id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0108076 | Gregory B. Cook | Gregory B. Cook | Corotating and irrotational binary black holes in quasi-circular orbits | 13 pages, no figures, revtex4; Content changed slightly to reflect
fact that regularized shift solutions do satisfy the isometry boundary
conditions | Phys.Rev. D65 (2002) 084003 | 10.1103/PhysRevD.65.084003 | null | gr-qc | null | A complete formalism for constructing initial data representing black-hole
binaries in quasi-equilibrium is developed. Radiation reaction prohibits, in
general, true equilibrium binary configurations. However, when the timescale
for orbital decay is much longer than the orbital period, a binary can be
considered to be in quasi-equilibrium. If each black hole is assumed to be in
quasi-equilibrium, then a complete set of boundary conditions for all initial
data variables can be developed. These boundary conditions are applied on the
apparent horizon of each black hole, and in fact force a specified surface to
be an apparent horizon. A global assumption of quasi-equilibrium is also used
to fix some of the freely specifiable pieces of the initial data and to
uniquely fix the asymptotic boundary conditions. This formalism should allow
for the construction of completely general quasi-equilibrium black hole binary
initial data.
| [
{
"created": "Thu, 30 Aug 2001 17:40:13 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Sep 2001 19:07:31 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Cook",
"Gregory B.",
""
]
] | A complete formalism for constructing initial data representing black-hole binaries in quasi-equilibrium is developed. Radiation reaction prohibits, in general, true equilibrium binary configurations. However, when the timescale for orbital decay is much longer than the orbital period, a binary can be considered to be in quasi-equilibrium. If each black hole is assumed to be in quasi-equilibrium, then a complete set of boundary conditions for all initial data variables can be developed. These boundary conditions are applied on the apparent horizon of each black hole, and in fact force a specified surface to be an apparent horizon. A global assumption of quasi-equilibrium is also used to fix some of the freely specifiable pieces of the initial data and to uniquely fix the asymptotic boundary conditions. This formalism should allow for the construction of completely general quasi-equilibrium black hole binary initial data. |
1301.5471 | Christian Boehmer | Christian G. Boehmer, Nicola Tamanini | A new approach to modifying theories of gravity | 9 pages, conservation equation discussion revised, Kasner type
solutions included | Foundations of Physics 43, 1478-1488 (2013) | 10.1007/s10701-013-9756-y | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new point of view for interpreting Newton's and Einstein's
theories of gravity. By taking inspiration from Continuum Mechanics and its
treatment of anisotropies, we formulate new gravitational actions for modified
theories of gravity. These models are simple and natural generalisations with
many interesting properties. Above all, their precise form can, in principle,
be determined experimentally.
| [
{
"created": "Wed, 23 Jan 2013 11:30:35 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Oct 2013 11:30:00 GMT",
"version": "v2"
}
] | 2015-10-09 | [
[
"Boehmer",
"Christian G.",
""
],
[
"Tamanini",
"Nicola",
""
]
] | We propose a new point of view for interpreting Newton's and Einstein's theories of gravity. By taking inspiration from Continuum Mechanics and its treatment of anisotropies, we formulate new gravitational actions for modified theories of gravity. These models are simple and natural generalisations with many interesting properties. Above all, their precise form can, in principle, be determined experimentally. |
0903.0661 | Stephen Minter | Stephen J. Minter, Kirk Wegter-McNelly, Raymond Y. Chiao | Do Mirrors for Gravitational Waves Exist? | 59 pages, 2 figures | null | 10.1016/j.physe.2009.06.056 | null | gr-qc cond-mat.supr-con | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Thin superconducting films are predicted to be highly reflective mirrors for
gravitational waves at microwave frequencies. The quantum mechanical
non-localizability of the negatively charged Cooper pairs, which is protected
from the localizing effect of decoherence by an energy gap, causes the pairs to
undergo non-picturable, non-geodesic motion in the presence of a gravitational
wave. This non-geodesic motion, which is accelerated motion through space,
leads to the existence of mass and charge supercurrents inside the
superconducting film. On the other hand, the decoherence-induced localizability
of the positively charged ions in the lattice causes them to undergo
picturable, geodesic motion as they are carried along with space in the
presence of the same gravitational wave. The resulting separation of charges
leads to a virtual plasma excitation within the film that enormously enhances
its interaction with the wave, relative to that of a neutral superfluid or any
normal matter. The existence of strong mass supercurrents within a
superconducting film in the presence of a gravitational wave, dubbed the
"Heisenberg-Coulomb effect," implies the specular reflection of a gravitational
microwave from a film whose thickness is much less than the London penetration
depth of the material, in close analogy with the electromagnetic case. The
argument is developed by allowing classical gravitational fields, which obey
Maxwell-like equations, to interact with quantum matter, which is described
using the BCS and Ginzburg-Landau theories of superconductivity, as well as a
collisionless plasma model. Several possible experimental tests of these ideas,
including mesoscopic ones, are presented alongside comments on the broader
theoretical implications of the central hypothesis.
| [
{
"created": "Wed, 4 Mar 2009 00:27:22 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Jun 2009 19:16:09 GMT",
"version": "v10"
},
{
"created": "Thu, 5 Mar 2009 23:47:14 GMT",
"version": "v2"
},
{
"created": "Mon, 16 Mar 2009 20:51:24 GMT",
"version": "v3"
},
{
"created": "Sun, 22 Mar 2009 16:50:04 GMT",
"version": "v4"
},
{
"created": "Mon, 23 Mar 2009 22:34:40 GMT",
"version": "v5"
},
{
"created": "Wed, 6 May 2009 19:57:23 GMT",
"version": "v6"
},
{
"created": "Tue, 2 Jun 2009 06:27:05 GMT",
"version": "v7"
},
{
"created": "Wed, 3 Jun 2009 04:34:22 GMT",
"version": "v8"
},
{
"created": "Tue, 9 Jun 2009 19:51:45 GMT",
"version": "v9"
}
] | 2015-05-13 | [
[
"Minter",
"Stephen J.",
""
],
[
"Wegter-McNelly",
"Kirk",
""
],
[
"Chiao",
"Raymond Y.",
""
]
] | Thin superconducting films are predicted to be highly reflective mirrors for gravitational waves at microwave frequencies. The quantum mechanical non-localizability of the negatively charged Cooper pairs, which is protected from the localizing effect of decoherence by an energy gap, causes the pairs to undergo non-picturable, non-geodesic motion in the presence of a gravitational wave. This non-geodesic motion, which is accelerated motion through space, leads to the existence of mass and charge supercurrents inside the superconducting film. On the other hand, the decoherence-induced localizability of the positively charged ions in the lattice causes them to undergo picturable, geodesic motion as they are carried along with space in the presence of the same gravitational wave. The resulting separation of charges leads to a virtual plasma excitation within the film that enormously enhances its interaction with the wave, relative to that of a neutral superfluid or any normal matter. The existence of strong mass supercurrents within a superconducting film in the presence of a gravitational wave, dubbed the "Heisenberg-Coulomb effect," implies the specular reflection of a gravitational microwave from a film whose thickness is much less than the London penetration depth of the material, in close analogy with the electromagnetic case. The argument is developed by allowing classical gravitational fields, which obey Maxwell-like equations, to interact with quantum matter, which is described using the BCS and Ginzburg-Landau theories of superconductivity, as well as a collisionless plasma model. Several possible experimental tests of these ideas, including mesoscopic ones, are presented alongside comments on the broader theoretical implications of the central hypothesis. |
1908.01312 | Vladimir Folomeev | Vladimir Dzhunushaliev, Vladimir Folomeev, Galia Nurtaeva, Sergei D.
Odintsov | Thick branes in higher-dimensional $f(R)$ gravity | 12 pages, 3 figures | Int. J. Geom. Meth. Mod. Phys. 17 (2020) no.03, 2050036 | 10.1142/S021988782050036X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the thick brane model within $f(R)\sim R^n$ modified gravity in
$D$-dimensional spacetimes with $D\geq 6$. The system under consideration
consists of two branes orthogonal to each other: the four-dimensional
Lorentzian brane and $(D-5)$-dimensional Euclidean one. It is numerically shown
that, for a given $D$, regular vacuum asymptotically anti-de Sitter solutions
exist only in the range $1<n<D/2$. Depending on the values of $n$ and boundary
conditions imposed on the Lorentzian brane, the solutions can pass or not pass
through a fixed point located on the Lorentzian brane, and also be
$Z_2$-symmetric or nonsymmetric. In the large-$D$ limit, we find approximate
analytic solutions. It is also shown that a test scalar field is trapped on the
Lorentzian brane at any $D$.
| [
{
"created": "Sun, 4 Aug 2019 10:29:48 GMT",
"version": "v1"
}
] | 2020-04-03 | [
[
"Dzhunushaliev",
"Vladimir",
""
],
[
"Folomeev",
"Vladimir",
""
],
[
"Nurtaeva",
"Galia",
""
],
[
"Odintsov",
"Sergei D.",
""
]
] | We study the thick brane model within $f(R)\sim R^n$ modified gravity in $D$-dimensional spacetimes with $D\geq 6$. The system under consideration consists of two branes orthogonal to each other: the four-dimensional Lorentzian brane and $(D-5)$-dimensional Euclidean one. It is numerically shown that, for a given $D$, regular vacuum asymptotically anti-de Sitter solutions exist only in the range $1<n<D/2$. Depending on the values of $n$ and boundary conditions imposed on the Lorentzian brane, the solutions can pass or not pass through a fixed point located on the Lorentzian brane, and also be $Z_2$-symmetric or nonsymmetric. In the large-$D$ limit, we find approximate analytic solutions. It is also shown that a test scalar field is trapped on the Lorentzian brane at any $D$. |
1201.5244 | David Keitel | David Keitel, Reinhard Prix, Maria Alessandra Papa, Maham Siddiqi | An F-statistic based multi-detector veto for detector artifacts in
continuous-wave gravitational wave data | 2 pages, 1 figure, to be published in Proceedings of Statistical
Challenges in Modern Astronomy V, Springer 2012 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Continuous gravitational waves (CW) are expected from spinning neutron stars
with non-axisymmetric deformations. A network of interferometric detectors
(LIGO, Virgo and GEO600) is looking for these signals. They are predicted to be
very weak and retrievable only by integration over long observation times. One
of the standard methods of CW data analysis is the multi-detector F-statistic.
In a typical search, the F-statistic is computed over a range in frequency,
spin-down and sky position, and the candidates with highest F values are kept
for further analysis. However, this detection statistic is susceptible to a
class of noise artifacts, strong monochromatic lines in a single detector. By
assuming an extended noise model - standard Gaussian noise plus single-detector
lines - we can use a Bayesian odds ratio to derive a generalized detection
statistic, the line veto (LV-) statistic. In the absence of lines, it behaves
similarly to the F-statistic, but it is more robust against line artifacts. In
the past, ad-hoc post-processing vetoes have been implemented in searches to
remove these artifacts. Here we provide a systematic framework to develop and
benchmark this class of vetoes. We present our results from testing this
LV-statistic on simulated data.
| [
{
"created": "Wed, 25 Jan 2012 12:05:33 GMT",
"version": "v1"
}
] | 2012-01-26 | [
[
"Keitel",
"David",
""
],
[
"Prix",
"Reinhard",
""
],
[
"Papa",
"Maria Alessandra",
""
],
[
"Siddiqi",
"Maham",
""
]
] | Continuous gravitational waves (CW) are expected from spinning neutron stars with non-axisymmetric deformations. A network of interferometric detectors (LIGO, Virgo and GEO600) is looking for these signals. They are predicted to be very weak and retrievable only by integration over long observation times. One of the standard methods of CW data analysis is the multi-detector F-statistic. In a typical search, the F-statistic is computed over a range in frequency, spin-down and sky position, and the candidates with highest F values are kept for further analysis. However, this detection statistic is susceptible to a class of noise artifacts, strong monochromatic lines in a single detector. By assuming an extended noise model - standard Gaussian noise plus single-detector lines - we can use a Bayesian odds ratio to derive a generalized detection statistic, the line veto (LV-) statistic. In the absence of lines, it behaves similarly to the F-statistic, but it is more robust against line artifacts. In the past, ad-hoc post-processing vetoes have been implemented in searches to remove these artifacts. Here we provide a systematic framework to develop and benchmark this class of vetoes. We present our results from testing this LV-statistic on simulated data. |
gr-qc/9712093 | Shin-ichi Nakariki | S. Nakariki, T. Masaki, K.Fukuma, T.Fukui, M.Mizouchi, T.Ohtani,
T.Tashiro | Interaction of massless Dirac field with a Poincar\'e gauge field | 10pages, RevTeX3.0 | Prog.Theor.Phys. 100 (1998) 179-190 | 10.1143/PTP.100.179 | null | gr-qc | null | In this paper we consider a model of Poincar\'e gauge theory (PGT) in which a
translational gauge field and a Lorentz gauge field are actually identified
with the Einstein's gravitational field and a pair of ``Yang-Mills'' field and
its partner, respectively.In this model we re-derive some special solutions and
take up one of them. The solution represents a ``Yang-Mills'' field without its
partner field and the Reissner-Nordstr\"om type spacetime, which are generated
by a PGT-gauge charge and its mass.It is main purpose of this paper to
investigate the interaction of massless Dirac fields with those fields. As a
result, we find an interesting fact that the left-handed massless Dirac fields
behave in the different manner from the right-handed ones. This can be
explained as to be caused by the direct interaction of Dirac fields with the
``Yang-Mills'' field. Accordingly, the phenomenon can not happen in the
behavior of the neutrino waves in ordinary Reissner-Nordstr\"om geometry. The
difference between left- and right-handed effects is calculated quantitatively,
considering the scattering problems of the massless Dirac fields by our
Reissner-Nordstr\"om type black-hole.
| [
{
"created": "Wed, 24 Dec 1997 06:35:12 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Nakariki",
"S.",
""
],
[
"Masaki",
"T.",
""
],
[
"Fukuma",
"K.",
""
],
[
"Fukui",
"T.",
""
],
[
"Mizouchi",
"M.",
""
],
[
"Ohtani",
"T.",
""
],
[
"Tashiro",
"T.",
""
]
] | In this paper we consider a model of Poincar\'e gauge theory (PGT) in which a translational gauge field and a Lorentz gauge field are actually identified with the Einstein's gravitational field and a pair of ``Yang-Mills'' field and its partner, respectively.In this model we re-derive some special solutions and take up one of them. The solution represents a ``Yang-Mills'' field without its partner field and the Reissner-Nordstr\"om type spacetime, which are generated by a PGT-gauge charge and its mass.It is main purpose of this paper to investigate the interaction of massless Dirac fields with those fields. As a result, we find an interesting fact that the left-handed massless Dirac fields behave in the different manner from the right-handed ones. This can be explained as to be caused by the direct interaction of Dirac fields with the ``Yang-Mills'' field. Accordingly, the phenomenon can not happen in the behavior of the neutrino waves in ordinary Reissner-Nordstr\"om geometry. The difference between left- and right-handed effects is calculated quantitatively, considering the scattering problems of the massless Dirac fields by our Reissner-Nordstr\"om type black-hole. |
0809.1933 | Yong-Wan Kim | Yun Soo Myung, Yong-Wan Kim, and Young-Jai Park | Quasinormal modes from potentials surrounding the charged dilaton black
hole | 19 pages, 8 figures | Eur.Phys.J.C58:617-625,2008 | 10.1140/epjc/s10052-008-0802-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We clarify the purely imaginary quasinormal frequencies of a massless scalar
perturbation on the 3D charged-dilaton black holes. This case is quite
interesting because the potential-step appears outside the event horizon
similar to the case of the electromagnetic perturbations on the large
Schwarzschild-AdS black holes. It turns out that the potential-step type
provides the purely imaginary quasinormal frequencies, while the
potential-barrier type gives the complex quasinormal modes.
| [
{
"created": "Thu, 11 Sep 2008 08:54:13 GMT",
"version": "v1"
}
] | 2008-12-18 | [
[
"Myung",
"Yun Soo",
""
],
[
"Kim",
"Yong-Wan",
""
],
[
"Park",
"Young-Jai",
""
]
] | We clarify the purely imaginary quasinormal frequencies of a massless scalar perturbation on the 3D charged-dilaton black holes. This case is quite interesting because the potential-step appears outside the event horizon similar to the case of the electromagnetic perturbations on the large Schwarzschild-AdS black holes. It turns out that the potential-step type provides the purely imaginary quasinormal frequencies, while the potential-barrier type gives the complex quasinormal modes. |
1212.6439 | Otakar Svitek | Otakar Svitek | Conformal infinity in Robinson-Trautman spacetimes with cosmological
constant | 4 pages, 2 figures, for ERE2011 Proceedings | AIP Conf. Proc. 1458: 531-534, 2012 | 10.1063/1.4734477 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/3.0/ | In past, the future asymptotic behavior (with respect to initial data on null
hypersurface) of Robinson-Trautman spacetime was examined and its past horizon
characterized. Therefore, only the investigation of conformal infinity is
missing from the picture. We would like to present some initial results
concerning conformal infinity when negative cosmological constant is present
motivated by the AdS/CFT correspondence.
| [
{
"created": "Fri, 28 Dec 2012 00:08:00 GMT",
"version": "v1"
}
] | 2013-01-01 | [
[
"Svitek",
"Otakar",
""
]
] | In past, the future asymptotic behavior (with respect to initial data on null hypersurface) of Robinson-Trautman spacetime was examined and its past horizon characterized. Therefore, only the investigation of conformal infinity is missing from the picture. We would like to present some initial results concerning conformal infinity when negative cosmological constant is present motivated by the AdS/CFT correspondence. |
gr-qc/0210054 | Nivaldo Agostinho Lemos | N. A. Lemos and G. A. Monerat | A Quantum Cosmological Model With Static and Dynamic Wormholes | LaTex file, 13 pages. To appear in General Relativity and Gravitation | Gen.Rel.Grav. 35 (2003) 423-436 | 10.1023/A:1022321916891 | null | gr-qc | null | Quantization is performed of a Friedmann-Robertson-Walker universe filled
with a conformally invariant scalar field and a perfect fluid with equation of
state $p=\alpha \rho$. A well-known discrete set of static quantum wormholes is
shown to exist for radiation ($\alpha =1/3$), and a novel continuous set is
found for cosmic strings ($\alpha = -1/3$), the latter states having throat
radii of any size. In both cases wave-packet solutions to the Wheeler-DeWitt
equation are obtained with all the properties of evolving quantum wormholes. In
the case of a radiation fluid, a detailed analysis of the quantum dynamics is
made in the context of the Bohm-de Broglie interpretation. It is shown that a
repulsive quantum force inversely proportional to the cube of the scale factor
prevents singularities in the quantum domain. For the states considered, there
are no particle horizons either.
| [
{
"created": "Thu, 17 Oct 2002 13:00:12 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Lemos",
"N. A.",
""
],
[
"Monerat",
"G. A.",
""
]
] | Quantization is performed of a Friedmann-Robertson-Walker universe filled with a conformally invariant scalar field and a perfect fluid with equation of state $p=\alpha \rho$. A well-known discrete set of static quantum wormholes is shown to exist for radiation ($\alpha =1/3$), and a novel continuous set is found for cosmic strings ($\alpha = -1/3$), the latter states having throat radii of any size. In both cases wave-packet solutions to the Wheeler-DeWitt equation are obtained with all the properties of evolving quantum wormholes. In the case of a radiation fluid, a detailed analysis of the quantum dynamics is made in the context of the Bohm-de Broglie interpretation. It is shown that a repulsive quantum force inversely proportional to the cube of the scale factor prevents singularities in the quantum domain. For the states considered, there are no particle horizons either. |
1212.1627 | Andronikos Paliathanasis | Andronikos Paliathanasis | Using Noether symmetries to specify f(R) gravity | 16 pages, no figures, Talk given at the 15th Conference on Recent
Developments in Gravity (NEB XV), 20-23 June 2012, Chania, Greece | J. Phys.: Conf. Ser. 453 (2013) 012009 | 10.1088/1742-6596/453/1/012009 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A detailed study of the modified gravity, f(R) models is performed, using
that the Noether point symmetries of these models are geometric symmetries of
the mini superspace of the theory. It is shown that the requirement that the
field equations admit Noether point symmetries selects definite models in a
self-consistent way. As an application in Cosmology we consider the Friedman
-Robertson-Walker spacetime and show that the only cosmological model which is
integrable via Noether point symmetries is the $(R^{b}-2\Lambda) ^{c}$ model,
which generalizes the Lambda Cosmology. Furthermore using the corresponding
Noether integrals we compute the analytic form of the main cosmological
functions.
| [
{
"created": "Fri, 7 Dec 2012 15:07:52 GMT",
"version": "v1"
}
] | 2015-01-05 | [
[
"Paliathanasis",
"Andronikos",
""
]
] | A detailed study of the modified gravity, f(R) models is performed, using that the Noether point symmetries of these models are geometric symmetries of the mini superspace of the theory. It is shown that the requirement that the field equations admit Noether point symmetries selects definite models in a self-consistent way. As an application in Cosmology we consider the Friedman -Robertson-Walker spacetime and show that the only cosmological model which is integrable via Noether point symmetries is the $(R^{b}-2\Lambda) ^{c}$ model, which generalizes the Lambda Cosmology. Furthermore using the corresponding Noether integrals we compute the analytic form of the main cosmological functions. |
2305.12611 | Jun-Jin Peng | Jun-Jin Peng, Yao Wang, Wei-Jie Guo | Conserved quantities for asymptotically AdS spacetimes in quadratic
curvature gravity in terms of a rank-4 tensor | 50 pages, no figures, accepted by PRD | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the conserved quantities associated to Killing isometries for
asymptotically AdS spacetimes within the framework of quadratic-curvature
gravity. By constructing a rank-4 tensor possessing the same index symmetries
as the ones of the Riemann tensor, we propose a 2-form potential resembling the
Noether one for quadratic-curvature gravity. Such a potential is compared with
the results via other methods existing in the literature to establish the
equivalence. Then this potential is adopted to define conserved quantities of
asymptotically AdS spacetimes. As applications, we explicitly compute the mass
of static spherically-symmetric spacetimes, as well as the mass and the angular
momentum for rotating spacetimes, such as the four(higher)-dimensional Kerr-AdS
black holes and black strings embedded in quadratic-curvature gravities.
Particularly, we emphasize the conserved charges of Einstein-Gauss-Bonnet, Weyl
and critical gravities, together with the ones for the asymptotically AdS
solutions satisfying vacuum Einstein field equations.
| [
{
"created": "Mon, 22 May 2023 00:32:55 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Jun 2023 23:52:27 GMT",
"version": "v2"
},
{
"created": "Wed, 25 Oct 2023 02:56:08 GMT",
"version": "v3"
}
] | 2023-10-26 | [
[
"Peng",
"Jun-Jin",
""
],
[
"Wang",
"Yao",
""
],
[
"Guo",
"Wei-Jie",
""
]
] | We investigate the conserved quantities associated to Killing isometries for asymptotically AdS spacetimes within the framework of quadratic-curvature gravity. By constructing a rank-4 tensor possessing the same index symmetries as the ones of the Riemann tensor, we propose a 2-form potential resembling the Noether one for quadratic-curvature gravity. Such a potential is compared with the results via other methods existing in the literature to establish the equivalence. Then this potential is adopted to define conserved quantities of asymptotically AdS spacetimes. As applications, we explicitly compute the mass of static spherically-symmetric spacetimes, as well as the mass and the angular momentum for rotating spacetimes, such as the four(higher)-dimensional Kerr-AdS black holes and black strings embedded in quadratic-curvature gravities. Particularly, we emphasize the conserved charges of Einstein-Gauss-Bonnet, Weyl and critical gravities, together with the ones for the asymptotically AdS solutions satisfying vacuum Einstein field equations. |
1801.04948 | Swagat Saurav Mishra | Swagat S. Mishra, Varun Sahni and Alexey V. Toporensky | Initial conditions for Inflation in an FRW Universe | 35 pages, 27 figures, matches the published version in PRD | Phys. Rev. D 98, 083538 (2018) | 10.1103/PhysRevD.98.083538 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the class of initial conditions which give rise to inflation. Our
analysis is carried out for several popular models including: Higgs inflation,
Starobinsky inflation, chaotic inflation, axion monodromy inflation and
non-canonical inflation. In each case we determine the set of initial
conditions which give rise to sufficient inflation, with at least $60$
e-foldings. A phase-space analysis has been performed for each of these models
and the effect of the initial inflationary energy scale on inflation has been
studied numerically. This paper discusses two scenarios of Higgs inflation: (i)
the Higgs is coupled to the scalar curvature, (ii) the Higgs Lagrangian
contains a non-canonical kinetic term. In both cases we find Higgs inflation to
be very robust since it can arise for a large class of initial conditions. One
of the central results of our analysis is that, for plateau-like potentials
associated with the Higgs and Starobinsky models, inflation can be realised
even for initial scalar field values which lie close to the minimum of the
potential. This dispels a misconception relating to plateau potentials
prevailing in the literature. We also find that inflation in all models is more
robust for larger values of the initial energy scale.
| [
{
"created": "Mon, 15 Jan 2018 19:02:33 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Nov 2018 10:05:07 GMT",
"version": "v2"
}
] | 2018-11-07 | [
[
"Mishra",
"Swagat S.",
""
],
[
"Sahni",
"Varun",
""
],
[
"Toporensky",
"Alexey V.",
""
]
] | We examine the class of initial conditions which give rise to inflation. Our analysis is carried out for several popular models including: Higgs inflation, Starobinsky inflation, chaotic inflation, axion monodromy inflation and non-canonical inflation. In each case we determine the set of initial conditions which give rise to sufficient inflation, with at least $60$ e-foldings. A phase-space analysis has been performed for each of these models and the effect of the initial inflationary energy scale on inflation has been studied numerically. This paper discusses two scenarios of Higgs inflation: (i) the Higgs is coupled to the scalar curvature, (ii) the Higgs Lagrangian contains a non-canonical kinetic term. In both cases we find Higgs inflation to be very robust since it can arise for a large class of initial conditions. One of the central results of our analysis is that, for plateau-like potentials associated with the Higgs and Starobinsky models, inflation can be realised even for initial scalar field values which lie close to the minimum of the potential. This dispels a misconception relating to plateau potentials prevailing in the literature. We also find that inflation in all models is more robust for larger values of the initial energy scale. |
gr-qc/9906110 | Jayashree Balakrishna | Jayashree Balakrishna | A Numerical Study of Boson Stars: Einstein Equations with a Matter
Source | 178 pages, 61 figures, Thesis submitted to Wahington Univ. St. Louis | null | null | Wugrav99-01T | gr-qc | null | The study of the properties and dynamics of self-gravitating bosonic objects
in Einstein gravity was conducted. We studied self-coupled boson stars and
determined the quasinormal mode (QNM) frequencies of stable boson stars in
spherical symmetry. The study was carried out in the standard Einstein theory
of General Relativity and in Brans-Dicke theory. We also studied the formation
of these objects in Brans-Dicke theory showing that they can form from the
self-gravitation of bosonic matter. We also studied the studied the possibility
of a bosonic halo surrounding galaxies.
After an extensive study in spherical symmetry we carried out numerical
studies of boson star dynamics in full 3+1 dimension. One focus of the 3D study
was on the validation of the numerical code constructed to solve Einstein
equations with matter sources. Boson Stars do not suffer from the surface
problems of neutron stars or the singularities of black holes. The code was
first tested with spherical perturbations and compared with the spherical
results. We determined the coordinate conditions needed to provide stable
evolutions. We then went on to study their behavior under non-spherical
perturbations. We reproduced the QNM frequencies of the stars, as determined by
perturbation studies carried out by other groups. The energy generated by the
perturbation was studied with different radiation indicators. We also observed
the collapse to black holes of unstable boson-star configurations. We simulated
the collision of two boson stars. This is of interest as the two body problem
is as yet unresolved in general relativity.
| [
{
"created": "Mon, 28 Jun 1999 17:05:15 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Balakrishna",
"Jayashree",
""
]
] | The study of the properties and dynamics of self-gravitating bosonic objects in Einstein gravity was conducted. We studied self-coupled boson stars and determined the quasinormal mode (QNM) frequencies of stable boson stars in spherical symmetry. The study was carried out in the standard Einstein theory of General Relativity and in Brans-Dicke theory. We also studied the formation of these objects in Brans-Dicke theory showing that they can form from the self-gravitation of bosonic matter. We also studied the studied the possibility of a bosonic halo surrounding galaxies. After an extensive study in spherical symmetry we carried out numerical studies of boson star dynamics in full 3+1 dimension. One focus of the 3D study was on the validation of the numerical code constructed to solve Einstein equations with matter sources. Boson Stars do not suffer from the surface problems of neutron stars or the singularities of black holes. The code was first tested with spherical perturbations and compared with the spherical results. We determined the coordinate conditions needed to provide stable evolutions. We then went on to study their behavior under non-spherical perturbations. We reproduced the QNM frequencies of the stars, as determined by perturbation studies carried out by other groups. The energy generated by the perturbation was studied with different radiation indicators. We also observed the collapse to black holes of unstable boson-star configurations. We simulated the collision of two boson stars. This is of interest as the two body problem is as yet unresolved in general relativity. |
2402.08039 | Katelyn Wagner | Katelyn J. Wagner and Richard O'Shaughnessy | Parameter Estimation for Low-Mass Eccentric Black Hole Binaries | null | null | null | LIGO-P2400032 | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | Recent studies have shown that orbital eccentricity may indicate dynamical
assembly as a formation mechanism for binary black holes. Eccentricity leaves a
distinct signature in gravitational wave signals and it may be measured if the
binary remains eccentric when it enters the LIGO band. Although eccentricity
has not yet been confidently detected, the possibility of detecting eccentric
binaries is becoming more likely with the improved sensitivity of gravitational
wave detectors such as LIGO, Virgo, and KAGRA. It is crucial to assess the
accuracy of current search pipelines in recovering eccentricity from
gravitational wave signals if it is present. In this study, we investigate the
ability of parameter estimation pipeline RIFT to recover eccentricity in the
non-spinning and aligned-spin cases for low mass binary black holes. We use
TaylorF2Ecc and TEOBResumS to inject sets of synthetic signals and test how
well RIFT accurately recovers key binary black hole parameters. Our findings
provide valuable insights into the capability of current parameter estimation
methods to detect and measure eccentricity in gravitational wave signals.
| [
{
"created": "Mon, 12 Feb 2024 20:13:37 GMT",
"version": "v1"
}
] | 2024-02-14 | [
[
"Wagner",
"Katelyn J.",
""
],
[
"O'Shaughnessy",
"Richard",
""
]
] | Recent studies have shown that orbital eccentricity may indicate dynamical assembly as a formation mechanism for binary black holes. Eccentricity leaves a distinct signature in gravitational wave signals and it may be measured if the binary remains eccentric when it enters the LIGO band. Although eccentricity has not yet been confidently detected, the possibility of detecting eccentric binaries is becoming more likely with the improved sensitivity of gravitational wave detectors such as LIGO, Virgo, and KAGRA. It is crucial to assess the accuracy of current search pipelines in recovering eccentricity from gravitational wave signals if it is present. In this study, we investigate the ability of parameter estimation pipeline RIFT to recover eccentricity in the non-spinning and aligned-spin cases for low mass binary black holes. We use TaylorF2Ecc and TEOBResumS to inject sets of synthetic signals and test how well RIFT accurately recovers key binary black hole parameters. Our findings provide valuable insights into the capability of current parameter estimation methods to detect and measure eccentricity in gravitational wave signals. |
gr-qc/9408015 | null | J. Gegenberg, G. Kunstatter and D. Louis-Martinez | Observables for Two-Dimensional Black Holes | 14 pages, latex | Phys. Rev. D 51, 1781 (1995) | 10.1103/PhysRevD.51.1781 | null | gr-qc | null | We consider the most general dilaton gravity theory in 1+1 dimensions. By
suitably parametrizing the metric and scalar field we find a simple expression
that relates the energy of a generic solution to the magnitude of the
corresponding Killing vector. In theories that admit black hole solutions, this
relationship leads directly to an expression for the entropy $S=2\pi \tau_0/G$,
where $\tau_0$ is the value of the scalar field (in this parametrization) at
the event horizon. This result agrees with the one obtained using the more
general method of Wald. Finally, we point out an intriguing connection between
the black hole entropy and the imaginary part of the ``phase" of the exact
Dirac quantum wave functionals for the theory.
| [
{
"created": "Thu, 11 Aug 1994 17:15:00 GMT",
"version": "v1"
}
] | 2016-08-24 | [
[
"Gegenberg",
"J.",
""
],
[
"Kunstatter",
"G.",
""
],
[
"Louis-Martinez",
"D.",
""
]
] | We consider the most general dilaton gravity theory in 1+1 dimensions. By suitably parametrizing the metric and scalar field we find a simple expression that relates the energy of a generic solution to the magnitude of the corresponding Killing vector. In theories that admit black hole solutions, this relationship leads directly to an expression for the entropy $S=2\pi \tau_0/G$, where $\tau_0$ is the value of the scalar field (in this parametrization) at the event horizon. This result agrees with the one obtained using the more general method of Wald. Finally, we point out an intriguing connection between the black hole entropy and the imaginary part of the ``phase" of the exact Dirac quantum wave functionals for the theory. |
gr-qc/0004035 | C. L. B. Correia da Silva | Cristovao Correia da Silva, and Ruth M. Williams | Wormholes in Simplicial Minisuperspace | 33 pages and 15 figures. Submitted to Classical and Quantum Gravity | null | null | null | gr-qc | null | Using simplicial minisuperspace techniques we obtain a wormhole
configuration, capable of modelling both a throat between two equal Euclidean
and Lorentzian universes. Computing the wavefunction associated to such
configuration we conclude that for Planck-size Euclidean wormholes there is a
prediction of a finite non-vanishing radius of their throat, even in the
absence of matter. The wavefunction associated to their Lorentzian counterparts
predicts the growth of the wormhole's throat as the two Lorentzian universes
expand.
| [
{
"created": "Wed, 12 Apr 2000 16:23:14 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"da Silva",
"Cristovao Correia",
""
],
[
"Williams",
"Ruth M.",
""
]
] | Using simplicial minisuperspace techniques we obtain a wormhole configuration, capable of modelling both a throat between two equal Euclidean and Lorentzian universes. Computing the wavefunction associated to such configuration we conclude that for Planck-size Euclidean wormholes there is a prediction of a finite non-vanishing radius of their throat, even in the absence of matter. The wavefunction associated to their Lorentzian counterparts predicts the growth of the wormhole's throat as the two Lorentzian universes expand. |
0707.4327 | Tania Regimbau | T. Regimbau and B. Chauvineau | Stochastic background from extra-galactic double neutron stars | 13 pages, 7 figures - proceeding of a talk given at the 11th GWDAW,
to appear in CQG | Class.Quant.Grav.24:S627-S638,2007 | 10.1088/0264-9381/24/19/S25 | null | gr-qc astro-ph | null | We present Monte Carlo simulations of the extra galactic population of
inspiralling double neutron stars, and estimate its contribution to the
astrophysical gravitational wave background, in the frequency range of ground
based interferometers, corresponding to the last thousand seconds before the
last stable orbit when more than 96 percent of the signal is released. We show
that sources at redshift z>0.5 contribute to a truly continuous background
which may be detected by correlating third generation interferometers.
| [
{
"created": "Mon, 30 Jul 2007 01:09:39 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Regimbau",
"T.",
""
],
[
"Chauvineau",
"B.",
""
]
] | We present Monte Carlo simulations of the extra galactic population of inspiralling double neutron stars, and estimate its contribution to the astrophysical gravitational wave background, in the frequency range of ground based interferometers, corresponding to the last thousand seconds before the last stable orbit when more than 96 percent of the signal is released. We show that sources at redshift z>0.5 contribute to a truly continuous background which may be detected by correlating third generation interferometers. |
1101.4997 | Kent Yagi | Kent Yagi, Norihiro Tanahashi and Takahiro Tanaka | Probing the size of extra dimension with gravitational wave astronomy | 19 pages, 10 figures. Published in PRD, typos corrected, references
and footnotes added | Phys.Rev.D83:084036,2011 | 10.1103/PhysRevD.83.084036 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Randall-Sundrum II (RS-II) braneworld model, it has been conjectured
according to the AdS/CFT correspondence that brane-localized black hole (BH)
larger than the bulk AdS curvature scale $\ell$ cannot be static, and it is
dual to a four dimensional BH emitting the Hawking radiation through some
quantum fields. In this scenario, the number of the quantum field species is so
large that this radiation changes the orbital evolution of a BH binary. We
derived the correction to the gravitational waveform phase due to this effect
and estimated the upper bounds on $\ell$ by performing Fisher analyses. We
found that DECIGO/BBO can put a stronger constraint than the current table-top
result by detecting gravitational waves from small mass BH/BH and BH/neutron
star (NS) binaries. Furthermore, DECIGO/BBO is expected to detect 10$^5$ BH/NS
binaries per year. Taking this advantage, we found that DECIGO/BBO can actually
measure $\ell$ down to $\ell=0.33 \mu$m for 5 year observation if we know that
binaries are circular a priori. This is about 40 times smaller than the upper
bound obtained from the table-top experiment. On the other hand, when we take
eccentricities into binary parameters, the detection limit weakens to $\ell=1.5
\mu$m due to strong degeneracies between $\ell$ and eccentricities. We also
derived the upper bound on $\ell$ from the expected detection number of extreme
mass ratio inspirals (EMRIs) with LISA and BH/NS binaries with DECIGO/BBO,
extending the discussion made recently by McWilliams. We found that these less
robust constraints are weaker than the ones from phase differences.
| [
{
"created": "Wed, 26 Jan 2011 07:30:22 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Dec 2011 01:52:56 GMT",
"version": "v2"
}
] | 2011-12-30 | [
[
"Yagi",
"Kent",
""
],
[
"Tanahashi",
"Norihiro",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | In Randall-Sundrum II (RS-II) braneworld model, it has been conjectured according to the AdS/CFT correspondence that brane-localized black hole (BH) larger than the bulk AdS curvature scale $\ell$ cannot be static, and it is dual to a four dimensional BH emitting the Hawking radiation through some quantum fields. In this scenario, the number of the quantum field species is so large that this radiation changes the orbital evolution of a BH binary. We derived the correction to the gravitational waveform phase due to this effect and estimated the upper bounds on $\ell$ by performing Fisher analyses. We found that DECIGO/BBO can put a stronger constraint than the current table-top result by detecting gravitational waves from small mass BH/BH and BH/neutron star (NS) binaries. Furthermore, DECIGO/BBO is expected to detect 10$^5$ BH/NS binaries per year. Taking this advantage, we found that DECIGO/BBO can actually measure $\ell$ down to $\ell=0.33 \mu$m for 5 year observation if we know that binaries are circular a priori. This is about 40 times smaller than the upper bound obtained from the table-top experiment. On the other hand, when we take eccentricities into binary parameters, the detection limit weakens to $\ell=1.5 \mu$m due to strong degeneracies between $\ell$ and eccentricities. We also derived the upper bound on $\ell$ from the expected detection number of extreme mass ratio inspirals (EMRIs) with LISA and BH/NS binaries with DECIGO/BBO, extending the discussion made recently by McWilliams. We found that these less robust constraints are weaker than the ones from phase differences. |
1610.05454 | Zhaoyi Xu | Zhaoyi Xu, Xian Hou, Jiancheng Wang and Yi Liao | Perfect fluid dark matter influence on thermodynamics and phase
transition for a Reissner-Nordstrom-anti-de Sitter black hole | 12 pages, 0 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on Reissner-Nordstrom-anti-de Sitter(RN-AdS) black hole surrounded by
perfect fluid dark matter, we study the thermodynamics and phase transition by
extending the phase space defined by the charge square $Q^{2}$ and the
conjugate quantity $\psi$, where $\psi$ is a function of horizon radius. The
first law of thermodynamics and the equation of state are derived in the form
$Q^{2}=Q^{2}(T,\psi)$. By investigating the critical behaviour of perfect fluid
dark matter around Reissner-Nordstrom-anti-de Sitter black hole, we find that
these thermodynamics system are similar to Van der Waals system, and can be
explained by mean field theory. We also explore the Ruppeiner thermodynamic
geometry feature and their connection with microscopic structure. We find that
in extended phase space there existence singularity points of Ruppeiner
curvature and it's could explained as phase transitions.
| [
{
"created": "Tue, 18 Oct 2016 07:00:28 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Nov 2017 07:10:39 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Jun 2018 02:01:08 GMT",
"version": "v3"
}
] | 2018-06-18 | [
[
"Xu",
"Zhaoyi",
""
],
[
"Hou",
"Xian",
""
],
[
"Wang",
"Jiancheng",
""
],
[
"Liao",
"Yi",
""
]
] | Based on Reissner-Nordstrom-anti-de Sitter(RN-AdS) black hole surrounded by perfect fluid dark matter, we study the thermodynamics and phase transition by extending the phase space defined by the charge square $Q^{2}$ and the conjugate quantity $\psi$, where $\psi$ is a function of horizon radius. The first law of thermodynamics and the equation of state are derived in the form $Q^{2}=Q^{2}(T,\psi)$. By investigating the critical behaviour of perfect fluid dark matter around Reissner-Nordstrom-anti-de Sitter black hole, we find that these thermodynamics system are similar to Van der Waals system, and can be explained by mean field theory. We also explore the Ruppeiner thermodynamic geometry feature and their connection with microscopic structure. We find that in extended phase space there existence singularity points of Ruppeiner curvature and it's could explained as phase transitions. |
1209.6029 | Bijan Saha Dr. | Bijan Saha | Bianchi type-VI anisotropic dark energy model with varying EoS parameter | 11 pages, 7 figures | Int. J. Theor. Phys., 52 (2013) 3646 - 3657 | 10.1007/s10773-013-1670-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the scope of an anisotropic Bianchi type-VI cosmological model we have
studied the evolution of the universe filled with perfect fluid and dark
energy. To get the deterministic model of Universe, we assume that the shear
scalar $(\sigma)$ in the model is proportional to expansion scalar
$(\vartheta)$. This assumption allows only isotropic distribution of fluid.
Exact solution to the corresponding equations are obtained. The EoS parameter
for dark energy as well as deceleration parameter is found to be the time
varying functions. Using the observational data qualitative picture of the
evolution of the universe corresponding to different of its stages is given.
The stability of the solutions obtained is also studied.
| [
{
"created": "Wed, 26 Sep 2012 18:51:43 GMT",
"version": "v1"
}
] | 2015-05-01 | [
[
"Saha",
"Bijan",
""
]
] | Within the scope of an anisotropic Bianchi type-VI cosmological model we have studied the evolution of the universe filled with perfect fluid and dark energy. To get the deterministic model of Universe, we assume that the shear scalar $(\sigma)$ in the model is proportional to expansion scalar $(\vartheta)$. This assumption allows only isotropic distribution of fluid. Exact solution to the corresponding equations are obtained. The EoS parameter for dark energy as well as deceleration parameter is found to be the time varying functions. Using the observational data qualitative picture of the evolution of the universe corresponding to different of its stages is given. The stability of the solutions obtained is also studied. |
1807.02163 | Diego S\'aez-Chill\'on G\'omez | Sergei D. Odintsov, Diego Saez-Chillon Gomez and German S. Sharov | Testing logarithmic corrections on $R^2$-exponential gravity by
observational data | 18 pages, 4 figures, analysis extended, version accepted for
publication in PRD | Phys. Rev. D 99, 024003 (2019) | 10.1103/PhysRevD.99.024003 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is devoted to the analysis of a class of $F(R)$ gravity, where
additional logarithmic corrections are assumed. The gravitational action
includes an exponential term and a $R^2$ inflationary term, both with
logarithmic corrections. This model can unify an early time inflationary era
and also the late time acceleration of the universe expansion. This model is
deeply analysed, confronting with recent observational data coming from the
largest Pantheon Type Ia supernovae sample, the latest measurements of the
Hubble parameter $H(z)$, manifestations of Baryon Acoustic Oscillations and
Cosmic Microwave Background radiation. The viability of the model is studied
and the corresponding constraints on the free parameters are obtained, leading
to an statistical analysis in comparison to $\Lambda$CDM model. The
inflationary era is also analysed within this model and its compatibility with
the latest observational data for the spectral index of primordial curvature
perturbations and the scalar-to-tensor ratio. Finally, possible corrections on
the Newton's law and constraints due to primordial nucleosynthesis are
analysed.
| [
{
"created": "Thu, 5 Jul 2018 19:39:38 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Dec 2018 11:43:11 GMT",
"version": "v2"
}
] | 2019-01-09 | [
[
"Odintsov",
"Sergei D.",
""
],
[
"Gomez",
"Diego Saez-Chillon",
""
],
[
"Sharov",
"German S.",
""
]
] | This paper is devoted to the analysis of a class of $F(R)$ gravity, where additional logarithmic corrections are assumed. The gravitational action includes an exponential term and a $R^2$ inflationary term, both with logarithmic corrections. This model can unify an early time inflationary era and also the late time acceleration of the universe expansion. This model is deeply analysed, confronting with recent observational data coming from the largest Pantheon Type Ia supernovae sample, the latest measurements of the Hubble parameter $H(z)$, manifestations of Baryon Acoustic Oscillations and Cosmic Microwave Background radiation. The viability of the model is studied and the corresponding constraints on the free parameters are obtained, leading to an statistical analysis in comparison to $\Lambda$CDM model. The inflationary era is also analysed within this model and its compatibility with the latest observational data for the spectral index of primordial curvature perturbations and the scalar-to-tensor ratio. Finally, possible corrections on the Newton's law and constraints due to primordial nucleosynthesis are analysed. |
1310.6915 | S. I. Kruglov | S. I. Kruglov | Modified arctan-gravity model mimicking a cosmological constant | 8 pages, 8 figures, minor corrections, journal version | Phys. Rev. D 89, 064004 (2014) | 10.1103/PhysRevD.89.064004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A novel theory of $F(R)$ gravity with the Lagrangian density ${\cal
L}=[R-(b/\beta)\arctan\left(\beta R\right)]/(2\kappa^2)$ is analyzed. Constant
curvature solutions of the model are found, and the potential of the scalar
field and the mass of a scalar degree of freedom in Einstein's frame are
derived. The cosmological parameters of the model are calculated, which are in
agreement with the PLANCK data. Critical points for the de Sitter phase and the
matter dominated epoch of autonomous equations are obtained and studied.
| [
{
"created": "Thu, 24 Oct 2013 17:57:31 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Jan 2014 21:29:09 GMT",
"version": "v2"
},
{
"created": "Thu, 6 Mar 2014 16:22:01 GMT",
"version": "v3"
}
] | 2014-03-07 | [
[
"Kruglov",
"S. I.",
""
]
] | A novel theory of $F(R)$ gravity with the Lagrangian density ${\cal L}=[R-(b/\beta)\arctan\left(\beta R\right)]/(2\kappa^2)$ is analyzed. Constant curvature solutions of the model are found, and the potential of the scalar field and the mass of a scalar degree of freedom in Einstein's frame are derived. The cosmological parameters of the model are calculated, which are in agreement with the PLANCK data. Critical points for the de Sitter phase and the matter dominated epoch of autonomous equations are obtained and studied. |
1109.4927 | Frank C Eckert | Bianca Dittrich, Frank C. Eckert, Mercedes Martin-Benito | Coarse graining methods for spin net and spin foam models | 39 pages, 13 figures, 1 table | New J. Phys. 14 (2012) 035008 | 10.1088/1367-2630/14/3/035008 | null | gr-qc cond-mat.str-el hep-lat quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We undertake first steps in making a class of discrete models of quantum
gravity, spin foams, accessible to a large scale analysis by numerical and
computational methods. In particular, we apply Migdal-Kadanoff and Tensor
Network Renormalization schemes to spin net and spin foam models based on
finite Abelian groups and introduce `cutoff models' to probe the fate of gauge
symmetries under various such approximated renormalization group flows. For the
Tensor Network Renormalization analysis, a new Gauss constraint preserving
algorithm is introduced to improve numerical stability and aid physical
interpretation. We also describe the fixed point structure and establish an
equivalence of certain models.
| [
{
"created": "Thu, 22 Sep 2011 19:44:50 GMT",
"version": "v1"
}
] | 2015-10-19 | [
[
"Dittrich",
"Bianca",
""
],
[
"Eckert",
"Frank C.",
""
],
[
"Martin-Benito",
"Mercedes",
""
]
] | We undertake first steps in making a class of discrete models of quantum gravity, spin foams, accessible to a large scale analysis by numerical and computational methods. In particular, we apply Migdal-Kadanoff and Tensor Network Renormalization schemes to spin net and spin foam models based on finite Abelian groups and introduce `cutoff models' to probe the fate of gauge symmetries under various such approximated renormalization group flows. For the Tensor Network Renormalization analysis, a new Gauss constraint preserving algorithm is introduced to improve numerical stability and aid physical interpretation. We also describe the fixed point structure and establish an equivalence of certain models. |
1109.2779 | Jorge Paramos | O. Bertolami, F. Francisco, P. J. S. Gil, J. P\'aramos | Probing the Flyby Anomaly with the Galileo Constellation | 5 pages, 1 figure, 4 tables. To appear in the Proceedings of the "3rd
International Colloquium - Scientific and Fundamental Aspects of the Galileo
Programme", 31 August - 2 September 2011, Copenhagen, Denmark | null | null | null | gr-qc physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the last few years, the so-called flyby anomaly has been widely discussed,
but remains still an illusive topic. This is due to the harsh conditions
experienced during an Earth flyby as well as due to the limited data available.
In this work, we assess the possibility of confirming and characterizing this
anomaly by resorting to the scientific capabilities of the future Galileo
constellation.
| [
{
"created": "Tue, 13 Sep 2011 13:21:46 GMT",
"version": "v1"
}
] | 2011-09-14 | [
[
"Bertolami",
"O.",
""
],
[
"Francisco",
"F.",
""
],
[
"Gil",
"P. J. S.",
""
],
[
"Páramos",
"J.",
""
]
] | In the last few years, the so-called flyby anomaly has been widely discussed, but remains still an illusive topic. This is due to the harsh conditions experienced during an Earth flyby as well as due to the limited data available. In this work, we assess the possibility of confirming and characterizing this anomaly by resorting to the scientific capabilities of the future Galileo constellation. |
2001.11736 | Alessandro Nagar | Danilo Chiaramello and Alessandro Nagar | A faithful analytical effective one body waveform model for
spin-aligned, moderately eccentric, coalescing black hole binaries | 6 pages, 5 figures. This version (v5) matches published version | null | 10.1103/PhysRevD.101.101501 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new effective-one-body (EOB) model for eccentric binary
coalescences. The model stems from the state-of-the-art model TEOBResumS$\_$SM
for circularized coalescing black-hole binaries, that is modified to explicitly
incorporate eccentricity effects both in the radiation reaction and in the
waveform. Using Regge-Wheeler-Zerilli type calculations of the gravitational
wave losses as benchmarks, we find that a rather accurate ($\sim 1\%$)
expression for the radiation reaction along mildly eccentric orbits ($e \sim
0.3$) is given by dressing the current, EOB-resummed, circularized angular
momentum flux, with a leading-order (Newtonian-like) prefactor valid along
general orbits. An analogous approach is implemented for the waveform
multipoles. The model is then completed by the usual merger-ringdown part
informed by circularized numerical relativity (NR) simulations. The model is
validated against the 22, publicly available, NR simulations calculated by the
Simulating eXtreme Spacetime (SXS) collaboration, with mild eccentricities,
mass ratios between 1 and 3 and up to rather large dimensionless spin values
($\pm 0.7$). The maximum maximum EOB/NR unfaithfulness, calculated with
Advanced LIGO noise, is at most of order $3\%$. The analytical framework
presented here should be seen as a promising starting point for developing
highly-faithful waveform templates driven by eccentric dynamics for present,
and possibly future, gravitational wave detectors.
| [
{
"created": "Fri, 31 Jan 2020 09:41:14 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Feb 2020 12:01:22 GMT",
"version": "v2"
},
{
"created": "Wed, 26 Feb 2020 09:41:43 GMT",
"version": "v3"
},
{
"created": "Mon, 16 Mar 2020 13:29:26 GMT",
"version": "v4"
},
{
"created": "Wed, 28 Oct 2020 08:18:25 GMT",
"version": "v5"
}
] | 2020-10-29 | [
[
"Chiaramello",
"Danilo",
""
],
[
"Nagar",
"Alessandro",
""
]
] | We present a new effective-one-body (EOB) model for eccentric binary coalescences. The model stems from the state-of-the-art model TEOBResumS$\_$SM for circularized coalescing black-hole binaries, that is modified to explicitly incorporate eccentricity effects both in the radiation reaction and in the waveform. Using Regge-Wheeler-Zerilli type calculations of the gravitational wave losses as benchmarks, we find that a rather accurate ($\sim 1\%$) expression for the radiation reaction along mildly eccentric orbits ($e \sim 0.3$) is given by dressing the current, EOB-resummed, circularized angular momentum flux, with a leading-order (Newtonian-like) prefactor valid along general orbits. An analogous approach is implemented for the waveform multipoles. The model is then completed by the usual merger-ringdown part informed by circularized numerical relativity (NR) simulations. The model is validated against the 22, publicly available, NR simulations calculated by the Simulating eXtreme Spacetime (SXS) collaboration, with mild eccentricities, mass ratios between 1 and 3 and up to rather large dimensionless spin values ($\pm 0.7$). The maximum maximum EOB/NR unfaithfulness, calculated with Advanced LIGO noise, is at most of order $3\%$. The analytical framework presented here should be seen as a promising starting point for developing highly-faithful waveform templates driven by eccentric dynamics for present, and possibly future, gravitational wave detectors. |
2212.10419 | Genly Le\'on | Genly Leon (Catolica del Norte U. and DUT, Durban), Saikat Chakraborty
(Naresuan U. and North West State Tech. U.), Sayantan Ghosh (Birla Inst.
Tech. Sci.), Raja Solanki (Birla Inst. Tech. Sci.), P.K. Sahoo (Birla Inst.
Tech. Sci.), Esteban Gonz\'alez (Chile U., Santiago) | Scalar field evolution at background and perturbation levels for a broad
class of potentials | 79 pages, 16 compound figures. Major revision. Discussion improved.
References added | Fortschr. Phys. 2023, 2300006 | 10.1002/prop.202300006 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate a non-interacting scalar field cosmology with
an arbitrary potential using the $f$-deviser method that relies on the
differentiability properties of the potential. Using this alternative
mathematical approach, we present a unified dynamical system analysis at a
scalar field's background and perturbation levels with arbitrary potentials.
For illustration, we consider a monomial and double exponential potential.
These two classes of potentials comprise the asymptotic behaviour of several
classes of scalar field potentials, and, therefore, they provide the skeleton
for the typical behaviour of arbitrary potentials. Moreover, we analyse the
linear cosmological perturbations in the matterless case by considering three
scalar perturbations: the evolution of the Bardeen potentials, the comoving
curvature perturbation, the so-called Sasaki-Mukhanov variable, or the scalar
field perturbation in uniform curvature gauge. Finally, an exhaustive dynamical
system analysis for each scalar perturbation is presented, including the
evolution of Bardeen potentials in the presence of matter.
| [
{
"created": "Tue, 20 Dec 2022 16:54:49 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Dec 2022 00:01:40 GMT",
"version": "v2"
},
{
"created": "Thu, 18 May 2023 21:52:46 GMT",
"version": "v3"
}
] | 2023-10-10 | [
[
"Leon",
"Genly",
"",
"Catolica del Norte U. and DUT, Durban"
],
[
"Chakraborty",
"Saikat",
"",
"Naresuan U. and North West State Tech. U."
],
[
"Ghosh",
"Sayantan",
"",
"Birla Inst.\n Tech. Sci."
],
[
"Solanki",
"Raja",
"",
"Birla Inst. Tech. Sci."
],
[
"Sahoo",
"P. K.",
"",
"Birla Inst.\n Tech. Sci."
],
[
"González",
"Esteban",
"",
"Chile U., Santiago"
]
] | In this paper, we investigate a non-interacting scalar field cosmology with an arbitrary potential using the $f$-deviser method that relies on the differentiability properties of the potential. Using this alternative mathematical approach, we present a unified dynamical system analysis at a scalar field's background and perturbation levels with arbitrary potentials. For illustration, we consider a monomial and double exponential potential. These two classes of potentials comprise the asymptotic behaviour of several classes of scalar field potentials, and, therefore, they provide the skeleton for the typical behaviour of arbitrary potentials. Moreover, we analyse the linear cosmological perturbations in the matterless case by considering three scalar perturbations: the evolution of the Bardeen potentials, the comoving curvature perturbation, the so-called Sasaki-Mukhanov variable, or the scalar field perturbation in uniform curvature gauge. Finally, an exhaustive dynamical system analysis for each scalar perturbation is presented, including the evolution of Bardeen potentials in the presence of matter. |
2210.01828 | Swagat Saurav Mishra | Yuri Shtanov, Varun Sahni, Swagat S. Mishra | Tabletop potentials for inflation from $f(R)$ gravity | 35 pages, 11 figures, revised version, some clarifications and
additional references, matches published version in JCAP | null | 10.1088/1475-7516/2023/03/023 | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | We show that a large class of modified gravity theories (MOG) with the
Jordan-frame Lagrangian $f(R)$ translate into scalar-field (scalaron) models
with hilltop potentials in the Einstein frame. (A rare exception to this rule
is provided by the Starobinsky model for which the corresponding scalaron
potential is plateau-like for $\phi > 0$.) We find that MOG models featuring
two distinct mass scales lead to scalaron potentials that have a flattened
hilltop, or tabletop. Inflationary evolution in tabletop models agrees very
well with CMB observations. Tabletop potentials therefore provide a new and
compelling class of MOG-based inflationary models. By contrast, MOG models with
a single mass scale generally correspond to steep hilltop potentials and fail
to reproduce the CMB power spectrum. Inflationary evolution in hilltop/tabletop
models can proceed in two alternative directions: towards the stable point at
small $R$ describing the observable universe, or towards the asymptotic region
at large $R$. The MOG models which we examine have several new properties
including the fact that gravity can become asymptotically vanishing, with
$G_{\rm eff} \to 0$, at infinite or large finite values of the scalar curvature
$R$. A universe evolving towards the asymptotically vanishing gravity region at
large $R$ will either run into a 'Big-Rip' singularity, or inflate eternally.
| [
{
"created": "Tue, 4 Oct 2022 18:01:02 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Oct 2022 13:25:19 GMT",
"version": "v2"
},
{
"created": "Tue, 4 Apr 2023 11:40:30 GMT",
"version": "v3"
}
] | 2023-04-05 | [
[
"Shtanov",
"Yuri",
""
],
[
"Sahni",
"Varun",
""
],
[
"Mishra",
"Swagat S.",
""
]
] | We show that a large class of modified gravity theories (MOG) with the Jordan-frame Lagrangian $f(R)$ translate into scalar-field (scalaron) models with hilltop potentials in the Einstein frame. (A rare exception to this rule is provided by the Starobinsky model for which the corresponding scalaron potential is plateau-like for $\phi > 0$.) We find that MOG models featuring two distinct mass scales lead to scalaron potentials that have a flattened hilltop, or tabletop. Inflationary evolution in tabletop models agrees very well with CMB observations. Tabletop potentials therefore provide a new and compelling class of MOG-based inflationary models. By contrast, MOG models with a single mass scale generally correspond to steep hilltop potentials and fail to reproduce the CMB power spectrum. Inflationary evolution in hilltop/tabletop models can proceed in two alternative directions: towards the stable point at small $R$ describing the observable universe, or towards the asymptotic region at large $R$. The MOG models which we examine have several new properties including the fact that gravity can become asymptotically vanishing, with $G_{\rm eff} \to 0$, at infinite or large finite values of the scalar curvature $R$. A universe evolving towards the asymptotically vanishing gravity region at large $R$ will either run into a 'Big-Rip' singularity, or inflate eternally. |
2004.13519 | Sushant Ghosh Prof | Sushant G. Ghosh and Sunil D. Maharaj | Noncommutative inspired black holes in regularised 4D
Einstein-Gauss-Bonnet theory | 10 pages, 4 figures, minor changes, Accepted in Phys. Dark Univ | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Low energy limits of string theory indicated that the standard gravity action
should be modified to include higher-order curvature terms, in the form of
dimensionally continued Gauss-Bonnet densities. If one includes only quadratic
curvature terms then the resulting theory is Einstein-Gauss-Bonnet (EGB)
gravity valid only in $D>4$ dimensions. Recently there has been a surge of
interest in regularizing, a $ D \to 4 $ limit, of EGB gravity, and the
resulting regularized $4D$ EGB gravities have nontrivial gravitational
dynamics. We obtain a static spherically symmetric noncommutative (NC) geometry
inspired black hole solution with Gaussian mass distribution as a source in the
regularized $4D$ EGB and also analyze their properties. The metric of the NC
inspired $4D$ EGB black hole smoothly interpolates between a de Sitter core
around the origin and $4D$ EGB metric as $r/\sqrt{\theta} \to \infty$. Owing to
the NC and GB term corrected black hole, the thermodynamic quantities have also
been altered. The phase transitions for the local thermodynamic stability, in
the theory, is outlined by a discontinuity of specific heat $C_{+}$ at a
critical radius $r_+=r_C$, and $C_{+}$ changes from infinitely negative to
infinitely positive and then down to a finite positive for the smaller $r_+$.
The thermal evaporation process leads to a thermodynamic stable extremal black
hole with vanishing temperature.
| [
{
"created": "Tue, 28 Apr 2020 14:16:50 GMT",
"version": "v1"
},
{
"created": "Fri, 1 May 2020 18:25:56 GMT",
"version": "v2"
},
{
"created": "Wed, 17 Feb 2021 11:06:07 GMT",
"version": "v3"
}
] | 2021-02-18 | [
[
"Ghosh",
"Sushant G.",
""
],
[
"Maharaj",
"Sunil D.",
""
]
] | Low energy limits of string theory indicated that the standard gravity action should be modified to include higher-order curvature terms, in the form of dimensionally continued Gauss-Bonnet densities. If one includes only quadratic curvature terms then the resulting theory is Einstein-Gauss-Bonnet (EGB) gravity valid only in $D>4$ dimensions. Recently there has been a surge of interest in regularizing, a $ D \to 4 $ limit, of EGB gravity, and the resulting regularized $4D$ EGB gravities have nontrivial gravitational dynamics. We obtain a static spherically symmetric noncommutative (NC) geometry inspired black hole solution with Gaussian mass distribution as a source in the regularized $4D$ EGB and also analyze their properties. The metric of the NC inspired $4D$ EGB black hole smoothly interpolates between a de Sitter core around the origin and $4D$ EGB metric as $r/\sqrt{\theta} \to \infty$. Owing to the NC and GB term corrected black hole, the thermodynamic quantities have also been altered. The phase transitions for the local thermodynamic stability, in the theory, is outlined by a discontinuity of specific heat $C_{+}$ at a critical radius $r_+=r_C$, and $C_{+}$ changes from infinitely negative to infinitely positive and then down to a finite positive for the smaller $r_+$. The thermal evaporation process leads to a thermodynamic stable extremal black hole with vanishing temperature. |
2102.12487 | Alexander C. Jenkins | Alexander C. Jenkins and Mairi Sakellariadou | Nonlinear gravitational-wave memory from cusps and kinks on cosmic
strings | 29 pages, 9 figures, version published in CQG | Class. Quantum Grav. 38 (2021) 165004 | 10.1088/1361-6382/ac1084 | KCL-PH-TH/2021-04, CERN-TH-2021-016 | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The nonlinear memory effect is a fascinating prediction of general relativity
(GR), in which oscillatory gravitational-wave (GW) signals are generically
accompanied by a monotonically-increasing strain which persists in the detector
long after the signal has passed. This effect presents a unique opportunity to
test GR in the dynamical and nonlinear regime. In this article we calculate the
nonlinear memory signal associated with GW bursts from cusps and kinks on
cosmic string loops, which are an important target for current and future GW
observatories. We obtain analytical waveforms for the GW memory from cusps and
kinks, and use these to calculate the "memory of the memory" and other
higher-order memory effects. These are among the first memory observables
computed for a cosmological source of GWs, with previous literature having
focused almost entirely on astrophysical sources. Surprisingly, we find that
the cusp GW signal diverges for sufficiently large loops, and argue that the
most plausible explanation for this divergence is a breakdown in the weak-field
treatment of GW emission from the cusp. This shows that previously-neglected
strong gravity effects must play an important role near cusps, although the
exact mechanism by which they cure the divergence is not currently understood.
We show that one possible resolution is for these cusps to collapse to form
primordial black holes (PBHs); the kink memory signal does not diverge, in
agreement with the fact that kinks are not predicted to form PBHs. Finally, we
investigate the prospects for detecting memory from cusps and kinks with GW
observatories. We find that in the scenario where the cusp memory divergence is
cured by PBH formation, the memory signal is strongly suppressed and is not
likely to be detected. However, alternative resolutions of the cusp divergence
may in principle lead to much more favourable observational prospects.
| [
{
"created": "Wed, 24 Feb 2021 19:00:01 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Jul 2021 17:49:54 GMT",
"version": "v2"
}
] | 2021-07-23 | [
[
"Jenkins",
"Alexander C.",
""
],
[
"Sakellariadou",
"Mairi",
""
]
] | The nonlinear memory effect is a fascinating prediction of general relativity (GR), in which oscillatory gravitational-wave (GW) signals are generically accompanied by a monotonically-increasing strain which persists in the detector long after the signal has passed. This effect presents a unique opportunity to test GR in the dynamical and nonlinear regime. In this article we calculate the nonlinear memory signal associated with GW bursts from cusps and kinks on cosmic string loops, which are an important target for current and future GW observatories. We obtain analytical waveforms for the GW memory from cusps and kinks, and use these to calculate the "memory of the memory" and other higher-order memory effects. These are among the first memory observables computed for a cosmological source of GWs, with previous literature having focused almost entirely on astrophysical sources. Surprisingly, we find that the cusp GW signal diverges for sufficiently large loops, and argue that the most plausible explanation for this divergence is a breakdown in the weak-field treatment of GW emission from the cusp. This shows that previously-neglected strong gravity effects must play an important role near cusps, although the exact mechanism by which they cure the divergence is not currently understood. We show that one possible resolution is for these cusps to collapse to form primordial black holes (PBHs); the kink memory signal does not diverge, in agreement with the fact that kinks are not predicted to form PBHs. Finally, we investigate the prospects for detecting memory from cusps and kinks with GW observatories. We find that in the scenario where the cusp memory divergence is cured by PBH formation, the memory signal is strongly suppressed and is not likely to be detected. However, alternative resolutions of the cusp divergence may in principle lead to much more favourable observational prospects. |
1010.4526 | Mauro Cambiaso | Mauro Cambiaso and Luis F. Urrutia | An extended solution space for Chern-Simons gravity: the slowly rotating
Kerr black hole | 5 pages, PRD accepted | Phys.Rev.D82:101502,2010 | 10.1103/PhysRevD.82.101502 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the Einstein-Cartan formulation, an iterative procedure to find solutions
in non-dynamical Chern-Simons (CS) gravity in vacuum is proposed. The
iterations, in powers of a small parameter $\beta$ which codifies the CS
coupling, start from an arbitrary torsionless solution of Einstein equations.
With Schwarzschild as the zeroth-order choice, we derive a second-order
differential equation for the $\mathcal{O}(\beta)$ corrections to the metric,
for an arbitrary zeroth-order embedding parameter. In particular, the slowly
rotating Kerr metric is an $\mathcal{O}(\beta)$ solution in either the
canonical or the axial embeddings.
| [
{
"created": "Thu, 21 Oct 2010 17:21:32 GMT",
"version": "v1"
}
] | 2010-12-21 | [
[
"Cambiaso",
"Mauro",
""
],
[
"Urrutia",
"Luis F.",
""
]
] | In the Einstein-Cartan formulation, an iterative procedure to find solutions in non-dynamical Chern-Simons (CS) gravity in vacuum is proposed. The iterations, in powers of a small parameter $\beta$ which codifies the CS coupling, start from an arbitrary torsionless solution of Einstein equations. With Schwarzschild as the zeroth-order choice, we derive a second-order differential equation for the $\mathcal{O}(\beta)$ corrections to the metric, for an arbitrary zeroth-order embedding parameter. In particular, the slowly rotating Kerr metric is an $\mathcal{O}(\beta)$ solution in either the canonical or the axial embeddings. |
1301.2674 | Lars Andersson | Steffen Aksteiner, Lars Andersson | Charges for linearized gravity | 19 pages. v3: Added comments and references | null | 10.1088/0264-9381/30/15/155016 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Maxwell test fields as well as solutions of linearized gravity on the Kerr
exterior admit non-radiating modes, i.e. non-trivial time-independent
solutions. These are closely related to conserved charges. In this paper we
discuss the non-radiating modes for linearized gravity, which may be seen to
correspond to the Poincare Lie-algebra. The 2-dimensional isometry group of
Kerr corresponds to a 2-parameter family of gauge-invariant non-radiating modes
representing infinitesimal perturbations of mass and azimuthal angular
momentum. We calculate the linearized mass charge in terms of linearized
Newman-Penrose scalars.
| [
{
"created": "Sat, 12 Jan 2013 10:57:15 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Jan 2013 21:44:49 GMT",
"version": "v2"
},
{
"created": "Mon, 4 Feb 2013 16:49:31 GMT",
"version": "v3"
}
] | 2015-06-12 | [
[
"Aksteiner",
"Steffen",
""
],
[
"Andersson",
"Lars",
""
]
] | Maxwell test fields as well as solutions of linearized gravity on the Kerr exterior admit non-radiating modes, i.e. non-trivial time-independent solutions. These are closely related to conserved charges. In this paper we discuss the non-radiating modes for linearized gravity, which may be seen to correspond to the Poincare Lie-algebra. The 2-dimensional isometry group of Kerr corresponds to a 2-parameter family of gauge-invariant non-radiating modes representing infinitesimal perturbations of mass and azimuthal angular momentum. We calculate the linearized mass charge in terms of linearized Newman-Penrose scalars. |
1811.04445 | Mahmood Roshan | Sara Jamali and Mahmood Roshan and Luca Amendola | Linear cosmological perturbations in Scalar-tensor-vector gravity | 7 pages, accepted version | Physics Letters B, Volume 802, 2020, 135238 | 10.1016/j.physletb.2020.135238 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the cosmological perturbations in the context of a
Scalar-Tensor-Vector theory of Gravity known as MOG in the literature. Recent
investigations show that MOG reproduces a viable background cosmological
evolution comparable to $\Lambda$CDM. However, the matter-dominated era is
slightly different. In this paper, we study the linear matter perturbations and
estimate the relevant modified gravity parameters. We show that MOG reduces the
growth rate of the perturbations and comparing with the RSD data reveals that
MOG suggests a higher value for $\sigma_8$, compare to $\Lambda$CDM. This
point, constitutes a powerful challenge to the cosmological viability of MOG.
| [
{
"created": "Sun, 11 Nov 2018 18:43:29 GMT",
"version": "v1"
},
{
"created": "Thu, 16 May 2019 06:32:34 GMT",
"version": "v2"
},
{
"created": "Sat, 15 Feb 2020 16:49:09 GMT",
"version": "v3"
}
] | 2020-02-18 | [
[
"Jamali",
"Sara",
""
],
[
"Roshan",
"Mahmood",
""
],
[
"Amendola",
"Luca",
""
]
] | We investigate the cosmological perturbations in the context of a Scalar-Tensor-Vector theory of Gravity known as MOG in the literature. Recent investigations show that MOG reproduces a viable background cosmological evolution comparable to $\Lambda$CDM. However, the matter-dominated era is slightly different. In this paper, we study the linear matter perturbations and estimate the relevant modified gravity parameters. We show that MOG reduces the growth rate of the perturbations and comparing with the RSD data reveals that MOG suggests a higher value for $\sigma_8$, compare to $\Lambda$CDM. This point, constitutes a powerful challenge to the cosmological viability of MOG. |
1603.02854 | Chopin Soo | Chopin Soo | Quantum geometrodynamics with intrinsic time development | 6 pages; Plenary talk, 2nd LeCosPA Symposium (Everything About
Gravity) Taipei, Dec. 17th. 2015, contribution to the Proceedings | Int. J. Mod. Phys. D, 25 (2016) 1645008 (10pp) | 10.1142/S0218271816450085 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum geometrodynamics with intrinsic time development is presented.
Paradigm shift from full space-time covariance to spatial diffeomorphism
invariance yields a non-vanishing Hamiltonian, a resolution of the `problem of
time', and gauge-invariant temporal ordering in an ever expanding universe.
Einstein's general relativity is a particular realization of a wider class of
theories; and the framework prompts natural extensions and improvements, with
the consequent dominance of Cotton-York potential at early times when the
universe was small.
| [
{
"created": "Wed, 9 Mar 2016 11:34:14 GMT",
"version": "v1"
}
] | 2016-12-16 | [
[
"Soo",
"Chopin",
""
]
] | Quantum geometrodynamics with intrinsic time development is presented. Paradigm shift from full space-time covariance to spatial diffeomorphism invariance yields a non-vanishing Hamiltonian, a resolution of the `problem of time', and gauge-invariant temporal ordering in an ever expanding universe. Einstein's general relativity is a particular realization of a wider class of theories; and the framework prompts natural extensions and improvements, with the consequent dominance of Cotton-York potential at early times when the universe was small. |
gr-qc/0108014 | Robert J. Low | Steven G. Harris, Robert J. low | Causal monotonicity, omniscient foliations and the shape of space | 19 pages, AMSTeX | Class.Quant.Grav. 18 (2001) 27-43 | 10.1088/0264-9381/18/1/303 | null | gr-qc | null | What is the shape of space in a spacetime? One way of addressing this issue
is to consider edgeless spacelike submanifolds of the spacetime. An alternative
is to foliate the spacetime by timelike curves and consider the quotient
obtained by identifying points on the same timelike curve. In this article we
investigate each of these notions and obtain conditions such that it yields a
meaningful shape of space. We also consider the relationship between these two
notions and find conditions for the quotient space to be diffeomorphic to any
edgeless spacelike hypersurface. In particular, we find conditions in which
merely local behavior (being spacelike) combined with the correct behavior on
the homotopy level guarantees that a putative shape of space really is
precisely that.
| [
{
"created": "Fri, 3 Aug 2001 19:47:40 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Harris",
"Steven G.",
""
],
[
"low",
"Robert J.",
""
]
] | What is the shape of space in a spacetime? One way of addressing this issue is to consider edgeless spacelike submanifolds of the spacetime. An alternative is to foliate the spacetime by timelike curves and consider the quotient obtained by identifying points on the same timelike curve. In this article we investigate each of these notions and obtain conditions such that it yields a meaningful shape of space. We also consider the relationship between these two notions and find conditions for the quotient space to be diffeomorphic to any edgeless spacelike hypersurface. In particular, we find conditions in which merely local behavior (being spacelike) combined with the correct behavior on the homotopy level guarantees that a putative shape of space really is precisely that. |
2103.06895 | Aron Kovacs | Aron D Kovacs | On the construction of asymptotically flat initial data in scalar-tensor
effective field theory | 33 pages | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We study the constraint equations for a class of scalar-tensor effective
field theories of gravity, including the operators up to $4$ derivatives in the
action ($4\partial$ST). We extend the conformal transverse traceless and
conformal thin sandwich methods of General Relativity to rewrite the constraint
equations of the scalar-tensor theory as a set of elliptic partial differential
equations. It is shown that, at weak coupling, a unique solution exists to the
corresponding elliptic boundary value problems on asymptotically Euclidean
initial slices under similar conditions as in the case of General Relativity.
Furthermore, we find a generalization of the Bowen-York solution for
$4\partial$ST theories, too. These results demonstrate that standard methods
for constructing initial data in General Relativity are applicable (with
minimal modification) to weakly coupled $4\partial$ST theories.
| [
{
"created": "Thu, 11 Mar 2021 19:00:02 GMT",
"version": "v1"
}
] | 2021-03-15 | [
[
"Kovacs",
"Aron D",
""
]
] | We study the constraint equations for a class of scalar-tensor effective field theories of gravity, including the operators up to $4$ derivatives in the action ($4\partial$ST). We extend the conformal transverse traceless and conformal thin sandwich methods of General Relativity to rewrite the constraint equations of the scalar-tensor theory as a set of elliptic partial differential equations. It is shown that, at weak coupling, a unique solution exists to the corresponding elliptic boundary value problems on asymptotically Euclidean initial slices under similar conditions as in the case of General Relativity. Furthermore, we find a generalization of the Bowen-York solution for $4\partial$ST theories, too. These results demonstrate that standard methods for constructing initial data in General Relativity are applicable (with minimal modification) to weakly coupled $4\partial$ST theories. |
2210.03750 | Sebastian Murk | Sebastian Murk | Nomen non est omen: Why it is too soon to identify ultra-compact objects
as black holes | 5 pages, 1 figure. Published version. Selected Honorable Mention in
the 2023 Gravity Research Foundation Essay Competition. Comments welcome! | Int. J. Mod. Phys. D 32, 2342012 (2023) | 10.1142/S0218271823420129 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes play a pivotal role in the foundations of physics, but there is
an alarming discrepancy between what is considered to be a black hole in
observational astronomy and theoretical studies. Despite claims to the
contrary, we argue that identifying the observed astrophysical black hole
candidates as genuine black holes is not justified based on the currently
available observational data, and elaborate on the necessary evidence required
to support such a remarkable claim. In addition, we investigate whether the
predictions of semiclassical gravity are equally compatible with competing
theoretical models, and find that semiclassical arguments favor horizonless
configurations.
| [
{
"created": "Fri, 7 Oct 2022 18:00:00 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Feb 2023 13:15:56 GMT",
"version": "v2"
},
{
"created": "Tue, 23 May 2023 14:14:01 GMT",
"version": "v3"
},
{
"created": "Thu, 14 Dec 2023 06:06:05 GMT",
"version": "v4"
}
] | 2023-12-15 | [
[
"Murk",
"Sebastian",
""
]
] | Black holes play a pivotal role in the foundations of physics, but there is an alarming discrepancy between what is considered to be a black hole in observational astronomy and theoretical studies. Despite claims to the contrary, we argue that identifying the observed astrophysical black hole candidates as genuine black holes is not justified based on the currently available observational data, and elaborate on the necessary evidence required to support such a remarkable claim. In addition, we investigate whether the predictions of semiclassical gravity are equally compatible with competing theoretical models, and find that semiclassical arguments favor horizonless configurations. |
gr-qc/9701048 | Romeo Brunetti | R. Brunetti and K. Fredenhagen | Interacting Quantum Fields in Curved Space: Renormalizability of
$\varphi^4$ | AMSTeX, 18 pages, to be published on the proceedings of the
conference `Operator Algebras and Quantum Field Theory` held at Accademia
Nazionale dei Lincei, Rome, Italy, July 1996 | null | null | Desy 97-005 | gr-qc funct-an hep-th math.FA | null | We present a perturbative construction of the $\varphi^4$ model on a smooth
globally hyperbolic space-time. Our method relies on a adaptation of the
Epstein and Glaser method of renormalization to curved space-times using
techniques from microlocal analysis.
| [
{
"created": "Tue, 21 Jan 1997 14:42:46 GMT",
"version": "v1"
}
] | 2008-02-03 | [
[
"Brunetti",
"R.",
""
],
[
"Fredenhagen",
"K.",
""
]
] | We present a perturbative construction of the $\varphi^4$ model on a smooth globally hyperbolic space-time. Our method relies on a adaptation of the Epstein and Glaser method of renormalization to curved space-times using techniques from microlocal analysis. |
1306.2601 | Arash Ranjbar | Amir Hadi Ziaie, Arash Ranjbar and Hamid Reza Sepangi | Trapped surfaces and nature of singularities in Lyra's geometry | 23 pages, 5 figures, title changed, major revision, version appeared
in CQG | Class. Quantum Grav. 32 025010, 2015 | 10.1088/0264-9381/32/2/025010 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the geometrical interpretation of Brans-Dicke (BD) scalar field
which may also act as a torsion potential in Lyra geometry, we study the
effects of spacetime torsion on the dynamics of a collapsing massive star.
Taking the interior spacetime as the FLRW metric and the matter content as
spherically symmetric, homogeneous perfect fluid with the equation of state
(EoS) $p=w\rho$, we show that the collapse ends in a spacetime singularity
which is of the strong curvature type in the sense of Tipler. Whether the
trapped surfaces form during the dynamical evolution of the collapse depends on
the torsion parameter, related to the BD coupling parameter, and the EoS
subject to the conditions on physical reasonableness of the collapse
configuration. Hence, the space of torsion and EoS parameters is divided into
two portions, one for which the collapse process leads to the formation of
apparent horizon and the other for which the apparent horizon is failed to form
in the interior region. The nature of the singularity is examined from the
exterior perspective, by searching for the existence of radial null geodesics
reaching the faraway observers. Moreover, it is found that the effects of a
dynamical torsion can be transferred to the outside region of the collapsing
star, making the exterior region dynamic.
| [
{
"created": "Tue, 11 Jun 2013 18:13:33 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Jan 2015 16:17:23 GMT",
"version": "v2"
}
] | 2015-01-13 | [
[
"Ziaie",
"Amir Hadi",
""
],
[
"Ranjbar",
"Arash",
""
],
[
"Sepangi",
"Hamid Reza",
""
]
] | Motivated by the geometrical interpretation of Brans-Dicke (BD) scalar field which may also act as a torsion potential in Lyra geometry, we study the effects of spacetime torsion on the dynamics of a collapsing massive star. Taking the interior spacetime as the FLRW metric and the matter content as spherically symmetric, homogeneous perfect fluid with the equation of state (EoS) $p=w\rho$, we show that the collapse ends in a spacetime singularity which is of the strong curvature type in the sense of Tipler. Whether the trapped surfaces form during the dynamical evolution of the collapse depends on the torsion parameter, related to the BD coupling parameter, and the EoS subject to the conditions on physical reasonableness of the collapse configuration. Hence, the space of torsion and EoS parameters is divided into two portions, one for which the collapse process leads to the formation of apparent horizon and the other for which the apparent horizon is failed to form in the interior region. The nature of the singularity is examined from the exterior perspective, by searching for the existence of radial null geodesics reaching the faraway observers. Moreover, it is found that the effects of a dynamical torsion can be transferred to the outside region of the collapsing star, making the exterior region dynamic. |
gr-qc/9704016 | Victor Revoltovich Krym | Victor Revoltovich Krym | Causal Structures in Linear Spaces | 13 pages, PostScript, generated by Word 7.0 (300 dpi) | Zap.Nauchn.Semin. 246 (1997) 152 | null | null | gr-qc | null | Linear topological spaces with partial ordering (linear kinematics) are
studied. They are defined by a set of 8 axioms implying that topology, linear
structure and ordering are compatible with each other. Most of the results are
valid for both the finite-dimensional and infinite-dimensional case. In
applications to physics, partial ordering is interpreted as the causal
structure. Both Newtonian and the special relativity causal structures are
studied, and some other possible types of causality are discussed.
Linear topological spaces with pseudometric which satisfies the time
inequality instead of the triangle inequality are studied (3 axioms).
Pseudometric (which is determined by a pseudonorm) is shown to define a
topology on a linear space, it being a continuous mapping in this topology.
Proved that for a space with pseudometric to be a linear kinematics it is
necessary and sufficient that mapping of multiplication by -1 (i.e. time
reversion) be continuous. Minkovskii space of the special relativity theory
proved to be a pseudometric linear kinematics.
| [
{
"created": "Mon, 7 Apr 1997 12:40:52 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Krym",
"Victor Revoltovich",
""
]
] | Linear topological spaces with partial ordering (linear kinematics) are studied. They are defined by a set of 8 axioms implying that topology, linear structure and ordering are compatible with each other. Most of the results are valid for both the finite-dimensional and infinite-dimensional case. In applications to physics, partial ordering is interpreted as the causal structure. Both Newtonian and the special relativity causal structures are studied, and some other possible types of causality are discussed. Linear topological spaces with pseudometric which satisfies the time inequality instead of the triangle inequality are studied (3 axioms). Pseudometric (which is determined by a pseudonorm) is shown to define a topology on a linear space, it being a continuous mapping in this topology. Proved that for a space with pseudometric to be a linear kinematics it is necessary and sufficient that mapping of multiplication by -1 (i.e. time reversion) be continuous. Minkovskii space of the special relativity theory proved to be a pseudometric linear kinematics. |
1401.2549 | Robert Lompay | Robert R. Lompay | On the Energy-Momentum and Spin Tensors in the Riemann-Cartan Space | RevTeX 4.1, 16 pages, 0 figures | Gen. Relativ. Gravit. 46, 1692 (2014) | 10.1007/s10714-014-1692-4 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General classical theories of material fields in an arbitrary Riemann-Cartan
space are considered. For these theories, with the help of equations of
balance, new non-trivially generalized, manifestly generally covariant
expressions for canonical energy-momentum and spin tensors are constructed in
the cases when a Lagrangian contains (a) an arbitrary set of tensorial material
fields and their covariant derivatives up to the second order, as well as (b)
the curvature tensor and (c) the torsion tensor with its covariant derivatives
up to the second order. A non-trivial manifestly generally covariant
generalization of the Belinfante symmetrization procedure, suitable for an
arbitrary Riemann-Cartan space, is carried out. A covariant symmetrized
energy-momentum tensor is constructed in a general form.
| [
{
"created": "Sat, 11 Jan 2014 17:36:47 GMT",
"version": "v1"
}
] | 2014-03-10 | [
[
"Lompay",
"Robert R.",
""
]
] | General classical theories of material fields in an arbitrary Riemann-Cartan space are considered. For these theories, with the help of equations of balance, new non-trivially generalized, manifestly generally covariant expressions for canonical energy-momentum and spin tensors are constructed in the cases when a Lagrangian contains (a) an arbitrary set of tensorial material fields and their covariant derivatives up to the second order, as well as (b) the curvature tensor and (c) the torsion tensor with its covariant derivatives up to the second order. A non-trivial manifestly generally covariant generalization of the Belinfante symmetrization procedure, suitable for an arbitrary Riemann-Cartan space, is carried out. A covariant symmetrized energy-momentum tensor is constructed in a general form. |
gr-qc/0401001 | Stephen R. Lau | Stephen R. Lau (Applied Math, UNC-Chapel Hill) | Rapid Evaluation of Radiation Boundary Kernels for Time-domain Wave
Propagation on Blackholes | AMS article, 105 pages, 45 figures. Version 3 has more minor
corrections as well as extra commentary added in response to reactions by
referees. Commentary added which compares and contrasts this work with work
of Leaver and work of Andersson. For publication, article has been cut in two
and appears as two separate articles in J. Comp. Phys. 199 (2004) 376-422 and
Class. Quantum Grav. 21 (2004) 4147-4192 | J.Comput.Phys. 199 (2004) 376-422 | 10.1016/j.jcp.2004.05.013 | null | gr-qc | null | For scalar, electromagnetic, or gravitational wave propagation on a fixed
Schwarzschild blackhole background, we describe the exact nonlocal radiation
outer boundary conditions (ROBC) appropriate for a spherical outer boundary of
finite radius enclosing the blackhole. Derivation of the ROBC is based on
Laplace and spherical-harmonic transformation of the Regge-Wheeler equation,
the PDE governing the wave propagation, with the resulting radial ODE an
incarnation of the confluent Heun equation. For a given angular index l the
ROBC feature integral convolution between a time-domain radiation boundary
kernel (TDRK) and each of the corresponding 2l+1 spherical-harmonic modes of
the radiating wave. The TDRK is the inverse Laplace transform of a
frequency-domain radiation kernel (FDRK) which is essentially the logarithmic
derivative of the asymptotically outgoing solution to the radial ODE. We
numerically implement the ROBC via a rapid algorithm involving approximation of
the FDRK by a rational function. Such an approximation is tailored to have
relative error \epsilon uniformly along the axis of imaginary Laplace
frequency. Theoretically, \epsilon is also a long-time bound on the relative
convolution error. Via study of one-dimensional radial evolutions, we
demonstrate that the ROBC capture the phenomena of quasinormal ringing and
decay tails. Moreover, carrying out a numerical experiment in which a wave
packet strikes the boundary at an angle, we find that the ROBC yield accurate
results in a three-dimensional setting. Our work is a partial generalization to
Schwarzschild wave propagation and Heun functions of the methods developed for
flatspace wave propagation and Bessel functions by Alpert, Greengard, and
Hagstrom.
| [
{
"created": "Sun, 4 Jan 2004 20:47:03 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jan 2004 20:18:40 GMT",
"version": "v2"
},
{
"created": "Mon, 4 Oct 2004 21:35:52 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Lau",
"Stephen R.",
"",
"Applied Math, UNC-Chapel Hill"
]
] | For scalar, electromagnetic, or gravitational wave propagation on a fixed Schwarzschild blackhole background, we describe the exact nonlocal radiation outer boundary conditions (ROBC) appropriate for a spherical outer boundary of finite radius enclosing the blackhole. Derivation of the ROBC is based on Laplace and spherical-harmonic transformation of the Regge-Wheeler equation, the PDE governing the wave propagation, with the resulting radial ODE an incarnation of the confluent Heun equation. For a given angular index l the ROBC feature integral convolution between a time-domain radiation boundary kernel (TDRK) and each of the corresponding 2l+1 spherical-harmonic modes of the radiating wave. The TDRK is the inverse Laplace transform of a frequency-domain radiation kernel (FDRK) which is essentially the logarithmic derivative of the asymptotically outgoing solution to the radial ODE. We numerically implement the ROBC via a rapid algorithm involving approximation of the FDRK by a rational function. Such an approximation is tailored to have relative error \epsilon uniformly along the axis of imaginary Laplace frequency. Theoretically, \epsilon is also a long-time bound on the relative convolution error. Via study of one-dimensional radial evolutions, we demonstrate that the ROBC capture the phenomena of quasinormal ringing and decay tails. Moreover, carrying out a numerical experiment in which a wave packet strikes the boundary at an angle, we find that the ROBC yield accurate results in a three-dimensional setting. Our work is a partial generalization to Schwarzschild wave propagation and Heun functions of the methods developed for flatspace wave propagation and Bessel functions by Alpert, Greengard, and Hagstrom. |
0805.4320 | J\"org Hennig | J\"org Hennig, Marcus Ansorg and Carla Cederbaum | A universal inequality between angular momentum and horizon area for
axisymmetric and stationary black holes with surrounding matter | 8 pages | Class.Quant.Grav.25:162002,2008 | 10.1088/0264-9381/25/16/162002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that for sub-extremal axisymmetric and stationary black holes with
arbitrary surrounding matter the inequality $8\pi|J|<A$ holds, where $J$ is the
angular momentum and $A$ the horizon area of the black hole.
| [
{
"created": "Wed, 28 May 2008 11:58:37 GMT",
"version": "v1"
}
] | 2010-11-09 | [
[
"Hennig",
"Jörg",
""
],
[
"Ansorg",
"Marcus",
""
],
[
"Cederbaum",
"Carla",
""
]
] | We prove that for sub-extremal axisymmetric and stationary black holes with arbitrary surrounding matter the inequality $8\pi|J|<A$ holds, where $J$ is the angular momentum and $A$ the horizon area of the black hole. |
2206.01147 | Christyan C. de Oliveira | Christyan C. de Oliveira and Ricardo A. Mosna | Analog model for the BTZ black hole | 7 pages, 3 figures | Phys. Rev. D 106, 064030 (2022) | 10.1103/PhysRevD.106.064030 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an analog model for the Ba\~nados, Teitelboim, Zanelli (BTZ) black
hole based on a hydrodynamical flow. We numerically solve the fully nonlinear
hydrodynamic equations of motion and observe the excitation and decay of the
analog BTZ quasinormal modes in the process. We consider both a small
perturbation in the steady state configuration of the fluid and a large
perturbation; the latter could be regarded as an example of formation of the
analog (acoustic) BTZ black hole.
| [
{
"created": "Thu, 2 Jun 2022 16:57:54 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Sep 2022 15:25:04 GMT",
"version": "v2"
}
] | 2022-09-19 | [
[
"de Oliveira",
"Christyan C.",
""
],
[
"Mosna",
"Ricardo A.",
""
]
] | We present an analog model for the Ba\~nados, Teitelboim, Zanelli (BTZ) black hole based on a hydrodynamical flow. We numerically solve the fully nonlinear hydrodynamic equations of motion and observe the excitation and decay of the analog BTZ quasinormal modes in the process. We consider both a small perturbation in the steady state configuration of the fluid and a large perturbation; the latter could be regarded as an example of formation of the analog (acoustic) BTZ black hole. |
gr-qc/0305109 | Zhang Chengmin | C.M. Zhang | Axial Torsion-Dirac spin Effect in Rotating Frame with Relativistic
Factor | 6 pages | Gen.Rel.Grav. 35 (2003) 1465-1470 | 10.1023/A:1024538803075 | null | gr-qc | null | In the framework of spacetime with torsion and without curvature, the Dirac
particle spin precession in the rotational system is studied. We write out the
equivalent tetrad of rotating frame, in the polar coordinate system, through
considering the relativistic factor, and the resultant equivalent metric is a
flat Minkowski one. The obtained rotation-spin coupling formula can be applied
to the high speed rotating case, which is consistent with the expectation.
| [
{
"created": "Fri, 30 May 2003 04:53:29 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Zhang",
"C. M.",
""
]
] | In the framework of spacetime with torsion and without curvature, the Dirac particle spin precession in the rotational system is studied. We write out the equivalent tetrad of rotating frame, in the polar coordinate system, through considering the relativistic factor, and the resultant equivalent metric is a flat Minkowski one. The obtained rotation-spin coupling formula can be applied to the high speed rotating case, which is consistent with the expectation. |
1610.01545 | Plyatsko Roman | Roman Plyatsko and Mykola Fenyk | Antigravity: Spin-gravity coupling in action | 8 pages, 9 figures; version matching publication in PRD | Phys. Rev. D, v.94, 044047 (2016) | 10.1103/PhysRevD.94.044047 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The typical motions of a spinning test particle in Schwarzschild's background
which show the strong repulsive action of the highly relativistic spin-gravity
coupling are considered using the exact Mathisson-Papapetrou equations. An
approximated approach to choice solutions of these equations which describe
motions of the particle's proper center of mass is developed.
| [
{
"created": "Wed, 5 Oct 2016 17:52:41 GMT",
"version": "v1"
},
{
"created": "Sun, 9 Oct 2016 17:05:50 GMT",
"version": "v2"
}
] | 2016-10-12 | [
[
"Plyatsko",
"Roman",
""
],
[
"Fenyk",
"Mykola",
""
]
] | The typical motions of a spinning test particle in Schwarzschild's background which show the strong repulsive action of the highly relativistic spin-gravity coupling are considered using the exact Mathisson-Papapetrou equations. An approximated approach to choice solutions of these equations which describe motions of the particle's proper center of mass is developed. |
gr-qc/0205112 | Sergio De Filippo | Sergio De Filippo | Non-unitary HD gravity classically equivalent to Einstein gravity | null | null | null | null | gr-qc | null | Runaway solutions can be avoided in fourth order gravity by a doubling of the
matter operator algebra with a symmetry constraint with respect to the exchange
of observable and hidden degrees of freedom together with the change in sign of
the ghost and the dilaton fields. The theory is classically equivalent to
Einstein gravity, while its non-unitary Newtonian limit is compatible with the
wavelike properties of microscopic particles and the classical behavior of
macroscopic bodies, as well as with a trans-Planckian regularization of
collapse singularities. A unified reading of ordinary and black hole entropy
emerges as entanglement entropy with hidden degrees of freedom.
| [
{
"created": "Mon, 27 May 2002 17:23:10 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"De Filippo",
"Sergio",
""
]
] | Runaway solutions can be avoided in fourth order gravity by a doubling of the matter operator algebra with a symmetry constraint with respect to the exchange of observable and hidden degrees of freedom together with the change in sign of the ghost and the dilaton fields. The theory is classically equivalent to Einstein gravity, while its non-unitary Newtonian limit is compatible with the wavelike properties of microscopic particles and the classical behavior of macroscopic bodies, as well as with a trans-Planckian regularization of collapse singularities. A unified reading of ordinary and black hole entropy emerges as entanglement entropy with hidden degrees of freedom. |
1106.1198 | Clifford M. Will | Clifford M. Will | Finally, results from Gravity Probe-B | A Viewpoint article, published in Physics 4, 43 (2011), available at
http://physics.aps.org/articles/v4/43 Submitted to the arXiv by permission of
the American Physical Society | Physics 4, 43 (2011) | 10.1103/Physics.4.43 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Nearly fifty years after its inception, the Gravity Probe B satellite mission
delivers the first measurements of how a spinning gyroscope precesses in the
gravitational warping of spacetime.
| [
{
"created": "Mon, 6 Jun 2011 21:03:31 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Will",
"Clifford M.",
""
]
] | Nearly fifty years after its inception, the Gravity Probe B satellite mission delivers the first measurements of how a spinning gyroscope precesses in the gravitational warping of spacetime. |
1709.00227 | Kimet Jusufi | Kimet Jusufi, Farook Rahaman, Ayan Banerjee | Semiclassical gravitational effects on the gravitational lensing in the
spacetime of topological defects | Accepted for publication in Annals of Physics | Ann. Phys. 389, 219 (2018) | 10.1016/j.aop.2017.12.013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The theory of gravitational lensing has revealed many generic and fundamental
properties of compact objects like black holes and wormholes. In this article,
we utilize a recent formulation to compute the quantum effects on the
deflection angle of a light ray, namely, the Gauss-Bonnet theorem (GBT) to
explore the semiclassical gravitational effects in the spacetime of a
point-like global monopole and a cosmic string. Previously, the Gauss-Bonnet
theorem [Class. Quant. Grav. 25, 235009 (2008)] was proposed as an alternative
way to compute the deflection angle of light in a static, spherically symmetric
and asymptotically flat spacetime. In the present article we have used the
celebrated GBT that applied to the optical metric as well as the geodesic
method in computing the deflection angle. Interestingly one can observe that we
have found an exact result between GBT and the standard approach up to the
third-order contributions terms by modifying the domain of integration for
cosmic string and global monopole deflection angles. Finally we have considered
the time delay in the cosmic string/global monopole spacetime and found that
the delay in time is proportional to the linear mass density of the cosmic
string and global monopole parameter, respectively.
| [
{
"created": "Fri, 1 Sep 2017 10:02:01 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Dec 2017 15:26:35 GMT",
"version": "v2"
}
] | 2018-01-11 | [
[
"Jusufi",
"Kimet",
""
],
[
"Rahaman",
"Farook",
""
],
[
"Banerjee",
"Ayan",
""
]
] | The theory of gravitational lensing has revealed many generic and fundamental properties of compact objects like black holes and wormholes. In this article, we utilize a recent formulation to compute the quantum effects on the deflection angle of a light ray, namely, the Gauss-Bonnet theorem (GBT) to explore the semiclassical gravitational effects in the spacetime of a point-like global monopole and a cosmic string. Previously, the Gauss-Bonnet theorem [Class. Quant. Grav. 25, 235009 (2008)] was proposed as an alternative way to compute the deflection angle of light in a static, spherically symmetric and asymptotically flat spacetime. In the present article we have used the celebrated GBT that applied to the optical metric as well as the geodesic method in computing the deflection angle. Interestingly one can observe that we have found an exact result between GBT and the standard approach up to the third-order contributions terms by modifying the domain of integration for cosmic string and global monopole deflection angles. Finally we have considered the time delay in the cosmic string/global monopole spacetime and found that the delay in time is proportional to the linear mass density of the cosmic string and global monopole parameter, respectively. |
gr-qc/0612101 | Jerzy Lewandowski | Lukasz Szulc, Wojciech Kaminski, Jerzy Lewandowski | Closed FRW model in Loop Quantum Cosmology | 19 pages, latex, no figures, high quality, neat | Class.Quant.Grav.24:2621-2636,2007 | 10.1088/0264-9381/24/10/008 | null | gr-qc hep-th | null | The basic idea of the LQC applies to every spatially homogeneous cosmological
model, however only the spatially flat (so called $k=0$) case has been
understood in detail in the literature thus far. In the closed (so called: k=1)
case certain technical difficulties have been the obstacle that stopped the
development. In this work the difficulties are overcome, and a new LQC model of
the spatially closed, homogeneous, isotropic universe is constructed. The
topology of the spacelike section of the universe is assumed to be that of
SU(2) or SO(3). Surprisingly, according to the results achieved in this work,
the two cases can be distinguished from each other just by the local properties
of the quantum geometry of the universe. The quantum hamiltonian operator of
the gravitational field takes the form of a difference operator, where the
elementary step is the quantum of the 3-volume derived in the flat case by
Ashtekar, Pawlowski and Singh. The mathematical properties of the operator are
studied: it is essentially self-adjoint, bounded from above by 0, the 0 itself
is not an eigenvalue, the eigenvectors form a basis. An estimate on the
dimension of the spectral projection on any finite interval is provided.
| [
{
"created": "Mon, 18 Dec 2006 00:21:37 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Dec 2006 14:37:05 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Szulc",
"Lukasz",
""
],
[
"Kaminski",
"Wojciech",
""
],
[
"Lewandowski",
"Jerzy",
""
]
] | The basic idea of the LQC applies to every spatially homogeneous cosmological model, however only the spatially flat (so called $k=0$) case has been understood in detail in the literature thus far. In the closed (so called: k=1) case certain technical difficulties have been the obstacle that stopped the development. In this work the difficulties are overcome, and a new LQC model of the spatially closed, homogeneous, isotropic universe is constructed. The topology of the spacelike section of the universe is assumed to be that of SU(2) or SO(3). Surprisingly, according to the results achieved in this work, the two cases can be distinguished from each other just by the local properties of the quantum geometry of the universe. The quantum hamiltonian operator of the gravitational field takes the form of a difference operator, where the elementary step is the quantum of the 3-volume derived in the flat case by Ashtekar, Pawlowski and Singh. The mathematical properties of the operator are studied: it is essentially self-adjoint, bounded from above by 0, the 0 itself is not an eigenvalue, the eigenvectors form a basis. An estimate on the dimension of the spectral projection on any finite interval is provided. |
1112.4481 | Diego S\'aez-G\'omez | \'Alvaro de la Cruz-Dombriz (ACGC and University Cape Town), Diego
S\'aez-G\'omez (University of the Basque Country) | On the stability of the cosmological solutions in f(R,G) gravity | 30 pages, 15 figures. Figures and conclusions improved, references
added. Version to be published in Classical and Quantum Gravity | Class. Quantum Grav. 29: 245014, 2012 | 10.1088/0264-9381/29/24/245014 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modified gravity is one of the most promising candidates for explaining the
current accelerating expansion of the Universe, and even its unification with
the inflationary epoch. Nevertheless, the wide range of models capable to
explain the phenomena of dark energy, imposes that current research focuses on
a more precise study of the possible effects of modified gravity may have on
both cosmological and local levels. In this paper, we focus on the analysis of
a type of modified gravity, the so-called f(R,G) gravity and we perform a deep
analysis on the stability of important cosmological solutions. This not only
can help to constrain the form of the gravitational action, but also facilitate
a better understanding of the behavior of the perturbations in this class of
higher order theories of gravity, which will lead to a more precise analysis of
the full spectrum of cosmological perturbations in future.
| [
{
"created": "Mon, 19 Dec 2011 21:00:05 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Dec 2012 16:37:09 GMT",
"version": "v2"
}
] | 2015-06-03 | [
[
"de la Cruz-Dombriz",
"Álvaro",
"",
"ACGC and University Cape Town"
],
[
"Sáez-Gómez",
"Diego",
"",
"University of the Basque Country"
]
] | Modified gravity is one of the most promising candidates for explaining the current accelerating expansion of the Universe, and even its unification with the inflationary epoch. Nevertheless, the wide range of models capable to explain the phenomena of dark energy, imposes that current research focuses on a more precise study of the possible effects of modified gravity may have on both cosmological and local levels. In this paper, we focus on the analysis of a type of modified gravity, the so-called f(R,G) gravity and we perform a deep analysis on the stability of important cosmological solutions. This not only can help to constrain the form of the gravitational action, but also facilitate a better understanding of the behavior of the perturbations in this class of higher order theories of gravity, which will lead to a more precise analysis of the full spectrum of cosmological perturbations in future. |
2109.07700 | Christoph Schiller | Christoph Schiller | Comment on "Maximum force and cosmic censorship" | 4 pages | Published as Physical Review D 104 (2021) 068501 | 10.1103/PhysRevD.104.068501 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Despite suggestions to the contrary, no counterargument to the principle of
maximum force or to the equivalent principle of maximum power has yet been
provided.
| [
{
"created": "Thu, 16 Sep 2021 03:47:55 GMT",
"version": "v1"
}
] | 2021-09-17 | [
[
"Schiller",
"Christoph",
""
]
] | Despite suggestions to the contrary, no counterargument to the principle of maximum force or to the equivalent principle of maximum power has yet been provided. |
gr-qc/0110090 | Yosef Verbin | Y. Verbin, S. Madsen, A.L. Larsen and M. Christensen | Classification of String-like Solutions in Dilaton Gravity | 15 pages, 6 figures. To be published in Phys. Rev. D | Phys.Rev. D65 (2002) 063503 | 10.1103/PhysRevD.65.063503 | null | gr-qc astro-ph hep-th | null | The static string-like solutions of the Abelian Higgs model coupled to
dilaton gravity are analyzed and compared to the non-dilatonic case. Except for
a special coupling between the Higgs Lagrangian and the dilaton, the solutions
are flux tubes that generate a non-asymptotically flat geometry. Any point in
parameter space corresponds to two branches of solutions with two different
asymptotic behaviors. Unlike the non-dilatonic case, where one branch is always
asymptotically conic, in the present case the asymptotic behavior changes
continuously along each branch.
| [
{
"created": "Mon, 22 Oct 2001 14:07:51 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Dec 2001 08:10:12 GMT",
"version": "v2"
},
{
"created": "Fri, 18 Jan 2002 09:00:46 GMT",
"version": "v3"
}
] | 2009-11-07 | [
[
"Verbin",
"Y.",
""
],
[
"Madsen",
"S.",
""
],
[
"Larsen",
"A. L.",
""
],
[
"Christensen",
"M.",
""
]
] | The static string-like solutions of the Abelian Higgs model coupled to dilaton gravity are analyzed and compared to the non-dilatonic case. Except for a special coupling between the Higgs Lagrangian and the dilaton, the solutions are flux tubes that generate a non-asymptotically flat geometry. Any point in parameter space corresponds to two branches of solutions with two different asymptotic behaviors. Unlike the non-dilatonic case, where one branch is always asymptotically conic, in the present case the asymptotic behavior changes continuously along each branch. |
1812.04481 | Diego Julio Cirilo-Lombardo | Diego Julio Cirilo-Lombardo | Non-Riemmanian geometry, force-free magnetospheres and the generalized
Grad-Shafranov equation | To be published in International Journal of Geometric Methods in
Modern Physics 2 Vol. 16 (2019) 1950013. 12 pages , no figures (final form in
Journal). arXiv admin note: text overlap with arXiv:1703.02273 by other
authors | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The magnetosphere structure of a magnetar is considered in the context of a
theory of gravity with dynamical torsion field beyond the standard General
Relativity (GR). To this end, the axially symmetric version of the
Grad-Shafranov equation (GSE) is obtained in this theoretical framework. The
resulting GSE solution in the case of the magnetosphere corresponds to a stream
function containing also a pseudoscalar part. This function solution under
axisymmetry presents a complex character that (as in the quantum field
theoretical case) could be associated with an axidilaton field. Magnetar-pulsar
mechanism is suggested and the conjecture about the origin of the excess energy
due the GSE describing the magnetosphere dynamics is claimed. We also show that
two main parameters of the electrodynamic processes (as described in GR
framework by Goldreich and Julian (GJ) in 1969 [5]) are modified but the
electron-positron pair rate N remains invariant. The possible application of
our generalized equation (defined in a non-Riemannian geometry) to
astrophysical scenarios involving emission of energy by gravitational waves, as
described in the context of GR in [18], is briefly discussed.
| [
{
"created": "Sun, 9 Dec 2018 07:58:13 GMT",
"version": "v1"
}
] | 2018-12-12 | [
[
"Cirilo-Lombardo",
"Diego Julio",
""
]
] | The magnetosphere structure of a magnetar is considered in the context of a theory of gravity with dynamical torsion field beyond the standard General Relativity (GR). To this end, the axially symmetric version of the Grad-Shafranov equation (GSE) is obtained in this theoretical framework. The resulting GSE solution in the case of the magnetosphere corresponds to a stream function containing also a pseudoscalar part. This function solution under axisymmetry presents a complex character that (as in the quantum field theoretical case) could be associated with an axidilaton field. Magnetar-pulsar mechanism is suggested and the conjecture about the origin of the excess energy due the GSE describing the magnetosphere dynamics is claimed. We also show that two main parameters of the electrodynamic processes (as described in GR framework by Goldreich and Julian (GJ) in 1969 [5]) are modified but the electron-positron pair rate N remains invariant. The possible application of our generalized equation (defined in a non-Riemannian geometry) to astrophysical scenarios involving emission of energy by gravitational waves, as described in the context of GR in [18], is briefly discussed. |
1401.7500 | Jansen Formiga | J. B. Formiga | Equivalence between an extension of teleparallelism to a Weyl geometry
and general relativity | 10 pages | null | 10.1007/s10773-014-2003-2 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, an extension of teleparallelism to a Weyl geometry which allows us
to easily establish conformal invariance and "geometrize" electromagnetism has
been presented. In this paper, I extend a result which concerns the existence
of the Schwarzschild solution to a particular class of this extension. In
addition, I obtain the field equations of some models based on this extension,
including the one which is equivalent to Einstein's field equations with a
massless scalar field.
| [
{
"created": "Wed, 29 Jan 2014 13:00:46 GMT",
"version": "v1"
}
] | 2014-01-30 | [
[
"Formiga",
"J. B.",
""
]
] | Recently, an extension of teleparallelism to a Weyl geometry which allows us to easily establish conformal invariance and "geometrize" electromagnetism has been presented. In this paper, I extend a result which concerns the existence of the Schwarzschild solution to a particular class of this extension. In addition, I obtain the field equations of some models based on this extension, including the one which is equivalent to Einstein's field equations with a massless scalar field. |
1805.07218 | T. Padmanabhan | T. Padmanabhan | The Kinetic Theory of the Mesoscopic Spacetime | This Essay received the Fourth Award in the Gravity Research
Foundation Essay Contest 2018; six pages; v2: minor revision | null | 10.1142/S0218271818460045 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | At the mesoscopic scales --- which interpolate between the macroscopic,
classical, geometry and the microscopic, quantum, structure of spacetime ---
one can identify the density of states of the geometry which arises from the
existence of a zero-point length in the spacetime. This spacetime discreteness
also associates an internal degree of freedom with each event, in the form of a
fluctuating vector of constant norm. The equilibrium state, corresponding to
the extremum of the total density of states of geometry plus matter, leads
precisely to Einstein's equations. In fact, the field equation can now be
reinterpreted as a zero-heat dissipation principle. The analysis of
fluctuations around the equilibrium state (described by Einstein's equations),
will provide new insights about quantum gravity.
| [
{
"created": "Wed, 16 May 2018 18:00:04 GMT",
"version": "v1"
},
{
"created": "Mon, 21 May 2018 06:51:58 GMT",
"version": "v2"
}
] | 2018-12-19 | [
[
"Padmanabhan",
"T.",
""
]
] | At the mesoscopic scales --- which interpolate between the macroscopic, classical, geometry and the microscopic, quantum, structure of spacetime --- one can identify the density of states of the geometry which arises from the existence of a zero-point length in the spacetime. This spacetime discreteness also associates an internal degree of freedom with each event, in the form of a fluctuating vector of constant norm. The equilibrium state, corresponding to the extremum of the total density of states of geometry plus matter, leads precisely to Einstein's equations. In fact, the field equation can now be reinterpreted as a zero-heat dissipation principle. The analysis of fluctuations around the equilibrium state (described by Einstein's equations), will provide new insights about quantum gravity. |
gr-qc/9807081 | Jiri Podolsky | J. Podolsky | Non-expanding impulsive gravitational waves | 12 pages, to appear in Class. Quantum Grav | Class.Quant.Grav. 15 (1998) 3229-3239 | 10.1088/0264-9381/15/10/023 | KTF MFF UK JP6 | gr-qc | null | We investigate a class of impulsive gravitational waves which propagate
either in Minkowski or in the (anti-)de Sitter background. These waves are
constructed as impulsive members of the Kundt class $P(\Lambda)$ of
non-twisting, non-expanding type N solutions of vacuum Einstein equations with
a cosmological constant $\Lambda$. We show that the only non-trivial waves of
this type in Minkowski spacetime are impulsive pp-waves. For $\Lambda\not=0$ we
demonstrate that the canonical subclasses of $P(\Lambda)$, which are
invariantly different for smooth profiles, are all locally equivalent for
impulsive profiles. Also, we present coordinate system for these impulsive
solutions which is explicitly continuous.
| [
{
"created": "Wed, 29 Jul 1998 14:25:29 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Podolsky",
"J.",
""
]
] | We investigate a class of impulsive gravitational waves which propagate either in Minkowski or in the (anti-)de Sitter background. These waves are constructed as impulsive members of the Kundt class $P(\Lambda)$ of non-twisting, non-expanding type N solutions of vacuum Einstein equations with a cosmological constant $\Lambda$. We show that the only non-trivial waves of this type in Minkowski spacetime are impulsive pp-waves. For $\Lambda\not=0$ we demonstrate that the canonical subclasses of $P(\Lambda)$, which are invariantly different for smooth profiles, are all locally equivalent for impulsive profiles. Also, we present coordinate system for these impulsive solutions which is explicitly continuous. |
gr-qc/0504067 | Nelson Christensen | Nelson Christensen (for the LIGO Scientific Collaboration) | Veto Studies for LIGO Inspiral Triggers | Submitted to Classical and Quantum Gravity for the special issue for
presentations at GWDAW 9 | Class.Quant.Grav.22:S1059-S1068,2005 | 10.1088/0264-9381/22/18/S20 | null | gr-qc | null | LIGO recently conducted its third scientific data run, S3. Here we summarize
the veto and data quality studies conducted by the LIGO Scientific
Collaboration in connection with the search for binary inspiral signals in the
S3 data. LIGO's interferometer channels and physical environmental monitors
were monitored, and events in these channels coincident with inspiral triggers
were examined.
| [
{
"created": "Fri, 15 Apr 2005 11:28:16 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Christensen",
"Nelson",
"",
"for the LIGO Scientific Collaboration"
]
] | LIGO recently conducted its third scientific data run, S3. Here we summarize the veto and data quality studies conducted by the LIGO Scientific Collaboration in connection with the search for binary inspiral signals in the S3 data. LIGO's interferometer channels and physical environmental monitors were monitored, and events in these channels coincident with inspiral triggers were examined. |
2307.02653 | Krish Jhurani | Krish Jhurani and Tyler McMaken | Existence of Time-like Geodesics in Asymptotically Flat Spacetimes: A
Generalized Topological Criterion | 11 pages, 0 figures | null | null | null | gr-qc math.DG | http://creativecommons.org/licenses/by/4.0/ | This paper examines the issue of the existence and nature of time-like
geodesics in asymptotically flat spacetimes and proposes a novel generalized
topological criterion for the existence of time-like geodesics. Its validity is
proved using theorems such as the Jordan-Brouwer Separation Theorem, the
Raychaudhuri Equation, and key elements of Differential Geometry. More
specifically, the proof primarily hinges on a closed, simply-connected subset
of the spacetime manifold and a continuous map, causing a non-trivial induction
on the first homology groups, from the boundary of this subset to a unit
circle. The mathematical analysis conclusively affirms the presence of these
geodesics, intersecting transversally within the said subset of spacetime.
Findings underscore these geodesics' significant implications for the structure
of asymptotically flat spacetimes, including stability, and hypothetical
existence of wormholes. The generalized topological criterion also has
implications on the problem of obstructions for the existence of Lorentzian
metrics, and Einstein's Constraint Equations. Future research should extend
this topological criterion to other classes of spacetimes, including those with
non-trivial topologies or non-zero cosmological constants. Also, the
criterion's application to study complex dynamical systems, such as
gravitational waves or rotating black holes, could offer significant insights.
| [
{
"created": "Wed, 5 Jul 2023 20:58:04 GMT",
"version": "v1"
}
] | 2023-07-07 | [
[
"Jhurani",
"Krish",
""
],
[
"McMaken",
"Tyler",
""
]
] | This paper examines the issue of the existence and nature of time-like geodesics in asymptotically flat spacetimes and proposes a novel generalized topological criterion for the existence of time-like geodesics. Its validity is proved using theorems such as the Jordan-Brouwer Separation Theorem, the Raychaudhuri Equation, and key elements of Differential Geometry. More specifically, the proof primarily hinges on a closed, simply-connected subset of the spacetime manifold and a continuous map, causing a non-trivial induction on the first homology groups, from the boundary of this subset to a unit circle. The mathematical analysis conclusively affirms the presence of these geodesics, intersecting transversally within the said subset of spacetime. Findings underscore these geodesics' significant implications for the structure of asymptotically flat spacetimes, including stability, and hypothetical existence of wormholes. The generalized topological criterion also has implications on the problem of obstructions for the existence of Lorentzian metrics, and Einstein's Constraint Equations. Future research should extend this topological criterion to other classes of spacetimes, including those with non-trivial topologies or non-zero cosmological constants. Also, the criterion's application to study complex dynamical systems, such as gravitational waves or rotating black holes, could offer significant insights. |
2003.09456 | Sudarshan Ghonge | Sudarshan Ghonge, Katerina Chatziioannou, James A. Clark, Tyson
Littenberg, Margaret Millhouse, Laura Cadonati, Neil Cornish | Reconstructing gravitational wave signals from binary black hole mergers
with minimal assumptions | 10 pages, 5 figures | Phys. Rev. D 102, 064056 (2020) | 10.1103/PhysRevD.102.064056 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a systematic comparison of the binary black hole (BBH) signal
waveform reconstructed by two independent and complementary approaches used in
LIGO and Virgo source inference: a template-based analysis, and a
morphology-independent analysis. We apply the two approaches to real events and
to two sets of simulated observations made by adding simulated BBH signals to
LIGO and Virgo detector noise. The first set is representative of the 10 BBH
events in the first Gravitational Wave Transient Catalog (GWTC-1). The second
set is constructed from a population of BBH systems with total mass and signal
strength in the ranges that ground based detectors are typically sensitive. We
find that the reconstruction quality of the GWTC-1 events is consistent with
the results of both sets of simulated signals. We also demonstrate a simulated
case where the presence of a mismodelled effect in the observed signal, namely
higher order modes, can be identified through the morphology-independent
analysis. This study is relevant for currently progressing and future
observational runs by LIGO and Virgo.
| [
{
"created": "Fri, 20 Mar 2020 18:49:57 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Sep 2020 16:41:14 GMT",
"version": "v2"
}
] | 2020-09-23 | [
[
"Ghonge",
"Sudarshan",
""
],
[
"Chatziioannou",
"Katerina",
""
],
[
"Clark",
"James A.",
""
],
[
"Littenberg",
"Tyson",
""
],
[
"Millhouse",
"Margaret",
""
],
[
"Cadonati",
"Laura",
""
],
[
"Cornish",
"Neil",
""
]
] | We present a systematic comparison of the binary black hole (BBH) signal waveform reconstructed by two independent and complementary approaches used in LIGO and Virgo source inference: a template-based analysis, and a morphology-independent analysis. We apply the two approaches to real events and to two sets of simulated observations made by adding simulated BBH signals to LIGO and Virgo detector noise. The first set is representative of the 10 BBH events in the first Gravitational Wave Transient Catalog (GWTC-1). The second set is constructed from a population of BBH systems with total mass and signal strength in the ranges that ground based detectors are typically sensitive. We find that the reconstruction quality of the GWTC-1 events is consistent with the results of both sets of simulated signals. We also demonstrate a simulated case where the presence of a mismodelled effect in the observed signal, namely higher order modes, can be identified through the morphology-independent analysis. This study is relevant for currently progressing and future observational runs by LIGO and Virgo. |
gr-qc/9810013 | Ricardo Schiappa | Orfeu Bertolami and Ricardo Schiappa | Modular Quantum Cosmology | Latex, 23 pages, 1 figure. Revised version to appear in Classical and
Quantum Gravity | Class.Quant.Grav. 16 (1999) 2545-2557 | 10.1088/0264-9381/16/7/326 | DF/IST-1.98, MIT-CTP-2786 | gr-qc hep-th | null | We study solutions of the Wheeler-DeWitt equation corresponding to an
S-modular invariant N=1 supergravity model and a closed homogeneous and
isotropic Friedmann-Robertson-Walker spacetime. The issues of inflation and of
the cosmological constant problem are addressed with the help of the relevant
wave functions. We find that topological type inflation is consistent from the
quantum mechanical point of view and that a solution for the cosmological
constant problem along the lines of the strong CP problem naturally arises.
| [
{
"created": "Sun, 4 Oct 1998 21:56:54 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Apr 1999 17:35:00 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Bertolami",
"Orfeu",
""
],
[
"Schiappa",
"Ricardo",
""
]
] | We study solutions of the Wheeler-DeWitt equation corresponding to an S-modular invariant N=1 supergravity model and a closed homogeneous and isotropic Friedmann-Robertson-Walker spacetime. The issues of inflation and of the cosmological constant problem are addressed with the help of the relevant wave functions. We find that topological type inflation is consistent from the quantum mechanical point of view and that a solution for the cosmological constant problem along the lines of the strong CP problem naturally arises. |
1201.5725 | H{\aa}kan Andr\'easson | H{\aa}kan Andr\'easson, Christian G. Boehmer, Atifah Mussa | Bounds on M/R for Charged Objects with positive Cosmological constant | 12 pages. Revised version to appear in Class. Quant. Grav | Classical and Quantum Gravity 29 (2012) 095012 | 10.1088/0264-9381/29/9/095012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider charged spherically symmetric static solutions of the
Einstein-Maxwell equations with a positive cosmological constant $\Lambda$. If
$r$ denotes the area radius, $m_g$ and $q$ the gravitational mass and charge of
a sphere with area radius $r$ respectively, we find that for any solution which
satisfies the condition $p+2p_{\perp}\leq \rho,$ where $p\geq 0$ and
$p_{\perp}$ are the radial and tangential pressures respectively, $\rho\geq 0$
is the energy density, and for which $0\leq \frac{q^2}{r^2}+\Lambda r^2\leq 1,$
the inequality $\frac{m_g}{r} \leq 2/9+\frac{q^2}{3r^2}-\frac{\Lambda
r^2}{3}+2/9\sqrt{1+\frac{3q^2}{r^2}+3\Lambda r^2}$ holds. We also investigate
the issue of sharpness, and we show that the inequality is sharp in a few cases
but generally this question is open.
| [
{
"created": "Fri, 27 Jan 2012 09:00:01 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Mar 2012 11:10:00 GMT",
"version": "v2"
}
] | 2012-11-13 | [
[
"Andréasson",
"Håkan",
""
],
[
"Boehmer",
"Christian G.",
""
],
[
"Mussa",
"Atifah",
""
]
] | We consider charged spherically symmetric static solutions of the Einstein-Maxwell equations with a positive cosmological constant $\Lambda$. If $r$ denotes the area radius, $m_g$ and $q$ the gravitational mass and charge of a sphere with area radius $r$ respectively, we find that for any solution which satisfies the condition $p+2p_{\perp}\leq \rho,$ where $p\geq 0$ and $p_{\perp}$ are the radial and tangential pressures respectively, $\rho\geq 0$ is the energy density, and for which $0\leq \frac{q^2}{r^2}+\Lambda r^2\leq 1,$ the inequality $\frac{m_g}{r} \leq 2/9+\frac{q^2}{3r^2}-\frac{\Lambda r^2}{3}+2/9\sqrt{1+\frac{3q^2}{r^2}+3\Lambda r^2}$ holds. We also investigate the issue of sharpness, and we show that the inequality is sharp in a few cases but generally this question is open. |
2112.06957 | Lu\'is Filipe Costa | L. Filipe O. Costa, Jos\'e Nat\'ario and N. O. Santos | Spinning cylinders in general relativity: a canonical form for the Lewis
metrics of the Weyl class | 15 pages, 2 figures. To appear in the Proceedings of the sixteenth
Marcel Grossmann Meeting (MG16), July 5-10 2021; based on the invited talk
"Gravitomagnetism in the Lewis cylindrical metrics", given in the parallel
session PT5 -- "Dragging is never draggy: MAss and CHarge flows in GR" | Proceedings of the MG16 Meeting on General Relativity, Online, 5 -
10 July 2021, pp. 3982-3998 (2023) | 10.1142/9789811269776_0332 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the main article [CQG 38 (2021) 055003], a new "canonical" form for the
Lewis metrics of the Weyl class has been obtained, depending only on three
parameters -- Komar mass and angular momentum per unit length, plus the angle
deficit -- corresponding to a coordinate system fixed to the "distant stars"
and an everywhere timelike Killing vector field. Such form evinces the local
but non-global static character of the spacetime, and striking parallelisms
with the electromagnetic analogue. We discuss here its generality, main
physical features and important limits (the Levi-Civita static cylinder, and
spinning cosmic strings). We contrast it on geometric and physical grounds with
the Kerr spacetime -- as an example of a metric which is locally non-static.
| [
{
"created": "Mon, 13 Dec 2021 19:00:31 GMT",
"version": "v1"
}
] | 2023-01-27 | [
[
"Costa",
"L. Filipe O.",
""
],
[
"Natário",
"José",
""
],
[
"Santos",
"N. O.",
""
]
] | In the main article [CQG 38 (2021) 055003], a new "canonical" form for the Lewis metrics of the Weyl class has been obtained, depending only on three parameters -- Komar mass and angular momentum per unit length, plus the angle deficit -- corresponding to a coordinate system fixed to the "distant stars" and an everywhere timelike Killing vector field. Such form evinces the local but non-global static character of the spacetime, and striking parallelisms with the electromagnetic analogue. We discuss here its generality, main physical features and important limits (the Levi-Civita static cylinder, and spinning cosmic strings). We contrast it on geometric and physical grounds with the Kerr spacetime -- as an example of a metric which is locally non-static. |
2009.07487 | Dipanjan Dey | Dipanjan Dey, Rajibul Shaikh, and Pankaj S. Joshi | Shadow of nulllike and timelike naked singularities without photon
spheres | 10 pages, 10 figures | Phys. Rev. D 103, 024015 (2021) | 10.1103/PhysRevD.103.024015 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we derive general conditions for a shadow to occur, without a
photon sphere in a spacetime, caused by central nulllike or timelike naked
singularities. Using these conditions, we propose classes of spacetimes which
have nulllike and timelike naked singularities at the center, and that fulfill
these `shadow without photon sphere' conditions. Considering additional
asymptotically flat conditions, we show that, for a fixed Schwarzschild mass,
the timelike naked singularities can cast a shadow of a size that is equal to,
greater or smaller, than the size of a black hole shadow. On the other hand,
the size of shadow of a nulllike naked singularity is always less than that of
a black hole. Such novel features of shadows of nulllike and timelike naked
singularities in the absence of photon spheres may help us to distinguish
between black holes and naked singularities observationally.
| [
{
"created": "Wed, 16 Sep 2020 06:15:49 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Sep 2020 04:10:59 GMT",
"version": "v2"
}
] | 2021-01-13 | [
[
"Dey",
"Dipanjan",
""
],
[
"Shaikh",
"Rajibul",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | In this paper, we derive general conditions for a shadow to occur, without a photon sphere in a spacetime, caused by central nulllike or timelike naked singularities. Using these conditions, we propose classes of spacetimes which have nulllike and timelike naked singularities at the center, and that fulfill these `shadow without photon sphere' conditions. Considering additional asymptotically flat conditions, we show that, for a fixed Schwarzschild mass, the timelike naked singularities can cast a shadow of a size that is equal to, greater or smaller, than the size of a black hole shadow. On the other hand, the size of shadow of a nulllike naked singularity is always less than that of a black hole. Such novel features of shadows of nulllike and timelike naked singularities in the absence of photon spheres may help us to distinguish between black holes and naked singularities observationally. |
1711.11106 | Andronikos Paliathanasis | Gabriele Gionti, S.J. and Andronikos Paliathanasis | Duality transformation and conformal equivalent scalar-tensor theories | 6 pages, no figures, minor revision, to appear in MPLA | null | 10.1142/S0217732318500931 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We deal with the duality symmetry of the Dilaton field in cosmology and
specifically with the so-called Gasperini-Veneziano duality transformation. In
particular, we determine two conformal equivalent theories to the Dilaton
field, and we show that under conformal transformations Gasperini-Veneziano
duality symmetry does not survive. Moreover, we show that those theories share
a common conservation law, of Noetherian kind, while the symmetry vector which
generates the conservation law is an isometry only for the Dilaton field.
Finally, we show that the Lagrangian of the Dilaton field is equivalent with
that of the two-dimensional \textquotedblright hyperbolic
oscillator\textquotedblright\ in a Lorentzian space whose $O(d,d)$ invariance
is transformed to the Gasperini-Veneziano duality invariance in the original
coordinates.
| [
{
"created": "Wed, 29 Nov 2017 21:16:40 GMT",
"version": "v1"
},
{
"created": "Wed, 2 May 2018 11:51:50 GMT",
"version": "v2"
}
] | 2018-06-27 | [
[
"Gionti",
"Gabriele",
""
],
[
"J.",
"S.",
""
],
[
"Paliathanasis",
"Andronikos",
""
]
] | We deal with the duality symmetry of the Dilaton field in cosmology and specifically with the so-called Gasperini-Veneziano duality transformation. In particular, we determine two conformal equivalent theories to the Dilaton field, and we show that under conformal transformations Gasperini-Veneziano duality symmetry does not survive. Moreover, we show that those theories share a common conservation law, of Noetherian kind, while the symmetry vector which generates the conservation law is an isometry only for the Dilaton field. Finally, we show that the Lagrangian of the Dilaton field is equivalent with that of the two-dimensional \textquotedblright hyperbolic oscillator\textquotedblright\ in a Lorentzian space whose $O(d,d)$ invariance is transformed to the Gasperini-Veneziano duality invariance in the original coordinates. |
gr-qc/0607124 | Nikodem Poplawski | Nikodem J. Poplawski | Interacting dark energy in $f(R)$ gravity | 8 pages; published version | Phys.Rev. D74 (2006) 084032 | 10.1103/PhysRevD.74.084032 | null | gr-qc astro-ph hep-th | null | The field equations in $f(R)$ gravity derived from the Palatini variational
principle and formulated in the Einstein conformal frame yield a cosmological
term which varies with time. Moreover, they break the conservation of the
energy--momentum tensor for matter, generating the interaction between matter
and dark energy. Unlike phenomenological models of interacting dark energy,
$f(R)$ gravity derives such an interaction from a covariant Lagrangian which is
a function of a relativistically invariant quantity (the curvature scalar $R$).
We derive the expressions for the quantities describing this interaction in
terms of an arbitrary function $f(R)$, and examine how the simplest
phenomenological models of a variable cosmological constant are related to
$f(R)$ gravity. Particularly, we show that $\Lambda c^2=H^2(1-2q)$ for a flat,
homogeneous and isotropic, pressureless universe. For the Lagrangian of form
$R-1/R$, which is the simplest way of introducing current cosmic acceleration
in $f(R)$ gravity, the predicted matter--dark energy interaction rate changes
significantly in time, and its current value is relatively weak (on the order
of 1% of $H_0$), in agreement with astronomical observations.
| [
{
"created": "Thu, 27 Jul 2006 04:21:35 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Sep 2006 07:04:42 GMT",
"version": "v2"
},
{
"created": "Mon, 30 Oct 2006 19:46:52 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Poplawski",
"Nikodem J.",
""
]
] | The field equations in $f(R)$ gravity derived from the Palatini variational principle and formulated in the Einstein conformal frame yield a cosmological term which varies with time. Moreover, they break the conservation of the energy--momentum tensor for matter, generating the interaction between matter and dark energy. Unlike phenomenological models of interacting dark energy, $f(R)$ gravity derives such an interaction from a covariant Lagrangian which is a function of a relativistically invariant quantity (the curvature scalar $R$). We derive the expressions for the quantities describing this interaction in terms of an arbitrary function $f(R)$, and examine how the simplest phenomenological models of a variable cosmological constant are related to $f(R)$ gravity. Particularly, we show that $\Lambda c^2=H^2(1-2q)$ for a flat, homogeneous and isotropic, pressureless universe. For the Lagrangian of form $R-1/R$, which is the simplest way of introducing current cosmic acceleration in $f(R)$ gravity, the predicted matter--dark energy interaction rate changes significantly in time, and its current value is relatively weak (on the order of 1% of $H_0$), in agreement with astronomical observations. |
0805.2284 | Ruth Lazkoz | L. Fern\'andez-Jambrina and Ruth Lazkoz | Singular fate of the universe in modified theories of gravity | 6 pages, final version, accepted for publication in Physics Letters
B, references added, revtex | Phys.Lett.B670:254-258,2009 | 10.1016/j.physletb.2008.10.061 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the final fate of the universe in modified theories of
gravity. As compared with general relativistic formulations, in these scenarios
the Friedmann equation has additional terms which are relevant for low density
epochs. We analyze the sort of future singularities to be found under the usual
assumption the expanding Universe is solely filled with a pressureless
component. We report our results using two schemes: one concerned with the
behavior of curvature scalars, and a more refined one linked to observers. Some
examples with a very solid theoretical motivation and some others with a more
phenomenological nature are used for illustration.
| [
{
"created": "Thu, 15 May 2008 12:38:03 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Nov 2008 15:38:22 GMT",
"version": "v2"
}
] | 2009-01-16 | [
[
"Fernández-Jambrina",
"L.",
""
],
[
"Lazkoz",
"Ruth",
""
]
] | In this paper we study the final fate of the universe in modified theories of gravity. As compared with general relativistic formulations, in these scenarios the Friedmann equation has additional terms which are relevant for low density epochs. We analyze the sort of future singularities to be found under the usual assumption the expanding Universe is solely filled with a pressureless component. We report our results using two schemes: one concerned with the behavior of curvature scalars, and a more refined one linked to observers. Some examples with a very solid theoretical motivation and some others with a more phenomenological nature are used for illustration. |
2307.14003 | Shao-Wen Wei | Shan-Ping Wu, Shao-Wen Wei | Topology of light rings for extremal and non-extremal Kerr-Newman
Taub-NUT black holes without $\mathbb{Z}_2$ symmetry | 22 pages, 10 figures, 2 tables | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Understanding the light ring, one kind fundamental orbit, shall provide us
with novel insight into the astronomical phenomena, such as the ringdown of
binary merger and shadow of black holes. Recently, topological approach has
preliminarily demonstrated its potential advantages on the properties of the
light rings. However, for the black holes without $\mathbb{Z}_2$ symmetry and
extremal spinning black holes are remained to be tested. In this paper, we aim
at these two issues. Due to the NUT charge, the Kerr-Newman Taub-NUT solution
has no $\mathbb{Z}_2$ symmetry. By constructing the corresponding topology for
the non-extremal spinning black holes, we find the topological number keeps
unchanged. This indicates that $\mathbb{Z}_2$ symmetry has no influence on the
topological number, while it indeed affects the locations of the light rings
and deviates them off the equatorial plane. For the extremal spinning black
holes, we find its topology is critically dependent of the leading term of the
vector's radial component at the zero point of its angular component on the
black hole horizon. The findings state that there exists a topological phase
transition, where the topological number changes, for the prograde light rings.
While no phase transition occurs for the retrograde light rings. Our study
uncovers some universal topological properties for the extremal and
non-extremal spinning black holes with or without $\mathbb{Z}_2$ symmetry. It
also has enlightening significance on understanding the light rings in a more
general black hole background.
| [
{
"created": "Wed, 26 Jul 2023 07:32:12 GMT",
"version": "v1"
}
] | 2023-07-27 | [
[
"Wu",
"Shan-Ping",
""
],
[
"Wei",
"Shao-Wen",
""
]
] | Understanding the light ring, one kind fundamental orbit, shall provide us with novel insight into the astronomical phenomena, such as the ringdown of binary merger and shadow of black holes. Recently, topological approach has preliminarily demonstrated its potential advantages on the properties of the light rings. However, for the black holes without $\mathbb{Z}_2$ symmetry and extremal spinning black holes are remained to be tested. In this paper, we aim at these two issues. Due to the NUT charge, the Kerr-Newman Taub-NUT solution has no $\mathbb{Z}_2$ symmetry. By constructing the corresponding topology for the non-extremal spinning black holes, we find the topological number keeps unchanged. This indicates that $\mathbb{Z}_2$ symmetry has no influence on the topological number, while it indeed affects the locations of the light rings and deviates them off the equatorial plane. For the extremal spinning black holes, we find its topology is critically dependent of the leading term of the vector's radial component at the zero point of its angular component on the black hole horizon. The findings state that there exists a topological phase transition, where the topological number changes, for the prograde light rings. While no phase transition occurs for the retrograde light rings. Our study uncovers some universal topological properties for the extremal and non-extremal spinning black holes with or without $\mathbb{Z}_2$ symmetry. It also has enlightening significance on understanding the light rings in a more general black hole background. |
gr-qc/9801068 | null | Jacek Jezierski (University of Warsaw) | Energy and angular momentum of the weak gravitational waves on the
Schwarzschild background -- quasilocal gauge-invariant formulation | 23 pages | Gen.Rel.Grav.31:1855-1890,1999 | 10.1023/A:1026786822107 | null | gr-qc | null | It is shown that the axial and polar perturbations of the spherically
symmetric black hole can be described in a gauge-invariant way. The reduced
phase space describing gravitational waves outside of the horizon is described
by the gauge-invariant quantities. Both degrees of freedom fulfill generalized
scalar wave equation. For the axial degree of freedom the radial part of the
equation corresponds to the Regge-Wheeler result (Phys. Rev. 108, 1063-1069
(1957)) and for the polar one we get Zerilli result (Phys. Rev. D2, 2141-2160
(1970)), see also Chandrasekhar (The Mathematical Theory of Black
Holes,(Clarendon Press Oxford, 1983)), Moncrief (Annals of Physics 88, 323-342
(1974)) for both. An important ingredient of the analysis is the concept of
quasilocality which does duty for the separation of the angular variables in
the usual approach. Moreover, there is no need to represent perturbations by
normal modes (with time dependence $\exp(-ikt)$), we have fields in spacetime
and the Cauchy problem for them is well defined outside of the horizon. The
reduced symplectic structure explains the origin of the axial and polar
invariants. It allows to introduce an energy and angular momentum for the
gravitational waves which is invariant with respect to the gauge
transformations. Both generators represent quadratic approximation of the ADM
nonlinear formulae in terms of the perturbations of the Schwarzschild metric.
We also discuss the boundary-initial value problem for the linearized Einstein
equations on a Schwarzschild background outside of the horizon.
| [
{
"created": "Tue, 20 Jan 1998 19:41:16 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Jezierski",
"Jacek",
"",
"University of Warsaw"
]
] | It is shown that the axial and polar perturbations of the spherically symmetric black hole can be described in a gauge-invariant way. The reduced phase space describing gravitational waves outside of the horizon is described by the gauge-invariant quantities. Both degrees of freedom fulfill generalized scalar wave equation. For the axial degree of freedom the radial part of the equation corresponds to the Regge-Wheeler result (Phys. Rev. 108, 1063-1069 (1957)) and for the polar one we get Zerilli result (Phys. Rev. D2, 2141-2160 (1970)), see also Chandrasekhar (The Mathematical Theory of Black Holes,(Clarendon Press Oxford, 1983)), Moncrief (Annals of Physics 88, 323-342 (1974)) for both. An important ingredient of the analysis is the concept of quasilocality which does duty for the separation of the angular variables in the usual approach. Moreover, there is no need to represent perturbations by normal modes (with time dependence $\exp(-ikt)$), we have fields in spacetime and the Cauchy problem for them is well defined outside of the horizon. The reduced symplectic structure explains the origin of the axial and polar invariants. It allows to introduce an energy and angular momentum for the gravitational waves which is invariant with respect to the gauge transformations. Both generators represent quadratic approximation of the ADM nonlinear formulae in terms of the perturbations of the Schwarzschild metric. We also discuss the boundary-initial value problem for the linearized Einstein equations on a Schwarzschild background outside of the horizon. |
1611.07209 | Y B Wu | Ya-Bo Wu, Xue Zhang, Bo-Hai Chen, Nan Zhang and Meng-Meng Wu | Energy conditions and constraints on the generalized non-local gravity
model | 12 pages, 14 figures, 1 table | null | 10.1088/0256-307X/34/7/079801 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study and derive the energy conditions in generalized non-local gravity,
which is the modified theory of general relativity (GR) obtained by adding a
term $m^{2n-2}R\Box^{-n}R$ to the Einstein-Hilbert action. Moreover, in order
to get some insight on the meaning of the energy conditions, we illustrate the
evolutions of four energy conditions with the model parameter $\varepsilon$ for
different $n$. By analysis we give the constraints on the model parameters
$\varepsilon$.
| [
{
"created": "Tue, 22 Nov 2016 09:18:08 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Mar 2017 03:28:25 GMT",
"version": "v2"
}
] | 2017-08-02 | [
[
"Wu",
"Ya-Bo",
""
],
[
"Zhang",
"Xue",
""
],
[
"Chen",
"Bo-Hai",
""
],
[
"Zhang",
"Nan",
""
],
[
"Wu",
"Meng-Meng",
""
]
] | We study and derive the energy conditions in generalized non-local gravity, which is the modified theory of general relativity (GR) obtained by adding a term $m^{2n-2}R\Box^{-n}R$ to the Einstein-Hilbert action. Moreover, in order to get some insight on the meaning of the energy conditions, we illustrate the evolutions of four energy conditions with the model parameter $\varepsilon$ for different $n$. By analysis we give the constraints on the model parameters $\varepsilon$. |
2006.16962 | Avishek Dusoye | Avishek Dusoye, Alvaro de la Cruz-Dombriz, Peter Dunsby, and Nelson J.
Nunes | Disformal couplings in a $\Lambda$CDM background cosmology | 32 pages, 11 figures, 5 tables, Version published in JCAP03(2021)002,
minor changes | JCAP03(2021)002 | 10.1088/1475-7516/2021/03/002 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The coupled quintessence model with disformal couplings is treated here to
mimic the $\Lambda$CDM background. Using this approach, the quintessence
potential does not have to be specified. The model considers a generic fluid
coupled to the quintessence, which is specified to be either dark matter or a
relativistic fluid. The background consists of a cosmological constant and
another uncoupled generic fluid, to cater for three studied scenarios. The
cosmological dynamics is investigated for the coupled quintessence model, whose
disformal couplings depend on the equation of state of both generic fluids. The
scenario, whereby both generic fluids are dark matter, was further analyzed for
an expansion history of the mimicking model. The analysis confirms that the
mass scale of the quintessence influences the disformal characteristics of the
dynamical system, which is portrayed by the evolution of an effective conformal
coupling.
| [
{
"created": "Tue, 30 Jun 2020 16:58:40 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Jul 2020 17:24:27 GMT",
"version": "v2"
},
{
"created": "Sat, 13 Mar 2021 10:53:52 GMT",
"version": "v3"
}
] | 2021-03-16 | [
[
"Dusoye",
"Avishek",
""
],
[
"de la Cruz-Dombriz",
"Alvaro",
""
],
[
"Dunsby",
"Peter",
""
],
[
"Nunes",
"Nelson J.",
""
]
] | The coupled quintessence model with disformal couplings is treated here to mimic the $\Lambda$CDM background. Using this approach, the quintessence potential does not have to be specified. The model considers a generic fluid coupled to the quintessence, which is specified to be either dark matter or a relativistic fluid. The background consists of a cosmological constant and another uncoupled generic fluid, to cater for three studied scenarios. The cosmological dynamics is investigated for the coupled quintessence model, whose disformal couplings depend on the equation of state of both generic fluids. The scenario, whereby both generic fluids are dark matter, was further analyzed for an expansion history of the mimicking model. The analysis confirms that the mass scale of the quintessence influences the disformal characteristics of the dynamical system, which is portrayed by the evolution of an effective conformal coupling. |
gr-qc/9906010 | Ms. Amita Shaw | S.Biswas, A.Shaw and B.Modak | Time in Quantum Gravity | 12 Pages, LaTeX, no figure | Int.J.Mod.Phys. D10 (2001) 595-606 | 10.1142/S0218271801001384 | null | gr-qc | null | The Wheeler-DeWitt equation in quantum gravity is timeless in character. In
order to discuss quantum to classical transition of the universe, one uses a
time prescription in quantum gravity to obtain a time contained description
starting from Wheeler-DeWitt equation and WKB ansatz for the WD wavefunction.
The approach has some drawbacks. In this work, we obtain the time-contained
Schroedinger-Wheeler-DeWitt equation without using the WD equation and the WKB
ansatz for the wavefunction. We further show that a Gaussian ansatz for SWD
wavefunction is consistent with the Hartle-Hawking or wormhole dominance
proposal boundary condition. We thus find an answer to the small scale boundary
conditions.
| [
{
"created": "Thu, 3 Jun 1999 09:01:48 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Biswas",
"S.",
""
],
[
"Shaw",
"A.",
""
],
[
"Modak",
"B.",
""
]
] | The Wheeler-DeWitt equation in quantum gravity is timeless in character. In order to discuss quantum to classical transition of the universe, one uses a time prescription in quantum gravity to obtain a time contained description starting from Wheeler-DeWitt equation and WKB ansatz for the WD wavefunction. The approach has some drawbacks. In this work, we obtain the time-contained Schroedinger-Wheeler-DeWitt equation without using the WD equation and the WKB ansatz for the wavefunction. We further show that a Gaussian ansatz for SWD wavefunction is consistent with the Hartle-Hawking or wormhole dominance proposal boundary condition. We thus find an answer to the small scale boundary conditions. |
2111.10455 | Charlie Hoy | Charlie Hoy, Cameron Mills, Stephen Fairhurst | Evidence for subdominant multipole moments and precession in merging
black-hole-binaries from GWTC-2.1 | 18 pages, 7 figures | null | 10.1103/PhysRevD.106.023019 | LIGO-P2100412 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The LIGO--Virgo--KAGRA collaborations (LVK) produced a catalogue containing
gravitational-wave (GW) observations from the first half of the third GW
observing run (O3a). This catalogue, GWTC-2.1, includes for the first time a
number of \emph{exceptional} GW candidates produced from merging
black-hole-binaries with unequivocally unequal component masses. Since
subdominant multipole moments and spin-induced orbital precession are more
likely to leave measurable imprints on the emitted GW from unequal component
mass binaries, these general relativistic phenomena may now be measurable.
Indeed, both GW190412 and GW190814 have already shown conclusive evidence for
subdominant multipole moments. This provides valuable insights into the
dynamics of the binary. We calculate the evidence for subdominant multipole
moments and spin-induced orbital precession for all merging black-hole-binaries
in GWTC-2.1 that were observed during O3a and show that (a) no
gravitational-wave candidate has measurable higher order multipole content
beyond $\ell = 3$, (b) in addition to the confident subdominant multipole
measurements in GW190412 and GW190814, GW190519\_153544 and GW190929\_012149
show marginal evidence for the $(\ell, |m|) = (3, 3)$ subdominant multipole,
(c) GW190521 may have measurable subdominant multipole content and (d) GW190412
may show evidence for spin-induced orbital precession.
| [
{
"created": "Fri, 19 Nov 2021 22:06:36 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Apr 2022 15:46:49 GMT",
"version": "v2"
}
] | 2022-07-27 | [
[
"Hoy",
"Charlie",
""
],
[
"Mills",
"Cameron",
""
],
[
"Fairhurst",
"Stephen",
""
]
] | The LIGO--Virgo--KAGRA collaborations (LVK) produced a catalogue containing gravitational-wave (GW) observations from the first half of the third GW observing run (O3a). This catalogue, GWTC-2.1, includes for the first time a number of \emph{exceptional} GW candidates produced from merging black-hole-binaries with unequivocally unequal component masses. Since subdominant multipole moments and spin-induced orbital precession are more likely to leave measurable imprints on the emitted GW from unequal component mass binaries, these general relativistic phenomena may now be measurable. Indeed, both GW190412 and GW190814 have already shown conclusive evidence for subdominant multipole moments. This provides valuable insights into the dynamics of the binary. We calculate the evidence for subdominant multipole moments and spin-induced orbital precession for all merging black-hole-binaries in GWTC-2.1 that were observed during O3a and show that (a) no gravitational-wave candidate has measurable higher order multipole content beyond $\ell = 3$, (b) in addition to the confident subdominant multipole measurements in GW190412 and GW190814, GW190519\_153544 and GW190929\_012149 show marginal evidence for the $(\ell, |m|) = (3, 3)$ subdominant multipole, (c) GW190521 may have measurable subdominant multipole content and (d) GW190412 may show evidence for spin-induced orbital precession. |
1405.7916 | Marcos Brum | Marcos Brum and Sergio E. Jor\'as | Hadamard state in Schwarzschild-de Sitter spacetime | More emphasis put on the result. 41 pages. Uses natbib and iopart.
This version is going to be published in Classical and Quantum Gravity. PACS
numbers: 04.62.+v,04.70.Dy,03.65.Fd. arXiv admin note: text overlap with
arXiv:0907.1034 by other authors | Class. Quantum Gravity 32 (2015) 015013 | 10.1088/0264-9381/32/1/015013 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a state in the Schwarzschild-de Sitter spacetime which is
invariant under the action of its group of symmetries. Our state is not defined
in the whole Kruskal extension of this spacetime, but rather in a subset of the
maximally extended conformal diagram. The construction is based on a careful
use of the bulk-to-boundary technique. We will show that our state is Hadamard
and that it is not a KMS state, differently from the case of states constructed
in spacetimes containing only one event horizon.
| [
{
"created": "Fri, 30 May 2014 17:06:37 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Jul 2014 18:20:58 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Nov 2014 19:18:38 GMT",
"version": "v3"
},
{
"created": "Thu, 27 Nov 2014 17:20:48 GMT",
"version": "v4"
}
] | 2014-12-09 | [
[
"Brum",
"Marcos",
""
],
[
"Jorás",
"Sergio E.",
""
]
] | We construct a state in the Schwarzschild-de Sitter spacetime which is invariant under the action of its group of symmetries. Our state is not defined in the whole Kruskal extension of this spacetime, but rather in a subset of the maximally extended conformal diagram. The construction is based on a careful use of the bulk-to-boundary technique. We will show that our state is Hadamard and that it is not a KMS state, differently from the case of states constructed in spacetimes containing only one event horizon. |
0712.2523 | Warren G. Anderson | Warren G. Anderson and Jolien D. E. Creighton | Searches for Gravitational Waves from Binary Neutron Stars: A Review | 30 pages, 5 Figures, to appear in "Short-Period Binary Stars:
Observations, Analyses, and Results", Ed.s Eugene F. Milone, Denis A. Leahy,
David W. Hobill | null | 10.1007/978-1-4020-6544-6_2 | null | gr-qc | null | A new generation of observatories is looking for gravitational waves. These
waves, emitted by highly relativistic systems, will open a new window for ob-
servation of the cosmos when they are detected. Among the most promising
sources of gravitational waves for these observatories are compact binaries in
the final min- utes before coalescence. In this article, we review in brief
interferometric searches for gravitational waves emitted by neutron star
binaries, including the theory, instru- mentation and methods. No detections
have been made to date. However, the best direct observational limits on
coalescence rates have been set, and instrumentation and analysis methods
continue to be refined toward the ultimate goal of defining the new field of
gravitational wave astronomy.
| [
{
"created": "Sat, 15 Dec 2007 15:51:21 GMT",
"version": "v1"
}
] | 2015-11-11 | [
[
"Anderson",
"Warren G.",
""
],
[
"Creighton",
"Jolien D. E.",
""
]
] | A new generation of observatories is looking for gravitational waves. These waves, emitted by highly relativistic systems, will open a new window for ob- servation of the cosmos when they are detected. Among the most promising sources of gravitational waves for these observatories are compact binaries in the final min- utes before coalescence. In this article, we review in brief interferometric searches for gravitational waves emitted by neutron star binaries, including the theory, instru- mentation and methods. No detections have been made to date. However, the best direct observational limits on coalescence rates have been set, and instrumentation and analysis methods continue to be refined toward the ultimate goal of defining the new field of gravitational wave astronomy. |
1004.0847 | Flavio Mercati | Flavio Mercati, Diego Maz\'on, Giovanni Amelino-Camelia, Jos\'e Manuel
Carmona, Jos\'e Luis Cort\'es, Javier Indur\'ain, Claus Laemmerzahl,
Guglielmo M. Tino | Probing the quantum-gravity realm with slow atoms | LaTex, 13 pages | Class.Quant.Grav.27:215003,2010 | 10.1088/0264-9381/27/21/215003 | null | gr-qc physics.atom-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For the study of Planck-scale modifications of the energy-momentum dispersion
relation, which had been previously focused on the implications for
ultrarelativistic (ultrafast) particles, we consider the possible role of
experiments involving nonrelativistic particles, and particularly atoms. We
extend a recent result establishing that measurements of "atom-recoil
frequency" can provide insight that is valuable for some theoretical models.
And from a broader perspective we analyze the complementarity of the
nonrelativistic and the ultrarelativistic regimes in this research area.
| [
{
"created": "Tue, 6 Apr 2010 13:25:20 GMT",
"version": "v1"
}
] | 2012-03-14 | [
[
"Mercati",
"Flavio",
""
],
[
"Mazón",
"Diego",
""
],
[
"Amelino-Camelia",
"Giovanni",
""
],
[
"Carmona",
"José Manuel",
""
],
[
"Cortés",
"José Luis",
""
],
[
"Induráin",
"Javier",
""
],
[
"Laemmerzahl",
"Claus",
""
],
[
"Tino",
"Guglielmo M.",
""
]
] | For the study of Planck-scale modifications of the energy-momentum dispersion relation, which had been previously focused on the implications for ultrarelativistic (ultrafast) particles, we consider the possible role of experiments involving nonrelativistic particles, and particularly atoms. We extend a recent result establishing that measurements of "atom-recoil frequency" can provide insight that is valuable for some theoretical models. And from a broader perspective we analyze the complementarity of the nonrelativistic and the ultrarelativistic regimes in this research area. |
2208.00599 | Bijan Bagchi | Bijan Bagchi, Sauvik Sen | Artificial Hawking radiation, weak pseudo-Hermiticity and Weyl semimetal
blackhole analogy | 9 pages. arXiv admin note: substantial text overlap with
arXiv:2108.11648 | J. Math. Phys. 63, 122102 (2022) | 10.1063/5.0084494 | null | gr-qc cond-mat.other math-ph math.MP quant-ph | http://creativecommons.org/publicdomain/zero/1.0/ | We examine the possibility of artificial Hawking radiation by proposing a
non-PT-symmetric weakly pseudo-Hermitian two-band model containing a tilting
parameter by pursuing Weyl semimetal blackhole analogy. We determine the
tunnelling probability using such a Hamiltonian through the event horizon that
acts as a classically forbidden barrier.
| [
{
"created": "Mon, 1 Aug 2022 04:10:17 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Aug 2022 06:06:35 GMT",
"version": "v2"
},
{
"created": "Mon, 19 Dec 2022 16:36:11 GMT",
"version": "v3"
}
] | 2022-12-20 | [
[
"Bagchi",
"Bijan",
""
],
[
"Sen",
"Sauvik",
""
]
] | We examine the possibility of artificial Hawking radiation by proposing a non-PT-symmetric weakly pseudo-Hermitian two-band model containing a tilting parameter by pursuing Weyl semimetal blackhole analogy. We determine the tunnelling probability using such a Hamiltonian through the event horizon that acts as a classically forbidden barrier. |
2105.02347 | Peter Hintz | Peter Hintz and YuQing Xie | Quasinormal modes of small Schwarzschild-de Sitter black holes | 31 pages, 8 figures | null | 10.1063/5.0062985 | null | gr-qc math.AP math.SP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the behavior of the quasinormal modes (QNMs) of massless and massive
linear waves on Schwarzschild-de Sitter black holes as the black hole mass
tends to 0. Via uniform estimates for a degenerating family of ODEs, we show
that in bounded subsets of the complex plane and for fixed angular momenta, the
QNMs converge to those of the static model of de Sitter space. Detailed
numerics illustrate our results and suggest a number of open problems.
| [
{
"created": "Wed, 5 May 2021 22:07:10 GMT",
"version": "v1"
}
] | 2022-02-02 | [
[
"Hintz",
"Peter",
""
],
[
"Xie",
"YuQing",
""
]
] | We study the behavior of the quasinormal modes (QNMs) of massless and massive linear waves on Schwarzschild-de Sitter black holes as the black hole mass tends to 0. Via uniform estimates for a degenerating family of ODEs, we show that in bounded subsets of the complex plane and for fixed angular momenta, the QNMs converge to those of the static model of de Sitter space. Detailed numerics illustrate our results and suggest a number of open problems. |
2001.05807 | Maxime Jacquet | Maxime J Jacquet and Friedrich Koenig | The influence of spacetime curvature on quantum emission in optical
analogues to gravity | Draft 2, Main 6 pages, Appendices 1 page, 7 figures, comments are
welcome! | null | 10.21468/SciPostPhysCore.3.1.005 | null | gr-qc cond-mat.other quant-ph | http://creativecommons.org/licenses/by-nc-sa/4.0/ | Quantum fluctuations on curved spacetimes cause the emission of pairs of
particles from the quantum vacuum, as in the Hawking effect from black holes.
We use an optical analogue to gravity to investigate the influence of the
curvature on quantum emission. Due to dispersion, the spacetime curvature
varies with frequency here. We analytically calculate for all frequencies the
particle flux, correlations and entanglement. We find that horizons increase
the flux with a characteristic spectral shape. The photon number correlations
transition from multi- to two-mode, with close to maximal entanglement. The
quantum state is a diagnostic for the mode conversion in laboratory tests of
quantum field theory on curved spacetimes.
| [
{
"created": "Thu, 16 Jan 2020 14:09:37 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Jun 2020 15:19:38 GMT",
"version": "v2"
}
] | 2020-11-04 | [
[
"Jacquet",
"Maxime J",
""
],
[
"Koenig",
"Friedrich",
""
]
] | Quantum fluctuations on curved spacetimes cause the emission of pairs of particles from the quantum vacuum, as in the Hawking effect from black holes. We use an optical analogue to gravity to investigate the influence of the curvature on quantum emission. Due to dispersion, the spacetime curvature varies with frequency here. We analytically calculate for all frequencies the particle flux, correlations and entanglement. We find that horizons increase the flux with a characteristic spectral shape. The photon number correlations transition from multi- to two-mode, with close to maximal entanglement. The quantum state is a diagnostic for the mode conversion in laboratory tests of quantum field theory on curved spacetimes. |
0808.0642 | Yen Cheong Lee | Atsushi Higuchi, Yen Cheong Lee | How to use retarded Green's functions in de Sitter spacetime | 31 pages with 7 figures | Phys.Rev.D78:084031,2008 | 10.1103/PhysRevD.78.084031 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate in examples that the covariant retarded Green's functions in
electromagnetism and linearized gravity work as expected in de Sitter
spacetime. We first clarify how retarded Green's functions should be used in
spacetimes with spacelike past infinity such as de Sitter spacetime. In
particular, we remind the reader of a general formula which gives the field for
given initial data on a Cauchy surface and a given source (a charge or
stress-energy tensor distribution) in its future. We then apply this formula to
three examples: (i) electromagnetism in the future of a Cauchy surface in
Minkowski spacetime, (ii) electromagnetism in de Sitter spacetime, and (iii)
linearized gravity in de Sitter spacetime. In each example the field is
reproduced correctly as predicted by the general argument. In the third example
we construct a linearized gravitational field from two equal point masses
located at the "North and South Poles" which is non-singular on the
cosmological horizon and satisfies a covariant gauge condition and show that
this field is reproduced by the retarded Green's function with corresponding
gauge parameters.
| [
{
"created": "Tue, 5 Aug 2008 15:39:20 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Sep 2008 15:01:30 GMT",
"version": "v2"
}
] | 2010-05-12 | [
[
"Higuchi",
"Atsushi",
""
],
[
"Lee",
"Yen Cheong",
""
]
] | We demonstrate in examples that the covariant retarded Green's functions in electromagnetism and linearized gravity work as expected in de Sitter spacetime. We first clarify how retarded Green's functions should be used in spacetimes with spacelike past infinity such as de Sitter spacetime. In particular, we remind the reader of a general formula which gives the field for given initial data on a Cauchy surface and a given source (a charge or stress-energy tensor distribution) in its future. We then apply this formula to three examples: (i) electromagnetism in the future of a Cauchy surface in Minkowski spacetime, (ii) electromagnetism in de Sitter spacetime, and (iii) linearized gravity in de Sitter spacetime. In each example the field is reproduced correctly as predicted by the general argument. In the third example we construct a linearized gravitational field from two equal point masses located at the "North and South Poles" which is non-singular on the cosmological horizon and satisfies a covariant gauge condition and show that this field is reproduced by the retarded Green's function with corresponding gauge parameters. |
2405.12049 | Michael Cramer Andersen | Michael Cramer Andersen | Micro-cosmos model of a nucleon | 18 pages, 5 figures | Modern Physics Letters A, Vol. 39, No. 12, 2450053 (2024) | 10.1142/S0217732324500536 | null | gr-qc nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This study explores the age-old quest to construct a geometric model of a
quantum particle. While static classical particle models have largely been
dismissed, the focus has now shifted to intricate dynamic models that hold the
promise of reconciling general relativity with quantum mechanics. We propose
that matter particles can be described as radiation confined within dynamically
curved spacetime regions, without the need for quantization of space and time,
and using standard field equations and natural Planck units. Specifically, we
investigate a cyclic or oscillating radiation-dominated micro cosmos undergoing
repeated bouncing. Our methodology employs integration, with carefully defined
initial conditions. The results include several observable properties
characteristic of quantum particles. We calculate the total mass, revealing a
compelling inverse proportionality between mass and radius identical with the
de Broglie relationship. Applying this model to protons, we discover a profound
and surprisingly simple relationship between the proton's radius and mass
expressed in Planck units. This enables a definition of the proton radius that
aligns remarkably well with the 2018 CODATA value. Furthermore, our analysis
demonstrates that the radial density profile of the proton (or nucleon),
averaged over a cycle time, increases toward the center. The problem of
embedding the micro cosmos within a background spacetime is also described.
These results underscore the relevance of general relativity in the domain of
nuclear physics. Moreover, the model offers a fresh perspective that can
stimulate new ideas in the ongoing quest to unify general relativity with
quantum physics.
| [
{
"created": "Mon, 20 May 2024 14:15:19 GMT",
"version": "v1"
}
] | 2024-05-21 | [
[
"Andersen",
"Michael Cramer",
""
]
] | This study explores the age-old quest to construct a geometric model of a quantum particle. While static classical particle models have largely been dismissed, the focus has now shifted to intricate dynamic models that hold the promise of reconciling general relativity with quantum mechanics. We propose that matter particles can be described as radiation confined within dynamically curved spacetime regions, without the need for quantization of space and time, and using standard field equations and natural Planck units. Specifically, we investigate a cyclic or oscillating radiation-dominated micro cosmos undergoing repeated bouncing. Our methodology employs integration, with carefully defined initial conditions. The results include several observable properties characteristic of quantum particles. We calculate the total mass, revealing a compelling inverse proportionality between mass and radius identical with the de Broglie relationship. Applying this model to protons, we discover a profound and surprisingly simple relationship between the proton's radius and mass expressed in Planck units. This enables a definition of the proton radius that aligns remarkably well with the 2018 CODATA value. Furthermore, our analysis demonstrates that the radial density profile of the proton (or nucleon), averaged over a cycle time, increases toward the center. The problem of embedding the micro cosmos within a background spacetime is also described. These results underscore the relevance of general relativity in the domain of nuclear physics. Moreover, the model offers a fresh perspective that can stimulate new ideas in the ongoing quest to unify general relativity with quantum physics. |
1905.00762 | Andronikos Paliathanasis | Antonios Mitsopoulos, Michael Tsamparlis and Andronikos Paliathanasis | Constructing the CKVs of Bianchi III and V spacetimes | 10 pages, no figures, to appear in MPLA | null | 10.1142/S0217732319503267 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We determine the conformal algebra of Bianchi III and Bianchi V spacetimes
or, equivalently, we determine all Bianchi III and Bianchi V spacetimes which
admit a proper conformal Killing vector. The algorithm that we use has been
developed in Class. Quantum. Grav. 15, 2909 (1998) and concerns the computation
of the CKVs of decomposable spacetimes. The main point of this method is that a
decomposable space admits a CKV if the reduced space admits a gradient
homothetic vector the latter being possible only if the reduced space is flat
or a space of constant curvature. We apply this method in a stepwise manner
starting from the two dimensional spacetime which admits an infinite number of
CKVs and we construct step by step the Bianchi III and V spacetimes by assuming
that CKVs survive as we increase the dimension of the space. We find that there
is only one Bianchi III and one Bianchi V spacetime which admit at maximum one
proper CKV. In each case we determine the conformal Killing vector and the
corresponding conformal factor. As an application in the spacetimes we found we
study the kinematics of the comoving observers and the dynamics of the
corresponding cosmological fluid. As a second application we determine in these
spacetimes generators of the Lie symmetries of the wave equation.
| [
{
"created": "Thu, 2 May 2019 14:18:34 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Jul 2019 09:39:15 GMT",
"version": "v2"
}
] | 2020-01-29 | [
[
"Mitsopoulos",
"Antonios",
""
],
[
"Tsamparlis",
"Michael",
""
],
[
"Paliathanasis",
"Andronikos",
""
]
] | We determine the conformal algebra of Bianchi III and Bianchi V spacetimes or, equivalently, we determine all Bianchi III and Bianchi V spacetimes which admit a proper conformal Killing vector. The algorithm that we use has been developed in Class. Quantum. Grav. 15, 2909 (1998) and concerns the computation of the CKVs of decomposable spacetimes. The main point of this method is that a decomposable space admits a CKV if the reduced space admits a gradient homothetic vector the latter being possible only if the reduced space is flat or a space of constant curvature. We apply this method in a stepwise manner starting from the two dimensional spacetime which admits an infinite number of CKVs and we construct step by step the Bianchi III and V spacetimes by assuming that CKVs survive as we increase the dimension of the space. We find that there is only one Bianchi III and one Bianchi V spacetime which admit at maximum one proper CKV. In each case we determine the conformal Killing vector and the corresponding conformal factor. As an application in the spacetimes we found we study the kinematics of the comoving observers and the dynamics of the corresponding cosmological fluid. As a second application we determine in these spacetimes generators of the Lie symmetries of the wave equation. |
2201.07180 | Luca Fabbri | Luca Fabbri | A note on singularity avoidance in fourth-order gravity | 5 pages | Universe:8,51(2022) | 10.3390/universe8010051 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the fourth-order differential theory of gravitation to treat the
problem of singularity avoidance: studying the short-distance behaviour in the
case of black-holes and the big-bang we are going to see a way to attack the
issue from a general perspective.
| [
{
"created": "Fri, 14 Jan 2022 14:23:45 GMT",
"version": "v1"
}
] | 2022-01-19 | [
[
"Fabbri",
"Luca",
""
]
] | We consider the fourth-order differential theory of gravitation to treat the problem of singularity avoidance: studying the short-distance behaviour in the case of black-holes and the big-bang we are going to see a way to attack the issue from a general perspective. |
1609.01149 | Enrico Santamato | Francesco De Martini and Enrico Santamato | The geometrical nature of the cosmological inflation in the framework of
the Weyl-Dirac conformal gravity theory | International Journal of Theoretical Physics 2017 | null | 10.1007/s10773-017-3465-9 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The nature of the scalar field responsible for the cosmological inflation,
the \qo{inflaton}, is found to be rooted in the most fundamental concept of the
Weyl's differential geometry: the parallel displacement of vectors in curved
space-time. The Euler-Lagrange theory based on a scalar-tensor Weyl-Dirac
Lagrangian leads straightforwardly to the Einstein equation admitting as a
source the characteristic energy-momentum tensor of the inflaton field. Within
the dynamics of the inflation, e.g. in the slow roll transition from a
\qo{false} toward a \qo{true vacuum}, the inflaton's geometry implies a
temperature driven symmetry change between a highly symmetrical \qo{Weylan} to
a low symmetry \qo{Riemannian} scenario. Since the dynamics of the Weyl
curvature scalar, constructed over differentials of the inflaton field, has
been found to account for the quantum phenomenology at the microscopic scale,
the present work suggests interesting connections between the \qo{micro} and
the \qo{macro} aspects of our Universe.
| [
{
"created": "Thu, 1 Sep 2016 07:53:02 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Oct 2017 13:33:56 GMT",
"version": "v2"
}
] | 2017-10-24 | [
[
"De Martini",
"Francesco",
""
],
[
"Santamato",
"Enrico",
""
]
] | The nature of the scalar field responsible for the cosmological inflation, the \qo{inflaton}, is found to be rooted in the most fundamental concept of the Weyl's differential geometry: the parallel displacement of vectors in curved space-time. The Euler-Lagrange theory based on a scalar-tensor Weyl-Dirac Lagrangian leads straightforwardly to the Einstein equation admitting as a source the characteristic energy-momentum tensor of the inflaton field. Within the dynamics of the inflation, e.g. in the slow roll transition from a \qo{false} toward a \qo{true vacuum}, the inflaton's geometry implies a temperature driven symmetry change between a highly symmetrical \qo{Weylan} to a low symmetry \qo{Riemannian} scenario. Since the dynamics of the Weyl curvature scalar, constructed over differentials of the inflaton field, has been found to account for the quantum phenomenology at the microscopic scale, the present work suggests interesting connections between the \qo{micro} and the \qo{macro} aspects of our Universe. |
2301.13180 | Robertus Potting | Robertus Potting | Massive Gravity and Lorentz Symmetry | Presented at the Ninth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, May 17-26, 2022 | null | null | null | gr-qc hep-ph | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We consider Lorentz-symmetry properties of the ghost-free massive gravity
theory proposed by de Rham, Gabadadze, and Tolley. In particular, we present
potentially observable effects in gravitational-wave propagation and in
Newton's law, including Lorentz-violating signals.
| [
{
"created": "Mon, 30 Jan 2023 18:48:10 GMT",
"version": "v1"
}
] | 2023-01-31 | [
[
"Potting",
"Robertus",
""
]
] | We consider Lorentz-symmetry properties of the ghost-free massive gravity theory proposed by de Rham, Gabadadze, and Tolley. In particular, we present potentially observable effects in gravitational-wave propagation and in Newton's law, including Lorentz-violating signals. |
1203.0294 | Nikodem Poplawski | Nikodem Poplawski | Affine theory of gravitation | 8 pages; revised version | Gen. Relativ. Gravit. 46, 1625 (2014) | 10.1007/s10714-013-1625-7 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new theory of gravitation, in which the affine connection is the
only dynamical variable describing the gravitational field. We construct the
simplest dynamical Lagrangian density that is entirely composed from the
connection, via its curvature and torsion, and is an algebraic function of its
derivatives. It is given by the contraction of the Ricci tensor with a tensor
which is inverse to the symmetric, contracted square of the torsion tensor,
$k_{\mu\nu}=S^\rho_{\lambda\mu}S^\lambda_{\rho\nu}$. We vary the total action
for the gravitational field and matter with respect to the affine connection,
assuming that the matter fields couple to the connection only through
$k_{\mu\nu}$. We derive the resulting field equations and show that they are
identical with the Einstein equations of general relativity with a nonzero
cosmological constant, if the tensor $k_{\mu\nu}$ is regarded as the metric
tensor. The cosmological constant is simply a constant of proportionality
between the two tensors, which together with $c$ and $G$ provides a natural
system of units in gravitational physics. This theory therefore provides a
physically valid construction of the metric as an algebraic function of the
connection, and naturally explains dark energy as an intrinsic property of
spacetime. The observed accelerating expansion of the Universe may be the
strongest evidence for torsion.
| [
{
"created": "Thu, 1 Mar 2012 20:59:23 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Aug 2012 23:41:29 GMT",
"version": "v2"
}
] | 2013-12-17 | [
[
"Poplawski",
"Nikodem",
""
]
] | We propose a new theory of gravitation, in which the affine connection is the only dynamical variable describing the gravitational field. We construct the simplest dynamical Lagrangian density that is entirely composed from the connection, via its curvature and torsion, and is an algebraic function of its derivatives. It is given by the contraction of the Ricci tensor with a tensor which is inverse to the symmetric, contracted square of the torsion tensor, $k_{\mu\nu}=S^\rho_{\lambda\mu}S^\lambda_{\rho\nu}$. We vary the total action for the gravitational field and matter with respect to the affine connection, assuming that the matter fields couple to the connection only through $k_{\mu\nu}$. We derive the resulting field equations and show that they are identical with the Einstein equations of general relativity with a nonzero cosmological constant, if the tensor $k_{\mu\nu}$ is regarded as the metric tensor. The cosmological constant is simply a constant of proportionality between the two tensors, which together with $c$ and $G$ provides a natural system of units in gravitational physics. This theory therefore provides a physically valid construction of the metric as an algebraic function of the connection, and naturally explains dark energy as an intrinsic property of spacetime. The observed accelerating expansion of the Universe may be the strongest evidence for torsion. |
2403.12286 | Pedro Cavalcanti Malta | P. C. Malta, C. A. D. Zarro | Bounds on the photon mass via the Shapiro effect in the solar system | 7 + 4 pages, 3 figures. Added appendix D | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the effects of a finite mass for the photon on its propagation in a
weak gravitational field. In particular, we analyse the gravitational time
delay, also known as the Shapiro effect. We work in isotropic coordinates in
the weak-field limit and find that the mass-dependent corrections enhance the
gravitational time delay. Doppler-tracking data from the Cassini mission allow
us to set an upper bound on the photon mass, namely $m_\gamma < 4.9 \times
10^{-7} \, {\rm eV/c^2}$ at $95\%$ CL. We also discuss next-generation
solar-system tests of general relativity that could improve this upper limit,
potentially by a factor of ten. Though not competitive with the currently best
limits, our bound is at the ballpark of earlier ones based on the gravitational
bending of light by the Sun.
| [
{
"created": "Mon, 18 Mar 2024 22:12:15 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Jun 2024 15:22:06 GMT",
"version": "v2"
},
{
"created": "Fri, 9 Aug 2024 07:25:26 GMT",
"version": "v3"
}
] | 2024-08-12 | [
[
"Malta",
"P. C.",
""
],
[
"Zarro",
"C. A. D.",
""
]
] | We study the effects of a finite mass for the photon on its propagation in a weak gravitational field. In particular, we analyse the gravitational time delay, also known as the Shapiro effect. We work in isotropic coordinates in the weak-field limit and find that the mass-dependent corrections enhance the gravitational time delay. Doppler-tracking data from the Cassini mission allow us to set an upper bound on the photon mass, namely $m_\gamma < 4.9 \times 10^{-7} \, {\rm eV/c^2}$ at $95\%$ CL. We also discuss next-generation solar-system tests of general relativity that could improve this upper limit, potentially by a factor of ten. Though not competitive with the currently best limits, our bound is at the ballpark of earlier ones based on the gravitational bending of light by the Sun. |
2310.17266 | Justin Feng | Justin C. Feng and Shinji Mukohyama and Sante Carloni | Singularity at the demise of a black hole | 12 pages, 7 figures. Added and corrected a reference, minor
formatting changes. Matches published version | Phys. Rev. D 109, 024040 (2024) | 10.1103/PhysRevD.109.024040 | YITP-23-134, IPMU23-0039 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a class of quasiregular singularities characterized by points
possessing two future-directed light cones and two past-directed light cones.
Such singularities appear in the $1+1$ trousers spacetime and the
Deutsch-Politzer spacetime. We argue that these singularities are relevant for
describing the end point of an evaporating black hole, and show that a class of
emergent Lorentz signature theories can provide a microscopic description for
these singularities.
| [
{
"created": "Thu, 26 Oct 2023 09:36:55 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Jan 2024 03:47:21 GMT",
"version": "v2"
}
] | 2024-01-29 | [
[
"Feng",
"Justin C.",
""
],
[
"Mukohyama",
"Shinji",
""
],
[
"Carloni",
"Sante",
""
]
] | We consider a class of quasiregular singularities characterized by points possessing two future-directed light cones and two past-directed light cones. Such singularities appear in the $1+1$ trousers spacetime and the Deutsch-Politzer spacetime. We argue that these singularities are relevant for describing the end point of an evaporating black hole, and show that a class of emergent Lorentz signature theories can provide a microscopic description for these singularities. |
gr-qc/0511113 | Erhard Scholz | Erhard Scholz | On the geometry of cosmological model building | null | null | null | null | gr-qc | null | This article analyzes the present anomalies of cosmology from the point of
view of integrable Weyl geometry. It uses P.A.M. Dirac's proposal for a weak
extension of general relativity, with some small adaptations. Simple models
with interesting geometrical and physical properties, not belonging to the
Friedmann-Lema\^{\i}tre class, are studied in this frame. Those with positive
spatial curvature (Einstein-Weyl universes) go well together with observed mass
density $\Omega_m$, CMB, supernovae Ia data, and quasar frequencies. They
suggest a physical role for an equilibrium state of the Maxwell field proposed
by I.E. Segal in the 1980s (Segal background) and for a time invariant
balancing condition of vacuum energy density. The latter leads to a surprising
agreement with the BF-theoretical calculation proposed by C. Castro (2002).
| [
{
"created": "Mon, 21 Nov 2005 08:33:28 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Scholz",
"Erhard",
""
]
] | This article analyzes the present anomalies of cosmology from the point of view of integrable Weyl geometry. It uses P.A.M. Dirac's proposal for a weak extension of general relativity, with some small adaptations. Simple models with interesting geometrical and physical properties, not belonging to the Friedmann-Lema\^{\i}tre class, are studied in this frame. Those with positive spatial curvature (Einstein-Weyl universes) go well together with observed mass density $\Omega_m$, CMB, supernovae Ia data, and quasar frequencies. They suggest a physical role for an equilibrium state of the Maxwell field proposed by I.E. Segal in the 1980s (Segal background) and for a time invariant balancing condition of vacuum energy density. The latter leads to a surprising agreement with the BF-theoretical calculation proposed by C. Castro (2002). |
1912.02832 | Merced Montesinos | Merced Montesinos, Mariano Celada | Canonical analysis with no second-class constraints of $BF$ gravity with
Immirzi parameter | Corrected typos, added references | Phys. Rev. D 101, 084043 (2020) | 10.1103/PhysRevD.101.084043 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we revisit the canonical analysis of $BF$ gravity with the
Immirzi parameter and a cosmological constant. By examining the constraint on
the $B$ field, we realize that the analysis can be performed in a
Lorentz-covariant fashion while utterly avoiding the introduction of
second-class constraints during the whole process. Finally, we make contact
with the description of the phase space of first-order general relativity in
terms of canonical variables with manifest Lorentz covariance subject to
first-class constraints only recently introduced.
| [
{
"created": "Thu, 5 Dec 2019 19:00:05 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Apr 2020 18:00:09 GMT",
"version": "v2"
}
] | 2020-04-27 | [
[
"Montesinos",
"Merced",
""
],
[
"Celada",
"Mariano",
""
]
] | In this paper we revisit the canonical analysis of $BF$ gravity with the Immirzi parameter and a cosmological constant. By examining the constraint on the $B$ field, we realize that the analysis can be performed in a Lorentz-covariant fashion while utterly avoiding the introduction of second-class constraints during the whole process. Finally, we make contact with the description of the phase space of first-order general relativity in terms of canonical variables with manifest Lorentz covariance subject to first-class constraints only recently introduced. |
2206.12250 | Yu-Xiao Liu | Yong-Qiang Wang, Shao-Wen Wei, Yu-Xiao Liu | Comment on ''Traversable Wormholes in General Relativity'' | 1 page, 1 figure, 1 table | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the letter titled ''Traversable Wormholes in General Relativity'' [Phys.
Rev. Lett. 128, 091104 (2022)], R. A. Konoplya and A. Zhidenko have constructed
an asymmetric wormhole solution, which is not symmetric about the throat and is
compounded from smooth gravitational and charged Dirac fields. However, the
authors have claimed that a physically relevant condition on the throat is
imposed to lead to no gravitational force experienced by a stationary observer
at the throat. In this comment, we point out that the above condition is
unnecessary.
| [
{
"created": "Fri, 24 Jun 2022 12:43:32 GMT",
"version": "v1"
}
] | 2022-06-27 | [
[
"Wang",
"Yong-Qiang",
""
],
[
"Wei",
"Shao-Wen",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | In the letter titled ''Traversable Wormholes in General Relativity'' [Phys. Rev. Lett. 128, 091104 (2022)], R. A. Konoplya and A. Zhidenko have constructed an asymmetric wormhole solution, which is not symmetric about the throat and is compounded from smooth gravitational and charged Dirac fields. However, the authors have claimed that a physically relevant condition on the throat is imposed to lead to no gravitational force experienced by a stationary observer at the throat. In this comment, we point out that the above condition is unnecessary. |
1912.01768 | Shun Arai | Shun Arai, Purnendu Karmakar, and Atsushi Nishizawa | Cosmological evolution of viable models in the generalized scalar-tensor
theory | 43 pages, 20 figures, updated to the PRD accepted version | Phys. Rev. D 102, 024003 (2020) | 10.1103/PhysRevD.102.024003 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the parameter distributions of the viable generalized
scalar-tensor theory with conventional dust matter after GW170817 in a
model-independent way. We numerically construct the models by computing the
time evolution of a scalar field, which leads to a positive definite
second-order Hamiltonian and are consistent with the observed Hubble parameter.
We show the model parameter distributions in the degenerate higher-order
scalar-tensor (DHOST) theory, and its popular subclasses, e.g., Horndeski and
GLPV theories, etc.. We find that 1) the Planck mass run rate, $\alpha_M$, is
insensitive to distinguish the theories. 2) the kinetic-braiding parameter,
$\alpha_B$, clearly discriminates the models from those of the Horndeski
theory, 3) the parameters for the higher-order theories, $\alpha_H$ and
$\beta_1$, are relatively smaller in magnitude (by several factors) than
$\alpha_M$ and $\alpha_B$, but can still be used for discriminating the
theories except for the GLPV theory. Based on the above three facts, we propose
a minimal set of parameters that sensibly distinguishes the subclasses of DHOST
theories, ($\alpha_M$, $\alpha_B-\alpha_M/2$, $\beta_1$).
| [
{
"created": "Wed, 4 Dec 2019 02:03:29 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Oct 2020 11:16:10 GMT",
"version": "v2"
}
] | 2020-10-22 | [
[
"Arai",
"Shun",
""
],
[
"Karmakar",
"Purnendu",
""
],
[
"Nishizawa",
"Atsushi",
""
]
] | We investigate the parameter distributions of the viable generalized scalar-tensor theory with conventional dust matter after GW170817 in a model-independent way. We numerically construct the models by computing the time evolution of a scalar field, which leads to a positive definite second-order Hamiltonian and are consistent with the observed Hubble parameter. We show the model parameter distributions in the degenerate higher-order scalar-tensor (DHOST) theory, and its popular subclasses, e.g., Horndeski and GLPV theories, etc.. We find that 1) the Planck mass run rate, $\alpha_M$, is insensitive to distinguish the theories. 2) the kinetic-braiding parameter, $\alpha_B$, clearly discriminates the models from those of the Horndeski theory, 3) the parameters for the higher-order theories, $\alpha_H$ and $\beta_1$, are relatively smaller in magnitude (by several factors) than $\alpha_M$ and $\alpha_B$, but can still be used for discriminating the theories except for the GLPV theory. Based on the above three facts, we propose a minimal set of parameters that sensibly distinguishes the subclasses of DHOST theories, ($\alpha_M$, $\alpha_B-\alpha_M/2$, $\beta_1$). |
gr-qc/0309062 | Bijan Saha | Bijan Saha | Interacting scalar and spinor fields in Bianchi type I universe filled
with magneto-fluid | RevTex4, 8 pages, no figures | Astrophys.Space Sci. 299 (2005) 149-158 | 10.1007/s10509-005-5162-z | null | gr-qc | null | Self-consistent system of spinor, scalar and BI gravitational fields in
presence of magneto-fluid and $\Lambda$-term is considered. Assuming that the
expansion of the BI universe is proportional to the $\sigma_1^1$ component of
the shear tensor, exact solutions for the metric functions, as well as for
scalar and spinor fields are obtained. For a non-positive $\Lambda$ the
initially anisotropic space-time becomes isotropic one in the process of
expansion, whereas, for $\Lambda > 0$ an oscillatory mode of expansion of the
BI model occurs.
| [
{
"created": "Fri, 12 Sep 2003 14:22:57 GMT",
"version": "v1"
}
] | 2015-05-01 | [
[
"Saha",
"Bijan",
""
]
] | Self-consistent system of spinor, scalar and BI gravitational fields in presence of magneto-fluid and $\Lambda$-term is considered. Assuming that the expansion of the BI universe is proportional to the $\sigma_1^1$ component of the shear tensor, exact solutions for the metric functions, as well as for scalar and spinor fields are obtained. For a non-positive $\Lambda$ the initially anisotropic space-time becomes isotropic one in the process of expansion, whereas, for $\Lambda > 0$ an oscillatory mode of expansion of the BI model occurs. |
1009.0671 | Jonathan Luk | Jonathan Luk | A Vector Field Method Approach to Improved Decay for Solutions to the
Wave Equation on a Slowly Rotating Kerr Black Hole | Typos corrected | null | null | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that sufficiently regular solutions to the wave equation
$\Box_{g_K}\Phi=0$ on the exterior of a sufficiently slowly rotating Kerr black
hole obey the estimates $|\Phi|\leq C (t^*)^{-3/2+\eta}$ on a compact region of
$r$. This is proved with the help of a new vector field commutator that is
analogous to the scaling vector field on Minkowski and Schwarzschild spacetime.
This result improves the known robust decay rates that are proved using the
vector field method in the region of finite $r$ and along the event horizon.
| [
{
"created": "Fri, 3 Sep 2010 13:54:08 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Apr 2011 14:04:09 GMT",
"version": "v2"
}
] | 2011-04-25 | [
[
"Luk",
"Jonathan",
""
]
] | We prove that sufficiently regular solutions to the wave equation $\Box_{g_K}\Phi=0$ on the exterior of a sufficiently slowly rotating Kerr black hole obey the estimates $|\Phi|\leq C (t^*)^{-3/2+\eta}$ on a compact region of $r$. This is proved with the help of a new vector field commutator that is analogous to the scaling vector field on Minkowski and Schwarzschild spacetime. This result improves the known robust decay rates that are proved using the vector field method in the region of finite $r$ and along the event horizon. |
1910.04372 | Chi-Yong Lin | You-Wei Hsiao, Da-Shin Lee, Chi-Yong Lin | Equatorial light bending around Kerr-Newman black holes | 24 pages, 10 figures. Revised version as published in Physical Review
D 101, 064070 (2020) | Phys. Rev. D 101, 064070 (2020) | 10.1103/PhysRevD.101.064070 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the deflection angle of a light ray as it traverses on the
equatorial plane of a charged spinning black hole. We provide detailed analysis
of the light ray's trajectory, and derive the closed-form expression of the
deflection angle due to the black hole in terms of elliptic integrals. In
particular, the geodesic equation of the light ray along the radial direction
can be used to define an appropriate ``effective potential". The nonzero charge
of the black hole shows stronger repulsive effects to prevent light rays from
falling into the black hole as compared with the Kerr case. As a result, the
radius of the innermost circular motion of light rays with the critical impact
parameter decreases as charge $Q$ of the black hole increases for both direct
and retrograde motions. Additionally, the deflection angle decreases when $Q$
increases with the fixed impact parameter. These results will have a direct
consequence on constructing the apparent shape of a rotating charged black
hole.
| [
{
"created": "Thu, 10 Oct 2019 05:24:26 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Apr 2020 08:06:06 GMT",
"version": "v2"
}
] | 2020-04-15 | [
[
"Hsiao",
"You-Wei",
""
],
[
"Lee",
"Da-Shin",
""
],
[
"Lin",
"Chi-Yong",
""
]
] | We study the deflection angle of a light ray as it traverses on the equatorial plane of a charged spinning black hole. We provide detailed analysis of the light ray's trajectory, and derive the closed-form expression of the deflection angle due to the black hole in terms of elliptic integrals. In particular, the geodesic equation of the light ray along the radial direction can be used to define an appropriate ``effective potential". The nonzero charge of the black hole shows stronger repulsive effects to prevent light rays from falling into the black hole as compared with the Kerr case. As a result, the radius of the innermost circular motion of light rays with the critical impact parameter decreases as charge $Q$ of the black hole increases for both direct and retrograde motions. Additionally, the deflection angle decreases when $Q$ increases with the fixed impact parameter. These results will have a direct consequence on constructing the apparent shape of a rotating charged black hole. |
2112.08480 | Luciano Petruzziello | Massimo Blasone, Salvatore Capozziello, Gaetano Lambiase, Luciano
Petruzziello | Violation of the equivalence principle in curvature based extended
gravity at finite temperature | null | null | 10.1142/S0219887822500554 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the possible violation of the Equivalence Principle at finite
temperature T in the framework of curvature based Extended Theories of Gravity.
Specifically, we first show how it is possible to derive Equivalence Principle
violation from Quantum Field Theory at non-vanishing T. Subsequently, we
exhibit how this result can be precisely recovered by following an alternative
path that envisages the employment of generalized Einstein equations with a
temperature-dependent energy-momentum tensor. Finally, we adopt the latter
formalism in the context of some Extended Gravity models to quantify the amount
of Equivalence Principle violation. Specifically, Brans-Dicke Theory, Standard
Model Extension and Conformal Gravity are considered in details.
| [
{
"created": "Wed, 15 Dec 2021 21:00:49 GMT",
"version": "v1"
}
] | 2022-05-23 | [
[
"Blasone",
"Massimo",
""
],
[
"Capozziello",
"Salvatore",
""
],
[
"Lambiase",
"Gaetano",
""
],
[
"Petruzziello",
"Luciano",
""
]
] | We review the possible violation of the Equivalence Principle at finite temperature T in the framework of curvature based Extended Theories of Gravity. Specifically, we first show how it is possible to derive Equivalence Principle violation from Quantum Field Theory at non-vanishing T. Subsequently, we exhibit how this result can be precisely recovered by following an alternative path that envisages the employment of generalized Einstein equations with a temperature-dependent energy-momentum tensor. Finally, we adopt the latter formalism in the context of some Extended Gravity models to quantify the amount of Equivalence Principle violation. Specifically, Brans-Dicke Theory, Standard Model Extension and Conformal Gravity are considered in details. |
1211.2246 | Gergely Sz\'ekely | Hajnal Andr\'eka, Judit X. Madar\'asz, Istv\'an N\'emeti, and Gergely
Sz\'ekely | A note on "Einstein's special relativity beyond the speed of light by
James M. Hill and Barry J. Cox" | 7 pages, 3 figures | Proceedings of the Royal Society A 469(2154):6pp. (2013) | 10.1098/rspa.2012.0672 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the transformations J. M. Hill and B. J. Cox introduce between
inertial observers moving faster than light with respect to each other are
consistent with Einstein's principle of relativity only if the spacetime is 2
dimensional.
| [
{
"created": "Fri, 9 Nov 2012 21:12:57 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Feb 2013 09:03:25 GMT",
"version": "v2"
}
] | 2014-09-30 | [
[
"Andréka",
"Hajnal",
""
],
[
"Madarász",
"Judit X.",
""
],
[
"Németi",
"István",
""
],
[
"Székely",
"Gergely",
""
]
] | We show that the transformations J. M. Hill and B. J. Cox introduce between inertial observers moving faster than light with respect to each other are consistent with Einstein's principle of relativity only if the spacetime is 2 dimensional. |
2111.13380 | Hocheol Lee | Bum-Hoon Lee, Hocheol Lee, Wonwoo Lee | Hairy black holes in dilatonic Einstein-Gauss-Bonnet theory | 14 pages, 10 figures. This article is prepared for the Proceedings of
the 17th Italian-Korean Symposium for Relativistic Astrophysics | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study black hole solutions in dilatonic Einstein-Gauss-Bonnet theory with
a coupling constant $\alpha$ between the dilaton field and the Gauss-Bonnet
term. In a previous study, we considered the black hole with the vanishing
cosmological constant in this theory and constructed the hairy black hole
solution with the negative $\alpha$. In this study, we present black hole
solutions numerically with various physical properties in anti-de Sitter
spacetime. We describe the procedure for constructing the black hole solutions
in detail.
| [
{
"created": "Fri, 26 Nov 2021 09:36:23 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Nov 2022 03:30:39 GMT",
"version": "v2"
}
] | 2022-11-04 | [
[
"Lee",
"Bum-Hoon",
""
],
[
"Lee",
"Hocheol",
""
],
[
"Lee",
"Wonwoo",
""
]
] | We study black hole solutions in dilatonic Einstein-Gauss-Bonnet theory with a coupling constant $\alpha$ between the dilaton field and the Gauss-Bonnet term. In a previous study, we considered the black hole with the vanishing cosmological constant in this theory and constructed the hairy black hole solution with the negative $\alpha$. In this study, we present black hole solutions numerically with various physical properties in anti-de Sitter spacetime. We describe the procedure for constructing the black hole solutions in detail. |
gr-qc/9605025 | Mark J. Gotay | Mark J. Gotay (University of Hawai`i), Jacques Demaret (Universite de
Liege) | Some remarks on singularities in quantum cosmology | 4 pps., LaTeX2e. Substantial revisions. To appear in: Proc. of the
Second Conference on Constrained Dynamics and Quantum Gravity, Santa
Margherita Ligure, Italy, 17-21 September 1996. Edited by V. de Alfaro et al | Nucl.Phys.Proc.Suppl. 57 (1997) 227-230 | 10.1016/S0920-5632(97)00385-X | null | gr-qc | null | We discuss to what extent classical singularities persist upon quantization
in two simple cosmological models.
| [
{
"created": "Mon, 13 May 1996 09:47:55 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Nov 1996 12:30:10 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Gotay",
"Mark J.",
"",
"University of Hawai`i"
],
[
"Demaret",
"Jacques",
"",
"Universite de\n Liege"
]
] | We discuss to what extent classical singularities persist upon quantization in two simple cosmological models. |
1807.09081 | Costantino Pacilio | Richard Brito and Costantino Pacilio | Quasinormal modes of weakly charged Einstein-Maxwell-dilaton black holes | 20 pages, 11 figures; v2: references added; v3: Matches published
version | Phys. Rev. D 98, 104042 (2018) | 10.1103/PhysRevD.98.104042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Einstein-Maxwell-dilaton theory is an interesting and well-motivated
theoretical laboratory to explore the impact of new fundamental degrees of
freedom in the context of testing the no-hair conjecture, due to the existence
of hairy black hole solutions together with the propagation of scalar, vector
and tensor modes. In this paper we compute the quasinormal mode spectrum of
static and slowly rotating black holes for generic values of the dilaton
coupling, within a weak electric charge approximation. Our results suggest that
these spacetimes are stable for generic values of the dilaton coupling and the
black hole charge. We also show that while gravitational modes are only weakly
affected by the coupling with the dilaton, the spectrum of electromagnetic
modes exhibits a more pronounced dilaton-dependent breaking of isospectrality
between the axial and polar sectors. We further show that the gravitational
quasinormal modes are well approximated by the properties of unstable null
circular geodesics in those spacetimes, while the treatment of electromagnetic
and scalar modes can be simplified by a suitably modified Dudley-Finley scheme
for the perturbed equations.
| [
{
"created": "Tue, 24 Jul 2018 13:15:25 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Jul 2018 15:20:01 GMT",
"version": "v2"
},
{
"created": "Tue, 27 Nov 2018 19:42:43 GMT",
"version": "v3"
}
] | 2018-12-05 | [
[
"Brito",
"Richard",
""
],
[
"Pacilio",
"Costantino",
""
]
] | Einstein-Maxwell-dilaton theory is an interesting and well-motivated theoretical laboratory to explore the impact of new fundamental degrees of freedom in the context of testing the no-hair conjecture, due to the existence of hairy black hole solutions together with the propagation of scalar, vector and tensor modes. In this paper we compute the quasinormal mode spectrum of static and slowly rotating black holes for generic values of the dilaton coupling, within a weak electric charge approximation. Our results suggest that these spacetimes are stable for generic values of the dilaton coupling and the black hole charge. We also show that while gravitational modes are only weakly affected by the coupling with the dilaton, the spectrum of electromagnetic modes exhibits a more pronounced dilaton-dependent breaking of isospectrality between the axial and polar sectors. We further show that the gravitational quasinormal modes are well approximated by the properties of unstable null circular geodesics in those spacetimes, while the treatment of electromagnetic and scalar modes can be simplified by a suitably modified Dudley-Finley scheme for the perturbed equations. |
gr-qc/0211073 | Stanislav Alexeyev | N.N.Popov (Russian Academy of Sciences Computing Center) | Two and Three parametric regular generalizations of spherically
symmetric and axially symmetric metrics | 5 pages, 1 figure | null | null | null | gr-qc | null | Regular generalizations of spherically and axially symmetric metrics and
their properties are considered. Newton gravity law generalizations are reduced
for null geodesic.
| [
{
"created": "Fri, 22 Nov 2002 12:33:36 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Popov",
"N. N.",
"",
"Russian Academy of Sciences Computing Center"
]
] | Regular generalizations of spherically and axially symmetric metrics and their properties are considered. Newton gravity law generalizations are reduced for null geodesic. |
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