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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9801023 | null | Brendan S. Guilfoyle and Brien C. Nolan | Yang's gravitational theory | 28 pages, to appear in Gen. Rel. Grav | Gen.Rel.Grav.30:473-495,1998 | 10.1023/A:1018815027071 | null | gr-qc | null | Yang's pure space equations (C.N. Yang, Phys. Rev. Lett. v.33, p.445 (1974))
generalize Einstein's gravitational equations, while coming from gauge theory.
We study these equations from a number of vantage points: summarizing the work
done previously, comparing them with the Einstein equations and investigating
their properties. In particular, the initial value problem is discussed and a
number of results are presented for these equations with common energy-momentum
tensors.
| [
{
"created": "Fri, 9 Jan 1998 12:50:15 GMT",
"version": "v1"
}
] | 2011-04-21 | [
[
"Guilfoyle",
"Brendan S.",
""
],
[
"Nolan",
"Brien C.",
""
]
] | Yang's pure space equations (C.N. Yang, Phys. Rev. Lett. v.33, p.445 (1974)) generalize Einstein's gravitational equations, while coming from gauge theory. We study these equations from a number of vantage points: summarizing the work done previously, comparing them with the Einstein equations and investigating their properties. In particular, the initial value problem is discussed and a number of results are presented for these equations with common energy-momentum tensors. |
gr-qc/0505014 | Tiberiu Harko | K. S. Cheng, T. Harko, X. Y. Wang | Radiation transport equations in non-Riemannian space-times | 12 pages, 3 figures, accepted for publication in PRD | Phys.Rev. D71 (2005) 103001 | 10.1103/PhysRevD.71.103001 | null | gr-qc astro-ph hep-th | null | The transport equations for polarized radiation transfer in non-Riemannian,
Weyl-Cartan type space-times are derived, with the effects of both torsion and
non-metricity included. To obtain the basic propagation equations we use the
tangent bundle approach. The equations describing the time evolution of the
Stokes parameters, of the photon distribution function and of the total
polarization degree can be formulated as a system of coupled first order
partial differential equations. As an application of our results we consider
the propagation of the cosmological gamma ray bursts in spatially homogeneous
and isotropic spaces with torsion and non-metricity. For this case the exact
general solution of the equation for the polarization degree is obtained, with
the effects of the torsion and non-metricity included. The presence of a
non-Riemannian geometrical background in which the electromagnetic fields
couple to torsion and/or non-metricity affect the polarization of photon beams.
Consequently, we suggest that the observed polarization of prompt cosmological
gamma ray bursts and of their optical afterglows may have a propagation effect
component, due to a torsion/non-metricity induced birefringence of the vacuum.
A cosmological redshift and frequency dependence of the polarization degree of
gamma ray bursts also follows from the model, thus providing a clear
observational signature of the torsional/non-metric effects. On the other hand,
observations of the polarization of the gamma ray bursts can impose strong
constraints on the torsion and non-metricity and discriminate between different
theoretical models.
| [
{
"created": "Tue, 3 May 2005 05:56:36 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Cheng",
"K. S.",
""
],
[
"Harko",
"T.",
""
],
[
"Wang",
"X. Y.",
""
]
] | The transport equations for polarized radiation transfer in non-Riemannian, Weyl-Cartan type space-times are derived, with the effects of both torsion and non-metricity included. To obtain the basic propagation equations we use the tangent bundle approach. The equations describing the time evolution of the Stokes parameters, of the photon distribution function and of the total polarization degree can be formulated as a system of coupled first order partial differential equations. As an application of our results we consider the propagation of the cosmological gamma ray bursts in spatially homogeneous and isotropic spaces with torsion and non-metricity. For this case the exact general solution of the equation for the polarization degree is obtained, with the effects of the torsion and non-metricity included. The presence of a non-Riemannian geometrical background in which the electromagnetic fields couple to torsion and/or non-metricity affect the polarization of photon beams. Consequently, we suggest that the observed polarization of prompt cosmological gamma ray bursts and of their optical afterglows may have a propagation effect component, due to a torsion/non-metricity induced birefringence of the vacuum. A cosmological redshift and frequency dependence of the polarization degree of gamma ray bursts also follows from the model, thus providing a clear observational signature of the torsional/non-metric effects. On the other hand, observations of the polarization of the gamma ray bursts can impose strong constraints on the torsion and non-metricity and discriminate between different theoretical models. |
gr-qc/0308014 | Golam Mortuza Hossain | Golam Mortuza Hossain | Hubble operator in isotropic loop quantum cosmology | 20 pages, 3 eps figures, few comments and clarifications added to
match with the published version | Class.Quant.Grav. 21 (2004) 179-196 | 10.1088/0264-9381/21/1/012 | IMSc/2003/06/11 | gr-qc hep-th | null | We present a construction of the Hubble operator for the spatially flat
isotropic loop quantum cosmology. This operator is a Dirac observable on a
subspace of the space of physical solutions. This subspace gets selected
dynamically, requiring that its action be invariant on the physical solution
space. As a simple illustrative application of the expectation value of the
operator, we do find a generic phase of (super)inflation, a feature shown by
Bojowald from the analysis of effective Friedmann equation of loop quantum
cosmology.
| [
{
"created": "Wed, 6 Aug 2003 13:56:58 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Dec 2003 15:56:08 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Hossain",
"Golam Mortuza",
""
]
] | We present a construction of the Hubble operator for the spatially flat isotropic loop quantum cosmology. This operator is a Dirac observable on a subspace of the space of physical solutions. This subspace gets selected dynamically, requiring that its action be invariant on the physical solution space. As a simple illustrative application of the expectation value of the operator, we do find a generic phase of (super)inflation, a feature shown by Bojowald from the analysis of effective Friedmann equation of loop quantum cosmology. |
gr-qc/0702060 | Muhammad Sharif | M. Sharif | Matter Collineations of Static Spacetimes with Maximal Symmetric
Transverse Spaces | 33 pages, accepted for publication in Acta Physica Polonica B | ActaPhys.Polon.B38:2003-2030,2007 | null | null | gr-qc | null | This paper is devoted to study the symmetries of the energy-momentum tensor
for the static spacetimes with maximal symmetric transverse spaces. We solve
matter collineation equations for the four main cases by taking one, two, three
and four non-zero components of the vector $\xi^a$. For one component non-zero,
we obtain only one matter collineation for the non-degenerate case and for two
components non-zero, the non-degenerate case yields maximum three matter
collineations. When we take three components non-zero, we obtain three, four
and five independent matter collineations for the non-degenerate and for the
degenerate cases respectively. This case generalizes the degenerate case of the
static spherically symmetric spacetimes. The last case (when all the four
components are non-zero) provides the generalization of the non-degenerate case
of the static spherically symmetric spacetimes. This gives either four, five,
six, seven or ten independent matter collineations in which four are the usual
Killing vectors and rest are the proper matter collineations. It is mentioned
here that we obtain different constraint equations which, on solving, may
provide some new exact solutions of the Einstein field equations.
| [
{
"created": "Sat, 10 Feb 2007 04:30:51 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Sharif",
"M.",
""
]
] | This paper is devoted to study the symmetries of the energy-momentum tensor for the static spacetimes with maximal symmetric transverse spaces. We solve matter collineation equations for the four main cases by taking one, two, three and four non-zero components of the vector $\xi^a$. For one component non-zero, we obtain only one matter collineation for the non-degenerate case and for two components non-zero, the non-degenerate case yields maximum three matter collineations. When we take three components non-zero, we obtain three, four and five independent matter collineations for the non-degenerate and for the degenerate cases respectively. This case generalizes the degenerate case of the static spherically symmetric spacetimes. The last case (when all the four components are non-zero) provides the generalization of the non-degenerate case of the static spherically symmetric spacetimes. This gives either four, five, six, seven or ten independent matter collineations in which four are the usual Killing vectors and rest are the proper matter collineations. It is mentioned here that we obtain different constraint equations which, on solving, may provide some new exact solutions of the Einstein field equations. |
1905.02275 | Yuri Bonder | Y. Bonder and J. E. Herrera-Flores | Measuring Relativistic Dragging with Quantum Interference | Contribution to the 2019 Gravitation session of the 54th Rencontres
de Moriond, 3 pages | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An experiment to test for relativistic frame dragging effects with quantum
interferometry is proposed. The idea that the classical trajectories of the
interferometer surround a spherical mass source whose angular momentum is
perpendicular to the plane containing these trajectories. A simple analysis
allows one to find the phase shift for particles traveling in the innermost
stable circular orbit; the result can be easily generalized for more realistic
orbits. The phase difference goes like the source's angular momentum per mass
times the quantum particles' mass. This is a small effect but it can be
amplified by making the classical paths go around the source several times.
Moreover, this experiment has the advantage that the source's angular momentum
can be easily controlled.
| [
{
"created": "Mon, 6 May 2019 22:05:05 GMT",
"version": "v1"
}
] | 2019-05-27 | [
[
"Bonder",
"Y.",
""
],
[
"Herrera-Flores",
"J. E.",
""
]
] | An experiment to test for relativistic frame dragging effects with quantum interferometry is proposed. The idea that the classical trajectories of the interferometer surround a spherical mass source whose angular momentum is perpendicular to the plane containing these trajectories. A simple analysis allows one to find the phase shift for particles traveling in the innermost stable circular orbit; the result can be easily generalized for more realistic orbits. The phase difference goes like the source's angular momentum per mass times the quantum particles' mass. This is a small effect but it can be amplified by making the classical paths go around the source several times. Moreover, this experiment has the advantage that the source's angular momentum can be easily controlled. |
gr-qc/9707036 | Stefan ]minneborg | Stefan Aminneborg (Norra Reals gymnasium, Stockholm), Ingemar
Bengtsson (Fysikum, Stockholm University), Dieter Brill (Department of
Physics, University of Maryland), Soren Holst and Peter Peldan (Fysikum,
Stockholm University) | Black Holes and Wormholes in 2+1 Dimensions | 23 pages, LaTeX, 11 figures | Class.Quant.Grav. 15 (1998) 627-644 | 10.1088/0264-9381/15/3/013 | USITP 97-13 | gr-qc | null | A large variety of spacetimes---including the BTZ black holes---can be
obtained by identifying points in 2+1 dimensional anti-de Sitter space by means
of a discrete group of isometries. We consider all such spacetimes that can be
obtained under a restriction to time symmetric initial data and one asymptotic
region only. The resulting spacetimes are non-eternal black holes with
collapsing wormhole topologies. Our approach is geometrical, and we discuss in
detail: The allowed topologies, the shape of the event horizons, topological
censorship and trapped curves.
| [
{
"created": "Tue, 15 Jul 1997 18:11:05 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Aminneborg",
"Stefan",
"",
"Norra Reals gymnasium, Stockholm"
],
[
"Bengtsson",
"Ingemar",
"",
"Fysikum, Stockholm University"
],
[
"Brill",
"Dieter",
"",
"Department of\n Physics, University of Maryland"
],
[
"Holst",
"Soren",
"",
"Fys... | A large variety of spacetimes---including the BTZ black holes---can be obtained by identifying points in 2+1 dimensional anti-de Sitter space by means of a discrete group of isometries. We consider all such spacetimes that can be obtained under a restriction to time symmetric initial data and one asymptotic region only. The resulting spacetimes are non-eternal black holes with collapsing wormhole topologies. Our approach is geometrical, and we discuss in detail: The allowed topologies, the shape of the event horizons, topological censorship and trapped curves. |
gr-qc/0011066 | Irina Radinschi | Irina Radinschi | Energy Distribution of a Charged Regular Black Hole | 6 pages, no figures | Mod.Phys.Lett. A16 (2001) 673 | 10.1142/S0217732301003711 | null | gr-qc | null | We calculate the energy distribution of a charged regular black hole by using
the energy-momentum complexes of Einstein and M{\o}ller.
| [
{
"created": "Mon, 20 Nov 2000 10:23:05 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Radinschi",
"Irina",
""
]
] | We calculate the energy distribution of a charged regular black hole by using the energy-momentum complexes of Einstein and M{\o}ller. |
1605.03128 | Luis Ak\'e Hau | J. Herrera and L. Ake Hau | Spacetimes Coverings and C-Boundary | Corrections of Cor. 4.11 and Cor. 4.21 (33 pages, 6 figures) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the relation between the c-completion of a Lorentz manifold V and
its quotient M = V/G, where G is an isometry group acting freely and properly
discontinuously. First, we consider the future causal completion case,
characterizing virtually when such a quotient is well behaved with the future
chronological topology and improving the existing results on the literature.
Secondly, we show that under some general assumptions, there exists an
homeomorphism and chronological isomorphism between both, the c-completion of M
and some adequate quotient of the c-completion of V defined by G. Our results
are optimal, as we show in several examples. Finally, we give a practical
application by considering isometric actions over Robertson-Walker spacetimes,
including in particular the Anti-de Sitter model.
| [
{
"created": "Tue, 10 May 2016 17:53:43 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Jul 2016 10:08:20 GMT",
"version": "v2"
}
] | 2016-07-18 | [
[
"Herrera",
"J.",
""
],
[
"Hau",
"L. Ake",
""
]
] | We consider the relation between the c-completion of a Lorentz manifold V and its quotient M = V/G, where G is an isometry group acting freely and properly discontinuously. First, we consider the future causal completion case, characterizing virtually when such a quotient is well behaved with the future chronological topology and improving the existing results on the literature. Secondly, we show that under some general assumptions, there exists an homeomorphism and chronological isomorphism between both, the c-completion of M and some adequate quotient of the c-completion of V defined by G. Our results are optimal, as we show in several examples. Finally, we give a practical application by considering isometric actions over Robertson-Walker spacetimes, including in particular the Anti-de Sitter model. |
2008.13384 | Shahar Hod | Shahar Hod | No-go theorem for spatially regular boson stars made of static
nonminimally coupled massive scalar fields | 6 pages | The European Physical Journal C 79, 26 (2019) | 10.1140/epjc/s10052-019-6546-5 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a compact theorem which reveals the fact that static spatially
regular massive scalar fields with nonminimal coupling to gravity cannot form
spherically symmetric asymptotically flat horizonless matter configurations. In
particular, the no-go theorem rules out the existence of boson stars made of
static scalar fields with generic values of the physical parameter $\xi$ which
quantifies the coupling between the spacetime curvature and the massive bosonic
fields.
| [
{
"created": "Mon, 31 Aug 2020 06:30:20 GMT",
"version": "v1"
}
] | 2020-09-09 | [
[
"Hod",
"Shahar",
""
]
] | We present a compact theorem which reveals the fact that static spatially regular massive scalar fields with nonminimal coupling to gravity cannot form spherically symmetric asymptotically flat horizonless matter configurations. In particular, the no-go theorem rules out the existence of boson stars made of static scalar fields with generic values of the physical parameter $\xi$ which quantifies the coupling between the spacetime curvature and the massive bosonic fields. |
1511.04277 | Alessandro D.A.M. Spallicci di Filottrano | P. Ritter, S. Aoudia, A. Spallicci, S. Cordier | Indirect (source-free) integration method. II. Self-force consistent
radial fall | To appear in Int. J. Geom. Meth. Mod. Phys | 2016, Int. J. Geom. Meth. Mod. Phys., 13, 1650019 | 10.1142/S0219887816500195 | null | gr-qc astro-ph.HE math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply our method of indirect integration, described in Part I, at fourth
order, to the radial fall affected by the self-force. The Mode-Sum
regularisation is performed in the Regge-Wheeler gauge using the equivalence
with the harmonic gauge for this orbit. We consider also the motion subjected
to a self-consistent and iterative correction determined by the self-force
through osculating stretches of geodesics. The convergence of the results
confirms the validity of the integration method. This work complements and
justifies the analysis and the results appeared in Int. J. Geom. Meth. Mod.
Phys., 11, 1450090 (2014).
| [
{
"created": "Fri, 13 Nov 2015 13:38:27 GMT",
"version": "v1"
}
] | 2016-03-22 | [
[
"Ritter",
"P.",
""
],
[
"Aoudia",
"S.",
""
],
[
"Spallicci",
"A.",
""
],
[
"Cordier",
"S.",
""
]
] | We apply our method of indirect integration, described in Part I, at fourth order, to the radial fall affected by the self-force. The Mode-Sum regularisation is performed in the Regge-Wheeler gauge using the equivalence with the harmonic gauge for this orbit. We consider also the motion subjected to a self-consistent and iterative correction determined by the self-force through osculating stretches of geodesics. The convergence of the results confirms the validity of the integration method. This work complements and justifies the analysis and the results appeared in Int. J. Geom. Meth. Mod. Phys., 11, 1450090 (2014). |
1910.06564 | Banibrata Mukhopadhyay | Surajit Kalita and Banibrata Mukhopadhyay | Asymptotically flat vacuum solution in modified theory of Einstein's
gravity | 8 pages including 5 figures; accepted for publication in European
Physical Journal C | Eur. Phys. J. C (2019) 79: 877 | 10.1140/epjc/s10052-019-7396-x | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A number of recent observations have suggested that the Einstein's theory of
general relativity may not be the ultimate theory of gravity. The f(R) gravity
model with R being the scalar curvature turns out to be one of the best bet to
surpass the general relativity which explains a number of phenomena where
Einstein's theory of gravity fails. In the f(R) gravity, behaviour of the
spacetime is modified as compared to that of given by the Einstein's theory of
general relativity. This theory has already been explored for understanding
various compact objects such as neutron stars, white dwarfs etc. and also
describing evolution of the universe. Although, researchers have already found
the vacuum spacetime solutions for the f(R) gravity, yet there is a caveat that
the metric does have some diverging terms and hence these solutions are not
asymptotically flat. We show that it is possible to have asymptotically flat
spherically symmetric vacuum solution for the f(R) gravity, which is different
from the Schwarzschild solution. We use this solution for explaining various
bound orbits around the black hole and eventually, as an immediate application,
in the spherical accretion flow around it.
| [
{
"created": "Tue, 15 Oct 2019 07:27:44 GMT",
"version": "v1"
}
] | 2019-11-26 | [
[
"Kalita",
"Surajit",
""
],
[
"Mukhopadhyay",
"Banibrata",
""
]
] | A number of recent observations have suggested that the Einstein's theory of general relativity may not be the ultimate theory of gravity. The f(R) gravity model with R being the scalar curvature turns out to be one of the best bet to surpass the general relativity which explains a number of phenomena where Einstein's theory of gravity fails. In the f(R) gravity, behaviour of the spacetime is modified as compared to that of given by the Einstein's theory of general relativity. This theory has already been explored for understanding various compact objects such as neutron stars, white dwarfs etc. and also describing evolution of the universe. Although, researchers have already found the vacuum spacetime solutions for the f(R) gravity, yet there is a caveat that the metric does have some diverging terms and hence these solutions are not asymptotically flat. We show that it is possible to have asymptotically flat spherically symmetric vacuum solution for the f(R) gravity, which is different from the Schwarzschild solution. We use this solution for explaining various bound orbits around the black hole and eventually, as an immediate application, in the spherical accretion flow around it. |
0707.3632 | Paschalis Karageorgis | Paschalis Karageorgis and John G. Stalker | Sharp bounds on 2m/r for static spherical objects | We changed a footnote in which an earlier result of H\aa{}kan
Andr\'{e}asson was not described correctly | Class.Quant.Grav.25:195021,2008 | 10.1088/0264-9381/25/19/195021 | null | gr-qc | null | Sharp bounds are obtained, under a variety of assumptions on the eigenvalues
of the Einstein tensor, for the ratio of the Hawking mass to the areal radius
in static, spherically symmetric space-times.
| [
{
"created": "Tue, 24 Jul 2007 20:48:53 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Oct 2007 17:26:48 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Karageorgis",
"Paschalis",
""
],
[
"Stalker",
"John G.",
""
]
] | Sharp bounds are obtained, under a variety of assumptions on the eigenvalues of the Einstein tensor, for the ratio of the Hawking mass to the areal radius in static, spherically symmetric space-times. |
1708.07527 | Gabriel R. Bengochea | Gabriel R. Bengochea, Gabriel Le\'on | Novel vacuum conditions in inflationary collapse models | 17 pages, 2 figures. Extended and revised version. To appear in
Physics Letters B | Phys. Lett. B 774 (2017) 338 | 10.1016/j.physletb.2017.09.085 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the framework of inflationary models that incorporate a spontaneous
reduction of the wave function for the emergence of the seeds of cosmic
structure, we study the effects on the primordial scalar power spectrum by
choosing a novel initial quantum state that characterizes the perturbations of
the inflaton. Specifically, we investigate under which conditions one can
recover an essentially scale free spectrum of primordial inhomogeneities when
the standard Bunch-Davies vacuum is replaced by another one that minimizes the
renormalized stress-energy tensor via a Hadamard procedure. We think that this
new prescription for selecting the vacuum state is better suited for the
self-induced collapse proposal than the traditional one in the semiclassical
gravity picture. We show that the parametrization for the time of collapse,
considered in previous works, is maintained. Also, we obtain an angular
spectrum for the CMB temperature anisotropies consistent with the one that best
fits the observational data. Therefore, we conclude that the collapse mechanism
might be of a more fundamental character than previously suspected.
| [
{
"created": "Thu, 24 Aug 2017 19:04:10 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Oct 2017 01:10:39 GMT",
"version": "v2"
}
] | 2017-10-16 | [
[
"Bengochea",
"Gabriel R.",
""
],
[
"León",
"Gabriel",
""
]
] | Within the framework of inflationary models that incorporate a spontaneous reduction of the wave function for the emergence of the seeds of cosmic structure, we study the effects on the primordial scalar power spectrum by choosing a novel initial quantum state that characterizes the perturbations of the inflaton. Specifically, we investigate under which conditions one can recover an essentially scale free spectrum of primordial inhomogeneities when the standard Bunch-Davies vacuum is replaced by another one that minimizes the renormalized stress-energy tensor via a Hadamard procedure. We think that this new prescription for selecting the vacuum state is better suited for the self-induced collapse proposal than the traditional one in the semiclassical gravity picture. We show that the parametrization for the time of collapse, considered in previous works, is maintained. Also, we obtain an angular spectrum for the CMB temperature anisotropies consistent with the one that best fits the observational data. Therefore, we conclude that the collapse mechanism might be of a more fundamental character than previously suspected. |
1306.3137 | Maur\'icio Richartz | Maur\'icio Richartz and Alberto Saa | Superradiance without event horizons in General Relativity | 5 pages; typos corrected; revised assumptions and revised argument in
section II, results unchanged | Phys. Rev. D 88, 044008 (2013) | 10.1103/PhysRevD.88.044008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Superradiant scattering processes are studied in general relativistic systems
which, unlike rotating and/or charged black holes, do not exhibit an event
horizon. Inspired by Zel'dovich's seminal works on the amplification of waves
by a rotating cylinder, we analyse, in the context of General Relativity, the
possibility of superradiance for electromagnetic waves reflecting off a
rotating star and for charged scalar perturbations impinging on a charged
sphere. The role of energy dissipation in these systems is analysed and
compared with the role of the event horizon in black hole superradiance.
| [
{
"created": "Thu, 13 Jun 2013 15:28:01 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jul 2013 06:02:29 GMT",
"version": "v2"
}
] | 2013-08-07 | [
[
"Richartz",
"Maurício",
""
],
[
"Saa",
"Alberto",
""
]
] | Superradiant scattering processes are studied in general relativistic systems which, unlike rotating and/or charged black holes, do not exhibit an event horizon. Inspired by Zel'dovich's seminal works on the amplification of waves by a rotating cylinder, we analyse, in the context of General Relativity, the possibility of superradiance for electromagnetic waves reflecting off a rotating star and for charged scalar perturbations impinging on a charged sphere. The role of energy dissipation in these systems is analysed and compared with the role of the event horizon in black hole superradiance. |
gr-qc/0511138 | Lorenzo Iorio | Lorenzo Iorio | Orbital effects of Sun's mass loss and the Earth's fate | Latex2e, 21 pages, 2 tables, 3 figures, 29 references. To appear in
Natural Science (NS) | Natural Science 2: 329-337, 2010 | 10.4236/ns.2010.24041 | null | gr-qc astro-ph hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I calculate the classical effects induced by an isotropic mass loss of a body
on the orbital motion of a test particle around it. By applying my results to
the phase in which the radius of the Sun, already moved to the Red Giant Branch
of the Hertzsprung-Russell Diagram, will become as large as 1.20 AU in about 1
Myr, I find that the Earth's perihelion position on the fixed line of the
apsides will increase by about 0.22-0.25 AU (for \dot M/M = 2 x 10^-7 yr^-1);
other researchers point towards an increase of 0.37-0.63 AU. Mercury will be
destroyed already at the end of the Main Sequence, while Venus should be
engulfed in the initial phase of the Red Giant Branch phase; the orbits of the
outer planets will increase by 1.2-7.5 AU. Simultane- ous long-term numerical
integrations of the equations of motion of all the major bodies of the solar
system, with the inclusion of a mass-loss term in the dynamical force models as
well, are required to check if the mutual N-body interactions may substantially
change the picture analytically outlined here, especially in the Red Giant
Branch phase in which Mercury and Venus may be removed from the integration.
| [
{
"created": "Fri, 25 Nov 2005 13:50:40 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jan 2010 13:23:24 GMT",
"version": "v2"
}
] | 2010-04-30 | [
[
"Iorio",
"Lorenzo",
""
]
] | I calculate the classical effects induced by an isotropic mass loss of a body on the orbital motion of a test particle around it. By applying my results to the phase in which the radius of the Sun, already moved to the Red Giant Branch of the Hertzsprung-Russell Diagram, will become as large as 1.20 AU in about 1 Myr, I find that the Earth's perihelion position on the fixed line of the apsides will increase by about 0.22-0.25 AU (for \dot M/M = 2 x 10^-7 yr^-1); other researchers point towards an increase of 0.37-0.63 AU. Mercury will be destroyed already at the end of the Main Sequence, while Venus should be engulfed in the initial phase of the Red Giant Branch phase; the orbits of the outer planets will increase by 1.2-7.5 AU. Simultane- ous long-term numerical integrations of the equations of motion of all the major bodies of the solar system, with the inclusion of a mass-loss term in the dynamical force models as well, are required to check if the mutual N-body interactions may substantially change the picture analytically outlined here, especially in the Red Giant Branch phase in which Mercury and Venus may be removed from the integration. |
gr-qc/9602046 | Abhay Ashtekar | Abhay Ashtekar, Jerzy Lewandowski | Quantum Theory of Gravity I: Area Operators | 33 pages, ReVTeX, Section 4 Revised: New results on the effect of
topology of a surface on the eigenvalues and eigenfunctions of its area
operator included. The proof of the bound on the level spacing of eigenvalues
(for large areas) simplified and its ramification to the Bekenstein-Mukhanov
analysis of black-hole evaporation made more explicit. To appear in CQG | Class.Quant.Grav.14:A55-A82,1997 | 10.1088/0264-9381/14/1A/006 | CGPG-96/2-4 | gr-qc | null | A new functional calculus, developed recently for a fully non-perturbative
treatment of quantum gravity, is used to begin a systematic construction of a
quantum theory of geometry. Regulated operators corresponding to areas of
2-surfaces are introduced and shown to be self-adjoint on the underlying
(kinematical) Hilbert space of states. It is shown that their spectra are {\it
purely} discrete indicating that the underlying quantum geometry is far from
what the continuum picture might suggest. Indeed, the fundamental excitations
of quantum geometry are 1-dimensional, rather like polymers, and the
3-dimensional continuum geometry emerges only on coarse graining. The full
Hilbert space admits an orthonormal decomposition into finite dimensional
sub-spaces which can be interpreted as the spaces of states of spin systems.
Using this property, the complete spectrum of the area operators is evaluated.
The general framework constructed here will be used in a subsequent paper to
discuss 3-dimensional geometric operators, e.g., the ones corresponding to
volumes of regions.
| [
{
"created": "Fri, 23 Feb 1996 20:29:06 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Aug 1996 23:20:53 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Lewandowski",
"Jerzy",
""
]
] | A new functional calculus, developed recently for a fully non-perturbative treatment of quantum gravity, is used to begin a systematic construction of a quantum theory of geometry. Regulated operators corresponding to areas of 2-surfaces are introduced and shown to be self-adjoint on the underlying (kinematical) Hilbert space of states. It is shown that their spectra are {\it purely} discrete indicating that the underlying quantum geometry is far from what the continuum picture might suggest. Indeed, the fundamental excitations of quantum geometry are 1-dimensional, rather like polymers, and the 3-dimensional continuum geometry emerges only on coarse graining. The full Hilbert space admits an orthonormal decomposition into finite dimensional sub-spaces which can be interpreted as the spaces of states of spin systems. Using this property, the complete spectrum of the area operators is evaluated. The general framework constructed here will be used in a subsequent paper to discuss 3-dimensional geometric operators, e.g., the ones corresponding to volumes of regions. |
1105.4579 | \"Ozcan Sert | Tekin Dereli and \"Ozcan Sert | Non-minimal $R^\beta F^2$-Coupled Electromagnetic Fields to Gravity and
Static, Spherically Symmetric Solutions | 9 pages | Modern Physics Letters A, Volume 26, Issue 20, pp. 1487-1494
(2011) | 10.1142/S0217732311036085 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate non-minimal $R^\beta F^2$-type couplings of electromagnetic
fields to gravity. We derive the field equations by a first order variational
principle using the method of Lagrange multipliers. Then we present various
static, spherically symmetric solutions describing the exterior fields in the
vicinity of electrically charged massive bodies.
| [
{
"created": "Mon, 23 May 2011 18:18:02 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jun 2011 09:59:21 GMT",
"version": "v2"
}
] | 2011-09-20 | [
[
"Dereli",
"Tekin",
""
],
[
"Sert",
"Özcan",
""
]
] | We investigate non-minimal $R^\beta F^2$-type couplings of electromagnetic fields to gravity. We derive the field equations by a first order variational principle using the method of Lagrange multipliers. Then we present various static, spherically symmetric solutions describing the exterior fields in the vicinity of electrically charged massive bodies. |
1509.01671 | James Quach Dr | James Q. Quach | Foldy-Wouthuysen transformation of the generalised Dirac Hamiltonian in
a gravitational-wave background | 4 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Goncalves et al. derived a non-relativistic limit of the generalised Dirac
Hamiltonian in the presence of a gravitational wave, using the exact
Foldy-Wouthuysen transformation. This gave rise to the intriguing notion that
spin-precession may occur even in the absence of a magnetic field. We argue
that this effect is not physical as it is the result of a gauge-variant term
that was an artefact of a flawed application of the exact Foldy-Wouthuysen
transformation. In this paper we derive the correct non-relativistic limit of
the generalised Dirac Hamiltonian in the presence of a gravitational wave,
using both the exact and standard Foldy-Wouthuysen transformation. We show that
both transformations consistently produce a Hamiltonian where all terms are
gauge-invariant. Unfortunately however, we also show that this means the novel
spin-precession effect does not exist.
| [
{
"created": "Sat, 5 Sep 2015 07:57:36 GMT",
"version": "v1"
}
] | 2015-09-08 | [
[
"Quach",
"James Q.",
""
]
] | Goncalves et al. derived a non-relativistic limit of the generalised Dirac Hamiltonian in the presence of a gravitational wave, using the exact Foldy-Wouthuysen transformation. This gave rise to the intriguing notion that spin-precession may occur even in the absence of a magnetic field. We argue that this effect is not physical as it is the result of a gauge-variant term that was an artefact of a flawed application of the exact Foldy-Wouthuysen transformation. In this paper we derive the correct non-relativistic limit of the generalised Dirac Hamiltonian in the presence of a gravitational wave, using both the exact and standard Foldy-Wouthuysen transformation. We show that both transformations consistently produce a Hamiltonian where all terms are gauge-invariant. Unfortunately however, we also show that this means the novel spin-precession effect does not exist. |
gr-qc/0005058 | Alicia M. Sintes | A.M. Sintes, A. Vecchio | Detection of gravitational waves from inspiraling compact binaries using
non-restricted post-Newtonian approximations | Latex, 6 pages. To appear in: "Rencontres de Moriond: Gravitational
waves and experimetal gravity". Edt. J. Dumarchez; Editions Frontieres,
France | null | null | null | gr-qc | null | The set up of matched filters for the detection of gravitational waves from
in-spiraling compact binaries is usually carried out using the restricted
post-Newtonian approximation: the filter phase is modelled including
post-Newtonian corrections, whereas the amplitude is retained at the Newtonian
order. Here we investigate the effects of the introduction of post-Newtonian
corrections also to the amplitude and we discuss some of the implications for
signal detection and parameter estimation.
| [
{
"created": "Tue, 16 May 2000 16:07:02 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sintes",
"A. M.",
""
],
[
"Vecchio",
"A.",
""
]
] | The set up of matched filters for the detection of gravitational waves from in-spiraling compact binaries is usually carried out using the restricted post-Newtonian approximation: the filter phase is modelled including post-Newtonian corrections, whereas the amplitude is retained at the Newtonian order. Here we investigate the effects of the introduction of post-Newtonian corrections also to the amplitude and we discuss some of the implications for signal detection and parameter estimation. |
1305.1702 | Nilanjana Mahata | Nilanjana Mahata, Subenoy Chakraborty | Dilatonic Scalar Field: A Dynamical System Analysis | 8 pages, 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The work deals with homogeneous and isotropic, flat FRW model of the universe
which is filled up with non-interacting dark matter and dark energy to
compatible with recent observational evidences. By choosing the dark energy in
the form of a dilatonic scalar field, the evolution equations are reduced to an
autonomous system. A phase space analysis is done around the critical points
and stability criteria is examined. Finally, cosmological implications of the
nature of the critical points are discussed.
| [
{
"created": "Wed, 8 May 2013 03:05:32 GMT",
"version": "v1"
}
] | 2013-05-09 | [
[
"Mahata",
"Nilanjana",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | The work deals with homogeneous and isotropic, flat FRW model of the universe which is filled up with non-interacting dark matter and dark energy to compatible with recent observational evidences. By choosing the dark energy in the form of a dilatonic scalar field, the evolution equations are reduced to an autonomous system. A phase space analysis is done around the critical points and stability criteria is examined. Finally, cosmological implications of the nature of the critical points are discussed. |
1506.08410 | Guoping Li | GuoPing Li, Biao Cao, Zhongwen Feng, Xiaotao Zu | Strong Gravitational Lensing in a Brane-World Black Hole | 12 pages. Accepted by International Journal of Theoretical Physics | null | 10.1007/s10773-015-2545-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Adopting the strong field limit approach, we investigated the strong
gravitational lensing in a Brane-World black hole, which means that the strong
field limit coefficients and the deflection angle in this gravitational field
are obtained. With this result, it can be said with certainly that the strong
gravitational lensing is related to the metric of gravitational fields closely,
the cosmology parameter {\alpha} and the dark matter parameter \b{eta} come
from the Brane-World black hole exerts a great influence on it. Comparing with
the Schwarzschild-AdS spacetime and the Schwarzschild-XCMD spacetime, the
parameters {\alpha}, \b{eta} of black holes have the similar effects on the
gravitational lensing. In some way, we infer that the real gravitational fields
in our universe can be described by this metric, so the results of the strong
gravitational lensing in this spacetime will be more reasonable for us to
observe. Finally, it has to be noticed that the influence which the parameters
{\alpha}, \b{eta} exerted on the main observable quantities of this
gravitational field is discussed.
| [
{
"created": "Sun, 28 Jun 2015 14:55:21 GMT",
"version": "v1"
}
] | 2015-06-30 | [
[
"Li",
"GuoPing",
""
],
[
"Cao",
"Biao",
""
],
[
"Feng",
"Zhongwen",
""
],
[
"Zu",
"Xiaotao",
""
]
] | Adopting the strong field limit approach, we investigated the strong gravitational lensing in a Brane-World black hole, which means that the strong field limit coefficients and the deflection angle in this gravitational field are obtained. With this result, it can be said with certainly that the strong gravitational lensing is related to the metric of gravitational fields closely, the cosmology parameter {\alpha} and the dark matter parameter \b{eta} come from the Brane-World black hole exerts a great influence on it. Comparing with the Schwarzschild-AdS spacetime and the Schwarzschild-XCMD spacetime, the parameters {\alpha}, \b{eta} of black holes have the similar effects on the gravitational lensing. In some way, we infer that the real gravitational fields in our universe can be described by this metric, so the results of the strong gravitational lensing in this spacetime will be more reasonable for us to observe. Finally, it has to be noticed that the influence which the parameters {\alpha}, \b{eta} exerted on the main observable quantities of this gravitational field is discussed. |
2402.04577 | Xiao Zhang | Jialue Li, Xiao Zhang | The Bondi-Sachs formalism for the Einstein scalar field equations with
the zero cosmological constant | 29 pages | null | null | null | gr-qc math.DG | http://creativecommons.org/publicdomain/zero/1.0/ | Inspired by interaction of gravitational waves and dark matters, we study the
Bondi-Sachs formalism for Einstein massless scalar field with zero cosmological
constant. We provide asymptotic expansions for the Bondi-Sachs metrics as well
as the scalar fields and prove the peeling property. We also prove the
positivity of the Bondi energy-momentum under conditions ensuring certain
asymptotically null hypersurfaces are of order 2.
| [
{
"created": "Wed, 7 Feb 2024 04:33:52 GMT",
"version": "v1"
}
] | 2024-02-08 | [
[
"Li",
"Jialue",
""
],
[
"Zhang",
"Xiao",
""
]
] | Inspired by interaction of gravitational waves and dark matters, we study the Bondi-Sachs formalism for Einstein massless scalar field with zero cosmological constant. We provide asymptotic expansions for the Bondi-Sachs metrics as well as the scalar fields and prove the peeling property. We also prove the positivity of the Bondi energy-momentum under conditions ensuring certain asymptotically null hypersurfaces are of order 2. |
gr-qc/9211002 | Jonathan Z. Simon | Leonard Parker and Jonathan Z. Simon | Einstein Equation with Quantum Corrections Reduced to Second Order | 47 pages plus 4 figure pages | Phys.Rev.D47:1339-1355,1993 | 10.1103/PhysRevD.47.1339 | WISC-MILW-92-TH-14 | gr-qc | null | We consider the Einstein equation with first order (semiclassical) quantum
corrections. Although the quantum corrections contain up to fourth order
derivatives of the metric, the solutions which are physically relevant satisfy
a reduced equations which contain derivatives no higher than second order. We
obtain the reduced equations for a range of stress-energy tensors. These
reduced equations are suitable for numerical solution, are expected to contain
fewer numerical instabilities than the original fourth order equations, and
yield only physically relevant solutions. We give analytic and numerical
solutions or reduced equations for particular examples, including
Friedmann-Lema\^\i tre universes with cosmological constant, a spherical body
of constant density, and more general conformally flat metrics.
| [
{
"created": "Tue, 3 Nov 1992 16:14:00 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Parker",
"Leonard",
""
],
[
"Simon",
"Jonathan Z.",
""
]
] | We consider the Einstein equation with first order (semiclassical) quantum corrections. Although the quantum corrections contain up to fourth order derivatives of the metric, the solutions which are physically relevant satisfy a reduced equations which contain derivatives no higher than second order. We obtain the reduced equations for a range of stress-energy tensors. These reduced equations are suitable for numerical solution, are expected to contain fewer numerical instabilities than the original fourth order equations, and yield only physically relevant solutions. We give analytic and numerical solutions or reduced equations for particular examples, including Friedmann-Lema\^\i tre universes with cosmological constant, a spherical body of constant density, and more general conformally flat metrics. |
gr-qc/9801035 | Yousuke Itoh | Y. Itoh, M. Hotta, M. Morikawa and T. Futamase | Dynamical Instability of a two-dimensional Quantum Black Hole | 7 pages, 2 figures, LaTeX, Phys. Rev. D (submitted) | Phys.Rev.D57:4516-4520,1998 | 10.1103/PhysRevD.57.4516 | TU-530 | gr-qc | null | We investigate dynamical instability of a two-dimensional quantum black hole
model considered by Lowe in his study of Hawking evaporation. The model is
supposed to express a black hole in equilibrium with a bath of Hawking
radiation. It turns out that the model has at least one instability modes for a
wide range of parameters, and thus it is unstable.
| [
{
"created": "Mon, 12 Jan 1998 05:51:19 GMT",
"version": "v1"
}
] | 2010-10-12 | [
[
"Itoh",
"Y.",
""
],
[
"Hotta",
"M.",
""
],
[
"Morikawa",
"M.",
""
],
[
"Futamase",
"T.",
""
]
] | We investigate dynamical instability of a two-dimensional quantum black hole model considered by Lowe in his study of Hawking evaporation. The model is supposed to express a black hole in equilibrium with a bath of Hawking radiation. It turns out that the model has at least one instability modes for a wide range of parameters, and thus it is unstable. |
gr-qc/0201057 | Spiros Cotsakis | Yvonne Choquet-Bruhat and Spiros Cotsakis | Global Hyperbolicity and Completeness | 7 pages. Accepted for publication in the Journal of Geometry and
Physics. v2: Minor typos corrected | J.Geom.Phys. 43 (2002) 345-350 | 10.1016/S0393-0440(02)00028-1 | null | gr-qc | null | We prove global hyperbolicity of spacetimes under generic regularity
conditions on the metric. We then show that these spacetimes are timelike and
null geodesically complete if the gradient of the lapse and the extrinsic
curvature $K$ are integrable. This last condition is required only for the
tracefree part of $K$ if the universe is expanding.
| [
{
"created": "Thu, 17 Jan 2002 12:23:23 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Jan 2002 16:33:10 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Choquet-Bruhat",
"Yvonne",
""
],
[
"Cotsakis",
"Spiros",
""
]
] | We prove global hyperbolicity of spacetimes under generic regularity conditions on the metric. We then show that these spacetimes are timelike and null geodesically complete if the gradient of the lapse and the extrinsic curvature $K$ are integrable. This last condition is required only for the tracefree part of $K$ if the universe is expanding. |
2102.00830 | Kouji Nakamura | Kouji Nakamura | Proposal of a gauge-invariant treatment of l=0,1-mode perturbations on
Schwarzschild Background Spacetime | (v1) 10 pages, no figure; (v2) 16 pages, Section 2 is added for the
explanation of our previous works, Additional explanations are added,
references are added and re-organized; (v3) Some explanations are added,
Typos are corrected | null | 10.1088/1361-6382/ac03f9 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A gauge-invariant treatment of the monopole- ($l=0$) and dipole ($l=1$) modes
in linear perturbations of the Schwarzschild background spacetime is proposed.
Through this gauge-invariant treatment, we derived the solutions to the
linearized Einstein equation for these modes with a generic matter field. In
the vacuum case, these solutions include the Kerr parameter perturbations in
the $l=1$ odd modes and the additional mass parameter perturbations of the
Schwarzschild mass in the $l=0$ even modes. The linearized version of
Birkhoff's theorem is also confirmed in a gauge-invariant manner. In this
sense, our proposal is reasonable.
| [
{
"created": "Mon, 1 Feb 2021 13:36:00 GMT",
"version": "v1"
},
{
"created": "Sat, 17 Apr 2021 09:44:44 GMT",
"version": "v2"
},
{
"created": "Fri, 14 May 2021 11:20:32 GMT",
"version": "v3"
}
] | 2021-08-11 | [
[
"Nakamura",
"Kouji",
""
]
] | A gauge-invariant treatment of the monopole- ($l=0$) and dipole ($l=1$) modes in linear perturbations of the Schwarzschild background spacetime is proposed. Through this gauge-invariant treatment, we derived the solutions to the linearized Einstein equation for these modes with a generic matter field. In the vacuum case, these solutions include the Kerr parameter perturbations in the $l=1$ odd modes and the additional mass parameter perturbations of the Schwarzschild mass in the $l=0$ even modes. The linearized version of Birkhoff's theorem is also confirmed in a gauge-invariant manner. In this sense, our proposal is reasonable. |
gr-qc/0612036 | Mayeul Arminjon | Mayeul Arminjon | A theory of gravity as a pressure force. II. Lorentz contraction and
"relativistic" effects | 21 pages | Rev.Roum.Sci.Tech.Ser.Mec.Appl. 38 (1993) 107-128 | null | null | gr-qc | null | In a foregoing paper, gravity has been interpreted as the pressure force
exerted on matter at the scale of elementary particles by a perfect fluid.
Under the condition that Newtonian gravity must be recovered in the
incompressible case, a scalar field equation has thus been proposed for
gravity, giving a new theory in the compressible case. Here the theory is
reinterpreted so as to describe the relativistic effects, by extending the
Lorentz-Poincar\'e interpretation of special relativity which is first
recalled. Gravitational space-contraction and time-dilatation are postulated,
as a consequence of the principle of local equivalence between the effects of
motion and gravitation. The space-time metric (expressing the proper time along
a trajectory) is hence curved also in the proposed theory. As the result of a
modified Newton law, it is proved that free test particles follow geodesic
lines of this metric. In the spherical static situation, Schwarzschild's
exterior metric is exactly recovered and with it the experimental support of
general relativity, but the interior solution as well as the problematic of
singularities are different in the proposed theory, e.g. the radius of the body
cannot be smaller than the Schwarzschild radius.
| [
{
"created": "Wed, 6 Dec 2006 09:57:05 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Arminjon",
"Mayeul",
""
]
] | In a foregoing paper, gravity has been interpreted as the pressure force exerted on matter at the scale of elementary particles by a perfect fluid. Under the condition that Newtonian gravity must be recovered in the incompressible case, a scalar field equation has thus been proposed for gravity, giving a new theory in the compressible case. Here the theory is reinterpreted so as to describe the relativistic effects, by extending the Lorentz-Poincar\'e interpretation of special relativity which is first recalled. Gravitational space-contraction and time-dilatation are postulated, as a consequence of the principle of local equivalence between the effects of motion and gravitation. The space-time metric (expressing the proper time along a trajectory) is hence curved also in the proposed theory. As the result of a modified Newton law, it is proved that free test particles follow geodesic lines of this metric. In the spherical static situation, Schwarzschild's exterior metric is exactly recovered and with it the experimental support of general relativity, but the interior solution as well as the problematic of singularities are different in the proposed theory, e.g. the radius of the body cannot be smaller than the Schwarzschild radius. |
1612.06207 | Sante Carloni Dr | Sante Carloni | Generalising the coupling between spacetime and matter | 11 pages, no figures, to appear on Physics letters B | null | 10.1016/j.physletb.2016.12.053 | null | gr-qc astro-ph.CO astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the idea that the coupling between matter and spacetime is more
complex than the one originally envisioned by Einstein. We propose that such
coupling takes the form of a new fundamental tensor in the Einstein field
equations. We then show that the introduction of this tensor can account for
dark phenomenology in General Relativity, maintaining a weak field limit
compatible with standard Newtonian gravitation. The same paradigm can be
applied any other theory of gravitation. We show, as an example, that in the
context of conformal gravity a generalised coupling is able to solve
compatibility issues between the matter and the gravitational sector.
| [
{
"created": "Mon, 19 Dec 2016 14:46:57 GMT",
"version": "v1"
}
] | 2017-02-01 | [
[
"Carloni",
"Sante",
""
]
] | We explore the idea that the coupling between matter and spacetime is more complex than the one originally envisioned by Einstein. We propose that such coupling takes the form of a new fundamental tensor in the Einstein field equations. We then show that the introduction of this tensor can account for dark phenomenology in General Relativity, maintaining a weak field limit compatible with standard Newtonian gravitation. The same paradigm can be applied any other theory of gravitation. We show, as an example, that in the context of conformal gravity a generalised coupling is able to solve compatibility issues between the matter and the gravitational sector. |
gr-qc/0505015 | Allan Joseph Michael Medved | A.J.M. Medved and Elias C. Vagenas | On Hawking Radiation as Tunneling with Logarithmic Corrections | 6 pages; (v2) references added and various cosmetic (but no physics)
changes | Mod.Phys.Lett. A20 (2005) 1723-1728 | 10.1142/S0217732305018025 | null | gr-qc hep-th | null | There has been recent speculation that the tunneling paradigm for Hawking
radiation could -- after quantum-gravitational effects have suitably been
incorporated -- provide a means for resolving the (black hole) information loss
paradox. A prospective quantum-gravitational effect is the logarithmic-order
correction to the Bekenstein-Hawking entropy/area law. In this letter, it is
demonstrated that, even with the inclusion of the logarithmic correction (or,
indeed, the quantum correction up to any perturbative order), the tunneling
formalism is still unable to resolve the stated paradox. Moreover, we go on to
show that the tunneling framework effectively constrains the coefficient of
this logarithmic term to be non-negative. Significantly, the latter observation
implies the necessity for including the canonical corrections in the quantum
formulation of the black hole entropy.
| [
{
"created": "Tue, 3 May 2005 19:29:39 GMT",
"version": "v1"
},
{
"created": "Thu, 12 May 2005 18:00:31 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Medved",
"A. J. M.",
""
],
[
"Vagenas",
"Elias C.",
""
]
] | There has been recent speculation that the tunneling paradigm for Hawking radiation could -- after quantum-gravitational effects have suitably been incorporated -- provide a means for resolving the (black hole) information loss paradox. A prospective quantum-gravitational effect is the logarithmic-order correction to the Bekenstein-Hawking entropy/area law. In this letter, it is demonstrated that, even with the inclusion of the logarithmic correction (or, indeed, the quantum correction up to any perturbative order), the tunneling formalism is still unable to resolve the stated paradox. Moreover, we go on to show that the tunneling framework effectively constrains the coefficient of this logarithmic term to be non-negative. Significantly, the latter observation implies the necessity for including the canonical corrections in the quantum formulation of the black hole entropy. |
gr-qc/9401029 | null | R.J. Henderson and S.G. Rajeev | Quantum Gravity on a Circle and the Diffeomorphism Invariance of the
Schrodinger Equation | 35 pages, Tex | Class.Quant.Grav.11:1631-1652,1994 | 10.1088/0264-9381/11/7/006 | University of Rochester Preprint UR1342 | gr-qc hep-th | null | We study a model for quantum gravity on a circle in which the notion of a
classical metric tensor is replaced by a quantum metric with an inhomogeneous
transformation law under diffeomorphisms. This transformation law corresponds
to the co--adjoint action of the Virasoro algebra, and resembles that of the
connection in Yang--Mills theory. The transformation property is motivated by
the diffeomorphism invariance of the one dimensional Schr\"odinger equation.
The quantum distance measured by the metric corresponds to the phase of a
quantum mechanical wavefunction. The dynamics of the quantum gravity theory are
specified by postulating a Riemann metric on the space $Q$ of quantum metrics
and taking the kinetic energy operator to be the resulting laplacian on the
configuration space $Q/\rm Diff_0(S^1)$. The resulting metric on the
configuration space is analyzed and found to have singularities. The
second--quantized Schr\"odinger equation is derived, some exact solutions are
found, and a generic wavefunction behavior near one of the metric singularities
is described. Finally some further directions are indicated, including an
analogue of the Yamabe problem of differential geometry.
| [
{
"created": "Tue, 25 Jan 1994 22:35:50 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Henderson",
"R. J.",
""
],
[
"Rajeev",
"S. G.",
""
]
] | We study a model for quantum gravity on a circle in which the notion of a classical metric tensor is replaced by a quantum metric with an inhomogeneous transformation law under diffeomorphisms. This transformation law corresponds to the co--adjoint action of the Virasoro algebra, and resembles that of the connection in Yang--Mills theory. The transformation property is motivated by the diffeomorphism invariance of the one dimensional Schr\"odinger equation. The quantum distance measured by the metric corresponds to the phase of a quantum mechanical wavefunction. The dynamics of the quantum gravity theory are specified by postulating a Riemann metric on the space $Q$ of quantum metrics and taking the kinetic energy operator to be the resulting laplacian on the configuration space $Q/\rm Diff_0(S^1)$. The resulting metric on the configuration space is analyzed and found to have singularities. The second--quantized Schr\"odinger equation is derived, some exact solutions are found, and a generic wavefunction behavior near one of the metric singularities is described. Finally some further directions are indicated, including an analogue of the Yamabe problem of differential geometry. |
2403.11527 | Jack Hughes | Jack C. M. Hughes, Fedor V. Kusmartsev | Connecting 2-Forms, Conformal Transformations, Curvature Invariants and
Topological Classes in Einstein Spacetimes | 19 pages, submitted to EPJ C | null | null | null | gr-qc hep-ph hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | The unique Nature of the Lorentz group in four dimensions is the root cause
of the many remarkable properties of the Einstein spacetimes, in particular
their operational structure on the 2-forms. We show how this operational
structure can be used for two ends. First, it allows for a simple
generalization of the Birkhoff theorem to Schwarzschild (A)de-Sitter spacetime.
Second, it provides the means to construct an Abelian endomorphism group on the
space of 2-forms. It is observed that taking the trace over this group
element-wise induces a further Abelian group which may be identified with a
tensor representation of conformal transformations, giving Einstein spacetimes
access to their own conformal equivalence class. A further trace over the group
yields the curvature invariants of the spacetime. The Kretschmann scalar
becomes the topological Euler density, which may be linked in a simple way to
the Hawking temperature of horizons.
| [
{
"created": "Mon, 18 Mar 2024 07:29:28 GMT",
"version": "v1"
}
] | 2024-03-19 | [
[
"Hughes",
"Jack C. M.",
""
],
[
"Kusmartsev",
"Fedor V.",
""
]
] | The unique Nature of the Lorentz group in four dimensions is the root cause of the many remarkable properties of the Einstein spacetimes, in particular their operational structure on the 2-forms. We show how this operational structure can be used for two ends. First, it allows for a simple generalization of the Birkhoff theorem to Schwarzschild (A)de-Sitter spacetime. Second, it provides the means to construct an Abelian endomorphism group on the space of 2-forms. It is observed that taking the trace over this group element-wise induces a further Abelian group which may be identified with a tensor representation of conformal transformations, giving Einstein spacetimes access to their own conformal equivalence class. A further trace over the group yields the curvature invariants of the spacetime. The Kretschmann scalar becomes the topological Euler density, which may be linked in a simple way to the Hawking temperature of horizons. |
gr-qc/9506036 | Patricio Anibal Letelier | Patricio S. Letelier | Spacetime Defects: Torsion Loops | 8 pages, LATEX | Class.Quant.Grav.12:2221-2224,1995 | 10.1088/0264-9381/12/9/009 | null | gr-qc | null | Spacetimes with everywhere vanishing curvature tensor, but with torsion
different from zero only on world sheets that represent closed loops in
ordinary space are presented, also defects along open curves with end points at
infinity are studied. The case of defects along timelike loops is also
considered and the geodesics in these spaces are briefly discussed.
| [
{
"created": "Mon, 19 Jun 1995 18:45:45 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Letelier",
"Patricio S.",
""
]
] | Spacetimes with everywhere vanishing curvature tensor, but with torsion different from zero only on world sheets that represent closed loops in ordinary space are presented, also defects along open curves with end points at infinity are studied. The case of defects along timelike loops is also considered and the geodesics in these spaces are briefly discussed. |
gr-qc/9903039 | Israel Quiroz | Israel Quiros (Dpto.Fisica. Universidad Central de Las Villas. Cuba) | The $\omega\to\infty$ limit of Brans-Dicke gravity revisited | 8 pages, LaTeX file, submitted to Phys.Lett.A | null | null | null | gr-qc | null | The $\omega\to\infty$ limit of Brans-Dicke theory is studied with the help of
the conformal transformation approach without resorting, however, to the
conformal invariance property of this formalism, that is shown to be spurious.
| [
{
"created": "Wed, 10 Mar 1999 22:21:35 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Quiros",
"Israel",
"",
"Dpto.Fisica. Universidad Central de Las Villas. Cuba"
]
] | The $\omega\to\infty$ limit of Brans-Dicke theory is studied with the help of the conformal transformation approach without resorting, however, to the conformal invariance property of this formalism, that is shown to be spurious. |
gr-qc/0005012 | Pinto Innocenzo M. | R.P. Croce, Th. Demma, V. Pierro, I.M. Pinto, F. Postiglione | A Nearly Minimum Redundant Correlator Interpolation Formula for
Gravitational Wave Chirp Detection | 13 pages, 1 table, 16 figures; scheduled for publication on Phys.
Rev. D 62 | Phys.Rev. D62 (2000) 124020 | 10.1103/PhysRevD.62.124020 | null | gr-qc | null | An absolute lower bound on the number of templates needed to keep the fitting
factor above a prescribed minimal value $\Gamma$ in correlator bank detection
of (newtonian) gravitational wave chirps from unknown inspiraling compact
binary sources is derived, resorting to the theory of quasi-bandlimited
functions in the $L^\infty$ norm. An explicit nearly-minimum redundant
cardinal-interpolation formula for the (reduced, noncoherent) correlator is
introduced. Its computational burden and statistical properties are compared to
those of the plain lattice of (reduced, noncoherent) correlators, for the same
$\Gamma$. Extension to post-newtonian models is outlined.
| [
{
"created": "Wed, 3 May 2000 17:21:34 GMT",
"version": "v1"
},
{
"created": "Thu, 4 May 2000 12:55:37 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Croce",
"R. P.",
""
],
[
"Demma",
"Th.",
""
],
[
"Pierro",
"V.",
""
],
[
"Pinto",
"I. M.",
""
],
[
"Postiglione",
"F.",
""
]
] | An absolute lower bound on the number of templates needed to keep the fitting factor above a prescribed minimal value $\Gamma$ in correlator bank detection of (newtonian) gravitational wave chirps from unknown inspiraling compact binary sources is derived, resorting to the theory of quasi-bandlimited functions in the $L^\infty$ norm. An explicit nearly-minimum redundant cardinal-interpolation formula for the (reduced, noncoherent) correlator is introduced. Its computational burden and statistical properties are compared to those of the plain lattice of (reduced, noncoherent) correlators, for the same $\Gamma$. Extension to post-newtonian models is outlined. |
0810.4673 | Mohammad Nouri-Zonoz | A. Azadi, D. Momeni and M. Nouri-Zonoz | Cylindrical solutions in metric f(R) gravity | 13 pages, RevTex, Typos corrected and references added | Phys.Lett.B670:210-214,2008 | 10.1016/j.physletb.2008.10.054 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study static cylindrically symmetric vacuum solutions in Weyl coordinates
in the context of the metric f(R) theories of gravity. The set of the modified
Einstein equations is reduced to a single equation and it is shown how one can
construct exact solutions corresponding to different $f(R)$ models. In
particular the family of solutions with constant Ricci scalar ($R=R_{0}$) is
found explicitly which, as a special case (R=0), includes the exterior
spacetime of a cosmic string. Another new solution with constant, non-zero
Ricci scalar is obtained and its possible relation to the Linet-Tian solution
in general relativity is discussed.
| [
{
"created": "Sun, 26 Oct 2008 09:33:04 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Dec 2008 07:57:13 GMT",
"version": "v2"
}
] | 2008-12-18 | [
[
"Azadi",
"A.",
""
],
[
"Momeni",
"D.",
""
],
[
"Nouri-Zonoz",
"M.",
""
]
] | We study static cylindrically symmetric vacuum solutions in Weyl coordinates in the context of the metric f(R) theories of gravity. The set of the modified Einstein equations is reduced to a single equation and it is shown how one can construct exact solutions corresponding to different $f(R)$ models. In particular the family of solutions with constant Ricci scalar ($R=R_{0}$) is found explicitly which, as a special case (R=0), includes the exterior spacetime of a cosmic string. Another new solution with constant, non-zero Ricci scalar is obtained and its possible relation to the Linet-Tian solution in general relativity is discussed. |
2201.06511 | Charles J. Horowitz | Tomoyo Namigata, C. J. Horowitz and R. Widmer-Schnidrig | Gravitational search for near Earth black holes or other compact dark
objects | six pages, 6 figures | null | null | null | gr-qc astro-ph.CO astro-ph.EP astro-ph.HE hep-ph nucl-th | http://creativecommons.org/licenses/by-sa/4.0/ | Primordial black holes, with masses comparable to asteroids, are an
attractive possibility for dark matter. In addition, other forms of dark matter
could form compact dark objects (CDO). We search for small tidal accelerations
from low mass black holes or CDOs orbiting near the Earth, and find none. Using
about 10 years of data from the superconducting gravimeters in the Black Forest
Observatory in South-Western Germany and at Djougou, Northern Benin in Western
Africa we set an upper limit on the maximum mass of any dark object orbiting
the Earth as a function of orbital radius. For semi-major axis less than two
earth radii we exclude all black holes or CDOs with masses larger than
6.7x10^{13} kg. Lower mass primordial black holes may be strongly constrained
by Hawking radiation. We conclude that near Earth black holes are extremely
unlikely.
| [
{
"created": "Mon, 17 Jan 2022 16:40:56 GMT",
"version": "v1"
}
] | 2022-01-19 | [
[
"Namigata",
"Tomoyo",
""
],
[
"Horowitz",
"C. J.",
""
],
[
"Widmer-Schnidrig",
"R.",
""
]
] | Primordial black holes, with masses comparable to asteroids, are an attractive possibility for dark matter. In addition, other forms of dark matter could form compact dark objects (CDO). We search for small tidal accelerations from low mass black holes or CDOs orbiting near the Earth, and find none. Using about 10 years of data from the superconducting gravimeters in the Black Forest Observatory in South-Western Germany and at Djougou, Northern Benin in Western Africa we set an upper limit on the maximum mass of any dark object orbiting the Earth as a function of orbital radius. For semi-major axis less than two earth radii we exclude all black holes or CDOs with masses larger than 6.7x10^{13} kg. Lower mass primordial black holes may be strongly constrained by Hawking radiation. We conclude that near Earth black holes are extremely unlikely. |
gr-qc/0512117 | Douglas Shaw | Douglas J. Shaw and John D. Barrow | Local Experiments See Cosmologically Varying Constants | 6 pages | Phys.Lett.B639:596-599,2006 | 10.1016/j.physletb.2006.07.016 | null | gr-qc astro-ph hep-th | null | We describe a rigorous construction, using matched asymptotic expansions,
which establishes under very general conditions that local terrestrial and
solar-system experiments will measure the effects of varying `constants' of
Nature occurring on cosmological scales to computable precision. In particular,
`constants' driven by scalar fields will still be found to evolve in time when
observed within virialised structures like clusters, galaxies, and planetary
systems. This provides a justification for combining cosmological and
terrestrial constraints on the possible time variation of many assumed
`constants' of Nature, including the fine structure constant and Newton's
gravitation constant.
| [
{
"created": "Tue, 20 Dec 2005 19:35:48 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Dec 2005 09:50:51 GMT",
"version": "v2"
}
] | 2011-07-19 | [
[
"Shaw",
"Douglas J.",
""
],
[
"Barrow",
"John D.",
""
]
] | We describe a rigorous construction, using matched asymptotic expansions, which establishes under very general conditions that local terrestrial and solar-system experiments will measure the effects of varying `constants' of Nature occurring on cosmological scales to computable precision. In particular, `constants' driven by scalar fields will still be found to evolve in time when observed within virialised structures like clusters, galaxies, and planetary systems. This provides a justification for combining cosmological and terrestrial constraints on the possible time variation of many assumed `constants' of Nature, including the fine structure constant and Newton's gravitation constant. |
1008.0345 | Quentin G. Bailey | Quentin G. Bailey | Gravity Couplings in the Standard-Model Extension | 5 pages, Presented at the Fifth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 28-July 2, 2010 | null | 10.1142/9789814327688_0030 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Standard-Model Extension (SME) is an action-based expansion describing
general Lorentz violation for known matter and fields, including gravity. In
this talk, I will discuss the Lorentz-violating gravity couplings in the SME.
Toy models that match the SME expansion, including vector and two-tensor
models, are reviewed. Finally I discuss the status of experiments and
observations probing gravity coefficients for Lorentz violation.
| [
{
"created": "Mon, 2 Aug 2010 16:49:08 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Bailey",
"Quentin G.",
""
]
] | The Standard-Model Extension (SME) is an action-based expansion describing general Lorentz violation for known matter and fields, including gravity. In this talk, I will discuss the Lorentz-violating gravity couplings in the SME. Toy models that match the SME expansion, including vector and two-tensor models, are reviewed. Finally I discuss the status of experiments and observations probing gravity coefficients for Lorentz violation. |
gr-qc/9602044 | null | Vicen\c{c} Mendez and Josep Triginer | Qualitative Analysis of Causal Cosmological Models | RevTeX file, 23 pages. Accepted for publication in J. Math. Phys | J.Math.Phys.37:2906-2919,1996 | 10.1063/1.531546 | null | gr-qc | null | The Einstein's field equations of Friedmann-Robertson-Walker universes filled
with a dissipative fluid described by both the {\em truncated} and {\em
non-truncated} causal transport equations are analyzed using techniques from
dynamical systems theory. The equations of state, as well as the phase space,
are different from those used in the recent literature. In the de Sitter
expansion both the hydrodynamic approximation and the non-thermalizing
condition can be fulfilled simultaneously. For $\Lambda=0$ these expansions
turn out to be stable provided a certain parameter of the fluid is lower than
1/2. The more general case $\Lambda>0$ is studied in detail as well.
| [
{
"created": "Fri, 23 Feb 1996 14:18:40 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Mendez",
"Vicenç",
""
],
[
"Triginer",
"Josep",
""
]
] | The Einstein's field equations of Friedmann-Robertson-Walker universes filled with a dissipative fluid described by both the {\em truncated} and {\em non-truncated} causal transport equations are analyzed using techniques from dynamical systems theory. The equations of state, as well as the phase space, are different from those used in the recent literature. In the de Sitter expansion both the hydrodynamic approximation and the non-thermalizing condition can be fulfilled simultaneously. For $\Lambda=0$ these expansions turn out to be stable provided a certain parameter of the fluid is lower than 1/2. The more general case $\Lambda>0$ is studied in detail as well. |
1212.2588 | Roldao da Rocha | J. M. Hoff da Silva, Roldao da Rocha | Schwarzschild generalized black hole horizon and the embedding space | 7 pages, to appear in European Phys. J. C | Eur. Phys. J. C 72 (2012) 2258 | 10.1140/epjc/s10052-012-2258-9 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By performing a Taylor expansion along the extra dimension of a metric
describing a black hole on a brane, we explore the influence of the embedding
space on the black hole horizon. In particular, it is shown that the existence
of a Kottler correction of the black hole on the brane, in a viable braneworld
scenario, might represent the radius of the black string collapsing to zero,
for some point(s) on the black string axis of symmetry along the extra
dimension. Further scrutiny on such black hole corrections by braneworld
effects is elicited, the well-known results in the literature are recovered as
limiting cases, and we assert and show that when the radius of the black string
transversal section is zero, as one moves away from the brane into the bulk, is
indeed a singularity.
| [
{
"created": "Tue, 11 Dec 2012 19:00:28 GMT",
"version": "v1"
}
] | 2012-12-19 | [
[
"da Silva",
"J. M. Hoff",
""
],
[
"da Rocha",
"Roldao",
""
]
] | By performing a Taylor expansion along the extra dimension of a metric describing a black hole on a brane, we explore the influence of the embedding space on the black hole horizon. In particular, it is shown that the existence of a Kottler correction of the black hole on the brane, in a viable braneworld scenario, might represent the radius of the black string collapsing to zero, for some point(s) on the black string axis of symmetry along the extra dimension. Further scrutiny on such black hole corrections by braneworld effects is elicited, the well-known results in the literature are recovered as limiting cases, and we assert and show that when the radius of the black string transversal section is zero, as one moves away from the brane into the bulk, is indeed a singularity. |
2004.10031 | Ahmadjon Abdujabbarov | Javlon Rayimbaev, Ahmadjon Abdujabbarov, Bobur Turimov, Farruh
Atamurotov | Magnetized particle motion around 4-D Einstein-Gauss-Bonnet Black Hole | 12 pages, 11 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have investigated the dynamics of magnetized particles
around 4-D Einstein-Gauss-Bonnet black hole immersed in an external
asymptotically uniform magnetic field. We have shown that the magnetic
interaction parameter responsible for circular orbits decreases for negative
values of the Gauss-Bonnet parameter $\alpha$ and the range where magnetized
particle's stable circular orbits are allowed increases for the positive values
of the parameter $\alpha$. The study of the collisions of magnetized, charged
and neutral particles has shown that the center-of-mass energy of the particles
increases in the presence of positive Gauss-Bonnet parameter. Finally, we show
how the magnetic interaction and Gauss-Bonnet parameter may mimic the effect of
rotation of the Kerr black hole giving the same ISCO radius for magnetized
particles. Detailed analysis of the ISCO show that spin of Kerr black hole can
not be mimicked by the effects of magnetic interaction and the Gauss-Bonnet
parameters when $\alpha<-4.37$ and the spin parameter $a > 0.237$.
| [
{
"created": "Tue, 21 Apr 2020 14:07:16 GMT",
"version": "v1"
}
] | 2020-04-22 | [
[
"Rayimbaev",
"Javlon",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
],
[
"Turimov",
"Bobur",
""
],
[
"Atamurotov",
"Farruh",
""
]
] | In this paper, we have investigated the dynamics of magnetized particles around 4-D Einstein-Gauss-Bonnet black hole immersed in an external asymptotically uniform magnetic field. We have shown that the magnetic interaction parameter responsible for circular orbits decreases for negative values of the Gauss-Bonnet parameter $\alpha$ and the range where magnetized particle's stable circular orbits are allowed increases for the positive values of the parameter $\alpha$. The study of the collisions of magnetized, charged and neutral particles has shown that the center-of-mass energy of the particles increases in the presence of positive Gauss-Bonnet parameter. Finally, we show how the magnetic interaction and Gauss-Bonnet parameter may mimic the effect of rotation of the Kerr black hole giving the same ISCO radius for magnetized particles. Detailed analysis of the ISCO show that spin of Kerr black hole can not be mimicked by the effects of magnetic interaction and the Gauss-Bonnet parameters when $\alpha<-4.37$ and the spin parameter $a > 0.237$. |
1511.08732 | Leandros Perivolaropoulos | A. Lykkas and L. Perivolaropoulos | Scalar-Tensor Quintessence with a linear potential: Avoiding the Big
Crunch cosmic doomsday | 6 pages, 5 figures. Extended version. Accepted in Phys. Rev. D as
regular article (to appear) | Phys. Rev. D 93, 043513 (2016) | 10.1103/PhysRevD.93.043513 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | All quintessence potentials that are either monotonic with negative interval
or have a minimum at negative values of the potential, generically predict a
future collapse of the scale factor to a "doomsday" singularity. We show that
this doomsday is generically avoided in models with a proper non-minimal
coupling of the quintessence scalar field to the curvature scalar $R$. For
simplicity we consider linear quintessence potential $V=-s\phi$ and linear
non-minimal coupling $F=1-\lambda \phi$. However our result is generic and is
due to the fact that the non-minimal coupling modifies the effective potential
that determines the dynamics of the scalar field. Thus for each positive value
of the parameter $s$ we find a critical value $\lambda_{crit}(s)$ such that for
$\lambda>\lambda_{crit}(s)$ the negative potential energy does not dominate the
universe and the cosmic doomsday Big Crunch singularity is avoided because the
scalar field eventually rolls up its potential. We find that
$\lambda_{crit}(s)$ increases approximately linearly with $s$. For
$\lambda>\lambda_{crit}(s)$ the potential energy of the scalar field becomes
positive and it eventually dominates while the dark energy equation of state
parameter tends to $w=-1$ leading to a deSitter Universe.
| [
{
"created": "Mon, 23 Nov 2015 08:30:25 GMT",
"version": "v1"
},
{
"created": "Sun, 31 Jan 2016 13:16:13 GMT",
"version": "v2"
}
] | 2016-03-08 | [
[
"Lykkas",
"A.",
""
],
[
"Perivolaropoulos",
"L.",
""
]
] | All quintessence potentials that are either monotonic with negative interval or have a minimum at negative values of the potential, generically predict a future collapse of the scale factor to a "doomsday" singularity. We show that this doomsday is generically avoided in models with a proper non-minimal coupling of the quintessence scalar field to the curvature scalar $R$. For simplicity we consider linear quintessence potential $V=-s\phi$ and linear non-minimal coupling $F=1-\lambda \phi$. However our result is generic and is due to the fact that the non-minimal coupling modifies the effective potential that determines the dynamics of the scalar field. Thus for each positive value of the parameter $s$ we find a critical value $\lambda_{crit}(s)$ such that for $\lambda>\lambda_{crit}(s)$ the negative potential energy does not dominate the universe and the cosmic doomsday Big Crunch singularity is avoided because the scalar field eventually rolls up its potential. We find that $\lambda_{crit}(s)$ increases approximately linearly with $s$. For $\lambda>\lambda_{crit}(s)$ the potential energy of the scalar field becomes positive and it eventually dominates while the dark energy equation of state parameter tends to $w=-1$ leading to a deSitter Universe. |
1910.04528 | Shao-Wen Wei | Shao-Wen Wei, Yu-Xiao Liu | Intriguing microstructures of five-dimensional neutral Gauss-Bonnet AdS
black hole | 12 pages, 5 figures, and 1 table | Phys.Lett. B 803, 135287 (2020) | 10.1016/j.physletb.2020.135287 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we analytically study the phase structure and construct the
Ruppeiner geometry in the extended phase space for the five-dimensional neutral
Gauss-Bonnet AdS black hole. Through calculating the scalar curvature of the
Ruppeiner geometry and combining the phase transition, we show that the
attractive interaction is dominant in the microstructure of the black hole
system. More significantly, there is an intriguing property that the normalized
scalar curvature has the same expression for the saturated small and large
black hole curves. This implies that although the microstructure is different
before and after the small-large black hole phase transition, the interaction
between the microscopic constituents keeps unchanged. These results are quite
valuable on further understanding the microstructure of the AdS black hole in
modified gravity.
| [
{
"created": "Thu, 10 Oct 2019 12:56:43 GMT",
"version": "v1"
},
{
"created": "Sun, 1 Mar 2020 09:49:50 GMT",
"version": "v2"
}
] | 2020-03-03 | [
[
"Wei",
"Shao-Wen",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | In this paper, we analytically study the phase structure and construct the Ruppeiner geometry in the extended phase space for the five-dimensional neutral Gauss-Bonnet AdS black hole. Through calculating the scalar curvature of the Ruppeiner geometry and combining the phase transition, we show that the attractive interaction is dominant in the microstructure of the black hole system. More significantly, there is an intriguing property that the normalized scalar curvature has the same expression for the saturated small and large black hole curves. This implies that although the microstructure is different before and after the small-large black hole phase transition, the interaction between the microscopic constituents keeps unchanged. These results are quite valuable on further understanding the microstructure of the AdS black hole in modified gravity. |
gr-qc/0311091 | Yuri Obukhov | Yuri N. Obukhov | Two-dimensional metric-affine gravity | Revtex, 15 pages, no figures | Phys.Rev. D69 (2004) 064009 | 10.1103/PhysRevD.69.064009 | ESI-1413 | gr-qc | null | There is a number of completely integrable gravity theories in two
dimensions. We study the metric-affine approach on a 2-dimensional spacetime
and display a new integrable model. Its properties are described and compared
with the known results of Poincare gauge gravity.
| [
{
"created": "Fri, 28 Nov 2003 12:41:43 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Obukhov",
"Yuri N.",
""
]
] | There is a number of completely integrable gravity theories in two dimensions. We study the metric-affine approach on a 2-dimensional spacetime and display a new integrable model. Its properties are described and compared with the known results of Poincare gauge gravity. |
gr-qc/0209066 | Hwei-Jang Yo | Hwei-Jang Yo (University of Illinois), Thomas W. Baumgarte (Bowdoin
College), and Stuart L. Shapiro (University of Illinois) | Improved numerical stability of stationary black hole evolution
calculations | 13 pages, 11 figures, 1 typo in Eq. (20) corrected | Phys.Rev. D66 (2002) 084026 | 10.1103/PhysRevD.66.084026 | null | gr-qc astro-ph | null | We experiment with modifications of the BSSN form of the Einstein field
equations (a reformulation of the ADM equations) and demonstrate how these
modifications affect the stability of numerical black hole evolution
calculations. We use excision to evolve both non-rotating and rotating
Kerr-Schild black holes in octant and equatorial symmetry, and without any
symmetry assumptions, and obtain accurate and stable simulations for specific
angular momenta J/M of up to about 0.9M.
| [
{
"created": "Thu, 19 Sep 2002 20:00:08 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Aug 2003 08:12:50 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Yo",
"Hwei-Jang",
"",
"University of Illinois"
],
[
"Baumgarte",
"Thomas W.",
"",
"Bowdoin\n College"
],
[
"Shapiro",
"Stuart L.",
"",
"University of Illinois"
]
] | We experiment with modifications of the BSSN form of the Einstein field equations (a reformulation of the ADM equations) and demonstrate how these modifications affect the stability of numerical black hole evolution calculations. We use excision to evolve both non-rotating and rotating Kerr-Schild black holes in octant and equatorial symmetry, and without any symmetry assumptions, and obtain accurate and stable simulations for specific angular momenta J/M of up to about 0.9M. |
2308.10612 | A. C. Khunt | Sagar V. Soni, A. C. Khunt and A. H. Hasmani | A Study of Morris-Thorne Wormhole in Einstein-Cartan Theory | 20 pages, 3 figures, 1 table. Preparing for submission to the
International Journal of Geometric Methods in Modern Physics | null | 10.1142/S0219887824501159 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This paper focuses on the Einstein-Cartan theory, an extension of general
relativity that incorporates a torsion tensor into spacetime. The differential
form technique is employed to analyze the Einstein-Cartan theory, which
replaces tensors with tetrads. A tetrad formalism, specifically the
Newmann-Penrose-Jogia-Griffiths formalism, is used to study the field
equations. The energy-momentum tensor is also determined, considering a
Weyssenhoff fluid with anisotropic matter. The spin density is derived in terms
of the red-shift function. We also examine the energy conditions at the throat
of a Morris-Thorne wormhole. The results shed light on the properties of
wormholes in the context of the Einstein-Cartan theory, including the energy
conditions at the throat.
| [
{
"created": "Mon, 21 Aug 2023 10:22:52 GMT",
"version": "v1"
}
] | 2024-02-27 | [
[
"Soni",
"Sagar V.",
""
],
[
"Khunt",
"A. C.",
""
],
[
"Hasmani",
"A. H.",
""
]
] | This paper focuses on the Einstein-Cartan theory, an extension of general relativity that incorporates a torsion tensor into spacetime. The differential form technique is employed to analyze the Einstein-Cartan theory, which replaces tensors with tetrads. A tetrad formalism, specifically the Newmann-Penrose-Jogia-Griffiths formalism, is used to study the field equations. The energy-momentum tensor is also determined, considering a Weyssenhoff fluid with anisotropic matter. The spin density is derived in terms of the red-shift function. We also examine the energy conditions at the throat of a Morris-Thorne wormhole. The results shed light on the properties of wormholes in the context of the Einstein-Cartan theory, including the energy conditions at the throat. |
gr-qc/9306032 | Pavol Kolnik | C. Klimcik, P. Kolnik, and A. Pompos | Black Hole with Non-Commutative Hair | 10 pages, LaTeX, PRA-HEP-93/9 | null | null | null | gr-qc hep-th | null | The specific nonlinear vector $\sigma$-model coupled to Einstein gravity is
investigated. The model arises in the studies of the gravitating matter in
non-commutative geometry. The static spherically symmetric spacetimes are
identified by direct solving of the field equations. The asymptotically flat
black hole with the ``non-commutative'' vector hair appears for the special
choice of the integration constants, giving thus another counterexample to the
famous ``no-hair'' theorem.
| [
{
"created": "Fri, 25 Jun 1993 13:30:49 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Klimcik",
"C.",
""
],
[
"Kolnik",
"P.",
""
],
[
"Pompos",
"A.",
""
]
] | The specific nonlinear vector $\sigma$-model coupled to Einstein gravity is investigated. The model arises in the studies of the gravitating matter in non-commutative geometry. The static spherically symmetric spacetimes are identified by direct solving of the field equations. The asymptotically flat black hole with the ``non-commutative'' vector hair appears for the special choice of the integration constants, giving thus another counterexample to the famous ``no-hair'' theorem. |
0707.0110 | J. Frauendiener | J. Frauendiener and A. Kabobel | The static spherically symmetric body in relativistic elasticity | 19 pages, 8 figures | Class.Quant.Grav.24:4817-4838,2007 | 10.1088/0264-9381/24/18/016 | null | gr-qc | null | In this paper is discussed a class of static spherically symmetric solutions
of the general relativistic elasticity equations. The main point of discussion
is the comparison of two matter models given in terms of their stored energy
functionals, i.e., the rule which gives the amount of energy stored in the
system when it is deformed. Both functionals mimic (and for small deformations
approximate) the classical Kirchhoff-St.Venant materials but differ in the
strain variable used. We discuss the behavior of the systems for large
deformations.
| [
{
"created": "Sun, 1 Jul 2007 14:43:30 GMT",
"version": "v1"
}
] | 2009-04-16 | [
[
"Frauendiener",
"J.",
""
],
[
"Kabobel",
"A.",
""
]
] | In this paper is discussed a class of static spherically symmetric solutions of the general relativistic elasticity equations. The main point of discussion is the comparison of two matter models given in terms of their stored energy functionals, i.e., the rule which gives the amount of energy stored in the system when it is deformed. Both functionals mimic (and for small deformations approximate) the classical Kirchhoff-St.Venant materials but differ in the strain variable used. We discuss the behavior of the systems for large deformations. |
1802.03470 | Vahid Amirkhani | Mohammad A. Ganjali, Vahid Amirkhani, Ahmad ShamlouMehr | Non-Relativistic Fermion-Fermion Scattering in Higher Derivative Gravity | 5 pages with 2 figures | null | 10.1007/s12648-019-01469-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note, we examine the scattering of two identical fermions in theories
where fermionic fields minimally coupled to higher derivative gravity. In
particular, we consider the extension of general relativity with $R^2$
corrections or non-local terms. We expand the action of fermions around the
flat space background and obtain two fermion-one graviton vertex. Then, by
considering the scattering amplitude of two fermions, we calculate the
non-relativistic limit and that obtain the potential for two fermion-fermion
interaction which would be the usual Newtonian potential corrected with a
Yukawa-like term. At the end, we briefly discuss the astronomical effects of
such Yukawa-like potential by computing the gravitational pressure of a
spherical star and use it for a white dwarf to obtain quantum corrections of
Chandrasekhar radius.
| [
{
"created": "Fri, 9 Feb 2018 22:23:15 GMT",
"version": "v1"
}
] | 2019-05-22 | [
[
"Ganjali",
"Mohammad A.",
""
],
[
"Amirkhani",
"Vahid",
""
],
[
"ShamlouMehr",
"Ahmad",
""
]
] | In this note, we examine the scattering of two identical fermions in theories where fermionic fields minimally coupled to higher derivative gravity. In particular, we consider the extension of general relativity with $R^2$ corrections or non-local terms. We expand the action of fermions around the flat space background and obtain two fermion-one graviton vertex. Then, by considering the scattering amplitude of two fermions, we calculate the non-relativistic limit and that obtain the potential for two fermion-fermion interaction which would be the usual Newtonian potential corrected with a Yukawa-like term. At the end, we briefly discuss the astronomical effects of such Yukawa-like potential by computing the gravitational pressure of a spherical star and use it for a white dwarf to obtain quantum corrections of Chandrasekhar radius. |
1504.04622 | Peter Taylor | Peter Taylor and \'Eanna \'E. Flanagan | Static Self-Forces in a Five-Dimensional Black Hole Spacetime | Agrees with published version | Phys. Rev. D 92, 084032 (2015) | 10.1103/PhysRevD.92.084032 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain the electric field and scalar field for a static point charge in
closed form in the 5D Schwarzschild-Tangherlini black hole spacetime. We then
compute the static self-force in each of these cases by assuming that the
appropriate singular field is a 4D Hadamard Green's function on the constant
time Riemannian slice. It is well known that the Hadamard Green's function
involves an arbitrary regular biscalar $W_{0}(x,x')$, whose coincidence limit
$w(x)$ appears in the expression for the self-force. We develop an axiomatic
approach to reduce this arbitrary function to a single arbitrary dimensionless
coefficient. We show that in the context of this approach to regularization,
the self-force does not depend on any undetermined length-scale and need not
depend on the internal structure of the charge.
| [
{
"created": "Fri, 17 Apr 2015 20:00:34 GMT",
"version": "v1"
},
{
"created": "Mon, 4 May 2015 18:25:47 GMT",
"version": "v2"
},
{
"created": "Wed, 18 Nov 2015 20:59:35 GMT",
"version": "v3"
}
] | 2015-11-19 | [
[
"Taylor",
"Peter",
""
],
[
"Flanagan",
"Éanna É.",
""
]
] | We obtain the electric field and scalar field for a static point charge in closed form in the 5D Schwarzschild-Tangherlini black hole spacetime. We then compute the static self-force in each of these cases by assuming that the appropriate singular field is a 4D Hadamard Green's function on the constant time Riemannian slice. It is well known that the Hadamard Green's function involves an arbitrary regular biscalar $W_{0}(x,x')$, whose coincidence limit $w(x)$ appears in the expression for the self-force. We develop an axiomatic approach to reduce this arbitrary function to a single arbitrary dimensionless coefficient. We show that in the context of this approach to regularization, the self-force does not depend on any undetermined length-scale and need not depend on the internal structure of the charge. |
1510.08024 | Otis Chodosh | Otis Chodosh, Yakov Shlapentokh-Rothman | Stationary axisymmetric black holes with matter | null | null | null | null | gr-qc math-ph math.AP math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide a geometric framework for the construction of non-vacuum black
holes whose metrics are stationary and axisymmetric. Under suitable assumptions
we show that the Einstein equations reduce to an Einstein-harmonic map type
system and analyze the compatibility of the resulting equations.
This framework will be fundamental to our forthcoming construction of
metric-stationary axisymmetric bifurcations of Kerr solving the
Einstein--Klein--Gordon system, and as such, we include specializations of all
of our formulas to the case of a time-periodic massive scalar field.
| [
{
"created": "Tue, 27 Oct 2015 18:39:53 GMT",
"version": "v1"
}
] | 2015-10-28 | [
[
"Chodosh",
"Otis",
""
],
[
"Shlapentokh-Rothman",
"Yakov",
""
]
] | We provide a geometric framework for the construction of non-vacuum black holes whose metrics are stationary and axisymmetric. Under suitable assumptions we show that the Einstein equations reduce to an Einstein-harmonic map type system and analyze the compatibility of the resulting equations. This framework will be fundamental to our forthcoming construction of metric-stationary axisymmetric bifurcations of Kerr solving the Einstein--Klein--Gordon system, and as such, we include specializations of all of our formulas to the case of a time-periodic massive scalar field. |
gr-qc/0601004 | Romesh K. Kaul | Romesh K. Kaul | Gauge Theory of Gravity and Supergravity | 27 pages | Phys.Rev.D73:065027,2006 | 10.1103/PhysRevD.73.065027 | null | gr-qc hep-th | null | We present a formulation of gravity in terms of a theory based on complex
SU(2) gauge fields with a general coordinate invariant action functional
quadratic in the field strength. Self-duality or anti-self-duality of the field
strength emerges as a constraint from the equations of motion of this theory.
This in turn leads to Einstein gravity equations for a dilaton and an axion
conformally coupled to gravity for the self-dual constraint. The analysis has
also been extended to N=1 and 2 super Yang-Mills theory of complex SU(2) gauge
fields. This leads, besides other equations of motion, to
self-duality/anti-self-duality of generalized supercovariant field-strengths.
The self-dual case is then shown to yield as its solutions $N = 1, 2$
supergravity equations respectively.
| [
{
"created": "Mon, 2 Jan 2006 08:25:55 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kaul",
"Romesh K.",
""
]
] | We present a formulation of gravity in terms of a theory based on complex SU(2) gauge fields with a general coordinate invariant action functional quadratic in the field strength. Self-duality or anti-self-duality of the field strength emerges as a constraint from the equations of motion of this theory. This in turn leads to Einstein gravity equations for a dilaton and an axion conformally coupled to gravity for the self-dual constraint. The analysis has also been extended to N=1 and 2 super Yang-Mills theory of complex SU(2) gauge fields. This leads, besides other equations of motion, to self-duality/anti-self-duality of generalized supercovariant field-strengths. The self-dual case is then shown to yield as its solutions $N = 1, 2$ supergravity equations respectively. |
2010.03462 | Emmanuel Frion | Emmanuel Frion | Quantum Effects in Cosmology | PhD Thesis, 163 pages, 30 figures | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum effects play an essential role in modern cosmology. Perhaps the most
striking example comes from large-scale structures, generally assumed to
originate from vacuum quantum fluctuations and stretched by an expansion phase.
Inflation is the leading paradigm in explaining this process. The various
observational successes of inflationary models drive the scientific community
into elaborating more and more stringent tests, which can simultaneously be
used to probe beyond the simple slow-roll, single field inflation. However,
inflation is not a theory, and going beyond inflation is a necessity. Various
alternatives and/or complementary mechanisms to inflation have been invoked in
the literature. The best-known cosmological models endowed with the capacity of
explaining large-scale observations while avoiding the singularity form a class
called non-singular bouncing models. The main features of these models are the
presence of a contraction phase before expansion, and a never-vanishing scale
factor. A non-singular bounce generally appears when quantum effects are part
of the model, playing the role of a regulator leading to the avoidance of
singularities. This thesis focuses on a Hamiltonian formulation of quantum
effects in cosmology. We first explore stochastic perturbations in a collapsing
universe. Then, we show that quantum cosmology with Bohmian mechanics resolves
the initial singularity. Adding a non-minimal coupling of gravity with
electromagnetism, we show that the generation of magnetic fields is possible.
Finally, we apply the affine quantisation on the Brans-Dicke Theory, the
prototype of modified gravity theories, and we discuss the quantum equivalence
of the Jordan and Einstein frames within this framework. We show that in both
frames a smooth bounce is expected, and that equivalence between frames holds
at the quantum level.
| [
{
"created": "Wed, 7 Oct 2020 14:56:19 GMT",
"version": "v1"
}
] | 2020-10-08 | [
[
"Frion",
"Emmanuel",
""
]
] | Quantum effects play an essential role in modern cosmology. Perhaps the most striking example comes from large-scale structures, generally assumed to originate from vacuum quantum fluctuations and stretched by an expansion phase. Inflation is the leading paradigm in explaining this process. The various observational successes of inflationary models drive the scientific community into elaborating more and more stringent tests, which can simultaneously be used to probe beyond the simple slow-roll, single field inflation. However, inflation is not a theory, and going beyond inflation is a necessity. Various alternatives and/or complementary mechanisms to inflation have been invoked in the literature. The best-known cosmological models endowed with the capacity of explaining large-scale observations while avoiding the singularity form a class called non-singular bouncing models. The main features of these models are the presence of a contraction phase before expansion, and a never-vanishing scale factor. A non-singular bounce generally appears when quantum effects are part of the model, playing the role of a regulator leading to the avoidance of singularities. This thesis focuses on a Hamiltonian formulation of quantum effects in cosmology. We first explore stochastic perturbations in a collapsing universe. Then, we show that quantum cosmology with Bohmian mechanics resolves the initial singularity. Adding a non-minimal coupling of gravity with electromagnetism, we show that the generation of magnetic fields is possible. Finally, we apply the affine quantisation on the Brans-Dicke Theory, the prototype of modified gravity theories, and we discuss the quantum equivalence of the Jordan and Einstein frames within this framework. We show that in both frames a smooth bounce is expected, and that equivalence between frames holds at the quantum level. |
0907.0414 | Robert M. Wald | Samuel E. Gralla and Robert M. Wald | Derivation of Gravitational Self-Force | 9 pages, no figures; to appear in proceedings of CNRS School on Mass | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the issue of ``particle motion'' in general relativity in a
systematic and rigorous way by considering a one-parameter family of metrics
corresponding to having a body (or black hole) that is ``scaled down'' to zero
size and mass in an appropriate manner. We prove that the limiting worldline of
such a one-parameter family must be a geodesic of the background metric and
obtain the leading order perturbative corrections, which include gravitational
self-force, spin force, and geodesic deviation effects. The status the
MiSaTaQuWa equation is explained as a candidate ``self-consistent perturbative
equation'' associated with our rigorous perturbative result
| [
{
"created": "Thu, 2 Jul 2009 15:51:45 GMT",
"version": "v1"
}
] | 2009-07-03 | [
[
"Gralla",
"Samuel E.",
""
],
[
"Wald",
"Robert M.",
""
]
] | We analyze the issue of ``particle motion'' in general relativity in a systematic and rigorous way by considering a one-parameter family of metrics corresponding to having a body (or black hole) that is ``scaled down'' to zero size and mass in an appropriate manner. We prove that the limiting worldline of such a one-parameter family must be a geodesic of the background metric and obtain the leading order perturbative corrections, which include gravitational self-force, spin force, and geodesic deviation effects. The status the MiSaTaQuWa equation is explained as a candidate ``self-consistent perturbative equation'' associated with our rigorous perturbative result |
1202.4951 | Alexis Larranaga PhD | Alexis Larranaga, Luis Cabarique | Advance of Planetary Perihelion in Post-Newtonian Gravity | 7 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an elementary derivation of the planetary advance of the
perihelion for a general spherically symmetric line element in the post-
newtonian approximation.
| [
{
"created": "Wed, 22 Feb 2012 16:16:57 GMT",
"version": "v1"
}
] | 2012-02-23 | [
[
"Larranaga",
"Alexis",
""
],
[
"Cabarique",
"Luis",
""
]
] | We present an elementary derivation of the planetary advance of the perihelion for a general spherically symmetric line element in the post- newtonian approximation. |
2105.00540 | Carlo Rovelli | Carlo Rovelli | The layers that build up the notion of time | 7 pages, Contribution to the volume 'Time and Science', R. Lestienne
and P. Harris eds., World Scientific | null | null | null | gr-qc physics.hist-ph | http://creativecommons.org/licenses/by/4.0/ | Confusion and disagreement around the notion of time is due to the fact that
we often fail to recognize that we call 'time' a variety of distinct notions,
only partially related to one another. Many apparently obvious properties of
time are results of different kinds of approximations, idealizations, or
special contexts. I illustrate a number of distinct notions of time, their
differences and relations; they are all relevant for describing the real world.
To understand time, we have to break it apart.
| [
{
"created": "Sun, 2 May 2021 19:49:42 GMT",
"version": "v1"
},
{
"created": "Fri, 14 May 2021 22:59:48 GMT",
"version": "v2"
}
] | 2021-05-18 | [
[
"Rovelli",
"Carlo",
""
]
] | Confusion and disagreement around the notion of time is due to the fact that we often fail to recognize that we call 'time' a variety of distinct notions, only partially related to one another. Many apparently obvious properties of time are results of different kinds of approximations, idealizations, or special contexts. I illustrate a number of distinct notions of time, their differences and relations; they are all relevant for describing the real world. To understand time, we have to break it apart. |
gr-qc/0010111 | Sanjay Jhingan | S. Jhingan, N. Dadhich and P. S. Joshi | Gravitational Collapse in Constant Potential Bath | LaTex 12 Pages, 2 figures. To appear in Physical Review D | Phys.Rev. D63 (2001) 044010 | 10.1103/PhysRevD.63.044010 | null | gr-qc | null | We analyse here the gravitational collapse of directed null radiation in a
background with a constant potential such as one produced by a star system like
galaxy in which the collapsing object is immersed. Both naked singularities and
black holes are shown to be developing as the final outcome of the collapse. An
interesting feature that emerges is that a part of the naked singularity
spectrum in collapsing Vaidya region gets covered in the corresponding
dual-Vaidya region, which corresponds to the Vaidya directed null radiation
sitting in constant potential bath. The implications of such a result towards
the issue of stability of naked singularities are discussed.
| [
{
"created": "Tue, 31 Oct 2000 08:40:54 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Jhingan",
"S.",
""
],
[
"Dadhich",
"N.",
""
],
[
"Joshi",
"P. S.",
""
]
] | We analyse here the gravitational collapse of directed null radiation in a background with a constant potential such as one produced by a star system like galaxy in which the collapsing object is immersed. Both naked singularities and black holes are shown to be developing as the final outcome of the collapse. An interesting feature that emerges is that a part of the naked singularity spectrum in collapsing Vaidya region gets covered in the corresponding dual-Vaidya region, which corresponds to the Vaidya directed null radiation sitting in constant potential bath. The implications of such a result towards the issue of stability of naked singularities are discussed. |
gr-qc/0307049 | Petr Slan\'y | Z. Stuchlik, P. Slany | Equatorial circular orbits in the Kerr-de Sitter spacetimes | 24 pages, 19 figures, REVTeX 4 | Phys.Rev. D69 (2004) 064001 | 10.1103/PhysRevD.69.064001 | null | gr-qc | null | Equatorial motion of test particles in the Kerr-de Sitter spacetimes is
considered. Circular orbits are determined, their properties are discussed for
both the black-hole and naked-singularity spacetimes, and their relevance for
thin accretion discs is established.
| [
{
"created": "Thu, 10 Jul 2003 12:47:02 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Apr 2004 07:05:09 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Stuchlik",
"Z.",
""
],
[
"Slany",
"P.",
""
]
] | Equatorial motion of test particles in the Kerr-de Sitter spacetimes is considered. Circular orbits are determined, their properties are discussed for both the black-hole and naked-singularity spacetimes, and their relevance for thin accretion discs is established. |
1412.7567 | Hemza Azri | Hemza Azri and A. Bounames | Cosmological Consequences of a Variable Cosmological Constant Model | Accepted in Int. J. Mod. Phys. D | Int. J. Mod. Phys. D 26, 1750060 (2017) | 10.1142/S0218271817500602 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive a model of dark energy which evolves with time via the scale
factor. The equation of state $\omega=(1-2\alpha)/(1+2\alpha)$ is studied as a
function of a parameter $\alpha$ introduced in this model. In addition to the
recent accelerated expansion, the model predicts another decelerated phase. The
age of the universe is found to be almost consistent with observation. In the
limiting case, the cosmological constant model, we find that vacuum energy
gravitates with a gravitational strength, different than Newton's constant.
This enables degravitation of the vacuum energy which in turn produces the tiny
observed curvature, rather than a 120 orders of magnitude larger value.
| [
{
"created": "Tue, 23 Dec 2014 22:25:30 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Sep 2016 11:40:52 GMT",
"version": "v2"
},
{
"created": "Fri, 9 Dec 2016 13:19:12 GMT",
"version": "v3"
}
] | 2017-06-20 | [
[
"Azri",
"Hemza",
""
],
[
"Bounames",
"A.",
""
]
] | We derive a model of dark energy which evolves with time via the scale factor. The equation of state $\omega=(1-2\alpha)/(1+2\alpha)$ is studied as a function of a parameter $\alpha$ introduced in this model. In addition to the recent accelerated expansion, the model predicts another decelerated phase. The age of the universe is found to be almost consistent with observation. In the limiting case, the cosmological constant model, we find that vacuum energy gravitates with a gravitational strength, different than Newton's constant. This enables degravitation of the vacuum energy which in turn produces the tiny observed curvature, rather than a 120 orders of magnitude larger value. |
1609.05901 | Tristan Smith | Tristan L. Smith (Swarthmore College) and Robert Caldwell (Dartmouth
College) | Sensitivity to a Frequency-Dependent Circular Polarization in an
Isotropic Stochastic Gravitational Wave Background | 18 pages, 8 figures, comments welcome | Phys. Rev. D 95, 044036 (2017) | 10.1103/PhysRevD.95.044036 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the sensitivity to a circular polarization of an isotropic
stochastic gravitational wave background (ISGWB) as a function of frequency for
ground- and space-based interferometers and observations of the cosmic
microwave background. The origin of a circularly polarized ISGWB may be due to
exotic primordial physics (i.e., parity violation in the early universe) and
may be strongly frequency dependent. We present calculations within a coherent
framework which clarifies the basic requirements for sensitivity to circular
polarization, in distinction from previous work which focused on each of these
techniques separately. We find that the addition of an interferometer with the
sensitivity of the Einstein Telescope in the southern hemisphere improves the
sensitivity of the ground-based network to circular polarization by about a
factor of two. The sensitivity curves presented in this paper make clear that
the wide range in frequencies of current and planned observations ($10^{-18}\
{\rm Hz} \lesssim f \lesssim 100\ {\rm Hz}$) will be critical to determining
the physics that underlies any positive detection of circular polarization in
the ISGWB. We also identify a desert in circular polarization sensitivity for
frequencies between $10^{-15}\ {\rm Hz} \lesssim f \lesssim 10^{-3}\ {\rm Hz}$,
given the inability for pulsar timing arrays and indirect-detection methods to
distinguish the gravitational wave polarization.
| [
{
"created": "Mon, 19 Sep 2016 20:00:01 GMT",
"version": "v1"
}
] | 2017-03-01 | [
[
"Smith",
"Tristan L.",
"",
"Swarthmore College"
],
[
"Caldwell",
"Robert",
"",
"Dartmouth\n College"
]
] | We calculate the sensitivity to a circular polarization of an isotropic stochastic gravitational wave background (ISGWB) as a function of frequency for ground- and space-based interferometers and observations of the cosmic microwave background. The origin of a circularly polarized ISGWB may be due to exotic primordial physics (i.e., parity violation in the early universe) and may be strongly frequency dependent. We present calculations within a coherent framework which clarifies the basic requirements for sensitivity to circular polarization, in distinction from previous work which focused on each of these techniques separately. We find that the addition of an interferometer with the sensitivity of the Einstein Telescope in the southern hemisphere improves the sensitivity of the ground-based network to circular polarization by about a factor of two. The sensitivity curves presented in this paper make clear that the wide range in frequencies of current and planned observations ($10^{-18}\ {\rm Hz} \lesssim f \lesssim 100\ {\rm Hz}$) will be critical to determining the physics that underlies any positive detection of circular polarization in the ISGWB. We also identify a desert in circular polarization sensitivity for frequencies between $10^{-15}\ {\rm Hz} \lesssim f \lesssim 10^{-3}\ {\rm Hz}$, given the inability for pulsar timing arrays and indirect-detection methods to distinguish the gravitational wave polarization. |
2209.10976 | Vitalii Vertogradov | Vitalii Vertogradov | The Negative Energy in Generalized Vaidya Spacetime | 18 pages | Universe 2020, 6(9), 155 | 10.3390/universe6090155 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper we consider the negative energy problem in generalized Vaidya
spacetime. We consider several models when we have the naked singularity as a
result of the gravitational collapse. In these models we investigate the
geodesics for particles with negative energy when the II type of the matter
field satisfies the equation of the state $P=\alpha \rho$ ($\alpha \in [0\,,
1]$).
| [
{
"created": "Thu, 22 Sep 2022 13:03:05 GMT",
"version": "v1"
}
] | 2022-09-23 | [
[
"Vertogradov",
"Vitalii",
""
]
] | In this paper we consider the negative energy problem in generalized Vaidya spacetime. We consider several models when we have the naked singularity as a result of the gravitational collapse. In these models we investigate the geodesics for particles with negative energy when the II type of the matter field satisfies the equation of the state $P=\alpha \rho$ ($\alpha \in [0\,, 1]$). |
2110.02448 | Barak Shoshany | Barak Shoshany and Jared Wogan | Wormhole Time Machines and Multiple Histories | 28 pages, 5 figures, source code available at
https://github.com/bshoshany/WormholeParadoxSimulation | Gen. Relativ. Gravit. 55, 44 (2023) | 10.1007/s10714-023-03094-8 | null | gr-qc physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a previous paper, we showed that a class of time travel paradoxes which
cannot be resolved using Novikov's self-consistency conjecture can be resolved
by assuming the existence of multiple histories or parallel timelines. However,
our proof was obtained using a simplistic toy model, which was formulated using
contrived laws of physics. In the present paper we define and analyze a new
model of time travel paradoxes, which is more compatible with known physics.
This model consists of a traversable Morris-Thorne wormhole time machine in 3+1
spacetime dimensions. We define the spacetime topology and geometry of the
model, calculate the geodesics of objects passing through the time machine, and
prove that this model inevitably leads to paradoxes which cannot be resolved
using Novikov's conjecture, but can be resolved using multiple histories. An
open-source simulation of our new model using Mathematica is available for
download on GitHub. We also provide additional arguments against the Novikov
self-consistency conjecture by considering two new paradoxes, the switch
paradox and the password paradox, for which assuming self-consistency
inevitably leads to counter-intuitive consequences. Our new results provide
more substantial support to our claim that if time travel is possible, then
multiple histories or parallel timelines must also be possible.
| [
{
"created": "Wed, 6 Oct 2021 01:36:08 GMT",
"version": "v1"
},
{
"created": "Sun, 21 Aug 2022 21:44:30 GMT",
"version": "v2"
},
{
"created": "Wed, 15 Mar 2023 15:42:05 GMT",
"version": "v3"
}
] | 2023-03-16 | [
[
"Shoshany",
"Barak",
""
],
[
"Wogan",
"Jared",
""
]
] | In a previous paper, we showed that a class of time travel paradoxes which cannot be resolved using Novikov's self-consistency conjecture can be resolved by assuming the existence of multiple histories or parallel timelines. However, our proof was obtained using a simplistic toy model, which was formulated using contrived laws of physics. In the present paper we define and analyze a new model of time travel paradoxes, which is more compatible with known physics. This model consists of a traversable Morris-Thorne wormhole time machine in 3+1 spacetime dimensions. We define the spacetime topology and geometry of the model, calculate the geodesics of objects passing through the time machine, and prove that this model inevitably leads to paradoxes which cannot be resolved using Novikov's conjecture, but can be resolved using multiple histories. An open-source simulation of our new model using Mathematica is available for download on GitHub. We also provide additional arguments against the Novikov self-consistency conjecture by considering two new paradoxes, the switch paradox and the password paradox, for which assuming self-consistency inevitably leads to counter-intuitive consequences. Our new results provide more substantial support to our claim that if time travel is possible, then multiple histories or parallel timelines must also be possible. |
2212.00804 | Ali \"Ovg\"un Dr. | Wajiha Javed, Sibgha Riaz, Reggie C. Pantig and Ali \"Ovg\"un | Weak Gravitational Lensing in Dark Matter and Plasma Mediums for
Wormhole-like Static Aether Solution | 12 pages. Accepted for publication in the European Physical Journal C
(https://link.springer.com/article/10.1140/epjc/s10052-022-11030-4) | Eur. Phys. J. C 82, 1057 (2022) | 10.1140/epjc/s10052-022-11030-4 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we study the deflection angle for wormhole-like static aether
solution by using Gibbons and Werner technique in non-plasma, plasma, and dark
matter mediums. For this purpose, we use optical spacetime geometry to
calculate the Gaussian optical curvature, then implement the Gauss-Bonnet
theorem in weak field limits. Moreover, we compute the deflection angle by
using a technique known as Keeton and Petters technique. Furthermore, we
analyze the graphical behavior of the bending angle $\psi$ with respect to the
impact parameter $b$, mass $m$ as an integration constant, and parameter $q$ in
non-plasma and plasma mediums. We examine that the deflection angle is
exponentially increasing as direct with charge. Also, we observe that for small
values of $b$, $\psi$ increases, and for large values of $b$ the angle
decreases. We also considered analysis to the shadow cast of the wormhole
relative to an observer at various locations. Comparing it the Schwarzschild
shadow, shadow cast is possible for wormhole as $r<2m$. At $r>2m$, the
Schwarzschild is larger. As $r\to \infty$, we have seen that the behavior of
the shadow, as well as the weak deflection angle, approaches that of the
Schwarzschild black hole. Overall, the effect of plasma tends to decrease the
value of the observables due to the wormhole geometry.
| [
{
"created": "Thu, 1 Dec 2022 16:54:43 GMT",
"version": "v1"
}
] | 2022-12-05 | [
[
"Javed",
"Wajiha",
""
],
[
"Riaz",
"Sibgha",
""
],
[
"Pantig",
"Reggie C.",
""
],
[
"Övgün",
"Ali",
""
]
] | In this paper, we study the deflection angle for wormhole-like static aether solution by using Gibbons and Werner technique in non-plasma, plasma, and dark matter mediums. For this purpose, we use optical spacetime geometry to calculate the Gaussian optical curvature, then implement the Gauss-Bonnet theorem in weak field limits. Moreover, we compute the deflection angle by using a technique known as Keeton and Petters technique. Furthermore, we analyze the graphical behavior of the bending angle $\psi$ with respect to the impact parameter $b$, mass $m$ as an integration constant, and parameter $q$ in non-plasma and plasma mediums. We examine that the deflection angle is exponentially increasing as direct with charge. Also, we observe that for small values of $b$, $\psi$ increases, and for large values of $b$ the angle decreases. We also considered analysis to the shadow cast of the wormhole relative to an observer at various locations. Comparing it the Schwarzschild shadow, shadow cast is possible for wormhole as $r<2m$. At $r>2m$, the Schwarzschild is larger. As $r\to \infty$, we have seen that the behavior of the shadow, as well as the weak deflection angle, approaches that of the Schwarzschild black hole. Overall, the effect of plasma tends to decrease the value of the observables due to the wormhole geometry. |
gr-qc/0505026 | Vojt\v{e}ch Pravda | A. Pravdova, V. Pravda, A. Coley | A note on the peeling theorem in higher dimensions | 5 pages, to appear in Class. Quantum Grav | Class.Quant.Grav.22:2535-2538,2005 | 10.1088/0264-9381/22/13/001 | null | gr-qc | null | We demonstrate the ``peeling property'' of the Weyl tensor in higher
dimensions in the case of even dimensions (and with some additional
assumptions), thereby providing a first step towards understanding of the
general peeling behaviour of the Weyl tensor, and the asymptotic structure at
null infinity, in higher dimensions.
| [
{
"created": "Thu, 5 May 2005 20:24:29 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Pravdova",
"A.",
""
],
[
"Pravda",
"V.",
""
],
[
"Coley",
"A.",
""
]
] | We demonstrate the ``peeling property'' of the Weyl tensor in higher dimensions in the case of even dimensions (and with some additional assumptions), thereby providing a first step towards understanding of the general peeling behaviour of the Weyl tensor, and the asymptotic structure at null infinity, in higher dimensions. |
gr-qc/0308015 | I. P. Costa E. Silva | J. Castineiras, I.P. Costa e Silva and G.E.A. Matsas | Interaction of Hawking radiation with static sources in deSitter and
Schwarzschild-deSitter spacetimes | ReVTeX4 file, 9 pages, 5 figures | Phys.Rev. D68 (2003) 084022 | 10.1103/PhysRevD.68.084022 | null | gr-qc | null | We study and look for similarities between the response rates $R^{\rm
dS}(a_0, \Lambda)$ and $R^{\rm SdS}(a_0, \Lambda, M)$ of a static scalar source
with constant proper acceleration $a_0$ interacting with a massless,
conformally coupled Klein-Gordon field in (i) deSitter spacetime, in the
Euclidean vacuum, which describes a thermal flux of radiation emanating from
the deSitter cosmological horizon, and in (ii) Schwarzschild-deSitter
spacetime, in the Gibbons-Hawking vacuum, which describes thermal fluxes of
radiation emanating from both the hole and the cosmological horizons,
respectively, where $\Lambda$ is the cosmological constant and $M$ is the black
hole mass. After performing the field quantization in each of the above
spacetimes, we obtain the response rates at the tree level in terms of an
infinite sum of zero-energy field modes possessing all possible angular
momentum quantum numbers. In the case of deSitter spacetime, this formula is
worked out and a closed, analytical form is obtained. In the case of
Schwarzschild-deSitter spacetime such a closed formula could not be obtained,
and a numerical analysis is performed. We conclude, in particular, that $R^{\rm
dS}(a_0, \Lambda)$ and $R^{\rm SdS}(a_0, \Lambda, M)$ do not coincide in
general, but tend to each other when $\Lambda \to 0$ or $a_0 \to \infty$. Our
results are also contrasted and shown to agree (in the proper limits) with
related ones in the literature.
| [
{
"created": "Wed, 6 Aug 2003 17:48:24 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Castineiras",
"J.",
""
],
[
"Silva",
"I. P. Costa e",
""
],
[
"Matsas",
"G. E. A.",
""
]
] | We study and look for similarities between the response rates $R^{\rm dS}(a_0, \Lambda)$ and $R^{\rm SdS}(a_0, \Lambda, M)$ of a static scalar source with constant proper acceleration $a_0$ interacting with a massless, conformally coupled Klein-Gordon field in (i) deSitter spacetime, in the Euclidean vacuum, which describes a thermal flux of radiation emanating from the deSitter cosmological horizon, and in (ii) Schwarzschild-deSitter spacetime, in the Gibbons-Hawking vacuum, which describes thermal fluxes of radiation emanating from both the hole and the cosmological horizons, respectively, where $\Lambda$ is the cosmological constant and $M$ is the black hole mass. After performing the field quantization in each of the above spacetimes, we obtain the response rates at the tree level in terms of an infinite sum of zero-energy field modes possessing all possible angular momentum quantum numbers. In the case of deSitter spacetime, this formula is worked out and a closed, analytical form is obtained. In the case of Schwarzschild-deSitter spacetime such a closed formula could not be obtained, and a numerical analysis is performed. We conclude, in particular, that $R^{\rm dS}(a_0, \Lambda)$ and $R^{\rm SdS}(a_0, \Lambda, M)$ do not coincide in general, but tend to each other when $\Lambda \to 0$ or $a_0 \to \infty$. Our results are also contrasted and shown to agree (in the proper limits) with related ones in the literature. |
1402.2592 | Behnam Pourhassan | E.O. Kahya, M. Khurshudyan, B. Pourhassan, R. Myrzakulov, A. Pasqua | Higher order corrections of the extended Chaplygin gas cosmology with
varying $G$ and $\Lambda$ | Perturbation analysis added, typos corrected, references added | The European Physical Journal C 75 (2015) 43 | 10.1140/epjc/s10052-015-3263-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study two different models of dark energy based on
Chaplygin gas equation of state. The first model is the variable modified
Chaplygin gas while the second one is the extended Chaplygin gas. Both models
are considered in the framework of higher order $f(R)$ modified gravity. We
also consider the case of time varying gravitational constant $G$ and $\Lambda$
for both models. We investigate some cosmological parameters such as the
Hubble, the deceleration and the equation of state parameters. Then we showed
that the model that we considered, extended Chaplygin gas with time-dependent
$G$ and $\Lambda$, is consistent with the observational data. Finally we
conclude with the discussion of cosmological perturbations of our model.
| [
{
"created": "Tue, 11 Feb 2014 18:23:36 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Aug 2014 20:31:32 GMT",
"version": "v2"
},
{
"created": "Tue, 14 Oct 2014 08:46:08 GMT",
"version": "v3"
},
{
"created": "Thu, 11 Dec 2014 19:17:56 GMT",
"version": "v4"
}
] | 2015-02-10 | [
[
"Kahya",
"E. O.",
""
],
[
"Khurshudyan",
"M.",
""
],
[
"Pourhassan",
"B.",
""
],
[
"Myrzakulov",
"R.",
""
],
[
"Pasqua",
"A.",
""
]
] | In this paper, we study two different models of dark energy based on Chaplygin gas equation of state. The first model is the variable modified Chaplygin gas while the second one is the extended Chaplygin gas. Both models are considered in the framework of higher order $f(R)$ modified gravity. We also consider the case of time varying gravitational constant $G$ and $\Lambda$ for both models. We investigate some cosmological parameters such as the Hubble, the deceleration and the equation of state parameters. Then we showed that the model that we considered, extended Chaplygin gas with time-dependent $G$ and $\Lambda$, is consistent with the observational data. Finally we conclude with the discussion of cosmological perturbations of our model. |
1402.6491 | Anuj Kumar Dubey Mr. | Anuj Kumar Dubey and A K Sen | An analysis of gravitational redshift from rotating body | arXiv admin note: substantial text overlap with arXiv:1310.0987 | International Journal of Theoretical Physics 54(7), 2398 (2014) | 10.1007/s10773-014-2464-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational redshift is generally calculated without considering the
rotation of a body. Neglecting the rotation, the geometry of space time can be
described by using the spherically symmetric Schwarzschild geometry. Rotation
has great effect on general relativity, which gives new challenges on
gravitational redshift. When rotation is taken into consideration spherical
symmetry is lost and off diagonal terms appear in the metric. The geometry of
space time can be then described by using the solutions of Kerr family. In the
present paper we discuss the gravitational redshift for rotating body by using
Kerr metric. The numerical calculations has been done under Newtonian
approximation of angular momentum. It has been found that the value of
gravitational redshift is influenced by the direction of spin of central body
and also on the position (latitude) on the central body at which the photon is
emitted. The variation of gravitational redshift from equatorial to non -
equatorial region has been calculated and its implications are discussed in
detail.
| [
{
"created": "Wed, 26 Feb 2014 11:13:49 GMT",
"version": "v1"
},
{
"created": "Wed, 21 May 2014 12:32:25 GMT",
"version": "v2"
}
] | 2015-10-19 | [
[
"Dubey",
"Anuj Kumar",
""
],
[
"Sen",
"A K",
""
]
] | Gravitational redshift is generally calculated without considering the rotation of a body. Neglecting the rotation, the geometry of space time can be described by using the spherically symmetric Schwarzschild geometry. Rotation has great effect on general relativity, which gives new challenges on gravitational redshift. When rotation is taken into consideration spherical symmetry is lost and off diagonal terms appear in the metric. The geometry of space time can be then described by using the solutions of Kerr family. In the present paper we discuss the gravitational redshift for rotating body by using Kerr metric. The numerical calculations has been done under Newtonian approximation of angular momentum. It has been found that the value of gravitational redshift is influenced by the direction of spin of central body and also on the position (latitude) on the central body at which the photon is emitted. The variation of gravitational redshift from equatorial to non - equatorial region has been calculated and its implications are discussed in detail. |
gr-qc/0301047 | Aleksandar Mikovic | A. Mikovic | Quantum Gravity Vacuum and Invariants of Embedded Spin Networks | 15 pages, revised version to appear in Class. Quant. Grav | Class.Quant.Grav.20:3483-3492,2003 | 10.1088/0264-9381/20/15/314 | null | gr-qc hep-th | null | We show that the path integral for the three-dimensional SU(2) BF theory with
a Wilson loop or a spin network function inserted can be understood as the
Rovelli-Smolin loop transform of a wavefunction in the Ashtekar connection
representation, where the wavefunction satisfies the constraints of quantum
general relativity with zero cosmological constant. This wavefunction is given
as a product of the delta functions of the SU(2) field strength and therefore
it can be naturally associated to a flat connection spacetime. The loop
transform can be defined rigorously via the quantum SU(2) group, as a spin foam
state sum model, so that one obtains invariants of spin networks embedded in a
three-manifold. These invariants define a flat connection vacuum state in the
q-deformed spin network basis. We then propose a modification of this
construction in order to obtain a vacuum state corresponding to the flat metric
spacetime.
| [
{
"created": "Tue, 14 Jan 2003 17:08:21 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jun 2003 13:06:48 GMT",
"version": "v2"
}
] | 2009-01-16 | [
[
"Mikovic",
"A.",
""
]
] | We show that the path integral for the three-dimensional SU(2) BF theory with a Wilson loop or a spin network function inserted can be understood as the Rovelli-Smolin loop transform of a wavefunction in the Ashtekar connection representation, where the wavefunction satisfies the constraints of quantum general relativity with zero cosmological constant. This wavefunction is given as a product of the delta functions of the SU(2) field strength and therefore it can be naturally associated to a flat connection spacetime. The loop transform can be defined rigorously via the quantum SU(2) group, as a spin foam state sum model, so that one obtains invariants of spin networks embedded in a three-manifold. These invariants define a flat connection vacuum state in the q-deformed spin network basis. We then propose a modification of this construction in order to obtain a vacuum state corresponding to the flat metric spacetime. |
2011.12305 | Justin Feng | Justin C. Feng and Shinji Mukohyama and Sante Carloni | Minimal exponential measure model in the post-Newtonian limit | 14 pages, 3 figures. Matches published version | Phys. Rev. D 103, 084055 (2021) | 10.1103/PhysRevD.103.084055 | YITP-20-152, IPMU20-0122 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the post-Newtonian limit of the minimal exponential measure (MEMe)
model presented in [J. C. Feng, S. Carloni, Phys. Rev. D 101, 064002 (2020)]
using an extension of the parameterized post-Newtonian (PPN) formalism which is
also suitable for other type-I minimally modified Gravity theories. The new PPN
expansion is then used to calculate the monopole term of the post-Newtonian
gravitational potential and to perform an analysis of circular orbits within
spherically symmetric matter distributions. The latter shows that the behavior
does not differ significantly from that of general relativity for realistic
values of the MEMe model parameter $q$. Instead the former shows that one can
use precision measurements of Newton's constant $G$ to improve the constraint
on $q$ by up to $10$ orders of magnitude.
| [
{
"created": "Tue, 24 Nov 2020 19:00:01 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Apr 2021 16:09:49 GMT",
"version": "v2"
}
] | 2021-04-30 | [
[
"Feng",
"Justin C.",
""
],
[
"Mukohyama",
"Shinji",
""
],
[
"Carloni",
"Sante",
""
]
] | We examine the post-Newtonian limit of the minimal exponential measure (MEMe) model presented in [J. C. Feng, S. Carloni, Phys. Rev. D 101, 064002 (2020)] using an extension of the parameterized post-Newtonian (PPN) formalism which is also suitable for other type-I minimally modified Gravity theories. The new PPN expansion is then used to calculate the monopole term of the post-Newtonian gravitational potential and to perform an analysis of circular orbits within spherically symmetric matter distributions. The latter shows that the behavior does not differ significantly from that of general relativity for realistic values of the MEMe model parameter $q$. Instead the former shows that one can use precision measurements of Newton's constant $G$ to improve the constraint on $q$ by up to $10$ orders of magnitude. |
2103.14555 | V. G. Gurzadyan | V.G. Gurzadyan, A. Stepanian | Cosmological constant, information and gedanken experiments with black
hole horizons | 7 pages; Eur Phys J Plus (in press); the published version | Eur. Phys. J. Plus 136, 361 (2021) | 10.1140/epjp/s13360-021-01374-3 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | The cosmological constant if considered as a fundamental constant, provides
an information treatment for gravitation problems, both cosmological and of
black holes. The efficiency of that approach is shown via gedanken experiments
for the information behavior of the horizons for Schwarzschild-de Sitter and
Kerr-de Sitter metrics. A notion of entropy regarding any observer and in all
possible non-extreme black hole solutions is suggested, linked also to
Bekenstein bound. The suggested information approach forbids the existence of
naked singularities.
| [
{
"created": "Thu, 25 Mar 2021 07:27:07 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Apr 2021 11:47:05 GMT",
"version": "v2"
}
] | 2021-04-08 | [
[
"Gurzadyan",
"V. G.",
""
],
[
"Stepanian",
"A.",
""
]
] | The cosmological constant if considered as a fundamental constant, provides an information treatment for gravitation problems, both cosmological and of black holes. The efficiency of that approach is shown via gedanken experiments for the information behavior of the horizons for Schwarzschild-de Sitter and Kerr-de Sitter metrics. A notion of entropy regarding any observer and in all possible non-extreme black hole solutions is suggested, linked also to Bekenstein bound. The suggested information approach forbids the existence of naked singularities. |
2406.05150 | Iarley P. Lobo Dr | Iarley P. Lobo, Christian Pfeifer | Experimental Bounds on Deformed Muon Lifetime Dilation | 4 pages | null | null | null | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | We analyze Planck scale induced modifications of the relativistic time
dilation using data from the Muon Storage Ring experiment at CERN. By examining
the lifetimes of muons, we establish, for the first time, a constraint on such
quantum gravity-inspired deformations using this channel.
| [
{
"created": "Mon, 3 Jun 2024 21:28:17 GMT",
"version": "v1"
}
] | 2024-06-11 | [
[
"Lobo",
"Iarley P.",
""
],
[
"Pfeifer",
"Christian",
""
]
] | We analyze Planck scale induced modifications of the relativistic time dilation using data from the Muon Storage Ring experiment at CERN. By examining the lifetimes of muons, we establish, for the first time, a constraint on such quantum gravity-inspired deformations using this channel. |
2211.08821 | David Rumler | David Rumler, Andreas Kleinw\"achter, Reinhard Meinel | Geometry of charged rotating discs of dust in Einstein-Maxwell theory | 26 pages, 16 figures; v4: correction in section 5.6 | Gen Relativ Gravit 55, 35 (2023) | 10.1007/s10714-023-03086-8 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Within the framework of Einstein-Maxwell theory geometric properties of
charged rotating discs of dust, using a post-Newtonian expansion up to tenth
order, are discussed. Investigating the disc's proper radius and the proper
circumference allows us to address questions related to the Ehrenfest paradox.
In the Newtonian limit there is an agreement with a rotating disc from special
relativity. The charged rotating disc of dust also possesses material-like
properties. A fundamental geometric property of the disc is its Gaussian
curvature. The result obtained for the charged rotating disc of dust is checked
by additionally calculating the Gaussian curvature of the analytic limiting
cases (charged rotating) Maclaurin disc, electrically counterpoised dust-disc
and uncharged rotating disc of dust. We find that by increasing the disc's
specific charge there occurs a transition from negative to positive curvature.
| [
{
"created": "Wed, 16 Nov 2022 10:40:10 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Dec 2022 15:10:31 GMT",
"version": "v2"
},
{
"created": "Tue, 31 Jan 2023 10:51:36 GMT",
"version": "v3"
},
{
"created": "Mon, 13 Feb 2023 14:39:14 GMT",
"version": "v4"
}
] | 2023-02-14 | [
[
"Rumler",
"David",
""
],
[
"Kleinwächter",
"Andreas",
""
],
[
"Meinel",
"Reinhard",
""
]
] | Within the framework of Einstein-Maxwell theory geometric properties of charged rotating discs of dust, using a post-Newtonian expansion up to tenth order, are discussed. Investigating the disc's proper radius and the proper circumference allows us to address questions related to the Ehrenfest paradox. In the Newtonian limit there is an agreement with a rotating disc from special relativity. The charged rotating disc of dust also possesses material-like properties. A fundamental geometric property of the disc is its Gaussian curvature. The result obtained for the charged rotating disc of dust is checked by additionally calculating the Gaussian curvature of the analytic limiting cases (charged rotating) Maclaurin disc, electrically counterpoised dust-disc and uncharged rotating disc of dust. We find that by increasing the disc's specific charge there occurs a transition from negative to positive curvature. |
1807.08628 | Alan Coley | Alan A. Coley | Mathematical General Relativity | null | null | 10.1007/s10714-019-2559-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a number of open problems within general relativity. After a brief
introduction to some technical mathematical issues and the famous singularity
theorems, we discuss the cosmic censorship hypothesis and the Penrose
inequality, the uniqueness of black hole solutions and the stability of Kerr
spacetime and the final state conjecture, critical phenomena and the
Einstein-Yang--Mills equations, and a number of other problems in classical
general relativity. We then broaden the scope and discuss some mathematical
problems motivated by quantum gravity, including AdS/CFT correspondence and
problems in higher dimensions and, in particular, the instability of anti-de
Sitter spacetime, and in cosmology, including the cosmological constant problem
and dark energy, the stability of de Sitter spacetime and cosmological
singularities and spikes. Finally, we briefly discuss some problems in
numerical relativity and relativistic astrophysics.
| [
{
"created": "Thu, 19 Jul 2018 23:18:35 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Aug 2018 01:57:17 GMT",
"version": "v2"
}
] | 2019-07-10 | [
[
"Coley",
"Alan A.",
""
]
] | We present a number of open problems within general relativity. After a brief introduction to some technical mathematical issues and the famous singularity theorems, we discuss the cosmic censorship hypothesis and the Penrose inequality, the uniqueness of black hole solutions and the stability of Kerr spacetime and the final state conjecture, critical phenomena and the Einstein-Yang--Mills equations, and a number of other problems in classical general relativity. We then broaden the scope and discuss some mathematical problems motivated by quantum gravity, including AdS/CFT correspondence and problems in higher dimensions and, in particular, the instability of anti-de Sitter spacetime, and in cosmology, including the cosmological constant problem and dark energy, the stability of de Sitter spacetime and cosmological singularities and spikes. Finally, we briefly discuss some problems in numerical relativity and relativistic astrophysics. |
gr-qc/0411024 | Lorenzo Iorio | Lorenzo Iorio | On the reliability of the so far performed tests for measuring the
Lense-Thirring effect with the LAGEOS satellites | LaTex2e, 22 pages, 1 figure, 1 table, 60 references. Conclusions and
Table of Contents added. Estimates of the impact of J6dot on the
node-node-perigee combination presented. Typos corrected and minor stylistic
changes. Small changes due to G. Melki useful remarks. Lense-Thirring
'memory' effect in EIGEN-GRACE02S discussed | New Astron. 10 (2005) 603-615 | 10.1016/j.newast.2005.01.001 | null | gr-qc astro-ph physics.geo-ph | null | In this paper we will show in detail that the performed attempts aimed at the
detection of the general relativistic Lense-Thirring effect in the
gravitational field of the Earth with the existing LAGEOS satellites are often
presented in an optimistic and misleading way which is inadequate for such an
important test of fundamental physics. E.g., in the latest reported measurement
of the gravitomagnetic shift with the nodes of the LAGEOS satellites and the
2nd generation GRACE-only EIGEN-GRACE02S Earth gravity model over an
observational time span of 11 years a 5-10% total accuracy is claimed at
1-3sigma, respectively. We will show that, instead, it might be 15-45%
(1-3sigma) if the impact of the secular variations of the even zonal harmonics
is considered as well.
| [
{
"created": "Thu, 4 Nov 2004 14:22:06 GMT",
"version": "v1"
},
{
"created": "Sun, 15 May 2005 14:19:27 GMT",
"version": "v10"
},
{
"created": "Fri, 5 Nov 2004 16:24:45 GMT",
"version": "v2"
},
{
"created": "Sun, 7 Nov 2004 14:32:41 GMT",
"version": "v3"
},
{
"cre... | 2007-05-23 | [
[
"Iorio",
"Lorenzo",
""
]
] | In this paper we will show in detail that the performed attempts aimed at the detection of the general relativistic Lense-Thirring effect in the gravitational field of the Earth with the existing LAGEOS satellites are often presented in an optimistic and misleading way which is inadequate for such an important test of fundamental physics. E.g., in the latest reported measurement of the gravitomagnetic shift with the nodes of the LAGEOS satellites and the 2nd generation GRACE-only EIGEN-GRACE02S Earth gravity model over an observational time span of 11 years a 5-10% total accuracy is claimed at 1-3sigma, respectively. We will show that, instead, it might be 15-45% (1-3sigma) if the impact of the secular variations of the even zonal harmonics is considered as well. |
2111.01065 | Ernesto Nungesser | Ho Lee, Ernesto Nungesser and John Stalker | On almost Ehlers-Geren-Sachs theorems | 26 pages, 1 figure; matches accepted version in CQG; presentation
improved, minor typos corrected | 2022 Class. Quantum Grav. 39 105006 | 10.1088/1361-6382/ac655c | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | We show assuming small data that massless solutions to the reflection
symmetric Einstein-Vlasov system with Bianchi VII$_0$ symmetry which are not
locally rotational symmetric, can be arbitrarily close to and will remain close
to isotropy as regards {to} the shear. However in general the shear will not
tend to zero and the Hubble normalised Weyl curvature will blow up. This
generalises the work \cite{NHW,WHU}, which considered a non-tilted radiation
fluid to the massless Vlasov case. This represents another example of the fact
that almost Ehlers-Geren-Sachs theorems do not hold in general and that
collisionless matter behaves differently than a perfect fluid.
| [
{
"created": "Mon, 1 Nov 2021 16:28:39 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Apr 2022 19:20:21 GMT",
"version": "v2"
}
] | 2024-06-18 | [
[
"Lee",
"Ho",
""
],
[
"Nungesser",
"Ernesto",
""
],
[
"Stalker",
"John",
""
]
] | We show assuming small data that massless solutions to the reflection symmetric Einstein-Vlasov system with Bianchi VII$_0$ symmetry which are not locally rotational symmetric, can be arbitrarily close to and will remain close to isotropy as regards {to} the shear. However in general the shear will not tend to zero and the Hubble normalised Weyl curvature will blow up. This generalises the work \cite{NHW,WHU}, which considered a non-tilted radiation fluid to the massless Vlasov case. This represents another example of the fact that almost Ehlers-Geren-Sachs theorems do not hold in general and that collisionless matter behaves differently than a perfect fluid. |
1103.2569 | Hideyoshi Arakida | Hideyoshi Arakida | Application of Time Transfer Function to McVittie Spacetime:
Gravitational Time Delay and Secular Increase in Astronomical Unit | 13 pages, 2 figures, accepted for publication in General Relativity
and Gravitation | General Relativity and Gravitation, Volume 43, Issue 8,
pp.2127-2139 (2011) | 10.1007/s10714-011-1170-1 | null | gr-qc astro-ph.CO astro-ph.EP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We attempt to calculate the gravitational time delay in a time-dependent
gravitational field, especially in McVittie spacetime, which can be considered
as the spacetime around a gravitating body such as the Sun, embedded in the
FLRW (Friedmann-Lema\^itre-Robertson-Walker) cosmological background metric. To
this end, we adopt the time transfer function method proposed by Le
Poncin-Lafitte {\it et al.} (Class. Quant. Grav. 21:4463, 2004) and Teyssandier
and Le Poncin-Lafitte (Class. Quant. Grav. 25:145020, 2008), which is
originally related to Synge's world function $\Omega(x_A, x_B)$ and enables to
circumvent the integration of the null geodesic equation. We re-examine the
global cosmological effect on light propagation in the solar system. The
round-trip time of a light ray/signal is given by the functions of not only the
spacial coordinates but also the emission time or reception time of light
ray/signal, which characterize the time-dependency of solutions. We also apply
the obtained results to the secular increase in the astronomical unit, reported
by Krasinsky and Brumberg (Celest. Mech. Dyn. Astron. 90:267, 2004), and we
show that the leading order terms of the time-dependent component due to
cosmological expansion is 9 orders of magnitude smaller than the observed value
of $d{\rm AU}/dt$, i.e., $15 \pm 4$ ~[m/century]. Therefore, it is not possible
to explain the secular increase in the astronomical unit in terms of
cosmological expansion.
| [
{
"created": "Mon, 14 Mar 2011 00:42:18 GMT",
"version": "v1"
}
] | 2012-02-07 | [
[
"Arakida",
"Hideyoshi",
""
]
] | We attempt to calculate the gravitational time delay in a time-dependent gravitational field, especially in McVittie spacetime, which can be considered as the spacetime around a gravitating body such as the Sun, embedded in the FLRW (Friedmann-Lema\^itre-Robertson-Walker) cosmological background metric. To this end, we adopt the time transfer function method proposed by Le Poncin-Lafitte {\it et al.} (Class. Quant. Grav. 21:4463, 2004) and Teyssandier and Le Poncin-Lafitte (Class. Quant. Grav. 25:145020, 2008), which is originally related to Synge's world function $\Omega(x_A, x_B)$ and enables to circumvent the integration of the null geodesic equation. We re-examine the global cosmological effect on light propagation in the solar system. The round-trip time of a light ray/signal is given by the functions of not only the spacial coordinates but also the emission time or reception time of light ray/signal, which characterize the time-dependency of solutions. We also apply the obtained results to the secular increase in the astronomical unit, reported by Krasinsky and Brumberg (Celest. Mech. Dyn. Astron. 90:267, 2004), and we show that the leading order terms of the time-dependent component due to cosmological expansion is 9 orders of magnitude smaller than the observed value of $d{\rm AU}/dt$, i.e., $15 \pm 4$ ~[m/century]. Therefore, it is not possible to explain the secular increase in the astronomical unit in terms of cosmological expansion. |
2103.09326 | Carlos O. Lousto | Nicole Rosato, James Healy, and Carlos O. Lousto | Adapted gauge to small mass ratio binary black hole evolutions | 22 pages, 21 figures, 8 tables | Phys. Rev. D 103, 104068 (2021) | 10.1103/PhysRevD.103.104068 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the benefits of adapted gauges to small mass ratio binary black
hole evolutions in the moving puncture formulation. We find expressions that
approximate the late time behavior of the lapse and shift,
$(\alpha_0,\beta_0)$, and use them as initial values for their evolutions. We
also use a position and black hole mass dependent damping term,
$\eta[\vec{x}_1(t),\vec{x}_2(t),m_1,m_2]$, in the shift evolution, rather than
a constant or conformal-factor dependent choice. We have found that this
substantially reduces noise generation at the start of the numerical
integration and keeps the numerical grid stable around both black holes,
allowing for more accuracy with lower resolutions. We test our choices for this
gauge in detail in a case study of a binary with a 7:1 mass ratio, and then use
15:1 and 32:1 binaries for a convergence study. Finally, we apply our new gauge
to a 64:1 binary and a 128:1 binary to well cover the comparable and small mass
ratio regimes.
| [
{
"created": "Tue, 16 Mar 2021 21:07:59 GMT",
"version": "v1"
}
] | 2021-06-02 | [
[
"Rosato",
"Nicole",
""
],
[
"Healy",
"James",
""
],
[
"Lousto",
"Carlos O.",
""
]
] | We explore the benefits of adapted gauges to small mass ratio binary black hole evolutions in the moving puncture formulation. We find expressions that approximate the late time behavior of the lapse and shift, $(\alpha_0,\beta_0)$, and use them as initial values for their evolutions. We also use a position and black hole mass dependent damping term, $\eta[\vec{x}_1(t),\vec{x}_2(t),m_1,m_2]$, in the shift evolution, rather than a constant or conformal-factor dependent choice. We have found that this substantially reduces noise generation at the start of the numerical integration and keeps the numerical grid stable around both black holes, allowing for more accuracy with lower resolutions. We test our choices for this gauge in detail in a case study of a binary with a 7:1 mass ratio, and then use 15:1 and 32:1 binaries for a convergence study. Finally, we apply our new gauge to a 64:1 binary and a 128:1 binary to well cover the comparable and small mass ratio regimes. |
1011.4987 | Christopher M. Hirata | Christopher M Hirata | Resonant recoil in extreme mass ratio binary black hole mergers | fixed references; matches PRD accepted version (minor revision); 9
pages, 2 figures | Phys.Rev.D83:104024,2011 | 10.1103/PhysRevD.83.104024 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The inspiral and merger of a binary black hole system generally leads to an
asymmetric distribution of emitted radiation, and hence a recoil of the remnant
black hole directed opposite to the net linear momentum radiated. The recoil
velocity is generally largest for comparable mass black holes and particular
spin configurations, and approaches zero in the extreme mass ratio limit. It is
generally believed that for extreme mass ratios eta<<1, the scaling of the
recoil velocity is V {\propto} eta^2, where the proportionality coefficient
depends on the spin of the larger hole and the geometry of the system (e.g.
orbital inclination). Here we show that for low but nonzero inclination
prograde orbits and very rapidly spinning large holes (spin parameter
a*>0.9678) the inspiralling binary can pass through resonances where the
orbit-averaged radiation-reaction force is nonzero. These resonance crossings
lead to a new contribution to the kick, V {\propto} eta^{3/2}. For these
configurations and sufficiently extreme mass ratios, this resonant recoil is
dominant. While it seems doubtful that the resonant recoil will be
astrophysically significant, its existence suggests caution when extrapolating
the results of numerical kick results to extreme mass ratios and near-maximal
spins.
| [
{
"created": "Tue, 23 Nov 2010 01:55:10 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Mar 2011 17:52:37 GMT",
"version": "v2"
},
{
"created": "Wed, 8 Jun 2011 21:35:41 GMT",
"version": "v3"
}
] | 2011-06-10 | [
[
"Hirata",
"Christopher M",
""
]
] | The inspiral and merger of a binary black hole system generally leads to an asymmetric distribution of emitted radiation, and hence a recoil of the remnant black hole directed opposite to the net linear momentum radiated. The recoil velocity is generally largest for comparable mass black holes and particular spin configurations, and approaches zero in the extreme mass ratio limit. It is generally believed that for extreme mass ratios eta<<1, the scaling of the recoil velocity is V {\propto} eta^2, where the proportionality coefficient depends on the spin of the larger hole and the geometry of the system (e.g. orbital inclination). Here we show that for low but nonzero inclination prograde orbits and very rapidly spinning large holes (spin parameter a*>0.9678) the inspiralling binary can pass through resonances where the orbit-averaged radiation-reaction force is nonzero. These resonance crossings lead to a new contribution to the kick, V {\propto} eta^{3/2}. For these configurations and sufficiently extreme mass ratios, this resonant recoil is dominant. While it seems doubtful that the resonant recoil will be astrophysically significant, its existence suggests caution when extrapolating the results of numerical kick results to extreme mass ratios and near-maximal spins. |
0909.3767 | Claus Kiefer | Claus Kiefer | Does time exist in quantum gravity? | 10 pages, second prize of the FQXi "The Nature of Time" essay contest | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Time is absolute in standard quantum theory and dynamical in general
relativity. The combination of both theories into a theory of quantum gravity
leads therefore to a "problem of time". In my essay I shall investigate those
consequences for the concept of time that may be drawn without a detailed
knowledge of quantum gravity. The only assumptions are the experimentally
supported universality of the linear structure of quantum theory and the
recovery of general relativity in the classical limit. Among the consequences
are the fundamental timelessness of quantum gravity, the approximate nature of
a semiclassical time, and the correlation of entropy with the size of the
Universe.
| [
{
"created": "Mon, 21 Sep 2009 13:19:59 GMT",
"version": "v1"
}
] | 2009-09-22 | [
[
"Kiefer",
"Claus",
""
]
] | Time is absolute in standard quantum theory and dynamical in general relativity. The combination of both theories into a theory of quantum gravity leads therefore to a "problem of time". In my essay I shall investigate those consequences for the concept of time that may be drawn without a detailed knowledge of quantum gravity. The only assumptions are the experimentally supported universality of the linear structure of quantum theory and the recovery of general relativity in the classical limit. Among the consequences are the fundamental timelessness of quantum gravity, the approximate nature of a semiclassical time, and the correlation of entropy with the size of the Universe. |
2006.09843 | Lorenzo Gavassino | Lorenzo Gavassino, Marco Antonelli and Brynmor Haskell | When the entropy has no maximum: A new perspective on the instability of
the first-order theories of dissipation | 18 pages, 5 figures, published on PRD | Phys. Rev. D 102, 043018 (2020) | 10.1103/PhysRevD.102.043018 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The first-order relativistic fluid theories of dissipation proposed by Eckart
and Landau-Lifshitz have been proved to be unstable. They admit solutions which
start in proximity of equilibrium and depart exponentially from it. We show
that this behaviour is due to the fact that the total entropy of these fluids,
restricted to the dynamically accessible states, has no upper bound. As a
result, these systems have the tendency to constantly change according to the
second law of thermodynamics and the unstable modes represent the directions of
growth of the entropy in state space. We, then, verify that the conditions of
stability of Israel and Stewart's theory are exactly the requirements for the
entropy to have an absolute maximum. Hence, we explain how the instability of
the first-order theories is a direct consequence of the truncation of the
entropy current at the first order, which turns the maximum into a saddle point
of the total entropy. Finally, we show that recently proposed first-order
stable theories, constructed using more general frames, do not solve the
instability problem by providing a maximum for the entropy, but, rather, are
made stable by allowing for small violations of the second law.
| [
{
"created": "Wed, 17 Jun 2020 13:15:30 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Aug 2020 06:15:29 GMT",
"version": "v2"
}
] | 2020-09-02 | [
[
"Gavassino",
"Lorenzo",
""
],
[
"Antonelli",
"Marco",
""
],
[
"Haskell",
"Brynmor",
""
]
] | The first-order relativistic fluid theories of dissipation proposed by Eckart and Landau-Lifshitz have been proved to be unstable. They admit solutions which start in proximity of equilibrium and depart exponentially from it. We show that this behaviour is due to the fact that the total entropy of these fluids, restricted to the dynamically accessible states, has no upper bound. As a result, these systems have the tendency to constantly change according to the second law of thermodynamics and the unstable modes represent the directions of growth of the entropy in state space. We, then, verify that the conditions of stability of Israel and Stewart's theory are exactly the requirements for the entropy to have an absolute maximum. Hence, we explain how the instability of the first-order theories is a direct consequence of the truncation of the entropy current at the first order, which turns the maximum into a saddle point of the total entropy. Finally, we show that recently proposed first-order stable theories, constructed using more general frames, do not solve the instability problem by providing a maximum for the entropy, but, rather, are made stable by allowing for small violations of the second law. |
1002.4168 | Willians Barreto | W. Barreto (ULA), L. Castillo (UDO) and E. Barrios (ULA) | Bondian frames to couple matter with radiation | 20 pages, 6 figures; to appear in General Relativity and Gravitation | General Relativity and Gravitation, 42, 1845 (2010) | 10.1007/s10714-010-0954-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A study is presented for the non linear evolution of a self gravitating
distribution of matter coupled to a massless scalar field. The characteristic
formulation for numerical relativity is used to follow the evolution by a
sequence of light cones open to the future. Bondian frames are used to endow
physical meaning to the matter variables and to the massless scalar field.
Asymptotic approaches to the origin and to infinity are achieved; at the
boundary surface interior and exterior solutions are matched guaranteeing the
Darmois--Lichnerowicz conditions. To show how the scheme works some numerical
models are discussed. We exemplify evolving scalar waves on the following fixed
backgrounds: A) an atmosphere between the boundary surface of an incompressible
mixtured fluid and infinity; B) a polytropic distribution matched to a
Schwarzschild exterior; C) a Schwarzschild- Schwarzschild spacetime. The
conservation of energy, the Newman--Penrose constant preservation and other
expected features are observed.
| [
{
"created": "Mon, 22 Feb 2010 19:11:18 GMT",
"version": "v1"
}
] | 2015-05-18 | [
[
"Barreto",
"W.",
"",
"ULA"
],
[
"Castillo",
"L.",
"",
"UDO"
],
[
"Barrios",
"E.",
"",
"ULA"
]
] | A study is presented for the non linear evolution of a self gravitating distribution of matter coupled to a massless scalar field. The characteristic formulation for numerical relativity is used to follow the evolution by a sequence of light cones open to the future. Bondian frames are used to endow physical meaning to the matter variables and to the massless scalar field. Asymptotic approaches to the origin and to infinity are achieved; at the boundary surface interior and exterior solutions are matched guaranteeing the Darmois--Lichnerowicz conditions. To show how the scheme works some numerical models are discussed. We exemplify evolving scalar waves on the following fixed backgrounds: A) an atmosphere between the boundary surface of an incompressible mixtured fluid and infinity; B) a polytropic distribution matched to a Schwarzschild exterior; C) a Schwarzschild- Schwarzschild spacetime. The conservation of energy, the Newman--Penrose constant preservation and other expected features are observed. |
1205.1037 | Taymaz Ghaneh | Taymaz Ghaneh, Farhad Darabi, Hossein Motavalli | Signature Change in Noncommutative FRW Cosmology | 15 pages, 4 figures, Minor revision, references added | Mod. Phys. Lett. A, Vol. 27, No. 37 (2012) 1250214 | 10.1142/S0217732312502148 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The conditions for which the no boundary proposal may have a classical
realization of a continuous change of signature, are investigated for a
cosmological model described by FRW metric coupled with a self interacting
scalar field, having a noncommutative phase space of dynamical variables. The
model is then quantized and a good correspondence is shown between the
classical and quantum cosmology indicating that the noncommutativity does not
destruct the classical-quantum correspondence. It is also shown that the
quantum cosmology supports a signature transition where the bare cosmological
constant takes a vast continuous spectrum of negative values. The bounds of
bare cosmological constant are limited by the values of noncommutative
parameters. Moreover, it turns out that the physical parameters are constrained
by the noncommutativity parametres.
| [
{
"created": "Fri, 4 May 2012 18:55:15 GMT",
"version": "v1"
},
{
"created": "Sun, 9 Sep 2012 05:37:47 GMT",
"version": "v2"
},
{
"created": "Wed, 5 Dec 2012 06:39:12 GMT",
"version": "v3"
}
] | 2012-12-06 | [
[
"Ghaneh",
"Taymaz",
""
],
[
"Darabi",
"Farhad",
""
],
[
"Motavalli",
"Hossein",
""
]
] | The conditions for which the no boundary proposal may have a classical realization of a continuous change of signature, are investigated for a cosmological model described by FRW metric coupled with a self interacting scalar field, having a noncommutative phase space of dynamical variables. The model is then quantized and a good correspondence is shown between the classical and quantum cosmology indicating that the noncommutativity does not destruct the classical-quantum correspondence. It is also shown that the quantum cosmology supports a signature transition where the bare cosmological constant takes a vast continuous spectrum of negative values. The bounds of bare cosmological constant are limited by the values of noncommutative parameters. Moreover, it turns out that the physical parameters are constrained by the noncommutativity parametres. |
0910.5925 | Douglas Urban | Douglas Urban, Ken D. Olum | Averaged null energy condition violation in a conformally flat spacetime | 11 pages | PhysRevD.81.024039,2010 | 10.1103/PhysRevD.81.024039 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the averaged null energy condition can be violated by a
conformally coupled scalar field in a conformally flat spacetime in 3+1
dimensions. The violation is dependent on the quantum state and can be made as
large as desired. It does not arise from the presence of anomalies, although
anomalous violations are also possible. Since all geodesics in conformally flat
spacetimes are achronal, the achronal averaged null energy condition is
likewise violated.
| [
{
"created": "Fri, 30 Oct 2009 19:59:16 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jan 2010 05:24:05 GMT",
"version": "v2"
}
] | 2010-01-28 | [
[
"Urban",
"Douglas",
""
],
[
"Olum",
"Ken D.",
""
]
] | We show that the averaged null energy condition can be violated by a conformally coupled scalar field in a conformally flat spacetime in 3+1 dimensions. The violation is dependent on the quantum state and can be made as large as desired. It does not arise from the presence of anomalies, although anomalous violations are also possible. Since all geodesics in conformally flat spacetimes are achronal, the achronal averaged null energy condition is likewise violated. |
gr-qc/0310065 | Sergei Kopeikin M. | Sergei M. Kopeikin (UMC) and Edward B. Fomalont (NRAO) | On the Speed of Gravity and Relativistic v/c Corrections to the Shapiro
Time Delay | 7 pages. Final version published in Physics Letters A | Phys.Lett. A355 (2006) 163-166 | 10.1016/j.physleta.2006.02.028 | null | gr-qc astro-ph hep-th | null | Recent papers by Samuel declared that the linearized post-Newtonian v/c
effects are too small to have been measured in the recent experiment involving
Jupiter and quasar J0842+1845 that was used to measure the ultimate speed of
gravity defined as a fundamental constant entering in front of each time
derivative of the metric tensor in the Einstein gravity field equations. We
describe our Lorentz-invariant formulation of the Jovian deflection experiment
and confirm that v/c effects are do observed, as contrasted to the erroneous
claim by Samuel, and that they vanish if and only if the speed of gravity is
infinite.
| [
{
"created": "Mon, 13 Oct 2003 20:10:00 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Mar 2004 05:36:19 GMT",
"version": "v2"
},
{
"created": "Thu, 9 Feb 2006 20:08:51 GMT",
"version": "v3"
},
{
"created": "Thu, 9 Feb 2006 22:44:44 GMT",
"version": "v4"
},
{
"cre... | 2007-05-23 | [
[
"Kopeikin",
"Sergei M.",
"",
"UMC"
],
[
"Fomalont",
"Edward B.",
"",
"NRAO"
]
] | Recent papers by Samuel declared that the linearized post-Newtonian v/c effects are too small to have been measured in the recent experiment involving Jupiter and quasar J0842+1845 that was used to measure the ultimate speed of gravity defined as a fundamental constant entering in front of each time derivative of the metric tensor in the Einstein gravity field equations. We describe our Lorentz-invariant formulation of the Jovian deflection experiment and confirm that v/c effects are do observed, as contrasted to the erroneous claim by Samuel, and that they vanish if and only if the speed of gravity is infinite. |
0806.2805 | Frans Klinkhamer | F.R. Klinkhamer, G.E. Volovik | Dynamic vacuum variable and equilibrium approach in cosmology | 24 (not 25) pages, v7(=v6 with latex problem corrected): published
version in preprint style | Phys.Rev.D78:063528,2008 | 10.1103/PhysRevD.78.063528 | KA-TP-14-2008 | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A modified-gravity theory is considered with a four-form field strength F, a
variable gravitational coupling parameter G(F), and a standard matter action.
This theory provides a concrete realization of the general vacuum variable q as
the four-form amplitude F and allows for a study of its dynamics. The theory
gives a flat Friedmann-Robertson-Walker universe with rapid oscillations of the
effective vacuum energy density (cosmological "constant"), whose amplitude
drops to zero asymptotically. Extrapolating to the present age of the Universe,
the order of magnitude of the average vacuum energy density agrees with the
observed near-critical vacuum energy density of the present universe. It may
even be that this type of oscillating vacuum energy density constitutes a
significant part of the so-called cold dark matter in the standard
Friedmann-Robertson-Walker framework.
| [
{
"created": "Tue, 17 Jun 2008 17:42:56 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Jun 2008 15:44:23 GMT",
"version": "v2"
},
{
"created": "Mon, 30 Jun 2008 12:32:48 GMT",
"version": "v3"
},
{
"created": "Fri, 25 Jul 2008 14:33:56 GMT",
"version": "v4"
},
{
"c... | 2009-11-13 | [
[
"Klinkhamer",
"F. R.",
""
],
[
"Volovik",
"G. E.",
""
]
] | A modified-gravity theory is considered with a four-form field strength F, a variable gravitational coupling parameter G(F), and a standard matter action. This theory provides a concrete realization of the general vacuum variable q as the four-form amplitude F and allows for a study of its dynamics. The theory gives a flat Friedmann-Robertson-Walker universe with rapid oscillations of the effective vacuum energy density (cosmological "constant"), whose amplitude drops to zero asymptotically. Extrapolating to the present age of the Universe, the order of magnitude of the average vacuum energy density agrees with the observed near-critical vacuum energy density of the present universe. It may even be that this type of oscillating vacuum energy density constitutes a significant part of the so-called cold dark matter in the standard Friedmann-Robertson-Walker framework. |
1304.7597 | Sandipan Sengupta | Sandipan Sengupta | Gravity Asymptotics with Topological Parameters | References added; Published version | Phys. Rev. D 88, 024031 (2013) | 10.1103/PhysRevD.88.024031 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In four dimensional gravity theory, the Barbero-Immirzi parameter has a
topological origin, and can be identified as the coefficient multiplying the
Nieh-Yan topological density in the gravity Lagrangian, as proposed by Date et
al.[1]. Based on this fact, a first order action formulation for spacetimes
with boundaries is introduced. The bulk Lagrangian, containing the Nieh-Yan
density, needs to be supplemented with suitable boundary terms so that it leads
to a well-defined variational principle. Within this general framework, we
analyse spacetimes with and without a cosmological constant.
For locally Anti de Sitter (or de Sitter) asymptotia, the action principle
has non-trivial implications. It admits an extremum for all such solutions
provided the SO(3,1) Pontryagin and Euler topological densities are added to it
with fixed coefficients. The resulting Lagrangian, while containing all three
topological densities, has only one independent topological coupling constant,
namely, the Barbero-Immirzi parameter. In the final analysis, it emerges as a
coefficient of the SO(3,2) (or SO(4,1)) Pontryagin density, and is present in
the action only for manifolds for which the corresponding topological index is
non-zero.
| [
{
"created": "Mon, 29 Apr 2013 09:06:52 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Jul 2013 06:20:00 GMT",
"version": "v2"
}
] | 2013-07-29 | [
[
"Sengupta",
"Sandipan",
""
]
] | In four dimensional gravity theory, the Barbero-Immirzi parameter has a topological origin, and can be identified as the coefficient multiplying the Nieh-Yan topological density in the gravity Lagrangian, as proposed by Date et al.[1]. Based on this fact, a first order action formulation for spacetimes with boundaries is introduced. The bulk Lagrangian, containing the Nieh-Yan density, needs to be supplemented with suitable boundary terms so that it leads to a well-defined variational principle. Within this general framework, we analyse spacetimes with and without a cosmological constant. For locally Anti de Sitter (or de Sitter) asymptotia, the action principle has non-trivial implications. It admits an extremum for all such solutions provided the SO(3,1) Pontryagin and Euler topological densities are added to it with fixed coefficients. The resulting Lagrangian, while containing all three topological densities, has only one independent topological coupling constant, namely, the Barbero-Immirzi parameter. In the final analysis, it emerges as a coefficient of the SO(3,2) (or SO(4,1)) Pontryagin density, and is present in the action only for manifolds for which the corresponding topological index is non-zero. |
gr-qc/0301007 | M. M. Akbar | M.M. Akbar | Classical Boundary-value Problem in Riemannian Quantum Gravity and
Taub-Bolt-anti-de Sitter Geometries | Minor changes and references added: Version in the Journal | Nucl.Phys. B663 (2003) 215-230 | 10.1016/S0550-3213(03)00376-6 | DAMTP-2002-36 | gr-qc hep-th | null | For an $SU(2)\times U(1)$-invariant $S^3$ boundary the classical Dirichlet
problem of Riemannian quantum gravity is studied for positive-definite regular
solutions of the Einstein equations with a negative cosmological constant
within biaxial Bianchi-IX metrics containing bolts, i.e., within the family of
Taub-Bolt-anti-de Sitter (Taub-Bolt-AdS) metrics. Such metrics are obtained
from the two-parameter Taub-NUT-anti-de Sitter family. The condition of
regularity requires them to have only one free parameter ($L$) and constrains
$L$ to take values within a narrow range; the other parameter is determined as
a double-valued function of $L$ and hence there is a bifurcation within the
family. We found that {\it{any}} axially symmetric $S^3$-boundary can be filled
in with at least one solution coming from each of these two branches despite
the severe limit on the permissible values of $L$. The number of infilling
solutions can be one, three or five and they appear or disappear
catastrophically in pairs as the values of the two radii of $S^3$ are varied.
The solutions occur simultaneously in both branches and hence the total number
of independent infillings is two, six or ten. We further showed that when the
two radii are of the same order and large the number of solutions is two. In
the isotropic limit this holds for small radii as well. These results are to be
contrasted with the one-parameter self-dual Taub-NUT-AdS infilling solutions of
the same boundary-value problem studied previously.
| [
{
"created": "Mon, 6 Jan 2003 19:30:32 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Aug 2003 23:47:02 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Akbar",
"M. M.",
""
]
] | For an $SU(2)\times U(1)$-invariant $S^3$ boundary the classical Dirichlet problem of Riemannian quantum gravity is studied for positive-definite regular solutions of the Einstein equations with a negative cosmological constant within biaxial Bianchi-IX metrics containing bolts, i.e., within the family of Taub-Bolt-anti-de Sitter (Taub-Bolt-AdS) metrics. Such metrics are obtained from the two-parameter Taub-NUT-anti-de Sitter family. The condition of regularity requires them to have only one free parameter ($L$) and constrains $L$ to take values within a narrow range; the other parameter is determined as a double-valued function of $L$ and hence there is a bifurcation within the family. We found that {\it{any}} axially symmetric $S^3$-boundary can be filled in with at least one solution coming from each of these two branches despite the severe limit on the permissible values of $L$. The number of infilling solutions can be one, three or five and they appear or disappear catastrophically in pairs as the values of the two radii of $S^3$ are varied. The solutions occur simultaneously in both branches and hence the total number of independent infillings is two, six or ten. We further showed that when the two radii are of the same order and large the number of solutions is two. In the isotropic limit this holds for small radii as well. These results are to be contrasted with the one-parameter self-dual Taub-NUT-AdS infilling solutions of the same boundary-value problem studied previously. |
2401.06863 | Lei Lu | Lei Lu, Philip A. May | Step-by-Step Canonical Quantum Gravity -- Part I: Ashtekar's New
Variables | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Canonical quantum gravity was first developed by Abhay Ashtekar, Lee Smolin,
Carlo Rovelli and their collaborators in the late 1980s. It was a major
breakthrough that successfully brought Einstein's theory of General Relativity
(GR) into a Yang-Mills-type gauge theory. A new era of quantum gravity research
has since started, and with decades of continued efforts from a relatively
small community, the area now known as Loop Quantum Gravity (LQG) has
flourished, making it a promising theory of quantum gravity. Due to its
incredibly high level of complexity, many technical details were left out in
introductory texts on LQG. In particular, resources that are appropriate to the
undergraduate level are extremely limited. Consequently, there exists a huge
gap between the knowledge base of an undergraduate physics major and the
necessary readiness to carry out LQG research. In an effort to fill this gap,
we aim to develop a pedagogical user guide that provides a step-by-step
walk-through of canonical quantum gravity, without compromising necessary
technical details. We hope that our attempt will bring more exposure to
undergraduates on the exciting early developments of canonical quantum gravity,
and provide them with the necessary foundation to explore active research
fields such as black hole thermodynamics, Wheeler-DeWitt equation, and so on.
This work will also serve as a solid base for anyone hoping to pursue further
study in LQG at a higher level.
| [
{
"created": "Fri, 12 Jan 2024 19:26:14 GMT",
"version": "v1"
}
] | 2024-01-17 | [
[
"Lu",
"Lei",
""
],
[
"May",
"Philip A.",
""
]
] | Canonical quantum gravity was first developed by Abhay Ashtekar, Lee Smolin, Carlo Rovelli and their collaborators in the late 1980s. It was a major breakthrough that successfully brought Einstein's theory of General Relativity (GR) into a Yang-Mills-type gauge theory. A new era of quantum gravity research has since started, and with decades of continued efforts from a relatively small community, the area now known as Loop Quantum Gravity (LQG) has flourished, making it a promising theory of quantum gravity. Due to its incredibly high level of complexity, many technical details were left out in introductory texts on LQG. In particular, resources that are appropriate to the undergraduate level are extremely limited. Consequently, there exists a huge gap between the knowledge base of an undergraduate physics major and the necessary readiness to carry out LQG research. In an effort to fill this gap, we aim to develop a pedagogical user guide that provides a step-by-step walk-through of canonical quantum gravity, without compromising necessary technical details. We hope that our attempt will bring more exposure to undergraduates on the exciting early developments of canonical quantum gravity, and provide them with the necessary foundation to explore active research fields such as black hole thermodynamics, Wheeler-DeWitt equation, and so on. This work will also serve as a solid base for anyone hoping to pursue further study in LQG at a higher level. |
2104.03660 | Masato Minamitsuji | Masato Minamitsuji | Disformal transformation of physical quantities associated with
relativistic stars | 11 pages, no figure, published version | Phys. Rev. D 103, 084002 (2021) | 10.1103/PhysRevD.103.084002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate how physical quantities associated with relativistic stars in
the Jordan and Einstein frames are related by the generalized disformal
transformations constructed by the scalar and vector fields within the
slow-rotation approximation. We consider the most general scalar disformal
transformation constructed by the scalar field, and by the vector field without
and with the $U(1)$ gauge symmetry, respectively. At the zeroth order of the
slow-rotation approximation, by imposing that both the metrics of the Jordan
and Einstein frames are asymptotically flat, we show that the
Arnowitt-Deser-Misner mass is frame invariant. At the first order of the
slow-rotation approximation, we discuss the disformal transformations of the
frame-dragging function, angular velocity, angular momentum, and moment of
inertia of the star. We show that the angular velocity of the star is frame
invariant in all the cases. While the angular momentum and moment of inertia
are invariant under the scalar disformal transformation, they are not under the
vector disformal transformation without and with the $U(1)$ gauge symmetry.
| [
{
"created": "Thu, 8 Apr 2021 10:22:37 GMT",
"version": "v1"
},
{
"created": "Sat, 16 Oct 2021 07:16:02 GMT",
"version": "v2"
}
] | 2021-10-19 | [
[
"Minamitsuji",
"Masato",
""
]
] | We investigate how physical quantities associated with relativistic stars in the Jordan and Einstein frames are related by the generalized disformal transformations constructed by the scalar and vector fields within the slow-rotation approximation. We consider the most general scalar disformal transformation constructed by the scalar field, and by the vector field without and with the $U(1)$ gauge symmetry, respectively. At the zeroth order of the slow-rotation approximation, by imposing that both the metrics of the Jordan and Einstein frames are asymptotically flat, we show that the Arnowitt-Deser-Misner mass is frame invariant. At the first order of the slow-rotation approximation, we discuss the disformal transformations of the frame-dragging function, angular velocity, angular momentum, and moment of inertia of the star. We show that the angular velocity of the star is frame invariant in all the cases. While the angular momentum and moment of inertia are invariant under the scalar disformal transformation, they are not under the vector disformal transformation without and with the $U(1)$ gauge symmetry. |
1807.11033 | Oleg Zaslavskii | O. B. Zaslavskii | Super-Penrose process and rotating wormholes | 9 pages. Presentation improved, misprints corrected. To appear in PRD | Phys. Rev. D 98, 104030 (2018) | 10.1103/PhysRevD.98.104030 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider collision of particles in a wormhole near its throat. Particles
come from the opposite mouths. If the lapse function is small enough there, the
energy $E$ of debris at infinity grows unbounded, so we are faced with the
so-called super-Penrose process. This requires the existence of the ergoregion,
so a wormhole should be rotating.
| [
{
"created": "Sun, 29 Jul 2018 09:59:34 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Nov 2018 19:09:03 GMT",
"version": "v2"
}
] | 2018-11-28 | [
[
"Zaslavskii",
"O. B.",
""
]
] | We consider collision of particles in a wormhole near its throat. Particles come from the opposite mouths. If the lapse function is small enough there, the energy $E$ of debris at infinity grows unbounded, so we are faced with the so-called super-Penrose process. This requires the existence of the ergoregion, so a wormhole should be rotating. |
gr-qc/0202069 | Marc Henneaux | Thibault Damour, Marc Henneaux, Alan D. Rendall and Marsha Weaver | Kasner-like behaviour for subcritical Einstein-matter systems | LaTeX, 56 pages; minor corrections; version to appear in ``Annales
Henri Poincar\'e" | Annales Henri Poincare 3 (2002) 1049-1111 | null | IHES/P/02/06, ULB-TH-02/01 | gr-qc hep-th | null | Confirming previous heuristic analyses \`a la Belinskii-Khalatnikov-Lifshitz,
it is rigorously proven that certain ``subcritical'' Einstein-matter systems
exhibit a monotone, generalized Kasner behaviour in the vicinity of a spacelike
singularity. The D-dimensional coupled Einstein-dilaton-p-form system is
subcritical if the dilaton couplings of the p-forms belong to some dimension
dependent open neighbourhood of zero, while pure gravity is subcritical if D is
greater than or equal to 11. Our proof relies, like the recent theorem dealing
with the (always subcritical) Einstein-dilaton system, on the use of Fuchsian
techniques, which enable one to construct local, analytic solutions to the full
set of equations of motion. The solutions constructed are ``general'' in the
sense that they depend on the maximal expected number of free functions.
| [
{
"created": "Tue, 19 Feb 2002 10:40:29 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Sep 2002 06:44:06 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Damour",
"Thibault",
""
],
[
"Henneaux",
"Marc",
""
],
[
"Rendall",
"Alan D.",
""
],
[
"Weaver",
"Marsha",
""
]
] | Confirming previous heuristic analyses \`a la Belinskii-Khalatnikov-Lifshitz, it is rigorously proven that certain ``subcritical'' Einstein-matter systems exhibit a monotone, generalized Kasner behaviour in the vicinity of a spacelike singularity. The D-dimensional coupled Einstein-dilaton-p-form system is subcritical if the dilaton couplings of the p-forms belong to some dimension dependent open neighbourhood of zero, while pure gravity is subcritical if D is greater than or equal to 11. Our proof relies, like the recent theorem dealing with the (always subcritical) Einstein-dilaton system, on the use of Fuchsian techniques, which enable one to construct local, analytic solutions to the full set of equations of motion. The solutions constructed are ``general'' in the sense that they depend on the maximal expected number of free functions. |
1809.03500 | Emanuele Berti | Vishal Baibhav, Emanuele Berti | Multi-mode black hole spectroscopy | 11 pages, 7 figures, 2 tables | Phys. Rev. D 99, 024005 (2019) | 10.1103/PhysRevD.99.024005 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The first two LIGO/Virgo observing runs have detected several black hole
binary mergers. One of the most exciting prospects of future observing runs is
the possibility to identify the remnants of these mergers as Kerr black holes
by measuring their (complex) quasinormal mode frequencies. This idea - similar
to the identification of atomic elements through their spectral lines - is
sometimes called "black hole spectroscopy". Third-generation Earth-based
detectors and the space-based interferometer LISA could measure multiple
spectral lines from different multipolar components of the radiation, and
therefore provide qualitatively better tests of the Kerr hypothesis. In this
paper we quantify the redshift out to which the various modes would be
detectable (or, conversely, the number of detectable modes at any given
redshift) as a function of the intrinsic parameters of the merging binary. LISA
could detect so many modes that current numerical relativity simulations would
not be sufficient to extract all available science from the data.
| [
{
"created": "Mon, 10 Sep 2018 18:00:00 GMT",
"version": "v1"
}
] | 2019-01-09 | [
[
"Baibhav",
"Vishal",
""
],
[
"Berti",
"Emanuele",
""
]
] | The first two LIGO/Virgo observing runs have detected several black hole binary mergers. One of the most exciting prospects of future observing runs is the possibility to identify the remnants of these mergers as Kerr black holes by measuring their (complex) quasinormal mode frequencies. This idea - similar to the identification of atomic elements through their spectral lines - is sometimes called "black hole spectroscopy". Third-generation Earth-based detectors and the space-based interferometer LISA could measure multiple spectral lines from different multipolar components of the radiation, and therefore provide qualitatively better tests of the Kerr hypothesis. In this paper we quantify the redshift out to which the various modes would be detectable (or, conversely, the number of detectable modes at any given redshift) as a function of the intrinsic parameters of the merging binary. LISA could detect so many modes that current numerical relativity simulations would not be sufficient to extract all available science from the data. |
1804.09101 | Adam Lewis | Adam G. M. Lewis and Harald P. Pfeiffer | GPU-Accelerated Simulations of Isolated Black Holes | 42 pages, 11 figures | Class. Quant. Grav. 35 (2018) 095017 | 10.1088/1361-6382/aab256 | null | gr-qc physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a port of the numerical relativity code SpEC which is capable of
running on NVIDIA GPUs. Since this code must be maintained in parallel with
SpEC itself, a primary design consideration is to perform as few explicit code
changes as possible. We therefore rely on a hierarchy of automated porting
strategies. At the highest level we use TLoops, a C++ library of our design, to
automatically emit CUDA code equivalent to tensorial expressions written into
C++ source using a syntax similar to analytic calculation. Next, we trace out
and cache explicit matrix representations of the numerous linear
transformations in the SpEC code, which allows these to be performed on the GPU
using pre-existing matrix-multiplication libraries. We port the few remaining
important modules by hand. In this paper we detail the specifics of our port,
and present benchmarks of it simulating isolated black hole spacetimes on
several generations of NVIDIA GPU.
| [
{
"created": "Tue, 24 Apr 2018 15:39:16 GMT",
"version": "v1"
}
] | 2018-05-09 | [
[
"Lewis",
"Adam G. M.",
""
],
[
"Pfeiffer",
"Harald P.",
""
]
] | We present a port of the numerical relativity code SpEC which is capable of running on NVIDIA GPUs. Since this code must be maintained in parallel with SpEC itself, a primary design consideration is to perform as few explicit code changes as possible. We therefore rely on a hierarchy of automated porting strategies. At the highest level we use TLoops, a C++ library of our design, to automatically emit CUDA code equivalent to tensorial expressions written into C++ source using a syntax similar to analytic calculation. Next, we trace out and cache explicit matrix representations of the numerous linear transformations in the SpEC code, which allows these to be performed on the GPU using pre-existing matrix-multiplication libraries. We port the few remaining important modules by hand. In this paper we detail the specifics of our port, and present benchmarks of it simulating isolated black hole spacetimes on several generations of NVIDIA GPU. |
2208.08582 | Nelson Velandia | Nelson Velandia SJ, Alfonso Leyva, Javier Alexander Cano-Arango | The Ricci Rotation Coefficients in the description of trajectories of
spinning test particles off-equatorial planes in a rotational gravitational
field | 15 pages, 4 figures, Numerical relativity | International Journal of Theoretical Physics, Volume 63, article
number 37, (2024) | 10.1007/s10773-024-05562-6 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We describe the trajectories of circular orbits of spinless and spinning test
particles around of rotating bodies in equatorial and non-equatorial planes via
the Mathisson-Papapetrou-Dixon equations which include the Ricci rotation
coefficients with the purpose of describing not only the curvature of space
time, but also the rotation of the spinning test particles that orbit around
the rotating masive bodies.
| [
{
"created": "Thu, 18 Aug 2022 01:00:07 GMT",
"version": "v1"
}
] | 2024-02-12 | [
[
"SJ",
"Nelson Velandia",
""
],
[
"Leyva",
"Alfonso",
""
],
[
"Cano-Arango",
"Javier Alexander",
""
]
] | We describe the trajectories of circular orbits of spinless and spinning test particles around of rotating bodies in equatorial and non-equatorial planes via the Mathisson-Papapetrou-Dixon equations which include the Ricci rotation coefficients with the purpose of describing not only the curvature of space time, but also the rotation of the spinning test particles that orbit around the rotating masive bodies. |
2011.04423 | Ali \"Ovg\"un Dr. | Ali \"Ovg\"un | Weak deflection angle of black-bounce traversable wormholes using
Gauss-Bonnet theorem in the dark matter medium | 8 pages. Accepted for publication in Turkish Journal of Physics | Turk J Phys, 44, (2020), 465-471 | 10.3906/fiz-2008-11 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we first use the optical metrics of black-bounce traversable
wormholes to calculate the Gaussian curvature. Then we use the Gauss-Bonnet
theorem to obtain the weak deflection angle of light from the black-bounce
traversable wormholes. Then we investigate the effect of dark matter medium on
weak deflection angle using the Gauss-Bonnet theorem. We show how weak
deflection angle of wormhole is affected by the bounce parameter $a$. Using the
Gauss-bonnet theorem for calculating weak deflection angle shows us that light
bending can be thought as a global and topological effect.
| [
{
"created": "Thu, 5 Nov 2020 18:34:31 GMT",
"version": "v1"
}
] | 2020-11-10 | [
[
"Övgün",
"Ali",
""
]
] | In this paper, we first use the optical metrics of black-bounce traversable wormholes to calculate the Gaussian curvature. Then we use the Gauss-Bonnet theorem to obtain the weak deflection angle of light from the black-bounce traversable wormholes. Then we investigate the effect of dark matter medium on weak deflection angle using the Gauss-Bonnet theorem. We show how weak deflection angle of wormhole is affected by the bounce parameter $a$. Using the Gauss-bonnet theorem for calculating weak deflection angle shows us that light bending can be thought as a global and topological effect. |
2404.19225 | Wenfu Cao | Wenfu Cao, Xin Wu, Jun Lyu | Electromagnetic field and chaotic charged-particle motion around hairy
black holes in Horndeski gravity | 18 pages,9 figures, EPJC (2024) | null | 10.1140/epjc/s10052-024-12804-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Wald vector potential is an exact solution of the source-less Maxwell
equations regarding an electromagnetic field of a vacuum uncharged black hole
like the Kerr background black hole in an asymptotically uniform magnetic
field. However, it is not if the black hole is a nonvacuum solution in a theory
of modified gravity with extra fields or a charged Kerr-Newman spacetime. To
satisfy the source-less Maxwell equations in this case, the Wald vector
potential must be modified and generalized appropriately. Following this idea,
we derive an expression for the vector potential of an electromagnetic field
surrounding a hairy black hole in the Horndeski modified gravity theory.
Explicit symplectic integrators with excellent long-term behaviour are used to
simulate the motion of charged particles around the hairy black hole immersed
in the external magnetic field. The recurrence plot method based on the
recurrence quantification analysis uses diagonal structures parallel to the
main diagonal to show regular dynamics, but adopts no diagonal structures to
indicate chaotic dynamics. The method is efficient to detect chaos from order
in the curved spacetime, as the Poincare map and the fast Lyapunov indicator
are.
| [
{
"created": "Tue, 30 Apr 2024 03:06:50 GMT",
"version": "v1"
}
] | 2024-05-01 | [
[
"Cao",
"Wenfu",
""
],
[
"Wu",
"Xin",
""
],
[
"Lyu",
"Jun",
""
]
] | The Wald vector potential is an exact solution of the source-less Maxwell equations regarding an electromagnetic field of a vacuum uncharged black hole like the Kerr background black hole in an asymptotically uniform magnetic field. However, it is not if the black hole is a nonvacuum solution in a theory of modified gravity with extra fields or a charged Kerr-Newman spacetime. To satisfy the source-less Maxwell equations in this case, the Wald vector potential must be modified and generalized appropriately. Following this idea, we derive an expression for the vector potential of an electromagnetic field surrounding a hairy black hole in the Horndeski modified gravity theory. Explicit symplectic integrators with excellent long-term behaviour are used to simulate the motion of charged particles around the hairy black hole immersed in the external magnetic field. The recurrence plot method based on the recurrence quantification analysis uses diagonal structures parallel to the main diagonal to show regular dynamics, but adopts no diagonal structures to indicate chaotic dynamics. The method is efficient to detect chaos from order in the curved spacetime, as the Poincare map and the fast Lyapunov indicator are. |
gr-qc/0109050 | Vladimir | V. Dzhunushaliev | Polarized Spacetime Foam | essential changes in the text | Found.Phys. 32 (2002) 1069-1090 | null | null | gr-qc astro-ph hep-th | null | An approximate model of a spacetime foam is presented. It is supposed that in
the spacetime foam each quantum handle is like to an electric dipole and
therefore the spacetime foam is similar to a dielectric. If we neglect of
linear sizes of the quantum handle then it can be described with an operator
containing a Grassman number and either a scalar or a spinor field. For both
fields the Lagrangian is presented. For the scalar field it is the dilaton
gravity + electrodynamics and the dilaton field is a dielectric permeability.
The spherically symmetric solution in this case give us the screening of a bare
electric charge surrounded by a polarized spacetime foam and the energy of the
electric field becomes finite one. In the case of the spinor field the
spherically symmetric solution give us a ball of the polarized spacetime foam
filled with the confined electric field. It is shown that the full energy of
the electric field in the ball can be very big.
| [
{
"created": "Fri, 14 Sep 2001 03:12:21 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Mar 2002 03:12:59 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Dzhunushaliev",
"V.",
""
]
] | An approximate model of a spacetime foam is presented. It is supposed that in the spacetime foam each quantum handle is like to an electric dipole and therefore the spacetime foam is similar to a dielectric. If we neglect of linear sizes of the quantum handle then it can be described with an operator containing a Grassman number and either a scalar or a spinor field. For both fields the Lagrangian is presented. For the scalar field it is the dilaton gravity + electrodynamics and the dilaton field is a dielectric permeability. The spherically symmetric solution in this case give us the screening of a bare electric charge surrounded by a polarized spacetime foam and the energy of the electric field becomes finite one. In the case of the spinor field the spherically symmetric solution give us a ball of the polarized spacetime foam filled with the confined electric field. It is shown that the full energy of the electric field in the ball can be very big. |
gr-qc/0403071 | Sophie Pireaux | S. Pireaux | Light deflection in Weyl gravity: critical distances for photon paths | 20 pages, 9 figures (see published version for a better resolution,
or online version at stacks.iop.org/CQG/21/1897) | Class.Quant.Grav. 21 (2004) 1897-1913 | 10.1088/0264-9381/21/7/011 | null | gr-qc astro-ph | null | The Weyl gravity appears to be a very peculiar theory. The contribution of
the Weyl linear parameter to the effective geodesic potential is opposite for
massive and nonmassive geodesics. However, photon geodesics do not depend on
the unknown conformal factor, unlike massive geodesics. Hence light deflection
offers an interesting test of the Weyl theory.
In order to investigate light deflection in the setting of Weyl gravity, we
first distinguish between a weak field and a strong field approximation.
Indeed, the Weyl gravity does not turn off asymptotically and becomes even
stronger at larger distances.
We then take full advantage of the conformal invariance of the photon
effective potential to provide the key radial distances in Weyl gravity.
According to those, we analyze the weak and strong field regime for light
deflection. We further show some amazing features of the Weyl theory in the
strong regime.
| [
{
"created": "Tue, 16 Mar 2004 18:21:27 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pireaux",
"S.",
""
]
] | The Weyl gravity appears to be a very peculiar theory. The contribution of the Weyl linear parameter to the effective geodesic potential is opposite for massive and nonmassive geodesics. However, photon geodesics do not depend on the unknown conformal factor, unlike massive geodesics. Hence light deflection offers an interesting test of the Weyl theory. In order to investigate light deflection in the setting of Weyl gravity, we first distinguish between a weak field and a strong field approximation. Indeed, the Weyl gravity does not turn off asymptotically and becomes even stronger at larger distances. We then take full advantage of the conformal invariance of the photon effective potential to provide the key radial distances in Weyl gravity. According to those, we analyze the weak and strong field regime for light deflection. We further show some amazing features of the Weyl theory in the strong regime. |
gr-qc/0502019 | Mohammad Vahid Takook | Shahriar Rouhani and Mohammad Vahid Takook | Abelian Gauge Theory in de Sitter Space | 10 pages, typos corrected, reference added | Mod.Phys.Lett. A20 (2005) 2387-2396 | 10.1142/S0217732305018347 | null | gr-qc | null | Quantization of spinor and vector free fields in 4-dimensional de Sitter
space-time, in the ambient space notation, has been studied in the previous
works. Various two-points functions for the above fields are presented in this
paper. The interaction between the spinor field and the vector field is then
studied by the abelian gauge theory. The U(1) gauge invariant spinor field
equation is obtained in a coordinate independent way notation and their
corresponding conserved currents are computed. The solution of the field
equation is obtained by use of the perturbation method in terms of the Green's
function. The null curvature limit is discussed in the final stage.
| [
{
"created": "Sat, 5 Feb 2005 17:47:02 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Oct 2005 12:51:24 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Rouhani",
"Shahriar",
""
],
[
"Takook",
"Mohammad Vahid",
""
]
] | Quantization of spinor and vector free fields in 4-dimensional de Sitter space-time, in the ambient space notation, has been studied in the previous works. Various two-points functions for the above fields are presented in this paper. The interaction between the spinor field and the vector field is then studied by the abelian gauge theory. The U(1) gauge invariant spinor field equation is obtained in a coordinate independent way notation and their corresponding conserved currents are computed. The solution of the field equation is obtained by use of the perturbation method in terms of the Green's function. The null curvature limit is discussed in the final stage. |
gr-qc/0405064 | Salvatore Antoci | S. Antoci, D.-E. Liebscher and L. Mihich | The Electrostatics of Einstein's Unified Field Theory | 15 pages. Misprints corrected. To appear in General Relativity and
Gravitation | Gen.Rel.Grav. 37 (2005) 1191-1203 | 10.1007/s10714-005-0104-1 | null | gr-qc | null | When sources are added at their right-hand sides, and g_{(ik)} is a priori
assumed to be the metric, the equations of Einstein's Hermitian theory of
relativity were shown to allow for an exact solution that describes the general
electrostatic field of n point charges. Moreover, the injunction of spherical
symmetry of g_{(ik)} in the infinitesimal neighbourhood of each of the charges
was proved to yield the equilibrium conditions of the n charges in keeping with
ordinary electrostatics. The tensor g_{(ik)}, however, cannot be the metric of
the theory, since it enters neither the eikonal equation nor the equation of
motion of uncharged test particles. A physically correct metric that rules both
the behaviour of wave fronts and of uncharged matter is the one indicated by
H\'ely. In the present paper it is shown how the electrostatic solution
predicts the structure of the n charged particles and their mutual positions of
electrostatic equilibrium when H\'ely's physically correct metric is adopted.
| [
{
"created": "Wed, 12 May 2004 16:44:45 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Jun 2004 15:31:59 GMT",
"version": "v2"
},
{
"created": "Tue, 1 Feb 2005 15:30:01 GMT",
"version": "v3"
},
{
"created": "Thu, 9 Jun 2005 09:53:49 GMT",
"version": "v4"
}
] | 2009-11-10 | [
[
"Antoci",
"S.",
""
],
[
"Liebscher",
"D. -E.",
""
],
[
"Mihich",
"L.",
""
]
] | When sources are added at their right-hand sides, and g_{(ik)} is a priori assumed to be the metric, the equations of Einstein's Hermitian theory of relativity were shown to allow for an exact solution that describes the general electrostatic field of n point charges. Moreover, the injunction of spherical symmetry of g_{(ik)} in the infinitesimal neighbourhood of each of the charges was proved to yield the equilibrium conditions of the n charges in keeping with ordinary electrostatics. The tensor g_{(ik)}, however, cannot be the metric of the theory, since it enters neither the eikonal equation nor the equation of motion of uncharged test particles. A physically correct metric that rules both the behaviour of wave fronts and of uncharged matter is the one indicated by H\'ely. In the present paper it is shown how the electrostatic solution predicts the structure of the n charged particles and their mutual positions of electrostatic equilibrium when H\'ely's physically correct metric is adopted. |
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