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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1107.1440 | Wolfgang Tichy | Wolfgang Tichy | Initial data for binary neutron stars with arbitrary spins | 9 pages | Phys.Rev.D84:024041,2011 | 10.1103/PhysRevD.84.024041 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In general neutron stars in binaries are spinning. Due to the existence of
millisecond pulsars we know that these spins can be substantial. We argue that
spins with periods on the order a few dozen milliseconds could influence the
late inspiral and merger dynamics. Thus numerical simulations of the last few
orbits and the merger should start from initial conditions that allow for
arbitrary spins. We discuss quasi-equilibrium approximations one can make in
the construction of binary neutron star initial data with spins. Using these
approximations we are able to derive two new matter equations. As in the case
of irrotational neutron star binaries one of these equations is algebraic and
the other elliptic. If these new matter equations are solved together with the
equations for the metric variables following the Wilson-Mathews or conformal
thin sandwich approach one can construct neutron star initial data. The spin of
each star is described by a rotational velocity that can be chosen freely so
that one can create stars in arbitrary rotation states. Our new matter
equations reduce to the well known limits of both corotating and irrotational
neutron star binaries.
| [
{
"created": "Thu, 7 Jul 2011 16:23:15 GMT",
"version": "v1"
}
] | 2011-08-11 | [
[
"Tichy",
"Wolfgang",
""
]
] | In general neutron stars in binaries are spinning. Due to the existence of millisecond pulsars we know that these spins can be substantial. We argue that spins with periods on the order a few dozen milliseconds could influence the late inspiral and merger dynamics. Thus numerical simulations of the last few orbits and the merger should start from initial conditions that allow for arbitrary spins. We discuss quasi-equilibrium approximations one can make in the construction of binary neutron star initial data with spins. Using these approximations we are able to derive two new matter equations. As in the case of irrotational neutron star binaries one of these equations is algebraic and the other elliptic. If these new matter equations are solved together with the equations for the metric variables following the Wilson-Mathews or conformal thin sandwich approach one can construct neutron star initial data. The spin of each star is described by a rotational velocity that can be chosen freely so that one can create stars in arbitrary rotation states. Our new matter equations reduce to the well known limits of both corotating and irrotational neutron star binaries. |
0902.0230 | Parthasarathi Mitra | Bhramar Chatterjee, P. Mitra | Hawking temperature and higher order calculations | 4 pages; minor changes; comments added about fermions; comment about
an 'maginary contribution included at the instance of PLB | Phys.Lett.B675:240-242,2009 | 10.1016/j.physletb.2009.04.009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hawking radiation has recently been explained by using solutions of wave
equations across black hole horizons in a WKB approximation. Higher order
calculations using both usual and non-singular coordinates are found to change
the solution for zero spin, but this change is not an alteration of the Hawking
temperature. For spin 1/2, there is no correction to the simplest form of the
solution.
| [
{
"created": "Mon, 2 Feb 2009 09:28:27 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Feb 2009 12:13:28 GMT",
"version": "v2"
},
{
"created": "Wed, 25 Feb 2009 10:40:57 GMT",
"version": "v3"
},
{
"created": "Thu, 9 Apr 2009 05:30:30 GMT",
"version": "v4"
}
] | 2011-03-28 | [
[
"Chatterjee",
"Bhramar",
""
],
[
"Mitra",
"P.",
""
]
] | Hawking radiation has recently been explained by using solutions of wave equations across black hole horizons in a WKB approximation. Higher order calculations using both usual and non-singular coordinates are found to change the solution for zero spin, but this change is not an alteration of the Hawking temperature. For spin 1/2, there is no correction to the simplest form of the solution. |
gr-qc/0404051 | Julio Cesar Fabris | F.G. Alvarenga, A.B. Batista, J.C. Fabris and G.T. Marques | Quantum modes around a scalar-tensor black hole: breakdown of the
normalization conditions | Latex file, 6 pages. To appear in Gravitation&Cosmology | Grav.Cosmol. 10 (2004) 184-186 | null | null | gr-qc hep-th | null | Black holes arising in the context of scalar-tensor gravity theories, where
the scalar field is non-minimally coupled to the curvature term, have zero
surface gravity. Hence, it is generally stated that their Hawking temperature
is zero, irrespectivelly of their gravitational and scalar charges. The proper
analysis of the Hawking temperature requires to study the propagation of
quantum fields in the space-time determined by these objects. We study scalar
fields in the vicinity of the horizon of these black holes. It is shown that
the scalar modes do not form an orthonormal set. Hence, the Hilbert space is
ill-definite in this case, and no notion of temperature can be extracted for
such objects.
| [
{
"created": "Mon, 12 Apr 2004 20:06:16 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Alvarenga",
"F. G.",
""
],
[
"Batista",
"A. B.",
""
],
[
"Fabris",
"J. C.",
""
],
[
"Marques",
"G. T.",
""
]
] | Black holes arising in the context of scalar-tensor gravity theories, where the scalar field is non-minimally coupled to the curvature term, have zero surface gravity. Hence, it is generally stated that their Hawking temperature is zero, irrespectivelly of their gravitational and scalar charges. The proper analysis of the Hawking temperature requires to study the propagation of quantum fields in the space-time determined by these objects. We study scalar fields in the vicinity of the horizon of these black holes. It is shown that the scalar modes do not form an orthonormal set. Hence, the Hilbert space is ill-definite in this case, and no notion of temperature can be extracted for such objects. |
2004.03228 | Yuri Pavlov | A. A. Grib, Yu. V. Pavlov | Particle properties outside of the static limit in cosmology | 4 pages | Int. J. Mod. Phys. A 35 (2020) 2040044 | 10.1142/S0217751X20400448 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that in the rest frame of the observer in expanding Universe
states of particles with negative energy exist.The properties of such states
are studied. The comparison with the case of negative energies of particles in
black holes and rotating coordinates out of the static limit is made.
| [
{
"created": "Tue, 7 Apr 2020 09:45:33 GMT",
"version": "v1"
}
] | 2020-04-08 | [
[
"Grib",
"A. A.",
""
],
[
"Pavlov",
"Yu. V.",
""
]
] | It is shown that in the rest frame of the observer in expanding Universe states of particles with negative energy exist.The properties of such states are studied. The comparison with the case of negative energies of particles in black holes and rotating coordinates out of the static limit is made. |
1701.00748 | Evan Halstead | G. Vardiashvili, E. Halstead, R. Poltis, A. Morgan, and D. Tobar | Inflationary Constraints on the Van der Waals Equation of State | null | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In spite of the strong observational evidence suggesting a period of rapid
expansion in the early universe, the identity of the inflaton field that drove
this expansion remains elusive. Many inflaton candidate particles (both known
and hypothesized) have been proposed to explain the early accelerated expansion
of the universe. Other explanations for an era of rapid expansion in the early
universe have been proposed via modifications of gravity in one form or
another.
In this paper, we consider the possibility of using a Van der Waals equation
of state to describe the early-time accelerated expansion of the universe. We
do not attempt to explain why the early universe may be filled with such a
fluid, but rather investigate what constraints may be placed on the parameters
which describe a Van der Waals fluid that sources an accelerated expansion in
the early universe. We consider three different versions of the Van der Waals
equation of state and constrain the parameters of each using CMB data. We find
that two of the models do not fit constraints from observation. A third model
may satisfy observational constraints, but only under very narrow
circumstances.
| [
{
"created": "Tue, 3 Jan 2017 17:08:22 GMT",
"version": "v1"
}
] | 2017-01-04 | [
[
"Vardiashvili",
"G.",
""
],
[
"Halstead",
"E.",
""
],
[
"Poltis",
"R.",
""
],
[
"Morgan",
"A.",
""
],
[
"Tobar",
"D.",
""
]
] | In spite of the strong observational evidence suggesting a period of rapid expansion in the early universe, the identity of the inflaton field that drove this expansion remains elusive. Many inflaton candidate particles (both known and hypothesized) have been proposed to explain the early accelerated expansion of the universe. Other explanations for an era of rapid expansion in the early universe have been proposed via modifications of gravity in one form or another. In this paper, we consider the possibility of using a Van der Waals equation of state to describe the early-time accelerated expansion of the universe. We do not attempt to explain why the early universe may be filled with such a fluid, but rather investigate what constraints may be placed on the parameters which describe a Van der Waals fluid that sources an accelerated expansion in the early universe. We consider three different versions of the Van der Waals equation of state and constrain the parameters of each using CMB data. We find that two of the models do not fit constraints from observation. A third model may satisfy observational constraints, but only under very narrow circumstances. |
gr-qc/0402080 | M. Raiteri | M. Francaviglia, M. Raiteri | Boundary Conditions, Energies and Gravitational Heat in General
Relativity (a Classical Analysis) | Latex file, 31 pages; one reference and two comments added, misprints
corrected | Class.Quant.Grav. 21 (2004) 3459-3482 | 10.1088/0264-9381/21/14/010 | null | gr-qc hep-th | null | The variation of the energy for a gravitational system is directly defined
from the Hamiltonian field equations of General Relativity. When the variation
of the energy is written in a covariant form it splits into two (covariant)
contributions: one of them is the Komar energy, while the other is the
so-called covariant ADM correction term. When specific boundary conditions are
analyzed one sees that the Komar energy is related to the gravitational heat
while the ADM correction term plays the role of the Helmholtz free energy.
These properties allow to establish, inside a classical geometric framework, a
formal analogy between gravitation and the laws governing the evolution of a
thermodynamic system. The analogy applies to stationary spacetimes admitting
multiple causal horizons as well as to AdS Taub-bolt solutions.
| [
{
"created": "Wed, 18 Feb 2004 14:28:58 GMT",
"version": "v1"
},
{
"created": "Tue, 25 May 2004 08:17:38 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Francaviglia",
"M.",
""
],
[
"Raiteri",
"M.",
""
]
] | The variation of the energy for a gravitational system is directly defined from the Hamiltonian field equations of General Relativity. When the variation of the energy is written in a covariant form it splits into two (covariant) contributions: one of them is the Komar energy, while the other is the so-called covariant ADM correction term. When specific boundary conditions are analyzed one sees that the Komar energy is related to the gravitational heat while the ADM correction term plays the role of the Helmholtz free energy. These properties allow to establish, inside a classical geometric framework, a formal analogy between gravitation and the laws governing the evolution of a thermodynamic system. The analogy applies to stationary spacetimes admitting multiple causal horizons as well as to AdS Taub-bolt solutions. |
2110.04807 | Takeshi Tomitsuka | Takeshi Tomitsuka and Koji Yamaguchi | Modification of a Lie-algebra-based approach and its application to
asymptotic symmetries on a Killing horizon | 21 pages, 1 figure | Prog Theor Exp Phys (2022) | 10.1093/ptep/ptac046 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a new approach to find asymptotic symmetries in general relativity
as a modification of the Lie-algebra-based approach proposed in T. Tomitsuka et
al. [Classical Quantum Gravity 38, 225007 (2021)]. Those authors proposed an
algorithmic protocol to investigate asymptotic symmetries. In particular, their
guiding principle helps us to find a non-vanishing charge that generates an
infinitesimal diffeomorphism. However, in order to check the integrability
condition for the charges, it is necessary to solve differential equations to
identify the integral curve of vector fields, which is usually quite hard. In
this paper, we provide a sufficient condition of the integrability condition
that can be checked without solving any differential equations, avoiding the
difficulties in the approach in the above reference. As a demonstration, we
investigate the asymptotic symmetries on a Killing horizon and find a new class
of asymptotic symmetries. In 4D spacetimes with a spherical Killing horizon, we
show that the algebra of the corresponding charges is a central extension of
the algebra of vector fields.
| [
{
"created": "Sun, 10 Oct 2021 14:32:53 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Apr 2022 13:38:50 GMT",
"version": "v2"
}
] | 2022-04-20 | [
[
"Tomitsuka",
"Takeshi",
""
],
[
"Yamaguchi",
"Koji",
""
]
] | We develop a new approach to find asymptotic symmetries in general relativity as a modification of the Lie-algebra-based approach proposed in T. Tomitsuka et al. [Classical Quantum Gravity 38, 225007 (2021)]. Those authors proposed an algorithmic protocol to investigate asymptotic symmetries. In particular, their guiding principle helps us to find a non-vanishing charge that generates an infinitesimal diffeomorphism. However, in order to check the integrability condition for the charges, it is necessary to solve differential equations to identify the integral curve of vector fields, which is usually quite hard. In this paper, we provide a sufficient condition of the integrability condition that can be checked without solving any differential equations, avoiding the difficulties in the approach in the above reference. As a demonstration, we investigate the asymptotic symmetries on a Killing horizon and find a new class of asymptotic symmetries. In 4D spacetimes with a spherical Killing horizon, we show that the algebra of the corresponding charges is a central extension of the algebra of vector fields. |
gr-qc/0504103 | Muhammad Sharif | M. Sharif and Sehar Aziz | Kinematic Self-Similar Cylindrically Symmetric Solutions | 22 pages, accepted for publication in Int. J. of Mod. Phys. D | Int.J.Mod.Phys. D14 (2005) 1527-1544 | 10.1142/S0218271805007115 | null | gr-qc | null | This paper is devoted to find out cylindrically symmetric kinematic
self-similar perfect fluid and dust solutions. We study the cylindrically
symmetric solutions which admit kinematic self-similar vectors of second,
zeroth and infinite kinds, not only for the tilted fluid case but also for the
parallel and orthogonal cases. It is found that the parallel case gives
contradiction both in perfect fluid and dust cases. The orthogonal perfect
fluid case yields a vacuum solution while the orthogonal dust case gives
contradiction. It is worth mentioning that the tilted case provides solution
both for the perfect as well as dust cases.
| [
{
"created": "Thu, 21 Apr 2005 09:31:48 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Sharif",
"M.",
""
],
[
"Aziz",
"Sehar",
""
]
] | This paper is devoted to find out cylindrically symmetric kinematic self-similar perfect fluid and dust solutions. We study the cylindrically symmetric solutions which admit kinematic self-similar vectors of second, zeroth and infinite kinds, not only for the tilted fluid case but also for the parallel and orthogonal cases. It is found that the parallel case gives contradiction both in perfect fluid and dust cases. The orthogonal perfect fluid case yields a vacuum solution while the orthogonal dust case gives contradiction. It is worth mentioning that the tilted case provides solution both for the perfect as well as dust cases. |
2311.16634 | Georgios Lukes-Gerakopoulos | Morteza Kerachian, Sajal Mukherjee, Georgios Lukes-Gerakopoulos, and
Sanjit Mitra | Detectability of stochastic gravitational wave background from weakly
hyperbolic encounters | 8 pages, 3 figures, 1 table | Astronomy & Astrophysics 684: A17 (2024) | 10.1051/0004-6361/202348747 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the stochastic gravitational wave (GW) background generated by
black hole-black hole (BH-BH) hyperbolic encounters with eccentricities close
to one and compare them with the respective sensitivity curves of planned GW
detectors. We use the Keplerian potential to model the orbits of the encounters
and the quadrupole formula to compute the emitted GWs. We take into account
hyperbolic encounters that take place in clusters up to redshift $5$ and with
BH masses spanning from $5 M_{\odot}$ to $55 M_{\odot}$. We assume the clusters
to be virialized and study several cluster models with different mass and
virial velocity, and finally obtain an accumulative result, displaying the
background as an average. Using the maxima and minima of our accumulative
result for each frequency, we provide analytical expressions for both
optimistic and pessimistic scenarios. Our results suggest that the background
from these encounters is likely to be detected by the third-generation
detectors Cosmic explorer and Einstein telescope, while the tail section at
lower frequencies intersects with DECIGO, making it a potential target source
for both ground- and space-based future GW detectors.
| [
{
"created": "Tue, 28 Nov 2023 09:37:24 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Apr 2024 09:31:13 GMT",
"version": "v2"
}
] | 2024-04-03 | [
[
"Kerachian",
"Morteza",
""
],
[
"Mukherjee",
"Sajal",
""
],
[
"Lukes-Gerakopoulos",
"Georgios",
""
],
[
"Mitra",
"Sanjit",
""
]
] | We compute the stochastic gravitational wave (GW) background generated by black hole-black hole (BH-BH) hyperbolic encounters with eccentricities close to one and compare them with the respective sensitivity curves of planned GW detectors. We use the Keplerian potential to model the orbits of the encounters and the quadrupole formula to compute the emitted GWs. We take into account hyperbolic encounters that take place in clusters up to redshift $5$ and with BH masses spanning from $5 M_{\odot}$ to $55 M_{\odot}$. We assume the clusters to be virialized and study several cluster models with different mass and virial velocity, and finally obtain an accumulative result, displaying the background as an average. Using the maxima and minima of our accumulative result for each frequency, we provide analytical expressions for both optimistic and pessimistic scenarios. Our results suggest that the background from these encounters is likely to be detected by the third-generation detectors Cosmic explorer and Einstein telescope, while the tail section at lower frequencies intersects with DECIGO, making it a potential target source for both ground- and space-based future GW detectors. |
2201.10732 | M.J. Luo | M.J.Luo | Local Conformal Instability and Local Non-Collapsing in the Ricci flow
of Quantum Spacetime | 14 pages. v2:introduction and references added, appendix moved to
section-II, generalization of the Ricci flow and the monotonic functionals to
the Lorentzian 4-spacetime emphasized. Final version published in Annals of
Physics. arXiv admin note: text overlap with arXiv:2112.00218 | Annals of Physics 441 (2022) 168861 | 10.1016/j.aop.2022.168861 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is known that the conformal instability or bottomless problem rises in the
path integral method in quantizing the general relativity. Does quantum
spacetime itself really suffer from such conformal instability? If so, does the
conformal instability cause the collapse of local spacetime region or even
collapse the whole spacetime? The problems are studied in the framework of the
Quantum Spacetime Reference Frame (QSRF) and induced spacetime Ricci flow. We
find that if the lowest eigenvalue of an operator, associated with the
F-functional in a local compact (closed and bounded) region, is positive, the
local region is conformally unstable and will tend to volume-shrinking and
curvature-pinching along the Ricci flow-time t; if the eigenvalue is negative
or zero, the local region is conformally stable up to a trivial rescaling.
However, the local non-collapsing theorem in the Ricci flow proved by Perelman
ensures that the instability will not cause the local compact spacetime region
collapse into nothing. The total effective action is also proved positive
defined and bounded from below keeping the whole spacetime conformally stable,
which can be considered as a generalization of the classical positive mass
theorem of gravitation to the quantum level.
| [
{
"created": "Wed, 26 Jan 2022 03:29:41 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Apr 2022 10:44:44 GMT",
"version": "v2"
}
] | 2022-04-19 | [
[
"Luo",
"M. J.",
""
]
] | It is known that the conformal instability or bottomless problem rises in the path integral method in quantizing the general relativity. Does quantum spacetime itself really suffer from such conformal instability? If so, does the conformal instability cause the collapse of local spacetime region or even collapse the whole spacetime? The problems are studied in the framework of the Quantum Spacetime Reference Frame (QSRF) and induced spacetime Ricci flow. We find that if the lowest eigenvalue of an operator, associated with the F-functional in a local compact (closed and bounded) region, is positive, the local region is conformally unstable and will tend to volume-shrinking and curvature-pinching along the Ricci flow-time t; if the eigenvalue is negative or zero, the local region is conformally stable up to a trivial rescaling. However, the local non-collapsing theorem in the Ricci flow proved by Perelman ensures that the instability will not cause the local compact spacetime region collapse into nothing. The total effective action is also proved positive defined and bounded from below keeping the whole spacetime conformally stable, which can be considered as a generalization of the classical positive mass theorem of gravitation to the quantum level. |
2309.09712 | Misbah Shahzadi | Misbah Shahzadi, Martin Kolo\v{s}, Rabia Saleem and Zden\v{e}k
Stuchl\'ik | Testing alternative spacetimes by high-frequency quasi-periodic
oscillations observed in microquasars and active galactic nuclei | 19 pages, 6 figures, 1 table | Classical and Quantum Gravity, 41, 075014, (2024) | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this article, we try to capture the influence of deviation from standard
Kerr black hole spacetime on observed high-frequency quasi-periodic
oscillations signal. We explore the dynamics of test particles in the field of
rotating compact objects governed by the various modifications of the standard
Kerr black hole spacetime and apply the model of epicyclic oscillations of
Keplerian discs to the observed microquasars and active galactic nuclei
high-frequency quasi-periodic oscillations data. We presented a generalized
formalism for the fitting of the high-frequency quasi-periodic oscillations
models so-called epicyclic resonance and relativistic precession models, under
the assumption of stationary, axisymmetric, and asymptotically flat spacetimes.
Recently, we have used the same set of stationary, axisymmetric, and
asymptotically flat spacetimes, and estimated the restrictions of spacetime
parameters with the help of hot-spot data of three flares observed at Sgr~A* by
GRAVITY instrument \citep{Shahzadi-et-al:2022:EPJC:}. The aim of this work is
not to test a particular theoretical model or to determine and constrain its
parameters, but to map a set of well-astrophysically motivated deviations from
classical Kerr black hole spacetime and demonstrate which ones provide the best
fit for high-frequency quasi-periodic oscillations data and could be fruitful
for future exploration.
| [
{
"created": "Mon, 18 Sep 2023 12:28:13 GMT",
"version": "v1"
}
] | 2024-03-19 | [
[
"Shahzadi",
"Misbah",
""
],
[
"Kološ",
"Martin",
""
],
[
"Saleem",
"Rabia",
""
],
[
"Stuchlík",
"Zdeněk",
""
]
] | In this article, we try to capture the influence of deviation from standard Kerr black hole spacetime on observed high-frequency quasi-periodic oscillations signal. We explore the dynamics of test particles in the field of rotating compact objects governed by the various modifications of the standard Kerr black hole spacetime and apply the model of epicyclic oscillations of Keplerian discs to the observed microquasars and active galactic nuclei high-frequency quasi-periodic oscillations data. We presented a generalized formalism for the fitting of the high-frequency quasi-periodic oscillations models so-called epicyclic resonance and relativistic precession models, under the assumption of stationary, axisymmetric, and asymptotically flat spacetimes. Recently, we have used the same set of stationary, axisymmetric, and asymptotically flat spacetimes, and estimated the restrictions of spacetime parameters with the help of hot-spot data of three flares observed at Sgr~A* by GRAVITY instrument \citep{Shahzadi-et-al:2022:EPJC:}. The aim of this work is not to test a particular theoretical model or to determine and constrain its parameters, but to map a set of well-astrophysically motivated deviations from classical Kerr black hole spacetime and demonstrate which ones provide the best fit for high-frequency quasi-periodic oscillations data and could be fruitful for future exploration. |
1105.6200 | Paul Tod | Paul Tod | A comment on positive mass for scalar field sources | 6 pages | General Relativity and Gravitation, 2011, Volume 43, Number 6,
1855-1860 | 10.1007/s10714-011-1165-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use a transformation due to Bekenstein to relate the ADM and Bondi masses
of asymptotically-flat solutions of the Einstein equations with, respectively,
scalar sources and conformal-scalar sources. Although the conformal-scalar
energy-momentum tensor does not satisfy the Dominant Energy Condition one may,
by this means, still conclude that the ADM mass is positive.
| [
{
"created": "Tue, 31 May 2011 08:30:27 GMT",
"version": "v1"
}
] | 2011-06-01 | [
[
"Tod",
"Paul",
""
]
] | We use a transformation due to Bekenstein to relate the ADM and Bondi masses of asymptotically-flat solutions of the Einstein equations with, respectively, scalar sources and conformal-scalar sources. Although the conformal-scalar energy-momentum tensor does not satisfy the Dominant Energy Condition one may, by this means, still conclude that the ADM mass is positive. |
gr-qc/9607039 | John F. Donoghue | John F.Donoghue (University of Massachusetts, Amherst) | The Quantum Theory of General Relativity at Low Energies | 9 pages, Latex, talk presented at Journees Relativistes 96, Ascona,
Switzerland, May 1996. To be published in Helv. Phys. Acta | Helv.Phys.Acta 69 (1996) 269-275 | null | null | gr-qc hep-th | null | In quantum field theory there is now a well developed technique, effective
field theory, which allows one to obtain low energy quantum predictions in
``non-renormalizable'' theories, using only the degrees of freedom and
interactions appropriate for those energies. Whether or not general relativity
is truly fundamental, at low energies it is automatically described as a
quantum effective field theory and this allows a consistent framework for
quantum gravity at ordinary energies. I briefly describe the nature and limits
of the technique.
| [
{
"created": "Wed, 17 Jul 1996 14:12:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Donoghue",
"John F.",
"",
"University of Massachusetts, Amherst"
]
] | In quantum field theory there is now a well developed technique, effective field theory, which allows one to obtain low energy quantum predictions in ``non-renormalizable'' theories, using only the degrees of freedom and interactions appropriate for those energies. Whether or not general relativity is truly fundamental, at low energies it is automatically described as a quantum effective field theory and this allows a consistent framework for quantum gravity at ordinary energies. I briefly describe the nature and limits of the technique. |
2406.08699 | Andrei Galiautdinov | Andrei Galiautdinov | Positive-energy Dirac particles in cosmology | 7 pages, no figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide general relativistic treatment of the single-component field
described by Dirac's positive-energy wave equation of 1971. It is motivated by
Bogomolny's proposal to regard that field as a possible candidate for dark
matter. Our emphasis is on standard (flat) Friedmann-Robertson-Walker
cosmology. The early universe is not considered, though there is a strong
indication that the field may play a role in internally driven generation of
cosmic anisotropy.
| [
{
"created": "Wed, 12 Jun 2024 23:43:02 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Aug 2024 22:03:55 GMT",
"version": "v2"
}
] | 2024-08-06 | [
[
"Galiautdinov",
"Andrei",
""
]
] | We provide general relativistic treatment of the single-component field described by Dirac's positive-energy wave equation of 1971. It is motivated by Bogomolny's proposal to regard that field as a possible candidate for dark matter. Our emphasis is on standard (flat) Friedmann-Robertson-Walker cosmology. The early universe is not considered, though there is a strong indication that the field may play a role in internally driven generation of cosmic anisotropy. |
2104.07134 | Kentaro Mogushi | Kentaro Mogushi | Application of a new transient-noise analysis tool for an unmodeled
gravitational-wave search pipeline | 19 pages, 12 figures, 1 table | Classical and Quantum Gravity 38 (2021) 155004 | 10.1088/1361-6382/ac08a7 | LIGO-P2100031 | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | Excess transient noise events, or glitches, impact the data quality of
ground-based ravitational-wave (GW) detectors and impair the detection of
signals produced by astrophysical sources. Identification of the causes of
these glitches is a crucial starting point for the improvement of GW signal
detectability. However, glitches are the product of linear and non-linear
couplings among the interrelated detector-control systems that include
mitigation of ground motion and regulation of optic motion, which generally
makes it difficult to find their origin. We present a new software called
PyChChoo which uses time series recorded in the instrumental control systems
and environmental sensors around times when glitches are present in the
detector's output to reveal essential clues about their origin. Applying
PyChChoo on the most adversely affecting glitches on background triggers
generated by one of unmodeled GW detection pipelines called coherent WaveBurst
(cWB) operated in the data from the LIGO detectors between January 1st, 2020
and February 3rd, 2020, we find that 80% of triggers are marked as either being
vetoed or unvetoed in common between our analysis and the current LIGO
infrastructure.
| [
{
"created": "Wed, 14 Apr 2021 21:37:01 GMT",
"version": "v1"
}
] | 2021-07-19 | [
[
"Mogushi",
"Kentaro",
""
]
] | Excess transient noise events, or glitches, impact the data quality of ground-based ravitational-wave (GW) detectors and impair the detection of signals produced by astrophysical sources. Identification of the causes of these glitches is a crucial starting point for the improvement of GW signal detectability. However, glitches are the product of linear and non-linear couplings among the interrelated detector-control systems that include mitigation of ground motion and regulation of optic motion, which generally makes it difficult to find their origin. We present a new software called PyChChoo which uses time series recorded in the instrumental control systems and environmental sensors around times when glitches are present in the detector's output to reveal essential clues about their origin. Applying PyChChoo on the most adversely affecting glitches on background triggers generated by one of unmodeled GW detection pipelines called coherent WaveBurst (cWB) operated in the data from the LIGO detectors between January 1st, 2020 and February 3rd, 2020, we find that 80% of triggers are marked as either being vetoed or unvetoed in common between our analysis and the current LIGO infrastructure. |
gr-qc/9406033 | null | Sean A. Hayward | Spin-Coefficient Form of the New Laws of Black-Hole Dynamics | 9 pages | Class.Quant.Grav.11:3025-3036,1994 | 10.1088/0264-9381/11/12/016 | null | gr-qc | null | General laws of black-hole dynamics, some of which are analogous to the laws
of thermodynamics, have recently been found for a general definition of black
hole in terms of a future outer trapping horizon, a hypersurface foliated by
marginal surfaces of a certain type. This theory is translated here into
spin-coefficient language. Second law: the area form of a future outer trapping
horizon is generically increasing, otherwise constant. First law: the rate of
change of the area form is given by an energy flux and the trapping gravity.
Zeroth law: the total trapping gravity of a compact outer marginal surface has
an upper bound, attained if and only if the trapping gravity is constant.
Topology law: a compact future outer marginal surface has spherical topology.
Signature law: an outer trapping horizon is generically spatial, otherwise
null. Trapping law: spatial surfaces sufficiently close to a compact future
outer marginal surface are trapped if they lie inside the trapping horizon.
Confinement law: if the interior and exterior of a future outer trapping
horizon are disjoint, an observer inside the horizon cannot get outside.
| [
{
"created": "Tue, 21 Jun 1994 07:35:09 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Hayward",
"Sean A.",
""
]
] | General laws of black-hole dynamics, some of which are analogous to the laws of thermodynamics, have recently been found for a general definition of black hole in terms of a future outer trapping horizon, a hypersurface foliated by marginal surfaces of a certain type. This theory is translated here into spin-coefficient language. Second law: the area form of a future outer trapping horizon is generically increasing, otherwise constant. First law: the rate of change of the area form is given by an energy flux and the trapping gravity. Zeroth law: the total trapping gravity of a compact outer marginal surface has an upper bound, attained if and only if the trapping gravity is constant. Topology law: a compact future outer marginal surface has spherical topology. Signature law: an outer trapping horizon is generically spatial, otherwise null. Trapping law: spatial surfaces sufficiently close to a compact future outer marginal surface are trapped if they lie inside the trapping horizon. Confinement law: if the interior and exterior of a future outer trapping horizon are disjoint, an observer inside the horizon cannot get outside. |
gr-qc/0404097 | Dmitriy Palatnik | Dmitriy Palatnik | BI action for gravitational and electroweak fields | 11 pages, 0 figures | null | null | null | gr-qc hep-th | null | This note suggests a generalization of the Born--Infeld action (1932) on case
of electroweak and gravitational fields in four-dimensional spacetime. The
action is constructed from Dirac matrices, $\gamma_a$, and dimensionless
covariant derivatives, $\pi_{a} = - i\ell \nabla_{a}$, where $\ell$ is of order
of magnitude of Planck's length. By a postulate, the action possesses
additional symmetry with respect to global transformations of the Lorentz group
imposed on pairs ($\gamma_{a}$, $\pi_{a}$). It's shown, that parameter of the
Lorentz group is associated with a constant value of the electroweak potential
at spatial infinity. It follows, that in linear and quadratic in $\ell^2$
approximation, action for gravitational field coincides with Einstein-Hilbert
(EH) and Gauss-Bonnet (GB).
| [
{
"created": "Thu, 22 Apr 2004 01:25:29 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Apr 2004 12:59:05 GMT",
"version": "v2"
},
{
"created": "Wed, 28 Apr 2004 22:59:19 GMT",
"version": "v3"
},
{
"created": "Fri, 15 Oct 2004 19:34:16 GMT",
"version": "v4"
},
{
"c... | 2007-05-23 | [
[
"Palatnik",
"Dmitriy",
""
]
] | This note suggests a generalization of the Born--Infeld action (1932) on case of electroweak and gravitational fields in four-dimensional spacetime. The action is constructed from Dirac matrices, $\gamma_a$, and dimensionless covariant derivatives, $\pi_{a} = - i\ell \nabla_{a}$, where $\ell$ is of order of magnitude of Planck's length. By a postulate, the action possesses additional symmetry with respect to global transformations of the Lorentz group imposed on pairs ($\gamma_{a}$, $\pi_{a}$). It's shown, that parameter of the Lorentz group is associated with a constant value of the electroweak potential at spatial infinity. It follows, that in linear and quadratic in $\ell^2$ approximation, action for gravitational field coincides with Einstein-Hilbert (EH) and Gauss-Bonnet (GB). |
gr-qc/9612015 | David Garfinkle | David Garfinkle | Choptuik scaling and the scale invariance of Einstein's equation | references added and discussion modified | Phys.Rev.D56:3169-3173,1997 | 10.1103/PhysRevD.56.3169 | null | gr-qc | null | The relationship of Choptuik scaling to the scale invariance of Einstein's
equation is explored. Ordinary dynamical systems often have limit cycles:
periodic orbits that are the asymptotic limit of generic solutions. We show how
to separate Einstein's equation into the dynamics of the overall scale and the
dynamics of the ``scale invariant'' part of the metric. Periodicity of the
scale invariant part implies periodic self-similarity of the spacetime. We also
analyze a toy model that exhibits many of the features of Choptuik scaling.
| [
{
"created": "Thu, 5 Dec 1996 19:19:07 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Jul 1997 21:35:11 GMT",
"version": "v2"
}
] | 2010-01-06 | [
[
"Garfinkle",
"David",
""
]
] | The relationship of Choptuik scaling to the scale invariance of Einstein's equation is explored. Ordinary dynamical systems often have limit cycles: periodic orbits that are the asymptotic limit of generic solutions. We show how to separate Einstein's equation into the dynamics of the overall scale and the dynamics of the ``scale invariant'' part of the metric. Periodicity of the scale invariant part implies periodic self-similarity of the spacetime. We also analyze a toy model that exhibits many of the features of Choptuik scaling. |
1003.0543 | Mohammad Malekjani | A. Khodam-Mohammadi and M. Malekjani | Cosmic Behavior, Statefinder Diagnostic and $w-w^{\prime}$ Analysis for
Interacting NADE model in Non-flat Universe | 18 pages, 4 figures, Accepted in Astrophysics & Space Science Journal | Astrophys.Space Sci.331:265-273,2011 | 10.1007/s10509-010-0422-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a brief review of interacting NADE model in non-flat universe. we
study the effect of spatial curvature $\Omega_{k}$, interaction coefficient
$\alpha $ and the main parameter of NADE, $n$, On EoS parameter $w_{d}$ and
deceleration parameter $q$. We obtain a minimum value for $n$ in both early and
present time, in order to that our DE model crosses the phantom divide. Also in
a closed universe, changing the sign of $q$ is strongly dependent on $\alpha$.
It has been shown that the quantities $w_{d}$ and $q$ have a different
treatment for various spatial curvature. At last, we calculate the statefinder
diagnostic and $ w-w^{\prime}$ analysis in non flat universe. In non flat
universe, the statefinder trajectory is discriminated by both $n$ and $\alpha$.
| [
{
"created": "Tue, 2 Mar 2010 09:58:07 GMT",
"version": "v1"
},
{
"created": "Sun, 6 Jun 2010 13:51:56 GMT",
"version": "v2"
}
] | 2011-02-03 | [
[
"Khodam-Mohammadi",
"A.",
""
],
[
"Malekjani",
"M.",
""
]
] | We give a brief review of interacting NADE model in non-flat universe. we study the effect of spatial curvature $\Omega_{k}$, interaction coefficient $\alpha $ and the main parameter of NADE, $n$, On EoS parameter $w_{d}$ and deceleration parameter $q$. We obtain a minimum value for $n$ in both early and present time, in order to that our DE model crosses the phantom divide. Also in a closed universe, changing the sign of $q$ is strongly dependent on $\alpha$. It has been shown that the quantities $w_{d}$ and $q$ have a different treatment for various spatial curvature. At last, we calculate the statefinder diagnostic and $ w-w^{\prime}$ analysis in non flat universe. In non flat universe, the statefinder trajectory is discriminated by both $n$ and $\alpha$. |
2202.01329 | F\'elix-Louis Juli\'e | F\'elix-Louis Juli\'e, Hector O. Silva, Emanuele Berti, Nicol\'as
Yunes | Black hole sensitivities in Einstein-scalar-Gauss-Bonnet gravity | 20 pages, 12 figures | null | 10.1103/PhysRevD.105.124031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The post-Newtonian dynamics of black hole binaries in
Einstein-scalar-Gauss-Bonnet theories of gravity depends on the so-called
"sensitivities", quantities which characterize a black hole's adiabatic
response to the time-dependent scalar field environment sourced by its
companion. In this work, we calculate numerically the sensitivities of
nonrotating black holes, including spontaneously scalarized ones, in three
classes of Einstein-scalar-Gauss-Bonnet gravity: the shift-symmetric, dilatonic
and Gaussian theories. When possible, we compare our results against
perturbative analytical results, finding excellent agreement. Unlike their
general relativistic counterparts, black holes in Einstein-scalar-Gauss-Bonnet
gravity only exist in a restricted parameter space controlled by the theory's
coupling constant. A preliminary study of the role played by the sensitivities
in black hole binaries suggests that, in principle, black holes can be driven
outside of their domain of existence during the inspiral, for binary parameters
which we determine.
| [
{
"created": "Wed, 2 Feb 2022 23:41:43 GMT",
"version": "v1"
}
] | 2022-06-29 | [
[
"Julié",
"Félix-Louis",
""
],
[
"Silva",
"Hector O.",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Yunes",
"Nicolás",
""
]
] | The post-Newtonian dynamics of black hole binaries in Einstein-scalar-Gauss-Bonnet theories of gravity depends on the so-called "sensitivities", quantities which characterize a black hole's adiabatic response to the time-dependent scalar field environment sourced by its companion. In this work, we calculate numerically the sensitivities of nonrotating black holes, including spontaneously scalarized ones, in three classes of Einstein-scalar-Gauss-Bonnet gravity: the shift-symmetric, dilatonic and Gaussian theories. When possible, we compare our results against perturbative analytical results, finding excellent agreement. Unlike their general relativistic counterparts, black holes in Einstein-scalar-Gauss-Bonnet gravity only exist in a restricted parameter space controlled by the theory's coupling constant. A preliminary study of the role played by the sensitivities in black hole binaries suggests that, in principle, black holes can be driven outside of their domain of existence during the inspiral, for binary parameters which we determine. |
gr-qc/9602058 | Julio Cesar Fabris | C.E.M. Batista, J.C.Fabris | Scalar Perturbations in a String Inspired Inflationary Scenario | 8 pages, latex file | null | null | null | gr-qc | null | We consider an inflationary model inspired in the low energy limit of string
theory. In this model, the scale factor grows exponentially with time. A
perturbation study is performed, and we show that there is a mode which
displays an exponential growth in the perturbation of the scalar field.
| [
{
"created": "Wed, 28 Feb 1996 16:26:49 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Batista",
"C. E. M.",
""
],
[
"Fabris",
"J. C.",
""
]
] | We consider an inflationary model inspired in the low energy limit of string theory. In this model, the scale factor grows exponentially with time. A perturbation study is performed, and we show that there is a mode which displays an exponential growth in the perturbation of the scalar field. |
0901.0800 | Patrik Sandin | Patrik Sandin | Tilted two-fluid Bianchi type I models | 14 pages, 3 figures | Gen.Rel.Grav.41:2707-2724,2009 | 10.1007/s10714-009-0799-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we investigate expanding Bianchi type I models with two tilted
fluids with the same linear equation of state, characterized by the equation of
state parameter w. Individually the fluids have non-zero energy fluxes w.r.t.
the symmetry surfaces, but these cancel each other because of the Codazzi
constraint. We prove that when w=0 the model isotropizes to the future. Using
numerical simulations and a linear analysis we also find the asymptotic states
of models with w>0. We find that future isotropization occurs if and only if $w
\leq 1/3$. The results are compared to similar models investigated previously
where the two fluids have different equation of state parameters.
| [
{
"created": "Wed, 7 Jan 2009 10:27:58 GMT",
"version": "v1"
}
] | 2011-12-08 | [
[
"Sandin",
"Patrik",
""
]
] | In this paper we investigate expanding Bianchi type I models with two tilted fluids with the same linear equation of state, characterized by the equation of state parameter w. Individually the fluids have non-zero energy fluxes w.r.t. the symmetry surfaces, but these cancel each other because of the Codazzi constraint. We prove that when w=0 the model isotropizes to the future. Using numerical simulations and a linear analysis we also find the asymptotic states of models with w>0. We find that future isotropization occurs if and only if $w \leq 1/3$. The results are compared to similar models investigated previously where the two fluids have different equation of state parameters. |
1811.08148 | Cosimo Bambi | Ashutosh Tripathi, Sourabh Nampalliwar, Askar B. Abdikamalov, Dimitry
Ayzenberg, Cosimo Bambi, Thomas Dauser, Javier A. Garcia, Andrea Marinucci | Towards precision tests of general relativity with black hole X-ray
reflection spectroscopy | 10 pages, 7 figures. v2: title slightly changed, arXiv version
shorter than published version | Astrophys.J. 875: 56 (2019) | 10.3847/1538-4357/ab0e7e | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Astrophysical black hole systems are the ideal laboratories for testing
Einstein's theory of gravity in the strong field regime. We have recently
developed a framework which uses the reflection spectrum of black hole systems
to perform precision tests of general relativity by testing the Kerr black hole
hypothesis. In this paper, we analyze XMM-Newton and NuSTAR observations of the
supermassive black hole in the Seyfert 1 galaxy MCG-06-30-15 with our disk
reflection model. We consider the Johannsen metric with the deformation
parameters $\alpha_{13}$ and $\alpha_{22}$, which quantify deviations from the
Kerr metric. For $\alpha_{22} = 0$, we obtain the black hole spin $0.928 < a_*
< 0.983$ and $-0.44 < \alpha_{13} < 0.15$. For $\alpha_{13} = 0$, we obtain
$0.885 < a_* < 0.987$ and $-0.12 < \alpha_{22} < 1.05$. The Kerr solution is
recovered for $\alpha_{13} = \alpha_{22} = 0$. Thus, our results include the
Kerr solution within statistical uncertainties. Systematic uncertainties are
difficult to account for, and we discuss some issues in this regard.
| [
{
"created": "Tue, 20 Nov 2018 09:39:50 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Apr 2019 00:04:08 GMT",
"version": "v2"
}
] | 2019-04-18 | [
[
"Tripathi",
"Ashutosh",
""
],
[
"Nampalliwar",
"Sourabh",
""
],
[
"Abdikamalov",
"Askar B.",
""
],
[
"Ayzenberg",
"Dimitry",
""
],
[
"Bambi",
"Cosimo",
""
],
[
"Dauser",
"Thomas",
""
],
[
"Garcia",
"Javier A.",... | Astrophysical black hole systems are the ideal laboratories for testing Einstein's theory of gravity in the strong field regime. We have recently developed a framework which uses the reflection spectrum of black hole systems to perform precision tests of general relativity by testing the Kerr black hole hypothesis. In this paper, we analyze XMM-Newton and NuSTAR observations of the supermassive black hole in the Seyfert 1 galaxy MCG-06-30-15 with our disk reflection model. We consider the Johannsen metric with the deformation parameters $\alpha_{13}$ and $\alpha_{22}$, which quantify deviations from the Kerr metric. For $\alpha_{22} = 0$, we obtain the black hole spin $0.928 < a_* < 0.983$ and $-0.44 < \alpha_{13} < 0.15$. For $\alpha_{13} = 0$, we obtain $0.885 < a_* < 0.987$ and $-0.12 < \alpha_{22} < 1.05$. The Kerr solution is recovered for $\alpha_{13} = \alpha_{22} = 0$. Thus, our results include the Kerr solution within statistical uncertainties. Systematic uncertainties are difficult to account for, and we discuss some issues in this regard. |
gr-qc/0612086 | L\'aszl\'o \'A Gergely | L\'aszl\'o \'A. Gergely, Zolt\'an Keresztes, Bal\'azs Mik\'oczi | The second post-Newtonian order generalized Kepler equation | to appear in the Proceedings of the Eleventh Marcel Grossmann Meeting
2006, World Scientific, Singapore (2007) | Proceedings of the Eleventh Marcel Grossmann Meeting 2006, Eds. H
Kleinert, RT Jantzen and R Ruffini, World Scientific, Singapore, p. 2503-2505
(2008) | null | null | gr-qc astro-ph | null | The radial component of the motion of compact binary systems composed of
neutron stars and/or black holes on eccentric orbit is integrated. We consider
all type of perturbations that emerge up to second post-Newtonian order. These
perturbations are either of relativistic origin or are related to the spin,
mass quadrupole and magnetic dipole moments of the binary components. We derive
a generalized Kepler equation and investigate its domain of validity, in which
it properly describes the radial motion.
| [
{
"created": "Wed, 13 Dec 2006 18:38:38 GMT",
"version": "v1"
}
] | 2009-05-15 | [
[
"Gergely",
"László Á.",
""
],
[
"Keresztes",
"Zoltán",
""
],
[
"Mikóczi",
"Balázs",
""
]
] | The radial component of the motion of compact binary systems composed of neutron stars and/or black holes on eccentric orbit is integrated. We consider all type of perturbations that emerge up to second post-Newtonian order. These perturbations are either of relativistic origin or are related to the spin, mass quadrupole and magnetic dipole moments of the binary components. We derive a generalized Kepler equation and investigate its domain of validity, in which it properly describes the radial motion. |
2208.05779 | Avik De Dr. | Avik De and Loo Tee How | Comment on "Energy conditions in $f(Q)$ gravity" | Accepted for publication in Phy. Rev. D | null | 10.1103/PhysRevD.106.048501 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In Phys. Rev. D 102, 024057 (2020), the authors studied energy conditions in
$f(Q)$ theory following the same path as researchers handled the energy
conditions in the curvature-based modified gravity theories, like $f(R)$ or
$f(R,G)$ theories. However, the field equations in the $f(Q)$ theory was not
expressed as an effective theory in the literature earlier and in the above
mentioned paper [1], the authors claimed that the pressure and energy density
follow a set of energy condition criteria without showing how they came to this
conclusion. In this comment, we express $f(Q)$ theory as an effective theory in
Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) universe. And from there, the
correct energy conditions are obtained in the traditional (general
relativistic) way. Unfortunately, some missing terms in the published work [1]
are noticed.
| [
{
"created": "Wed, 10 Aug 2022 10:56:23 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Aug 2022 08:52:13 GMT",
"version": "v2"
}
] | 2022-09-14 | [
[
"De",
"Avik",
""
],
[
"How",
"Loo Tee",
""
]
] | In Phys. Rev. D 102, 024057 (2020), the authors studied energy conditions in $f(Q)$ theory following the same path as researchers handled the energy conditions in the curvature-based modified gravity theories, like $f(R)$ or $f(R,G)$ theories. However, the field equations in the $f(Q)$ theory was not expressed as an effective theory in the literature earlier and in the above mentioned paper [1], the authors claimed that the pressure and energy density follow a set of energy condition criteria without showing how they came to this conclusion. In this comment, we express $f(Q)$ theory as an effective theory in Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) universe. And from there, the correct energy conditions are obtained in the traditional (general relativistic) way. Unfortunately, some missing terms in the published work [1] are noticed. |
0711.1967 | Ilya Gurwich | Aharon Davidson and Ilya Gurwich | Radiation Driven Inflation | 5 (two column) pages, 3 figures | JCAP0806:001,2008 | 10.1088/1475-7516/2008/06/001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A novel scalar field free approach to cosmic inflation is presented. The
inflationary Universe and the radiation dominated Universe are shown, within
the framework of unified brane cosmology, to be two different phases governed
by one and the same energy density. The phase transition of second order (the
Hubble constant exhibits a finite jump) appears naturally and serves as the
exit mechanism. No re-heating is needed. The required number of e-folds is
achieved without fine tuning.
| [
{
"created": "Tue, 13 Nov 2007 12:51:09 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Jun 2008 18:40:53 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Davidson",
"Aharon",
""
],
[
"Gurwich",
"Ilya",
""
]
] | A novel scalar field free approach to cosmic inflation is presented. The inflationary Universe and the radiation dominated Universe are shown, within the framework of unified brane cosmology, to be two different phases governed by one and the same energy density. The phase transition of second order (the Hubble constant exhibits a finite jump) appears naturally and serves as the exit mechanism. No re-heating is needed. The required number of e-folds is achieved without fine tuning. |
0904.4501 | Carlos F. Sopuerta | Carlos F. Sopuerta (ICE, CSIC-IEEC), Nicolas Yunes (Princeton) | Extreme- and Intermediate-Mass Ratio Inspirals in Dynamical Chern-Simons
Modified Gravity | 24 pages, 8 figures, Revtex 4 | Phys.Rev.D80:064006,2009 | 10.1103/PhysRevD.80.064006 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | [abridged] Chern-Simons (CS) modified gravity is a 4D effective theory that
descends both from string theory and loop quantum gravity, and that corrects
the Einstein-Hilbert action by adding the product of a scalar field and the
parity-violating, Pontryagin density. In this theory, the gravitational field
of spinning black holes is described by a modified Kerr geometry whose
multipole moments deviate from the Kerr ones only at the fourth multipole, l =
4. We investigate possible signatures of this theory in the gravitational wave
emission produced in the inspiral of stellar compact objects into massive black
holes, both for intermediate- and extreme-mass ratios. We use the
semi-relativistic approximation, where the trajectories are geodesics of the
massive black hole geometry and the gravitational waveforms are obtained from a
multipolar decomposition of the radiative field. The main CS corrections to the
waveforms arise from modifications to the geodesic trajectories, due to changes
to the massive black hole geometry, and manifest themselves as an accumulating
dephasing relative to the general relativistic case. We also explore the
propagation and the stress-energy tensor of gravitational waves in this theory.
We find that, although this tensor has the same form as in General Relativity,
the energy and angular momentum balance laws are indeed modified through the
stress-energy tensor of the CS scalar field. These balance laws could be used
to describe the inspiral through adiabatic changes in the orbital parameters,
which in turn would enhance the dephasing effect. Gravitational-wave
observations of intermediate- or extreme-mass ratio inspirals with advanced
ground detectors or with LISA could use such dephasing to test the dynamical
theory to unprecedented levels.
| [
{
"created": "Wed, 29 Apr 2009 08:48:10 GMT",
"version": "v1"
}
] | 2009-11-06 | [
[
"Sopuerta",
"Carlos F.",
"",
"ICE, CSIC-IEEC"
],
[
"Yunes",
"Nicolas",
"",
"Princeton"
]
] | [abridged] Chern-Simons (CS) modified gravity is a 4D effective theory that descends both from string theory and loop quantum gravity, and that corrects the Einstein-Hilbert action by adding the product of a scalar field and the parity-violating, Pontryagin density. In this theory, the gravitational field of spinning black holes is described by a modified Kerr geometry whose multipole moments deviate from the Kerr ones only at the fourth multipole, l = 4. We investigate possible signatures of this theory in the gravitational wave emission produced in the inspiral of stellar compact objects into massive black holes, both for intermediate- and extreme-mass ratios. We use the semi-relativistic approximation, where the trajectories are geodesics of the massive black hole geometry and the gravitational waveforms are obtained from a multipolar decomposition of the radiative field. The main CS corrections to the waveforms arise from modifications to the geodesic trajectories, due to changes to the massive black hole geometry, and manifest themselves as an accumulating dephasing relative to the general relativistic case. We also explore the propagation and the stress-energy tensor of gravitational waves in this theory. We find that, although this tensor has the same form as in General Relativity, the energy and angular momentum balance laws are indeed modified through the stress-energy tensor of the CS scalar field. These balance laws could be used to describe the inspiral through adiabatic changes in the orbital parameters, which in turn would enhance the dephasing effect. Gravitational-wave observations of intermediate- or extreme-mass ratio inspirals with advanced ground detectors or with LISA could use such dephasing to test the dynamical theory to unprecedented levels. |
1804.03725 | James Rankin | J. E. Rankin | Quaternionic Gauge Transformations and Yang-Mills Fields in Weyl Type
Geometries | 31 pages. The second half of the paper is new material. This uses
some material from arXiv:1101.3606 | null | null | RCTP-1801 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This elementary discussion generalizes a Weyl geometry to allow quaternion
valued gauge transformations and classical Yang-Mills geometric fields. This
development will assume that the symmetric metric tensor is real in some gauge,
and will develop the left and right handed approaches to quaternionic gauge
transformations. Quaternionic gauge transformations are shown actually to
require the shifting of some of Weyl's nonmetricity into torsion to define a
properly transforming gauge field full curvature tensor, which is constructed
as an asymmetric sum of left and right handed forms. Natural, gauge invariant,
dimensionless variables are defined suitable for physics, and for use as a
general formalism to describe these geometries, including General Relativity,
in rather general circumstances. The geometry "self measures" these variables.
Weyl's original action principle provides an example of an action rephrased in
these gauge invariant variables, along with some unexpected possible insights
on mechanics promoted by such a formulation of that action. Those include the
torsion tensor and nonmetricity being constructed from mechanical
energy-momentum. The Weyl form of action is then generalized to a quaternionic
gauge field. The insights on mechanics now include spin 1/2 Dirac free fields.
For physically reasonable choices of free parameters, the dimensionless Ricci
tensor becomes nonnegligible in particle physics at distances much greater than
the Planck length, along with limited general relativistic effects.
| [
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"c... | 2019-10-10 | [
[
"Rankin",
"J. E.",
""
]
] | This elementary discussion generalizes a Weyl geometry to allow quaternion valued gauge transformations and classical Yang-Mills geometric fields. This development will assume that the symmetric metric tensor is real in some gauge, and will develop the left and right handed approaches to quaternionic gauge transformations. Quaternionic gauge transformations are shown actually to require the shifting of some of Weyl's nonmetricity into torsion to define a properly transforming gauge field full curvature tensor, which is constructed as an asymmetric sum of left and right handed forms. Natural, gauge invariant, dimensionless variables are defined suitable for physics, and for use as a general formalism to describe these geometries, including General Relativity, in rather general circumstances. The geometry "self measures" these variables. Weyl's original action principle provides an example of an action rephrased in these gauge invariant variables, along with some unexpected possible insights on mechanics promoted by such a formulation of that action. Those include the torsion tensor and nonmetricity being constructed from mechanical energy-momentum. The Weyl form of action is then generalized to a quaternionic gauge field. The insights on mechanics now include spin 1/2 Dirac free fields. For physically reasonable choices of free parameters, the dimensionless Ricci tensor becomes nonnegligible in particle physics at distances much greater than the Planck length, along with limited general relativistic effects. |
gr-qc/9405001 | Andrew Chamblin | Andrew Chamblin, Gary Gibbons, Alan R. Steif | Kinks and Time Machines | 5 pages of text and 3 figures (obtain figures from A. Chamblin at
hachamblin@damtp.cam.ac.uk), DAMTP preprint # R/94/17 (Original submission
was slightly garbled.) | Phys.Rev.D50:2353-2355,1994 | 10.1103/PhysRevD.50.R2353 | null | gr-qc | null | We show that it is not possible to smooth out the metric on the
Deutsch-Politzer time machine to obtain an everywhere non-singular
asymptotically flat Lorentzian metric.
| [
{
"created": "Mon, 2 May 1994 12:54:02 GMT",
"version": "v1"
},
{
"created": "Sat, 7 May 1994 16:24:48 GMT",
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] | 2009-10-07 | [
[
"Chamblin",
"Andrew",
""
],
[
"Gibbons",
"Gary",
""
],
[
"Steif",
"Alan R.",
""
]
] | We show that it is not possible to smooth out the metric on the Deutsch-Politzer time machine to obtain an everywhere non-singular asymptotically flat Lorentzian metric. |
2111.15116 | LVK Publications | The LIGO Scientific Collaboration and the Virgo Collaboration: R.
Abbott, T. D. Abbott, F. Acernese, K. Ackley, C. Adams, N. Adhikari, R. X.
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Richardson, G. Riemenschneider, K. Riles, S. Rinaldi, K. Rink, M. Rizzo, N.
A. Robertson, R. Robie, F. Robinet, A. Rocchi, S. Rodriguez, L. Rolland, J.
G. Rollins, M. Romanelli, R. Romano, C. L. Romel, A. Romero-Rodr\'iguez, I.
M. Romero-Shaw, J. H. Romie, S. Ronchini, L. Rosa, C. A. Rose, D. Rosi\'nska,
M. P. Ross, S. Rowan, S. J. Rowlinson, S. Roy, Santosh Roy, Soumen Roy, D.
Rozza, P. Ruggi, K. Ryan, S. Sachdev, T. Sadecki, J. Sadiq, M. Sakellariadou,
O. S. Salafia, L. Salconi, M. Saleem, F. Salemi, A. Samajdar, E. J. Sanchez,
J. H. Sanchez, L. E. Sanchez, N. Sanchis-Gual, J. R. Sanders, A. Sanuy, T. R.
Saravanan, N. Sarin, B. Sassolas, H. Satari, B. S. Sathyaprakash, O. Sauter,
R. L. Savage, D. Sawant, H. L. Sawant, S. Sayah, D. Schaetzl, M. Scheel, J.
Scheuer, M. Schiworski, P. Schmidt, S. Schmidt, R. Schnabel, M. Schneewind,
R. M. S. Schofield, A. Sch\"onbeck, B. W. Schulte, B. F. Schutz, E. Schwartz,
J. Scott, S. M. Scott, M. Seglar-Arroyo, D. Sellers, A. S. Sengupta, D.
Sentenac, E. G. Seo, V. Sequino, A. Sergeev, Y. Setyawati, T. Shaffer, M. S.
Shahriar, B. Shams, A. Sharma, P. Sharma, P. Shawhan, N. S. Shcheblanov, M.
Shikauchi, D. H. Shoemaker, D. M. Shoemaker, S. ShyamSundar, M. Sieniawska,
D. Sigg, L. P. Singer, D. Singh, N. Singh, A. Singha, A. M. Sintes, V.
Sipala, V. Skliris, B. J. J. Slagmolen, T. J. Slaven-Blair, J. Smetana, J. R.
Smith, R. J. E. Smith, J. Soldateschi, S. N. Somala, E. J. Son, K. Soni, S.
Soni, V. Sordini, F. Sorrentino, N. Sorrentino, R. Soulard, T. Souradeep, E.
Sowell, V. Spagnuolo, A. P. Spencer, M. Spera, R. Srinivasan, A. K.
Srivastava, V. Srivastava, K. Staats, C. Stachie, D. A. Steer, J.
Steinlechner, S. Steinlechner, D. J. Stops, M. Stover, K. A. Strain, L. C.
Strang, G. Stratta, A. Strunk, R. Sturani, A. L. Stuver, S. Sudhagar, V.
Sudhir, H. G. Suh, T. Z. Summerscales, H. Sun, L. Sun, S. Sunil, A. Sur, J.
Suresh, P. J. Sutton, B. L. Swinkels, M. J. Szczepa\'nczyk, P. Szewczyk, M.
Tacca, S. C. Tait, C. J. Talbot, C. Talbot, A. J. Tanasijczuk, D. B. Tanner,
D. Tao, L. Tao, E. N. Tapia San Mart\'in, C. Taranto, J. D. Tasson, R.
Tenorio, J. E. Terhune, L. Terkowski, M. P. Thirugnanasambandam, M. Thomas,
P. Thomas, J. E. Thompson, S. R. Thondapu, K. A. Thorne, E. Thrane,
Shubhanshu Tiwari, Srishti Tiwari, V. Tiwari, A. M. Toivonen, K. Toland, A.
E. Tolley, M. Tonelli, A. Torres-Forn\'e, C. I. Torrie, I. Tosta e Melo, D.
T\"oyr\"a, A. Trapananti, F. Travasso, G. Traylor, M. Trevor, M. C. Tringali,
A. Tripathee, L. Troiano, A. Trovato, L. Trozzo, R. J. Trudeau, D. S. Tsai,
D. Tsai, K. W. Tsang, M. Tse, R. Tso, L. Tsukada, D. Tsuna, T. Tsutsui, K.
Turbang, M. Turconi, A. S. Ubhi, R. P. Udall, K. Ueno, C. S. Unnikrishnan, A.
L. Urban, A. Utina, H. Vahlbruch, G. Vajente, A. Vajpeyi, G. Valdes, M.
Valentini, V. Valsan, N. van Bakel, M. van Beuzekom, J. F. J. van den Brand,
C. Van Den Broeck, D. C. Vander-Hyde, L. van der Schaaf, J. V. van
Heijningen, J. Vanosky, N. van Remortel, M. Vardaro, A. F. Vargas, V. Varma,
M. Vas\'uth, A. Vecchio, G. Vedovato, J. Veitch, P. J. Veitch, J. Venneberg,
G. Venugopalan, D. Verkindt, P. Verma, Y. Verma, D. Veske, F. Vetrano, A.
Vicer\'e, S. Vidyant, A. D. Viets, A. Vijaykumar, V. Villa-Ortega, J.-Y.
Vinet, A. Virtuoso, S. Vitale, T. Vo, H. Vocca, E. R. G. von Reis, J. S. A.
von Wrangel, C. Vorvick, S. P. Vyatchanin, L. E. Wade, M. Wade, K. J. Wagner,
R. C. Walet, M. Walker, G. S. Wallace, L. Wallace, S. Walsh, J. Z. Wang, W.
H. Wang, R. L. Ward, J. Warner, M. Was, N. Y. Washington, J. Watchi, B.
Weaver, S. A. Webster, M. Weinert, A. J. Weinstein, R. Weiss, G. Weldon, C.
M. Weller, F. Wellmann, L. Wen, P. We{\ss}els, K. Wette, J. T. Whelan, D. D.
White, B. F. Whiting, C. Whittle, D. Wilken, D. Williams, M. J. Williams, A.
R. Williamson, J. L. Willis, B. Willke, D. J. Wilson, W. Winkler, C. C. Wipf,
T. Wlodarczyk, G. Woan, J. Woehler, J. K. Wofford, I. C. F. Wong, D. S. Wu,
D. M. Wysocki, L. Xiao, H. Yamamoto, F. W. Yang, L. Yang, Yang Yang, Z. Yang,
M. J. Yap, D. W. Yeeles, A. B. Yelikar, M. Ying, J. Yoo, Hang Yu, Haocun Yu,
A. Zadro\.zny, M. Zanolin, T. Zelenova, J.-P. Zendri, M. Zevin, J. Zhang, L.
Zhang, T. Zhang, Y. Zhang, C. Zhao, G. Zhao, Yue Zhao, R. Zhou, Z. Zhou, X.
J. Zhu, A. B. Zimmerman, M. E. Zucker, J. Zweizig | Search of the Early O3 LIGO Data for Continuous Gravitational Waves from
the Cassiopeia A and Vela Jr. Supernova Remnants | 24 pages, 8 figures. To appear in Physical Review D | null | 10.1103/PhysRevD.105.082005 | LIGO-P2100298-v8 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present directed searches for continuous gravitational waves from the
neutron stars in the Cassiopeia A (Cas A) and Vela Jr. supernova remnants. We
carry out the searches in the LIGO data from the first six months of the third
Advanced LIGO and Virgo observing run, using the Weave semi-coherent method,
which sums matched-filter detection-statistic values over many time segments
spanning the observation period. No gravitational wave signal is detected in
the search band of 20--976 Hz for assumed source ages greater than 300 years
for Cas A and greater than 700 years for Vela Jr. Estimates from simulated
continuous wave signals indicate we achieve the most sensitive results to date
across the explored parameter space volume, probing to strain magnitudes as low
as ~$6.3\times10^{-26}$ for Cas A and ~$5.6\times10^{-26}$ for Vela Jr. at
frequencies near 166 Hz at 95% efficiency.
| [
{
"created": "Tue, 30 Nov 2021 04:17:59 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Mar 2022 15:15:40 GMT",
"version": "v2"
}
] | 2022-05-18 | [
[
"The LIGO Scientific Collaboration",
"",
""
],
[
"the Virgo Collaboration",
"",
""
],
[
"Abbott",
"R.",
""
],
[
"Abbott",
"T. D.",
""
],
[
"Acernese",
"F.",
""
],
[
"Ackley",
"K.",
""
],
[
"Adams",
"C.",
""... | We present directed searches for continuous gravitational waves from the neutron stars in the Cassiopeia A (Cas A) and Vela Jr. supernova remnants. We carry out the searches in the LIGO data from the first six months of the third Advanced LIGO and Virgo observing run, using the Weave semi-coherent method, which sums matched-filter detection-statistic values over many time segments spanning the observation period. No gravitational wave signal is detected in the search band of 20--976 Hz for assumed source ages greater than 300 years for Cas A and greater than 700 years for Vela Jr. Estimates from simulated continuous wave signals indicate we achieve the most sensitive results to date across the explored parameter space volume, probing to strain magnitudes as low as ~$6.3\times10^{-26}$ for Cas A and ~$5.6\times10^{-26}$ for Vela Jr. at frequencies near 166 Hz at 95% efficiency. |
gr-qc/9611056 | Chris Chambers | Patrick R. Brady (Caltech), Chris M. Chambers (Montana State), William
Krivan (Tubingen, Penn State) and Pablo Laguna (Penn State) | Telling Tails In The Presence Of A Cosmological Constant | 7 pages (including 10 postscript figures), Revtex, uses epsf.tex and
twocolumn.sty. Submitted to Physical Review D | Phys.Rev. D55 (1997) 7538-7545 | 10.1103/PhysRevD.55.7538 | CGPG-96/11-3 | gr-qc | null | We study the evolution of massless scalar waves propagating on spherically
symmetric spacetimes with a non-zero cosmological constant. Considering test
fields on both Schwarzschild-de Sitter and Reissner-Nordstrom-de Sitter
backgrounds, we demonstrate the existence of exponentially decaying tails at
late times. Interestingly the l=0 mode asymptotes to a non-zero value,
contrasting the asymptotically flat situation. We also compare these results,
for l=0, with a numerical integration of the Einstein-Scalar field equations,
finding good agreement between the two. Finally, the significance of these
results to the study of the Cauchy horizon stability in black hole-de Sitter
spacetimes is discussed.
| [
{
"created": "Sun, 24 Nov 1996 00:32:34 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Brady",
"Patrick R.",
"",
"Caltech"
],
[
"Chambers",
"Chris M.",
"",
"Montana State"
],
[
"Krivan",
"William",
"",
"Tubingen, Penn State"
],
[
"Laguna",
"Pablo",
"",
"Penn State"
]
] | We study the evolution of massless scalar waves propagating on spherically symmetric spacetimes with a non-zero cosmological constant. Considering test fields on both Schwarzschild-de Sitter and Reissner-Nordstrom-de Sitter backgrounds, we demonstrate the existence of exponentially decaying tails at late times. Interestingly the l=0 mode asymptotes to a non-zero value, contrasting the asymptotically flat situation. We also compare these results, for l=0, with a numerical integration of the Einstein-Scalar field equations, finding good agreement between the two. Finally, the significance of these results to the study of the Cauchy horizon stability in black hole-de Sitter spacetimes is discussed. |
gr-qc/0003011 | Martin Tajmar | M. Tajmar, C. de Matos | Coupling of Gravitation and Electromagnetism in the Weak Field
Approximation | This work does not reflect the opinion of any official institution | null | null | null | gr-qc | null | Using the weak field approximation, we can express the theory of general
relativity in a Maxwell-type structure comparable to electromagnetism. We find
that every electromagnetic field is coupled to a gravitoelectric and
gravitomagnetic field. Acknowledging the fact that both fields originate from
the same source, the particle, we can express the magnetic and electric field
through their gravitational respective analogues using the proportionality
coefficient k. This coefficient depends on the ratio of mass and charge and the
ratio between the electromagnetic and gravitic-gravitomagnetic permittivity and
permeability respectively. Although the coefficient is very small, the fact
that electromagnetic fields in material media can be used to generate
gravitational and gravitomagnetic fields and vice versa is not commonly known.
We find that the coupling coefficient can be increased by massive ion currents,
electron and nuclear spin-alignment. Advances in material sciences, cryogenic
technology and high frequency electromagnetic fields in material media may lead
to applications of the derived relationships.
| [
{
"created": "Fri, 3 Mar 2000 13:25:48 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Tajmar",
"M.",
""
],
[
"de Matos",
"C.",
""
]
] | Using the weak field approximation, we can express the theory of general relativity in a Maxwell-type structure comparable to electromagnetism. We find that every electromagnetic field is coupled to a gravitoelectric and gravitomagnetic field. Acknowledging the fact that both fields originate from the same source, the particle, we can express the magnetic and electric field through their gravitational respective analogues using the proportionality coefficient k. This coefficient depends on the ratio of mass and charge and the ratio between the electromagnetic and gravitic-gravitomagnetic permittivity and permeability respectively. Although the coefficient is very small, the fact that electromagnetic fields in material media can be used to generate gravitational and gravitomagnetic fields and vice versa is not commonly known. We find that the coupling coefficient can be increased by massive ion currents, electron and nuclear spin-alignment. Advances in material sciences, cryogenic technology and high frequency electromagnetic fields in material media may lead to applications of the derived relationships. |
2405.00762 | Homa Shababi | Homa Shababi, Sayani Maity, Prabir Rudra, Ujjal Debnath | The effects of the pole dark energy on gravitational waves | 9 pages, 3 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper, we have studied the effects of pole dark energy on the
evolution of gravitational waves. The background evolution of gravitational
waves in a flat FRW universe is considered and its dynamics are studied in the
presence of pole dark energy. Two different potential functions are considered
for the study. Using the field equations, we formulated the perturbed equations
governing the evolution of gravitational waves with respect to redshift z
within the background of the FRW Universe. Subsequently, we delved into the
characteristics of gravitational waves for the pole dark energy model and
reached interesting results.
| [
{
"created": "Wed, 1 May 2024 16:05:37 GMT",
"version": "v1"
}
] | 2024-05-03 | [
[
"Shababi",
"Homa",
""
],
[
"Maity",
"Sayani",
""
],
[
"Rudra",
"Prabir",
""
],
[
"Debnath",
"Ujjal",
""
]
] | In this paper, we have studied the effects of pole dark energy on the evolution of gravitational waves. The background evolution of gravitational waves in a flat FRW universe is considered and its dynamics are studied in the presence of pole dark energy. Two different potential functions are considered for the study. Using the field equations, we formulated the perturbed equations governing the evolution of gravitational waves with respect to redshift z within the background of the FRW Universe. Subsequently, we delved into the characteristics of gravitational waves for the pole dark energy model and reached interesting results. |
2208.10219 | Mingzhi Wang | Mingzhi Wang, Songbai Chen, Jiliang Jing | Determination of the spin parameter and the inclination angle by the
relativistic images in black hole image | 16 pages, 12 figures | Science China Physics, Mechanics & Astronomy. Volume: 66. Issue:
11. 2023 | 10.1007/s11433-023-2152-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We studied the relativistic images caused by strong gravitational lensing in
Kerr black hole images, which carry some essential signatures about the black
hole space-time. We defined a new celestial coordinates whose origin is the
center of black hole shadow to locate the relativistic images. Under the
influences of the dragging effect caused by rotating black hole and the
inclination angle of observer, the relative positions between the primary and
secondary images are different with the different Kerr spin parameter $a$ and
the observer's inclination angle $i$, so it can be used to determine the value
of $a$ and $i$. We provided the specific approach to measure the value of $a$
and $i$ by the relativistic images. The time delays between the primary and
secondary images are different with the different $a$ and $i$. The time delays
in conjunction with the relative positions between the primary and secondary
images could allow us to measure the value of $a$ and $i$ more precisely. These
relativistic images are as unique as fingerprints for black hole space-time, by
which one can further determine other parameters of all kinds of compact
objects and verify various theories of gravity. Our results provide a new
method to implement parameter estimation in the study of black hole physics and
astrophysics.
| [
{
"created": "Mon, 22 Aug 2022 11:58:15 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Dec 2022 06:15:57 GMT",
"version": "v2"
},
{
"created": "Wed, 4 Jan 2023 04:50:44 GMT",
"version": "v3"
}
] | 2023-10-25 | [
[
"Wang",
"Mingzhi",
""
],
[
"Chen",
"Songbai",
""
],
[
"Jing",
"Jiliang",
""
]
] | We studied the relativistic images caused by strong gravitational lensing in Kerr black hole images, which carry some essential signatures about the black hole space-time. We defined a new celestial coordinates whose origin is the center of black hole shadow to locate the relativistic images. Under the influences of the dragging effect caused by rotating black hole and the inclination angle of observer, the relative positions between the primary and secondary images are different with the different Kerr spin parameter $a$ and the observer's inclination angle $i$, so it can be used to determine the value of $a$ and $i$. We provided the specific approach to measure the value of $a$ and $i$ by the relativistic images. The time delays between the primary and secondary images are different with the different $a$ and $i$. The time delays in conjunction with the relative positions between the primary and secondary images could allow us to measure the value of $a$ and $i$ more precisely. These relativistic images are as unique as fingerprints for black hole space-time, by which one can further determine other parameters of all kinds of compact objects and verify various theories of gravity. Our results provide a new method to implement parameter estimation in the study of black hole physics and astrophysics. |
0911.0334 | Nikodem Poplawski | Nikodem Pop{\l}awski | Classical Physics: Spacetime and Fields | 151 pages, 3 figures | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a self-contained introduction to the classical theory of spacetime
and fields. This exposition is based on the most general principles: the
principle of general covariance (relativity) and the principle of least action.
The order of the exposition is: 1. Spacetime (principle of general covariance
and tensors, affine connection, curvature, metric, space and time, tetrad and
spin connection, Lorentz group, spinors); 2. Fields (principle of least action,
gravitational field, matter, symmetries and conservation laws, particle limit
of field, gravitational field equations, spinor fields, electromagnetic field).
In this order, a particle is a special case of a field existing in spacetime,
and classical mechanics can be derived from field theory.
| [
{
"created": "Mon, 2 Nov 2009 16:32:00 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Jul 2020 21:13:22 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Jan 2024 22:49:58 GMT",
"version": "v3"
}
] | 2024-01-15 | [
[
"Popławski",
"Nikodem",
""
]
] | We present a self-contained introduction to the classical theory of spacetime and fields. This exposition is based on the most general principles: the principle of general covariance (relativity) and the principle of least action. The order of the exposition is: 1. Spacetime (principle of general covariance and tensors, affine connection, curvature, metric, space and time, tetrad and spin connection, Lorentz group, spinors); 2. Fields (principle of least action, gravitational field, matter, symmetries and conservation laws, particle limit of field, gravitational field equations, spinor fields, electromagnetic field). In this order, a particle is a special case of a field existing in spacetime, and classical mechanics can be derived from field theory. |
2404.01395 | Raimon Luna | Raimon Luna, Miquel Llorens-Monteagudo, Ana Lorenzo-Medina, Juan
Calder\'on Bustillo, Nicolas Sanchis-Gual, Alejandro Torres-Forn\'e, Jos\'e
A. Font, Carlos A. R. Herdeiro, Eugen Radu | Numerical relativity surrogate models for exotic compact objects: the
case of head-on mergers of equal-mass Proca stars | 16 pages, 14 figures. v2: Matches published version | Phys.Rev.D 110 (2024) 2, 024004 | 10.1103/PhysRevD.110.024004 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present several high-accuracy surrogate models for gravitational-wave
signals from equal-mass head-on mergers of Proca stars, computed through the
Newman-Penrose scalar $\psi_4$. We also discuss the current state of the model
extensions to mergers of Proca stars with different masses, and the particular
challenges that these present. The models are divided in two main categories:
two-stage and monolithic. In the two-stage models, a dimensional reduction
algorithm is applied to embed the data in a reduced feature space, which is
then interpolated in terms of the physical parameters. For the monolithic
models, a single neural network is trained to predict the waveform from the
input physical parameter. Our model displays mismatches below $10^{-3}$ with
respect to the original numerical waveforms. Finally, we demonstrate the usage
of our model in full Bayesian parameter inference through the accurate recovery
of numerical relativity signals injected in zero-noise, together with the
analysis of GW190521. For the latter, we observe excellent agreement with
existing results that make use of full numerical relativity.
| [
{
"created": "Mon, 1 Apr 2024 18:07:18 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jul 2024 16:01:43 GMT",
"version": "v2"
}
] | 2024-07-30 | [
[
"Luna",
"Raimon",
""
],
[
"Llorens-Monteagudo",
"Miquel",
""
],
[
"Lorenzo-Medina",
"Ana",
""
],
[
"Bustillo",
"Juan Calderón",
""
],
[
"Sanchis-Gual",
"Nicolas",
""
],
[
"Torres-Forné",
"Alejandro",
""
],
[
"Font"... | We present several high-accuracy surrogate models for gravitational-wave signals from equal-mass head-on mergers of Proca stars, computed through the Newman-Penrose scalar $\psi_4$. We also discuss the current state of the model extensions to mergers of Proca stars with different masses, and the particular challenges that these present. The models are divided in two main categories: two-stage and monolithic. In the two-stage models, a dimensional reduction algorithm is applied to embed the data in a reduced feature space, which is then interpolated in terms of the physical parameters. For the monolithic models, a single neural network is trained to predict the waveform from the input physical parameter. Our model displays mismatches below $10^{-3}$ with respect to the original numerical waveforms. Finally, we demonstrate the usage of our model in full Bayesian parameter inference through the accurate recovery of numerical relativity signals injected in zero-noise, together with the analysis of GW190521. For the latter, we observe excellent agreement with existing results that make use of full numerical relativity. |
2203.00957 | Shafqat Ul Islam | Shafqat Ul Islam, Sushant G. Ghosh, Sunil D. Maharaj | Strong gravitational lensing by Bardeen black holes in 4D EGB gravity:
constraints from supermassive black holes | 14 pages, 13 figures, 4 tables, references updated | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Observation indicates that many nearby galaxies host supermassive central
black holes. Modelling Bardeen models in four-dimensional Einstein-Gauss-Bonnet
(4D EGB) gravity, with additional parameters $\tilde{\alpha}$ and charge $q$,
as central black holes in various galaxies, we investigate gravitational
lensing properties in strong deflection limits. Interestingly, the spherical
photon orbit radius $x_m$, the critical impact parameter $u_m$, the lensing
coefficient $\bar{b}$, the deflection angle $\alpha_D(\theta)$, angular
position $\theta_{\infty}$ are decreasing with $q$ and $\alpha$ whereas the
other lensing coefficient $\bar{a}$ and angular separation $s$ have opposite
behaviour. Taking the supermassive black holes Sgr A* and M87* as the lens, we
also compare observable signatures of 4D EGB Bardeen black holes with those of
the Schwarzschild black holes. The angular position $\theta_\infty$ for Sgr A*
$\in$ (23.1853, \; 25.56427) $\mu$as, whereas for M87* it is $\in$ ( 17.941,\;
19.7819) $\mu$as. Further, the angular separation $s$, which is an increasing
function of $\tilde{\alpha}$ and $q$ for Sgr A* and M87* differs significantly,
respectively, in (0.031997,0.14895) $\mu$as and (0.0247, 0.1152) $\mu$as. The
deviations of the lensing observables $\Delta \theta_{\infty}$ and $\Delta s$
for 4D EGB Bardeen black hole ($\tilde{\alpha}=0.9,~q=0.09$) from the
Schwarzschild black hole, respectively, can reach up to $2.3789~\mu$as and
$0.11695~\mu$as for Sgr A* , $1.84084~\mu$as and $0.0905~\mu$as for M87*. On
the other hand, the relative magnification $\in$ (4.65751,\; 6.82173).
Considering twenty-two massive central black holes as lens, we also estimate
the time delay $\Delta T^s_{2,1}$ between the first and second relativistic
image to find that, e.g., the time delay for Sgr A* and M87*, respectively, can
reach $\sim9.86088$~min and $\sim16023.93$~min.
| [
{
"created": "Wed, 2 Mar 2022 09:09:07 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jul 2022 15:20:55 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Jul 2022 14:12:56 GMT",
"version": "v3"
}
] | 2022-07-15 | [
[
"Islam",
"Shafqat Ul",
""
],
[
"Ghosh",
"Sushant G.",
""
],
[
"Maharaj",
"Sunil D.",
""
]
] | Observation indicates that many nearby galaxies host supermassive central black holes. Modelling Bardeen models in four-dimensional Einstein-Gauss-Bonnet (4D EGB) gravity, with additional parameters $\tilde{\alpha}$ and charge $q$, as central black holes in various galaxies, we investigate gravitational lensing properties in strong deflection limits. Interestingly, the spherical photon orbit radius $x_m$, the critical impact parameter $u_m$, the lensing coefficient $\bar{b}$, the deflection angle $\alpha_D(\theta)$, angular position $\theta_{\infty}$ are decreasing with $q$ and $\alpha$ whereas the other lensing coefficient $\bar{a}$ and angular separation $s$ have opposite behaviour. Taking the supermassive black holes Sgr A* and M87* as the lens, we also compare observable signatures of 4D EGB Bardeen black holes with those of the Schwarzschild black holes. The angular position $\theta_\infty$ for Sgr A* $\in$ (23.1853, \; 25.56427) $\mu$as, whereas for M87* it is $\in$ ( 17.941,\; 19.7819) $\mu$as. Further, the angular separation $s$, which is an increasing function of $\tilde{\alpha}$ and $q$ for Sgr A* and M87* differs significantly, respectively, in (0.031997,0.14895) $\mu$as and (0.0247, 0.1152) $\mu$as. The deviations of the lensing observables $\Delta \theta_{\infty}$ and $\Delta s$ for 4D EGB Bardeen black hole ($\tilde{\alpha}=0.9,~q=0.09$) from the Schwarzschild black hole, respectively, can reach up to $2.3789~\mu$as and $0.11695~\mu$as for Sgr A* , $1.84084~\mu$as and $0.0905~\mu$as for M87*. On the other hand, the relative magnification $\in$ (4.65751,\; 6.82173). Considering twenty-two massive central black holes as lens, we also estimate the time delay $\Delta T^s_{2,1}$ between the first and second relativistic image to find that, e.g., the time delay for Sgr A* and M87*, respectively, can reach $\sim9.86088$~min and $\sim16023.93$~min. |
gr-qc/0004018 | Marc Mars | Marc Mars | Uniqueness properties of the Kerr metric | 30 pages, LaTeX, submitted to Classical and Quantum Gravity | Class.Quant.Grav. 17 (2000) 3353 | 10.1088/0264-9381/17/16/317 | null | gr-qc | null | We obtain a geometrical condition on vacuum, stationary, asymptotically flat
spacetimes which is necessary and sufficient for the spacetime to be locally
isometric to Kerr. Namely, we prove a theorem stating that an asymptotically
flat, stationary, vacuum spacetime such that the so-called Killing form is an
eigenvector of the self-dual Weyl tensor must be locally isometric to Kerr.
Asymptotic flatness is a fundamental hypothesis of the theorem, as we
demonstrate by writing down the family of metrics obtained when this
requirement is dropped. This result indicates why the Kerr metric plays such an
important role in general relativity. It may also be of interest in order to
extend the uniqueness theorems of black holes to the non-connected and to the
non-analytic case.
| [
{
"created": "Thu, 6 Apr 2000 12:45:13 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Mars",
"Marc",
""
]
] | We obtain a geometrical condition on vacuum, stationary, asymptotically flat spacetimes which is necessary and sufficient for the spacetime to be locally isometric to Kerr. Namely, we prove a theorem stating that an asymptotically flat, stationary, vacuum spacetime such that the so-called Killing form is an eigenvector of the self-dual Weyl tensor must be locally isometric to Kerr. Asymptotic flatness is a fundamental hypothesis of the theorem, as we demonstrate by writing down the family of metrics obtained when this requirement is dropped. This result indicates why the Kerr metric plays such an important role in general relativity. It may also be of interest in order to extend the uniqueness theorems of black holes to the non-connected and to the non-analytic case. |
1802.01371 | Janusz Garecki Prof | Marta Dudek, Janusz Garecki | General relativity with nonzero cosmological constant as a gauge theory | 13 pages, no figure,paper delivered on the conference Hypercomplex
Seminar 2017 in Bedlewo (Poland, EU) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show in a new way that the general relativity action (and Lagrangian)in
recent Einstein-Palatini formulation is equivalent in four dimensions to the
action (and Lagrangian) of a gauge field. This paper is a continuation of the
previous paper [17] and it also gives an amended version of the lecture
delivered by one of the authors [M.D.] at Hypercomplex Seminar in Bedlewo.
| [
{
"created": "Mon, 5 Feb 2018 12:43:52 GMT",
"version": "v1"
}
] | 2018-02-06 | [
[
"Dudek",
"Marta",
""
],
[
"Garecki",
"Janusz",
""
]
] | We show in a new way that the general relativity action (and Lagrangian)in recent Einstein-Palatini formulation is equivalent in four dimensions to the action (and Lagrangian) of a gauge field. This paper is a continuation of the previous paper [17] and it also gives an amended version of the lecture delivered by one of the authors [M.D.] at Hypercomplex Seminar in Bedlewo. |
1102.1062 | Javad Taghizadeh Firouzjaee | J. T. Firouzjaee | The spherical symmetry Black hole collapse in expanding universe | 14 pages, 3 figures. Page layout and Some typos corrected | null | 10.1142/S0218271812500393 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The spherical symmetry Black holes are considered in expanding background.
The singularity line and the marginally trapped tube surface behavior are
discussed. In particular, we address the conditions of whether a dynamical
horizon forms for these cosmological black holes. We also discuss the
cosmological constant effect on these black holes and the redshift of the light
which comes from the marginally trapped tube surface.
| [
{
"created": "Sat, 5 Feb 2011 11:12:24 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Sep 2011 20:05:30 GMT",
"version": "v2"
},
{
"created": "Mon, 9 Apr 2012 08:27:34 GMT",
"version": "v3"
},
{
"created": "Thu, 9 Dec 2021 05:06:41 GMT",
"version": "v4"
}
] | 2021-12-10 | [
[
"Firouzjaee",
"J. T.",
""
]
] | The spherical symmetry Black holes are considered in expanding background. The singularity line and the marginally trapped tube surface behavior are discussed. In particular, we address the conditions of whether a dynamical horizon forms for these cosmological black holes. We also discuss the cosmological constant effect on these black holes and the redshift of the light which comes from the marginally trapped tube surface. |
1604.00468 | \.Ibrahim Semiz | \.Ibrahim Semiz | Random-walk baryogenesis via primordial black holes | Essay written for the Gravity Research Foundation 2016 Awards for
Essays on Gravitation. No figures | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitation violates baryon number $B$: A star has a huge amount of it, while
a black hole forming from the star has none. Consider primordial black holes
before the hadronic annihiliation in the early universe, encountering and
absorbing baryons and antibaryons: Each such absorption changes $B$ of the
universe by one unit, up or down. But the absorption events are $uncorrelated$
$and$ $random$, hence they amount to a random walk in $B$-space, leading to the
expectation of a net $|B|$ at the end.
While the scale of this effect is most uncertain, it must exist. We explore
some ramifications, including the change of net $|B|$ with expansion,
connection with universe topology, and possible observational signatures.
| [
{
"created": "Sat, 2 Apr 2016 07:22:48 GMT",
"version": "v1"
}
] | 2016-04-05 | [
[
"Semiz",
"İbrahim",
""
]
] | Gravitation violates baryon number $B$: A star has a huge amount of it, while a black hole forming from the star has none. Consider primordial black holes before the hadronic annihiliation in the early universe, encountering and absorbing baryons and antibaryons: Each such absorption changes $B$ of the universe by one unit, up or down. But the absorption events are $uncorrelated$ $and$ $random$, hence they amount to a random walk in $B$-space, leading to the expectation of a net $|B|$ at the end. While the scale of this effect is most uncertain, it must exist. We explore some ramifications, including the change of net $|B|$ with expansion, connection with universe topology, and possible observational signatures. |
gr-qc/0607098 | Rafal Moderski | R. Moderski and M. Rogatko | Thick Domain Walls in AdS Black Hole Spacetimes | 20 pages, 19 figures, accepted for publication in Phys. Rev. D | Phys.Rev. D74 (2006) 044002 | 10.1103/PhysRevD.74.044002 | null | gr-qc hep-th | null | Equations of motion for a real self-gravitating scalar field in the
background of a black hole with negative cosmological constant were solved
numerically. We obtain a sequence of static axisymmetric solutions representing
thick domain wall cosmological black hole systems, depending on the mass of
black hole, cosmological parameter and the parameter binding black hole mass
with the width of the domain wall. For the case of extremal cosmological black
hole the expulsion of scalar field from the black hole strongly depends on it.
| [
{
"created": "Sun, 23 Jul 2006 14:32:03 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Moderski",
"R.",
""
],
[
"Rogatko",
"M.",
""
]
] | Equations of motion for a real self-gravitating scalar field in the background of a black hole with negative cosmological constant were solved numerically. We obtain a sequence of static axisymmetric solutions representing thick domain wall cosmological black hole systems, depending on the mass of black hole, cosmological parameter and the parameter binding black hole mass with the width of the domain wall. For the case of extremal cosmological black hole the expulsion of scalar field from the black hole strongly depends on it. |
1103.3961 | Matteo Smerlak | Valentin Bonzom and Matteo Smerlak | Bubble divergences: sorting out topology from cell structure | 19 pages | Annales Henri Poincar\'e: 13 (2012) 185-208 | 10.1007/s00023-011-0127-y | pi-qg-217 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We conclude our analysis of bubble divergences in the flat spinfoam model. In
[arXiv:1008.1476] we showed that the divergence degree of an arbitrary
two-complex Gamma can be evaluated exactly by means of twisted cohomology.
Here, we specialize this result to the case where Gamma is the two-skeleton of
the cell decomposition of a pseudomanifold, and sharpen it with a careful
analysis of the cellular and topological structures involved. Moreover, we
explain in detail how this approach reproduces all the previous powercounting
results for the Boulatov-Ooguri (colored) tensor models, and sheds light on
algebraic-topological aspects of Gurau's 1/N expansion.
| [
{
"created": "Mon, 21 Mar 2011 10:23:28 GMT",
"version": "v1"
}
] | 2012-02-03 | [
[
"Bonzom",
"Valentin",
""
],
[
"Smerlak",
"Matteo",
""
]
] | We conclude our analysis of bubble divergences in the flat spinfoam model. In [arXiv:1008.1476] we showed that the divergence degree of an arbitrary two-complex Gamma can be evaluated exactly by means of twisted cohomology. Here, we specialize this result to the case where Gamma is the two-skeleton of the cell decomposition of a pseudomanifold, and sharpen it with a careful analysis of the cellular and topological structures involved. Moreover, we explain in detail how this approach reproduces all the previous powercounting results for the Boulatov-Ooguri (colored) tensor models, and sheds light on algebraic-topological aspects of Gurau's 1/N expansion. |
gr-qc/0103073 | Daniele Amati | Daniele Amati | How strings solve the apparent contradiction between black holes and
quantum coherence | Talk delivered at the symposium on ``50 years of electroweak
physics'' NYU, 27-28 Oct. 2000, in honor of Alberto Sirlin 70'th anniversary | J.Phys.G29:31-34,2003 | 10.1088/0954-3899/29/1/304 | SISSA 23/01/EP | gr-qc | null | Computations in the calculable small coupling regime of string theories and
the general consensus that no new physics has to be invoked in continuing to
the large coupling (black hole) regime, suggest the following picture. Quantum
states are not black holes even if energy distributions would suggest so. Black
holes appear as macrostates, i.e. with the same procedure that blures the
quantum coherence of microstates. It is also discussed how a spacetime
description - and thus geometry, causal properties and event horizons - may
stem from decoherence in the pregeometric approach represented by string
theories.
| [
{
"created": "Tue, 20 Mar 2001 15:25:19 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Amati",
"Daniele",
""
]
] | Computations in the calculable small coupling regime of string theories and the general consensus that no new physics has to be invoked in continuing to the large coupling (black hole) regime, suggest the following picture. Quantum states are not black holes even if energy distributions would suggest so. Black holes appear as macrostates, i.e. with the same procedure that blures the quantum coherence of microstates. It is also discussed how a spacetime description - and thus geometry, causal properties and event horizons - may stem from decoherence in the pregeometric approach represented by string theories. |
1907.00974 | Zoltan Keresztes | Bal\'azs Mik\'oczi, Zolt\'an Keresztes | Spin dynamics of moving bodies in rotating black hole spacetimes | 24 pages; 14 figures | Ann. Phys. (Berlin) 2022, 2100444 | 10.1002/andp.202100444 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamics of spinning test bodies, moving in rotating black hole (Kerr,
Bardeen-like and Hayward-like) spacetimes, are investigated. In Kerr spacetime,
all the spherical, zoom-whirl and unbound orbits are considered numerically.
Along spherical orbits and for high spin, an amplitude modulation is found in
the harmonic evolution of the spin precessional angular velocity, caused by the
spin-curvature coupling. Along the discussed zoom-whirl and unbound orbits, the
test body approaches the center so much that it passes through the ergosphere.
Near and inside the ergosphere, the variation of the spin direction can be very
rapid. The effects of the spin-curvature coupling is also investigated. The
initial values are chosen such a way, that the body and its spin move in the
equatorial plane of the coordinate space and of the comoving frame,
respectively. Hence, a clear effect of the spin-curvature coupling is observed
as the orbit and the spin vector leave the equatorial plane. Additional effects
in the spin precessional angular velocity and in the evolution of the
Boyer-Lindquist coordinate components of the spin vector is also considered.
Finally, in case of different regular black holes, the spin-curvature coupling
influences differently the orbit and the spin evolutions.
| [
{
"created": "Mon, 1 Jul 2019 17:58:21 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Feb 2022 15:45:53 GMT",
"version": "v2"
}
] | 2022-02-10 | [
[
"Mikóczi",
"Balázs",
""
],
[
"Keresztes",
"Zoltán",
""
]
] | The dynamics of spinning test bodies, moving in rotating black hole (Kerr, Bardeen-like and Hayward-like) spacetimes, are investigated. In Kerr spacetime, all the spherical, zoom-whirl and unbound orbits are considered numerically. Along spherical orbits and for high spin, an amplitude modulation is found in the harmonic evolution of the spin precessional angular velocity, caused by the spin-curvature coupling. Along the discussed zoom-whirl and unbound orbits, the test body approaches the center so much that it passes through the ergosphere. Near and inside the ergosphere, the variation of the spin direction can be very rapid. The effects of the spin-curvature coupling is also investigated. The initial values are chosen such a way, that the body and its spin move in the equatorial plane of the coordinate space and of the comoving frame, respectively. Hence, a clear effect of the spin-curvature coupling is observed as the orbit and the spin vector leave the equatorial plane. Additional effects in the spin precessional angular velocity and in the evolution of the Boyer-Lindquist coordinate components of the spin vector is also considered. Finally, in case of different regular black holes, the spin-curvature coupling influences differently the orbit and the spin evolutions. |
2402.10916 | Abdelmalek Bouzenada . | Faizuddin Ahmed and Abdelmalek Bouzenada | PDM relativistic quantum oscillator in Einstein-Maxwell-Lambda
space-time | null | null | 10.1142/S0219887824502530 | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | In this analysis, we study the dynamics of quantum oscillator fields within
the context of a position-dependent mass (PDM) system situated in an
Einstein-Maxwell space-time, incorporating a non-zero cosmological constant.
The magnetic field is aligned along the symmetry axis direction. To analyze PDM
quantum oscillator fields, we introduce a modification to the Klein-Gordon
equation by substituting the four-momentum vector $p_{\mu} \to
\Big(p_{\mu}+i\,\eta\,X_{\mu}+i\,\mathcal{F}_{\mu}\Big)$ into the Klein-Gordon
equation, where the four-vector is defibed by $X_{\mu}=(0, r, 0, 0)$,
$\mathcal{F}_{\mu}=(0, \mathcal{F}_r, 0, 0)$ with
$\mathcal{F}_r=\frac{f'(r)}{4\,f(r)}$, and $\eta$ is the mass oscillator
frequency. The radial wave equation for the relativistic modified Klein-Gordon
equation is derived and subsequently solved for two distinct cases: (i)
$f(r)=e^{\frac{1}{2}\,\alpha\,r^2}$, and (ii) $f(r)=r^{\beta}$, where $\alpha
\geq 0, \beta \geq 0$. The resultant energy levels and wave functions for
quantum oscillator fields are demonstrated to be influenced by both the
cosmological constant and the geometrical topology parameter which breaks the
degeneracy of the energy spectrum. Furthermore, we observed noteworthy
modifications in the energy levels and wave functions when compared to the
results derived in the flat space background.
| [
{
"created": "Sat, 20 Jan 2024 16:02:04 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Jun 2024 16:15:50 GMT",
"version": "v2"
}
] | 2024-06-10 | [
[
"Ahmed",
"Faizuddin",
""
],
[
"Bouzenada",
"Abdelmalek",
""
]
] | In this analysis, we study the dynamics of quantum oscillator fields within the context of a position-dependent mass (PDM) system situated in an Einstein-Maxwell space-time, incorporating a non-zero cosmological constant. The magnetic field is aligned along the symmetry axis direction. To analyze PDM quantum oscillator fields, we introduce a modification to the Klein-Gordon equation by substituting the four-momentum vector $p_{\mu} \to \Big(p_{\mu}+i\,\eta\,X_{\mu}+i\,\mathcal{F}_{\mu}\Big)$ into the Klein-Gordon equation, where the four-vector is defibed by $X_{\mu}=(0, r, 0, 0)$, $\mathcal{F}_{\mu}=(0, \mathcal{F}_r, 0, 0)$ with $\mathcal{F}_r=\frac{f'(r)}{4\,f(r)}$, and $\eta$ is the mass oscillator frequency. The radial wave equation for the relativistic modified Klein-Gordon equation is derived and subsequently solved for two distinct cases: (i) $f(r)=e^{\frac{1}{2}\,\alpha\,r^2}$, and (ii) $f(r)=r^{\beta}$, where $\alpha \geq 0, \beta \geq 0$. The resultant energy levels and wave functions for quantum oscillator fields are demonstrated to be influenced by both the cosmological constant and the geometrical topology parameter which breaks the degeneracy of the energy spectrum. Furthermore, we observed noteworthy modifications in the energy levels and wave functions when compared to the results derived in the flat space background. |
gr-qc/0603135 | Shun-Pei Miao | Shun-Pei Miao, R. P. Woodard (University of Florida) | Gravitons Enhance Fermions during Inflation | 31 pages, Latex 2epsilon, 1 figure, version 3 has updated references | Phys.Rev.D74:024021,2006 | 10.1103/PhysRevD.74.024021 | null | gr-qc hep-th | null | We solve the effective Dirac equation for massless fermions during inflation
in the simplest gauge, including all one loop corrections from quantum gravity.
At late times the result for a spatial plane wave behaves as if the classical
solution were subjected to a time dependent field strength renormalization of
Z_2(t) = 1 - \frac{17}{4 \pi} G H^2 \ln(a) + O(G^2). We show that this also
follows from making the Hartree approximation, although the numerical
coefficients differ.
| [
{
"created": "Fri, 31 Mar 2006 18:25:49 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Jul 2006 20:09:14 GMT",
"version": "v2"
},
{
"created": "Sun, 11 May 2008 11:50:19 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Miao",
"Shun-Pei",
"",
"University of Florida"
],
[
"Woodard",
"R. P.",
"",
"University of Florida"
]
] | We solve the effective Dirac equation for massless fermions during inflation in the simplest gauge, including all one loop corrections from quantum gravity. At late times the result for a spatial plane wave behaves as if the classical solution were subjected to a time dependent field strength renormalization of Z_2(t) = 1 - \frac{17}{4 \pi} G H^2 \ln(a) + O(G^2). We show that this also follows from making the Hartree approximation, although the numerical coefficients differ. |
2407.10968 | Bruce Allen | Bruce Allen and Joseph D. Romano | Optimal reconstruction of the Hellings and Downs correlation | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Pulsar timing arrays (PTAs) detect gravitational waves (GWs) via the
correlations they create in the arrival times of pulses from different pulsars.
The mean correlation, a function of the angle between the directions to two
pulsars, was predicted in 1983 by Hellings and Downs (HD). Observation of this
angular pattern is the ``smoking gun'' that GWs are present, so PTAs
``reconstruct the HD curve'' by estimating the correlation using pulsar pairs
separated by similar angles. Several studies have examined the amount by which
this curve is expected to differ from the HD mean. The variance arises because
(a) a finite set of pulsars at specific sky locations is used, (b) the GW
sources interfere, and (c) the data are contaminated by noise. Here, for a
Gaussian ensemble of sources, we predict that variance using an optimal
estimator of the HD correlation, taking into account the pulsar sky locations
and the power spectrum of the GWs. The variance is a ratio: the numerator
depends upon the pulsar sky locations, and the denominator is the number of
frequency bins for which the GW signal dominates the noise. In effect, after
suitable combination, each frequency bin gives an independent estimate of the
HD correlation.
| [
{
"created": "Mon, 15 Jul 2024 17:59:24 GMT",
"version": "v1"
}
] | 2024-07-16 | [
[
"Allen",
"Bruce",
""
],
[
"Romano",
"Joseph D.",
""
]
] | Pulsar timing arrays (PTAs) detect gravitational waves (GWs) via the correlations they create in the arrival times of pulses from different pulsars. The mean correlation, a function of the angle between the directions to two pulsars, was predicted in 1983 by Hellings and Downs (HD). Observation of this angular pattern is the ``smoking gun'' that GWs are present, so PTAs ``reconstruct the HD curve'' by estimating the correlation using pulsar pairs separated by similar angles. Several studies have examined the amount by which this curve is expected to differ from the HD mean. The variance arises because (a) a finite set of pulsars at specific sky locations is used, (b) the GW sources interfere, and (c) the data are contaminated by noise. Here, for a Gaussian ensemble of sources, we predict that variance using an optimal estimator of the HD correlation, taking into account the pulsar sky locations and the power spectrum of the GWs. The variance is a ratio: the numerator depends upon the pulsar sky locations, and the denominator is the number of frequency bins for which the GW signal dominates the noise. In effect, after suitable combination, each frequency bin gives an independent estimate of the HD correlation. |
2007.04283 | Sharmila Gunasekaran | Sharmila Gunasekaran, Hari K. Kunduri | Slow decay of waves in gravitational solitons | 43 pages, 16 figures; v2 : typos corrected, various minor
improvements and clarifications | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a family of globally stationary (horizonless), asymptotically
flat solutions of five-dimensional supergravity. We prove that massless linear
scalar waves in such soliton spacetimes cannot have a uniform decay rate faster
than inverse logarithmically in time. This slow decay can be attributed to the
stable trapping of null geodesics. Our proof uses the construction of
quasimodes which are time periodic approximate solutions to the wave equation.
The proof is based on previous work to prove an analogous result in Kerr-AdS
black holes \cite{holzegel:2013kna}. We remark that this slow decay is
suggestive of an instability at the nonlinear level.
| [
{
"created": "Wed, 8 Jul 2020 17:33:05 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Aug 2020 14:28:27 GMT",
"version": "v2"
}
] | 2020-08-11 | [
[
"Gunasekaran",
"Sharmila",
""
],
[
"Kunduri",
"Hari K.",
""
]
] | We consider a family of globally stationary (horizonless), asymptotically flat solutions of five-dimensional supergravity. We prove that massless linear scalar waves in such soliton spacetimes cannot have a uniform decay rate faster than inverse logarithmically in time. This slow decay can be attributed to the stable trapping of null geodesics. Our proof uses the construction of quasimodes which are time periodic approximate solutions to the wave equation. The proof is based on previous work to prove an analogous result in Kerr-AdS black holes \cite{holzegel:2013kna}. We remark that this slow decay is suggestive of an instability at the nonlinear level. |
1909.07224 | Dr. Goutam Manna | Goutam Manna, Parthasarathi Majumdar and Bivash Majumder | K-essence Emergent Spacetime as Generalized Vaidya Geometry | 8 pages, 6 figures, Accepted from Physical Review D | Phys. Rev. D 101, 124034 (2020) | 10.1103/PhysRevD.101.124034 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We establish a formal connection between the {\bf K}-essence emergent gravity
scenario and generalizations of Vaidya spacetime. Choosing the {\bf K}-essence
action to be of the Dirac-Born-Infeld variety, the physical spacetime to be a
general static spherically symmetric black hole and restricting the {\bf
K}-essence scalar field to be a function solely of the advanced or the retarded
time, we show that the emergent gravity metric resembles closely the
generalized Vaidya metrics for null fluid collapse proposed by Husain. Imposing
null energy conditions on the emergent energy-momentum tensor derived from the
emergent Einstein equation, restrictions are obtained on the functions
characterizing the emergent metric for consistent identification with
generalized Vaidya spacetimes. We discuss the possibility of dynamical horizons
in the {\bf K-}essence emergent Vaidya spacetime. Admissible explicit black
hole background metrics are discussed as examples.
| [
{
"created": "Fri, 13 Sep 2019 17:06:37 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Apr 2020 02:03:08 GMT",
"version": "v2"
},
{
"created": "Fri, 29 May 2020 01:04:23 GMT",
"version": "v3"
}
] | 2020-07-01 | [
[
"Manna",
"Goutam",
""
],
[
"Majumdar",
"Parthasarathi",
""
],
[
"Majumder",
"Bivash",
""
]
] | We establish a formal connection between the {\bf K}-essence emergent gravity scenario and generalizations of Vaidya spacetime. Choosing the {\bf K}-essence action to be of the Dirac-Born-Infeld variety, the physical spacetime to be a general static spherically symmetric black hole and restricting the {\bf K}-essence scalar field to be a function solely of the advanced or the retarded time, we show that the emergent gravity metric resembles closely the generalized Vaidya metrics for null fluid collapse proposed by Husain. Imposing null energy conditions on the emergent energy-momentum tensor derived from the emergent Einstein equation, restrictions are obtained on the functions characterizing the emergent metric for consistent identification with generalized Vaidya spacetimes. We discuss the possibility of dynamical horizons in the {\bf K-}essence emergent Vaidya spacetime. Admissible explicit black hole background metrics are discussed as examples. |
2407.14909 | Francisco Fern\'andez-\'Alvarez | Francisco Fern\'andez-\'Alvarez | News tensor on null hypersurfaces | 25 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A geometric definition of news tensor on null hypersurfaces in four
space-time dimensions is presented. When the conformal Einstein field equations
hold, this news tensor yields the correct expression for the radiative
components of the rescaled Weyl tensor at infinity with vanishing cosmological
constant in arbitrary conformal gauge. Also, a generalised transport equation
for the Geroch tensor is derived. Important differences between null
hypersurfaces in the bulk of the space-time and null infinity with vanishing
cosmological constant are reviewed, and their impact on the role of the news is
discussed.
| [
{
"created": "Sat, 20 Jul 2024 15:40:15 GMT",
"version": "v1"
}
] | 2024-07-23 | [
[
"Fernández-Álvarez",
"Francisco",
""
]
] | A geometric definition of news tensor on null hypersurfaces in four space-time dimensions is presented. When the conformal Einstein field equations hold, this news tensor yields the correct expression for the radiative components of the rescaled Weyl tensor at infinity with vanishing cosmological constant in arbitrary conformal gauge. Also, a generalised transport equation for the Geroch tensor is derived. Important differences between null hypersurfaces in the bulk of the space-time and null infinity with vanishing cosmological constant are reviewed, and their impact on the role of the news is discussed. |
1511.07379 | Rafael A. Porto | Chad R. Galley, Adam K. Leibovich, Rafael A. Porto and Andreas Ross | The tail effect in gravitational radiation-reaction: time non-locality
and renormalization group evolution | 24 pages. 3 figures. v2: Extended discussion on the nature of IR/UV
singularities. Published version | Phys. Rev. D 93, 124010 (2016) | 10.1103/PhysRevD.93.124010 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the effective field theory (EFT) framework to calculate the tail
effect in gravitational radiation reaction, which enters at 4PN order in the
dynamics of a binary system. The computation entails a subtle interplay between
the near (or potential) and far (or radiation) zones. In particular, we find
that the tail contribution to the effective action is non-local in time, and
features both a dissipative and a `conservative' term. The latter includes a
logarithmic ultraviolet (UV) divergence, which we show cancels against an
infrared (IR) singularity found in the (conservative) near zone. The origin of
this behavior in the long-distance EFT is due to the point-particle limit
-shrinking the binary to a point- which transforms a would-be infrared
singularity into an ultraviolet divergence. This is a common occurrence in an
EFT approach, which furthermore allows us to use renormalization group (RG)
techniques to resum the resulting logarithmic contributions. We then derive the
RG evolution for the binding potential and total mass/energy, and find
agreement with the results obtained imposing the conservation of the (pseudo)
stress-energy tensor in the radiation theory. While the calculation of the
leading tail contribution to the effective action involves only one diagram,
five are needed for the one-point function. This suggests logarithmic
corrections may be easier to incorporate in this fashion. We conclude with a
few remarks on the nature of these IR/UV singularities, the (lack of)
ambiguities recently discussed in the literature, and the completeness of the
analytic Post-Newtonian framework.
| [
{
"created": "Mon, 23 Nov 2015 19:40:28 GMT",
"version": "v1"
},
{
"created": "Sun, 15 May 2016 20:09:14 GMT",
"version": "v2"
}
] | 2016-06-15 | [
[
"Galley",
"Chad R.",
""
],
[
"Leibovich",
"Adam K.",
""
],
[
"Porto",
"Rafael A.",
""
],
[
"Ross",
"Andreas",
""
]
] | We use the effective field theory (EFT) framework to calculate the tail effect in gravitational radiation reaction, which enters at 4PN order in the dynamics of a binary system. The computation entails a subtle interplay between the near (or potential) and far (or radiation) zones. In particular, we find that the tail contribution to the effective action is non-local in time, and features both a dissipative and a `conservative' term. The latter includes a logarithmic ultraviolet (UV) divergence, which we show cancels against an infrared (IR) singularity found in the (conservative) near zone. The origin of this behavior in the long-distance EFT is due to the point-particle limit -shrinking the binary to a point- which transforms a would-be infrared singularity into an ultraviolet divergence. This is a common occurrence in an EFT approach, which furthermore allows us to use renormalization group (RG) techniques to resum the resulting logarithmic contributions. We then derive the RG evolution for the binding potential and total mass/energy, and find agreement with the results obtained imposing the conservation of the (pseudo) stress-energy tensor in the radiation theory. While the calculation of the leading tail contribution to the effective action involves only one diagram, five are needed for the one-point function. This suggests logarithmic corrections may be easier to incorporate in this fashion. We conclude with a few remarks on the nature of these IR/UV singularities, the (lack of) ambiguities recently discussed in the literature, and the completeness of the analytic Post-Newtonian framework. |
2103.15135 | Salvatore Capozziello | Salvatore Capozziello, Carlo Altucci, Francesco Bajardi, Andrea Basti,
Nicol\`o Beverini, Giorgio Carelli, Donatella Ciampini, Angela D. V. Di
Virgilio, Francesco Fuso, Umberto Giacomelli, Enrico Maccioni, Paolo Marsili,
Antonello Ortolan, Alberto Porzio, Andrea Simonelli, Giuseppe Terreni, and
Raffaele Velotta | Constraining Theories of Gravity by GINGER experiment | 15 pages, 3 figures, accepted for publication in EPJP | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The debate on gravity theories to extend or modify General Relativity is very
active today because of the issues related to ultra-violet and infra-red
behavior of Einstein's theory. In the first case, we have to address the
Quantum Gravity problem. In the latter, dark matter and dark energy, governing
the large scale structure and the cosmological evolution, seem to escape from
any final fundamental theory and detection. The state of art is that, up to
now, no final theory, capable of explaining gravitational interaction at any
scale, has been formulated. In this perspective, many research efforts are
devoted to test theories of gravity by space-based experiments. Here we propose
straightforward tests by the GINGER experiment, which, being Earth based,
requires little modeling of external perturbation, allowing a thorough analysis
of the systematics, crucial for experiments where sensitivity breakthrough is
required. Specifically, we want to show that it is possible to constrain
parameters of gravity theories, like scalar-tensor or Horava-Lifshitz gravity,
by considering their post-Newtonian limits matched with experimental data. In
particular, we use the Lense-Thirring measurements provided by GINGER to find
out relations among the parameters of theories and finally compare the results
with those provided by LARES and Gravity Probe-B satellites.
| [
{
"created": "Sun, 28 Mar 2021 13:44:35 GMT",
"version": "v1"
}
] | 2021-03-30 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Altucci",
"Carlo",
""
],
[
"Bajardi",
"Francesco",
""
],
[
"Basti",
"Andrea",
""
],
[
"Beverini",
"Nicolò",
""
],
[
"Carelli",
"Giorgio",
""
],
[
"Ciampini",
"Donatella",
... | The debate on gravity theories to extend or modify General Relativity is very active today because of the issues related to ultra-violet and infra-red behavior of Einstein's theory. In the first case, we have to address the Quantum Gravity problem. In the latter, dark matter and dark energy, governing the large scale structure and the cosmological evolution, seem to escape from any final fundamental theory and detection. The state of art is that, up to now, no final theory, capable of explaining gravitational interaction at any scale, has been formulated. In this perspective, many research efforts are devoted to test theories of gravity by space-based experiments. Here we propose straightforward tests by the GINGER experiment, which, being Earth based, requires little modeling of external perturbation, allowing a thorough analysis of the systematics, crucial for experiments where sensitivity breakthrough is required. Specifically, we want to show that it is possible to constrain parameters of gravity theories, like scalar-tensor or Horava-Lifshitz gravity, by considering their post-Newtonian limits matched with experimental data. In particular, we use the Lense-Thirring measurements provided by GINGER to find out relations among the parameters of theories and finally compare the results with those provided by LARES and Gravity Probe-B satellites. |
2404.14641 | Horng Sheng Chia | Horng Sheng Chia, Zihan Zhou, Mikhail M. Ivanov | Bring the Heat: Tidal Heating Constraints for Black Holes and Exotic
Compact Objects from the LIGO-Virgo-KAGRA Data | 30+18 pages, 7 figures | null | null | MIT-CTP/5710 | gr-qc astro-ph.CO astro-ph.HE hep-ph hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | We present the first constraints on tidal heating for the binary systems
detected in the LIGO-Virgo-KAGRA (LVK) gravitational wave data. Tidal heating,
also known as tidal dissipation, characterizes the viscous nature of an
astrophysical body and provides a channel for exchanging energy and angular
momentum with the tidal environment. Using the worldline effective field theory
formalism, we introduce a physically motivated and easily interpretable
parametrization of tidal heating valid for an arbitrary compact astrophysical
object. We then derive the imprints of the spin-independent and linear-in-spin
tidal heating effects of generic binary components on the waveform phases and
amplitudes of quasi-circular orbits. Notably, the mass-weighted
spin-independent tidal heating coefficient derived in this work,
$\mathcal{H}_0$, is the dissipative analog of the tidal Love number. We
constrain the tidal heating coefficients using the public LVK O1-O3 data. Our
parameter estimation study includes two separate analyses: the first treats the
catalog of binary events as binary black holes (BBH), while the second makes no
assumption about the nature of the binary constituents and can therefore be
interpreted as constraints for exotic compact objects. In the former case, we
combine the posterior distributions of the individual BBH events and obtain a
joint constraint of $-13 < \mathcal{H}_0 < 20$ at the $90\%$ credible interval
for the BBH population. This translates into a bound on the fraction of the
emitted gravitational wave energy lost due to tidal heating (or gained due to
radiation enhancement effects) at $|\Delta E_H/\Delta E_{\infty}|\lesssim
3\cdot 10^{-3}$. Our work provides the first robust framework for deriving and
measuring tidal heating effects in merging binary systems, demonstrating its
potential as a powerful probe of the nature of binary constituents and tests of
new physics.
| [
{
"created": "Tue, 23 Apr 2024 00:34:38 GMT",
"version": "v1"
}
] | 2024-04-24 | [
[
"Chia",
"Horng Sheng",
""
],
[
"Zhou",
"Zihan",
""
],
[
"Ivanov",
"Mikhail M.",
""
]
] | We present the first constraints on tidal heating for the binary systems detected in the LIGO-Virgo-KAGRA (LVK) gravitational wave data. Tidal heating, also known as tidal dissipation, characterizes the viscous nature of an astrophysical body and provides a channel for exchanging energy and angular momentum with the tidal environment. Using the worldline effective field theory formalism, we introduce a physically motivated and easily interpretable parametrization of tidal heating valid for an arbitrary compact astrophysical object. We then derive the imprints of the spin-independent and linear-in-spin tidal heating effects of generic binary components on the waveform phases and amplitudes of quasi-circular orbits. Notably, the mass-weighted spin-independent tidal heating coefficient derived in this work, $\mathcal{H}_0$, is the dissipative analog of the tidal Love number. We constrain the tidal heating coefficients using the public LVK O1-O3 data. Our parameter estimation study includes two separate analyses: the first treats the catalog of binary events as binary black holes (BBH), while the second makes no assumption about the nature of the binary constituents and can therefore be interpreted as constraints for exotic compact objects. In the former case, we combine the posterior distributions of the individual BBH events and obtain a joint constraint of $-13 < \mathcal{H}_0 < 20$ at the $90\%$ credible interval for the BBH population. This translates into a bound on the fraction of the emitted gravitational wave energy lost due to tidal heating (or gained due to radiation enhancement effects) at $|\Delta E_H/\Delta E_{\infty}|\lesssim 3\cdot 10^{-3}$. Our work provides the first robust framework for deriving and measuring tidal heating effects in merging binary systems, demonstrating its potential as a powerful probe of the nature of binary constituents and tests of new physics. |
2106.08070 | Cosimo Bambi | Kimet Jusufi, Saurabh Kumar, Mustapha Azreg-A\"inou, Mubasher Jamil,
Qiang Wu, Cosimo Bambi | Constraining Wormhole Geometries using the Orbit of S2 Star and the
Event Horizon Telescope | 14 pages, 7 figures. v2: refereed version | Eur. Phys. J. C (2022) 82:633 | 10.1140/epjc/s10052-022-10603-7 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the possibility of having a wormhole (WH) as a
candidate for the Sgr A$^\star$ central object and test this idea by
constraining their geometry using the motion of S2 star and the reconstructed
shadow images. In particular, we consider three WH models, including WHs in
Einstein theory, brane-world gravity, and Einstein-Dirac-Maxwell theory. To
this end, we have constrained the WH throat using the motion of S2 star and
shown that the flare out condition is satisfied. We also consider the accretion
of infalling gas model and study the accretion rate and the intensity of the
electromagnetic radiation as well as the shadow images.
| [
{
"created": "Tue, 15 Jun 2021 11:54:41 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Jul 2022 06:24:28 GMT",
"version": "v2"
}
] | 2022-07-26 | [
[
"Jusufi",
"Kimet",
""
],
[
"Kumar",
"Saurabh",
""
],
[
"Azreg-Aïnou",
"Mustapha",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Wu",
"Qiang",
""
],
[
"Bambi",
"Cosimo",
""
]
] | In this paper we study the possibility of having a wormhole (WH) as a candidate for the Sgr A$^\star$ central object and test this idea by constraining their geometry using the motion of S2 star and the reconstructed shadow images. In particular, we consider three WH models, including WHs in Einstein theory, brane-world gravity, and Einstein-Dirac-Maxwell theory. To this end, we have constrained the WH throat using the motion of S2 star and shown that the flare out condition is satisfied. We also consider the accretion of infalling gas model and study the accretion rate and the intensity of the electromagnetic radiation as well as the shadow images. |
gr-qc/0501025 | Noriko Shiiki | Noriko Shiiki and Nobuyuki Sawado | Black Holes with Skyrme Hair | 40 pages, 14 figures; Invited paper for "Black Holes: Research and
Development", Nova Science Publishers, Inc. NY | null | null | null | gr-qc | null | This paper is intended to give a review of the recent developments on black
holes with Skyrme hair. The Einstein-Skyrme system is known to possess black
hole solutions with Skyrme hair. The spherically symmetric black hole skyrmion
with B=1 was the first discovered counter example of the no-hair conjecture for
black holes. Recently we found the B=2 axially symmetric black hole skyrmion.
In this system, the black hole at the center of the skyrmion absorbs the baryon
number partially, leaving fractional charge outside the horizon. Therefore the
baryon number is no longer conserved. We examine the B=1, 2 black hole
solutions in detail in this paper. The model has a natural extension to the
gauged version which can describe monopole black hole skyrmions. Callan and
Witten discussed the monopole catalysis of proton decay within the Skyrme
model. We apply the idea to the Einstein-Maxwell-Skyrme system and obtain
monopole black hole skyrmions. Remarkably there exist multi-black hole skyrmion
solutions in which the gravitational, electromagnetic, and strong forces
between the monopoles are all in balance. The solutions turn out to be stable
under spherically symmetric linear perturbations.
| [
{
"created": "Sun, 9 Jan 2005 06:47:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Shiiki",
"Noriko",
""
],
[
"Sawado",
"Nobuyuki",
""
]
] | This paper is intended to give a review of the recent developments on black holes with Skyrme hair. The Einstein-Skyrme system is known to possess black hole solutions with Skyrme hair. The spherically symmetric black hole skyrmion with B=1 was the first discovered counter example of the no-hair conjecture for black holes. Recently we found the B=2 axially symmetric black hole skyrmion. In this system, the black hole at the center of the skyrmion absorbs the baryon number partially, leaving fractional charge outside the horizon. Therefore the baryon number is no longer conserved. We examine the B=1, 2 black hole solutions in detail in this paper. The model has a natural extension to the gauged version which can describe monopole black hole skyrmions. Callan and Witten discussed the monopole catalysis of proton decay within the Skyrme model. We apply the idea to the Einstein-Maxwell-Skyrme system and obtain monopole black hole skyrmions. Remarkably there exist multi-black hole skyrmion solutions in which the gravitational, electromagnetic, and strong forces between the monopoles are all in balance. The solutions turn out to be stable under spherically symmetric linear perturbations. |
2207.06034 | Subhadip Sau | Indrani Banerjee, Subhadip Sau and Soumitra SenGupta | Do shadows of Sgr A* and M87* indicate black holes with a magnetic
monopole charge? | 24 pages, 8 figures | null | null | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | We study the prospect of Bardeen black holes in explaining the observed
shadow of Sgr A* and M87*. Bardeen black holes are regular black holes endowed
with a magnetic monopole charge that arise in Einstein gravity coupled to
non-linear electrodynamics. These black holes are interesting as they can evade
the r = 0 curvature singularity arising in general relativity. It is therefore
worthwhile to look for signatures of Bardeen black holes in astrophysical
observations. With two successive release of black hole images by the Event
Horizon Telescope (EHT) collaboration, the scope to test the nature of strong
gravity has substantially increased. We compare the theoretically computed
shadow observables with the observed image of Sgr A* and M87*. Our analysis
reveals that while the observed angular diameter of M87* favors the Kerr
scenario, the shadow of Sgr A* can be better explained by the Bardeen
background. This indicates that although rare, certain black holes exhibit a
preference towards regular black holes like the Bardeen spacetime.
| [
{
"created": "Wed, 13 Jul 2022 08:30:41 GMT",
"version": "v1"
}
] | 2022-07-14 | [
[
"Banerjee",
"Indrani",
""
],
[
"Sau",
"Subhadip",
""
],
[
"SenGupta",
"Soumitra",
""
]
] | We study the prospect of Bardeen black holes in explaining the observed shadow of Sgr A* and M87*. Bardeen black holes are regular black holes endowed with a magnetic monopole charge that arise in Einstein gravity coupled to non-linear electrodynamics. These black holes are interesting as they can evade the r = 0 curvature singularity arising in general relativity. It is therefore worthwhile to look for signatures of Bardeen black holes in astrophysical observations. With two successive release of black hole images by the Event Horizon Telescope (EHT) collaboration, the scope to test the nature of strong gravity has substantially increased. We compare the theoretically computed shadow observables with the observed image of Sgr A* and M87*. Our analysis reveals that while the observed angular diameter of M87* favors the Kerr scenario, the shadow of Sgr A* can be better explained by the Bardeen background. This indicates that although rare, certain black holes exhibit a preference towards regular black holes like the Bardeen spacetime. |
1403.6316 | Matej Pavsic | Matej Pav\v{s}i\v{c} | On the quantisation of gravity by embedding spacetime in a higher
dimensional space | 25 pages, 3 figures | Classical and Quantum Gravity 2 (1985) 869--889 | 10.1088/0264-9381/2/6/012 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Certain difficulties of quantum gravity can be avoided if we embed the
spacetime $V_4$ into a higher dimensional space $V_N$; then our spacetime is
merely a 4-surface in $V_N$.What remains is conceptually not so difficult: just
to quantise this 4-surface. Our formal procedure generalises our version of
Stueckelberg's proper time method of worldline quantisation. We write the
equations of $V_4$ in the covariant canonical form starting from a model
Lagrangian which contains the classical Einstein gravity as a particular case.
Then we perform quantisation in the Schr\"odinger picture by using the concepts
of a phase functional and wave functional. As a result we obtain the
uncertainty relations which imply that an observer is `aware' either of a
particular spacetime surface and has no information about other spacetime
surfaces (which represent alternative histories); or conversely, he loses
information about a particular $V_4$ whilst he obtains some information about
other spacetimes (and histories). Equivalently, one cannot measure to an
arbitrary precision both the metric on $V_4$ and matter distribution on various
alternative spacetime surfaces. We show how this special case in the
`coordinate' representations can be generalised to an arbitrary vector in an
abstract Hilbert space.
| [
{
"created": "Tue, 25 Mar 2014 11:51:40 GMT",
"version": "v1"
}
] | 2014-03-26 | [
[
"Pavšič",
"Matej",
""
]
] | Certain difficulties of quantum gravity can be avoided if we embed the spacetime $V_4$ into a higher dimensional space $V_N$; then our spacetime is merely a 4-surface in $V_N$.What remains is conceptually not so difficult: just to quantise this 4-surface. Our formal procedure generalises our version of Stueckelberg's proper time method of worldline quantisation. We write the equations of $V_4$ in the covariant canonical form starting from a model Lagrangian which contains the classical Einstein gravity as a particular case. Then we perform quantisation in the Schr\"odinger picture by using the concepts of a phase functional and wave functional. As a result we obtain the uncertainty relations which imply that an observer is `aware' either of a particular spacetime surface and has no information about other spacetime surfaces (which represent alternative histories); or conversely, he loses information about a particular $V_4$ whilst he obtains some information about other spacetimes (and histories). Equivalently, one cannot measure to an arbitrary precision both the metric on $V_4$ and matter distribution on various alternative spacetime surfaces. We show how this special case in the `coordinate' representations can be generalised to an arbitrary vector in an abstract Hilbert space. |
2404.02479 | Georgios Antoniou | Georgios Antoniou, Caio F. B. Macedo, Andrea Maselli, Thomas P.
Sotiriou | Axial perturbations of hairy black holes in generalised scalar-tensor
theories | 12 pages, 7 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave observations can test the validity of General Relativity
(GR) in the strong field regime. Certain classes of scalar-tensor theories
indeed predict that compact objects can exhibit significant deviations from
their GR counterparts. Here we explore the quasinormal modes of axial
perturbations in spherically symmetric black holes in three such classes: (i)
dilatonic black holes with an additional scalar-Ricci coupling (EdRGB), (ii)
spontaneously scalarized black holes (EsRGB) with a quadratic coupling to the
Gauss-Bonnet invariant and the Ricci scalar, (iii) spontaneously scalarized
black holes with a quadratic and a quartic coupling to the Gauss-Bonnet
invariant.
| [
{
"created": "Wed, 3 Apr 2024 05:37:52 GMT",
"version": "v1"
}
] | 2024-04-04 | [
[
"Antoniou",
"Georgios",
""
],
[
"Macedo",
"Caio F. B.",
""
],
[
"Maselli",
"Andrea",
""
],
[
"Sotiriou",
"Thomas P.",
""
]
] | Gravitational wave observations can test the validity of General Relativity (GR) in the strong field regime. Certain classes of scalar-tensor theories indeed predict that compact objects can exhibit significant deviations from their GR counterparts. Here we explore the quasinormal modes of axial perturbations in spherically symmetric black holes in three such classes: (i) dilatonic black holes with an additional scalar-Ricci coupling (EdRGB), (ii) spontaneously scalarized black holes (EsRGB) with a quadratic coupling to the Gauss-Bonnet invariant and the Ricci scalar, (iii) spontaneously scalarized black holes with a quadratic and a quartic coupling to the Gauss-Bonnet invariant. |
gr-qc/0511015 | G. Dautcourt | G.Dautcourt, M. Abdel-Megied | Revisiting the Light Cone of the Goedel Universe | 23 pages, 3 figures, iopart | Class.Quant.Grav. 23 (2006) 1269-1288 | 10.1088/0264-9381/23/4/013 | null | gr-qc | null | The structure of a light cone in the Goedel universe is studied. We derive
the intrinsic cone metric, calculate the rotation coefficients of the ray
congruence forming the cone, determine local differential invariants up to
second order, describe the crossover (keel) singularities and give a first
discussion of its focal points. Contrary to many rotation coefficients, some
inner differential invariants attain simple finite standard values at focal
singularities.
| [
{
"created": "Thu, 3 Nov 2005 12:39:52 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Dautcourt",
"G.",
""
],
[
"Abdel-Megied",
"M.",
""
]
] | The structure of a light cone in the Goedel universe is studied. We derive the intrinsic cone metric, calculate the rotation coefficients of the ray congruence forming the cone, determine local differential invariants up to second order, describe the crossover (keel) singularities and give a first discussion of its focal points. Contrary to many rotation coefficients, some inner differential invariants attain simple finite standard values at focal singularities. |
0802.2381 | Vasily Borodikhin | V.N. Borodikhin | Vector Theory of Gravity | 9 pages | Grav.Cosmol.17:161-165,2011 | 10.1134/S0202289311020071 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We proposed a gravitation theory based on an analogy with electrodynamics on
the basis of a vector field. For the first time, to calculate the basic
gravitational effects in the framework of a vector theory of gravity, we use a
Lagrangian written with gravitational radiation neglected and generalized to
the case of ultra-relativistic speeds. This allows us to accurately calculate
the values of all three major gravity experiments: the values of the perihelion
shift of Mercury, the light deflection angle in the gravity field of the Sun
and the value of radar echo delay. The calculated values coincide with the
observed ones. It is shown that, in this theory, there exists a model of an
expanding Universe.
| [
{
"created": "Sun, 17 Feb 2008 13:19:42 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Apr 2011 06:44:30 GMT",
"version": "v2"
}
] | 2011-04-20 | [
[
"Borodikhin",
"V. N.",
""
]
] | We proposed a gravitation theory based on an analogy with electrodynamics on the basis of a vector field. For the first time, to calculate the basic gravitational effects in the framework of a vector theory of gravity, we use a Lagrangian written with gravitational radiation neglected and generalized to the case of ultra-relativistic speeds. This allows us to accurately calculate the values of all three major gravity experiments: the values of the perihelion shift of Mercury, the light deflection angle in the gravity field of the Sun and the value of radar echo delay. The calculated values coincide with the observed ones. It is shown that, in this theory, there exists a model of an expanding Universe. |
0908.2638 | Leon Heller | Leon Heller | On the Penrose process for rotating black holes | 10 pages, 3 figures | null | null | LA-UR 09-05070 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Penrose described a process that, in principle, could extract energy and
angular momentum from a rotating black hole. Here we examine two procedures
that were claimed to be capable of implementing the Penrose idea; both make use
of a particle moving at the horizon. In one, the particle is swallowed, and in
the other the particle and black hole gradually exchange energy and angular
momentum. We show that if the particle has negative energy and negative angular
momentum but no radial momentum both procedures violate the requirement that
the area of a black hole not decrease. For the gradual exchange method,
however, it appears that the Penrose process could proceed if the particle has
positive energy and angular momentum, but nevertheless removes energy from the
black hole. It does not, however, lead to a Schwarzschild black hole. For an
extreme Kerr black hole it's mass decreases by at most 9.7%, well short of the
theoretical limit for a reversible process of 1-1/sqrt{2} =29%.
| [
{
"created": "Tue, 18 Aug 2009 20:46:51 GMT",
"version": "v1"
}
] | 2009-08-20 | [
[
"Heller",
"Leon",
""
]
] | Penrose described a process that, in principle, could extract energy and angular momentum from a rotating black hole. Here we examine two procedures that were claimed to be capable of implementing the Penrose idea; both make use of a particle moving at the horizon. In one, the particle is swallowed, and in the other the particle and black hole gradually exchange energy and angular momentum. We show that if the particle has negative energy and negative angular momentum but no radial momentum both procedures violate the requirement that the area of a black hole not decrease. For the gradual exchange method, however, it appears that the Penrose process could proceed if the particle has positive energy and angular momentum, but nevertheless removes energy from the black hole. It does not, however, lead to a Schwarzschild black hole. For an extreme Kerr black hole it's mass decreases by at most 9.7%, well short of the theoretical limit for a reversible process of 1-1/sqrt{2} =29%. |
gr-qc/0502086 | Parampreet Singh | Parampreet Singh | Effective State Metamorphosis in Semi-Classical Loop Quantum Cosmology | Revised version; includes expanded discussion of natural
trans-Planckian modifications to frequency dispersion and robustness to
quantization ambiguities. To appear in Class. Quant. Grav | Class.Quant.Grav. 22 (2005) 4203-4216 | 10.1088/0264-9381/22/20/003 | IGPG-05/2-2 | gr-qc astro-ph hep-th | null | Modification to the behavior of geometrical density at short scales is a key
result of loop quantum cosmology, responsible for an interesting phenomenology
in the very early universe. We demonstrate the way matter with arbitrary scale
factor dependence in Hamiltonian incorporates this change in its effective
dynamics in the loop modified phase. For generic matter, the equation of state
starts varying near a critical scale factor, becomes negative below it and
violates strong energy condition. This opens a new avenue to generalize various
phenomenological applications in loop quantum cosmology. We show that different
ways to define energy density may yield radically different results, especially
for the case corresponding to classical dust. We also discuss implications for
frequency dispersion induced by modification to geometric density at small
scales.
| [
{
"created": "Mon, 21 Feb 2005 17:59:36 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Aug 2005 14:08:26 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Singh",
"Parampreet",
""
]
] | Modification to the behavior of geometrical density at short scales is a key result of loop quantum cosmology, responsible for an interesting phenomenology in the very early universe. We demonstrate the way matter with arbitrary scale factor dependence in Hamiltonian incorporates this change in its effective dynamics in the loop modified phase. For generic matter, the equation of state starts varying near a critical scale factor, becomes negative below it and violates strong energy condition. This opens a new avenue to generalize various phenomenological applications in loop quantum cosmology. We show that different ways to define energy density may yield radically different results, especially for the case corresponding to classical dust. We also discuss implications for frequency dispersion induced by modification to geometric density at small scales. |
1112.6211 | Alfredo Lopez Ortega | A. Lopez-Ortega | Entropy spectra of single horizon black holes in two dimensions | 13 pages | null | 10.1142/S0218271811020524 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hod conjecture proposes that the asymptotic quasinormal frequencies
determine the entropy quantum of a black hole. Considering the Maggiore
modification of this conjecture we calculate the entropy spectra of general,
single horizon, asymptotically flat black holes in two-dimensional dilaton
gravity. We also compute the entropy quanta of the two-dimensional Witten and
AdS(2) black holes. Using the results for the entropy quanta of these
two-dimensional black holes we discuss whether the produced values are generic.
Finally we extend the results on the entropy spectra of other black holes.
| [
{
"created": "Thu, 29 Dec 2011 01:12:00 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Lopez-Ortega",
"A.",
""
]
] | The Hod conjecture proposes that the asymptotic quasinormal frequencies determine the entropy quantum of a black hole. Considering the Maggiore modification of this conjecture we calculate the entropy spectra of general, single horizon, asymptotically flat black holes in two-dimensional dilaton gravity. We also compute the entropy quanta of the two-dimensional Witten and AdS(2) black holes. Using the results for the entropy quanta of these two-dimensional black holes we discuss whether the produced values are generic. Finally we extend the results on the entropy spectra of other black holes. |
0904.2559 | Rituparno Goswami | Naureen Goheer, Rituparno Goswami, Peter K. S. Dunsby, Kishore Ananda | On the co-existence of matter dominated and accelerating solutions in
f(G)-gravity | 5 pages, revtex4, letter | Phys.Rev.D79:121301,2009 | 10.1103/PhysRevD.79.121301 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Working within the theory of modified Gauss-Bonnet gravity, we show that
FLRW--like power--law solutions only exist for a very special class of
f(G)theories. Furthermore, we point out that any transition from decelerated to
accelerated expansion must pass through G=0, and no function f(G) that is
differentiable at this point can admit both a decelerating power--law solution
and any accelerating solution. This strongly constrains the cosmological
viability of f(G)-gravity, since it may not be possible to obtain an expansion
history of the universe which is compatible with observations. We explain why
the same issue does not occur in f(R)-gravity and discuss possible caveats for
the case of f(G)-gravity.
| [
{
"created": "Thu, 16 Apr 2009 18:50:29 GMT",
"version": "v1"
}
] | 2009-06-30 | [
[
"Goheer",
"Naureen",
""
],
[
"Goswami",
"Rituparno",
""
],
[
"Dunsby",
"Peter K. S.",
""
],
[
"Ananda",
"Kishore",
""
]
] | Working within the theory of modified Gauss-Bonnet gravity, we show that FLRW--like power--law solutions only exist for a very special class of f(G)theories. Furthermore, we point out that any transition from decelerated to accelerated expansion must pass through G=0, and no function f(G) that is differentiable at this point can admit both a decelerating power--law solution and any accelerating solution. This strongly constrains the cosmological viability of f(G)-gravity, since it may not be possible to obtain an expansion history of the universe which is compatible with observations. We explain why the same issue does not occur in f(R)-gravity and discuss possible caveats for the case of f(G)-gravity. |
1809.10586 | Stefano Lucat | A.Barnaveli, S.Lucat, T.Prokopec | Inflation as a spontaneous symmetry breaking of Weyl symmetry | 27 pages, 9 figures | null | 10.1088/1475-7516/2019/01/022 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study a novel realization of inflation, based on Weyl
invariant gravity with torsion. We show that requiring the classical action for
the scalar field to be Weyl invariant introduces a dilaton which induces a non
trivial modification of the field space geometry of the scalar sector, which
allows for inflationary phase that begins at the conformal point of the
inflaton $\psi$, i.e. $\langle\psi\rangle=0$. Since the model is Weyl
invariant, the inflaton condensation models a process of spontaneous Weyl
symmetry breaking. For a wide range of parameters the spectral observables of
the model are in good agreement with the CMB measurements, such that the scalar
spectral index and the tensor-to-scalar ratio approximately agree with those of
Starobinsky's inflation, i.e. $n_s\simeq 0.96-0.97$ and $r \approx 3\times
10^{-3}$. The simplest version of our model contains two scalar degrees of
freedom, one of them being an exactly flat direction. If that degree is excited
early on in inflation and if inflation lasts for about 60 e-foldings, we find
that the Unverse undergoes a short period of kination that predates inflation.
Such a period strongly suppresses the amplitude of large scale CMB temperature
fluctuations providing thus an elegant explanation for the lack of power in the
lowest CMB multipoles.
| [
{
"created": "Thu, 27 Sep 2018 15:47:03 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Oct 2018 09:17:56 GMT",
"version": "v2"
}
] | 2019-01-16 | [
[
"Barnaveli",
"A.",
""
],
[
"Lucat",
"S.",
""
],
[
"Prokopec",
"T.",
""
]
] | In this paper we study a novel realization of inflation, based on Weyl invariant gravity with torsion. We show that requiring the classical action for the scalar field to be Weyl invariant introduces a dilaton which induces a non trivial modification of the field space geometry of the scalar sector, which allows for inflationary phase that begins at the conformal point of the inflaton $\psi$, i.e. $\langle\psi\rangle=0$. Since the model is Weyl invariant, the inflaton condensation models a process of spontaneous Weyl symmetry breaking. For a wide range of parameters the spectral observables of the model are in good agreement with the CMB measurements, such that the scalar spectral index and the tensor-to-scalar ratio approximately agree with those of Starobinsky's inflation, i.e. $n_s\simeq 0.96-0.97$ and $r \approx 3\times 10^{-3}$. The simplest version of our model contains two scalar degrees of freedom, one of them being an exactly flat direction. If that degree is excited early on in inflation and if inflation lasts for about 60 e-foldings, we find that the Unverse undergoes a short period of kination that predates inflation. Such a period strongly suppresses the amplitude of large scale CMB temperature fluctuations providing thus an elegant explanation for the lack of power in the lowest CMB multipoles. |
gr-qc/0204029 | Lixiang | Li Xiang | Black hole entropy without brick walls | 7 pages | Phys.Lett. B540 (2002) 9-13 | 10.1016/S0370-2693(02)02123-8 | null | gr-qc hep-th | null | The properties of the thermal radiation are discussed by using the new
equation of state density motivated by the generalized uncertainty relation in
the quantum gravity. There is no burst at the last stage of the emission of a
Schwarzshild black hole. When the new equation of state density is utilized to
investigate the entropy of a scalar field outside the horizon of a static black
hole, the divergence appearing in the brick wall model is removed, without any
cutoff. The entropy proportional to the horizon area is derived from the
contribution of the vicinity of the horizon.
| [
{
"created": "Sat, 6 Apr 2002 06:56:36 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Aug 2002 00:47:37 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Xiang",
"Li",
""
]
] | The properties of the thermal radiation are discussed by using the new equation of state density motivated by the generalized uncertainty relation in the quantum gravity. There is no burst at the last stage of the emission of a Schwarzshild black hole. When the new equation of state density is utilized to investigate the entropy of a scalar field outside the horizon of a static black hole, the divergence appearing in the brick wall model is removed, without any cutoff. The entropy proportional to the horizon area is derived from the contribution of the vicinity of the horizon. |
1406.2089 | Titus K Mathew | Titus K Mathew, Aswathy M B and Manoj M | Cosmology and thermodynamics of FRW universe with bulk viscous stiff
fluid | null | null | 10.1140/epjc/s10052-014-3188-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a cosmological model dominated by stiff fluid with a constant
bulk viscosity. We classify all the possible cases of the universe predicted by
the model and analyzing the scale factor, density as well as the curvature
scalar. We find that when the dimensionless constant bulk viscous parameter is
in the range $0 < \bar\zeta <6$ the model began with a Big Bang, and make a
transition form the decelerating expansion epoch to an accelerating epoch, then
tends to the de Sitter phase as $ t\to \infty$. The transition into the
accelerating epoch would be in the recent past, when $4<\bar\zeta<6.$ For
$\bar\zeta>6$ the model doesn't have a Big Bang and suffered an increase in the
fluid density and scalar curvature as the universe expands, which are
eventually saturates as the scale factor $a \to \infty$ in the future. We have
analyzed the model with statefinder diagnostics and find that the model is
different from $\Lambda$CDM model but approaches $\Lambda$CDM point as $a \to
\infty.$ We have also analyzed the status of the generalized second law of
thermodynamics with apparent horizon as the boundary of the universe and found
that the law is generally satisfied when $0 \leq \bar\zeta <6$ and for
$\bar\zeta >6$ the law is satisfied when the scale factor is larger than a
minimum value.
| [
{
"created": "Mon, 9 Jun 2014 06:54:02 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Mathew",
"Titus K",
""
],
[
"B",
"Aswathy M",
""
],
[
"M",
"Manoj",
""
]
] | We consider a cosmological model dominated by stiff fluid with a constant bulk viscosity. We classify all the possible cases of the universe predicted by the model and analyzing the scale factor, density as well as the curvature scalar. We find that when the dimensionless constant bulk viscous parameter is in the range $0 < \bar\zeta <6$ the model began with a Big Bang, and make a transition form the decelerating expansion epoch to an accelerating epoch, then tends to the de Sitter phase as $ t\to \infty$. The transition into the accelerating epoch would be in the recent past, when $4<\bar\zeta<6.$ For $\bar\zeta>6$ the model doesn't have a Big Bang and suffered an increase in the fluid density and scalar curvature as the universe expands, which are eventually saturates as the scale factor $a \to \infty$ in the future. We have analyzed the model with statefinder diagnostics and find that the model is different from $\Lambda$CDM model but approaches $\Lambda$CDM point as $a \to \infty.$ We have also analyzed the status of the generalized second law of thermodynamics with apparent horizon as the boundary of the universe and found that the law is generally satisfied when $0 \leq \bar\zeta <6$ and for $\bar\zeta >6$ the law is satisfied when the scale factor is larger than a minimum value. |
2007.04065 | Diego Rubiera-Garcia | Gonzalo J. Olmo, Diego Rubiera-Garcia | Junction conditions in Palatini $f(R)$ gravity | 7 pages; some additions in conclusions and references' list. Version
accepted for publication on Class. Quant. Grav | null | 10.1088/1361-6382/abb924 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We work out the junction conditions for $f(R)$ gravity formulated in
metric-affine (Palatini) spaces using a tensor distributional approach. These
conditions are needed for building consistent models of gravitating bodies with
an interior and exterior regions matched at some hypersurface. Some of these
conditions depart from the standard Darmois-Israel ones of General Relativity
and from their metric $f(R)$ counterparts. In particular, we find that the
trace of the stress-energy momentum tensor in the bulk must be continuous
across the matching hypersurface, though its normal derivative need not to. We
illustrate the relevance of these conditions by considering the properties of
stellar surfaces in polytropic models, showing that the range of equations of
state with potentially pathological effects is shifted beyond the domain of
physical interest. This confirms, in particular, that neutron stars and white
dwarfs can be safely modelled within the Palatini $f(R)$ framework.
| [
{
"created": "Wed, 8 Jul 2020 12:31:49 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Sep 2020 08:49:50 GMT",
"version": "v2"
}
] | 2020-10-28 | [
[
"Olmo",
"Gonzalo J.",
""
],
[
"Rubiera-Garcia",
"Diego",
""
]
] | We work out the junction conditions for $f(R)$ gravity formulated in metric-affine (Palatini) spaces using a tensor distributional approach. These conditions are needed for building consistent models of gravitating bodies with an interior and exterior regions matched at some hypersurface. Some of these conditions depart from the standard Darmois-Israel ones of General Relativity and from their metric $f(R)$ counterparts. In particular, we find that the trace of the stress-energy momentum tensor in the bulk must be continuous across the matching hypersurface, though its normal derivative need not to. We illustrate the relevance of these conditions by considering the properties of stellar surfaces in polytropic models, showing that the range of equations of state with potentially pathological effects is shifted beyond the domain of physical interest. This confirms, in particular, that neutron stars and white dwarfs can be safely modelled within the Palatini $f(R)$ framework. |
0812.1889 | Roy Maartens | Roy Maartens, Kevin Vandersloot | Magnetic Bianchi I Universe in Loop Quantum Cosmology | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the dynamical consequences of homogeneous cosmological magnetic
fields in the framework of loop quantum cosmology. We show that a big-bounce
occurs in a collapsing magnetized Bianchi I universe, thus extending the known
cases of singularity-avoidance. Previous work has shown that perfect fluid
Bianchi I universes in loop quantum cosmology avoid the singularity via a
bounce. The fluid has zero anisotropic stress, and the shear anisotropy in this
case is conserved through the bounce. By contrast, the magnetic field has
nonzero anisotropic stress, and shear anisotropy is not conserved through the
bounce. After the bounce, the universe enters a classical phase. The addition
of a dust fluid does not change these results qualitatively.
| [
{
"created": "Wed, 10 Dec 2008 11:00:04 GMT",
"version": "v1"
}
] | 2008-12-11 | [
[
"Maartens",
"Roy",
""
],
[
"Vandersloot",
"Kevin",
""
]
] | We examine the dynamical consequences of homogeneous cosmological magnetic fields in the framework of loop quantum cosmology. We show that a big-bounce occurs in a collapsing magnetized Bianchi I universe, thus extending the known cases of singularity-avoidance. Previous work has shown that perfect fluid Bianchi I universes in loop quantum cosmology avoid the singularity via a bounce. The fluid has zero anisotropic stress, and the shear anisotropy in this case is conserved through the bounce. By contrast, the magnetic field has nonzero anisotropic stress, and shear anisotropy is not conserved through the bounce. After the bounce, the universe enters a classical phase. The addition of a dust fluid does not change these results qualitatively. |
gr-qc/0602111 | Waldyr A. Rodrigues Jr. | Waldyr A. Rodrigues Jr | A Comment on Emergent Gravity | 21 pages. In this version some misprints have been corrected, two new
references have been added and some (eventual) offensive observations have
been deleted | null | null | null | gr-qc | null | This paper is a set of notes that we wrote concerning the first version of
Emergent Gravity [gr-qc/0602022]. It is our version of an exercise that we
proposed to some of our students. The idea was to find mathematical errors and
inconsistencies on some recent articles published in scientific journals and in
the arXiv, and we did.
| [
{
"created": "Mon, 27 Feb 2006 12:17:17 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Mar 2006 10:57:06 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Rodrigues",
"Waldyr A.",
"Jr"
]
] | This paper is a set of notes that we wrote concerning the first version of Emergent Gravity [gr-qc/0602022]. It is our version of an exercise that we proposed to some of our students. The idea was to find mathematical errors and inconsistencies on some recent articles published in scientific journals and in the arXiv, and we did. |
2308.08639 | Yu-Meng Xu | Yumeng Xu, Shubhanshu Tiwari, Marco Drago | PycWB: A User-friendly, Modular, and Python-based Framework for
Gravitational Wave Unmodelled Search | 16 pages, 4 figures | SoftwareX Volume 26, May 2024, 101639 | 10.1016/j.softx.2024.101639 | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | Unmodelled searches and reconstruction is a critical aspect of gravitational
wave data analysis, requiring sophisticated software tools for robust data
analysis. This paper introduces PycWB, a user-friendly and modular Python-based
framework developed to enhance such analyses based on the widely used
unmodelled search and reconstruction algorithm Coherent Wave Burst (cWB). The
main features include a transition from C++ scripts to YAML format for
user-defined parameters, improved modularity, and a shift from complex
class-encapsulated algorithms to compartmentalized modules. The pycWB
architecture facilitates efficient dependency management, better
error-checking, and the use of parallel computation for performance
enhancement. Moreover, the use of Python harnesses its rich library of
packages, facilitating post-production analysis and visualization. The PycWB
framework is designed to improve the user experience and accelerate the
development of unmodelled gravitational wave analysis.
| [
{
"created": "Wed, 16 Aug 2023 19:20:26 GMT",
"version": "v1"
}
] | 2024-03-05 | [
[
"Xu",
"Yumeng",
""
],
[
"Tiwari",
"Shubhanshu",
""
],
[
"Drago",
"Marco",
""
]
] | Unmodelled searches and reconstruction is a critical aspect of gravitational wave data analysis, requiring sophisticated software tools for robust data analysis. This paper introduces PycWB, a user-friendly and modular Python-based framework developed to enhance such analyses based on the widely used unmodelled search and reconstruction algorithm Coherent Wave Burst (cWB). The main features include a transition from C++ scripts to YAML format for user-defined parameters, improved modularity, and a shift from complex class-encapsulated algorithms to compartmentalized modules. The pycWB architecture facilitates efficient dependency management, better error-checking, and the use of parallel computation for performance enhancement. Moreover, the use of Python harnesses its rich library of packages, facilitating post-production analysis and visualization. The PycWB framework is designed to improve the user experience and accelerate the development of unmodelled gravitational wave analysis. |
2402.17814 | Marcos Vinicius De Sousa Silva | Manuel E. Rodrigues, Marcos V. de S. Silva | Comment on "Source of black bounces in Rastall gravity'' | Comment on arXiv:2311.07637. V2: Some typos corrected. Version
published in JCAP | JCAP05(2024)012 | 10.1088/1475-7516/2024/05/012 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In Atazadeh and Hadi (JCAP \textbf{01}, 067 (2024)), the authors proposed
that black bounce solutions, such as the Simpson-Visser and the Bardeen-type
spacetimes, can be obtained from Rastall gravity. To achieve these spacetimes,
the authors consider the presence of a phantom scalar field with nonlinear
electrodynamics. However, in this comment, we obtained different
electromagnetic Lagrangians from the original work. The most problematic issue
is not the incorrect expression of the electromagnetic Lagrangian itself. We
show that the method obtains electromagnetic functions that are inconsistent.
To obtain the black bounce spacetimes as solutions of Rastall gravity, it is
necessary to consider an isotropic fluid, combined with the nonlinear
electrodynamics and the phantom scalar field.
| [
{
"created": "Tue, 27 Feb 2024 15:00:13 GMT",
"version": "v1"
},
{
"created": "Thu, 2 May 2024 16:12:06 GMT",
"version": "v2"
}
] | 2024-05-03 | [
[
"Rodrigues",
"Manuel E.",
""
],
[
"Silva",
"Marcos V. de S.",
""
]
] | In Atazadeh and Hadi (JCAP \textbf{01}, 067 (2024)), the authors proposed that black bounce solutions, such as the Simpson-Visser and the Bardeen-type spacetimes, can be obtained from Rastall gravity. To achieve these spacetimes, the authors consider the presence of a phantom scalar field with nonlinear electrodynamics. However, in this comment, we obtained different electromagnetic Lagrangians from the original work. The most problematic issue is not the incorrect expression of the electromagnetic Lagrangian itself. We show that the method obtains electromagnetic functions that are inconsistent. To obtain the black bounce spacetimes as solutions of Rastall gravity, it is necessary to consider an isotropic fluid, combined with the nonlinear electrodynamics and the phantom scalar field. |
2308.00049 | Ben Kain | Ben Kain | Einstein-Dirac-Maxwell wormholes in quantum field theory | 12 pages, 5 figures; v2: typos corrected | Phys. Rev. D 108, 084010 (2023) | 10.1103/PhysRevD.108.084010 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Charged Dirac fields minimally coupled to gravity have spherically symmetric
wormhole solutions known as Einstein-Dirac-Maxwell (EDM) wormholes. EDM
wormholes do not make use of exotic matter and exist in asymptotically flat
general relativity. We construct static spherically symmetric EDM wormhole
configurations in quantum field theory using semiclassical approximations for
gravity and the electromagnetic field. Our framework is able to describe a
broader class of EDM wormholes than previously considered and, being
constructed in quantum field theory, puts EDM wormholes on firmer theoretical
ground.
| [
{
"created": "Mon, 31 Jul 2023 18:10:05 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Oct 2023 15:45:29 GMT",
"version": "v2"
}
] | 2023-10-11 | [
[
"Kain",
"Ben",
""
]
] | Charged Dirac fields minimally coupled to gravity have spherically symmetric wormhole solutions known as Einstein-Dirac-Maxwell (EDM) wormholes. EDM wormholes do not make use of exotic matter and exist in asymptotically flat general relativity. We construct static spherically symmetric EDM wormhole configurations in quantum field theory using semiclassical approximations for gravity and the electromagnetic field. Our framework is able to describe a broader class of EDM wormholes than previously considered and, being constructed in quantum field theory, puts EDM wormholes on firmer theoretical ground. |
2012.12778 | Yang Huang | Yang Huang and Hongsheng Zhang | Quasibound states of charged dilatonic black holes | 9 pages, 17 figures | Phys. Rev. D 103, 044062 (2021) | 10.1103/PhysRevD.103.044062 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Investigation of quasibound states of black holes is significant for expected
ultra light particles, as well as black holes through gravitational waves. We
first investigate quasibound states of a massive scalar field for dilatonic
charged black holes via numerical analysis. We study the complex eigen
frequencies of the massive scalar field in a wide range of gravitational fine
structure constant $\mu M$ in detail, and show the effects of charge. Further,
we study the eigen frequencies of the massive field through analytical approach
by matching the near horizon solution and far field solution, and find its
spectra for excited states by iteration method. We demonstrate the numerical
solution and analytical solution perfectly agree with each other in the region
where charge of the black hole is large, both for real and imaginary parts of
the eigen frequencies.
| [
{
"created": "Wed, 23 Dec 2020 16:34:32 GMT",
"version": "v1"
}
] | 2021-03-03 | [
[
"Huang",
"Yang",
""
],
[
"Zhang",
"Hongsheng",
""
]
] | Investigation of quasibound states of black holes is significant for expected ultra light particles, as well as black holes through gravitational waves. We first investigate quasibound states of a massive scalar field for dilatonic charged black holes via numerical analysis. We study the complex eigen frequencies of the massive scalar field in a wide range of gravitational fine structure constant $\mu M$ in detail, and show the effects of charge. Further, we study the eigen frequencies of the massive field through analytical approach by matching the near horizon solution and far field solution, and find its spectra for excited states by iteration method. We demonstrate the numerical solution and analytical solution perfectly agree with each other in the region where charge of the black hole is large, both for real and imaginary parts of the eigen frequencies. |
1309.2933 | David Delphenich | D. H. Delphenich | Line geometry and electromagnetism I: basic structures | 26 pages, one figure, one table, part I of two-part article | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some key notions of line geometry are recalled, along with their application
to mechanics. It is then shown that most of the basic structures that one
introduces in the pre-metric formulation of electromagnetism can be interpreted
directly in terms of corresponding concepts in line geometry. The results are
summarized in a table.
| [
{
"created": "Wed, 11 Sep 2013 18:00:52 GMT",
"version": "v1"
}
] | 2013-09-13 | [
[
"Delphenich",
"D. H.",
""
]
] | Some key notions of line geometry are recalled, along with their application to mechanics. It is then shown that most of the basic structures that one introduces in the pre-metric formulation of electromagnetism can be interpreted directly in terms of corresponding concepts in line geometry. The results are summarized in a table. |
2302.11460 | Adailton Ara\'ujo Filho | P. Sedaghatnia, H. Hassanabadi, A. A. Ara\'ujo Filho, J. Porf\'irio,
W. S. Chung | Thermodynamical properties of a deformed Schwarzschild black hole via
Dunkl generalization | 12 pages and 5 figures | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we construct a deformed Schwarzschild black hole from the de
Sitter gauge theory of gravity within Dunkl generalization and we determine the
metric coefficients versus Dunkl parameter and parity operators. Since the
spacetime coordinates are not affected by the group transformations, only
fields are allowed to change under the action of the symmetry group. A
particular ansatz for the gauge fields is chosen and the components of the
strength tensor are computed as well. Additionally, we analyze the
modifications on the thermodynamic properties to a spherically symmetric black
hole due to Dunkl parameters for even and odd parities. Finally, we verify a
novel remark highlighted from heat capacity: the appearance of a phase
transition when the odd parity is taken into account.
| [
{
"created": "Wed, 22 Feb 2023 15:53:28 GMT",
"version": "v1"
}
] | 2023-02-23 | [
[
"Sedaghatnia",
"P.",
""
],
[
"Hassanabadi",
"H.",
""
],
[
"Filho",
"A. A. Araújo",
""
],
[
"Porfírio",
"J.",
""
],
[
"Chung",
"W. S.",
""
]
] | In this paper, we construct a deformed Schwarzschild black hole from the de Sitter gauge theory of gravity within Dunkl generalization and we determine the metric coefficients versus Dunkl parameter and parity operators. Since the spacetime coordinates are not affected by the group transformations, only fields are allowed to change under the action of the symmetry group. A particular ansatz for the gauge fields is chosen and the components of the strength tensor are computed as well. Additionally, we analyze the modifications on the thermodynamic properties to a spherically symmetric black hole due to Dunkl parameters for even and odd parities. Finally, we verify a novel remark highlighted from heat capacity: the appearance of a phase transition when the odd parity is taken into account. |
gr-qc/0208050 | Yuan-Zhong Zhang | K.K. Nandi and Yuan-Zhong Zhang | General Relativistic Effects on Quantum Interference and the Principle
of Equivalence | 14 pages, 1 figure | Phys.Rev. D66 (2002) 063005 | 10.1103/PhysRevD.66.063005 | null | gr-qc | null | Using a novel approach, we work out the general relativistic effects on the
quantum interference of de Broglie waves associated with thermal neutrons. The
unified general formula is consistent with special relativistic results in the
flat space limit. It is also shown that the exact geodesic equation contains in
a natural way a gravitational analog of the Aharonov-Bohm effect. We work out
two examples, one in general relativity and the other in heterotic string
theory, in order to obtain the first order gravitational correction terms to
the quantum fringe shift. Measurement of these terms is closely related to the
validity of the equivalence principle at a quantum level.
| [
{
"created": "Sat, 17 Aug 2002 10:33:59 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Nandi",
"K. K.",
""
],
[
"Zhang",
"Yuan-Zhong",
""
]
] | Using a novel approach, we work out the general relativistic effects on the quantum interference of de Broglie waves associated with thermal neutrons. The unified general formula is consistent with special relativistic results in the flat space limit. It is also shown that the exact geodesic equation contains in a natural way a gravitational analog of the Aharonov-Bohm effect. We work out two examples, one in general relativity and the other in heterotic string theory, in order to obtain the first order gravitational correction terms to the quantum fringe shift. Measurement of these terms is closely related to the validity of the equivalence principle at a quantum level. |
1211.2166 | Hal Haggard | Hal M. Haggard, Carlo Rovelli, Francesca Vidotto, Wolfgang Wieland | The spin connection of twisted geometry | 5 pages, 2 figures | Phys. Rev. D 87, 024038 (2013) | 10.1103/PhysRevD.87.024038 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Twisted geometry is a piecewise-flat geometry less rigid than Regge geometry.
In Loop Gravity, it provides the classical limit for each step of the
truncation utilized in the definition of the quantum theory. We define the
torsionless spin-connection of a twisted geometry. The difficulty given by the
discontinuity of the triad is addressed by interpolating between triads. The
curvature of the resulting spin connection reduces to the Regge curvature in
the case of a Regge geometry.
| [
{
"created": "Fri, 9 Nov 2012 15:59:26 GMT",
"version": "v1"
}
] | 2014-03-12 | [
[
"Haggard",
"Hal M.",
""
],
[
"Rovelli",
"Carlo",
""
],
[
"Vidotto",
"Francesca",
""
],
[
"Wieland",
"Wolfgang",
""
]
] | Twisted geometry is a piecewise-flat geometry less rigid than Regge geometry. In Loop Gravity, it provides the classical limit for each step of the truncation utilized in the definition of the quantum theory. We define the torsionless spin-connection of a twisted geometry. The difficulty given by the discontinuity of the triad is addressed by interpolating between triads. The curvature of the resulting spin connection reduces to the Regge curvature in the case of a Regge geometry. |
0911.4950 | Martin Bojowald | Martin Bojowald and Artur Tsobanjan | Effective Constraints and Physical Coherent States in Quantum Cosmology:
A Numerical Comparison | 32 pages, 25 figures | Class. Quant Grav.27:145004, 2010 | 10.1088/0264-9381/27/14/145004 | IGC-09/11-4 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A cosmological model with a cyclic interpretation is introduced, which is
subject to quantum back-reaction and yet can be treated rather completely by
physical coherent state as well as effective constraint techniques. By this
comparison, the role of quantum back-reaction in quantum cosmology is
unambiguously demonstrated. Also the complementary nature of strengths and
weaknesses of the two procedures is illustrated. Finally, effective constraint
techniques are applied to a more realistic model filled with radiation, where
physical coherent states are not available.
| [
{
"created": "Wed, 25 Nov 2009 20:37:21 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Bojowald",
"Martin",
""
],
[
"Tsobanjan",
"Artur",
""
]
] | A cosmological model with a cyclic interpretation is introduced, which is subject to quantum back-reaction and yet can be treated rather completely by physical coherent state as well as effective constraint techniques. By this comparison, the role of quantum back-reaction in quantum cosmology is unambiguously demonstrated. Also the complementary nature of strengths and weaknesses of the two procedures is illustrated. Finally, effective constraint techniques are applied to a more realistic model filled with radiation, where physical coherent states are not available. |
0911.1479 | Rafael Sorkin | Rafael D. Sorkin (Perimeter Institute and Syracuse University) | Is the spacetime metric Euclidean rather than Lorentzian? | plainTeX, 21 pages, 1 figure (in color). A few minor corrections and
some re-wording. A previous version erroneously gave Re(f(z)) rather than
Im(f(z)) (Thanks to Adam Brown for this correction.) Most current version is
available at
http://www.perimeterinstitute.ca/personal/rsorkin/some.papers/134.tunneling.pdf
(or wherever my home-page may be) | {\it Recent Research in Quantum Gravity}, edited by Arundhati
Dasgupta (Nova Science Publishers NY, 2013, ISBN: 978-1-61942-392-3) pp.
115-135 | null | null | gr-qc hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | My answer to the question in the title is "No". In support of this point of
view, we analyze some examples of saddle-point methods, especially as applied
to quantum "tunneling" in nonrelativistic particle mechanics and in cosmology.
Along the way we explore some of the interrelationships among different ways of
thinking about path-integrals and saddle-point approximations to them.
| [
{
"created": "Sun, 8 Nov 2009 00:44:15 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Nov 2009 06:19:24 GMT",
"version": "v2"
},
{
"created": "Mon, 5 Jun 2017 00:13:46 GMT",
"version": "v3"
}
] | 2017-06-06 | [
[
"Sorkin",
"Rafael D.",
"",
"Perimeter Institute and Syracuse University"
]
] | My answer to the question in the title is "No". In support of this point of view, we analyze some examples of saddle-point methods, especially as applied to quantum "tunneling" in nonrelativistic particle mechanics and in cosmology. Along the way we explore some of the interrelationships among different ways of thinking about path-integrals and saddle-point approximations to them. |
gr-qc/0508053 | Yungui Gong | Yungui Gong and Yuan-Zhong Zhang | Dark energy and the future fate of the Universe | 2 figures, 11 pages, Mod. Phys. Lett. A in press | Mod.Phys.Lett.A22:2689-2699,2007 | 10.1142/S021773230702292X | null | gr-qc astro-ph hep-th | null | We consider the possibility of observing the onset of the late time inflation
of our patch of the Universe. The Hubble size criterion and the event horizon
criterion are applied to several dark energy models to discuss the problem of
future inflation of the Universe. We find that the acceleration has not lasted
long enough to confirm the onset of inflation by present observations for the
dark energy model with constant equation of state, the holographic dark energy
model and the generalized Chaplygin gas (GCG) model. For the flat $\Lambda$CDM
model with $\Omega_{m0}=0.3$, we find that if we use the Hubble size criterion,
we need to wait until the $a_v$ which is the scale factor at the time when the
onset of inflation is observed reaches 3.59 times of the scale factor $a_T$
when the Universe started acceleration, and we need to wait until $a_v=2.3 a_T$
to see the onset of inflation if we use the event horizon criterion. For the
flat holographic dark energy model with $d=1$, we find that $a_v=3.46 a_T$ with
the Hubble horizon and $a_v=2.34 a_T$ with the event horizon, respectively. For
the flat GCG model with the best supernova fitting parameter $\alpha=1.2$, we
find that $a_v=5.50 a_T$ with the Hubble horizon and $a_v=2.08 a_T$ with the
event horizon, respectively.
| [
{
"created": "Fri, 12 Aug 2005 14:53:09 GMT",
"version": "v1"
},
{
"created": "Sat, 13 Aug 2005 07:09:18 GMT",
"version": "v2"
},
{
"created": "Tue, 23 Oct 2007 10:01:37 GMT",
"version": "v3"
}
] | 2010-10-27 | [
[
"Gong",
"Yungui",
""
],
[
"Zhang",
"Yuan-Zhong",
""
]
] | We consider the possibility of observing the onset of the late time inflation of our patch of the Universe. The Hubble size criterion and the event horizon criterion are applied to several dark energy models to discuss the problem of future inflation of the Universe. We find that the acceleration has not lasted long enough to confirm the onset of inflation by present observations for the dark energy model with constant equation of state, the holographic dark energy model and the generalized Chaplygin gas (GCG) model. For the flat $\Lambda$CDM model with $\Omega_{m0}=0.3$, we find that if we use the Hubble size criterion, we need to wait until the $a_v$ which is the scale factor at the time when the onset of inflation is observed reaches 3.59 times of the scale factor $a_T$ when the Universe started acceleration, and we need to wait until $a_v=2.3 a_T$ to see the onset of inflation if we use the event horizon criterion. For the flat holographic dark energy model with $d=1$, we find that $a_v=3.46 a_T$ with the Hubble horizon and $a_v=2.34 a_T$ with the event horizon, respectively. For the flat GCG model with the best supernova fitting parameter $\alpha=1.2$, we find that $a_v=5.50 a_T$ with the Hubble horizon and $a_v=2.08 a_T$ with the event horizon, respectively. |
gr-qc/9606030 | Haret Rosu | H.C. Rosu, J. Socorro | Supersymmetric strictly isospectral FRW models for zero factor ordering | 6 twocolumn pages including 6 eps figs | Nuovo Cimento B 113 (May 1998) 683-689 | null | null | gr-qc | null | We apply the strictly isospectral technique of standard supersymmetric
quantum mechanics to the Q=0 factor ordered Wheeler-DeWitt equation for the
Friedmann-Robertson-Walker (FRW) minisuperspace model. The resulting strictly
isospectral one-parameter families of both FRW cosmological potentials and
"wavefunctions of the universe" are exhibited with relevant plots
| [
{
"created": "Fri, 14 Jun 1996 00:42:00 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Jul 1996 04:21:00 GMT",
"version": "v2"
},
{
"created": "Tue, 27 May 1997 23:10:24 GMT",
"version": "v3"
},
{
"created": "Sun, 11 Jul 1999 01:23:05 GMT",
"version": "v4"
}
] | 2009-09-25 | [
[
"Rosu",
"H. C.",
""
],
[
"Socorro",
"J.",
""
]
] | We apply the strictly isospectral technique of standard supersymmetric quantum mechanics to the Q=0 factor ordered Wheeler-DeWitt equation for the Friedmann-Robertson-Walker (FRW) minisuperspace model. The resulting strictly isospectral one-parameter families of both FRW cosmological potentials and "wavefunctions of the universe" are exhibited with relevant plots |
1610.07750 | Marcello Ortaggio | Marcello Ortaggio | On the uniqueness of the Myers-Perry spacetime as a type II(D) solution
in six dimensions | 30 pages. v2: a few typos fixed, added references, minor improvements
(results unchanged) | JHEP 1706 (2017) 042 | 10.1007/JHEP06(2017)042 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the class of vacuum (Ricci flat) six-dimensional spacetimes
admitting a non-degenerate multiple Weyl aligned null direction l, thus being
of Weyl type II or more special. Subject to an additional assumption on the
asymptotic fall-off of the Weyl tensor, we prove that these spacetimes can be
completely classified in terms of the two eigenvalues of the (asymptotic) twist
matrix of l and of a discrete parameter $U^0=\pm 1/2, 0$. All solutions turn
out to be Kerr-Schild spacetimes of type D and reduce to a family of
"generalized" Myers-Perry metrics (which include limits and analytic
continuations of the original Myers-Perry black hole metric, such as certain
NUT spacetimes). A special subcase corresponds to twisting solutions with zero
shear. In passing, limits connecting various branches of solutions are briefly
discussed.
| [
{
"created": "Tue, 25 Oct 2016 07:05:02 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Jun 2017 11:50:43 GMT",
"version": "v2"
}
] | 2017-06-26 | [
[
"Ortaggio",
"Marcello",
""
]
] | We study the class of vacuum (Ricci flat) six-dimensional spacetimes admitting a non-degenerate multiple Weyl aligned null direction l, thus being of Weyl type II or more special. Subject to an additional assumption on the asymptotic fall-off of the Weyl tensor, we prove that these spacetimes can be completely classified in terms of the two eigenvalues of the (asymptotic) twist matrix of l and of a discrete parameter $U^0=\pm 1/2, 0$. All solutions turn out to be Kerr-Schild spacetimes of type D and reduce to a family of "generalized" Myers-Perry metrics (which include limits and analytic continuations of the original Myers-Perry black hole metric, such as certain NUT spacetimes). A special subcase corresponds to twisting solutions with zero shear. In passing, limits connecting various branches of solutions are briefly discussed. |
gr-qc/0402020 | William Joseph Weber | D. Bortoluzzi, L. Carbone, A. Cavalleri, M. Da Lio, R. Dolesi, C. D.
Hoyle, M.Hueller, S. Vitale, and W. J. Weber | Measuring random force noise for LISA aboard the LISA Pathfinder mission | 7 pages, 3 figures. To be published in Classical and Quantum Gravity
with the proceedings of the 2003 Amaldi Meeting | Class.Quant.Grav. 21 (2004) S573-S580 | 10.1088/0264-9381/21/5/028 | null | gr-qc | null | The LTP (LISA Testflight Package), to be flown aboard the ESA / NASA LISA
Pathfinder mission, aims to demonstrate drag-free control for LISA test masses
with acceleration noise below 30 fm/s^2/Hz^1/2 from 1-30 mHz. This paper
describes the LTP measurement of random, position independent forces acting on
the test masses. In addition to putting an overall upper limit for all source
of random force noise, LTP will measure the conversion of several key
disturbances into acceleration noise and thus allow a more detailed
characterization of the drag-free performance to be expected for LISA.
| [
{
"created": "Wed, 4 Feb 2004 16:41:11 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Bortoluzzi",
"D.",
""
],
[
"Carbone",
"L.",
""
],
[
"Cavalleri",
"A.",
""
],
[
"Da Lio",
"M.",
""
],
[
"Dolesi",
"R.",
""
],
[
"Hoyle",
"C. D.",
""
],
[
"Hueller",
"M.",
""
],
[
"Vitale",
"S.",... | The LTP (LISA Testflight Package), to be flown aboard the ESA / NASA LISA Pathfinder mission, aims to demonstrate drag-free control for LISA test masses with acceleration noise below 30 fm/s^2/Hz^1/2 from 1-30 mHz. This paper describes the LTP measurement of random, position independent forces acting on the test masses. In addition to putting an overall upper limit for all source of random force noise, LTP will measure the conversion of several key disturbances into acceleration noise and thus allow a more detailed characterization of the drag-free performance to be expected for LISA. |
1507.07257 | S Habib Mazharimousavi | S. Habib Mazharimousavi and M. Halilsoy | 2+1-dimensional wormhole from a doublet of scalar fields | 6 pages, 4 figures, final version published in PRD | Phys. Rev. D 92, 024040 (2015) | 10.1103/PhysRevD.92.024040 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a class of exact solutions in the framework of $2+1-$dimensional
Einstein gravity coupled minimally to a doublet of scalar fields. Our solution
can be interpreted upon tuning of parameters as an asymptotically flat wormhole
as well as a particle model in $2+1-$dimensions.
| [
{
"created": "Sun, 26 Jul 2015 22:12:33 GMT",
"version": "v1"
}
] | 2015-07-28 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"M.",
""
]
] | We present a class of exact solutions in the framework of $2+1-$dimensional Einstein gravity coupled minimally to a doublet of scalar fields. Our solution can be interpreted upon tuning of parameters as an asymptotically flat wormhole as well as a particle model in $2+1-$dimensions. |
gr-qc/9906119 | Anchordoqui Luis Alfredo | L. A. Anchordoqui, M. L. Trobo, H. Vucetich and F. Zyserman | Gravitational memory of natural wormholes | 14 pages revtex, 1 ps figure | Mod.Phys.Lett. A15 (2000) 429-438 | 10.1142/S0217732300000414 | null | gr-qc | null | A traversable wormhole solution of general scalar-tensor field equations is
presented. We have shown, after a numerical analysis for the behavior of the
scalar field of Brans-Dicke theory, that the solution is completely
singularity--free. Furthermore, the analysis of more general scalar field
dependent coupling constants indicates that the gravitational memory phenomenon
may play an important role in the fate of natural wormholes.
| [
{
"created": "Tue, 29 Jun 1999 20:34:41 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Aug 1999 23:18:38 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Anchordoqui",
"L. A.",
""
],
[
"Trobo",
"M. L.",
""
],
[
"Vucetich",
"H.",
""
],
[
"Zyserman",
"F.",
""
]
] | A traversable wormhole solution of general scalar-tensor field equations is presented. We have shown, after a numerical analysis for the behavior of the scalar field of Brans-Dicke theory, that the solution is completely singularity--free. Furthermore, the analysis of more general scalar field dependent coupling constants indicates that the gravitational memory phenomenon may play an important role in the fate of natural wormholes. |
1012.3894 | Manuel Tessmer | Manuel Tessmer and Gerhard Schaefer | Full-analytic frequency-domain gravitational wave forms from eccentric
compact binaries to 2PN accuracy | 48 pages | Ann. Phys. (Berlin) 523 (2011) 813-864 | 10.1002/andp.201100007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The article provides full-analytic gravitational wave (GW) forms for
eccentric nonspinning compact binaries of arbitrary mass ratio in the time
Fourier domain. The semi-analytical property of recent descriptions, i.e. the
demand of inverting the higher-order Kepler equation numerically but keeping
all other computations analytic, is avoided for the first time. The article is
a completion of a previous one (Tessmer and Sch\"afer, Phys. Rev. D 82, 124064
(2010)) to second post-Newtonian (2PN) order in the harmonic GW amplitude and
conservative orbital dynamics. A fully analytical inversion formula of the
Kepler equation in harmonic coordinates is provided, as well as the analytic
time Fourier expansion of trigonometric functions of the eccentric anomaly in
terms of sines and cosines of the mean anomaly. Tail terms are not considered.
| [
{
"created": "Fri, 17 Dec 2010 14:43:47 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Apr 2011 12:29:38 GMT",
"version": "v2"
}
] | 2013-03-25 | [
[
"Tessmer",
"Manuel",
""
],
[
"Schaefer",
"Gerhard",
""
]
] | The article provides full-analytic gravitational wave (GW) forms for eccentric nonspinning compact binaries of arbitrary mass ratio in the time Fourier domain. The semi-analytical property of recent descriptions, i.e. the demand of inverting the higher-order Kepler equation numerically but keeping all other computations analytic, is avoided for the first time. The article is a completion of a previous one (Tessmer and Sch\"afer, Phys. Rev. D 82, 124064 (2010)) to second post-Newtonian (2PN) order in the harmonic GW amplitude and conservative orbital dynamics. A fully analytical inversion formula of the Kepler equation in harmonic coordinates is provided, as well as the analytic time Fourier expansion of trigonometric functions of the eccentric anomaly in terms of sines and cosines of the mean anomaly. Tail terms are not considered. |
1602.04524 | Gustav Holzegel | Gustav Holzegel | Conservation laws and flux bounds for gravitational perturbations of the
Schwarzschild metric | 21 pages, 2 figures | null | 10.1088/0264-9381/33/20/205004 | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive an energy conservation law for the system of gravitational
perturbations on the Schwarzschild spacetime expressed in a double null gauge.
The resulting identity involves only first derivatives of the metric
perturbation. Exploiting the gauge invariance up to boundary terms of the
fluxes that appear, we are able to establish positivity of the flux on any
outgoing null hypersurface to the future of the initial data. This allows us to
bound the total energy flux through any such hypersurface, including the event
horizon, in terms of initial data. We similarly bound the total energy radiated
to null infinity. Our estimates provide a direct approach to a weak form of
stability, thereby complementing the proof of the full linear stability of the
Schwarzschild solution recently obtained in [M. Dafermos, G. Holzegel and I.
Rodnianski \emph{The linear stability of the Schwarzschild solution to
gravitational perturbations}, arXiv:1601.06467].
| [
{
"created": "Sun, 14 Feb 2016 23:06:41 GMT",
"version": "v1"
}
] | 2016-10-05 | [
[
"Holzegel",
"Gustav",
""
]
] | We derive an energy conservation law for the system of gravitational perturbations on the Schwarzschild spacetime expressed in a double null gauge. The resulting identity involves only first derivatives of the metric perturbation. Exploiting the gauge invariance up to boundary terms of the fluxes that appear, we are able to establish positivity of the flux on any outgoing null hypersurface to the future of the initial data. This allows us to bound the total energy flux through any such hypersurface, including the event horizon, in terms of initial data. We similarly bound the total energy radiated to null infinity. Our estimates provide a direct approach to a weak form of stability, thereby complementing the proof of the full linear stability of the Schwarzschild solution recently obtained in [M. Dafermos, G. Holzegel and I. Rodnianski \emph{The linear stability of the Schwarzschild solution to gravitational perturbations}, arXiv:1601.06467]. |
gr-qc/0701091 | Ricardo Gallego | Ricardo Gallego Torrome | On a covariant version of Caianiello's Model | 15 pages, no figures; notation clarified and other important changes | Gen.Rel.Grav.39:1833-1845,2007 | 10.1007/s10714-007-0491-6 | null | gr-qc hep-th math-ph math.MP | null | Caianiello's derivation of Quantum Geometry through an isometric embedding of
the spacetime ({\bf M},\tilde{g}) in the pseudo-Riemannian structure ({\bf
T^*M},g^*_{AB}) is reconsidered. In the new derivation, a non-linear connection
and the bundle %%@ formalism induce a Lorentzian-type structure in the
4-dimensional manifold {\bf M} that is covariant %%@ under arbitrary local
coordinate transformations in {\bf M}. If models with maximal acceleration are
required to be non-trivial, gravity should be supplied with other interactions
in a unification framework.
| [
{
"created": "Tue, 16 Jan 2007 13:04:42 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Jan 2007 14:26:09 GMT",
"version": "v2"
},
{
"created": "Mon, 22 Jan 2007 12:55:48 GMT",
"version": "v3"
},
{
"created": "Wed, 23 May 2007 07:06:19 GMT",
"version": "v4"
}
] | 2020-12-01 | [
[
"Torrome",
"Ricardo Gallego",
""
]
] | Caianiello's derivation of Quantum Geometry through an isometric embedding of the spacetime ({\bf M},\tilde{g}) in the pseudo-Riemannian structure ({\bf T^*M},g^*_{AB}) is reconsidered. In the new derivation, a non-linear connection and the bundle %%@ formalism induce a Lorentzian-type structure in the 4-dimensional manifold {\bf M} that is covariant %%@ under arbitrary local coordinate transformations in {\bf M}. If models with maximal acceleration are required to be non-trivial, gravity should be supplied with other interactions in a unification framework. |
1205.6127 | Bianca Dittrich | Bianca Dittrich (Perimeter Institute for Theoretical Physics, Max
Planck Institute for Gravitational Physics) | From the discrete to the continuous - towards a cylindrically consistent
dynamics | 22 pages | null | 10.1088/1367-2630/14/12/123004 | null | gr-qc hep-lat quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Discrete models usually represent approximations to continuum physics.
Cylindrical consistency provides a framework in which discretizations mirror
exactly the continuum limit. Being a standard tool for the kinematics of loop
quantum gravity we propose a coarse graining procedure that aims at
constructing a cylindrically consistent dynamics in the form of transition
amplitudes and Hamilton's principal functions. The coarse graining procedure,
which is motivated by tensor network renormalization methods, provides a
systematic approximation scheme towards this end. A crucial role in this coarse
graining scheme is played by embedding maps that allow the interpretation of
discrete boundary data as continuum configurations. These embedding maps should
be selected according to the dynamics of the system, as a choice of embedding
maps will determine a truncation of the renormalization flow.
| [
{
"created": "Mon, 28 May 2012 14:30:33 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Dittrich",
"Bianca",
"",
"Perimeter Institute for Theoretical Physics, Max\n Planck Institute for Gravitational Physics"
]
] | Discrete models usually represent approximations to continuum physics. Cylindrical consistency provides a framework in which discretizations mirror exactly the continuum limit. Being a standard tool for the kinematics of loop quantum gravity we propose a coarse graining procedure that aims at constructing a cylindrically consistent dynamics in the form of transition amplitudes and Hamilton's principal functions. The coarse graining procedure, which is motivated by tensor network renormalization methods, provides a systematic approximation scheme towards this end. A crucial role in this coarse graining scheme is played by embedding maps that allow the interpretation of discrete boundary data as continuum configurations. These embedding maps should be selected according to the dynamics of the system, as a choice of embedding maps will determine a truncation of the renormalization flow. |
0707.0579 | Vincenzo Galdi | Vincenzo Pierro, Vincenzo Galdi, Giuseppe Castaldi, Innocenzo M.
Pinto, Juri Agresti, and Riccardo DeSalvo | Perspectives on Beam-Shaping Optimization for Thermal-Noise Reduction in
Advanced Gravitational-Wave Interferometric Detectors: Bounds, Profiles, and
Critical Parameters | 12 pages, 9 figures, 2 tables | Phys.Rev.D76:122003,2007 | 10.1103/PhysRevD.76.122003 | LIGO-P070066-01-Z | gr-qc | null | Suitable shaping (in particular, flattening and broadening) of the laser beam
has recently been proposed as an effective device to reduce internal (mirror)
thermal noise in advanced gravitational wave interferometric detectors. Based
on some recently published analytic approximations (valid in the
infinite-test-mass limit) for the Brownian and thermoelastic mirror noises in
the presence of arbitrary-shaped beams, this paper addresses certain
preliminary issues related to the optimal beam-shaping problem. In particular,
with specific reference to the Laser Interferometer Gravitational-wave
Observatory (LIGO) experiment, absolute and realistic lower-bounds for the
various thermal noise constituents are obtained and compared with the current
status (Gaussian beams) and trends ("mesa" beams), indicating fairly ample
margins for further reduction. In this framework, the effective dimension of
the related optimization problem, and its relationship to the critical design
parameters are identified, physical-feasibility and model-consistency issues
are considered, and possible additional requirements and/or prior information
exploitable to drive the subsequent optimization process are highlighted.
| [
{
"created": "Wed, 4 Jul 2007 15:31:10 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Pierro",
"Vincenzo",
""
],
[
"Galdi",
"Vincenzo",
""
],
[
"Castaldi",
"Giuseppe",
""
],
[
"Pinto",
"Innocenzo M.",
""
],
[
"Agresti",
"Juri",
""
],
[
"DeSalvo",
"Riccardo",
""
]
] | Suitable shaping (in particular, flattening and broadening) of the laser beam has recently been proposed as an effective device to reduce internal (mirror) thermal noise in advanced gravitational wave interferometric detectors. Based on some recently published analytic approximations (valid in the infinite-test-mass limit) for the Brownian and thermoelastic mirror noises in the presence of arbitrary-shaped beams, this paper addresses certain preliminary issues related to the optimal beam-shaping problem. In particular, with specific reference to the Laser Interferometer Gravitational-wave Observatory (LIGO) experiment, absolute and realistic lower-bounds for the various thermal noise constituents are obtained and compared with the current status (Gaussian beams) and trends ("mesa" beams), indicating fairly ample margins for further reduction. In this framework, the effective dimension of the related optimization problem, and its relationship to the critical design parameters are identified, physical-feasibility and model-consistency issues are considered, and possible additional requirements and/or prior information exploitable to drive the subsequent optimization process are highlighted. |
2004.07105 | Andrea Campolongo | Andrea Campolongo, Giovanni Montani | The Role of Entropy in the Evolutionary Quantization of the Isotropic
Universe | null | null | 10.1140/epjc/s10052-020-08544-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we analyze the dynamics of an isotropic closed Universe in the
presence of a cosmological constant term and we compare its behavior in the
standard Wheeler-DeWitt equation approach with the one when a Lagrangian fluid
is considered in the spirit of the Kuchar-Brown paradigm. In particular, we
compare the tunnelling of the Universe from the classically forbidden region to
the allowed one, showing that considering a time evolution deeply influences
the nature of the model. In fact, we show that in the presence of the
Lagrangian fluid, the cosmological singularity is restored both in the
classical and the quantum regime. However, in the quantum regime the
singularity is probabilistically suppressed for some energy eigenvalues and in
the case the latter is equal to zero, one recovers the standard WDW case.
Finally, we introduce a cut-off physics feature in the Minisuperspace by
considering a Polymer quantum mechanical approach, mainly limiting our
attention to the semi-classical dynamics (the quantum treatment is inhibited by
the non-local nature of the Hamiltonian operator). We show that the singularity
is again removed, like in the fluid-free model, and a bouncing cosmology
emerges so that the present model could mimic a cyclic cosmology.
| [
{
"created": "Wed, 15 Apr 2020 14:14:00 GMT",
"version": "v1"
}
] | 2020-12-02 | [
[
"Campolongo",
"Andrea",
""
],
[
"Montani",
"Giovanni",
""
]
] | In this paper, we analyze the dynamics of an isotropic closed Universe in the presence of a cosmological constant term and we compare its behavior in the standard Wheeler-DeWitt equation approach with the one when a Lagrangian fluid is considered in the spirit of the Kuchar-Brown paradigm. In particular, we compare the tunnelling of the Universe from the classically forbidden region to the allowed one, showing that considering a time evolution deeply influences the nature of the model. In fact, we show that in the presence of the Lagrangian fluid, the cosmological singularity is restored both in the classical and the quantum regime. However, in the quantum regime the singularity is probabilistically suppressed for some energy eigenvalues and in the case the latter is equal to zero, one recovers the standard WDW case. Finally, we introduce a cut-off physics feature in the Minisuperspace by considering a Polymer quantum mechanical approach, mainly limiting our attention to the semi-classical dynamics (the quantum treatment is inhibited by the non-local nature of the Hamiltonian operator). We show that the singularity is again removed, like in the fluid-free model, and a bouncing cosmology emerges so that the present model could mimic a cyclic cosmology. |
2305.10478 | Leah Jenks | Leah Jenks, Lyla Choi, Macarena Lagos, and Nicol\'as Yunes | Parameterized Parity Violation in Gravitational Wave Propagation | 19 pages | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational parity violation arises in a variety of theories beyond general
relativity. Gravitational waves in such theories have their propagation
altered, leading to birefringence effects in both the amplitude and speed of
the wave. In this work, we introduce a generalized, theory-motivated
parametrization scheme to study parity violation in gravitational wave
propagation. This parametrization maps to parity-violating gravity theories in
a straightforward way. We find that the amplitude and velocity birefringence
effects scale with an effective distance measure that depends on how the
dispersion relation is modified. Furthermore, we show that this generic
parametrization can be mapped to the parametrized-post-Einsteinian (ppE)
formalism with convenient applications to gravitational wave observations and
model-agnostic tests of general relativity. We derive a mapping to the standard
ppE waveform of the gravitational wave response function, and also find a ppE
waveform mapping at the level of the polarization modes, $h_+$ and $h_\times$.
Finally, we show how existing constraints in the literature translate to bounds
on our new parity-violating parameters and discuss avenues for future analysis.
| [
{
"created": "Wed, 17 May 2023 18:00:00 GMT",
"version": "v1"
}
] | 2023-05-19 | [
[
"Jenks",
"Leah",
""
],
[
"Choi",
"Lyla",
""
],
[
"Lagos",
"Macarena",
""
],
[
"Yunes",
"Nicolás",
""
]
] | Gravitational parity violation arises in a variety of theories beyond general relativity. Gravitational waves in such theories have their propagation altered, leading to birefringence effects in both the amplitude and speed of the wave. In this work, we introduce a generalized, theory-motivated parametrization scheme to study parity violation in gravitational wave propagation. This parametrization maps to parity-violating gravity theories in a straightforward way. We find that the amplitude and velocity birefringence effects scale with an effective distance measure that depends on how the dispersion relation is modified. Furthermore, we show that this generic parametrization can be mapped to the parametrized-post-Einsteinian (ppE) formalism with convenient applications to gravitational wave observations and model-agnostic tests of general relativity. We derive a mapping to the standard ppE waveform of the gravitational wave response function, and also find a ppE waveform mapping at the level of the polarization modes, $h_+$ and $h_\times$. Finally, we show how existing constraints in the literature translate to bounds on our new parity-violating parameters and discuss avenues for future analysis. |
2210.14106 | M\'ario Raia Neto Raia | M\'ario Raia Neto, Daniela P\'erez, Joaqu\'in Pelle | The Shadow of Charged Traversable Wormholes | 19 pages, 3 figures, accepted for publication in International
Journal of Modern Physics D | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We compute the shadow cast by a charged Morris-Thorne wormhole when the light
source is a star located beyond the mouth which is opposite to the observer.
First, we provide an extensive analysis of the geodesic properties of the
spacetime, both for null and massive particles. The geometrical properties of
this solution are such that independently of the viewing angle, some light rays
always reach the observer. Additionally, the structure of the images is
preserved among the different values of the charge and scales proportionally to
the charge value.
| [
{
"created": "Tue, 25 Oct 2022 15:44:15 GMT",
"version": "v1"
}
] | 2022-10-26 | [
[
"Neto",
"Mário Raia",
""
],
[
"Pérez",
"Daniela",
""
],
[
"Pelle",
"Joaquín",
""
]
] | We compute the shadow cast by a charged Morris-Thorne wormhole when the light source is a star located beyond the mouth which is opposite to the observer. First, we provide an extensive analysis of the geodesic properties of the spacetime, both for null and massive particles. The geometrical properties of this solution are such that independently of the viewing angle, some light rays always reach the observer. Additionally, the structure of the images is preserved among the different values of the charge and scales proportionally to the charge value. |
gr-qc/9812034 | Antonio Campos | Antonio Campos and B. L. Hu | Fluctuations in a Thermal Field and Dissipation of a Black Hole
Spacetime: Far-Field Limit | To appear in the proceedings of the Conference on Quantum Gravity in
the Southern Cone | Int.J.Theor.Phys.38:1253-1271,1999 | 10.1023/A:1026670816596 | null | gr-qc | null | We study the back reaction of a thermal field in a weak gravitational
background depicting the far-field limit of a black hole enclosed in a box by
the Close Time Path (CTP) effective action and the influence functional method.
We derive the noise and dissipation kernels of this system in terms of
quantities in quasi-equilibrium, and formally prove the existence of a
Fluctuation-Dissipation Relation (FDR) at all temperatures between the quantum
fluctuations of the thermal radiance and the dissipation of the gravitational
field. This dynamical self-consistent interplay between the quantum field and
the classical spacetime is, we believe, the correct way to treat back-reaction
problems. To emphasize this point we derive an Einstein-Langevin equation which
describes the non-equilibrium dynamics of the gravitational perturbations under
the influence of the thermal field. We show the connection between our method
and the linear response theory (LRT), and indicate how the functional method
can provide more accurate results than prior derivations of FDRs via LRT in the
test-field, static conditions. This method is in principle useful for treating
fully non-equilibrium cases such as back reaction in black hole collapse.
| [
{
"created": "Thu, 10 Dec 1998 18:38:43 GMT",
"version": "v1"
}
] | 2011-04-15 | [
[
"Campos",
"Antonio",
""
],
[
"Hu",
"B. L.",
""
]
] | We study the back reaction of a thermal field in a weak gravitational background depicting the far-field limit of a black hole enclosed in a box by the Close Time Path (CTP) effective action and the influence functional method. We derive the noise and dissipation kernels of this system in terms of quantities in quasi-equilibrium, and formally prove the existence of a Fluctuation-Dissipation Relation (FDR) at all temperatures between the quantum fluctuations of the thermal radiance and the dissipation of the gravitational field. This dynamical self-consistent interplay between the quantum field and the classical spacetime is, we believe, the correct way to treat back-reaction problems. To emphasize this point we derive an Einstein-Langevin equation which describes the non-equilibrium dynamics of the gravitational perturbations under the influence of the thermal field. We show the connection between our method and the linear response theory (LRT), and indicate how the functional method can provide more accurate results than prior derivations of FDRs via LRT in the test-field, static conditions. This method is in principle useful for treating fully non-equilibrium cases such as back reaction in black hole collapse. |
0804.3222 | Lode Wylleman | Lode Wylleman | Algebraically general, gravito-electric rotating dust | 10 pages, changed to revtex style, extended discussion section, minor
corrections | null | 10.1051/eas:0830034 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The class of gravito-electric, algebraically general, rotating `silent' dust
space-times is studied. The main invariant properties are deduced. The number
$t_0$ of functionally independent zero-order Riemann invariants satisfies
$1\leq t_0\leq 2$ and special attention is given to the subclass $t_0=1$.
Whereas there are no $\Lambda$-term limits comprised in the class, the limit
for vanishing vorticity leads to two previously derived irrotational dust
families with $\Lambda>0$, and the shear-free limit is the G\"{o}del universe.
| [
{
"created": "Sun, 20 Apr 2008 23:26:57 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Jun 2008 22:14:18 GMT",
"version": "v2"
}
] | 2009-11-13 | [
[
"Wylleman",
"Lode",
""
]
] | The class of gravito-electric, algebraically general, rotating `silent' dust space-times is studied. The main invariant properties are deduced. The number $t_0$ of functionally independent zero-order Riemann invariants satisfies $1\leq t_0\leq 2$ and special attention is given to the subclass $t_0=1$. Whereas there are no $\Lambda$-term limits comprised in the class, the limit for vanishing vorticity leads to two previously derived irrotational dust families with $\Lambda>0$, and the shear-free limit is the G\"{o}del universe. |
0910.4066 | Michael Bebronne | Michael V. Bebronne | Theoretical and phenomenological aspects of theories with massive
gravitons | PhD thesis, 116 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this thesis, we study three aspects of theories with massive gravitational
waves. In the first part, we review to problems and issues of theories with
massive gravitons before introducing models where Lorentz invariance is
spontaneously broken by the vacuum expectation value of four scalar fields. In
the second part, we discuss three aspects of these models: instantaneous
interaction, spherically vacuum solutions and cosmological perturbations.
| [
{
"created": "Wed, 21 Oct 2009 12:14:54 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Bebronne",
"Michael V.",
""
]
] | In this thesis, we study three aspects of theories with massive gravitational waves. In the first part, we review to problems and issues of theories with massive gravitons before introducing models where Lorentz invariance is spontaneously broken by the vacuum expectation value of four scalar fields. In the second part, we discuss three aspects of these models: instantaneous interaction, spherically vacuum solutions and cosmological perturbations. |
1210.1891 | Larne Pekowsky | Larne Pekowsky, James Healy, Deirdre Shoemaker, Pablo Laguna | Impact of Higher-order Modes on the Detection of Binary Black Hole
Coalescences | null | null | 10.1103/PhysRevD.87.084008 | NSF-KITP-12-174 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The inspiral and merger of black-hole binary systems are a promising source
of gravitational waves. The most effective method to look for a signal with a
well understood waveform, such as the binary black hole signal, is matched
filtering against a library of model waveforms. Current model waveforms are
comprised solely of the dominant radiation mode, the quadrupole mode, although
it is known that there can be significant power in the higher-order modes. The
binary black hole waveforms produced by numerical relativity are accurate
through late inspiral, merger, and ringdown and include the higher-order modes.
The available numerical-relativity waveforms span an increasing portion of the
physical parameter space of unequal mass, spin and precession. In this paper,
we investigate the degree to which gravitational-wave searches could be
improved by the inclusion of higher modes in the model waveforms, for signals
with a variety of initial mass ratios and generic spins. Our investigation
studies how well the quadrupole-only waveform model matches the signal as a
function of the inclination and orientation of the source and how the modes
contribute to the distance reach into the Universe of Advanced LIGO for a fixed
set of internal source parameters. The mismatch between signals and
quadrupole-only waveform can be large, dropping below 0.97 for up to 65% of the
source-sky for the non-precessing cases we studied, and over a larger area in
one precessing case. There is a corresponding 30% increase in detection volume
that could be achieved by adding higher modes to the search; however, this is
mitigated by the fact that the mismatch is largest for signals which radiate
the least energy and to which the search is therefore least sensitive.
Likewise, the mismatch is largest in directions from the source along which the
least energy is radiated.
| [
{
"created": "Fri, 5 Oct 2012 23:30:51 GMT",
"version": "v1"
}
] | 2014-05-15 | [
[
"Pekowsky",
"Larne",
""
],
[
"Healy",
"James",
""
],
[
"Shoemaker",
"Deirdre",
""
],
[
"Laguna",
"Pablo",
""
]
] | The inspiral and merger of black-hole binary systems are a promising source of gravitational waves. The most effective method to look for a signal with a well understood waveform, such as the binary black hole signal, is matched filtering against a library of model waveforms. Current model waveforms are comprised solely of the dominant radiation mode, the quadrupole mode, although it is known that there can be significant power in the higher-order modes. The binary black hole waveforms produced by numerical relativity are accurate through late inspiral, merger, and ringdown and include the higher-order modes. The available numerical-relativity waveforms span an increasing portion of the physical parameter space of unequal mass, spin and precession. In this paper, we investigate the degree to which gravitational-wave searches could be improved by the inclusion of higher modes in the model waveforms, for signals with a variety of initial mass ratios and generic spins. Our investigation studies how well the quadrupole-only waveform model matches the signal as a function of the inclination and orientation of the source and how the modes contribute to the distance reach into the Universe of Advanced LIGO for a fixed set of internal source parameters. The mismatch between signals and quadrupole-only waveform can be large, dropping below 0.97 for up to 65% of the source-sky for the non-precessing cases we studied, and over a larger area in one precessing case. There is a corresponding 30% increase in detection volume that could be achieved by adding higher modes to the search; however, this is mitigated by the fact that the mismatch is largest for signals which radiate the least energy and to which the search is therefore least sensitive. Likewise, the mismatch is largest in directions from the source along which the least energy is radiated. |
1508.02511 | Francisco Lobo | Tiberiu Harko, Francisco S. N. Lobo, Jos\'e P. Mimoso, Diego Pav\'on | Gravitational induced particle production through a nonminimal
curvature-matter coupling | 15 pages; accepted for publication in the European Physical Journal C | Eur. Phys. J. C 75 (2015) 386 | 10.1140/epjc/s10052-015-3620-5 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the possibility of a gravitationally induced particle production
through the mechanism of a nonminimal curvature-matter coupling. An interesting
feature of this gravitational theory is that the divergence of the
energy-momentum tensor is nonzero. As a first step in our study we reformulate
the model in terms of an equivalent scalar-tensor theory, with two arbitrary
potentials. By using the formalism of open thermodynamic systems, we interpret
the energy balance equations in this gravitational theory from a thermodynamic
point of view, as describing irreversible matter creation processes. The
particle number creation rates, the creation pressure, and the entropy
production rates are explicitly obtained as functions of the scalar field and
its potentials, as well as of the matter Lagrangian. The temperature evolution
laws of the newly created particles are also obtained. The cosmological
implications of the model are briefly investigated, and it is shown that the
late-time cosmic acceleration may be due to particle creation processes.
Furthermore, it is also shown that due to the curvature--matter coupling,
during the cosmological evolution a large amount of comoving entropy is also
produced.
| [
{
"created": "Tue, 11 Aug 2015 08:03:18 GMT",
"version": "v1"
}
] | 2015-08-31 | [
[
"Harko",
"Tiberiu",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Mimoso",
"José P.",
""
],
[
"Pavón",
"Diego",
""
]
] | We consider the possibility of a gravitationally induced particle production through the mechanism of a nonminimal curvature-matter coupling. An interesting feature of this gravitational theory is that the divergence of the energy-momentum tensor is nonzero. As a first step in our study we reformulate the model in terms of an equivalent scalar-tensor theory, with two arbitrary potentials. By using the formalism of open thermodynamic systems, we interpret the energy balance equations in this gravitational theory from a thermodynamic point of view, as describing irreversible matter creation processes. The particle number creation rates, the creation pressure, and the entropy production rates are explicitly obtained as functions of the scalar field and its potentials, as well as of the matter Lagrangian. The temperature evolution laws of the newly created particles are also obtained. The cosmological implications of the model are briefly investigated, and it is shown that the late-time cosmic acceleration may be due to particle creation processes. Furthermore, it is also shown that due to the curvature--matter coupling, during the cosmological evolution a large amount of comoving entropy is also produced. |
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