id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0401038 | Deborah A. Konkowski | D.A. Konkowski, T.M. Helliwell and C. Wieland | "Singularity" of Levi-Civita Spacetimes | 3 pages, no figures, submitted to Proceedings of the Tenth Marcel
Grossmann Meeting on General Relativity, Rio de Janeiro, July 20-26, 2003 | null | null | null | gr-qc | null | Levi-Civita spacetimes have both classical and quantum singularities. The
relationship between the two is used here to study and clarify the physical
aspects of the enigmatic Levi-Civita spacetimes.
| [
{
"created": "Sat, 10 Jan 2004 23:32:22 GMT",
"version": "v1"
}
] | 2009-09-29 | [
[
"Konkowski",
"D. A.",
""
],
[
"Helliwell",
"T. M.",
""
],
[
"Wieland",
"C.",
""
]
] | Levi-Civita spacetimes have both classical and quantum singularities. The relationship between the two is used here to study and clarify the physical aspects of the enigmatic Levi-Civita spacetimes. |
2208.11406 | Iarley P. Lobo Dr | Ernesto Rodrigues and Iarley P. Lobo | Revisiting Legendre transformations in Finsler geometry | 23+2 pages, 2 figures. Version with examples, improved discussion of
the results, inclusion of an appendix, typos fixed. Matches published
version. Updated Journal information | Int.J.Geom.Meth.Mod.Phys. (2024) 2450155 | 10.1142/S021988782450155X | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | We discuss the conditions for mapping the geometric description of the
kinematics of particles that probe a given Hamiltonian in phase space to a
description in terms of Finsler geometry (and vice-versa).
| [
{
"created": "Wed, 24 Aug 2022 09:57:25 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Mar 2024 18:06:45 GMT",
"version": "v2"
},
{
"created": "Mon, 25 Mar 2024 13:03:46 GMT",
"version": "v3"
}
] | 2024-03-26 | [
[
"Rodrigues",
"Ernesto",
""
],
[
"Lobo",
"Iarley P.",
""
]
] | We discuss the conditions for mapping the geometric description of the kinematics of particles that probe a given Hamiltonian in phase space to a description in terms of Finsler geometry (and vice-versa). |
0811.1286 | Masoud Alimohammadi | M. Alimohammadi and A. Ghalee | Remarks on generalized Gauss-Bonnet dark energy | 11 pages, LaTeX, a paragraph added, to be appeared in Phys. Rev. D | Phys.Rev.D79:063006,2009 | 10.1103/PhysRevD.79.063006 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The modified gravity with F(R,G) Lagrangian, G is the Gauss-Bonnet invariant,
is considered. It is shown that the phantom-divide-line crossing and the
deceleration to acceleration transition generally occur in these models. Our
results coincide with the known results of f(R)-gravity and f(G)-gravity
models. The contribution of quantum effects to these transitions is calculated,
and it is shown that in some special cases where there are no transitions in
classical level, quantum contributions can induce transitions. The quantum
effects are described via the account of conformal anomaly.
| [
{
"created": "Sat, 8 Nov 2008 18:12:06 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Mar 2009 06:41:00 GMT",
"version": "v2"
}
] | 2009-12-04 | [
[
"Alimohammadi",
"M.",
""
],
[
"Ghalee",
"A.",
""
]
] | The modified gravity with F(R,G) Lagrangian, G is the Gauss-Bonnet invariant, is considered. It is shown that the phantom-divide-line crossing and the deceleration to acceleration transition generally occur in these models. Our results coincide with the known results of f(R)-gravity and f(G)-gravity models. The contribution of quantum effects to these transitions is calculated, and it is shown that in some special cases where there are no transitions in classical level, quantum contributions can induce transitions. The quantum effects are described via the account of conformal anomaly. |
1303.6193 | Thomas Buchert | Thomas Buchert, Charly Nayet and Alexander Wiegand | Lagrangian theory of structure formation in relativistic cosmology II:
average properties of a generic evolution model | 24 pages, 15 figures, matches published version in PRD | Phys.Rev.D87:123503,2013 | 10.1103/PhysRevD.87.123503 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Kinematical and dynamical properties of a generic inhomogeneous cosmological
model, spatially averaged with respect to free-falling (generalized
fundamental) observers, are investigated for the matter model irrotational
dust. Paraphrasing a previous Newtonian investigation, we present a
relativistic generalization of a backreaction model based on volume-averaging
the Relativistic Zeldovich Approximation. In this model we investigate the
effect of kinematical backreaction on the evolution of cosmological parameters
as they are defined in an averaged inhomogeneous cosmology, and we show that
the backreaction model interpolates between orthogonal symmetry properties by
covering subcases of the plane-symmetric solution, the Lemaitre-Tolman-Bondi
solution and the Szekeres solution. We so obtain a powerful model that lays the
foundations for quantitatively addressing curvature inhomogeneities as they
would be interpreted as Dark Energy or Dark Matter in a quasi-Newtonian
cosmology. The present model, having a limited architecture due to an assumed
FLRW background, is nevertheless capable of replacing 1/4 of the needed amount
for Dark Energy on domains of 200 Mpc in diameter for typical (one-sigma)
fluctuations in a CDM initial power spectrum. However, the model is far from
explaining Dark Energy on larger scales (spatially), where a 6% effect on 400
Mpc domains is identified that can be traced back to an on average negative
intrinsic curvature today. One drawback of the quantitative results presented
is the fact that the epoch when backreaction is effective on large scales and
leads to volume acceleration lies in the future. We discuss this issue in
relation to the initial spectrum, the Dark Matter problem, the coincidence
problem, and the fact that large-scale Dark Energy is an effect on the past
light cone (not spatial), and we pinpoint key elements of future research.
| [
{
"created": "Mon, 25 Mar 2013 16:14:27 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Jun 2013 12:06:06 GMT",
"version": "v2"
}
] | 2013-06-12 | [
[
"Buchert",
"Thomas",
""
],
[
"Nayet",
"Charly",
""
],
[
"Wiegand",
"Alexander",
""
]
] | Kinematical and dynamical properties of a generic inhomogeneous cosmological model, spatially averaged with respect to free-falling (generalized fundamental) observers, are investigated for the matter model irrotational dust. Paraphrasing a previous Newtonian investigation, we present a relativistic generalization of a backreaction model based on volume-averaging the Relativistic Zeldovich Approximation. In this model we investigate the effect of kinematical backreaction on the evolution of cosmological parameters as they are defined in an averaged inhomogeneous cosmology, and we show that the backreaction model interpolates between orthogonal symmetry properties by covering subcases of the plane-symmetric solution, the Lemaitre-Tolman-Bondi solution and the Szekeres solution. We so obtain a powerful model that lays the foundations for quantitatively addressing curvature inhomogeneities as they would be interpreted as Dark Energy or Dark Matter in a quasi-Newtonian cosmology. The present model, having a limited architecture due to an assumed FLRW background, is nevertheless capable of replacing 1/4 of the needed amount for Dark Energy on domains of 200 Mpc in diameter for typical (one-sigma) fluctuations in a CDM initial power spectrum. However, the model is far from explaining Dark Energy on larger scales (spatially), where a 6% effect on 400 Mpc domains is identified that can be traced back to an on average negative intrinsic curvature today. One drawback of the quantitative results presented is the fact that the epoch when backreaction is effective on large scales and leads to volume acceleration lies in the future. We discuss this issue in relation to the initial spectrum, the Dark Matter problem, the coincidence problem, and the fact that large-scale Dark Energy is an effect on the past light cone (not spatial), and we pinpoint key elements of future research. |
1208.3028 | Sushant Ghosh Prof | Sushant G. Ghosh, Sunil D. Maharaj and Uma Papnoi | Radiating Kerr-Newman black hole in $f(R)$ gravity | 11 pages, 6 figures, new text and reference added | null | 10.1140/epjc/s10052-013-2473-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive an exact radiating Kerr-Newman like black hole solution, with
constant curvature $R=R_0$ imposed, to {\it metric} $f(R)$ gravity via complex
transformations suggested by Newman-Janis. This generates a geometry which is
precisely that of radiating Kerr-Newman-de Sitter / anti-de Sitter with the
$f(R)$ gravity contributing an $R_0$ cosmological-like term. The structure of
three horizon-like surfaces, {\it viz.} timelike limit surface, apparent
horizon and event horizon, are determined. We demonstrate the existence of an
additional cosmological horizon, in $f(R)$ gravity model, apart from the
regular black hole horizons that exist in the analogous general relativity
case. In particular, the known stationary Kerr-Newman black hole solutions of
$f(R)$ gravity and general relativity are retrieved. We find that the timelike
limit surface becomes less prolate with $R_0$ thereby affecting the shape of
the corresponding ergosphere.
| [
{
"created": "Wed, 15 Aug 2012 04:30:29 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Jun 2013 09:32:18 GMT",
"version": "v2"
}
] | 2015-06-11 | [
[
"Ghosh",
"Sushant G.",
""
],
[
"Maharaj",
"Sunil D.",
""
],
[
"Papnoi",
"Uma",
""
]
] | We derive an exact radiating Kerr-Newman like black hole solution, with constant curvature $R=R_0$ imposed, to {\it metric} $f(R)$ gravity via complex transformations suggested by Newman-Janis. This generates a geometry which is precisely that of radiating Kerr-Newman-de Sitter / anti-de Sitter with the $f(R)$ gravity contributing an $R_0$ cosmological-like term. The structure of three horizon-like surfaces, {\it viz.} timelike limit surface, apparent horizon and event horizon, are determined. We demonstrate the existence of an additional cosmological horizon, in $f(R)$ gravity model, apart from the regular black hole horizons that exist in the analogous general relativity case. In particular, the known stationary Kerr-Newman black hole solutions of $f(R)$ gravity and general relativity are retrieved. We find that the timelike limit surface becomes less prolate with $R_0$ thereby affecting the shape of the corresponding ergosphere. |
gr-qc/0603075 | Ragab Gad | Ragab M. Gad | Energy and Momentum densities of cosmological models, with equation of
state $\rho=\mu$, in general relativity and teleparallel gravity | 15 pages, no figures, Minor typos corrected; version to appear in
International Journal of Theoretical Physics | Int.J.Theor.Phys.46:3263-3274,2007 | 10.1007/s10773-007-9445-8 | null | gr-qc | null | We calculated the energy and momentum densities of stiff fluid solutions,
using Einstein, Bergmann-Thomson and Landau-Lifshitz energy-momentum complexes,
in both general relativity and teleparallel gravity. In our analysis we get
different results comparing the aforementioned complexes with each other when
calculated in the same gravitational theory, either this is in general
relativity and teleparallel gravity. However, interestingly enough, each
complex's value is the same either in general relativity or teleparallel
gravity. Our results sustain that (i) general relativity or teleparallel
gravity are equivalent theories (ii) different energy-momentum complexes do not
provide the same energy and momentum densities neither in general relativity
nor in teleparallel gravity. In the context of the theory of teleparallel
gravity, the vector and axial-vector parts of the torsion are obtained. We show
that the axial-vector torsion vanishes for the space-time under study.
| [
{
"created": "Sun, 19 Mar 2006 13:44:36 GMT",
"version": "v1"
},
{
"created": "Sat, 19 Aug 2006 11:08:53 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Gad",
"Ragab M.",
""
]
] | We calculated the energy and momentum densities of stiff fluid solutions, using Einstein, Bergmann-Thomson and Landau-Lifshitz energy-momentum complexes, in both general relativity and teleparallel gravity. In our analysis we get different results comparing the aforementioned complexes with each other when calculated in the same gravitational theory, either this is in general relativity and teleparallel gravity. However, interestingly enough, each complex's value is the same either in general relativity or teleparallel gravity. Our results sustain that (i) general relativity or teleparallel gravity are equivalent theories (ii) different energy-momentum complexes do not provide the same energy and momentum densities neither in general relativity nor in teleparallel gravity. In the context of the theory of teleparallel gravity, the vector and axial-vector parts of the torsion are obtained. We show that the axial-vector torsion vanishes for the space-time under study. |
1911.04479 | Yan-Gang Miao | Yang Guo, Yan-Gang Miao | Quasinormal mode and stability of optical black holes in moving
dielectrics | v1: 13 pages, 5 figures, 2 tables; v2: clarifications and references
added; v3: clarifications added, final version to appear in Physical Review D | Phys. Rev. D 101, 024048 (2020) | 10.1103/PhysRevD.101.024048 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the quasinormal mode and stability of optical black holes in moving
dielectrics. The results show that the real part of complex frequencies is
inversely proportional to but the absolute value of an imaginary part is
proportional to a refractive index. We obtain the conditions for forming a
black hole horizon in moving dielectrics. Moreover, we investigate the
evolution behavior of optical black holes with respect to a refractive index at
a high overtone number and find that an optical black hole undergoes one phase
transition from an unstable mode to a stable one when the refractive index is
big enough.
| [
{
"created": "Mon, 11 Nov 2019 09:38:13 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Nov 2019 13:51:58 GMT",
"version": "v2"
},
{
"created": "Thu, 23 Jan 2020 14:44:33 GMT",
"version": "v3"
}
] | 2020-02-05 | [
[
"Guo",
"Yang",
""
],
[
"Miao",
"Yan-Gang",
""
]
] | We study the quasinormal mode and stability of optical black holes in moving dielectrics. The results show that the real part of complex frequencies is inversely proportional to but the absolute value of an imaginary part is proportional to a refractive index. We obtain the conditions for forming a black hole horizon in moving dielectrics. Moreover, we investigate the evolution behavior of optical black holes with respect to a refractive index at a high overtone number and find that an optical black hole undergoes one phase transition from an unstable mode to a stable one when the refractive index is big enough. |
2405.01212 | Thomas Thiemann | Thomas Thiemann | Non-perturbative Quantum Gravity in Fock representations | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Perturbative quantum gravity starts from prescribing a background metric.
That background metric is then used in order to carry out two separate steps:
1. One splits the non-perturbative metric into background and deviation from it
(graviton) and expands the action in terms of the graviton which results in an
ifinite series of unknown radius of convergence. 2. One constructs a Fock
representation for the graviton and performs perturbative graviton quantum
field theory on the fixed background as dictated by the perturbative action.
The result is a non-renormalisable theory without predictive power.
It is therefore widely believed that a non-perturbative approach is mandatory
in order to construct a fundamental, not only effective, predictive quantum
field theory of the gravitational interaction. Since perturbation theory is by
definition background dependent, the notions of background dependence (BD) and
perturbation theory (PT) are often considered as symbiotic, as if they imply
each other.
In the present work we point out that there is no such symbiosis, these two
notions are in fact logically independent. In particular, one can use BD
structures while while not using PT at all. Specifically, we construct BD Fock
representations (step 2 above) for the full, non-perturbative metric rather
than the graviton (not step 1 above) and therefore never perform a perturbative
expansion. Despite the fact that the gravitational Lagrangean is a
non-polynomial, not even analytic, function of the metric we show that e.g. the
Hamiltonian constraint with any density weight can be defined as a quadratic
form with dense form domain in such a representation.
| [
{
"created": "Thu, 2 May 2024 11:50:14 GMT",
"version": "v1"
}
] | 2024-05-03 | [
[
"Thiemann",
"Thomas",
""
]
] | Perturbative quantum gravity starts from prescribing a background metric. That background metric is then used in order to carry out two separate steps: 1. One splits the non-perturbative metric into background and deviation from it (graviton) and expands the action in terms of the graviton which results in an ifinite series of unknown radius of convergence. 2. One constructs a Fock representation for the graviton and performs perturbative graviton quantum field theory on the fixed background as dictated by the perturbative action. The result is a non-renormalisable theory without predictive power. It is therefore widely believed that a non-perturbative approach is mandatory in order to construct a fundamental, not only effective, predictive quantum field theory of the gravitational interaction. Since perturbation theory is by definition background dependent, the notions of background dependence (BD) and perturbation theory (PT) are often considered as symbiotic, as if they imply each other. In the present work we point out that there is no such symbiosis, these two notions are in fact logically independent. In particular, one can use BD structures while while not using PT at all. Specifically, we construct BD Fock representations (step 2 above) for the full, non-perturbative metric rather than the graviton (not step 1 above) and therefore never perform a perturbative expansion. Despite the fact that the gravitational Lagrangean is a non-polynomial, not even analytic, function of the metric we show that e.g. the Hamiltonian constraint with any density weight can be defined as a quadratic form with dense form domain in such a representation. |
gr-qc/9708059 | Martin Rainer | M. Rainer and H. Salehi | A regularizing commutant duality for a kinematically covariant partial
ordered net of observables | LaTeX, to appear in: Proc. XXI. Int. Sem. on Group Theor. Methods,
Goslar (1996), eds. Doebner et al | null | null | IPM-96 | gr-qc | null | We consider a net of *-algebras, locally around any point of observation,
equipped with a natural partial order related to the isotony property. Assuming
the underlying manifold of the net to be a differentiable, this net shall be
kinematically covariant under general diffeomorphisms. However, the dynamical
relations, induced by the physical state defining the related net of (von
Neumann) observables, are in general not covariant under all diffeomorphisms,
but only under the subgroup of dynamical symmetries.
We introduce algebraically both, IR and UV cutoffs, and assume that these are
related by a commutant duality. The latter, having strong implications on the
net, allows us to identify a 1-parameter group of the dynamical symmetries with
the group of outer modular automorphisms.
For thermal equilibrium states, the modular dilation parameter may be used
locally to define the notions of both, time and a causal structure.
| [
{
"created": "Sun, 24 Aug 1997 15:17:05 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Rainer",
"M.",
""
],
[
"Salehi",
"H.",
""
]
] | We consider a net of *-algebras, locally around any point of observation, equipped with a natural partial order related to the isotony property. Assuming the underlying manifold of the net to be a differentiable, this net shall be kinematically covariant under general diffeomorphisms. However, the dynamical relations, induced by the physical state defining the related net of (von Neumann) observables, are in general not covariant under all diffeomorphisms, but only under the subgroup of dynamical symmetries. We introduce algebraically both, IR and UV cutoffs, and assume that these are related by a commutant duality. The latter, having strong implications on the net, allows us to identify a 1-parameter group of the dynamical symmetries with the group of outer modular automorphisms. For thermal equilibrium states, the modular dilation parameter may be used locally to define the notions of both, time and a causal structure. |
1112.5639 | Natalia Kiriushcheva | N. Kiriushcheva, P. G. Komorowski, and S. V. Kuzmin | Comment on "Modified F(R) Ho\v{r}ava-Lifshitz gravity: a way to
accelerating FRW cosmology" by M. Chaichian, S. Nojiri, S. D. Odintsov, M.
Oksanen, A. Tureanu | 8 pages, minor corrections | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The partial Hamiltonian analysis of the Ho\v{r}ava-type action presented in
the paper by M. Chaichian, S. Nojiri, S. D. Odintsov, M. Oksanen, A. Tureanu
(Class. Quant. Grav. 27 (2011) 185021) is incorrect; for the authors' choice of
variables, a covariant shift, instead of a contravariant shift which is the one
usually used in General Relativity (GR) in ADM variables, the true algebra of
constraints differs from what they presented. The algebra of constraints for
their choice of variables is explicitly given for GR and compared with the
standard algebra.
| [
{
"created": "Fri, 23 Dec 2011 19:10:55 GMT",
"version": "v1"
},
{
"created": "Sun, 29 Jan 2012 23:41:35 GMT",
"version": "v2"
}
] | 2012-01-31 | [
[
"Kiriushcheva",
"N.",
""
],
[
"Komorowski",
"P. G.",
""
],
[
"Kuzmin",
"S. V.",
""
]
] | The partial Hamiltonian analysis of the Ho\v{r}ava-type action presented in the paper by M. Chaichian, S. Nojiri, S. D. Odintsov, M. Oksanen, A. Tureanu (Class. Quant. Grav. 27 (2011) 185021) is incorrect; for the authors' choice of variables, a covariant shift, instead of a contravariant shift which is the one usually used in General Relativity (GR) in ADM variables, the true algebra of constraints differs from what they presented. The algebra of constraints for their choice of variables is explicitly given for GR and compared with the standard algebra. |
1612.04228 | Yoshimasa Kurihara | Yoshimasa Kurihara | Stochastic Metric Space and Quantum Mechanics | 39 pages, 0 figures | J. Phys. Commun. 2 (2018) 035025 | 10.1088/2399-6528/aaa851 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new idea for the quantization of dynamic systems, as well as space time
itself, using a stochastic metric is proposed. The quantum mechanics of a mass
point is constructed on a space time manifold using a stochastic metric. A
stochastic metric space is, in brief, a metric space whose metric tensor is
given stochastically according to some appropriate distribution function. A
mathematically consistent model of a space time manifold equipping a stochastic
metric is proposed in this report. The quantum theory in the local Minkowski
space can be recognized as a classical theory on the stochastic
Lorentz-metric-space. A stochastic calculus on the space time manifold is
performed using white noise functional analysis. A path-integral quantization
is introduced as a stochastic integration of a function of the action integral,
and it is shown that path-integrals on the stochastic metric space are
mathematically well-defined for large variety of potential functions. The
Newton--Nelson equation of motion can also be obtained from the Newtonian
equation of motion on the stochastic metric space. It is also shown that the
commutation relation required under the canonical quantization is consistent
with the stochastic quantization introduced in this report.
The quantum effects of general relativity are also analyzed through natural
use of the stochastic metrics. Some example of quantum effects on the universe
is discussed.
| [
{
"created": "Tue, 13 Dec 2016 15:21:15 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Mar 2017 16:37:10 GMT",
"version": "v2"
},
{
"created": "Wed, 30 Aug 2017 03:20:55 GMT",
"version": "v3"
},
{
"created": "Mon, 18 Sep 2017 09:13:04 GMT",
"version": "v4"
},
{
"created": "Fri, 22 Dec 2017 16:11:11 GMT",
"version": "v5"
}
] | 2018-03-22 | [
[
"Kurihara",
"Yoshimasa",
""
]
] | A new idea for the quantization of dynamic systems, as well as space time itself, using a stochastic metric is proposed. The quantum mechanics of a mass point is constructed on a space time manifold using a stochastic metric. A stochastic metric space is, in brief, a metric space whose metric tensor is given stochastically according to some appropriate distribution function. A mathematically consistent model of a space time manifold equipping a stochastic metric is proposed in this report. The quantum theory in the local Minkowski space can be recognized as a classical theory on the stochastic Lorentz-metric-space. A stochastic calculus on the space time manifold is performed using white noise functional analysis. A path-integral quantization is introduced as a stochastic integration of a function of the action integral, and it is shown that path-integrals on the stochastic metric space are mathematically well-defined for large variety of potential functions. The Newton--Nelson equation of motion can also be obtained from the Newtonian equation of motion on the stochastic metric space. It is also shown that the commutation relation required under the canonical quantization is consistent with the stochastic quantization introduced in this report. The quantum effects of general relativity are also analyzed through natural use of the stochastic metrics. Some example of quantum effects on the universe is discussed. |
1107.3975 | Jarmo M\"akel\"a Dr. | Jarmo M\"akel\"a | Partition Function of the Schwarzschild Black Hole | 33 pages, 1 figure. Published in the special issue "Black Hole
Thermodynamics" of the Journal Entropy | Entropy 2011, 13, 1324-1325 | 10.3390/e13071324 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a microscopic model of a stretched horizon of the Schwarzschild
black hole. In our model the stretched horizon consists of a finite number of
discrete constituents. Assuming that the quantum states of the Schwarzschild
black hole are encoded in the quantum states of the constituents of its
stretched horizon in a certain manner we obtain an explicit, analytic
expression for the partition function of the hole. Our partition function
predicts, among other things, the Hawking effect, and provides it with a
microscopic, statistical interpretation.
| [
{
"created": "Tue, 19 Jul 2011 10:16:41 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Mäkelä",
"Jarmo",
""
]
] | We consider a microscopic model of a stretched horizon of the Schwarzschild black hole. In our model the stretched horizon consists of a finite number of discrete constituents. Assuming that the quantum states of the Schwarzschild black hole are encoded in the quantum states of the constituents of its stretched horizon in a certain manner we obtain an explicit, analytic expression for the partition function of the hole. Our partition function predicts, among other things, the Hawking effect, and provides it with a microscopic, statistical interpretation. |
1105.3396 | Naresh Dadhich | Naresh Dadhich | On the measure of spacetime and gravity | 5 pages, revtex, Received Honorable Mention in the 2011 Gravity
Research Foundation Awards for Essays on Gravitation | Int. J. Mod.Phys. D20 (2011) 2739-2747 | 10.1142/S0218271811020573 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By following the general guiding principle that nothing should be prescribed
or imposed on the universal entity, spacetime, we establish that it is the
homogeneity (by which we mean homogeneity and isotropy of space and homogeneity
of time) that requires not only a universally constant invariant velocity but
also an invariant length given by its constant curvature, $\Lambda$ and
spacetime is completely free of dynamics. Thus $c$ and $\Lambda$ are the only
two true constants of the spacetime structure and no other physical constant
could claim this degree of fundamentalness. When matter is introduced, the
spacetime becomes inhomogeneous and dynamic, and its curvature then determines
by the Bianchi differential identity the equation of motion for the Einstein
gravity. The homogeneity thus demands that the natural state of \textit{free
spacetime} is of constant curvature and the cosmological constant thus emerges
as a clear prediction which seems to be borne out by the observations of
accelerating expansion of the Universe. However it has no relation to the
vacuum energy and it could be envisioned that in terms of the Planck area the
Universe measures $10^{120}$ units!
| [
{
"created": "Sat, 14 May 2011 07:06:06 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Dadhich",
"Naresh",
""
]
] | By following the general guiding principle that nothing should be prescribed or imposed on the universal entity, spacetime, we establish that it is the homogeneity (by which we mean homogeneity and isotropy of space and homogeneity of time) that requires not only a universally constant invariant velocity but also an invariant length given by its constant curvature, $\Lambda$ and spacetime is completely free of dynamics. Thus $c$ and $\Lambda$ are the only two true constants of the spacetime structure and no other physical constant could claim this degree of fundamentalness. When matter is introduced, the spacetime becomes inhomogeneous and dynamic, and its curvature then determines by the Bianchi differential identity the equation of motion for the Einstein gravity. The homogeneity thus demands that the natural state of \textit{free spacetime} is of constant curvature and the cosmological constant thus emerges as a clear prediction which seems to be borne out by the observations of accelerating expansion of the Universe. However it has no relation to the vacuum energy and it could be envisioned that in terms of the Planck area the Universe measures $10^{120}$ units! |
1210.1615 | Jansen Formiga | J. B. Formiga and C. Romero | Dirac equation in non-Riemannian geometries | 13 pages; one reference added | null | 10.1142/S0219887813200120 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the Dirac equation in a geometry with torsion and non-metricity
balancing generality and simplicity as much as possible. In doing so, we use
the vielbein formalism and the Clifford algebra. We also use an index-free
formalism which allows us to construct objects that are totally invariant. It
turns out that the previous apparatuses not only make possible a simple
deduction of the Dirac equation but also allow us to exhibit some details that
is generally obscure in the literature.
| [
{
"created": "Fri, 5 Oct 2012 00:13:40 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Oct 2012 16:06:35 GMT",
"version": "v2"
}
] | 2013-05-28 | [
[
"Formiga",
"J. B.",
""
],
[
"Romero",
"C.",
""
]
] | We present the Dirac equation in a geometry with torsion and non-metricity balancing generality and simplicity as much as possible. In doing so, we use the vielbein formalism and the Clifford algebra. We also use an index-free formalism which allows us to construct objects that are totally invariant. It turns out that the previous apparatuses not only make possible a simple deduction of the Dirac equation but also allow us to exhibit some details that is generally obscure in the literature. |
1001.3739 | Izzet Sakalli | I.Sakalli, H.Pasaoglu and M.Halilsoy | Entropy Conservation of Linear Dilaton Black Holes in Quantum Corrected
Hawking Radiation | 15 pages, no figures | International Journal of Theoretical Physics 50 (10): 3212-3224,
2011 | 10.1007/s10773-011-0824-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been shown recently that information is lost in the Hawking radiation
of the linear dilaton black holes in various theories when applying the
tunneling formulism without considering quantum gravity effects. In this
Letter, we recalculate the emission probability by taking into account of the
log-area correction to the Bekenstein-Hawking entropy and the statistical
correlation between quanta emitted. The crucial role of the black hole remnant
on the entropy conservation is highlighted. We model the remnant as a higher
dimensional linear dilaton vacuum in order to show that such a remnant model
cannot radiate and its temperature would be zero. In addition to this, the
entropy conservation in the higher dimensional linear dilaton black holes is
also discussed. In summary, we show in detail that the information can also
leak out from the linear dilaton black holes together with preserving unitarity
in quantum mechanics.
| [
{
"created": "Thu, 21 Jan 2010 08:11:17 GMT",
"version": "v1"
}
] | 2012-02-16 | [
[
"Sakalli",
"I.",
""
],
[
"Pasaoglu",
"H.",
""
],
[
"Halilsoy",
"M.",
""
]
] | It has been shown recently that information is lost in the Hawking radiation of the linear dilaton black holes in various theories when applying the tunneling formulism without considering quantum gravity effects. In this Letter, we recalculate the emission probability by taking into account of the log-area correction to the Bekenstein-Hawking entropy and the statistical correlation between quanta emitted. The crucial role of the black hole remnant on the entropy conservation is highlighted. We model the remnant as a higher dimensional linear dilaton vacuum in order to show that such a remnant model cannot radiate and its temperature would be zero. In addition to this, the entropy conservation in the higher dimensional linear dilaton black holes is also discussed. In summary, we show in detail that the information can also leak out from the linear dilaton black holes together with preserving unitarity in quantum mechanics. |
2202.12133 | Soham Mukherjee | Soham Mukherjee, Nathan K. Johnson-McDaniel, Wolfgang Tichy, Steven L.
Liebling | Conformally curved initial data for charged, spinning black hole
binaries on arbitrary orbits | 17 pages, 7 figures | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a method to construct conformally curved initial data for charged
black hole binaries with spin on arbitrary orbits. We generalize the superposed
Kerr-Schild, extended conformal thin sandwich construction from [Lovelace et
al., Phys. Rev. D {78}, 084017 (2008)] to use Kerr-Newman metrics for the
superposed black holes and to solve the electromagnetic constraint equations.
We implement the construction in the pseudospectral code SGRID. The code thus
provides a complementary and completely independent excision-based
construction, compared to the existing charged black hole initial data
constructed using the puncture method [Bozzola and Paschalidis, Phys. Rev. D
{99}, 104044 (2019)]. It also provides an independent implementation (with some
small changes) of the Lovelace et al. vacuum construction. We construct initial
data for different configurations of orbiting binaries, e.g., with black holes
that are highly charged or rapidly spinning (90 and 80 percent of the extremal
values, respectively, for this initial test, though the code should be able to
produce data with even higher values of these parameters using higher
resolutions), as well as for generic spinning, charged black holes. We carry
out exploratory evolutions with the finite difference, moving punctures codes
BAM (in the vacuum case) and HAD (for head-on collisions including charge),
filling inside the excision surfaces. In the charged case, evolutions of these
initial data provide a proxy for binary black hole waveforms in modified
theories of gravity. Moreover, the generalization of the construction to
Einstein-Maxwell-dilaton theory should be straightforward.
| [
{
"created": "Thu, 24 Feb 2022 14:50:03 GMT",
"version": "v1"
}
] | 2022-02-25 | [
[
"Mukherjee",
"Soham",
""
],
[
"Johnson-McDaniel",
"Nathan K.",
""
],
[
"Tichy",
"Wolfgang",
""
],
[
"Liebling",
"Steven L.",
""
]
] | We present a method to construct conformally curved initial data for charged black hole binaries with spin on arbitrary orbits. We generalize the superposed Kerr-Schild, extended conformal thin sandwich construction from [Lovelace et al., Phys. Rev. D {78}, 084017 (2008)] to use Kerr-Newman metrics for the superposed black holes and to solve the electromagnetic constraint equations. We implement the construction in the pseudospectral code SGRID. The code thus provides a complementary and completely independent excision-based construction, compared to the existing charged black hole initial data constructed using the puncture method [Bozzola and Paschalidis, Phys. Rev. D {99}, 104044 (2019)]. It also provides an independent implementation (with some small changes) of the Lovelace et al. vacuum construction. We construct initial data for different configurations of orbiting binaries, e.g., with black holes that are highly charged or rapidly spinning (90 and 80 percent of the extremal values, respectively, for this initial test, though the code should be able to produce data with even higher values of these parameters using higher resolutions), as well as for generic spinning, charged black holes. We carry out exploratory evolutions with the finite difference, moving punctures codes BAM (in the vacuum case) and HAD (for head-on collisions including charge), filling inside the excision surfaces. In the charged case, evolutions of these initial data provide a proxy for binary black hole waveforms in modified theories of gravity. Moreover, the generalization of the construction to Einstein-Maxwell-dilaton theory should be straightforward. |
1602.03176 | Mohd Shahalam | M. Shahalam, S. K. J. Pacif, R. Myrzakulov | Galileons, phantom fields, and the fate of the Universe | 10 pages, 3 figures, Accepted for publication in Eur. Phys. J. C | European Physical Journal C (2016) 76: 410 | 10.1140/epjc/s10052-016-4254-y | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study cosmological dynamics of phantom as well as
non-phantom fields with linear potential in presence of Galileon correction
$(\partial_\mu\phi \partial^\mu\phi) \Box \phi$. We show that the Big Crunch
singularity is delayed compared to the standard case; the delay crucially
depends upon the strength of Galileon correction. As for the phantom Galileon,
$\rho_{\phi}$ is shown to grow more slowly compared to the standard phantom
delaying the approach to singularity. In case, $V\sim \phi^n, n>4$, Big Rip is
also delayed, similar phenomenon is shown to take place for potentials steeper
than the exponential.
| [
{
"created": "Tue, 9 Feb 2016 13:39:42 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Mar 2016 09:09:51 GMT",
"version": "v2"
},
{
"created": "Tue, 26 Apr 2016 10:38:44 GMT",
"version": "v3"
},
{
"created": "Fri, 8 Jul 2016 05:14:34 GMT",
"version": "v4"
}
] | 2022-07-20 | [
[
"Shahalam",
"M.",
""
],
[
"Pacif",
"S. K. J.",
""
],
[
"Myrzakulov",
"R.",
""
]
] | In this paper we study cosmological dynamics of phantom as well as non-phantom fields with linear potential in presence of Galileon correction $(\partial_\mu\phi \partial^\mu\phi) \Box \phi$. We show that the Big Crunch singularity is delayed compared to the standard case; the delay crucially depends upon the strength of Galileon correction. As for the phantom Galileon, $\rho_{\phi}$ is shown to grow more slowly compared to the standard phantom delaying the approach to singularity. In case, $V\sim \phi^n, n>4$, Big Rip is also delayed, similar phenomenon is shown to take place for potentials steeper than the exponential. |
1512.08280 | Sergey Paston | A.A. Sheykin, S.A. Paston | Classification of global minimal embeddings for nonrotating black holes | LaTeX, 12 pages | Theor. Math. Phys. 185:1 (2015), 1547-1556 | 10.1007/s11232-015-0364-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the problem of the existence of global embeddings of metrics of
spherically symmetric black holes into an ambient space with the minimal
possible dimension. We classify the possible types of embeddings by the type of
realization of the metric symmetry by ambient space symmetries. For the
Schwarzschild, Schwarzschild-de Sitter, and Reissner-Nordstrom black holes, we
prove that the known global embeddings are the only ones. We obtain a new
global embedding for the Reissner-Nordstrom-de Sitter metrics and prove that
constructing such embeddings is impossible for the Schwarzschild-anti-de Sitter
metric. We also discuss the possibility of constructing global embeddings of
the Reissner-Nordstrom-anti-de Sitter metric.
| [
{
"created": "Sun, 27 Dec 2015 21:46:59 GMT",
"version": "v1"
}
] | 2015-12-29 | [
[
"Sheykin",
"A. A.",
""
],
[
"Paston",
"S. A.",
""
]
] | We consider the problem of the existence of global embeddings of metrics of spherically symmetric black holes into an ambient space with the minimal possible dimension. We classify the possible types of embeddings by the type of realization of the metric symmetry by ambient space symmetries. For the Schwarzschild, Schwarzschild-de Sitter, and Reissner-Nordstrom black holes, we prove that the known global embeddings are the only ones. We obtain a new global embedding for the Reissner-Nordstrom-de Sitter metrics and prove that constructing such embeddings is impossible for the Schwarzschild-anti-de Sitter metric. We also discuss the possibility of constructing global embeddings of the Reissner-Nordstrom-anti-de Sitter metric. |
1303.5566 | Remo Garattini | Remo Garattini and Francisco S. N. Lobo | Gravity's Rainbow induces Topology Change | Updated to match published version. The "Topology Change" section has
been revised introducing a connection with the "Ricci flow". RevTeX4, 13
Pages | Eur.Phys.J.C74:2884,2014 | 10.1140/epjc/s10052-014-2884-5 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we explore the possibility that quantum fluctuations induce a
topology change, in the context of Gravity's Rainbow. A semi-classical approach
is adopted, where the graviton one-loop contribution to a classical energy in a
background spacetime is computed through a variational approach with Gaussian
trial wave functionals. The energy density of the graviton one-loop
contribution, or equivalently the background spacetime, is then let to evolve,
and consequently the classical energy is determined. More specifically, the
background metric is fixed to be Minkowskian in the equation governing the
quantum fluctuations, which behaves essentially as a backreaction equation, and
the quantum fluctuations are let to evolve; the classical energy, which depends
on the evolved metric functions, is then evaluated. Analysing this procedure, a
natural ultraviolet (UV) cutoff is obtained, which forbids the presence of an
interior spacetime region, and may result in a multipy-connected spacetime.
Thus, in the context of Gravity's Rainbow, this process may be interpreted as a
change in topology, and in principle results in the presence of a Planckian
wormhole.
| [
{
"created": "Fri, 22 Mar 2013 10:06:04 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Aug 2014 10:48:00 GMT",
"version": "v2"
}
] | 2014-08-21 | [
[
"Garattini",
"Remo",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | In this work, we explore the possibility that quantum fluctuations induce a topology change, in the context of Gravity's Rainbow. A semi-classical approach is adopted, where the graviton one-loop contribution to a classical energy in a background spacetime is computed through a variational approach with Gaussian trial wave functionals. The energy density of the graviton one-loop contribution, or equivalently the background spacetime, is then let to evolve, and consequently the classical energy is determined. More specifically, the background metric is fixed to be Minkowskian in the equation governing the quantum fluctuations, which behaves essentially as a backreaction equation, and the quantum fluctuations are let to evolve; the classical energy, which depends on the evolved metric functions, is then evaluated. Analysing this procedure, a natural ultraviolet (UV) cutoff is obtained, which forbids the presence of an interior spacetime region, and may result in a multipy-connected spacetime. Thus, in the context of Gravity's Rainbow, this process may be interpreted as a change in topology, and in principle results in the presence of a Planckian wormhole. |
0901.3226 | Shinji Tsujikawa | Shinji Tsujikawa, Takashi Tamaki, Reza Tavakol | Chameleon scalar fields in relativistic gravitational backgrounds | 17 pages, 8 figures | JCAP 0905:020,2009 | 10.1088/1475-7516/2009/05/020 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the field profile of a scalar field $\phi$ that couples to a matter
fluid (dubbed a chameleon field) in the relativistic gravitational background
of a spherically symmetric spacetime. Employing a linear expansion in terms of
the gravitational potential $\Phi_c$ at the surface of a compact object with a
constant density, we derive the thin-shell field profile both inside and
outside the object, as well as the resulting effective coupling with matter,
analytically. We also carry out numerical simulations for the class of inverse
power-law potentials $V(\phi)=M^{4+n} \phi^{-n}$ by employing the information
provided by our analytical solutions to set the boundary conditions around the
centre of the object and show that thin-shell solutions in fact exist if the
gravitational potential $\Phi_c$ is smaller than 0.3, which marginally covers
the case of neutron stars. Thus the chameleon mechanism is present in the
relativistic gravitational backgrounds, capable of reducing the effective
coupling. Since thin-shell solutions are sensitive to the choice of boundary
conditions, our analytic field profile is very helpful to provide appropriate
boundary conditions for $\Phi_c \lesssim O(0.1)$.
| [
{
"created": "Wed, 21 Jan 2009 10:34:13 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Apr 2009 15:49:03 GMT",
"version": "v2"
}
] | 2010-04-14 | [
[
"Tsujikawa",
"Shinji",
""
],
[
"Tamaki",
"Takashi",
""
],
[
"Tavakol",
"Reza",
""
]
] | We study the field profile of a scalar field $\phi$ that couples to a matter fluid (dubbed a chameleon field) in the relativistic gravitational background of a spherically symmetric spacetime. Employing a linear expansion in terms of the gravitational potential $\Phi_c$ at the surface of a compact object with a constant density, we derive the thin-shell field profile both inside and outside the object, as well as the resulting effective coupling with matter, analytically. We also carry out numerical simulations for the class of inverse power-law potentials $V(\phi)=M^{4+n} \phi^{-n}$ by employing the information provided by our analytical solutions to set the boundary conditions around the centre of the object and show that thin-shell solutions in fact exist if the gravitational potential $\Phi_c$ is smaller than 0.3, which marginally covers the case of neutron stars. Thus the chameleon mechanism is present in the relativistic gravitational backgrounds, capable of reducing the effective coupling. Since thin-shell solutions are sensitive to the choice of boundary conditions, our analytic field profile is very helpful to provide appropriate boundary conditions for $\Phi_c \lesssim O(0.1)$. |
gr-qc/0309114 | Yuri Obukhov | Yuri N. Obukhov | Black hole hydrodynamics | Revtex, 8 pages, no figures | null | null | null | gr-qc | null | The curved geometry of a spacetime manifold arises as a solution of
Einstein's gravitational field equation. We show that the metric of a
spherically symmetric gravitational field configuration can be viewed as an
optical metric created by the moving material fluid with nontrivial dielectric
and magnetic properties. Such a "hydrodynamical" approach provides a simple
physical interpretation of a horizon.
| [
{
"created": "Tue, 23 Sep 2003 19:58:16 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Obukhov",
"Yuri N.",
""
]
] | The curved geometry of a spacetime manifold arises as a solution of Einstein's gravitational field equation. We show that the metric of a spherically symmetric gravitational field configuration can be viewed as an optical metric created by the moving material fluid with nontrivial dielectric and magnetic properties. Such a "hydrodynamical" approach provides a simple physical interpretation of a horizon. |
2104.07721 | Mohsen Fathi | Mohsen Fathi, Marco Olivares, J.R. Villanueva | Analytical study of light ray trajectories in Kerr spacetime in the
presence of an inhomogeneous anisotropic plasma | 22 pages, 32 figures, to appear in EPJC | Eur. Phys. J. C (2021) 81:987 | 10.1140/epjc/s10052-021-09787-1 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the exact solutions to the equations of motion that govern the
light ray trajectories as they travel in a Kerr black hole's exterior that is
considered to be filled with an inhomogeneous and anisotropic plasmic medium.
This is approached by characterizing the plasma through conceiving a radial and
an angular structure function, which are let to be constant. The description of
the motion is carried out by using the Hamilton-Jacobi method, that allows
defining two effective potentials, characterizing the evolution of the polar
coordinates. The elliptic integrals of motion are then solved analytically, and
the evolution of coordinates is expressed in terms of the Mino time. This way,
the three-dimensional demonstrations of the light ray trajectories are given
respectively.
| [
{
"created": "Thu, 15 Apr 2021 19:11:29 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Apr 2021 21:07:11 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Apr 2021 15:30:42 GMT",
"version": "v3"
},
{
"created": "Tue, 31 Aug 2021 15:49:48 GMT",
"version": "v4"
},
{
"created": "Sat, 6 Nov 2021 20:55:26 GMT",
"version": "v5"
}
] | 2021-11-11 | [
[
"Fathi",
"Mohsen",
""
],
[
"Olivares",
"Marco",
""
],
[
"Villanueva",
"J. R.",
""
]
] | We calculate the exact solutions to the equations of motion that govern the light ray trajectories as they travel in a Kerr black hole's exterior that is considered to be filled with an inhomogeneous and anisotropic plasmic medium. This is approached by characterizing the plasma through conceiving a radial and an angular structure function, which are let to be constant. The description of the motion is carried out by using the Hamilton-Jacobi method, that allows defining two effective potentials, characterizing the evolution of the polar coordinates. The elliptic integrals of motion are then solved analytically, and the evolution of coordinates is expressed in terms of the Mino time. This way, the three-dimensional demonstrations of the light ray trajectories are given respectively. |
1105.4007 | Kouji Nakamura | Kouji Nakamura | Construction of gauge-invariant variables of linear metric perturbations
on an arbitrary background spacetime | 26 pages, no figure. Compacted version of arXiv:1101.1147v1[gr-qc]
but includes new ingredients; (v2) Title is slightly changed. Some
discussions and references are added. Some typos are corrected | null | 10.1093/ptep/ptt006 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An outline of a proof of the decomposition of linear metric perturbations
into gauge-invariant and gauge-variant parts on the an arbitrary background
spacetime which admits ADM decomposition is discussed. We explicitly construct
the gauge-invariant and gauge-variant parts of the linear metric perturbations
through the assumption of the existence of some Green functions. We also
confirm the result through another approach. This implies that we can develop
the higher-order gauge-invariant perturbation theory on an arbitrary background
spacetime. Remaining issues to complete the general-framework of the
general-relativistic higher-order gauge-invariant perturbation theories are
also discussed.
| [
{
"created": "Fri, 20 May 2011 03:25:44 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Jan 2013 02:15:27 GMT",
"version": "v2"
}
] | 2016-06-21 | [
[
"Nakamura",
"Kouji",
""
]
] | An outline of a proof of the decomposition of linear metric perturbations into gauge-invariant and gauge-variant parts on the an arbitrary background spacetime which admits ADM decomposition is discussed. We explicitly construct the gauge-invariant and gauge-variant parts of the linear metric perturbations through the assumption of the existence of some Green functions. We also confirm the result through another approach. This implies that we can develop the higher-order gauge-invariant perturbation theory on an arbitrary background spacetime. Remaining issues to complete the general-framework of the general-relativistic higher-order gauge-invariant perturbation theories are also discussed. |
1709.03013 | William J. Cunningham | William J. Cunningham and Dmitri Krioukov | Causal Set Generator and Action Computer | 14 pages, 6 figures. Code may be downloaded at
<https://bitbucket.org/dk-lab/causalsetgenerator> | Comput. Phys. Commun. 233, 123 (2018) | 10.1016/j.cpc.2018.06.008 | null | gr-qc math.NA physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The causal set approach to quantum gravity has gained traction over the past
three decades, but numerical experiments involving causal sets have been
limited to relatively small scales. The software suite presented here provides
a new framework for the generation and study of causal sets. Its efficiency
surpasses previous implementations by several orders of magnitude. We highlight
several important features of the code, including the compact data structures,
the $O(N^2)$ causal set generation process, and several implementations of the
$O(N^3)$ algorithm to compute the Benincasa-Dowker action of compact regions of
spacetime. We show that by tailoring the data structures and algorithms to take
advantage of low-level CPU and GPU architecture designs, we are able to
increase the efficiency and reduce the amount of required memory significantly.
The presented algorithms and their implementations rely on methods that use
CUDA, OpenMP, x86 Assembly, SSE/AVX, Pthreads, and MPI. We also analyze the
scaling of the algorithms' running times with respect to the problem size and
available resources, with suggestions on how to modify the code for future
hardware architectures.
| [
{
"created": "Sat, 9 Sep 2017 22:41:10 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Sep 2018 21:56:07 GMT",
"version": "v2"
}
] | 2018-09-17 | [
[
"Cunningham",
"William J.",
""
],
[
"Krioukov",
"Dmitri",
""
]
] | The causal set approach to quantum gravity has gained traction over the past three decades, but numerical experiments involving causal sets have been limited to relatively small scales. The software suite presented here provides a new framework for the generation and study of causal sets. Its efficiency surpasses previous implementations by several orders of magnitude. We highlight several important features of the code, including the compact data structures, the $O(N^2)$ causal set generation process, and several implementations of the $O(N^3)$ algorithm to compute the Benincasa-Dowker action of compact regions of spacetime. We show that by tailoring the data structures and algorithms to take advantage of low-level CPU and GPU architecture designs, we are able to increase the efficiency and reduce the amount of required memory significantly. The presented algorithms and their implementations rely on methods that use CUDA, OpenMP, x86 Assembly, SSE/AVX, Pthreads, and MPI. We also analyze the scaling of the algorithms' running times with respect to the problem size and available resources, with suggestions on how to modify the code for future hardware architectures. |
gr-qc/9912092 | Piotr Jaranowski | Thibault Damour, Piotr Jaranowski, and Gerhard Sch\"afer | Dynamical invariants for general relativistic two-body systems at the
third post-Newtonian approximation | REVTeX, 21 pages, submitted to Phys. Rev. D | Phys.Rev.D62:044024,2000 | 10.1103/PhysRevD.62.044024 | null | gr-qc | null | We extract all the invariants (i.e. all the functions which do not depend on
the choice of phase-space coordinates) of the dynamics of two point-masses, at
the third post-Newtonian (3PN) approximation of general relativity. We start by
showing how a contact transformation can be used to reduce the 3PN higher-order
Hamiltonian derived by Jaranowski and Sch\"afer to an ordinary Hamiltonian. The
dynamical invariants for general orbits (considered in the center-of-mass
frame) are then extracted by computing the radial action variable
$\oint{p_r}dr$ as a function of energy and angular momentum. The important case
of circular orbits is given special consideration. We discuss in detail the
plausible ranges of values of the two quantities $\oms$, $\omk$ which
parametrize the existence of ambiguities in the regularization of some of the
divergent integrals making up the Hamiltonian. The physical applications of the
invariant functions derived here (e.g. to the determination of the location of
the last stable circular orbit) are left to subsequent work.
| [
{
"created": "Tue, 21 Dec 1999 16:26:33 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Damour",
"Thibault",
""
],
[
"Jaranowski",
"Piotr",
""
],
[
"Schäfer",
"Gerhard",
""
]
] | We extract all the invariants (i.e. all the functions which do not depend on the choice of phase-space coordinates) of the dynamics of two point-masses, at the third post-Newtonian (3PN) approximation of general relativity. We start by showing how a contact transformation can be used to reduce the 3PN higher-order Hamiltonian derived by Jaranowski and Sch\"afer to an ordinary Hamiltonian. The dynamical invariants for general orbits (considered in the center-of-mass frame) are then extracted by computing the radial action variable $\oint{p_r}dr$ as a function of energy and angular momentum. The important case of circular orbits is given special consideration. We discuss in detail the plausible ranges of values of the two quantities $\oms$, $\omk$ which parametrize the existence of ambiguities in the regularization of some of the divergent integrals making up the Hamiltonian. The physical applications of the invariant functions derived here (e.g. to the determination of the location of the last stable circular orbit) are left to subsequent work. |
1709.03301 | Killian Martineau | Killian Martineau, Aur\'elien Barrau and Julien Grain | A first step towards the inflationary trans-planckian problem treatment
in Loop Quantum Cosmology | 11 pages, 10 figures | null | 10.1142/S0218271818500670 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For most initial conditions, cosmologically relevant physical modes were
trans-planckian at the bounce time, often by many magnitude orders. We improve
the usual loop quantum cosmology calculation of the primordial power spectra --
in the inflationary framework -- by accounting for those trans-planckian
effects through modified dispersion relations. This can induce drastic changes
in the spectrum, making it either compatible or incompatible with observational
data, depending on the details of the choices operated.
| [
{
"created": "Mon, 11 Sep 2017 09:08:52 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Jan 2018 09:18:51 GMT",
"version": "v2"
}
] | 2018-05-23 | [
[
"Martineau",
"Killian",
""
],
[
"Barrau",
"Aurélien",
""
],
[
"Grain",
"Julien",
""
]
] | For most initial conditions, cosmologically relevant physical modes were trans-planckian at the bounce time, often by many magnitude orders. We improve the usual loop quantum cosmology calculation of the primordial power spectra -- in the inflationary framework -- by accounting for those trans-planckian effects through modified dispersion relations. This can induce drastic changes in the spectrum, making it either compatible or incompatible with observational data, depending on the details of the choices operated. |
2207.10610 | Biswajit Deb | Biswajit Deb, Atri Deshamukhya | Constraining logarithmic $f(R,T)$ model using Dark Energy density
parameter $\Omega_{\Lambda}$ and Hubble parameter $H_0$ | 6 pages, Paper presented in the 23rd International Conference on
General Relativity and Gravitation, 3-8 July, 2022, Beijing organized by
ISGRG | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Of many extended theories of gravity, $f(R,T)$ gravity has gained reasonable
interest in recent times as it provides interesting results in cosmology.
Logarithmic corrections in modified theories of gravity has been studied
extensively. In this work, we considered logarithmic correction to the trace
term T and take the functional form as $f(R,T)=R + 16 \pi G \alpha \ln T$ where
$\alpha$ is a free parameter. The free parameter is constrained using dark
energy density parameter $\Omega_{\Lambda}$ and Hubble parameter $H_0$. The
lower bound is found to be $\alpha \ge - 9.93 \times 10^{-29}$. The
cosmological implications are also studied.
| [
{
"created": "Thu, 21 Jul 2022 17:06:52 GMT",
"version": "v1"
}
] | 2022-07-22 | [
[
"Deb",
"Biswajit",
""
],
[
"Deshamukhya",
"Atri",
""
]
] | Of many extended theories of gravity, $f(R,T)$ gravity has gained reasonable interest in recent times as it provides interesting results in cosmology. Logarithmic corrections in modified theories of gravity has been studied extensively. In this work, we considered logarithmic correction to the trace term T and take the functional form as $f(R,T)=R + 16 \pi G \alpha \ln T$ where $\alpha$ is a free parameter. The free parameter is constrained using dark energy density parameter $\Omega_{\Lambda}$ and Hubble parameter $H_0$. The lower bound is found to be $\alpha \ge - 9.93 \times 10^{-29}$. The cosmological implications are also studied. |
2401.13894 | Yen-Kheng Lim PhD | Yen-Kheng Lim and Zhi Cheng Yeo | Energies and angular momenta of periodic Schwarzschild geodesics | 28 pages, 11 figures | Phys. Rev. D 109, 024037 (2024) | 10.1103/PhysRevD.109.024037 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider physical parameters of Levin and Perez-Giz's `periodic table of
orbits' around the Schwarzschild black hole, where each periodic orbit is
classified according to three integers $(z,w,v)$. In particular, we chart its
distribution in terms of its angular momenta $L$ and energy $E$. In the
$(L,E)$-parameter space, the set of all periodic orbits can be partitioned into
domains according to their whirl number $w$, where the limit of infinite $w$
approaches the branch of unstable circular orbits. Within each domain of a
given whirl number $w$, the infinite zoom limit
$\lim_{z\rightarrow\infty}(z,w,v)$ converges to the common boundary with the
adjacent domain of whirl number $w-1$. The distribution of the periodic orbit
branches can also be inferred from perturbing stable circular orbits, using the
fact that every stable circular orbit is the zero-eccentricity limit of some
periodic orbit, or arbitrarily close to one.
| [
{
"created": "Thu, 25 Jan 2024 02:23:06 GMT",
"version": "v1"
}
] | 2024-01-26 | [
[
"Lim",
"Yen-Kheng",
""
],
[
"Yeo",
"Zhi Cheng",
""
]
] | We consider physical parameters of Levin and Perez-Giz's `periodic table of orbits' around the Schwarzschild black hole, where each periodic orbit is classified according to three integers $(z,w,v)$. In particular, we chart its distribution in terms of its angular momenta $L$ and energy $E$. In the $(L,E)$-parameter space, the set of all periodic orbits can be partitioned into domains according to their whirl number $w$, where the limit of infinite $w$ approaches the branch of unstable circular orbits. Within each domain of a given whirl number $w$, the infinite zoom limit $\lim_{z\rightarrow\infty}(z,w,v)$ converges to the common boundary with the adjacent domain of whirl number $w-1$. The distribution of the periodic orbit branches can also be inferred from perturbing stable circular orbits, using the fact that every stable circular orbit is the zero-eccentricity limit of some periodic orbit, or arbitrarily close to one. |
2204.11738 | Barak Rom | Barak Rom, Re'em Sari | Extreme Mass-Ratio Binary Black Hole Merger: Characteristics of the
Test-Particle Limit | 11 pages, 7 figures. Accepted for publication in Physical Review D | Phys. Rev. D 106, 104040 (2022) | 10.1103/PhysRevD.106.104040 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We study binary black hole mergers in the extreme mass-ratio limit. We
determine the energy, angular momentum, and linear momentum of the post-merger,
remnant black hole. Unlike previous works, we perform our analysis directly in
the test-particle limit by solving the Regge-Wheeler-Zerilli wave equation with
a source that moves along a geodesic. We rely on the fact that toward the
merger, small mass-ratio binary systems follow a quasiuniversal geodesic
trajectory. This formalism captures the final premerger stages of small
mass-ratio binaries and thus provides a straightforward universal description
in a region inaccessible to numerical relativity simulations. We present a
general waveform template that may be used in the search for gravitational wave
bursts from small and intermediate mass-ratio binary systems. Finally, this
formalism gives a formal proof that the recoil velocity is quadratic in the
symmetric mass ratio $\nu$. Specifically, the velocity is given by $V/c\approx
0.0467 \nu^2$. This result is about $4\%$ larger than previously estimated.
Most of this difference stems from the inclusion of higher multipoles in our
calculation.
| [
{
"created": "Mon, 25 Apr 2022 15:50:27 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Oct 2022 14:02:30 GMT",
"version": "v2"
}
] | 2022-11-22 | [
[
"Rom",
"Barak",
""
],
[
"Sari",
"Re'em",
""
]
] | We study binary black hole mergers in the extreme mass-ratio limit. We determine the energy, angular momentum, and linear momentum of the post-merger, remnant black hole. Unlike previous works, we perform our analysis directly in the test-particle limit by solving the Regge-Wheeler-Zerilli wave equation with a source that moves along a geodesic. We rely on the fact that toward the merger, small mass-ratio binary systems follow a quasiuniversal geodesic trajectory. This formalism captures the final premerger stages of small mass-ratio binaries and thus provides a straightforward universal description in a region inaccessible to numerical relativity simulations. We present a general waveform template that may be used in the search for gravitational wave bursts from small and intermediate mass-ratio binary systems. Finally, this formalism gives a formal proof that the recoil velocity is quadratic in the symmetric mass ratio $\nu$. Specifically, the velocity is given by $V/c\approx 0.0467 \nu^2$. This result is about $4\%$ larger than previously estimated. Most of this difference stems from the inclusion of higher multipoles in our calculation. |
gr-qc/0002024 | Merced Montesinos | Merced Montesinos and Carlo Rovelli | Statistical mechanics of generally covariant quantum theories: A
Boltzmann-like approach | 18 pages, no figures, Latex file. Revised version. Accepted for
publication in Class. Quantum Grav | Class.Quant.Grav. 18 (2001) 555-569 | 10.1088/0264-9381/18/3/314 | null | gr-qc hep-th quant-ph | null | We study the possibility of applying statistical mechanics to generally
covariant quantum theories with a vanishing Hamiltonian. We show that (under
certain appropiate conditions) this makes sense, in spite of the absence of a
notion of energy and external time. We consider a composite system formed by a
large number of identical components, and apply Boltzmann's ideas and the
fundamental postulates of ordinary statistical physics. The thermodynamical
parameters are determined by the properties of the thermalizing interaction. We
apply these ideas to a simple example, in which the component system has one
physical degree of freedom and mimics the constraint algebra of general
relativity.
| [
{
"created": "Fri, 4 Feb 2000 17:39:55 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Jan 2001 18:06:19 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Montesinos",
"Merced",
""
],
[
"Rovelli",
"Carlo",
""
]
] | We study the possibility of applying statistical mechanics to generally covariant quantum theories with a vanishing Hamiltonian. We show that (under certain appropiate conditions) this makes sense, in spite of the absence of a notion of energy and external time. We consider a composite system formed by a large number of identical components, and apply Boltzmann's ideas and the fundamental postulates of ordinary statistical physics. The thermodynamical parameters are determined by the properties of the thermalizing interaction. We apply these ideas to a simple example, in which the component system has one physical degree of freedom and mimics the constraint algebra of general relativity. |
1705.01048 | Srimanta Banerjee | Srimanta Banerjee, Swapnil Shankar and Tejinder P. Singh | Constraints on Modified Gravity Models from White Dwarfs | 27 pages, 22 figures, 1 Table; Matches the version published in JCAP | JCAP 10 (2017) 004 | 10.1088/1475-7516/2017/10/004 | null | gr-qc astro-ph.CO astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modified gravity theories can introduce modifications to the Poisson equation
in the Newtonian limit. As a result, we expect to see interesting features of
these modifications inside stellar objects. White dwarf stars are one of the
most well studied stars in stellar astrophysics. We explore the effect of
modified gravity theories inside white dwarfs. We derive the modified stellar
structure equations and solve them to study the mass-radius relationships for
various modified gravity theories. We also constrain the parameter space of
these theories from observations.
| [
{
"created": "Tue, 2 May 2017 16:15:27 GMT",
"version": "v1"
},
{
"created": "Fri, 26 May 2017 13:42:43 GMT",
"version": "v2"
},
{
"created": "Thu, 5 Oct 2017 02:42:10 GMT",
"version": "v3"
}
] | 2017-10-06 | [
[
"Banerjee",
"Srimanta",
""
],
[
"Shankar",
"Swapnil",
""
],
[
"Singh",
"Tejinder P.",
""
]
] | Modified gravity theories can introduce modifications to the Poisson equation in the Newtonian limit. As a result, we expect to see interesting features of these modifications inside stellar objects. White dwarf stars are one of the most well studied stars in stellar astrophysics. We explore the effect of modified gravity theories inside white dwarfs. We derive the modified stellar structure equations and solve them to study the mass-radius relationships for various modified gravity theories. We also constrain the parameter space of these theories from observations. |
2205.06867 | Cenalo Vaz | Cenalo Vaz | Proper time Quantization of a Thin Shell | This essay was selected for the First Award in the 2022 Gravity
Research Foundation Essay Competition. arXiv admin note: substantial text
overlap with arXiv:2204.02435 | null | 10.1142/S0218271822410012 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | "Time" has different meanings in classical general relativity and in quantum
theory. While all choices of a time function yield the same local classical
geometries, quantum theories built on different time functions are not
unitarily equivalent. This incompatibility is most vivid in model systems for
which exact quantum descriptions in different time variables are available. One
such system is a spherically symmetric, thin dust shell. In this essay we will
compare the quantum theories of the shell built on proper time and on a
particular coordinate time. We find wholly incompatible descriptions: whereas
the shell quantum mechanics in coordinate time admits no solutions when the
mass is greater than the Planck mass, its proper time quantum mechanics only
admits solutions when the mass is greater than the Planck mass. The latter is
in better agreement with what is expected from observation. We argue that
proper time quantization provides a superior approach to the problem of time in
canonical quantization.
| [
{
"created": "Fri, 13 May 2022 19:54:10 GMT",
"version": "v1"
}
] | 2022-07-06 | [
[
"Vaz",
"Cenalo",
""
]
] | "Time" has different meanings in classical general relativity and in quantum theory. While all choices of a time function yield the same local classical geometries, quantum theories built on different time functions are not unitarily equivalent. This incompatibility is most vivid in model systems for which exact quantum descriptions in different time variables are available. One such system is a spherically symmetric, thin dust shell. In this essay we will compare the quantum theories of the shell built on proper time and on a particular coordinate time. We find wholly incompatible descriptions: whereas the shell quantum mechanics in coordinate time admits no solutions when the mass is greater than the Planck mass, its proper time quantum mechanics only admits solutions when the mass is greater than the Planck mass. The latter is in better agreement with what is expected from observation. We argue that proper time quantization provides a superior approach to the problem of time in canonical quantization. |
1512.07835 | Winfried Zimdahl | Rodrigo M. Barbosa, G. Eddy, I. Chirinos, Winfried Zimdahl, Oliver F.
Piattella | Cosmic bulk viscosity through backreaction | 18 pages, 6 figures, comments and references added, accepted for
publication in GRG | null | 10.1007/s10714-016-2043-4 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider an effective viscous pressure as the result of a backreaction of
inhomogeneities within Buchert's formalism. The use of an effective metric with
a time-dependent curvature radius allows us to calculate the luminosity
distance of the backreaction model. This quantity is different from its
counterpart for a "conventional" spatially flat bulk viscous fluid universe.
Both expressions are tested against the SNIa data of the Union2.1 sample with
only marginally different results for the distance-redshift relation and in
accordance with the $\Lambda$CDM model. Future observations are expected to be
able to discriminate among these models on the basis of indirect measurements
of the curvature evolution.
| [
{
"created": "Thu, 24 Dec 2015 15:12:50 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Mar 2016 12:30:48 GMT",
"version": "v2"
}
] | 2016-04-13 | [
[
"Barbosa",
"Rodrigo M.",
""
],
[
"Eddy",
"G.",
""
],
[
"Chirinos",
"I.",
""
],
[
"Zimdahl",
"Winfried",
""
],
[
"Piattella",
"Oliver F.",
""
]
] | We consider an effective viscous pressure as the result of a backreaction of inhomogeneities within Buchert's formalism. The use of an effective metric with a time-dependent curvature radius allows us to calculate the luminosity distance of the backreaction model. This quantity is different from its counterpart for a "conventional" spatially flat bulk viscous fluid universe. Both expressions are tested against the SNIa data of the Union2.1 sample with only marginally different results for the distance-redshift relation and in accordance with the $\Lambda$CDM model. Future observations are expected to be able to discriminate among these models on the basis of indirect measurements of the curvature evolution. |
gr-qc/0512084 | Yi Ling | Yi Ling, Xiang Li and Hongbao Zhang | Thermodynamics of modified black holes from gravity's rainbow | 3 pages, Revtex | Mod.Phys.Lett.A22:2749-2756,2007 | 10.1142/S0217732307022931 | null | gr-qc | null | We study the thermodynamics of modified black holes proposed in the context
of gravity's rainbow. A notion of intrinsic temperature and entropy for these
black holes is introduced. In particular for a specific class of modified
Schwarzschild solutions, their temperature and entropy are obtained and
compared with those previously obtained from modified dispersion relations in
deformed special relativity. It turns out that the results of these two
different strategies coincide, and this may be viewed as a support for the
proposal of deformed equivalence principle.
| [
{
"created": "Wed, 14 Dec 2005 13:15:41 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ling",
"Yi",
""
],
[
"Li",
"Xiang",
""
],
[
"Zhang",
"Hongbao",
""
]
] | We study the thermodynamics of modified black holes proposed in the context of gravity's rainbow. A notion of intrinsic temperature and entropy for these black holes is introduced. In particular for a specific class of modified Schwarzschild solutions, their temperature and entropy are obtained and compared with those previously obtained from modified dispersion relations in deformed special relativity. It turns out that the results of these two different strategies coincide, and this may be viewed as a support for the proposal of deformed equivalence principle. |
2102.00478 | Giampiero Esposito Dr. | Roberto Niardi, Giampiero Esposito, Francesco Tramontano | Divergent part of the stress-energy tensor for Maxwell's theory in
curved space-time: a systematic derivation | 42 pages, Latex | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper the Feynman Green function for Maxwell's theory in curved
space-time is studied by using the Fock-Schwinger-DeWitt asymptotic expansion;
the point-splitting method is then applied, since it is a valuable tool for
regularizing divergent observables. Among these, the stress-energy tensor is
expressed in terms of second covariant derivatives of the Hadamard Green
function, which is also closely linked to the effective action; therefore one
obtains a series expansion for the stress-energy tensor. Its divergent part can
be isolated, and a concise formula is here obtained: by dimensional analysis
and combinatorics, there are two kinds of terms: quadratic in curvature tensors
(Riemann, Ricci tensors and scalar curvature) and linear in their second
covariant derivatives. This formula holds for every space-time metric; it is
made even more explicit in the physically relevant particular cases of
Ricci-flat and maximally symmetric spaces, and fully evaluated for some
examples of physical interest: Kerr and Schwarzschild metrics and de Sitter
space-time.
| [
{
"created": "Sun, 31 Jan 2021 16:14:55 GMT",
"version": "v1"
}
] | 2021-02-02 | [
[
"Niardi",
"Roberto",
""
],
[
"Esposito",
"Giampiero",
""
],
[
"Tramontano",
"Francesco",
""
]
] | In this paper the Feynman Green function for Maxwell's theory in curved space-time is studied by using the Fock-Schwinger-DeWitt asymptotic expansion; the point-splitting method is then applied, since it is a valuable tool for regularizing divergent observables. Among these, the stress-energy tensor is expressed in terms of second covariant derivatives of the Hadamard Green function, which is also closely linked to the effective action; therefore one obtains a series expansion for the stress-energy tensor. Its divergent part can be isolated, and a concise formula is here obtained: by dimensional analysis and combinatorics, there are two kinds of terms: quadratic in curvature tensors (Riemann, Ricci tensors and scalar curvature) and linear in their second covariant derivatives. This formula holds for every space-time metric; it is made even more explicit in the physically relevant particular cases of Ricci-flat and maximally symmetric spaces, and fully evaluated for some examples of physical interest: Kerr and Schwarzschild metrics and de Sitter space-time. |
2403.09966 | Rakshak Adhikari | Rakshak Adhikari, Govind Menon, Mikhail V. Medvedev | Force-free Electromagnetic Configurations in FLRW Geometry | null | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Force-free electrodynamics is the theoretical paradigm used to describe
electromagnetic fields in a region where the inertia of plasma is negligible
compared to the strength of the electromagnetic field. While these fields are
studied extensively around accreting black holes in an attempt to describe
energy extraction, force-free fields also routinely appear in the study of
cosmological magnetic fields. Despite this, there are no systematic studies of
exact force-free fields in an expanding universe. In this paper, we use
geometric methods to find a wide variety of force-free solutions in a fixed
Friedmann-Lemaitre-Robertson-Walker metric background. The method we use can be
directly generalized to any arbitrary electrically neutral space-time, and
hence, provides a powerful tool to study force-free fields in general.
| [
{
"created": "Fri, 15 Mar 2024 02:09:39 GMT",
"version": "v1"
}
] | 2024-03-18 | [
[
"Adhikari",
"Rakshak",
""
],
[
"Menon",
"Govind",
""
],
[
"Medvedev",
"Mikhail V.",
""
]
] | Force-free electrodynamics is the theoretical paradigm used to describe electromagnetic fields in a region where the inertia of plasma is negligible compared to the strength of the electromagnetic field. While these fields are studied extensively around accreting black holes in an attempt to describe energy extraction, force-free fields also routinely appear in the study of cosmological magnetic fields. Despite this, there are no systematic studies of exact force-free fields in an expanding universe. In this paper, we use geometric methods to find a wide variety of force-free solutions in a fixed Friedmann-Lemaitre-Robertson-Walker metric background. The method we use can be directly generalized to any arbitrary electrically neutral space-time, and hence, provides a powerful tool to study force-free fields in general. |
2312.02295 | Alexander Grant | Alexander M. Grant and Keefe Mitman | Higher Memory Effects in Numerical Simulations of Binary Black Hole
Mergers | 14 pages, 4 figures; v2: added references (including to public source
code); v3: matches published version | Class. Quant. Grav. 41 175003 (2024) | 10.1088/1361-6382/ad5d46 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational memory effects are predictions of general relativity that are
characterized by an observable effect that persists after the passage of
gravitational waves. In recent years, they have garnered particular interest,
both due to their connection to asymptotic symmetries and soft theorems and
because their observation would serve as a unique test of the nonlinear nature
of general relativity. Apart from the more commonly known displacement and spin
memories, however, there are other memory effects predicted by Einstein's
equations that are associated with more subleading terms in the asymptotic
expansion of the Bondi-Sachs metric. In this paper, we write explicit
expressions for these higher memory effects in terms of their charge and flux
contributions. Further, by using a numerical relativity simulation of a binary
black hole merger, we compute the magnitude and morphology of these terms and
compare them to those of the displacement and spin memory. We find that,
although these terms are interesting from a theoretical perspective, due to
their small magnitude they will be particularly challenging to observe with
current and future detectors.
| [
{
"created": "Mon, 4 Dec 2023 19:18:51 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Mar 2024 21:03:07 GMT",
"version": "v2"
},
{
"created": "Mon, 29 Jul 2024 17:24:23 GMT",
"version": "v3"
}
] | 2024-07-30 | [
[
"Grant",
"Alexander M.",
""
],
[
"Mitman",
"Keefe",
""
]
] | Gravitational memory effects are predictions of general relativity that are characterized by an observable effect that persists after the passage of gravitational waves. In recent years, they have garnered particular interest, both due to their connection to asymptotic symmetries and soft theorems and because their observation would serve as a unique test of the nonlinear nature of general relativity. Apart from the more commonly known displacement and spin memories, however, there are other memory effects predicted by Einstein's equations that are associated with more subleading terms in the asymptotic expansion of the Bondi-Sachs metric. In this paper, we write explicit expressions for these higher memory effects in terms of their charge and flux contributions. Further, by using a numerical relativity simulation of a binary black hole merger, we compute the magnitude and morphology of these terms and compare them to those of the displacement and spin memory. We find that, although these terms are interesting from a theoretical perspective, due to their small magnitude they will be particularly challenging to observe with current and future detectors. |
2208.07874 | Hamid Shabani | Hamid Shabani, Amir Hadi Ziaie, Hooman Moradpour | Einstein Static Universe and its Stability in Generalized Rastall
Gravity | 12 pages, 4 figures | Ann. Phys. 444 (2022) 169058 | 10.1016/j.aop.2022.169058 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The Einstein static (ES) state is a good candidate for describing the very
early universe in terms of a regular cosmological model in which the Big Bang
singularity is avoided. In the present study we propose an ES solution in the
framework of generalized Rastall gravity (GRG), a modified version of original
Rastall theory in which the coupling parameter is allowed to vary with respect
to the spacetime coordinates. Introducing an ansatz for the Rastall parameter,
existence and the corresponding stability of the solutions are investigated. We
show that the GRG is capable of describing a stable singularity-free state for
the universe. The problem of transition from an ES to an inflationary state is
also addressed. We find that a time variation of the equation of state
parameter from values lying in the range |w|<1/3 to the value w=-1/3 can give
rise to such a phase transition. The vector and tensor perturbations around the
ES solution are studied, as well. In the case of GRG, the vector perturbations
remain frozen, nevertheless, the tenor perturbations can grow in such a way
that the ES solution remains stable provided the ratio of Rastall gravitational
constant to the Einsteinian one always exceeds a minimum value for each tensor
mode.
| [
{
"created": "Tue, 16 Aug 2022 06:04:28 GMT",
"version": "v1"
}
] | 2022-08-18 | [
[
"Shabani",
"Hamid",
""
],
[
"Ziaie",
"Amir Hadi",
""
],
[
"Moradpour",
"Hooman",
""
]
] | The Einstein static (ES) state is a good candidate for describing the very early universe in terms of a regular cosmological model in which the Big Bang singularity is avoided. In the present study we propose an ES solution in the framework of generalized Rastall gravity (GRG), a modified version of original Rastall theory in which the coupling parameter is allowed to vary with respect to the spacetime coordinates. Introducing an ansatz for the Rastall parameter, existence and the corresponding stability of the solutions are investigated. We show that the GRG is capable of describing a stable singularity-free state for the universe. The problem of transition from an ES to an inflationary state is also addressed. We find that a time variation of the equation of state parameter from values lying in the range |w|<1/3 to the value w=-1/3 can give rise to such a phase transition. The vector and tensor perturbations around the ES solution are studied, as well. In the case of GRG, the vector perturbations remain frozen, nevertheless, the tenor perturbations can grow in such a way that the ES solution remains stable provided the ratio of Rastall gravitational constant to the Einsteinian one always exceeds a minimum value for each tensor mode. |
0709.2109 | Dmitriy Pak | H. Niu and D. G. Pak | Non-Topological Gauss-Bonnet type model of gravity with torsion | 9 pages, no figures, minor corrections, text improved | null | null | null | gr-qc | null | A non-topological Lorentz gauge model of gravity with torsion based on
Gauss-Bonnet type Lagrangian is considered. The Lagrangian differs from the
Lovelock term in four-dimensional space-time and has a number of interesting
features. We demonstrate that the model admits a propagating torsion unlike the
case of the topological Lovelock gravity. Due to additional symmetries of the
proposed Gauss-Bonnet type Lagrangian the torsion has a reduced set of
dynamical degrees of freedom corresponding to the spin two field, U(1) gauge
vector field and spin zero field. A remarkable feature is that the kinetic part
of the Hamiltonian containing the spin two field is positively defined. We
perform one-loop quantization of the model for a special case of constant
Riemann curvature space-time background treating the torsion as a quantum field
variable. We discuss a possible mechanism of emergent Einstein gravity as an
effective theory which can be induced due to quantum dynamics of torsion.
| [
{
"created": "Thu, 13 Sep 2007 16:10:29 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Oct 2007 12:10:59 GMT",
"version": "v2"
},
{
"created": "Thu, 6 Mar 2008 12:41:55 GMT",
"version": "v3"
}
] | 2008-03-06 | [
[
"Niu",
"H.",
""
],
[
"Pak",
"D. G.",
""
]
] | A non-topological Lorentz gauge model of gravity with torsion based on Gauss-Bonnet type Lagrangian is considered. The Lagrangian differs from the Lovelock term in four-dimensional space-time and has a number of interesting features. We demonstrate that the model admits a propagating torsion unlike the case of the topological Lovelock gravity. Due to additional symmetries of the proposed Gauss-Bonnet type Lagrangian the torsion has a reduced set of dynamical degrees of freedom corresponding to the spin two field, U(1) gauge vector field and spin zero field. A remarkable feature is that the kinetic part of the Hamiltonian containing the spin two field is positively defined. We perform one-loop quantization of the model for a special case of constant Riemann curvature space-time background treating the torsion as a quantum field variable. We discuss a possible mechanism of emergent Einstein gravity as an effective theory which can be induced due to quantum dynamics of torsion. |
gr-qc/9901017 | Guendel Eduardo | E.I.Guendelman | Scale invariance, new inflation and decaying Lambda terms | 12 pages | Mod.Phys.Lett. A14 (1999) 1043-1052 | 10.1142/S0217732399001103 | null | gr-qc | null | Realizations of scale invariance are studied in the context of a
gravitational theory where the action (in the first order formalism) is of the
form $S = \int L_{1} \Phi d^{4}x$ + $\int L_{2}\sqrt{-g}d^{4}x$ where $\Phi$ is
a density built out of degrees of freedom, the "measure fields" independent of
$g_{\mu\nu}$ and matter fields appearing in $L_{1}$, $L_{2}$. If $L_{1}$
contains the curvature, scalar potential $V(\phi)$ and kinetic term for $\phi$,
$L_{2}$ another potential for $\phi$, $U(\phi)$, then the true vacuum state has
zero energy density, when theory is analyzed in the conformal Einstein frame
(CEF), where the equations assume the Einstein form. Global Scale invariance is
realized when $V(\phi)$ = $f_{1}e^{\alpha\phi}$ and $U(\phi)$ =
$f_{2}e^{2\alpha\phi}$. In the CEF the scalar field potential energy
$V_{eff}(\phi)$ has in, addition to a minimum at zero, a flat region for
$\alpha\phi \to\infty$, with non zero vacuum energy, which is suitable for
either a New Inflationary scenario for the Early Universe or for a slowly
rolling decaying $\Lambda$-scenario for the late universe, where the smallness
of the vacuum energy can be understood as a kind of see-saw mechanism.
| [
{
"created": "Thu, 7 Jan 1999 12:55:44 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Guendelman",
"E. I.",
""
]
] | Realizations of scale invariance are studied in the context of a gravitational theory where the action (in the first order formalism) is of the form $S = \int L_{1} \Phi d^{4}x$ + $\int L_{2}\sqrt{-g}d^{4}x$ where $\Phi$ is a density built out of degrees of freedom, the "measure fields" independent of $g_{\mu\nu}$ and matter fields appearing in $L_{1}$, $L_{2}$. If $L_{1}$ contains the curvature, scalar potential $V(\phi)$ and kinetic term for $\phi$, $L_{2}$ another potential for $\phi$, $U(\phi)$, then the true vacuum state has zero energy density, when theory is analyzed in the conformal Einstein frame (CEF), where the equations assume the Einstein form. Global Scale invariance is realized when $V(\phi)$ = $f_{1}e^{\alpha\phi}$ and $U(\phi)$ = $f_{2}e^{2\alpha\phi}$. In the CEF the scalar field potential energy $V_{eff}(\phi)$ has in, addition to a minimum at zero, a flat region for $\alpha\phi \to\infty$, with non zero vacuum energy, which is suitable for either a New Inflationary scenario for the Early Universe or for a slowly rolling decaying $\Lambda$-scenario for the late universe, where the smallness of the vacuum energy can be understood as a kind of see-saw mechanism. |
2105.05630 | Oliver Long | Oliver Long and Leor Barack | Time-domain metric reconstruction for hyperbolic scattering | 28 pages, 11 figures; v3 corrected typo in Eq. (103) | Phys. Rev. D 104, 024014 (2021) | 10.1103/PhysRevD.104.024014 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Self-force methods can be applied in calculations of the scatter angle in
two-body hyperbolic encounters, working order by order in the mass ratio
(assumed small) but with no recourse to a weak-field approximation. This, in
turn, can inform ongoing efforts to construct an accurate model of the
general-relativistic binary dynamics via an effective-one-body description and
other semi-analytical approaches. Existing self-force methods are to a large
extent specialised to bound, inspiral orbits. Here we develop a technique for
(numerical) self-force calculations that can efficiently tackle scatter orbits.
The method is based on a time-domain reconstruction of the metric perturbation
from a scalar-like Hertz potential that satisfies the Teukolsky equation, an
idea pursued so far only for bound orbits. The crucial ingredient in this
formulation are certain jump conditions that (each multipole mode of) the Hertz
potential must satisfy along the orbit, in a 1+1-dimensional multipole
reduction of the problem. We obtain a closed-form expression for these jumps,
for an arbitrary geodesic orbit in Schwarzschild spacetime, and present a full
numerical implementation for a scatter orbit. In this paper we focus on method
development, and go only as far as calculating the Hertz potential; a
calculation of the self-force and its physical effects on the scatter orbit
will be the subject of forthcoming work.
| [
{
"created": "Wed, 12 May 2021 12:58:28 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jun 2021 14:38:08 GMT",
"version": "v2"
},
{
"created": "Wed, 15 Sep 2021 10:26:55 GMT",
"version": "v3"
},
{
"created": "Mon, 21 Feb 2022 10:22:28 GMT",
"version": "v4"
}
] | 2022-02-22 | [
[
"Long",
"Oliver",
""
],
[
"Barack",
"Leor",
""
]
] | Self-force methods can be applied in calculations of the scatter angle in two-body hyperbolic encounters, working order by order in the mass ratio (assumed small) but with no recourse to a weak-field approximation. This, in turn, can inform ongoing efforts to construct an accurate model of the general-relativistic binary dynamics via an effective-one-body description and other semi-analytical approaches. Existing self-force methods are to a large extent specialised to bound, inspiral orbits. Here we develop a technique for (numerical) self-force calculations that can efficiently tackle scatter orbits. The method is based on a time-domain reconstruction of the metric perturbation from a scalar-like Hertz potential that satisfies the Teukolsky equation, an idea pursued so far only for bound orbits. The crucial ingredient in this formulation are certain jump conditions that (each multipole mode of) the Hertz potential must satisfy along the orbit, in a 1+1-dimensional multipole reduction of the problem. We obtain a closed-form expression for these jumps, for an arbitrary geodesic orbit in Schwarzschild spacetime, and present a full numerical implementation for a scatter orbit. In this paper we focus on method development, and go only as far as calculating the Hertz potential; a calculation of the self-force and its physical effects on the scatter orbit will be the subject of forthcoming work. |
1005.2685 | Viktor Toth | J. W. Moffat and V. T. Toth | Can Modified Gravity (MOG) explain the speeding Bullet (Cluster)? | 4 pages | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply our scalar-tensor-vector (STVG) modified gravity theory (MOG) to
calculate the infall velocities of the two clusters constituting the Bullet
Cluster 1E0657-06. In the absence of an applicable two-body solution to the MOG
field equations, we adopt an approximate acceleration formula based on the
spherically symmetric, static, vacuum solution of the theory in the presence of
a point source. We find that this formula predicts an infall velocity of the
two clusters that is consistent with estimates based on hydrodynamic
simulations.
| [
{
"created": "Sat, 15 May 2010 16:07:00 GMT",
"version": "v1"
}
] | 2010-05-18 | [
[
"Moffat",
"J. W.",
""
],
[
"Toth",
"V. T.",
""
]
] | We apply our scalar-tensor-vector (STVG) modified gravity theory (MOG) to calculate the infall velocities of the two clusters constituting the Bullet Cluster 1E0657-06. In the absence of an applicable two-body solution to the MOG field equations, we adopt an approximate acceleration formula based on the spherically symmetric, static, vacuum solution of the theory in the presence of a point source. We find that this formula predicts an infall velocity of the two clusters that is consistent with estimates based on hydrodynamic simulations. |
gr-qc/0408034 | T. Padmanabhan | L.Sriramkumar, T.Padmanabhan | Initial state of matter fields and trans-Planckian physics: Can CMB
observations disentangle the two? | revtex4; 17 pages | Phys.Rev. D71 (2005) 103512 | 10.1103/PhysRevD.71.103512 | null | gr-qc astro-ph hep-th | null | The standard, scale-invariant, inflationary perturbation spectrum will be
modified if the effects of trans-Planckian physics are incorporated into the
dynamics of the matter field in a phenomenological manner, say, by the
modification of the dispersion relation. The spectrum also changes if we retain
the standard dynamics but modify the initial quantum state of the matter field.
We show that, given {\it any} spectrum of perturbations, it is possible to
choose a class of initial quantum states which can exactly reproduce this
spectrum with the standard dynamics. We provide an explicit construction of the
quantum state which will produce the given spectrum. We find that the various
modified spectra that have been recently obtained from `trans-Planckian
considerations' can be constructed from suitable squeezed states above the
Bunch-Davies vacuum in the standard theory. Hence, the CMB observations can, at
most, be useful in determining the initial state of the matter field in the
standard theory, but it can {\it not} help us to discriminate between the
various Planck scale models of matter fields. We study the problem in the
Schrodinger picture, clarify various conceptual issues and determine the
criterion for negligible back reaction due to modified initial conditions.
| [
{
"created": "Thu, 12 Aug 2004 11:09:49 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Sriramkumar",
"L.",
""
],
[
"Padmanabhan",
"T.",
""
]
] | The standard, scale-invariant, inflationary perturbation spectrum will be modified if the effects of trans-Planckian physics are incorporated into the dynamics of the matter field in a phenomenological manner, say, by the modification of the dispersion relation. The spectrum also changes if we retain the standard dynamics but modify the initial quantum state of the matter field. We show that, given {\it any} spectrum of perturbations, it is possible to choose a class of initial quantum states which can exactly reproduce this spectrum with the standard dynamics. We provide an explicit construction of the quantum state which will produce the given spectrum. We find that the various modified spectra that have been recently obtained from `trans-Planckian considerations' can be constructed from suitable squeezed states above the Bunch-Davies vacuum in the standard theory. Hence, the CMB observations can, at most, be useful in determining the initial state of the matter field in the standard theory, but it can {\it not} help us to discriminate between the various Planck scale models of matter fields. We study the problem in the Schrodinger picture, clarify various conceptual issues and determine the criterion for negligible back reaction due to modified initial conditions. |
2309.06376 | Tuhina Ghorui | Tuhina Ghorui, Prabir Rudra, Farook Rahaman | Reconstruction of $f(T,\mathcal{T})$ Lagrangian for various cosmological
scenarios | 23 pages, 4 figures | Physics of the Dark Universe, 42 (2023) 101352 | 10.1016/j.dark.2023.101352 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we explore a reconstruction scheme in the background of the
$f(T,\mathcal{T})$ gravity theory for different cosmological scenarios, where
$T$ is the scalar torsion and $\mathcal{T}$ is the trace of the energy-momentum
tensor. Using the reconstruction technique $f(T, \mathcal{T})$ Lagrangian is
constructed for different cosmological eras such as dust, $\Lambda CDM$,
perfect fluid, etc. Both minimal and non-minimal matter-coupled models are
considered for this purpose. Different cosmological scenarios such as power law
expansion, de-Sitter expansion, etc. have been considered, and using them
Lagrangian functionals are constructed. Mathematical viabilities of all the
constructed functionals have been investigated. The physical implications of
the obtained solutions are discussed in detail. To check the cosmological
compatibility of the constructed $f(T,\mathcal{T})$ functionals we have
generated plots of important parameters like the equation of state parameter
and deceleration parameter. It is seen that the reconstructed models are
perfectly compatible with the late-time accelerated expansion of the universe.
| [
{
"created": "Sat, 9 Sep 2023 08:51:41 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Oct 2023 14:28:25 GMT",
"version": "v2"
}
] | 2023-10-17 | [
[
"Ghorui",
"Tuhina",
""
],
[
"Rudra",
"Prabir",
""
],
[
"Rahaman",
"Farook",
""
]
] | In this paper, we explore a reconstruction scheme in the background of the $f(T,\mathcal{T})$ gravity theory for different cosmological scenarios, where $T$ is the scalar torsion and $\mathcal{T}$ is the trace of the energy-momentum tensor. Using the reconstruction technique $f(T, \mathcal{T})$ Lagrangian is constructed for different cosmological eras such as dust, $\Lambda CDM$, perfect fluid, etc. Both minimal and non-minimal matter-coupled models are considered for this purpose. Different cosmological scenarios such as power law expansion, de-Sitter expansion, etc. have been considered, and using them Lagrangian functionals are constructed. Mathematical viabilities of all the constructed functionals have been investigated. The physical implications of the obtained solutions are discussed in detail. To check the cosmological compatibility of the constructed $f(T,\mathcal{T})$ functionals we have generated plots of important parameters like the equation of state parameter and deceleration parameter. It is seen that the reconstructed models are perfectly compatible with the late-time accelerated expansion of the universe. |
gr-qc/0603056 | Christian Koenigsdoerffer | Christian Koenigsdoerffer, Achamveedu Gopakumar | Phasing of gravitational waves from inspiralling eccentric binaries at
the third-and-a-half post-Newtonian order | 22 pages including 2 figures; submitted to PRD | Phys.Rev.D73:124012,2006 | 10.1103/PhysRevD.73.124012 | null | gr-qc astro-ph | null | We obtain an efficient description for the dynamics of nonspinning compact
binaries moving in inspiralling eccentric orbits to implement the phasing of
gravitational waves from such binaries at the 3.5 post-Newtonian (PN) order.
Our computation heavily depends on the phasing formalism, presented in [T.
Damour, A. Gopakumar, and B. R. Iyer, Phys. Rev. D \textbf{70}, 064028 (2004)],
and the 3PN accurate generalized quasi-Keplerian parametric solution to the
conservative dynamics of nonspinning compact binaries moving in eccentric
orbits, available in [R.-M. Memmesheimer, A. Gopakumar, and G. Sch\"afer, Phys.
Rev. D \textbf{70}, 104011 (2004)]. The gravitational-wave (GW) polarizations
$h_{+}$ and $h_{\times}$ with 3.5PN accurate phasing should be useful for the
earth-based GW interferometers, current and advanced, if they plan to search
for gravitational waves from inspiralling eccentric binaries. Our results will
be required to do \emph{astrophysics} with the proposed space-based GW
interferometers like LISA, BBO, and DECIGO.
| [
{
"created": "Tue, 14 Mar 2006 18:39:25 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Koenigsdoerffer",
"Christian",
""
],
[
"Gopakumar",
"Achamveedu",
""
]
] | We obtain an efficient description for the dynamics of nonspinning compact binaries moving in inspiralling eccentric orbits to implement the phasing of gravitational waves from such binaries at the 3.5 post-Newtonian (PN) order. Our computation heavily depends on the phasing formalism, presented in [T. Damour, A. Gopakumar, and B. R. Iyer, Phys. Rev. D \textbf{70}, 064028 (2004)], and the 3PN accurate generalized quasi-Keplerian parametric solution to the conservative dynamics of nonspinning compact binaries moving in eccentric orbits, available in [R.-M. Memmesheimer, A. Gopakumar, and G. Sch\"afer, Phys. Rev. D \textbf{70}, 104011 (2004)]. The gravitational-wave (GW) polarizations $h_{+}$ and $h_{\times}$ with 3.5PN accurate phasing should be useful for the earth-based GW interferometers, current and advanced, if they plan to search for gravitational waves from inspiralling eccentric binaries. Our results will be required to do \emph{astrophysics} with the proposed space-based GW interferometers like LISA, BBO, and DECIGO. |
gr-qc/0408074 | Daniel Green | Daniel Green and William G. Unruh | Difficulties with Recollapsing models in Closed Isotropic Loop Quantum
Cosmology | 10 pages, accepted to Phys. Rev. D | Phys.Rev. D70 (2004) 103502 | 10.1103/PhysRevD.70.103502 | null | gr-qc | null | The use of techniques from loop quantum gravity for cosmological models may
solve some difficult problems in quantum cosmology. The solutions under a
number of circumstances have been well studied. We will analyse the behaviour
of solutions in the closed model, focusing on the behaviour of a universe
containing a massless scalar field. The asymptotic behaviour of the solutions
is examined, and is used to determine requirements of the initial conditions.
| [
{
"created": "Sun, 22 Aug 2004 23:26:46 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Aug 2004 05:40:52 GMT",
"version": "v2"
},
{
"created": "Tue, 9 Nov 2004 18:17:39 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Green",
"Daniel",
""
],
[
"Unruh",
"William G.",
""
]
] | The use of techniques from loop quantum gravity for cosmological models may solve some difficult problems in quantum cosmology. The solutions under a number of circumstances have been well studied. We will analyse the behaviour of solutions in the closed model, focusing on the behaviour of a universe containing a massless scalar field. The asymptotic behaviour of the solutions is examined, and is used to determine requirements of the initial conditions. |
0902.2443 | Sunil Maharaj | S. D. Maharaj, S. Thirukkanesh | Some new static charged spheres | 14 pages, To appear in Nonlinear Analysis RWA | Nonlinear Analysis: RWA 10:3396-3403, 2009 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present new exact solutions for the Einstein-Maxwell system in static
spherically symmetric interior spacetimes. For a particular form of the
gravitational potentials and the electric field intensity, it is possible to
integrate the system in closed form. For specific parameter values it is
possible to find new exact models for the Einstein-Maxwell system in terms of
elementary functions. Our model includes a particular charged solution found
previously; this suggests that our generalised solution could be used to
describe a relativistic compact sphere. A physical analysis indicates that the
solutions describe realistic matter distributions.
| [
{
"created": "Sat, 14 Feb 2009 09:03:14 GMT",
"version": "v1"
}
] | 2009-10-16 | [
[
"Maharaj",
"S. D.",
""
],
[
"Thirukkanesh",
"S.",
""
]
] | We present new exact solutions for the Einstein-Maxwell system in static spherically symmetric interior spacetimes. For a particular form of the gravitational potentials and the electric field intensity, it is possible to integrate the system in closed form. For specific parameter values it is possible to find new exact models for the Einstein-Maxwell system in terms of elementary functions. Our model includes a particular charged solution found previously; this suggests that our generalised solution could be used to describe a relativistic compact sphere. A physical analysis indicates that the solutions describe realistic matter distributions. |
2402.00844 | Saulo Pereira H | A. M. Vicente, J. F. Jesus and S. H. Pereira | Kinematic reconstruction of torsion as dark energy in Friedmann
cosmology | 19 pages, 6 figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the effects of torsion of space-time in the expansion
of the universe as a candidate to dark energy. The analysis is done by
reconstructing the torsion function along cosmic evolution by using
observational data of Supernovae type Ia and Hubble parameter measurements. We
have used a kinematic model for the parameterization of the comoving distance
and the Hubble parameter, then the free parameters of the models are
constrained by observational data. The reconstruction of the torsion function
is obtained directly from the data, using the kinematic parameterizations, and
the values for the Hubble parameter and the deceleration parameter are in good
agreement to the standard model estimates.
| [
{
"created": "Thu, 1 Feb 2024 18:34:32 GMT",
"version": "v1"
}
] | 2024-02-02 | [
[
"Vicente",
"A. M.",
""
],
[
"Jesus",
"J. F.",
""
],
[
"Pereira",
"S. H.",
""
]
] | In this paper we study the effects of torsion of space-time in the expansion of the universe as a candidate to dark energy. The analysis is done by reconstructing the torsion function along cosmic evolution by using observational data of Supernovae type Ia and Hubble parameter measurements. We have used a kinematic model for the parameterization of the comoving distance and the Hubble parameter, then the free parameters of the models are constrained by observational data. The reconstruction of the torsion function is obtained directly from the data, using the kinematic parameterizations, and the values for the Hubble parameter and the deceleration parameter are in good agreement to the standard model estimates. |
0712.3934 | Gerhard Forst | G. Forst | A critical analysis of the GP-B mission. I: on the impossibility of a
reliable measurement of the gravitomagnetic precession of the GP-B gyroscopes | This submission has been removed because 'G. Forst' is an apparent
pseudonym, in violation of arXiv policies | null | null | null | gr-qc | null | This submission has been removed because 'G. Forst' is an apparent pseudonym,
in violation of arXiv policies.
| [
{
"created": "Sun, 23 Dec 2007 16:59:42 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jan 2008 19:42:51 GMT",
"version": "v2"
}
] | 2014-02-14 | [
[
"Forst",
"G.",
""
]
] | This submission has been removed because 'G. Forst' is an apparent pseudonym, in violation of arXiv policies. |
1407.1504 | Cristina Blaga | Cristina Blaga | Timelike geodesics around a charged spherically symmetric dilaton black
hole | 10 pages, 16 figures | Serb. Astron. J, vol. 190(2015), 41-48 | 10.2298/SAJ1590041B | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the timelike geodesics around a spherically symmetric
charged dilaton black hole. The trajectories around the black hole are
classified using the effective potential of a free test particle. This
qualitative approach enables us to determine the type of the orbit described by
the test particle without solving the equations of motion, if the parameters of
the black hole and the particle are known. The connections between these
parameters and the type of orbit described by the particle are obtained. To
visualize the orbits we solve numerically the equation of motions for different
values of the parameters envolved in our analysis. The effective potential of a
free test particle looks different for a non-extremal and an extremal black
hole, therefore we have examined separately these two types of black holes.
| [
{
"created": "Sun, 6 Jul 2014 14:53:55 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jul 2014 18:28:56 GMT",
"version": "v2"
},
{
"created": "Sun, 19 Jul 2015 14:46:04 GMT",
"version": "v3"
}
] | 2015-07-21 | [
[
"Blaga",
"Cristina",
""
]
] | In this paper we study the timelike geodesics around a spherically symmetric charged dilaton black hole. The trajectories around the black hole are classified using the effective potential of a free test particle. This qualitative approach enables us to determine the type of the orbit described by the test particle without solving the equations of motion, if the parameters of the black hole and the particle are known. The connections between these parameters and the type of orbit described by the particle are obtained. To visualize the orbits we solve numerically the equation of motions for different values of the parameters envolved in our analysis. The effective potential of a free test particle looks different for a non-extremal and an extremal black hole, therefore we have examined separately these two types of black holes. |
2010.04603 | Ibrahim G\"ull\"u | Ibrahim Gullu, S. Habib Mazharimousavi | Black Holes in Double-Logarithmic Nonlinear Electrodynamics | 10 pages, 2 figures | null | 10.1088/1402-4896/ac098f | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The electric and magnetic black hole solutions are found by coupling the
recently introduced nonlinear electrodynamics (NED) model, called "double
logharitmic nonlinear electrodynamics" with cosmological Einstein gravity. The
solutions become Reissner-Nordstrom (RN) black hole in the weak field limit and
asymptotically. The electric solution is expressed as an integral equation
while the magnetic black hole solution is expressed in terms of elementary
functions. Hence, the thermodynamic structure of the magnetic black hole
solution is analyzed by deriving the modified Smarr's formula and studying the
first law of thermodynamics. Moreover, its stability is investigated by
deriving the heat capacity.
| [
{
"created": "Fri, 9 Oct 2020 14:29:53 GMT",
"version": "v1"
}
] | 2021-08-11 | [
[
"Gullu",
"Ibrahim",
""
],
[
"Mazharimousavi",
"S. Habib",
""
]
] | The electric and magnetic black hole solutions are found by coupling the recently introduced nonlinear electrodynamics (NED) model, called "double logharitmic nonlinear electrodynamics" with cosmological Einstein gravity. The solutions become Reissner-Nordstrom (RN) black hole in the weak field limit and asymptotically. The electric solution is expressed as an integral equation while the magnetic black hole solution is expressed in terms of elementary functions. Hence, the thermodynamic structure of the magnetic black hole solution is analyzed by deriving the modified Smarr's formula and studying the first law of thermodynamics. Moreover, its stability is investigated by deriving the heat capacity. |
1712.10012 | Jorge L. Fuentes | Andrew J. Wren, Jorge L. Fuentes and Karim A. Malik | Gravitational waves in a flat radiation-matter universe including
anisotropic stress | 14 pages, 7 figures, 2 appendices. Mathematica notebook available
from Github TBA | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present novel analytical solutions for linear-order gravitational waves or
tensor perturbations in a flat Friedmann-Robertson-Walker universe containing
two perfect fluids, radiation and pressureless dust, and allowing for neutrino
anisotropic stress. One of the results is applicable to any sub-horizon
gravitational wave in such a universe. Another result is applicable to
gravitational waves of primordial origin, for example produced during
inflation, and works both before and after they cross the horizon. These
results improve on analytical approximations previously set out in the
literature. Comparison with numerical solutions shows that both these
approximations are accurate to within $1\%$, or better, for a wide range of
wave-numbers relevant for cosmology.
| [
{
"created": "Tue, 26 Dec 2017 21:15:21 GMT",
"version": "v1"
}
] | 2018-01-01 | [
[
"Wren",
"Andrew J.",
""
],
[
"Fuentes",
"Jorge L.",
""
],
[
"Malik",
"Karim A.",
""
]
] | We present novel analytical solutions for linear-order gravitational waves or tensor perturbations in a flat Friedmann-Robertson-Walker universe containing two perfect fluids, radiation and pressureless dust, and allowing for neutrino anisotropic stress. One of the results is applicable to any sub-horizon gravitational wave in such a universe. Another result is applicable to gravitational waves of primordial origin, for example produced during inflation, and works both before and after they cross the horizon. These results improve on analytical approximations previously set out in the literature. Comparison with numerical solutions shows that both these approximations are accurate to within $1\%$, or better, for a wide range of wave-numbers relevant for cosmology. |
gr-qc/9802032 | Wang Bin | Bin Wang, Ru-Keng Su, P.K.N.Yu and E.C.M.Young | Can nonextremal Reissner-Nordstrom black hole become extremal by
assimilating infalling charged particle and shell? | 6 pages, Latex version, accepted for publication on Phys.Rev.D | Phys.Rev. D57 (1998) 5284-5286 | 10.1103/PhysRevD.57.5284 | null | gr-qc | null | By using the gedanken experiments suggested by Bekenstein and Rosenzweig, we
have shown that nonextremal Reissner-Nordstrom black hole cannot turn into
extremal one by assimilating infalling charged particle and charged spherical
shell.
| [
{
"created": "Mon, 16 Feb 1998 01:21:24 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Wang",
"Bin",
""
],
[
"Su",
"Ru-Keng",
""
],
[
"Yu",
"P. K. N.",
""
],
[
"Young",
"E. C. M.",
""
]
] | By using the gedanken experiments suggested by Bekenstein and Rosenzweig, we have shown that nonextremal Reissner-Nordstrom black hole cannot turn into extremal one by assimilating infalling charged particle and charged spherical shell. |
2312.14258 | Francisco A. Brito | J. A. V. Campos, M. A. Anacleto, F. A. Brito, E. Passos | Absorption, scattering, quasinormal modes and shadow by canonical
acoustic black holes in Lorentz-violating background | Latex, 18 pages, 11 figures; version to appear in General Relativity
and Gravitation | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work, we study the scattering for a black hole described by
the canonical acoustic metric with Lorentz violation using asymptotic and
numerical methods. In this scenario, we also check the effects of quasinormal
modes and the acoustic shadow radius. In the eikonal limit the relationship
between the shadow radius and the real part of the quasinormal frequency is
preserved.
| [
{
"created": "Thu, 21 Dec 2023 19:19:57 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Jun 2024 03:06:29 GMT",
"version": "v2"
}
] | 2024-06-12 | [
[
"Campos",
"J. A. V.",
""
],
[
"Anacleto",
"M. A.",
""
],
[
"Brito",
"F. A.",
""
],
[
"Passos",
"E.",
""
]
] | In the present work, we study the scattering for a black hole described by the canonical acoustic metric with Lorentz violation using asymptotic and numerical methods. In this scenario, we also check the effects of quasinormal modes and the acoustic shadow radius. In the eikonal limit the relationship between the shadow radius and the real part of the quasinormal frequency is preserved. |
gr-qc/9903051 | Cenalo T. A. Vaz | Cenalo Vaz (Universidade do Algarve) | Canonical Quantization and the Statistical Entropy of the Schwarzschild
Black Hole | 21 pages, PHYZZX macros. The counting of physical states has been
corrected. Revised version to appear in Phys. Rev. D | Phys.Rev. D61 (2000) 064017 | 10.1103/PhysRevD.61.064017 | UATP-01/99 | gr-qc hep-th | null | The canonical quantization of a Schwarzschild black hole yields a picture of
the black hole that is shown to be equivalent to a collection of oscillators
whose density of levels is commensurate with that of the statistical bootstrap
model. Energy eigenstates of definite parity exhibit the Bekenstein mass
spectrum, $M \sim \sqrt{\cal N} M_p$, where ${\cal N} \in {\bf N}$. From the
microcanonical ensemble, we derive the statistical entropy of the black hole by
explicitly counting the microstates corresponding to a macrostate of fixed
total energy.
| [
{
"created": "Sat, 13 Mar 1999 22:32:42 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Sep 1999 11:44:21 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Vaz",
"Cenalo",
"",
"Universidade do Algarve"
]
] | The canonical quantization of a Schwarzschild black hole yields a picture of the black hole that is shown to be equivalent to a collection of oscillators whose density of levels is commensurate with that of the statistical bootstrap model. Energy eigenstates of definite parity exhibit the Bekenstein mass spectrum, $M \sim \sqrt{\cal N} M_p$, where ${\cal N} \in {\bf N}$. From the microcanonical ensemble, we derive the statistical entropy of the black hole by explicitly counting the microstates corresponding to a macrostate of fixed total energy. |
2107.08061 | Anzhong Wang | Shinji Tsujikawa, Chao Zhang, Xiang Zhao, and Anzhong Wang | Odd-parity stability of black holes in Einstein-Aether gravity | Revtex4-1, no tables and figures. The analysis of stability against
the inclined modes is added, and some typos are further corrected. Version to
appear in Phys. Rev. D | Phys. Rev. D 104, 064024 (2021) | 10.1103/PhysRevD.104.064024 | null | gr-qc astro-ph.GA hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | In Einstein-Aether theory, we study the stability of black holes against
odd-parity perturbations on a spherically symmetric and static background. For
odd-parity modes, there are two dynamical degrees of freedom arising from the
tensor gravitational sector and Aether vector field. We derive general
conditions under which neither ghosts nor Laplacian instabilities are present
for these dynamical fields. We apply these results to concrete black hole
solutions known in the literature and show that some of those solutions can be
excluded by the violation of stability conditions. The exact Schwarzschild
solution present for $c_{13} = c_{14} = 0$, where $c_i$'s are the four coupling
constants of the theory with $c_{ij}=c_i + c_j$, is prone to Laplacian
instabilities along the angular direction throughout the horizon exterior.
However, we find that the odd-parity instability of high radial and angular
momentum modes is absent for black hole solutions with $c_{13} = c_4 = 0$ and
$c_1 \geq 0$.
| [
{
"created": "Fri, 16 Jul 2021 18:03:16 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Aug 2021 15:28:50 GMT",
"version": "v2"
}
] | 2021-09-15 | [
[
"Tsujikawa",
"Shinji",
""
],
[
"Zhang",
"Chao",
""
],
[
"Zhao",
"Xiang",
""
],
[
"Wang",
"Anzhong",
""
]
] | In Einstein-Aether theory, we study the stability of black holes against odd-parity perturbations on a spherically symmetric and static background. For odd-parity modes, there are two dynamical degrees of freedom arising from the tensor gravitational sector and Aether vector field. We derive general conditions under which neither ghosts nor Laplacian instabilities are present for these dynamical fields. We apply these results to concrete black hole solutions known in the literature and show that some of those solutions can be excluded by the violation of stability conditions. The exact Schwarzschild solution present for $c_{13} = c_{14} = 0$, where $c_i$'s are the four coupling constants of the theory with $c_{ij}=c_i + c_j$, is prone to Laplacian instabilities along the angular direction throughout the horizon exterior. However, we find that the odd-parity instability of high radial and angular momentum modes is absent for black hole solutions with $c_{13} = c_4 = 0$ and $c_1 \geq 0$. |
gr-qc/9405024 | null | J.D. Brown and J.W. York | The Path Integral Formulation of Gravitational Thermodynamics | 24 pages, LaTeX. Revised version contains additional remarks in the
introduction and minor corrections | null | null | CTMP/007/NCSU, IFP-UNC-491, TAR-UNC-043 | gr-qc hep-th | null | The first objective of this article is to show that the black hole partition
function can be placed on a firm logical foundation by enclosing the black hole
in a spatially finite "box" or boundary. The presence of the box has the effect
of stabilizing the black hole and yields a system with a positive heat
capacity. The second objective of this article is to explore the origin of
black hole entropy. This is accomplished through the construction of a path
integral expression for the density matrix for the gravitational field, and
through an analysis of the connection between the density matrix and the black
hole density of states. Our results suggest that black hole entropy can be
associated with an absence of certain "inner boundary information" for the
system. (Based on the talk presented by J.D. Brown at the conference "The Black
Hole 25 Years After", Santiago, Chile, January 1994.)
| [
{
"created": "Mon, 9 May 1994 21:02:34 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Jan 1996 21:19:53 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Brown",
"J. D.",
""
],
[
"York",
"J. W.",
""
]
] | The first objective of this article is to show that the black hole partition function can be placed on a firm logical foundation by enclosing the black hole in a spatially finite "box" or boundary. The presence of the box has the effect of stabilizing the black hole and yields a system with a positive heat capacity. The second objective of this article is to explore the origin of black hole entropy. This is accomplished through the construction of a path integral expression for the density matrix for the gravitational field, and through an analysis of the connection between the density matrix and the black hole density of states. Our results suggest that black hole entropy can be associated with an absence of certain "inner boundary information" for the system. (Based on the talk presented by J.D. Brown at the conference "The Black Hole 25 Years After", Santiago, Chile, January 1994.) |
1411.7969 | Adrian Ciprian Sporea | Ciprian A. Sporea, Dumitru N. Vulcanov | Using Maple + GRTensorII in teaching basics of General Relativity and
Cosmology | 12 pages, 2 fig. To accepted for publication in Romanian Reports in
Physics (2016) | Rom. Rep. Phys. 68, 29 (2016) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we propose some Maple procedures, for teaching purposes, to
study the basics of General Relativity (GR) and Cosmology. After presenting
some features of GRTensorII, a package specially built to deal with GR, we give
two examples of how one can use these procedures. In the first example we build
the Schwarzschild solution of Einstein equations, while in the second one we
study some simple cosmological models.
| [
{
"created": "Fri, 28 Nov 2014 18:34:43 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Jan 2016 07:36:07 GMT",
"version": "v2"
}
] | 2016-04-15 | [
[
"Sporea",
"Ciprian A.",
""
],
[
"Vulcanov",
"Dumitru N.",
""
]
] | In this article we propose some Maple procedures, for teaching purposes, to study the basics of General Relativity (GR) and Cosmology. After presenting some features of GRTensorII, a package specially built to deal with GR, we give two examples of how one can use these procedures. In the first example we build the Schwarzschild solution of Einstein equations, while in the second one we study some simple cosmological models. |
gr-qc/0511106 | Chen Songbai | Songbai Chen, Jiliang Jing | Asymptotic quasinormal modes of a coupled scalar field in the
Gibbons-Maeda dilaton spacetime | 6 pages, 1 figure | Class.Quant.Grav. 22 (2005) 2159-2165 | 10.1088/0264-9381/22/11/016 | null | gr-qc | null | Adopting the monodromy technique devised by Motl and Neitzke, we investigate
analytically the asymptotic quasinormal frequencies of a coupled scalar field
in the Gibbons-Maeda dilaton spacetime. We find that it is described by $
e^{\beta \omega}=-[1+2\cos{(\frac{\sqrt{2\xi+1}}{2} \pi)}]-e^{-\beta_I
\omega}[2+2\cos{(\frac{\sqrt{2\xi+1}}{2}\pi)}]$, which depends on the structure
parameters of the background spacetime and on the coupling between the scalar
and gravitational fields. As the parameters $\xi$ and $\beta_I$ tend to zero,
the real parts of the asymptotic quasinormal frequencies becomes $T_H\ln{3}$,
which is consistent with Hod's conjecture. When $\xi={91/18} $, the formula
becomes that of the Reissner-Nordstr\"{o}m spacetime.
| [
{
"created": "Fri, 18 Nov 2005 05:37:59 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Chen",
"Songbai",
""
],
[
"Jing",
"Jiliang",
""
]
] | Adopting the monodromy technique devised by Motl and Neitzke, we investigate analytically the asymptotic quasinormal frequencies of a coupled scalar field in the Gibbons-Maeda dilaton spacetime. We find that it is described by $ e^{\beta \omega}=-[1+2\cos{(\frac{\sqrt{2\xi+1}}{2} \pi)}]-e^{-\beta_I \omega}[2+2\cos{(\frac{\sqrt{2\xi+1}}{2}\pi)}]$, which depends on the structure parameters of the background spacetime and on the coupling between the scalar and gravitational fields. As the parameters $\xi$ and $\beta_I$ tend to zero, the real parts of the asymptotic quasinormal frequencies becomes $T_H\ln{3}$, which is consistent with Hod's conjecture. When $\xi={91/18} $, the formula becomes that of the Reissner-Nordstr\"{o}m spacetime. |
2004.07988 | Andrea Addazi AndAdd | Andrea Addazi | Holographic Naturalness and Cosmological Relaxation | Comments rephrased, main conclusions and results unchanged | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We rediscuss the main Cosmological Problems as illusions originated from our
ignorance of the hidden information holographically stored in {\it vacuo}. The
Cosmological vacuum state is full of a large number of dynamical quantum hairs,
dubbed {\it hairons}, which dominate the Cosmological Entropy. We elaborate on
the Cosmological Constant (CC) problem, in both the dynamical and time-constant
possibilities. We show that all dangerous quantum mixings between the CC and
the Planck energy scales are exponentially suppressed as an entropic collective
effect of the hairon environment. As a consequence, the dark energy scale is UV
insensitive to any planckian corrections. On the other hand, the inflation
scale is similarly stabilized from any radiative effects. In the case of the
Dark energy, we show the presence of a holographic entropic attractor, favoring
a time variation of $\Lambda\rightarrow 0$ in future rather than a static CC
case; i.e. $w>-1$ Dynamical DE is favored over a CC or a $w<-1$ phantom
cosmology. In both the inflation and dark energy sectors, we elaborate on the
Trans-Planckian problem, in relation with the recently proposed Trans-Planckian
Censorship Conjecture (TCC). We show that the probability for any sub-planckian
wavelength modes to survive after inflation is completely negligible as a
holographic wash-out mechanism. In other words, the hairons provide for a
holographic decoherence of the transplanckian modes in a holographic scrambling
time. This avoids the TCC strong bounds on the Inflaton and DE potentials.
| [
{
"created": "Thu, 16 Apr 2020 23:00:32 GMT",
"version": "v1"
},
{
"created": "Mon, 25 May 2020 14:31:36 GMT",
"version": "v2"
}
] | 2020-05-26 | [
[
"Addazi",
"Andrea",
""
]
] | We rediscuss the main Cosmological Problems as illusions originated from our ignorance of the hidden information holographically stored in {\it vacuo}. The Cosmological vacuum state is full of a large number of dynamical quantum hairs, dubbed {\it hairons}, which dominate the Cosmological Entropy. We elaborate on the Cosmological Constant (CC) problem, in both the dynamical and time-constant possibilities. We show that all dangerous quantum mixings between the CC and the Planck energy scales are exponentially suppressed as an entropic collective effect of the hairon environment. As a consequence, the dark energy scale is UV insensitive to any planckian corrections. On the other hand, the inflation scale is similarly stabilized from any radiative effects. In the case of the Dark energy, we show the presence of a holographic entropic attractor, favoring a time variation of $\Lambda\rightarrow 0$ in future rather than a static CC case; i.e. $w>-1$ Dynamical DE is favored over a CC or a $w<-1$ phantom cosmology. In both the inflation and dark energy sectors, we elaborate on the Trans-Planckian problem, in relation with the recently proposed Trans-Planckian Censorship Conjecture (TCC). We show that the probability for any sub-planckian wavelength modes to survive after inflation is completely negligible as a holographic wash-out mechanism. In other words, the hairons provide for a holographic decoherence of the transplanckian modes in a holographic scrambling time. This avoids the TCC strong bounds on the Inflaton and DE potentials. |
0907.1936 | Elena Novikova Ph.D. | Elena I. Novikova and Igor D. Novikov | Homogeneous singularities inside collapsing wormholes | 10 pages, 5 figures each of which has a),b),c),and d) sub-figures. To
be published in "Physical review. D, Particles, fields, gravitation, and
cosmology" | Phys.Rev.D81:104034,2010 | 10.1103/PhysRevD.81.104034 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze analytically and numerically the origin of the singularity in the
course of the collapse of a wormhole with the exotic scalar field Psi with
negative energy density, and with this field Psi together with the ordered
magnetic field H. We do this under the simplifying assumptions of the spherical
symmetry and that in the vicinity of the singularity the solution of the
Einstein equations depends only on one coordinate (the homogeneous
approximation). In the framework of these assumptions we found the principal
difference between the case of the collapse of the ordinary scalar field Phi
with the positive energy density together with an ordered magnetic field H and
the collapse of the exotic scalar field Psi together with the magnetic field H.
The later case is important for the possible astrophysical manifestation of the
wormholes.
| [
{
"created": "Sat, 11 Jul 2009 03:58:07 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Jul 2009 02:23:45 GMT",
"version": "v2"
},
{
"created": "Mon, 31 Aug 2009 23:18:14 GMT",
"version": "v3"
}
] | 2014-11-20 | [
[
"Novikova",
"Elena I.",
""
],
[
"Novikov",
"Igor D.",
""
]
] | We analyze analytically and numerically the origin of the singularity in the course of the collapse of a wormhole with the exotic scalar field Psi with negative energy density, and with this field Psi together with the ordered magnetic field H. We do this under the simplifying assumptions of the spherical symmetry and that in the vicinity of the singularity the solution of the Einstein equations depends only on one coordinate (the homogeneous approximation). In the framework of these assumptions we found the principal difference between the case of the collapse of the ordinary scalar field Phi with the positive energy density together with an ordered magnetic field H and the collapse of the exotic scalar field Psi together with the magnetic field H. The later case is important for the possible astrophysical manifestation of the wormholes. |
1005.4735 | Bernard Schutz | Bernard F Schutz and Franco Ricci | Gravitational Waves, Sources, and Detectors | 82 pages, 9 figures, lecture notes from 1999, not posted to ArXiV at
the time because they exceeded the article/figure size limits | Schutz, B. F.; Ricci, F.: Gravitational Waves, Sources and
Detectors. In: Gravitational Waves, Ciufolini, I, et al, eds. (Institute of
Physics, Bristol, 2001) | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Notes of lectures for graduate students that were given at Lake Como in 1999,
covering the theory of linearized gravitational waves, their sources, and the
prospects at the time for detecting gravitational waves. The lectures remain of
interest for pedagogical reasons, and in particular because they contain a
treatment of current-quadrupole gravitational radiation (in connection with the
r-modes of neutron stars) that is not readily available in other sources.
| [
{
"created": "Wed, 26 May 2010 05:37:57 GMT",
"version": "v1"
}
] | 2010-05-27 | [
[
"Schutz",
"Bernard F",
""
],
[
"Ricci",
"Franco",
""
]
] | Notes of lectures for graduate students that were given at Lake Como in 1999, covering the theory of linearized gravitational waves, their sources, and the prospects at the time for detecting gravitational waves. The lectures remain of interest for pedagogical reasons, and in particular because they contain a treatment of current-quadrupole gravitational radiation (in connection with the r-modes of neutron stars) that is not readily available in other sources. |
gr-qc/0105053 | A. Latif Choudhury | A. L. Choudhury and Hemant Pendharkar | Wormhole-generated physical universe | 9 pages | Hadronic J. 24 (2001) 275-290 | null | null | gr-qc | null | We constructed a model where the central core of the universe is a modified
Gidding-Strominger wormhole and surrounding the core is a Robertson-Walker
Universe with k=0. They are separated by a thin wall which does not allow the
content of the inner core to travel to the outer universe. But this wall allows
the pressure of the inner core to be transferred to the outer physical
universe. Assuming that the fluid density of the physical universe is
practically independent of time, we have calculated the Hubble constant and the
deacceleration parameter, qo, of the physical universe at the present time. The
Hubble constant comes out to be positive, whereas qo becomes negative. The
negative signature of this deacceleration parameter conforms to present
experimental data.
| [
{
"created": "Tue, 15 May 2001 20:55:21 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Choudhury",
"A. L.",
""
],
[
"Pendharkar",
"Hemant",
""
]
] | We constructed a model where the central core of the universe is a modified Gidding-Strominger wormhole and surrounding the core is a Robertson-Walker Universe with k=0. They are separated by a thin wall which does not allow the content of the inner core to travel to the outer universe. But this wall allows the pressure of the inner core to be transferred to the outer physical universe. Assuming that the fluid density of the physical universe is practically independent of time, we have calculated the Hubble constant and the deacceleration parameter, qo, of the physical universe at the present time. The Hubble constant comes out to be positive, whereas qo becomes negative. The negative signature of this deacceleration parameter conforms to present experimental data. |
1908.09293 | Matti Raasakka | Matti Raasakka | Spacetime granularity from finite-dimensionality of local observable
algebras | 16 pages; changes to v3: title modified, multiple references added,
minor changes to the text | Class. Quantum Grav. 37, 045014 (2020) | 10.1088/1361-6382/ab5eb0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There are important indications that nature may be locally
finite-dimensional, i.e., that any spatially bounded subsystem can be described
by a finite-dimensional local observable algebra. Motivated by these ideas, we
show that operational spacetime topology is described by an atomistic Boolean
algebra if (i) local observable algebras are finite-dimensional factors, (ii)
the intersection of two local algebras is also local, and (iii) the commutant
of a local algebra is also local. Thus, in this case, spacetime has a
point-free granular behavior at small scales.
| [
{
"created": "Sun, 25 Aug 2019 10:02:30 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Sep 2019 09:09:03 GMT",
"version": "v2"
},
{
"created": "Mon, 25 Nov 2019 20:49:41 GMT",
"version": "v3"
}
] | 2020-01-28 | [
[
"Raasakka",
"Matti",
""
]
] | There are important indications that nature may be locally finite-dimensional, i.e., that any spatially bounded subsystem can be described by a finite-dimensional local observable algebra. Motivated by these ideas, we show that operational spacetime topology is described by an atomistic Boolean algebra if (i) local observable algebras are finite-dimensional factors, (ii) the intersection of two local algebras is also local, and (iii) the commutant of a local algebra is also local. Thus, in this case, spacetime has a point-free granular behavior at small scales. |
1711.00479 | Carlos Molina Mendes | A. F. Cardona and C. Molina | Quasinormal modes of generalized P\"oschl-Teller potentials | 14 pages, 2 figures. Accepted for publication in Classical and
Quantum Gravity | Class. Quantum Grav. 34 (2017) 245002 | 10.1088/1361-6382/aa9428 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using algebraic techniques we obtain quasinormal modes and frequencies
associated to generalized forms of the scattering P\"oschl-Teller potential.
This approach is based on the association of the corresponding equations of
motion with Casimir invariants of differential representations of the Lie
algebra sl(2). In the presented development, highest weight representations are
constructed and fundamental states are calculated. An infinite tower of
quasinormal mode solutions is obtained by the action of a lowering operator.
The algebraic results are used in the analysis of the Cauchy initial value
problem associated to the generalized P\"oschl-Teller potentials. For the
scattering potentials considered, there are no late-time tails and the dynamics
is always stable.
| [
{
"created": "Wed, 1 Nov 2017 18:00:07 GMT",
"version": "v1"
}
] | 2017-11-21 | [
[
"Cardona",
"A. F.",
""
],
[
"Molina",
"C.",
""
]
] | Using algebraic techniques we obtain quasinormal modes and frequencies associated to generalized forms of the scattering P\"oschl-Teller potential. This approach is based on the association of the corresponding equations of motion with Casimir invariants of differential representations of the Lie algebra sl(2). In the presented development, highest weight representations are constructed and fundamental states are calculated. An infinite tower of quasinormal mode solutions is obtained by the action of a lowering operator. The algebraic results are used in the analysis of the Cauchy initial value problem associated to the generalized P\"oschl-Teller potentials. For the scattering potentials considered, there are no late-time tails and the dynamics is always stable. |
2003.09227 | Bobir Toshmatov | Bobir Toshmatov, Ozodbek Rahimov, Bobomurat Ahmedov, Daniele
Malafarina | Motion of spinning particles in non asymptotically flat spacetimes | 10 pages, 5 figures, 4 tables | Eur. Phys. J. C, 80 (2020) 675 | 10.1140/epjc/s10052-020-8254-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The assumption of asymptotic flatness for isolated astrophysical bodies may
be considered an approximation when one considers a cosmological context where
a cosmological constant or vacuum energy is present. In this framework we study
the motion of spinning particles in static, spherically symmetric and
asymptotically non-flat spacetimes with repulsive cosmological vacuum energy
and quintessential field. Due to the combined effects of gravitational
attraction and cosmological repulsion, the region where stable circular orbits
are allowed is restricted by an innermost and an outermost stable circular
orbits. We show that taking into account the spin of test particles may enlarge
or shrink the region of allowed stable circular orbits depending on whether the
spin is co-rotating or counter-rotating with the angular momentum of the
particles.
| [
{
"created": "Fri, 20 Mar 2020 12:35:57 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Jul 2020 09:01:48 GMT",
"version": "v2"
}
] | 2020-07-29 | [
[
"Toshmatov",
"Bobir",
""
],
[
"Rahimov",
"Ozodbek",
""
],
[
"Ahmedov",
"Bobomurat",
""
],
[
"Malafarina",
"Daniele",
""
]
] | The assumption of asymptotic flatness for isolated astrophysical bodies may be considered an approximation when one considers a cosmological context where a cosmological constant or vacuum energy is present. In this framework we study the motion of spinning particles in static, spherically symmetric and asymptotically non-flat spacetimes with repulsive cosmological vacuum energy and quintessential field. Due to the combined effects of gravitational attraction and cosmological repulsion, the region where stable circular orbits are allowed is restricted by an innermost and an outermost stable circular orbits. We show that taking into account the spin of test particles may enlarge or shrink the region of allowed stable circular orbits depending on whether the spin is co-rotating or counter-rotating with the angular momentum of the particles. |
gr-qc/0310076 | Graham Hall | G.S. Hall and D.P. Lonie | Holonomy groups and spacetimes | Latex, 14 pages, no figure | Class.Quant.Grav.17:1369-1382,2000 | 10.1088/0264-9381/17/6/304 | null | gr-qc | null | A study is made of the possible holonomy group types of a space-time for
which the energy-momentum tensor corresponds to a null or non-null
electromagnetic field, a perfect fluid or a massive scalar field. The case of
an Einstein space is also included. The techniques developed are also applied
to vacuum and conformally flat space-times and contrasted with already known
results in these two cases. Examples are given.
| [
{
"created": "Wed, 15 Oct 2003 09:21:05 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Hall",
"G. S.",
""
],
[
"Lonie",
"D. P.",
""
]
] | A study is made of the possible holonomy group types of a space-time for which the energy-momentum tensor corresponds to a null or non-null electromagnetic field, a perfect fluid or a massive scalar field. The case of an Einstein space is also included. The techniques developed are also applied to vacuum and conformally flat space-times and contrasted with already known results in these two cases. Examples are given. |
1505.00744 | Ifra Noureen | M. Zubair, Ifra Noureen | Evolution of Axially Symmetric Anisotropic Sources in $f(R,T)$ Gravity | 19 pages | Eur. Phys. J. C (2015) 75:265 | 10.1140/epjc/s10052-015-3496-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the dynamical analysis in $f(R,T)$ gravity (where $R$ is Ricci
scalar and $T$ is trace of energy momentum tensor) for gravitating sources
carrying axial symmetry. The self gravitating system is taken to be anisotropic
and line element describes axially symmetric geometry avoiding rotation about
symmetry axis and meridional motions (zero vorticity case). The modified field
equations for axial symmetry in $f(R,T)$ theory are formulated, together with
the dynamical equations. Linearly perturbed dynamical equations lead to the
evolution equation carrying adiabatic index $\Gamma$ that defines impact of
non-minimal matter to geometry coupling on range of instability for Newtonian
(N) and post-Newtonian (pN) approximations.
| [
{
"created": "Thu, 30 Apr 2015 07:02:59 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Zubair",
"M.",
""
],
[
"Noureen",
"Ifra",
""
]
] | We discuss the dynamical analysis in $f(R,T)$ gravity (where $R$ is Ricci scalar and $T$ is trace of energy momentum tensor) for gravitating sources carrying axial symmetry. The self gravitating system is taken to be anisotropic and line element describes axially symmetric geometry avoiding rotation about symmetry axis and meridional motions (zero vorticity case). The modified field equations for axial symmetry in $f(R,T)$ theory are formulated, together with the dynamical equations. Linearly perturbed dynamical equations lead to the evolution equation carrying adiabatic index $\Gamma$ that defines impact of non-minimal matter to geometry coupling on range of instability for Newtonian (N) and post-Newtonian (pN) approximations. |
0902.3004 | Slava G. Turyshev | Slava G. Turyshev, Thomas W. Murphy, Jr., Eric G. Adelberger, James
Battat, Douglas Currie, William M. Folkner, Jens Gundlach, Stephen M.
Merkowitz, Kenneth L. Nordtvedt, Robert D. Reasenberg, Irwin I. Shapiro,
Michael Shao, Christopher W. Stubbs, Massimo Tinto, James G. Williams, and
Nan Yu | Opportunities for Probing Fundamental Gravity with Solar System
Experiments | 8 pages, LaTeX, Astro2010 Science White Paper | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent discovery of "dark energy" has challenged Einstein's general
theory of relativity as a complete model for our macroscopic universe. From a
theoretical view, the challenge is even stronger: general relativity clearly
does not extend to the very small, where quantum mechanics holds sway.
Fundamental physics models thus require some major revisions. We must explore
deeper to both constrain and inspire this needed new physics. In the realm of
the solar-system, we can effectively probe for small deviations from the
predictions of general relativity: Technology now offers a wide range of
opportunities to pursue experiments with accuracies orders of magnitude better
than yet achieved. We describe both the relevant theoretical backgrounds and
the opportunities for far more accurate solar system experiments.
| [
{
"created": "Tue, 17 Feb 2009 21:17:46 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Feb 2009 00:07:43 GMT",
"version": "v2"
}
] | 2012-08-27 | [
[
"Turyshev",
"Slava G.",
""
],
[
"Murphy,",
"Thomas W.",
"Jr."
],
[
"Adelberger",
"Eric G.",
""
],
[
"Battat",
"James",
""
],
[
"Currie",
"Douglas",
""
],
[
"Folkner",
"William M.",
""
],
[
"Gundlach",
"Jens",
""
],
[
"Merkowitz",
"Stephen M.",
""
],
[
"Nordtvedt",
"Kenneth L.",
""
],
[
"Reasenberg",
"Robert D.",
""
],
[
"Shapiro",
"Irwin I.",
""
],
[
"Shao",
"Michael",
""
],
[
"Stubbs",
"Christopher W.",
""
],
[
"Tinto",
"Massimo",
""
],
[
"Williams",
"James G.",
""
],
[
"Yu",
"Nan",
""
]
] | The recent discovery of "dark energy" has challenged Einstein's general theory of relativity as a complete model for our macroscopic universe. From a theoretical view, the challenge is even stronger: general relativity clearly does not extend to the very small, where quantum mechanics holds sway. Fundamental physics models thus require some major revisions. We must explore deeper to both constrain and inspire this needed new physics. In the realm of the solar-system, we can effectively probe for small deviations from the predictions of general relativity: Technology now offers a wide range of opportunities to pursue experiments with accuracies orders of magnitude better than yet achieved. We describe both the relevant theoretical backgrounds and the opportunities for far more accurate solar system experiments. |
1504.07782 | Anja Marunovic | Dra\v{z}en Glavan, Anja Marunovi\'c and Tomislav Prokopec | Inflation from cosmological constant and nonminimally coupled scalar | 19 pages, 13 figures | Phys. Rev. D 92, 044008 (2015) | 10.1103/PhysRevD.92.044008 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider inflation in a universe with a positive cosmological constant and
a nonminimally coupled scalar field, in which the field couples both
quadratically and quartically to the Ricci scalar. When considered in the
Einstein frame and when the nonminimal couplings are negative, the field starts
in slow roll and inflation ends with an asymptotic value of the principal slow
roll parameter, $\epsilon_E=4/3$. Graceful exit can be achieved by suitably
(tightly) coupling the scalar field to matter, such that at late time the total
energy density reaches the scaling of matter, $\epsilon_E=\epsilon_m$. Quite
generically the model produces a red spectrum of scalar cosmological
perturbations and a small amount of gravitational radiation. With a suitable
choice of the nonminimal couplings, the spectral slope can be as large as
$n_s\simeq 0.955$, which is about one standard deviation away from the central
value measured by the Planck satellite. The model can be ruled out by future
measurements if any of the following is observed: (a) the spectral index of
scalar perturbations is $n_s>0.960$; (b) the amplitude of tensor perturbations
is above about $r\sim 10^{-2}$; (c) the running of the spectral index of scalar
perturbations is positive.
| [
{
"created": "Wed, 29 Apr 2015 09:23:18 GMT",
"version": "v1"
}
] | 2015-08-21 | [
[
"Glavan",
"Dražen",
""
],
[
"Marunović",
"Anja",
""
],
[
"Prokopec",
"Tomislav",
""
]
] | We consider inflation in a universe with a positive cosmological constant and a nonminimally coupled scalar field, in which the field couples both quadratically and quartically to the Ricci scalar. When considered in the Einstein frame and when the nonminimal couplings are negative, the field starts in slow roll and inflation ends with an asymptotic value of the principal slow roll parameter, $\epsilon_E=4/3$. Graceful exit can be achieved by suitably (tightly) coupling the scalar field to matter, such that at late time the total energy density reaches the scaling of matter, $\epsilon_E=\epsilon_m$. Quite generically the model produces a red spectrum of scalar cosmological perturbations and a small amount of gravitational radiation. With a suitable choice of the nonminimal couplings, the spectral slope can be as large as $n_s\simeq 0.955$, which is about one standard deviation away from the central value measured by the Planck satellite. The model can be ruled out by future measurements if any of the following is observed: (a) the spectral index of scalar perturbations is $n_s>0.960$; (b) the amplitude of tensor perturbations is above about $r\sim 10^{-2}$; (c) the running of the spectral index of scalar perturbations is positive. |
gr-qc/9603035 | Saha Bijan | R. Alvarado, Yu. P. Rybakov, B. Saha and G. N. Shikin | Exact Self-consistent Solutions to the Interacting Spinor and Scalar
Field Equations in Bianchi Type-I Space-time | LaTeX, 10 pages | Russ.Phys.J. 38 (1995) 700-705; Izv.Vuz.Fiz. 38N7 (1995) 53-58 | null | JINR Preprint E2-95-16 | gr-qc | null | Self-consistent solutions to the system of spinor and scalar field equations
in General Relativity are studied for the case of Bianchi type-I space-time. It
should be emphasized the absence of initial singularity for some types of
solutions and also the isotropic mode of space-time in some special case.
| [
{
"created": "Fri, 22 Mar 1996 13:54:31 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Alvarado",
"R.",
""
],
[
"Rybakov",
"Yu. P.",
""
],
[
"Saha",
"B.",
""
],
[
"Shikin",
"G. N.",
""
]
] | Self-consistent solutions to the system of spinor and scalar field equations in General Relativity are studied for the case of Bianchi type-I space-time. It should be emphasized the absence of initial singularity for some types of solutions and also the isotropic mode of space-time in some special case. |
0710.4898 | Alicia M. Sintes | Alicia M. Sintes (for the LIGO Scientific Collaboration) | Report on an all-sky LIGO search for periodic gravitational waves in the
S4 data | 5 pages, 1 figure, presented at Amaldi7, Sydney (July 2007) | J.Phys.Conf.Ser.122:012033,2008 | 10.1088/1742-6596/122/1/012033 | LIGO-P070121 | gr-qc | null | We report on an all-sky search with the LIGO detectors for periodic
gravitational waves in the frequency range 50-1000 Hz and having a negative
frequency time derivative with magnitude between zero and $10^{-8}$ Hz/s. Data
from the fourth LIGO science run have been used in this search. Three different
semi-coherent methods of summing strain power were applied. Observing no
evidence for periodic gravitational radiation, we report upper limits on strain
amplitude and interpret these limits to constrain radiation from rotating
neutron stars.
| [
{
"created": "Thu, 25 Oct 2007 15:39:44 GMT",
"version": "v1"
}
] | 2019-08-13 | [
[
"Sintes",
"Alicia M.",
"",
"for the LIGO Scientific Collaboration"
]
] | We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50-1000 Hz and having a negative frequency time derivative with magnitude between zero and $10^{-8}$ Hz/s. Data from the fourth LIGO science run have been used in this search. Three different semi-coherent methods of summing strain power were applied. Observing no evidence for periodic gravitational radiation, we report upper limits on strain amplitude and interpret these limits to constrain radiation from rotating neutron stars. |
gr-qc/0201094 | Reza Tavakol | W.B.Bonnor | Classical gravitational spin-spin interaction | six pages, no figures, journal ref:accepted for Classical and Quantum
Gravity | null | 10.1088/0264-9381/19/1/308 | null | gr-qc | null | I obtain an exact, axially symmetric, stationary solution of Einstein's
equations for two massless spinning particles. The term representing the
spin-spin interaction agrees with recently published approximate work. The
spin-spin force appears to be proportional to the inverse fourth power of the
coordinate distance between the particles.
| [
{
"created": "Wed, 30 Jan 2002 12:11:50 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Bonnor",
"W. B.",
""
]
] | I obtain an exact, axially symmetric, stationary solution of Einstein's equations for two massless spinning particles. The term representing the spin-spin interaction agrees with recently published approximate work. The spin-spin force appears to be proportional to the inverse fourth power of the coordinate distance between the particles. |
1905.03408 | Carlos Rodriguez Benites | Carlos Rodriguez-Benites, Mauricio Cataldo, Antonella Cid and Carlos
R\'ios | Modelling the current accelerated expansion of the Universe with
Holographic Dark Energy | 5 pages, 1 figure, XXI Simposio Chileno de F\'isica | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we explore a Holographic Dark Energy Model in a flat
Friedmann-Lema\^itre-Robertson-Walker Universe, which contains baryons,
radiation, cold dark matter and dark energy within the framework of General
Relativity. Furthermore, we consider three types of phenomenological
interactions in the dark sector. With the proposed model we obtained the
algebraic expressions for the cosmological parameters of our interest: the
deceleration and coincidence parameters. Likewise, we graphically compare the
proposed model with the $\Lambda$CDM model.
| [
{
"created": "Thu, 9 May 2019 02:05:40 GMT",
"version": "v1"
}
] | 2019-05-10 | [
[
"Rodriguez-Benites",
"Carlos",
""
],
[
"Cataldo",
"Mauricio",
""
],
[
"Cid",
"Antonella",
""
],
[
"Ríos",
"Carlos",
""
]
] | In this work we explore a Holographic Dark Energy Model in a flat Friedmann-Lema\^itre-Robertson-Walker Universe, which contains baryons, radiation, cold dark matter and dark energy within the framework of General Relativity. Furthermore, we consider three types of phenomenological interactions in the dark sector. With the proposed model we obtained the algebraic expressions for the cosmological parameters of our interest: the deceleration and coincidence parameters. Likewise, we graphically compare the proposed model with the $\Lambda$CDM model. |
1910.07256 | Sebastian Schuster | Sebastian Schuster (Victoria University of Wellington) | Sparsity of Hawking Radiation in $D+1$ Space-Time Dimensions Including
Particle Masses | 6 pages, 2 figures | Class.Quant.Grav. 38 (2021) 4, 047002 | 10.1088/1361-6382/abd144 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hawking radiation from an evaporating black hole has often been compared to
black body radiation. However, this comparison misses an important feature of
Hawking radiation: Its low density of states. This can be captured in an easy
to calculate, heuristic, and semi-analytic measure called "sparsity". In this
letter we shall present both the concept of sparsities and its application to
$D+1$-dimensional Tangherlini black holes and their evaporation. In particular,
we shall also publish for the first time sparsity expressions taking into
account in closed form effects of non-zero particle mass. We will also see how
this comparatively simple method reproduces results of (massless) Hawking
radiation in higher dimensions and how different spins contribute to the total
radiation in this context.
| [
{
"created": "Wed, 16 Oct 2019 10:00:53 GMT",
"version": "v1"
}
] | 2021-02-17 | [
[
"Schuster",
"Sebastian",
"",
"Victoria University of Wellington"
]
] | Hawking radiation from an evaporating black hole has often been compared to black body radiation. However, this comparison misses an important feature of Hawking radiation: Its low density of states. This can be captured in an easy to calculate, heuristic, and semi-analytic measure called "sparsity". In this letter we shall present both the concept of sparsities and its application to $D+1$-dimensional Tangherlini black holes and their evaporation. In particular, we shall also publish for the first time sparsity expressions taking into account in closed form effects of non-zero particle mass. We will also see how this comparatively simple method reproduces results of (massless) Hawking radiation in higher dimensions and how different spins contribute to the total radiation in this context. |
2207.08571 | Andronikos Paliathanasis | Genly Leon and Andronikos Paliathanasis | Anisotropic spacetimes in $f(T,B)$ theory III: LRS Bianchi III Universe | 14 pages, 2 figures | null | null | null | gr-qc astro-ph.CO math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | We study the asymptotic dynamics of $f(T, B)$-theory in an anisotropic
Bianchi III background geometry. We show that an attractor always exists for
the field equations, which depends on a free parameter provided by the specific
$f(T, B)$ functional form. The attractor is an accelerated spatially flat FLRW
or non-accelerated LRS Bianchi III geometry. Consequently, the $f(T, B)$-theory
provides a spatially flat and isotropic accelerated Universe.
| [
{
"created": "Mon, 18 Jul 2022 12:56:54 GMT",
"version": "v1"
}
] | 2022-07-19 | [
[
"Leon",
"Genly",
""
],
[
"Paliathanasis",
"Andronikos",
""
]
] | We study the asymptotic dynamics of $f(T, B)$-theory in an anisotropic Bianchi III background geometry. We show that an attractor always exists for the field equations, which depends on a free parameter provided by the specific $f(T, B)$ functional form. The attractor is an accelerated spatially flat FLRW or non-accelerated LRS Bianchi III geometry. Consequently, the $f(T, B)$-theory provides a spatially flat and isotropic accelerated Universe. |
0904.0067 | Hongsheng Zhang | Hongsheng Zhang and Hyerim Noh | Braneworld cosmology in the sourced-Taub background | 10 pages, 3 figures, v2: a section to review the previous results on
the source of Taub space added, PLB in press | Phys.Lett.B679:81-87,2009 | 10.1016/j.physletb.2009.07.021 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new braneworld in the sourced-Taub background is proposed. The gravity
field equations in the internal source region and external vacuum region are
investigated, respectively. We find that the equation of state for the
effective dark energy of a dust brane in the source region can cross the
phantom divide $w=-1$. Furthermore, there is a drop on $H(z)$ diagram, which
presents a possible mechanism for the recent direct data of $H(z)$.
| [
{
"created": "Wed, 1 Apr 2009 06:12:27 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jul 2009 05:13:46 GMT",
"version": "v2"
}
] | 2010-03-12 | [
[
"Zhang",
"Hongsheng",
""
],
[
"Noh",
"Hyerim",
""
]
] | A new braneworld in the sourced-Taub background is proposed. The gravity field equations in the internal source region and external vacuum region are investigated, respectively. We find that the equation of state for the effective dark energy of a dust brane in the source region can cross the phantom divide $w=-1$. Furthermore, there is a drop on $H(z)$ diagram, which presents a possible mechanism for the recent direct data of $H(z)$. |
2210.04668 | N. Merve Uzun | Ozgur Akarsu, A. Kazim Camlibel, Nihan Katirci, Ibrahim Semiz, N.
Merve Uzun | Weak field and slow motion limits in energy-momentum powered gravity | 13 pages, no figures and tables; matches the version published in
Physics of the Dark Universe | Phys. Dark Univ. 42, 101305 (2023) | 10.1016/j.dark.2023.101305 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the weak field and slow motion limits, Newtonian and
Post-Newtonian limits, of the energy-momentum powered gravity (EMPG), viz., the
energy-momentum squared gravity (EMSG) of the form
$f(T_{\mu\nu}T^{\mu\nu})=\alpha (T_{\mu\nu}T^{\mu\nu})^{\eta}$ with $\alpha$
and $\eta$ being constants. We have shown that EMPG with $\eta\geq0$ and
general relativity (GR) are not distinguishable by local tests, say, the Solar
System tests; as they lead to the same gravitational potential form, PPN
parameters, and geodesics for the test particles. However, within the EMPG
framework, $M_{\rm ast}$, the mass of an astrophysical object inferred from
astronomical observations such as planetary orbits and deflection of light,
corresponds to the effective mass $M_{\rm eff}(\alpha,\eta,M)=M+M_{\rm
empg}(\alpha,\eta,M)$, $M$ being the actual physical mass and $M_{\rm empg}$
being the modification due to EMPG. Accordingly, while in GR we simply have the
relation $M_{\rm ast}=M$, in EMPG we have $M_{\rm ast}=M+M_{\rm empg}$. Within
the framework of EMPG, if there is information about the values of
$\{\alpha,\eta\}$ pair or $M$ from other independent phenomena (from
cosmological observations, structure of the astrophysical object, etc.), then
in principle it is possible to infer not only $M_{\rm ast}$ alone from
astronomical observations, but $M$ and $M_{\rm empg}$ separately. For a proper
analysis within EMPG framework, it is necessary to describe the slow motion
condition (also related to the Newtonian limit approximation) by $|p_{\rm
eff}/\rho_{\rm eff}|\ll1$ (where $p_{\rm eff}=p+p_{\rm empg}$ and $\rho_{\rm
eff}=\rho+\rho_{\rm empg}$), whereas this condition leads to $|p/\rho|\ll1$ in
GR.
| [
{
"created": "Mon, 10 Oct 2022 13:15:50 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Aug 2023 20:12:39 GMT",
"version": "v2"
}
] | 2023-08-21 | [
[
"Akarsu",
"Ozgur",
""
],
[
"Camlibel",
"A. Kazim",
""
],
[
"Katirci",
"Nihan",
""
],
[
"Semiz",
"Ibrahim",
""
],
[
"Uzun",
"N. Merve",
""
]
] | We explore the weak field and slow motion limits, Newtonian and Post-Newtonian limits, of the energy-momentum powered gravity (EMPG), viz., the energy-momentum squared gravity (EMSG) of the form $f(T_{\mu\nu}T^{\mu\nu})=\alpha (T_{\mu\nu}T^{\mu\nu})^{\eta}$ with $\alpha$ and $\eta$ being constants. We have shown that EMPG with $\eta\geq0$ and general relativity (GR) are not distinguishable by local tests, say, the Solar System tests; as they lead to the same gravitational potential form, PPN parameters, and geodesics for the test particles. However, within the EMPG framework, $M_{\rm ast}$, the mass of an astrophysical object inferred from astronomical observations such as planetary orbits and deflection of light, corresponds to the effective mass $M_{\rm eff}(\alpha,\eta,M)=M+M_{\rm empg}(\alpha,\eta,M)$, $M$ being the actual physical mass and $M_{\rm empg}$ being the modification due to EMPG. Accordingly, while in GR we simply have the relation $M_{\rm ast}=M$, in EMPG we have $M_{\rm ast}=M+M_{\rm empg}$. Within the framework of EMPG, if there is information about the values of $\{\alpha,\eta\}$ pair or $M$ from other independent phenomena (from cosmological observations, structure of the astrophysical object, etc.), then in principle it is possible to infer not only $M_{\rm ast}$ alone from astronomical observations, but $M$ and $M_{\rm empg}$ separately. For a proper analysis within EMPG framework, it is necessary to describe the slow motion condition (also related to the Newtonian limit approximation) by $|p_{\rm eff}/\rho_{\rm eff}|\ll1$ (where $p_{\rm eff}=p+p_{\rm empg}$ and $\rho_{\rm eff}=\rho+\rho_{\rm empg}$), whereas this condition leads to $|p/\rho|\ll1$ in GR. |
1612.00353 | Martin Bojowald | Martin Bojowald and Theodore Halnon | Time in quantum cosmology | 20 pages | Phys. Rev. D 98, 066001 (2018) | 10.1103/PhysRevD.98.066001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A cosmological model with two global internal times shows that time
reparameterization invariance, and therefore covariance, is not guaranteed by
deparameterization. In particular, it is impossible to derive proper-time
effective equations from a single deparameterized model if quantum corrections
from fluctuations and higher moments are included. The framework of effective
constraints shows how proper-time evolution can consistently be defined in
quantum cosmological systems, such that it is time reparameterization invariant
when compared with other choices of coordinate time. At the same time, it
allows transformations of moment corrections in different deparameterizations
of the same model, indicating partial time reparameterization of internal-time
evolution. However, in addition to corrections from moments such as quantum
fluctuations, also factor ordering corrections may appear. The latter
generically break covariance in internal-time formulations. Fluctuation effects
in quantum cosmology are therefore problematic, in particular if derivations
are made with a single choice of internal time or a fixed physical Hilbert
space.
| [
{
"created": "Thu, 1 Dec 2016 17:20:37 GMT",
"version": "v1"
}
] | 2018-09-13 | [
[
"Bojowald",
"Martin",
""
],
[
"Halnon",
"Theodore",
""
]
] | A cosmological model with two global internal times shows that time reparameterization invariance, and therefore covariance, is not guaranteed by deparameterization. In particular, it is impossible to derive proper-time effective equations from a single deparameterized model if quantum corrections from fluctuations and higher moments are included. The framework of effective constraints shows how proper-time evolution can consistently be defined in quantum cosmological systems, such that it is time reparameterization invariant when compared with other choices of coordinate time. At the same time, it allows transformations of moment corrections in different deparameterizations of the same model, indicating partial time reparameterization of internal-time evolution. However, in addition to corrections from moments such as quantum fluctuations, also factor ordering corrections may appear. The latter generically break covariance in internal-time formulations. Fluctuation effects in quantum cosmology are therefore problematic, in particular if derivations are made with a single choice of internal time or a fixed physical Hilbert space. |
0811.3869 | Guillermo A. Gonzalez | Guillermo A. Gonz\'alez, Antonio C. Guti\'errez-Pi\~neres, Viviana M.
Vi\~na-Cervantes | Relativistic static thin dust disks with an inner edge: An infinite
family of new exact solutions | 9 pages, 3 figures | Phys.Rev.D79:124048,2009 | 10.1103/PhysRevD.79.124048 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An infinite family of new exact solutions of the Einstein vacuum equations
for static and axially symmetric spacetimes is presented. All the metric
functions of the solutions are explicitly computed and the obtained expressions
are simply written in terms of oblate spheroidal coordinates. Furthermore, the
solutions are asymptotically flat and regular everywhere, as it is shown by
computing all the curvature scalars. These solutions describe an infinite
family of thin dust disks with a central inner edge, whose energy densities are
everywhere positive and well behaved, in such a way that their energy-momentum
tensor are in fully agreement with all the energy conditions. Now, although the
disks are of infinite extension, all of them have finite mass. The
superposition of the first member of this family with a Schwarzschild black
hole was presented previously [G. A. Gonz\'alez and A. C.
Guti\'errez-Pi\~neres, arXiv: 0811.3002v1 (2008)], whereas that in a subsequent
paper a detailed analysis of the corresponding superposition for the full
family will be presented.
| [
{
"created": "Mon, 24 Nov 2008 17:43:54 GMT",
"version": "v1"
}
] | 2009-07-09 | [
[
"González",
"Guillermo A.",
""
],
[
"Gutiérrez-Piñeres",
"Antonio C.",
""
],
[
"Viña-Cervantes",
"Viviana M.",
""
]
] | An infinite family of new exact solutions of the Einstein vacuum equations for static and axially symmetric spacetimes is presented. All the metric functions of the solutions are explicitly computed and the obtained expressions are simply written in terms of oblate spheroidal coordinates. Furthermore, the solutions are asymptotically flat and regular everywhere, as it is shown by computing all the curvature scalars. These solutions describe an infinite family of thin dust disks with a central inner edge, whose energy densities are everywhere positive and well behaved, in such a way that their energy-momentum tensor are in fully agreement with all the energy conditions. Now, although the disks are of infinite extension, all of them have finite mass. The superposition of the first member of this family with a Schwarzschild black hole was presented previously [G. A. Gonz\'alez and A. C. Guti\'errez-Pi\~neres, arXiv: 0811.3002v1 (2008)], whereas that in a subsequent paper a detailed analysis of the corresponding superposition for the full family will be presented. |
2406.13845 | Hugo Garcia-Compean | H. Garc\'ia-Compe\'an, J. Hern\'andez-Aguilar, D. Mata-Pacheco, C.
Ram\'irez | Effects of quantum corrections to Lorentzian vacuum transitions in the
presence of gravity | 36 pages, 4 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a study of the vacuum transition probabilities taking into account
quantum corrections. We first introduce a general method that expand previous
works employing the Lorentzian formalism of the Wheeler-De Witt equation by
considering higher order terms in the semiclassical expansion. The method
presented is applicable in principle to any model in the superspace and up to
any desired order in the quantum correction terms. Then, we apply this method
to obtain analytical solutions for the probabilities up to second quantum
corrections for homogeneous isotropic and anisotropic universes. We use the
Friedmann-Lemaitre-Robertson-Walker with positive and zero curvature for the
isotropic case and the Bianchi III and Kantwowski-Sachs metrics for the
anisotropic case. Interpreting the results as distribution probabilities of
creating universes by vacuum decay with a given size, we found that the general
behaviour is that considering up to the second quantum correction leads to an
avoidance of the initial singularity. However, we show that this result can
only be achieved for the isotropic universe. Furthermore, we also study the
effect of anisotropy on the transition probabilities.
| [
{
"created": "Wed, 19 Jun 2024 21:17:34 GMT",
"version": "v1"
}
] | 2024-06-21 | [
[
"García-Compeán",
"H.",
""
],
[
"Hernández-Aguilar",
"J.",
""
],
[
"Mata-Pacheco",
"D.",
""
],
[
"Ramírez",
"C.",
""
]
] | We present a study of the vacuum transition probabilities taking into account quantum corrections. We first introduce a general method that expand previous works employing the Lorentzian formalism of the Wheeler-De Witt equation by considering higher order terms in the semiclassical expansion. The method presented is applicable in principle to any model in the superspace and up to any desired order in the quantum correction terms. Then, we apply this method to obtain analytical solutions for the probabilities up to second quantum corrections for homogeneous isotropic and anisotropic universes. We use the Friedmann-Lemaitre-Robertson-Walker with positive and zero curvature for the isotropic case and the Bianchi III and Kantwowski-Sachs metrics for the anisotropic case. Interpreting the results as distribution probabilities of creating universes by vacuum decay with a given size, we found that the general behaviour is that considering up to the second quantum correction leads to an avoidance of the initial singularity. However, we show that this result can only be achieved for the isotropic universe. Furthermore, we also study the effect of anisotropy on the transition probabilities. |
gr-qc/0611090 | Carlos Barcelo | Carlos Barcelo | Cosmology as a search for overall equilibrium | 9 pages, 1 figure | JETPLett.84:635-639,2007 | 10.1134/S0021364006240015 | null | gr-qc astro-ph | null | In this letter we will revise the steps followed by A. Einstein when he first
wrote on cosmology from the point of view of the general theory of relativity.
We will argue that his insightful line of thought leading to the introduction
of the cosmological constant in the equations of motion has only one weakness:
The constancy of the cosmological term, or what is the same, its independence
of the matter content of the universe. Eliminating this feature, I will propose
what I see as a simple and reasonable modification of the cosmological
equations of motion. The solutions of the new cosmological equations give place
to a cosmological model that tries to approach the Einstein static solution.
This model shows very appealing features in terms of fitting current
observations.
| [
{
"created": "Thu, 16 Nov 2006 18:19:50 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Barcelo",
"Carlos",
""
]
] | In this letter we will revise the steps followed by A. Einstein when he first wrote on cosmology from the point of view of the general theory of relativity. We will argue that his insightful line of thought leading to the introduction of the cosmological constant in the equations of motion has only one weakness: The constancy of the cosmological term, or what is the same, its independence of the matter content of the universe. Eliminating this feature, I will propose what I see as a simple and reasonable modification of the cosmological equations of motion. The solutions of the new cosmological equations give place to a cosmological model that tries to approach the Einstein static solution. This model shows very appealing features in terms of fitting current observations. |
1412.3015 | Plamen Fiziev | Plamen Fiziev and Kalin Marinov | Compact statis stars with polytropic equation of state in minimal
dilatonic gravity | 10 pages, 10 figures, TeX file. New commnets, references and
acknowledgments added. The jpg files for figures are replaced by eps ones.
Accepted for publication in Bulgarian Astronomical Journal, vol. 22 | Bulgarian Astronomical Journal, Vol. 23, p.3, (2015) | null | TIFA 12-2014 | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present solution of the equations for relativistic static spherically
symmetric stars (SSSS) in the model of minimal dilatonic gravity (MDG) using
the polytropic equation of state. A polytropic equation of state, which has a
good fitting with a more realistic one, is used. Results are obtained for all
variables of a single neutron star in the model of MDG. The maximum mass about
two solar masses is in accordance with the latest observations of pulsars.
Several new effects are observed for the variables related with the dilaton
$\Phi$ and the cosmological constant $\Lambda$. The mass-radius relation is
also obtained. Special attention is paid to the behavior of the quantities
which describe the effects analogous to those of dark energy and dark matter in
MDG. The results of the present paper confirm the conclusion that the dilaton
$\Phi$ is able to play simultaneously the role of dark energy and dark matter.
| [
{
"created": "Tue, 9 Dec 2014 16:37:43 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Jan 2015 14:39:52 GMT",
"version": "v2"
}
] | 2015-02-03 | [
[
"Fiziev",
"Plamen",
""
],
[
"Marinov",
"Kalin",
""
]
] | We present solution of the equations for relativistic static spherically symmetric stars (SSSS) in the model of minimal dilatonic gravity (MDG) using the polytropic equation of state. A polytropic equation of state, which has a good fitting with a more realistic one, is used. Results are obtained for all variables of a single neutron star in the model of MDG. The maximum mass about two solar masses is in accordance with the latest observations of pulsars. Several new effects are observed for the variables related with the dilaton $\Phi$ and the cosmological constant $\Lambda$. The mass-radius relation is also obtained. Special attention is paid to the behavior of the quantities which describe the effects analogous to those of dark energy and dark matter in MDG. The results of the present paper confirm the conclusion that the dilaton $\Phi$ is able to play simultaneously the role of dark energy and dark matter. |
gr-qc/0203090 | Laszlo A. Gergely | L\'aszl\'o \'A. Gergely, Zolt\'an Perj\'es | Kerr-Schild metrics revisited II. The complete vacuum solution | 21 pages | J.Math.Phys. 35 (1994) 2448-2462 | 10.1063/1.530516 | null | gr-qc | null | The complete solution of Einstein's gravitational equations with a
vacuum-vacuum Kerr-Schild pencil of metrics $g_{ab}+V l_al_b$ is obtained. Our
result generalizes the solution of the Kerr-Schild problem with a flat metric
$g_{ab}$ (represented by the Kerr theorem) to the case when $g_{ab}$ is the
metric of a curved space-time.
| [
{
"created": "Tue, 26 Mar 2002 12:35:10 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Gergely",
"László Á.",
""
],
[
"Perjés",
"Zoltán",
""
]
] | The complete solution of Einstein's gravitational equations with a vacuum-vacuum Kerr-Schild pencil of metrics $g_{ab}+V l_al_b$ is obtained. Our result generalizes the solution of the Kerr-Schild problem with a flat metric $g_{ab}$ (represented by the Kerr theorem) to the case when $g_{ab}$ is the metric of a curved space-time. |
gr-qc/9504049 | Rainer Mueller | Rainer Mueller and Carlos O. Lousto | Entanglement entropy in curved spacetimes with event horizons | 12 pages, RevTex 3.0, 2 figures as uuencoded compressed Postscript
files | Phys.Rev. D52 (1995) 4512-4517 | 10.1103/PhysRevD.52.4512 | UAB-FT-362 | gr-qc astro-ph hep-th | null | We consider the computation of the entanglement entropy in curved backgrounds
with event horizons. We use a Hamiltonian approach to the problem and perform
numerical computations on a spherical lattice of spacing $a$. We study the
cosmological case and make explicit computations for the
Friedmann-Robertson-Walker universe. Our results for a massless, minimally
coupled scalar field can be summarized by $S_{ent}=0.30 r_H^2/a^2$,which
resembles the flat space formula, although here the horizon radius, $r_H$, is
time-dependent.
| [
{
"created": "Fri, 28 Apr 1995 06:40:15 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Mueller",
"Rainer",
""
],
[
"Lousto",
"Carlos O.",
""
]
] | We consider the computation of the entanglement entropy in curved backgrounds with event horizons. We use a Hamiltonian approach to the problem and perform numerical computations on a spherical lattice of spacing $a$. We study the cosmological case and make explicit computations for the Friedmann-Robertson-Walker universe. Our results for a massless, minimally coupled scalar field can be summarized by $S_{ent}=0.30 r_H^2/a^2$,which resembles the flat space formula, although here the horizon radius, $r_H$, is time-dependent. |
gr-qc/9511028 | Robert Mann | C. Alvarez and R.B. Mann | The Equivalence Principle and Anomalous Magnetic Moment Experiments | 26 pages, latex, epsf, 1 figure, final version which appears in
Physical Review D | Phys.Rev.D54:7097-7107,1996 | 10.1103/PhysRevD.54.7097 | null | gr-qc | null | We investigate the possibility of testing of the Einstein Equivalence
Principle (EEP) using measurements of anomalous magnetic moments of elementary
particles. We compute the one loop correction for the $g-2$ anomaly within the
class of non metric theories of gravity described by the \tmu formalism. We
find several novel mechanisms for breaking the EEP whose origin is due purely
to radiative corrections. We discuss the possibilities of setting new empirical
constraints on these effects.
| [
{
"created": "Wed, 8 Nov 1995 17:48:09 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Nov 1995 20:26:52 GMT",
"version": "v2"
},
{
"created": "Thu, 12 Dec 1996 18:35:20 GMT",
"version": "v3"
}
] | 2010-01-06 | [
[
"Alvarez",
"C.",
""
],
[
"Mann",
"R. B.",
""
]
] | We investigate the possibility of testing of the Einstein Equivalence Principle (EEP) using measurements of anomalous magnetic moments of elementary particles. We compute the one loop correction for the $g-2$ anomaly within the class of non metric theories of gravity described by the \tmu formalism. We find several novel mechanisms for breaking the EEP whose origin is due purely to radiative corrections. We discuss the possibilities of setting new empirical constraints on these effects. |
1911.02415 | Omar Zanusso | Maximilian Becker, Carlo Pagani and Omar Zanusso | Fractal geometry of higher derivative gravity | 5 pages, to appear in PRL | Phys. Rev. Lett. 124, 151302 (2020) | 10.1103/PhysRevLett.124.151302 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We determine the scaling properties of geometric operators such as lengths,
areas, and volumes in models of higher derivative quantum gravity by
renormalizing appropriate composite operators. We use these results to deduce
the fractal dimensions of such hypersurfaces embedded in a quantum spacetime at
very small distances.
| [
{
"created": "Wed, 6 Nov 2019 14:46:44 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Apr 2020 10:39:18 GMT",
"version": "v2"
}
] | 2020-04-22 | [
[
"Becker",
"Maximilian",
""
],
[
"Pagani",
"Carlo",
""
],
[
"Zanusso",
"Omar",
""
]
] | We determine the scaling properties of geometric operators such as lengths, areas, and volumes in models of higher derivative quantum gravity by renormalizing appropriate composite operators. We use these results to deduce the fractal dimensions of such hypersurfaces embedded in a quantum spacetime at very small distances. |
gr-qc/9308007 | D. V. Ahluwalia | D. V. Ahluwalia | Quantum Measurement, Gravitation, and Locality | LA-UR-93-2890-REV, "honorable mention" for the 1994 Awards by Gravity
Research Foundation | Phys.Lett.B339:301-303,1994 | 10.1016/0370-2693(94)90622-X | null | gr-qc hep-th | null | This essay argues that when measurement processes involve energies of the
order of the Planck scale, the fundamental assumption of locality may no longer
be a good approximation. Idealized position measurements of two distinguishable
spin-$0$ particles are considered. The measurements alter the space-time metric
in a fundamental manner governed by the commutation relations $[x_i\,\,p_j]=
i\hbar\,\delta_{ij}$ and the classical field equations of gravitation. This
{\it in-principle} unavoidable change in the space-time metric destroys the
commutativity (and hence locality) of position measurement operators.
| [
{
"created": "Mon, 9 Aug 1993 17:59:32 GMT",
"version": "v1"
},
{
"created": "Tue, 17 May 1994 01:55:32 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Ahluwalia",
"D. V.",
""
]
] | This essay argues that when measurement processes involve energies of the order of the Planck scale, the fundamental assumption of locality may no longer be a good approximation. Idealized position measurements of two distinguishable spin-$0$ particles are considered. The measurements alter the space-time metric in a fundamental manner governed by the commutation relations $[x_i\,\,p_j]= i\hbar\,\delta_{ij}$ and the classical field equations of gravitation. This {\it in-principle} unavoidable change in the space-time metric destroys the commutativity (and hence locality) of position measurement operators. |
1309.7582 | Sang Pyo Kim | Sang Pyo Kim | Particle Production from Geometric Transition in Expanding Universe | Latex 4 pages, 1 figure; Proceedings of APPC12, to be published in J.
Phys. Soc. Japan, Supplement | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The geometric transitions from the evolution in the complex plane of time
provide channels for particle production for a quantum field in expanding
universes. The production rate for one pair is obtained by squaring and summing
the scattering matrix between the in-vacuum and the transported one over all
possible independent closed paths of winding number 1.
| [
{
"created": "Sun, 29 Sep 2013 12:18:29 GMT",
"version": "v1"
}
] | 2013-10-01 | [
[
"Kim",
"Sang Pyo",
""
]
] | The geometric transitions from the evolution in the complex plane of time provide channels for particle production for a quantum field in expanding universes. The production rate for one pair is obtained by squaring and summing the scattering matrix between the in-vacuum and the transported one over all possible independent closed paths of winding number 1. |
gr-qc/9703005 | Yuri Levin | Yu. Levin | QND and higher order effects for a nonlinear meter in an interferometric
gravitational wave antenna | LaTex, 17 pages, 3 figures | Phys.Rev. D57 (1998) 2069-2078 | 10.1103/PhysRevD.57.2069 | null | gr-qc quant-ph | null | A new optical topology and signal readout strategy for a laser interferometer
gravitational wave detector were proposed recently by Braginsky and Khalili .
Their method is based on using a nonlinear medium inside a microwave oscillator
to detect the gravitational-wave-induced spatial shift of the interferometer's
standing optical wave. This paper proposes a quantum nondemolition (QND) scheme
that could be realistically used for such a readout device and discusses a
"fundamental" sensitivity limit imposed by a higher order optical effect.
| [
{
"created": "Sat, 1 Mar 1997 00:37:05 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Levin",
"Yu.",
""
]
] | A new optical topology and signal readout strategy for a laser interferometer gravitational wave detector were proposed recently by Braginsky and Khalili . Their method is based on using a nonlinear medium inside a microwave oscillator to detect the gravitational-wave-induced spatial shift of the interferometer's standing optical wave. This paper proposes a quantum nondemolition (QND) scheme that could be realistically used for such a readout device and discusses a "fundamental" sensitivity limit imposed by a higher order optical effect. |
1408.4273 | Andrea Geralico | Donato Bini, Fernando de Felice, Andrea Geralico, Andrea Lunari | Spinning test particles in Weyl spacetimes | 25 pages, 6 figures; published version | J. Phys. A: Math. Gen. 38, 1163 (2005) | 10.1088/0305-4470/38/5/017 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The motion of spinning test particles along circular orbits in static vacuum
spacetimes belonging to the Weyl class is discussed. Spin alignment and
coupling with background parameters in the case of superimposed Weyl fields,
corresponding to a single Schwarzschild black hole and single Chazy-Curzon
particle as well as to two Schwarzschild black holes and two Chazy-Curzon
particles, are studied in detail for standard choices of supplementary
conditions. Applications to the gravitomagnetic "clock effect" are also
discussed.
| [
{
"created": "Tue, 19 Aug 2014 10:03:29 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Bini",
"Donato",
""
],
[
"de Felice",
"Fernando",
""
],
[
"Geralico",
"Andrea",
""
],
[
"Lunari",
"Andrea",
""
]
] | The motion of spinning test particles along circular orbits in static vacuum spacetimes belonging to the Weyl class is discussed. Spin alignment and coupling with background parameters in the case of superimposed Weyl fields, corresponding to a single Schwarzschild black hole and single Chazy-Curzon particle as well as to two Schwarzschild black holes and two Chazy-Curzon particles, are studied in detail for standard choices of supplementary conditions. Applications to the gravitomagnetic "clock effect" are also discussed. |
gr-qc/0603133 | Jacek Tafel | M. Jakimowicz and J. Tafel | Self-dual metrics in Husain's approach | 8 pages | Class. Quantum Grav. 23 (2006) 4907-4913 | 10.1088/0264-9381/23/15/010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that Husain's reduction of the self-dual Einstein equations is
equivalent to the Pleba\'nski equation. The B\"acklund transformation between
these equations is found. Contact symmetries of the Husain-Park equation and
corresponding conservation laws are derived.
| [
{
"created": "Fri, 31 Mar 2006 15:36:59 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Feb 2016 16:11:05 GMT",
"version": "v2"
}
] | 2016-02-12 | [
[
"Jakimowicz",
"M.",
""
],
[
"Tafel",
"J.",
""
]
] | We show that Husain's reduction of the self-dual Einstein equations is equivalent to the Pleba\'nski equation. The B\"acklund transformation between these equations is found. Contact symmetries of the Husain-Park equation and corresponding conservation laws are derived. |
0912.1722 | Mustapha Azreg-A\"inou | Mustapha Azreg-A\"inou | Selection criteria for two-parameter solutions to scalar-tensor gravity | 24 pages, 7 figures, 2 tables | Gen.Rel.Grav.42:1427-1456,2010 | 10.1007/s10714-009-0915-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We make a systematic investigation of the generic properties of static,
spherically symmetric, asymptotically flat solutions to the field equations
describing gravity minimally coupled to a nonlinear self-gravitating real
scalar field. Seven corollaries and a theorem on selection criteria for two-
and one-parametric solutions are proven and conditions for obtaining
particle-like solution, black holes or naked singularities are derived. A
series of exact solutions in closed forms describing different black holes,
naked singularities and particle-like solutions are provided.
| [
{
"created": "Wed, 9 Dec 2009 11:18:55 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Azreg-Aïnou",
"Mustapha",
""
]
] | We make a systematic investigation of the generic properties of static, spherically symmetric, asymptotically flat solutions to the field equations describing gravity minimally coupled to a nonlinear self-gravitating real scalar field. Seven corollaries and a theorem on selection criteria for two- and one-parametric solutions are proven and conditions for obtaining particle-like solution, black holes or naked singularities are derived. A series of exact solutions in closed forms describing different black holes, naked singularities and particle-like solutions are provided. |
0804.3393 | Shantanu Desai | Shantanu Desai, Kazuhiro Hayama, Soumya Mohanty, Malik Rakhmanov,
Tiffany Summerscales, Sanichiro Yoshida | Proposed method for searches of gravitational waves from PKS 2155-304
and other blazar flares | 10 pages, 7 figures. Contribution to 12th Gravitational Wave Data
Analysis Workshop. Submitted to Classical and Quantum Gravity. Changes in
response to referee comments | Class.Quant.Grav.25:184024,2008 | 10.1088/0264-9381/25/18/184024 | LIGO-P080023 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose to search for gravitational waves from PKS 2155-304 as well as
other blazars. PKS 2155-304 emitted a long duration energetic flare in July
2006, with total isotropic equivalent energy released in TeV gamma rays of
approximately $10^{45}$ ergs. Any possible gravitational wave signals
associated with this outburst should be seen by gravitational wave detectors at
the same time as the electromagnetic signal. During this flare, the two LIGO
interferometers at Hanford and the GEO detector were in operation and
collecting data. For this search we will use the data from multiple
gravitational wave detectors. The method we use for this purpose is a coherent
network analysis algorithm and is called {\tt RIDGE}. To estimate the
sensitivity of the search, we perform numerical simulations. The sensitivity to
estimated gravitational wave energy at the source is about $2.5 \times 10^{55}$
ergs for a detection probability of 20%. For this search, an end-to-end
analysis pipeline has been developed, which takes into account the motion of
the source across the sky.
| [
{
"created": "Mon, 21 Apr 2008 20:00:26 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Jul 2008 05:21:44 GMT",
"version": "v2"
}
] | 2008-12-06 | [
[
"Desai",
"Shantanu",
""
],
[
"Hayama",
"Kazuhiro",
""
],
[
"Mohanty",
"Soumya",
""
],
[
"Rakhmanov",
"Malik",
""
],
[
"Summerscales",
"Tiffany",
""
],
[
"Yoshida",
"Sanichiro",
""
]
] | We propose to search for gravitational waves from PKS 2155-304 as well as other blazars. PKS 2155-304 emitted a long duration energetic flare in July 2006, with total isotropic equivalent energy released in TeV gamma rays of approximately $10^{45}$ ergs. Any possible gravitational wave signals associated with this outburst should be seen by gravitational wave detectors at the same time as the electromagnetic signal. During this flare, the two LIGO interferometers at Hanford and the GEO detector were in operation and collecting data. For this search we will use the data from multiple gravitational wave detectors. The method we use for this purpose is a coherent network analysis algorithm and is called {\tt RIDGE}. To estimate the sensitivity of the search, we perform numerical simulations. The sensitivity to estimated gravitational wave energy at the source is about $2.5 \times 10^{55}$ ergs for a detection probability of 20%. For this search, an end-to-end analysis pipeline has been developed, which takes into account the motion of the source across the sky. |
gr-qc/9806070 | Ulises Nucamendi | Marcelo Salgado, Daniel Sudarsky (ICN-UNAM) and Ulises Nucamendi
(CINVESTAV) | On spontaneous scalarization | 41 pages, RevTex, 10 ps figures, submitted to Phys. Rev. D | Phys.Rev. D58 (1998) 124003 | 10.1103/PhysRevD.58.124003 | null | gr-qc | null | We study in the physical frame the phenomenon of spontaneous scalarization
that occurs in scalar-tensor theories of gravity for compact objects. We
discuss the fact that the phenomenon occurs exactly in the regime where the
Newtonian analysis indicates it should not. Finally we discuss the way the
phenomenon depends on the equation of state used to describe the nuclear
matter.
| [
{
"created": "Tue, 16 Jun 1998 18:34:16 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Salgado",
"Marcelo",
"",
"ICN-UNAM"
],
[
"Sudarsky",
"Daniel",
"",
"ICN-UNAM"
],
[
"Nucamendi",
"Ulises",
"",
"CINVESTAV"
]
] | We study in the physical frame the phenomenon of spontaneous scalarization that occurs in scalar-tensor theories of gravity for compact objects. We discuss the fact that the phenomenon occurs exactly in the regime where the Newtonian analysis indicates it should not. Finally we discuss the way the phenomenon depends on the equation of state used to describe the nuclear matter. |
1510.04170 | Frederic H. Vincent | F. H. Vincent, Z. Meliani, P. Grandclement, E. Gourgoulhon, O. Straub | Imaging a boson star at the Galactic center | 21 pages, 9 figures, accepted in CQG; main difference wrt previous
version is the last paragraph of the conclusion | null | 10.1088/0264-9381/33/10/105015 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Millimeter very long baseline interferometry will soon produce accurate
images of the closest surroundings of the supermassive compact object at the
center of the Galaxy, Sgr A*. These images may reveal the existence of a
central faint region, the so-called shadow, which is often interpreted as the
observable consequence of the event horizon of a black hole. In this paper, we
compute images of an accretion torus around Sgr A* assuming this compact object
is a boson star, i.e. an alternative to black holes within general relativity,
with no event horizon and no hard surface. We show that very relativistic
rotating boson stars produce images extremely similar to Kerr black holes,
showing in particular shadow-like and photon-ring-like structures. This result
highlights the extreme difficulty of unambiguously telling the existence of an
event horizon from strong-field images.
| [
{
"created": "Wed, 14 Oct 2015 15:53:21 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Mar 2016 09:19:52 GMT",
"version": "v2"
}
] | 2016-05-25 | [
[
"Vincent",
"F. H.",
""
],
[
"Meliani",
"Z.",
""
],
[
"Grandclement",
"P.",
""
],
[
"Gourgoulhon",
"E.",
""
],
[
"Straub",
"O.",
""
]
] | Millimeter very long baseline interferometry will soon produce accurate images of the closest surroundings of the supermassive compact object at the center of the Galaxy, Sgr A*. These images may reveal the existence of a central faint region, the so-called shadow, which is often interpreted as the observable consequence of the event horizon of a black hole. In this paper, we compute images of an accretion torus around Sgr A* assuming this compact object is a boson star, i.e. an alternative to black holes within general relativity, with no event horizon and no hard surface. We show that very relativistic rotating boson stars produce images extremely similar to Kerr black holes, showing in particular shadow-like and photon-ring-like structures. This result highlights the extreme difficulty of unambiguously telling the existence of an event horizon from strong-field images. |
2301.07678 | Tiberiu Harko | Cristina Blaga, Paul Blaga, Tiberiu Harko | Jacobi and Lyapunov stability analysis of circular geodesics around a
spherically symmetric dilaton black hole | 20 pages, 7 figures, accepted for publication in Symmetry | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the stability of the geodesic curves in the geometry of the
Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole, describing the space
time of a charged black hole in the low energy limit of the string theory. The
stability analysis is performed by using both the linear (Lyapunov) stability
method, as well as the notion of Jacobi stability, based on the
Kosambi-Cartan-Chern theory. Brief reviews of the two stability methods are
also presented. After obtaining the geodesic equations in spherical symmetry,
we reformulate them as a two-dimensional dynamic system. The Jacobi stability
analysis of the geodesic equations is performed by considering the important
geometric invariants that can be used for the description of this system (the
nonlinear and the Berwald connections), as well as the deviation curvature
tensor, respectively. The characteristic values of the deviation curvature
tensor are specifically calculated, as given by the second derivative of
effective potential of the geodesic motion. The Lyapunov stability analysis
leads to the same results. Hence, we can conclude that in the particular case
of the geodesic motion on circular orbits in the
Gibbons-Maeda-Garfinkle-Horowitz-Strominger, the Lyapunov and the Jacobi
stability analysis gives equivalent results.
| [
{
"created": "Wed, 18 Jan 2023 17:56:23 GMT",
"version": "v1"
}
] | 2023-01-19 | [
[
"Blaga",
"Cristina",
""
],
[
"Blaga",
"Paul",
""
],
[
"Harko",
"Tiberiu",
""
]
] | We analyze the stability of the geodesic curves in the geometry of the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole, describing the space time of a charged black hole in the low energy limit of the string theory. The stability analysis is performed by using both the linear (Lyapunov) stability method, as well as the notion of Jacobi stability, based on the Kosambi-Cartan-Chern theory. Brief reviews of the two stability methods are also presented. After obtaining the geodesic equations in spherical symmetry, we reformulate them as a two-dimensional dynamic system. The Jacobi stability analysis of the geodesic equations is performed by considering the important geometric invariants that can be used for the description of this system (the nonlinear and the Berwald connections), as well as the deviation curvature tensor, respectively. The characteristic values of the deviation curvature tensor are specifically calculated, as given by the second derivative of effective potential of the geodesic motion. The Lyapunov stability analysis leads to the same results. Hence, we can conclude that in the particular case of the geodesic motion on circular orbits in the Gibbons-Maeda-Garfinkle-Horowitz-Strominger, the Lyapunov and the Jacobi stability analysis gives equivalent results. |
gr-qc/9809050 | Shinji Mukohyama | Shinji Mukohyama | On the Noether charge form of the first law of black hole mechanics | Latex, 16 pages, arguments on gauge conditions and near-stationary
entropy are added, accepted for publication in Physical Review D | Phys. Rev. D 59, 064009 (1999) | 10.1103/PhysRevD.59.064009 | YITP-98-61 | gr-qc | null | The first law of black hole mechanics was derived by Wald in a general
covariant theory of gravity for stationary variations around a stationary black
hole. It is formulated in terms of Noether charges, and has many advantages. In
this paper several issues are discussed to strengthen the validity of the
Noether charge form of the first law. In particular, a gauge condition used in
the derivation is justified. After that, we justify the generalization to
non-stationary variations done by Iyer-Wald.
| [
{
"created": "Thu, 17 Sep 1998 08:32:49 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Sep 1998 06:33:11 GMT",
"version": "v2"
},
{
"created": "Sat, 24 Oct 1998 08:35:51 GMT",
"version": "v3"
},
{
"created": "Wed, 18 Nov 1998 06:06:48 GMT",
"version": "v4"
}
] | 2016-08-25 | [
[
"Mukohyama",
"Shinji",
""
]
] | The first law of black hole mechanics was derived by Wald in a general covariant theory of gravity for stationary variations around a stationary black hole. It is formulated in terms of Noether charges, and has many advantages. In this paper several issues are discussed to strengthen the validity of the Noether charge form of the first law. In particular, a gauge condition used in the derivation is justified. After that, we justify the generalization to non-stationary variations done by Iyer-Wald. |
gr-qc/0007031 | Theodore A. Jacobson | Ted Jacobson and David Mattingly | Gravity with a dynamical preferred frame | 9 pages; title changed, references added, relation to prior work of
Gasperini discussed, errors in scalar field stress tensor corrected, various
minor changes to Introduction; Final version to be published in PRD: relation
to prior work of Kostelecky and Samuel spelled out in detail, clarifications
and sign errors corrected in section on linearized solutions, references
added; Really final version: (u^m \nabla_m u^a)^2 term added to most general
Lagrangian eqn.(3.1) | Phys.Rev. D64 (2001) 024028 | 10.1103/PhysRevD.64.024028 | null | gr-qc hep-ph hep-th | null | We study a generally covariant model in which local Lorentz invariance is
broken "spontaneously" by a dynamical unit timelike vector field $u^a$---the
"aether". Such a model makes it possible to study the gravitational and
cosmological consequences of preferred frame effects, such as ``variable speed
of light" or high frequency dispersion, while preserving a generally covariant
metric theory of gravity. In this paper we restrict attention to an action for
an effective theory of the aether which involves only the antisymmetrized
derivative $\nabla_{[a}u_{b]}$. Without matter this theory is equivalent to a
sector of the Einstein-Maxwell-charged dust system. The aether has two massless
transverse excitations, and the solutions of the model include all vacuum
solutions of general relativity (as well as other solutions). However, the
aether generally develops gradient singularities which signal a breakdown of
this effective theory. Including the symmetrized derivative in the action for
the aether field may cure this problem.
| [
{
"created": "Fri, 14 Jul 2000 18:56:24 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Sep 2000 01:04:03 GMT",
"version": "v2"
},
{
"created": "Fri, 27 Apr 2001 19:44:04 GMT",
"version": "v3"
},
{
"created": "Sat, 2 Jun 2001 01:29:20 GMT",
"version": "v4"
}
] | 2009-10-31 | [
[
"Jacobson",
"Ted",
""
],
[
"Mattingly",
"David",
""
]
] | We study a generally covariant model in which local Lorentz invariance is broken "spontaneously" by a dynamical unit timelike vector field $u^a$---the "aether". Such a model makes it possible to study the gravitational and cosmological consequences of preferred frame effects, such as ``variable speed of light" or high frequency dispersion, while preserving a generally covariant metric theory of gravity. In this paper we restrict attention to an action for an effective theory of the aether which involves only the antisymmetrized derivative $\nabla_{[a}u_{b]}$. Without matter this theory is equivalent to a sector of the Einstein-Maxwell-charged dust system. The aether has two massless transverse excitations, and the solutions of the model include all vacuum solutions of general relativity (as well as other solutions). However, the aether generally develops gradient singularities which signal a breakdown of this effective theory. Including the symmetrized derivative in the action for the aether field may cure this problem. |
gr-qc/0010065 | Paul M. Alsing | P.M. Alsing, J.C. Evans and K.K. Nandi | The phase of a quantum mechanical particle in curved spacetime | 30 pages, no figures. Submitted to Gen.Rel.Grav 17 Oct 00 | Gen.Rel.Grav. 33 (2001) 1459-1487 | 10.1023/A:1012284625541 | null | gr-qc | null | We investigate the quantum mechanical wave equations for free particles of
spin 0,1/2,1 in the background of an arbitrary static gravitational field in
order to explicitly determine if the phase of the wavefunction is $S/\hbar =
\int p_{\mu} dx^{\mu} / \hbar$, as is often quoted in the literature. We work
in isotropic coordinates where the wave equations have a simple managable form
and do not make a weak gravitational field approximation. We interpret these
wave equations in terms of a quantum mechanical particle moving in medium with
a spatially varying effective index of refraction. Due to the first order
spatial derivative structure of the Dirac equation in curved spacetime, only
the spin 1/2 particle has \textit{exactly} the quantum mechanical phase as
indicated above. The second order spatial derivative structure of the spin 0
and spin 1 wave equations yield the above phase only to lowest order in
$\hbar$. We develop a WKB approximation for the solution of the spin 0 and spin
1 wave equations and explore amplitude and phase corrections beyond the lowest
order in $\hbar$. For the spin 1/2 particle we calculate the phase appropriate
for neutrino flavor oscillations.
| [
{
"created": "Wed, 18 Oct 2000 20:52:39 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Alsing",
"P. M.",
""
],
[
"Evans",
"J. C.",
""
],
[
"Nandi",
"K. K.",
""
]
] | We investigate the quantum mechanical wave equations for free particles of spin 0,1/2,1 in the background of an arbitrary static gravitational field in order to explicitly determine if the phase of the wavefunction is $S/\hbar = \int p_{\mu} dx^{\mu} / \hbar$, as is often quoted in the literature. We work in isotropic coordinates where the wave equations have a simple managable form and do not make a weak gravitational field approximation. We interpret these wave equations in terms of a quantum mechanical particle moving in medium with a spatially varying effective index of refraction. Due to the first order spatial derivative structure of the Dirac equation in curved spacetime, only the spin 1/2 particle has \textit{exactly} the quantum mechanical phase as indicated above. The second order spatial derivative structure of the spin 0 and spin 1 wave equations yield the above phase only to lowest order in $\hbar$. We develop a WKB approximation for the solution of the spin 0 and spin 1 wave equations and explore amplitude and phase corrections beyond the lowest order in $\hbar$. For the spin 1/2 particle we calculate the phase appropriate for neutrino flavor oscillations. |
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