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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0805.3329 | Kayll Lake | C\'edric Grenon, Pascal J. Elahi and Kayll Lake | Transforming the Einstein static Universe into physically acceptable
static fluid spheres II: A two - fold infinity of exact solutions | 6 pages, 6 figures, revtex4,improved figures. To appear in Phys. Rev.
D | Phys.Rev.D78:044028,2008 | 10.1103/PhysRevD.78.044028 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following a solution generating technique introduced recently by one of us,
we transform the Einstein static Universe into a two - fold infinity class of
physically acceptable exact perfect fluid solutions of Einstein's equations.
Whereas the entire class of solutions can be considered as generalizations of
the familiar Tolman IV solution, no member of the class can be written
explicitly in isotropic coordinates. Further, except for a set of measure zero,
no member of the class can be written explicitly in curvature coordinates
either.
| [
{
"created": "Wed, 21 May 2008 18:41:49 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Jul 2008 21:13:10 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Grenon",
"Cédric",
""
],
[
"Elahi",
"Pascal J.",
""
],
[
"Lake",
"Kayll",
""
]
] | Following a solution generating technique introduced recently by one of us, we transform the Einstein static Universe into a two - fold infinity class of physically acceptable exact perfect fluid solutions of Einstein's equations. Whereas the entire class of solutions can be considered as generalizations of the familiar Tolman IV solution, no member of the class can be written explicitly in isotropic coordinates. Further, except for a set of measure zero, no member of the class can be written explicitly in curvature coordinates either. |
0707.0347 | Metin Gurses | Metin Gurses | Gauss-Bonnet Gravity with Scalar Field in Four Dimensions | Latex file, 7 pages | null | 10.1007/s10714-007-0579-z | null | gr-qc hep-th | null | We give all exact solutions of the Einstein-Gauss-Bonnet Field Equations
coupled with a scalar field in four dimensions under certain assumptions.
| [
{
"created": "Tue, 3 Jul 2007 07:20:31 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Jul 2007 18:22:34 GMT",
"version": "v2"
},
{
"created": "Fri, 13 Jul 2007 10:32:59 GMT",
"version": "v3"
},
{
"created": "Thu, 3 Jan 2008 14:00:31 GMT",
"version": "v4"
}
] | 2015-05-13 | [
[
"Gurses",
"Metin",
""
]
] | We give all exact solutions of the Einstein-Gauss-Bonnet Field Equations coupled with a scalar field in four dimensions under certain assumptions. |
gr-qc/0507072 | Bernard Linet | Bernard Linet | Black holes in which the electrostatic or scalar equation is solvable in
closed form | 20 pages, no figure | Gen.Rel.Grav.37:2145-2163,2005 | 10.1007/s10714-005-0200-2 | null | gr-qc | null | We show that the method used in the Schwarzschild black hole for finding the
elementary solution of the electrostatic equation in closed form cannot extend
in higher dimensions. By contrast, we prove the existence of static,
spherically symmetric geometries with a non-degenerated horizon in which the
static scalar equation can be solved in closed form. We give the explicit
results in 6 dimensions. We determine moreover the expressions of the
electrostatic potential and of the static scalar field for a point source in
the extremal Reissner-Nordstrom black holes in higher dimensions.
| [
{
"created": "Mon, 18 Jul 2005 08:26:22 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Linet",
"Bernard",
""
]
] | We show that the method used in the Schwarzschild black hole for finding the elementary solution of the electrostatic equation in closed form cannot extend in higher dimensions. By contrast, we prove the existence of static, spherically symmetric geometries with a non-degenerated horizon in which the static scalar equation can be solved in closed form. We give the explicit results in 6 dimensions. We determine moreover the expressions of the electrostatic potential and of the static scalar field for a point source in the extremal Reissner-Nordstrom black holes in higher dimensions. |
1407.2009 | Saskia Grunau | Saskia Grunau | Charged dilatonic black rings and black saturns and their thermodynamics | Added references; added calculation of the indivudial charges of the
ring and the sphere part of the dilatonic black saturn | Phys. Rev. D 90, 064022 (2014) | 10.1103/PhysRevD.90.064022 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article charged black rings and black saturns are constructed in
Einstein-Maxwell-dilaton theory in five dimensions. The neutral black ring and
black saturn solutions are embedded in six dimensions and boosted with respect
to the time coordinate and the added sixth dimension. Then the charged
solutions are obtained by a Kaluza-Klein reduction. The influence of the charge
is studied by analysing the physical properties and the phase diagram. The
different dilatonic solutions are compared and their thermodynamic stability is
considered.
| [
{
"created": "Tue, 8 Jul 2014 09:32:58 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Sep 2014 10:51:08 GMT",
"version": "v2"
}
] | 2014-09-16 | [
[
"Grunau",
"Saskia",
""
]
] | In this article charged black rings and black saturns are constructed in Einstein-Maxwell-dilaton theory in five dimensions. The neutral black ring and black saturn solutions are embedded in six dimensions and boosted with respect to the time coordinate and the added sixth dimension. Then the charged solutions are obtained by a Kaluza-Klein reduction. The influence of the charge is studied by analysing the physical properties and the phase diagram. The different dilatonic solutions are compared and their thermodynamic stability is considered. |
1312.5247 | Lior M. Burko | Lior M. Burko and Gaurav Khanna | Mode coupling mechanism for late-time Kerr tails | 22 pages, 12 figures, 4 tables | Phys. Rev. D 89, 044037 (2014) | 10.1103/PhysRevD.89.044037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the decay rate for scalar fields in Kerr spacetime. We consider
pure initial (azimuthal) multipoles $\ell'$ with respect to the class which
includes Boyer-Lindquist coordinates, and focus attention on the decay rate of
the multipole $\ell$. We use an iterative method proposed by Gleiser, Price,
and Pullin, and identify the mode coupling mechanism through the iterations in
powers of the square of the Kerr black hole's specific angular momentum that
gives rise to a decay rate formula recently proposed by Zengino\u{g}lu, Khanna,
and Burko. Modes $\ell$ may be excited through different channels, each leading
to its own decay rate. The asymptotic decay rate of the mode $\ell$ is the
slowest of the decay rate of the various channels. In some cases, more than one
channel leads to the same decay rate, and then the amplitude of the mode is the
sum of the amplitudes of the partial fields generated by the individual
channels. We also show that one may identify the asymptotically-dominant
channel of mode excitations, and obtain approximate results for the mode of
interest by studying the dominant channel. The results of the dominant channel
approximation approach the full-mode results at late times, and their
difference approaches zero quadratically in inverse time.
| [
{
"created": "Wed, 18 Dec 2013 18:00:30 GMT",
"version": "v1"
}
] | 2014-04-15 | [
[
"Burko",
"Lior M.",
""
],
[
"Khanna",
"Gaurav",
""
]
] | We consider the decay rate for scalar fields in Kerr spacetime. We consider pure initial (azimuthal) multipoles $\ell'$ with respect to the class which includes Boyer-Lindquist coordinates, and focus attention on the decay rate of the multipole $\ell$. We use an iterative method proposed by Gleiser, Price, and Pullin, and identify the mode coupling mechanism through the iterations in powers of the square of the Kerr black hole's specific angular momentum that gives rise to a decay rate formula recently proposed by Zengino\u{g}lu, Khanna, and Burko. Modes $\ell$ may be excited through different channels, each leading to its own decay rate. The asymptotic decay rate of the mode $\ell$ is the slowest of the decay rate of the various channels. In some cases, more than one channel leads to the same decay rate, and then the amplitude of the mode is the sum of the amplitudes of the partial fields generated by the individual channels. We also show that one may identify the asymptotically-dominant channel of mode excitations, and obtain approximate results for the mode of interest by studying the dominant channel. The results of the dominant channel approximation approach the full-mode results at late times, and their difference approaches zero quadratically in inverse time. |
2207.13732 | Anthony Guillen | Ignatios Antoniadis, Anthony Guillen and Kyriakos Tamvakis | Late time acceleration in Palatini gravity | 25 pages, 3 figures, some paragraphs added | null | 10.1007/JHEP11(2022)144 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the effect of the quadratic correction $\alpha R^2$ and
non-minimal coupling $\xi \phi^2 R$ on a quintessence model with an exponential
potential $V(\phi) = M^4\exp(-\lambda\phi)$ in the Palatini formulation of
gravity. We use dynamical system techniques to analyze the attractor structure
of the model and uncover the possible trajectories of the system. We find that
the quadratic correction cannot play a role in the late time dynamics, except
for unacceptably large values of the parameter $\alpha$; although it can play a
role at early times. We find viable evolutions, from a matter-dominated phase
to an accelerated expansion phase, with the dynamics driven by the non-minimal
coupling. These evolutions correspond to trajectories where the field ends up
frozen, thus acting as a cosmological constant.
| [
{
"created": "Wed, 27 Jul 2022 18:15:19 GMT",
"version": "v1"
},
{
"created": "Sat, 13 Aug 2022 20:27:29 GMT",
"version": "v2"
},
{
"created": "Mon, 7 Nov 2022 07:48:21 GMT",
"version": "v3"
}
] | 2022-12-14 | [
[
"Antoniadis",
"Ignatios",
""
],
[
"Guillen",
"Anthony",
""
],
[
"Tamvakis",
"Kyriakos",
""
]
] | We investigate the effect of the quadratic correction $\alpha R^2$ and non-minimal coupling $\xi \phi^2 R$ on a quintessence model with an exponential potential $V(\phi) = M^4\exp(-\lambda\phi)$ in the Palatini formulation of gravity. We use dynamical system techniques to analyze the attractor structure of the model and uncover the possible trajectories of the system. We find that the quadratic correction cannot play a role in the late time dynamics, except for unacceptably large values of the parameter $\alpha$; although it can play a role at early times. We find viable evolutions, from a matter-dominated phase to an accelerated expansion phase, with the dynamics driven by the non-minimal coupling. These evolutions correspond to trajectories where the field ends up frozen, thus acting as a cosmological constant. |
1410.0800 | Branislav Cvetkovi\'c | M. Blagojevi\'c, B. Cvetkovi\'c | Siklos waves with torsion in 3D | LaTeX, 17 pages; v2 minor changes, 4 references added | JHEP11(2014)141 | 10.1007/JHEP11(2014)141 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Starting from the Siklos waves in general relativity with a cosmological
constant, interpreted as gravitational waves on the anti-de Sitter background,
a new class of exact torsion waves is constructed in the framework of
three-dimensional gravity with propagating torsion. In the asymptotic limit,
the geometry of torsion waves takes the anti-de Sitter form. In the sector with
massless torsion modes, we found a set of asymptotic conditions that leads to
the conformal asymptotic symmetry.
| [
{
"created": "Fri, 3 Oct 2014 09:58:34 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Dec 2014 12:28:24 GMT",
"version": "v2"
}
] | 2014-12-08 | [
[
"Blagojević",
"M.",
""
],
[
"Cvetković",
"B.",
""
]
] | Starting from the Siklos waves in general relativity with a cosmological constant, interpreted as gravitational waves on the anti-de Sitter background, a new class of exact torsion waves is constructed in the framework of three-dimensional gravity with propagating torsion. In the asymptotic limit, the geometry of torsion waves takes the anti-de Sitter form. In the sector with massless torsion modes, we found a set of asymptotic conditions that leads to the conformal asymptotic symmetry. |
0904.0953 | Everton Murilo Carvalho Abreu | E. M. C. Abreu, L. P. G. De Assis, C. M. L. dos Reis | Analytical considerations about the cosmological constant and dark
energy | 15 pages, 5 figures. Revtex4 | Int.J.Mod.Phys.A24:5427-5444,2009 | 10.1142/S0217751X09046254 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The accelerated expansion of the universe has now been confirmed by several
independent observations including those of high redshift type Ia supernovae,
and the cosmic microwave background combined with the large scale structure of
the Universe. In this work we introduce families of analytical solutions for
the scale factor different from the current literature. The knowledge of the
scale factor behavior might shed some light on these questions since the entire
evolution of a homogeneous isotropic Universe is contained in the scale factor.
We use different parameters for these solutions and with these parameters we
stablish a connection with the equation of state for different dark energy
scenarios.
| [
{
"created": "Mon, 6 Apr 2009 15:20:10 GMT",
"version": "v1"
}
] | 2009-11-30 | [
[
"Abreu",
"E. M. C.",
""
],
[
"De Assis",
"L. P. G.",
""
],
[
"Reis",
"C. M. L. dos",
""
]
] | The accelerated expansion of the universe has now been confirmed by several independent observations including those of high redshift type Ia supernovae, and the cosmic microwave background combined with the large scale structure of the Universe. In this work we introduce families of analytical solutions for the scale factor different from the current literature. The knowledge of the scale factor behavior might shed some light on these questions since the entire evolution of a homogeneous isotropic Universe is contained in the scale factor. We use different parameters for these solutions and with these parameters we stablish a connection with the equation of state for different dark energy scenarios. |
1502.02982 | Ujjal Debnath | Ujjal Debnath | Accretions of Dark Matter and Dark Energy onto ($n+2$)-dimensional
Schwarzschild Black Hole and Morris-Thorne Wormhole | 11 pages, 10 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have studied accretion of the dark matter and dark energy onto of
$(n+2)$-dimensional Schwarzschild black hole and Morris-Thorne wormhole. The
mass and the rate of change of mass for $(n+2)$-dimensional Schwarzschild black
hole and Morris-Thorne wormhole have been found. We have assumed some
candidates of dark energy like holographic dark energy, new agegraphic dark
energy, quintessence, tachyon, DBI-essence, etc. The black hole mass and the
wormhole mass have been calculated in term of redshift when dark matter and
above types of dark energies accrete onto them separately. We have shown that
the black hole mass increases and wormhole mass decreases for holographic dark
energy, new agegraphic dark energy, quintessence, tachyon accretion and the
slope of increasing/decreasing of mass sensitively depends on the dimension.
But for DBI-essence accretion, the black hole mass first increases and then
decreases and the wormhole mass first decreases and then increases and the
slope of increasing/decreasing of mass not sensitively depends on the
dimension.
| [
{
"created": "Sun, 8 Feb 2015 18:21:45 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Mar 2015 09:52:58 GMT",
"version": "v2"
}
] | 2015-03-09 | [
[
"Debnath",
"Ujjal",
""
]
] | We have studied accretion of the dark matter and dark energy onto of $(n+2)$-dimensional Schwarzschild black hole and Morris-Thorne wormhole. The mass and the rate of change of mass for $(n+2)$-dimensional Schwarzschild black hole and Morris-Thorne wormhole have been found. We have assumed some candidates of dark energy like holographic dark energy, new agegraphic dark energy, quintessence, tachyon, DBI-essence, etc. The black hole mass and the wormhole mass have been calculated in term of redshift when dark matter and above types of dark energies accrete onto them separately. We have shown that the black hole mass increases and wormhole mass decreases for holographic dark energy, new agegraphic dark energy, quintessence, tachyon accretion and the slope of increasing/decreasing of mass sensitively depends on the dimension. But for DBI-essence accretion, the black hole mass first increases and then decreases and the wormhole mass first decreases and then increases and the slope of increasing/decreasing of mass not sensitively depends on the dimension. |
1801.05692 | Mohammad Ghanaatian | M. Ghanaatian, F. Naeimipour, A. Bazrafshan, M. Abkar | Reissner-Nordstrom Black Holes in Quartic Quasi-Topological Gravity
Theory | 14 Pages and 28 figures | Phys. Rev. D 97, 104054 (2018) | 10.1103/PhysRevD.97.104054 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we construct the exact solutions of Reissner-Nordstrom black
holes in the presence of quartic quasi-topological gravity. we obtain the
thermodynamics and conserved quantities of the solutions and check the first
law of thermodynamics. In studying the physical properties of the solutions, we
consider asymptotically Ads, dS and flat solutions of Reissner-Nordstrom black
hole in quartic quasi-topological gravity and compare them with Einstein and
third-order quasi-topological gravities. we also investigate the thermal
stability of the solutions that we show the thermal stability are just for AdS
solutions not for dS and flat ones.
| [
{
"created": "Sun, 14 Jan 2018 23:13:40 GMT",
"version": "v1"
}
] | 2018-06-06 | [
[
"Ghanaatian",
"M.",
""
],
[
"Naeimipour",
"F.",
""
],
[
"Bazrafshan",
"A.",
""
],
[
"Abkar",
"M.",
""
]
] | In this paper, we construct the exact solutions of Reissner-Nordstrom black holes in the presence of quartic quasi-topological gravity. we obtain the thermodynamics and conserved quantities of the solutions and check the first law of thermodynamics. In studying the physical properties of the solutions, we consider asymptotically Ads, dS and flat solutions of Reissner-Nordstrom black hole in quartic quasi-topological gravity and compare them with Einstein and third-order quasi-topological gravities. we also investigate the thermal stability of the solutions that we show the thermal stability are just for AdS solutions not for dS and flat ones. |
1804.05949 | Eric Ling | Gregory J. Galloway and Eric Ling | Existence of CMC Cauchy surfaces from a spacetime curvature condition | 7 pages; (v2) proof of Proposition 3 (and associated claims)
corrected, references and several comments added; (v3) to appear in GRG | null | 10.1007/s10714-018-2428-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note we present a result establishing the existence of a compact CMC
Cauchy surface from a curvature condition related to the strong energy
condition.
| [
{
"created": "Mon, 16 Apr 2018 21:37:52 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jun 2018 03:11:54 GMT",
"version": "v2"
},
{
"created": "Thu, 2 Aug 2018 21:44:53 GMT",
"version": "v3"
}
] | 2018-08-22 | [
[
"Galloway",
"Gregory J.",
""
],
[
"Ling",
"Eric",
""
]
] | In this note we present a result establishing the existence of a compact CMC Cauchy surface from a curvature condition related to the strong energy condition. |
gr-qc/0609123 | Achim Kempf | Achim Kempf, Larissa Lorenz | Exact solution of inflationary model with minimum length | 19 pages, LaTeX | Phys.Rev.D74:103517,2006 | 10.1103/PhysRevD.74.103517 | null | gr-qc | null | Within the inflationary scenario, Planck scale physics should have affected
the comoving modes' initial conditions and early evolution, thereby potentially
affecting the inflationary predictions for the cosmic microwave background
(CMB). This issue has been studied extensively on the basis of various models
for how quantum field theory (QFT) is modified and finally breaks down towards
the Planck scale. In one model, in particular, an ultraviolet cutoff was
implemented into QFT through generalized uncertainty relations which have been
motivated from general quantum gravity arguments and from string theory. Here,
we improve upon prior numerical and semi-analytical results by presenting the
exact mode solutions for both de Sitter and power-law inflation in this model.
This provides an explicit map from the modes' initial conditions, which are
presumably set by quantum gravity, to the modes' amplitudes at horizon crossing
and thus to the inflationary predictions for the CMB. The solutions' particular
behaviour close to the cutoff scale suggests unexpected possibilities for how
the degrees of freedom of QFT emerge from the Planck scale.
| [
{
"created": "Wed, 27 Sep 2006 06:50:13 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kempf",
"Achim",
""
],
[
"Lorenz",
"Larissa",
""
]
] | Within the inflationary scenario, Planck scale physics should have affected the comoving modes' initial conditions and early evolution, thereby potentially affecting the inflationary predictions for the cosmic microwave background (CMB). This issue has been studied extensively on the basis of various models for how quantum field theory (QFT) is modified and finally breaks down towards the Planck scale. In one model, in particular, an ultraviolet cutoff was implemented into QFT through generalized uncertainty relations which have been motivated from general quantum gravity arguments and from string theory. Here, we improve upon prior numerical and semi-analytical results by presenting the exact mode solutions for both de Sitter and power-law inflation in this model. This provides an explicit map from the modes' initial conditions, which are presumably set by quantum gravity, to the modes' amplitudes at horizon crossing and thus to the inflationary predictions for the CMB. The solutions' particular behaviour close to the cutoff scale suggests unexpected possibilities for how the degrees of freedom of QFT emerge from the Planck scale. |
1506.04081 | Moritz Reintjes | Moritz Reintjes and Blake Temple | No Regularity Singularities Exist at Points of General Relativistic
Shock Wave Interaction between Shocks from Different Characteristic Families | 21 pages. In this paper we summarise the results and proofs in
arXiv:1409.5060. The result here corrects the wrong conclusion in
arXiv:1105.0798 and arXiv:1112.1803 | Proc. R. Soc. A 471 : 20140834, 2015 | 10.1098/rspa.2014.0834 | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a constructive proof that coordinate transformations exist which
raise the regularity of the gravitational metric tensor from $C^{0,1}$ to
$C^{1,1}$ in a neighborhood of points of shock wave collision in General
Relativity. The proof applies to collisions between shock waves coming from
different characteristic families, in spherically symmetric spacetimes. Our
result here implies that spacetime is locally inertial and corrects an error in
our earlier RSPA-publication, which led us to the false conclusion that such
coordinate transformations, which smooth the metric to $C^{1,1}$, cannot exist.
Thus, our result implies that regularity singularities, (a type of mild
singularity introduced in our RSPA-paper), do not exist at points of
interacting shock waves from different families in spherically symmetric
spacetimes. Our result generalizes Israel's celebrated 1966 paper to the case
of such shock wave interactions but our proof strategy differs fundamentally
from that used by Israel and is an extension of the strategy outlined in our
original RSPA-publication. Whether regularity singularities exist in more
complicated shock wave solutions of the Einstein Euler equations remains open.
| [
{
"created": "Fri, 12 Jun 2015 17:39:46 GMT",
"version": "v1"
}
] | 2015-06-15 | [
[
"Reintjes",
"Moritz",
""
],
[
"Temple",
"Blake",
""
]
] | We give a constructive proof that coordinate transformations exist which raise the regularity of the gravitational metric tensor from $C^{0,1}$ to $C^{1,1}$ in a neighborhood of points of shock wave collision in General Relativity. The proof applies to collisions between shock waves coming from different characteristic families, in spherically symmetric spacetimes. Our result here implies that spacetime is locally inertial and corrects an error in our earlier RSPA-publication, which led us to the false conclusion that such coordinate transformations, which smooth the metric to $C^{1,1}$, cannot exist. Thus, our result implies that regularity singularities, (a type of mild singularity introduced in our RSPA-paper), do not exist at points of interacting shock waves from different families in spherically symmetric spacetimes. Our result generalizes Israel's celebrated 1966 paper to the case of such shock wave interactions but our proof strategy differs fundamentally from that used by Israel and is an extension of the strategy outlined in our original RSPA-publication. Whether regularity singularities exist in more complicated shock wave solutions of the Einstein Euler equations remains open. |
gr-qc/0610152 | Alexander Alexandrov | A. N. Alexandrov, I. B. Vavilova, V. I. Zhdanov | Non-metric Generalizations of Relativistic Gravitational Theory and
Observational Data Interpretation | Reported at 35th COSPAR Scientific Assembly, H0.1-1 "Tests of General
Relativity" (Paris, France, 2004) | null | null | null | gr-qc | null | We discuss theoretical formalisms concerning with experimental verification
of General Relativity (GR). Non-metric generalizations of GR are considered and
a system of postulates is formulated for metric-affine and Finsler
gravitational theories. We consider local observer reference frames to be a
proper tool for comparing predictions of alternative theories with each other
and with the observational data. Integral formula for geodesic deviation due to
the deformation of connection is obtained. This formula can be applied for
calculations of such effects as the bending of light and time-delay in presence
of non-metrical effects.
| [
{
"created": "Mon, 30 Oct 2006 19:39:47 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Alexandrov",
"A. N.",
""
],
[
"Vavilova",
"I. B.",
""
],
[
"Zhdanov",
"V. I.",
""
]
] | We discuss theoretical formalisms concerning with experimental verification of General Relativity (GR). Non-metric generalizations of GR are considered and a system of postulates is formulated for metric-affine and Finsler gravitational theories. We consider local observer reference frames to be a proper tool for comparing predictions of alternative theories with each other and with the observational data. Integral formula for geodesic deviation due to the deformation of connection is obtained. This formula can be applied for calculations of such effects as the bending of light and time-delay in presence of non-metrical effects. |
1108.4731 | Karim Thebault Mr. | Karim P. Y. Thebault | Quantisation, Representation and Reduction; How Should We Interpret the
Quantum Hamiltonian Constraints of Canonical Gravity? | 18 Pages | Symmetry 2011, 3, 134-154 | 10.3390/sym3020134 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hamiltonian constraints feature in the canonical formulation of general
relativity. Unlike typical constraints they cannot be associated with a
reduction procedure leading to a non-trivial reduced phase space and this means
the physical interpretation of their quantum analogues is ambiguous. In
particular, can we assume that `quantisation commutes with reduction' and treat
the promotion of these constraints to operators annihilating the wave function,
according to a Dirac type procedure, as leading to a Hilbert space equivalent
to that reached by quantisation of the problematic reduced space? If not, how
should we interpret Hamiltonian constraints quantum mechanically? And on what
basis do we assert that quantisation and reduction commute anyway? These
questions will be refined and explored in the context of modern approaches to
the quantisation of canonical general relativity.
| [
{
"created": "Wed, 24 Aug 2011 01:19:37 GMT",
"version": "v1"
}
] | 2011-08-25 | [
[
"Thebault",
"Karim P. Y.",
""
]
] | Hamiltonian constraints feature in the canonical formulation of general relativity. Unlike typical constraints they cannot be associated with a reduction procedure leading to a non-trivial reduced phase space and this means the physical interpretation of their quantum analogues is ambiguous. In particular, can we assume that `quantisation commutes with reduction' and treat the promotion of these constraints to operators annihilating the wave function, according to a Dirac type procedure, as leading to a Hilbert space equivalent to that reached by quantisation of the problematic reduced space? If not, how should we interpret Hamiltonian constraints quantum mechanically? And on what basis do we assert that quantisation and reduction commute anyway? These questions will be refined and explored in the context of modern approaches to the quantisation of canonical general relativity. |
gr-qc/9311012 | null | Daniel Kennefick and Niall \'O Murchadha | Weakly decaying asymptotically flat static and stationary solutions to
the Einstein equations | 14 pages, plain Tex | Class.Quant.Grav.12:149-158,1995 | 10.1088/0264-9381/12/1/013 | null | gr-qc | null | The assumption that a solution to the Einstein equations is static (or
stationary) very strongly constrains the asymptotic behaviour of the metric. It
is shown that one need only impose very weak differentiability and decay
conditions {\it a priori} on the metric for the field equations to force the
metric to be analytic near infinity and to have the standard Schwarzschildian
falloff.
| [
{
"created": "Mon, 8 Nov 1993 12:17:57 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Kennefick",
"Daniel",
""
],
[
"Murchadha",
"Niall Ó",
""
]
] | The assumption that a solution to the Einstein equations is static (or stationary) very strongly constrains the asymptotic behaviour of the metric. It is shown that one need only impose very weak differentiability and decay conditions {\it a priori} on the metric for the field equations to force the metric to be analytic near infinity and to have the standard Schwarzschildian falloff. |
1805.07080 | Donato Bini | Donato Bini, Carmen Chicone, Bahram Mashhoon, Kjell Rosquist | Spinning Particles in Twisted Gravitational Wave Spacetimes | 27 pages, RevTex macros, v2: typos corrected, reference added, v3:
slightly expanded version, v4: new Appendix A, references added; v5:
reference added, matches published version; v6: typos corrected in the
sentence following Eq. (C7) | Phys. Rev. D 98, 024043 (2018) | 10.1103/PhysRevD.98.024043 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Twisted gravitational waves (TGWs) are nonplanar waves with twisted rays that
move along a fixed direction in space. We study further the physical
characteristics of a recent class of Ricci-flat solutions of general relativity
representing TGWs with wave fronts that have negative Gaussian curvature. In
particular, we investigate the influence of TGWs on the polarization of test
electromagnetic waves and on the motion of classical spinning test particles in
such radiation fields. To distinguish the polarization effects of twisted waves
from plane waves, we examine the theoretical possibility of existence of
spin-twist coupling and show that this interaction is generally consistent with
our results.
| [
{
"created": "Fri, 18 May 2018 07:42:01 GMT",
"version": "v1"
},
{
"created": "Tue, 29 May 2018 09:21:43 GMT",
"version": "v2"
},
{
"created": "Sun, 3 Jun 2018 16:00:26 GMT",
"version": "v3"
},
{
"created": "Fri, 6 Jul 2018 07:04:48 GMT",
"version": "v4"
},
{
"cre... | 2021-01-19 | [
[
"Bini",
"Donato",
""
],
[
"Chicone",
"Carmen",
""
],
[
"Mashhoon",
"Bahram",
""
],
[
"Rosquist",
"Kjell",
""
]
] | Twisted gravitational waves (TGWs) are nonplanar waves with twisted rays that move along a fixed direction in space. We study further the physical characteristics of a recent class of Ricci-flat solutions of general relativity representing TGWs with wave fronts that have negative Gaussian curvature. In particular, we investigate the influence of TGWs on the polarization of test electromagnetic waves and on the motion of classical spinning test particles in such radiation fields. To distinguish the polarization effects of twisted waves from plane waves, we examine the theoretical possibility of existence of spin-twist coupling and show that this interaction is generally consistent with our results. |
1711.02670 | Friedrich Sch\"oller | Friedrich Sch\"oller | Distinct Minkowski Spaces from BMS Supertranslations | 4 pages, 1 figure, matches published version | Phys. Rev. D 97, 046009 (2018) | 10.1103/PhysRevD.97.046009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work provides a smooth and everywhere well-defined extension of
Bondi-Metzner-Sachs (BMS) supertranslations into the bulk of Minkowski space.
The supertranslations lead to physically distinct spacetimes, all isometric to
Minkowski space. This construction is in contrast to the often used, non-smooth
BMS transformations that appear in a gauge-fixed description of the theory.
| [
{
"created": "Tue, 7 Nov 2017 19:00:01 GMT",
"version": "v1"
},
{
"created": "Sun, 18 Feb 2018 16:12:47 GMT",
"version": "v2"
}
] | 2018-02-20 | [
[
"Schöller",
"Friedrich",
""
]
] | This work provides a smooth and everywhere well-defined extension of Bondi-Metzner-Sachs (BMS) supertranslations into the bulk of Minkowski space. The supertranslations lead to physically distinct spacetimes, all isometric to Minkowski space. This construction is in contrast to the often used, non-smooth BMS transformations that appear in a gauge-fixed description of the theory. |
1812.04383 | Joan Josep Ferrando | Bartolom\'e Coll, Joan Josep Ferrando and Juan Antonio S\'aez | On the relativistic compressibility conditions | 21 pages, no figures, submitted to General Relativity and Gravitation | Phys. Rev. D 101, 064058 (2020) | 10.1103/PhysRevD.101.064058 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The constraints imposed by the relativistic compressibility hypothesis on the
square of the speed of sound in a medium are obtained. This result allows to
obtain purely hydrodynamic conditions for the physical reality of a perfect
energy tensor representing the energetic evolution of a perfect fluid in local
thermal equilibrium. The results are applied to the paradigmatic case of the
generic ideal gases. Then the physical reality of the ideal gas Stephani models
is analyzed and the Rainich-like theory for ideal gas solutions is built.
| [
{
"created": "Tue, 11 Dec 2018 13:21:11 GMT",
"version": "v1"
}
] | 2020-04-01 | [
[
"Coll",
"Bartolomé",
""
],
[
"Ferrando",
"Joan Josep",
""
],
[
"Sáez",
"Juan Antonio",
""
]
] | The constraints imposed by the relativistic compressibility hypothesis on the square of the speed of sound in a medium are obtained. This result allows to obtain purely hydrodynamic conditions for the physical reality of a perfect energy tensor representing the energetic evolution of a perfect fluid in local thermal equilibrium. The results are applied to the paradigmatic case of the generic ideal gases. Then the physical reality of the ideal gas Stephani models is analyzed and the Rainich-like theory for ideal gas solutions is built. |
1012.3353 | William Nelson | William Nelson | Restricting Fourth Order Gravity via Cosmology | To appear in PRD | Phys.Rev.D82:124044,2010 | 10.1103/PhysRevD.82.124044 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmology of general fourth order corrections to Einstein gravity is
considered, both for a homogeneous and isotropic background and for general
tensor perturbations. It is explicitly shown how the standard cosmological
history can be (approximately) reproduced and under what condition the
evolution of the tensor modes remain (approximately) unchanged. Requiring that
the deviations from General Relativity are small during inflation sharpens the
current constraints on such corrections terms by some thirty orders of
magnitude. Taking a more conservative approach and requiring only that
cosmology be approximately that of GR during Big Bang Nucleosynthesis, the
constraints are improved by 4 - 6 orders of magnitude.
| [
{
"created": "Wed, 15 Dec 2010 15:03:45 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Dec 2010 16:47:16 GMT",
"version": "v2"
}
] | 2011-03-07 | [
[
"Nelson",
"William",
""
]
] | The cosmology of general fourth order corrections to Einstein gravity is considered, both for a homogeneous and isotropic background and for general tensor perturbations. It is explicitly shown how the standard cosmological history can be (approximately) reproduced and under what condition the evolution of the tensor modes remain (approximately) unchanged. Requiring that the deviations from General Relativity are small during inflation sharpens the current constraints on such corrections terms by some thirty orders of magnitude. Taking a more conservative approach and requiring only that cosmology be approximately that of GR during Big Bang Nucleosynthesis, the constraints are improved by 4 - 6 orders of magnitude. |
1407.5440 | Oleg Zaslavskii | O. B. Zaslavskii | Kinematics of ultra-high energy particle collisions near black holes in
the magnetic field | 8 pages. Final version | Mod. Phys. Lett. A 30, 1550027 (2015) | 10.1142/S0217732315500273 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There are different versions of collisions of two particles near black holes
with unbound energy $E_{c.m.}$ in the centre of mass frame. The so-called BSW
effect arises when a slow fine-tuned "critical" particle hits a rapid "usual"
one. We discuss a scenario of collision in the strong magnetic field for which
explanation tuns out to be different. Both particles are rapid but the nonzero
angle between their velocities (which are both close to $c$, the speed of
light) results in a relative velocity close to $c$ and, hence, big $% E_{c.m.}
| [
{
"created": "Mon, 21 Jul 2014 09:51:44 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Nov 2014 16:34:57 GMT",
"version": "v2"
},
{
"created": "Wed, 18 Feb 2015 22:41:26 GMT",
"version": "v3"
}
] | 2015-02-20 | [
[
"Zaslavskii",
"O. B.",
""
]
] | There are different versions of collisions of two particles near black holes with unbound energy $E_{c.m.}$ in the centre of mass frame. The so-called BSW effect arises when a slow fine-tuned "critical" particle hits a rapid "usual" one. We discuss a scenario of collision in the strong magnetic field for which explanation tuns out to be different. Both particles are rapid but the nonzero angle between their velocities (which are both close to $c$, the speed of light) results in a relative velocity close to $c$ and, hence, big $% E_{c.m.} |
1406.6157 | Mariam Bouhmadi-Lopez | Mariam Bouhmadi-Lopez, Che-Yu Chen, Pisin Chen | Eddington-Born-Infeld cosmology: a cosmographic approach, a tale of
doomsdays and the fate of bound structures | 23 pages, 6 figures. RevTex4-1. Revised/clarified version accepted in
EPJC | null | 10.1140/epjc/s10052-015-3257-4 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Eddington-inspired-Born-Infeld scenario (EiBI) can prevent the Big Bang
singularity for a matter content whose equation of state is constant and
positive. In a recent paper we showed that, on the contrary, it is impossible
to smooth a big rip in the EiBI setup. In fact the situations are still
different for other singularities. In this paper we show that a big freeze
singularity in general relativity (GR) can in some cases be smoothed to a
sudden or a type IV singularity under the EiBI scenario. Similarly, a sudden or
a type IV singularity in GR can be replaced in some regions of the parameter
space by a type IV singularity or a loitering behaviour, respectively, in the
EiBI framework. Furthermore, we find that the auxiliary metric related to the
physical connection usually has a smoother behaviour than that based on the
physical metric. In addition, we show that bound structures close to a big rip
or a little rip will be destroyed before the advent of the singularity and will
remain bound close to a sudden, big freeze or type IV singularity. We then
constrain the model following a cosmographic approach, which is well-known to
be model-independent, for a given Friedmann-Lema\^itre-Robertson-Walker
geometry. It turns out that among the various past or present singularities,
the cosmographic analysis can pick up the physical region that determines the
occurrence of a type IV singularity or a loitering effect in the past.
Moreover, to determine which of the future singularities or doomsdays is more
probable, observational constraints on higher order cosmographic parameters is
required.
| [
{
"created": "Tue, 24 Jun 2014 07:40:29 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Dec 2014 21:40:08 GMT",
"version": "v2"
}
] | 2015-06-22 | [
[
"Bouhmadi-Lopez",
"Mariam",
""
],
[
"Chen",
"Che-Yu",
""
],
[
"Chen",
"Pisin",
""
]
] | The Eddington-inspired-Born-Infeld scenario (EiBI) can prevent the Big Bang singularity for a matter content whose equation of state is constant and positive. In a recent paper we showed that, on the contrary, it is impossible to smooth a big rip in the EiBI setup. In fact the situations are still different for other singularities. In this paper we show that a big freeze singularity in general relativity (GR) can in some cases be smoothed to a sudden or a type IV singularity under the EiBI scenario. Similarly, a sudden or a type IV singularity in GR can be replaced in some regions of the parameter space by a type IV singularity or a loitering behaviour, respectively, in the EiBI framework. Furthermore, we find that the auxiliary metric related to the physical connection usually has a smoother behaviour than that based on the physical metric. In addition, we show that bound structures close to a big rip or a little rip will be destroyed before the advent of the singularity and will remain bound close to a sudden, big freeze or type IV singularity. We then constrain the model following a cosmographic approach, which is well-known to be model-independent, for a given Friedmann-Lema\^itre-Robertson-Walker geometry. It turns out that among the various past or present singularities, the cosmographic analysis can pick up the physical region that determines the occurrence of a type IV singularity or a loitering effect in the past. Moreover, to determine which of the future singularities or doomsdays is more probable, observational constraints on higher order cosmographic parameters is required. |
1707.07864 | Oleg Zaslavskii | O. B. Zaslavskii | On white holes as particle accelerators | 10 pages. 2 figures. Presentation improved, Ref. 11 added. To appear
in Grav. Cosmol | Gravitation and Cosmology, vol. 24, 92 (2018) | 10.1134/S0202289318010164 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze scenarios of particle collisions in the metric of a nonextremal
black hole that can potentially lead to ultrahigh energy $E_{c.m.}$ in their
centre of mass frame. Particle 1 comes from infinity to the black hole horizon
while particle 2 emerges from a white hole region. It is shown that unbounded
$E_{c.m.}$ $\ $require that particle 2 pass close to the bifurcation point. The
analogy with collisions inside the horizon is discussed.
| [
{
"created": "Tue, 25 Jul 2017 09:16:18 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Nov 2017 21:24:53 GMT",
"version": "v2"
},
{
"created": "Mon, 22 Jan 2018 17:58:45 GMT",
"version": "v3"
}
] | 2018-04-04 | [
[
"Zaslavskii",
"O. B.",
""
]
] | We analyze scenarios of particle collisions in the metric of a nonextremal black hole that can potentially lead to ultrahigh energy $E_{c.m.}$ in their centre of mass frame. Particle 1 comes from infinity to the black hole horizon while particle 2 emerges from a white hole region. It is shown that unbounded $E_{c.m.}$ $\ $require that particle 2 pass close to the bifurcation point. The analogy with collisions inside the horizon is discussed. |
2202.13113 | Filip Hejda | Filip Hejda, Jos\'e P. S. Lemos, Oleg B. Zaslavskii | Notes on extraction of energy from an extremal Kerr-Newman black hole
via charged particle collisions | 7 pages | Acta Phys. Pol. B Proc. Suppl. 15, 1-A5 (2022) | 10.5506/APhysPolBSupp.15.1-A5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The so-called BSW effect is an idealised scenario for high-energy test
particle collisions in the vicinity of black holes; if the black hole is
extremal and one of the particles fine-tuned, the centre-of-mass collision
energy can be arbitrarily high. It has been recently shown that the energy of
escaping particles produced in this process can also be arbitrarily high in the
given approximation, as long as both the black hole and the escaping particles
are charged, regardless of how small the black-hole charge might be. We revisit
these results and show that they are also compatible with properties of
microscopic particles for the case of motion in the equatorial plane of an
extremal Kerr-Newman black hole.
| [
{
"created": "Sat, 26 Feb 2022 11:02:58 GMT",
"version": "v1"
}
] | 2022-03-02 | [
[
"Hejda",
"Filip",
""
],
[
"Lemos",
"José P. S.",
""
],
[
"Zaslavskii",
"Oleg B.",
""
]
] | The so-called BSW effect is an idealised scenario for high-energy test particle collisions in the vicinity of black holes; if the black hole is extremal and one of the particles fine-tuned, the centre-of-mass collision energy can be arbitrarily high. It has been recently shown that the energy of escaping particles produced in this process can also be arbitrarily high in the given approximation, as long as both the black hole and the escaping particles are charged, regardless of how small the black-hole charge might be. We revisit these results and show that they are also compatible with properties of microscopic particles for the case of motion in the equatorial plane of an extremal Kerr-Newman black hole. |
2012.12752 | Mario Pitschmann | Mario Pitschmann | Exact Solutions to Non-Linear Symmetron Theory II: One and Two Mirror
Systems | 12 pages, 4 figures | Phys. Rev. D 103, 084013 (2021) | 10.1103/PhysRevD.103.084013 | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | We derive the exact analytical solutions to the symmetron field theory
equations in the presence of a one or two mirror system in the case of a
spontaneously broken phase in vacuum as well as in matter. This complements a
similar analysis performed in a previous article [1], in which the symmetron is
in the spontaneously broken phase in vacuum but in the symmetric phase in
matter. Here again, the one dimensional equations of motion are integrated
exactly for both systems and their solutions are expressed in terms of Jacobi
elliptic functions. In the case of two parallel mirrors the equations of motion
provide also in this case a discrete set of solutions with increasing number of
nodes and energies. The solutions obtained herein can be applied to qBOUNCE
experiments, neutron interferometry and to the calculation of the symmetron
field induced "Casimir force" in the Cannex experiment and allow to extend the
investigation to hitherto unavailable regions in symmetron parameter space.
| [
{
"created": "Wed, 23 Dec 2020 15:45:47 GMT",
"version": "v1"
}
] | 2021-04-14 | [
[
"Pitschmann",
"Mario",
""
]
] | We derive the exact analytical solutions to the symmetron field theory equations in the presence of a one or two mirror system in the case of a spontaneously broken phase in vacuum as well as in matter. This complements a similar analysis performed in a previous article [1], in which the symmetron is in the spontaneously broken phase in vacuum but in the symmetric phase in matter. Here again, the one dimensional equations of motion are integrated exactly for both systems and their solutions are expressed in terms of Jacobi elliptic functions. In the case of two parallel mirrors the equations of motion provide also in this case a discrete set of solutions with increasing number of nodes and energies. The solutions obtained herein can be applied to qBOUNCE experiments, neutron interferometry and to the calculation of the symmetron field induced "Casimir force" in the Cannex experiment and allow to extend the investigation to hitherto unavailable regions in symmetron parameter space. |
1905.13498 | Astrid Eichhorn | Astrid Eichhorn, Sumati Surya and Fleur Versteegen | Spectral dimension on spatial hypersurfaces in causal set quantum
gravity | 13 pages, 11 figures | null | 10.1088/1361-6382/ab47cd | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An important probe of quantum geometry is its spectral dimension, defined via
a spatial diffusion process. In this work we study the spectral dimension of a
``spatial hypersurface'' in a manifoldlike causal set using the induced spatial
distance function. In previous work, the diffusion was taken on the full causal
set, where the nearest neighbours are unbounded in number. The resulting
super-diffusion leads to an increase in the spectral dimension at short
diffusion times, in contrast to other approaches to quantum gravity. In the
current work, by using a temporal localisation in the causal set, the number of
nearest spatial neighbours is rendered finite. Using numerical simulations of
causal sets obtained from $d=3$ Minkowski spacetime, we find that for a flat
spatial hypersurface, the spectral dimension agrees with the Hausdorff
dimension at intermediate scales, but shows clear indications of dimensional
reduction at small scales, i.e., in the ultraviolet. The latter is a direct
consequence of ``discrete asymptotic silence'' at small scales in causal sets.
| [
{
"created": "Fri, 31 May 2019 10:28:01 GMT",
"version": "v1"
}
] | 2020-01-08 | [
[
"Eichhorn",
"Astrid",
""
],
[
"Surya",
"Sumati",
""
],
[
"Versteegen",
"Fleur",
""
]
] | An important probe of quantum geometry is its spectral dimension, defined via a spatial diffusion process. In this work we study the spectral dimension of a ``spatial hypersurface'' in a manifoldlike causal set using the induced spatial distance function. In previous work, the diffusion was taken on the full causal set, where the nearest neighbours are unbounded in number. The resulting super-diffusion leads to an increase in the spectral dimension at short diffusion times, in contrast to other approaches to quantum gravity. In the current work, by using a temporal localisation in the causal set, the number of nearest spatial neighbours is rendered finite. Using numerical simulations of causal sets obtained from $d=3$ Minkowski spacetime, we find that for a flat spatial hypersurface, the spectral dimension agrees with the Hausdorff dimension at intermediate scales, but shows clear indications of dimensional reduction at small scales, i.e., in the ultraviolet. The latter is a direct consequence of ``discrete asymptotic silence'' at small scales in causal sets. |
1511.07071 | Emil Nissimov | Eduardo Guendelman, Emil Nissimov and Svetlana Pacheva | Unified Dark Energy and Dust Dark Matter Dual to Quadratic Purely
Kinetic K-Essence | 11 pages two-column style; v.2 few explanatory paragraphs and
references added, 12 pages, to appear in "European Physical Journal C" | European Physical Journal C76:90 (2016) | 10.1140/epjc/s10052-016-3938-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a modified gravity plus single-scalar-field model, where the
scalar Lagrangian couples symmetrically both to the standard Riemannian
volume-form (spacetime integration measure density) given by the square-root of
the determinant of the Riemannian metric, as well as to another non-Riemannian
volume-form in terms of an auxiliary maximal-rank antisymmetric tensor gauge
field. As shown in a previous paper, the pertinent scalar field dynamics
provides an exact unified description of both dark energy via dynamical
generation of a cosmological constant, and dark matter as a "dust" fluid with
geodesic flow as a result of a hidden Noether symmetry. Here we extend the
discussion by considering a non-trivial modification of the purely
gravitational action in the form of f(R) = R - \alpha R^2 generalized gravity.
Upon deriving the corresponding "Einstein-frame" effective action of the latter
modified gravity-scalar-field theory we find explicit duality (in the sense of
weak versus strong coupling) between the original model of unified dynamical
dark energy and dust fluid dark matter, on one hand, and a specific quadratic
purely kinetic "k-essence" gravity-matter model with special dependence of its
coupling constants on only two independent parameters, on the other hand. The
canonical Hamiltonian treatment and Wheeler-DeWitt quantization of the dual
purely kinetic "k-essence" gravity-matter model is also briefly discussed.
| [
{
"created": "Sun, 22 Nov 2015 21:24:42 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Feb 2016 11:11:07 GMT",
"version": "v2"
}
] | 2016-03-21 | [
[
"Guendelman",
"Eduardo",
""
],
[
"Nissimov",
"Emil",
""
],
[
"Pacheva",
"Svetlana",
""
]
] | We consider a modified gravity plus single-scalar-field model, where the scalar Lagrangian couples symmetrically both to the standard Riemannian volume-form (spacetime integration measure density) given by the square-root of the determinant of the Riemannian metric, as well as to another non-Riemannian volume-form in terms of an auxiliary maximal-rank antisymmetric tensor gauge field. As shown in a previous paper, the pertinent scalar field dynamics provides an exact unified description of both dark energy via dynamical generation of a cosmological constant, and dark matter as a "dust" fluid with geodesic flow as a result of a hidden Noether symmetry. Here we extend the discussion by considering a non-trivial modification of the purely gravitational action in the form of f(R) = R - \alpha R^2 generalized gravity. Upon deriving the corresponding "Einstein-frame" effective action of the latter modified gravity-scalar-field theory we find explicit duality (in the sense of weak versus strong coupling) between the original model of unified dynamical dark energy and dust fluid dark matter, on one hand, and a specific quadratic purely kinetic "k-essence" gravity-matter model with special dependence of its coupling constants on only two independent parameters, on the other hand. The canonical Hamiltonian treatment and Wheeler-DeWitt quantization of the dual purely kinetic "k-essence" gravity-matter model is also briefly discussed. |
2304.03559 | Jakub Mielczarek Ph.D. | Grzegorz Czelusta, Jakub Mielczarek | Quantum circuits for the Ising spin networks | 16 pages, 33 figures | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spin network states are a powerful tool for constructing the $SU(2)$ gauge
theories on a graph. In loop quantum gravity (LQG), they have yielded many
promising predictions, although progress has been limited by the computational
challenge of dealing with high-dimensional Hilbert spaces. To explore more
general configurations, quantum computing methods can be applied by
representing spin network states as quantum circuits. In this article, we
introduce an improved method for constructing quantum circuits for 4-valent
Ising spin networks, which utilizes a smaller number of qubits than previous
approaches. This has practical implications for the implementation of quantum
circuits. We also demonstrate the procedure with various examples, including
the construction of a 10-node Ising spin network state. The key ingredient of
the method is the variational transfer of partial states, which we illustrate
through numerous examples. Our improved construction provides a promising
avenue for further exploring the potential of quantum computing methods in
quantum gravity research.
| [
{
"created": "Fri, 7 Apr 2023 09:42:29 GMT",
"version": "v1"
}
] | 2023-04-10 | [
[
"Czelusta",
"Grzegorz",
""
],
[
"Mielczarek",
"Jakub",
""
]
] | Spin network states are a powerful tool for constructing the $SU(2)$ gauge theories on a graph. In loop quantum gravity (LQG), they have yielded many promising predictions, although progress has been limited by the computational challenge of dealing with high-dimensional Hilbert spaces. To explore more general configurations, quantum computing methods can be applied by representing spin network states as quantum circuits. In this article, we introduce an improved method for constructing quantum circuits for 4-valent Ising spin networks, which utilizes a smaller number of qubits than previous approaches. This has practical implications for the implementation of quantum circuits. We also demonstrate the procedure with various examples, including the construction of a 10-node Ising spin network state. The key ingredient of the method is the variational transfer of partial states, which we illustrate through numerous examples. Our improved construction provides a promising avenue for further exploring the potential of quantum computing methods in quantum gravity research. |
1010.2963 | Maciej Dunajski | Maciej Dunajski, Prim Plansangkate | Scalar--flat K\"ahler metrics with conformal Bianchi V symmetry | Dedicated to Maciej Przanowski on the occasion of his 65th birthday.
Minor corrections. To appear in CQG | Class.Quant.Grav.28:125004,2011 | 10.1088/0264-9381/28/12/125004 | DAMTP-2010-79 | gr-qc hep-th math.DG nlin.SI | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide an affirmative answer to a question posed by Tod \cite{Tod:1995b},
and construct all four-dimensional Kahler metrics with vanishing scalar
curvature which are invariant under the conformal action of Bianchi V group.
The construction is based on the combination of twistor theory and the
isomonodromic problem with two double poles. The resulting metrics are
non-diagonal in the left-invariant basis and are explicitly given in terms of
Bessel functions and their integrals. We also make a connection with the LeBrun
ansatz, and characterise the associated solutions of the SU(\infty) Toda
equation by the existence a non-abelian two-dimensional group of point
symmetries.
| [
{
"created": "Thu, 14 Oct 2010 16:11:39 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Apr 2011 12:48:43 GMT",
"version": "v2"
}
] | 2011-05-09 | [
[
"Dunajski",
"Maciej",
""
],
[
"Plansangkate",
"Prim",
""
]
] | We provide an affirmative answer to a question posed by Tod \cite{Tod:1995b}, and construct all four-dimensional Kahler metrics with vanishing scalar curvature which are invariant under the conformal action of Bianchi V group. The construction is based on the combination of twistor theory and the isomonodromic problem with two double poles. The resulting metrics are non-diagonal in the left-invariant basis and are explicitly given in terms of Bessel functions and their integrals. We also make a connection with the LeBrun ansatz, and characterise the associated solutions of the SU(\infty) Toda equation by the existence a non-abelian two-dimensional group of point symmetries. |
1002.3245 | Sanjay Jhingan | S. Jhingan and Sushant G. Ghosh | Inhomogeneous Dust Collapse in 5D Einstein-Gauss-Bonnet Gravity | 8 Latex Pages, 2 EPS figures | Physical Review D 81, 024010 (2010) | 10.1103/PhysRevD.81.024010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a Lemaitre - Tolman - Bondi type space-time in Einstein gravity
with the Gauss-Bonnet combination of quadratic curvature terms, and present
exact solution in closed form. It turns out that the presence of the coupling
constant of the Gauss-Bonnet terms alpha > 0 completely changes the causal
structure of the singularities from the analogous general relativistic case.
The gravitational collapse of inhomogeneous dust in the five-dimensional
Gauss-Bonnet extended Einstein equations leads to formation of a massive, but
weak, timelike singularity which is forbidden in general relativity.
Interestingly, this is a counterexample to three conjecture viz. cosmic
censorship conjecture, hoop conjecture and Seifert's conjecture.
| [
{
"created": "Wed, 17 Feb 2010 11:49:27 GMT",
"version": "v1"
}
] | 2015-05-18 | [
[
"Jhingan",
"S.",
""
],
[
"Ghosh",
"Sushant G.",
""
]
] | We consider a Lemaitre - Tolman - Bondi type space-time in Einstein gravity with the Gauss-Bonnet combination of quadratic curvature terms, and present exact solution in closed form. It turns out that the presence of the coupling constant of the Gauss-Bonnet terms alpha > 0 completely changes the causal structure of the singularities from the analogous general relativistic case. The gravitational collapse of inhomogeneous dust in the five-dimensional Gauss-Bonnet extended Einstein equations leads to formation of a massive, but weak, timelike singularity which is forbidden in general relativity. Interestingly, this is a counterexample to three conjecture viz. cosmic censorship conjecture, hoop conjecture and Seifert's conjecture. |
2203.09232 | Ilya Lvovich Shapiro | E.V. Gorbar and Ilya L. Shapiro | Nonlocality of quantum matter corrections and cosmological constant
running | Explanations extended, results unchanged, fits the published version.
15 pages, 1 figure | null | 10.1007/JHEP07(2022)103 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Semiclassical contributions to the gravitational action include various terms
with zero, two, and four derivatives of the metric as well as nonlocal form
factors for these terms. Contributions to some of these terms could be confused
with others on a specific metric background or for a particular gauge fixing.
We present a critical analysis of the recent works where the tensor structure
and the number of derivatives in the action of gravity were not properly taken
into account. Taking these relevant aspects into account, we show that although
some contributions owing to the quantum fluctuations of massive or massless
scalar as well as fermion and vector fields may be attributed to the "running"
of the cosmological constant, in reality they correspond to the fourth
derivative terms of the action.
| [
{
"created": "Thu, 17 Mar 2022 10:40:20 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Aug 2022 13:47:30 GMT",
"version": "v2"
}
] | 2022-08-10 | [
[
"Gorbar",
"E. V.",
""
],
[
"Shapiro",
"Ilya L.",
""
]
] | Semiclassical contributions to the gravitational action include various terms with zero, two, and four derivatives of the metric as well as nonlocal form factors for these terms. Contributions to some of these terms could be confused with others on a specific metric background or for a particular gauge fixing. We present a critical analysis of the recent works where the tensor structure and the number of derivatives in the action of gravity were not properly taken into account. Taking these relevant aspects into account, we show that although some contributions owing to the quantum fluctuations of massive or massless scalar as well as fermion and vector fields may be attributed to the "running" of the cosmological constant, in reality they correspond to the fourth derivative terms of the action. |
2301.04879 | Roberto Oliveri | Filippo Camilloni, Gianluca Grignani, Troels Harmark, Roberto Oliveri,
Marta Orselli, Daniele Pica | Tidal deformations of a binary system induced by an external Kerr black
hole | v1: 27 pages, 3 figures; v2: minor changes, matches published version
in Phys. Rev. D | Phys. Rev. D 107 (2023) 8, 084011 | 10.1103/PhysRevD.107.084011 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamics of a binary system moving in the background of a black hole is
affected by tidal forces. In this work, for the Kerr black hole, we derive the
electric and magnetic tidal moments at quadrupole order, where the latter are
computed for the first time in full generality. We make use of these moments in
the scenario of a hierarchical triple system made of a Kerr black hole and an
extreme-mass ratio binary system consisting of a Schwarzschild black hole and a
test particle. We study how the secular dynamics of the test particle in the
binary system is distorted by the presence of tidal forces from a much larger
Kerr black hole. Our treatment includes strong gravitational effects beyond the
post-Newtonian approximation both for the binary system and for the tidal
forces since the binary system is allowed to be close to the event horizon of
the Kerr black hole. We compute the shifts in the physical quantities for the
secular dynamics of the test particle and show that they are gauge-invariant.
In particular, we apply our formalism to the innermost stable circular orbit
for the test particle and to the case of the photon sphere. Our results are
relevant for the astrophysical situation in which the binary system is in the
vicinity of a supermassive black hole.
| [
{
"created": "Thu, 12 Jan 2023 08:55:27 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Apr 2023 09:35:48 GMT",
"version": "v2"
}
] | 2023-04-10 | [
[
"Camilloni",
"Filippo",
""
],
[
"Grignani",
"Gianluca",
""
],
[
"Harmark",
"Troels",
""
],
[
"Oliveri",
"Roberto",
""
],
[
"Orselli",
"Marta",
""
],
[
"Pica",
"Daniele",
""
]
] | The dynamics of a binary system moving in the background of a black hole is affected by tidal forces. In this work, for the Kerr black hole, we derive the electric and magnetic tidal moments at quadrupole order, where the latter are computed for the first time in full generality. We make use of these moments in the scenario of a hierarchical triple system made of a Kerr black hole and an extreme-mass ratio binary system consisting of a Schwarzschild black hole and a test particle. We study how the secular dynamics of the test particle in the binary system is distorted by the presence of tidal forces from a much larger Kerr black hole. Our treatment includes strong gravitational effects beyond the post-Newtonian approximation both for the binary system and for the tidal forces since the binary system is allowed to be close to the event horizon of the Kerr black hole. We compute the shifts in the physical quantities for the secular dynamics of the test particle and show that they are gauge-invariant. In particular, we apply our formalism to the innermost stable circular orbit for the test particle and to the case of the photon sphere. Our results are relevant for the astrophysical situation in which the binary system is in the vicinity of a supermassive black hole. |
2102.03535 | Farrukh A. Chishtie | Farrukh A. Chishtie | On the breakdown of space-time in general relativity | 9 pages, LaTeX, accepted at Canadian Journal of Physics | null | 10.1139/cjp-2022-0159 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on the canonical quantization of $d>2$ dimensional general relativity
(GR) via the Dirac constraint formalism (also termed as `constraint
quantization'), we propose the loss of covariance as a fundamental property of
the theory. This breakdown occurs for the first-order Einstein Hilbert action,
whereby loss of diffeomorphism invariance, besides first class constraints,
second class constriants also exist leading to non-standard ghost fields which
render the path integral non-covariant. We also attempt, for the first time,
the canonical quantization via calculation of the path integral for the
equivalent Hamiltonian formulation of GR for which only first class constraints
exist. However, loss of covariance still occurs in this action due to loss of
diffeomorphism invariance and structures arising from non-covariant constraints
in the path integral. In contrast, we find that covariance as a symmetry is
restored and quantization with perturbative calculations is possible in the
weak limit of the gravitational field of these actions. Hence, we firstly
establish, for the first time, that the breakdown in space-time is a property
of GR itself as its limitation, indicating it to be an Effective Field Theory
(EFT). We further propose that the breakdown of space-time occurs as a
non-perturbative feature of GR in the strong field limit of the theory. Besides
GR, we also note that covariance is preserved when constraint quantization is
conducted for non-Abelian gauge theories, such as the Yang-Mills theory. These
findings are novel from a canonical gravity formalism and EFT approach, and are
consistent with GR singularity theorems, yet are general and extend them, as
the singularity theorems indicate breakdown at a strong field limit of GR in
black holes.
| [
{
"created": "Sat, 6 Feb 2021 08:35:00 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Jan 2022 01:46:19 GMT",
"version": "v2"
},
{
"created": "Sat, 4 Jun 2022 01:50:21 GMT",
"version": "v3"
},
{
"created": "Tue, 20 Dec 2022 22:11:01 GMT",
"version": "v4"
},
{
"cre... | 2023-03-28 | [
[
"Chishtie",
"Farrukh A.",
""
]
] | Based on the canonical quantization of $d>2$ dimensional general relativity (GR) via the Dirac constraint formalism (also termed as `constraint quantization'), we propose the loss of covariance as a fundamental property of the theory. This breakdown occurs for the first-order Einstein Hilbert action, whereby loss of diffeomorphism invariance, besides first class constraints, second class constriants also exist leading to non-standard ghost fields which render the path integral non-covariant. We also attempt, for the first time, the canonical quantization via calculation of the path integral for the equivalent Hamiltonian formulation of GR for which only first class constraints exist. However, loss of covariance still occurs in this action due to loss of diffeomorphism invariance and structures arising from non-covariant constraints in the path integral. In contrast, we find that covariance as a symmetry is restored and quantization with perturbative calculations is possible in the weak limit of the gravitational field of these actions. Hence, we firstly establish, for the first time, that the breakdown in space-time is a property of GR itself as its limitation, indicating it to be an Effective Field Theory (EFT). We further propose that the breakdown of space-time occurs as a non-perturbative feature of GR in the strong field limit of the theory. Besides GR, we also note that covariance is preserved when constraint quantization is conducted for non-Abelian gauge theories, such as the Yang-Mills theory. These findings are novel from a canonical gravity formalism and EFT approach, and are consistent with GR singularity theorems, yet are general and extend them, as the singularity theorems indicate breakdown at a strong field limit of GR in black holes. |
1107.1689 | Burkhard Zink | Burkhard Zink, Paul D. Lasky, Kostas D. Kokkotas | Are gravitational waves from giant magnetar flares observable? | 4 pages, 3 figures. Further information can be found at
http://www.physik.uni-tuebingen.de/institute/astronomie-astrophysik/institut/theoretische-astrophysik/forschung.html | Phys. Rev. D 85, 024030 (2012) | 10.1103/PhysRevD.85.024030 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Are giant flares in magnetars viable sources of gravitational radiation? Few
theoretical studies have been concerned with this problem, with the small
number using either highly idealized models or assuming a magnetic field orders
of magnitude beyond what is supported by observations. We perform nonlinear
general-relativistic magnetohydrodynamics simulations of large-scale
hydromagnetic instabilities in magnetar models. We utilise these models to find
gravitational wave emissions over a wide range of energies, from 10^40 to 10^47
erg. This allows us to derive a systematic relationship between the surface
field strength and the gravitational wave strain, which we find to be highly
nonlinear. In particular, for typical magnetar fields of a few times 10^15 G,
we conclude that a direct observation of f-modes excited by global magnetic
field reconfigurations is unlikely with present or near-future gravitational
wave observatories, though we also discuss the possibility that modes in a
low-frequency band up to 100 Hz could be sufficiently excited to be relevant
for observation.
| [
{
"created": "Fri, 8 Jul 2011 18:11:45 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Jul 2011 18:04:04 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Jul 2011 14:39:17 GMT",
"version": "v3"
}
] | 2013-05-30 | [
[
"Zink",
"Burkhard",
""
],
[
"Lasky",
"Paul D.",
""
],
[
"Kokkotas",
"Kostas D.",
""
]
] | Are giant flares in magnetars viable sources of gravitational radiation? Few theoretical studies have been concerned with this problem, with the small number using either highly idealized models or assuming a magnetic field orders of magnitude beyond what is supported by observations. We perform nonlinear general-relativistic magnetohydrodynamics simulations of large-scale hydromagnetic instabilities in magnetar models. We utilise these models to find gravitational wave emissions over a wide range of energies, from 10^40 to 10^47 erg. This allows us to derive a systematic relationship between the surface field strength and the gravitational wave strain, which we find to be highly nonlinear. In particular, for typical magnetar fields of a few times 10^15 G, we conclude that a direct observation of f-modes excited by global magnetic field reconfigurations is unlikely with present or near-future gravitational wave observatories, though we also discuss the possibility that modes in a low-frequency band up to 100 Hz could be sufficiently excited to be relevant for observation. |
1408.0766 | Reinaldo Gleiser | Reinaldo J. Gleiser | Axial gravitational perturbations of an infinite static line source | 17 pages, 2 figures | null | 10.1088/0264-9381/32/6/065003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study axial gravitational perturbations of an infinite
static line source, represented by a form of the Levi-Civita metric. The
perturbations are restricted to axial symmetry but break the cylindrical
symmetry of the background metric. We analyze the gauge issues that arise in
setting up the appropriate form of the perturbed metric and show that it is
possible to restrict to diagonal terms, but that this does not fix the gauge
completely. We derive the perturbation equations and show that they can be
solved by solving a third order ordinary differential equation for an
appropriately chosen function of the perturbed metric coefficients. The set of
solutions of this equation contains gauge trivial parts, and we show how to
extract the gauge non trivial components. We introduce appropriate boundary
conditions on the solutions and show that these lead to a boundary value
problem that determines the allowed functional forms of the perturbation modes.
The associated eigenvalues determine a sort of "dispersion relation" for the
frequencies and corresponding "wave vector" components. The central result of
this analysis is that the spectrum of allowed frequencies contains one unstable
(imaginary frequency) mode for every possible choice of the background metric.
The completeness of the mode expansion in relation to the initial value problem
and to the gauge problem is discussed in detail, and we show that the
perturbations contain an unstable component for generic initial data, and,
therefore, that the Levi-Civita space times are gravitationally unstable. We
also include, for completeness, a set of approximate eigenvalues, and examples
of the functional form of the solutions.
| [
{
"created": "Mon, 4 Aug 2014 18:58:44 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Gleiser",
"Reinaldo J.",
""
]
] | In this paper we study axial gravitational perturbations of an infinite static line source, represented by a form of the Levi-Civita metric. The perturbations are restricted to axial symmetry but break the cylindrical symmetry of the background metric. We analyze the gauge issues that arise in setting up the appropriate form of the perturbed metric and show that it is possible to restrict to diagonal terms, but that this does not fix the gauge completely. We derive the perturbation equations and show that they can be solved by solving a third order ordinary differential equation for an appropriately chosen function of the perturbed metric coefficients. The set of solutions of this equation contains gauge trivial parts, and we show how to extract the gauge non trivial components. We introduce appropriate boundary conditions on the solutions and show that these lead to a boundary value problem that determines the allowed functional forms of the perturbation modes. The associated eigenvalues determine a sort of "dispersion relation" for the frequencies and corresponding "wave vector" components. The central result of this analysis is that the spectrum of allowed frequencies contains one unstable (imaginary frequency) mode for every possible choice of the background metric. The completeness of the mode expansion in relation to the initial value problem and to the gauge problem is discussed in detail, and we show that the perturbations contain an unstable component for generic initial data, and, therefore, that the Levi-Civita space times are gravitationally unstable. We also include, for completeness, a set of approximate eigenvalues, and examples of the functional form of the solutions. |
1610.02390 | Moritz Reintjes | Moritz Reintjes and Blake Temple | Shock Wave Interactions and the Riemann-flat Condition: The Geometry
behind Metric Smoothing and the Existence of Locally Inertial Frames in
General Relativity | V5: Improved presentation, in particular, to Section 6. Results
unchanged. V4: We shortened the presentation, added Def 3.1 and removed last
section of previous version. V3: We extended results from connections of
bounded variation to connections bounded in $L^\infty$, otherwise main
results remain identical. V2: Result of Theorem 1.5 was extended from 2-D to
spherically symmetric space-times | Arch. Rat. Mech. Anal. 235 (2020), 1873-1904 | 10.1007/s00205-019-01456-8 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that the essential smoothness of the gravitational metric at shock
waves in GR, a PDE regularity issue for weak solutions of the Einstein
equations, is determined by a geometrical condition which we introduce and name
the {\it Riemann-flat condition}. The Riemann-flat condition determines whether
or not the essential smoothness of the gravitational metric is two full
derivatives more regular than the Riemann curvature tensor. This provides a
geometric framework for the open problem as to whether {\it regularity
singularities} (points where the curvature is in $L^\infty$ but the essential
smoothness of the gravitational metric is only Lipschitz continuous) can be
created by shock wave interaction in GR, or whether metrics Lipschitz at shocks
can always be smoothed one level to $C^{1,1}$ by coordinate transformation. As
a corollary of the ideas we give a proof that locally inertial frames always
exist in a natural sense for shock wave metrics in spherically symmetric
spacetimes, independent of whether the metric itself can be smoothed to
$C^{1,1}$ locally. This latter result yields an explicit procedure (analogous
to Riemann Normal Coordinates in smooth spacetimes) for constructing locally
inertial coordinates for Lipschitz metrics, and is a new regularity result for
GR solutions constructed by the Glimm scheme.
| [
{
"created": "Fri, 7 Oct 2016 19:49:10 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Feb 2017 14:53:25 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Apr 2017 08:00:44 GMT",
"version": "v3"
},
{
"created": "Wed, 22 Aug 2018 09:56:10 GMT",
"version": "v4"
},
{
"cr... | 2020-11-10 | [
[
"Reintjes",
"Moritz",
""
],
[
"Temple",
"Blake",
""
]
] | We prove that the essential smoothness of the gravitational metric at shock waves in GR, a PDE regularity issue for weak solutions of the Einstein equations, is determined by a geometrical condition which we introduce and name the {\it Riemann-flat condition}. The Riemann-flat condition determines whether or not the essential smoothness of the gravitational metric is two full derivatives more regular than the Riemann curvature tensor. This provides a geometric framework for the open problem as to whether {\it regularity singularities} (points where the curvature is in $L^\infty$ but the essential smoothness of the gravitational metric is only Lipschitz continuous) can be created by shock wave interaction in GR, or whether metrics Lipschitz at shocks can always be smoothed one level to $C^{1,1}$ by coordinate transformation. As a corollary of the ideas we give a proof that locally inertial frames always exist in a natural sense for shock wave metrics in spherically symmetric spacetimes, independent of whether the metric itself can be smoothed to $C^{1,1}$ locally. This latter result yields an explicit procedure (analogous to Riemann Normal Coordinates in smooth spacetimes) for constructing locally inertial coordinates for Lipschitz metrics, and is a new regularity result for GR solutions constructed by the Glimm scheme. |
1903.05725 | Valery Nikulin V | Valery V. Nikulin, Sergey G. Rubin | Inflationary limits on the size of compact extra space | 13 pages, 3 figures, accepted by IJMPD | International Journal of Modern Physics D Vol. 28, No. 13 (2019)
1941004 | 10.1142/S0218271819410049 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study restrictions imposed on the parameters of the Kaluza-Klein extra
space supplied by the standard inflationary models. It is shown that the size
of the extra space cannot be larger than $\sim 10^{-27}$cm and the
$D$-dimensional Planck mass should be larger than $\sim 10^{13}$GeV. The
validity of these estimates is discussed.
We also study the creation of stable excitations of scalar field as the
result of the extra metric evolution.
| [
{
"created": "Wed, 13 Mar 2019 21:34:36 GMT",
"version": "v1"
}
] | 2019-12-02 | [
[
"Nikulin",
"Valery V.",
""
],
[
"Rubin",
"Sergey G.",
""
]
] | We study restrictions imposed on the parameters of the Kaluza-Klein extra space supplied by the standard inflationary models. It is shown that the size of the extra space cannot be larger than $\sim 10^{-27}$cm and the $D$-dimensional Planck mass should be larger than $\sim 10^{13}$GeV. The validity of these estimates is discussed. We also study the creation of stable excitations of scalar field as the result of the extra metric evolution. |
1208.3168 | Frans Klinkhamer | F. R. Klinkhamer | Gravity Without Curved Spacetime: A Simple Calculation | 9 pages, v3: expanded version | null | null | KA-TP-34-2012 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Classical-particle trajectories are calculated for the static Einstein
universe without requiring that the 3-space be closed and curved. Freely-moving
test particles are found to return to their starting positions because of
strong gravitational-field effects. Possible implications for the underlying
(quantum) theory of gravity are briefly discussed.
| [
{
"created": "Wed, 15 Aug 2012 18:07:24 GMT",
"version": "v1"
},
{
"created": "Sun, 19 Aug 2012 15:39:53 GMT",
"version": "v2"
},
{
"created": "Thu, 6 Sep 2012 14:48:07 GMT",
"version": "v3"
}
] | 2012-09-07 | [
[
"Klinkhamer",
"F. R.",
""
]
] | Classical-particle trajectories are calculated for the static Einstein universe without requiring that the 3-space be closed and curved. Freely-moving test particles are found to return to their starting positions because of strong gravitational-field effects. Possible implications for the underlying (quantum) theory of gravity are briefly discussed. |
1708.06244 | Emilio Elizalde | I. Brevik, E. Elizalde, S.D. Odintsov, A.V. Timoshkin | Inflationary universe in terms of a van der Waals viscous fluid | 7 pages, no figures, to appear in IJGMMP | null | 10.1142/S0219887817501857 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The inflationary expansion of our early-time universe is considered in terms
of the van der Waals equation, as equation of state for the cosmic fluid, where
a bulk viscosity contribution is assumed to be present. The corresponding
gravitational equations for the energy density in a homogeneous and isotropic
Friedmann-Lema\^{\i}tre-Robertson-Walker universe are solved, and an analytic
expression for the scale factor is obtained. Attention is paid, specifically,
to the role of the viscosity term in the accelerated expansion; the values of
the slow-roll parameters, the spectral index, and the tensor-to-scalar ratio
for the van der Waals model are calculated and compared with the most recent
astronomical data from the Planck satellite. By imposing reasonable
restrictions on the parameters of the van der Waals equation, in the presence
of viscosity, it is shown to be possible for this model to comply quite
precisely with the observational data. One can therefore conclude that the
inclusion of viscosity in the theory of the inflationary epoch definitely
improves the cosmological models.
| [
{
"created": "Fri, 18 Aug 2017 02:11:59 GMT",
"version": "v1"
}
] | 2017-12-06 | [
[
"Brevik",
"I.",
""
],
[
"Elizalde",
"E.",
""
],
[
"Odintsov",
"S. D.",
""
],
[
"Timoshkin",
"A. V.",
""
]
] | The inflationary expansion of our early-time universe is considered in terms of the van der Waals equation, as equation of state for the cosmic fluid, where a bulk viscosity contribution is assumed to be present. The corresponding gravitational equations for the energy density in a homogeneous and isotropic Friedmann-Lema\^{\i}tre-Robertson-Walker universe are solved, and an analytic expression for the scale factor is obtained. Attention is paid, specifically, to the role of the viscosity term in the accelerated expansion; the values of the slow-roll parameters, the spectral index, and the tensor-to-scalar ratio for the van der Waals model are calculated and compared with the most recent astronomical data from the Planck satellite. By imposing reasonable restrictions on the parameters of the van der Waals equation, in the presence of viscosity, it is shown to be possible for this model to comply quite precisely with the observational data. One can therefore conclude that the inclusion of viscosity in the theory of the inflationary epoch definitely improves the cosmological models. |
0905.2391 | Samuel E. Gralla | Samuel E. Gralla, Abraham I. Harte, and Robert M. Wald | A Rigorous Derivation of Electromagnetic Self-force | 52 pages, minor corrections | Phys.Rev.D80:024031,2009 | 10.1103/PhysRevD.80.024031 | null | gr-qc hep-th physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | During the past century, there has been considerable discussion and analysis
of the motion of a point charge, taking into account "self-force" effects due
to the particle's own electromagnetic field. We analyze the issue of "particle
motion" in classical electromagnetism in a rigorous and systematic way by
considering a one-parameter family of solutions to the coupled Maxwell and
matter equations corresponding to having a body whose charge-current density
$J^a(\lambda)$ and stress-energy tensor $T_{ab} (\lambda)$ scale to zero size
in an asymptotically self-similar manner about a worldline $\gamma$ as $\lambda
\to 0$. In this limit, the charge, $q$, and total mass, $m$, of the body go to
zero, and $q/m$ goes to a well defined limit. The Maxwell field
$F_{ab}(\lambda)$ is assumed to be the retarded solution associated with
$J^a(\lambda)$ plus a homogeneous solution (the "external field") that varies
smoothly with $\lambda$. We prove that the worldline $\gamma$ must be a
solution to the Lorentz force equations of motion in the external field
$F_{ab}(\lambda=0)$. We then obtain self-force, dipole forces, and spin force
as first order perturbative corrections to the center of mass motion of the
body. We believe that this is the first rigorous derivation of the complete
first order correction to Lorentz force motion. We also address the issue of
obtaining a self-consistent perturbative equation of motion associated with our
perturbative result, and argue that the self-force equations of motion that
have previously been written down in conjunction with the "reduction of order"
procedure should provide accurate equations of motion for a sufficiently small
charged body with negligible dipole moments and spin. There is no corresponding
justification for the non-reduced-order equations.
| [
{
"created": "Thu, 14 May 2009 18:21:02 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Jul 2009 16:23:26 GMT",
"version": "v2"
}
] | 2009-08-12 | [
[
"Gralla",
"Samuel E.",
""
],
[
"Harte",
"Abraham I.",
""
],
[
"Wald",
"Robert M.",
""
]
] | During the past century, there has been considerable discussion and analysis of the motion of a point charge, taking into account "self-force" effects due to the particle's own electromagnetic field. We analyze the issue of "particle motion" in classical electromagnetism in a rigorous and systematic way by considering a one-parameter family of solutions to the coupled Maxwell and matter equations corresponding to having a body whose charge-current density $J^a(\lambda)$ and stress-energy tensor $T_{ab} (\lambda)$ scale to zero size in an asymptotically self-similar manner about a worldline $\gamma$ as $\lambda \to 0$. In this limit, the charge, $q$, and total mass, $m$, of the body go to zero, and $q/m$ goes to a well defined limit. The Maxwell field $F_{ab}(\lambda)$ is assumed to be the retarded solution associated with $J^a(\lambda)$ plus a homogeneous solution (the "external field") that varies smoothly with $\lambda$. We prove that the worldline $\gamma$ must be a solution to the Lorentz force equations of motion in the external field $F_{ab}(\lambda=0)$. We then obtain self-force, dipole forces, and spin force as first order perturbative corrections to the center of mass motion of the body. We believe that this is the first rigorous derivation of the complete first order correction to Lorentz force motion. We also address the issue of obtaining a self-consistent perturbative equation of motion associated with our perturbative result, and argue that the self-force equations of motion that have previously been written down in conjunction with the "reduction of order" procedure should provide accurate equations of motion for a sufficiently small charged body with negligible dipole moments and spin. There is no corresponding justification for the non-reduced-order equations. |
2311.04620 | Remo Garattini | Remo Garattini and Phongpichit Channuie | Traversable Wormholes supported by Holographic Dark Energy with a
modified Equation of State | RevTeX 4, 13 pages | Nucl. Phys. B 1005 (2024) 116589 | 10.1016/j.nuclphysb.2024.116589 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspired by holographic dark energy models, we consider different energy
density profiles as possible sources needed to have traversable wormholes
solutions. Since such energy densities are all positive, we are forced to
introduce an equation of state of the form $p_{r}% (r)=\omega_{r}\left(
r\right) \rho(r)$. We will find that Zero Tidal Forces can be imposed at the
price of having the function $\omega_{r}\left( r\right) $ divergent for
$r\rightarrow\infty$. To overcome this inconvenient, we abandon the request of
having Zero Tidal Forces, by introducing appropriate modifications on the
function $\omega_{r}\left( r\right) $ in such a way to obtain a finite result
everywhere. We will find that such modifications will leave the behavior of the
Equation of State close to the throat invariant. Moreover, despite of the
initial assumption, we will find that every dark energy profile will be moved
into the phantom region. Among the different energy density proposals, only one
profile will not require a modification of the original $\omega
_{r}\left(r\right) $ to have Zero Tidal Forces. Such an energy density profile
will be consistent with the appearance of a Global Monopole.
| [
{
"created": "Wed, 8 Nov 2023 11:41:49 GMT",
"version": "v1"
}
] | 2024-06-12 | [
[
"Garattini",
"Remo",
""
],
[
"Channuie",
"Phongpichit",
""
]
] | Inspired by holographic dark energy models, we consider different energy density profiles as possible sources needed to have traversable wormholes solutions. Since such energy densities are all positive, we are forced to introduce an equation of state of the form $p_{r}% (r)=\omega_{r}\left( r\right) \rho(r)$. We will find that Zero Tidal Forces can be imposed at the price of having the function $\omega_{r}\left( r\right) $ divergent for $r\rightarrow\infty$. To overcome this inconvenient, we abandon the request of having Zero Tidal Forces, by introducing appropriate modifications on the function $\omega_{r}\left( r\right) $ in such a way to obtain a finite result everywhere. We will find that such modifications will leave the behavior of the Equation of State close to the throat invariant. Moreover, despite of the initial assumption, we will find that every dark energy profile will be moved into the phantom region. Among the different energy density proposals, only one profile will not require a modification of the original $\omega _{r}\left(r\right) $ to have Zero Tidal Forces. Such an energy density profile will be consistent with the appearance of a Global Monopole. |
2103.11090 | Cosimo Bambi | Bakhtiyor Narzilloev, Javlon Rayimbaev, Ahmadjon Abdujabbarov,
Bobomurat Ahmedov, Cosimo Bambi | Dynamics of charged particles and magnetic dipoles around magnetized
quasi-Schwarzschild black holes | 14 pages, 11 figures. Accepted for publication in EPJC | Eur. Phys. J. C (2021) 81:269 | 10.1140/epjc/s10052-021-09074-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present paper, we have investigated the motion of charged particles
together with magnetic dipoles to determine how well the spacetime deviation
parameter $\epsilon$ and external uniform magnetic field can mimic the spin of
a rotating Kerr black hole. Investigation of charged particle motion has shown
that the deviation parameter $\epsilon$ in the absence of external magnetic
fields can mimic the rotation parameter of Kerr spacetime up to $a/M
\approx0.5$. The combination of external magnetic field and deviation parameter
can do even a better job mimicking the rotation parameter up to
$a/M\simeq0.93$, which corresponds to the rapidly rotating case. Study of the
dynamics of magnetic dipoles around quasi-Schwarzschild black holes in the
external magnetic field has shown that there are degeneracy values of ISCO
radius of test particles at $\epsilon_{cr}>\epsilon\geq 0.35$ which may lead to
two different values of the innermost stable circular orbit (ISCO) radius. When
the deviation parameter is in the range of $\epsilon \in (-1,\ 1)$, it can
mimic the spin of a rotating Kerr black hole in the range $a/M \in (0.0537, \
0.3952)$ for magnetic dipoles with values of magnetic coupling parameter $\beta
\in [-0.25,\ 0.25]$ in corotating orbits.
| [
{
"created": "Sat, 20 Mar 2021 04:22:49 GMT",
"version": "v1"
}
] | 2021-04-06 | [
[
"Narzilloev",
"Bakhtiyor",
""
],
[
"Rayimbaev",
"Javlon",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
],
[
"Ahmedov",
"Bobomurat",
""
],
[
"Bambi",
"Cosimo",
""
]
] | In the present paper, we have investigated the motion of charged particles together with magnetic dipoles to determine how well the spacetime deviation parameter $\epsilon$ and external uniform magnetic field can mimic the spin of a rotating Kerr black hole. Investigation of charged particle motion has shown that the deviation parameter $\epsilon$ in the absence of external magnetic fields can mimic the rotation parameter of Kerr spacetime up to $a/M \approx0.5$. The combination of external magnetic field and deviation parameter can do even a better job mimicking the rotation parameter up to $a/M\simeq0.93$, which corresponds to the rapidly rotating case. Study of the dynamics of magnetic dipoles around quasi-Schwarzschild black holes in the external magnetic field has shown that there are degeneracy values of ISCO radius of test particles at $\epsilon_{cr}>\epsilon\geq 0.35$ which may lead to two different values of the innermost stable circular orbit (ISCO) radius. When the deviation parameter is in the range of $\epsilon \in (-1,\ 1)$, it can mimic the spin of a rotating Kerr black hole in the range $a/M \in (0.0537, \ 0.3952)$ for magnetic dipoles with values of magnetic coupling parameter $\beta \in [-0.25,\ 0.25]$ in corotating orbits. |
gr-qc/0310009 | Matt Visser | A J M Medved, Damien Martin, and Matt Visser | Dirty black holes: Quasinormal modes | 15 pages; uses iopart.cls setstack.sty; V2: one additional reference
added, no physics changes; V3: two extra references, minor changes in
response to referee comments | Class.Quant.Grav. 21 (2004) 1393-1406 | 10.1088/0264-9381/21/6/008 | null | gr-qc | null | In this paper, we investigate the asymptotic nature of the quasinormal modes
for "dirty" black holes -- generic static and spherically symmetric spacetimes
for which a central black hole is surrounded by arbitrary "matter" fields. We
demonstrate that, to the leading asymptotic order, the [imaginary] spacing
between modes is precisely equal to the surface gravity, independent of the
specifics of the black hole system.
Our analytical method is based on locating the complex poles in the first
Born approximation for the scattering amplitude. We first verify that our
formalism agrees, asymptotically, with previous studies on the Schwarzschild
black hole. The analysis is then generalized to more exotic black hole
geometries. We also extend considerations to spacetimes with two horizons and
briefly discuss the degenerate-horizon scenario.
| [
{
"created": "Thu, 2 Oct 2003 06:06:10 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Oct 2003 19:53:35 GMT",
"version": "v2"
},
{
"created": "Wed, 3 Dec 2003 05:55:30 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Medved",
"A J M",
""
],
[
"Martin",
"Damien",
""
],
[
"Visser",
"Matt",
""
]
] | In this paper, we investigate the asymptotic nature of the quasinormal modes for "dirty" black holes -- generic static and spherically symmetric spacetimes for which a central black hole is surrounded by arbitrary "matter" fields. We demonstrate that, to the leading asymptotic order, the [imaginary] spacing between modes is precisely equal to the surface gravity, independent of the specifics of the black hole system. Our analytical method is based on locating the complex poles in the first Born approximation for the scattering amplitude. We first verify that our formalism agrees, asymptotically, with previous studies on the Schwarzschild black hole. The analysis is then generalized to more exotic black hole geometries. We also extend considerations to spacetimes with two horizons and briefly discuss the degenerate-horizon scenario. |
2206.01337 | Maximiliano Ujevic | Henrique Gieg, Federico Schianchi, Tim Dietrich, Maximiliano Ujevic | Incorporating a radiative hydrodynamics scheme in the
numerical-relativity code BAM | 28 pages, 14 figures | Universe 2022, 8(7), 370 | 10.3390/universe8070370 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To study binary neutron star systems and to interpret observational data such
as gravitational-wave and kilonova signals, one needs an accurate description
of the processes that take place during the final stages of the coalescence,
e.g., through numerical-relativity simulations. In this work, we present an
updated version of the numerical-relativity code BAM in order to incorporate
nuclear-theory based Equations of State and a simple description of neutrino
interactions through a Neutrino Leakage Scheme. Different test simulations, for
stars undergoing a neutrino-induced gravitational collapse and for binary
neutron stars systems, validate our new implementation. For the binary neutron
stars systems, we show that we can evolve stably and accurately distinct
microphysical models employing the different equations of state: SFHo, DD2, and
the hyperonic BHB$\Lambda \phi$. Overall, our test simulations have good
agreement with those reported in the literature.
| [
{
"created": "Thu, 2 Jun 2022 23:36:31 GMT",
"version": "v1"
},
{
"created": "Sun, 10 Jul 2022 22:44:25 GMT",
"version": "v2"
}
] | 2022-07-12 | [
[
"Gieg",
"Henrique",
""
],
[
"Schianchi",
"Federico",
""
],
[
"Dietrich",
"Tim",
""
],
[
"Ujevic",
"Maximiliano",
""
]
] | To study binary neutron star systems and to interpret observational data such as gravitational-wave and kilonova signals, one needs an accurate description of the processes that take place during the final stages of the coalescence, e.g., through numerical-relativity simulations. In this work, we present an updated version of the numerical-relativity code BAM in order to incorporate nuclear-theory based Equations of State and a simple description of neutrino interactions through a Neutrino Leakage Scheme. Different test simulations, for stars undergoing a neutrino-induced gravitational collapse and for binary neutron stars systems, validate our new implementation. For the binary neutron stars systems, we show that we can evolve stably and accurately distinct microphysical models employing the different equations of state: SFHo, DD2, and the hyperonic BHB$\Lambda \phi$. Overall, our test simulations have good agreement with those reported in the literature. |
gr-qc/0109086 | Jerome Gariel | J. Gariel, G. Marcilhacy and N. O. Santos | Some Properties of a New Solution of the Ernst Equation | 17 pages, LaTeX, 10 EPS figures, uses graficx.sty | Class.Quant.Grav.19:2157-2170,2002 | 10.1088/0264-9381/19/8/307 | null | gr-qc | null | From a particularly simple solution of the Ernst equation, we build a
solution of the vacuum stationary axisymmetric Einstein equations depending on
three parameters. The parameters are associated to the total mass of the source
and its angular momentum. The third parameter produces a topological
deformation of the ergosphere making it a two-sheet surface, and for some of
its values forbids the Penrose process.
| [
{
"created": "Tue, 25 Sep 2001 16:42:48 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Gariel",
"J.",
""
],
[
"Marcilhacy",
"G.",
""
],
[
"Santos",
"N. O.",
""
]
] | From a particularly simple solution of the Ernst equation, we build a solution of the vacuum stationary axisymmetric Einstein equations depending on three parameters. The parameters are associated to the total mass of the source and its angular momentum. The third parameter produces a topological deformation of the ergosphere making it a two-sheet surface, and for some of its values forbids the Penrose process. |
1509.05679 | Jeremy Sakstein | Jeremy Sakstein, Sarunas Verner | Disformal Gravity Theories: A Jordan Frame Analysis | Updated to reflect published version, results unchanged. 15 pages, 9
figures, 4 tables | Phys. Rev. D 92, 123005 (2015) | 10.1103/PhysRevD.92.123005 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Jordan frame action for general disformal theories is presented and
studied for the first time, motivated by several unresolved mysteries that
arise when working in the Einstein frame. We present the Friedmann equations
and, specialising to exponential functions, study the late-time cosmology using
dynamical systems methods and by finding approximate solutions. Our analysis
reveals that either the disformal effects are irrelevant or the universe
evolves towards a phantom phase where the equation of state of dark energy is
$-3$. There is a marginal case where the asymptotic state of the universe
depends on the model parameters and de-Sitter solutions can be obtained. Our
findings indicate that the metric singularity found using the Einstein frame
construction corresponds phantom behaviour in the Jordan frame and we argue
that this is the case for general disformal theories.
| [
{
"created": "Thu, 17 Sep 2015 09:52:33 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Nov 2015 11:29:13 GMT",
"version": "v2"
},
{
"created": "Wed, 9 Dec 2015 16:34:17 GMT",
"version": "v3"
}
] | 2015-12-23 | [
[
"Sakstein",
"Jeremy",
""
],
[
"Verner",
"Sarunas",
""
]
] | The Jordan frame action for general disformal theories is presented and studied for the first time, motivated by several unresolved mysteries that arise when working in the Einstein frame. We present the Friedmann equations and, specialising to exponential functions, study the late-time cosmology using dynamical systems methods and by finding approximate solutions. Our analysis reveals that either the disformal effects are irrelevant or the universe evolves towards a phantom phase where the equation of state of dark energy is $-3$. There is a marginal case where the asymptotic state of the universe depends on the model parameters and de-Sitter solutions can be obtained. Our findings indicate that the metric singularity found using the Einstein frame construction corresponds phantom behaviour in the Jordan frame and we argue that this is the case for general disformal theories. |
1609.07465 | Andrew DeBenedictis | Andrew DeBenedictis, Sasa Ilijic | The Spherically Symmetric Vacuum in Covariant $F(T) = T +
\frac{\alpha}{2}T^{2} + \mathcal{O}(T^{\gamma})$ Gravity Theory | 13 pages, 4 figures. A Mathematica notebook which calculates the
various quantities required for f(T) gravity is available at
http://sail.zpf.fer.hr/tetradsFofT/ . In v3 some typographical errors have
been fixed in equations (19) and (20). We thank C. Pfeifer, S. Bahamonde, and
K. Flathmann for pointing this out to us. Results are unchanged due to the
purely typographical nature of the issue | Phys. Rev. D 94, 124025 (2016) | 10.1103/PhysRevD.94.124025 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, a fully covariant version of the theory of $F(T)$ torsion gravity
has been introduced (arXiv:1510.08432v2 [gr-qc]). In covariant $F(T)$ gravity
the Schwarzschild solution is not a vacuum solution for $F(T)\neq T$ and
therefore determining the spherically symmetric vacuum is an important open
problem. Within the covariant framework we perturbatively solve the spherically
symmetric vacuum gravitational equations around the Schwarzschild solution for
the scenario with $F(T)=T + (\alpha/2)\, T^{2}$, representing the dominant
terms in theories governed by Lagrangians analytic in the torsion scalar. From
this we compute the perihelion shift correction to solar system planetary
orbits as well as perturbative gravitational effects near neutron stars. This
allows us to set an upper bound on the magnitude of the coupling constant,
$\alpha$, which governs deviations from General Relativity. We find the bound
on this nonlinear torsion coupling constant by specifically considering the
uncertainty in the perihelion shift of Mercury. We also analyze a bound from a
similar comparison with the periastron orbit of the binary pulsar PSR
J0045-7319 as an independent check for consistency. Setting bounds on the
dominant nonlinear coupling is important in determining if other effects in the
solar system or greater universe could be attributable to nonlinear torsion.
| [
{
"created": "Fri, 23 Sep 2016 18:57:02 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Nov 2016 18:43:49 GMT",
"version": "v2"
},
{
"created": "Wed, 31 Jul 2019 21:38:09 GMT",
"version": "v3"
}
] | 2019-08-02 | [
[
"DeBenedictis",
"Andrew",
""
],
[
"Ilijic",
"Sasa",
""
]
] | Recently, a fully covariant version of the theory of $F(T)$ torsion gravity has been introduced (arXiv:1510.08432v2 [gr-qc]). In covariant $F(T)$ gravity the Schwarzschild solution is not a vacuum solution for $F(T)\neq T$ and therefore determining the spherically symmetric vacuum is an important open problem. Within the covariant framework we perturbatively solve the spherically symmetric vacuum gravitational equations around the Schwarzschild solution for the scenario with $F(T)=T + (\alpha/2)\, T^{2}$, representing the dominant terms in theories governed by Lagrangians analytic in the torsion scalar. From this we compute the perihelion shift correction to solar system planetary orbits as well as perturbative gravitational effects near neutron stars. This allows us to set an upper bound on the magnitude of the coupling constant, $\alpha$, which governs deviations from General Relativity. We find the bound on this nonlinear torsion coupling constant by specifically considering the uncertainty in the perihelion shift of Mercury. We also analyze a bound from a similar comparison with the periastron orbit of the binary pulsar PSR J0045-7319 as an independent check for consistency. Setting bounds on the dominant nonlinear coupling is important in determining if other effects in the solar system or greater universe could be attributable to nonlinear torsion. |
1610.08090 | Ritwick Banerjee | Ritwick Banerjee, Ritabrata Biswas | Thermodynamics of black holes in rainbow gravity | 24 pages, 21 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the thermodynamic properties of black holes
under the influence of rainbow gravity. In the metric of Schwarzschild,
Reissner-Nordstrom and Reissner-Nordstrom-de-Sitter black hole surrounded by
quintessence, we consider a rainbow function and derive the existence of
remnant and critical masses of a black hole. Using the Hawking temperature
relation we derive the heat capacity and the entropy of the rainbow gravity
inspired black holes and closely study the relation between entropy and area of
the horizon for different values of n of the rainbow function.
| [
{
"created": "Sun, 23 Oct 2016 11:47:17 GMT",
"version": "v1"
}
] | 2016-10-27 | [
[
"Banerjee",
"Ritwick",
""
],
[
"Biswas",
"Ritabrata",
""
]
] | In this paper, we investigate the thermodynamic properties of black holes under the influence of rainbow gravity. In the metric of Schwarzschild, Reissner-Nordstrom and Reissner-Nordstrom-de-Sitter black hole surrounded by quintessence, we consider a rainbow function and derive the existence of remnant and critical masses of a black hole. Using the Hawking temperature relation we derive the heat capacity and the entropy of the rainbow gravity inspired black holes and closely study the relation between entropy and area of the horizon for different values of n of the rainbow function. |
gr-qc/0603121 | Mohammad Ansari | Mohammad H. Ansari | Generic degeneracy and entropy in loop quantum gravity | 6 pages, 5 figures, and 2 tables. Published in section: Field Theory
And Statistical Systems | Nucl.Phys.B795:635-644,2008 | 10.1016/j.nuclphysb.2007.11.038 | null | gr-qc hep-th | null | Without imposing the trapping boundary conditions and only from within the
very definition of area it is shown that the loop quantization of area
manifests an unexpected degeneracy in area eigenvalues. This could lead to a
deeper understanding of the microscopic description of a quantum black hole. If
a certain number of semi-classically expected properties of black holes are
imposed on a quantum surface its entropy coincides with the Bekenstein-Hawking
entropy.
| [
{
"created": "Thu, 30 Mar 2006 04:59:49 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Dec 2006 17:50:11 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Dec 2006 00:36:44 GMT",
"version": "v3"
},
{
"created": "Thu, 29 Nov 2007 23:08:10 GMT",
"version": "v4"
},
{
"cre... | 2008-11-26 | [
[
"Ansari",
"Mohammad H.",
""
]
] | Without imposing the trapping boundary conditions and only from within the very definition of area it is shown that the loop quantization of area manifests an unexpected degeneracy in area eigenvalues. This could lead to a deeper understanding of the microscopic description of a quantum black hole. If a certain number of semi-classically expected properties of black holes are imposed on a quantum surface its entropy coincides with the Bekenstein-Hawking entropy. |
1605.07038 | Adam Szereszewski | Jerzy Lewandowski, Adam Szereszewski, Piotr Waluk | Spacetimes foliated by non-expanding and Killing horizons: higher
dimension | 19 pages | Phys. Rev. D 94, 064018 (2016) | 10.1103/PhysRevD.94.064018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The theory of non-expanding horizons (NEH) geometry and the theory of near
horizon geometries (NHG) are two mathematical relativity frameworks
generalizing the black hole theory. From the point of view of the NEHs theory,
a NHG is just a very special case of a spacetime containing an NEH of many
extra symmetries. It can be obtained as the Horowitz limit of a neighborhood of
an arbitrary extremal Killing horizon. An unexpected relation between the two
of them, was discovered in the study of spacetimes foliated by a family of
NEHs. The class of 4-dimensional NHG solutions (either vacuum or coupled to a
Maxwell field) was found as a family of examples of spacetimes admitting a NEH
foliation. In the current paper we systematically investigate geometries of the
NEHs foliating a spacetime for arbitrary matter content and in arbitrary
spacetime dimension. We find that each horizon belonging to the foliation
satisfies a condition that may be interpreted as an invitation for a
transversal extremal Killing horizon to exist. Assuming the existence of a
transversal extremal Killing horizon, we derive all the spacetime metrics
satisfying the vacuum Einstein's equations.
| [
{
"created": "Mon, 23 May 2016 14:44:33 GMT",
"version": "v1"
}
] | 2016-09-14 | [
[
"Lewandowski",
"Jerzy",
""
],
[
"Szereszewski",
"Adam",
""
],
[
"Waluk",
"Piotr",
""
]
] | The theory of non-expanding horizons (NEH) geometry and the theory of near horizon geometries (NHG) are two mathematical relativity frameworks generalizing the black hole theory. From the point of view of the NEHs theory, a NHG is just a very special case of a spacetime containing an NEH of many extra symmetries. It can be obtained as the Horowitz limit of a neighborhood of an arbitrary extremal Killing horizon. An unexpected relation between the two of them, was discovered in the study of spacetimes foliated by a family of NEHs. The class of 4-dimensional NHG solutions (either vacuum or coupled to a Maxwell field) was found as a family of examples of spacetimes admitting a NEH foliation. In the current paper we systematically investigate geometries of the NEHs foliating a spacetime for arbitrary matter content and in arbitrary spacetime dimension. We find that each horizon belonging to the foliation satisfies a condition that may be interpreted as an invitation for a transversal extremal Killing horizon to exist. Assuming the existence of a transversal extremal Killing horizon, we derive all the spacetime metrics satisfying the vacuum Einstein's equations. |
2001.07728 | Jose Natario | Anne T. Franzen and Jos\'e Nat\'ario | Linear relativistic thermoelastic rod | 19 pages, no figures | J. Hyperbolic Differ. Equ. 17 (2020) 863-882 | 10.1142/S0219891620500289 | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive and analyze the linearized hyperbolic equations describing a
relativistic heat-conducting elastic rod. We construct a decreasing energy
integral for these equations, compute the associated characteristic propagation
speeds, and prove that the solutions decay in time by using a Fourier
decomposition. For comparison purposes, we obtain analogous results for the
classical system with heat waves, in which the finite propagation speed of heat
is kept but the other relativistic terms are neglected, and also for the usual
classical system.
| [
{
"created": "Tue, 21 Jan 2020 19:00:10 GMT",
"version": "v1"
}
] | 2021-02-09 | [
[
"Franzen",
"Anne T.",
""
],
[
"Natário",
"José",
""
]
] | We derive and analyze the linearized hyperbolic equations describing a relativistic heat-conducting elastic rod. We construct a decreasing energy integral for these equations, compute the associated characteristic propagation speeds, and prove that the solutions decay in time by using a Fourier decomposition. For comparison purposes, we obtain analogous results for the classical system with heat waves, in which the finite propagation speed of heat is kept but the other relativistic terms are neglected, and also for the usual classical system. |
gr-qc/9705075 | Mike Cassidy | M. J. Cassidy | Divergences in the Effective Action for Acausal Spacetimes | 17 pages, Latex | Class.Quant.Grav. 14 (1997) 3031-3040 | 10.1088/0264-9381/14/11/006 | DAMTP/R-97/24 | gr-qc | null | The 1--loop effective Lagrangian for a massive scalar field on an arbitrary
causality violating spacetime is calculated using the methods of Euclidean
quantum field theory in curved spacetime. Fields of spin 1/2, spin 1 and
twisted field configurations are also considered. In general, we find that the
Lagrangian diverges to minus infinity at each of the nth polarised
hypersurfaces of the spacetime with a structure governed by a DeWitt-Schwinger
type expansion.
| [
{
"created": "Wed, 28 May 1997 11:00:00 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Cassidy",
"M. J.",
""
]
] | The 1--loop effective Lagrangian for a massive scalar field on an arbitrary causality violating spacetime is calculated using the methods of Euclidean quantum field theory in curved spacetime. Fields of spin 1/2, spin 1 and twisted field configurations are also considered. In general, we find that the Lagrangian diverges to minus infinity at each of the nth polarised hypersurfaces of the spacetime with a structure governed by a DeWitt-Schwinger type expansion. |
1110.2965 | Michael Boyle | Michael Boyle, Robert Owen, and Harald P. Pfeiffer | A geometric approach to the precession of compact binaries | Minor clarifications and journal reference | Phys. Rev. D 84, 124011 (2011) | 10.1103/PhysRevD.84.124011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a geometrical method to define a preferred reference frame for
precessing binary systems and the gravitational waves they emit. This
minimal-rotation frame is aligned with the angular-momentum axis and fixes the
rotation about that axis up to a constant angle, resulting in an essentially
invariant frame. Gravitational waveforms decomposed in this frame are similarly
invariant under rotations of the inertial frame and exhibit relatively smoothly
varying phase. By contrast, earlier prescriptions for radiation-aligned frames
induce extraneous features in the gravitational-wave phase which depend on the
orientation of the inertial frame, leading to fluctuations in the frequency
that may compound to many gravitational-wave cycles. We explore a simplified
description of post-Newtonian approximations for precessing systems using the
minimal-rotation frame, and describe the construction of analytical/numerical
hybrid waveforms for such systems.
| [
{
"created": "Thu, 13 Oct 2011 14:43:43 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Oct 2011 15:48:09 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Feb 2012 15:21:14 GMT",
"version": "v3"
}
] | 2012-02-02 | [
[
"Boyle",
"Michael",
""
],
[
"Owen",
"Robert",
""
],
[
"Pfeiffer",
"Harald P.",
""
]
] | We discuss a geometrical method to define a preferred reference frame for precessing binary systems and the gravitational waves they emit. This minimal-rotation frame is aligned with the angular-momentum axis and fixes the rotation about that axis up to a constant angle, resulting in an essentially invariant frame. Gravitational waveforms decomposed in this frame are similarly invariant under rotations of the inertial frame and exhibit relatively smoothly varying phase. By contrast, earlier prescriptions for radiation-aligned frames induce extraneous features in the gravitational-wave phase which depend on the orientation of the inertial frame, leading to fluctuations in the frequency that may compound to many gravitational-wave cycles. We explore a simplified description of post-Newtonian approximations for precessing systems using the minimal-rotation frame, and describe the construction of analytical/numerical hybrid waveforms for such systems. |
1004.1798 | Lorenzo Iorio | Lorenzo Iorio | Solar system constraints on planetary Coriolis-type effects induced by
rotation of distant masses | LaTex2e, 22 pages, 4 tables, no figures. Part on the Oort cloud
restored. Reference updated. Accepted for publication in Journal of Cosmology
and Astroparticle Physics (JCAP) | JCAP 1008:030,2010 | 10.1088/1475-7516/2010/08/030 | null | gr-qc astro-ph.CO astro-ph.EP physics.gen-ph physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We phenomenologically put local constraints on the rotation of distant masses
by using the planets of the solar system. First, we analytically compute the
orbital secular precessions induced on the motion of a test particle about a
massive primary by a Coriolis-like force, treated as a small perturbation of
first order in the rotation, in the case of a constant angular velocity vector
\Psi directed along a generic direction in space. The semimajor axis a and the
eccentricity e of the test particle do not secularly precess, contrary to the
inclination I, the longitude of the ascending node \Omega, the longitude of the
pericenter \varpi and the mean anomaly M. Then, we compare our prediction for
<\dot\varpi> with the corrections \Delta\dot\varpi to the usual perihelion
precessions of the inner planets recently estimated by fitting long data sets
with different versions of the EPM ephemerides. We obtain |\Psi_z| <=
0.0006-0.013 arcsec cty^-1, |\Psi_x| <= 0.1-2.7 arcsec cty-1, |\Psi_y| <=
0.3-2.3 arcsec cty^-1. Interpreted in terms of models of space-time involving
cosmic rotation, our results are able to yield constraints on cosmological
parameters like the cosmological constant \Lambda and the Hubble parameter H_0
not too far from their values determined with cosmological observations and, in
some cases, several orders of magnitude better than the constraints usually
obtained so far from space-time models not involving rotation. In the case of
the rotation of the solar system throughout the Galaxy, occurring clockwise
about the North Galactic Pole, our results for \Psi_z are in disagreement with
the expected value of it at more than 3-\sigma level.
| [
{
"created": "Sun, 11 Apr 2010 11:36:27 GMT",
"version": "v1"
},
{
"created": "Tue, 25 May 2010 15:52:22 GMT",
"version": "v2"
},
{
"created": "Wed, 26 May 2010 13:54:12 GMT",
"version": "v3"
},
{
"created": "Fri, 6 Aug 2010 13:37:38 GMT",
"version": "v4"
}
] | 2011-03-28 | [
[
"Iorio",
"Lorenzo",
""
]
] | We phenomenologically put local constraints on the rotation of distant masses by using the planets of the solar system. First, we analytically compute the orbital secular precessions induced on the motion of a test particle about a massive primary by a Coriolis-like force, treated as a small perturbation of first order in the rotation, in the case of a constant angular velocity vector \Psi directed along a generic direction in space. The semimajor axis a and the eccentricity e of the test particle do not secularly precess, contrary to the inclination I, the longitude of the ascending node \Omega, the longitude of the pericenter \varpi and the mean anomaly M. Then, we compare our prediction for <\dot\varpi> with the corrections \Delta\dot\varpi to the usual perihelion precessions of the inner planets recently estimated by fitting long data sets with different versions of the EPM ephemerides. We obtain |\Psi_z| <= 0.0006-0.013 arcsec cty^-1, |\Psi_x| <= 0.1-2.7 arcsec cty-1, |\Psi_y| <= 0.3-2.3 arcsec cty^-1. Interpreted in terms of models of space-time involving cosmic rotation, our results are able to yield constraints on cosmological parameters like the cosmological constant \Lambda and the Hubble parameter H_0 not too far from their values determined with cosmological observations and, in some cases, several orders of magnitude better than the constraints usually obtained so far from space-time models not involving rotation. In the case of the rotation of the solar system throughout the Galaxy, occurring clockwise about the North Galactic Pole, our results for \Psi_z are in disagreement with the expected value of it at more than 3-\sigma level. |
gr-qc/0101113 | Giovanni Montani | G. Montani (ICRA - Phys. Dept. - University of Rome "La Sapienza") | Influence of the Particles Creation on the Flat and Negative Curved FLRW
Universes | 14 pages, no figures, appeared in Class. Quantum Grav., 18, 193, 2001 | Class.Quant.Grav. 18 (2001) 193-203 | 10.1088/0264-9381/18/1/311 | null | gr-qc | null | We present a dynamical analysis of the (classical) spatially flat and
negative curved Friedmann-Lameitre-Robertson-Walker (FLRW) universes evolving,
(by assumption) close to the thermodynamic equilibrium, in presence of a
particles creation process, described by means of a realiable phenomenological
approach, based on the application to the comoving volume (i. e. spatial volume
of unit comoving coordinates) of the theory for open thermodynamic systems. In
particular we show how, since the particles creation phenomenon induces a
negative pressure term, then the choice of a well-grounded ansatz for the time
variation of the particles number, leads to a deep modification of the very
early standard FLRW dynamics. More precisely for the considered FLRW models, we
find (in addition to the limiting case of their standard behaviours) solutions
corresponding to an early universe characterized respectively by an "eternal"
inflationary-like birth and a spatial curvature dominated singularity. In both
these cases the so-called horizon problem finds a natural solution.
| [
{
"created": "Mon, 29 Jan 2001 19:02:08 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Montani",
"G.",
"",
"ICRA - Phys. Dept. - University of Rome \"La Sapienza\""
]
] | We present a dynamical analysis of the (classical) spatially flat and negative curved Friedmann-Lameitre-Robertson-Walker (FLRW) universes evolving, (by assumption) close to the thermodynamic equilibrium, in presence of a particles creation process, described by means of a realiable phenomenological approach, based on the application to the comoving volume (i. e. spatial volume of unit comoving coordinates) of the theory for open thermodynamic systems. In particular we show how, since the particles creation phenomenon induces a negative pressure term, then the choice of a well-grounded ansatz for the time variation of the particles number, leads to a deep modification of the very early standard FLRW dynamics. More precisely for the considered FLRW models, we find (in addition to the limiting case of their standard behaviours) solutions corresponding to an early universe characterized respectively by an "eternal" inflationary-like birth and a spatial curvature dominated singularity. In both these cases the so-called horizon problem finds a natural solution. |
1905.10509 | Oleg Tsupko | Oleg Yu. Tsupko, Zuhui Fan, and Gennady S. Bisnovatyi-Kogan | Black hole shadow as a standard ruler in cosmology | null | Classical and Quantum Gravity, 37, 065016 (2020) | 10.1088/1361-6382/ab6f7d | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Advancements in the black hole shadow observations may allow us not only to
investigate physics in the strong gravity regime, but also to use them in
cosmological studies. In this paper, we propose to use the shadow of
supermassive black holes as a standard ruler for cosmological applications
assuming the black hole mass can be determined independently. First,
observations at low redshift distances can be used to constrain the Hubble
constant independently. Secondly, the angular size of shadows of high redshift
black holes is increased due to cosmic expansion and may also be reachable with
future observations. This would allow us to probe the cosmic expansion history
for the redshift range elusive to other distance measurements. Additionally,
shadow can be used to estimate the mass of black holes at high redshift,
assuming that cosmology is known.
| [
{
"created": "Sat, 25 May 2019 03:31:38 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Aug 2019 09:49:11 GMT",
"version": "v2"
},
{
"created": "Thu, 20 Feb 2020 15:40:09 GMT",
"version": "v3"
}
] | 2020-02-21 | [
[
"Tsupko",
"Oleg Yu.",
""
],
[
"Fan",
"Zuhui",
""
],
[
"Bisnovatyi-Kogan",
"Gennady S.",
""
]
] | Advancements in the black hole shadow observations may allow us not only to investigate physics in the strong gravity regime, but also to use them in cosmological studies. In this paper, we propose to use the shadow of supermassive black holes as a standard ruler for cosmological applications assuming the black hole mass can be determined independently. First, observations at low redshift distances can be used to constrain the Hubble constant independently. Secondly, the angular size of shadows of high redshift black holes is increased due to cosmic expansion and may also be reachable with future observations. This would allow us to probe the cosmic expansion history for the redshift range elusive to other distance measurements. Additionally, shadow can be used to estimate the mass of black holes at high redshift, assuming that cosmology is known. |
1210.5505 | Martin Richarte MR | Luis P. Chimento and Mart\'in G. Richarte | Dark matter, dark energy, and dark radiation coupled with a transversal
interaction | 9 pages, 4 figures. Accepted for publication in Physical Review D | Phys. Rev. D 86, 103501 (2012) | 10.1103/PhysRevD.86.103501 | Phys. Rev. D 86, 103501 (2012) | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate a cosmological scenario with three interacting components that
includes dark matter, dark energy, and radiation in the spatially flat
Friedmann-Robertson-Walker universe. We introduce a 3-dimensional internal
space, the interaction vector $\mathbf{Q}=(Q_{x}, Q_{m}, Q_{r})$ satisfying the
constraint plane $Q_{x}+ Q_{m}+ Q_{r}=0$, the barotropic index vector $
\boldmath ${\gamma}$=(\ga_x,\ga_m,\ga_r)$ and select a transversal interaction
vector $\mathbf{Q_t}$ in a sense that $\mathbf{Q_t}\cdot \boldmath
${\gamma}$=0$. We exactly solve the source equation for a linear
$\mathbf{Q_t}$, that depends on the total energy density and its derivatives up
to third order, and find all the component energy densities. We obtain a large
set of interactions for which the source equation admits a power law solution
and show its asymptotic stability by constructing the Lyapunov function. We
apply the $\chi^{2}$ method to the observational Hubble data for constraining
the cosmic parameters, and analyze the amount of dark energy in the radiation
era for the above linear $\mathbf{Q_t}$. It turns to be that our model fulfills
the severe bound of $\Omega_{x}(z\simeq 1100)<0.1$ and is consistent with the
future constraints achievable by Planck and CMBPol experiments.
| [
{
"created": "Fri, 19 Oct 2012 19:32:25 GMT",
"version": "v1"
}
] | 2013-04-02 | [
[
"Chimento",
"Luis P.",
""
],
[
"Richarte",
"Martín G.",
""
]
] | We investigate a cosmological scenario with three interacting components that includes dark matter, dark energy, and radiation in the spatially flat Friedmann-Robertson-Walker universe. We introduce a 3-dimensional internal space, the interaction vector $\mathbf{Q}=(Q_{x}, Q_{m}, Q_{r})$ satisfying the constraint plane $Q_{x}+ Q_{m}+ Q_{r}=0$, the barotropic index vector $ \boldmath ${\gamma}$=(\ga_x,\ga_m,\ga_r)$ and select a transversal interaction vector $\mathbf{Q_t}$ in a sense that $\mathbf{Q_t}\cdot \boldmath ${\gamma}$=0$. We exactly solve the source equation for a linear $\mathbf{Q_t}$, that depends on the total energy density and its derivatives up to third order, and find all the component energy densities. We obtain a large set of interactions for which the source equation admits a power law solution and show its asymptotic stability by constructing the Lyapunov function. We apply the $\chi^{2}$ method to the observational Hubble data for constraining the cosmic parameters, and analyze the amount of dark energy in the radiation era for the above linear $\mathbf{Q_t}$. It turns to be that our model fulfills the severe bound of $\Omega_{x}(z\simeq 1100)<0.1$ and is consistent with the future constraints achievable by Planck and CMBPol experiments. |
1609.01227 | Cesar Merlin | Cesar Merlin, Amos Ori, Leor Barack, Adam Pound, Maarten van de Meent | Completion of metric reconstruction for a particle orbiting a Kerr black
hole | 27 pages, Minor typos corrected | Phys. Rev. D 94, 104066 (2016) | 10.1103/PhysRevD.94.104066 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Vacuum perturbations of the Kerr metric can be reconstructed from the
corresponding perturbation in either of the two Weyl scalars $\psi_0$ or
$\psi_4$, using a procedure described by Chrzanowski and others in the 1970s.
More recent work, motivated within the context of self-force physics, extends
the procedure to metric perturbations sourced by a particle in a bound geodesic
orbit. However, the existing procedure leaves undetermined a certain
stationary, axially-symmetric piece of the metric perturbation. In the vacuum
region away from the particle, this "completion" piece corresponds simply to
mass and angular-momentum perturbations of the Kerr background, with amplitudes
that are, however, a priori unknown. Here we present and implement a rigorous
method for finding the completion piece. The key idea is to impose continuity,
off the particle, of certain gauge-invariant fields constructed from the full
(completed) perturbation, in order to determine the unknown amplitude
parameters of the completion piece. We implement this method in full for bound
(eccentric) geodesic orbits in the equatorial plane of the Kerr black hole. Our
results provide a rigorous underpinning of recent results by Friedman {\it et
al.}\ for circular orbits, and extend them to non-circular orbits.
| [
{
"created": "Mon, 5 Sep 2016 17:29:30 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Sep 2016 15:34:51 GMT",
"version": "v2"
},
{
"created": "Mon, 5 Dec 2016 11:59:19 GMT",
"version": "v3"
}
] | 2016-12-06 | [
[
"Merlin",
"Cesar",
""
],
[
"Ori",
"Amos",
""
],
[
"Barack",
"Leor",
""
],
[
"Pound",
"Adam",
""
],
[
"van de Meent",
"Maarten",
""
]
] | Vacuum perturbations of the Kerr metric can be reconstructed from the corresponding perturbation in either of the two Weyl scalars $\psi_0$ or $\psi_4$, using a procedure described by Chrzanowski and others in the 1970s. More recent work, motivated within the context of self-force physics, extends the procedure to metric perturbations sourced by a particle in a bound geodesic orbit. However, the existing procedure leaves undetermined a certain stationary, axially-symmetric piece of the metric perturbation. In the vacuum region away from the particle, this "completion" piece corresponds simply to mass and angular-momentum perturbations of the Kerr background, with amplitudes that are, however, a priori unknown. Here we present and implement a rigorous method for finding the completion piece. The key idea is to impose continuity, off the particle, of certain gauge-invariant fields constructed from the full (completed) perturbation, in order to determine the unknown amplitude parameters of the completion piece. We implement this method in full for bound (eccentric) geodesic orbits in the equatorial plane of the Kerr black hole. Our results provide a rigorous underpinning of recent results by Friedman {\it et al.}\ for circular orbits, and extend them to non-circular orbits. |
2303.02765 | Craig J. Hogan | Craig Hogan, Stephan S. Meyer, Nathaniel Selub, and Frederick Wehlen | Angular correlations on causally-coherent inflationary horizons | null | null | 10.1088/1361-6382/ace608 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a model for correlations of cosmic microwave background anisotropy
on the largest angular scales, based on standard causal geometrical
relationships in slow-roll inflation. Unlike standard models based on quantized
field modes, it describes perturbations with nonlocal directional coherence on
spherical boundaries of causal diamonds. Causal constraints reduce the number
of independent degrees of freedom, impose new angular symmetries, and eliminate
cosmic variance for purely angular 2-point correlations. Distortions of causal
structure from vacuum fluctuations are modeled as gravitational memory from
randomly oriented outgoing and incoming gravitational null shocks, with
nonlocally coherent directional displacements on curved surfaces of causal
diamonds formed by standard inflationary horizons. The angular distribution is
determined by axially symmetric shock displacements on circular intersections
of the comoving sphere that represents the CMB photosphere with other
inflationary horizons. Displacements on thin spheres at the end of inflation
have a unique angular power spectrum $C_\ell$ that approximates the standard
expectation on small angular scales, but differs substantially at large angular
scales due to horizon curvature. For a thin sphere, the model predicts a
universal angular correlation function $C(\Theta)$ with an exact ``causal
shadow'' symmetry, $C(\pi/4<\Theta<3\pi/4)= 0$, and significant large-angle
parity violation. We apply a rank statistic to compare models with WMAP and
Planck satellite data, and find that a causally-coherent model with no shape
parameters or cosmic variance agrees with the measured $C(\Theta)$ better than
a large fraction ($> 0.9999$) of standard model realizations. Model-independent
tests of holographic causal symmetries are proposed.
| [
{
"created": "Sun, 5 Mar 2023 20:11:54 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Jun 2023 18:20:10 GMT",
"version": "v2"
}
] | 2023-08-02 | [
[
"Hogan",
"Craig",
""
],
[
"Meyer",
"Stephan S.",
""
],
[
"Selub",
"Nathaniel",
""
],
[
"Wehlen",
"Frederick",
""
]
] | We develop a model for correlations of cosmic microwave background anisotropy on the largest angular scales, based on standard causal geometrical relationships in slow-roll inflation. Unlike standard models based on quantized field modes, it describes perturbations with nonlocal directional coherence on spherical boundaries of causal diamonds. Causal constraints reduce the number of independent degrees of freedom, impose new angular symmetries, and eliminate cosmic variance for purely angular 2-point correlations. Distortions of causal structure from vacuum fluctuations are modeled as gravitational memory from randomly oriented outgoing and incoming gravitational null shocks, with nonlocally coherent directional displacements on curved surfaces of causal diamonds formed by standard inflationary horizons. The angular distribution is determined by axially symmetric shock displacements on circular intersections of the comoving sphere that represents the CMB photosphere with other inflationary horizons. Displacements on thin spheres at the end of inflation have a unique angular power spectrum $C_\ell$ that approximates the standard expectation on small angular scales, but differs substantially at large angular scales due to horizon curvature. For a thin sphere, the model predicts a universal angular correlation function $C(\Theta)$ with an exact ``causal shadow'' symmetry, $C(\pi/4<\Theta<3\pi/4)= 0$, and significant large-angle parity violation. We apply a rank statistic to compare models with WMAP and Planck satellite data, and find that a causally-coherent model with no shape parameters or cosmic variance agrees with the measured $C(\Theta)$ better than a large fraction ($> 0.9999$) of standard model realizations. Model-independent tests of holographic causal symmetries are proposed. |
2407.18084 | Filippo Bouch\`e | Filippo Bouch\`e, Salvatore Capozziello, Ciro De Simone, Vincenzo
Salzano | Testing non-local gravity through Ultra-Diffuse Galaxies kinematics | null | Physics of the Dark Universe 46, 101579 (2024) | 10.1016/j.dark.2024.101579 | null | gr-qc astro-ph.CO astro-ph.GA hep-th | http://creativecommons.org/licenses/by-nc-nd/4.0/ | The emergence of the Ultra-Diffuse Galaxies in recent years has posed a
severe challenge to the galaxy formation models as well as the Extended
Theories of Gravity. The existence of both dark matter lacking and dark matter
dominated systems within the same family of astrophysical objects indeed
requires the gravity models to be versatile enough to describe very different
gravitational regimes. In this work, we study a non-local extension of the
theory of General Relativity that has drawn increasing attention in recent
years due to its capability to account for the late time cosmic acceleration
without introducing any dark energy fluid. We leverage the kinematic data of
three Ultra-Diffuse Galaxies: NGC 1052-DF2 and NGC 1052-DF4, which are dark
matter lacking, and Dragonfly 44, which exhibits a highly dominant dark matter
component. Our analysis shows that the non-local corrections to the Newtonian
potential do not affect the kinematic predictions, hence no spoiling effects
emerge when the Non-local Gravity model serves as a dark energy model. We
additionally provide the minimum value that the characteristic non-local radii
can reach at these mass scales.
| [
{
"created": "Thu, 25 Jul 2024 14:47:18 GMT",
"version": "v1"
}
] | 2024-07-26 | [
[
"Bouchè",
"Filippo",
""
],
[
"Capozziello",
"Salvatore",
""
],
[
"De Simone",
"Ciro",
""
],
[
"Salzano",
"Vincenzo",
""
]
] | The emergence of the Ultra-Diffuse Galaxies in recent years has posed a severe challenge to the galaxy formation models as well as the Extended Theories of Gravity. The existence of both dark matter lacking and dark matter dominated systems within the same family of astrophysical objects indeed requires the gravity models to be versatile enough to describe very different gravitational regimes. In this work, we study a non-local extension of the theory of General Relativity that has drawn increasing attention in recent years due to its capability to account for the late time cosmic acceleration without introducing any dark energy fluid. We leverage the kinematic data of three Ultra-Diffuse Galaxies: NGC 1052-DF2 and NGC 1052-DF4, which are dark matter lacking, and Dragonfly 44, which exhibits a highly dominant dark matter component. Our analysis shows that the non-local corrections to the Newtonian potential do not affect the kinematic predictions, hence no spoiling effects emerge when the Non-local Gravity model serves as a dark energy model. We additionally provide the minimum value that the characteristic non-local radii can reach at these mass scales. |
0904.1960 | David Delphenich | D. H. Delphenich | On the pre-metric foundations of wave mechanics I: massless waves | 25 pages, 1 figure | Annalen Phys.18:206-230,2009 | 10.1002/andp.200810343 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The mechanics of wave motion in a medium are founded in conservation laws for
the physical quantities that the waves carry, combined with the constitutive
laws of the medium, and define Lorentzian structures only in degenerate cases
of the dispersion laws that follow from the field equations. It is suggested
that the transition from wave motion to point motion is best factored into an
intermediate step of extended matter motion, which then makes the
dimension-codimension duality of waves and trajectories a natural consequence
of the bicharacteristic (geodesic) foliation associated with the dispersion
law. This process is illustrated in the conventional case of quadratic
dispersion, as well as quartic ones, which include the Heisenberg-Euler
dispersion law. It is suggested that the contributions to geodesic motion from
the non-quadratic nature of a dispersion law might represent another source of
quantum fluctuations about classical extremals, in addition to the diffraction
effects that are left out by the geometrical optics approximation.
| [
{
"created": "Mon, 13 Apr 2009 15:54:58 GMT",
"version": "v1"
}
] | 2009-09-28 | [
[
"Delphenich",
"D. H.",
""
]
] | The mechanics of wave motion in a medium are founded in conservation laws for the physical quantities that the waves carry, combined with the constitutive laws of the medium, and define Lorentzian structures only in degenerate cases of the dispersion laws that follow from the field equations. It is suggested that the transition from wave motion to point motion is best factored into an intermediate step of extended matter motion, which then makes the dimension-codimension duality of waves and trajectories a natural consequence of the bicharacteristic (geodesic) foliation associated with the dispersion law. This process is illustrated in the conventional case of quadratic dispersion, as well as quartic ones, which include the Heisenberg-Euler dispersion law. It is suggested that the contributions to geodesic motion from the non-quadratic nature of a dispersion law might represent another source of quantum fluctuations about classical extremals, in addition to the diffraction effects that are left out by the geometrical optics approximation. |
1408.2182 | Jaedong Choi | Jaedong Choi | Anisotropy universe in doubly warped product scheme | arXiv admin note: substantial text overlap with arXiv:1306.3020; and
text overlap with arXiv:gr-qc/0410090 by other authors | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the GMGHS spacetimes to analyze the evolution of the anisotropy
universe, which can be treated as a doubly warped products manifold possessing
warping functions (or scale factor) having the Kantowski-Sachs solution which
represents homogeneous but anisotropically expanding(contracting) cosmology. We
investigate the curvature associated with three phases in the evolution of the
universe.
| [
{
"created": "Sun, 10 Aug 2014 03:38:01 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Jul 2015 05:43:22 GMT",
"version": "v2"
},
{
"created": "Wed, 6 Jan 2016 11:51:34 GMT",
"version": "v3"
},
{
"created": "Mon, 11 Jan 2016 06:36:22 GMT",
"version": "v4"
}
] | 2016-01-12 | [
[
"Choi",
"Jaedong",
""
]
] | We study the GMGHS spacetimes to analyze the evolution of the anisotropy universe, which can be treated as a doubly warped products manifold possessing warping functions (or scale factor) having the Kantowski-Sachs solution which represents homogeneous but anisotropically expanding(contracting) cosmology. We investigate the curvature associated with three phases in the evolution of the universe. |
1801.03757 | Juho Lankinen | Juho Lankinen and Iiro Vilja | Decaying Massive Particle in Matter and Radiation Dominated Eras | 6 pages, 2 figures | Phys. Rev. D 97, 065004 (2018) | 10.1103/PhysRevD.97.065004 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | According to the standard model of cosmology, the early universe has been
dominated by radiation or non-relativistic matter in several eras of its
history. However, many cosmological calculations involving particle processes
are commonly done using Minkowskian results for them, although, for more
precise treatment, quantum field theory in curved spacetime is needed. This
paper aims to fill this gap by presenting decay rates for matter and radiation
dominated universes in this more precise treatment. We provide a study of the
average decay rates for a process where a conformally coupled massive scalar
field decays into massless scalar particles. It is found that the presence of a
curved spacetime modifies the Minkowskian result considerably for early times
but asymptotically only by an additive term proportional to the inverse of mass
and interaction time. Thus, the correction is small for large time scales, but
on the time scales of the order of $m\sim t$, the relative correction term may
be of importance.
| [
{
"created": "Thu, 11 Jan 2018 13:47:42 GMT",
"version": "v1"
}
] | 2018-03-12 | [
[
"Lankinen",
"Juho",
""
],
[
"Vilja",
"Iiro",
""
]
] | According to the standard model of cosmology, the early universe has been dominated by radiation or non-relativistic matter in several eras of its history. However, many cosmological calculations involving particle processes are commonly done using Minkowskian results for them, although, for more precise treatment, quantum field theory in curved spacetime is needed. This paper aims to fill this gap by presenting decay rates for matter and radiation dominated universes in this more precise treatment. We provide a study of the average decay rates for a process where a conformally coupled massive scalar field decays into massless scalar particles. It is found that the presence of a curved spacetime modifies the Minkowskian result considerably for early times but asymptotically only by an additive term proportional to the inverse of mass and interaction time. Thus, the correction is small for large time scales, but on the time scales of the order of $m\sim t$, the relative correction term may be of importance. |
1805.08156 | Mauricio Bellini | Luis Santiago Ridao, Marcos Ramiro Alfredo Arcod\'iia, Jes\'us
Mart\'in Romero, Mauricio Bellini (IFIMAR - CONICET & UNMdP) | Inflationary gravitational waves from unified spinor fields | Version accepted in Eur. Phys. J. Plus | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent observations of Gravitational Waves (GW) generated by black-hole
collisions have opened a new window to explore the universe in diverse scales.
Detection of primordial gravitational waves is expected to happen in the next
years. However, the standard theory to describe these effects was developed for
weak gravitational waves, when their dynamics can be linearized. In this work
we develop a non-perturbative formalism to describe GW using the Unified Spinor
Fields (USF) theory. The tensor index is calculated and we obtain that it must
be $0.0283 <n_T < 0.0407$, in order for the $+$ and $\times$ polarisations
modes to have the same spectrum. This imposes some restriction on the constant
of self-interaction $3.0018\,<\,\xi^2\,< \,3.0025$ of the fermionic source. The
most relevant result here obtained is that the intensity of energy density for
GW during inflation is $1.25\times 10^{-4} \left(\frac{m}{H}\right)^2 \, <
\,\Omega_{GW} \, < \,1.75\times 10^{-4} \left(\frac{m}{H}\right)^2$, where $m$
is the mass of the $1/2$-spin fermionic fields and $H$ the Hubble parameter
during inflation. This cut imposes restrictions on the mass of these fields:
$\left({m\over H}\right)^2\lesssim 1.1\,h_0^2\times 10^{-11}$.
| [
{
"created": "Mon, 21 May 2018 16:20:44 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Sep 2018 00:04:30 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Oct 2018 16:04:53 GMT",
"version": "v3"
},
{
"created": "Fri, 2 Nov 2018 16:22:46 GMT",
"version": "v4"
}
] | 2018-11-05 | [
[
"Ridao",
"Luis Santiago",
"",
"IFIMAR - CONICET & UNMdP"
],
[
"Arcodíia",
"Marcos Ramiro Alfredo",
"",
"IFIMAR - CONICET & UNMdP"
],
[
"Romero",
"Jesús Martín",
"",
"IFIMAR - CONICET & UNMdP"
],
[
"Bellini",
"Mauricio",
"",
"IFIMAR - CONI... | Recent observations of Gravitational Waves (GW) generated by black-hole collisions have opened a new window to explore the universe in diverse scales. Detection of primordial gravitational waves is expected to happen in the next years. However, the standard theory to describe these effects was developed for weak gravitational waves, when their dynamics can be linearized. In this work we develop a non-perturbative formalism to describe GW using the Unified Spinor Fields (USF) theory. The tensor index is calculated and we obtain that it must be $0.0283 <n_T < 0.0407$, in order for the $+$ and $\times$ polarisations modes to have the same spectrum. This imposes some restriction on the constant of self-interaction $3.0018\,<\,\xi^2\,< \,3.0025$ of the fermionic source. The most relevant result here obtained is that the intensity of energy density for GW during inflation is $1.25\times 10^{-4} \left(\frac{m}{H}\right)^2 \, < \,\Omega_{GW} \, < \,1.75\times 10^{-4} \left(\frac{m}{H}\right)^2$, where $m$ is the mass of the $1/2$-spin fermionic fields and $H$ the Hubble parameter during inflation. This cut imposes restrictions on the mass of these fields: $\left({m\over H}\right)^2\lesssim 1.1\,h_0^2\times 10^{-11}$. |
1611.05832 | Ezequiel Boero | Ezequiel F. Boero and Osvaldo M. Moreschi | Geometrical models for the study of astrophysical systems with
spheroidal symmetry imbedded in a standard cosmology: The case of cosmic
voids | 10 pages, 7 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a class of general prolate and oblate spheroidal spacetimes for
the description of cosmic structures in the Universe. They are exact geometries
which represent, in an appropriated way, the imbedding of spheroidal
matter-energy distributions within a standard cosmological scenario, and
therefore they allow for an improved description of a wider class of
astrophysical systems from a more accurate point of view. These spacetimes can
be used to describe overdensity or underdensity regions; in this work we
consider the last case, that is, the description of cosmic voids. We introduce
and study a model of void which is a generalization of a simpler one in
spherical symmetry and we use it for the calculation of weak lensing optical
scalars as a non-trivial and interesting application. In this particular
example we show the rich observable features that can be found in such models.
| [
{
"created": "Thu, 17 Nov 2016 19:53:28 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Nov 2016 13:53:43 GMT",
"version": "v2"
},
{
"created": "Thu, 26 Jan 2017 15:30:26 GMT",
"version": "v3"
}
] | 2017-01-27 | [
[
"Boero",
"Ezequiel F.",
""
],
[
"Moreschi",
"Osvaldo M.",
""
]
] | We present a class of general prolate and oblate spheroidal spacetimes for the description of cosmic structures in the Universe. They are exact geometries which represent, in an appropriated way, the imbedding of spheroidal matter-energy distributions within a standard cosmological scenario, and therefore they allow for an improved description of a wider class of astrophysical systems from a more accurate point of view. These spacetimes can be used to describe overdensity or underdensity regions; in this work we consider the last case, that is, the description of cosmic voids. We introduce and study a model of void which is a generalization of a simpler one in spherical symmetry and we use it for the calculation of weak lensing optical scalars as a non-trivial and interesting application. In this particular example we show the rich observable features that can be found in such models. |
gr-qc/0305079 | Buffenoir | E. Buffenoir, K. Noui | Unfashionable observations about three dimensional gravity | 50 pages, written in LaTex, 3 pictures in encapsulated postscript | null | null | null | gr-qc hep-th | null | It is commonly accepted that the study of 2+1 dimensional quantum gravity
could teach us something about the 3+1 dimensional case. The non-perturbative
methods developed in this case share, as basic ingredient, a reformulation of
gravity as a gauge field theory. However, these methods suffer many problems.
Firstly, this perspective abandon the non-degeneracy of the metric and
causality as fundamental principles, hoping to recover them in a certain
low-energy limit. Then, it is not clear how these combinatorial techniques
could be used in the case where matter fields are added, which are however the
essential ingredients in order to produce non trivial observables in a
generally covariant approach. Endly, considering the status of the observer in
these approaches, it is not clear at all if they really could produce a
completely covariant description of quantum gravity. We propose to re-analyse
carefully these points. This study leads us to a really covariant description
of a set of self-gravitating point masses in a closed universe. This approach
is based on a set of observables associated to the measurements accessible to a
participant-observer, they manage to capture the whole dynamic in Chern-Simons
gravity as well as in true gravity. The Dirac algebra of these observables can
be explicitely computed, and exhibits interesting algebraic features related to
Poisson-Lie groupoids theory.
| [
{
"created": "Wed, 21 May 2003 08:31:51 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Jun 2003 08:17:28 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Buffenoir",
"E.",
""
],
[
"Noui",
"K.",
""
]
] | It is commonly accepted that the study of 2+1 dimensional quantum gravity could teach us something about the 3+1 dimensional case. The non-perturbative methods developed in this case share, as basic ingredient, a reformulation of gravity as a gauge field theory. However, these methods suffer many problems. Firstly, this perspective abandon the non-degeneracy of the metric and causality as fundamental principles, hoping to recover them in a certain low-energy limit. Then, it is not clear how these combinatorial techniques could be used in the case where matter fields are added, which are however the essential ingredients in order to produce non trivial observables in a generally covariant approach. Endly, considering the status of the observer in these approaches, it is not clear at all if they really could produce a completely covariant description of quantum gravity. We propose to re-analyse carefully these points. This study leads us to a really covariant description of a set of self-gravitating point masses in a closed universe. This approach is based on a set of observables associated to the measurements accessible to a participant-observer, they manage to capture the whole dynamic in Chern-Simons gravity as well as in true gravity. The Dirac algebra of these observables can be explicitely computed, and exhibits interesting algebraic features related to Poisson-Lie groupoids theory. |
gr-qc/9507034 | null | E.S.C. Ching, P.T. Leung, W.M. Suen and K. Young | Wave Propagation in Gravitational Systems: Completeness of Quasinormal
Modes | null | Phys.Rev.D54:3778-3791,1996 | 10.1103/PhysRevD.54.3778 | WUGRAV-94-15 | gr-qc | null | The dynamics of relativistic stars and black holes are often studied in terms
of the quasinormal modes (QNM's) of the Klein-Gordon (KG) equation with
different effective potentials $V(x)$. In this paper we present a systematic
study of the relation between the structure of the QNM's of the KG equation and
the form of $V(x)$. In particular, we determine the requirements on $V(x)$ in
order for the QNM's to form complete sets, and discuss in what sense they form
complete sets. Among other implications, this study opens up the possibility of
using QNM expansions to analyse the behavior of waves in relativistic systems,
even for systems whose QNM's do {\it not} form a complete set. For such
systems, we show that a complete set of QNM's can often be obtained by
introducing an infinitesimal change in the effective potential.
| [
{
"created": "Fri, 14 Jul 1995 18:49:09 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Ching",
"E. S. C.",
""
],
[
"Leung",
"P. T.",
""
],
[
"Suen",
"W. M.",
""
],
[
"Young",
"K.",
""
]
] | The dynamics of relativistic stars and black holes are often studied in terms of the quasinormal modes (QNM's) of the Klein-Gordon (KG) equation with different effective potentials $V(x)$. In this paper we present a systematic study of the relation between the structure of the QNM's of the KG equation and the form of $V(x)$. In particular, we determine the requirements on $V(x)$ in order for the QNM's to form complete sets, and discuss in what sense they form complete sets. Among other implications, this study opens up the possibility of using QNM expansions to analyse the behavior of waves in relativistic systems, even for systems whose QNM's do {\it not} form a complete set. For such systems, we show that a complete set of QNM's can often be obtained by introducing an infinitesimal change in the effective potential. |
1108.3471 | Masahiro Shimano | Masahiro Shimano, Tomohiro Harada and Naoki Tsukamoto | A trapped surface in the higher-dimensional self-similar Vaidya
spacetime | 13 pages, 5 figures | null | 10.1088/1742-6596/314/1/012068 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate a trapped surface and naked singularity in a $D$-dimensional
Vaidya spacetime with a self-similar mass function. A trapped surface is
defined as a closed spacelike $(D-2)$-surface which has negative both null
expansions. There is no trapped surface in the Minkowski spacetime. However, in
a four-dimensional self-similar Vaidya spacetime, Bengtsson and Senovilla
considered non-spherical trapped surfaces and showed that a trapped surface can
penetrate into a flat region, if and only if the mass function rises fast
enough [I. Bengtsson and J. M. M. Senovilla, Phys. Rev. D \textbf{79}, 024027
(2009).]. We apply this result to a $D$-dimensional spacetime motivated by the
context of large extra dimensions or TeV-scale gravity. In this paper,
similarly to Bengtsson and Senovilla's study, we match four types of
$(D-2)$-surfaces and show that a trapped surface extended into the flat region
can be constructed in the $D$-dimensional Vaidya spacetime, if the increasing
rate of the mass function is greater than 0.4628. Moreover, we show that the
maximum radius of the trapped surface constructed here approaches the
Schwarzschild-Tangherlini radius in the large $D$ limit. Also, we show that
there is no naked singularity, if the spacetime has the trapped surface
constructed here.
| [
{
"created": "Wed, 17 Aug 2011 13:01:33 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Shimano",
"Masahiro",
""
],
[
"Harada",
"Tomohiro",
""
],
[
"Tsukamoto",
"Naoki",
""
]
] | We investigate a trapped surface and naked singularity in a $D$-dimensional Vaidya spacetime with a self-similar mass function. A trapped surface is defined as a closed spacelike $(D-2)$-surface which has negative both null expansions. There is no trapped surface in the Minkowski spacetime. However, in a four-dimensional self-similar Vaidya spacetime, Bengtsson and Senovilla considered non-spherical trapped surfaces and showed that a trapped surface can penetrate into a flat region, if and only if the mass function rises fast enough [I. Bengtsson and J. M. M. Senovilla, Phys. Rev. D \textbf{79}, 024027 (2009).]. We apply this result to a $D$-dimensional spacetime motivated by the context of large extra dimensions or TeV-scale gravity. In this paper, similarly to Bengtsson and Senovilla's study, we match four types of $(D-2)$-surfaces and show that a trapped surface extended into the flat region can be constructed in the $D$-dimensional Vaidya spacetime, if the increasing rate of the mass function is greater than 0.4628. Moreover, we show that the maximum radius of the trapped surface constructed here approaches the Schwarzschild-Tangherlini radius in the large $D$ limit. Also, we show that there is no naked singularity, if the spacetime has the trapped surface constructed here. |
1504.07335 | T\'erence Delsate | T\'erence Delsate | I-Love irrotationally | short note, 6 pages, 6 figures, 2 tables | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this short note, we investigate the existence of universal relations
between the gravimagnetic Love number of irrotational stars and the
dimensionless moment of inertia. These Love numbers take into account the
internal motion of the fluid, while the star is globally irrotational. The goal
is to extend the so-called I-Love-Q relations - providing a strong correlation
between the gravitoelectric Love number, the dimensionless moment of inertia
and the dimensionless rotation-induced quadrupole - to the gravitomagnetic
sector, where internal motion is taken into account. As a byproduct, we present
for the first time this new gravitomagnetic Love number for realistic equations
of state.
| [
{
"created": "Tue, 28 Apr 2015 03:04:35 GMT",
"version": "v1"
}
] | 2015-04-29 | [
[
"Delsate",
"Térence",
""
]
] | In this short note, we investigate the existence of universal relations between the gravimagnetic Love number of irrotational stars and the dimensionless moment of inertia. These Love numbers take into account the internal motion of the fluid, while the star is globally irrotational. The goal is to extend the so-called I-Love-Q relations - providing a strong correlation between the gravitoelectric Love number, the dimensionless moment of inertia and the dimensionless rotation-induced quadrupole - to the gravitomagnetic sector, where internal motion is taken into account. As a byproduct, we present for the first time this new gravitomagnetic Love number for realistic equations of state. |
1602.02676 | James Franson | J.D. Franson | Numerical calculation of the relativistic acceleration of an electron in
curved spacetime using the Dirac equation | 13 pages, 4 figures | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The relativistic acceleration of an electron in a uniform gravitational field
is calculated numerically using the generalization of the Dirac equation to
curved spacetime. Equivalent results are also obtained analytically using an
iterative approach that is not based on the WKB approximation, which has been
used extensively in the past. The acceleration is found to be proportional to a
factor of $(1-3v^2/c^2)$ using Schwarzschild coordinates, which is consistent
with the classical geodesic of a particle. These techniques may be useful in
resolving the differences between commonly-used approximations.
| [
{
"created": "Mon, 8 Feb 2016 18:20:42 GMT",
"version": "v1"
}
] | 2016-02-09 | [
[
"Franson",
"J. D.",
""
]
] | The relativistic acceleration of an electron in a uniform gravitational field is calculated numerically using the generalization of the Dirac equation to curved spacetime. Equivalent results are also obtained analytically using an iterative approach that is not based on the WKB approximation, which has been used extensively in the past. The acceleration is found to be proportional to a factor of $(1-3v^2/c^2)$ using Schwarzschild coordinates, which is consistent with the classical geodesic of a particle. These techniques may be useful in resolving the differences between commonly-used approximations. |
2101.12066 | Sergey Pavluchenko A. | Dmitry Chirkov and Sergey A. Pavluchenko | Some aspects of the cosmological dynamics in Einstein-Gauss-Bonnet
gravity | 14 pages, 2 figures | Mod. Phys. Lett. A 36, 2150092 (2021) | 10.1142/S0217732321500929 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study some aspects of dynamical compactification scenario where
stabilisation of extra dimensions occurs due to presence the Gauss-Bonnet term
and non-zero spatial curvature. In the framework of the model under
consideration there exists two-stages scenario of evolution of a Universe: on
the first stage, the space evolves from a totally anisotropic state to the
state with 3-dimensional (corresponding to our "real", world) expanding and
$D$-dimensional contracting isotropic subspaces; on the second stage, constant
curvature of extra dimensions begins to play role and provide compactification
of extra dimensions. It is already known that such a scenario is realizable
when constant curvature of extra dimensions is negative. Here we show that a
range of coupling constants for which exponential solutions with 3-dimensional
expanding and $D$-dimensional contracting isotropic subspaces are stable is
located in a zone where compactification solutions with positively curved extra
space are unstable, so that two-stage scenario analogous to the one described
above is \emph{not} realizable. Also we study "nearly-Friedmann", regime for
the case of arbitrary constant curvature of extra dimensions and describe new
parametrization of the general solution for the model under consideration which
provide elegant way of describing areas of existence over parameters space.
| [
{
"created": "Thu, 28 Jan 2021 15:38:32 GMT",
"version": "v1"
}
] | 2021-05-12 | [
[
"Chirkov",
"Dmitry",
""
],
[
"Pavluchenko",
"Sergey A.",
""
]
] | We study some aspects of dynamical compactification scenario where stabilisation of extra dimensions occurs due to presence the Gauss-Bonnet term and non-zero spatial curvature. In the framework of the model under consideration there exists two-stages scenario of evolution of a Universe: on the first stage, the space evolves from a totally anisotropic state to the state with 3-dimensional (corresponding to our "real", world) expanding and $D$-dimensional contracting isotropic subspaces; on the second stage, constant curvature of extra dimensions begins to play role and provide compactification of extra dimensions. It is already known that such a scenario is realizable when constant curvature of extra dimensions is negative. Here we show that a range of coupling constants for which exponential solutions with 3-dimensional expanding and $D$-dimensional contracting isotropic subspaces are stable is located in a zone where compactification solutions with positively curved extra space are unstable, so that two-stage scenario analogous to the one described above is \emph{not} realizable. Also we study "nearly-Friedmann", regime for the case of arbitrary constant curvature of extra dimensions and describe new parametrization of the general solution for the model under consideration which provide elegant way of describing areas of existence over parameters space. |
1206.5462 | Chen Songbai | Songbai Chen, Qiyuan Pan, Jiliang Jing | Effects of quintessence on holographic p-wave superconductors | 15 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1206.2069, and with arXiv:1007.3321, arXiv:1106.0784 by other authors | Commun. Theor. Phys. 60, 471 (2013) | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a holographic p-wave superconductor model in the background of
quintessence AdS black hole with an SU(2) Yang-Mills gauge field and then probe
the effects of quintessence on the holographic p-wave superconductor. We
investigate the relation between the critical temperature and the state
parameter of quintessence, and present the numerical results for electric
conductivity. It is shown that the condensation of the vector field becomes
harder as the absolute value of the state parameter increases. Unlike the
scalar condensate in the s-wave model, the condensation of the vector field in
p-wave model can occur in the total value range of the state parameter $w_q$ of
quintessence. These results could help us know more about holographic
superconductor and dark energy.
| [
{
"created": "Sun, 24 Jun 2012 03:56:21 GMT",
"version": "v1"
}
] | 2013-10-08 | [
[
"Chen",
"Songbai",
""
],
[
"Pan",
"Qiyuan",
""
],
[
"Jing",
"Jiliang",
""
]
] | We construct a holographic p-wave superconductor model in the background of quintessence AdS black hole with an SU(2) Yang-Mills gauge field and then probe the effects of quintessence on the holographic p-wave superconductor. We investigate the relation between the critical temperature and the state parameter of quintessence, and present the numerical results for electric conductivity. It is shown that the condensation of the vector field becomes harder as the absolute value of the state parameter increases. Unlike the scalar condensate in the s-wave model, the condensation of the vector field in p-wave model can occur in the total value range of the state parameter $w_q$ of quintessence. These results could help us know more about holographic superconductor and dark energy. |
0705.0484 | Ella Jamsin | Ella Jamsin | A Note on Conserved Charges of Asymptotically Flat and Anti-de Sitter
Spaces in Arbitrary Dimensions | 27 pages; v2 : references added, minor corrections; v3 : replaced to
match published version forthcoming in General Relativity and Gravitation | Gen.Rel.Grav.40:2569-2590,2008 | 10.1007/s10714-008-0640-6 | ULB-TH/07-18 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The calculation of conserved charges of black holes is a rich problem, for
which many methods are known. Until recently, there was some controversy on the
proper definition of conserved charges in asymptotically anti-de Sitter (AdS)
spaces in arbitrary dimensions. This paper provides a systematic and explicit
Hamiltonian derivation of the energy and the angular momenta of both
asymptotically flat and asymptotically AdS spacetimes in any dimension D bigger
or equal to 4. This requires as a first step a precise determination of the
asymptotic conditions of the metric and of its conjugate momentum. These
conditions happen to be achieved in ellipsoidal coordinates adapted to the
rotating solutions.The asymptotic symmetry algebra is found to be isomorphic
either to the Poincare algebra or to the so(D-1, 2) algebra, as expected. In
the asymptotically flat case, the boundary conditions involve a generalization
of the parity conditions, introduced by Regge and Teitelboim, which are
necessary to make the angular momenta finite. The charges are explicitly
computed for Kerr and Kerr-AdS black holes for arbitrary D and they are shown
to be in agreement with thermodynamical arguments.
| [
{
"created": "Thu, 3 May 2007 15:58:07 GMT",
"version": "v1"
},
{
"created": "Tue, 29 May 2007 12:42:29 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Aug 2008 16:38:11 GMT",
"version": "v3"
}
] | 2008-12-18 | [
[
"Jamsin",
"Ella",
""
]
] | The calculation of conserved charges of black holes is a rich problem, for which many methods are known. Until recently, there was some controversy on the proper definition of conserved charges in asymptotically anti-de Sitter (AdS) spaces in arbitrary dimensions. This paper provides a systematic and explicit Hamiltonian derivation of the energy and the angular momenta of both asymptotically flat and asymptotically AdS spacetimes in any dimension D bigger or equal to 4. This requires as a first step a precise determination of the asymptotic conditions of the metric and of its conjugate momentum. These conditions happen to be achieved in ellipsoidal coordinates adapted to the rotating solutions.The asymptotic symmetry algebra is found to be isomorphic either to the Poincare algebra or to the so(D-1, 2) algebra, as expected. In the asymptotically flat case, the boundary conditions involve a generalization of the parity conditions, introduced by Regge and Teitelboim, which are necessary to make the angular momenta finite. The charges are explicitly computed for Kerr and Kerr-AdS black holes for arbitrary D and they are shown to be in agreement with thermodynamical arguments. |
gr-qc/0411085 | Takashi Hamazaki | Takashi Hamazaki | Evolution of Cosmological Perturbations in the Universe dominated by
Resonant Scalar Fields | 50 pages | Nucl. Phys.B698:335-385,2004 | 10.1016/j.nuclphysb.2004.08.008 | null | gr-qc | null | Recently a Hamiltonian formulation for the evolution of the universe
dominated by multiple oscillatory scalar fields was developed by the present
author and was applied to the investigation of the evolution of cosmological
perturbations on superhorizon scales in the case that the scalar fields have
incommensurable masses. In the present paper, the analysis is extended to the
case that the masses of the scalar fields satisfy resonance relations
approximately. In this case, the action-angle variables for the system can be
classified into fast changing variables and slowly changing variables. We show
that after an appropriate canonical transformation, the part of the Hamiltonian
that depends on fast changing angle variables can be made negligibley small, so
that the dynamics of the system can be effectively determined by a truncated
Hamiltonian that describes a closed dynamics of the slowly changing varables.
Utilizing this formulation, we show that the system is unstable if this
truncated Hamiltonian system has hyperbolic fixed point and as a consequence,
the Bardeen parameter for a perturbation of the system grows.
| [
{
"created": "Wed, 17 Nov 2004 01:36:46 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Hamazaki",
"Takashi",
""
]
] | Recently a Hamiltonian formulation for the evolution of the universe dominated by multiple oscillatory scalar fields was developed by the present author and was applied to the investigation of the evolution of cosmological perturbations on superhorizon scales in the case that the scalar fields have incommensurable masses. In the present paper, the analysis is extended to the case that the masses of the scalar fields satisfy resonance relations approximately. In this case, the action-angle variables for the system can be classified into fast changing variables and slowly changing variables. We show that after an appropriate canonical transformation, the part of the Hamiltonian that depends on fast changing angle variables can be made negligibley small, so that the dynamics of the system can be effectively determined by a truncated Hamiltonian that describes a closed dynamics of the slowly changing varables. Utilizing this formulation, we show that the system is unstable if this truncated Hamiltonian system has hyperbolic fixed point and as a consequence, the Bardeen parameter for a perturbation of the system grows. |
1511.00439 | Andronikos Paliathanasis | Andronikos Paliathanasis, Michael Tsamparlis, Spyros Basilakos and
John D. Barrow | Classical and Quantum Solutions in Brans-Dicke Cosmology with a Perfect
Fluid | 13 pages, 2 figures, discussion improved, accepted for publication by
Phys. Rev. D | Phys. Rev. D 93, 043528 (2016) | 10.1103/PhysRevD.93.043528 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the application of group invariant transformations in order to
constrain a flat isotropic and homogeneous cosmological model, containing of a
Brans-Dicke scalar field and a perfect fluid with a constant equation of state
parameter $w$, where the latter is not interacting with the scalar field in the
gravitational action integral. The requirement that the Wheeler-DeWitt equation
be invariant under one-parameter point transformations provides us with two
families of power-law potentials for the Brans-Dicke field, in which the powers
are functions of the Brans-Dicke parameter $\omega_{BD}$ and the parameter $w$.
The existence of the Lie symmetry in the Wheeler-DeWitt equation is equivalent
to the existence of a conserved quantity in field equations and with
oscillatory terms in the wavefunction of the universe. This enables us to solve
the field equations. For a specific value of the conserved quantity, we find a
closed-form solution for the Hubble factor, which is equivalent to a
cosmological model in general relativity containing two perfect fluids. This
provides us with different models for specific values of the parameters
$\omega_{BD},$ and $w$. Finally, the results hold for the specific case where
the Brans-Dicke parameter $\omega_{BD}$ is zero, that is, for the O'Hanlon
massive dilaton theory, and consequently for $f\left( R\right) $ gravity in the
metric formalism.
| [
{
"created": "Mon, 2 Nov 2015 10:55:31 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jan 2016 16:28:51 GMT",
"version": "v2"
}
] | 2016-03-02 | [
[
"Paliathanasis",
"Andronikos",
""
],
[
"Tsamparlis",
"Michael",
""
],
[
"Basilakos",
"Spyros",
""
],
[
"Barrow",
"John D.",
""
]
] | We consider the application of group invariant transformations in order to constrain a flat isotropic and homogeneous cosmological model, containing of a Brans-Dicke scalar field and a perfect fluid with a constant equation of state parameter $w$, where the latter is not interacting with the scalar field in the gravitational action integral. The requirement that the Wheeler-DeWitt equation be invariant under one-parameter point transformations provides us with two families of power-law potentials for the Brans-Dicke field, in which the powers are functions of the Brans-Dicke parameter $\omega_{BD}$ and the parameter $w$. The existence of the Lie symmetry in the Wheeler-DeWitt equation is equivalent to the existence of a conserved quantity in field equations and with oscillatory terms in the wavefunction of the universe. This enables us to solve the field equations. For a specific value of the conserved quantity, we find a closed-form solution for the Hubble factor, which is equivalent to a cosmological model in general relativity containing two perfect fluids. This provides us with different models for specific values of the parameters $\omega_{BD},$ and $w$. Finally, the results hold for the specific case where the Brans-Dicke parameter $\omega_{BD}$ is zero, that is, for the O'Hanlon massive dilaton theory, and consequently for $f\left( R\right) $ gravity in the metric formalism. |
0707.0867 | Luis Herrera | L. Herrera, J. Carot, A. Di Prisco | Frame dragging and super-energy | 12 pages Latex. To appear in Phys.Rev. D. Typos corrected | Phys.Rev.D76:044012,2007 | 10.1103/PhysRevD.76.044012 | null | gr-qc math-ph math.MP | null | We show that the vorticity appearing in stationary vacuum spacetimes is
always related to the existence of a flow of super-energy on the plane
orthogonal to the vorticity vector. This result, toghether with the previously
established link between vorticity and super--energy in radiative (Bondi-Sachs)
spacetimes strength further the case for this latter quantity as the cause of
frame dragging.
| [
{
"created": "Thu, 5 Jul 2007 21:35:49 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Aug 2007 14:45:27 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Herrera",
"L.",
""
],
[
"Carot",
"J.",
""
],
[
"Di Prisco",
"A.",
""
]
] | We show that the vorticity appearing in stationary vacuum spacetimes is always related to the existence of a flow of super-energy on the plane orthogonal to the vorticity vector. This result, toghether with the previously established link between vorticity and super--energy in radiative (Bondi-Sachs) spacetimes strength further the case for this latter quantity as the cause of frame dragging. |
gr-qc/9702012 | KZWin | Jennie Traschen and K. Z. Win | Instanton Supported Scalar Hair on Black Holes | plain TeX 14 pages. Uses harvmac b and epsf. 14 figures | null | null | null | gr-qc hep-th | null | We present analytical perturbative, and numerical solutions of the Einstein
equation which describe a black hole with a nontrivial dilaton field and a
purely topological gauge potential. The gauge potential has zero field strength
and hence no stress-energy, but it does couple to virtual string worldsheets
which wrap around the Euclidean horizon two-sphere, and generate an effective
interaction in the spacetime lagrangian. We use the lagrangian with a
nonstandard potential for a scalar field that reproduces the effect of the
worldsheet instantons. As has been previously pointed out the topological
charge Q of the gauge field can be detected by an Anharonov-Bohm type
experiment using quantum strings; the classical scalar hair of the solutions
here is a classical detection of Q. ADM mass, dilaton charge and Hawking
temperature are calculated and compared with the known cases when appropriate.
We discuss why these solutions do not violate the no-hair theorems and show
that, for sufficiently small interaction coupling, the solutions are stable
under linear time dependent perturbations.
| [
{
"created": "Wed, 5 Feb 1997 20:29:25 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Traschen",
"Jennie",
""
],
[
"Win",
"K. Z.",
""
]
] | We present analytical perturbative, and numerical solutions of the Einstein equation which describe a black hole with a nontrivial dilaton field and a purely topological gauge potential. The gauge potential has zero field strength and hence no stress-energy, but it does couple to virtual string worldsheets which wrap around the Euclidean horizon two-sphere, and generate an effective interaction in the spacetime lagrangian. We use the lagrangian with a nonstandard potential for a scalar field that reproduces the effect of the worldsheet instantons. As has been previously pointed out the topological charge Q of the gauge field can be detected by an Anharonov-Bohm type experiment using quantum strings; the classical scalar hair of the solutions here is a classical detection of Q. ADM mass, dilaton charge and Hawking temperature are calculated and compared with the known cases when appropriate. We discuss why these solutions do not violate the no-hair theorems and show that, for sufficiently small interaction coupling, the solutions are stable under linear time dependent perturbations. |
2205.03789 | Soumya Chakrabarti | Soumya Chakrabarti, Koushik Dutta and Jackson Levi Said | Screening Mechanism and Late-time Cosmology: Role of a
Chameleon-Brans-Dicke Scalar Field | 14 pages, 10 figures, Accepted for publication in MNRAS | null | 10.1093/mnras/stac1321 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a way in which the geometric scalar field in a Brans-Dicke theory
can evade local astronomical tests and act as a driver of the late-time cosmic
acceleration. This requires a self-interaction of the Brans-Dicke scalar as
well as an interaction with ordinary matter. The scalar field in this construct
acquires a density-dependent effective mass much like a Chameleon field. We
discuss the viability of this setup in the context of the Equivalence
Principle, Fifth Force, and Solar System tests. The cosmological consistency is
adjudged in comparison with observational data from recalibrated light curves
of type Ia supernova (JLA), the Hubble parameter measurements (OHD), and the
Baryon Acoustic Oscillation (BAO). We deduct that the astrophysical constraints
indeed favor the existence of a mild scalar-matter interaction in the Jordan
Frame.
| [
{
"created": "Sun, 8 May 2022 05:37:03 GMT",
"version": "v1"
}
] | 2022-05-25 | [
[
"Chakrabarti",
"Soumya",
""
],
[
"Dutta",
"Koushik",
""
],
[
"Said",
"Jackson Levi",
""
]
] | We discuss a way in which the geometric scalar field in a Brans-Dicke theory can evade local astronomical tests and act as a driver of the late-time cosmic acceleration. This requires a self-interaction of the Brans-Dicke scalar as well as an interaction with ordinary matter. The scalar field in this construct acquires a density-dependent effective mass much like a Chameleon field. We discuss the viability of this setup in the context of the Equivalence Principle, Fifth Force, and Solar System tests. The cosmological consistency is adjudged in comparison with observational data from recalibrated light curves of type Ia supernova (JLA), the Hubble parameter measurements (OHD), and the Baryon Acoustic Oscillation (BAO). We deduct that the astrophysical constraints indeed favor the existence of a mild scalar-matter interaction in the Jordan Frame. |
gr-qc/0510021 | Jorge Pullin | Jorge Pullin | Matters of Gravity, the newsletter of the Topical Group in Gravitation
of APS | 21 pages. Jorge Pullin (editor) | null | null | MOG-26 | gr-qc | null | GGR News:
The WYP speakers program, by Richard Price
We hear that..., by Jorge Pullin
100 Years ago, by Jorge Pullin
Research Briefs:
What's new in LIGO, by David Shoemaker
Recent developments in the information loss paradox, by Eanna Flanagan
Gravity Probe B mission ends, by Bob Kahn
Conference reports:
6th Edoardo Amaldi Meeting, by Matthew Benacquista
Workshop on Numerical Relativity, BIRS, by Carsten Gundlach
8th Capra Meeting on Radiation Reaction, by Leor Barack
Theory and experiment in quantum gravity, by Elizabeth Winstanley
| [
{
"created": "Wed, 5 Oct 2005 20:45:58 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Pullin",
"Jorge",
""
]
] | GGR News: The WYP speakers program, by Richard Price We hear that..., by Jorge Pullin 100 Years ago, by Jorge Pullin Research Briefs: What's new in LIGO, by David Shoemaker Recent developments in the information loss paradox, by Eanna Flanagan Gravity Probe B mission ends, by Bob Kahn Conference reports: 6th Edoardo Amaldi Meeting, by Matthew Benacquista Workshop on Numerical Relativity, BIRS, by Carsten Gundlach 8th Capra Meeting on Radiation Reaction, by Leor Barack Theory and experiment in quantum gravity, by Elizabeth Winstanley |
1806.04719 | Junji Jia | Xiankai Pang, Junji Jia | Gravitational lensing of massive particles in Reissner-Nordstr\"om
spacetime | Revised version: references added; some figures improved. 27 pages, 8
figures and 2 tables | null | 10.1088/1361-6382/ab0512 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study the deflection angle $\Delta \varphi$ and gravitational
lensing of both lightlike and timelike neutral rays in Reissner-Nordstr\"om
(RN) spacetimes. The exact deflection angle is found as an elliptical function
of the impact parameter $b$ and velocity $v$ of the ray, and the charge $Q$ of
the spacetime. In obtaining this angle, we found the critical impact parameter
$b_c$ and radius of particle sphere $r_c$ that are also dependent on $v$ and
$Q$. In general, both the increase of velocity and charge reduces the $b_c$ as
well as $r_c$. To study the effect of $v$ and $Q$ on the deflection angle
$\Delta\varphi$, its weak and strong deflection limits, relativistic and
non-relativistic limits, and small charge and extremal RN limits are analyzed
carefully. It is found that both the increase of velocity and charge reduces
the deflection angle. For weak deflection, the velocity and charge corrections
appear respectively in the $\mathcal{O}(1/b)$ and $\mathcal{O}(1/b^2)$ orders.
For strong deflections, these two corrections appear in the same order. The
apparent angles and magnifications of weak and strong regular lensing, and
retro-lensing are studied for both lightlike and timelike rays. In general, in
all cases the increase of velocity or charge will decrease the apparent angle
of any order. We show that velocity correction is much larger than that of
charge in the weak lensing case, while their effects in the strong regular
lensing and retro-lensing are comparable. It is further shown that the apparent
angle and magnification in strong regular lensing and retro-lensing can be
effectively unified. Finally, we argue that the correction of $v$ and $Q$ on
the apparent angle can be correlated to mass or mass hierarchy of timelike
particles with certain energy. In addition, the effects of $v$ and $Q$ on
shadow size of black holes are discussed.
| [
{
"created": "Tue, 12 Jun 2018 19:02:42 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Nov 2018 09:12:05 GMT",
"version": "v2"
}
] | 2019-03-20 | [
[
"Pang",
"Xiankai",
""
],
[
"Jia",
"Junji",
""
]
] | In this work we study the deflection angle $\Delta \varphi$ and gravitational lensing of both lightlike and timelike neutral rays in Reissner-Nordstr\"om (RN) spacetimes. The exact deflection angle is found as an elliptical function of the impact parameter $b$ and velocity $v$ of the ray, and the charge $Q$ of the spacetime. In obtaining this angle, we found the critical impact parameter $b_c$ and radius of particle sphere $r_c$ that are also dependent on $v$ and $Q$. In general, both the increase of velocity and charge reduces the $b_c$ as well as $r_c$. To study the effect of $v$ and $Q$ on the deflection angle $\Delta\varphi$, its weak and strong deflection limits, relativistic and non-relativistic limits, and small charge and extremal RN limits are analyzed carefully. It is found that both the increase of velocity and charge reduces the deflection angle. For weak deflection, the velocity and charge corrections appear respectively in the $\mathcal{O}(1/b)$ and $\mathcal{O}(1/b^2)$ orders. For strong deflections, these two corrections appear in the same order. The apparent angles and magnifications of weak and strong regular lensing, and retro-lensing are studied for both lightlike and timelike rays. In general, in all cases the increase of velocity or charge will decrease the apparent angle of any order. We show that velocity correction is much larger than that of charge in the weak lensing case, while their effects in the strong regular lensing and retro-lensing are comparable. It is further shown that the apparent angle and magnification in strong regular lensing and retro-lensing can be effectively unified. Finally, we argue that the correction of $v$ and $Q$ on the apparent angle can be correlated to mass or mass hierarchy of timelike particles with certain energy. In addition, the effects of $v$ and $Q$ on shadow size of black holes are discussed. |
2309.01976 | Ayan Banerjee | Takol Tangphati, C. R. Muniz, Anirudh Pradhan and Ayan Banerjee | Traversable wormholes in Rastall-Rainbow Gravity | 12 pages, 6 figures, Minor typos corrected, few short comments added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the existence of asymptotically flat wormhole
geometries within the framework of Rastall-Rainbow modified gravity, a
synthesis of two distinct theoretical models: Rastall theory and the Rainbow
description. Our study uncovers that, when considering specific combinations of
free parameters and equations of state, the emergence of static and spherically
symmetric wormholes is not feasible within a zero-tidal-force context. By
considering the subset of viable solutions, we conduct a rigorous assessment of
their stability through adiabatic sound velocity analysis and scrutinize their
compliance with the Weak Energy Condition (WEC). In summary, our inquiry
provides insights into how the interplay between Rastall parameters and Rainbow
functions may alleviate violations of energy conditions in these modified
gravity scenarios.
| [
{
"created": "Tue, 5 Sep 2023 06:12:22 GMT",
"version": "v1"
},
{
"created": "Sun, 10 Sep 2023 04:08:53 GMT",
"version": "v2"
}
] | 2023-09-12 | [
[
"Tangphati",
"Takol",
""
],
[
"Muniz",
"C. R.",
""
],
[
"Pradhan",
"Anirudh",
""
],
[
"Banerjee",
"Ayan",
""
]
] | In this paper, we investigate the existence of asymptotically flat wormhole geometries within the framework of Rastall-Rainbow modified gravity, a synthesis of two distinct theoretical models: Rastall theory and the Rainbow description. Our study uncovers that, when considering specific combinations of free parameters and equations of state, the emergence of static and spherically symmetric wormholes is not feasible within a zero-tidal-force context. By considering the subset of viable solutions, we conduct a rigorous assessment of their stability through adiabatic sound velocity analysis and scrutinize their compliance with the Weak Energy Condition (WEC). In summary, our inquiry provides insights into how the interplay between Rastall parameters and Rainbow functions may alleviate violations of energy conditions in these modified gravity scenarios. |
gr-qc/9801073 | Piotr Chrusciel | Piotr T. Chrusciel, Jacek Jezierski and Malcolm A.H. MacCallum | Uniqueness of the mass in the radiating regime | 8 pages, revtex | Phys.Rev.Lett. 80 (1998) 5052-5055 | 10.1103/PhysRevLett.80.5052 | A. Einstein Institute preprint AEI-055 | gr-qc | null | The usual approaches to the definition of energy give an ambiguous result for
the energy of fields in the radiating regime. We show that for a massless
scalar field in Minkowski space-time the definition may be rendered unambiguous
by adding the requirement that the energy cannot increase in retarded time. We
present a similar theorem for the gravitational field, proved elsewhere, which
establishes that the Trautman-Bondi energy is the unique (up to a
multiplicative factor) functional, within a natural class, which is monotonic
in time for all solutions of the vacuum Einstein equations admitting a smooth
``piece'' of conformal null infinity Scri.
| [
{
"created": "Wed, 21 Jan 1998 19:00:57 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Chrusciel",
"Piotr T.",
""
],
[
"Jezierski",
"Jacek",
""
],
[
"MacCallum",
"Malcolm A. H.",
""
]
] | The usual approaches to the definition of energy give an ambiguous result for the energy of fields in the radiating regime. We show that for a massless scalar field in Minkowski space-time the definition may be rendered unambiguous by adding the requirement that the energy cannot increase in retarded time. We present a similar theorem for the gravitational field, proved elsewhere, which establishes that the Trautman-Bondi energy is the unique (up to a multiplicative factor) functional, within a natural class, which is monotonic in time for all solutions of the vacuum Einstein equations admitting a smooth ``piece'' of conformal null infinity Scri. |
2005.12370 | Paul R. Anderson | Paul R. Anderson, Eric D. Carlson, Taylor M. Ordines, and Bradley
Hicks | Semiclassical predictions regarding a pre-inflationary era and its
effects on the power spectrum | Parts of the paper have been substantially rewritten, minor changes
and corrections elsewhere, references added, Phys. Rev. D version, 34 pages,
6 figures | Phys. Rev. D 102, 063528 (2020) | 10.1103/PhysRevD.102.063528 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An investigation is undertaken into the properties and effects of a
preinflationary era during at least part of which semiclassical gravity was
valid. It is argued that if the Universe (or our part of it) was approximately
homogeneous and isotropic during that era, then the Universe was likely to have
been radiation dominated. A simple model in which the Universe contains
classical radiation and a cosmological constant is used to investigate
potential effects of such a preinflationary era on the cosmic microwave
background. The power spectrum is computed using the mode functions of a
quantized massless minimally coupled scalar field. Various choices of state for
this field are considered, including adiabatic vacuum states of various orders
and the vacuum state that would naturally occur if the Universe made a sudden
transition from being radiation dominated to de Sitter space. In all cases
investigated, there is a suppression of the power spectrum at large angles,
and, when plotted as a function of the momentum parameter, there are always
oscillations with state-dependent amplitudes.
| [
{
"created": "Mon, 25 May 2020 20:03:47 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Jun 2020 15:51:10 GMT",
"version": "v2"
},
{
"created": "Mon, 24 May 2021 12:32:06 GMT",
"version": "v3"
}
] | 2021-05-25 | [
[
"Anderson",
"Paul R.",
""
],
[
"Carlson",
"Eric D.",
""
],
[
"Ordines",
"Taylor M.",
""
],
[
"Hicks",
"Bradley",
""
]
] | An investigation is undertaken into the properties and effects of a preinflationary era during at least part of which semiclassical gravity was valid. It is argued that if the Universe (or our part of it) was approximately homogeneous and isotropic during that era, then the Universe was likely to have been radiation dominated. A simple model in which the Universe contains classical radiation and a cosmological constant is used to investigate potential effects of such a preinflationary era on the cosmic microwave background. The power spectrum is computed using the mode functions of a quantized massless minimally coupled scalar field. Various choices of state for this field are considered, including adiabatic vacuum states of various orders and the vacuum state that would naturally occur if the Universe made a sudden transition from being radiation dominated to de Sitter space. In all cases investigated, there is a suppression of the power spectrum at large angles, and, when plotted as a function of the momentum parameter, there are always oscillations with state-dependent amplitudes. |
gr-qc/0301011 | Wai-Mo Suen | Edwin Evans, A. Gopakumar, Philip Gressman, Sai Iyer, Mark Miller,
Wai-Mo Suen, and Hui-Min Zhang | Head-on/Near Head-on Collisions of Neutron Stars With a Realistic EOS | 5 pages, 7 figures, submitted to Phy. Rev. D Rapid Comm | Phys.Rev. D67 (2003) 104001 | 10.1103/PhysRevD.67.104001 | Wugrav-03-02 | gr-qc | null | It has been conjectured that in head-on collisions of neutron stars (NSs),
the merged object would not collapse promptly even if the total mass is higher
than the maximum stable mass of a cold NS. In this paper, we show that the
reverse is true: even if the total mass is {\it less} than the maximum stable
mass, the merged object can collapse promptly. We demonstrate this for the case
of NSs with a realistic equation of state (the Lattimer-Swesty EOS) in head-on
{\it and} near head-on collisions. We propose a ``Prompt Collapse Conjecture''
for a generic NS EOS for head on and near head-on collisions.
| [
{
"created": "Sun, 5 Jan 2003 15:21:57 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Evans",
"Edwin",
""
],
[
"Gopakumar",
"A.",
""
],
[
"Gressman",
"Philip",
""
],
[
"Iyer",
"Sai",
""
],
[
"Miller",
"Mark",
""
],
[
"Suen",
"Wai-Mo",
""
],
[
"Zhang",
"Hui-Min",
""
]
] | It has been conjectured that in head-on collisions of neutron stars (NSs), the merged object would not collapse promptly even if the total mass is higher than the maximum stable mass of a cold NS. In this paper, we show that the reverse is true: even if the total mass is {\it less} than the maximum stable mass, the merged object can collapse promptly. We demonstrate this for the case of NSs with a realistic equation of state (the Lattimer-Swesty EOS) in head-on {\it and} near head-on collisions. We propose a ``Prompt Collapse Conjecture'' for a generic NS EOS for head on and near head-on collisions. |
1908.02104 | Yan Peng | Yan Peng | On instabilities of stationary scalar field configurations supported by
reflecting compact stars | 9 pages | Physics Letters B 798(2019)134931 | 10.1016/j.physletb.2019.134931 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study instabilities of the system composed of stationary scalar fields and
asymptotically flat horizonless reflecting compact stars. In the probe limit,
we obtain bounds on the scalar field frequency. Below this bound, stationary
hairy stars are expected to suffer from nonlinear instabilities under massless
field perturbations. In other words, we prove that stationary scalar hairy
stars are unstable for scalar fields with small frequency.
| [
{
"created": "Tue, 6 Aug 2019 12:29:07 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Sep 2019 04:54:17 GMT",
"version": "v2"
}
] | 2019-09-18 | [
[
"Peng",
"Yan",
""
]
] | We study instabilities of the system composed of stationary scalar fields and asymptotically flat horizonless reflecting compact stars. In the probe limit, we obtain bounds on the scalar field frequency. Below this bound, stationary hairy stars are expected to suffer from nonlinear instabilities under massless field perturbations. In other words, we prove that stationary scalar hairy stars are unstable for scalar fields with small frequency. |
gr-qc/9605038 | Hans Kastrup | H.A. Kastrup (RWTH Aachen) | On the Quantum Levels of Isolated Spherically Symmetric Gravitational
Systems | 13 pages, LaTeX, Replacement corrects a few misprints. No change of
content! | Phys.Lett.B385:75-80,1996 | 10.1016/0370-2693(96)00846-5 | PITHA 96/16 | gr-qc astro-ph hep-th | null | The known canonical quantum theory of a spherically symmetric pure
(Schwarzschild) gravitational system describes isolated black holes by plane
waves exp(-iMc^2\tau/\hbar) with respect to their continuous masses M and the
proper time \tau of obsevers at spatial infinity. On the other hand Bekenstein
and Mukhanov postulated discrete mass levels for such black holes in the spirit
of the Bohr-Sommerfeld quantisation in atomic physics. The two approaches can
be related by postulating periodic boundary conditions in time for the plane
waves and by identifying the period \Delta in real time with the period
\Delta_H= 8\pi GM/c^3 in Euclidean time. This yields the mass spectrum
M_n=(1/2)\sqrt{n}m_P, n=1,2,... .
| [
{
"created": "Fri, 17 May 1996 15:21:00 GMT",
"version": "v1"
},
{
"created": "Wed, 29 May 1996 14:50:48 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Kastrup",
"H. A.",
"",
"RWTH Aachen"
]
] | The known canonical quantum theory of a spherically symmetric pure (Schwarzschild) gravitational system describes isolated black holes by plane waves exp(-iMc^2\tau/\hbar) with respect to their continuous masses M and the proper time \tau of obsevers at spatial infinity. On the other hand Bekenstein and Mukhanov postulated discrete mass levels for such black holes in the spirit of the Bohr-Sommerfeld quantisation in atomic physics. The two approaches can be related by postulating periodic boundary conditions in time for the plane waves and by identifying the period \Delta in real time with the period \Delta_H= 8\pi GM/c^3 in Euclidean time. This yields the mass spectrum M_n=(1/2)\sqrt{n}m_P, n=1,2,... . |
1711.01282 | Francesc Cunillera | Francesc Cunillera and Cristiano Germani | The Gross-Pitaevskii equations of a static and spherically symmetric
condensate of gravitons | v.4: Accepted for publication. 10 pages | null | 10.1088/1361-6382/aab97b | ICCUB-17-021 | gr-qc astro-ph.CO cond-mat.other hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we consider the Dvali and G\'omez assumption that the end state
of a gravitational collapse is a Bose-Einstein condensate of gravitons. We then
construct the two Gross-Pitaevskii equations for a static and spherically
symmetric configuration of the condensate. These two equations correspond to
the constrained minimisation of the gravitational Hamiltonian with respect to
the redshift and the Newtonian potential, per given number of gravitons. We
find that the effective geometry of the condensate is the one of a gravastar (a
DeSitter star) with a sub-Planckian cosmological constant, for masses larger
than the Planck scale. Thus, a condensate corresponding to a semiclassical
black hole, is always quantum and weakly coupled. Finally, we obtain that the
boundary of our gravastar, although it is not the location of a horizon,
corresponds to the Schwarzschild radius.
| [
{
"created": "Fri, 3 Nov 2017 18:03:42 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Nov 2017 18:38:38 GMT",
"version": "v2"
},
{
"created": "Wed, 31 Jan 2018 22:30:05 GMT",
"version": "v3"
},
{
"created": "Fri, 23 Mar 2018 19:28:29 GMT",
"version": "v4"
}
] | 2018-05-02 | [
[
"Cunillera",
"Francesc",
""
],
[
"Germani",
"Cristiano",
""
]
] | In this paper we consider the Dvali and G\'omez assumption that the end state of a gravitational collapse is a Bose-Einstein condensate of gravitons. We then construct the two Gross-Pitaevskii equations for a static and spherically symmetric configuration of the condensate. These two equations correspond to the constrained minimisation of the gravitational Hamiltonian with respect to the redshift and the Newtonian potential, per given number of gravitons. We find that the effective geometry of the condensate is the one of a gravastar (a DeSitter star) with a sub-Planckian cosmological constant, for masses larger than the Planck scale. Thus, a condensate corresponding to a semiclassical black hole, is always quantum and weakly coupled. Finally, we obtain that the boundary of our gravastar, although it is not the location of a horizon, corresponds to the Schwarzschild radius. |
gr-qc/0603066 | Diego Julio Cirilo-Lombardo | Diego Julio Cirilo-Lombardo | Rotating charged Black Holes in Einstein-Born-Infeld theories and their
ADM mass | Final version and figures in journal. References and comments added | Gen.Rel.Grav.37:847-856,2005 | 10.1007/s10714-005-0071-6 | null | gr-qc hep-th | null | In this work, the solution of the Einstein equations for a slowly rotating
black hole with Born-Infeld charge is obtained. Geometrical properties and
horizons of this solution are analyzed. The conditions when the ADM mass (as in
the nonlinear static cases) and the ADM angular momentum of the system have
been modified by the non linear electromagnetic field of the black hole, are
considered.
| [
{
"created": "Thu, 16 Mar 2006 08:36:25 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Jan 2007 08:07:26 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Cirilo-Lombardo",
"Diego Julio",
""
]
] | In this work, the solution of the Einstein equations for a slowly rotating black hole with Born-Infeld charge is obtained. Geometrical properties and horizons of this solution are analyzed. The conditions when the ADM mass (as in the nonlinear static cases) and the ADM angular momentum of the system have been modified by the non linear electromagnetic field of the black hole, are considered. |
1811.07972 | Kristina Giesel | Kristina Giesel, Parampreet Singh, David Winnekens | Dynamics of Dirac observables in canonical cosmological perturbation
theory | 43 pages, appendix on Dirac observables in perturbation theory added.
To appear in Class. Quant. Grav | 2019 Class. Quantum Grav. 36 085009 | 10.1088/1361-6382/ab0ed3 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The relational formalism based on geometrical clocks and Dirac observables in
linearized canonical cosmological perturbation theory is used to introduce an
efficient method to find evolution equations for gauge invariant variables. Our
method generalizes an existing technique by Pons, Salisbury and Sundermeyer [1,
2] to relate the evolution of gauge invariant observables with the one of gauge
variant quantities, and is applied as a demonstration for the longitudinal and
spatially flat gauges. Gauge invariant evolution equations for the Bardeen
potential and the Mukhanov-Sasaki variable are derived in the extended ADM
phase space. Our method establishes a full agreement at the dynamical level
between the canonical and conventional cosmological perturbation theory at the
linear order using Dirac observables.
| [
{
"created": "Mon, 19 Nov 2018 20:50:04 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Mar 2019 12:47:46 GMT",
"version": "v2"
}
] | 2019-04-16 | [
[
"Giesel",
"Kristina",
""
],
[
"Singh",
"Parampreet",
""
],
[
"Winnekens",
"David",
""
]
] | The relational formalism based on geometrical clocks and Dirac observables in linearized canonical cosmological perturbation theory is used to introduce an efficient method to find evolution equations for gauge invariant variables. Our method generalizes an existing technique by Pons, Salisbury and Sundermeyer [1, 2] to relate the evolution of gauge invariant observables with the one of gauge variant quantities, and is applied as a demonstration for the longitudinal and spatially flat gauges. Gauge invariant evolution equations for the Bardeen potential and the Mukhanov-Sasaki variable are derived in the extended ADM phase space. Our method establishes a full agreement at the dynamical level between the canonical and conventional cosmological perturbation theory at the linear order using Dirac observables. |
2311.14017 | Mohsen Fathi | Mohsen Fathi, Marco Olivares, Jos\'e R. Villanueva, Norman Cruz | Light propagation around a Kerr-like black hole immersed in an
inhomogeneous anisotropic plasma in Rastall gravity I: Analytical solutions
to the equations of motion | 33 pages, 37 figures | null | null | null | gr-qc astro-ph.HE math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | In this paper, we explore the behavior of light ray trajectories in the
exterior geometry of a rotating black hole within the Rastall theory of
gravity, which is surrounded by an inhomogeneous anisotropic electronic cold
plasma. By specifying the plasma's frequency profile, we derive fully
analytical solutions for the temporal evolution of spacetime coordinates using
elliptic integrals and Jacobi elliptic functions. These solutions illustrate
various possible orbits. Throughout the study, we compare results with the
vacuum case, emphasizing the influence of the plasma. Additionally, we utilize
the analytical solutions to establish the lens equation for the considered
spacetime. The investigation also addresses the significance of spherical
photon orbits in critical trajectories, by presenting several examples.
| [
{
"created": "Thu, 23 Nov 2023 14:17:52 GMT",
"version": "v1"
}
] | 2023-11-27 | [
[
"Fathi",
"Mohsen",
""
],
[
"Olivares",
"Marco",
""
],
[
"Villanueva",
"José R.",
""
],
[
"Cruz",
"Norman",
""
]
] | In this paper, we explore the behavior of light ray trajectories in the exterior geometry of a rotating black hole within the Rastall theory of gravity, which is surrounded by an inhomogeneous anisotropic electronic cold plasma. By specifying the plasma's frequency profile, we derive fully analytical solutions for the temporal evolution of spacetime coordinates using elliptic integrals and Jacobi elliptic functions. These solutions illustrate various possible orbits. Throughout the study, we compare results with the vacuum case, emphasizing the influence of the plasma. Additionally, we utilize the analytical solutions to establish the lens equation for the considered spacetime. The investigation also addresses the significance of spherical photon orbits in critical trajectories, by presenting several examples. |
2102.08084 | Philippe Spindel | Philippe Spindel | Dynamical torsion gravity backgrounds | 40 pages, a few more typos corrected | Phys. Rev. D 103, 124054 (2021) | 10.1103/PhysRevD.103.124054 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We write the field equations of torsion gravity theories and the N\oe ther
identity they obey directly in terms of metric and contorsion tensor components
expressed with respect to natural coordinates, i.e. without using vierbien but
Lagrange multipliers. Then we obtain explicit solutions of these equations,
under specific ans\"atze for the contorsion field, by assuming the metric to be
respectively of the Bertotti-Robinson, pp-wave,
Friedmann-Lema\^itre-Robertson-Walker or static spherically symmetric type.
Among these various solutions we obtain some of them have their contorsion
tensor depending on arbitrary functions that didn't influence their geometry.
This raises question about the predictability of the theory.
| [
{
"created": "Tue, 16 Feb 2021 11:15:09 GMT",
"version": "v1"
},
{
"created": "Tue, 4 May 2021 09:02:31 GMT",
"version": "v2"
},
{
"created": "Wed, 9 Jun 2021 11:57:12 GMT",
"version": "v3"
}
] | 2021-06-30 | [
[
"Spindel",
"Philippe",
""
]
] | We write the field equations of torsion gravity theories and the N\oe ther identity they obey directly in terms of metric and contorsion tensor components expressed with respect to natural coordinates, i.e. without using vierbien but Lagrange multipliers. Then we obtain explicit solutions of these equations, under specific ans\"atze for the contorsion field, by assuming the metric to be respectively of the Bertotti-Robinson, pp-wave, Friedmann-Lema\^itre-Robertson-Walker or static spherically symmetric type. Among these various solutions we obtain some of them have their contorsion tensor depending on arbitrary functions that didn't influence their geometry. This raises question about the predictability of the theory. |
gr-qc/0410102 | Thomas Sotiriou | T. P. Sotiriou, T. A. Apostolatos | Tracing the geometry around a massive, axisymmetric body to measure,
through gravitational waves, its mass moments and electromagnetic moments | Submitted to Phys. Rev. D | Phys.Rev. D71 (2005) 044005 | 10.1103/PhysRevD.71.044005 | null | gr-qc | null | The geometry around a rotating massive body, which carries charge and
electrical currents, could be described by its multipole moments (mass moments,
mass-current moments, electric moments, and magnetic moments). When a small
body is orbiting this massive body, it will move on geodesics, at least for a
time interval that is short with respect to the characteristic time of the
binary due to gravitational radiation. By monitoring the waves emitted by the
small body we are actually tracing the geometry of the central object, and
hence, in principle, we can infer all its multipole moments. This paper is a
generalization of previous similar results by Ryan. The fact that the
electromagnetic moments of spacetime can be measured demonstrates that one can
obtain information about the electromagnetic field purely from gravitational
wave analysis. Additionally, these measurements could be used as a test of the
no-hair theorem for black holes.
| [
{
"created": "Wed, 20 Oct 2004 17:53:49 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Oct 2004 12:28:12 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Sotiriou",
"T. P.",
""
],
[
"Apostolatos",
"T. A.",
""
]
] | The geometry around a rotating massive body, which carries charge and electrical currents, could be described by its multipole moments (mass moments, mass-current moments, electric moments, and magnetic moments). When a small body is orbiting this massive body, it will move on geodesics, at least for a time interval that is short with respect to the characteristic time of the binary due to gravitational radiation. By monitoring the waves emitted by the small body we are actually tracing the geometry of the central object, and hence, in principle, we can infer all its multipole moments. This paper is a generalization of previous similar results by Ryan. The fact that the electromagnetic moments of spacetime can be measured demonstrates that one can obtain information about the electromagnetic field purely from gravitational wave analysis. Additionally, these measurements could be used as a test of the no-hair theorem for black holes. |
2108.11704 | Chiranjeeb Singha | Chiranjeeb Singha | Thermodynamics of multi-horizon spacetimes | 8 pages, revtex4, accepted for publication in General Relativity and
Gravitation | null | 10.1007/s10714-022-02924-5 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | There exist several well-established procedures for computing thermodynamics
for a single horizon spacetime. However, for a spacetime with multi-horizon,
the thermodynamics is not very clear. It is not fully understood whether there
exists a global temperature for the multi-horizon spacetime or not. Here we
show that a global temperature can exist for Schwarzschild-de Sitter spacetime,
Reissner-Nordstrom-de Sitter spacetime, and rotating BTZ black hole. This
temperature does not coincide with the conventional Hawking temperature related
to the outer horizon. We also show that the total entropy for these spacetimes
can not be determined only by the outer horizon. The correlations between the
horizons of these spacetimes determine it.
| [
{
"created": "Thu, 26 Aug 2021 11:01:11 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Aug 2021 10:44:02 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Apr 2022 13:03:52 GMT",
"version": "v3"
}
] | 2022-04-27 | [
[
"Singha",
"Chiranjeeb",
""
]
] | There exist several well-established procedures for computing thermodynamics for a single horizon spacetime. However, for a spacetime with multi-horizon, the thermodynamics is not very clear. It is not fully understood whether there exists a global temperature for the multi-horizon spacetime or not. Here we show that a global temperature can exist for Schwarzschild-de Sitter spacetime, Reissner-Nordstrom-de Sitter spacetime, and rotating BTZ black hole. This temperature does not coincide with the conventional Hawking temperature related to the outer horizon. We also show that the total entropy for these spacetimes can not be determined only by the outer horizon. The correlations between the horizons of these spacetimes determine it. |
gr-qc/9704085 | Cesar F. Talavera | J. Cruz, J. Navarro-Salas, M. Navarro and C. F. Talavera | Symmetries and solvable models for evaporating 2D black holes | 4 pages, Latex. Talk given at the Second Conference on Quantum
Gravity and Constrained Dynamics. To appear in Proc. Supp. Nucl. Phys. B | Nucl.Phys.Proc.Suppl. 57 (1997) 184-187 | 10.1016/S0920-5632(97)00371-X | null | gr-qc | null | We study the evaporation process of a 2D black hole in thermal equilibrium
when the ingoing radiation is switched off suddenly. We also introduce global
symmetries of generic 2D dilaton gravity models which generalize the extra
symmetry of the CGHS model.
| [
{
"created": "Wed, 30 Apr 1997 10:22:30 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Cruz",
"J.",
""
],
[
"Navarro-Salas",
"J.",
""
],
[
"Navarro",
"M.",
""
],
[
"Talavera",
"C. F.",
""
]
] | We study the evaporation process of a 2D black hole in thermal equilibrium when the ingoing radiation is switched off suddenly. We also introduce global symmetries of generic 2D dilaton gravity models which generalize the extra symmetry of the CGHS model. |
0902.3816 | Khalid Saifullah | K. Saifullah | Geometric symmetries on Lorentzian manifolds | 16 pages | Nuovo Cim.B122:447,2007 | 10.1393/ncb/i2007-10373-y | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lie derivatives of various geometrical and physical quantities define
symmetries and conformal symmetries in general relativity. Thus we obtain
motions, collineations, conformal motions and conformal collineations. These
symmetries are used not only to find new solutions of Einstein's field
equations but to classify the spaces also. Different classification schemes are
presented here. Relationships between these symmetries are discussed and
illustrating examples are presented.
| [
{
"created": "Sun, 22 Feb 2009 19:07:28 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Saifullah",
"K.",
""
]
] | Lie derivatives of various geometrical and physical quantities define symmetries and conformal symmetries in general relativity. Thus we obtain motions, collineations, conformal motions and conformal collineations. These symmetries are used not only to find new solutions of Einstein's field equations but to classify the spaces also. Different classification schemes are presented here. Relationships between these symmetries are discussed and illustrating examples are presented. |
gr-qc/9207002 | null | Riccardo Capovilla and Ted Jacobson | Remarks on Pure Spin Connection Formulations of Gravity | null | Mod.Phys.Lett.A7:1871-1878,1992 | 10.1142/S0217732392001579 | null | gr-qc | null | In the derivation of a pure spin connection action functional for gravity two
methods have been proposed. The first starts from a first order lagrangian
formulation, the second from a hamiltonian formulation. In this note we show
that they lead to identical results for the specific cases of pure gravity with
or without a cosmological constant.
| [
{
"created": "Tue, 21 Jul 1992 23:52:00 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Capovilla",
"Riccardo",
""
],
[
"Jacobson",
"Ted",
""
]
] | In the derivation of a pure spin connection action functional for gravity two methods have been proposed. The first starts from a first order lagrangian formulation, the second from a hamiltonian formulation. In this note we show that they lead to identical results for the specific cases of pure gravity with or without a cosmological constant. |
1801.04358 | Puxun Wu | Qihong Huang, Puxun Wu and Hongwei Yu | Stability of Einstein static universe in gravity theory with a
non-minimal derivative coupling | 19 pages, 1 figure, reference added | Eur.Phys.J. C78 (2018) no.1, 51 | 10.1140/epjc/s10052-018-5533-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The emergent mechanism provides a possible way to resolve the big bang
singularity problem by assuming that our universe originates from the Einstein
static (ES) state. Thus, the existence of a stable ES solution becomes a very
crucial prerequisite for the emergent scenario. In this paper, we study the
stability of an ES universe in gravity theory with a non-minimal coupling
between the kinetic term of a scalar field and the Einstein tensor. We find
that the ES solution is stable under both scalar and tensor perturbations when
the model parameters satisfy certain conditions, which indicates that the big
bang singularity can be avoided successfully by the emergent mechanism in the
non-minimally kinetic coupled gravity.
| [
{
"created": "Sat, 13 Jan 2018 01:06:13 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jan 2018 12:23:47 GMT",
"version": "v2"
}
] | 2018-02-14 | [
[
"Huang",
"Qihong",
""
],
[
"Wu",
"Puxun",
""
],
[
"Yu",
"Hongwei",
""
]
] | The emergent mechanism provides a possible way to resolve the big bang singularity problem by assuming that our universe originates from the Einstein static (ES) state. Thus, the existence of a stable ES solution becomes a very crucial prerequisite for the emergent scenario. In this paper, we study the stability of an ES universe in gravity theory with a non-minimal coupling between the kinetic term of a scalar field and the Einstein tensor. We find that the ES solution is stable under both scalar and tensor perturbations when the model parameters satisfy certain conditions, which indicates that the big bang singularity can be avoided successfully by the emergent mechanism in the non-minimally kinetic coupled gravity. |
1307.3009 | Luca Fabbri | Luca Fabbri | On the geometry of the Dirac matter with the Fermionic potentials and
its quantum properties | 11 pages | Int.J.Theor.Phys.53,3744-3755(2014) | 10.1007/s10773-014-2127-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the torsional completion of gravity with electrodynamics for
Dirac matter fields; we will see that these Dirac matter field equations will
develop torsionally-induced non-linear interactions, which can be manipulated
in order to be rearranged in the form of self-fermion potentials of a specific
structure: eventually we will see that these non-linear interactions result
into dynamical effects that are formally equivalent to those due to the quantum
corrections.
| [
{
"created": "Thu, 11 Jul 2013 08:18:39 GMT",
"version": "v1"
},
{
"created": "Tue, 13 May 2014 14:21:52 GMT",
"version": "v2"
},
{
"created": "Thu, 22 May 2014 10:20:25 GMT",
"version": "v3"
}
] | 2014-10-07 | [
[
"Fabbri",
"Luca",
""
]
] | We consider the torsional completion of gravity with electrodynamics for Dirac matter fields; we will see that these Dirac matter field equations will develop torsionally-induced non-linear interactions, which can be manipulated in order to be rearranged in the form of self-fermion potentials of a specific structure: eventually we will see that these non-linear interactions result into dynamical effects that are formally equivalent to those due to the quantum corrections. |
0806.0175 | Zeev Alexandrowicz | Zeev Alexandrowicz | Stochastic model Of universe which constantly creates dark energy
(Omega=0.7) and dark matter (Omega=0.3) but instantly at 0.12Gyr created
nucleons and radiation | 10 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An assumption attributing vacuum mass energy to symmetric 'Null' fluctuation
which with equal probability either adds or subtracts, virtual planck either
particles or antiparticles leads to the following net resultant: 'Dark Energy'
virtual particle-antiparticle pairs and 'Dark Matter' real planck particles,
constantly give $\Omega_{DE}=0.7$ and $\Omega_{DM}=03$. Second assumption that
gravitational attraction propagates as particle-bridging wavelength, leads to
following estimates: Instantly, astonishingly recently and utilizing the
wavelength, the Dark Energy particles converted into nucleons(n) and the
antiparticles into radiation (ultimately CMB). Baryogenesis occurred almost
immediately in their ultra-hot clusters. Nucleonic matter declined from
$\Omega_n=0.7$ at creation, to present time $\Omega_n=0.03$. Famous
'Acceleration' is attributed to the cohesion of a supreme cluster of nucleonic
matter, giving $z/\ell=(1-\ell/\ell_H)^{2/3}$, $z,$ $\ell$ and $\ell_H$ being
respectively, redshift, luminosity and Hubble distances.
| [
{
"created": "Sun, 1 Jun 2008 21:21:21 GMT",
"version": "v1"
}
] | 2008-06-03 | [
[
"Alexandrowicz",
"Zeev",
""
]
] | An assumption attributing vacuum mass energy to symmetric 'Null' fluctuation which with equal probability either adds or subtracts, virtual planck either particles or antiparticles leads to the following net resultant: 'Dark Energy' virtual particle-antiparticle pairs and 'Dark Matter' real planck particles, constantly give $\Omega_{DE}=0.7$ and $\Omega_{DM}=03$. Second assumption that gravitational attraction propagates as particle-bridging wavelength, leads to following estimates: Instantly, astonishingly recently and utilizing the wavelength, the Dark Energy particles converted into nucleons(n) and the antiparticles into radiation (ultimately CMB). Baryogenesis occurred almost immediately in their ultra-hot clusters. Nucleonic matter declined from $\Omega_n=0.7$ at creation, to present time $\Omega_n=0.03$. Famous 'Acceleration' is attributed to the cohesion of a supreme cluster of nucleonic matter, giving $z/\ell=(1-\ell/\ell_H)^{2/3}$, $z,$ $\ell$ and $\ell_H$ being respectively, redshift, luminosity and Hubble distances. |
1801.06149 | Daniela Pugliese Dr | D. Pugliese and H. Quevedo | Observers in Kerr spacetimes: the ergoregion on the equatorial plane | 20 pages, 13 multi-panels figures, 2 tables | null | 10.1140/epjc/s10052-018-5569-7 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a detailed analysis of the properties of stationary observers
located on the equatorial plane of the ergosphere in a Kerr spacetime,
including light-surfaces. This study highlights crucial differences between
black hole and the super-spinner sources. In the case of Kerr naked
singularities, the results allow us to distinguish between "weak" and "strong"
singularities, corresponding to spin values close to or distant from the
limiting case of extreme black holes, respectively. We derive important
limiting angular frequencies for naked singularities. We especially study very
weak singularities as resulting from the spin variation of black holes. We also
explore the main properties of zero angular momentum observers for different
classes of black hole and naked singularity spacetimes.
| [
{
"created": "Thu, 18 Jan 2018 17:57:28 GMT",
"version": "v1"
}
] | 2018-03-14 | [
[
"Pugliese",
"D.",
""
],
[
"Quevedo",
"H.",
""
]
] | We perform a detailed analysis of the properties of stationary observers located on the equatorial plane of the ergosphere in a Kerr spacetime, including light-surfaces. This study highlights crucial differences between black hole and the super-spinner sources. In the case of Kerr naked singularities, the results allow us to distinguish between "weak" and "strong" singularities, corresponding to spin values close to or distant from the limiting case of extreme black holes, respectively. We derive important limiting angular frequencies for naked singularities. We especially study very weak singularities as resulting from the spin variation of black holes. We also explore the main properties of zero angular momentum observers for different classes of black hole and naked singularity spacetimes. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.