id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1111.0171 | Muhmmed Abdelwahab | Mohamed Abdelwahab, Rituparno Goswami and Peter K. S. Dunsby | Cosmological dynamics of fourth order gravity: A compact view | 8 pages, 3 figures, revtex4-1 | Phys. Rev. D 85, 083511 (2012) | 10.1103/PhysRevD.85.083511 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a compact phase space for flat FLRW spacetimes with standard
matter described by a perfect fluid with a barotropic equation of state for
general f(R) theories of gravity, subject to certain conditions on the function
f. We then use this framework to study the behaviour of the phase space of
Universes with a non-negative Ricci scalar in R + {\alpha}R^n gravity. We find
a number of interesting cosmological evolutions which include the possibility
of an initial unstable power-law inflationary point, followed by a curvature
fluid dominated phase mimicking standard radiation, then passing through a
standard matter (CDM) era and ultimately evolving asymptotically towards a
de-Sitter-like late-time accelerated phase.
| [
{
"created": "Tue, 1 Nov 2011 11:16:04 GMT",
"version": "v1"
},
{
"created": "Wed, 2 May 2012 15:02:59 GMT",
"version": "v2"
},
{
"created": "Tue, 24 Jul 2012 09:44:17 GMT",
"version": "v3"
}
] | 2015-06-03 | [
[
"Abdelwahab",
"Mohamed",
""
],
[
"Goswami",
"Rituparno",
""
],
[
"Dunsby",
"Peter K. S.",
""
]
] | We construct a compact phase space for flat FLRW spacetimes with standard matter described by a perfect fluid with a barotropic equation of state for general f(R) theories of gravity, subject to certain conditions on the function f. We then use this framework to study the behaviour of the phase space of Universes with a non-negative Ricci scalar in R + {\alpha}R^n gravity. We find a number of interesting cosmological evolutions which include the possibility of an initial unstable power-law inflationary point, followed by a curvature fluid dominated phase mimicking standard radiation, then passing through a standard matter (CDM) era and ultimately evolving asymptotically towards a de-Sitter-like late-time accelerated phase. |
1110.5697 | Kiyoshi Shiraishi | Nahomi Kan (Yamaguchi Junior College), Koichiro Kobayashi and Kiyoshi
Shiraishi (Yamaguchi University) | Graph-theory induced gravity and strongly-degenerate fermions in a
self-consistent Einstein universe | 16pages, 1figure | International Journal of Modern Physics A, Vol. 27, Issue 23
(2012) 1250131 (15 pages) | 10.1142/S0217751X1250131X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study UV-finite theory of induced gravity. We use scalar fields, Dirac
fields and vector fields as matter fields whose one-loop effects induce the
gravitational action. To obtain the mass spectrum which satisfies the
UV-finiteness condition, we use a graph-based construction of mass matrices.
The existence of a self-consistent static solution for an Einstein universe is
shown in the presence of degenerate fermion.
| [
{
"created": "Wed, 26 Oct 2011 02:41:30 GMT",
"version": "v1"
}
] | 2012-09-07 | [
[
"Kan",
"Nahomi",
"",
"Yamaguchi Junior College"
],
[
"Kobayashi",
"Koichiro",
"",
"Yamaguchi University"
],
[
"Shiraishi",
"Kiyoshi",
"",
"Yamaguchi University"
]
] | We study UV-finite theory of induced gravity. We use scalar fields, Dirac fields and vector fields as matter fields whose one-loop effects induce the gravitational action. To obtain the mass spectrum which satisfies the UV-finiteness condition, we use a graph-based construction of mass matrices. The existence of a self-consistent static solution for an Einstein universe is shown in the presence of degenerate fermion. |
1305.0474 | Giovanni Otalora | G. Otalora | Scaling attractors in interacting teleparallel dark energy | 17 pages, 4 tables, 1 figure | JCAP 07 (2013) 044 | 10.1088/1475-7516/2013/07/044 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been proposed recently the existence of a non-minimal coupling between
a canonical scalar field (quintessence) and gravity in the framework of
teleparallel gravity, motivated by similar constructions in the context of
General Relativity. The dynamics of the model, known as teleparallel dark
energy, has been further developed, but no scaling attractor has been found.
Here we consider a model in which the non-minimal coupling is ruled by a
dynamically changing coefficient $\alpha\equiv f_{,\phi}/\sqrt{f}$, with
$f(\phi)$ an arbitrary function of the scalar field $\phi$. It is shown that in
this case the existence of scaling attractors is possible, which means that the
universe will eventually enter these scaling attractors, regardless of the
initial conditions. As a consequence, the cosmological coincidence problem
could be alleviated without fine-tunings.
| [
{
"created": "Thu, 2 May 2013 15:20:30 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Jul 2013 17:46:44 GMT",
"version": "v2"
}
] | 2013-09-06 | [
[
"Otalora",
"G.",
""
]
] | It has been proposed recently the existence of a non-minimal coupling between a canonical scalar field (quintessence) and gravity in the framework of teleparallel gravity, motivated by similar constructions in the context of General Relativity. The dynamics of the model, known as teleparallel dark energy, has been further developed, but no scaling attractor has been found. Here we consider a model in which the non-minimal coupling is ruled by a dynamically changing coefficient $\alpha\equiv f_{,\phi}/\sqrt{f}$, with $f(\phi)$ an arbitrary function of the scalar field $\phi$. It is shown that in this case the existence of scaling attractors is possible, which means that the universe will eventually enter these scaling attractors, regardless of the initial conditions. As a consequence, the cosmological coincidence problem could be alleviated without fine-tunings. |
2308.11004 | M. Ilyas | M. Ilyas and Kazuharu Bamba | Traversable wormholes with static spherical symmetry and their stability
in higher-curvature gravity | 18 pages, 11 figures,1 table, version accepted for publication in
JCAP | null | null | FU-PCG-121 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The solutions of traversable wormholes and their geometries are investigated
in higher-curvature gravity with boundary terms for each case under the
presence of anisotropic, isotropic and barotropic fluids in detail. For each
case, the effective energy-momentum tensor violates the null energy condition
throughout the wormhole throat. The null and weak energy conditions are also
analyzed for ordinary matters. The regions that physically viable wormhole
solutions can exist are explicitly shown. Furthermore, it is found that the
range of the viable regions exhibits an alternating pattern of expansion and
contraction. The present analyses can reveal the regions in which traversable
wormholes can be constructed for anisotropic, isotropic and barotropic fluids
cases with incorporating realistic matter contents, leading to fundamental
physics insights into the feasible construction of wormholes in
higher-curvature gravity with boundary term. The main achievements of this
work, in contrast to previous studies, are its thorough investigation of
traversable wormholes within the framework of higher-curvature gravity with
boundary terms, its extensive consideration of various fluid types, and the
explicit identification of regions where stable wormhole solutions can exist.
| [
{
"created": "Fri, 18 Aug 2023 09:10:49 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Oct 2023 07:30:36 GMT",
"version": "v2"
}
] | 2023-10-03 | [
[
"Ilyas",
"M.",
""
],
[
"Bamba",
"Kazuharu",
""
]
] | The solutions of traversable wormholes and their geometries are investigated in higher-curvature gravity with boundary terms for each case under the presence of anisotropic, isotropic and barotropic fluids in detail. For each case, the effective energy-momentum tensor violates the null energy condition throughout the wormhole throat. The null and weak energy conditions are also analyzed for ordinary matters. The regions that physically viable wormhole solutions can exist are explicitly shown. Furthermore, it is found that the range of the viable regions exhibits an alternating pattern of expansion and contraction. The present analyses can reveal the regions in which traversable wormholes can be constructed for anisotropic, isotropic and barotropic fluids cases with incorporating realistic matter contents, leading to fundamental physics insights into the feasible construction of wormholes in higher-curvature gravity with boundary term. The main achievements of this work, in contrast to previous studies, are its thorough investigation of traversable wormholes within the framework of higher-curvature gravity with boundary terms, its extensive consideration of various fluid types, and the explicit identification of regions where stable wormhole solutions can exist. |
gr-qc/0608082 | Farook Rahaman | F. Rahaman and S. Mandal | Gravitational field of higher dimensional domain walls in Lyra geometry | 9 papges, Submitted to Theo.Math.Com.Phys, refereces corrections | null | null | null | gr-qc | null | This paper studies Thick domain wall within the framework of Lyra geometry.
Their exact solutions are obtained in the background of a five dimensional
space-time. The space-time is nonsingular in its both spatial and temporal
behavior. The gravitational field of the wall is shown to be attractive in
nature.
| [
{
"created": "Thu, 17 Aug 2006 09:44:30 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Oct 2006 10:42:37 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Rahaman",
"F.",
""
],
[
"Mandal",
"S.",
""
]
] | This paper studies Thick domain wall within the framework of Lyra geometry. Their exact solutions are obtained in the background of a five dimensional space-time. The space-time is nonsingular in its both spatial and temporal behavior. The gravitational field of the wall is shown to be attractive in nature. |
0808.2696 | Sanjeev Dhurandhar | S. V. Dhurandhar | Time-delay interferometry and the relativistic treatment of LISA optical
links | 10 pages, 3 figures, 7th LISA symposium, Barcelona, Spain | null | 10.1088/1742-6596/154/1/012047 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | LISA is a joint space mission of the ESA and NASA for detecting low frequency
gravitational radiation in the band $10^{-5} - 1$ Hz. In order to attain the
requisite sensitivity for LISA, the laser frequency noise must be suppressed
below the other secondary noises such as the optical path noise, acceleration
noise etc. This is achieved because of the redundancy in the data, more
specifically, by combining six appropriately time-delayed data streams
containing fractional Doppler shifts - time delay interferometry (TDI). The
orbits of the spacecraft are computed in the gravitational field of the Sun and
Earth in the Newtonian framework, while the optical links are treated fully
general relativistically and thus, effects such as the Sagnac, Shapiro delay,
etc. are automatically incorporated. We show that in the model of LISA that we
consider here, there are symmetries inherent in the physics, which may be used
effectively to suppress the residual laser frequency noise and simplify the
algebraic approach to TDI.
| [
{
"created": "Wed, 20 Aug 2008 06:29:56 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Dhurandhar",
"S. V.",
""
]
] | LISA is a joint space mission of the ESA and NASA for detecting low frequency gravitational radiation in the band $10^{-5} - 1$ Hz. In order to attain the requisite sensitivity for LISA, the laser frequency noise must be suppressed below the other secondary noises such as the optical path noise, acceleration noise etc. This is achieved because of the redundancy in the data, more specifically, by combining six appropriately time-delayed data streams containing fractional Doppler shifts - time delay interferometry (TDI). The orbits of the spacecraft are computed in the gravitational field of the Sun and Earth in the Newtonian framework, while the optical links are treated fully general relativistically and thus, effects such as the Sagnac, Shapiro delay, etc. are automatically incorporated. We show that in the model of LISA that we consider here, there are symmetries inherent in the physics, which may be used effectively to suppress the residual laser frequency noise and simplify the algebraic approach to TDI. |
2211.01949 | Hidetoshi Omiya | Hidetoshi Omiya, Takuya Takahashi, Takahiro Tanaka, Hirotaka Yoshino | Impact of multiple modes on the evolution of self-interacting axion
condensate around rotating black holes | 29 pages, 25 figures, 1 table | null | 10.1088/1475-7516/2023/06/016 | KUNS 2945 | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Ultra-light particles, such as axions, form a macroscopic condensate around a
highly spinning black hole by the superradiant instability. Due to its
macroscopic nature, the condensate opens the possibility of detecting the axion
through gravitational wave observations. However, the precise evolution of the
condensate must be known for the actual detection. For future observation, we
numerically study the influence of the self-interaction, especially interaction
between different modes, on the evolution of the condensate in detail. First,
we focus on the case when condensate starts with the smallest possible angular
quantum number. For this case, we perform the non-linear calculation and show
that the dissipation induced by the mode interaction is strong enough to
saturate the superradiant instability, even if the secondary cloud starts with
quantum fluctuations. Our result indicates that explosive phenomena such as
bosenova do not occur in this case. We also show that the condensate settles to
a quasi-stationary state mainly composed of two modes, one with the smallest
angular quantum number for which the superradiant instability occurs and the
other with the adjacent higher angular quantum number. We also study the case
when the condensate starts with the dominance of the higher angular quantum
number. We show that the dissipation process induced by the mode coupling does
not occur for small gravitational coupling. Therefore, bosenova might occur in
this case.
| [
{
"created": "Thu, 3 Nov 2022 16:34:44 GMT",
"version": "v1"
}
] | 2023-06-28 | [
[
"Omiya",
"Hidetoshi",
""
],
[
"Takahashi",
"Takuya",
""
],
[
"Tanaka",
"Takahiro",
""
],
[
"Yoshino",
"Hirotaka",
""
]
] | Ultra-light particles, such as axions, form a macroscopic condensate around a highly spinning black hole by the superradiant instability. Due to its macroscopic nature, the condensate opens the possibility of detecting the axion through gravitational wave observations. However, the precise evolution of the condensate must be known for the actual detection. For future observation, we numerically study the influence of the self-interaction, especially interaction between different modes, on the evolution of the condensate in detail. First, we focus on the case when condensate starts with the smallest possible angular quantum number. For this case, we perform the non-linear calculation and show that the dissipation induced by the mode interaction is strong enough to saturate the superradiant instability, even if the secondary cloud starts with quantum fluctuations. Our result indicates that explosive phenomena such as bosenova do not occur in this case. We also show that the condensate settles to a quasi-stationary state mainly composed of two modes, one with the smallest angular quantum number for which the superradiant instability occurs and the other with the adjacent higher angular quantum number. We also study the case when the condensate starts with the dominance of the higher angular quantum number. We show that the dissipation process induced by the mode coupling does not occur for small gravitational coupling. Therefore, bosenova might occur in this case. |
2012.04694 | Salah Nasri | Hemza Azri and Salah Nasri | Scalar-Connection Gravity and Spontaneous Scalarization | null | Phys. Rev. D 103, 024035 (2021) | 10.1103/PhysRevD.103.024035 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scalar-tensor theories of gravity are known to allow significant deviations
from general relativity through various astrophysical phenomena. In this paper,
we formulate a scalar-connection gravity by setting up scalars and connection
configurations instead of metric. Since the matter sector is not
straightforward to conceive without a metric, we invoke cosmological fluids in
terms of their one-form velocity in the volume element of the invariant action.
This leads to gravitational equations with a perfect fluid source and a
generated metric, which are expected to produce reasonable deviations from
general relativity in the strong-field regime. As a relevant application, we
study spontaneous scalarization mechanism and show that the
Damour-Esposito-Far\`{e}se model arises in a certain class of scalar-connection
gravity. Furthermore, we investigate a general study in which the present
framework becomes distinguishable from the famed scalar-tensor theories.
| [
{
"created": "Tue, 8 Dec 2020 19:28:00 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Jan 2021 17:28:46 GMT",
"version": "v2"
}
] | 2021-01-21 | [
[
"Azri",
"Hemza",
""
],
[
"Nasri",
"Salah",
""
]
] | Scalar-tensor theories of gravity are known to allow significant deviations from general relativity through various astrophysical phenomena. In this paper, we formulate a scalar-connection gravity by setting up scalars and connection configurations instead of metric. Since the matter sector is not straightforward to conceive without a metric, we invoke cosmological fluids in terms of their one-form velocity in the volume element of the invariant action. This leads to gravitational equations with a perfect fluid source and a generated metric, which are expected to produce reasonable deviations from general relativity in the strong-field regime. As a relevant application, we study spontaneous scalarization mechanism and show that the Damour-Esposito-Far\`{e}se model arises in a certain class of scalar-connection gravity. Furthermore, we investigate a general study in which the present framework becomes distinguishable from the famed scalar-tensor theories. |
2211.16899 | Pedro Bargue\~no | P. Bargueno | Light rings in static and extremal black holes | To be submitted to Phys. Rev. D | null | 10.1103/PhysRevD.107.104029 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work we establish some results concerning the existence of external
light rings in extremal black hole spacetimes through the Newman-Penrose
formalism. Specifically, assuming conformal flatness, staticity and the null
energy condition, we show that a sufficient condition for the existence of
external light rings is $R < 2 K_{G}$, where $R$, the curvature scalar of the
spacetime and $K_{G}$, the Gaussian curvature of a spacelike two-surface, are
both evaluated at the outermost event horizon, which can be endowed with
spherical, hyperbolic or planar geometry. Our results are valid for any metric
gravity theory where photons follow null geodesics.
| [
{
"created": "Wed, 30 Nov 2022 10:58:19 GMT",
"version": "v1"
}
] | 2023-05-24 | [
[
"Bargueno",
"P.",
""
]
] | In this work we establish some results concerning the existence of external light rings in extremal black hole spacetimes through the Newman-Penrose formalism. Specifically, assuming conformal flatness, staticity and the null energy condition, we show that a sufficient condition for the existence of external light rings is $R < 2 K_{G}$, where $R$, the curvature scalar of the spacetime and $K_{G}$, the Gaussian curvature of a spacelike two-surface, are both evaluated at the outermost event horizon, which can be endowed with spherical, hyperbolic or planar geometry. Our results are valid for any metric gravity theory where photons follow null geodesics. |
1811.11563 | Alberto Escalante | Alberto Escalante, I. Vallejo-Fabila (Puebla U., Inst. Fis.) | Hamilton-Jacobi analysis for three dimensional gravity without dynamics | null | null | 10.1016/j.aop.2019.03.013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hamilton-Jacobi analysis for gravity without dynamics is performed. We
report a detailed analysis where the complete set of Hamilton-Jacobi
constraints, the characteristic equations and the gauge transformations of the
theory are found. We compare our results with those reported in the literature
where alternative approaches are used. In addition, we complete our work by
performing the canonical covariant analysis by constructing a gauge invariant
symplectic structure, and we find a full consistency between the results
obtained from both approaches.
| [
{
"created": "Mon, 26 Nov 2018 16:41:44 GMT",
"version": "v1"
}
] | 2019-05-01 | [
[
"Escalante",
"Alberto",
"",
"Puebla U., Inst. Fis."
],
[
"Vallejo-Fabila",
"I.",
"",
"Puebla U., Inst. Fis."
]
] | The Hamilton-Jacobi analysis for gravity without dynamics is performed. We report a detailed analysis where the complete set of Hamilton-Jacobi constraints, the characteristic equations and the gauge transformations of the theory are found. We compare our results with those reported in the literature where alternative approaches are used. In addition, we complete our work by performing the canonical covariant analysis by constructing a gauge invariant symplectic structure, and we find a full consistency between the results obtained from both approaches. |
1705.01072 | Martin Kr\v{s}\v{s}\'ak | Martin Krssak | Variational Problem and Bigravity Nature of Modified Teleparallel
Theories | 15 pages, v3: significantly updated version including new results | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the variational principle in the covariant formulation of
modified teleparallel theories with second order field equations. We vary the
action with respect to the spin connection and obtain a consistency condition
relating the spin connection with the tetrad. We argue that since the spin
connection can be calculated using an additional reference tetrad, modified
teleparallel theories can be interpreted as effectively bigravity theories. We
conclude with discussion about the relation of our results and those obtained
in the usual, non-covariant, formulation of teleparallel theories and present
the solution to the problem of choosing the tetrad in $f(T)$ gravity theories.
| [
{
"created": "Tue, 2 May 2017 16:56:18 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Jun 2017 11:38:34 GMT",
"version": "v2"
},
{
"created": "Sun, 13 Aug 2017 16:31:43 GMT",
"version": "v3"
}
] | 2017-08-15 | [
[
"Krssak",
"Martin",
""
]
] | We consider the variational principle in the covariant formulation of modified teleparallel theories with second order field equations. We vary the action with respect to the spin connection and obtain a consistency condition relating the spin connection with the tetrad. We argue that since the spin connection can be calculated using an additional reference tetrad, modified teleparallel theories can be interpreted as effectively bigravity theories. We conclude with discussion about the relation of our results and those obtained in the usual, non-covariant, formulation of teleparallel theories and present the solution to the problem of choosing the tetrad in $f(T)$ gravity theories. |
2010.05161 | Akira Matsumura | Akira Matsumura, Kazuhiro Yamamoto | Gravity-induced entanglement in optomechanical systems | 21 pages, 3 figures | Phys. Rev. D 102, 106021 (2020) | 10.1103/PhysRevD.102.106021 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the phenomenon of gravity-induced entanglement in
optomechanical systems. Assuming photon number conservation and the Newtonian
potential expanded up to the quadratic order of the oscillator positions, we
exactly solve the dynamics of the optomehcanical systems. Then, we find that
the phase difference due to the Newtonian gravity leads to the large
entanglement of photons in separated cavities. We clarify the generating
mechanism of large gravity-induced entanglements in optomechanical systems in
an exact manner. We also determine the characteristic time to generate the
maximal entanglement of photons. Finally, by comparing the characteristic time
with the decoherence time due to photon leakage, we evaluate the range of the
dissipation rate required for testing the gravity-induced entanglement.
| [
{
"created": "Sun, 11 Oct 2020 04:28:07 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Nov 2020 03:13:24 GMT",
"version": "v2"
}
] | 2020-11-20 | [
[
"Matsumura",
"Akira",
""
],
[
"Yamamoto",
"Kazuhiro",
""
]
] | We investigate the phenomenon of gravity-induced entanglement in optomechanical systems. Assuming photon number conservation and the Newtonian potential expanded up to the quadratic order of the oscillator positions, we exactly solve the dynamics of the optomehcanical systems. Then, we find that the phase difference due to the Newtonian gravity leads to the large entanglement of photons in separated cavities. We clarify the generating mechanism of large gravity-induced entanglements in optomechanical systems in an exact manner. We also determine the characteristic time to generate the maximal entanglement of photons. Finally, by comparing the characteristic time with the decoherence time due to photon leakage, we evaluate the range of the dissipation rate required for testing the gravity-induced entanglement. |
0904.1767 | Rafael Ferraro | Franco Fiorini, Rafael Ferraro | A type of Born-Infeld regular gravity and its cosmological consequences | 3 pages. Talk given at the 7th Alexander Friedmann International
Seminar on Gravitation and Cosmology, Joao Pessoa, Brazil, July 2008 | Int.J.Mod.Phys.A24:1686-1689,2009 | 10.1142/S0217751X09045236 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Born-Infeld deformation strategy to smooth theories having divergent
solutions is applied to the teleparallel equivalent of General Relativity. The
equivalence between teleparallelism and General Relativity is exploited to
obtain a deformed theory of gravity based on second order differential
equations, since teleparallel Lagrangian is built just from first derivatives
of the vierbein. We show that Born-Infeld teleparallelism cures the initial
singularity in a spatially flat FRW universe; moreover, it provides a natural
inflationary stage without resorting to an inflaton field. The Born-Infeld
parameter bounds the dynamics of Hubble parameter H(t) and establishes a
maximum attainable spacetime curvature.
| [
{
"created": "Fri, 10 Apr 2009 23:46:35 GMT",
"version": "v1"
}
] | 2009-05-20 | [
[
"Fiorini",
"Franco",
""
],
[
"Ferraro",
"Rafael",
""
]
] | Born-Infeld deformation strategy to smooth theories having divergent solutions is applied to the teleparallel equivalent of General Relativity. The equivalence between teleparallelism and General Relativity is exploited to obtain a deformed theory of gravity based on second order differential equations, since teleparallel Lagrangian is built just from first derivatives of the vierbein. We show that Born-Infeld teleparallelism cures the initial singularity in a spatially flat FRW universe; moreover, it provides a natural inflationary stage without resorting to an inflaton field. The Born-Infeld parameter bounds the dynamics of Hubble parameter H(t) and establishes a maximum attainable spacetime curvature. |
1411.3589 | Suzanne Lan\'ery | Suzanne Lan\'ery and Thomas Thiemann | Projective Limits of State Spaces I. Classical Formalism | 51 pages, many figures | J. Geometry Phys., Volume 111, Pages 6-39, January 2017 | 10.1016/j.geomphys.2016.10.010 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this series of papers, we investigate the projective framework initiated
by Jerzy Kijowski and Andrzej Oko{\l}\'ow, which describes the states of a
quantum (field) theory as projective families of density matrices. The present
first paper aims at clarifying the classical structures that underlies this
formalism, namely projective limits of symplectic manifolds. In particular,
this allows us to discuss accurately the issues hindering an easy
implementation of the dynamics in this context, and to formulate a strategy for
overcoming them.
| [
{
"created": "Tue, 11 Nov 2014 22:33:27 GMT",
"version": "v1"
}
] | 2016-11-18 | [
[
"Lanéry",
"Suzanne",
""
],
[
"Thiemann",
"Thomas",
""
]
] | In this series of papers, we investigate the projective framework initiated by Jerzy Kijowski and Andrzej Oko{\l}\'ow, which describes the states of a quantum (field) theory as projective families of density matrices. The present first paper aims at clarifying the classical structures that underlies this formalism, namely projective limits of symplectic manifolds. In particular, this allows us to discuss accurately the issues hindering an easy implementation of the dynamics in this context, and to formulate a strategy for overcoming them. |
1709.00007 | Thiago Pereira | Felipe O. Franco and Thiago S. Pereira | Tensor Perturbations in Anisotropically Curved Cosmologies | 29 pages, 7 figures. This version matches the published one | null | 10.1088/1475-7516/2017/11/022 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Besides expanding anisotropically, the universe can also be anisotropic at
the level of its (spatial) curvature. In particular, models with anisotropic
curvature and isotropic expansion leads both to a $\Lambda$CDM-like
phenomenology and to an isotropic and homogeneous CMB at the background level.
Thus, they offer an interesting and viable example where the cosmological
principle does not follow from the isotropy of observational data. In this
paper we extract the linear dynamics of tensor perturbations in two classes of
cosmologies with anisotropic spatial curvature. Two difficulties arise in
comparison to the same computation in isotropic cosmologies. First, the two
tensor polarizations do not behave as a spin-2 field, but rather as the spin-0
and spin-1 irreducible components of a symmetric, traceless and transverse
tensor field, each with its own dynamics. Second, because metric perturbations
are algebraically coupled, one cannot ignore scalar and vector modes and focus
just on tensors --- even if one is only interested in the latter --- under the
penalty of obtaining the wrong equations of motion. We illustrate our results
by finding analytical solutions and evaluating the power-spectra of tensor
polarizations in a radiation dominated universe. We conclude with some comments
on how these models could be constrained with future experiments on CMB
polarization.
| [
{
"created": "Thu, 31 Aug 2017 13:42:08 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Nov 2017 18:53:48 GMT",
"version": "v2"
}
] | 2017-11-17 | [
[
"Franco",
"Felipe O.",
""
],
[
"Pereira",
"Thiago S.",
""
]
] | Besides expanding anisotropically, the universe can also be anisotropic at the level of its (spatial) curvature. In particular, models with anisotropic curvature and isotropic expansion leads both to a $\Lambda$CDM-like phenomenology and to an isotropic and homogeneous CMB at the background level. Thus, they offer an interesting and viable example where the cosmological principle does not follow from the isotropy of observational data. In this paper we extract the linear dynamics of tensor perturbations in two classes of cosmologies with anisotropic spatial curvature. Two difficulties arise in comparison to the same computation in isotropic cosmologies. First, the two tensor polarizations do not behave as a spin-2 field, but rather as the spin-0 and spin-1 irreducible components of a symmetric, traceless and transverse tensor field, each with its own dynamics. Second, because metric perturbations are algebraically coupled, one cannot ignore scalar and vector modes and focus just on tensors --- even if one is only interested in the latter --- under the penalty of obtaining the wrong equations of motion. We illustrate our results by finding analytical solutions and evaluating the power-spectra of tensor polarizations in a radiation dominated universe. We conclude with some comments on how these models could be constrained with future experiments on CMB polarization. |
2002.08875 | Bob Osano | Bob Osano | Evolution of Cosmological Total Energy Density and Transient Periods in
Cosmology | 13 pages , 1 figure. Submitted to IJMPD | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The evolution of the Universe is traditionally examined by monitoring how its
material content evolves as it expands. This model of an isolated system is
expressed as the equation of motion of the bulk but segmented into different
epochs. In particular, the evolution of the {\it
$Friedmann-Lema\hat{i}tre-Robertson - Walker$} (FRLW) Universe is separated
into different epochs that are characterised by the dynamics of whichever
mass-energy density constituent is dominant at the time. The standard analysis
of the evolution of the Universe in a particular epoch often considers the
evolution of the dominant energy density only, disregarding all others. Whereas
this represents the limiting case, in principle the contributions from others
cannot always be ignored particularly in the vicinity of the equality of the
various competing mass-energy densities or the transition periods between
epochs. We examine the evolution of the total energy density rather than
individual energy densities during the different epochs. We find that taking
into account the contributions from the various constituents lead to a broader
range of possible evolution histories which enriches the standard picture.
| [
{
"created": "Thu, 20 Feb 2020 17:24:14 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Mar 2021 15:16:50 GMT",
"version": "v2"
},
{
"created": "Sun, 2 Jun 2024 09:33:39 GMT",
"version": "v3"
}
] | 2024-06-04 | [
[
"Osano",
"Bob",
""
]
] | The evolution of the Universe is traditionally examined by monitoring how its material content evolves as it expands. This model of an isolated system is expressed as the equation of motion of the bulk but segmented into different epochs. In particular, the evolution of the {\it $Friedmann-Lema\hat{i}tre-Robertson - Walker$} (FRLW) Universe is separated into different epochs that are characterised by the dynamics of whichever mass-energy density constituent is dominant at the time. The standard analysis of the evolution of the Universe in a particular epoch often considers the evolution of the dominant energy density only, disregarding all others. Whereas this represents the limiting case, in principle the contributions from others cannot always be ignored particularly in the vicinity of the equality of the various competing mass-energy densities or the transition periods between epochs. We examine the evolution of the total energy density rather than individual energy densities during the different epochs. We find that taking into account the contributions from the various constituents lead to a broader range of possible evolution histories which enriches the standard picture. |
1507.05424 | Francesca Vidotto | Aurelien Barrau, Boris Bolliet, Francesca Vidotto, Celine Weimer | Phenomenology of bouncing black holes in quantum gravity: a closer look | 8 pages, 8 figures | JCAP02(2016)022 | 10.1088/1475-7516/2016/02/022 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was recently shown that black holes could be bouncing stars as a
consequence of quantum gravity. We investigate the astrophysical signals
implied by this hypothesis, focusing on primordial black holes. We consider
different possible bounce times and study the integrated diffuse emission.
| [
{
"created": "Mon, 20 Jul 2015 09:22:22 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Aug 2015 16:27:30 GMT",
"version": "v2"
},
{
"created": "Fri, 19 Feb 2016 11:03:31 GMT",
"version": "v3"
}
] | 2016-02-22 | [
[
"Barrau",
"Aurelien",
""
],
[
"Bolliet",
"Boris",
""
],
[
"Vidotto",
"Francesca",
""
],
[
"Weimer",
"Celine",
""
]
] | It was recently shown that black holes could be bouncing stars as a consequence of quantum gravity. We investigate the astrophysical signals implied by this hypothesis, focusing on primordial black holes. We consider different possible bounce times and study the integrated diffuse emission. |
1410.8787 | Daniel Katz | Daniel Katz | Recombination of H and He in Yang-Mills Gravity | null | International Journal of Modern Physics A, v30, 1550119 (2015) | 10.1142/S0217751X15501195 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate some aspects of the thermal history of the early universe
according to Yang-Mills Gravity (YMG); a gauge theory of gravity set in flat
spacetime. Specifically, equations for the ionization fractions of hydrogen and
singly ionized helium during the recombination epoch are deduced analytically
and then solved numerically. By considering several approximations we find that
the presence of primordial helium and its interaction with Lyman series photons
has a much stronger effect on the overall free electron density in YMG than it
does in the standard, General Relativity (GR) based, model. Compared to the
standard model recombination happens over a much larger range of temperatures,
although there is still a very sharp temperature of last scattering around 2000
K. Since the ionization history of the universe is not directly observable we
discuss how one may use it to predict the CMB power spectrum and thus test YMG.
This topic will be explored in detail in an upcoming paper.
| [
{
"created": "Fri, 31 Oct 2014 16:02:33 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Jun 2015 17:49:34 GMT",
"version": "v2"
}
] | 2015-06-29 | [
[
"Katz",
"Daniel",
""
]
] | We investigate some aspects of the thermal history of the early universe according to Yang-Mills Gravity (YMG); a gauge theory of gravity set in flat spacetime. Specifically, equations for the ionization fractions of hydrogen and singly ionized helium during the recombination epoch are deduced analytically and then solved numerically. By considering several approximations we find that the presence of primordial helium and its interaction with Lyman series photons has a much stronger effect on the overall free electron density in YMG than it does in the standard, General Relativity (GR) based, model. Compared to the standard model recombination happens over a much larger range of temperatures, although there is still a very sharp temperature of last scattering around 2000 K. Since the ionization history of the universe is not directly observable we discuss how one may use it to predict the CMB power spectrum and thus test YMG. This topic will be explored in detail in an upcoming paper. |
1402.3258 | Joachim Frieben | Joachim Frieben, Luciano Rezzolla | Distortion of neutron stars with a toroidal magnetic field | 3 pages, 2 figures, to appear in the Proceedings of the 13th Marcel
Grossmann Meeting held in Stockholm 1-7 July, 2012, based on arXiv:1207.4035.
Updated to final published version | null | 10.1142/9789814623995_0447 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Models of rotating relativistic stars with a toroidal magnetic field have
been computed for a sample of eight equations of state of cold dense matter.
Non-rotating models admit important levels of magnetization and quadrupole
distortion accompanied by a seemingly unlimited growth in size. Rotating models
reach the mass-shedding limit at smaller angular velocities than in the
non-magnetized case according to the larger circumferential equatorial radius
induced by the magnetic field. Moreover, they can be classified as
prolate-prolate, oblate-prolate, or oblate-oblate with respect to surface
deformation and quadrupole distortion. Simple expressions for surface and
quadrupole deformation are provided that are valid up to magnetar field
strengths and rapid rotation.
| [
{
"created": "Thu, 13 Feb 2014 19:15:01 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Sep 2014 17:44:28 GMT",
"version": "v2"
}
] | 2015-06-18 | [
[
"Frieben",
"Joachim",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | Models of rotating relativistic stars with a toroidal magnetic field have been computed for a sample of eight equations of state of cold dense matter. Non-rotating models admit important levels of magnetization and quadrupole distortion accompanied by a seemingly unlimited growth in size. Rotating models reach the mass-shedding limit at smaller angular velocities than in the non-magnetized case according to the larger circumferential equatorial radius induced by the magnetic field. Moreover, they can be classified as prolate-prolate, oblate-prolate, or oblate-oblate with respect to surface deformation and quadrupole distortion. Simple expressions for surface and quadrupole deformation are provided that are valid up to magnetar field strengths and rapid rotation. |
1412.8371 | Giuseppe Fanizza | G. Fanizza, L. Tedesco | Inhomogeneous and anisotropic Universe and apparent acceleration | 9 pages, 1 figure. Accepted for pubblication on Physical Review D | Phys.Rev. D91 (2015) 023006 | 10.1103/PhysRevD.91.023006 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we introduce a LTB-Bianchi I (plane symmetric) model of
Universe. We study and solve Einstein field equations. We investigate the
effects of such model of Universe in particular these results are important in
understanding the effect of the combined presence of an inhomogeneous and
anisotropic Universe. The observational magnitude-redshift data deviated from
UNION 2 catalog has been analyzed in the framework of this LTB-anisotropic
Universe and the fit has been achieved without the inclusion of any dark
energy.
| [
{
"created": "Tue, 23 Dec 2014 16:38:04 GMT",
"version": "v1"
}
] | 2015-01-28 | [
[
"Fanizza",
"G.",
""
],
[
"Tedesco",
"L.",
""
]
] | In this paper we introduce a LTB-Bianchi I (plane symmetric) model of Universe. We study and solve Einstein field equations. We investigate the effects of such model of Universe in particular these results are important in understanding the effect of the combined presence of an inhomogeneous and anisotropic Universe. The observational magnitude-redshift data deviated from UNION 2 catalog has been analyzed in the framework of this LTB-anisotropic Universe and the fit has been achieved without the inclusion of any dark energy. |
2109.08886 | Marcello Ortaggio | David Koko\v{s}ka, Marcello Ortaggio | Static and radiating dyonic black holes coupled to conformally invariant
electrodynamics in higher dimensions | 25 pages, 1 table, 4 figures. v2: a few comments and references
added, results unchanged | Phys. Rev. D 104, 124051 (2021) | 10.1103/PhysRevD.104.124051 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the complete family of (aligned) Robinson-Trautman spacetimes
sourced by conformally invariant non-linear electrodynamics in $D$ dimensions
in the presence of an arbitrary cosmological constant. After presenting general
features of the solutions (which exist only in even dimensions), we discuss in
more detail some particular subclasses. Static metrics contain dyonic black
holes with various possible horizon geometries (K\"ahler if there is a magnetic
field, including flat branes) and different asymptotics. In addition, there
exist also time-dependent solutions (not possible in the $D>4$ linear theory)
which may represent white hole evaporation by emission of electromagnetic
radiation (or a time-reversed picture of black hole formation). For those, we
comment on a quasi-local characterization of possible past horizons. Finally,
we briefly discuss the special case of stealth solutions. In an appendix, a
theory-independent result on the redundancy of the gravity part of the field
equations for Robinson-Trautman spacetimes is further obtained.
| [
{
"created": "Sat, 18 Sep 2021 09:10:55 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Dec 2021 17:59:14 GMT",
"version": "v2"
}
] | 2021-12-24 | [
[
"Kokoška",
"David",
""
],
[
"Ortaggio",
"Marcello",
""
]
] | We investigate the complete family of (aligned) Robinson-Trautman spacetimes sourced by conformally invariant non-linear electrodynamics in $D$ dimensions in the presence of an arbitrary cosmological constant. After presenting general features of the solutions (which exist only in even dimensions), we discuss in more detail some particular subclasses. Static metrics contain dyonic black holes with various possible horizon geometries (K\"ahler if there is a magnetic field, including flat branes) and different asymptotics. In addition, there exist also time-dependent solutions (not possible in the $D>4$ linear theory) which may represent white hole evaporation by emission of electromagnetic radiation (or a time-reversed picture of black hole formation). For those, we comment on a quasi-local characterization of possible past horizons. Finally, we briefly discuss the special case of stealth solutions. In an appendix, a theory-independent result on the redundancy of the gravity part of the field equations for Robinson-Trautman spacetimes is further obtained. |
2006.12312 | Ozay Gurtug | M. Mangut, O. Gurtug | Quantum Probe of Time-like Naked Singularities for Electrically and
Magnetically Charged Black Holes in a Model of Nonlinear Electrodynamics | 10 pages, 1 figure, accepted for publication in Modern Physics
Letters A (MPLA) on June 21, 2020 | null | 10.1142/S0217732320502429 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The time-like naked singularities of the electrically and magnetically
charged black hole solutions obtained in a model of nonlinear electrodynamics
proposed by Kruglov is investigated within the framework of quantum mechanics.
In view of quantum mechanics, the space-time is quantum regular provided that
the time evolution of the test quantum wave packet uniquely propagates on an
underlying background. Rigorous calculations have shown that when the
singularity is probed with specific quantum wave/particle modes, the quantum
wave operator turns out to be essentially self-adjoint. Thus, the time
evolution of the quantum wave/particle is determined uniquely. In the case of
electrically charged black hole background, the unique evolution is restricted
to s-wave only. For the two different magnetically charged black hole
backgrounds, the time evolution is restricted to different modes for each case.
| [
{
"created": "Mon, 22 Jun 2020 14:49:52 GMT",
"version": "v1"
}
] | 2020-08-04 | [
[
"Mangut",
"M.",
""
],
[
"Gurtug",
"O.",
""
]
] | The time-like naked singularities of the electrically and magnetically charged black hole solutions obtained in a model of nonlinear electrodynamics proposed by Kruglov is investigated within the framework of quantum mechanics. In view of quantum mechanics, the space-time is quantum regular provided that the time evolution of the test quantum wave packet uniquely propagates on an underlying background. Rigorous calculations have shown that when the singularity is probed with specific quantum wave/particle modes, the quantum wave operator turns out to be essentially self-adjoint. Thus, the time evolution of the quantum wave/particle is determined uniquely. In the case of electrically charged black hole background, the unique evolution is restricted to s-wave only. For the two different magnetically charged black hole backgrounds, the time evolution is restricted to different modes for each case. |
1709.10348 | Andrea Giusti | Andrea Giusti | Horizon Quantum Mechanics: spherically symmetric and rotating sources | 5 pages, no figures, Talk presented at the 3rd Karl Schwarzschild
Meeting (2017) | Journal of Physics: Conference Series 942 (2017), 012013 | 10.1088/1742-6596/942/1/012013 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we discuss some mathematical aspects of the horizon
wave-function formalism, also known in the literature as horizon quantum
mechanics. In particular, first we review the structure of both the global and
local formalism for static spherically symmetric sources. Then, we present an
extension of the global analysis for rotating black holes and we also point out
some technical difficulties that arise while attempting the local analysis for
non-spherically symmetric sources.
| [
{
"created": "Fri, 29 Sep 2017 11:49:53 GMT",
"version": "v1"
}
] | 2018-01-17 | [
[
"Giusti",
"Andrea",
""
]
] | In this paper we discuss some mathematical aspects of the horizon wave-function formalism, also known in the literature as horizon quantum mechanics. In particular, first we review the structure of both the global and local formalism for static spherically symmetric sources. Then, we present an extension of the global analysis for rotating black holes and we also point out some technical difficulties that arise while attempting the local analysis for non-spherically symmetric sources. |
1507.05886 | Massimiliano Rinaldi | Massimiliano Rinaldi | Quasi Scale-Invariant Inflationary Attractors | Contribution to the Proceedings of the 14th Marcel Grossmann Meeting,
Rome 2015 | null | 10.1142/9789813226609_0096 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that pure quadratic gravity with quantum loop corrections yields a
viable inflationary scenario. We also show that a large family of models in the
Jordan frame, with softly-broken scale invariance, corresponds to the same
theory with linear inflaton potential in the Einstein frame. It follows that
all these quasi scale-invariant models have the same relation between the
tensor-to-scalar ratio and the scalar spectral index, which is also consistent
with the current data. Thus, they form a family of attractors, which is sharply
distinct from the recently discovered $\alpha$-attractors of Kallosh, Linde et
al.
| [
{
"created": "Tue, 21 Jul 2015 16:02:36 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Dec 2015 14:21:58 GMT",
"version": "v2"
}
] | 2017-11-30 | [
[
"Rinaldi",
"Massimiliano",
""
]
] | We show that pure quadratic gravity with quantum loop corrections yields a viable inflationary scenario. We also show that a large family of models in the Jordan frame, with softly-broken scale invariance, corresponds to the same theory with linear inflaton potential in the Einstein frame. It follows that all these quasi scale-invariant models have the same relation between the tensor-to-scalar ratio and the scalar spectral index, which is also consistent with the current data. Thus, they form a family of attractors, which is sharply distinct from the recently discovered $\alpha$-attractors of Kallosh, Linde et al. |
2302.01726 | Filipe Mena | Christian L\"ubbe, Filipe C. Mena | Asymptotic structure and stability of spatially homogeneous space-times
with a positive cosmological constant | 43 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the future asymptotics of spatially homogeneous space-times
with a positive cosmological constant by using and further developing geometric
conformal methods in General Relativity. For a large class of source fields,
including fluids with anisotropic stress, we prove that the space-times are
future asymptotically simple and geometrically conformally regular. We use that
result in order to show the global conformal regularity of the Einstein-Maxwell
system as well as the Einstein-radiation, Einstein-dust, massless
Einstein-Vlasov and particular Einstein-scalar field systems for Bianchi
space-times. Taking into account previous results, this implies the future
non-linear stability of some of those space-times in the sense that, for small
perturbations, the space-times approach locally the de Sitter solution
asymptotically in time. This extends some cosmic no-hair theorems to almost
spatially homogeneous space-times. However, we find that the conformal Einstein
field equations preserve the Bianchi type even at conformal infinity, so the
resulting asymptotic space-times have conformal hair.
| [
{
"created": "Fri, 3 Feb 2023 13:37:02 GMT",
"version": "v1"
}
] | 2023-02-06 | [
[
"Lübbe",
"Christian",
""
],
[
"Mena",
"Filipe C.",
""
]
] | We investigate the future asymptotics of spatially homogeneous space-times with a positive cosmological constant by using and further developing geometric conformal methods in General Relativity. For a large class of source fields, including fluids with anisotropic stress, we prove that the space-times are future asymptotically simple and geometrically conformally regular. We use that result in order to show the global conformal regularity of the Einstein-Maxwell system as well as the Einstein-radiation, Einstein-dust, massless Einstein-Vlasov and particular Einstein-scalar field systems for Bianchi space-times. Taking into account previous results, this implies the future non-linear stability of some of those space-times in the sense that, for small perturbations, the space-times approach locally the de Sitter solution asymptotically in time. This extends some cosmic no-hair theorems to almost spatially homogeneous space-times. However, we find that the conformal Einstein field equations preserve the Bianchi type even at conformal infinity, so the resulting asymptotic space-times have conformal hair. |
gr-qc/0611076 | Ettore Minguzzi | E. Minguzzi | Towards a closed differential aging formula in special relativity | Latex2e, 6 pages, 1 figure, uses psfrag. Contribution to the
Proceedings of The Spanish Relativity Meeting (ERE 2006), Palma de Mallorca,
Spain September 4-8, 2006 | J.Phys.Conf.Ser.66:012020,2007 | 10.1088/1742-6596/66/1/012020 | null | gr-qc | null | It is well known that the Lorentzian length of a timelike curve in Minkowski
spacetime is smaller than the Lorentzian length of the geodesic connecting its
initial and final endpoints. The difference is known as the 'differential
aging' and its calculation in terms of the proper acceleration history of the
timelike curve would provide an important tool for the autonomous spacetime
navigation of non-inertial observers. I give a solution in 3+1 dimensions which
holds whenever the acceleration is decomposed with respect to a lightlike
transported frame (lightlike transport will be defined), the analogous and more
natural problem for a Fermi-Walker decomposition being still open.
| [
{
"created": "Tue, 14 Nov 2006 15:24:12 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Minguzzi",
"E.",
""
]
] | It is well known that the Lorentzian length of a timelike curve in Minkowski spacetime is smaller than the Lorentzian length of the geodesic connecting its initial and final endpoints. The difference is known as the 'differential aging' and its calculation in terms of the proper acceleration history of the timelike curve would provide an important tool for the autonomous spacetime navigation of non-inertial observers. I give a solution in 3+1 dimensions which holds whenever the acceleration is decomposed with respect to a lightlike transported frame (lightlike transport will be defined), the analogous and more natural problem for a Fermi-Walker decomposition being still open. |
1706.06863 | Christian Corda Prof. | I. Licata, H. Moradpour and C. Corda | The commutator algebra of covariant derivative as general framework for
extended gravity. The Rastall theory case and the role of the torsion | 20 pages, final version. Invited short review published in IJGMMP | International Journal of Geometric Methods in Modern Physics, Vol.
14 (2017) 1730003 | 10.1142/S0219887817300033 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this short review, we discuss the approach of the commutator algebra of
covariant derivative to analyse the gravitational theories, starting from the
standard Einstein's general theory of relativity and focusing on the Rastall
theory. After that, we discuss the important role of the torsion in this
mathematical framework. In the Appendix of the paper we analyse the importance
of the nascent gravitational wave astronomy as a tool to discriminate among the
general theory of relativity and alternative theories of gravity.
| [
{
"created": "Sun, 18 Jun 2017 14:58:58 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Aug 2017 16:00:02 GMT",
"version": "v2"
},
{
"created": "Wed, 13 Sep 2017 14:25:25 GMT",
"version": "v3"
}
] | 2017-09-14 | [
[
"Licata",
"I.",
""
],
[
"Moradpour",
"H.",
""
],
[
"Corda",
"C.",
""
]
] | In this short review, we discuss the approach of the commutator algebra of covariant derivative to analyse the gravitational theories, starting from the standard Einstein's general theory of relativity and focusing on the Rastall theory. After that, we discuss the important role of the torsion in this mathematical framework. In the Appendix of the paper we analyse the importance of the nascent gravitational wave astronomy as a tool to discriminate among the general theory of relativity and alternative theories of gravity. |
1512.02028 | Cetin Senturk | Metin Gurses, Cetin Senturk | Godel Type Metrics in Einstein-Aether Theory II: Nonflat Background in
Arbitrary Dimensions | 18 pages, no figures, matches the published version | Gen. Rel. Grav. 48 (2016) 63 | 10.1007/s10714-016-2058-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was previously proved that the G\"{o}del-type metrics with flat
three-dimensional background metric solve exactly the field equations of the
Einstein-Aether theory in four dimensions. We generalize this result by showing
that the stationary G\"{o}del-type metrics with nonflat background in $D$
dimensions solve exactly the field equations of the Einstein-Aether theory. The
reduced field equations are the $(D-1)$-dimensional Euclidean Ricci-flat and
the $(D-1)$-dimensional source-free Maxwell equations, and the parameters of
the theory are left free except $c_{1}-c_{3}=1$. We give a method to produce
exact solutions of the Einstein-Aether theory from the G\"{o}del-type metrics
in $D$ dimensions. By using this method, we present explicit exact solutions to
the theory by considering the particular cases: ($D-1$)-dimensional Euclidean
flat, conformally flat, and Tangherlini backgrounds.
| [
{
"created": "Mon, 7 Dec 2015 13:07:34 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Apr 2016 11:54:45 GMT",
"version": "v2"
}
] | 2016-04-19 | [
[
"Gurses",
"Metin",
""
],
[
"Senturk",
"Cetin",
""
]
] | It was previously proved that the G\"{o}del-type metrics with flat three-dimensional background metric solve exactly the field equations of the Einstein-Aether theory in four dimensions. We generalize this result by showing that the stationary G\"{o}del-type metrics with nonflat background in $D$ dimensions solve exactly the field equations of the Einstein-Aether theory. The reduced field equations are the $(D-1)$-dimensional Euclidean Ricci-flat and the $(D-1)$-dimensional source-free Maxwell equations, and the parameters of the theory are left free except $c_{1}-c_{3}=1$. We give a method to produce exact solutions of the Einstein-Aether theory from the G\"{o}del-type metrics in $D$ dimensions. By using this method, we present explicit exact solutions to the theory by considering the particular cases: ($D-1$)-dimensional Euclidean flat, conformally flat, and Tangherlini backgrounds. |
2206.00670 | Hongbo Cheng | Yuxuan Shi, Hongbo Cheng | The neutrino pair annihilation ($\nu\bar{\nu}\longrightarrow
e^{-}e^{+}$)around a massive source with an $f(R)$ global monopole | 4 figures | EPL(Europhysics Letters) 140(2022)49001 | 10.1209/0295-5075/aca0b9 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work we investigate the neutrino pair annihilation around a
gravitational object involving an $f(R)$ global monopole. We derive and
calculate the ratio $\frac{\dot{Q}}{\dot{Q_{Newt}}}$ meaning that the energy
deposition per unit time is over that in the Newtonian case. It is found that
the more deviation from general relativity leads more energy to set free from
the annihilation with greater ratio value. It should also be pointed out that
the existence of global monopole makes a sharp increase in the ratio
$\frac{\dot{Q}}{\dot{Q_{Newt}}}$, causing heavier gamma-ray burst. We also
discuss the derivative $\frac{d\dot{Q}}{dr}$ as a function of radius $r$ of
star to show the similar characters that the considerable modification of
Einstein's gravity and the global monopole with unified theory order will raise
the amount of $\frac{d\dot{Q}}{dr}$ greatly. The stellar body with $f(R)$
global monopole can be well qualified as a source of gamma-ray bursts.
Moreover, we can select the factor $\psi_{0}$ to be comparable with the
accelerating universe while regulate the parameter $\eta$ for the global
monopole in order to make the ratio curves to coincide with the results from
astronomy. It is possible to probe the monopole from astrophysical
observations.
| [
{
"created": "Wed, 1 Jun 2022 13:32:58 GMT",
"version": "v1"
}
] | 2022-12-06 | [
[
"Shi",
"Yuxuan",
""
],
[
"Cheng",
"Hongbo",
""
]
] | In this work we investigate the neutrino pair annihilation around a gravitational object involving an $f(R)$ global monopole. We derive and calculate the ratio $\frac{\dot{Q}}{\dot{Q_{Newt}}}$ meaning that the energy deposition per unit time is over that in the Newtonian case. It is found that the more deviation from general relativity leads more energy to set free from the annihilation with greater ratio value. It should also be pointed out that the existence of global monopole makes a sharp increase in the ratio $\frac{\dot{Q}}{\dot{Q_{Newt}}}$, causing heavier gamma-ray burst. We also discuss the derivative $\frac{d\dot{Q}}{dr}$ as a function of radius $r$ of star to show the similar characters that the considerable modification of Einstein's gravity and the global monopole with unified theory order will raise the amount of $\frac{d\dot{Q}}{dr}$ greatly. The stellar body with $f(R)$ global monopole can be well qualified as a source of gamma-ray bursts. Moreover, we can select the factor $\psi_{0}$ to be comparable with the accelerating universe while regulate the parameter $\eta$ for the global monopole in order to make the ratio curves to coincide with the results from astronomy. It is possible to probe the monopole from astrophysical observations. |
1807.00346 | Emmanuil Saridakis | Emmanuel N. Saridakis, Shreya Banerjee, R. Myrzakulov | Bounce and cyclic cosmology in new gravitational scalar-tensor theories | 9 pages, 8 figures | Phys. Rev. D 98, 063513 (2018) | 10.1103/PhysRevD.98.063513 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the bounce and cyclicity realization in the framework of new
gravitational scalar-tensor theories. In these theories the Lagrangian contains
the Ricci scalar and its first and second derivatives, in a specific
combination that makes them free of ghosts, and transformed into the Einstein
frame they are proved to be a subclass of bi-scalar extensions of general
relativity. We present analytical expressions for the bounce requirements, and
we examine the necessary qualitative behavior of the involved functions that
can give rise to a given scale factor. Having in mind these qualitative forms,
we reverse the procedure and we construct suitable simple Lagrangian functions
that can give rise to a bounce or cyclic scale factor.
| [
{
"created": "Sun, 1 Jul 2018 15:51:00 GMT",
"version": "v1"
}
] | 2018-09-19 | [
[
"Saridakis",
"Emmanuel N.",
""
],
[
"Banerjee",
"Shreya",
""
],
[
"Myrzakulov",
"R.",
""
]
] | We study the bounce and cyclicity realization in the framework of new gravitational scalar-tensor theories. In these theories the Lagrangian contains the Ricci scalar and its first and second derivatives, in a specific combination that makes them free of ghosts, and transformed into the Einstein frame they are proved to be a subclass of bi-scalar extensions of general relativity. We present analytical expressions for the bounce requirements, and we examine the necessary qualitative behavior of the involved functions that can give rise to a given scale factor. Having in mind these qualitative forms, we reverse the procedure and we construct suitable simple Lagrangian functions that can give rise to a bounce or cyclic scale factor. |
1212.5476 | Irene Brito | Irene Brito, M. F. A. da Silva, Filipe C. Mena, N. O. Santos | Conformally flat sources for the Linet-Tian spacetime | Accepted for publication in General Relativity and Gravitation | null | 10.1007/s10714-012-1485-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the matching, across cylindrical surfaces, of static
cylindrically symmetric conformally flat spacetimes with a cosmological
constant $\Lambda$, satisfying regularity conditions at the axis, to an
exterior Linet-Tian spacetime. We prove that for $\Lambda\leq 0$ such matching
is impossible. On the other hand, we show through simple examples that the
matching is possible for $\Lambda>0$. We suggest a physical argument that might
explain these results.
| [
{
"created": "Fri, 21 Dec 2012 15:09:20 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Dec 2012 18:00:02 GMT",
"version": "v2"
}
] | 2013-01-01 | [
[
"Brito",
"Irene",
""
],
[
"da Silva",
"M. F. A.",
""
],
[
"Mena",
"Filipe C.",
""
],
[
"Santos",
"N. O.",
""
]
] | We investigate the matching, across cylindrical surfaces, of static cylindrically symmetric conformally flat spacetimes with a cosmological constant $\Lambda$, satisfying regularity conditions at the axis, to an exterior Linet-Tian spacetime. We prove that for $\Lambda\leq 0$ such matching is impossible. On the other hand, we show through simple examples that the matching is possible for $\Lambda>0$. We suggest a physical argument that might explain these results. |
gr-qc/9405005 | Paul Henry Casper | Bruce Allen and Paul Casper | A Closed-Form Expression for the Gravitational Radiation Rate from
Cosmic Strings | 29 pages TeX, 16 figures and computer C-code available via anonymous
ftp from directory pub/pcasper at alpha1.csd.uwm.edu, WISC-MILW-94-TH-10,
(section 7 has been expanded, two figures added, and minor grammatical
changes made.) | Phys.Rev. D50 (1994) 2496-2518 | 10.1103/PhysRevD.50.2496 | null | gr-qc astro-ph | null | We present a new formula for the rate at which cosmic strings lose energy
into gravitational radiation, valid for all piecewise-linear cosmic string
loops. At any time, such a loop is composed of $N$ straight segments, each of
which has constant velocity. Any cosmic string loop can be arbitrarily-well
approximated by a piecewise-linear loop with $N$ sufficiently large. The
formula is a sum of $O(N^4)$ polynomial and log terms, and is exact when the
effects of gravitational back-reaction are neglected. For a given loop, the
large number of terms makes evaluation ``by hand" impractical, but a computer
or symbolic manipulator yields accurate results. The formula is more accurate
and convenient than previous methods for finding the gravitational radiation
rate, which require numerical evaluation of a four-dimensional integral for
each term in an infinite sum. It also avoids the need to estimate the
contribution from the tail of the infinite sum. The formula has been tested
against all previously published radiation rates for different loop
configurations. In the cases where discrepancies were found, they were due to
errors in the published work. We have isolated and corrected both the analytic
and numerical errors in these cases. To assist future work in this area, a
small catalog of results for some simple loop shapes is provided.
| [
{
"created": "Mon, 2 May 1994 19:06:08 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Jul 1994 19:09:44 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Allen",
"Bruce",
""
],
[
"Casper",
"Paul",
""
]
] | We present a new formula for the rate at which cosmic strings lose energy into gravitational radiation, valid for all piecewise-linear cosmic string loops. At any time, such a loop is composed of $N$ straight segments, each of which has constant velocity. Any cosmic string loop can be arbitrarily-well approximated by a piecewise-linear loop with $N$ sufficiently large. The formula is a sum of $O(N^4)$ polynomial and log terms, and is exact when the effects of gravitational back-reaction are neglected. For a given loop, the large number of terms makes evaluation ``by hand" impractical, but a computer or symbolic manipulator yields accurate results. The formula is more accurate and convenient than previous methods for finding the gravitational radiation rate, which require numerical evaluation of a four-dimensional integral for each term in an infinite sum. It also avoids the need to estimate the contribution from the tail of the infinite sum. The formula has been tested against all previously published radiation rates for different loop configurations. In the cases where discrepancies were found, they were due to errors in the published work. We have isolated and corrected both the analytic and numerical errors in these cases. To assist future work in this area, a small catalog of results for some simple loop shapes is provided. |
1904.12153 | M. Abdul Wasay | Asma Bashir, Benjamin Koch, Muhammad Abdul Wasay | Geometric Description of Schr\"{o}dinger Equation in Finsler and Funk
Geometry | 9 pages, to appear in IJGMMP | null | 10.1142/S0219887819500981 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a system of $n$ non-relativistic spinless bosons, we show by using a set
of suitable matching conditions that the quantum equations in the pilot-wave
limit can be translated into a geometric language for a Finslerian manifold. We
further link these equations to Euclidean timelike relative Funk geometry and
show that the two different metrics in both of these geometric frameworks lead
to the same coupling.
| [
{
"created": "Sat, 27 Apr 2019 12:55:55 GMT",
"version": "v1"
}
] | 2019-04-30 | [
[
"Bashir",
"Asma",
""
],
[
"Koch",
"Benjamin",
""
],
[
"Wasay",
"Muhammad Abdul",
""
]
] | For a system of $n$ non-relativistic spinless bosons, we show by using a set of suitable matching conditions that the quantum equations in the pilot-wave limit can be translated into a geometric language for a Finslerian manifold. We further link these equations to Euclidean timelike relative Funk geometry and show that the two different metrics in both of these geometric frameworks lead to the same coupling. |
2008.00105 | Roberto Ivan Cabrera Munguia Dr. | I. Cabrera-Munguia | Corotating dyonic binary black holes | 12 pages, 1 figure, published version | Physics Letters B 811 (2020) 135945 | 10.1016/j.physletb.2020.135945 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is dedicated to derive and study binary systems of identical
corotating dyonic black holes separated by a massless strut -- two 5-parametric
corotating binary black hole models endowed with both electric and magnetic
charges-- where the dyonic black holes carrying equal/opposite electromagnetic
charges in the first/second model satisfy the extended Smarr formula for the
mass including the magnetic charge as a fourth conserved parameter.
| [
{
"created": "Fri, 31 Jul 2020 22:59:37 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Nov 2020 05:17:50 GMT",
"version": "v2"
}
] | 2020-11-18 | [
[
"Cabrera-Munguia",
"I.",
""
]
] | This paper is dedicated to derive and study binary systems of identical corotating dyonic black holes separated by a massless strut -- two 5-parametric corotating binary black hole models endowed with both electric and magnetic charges-- where the dyonic black holes carrying equal/opposite electromagnetic charges in the first/second model satisfy the extended Smarr formula for the mass including the magnetic charge as a fourth conserved parameter. |
2108.00423 | Shahab Shahidi | Shahab Shahidi | Cosmological implications of Rastall-$f(R)$ theory | 10 pages, 5 figures | Phys. Rev. D 104, 084033 (2021) | 10.1103/PhysRevD.104.084033 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Cosmological implications of a generalized Rastall theory where the
non-conservation equation is promoted to accepts arbitrary functions of the
Ricci scalar is considered. We have obtain the model parameters of the
power-law ansatz $f\propto R^\eta$, using $H_0$ and $f\sigma_8$ data sets and
show that the generalized Rastall theory could satisfy observational data. The
dynamical analysis of the model shows that for $\eta\in(0,1)$, the dust
dominated fixed point is lost and as a result the parameter range of $\eta$
should be restricted to $\eta\geq1$. We will also show that the genralized
Rastall theory will predict more accelerating universe with larger radius,
compared to the $\Lambda$CDM model.
| [
{
"created": "Sun, 1 Aug 2021 10:24:17 GMT",
"version": "v1"
}
] | 2021-10-13 | [
[
"Shahidi",
"Shahab",
""
]
] | Cosmological implications of a generalized Rastall theory where the non-conservation equation is promoted to accepts arbitrary functions of the Ricci scalar is considered. We have obtain the model parameters of the power-law ansatz $f\propto R^\eta$, using $H_0$ and $f\sigma_8$ data sets and show that the generalized Rastall theory could satisfy observational data. The dynamical analysis of the model shows that for $\eta\in(0,1)$, the dust dominated fixed point is lost and as a result the parameter range of $\eta$ should be restricted to $\eta\geq1$. We will also show that the genralized Rastall theory will predict more accelerating universe with larger radius, compared to the $\Lambda$CDM model. |
gr-qc/9710085 | Uwe Gunther | U. Guenther, A. Zhuk | Gravitational excitons from extra dimensions | 3 pages, Latex. To appear in the proceedings of the 8-th Marcel
Grossmann Meeting, 22-27 June 1997, Hebrew University, Jerusalem, Israel | null | null | MG8 | gr-qc | null | We study inhomogeneous multidimensional cosmological models with a higher
dimensional space-time manifold under dimensional reduction and show that small
inhomogeneous excitations of the scale factors of the internal spaces near
minima of effective potentials should be observable as massive scalar particles
(gravitational excitons) in the external space-time.
| [
{
"created": "Fri, 17 Oct 1997 16:28:35 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Guenther",
"U.",
""
],
[
"Zhuk",
"A.",
""
]
] | We study inhomogeneous multidimensional cosmological models with a higher dimensional space-time manifold under dimensional reduction and show that small inhomogeneous excitations of the scale factors of the internal spaces near minima of effective potentials should be observable as massive scalar particles (gravitational excitons) in the external space-time. |
2304.07621 | Kate Z. Yang | Kate Z.Yang, Jishnu Suresh, Giulia Cusin, Sharan Banagiri, Noelle
Feist, Vuk Mandic, Claudia Scarlata, Ioannis Michaloliakos | Measurement of the Cross-Correlation Angular Power Spectrum Between the
Stochastic Gravitational Wave Background and Galaxy Over-Density | 19 pages, 12 figures | the 15 August 2023 issue of Physical Review D (Vol. 108, No. 4) | 10.1103/PhysRevD.108.043025 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the cross-correlation between the stochastic gravitational-wave
background (SGWB) generated by binary black hole (BBH) mergers across the
universe and the distribution of galaxies across the sky. We use the
anisotropic SGWB measurement obtained using data from the third observing run
(O3) of Advanced LIGO detectors and galaxy over-density obtained from the Sloan
Digital Sky Survey (SDSS) spectroscopic catalog. We compute, for the first
time, the angular power spectrum of their cross-correlation. Instead of
integrating the SGWB across frequencies, we analyze the cross-correlation in 10
Hz wide SGWB frequency bands to study the frequency dependence of the
cross-correlation angular power spectrum. Finally, we compare the observed
cross-correlation to the spectra predicted by astrophysical models. We apply a
Bayesian formalism to explore the parameter space of the theoretical models,
and we set constraints on a set of (effective) astrophysical parameters
describing the galactic process of gravitational wave (GW) emission.
Parameterizing with a Gaussian function the astrophysical kernel describing the
local process of GW emission at galactic scales, we find the 95\% upper limit
on kernel amplitude to be $2.7 \times 10^{-32}$ erg cm$^{-3}$s$^{-1/3}$ when
ignoring the shot noise in the GW emission process, and $2.16 \times 10^{-32}$
erg cm$^{-3}$s$^{-1/3}$ when the shot noise is included in the analysis. As the
sensitivity of the LIGO-Virgo-KAGRA network improves, we expect to be able to
set more stringent bounds on this kernel function and constrain its parameters.
| [
{
"created": "Sat, 15 Apr 2023 19:35:47 GMT",
"version": "v1"
}
] | 2023-08-29 | [
[
"Yang",
"Kate Z.",
""
],
[
"Suresh",
"Jishnu",
""
],
[
"Cusin",
"Giulia",
""
],
[
"Banagiri",
"Sharan",
""
],
[
"Feist",
"Noelle",
""
],
[
"Mandic",
"Vuk",
""
],
[
"Scarlata",
"Claudia",
""
],
[
"Michaloliakos",
"Ioannis",
""
]
] | We study the cross-correlation between the stochastic gravitational-wave background (SGWB) generated by binary black hole (BBH) mergers across the universe and the distribution of galaxies across the sky. We use the anisotropic SGWB measurement obtained using data from the third observing run (O3) of Advanced LIGO detectors and galaxy over-density obtained from the Sloan Digital Sky Survey (SDSS) spectroscopic catalog. We compute, for the first time, the angular power spectrum of their cross-correlation. Instead of integrating the SGWB across frequencies, we analyze the cross-correlation in 10 Hz wide SGWB frequency bands to study the frequency dependence of the cross-correlation angular power spectrum. Finally, we compare the observed cross-correlation to the spectra predicted by astrophysical models. We apply a Bayesian formalism to explore the parameter space of the theoretical models, and we set constraints on a set of (effective) astrophysical parameters describing the galactic process of gravitational wave (GW) emission. Parameterizing with a Gaussian function the astrophysical kernel describing the local process of GW emission at galactic scales, we find the 95\% upper limit on kernel amplitude to be $2.7 \times 10^{-32}$ erg cm$^{-3}$s$^{-1/3}$ when ignoring the shot noise in the GW emission process, and $2.16 \times 10^{-32}$ erg cm$^{-3}$s$^{-1/3}$ when the shot noise is included in the analysis. As the sensitivity of the LIGO-Virgo-KAGRA network improves, we expect to be able to set more stringent bounds on this kernel function and constrain its parameters. |
1107.5693 | Etera R. Livine | Mait\'e Dupuis, Florian Girelli, Etera R. Livine | Spinors and Voros star-product for Group Field Theory: First Contact | 23 pages | null | 10.1103/PhysRevD.86.105034 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of non-commutative geometries, we develop a group Fourier
transform for the Lie group SU(2). Our method is based on the Schwinger
representation of the Lie algebra su(2) in terms of spinors. It allows us to
prove that the non-commutative R^3 space dual to the SU(2) group is in fact of
the Moyal-type and endowed with the Voros star-product when expressed in the
spinor variables. Finally, from the perspective of quantum gravity, we discuss
the application of these new tools to group field theories for spinfoam models
and their interpretation as non-commutative field theories with
quantum-deformed symmetries.
| [
{
"created": "Thu, 28 Jul 2011 12:12:10 GMT",
"version": "v1"
}
] | 2013-05-30 | [
[
"Dupuis",
"Maité",
""
],
[
"Girelli",
"Florian",
""
],
[
"Livine",
"Etera R.",
""
]
] | In the context of non-commutative geometries, we develop a group Fourier transform for the Lie group SU(2). Our method is based on the Schwinger representation of the Lie algebra su(2) in terms of spinors. It allows us to prove that the non-commutative R^3 space dual to the SU(2) group is in fact of the Moyal-type and endowed with the Voros star-product when expressed in the spinor variables. Finally, from the perspective of quantum gravity, we discuss the application of these new tools to group field theories for spinfoam models and their interpretation as non-commutative field theories with quantum-deformed symmetries. |
gr-qc/9803086 | Jun-ichirou Koga | Jun-ichirou Koga and Kei-ichi Maeda | Equivalence of black hole thermodynamics between a generalized theory of
gravity and the Einstein theory | 14 pages, no figures | Phys.Rev. D58 (1998) 064020 | 10.1103/PhysRevD.58.064020 | WU-AP/72/98 | gr-qc hep-th | null | We analyze black hole thermodynamics in a generalized theory of gravity whose
Lagrangian is an arbitrary function of the metric, the Ricci tensor and a
scalar field. We can convert the theory into the Einstein frame via a
"Legendre" transformation or a conformal transformation. We calculate
thermodynamical variables both in the original frame and in the Einstein frame,
following the Iyer--Wald definition which satisfies the first law of
thermodynamics. We show that all thermodynamical variables defined in the
original frame are the same as those in the Einstein frame, if the spacetimes
in both frames are asymptotically flat, regular and possess event horizons with
non-zero temperatures. This result may be useful to study whether the second
law is still valid in the generalized theory of gravity.
| [
{
"created": "Thu, 26 Mar 1998 18:10:06 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Koga",
"Jun-ichirou",
""
],
[
"Maeda",
"Kei-ichi",
""
]
] | We analyze black hole thermodynamics in a generalized theory of gravity whose Lagrangian is an arbitrary function of the metric, the Ricci tensor and a scalar field. We can convert the theory into the Einstein frame via a "Legendre" transformation or a conformal transformation. We calculate thermodynamical variables both in the original frame and in the Einstein frame, following the Iyer--Wald definition which satisfies the first law of thermodynamics. We show that all thermodynamical variables defined in the original frame are the same as those in the Einstein frame, if the spacetimes in both frames are asymptotically flat, regular and possess event horizons with non-zero temperatures. This result may be useful to study whether the second law is still valid in the generalized theory of gravity. |
1201.1448 | Valerio Faraoni | Valerio Faraoni (Bishop's University) | The correspondence between a scalar field and an effective perfect fluid | 5 pages, no figures, to appear in Phys. Rev. D | null | 10.1103/PhysRevD.85.024040 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is widely acknowledged that, for formal purposes, a minimally coupled
scalar field is equivalent to an effective perfect fluid with equation of state
determined by the scalar potential. This correspondence is not complete because
the Lagrangian densities P and -rho, which are equivalent for a perfect fluid,
are not equivalent for a minimally coupled scalar field. The exchange between
these two Lagrangian densities amounts to exchanging a canonical scalar field
with a phantom scalar field.
| [
{
"created": "Fri, 6 Jan 2012 16:39:50 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
]
] | It is widely acknowledged that, for formal purposes, a minimally coupled scalar field is equivalent to an effective perfect fluid with equation of state determined by the scalar potential. This correspondence is not complete because the Lagrangian densities P and -rho, which are equivalent for a perfect fluid, are not equivalent for a minimally coupled scalar field. The exchange between these two Lagrangian densities amounts to exchanging a canonical scalar field with a phantom scalar field. |
2104.12968 | Nami Uchikata | Nami Uchikata and Tatsuya Narikawa | Prospects for estimating parameters from gravitational waves of
superspinar binaries | null | Phys. Rev. D 104, 024059 (2021) | 10.1103/PhysRevD.104.024059 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To date, close to fifty presumed black hole binary mergers were observed by
the LIGO and Virgo detectors. The analyses have been done with an assumption
that these objects are black holes by limiting the spin prior to the Kerr
bound. However, the above assumption is not valid for superspinars, which have
the Kerr geometry but rotate beyond the Kerr bound. In this study, we
investigate whether and how the limited spin prior range causes a bias in
parameter estimation for superspinars if they are detected. To this end, we
estimate binary parameters of the simulated inspiral signals of the
gravitational waves of compact binaries by assuming that at least one component
of them is a superspinar. We have found that when the primary is a superspinar,
both mass and spin parameters are biased in parameter estimation due to the
limited spin prior range. In this case, the extended prior range is strongly
favored compared to the limited one. On the other hand, when the primary is a
black hole, we do not see much bias in parameter estimation due to the limited
spin prior range, even though the secondary is a superspinar. We also apply the
analysis to black hole binary merger events GW170608 and GW190814, which have a
long and loud inspiral signal. We do not see any preference of superspinars
from the model selection for both events. We conclude that the extension of the
spin prior range is necessary for accurate parameter estimation if highly
spinning primary objects are found, while it is difficult to identify
superspinars if they are only the secondary objects. Nevertheless, the bias in
parameter estimation of spin for the limited spin prior range can be a clue of
the existence of superspinars.
| [
{
"created": "Tue, 27 Apr 2021 04:18:48 GMT",
"version": "v1"
},
{
"created": "Thu, 6 May 2021 07:50:15 GMT",
"version": "v2"
}
] | 2021-08-04 | [
[
"Uchikata",
"Nami",
""
],
[
"Narikawa",
"Tatsuya",
""
]
] | To date, close to fifty presumed black hole binary mergers were observed by the LIGO and Virgo detectors. The analyses have been done with an assumption that these objects are black holes by limiting the spin prior to the Kerr bound. However, the above assumption is not valid for superspinars, which have the Kerr geometry but rotate beyond the Kerr bound. In this study, we investigate whether and how the limited spin prior range causes a bias in parameter estimation for superspinars if they are detected. To this end, we estimate binary parameters of the simulated inspiral signals of the gravitational waves of compact binaries by assuming that at least one component of them is a superspinar. We have found that when the primary is a superspinar, both mass and spin parameters are biased in parameter estimation due to the limited spin prior range. In this case, the extended prior range is strongly favored compared to the limited one. On the other hand, when the primary is a black hole, we do not see much bias in parameter estimation due to the limited spin prior range, even though the secondary is a superspinar. We also apply the analysis to black hole binary merger events GW170608 and GW190814, which have a long and loud inspiral signal. We do not see any preference of superspinars from the model selection for both events. We conclude that the extension of the spin prior range is necessary for accurate parameter estimation if highly spinning primary objects are found, while it is difficult to identify superspinars if they are only the secondary objects. Nevertheless, the bias in parameter estimation of spin for the limited spin prior range can be a clue of the existence of superspinars. |
1309.2833 | Neven Bili\'c | Neven Bilic and Dijana Tolic | FRW universe in the laboratory | 21 pages, 2 figures, title changed, typos corrected, seven references
added, a few clarifications and a comment on emergent gravity added, to
appear in PRD | Phys. Rev. D 88, 105002 (2013) | 10.1103/PhysRevD.88.105002 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider an expanding relativistic fluid with spherical symmetry as a
model for an analog FRW spacetime. In the framework of relativistic acoustic
geometry we demonstrate how to mimic an arbitrary FRW spacetime with positive,
zero or negative spatial curvature. In the Lagrangian description we show that
a particular FRW spacetime is obtained by choosing the appropriate potential.
We discuss several examples and in particular the analog de Sitter spacetime in
the coordinate representation with positive and negative spatial curvature.
| [
{
"created": "Wed, 11 Sep 2013 14:07:41 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Sep 2013 13:51:27 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Nov 2013 18:01:18 GMT",
"version": "v3"
}
] | 2013-11-13 | [
[
"Bilic",
"Neven",
""
],
[
"Tolic",
"Dijana",
""
]
] | We consider an expanding relativistic fluid with spherical symmetry as a model for an analog FRW spacetime. In the framework of relativistic acoustic geometry we demonstrate how to mimic an arbitrary FRW spacetime with positive, zero or negative spatial curvature. In the Lagrangian description we show that a particular FRW spacetime is obtained by choosing the appropriate potential. We discuss several examples and in particular the analog de Sitter spacetime in the coordinate representation with positive and negative spatial curvature. |
1802.07035 | Lavinia Heisenberg | Lavinia Heisenberg and Shinji Tsujikawa | Hairy black hole solutions in $U(1)$ gauge-invariant
scalar-vector-tensor theories | 10 pages, 1 figure | Physics Letters B 780 (2018)0370-2693, 638 - 646 | 10.1016/j.physletb.2018.03.059 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In $U(1)$ gauge-invariant scalar-vector-tensor theories with second-order
equations of motion, we study the properties of black holes (BH) on a static
and spherically symmetric background. In shift-symmetric theories invariant
under the shift of scalar $\phi \to \phi+c$, we show the existence of new hairy
BH solutions where a cubic-order scalar-vector interaction gives rise to a
scalar hair manifesting itself around the event horizon. In the presence of a
quartic-order interaction besides the cubic coupling, there are also regular BH
solutions endowed with scalar and vector hairs.
| [
{
"created": "Tue, 20 Feb 2018 09:56:10 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Apr 2018 13:29:08 GMT",
"version": "v2"
}
] | 2018-04-10 | [
[
"Heisenberg",
"Lavinia",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | In $U(1)$ gauge-invariant scalar-vector-tensor theories with second-order equations of motion, we study the properties of black holes (BH) on a static and spherically symmetric background. In shift-symmetric theories invariant under the shift of scalar $\phi \to \phi+c$, we show the existence of new hairy BH solutions where a cubic-order scalar-vector interaction gives rise to a scalar hair manifesting itself around the event horizon. In the presence of a quartic-order interaction besides the cubic coupling, there are also regular BH solutions endowed with scalar and vector hairs. |
gr-qc/9701019 | Maurice van Putten | Maurice H.P.M. van Putten | Numerical Integration of Nonlinear Wave Equations for General Relativity | 19 pages (LaTex), 3 figures (ps) | Phys.Rev. D55 (1997) 4705-4711 | 10.1103/PhysRevD.55.4705 | null | gr-qc | null | A second-order numerical implementation is given for recently derived
nonlinear wave equations for general relativity. The Gowdy T$^3$ cosmology is
used as a test bed for studying the accuracy and convergence of simulations of
one-dimensional nonlinear waves. The complete freedom in space-time slicing in
the present formulation is exploited to compute in the Gowdy line-element.
Second-order convergence is found by direct comparison of the results with
either analytical solutions for polarized waves, or solutions obtained from
Gowdy's reduced wave equations for the more general unpolarized waves. Some
directions for extensions are discussed.
| [
{
"created": "Fri, 10 Jan 1997 17:42:11 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"van Putten",
"Maurice H. P. M.",
""
]
] | A second-order numerical implementation is given for recently derived nonlinear wave equations for general relativity. The Gowdy T$^3$ cosmology is used as a test bed for studying the accuracy and convergence of simulations of one-dimensional nonlinear waves. The complete freedom in space-time slicing in the present formulation is exploited to compute in the Gowdy line-element. Second-order convergence is found by direct comparison of the results with either analytical solutions for polarized waves, or solutions obtained from Gowdy's reduced wave equations for the more general unpolarized waves. Some directions for extensions are discussed. |
2005.14151 | Ramon Herrera | Eduardo I. Guendelman, Ramon Herrera and Pedro Labrana | Instant preheating in a scale invariant two measures theory | 24 pages | Phys. Rev. D 103, 123515 (2021) | 10.1103/PhysRevD.103.123515 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The instant preheating mechanism in the framework of a scale invariant two
measures theory is studied. We introduce this mechanism into a non oscillating
inflationary model as another possible solution to the reheating of the
universe in this theory. In this framework, we consider that the model includes
two scalar matter fields, the first a dilaton field, that transforms under
scale transformations and it will be considered also as the field that drives
inflation and the second, a scalar field which will interact with the inflaton
through an effective potential. By assuming this interaction term, we obtain a
scenario of instant radiation or decay of particles according to the domain the
effective mass of the field that interacts with the inflaton. Also, we consider
a scale invariant Yukawa interaction and then after performing the transition
to the physical Einstein frame we obtain an expression for the decay rate from
our scalar field going into two fermions. Besides, from specific decay rates,
different constraints and bounds for the coupling parameters associated with
our model are found.
| [
{
"created": "Thu, 28 May 2020 17:13:10 GMT",
"version": "v1"
}
] | 2021-06-16 | [
[
"Guendelman",
"Eduardo I.",
""
],
[
"Herrera",
"Ramon",
""
],
[
"Labrana",
"Pedro",
""
]
] | The instant preheating mechanism in the framework of a scale invariant two measures theory is studied. We introduce this mechanism into a non oscillating inflationary model as another possible solution to the reheating of the universe in this theory. In this framework, we consider that the model includes two scalar matter fields, the first a dilaton field, that transforms under scale transformations and it will be considered also as the field that drives inflation and the second, a scalar field which will interact with the inflaton through an effective potential. By assuming this interaction term, we obtain a scenario of instant radiation or decay of particles according to the domain the effective mass of the field that interacts with the inflaton. Also, we consider a scale invariant Yukawa interaction and then after performing the transition to the physical Einstein frame we obtain an expression for the decay rate from our scalar field going into two fermions. Besides, from specific decay rates, different constraints and bounds for the coupling parameters associated with our model are found. |
1407.1649 | Tommaso Bolognesi | Tommaso Bolognesi and Alexander Lamb | Simple indicators for Lorentzian causets | 43 pages, 23 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several classes of directed acyclic graphs have been investigated in the last
two decades, in the context of the Causal Set Program, in search for good
discrete models of spacetime. We introduce some statistical indicators that can
be used for comparing these graphs and for assessing their closeness to the
ideal Lorentzian causal sets ('causets') -- those obtained by sprinkling points
in a Lorentzian manifold. In particular, with the reversed triangular
inequality of Special Relativity in mind, we introduce 'longest/shortest path
plots', an easily implemented tool to visually detect the extent to which a
generic causet matches the wide range of path lengths between events of
Lorentzian causets. This tool can attribute some degree of 'Lorentzianity' - in
particular 'non-locality' - also to causets that are not (directly) embeddable
and that, due to some regularity in their structure, would not pass the key
test for Lorentz invariance: the absence of preferred reference frames. We
compare the discussed indicators and use them for assessing causets both of
stochastic and of deterministic, algorithmic origin, finding examples of the
latter that behave optimally w.r.t. our longest/shortest path plots.
| [
{
"created": "Mon, 7 Jul 2014 10:09:51 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Dec 2014 09:09:55 GMT",
"version": "v2"
},
{
"created": "Fri, 1 Jul 2016 10:57:49 GMT",
"version": "v3"
}
] | 2016-07-04 | [
[
"Bolognesi",
"Tommaso",
""
],
[
"Lamb",
"Alexander",
""
]
] | Several classes of directed acyclic graphs have been investigated in the last two decades, in the context of the Causal Set Program, in search for good discrete models of spacetime. We introduce some statistical indicators that can be used for comparing these graphs and for assessing their closeness to the ideal Lorentzian causal sets ('causets') -- those obtained by sprinkling points in a Lorentzian manifold. In particular, with the reversed triangular inequality of Special Relativity in mind, we introduce 'longest/shortest path plots', an easily implemented tool to visually detect the extent to which a generic causet matches the wide range of path lengths between events of Lorentzian causets. This tool can attribute some degree of 'Lorentzianity' - in particular 'non-locality' - also to causets that are not (directly) embeddable and that, due to some regularity in their structure, would not pass the key test for Lorentz invariance: the absence of preferred reference frames. We compare the discussed indicators and use them for assessing causets both of stochastic and of deterministic, algorithmic origin, finding examples of the latter that behave optimally w.r.t. our longest/shortest path plots. |
1406.5544 | Atsushi Nishizawa | Atsushi Nishizawa and Takashi Nakamura | Measuring Speed of Gravitational Waves by Observations of Photons and
Neutrinos from Compact Binary Mergers and Supernovae | 8 pages, 6 figures | Phys. Rev. D 90, 044048 (2014) | 10.1103/PhysRevD.90.044048 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Detection of gravitational waves (GW) provides us an opportunity to test
general relativity in strong and dynamical regimes of gravity. One of the tests
is checking whether GW propagates with the speed of light or not. This test is
crucial because the velocity of GW has not ever been directly measured.
Propagation speed of a GW can deviate from the speed of light due to the
modification of gravity, graviton mass, and the nontrivial spacetime structure
such as extra dimensions and quantum gravity effects. Here we report a simple
method to measure the propagation speed of a GW by directly comparing arrival
times between gravitational waves, and neutrinos from supernovae or photons
from short gamma-ray bursts. As a result, we found that the future
multimessenger observations of a GW, neutrinos, and photons can test the GW
propagation speed with the precision of ~10^{-16} improving the previous
suggestions by 8-10 orders of magnitude. We also propose a novel method that
distinguishes the true signal due to the deviation of GW propagation speed from
the speed of light and the intrinsic time delay of the emission at a source by
looking at the redshift dependence.
| [
{
"created": "Fri, 20 Jun 2014 21:30:11 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Jul 2014 19:36:46 GMT",
"version": "v2"
},
{
"created": "Wed, 20 Aug 2014 21:52:30 GMT",
"version": "v3"
}
] | 2014-08-27 | [
[
"Nishizawa",
"Atsushi",
""
],
[
"Nakamura",
"Takashi",
""
]
] | Detection of gravitational waves (GW) provides us an opportunity to test general relativity in strong and dynamical regimes of gravity. One of the tests is checking whether GW propagates with the speed of light or not. This test is crucial because the velocity of GW has not ever been directly measured. Propagation speed of a GW can deviate from the speed of light due to the modification of gravity, graviton mass, and the nontrivial spacetime structure such as extra dimensions and quantum gravity effects. Here we report a simple method to measure the propagation speed of a GW by directly comparing arrival times between gravitational waves, and neutrinos from supernovae or photons from short gamma-ray bursts. As a result, we found that the future multimessenger observations of a GW, neutrinos, and photons can test the GW propagation speed with the precision of ~10^{-16} improving the previous suggestions by 8-10 orders of magnitude. We also propose a novel method that distinguishes the true signal due to the deviation of GW propagation speed from the speed of light and the intrinsic time delay of the emission at a source by looking at the redshift dependence. |
2212.04837 | Fabian Gittins | Nils Andersson, Fabian Gittins | Formulating the r-mode problem for slowly rotating neutron stars | 22 pages, 1 figure. Accepted for publication in ApJ | Astrophys. J. 945, 139 (2023) | 10.3847/1538-4357/acbc1e | null | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the problem of inertial r-modes in stratified stars, drawing on a
more precise description of the composition stratification in a mature neutron
star. The results highlight issues with the traditional approach to the
problem, leading us to rethink the computational strategy for r-modes of
non-barotropic neutron stars. We outline two strategies for dealing with the
problem. For moderate to slowly rotating neutron stars the only viable
alternative may be to approach the problem numerically from the outset, while a
meaningful slow-rotation calculation can be carried out for the fastest known
spinning stars (which may be close to being driven unstable by the emission of
gravitational waves). We demonstrate that the latter approach leads to a
problem close, but not identical, to that for barotropic inertial modes. We
also suggest that these reformulations of the problem likely resolve the
long-standing problem of singular behaviour associated with a co-rotation point
in rotating relativistic neutron stars. This issue needs to be resolved in
order to guide future gravitational-wave searches.
| [
{
"created": "Fri, 9 Dec 2022 13:09:00 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Mar 2023 11:47:25 GMT",
"version": "v2"
}
] | 2023-05-23 | [
[
"Andersson",
"Nils",
""
],
[
"Gittins",
"Fabian",
""
]
] | We revisit the problem of inertial r-modes in stratified stars, drawing on a more precise description of the composition stratification in a mature neutron star. The results highlight issues with the traditional approach to the problem, leading us to rethink the computational strategy for r-modes of non-barotropic neutron stars. We outline two strategies for dealing with the problem. For moderate to slowly rotating neutron stars the only viable alternative may be to approach the problem numerically from the outset, while a meaningful slow-rotation calculation can be carried out for the fastest known spinning stars (which may be close to being driven unstable by the emission of gravitational waves). We demonstrate that the latter approach leads to a problem close, but not identical, to that for barotropic inertial modes. We also suggest that these reformulations of the problem likely resolve the long-standing problem of singular behaviour associated with a co-rotation point in rotating relativistic neutron stars. This issue needs to be resolved in order to guide future gravitational-wave searches. |
0711.0373 | Benjamin Bahr | Benjamin Bahr, Thomas Thiemann | Automorphisms in Loop Quantum Gravity | 57 pages, 7 figures | Class.Quant.Grav.26:235022,2009 | 10.1088/0264-9381/26/23/235022 | null | gr-qc | null | We investigate a certain distributional extension of the group of spatial
diffeomorphisms in Loop Quantum Gravity. This extension, which is given by the
automorphisms Aut(P) of the path groupoid P, was proposed by Velhinho and is
inspired by category theory. This group is much larger than the group of
piecewise analytic diffeomorphisms. In particular, we will show that graphs
with the same combinatorics but different generalized knotting classes can be
mapped into each other. We describe the automorphism-invariant Hilbert space
and comment on how a combinatorial formulation of LQG might arise.
| [
{
"created": "Fri, 2 Nov 2007 19:02:18 GMT",
"version": "v1"
}
] | 2009-11-18 | [
[
"Bahr",
"Benjamin",
""
],
[
"Thiemann",
"Thomas",
""
]
] | We investigate a certain distributional extension of the group of spatial diffeomorphisms in Loop Quantum Gravity. This extension, which is given by the automorphisms Aut(P) of the path groupoid P, was proposed by Velhinho and is inspired by category theory. This group is much larger than the group of piecewise analytic diffeomorphisms. In particular, we will show that graphs with the same combinatorics but different generalized knotting classes can be mapped into each other. We describe the automorphism-invariant Hilbert space and comment on how a combinatorial formulation of LQG might arise. |
0802.4453 | Nikodem Poplawski | Nikodem J. Poplawski | Geometrical formulation of classical electromagnetism | 5 pages, REVTeX4 | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A general affine connection has enough degrees of freedom to describe the
classical gravitational and electromagnetic fields in the metric-affine
formulation of gravity. The gravitational field is represented in the
Lagrangian by the symmetric part of the Ricci tensor, while the classical
electromagnetic field is represented geometrically by the tensor of homothetic
curvature. We introduce matter as the four-velocity field subject to the
kinematical constraint in which the Lagrange multiplier represents the energy
density. A coupling between the four-velocity and the trace of the nonmetricity
tensor represents the electric charge density. We show that the simplest
metric-affine Lagrangian that depends on the Ricci tensor and the tensor of
homothetic curvature generates the Einstein-Maxwell field equations, while the
Bianchi identity gives the Lorentz equation of motion. If the four-velocity
couples to the torsion vector, the Einstein equations are modified by a term
that is significant at the Planck scale and may prevent the formation of
spacetime singularities.
| [
{
"created": "Fri, 29 Feb 2008 19:20:41 GMT",
"version": "v1"
}
] | 2008-03-03 | [
[
"Poplawski",
"Nikodem J.",
""
]
] | A general affine connection has enough degrees of freedom to describe the classical gravitational and electromagnetic fields in the metric-affine formulation of gravity. The gravitational field is represented in the Lagrangian by the symmetric part of the Ricci tensor, while the classical electromagnetic field is represented geometrically by the tensor of homothetic curvature. We introduce matter as the four-velocity field subject to the kinematical constraint in which the Lagrange multiplier represents the energy density. A coupling between the four-velocity and the trace of the nonmetricity tensor represents the electric charge density. We show that the simplest metric-affine Lagrangian that depends on the Ricci tensor and the tensor of homothetic curvature generates the Einstein-Maxwell field equations, while the Bianchi identity gives the Lorentz equation of motion. If the four-velocity couples to the torsion vector, the Einstein equations are modified by a term that is significant at the Planck scale and may prevent the formation of spacetime singularities. |
gr-qc/0701061 | Jerry B. Griffiths | J. B. Griffiths and R. G. Halburd | The C-metric as a colliding plane wave space-time | 6 pages. To appear in Classical and Quantum Gravity | Class.Quant.Grav.24:1049-1054,2007 | 10.1088/0264-9381/24/5/002 | null | gr-qc | null | It is explicitly shown that part of the C-metric space-time inside the black
hole horizon may be interpreted as the interaction region of two colliding
plane waves with aligned linear polarization, provided the rotational
coordinate is replaced by a linear one. This is a one-parameter generalization
of the degenerate Ferrari-Ibanez solution in which the focussing singularity is
a Cauchy horizon rather than a curvature singularity.
| [
{
"created": "Wed, 10 Jan 2007 16:00:22 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Griffiths",
"J. B.",
""
],
[
"Halburd",
"R. G.",
""
]
] | It is explicitly shown that part of the C-metric space-time inside the black hole horizon may be interpreted as the interaction region of two colliding plane waves with aligned linear polarization, provided the rotational coordinate is replaced by a linear one. This is a one-parameter generalization of the degenerate Ferrari-Ibanez solution in which the focussing singularity is a Cauchy horizon rather than a curvature singularity. |
2012.08077 | Lance Williams | L.L. Williams and N. Inan | Maxwellian mirages in general relativity | null | 2021 New J. Phys. 23 053019 | 10.1088/1367-2630/abf322 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Maxwellian approximations to linear general relativity are revisited in light
of relatively recent results on the degrees of freedom in the linear
gravitational field. The well-known Maxwellian formalism obtained in harmonic
coordinates is compared with a Maxwellian formalism obtained under a coordinate
choice where each of the metric components corresponds to each of the
coordinate-invariant degrees of freedom of the linear gravitational field. The
coordinate freedom of general relativity can be exploited to cast the field
equations into Maxwellian form, but such forms can be mere mirages of the
coordinate choice -- mirages such as vector gravitational waves. A coordinate
choice that yields perfectly-Maxwellian field equations, will yield a force
equation that is not Lorentzian. If field definitions are chosen to obtain
Lorentz-like terms in the force equation, then Maxwellian forms are compromised
in the field equations. Many treatments of gravito-electromagnetism will make
inconsistent ordering choices between the field equations and force equations,
or else truncate terms of relevant order from the force equation. Often such
mistakes reflect an attempt to force exact Maxwellian analogs simultaneously in
both the field equations and the force equation, with the result that terms
dropped are as large as those kept.
| [
{
"created": "Tue, 15 Dec 2020 04:07:57 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Mar 2021 23:34:16 GMT",
"version": "v2"
}
] | 2021-06-21 | [
[
"Williams",
"L. L.",
""
],
[
"Inan",
"N.",
""
]
] | Maxwellian approximations to linear general relativity are revisited in light of relatively recent results on the degrees of freedom in the linear gravitational field. The well-known Maxwellian formalism obtained in harmonic coordinates is compared with a Maxwellian formalism obtained under a coordinate choice where each of the metric components corresponds to each of the coordinate-invariant degrees of freedom of the linear gravitational field. The coordinate freedom of general relativity can be exploited to cast the field equations into Maxwellian form, but such forms can be mere mirages of the coordinate choice -- mirages such as vector gravitational waves. A coordinate choice that yields perfectly-Maxwellian field equations, will yield a force equation that is not Lorentzian. If field definitions are chosen to obtain Lorentz-like terms in the force equation, then Maxwellian forms are compromised in the field equations. Many treatments of gravito-electromagnetism will make inconsistent ordering choices between the field equations and force equations, or else truncate terms of relevant order from the force equation. Often such mistakes reflect an attempt to force exact Maxwellian analogs simultaneously in both the field equations and the force equation, with the result that terms dropped are as large as those kept. |
gr-qc/0207121 | Eric W. Hirschmann | Eric W. Hirschmann, Anzhong Wang, Yumei Wu | Collapse of a Scalar Field in 2+1 Gravity | null | Class.Quant.Grav.21:1791-1824,2004 | 10.1088/0264-9381/21/7/006 | null | gr-qc | null | We consider the problem of critical gravitational collapse of a scalar field
in 2+1 dimensions with spherical (circular) symmetry. After surveying all the
analytic, continuously self-similar solutions and considering their global
structure, we examine their perturbations with the intent of understanding
which are the critical solutions with a single unstable mode. The critical
solution which we find is the one which agrees most closely with that found in
numerical evolutions. However, the critical exponent which we find does not
seem to agree with the numerical result.
| [
{
"created": "Tue, 30 Jul 2002 19:53:06 GMT",
"version": "v1"
}
] | 2009-07-07 | [
[
"Hirschmann",
"Eric W.",
""
],
[
"Wang",
"Anzhong",
""
],
[
"Wu",
"Yumei",
""
]
] | We consider the problem of critical gravitational collapse of a scalar field in 2+1 dimensions with spherical (circular) symmetry. After surveying all the analytic, continuously self-similar solutions and considering their global structure, we examine their perturbations with the intent of understanding which are the critical solutions with a single unstable mode. The critical solution which we find is the one which agrees most closely with that found in numerical evolutions. However, the critical exponent which we find does not seem to agree with the numerical result. |
1810.00202 | YanLi He | Yan-Li He, Yun-Song Piao | Derivative coupling of inflaton to $R^{(3)}$ | 14 pages, 3 figures | Phys. Rev. D 99, 083511 (2019) | 10.1103/PhysRevD.99.083511 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the inflation scenario with the non-minimally derivative coupling
$XR^{(3)}$, where $X=\nabla_\mu\phi \nabla^\mu\phi$, $\phi$ is the inflaton and
$R^{(3)}$ is the 3-dimensional intrinsic Ricci scalar on the spacelike
hypersurface, and analytically calculate the corrections of $XR^{(3)}$ on the
power spectra of primordial perturbations. It is found that for the $\phi^2$
inflation model, the corresponding predictions can be driven to the best-fit
region of the $n_s$-$r$ diagram.
| [
{
"created": "Sat, 29 Sep 2018 12:45:40 GMT",
"version": "v1"
}
] | 2019-04-17 | [
[
"He",
"Yan-Li",
""
],
[
"Piao",
"Yun-Song",
""
]
] | We study the inflation scenario with the non-minimally derivative coupling $XR^{(3)}$, where $X=\nabla_\mu\phi \nabla^\mu\phi$, $\phi$ is the inflaton and $R^{(3)}$ is the 3-dimensional intrinsic Ricci scalar on the spacelike hypersurface, and analytically calculate the corrections of $XR^{(3)}$ on the power spectra of primordial perturbations. It is found that for the $\phi^2$ inflation model, the corresponding predictions can be driven to the best-fit region of the $n_s$-$r$ diagram. |
2101.08517 | Ritam Mallick | Kamal Krishna Nath, Debojoti Kuzur and Ritam Mallick | Tidal effect on the gyroscopic precession around a compact star | 10 pages, 11 figures | International Journal of Modern Physics D, Vol. 31, No. 06,
2250047 (2022) | 10.1142/S021827182250047X | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General relativistic effects in the spacetime around the massive
astrophysical objects can be captured using a spinning test gyro orbiting
around the object in a circular geodesic. This article discusses how the tidal
disruption due to a companion object affects the precession frequency of a
spinning gyro orbiting around a compact astrophysical object. The precession
frequency is studied in a region of space around the central object using a
perturbative approach. In this study, the central object is either a neutron
star or a white dwarf. The gyro is any planetary or asteroid-like object
orbiting the neutron star or a white dwarf. Moreover, the companion object that
causes the tidal field can be a neutron star, white dwarf, a black hole, or a
main-sequence star. The tidal effect significantly affects the spacetime around
the host star, which affects the gyro precession frequency. The gyro's
precession frequency increases with the mass of the companion object and
decreases as the separation between the host star and the companion star
increases. The tidal effect also varies with the stiffness of the equation of
state of matter describing the neutron star. We also find that the tidal field
affects the spacetime around a white dwarf more than that of the neutron star.
| [
{
"created": "Thu, 21 Jan 2021 09:51:17 GMT",
"version": "v1"
}
] | 2022-05-24 | [
[
"Nath",
"Kamal Krishna",
""
],
[
"Kuzur",
"Debojoti",
""
],
[
"Mallick",
"Ritam",
""
]
] | General relativistic effects in the spacetime around the massive astrophysical objects can be captured using a spinning test gyro orbiting around the object in a circular geodesic. This article discusses how the tidal disruption due to a companion object affects the precession frequency of a spinning gyro orbiting around a compact astrophysical object. The precession frequency is studied in a region of space around the central object using a perturbative approach. In this study, the central object is either a neutron star or a white dwarf. The gyro is any planetary or asteroid-like object orbiting the neutron star or a white dwarf. Moreover, the companion object that causes the tidal field can be a neutron star, white dwarf, a black hole, or a main-sequence star. The tidal effect significantly affects the spacetime around the host star, which affects the gyro precession frequency. The gyro's precession frequency increases with the mass of the companion object and decreases as the separation between the host star and the companion star increases. The tidal effect also varies with the stiffness of the equation of state of matter describing the neutron star. We also find that the tidal field affects the spacetime around a white dwarf more than that of the neutron star. |
1802.10377 | Banibrata Mukhopadhyay | Banibrata Mukhopadhyay, Soumya Kanti Ganguly | Gravity-Induced Geometric Phases and Entanglement in Spinors and
Neutrinos: Gravitational Zeeman Effect | 28 pages including 5 figures; Version published in Universe | Universe 6 (2020) 160 | 10.3390/universe6100160 | null | gr-qc astro-ph.HE quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show Zeeman-like splitting in the energy of spinors propagating in a
background gravitational field, analogous to the spinors in an electromagnetic
field, otherwise termed the Gravitational Zeeman Effect. These spinors are also
found to acquire a geometric phase, in a similar way as they do in the presence
of magnetic fields. However, in a gravitational background, the Aharonov-Bohm
type effect, in addition to Berry-like phase, arises. Based on this result, we
investigate geometric phases acquired by neutrinos propagating in a strong
gravitational field. We also explore entanglement of neutrino states due to
gravity, which could induce neutrino-antineutrino oscillation in the first
place. We show that entangled states also acquire geometric phases which are
determined by the relative strength between gravitational field and neutrino
masses.
| [
{
"created": "Wed, 28 Feb 2018 12:00:54 GMT",
"version": "v1"
},
{
"created": "Sat, 17 Aug 2019 13:04:48 GMT",
"version": "v2"
},
{
"created": "Thu, 1 Oct 2020 06:27:35 GMT",
"version": "v3"
}
] | 2020-10-02 | [
[
"Mukhopadhyay",
"Banibrata",
""
],
[
"Ganguly",
"Soumya Kanti",
""
]
] | We show Zeeman-like splitting in the energy of spinors propagating in a background gravitational field, analogous to the spinors in an electromagnetic field, otherwise termed the Gravitational Zeeman Effect. These spinors are also found to acquire a geometric phase, in a similar way as they do in the presence of magnetic fields. However, in a gravitational background, the Aharonov-Bohm type effect, in addition to Berry-like phase, arises. Based on this result, we investigate geometric phases acquired by neutrinos propagating in a strong gravitational field. We also explore entanglement of neutrino states due to gravity, which could induce neutrino-antineutrino oscillation in the first place. We show that entangled states also acquire geometric phases which are determined by the relative strength between gravitational field and neutrino masses. |
gr-qc/0309104 | Kjell Rosquist | Kjell Rosquist | A moving medium simulation of Schwarzschild black hole optics | 4 pages, no figures; V2: preprint number added | Gen.Rel.Grav. 36 (2004) 1977-1982 | 10.1023/B:GERG.0000036055.82140.06 | null | gr-qc | null | An explicit fluid flow simulation of electromagnetic wave propagation in the
gravitational field of a Schwarzschild black hole is given. The fluid has a
constant refractive index and a spherically symmetric inward directed flow. The
resulting form of the metric leads to a new coordinate system in which the
Schwarzschild vacuum is written in Gordon's form. It is shown that a closely
related coordinate system interpolates between the Kerr-Schild and
Painleve-Gullstrand coordinates.
| [
{
"created": "Mon, 22 Sep 2003 11:01:55 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Sep 2003 09:13:30 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Rosquist",
"Kjell",
""
]
] | An explicit fluid flow simulation of electromagnetic wave propagation in the gravitational field of a Schwarzschild black hole is given. The fluid has a constant refractive index and a spherically symmetric inward directed flow. The resulting form of the metric leads to a new coordinate system in which the Schwarzschild vacuum is written in Gordon's form. It is shown that a closely related coordinate system interpolates between the Kerr-Schild and Painleve-Gullstrand coordinates. |
1404.3197 | Lionel London | Lionel London, James Healy and Deirdre Shoemaker | Modeling Ringdown: Beyond the Fundamental Quasi-Normal Modes | null | Phys. Rev. D 90, 124032 (2014) | 10.1103/PhysRevD.90.124032 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | While black hole perturbation theory predicts a rich quasi-normal mode
structure, technical challenges have limited the numerical study of excitations
to the fundamental, lowest order modes caused by the coalescence of black
holes. Here, we present a robust method to identify quasi-normal mode
excitations beyond the fundamentals within currently available numerical
relativity waveforms. In applying this method to waveforms of initially
non-spinning black hole binaries, of mass ratios 1 to 15, we find not only the
fundamental quasi-normal mode amplitudes, but also overtones, and evidence for
2nd order quasi-normal modes. We find that the mass-ratio dependence of
quasi-normal mode excitation is very well modeled by a Post-Newtonian like sum
in symmetric mass ratio. Concurrently, we find that the mass ratio dependence
of some quasi-normal modes is qualitatively different from their Post-Newtonian
inspired counterparts, suggesting that the imprints of nonlinear merger are
more evident in some modes than in others. We present new fitting formulas for
the related quasi-normal mode excitations, as well as for remnant black hole
spin and mass. We also discuss the relevance of our results in terms of
gravitational wave detection and characterization.
| [
{
"created": "Fri, 11 Apr 2014 19:35:11 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Mar 2015 19:02:41 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Sep 2016 14:44:13 GMT",
"version": "v3"
},
{
"created": "Tue, 21 Feb 2017 10:20:08 GMT",
"version": "v4"
}
] | 2017-02-22 | [
[
"London",
"Lionel",
""
],
[
"Healy",
"James",
""
],
[
"Shoemaker",
"Deirdre",
""
]
] | While black hole perturbation theory predicts a rich quasi-normal mode structure, technical challenges have limited the numerical study of excitations to the fundamental, lowest order modes caused by the coalescence of black holes. Here, we present a robust method to identify quasi-normal mode excitations beyond the fundamentals within currently available numerical relativity waveforms. In applying this method to waveforms of initially non-spinning black hole binaries, of mass ratios 1 to 15, we find not only the fundamental quasi-normal mode amplitudes, but also overtones, and evidence for 2nd order quasi-normal modes. We find that the mass-ratio dependence of quasi-normal mode excitation is very well modeled by a Post-Newtonian like sum in symmetric mass ratio. Concurrently, we find that the mass ratio dependence of some quasi-normal modes is qualitatively different from their Post-Newtonian inspired counterparts, suggesting that the imprints of nonlinear merger are more evident in some modes than in others. We present new fitting formulas for the related quasi-normal mode excitations, as well as for remnant black hole spin and mass. We also discuss the relevance of our results in terms of gravitational wave detection and characterization. |
2209.07281 | Ernesto Nungesser | Ho Lee, Jiho Lee and Ernesto Nungesser | Small solutions of the Einstein-Boltzmann-scalar field system with
Bianchi symmetry | 42 pages | J. Math. Phys. 64, 011507 (2023) | 10.1063/5.0125996 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that small homogeneous solutions to the Einstein-Boltzmann-scalar
field system exist globally towards the future and tend to the de Sitter
solution in a suitable sense. More specifically, we assume that the spacetime
is of Bianchi type I--VIII, that the matter is described by Israel particles
and that there exists a scalar field with a potential which has a positive
lower bound. This represents a generalization of the work [19], where a
cosmological constant was considered, and a generalization of [16], where a
spatially flat FLRW spacetime was considered. We obtain the global existence
and asymptotic behavior of classical solutions to the Einstein-Boltzmann-scalar
field system for small initial data.
| [
{
"created": "Thu, 15 Sep 2022 13:17:35 GMT",
"version": "v1"
}
] | 2024-06-18 | [
[
"Lee",
"Ho",
""
],
[
"Lee",
"Jiho",
""
],
[
"Nungesser",
"Ernesto",
""
]
] | We show that small homogeneous solutions to the Einstein-Boltzmann-scalar field system exist globally towards the future and tend to the de Sitter solution in a suitable sense. More specifically, we assume that the spacetime is of Bianchi type I--VIII, that the matter is described by Israel particles and that there exists a scalar field with a potential which has a positive lower bound. This represents a generalization of the work [19], where a cosmological constant was considered, and a generalization of [16], where a spatially flat FLRW spacetime was considered. We obtain the global existence and asymptotic behavior of classical solutions to the Einstein-Boltzmann-scalar field system for small initial data. |
1911.12368 | Hong Lu | Xing-Hui Feng and H. Lu | On the Size of Rotating Black Holes | Latex, 33 pages | null | 10.1140/epjc/s10052-020-8119-z | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently a sequence of inequalities relating the black hole horizon, photon
sphere, shadow were proposed for spherically symmetric and static black holes,
providing the upper bound for given mass. In this paper, we extend the
discussion to include rotating black holes. When viewed from the north pole
direction, the shadow remains a round disk, but the image is skewed when viewed
from the equatorial plane. After properly implementing the ``size'' parameters
for the rotating black holes, we verify that the sequence of inequalities
remain valid for a variety of solutions, including Kerr, Kerr-Newman, Kerr-Sen
and Kerr-Cveti\v c-Youm black holes. The upshot is that rotation makes both the
actual and apparent sizes of a black hole smaller.
| [
{
"created": "Wed, 27 Nov 2019 19:00:02 GMT",
"version": "v1"
}
] | 2020-07-15 | [
[
"Feng",
"Xing-Hui",
""
],
[
"Lu",
"H.",
""
]
] | Recently a sequence of inequalities relating the black hole horizon, photon sphere, shadow were proposed for spherically symmetric and static black holes, providing the upper bound for given mass. In this paper, we extend the discussion to include rotating black holes. When viewed from the north pole direction, the shadow remains a round disk, but the image is skewed when viewed from the equatorial plane. After properly implementing the ``size'' parameters for the rotating black holes, we verify that the sequence of inequalities remain valid for a variety of solutions, including Kerr, Kerr-Newman, Kerr-Sen and Kerr-Cveti\v c-Youm black holes. The upshot is that rotation makes both the actual and apparent sizes of a black hole smaller. |
gr-qc/9605058 | Jorma Louko | Jorma Louko and Jarmo Makela | Area spectrum of the Schwarzschild black hole | 30 pages, REVTeX v3.0. (Minor additions, several added references.) | Phys.Rev. D54 (1996) 4982-4996 | 10.1103/PhysRevD.54.4982 | DAMTP 96--53, PP96--98 | gr-qc hep-th | null | We consider a Hamiltonian theory of spherically symmetric vacuum Einstein
gravity under Kruskal-like boundary conditions in variables associated with the
Einstein-Rosen wormhole throat. The configuration variable in the reduced
classical theory is the radius of the throat, in a foliation that is frozen at
the left hand side infinity but asymptotically Minkowski at the right hand side
infinity, and such that the proper time at the throat agrees with the right
hand side Minkowski time. The classical Hamiltonian is numerically equal to the
Schwarzschild mass. Within a class of Hamiltonian quantizations, we show that
the spectrum of the Hamiltonian operator is discrete and bounded below, and can
be made positive definite. The large eigenvalues behave asymptotically
as~$\sqrt{2k}$, where $k$ is an integer. The resulting area spectrum agrees
with that proposed by Bekenstein and others. Analogous results hold in the
presence of a negative cosmological constant and electric charge. The classical
input that led to the quantum results is discussed.
| [
{
"created": "Mon, 27 May 1996 20:45:20 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Oct 1996 19:33:19 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Louko",
"Jorma",
""
],
[
"Makela",
"Jarmo",
""
]
] | We consider a Hamiltonian theory of spherically symmetric vacuum Einstein gravity under Kruskal-like boundary conditions in variables associated with the Einstein-Rosen wormhole throat. The configuration variable in the reduced classical theory is the radius of the throat, in a foliation that is frozen at the left hand side infinity but asymptotically Minkowski at the right hand side infinity, and such that the proper time at the throat agrees with the right hand side Minkowski time. The classical Hamiltonian is numerically equal to the Schwarzschild mass. Within a class of Hamiltonian quantizations, we show that the spectrum of the Hamiltonian operator is discrete and bounded below, and can be made positive definite. The large eigenvalues behave asymptotically as~$\sqrt{2k}$, where $k$ is an integer. The resulting area spectrum agrees with that proposed by Bekenstein and others. Analogous results hold in the presence of a negative cosmological constant and electric charge. The classical input that led to the quantum results is discussed. |
1812.09938 | Ya-Peng Hu | Ya-Peng Hu, Hong-An Zeng, Zhi-Ming Jiang and Hongsheng Zhang | P-V criticality in the extended phase space of black holes in
Einstein-Horndeski gravity | 14 pages, 5 figures, two appendixes and more contents added, version
accepted by PRD | Phys. Rev. D 100, 084004 (2019) | 10.1103/PhysRevD.100.084004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravity is believed to have deep and inherent relation to thermodynamics. We
study phase transition and critical behavior in the extended phase space of
asymptotic anti de-Sitter (AdS) black holes in Einstein-Horndeski gravity. We
demonstrate that the black hole in Einstein-Horndeski gravity undergo phase
transition and P-V criticality mimicking the van der Waals gas-liquid system.
The key approach in our study is to introduce a more reasonable pressure
instead of previous pressure $P=-\Lambda/8\pi$ related to cosmological constant
$\Lambda$, and this proper pressure is given insight from the asymptotical
behaviour of this black hole. Moreover, we also first obtain P-V criticality in
the two cases with $\Lambda=0$ and $\Lambda>0$ in our paper, which implicates
that the cosmological constant $\Lambda$ may be not a necessary pressure
candidate for black holes at the microscopic level. We present critical
exponents for these phase transition processes.
| [
{
"created": "Mon, 24 Dec 2018 15:34:38 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Apr 2019 15:01:27 GMT",
"version": "v2"
},
{
"created": "Sun, 22 Sep 2019 16:01:19 GMT",
"version": "v3"
}
] | 2019-10-09 | [
[
"Hu",
"Ya-Peng",
""
],
[
"Zeng",
"Hong-An",
""
],
[
"Jiang",
"Zhi-Ming",
""
],
[
"Zhang",
"Hongsheng",
""
]
] | Gravity is believed to have deep and inherent relation to thermodynamics. We study phase transition and critical behavior in the extended phase space of asymptotic anti de-Sitter (AdS) black holes in Einstein-Horndeski gravity. We demonstrate that the black hole in Einstein-Horndeski gravity undergo phase transition and P-V criticality mimicking the van der Waals gas-liquid system. The key approach in our study is to introduce a more reasonable pressure instead of previous pressure $P=-\Lambda/8\pi$ related to cosmological constant $\Lambda$, and this proper pressure is given insight from the asymptotical behaviour of this black hole. Moreover, we also first obtain P-V criticality in the two cases with $\Lambda=0$ and $\Lambda>0$ in our paper, which implicates that the cosmological constant $\Lambda$ may be not a necessary pressure candidate for black holes at the microscopic level. We present critical exponents for these phase transition processes. |
gr-qc/0504044 | Vladimir Ivashchuk | J.-M. Alimi, V. D. Ivashchuk and V. N. Melnikov | Non-singular solutions in multidimensional model with scalar fields and
exponential potential | 13 pages, Latex, to appear in Gravitation and Cosmology; 5 refs. are
added | Grav.Cosmol. 11 (2005) 111-115 | null | IGC-PFUR-01/05 | gr-qc hep-th | null | Using developed earlier our methods for multidimensional models
\cite{M1,M2,M3} a family of cosmological-type solutions in D-dimensional model
with two sets of scalar fields \vec{\phi} and \vec{\psi} and exponential
potential depending upon \vec{\phi} is considered. The solutions are defined on
a product of n Ricci-flat spaces. The fields from \vec{\phi} have positive
kinetic terms and \vec{\psi} are "phantom" fields with negative kinetic terms.
For vector coupling constant obeying 0< \vec{\lambda}^2 < (D-1)/(D-2) a
subclass of non-singular solutions is singled out. The solutions from this
subclass are regular for all values of synchronous "time" \tau \in (- \infty, +
\infty). For \vec{\lambda}^2 < 1/(D-2) we get an asymptotically accelerated and
isotropic expansion for large values of \tau.
| [
{
"created": "Mon, 11 Apr 2005 14:04:10 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jul 2005 13:24:18 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Alimi",
"J. -M.",
""
],
[
"Ivashchuk",
"V. D.",
""
],
[
"Melnikov",
"V. N.",
""
]
] | Using developed earlier our methods for multidimensional models \cite{M1,M2,M3} a family of cosmological-type solutions in D-dimensional model with two sets of scalar fields \vec{\phi} and \vec{\psi} and exponential potential depending upon \vec{\phi} is considered. The solutions are defined on a product of n Ricci-flat spaces. The fields from \vec{\phi} have positive kinetic terms and \vec{\psi} are "phantom" fields with negative kinetic terms. For vector coupling constant obeying 0< \vec{\lambda}^2 < (D-1)/(D-2) a subclass of non-singular solutions is singled out. The solutions from this subclass are regular for all values of synchronous "time" \tau \in (- \infty, + \infty). For \vec{\lambda}^2 < 1/(D-2) we get an asymptotically accelerated and isotropic expansion for large values of \tau. |
1104.3079 | Johannes Hartung | Johannes Hartung and Jan Steinhoff | Next-to-next-to-leading order post-Newtonian spin-orbit Hamiltonian for
self-gravitating binaries | 9 pages, v2: revised version, v3: published version, v4: typo
corrected | Annalen Phys. 523:783,2011 | 10.1002/andp.201100094 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the next-to-next-to-leading order post-Newtonian (PN) spin-orbit
Hamiltonian for two self-gravitating spinning compact objects. If at least one
of the objects is rapidly rotating, then the corresponding interaction is
comparable in strength to a 3.5PN effect. The result in the present paper in
fact completes the knowledge of the post-Newtonian Hamiltonian for binary
spinning black holes up to and including 3.5PN. The Hamiltonian is checked via
known results for the test-spin case and via the global Poincare algebra with
the center-of-mass vector uniquely determined by an ansatz.
| [
{
"created": "Fri, 15 Apr 2011 15:04:40 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Sep 2011 10:53:14 GMT",
"version": "v2"
},
{
"created": "Tue, 4 Oct 2011 10:27:12 GMT",
"version": "v3"
},
{
"created": "Wed, 15 Aug 2012 15:25:06 GMT",
"version": "v4"
}
] | 2012-08-16 | [
[
"Hartung",
"Johannes",
""
],
[
"Steinhoff",
"Jan",
""
]
] | We present the next-to-next-to-leading order post-Newtonian (PN) spin-orbit Hamiltonian for two self-gravitating spinning compact objects. If at least one of the objects is rapidly rotating, then the corresponding interaction is comparable in strength to a 3.5PN effect. The result in the present paper in fact completes the knowledge of the post-Newtonian Hamiltonian for binary spinning black holes up to and including 3.5PN. The Hamiltonian is checked via known results for the test-spin case and via the global Poincare algebra with the center-of-mass vector uniquely determined by an ansatz. |
0909.1989 | Jeffrey Winicour | Jeffrey Winicour | Disembodied boundary data for Einstein's equations | Section added on numerical application. New figure | Phys.Rev.D80:124043,2009 | 10.1103/PhysRevD.80.124043 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A strongly well-posed initial boundary value problem based upon
constraint-preserving boundary conditions of the Sommerfeld type has been
established for the harmonic formulation of the vacuum Einstein's equations.
These Sommerfeld conditions have been previously presented in a 4-dimensional
geometric form. Here we recast the associated boundary data as 3-dimensional
tensor fields intrinsic to the boundary. This provides a geometric presentation
of the boundary data analogous to the 3-dimensional presentation of Cauchy data
in terms of 3-metric and extrinsic curvature. In particular, diffeomorphisms of
the boundary data lead to vacuum spacetimes with isometric geometries. The
proof of well-posedness is valid for the harmonic formulation and its
generalizations. The Sommerfeld conditions can be directly applied to existing
harmonic codes which have been used in simulating binary black holes, thus
ensuring boundary stability of the underlying analytic system. The geometric
form of the boundary conditions also allows them to be formally applied to any
metric formulation of Einstein's equations, although well-posedness of the
boundary problem is no longer ensured. We discuss to what extent such a formal
application might be implemented in a constraint preserving manner to 3+1
formulations, such as the Baumgarte-Shapiro-Shibata-Nakamura system which has
been highly successful in binary black hole simulation.
| [
{
"created": "Thu, 10 Sep 2009 17:03:24 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Nov 2009 13:57:15 GMT",
"version": "v2"
}
] | 2010-01-07 | [
[
"Winicour",
"Jeffrey",
""
]
] | A strongly well-posed initial boundary value problem based upon constraint-preserving boundary conditions of the Sommerfeld type has been established for the harmonic formulation of the vacuum Einstein's equations. These Sommerfeld conditions have been previously presented in a 4-dimensional geometric form. Here we recast the associated boundary data as 3-dimensional tensor fields intrinsic to the boundary. This provides a geometric presentation of the boundary data analogous to the 3-dimensional presentation of Cauchy data in terms of 3-metric and extrinsic curvature. In particular, diffeomorphisms of the boundary data lead to vacuum spacetimes with isometric geometries. The proof of well-posedness is valid for the harmonic formulation and its generalizations. The Sommerfeld conditions can be directly applied to existing harmonic codes which have been used in simulating binary black holes, thus ensuring boundary stability of the underlying analytic system. The geometric form of the boundary conditions also allows them to be formally applied to any metric formulation of Einstein's equations, although well-posedness of the boundary problem is no longer ensured. We discuss to what extent such a formal application might be implemented in a constraint preserving manner to 3+1 formulations, such as the Baumgarte-Shapiro-Shibata-Nakamura system which has been highly successful in binary black hole simulation. |
2310.04359 | Cameron Bunney | Cameron R. D. Bunney | Stationary trajectories in Minkowski spacetimes | 13 pages. v2: Added sentence to Section II B 2. after referee
comments | J. Math. Phys. 65, 052501 (2024) | 10.1063/5.0205471 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We determine the conjugacy classes of the Poincar\'e group
$\mathrm{ISO}^+(n,1)$ and apply this to classify the stationary trajectories of
Minkowski spacetimes in terms of timelike Killing vectors. Stationary
trajectories are the orbits of timelike Killing vectors and, equivalently, the
solutions to Frenet-Serret equations with constant curvature coefficients. We
extend the $3+1$ Minkowski spacetime Frenet-Serret equations due to Letaw to
Minkowski spacetimes of arbitrary dimension. We present the explicit families
of stationary trajectories in $4+1$ Minkowski spacetime.
| [
{
"created": "Fri, 6 Oct 2023 16:29:35 GMT",
"version": "v1"
},
{
"created": "Mon, 6 May 2024 20:53:30 GMT",
"version": "v2"
}
] | 2024-05-08 | [
[
"Bunney",
"Cameron R. D.",
""
]
] | We determine the conjugacy classes of the Poincar\'e group $\mathrm{ISO}^+(n,1)$ and apply this to classify the stationary trajectories of Minkowski spacetimes in terms of timelike Killing vectors. Stationary trajectories are the orbits of timelike Killing vectors and, equivalently, the solutions to Frenet-Serret equations with constant curvature coefficients. We extend the $3+1$ Minkowski spacetime Frenet-Serret equations due to Letaw to Minkowski spacetimes of arbitrary dimension. We present the explicit families of stationary trajectories in $4+1$ Minkowski spacetime. |
2404.01880 | Alessio Lapponi | Alessio Lapponi, Jorma Louko, Stefano Mancini | Making two particle detectors in flat spacetime communicate quantumly | 29 pages, 4 figures | Phys. Rev. D 110, 025018 (2024) | 10.1103/PhysRevD.110.025018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A communication protocol with non-zero quantum capacity is found when the two
communicating parts are particle detector models in (3+1)-dimensional
spacetime. In particular, as detectors, we consider two harmonic oscillators
interacting with a scalar field, whose evolution is generalized for whatever
background spacetime and whatever spacetime smearing of the detectors. We then
specialize to Minkowski spacetime and an initial Minkowski vacuum, considering
a rapid interaction between the field and the two detectors, studying the case
where the receiver is static and the sender is moving. The possibility to have
a quantum capacity greater than zero stems from a relative acceleration between
the detectors. Indeed, no reliable quantum communication is possible when the
two detectors are static or moving inertially with respect to each other, but a
reliable quantum communication can be achieved between a uniformly accelerated
sender and an inertial receiver.
| [
{
"created": "Tue, 2 Apr 2024 12:13:40 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Jul 2024 12:52:51 GMT",
"version": "v2"
}
] | 2024-07-25 | [
[
"Lapponi",
"Alessio",
""
],
[
"Louko",
"Jorma",
""
],
[
"Mancini",
"Stefano",
""
]
] | A communication protocol with non-zero quantum capacity is found when the two communicating parts are particle detector models in (3+1)-dimensional spacetime. In particular, as detectors, we consider two harmonic oscillators interacting with a scalar field, whose evolution is generalized for whatever background spacetime and whatever spacetime smearing of the detectors. We then specialize to Minkowski spacetime and an initial Minkowski vacuum, considering a rapid interaction between the field and the two detectors, studying the case where the receiver is static and the sender is moving. The possibility to have a quantum capacity greater than zero stems from a relative acceleration between the detectors. Indeed, no reliable quantum communication is possible when the two detectors are static or moving inertially with respect to each other, but a reliable quantum communication can be achieved between a uniformly accelerated sender and an inertial receiver. |
gr-qc/0510027 | Peter D'Eath | A.N.St.J. Farley, P.D.D'Eath | Bogoliubov transformations for amplitudes in black-hole evaporation | null | Phys.Lett. B613 (2005) 181-188 | 10.1016/j.physletb.2005.03.034 | null | gr-qc | null | The familiar approach to quantum radiation following collapse to a black hole
proceeds via Bogoliubov transformations, and yields probabilities for final
outcomes. In our (complex) approach, we find quantum amplitudes, not just
probabilities, by following Feynman's $+i\epsilon$ prescription. Initial and
final data for Einstein gravity and (say) a massless scalar field are specified
on a pair of asymptotically-flat space-like hypersurfaces $\Sigma_I$ and
$\Sigma_F$; both are diffeomorphic to ${\Bbb R}^3$. Denote by $T$ the (real)
Lorentzian proper-time interval between the surfaces, as measured at spatial
infinity. Then rotate: $T\to{\mid}T{\mid}\exp(-i\theta),0<\theta\leq \pi/2$.
The {\it classical} boundary-value problem is expected to be well-posed on a
region of topology $I\times{\Bbb R}^3$, where $I$ is a closed interval. For a
locally-supersymmetric theory, the quantum amplitude should be dominated by the
semi-classical expression $\exp(iS_{\rm class})$, where $S_{\rm class}$ is the
classical action. One finds the Lorentzian quantum amplitude from the limit
$\theta\to 0_+$. In the usual approach, the only possible such final surfaces
are in the strong-field region shortly before the curvature singularity. In our
approach one can put arbitrary smooth gravitational data on $\Sigma_F$,
provided that it has the correct mass $M$ -- the singularity is by-passed in
the analytic continuation. Here, we consider Bogoliubov transformations and
their possible relation to the probability distribution and density matrix in
the traditional approach. We find that our probability distribution for
configurations of the final scalar field cannot be expressed in terms of the
diagonal elements of some non-trivial density-matrix distribution.
| [
{
"created": "Fri, 7 Oct 2005 15:37:55 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Farley",
"A. N. St. J.",
""
],
[
"D'Eath",
"P. D.",
""
]
] | The familiar approach to quantum radiation following collapse to a black hole proceeds via Bogoliubov transformations, and yields probabilities for final outcomes. In our (complex) approach, we find quantum amplitudes, not just probabilities, by following Feynman's $+i\epsilon$ prescription. Initial and final data for Einstein gravity and (say) a massless scalar field are specified on a pair of asymptotically-flat space-like hypersurfaces $\Sigma_I$ and $\Sigma_F$; both are diffeomorphic to ${\Bbb R}^3$. Denote by $T$ the (real) Lorentzian proper-time interval between the surfaces, as measured at spatial infinity. Then rotate: $T\to{\mid}T{\mid}\exp(-i\theta),0<\theta\leq \pi/2$. The {\it classical} boundary-value problem is expected to be well-posed on a region of topology $I\times{\Bbb R}^3$, where $I$ is a closed interval. For a locally-supersymmetric theory, the quantum amplitude should be dominated by the semi-classical expression $\exp(iS_{\rm class})$, where $S_{\rm class}$ is the classical action. One finds the Lorentzian quantum amplitude from the limit $\theta\to 0_+$. In the usual approach, the only possible such final surfaces are in the strong-field region shortly before the curvature singularity. In our approach one can put arbitrary smooth gravitational data on $\Sigma_F$, provided that it has the correct mass $M$ -- the singularity is by-passed in the analytic continuation. Here, we consider Bogoliubov transformations and their possible relation to the probability distribution and density matrix in the traditional approach. We find that our probability distribution for configurations of the final scalar field cannot be expressed in terms of the diagonal elements of some non-trivial density-matrix distribution. |
1706.00368 | Aharon Davidson | Aharon Davidson and Tomer Ygael | Frozen up Dilaton and the GUT/Planck Mass Ratio | 6 pages, v.2 References added, Phys. Lett. B, in press | Phys. Lett. B722, 5 (2017) | 10.1016/j.physletb.2017.06.001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By treating modulus and phase on equal footing, as prescribed by Dirac, local
scale invariance can consistently accompany any Brans-Dicke $\omega$-theory. We
show that in the presence of a soft scale symmetry breaking term, the classical
solution, if it exists, cannot be anything else but general relativistic. The
dilaton modulus gets frozen up by the Weyl-Proca vector field, thereby
constituting a gravitational quasi-Higgs mechanism. Assigning all grand unified
scalars as dilatons, they enjoy Weyl universality, and upon symmetry breaking,
the Planck (mass)$^2$ becomes the sum of all their individual (VEV)$^2$s. The
emerging GUT/Planck (mass)$^2$ ratio is thus $\sim \omega g_{GUT}^2/4\pi$.
| [
{
"created": "Thu, 1 Jun 2017 16:26:15 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Jun 2017 08:32:36 GMT",
"version": "v2"
}
] | 2017-06-27 | [
[
"Davidson",
"Aharon",
""
],
[
"Ygael",
"Tomer",
""
]
] | By treating modulus and phase on equal footing, as prescribed by Dirac, local scale invariance can consistently accompany any Brans-Dicke $\omega$-theory. We show that in the presence of a soft scale symmetry breaking term, the classical solution, if it exists, cannot be anything else but general relativistic. The dilaton modulus gets frozen up by the Weyl-Proca vector field, thereby constituting a gravitational quasi-Higgs mechanism. Assigning all grand unified scalars as dilatons, they enjoy Weyl universality, and upon symmetry breaking, the Planck (mass)$^2$ becomes the sum of all their individual (VEV)$^2$s. The emerging GUT/Planck (mass)$^2$ ratio is thus $\sim \omega g_{GUT}^2/4\pi$. |
2407.10946 | Dhruba Jyoti Gogoi Dr. | Dhruba Jyoti Gogoi, Yassine Sekhmani, Shyamalee Bora, Javlon
Rayimbaev, Jyatsnasree Bora and Ratbay Myrzakulov | Corrected Thermodynamics and Stability of Magnetic charged AdS Black
Holes surrounded by Quintessence | 18 pages, 6 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this study, we explore the corrected thermodynamics of non-linear magnetic
charged anti-de Sitter (AdS) black holes surrounded by quintessence,
incorporating thermal fluctuations and deriving the corrected thermodynamic
potentials. We analyze the effects of corrections due to thermal fluctuations
on various thermodynamic potentials, including enthalpy, Helmholtz free energy,
and Gibbs free energy. Our results show significant impacts on smaller black
holes, with first-order corrections destabilizing them, while second-order
corrections enhance stability with increasing parameter values. The specific
heat analysis further elucidates the stability criteria, indicating that the
large black holes ensure stability against phase transitions. However, the
thermal fluctuations do not affect the physical limitation points as well as
the second-order phase transition points of the black hole. Our findings
highlight the intricate role of thermal fluctuations in black hole
thermodynamics and their influence on stability, providing deeper insights into
the behaviour of black holes under corrected thermodynamic conditions.
| [
{
"created": "Mon, 15 Jul 2024 17:44:30 GMT",
"version": "v1"
}
] | 2024-07-16 | [
[
"Gogoi",
"Dhruba Jyoti",
""
],
[
"Sekhmani",
"Yassine",
""
],
[
"Bora",
"Shyamalee",
""
],
[
"Rayimbaev",
"Javlon",
""
],
[
"Bora",
"Jyatsnasree",
""
],
[
"Myrzakulov",
"Ratbay",
""
]
] | In this study, we explore the corrected thermodynamics of non-linear magnetic charged anti-de Sitter (AdS) black holes surrounded by quintessence, incorporating thermal fluctuations and deriving the corrected thermodynamic potentials. We analyze the effects of corrections due to thermal fluctuations on various thermodynamic potentials, including enthalpy, Helmholtz free energy, and Gibbs free energy. Our results show significant impacts on smaller black holes, with first-order corrections destabilizing them, while second-order corrections enhance stability with increasing parameter values. The specific heat analysis further elucidates the stability criteria, indicating that the large black holes ensure stability against phase transitions. However, the thermal fluctuations do not affect the physical limitation points as well as the second-order phase transition points of the black hole. Our findings highlight the intricate role of thermal fluctuations in black hole thermodynamics and their influence on stability, providing deeper insights into the behaviour of black holes under corrected thermodynamic conditions. |
gr-qc/0604076 | Franklin Felber | Franklin S. Felber | 'Antigravity' Propulsion and Relativistic Hyperdrive | 4 pages, 4 figures, 2 video clips. To be presented at 25th
International Space Development Conference, Los Angeles, 4-7 May 2006 | null | null | null | gr-qc | null | Exact payload trajectories in the strong gravitational fields of compact
masses moving with constant relativistic velocities are calculated. The strong
field of a suitable driver mass at relativistic speeds can quickly propel a
heavy payload from rest to a speed significantly faster than the driver, a
condition called hyperdrive. Hyperdrive thresholds and maxima are calculated as
functions of driver mass and velocity.
| [
{
"created": "Tue, 18 Apr 2006 14:01:15 GMT",
"version": "v1"
}
] | 2009-10-15 | [
[
"Felber",
"Franklin S.",
""
]
] | Exact payload trajectories in the strong gravitational fields of compact masses moving with constant relativistic velocities are calculated. The strong field of a suitable driver mass at relativistic speeds can quickly propel a heavy payload from rest to a speed significantly faster than the driver, a condition called hyperdrive. Hyperdrive thresholds and maxima are calculated as functions of driver mass and velocity. |
1012.2374 | Umpei Miyamoto | Umpei Miyamoto, Hiroya Nemoto, Masahiro Shimano | Particle Creation by Naked Singularities in Higher Dimensions | 1+14 pages, 3 figures, 1 table; v2: footnotes 1 and 5 added | Phys.Rev.D83:084054,2011 | 10.1103/PhysRevD.83.084054 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, the possibility was pointed out by one of the present authors and
his collaborators that an effective naked singularity referred to as "a visible
border of spacetime" is generated by high-energy particle collision in the
context of large extra dimensions or TeV-scale gravity. In this paper, we
investigate the particle creation by a naked singularity in general dimensions,
while adopting a model in which a marginally naked singularity forms in the
collapse of a homothetic lightlike pressureless fluid. We find that the
spectrum deviates from that of Hawking radiation due to scattering near the
singularity but can be recast in quasi-thermal form. The temperature is always
higher than that of Hawking radiation of a same-mass black hole, and can be
arbitrarily high depending on a parameter in the model. This implies that, in
principle, the naked singularity may be distinguished from a black hole in
collider experiments.
| [
{
"created": "Fri, 10 Dec 2010 20:40:49 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Mar 2011 23:12:54 GMT",
"version": "v2"
}
] | 2011-05-12 | [
[
"Miyamoto",
"Umpei",
""
],
[
"Nemoto",
"Hiroya",
""
],
[
"Shimano",
"Masahiro",
""
]
] | Recently, the possibility was pointed out by one of the present authors and his collaborators that an effective naked singularity referred to as "a visible border of spacetime" is generated by high-energy particle collision in the context of large extra dimensions or TeV-scale gravity. In this paper, we investigate the particle creation by a naked singularity in general dimensions, while adopting a model in which a marginally naked singularity forms in the collapse of a homothetic lightlike pressureless fluid. We find that the spectrum deviates from that of Hawking radiation due to scattering near the singularity but can be recast in quasi-thermal form. The temperature is always higher than that of Hawking radiation of a same-mass black hole, and can be arbitrarily high depending on a parameter in the model. This implies that, in principle, the naked singularity may be distinguished from a black hole in collider experiments. |
gr-qc/9805063 | Beverly K. Berger | Beverly K. Berger, David Garfinkle, James Isenberg, Vincent Moncrief,
Marsha Weaver | The Singularity in Generic Gravitational Collapse Is Spacelike, Local,
and Oscillatory | 7 pages includes 4 figures. Uses Revtex and psfig. Received
"honorable mention" in 1998 Gravity Research Foundation essay contest.
Submitted to Mod. Phys. Lett. A | Mod.Phys.Lett. A13 (1998) 1565-1574 | 10.1142/S0217732398001649 | null | gr-qc | null | A longstanding conjecture by Belinskii, Khalatnikov, and Lifshitz that the
singularity in generic gravitational collapse is spacelike, local, and
oscillatory is explored analytically and numerically in spatially inhomogeneous
cosmological spacetimes. With a convenient choice of variables, it can be seen
analytically how nonlinear terms in Einstein's equations control the approach
to the singularity and cause oscillatory behavior. The analytic picture
requires the drastic assumption that each spatial point evolves toward the
singularity as an independent spatially homogeneous universe. In every case,
detailed numerical simulations of the full Einstein evolution equations support
this assumption.
| [
{
"created": "Sun, 17 May 1998 19:22:03 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Berger",
"Beverly K.",
""
],
[
"Garfinkle",
"David",
""
],
[
"Isenberg",
"James",
""
],
[
"Moncrief",
"Vincent",
""
],
[
"Weaver",
"Marsha",
""
]
] | A longstanding conjecture by Belinskii, Khalatnikov, and Lifshitz that the singularity in generic gravitational collapse is spacelike, local, and oscillatory is explored analytically and numerically in spatially inhomogeneous cosmological spacetimes. With a convenient choice of variables, it can be seen analytically how nonlinear terms in Einstein's equations control the approach to the singularity and cause oscillatory behavior. The analytic picture requires the drastic assumption that each spatial point evolves toward the singularity as an independent spatially homogeneous universe. In every case, detailed numerical simulations of the full Einstein evolution equations support this assumption. |
gr-qc/0011052 | Alessandra Buonanno | Alessandra Buonanno and Thibault Damour | Binary black holes coalescence: transition from adiabatic inspiral to
plunge | 2 pages; contributed paper to the IX Marcel Grossmann Meeting in
Rome, July 2000 | null | null | null | gr-qc | null | Using two recent techniques giving non-perturbative re-summed estimates of
the damping and of the conservative part of the dynamics of two-body systems,
we describe the transition between adiabatic inspiral and plunge in binary
non-spinning black holes moving along quasi-circular orbits.
| [
{
"created": "Tue, 14 Nov 2000 21:38:55 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Buonanno",
"Alessandra",
""
],
[
"Damour",
"Thibault",
""
]
] | Using two recent techniques giving non-perturbative re-summed estimates of the damping and of the conservative part of the dynamics of two-body systems, we describe the transition between adiabatic inspiral and plunge in binary non-spinning black holes moving along quasi-circular orbits. |
gr-qc/9305016 | null | Alan Daughton, Jorma Louko, and Rafael D. Sorkin | Initial conditions and unitarity in unimodular quantum cosmology | 5 pages, Plain TeX, SU-GP-93/5-3 | null | null | null | gr-qc hep-th | null | We consider quantization of the positive curvature Friedmann cosmology in the
unimodular modification of Einstein's theory, in which the spacetime
four-volume appears as an explicit time variable. The Hamiltonian admits
self-adjoint extensions that give unitary evolution in the Hilbert space
associated with the Schr\"odinger equation. The semiclassical estimate to the
no-boundary wave function of Hartle and Hawking is found. If this estimate is
accurate, there is a continuous flux of probability into the configuration
space from vanishing three-volume, and the no-boundary wave function evolves
nonunitarily. Generalizations of these results hold in a class of anisotropic
cosmologies. (Talk given at the 5th Canadian Conference on General Relativity
and Relativistic Astrophysics, Waterloo, Ontario, Canada, May 1993.)
| [
{
"created": "Tue, 18 May 1993 22:42:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Daughton",
"Alan",
""
],
[
"Louko",
"Jorma",
""
],
[
"Sorkin",
"Rafael D.",
""
]
] | We consider quantization of the positive curvature Friedmann cosmology in the unimodular modification of Einstein's theory, in which the spacetime four-volume appears as an explicit time variable. The Hamiltonian admits self-adjoint extensions that give unitary evolution in the Hilbert space associated with the Schr\"odinger equation. The semiclassical estimate to the no-boundary wave function of Hartle and Hawking is found. If this estimate is accurate, there is a continuous flux of probability into the configuration space from vanishing three-volume, and the no-boundary wave function evolves nonunitarily. Generalizations of these results hold in a class of anisotropic cosmologies. (Talk given at the 5th Canadian Conference on General Relativity and Relativistic Astrophysics, Waterloo, Ontario, Canada, May 1993.) |
0704.2983 | John T. Whelan | Giancarlo Cella, Carlo Nicola Colacino, Elena Cuoco, Angela Di
Virgilio, Tania Regimbau, Emma L Robinson and John T Whelan (for the
LSC-Virgo working group on stochastic backgrounds) | Prospects for Stochastic Background Searches Using Virgo and LSC
Interferometers | 11 pages, uses IOP style files, submitted to CQG for GWDAW11
proceedings; revised in response to referee comments | Class.Quant.Grav.24:S639-S648,2007 | 10.1088/0264-9381/24/19/S26 | LIGO-P070028-03-Z; AEI-2007-017 | gr-qc | null | We consider the question of cross-correlation measurements using Virgo and
the LSC Interferometers (LIGO Livingston, LIGO Hanford, and GEO600) to search
for a stochastic gravitational-wave background. We find that inclusion of Virgo
into the network will substantially improve the sensitivity to correlations
above 200 Hz if all detectors are operating at their design sensitivity. This
is illustrated using a simulated isotropic stochastic background signal,
generated with an astrophysically-motivated spectrum, injected into 24 hours of
simulated noise for the LIGO and Virgo interferometers.
| [
{
"created": "Mon, 23 Apr 2007 12:09:47 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Jul 2007 10:41:16 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Cella",
"Giancarlo",
"",
"for the\n LSC-Virgo working group on stochastic backgrounds"
],
[
"Colacino",
"Carlo Nicola",
"",
"for the\n LSC-Virgo working group on stochastic backgrounds"
],
[
"Cuoco",
"Elena",
"",
"for the\n LSC-Virgo working group on stochastic backgrounds"
],
[
"Di Virgilio",
"Angela",
"",
"for the\n LSC-Virgo working group on stochastic backgrounds"
],
[
"Regimbau",
"Tania",
"",
"for the\n LSC-Virgo working group on stochastic backgrounds"
],
[
"Robinson",
"Emma L",
"",
"for the\n LSC-Virgo working group on stochastic backgrounds"
],
[
"Whelan",
"John T",
"",
"for the\n LSC-Virgo working group on stochastic backgrounds"
]
] | We consider the question of cross-correlation measurements using Virgo and the LSC Interferometers (LIGO Livingston, LIGO Hanford, and GEO600) to search for a stochastic gravitational-wave background. We find that inclusion of Virgo into the network will substantially improve the sensitivity to correlations above 200 Hz if all detectors are operating at their design sensitivity. This is illustrated using a simulated isotropic stochastic background signal, generated with an astrophysically-motivated spectrum, injected into 24 hours of simulated noise for the LIGO and Virgo interferometers. |
1604.02513 | Thomas Callister | Thomas Callister, Letizia Sammut, Shi Qiu, Ilya Mandel, and Eric
Thrane | Limits of Astrophysics with Gravitational-Wave Backgrounds | 11 pages, 6 figures, published in PRX. Minor updates to match
published version | Phys. Rev. X 6, 031018 (2016) | 10.1103/PhysRevX.6.031018 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent Advanced LIGO detection of gravitational waves from the binary
black hole GW150914 suggests there exists a large population of merging binary
black holes in the Universe. Although most are too distant to be individually
resolved by advanced detectors, the superposition of gravitational waves from
many unresolvable binaries is expected to create an astrophysical stochastic
background. Recent results from the LIGO and Virgo collaborations show that
this astrophysical background is within reach of Advanced LIGO. In principle,
the binary black hole background encodes interesting astrophysical properties,
such as the mass distribution and redshift distribution of distant binaries.
However, we show that this information will be difficult to extract with the
current configuration of advanced detectors (and using current data analysis
tools). Additionally, the binary black hole background also constitutes a
foreground that limits the ability of advanced detectors to observe other
interesting stochastic background signals, for example from cosmic strings or
phase transitions in the early Universe. We quantify this effect.
| [
{
"created": "Sat, 9 Apr 2016 02:33:57 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Aug 2016 20:40:19 GMT",
"version": "v2"
}
] | 2016-08-17 | [
[
"Callister",
"Thomas",
""
],
[
"Sammut",
"Letizia",
""
],
[
"Qiu",
"Shi",
""
],
[
"Mandel",
"Ilya",
""
],
[
"Thrane",
"Eric",
""
]
] | The recent Advanced LIGO detection of gravitational waves from the binary black hole GW150914 suggests there exists a large population of merging binary black holes in the Universe. Although most are too distant to be individually resolved by advanced detectors, the superposition of gravitational waves from many unresolvable binaries is expected to create an astrophysical stochastic background. Recent results from the LIGO and Virgo collaborations show that this astrophysical background is within reach of Advanced LIGO. In principle, the binary black hole background encodes interesting astrophysical properties, such as the mass distribution and redshift distribution of distant binaries. However, we show that this information will be difficult to extract with the current configuration of advanced detectors (and using current data analysis tools). Additionally, the binary black hole background also constitutes a foreground that limits the ability of advanced detectors to observe other interesting stochastic background signals, for example from cosmic strings or phase transitions in the early Universe. We quantify this effect. |
gr-qc/9701033 | Thomas Baumgarte | Thomas W. Baumgarte, Stuart L. Shapiro, Gregory B. Cook, Mark A.
Scheel, Saul A. Teukolsky | Binary Neutron Stars in Quasi-Equilibrium Circular Orbit: A Fully
Relativistic Treatment | 3 pages LaTeX using sprocl.sty, 2 figures, to appear in: Proceedings
of the 18th Texas Symposium on Relativistic Astrophysics (eds Olinto, Frieman
and Schramm, World Scientific) | null | null | null | gr-qc astro-ph | null | We present a numerical scheme that solves the initial value problem in full
general relativity for a binary neutron star in quasi-equilibrium. While
Newtonian gravity allows for a strict equilibrium, a relativistic binary system
emits gravitational radiation, causing the system to lose energy and slowly
spiral inwards. However, since inspiral occurs on a time scale much longer than
the orbital period, we can adopt a quasi-equilibrium approximation. In this
approximation, we integrate a subset of the Einstein equations coupled to the
equations of relativistic hydrodynamics to solve the initial value problem for
binaries of arbitrary separation, down to the innermost stable orbit.
| [
{
"created": "Tue, 14 Jan 1997 23:29:03 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Baumgarte",
"Thomas W.",
""
],
[
"Shapiro",
"Stuart L.",
""
],
[
"Cook",
"Gregory B.",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Teukolsky",
"Saul A.",
""
]
] | We present a numerical scheme that solves the initial value problem in full general relativity for a binary neutron star in quasi-equilibrium. While Newtonian gravity allows for a strict equilibrium, a relativistic binary system emits gravitational radiation, causing the system to lose energy and slowly spiral inwards. However, since inspiral occurs on a time scale much longer than the orbital period, we can adopt a quasi-equilibrium approximation. In this approximation, we integrate a subset of the Einstein equations coupled to the equations of relativistic hydrodynamics to solve the initial value problem for binaries of arbitrary separation, down to the innermost stable orbit. |
1808.04668 | Katy Clough Dr | Katy Clough, Tim Dietrich and Jens C. Niemeyer | Axion star collisions with black holes and neutron stars in full 3D
numerical relativity | 13 pages, 14 figures | Phys. Rev. D 98, 083020 (2018) | 10.1103/PhysRevD.98.083020 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Axions are a potential dark matter candidate, which may condense and form
self gravitating compact objects, called axion stars (ASs). In this work, we
study for the first time head-on collisions of relativistic ASs with black
holes (BHs) and neutron stars (NSs). In the case of BH-AS mergers we find that,
in general, the largest scalar clouds are produced by mergers of low
compactness ASs and spinning BHs. Although in most of the cases which we study
the majority of the mass is absorbed by the BH within a short time after the
merger, in favourable cases the remaining cloud surrounding the final BH
remnant can be as large as 30% of the initial axion star mass, with a bosonic
cloud mass of order ~ 0.1 M_BH and peak energy density comparable to that
obtained in a superradiant build up. This provides a dynamical mechanism for
the formation of long lived scalar hair, which could lead to observable signals
in cases where the axion interacts with baryonic matter around the BH, or where
it forms the seed of a future superradiant build up in highly spinning cases.
Considering NS-AS collisions we find two possible final states (i) a BH
surrounded by a (small) scalar cloud, or (ii) a stable NS enveloped in an axion
cloud of roughly the same mass as the initial AS. Whilst for low mass ASs the
NS is only mildly perturbed by the collision, a larger mass AS gives rise to a
massive ejection of baryonic mass from the system, purely due to gravitational
effects. Therefore, even in the absence of a direct axion coupling to baryonic
matter, NS-AS collisions could give rise to electromagnetic observables in
addition to their gravitational wave signatures.
| [
{
"created": "Tue, 14 Aug 2018 13:07:26 GMT",
"version": "v1"
}
] | 2018-10-31 | [
[
"Clough",
"Katy",
""
],
[
"Dietrich",
"Tim",
""
],
[
"Niemeyer",
"Jens C.",
""
]
] | Axions are a potential dark matter candidate, which may condense and form self gravitating compact objects, called axion stars (ASs). In this work, we study for the first time head-on collisions of relativistic ASs with black holes (BHs) and neutron stars (NSs). In the case of BH-AS mergers we find that, in general, the largest scalar clouds are produced by mergers of low compactness ASs and spinning BHs. Although in most of the cases which we study the majority of the mass is absorbed by the BH within a short time after the merger, in favourable cases the remaining cloud surrounding the final BH remnant can be as large as 30% of the initial axion star mass, with a bosonic cloud mass of order ~ 0.1 M_BH and peak energy density comparable to that obtained in a superradiant build up. This provides a dynamical mechanism for the formation of long lived scalar hair, which could lead to observable signals in cases where the axion interacts with baryonic matter around the BH, or where it forms the seed of a future superradiant build up in highly spinning cases. Considering NS-AS collisions we find two possible final states (i) a BH surrounded by a (small) scalar cloud, or (ii) a stable NS enveloped in an axion cloud of roughly the same mass as the initial AS. Whilst for low mass ASs the NS is only mildly perturbed by the collision, a larger mass AS gives rise to a massive ejection of baryonic mass from the system, purely due to gravitational effects. Therefore, even in the absence of a direct axion coupling to baryonic matter, NS-AS collisions could give rise to electromagnetic observables in addition to their gravitational wave signatures. |
0802.3990 | S Habib Mazharimousavi | S. Habib Mazharimousavi, M. Halilsoy and Z. Amirabi | N-Dimensional non-abelian dilatonic, stable black holes and their
Born-Infeld extension | 21 pages, no figures, to appear in in GRG | Gen Rel.Grav.42:261-280,2010 | 10.1007/s10714-009-0835-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find large classes of non-asymptotically flat Einstein-Yang-Mills-Dilaton
(EYMD) and Einstein-Yang-Mills-Born-Infeld-Dilaton (EYMBID) black holes in
N-dimensional spherically symmetric spacetime expressed in terms of the
quasilocal mass. Extension of the dilatonic YM solution to N-dimensions has
been possible by employing the generalized Wu-Yang ansatz. Another metric
ansatz, which aided in finding exact solutions is the functional dependence of
the radius function on the dilaton field. These classes of black holes are
stable against linear radial perturbations. In the limit of vanishing dilaton
we obtain Bertotti-Robinson (BR) type metrics with the topology of
$AdS_{2}\times S^{N-2}.$ Since connection can be established between dilaton
and a scalar field of Brans-Dicke (BD) type we obtain black hole solutions also
in the Brans-Dicke-Yang-Mills (BDYM) theory as well.
| [
{
"created": "Wed, 27 Feb 2008 10:56:45 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Jun 2008 07:52:08 GMT",
"version": "v2"
},
{
"created": "Sun, 2 Nov 2008 18:24:51 GMT",
"version": "v3"
},
{
"created": "Fri, 22 May 2009 20:26:02 GMT",
"version": "v4"
}
] | 2010-05-25 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"M.",
""
],
[
"Amirabi",
"Z.",
""
]
] | We find large classes of non-asymptotically flat Einstein-Yang-Mills-Dilaton (EYMD) and Einstein-Yang-Mills-Born-Infeld-Dilaton (EYMBID) black holes in N-dimensional spherically symmetric spacetime expressed in terms of the quasilocal mass. Extension of the dilatonic YM solution to N-dimensions has been possible by employing the generalized Wu-Yang ansatz. Another metric ansatz, which aided in finding exact solutions is the functional dependence of the radius function on the dilaton field. These classes of black holes are stable against linear radial perturbations. In the limit of vanishing dilaton we obtain Bertotti-Robinson (BR) type metrics with the topology of $AdS_{2}\times S^{N-2}.$ Since connection can be established between dilaton and a scalar field of Brans-Dicke (BD) type we obtain black hole solutions also in the Brans-Dicke-Yang-Mills (BDYM) theory as well. |
gr-qc/0004028 | Jan Fikar | J. Fikar, J. Horsky | Generating conjecture and Einstein-Maxwell field of plane symmetry | 11 pages, 6 figures | Czech.J.Phys. 49 (1999) 1423-1432 | 10.1023/A:1021153827506 | null | gr-qc | null | For the plane symmetry we have found the electro-vacuum exact solutions of
the Einstein-Maxwell equations and we have shown that one of them is equivalent
to the McVittie solution of a charged infinite thin plane. The analytical
extension has been accomplished and the Penrose conformal diagram has been
obtained as well.
| [
{
"created": "Mon, 10 Apr 2000 08:33:21 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Fikar",
"J.",
""
],
[
"Horsky",
"J.",
""
]
] | For the plane symmetry we have found the electro-vacuum exact solutions of the Einstein-Maxwell equations and we have shown that one of them is equivalent to the McVittie solution of a charged infinite thin plane. The analytical extension has been accomplished and the Penrose conformal diagram has been obtained as well. |
1309.2452 | Mohammad Reza Setare | M. R. Setare and V. Kamali | Warm Vector Inflation | 23 pages, 8 figures. Accepted for publication in PLB (2013) | null | 10.1016/j.physletb.2013.08.076 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we introduce the "warm vector inflation" scenario. In warm
inflation scenario radiation is produced during the inflation epoch and
reheating is avoided. Slow-roll and perturbation parameters of this model are
presented. We develop our model using intermediate inflation model. In this
case, the model is compatible with observational data. We also study the model
using another exact cosmological solution, named logamediate scenario. We
present slow-roll and Hubble parameters, power spectrum and tensor-scalar ratio
in terms of inflaton. The model is compatible with WMAP7 and Planck
observational data.
| [
{
"created": "Tue, 10 Sep 2013 10:39:07 GMT",
"version": "v1"
}
] | 2015-06-17 | [
[
"Setare",
"M. R.",
""
],
[
"Kamali",
"V.",
""
]
] | In this paper we introduce the "warm vector inflation" scenario. In warm inflation scenario radiation is produced during the inflation epoch and reheating is avoided. Slow-roll and perturbation parameters of this model are presented. We develop our model using intermediate inflation model. In this case, the model is compatible with observational data. We also study the model using another exact cosmological solution, named logamediate scenario. We present slow-roll and Hubble parameters, power spectrum and tensor-scalar ratio in terms of inflaton. The model is compatible with WMAP7 and Planck observational data. |
1502.00688 | Manuela G. Rodrigues | Manuela G. Rodrigues, Vilson T. Zanchin | Charged black holes in expanding Einstein-de Sitter universes | Accepted for publication in Class. Quant. Grav | Class.Quant.Grav. 32 (2015) 11, 115004 | 10.1088/0264-9381/32/11/115004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspired in a previous work by McClure and Dyer (Classical Quantum Gravity
23, 1971 (2006)), we analyze some solutions of the Einstein-Maxwell equations
which were originally written to describe charged black holes in cosmological
backgrounds. A detailed analysis of the electromagnetic sources for a
sufficiently general metric is performed, and then we focus on deriving the
electromagnetic four-current as well as the conserved electric charge of each
metric. The charged McVittie solution is revisited and a brief study of its
causal structure is performed, showing that it may represent a charged black
hole in an expanding universe, with the black hole horizon being formed at
infinite late times. Charged versions of solutions originally put forward by
Vaidya (Vd) and Sultana and Dyer (SD) are also analyzed. It is shown that the
charged Sultana-Dyer metric requires a global electric current, besides a
central (pointlike) electric charge. With the aim of comparing to the charged
McVittie metric, new charged solutions of Vd and SD type are considered. In
these cases, the original mass and charge parameters are replaced by particular
functions of the cosmological time. In the new generalized charged Vaidya
metric the black hole horizon never forms, whereas in the new generalized
Sultana-Dyer case both the Cauchy and the black hole horizons develop at
infinite late times. A charged version of the Thakurta metric is also studied
here. It is also a new solution. As in the charged Sultana-Dyer case, the
natural source of the electromagnetic field is a central electric charge with
an additional global electric current. The global structure is briefly studied
and it is verified that the corresponding spacetime may represent a charged
black hole in a cosmological background. All the solutions present initial
singularities as found in the McVittie metric.
| [
{
"created": "Mon, 2 Feb 2015 23:53:12 GMT",
"version": "v1"
},
{
"created": "Sat, 9 May 2015 15:02:04 GMT",
"version": "v2"
}
] | 2015-07-01 | [
[
"Rodrigues",
"Manuela G.",
""
],
[
"Zanchin",
"Vilson T.",
""
]
] | Inspired in a previous work by McClure and Dyer (Classical Quantum Gravity 23, 1971 (2006)), we analyze some solutions of the Einstein-Maxwell equations which were originally written to describe charged black holes in cosmological backgrounds. A detailed analysis of the electromagnetic sources for a sufficiently general metric is performed, and then we focus on deriving the electromagnetic four-current as well as the conserved electric charge of each metric. The charged McVittie solution is revisited and a brief study of its causal structure is performed, showing that it may represent a charged black hole in an expanding universe, with the black hole horizon being formed at infinite late times. Charged versions of solutions originally put forward by Vaidya (Vd) and Sultana and Dyer (SD) are also analyzed. It is shown that the charged Sultana-Dyer metric requires a global electric current, besides a central (pointlike) electric charge. With the aim of comparing to the charged McVittie metric, new charged solutions of Vd and SD type are considered. In these cases, the original mass and charge parameters are replaced by particular functions of the cosmological time. In the new generalized charged Vaidya metric the black hole horizon never forms, whereas in the new generalized Sultana-Dyer case both the Cauchy and the black hole horizons develop at infinite late times. A charged version of the Thakurta metric is also studied here. It is also a new solution. As in the charged Sultana-Dyer case, the natural source of the electromagnetic field is a central electric charge with an additional global electric current. The global structure is briefly studied and it is verified that the corresponding spacetime may represent a charged black hole in a cosmological background. All the solutions present initial singularities as found in the McVittie metric. |
gr-qc/9904051 | Diego A. R. Dalvit | Diego A. R. Dalvit and Francisco D. Mazzitelli | Quantum corrected geodesics | LaTeX file, 15 pages, no figures | Phys.Rev. D60 (1999) 084018 | 10.1103/PhysRevD.60.084018 | null | gr-qc hep-th | null | We compute the graviton-induced corrections to the trajectory of a classical
test particle. We show that the motion of the test particle is governed by an
effective action given by the expectation value (with respect to the graviton
state) of the classical action. We analyze the quantum corrected equations of
motion for the test particle in two particular backgrounds: a Robertson Walker
spacetime and a 2+1 dimensional spacetime with rotational symmetry. In both
cases we show that the quantum corrected trajectory is not a geodesic of the
background metric.
| [
{
"created": "Tue, 20 Apr 1999 18:06:26 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Dalvit",
"Diego A. R.",
""
],
[
"Mazzitelli",
"Francisco D.",
""
]
] | We compute the graviton-induced corrections to the trajectory of a classical test particle. We show that the motion of the test particle is governed by an effective action given by the expectation value (with respect to the graviton state) of the classical action. We analyze the quantum corrected equations of motion for the test particle in two particular backgrounds: a Robertson Walker spacetime and a 2+1 dimensional spacetime with rotational symmetry. In both cases we show that the quantum corrected trajectory is not a geodesic of the background metric. |
1405.4898 | Cenalo Vaz | Cenalo Vaz | Black holes as Gravitational Atoms | 5 pages, no figures. This essay received the Second Award in the 2014
Gravity Research Foundation Essay Competition | Int. J. Mod. Phys. D 23 (2014) 1441002 | 10.1142/S0218271814410028 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, Almheiri et. al. argued, via a delicate thought experiment, that it
is not consistent to simultaneosuly require that (a) Hawking radiation is pure,
(b) effective field theory is valid outside a stretched horizon and (c)
infalling observers encounter nothing unusual as they cross the horizon. These
are the three fundamental assumptions underlying Black Hole Complementarity and
the authors proposed that the most conservative resolution of the paradox is
that (c) is false and the infalling observer burns up at the horizon (the
horizon acts as a "firewall"). However, the firewall violates the equivalence
principle and breaks the CPT invariance of quantum gravity. This led Hawking to
propose recently that gravitational collapse may not end up producing event
horizons, although he did not give a mechanism for how this may happen. Here we
will support Hawking's conclusion in a quantum gravitational model of dust
collapse. We will show that continued collapse to a singularity can only be
achieved by combining two independent and entire solutions of the
Wheeler-DeWitt equation. We interpret the paradox as simply forbidding such a
combination, which leads naturally to a picture in which matter condenses on
the apparent horizon during quantum collapse.
| [
{
"created": "Mon, 19 May 2014 21:12:46 GMT",
"version": "v1"
}
] | 2014-06-11 | [
[
"Vaz",
"Cenalo",
""
]
] | Recently, Almheiri et. al. argued, via a delicate thought experiment, that it is not consistent to simultaneosuly require that (a) Hawking radiation is pure, (b) effective field theory is valid outside a stretched horizon and (c) infalling observers encounter nothing unusual as they cross the horizon. These are the three fundamental assumptions underlying Black Hole Complementarity and the authors proposed that the most conservative resolution of the paradox is that (c) is false and the infalling observer burns up at the horizon (the horizon acts as a "firewall"). However, the firewall violates the equivalence principle and breaks the CPT invariance of quantum gravity. This led Hawking to propose recently that gravitational collapse may not end up producing event horizons, although he did not give a mechanism for how this may happen. Here we will support Hawking's conclusion in a quantum gravitational model of dust collapse. We will show that continued collapse to a singularity can only be achieved by combining two independent and entire solutions of the Wheeler-DeWitt equation. We interpret the paradox as simply forbidding such a combination, which leads naturally to a picture in which matter condenses on the apparent horizon during quantum collapse. |
1206.0841 | Marta W{\l}odarczyk | Jakub Rembielinski and Marta Wlodarczyk | "Meta" relativity: Against special relativity? | 14 pages, 4 figures | null | null | null | gr-qc hep-th physics.class-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a Lorentz-covariant description of tachyons, free of
inconsistencies. Our approach is based on an appropriate extension of the
special relativity beyond the light barrier, owing to the freedom of
synchronization of distant clocks.
| [
{
"created": "Tue, 5 Jun 2012 08:44:29 GMT",
"version": "v1"
}
] | 2012-06-06 | [
[
"Rembielinski",
"Jakub",
""
],
[
"Wlodarczyk",
"Marta",
""
]
] | We introduce a Lorentz-covariant description of tachyons, free of inconsistencies. Our approach is based on an appropriate extension of the special relativity beyond the light barrier, owing to the freedom of synchronization of distant clocks. |
1002.4572 | Grigoris Panotopoulos | Grigoris Panotopoulos | Bound states between dark matter particles and emission of gravitational
radiation | Accepted for publication in GERG | Gen.Rel.Grav.42:1755-1764,2010 | 10.1007/s10714-010-0946-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Bound states of two weakly interactive massive particles are studied. It is
assumed that the WIMPonium is formed due to the gravitational interaction,
since the weak interaction can sometimes be repulsive. The lifetimes of the
spontaneous emission of gravitational radiation and of the WIMPs annihilation
into a pair of gravitons are computed, and are shown to be many orders of
magnitude larger than the age of the universe.
| [
{
"created": "Wed, 24 Feb 2010 16:01:55 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Panotopoulos",
"Grigoris",
""
]
] | Bound states of two weakly interactive massive particles are studied. It is assumed that the WIMPonium is formed due to the gravitational interaction, since the weak interaction can sometimes be repulsive. The lifetimes of the spontaneous emission of gravitational radiation and of the WIMPs annihilation into a pair of gravitons are computed, and are shown to be many orders of magnitude larger than the age of the universe. |
1402.2813 | Plamen Fiziev | Plamen P Fiziev | Compact static stars in minimal dilatonic gravity | 13 pages, 14 figures, LaTeX file. The present version matches the
journal publication. According to the unknown referee suggestions Section 4.2
and Appendix are added. An essential new estimate for dilaton mass from two
solar masses limit are derived | Modern Physics Letters A, Vol. 32, 1750141 (2017) | 10.1142/S0217732317501413 | SU 2014-1 | gr-qc hep-th math-ph math.MP nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the version \cite{Fiziev14} of this paper we presented for the first time
the basic equations and relations for relativistic static spherically symmetric
stars (SSSS) in the model of minimal dilatonic gravity (MDG). This model is
{\em locally} equivalent to the f(R) theory of gravity and gives an alternative
description of the effects of dark matter and dark energy using the
Branse-Dicke dilaton $\Phi$. To outline the basic properties of the MDG model
of SSSS and to compare them with general relativistic results, in the present
paper we use the relativistic equation of state (EOS) of neutron matter as an
ideal Fermi neutron gas at zero temperature. We overcome the well-known
difficulties of the physics of SSSS in the f(R) theories of gravity
\cite{Felice10,Berti} applying novel highly nontrivial nonlinear boundary
conditions, which depend on the global properties of the solution and on the
EOS. We also introduce two pairs of new notions: cosmological-energy-pressure
densities and dilaton-energy-pressure densities, as well as two new EOS for
them: cosmological EOS (CEOS) and dilaton EOS (DEOS). Special attention is paid
to the dilatonic sphere (in brief -- disphere) of SSSS, introduced in this
paper for the first time. Using several realistic EOS for neutron star (NS):
SLy, BSk19, BSk20 and BSk21, and current observational two-solar-masses-limit,
we derive an estimate for scalar-field-mass $m_\Phi \sim 10^{-13} eV/c^2 \div
4\times 10^{-11} eV/c^2$. Thus, the present version of the paper reflects some
of the recent developments of the topic.
| [
{
"created": "Wed, 12 Feb 2014 13:32:36 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Aug 2017 08:13:25 GMT",
"version": "v2"
}
] | 2017-08-14 | [
[
"Fiziev",
"Plamen P",
""
]
] | In the version \cite{Fiziev14} of this paper we presented for the first time the basic equations and relations for relativistic static spherically symmetric stars (SSSS) in the model of minimal dilatonic gravity (MDG). This model is {\em locally} equivalent to the f(R) theory of gravity and gives an alternative description of the effects of dark matter and dark energy using the Branse-Dicke dilaton $\Phi$. To outline the basic properties of the MDG model of SSSS and to compare them with general relativistic results, in the present paper we use the relativistic equation of state (EOS) of neutron matter as an ideal Fermi neutron gas at zero temperature. We overcome the well-known difficulties of the physics of SSSS in the f(R) theories of gravity \cite{Felice10,Berti} applying novel highly nontrivial nonlinear boundary conditions, which depend on the global properties of the solution and on the EOS. We also introduce two pairs of new notions: cosmological-energy-pressure densities and dilaton-energy-pressure densities, as well as two new EOS for them: cosmological EOS (CEOS) and dilaton EOS (DEOS). Special attention is paid to the dilatonic sphere (in brief -- disphere) of SSSS, introduced in this paper for the first time. Using several realistic EOS for neutron star (NS): SLy, BSk19, BSk20 and BSk21, and current observational two-solar-masses-limit, we derive an estimate for scalar-field-mass $m_\Phi \sim 10^{-13} eV/c^2 \div 4\times 10^{-11} eV/c^2$. Thus, the present version of the paper reflects some of the recent developments of the topic. |
1607.06578 | Peng Qian | Peng Qian, Yi-Fu Cai, Damien A. Easson and Zong-Kuan Guo | Magnetogenesis in bouncing cosmology | null | Phys. Rev. D 94, 083524 (2016) | 10.1103/PhysRevD.94.083524 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the process of magnetogenesis in the context of nonsingular
bounce cosmology. We show that large primordial magnetic fields can be
generated during contraction without encountering strong coupling and
backreaction issues. The fields may seed large-scale magnetic fields with
observationally interesting strengths. This result leads to a theoretical
constraint on the relation of the energy scale of the bounce cosmology to the
number of effective e-folding of the contracting phase in the case of scale
invariance for the power spectrum of primordial magnetic fields. We show that
this constraint can be satisfied in a sizable region of the parameter space for
the nonsingular bounce cosmology.
| [
{
"created": "Fri, 22 Jul 2016 07:16:42 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Aug 2016 12:06:04 GMT",
"version": "v2"
},
{
"created": "Tue, 27 Sep 2016 01:37:35 GMT",
"version": "v3"
}
] | 2016-11-02 | [
[
"Qian",
"Peng",
""
],
[
"Cai",
"Yi-Fu",
""
],
[
"Easson",
"Damien A.",
""
],
[
"Guo",
"Zong-Kuan",
""
]
] | We consider the process of magnetogenesis in the context of nonsingular bounce cosmology. We show that large primordial magnetic fields can be generated during contraction without encountering strong coupling and backreaction issues. The fields may seed large-scale magnetic fields with observationally interesting strengths. This result leads to a theoretical constraint on the relation of the energy scale of the bounce cosmology to the number of effective e-folding of the contracting phase in the case of scale invariance for the power spectrum of primordial magnetic fields. We show that this constraint can be satisfied in a sizable region of the parameter space for the nonsingular bounce cosmology. |
2406.07319 | D\'aniel Barta | D\'aniel Barta | The representation and computational efficiency of the
Tolman-Oppenheimer-Volkoff equations in isotropic coordinates | 20 pages, 9 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This study aims to provide an analytical scheme for computing equilibrium
configurations of relativistic stars by solving the Tolman-Oppenheimer-Volkoff
equations directly in isotropic polar coordinates, as opposed to the commonly
applied methods of rescaling the radial profile of corresponding solutions
obtained in curvature coordinates. This study also provides evidence that the
differential equation for gravitational mass may be replaced by an algebraic
expression relating the metric potential to the energy density in the form of
the quartic equation. Nevertheless, the greater computational expense of
evaluating the algebraic equation renders its application less efficient. A
further objective of this study was to evaluate the performance of the present
computational scheme in the computational time and numerical accuracy. Our
results indicate that the computational time increases with the stiffness of
the constituent matter inside the star. Conversely, the absolute difference
between the gravitational mass obtained by the proposed method and that
computed via the use of LORENE packages initially increases rapidly with the
central energy density, but the rate of growth subsequently declines as the
maximum mass configuration is approached.
| [
{
"created": "Tue, 11 Jun 2024 14:48:52 GMT",
"version": "v1"
}
] | 2024-06-12 | [
[
"Barta",
"Dániel",
""
]
] | This study aims to provide an analytical scheme for computing equilibrium configurations of relativistic stars by solving the Tolman-Oppenheimer-Volkoff equations directly in isotropic polar coordinates, as opposed to the commonly applied methods of rescaling the radial profile of corresponding solutions obtained in curvature coordinates. This study also provides evidence that the differential equation for gravitational mass may be replaced by an algebraic expression relating the metric potential to the energy density in the form of the quartic equation. Nevertheless, the greater computational expense of evaluating the algebraic equation renders its application less efficient. A further objective of this study was to evaluate the performance of the present computational scheme in the computational time and numerical accuracy. Our results indicate that the computational time increases with the stiffness of the constituent matter inside the star. Conversely, the absolute difference between the gravitational mass obtained by the proposed method and that computed via the use of LORENE packages initially increases rapidly with the central energy density, but the rate of growth subsequently declines as the maximum mass configuration is approached. |
2407.16587 | Rodrigo Maier | Rafael F. Aranha, Rodrigo Maier | Boosted Kerr-Newman Black Holes | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we obtain a new solution of Einstein field equations which
describes a boosted Kerr-Newman black hole relative to a Lorentz frame at
future null infinity. To simplify our analysis we consider a particular
configuration in which the boost is aligned with the black hole angular
momentum. The boosted Kerr-Newman black hole is obtained considering the
complete asymptotic Lorentz transformations of Robinson-Trautman coordinates to
Bondi-Sachs, including the perturbation term of the boosted Robinson-Trautman
metric. To verify that the final form of the metric is indeed a solution of
Einstein field equations, we evaluate the corresponding energy-momentum tensor
the boosted Kerr-Newman solution. To this end, we consider the electromagnetic
energy-momentum tensor built with the Kerr boosted metric together with its
timelike killing vector. We show that the Papapetrou field thus obtained
engender an energy-momentum tensor which satisfies Einstein field equations up
to 4th order for the Kerr-Newman metric. To proceed, we examine the causal
structure of the boosted Kerr-Newman black hole in Bondi-Sachs coordinates as
in a preferred timelike foliation. We show that the ultimate effect of a
nonvanishing charge is to shrink the overall size of the event horizon and
ergosphere areas when compared to the neutral boosted Kerr black holes.
Considering the preferred timelike foliation we obtain the electromagnetic
fields for a proper nonrotating frame of reference. We show that while the
electric field displays a pure radial behaviour, the magnetic counterpart
develops an involved structure with two intense lobes of the magnetic field
observed in the direction opposite to the boost.
| [
{
"created": "Tue, 23 Jul 2024 15:40:03 GMT",
"version": "v1"
}
] | 2024-07-24 | [
[
"Aranha",
"Rafael F.",
""
],
[
"Maier",
"Rodrigo",
""
]
] | In this paper we obtain a new solution of Einstein field equations which describes a boosted Kerr-Newman black hole relative to a Lorentz frame at future null infinity. To simplify our analysis we consider a particular configuration in which the boost is aligned with the black hole angular momentum. The boosted Kerr-Newman black hole is obtained considering the complete asymptotic Lorentz transformations of Robinson-Trautman coordinates to Bondi-Sachs, including the perturbation term of the boosted Robinson-Trautman metric. To verify that the final form of the metric is indeed a solution of Einstein field equations, we evaluate the corresponding energy-momentum tensor the boosted Kerr-Newman solution. To this end, we consider the electromagnetic energy-momentum tensor built with the Kerr boosted metric together with its timelike killing vector. We show that the Papapetrou field thus obtained engender an energy-momentum tensor which satisfies Einstein field equations up to 4th order for the Kerr-Newman metric. To proceed, we examine the causal structure of the boosted Kerr-Newman black hole in Bondi-Sachs coordinates as in a preferred timelike foliation. We show that the ultimate effect of a nonvanishing charge is to shrink the overall size of the event horizon and ergosphere areas when compared to the neutral boosted Kerr black holes. Considering the preferred timelike foliation we obtain the electromagnetic fields for a proper nonrotating frame of reference. We show that while the electric field displays a pure radial behaviour, the magnetic counterpart develops an involved structure with two intense lobes of the magnetic field observed in the direction opposite to the boost. |
1204.5122 | Eugenio Bianchi | Eugenio Bianchi | Entropy of Non-Extremal Black Holes from Loop Gravity | 6 pages, 1 figure | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the entropy of non-extremal black holes using the quantum dynamics
of Loop Gravity. The horizon entropy is finite, scales linearly with the area
A, and reproduces the Bekenstein-Hawking expression S = A/4 with the one-fourth
coefficient for all values of the Immirzi parameter. The near-horizon geometry
of a non-extremal black hole - as seen by a stationary observer - is described
by a Rindler horizon. We introduce the notion of a quantum Rindler horizon in
the framework of Loop Gravity. The system is described by a quantum surface and
the dynamics is generated by the boost Hamiltonion of Lorentzian Spinfoams. We
show that the expectation value of the boost Hamiltonian reproduces the local
horizon energy of Frodden, Ghosh and Perez. We study the coupling of the
geometry of the quantum horizon to a two-level system and show that it
thermalizes to the local Unruh temperature. The derived values of the energy
and the temperature allow one to compute the thermodynamic entropy of the
quantum horizon. The relation with the Spinfoam partition function is
discussed.
| [
{
"created": "Mon, 23 Apr 2012 17:43:42 GMT",
"version": "v1"
}
] | 2012-04-24 | [
[
"Bianchi",
"Eugenio",
""
]
] | We compute the entropy of non-extremal black holes using the quantum dynamics of Loop Gravity. The horizon entropy is finite, scales linearly with the area A, and reproduces the Bekenstein-Hawking expression S = A/4 with the one-fourth coefficient for all values of the Immirzi parameter. The near-horizon geometry of a non-extremal black hole - as seen by a stationary observer - is described by a Rindler horizon. We introduce the notion of a quantum Rindler horizon in the framework of Loop Gravity. The system is described by a quantum surface and the dynamics is generated by the boost Hamiltonion of Lorentzian Spinfoams. We show that the expectation value of the boost Hamiltonian reproduces the local horizon energy of Frodden, Ghosh and Perez. We study the coupling of the geometry of the quantum horizon to a two-level system and show that it thermalizes to the local Unruh temperature. The derived values of the energy and the temperature allow one to compute the thermodynamic entropy of the quantum horizon. The relation with the Spinfoam partition function is discussed. |
2208.08736 | Manosh T. Manoharan | Manosh T. Manoharan, N. Shaji, Titus K. Mathew | Holographic dark energy from the laws of thermodynamics with R\'enyi
entropy | 21 pages, 13 figures (including sub-figures). Published in The
European Physical Journal C | Eur. Phys. J. C 83, 19 (2023) | 10.1140/epjc/s10052-023-11202-w | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article investigates the relationship between the holographic principle
and the laws of thermodynamics in explaining the late-time acceleration of the
universe. First, we explore the possibilities of generating the standard
holographic dark energy (SHDE) from the laws of horizon thermodynamics. Except
for entropies that follow an exponent stretched area law, unless we redefine
the horizon temperature, we found it challenging to construct a one-to-one
correspondence between the dark energies defined by the holographic principle
and the laws of thermodynamics. Secondly, in SHDE models, unless we invoke some
phenomenological interactions, it is impossible to explain the late-time cosmic
acceleration with the Hubble horizon as the IR cutoff. On the other hand, it is
possible to induce dark energy as an integration constant using the laws of
thermodynamics on the Hubble horizon. These motivated us to explore a feasible
way to invoke the holographic principle from the laws of horizon
thermodynamics. We show that the additional terms that appear in the modified
Friedmann equations on using entropies other than the Bekenstein-Hawking
entropy in the first law of thermodynamics can behave like a dynamic
holographic dark energy (HDE). We study the features of such an HDE with
R\'enyi entropy as the choice without considering any non-standard
interactions. Interestingly, the resulting form of dark energy reduces to the
standard cosmological constant when R\'enyi entropy reduces to the
Bekenstein-Hawking entropy. By examining different parameters, we affirm the
validity of our approach to dark energy, which respects both holographic
principle and thermodynamics.
| [
{
"created": "Thu, 18 Aug 2022 09:34:56 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Jan 2023 10:29:01 GMT",
"version": "v2"
}
] | 2023-01-18 | [
[
"Manoharan",
"Manosh T.",
""
],
[
"Shaji",
"N.",
""
],
[
"Mathew",
"Titus K.",
""
]
] | This article investigates the relationship between the holographic principle and the laws of thermodynamics in explaining the late-time acceleration of the universe. First, we explore the possibilities of generating the standard holographic dark energy (SHDE) from the laws of horizon thermodynamics. Except for entropies that follow an exponent stretched area law, unless we redefine the horizon temperature, we found it challenging to construct a one-to-one correspondence between the dark energies defined by the holographic principle and the laws of thermodynamics. Secondly, in SHDE models, unless we invoke some phenomenological interactions, it is impossible to explain the late-time cosmic acceleration with the Hubble horizon as the IR cutoff. On the other hand, it is possible to induce dark energy as an integration constant using the laws of thermodynamics on the Hubble horizon. These motivated us to explore a feasible way to invoke the holographic principle from the laws of horizon thermodynamics. We show that the additional terms that appear in the modified Friedmann equations on using entropies other than the Bekenstein-Hawking entropy in the first law of thermodynamics can behave like a dynamic holographic dark energy (HDE). We study the features of such an HDE with R\'enyi entropy as the choice without considering any non-standard interactions. Interestingly, the resulting form of dark energy reduces to the standard cosmological constant when R\'enyi entropy reduces to the Bekenstein-Hawking entropy. By examining different parameters, we affirm the validity of our approach to dark energy, which respects both holographic principle and thermodynamics. |
1808.09291 | Pedro Labra\~na | Pedro Labrana and Hobby Cossio | Emergent Universe by Tunneling in a Jordan-Brans-Dicke Theory | 27 pages, 7 figures, typos corrected, some improvements in section II
and comments added in conclusions. References added. Accepted for publication
in EPJC. arXiv admin note: text overlap with arXiv:1111.5360 | null | 10.1140/epjc/s10052-019-6811-7 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study an alternative scheme for an Emergent Universe scenario
in the context of a Jordan-Brans-Dicke theory, where the universe is initially
in a truly static state supported by a scalar field located in a false vacuum.
The model presents a classically stable past eternal static state which is
broken when, by quantum tunneling, the scalar field decays into a state of true
vacuum and the universe begins to evolve following the extended open
inflationary scheme.
| [
{
"created": "Sat, 25 Aug 2018 18:13:46 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Dec 2018 20:19:11 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Apr 2019 20:42:57 GMT",
"version": "v3"
}
] | 2019-05-01 | [
[
"Labrana",
"Pedro",
""
],
[
"Cossio",
"Hobby",
""
]
] | In this work we study an alternative scheme for an Emergent Universe scenario in the context of a Jordan-Brans-Dicke theory, where the universe is initially in a truly static state supported by a scalar field located in a false vacuum. The model presents a classically stable past eternal static state which is broken when, by quantum tunneling, the scalar field decays into a state of true vacuum and the universe begins to evolve following the extended open inflationary scheme. |
2102.09534 | Fay\c{c}al Hammad | F. Hammad, P. Sadeghi, N. Fleury, A. Leblanc | Fresh look at the effects of gravitational tidal forces on a
freely-falling quantum particle | 33 pages. References added and typos corrected. Accepted for
publication in IJMPD | Int. J. Mod. Phys. D 31, 2150121 (2022) | 10.1142/S0218271821501212 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We take a closer and new look at the effects of tidal forces on the free fall
of a quantum particle inside a spherically symmetric gravitational field. We
derive the corresponding Schr\"odinger equation for the particle by starting
from the fully relativistic Klein-Gordon equation in order (i) to briefly
discuss the issue of the equivalence principle and (ii) to be able to compare
the relativistic terms in the equation to the tidal-force terms. To the second
order of the nonrelativistic approximation, the resulting Schr\"odinger
equation is that of a simple harmonic oscillator in the horizontal direction
and that of an inverted harmonic oscillator in the vertical direction. Two
methods are used for solving the equation in the vertical direction. The first
method is based on a fixed boundary condition, and yields a discrete-energy
spectrum with a wavefunction that is asymptotic to that of a particle in a
linear gravitational field. The second method is based on time-varying boundary
conditions and yields a quantized-energy spectrum that is decaying in time.
Moving on to a freely-falling reference frame, we derive the corresponding
time-dependent energy spectrum. The effects of tidal forces yield an
expectation value for the Hamiltonian and a relative change in time of a
wavepacket's width that are mass-independent. The equivalence principle, which
we understand here as the empirical equivalence between gravitation and
inertia, is discussed based on these various results. For completeness, we
briefly discuss the consequences expected to be obtained for a Bose-Einstein
condensate or a superfluid in free fall using the nonlinear Gross-Pitaevskii
equation.
| [
{
"created": "Thu, 18 Feb 2021 18:25:08 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Sep 2021 13:19:33 GMT",
"version": "v2"
}
] | 2022-03-01 | [
[
"Hammad",
"F.",
""
],
[
"Sadeghi",
"P.",
""
],
[
"Fleury",
"N.",
""
],
[
"Leblanc",
"A.",
""
]
] | We take a closer and new look at the effects of tidal forces on the free fall of a quantum particle inside a spherically symmetric gravitational field. We derive the corresponding Schr\"odinger equation for the particle by starting from the fully relativistic Klein-Gordon equation in order (i) to briefly discuss the issue of the equivalence principle and (ii) to be able to compare the relativistic terms in the equation to the tidal-force terms. To the second order of the nonrelativistic approximation, the resulting Schr\"odinger equation is that of a simple harmonic oscillator in the horizontal direction and that of an inverted harmonic oscillator in the vertical direction. Two methods are used for solving the equation in the vertical direction. The first method is based on a fixed boundary condition, and yields a discrete-energy spectrum with a wavefunction that is asymptotic to that of a particle in a linear gravitational field. The second method is based on time-varying boundary conditions and yields a quantized-energy spectrum that is decaying in time. Moving on to a freely-falling reference frame, we derive the corresponding time-dependent energy spectrum. The effects of tidal forces yield an expectation value for the Hamiltonian and a relative change in time of a wavepacket's width that are mass-independent. The equivalence principle, which we understand here as the empirical equivalence between gravitation and inertia, is discussed based on these various results. For completeness, we briefly discuss the consequences expected to be obtained for a Bose-Einstein condensate or a superfluid in free fall using the nonlinear Gross-Pitaevskii equation. |
gr-qc/9610075 | Adrian Kent | Adrian Kent (DAMTP, University of Cambridge) | Comment on "Spacetime Information" | 11 pages, LaTeX with ReVTeX. References updated | Phys.Rev. D56 (1997) 2469-2472 | 10.1103/PhysRevD.56.2469 | DAMTP/96-93 (revised) | gr-qc quant-ph | null | A recent paper by Hartle [Phys. Rev. D 51, 1800 (1995)] proposes a definition
of "spacetime information" - the information available about a quantum system's
boundary conditions in the various sets of decohering histories it may display
- and investigates its properties. We note here that Hartle's analysis contains
errors which invalidate several of the conclusions. In particular, the proof
that the proposed definition agrees with the standard definition for ordinary
quantum mechanics is invalid, the evaluations of the spacetime information for
time-neutral generalized quantum theories and for generalized quantum theories
with non-unitary evolution are incorrect, and the argument that spacetime
information is conserved on spacelike surfaces in these last theories is
erroneous. We show however that the proposed definition does, in fact, agree
with the standard definition for ordinary quantum mechanics. Hartle's
definition relies on choosing, case by case, a class of fine-grained consistent
sets of histories. We supply a general definition of the relevant class of sets
that agrees with Hartle's definition in the cases explicitly considered and
that generalizes to other cases.
| [
{
"created": "Thu, 31 Oct 1996 19:30:13 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Nov 1996 23:25:49 GMT",
"version": "v2"
},
{
"created": "Fri, 21 Mar 1997 18:20:36 GMT",
"version": "v3"
}
] | 2009-10-28 | [
[
"Kent",
"Adrian",
"",
"DAMTP, University of Cambridge"
]
] | A recent paper by Hartle [Phys. Rev. D 51, 1800 (1995)] proposes a definition of "spacetime information" - the information available about a quantum system's boundary conditions in the various sets of decohering histories it may display - and investigates its properties. We note here that Hartle's analysis contains errors which invalidate several of the conclusions. In particular, the proof that the proposed definition agrees with the standard definition for ordinary quantum mechanics is invalid, the evaluations of the spacetime information for time-neutral generalized quantum theories and for generalized quantum theories with non-unitary evolution are incorrect, and the argument that spacetime information is conserved on spacelike surfaces in these last theories is erroneous. We show however that the proposed definition does, in fact, agree with the standard definition for ordinary quantum mechanics. Hartle's definition relies on choosing, case by case, a class of fine-grained consistent sets of histories. We supply a general definition of the relevant class of sets that agrees with Hartle's definition in the cases explicitly considered and that generalizes to other cases. |
2109.14254 | Alvin Chua | Alvin J. K. Chua, Curt J. Cutler | Non-local parameter degeneracy in the intrinsic space of
gravitational-wave signals from extreme-mass-ratio inspirals | 39 pages, 22 figures. This paper is long - but mainly because it is
written in an expository/pedagogical manner, is thoroughly signposted, and
contains multiple large figures | Phys. Rev. D 106, 124046 (2022) | 10.1103/PhysRevD.106.124046 | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Extreme-mass-ratio inspirals will be prized sources for the upcoming
space-based gravitational-wave observatory LISA. The hunt for these is beset by
many open theoretical and computational problems in both source modeling and
data analysis. We draw attention here to one of the most poorly understood: the
phenomenon of non-local correlations in the space of
extreme-mass-ratio-inspiral signals. Such correlations are ubiquitous in the
continuum of possible signals (degeneracy), and severely hinder the search for
actual signals in LISA data. However, they are unlikely to manifest in a
realistic set of putative signals (confusion). We develop an inventory of new
analysis tools in order to conduct an extensive qualitative study of degeneracy
- its nature, causes, and implications. Previously proposed search strategies
for extreme-mass-ratio inspirals are reviewed in the light of our results, and
additional guidelines are suggested for the scientific analysis of such
sources.
| [
{
"created": "Wed, 29 Sep 2021 08:00:10 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Feb 2022 19:21:46 GMT",
"version": "v2"
},
{
"created": "Sat, 31 Dec 2022 08:07:33 GMT",
"version": "v3"
}
] | 2023-01-03 | [
[
"Chua",
"Alvin J. K.",
""
],
[
"Cutler",
"Curt J.",
""
]
] | Extreme-mass-ratio inspirals will be prized sources for the upcoming space-based gravitational-wave observatory LISA. The hunt for these is beset by many open theoretical and computational problems in both source modeling and data analysis. We draw attention here to one of the most poorly understood: the phenomenon of non-local correlations in the space of extreme-mass-ratio-inspiral signals. Such correlations are ubiquitous in the continuum of possible signals (degeneracy), and severely hinder the search for actual signals in LISA data. However, they are unlikely to manifest in a realistic set of putative signals (confusion). We develop an inventory of new analysis tools in order to conduct an extensive qualitative study of degeneracy - its nature, causes, and implications. Previously proposed search strategies for extreme-mass-ratio inspirals are reviewed in the light of our results, and additional guidelines are suggested for the scientific analysis of such sources. |
gr-qc/9402016 | Piotr Bizon | Piotr Bizo\'n | Gravitating Solitons and Hairy Black Holes | 29 pages, latex, preprint UWThPh-1994-5 | Acta Phys.Polon. B25 (1994) 877-898 | null | null | gr-qc hep-th | null | A brief review of recent research on soliton and black hole solutions of
Einstein's equations with nonlinear field sources is presented and some open
questions are pointed out.
| [
{
"created": "Tue, 8 Feb 1994 10:53:53 GMT",
"version": "v1"
}
] | 2016-08-14 | [
[
"Bizoń",
"Piotr",
""
]
] | A brief review of recent research on soliton and black hole solutions of Einstein's equations with nonlinear field sources is presented and some open questions are pointed out. |
1208.3911 | Antonio Enea Romano | Antonio Enea Romano, Pisin chen | Apparent versus true value of the cosmological constant | Some parts need to be revised | International Journal of Modern Physics D Vol. 20, No. 14 (2011)
2823-2830 | 10.1142/S0218271811020688 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Supernovae observations strongly support the presence of a cosmological
constant, but its value, which we will call apparent, is normally determined
assuming that the universe can be accurately described by a homogeneous model.
Even in the presence of a cosmological constant we cannot exclude nevertheless
the presence of a small local inhomogeneity which could affect the apparent
value of the cosmological constant. Neglecting the presence of the
inhomogeneity can in fact introduce a systematic misinterpretation of
cosmological data, leading to the distinction between an apparent and the true
value of the cosmological constant. But is such a difference distinguishable?
Recently we set out to model the local inhomogeneity with a {\Lambda}LTB
solution and computed the relation between the apparent and the true value of
the cosmological constant. In this essay we reproduce the essence of our model
with the emphasis on its physical implications.
| [
{
"created": "Mon, 20 Aug 2012 02:58:12 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Nov 2012 04:20:50 GMT",
"version": "v2"
}
] | 2012-11-07 | [
[
"Romano",
"Antonio Enea",
""
],
[
"chen",
"Pisin",
""
]
] | Supernovae observations strongly support the presence of a cosmological constant, but its value, which we will call apparent, is normally determined assuming that the universe can be accurately described by a homogeneous model. Even in the presence of a cosmological constant we cannot exclude nevertheless the presence of a small local inhomogeneity which could affect the apparent value of the cosmological constant. Neglecting the presence of the inhomogeneity can in fact introduce a systematic misinterpretation of cosmological data, leading to the distinction between an apparent and the true value of the cosmological constant. But is such a difference distinguishable? Recently we set out to model the local inhomogeneity with a {\Lambda}LTB solution and computed the relation between the apparent and the true value of the cosmological constant. In this essay we reproduce the essence of our model with the emphasis on its physical implications. |
2305.12215 | Pietropaolo Frisoni | Pietropaolo Frisoni | Introduction to Loop Quantum Gravity: Rovelli's lectures on LQG | 107 pages, 50 figures | null | null | null | gr-qc math-ph math.MP quant-ph | http://creativecommons.org/licenses/by/4.0/ | These notes are a transcript of Carlo Rovelli's lectures on Loop Quantum
Gravity, given in Marseille in 2018, which (at present) can be entirely found
on YouTube. I transcribed them in LaTeX in early 2020 as an exercise to get
ready for my Ph.D. in LQG at Western University. This transcript is meant to be
a (hopefully helpful) integration for the video version. I reported the order
of the topics and the chronological structure exactly as presented by Rovelli
throughout the course, primarily to facilitate the comparison. Each Section
corresponds to a different Lecture. The parts written in textit are my
additions. Sometimes in the text, I report references, which specify precisely
the minute and the second of the corresponding video on YouTube, to very short
historical digressions or excursus made during the lectures by Rovelli that I
have not explicitly transcribed in these notes. Where appropriate, I took some
figures from the book "Covariant Loop Quantum Gravity - An elementary
introduction to Quantum Gravity and Spinfoam Theory" by Carlo Rovelli and
Francesca Vidotto, to which I always refer by the term "the book" in the
following. For what concerns the equations, where possible, I tried to write
down the "correct" versions present within the book. Finally, I thank Carlo
Rovelli himself for reviewing these notes. I apologize in advance for any
errors, and I wish everyone a lot of fun!
| [
{
"created": "Sat, 20 May 2023 15:44:40 GMT",
"version": "v1"
}
] | 2023-05-23 | [
[
"Frisoni",
"Pietropaolo",
""
]
] | These notes are a transcript of Carlo Rovelli's lectures on Loop Quantum Gravity, given in Marseille in 2018, which (at present) can be entirely found on YouTube. I transcribed them in LaTeX in early 2020 as an exercise to get ready for my Ph.D. in LQG at Western University. This transcript is meant to be a (hopefully helpful) integration for the video version. I reported the order of the topics and the chronological structure exactly as presented by Rovelli throughout the course, primarily to facilitate the comparison. Each Section corresponds to a different Lecture. The parts written in textit are my additions. Sometimes in the text, I report references, which specify precisely the minute and the second of the corresponding video on YouTube, to very short historical digressions or excursus made during the lectures by Rovelli that I have not explicitly transcribed in these notes. Where appropriate, I took some figures from the book "Covariant Loop Quantum Gravity - An elementary introduction to Quantum Gravity and Spinfoam Theory" by Carlo Rovelli and Francesca Vidotto, to which I always refer by the term "the book" in the following. For what concerns the equations, where possible, I tried to write down the "correct" versions present within the book. Finally, I thank Carlo Rovelli himself for reviewing these notes. I apologize in advance for any errors, and I wish everyone a lot of fun! |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.