": "Wed, 1 Feb 1995 12:56:21 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Loll",
"R.",
"",
"INFN, Florence"
]
] | We propose a new, discretized model for the study of 3+1-dimensional canonical quantum gravity, based on the classical $SL(2,\C)$-connection formulation. The discretization takes place on a topological $N^3$- lattice with periodic boundary conditions. All operators and wave functions are constructed from one-dimensional link variables, which are regarded as the fundamental building blocks of the theory. The kinematical Hilbert space is spanned by polynomials of certain Wilson loops on the lattice and is manifestly gauge- and diffeomorphism- invariant. The discretized quantum Hamiltonian $\hat H$ maps this space into itself. We find a large sector of solutions to the discretized Wheeler-DeWitt equation $\hat H\psi=0$, which are labelled by single and multiple Polyakov loops. These states have a finite norm with respect to a natural scalar product on the space of holomorphic $SL(2,\C)$-Wilson loops. We also investigate the existence of further solutions for the case of the $1^3$-lattice. - Our results provide for the first time a rigorous, regularized framework for studying non-perturbative quantum gravity. |
1107.2728 | Zou De Cheng | Kang Zhou, Zhan-Ying Yang, De-Cheng Zou and Rui-Hong Yue | Spherically symmetric gravitational collapse of a dust cloud in
Einstein-Gauss-Bonnet Gravity | 16 pages, 4 figures and accepted by Mod. Phys. Lett. A | Mod.Phys.Lett.A26:2135-2147,2011 | 10.1142/S0217732311036449 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the gravitational collapse of a spherically symmetric dust cloud
in the Einstein-Gauss-Bonnet gravity without a cosmological constant, and
obtain three families of LTB-like solutions. It is shown that the Gauss-Bonnet
term has a profound influence on the nature of singularities, and the global
structure of space-time changes drastically from the analogous general
relativistic case. Interestingly, the formation of a naked, massive and
uncentral singularity, allowed in 5-dimensional space-time, is forbidden if
$D\geq6$. Moreover, such singularity is gravitational strong and a serious
counter example to CCH.
| [
{
"created": "Thu, 14 Jul 2011 05:29:51 GMT",
"version": "v1"
}
] | 2011-10-04 | [
[
"Zhou",
"Kang",
""
],
[
"Yang",
"Zhan-Ying",
""
],
[
"Zou",
"De-Cheng",
""
],
[
"Yue",
"Rui-Hong",
""
]
] | We explore the gravitational collapse of a spherically symmetric dust cloud in the Einstein-Gauss-Bonnet gravity without a cosmological constant, and obtain three families of LTB-like solutions. It is shown that the Gauss-Bonnet term has a profound influence on the nature of singularities, and the global structure of space-time changes drastically from the analogous general relativistic case. Interestingly, the formation of a naked, massive and uncentral singularity, allowed in 5-dimensional space-time, is forbidden if $D\geq6$. Moreover, such singularity is gravitational strong and a serious counter example to CCH. |
1602.03081 | Maria Haney | Sashwat Tanay, Maria Haney and Achamveedu Gopakumar | Frequency and time domain inspiral templates for comparable mass compact
binaries in eccentric orbits | 30 pages, 5 figures | Phys. Rev. D 93, 064031 (2016) | 10.1103/PhysRevD.93.064031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspiraling compact binaries with non-negligible orbital eccentricities are
plausible gravitational wave (GW) sources for the upcoming network of GW
observatories. In this paper, we present two prescriptions to compute
post-Newtonian (PN) accurate inspiral templates for such binaries. First, we
adapt and extend the post-circular scheme of Yunes {\it et al.} [Phys. Rev. D
80, 084001 (2009)] to obtain a Fourier-domain inspiral approximant that
incorporates the effects of PN-accurate orbital eccentricity evolution. This
results in a fully analytic frequency-domain inspiral waveform with Newtonian
amplitude and 2PN order Fourier phase while incorporating eccentricity effects
up to sixth order at each PN order. The importance of incorporating
eccentricity evolution contributions to the Fourier phase in a PN consistent
manner is also demonstrated. Second, we present an accurate and efficient
prescription to incorporate orbital eccentricity into the quasi-circular
time-domain {\texttt{TaylorT4}} approximant at 2PN order. New features include
the use of rational functions in orbital eccentricity to implement the 1.5PN
order tail contributions to the far-zone fluxes. This leads to closed form
PN-accurate differential equations for evolving eccentric orbits and the
resulting time-domain approximant is accurate and efficient to handle initial
orbital eccentricities $\leq 0.9$. Preliminary GW data analysis implications
are probed using match estimates.
| [
{
"created": "Tue, 9 Feb 2016 17:19:06 GMT",
"version": "v1"
},
{
"created": "Sat, 14 May 2016 17:47:58 GMT",
"version": "v2"
}
] | 2016-05-17 | [
[
"Tanay",
"Sashwat",
""
],
[
"Haney",
"Maria",
""
],
[
"Gopakumar",
"Achamveedu",
""
]
] | Inspiraling compact binaries with non-negligible orbital eccentricities are plausible gravitational wave (GW) sources for the upcoming network of GW observatories. In this paper, we present two prescriptions to compute post-Newtonian (PN) accurate inspiral templates for such binaries. First, we adapt and extend the post-circular scheme of Yunes {\it et al.} [Phys. Rev. D 80, 084001 (2009)] to obtain a Fourier-domain inspiral approximant that incorporates the effects of PN-accurate orbital eccentricity evolution. This results in a fully analytic frequency-domain inspiral waveform with Newtonian amplitude and 2PN order Fourier phase while incorporating eccentricity effects up to sixth order at each PN order. The importance of incorporating eccentricity evolution contributions to the Fourier phase in a PN consistent manner is also demonstrated. Second, we present an accurate and efficient prescription to incorporate orbital eccentricity into the quasi-circular time-domain {\texttt{TaylorT4}} approximant at 2PN order. New features include the use of rational functions in orbital eccentricity to implement the 1.5PN order tail contributions to the far-zone fluxes. This leads to closed form PN-accurate differential equations for evolving eccentric orbits and the resulting time-domain approximant is accurate and efficient to handle initial orbital eccentricities $\leq 0.9$. Preliminary GW data analysis implications are probed using match estimates. |
1705.00584 | Fatemeh Zahra Majidi | F. Z. Majidi | Another Kerr interior solution | 14 pages, 3 figures, 2 tables | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A stationary axially symmetric solution describing a rotating anisotropic
source for Einstein Field Equations(EFE) is proposed which matches to the
exterior Kerr metric. The anisotropic source satisfies all energy conditions -
weak, strong, and dominant energy condition - for a wide range of metric's free
parameters values. The resultant energy-momentum tensor components, and
consequently energy density and pressure profiles, redshift function and
angular velocity are singularity free and behave as expected. As rotation
parameter goes to zero a spherical source consisting of normal and exotic
matter is retrieved for the exterior Schwarzschild solution; the corresponding
redshift function, however, is well-behaved and positive definite. This is the
first solution of its kind.
| [
{
"created": "Mon, 1 May 2017 16:40:29 GMT",
"version": "v1"
},
{
"created": "Sun, 14 May 2017 17:33:02 GMT",
"version": "v2"
},
{
"created": "Sun, 2 Jul 2017 18:09:08 GMT",
"version": "v3"
}
] | 2017-07-04 | [
[
"Majidi",
"F. Z.",
""
]
] | A stationary axially symmetric solution describing a rotating anisotropic source for Einstein Field Equations(EFE) is proposed which matches to the exterior Kerr metric. The anisotropic source satisfies all energy conditions - weak, strong, and dominant energy condition - for a wide range of metric's free parameters values. The resultant energy-momentum tensor components, and consequently energy density and pressure profiles, redshift function and angular velocity are singularity free and behave as expected. As rotation parameter goes to zero a spherical source consisting of normal and exotic matter is retrieved for the exterior Schwarzschild solution; the corresponding redshift function, however, is well-behaved and positive definite. This is the first solution of its kind. |
gr-qc/9608010 | null | Dieter R. Brill | Multi-Black-Holes in 3D and 4D anti-de Sitter Spacetimes | Talk given at the Journees Relativistes 96 (Ascona, Switzerland). 4
pages, LaTeX, includes 1 LaTeX figure | Helv.Phys.Acta 69:249-252,1996 | null | PP97--13 | gr-qc | null | The (single) black hole solutions of Ba\~nados, Teitelboim and Zanelli (BTZ)
in 2+1 dimensional anti-de Sitter space are generalized to an arbitrary number
$n$ of such black holes. The resulting multi-black-hole (MBH) spacetime is
locally isometric to anti-de Sitter space, and globally it is obtained from the
latter as a quotient space by means of suitable identifications. The MBH
spacetime has $n$ asymptotically anti-de Sitter exterior regions, each of which
has the geometry of a single BTZ black hole. These exterior regions are
separated by $n$ horizons from a common interior region. This interior region
can be described as a ``closed" universe containing $n$ black holes. Similar
configurations in 3+1 dimensions, with horizons of toroidal and higher genus
topologies, are also presented.
| [
{
"created": "Mon, 5 Aug 1996 15:59:41 GMT",
"version": "v1"
}
] | 2011-04-15 | [
[
"Brill",
"Dieter R.",
""
]
] | The (single) black hole solutions of Ba\~nados, Teitelboim and Zanelli (BTZ) in 2+1 dimensional anti-de Sitter space are generalized to an arbitrary number $n$ of such black holes. The resulting multi-black-hole (MBH) spacetime is locally isometric to anti-de Sitter space, and globally it is obtained from the latter as a quotient space by means of suitable identifications. The MBH spacetime has $n$ asymptotically anti-de Sitter exterior regions, each of which has the geometry of a single BTZ black hole. These exterior regions are separated by $n$ horizons from a common interior region. This interior region can be described as a ``closed" universe containing $n$ black holes. Similar configurations in 3+1 dimensions, with horizons of toroidal and higher genus topologies, are also presented. |
gr-qc/0209013 | J. Ponce de Leon | J. Ponce de Leon | Invariant definition of rest mass and dynamics of particles in 4D from
bulk geodesics in brane-world and non-compact Kaluza-Klein theories | The same article, just references updated. To appear in Int. J. of
Mod. Phys. D | Int.J.Mod.Phys.D12:757-780,2003 | 10.1142/S0218271803003384 | null | gr-qc | null | In the Randall-Sundrum brane-world scenario and other non-compact
Kaluza-Klein theories, the motion of test particles is higher-dimensional in
nature. In other words, all test particles travel on five-dimensional geodesics
but observers, who are bounded to spacetime, have access only to the 4D part of
the trajectory. Conventionally, the dynamics of test particles as observed in
4D is discussed on the basis of the splitting of the geodesic equation in 5D.
However, this procedure is {\em not} unique and therefore leads to some
problems. The most serious one is the ambiguity in the definition of rest mass
in 4D, which is crucial for the discussion of the dynamics. We propose the
Hamilton-Jacobi formalism, instead of the geodesic one, to study the dynamics
in 4D. On the basis of this formalism we provide an unambiguous expression for
the rest mass and its variation along the motion as observed in 4D. It is
independent of the coordinates and any parameterization used along the motion.
Also, we are able to show a comprehensive picture of the various physical
scenarios allowed in 4D, without having to deal with the subtle details of the
splitting formalism. Moreover we study the extra non-gravitational forces
perceived by an observer in 4D who describes the geodesic motion of a bulk test
particle in 5D. Firstly, we show that the so-called fifth force fails to
account for the variation of rest mass along the particle's worldline.
Secondly, we offer here a new definition that correctly takes into account the
change of mass observed in 4D.
| [
{
"created": "Wed, 4 Sep 2002 14:34:15 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Jan 2003 13:08:19 GMT",
"version": "v2"
}
] | 2011-07-19 | [
[
"de Leon",
"J. Ponce",
""
]
] | In the Randall-Sundrum brane-world scenario and other non-compact Kaluza-Klein theories, the motion of test particles is higher-dimensional in nature. In other words, all test particles travel on five-dimensional geodesics but observers, who are bounded to spacetime, have access only to the 4D part of the trajectory. Conventionally, the dynamics of test particles as observed in 4D is discussed on the basis of the splitting of the geodesic equation in 5D. However, this procedure is {\em not} unique and therefore leads to some problems. The most serious one is the ambiguity in the definition of rest mass in 4D, which is crucial for the discussion of the dynamics. We propose the Hamilton-Jacobi formalism, instead of the geodesic one, to study the dynamics in 4D. On the basis of this formalism we provide an unambiguous expression for the rest mass and its variation along the motion as observed in 4D. It is independent of the coordinates and any parameterization used along the motion. Also, we are able to show a comprehensive picture of the various physical scenarios allowed in 4D, without having to deal with the subtle details of the splitting formalism. Moreover we study the extra non-gravitational forces perceived by an observer in 4D who describes the geodesic motion of a bulk test particle in 5D. Firstly, we show that the so-called fifth force fails to account for the variation of rest mass along the particle's worldline. Secondly, we offer here a new definition that correctly takes into account the change of mass observed in 4D. |
1004.3768 | Robert Owen | Robert Owen | Degeneracy measures for the algebraic classification of numerical
spacetimes | 14 pages, 7 figures. Version 2 adds two references. | Phys. Rev. D 81, 124042 (2010) | 10.1103/PhysRevD.81.124042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the issue of algebraic classification of the Weyl curvature tensor,
with a particular focus on numerical relativity simulations. The spacetimes of
interest in this context, binary black hole mergers, and the ringdowns that
follow them, present subtleties in that they are generically, strictly
speaking, Type I, but in many regions approximately, in some sense, Type D. To
provide meaning to any claims of "approximate" Petrov class, one must define a
measure of degeneracy on the space of null rays at a point. We will investigate
such a measure, used recently to argue that certain binary black hole merger
simulations ring down to the Kerr geometry, after hanging up for some time in
Petrov Type II. In particular, we argue that this hangup in Petrov Type II is
an artefact of the particular measure being used, and that a geometrically
better-motivated measure shows a black hole merger produced by our group
settling directly to Petrov Type D.
| [
{
"created": "Wed, 21 Apr 2010 18:41:55 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Apr 2010 21:21:58 GMT",
"version": "v2"
}
] | 2013-05-29 | [
[
"Owen",
"Robert",
""
]
] | We study the issue of algebraic classification of the Weyl curvature tensor, with a particular focus on numerical relativity simulations. The spacetimes of interest in this context, binary black hole mergers, and the ringdowns that follow them, present subtleties in that they are generically, strictly speaking, Type I, but in many regions approximately, in some sense, Type D. To provide meaning to any claims of "approximate" Petrov class, one must define a measure of degeneracy on the space of null rays at a point. We will investigate such a measure, used recently to argue that certain binary black hole merger simulations ring down to the Kerr geometry, after hanging up for some time in Petrov Type II. In particular, we argue that this hangup in Petrov Type II is an artefact of the particular measure being used, and that a geometrically better-motivated measure shows a black hole merger produced by our group settling directly to Petrov Type D. |
1702.02983 | Philippe Brax | Philippe Brax, Anne-Christine Davis and Rahul Jha | Neutron Stars in Screened Modified Gravity: Chameleon vs Dilaton | 24 pages, 7 figures | Phys. Rev. D 95, 083514 (2017) | 10.1103/PhysRevD.95.083514 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the scalar field profile around relativistic compact objects such
as neutron stars for a range of modified gravity models with screening
mechanisms of the chameleon and Damour-Polyakov types. We focus primarily on
inverse power law chameleons and the environmentally dependent dilaton as
examples of both mechanisms. We discuss the modified Tolman-Oppenheimer-Volkoff
equation and then implement a relaxation algorithm to solve for the scalar
profiles numerically. We find that chameleons and dilatons behave in a similar
manner and that there is a large degeneracy between the modified gravity
parameters and the neutron star equation of state. This is exemplified by the
modifications to the mass-radius relationship for a variety of model
parameters.
| [
{
"created": "Thu, 9 Feb 2017 21:11:07 GMT",
"version": "v1"
}
] | 2017-04-19 | [
[
"Brax",
"Philippe",
""
],
[
"Davis",
"Anne-Christine",
""
],
[
"Jha",
"Rahul",
""
]
] | We consider the scalar field profile around relativistic compact objects such as neutron stars for a range of modified gravity models with screening mechanisms of the chameleon and Damour-Polyakov types. We focus primarily on inverse power law chameleons and the environmentally dependent dilaton as examples of both mechanisms. We discuss the modified Tolman-Oppenheimer-Volkoff equation and then implement a relaxation algorithm to solve for the scalar profiles numerically. We find that chameleons and dilatons behave in a similar manner and that there is a large degeneracy between the modified gravity parameters and the neutron star equation of state. This is exemplified by the modifications to the mass-radius relationship for a variety of model parameters. |
gr-qc/9503011 | null | Pedro F. Gonzalez-Diaz | The Schwarzschild Black-Hole Pair | 17 pages, plain latex, figure available upon request | null | null | IMAFF-RC-04-95 | gr-qc | null | By allowing the lightcones to tip over according to the conservation laws of
an one-kink in static, Schwarzschild metric, we show that there also exists an
instanton which represents production of pairs of chargeless, nonrotating black
holes with mass $M$, joined on an interior surface beyond the horizon ar $r=M$.
Evaluation of the thermal properties of each of the black hole in a pair leads
one to check that each black hole is exactly the antiblack hole to the other
black hole in the pair. The instantonic action has been calculated and seen to
be smaller than that corresponding to pair production by factors that associate
with the Bekenstein-Hawking entropy and a baby universe entropy $2pi^{2}M^{2}$.
This suggests these entropies to count numbers of internal states.
| [
{
"created": "Tue, 7 Mar 1995 08:33:33 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Gonzalez-Diaz",
"Pedro F.",
""
]
] | By allowing the lightcones to tip over according to the conservation laws of an one-kink in static, Schwarzschild metric, we show that there also exists an instanton which represents production of pairs of chargeless, nonrotating black holes with mass $M$, joined on an interior surface beyond the horizon ar $r=M$. Evaluation of the thermal properties of each of the black hole in a pair leads one to check that each black hole is exactly the antiblack hole to the other black hole in the pair. The instantonic action has been calculated and seen to be smaller than that corresponding to pair production by factors that associate with the Bekenstein-Hawking entropy and a baby universe entropy $2pi^{2}M^{2}$. This suggests these entropies to count numbers of internal states. |
2309.09391 | Praveen Dennis Xavier DPhil | Praveen Dennis Xavier | Towards a dual formulation of quantum gravity via metric-curvature
bijections | 12 pages, 2 figures. Submitted to Classical and Quantum Gravity, IOP.
ver2: Extended introduction | null | null | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | We prove that Riemannian metrics in General Relativity in the
\emph{`normal-coordinates'} gauge are in one-to-one correspondence with
curvature 2-forms. We discuss how this can be used as a change of variables in
the operator formalism to construct a dual formulation of quantum gravity
pertinent in the context of asymptotic safety-like approaches to quantum
gravity.
| [
{
"created": "Sun, 17 Sep 2023 22:44:48 GMT",
"version": "v1"
},
{
"created": "Sat, 30 Sep 2023 12:48:16 GMT",
"version": "v2"
}
] | 2023-10-03 | [
[
"Xavier",
"Praveen Dennis",
""
]
] | We prove that Riemannian metrics in General Relativity in the \emph{`normal-coordinates'} gauge are in one-to-one correspondence with curvature 2-forms. We discuss how this can be used as a change of variables in the operator formalism to construct a dual formulation of quantum gravity pertinent in the context of asymptotic safety-like approaches to quantum gravity. |
1706.02719 | Noemi Frusciante | Noemi Frusciante and Georgios Papadomanolakis | Tackling non-linearities with the effective field theory of dark energy
and modified gravity | 19 pages. Sec IV and Appendix B added. Matches JCAP version | null | 10.1088/1475-7516/2017/12/014 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the extension of the effective field theory framework to the
mildly non-linear scales. The effective field theory approach has been
successfully applied to the late time cosmic acceleration phenomenon and it has
been shown to be a powerful method to obtain predictions about cosmological
observables on linear scales. However, mildly non-linear scales need to be
consistently considered when testing gravity theories because a large part of
the data comes from those scales. Thus, non-linear corrections to predictions
on observables coming from the linear analysis can help in discriminating among
different gravity theories. We proceed firstly by identifying the necessary
operators which need to be included in the effective field theory Lagrangian in
order to go beyond the linear order in perturbations and then we construct the
corresponding non-linear action. Moreover, we present the complete recipe to
map any single field dark energy and modified gravity models into the
non-linear effective field theory framework by considering a general action in
the Arnowitt-Deser-Misner formalism. In order to illustrate this recipe we
proceed to map the beyond-Horndeski theory and low-energy Horava gravity into
the effective field theory formalism. As a final step we derived the 4th order
action in term of the curvature perturbation. This allowed us to identify the
non-linear contributions coming from the linear order perturbations which at
the next order act like source terms. Moreover, we confirm that the stability
requirements, ensuring the positivity of the kinetic term and the speed of
propagation for scalar mode, are automatically satisfied once the viability of
the theory is demanded at linear level. The approach we present here will allow
to construct, in a model independent way, all the relevant predictions on
observables at mildly non-linear scales.
| [
{
"created": "Thu, 8 Jun 2017 18:05:43 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Nov 2017 11:32:54 GMT",
"version": "v2"
}
] | 2017-12-20 | [
[
"Frusciante",
"Noemi",
""
],
[
"Papadomanolakis",
"Georgios",
""
]
] | We present the extension of the effective field theory framework to the mildly non-linear scales. The effective field theory approach has been successfully applied to the late time cosmic acceleration phenomenon and it has been shown to be a powerful method to obtain predictions about cosmological observables on linear scales. However, mildly non-linear scales need to be consistently considered when testing gravity theories because a large part of the data comes from those scales. Thus, non-linear corrections to predictions on observables coming from the linear analysis can help in discriminating among different gravity theories. We proceed firstly by identifying the necessary operators which need to be included in the effective field theory Lagrangian in order to go beyond the linear order in perturbations and then we construct the corresponding non-linear action. Moreover, we present the complete recipe to map any single field dark energy and modified gravity models into the non-linear effective field theory framework by considering a general action in the Arnowitt-Deser-Misner formalism. In order to illustrate this recipe we proceed to map the beyond-Horndeski theory and low-energy Horava gravity into the effective field theory formalism. As a final step we derived the 4th order action in term of the curvature perturbation. This allowed us to identify the non-linear contributions coming from the linear order perturbations which at the next order act like source terms. Moreover, we confirm that the stability requirements, ensuring the positivity of the kinetic term and the speed of propagation for scalar mode, are automatically satisfied once the viability of the theory is demanded at linear level. The approach we present here will allow to construct, in a model independent way, all the relevant predictions on observables at mildly non-linear scales. |
1005.1232 | Mauricio Bellini | Luz Marina Reyes, Jose Edgar Madriz Aguilar (Guanajuato University),
and Mauricio Bellini (Mar del Plata University & IFM, CONICET) | Stochastic emergence of inflaton fluctuations in a SdS primordial
universe with large-scale repulsive gravity from a 5D vacuum | version accepted in European Physical Journal Plus | Eur.Phys.J.Plus 126:56,2011 | 10.1140/epjp/i2011-11056-2 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a stochastic approach to study scalar field fluctuations of the
inflaton field in an early inflationary universe with a black-hole (BH), which
is described by an effective 4D SdS metric. Considering a 5D Ricci-flat SdS
static metric, we implement a planar coordinate transformation, in order to
obtain a 5D cosmological metric, from which the effective 4D SdS metric can be
induced on a 4D hypersurface. We found that at the end of inflation, the
squared fluctuations of the inflaton field are not exactly scale independent
and becomes sensitive with the mass of the BH.
| [
{
"created": "Fri, 7 May 2010 15:30:37 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Jun 2010 21:48:54 GMT",
"version": "v2"
},
{
"created": "Mon, 23 Aug 2010 15:31:39 GMT",
"version": "v3"
},
{
"created": "Sat, 4 Dec 2010 16:53:57 GMT",
"version": "v4"
},
{
"cre... | 2011-06-15 | [
[
"Reyes",
"Luz Marina",
"",
"Guanajuato University"
],
[
"Aguilar",
"Jose Edgar Madriz",
"",
"Guanajuato University"
],
[
"Bellini",
"Mauricio",
"",
"Mar del Plata University & IFM, CONICET"
]
] | We develop a stochastic approach to study scalar field fluctuations of the inflaton field in an early inflationary universe with a black-hole (BH), which is described by an effective 4D SdS metric. Considering a 5D Ricci-flat SdS static metric, we implement a planar coordinate transformation, in order to obtain a 5D cosmological metric, from which the effective 4D SdS metric can be induced on a 4D hypersurface. We found that at the end of inflation, the squared fluctuations of the inflaton field are not exactly scale independent and becomes sensitive with the mass of the BH. |
gr-qc/0605032 | Alan Pavan Bendasoli | A. B. Pavan | Analysis of spherically symmetric black holes in Braneworld models | Master Degree thesis (in portuguese), Advisor: Prof. Dr. Elcio
Abdalla, 126 pages, 16 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Research on black holes and their physical proprieties has been active on
last 90 years. With the appearance of the String Theory and the Braneworld
models as alternative descriptions of our Universe, the interest on black
holes, in these context, increased. In this work we studied black holes in
Braneworld models. A class of spherically symmetric black holes is investigaded
as well its stability under general perturbations. Thermodynamic proprieties
and quasi-normal modes are discussed. The black holes studied are the SM (zero
mass) and CFM solutions, obtained by Casadio {\it et al.} and Bronnikov {\it et
al.}. The geometry of bulk is unknown. However the Campbell-Magaard Theorem
guarantees the existence of a 5-dimensional solution in the bulk whose
projection on the brane is the class of black holes considered. They are stable
under scalar perturbations. Quasi-normal modes were observed in both models.
The tail behavior of the perturbations is the same. The entropy upper bound of
a body absorved by the black holes studied was calculated. This limit turned
out to be independent of the black hole parameters.
| [
{
"created": "Fri, 5 May 2006 16:45:01 GMT",
"version": "v1"
},
{
"created": "Tue, 25 May 2010 13:30:13 GMT",
"version": "v2"
}
] | 2010-05-26 | [
[
"Pavan",
"A. B.",
""
]
] | Research on black holes and their physical proprieties has been active on last 90 years. With the appearance of the String Theory and the Braneworld models as alternative descriptions of our Universe, the interest on black holes, in these context, increased. In this work we studied black holes in Braneworld models. A class of spherically symmetric black holes is investigaded as well its stability under general perturbations. Thermodynamic proprieties and quasi-normal modes are discussed. The black holes studied are the SM (zero mass) and CFM solutions, obtained by Casadio {\it et al.} and Bronnikov {\it et al.}. The geometry of bulk is unknown. However the Campbell-Magaard Theorem guarantees the existence of a 5-dimensional solution in the bulk whose projection on the brane is the class of black holes considered. They are stable under scalar perturbations. Quasi-normal modes were observed in both models. The tail behavior of the perturbations is the same. The entropy upper bound of a body absorved by the black holes studied was calculated. This limit turned out to be independent of the black hole parameters. |
1503.05737 | Bobir Toshmatov | Bobir Toshmatov, Ahmadjon Abdujabbarov, Zden\v{e}k Stuchl\'ik,
Bobomurat Ahmedov | Quasinormal modes of test fields around regular black holes | 13 pages, 11 figures, 4 tables | Phys. Rev. D 91, 083008 (2015) | 10.1103/PhysRevD.91.083008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study scalar, electromagnetic and gravitational test fields in the
Hayward, Bardeen and Ay\'on-Beato-Garc\'ia regular black hole spacetimes and
demonstrate that the test fields are stable in all these spacetimes. Using the
sixth order WKB approximation of the linear "axial" perturbative scheme, we
determine dependence of the quasinormal mode (QNM) frequencies on the
characteristic parameters of the test fields and the spacetime charge
parameters of the regular black holes. We give also the greybody factors,
namely the transmission and reflection coefficients of scattered scalar,
electromagnetic and gravitational waves. We show that damping of the QNMs in
regular black hole spacetimes is suppressed in comparison to the case of
Schwarzschild black holes, and increasing charge parameter of the regular black
holes increases reflection and decreases transmission factor of incident waves
for each of the test fields.
| [
{
"created": "Thu, 19 Mar 2015 12:28:35 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Apr 2015 00:44:41 GMT",
"version": "v2"
}
] | 2015-04-28 | [
[
"Toshmatov",
"Bobir",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
],
[
"Stuchlík",
"Zdeněk",
""
],
[
"Ahmedov",
"Bobomurat",
""
]
] | We study scalar, electromagnetic and gravitational test fields in the Hayward, Bardeen and Ay\'on-Beato-Garc\'ia regular black hole spacetimes and demonstrate that the test fields are stable in all these spacetimes. Using the sixth order WKB approximation of the linear "axial" perturbative scheme, we determine dependence of the quasinormal mode (QNM) frequencies on the characteristic parameters of the test fields and the spacetime charge parameters of the regular black holes. We give also the greybody factors, namely the transmission and reflection coefficients of scattered scalar, electromagnetic and gravitational waves. We show that damping of the QNMs in regular black hole spacetimes is suppressed in comparison to the case of Schwarzschild black holes, and increasing charge parameter of the regular black holes increases reflection and decreases transmission factor of incident waves for each of the test fields. |
2206.11257 | Kazunori Kohri | Kazunori Kohri, and Kei-ichi Maeda | A Possible Solution to the Helium Anomaly of EMPRESS VIII by Cuscuton
Gravity Theory | 7 pages, 1 figure, to appear in PTEP | null | null | KEK-TH-2433, KEK-Cosmo-0290 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss cosmology based on the cuscuton gravity theory to resolve the
anomaly of the observational $^4$He abundance reported by the EMPRESS
collaboration. We find that the gravitational constant $G_{\rm cos}$ in
Friedmann equation should be smaller than the Newton's constant ${G_{\rm N}}$
such that ${\Delta G_{\rm N}}/{G_{\rm N}} \equiv (G_{\rm cos}-G_{\rm
N})/{G_{\rm N}} = -0.085_{-0.028}^{+0.026} \quad(68 \% \text { C.L. })$ in
terms of big-bang nucleosynthesis, which excludes ${\Delta G_{\rm N}}=0$ at
more than 95~$\% \text { C.L. }$ To fit the data, we obtain a negative mass
squared of a non-dynamical scalar field with the Planck-mass scale as $\sim -
{\mathcal{O}}(1) {M_{\rm PL}^2} ({\mu}/{0.5 M_{\rm PL}})^{4}$ with the cuscuton
mass parameter $\mu$. This fact could suggest the need for modified gravity
theories such as the cuscuton gravity theory with a quadratic potential, which
can be regarded as the low-energy Ho\v{r}ava-Lifshitz gravity and might give a
hint of quantum gravity.
| [
{
"created": "Tue, 21 Jun 2022 18:52:54 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Aug 2022 16:07:48 GMT",
"version": "v2"
}
] | 2022-08-31 | [
[
"Kohri",
"Kazunori",
""
],
[
"Maeda",
"Kei-ichi",
""
]
] | We discuss cosmology based on the cuscuton gravity theory to resolve the anomaly of the observational $^4$He abundance reported by the EMPRESS collaboration. We find that the gravitational constant $G_{\rm cos}$ in Friedmann equation should be smaller than the Newton's constant ${G_{\rm N}}$ such that ${\Delta G_{\rm N}}/{G_{\rm N}} \equiv (G_{\rm cos}-G_{\rm N})/{G_{\rm N}} = -0.085_{-0.028}^{+0.026} \quad(68 \% \text { C.L. })$ in terms of big-bang nucleosynthesis, which excludes ${\Delta G_{\rm N}}=0$ at more than 95~$\% \text { C.L. }$ To fit the data, we obtain a negative mass squared of a non-dynamical scalar field with the Planck-mass scale as $\sim - {\mathcal{O}}(1) {M_{\rm PL}^2} ({\mu}/{0.5 M_{\rm PL}})^{4}$ with the cuscuton mass parameter $\mu$. This fact could suggest the need for modified gravity theories such as the cuscuton gravity theory with a quadratic potential, which can be regarded as the low-energy Ho\v{r}ava-Lifshitz gravity and might give a hint of quantum gravity. |
1907.10851 | V Gayathri | V. Gayathri, P. Bacon, A. Pai, E. Chassande-Mottin, F. Salemi, G.
Vedovato | Astrophysical signal consistency test adapted for gravitational-wave
transient searches | main paper: 8 page and 13 figures, total with appendices: 10 pages
and 13 figures | Phys. Rev. D 100, 124022 (2019) | 10.1103/PhysRevD.100.124022 | LIGO-P1900221 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave astronomy is established with direct observation of
gravitational wave from merging binary black holes and binary neutron stars
during the first and second observing run of LIGO and Virgo detectors. The
gravitational-wave transient searches mainly categories into two families:
modeled and modeled-independent searches. The modeled searches are based on
matched filtering techniques and model-independent searches are based on the
extraction of excess power from time-frequency representations. We have
proposed a hybrid method, called wavegraph that mixes the two approaches. It
uses astrophysical information at the extraction stage of model-independent
search using a mathematical graph. In this work, we assess the performance of
wavegraph clustering in real LIGO and Virgo noises (the sixth science run and
the first observing run) and using the coherent WaveBurst transient search as a
backbone. Further, we propose a new signal consistency test for this algorithm.
This test uses the amplitude profile information to distinguish between the
gravitational wave transients from the noisy glitches. This test is able to
remove a large fraction of loud glitches, which thus results in additional
overall sensitivity in the context of searches for binary black-hole mergers in
the low-mass range.
| [
{
"created": "Thu, 25 Jul 2019 06:21:23 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Dec 2019 05:08:01 GMT",
"version": "v2"
}
] | 2019-12-24 | [
[
"Gayathri",
"V.",
""
],
[
"Bacon",
"P.",
""
],
[
"Pai",
"A.",
""
],
[
"Chassande-Mottin",
"E.",
""
],
[
"Salemi",
"F.",
""
],
[
"Vedovato",
"G.",
""
]
] | Gravitational wave astronomy is established with direct observation of gravitational wave from merging binary black holes and binary neutron stars during the first and second observing run of LIGO and Virgo detectors. The gravitational-wave transient searches mainly categories into two families: modeled and modeled-independent searches. The modeled searches are based on matched filtering techniques and model-independent searches are based on the extraction of excess power from time-frequency representations. We have proposed a hybrid method, called wavegraph that mixes the two approaches. It uses astrophysical information at the extraction stage of model-independent search using a mathematical graph. In this work, we assess the performance of wavegraph clustering in real LIGO and Virgo noises (the sixth science run and the first observing run) and using the coherent WaveBurst transient search as a backbone. Further, we propose a new signal consistency test for this algorithm. This test uses the amplitude profile information to distinguish between the gravitational wave transients from the noisy glitches. This test is able to remove a large fraction of loud glitches, which thus results in additional overall sensitivity in the context of searches for binary black-hole mergers in the low-mass range. |
1312.2228 | Cosimo Bambi | Cosimo Bambi | Testing the nature of the black hole candidate in GRO J1655-40 with the
relativistic precession model | 9 pages, 4 figures. v2: added new material and found different
conclusions | Eur.Phys.J.C75:162,2015 | 10.1140/epjc/s10052-015-3396-7 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quasi-periodic oscillations (QPOs) are a common feature in the X-ray flux of
stellar-mass black hole candidates, but their exact origin is not yet known.
Recently, some authors have pointed out that data of GRO J1655-40
simultaneously show three QPOs that nicely fit in the relativistic precession
model. However, they find an estimate of the spin parameter that disagrees with
the measurement of the disk's thermal spectrum. In the present work, I explore
the possibility of using the relativistic precession model to test the nature
of the black hole candidate in GRO J1655-40. If properly understood, QPOs may
become a quite powerful tool to probe the spacetime geometry around black hole
candidates, especially if used in combination with other techniques. It turns
out that the measurements of the relativistic precession model and of the
disk's thermal spectrum may be consistent if we admit that the black hole
candidate in GRO J1655-40 is not of the Kerr type.
| [
{
"created": "Sun, 8 Dec 2013 15:31:39 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Mar 2014 01:31:35 GMT",
"version": "v2"
}
] | 2015-04-28 | [
[
"Bambi",
"Cosimo",
""
]
] | Quasi-periodic oscillations (QPOs) are a common feature in the X-ray flux of stellar-mass black hole candidates, but their exact origin is not yet known. Recently, some authors have pointed out that data of GRO J1655-40 simultaneously show three QPOs that nicely fit in the relativistic precession model. However, they find an estimate of the spin parameter that disagrees with the measurement of the disk's thermal spectrum. In the present work, I explore the possibility of using the relativistic precession model to test the nature of the black hole candidate in GRO J1655-40. If properly understood, QPOs may become a quite powerful tool to probe the spacetime geometry around black hole candidates, especially if used in combination with other techniques. It turns out that the measurements of the relativistic precession model and of the disk's thermal spectrum may be consistent if we admit that the black hole candidate in GRO J1655-40 is not of the Kerr type. |
1208.3891 | Christian Reisswig | Christian Reisswig, Nigel T. Bishop, Denis Pollney | General relativistic null-cone evolutions with a high-order scheme | 24 pages, 3 figures | null | 10.1007/s10714-013-1513-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a high-order scheme for solving the full non-linear Einstein
equations on characteristic null hypersurfaces using the framework established
by Bondi and Sachs. This formalism allows asymptotically flat spaces to be
represented on a finite, compactified grid, and is thus ideal for far-field
studies of gravitational radiation. We have designed an algorithm based on
4th-order radial integration and finite differencing, and a spectral
representation of angular components. The scheme can offer significantly more
accuracy with relatively low computational cost compared to previous methods as
a result of the higher-order discretization. Based on a newly implemented code,
we show that the new numerical scheme remains stable and is convergent at the
expected order of accuracy.
| [
{
"created": "Sun, 19 Aug 2012 20:37:22 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Reisswig",
"Christian",
""
],
[
"Bishop",
"Nigel T.",
""
],
[
"Pollney",
"Denis",
""
]
] | We present a high-order scheme for solving the full non-linear Einstein equations on characteristic null hypersurfaces using the framework established by Bondi and Sachs. This formalism allows asymptotically flat spaces to be represented on a finite, compactified grid, and is thus ideal for far-field studies of gravitational radiation. We have designed an algorithm based on 4th-order radial integration and finite differencing, and a spectral representation of angular components. The scheme can offer significantly more accuracy with relatively low computational cost compared to previous methods as a result of the higher-order discretization. Based on a newly implemented code, we show that the new numerical scheme remains stable and is convergent at the expected order of accuracy. |
gr-qc/0506008 | Yasushi Mino | Yasushi Mino | Extreme Mass Ratio Binary: Radiation reaction and gravitational waveform | Classical and Quantum Gravity 22 (2005) S375-S379, Proceedings for
5th International LISA Symposium | Class.Quant.Grav.22:S375-S379,2005 | 10.1088/0264-9381/22/10/032 | null | gr-qc | null | For a successful detection of gravitational waves by LISA, it is essential to
construct theoretical waveforms in a reliable manner. We discuss gravitational
waves from an extreme mass ratio binary system which is expected to be a
promising target of the LISA project.
The extreme mass ratio binary is a binary system of a supermassive black hole
and a stellar mass compact object. As the supermassive black hole dominates the
gravitational field of the system, we suppose that the system might be well
approximated by a metric perturbation of a Kerr black hole. We discuss a recent
theoretical progress in calculating the waveforms from such a system.
| [
{
"created": "Wed, 1 Jun 2005 16:37:57 GMT",
"version": "v1"
}
] | 2010-11-26 | [
[
"Mino",
"Yasushi",
""
]
] | For a successful detection of gravitational waves by LISA, it is essential to construct theoretical waveforms in a reliable manner. We discuss gravitational waves from an extreme mass ratio binary system which is expected to be a promising target of the LISA project. The extreme mass ratio binary is a binary system of a supermassive black hole and a stellar mass compact object. As the supermassive black hole dominates the gravitational field of the system, we suppose that the system might be well approximated by a metric perturbation of a Kerr black hole. We discuss a recent theoretical progress in calculating the waveforms from such a system. |
gr-qc/0110067 | Margarita Safonova | Zafar Turakulov (IUCAA, Pune) and Margarita Safonova (University of
Delhi, New Delhi) | Motion of a Vector Particle in a Curved Spacetime. I. Lagrangian
Approach | 6 pages, uses mpla1.sty, published in MPLA, replaced with corrected
typos | Mod.Phys.Lett. A18 (2003) 579-586 | 10.1142/S0217732303009113 | null | gr-qc | null | From the simple Lagrangian the equations of motion for the particle with spin
are derived. The spin is shown to be conserved on the particle world-line. In
the absence of a spin the equation coincides with that of a geodesic. The
equations of motion are valid for massless particles as well, since mass does
not enter the equations explicitely.
| [
{
"created": "Sun, 14 Oct 2001 13:28:16 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Mar 2005 06:40:08 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Turakulov",
"Zafar",
"",
"IUCAA, Pune"
],
[
"Safonova",
"Margarita",
"",
"University of\n Delhi, New Delhi"
]
] | From the simple Lagrangian the equations of motion for the particle with spin are derived. The spin is shown to be conserved on the particle world-line. In the absence of a spin the equation coincides with that of a geodesic. The equations of motion are valid for massless particles as well, since mass does not enter the equations explicitely. |
1405.7887 | Wlodzimierz Piechocki | Herv\'e Bergeron, Orest Hrycyna, Przemys{\l}aw Ma{\l}kiewicz, and
W{\l}odzimierz Piechocki | Quantum theory of the Bianchi II model | 12 pages, 3 figures, version accepted by PRD | Physical Review D 90, 044041 (2014) | 10.1103/PhysRevD.90.044041 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe the quantum evolution of the vacuum Bianchi II universe in terms
of the transition amplitude between two asymptotic quantum Kasner-like states.
For large values of the momentum variable the classical and quantum
calculations give similar results. The difference occurs for small values of
this variable due to the Heisenberg uncertainty principle. Our results can be
used, to some extent, as a building block of the quantum evolution of the
vacuum Bianchi IX universe.
| [
{
"created": "Fri, 30 May 2014 15:16:42 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Aug 2014 06:12:57 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Bergeron",
"Hervé",
""
],
[
"Hrycyna",
"Orest",
""
],
[
"Małkiewicz",
"Przemysław",
""
],
[
"Piechocki",
"Włodzimierz",
""
]
] | We describe the quantum evolution of the vacuum Bianchi II universe in terms of the transition amplitude between two asymptotic quantum Kasner-like states. For large values of the momentum variable the classical and quantum calculations give similar results. The difference occurs for small values of this variable due to the Heisenberg uncertainty principle. Our results can be used, to some extent, as a building block of the quantum evolution of the vacuum Bianchi IX universe. |
2208.07504 | Daiki Saito | Daiki Saito and Chul-Moon Yoo | Stationary Vacuum Bubble in a Kerr-de Sitter Spacetime | 17 pages, 8 figures; v2:accepted for publication in Phys. Rev. D | null | 10.1103/PhysRevD.107.064043 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study false vacuum decay in a black hole (BH) spacetime with an angular
momentum. Considering the false vacuum region described by a Kerr-de Sitter
geometry, under the thin wall approximation, we can obtain the stationary
configuration of the vacuum bubble seen from the outside false vacuum region
without specifying the geometry inside the domain wall. Then, assuming the true
vacuum region is described by a Kerr geometry, we can fix the mass and the spin
parameter for the Kerr geometry by imposing the 1st junction conditions and
conservation of the angular momentum. Although the assumption of the Kerr
geometry inside the domain wall cannot be fully consistent with the 2nd
junction conditions, we can roughly evaluate the error associated with this
inconsistency by calculating the Brown-York quasi-local energy on the domain
wall. Then the decay rate can be estimated by using the obtained parameters for
the inside Kerr geometry and the Brown-York quasi-local energy. Our results
support the statement that the BH spin suppresses the false vacuum decay in a
BH spacetime.
| [
{
"created": "Tue, 16 Aug 2022 02:27:35 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Mar 2023 02:08:57 GMT",
"version": "v2"
}
] | 2023-03-29 | [
[
"Saito",
"Daiki",
""
],
[
"Yoo",
"Chul-Moon",
""
]
] | We study false vacuum decay in a black hole (BH) spacetime with an angular momentum. Considering the false vacuum region described by a Kerr-de Sitter geometry, under the thin wall approximation, we can obtain the stationary configuration of the vacuum bubble seen from the outside false vacuum region without specifying the geometry inside the domain wall. Then, assuming the true vacuum region is described by a Kerr geometry, we can fix the mass and the spin parameter for the Kerr geometry by imposing the 1st junction conditions and conservation of the angular momentum. Although the assumption of the Kerr geometry inside the domain wall cannot be fully consistent with the 2nd junction conditions, we can roughly evaluate the error associated with this inconsistency by calculating the Brown-York quasi-local energy on the domain wall. Then the decay rate can be estimated by using the obtained parameters for the inside Kerr geometry and the Brown-York quasi-local energy. Our results support the statement that the BH spin suppresses the false vacuum decay in a BH spacetime. |
1809.08691 | Caio Macedo | Caio F. B. Macedo | Dynamical signatures of black holes in massive Chern-Simons gravity:
Quasibound modes and time evolution | 7 pages, 4 figures. V2: Matches version in PRD | Phys. Rev. D 98, 084054 (2018) | 10.1103/PhysRevD.98.084054 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dynamical Chern-Simons (dCS) gravity is a promising extension of general
relativity (GR), arising naturally from the low-energy limit of some string
motivated theories. Even though dCS possesses an additional scalar degree of
freedom, interestingly, the Schwarzschild black hole is an exact solution of
it. Concerning dynamical phenomena, however, gravitational and scalar
perturbations couple with each other, generating possible scenarios to
understand the differences between dCS and GR. We study dynamical signatures of
dCS considering that the scalar field potential has a mass term. We analyze the
influence of the theory's parameter into the quasibound states and in the time
evolution of purely gravitational initial profiles. We find that the coupling
can make the dipolar modes \textit{less stable} and that at late times initial
gravitational perturbations become contaminated with the scalar sector,
presenting an oscillation that depends on the quasibound state frequencies.
These results may be interesting in the light of superradiant instabilities in
rotating systems and to find signatures of alternative theories in
gravitational wave detections.
| [
{
"created": "Sun, 23 Sep 2018 22:42:12 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Oct 2018 14:31:04 GMT",
"version": "v2"
}
] | 2018-11-07 | [
[
"Macedo",
"Caio F. B.",
""
]
] | Dynamical Chern-Simons (dCS) gravity is a promising extension of general relativity (GR), arising naturally from the low-energy limit of some string motivated theories. Even though dCS possesses an additional scalar degree of freedom, interestingly, the Schwarzschild black hole is an exact solution of it. Concerning dynamical phenomena, however, gravitational and scalar perturbations couple with each other, generating possible scenarios to understand the differences between dCS and GR. We study dynamical signatures of dCS considering that the scalar field potential has a mass term. We analyze the influence of the theory's parameter into the quasibound states and in the time evolution of purely gravitational initial profiles. We find that the coupling can make the dipolar modes \textit{less stable} and that at late times initial gravitational perturbations become contaminated with the scalar sector, presenting an oscillation that depends on the quasibound state frequencies. These results may be interesting in the light of superradiant instabilities in rotating systems and to find signatures of alternative theories in gravitational wave detections. |
1704.05880 | Sohyun Park | Sibel Boran, Emre Onur Kahya, Sohyun Park | Quantum gravity corrections to the conformally coupled scalar
self-mass-squared on de Sitter II: kinetic-conformal cross terms | 44 pages, 31 tables, comments welcome, v2: made some clarifications,
v3: matches the published version in PRD | Phys. Rev. D 96, 025001 (2017) | 10.1103/PhysRevD.96.025001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present work is the second part of a series of computations for the
self-mass-squared of the conformally coupled (CC) scalar interacting with
gravitons. This work includes the kinetic-kinetic and kinetic-conformal parts,
and thus completes the full scalar self-mass squared at one loop order in de
Sitter background when combined with the conformal-conformal part previously
evaluated. We use dimensional regularization and renormalize the results by
subtracting appropriate counterterms. The self-mass squared is finally ready to
quantum-correct the CC scalar field equation so that one can study the effect
of inflationary produced gravitons on the CC scalar and its observational
consequences.
| [
{
"created": "Wed, 19 Apr 2017 18:18:31 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Apr 2017 07:11:11 GMT",
"version": "v2"
},
{
"created": "Sun, 6 Aug 2017 01:36:58 GMT",
"version": "v3"
}
] | 2017-08-08 | [
[
"Boran",
"Sibel",
""
],
[
"Kahya",
"Emre Onur",
""
],
[
"Park",
"Sohyun",
""
]
] | The present work is the second part of a series of computations for the self-mass-squared of the conformally coupled (CC) scalar interacting with gravitons. This work includes the kinetic-kinetic and kinetic-conformal parts, and thus completes the full scalar self-mass squared at one loop order in de Sitter background when combined with the conformal-conformal part previously evaluated. We use dimensional regularization and renormalize the results by subtracting appropriate counterterms. The self-mass squared is finally ready to quantum-correct the CC scalar field equation so that one can study the effect of inflationary produced gravitons on the CC scalar and its observational consequences. |
1906.10791 | Xing Zhang | Xing Zhang, Rui Niu, Wen Zhao | Constraining the scalar-tensor gravity theories with and without
screening mechanisms by combined observations | 6 pages, 2 figures, 1 table, Phys. Rev. D accepted | Phys. Rev. D 100, 024038 (2019) | 10.1103/PhysRevD.100.024038 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Screened modified gravity (SMG) and Brans-Dicke (BD) gravity are typical
examples of scalar-tensor theories with and without screening mechanisms, which
can suppress the scalar field in dense regions. In this paper, we investigate
the tests of time-varying gravitational constant $G$, gravitational dipole
radiation, and Nordtvedt effect in BD and SMG theories, respectively. We place
new constraints on these theories by combining Cassini experiment, lunar laser
ranging (LLR) measurements, and pulsar observations from PSRs J1738$+$0333 and
J0348$+$0432. We find that screening mechanism has important influence on
theoretical constraints. The strongest, second, and weakest constraints on BD
are from Cassini, pulsar, and LLR tests, respectively. The most stringent
constraint on SMG comes from LLR measurements and improves the previous best
constraint by more than seven orders of magnitude. We derive the bounds on the
cosmological evolution of the scalar background in these theories using the
time variation of $G$. The results of all tests agree well with general
relativity (GR) and give more stringent constraints on the deviations from GR.
Finally, as an example, we consider the chameleon model and derive the
constraints on the model parameters.
| [
{
"created": "Wed, 26 Jun 2019 00:27:27 GMT",
"version": "v1"
}
] | 2019-07-22 | [
[
"Zhang",
"Xing",
""
],
[
"Niu",
"Rui",
""
],
[
"Zhao",
"Wen",
""
]
] | Screened modified gravity (SMG) and Brans-Dicke (BD) gravity are typical examples of scalar-tensor theories with and without screening mechanisms, which can suppress the scalar field in dense regions. In this paper, we investigate the tests of time-varying gravitational constant $G$, gravitational dipole radiation, and Nordtvedt effect in BD and SMG theories, respectively. We place new constraints on these theories by combining Cassini experiment, lunar laser ranging (LLR) measurements, and pulsar observations from PSRs J1738$+$0333 and J0348$+$0432. We find that screening mechanism has important influence on theoretical constraints. The strongest, second, and weakest constraints on BD are from Cassini, pulsar, and LLR tests, respectively. The most stringent constraint on SMG comes from LLR measurements and improves the previous best constraint by more than seven orders of magnitude. We derive the bounds on the cosmological evolution of the scalar background in these theories using the time variation of $G$. The results of all tests agree well with general relativity (GR) and give more stringent constraints on the deviations from GR. Finally, as an example, we consider the chameleon model and derive the constraints on the model parameters. |
1908.10176 | Salvatore Capozziello | Salvatore Capozziello, Carlo Alberto Mantica, and Luca Guido Molinari | Cosmological perfect fluids in higher-order gravity | 6 pages | null | 10.1007/s10714-020-02690-2 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that in Robertson-Walker space-times (and in generalized
Robertson-Walker spacetimes of dimension greater than 3 with divergence-free
Weyl tensor) all higher-order gravitational corrections of the Hilbert-Einstein
Lagrangian density $F(R,\square R, ... , \square^k R)$ have the form of perfect
fluids in the field equations. This statement definitively allows to deal with
dark energy fluids as curvature effects.
| [
{
"created": "Tue, 27 Aug 2019 13:11:17 GMT",
"version": "v1"
}
] | 2020-04-29 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Mantica",
"Carlo Alberto",
""
],
[
"Molinari",
"Luca Guido",
""
]
] | We prove that in Robertson-Walker space-times (and in generalized Robertson-Walker spacetimes of dimension greater than 3 with divergence-free Weyl tensor) all higher-order gravitational corrections of the Hilbert-Einstein Lagrangian density $F(R,\square R, ... , \square^k R)$ have the form of perfect fluids in the field equations. This statement definitively allows to deal with dark energy fluids as curvature effects. |
0904.4910 | Brennan Hughey | LIGO Scientific Collaboration: B. Abbott, et al | Search for High Frequency Gravitational Wave Bursts in the First
Calendar Year of LIGO's Fifth Science Run | 13 pages, accepted for publication in Physical Review D | Phys.Rev.D80:102002,2009 | 10.1103/PhysRevD.80.102002 | LIGO-P080080 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an all-sky search for gravitational waves in the frequency range 1
to 6 kHz during the first calendar year of LIGO's fifth science run. This is
the first untriggered LIGO burst analysis to be conducted above 3 kHz. We
discuss the unique properties of interferometric data in this regime. 161.3
days of triple-coincident data were analyzed. No gravitational events above
threshold were observed and a frequentist upper limit of 5.4 events per year on
the rate of strong gravitational wave bursts was placed at a 90% confidence
level. Implications for specific theoretical models of gravitational wave
emission are also discussed.
| [
{
"created": "Thu, 30 Apr 2009 18:27:08 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Jun 2009 21:47:29 GMT",
"version": "v2"
},
{
"created": "Fri, 16 Oct 2009 22:01:26 GMT",
"version": "v3"
}
] | 2009-12-04 | [
[
"LIGO Scientific Collaboration",
"",
""
],
[
"Abbott",
"B.",
""
]
] | We present an all-sky search for gravitational waves in the frequency range 1 to 6 kHz during the first calendar year of LIGO's fifth science run. This is the first untriggered LIGO burst analysis to be conducted above 3 kHz. We discuss the unique properties of interferometric data in this regime. 161.3 days of triple-coincident data were analyzed. No gravitational events above threshold were observed and a frequentist upper limit of 5.4 events per year on the rate of strong gravitational wave bursts was placed at a 90% confidence level. Implications for specific theoretical models of gravitational wave emission are also discussed. |
2003.01545 | Ayan Banerjee | Ayan Banerjee, M. K. Jasim and Sushant G. Ghosh | Wormholes in $f(R,T)$ gravity satisfying the null energy condition with
isotropic pressure | 10 pages, 5 figures, accepted for publication in Annals of Physics | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider $f(R, T)$ theory of gravity, in which the gravitational
Lagrangian is given by an arbitrary function of the Ricci scalar and the trace
of the energy-momentum tensor, to study static spherically symmetric wormhole
geometries sustained by matter sources with isotropic pressure. According to
restrictions on the wormhole geometries, we carefully adopt different
strategies to construct solutions with the properties and characteristics of
wormholes. Using a completely general procedure, we provide several examples of
wormholes in which the matter threading the wormhole throat satisfies all of
the energy conditions and discuss general mechanisms for finding them. Finally,
we postulate a smooth transformation for simplifying the nonlinear field
equations and have more consistent results than the other ones to conclude that
the results can be viewed as specific exact wormhole solutions without the
presence of exotic matter.
| [
{
"created": "Mon, 2 Mar 2020 14:35:59 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Aug 2021 07:14:06 GMT",
"version": "v2"
}
] | 2021-08-03 | [
[
"Banerjee",
"Ayan",
""
],
[
"Jasim",
"M. K.",
""
],
[
"Ghosh",
"Sushant G.",
""
]
] | We consider $f(R, T)$ theory of gravity, in which the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar and the trace of the energy-momentum tensor, to study static spherically symmetric wormhole geometries sustained by matter sources with isotropic pressure. According to restrictions on the wormhole geometries, we carefully adopt different strategies to construct solutions with the properties and characteristics of wormholes. Using a completely general procedure, we provide several examples of wormholes in which the matter threading the wormhole throat satisfies all of the energy conditions and discuss general mechanisms for finding them. Finally, we postulate a smooth transformation for simplifying the nonlinear field equations and have more consistent results than the other ones to conclude that the results can be viewed as specific exact wormhole solutions without the presence of exotic matter. |
1908.01886 | Brandon Bautista | Brandon Bautista-Olvera, Juan Carlos Degollado, Gabriel German | Geodesic structure of a rotating regular black hole | 18 pages, 16 figures | null | 10.1007/s10714-023-03114-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the dynamics of particles around a rotating regular black hole. In
particular we focus on the effects of the characteristic length parameter of
the spinning black hole on the motion of the particles by solving the equation
of orbital motion. We have found that there is a fourth constant of motion that
determines the dynamics of orbits out the equatorial plane similar as in the
Kerr black hole. Through detailed analyses of the corresponding effective
potentials for massive particles the possible orbits are numerically simulated.
A comparison with the trajectories in a Kerr spacetime shows that the
differences appear when the black holes rotate slowly for large values of the
characteristic length parameter.
| [
{
"created": "Mon, 5 Aug 2019 22:16:45 GMT",
"version": "v1"
}
] | 2023-05-23 | [
[
"Bautista-Olvera",
"Brandon",
""
],
[
"Degollado",
"Juan Carlos",
""
],
[
"German",
"Gabriel",
""
]
] | We examine the dynamics of particles around a rotating regular black hole. In particular we focus on the effects of the characteristic length parameter of the spinning black hole on the motion of the particles by solving the equation of orbital motion. We have found that there is a fourth constant of motion that determines the dynamics of orbits out the equatorial plane similar as in the Kerr black hole. Through detailed analyses of the corresponding effective potentials for massive particles the possible orbits are numerically simulated. A comparison with the trajectories in a Kerr spacetime shows that the differences appear when the black holes rotate slowly for large values of the characteristic length parameter. |
2105.09515 | J\"org Frauendiener | J\"org Frauendiener and Chris Stevens | The non-linear perturbation of a black hole by gravitational waves. I.
The Bondi-Sachs mass loss | 27 pages, 9 figures. Submitted to CQG focus issue on time-like
boundaries | null | 10.1088/1361-6382/ac1be3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The excitation of a black hole by infalling matter or radiation has been
studied for a long time, mostly in linear perturbation theory. In this paper we
study numerically the response of a Schwarzschild black hole to an incoming
gravitational wave pulse. We present a numerically well-posed initial boundary
value problem for the generalized conformal field equations in which a wave
profile for the ingoing wave is specified at an outer time-like boundary which
then hits an initially static and spherically symmetric black hole. The
non-linear interaction of the black hole with the gravitational wave leads to
scattered radiation moving back out. The clean separation between initial state
and incoming radiation makes this setup ideal to study scattering problems. The
use of the conformal field equations allows us to trace the response of the
black hole to null infinity where we can read off the scattered gravitational
waves and compute the Bondi-Sachs mass and the gravitational flux through
$\mathscr{I}$. In this way we check the Bondi-Sachs mass loss formula directly
on null infinity. We also comment on comparisons with quasinormal modes.
| [
{
"created": "Thu, 20 May 2021 04:56:54 GMT",
"version": "v1"
}
] | 2021-09-22 | [
[
"Frauendiener",
"Jörg",
""
],
[
"Stevens",
"Chris",
""
]
] | The excitation of a black hole by infalling matter or radiation has been studied for a long time, mostly in linear perturbation theory. In this paper we study numerically the response of a Schwarzschild black hole to an incoming gravitational wave pulse. We present a numerically well-posed initial boundary value problem for the generalized conformal field equations in which a wave profile for the ingoing wave is specified at an outer time-like boundary which then hits an initially static and spherically symmetric black hole. The non-linear interaction of the black hole with the gravitational wave leads to scattered radiation moving back out. The clean separation between initial state and incoming radiation makes this setup ideal to study scattering problems. The use of the conformal field equations allows us to trace the response of the black hole to null infinity where we can read off the scattered gravitational waves and compute the Bondi-Sachs mass and the gravitational flux through $\mathscr{I}$. In this way we check the Bondi-Sachs mass loss formula directly on null infinity. We also comment on comparisons with quasinormal modes. |
1103.3019 | Zahra Amirabi | Z. Amirabi, M. Halilsoy and S. Habib Mazharimousavi | Stable thin-shell wormholes with a Chaplygin gas in
Einstein-Maxwell-Gauss-Bonnet gravity | 7 pages, 7 figures, final version accepted for publication in Phys.
Rev. D | Phys. Rev. D 88, 124023 (2013) | 10.1103/PhysRevD.88.124023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the stability of thin-shell wormholes in
Einstein-Maxwell-Gauss-Bonnet gravity. The equation of state of the thin shell
wormhole is considered first to obey a generalized Chaplygin gas and then we
generalize it to an arbitrary state function which covers all known cases
studied so far. In particular we study the modified Chaplygin gas and give an
assessment for a general parotropic fluid. Our study is in d-dimensions and
with numerical analysis in d=5 we show the effect of the GB parameter in the
stability of thin-shell wormholes against the radial perturbations.
| [
{
"created": "Tue, 15 Mar 2011 20:16:16 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Nov 2013 22:08:40 GMT",
"version": "v2"
}
] | 2013-12-10 | [
[
"Amirabi",
"Z.",
""
],
[
"Halilsoy",
"M.",
""
],
[
"Mazharimousavi",
"S. Habib",
""
]
] | We study the stability of thin-shell wormholes in Einstein-Maxwell-Gauss-Bonnet gravity. The equation of state of the thin shell wormhole is considered first to obey a generalized Chaplygin gas and then we generalize it to an arbitrary state function which covers all known cases studied so far. In particular we study the modified Chaplygin gas and give an assessment for a general parotropic fluid. Our study is in d-dimensions and with numerical analysis in d=5 we show the effect of the GB parameter in the stability of thin-shell wormholes against the radial perturbations. |
gr-qc/9610029 | Elisha Atzmon | E. Atzmon | A Comment on The A/4 Black Hole Entropy | 8 pages, Latex, 2 ps-files | null | null | TAUP-2380, IHES/p/96/69 | gr-qc | null | Using a simple analysis based on the measurement procedure for a quantized
area we explain the 1/4 factor in the Bekenstein-Hawking black hole formula A/4
for the entropy.
| [
{
"created": "Tue, 15 Oct 1996 09:47:10 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Atzmon",
"E.",
""
]
] | Using a simple analysis based on the measurement procedure for a quantized area we explain the 1/4 factor in the Bekenstein-Hawking black hole formula A/4 for the entropy. |
gr-qc/9910050 | John Baez | John C. Baez | Spin Foam Perturbation Theory | 16 pages LaTeX, 2 encapsulated Postscript figures | in Diagrammatic Morphisms and Applications, eds. David Radford,
Fernando Souza, and David Yetter, Contemp. Math. 318, 2003, pp. 9-21 | null | null | gr-qc | null | We study perturbation theory for spin foam models on triangulated manifolds.
Starting with any model of this sort, we consider an arbitrary perturbation of
the vertex amplitudes, and write the evolution operators of the perturbed model
as convergent power series in the coupling constant governing the perturbation.
The terms in the power series can be efficiently computed when the unperturbed
model is a topological quantum field theory. Moreover, in this case we can
explicitly sum the whole power series in the limit where the number of
top-dimensional simplices goes to infinity while the coupling constant is
suitably renormalized. This `dilute gas limit' gives spin foam models that are
triangulation-independent but not topological quantum field theories. However,
we show that models of this sort are rather trivial except in dimension 2.
| [
{
"created": "Thu, 14 Oct 1999 01:29:59 GMT",
"version": "v1"
}
] | 2023-03-07 | [
[
"Baez",
"John C.",
""
]
] | We study perturbation theory for spin foam models on triangulated manifolds. Starting with any model of this sort, we consider an arbitrary perturbation of the vertex amplitudes, and write the evolution operators of the perturbed model as convergent power series in the coupling constant governing the perturbation. The terms in the power series can be efficiently computed when the unperturbed model is a topological quantum field theory. Moreover, in this case we can explicitly sum the whole power series in the limit where the number of top-dimensional simplices goes to infinity while the coupling constant is suitably renormalized. This `dilute gas limit' gives spin foam models that are triangulation-independent but not topological quantum field theories. However, we show that models of this sort are rather trivial except in dimension 2. |
1106.3569 | Paolo Pani | Paolo Pani, Vitor Cardoso, Terence Delsate | Compact stars in Eddington inspired gravity | accepted for publication in Phys. Rev. Lett | Phys.Rev.Lett. 107 (2011) 031101 | 10.1103/PhysRevLett.107.031101 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new, Eddington inspired theory of gravity was recently proposed by Banados
and Ferreira. It is equivalent to General Relativity in vacuum, but differs
from it inside matter. This viable, one parameter theory was shown to avoid
cosmological singularities and turns out to lead to many other exciting new
features that we report here. First, for a positive coupling parameter, the
field equations have a dramatic impact on the collapse of dust, and do not lead
to singularities. We further find that the theory supports stable, compact
pressureless stars made of perfect fluid, which provide interesting models of
self-gravitating dark matter. Finally, we show that the mere existence of
relativistic stars imposes a strong, near optimal constraint on the coupling
parameter, which can even be improved by observations of the moment of inertia
of the double pulsar.
| [
{
"created": "Fri, 17 Jun 2011 20:00:20 GMT",
"version": "v1"
}
] | 2015-01-30 | [
[
"Pani",
"Paolo",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Delsate",
"Terence",
""
]
] | A new, Eddington inspired theory of gravity was recently proposed by Banados and Ferreira. It is equivalent to General Relativity in vacuum, but differs from it inside matter. This viable, one parameter theory was shown to avoid cosmological singularities and turns out to lead to many other exciting new features that we report here. First, for a positive coupling parameter, the field equations have a dramatic impact on the collapse of dust, and do not lead to singularities. We further find that the theory supports stable, compact pressureless stars made of perfect fluid, which provide interesting models of self-gravitating dark matter. Finally, we show that the mere existence of relativistic stars imposes a strong, near optimal constraint on the coupling parameter, which can even be improved by observations of the moment of inertia of the double pulsar. |
1605.00304 | Marc Favata | Blake Moore, Marc Favata, K. G. Arun, Chandra Kant Mishra | Gravitational-wave phasing for low-eccentricity inspiralling compact
binaries to 3PN order | 49 pages, 4 figures. Submitted to Phys. Rev. D. Supplementary
materials available at
http://link.aps.org/supplemental/10.1103/PhysRevD.93.124061. V2: minor
updates to match published version | Phys. Rev. D 93, 124061 (2016) | 10.1103/PhysRevD.93.124061 | LIGO DCC P1500268 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | [abridged] Although gravitational radiation causes inspiralling compact
binaries to circularize, a variety of astrophysical scenarios suggest that
binaries might have small but nonnegligible orbital eccentricities when they
enter the low-frequency bands of ground and space-based gravitational-wave
detectors. If not accounted for, even a small orbital eccentricity can cause a
potentially significant systematic error in the mass parameters of an
inspiralling binary. Gravitational-wave search templates typically rely on the
quasi-circular approximation, which provides relatively simple expressions for
the gravitational-wave phase to 3.5 post-Newtonian (PN) order. The
quasi-Keplerian formalism provides an elegant but complex description of the
post-Newtonian corrections to the orbits and waveforms of inspiralling binaries
with any eccentricity. Here we specialize the quasi-Keplerian formalism to
binaries with low eccentricity. In this limit the non-periodic contribution to
the gravitational-wave phasing can be expressed explicitly as simple functions
of frequency or time, with little additional complexity beyond the well-known
formulas for circular binaries. These eccentric phase corrections are computed
to 3PN order and to leading order in the eccentricity for the standard PN
approximants. For a variety of systems these eccentricity corrections cause
significant corrections to the number of gravitational wave cycles that sweep
through a detector's frequency band. This is evaluated using several measures,
including a modification of the useful cycles. We also evaluate the role of
periodic terms that enter the phasing and discuss how they can be incorporated
into some of the PN approximants. While the eccentric extension of the PN
approximants is our main objective, this work collects a variety of results
that may be of interest to others modeling eccentric relativistic binaries.
| [
{
"created": "Sun, 1 May 2016 20:22:23 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Jun 2016 00:28:06 GMT",
"version": "v2"
}
] | 2016-06-30 | [
[
"Moore",
"Blake",
""
],
[
"Favata",
"Marc",
""
],
[
"Arun",
"K. G.",
""
],
[
"Mishra",
"Chandra Kant",
""
]
] | [abridged] Although gravitational radiation causes inspiralling compact binaries to circularize, a variety of astrophysical scenarios suggest that binaries might have small but nonnegligible orbital eccentricities when they enter the low-frequency bands of ground and space-based gravitational-wave detectors. If not accounted for, even a small orbital eccentricity can cause a potentially significant systematic error in the mass parameters of an inspiralling binary. Gravitational-wave search templates typically rely on the quasi-circular approximation, which provides relatively simple expressions for the gravitational-wave phase to 3.5 post-Newtonian (PN) order. The quasi-Keplerian formalism provides an elegant but complex description of the post-Newtonian corrections to the orbits and waveforms of inspiralling binaries with any eccentricity. Here we specialize the quasi-Keplerian formalism to binaries with low eccentricity. In this limit the non-periodic contribution to the gravitational-wave phasing can be expressed explicitly as simple functions of frequency or time, with little additional complexity beyond the well-known formulas for circular binaries. These eccentric phase corrections are computed to 3PN order and to leading order in the eccentricity for the standard PN approximants. For a variety of systems these eccentricity corrections cause significant corrections to the number of gravitational wave cycles that sweep through a detector's frequency band. This is evaluated using several measures, including a modification of the useful cycles. We also evaluate the role of periodic terms that enter the phasing and discuss how they can be incorporated into some of the PN approximants. While the eccentric extension of the PN approximants is our main objective, this work collects a variety of results that may be of interest to others modeling eccentric relativistic binaries. |
2106.06209 | Manu Srivastava | Manu Srivastava (IIT Bombay), Yanbei Chen (CalTech), S.
Shankaranarayanan (IIT Bombay) | Analytical computation of quasi-normal modes of slowly-rotating
black-holes in dCS gravity | v2: 19 pages, 2 figures, added a few references, version accepted in
Phys. Rev. D | Phys. Rev. D 104, 064034 (2021) | 10.1103/PhysRevD.104.064034 | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using gravitational wave observations to search for deviations from general
relativity in the strong-gravity regime has become an important research
direction. Chern Simons (CS) gravity is one of the most frequently studied
parity-violating models of strong gravity. It is known that the Kerr black-hole
is not a solution for CS gravity. At the same time, the only rotating solution
available in the literature for dynamical CS (dCS) gravity is the slow-rotating
case most accurately known to quadratic order in spin. In this work, for the
slow-rotating case (accurate to first order in spin), we derive the linear
perturbation equations governing the metric and the dCS field accurate to
linear order in spin and quadratic order in the CS coupling parameter
($\alpha$) and obtain the quasi-normal mode (QNM) frequencies. After confirming
the recent results of Wagle et al. (2021), we find an additional contribution
to the eigenfrequency correction at the leading perturbative order of
$\alpha^2$. Unlike Wagle et al., we also find corrections to frequencies in the
polar sector. We compute these extra corrections by evaluating the expectation
values of the perturbative potential on unperturbed QNM wavefunctions along a
contour deformed into the complex-$r$ plane. For $\alpha=0.1 M^2$, we obtain
the ratio of the imaginary parts of the dCS correction to the GR correction in
the first QNM frequency (in the polar sector) to be $0.263$ implying
significant change. For the $(2,2)-$mode, the dCS corrections make the
imaginary part of the first QNM of the fundamental mode less negative, thereby
decreasing the decay rate. Our results, along with future gravitational wave
observations, can be used to test for dCS gravity and further constrain the CS
coupling parameters. [abridged]
| [
{
"created": "Fri, 11 Jun 2021 07:28:26 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Aug 2021 16:33:07 GMT",
"version": "v2"
}
] | 2021-09-22 | [
[
"Srivastava",
"Manu",
"",
"IIT Bombay"
],
[
"Chen",
"Yanbei",
"",
"CalTech"
],
[
"Shankaranarayanan",
"S.",
"",
"IIT Bombay"
]
] | Using gravitational wave observations to search for deviations from general relativity in the strong-gravity regime has become an important research direction. Chern Simons (CS) gravity is one of the most frequently studied parity-violating models of strong gravity. It is known that the Kerr black-hole is not a solution for CS gravity. At the same time, the only rotating solution available in the literature for dynamical CS (dCS) gravity is the slow-rotating case most accurately known to quadratic order in spin. In this work, for the slow-rotating case (accurate to first order in spin), we derive the linear perturbation equations governing the metric and the dCS field accurate to linear order in spin and quadratic order in the CS coupling parameter ($\alpha$) and obtain the quasi-normal mode (QNM) frequencies. After confirming the recent results of Wagle et al. (2021), we find an additional contribution to the eigenfrequency correction at the leading perturbative order of $\alpha^2$. Unlike Wagle et al., we also find corrections to frequencies in the polar sector. We compute these extra corrections by evaluating the expectation values of the perturbative potential on unperturbed QNM wavefunctions along a contour deformed into the complex-$r$ plane. For $\alpha=0.1 M^2$, we obtain the ratio of the imaginary parts of the dCS correction to the GR correction in the first QNM frequency (in the polar sector) to be $0.263$ implying significant change. For the $(2,2)-$mode, the dCS corrections make the imaginary part of the first QNM of the fundamental mode less negative, thereby decreasing the decay rate. Our results, along with future gravitational wave observations, can be used to test for dCS gravity and further constrain the CS coupling parameters. [abridged] |
1707.03625 | David Langlois | David Langlois | Degenerate Higher-Order Scalar-Tensor (DHOST) theories | 9 pages, no figure; proceedings of Rencontres de Moriond 2017
(session gravitation) | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This contribution reviews scalar-tensor theories whose Lagrangian contains
second-order derivatives of a scalar field but nevertheless propagate only one
scalar mode (in addition to the usual two tensor modes), and are thus not
plagued with the Ostrodradsky instability. These theories, which encompass the
so-called Horndeski and Beyond Horndeski theories, have recently been fully
classified up to cubic order in second-order derivatives. After introducing
these theories, I present a few phenomenological aspects. In cosmology, these
theories can be included in the unified effective description of dark energy
and modified gravity. Finally, neutron star solutions in some specific models
are discussed.
| [
{
"created": "Wed, 12 Jul 2017 10:05:13 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Mar 2018 09:21:15 GMT",
"version": "v2"
}
] | 2018-03-05 | [
[
"Langlois",
"David",
""
]
] | This contribution reviews scalar-tensor theories whose Lagrangian contains second-order derivatives of a scalar field but nevertheless propagate only one scalar mode (in addition to the usual two tensor modes), and are thus not plagued with the Ostrodradsky instability. These theories, which encompass the so-called Horndeski and Beyond Horndeski theories, have recently been fully classified up to cubic order in second-order derivatives. After introducing these theories, I present a few phenomenological aspects. In cosmology, these theories can be included in the unified effective description of dark energy and modified gravity. Finally, neutron star solutions in some specific models are discussed. |
1810.11788 | Chao Liu | Chao Liu, Changhua Wei | Future stability of the FLRW spacetime for a large class of perfect
fluids | 47 pages. Agrees with published version | Annales Henri Poincar\'e (2021) | 10.1007/s00023-020-00987-1 | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We establish the future non-linear stability of
Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) solutions to the Einstein-Euler
equations of the universe filled with a large class of perfect fluids (the
equations of state are allowed to be certain nonlinear or linear types both).
Several previous results as specific examples can be covered in the results of
this article. We emphasize that the future stability of FLRW metric for
polytropic fluids with positive cosmological constant has been a difficult
problem and can not be directly generalized from the previous known results.
Our result in this article has not only covered this difficult case for the
polytropic fluids, but also unified more types of fluids in a same scheme of
proofs.
| [
{
"created": "Sun, 28 Oct 2018 09:48:07 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Apr 2019 08:12:39 GMT",
"version": "v2"
},
{
"created": "Tue, 2 Feb 2021 04:26:44 GMT",
"version": "v3"
}
] | 2021-02-03 | [
[
"Liu",
"Chao",
""
],
[
"Wei",
"Changhua",
""
]
] | We establish the future non-linear stability of Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) solutions to the Einstein-Euler equations of the universe filled with a large class of perfect fluids (the equations of state are allowed to be certain nonlinear or linear types both). Several previous results as specific examples can be covered in the results of this article. We emphasize that the future stability of FLRW metric for polytropic fluids with positive cosmological constant has been a difficult problem and can not be directly generalized from the previous known results. Our result in this article has not only covered this difficult case for the polytropic fluids, but also unified more types of fluids in a same scheme of proofs. |
gr-qc/0312043 | Zolt\'an K\'ad\'ar | Z. Kadar (U. Utrecht), R. Loll (Perimeter Inst. and U. Utrecht) | (2+1) gravity for higher genus in the polygon model | 35 pages, 22 figures | Class.Quant.Grav. 21 (2004) 2465-2491 | 10.1088/0264-9381/21/9/020 | SPIN-2003/42, ITP-UU-03/65 | gr-qc hep-th | null | We construct explicitly a (12g-12)-dimensional space P of unconstrained and
independent initial data for 't Hooft's polygon model of (2+1) gravity for
vacuum spacetimes with compact genus-g spacelike slices, for any g >= 2. Our
method relies on interpreting the boost parameters of the gluing data between
flat Minkowskian patches as the lengths of certain geodesic curves of an
associated smooth Riemann surface of the same genus. The appearance of an
initial big-bang or a final big-crunch singularity (but never both) is verified
for all configurations. Points in P correspond to spacetimes which admit a
one-polygon tessellation, and we conjecture that P is already the complete
physical phase space of the polygon model. Our results open the way for
numerical investigations of pure (2+1) gravity.
| [
{
"created": "Sun, 7 Dec 2003 22:07:25 GMT",
"version": "v1"
},
{
"created": "Mon, 10 May 2004 14:53:29 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Kadar",
"Z.",
"",
"U. Utrecht"
],
[
"Loll",
"R.",
"",
"Perimeter Inst. and U. Utrecht"
]
] | We construct explicitly a (12g-12)-dimensional space P of unconstrained and independent initial data for 't Hooft's polygon model of (2+1) gravity for vacuum spacetimes with compact genus-g spacelike slices, for any g >= 2. Our method relies on interpreting the boost parameters of the gluing data between flat Minkowskian patches as the lengths of certain geodesic curves of an associated smooth Riemann surface of the same genus. The appearance of an initial big-bang or a final big-crunch singularity (but never both) is verified for all configurations. Points in P correspond to spacetimes which admit a one-polygon tessellation, and we conjecture that P is already the complete physical phase space of the polygon model. Our results open the way for numerical investigations of pure (2+1) gravity. |
gr-qc/0005055 | Yavuz Nutku | A. N. Aliev, Y. Nutku and K. Sayg{\i}l{\i} | Topologically massive magnetic monopoles | null | Class.Quant.Grav. 17 (2000) 4111-4124 | 10.1088/0264-9381/17/19/310 | null | gr-qc | null | We show that in the Maxwell-Chern-Simons theory of topologically massive
electrodynamics the Dirac string of a monopole becomes a cone in anti-de Sitter
space with the opening angle of the cone determined by the topological mass
which in turn is related to the square root of the cosmological constant. This
proves to be an example of a physical system, {\it a priory} completely
unrelated to gravity, which nevertheless requires curved spacetime for its very
existence. We extend this result to topologically massive gravity coupled to
topologically massive electrodynamics in the framework of the theory of Deser,
Jackiw and Templeton. These are homogeneous spaces with conical deficit. Pure
Einstein gravity coupled to Maxwell-Chern-Simons field does not admit such a
monopole solution.
| [
{
"created": "Mon, 15 May 2000 17:01:22 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Aliev",
"A. N.",
""
],
[
"Nutku",
"Y.",
""
],
[
"Saygılı",
"K.",
""
]
] | We show that in the Maxwell-Chern-Simons theory of topologically massive electrodynamics the Dirac string of a monopole becomes a cone in anti-de Sitter space with the opening angle of the cone determined by the topological mass which in turn is related to the square root of the cosmological constant. This proves to be an example of a physical system, {\it a priory} completely unrelated to gravity, which nevertheless requires curved spacetime for its very existence. We extend this result to topologically massive gravity coupled to topologically massive electrodynamics in the framework of the theory of Deser, Jackiw and Templeton. These are homogeneous spaces with conical deficit. Pure Einstein gravity coupled to Maxwell-Chern-Simons field does not admit such a monopole solution. |
0807.2625 | Yakov Itin | Y. Itin and Y. Friedman (Jerusalem College of Technology and Institute
of Mathematics, The Hebrew University of Jerusalem) | Backwards on Minkowski's road. From 4D to 3D Maxwellian electromagnetism | to appear in the special (Sept/Oct 2008) issue of Annalen der Physik
(Berlin) commemorating H. Minkowski's 1908 lecture in Cologne | Annalen der Physik 17, 769-786, 2008 | 10.1002/andp.200810317 | null | gr-qc cond-mat.mtrl-sci physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Minkowski's concept of a four-dimensional physical space is a central
paradigm of modern physics. The three-dimensional Maxwellian electrodynamics is
uniquely generalized to the covariant four-dimensional form. Is the (1+3)
decomposition of the covariant four-dimensional form unique? How do the
different sign assumptions of electrodynamics emerge from this decomposition?
Which of these assumptions are fundamental and which of them may be modified?
How does the Minkowski space-time metric emerge from this preliminary
metric-free construction? In this paper we are looking for answers to the
problems mentioned. Our main result is the derivation of four different
possible sets of electrodynamic equations which may occur in different types of
isotropic electromagnetic media. The wave propagation in each of these media is
described by the Minkowskian optical metrics. Moreover, the electric and
magnetic energies are nonnegative in all cases. We also show that the correct
directions of the Lorentz force (as a consequence of the Dufay and the Lenz
rules) hold true for all these cases. However, the differences between these
four types of media must have a physical meaning. In particular, the signs of
the three electromagnetic invariants are different.
| [
{
"created": "Wed, 16 Jul 2008 18:22:32 GMT",
"version": "v1"
}
] | 2013-03-08 | [
[
"Itin",
"Y.",
"",
"Jerusalem College of Technology and Institute\n of Mathematics, The Hebrew University of Jerusalem"
],
[
"Friedman",
"Y.",
"",
"Jerusalem College of Technology and Institute\n of Mathematics, The Hebrew University of Jerusalem"
]
] | Minkowski's concept of a four-dimensional physical space is a central paradigm of modern physics. The three-dimensional Maxwellian electrodynamics is uniquely generalized to the covariant four-dimensional form. Is the (1+3) decomposition of the covariant four-dimensional form unique? How do the different sign assumptions of electrodynamics emerge from this decomposition? Which of these assumptions are fundamental and which of them may be modified? How does the Minkowski space-time metric emerge from this preliminary metric-free construction? In this paper we are looking for answers to the problems mentioned. Our main result is the derivation of four different possible sets of electrodynamic equations which may occur in different types of isotropic electromagnetic media. The wave propagation in each of these media is described by the Minkowskian optical metrics. Moreover, the electric and magnetic energies are nonnegative in all cases. We also show that the correct directions of the Lorentz force (as a consequence of the Dufay and the Lenz rules) hold true for all these cases. However, the differences between these four types of media must have a physical meaning. In particular, the signs of the three electromagnetic invariants are different. |
0905.2226 | Yi Xie | Xue-Mei Deng, Yi Xie, Tian-Yi Huang | Reply to "the Comment on 'Modified Scalar-Tensor-Vector Gravity Theory
and the Constraint on its Parameters' " | 4 pages, no figure | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/3.0/ | J. W. Moffat and V. T. Toth submitted recently a comment (arXiv:0903.5291) on
our latest paper "Modified scalar-tensor-vector gravity theory and the
constraint on its parameters" [Deng, et al., Phys. Rev. D 79, 044014 (2009);
arXiv:0901.3730 ]. We reply to each of their comments and justify our work and
conclusions. Especially, their general STVG (MOG) theory has to be modified to
fit the modern precision experiments.
| [
{
"created": "Thu, 14 May 2009 00:48:18 GMT",
"version": "v1"
}
] | 2009-05-15 | [
[
"Deng",
"Xue-Mei",
""
],
[
"Xie",
"Yi",
""
],
[
"Huang",
"Tian-Yi",
""
]
] | J. W. Moffat and V. T. Toth submitted recently a comment (arXiv:0903.5291) on our latest paper "Modified scalar-tensor-vector gravity theory and the constraint on its parameters" [Deng, et al., Phys. Rev. D 79, 044014 (2009); arXiv:0901.3730 ]. We reply to each of their comments and justify our work and conclusions. Especially, their general STVG (MOG) theory has to be modified to fit the modern precision experiments. |
gr-qc/0403121 | Hrvoje Nikolic | H. Nikolic | Causal paradoxes: a conflict between relativity and the arrow of time | 7 pages, revised, new references, to appear in Found. Phys. Lett | Found.Phys.Lett.19:259-267,2006 | 10.1007/s10702-006-0516-5 | null | gr-qc physics.class-ph | null | It is often argued that superluminal velocities and nontrivial spacetime
topologies, allowed by the theory of relativity, may lead to causal paradoxes.
By emphasizing that the notion of causality assumes the existence of a time
arrow (TA) that points from the past to the future, the apparent paradoxes
appear to be an artefact of the wrong tacit assumption that the relativistic
coordinate TA coincides with the physical TA. The latter should be identified
with the thermodynamic TA, which, by being absolute and irrotational, does not
lead to paradoxes.
| [
{
"created": "Wed, 31 Mar 2004 15:54:26 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Dec 2005 14:51:48 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Nikolic",
"H.",
""
]
] | It is often argued that superluminal velocities and nontrivial spacetime topologies, allowed by the theory of relativity, may lead to causal paradoxes. By emphasizing that the notion of causality assumes the existence of a time arrow (TA) that points from the past to the future, the apparent paradoxes appear to be an artefact of the wrong tacit assumption that the relativistic coordinate TA coincides with the physical TA. The latter should be identified with the thermodynamic TA, which, by being absolute and irrotational, does not lead to paradoxes. |
gr-qc/0307060 | Shahar Hod | Shahar Hod | Asymptotic quasinormal mode spectrum of rotating black holes | 4 pages | null | null | null | gr-qc astro-ph cond-mat hep-th quant-ph | null | Motivated by novel results in the theory of black-hole quantization, we study
{\it analytically} the quasinormal modes (QNM) of ({\it rotating}) Kerr black
holes. The black-hole oscillation frequencies tend to the asymptotic value
$\omega_n=m\Omega+i2\pi T_{BH}n$ in the $n \to \infty$ limit. This simple
formula is in agreement with Bohr's correspondence principle. Possible
implications of this result to the area spectrum of quantum black holes are
discussed.
| [
{
"created": "Mon, 14 Jul 2003 15:47:37 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hod",
"Shahar",
""
]
] | Motivated by novel results in the theory of black-hole quantization, we study {\it analytically} the quasinormal modes (QNM) of ({\it rotating}) Kerr black holes. The black-hole oscillation frequencies tend to the asymptotic value $\omega_n=m\Omega+i2\pi T_{BH}n$ in the $n \to \infty$ limit. This simple formula is in agreement with Bohr's correspondence principle. Possible implications of this result to the area spectrum of quantum black holes are discussed. |
1702.04926 | Rituparno Goswami | Dan B. Sibandze, Rituparno Goswami, Sunil D. Maharaj, Peter K. S.
Dunsby | Echoes from the black holes: Evidence of higher order corrections to
General Relativity in strong gravity regime | 4 pages, 1 figure, Revtex 4 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the higher order curvature corrections to general relativity in
the strong gravity regime of near horizon scales produce a rapidly oscillating
and infalling Ricci scalar fireball just outside the horizon. This can generate
the ringdown modes of gravitational waves having the same natural frequency as
those which are generated by the black hole mergers. Our analysis provides a
viable explanation to the echoes in the ringdown modes recently detected from
the LIGO data, without invoking the existence of any exotic structures at the
horizon.
| [
{
"created": "Thu, 16 Feb 2017 11:24:18 GMT",
"version": "v1"
}
] | 2017-02-17 | [
[
"Sibandze",
"Dan B.",
""
],
[
"Goswami",
"Rituparno",
""
],
[
"Maharaj",
"Sunil D.",
""
],
[
"Dunsby",
"Peter K. S.",
""
]
] | We show that the higher order curvature corrections to general relativity in the strong gravity regime of near horizon scales produce a rapidly oscillating and infalling Ricci scalar fireball just outside the horizon. This can generate the ringdown modes of gravitational waves having the same natural frequency as those which are generated by the black hole mergers. Our analysis provides a viable explanation to the echoes in the ringdown modes recently detected from the LIGO data, without invoking the existence of any exotic structures at the horizon. |
0704.0749 | T. Damour | Thibault Damour | Binary Systems as Test-beds of Gravity Theories | 42 pages, 3 figures, Based on lectures given at the SIGRAV School ``A
Century from Einstein Relativity: Probing Gravity Theories in Binary
Systems'', Villa Olmo (Como Lake, Italy), 17-21 May 2005. To appear in the
Proceedings, edited by M. Colpi et al. (to be published by Springer) | null | null | null | gr-qc | null | We review the general relativistic theory of the motion, and of the timing,
of binary systems containing compact objects (neutron stars or black holes).
Then we indicate the various ways one can use binary pulsar data to test the
strong-field and/or radiative aspects of General Relativity, and of general
classes of alternative theories of relativistic gravity.
| [
{
"created": "Thu, 5 Apr 2007 15:52:46 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Damour",
"Thibault",
""
]
] | We review the general relativistic theory of the motion, and of the timing, of binary systems containing compact objects (neutron stars or black holes). Then we indicate the various ways one can use binary pulsar data to test the strong-field and/or radiative aspects of General Relativity, and of general classes of alternative theories of relativistic gravity. |
gr-qc/0201052 | Gaurav Khanna | Gaurav Khanna | Evolution of Kerr-Schild type initial data for binary black holes using
the horizon penetrating Teukolsky equation | 6 pages, 3 figures; minor error fixed, no changes in conclusions | Phys.Rev. D65 (2002) 124018 | 10.1103/PhysRevD.65.124018 | null | gr-qc | null | We use the Kerr-Schild type Teukolsky equation (horizon penetrating) to
evolve binary black hole initial data as proposed by Bishop {\em et al.} in the
close limit. Our results are in agreement with those recently obtained by
Sarbach {\em et al.} from the Zerilli equation evolution of the same initial
data.
| [
{
"created": "Wed, 16 Jan 2002 02:28:19 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Jan 2002 19:24:32 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Khanna",
"Gaurav",
""
]
] | We use the Kerr-Schild type Teukolsky equation (horizon penetrating) to evolve binary black hole initial data as proposed by Bishop {\em et al.} in the close limit. Our results are in agreement with those recently obtained by Sarbach {\em et al.} from the Zerilli equation evolution of the same initial data. |
2406.16324 | Rajes Ghosh | Rajes Ghosh | Theoretical and Observational Constraints on Theories Beyond General
Relativity | Ph.D. thesis (168 pages, detailed abstract in the thesis),
Supervisor: Dr. Sudipta Sarkar, Submitted at Indian Institute of Technology
Gandhinagar, Largely based on: arXiv:2009.01543[gr-qc],
arXiv:2107.07424[hep-th], arXiv:2107.07370[gr-qc], arXiv:2108.02444[gr-qc],
arXiv:2112.10109[gr-qc], arXiv:2201.08700[gr-qc], arXiv:2303.00088[gr-qc],
arXiv: 2306.14193[gr-qc] | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This thesis embarks on a comprehensive investigation of modified gravity
theories and their implications on the properties of compact objects. Our
primary objective is to shed light on the fundamental nature of gravity by
exploring potential departures from General Relativity (GR) through a
combination of theoretical analyses and observational techniques. On the
theoretical side, we consider black hole thermodynamics, stability of compact
objects, presence of black hole hairs, and the issue of causality that may
provide valuable input towards the ultimate quantum theory of gravity.
Moreover, on the observational side, we employ gravitational wave observations
and black hole perturbation theory to explore new aspects of gravity and put
stringent bounds on the beyond-GR parameters.
To provide a structured overview of the thesis, we have organized it into
chapters that progressively delve deeper into these diverse aspects of modified
gravity and compact objects. Each chapter is dedicated to a specific facet of
our investigation, building a coherent narrative that spans both theoretical
and observational explorations. We aspire to achieve nothing less than
imparting valuable insights and novel perspectives that may significantly
enhance our understanding of the fundamental nature of gravitation.
| [
{
"created": "Mon, 24 Jun 2024 05:24:57 GMT",
"version": "v1"
}
] | 2024-06-25 | [
[
"Ghosh",
"Rajes",
""
]
] | This thesis embarks on a comprehensive investigation of modified gravity theories and their implications on the properties of compact objects. Our primary objective is to shed light on the fundamental nature of gravity by exploring potential departures from General Relativity (GR) through a combination of theoretical analyses and observational techniques. On the theoretical side, we consider black hole thermodynamics, stability of compact objects, presence of black hole hairs, and the issue of causality that may provide valuable input towards the ultimate quantum theory of gravity. Moreover, on the observational side, we employ gravitational wave observations and black hole perturbation theory to explore new aspects of gravity and put stringent bounds on the beyond-GR parameters. To provide a structured overview of the thesis, we have organized it into chapters that progressively delve deeper into these diverse aspects of modified gravity and compact objects. Each chapter is dedicated to a specific facet of our investigation, building a coherent narrative that spans both theoretical and observational explorations. We aspire to achieve nothing less than imparting valuable insights and novel perspectives that may significantly enhance our understanding of the fundamental nature of gravitation. |
gr-qc/0302035 | Edward Anderson | E. Anderson | Variations on the Seventh Route to Relativity | Revtex version; Journal-ref added | Phys.Rev.D68:104001,2003 | 10.1103/PhysRevD.68.104001 | null | gr-qc | null | As motivated in the full abstract, this paper further investigates Barbour,
Foster and O Murchadha (BFO)'s 3-space formulation of GR. This is based on
best-matched lapse-eliminated actions and gives rise to several theories
including GR and a conformal gravity theory. We study the simplicity postulates
assumed in BFO's work and how to weaken them, so as to permit the inclusion of
the full set of matter fields known to occur in nature.
We study the configuration spaces of gravity-matter systems upon which BFO's
formulation leans. In further developments the lapse-eliminated actions used by
BFO become impractical and require generalization. We circumvent many of these
problems by the equivalent use of lapse-uneliminated actions, which furthermore
permit us to interpret BFO's formulation within Kuchar's generally covariant
hypersurface framework. This viewpoint provides alternative reasons to BFO's as
to why the inclusion of bosonic fields in the 3-space approach gives rise to
minimally-coupled scalar fields, electromagnetism and Yang--Mills theory. This
viewpoint also permits us to quickly exhibit further GR-matter theories
admitted by the 3-space formulation. In particular, we show that the spin-1/2
fermions of the theories of Dirac, Maxwell--Dirac and Yang--Mills--Dirac, all
coupled to GR, are admitted by the generalized 3-space formulation we present.
Thus all the known fundamental matter fields can be accommodated. This
corresponds to being able to pick actions for all these theories which have
less kinematics than suggested by the generally covariant hypersurface
framework. For all these theories, Wheeler's thin sandwich conjecture may be
posed, rendering them timeless in Barbour's sense.
| [
{
"created": "Mon, 10 Feb 2003 18:30:57 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Nov 2003 21:17:38 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Anderson",
"E.",
""
]
] | As motivated in the full abstract, this paper further investigates Barbour, Foster and O Murchadha (BFO)'s 3-space formulation of GR. This is based on best-matched lapse-eliminated actions and gives rise to several theories including GR and a conformal gravity theory. We study the simplicity postulates assumed in BFO's work and how to weaken them, so as to permit the inclusion of the full set of matter fields known to occur in nature. We study the configuration spaces of gravity-matter systems upon which BFO's formulation leans. In further developments the lapse-eliminated actions used by BFO become impractical and require generalization. We circumvent many of these problems by the equivalent use of lapse-uneliminated actions, which furthermore permit us to interpret BFO's formulation within Kuchar's generally covariant hypersurface framework. This viewpoint provides alternative reasons to BFO's as to why the inclusion of bosonic fields in the 3-space approach gives rise to minimally-coupled scalar fields, electromagnetism and Yang--Mills theory. This viewpoint also permits us to quickly exhibit further GR-matter theories admitted by the 3-space formulation. In particular, we show that the spin-1/2 fermions of the theories of Dirac, Maxwell--Dirac and Yang--Mills--Dirac, all coupled to GR, are admitted by the generalized 3-space formulation we present. Thus all the known fundamental matter fields can be accommodated. This corresponds to being able to pick actions for all these theories which have less kinematics than suggested by the generally covariant hypersurface framework. For all these theories, Wheeler's thin sandwich conjecture may be posed, rendering them timeless in Barbour's sense. |
2107.09276 | Remo Garattini | Remo Garattini | Yukawa-Casimir Wormholes | Revtex4 19 pages | null | 10.1140/epjc/s10052-021-09634-3 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work, we consider a Yukawa modification of the Casimir wormhole. With
the help of an Equation of State, we impose Zero Tidal Forces. We will examine
two different approaches: in a first approach, we will fix the form of the
shape function of the Casimir wormholes modified by a Yukawa term in three
different ways and finally a superposition of different profiles. In the second
approach, we will consider the original Casimir source modified by a Yukawa
term in three different ways and we will deduce the form of the shape function
In both the approaches the reference energy density will be that of the Casimir
source. Connection with the Absurdly Benign Traversable Wormhole are also
discussed.
| [
{
"created": "Tue, 20 Jul 2021 06:39:15 GMT",
"version": "v1"
}
] | 2021-10-04 | [
[
"Garattini",
"Remo",
""
]
] | In this work, we consider a Yukawa modification of the Casimir wormhole. With the help of an Equation of State, we impose Zero Tidal Forces. We will examine two different approaches: in a first approach, we will fix the form of the shape function of the Casimir wormholes modified by a Yukawa term in three different ways and finally a superposition of different profiles. In the second approach, we will consider the original Casimir source modified by a Yukawa term in three different ways and we will deduce the form of the shape function In both the approaches the reference energy density will be that of the Casimir source. Connection with the Absurdly Benign Traversable Wormhole are also discussed. |
1911.09790 | Oldrich Semerak | L. Polcar, O. Semer\'ak | Free motion around black holes with discs or rings: between
integrability and chaos -- VI. The Melnikov method | 32 pages (PRD preprint style), 7 figures | Phys. Rev. D 100 (2019) 103013 | 10.1103/PhysRevD.100.103013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by black holes surrounded by accretion structures, we consider in
this series static and axially symmetric black holes "perturbed"
gravitationally as being encircled by a thin disc or a ring. In previous
papers, we employed several different methods to detect, classify and evaluate
chaos which can occur, due to the presence of the additional source, in
time-like geodesic motion. Here we apply the Melnikov-integral method which is
able to recognize how stable and unstable manifolds behave along the perturbed
homoclinic orbit. Since the method standardly works for systems with one degree
of freedom, we first suggest its modification applicable to two degrees of
freedom (which is the our case), starting from a suitable canonical
transformation of the corresponding Hamiltonian. The Melnikov function reveals
that, after the perturbation, the asymptotic manifolds tend to split and
intersect, consistently with the chaos found by other methods in the previous
papers.
| [
{
"created": "Fri, 22 Nov 2019 00:09:44 GMT",
"version": "v1"
}
] | 2019-11-25 | [
[
"Polcar",
"L.",
""
],
[
"Semerák",
"O.",
""
]
] | Motivated by black holes surrounded by accretion structures, we consider in this series static and axially symmetric black holes "perturbed" gravitationally as being encircled by a thin disc or a ring. In previous papers, we employed several different methods to detect, classify and evaluate chaos which can occur, due to the presence of the additional source, in time-like geodesic motion. Here we apply the Melnikov-integral method which is able to recognize how stable and unstable manifolds behave along the perturbed homoclinic orbit. Since the method standardly works for systems with one degree of freedom, we first suggest its modification applicable to two degrees of freedom (which is the our case), starting from a suitable canonical transformation of the corresponding Hamiltonian. The Melnikov function reveals that, after the perturbation, the asymptotic manifolds tend to split and intersect, consistently with the chaos found by other methods in the previous papers. |
gr-qc/0207025 | Bijan Saha | Bijan Saha (LIT, Jinr) | Nonlinear Spinor Field in Anisotropic Universes | RevTex, 12 pages; Talk, given at the International Conference
``Scientific Reading devoted to 90 years anniversary of Professor Yakov
Petrovich Terletski''July 1-3, 2002, Russian Peoples' Friendship University,
Moscow, Russia | null | null | null | gr-qc | null | Evolution of an anisotropic universe described by a Bianchi type I (BI) model
in presence of nonlinear spinor field has been studied by us recently in a
series of papers. On offer the Bianchi models, those are both inhomogeneous and
anisotropic. Within the scope of Bianchi type VI (BVI) model the
self-consistent system of nonlinear spinor and gravitational fields are
considered. The role of inhomogeneity in the evolution of spinor and
gravitational field is studied.
| [
{
"created": "Thu, 4 Jul 2002 09:15:13 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Saha",
"Bijan",
"",
"LIT, Jinr"
]
] | Evolution of an anisotropic universe described by a Bianchi type I (BI) model in presence of nonlinear spinor field has been studied by us recently in a series of papers. On offer the Bianchi models, those are both inhomogeneous and anisotropic. Within the scope of Bianchi type VI (BVI) model the self-consistent system of nonlinear spinor and gravitational fields are considered. The role of inhomogeneity in the evolution of spinor and gravitational field is studied. |
2110.10670 | Dongxue Qu | Muxin Han, Zichang Huang, Hongguang Liu, Dongxue Qu | Complex critical points and curved geometries in four-dimensional
Lorentzian spinfoam quantum gravity | 5 pages, 12 pages appendix, 4 figures, ILQGS talk:
https://tigers.phys.lsu.edu/relativity/ilqgs/qu100521.mp4 | Phys. Rev. D 106, 044005 (2022) | 10.1103/PhysRevD.106.044005 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper focuses on the semiclassical behavior of the spinfoam quantum
gravity in 4 dimensions. There has been long-standing confusion, known as the
flatness problem, about whether the curved geometry exists in the semiclassical
regime of the spinfoam amplitude. The confusion is resolved by the present
work. By numerical computations, we explicitly find curved Regge geometries
from the large-$j$ Lorentzian Engle-Pereira-Rovelli-Livine (EPRL) spinfoam
amplitudes on triangulations. These curved geometries are with small deficit
angles and relate to the complex critical points of the amplitude. The dominant
contribution from the curved geometry to the spinfoam amplitude is proportional
to $e^{i \mathcal{I}}$, where $\mathcal{I}$ is the Regge action of the geometry
plus corrections of higher order in curvature. As a result, the spinfoam
amplitude reduces to an integral over Regge geometries weighted by $e^{i
\mathcal{I}}$ in the semiclassical regime. As a byproduct, our result also
provides a mechanism to relax the cosine problem in the spinfoam model. Our
results provide important evidence supporting the semiclassical consistency of
the spinfoam quantum gravity.
| [
{
"created": "Wed, 20 Oct 2021 17:23:28 GMT",
"version": "v1"
}
] | 2022-08-12 | [
[
"Han",
"Muxin",
""
],
[
"Huang",
"Zichang",
""
],
[
"Liu",
"Hongguang",
""
],
[
"Qu",
"Dongxue",
""
]
] | This paper focuses on the semiclassical behavior of the spinfoam quantum gravity in 4 dimensions. There has been long-standing confusion, known as the flatness problem, about whether the curved geometry exists in the semiclassical regime of the spinfoam amplitude. The confusion is resolved by the present work. By numerical computations, we explicitly find curved Regge geometries from the large-$j$ Lorentzian Engle-Pereira-Rovelli-Livine (EPRL) spinfoam amplitudes on triangulations. These curved geometries are with small deficit angles and relate to the complex critical points of the amplitude. The dominant contribution from the curved geometry to the spinfoam amplitude is proportional to $e^{i \mathcal{I}}$, where $\mathcal{I}$ is the Regge action of the geometry plus corrections of higher order in curvature. As a result, the spinfoam amplitude reduces to an integral over Regge geometries weighted by $e^{i \mathcal{I}}$ in the semiclassical regime. As a byproduct, our result also provides a mechanism to relax the cosine problem in the spinfoam model. Our results provide important evidence supporting the semiclassical consistency of the spinfoam quantum gravity. |
1811.12201 | Fay\c{c}al Hammad | Fay\c{c}al Hammad, \'Etienne Mass\'e, Patrick Labelle | Black hole mechanics and thermodynamics in the light of Weyl
transformations | 12 pages | Phys. Rev. D 98, 104049 (2018) | 10.1103/PhysRevD.98.104049 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The fate of black hole thermodynamics under Weyl transformations is
investigated by going back to the laws of black hole mechanics. It is shown
that the transformed surface gravity, that one would identify with the black
hole temperature in the conformal frame, as well as the black hole entropy,
that one would identify with the horizon area, cannot be invariant. It is also
shown that the conformally invariant surface gravity, attributed to the
so-called "conformal Killing horizon", cannot represent the black hole
temperature in the conformal frame. Finally, using familiar thought
experiments, we find that the effect a Weyl transformation should have on black
hole thermodynamics becomes even subtler than what is suggested by the laws of
black hole mechanics
| [
{
"created": "Wed, 28 Nov 2018 02:57:43 GMT",
"version": "v1"
}
] | 2018-11-30 | [
[
"Hammad",
"Fayçal",
""
],
[
"Massé",
"Étienne",
""
],
[
"Labelle",
"Patrick",
""
]
] | The fate of black hole thermodynamics under Weyl transformations is investigated by going back to the laws of black hole mechanics. It is shown that the transformed surface gravity, that one would identify with the black hole temperature in the conformal frame, as well as the black hole entropy, that one would identify with the horizon area, cannot be invariant. It is also shown that the conformally invariant surface gravity, attributed to the so-called "conformal Killing horizon", cannot represent the black hole temperature in the conformal frame. Finally, using familiar thought experiments, we find that the effect a Weyl transformation should have on black hole thermodynamics becomes even subtler than what is suggested by the laws of black hole mechanics |
2302.03259 | Joshua Foo | Joshua Foo, Robert B. Mann, Magdalena Zych | Relativity and decoherence of spacetime superpositions | 14 pages, 3 figures | null | null | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | It is univocally anticipated that in a theory of quantum gravity, there exist
quantum superpositions of semiclassical states of spacetime geometry. Such
states could arise for example, from a source mass in a superposition of
spatial configurations. In this paper we introduce a framework for describing
such ''quantum superpositions of spacetime states.'' We introduce the notion of
the relativity of spacetime superpositions, demonstrating that for states in
which the superposed amplitudes differ by a coordinate transformation, it is
always possible to re-express the scenario in terms of dynamics on a single,
fixed background. Our result unveils an inherent ambiguity in labelling such
superpositions as genuinely quantum-gravitational, which has been done
extensively in the literature, most notably with reference to recent proposals
to test gravitationally-induced entanglement. We apply our framework to the the
above mentioned scenarios looking at gravitationally-induced entanglement, the
problem of decoherence of gravitational sources, and clarify commonly
overlooked assumptions. In the context of decoherence of gravitational sources,
our result implies that the resulting decoherence is not fundamental, but
depends on the existence of external systems that define a relative set of
coordinates through which the notion of spatial superposition obtains physical
meaning.
| [
{
"created": "Tue, 7 Feb 2023 05:10:52 GMT",
"version": "v1"
}
] | 2023-02-08 | [
[
"Foo",
"Joshua",
""
],
[
"Mann",
"Robert B.",
""
],
[
"Zych",
"Magdalena",
""
]
] | It is univocally anticipated that in a theory of quantum gravity, there exist quantum superpositions of semiclassical states of spacetime geometry. Such states could arise for example, from a source mass in a superposition of spatial configurations. In this paper we introduce a framework for describing such ''quantum superpositions of spacetime states.'' We introduce the notion of the relativity of spacetime superpositions, demonstrating that for states in which the superposed amplitudes differ by a coordinate transformation, it is always possible to re-express the scenario in terms of dynamics on a single, fixed background. Our result unveils an inherent ambiguity in labelling such superpositions as genuinely quantum-gravitational, which has been done extensively in the literature, most notably with reference to recent proposals to test gravitationally-induced entanglement. We apply our framework to the the above mentioned scenarios looking at gravitationally-induced entanglement, the problem of decoherence of gravitational sources, and clarify commonly overlooked assumptions. In the context of decoherence of gravitational sources, our result implies that the resulting decoherence is not fundamental, but depends on the existence of external systems that define a relative set of coordinates through which the notion of spatial superposition obtains physical meaning. |
gr-qc/0703132 | Enrico Barausse | Enrico Barausse, Thomas P. Sotiriou, John C. Miller | A no-go theorem for polytropic spheres in Palatini f(R) gravity | 7 pages, 1 figure. Version accepted for publication as a Fast Track
Communication in CQG | Class.Quant.Grav.25:062001,2008 | 10.1088/0264-9381/25/6/062001 | null | gr-qc astro-ph hep-th | null | Non-vacuum static spherically-symmetric solutions in Palatini f(R) gravity
are examined. It is shown that for generic choices of f(R), there are
commonly-used equations of state for which no satisfactory physical solution of
the field equations can be found within this framework, apart from in the
special case of General Relativity, casting doubt on whether Palatini f(R)
gravity can be considered as giving viable alternatives to General Relativity.
| [
{
"created": "Tue, 27 Mar 2007 14:19:56 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Jan 2008 11:38:12 GMT",
"version": "v2"
}
] | 2008-09-29 | [
[
"Barausse",
"Enrico",
""
],
[
"Sotiriou",
"Thomas P.",
""
],
[
"Miller",
"John C.",
""
]
] | Non-vacuum static spherically-symmetric solutions in Palatini f(R) gravity are examined. It is shown that for generic choices of f(R), there are commonly-used equations of state for which no satisfactory physical solution of the field equations can be found within this framework, apart from in the special case of General Relativity, casting doubt on whether Palatini f(R) gravity can be considered as giving viable alternatives to General Relativity. |
1111.5610 | Enrico Barausse | Enrico Barausse, Alessandra Buonanno and Alexandre Le Tiec | The complete non-spinning effective-one-body metric at linear order in
the mass ratio | 11 pages, 2 figures; appendix generalized to include the logarithmic
contributions in the post-Newtonian Hamiltonian. Results unchanged. Matches
version to be published in Phys. Rev. D | Phys. Rev. D 85, 064010 (2012) | 10.1103/PhysRevD.85.064010 | null | gr-qc astro-ph.CO astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the main result of a companion paper, in which the binding energy of a
circular-orbit non-spinning compact binary system is computed at leading-order
beyond the test-particle approximation, the exact expression of the
effective-one-body (EOB) metric component g^eff_tt is obtained through first
order in the mass ratio. Combining these results with the recent gravitational
self-force calculation of the periastron advance for circular orbits in the
Schwarzschild geometry, the EOB metric component g^eff_rr is also determined at
linear order in the mass ratio. These results assume that the mapping between
the real and effective Hamiltonians at the second and third post-Newtonian (PN)
orders holds at all PN orders. Our findings also confirm the advantage of
resumming the PN dynamics around the test-particle limit if the goal is to
obtain a flexible model that can smoothly connect the test-mass and equal-mass
limits.
| [
{
"created": "Wed, 23 Nov 2011 20:58:32 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Feb 2012 21:58:04 GMT",
"version": "v2"
}
] | 2012-03-08 | [
[
"Barausse",
"Enrico",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Tiec",
"Alexandre Le",
""
]
] | Using the main result of a companion paper, in which the binding energy of a circular-orbit non-spinning compact binary system is computed at leading-order beyond the test-particle approximation, the exact expression of the effective-one-body (EOB) metric component g^eff_tt is obtained through first order in the mass ratio. Combining these results with the recent gravitational self-force calculation of the periastron advance for circular orbits in the Schwarzschild geometry, the EOB metric component g^eff_rr is also determined at linear order in the mass ratio. These results assume that the mapping between the real and effective Hamiltonians at the second and third post-Newtonian (PN) orders holds at all PN orders. Our findings also confirm the advantage of resumming the PN dynamics around the test-particle limit if the goal is to obtain a flexible model that can smoothly connect the test-mass and equal-mass limits. |
1702.07607 | Vladimir Popov | Alexander Balakin and Vladimir Popov | Einstein-aether theory: Dynamics of relativistic particles with spin or
polarization in a G\"odel-type universe | 15 pages | JCAP04(2017)025 | 10.1088/1475-7516/2017/04/025 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of the Einstein-aether theory we consider a cosmological
model, which describes the evolution of the unit dynamic vector field with
activated rotational degree of freedom. We discuss exact solutions of the
Einstein-aether theory, for which the space-time is of the G\"odel-type, the
velocity four-vector of the aether motion is characterized by a non-vanishing
vorticity, thus the rotational vectorial modes can be associated with the
source of the universe rotation. The main goal of our paper is to study the
motion of test relativistic particles with vectorial internal degree of freedom
(spin or polarization), which is coupled to the unit dynamic vector field. The
particles are considered as the test ones in the given space-time background of
the G\"odel-type; the spin (polarization) coupling to the unit dynamic vector
field is modeled using exact solutions of three types. The first exact solution
describes the aether with arbitrary Jacobson's coupling constants; the second
one relates to the case, when the Jacobson's constant responsible for the
vorticity is vanishing; the third exact solution is obtained using three
constraints for the coupling constants. The analysis of the exact expressions,
which are obtained for the particle momentum and for the spin (polarization)
four-vector components, shows that the interaction of the spin (polarization)
with the unit vector field induces a rotation, which is additional to the
geodesic precession of the spin (polarization) associated with the universe
rotation as a whole.
| [
{
"created": "Fri, 24 Feb 2017 14:40:37 GMT",
"version": "v1"
}
] | 2017-04-25 | [
[
"Balakin",
"Alexander",
""
],
[
"Popov",
"Vladimir",
""
]
] | In the framework of the Einstein-aether theory we consider a cosmological model, which describes the evolution of the unit dynamic vector field with activated rotational degree of freedom. We discuss exact solutions of the Einstein-aether theory, for which the space-time is of the G\"odel-type, the velocity four-vector of the aether motion is characterized by a non-vanishing vorticity, thus the rotational vectorial modes can be associated with the source of the universe rotation. The main goal of our paper is to study the motion of test relativistic particles with vectorial internal degree of freedom (spin or polarization), which is coupled to the unit dynamic vector field. The particles are considered as the test ones in the given space-time background of the G\"odel-type; the spin (polarization) coupling to the unit dynamic vector field is modeled using exact solutions of three types. The first exact solution describes the aether with arbitrary Jacobson's coupling constants; the second one relates to the case, when the Jacobson's constant responsible for the vorticity is vanishing; the third exact solution is obtained using three constraints for the coupling constants. The analysis of the exact expressions, which are obtained for the particle momentum and for the spin (polarization) four-vector components, shows that the interaction of the spin (polarization) with the unit vector field induces a rotation, which is additional to the geodesic precession of the spin (polarization) associated with the universe rotation as a whole. |
gr-qc/0405088 | David Maxwell | David Maxwell | Rough Solutions of the Einstein Constraint Equations | 30 pages | null | null | null | gr-qc math.AP math.DG | null | We construct low regularity solutions of the vacuum Einstein constraint
equations. In particular, on 3-manifolds we obtain solutions with metrics in
$H^s\loc$ with $s>{3\over 2}$. The theory of maximal asymptotically Euclidean
solutions of the constraint equations descends completely the low regularity
setting. Moreover, every rough, maximal, asymptotically Euclidean solution can
be approximated in an appropriate topology by smooth solutions. These results
have application in an existence theorem for rough solutions of the Einstein
evolution equations.
| [
{
"created": "Mon, 17 May 2004 16:51:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Maxwell",
"David",
""
]
] | We construct low regularity solutions of the vacuum Einstein constraint equations. In particular, on 3-manifolds we obtain solutions with metrics in $H^s\loc$ with $s>{3\over 2}$. The theory of maximal asymptotically Euclidean solutions of the constraint equations descends completely the low regularity setting. Moreover, every rough, maximal, asymptotically Euclidean solution can be approximated in an appropriate topology by smooth solutions. These results have application in an existence theorem for rough solutions of the Einstein evolution equations. |
1804.09685 | Simone Speziale | Elena De Paoli and Simone Speziale | A gauge-invariant symplectic potential for tetrad general relativity | 19 pages. V2: some amendments to the text, typos corrected, updated
references and more details in Section 5. Matches published version | null | 10.1007/JHEP07(2018)040 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We identify a symplectic potential for general relativity in tetrad and
connection variables that is fully gauge-invariant, using the freedom to add
surface terms. When torsion vanishes, it does not lead to surface charges
associated with the internal Lorentz transformations, and reduces exactly to
the symplectic potential given by the Einstein-Hilbert action. In particular,
it reproduces the Komar form when the variation is a Lie derivative, and the
geometric expression in terms of extrinsic curvature and 2d corner data for a
general variation. The additional surface term vanishes at spatial infinity for
asymptotically flat spacetimes, thus the usual Poincare charges are obtained.
We prove that the first law of black hole mechanics follows from the Noether
identity associated with the covariant Lie derivative, and that it is
independent of the ambiguities in the symplectic potential provided one takes
into account the presence of non-trivial Lorentz charges that these ambiguities
can introduce.
| [
{
"created": "Wed, 25 Apr 2018 17:26:22 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jul 2018 13:04:25 GMT",
"version": "v2"
}
] | 2018-08-01 | [
[
"De Paoli",
"Elena",
""
],
[
"Speziale",
"Simone",
""
]
] | We identify a symplectic potential for general relativity in tetrad and connection variables that is fully gauge-invariant, using the freedom to add surface terms. When torsion vanishes, it does not lead to surface charges associated with the internal Lorentz transformations, and reduces exactly to the symplectic potential given by the Einstein-Hilbert action. In particular, it reproduces the Komar form when the variation is a Lie derivative, and the geometric expression in terms of extrinsic curvature and 2d corner data for a general variation. The additional surface term vanishes at spatial infinity for asymptotically flat spacetimes, thus the usual Poincare charges are obtained. We prove that the first law of black hole mechanics follows from the Noether identity associated with the covariant Lie derivative, and that it is independent of the ambiguities in the symplectic potential provided one takes into account the presence of non-trivial Lorentz charges that these ambiguities can introduce. |
gr-qc/0312021 | Pieter-Jan De Smet | Pieter-Jan De Smet | The Petrov type of the five-dimensional Myers-Perry metric | 4 pages, 1 figure | Gen.Rel.Grav. 36 (2004) 1501-1504 | 10.1023/B:GERG.0000022586.06313.fc | YITP-SB-03-63 | gr-qc hep-th | null | We point out that the Myers-Perry metric in five dimensions is algebraically
special. It has Petrov type \underline{22}, which is the Petrov type of the
five-dimensional Schwarzschild metric.
| [
{
"created": "Wed, 3 Dec 2003 15:33:25 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"De Smet",
"Pieter-Jan",
""
]
] | We point out that the Myers-Perry metric in five dimensions is algebraically special. It has Petrov type \underline{22}, which is the Petrov type of the five-dimensional Schwarzschild metric. |
2012.13594 | Jia-Hui Huang | Jun-Huai Xu, Zi-Han Zheng, Ming-Jian Luo, and Jia-Hui Huang | Analytic study of superradiant stability of Kerr-Newman black holes
under charged massive scalar perturbation | 7 pages, references added | null | 10.1140/epjc/s10052-021-09180-y | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The superradiant stability of a Kerr-Newman black hole and charged massive
scalar perturbation is investigated. We treat the black hole as a background
geometry and study the equation of motion of the scalar perturbation. From the
radial equation of motion, we derive the effective potential experienced by the
scalar perturbation. By a careful analysis of this effective potential, it is
found that when the inner and outer horizons of Kerr-Newman black hole satisfy
$\frac{r_-}{r_+}\leqslant\frac{1}{3}$ and the charge-to-mass ratios of scalar
perturbation and black hole satisfy $ \frac{q}{\mu }\frac{Q}{ M}>1 $, the
Kerr-Newman black hole and scalar perturbation system is superradiantly stable.
| [
{
"created": "Fri, 25 Dec 2020 15:29:11 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Jan 2021 02:27:15 GMT",
"version": "v2"
}
] | 2021-05-26 | [
[
"Xu",
"Jun-Huai",
""
],
[
"Zheng",
"Zi-Han",
""
],
[
"Luo",
"Ming-Jian",
""
],
[
"Huang",
"Jia-Hui",
""
]
] | The superradiant stability of a Kerr-Newman black hole and charged massive scalar perturbation is investigated. We treat the black hole as a background geometry and study the equation of motion of the scalar perturbation. From the radial equation of motion, we derive the effective potential experienced by the scalar perturbation. By a careful analysis of this effective potential, it is found that when the inner and outer horizons of Kerr-Newman black hole satisfy $\frac{r_-}{r_+}\leqslant\frac{1}{3}$ and the charge-to-mass ratios of scalar perturbation and black hole satisfy $ \frac{q}{\mu }\frac{Q}{ M}>1 $, the Kerr-Newman black hole and scalar perturbation system is superradiantly stable. |
2206.12339 | George Macaulay Mr | Mahdi Godazgar, George Macaulay, Ali Seraj | Gravitational memory effects and higher derivative actions | 15 pages | null | 10.1007/JHEP09(2022)150 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that charges associated with the internal Lorentz symmetries of
general relativity, with higher derivative boundary terms included in the
action, capture observable gravitational wave effects. In particular, the
Gauss-Bonnet charge measures the precession rate of a freely-falling gyroscope,
while the Pontryagin charge encodes the relative radial acceleration of
freely-falling test masses. This relation highlights the importance of the
tetrad formalism and the physical significance of asymptotic internal Lorentz
symmetries.
| [
{
"created": "Fri, 24 Jun 2022 15:21:26 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Sep 2022 08:37:49 GMT",
"version": "v2"
},
{
"created": "Tue, 25 Apr 2023 11:43:51 GMT",
"version": "v3"
}
] | 2023-04-26 | [
[
"Godazgar",
"Mahdi",
""
],
[
"Macaulay",
"George",
""
],
[
"Seraj",
"Ali",
""
]
] | We show that charges associated with the internal Lorentz symmetries of general relativity, with higher derivative boundary terms included in the action, capture observable gravitational wave effects. In particular, the Gauss-Bonnet charge measures the precession rate of a freely-falling gyroscope, while the Pontryagin charge encodes the relative radial acceleration of freely-falling test masses. This relation highlights the importance of the tetrad formalism and the physical significance of asymptotic internal Lorentz symmetries. |
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