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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1009.3974 | Paul Nation | P. D. Nation, M. P. Blencowe, and Franco Nori | Non-equilibrium Landauer Transport Model for Hawking radiation from a
Black Hole | 14 pages, 2 figures, published version | New J. Phys. 14, 033013 (2012) | 10.1088/1367-2630/14/3/033013 | null | gr-qc cond-mat.mes-hall quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose that the Hawking radiation energy and entropy flow rates from a
black hole can be viewed as a one-dimensional (1D), non-equilibrium Landauer
transport process. Support for this viewpoint comes from previous calculations
invoking conformal symmetry in the near-horizon region, which give radiation
rates that are identical to those of a single 1D quantum channel connected to a
thermal reservoir at the Hawking temperature. The Landauer approach shows in a
direct way the particle statistics independence of the energy and entropy
fluxes of a black hole radiating into vacuum, as well as one near thermal
equilibrium with its environment. As an application of the Landauer approach,
we show that Hawking radiation gives a net entropy production that is 50%
larger than that obtained assuming standard three-dimensional emission into
vacuum.
| [
{
"created": "Tue, 21 Sep 2010 00:52:28 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Jan 2011 00:45:40 GMT",
"version": "v2"
},
{
"created": "Mon, 23 May 2011 01:08:52 GMT",
"version": "v3"
},
{
"created": "Tue, 13 Mar 2012 00:09:13 GMT",
"version": "v4"
}
] | 2012-03-14 | [
[
"Nation",
"P. D.",
""
],
[
"Blencowe",
"M. P.",
""
],
[
"Nori",
"Franco",
""
]
] | We propose that the Hawking radiation energy and entropy flow rates from a black hole can be viewed as a one-dimensional (1D), non-equilibrium Landauer transport process. Support for this viewpoint comes from previous calculations invoking conformal symmetry in the near-horizon region, which give radiation rates that are identical to those of a single 1D quantum channel connected to a thermal reservoir at the Hawking temperature. The Landauer approach shows in a direct way the particle statistics independence of the energy and entropy fluxes of a black hole radiating into vacuum, as well as one near thermal equilibrium with its environment. As an application of the Landauer approach, we show that Hawking radiation gives a net entropy production that is 50% larger than that obtained assuming standard three-dimensional emission into vacuum. |
1312.7798 | Craig J. Hogan | Craig J. Hogan | Directional Entanglement of Quantum Fields with Quantum Geometry | 13 pages, 3 figures | null | null | FERMILAB-PUB-13-581-A | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is conjectured that the spatial structure of quantum field states is
influenced by a new kind of directional indeterminacy of quantum geometry set
by the Planck length, $l_P$, that does not occur in a classical background
geometry. Entanglement of fields with geometry modifies the transverse phase of
field states at wavelength $\lambda$ and propagation distance $c\tau$ by about
$ \Delta \phi\approx \sqrt{l_P\tau}/\lambda$. The new effect is not detectable
in measurements of propagating states that depend only on longitudinal
coordinates. The reduced information content of fields in large systems is
consistent with holographic bounds from gravitation theory, and may appear as
measurable quantum-geometrical noise in interferometers.
| [
{
"created": "Mon, 30 Dec 2013 17:59:01 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Jan 2014 21:42:20 GMT",
"version": "v2"
},
{
"created": "Sat, 25 Jan 2014 15:50:13 GMT",
"version": "v3"
},
{
"created": "Tue, 11 Mar 2014 15:53:27 GMT",
"version": "v4"
},
{
"c... | 2014-12-05 | [
[
"Hogan",
"Craig J.",
""
]
] | It is conjectured that the spatial structure of quantum field states is influenced by a new kind of directional indeterminacy of quantum geometry set by the Planck length, $l_P$, that does not occur in a classical background geometry. Entanglement of fields with geometry modifies the transverse phase of field states at wavelength $\lambda$ and propagation distance $c\tau$ by about $ \Delta \phi\approx \sqrt{l_P\tau}/\lambda$. The new effect is not detectable in measurements of propagating states that depend only on longitudinal coordinates. The reduced information content of fields in large systems is consistent with holographic bounds from gravitation theory, and may appear as measurable quantum-geometrical noise in interferometers. |
gr-qc/9412041 | Sardanashvily Gennadi | G.Sardanashvily (Moscow State University) | Energy-Momentum Conservation Laws in Hamiltonian Field Theory | 21 pp, LaTeX file | null | null | TP\94\246 | gr-qc hep-th | null | In the Lagrangian field theory, one gets different identities for different
stress energy-momentum tensors, e.g., canonical energy-momentum tensors.
Moreover, these identities are not conservation laws of the above-mentioned
energy-momentum tensors in general. In the framework of the multimomentum
Hamiltonian formalism, we have the fundamental identity whose restriction to a
constraint space can be treated the energy-momentum conservation law. In
standard field models, this appears the metric energy-momentum conservation
law.
| [
{
"created": "Wed, 14 Dec 1994 03:51:37 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sardanashvily",
"G.",
"",
"Moscow State University"
]
] | In the Lagrangian field theory, one gets different identities for different stress energy-momentum tensors, e.g., canonical energy-momentum tensors. Moreover, these identities are not conservation laws of the above-mentioned energy-momentum tensors in general. In the framework of the multimomentum Hamiltonian formalism, we have the fundamental identity whose restriction to a constraint space can be treated the energy-momentum conservation law. In standard field models, this appears the metric energy-momentum conservation law. |
1909.07733 | Davood Mahdavian Yekta | Davood Mahdavian Yekta, S. A. Alavi, Majid Karimabadi | Gravitational measurements in higher dimensions | 22 pages, 10 figures and 2 tables, Accepted version | Galaxies 2021, 9, 4 | 10.3390/galaxies9010004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We attempt to study three significant tests of general relativity in higher
dimensions both in commutative and non-commutative spaces. In the context of
non-commutative geometry, we will consider a solution of the Einstein equation
in higher dimensions with a source given by a static, spherically symmetric
Gaussian distribution of mass. The resulting metric would describe a regular or
curvature singularity free black hole in higher dimensions. The metric should
smoothly interpolate between Schwarzschild geometry at large distance and
de-Sitter spacetime at short distance. We will consider gravitational redshift,
lensing, and time delay in each sector. It will be shown that, compared to the
four-dimensional spacetime, there can be significant modifications due to the
presence of extra dimensions and the non-commutative corrected black holes.
Finally, we shall attempt to obtain a lower bound on the size of the extra
dimensions and on the mass needed to form a black hole in different dimensions.
| [
{
"created": "Tue, 17 Sep 2019 11:52:07 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Nov 2019 14:15:25 GMT",
"version": "v2"
},
{
"created": "Sun, 18 Oct 2020 18:55:40 GMT",
"version": "v3"
},
{
"created": "Tue, 5 Jan 2021 15:05:51 GMT",
"version": "v4"
}
] | 2021-05-04 | [
[
"Yekta",
"Davood Mahdavian",
""
],
[
"Alavi",
"S. A.",
""
],
[
"Karimabadi",
"Majid",
""
]
] | We attempt to study three significant tests of general relativity in higher dimensions both in commutative and non-commutative spaces. In the context of non-commutative geometry, we will consider a solution of the Einstein equation in higher dimensions with a source given by a static, spherically symmetric Gaussian distribution of mass. The resulting metric would describe a regular or curvature singularity free black hole in higher dimensions. The metric should smoothly interpolate between Schwarzschild geometry at large distance and de-Sitter spacetime at short distance. We will consider gravitational redshift, lensing, and time delay in each sector. It will be shown that, compared to the four-dimensional spacetime, there can be significant modifications due to the presence of extra dimensions and the non-commutative corrected black holes. Finally, we shall attempt to obtain a lower bound on the size of the extra dimensions and on the mass needed to form a black hole in different dimensions. |
1912.03576 | Puxun Wu | Di Wu, Puxun Wu, Hongwei Yu, Shuang-Qing Wu | Notes on thermodynamics of super-entropic AdS black holes | 14 pages; to appear in PRD | null | 10.1103/PhysRevD.101.024057 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The super-entropic black hole, which possesses a noncompact horizon topology
and violates the reverse isoperimetric inequality, has been found to satisfy
both the thermodynamic first law and the Bekenstein-Smarr mass formula. In this
paper, we first derive a new Christodoulou-Ruffini-like squared-mass formula
for the four-dimensional Kerr-Newman-AdS super-entropic black hole, and then
establish a set of very simple relations between thermodynamic quantities of
the super-entropic Kerr-Newman-AdS$_4$ black hole and its usual counterparts.
Using these relations, the thermodynamic quantities of the Kerr-Newman-AdS$_4$
super-entropic black hole can be obtained from those of the usual pro-type by
taking the ultra-spinning limit properly. Then these relations are extended to
the singly-rotating Kerr-AdS black holes in arbitrary dimensions and the
double-rotating charged black hole in the five-dimensional minimal gauged
supergravity. It can be inferred that the thermodynamic quantities of all
super-entropic black holes obey similar limiting relations to those of their
corresponding conventional rotating AdS black holes, and thus can be obtained
by taking the ultra-spinning limit appropriately.
| [
{
"created": "Sat, 7 Dec 2019 23:28:12 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Jan 2020 01:23:56 GMT",
"version": "v2"
}
] | 2020-02-05 | [
[
"Wu",
"Di",
""
],
[
"Wu",
"Puxun",
""
],
[
"Yu",
"Hongwei",
""
],
[
"Wu",
"Shuang-Qing",
""
]
] | The super-entropic black hole, which possesses a noncompact horizon topology and violates the reverse isoperimetric inequality, has been found to satisfy both the thermodynamic first law and the Bekenstein-Smarr mass formula. In this paper, we first derive a new Christodoulou-Ruffini-like squared-mass formula for the four-dimensional Kerr-Newman-AdS super-entropic black hole, and then establish a set of very simple relations between thermodynamic quantities of the super-entropic Kerr-Newman-AdS$_4$ black hole and its usual counterparts. Using these relations, the thermodynamic quantities of the Kerr-Newman-AdS$_4$ super-entropic black hole can be obtained from those of the usual pro-type by taking the ultra-spinning limit properly. Then these relations are extended to the singly-rotating Kerr-AdS black holes in arbitrary dimensions and the double-rotating charged black hole in the five-dimensional minimal gauged supergravity. It can be inferred that the thermodynamic quantities of all super-entropic black holes obey similar limiting relations to those of their corresponding conventional rotating AdS black holes, and thus can be obtained by taking the ultra-spinning limit appropriately. |
1108.1908 | Alessandro Codello | A. Codello | Large N Quantum Gravity | 19 pages, 1 figure, contribution published in "New Journal of Physics
Focus Issue on Quantum Einstein Gravity" | New J. Phys. 14 (2012) 015009 | 10.1088/1367-2630/14/1/015009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain the effective action of four dimensional quantum gravity, induced
by N massless matter fields, by integrating the RG flow of the relative
effective average action. By considering the leading approximation in the large
N limit, where one neglects the gravitational contributions with respect to the
matter contributions, we show how different aspects of quantum gravity, as
asymptotic safety, quantum corrections to the Newtonian potential and the
conformal anomaly induced effective action, are all represented by different
terms of the effective action when this is expanded in powers of the curvature.
| [
{
"created": "Tue, 9 Aug 2011 12:24:13 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Jan 2012 19:03:47 GMT",
"version": "v2"
}
] | 2012-12-18 | [
[
"Codello",
"A.",
""
]
] | We obtain the effective action of four dimensional quantum gravity, induced by N massless matter fields, by integrating the RG flow of the relative effective average action. By considering the leading approximation in the large N limit, where one neglects the gravitational contributions with respect to the matter contributions, we show how different aspects of quantum gravity, as asymptotic safety, quantum corrections to the Newtonian potential and the conformal anomaly induced effective action, are all represented by different terms of the effective action when this is expanded in powers of the curvature. |
0804.1278 | Alexander Kaganovich B. | E. I. Guendelman and A. B. Kaganovich | Transition to Zero Cosmological Constant and Phantom Dark Energy as
Solutions Involving Change of Orientation of Space-Time Manifold | 24 pages, 5 figures, to appear in Class.Quant.Grav.; discussion of a
possibility of a strong gravity effect in LHC experiments added | Class.Quant.Grav.25:235015,2008 | 10.1088/0264-9381/25/23/235015 | null | gr-qc astro-ph hep-th | http://creativecommons.org/licenses/by/3.0/ | Solutions with degenerate metric ($det(g_{\mu\nu})=0$ or $g_{\mu\nu}=0$) in
the first order formalism (FOF) are physically acceptable: they may describe
topology changes (Horowitz) and reduction of "metrical dimension" (Tseytlin) of
space-time. The latter implies disappearance of the volume element
$\sqrt{-g}d^4x$ of 4-D space-time. We pay attention that besides $\sqrt{-g}$,
the 4-D space-time differentiable manifold possesses also a "manifold volume
measure" (MVM)described by a 4-form which is sign indefinite and generically
independent of the metric. The FOF proceeds with originally independent
connection and metric structures of the space-time manifold. We bring up the
question whether the FOF should be supplemented with degrees of freedom of MVM.
Adding such manifold degrees of freedom to the action principle in the FOF we
realize very interesting dynamics. Such Two Measures Theory enables radically
new approaches to resolution of the cosmological constant problem. We show that
fine tuning free solutions describing a transition to $\Lambda =0$ state
involve oscillations of $g_{\mu\nu}$ and MVM around zero. The latter can be
treated as a dynamics involving changes of orientation of the space-time
manifold. As we have shown earlier, in realistic scale invariant models (SIM),
solutions formulated in the Einstein frame satisfy all existing tests of
General Relativity (GR). Here we reveal surprisingly that in SIM, all ground
state solutions with $\Lambda\neq 0$ appear to be degenerate either in $g_{00}$
or in MVM. Sign indefiniteness of MVM in a natural way yields a dynamical
realization of a phantom cosmology ($w<-1$). For all solutions, the metric
tensor rewritten in the Einstein frame has regularity properties exactly as in
GR. A possibility of a strong gravity effect in LHC experiments is discussed.
| [
{
"created": "Tue, 8 Apr 2008 13:57:06 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Apr 2008 12:07:24 GMT",
"version": "v2"
},
{
"created": "Tue, 28 Oct 2008 10:08:44 GMT",
"version": "v3"
}
] | 2008-12-18 | [
[
"Guendelman",
"E. I.",
""
],
[
"Kaganovich",
"A. B.",
""
]
] | Solutions with degenerate metric ($det(g_{\mu\nu})=0$ or $g_{\mu\nu}=0$) in the first order formalism (FOF) are physically acceptable: they may describe topology changes (Horowitz) and reduction of "metrical dimension" (Tseytlin) of space-time. The latter implies disappearance of the volume element $\sqrt{-g}d^4x$ of 4-D space-time. We pay attention that besides $\sqrt{-g}$, the 4-D space-time differentiable manifold possesses also a "manifold volume measure" (MVM)described by a 4-form which is sign indefinite and generically independent of the metric. The FOF proceeds with originally independent connection and metric structures of the space-time manifold. We bring up the question whether the FOF should be supplemented with degrees of freedom of MVM. Adding such manifold degrees of freedom to the action principle in the FOF we realize very interesting dynamics. Such Two Measures Theory enables radically new approaches to resolution of the cosmological constant problem. We show that fine tuning free solutions describing a transition to $\Lambda =0$ state involve oscillations of $g_{\mu\nu}$ and MVM around zero. The latter can be treated as a dynamics involving changes of orientation of the space-time manifold. As we have shown earlier, in realistic scale invariant models (SIM), solutions formulated in the Einstein frame satisfy all existing tests of General Relativity (GR). Here we reveal surprisingly that in SIM, all ground state solutions with $\Lambda\neq 0$ appear to be degenerate either in $g_{00}$ or in MVM. Sign indefiniteness of MVM in a natural way yields a dynamical realization of a phantom cosmology ($w<-1$). For all solutions, the metric tensor rewritten in the Einstein frame has regularity properties exactly as in GR. A possibility of a strong gravity effect in LHC experiments is discussed. |
gr-qc/0603024 | Daniela Mugnai | Daniela Mugnai | Superluminal behavior and the Minkowski space-time | 3 pages, 2 figures | Phys.Lett.A364:435-437,2007 | 10.1016/j.physleta.2006.11.096 | null | gr-qc | null | Bessel X-waves, or Bessel beams, have been extensively studied in last years,
especially with regard to the topic of superluminality in the propagation of a
signal. However, in spite of many efforts devoted to this subject, no definite
answer has been found, mainly for lack of an exact definition of signal
velocity. The purpose of the present work is to investigate the field of
existence of Bessel beams in order to overcome the specific question related to
the definition of signal velocity. Quite surprisingly, this field of existence
can be represented in the Minkowski space-time by a Super-Light Cone which
wraps itself around the well-known Light Cone. So, the change in the upper
limit of the light velocity does not modify the fundamental low of the
relativity and the causal principle.
| [
{
"created": "Wed, 8 Mar 2006 11:25:06 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Mugnai",
"Daniela",
""
]
] | Bessel X-waves, or Bessel beams, have been extensively studied in last years, especially with regard to the topic of superluminality in the propagation of a signal. However, in spite of many efforts devoted to this subject, no definite answer has been found, mainly for lack of an exact definition of signal velocity. The purpose of the present work is to investigate the field of existence of Bessel beams in order to overcome the specific question related to the definition of signal velocity. Quite surprisingly, this field of existence can be represented in the Minkowski space-time by a Super-Light Cone which wraps itself around the well-known Light Cone. So, the change in the upper limit of the light velocity does not modify the fundamental low of the relativity and the causal principle. |
2304.00984 | Shu-Min Wu | Shu-Min Wu, Xiao-Wei Fan, Rui-Di Wang, Hao-Yu Wu, Xiao-Li Huang,
Hao-Sheng Zeng | Does Hawking effect always degrade fidelity of quantum teleportation in
Schwarzschild spacetime? | 21 pages, 3 figures, accepted for publication in JHEP | null | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | Previous studies have shown that the Hawking effect always destroys quantum
correlations and the fidelity of quantum teleportation in the Schwarzschild
black hole. Here, we investigate the fidelity of quantum teleportation of Dirac
fields between users in Schwarzschild spacetime. We find that, with the
increase of the Hawking temperature, the fidelity of quantum teleportation can
monotonically increase, monotonically decrease, or non-monotonically increase,
depending on the choice of the initial state, which means that the Hawking
effect can create net fidelity of quantum teleportation. This striking result
banishes the extended belief that the Hawking effect of the black hole can only
destroy the fidelity of quantum teleportation. We also find that quantum
steering cannot fully guarantee the fidelity of quantum teleportation in
Schwarzschild spacetime. This new unexpected source may provide a new idea for
the experimental evidence of the Hawking effect.
| [
{
"created": "Mon, 3 Apr 2023 13:52:07 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Nov 2023 02:37:00 GMT",
"version": "v2"
}
] | 2023-11-30 | [
[
"Wu",
"Shu-Min",
""
],
[
"Fan",
"Xiao-Wei",
""
],
[
"Wang",
"Rui-Di",
""
],
[
"Wu",
"Hao-Yu",
""
],
[
"Huang",
"Xiao-Li",
""
],
[
"Zeng",
"Hao-Sheng",
""
]
] | Previous studies have shown that the Hawking effect always destroys quantum correlations and the fidelity of quantum teleportation in the Schwarzschild black hole. Here, we investigate the fidelity of quantum teleportation of Dirac fields between users in Schwarzschild spacetime. We find that, with the increase of the Hawking temperature, the fidelity of quantum teleportation can monotonically increase, monotonically decrease, or non-monotonically increase, depending on the choice of the initial state, which means that the Hawking effect can create net fidelity of quantum teleportation. This striking result banishes the extended belief that the Hawking effect of the black hole can only destroy the fidelity of quantum teleportation. We also find that quantum steering cannot fully guarantee the fidelity of quantum teleportation in Schwarzschild spacetime. This new unexpected source may provide a new idea for the experimental evidence of the Hawking effect. |
2311.17730 | Edward Teo | Edward Teo, Thomas Wan | Multi-centered rotating black holes in Kaluza-Klein theory | 19 pages, more details added to Sec. 4, published version | Phys. Rev. D 109, 044054 (2024) | 10.1103/PhysRevD.109.044054 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The most general charged and rotating black hole in Kaluza-Klein theory is
known to be described by the Rasheed-Larsen solution. When the under-rotating
extremal limit of this solution is taken, it falls into a general class of
solutions of Kaluza-Klein theory found by Cl\'ement, and is specified by two
harmonic functions on a three-dimensional flat base space. We use this fact to
generalise the single extremal black hole solution to one describing an
arbitrary superposition of such black holes. These black holes carry non-zero
electric and magnetic charges, which we set to be equal for simplicity, and are
in general rotating with parallel or anti-parallel spin vectors. It is checked
that the space-time outside the black holes is free of pathologies such as
naked singularities and closed time-like curves.
| [
{
"created": "Wed, 29 Nov 2023 15:35:54 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Feb 2024 11:22:37 GMT",
"version": "v2"
}
] | 2024-02-23 | [
[
"Teo",
"Edward",
""
],
[
"Wan",
"Thomas",
""
]
] | The most general charged and rotating black hole in Kaluza-Klein theory is known to be described by the Rasheed-Larsen solution. When the under-rotating extremal limit of this solution is taken, it falls into a general class of solutions of Kaluza-Klein theory found by Cl\'ement, and is specified by two harmonic functions on a three-dimensional flat base space. We use this fact to generalise the single extremal black hole solution to one describing an arbitrary superposition of such black holes. These black holes carry non-zero electric and magnetic charges, which we set to be equal for simplicity, and are in general rotating with parallel or anti-parallel spin vectors. It is checked that the space-time outside the black holes is free of pathologies such as naked singularities and closed time-like curves. |
gr-qc/0311065 | Daniel Arteaga | Daniel Arteaga, Renaud Parentani and Enric Verdaguer | Propagation in a thermal graviton background | 16 pages, 4 figures. This version matches the published paper | Phys.Rev. D70 (2004) 044019 | 10.1103/PhysRevD.70.044019 | null | gr-qc astro-ph hep-th | null | It is well known that radiative corrections evaluated in nontrivial
backgrounds lead to effective dispersion relations which are not Lorentz
invariant. Since gravitational interactions increase with energy,
gravity-induced radiative corrections could be relevant for the trans-Planckian
problem. As a first step to explore this possibility, we compute the one-loop
radiative corrections to the self-energy of a scalar particle propagating in a
thermal bath of gravitons in Minkowski spacetime. We obtain terms which
originate from the thermal bath and which indeed break the Lorentz invariance
that possessed the propagator in the vacuum. Rather unexpectedly, however, the
terms which break Lorentz invariance vanish in the high three-momentum limit.
We also found that the imaginary part, which gives the rate of approach to
thermal equilibrium, vanishes at one loop.
| [
{
"created": "Thu, 20 Nov 2003 14:53:03 GMT",
"version": "v1"
},
{
"created": "Tue, 25 May 2004 10:02:53 GMT",
"version": "v2"
},
{
"created": "Mon, 30 Aug 2004 09:41:33 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Arteaga",
"Daniel",
""
],
[
"Parentani",
"Renaud",
""
],
[
"Verdaguer",
"Enric",
""
]
] | It is well known that radiative corrections evaluated in nontrivial backgrounds lead to effective dispersion relations which are not Lorentz invariant. Since gravitational interactions increase with energy, gravity-induced radiative corrections could be relevant for the trans-Planckian problem. As a first step to explore this possibility, we compute the one-loop radiative corrections to the self-energy of a scalar particle propagating in a thermal bath of gravitons in Minkowski spacetime. We obtain terms which originate from the thermal bath and which indeed break the Lorentz invariance that possessed the propagator in the vacuum. Rather unexpectedly, however, the terms which break Lorentz invariance vanish in the high three-momentum limit. We also found that the imaginary part, which gives the rate of approach to thermal equilibrium, vanishes at one loop. |
1207.5410 | Fabio Garufi | Mariafelicia De Laurentis, Rosario De Rosa, Fabio Garufi and Leopoldo
Milano | Testing gravitational theories using Eccentric Eclipsing Detached
Binaries | 15 pages, 8 figures, 5 tables; Monthly Notices of the Royal
Astronomical Society (2012) "Early View". arXiv admin note: text overlap with
arXiv:gr-qc/0603071 by other authors | null | 10.1111/j.1365-2966.2012.21410.x | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we compare the effects of different theories of gravitation on
the apsidal motion of a sample of Eccentric Eclipsing Detached Binary stars.
The comparison is performed by using the formalism of the Post-Newtonian
parametrization to calculate the theoretical advance at periastron and compare
it to the observed one, after having considered the effects of the structure
and rotation of the involved stars. A variance analysis on the results of this
comparison, shows that no significant difference can be found due to the effect
of the different theories under test with respect to the standard General
Relativity. It will be possible to observe differences, as we would expect, by
checking the observed period variation on a much larger lapse of time. It can
also be noticed from our results, that f(R) theory is the nearest to GR with
respect to the other tested theories.
| [
{
"created": "Mon, 23 Jul 2012 14:24:19 GMT",
"version": "v1"
}
] | 2012-07-24 | [
[
"De Laurentis",
"Mariafelicia",
""
],
[
"De Rosa",
"Rosario",
""
],
[
"Garufi",
"Fabio",
""
],
[
"Milano",
"Leopoldo",
""
]
] | In this paper we compare the effects of different theories of gravitation on the apsidal motion of a sample of Eccentric Eclipsing Detached Binary stars. The comparison is performed by using the formalism of the Post-Newtonian parametrization to calculate the theoretical advance at periastron and compare it to the observed one, after having considered the effects of the structure and rotation of the involved stars. A variance analysis on the results of this comparison, shows that no significant difference can be found due to the effect of the different theories under test with respect to the standard General Relativity. It will be possible to observe differences, as we would expect, by checking the observed period variation on a much larger lapse of time. It can also be noticed from our results, that f(R) theory is the nearest to GR with respect to the other tested theories. |
gr-qc/0103038 | Diego Pavon | Luis P Chimento, Alejandro S Jakubi, Diego Pavon | Varying c and Particle Horizons | Latex file, 8 pages, to be published in Physics Letters B | Phys.Lett. B508 (2001) 1-5 | 10.1016/S0370-2693(01)00400-2 | null | gr-qc astro-ph | null | We explore what restrictions may impose the second law of thermodynamics on
varying speed of light theories. We find that the attractor scenario solving
the flatness problem is consistent with the generalized second law at late
time.
| [
{
"created": "Tue, 13 Mar 2001 11:21:06 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Chimento",
"Luis P",
""
],
[
"Jakubi",
"Alejandro S",
""
],
[
"Pavon",
"Diego",
""
]
] | We explore what restrictions may impose the second law of thermodynamics on varying speed of light theories. We find that the attractor scenario solving the flatness problem is consistent with the generalized second law at late time. |
gr-qc/9907100 | Banibrata Mukhopadhyay | Banibrata Mukhopadhyay and Sandip K. Chakrabarti | Semi-analytical Solution of Dirac equation in Schwarzschild Geometry | RevTex, 11 Latex pages and 12 Figures ; Classical and Quantum Gravity
(in Press) (1999) | Class.Quant.Grav. 16 (1999) 3165-3181 | 10.1088/0264-9381/16/10/309 | null | gr-qc astro-ph | null | Separation of the Dirac equation in the spacetime around a Kerr black hole
into radial and angular coordinates was done by Chandrasekhar in 1976. In the
present paper, we solve the radial equations in a Schwarzschild geometry
semi-analytically using Wentzel-Kramers-Brillouin approximation (in short WKB)
method. Among other things, we present analytical expression of the
instantaneous reflection and transmission coefficients and the radial wave
functions of the Dirac particles. Complete physical parameter space was divided
into two parts depending on the height of the potential well and energy of the
incoming waves. We show the general solution for these two regions. We also
solve the equations by a Quantum Mechanical approach, in which the potential is
approximated by a series of steps and found that these two solutions agree. We
compare solutions of different initial parameters and show how the properties
of the scattered wave depend on these parameters.
| [
{
"created": "Thu, 29 Jul 1999 06:29:42 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Mukhopadhyay",
"Banibrata",
""
],
[
"Chakrabarti",
"Sandip K.",
""
]
] | Separation of the Dirac equation in the spacetime around a Kerr black hole into radial and angular coordinates was done by Chandrasekhar in 1976. In the present paper, we solve the radial equations in a Schwarzschild geometry semi-analytically using Wentzel-Kramers-Brillouin approximation (in short WKB) method. Among other things, we present analytical expression of the instantaneous reflection and transmission coefficients and the radial wave functions of the Dirac particles. Complete physical parameter space was divided into two parts depending on the height of the potential well and energy of the incoming waves. We show the general solution for these two regions. We also solve the equations by a Quantum Mechanical approach, in which the potential is approximated by a series of steps and found that these two solutions agree. We compare solutions of different initial parameters and show how the properties of the scattered wave depend on these parameters. |
gr-qc/0701152 | Steven Willison | Elias Gravanis and Steven Willison | `Mass without mass' from thin shells in Gauss-Bonnet gravity | 13 pages, RevTex, 8 figures. Version 2: includes discussion on the
well-defined thin shell limit. Version 3: typos fixed, a reference added,
accepted for publication in Phys. Rev. D | Phys.Rev.D75:084025,2007 | 10.1103/PhysRevD.75.084025 | CECS-PHY-07/01 | gr-qc hep-th | null | Five tensor equations are obtained for a thin shell in Gauss-Bonnet gravity.
There is the well known junction condition for the singular part of the stress
tensor intrinsic to the shell, which we also prove to be well defined. There
are also equations relating the geometry of the shell (jump and average of the
extrinsic curvature as well as the intrinsic curvature) to the non-singular
components of the bulk stress tensor on the sides of the thin shell.
The equations are applied to spherically symmetric thin shells in vacuum. The
shells are part of the vacuum, they carry no energy tensor. We classify these
solutions of `thin shells of nothingness' in the pure Gauss-Bonnet theory.
There are three types of solutions, with one, zero or two asymptotic regions
respectively. The third kind of solution are wormholes. Although vacuum
solutions, they have the appearance of mass in the asymptotic regions. It is
striking that in this theory, exotic matter is not needed in order for
wormholes to exist- they can exist even with no matter.
| [
{
"created": "Sun, 28 Jan 2007 00:00:39 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Feb 2007 21:52:40 GMT",
"version": "v2"
},
{
"created": "Thu, 22 Mar 2007 16:17:50 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Gravanis",
"Elias",
""
],
[
"Willison",
"Steven",
""
]
] | Five tensor equations are obtained for a thin shell in Gauss-Bonnet gravity. There is the well known junction condition for the singular part of the stress tensor intrinsic to the shell, which we also prove to be well defined. There are also equations relating the geometry of the shell (jump and average of the extrinsic curvature as well as the intrinsic curvature) to the non-singular components of the bulk stress tensor on the sides of the thin shell. The equations are applied to spherically symmetric thin shells in vacuum. The shells are part of the vacuum, they carry no energy tensor. We classify these solutions of `thin shells of nothingness' in the pure Gauss-Bonnet theory. There are three types of solutions, with one, zero or two asymptotic regions respectively. The third kind of solution are wormholes. Although vacuum solutions, they have the appearance of mass in the asymptotic regions. It is striking that in this theory, exotic matter is not needed in order for wormholes to exist- they can exist even with no matter. |
gr-qc/0606073 | L\'aszl\'o \'A Gergely | L\'aszl\'o \'A. Gergely | Dark energy from gravitational collapse? | 6 pages, Honorable Mention in the Gravity Research Foundation's 2006
Essays in Gravitation Competition | null | null | null | gr-qc astro-ph hep-th | null | We discuss the status of both cosmological and black hole type singularities
in the framework of the brane-world model of gravity. We point out that the Big
Bang is not properly understood yet. We also show new features of the
gravitational collapse on the brane, the most important being the production of
dark energy during the collapse.
| [
{
"created": "Fri, 16 Jun 2006 17:47:40 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gergely",
"László Á.",
""
]
] | We discuss the status of both cosmological and black hole type singularities in the framework of the brane-world model of gravity. We point out that the Big Bang is not properly understood yet. We also show new features of the gravitational collapse on the brane, the most important being the production of dark energy during the collapse. |
2209.06670 | Salvatore Capozziello | Salvatore Capozziello and Mehdi Shokri | Slow-roll inflation in $f(Q)$ non-metric gravity | 18 pages, 7 figures, accepted for publication ion Physics of the Dark
Universe | Phys.Dark Univ. 37 (2022) 101113 | 10.1016/j.dark.2022.101113 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | We discuss the cosmological inflation in the context of $f(Q)$ non-metric
gravity, where $Q$ is the non-metric scalar. After introducing conformal
transformations for $f(Q)$ gravity, we first focus on the potential-slow-roll
inflation by studying the corresponding potentials for different forms of the
function $f(Q)$ in the Einstein frame. Secondly, we investigate the
Hubble-slow-roll inflation for three classes of inflationary potentials
considered for the specific form $f(Q)\propto Q^{2}$, in the Jordan frame. We
compare results in both approaches with observations coming from Planck and
BICEP2/Keck array satellites. Observational constraints on the parameters space
of the models are obtained as well.
| [
{
"created": "Wed, 14 Sep 2022 14:27:42 GMT",
"version": "v1"
}
] | 2022-09-23 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Shokri",
"Mehdi",
""
]
] | We discuss the cosmological inflation in the context of $f(Q)$ non-metric gravity, where $Q$ is the non-metric scalar. After introducing conformal transformations for $f(Q)$ gravity, we first focus on the potential-slow-roll inflation by studying the corresponding potentials for different forms of the function $f(Q)$ in the Einstein frame. Secondly, we investigate the Hubble-slow-roll inflation for three classes of inflationary potentials considered for the specific form $f(Q)\propto Q^{2}$, in the Jordan frame. We compare results in both approaches with observations coming from Planck and BICEP2/Keck array satellites. Observational constraints on the parameters space of the models are obtained as well. |
1808.06683 | David Garfinkle | David Garfinkle, Lawrence R. Mead, H.I. Ringermacher | The shape of the orbit in FLRW spacetimes | submitted as a Note to CQG | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The shape of the orbit of a free particle is examined in FLRW cosmologies.
The spatial projection of the orbit is time-independent and has a simple
geometric description. We relate this description to the expression in terms of
standard FLRW coordinates.
| [
{
"created": "Mon, 20 Aug 2018 20:29:58 GMT",
"version": "v1"
}
] | 2018-08-22 | [
[
"Garfinkle",
"David",
""
],
[
"Mead",
"Lawrence R.",
""
],
[
"Ringermacher",
"H. I.",
""
]
] | The shape of the orbit of a free particle is examined in FLRW cosmologies. The spatial projection of the orbit is time-independent and has a simple geometric description. We relate this description to the expression in terms of standard FLRW coordinates. |
gr-qc/0208061 | Luz Maria Diaz-Rivera | L. M. Diaz-Rivera and Luis O. Pimentel | Required Conditions for Late Time Acceleration and Early Time
Deceleration in Generalized Scalar-Tensor Theories | 21 pages, 5 figures, to appear in Int. J. Mod. Phys. A | Int.J.Mod.Phys. A18 (2003) 651-672 | 10.1142/S0217751X03012205 | null | gr-qc | null | We consider a generalized scalar-tensor theory, where we let the coupling
function $\omega(\phi)$ and the effective cosmological constants
$\Lambda(\phi)$ undetermined. We obtain general expressions for $\omega(\phi)$
and $\Lambda(\phi)$ in terms of the scalar field and the scale factor, and show
that $\omega(\phi)$ depends on the scalar field and the scale factor in a
complicated way. In order to study the conditions for an accelerated expansion
at the present time and a decelerated expansion in the past, we assume a power
law evolution for the scalar field and the scale factor. We analyse the
required conditions that allow our model to satisfy the weak field limits on
$\omega(\phi)$, and at the same time, to obtain the correct values of
cosmological parameters, as the energy density $ \Omega_{m0}$ and cosmological
constant $\Lambda(t_0)$. We also study the conditions for a decelerated
expansion at an early time dominated by radiation. We find values for
$\omega(\phi)$ and $\Lambda(\phi)$ consistent with the expectations of a theory
where the cosmological constant decreases with the time and the coupling
function increases until the values accepted today.
| [
{
"created": "Wed, 21 Aug 2002 19:08:51 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Diaz-Rivera",
"L. M.",
""
],
[
"Pimentel",
"Luis O.",
""
]
] | We consider a generalized scalar-tensor theory, where we let the coupling function $\omega(\phi)$ and the effective cosmological constants $\Lambda(\phi)$ undetermined. We obtain general expressions for $\omega(\phi)$ and $\Lambda(\phi)$ in terms of the scalar field and the scale factor, and show that $\omega(\phi)$ depends on the scalar field and the scale factor in a complicated way. In order to study the conditions for an accelerated expansion at the present time and a decelerated expansion in the past, we assume a power law evolution for the scalar field and the scale factor. We analyse the required conditions that allow our model to satisfy the weak field limits on $\omega(\phi)$, and at the same time, to obtain the correct values of cosmological parameters, as the energy density $ \Omega_{m0}$ and cosmological constant $\Lambda(t_0)$. We also study the conditions for a decelerated expansion at an early time dominated by radiation. We find values for $\omega(\phi)$ and $\Lambda(\phi)$ consistent with the expectations of a theory where the cosmological constant decreases with the time and the coupling function increases until the values accepted today. |
2310.01447 | Fabrice Debbasch | Fabrice Debbasch | Space-Time from quantum Physics | null | null | null | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | A construction of the real 4D Minkowski space-time starting from quantum
harmonic oscillators is proposed. First, a 2D spinor space and its dual are
derived from the standard commutation relations obeyed by the ladder operators
of two independent 1D harmonic oscillators. The complex 4D Minkowvski vector
space V is then constructed from these spinor space. The flat, real 4D
Minkowski manifold is finally built as an approximate description of a manifold
of unitary operators constructed from V. Lorentz invariance is recovered and
several possible extensions are discussed, which connections to quantum optics
and condensed matter physics.
| [
{
"created": "Sun, 1 Oct 2023 14:50:46 GMT",
"version": "v1"
}
] | 2023-10-04 | [
[
"Debbasch",
"Fabrice",
""
]
] | A construction of the real 4D Minkowski space-time starting from quantum harmonic oscillators is proposed. First, a 2D spinor space and its dual are derived from the standard commutation relations obeyed by the ladder operators of two independent 1D harmonic oscillators. The complex 4D Minkowvski vector space V is then constructed from these spinor space. The flat, real 4D Minkowski manifold is finally built as an approximate description of a manifold of unitary operators constructed from V. Lorentz invariance is recovered and several possible extensions are discussed, which connections to quantum optics and condensed matter physics. |
0912.5443 | Emilio Santos Corchero | Emilio Santos | Space-time curvature due to quantum vacuum fluctuations: An alternative
to dark energy? | null | Phys.Lett.A374:709-712,2010 | 10.1016/j.physleta.2009.11.079 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is pointed out that quantum vacuum fluctuations may give rise to a
curvature of space-time equivalent to the curvature currently attributed to
dark energy. A simple calculation is made, which suggests that the value of the
dark energy density is roughly given by the product of Newton constant time the
quantity m^6 c^4 h^-4, m being a typical mass of elementary particles. The
estimate is compatible with observations.
| [
{
"created": "Wed, 30 Dec 2009 10:35:46 GMT",
"version": "v1"
}
] | 2010-05-12 | [
[
"Santos",
"Emilio",
""
]
] | It is pointed out that quantum vacuum fluctuations may give rise to a curvature of space-time equivalent to the curvature currently attributed to dark energy. A simple calculation is made, which suggests that the value of the dark energy density is roughly given by the product of Newton constant time the quantity m^6 c^4 h^-4, m being a typical mass of elementary particles. The estimate is compatible with observations. |
1806.07242 | Hossein Ghaffarnejad | Emad Yaraie, Hossein Ghaffarnejad, Mohammad Farsam | Complexity growth and shock wave geometry in
AdS-Maxwell-power-Yang-Mills theory | 18 pages, 2 Figures and improved with some additional sentences | The European Physical Journal C 2018 | 10.1140/epjc/s10052-018-6456-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study effects of non-abelian gauge fields on the holographic
characteristics for instance the evolution of computational complexity. To do
so we choose Maxwell-power-Yang-Mills theory defined in the AdS space-time.
Then we seek the impact of charge of the YM field on the complexity growth rate
by using $complexity=action$ (CA) conjecture. We also investigate the spreading
of perturbations near the horizon and the complexity growth rate in local shock
wave geometry in presence of the YM charge. At last we check validity regime of
Lloyd bound.
| [
{
"created": "Fri, 15 Jun 2018 22:13:36 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Sep 2018 20:48:48 GMT",
"version": "v2"
},
{
"created": "Sat, 10 Nov 2018 21:55:12 GMT",
"version": "v3"
}
] | 2018-11-19 | [
[
"Yaraie",
"Emad",
""
],
[
"Ghaffarnejad",
"Hossein",
""
],
[
"Farsam",
"Mohammad",
""
]
] | We study effects of non-abelian gauge fields on the holographic characteristics for instance the evolution of computational complexity. To do so we choose Maxwell-power-Yang-Mills theory defined in the AdS space-time. Then we seek the impact of charge of the YM field on the complexity growth rate by using $complexity=action$ (CA) conjecture. We also investigate the spreading of perturbations near the horizon and the complexity growth rate in local shock wave geometry in presence of the YM charge. At last we check validity regime of Lloyd bound. |
gr-qc/9801045 | Remo Garattini | Remo Garattini | Space-time Foam, Casimir energy and black hole pair creation | Revtex 3.0, 9 pages, to appear in Mod. Phys. Lett. A | Mod.Phys.Lett. A13 (1998) 159-164 | 10.1142/S0217732398000206 | null | gr-qc hep-th | null | We conjecture that the neutral black hole pair production is related to the
vacuum fluctuation of pure gravity via the Casimir-like energy. Implications on
the foam-like structure of spacetime are discussed.
| [
{
"created": "Wed, 14 Jan 1998 22:55:29 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Garattini",
"Remo",
""
]
] | We conjecture that the neutral black hole pair production is related to the vacuum fluctuation of pure gravity via the Casimir-like energy. Implications on the foam-like structure of spacetime are discussed. |
1904.01249 | Bahram Mashhoon | Hassan Firouzjahi and Bahram Mashhoon | Twisted Gravitational Waves in the Presence of a Cosmological Constant | 30 pages, 1 figure; v2: Section V improved, reference added; v3:
revised version, figures added; v4: minor corrections, matches published
version | Phys. Rev. D 100, 084027 (2019) | 10.1103/PhysRevD.100.084027 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find exact nonlinear solutions of general relativity that represent
twisted gravitational waves (TGWs) in the presence of a cosmological constant.
A TGW is a nonplanar wave propagating along a fixed spatial direction with a
null Killing wave vector that has a nonzero twist tensor. The solutions all
turn out to have wave fronts with negative Gaussian curvature. Among the
classes of solutions presented in this paper, we find a unique class of simple
conformally flat TGWs that is due to the presence of a negative cosmological
constant and therefore represents part of anti-de Sitter spacetime. The
properties of this special solution are studied in detail.
| [
{
"created": "Tue, 2 Apr 2019 07:18:51 GMT",
"version": "v1"
},
{
"created": "Tue, 14 May 2019 12:26:01 GMT",
"version": "v2"
},
{
"created": "Sun, 21 Jul 2019 15:06:58 GMT",
"version": "v3"
},
{
"created": "Mon, 14 Oct 2019 19:20:15 GMT",
"version": "v4"
}
] | 2019-10-23 | [
[
"Firouzjahi",
"Hassan",
""
],
[
"Mashhoon",
"Bahram",
""
]
] | We find exact nonlinear solutions of general relativity that represent twisted gravitational waves (TGWs) in the presence of a cosmological constant. A TGW is a nonplanar wave propagating along a fixed spatial direction with a null Killing wave vector that has a nonzero twist tensor. The solutions all turn out to have wave fronts with negative Gaussian curvature. Among the classes of solutions presented in this paper, we find a unique class of simple conformally flat TGWs that is due to the presence of a negative cosmological constant and therefore represents part of anti-de Sitter spacetime. The properties of this special solution are studied in detail. |
2006.01452 | Vittorio De Falco Dr | Vittorio De Falco, Pavel Bakala, Maurizio Falanga | Three-dimensional general relativistic Poynting-Robertson effect. III.
Static and non-spherical quadrupolar massive source | 16 pages, 11 figures. Paper accepted on the 2nd of June 2020 on Phys.
Rev. D | null | 10.1103/PhysRevD.101.124031 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the three-dimensional motion of a test particle in the
gravitational field generated by a non-spherical compact object endowed with a
mass quadrupole moment, described by the Erez-Rosen metric, and a radiation
field, including the general relativistic Poynting-Robertson effect, coming
from a rigidly rotating spherical emitting source located outside of the
compact object. We derive the equations of motion for test particles influenced
by such radiation field, recovering the two-dimensional description, and the
weak-field approximation. This dynamical system admits the existence of a
critical hypersurface, region where gravitational and radiation forces balance.
Selected test particle orbits for different set of input parameters are
displayed. The possible configurations on the critical hypersurfaces can be
either latitudinal drift towards the equatorial ring or suspended orbits. We
discuss about the existence of multiple hypersurface solutions through a simple
method to perform the calculations. We graphically prove also that the critical
hypersurfaces are stable configurations within the Lyapunov theory.
| [
{
"created": "Tue, 2 Jun 2020 08:46:54 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jun 2020 09:36:03 GMT",
"version": "v2"
}
] | 2020-07-01 | [
[
"De Falco",
"Vittorio",
""
],
[
"Bakala",
"Pavel",
""
],
[
"Falanga",
"Maurizio",
""
]
] | We investigate the three-dimensional motion of a test particle in the gravitational field generated by a non-spherical compact object endowed with a mass quadrupole moment, described by the Erez-Rosen metric, and a radiation field, including the general relativistic Poynting-Robertson effect, coming from a rigidly rotating spherical emitting source located outside of the compact object. We derive the equations of motion for test particles influenced by such radiation field, recovering the two-dimensional description, and the weak-field approximation. This dynamical system admits the existence of a critical hypersurface, region where gravitational and radiation forces balance. Selected test particle orbits for different set of input parameters are displayed. The possible configurations on the critical hypersurfaces can be either latitudinal drift towards the equatorial ring or suspended orbits. We discuss about the existence of multiple hypersurface solutions through a simple method to perform the calculations. We graphically prove also that the critical hypersurfaces are stable configurations within the Lyapunov theory. |
gr-qc/0303047 | Koryukin | Valery Koryukin (Mari State Technical University) | Gravitational fields and dark matter | plain tex, 7 pages | null | null | null | gr-qc | null | In this paper a hypothesis is considered, in which neutrinos and other weakly
interacting particles play a fundamental role in Universe. In addition the
Newton gravitational constant $G_N$ and the Hubble constant $H$ are interpreted
as parameters, characterizing the neutrinos background of Universe.
| [
{
"created": "Wed, 12 Mar 2003 06:43:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Koryukin",
"Valery",
"",
"Mari State Technical University"
]
] | In this paper a hypothesis is considered, in which neutrinos and other weakly interacting particles play a fundamental role in Universe. In addition the Newton gravitational constant $G_N$ and the Hubble constant $H$ are interpreted as parameters, characterizing the neutrinos background of Universe. |
2408.03978 | Stefano Vignolo Professor | Stefano Vignolo, Fabrizio Esposito, Sante Carloni | A note on the junction conditions in f(Q)-gravity | in press | Classical and Quantum Gravity, 2024 | 10.1088/1361-6382/ad6be0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the notion of distribution-valued tensor, we discuss the junction
conditions within the framework of f(Q)-gravity. We obtain the necessary and
sufficient conditions for two distinct solutions of the field equations to be
smoothly joined on a given separation hypersurface.
| [
{
"created": "Wed, 7 Aug 2024 14:53:14 GMT",
"version": "v1"
}
] | 2024-08-09 | [
[
"Vignolo",
"Stefano",
""
],
[
"Esposito",
"Fabrizio",
""
],
[
"Carloni",
"Sante",
""
]
] | Using the notion of distribution-valued tensor, we discuss the junction conditions within the framework of f(Q)-gravity. We obtain the necessary and sufficient conditions for two distinct solutions of the field equations to be smoothly joined on a given separation hypersurface. |
gr-qc/0601116 | Kourosh Nozari | Kourosh Nozari and A. S. Sefiedgar | Comparison of Approaches to Quantum Correction of Black Hole
Thermodynamics | 10 Pages, No Figures | Phys.Lett.B635:156-160,2006 | 10.1016/j.physletb.2006.01.043 | null | gr-qc | null | There are several approaches to quantum gravitational corrections of black
hole thermodynamics. String theory and loop quantum gravity, by direct analysis
on the basis of quantum properties of black holes, show that in the
entropy-area relation the leading order correction should be of log-area type.
On the other hand, generalized uncertainty principle(GUP) and modified
dispersion relations(MDRs) provide perturbational framework for such
modifications. Although both GUP and MDRs are common features of all quantum
gravity scenarios, their functional forms are quantum gravity model dependent.
Since both string theory and loop quantum gravity give more reliable solution
of the black hole thermodynamics, one can use their results to test approximate
results of GUP and MDRs. In this paper, we find quantum corrected black hole
thermodynamics in the framework of GUP and MDR and then we compare our results
with string theory solutions. This comparison suggests severe constraints on
the functional form of GUP and MDRs. These constraints may reflect
characteristic features of ultimate quantum gravity theory.
| [
{
"created": "Fri, 27 Jan 2006 08:32:18 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Nozari",
"Kourosh",
""
],
[
"Sefiedgar",
"A. S.",
""
]
] | There are several approaches to quantum gravitational corrections of black hole thermodynamics. String theory and loop quantum gravity, by direct analysis on the basis of quantum properties of black holes, show that in the entropy-area relation the leading order correction should be of log-area type. On the other hand, generalized uncertainty principle(GUP) and modified dispersion relations(MDRs) provide perturbational framework for such modifications. Although both GUP and MDRs are common features of all quantum gravity scenarios, their functional forms are quantum gravity model dependent. Since both string theory and loop quantum gravity give more reliable solution of the black hole thermodynamics, one can use their results to test approximate results of GUP and MDRs. In this paper, we find quantum corrected black hole thermodynamics in the framework of GUP and MDR and then we compare our results with string theory solutions. This comparison suggests severe constraints on the functional form of GUP and MDRs. These constraints may reflect characteristic features of ultimate quantum gravity theory. |
1601.05396 | Prayush Kumar | Prayush Kumar, Tony Chu, Heather Fong, Harald P. Pfeiffer, Michael
Boyle, Daniel A. Hemberger, Lawrence E. Kidder, Mark A. Scheel, and Bela
Szilagyi | Accuracy of binary black hole waveform models for aligned-spin binaries | 24 pages, 15 figures, minor changes | Phys. Rev. D 93, 104050 (2016) | 10.1103/PhysRevD.93.104050 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Coalescing binary black holes are among the primary science targets for
second generation ground-based gravitational wave (GW) detectors. Reliable GW
models are central to detection of such systems and subsequent parameter
estimation. This paper performs a comprehensive analysis of the accuracy of
recent waveform models for binary black holes with aligned spins, utilizing a
new set of $84$ high-accuracy numerical relativity simulations. Our analysis
covers comparable mass binaries ($1\le m_1/m_2\le 3$), and samples
independently both black hole spins up to dimensionless spin-magnitude of $0.9$
for equal-mass binaries and $0.85$ for unequal mass binaries. Furthermore, we
focus on the high-mass regime (total mass $\gtrsim 50M_\odot$). The two most
recent waveform models considered (PhenomD and SEOBNRv2) both perform very well
for signal detection, losing less than 0.5\% of the recoverable signal-to-noise
ratio $\rho$, except that SEOBNRv2's efficiency drops mildly for both black
hole spins aligned with large magnitude. For parameter estimation, modeling
inaccuracies of SEOBNRv2 are found to be smaller than systematic uncertainties
for moderately strong GW events up to roughly $\rho\lesssim 15$. PhenomD's
modeling errors are found to be smaller than SEOBNRv2's, and are generally
irrelevant for $\rho\lesssim 20$. Both models' accuracy deteriorates with
increased mass-ratio, and when at least one black hole spin is large and
aligned. The SEOBNRv2 model shows a pronounced disagreement with the numerical
relativity simulation in the merger phase, for unequal masses and
simultaneously both black hole spins very large and aligned. Two older waveform
models (PhenomC and SEOBNRv1) are found to be distinctly less accurate than the
more recent PhenomD and SEOBNRv2 models. Finally, we quantify the bias expected
from all GW models during parameter estimation for recovery of binary's masses
and spins.
| [
{
"created": "Wed, 20 Jan 2016 20:11:34 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jan 2016 21:45:29 GMT",
"version": "v2"
}
] | 2016-06-01 | [
[
"Kumar",
"Prayush",
""
],
[
"Chu",
"Tony",
""
],
[
"Fong",
"Heather",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Boyle",
"Michael",
""
],
[
"Hemberger",
"Daniel A.",
""
],
[
"Kidder",
"Lawrence E.",
""
],
... | Coalescing binary black holes are among the primary science targets for second generation ground-based gravitational wave (GW) detectors. Reliable GW models are central to detection of such systems and subsequent parameter estimation. This paper performs a comprehensive analysis of the accuracy of recent waveform models for binary black holes with aligned spins, utilizing a new set of $84$ high-accuracy numerical relativity simulations. Our analysis covers comparable mass binaries ($1\le m_1/m_2\le 3$), and samples independently both black hole spins up to dimensionless spin-magnitude of $0.9$ for equal-mass binaries and $0.85$ for unequal mass binaries. Furthermore, we focus on the high-mass regime (total mass $\gtrsim 50M_\odot$). The two most recent waveform models considered (PhenomD and SEOBNRv2) both perform very well for signal detection, losing less than 0.5\% of the recoverable signal-to-noise ratio $\rho$, except that SEOBNRv2's efficiency drops mildly for both black hole spins aligned with large magnitude. For parameter estimation, modeling inaccuracies of SEOBNRv2 are found to be smaller than systematic uncertainties for moderately strong GW events up to roughly $\rho\lesssim 15$. PhenomD's modeling errors are found to be smaller than SEOBNRv2's, and are generally irrelevant for $\rho\lesssim 20$. Both models' accuracy deteriorates with increased mass-ratio, and when at least one black hole spin is large and aligned. The SEOBNRv2 model shows a pronounced disagreement with the numerical relativity simulation in the merger phase, for unequal masses and simultaneously both black hole spins very large and aligned. Two older waveform models (PhenomC and SEOBNRv1) are found to be distinctly less accurate than the more recent PhenomD and SEOBNRv2 models. Finally, we quantify the bias expected from all GW models during parameter estimation for recovery of binary's masses and spins. |
0901.3865 | Aron Wall | Aron C. Wall | Ten Proofs of the Generalized Second Law | 60 pages, 2 figures, 1 table. v2: corrected typos and added a
footnote to match the published version | JHEP 0906:021,2009 | 10.1088/1126-6708/2009/06/021 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Ten attempts to prove the Generalized Second Law of Thermodyanmics (GSL) are
described and critiqued. Each proof provides valuable insights which should be
useful for constructing future, more complete proofs. Rather than merely
summarizing previous research, this review offers new perspectives, and
strategies for overcoming limitations of the existing proofs. A long
introductory section addresses some choices that must be made in any
formulation the GSL: Should one use the Gibbs or the Boltzmann entropy? Should
one use the global or the apparent horizon? Is it necessary to assume any
entropy bounds? If the area has quantum fluctuations, should the GSL apply to
the average area? The definition and implications of the classical,
hydrodynamic, semiclassical and full quantum gravity regimes are also
discussed. A lack of agreement regarding how to define the "quasi-stationary"
regime is addressed by distinguishing it from the "quasi-steady" regime.
| [
{
"created": "Sat, 24 Jan 2009 23:48:14 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Oct 2009 00:48:13 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Wall",
"Aron C.",
""
]
] | Ten attempts to prove the Generalized Second Law of Thermodyanmics (GSL) are described and critiqued. Each proof provides valuable insights which should be useful for constructing future, more complete proofs. Rather than merely summarizing previous research, this review offers new perspectives, and strategies for overcoming limitations of the existing proofs. A long introductory section addresses some choices that must be made in any formulation the GSL: Should one use the Gibbs or the Boltzmann entropy? Should one use the global or the apparent horizon? Is it necessary to assume any entropy bounds? If the area has quantum fluctuations, should the GSL apply to the average area? The definition and implications of the classical, hydrodynamic, semiclassical and full quantum gravity regimes are also discussed. A lack of agreement regarding how to define the "quasi-stationary" regime is addressed by distinguishing it from the "quasi-steady" regime. |
gr-qc/9409054 | Misao Sasaki | Masaru Shibata, Misao Sasaki, Hideyuki Tagoshi and Takahiro Tanaka | Gravitational Waves from a Particle Orbiting Around a Rotating Black
Holes: Post-Newtonian Expansion | phyzzx 41 pages | Phys.Rev.D51:1646-1663,1995 | 10.1103/PhysRevD.51.1646 | KUNS 1268 / OU-TAP-9 | gr-qc astro-ph | null | Using the Teukolsky and Sasaki-Nakamura equations for the gravitational
perturbation of the Kerr spacetime, we calculate the post-Newtonian expansion
of the energy and angular momentum luminosities of gravitational waves from a
test particle orbiting around a rotating black hole up through ${\rm P^{5/2}N}$
order beyond the quadrupole formula. We apply a method recently developed by
Sasaki to the case of a rotating black hole. We take into account a small
inclination of the orbital plane to the lowest order of the Carter constant.
The result to $ P^{3/2}N}$ order is in agreement with a similar calculation by
Poisson as well as with the standard post-Newtonian calculation by Kidder et
al. Using our result, we calculate the integrated phase of gravitational waves
from a neutron star-neutron star binary and a black hole-neutron star binary
during their inspiral stage. We find that, in both cases, spin-dependent terms
in the P$^2$N and P$^{5/2}$N corrections are important to construct effective
template waveforms which will be used for future laser-interferometric
gravitational wave detectors.
| [
{
"created": "Tue, 27 Sep 1994 10:26:08 GMT",
"version": "v1"
}
] | 2009-10-09 | [
[
"Shibata",
"Masaru",
""
],
[
"Sasaki",
"Misao",
""
],
[
"Tagoshi",
"Hideyuki",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | Using the Teukolsky and Sasaki-Nakamura equations for the gravitational perturbation of the Kerr spacetime, we calculate the post-Newtonian expansion of the energy and angular momentum luminosities of gravitational waves from a test particle orbiting around a rotating black hole up through ${\rm P^{5/2}N}$ order beyond the quadrupole formula. We apply a method recently developed by Sasaki to the case of a rotating black hole. We take into account a small inclination of the orbital plane to the lowest order of the Carter constant. The result to $ P^{3/2}N}$ order is in agreement with a similar calculation by Poisson as well as with the standard post-Newtonian calculation by Kidder et al. Using our result, we calculate the integrated phase of gravitational waves from a neutron star-neutron star binary and a black hole-neutron star binary during their inspiral stage. We find that, in both cases, spin-dependent terms in the P$^2$N and P$^{5/2}$N corrections are important to construct effective template waveforms which will be used for future laser-interferometric gravitational wave detectors. |
1511.00609 | Giampiero Esposito Dr. | Enrico Calloni, S. Caprara, Martina De Laurentis, Giampiero Esposito,
M. Grilli, Ettore Majorana, G.P. Pepe, S. Petrarca, Paola Puppo, P.
Rapagnini, F. Ricci, Luigi Rosa, Carlo Rovelli, P. Ruggi, N.L. Saini, Cosimo
Stornaiolo, Francesco Tafuri | The Archimedes experiment | 4 pages, 2 figures | null | 10.1016/j.nima.2015.09.071 | null | gr-qc physics.ins-det | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Archimedes is an INFN-funded pathfinder experiment aimed at verifying the
feasibility of measuring the interaction of vacuum fluctuations with gravity.
The final experiment will measure the force exerted by the gravitational field
on a Casimir cavity whose vacuum energy is modulated with a superconductive
transition, by using a balance as a small force detector. Archimedes is a
two-year project devoted to test the most critical experimental aspects, in
particular the balance resonance frequency and quality factor, the thermal
modulation efficiency and the superconductive sample realization.
| [
{
"created": "Mon, 2 Nov 2015 17:42:46 GMT",
"version": "v1"
}
] | 2016-06-22 | [
[
"Calloni",
"Enrico",
""
],
[
"Caprara",
"S.",
""
],
[
"De Laurentis",
"Martina",
""
],
[
"Esposito",
"Giampiero",
""
],
[
"Grilli",
"M.",
""
],
[
"Majorana",
"Ettore",
""
],
[
"Pepe",
"G. P.",
""
],
[
... | Archimedes is an INFN-funded pathfinder experiment aimed at verifying the feasibility of measuring the interaction of vacuum fluctuations with gravity. The final experiment will measure the force exerted by the gravitational field on a Casimir cavity whose vacuum energy is modulated with a superconductive transition, by using a balance as a small force detector. Archimedes is a two-year project devoted to test the most critical experimental aspects, in particular the balance resonance frequency and quality factor, the thermal modulation efficiency and the superconductive sample realization. |
1607.02750 | Hor\'acio Santana Vieira | H. S. Vieira | Analytic solutions in the acoustic black hole analogue of the conical
Kerr metric | 6 pages | Chinese Physics C 41 (2017) 043105 | 10.1088/1674-1137/41/4/043105 | null | gr-qc cond-mat.other | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the sound perturbation of a rotating acoustic black hole in the
presence of a disclination. The radial part of the massless Klein-Gordon
equation is written into a Heun form, and its analytical solution is obtained.
These solutions have an explicit dependence on the parameter of the
disclination. We obtain the exact Hawking-Unruh radiation spectrum.
| [
{
"created": "Sun, 10 Jul 2016 14:26:22 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Apr 2017 12:18:38 GMT",
"version": "v2"
}
] | 2017-04-04 | [
[
"Vieira",
"H. S.",
""
]
] | We study the sound perturbation of a rotating acoustic black hole in the presence of a disclination. The radial part of the massless Klein-Gordon equation is written into a Heun form, and its analytical solution is obtained. These solutions have an explicit dependence on the parameter of the disclination. We obtain the exact Hawking-Unruh radiation spectrum. |
1210.6257 | Thomas Krajewski | Thomas Krajewski | Group field theories | Lectures given at the "3rd Quantum Gravity and Quantum Geometry
School", march 2011, Zakopane | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Group field theories are particular quantum field theories defined on D
copies of a group which reproduce spin foam amplitudes on a space-time of
dimension D. In these lecture notes, we present the general construction of
group field theories, merging ideas from tensor models and loop quantum
gravity. This lecture is organized as follows. In the first section, we present
basic aspects of quantum field theory and matrix models. The second section is
devoted to general aspects of tensor models and group field theory and in the
last section we examine properties of the group field formulation of BF theory
and the EPRL model. We conclude with a few possible research topics, like the
construction of a continuum limit based on the double scaling limit or the
relation to loop quantum gravity through Schwinger-Dyson equations
| [
{
"created": "Tue, 23 Oct 2012 14:57:43 GMT",
"version": "v1"
}
] | 2012-10-24 | [
[
"Krajewski",
"Thomas",
""
]
] | Group field theories are particular quantum field theories defined on D copies of a group which reproduce spin foam amplitudes on a space-time of dimension D. In these lecture notes, we present the general construction of group field theories, merging ideas from tensor models and loop quantum gravity. This lecture is organized as follows. In the first section, we present basic aspects of quantum field theory and matrix models. The second section is devoted to general aspects of tensor models and group field theory and in the last section we examine properties of the group field formulation of BF theory and the EPRL model. We conclude with a few possible research topics, like the construction of a continuum limit based on the double scaling limit or the relation to loop quantum gravity through Schwinger-Dyson equations |
2207.06957 | Antonio Tedesco | Antonio Capolupo, Gaetano Lambiase, Antonio Tedesco | Precession shift in curvature based Extended Theories of Gravity and
Quintessence fields | null | Eur. Phys. J. C (2022) 82:286 | 10.1140/epjc/s10052-022-10235-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we constrain the sizes of hypothetical new weak forces by
making use the data coming from the precession of Planets. We consider the weak
field approximation of Scalar-Tensor Fourth Order Gravity (STFOG), which
include several models of modified gravity. The form of the corrections to the
Newtonian potential if of the form of Yukawa-like potential (5th force), i.e.
$V(r) = {\alpha} \dfrac{e^{-\beta r}}{r}$, where ${\alpha}$ is the parameter
related to the strength of the potential, and ${\beta}$ to the range of the
force. The present data on periastron advance allow to infer a constraint on
the free parameter of the gravitational models. Moreover, the Non-Commutative
Spectral Gravity (NCSG) is also studied, being a particular case STFOG. Here we
show that the precession shift of Planet allows to improve the bounds on
parameter ${\beta}$ by several orders of magnitude. Finally such an analysis is
studied to the case of power-like potential, referring in particular to
deformation of the Schwarzschild geometry induced by a quintessence field,
responsible of the present accelerated phase of the Universe.
| [
{
"created": "Thu, 14 Jul 2022 14:26:28 GMT",
"version": "v1"
}
] | 2022-07-20 | [
[
"Capolupo",
"Antonio",
""
],
[
"Lambiase",
"Gaetano",
""
],
[
"Tedesco",
"Antonio",
""
]
] | In this paper we constrain the sizes of hypothetical new weak forces by making use the data coming from the precession of Planets. We consider the weak field approximation of Scalar-Tensor Fourth Order Gravity (STFOG), which include several models of modified gravity. The form of the corrections to the Newtonian potential if of the form of Yukawa-like potential (5th force), i.e. $V(r) = {\alpha} \dfrac{e^{-\beta r}}{r}$, where ${\alpha}$ is the parameter related to the strength of the potential, and ${\beta}$ to the range of the force. The present data on periastron advance allow to infer a constraint on the free parameter of the gravitational models. Moreover, the Non-Commutative Spectral Gravity (NCSG) is also studied, being a particular case STFOG. Here we show that the precession shift of Planet allows to improve the bounds on parameter ${\beta}$ by several orders of magnitude. Finally such an analysis is studied to the case of power-like potential, referring in particular to deformation of the Schwarzschild geometry induced by a quintessence field, responsible of the present accelerated phase of the Universe. |
1607.06229 | Alfred Molina | Alfred Molina, Naresh Dadhich and Avas Khugaev | Buchdahl-Vaidya-Tikekar model for stellar interior in pure Lovelock
gravity - II | 18 pages, 7 figures | null | 10.1007/s10714-017-2259-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a given Lovelock order $N$, it turns out that static fluid solutions of
the pure Lovelock equation for a star interior have the universal behavior in
all $n\geq 2N+2$ dimensions relative to an appropriately defined variable and
the Vaidya-Tikekar parameter $K$, indicating deviation from sphericity of
$3$-space geometry. We employ the Buchdahl metric ansatz which encompasses
almost all the known physically acceptable models including in particular the
Vaidya-Tikekar and Finch-Skea. Further for a given star radius, the constant
density star, always described by the Schwarzschild interior solution, defines
the most compact state of distribution while the other end is marked by the
Finch-Skea model, and all the other physically tenable models lie in between
these two limiting distributions.
| [
{
"created": "Thu, 21 Jul 2016 08:31:21 GMT",
"version": "v1"
}
] | 2017-06-30 | [
[
"Molina",
"Alfred",
""
],
[
"Dadhich",
"Naresh",
""
],
[
"Khugaev",
"Avas",
""
]
] | For a given Lovelock order $N$, it turns out that static fluid solutions of the pure Lovelock equation for a star interior have the universal behavior in all $n\geq 2N+2$ dimensions relative to an appropriately defined variable and the Vaidya-Tikekar parameter $K$, indicating deviation from sphericity of $3$-space geometry. We employ the Buchdahl metric ansatz which encompasses almost all the known physically acceptable models including in particular the Vaidya-Tikekar and Finch-Skea. Further for a given star radius, the constant density star, always described by the Schwarzschild interior solution, defines the most compact state of distribution while the other end is marked by the Finch-Skea model, and all the other physically tenable models lie in between these two limiting distributions. |
gr-qc/0401050 | Mohammad Reza Setare | M. R. Setare and Khaled Saaidi | Spin Zero Quantum Relativistic Particles in Einstein Universe | 4 pages, no figure, accepted for publication in International Journal
of Theoretical Physics | Int.J.Theor.Phys. 43 (2004) 421-424 | 10.1023/B:IJTP.0000028874.48865.d6 | null | gr-qc | null | In this letter we have considered the eigenvalues and eigenfunctions of
relativistic massless scalar particle which conformally coupled to the
background of Einstein universe. We found the eigenvalues and eigenfunctions
exactly.
| [
{
"created": "Tue, 13 Jan 2004 07:38:19 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Setare",
"M. R.",
""
],
[
"Saaidi",
"Khaled",
""
]
] | In this letter we have considered the eigenvalues and eigenfunctions of relativistic massless scalar particle which conformally coupled to the background of Einstein universe. We found the eigenvalues and eigenfunctions exactly. |
2012.08249 | Anna Ijjas | Anna Ijjas and Roman Kolevatov | Sourcing curvature modes with entropy perturbations in non-singular
bouncing cosmologies | 17 pages | JCAP 06 (2021) 012 | 10.1088/1475-7516/2021/06/012 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | The observed temperature fluctuations in the cosmic microwave background can
be traced back to primordial curvature modes that are sourced by adiabatic
and/or entropic matter perturbations. In this paper, we explore the entropic
mechanism in the context of non-singular bouncing cosmologies. We show that
curvature modes are naturally generated during `graceful exit,' i.e., when the
smoothing slow contraction phase ends and the universe enters the bounce stage.
Here, the key role is played by the kinetic energy components that come to
dominate the energy density and drive the evolution towards the cosmological
bounce.
| [
{
"created": "Tue, 15 Dec 2020 12:29:20 GMT",
"version": "v1"
}
] | 2021-06-09 | [
[
"Ijjas",
"Anna",
""
],
[
"Kolevatov",
"Roman",
""
]
] | The observed temperature fluctuations in the cosmic microwave background can be traced back to primordial curvature modes that are sourced by adiabatic and/or entropic matter perturbations. In this paper, we explore the entropic mechanism in the context of non-singular bouncing cosmologies. We show that curvature modes are naturally generated during `graceful exit,' i.e., when the smoothing slow contraction phase ends and the universe enters the bounce stage. Here, the key role is played by the kinetic energy components that come to dominate the energy density and drive the evolution towards the cosmological bounce. |
gr-qc/0402026 | Dirk Puetzfeld | Dirk Puetzfeld, Xuelei Chen | Testing non-standard cosmological models with supernovae | 21 pages, 10 figures, uses IOP preprint style, submitted to Class.
Quantum Grav | Class.Quant.Grav. 21 (2004) 2703-2722 | 10.1088/0264-9381/21/11/013 | null | gr-qc astro-ph | null | In this work we study the magnitude-redshift relation of a non-standard
cosmological model. The model under consideration was firstly investigated
within a special case of metric-affine gravity (MAG) and was recently recovered
via different approaches by two other groups. Apart from the usual cosmological
parameters for pressure-less matter $\Omega_{\rm m}$, cosmological
constant/dark energy $\Omega_{\lambda}$, and radiation $\Omega_{\rm r}$ a new
density parameter $\Omega_\psi$ emerges. The field equations of the model
reduce to a system which is effectively given by the usual Friedmann equations
of general relativity, supplied by a correction to the energy density and
pressure in form of $\Omega_\psi$, which is related to the non-Riemannian
structure of the underlying spacetime. We search for the best-fit parameters by
using recent SN Ia data sets and constrain the possible contribution of a new
dark-energy like component at low redshifts, thereby we put an upper limit on
the presence of non-Riemannian quantities in the late stages of the universe.
In addition the impact of placing the data in redshift bins of variable size is
studied. The numerical results of this work also apply to several anisotropic
cosmological models which, on the level of the field equations, exhibit a
similar scaling behavior of the density parameters like our non-Riemannian
model.
| [
{
"created": "Wed, 4 Feb 2004 20:47:41 GMT",
"version": "v1"
}
] | 2009-04-03 | [
[
"Puetzfeld",
"Dirk",
""
],
[
"Chen",
"Xuelei",
""
]
] | In this work we study the magnitude-redshift relation of a non-standard cosmological model. The model under consideration was firstly investigated within a special case of metric-affine gravity (MAG) and was recently recovered via different approaches by two other groups. Apart from the usual cosmological parameters for pressure-less matter $\Omega_{\rm m}$, cosmological constant/dark energy $\Omega_{\lambda}$, and radiation $\Omega_{\rm r}$ a new density parameter $\Omega_\psi$ emerges. The field equations of the model reduce to a system which is effectively given by the usual Friedmann equations of general relativity, supplied by a correction to the energy density and pressure in form of $\Omega_\psi$, which is related to the non-Riemannian structure of the underlying spacetime. We search for the best-fit parameters by using recent SN Ia data sets and constrain the possible contribution of a new dark-energy like component at low redshifts, thereby we put an upper limit on the presence of non-Riemannian quantities in the late stages of the universe. In addition the impact of placing the data in redshift bins of variable size is studied. The numerical results of this work also apply to several anisotropic cosmological models which, on the level of the field equations, exhibit a similar scaling behavior of the density parameters like our non-Riemannian model. |
2305.07683 | Pardyumn Kumar Sahoo | Raja Solanki, Bina Patel, Lakhan V. Jaybhaye, P.K. Sahoo | Cosmic acceleration with bulk viscosity in an anisotropic $f(R,L_m)$
background | Communications in Theoretical Physics accepted version | Communications in Theoretical Physics, 75(7) (2023) 075401 | 10.1088/1572-9494/acd4aa | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this article, we investigate the observed cosmic acceleration in the
framework of a cosmological $f(R,L_m)$ model dominated by bulk viscous matter
in an anisotropic background. We consider the LRS Bianchi type I metric and
derive the Friedmann equations that drive the gravitational interactions in
$f(R,L_m)$ gravity. Further, we assume the functional form
$f(R,L_m)=\frac{R}{2}+L_m^\alpha $, where $\alpha$ is a free model parameter,
and then find the exact solutions of fields equations corresponding to our
viscous matter dominated model. We incorporate the updated H(z) data and the
Pantheon data to acquire the best-fit values of parameters of our model by
utilizing the $\chi^2$ minimization technique along with the Markov Chain Monte
Carlo (MCMC) random sampling method. Further, we present the behavior of
physical parameters that describe the universe's evolution phase, such as
density, effective pressure and EoS parameters, skewness parameter, and the
statefinder diagnostic parameters. We found that the energy density indicates
expected positive behavior, whereas the negative behavior of bulk viscous
pressure contributes to the universe's expansion. The effective EoS parameter
favors the accelerating phase of the universe's expansion. Moreover, the
skewness parameter shows the anisotropic nature of spacetime during the entire
evolution phase of the universe. Finally, from statefinder diagnostic test, we
found that our cosmological $f(R,L_m)$ model lies in the quintessence region,
and it behaves like a de-Sitter universe in the far future. We analyze
different energy conditions in order to test the consistency of the obtained
solution. We found that all energy conditions except SEC show positive
behavior, while the violation of SEC favors the recently observed acceleration
with the transition from decelerated to an accelerated epoch of the universe's
expansion in the recent past.
| [
{
"created": "Fri, 12 May 2023 11:20:50 GMT",
"version": "v1"
}
] | 2023-06-14 | [
[
"Solanki",
"Raja",
""
],
[
"Patel",
"Bina",
""
],
[
"Jaybhaye",
"Lakhan V.",
""
],
[
"Sahoo",
"P. K.",
""
]
] | In this article, we investigate the observed cosmic acceleration in the framework of a cosmological $f(R,L_m)$ model dominated by bulk viscous matter in an anisotropic background. We consider the LRS Bianchi type I metric and derive the Friedmann equations that drive the gravitational interactions in $f(R,L_m)$ gravity. Further, we assume the functional form $f(R,L_m)=\frac{R}{2}+L_m^\alpha $, where $\alpha$ is a free model parameter, and then find the exact solutions of fields equations corresponding to our viscous matter dominated model. We incorporate the updated H(z) data and the Pantheon data to acquire the best-fit values of parameters of our model by utilizing the $\chi^2$ minimization technique along with the Markov Chain Monte Carlo (MCMC) random sampling method. Further, we present the behavior of physical parameters that describe the universe's evolution phase, such as density, effective pressure and EoS parameters, skewness parameter, and the statefinder diagnostic parameters. We found that the energy density indicates expected positive behavior, whereas the negative behavior of bulk viscous pressure contributes to the universe's expansion. The effective EoS parameter favors the accelerating phase of the universe's expansion. Moreover, the skewness parameter shows the anisotropic nature of spacetime during the entire evolution phase of the universe. Finally, from statefinder diagnostic test, we found that our cosmological $f(R,L_m)$ model lies in the quintessence region, and it behaves like a de-Sitter universe in the far future. We analyze different energy conditions in order to test the consistency of the obtained solution. We found that all energy conditions except SEC show positive behavior, while the violation of SEC favors the recently observed acceleration with the transition from decelerated to an accelerated epoch of the universe's expansion in the recent past. |
gr-qc/9911123 | Carmen Chicone | C. Chicone, B. Mashhoon, and D. G. Retzloff | Sustained resonance: a binary system perturbed by gravitational
radiation | 21 pages, 5 figures. To appear in Journal of Physics A | J.Phys.A33:513-530,2000 | 10.1088/0305-4470/33/3/307 | null | gr-qc astro-ph nlin.CD | null | The general phenomena associated with sustained resonance are studied in this
paper in connection with relativistic binary pulsars. We represent such a
system by two point masses in a Keplerian binary system that evolves via
gravitational radiation damping as well as an external tidal perturbation. For
further simplification, we assume that the external tidal perturbation is
caused by a normally incident circularly polarized monochromatic gravitational
wave. In this case, the second-order partially averaged equations are studied
and a theorem of C. Robinson is employed to prove that for certain values of
the physical parameters resonance capture followed by sustained resonance is
possible in the averaged system. We conjecture that sustained resonance can
occur in the physical system when the perturbing influences nearly balance each
other.
| [
{
"created": "Tue, 30 Nov 1999 22:54:51 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Chicone",
"C.",
""
],
[
"Mashhoon",
"B.",
""
],
[
"Retzloff",
"D. G.",
""
]
] | The general phenomena associated with sustained resonance are studied in this paper in connection with relativistic binary pulsars. We represent such a system by two point masses in a Keplerian binary system that evolves via gravitational radiation damping as well as an external tidal perturbation. For further simplification, we assume that the external tidal perturbation is caused by a normally incident circularly polarized monochromatic gravitational wave. In this case, the second-order partially averaged equations are studied and a theorem of C. Robinson is employed to prove that for certain values of the physical parameters resonance capture followed by sustained resonance is possible in the averaged system. We conjecture that sustained resonance can occur in the physical system when the perturbing influences nearly balance each other. |
1811.03634 | Ismael Delgado Gaspar PhD | Ismael Delgado Gaspar, Juan Carlos Hidalgo, Roberto A. Sussman | Non-comoving baryons and cold dark matter in cosmic voids | Discussion of the evolution of baryon-CDM relative velocity added.
Other minor but important corrections were incorporated. Version accepted for
publication in EPJC | null | 10.1140/epjc/s10052-019-6606-x | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the fully relativistic evolution of cosmic voids constituted by
baryons and cold dark matter (CDM), represented by two non-comoving dust
sources in a $\Lambda$CDM background. For this purpose, we consider numerical
solutions of Einstein's field equations in a fluid-flow representation adapted
to spherical symmetry and multiple components. We present a simple example that
explores the frame-dependence of the local expansion and the Hubble flow for
this mixture of two dusts, revealing that the relative velocity between the
sources yields a significantly different evolution in comparison with that of
the two sources in a common 4-velocity (which reduces to a
Lemaitre-Tolman-Bondi model). In particular, significant modifications arise
for the density contrast depth and void size, as well as in the amplitude of
the surrounding over-densities. We show that an adequate model of a
frame-dependent evolution that incorporates initial conditions from peculiar
velocities and large-scale density contrast observations may contribute to
understand the discrepancy between the local value of $H_0$ and that inferred
from the CMB.
| [
{
"created": "Thu, 8 Nov 2018 19:00:28 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Jan 2019 06:43:13 GMT",
"version": "v2"
}
] | 2019-02-12 | [
[
"Gaspar",
"Ismael Delgado",
""
],
[
"Hidalgo",
"Juan Carlos",
""
],
[
"Sussman",
"Roberto A.",
""
]
] | We examine the fully relativistic evolution of cosmic voids constituted by baryons and cold dark matter (CDM), represented by two non-comoving dust sources in a $\Lambda$CDM background. For this purpose, we consider numerical solutions of Einstein's field equations in a fluid-flow representation adapted to spherical symmetry and multiple components. We present a simple example that explores the frame-dependence of the local expansion and the Hubble flow for this mixture of two dusts, revealing that the relative velocity between the sources yields a significantly different evolution in comparison with that of the two sources in a common 4-velocity (which reduces to a Lemaitre-Tolman-Bondi model). In particular, significant modifications arise for the density contrast depth and void size, as well as in the amplitude of the surrounding over-densities. We show that an adequate model of a frame-dependent evolution that incorporates initial conditions from peculiar velocities and large-scale density contrast observations may contribute to understand the discrepancy between the local value of $H_0$ and that inferred from the CMB. |
gr-qc/9406021 | Robert Mann | J.S.F. Chan and R.B. Mann | Mass inflation in (1+1)-dimensional Dilaton Gravity | 15 pages, 4 figures (appended as postscript files) (uses epsf.tex) | Phys.Rev. D50 (1994) 7376-7384 | 10.1103/PhysRevD.50.7376 | null | gr-qc | null | We investigate the phenomenon of mass inflation in two-dimensional dilaton
theories of gravity. We consider two distinct black hole spacetimes and
construct the mass-inflation solution for each. Our analysis is extended to
include multi-horizon spacetimes. We find that the mass function diverges in a
manner quantitatively similar to its four-dimensional counterpart.
| [
{
"created": "Tue, 14 Jun 1994 17:17:16 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Chan",
"J. S. F.",
""
],
[
"Mann",
"R. B.",
""
]
] | We investigate the phenomenon of mass inflation in two-dimensional dilaton theories of gravity. We consider two distinct black hole spacetimes and construct the mass-inflation solution for each. Our analysis is extended to include multi-horizon spacetimes. We find that the mass function diverges in a manner quantitatively similar to its four-dimensional counterpart. |
1405.1026 | Kenji Tomita | Kenji Tomita | Cosmological entropy production and viscous processes in the
(1+3+6)-dimensional space-times | 21 pages, 13 figures | Prog. Theor. Exp. Phys. 2014, 053E01 | 10.1093/ptep/ptu061 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmological entropy production is studied in the (1+3+6)-dimensional
space-times consisting of the outer space (the 3-dimensional expanding section)
and the inner space (the 6-dimensional section). The inner space expands
initially and contracts later. First it is shown how the production of the
3-dimensional entropy S_3 within the horizon is strengthened by the dissipation
due to viscous processes between the two spaces, in which we consider the
viscosity caused by the gravitational-wave transport. Next it is shown under
what conditions we can have the critical epoch when S_3 reaches the value
10^{88} in the Guth level and at the same time the outer space is decoupled
from the inner space. Moreover, the total entropy S_9 in the 9-dimensional
space at the primeval expanding stage is also shown corresponding to S_3.
| [
{
"created": "Mon, 5 May 2014 02:08:59 GMT",
"version": "v1"
},
{
"created": "Fri, 23 May 2014 00:17:12 GMT",
"version": "v2"
}
] | 2014-05-26 | [
[
"Tomita",
"Kenji",
""
]
] | The cosmological entropy production is studied in the (1+3+6)-dimensional space-times consisting of the outer space (the 3-dimensional expanding section) and the inner space (the 6-dimensional section). The inner space expands initially and contracts later. First it is shown how the production of the 3-dimensional entropy S_3 within the horizon is strengthened by the dissipation due to viscous processes between the two spaces, in which we consider the viscosity caused by the gravitational-wave transport. Next it is shown under what conditions we can have the critical epoch when S_3 reaches the value 10^{88} in the Guth level and at the same time the outer space is decoupled from the inner space. Moreover, the total entropy S_9 in the 9-dimensional space at the primeval expanding stage is also shown corresponding to S_3. |
1012.3703 | Marcus Thierfelder | Marcus Thierfelder, Sebastiano Bernuzzi, David Hilditch, Bernd
Bruegmann and Luciano Rezzolla | The trumpet solution from spherical gravitational collapse with puncture
gauges | null | Phys.Rev.D83:064022,2011 | 10.1103/PhysRevD.83.064022 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the stationary end-state obtained by evolving a collapsing
spherical star with the gauges routinely adopted to study puncture black holes.
We compare the end-state of the collapse with the trumpet solution found in the
evolution of a single wormhole slice and show that the two solutions closely
agree. We demonstrate that the agreement is caused by the use of the
Gamma-driver shift condition, which allows the matter to fall inwards into a
region of spacetime that is not resolved by the numerical grid, and which
simultaneously finds the stationary coordinates of the trumpet outside the
matter.
| [
{
"created": "Thu, 16 Dec 2010 18:08:37 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Mar 2011 09:47:44 GMT",
"version": "v2"
}
] | 2011-03-28 | [
[
"Thierfelder",
"Marcus",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Hilditch",
"David",
""
],
[
"Bruegmann",
"Bernd",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | We investigate the stationary end-state obtained by evolving a collapsing spherical star with the gauges routinely adopted to study puncture black holes. We compare the end-state of the collapse with the trumpet solution found in the evolution of a single wormhole slice and show that the two solutions closely agree. We demonstrate that the agreement is caused by the use of the Gamma-driver shift condition, which allows the matter to fall inwards into a region of spacetime that is not resolved by the numerical grid, and which simultaneously finds the stationary coordinates of the trumpet outside the matter. |
gr-qc/9708031 | Melnikov Vitaly | M. A. Grebeniuk, V. D. Ivashchuk and V. N. Melnikov | Integrable Multidimensional Classical and Quantum Cosmology for
Intersecting p-branes | 10 pages, Latex., Submit. to Phys. Lett. B | Grav.Cosmol. 3 (1997) 243-249 | null | null | gr-qc | null | Multidimensional cosmological model describing the evolution of one Einstein
space of non-zero curvature and n Ricci-flat internal spaces is considered. The
action contains several dilatonic scalar fields and antisymmetric forms. When
forms are chosen to be proportional of volume forms of p-brane submanifolds of
internal space manifold, the Toda-like Lagrange representation is obtained.
Wheeler-De Witt equation for the model is presented. The exact solutions in
classical and quantum cases are obtained when dimensions of p-branes and
dilatonic couplings obey some orthogonality conditions.
| [
{
"created": "Fri, 15 Aug 1997 20:29:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Grebeniuk",
"M. A.",
""
],
[
"Ivashchuk",
"V. D.",
""
],
[
"Melnikov",
"V. N.",
""
]
] | Multidimensional cosmological model describing the evolution of one Einstein space of non-zero curvature and n Ricci-flat internal spaces is considered. The action contains several dilatonic scalar fields and antisymmetric forms. When forms are chosen to be proportional of volume forms of p-brane submanifolds of internal space manifold, the Toda-like Lagrange representation is obtained. Wheeler-De Witt equation for the model is presented. The exact solutions in classical and quantum cases are obtained when dimensions of p-branes and dilatonic couplings obey some orthogonality conditions. |
gr-qc/9409010 | null | Vladimir S. Mashkevich | Indeterministic Quantum Gravity | 11 pages, LATEX, Kiev Institute of Physics preprint IP 9/94 | null | null | null | gr-qc | null | A theory which claims to describe all the universe is advanced. It unifies
general relativity, quantum field theory, and indeterministic conception. Basic
entities are: classical metric tensor $g$, cosmic reference frame (including
cosmic time $t$), operator $T$ of energy-momentum tensor, Hamiltonian $H_t$,
and state vector $\Psi$. Dynamical equations are: the Einstein equation
$G[g]=(\Psi,T\Psi)$ ($G$ is the Einstein tensor), the Heisenberg equation
$dT/dt=i[H_t,T]$, and the condition $H_t\Psi_t=\epsilon_t \Psi_t$ arising from
the cosmic energy determinacy principle advanced in the theory. The last
equation describes quantum jump dynamics. Quantum jumps lead to the
instantaneous transferring of action and information, which, however, neither
violates the causality principle, nor contradicts quantum field theory and
general relativity. The cosmic energy determinacy principle implies the eternal
universe, i.e., the cyclic one without beginning and ending, the minimal energy
in every cycle being finite.
| [
{
"created": "Mon, 5 Sep 1994 20:40:57 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mashkevich",
"Vladimir S.",
""
]
] | A theory which claims to describe all the universe is advanced. It unifies general relativity, quantum field theory, and indeterministic conception. Basic entities are: classical metric tensor $g$, cosmic reference frame (including cosmic time $t$), operator $T$ of energy-momentum tensor, Hamiltonian $H_t$, and state vector $\Psi$. Dynamical equations are: the Einstein equation $G[g]=(\Psi,T\Psi)$ ($G$ is the Einstein tensor), the Heisenberg equation $dT/dt=i[H_t,T]$, and the condition $H_t\Psi_t=\epsilon_t \Psi_t$ arising from the cosmic energy determinacy principle advanced in the theory. The last equation describes quantum jump dynamics. Quantum jumps lead to the instantaneous transferring of action and information, which, however, neither violates the causality principle, nor contradicts quantum field theory and general relativity. The cosmic energy determinacy principle implies the eternal universe, i.e., the cyclic one without beginning and ending, the minimal energy in every cycle being finite. |
1401.1074 | Bibhas Majhi Ranjan | Bibhas Ranjan Majhi | Connection between response parameter and anomaly coefficient in two
dimensional anomalous fluid | Revised version, to appear in JHEP | JHEP03(2014)001 | 10.1007/JHEP03(2014)001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In (1+1) dimensional hydrodynamics in presence of the gravitational
anomalies, the constitutive relations for the stress tensor contain the
response parameters $\bar{C}_1$, $\bar{C}_2$ and the gravitation anomaly
coefficients $c_g$, $c_w$. Here it is shown that they are related by the two
relations $\bar{C}_1 = 4\pi^2 c_w$ and $\bar{C}_2 = 8\pi^2 c_g$. This agrees
with the earlier findings. I argue that the Israel-Hartle-Hawking vacuum is the
natural boundary condition which leads to such relation. Finally, the possible
physical implications are discussed.
| [
{
"created": "Mon, 6 Jan 2014 13:37:15 GMT",
"version": "v1"
},
{
"created": "Sun, 9 Feb 2014 08:13:07 GMT",
"version": "v2"
}
] | 2014-03-04 | [
[
"Majhi",
"Bibhas Ranjan",
""
]
] | In (1+1) dimensional hydrodynamics in presence of the gravitational anomalies, the constitutive relations for the stress tensor contain the response parameters $\bar{C}_1$, $\bar{C}_2$ and the gravitation anomaly coefficients $c_g$, $c_w$. Here it is shown that they are related by the two relations $\bar{C}_1 = 4\pi^2 c_w$ and $\bar{C}_2 = 8\pi^2 c_g$. This agrees with the earlier findings. I argue that the Israel-Hartle-Hawking vacuum is the natural boundary condition which leads to such relation. Finally, the possible physical implications are discussed. |
1307.6167 | Marina Cort\^es | Marina Cort\^es and Lee Smolin | The Universe as a Process of Unique Events | 26 pages, 5 figures | Phys. Rev. D 90, 084007 (2014) | 10.1103/PhysRevD.90.084007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a new class of models of quantum space-time based on energetic
causal sets and show that under natural conditions space-time emerges from
them. These are causal sets whose causal links are labelled by energy and
momentum and conservation laws are applied at events. The models are motivated
by principles we propose govern microscopic physics which posit a fundamental
irreversibility of time. One consequence is that each event in the history of
the universe has a distinct causal relationship to the rest; this requires a
novel form of dynamics which an be applied to uniquely distinctive events. We
hence introduce a new kind of deterministic dynamics for a causal set in which
new events are generated from pairs of progenitor events by a rule which is
based on extremizing the distinctions between causal past sets of events. This
dynamics is asymmetric in time, but we find evidence from numerical simulations
of a 1+1 dimensional model, that an effective dynamics emerges which restores
approximate time reversal symmetry. Energetic causal set models differ from
other spacetime-free causal set approaches, e.g. Ref. [1] proposed causal sets
based on quantum information processing systems, and Ref. [2] proposed causal
sets constructed out of standard model particles. Finally we also present a
natural twistorial representation of energetic causal sets.
| [
{
"created": "Tue, 23 Jul 2013 17:29:39 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Jul 2013 16:24:57 GMT",
"version": "v2"
},
{
"created": "Wed, 25 Nov 2015 21:27:00 GMT",
"version": "v3"
}
] | 2016-02-22 | [
[
"Cortês",
"Marina",
""
],
[
"Smolin",
"Lee",
""
]
] | We describe a new class of models of quantum space-time based on energetic causal sets and show that under natural conditions space-time emerges from them. These are causal sets whose causal links are labelled by energy and momentum and conservation laws are applied at events. The models are motivated by principles we propose govern microscopic physics which posit a fundamental irreversibility of time. One consequence is that each event in the history of the universe has a distinct causal relationship to the rest; this requires a novel form of dynamics which an be applied to uniquely distinctive events. We hence introduce a new kind of deterministic dynamics for a causal set in which new events are generated from pairs of progenitor events by a rule which is based on extremizing the distinctions between causal past sets of events. This dynamics is asymmetric in time, but we find evidence from numerical simulations of a 1+1 dimensional model, that an effective dynamics emerges which restores approximate time reversal symmetry. Energetic causal set models differ from other spacetime-free causal set approaches, e.g. Ref. [1] proposed causal sets based on quantum information processing systems, and Ref. [2] proposed causal sets constructed out of standard model particles. Finally we also present a natural twistorial representation of energetic causal sets. |
1403.6243 | Kent Yagi | Kent Yagi, Koutarou Kyutoku, George Pappas, Nicolas Yunes, Theocharis
A. Apostolatos | Effective No-Hair Relations for Neutron Stars and Quark Stars:
Relativistic Results | 36 pages, 14 figures; matches version published in PRD | Phys. Rev. D 89 124013 (2014) | 10.1103/PhysRevD.89.124013 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Astrophysical charge-free black holes are known to satisfy no-hair relations
through which all multipole moments can be specified in terms of just their
mass and spin angular momentum. We here investigate the possible existence of
no-hair-like relations among multipole moments for neutron stars and quark
stars that are independent of their equation of state. We calculate the
multipole moments of these stars up to hexadecapole order by constructing
uniformly-rotating and unmagnetized stellar solutions to the Einstein
equations. For slowly-rotating stars, we construct stellar solutions to quartic
order in spin in a slow-rotation expansion, while for rapidly-rotating stars,
we solve the Einstein equations numerically with the LORENE and RNS codes. We
find that the multipole moments extracted from these numerical solutions are
consistent with each other. We confirm that the current-dipole is related to
the mass-quadrupole in an approximately equation of state independent fashion,
which does not break for rapidly rotating neutron stars or quark stars. We
further find that the current-octupole and the mass-hexadecapole moments are
related to the mass-quadrupole in an approximately equation of state
independent way to $\sim 10%$, worsening in the hexadecapole case. All of our
findings are in good agreement with previous work that considered stellar
solutions to leading-order in a weak-field expansion. The quartic in spin,
slowly-rotating solutions found here allow us to estimate the systematic errors
in the measurement of the neutron star's mass and radius with future X-ray
observations, such as NICER and LOFT. We find that the effect of these
quartic-in-spin terms on the quadrupole and hexadecapole moments and stellar
eccentricity may dominate the error budget for very rapidly-rotating neutron
stars. The new universal relations found here should help to reduce such
systematic errors.
| [
{
"created": "Tue, 25 Mar 2014 06:52:41 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Sep 2014 17:35:14 GMT",
"version": "v2"
}
] | 2014-09-09 | [
[
"Yagi",
"Kent",
""
],
[
"Kyutoku",
"Koutarou",
""
],
[
"Pappas",
"George",
""
],
[
"Yunes",
"Nicolas",
""
],
[
"Apostolatos",
"Theocharis A.",
""
]
] | Astrophysical charge-free black holes are known to satisfy no-hair relations through which all multipole moments can be specified in terms of just their mass and spin angular momentum. We here investigate the possible existence of no-hair-like relations among multipole moments for neutron stars and quark stars that are independent of their equation of state. We calculate the multipole moments of these stars up to hexadecapole order by constructing uniformly-rotating and unmagnetized stellar solutions to the Einstein equations. For slowly-rotating stars, we construct stellar solutions to quartic order in spin in a slow-rotation expansion, while for rapidly-rotating stars, we solve the Einstein equations numerically with the LORENE and RNS codes. We find that the multipole moments extracted from these numerical solutions are consistent with each other. We confirm that the current-dipole is related to the mass-quadrupole in an approximately equation of state independent fashion, which does not break for rapidly rotating neutron stars or quark stars. We further find that the current-octupole and the mass-hexadecapole moments are related to the mass-quadrupole in an approximately equation of state independent way to $\sim 10%$, worsening in the hexadecapole case. All of our findings are in good agreement with previous work that considered stellar solutions to leading-order in a weak-field expansion. The quartic in spin, slowly-rotating solutions found here allow us to estimate the systematic errors in the measurement of the neutron star's mass and radius with future X-ray observations, such as NICER and LOFT. We find that the effect of these quartic-in-spin terms on the quadrupole and hexadecapole moments and stellar eccentricity may dominate the error budget for very rapidly-rotating neutron stars. The new universal relations found here should help to reduce such systematic errors. |
gr-qc/0404021 | Aleksandar Mikovic | A. Mikovic | Flat Spacetime Vacuum in Loop Quantum Gravity | 20 pages, 6 figures | Class.Quant.Grav.21:3909-3922,2004 | 10.1088/0256-307X/21/8/007 | null | gr-qc | null | We construct a state in the loop quantum gravity theory with zero
cosmological constant, which should correspond to the flat spacetime vacuum
solution. This is done by defining the loop transform coefficients of a flat
connection wavefunction in the holomorphic representation which satisfies all
the constraints of quantum General Relativity and it is peaked around the flat
space triads. The loop transform coefficients are defined as spin foam state
sum invariants of the spin networks embedded in the spatial manifold for the
SU(2) quantum group. We also obtain an expression for the vacuum wavefunction
in the triad represntation, by defining the corresponding spin networks
functional integrals as SU(2) quantum group state sums.
| [
{
"created": "Tue, 6 Apr 2004 12:09:14 GMT",
"version": "v1"
}
] | 2009-01-16 | [
[
"Mikovic",
"A.",
""
]
] | We construct a state in the loop quantum gravity theory with zero cosmological constant, which should correspond to the flat spacetime vacuum solution. This is done by defining the loop transform coefficients of a flat connection wavefunction in the holomorphic representation which satisfies all the constraints of quantum General Relativity and it is peaked around the flat space triads. The loop transform coefficients are defined as spin foam state sum invariants of the spin networks embedded in the spatial manifold for the SU(2) quantum group. We also obtain an expression for the vacuum wavefunction in the triad represntation, by defining the corresponding spin networks functional integrals as SU(2) quantum group state sums. |
gr-qc/9803027 | Vladimir M. Khatsymovsky | V.M.Khatsymovsky | Rotating vacuum wormhole | 10 pages, uses LaTeX, submitted to Physics Letters B | Phys.Lett. B429 (1998) 254-262 | 10.1016/S0370-2693(98)00448-1 | null | gr-qc | null | We investigate whether self-maintained vacuum traversible wormhole can exist
described by stationary but nonstatic metric. We consider metric being the sum
of static spherically symmetric one and a small nondiagonal component which
describes rotation sufficiently slow to be taken into account in the linear
approximation. We study semiclassical Einstein equations for this metric with
vacuum expectation value of stress-energy of physical fields as the source. In
suggestion that the static traversible wormhole solution exists we reveal
possible azimuthal angle dependence of angular velocity of the rotation
(angular velocity of the local inertial frame) that solves semiclassical
Einstein equations. We find that in the macroscopic (in the Plank scale)
wormhole case a rotational solution exists but only such that, first, angular
velocity depends on radial coordinate only and, second, the wormhole connects
the two asymptotically flat spacetimes rotating with angular velocities
different in asymptotic regions.
| [
{
"created": "Fri, 6 Mar 1998 13:16:14 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Khatsymovsky",
"V. M.",
""
]
] | We investigate whether self-maintained vacuum traversible wormhole can exist described by stationary but nonstatic metric. We consider metric being the sum of static spherically symmetric one and a small nondiagonal component which describes rotation sufficiently slow to be taken into account in the linear approximation. We study semiclassical Einstein equations for this metric with vacuum expectation value of stress-energy of physical fields as the source. In suggestion that the static traversible wormhole solution exists we reveal possible azimuthal angle dependence of angular velocity of the rotation (angular velocity of the local inertial frame) that solves semiclassical Einstein equations. We find that in the macroscopic (in the Plank scale) wormhole case a rotational solution exists but only such that, first, angular velocity depends on radial coordinate only and, second, the wormhole connects the two asymptotically flat spacetimes rotating with angular velocities different in asymptotic regions. |
1611.03821 | \"Ozcan Sert | \"Ozcan Sert | Radiation Fluid Stars in the Non-minimally Coupled $Y(R)F^2$ Gravity | 21 pages, accepted for publication in EPJC | null | 10.1140/epjc/s10052-017-4664-5 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a non-minimally coupled gravity model in $ Y(R)F^2 $ form to
describe the radiation fluid stars which have the radiative equation of state
between the energy density $ \rho $ and the pressure $p$ as $\rho=3p $. Here
$F^2$ is the Maxwell invariant and $Y(R)$ is a function of the Ricci scalar
$R$. We give the gravitational and electromagnetic field equations in
differential form notation taking the infinitesimal variations of the model. We
look for electrically charged star solutions to the field equations under a
constraint which eliminating complexity of the higher order terms in the field
equations. We determine the non-minimally coupled function $Y(R)$ and the
corresponding model which admits new exact solutions in the interior of star
and Reissner-Nordstrom solution at the exterior region. Using vanishing
pressure condition at the boundary together with the continuity conditions of
the metric functions and the electric charge, we find the mass-radius ratio,
charge-radius ratio and gravitational surface redshift depending on the
parameter of the model for the radiation fluid star. We derive general
restrictions for the ratios and redshift of the charged compact stars. We
obtain a slightly smaller upper mass-radius ratio limit than the Buchdahl bound
$ 4/9 $ and a smaller upper redshift limit than the bound of the standard
General Relativistic stars.
| [
{
"created": "Fri, 11 Nov 2016 19:25:02 GMT",
"version": "v1"
},
{
"created": "Sat, 28 Jan 2017 19:54:32 GMT",
"version": "v2"
}
] | 2017-03-08 | [
[
"Sert",
"Özcan",
""
]
] | We propose a non-minimally coupled gravity model in $ Y(R)F^2 $ form to describe the radiation fluid stars which have the radiative equation of state between the energy density $ \rho $ and the pressure $p$ as $\rho=3p $. Here $F^2$ is the Maxwell invariant and $Y(R)$ is a function of the Ricci scalar $R$. We give the gravitational and electromagnetic field equations in differential form notation taking the infinitesimal variations of the model. We look for electrically charged star solutions to the field equations under a constraint which eliminating complexity of the higher order terms in the field equations. We determine the non-minimally coupled function $Y(R)$ and the corresponding model which admits new exact solutions in the interior of star and Reissner-Nordstrom solution at the exterior region. Using vanishing pressure condition at the boundary together with the continuity conditions of the metric functions and the electric charge, we find the mass-radius ratio, charge-radius ratio and gravitational surface redshift depending on the parameter of the model for the radiation fluid star. We derive general restrictions for the ratios and redshift of the charged compact stars. We obtain a slightly smaller upper mass-radius ratio limit than the Buchdahl bound $ 4/9 $ and a smaller upper redshift limit than the bound of the standard General Relativistic stars. |
1309.7827 | Behrouz Mirza | Maryam Aghaei Abchouyeh, Behrouz Mirza, Zeinab Sherkatghanad | Entropic force, running gravitational coupling and future singularities | 7 pages, 5 figures, references added | Gen Relativ Gravit (2014) 46:1617 | 10.1007/s10714-013-1617-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The effects of a running gravitational coupling and the entropic force on
future singularities are considered. Although it is expected that the quantum
corrections remove the future singularities or change the singularity type,
treating the running gravitational coupling as a function of energy density is
found to cause no change in the type of singularity but causes a delay in the
time that a singularity occurs. The entropic force is found to replaces the
singularity type $II$ by $\bar{III}$ ($a=$const., $H=$const., $\dot{H} \to
\infty$, $p \to \infty$, $\rho \to \infty$) which differs from previously known
type $III$ and to remove the $w$-singularity. We also consider an effective
cosmological model and show that the types $I$ and $II$ are replaced by the
singularity type $III$.
| [
{
"created": "Mon, 30 Sep 2013 12:59:49 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Feb 2014 05:37:04 GMT",
"version": "v2"
}
] | 2014-02-25 | [
[
"Abchouyeh",
"Maryam Aghaei",
""
],
[
"Mirza",
"Behrouz",
""
],
[
"Sherkatghanad",
"Zeinab",
""
]
] | The effects of a running gravitational coupling and the entropic force on future singularities are considered. Although it is expected that the quantum corrections remove the future singularities or change the singularity type, treating the running gravitational coupling as a function of energy density is found to cause no change in the type of singularity but causes a delay in the time that a singularity occurs. The entropic force is found to replaces the singularity type $II$ by $\bar{III}$ ($a=$const., $H=$const., $\dot{H} \to \infty$, $p \to \infty$, $\rho \to \infty$) which differs from previously known type $III$ and to remove the $w$-singularity. We also consider an effective cosmological model and show that the types $I$ and $II$ are replaced by the singularity type $III$. |
gr-qc/9511043 | null | David R Taylor and Roy Maartens | Almost-homogeneity of the universe in higher-order gravity | 14 pages LaTeX, no figures; to appear in General Relativity and
Gravitation | Gen.Rel.Grav. 27 (1995) 1309 | 10.1007/BF02153319 | RCG 95/06 | gr-qc | null | In the $R+\alpha R^2$ gravity theory, we show that if freely propagating
massless particles have an almost isotropic distribution, then the spacetime is
almost Friedmann-Robertson-Walker (FRW). This extends the result proved
recently in general relativity ($\alpha=0$), which is applicable to the
microwave background after photon decoupling. The higher-order result is in
principle applicable to a massless species that decouples in the early
universe, such as a relic graviton background. Any future observations that
show small anisotropies in such a background would imply that the geometry of
the early universe were almost FRW.
| [
{
"created": "Wed, 15 Nov 1995 12:29:05 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Taylor",
"David R",
""
],
[
"Maartens",
"Roy",
""
]
] | In the $R+\alpha R^2$ gravity theory, we show that if freely propagating massless particles have an almost isotropic distribution, then the spacetime is almost Friedmann-Robertson-Walker (FRW). This extends the result proved recently in general relativity ($\alpha=0$), which is applicable to the microwave background after photon decoupling. The higher-order result is in principle applicable to a massless species that decouples in the early universe, such as a relic graviton background. Any future observations that show small anisotropies in such a background would imply that the geometry of the early universe were almost FRW. |
gr-qc/0006017 | Adrian P. Gentle | Leo C. Brewin and Adrian P. Gentle | On the convergence of Regge calculus to general relativity | Updated to match published version. Details of numerical calculations
added, several sections rewritten. 9 pages, 4 EPS figures | Class.Quant.Grav. 18 (2001) 517-526 | 10.1088/0264-9381/18/3/311 | LAUR-00-2300 | gr-qc | null | Motivated by a recent study casting doubt on the correspondence between Regge
calculus and general relativity in the continuum limit, we explore a mechanism
by which the simplicial solutions can converge whilst the residual of the Regge
equations evaluated on the continuum solutions does not. By directly
constructing simplicial solutions for the Kasner cosmology we show that the
oscillatory behaviour of the discrepancy between the Einstein and Regge
solutions reconciles the apparent conflict between the results of Brewin and
those of previous studies. We conclude that solutions of Regge calculus are, in
general, expected to be second order accurate approximations to the
corresponding continuum solutions.
| [
{
"created": "Mon, 5 Jun 2000 23:05:23 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Mar 2001 19:14:04 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Brewin",
"Leo C.",
""
],
[
"Gentle",
"Adrian P.",
""
]
] | Motivated by a recent study casting doubt on the correspondence between Regge calculus and general relativity in the continuum limit, we explore a mechanism by which the simplicial solutions can converge whilst the residual of the Regge equations evaluated on the continuum solutions does not. By directly constructing simplicial solutions for the Kasner cosmology we show that the oscillatory behaviour of the discrepancy between the Einstein and Regge solutions reconciles the apparent conflict between the results of Brewin and those of previous studies. We conclude that solutions of Regge calculus are, in general, expected to be second order accurate approximations to the corresponding continuum solutions. |
gr-qc/9301015 | null | R.Penrose, R.D. Sorkin, and E. Woolgar | A Positive Mass Theorem Based on the Focusing and Retardation of Null
Geodesics | (replaced version corrects an errant TEX offset command -- those who
successfully TEXed the first version have no need to re-TEX) | null | null | null | gr-qc hep-th | null | A positive mass theorem for General Relativity Theory is proved. The proof is
4-dimensional in nature, and relies completely on arguments pertaining to
causal structure, the basic idea being that positive energy-density focuses
null geodesics, and correspondingly retards them, whereas a negative total mass
would advance them. Because it is not concerned with what lies behind horizons,
this new theorem applies in some situations not covered by previous positivity
theorems. Also, because geodesic focusing is a global condition, the proof
might allow a generalisation to semi-classical gravity, even though quantum
violations of local energy conditions can occur there.
| [
{
"created": "Thu, 14 Jan 1993 20:00:57 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Jan 1993 21:00:19 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Penrose",
"R.",
""
],
[
"Sorkin",
"R. D.",
""
],
[
"Woolgar",
"E.",
""
]
] | A positive mass theorem for General Relativity Theory is proved. The proof is 4-dimensional in nature, and relies completely on arguments pertaining to causal structure, the basic idea being that positive energy-density focuses null geodesics, and correspondingly retards them, whereas a negative total mass would advance them. Because it is not concerned with what lies behind horizons, this new theorem applies in some situations not covered by previous positivity theorems. Also, because geodesic focusing is a global condition, the proof might allow a generalisation to semi-classical gravity, even though quantum violations of local energy conditions can occur there. |
gr-qc/0010101 | T. P. Singh | Tomohiro Harada, Hideo Iguchi, Ken-ichi Nakao, T. P. Singh, Takahiro
Tanaka and Cenalo Vaz | Naked singularities and quantum gravity | 16 pages, paper rewritten into sections, conclusions unchanged, 4
references added, to appear in Phys. Rev. D (Rapid Communication) | Phys.Rev.D64:041501,2001 | 10.1103/PhysRevD.64.041501 | OSU-PHYS-178, WU-AP/115/00, YITP-00-56 | gr-qc | null | There are known models of spherical gravitational collapse in which the
collapse ends in a naked shell-focusing singularity for some initial data. If a
massless scalar field is quantized on the classical background provided by such
a star, it is found that the outgoing quantum flux of the scalar field diverges
in the approach to the Cauchy horizon. We argue that the semiclassical
approximation (i.e. quantum field theory on a classical curved background) used
in these analyses ceases to be valid about one Planck time before the epoch of
naked singularity formation, because by then the curvature in the central
region of the star reaches Planck scale. It is shown that during the epoch in
which the semiclassical approximation is valid, the total emitted energy is
about one Planck unit, and is not divergent. We also argue that back reaction
in this model does not become important so long as gravity can be treated
classically. It follows that the further evolution of the star will be
determined by quantum gravitational effects, and without invoking quantum
gravity it is not possible to say whether the star radiates away on a short
time scale or settles down into a black hole state.
| [
{
"created": "Fri, 27 Oct 2000 05:49:48 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jun 2001 06:00:32 GMT",
"version": "v2"
}
] | 2009-12-31 | [
[
"Harada",
"Tomohiro",
""
],
[
"Iguchi",
"Hideo",
""
],
[
"Nakao",
"Ken-ichi",
""
],
[
"Singh",
"T. P.",
""
],
[
"Tanaka",
"Takahiro",
""
],
[
"Vaz",
"Cenalo",
""
]
] | There are known models of spherical gravitational collapse in which the collapse ends in a naked shell-focusing singularity for some initial data. If a massless scalar field is quantized on the classical background provided by such a star, it is found that the outgoing quantum flux of the scalar field diverges in the approach to the Cauchy horizon. We argue that the semiclassical approximation (i.e. quantum field theory on a classical curved background) used in these analyses ceases to be valid about one Planck time before the epoch of naked singularity formation, because by then the curvature in the central region of the star reaches Planck scale. It is shown that during the epoch in which the semiclassical approximation is valid, the total emitted energy is about one Planck unit, and is not divergent. We also argue that back reaction in this model does not become important so long as gravity can be treated classically. It follows that the further evolution of the star will be determined by quantum gravitational effects, and without invoking quantum gravity it is not possible to say whether the star radiates away on a short time scale or settles down into a black hole state. |
1608.03992 | Kimet Jusufi | Kimet Jusufi, Gordana Apostolovska | Hawking radiation of Dirac monopoles from the global monopole black hole
with quantum gravity effects | 8 pages, 1 figure, to appear in Astrophysics and Space Science | Astrophys Space Sci (2016) 361: 374 | 10.1007/s10509-016-2962-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the quantum tunneling of Dirac magnetic monopoles from
the global monopole black hole under quantum gravity effects. We start from the
modified Maxwell's equations and the Generalized Uncertainty Relation (GUP), to
recover the GUP corrected temperature for the global monopole black hole by
solving the modified Dirac equation via Hamilton-Jacobi method. Furthermore, we
also include the quantum corrections beyond the semiclassical approximation, in
particular, first we find the logarithmic corrections of GUP corrected entropy
and finally we calculate the GUP corrected specific heat capacity. It is argued
that the GUP effects may prevent a black hole from complete evaporation and
leave remnants.
| [
{
"created": "Sat, 13 Aug 2016 15:19:52 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Oct 2016 23:19:35 GMT",
"version": "v2"
}
] | 2016-11-10 | [
[
"Jusufi",
"Kimet",
""
],
[
"Apostolovska",
"Gordana",
""
]
] | In this paper we study the quantum tunneling of Dirac magnetic monopoles from the global monopole black hole under quantum gravity effects. We start from the modified Maxwell's equations and the Generalized Uncertainty Relation (GUP), to recover the GUP corrected temperature for the global monopole black hole by solving the modified Dirac equation via Hamilton-Jacobi method. Furthermore, we also include the quantum corrections beyond the semiclassical approximation, in particular, first we find the logarithmic corrections of GUP corrected entropy and finally we calculate the GUP corrected specific heat capacity. It is argued that the GUP effects may prevent a black hole from complete evaporation and leave remnants. |
1911.04233 | Zurab Silagadze | S. Dhasmana, Z.K. Silagadze | Finsler space-time in light of Segal's principle | 6 pages, revtex4, to be published in Modern Physics Letters A. The
article is heavily based on arXiv:1609.08647 | Mod. Phys. Lett. A 35 (2020), 2050019 | 10.1142/S0217732320500194 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | ISIM(2) symmetry group of Cohen and Glashow's very special relativity is
unstable with respect to small deformations of its underlying algebraic
structure and according to Segal's principle cannot be a true symmetry of
nature. However, like special relativity, which is a very good description of
nature thanks to the smallness of the cosmological constant, which
characterizes the deformation of the Poincare group, the very special
relativity can also be a very good approximation thanks to the smallness of the
dimensionless parameter characterizing the deformation of ISIM(2).
| [
{
"created": "Fri, 1 Nov 2019 07:29:09 GMT",
"version": "v1"
}
] | 2020-03-09 | [
[
"Dhasmana",
"S.",
""
],
[
"Silagadze",
"Z. K.",
""
]
] | ISIM(2) symmetry group of Cohen and Glashow's very special relativity is unstable with respect to small deformations of its underlying algebraic structure and according to Segal's principle cannot be a true symmetry of nature. However, like special relativity, which is a very good description of nature thanks to the smallness of the cosmological constant, which characterizes the deformation of the Poincare group, the very special relativity can also be a very good approximation thanks to the smallness of the dimensionless parameter characterizing the deformation of ISIM(2). |
1308.3771 | Gilbert Weinstein | Marcus Khuri, Gilbert Weinstein and Sumio Yamada | The Riemannian Penrose Inequality with Charge for Multiple Black Holes | 7 pages; minor revisions | Contemporary Mathematics, 653 (2015), 219-226 | null | null | gr-qc math-ph math.DG math.MP | http://creativecommons.org/licenses/by/3.0/ | We present a proof of the Riemannian Penrose inequality with charge $r\leq m
+ \sqrt{m^2-q^2}$, where $A=4\pi r^2$ is the area of the outermost apparent
horizon with possibly multiple connected components, $m$ is the total ADM mass,
and $q$ the total charge of a strongly asymptotically flat initial data set for
the Einstein-Maxwell equations, satisfying the charged dominant energy
condition, with no charged matter outside the horizon.
| [
{
"created": "Sat, 17 Aug 2013 10:23:27 GMT",
"version": "v1"
},
{
"created": "Thu, 8 May 2014 16:37:51 GMT",
"version": "v2"
},
{
"created": "Tue, 9 Sep 2014 04:59:46 GMT",
"version": "v3"
}
] | 2015-12-04 | [
[
"Khuri",
"Marcus",
""
],
[
"Weinstein",
"Gilbert",
""
],
[
"Yamada",
"Sumio",
""
]
] | We present a proof of the Riemannian Penrose inequality with charge $r\leq m + \sqrt{m^2-q^2}$, where $A=4\pi r^2$ is the area of the outermost apparent horizon with possibly multiple connected components, $m$ is the total ADM mass, and $q$ the total charge of a strongly asymptotically flat initial data set for the Einstein-Maxwell equations, satisfying the charged dominant energy condition, with no charged matter outside the horizon. |
gr-qc/0304053 | Carlos Molina Mendes | C. Molina | Quasinormal modes of d-dimensional spherical black holes with a near
extreme cosmological constant | 5 pages, REVTeX4, version to be published in Physical Review D | Phys.Rev. D68 (2003) 064007 | 10.1103/PhysRevD.68.064007 | 1565/2003 | gr-qc astro-ph hep-th | null | We derive an expression for the quasinormal modes of scalar perturbations in
near extreme d-dimensional Schwarzschild-de Sitter and Reissner-Nordstrom-de
Sitter black holes. We show that, in the near extreme limit, the dynamics of
the scalar field is characterized by a Poschl-Teller effective potential. The
results are qualitatively independent of the spacetime dimension and field
mass.
| [
{
"created": "Mon, 14 Apr 2003 18:58:10 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Aug 2003 03:32:30 GMT",
"version": "v2"
},
{
"created": "Fri, 26 Sep 2003 14:12:35 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Molina",
"C.",
""
]
] | We derive an expression for the quasinormal modes of scalar perturbations in near extreme d-dimensional Schwarzschild-de Sitter and Reissner-Nordstrom-de Sitter black holes. We show that, in the near extreme limit, the dynamics of the scalar field is characterized by a Poschl-Teller effective potential. The results are qualitatively independent of the spacetime dimension and field mass. |
gr-qc/0701036 | Marcello Ortaggio | Marcello Ortaggio | Higher dimensional spacetimes with a geodesic, shearfree, twistfree and
expanding null congruence | 1+12 pages. Proceedings of the XVII SIGRAV Conference, Turin,
September 4--7, 2006. v2: minor changes | null | null | null | gr-qc hep-th | null | We present the complete family of higher dimensional spacetimes that admit a
geodesic, shearfree, twistfree and expanding null congruence, thus extending
the well-known D=4 class of Robinson-Trautman solutions. Einstein's equations
are solved for empty space with an arbitrary cosmological constant and for
aligned pure radiation. Main differences with respect to the D=4 case (such as
the absence of type III/N solutions, related to ``violations'' of the
Goldberg-Sachs theorem in D>4) are pointed out, also in connection with other
recent works. A formal analogy with electromagnetic fields is briefly discussed
in an appendix, where we demonstrate that multiple principal null directions of
null Maxwell fields are necessarily geodesic, and that in D>4 they are also
shearing if expanding.
| [
{
"created": "Fri, 5 Jan 2007 15:52:42 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Aug 2007 14:30:35 GMT",
"version": "v2"
}
] | 2007-08-30 | [
[
"Ortaggio",
"Marcello",
""
]
] | We present the complete family of higher dimensional spacetimes that admit a geodesic, shearfree, twistfree and expanding null congruence, thus extending the well-known D=4 class of Robinson-Trautman solutions. Einstein's equations are solved for empty space with an arbitrary cosmological constant and for aligned pure radiation. Main differences with respect to the D=4 case (such as the absence of type III/N solutions, related to ``violations'' of the Goldberg-Sachs theorem in D>4) are pointed out, also in connection with other recent works. A formal analogy with electromagnetic fields is briefly discussed in an appendix, where we demonstrate that multiple principal null directions of null Maxwell fields are necessarily geodesic, and that in D>4 they are also shearing if expanding. |
gr-qc/9605045 | Tigran Aivazian | Tigran Aivazian | Cosmological Solution To Einstein-Vlasov System | 7 pages, LaTex, no figures minor corrections | null | null | null | gr-qc | null | Einstein-Vlasov system is solved for a homogeneous isotropic spacetime with
positive curvature. In the case of the Universe consisting of massless
particles the equation for R(t) is solved analytically.
| [
{
"created": "Mon, 20 May 1996 16:32:37 GMT",
"version": "v1"
},
{
"created": "Tue, 28 May 1996 20:08:14 GMT",
"version": "v2"
},
{
"created": "Thu, 30 May 1996 20:02:51 GMT",
"version": "v3"
},
{
"created": "Wed, 5 Jun 1996 22:40:46 GMT",
"version": "v4"
}
] | 2008-02-03 | [
[
"Aivazian",
"Tigran",
""
]
] | Einstein-Vlasov system is solved for a homogeneous isotropic spacetime with positive curvature. In the case of the Universe consisting of massless particles the equation for R(t) is solved analytically. |
2407.04627 | Ribamar Reis R. R. | Lucas T. Santana, Jo\~ao C. Lobato, Ribamar R. R. Reis, Maur\'icio O.
Calv\~ao | A unified approach to coupled homogeneous linear wave propagation in
generic gravity | 24 pages, 2 figures | null | null | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | Wave propagation is a common occurrence in all of physics. A linear
approximation provides a simpler way to describe various fields related to
observable phenomena in laboratory physics as well as astronomy and cosmology,
allowing us to probe gravitation through its effect on the trajectories of
particles associated with those fields. This paper proposes a unified framework
to describe the wave propagation of a set of interacting tensor fields that
obey coupled homogeneous linear second-order partial differential equations for
arbitrary curved spacetimes, both Lorentzian and metric-affine. We use JWKB
Ans\"atze for all fields, written in terms of a perturbation parameter
proportional to a representative wavelength among them, deriving a set of
hierarchical algebraic and differential equations that link the fields' phases
and different order amplitudes. This allows us to reobtain the well-known laws
of geometrical optics and beyond geometrical optics in a generalized form,
showing that these laws are independent of the rank of the fields involved.
This is true as long as what we refer to as the kinetic tensor of a given field
satisfies a set of diagonality conditions, which further imply a handful of
simplifications on the transport equations obtained in the subleading orders of
the JWKB Ans\"atze. We explore these results in several notable examples in
Lorentzian and metric-affine spacetimes, illustrating the reach of our
derivations in general relativity, reduced Horndeski theories, spacetimes with
completely antisymmetric torsion and Weyl spacetimes. The formalism presented
herein lays the groundwork for the study of rays associated with different
types of waves in curved spacetimes and provides the tools to compute
modifications to their brightness evolution laws, consequential distance
duality relations, and beyond geometrical optics phenomena.
| [
{
"created": "Fri, 5 Jul 2024 16:34:18 GMT",
"version": "v1"
}
] | 2024-07-08 | [
[
"Santana",
"Lucas T.",
""
],
[
"Lobato",
"João C.",
""
],
[
"Reis",
"Ribamar R. R.",
""
],
[
"Calvão",
"Maurício O.",
""
]
] | Wave propagation is a common occurrence in all of physics. A linear approximation provides a simpler way to describe various fields related to observable phenomena in laboratory physics as well as astronomy and cosmology, allowing us to probe gravitation through its effect on the trajectories of particles associated with those fields. This paper proposes a unified framework to describe the wave propagation of a set of interacting tensor fields that obey coupled homogeneous linear second-order partial differential equations for arbitrary curved spacetimes, both Lorentzian and metric-affine. We use JWKB Ans\"atze for all fields, written in terms of a perturbation parameter proportional to a representative wavelength among them, deriving a set of hierarchical algebraic and differential equations that link the fields' phases and different order amplitudes. This allows us to reobtain the well-known laws of geometrical optics and beyond geometrical optics in a generalized form, showing that these laws are independent of the rank of the fields involved. This is true as long as what we refer to as the kinetic tensor of a given field satisfies a set of diagonality conditions, which further imply a handful of simplifications on the transport equations obtained in the subleading orders of the JWKB Ans\"atze. We explore these results in several notable examples in Lorentzian and metric-affine spacetimes, illustrating the reach of our derivations in general relativity, reduced Horndeski theories, spacetimes with completely antisymmetric torsion and Weyl spacetimes. The formalism presented herein lays the groundwork for the study of rays associated with different types of waves in curved spacetimes and provides the tools to compute modifications to their brightness evolution laws, consequential distance duality relations, and beyond geometrical optics phenomena. |
2308.11535 | Akshat Pandey | Akshat Pandey | Geodesic congruences in acoustic spacetimes and the role of Raychaudhuri
equation | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | It has been known that the propagation of sound in fluids can be used to
model acoustic spacetimes. These acoustic spacetimes offer analogue models for
gravity. We use the Raychaudhuri equation to study the propagation of sound in
these fluids, which, via the Eikonal approximation, correspond to null geodesic
congruences in the acoustic spacetimes. We explore this within the acoustic
analogues of black holes and cosmological spacetimes. The robustness of the
Raychaudhuri equation and the limits of the acoustic analogue are emphasised.
| [
{
"created": "Thu, 17 Aug 2023 18:59:48 GMT",
"version": "v1"
}
] | 2023-08-23 | [
[
"Pandey",
"Akshat",
""
]
] | It has been known that the propagation of sound in fluids can be used to model acoustic spacetimes. These acoustic spacetimes offer analogue models for gravity. We use the Raychaudhuri equation to study the propagation of sound in these fluids, which, via the Eikonal approximation, correspond to null geodesic congruences in the acoustic spacetimes. We explore this within the acoustic analogues of black holes and cosmological spacetimes. The robustness of the Raychaudhuri equation and the limits of the acoustic analogue are emphasised. |
gr-qc/9311010 | Jerzy Lewandowski | Abhay Ashtekar and Jerzy Lewandowski | Representation Theory of Analytic Holonomy C* Algebras | 42 pages, To be published in ``Knots and Quantum Gravity'' (ed.
J.Baez, Oxford U.Press) | null | null | null | gr-qc alg-geom hep-th math.AG | null | Integral calculus on the space of gauge equivalent connections is developed.
Loops, knots, links and graphs feature prominently in this description. The
framework is well--suited for quantization of diffeomorphism invariant theories
of connections.
The general setting is provided by the abelian C* algebra of functions on the
quotient space of connections generated by Wilson loops (i.e., by the traces of
holonomies of connections around closed loops). The representation theory of
this algebra leads to an interesting and powerful ``duality'' between
gauge--equivalence classes of connections and certain equivalence classes of
closed loops. In particular, regular measures on (a suitable completion of)
connections/gauges are in 1--1 correspondence with certain functions of loops
and diffeomorphism invariant measures correspond to (generalized) knot and link
invariants. By carrying out a non--linear extension of the theory of
cylindrical measures on topological vector spaces, a faithful, diffeomorphism
invariant measure is introduced. This measure can be used to define the Hilbert
space of quantum states in theories of connections. The Wilson--loop
functionals then serve as the configuration operators in the quantum theory.
| [
{
"created": "Sun, 7 Nov 1993 00:45:18 GMT",
"version": "v1"
},
{
"created": "Sun, 7 Nov 1993 14:41:01 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Lewandowski",
"Jerzy",
""
]
] | Integral calculus on the space of gauge equivalent connections is developed. Loops, knots, links and graphs feature prominently in this description. The framework is well--suited for quantization of diffeomorphism invariant theories of connections. The general setting is provided by the abelian C* algebra of functions on the quotient space of connections generated by Wilson loops (i.e., by the traces of holonomies of connections around closed loops). The representation theory of this algebra leads to an interesting and powerful ``duality'' between gauge--equivalence classes of connections and certain equivalence classes of closed loops. In particular, regular measures on (a suitable completion of) connections/gauges are in 1--1 correspondence with certain functions of loops and diffeomorphism invariant measures correspond to (generalized) knot and link invariants. By carrying out a non--linear extension of the theory of cylindrical measures on topological vector spaces, a faithful, diffeomorphism invariant measure is introduced. This measure can be used to define the Hilbert space of quantum states in theories of connections. The Wilson--loop functionals then serve as the configuration operators in the quantum theory. |
1610.09952 | Eugen Radu | Yves Brihaye and Eugen Radu | Remarks on the Taub-NUT solution in Chern-Simons modified gravity | 10 pages, 3 figures | null | 10.1016/j.physletb.2016.11.055 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the generalization of the NUT spacetime in General Relativity (GR)
within the framework of the (dynamical) Einstein--Chern-Simons (ECS) theory
with a massless scalar field. These configurations approach asymptotically the
NUT spacetime and are characterized by the `electric' and `magnetic' mass
parameters and a scalar `charge'. The solutions are found both analytically and
numerically. The analytical approach is perturbative around the Einstein
gravity background. Our results indicate that the ECS configurations share all
basic properties of the NUT spacetime in GR. However, when considering the
solutions inside the event horizon, we find that in contrast to the GR case,
the spacetime curvature grows (apparently) without bound.
| [
{
"created": "Mon, 31 Oct 2016 14:51:08 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Nov 2016 13:23:58 GMT",
"version": "v2"
}
] | 2016-12-07 | [
[
"Brihaye",
"Yves",
""
],
[
"Radu",
"Eugen",
""
]
] | We discuss the generalization of the NUT spacetime in General Relativity (GR) within the framework of the (dynamical) Einstein--Chern-Simons (ECS) theory with a massless scalar field. These configurations approach asymptotically the NUT spacetime and are characterized by the `electric' and `magnetic' mass parameters and a scalar `charge'. The solutions are found both analytically and numerically. The analytical approach is perturbative around the Einstein gravity background. Our results indicate that the ECS configurations share all basic properties of the NUT spacetime in GR. However, when considering the solutions inside the event horizon, we find that in contrast to the GR case, the spacetime curvature grows (apparently) without bound. |
1506.07484 | Francesco Cianfrani dr | Emanuele Alesci, Francesco Cianfrani | Quantum Reduced Loop Gravity | 6 pages, proceedings of Frontiers of Fundamental Physics 14 - FFP14,
15-18 July 2014, Marseille, accepted for publication in Proceedings of
Science | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum Reduced Loop Gravity provides a promising framework for a consistent
characterization of the early Universe dynamics. Inspired by BKL conjecture, a
flat Universe is described as a collection of Bianchi I homogeneous patches.
The resulting quantum dynamics is described by the scalar constraint operator,
whose matrix elements can be analytically computed. The effective semiclassical
dynamics is discussed, and the differences with Loop Quantum Cosmology are
emphasized.
| [
{
"created": "Wed, 24 Jun 2015 17:59:07 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Alesci",
"Emanuele",
""
],
[
"Cianfrani",
"Francesco",
""
]
] | Quantum Reduced Loop Gravity provides a promising framework for a consistent characterization of the early Universe dynamics. Inspired by BKL conjecture, a flat Universe is described as a collection of Bianchi I homogeneous patches. The resulting quantum dynamics is described by the scalar constraint operator, whose matrix elements can be analytically computed. The effective semiclassical dynamics is discussed, and the differences with Loop Quantum Cosmology are emphasized. |
2106.12564 | Vittorio De Falco Dr | Vittorio De Falco, Mariafelicia De Laurentis, Salvatore Capozziello | Epicyclic frequencies in static and spherically symmetric wormhole
geometries | 11 pages, 6 figures, 2 tables; accepted for publication on Phys. Rev.
D on 23/06/2021 | null | 10.1103/PhysRevD.104.024053 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | The measurement of the epicyclic frequencies is a widely used astrophysical
technique to infer information on a given self-gravitating system and on the
related gravity background. We derive their explicit expressions in static and
spherically symmetric wormhole spacetimes. We discuss how these theoretical
results can be applied to: (1) detect the presence of a wormhole,
distinguishing it by a black hole; (2) reconstruct wormhole solutions through
the fit of the observational data, once we have them. Finally, we discuss the
physical implications of our proposed epicyclic method.
| [
{
"created": "Wed, 23 Jun 2021 17:45:16 GMT",
"version": "v1"
}
] | 2021-08-04 | [
[
"De Falco",
"Vittorio",
""
],
[
"De Laurentis",
"Mariafelicia",
""
],
[
"Capozziello",
"Salvatore",
""
]
] | The measurement of the epicyclic frequencies is a widely used astrophysical technique to infer information on a given self-gravitating system and on the related gravity background. We derive their explicit expressions in static and spherically symmetric wormhole spacetimes. We discuss how these theoretical results can be applied to: (1) detect the presence of a wormhole, distinguishing it by a black hole; (2) reconstruct wormhole solutions through the fit of the observational data, once we have them. Finally, we discuss the physical implications of our proposed epicyclic method. |
2011.11086 | Alessio Marrani | Sergio Cacciatori, Alessio Marrani, Federico Re | On Generalized Lemaitre-Tolman-Bondi Metric. Fractal Matter at the end
of Matter-Antimatter Recombination | 1+26 pages, 0 figures | null | 10.1142/S0218271821500863 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Many recent researches have investigated the deviations from the Friedmannian
cosmological model, as well as their consequences on unexplained cosmological
phenomena, such as dark matter and the acceleration of the Universe. On the one
hand, a first order perturbative study of matter inhomogeneity returned a
partial explanation of dark matter and dark energy, as relativistic effects due
to the retarded potentials of far objects. On the other hand, the fractal
cosmology, now modeled with a Lemaitre-Tolman-Bondi (LTB) metric, results in
distortions of the luminosity distances of SNe Ia, explaining the acceleration
as apparent. In this work we extend the LTB metric to ancient times. The origin
of the fractal distribution of matter is explained as the matter remnant after
the matter-antimatter recombination epoch. We show that the evolution of such a
inhomogeneity necessarily requires a dynamical generalization of LTB, and we
propose a particular solution.
| [
{
"created": "Sun, 22 Nov 2020 18:55:28 GMT",
"version": "v1"
}
] | 2021-09-22 | [
[
"Cacciatori",
"Sergio",
""
],
[
"Marrani",
"Alessio",
""
],
[
"Re",
"Federico",
""
]
] | Many recent researches have investigated the deviations from the Friedmannian cosmological model, as well as their consequences on unexplained cosmological phenomena, such as dark matter and the acceleration of the Universe. On the one hand, a first order perturbative study of matter inhomogeneity returned a partial explanation of dark matter and dark energy, as relativistic effects due to the retarded potentials of far objects. On the other hand, the fractal cosmology, now modeled with a Lemaitre-Tolman-Bondi (LTB) metric, results in distortions of the luminosity distances of SNe Ia, explaining the acceleration as apparent. In this work we extend the LTB metric to ancient times. The origin of the fractal distribution of matter is explained as the matter remnant after the matter-antimatter recombination epoch. We show that the evolution of such a inhomogeneity necessarily requires a dynamical generalization of LTB, and we propose a particular solution. |
1706.03855 | Jose Luis Flores | Jos\'e L. Flores, Miguel S\'anchez | Ehlers-Kundt Conjecture about Gravitational Waves and Dynamical Systems | Final version with minor changes and some new references | Journal of Differential Equations, Volume 268, Issue 12, 5 June
2020, Pages 7505-7534 | 10.1016/j.jde.2019.11.061 | null | gr-qc math-ph math.CV math.DG math.DS math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Ehlers-Kundt conjecture is a physical assertion about the fundamental role of
plane waves for the description of gravitational waves. Mathematically, it
becomes equivalent to a problem on the Euclidean plane ${\mathbb R}^2$ with a
very simple formulation in Classical Mechanics: given a non-necessarily
autonomous potential $V(z,u)$, $(z,u)\in {\mathbb R}^2\times {\mathbb R}$,
harmonic in $z$ (i.e. source-free), the trajectories of its associated
dynamical system $\ddot{z}(s)=-\nabla_z V(z(s),s)$ are complete (they live
eternally) if and only if $V(z,u)$ is a polynomial in $z$ of degree at most $2$
(so that $V$ is a standard mathematical idealization of vacuum). Here, the
conjecture is solved in the significative case that $V$ is bounded polynomially
in $z$ for finite values of $u\in {\mathbb R}$. The mathematical and physical
implications of this {\em polynomial EK conjecture}, as well as the
non-polynomial one, are discussed beyond their original scope.
| [
{
"created": "Mon, 12 Jun 2017 21:16:38 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Nov 2017 06:27:51 GMT",
"version": "v2"
},
{
"created": "Fri, 29 Jun 2018 04:59:37 GMT",
"version": "v3"
},
{
"created": "Tue, 26 Nov 2019 18:19:27 GMT",
"version": "v4"
}
] | 2020-09-28 | [
[
"Flores",
"José L.",
""
],
[
"Sánchez",
"Miguel",
""
]
] | Ehlers-Kundt conjecture is a physical assertion about the fundamental role of plane waves for the description of gravitational waves. Mathematically, it becomes equivalent to a problem on the Euclidean plane ${\mathbb R}^2$ with a very simple formulation in Classical Mechanics: given a non-necessarily autonomous potential $V(z,u)$, $(z,u)\in {\mathbb R}^2\times {\mathbb R}$, harmonic in $z$ (i.e. source-free), the trajectories of its associated dynamical system $\ddot{z}(s)=-\nabla_z V(z(s),s)$ are complete (they live eternally) if and only if $V(z,u)$ is a polynomial in $z$ of degree at most $2$ (so that $V$ is a standard mathematical idealization of vacuum). Here, the conjecture is solved in the significative case that $V$ is bounded polynomially in $z$ for finite values of $u\in {\mathbb R}$. The mathematical and physical implications of this {\em polynomial EK conjecture}, as well as the non-polynomial one, are discussed beyond their original scope. |
1007.3306 | Jose Socorro Garcia | J. Socorro, M. Sabido, M.A. S\'anchez G. and M.G. Fr\'ias Palos | Anisotropic cosmology in S\'aez-Ballester theory: classical and quantum
solutions | 8 pages, Latex2e, | Rev.Mex.Fis.56:166-171,2010 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the S\'aez-Ballester theory on anisotropic Bianchi I cosmological
model, with barotropic fluid and cosmological constant. We obtain the classical
solution by using the Hamilton-Jacobi approach. Also the quantum regime is
constructed and exact solutions to the Wheeler-DeWitt equation are found.
| [
{
"created": "Mon, 19 Jul 2010 23:23:17 GMT",
"version": "v1"
}
] | 2016-08-14 | [
[
"Socorro",
"J.",
""
],
[
"Sabido",
"M.",
""
],
[
"G.",
"M. A. Sánchez",
""
],
[
"Palos",
"M. G. Frías",
""
]
] | We use the S\'aez-Ballester theory on anisotropic Bianchi I cosmological model, with barotropic fluid and cosmological constant. We obtain the classical solution by using the Hamilton-Jacobi approach. Also the quantum regime is constructed and exact solutions to the Wheeler-DeWitt equation are found. |
1312.1825 | Mariafelicia De Laurentis Dr. | Salvatore Capozziello, Mariafelicia De Laurentis, Orlando Luongo and
Alan Cosimo Ruggeri | Cosmographic Constraints and Cosmic Fluids | 45 pages, 1 figure | Galaxies 2013, 1(3), 216-260; | 10.3390/galaxies1030216 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The problem of reproducing dark energy effects is reviewed here with
particular interest devoted to cosmography. We summarize some of the most
relevant cosmological models, based on the assumption that the corresponding
barotropic equations of state evolve as the universe expands, giving rise to
the accelerated expansion. We describe in detail the $\Lambda$CDM
($\Lambda$-Cold Dark Matter) and $\omega$CDM models, considering also some
specific examples, e.g., Chevallier-Polarsky-Linder, the Chaplygin gas and the
Dvali-Gabadadze-Porrati cosmological model. Finally, we consider the
cosmological consequences of $f(\mathcal{R})$ and $f(\mathcal{T})$ gravities
and their impact on the framework of cosmography. Keeping these considerations
in mind, we point out the \emph{model-independent} procedure related to
cosmography, showing how to match the series of cosmological observables to the
free parameters of each model. We critically discuss the role played by
cosmography, as a \emph{selection criterion} to check whether a particular
model passes or does not present cosmological constraints. In so doing, we find
out cosmological bounds by fitting the luminosity distance expansion of the
redshift, z, adopting the recent Union 2.1 dataset of supernovae, combined with
the baryonic acoustic oscillation and the cosmic microwave background
measurements. We perform cosmographic analyses, imposing different priors on
the Hubble rate present value. In addition, we compare our results with recent
PLANCK limits, showing that the $\Lambda$CDM and $\omega$CDM models seem to be
the favorite with respect to other dark energy models. However, we show that
cosmographic constraints on $f(\mathcal{R})$ and $f(\mathcal{T})$ cannot
discriminate between extensions of General Relativity and dark energy models,
leading to a disadvantageous degeneracy problem.
| [
{
"created": "Fri, 6 Dec 2013 10:33:34 GMT",
"version": "v1"
}
] | 2013-12-09 | [
[
"Capozziello",
"Salvatore",
""
],
[
"De Laurentis",
"Mariafelicia",
""
],
[
"Luongo",
"Orlando",
""
],
[
"Ruggeri",
"Alan Cosimo",
""
]
] | The problem of reproducing dark energy effects is reviewed here with particular interest devoted to cosmography. We summarize some of the most relevant cosmological models, based on the assumption that the corresponding barotropic equations of state evolve as the universe expands, giving rise to the accelerated expansion. We describe in detail the $\Lambda$CDM ($\Lambda$-Cold Dark Matter) and $\omega$CDM models, considering also some specific examples, e.g., Chevallier-Polarsky-Linder, the Chaplygin gas and the Dvali-Gabadadze-Porrati cosmological model. Finally, we consider the cosmological consequences of $f(\mathcal{R})$ and $f(\mathcal{T})$ gravities and their impact on the framework of cosmography. Keeping these considerations in mind, we point out the \emph{model-independent} procedure related to cosmography, showing how to match the series of cosmological observables to the free parameters of each model. We critically discuss the role played by cosmography, as a \emph{selection criterion} to check whether a particular model passes or does not present cosmological constraints. In so doing, we find out cosmological bounds by fitting the luminosity distance expansion of the redshift, z, adopting the recent Union 2.1 dataset of supernovae, combined with the baryonic acoustic oscillation and the cosmic microwave background measurements. We perform cosmographic analyses, imposing different priors on the Hubble rate present value. In addition, we compare our results with recent PLANCK limits, showing that the $\Lambda$CDM and $\omega$CDM models seem to be the favorite with respect to other dark energy models. However, we show that cosmographic constraints on $f(\mathcal{R})$ and $f(\mathcal{T})$ cannot discriminate between extensions of General Relativity and dark energy models, leading to a disadvantageous degeneracy problem. |
gr-qc/0402009 | Giovanni Amelino-Camelia | Giovanni Amelino-Camelia | A perspective on Quantum Gravity Phenomenology | 15 pages, LaTex. These notes provided the basis for the ``summary
talk" which I gave as chairman of the QG1 session (``Quantum Gravity
Phenomenology") at the "10th Marcel Grossmann Meeting on General Relativity"
(Rio de Janeiro, July 20-26, 2003). V2: Additional remarks (especially on
synchrotron radiation) and additional references | null | 10.1142/9789812704030_0015 | null | gr-qc | null | I give a brief overview of some Quantum-Gravity-Phenomenology research lines,
focusing on studies of cosmic rays and gamma-ray bursts that concern the fate
of Lorentz symmetry in quantum spacetime. I also stress that the most valuable
phenomenological analyses should not mix too many conjectured new features of
quantum spacetime, and from this perspective it appears that it should be
difficult to obtain reliable guidance on the quantum-gravity problem from the
analysis of synchrotron radiation from the Crab nebula and from the analysis of
phase coherence of light from extragalactic sources. Forthcoming observatories
of ultra-high-energy neutrinos should provide several opportunities for clean
tests of some simple hypothesis for the short-distance structure of spacetime.
In particular, these neutrino studies, and some related cosmic-ray studies,
should provide access to the regime $E>\sqrt{m E_p}$.
| [
{
"created": "Mon, 2 Feb 2004 21:02:12 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Feb 2004 07:26:23 GMT",
"version": "v2"
}
] | 2016-11-09 | [
[
"Amelino-Camelia",
"Giovanni",
""
]
] | I give a brief overview of some Quantum-Gravity-Phenomenology research lines, focusing on studies of cosmic rays and gamma-ray bursts that concern the fate of Lorentz symmetry in quantum spacetime. I also stress that the most valuable phenomenological analyses should not mix too many conjectured new features of quantum spacetime, and from this perspective it appears that it should be difficult to obtain reliable guidance on the quantum-gravity problem from the analysis of synchrotron radiation from the Crab nebula and from the analysis of phase coherence of light from extragalactic sources. Forthcoming observatories of ultra-high-energy neutrinos should provide several opportunities for clean tests of some simple hypothesis for the short-distance structure of spacetime. In particular, these neutrino studies, and some related cosmic-ray studies, should provide access to the regime $E>\sqrt{m E_p}$. |
1709.02367 | \"Ozg\"ur Akarsu | Ozgur Akarsu, Nihan Katirci, Suresh Kumar | Cosmic acceleration in dust only Universe via energy-momentum powered
gravity | 15 pages, 7 figures, 2 tables | Phys. Rev. D 97, 024011 (2018) | 10.1103/PhysRevD.97.024011 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a modified theory of gravitation constructed by the addition of
the term $f(T_{\mu\nu}T^{\mu\nu})$ to the Einstein-Hilbert action, and
elaborate a particular case
$f(T_{\mu\nu}T^{\mu\nu})=\alpha(T_{\mu\nu}T^{\mu\nu})^{\eta}$, where $\alpha$
and $\eta$ are real constants, dubbed as energy-momentum powered gravity
(EMPG). We search for viable cosmologies arising from EMPG especially in the
context of the late-time accelerated expansion of the Universe. We investigate
the ranges of the EMPG parameters $(\alpha,\eta)$ on theoretical as well as
observational grounds leading to the late-time acceleration of the Universe
with pressureless matter only, while keeping the successes of standard general
relativity at early times. We find that $\eta=0$ corresponds to the
$\Lambda$CDM model, whereas $\eta\neq 0$ leads to a $w$CDM-type model. However,
the underlying physics of the EMPG model is entirely different in the sense
that the energy in the EMPG Universe is sourced by pressureless matter only.
Moreover, the energy of the pressureless matter is not conserved, namely, in
general it does not dilute as $\rho\propto a^{-3}$ with the expansion of the
Universe. Finally, we constrain the parameters of an EMPG-based cosmology with
a recent compilation of 28 Hubble parameter measurements, and find that this
model describes an evolution of the Universe similar to that in the
$\Lambda$CDM model. We briefly discuss that EMPG can be unified with
Starobinsky gravity to describe the complete history of the Universe including
the inflationary era.
| [
{
"created": "Thu, 7 Sep 2017 17:39:09 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Sep 2017 16:29:24 GMT",
"version": "v2"
},
{
"created": "Thu, 8 Feb 2018 18:33:13 GMT",
"version": "v3"
}
] | 2018-02-09 | [
[
"Akarsu",
"Ozgur",
""
],
[
"Katirci",
"Nihan",
""
],
[
"Kumar",
"Suresh",
""
]
] | We propose a modified theory of gravitation constructed by the addition of the term $f(T_{\mu\nu}T^{\mu\nu})$ to the Einstein-Hilbert action, and elaborate a particular case $f(T_{\mu\nu}T^{\mu\nu})=\alpha(T_{\mu\nu}T^{\mu\nu})^{\eta}$, where $\alpha$ and $\eta$ are real constants, dubbed as energy-momentum powered gravity (EMPG). We search for viable cosmologies arising from EMPG especially in the context of the late-time accelerated expansion of the Universe. We investigate the ranges of the EMPG parameters $(\alpha,\eta)$ on theoretical as well as observational grounds leading to the late-time acceleration of the Universe with pressureless matter only, while keeping the successes of standard general relativity at early times. We find that $\eta=0$ corresponds to the $\Lambda$CDM model, whereas $\eta\neq 0$ leads to a $w$CDM-type model. However, the underlying physics of the EMPG model is entirely different in the sense that the energy in the EMPG Universe is sourced by pressureless matter only. Moreover, the energy of the pressureless matter is not conserved, namely, in general it does not dilute as $\rho\propto a^{-3}$ with the expansion of the Universe. Finally, we constrain the parameters of an EMPG-based cosmology with a recent compilation of 28 Hubble parameter measurements, and find that this model describes an evolution of the Universe similar to that in the $\Lambda$CDM model. We briefly discuss that EMPG can be unified with Starobinsky gravity to describe the complete history of the Universe including the inflationary era. |
0912.0432 | Taeyoon Moon | Tae Yoon Moon, Joohan Lee and Phillial Oh | Conformal Invariance in Einstein-Cartan-Weyl space | 10 pages, version to appear MPLA | Mod.Phys.Lett.A25:3129-3143,2010 | 10.1142/S0217732310034201 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider conformally invariant form of the actions in Einstein, Weyl,
Einstein-Cartan and Einstein-Cartan-Weyl space in general dimensions($>2$) and
investigate the relations among them. In Weyl space, the observational
consistency condition for the vector field determining non-metricity of the
connection can be obtained from the equation of motion. In Einstein-Cartan
space a similar role is played by the vector part of the torsion tensor. We
consider the case where the trace part of the torsion is the Kalb-Ramond type
of field. In this case, we express conformally invariant action in terms of two
scalar fields of conformal weight -1, which can be cast into some interesting
form. We discuss some applications of the result.
| [
{
"created": "Wed, 2 Dec 2009 15:19:34 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Dec 2009 15:36:48 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Nov 2010 04:11:05 GMT",
"version": "v3"
}
] | 2010-11-23 | [
[
"Moon",
"Tae Yoon",
""
],
[
"Lee",
"Joohan",
""
],
[
"Oh",
"Phillial",
""
]
] | We consider conformally invariant form of the actions in Einstein, Weyl, Einstein-Cartan and Einstein-Cartan-Weyl space in general dimensions($>2$) and investigate the relations among them. In Weyl space, the observational consistency condition for the vector field determining non-metricity of the connection can be obtained from the equation of motion. In Einstein-Cartan space a similar role is played by the vector part of the torsion tensor. We consider the case where the trace part of the torsion is the Kalb-Ramond type of field. In this case, we express conformally invariant action in terms of two scalar fields of conformal weight -1, which can be cast into some interesting form. We discuss some applications of the result. |
gr-qc/9602014 | Yuri N. Obukhov | Yuri N. Obukhov and Friedrich W. Hehl | On the Relation Between Quadratic and Linear Curvature Lagrangians in
Poincar\'e Gauge Gravity | 13 pages, RevTex | Acta Phys.Polon.B27:2685-2694,1996 | null | null | gr-qc astro-ph hep-th | null | We discuss the choice of the Lagrangian in the Poincar\'e gauge theory of
gravity. Drawing analogies to earlier de Sitter gauge models, we point out the
possibility of deriving the Einstein-Cartan Lagrangian {\it without}
cosmological term from a {\it modified} quadratic curvature invariant of {\it
topological} type.
| [
{
"created": "Thu, 8 Feb 1996 18:57:17 GMT",
"version": "v1"
}
] | 2011-04-15 | [
[
"Obukhov",
"Yuri N.",
""
],
[
"Hehl",
"Friedrich W.",
""
]
] | We discuss the choice of the Lagrangian in the Poincar\'e gauge theory of gravity. Drawing analogies to earlier de Sitter gauge models, we point out the possibility of deriving the Einstein-Cartan Lagrangian {\it without} cosmological term from a {\it modified} quadratic curvature invariant of {\it topological} type. |
2310.07537 | Reginald Christian Bernardo | Reginald Christian Bernardo and Kin-Wang Ng | Beyond the Hellings-Downs curve: Non-Einsteinian gravitational waves in
pulsar timing array correlations | 8 pages + refs, 6 figures, comments welcome | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent astronomical milestone by the pulsar timing arrays (PTA) has
revealed galactic-size gravitational waves (GW) in the form of a stochastic
gravitational wave background (SGWB), correlating the radio pulses emitted by
millisecond pulsars. This draws the outstanding questions toward the origin and
the nature of the SGWB; the latter is synonymous to testing how quadrupolar the
inter-pulsar spatial correlation is. In this paper, we tackle the nature of the
SGWB by considering correlations beyond the Hellings-Downs (HD) curve of
Einstein's general relativity. We put the HD and non-Einsteinian GW
correlations under scrutiny with the NANOGrav and the CPTA data, and find that
both data sets allow a graviton mass $m_{\rm g} \lesssim 1.04 \times 10^{-22} \
{\rm eV}/c^2$ and subluminal traveling waves. We discuss gravitational physics
scenarios beyond general relativity that could host non-Einsteinian GW
correlations in the SGWB and highlight the importance of the cosmic variance
inherited from the stochasticity in interpreting PTA observation.
| [
{
"created": "Wed, 11 Oct 2023 14:40:52 GMT",
"version": "v1"
}
] | 2023-10-12 | [
[
"Bernardo",
"Reginald Christian",
""
],
[
"Ng",
"Kin-Wang",
""
]
] | The recent astronomical milestone by the pulsar timing arrays (PTA) has revealed galactic-size gravitational waves (GW) in the form of a stochastic gravitational wave background (SGWB), correlating the radio pulses emitted by millisecond pulsars. This draws the outstanding questions toward the origin and the nature of the SGWB; the latter is synonymous to testing how quadrupolar the inter-pulsar spatial correlation is. In this paper, we tackle the nature of the SGWB by considering correlations beyond the Hellings-Downs (HD) curve of Einstein's general relativity. We put the HD and non-Einsteinian GW correlations under scrutiny with the NANOGrav and the CPTA data, and find that both data sets allow a graviton mass $m_{\rm g} \lesssim 1.04 \times 10^{-22} \ {\rm eV}/c^2$ and subluminal traveling waves. We discuss gravitational physics scenarios beyond general relativity that could host non-Einsteinian GW correlations in the SGWB and highlight the importance of the cosmic variance inherited from the stochasticity in interpreting PTA observation. |
1205.4792 | Dao-Jun Liu | Dao-Jun Liu, Bin Yang, Yong-Jia Zhai, Xin-Zhou Li | Quasinormal modes for asymptotic safe black holes | 11 pages, 1 figures, accepted for publication in CQG. arXiv admin
note: text overlap with arXiv:1007.1317 | null | 10.1088/0264-9381/29/14/145009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Under the hypothesis of asymptotic safety of gravity, the static, spherically
symmetric black hole solutions in the infrared limit are corrected by
non-perturbative effects. Specifically, the metric is modified by the running
of gravitational couplings. In this work, we investigate the effects of this
correction to the quasinormal modes (QNMs) of a test scalar field propagating
in this kind of black hole background analytically and numerically. It is found
that although the quasi-period frequencies and the damping of oscillations are
respectively enhanced and weakened by the quantum correction term, the
stability of the black hole remains.
| [
{
"created": "Tue, 22 May 2012 03:20:04 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Liu",
"Dao-Jun",
""
],
[
"Yang",
"Bin",
""
],
[
"Zhai",
"Yong-Jia",
""
],
[
"Li",
"Xin-Zhou",
""
]
] | Under the hypothesis of asymptotic safety of gravity, the static, spherically symmetric black hole solutions in the infrared limit are corrected by non-perturbative effects. Specifically, the metric is modified by the running of gravitational couplings. In this work, we investigate the effects of this correction to the quasinormal modes (QNMs) of a test scalar field propagating in this kind of black hole background analytically and numerically. It is found that although the quasi-period frequencies and the damping of oscillations are respectively enhanced and weakened by the quantum correction term, the stability of the black hole remains. |
1203.5070 | Hirotaka Yoshino | Hirotaka Yoshino, Hideo Kodama | Bosenova collapse of axion cloud around a rotating black hole | 38 pages, 18 figures | Prog. Theor. Phys. 128 (2012), 153-190 | 10.1143/PTP.128.153 | KEK-TH-1530 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by possible existence of stringy axions with ultralight mass, we
study the behavior of an axion field around a rapidly rotating black hole (BH)
obeying the sine-Gordon equation by numerical simulations. Due to superradiant
instability, the axion field extracts the rotational energy of the BH and the
nonlinear self-interaction becomes important as the field grows larger. We
present clear numerical evidences that the nonlinear effect leads to a collapse
of the axion cloud and a subsequent explosive phenomena, which is analogous to
the "bosenova" observed in experiments of Bose-Einstein condensate. The
criterion for the onset of the bosenova collapse is given. We also discuss the
reason why the bosenova happens by constructing an effective theory of a
wavepacket model under the nonrelativistic approximation.
| [
{
"created": "Thu, 22 Mar 2012 18:22:03 GMT",
"version": "v1"
}
] | 2012-08-03 | [
[
"Yoshino",
"Hirotaka",
""
],
[
"Kodama",
"Hideo",
""
]
] | Motivated by possible existence of stringy axions with ultralight mass, we study the behavior of an axion field around a rapidly rotating black hole (BH) obeying the sine-Gordon equation by numerical simulations. Due to superradiant instability, the axion field extracts the rotational energy of the BH and the nonlinear self-interaction becomes important as the field grows larger. We present clear numerical evidences that the nonlinear effect leads to a collapse of the axion cloud and a subsequent explosive phenomena, which is analogous to the "bosenova" observed in experiments of Bose-Einstein condensate. The criterion for the onset of the bosenova collapse is given. We also discuss the reason why the bosenova happens by constructing an effective theory of a wavepacket model under the nonrelativistic approximation. |
1508.03119 | Hajime Sotani | Hajime Sotani and Umpei Miyamoto | Strong gravitational lensing by an electrically charged black hole in
Eddington-inspired Born-Infeld gravity | accepted for publication in PRD | Phys. Rev. D 92, 044052 (2015) | 10.1103/PhysRevD.92.044052 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We systematically examine the properties of null geodesics around an
electrically charged, asymptotically flat black hole in Eddington-inspired
Born-Infeld gravity, varying the electric charge of black hole and the coupling
constant in the theory. We find that the radius of the unstable circular orbit
for massless particle decreases with the coupling constant, if the value of the
electrical charge is fixed. Additionally, we consider the strong gravitational
lensing around such a black hole. We show that the deflection angle, the
position angle of the relativistic images, and the magnification due to the
light bending in strong gravitational field are quite sensitive to the
parameters determining the black hole solution. Thus, through the accurate
observations associated with the strong gravitational lensing, it might be
possible to reveal the gravitational theory in a strong field regime.
| [
{
"created": "Thu, 13 Aug 2015 05:04:49 GMT",
"version": "v1"
}
] | 2015-09-30 | [
[
"Sotani",
"Hajime",
""
],
[
"Miyamoto",
"Umpei",
""
]
] | We systematically examine the properties of null geodesics around an electrically charged, asymptotically flat black hole in Eddington-inspired Born-Infeld gravity, varying the electric charge of black hole and the coupling constant in the theory. We find that the radius of the unstable circular orbit for massless particle decreases with the coupling constant, if the value of the electrical charge is fixed. Additionally, we consider the strong gravitational lensing around such a black hole. We show that the deflection angle, the position angle of the relativistic images, and the magnification due to the light bending in strong gravitational field are quite sensitive to the parameters determining the black hole solution. Thus, through the accurate observations associated with the strong gravitational lensing, it might be possible to reveal the gravitational theory in a strong field regime. |
1403.5985 | Abigail Alvarez Dr. Sc. | Abigail Alvarez, Eloy Ay\'on-Beato, Hern\'an A. Gonz\'alez and Mokhtar
Hassa\"ine | Nonlinearly charged Lifshitz black holes for any exponent $z>1$ | null | JHEP06(2014)041 | 10.1007/JHEP06(2014)041 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Charged Lifshitz black holes for the Einstein-Proca-Maxwell system with a
negative cosmological constant in arbitrary dimension $D$ are known only if the
dynamical critical exponent is fixed as $z=2(D-2)$. In the present work, we
show that these configurations can be extended to much more general charged
black holes which in addition exist for any value of the dynamical exponent
$z>1$ by considering a nonlinear electrodynamics instead of the Maxwell theory.
More precisely, we introduce a two-parametric nonlinear electrodynamics defined
in the more general, but less known, so-called $(\mathcal{H},P)$-formalism and
obtain a family of charged black hole solutions depending on two parameters. We
also remark that the value of the dynamical exponent $z=D-2$ turns out to be
critical in the sense that it yields asymptotically Lifshitz black holes with
logarithmic decay supported by a particular logarithmic electrodynamics. All
these configurations include extremal Lifshitz black holes. Charged topological
Lifshitz black holes are also shown to emerge by slightly generalizing the
proposed electrodynamics.
| [
{
"created": "Mon, 24 Mar 2014 14:59:39 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jan 2015 17:43:18 GMT",
"version": "v2"
}
] | 2015-01-28 | [
[
"Alvarez",
"Abigail",
""
],
[
"Ayón-Beato",
"Eloy",
""
],
[
"González",
"Hernán A.",
""
],
[
"Hassaïne",
"Mokhtar",
""
]
] | Charged Lifshitz black holes for the Einstein-Proca-Maxwell system with a negative cosmological constant in arbitrary dimension $D$ are known only if the dynamical critical exponent is fixed as $z=2(D-2)$. In the present work, we show that these configurations can be extended to much more general charged black holes which in addition exist for any value of the dynamical exponent $z>1$ by considering a nonlinear electrodynamics instead of the Maxwell theory. More precisely, we introduce a two-parametric nonlinear electrodynamics defined in the more general, but less known, so-called $(\mathcal{H},P)$-formalism and obtain a family of charged black hole solutions depending on two parameters. We also remark that the value of the dynamical exponent $z=D-2$ turns out to be critical in the sense that it yields asymptotically Lifshitz black holes with logarithmic decay supported by a particular logarithmic electrodynamics. All these configurations include extremal Lifshitz black holes. Charged topological Lifshitz black holes are also shown to emerge by slightly generalizing the proposed electrodynamics. |
0905.4353 | Valery Kiselev | V.V.Kiselev, S.A.Timofeev | Quasiattractor in models of new and chaotic inflation | 10 pages, 2 eps-figures, revtex4, submitted to Gen.Rel.Grav | Gen.Rel.Grav.42:183-197,2010 | 10.1007/s10714-009-0827-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inflation with a scalar-field potential of the form \lambda (\phi^2-v^2)^2
can be described in terms of a parametrical attractor with critical points,
whose driftage depends on the control value of the slowly changing Hubble rate.
The method allows us to easily obtain theoretical expressions for fluctuations
of inhomogeneity in both the cosmic microwave background and distribution of
matter. We find the region for admissible values of potential parameters,
wherein theoretical predictions are consistent with experimental results within
the limits of measurement uncertainties.
| [
{
"created": "Wed, 27 May 2009 08:09:34 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Kiselev",
"V. V.",
""
],
[
"Timofeev",
"S. A.",
""
]
] | Inflation with a scalar-field potential of the form \lambda (\phi^2-v^2)^2 can be described in terms of a parametrical attractor with critical points, whose driftage depends on the control value of the slowly changing Hubble rate. The method allows us to easily obtain theoretical expressions for fluctuations of inhomogeneity in both the cosmic microwave background and distribution of matter. We find the region for admissible values of potential parameters, wherein theoretical predictions are consistent with experimental results within the limits of measurement uncertainties. |
2403.06147 | Ekaterina Pozdeeva | E.O. Pozdeeva, M.A. Skugoreva, A.V. Toporensky, S.Yu. Vernov | New slow-roll approximations for inflation in Einstein-Gauss-Bonnet
gravity | 20 pages, 6 figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose new slow-roll approximations for inflationary models with the
Gauss-Bonnet term. We find more accurate expressions of the standard slow-roll
parameters as functions of the scalar field. To check the accuracy of
approximations considered we construct inflationary models with quadratic and
quartic monomial potentials and the Gauss-Bonnet term. Numerical analysis of
these models indicates that the proposed inflationary scenarios do not
contradict to the observation data. New slow-roll approximations show that the
constructed inflationary models are in agreement with the observation data,
whereas one does not get allowed observational parameters at the same values of
parameters of the constructed models in the standard slow-roll approximation.
| [
{
"created": "Sun, 10 Mar 2024 09:33:39 GMT",
"version": "v1"
}
] | 2024-03-12 | [
[
"Pozdeeva",
"E. O.",
""
],
[
"Skugoreva",
"M. A.",
""
],
[
"Toporensky",
"A. V.",
""
],
[
"Vernov",
"S. Yu.",
""
]
] | We propose new slow-roll approximations for inflationary models with the Gauss-Bonnet term. We find more accurate expressions of the standard slow-roll parameters as functions of the scalar field. To check the accuracy of approximations considered we construct inflationary models with quadratic and quartic monomial potentials and the Gauss-Bonnet term. Numerical analysis of these models indicates that the proposed inflationary scenarios do not contradict to the observation data. New slow-roll approximations show that the constructed inflationary models are in agreement with the observation data, whereas one does not get allowed observational parameters at the same values of parameters of the constructed models in the standard slow-roll approximation. |
1204.4225 | Diego Gonzalez | Diego Gonzalez, Merced Montesinos, Mercedes Velazquez | Gauge and spacetime connections in the Plebanski formulation of complex
general relativity | LaTeX File | null | null | null | gr-qc hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Plebanski formulation of complex general relativity is given in terms of
variables valued in the complexification of the $so(3)$ Lie algebra. Therefore,
it is genuinely a gauge theory that is also diffeomorphism-invariant. For this
reason, the way that the Levi-Civita connection emerges from this formulation
is not direct because both the internal (gauge) and the spacetime connections
are geometrical structures a priori not related, there is not a natural link
between them. Any possible relationship must be put in by hand or must come
from extra hypotheses. In this paper, we analyze the correct relationship
between these connections and show how they are related.
| [
{
"created": "Wed, 18 Apr 2012 23:50:12 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Jan 2013 22:06:45 GMT",
"version": "v2"
}
] | 2013-01-28 | [
[
"Gonzalez",
"Diego",
""
],
[
"Montesinos",
"Merced",
""
],
[
"Velazquez",
"Mercedes",
""
]
] | The Plebanski formulation of complex general relativity is given in terms of variables valued in the complexification of the $so(3)$ Lie algebra. Therefore, it is genuinely a gauge theory that is also diffeomorphism-invariant. For this reason, the way that the Levi-Civita connection emerges from this formulation is not direct because both the internal (gauge) and the spacetime connections are geometrical structures a priori not related, there is not a natural link between them. Any possible relationship must be put in by hand or must come from extra hypotheses. In this paper, we analyze the correct relationship between these connections and show how they are related. |
gr-qc/9209002 | David Garfinkle | David Garfinkle | Results on exact solutions of low energy string theory | 8 pages, plain tex | Phys.Rev. D46 (1992) 4286-4288 | 10.1103/PhysRevD.46.4286 | null | gr-qc | null | A family of solutions to low energy string theory is found. These solutions
represent waves traveling along "extremal black strings"
| [
{
"created": "Sat, 5 Sep 1992 15:11:44 GMT",
"version": "v1"
},
{
"created": "Sat, 31 Oct 1992 20:08:55 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Garfinkle",
"David",
""
]
] | A family of solutions to low energy string theory is found. These solutions represent waves traveling along "extremal black strings" |
1807.07550 | Bjoern S. Schmekel | Bjoern S. Schmekel | Quasi-Local Energy of a Rotating Object Described by Kerr Spacetime | 9 pages, 6 figures | Phys. Rev. D 98, 104051 (2018) | 10.1103/PhysRevD.98.104051 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Brown-York quasi-local energy of a rotating black hole described by the
Kerr metric and enclosed by a fixed-radius surface is calculated by direct
computation. No special assumptions on the angular momentum or the radial
coordinate in Boyer-Lindquist coordinates were placed. The arbitrary reference
term has been set to zero. The result may be relevant for applications in
astrophysics, for modeling elementary particles or for extensions of the
framework of quasi-local quantities. An analytic expression in terms of
incomplete elliptic integrals is given.
| [
{
"created": "Thu, 19 Jul 2018 17:42:05 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Aug 2018 06:52:40 GMT",
"version": "v2"
},
{
"created": "Sat, 17 Nov 2018 21:39:59 GMT",
"version": "v3"
}
] | 2018-12-05 | [
[
"Schmekel",
"Bjoern S.",
""
]
] | The Brown-York quasi-local energy of a rotating black hole described by the Kerr metric and enclosed by a fixed-radius surface is calculated by direct computation. No special assumptions on the angular momentum or the radial coordinate in Boyer-Lindquist coordinates were placed. The arbitrary reference term has been set to zero. The result may be relevant for applications in astrophysics, for modeling elementary particles or for extensions of the framework of quasi-local quantities. An analytic expression in terms of incomplete elliptic integrals is given. |
1810.06211 | Sergey L Cherkas | S.L. Cherkas, V.L. Kalashnikov | The equation of vacuum state and the structure formation in universe | 15 pages | Nonlin. Phenom. Complex Syst. 23 (2020) 332-337 | 10.33581/1561-4085-2020-23-3-332-337 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The vacuum is considered as some fluid emergent from the zero-point
fluctuations of the quantum fields contributing to the vacuum energy density
and pressure. The equation of vacuum state and the speed of vacuum sound-waves
are deduced under the assumption of zero vacuum entropy. The evolution of the
background space-time metric resembles that of the Milne's-like universe. In
the framework of the five-vector theory of gravitation allowing an arbitrary
choice of the energy density reference level, the dynamics of the vacuum,
pressureless matter, and space-time metrics perturbations are traced under this
background. The obtained results show the very early formation of the Universe
structure without the need for dark matter. Thus, a vacuum can be considered as
some of the dark-energy-matter unification.
| [
{
"created": "Mon, 15 Oct 2018 07:56:56 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Jun 2020 14:13:58 GMT",
"version": "v2"
}
] | 2021-08-24 | [
[
"Cherkas",
"S. L.",
""
],
[
"Kalashnikov",
"V. L.",
""
]
] | The vacuum is considered as some fluid emergent from the zero-point fluctuations of the quantum fields contributing to the vacuum energy density and pressure. The equation of vacuum state and the speed of vacuum sound-waves are deduced under the assumption of zero vacuum entropy. The evolution of the background space-time metric resembles that of the Milne's-like universe. In the framework of the five-vector theory of gravitation allowing an arbitrary choice of the energy density reference level, the dynamics of the vacuum, pressureless matter, and space-time metrics perturbations are traced under this background. The obtained results show the very early formation of the Universe structure without the need for dark matter. Thus, a vacuum can be considered as some of the dark-energy-matter unification. |
1703.02143 | Don Marolf | Donald Marolf | The Black Hole information problem: past, present, and future | Key Issues Review for Reports on Progress of Physics, 20 pages, minor
changes | null | 10.1088/1361-6633/aa77cc | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a brief overview of the black hole information problem emphasizing
fundamental issues and recent proposals for its resolution. The focus is on
broad perspective and providing a guide to current literature rather than
presenting full details. We concentrate on resolutions restoring naive
unitarity.
| [
{
"created": "Mon, 6 Mar 2017 22:53:43 GMT",
"version": "v1"
},
{
"created": "Thu, 25 May 2017 22:31:06 GMT",
"version": "v2"
}
] | 2017-08-02 | [
[
"Marolf",
"Donald",
""
]
] | We give a brief overview of the black hole information problem emphasizing fundamental issues and recent proposals for its resolution. The focus is on broad perspective and providing a guide to current literature rather than presenting full details. We concentrate on resolutions restoring naive unitarity. |
1912.07058 | Ka - Wai Chung | Ka-Wai Chung, Tjonnie Guang Feng Li | Probing the Purely Ingoing Nature of the Black-hole Event Horizon | 17 pages, 2 figures | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the most fundamental results of general relativity is that the event
horizon of black hole is purely ingoing. On the other hand,
semiclassical-gravity effects, such as particle creation and the quantization
of black-hole area, suggest that black holes can emit energy. Since a black
hole is characterized by the presence of the event horizon, the emitted energy
must be extracted from the black hole through its horizon. These considerations
provide a motivation to test the validity of the purely ingoing nature of
black-hole horizon. In this paper, we propose a novel test of the purely
ingoing nature of black-hole horizon through gravitational-wave detection. We
study the effects of hypothetical out-going gravitational waves to a perturbed
black hole by supplementing the boundary condition of gravitational waves at
the horizon with a phenomenological outgoing part. We show that this leads to
extra excitation of the usual quasinormal modes of a perturbed black hole and
continuous emission of gravitational waves. These additional signatures enable
us to test the boundary condition(s) of the black-hole event horizon through
gravitational-wave detection. Reanalysing the merger remnant of GW150914, we
constrain the intensity of the outgoing gravitational-horizon flux to be $ <
10^{40} \rm W$, which is roughly $ 10^{-9} $ of peak luminosity of GW150914.
| [
{
"created": "Sun, 15 Dec 2019 15:29:49 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Oct 2020 12:17:38 GMT",
"version": "v2"
}
] | 2020-10-26 | [
[
"Chung",
"Ka-Wai",
""
],
[
"Li",
"Tjonnie Guang Feng",
""
]
] | One of the most fundamental results of general relativity is that the event horizon of black hole is purely ingoing. On the other hand, semiclassical-gravity effects, such as particle creation and the quantization of black-hole area, suggest that black holes can emit energy. Since a black hole is characterized by the presence of the event horizon, the emitted energy must be extracted from the black hole through its horizon. These considerations provide a motivation to test the validity of the purely ingoing nature of black-hole horizon. In this paper, we propose a novel test of the purely ingoing nature of black-hole horizon through gravitational-wave detection. We study the effects of hypothetical out-going gravitational waves to a perturbed black hole by supplementing the boundary condition of gravitational waves at the horizon with a phenomenological outgoing part. We show that this leads to extra excitation of the usual quasinormal modes of a perturbed black hole and continuous emission of gravitational waves. These additional signatures enable us to test the boundary condition(s) of the black-hole event horizon through gravitational-wave detection. Reanalysing the merger remnant of GW150914, we constrain the intensity of the outgoing gravitational-horizon flux to be $ < 10^{40} \rm W$, which is roughly $ 10^{-9} $ of peak luminosity of GW150914. |
0705.2984 | Wei He | Bin Chen, Wei He | Hawking Radiation of Black Rings from Anomalies | 15 pages,Latex; revised version, typos corrected, reference added; | Class.Quant.Grav.25:135011,2008 | 10.1088/0264-9381/25/13/135011 | null | gr-qc hep-th | null | We derive Hawking radiation of 5-dimensional black rings from gauge and
gravitational anomalies using the method proposed by Robinson and Wilczek. We
find as in the black hole case, the problem could reduce to a (1+1) dimensional
field theory and the anomalies result in correct Hawking temperature for
neutral,dipole and charged black rings.
| [
{
"created": "Mon, 21 May 2007 14:02:37 GMT",
"version": "v1"
},
{
"created": "Tue, 29 May 2007 13:19:32 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Chen",
"Bin",
""
],
[
"He",
"Wei",
""
]
] | We derive Hawking radiation of 5-dimensional black rings from gauge and gravitational anomalies using the method proposed by Robinson and Wilczek. We find as in the black hole case, the problem could reduce to a (1+1) dimensional field theory and the anomalies result in correct Hawking temperature for neutral,dipole and charged black rings. |
0802.0233 | Richard Gott III | J. Richard Gott III | Boltzmann Brains--I'd Rather See Than Be One | 18 pages | null | null | null | gr-qc | null | A perceived problem with the standard flat-lambda model is that in the far
future spacetime becomes an exponentially expanding de Sitter space, filled
with Gibbons-Hawking thermal radiation, and given infinite time there will
appear an infinite number of Boltzmann Brains (BB's) per finite co-moving
volume today. If BB's outnumber ordinary observers by an infinite factor, why
am I not one? This Gibbons-Hawking thermal radiation is observer dependent--due
to observer dependent event horizons. Different observers moving relative to
each other will see different photons, and different BB's. I will argue that
the only particles that are real are the particles dredged out of the quantum
vacuum state by particular real material detectors. (In much the same way,
accelerated detectors dredge thermal Unruh radiation out of the Minkowski
vacuum due to their observer dependent event horizons.) Thus, I may see a
thermal BB, but cannot be one. Observer independent BB's can be created by
quantum tunneling events, but the rate at which ordinary observers are being
added to the universe by tunneling events to inflating regions exceeds the rate
for producing BB's by tunneling by an infinite factor. I also argue that BB's
do not really pass the Turing test for intelligent observers. Thus, the
standard flat-lambda model is safe.
| [
{
"created": "Sat, 2 Feb 2008 04:05:05 GMT",
"version": "v1"
}
] | 2008-02-05 | [
[
"Gott",
"J. Richard",
"III"
]
] | A perceived problem with the standard flat-lambda model is that in the far future spacetime becomes an exponentially expanding de Sitter space, filled with Gibbons-Hawking thermal radiation, and given infinite time there will appear an infinite number of Boltzmann Brains (BB's) per finite co-moving volume today. If BB's outnumber ordinary observers by an infinite factor, why am I not one? This Gibbons-Hawking thermal radiation is observer dependent--due to observer dependent event horizons. Different observers moving relative to each other will see different photons, and different BB's. I will argue that the only particles that are real are the particles dredged out of the quantum vacuum state by particular real material detectors. (In much the same way, accelerated detectors dredge thermal Unruh radiation out of the Minkowski vacuum due to their observer dependent event horizons.) Thus, I may see a thermal BB, but cannot be one. Observer independent BB's can be created by quantum tunneling events, but the rate at which ordinary observers are being added to the universe by tunneling events to inflating regions exceeds the rate for producing BB's by tunneling by an infinite factor. I also argue that BB's do not really pass the Turing test for intelligent observers. Thus, the standard flat-lambda model is safe. |
1504.05496 | Mahouton J. Stephane Houndjo Dr | E. H. Baffou, M. J. S. Houndjo, M. E. Rodrigues, A. V. Kpadonou and J.
Tossa | Cosmological Evolution in f(R,T) theory with Collisional Matter | 17 pages and 8 figues | Phys.Rev. D 92 (2015) 8, 084043 | 10.1103/PhysRevD.92.084043 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the evolution of the cosmological parameters, namely, the
deceleration parameter $q(z)$ and the parameter of effective equation of state
in a universe contains, besides the ordinary matter and dark energy, a
self-interacting (collisional matter), in the generalized $f(R,T)$ theory of
gravity, where $R$ and $T$ are the curvature scalar and the trace of the
energy-momentum tensor, respectively. We use the generalized FRW equations the
equation of continuity and obtain a differential equation of second order in
$H(z)$, and solve it numerically for studying the evolution of the cosmological
parameters. Two $f(R,T)$ models are considered and the results with collisional
matter are compared with the ones of the $\Lambda$CDM model, and also with the
model where there exists only non-collisional matter. The curves show that the
models are acceptable because the values found for $w_{eff}$ are consistent
with the observational data.
| [
{
"created": "Fri, 17 Apr 2015 20:24:32 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Nov 2015 09:39:41 GMT",
"version": "v2"
}
] | 2015-11-04 | [
[
"Baffou",
"E. H.",
""
],
[
"Houndjo",
"M. J. S.",
""
],
[
"Rodrigues",
"M. E.",
""
],
[
"Kpadonou",
"A. V.",
""
],
[
"Tossa",
"J.",
""
]
] | We study the evolution of the cosmological parameters, namely, the deceleration parameter $q(z)$ and the parameter of effective equation of state in a universe contains, besides the ordinary matter and dark energy, a self-interacting (collisional matter), in the generalized $f(R,T)$ theory of gravity, where $R$ and $T$ are the curvature scalar and the trace of the energy-momentum tensor, respectively. We use the generalized FRW equations the equation of continuity and obtain a differential equation of second order in $H(z)$, and solve it numerically for studying the evolution of the cosmological parameters. Two $f(R,T)$ models are considered and the results with collisional matter are compared with the ones of the $\Lambda$CDM model, and also with the model where there exists only non-collisional matter. The curves show that the models are acceptable because the values found for $w_{eff}$ are consistent with the observational data. |
1810.11595 | Matthew Fox | Matthew S. Fox | Palatini $f(\mathcal{R}, \mathcal{L}_m, \mathcal{R}_{\mu\nu}T^{\mu\nu})$
gravity and its Born-Infeld semblance | 13 pages, minor revisions, references added | Phys. Rev. D 99, 124027 (2019) | 10.1103/PhysRevD.99.124027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate Palatini $f(\mathcal{R},\mathcal{L}_m,
\mathcal{R}_{\mu\nu}T^{\mu\nu})$ modified theories of gravity wherein the
metric and affine connection are treated as independent dynamical fields and
the gravitational Lagrangian is made a function of the Ricci scalar
$\mathcal{R}$, the matter Lagrangian density $\mathcal{L}_m,$ and a
"matter-curvature scalar" $\mathcal{R}_{\mu\nu}T^{\mu\nu}$. The field equations
and the equations of motion for massive test particles are derived, and we show
that the independent connection can be expressed as the Levi-Civita connection
of an auxiliary, energy-momentum dependent metric, related to the physical
metric by a matrix transformation. Similar to metric $f(\mathcal{R}, T,
\mathcal{R}_{\mu\nu}T^{\mu\nu})$ gravity, the field equations impose the
non-conservation of the energy-momentum tensor, leading to an appearance of an
extra force on massive test particles. We obtain the explicit form of the field
equations for massive test particles in the case of a perfect fluid, and an
expression for the extra force. The nontrivial modifications to scalar fields
and both linear and nonlinear electrodynamics are also considered. Finally, we
detail the conditions under which the present theory is equivalent to the
Eddington-inspired Born-Infeld (EiBI) model.
| [
{
"created": "Sat, 27 Oct 2018 04:40:48 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Nov 2018 00:26:17 GMT",
"version": "v2"
}
] | 2019-06-26 | [
[
"Fox",
"Matthew S.",
""
]
] | We investigate Palatini $f(\mathcal{R},\mathcal{L}_m, \mathcal{R}_{\mu\nu}T^{\mu\nu})$ modified theories of gravity wherein the metric and affine connection are treated as independent dynamical fields and the gravitational Lagrangian is made a function of the Ricci scalar $\mathcal{R}$, the matter Lagrangian density $\mathcal{L}_m,$ and a "matter-curvature scalar" $\mathcal{R}_{\mu\nu}T^{\mu\nu}$. The field equations and the equations of motion for massive test particles are derived, and we show that the independent connection can be expressed as the Levi-Civita connection of an auxiliary, energy-momentum dependent metric, related to the physical metric by a matrix transformation. Similar to metric $f(\mathcal{R}, T, \mathcal{R}_{\mu\nu}T^{\mu\nu})$ gravity, the field equations impose the non-conservation of the energy-momentum tensor, leading to an appearance of an extra force on massive test particles. We obtain the explicit form of the field equations for massive test particles in the case of a perfect fluid, and an expression for the extra force. The nontrivial modifications to scalar fields and both linear and nonlinear electrodynamics are also considered. Finally, we detail the conditions under which the present theory is equivalent to the Eddington-inspired Born-Infeld (EiBI) model. |
gr-qc/9302016 | null | Alexander Vilenkin | Quantum Cosmology | 10 pages, TUTP-92-13 | null | 10.1111/j.1749-6632.1993.tb43903.x | null | gr-qc | null | An elementary review of quantum cosmology. (Talk given at Texas/Pascos 1992
at Berkeley)
| [
{
"created": "Thu, 11 Feb 1993 17:17:00 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Vilenkin",
"Alexander",
""
]
] | An elementary review of quantum cosmology. (Talk given at Texas/Pascos 1992 at Berkeley) |
1108.2133 | Bijan Saha Dr. | Bijan Saha, Hassan Amirhashchi, Anirudh Pradhan | Two-Fluid Scenario for Dark Energy Models in an FRW Universe-Revisited | 10 pages, 4 figures. arXiv admin note: substantial overlap with
arXiv:1011.3940 | Astrophys. Space Sci., 342 (2012) 257 - 267 | 10.1007/s10509-012-1155-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the evolution of the dark energy parameter within the
scope of a spatially homogeneous and isotropic Friedmann-Robertson-Walker (FRW)
model filled with barotropic fluid and dark energy by revisiting the recent
results (Amirhashchi et al. in Chin. Phys. Lett. 28:039801, 2011a). To prevail
the deterministic solution we select the scale factor $a(t) =
\sqrt{t^{n}e^{t}}$ which generates a time-dependent deceleration parameter
(DP), representing a model which generates a transition of the universe from
the early decelerating phase to the recent accelerating phase. We consider the
two cases of an interacting and non-interacting two-fluid (barotropic and dark
energy) scenario and obtained general results. The cosmic jerk parameter in our
derived model is also found to be in good agreement with the recent data of
astrophysical observations under the suitable condition. The physical aspects
of the models and the stability of the corresponding solutions are also
discussed.
| [
{
"created": "Wed, 10 Aug 2011 09:43:49 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Sep 2011 08:42:17 GMT",
"version": "v2"
},
{
"created": "Mon, 2 Jul 2012 16:16:22 GMT",
"version": "v3"
}
] | 2015-05-01 | [
[
"Saha",
"Bijan",
""
],
[
"Amirhashchi",
"Hassan",
""
],
[
"Pradhan",
"Anirudh",
""
]
] | In this paper we study the evolution of the dark energy parameter within the scope of a spatially homogeneous and isotropic Friedmann-Robertson-Walker (FRW) model filled with barotropic fluid and dark energy by revisiting the recent results (Amirhashchi et al. in Chin. Phys. Lett. 28:039801, 2011a). To prevail the deterministic solution we select the scale factor $a(t) = \sqrt{t^{n}e^{t}}$ which generates a time-dependent deceleration parameter (DP), representing a model which generates a transition of the universe from the early decelerating phase to the recent accelerating phase. We consider the two cases of an interacting and non-interacting two-fluid (barotropic and dark energy) scenario and obtained general results. The cosmic jerk parameter in our derived model is also found to be in good agreement with the recent data of astrophysical observations under the suitable condition. The physical aspects of the models and the stability of the corresponding solutions are also discussed. |
2306.03305 | Jose Edgar Madriz Aguilar Dr. | Jos\'e Edgar Madriz Aguilar, A. Bernal, F. Aceves de la Cruz, J. A.
Licea | Gravitational waves during Higgs inflation from complex geometrical
scalar-tensor theory of gravity | 9 pages, 2 figures | null | 10.1016/j.dark.2023.101372 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper we investigate tensor fluctuations of the metric at the end of
a Higgs inflationary period in the context of a recently introduced complex
geometrical scalar-tensor theory of gravity. In our model the Higgs field has a
geometrical origin and the affine connection is determined by the Palatini's
principle. Additionally, we consider an extra contribution to the
tensor-fluctuations equation coming from the vacuum term in the energy momentum
tensor associated to the Higgs field. The Higgs potential is rescaled by the
non-canonicity function of the kinetic term of the field which is modified by
the symmetry group of the background geometry. We obtain a nearly scale
invariant spectrum and a scalar to tensor ratio in agreement with PLANCK 2018
cosmological results.
| [
{
"created": "Mon, 5 Jun 2023 23:13:57 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Jun 2023 21:28:26 GMT",
"version": "v2"
}
] | 2024-04-16 | [
[
"Aguilar",
"José Edgar Madriz",
""
],
[
"Bernal",
"A.",
""
],
[
"de la Cruz",
"F. Aceves",
""
],
[
"Licea",
"J. A.",
""
]
] | In this paper we investigate tensor fluctuations of the metric at the end of a Higgs inflationary period in the context of a recently introduced complex geometrical scalar-tensor theory of gravity. In our model the Higgs field has a geometrical origin and the affine connection is determined by the Palatini's principle. Additionally, we consider an extra contribution to the tensor-fluctuations equation coming from the vacuum term in the energy momentum tensor associated to the Higgs field. The Higgs potential is rescaled by the non-canonicity function of the kinetic term of the field which is modified by the symmetry group of the background geometry. We obtain a nearly scale invariant spectrum and a scalar to tensor ratio in agreement with PLANCK 2018 cosmological results. |
2212.13031 | Kazufumi Takahashi | Antonio De Felice, Shinji Mukohyama, Kazufumi Takahashi | Approximately stealth black hole in higher-order scalar-tensor theories | 10 pages | JCAP 03 (2023) 050 | 10.1088/1475-7516/2023/03/050 | YITP-22-161, IPMU22-0071 | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We investigate a generic quadratic higher-order scalar-tensor theory with a
scordatura term, which is expected to provide a consistent perturbative
description of stealth solutions with a timelike scalar field profile. In the
DHOST subclass, exactly stealth solutions are known to yield perturbations
infinitely strongly coupled and thus cannot be trusted. Beyond DHOST theories
with the scordatura term, such as in ghost condensation and U-DHOST, we show
that stealth configurations cannot be realized as exact solutions but those
theories instead admit approximately stealth solutions where the deviation from
the exactly stealth configuration is controlled by the mass scale $M$ of
derivative expansion. The approximately stealth solution is time-dependent,
which can be interpreted as the black hole mass growth due to the accretion of
the scalar field. From observed astrophysical black holes, we put an upper
bound on $M$ as $\hat{c}_{\rm D1}^{1/2} M\lesssim 2\times 10^{11}$ GeV, where
$\hat{c}_{\rm D1}$ is a dimensionless parameter of order unity that
characterizes the scordatura term. As far as $M$ is sufficiently below the
upper bound, the accretion is slow and the approximately stealth solutions can
be considered as stealth at astrophysical scales for all practical purposes
while perturbations are weakly coupled all the way up to the cutoff $M$ and the
apparent ghost is as heavy as or heavier than $M$.
| [
{
"created": "Mon, 26 Dec 2022 08:04:20 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Mar 2023 21:48:13 GMT",
"version": "v2"
}
] | 2023-03-27 | [
[
"De Felice",
"Antonio",
""
],
[
"Mukohyama",
"Shinji",
""
],
[
"Takahashi",
"Kazufumi",
""
]
] | We investigate a generic quadratic higher-order scalar-tensor theory with a scordatura term, which is expected to provide a consistent perturbative description of stealth solutions with a timelike scalar field profile. In the DHOST subclass, exactly stealth solutions are known to yield perturbations infinitely strongly coupled and thus cannot be trusted. Beyond DHOST theories with the scordatura term, such as in ghost condensation and U-DHOST, we show that stealth configurations cannot be realized as exact solutions but those theories instead admit approximately stealth solutions where the deviation from the exactly stealth configuration is controlled by the mass scale $M$ of derivative expansion. The approximately stealth solution is time-dependent, which can be interpreted as the black hole mass growth due to the accretion of the scalar field. From observed astrophysical black holes, we put an upper bound on $M$ as $\hat{c}_{\rm D1}^{1/2} M\lesssim 2\times 10^{11}$ GeV, where $\hat{c}_{\rm D1}$ is a dimensionless parameter of order unity that characterizes the scordatura term. As far as $M$ is sufficiently below the upper bound, the accretion is slow and the approximately stealth solutions can be considered as stealth at astrophysical scales for all practical purposes while perturbations are weakly coupled all the way up to the cutoff $M$ and the apparent ghost is as heavy as or heavier than $M$. |
gr-qc/9706014 | Tomohiro Harada | Tomohiro Harada | Stability Analysis of Spherically Symmetric Star in Scalar-Tensor
Theories of Gravity | 17 pages, including 6 eps figures. Accepted for publication in
Progress of Theoretical Physics. Grammatical errors corrected | Prog.Theor.Phys.98:359-379,1997 | 10.1143/PTP.98.359 | KUNS-1439 | gr-qc astro-ph | null | A stability analysis of a spherically symmetric star in scalar-tensor
theories of gravity is given in terms of the frequencies of quasi-normal modes.
The scalar-tensor theories have a scalar field which is related to gravitation.
There is an arbitrary function, the so-called coupling function, which
determines the strength of the coupling between the gravitational scalar field
and matter. Instability is induced by the scalar field for some ranges of the
value of the first derivative of the coupling function. This instability leads
to significant discrepancies with the results of binary-pulsar-timing
experiments and hence, by the stability analysis, we can exclude the ranges of
the first derivative of the coupling function in which the instability sets in.
In this article, the constraint on the first derivative of the coupling
function from the stability of relativistic stars is found. Analysis in terms
of the quasi-normal mode frequencies accounts for the parameter dependence of
the wave form of the scalar gravitational waves emitted from the
Oppenheimer-Snyder collapse. The spontaneous scalarization is also discussed.
| [
{
"created": "Thu, 5 Jun 1997 08:50:34 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Jun 1997 02:34:48 GMT",
"version": "v2"
},
{
"created": "Wed, 23 Jul 1997 10:53:31 GMT",
"version": "v3"
}
] | 2010-11-19 | [
[
"Harada",
"Tomohiro",
""
]
] | A stability analysis of a spherically symmetric star in scalar-tensor theories of gravity is given in terms of the frequencies of quasi-normal modes. The scalar-tensor theories have a scalar field which is related to gravitation. There is an arbitrary function, the so-called coupling function, which determines the strength of the coupling between the gravitational scalar field and matter. Instability is induced by the scalar field for some ranges of the value of the first derivative of the coupling function. This instability leads to significant discrepancies with the results of binary-pulsar-timing experiments and hence, by the stability analysis, we can exclude the ranges of the first derivative of the coupling function in which the instability sets in. In this article, the constraint on the first derivative of the coupling function from the stability of relativistic stars is found. Analysis in terms of the quasi-normal mode frequencies accounts for the parameter dependence of the wave form of the scalar gravitational waves emitted from the Oppenheimer-Snyder collapse. The spontaneous scalarization is also discussed. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.