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/0701153 | Alberto Saa | Alberto Saa | N-dimensional Vaidya metric with cosmological constant in double-null
coordinates | 11 pages, 5 figs. Final version to appear in PRD | Phys.Rev.D75:124019,2007 | 10.1103/PhysRevD.75.124019 | null | gr-qc | null | A recently proposed approach to the construction of the Vaidya metric in
double-null coordinates for generic mass functions is extended to the
$n$-dimensional $(n>2)$ case and to allow the inclusion of a cosmological
constant. The approach is based on a qualitative study of the null-geodesics,
allowing the description of light-cones and revealing many features of the
underlying causal structure. Possible applications are illustrated by explicit
examples. Some new exact solutions are also presented and discussed. The
results presented here can simplify considerably the study of spherically
symmetric gravitational collapse and mass accretion in arbitrary dimensions.
| [
{
"created": "Mon, 29 Jan 2007 02:26:57 GMT",
"version": "v1"
},
{
"created": "Fri, 25 May 2007 13:27:21 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Saa",
"Alberto",
""
]
] | A recently proposed approach to the construction of the Vaidya metric in double-null coordinates for generic mass functions is extended to the $n$-dimensional $(n>2)$ case and to allow the inclusion of a cosmological constant. The approach is based on a qualitative study of the null-geodesics, allowing the description of light-cones and revealing many features of the underlying causal structure. Possible applications are illustrated by explicit examples. Some new exact solutions are also presented and discussed. The results presented here can simplify considerably the study of spherically symmetric gravitational collapse and mass accretion in arbitrary dimensions. |
1309.4424 | Sanved Kolekar | Sanved Kolekar and T. Padmanabhan | Quantum field theory in the Rindler-Rindler spacetime | v1: 12 pages, no figure, v2: typo fixed in eq.39 | Phys. Rev. D 89, 064055 (2014) | 10.1103/PhysRevD.89.064055 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known that Minkowski vacuum appears as a thermal bath in the
Rindler spacetime when the modes on the left wedge are traced out. We introduce
the concept of a Rindler-Rindler spacetime, obtained by a further coordinate
transformation from the Rindler spacetime, in a manner similar to the
transformation from inertial to Rindler frame. We show that the Rindler vacuum
appears as a thermal state in the Rindler-Rindler frame. Further, the spectrum
of particles seen by the Rindler-Rindler observers in the original Minkowski
vacuum state is shown to be identical to that seen by detector accelerating
through a real thermal bath. Thus the Davies-Unruh effect acts as a proxy for a
real thermal bath, for a certain class of observers in the Rindler-Rindler
spacetime. We interpret this similarity as indicating further evidence of the
indistinguishablity between thermal and quantum fluctuations along the lines of
the recent work in arXiv:1308.6289. The implications are briefly discussed.
| [
{
"created": "Tue, 17 Sep 2013 18:49:45 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Jun 2018 14:50:27 GMT",
"version": "v2"
}
] | 2018-06-20 | [
[
"Kolekar",
"Sanved",
""
],
[
"Padmanabhan",
"T.",
""
]
] | It is well known that Minkowski vacuum appears as a thermal bath in the Rindler spacetime when the modes on the left wedge are traced out. We introduce the concept of a Rindler-Rindler spacetime, obtained by a further coordinate transformation from the Rindler spacetime, in a manner similar to the transformation from inertial to Rindler frame. We show that the Rindler vacuum appears as a thermal state in the Rindler-Rindler frame. Further, the spectrum of particles seen by the Rindler-Rindler observers in the original Minkowski vacuum state is shown to be identical to that seen by detector accelerating through a real thermal bath. Thus the Davies-Unruh effect acts as a proxy for a real thermal bath, for a certain class of observers in the Rindler-Rindler spacetime. We interpret this similarity as indicating further evidence of the indistinguishablity between thermal and quantum fluctuations along the lines of the recent work in arXiv:1308.6289. The implications are briefly discussed. |
1308.0860 | Mart\'in G. Richarte MR | Luis P. Chimento and Mart\'in G. Richarte | Nonbaryonic dark matter and scalar field coupled with a transversal
interaction plus decoupled radiation | 12 pages plus 5 pages of figures. In order to see the figures go to
the journal website
(http://link.springer.com/article/10.1140%2Fepjc%2Fs10052-013-2497-4). arXiv
admin note: substantial text overlap with arXiv:1303.3356, arXiv:1210.5505 | The European Physical Journal C July 2013, 73:2497 | 10.1140/epjc/s10052-013-2497-4 | null | gr-qc astro-ph.CO hep-ph hep-th physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze a universe filled with interacting dark matter, a scalar field
accommodated as dark radiation along with dark energy plus a decoupled
radiation term within the framework of spatially flat
Friedmann-Robertson-Walker (FRW) spacetime. We work in a three-dimensional
internal space spanned by the interaction vector and use a transversal
interaction $\mathbf{Q_t}$ for solving the source equation in order to find all
the interacting component energy densities. We asymptotically reconstruct the
scalar field and potential from an early radiation era to the late dominate
dark energy one, passing through an intermediate epoch dominated by dark
matter. We apply the $\chi^{2}$ method to the updated observational Hubble data
for constraining the cosmic parameters, contrast with the Union 2 sample of
supernovae, and analyze the amount of dark energy in the radiation era. It
turns out that our model fulfills the severe bound of $\Omega_{\rm
\phi}(z\simeq 1100)<0.018$ at $2\sigma$ level, is consistent with the recent
analysis that includes cosmic microwave background anisotropy measurements from
the Atacama Cosmology Telescope and the South Pole Telescope along with the
future constraints achievable by Planck and CMBPol experiments, and satisfies
the stringent bound $\Omega_{\rm \phi}(z\simeq 10^{10})<0.04$ at $2\sigma$
level in the big-bang nucleosynthesis epoch.
| [
{
"created": "Mon, 5 Aug 2013 00:05:13 GMT",
"version": "v1"
}
] | 2013-08-06 | [
[
"Chimento",
"Luis P.",
""
],
[
"Richarte",
"Martín G.",
""
]
] | We analyze a universe filled with interacting dark matter, a scalar field accommodated as dark radiation along with dark energy plus a decoupled radiation term within the framework of spatially flat Friedmann-Robertson-Walker (FRW) spacetime. We work in a three-dimensional internal space spanned by the interaction vector and use a transversal interaction $\mathbf{Q_t}$ for solving the source equation in order to find all the interacting component energy densities. We asymptotically reconstruct the scalar field and potential from an early radiation era to the late dominate dark energy one, passing through an intermediate epoch dominated by dark matter. We apply the $\chi^{2}$ method to the updated observational Hubble data for constraining the cosmic parameters, contrast with the Union 2 sample of supernovae, and analyze the amount of dark energy in the radiation era. It turns out that our model fulfills the severe bound of $\Omega_{\rm \phi}(z\simeq 1100)<0.018$ at $2\sigma$ level, is consistent with the recent analysis that includes cosmic microwave background anisotropy measurements from the Atacama Cosmology Telescope and the South Pole Telescope along with the future constraints achievable by Planck and CMBPol experiments, and satisfies the stringent bound $\Omega_{\rm \phi}(z\simeq 10^{10})<0.04$ at $2\sigma$ level in the big-bang nucleosynthesis epoch. |
gr-qc/0303111 | Ettore Minguzzi | E. Minguzzi | On the existence of maximizing curves for the charged-particle action | AMSLatex, 6 pages | Class.Quant.Grav. 20 (2003) 4169-4175 | 10.1088/0264-9381/20/19/303 | null | gr-qc | null | The classical Avez-Seifert theorem is generalized to the case of the Lorentz
force equation for charged test particles with fixed charge-to-mass ratio.
Given two events x_{0} and x_{1}, with x_{1} in the chronological future of
x_{0}, and a ratio q/m, it is proved that a timelike connecting solution of the
Lorentz force equation exists provided there is no null connecting geodesic and
the spacetime is globally hyperbolic. As a result, the theorem answers
affirmatively to the existence of timelike connecting solutions for the
particular case of Minkowski spacetime. Moreover, it is proved that there is at
least one C^{1} connecting curve that maximizes the functional
I[\gamma]=\int_{\gamma} ds+q/(mc^2) \omega over the set of C^{1}
future-directed non-spacelike connecting curves.
| [
{
"created": "Fri, 28 Mar 2003 14:24:48 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Mar 2003 13:26:29 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Minguzzi",
"E.",
""
]
] | The classical Avez-Seifert theorem is generalized to the case of the Lorentz force equation for charged test particles with fixed charge-to-mass ratio. Given two events x_{0} and x_{1}, with x_{1} in the chronological future of x_{0}, and a ratio q/m, it is proved that a timelike connecting solution of the Lorentz force equation exists provided there is no null connecting geodesic and the spacetime is globally hyperbolic. As a result, the theorem answers affirmatively to the existence of timelike connecting solutions for the particular case of Minkowski spacetime. Moreover, it is proved that there is at least one C^{1} connecting curve that maximizes the functional I[\gamma]=\int_{\gamma} ds+q/(mc^2) \omega over the set of C^{1} future-directed non-spacelike connecting curves. |
gr-qc/0512001 | Peter Diener | Peter Diener, Ernst Nils Dorband, Erik Schnetter, Manuel Tiglio | New, efficient, and accurate high order derivative and dissipation
operators satisfying summation by parts, and applications in
three-dimensional multi-block evolutions | 16 pages, 9 figures. The files with the coefficients for the
derivative and dissipation operators can be accessed by downloading the
source code for the document. The files are located in the "coeffs"
subdirectory | J.Sci.Comput.32:109-145,2007 | 10.1007/s10915-006-9123-7 | LSU-REL-113005, AEI-2005-175 | gr-qc | null | We construct new, efficient, and accurate high-order finite differencing
operators which satisfy summation by parts. Since these operators are not
uniquely defined, we consider several optimization criteria: minimizing the
bandwidth, the truncation error on the boundary points, the spectral radius, or
a combination of these. We examine in detail a set of operators that are up to
tenth order accurate in the interior, and we surprisingly find that a
combination of these optimizations can improve the operators' spectral radius
and accuracy by orders of magnitude in certain cases. We also construct
high-order dissipation operators that are compatible with these new finite
difference operators and which are semi-definite with respect to the
appropriate summation by parts scalar product. We test the stability and
accuracy of these new difference and dissipation operators by evolving a
three-dimensional scalar wave equation on a spherical domain consisting of
seven blocks, each discretized with a structured grid, and connected through
penalty boundary conditions.
| [
{
"created": "Wed, 30 Nov 2005 22:07:28 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Diener",
"Peter",
""
],
[
"Dorband",
"Ernst Nils",
""
],
[
"Schnetter",
"Erik",
""
],
[
"Tiglio",
"Manuel",
""
]
] | We construct new, efficient, and accurate high-order finite differencing operators which satisfy summation by parts. Since these operators are not uniquely defined, we consider several optimization criteria: minimizing the bandwidth, the truncation error on the boundary points, the spectral radius, or a combination of these. We examine in detail a set of operators that are up to tenth order accurate in the interior, and we surprisingly find that a combination of these optimizations can improve the operators' spectral radius and accuracy by orders of magnitude in certain cases. We also construct high-order dissipation operators that are compatible with these new finite difference operators and which are semi-definite with respect to the appropriate summation by parts scalar product. We test the stability and accuracy of these new difference and dissipation operators by evolving a three-dimensional scalar wave equation on a spherical domain consisting of seven blocks, each discretized with a structured grid, and connected through penalty boundary conditions. |
2011.11568 | Diego S\'aez-Chill\'on G\'omez | Diego S\'aez-Chill\'on G\'omez | Variational principle and boundary terms in gravity \`a la Palatini | 5 pages, version to be published in PLB | Phys. Lett. B 814, 136103 (2021) | 10.1016/j.physletb.2021.136103 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A general $f(\mathcal{R})$ gravitational theory is considered within the
Palatini formalism. By applying the variational principle and the usual
conditions on the boundary, we show explicitly that a surface term remains such
that as in their metric-compatible counterparts, an additional surface term has
to be added in the gravitational action, which plays a fundamental role when
calculating the entropy of the black hole.
| [
{
"created": "Mon, 23 Nov 2020 17:27:30 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jan 2021 09:50:12 GMT",
"version": "v2"
}
] | 2021-02-02 | [
[
"Gómez",
"Diego Sáez-Chillón",
""
]
] | A general $f(\mathcal{R})$ gravitational theory is considered within the Palatini formalism. By applying the variational principle and the usual conditions on the boundary, we show explicitly that a surface term remains such that as in their metric-compatible counterparts, an additional surface term has to be added in the gravitational action, which plays a fundamental role when calculating the entropy of the black hole. |
gr-qc/9710073 | Hisaaki Shinkai | Hisa-aki Shinkai, Wai-Mo Suen, F.Douglas Swesty, Malcolm Tobias,
Edward Y.M. Wang and Clifford M. Will | Newtonian and post-Newtonian binary neutron star mergers | 3 pages, LaTeX, 2 figures, Proceedings of the 8th Marcel Grossmann
Meeting, Jerusalem, June 1997 (World Scientific); mprocl.sty and epsf.sty are
included | null | null | null | gr-qc | null | We present two of our efforts directed toward the numerical analysis of
neutron star mergers, which are the most plausible sources for gravitational
wave detectors that should begin operating in the near future. First we present
Newtonian 3D simulations including radiation reaction (2.5PN) effects. We
discuss the gravitational wave signals and luminosity from the merger
with/without radiation reaction effects. Second we present the matching problem
between post-Newtonian formulations and general relativity in numerical
treatments. We prepare a spherical, static neutron star in a post-Newtonian
matched spacetime, and find that discontinuities at the matching surface become
smoothed out during fully relativistic evolution if we use a proper slicing
condition.
| [
{
"created": "Tue, 14 Oct 1997 20:19:46 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Shinkai",
"Hisa-aki",
""
],
[
"Suen",
"Wai-Mo",
""
],
[
"Swesty",
"F. Douglas",
""
],
[
"Tobias",
"Malcolm",
""
],
[
"Wang",
"Edward Y. M.",
""
],
[
"Will",
"Clifford M.",
""
]
] | We present two of our efforts directed toward the numerical analysis of neutron star mergers, which are the most plausible sources for gravitational wave detectors that should begin operating in the near future. First we present Newtonian 3D simulations including radiation reaction (2.5PN) effects. We discuss the gravitational wave signals and luminosity from the merger with/without radiation reaction effects. Second we present the matching problem between post-Newtonian formulations and general relativity in numerical treatments. We prepare a spherical, static neutron star in a post-Newtonian matched spacetime, and find that discontinuities at the matching surface become smoothed out during fully relativistic evolution if we use a proper slicing condition. |
0802.3362 | Israel Quiros | Israel Quiros, Ricardo Garcia-Salcedo, Tonatiuh Matos, Claudia Moreno | Self accelerating solutions in a DGP brane with a scalar field trapped
on it: the dynamical systems perspective | 9 pages, 8 figures. Version that matches the one published by PLB | Phys.Lett.B670:259-265,2009 | 10.1016/j.physletb.2008.11.019 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the dynamical systems tools to study the linear dynamics of a
self-interacting scalar field trapped on a DGP brane. The simplest kinds of
self-interaction potentials are investigated: a) constant potential, and b)
exponential potential. It is shown that the dynamics of DGP models can be very
rich and complex. One of the most interesting results of this study shows that
dynamical screening of the scalar field self-interaction potential, occuring
within the Minkowski cosmological phase of the DGP model and mimetizing 4D
phantom behaviour, is an attractor solution for a constant self-interaction
potential but not for the exponential one. In the latter case gravitational
screening is not even a critical point of the corresponding autonomous system
of ordinary differential equations.
| [
{
"created": "Fri, 22 Feb 2008 18:51:38 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Feb 2008 18:27:25 GMT",
"version": "v2"
},
{
"created": "Tue, 9 Dec 2008 16:06:45 GMT",
"version": "v3"
}
] | 2009-02-16 | [
[
"Quiros",
"Israel",
""
],
[
"Garcia-Salcedo",
"Ricardo",
""
],
[
"Matos",
"Tonatiuh",
""
],
[
"Moreno",
"Claudia",
""
]
] | We apply the dynamical systems tools to study the linear dynamics of a self-interacting scalar field trapped on a DGP brane. The simplest kinds of self-interaction potentials are investigated: a) constant potential, and b) exponential potential. It is shown that the dynamics of DGP models can be very rich and complex. One of the most interesting results of this study shows that dynamical screening of the scalar field self-interaction potential, occuring within the Minkowski cosmological phase of the DGP model and mimetizing 4D phantom behaviour, is an attractor solution for a constant self-interaction potential but not for the exponential one. In the latter case gravitational screening is not even a critical point of the corresponding autonomous system of ordinary differential equations. |
2108.01472 | Gabriel R. Bengochea | Gabriel R. Bengochea, Mar\'ia P\'ia Piccirilli, Gabriel Le\'on | Emergent universe revisited through the CSL theory | 15 pages, 5 figures. Some references added. Version accepted in EPJC | Eur. Phys. J. C 81, 1049 (2021) | 10.1140/epjc/s10052-021-09842-x | null | gr-qc astro-ph.CO quant-ph | http://creativecommons.org/licenses/by/4.0/ | In this work we analyze how the spectrum of primordial scalar perturbations
is modified, within the emergent universe scenario, when a particular version
of the Continuous Spontaneous Localization (CSL) model is incorporated as the
generating mechanism of initial perturbations, providing also an explanation to
the quantum-to-classical transition of such perturbations. On the other hand, a
phase of super-inflation, prior to slow-roll inflation, is a characteristic
feature of the emergent universe hypothesis. In recent works, it was shown that
the super-inflation phase could generically induce a suppression of the
temperature anisotropies of the CMB at large angular scales. We study here
under what conditions the CSL maintains or modifies these characteristics of
the emergent universe and their compatibility with the CMB observations.
| [
{
"created": "Mon, 2 Aug 2021 13:38:04 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Dec 2021 16:18:11 GMT",
"version": "v2"
}
] | 2021-12-03 | [
[
"Bengochea",
"Gabriel R.",
""
],
[
"Piccirilli",
"María Pía",
""
],
[
"León",
"Gabriel",
""
]
] | In this work we analyze how the spectrum of primordial scalar perturbations is modified, within the emergent universe scenario, when a particular version of the Continuous Spontaneous Localization (CSL) model is incorporated as the generating mechanism of initial perturbations, providing also an explanation to the quantum-to-classical transition of such perturbations. On the other hand, a phase of super-inflation, prior to slow-roll inflation, is a characteristic feature of the emergent universe hypothesis. In recent works, it was shown that the super-inflation phase could generically induce a suppression of the temperature anisotropies of the CMB at large angular scales. We study here under what conditions the CSL maintains or modifies these characteristics of the emergent universe and their compatibility with the CMB observations. |
0903.3475 | Etera R. Livine | Florian Girelli, Etera R. Livine, Daniele Oriti | 4d Deformed Special Relativity from Group Field Theories | 23 pages | Phys.Rev.D81:024015,2010 | 10.1103/PhysRevD.81.024015 | ITP-UU-08/57, SPIN-08/44, AEI-2009-029 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive a scalar field theory of the deformed special relativity type,
living on non-commutative kappa-Minkowski spacetime and with a kappa-deformed
Poincare symmetry, from the SO(4,1) group field theory defining the transition
amplitudes for topological BF-theory in 4 space-time dimensions. This is done
at a non-perturbative level of the spin foam formalism working directly with
the group field theory (GFT). We show that matter fields emerge from the
fundamental model as perturbations around a specific phase of the GFT,
corresponding to a solution of the fundamental equations of motion, and that
the non-commutative field theory governs their effective dynamics.
| [
{
"created": "Fri, 20 Mar 2009 09:25:40 GMT",
"version": "v1"
}
] | 2010-03-12 | [
[
"Girelli",
"Florian",
""
],
[
"Livine",
"Etera R.",
""
],
[
"Oriti",
"Daniele",
""
]
] | We derive a scalar field theory of the deformed special relativity type, living on non-commutative kappa-Minkowski spacetime and with a kappa-deformed Poincare symmetry, from the SO(4,1) group field theory defining the transition amplitudes for topological BF-theory in 4 space-time dimensions. This is done at a non-perturbative level of the spin foam formalism working directly with the group field theory (GFT). We show that matter fields emerge from the fundamental model as perturbations around a specific phase of the GFT, corresponding to a solution of the fundamental equations of motion, and that the non-commutative field theory governs their effective dynamics. |
1403.2231 | T. P. Singh | Anushrut Sharma and Tejinder P. Singh | A possible correspondence between Ricci identities and Dirac equations
in the Newman-Penrose formalism: towards an understanding of gravity induced
collapse of the wave-function? | v2. 30 pages. Additional discussion in Sections IV and V. References
added. To appear in Gen. Rel. Grav | null | 10.1007/s10714-014-1821-0 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well-known that in the Newman-Penrose formalism the Riemann tensor can
be expressed as a set of eighteen complex first-order equations, in terms of
the twelve spin coefficients, known as Ricci identities. The Ricci tensor
herein is determined via the Einstein equations. It is also known that the
Dirac equation in a curved spacetime can be written in the Newman-Penrose
formalism as a set of four first-order coupled equations for the spinor
components of the wave-function. In the present article we suggest that it
might be possible to think of the Dirac equations in the N-P formalism as a
special case of the Ricci identities, after an appropriate identification of
the four Dirac spinor components with four of the spin coefficients, provided
torsion is included in the connection, and after a suitable generalization of
the energy-momentum tensor. We briefly comment on similarities with the
Einstein-Cartan-Sciama-Kibble theory. The motivation for this study is to take
some very preliminary steps towards developing a rigorous description of the
hypothesis that dynamical collapse of the wave-function during a quantum
measurement is caused by gravity.
| [
{
"created": "Mon, 10 Mar 2014 12:58:57 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Oct 2014 17:02:59 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Sharma",
"Anushrut",
""
],
[
"Singh",
"Tejinder P.",
""
]
] | It is well-known that in the Newman-Penrose formalism the Riemann tensor can be expressed as a set of eighteen complex first-order equations, in terms of the twelve spin coefficients, known as Ricci identities. The Ricci tensor herein is determined via the Einstein equations. It is also known that the Dirac equation in a curved spacetime can be written in the Newman-Penrose formalism as a set of four first-order coupled equations for the spinor components of the wave-function. In the present article we suggest that it might be possible to think of the Dirac equations in the N-P formalism as a special case of the Ricci identities, after an appropriate identification of the four Dirac spinor components with four of the spin coefficients, provided torsion is included in the connection, and after a suitable generalization of the energy-momentum tensor. We briefly comment on similarities with the Einstein-Cartan-Sciama-Kibble theory. The motivation for this study is to take some very preliminary steps towards developing a rigorous description of the hypothesis that dynamical collapse of the wave-function during a quantum measurement is caused by gravity. |
2106.00035 | Leonhard Kehrberger | Leonhard M. A. Kehrberger | The Case Against Smooth Null Infinity III: Early-Time Asymptotics for
Higher $\ell$-Modes of Linear Waves on a Schwarzschild Background | 100 pages, 6 figures. v3: Comments by reviewer worked in. v4:
correction to Figure 6, v5: Fixed typesetting error added in v4 | Annals of PDE 8, 12 (2022) | 10.1007/s40818-022-00129-2 | null | gr-qc hep-th math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we derive the early-time asymptotics for fixed-frequency
solutions $\phi_\ell$ to the wave equation $\Box_g \phi_\ell=0$ on a fixed
Schwarzschild background ($M>0$) arising from the no incoming radiation
condition on $\mathcal I^-$ and polynomially decaying data, $r\phi_\ell\sim
t^{-1}$ as $t\to-\infty$, on either a timelike boundary of constant area radius
(I) or an ingoing null hypersurface (II). In case (I), we show that the
asymptotic expansion of $\partial_v(r\phi_\ell)$ along outgoing null
hypersurfaces near spacelike infinity $i^0$ contains logarithmic terms at order
$r^{-3-\ell}\log r$. In contrast, in case (II), we obtain that the asymptotic
expansion of $\partial_v(r\phi_\ell)$ near spacelike infinity $i^0$ contains
logarithmic terms already at order $r^{-3}\log r$ (unless $\ell=1$).
These results suggest an alternative approach to the study of late-time
asymptotics near future timelike infinity $i^+$ that does not assume
conformally smooth or compactly supported Cauchy data: In case (I), our results
indicate logarithmic modifications to Price's law for each $\ell$-mode. On the
other hand, the data of case (II) lead to much stronger deviations from Price's
law. In particular, we conjecture that compactly supported scattering data on
$\mathcal H^-$ and $\mathcal I^-$ lead to solutions that exhibit the same
late-time asymptotics on $\mathcal I^+$ for each $\ell$: $r\phi_\ell|_{\mathcal
I^+}\sim u^{-2}$ as $u\to\infty$.
| [
{
"created": "Mon, 31 May 2021 18:03:47 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Jul 2021 17:43:58 GMT",
"version": "v2"
},
{
"created": "Thu, 2 Jun 2022 13:06:15 GMT",
"version": "v3"
},
{
"created": "Fri, 29 Sep 2023 09:30:27 GMT",
"version": "v4"
},
{
"cr... | 2024-04-30 | [
[
"Kehrberger",
"Leonhard M. A.",
""
]
] | In this paper, we derive the early-time asymptotics for fixed-frequency solutions $\phi_\ell$ to the wave equation $\Box_g \phi_\ell=0$ on a fixed Schwarzschild background ($M>0$) arising from the no incoming radiation condition on $\mathcal I^-$ and polynomially decaying data, $r\phi_\ell\sim t^{-1}$ as $t\to-\infty$, on either a timelike boundary of constant area radius (I) or an ingoing null hypersurface (II). In case (I), we show that the asymptotic expansion of $\partial_v(r\phi_\ell)$ along outgoing null hypersurfaces near spacelike infinity $i^0$ contains logarithmic terms at order $r^{-3-\ell}\log r$. In contrast, in case (II), we obtain that the asymptotic expansion of $\partial_v(r\phi_\ell)$ near spacelike infinity $i^0$ contains logarithmic terms already at order $r^{-3}\log r$ (unless $\ell=1$). These results suggest an alternative approach to the study of late-time asymptotics near future timelike infinity $i^+$ that does not assume conformally smooth or compactly supported Cauchy data: In case (I), our results indicate logarithmic modifications to Price's law for each $\ell$-mode. On the other hand, the data of case (II) lead to much stronger deviations from Price's law. In particular, we conjecture that compactly supported scattering data on $\mathcal H^-$ and $\mathcal I^-$ lead to solutions that exhibit the same late-time asymptotics on $\mathcal I^+$ for each $\ell$: $r\phi_\ell|_{\mathcal I^+}\sim u^{-2}$ as $u\to\infty$. |
gr-qc/9903069 | Roberto Casadio | R. Casadio and B. Harms | Testing string theory via black hole space-times | 12 pages, 4 figures, to appear in the proceedings of the 19th Texas
Symposium, Paris, 14-18 Dec 1998 | null | null | UAHEP 992 | gr-qc | null | Charged black holes, both spherically symmetric and rotating, in the low
energy limit of string theory (Einstein-Maxwell-dilaton theory) are compared to
analogous geometries in pure general relativity. We describe various physical
differences and investigate some experiments which can distinguish between the
two theories. In particular we discuss the gyro-magnetic ratios of rotating
black holes and the propagation of light on black hole backgrounds. For the
former we obtain an expression in the Einstein frame (EF) which is different
from the one in the String frame (SF). This (and other results) can be used to
test the stringy nature of matter. For a binary system consisting of a star and
a rotating black hole, we give estimates of the damping of electro-magnetic
radiation coming from the star due to the existence of a scalar component of
gravity.
| [
{
"created": "Thu, 18 Mar 1999 09:51:49 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Casadio",
"R.",
""
],
[
"Harms",
"B.",
""
]
] | Charged black holes, both spherically symmetric and rotating, in the low energy limit of string theory (Einstein-Maxwell-dilaton theory) are compared to analogous geometries in pure general relativity. We describe various physical differences and investigate some experiments which can distinguish between the two theories. In particular we discuss the gyro-magnetic ratios of rotating black holes and the propagation of light on black hole backgrounds. For the former we obtain an expression in the Einstein frame (EF) which is different from the one in the String frame (SF). This (and other results) can be used to test the stringy nature of matter. For a binary system consisting of a star and a rotating black hole, we give estimates of the damping of electro-magnetic radiation coming from the star due to the existence of a scalar component of gravity. |
1505.06760 | Ichiro Oda | Ichiro Oda | Conformal Higgs Gravity | 11 pages | null | null | DPUR/TH/45 | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a model of conformal gravity with Higgs field. This model has a
positive Newton's constant and exhibits a novel symmetry breaking mechanism of
gauge symmetries. A possible application to cosmology is briefly mentioned.
| [
{
"created": "Mon, 25 May 2015 21:25:16 GMT",
"version": "v1"
}
] | 2015-05-27 | [
[
"Oda",
"Ichiro",
""
]
] | We construct a model of conformal gravity with Higgs field. This model has a positive Newton's constant and exhibits a novel symmetry breaking mechanism of gauge symmetries. A possible application to cosmology is briefly mentioned. |
2212.09485 | Hossein Ghaffarnejad | Hossein Ghaffarnejad and Leyla Naderi | Modified Gauge Invariant Einstein Maxwell Gravity and Stability of
Spherical perfect fluid Stars with Magnetic Monopoles | 26 pages, 4 figures, presented as virtual in the 7th Gravity and
Particles Meeting of Northeast Iran, 14-15 Desember 2022, Shahrood University
of Technology
https://www.hsu.ac.ir/wp-content/uploads/2022/12/poster_221206_195327-1.jpg | Iranian Journal of Astronomy & Astrophysics 2024 | 10.22128/ijaa.2024.759.1175 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As an alternative gravity model we consider an extended Einstein-Maxwell
gravity containing a gauge invariance property. Extension is assumed to be
addition of a directional coupling between spatial electromagnetic fields with
the Ricci tensor. We will see importance of the additional term in making a
compact stellar object and value of its radius. As an application of this model
we substitute ansatz of magnetic field of a hypothetical magnetic monopole
which has just time independent radial component and for matter part we assume
a perfect fluid stress tensor. To obtain spherically symmetric internal metric
of the perfect fluid stellar compact object we solve Tolman-Oppenheimer-Volkoff
equation with a polytropic form of equation of state as $p(\rho)=a\rho^2$.
Using dynamical system approach we study stability of the solutions for which
arrow diagrams show saddle (quasi stable) for $a<0$ (dark stars) and sink
(stable) for $a>0$ (normal visible stars). We check also the energy conditions,
speed of sound and Harrison-Zeldovich-Novikov static stability criterion for
obtained solution and confirm that they make stable state.
| [
{
"created": "Mon, 19 Dec 2022 14:42:00 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Feb 2023 18:37:20 GMT",
"version": "v2"
},
{
"created": "Fri, 5 Jan 2024 07:19:55 GMT",
"version": "v3"
}
] | 2024-01-08 | [
[
"Ghaffarnejad",
"Hossein",
""
],
[
"Naderi",
"Leyla",
""
]
] | As an alternative gravity model we consider an extended Einstein-Maxwell gravity containing a gauge invariance property. Extension is assumed to be addition of a directional coupling between spatial electromagnetic fields with the Ricci tensor. We will see importance of the additional term in making a compact stellar object and value of its radius. As an application of this model we substitute ansatz of magnetic field of a hypothetical magnetic monopole which has just time independent radial component and for matter part we assume a perfect fluid stress tensor. To obtain spherically symmetric internal metric of the perfect fluid stellar compact object we solve Tolman-Oppenheimer-Volkoff equation with a polytropic form of equation of state as $p(\rho)=a\rho^2$. Using dynamical system approach we study stability of the solutions for which arrow diagrams show saddle (quasi stable) for $a<0$ (dark stars) and sink (stable) for $a>0$ (normal visible stars). We check also the energy conditions, speed of sound and Harrison-Zeldovich-Novikov static stability criterion for obtained solution and confirm that they make stable state. |
2301.07675 | Jessica Lawrence | Jessica Lawrence, Kevin Turbang, Andrew Matas, Arianna I. Renzini,
Nick van Remortel, Joseph D. Romano | A stochastic search for intermittent gravitational-wave backgrounds | 23 pages, 8 figures, 1 table | null | 10.1103/PhysRevD.107.103026 | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | A likely source of a gravitational-wave background (GWB) in the frequency
band of the Advanced LIGO, Virgo and KAGRA detectors is the superposition of
signals from the population of unresolvable stellar-mass binary-black-hole
(BBH) mergers throughout the Universe. Since the duration of a BBH merger in
band ($\sim\!1~{\rm s}$) is much shorter than the expected separation between
neighboring mergers ($\sim\!10^3~{\rm s}$), the observed signal will be
"popcorn-like" or intermittent with duty cycles of order $10^{-3}$. However,
the standard cross-correlation search for stochastic GWBs currently performed
by the LIGO-Virgo-KAGRA collaboration is based on a continuous-Gaussian signal
model, which does not take into account the intermittent nature of the
background. The latter is better described by a Gaussian mixture-model, which
includes a duty cycle parameter that quantifies the degree of intermittence.
Building on an earlier paper by Drasco and Flanagan, we propose a
stochastic-signal-based search for intermittent GWBs. For such signals, this
search performs better than the standard continuous cross-correlation search.
We present results of our stochastic-signal-based approach for intermittent
GWBs applied to simulated data for some simple models, and compare its
performance to the other search methods, both in terms of detection and signal
characterization. Additional testing on more realistic simulated data sets,
e.g., consisting of astrophysically-motivated BBH merger signals injected into
colored detector noise containing noise transients, will be needed before this
method can be applied with confidence on real gravitational-wave data.
| [
{
"created": "Wed, 18 Jan 2023 17:52:33 GMT",
"version": "v1"
}
] | 2023-05-24 | [
[
"Lawrence",
"Jessica",
""
],
[
"Turbang",
"Kevin",
""
],
[
"Matas",
"Andrew",
""
],
[
"Renzini",
"Arianna I.",
""
],
[
"van Remortel",
"Nick",
""
],
[
"Romano",
"Joseph D.",
""
]
] | A likely source of a gravitational-wave background (GWB) in the frequency band of the Advanced LIGO, Virgo and KAGRA detectors is the superposition of signals from the population of unresolvable stellar-mass binary-black-hole (BBH) mergers throughout the Universe. Since the duration of a BBH merger in band ($\sim\!1~{\rm s}$) is much shorter than the expected separation between neighboring mergers ($\sim\!10^3~{\rm s}$), the observed signal will be "popcorn-like" or intermittent with duty cycles of order $10^{-3}$. However, the standard cross-correlation search for stochastic GWBs currently performed by the LIGO-Virgo-KAGRA collaboration is based on a continuous-Gaussian signal model, which does not take into account the intermittent nature of the background. The latter is better described by a Gaussian mixture-model, which includes a duty cycle parameter that quantifies the degree of intermittence. Building on an earlier paper by Drasco and Flanagan, we propose a stochastic-signal-based search for intermittent GWBs. For such signals, this search performs better than the standard continuous cross-correlation search. We present results of our stochastic-signal-based approach for intermittent GWBs applied to simulated data for some simple models, and compare its performance to the other search methods, both in terms of detection and signal characterization. Additional testing on more realistic simulated data sets, e.g., consisting of astrophysically-motivated BBH merger signals injected into colored detector noise containing noise transients, will be needed before this method can be applied with confidence on real gravitational-wave data. |
2405.18640 | Lorenzo Gavassino | Lorenzo Gavassino | Life on a closed timelike curve | 8 pages, 3 figures, comments welcome! | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the internal dynamics of a hypothetical spaceship traveling on a
close timelike curve in a G\"{o}del-type universe. We choose the curve so that
the generator of evolution in proper time is the angular momentum. Using
Wigner's theorem, we prove that the energy levels internal to the spaceship
must undergo spontaneous discretization. The level separation turns out to be
finely tuned so that, after completing a roundtrip of the curve, all systems
are back to their initial state. This implies, for example, that the memories
of an observer inside the spaceship are necessarily erased by the end of the
journey. More in general, if there is an increase in entropy, a Poincar\'{e}
cycle will eventually reverse it by the end of the loop, forcing entropy to
decrease back to its initial value. We show that such decrease in entropy is in
agreement with the eigenstate thermalization hypothesis. The non-existence of
time-travel paradoxes follows as a rigorous corollary of our analysis.
| [
{
"created": "Tue, 28 May 2024 22:51:54 GMT",
"version": "v1"
}
] | 2024-05-30 | [
[
"Gavassino",
"Lorenzo",
""
]
] | We study the internal dynamics of a hypothetical spaceship traveling on a close timelike curve in a G\"{o}del-type universe. We choose the curve so that the generator of evolution in proper time is the angular momentum. Using Wigner's theorem, we prove that the energy levels internal to the spaceship must undergo spontaneous discretization. The level separation turns out to be finely tuned so that, after completing a roundtrip of the curve, all systems are back to their initial state. This implies, for example, that the memories of an observer inside the spaceship are necessarily erased by the end of the journey. More in general, if there is an increase in entropy, a Poincar\'{e} cycle will eventually reverse it by the end of the loop, forcing entropy to decrease back to its initial value. We show that such decrease in entropy is in agreement with the eigenstate thermalization hypothesis. The non-existence of time-travel paradoxes follows as a rigorous corollary of our analysis. |
2208.05436 | Jose M. M. Senovilla | Jos\'e M. M. Senovilla | Gravitational radiation at infinity with non-negative cosmological
constant | 56 pages, 6 figures. Invited paper to the `Universe' Special Issue
"Gravitational Radiation in Cosmological Spacetimes" | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The existence of gravitational radiation arriving at null infinity -- i.e.
escaping from the physical system -- is addressed in the presence of a
non-negative cosmological constant $\Lambda\geq 0$. The case with vanishing
$\Lambda$ is well understood and relies on the properties of the News tensor
field (or the News function) defined at infinity. The situation is drastically
different when $\Lambda>0$ where there is no known notion of `News' with
similar good properties. In this paper both situations are considered jointly
from a {\em tidal} point of view, that is, taking into account the strength (or
energy) of the curvature tensors. The fundamental object used for that purposes
in the {\em asymptotic (radiant) super-momentum}, a causal vector defined at
infinity with remarkable properties. This leads to a novel characterization of
gravitational radiation valid for the general case with $\Lambda\geq 0$ that
has been proven to be equivalent, when $\Lambda =0$, to the standard one based
on News. The implications of this result are analyzed in some detail when
$\Lambda >0$. A general procedure to construct `news tensors' when $\Lambda >0$
is depicted, a proposal for asymptotic symmetries provided, and an example of a
conserved charge that may detect gravitational radiation at infinity exhibited.
A series of illustrative examples is listed.
| [
{
"created": "Wed, 10 Aug 2022 16:50:14 GMT",
"version": "v1"
}
] | 2022-08-11 | [
[
"Senovilla",
"José M. M.",
""
]
] | The existence of gravitational radiation arriving at null infinity -- i.e. escaping from the physical system -- is addressed in the presence of a non-negative cosmological constant $\Lambda\geq 0$. The case with vanishing $\Lambda$ is well understood and relies on the properties of the News tensor field (or the News function) defined at infinity. The situation is drastically different when $\Lambda>0$ where there is no known notion of `News' with similar good properties. In this paper both situations are considered jointly from a {\em tidal} point of view, that is, taking into account the strength (or energy) of the curvature tensors. The fundamental object used for that purposes in the {\em asymptotic (radiant) super-momentum}, a causal vector defined at infinity with remarkable properties. This leads to a novel characterization of gravitational radiation valid for the general case with $\Lambda\geq 0$ that has been proven to be equivalent, when $\Lambda =0$, to the standard one based on News. The implications of this result are analyzed in some detail when $\Lambda >0$. A general procedure to construct `news tensors' when $\Lambda >0$ is depicted, a proposal for asymptotic symmetries provided, and an example of a conserved charge that may detect gravitational radiation at infinity exhibited. A series of illustrative examples is listed. |
2009.08163 | Christopher Straub | Sebastian G\"unther, Jacob K\"orner, Timo Lebeda, Bastian P\"otzl,
Gerhard Rein, Christopher Straub, J\"org Weber | A numerical stability analysis for the Einstein-Vlasov system | 35 pages, 12 figures | Classical Quantum Gravity 38, 035003 (2021) | 10.1088/1361-6382/abcbdf | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate stability issues for steady states of the spherically
symmetric Einstein-Vlasov system numerically in Schwarzschild, maximal areal,
and Eddington-Finkelstein coordinates. Across all coordinate systems we confirm
the conjecture that the first binding energy maximum along a one-parameter
family of steady states signals the onset of instability. Beyond this maximum
perturbed solutions either collapse to a black hole, form heteroclinic orbits,
or eventually fully disperse. Contrary to earlier research, we find that a
negative binding energy does not necessarily correspond to fully dispersing
solutions. We also comment on the so-called turning point principle from the
viewpoint of our numerical results. The physical reliability of the latter is
strengthened by obtaining consistent results in the three different coordinate
systems and by the systematic use of dynamically accessible perturbations.
| [
{
"created": "Thu, 17 Sep 2020 09:17:11 GMT",
"version": "v1"
}
] | 2022-04-27 | [
[
"Günther",
"Sebastian",
""
],
[
"Körner",
"Jacob",
""
],
[
"Lebeda",
"Timo",
""
],
[
"Pötzl",
"Bastian",
""
],
[
"Rein",
"Gerhard",
""
],
[
"Straub",
"Christopher",
""
],
[
"Weber",
"Jörg",
""
]
] | We investigate stability issues for steady states of the spherically symmetric Einstein-Vlasov system numerically in Schwarzschild, maximal areal, and Eddington-Finkelstein coordinates. Across all coordinate systems we confirm the conjecture that the first binding energy maximum along a one-parameter family of steady states signals the onset of instability. Beyond this maximum perturbed solutions either collapse to a black hole, form heteroclinic orbits, or eventually fully disperse. Contrary to earlier research, we find that a negative binding energy does not necessarily correspond to fully dispersing solutions. We also comment on the so-called turning point principle from the viewpoint of our numerical results. The physical reliability of the latter is strengthened by obtaining consistent results in the three different coordinate systems and by the systematic use of dynamically accessible perturbations. |
2406.14982 | Naoki Yoshioka | Tomohiro Inagaki, Naoki Yoshioka | Non-thermal particle production in Einstein-Cartan gravity with modified
Holst term and non-minimal couplings | null | null | null | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | Non-thermal fermionic particle production is investigated in Einstein-Cartan
modified gravity with a modified Holst term and non-minimal couplings between
the spin connection and a fermion. By using the auxiliary field method, the
theory is rewritten into a pseudoscalar-tensor theory with Einstein-Hilbert
action and canonical kinetic and potential terms for a pseudoscalar field. The
introduced field is called Einstein-Cartan pseudoscalaron. If the potential
energy of the Einstein-Cartan pseudoscalaron dominates the energy density of
the early universe, it causes inflationary expansion. After the end of
inflation, the pseudoscalaron develops a large value and the non-minimal
couplings destabilize the vacuum. Evaluating the non-thermal fermionic particle
production process, we obtain the mass and the helicity dependences of the
produced particle number density. We show the model parameters to enhance the
preheating and reheating processes.
| [
{
"created": "Fri, 21 Jun 2024 08:46:34 GMT",
"version": "v1"
}
] | 2024-06-24 | [
[
"Inagaki",
"Tomohiro",
""
],
[
"Yoshioka",
"Naoki",
""
]
] | Non-thermal fermionic particle production is investigated in Einstein-Cartan modified gravity with a modified Holst term and non-minimal couplings between the spin connection and a fermion. By using the auxiliary field method, the theory is rewritten into a pseudoscalar-tensor theory with Einstein-Hilbert action and canonical kinetic and potential terms for a pseudoscalar field. The introduced field is called Einstein-Cartan pseudoscalaron. If the potential energy of the Einstein-Cartan pseudoscalaron dominates the energy density of the early universe, it causes inflationary expansion. After the end of inflation, the pseudoscalaron develops a large value and the non-minimal couplings destabilize the vacuum. Evaluating the non-thermal fermionic particle production process, we obtain the mass and the helicity dependences of the produced particle number density. We show the model parameters to enhance the preheating and reheating processes. |
gr-qc/9711019 | Perjes Zoltan | Mattias Marklund (Ume{\aa} University), Gyula Fodor, Zolt\'an Perj\'es
(KFKI Research Institute for Particle and Nuclear Physics) | Nonholonomic approach to rotating matter in general relativity | 3 pages, Latex, in: Proc. 8th Marcel Grossmann Meeting | null | null | null | gr-qc | null | Rigidly rotating stationary matter in general relativity has been
investigated by Kramer by the Ernst coordinate method. A weakness of this
approach is that the Ernst potential does not exist for differential rotation.
We now generalize the techniques by the use of a nonholonomic and nonrigid
frame. We apply these techniques for differentially rotating perfect fluids. We
construct a complex analytic tensor, characterizing the class of matter states
in which both the interior Schwarzschild and the Kerr solution are contained.
We derive consistency relations for this class of perfect fluids. We
investigate incompressible fluids characterized by these tensors.
| [
{
"created": "Thu, 6 Nov 1997 13:29:41 GMT",
"version": "v1"
}
] | 2016-08-15 | [
[
"Marklund",
"Mattias",
"",
"Umeå University"
],
[
"Fodor",
"Gyula",
"",
"KFKI Research Institute for Particle and Nuclear Physics"
],
[
"Perjés",
"Zoltán",
"",
"KFKI Research Institute for Particle and Nuclear Physics"
]
] | Rigidly rotating stationary matter in general relativity has been investigated by Kramer by the Ernst coordinate method. A weakness of this approach is that the Ernst potential does not exist for differential rotation. We now generalize the techniques by the use of a nonholonomic and nonrigid frame. We apply these techniques for differentially rotating perfect fluids. We construct a complex analytic tensor, characterizing the class of matter states in which both the interior Schwarzschild and the Kerr solution are contained. We derive consistency relations for this class of perfect fluids. We investigate incompressible fluids characterized by these tensors. |
2004.01750 | Foad Parsaei | Foad Parsaei and Nematollah Riazi | Evolving wormhole in the brane-world scenario | 11 pages, 7 figures | Phys. Rev. D 102, 044003 (2020) | 10.1103/PhysRevD.102.044003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, evolving wormholes in the context of brane-world scenario are
investigated. We have studied the possible dynamic solutions with different
forms of Ricci scalar. The possibility of existence of dynamic traversable
wormholes, without resorting to an exotic matter, has been studied. By using
the fact that the Einstein field equations are modified in 3+1 dimensions due
to the brane corrections, we investigate the exact solutions which satisfy null
energy condition. Asymptotic flatness is an important property of these
solutions. We discuss some physical and mathematical properties of the
solutions.
| [
{
"created": "Fri, 3 Apr 2020 19:55:32 GMT",
"version": "v1"
}
] | 2020-08-12 | [
[
"Parsaei",
"Foad",
""
],
[
"Riazi",
"Nematollah",
""
]
] | In this paper, evolving wormholes in the context of brane-world scenario are investigated. We have studied the possible dynamic solutions with different forms of Ricci scalar. The possibility of existence of dynamic traversable wormholes, without resorting to an exotic matter, has been studied. By using the fact that the Einstein field equations are modified in 3+1 dimensions due to the brane corrections, we investigate the exact solutions which satisfy null energy condition. Asymptotic flatness is an important property of these solutions. We discuss some physical and mathematical properties of the solutions. |
1403.7515 | Giorgio Papini | Giorgio Papini | Covariance and gauge invariance in relativistic theories of gravity | 8 pages, to appear in Modern Physics Letters A | Modern Physics Letters A Vol. 29, No. 14 (2014) 1450075 | 10.1142/S0217732314500758 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Any metric theory of gravity whose interaction with quantum particles is
described by a covariant wave equation is equivalent to a vector theory that
satisfies Maxwell-type equations identically. This result does not depend on
any particular set of field equations for the metric tensor, but only on
covariance. It is derived in the linear case, but can be extended to any order
of approximation in the metric deviation. In this formulation of the
interaction of gravity with matter, angular momentum and momentum are conserved
locally.
| [
{
"created": "Fri, 28 Mar 2014 19:48:52 GMT",
"version": "v1"
}
] | 2014-04-30 | [
[
"Papini",
"Giorgio",
""
]
] | Any metric theory of gravity whose interaction with quantum particles is described by a covariant wave equation is equivalent to a vector theory that satisfies Maxwell-type equations identically. This result does not depend on any particular set of field equations for the metric tensor, but only on covariance. It is derived in the linear case, but can be extended to any order of approximation in the metric deviation. In this formulation of the interaction of gravity with matter, angular momentum and momentum are conserved locally. |
2404.11395 | Cooper Watson | Cooper Watson, William Julius, Patrick Brown, Donald Salisbury, Gerald
Cleaver | An Intrinsic Coordinate Reference Frame Procedure I: Tensorial Canonical
Weyl Scalars | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Canonical quantization of gravity in general relativity is greatly simplified
by the artificial decomposition of space and time into a 3+1 formalism. Such a
simplification may appear to come at the cost of general covariance. This
requires tangential and perpendicular infinitesimal diffeomorphisms generated
by the symmetry group under the Legendre transformation of the given action.
This gauge generator, along with the fact that Weyl curvature scalars may act
as ``intrinsic coordinates" (or a dynamical reference frame) which depend only
on the spatial metric $g_{ab}$ and the conjugate momenta $p^{cd}$, allow for an
alternative approach to canonical quantization of gravity. In this paper we
present the tensorial solution of the set of Weyl scalars in terms of canonical
phase-space variables.
| [
{
"created": "Wed, 17 Apr 2024 13:58:44 GMT",
"version": "v1"
}
] | 2024-04-18 | [
[
"Watson",
"Cooper",
""
],
[
"Julius",
"William",
""
],
[
"Brown",
"Patrick",
""
],
[
"Salisbury",
"Donald",
""
],
[
"Cleaver",
"Gerald",
""
]
] | Canonical quantization of gravity in general relativity is greatly simplified by the artificial decomposition of space and time into a 3+1 formalism. Such a simplification may appear to come at the cost of general covariance. This requires tangential and perpendicular infinitesimal diffeomorphisms generated by the symmetry group under the Legendre transformation of the given action. This gauge generator, along with the fact that Weyl curvature scalars may act as ``intrinsic coordinates" (or a dynamical reference frame) which depend only on the spatial metric $g_{ab}$ and the conjugate momenta $p^{cd}$, allow for an alternative approach to canonical quantization of gravity. In this paper we present the tensorial solution of the set of Weyl scalars in terms of canonical phase-space variables. |
gr-qc/0303003 | Sigbjorn Hervik | Alan A. Coley and Sigbjorn Hervik | Brane-world Singularities | 12 pages | Class.Quant.Grav. 20 (2003) 3061-3070 | 10.1088/0264-9381/20/14/308 | null | gr-qc astro-ph | null | We study the behavior of spatially homogeneous brane-worlds close to the
initial singularity in the presence of both local and nonlocal stresses. It is
found that the singularity in these brane-worlds can be locally either
isotropic or anisotropic. We then investigate the Weyl curvature conjecture,
according to which some measure of the Weyl curvature is related to a
gravitational entropy. In particular, we study the Weyl curvature conjecture on
the brane with respect to the dimensionless ratio of the Weyl invariant and the
Ricci square and the measure proposed by Gr{\o}n and Hervik. We also argue that
the Weyl curvature conjecture should be formulated on brane
(i.e., in the four-dimensional context).
| [
{
"created": "Sat, 1 Mar 2003 11:09:08 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Coley",
"Alan A.",
""
],
[
"Hervik",
"Sigbjorn",
""
]
] | We study the behavior of spatially homogeneous brane-worlds close to the initial singularity in the presence of both local and nonlocal stresses. It is found that the singularity in these brane-worlds can be locally either isotropic or anisotropic. We then investigate the Weyl curvature conjecture, according to which some measure of the Weyl curvature is related to a gravitational entropy. In particular, we study the Weyl curvature conjecture on the brane with respect to the dimensionless ratio of the Weyl invariant and the Ricci square and the measure proposed by Gr{\o}n and Hervik. We also argue that the Weyl curvature conjecture should be formulated on brane (i.e., in the four-dimensional context). |
gr-qc/0204089 | Dr. Bikash Chandra Paul | B. C. Paul (North Bengal University) | Inflation in Bianchi models and the cosmic no hair theorem in brane
world | 12 pages, no figures, submitted to Phys. Rev. D | Phys.Rev. D66 (2002) 124019 | 10.1103/PhysRevD.66.124019 | null | gr-qc | null | In this paper, the cosmic no hair theorem for anisotropic Bianchi models
which admit inflation with a scalar field is studied in the framework of Brane
world. It is found that all Bianchi models except Bianchi type IX, transit to
an inflationary regime with vanishing anisotropy. In the Brane world,
anisotropic universe approaches the inflationary era much faster than that in
the general theory of relativity. The form of the potential does not affect the
evolution in the inflationary epoch. However, the late time behaviour is
controlled by a constant additive factor in the potential for the inflaton
field.
| [
{
"created": "Tue, 30 Apr 2002 08:26:22 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Paul",
"B. C.",
"",
"North Bengal University"
]
] | In this paper, the cosmic no hair theorem for anisotropic Bianchi models which admit inflation with a scalar field is studied in the framework of Brane world. It is found that all Bianchi models except Bianchi type IX, transit to an inflationary regime with vanishing anisotropy. In the Brane world, anisotropic universe approaches the inflationary era much faster than that in the general theory of relativity. The form of the potential does not affect the evolution in the inflationary epoch. However, the late time behaviour is controlled by a constant additive factor in the potential for the inflaton field. |
2112.14781 | Francesca Vidotto | Pietropaolo Frisoni, Francesco Gozzini, Francesca Vidotto | Numerical analysis of the self-energy in covariant Loop Quantum Gravity | 16 pages, 13 figures | Phys. Rev. D 105 (2022), 106018 | 10.1103/PhysRevD.105.106018 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We study numerically the first order radiative corrections to the
self-energy, in covariant loop quantum gravity. We employ the recently
developed 'sl2cfoam-next' spinfoam amplitudes library, and some original
numerical methods. We analyze the scaling of the divergence with the infrared
cutoff, for which previous analytical estimates provided widely different lower
and upper bounds. Our findings suggest that the divergence is approximately
linear in the cutoff. We also investigate the role of the Barbero-Immirzi
parameter in the asymptotic behavior, the dependence of the scaling on some
boundary data and the expectation values of boundary operators.
| [
{
"created": "Wed, 29 Dec 2021 19:00:01 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jul 2022 17:54:45 GMT",
"version": "v2"
}
] | 2022-09-29 | [
[
"Frisoni",
"Pietropaolo",
""
],
[
"Gozzini",
"Francesco",
""
],
[
"Vidotto",
"Francesca",
""
]
] | We study numerically the first order radiative corrections to the self-energy, in covariant loop quantum gravity. We employ the recently developed 'sl2cfoam-next' spinfoam amplitudes library, and some original numerical methods. We analyze the scaling of the divergence with the infrared cutoff, for which previous analytical estimates provided widely different lower and upper bounds. Our findings suggest that the divergence is approximately linear in the cutoff. We also investigate the role of the Barbero-Immirzi parameter in the asymptotic behavior, the dependence of the scaling on some boundary data and the expectation values of boundary operators. |
2312.02938 | Dirk Puetzfeld | Peter A. Hogan, Dirk Puetzfeld | Gravitational Radiation from an Accelerating Massive Particle in General
Relativity | 9 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A comprehensive description is given of a space--time model of an
accelerating massive particle. The particle radiates gravitational waves with
optical shear. The wave fronts are smoothly deformed spheres and the particle
experiences radiation reaction, similar to an accelerating charged particle,
and a loss of mass described by a Bondi mass--loss formula. The space--time is
one of the Bondi--Sachs forms but presented in a form here which is
particularly suited to the construction of the model particle. All details of
the calculations are given. A detailed examination of the gravitational field
of the particle is provided which illustrates the presence of gravitational
radiation and also exhibits, in the form of a type of singularity found in some
Robinson--Trautman space--times, the absence of an external field to supply
energy to the particle.
| [
{
"created": "Tue, 5 Dec 2023 18:09:06 GMT",
"version": "v1"
}
] | 2023-12-06 | [
[
"Hogan",
"Peter A.",
""
],
[
"Puetzfeld",
"Dirk",
""
]
] | A comprehensive description is given of a space--time model of an accelerating massive particle. The particle radiates gravitational waves with optical shear. The wave fronts are smoothly deformed spheres and the particle experiences radiation reaction, similar to an accelerating charged particle, and a loss of mass described by a Bondi mass--loss formula. The space--time is one of the Bondi--Sachs forms but presented in a form here which is particularly suited to the construction of the model particle. All details of the calculations are given. A detailed examination of the gravitational field of the particle is provided which illustrates the presence of gravitational radiation and also exhibits, in the form of a type of singularity found in some Robinson--Trautman space--times, the absence of an external field to supply energy to the particle. |
1811.06870 | Ali \"Ovg\"un Assist. Prof. | Ali \"Ovg\"un | Reply to "Comment on Light deflection by Damour-Solodukhin wormholes and
Gauss-Bonnet theorem" by Amrita Bhattacharya and Kh. Karimov Ramis | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reply to the Comment of Bhattacharya and Karimov on our paper Light
deflection by Damour-Solodukhin wormholes and Gauss-Bonnet theorem
[arXiv:1811.00768 [gr-qc]]. We address a number of incorrect claims made about
our calculations and methodology. We show below that the claims of BK are
incorrect, and that there are no problems with the results of \"{O}vg\"{u}n's
paper or its implications.
| [
{
"created": "Thu, 8 Nov 2018 20:31:03 GMT",
"version": "v1"
}
] | 2018-11-19 | [
[
"Övgün",
"Ali",
""
]
] | We reply to the Comment of Bhattacharya and Karimov on our paper Light deflection by Damour-Solodukhin wormholes and Gauss-Bonnet theorem [arXiv:1811.00768 [gr-qc]]. We address a number of incorrect claims made about our calculations and methodology. We show below that the claims of BK are incorrect, and that there are no problems with the results of \"{O}vg\"{u}n's paper or its implications. |
gr-qc/0006035 | Hans Ringstrom | Hans Ringstrom | The Bianchi IX attractor | 82 pages and 8 figures | Annales Henri Poincare 2 (2001) 405-500 | 10.1007/PL00001041 | null | gr-qc | null | We consider the asymptotic behaviour of spatially homogeneous spacetimes of
Bianchi type IX close to the singularity (we also consider some of the other
Bianchi types, e. g. Bianchi VIII in the stiff fluid case). The matter content
is assumed to be an orthogonal perfect fluid with linear equation of state and
zero cosmological constant. In terms of the variables of Wainwright and Hsu, we
have the following results. In the stiff fluid case, the solution converges to
a point for all the Bianchi class A types. For the other matter models we
consider, the Bianchi IX solutions generically converge to an attractor
consisting of the closure of the vacuum type II orbits. Furthermore, we observe
that for all the Bianchi class A spacetimes, except those of vacuum Taub type,
a curvature invariant is unbounded in the incomplete directions of inextendible
causal geodesics.
| [
{
"created": "Sat, 10 Jun 2000 08:35:37 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Ringstrom",
"Hans",
""
]
] | We consider the asymptotic behaviour of spatially homogeneous spacetimes of Bianchi type IX close to the singularity (we also consider some of the other Bianchi types, e. g. Bianchi VIII in the stiff fluid case). The matter content is assumed to be an orthogonal perfect fluid with linear equation of state and zero cosmological constant. In terms of the variables of Wainwright and Hsu, we have the following results. In the stiff fluid case, the solution converges to a point for all the Bianchi class A types. For the other matter models we consider, the Bianchi IX solutions generically converge to an attractor consisting of the closure of the vacuum type II orbits. Furthermore, we observe that for all the Bianchi class A spacetimes, except those of vacuum Taub type, a curvature invariant is unbounded in the incomplete directions of inextendible causal geodesics. |
1305.0310 | Henrique de Andrade Gomes | Henrique Gomes | A Birkhoff theorem for Shape Dynamics | 10 pages, matches published version | Class. Quantum Grav. 31 (2014) 085008 | 10.1088/0264-9381/31/8/085008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Shape Dynamics is a theory of gravity that replaces refoliation invariance
for spatial Weyl invariance. Those solutions of the Einstein equations that
have global, constant mean curvature slicings, are mirrored by solutions in
Shape Dynamics. However, there are solutions of Shape Dynamics that have no
counterpart in General relativity, just as there are solutions of GR that are
not completely foliable by global constant mean curvature slicings (such as the
Schwarzschild spacetime). It is therefore interesting to analyze directly the
equations of motion of Shape Dynamics in order to find its own solutions,
irrespective of properties of known solutions of GR. Here I perform a first
study in this direction by utilizing the equations of motion of Shape Dynamics
in a spherically symmetric, asymptotically flat ansatz to derive an analogue of
the Birkhoff theorem. There are two significant differences with respect to the
usual Birkhoff theorem in GR. The first regards the construction of the
solution: the spatial Weyl gauge freedom of shape dynamics is used to simplify
the problem, and boundary conditions are required. In fact the derivation is
simpler than the usual Birkhof theorem as no Christoffel symbols are needed.
The second, and most important difference is that the solution obtained is
uniquely the isotropic wormhole solution, in which no singularity is present,
as opposed to maximally extended Schwarzschild. This provides an explicit
example of the breaking of the duality between General relativity and Shape
Dynamics, and exhibits some of its consequences.
| [
{
"created": "Wed, 1 May 2013 23:03:40 GMT",
"version": "v1"
},
{
"created": "Mon, 27 May 2013 00:01:33 GMT",
"version": "v2"
},
{
"created": "Wed, 31 Jul 2013 18:40:49 GMT",
"version": "v3"
},
{
"created": "Mon, 7 Oct 2013 08:24:32 GMT",
"version": "v4"
},
{
"cre... | 2015-06-15 | [
[
"Gomes",
"Henrique",
""
]
] | Shape Dynamics is a theory of gravity that replaces refoliation invariance for spatial Weyl invariance. Those solutions of the Einstein equations that have global, constant mean curvature slicings, are mirrored by solutions in Shape Dynamics. However, there are solutions of Shape Dynamics that have no counterpart in General relativity, just as there are solutions of GR that are not completely foliable by global constant mean curvature slicings (such as the Schwarzschild spacetime). It is therefore interesting to analyze directly the equations of motion of Shape Dynamics in order to find its own solutions, irrespective of properties of known solutions of GR. Here I perform a first study in this direction by utilizing the equations of motion of Shape Dynamics in a spherically symmetric, asymptotically flat ansatz to derive an analogue of the Birkhoff theorem. There are two significant differences with respect to the usual Birkhoff theorem in GR. The first regards the construction of the solution: the spatial Weyl gauge freedom of shape dynamics is used to simplify the problem, and boundary conditions are required. In fact the derivation is simpler than the usual Birkhof theorem as no Christoffel symbols are needed. The second, and most important difference is that the solution obtained is uniquely the isotropic wormhole solution, in which no singularity is present, as opposed to maximally extended Schwarzschild. This provides an explicit example of the breaking of the duality between General relativity and Shape Dynamics, and exhibits some of its consequences. |
1009.5651 | Alberto Lobo | Priscilla Canizares, Aleix Conchillo, Marc Diaz--Aguilo, Enrique
Garcia-Berro, Lluis Gesa, Ferran Gibert, Catia Grimani, Ivan Lloro, Alberto
Lobo, Ignacio Mateos, Miquel Nofrarias, Juan Ramos-Castro, Josep Sanjuan and
Carlos F Sopuerta | The LISA PathFinder DMU and Radiation Monitor | 11 pages, 7 figures, prepared for the Proceedings of the 8th
International LISA Symposium, Classical and Quantum Gravity | Class.Quant.Grav.28:094004,2011 | 10.1088/0264-9381/28/9/094004 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The LISA PathFinder DMU (Data Management Unit) flight model was formally
accepted by ESA and ASD on 11 February 2010, after all hardware and software
tests had been successfully completed. The diagnostics items are scheduled to
be delivered by the end of 2010. In this paper we review the requirements and
performance of this instrumentation, specially focusing on the Radiation
Monitor and the DMU, as well as the status of their programmed use during
mission operations, on which work is ongoing at the time of writing.
| [
{
"created": "Tue, 28 Sep 2010 18:38:34 GMT",
"version": "v1"
}
] | 2011-04-22 | [
[
"Canizares",
"Priscilla",
""
],
[
"Conchillo",
"Aleix",
""
],
[
"Diaz--Aguilo",
"Marc",
""
],
[
"Garcia-Berro",
"Enrique",
""
],
[
"Gesa",
"Lluis",
""
],
[
"Gibert",
"Ferran",
""
],
[
"Grimani",
"Catia",
""... | The LISA PathFinder DMU (Data Management Unit) flight model was formally accepted by ESA and ASD on 11 February 2010, after all hardware and software tests had been successfully completed. The diagnostics items are scheduled to be delivered by the end of 2010. In this paper we review the requirements and performance of this instrumentation, specially focusing on the Radiation Monitor and the DMU, as well as the status of their programmed use during mission operations, on which work is ongoing at the time of writing. |
1504.06548 | Valentin Rudenko | N. I. Kolosnitsyn and V. N. Rudenko | Gravitational Hertz experiment with electromagnetic radiation in a
strong magnetic field | 10 pages , to be published in Physica Scripta | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Brief review of principal ideas in respect of the high frequency
gravitational radiation generated and detected in the laboratory condition is
presented. Interaction of electro-magnetic and gravitational waves into a
strong magnetic field is considered as a more promising variant of the
laboratory GW-Hertz experiment. The formulae of the direct and inverse
Gertsenshtein-Zeldovich effect are derived. Numerical estimates are given and a
discussion of a possibility of observation of these effects in a lab is carried
out.
| [
{
"created": "Fri, 24 Apr 2015 16:01:34 GMT",
"version": "v1"
}
] | 2015-04-27 | [
[
"Kolosnitsyn",
"N. I.",
""
],
[
"Rudenko",
"V. N.",
""
]
] | Brief review of principal ideas in respect of the high frequency gravitational radiation generated and detected in the laboratory condition is presented. Interaction of electro-magnetic and gravitational waves into a strong magnetic field is considered as a more promising variant of the laboratory GW-Hertz experiment. The formulae of the direct and inverse Gertsenshtein-Zeldovich effect are derived. Numerical estimates are given and a discussion of a possibility of observation of these effects in a lab is carried out. |
2210.04173 | Mohaddese Heydari-Fard | Malihe Heydari-Fard, Sara Ghassemi Honarvar, Mohaddese Heydari-Fard | Thin accretion disk luminosity and its image around rotating black holes
in perfect fluid dark matter | 9 pages(two columns), 9 figures | Monthly Notices of the Royal Astronomical Society, 521 (2023)
708-716 | 10.1093/mnras/stad558 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | Motivated by the fact that the universe is dominated by dark matter and dark
energy, we consider rotating black holes surrounded by perfect fluid dark
matter and study the accretion process in thin disk around such black holes.
Here, we are interested in how the presence of dark matter affects the
properties of the electromagnetic radiation emitted from a thin accretion disk.
For this purpose, we use the Novikov-Thorne model and obtain the
electromagnetic spectrum of an accretion disk around a rotating black hole in
perfect fluid dark matter and compare with the general relativistic case. The
results indicate that for small values of dark matter parameter we considered
here, the size of the innermost stable circular orbits would decrease and thus
the electromagnetic spectrum of the accretion disk increases. Therefore, disks
in the presence of perfect fluid dark matter are hotter and more luminous than
in general relativity. Finally, we construct thin accretion disk images around
these black holes using the numerical ray-tracing technique. We show that the
inclination angle has a remarkable effect on the images, while the effect of
dark matter parameter is small.
| [
{
"created": "Sun, 9 Oct 2022 05:46:41 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Mar 2023 07:59:52 GMT",
"version": "v2"
}
] | 2023-03-09 | [
[
"Heydari-Fard",
"Malihe",
""
],
[
"Honarvar",
"Sara Ghassemi",
""
],
[
"Heydari-Fard",
"Mohaddese",
""
]
] | Motivated by the fact that the universe is dominated by dark matter and dark energy, we consider rotating black holes surrounded by perfect fluid dark matter and study the accretion process in thin disk around such black holes. Here, we are interested in how the presence of dark matter affects the properties of the electromagnetic radiation emitted from a thin accretion disk. For this purpose, we use the Novikov-Thorne model and obtain the electromagnetic spectrum of an accretion disk around a rotating black hole in perfect fluid dark matter and compare with the general relativistic case. The results indicate that for small values of dark matter parameter we considered here, the size of the innermost stable circular orbits would decrease and thus the electromagnetic spectrum of the accretion disk increases. Therefore, disks in the presence of perfect fluid dark matter are hotter and more luminous than in general relativity. Finally, we construct thin accretion disk images around these black holes using the numerical ray-tracing technique. We show that the inclination angle has a remarkable effect on the images, while the effect of dark matter parameter is small. |
gr-qc/0304050 | Sigbjorn Hervik | John D. Barrow and Sigbjorn Hervik | The Future of Tilted Bianchi Universes | 17 pages; 2 figures; v2:paragraph added | Class.Quant.Grav. 20 (2003) 2841-2854 | 10.1088/0264-9381/20/13/329 | null | gr-qc astro-ph | null | An asymptotic stability analysis of spatially homogeneous models of Bianchi
type containing tilted perfect fluids is performed. Using the known attractors
for the non-tilted Bianchi type universes, we check whether they are stable
against perturbations with respect to tilted perfect fluids. We perform the
analysis for all Bianchi class B models and the Bianchi type VI_0 model. In
particular, we find that none of the non-tilted equilibrium points are stable
against tilted perfect fluids stiffer than radiation. We also indicate parts of
the phase space where new tilted exact solutions might be found.
| [
{
"created": "Mon, 14 Apr 2003 08:35:58 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Apr 2003 15:09:52 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Barrow",
"John D.",
""
],
[
"Hervik",
"Sigbjorn",
""
]
] | An asymptotic stability analysis of spatially homogeneous models of Bianchi type containing tilted perfect fluids is performed. Using the known attractors for the non-tilted Bianchi type universes, we check whether they are stable against perturbations with respect to tilted perfect fluids. We perform the analysis for all Bianchi class B models and the Bianchi type VI_0 model. In particular, we find that none of the non-tilted equilibrium points are stable against tilted perfect fluids stiffer than radiation. We also indicate parts of the phase space where new tilted exact solutions might be found. |
gr-qc/0306028 | Charles R. Evans | Mark D. Hannam, Charles R. Evans, Gregory B. Cook, Thomas W. Baumgarte | Can a combination of the conformal thin-sandwich and puncture methods
yield binary black hole solutions in quasi-equilibrium? | 8 pages, LaTeX2e, 2 postscript figures | Phys.Rev. D68 (2003) 064003 | 10.1103/PhysRevD.68.064003 | NSF-KITP-03-42, TAR-076-UNC | gr-qc | null | We consider combining two important methods for constructing
quasi-equilibrium initial data for binary black holes: the conformal
thin-sandwich formalism and the puncture method. The former seeks to enforce
stationarity in the conformal three-metric and the latter attempts to avoid
internal boundaries, like minimal surfaces or apparent horizons. We show that
these two methods make partially conflicting requirements on the boundary
conditions that determine the time slices. In particular, it does not seem
possible to construct slices that are quasi-stationary and avoid physical
singularities and simultaneously are connected by an everywhere positive lapse
function, a condition which must obtain if internal boundaries are to be
avoided. Some relaxation of these conflicting requirements may yield a soluble
system, but some of the advantages that were sought in combining these
approaches will be lost.
| [
{
"created": "Fri, 6 Jun 2003 20:44:48 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Hannam",
"Mark D.",
""
],
[
"Evans",
"Charles R.",
""
],
[
"Cook",
"Gregory B.",
""
],
[
"Baumgarte",
"Thomas W.",
""
]
] | We consider combining two important methods for constructing quasi-equilibrium initial data for binary black holes: the conformal thin-sandwich formalism and the puncture method. The former seeks to enforce stationarity in the conformal three-metric and the latter attempts to avoid internal boundaries, like minimal surfaces or apparent horizons. We show that these two methods make partially conflicting requirements on the boundary conditions that determine the time slices. In particular, it does not seem possible to construct slices that are quasi-stationary and avoid physical singularities and simultaneously are connected by an everywhere positive lapse function, a condition which must obtain if internal boundaries are to be avoided. Some relaxation of these conflicting requirements may yield a soluble system, but some of the advantages that were sought in combining these approaches will be lost. |
1709.07760 | Satyanad Kichenassamy | Satyanad Kichenassamy | Soliton stars in the breather limit | null | Classical and Quantum Gravity, 25 (2008) 245004 | 10.1088/0264-9381/25/24/245004 | null | gr-qc math.AP nlin.PS | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper presents an asymptotic reduction of the Einstein-Klein-Gordon
system with real scalar field ("soliton star problem"). A periodic solution of
the reduced system, similar to the sine-Gordon breather, is obtained by a
variational method. This tallies with numerical computations. As a consequence,
a time-periodic redshift for sources close to the center of the star is
obtained.
| [
{
"created": "Fri, 22 Sep 2017 14:04:33 GMT",
"version": "v1"
}
] | 2017-09-25 | [
[
"Kichenassamy",
"Satyanad",
""
]
] | This paper presents an asymptotic reduction of the Einstein-Klein-Gordon system with real scalar field ("soliton star problem"). A periodic solution of the reduced system, similar to the sine-Gordon breather, is obtained by a variational method. This tallies with numerical computations. As a consequence, a time-periodic redshift for sources close to the center of the star is obtained. |
2404.17616 | Sanasam Surendra Singh | Amit Samaddar, S. Surendra Singh, Shah Muhammad, Euaggelos E. Zotos | Behaviours of rip cosmological models in $f(Q,C)$ gravity | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this study, the Universe's rip cosmology theories have been provided for
the $f(Q,C)$ gravity theory, where $Q$ and $C$ stand for the non-metricity
scalar and boundary term. We assumed $f(Q,C)=\alpha Q^{n}+\beta C$ and analyzed
the nature of the physical parameters for the Little Rip, Big Rip and Pseudo
Rip models. In the LR and PR models, the EoS parameter exhibits phantom
characteristics but remains closely aligned with the $\Lambda$CDM line. After
investigating the energy conditions, we recognised that our model violates the
strong energy constraint. Avoiding singularity situations has been noted in all
of these accelerated models. The characteristics of the jerk and snap
parameters have been investigated. Our model provides an effective description
of the Universe's evolutionary history and fits well with contemporary cosmic
data.
| [
{
"created": "Fri, 26 Apr 2024 10:06:56 GMT",
"version": "v1"
}
] | 2024-04-30 | [
[
"Samaddar",
"Amit",
""
],
[
"Singh",
"S. Surendra",
""
],
[
"Muhammad",
"Shah",
""
],
[
"Zotos",
"Euaggelos E.",
""
]
] | In this study, the Universe's rip cosmology theories have been provided for the $f(Q,C)$ gravity theory, where $Q$ and $C$ stand for the non-metricity scalar and boundary term. We assumed $f(Q,C)=\alpha Q^{n}+\beta C$ and analyzed the nature of the physical parameters for the Little Rip, Big Rip and Pseudo Rip models. In the LR and PR models, the EoS parameter exhibits phantom characteristics but remains closely aligned with the $\Lambda$CDM line. After investigating the energy conditions, we recognised that our model violates the strong energy constraint. Avoiding singularity situations has been noted in all of these accelerated models. The characteristics of the jerk and snap parameters have been investigated. Our model provides an effective description of the Universe's evolutionary history and fits well with contemporary cosmic data. |
gr-qc/9605007 | Miquel Dorca. Fisica Teorica Uab. Telf: | M. Dorca and E. Verdaguer | Quantum fields interacting with colliding plane waves: the stress-energy
tensor and backreaction | 37 pages, LaTeX, 1 figure as a separate postscript file using
uufiles. Full postscript version soon available at
ftp://ftp.ifae.es/preprint/ft/uabft390.ps. A change in voffset latex command
has been performed | Nucl.Phys. B484 (1997) 435-475 | 10.1016/S0550-3213(96)00575-5 | UAB-FT-390 | gr-qc | null | Following a previous work on the quantization of a massless scalar field in a
spacetime representing the head on collision of two plane waves which fucus
into a Killing-Cauchy horizon, we compute the renormalized expectation value of
the stress-energy tensor of the quantum field near that horizon in the physical
state which corresponds to the Minkowski vacuum before the collision of the
waves. It is found that for minimally coupled and conformally coupled scalar
fields the respective stress-energy tensors are unbounded in the horizon. The
specific form of the divergences suggests that when the semiclassical Einstein
equations describing the backreaction of the quantum fields on the spacetime
geometry are taken into account, the horizon will acquire a curvature
singularity. Thus the Killing-Cauchy horizon which is known to be unstable
under ``generic" classical perturbations is also unstable by vacuum
polarization. The calculation is done following the point splitting
regularization technique. The dynamical colliding wave spacetime has four quite
distinct spacetime regions, namely, one flat region, two single plane wave
regions, and one interaction region. Exact mode solutions of the quantum field
equation cannot be found exactly, but the blueshift suffered by the initial
modes in the plane wave and interaction regions makes the use of the WKB
expansion a suitable method of solution. To ensure the correct regularization
of the stress-energy tensor, the initial flat modes propagated into the
interaction region must be given to a rather high adiabatic order of
approximation.
| [
{
"created": "Thu, 2 May 1996 21:03:48 GMT",
"version": "v1"
},
{
"created": "Fri, 3 May 1996 11:56:49 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Dorca",
"M.",
""
],
[
"Verdaguer",
"E.",
""
]
] | Following a previous work on the quantization of a massless scalar field in a spacetime representing the head on collision of two plane waves which fucus into a Killing-Cauchy horizon, we compute the renormalized expectation value of the stress-energy tensor of the quantum field near that horizon in the physical state which corresponds to the Minkowski vacuum before the collision of the waves. It is found that for minimally coupled and conformally coupled scalar fields the respective stress-energy tensors are unbounded in the horizon. The specific form of the divergences suggests that when the semiclassical Einstein equations describing the backreaction of the quantum fields on the spacetime geometry are taken into account, the horizon will acquire a curvature singularity. Thus the Killing-Cauchy horizon which is known to be unstable under ``generic" classical perturbations is also unstable by vacuum polarization. The calculation is done following the point splitting regularization technique. The dynamical colliding wave spacetime has four quite distinct spacetime regions, namely, one flat region, two single plane wave regions, and one interaction region. Exact mode solutions of the quantum field equation cannot be found exactly, but the blueshift suffered by the initial modes in the plane wave and interaction regions makes the use of the WKB expansion a suitable method of solution. To ensure the correct regularization of the stress-energy tensor, the initial flat modes propagated into the interaction region must be given to a rather high adiabatic order of approximation. |
1212.1253 | Wei-Tou Ni | An-Ming Wu and Wei-Tou Ni | Deployment and simulation of the ASTROD-GW formation | 15 pages, 5 figures, 3 tables, to be published in IJMPD vol.
22,1341005 (2013); this version to match the printed version | International Journal of Modern Physics D Vol. 22, No. 1 (2013)
1341005 (16 pages) | 10.1142/S0218271813410058 | null | gr-qc astro-ph.CO astro-ph.IM physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Constellation or formation flying is a common concept in space Gravitational
Wave (GW) mission proposals for the required interferometry implementation. The
spacecraft of most of these mission proposals go to deep space and many have
Earthlike orbits around the Sun. ASTROD-GW, Big Bang Observer and DECIGO have
spacecraft distributed in Earthlike orbits in formation. The deployment of
orbit formation is an important issue for these missions. ASTROD-GW
(Astrodynamical Space Test of Relativity using Optical Devices optimized for
Gravitation Wave detection) is to focus on the goal of detection of GWs. The
mission orbits of the 3 spacecraft forming a nearly equilateral triangular
array are chosen to be near the Sun-Earth Lagrange points L3, L4 and L5. The 3
spacecraft range interferometrically with one another with arm length about 260
million kilometers with the scientific goals including detection of GWs from
Massive Black Holes (MBH), and Extreme-Mass-Ratio Black Hole Inspirals (EMRI),
and using these observations to find the evolution of the equation of state of
dark energy and to explore the co-evolution of massive black holes with
galaxies. In this paper, we review the formation flying for fundamental physics
missions, design the preliminary transfer orbits of the ASTROD-GW spacecraft
from the separations of the launch vehicles to the mission orbits, and simulate
the arm lengths of the triangular formation. From our study, the optimal
delta-Vs and propellant ratios of the transfer orbits could be within about 2.5
km/s and 0.55, respectively. From the simulation of the formation for 10 years,
the arm lengths of the formation vary in the range 1.73210 +- 0.00015 AU with
the arm length differences varying in the range +- 0.00025 AU for formation
with 1 degree inclination to the ecliptic plane. This meets the measurement
requirements.
| [
{
"created": "Thu, 6 Dec 2012 07:53:07 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Dec 2012 12:14:24 GMT",
"version": "v2"
},
{
"created": "Fri, 18 Jan 2013 07:02:30 GMT",
"version": "v3"
}
] | 2013-02-01 | [
[
"Wu",
"An-Ming",
""
],
[
"Ni",
"Wei-Tou",
""
]
] | Constellation or formation flying is a common concept in space Gravitational Wave (GW) mission proposals for the required interferometry implementation. The spacecraft of most of these mission proposals go to deep space and many have Earthlike orbits around the Sun. ASTROD-GW, Big Bang Observer and DECIGO have spacecraft distributed in Earthlike orbits in formation. The deployment of orbit formation is an important issue for these missions. ASTROD-GW (Astrodynamical Space Test of Relativity using Optical Devices optimized for Gravitation Wave detection) is to focus on the goal of detection of GWs. The mission orbits of the 3 spacecraft forming a nearly equilateral triangular array are chosen to be near the Sun-Earth Lagrange points L3, L4 and L5. The 3 spacecraft range interferometrically with one another with arm length about 260 million kilometers with the scientific goals including detection of GWs from Massive Black Holes (MBH), and Extreme-Mass-Ratio Black Hole Inspirals (EMRI), and using these observations to find the evolution of the equation of state of dark energy and to explore the co-evolution of massive black holes with galaxies. In this paper, we review the formation flying for fundamental physics missions, design the preliminary transfer orbits of the ASTROD-GW spacecraft from the separations of the launch vehicles to the mission orbits, and simulate the arm lengths of the triangular formation. From our study, the optimal delta-Vs and propellant ratios of the transfer orbits could be within about 2.5 km/s and 0.55, respectively. From the simulation of the formation for 10 years, the arm lengths of the formation vary in the range 1.73210 +- 0.00015 AU with the arm length differences varying in the range +- 0.00025 AU for formation with 1 degree inclination to the ecliptic plane. This meets the measurement requirements. |
2304.14174 | Bijan Bagchi | Bijan Bagchi, Rahul Ghosh, Sauvik Sen | Analogue Hawking radiation as a tunneling in a two-level
$\mathcal{PT}$-symmetric system | Entropy 2023, 25, 1202 | null | 10.3390/e25081202 | null | gr-qc cond-mat.other hep-th quant-ph | http://creativecommons.org/publicdomain/zero/1.0/ | In the light of a general scenario of a two-level non-Hermitian
$\mathcal{PT}$-symmetric Hamiltonian we apply the tetrad-based method to
analyze the possibility of analogue Hawking radiation. It is done by making use
of the conventional null-geodesic approach wherein the associated Hawking
radiation is described as a quantum tunneling process across a classically
forbidden barrier which the event horizon imposes. An interesting aspect of our
result is that our estimate for the tunneling probability is independent of the
non-Hermitian parameter that defines the guiding Hamiltonian.
| [
{
"created": "Thu, 27 Apr 2023 13:23:32 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Aug 2023 03:05:27 GMT",
"version": "v2"
}
] | 2023-08-16 | [
[
"Bagchi",
"Bijan",
""
],
[
"Ghosh",
"Rahul",
""
],
[
"Sen",
"Sauvik",
""
]
] | In the light of a general scenario of a two-level non-Hermitian $\mathcal{PT}$-symmetric Hamiltonian we apply the tetrad-based method to analyze the possibility of analogue Hawking radiation. It is done by making use of the conventional null-geodesic approach wherein the associated Hawking radiation is described as a quantum tunneling process across a classically forbidden barrier which the event horizon imposes. An interesting aspect of our result is that our estimate for the tunneling probability is independent of the non-Hermitian parameter that defines the guiding Hamiltonian. |
1704.04020 | Guillem Dom\`enech | Pisin Chen, Guillem Dom\`enech, Misao Sasaki and Dong-han Yeom | Thermal activation of thin-shells in anti-de Sitter black hole spacetime | published version | null | 10.1007/JHEP07(2017)134 | YITP-17-39 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate thermal activation of thin-shells around anti-de Sitter black
holes. Under the thin-shell approximation, we extensively study the parameter
region that allows a bubble nucleation bounded by a thin-shell out of a thermal
bath. We show that in general if one fixes the temperature outside the shell,
one needs to consider the presence of a conical deficit inside the shell in the
Euclidean manifold, due to the lack of solutions with a smooth manifold. We
show that for a given set of theoretical parameters, i.e., vacuum and shell
energy density, there is a finite range of black hole masses that allow this
transition. Most interestingly, one of them describes the complete evaporation
of the initial black hole.
| [
{
"created": "Thu, 13 Apr 2017 07:34:33 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Sep 2017 05:30:02 GMT",
"version": "v2"
}
] | 2017-09-29 | [
[
"Chen",
"Pisin",
""
],
[
"Domènech",
"Guillem",
""
],
[
"Sasaki",
"Misao",
""
],
[
"Yeom",
"Dong-han",
""
]
] | We investigate thermal activation of thin-shells around anti-de Sitter black holes. Under the thin-shell approximation, we extensively study the parameter region that allows a bubble nucleation bounded by a thin-shell out of a thermal bath. We show that in general if one fixes the temperature outside the shell, one needs to consider the presence of a conical deficit inside the shell in the Euclidean manifold, due to the lack of solutions with a smooth manifold. We show that for a given set of theoretical parameters, i.e., vacuum and shell energy density, there is a finite range of black hole masses that allow this transition. Most interestingly, one of them describes the complete evaporation of the initial black hole. |
2007.11562 | Keefe Mitman | Keefe Mitman, Jordan Moxon, Mark A. Scheel, Saul A. Teukolsky, Michael
Boyle, Nils Deppe, Lawrence E. Kidder, William Throwe | Computation of Displacement and Spin Gravitational Memory in Numerical
Relativity | 20 pages, 11 figures; 10.1103/PhysRevD.102.104007. Corrected a minor
sign error in Eqs. 27, 40, 42, 43, and 51 | Phys. Rev. D 102, 104007 (2020) | 10.1103/PhysRevD.102.104007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first numerical relativity waveforms for binary black hole
mergers produced using spectral methods that show both the displacement and the
spin memory effects. Explicitly, we use the SXS Collaboration's $\texttt{SpEC}$
code to run a Cauchy evolution of a binary black hole merger and then extract
the gravitational wave strain using $\texttt{SpECTRE}$'s version of a
Cauchy-characteristic extraction. We find that we can accurately resolve the
strain's traditional $m=0$ memory modes and some of the $m\not=0$ oscillatory
memory modes that have previously only been theorized. We also perform a
separate calculation of the memory using equations for the Bondi-Metzner-Sachs
charges as well as the energy and angular momentum fluxes at asymptotic
infinity. Our new calculation uses only the gravitational wave strain and two
of the Weyl scalars at infinity. Also, this computation shows that the memory
modes can be understood as a combination of a memory signal throughout the
binary's inspiral and merger phases, and a quasinormal mode signal near the
ringdown phase. Additionally, we find that the magnetic memory, up to numerical
error, is indeed zero as previously conjectured. Lastly, we find that
signal-to-noise ratios of memory for LIGO, the Einstein Telescope (ET), and the
Laser Interferometer Space Antenna (LISA) with these new waveforms and new
memory calculation are larger than previous expectations based on
post-Newtonian or Minimal Waveform models.
| [
{
"created": "Wed, 22 Jul 2020 17:40:05 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Aug 2020 20:04:11 GMT",
"version": "v2"
},
{
"created": "Wed, 4 Nov 2020 00:58:10 GMT",
"version": "v3"
},
{
"created": "Tue, 26 Jan 2021 16:34:48 GMT",
"version": "v4"
}
] | 2021-01-27 | [
[
"Mitman",
"Keefe",
""
],
[
"Moxon",
"Jordan",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Teukolsky",
"Saul A.",
""
],
[
"Boyle",
"Michael",
""
],
[
"Deppe",
"Nils",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
... | We present the first numerical relativity waveforms for binary black hole mergers produced using spectral methods that show both the displacement and the spin memory effects. Explicitly, we use the SXS Collaboration's $\texttt{SpEC}$ code to run a Cauchy evolution of a binary black hole merger and then extract the gravitational wave strain using $\texttt{SpECTRE}$'s version of a Cauchy-characteristic extraction. We find that we can accurately resolve the strain's traditional $m=0$ memory modes and some of the $m\not=0$ oscillatory memory modes that have previously only been theorized. We also perform a separate calculation of the memory using equations for the Bondi-Metzner-Sachs charges as well as the energy and angular momentum fluxes at asymptotic infinity. Our new calculation uses only the gravitational wave strain and two of the Weyl scalars at infinity. Also, this computation shows that the memory modes can be understood as a combination of a memory signal throughout the binary's inspiral and merger phases, and a quasinormal mode signal near the ringdown phase. Additionally, we find that the magnetic memory, up to numerical error, is indeed zero as previously conjectured. Lastly, we find that signal-to-noise ratios of memory for LIGO, the Einstein Telescope (ET), and the Laser Interferometer Space Antenna (LISA) with these new waveforms and new memory calculation are larger than previous expectations based on post-Newtonian or Minimal Waveform models. |
gr-qc/9412067 | Adrian Kent | Fay Dowker, Adrian Kent | On the Consistent Histories Approach to Quantum Mechanics | Published version, to appear in J. Stat. Phys. in early 1996. The
main arguments and conclusions remain unaltered, but there are significant
revisions from the earlier archive version. These include a new subsection on
interpretations of the formalism, other additions clarifying various
arguments in response to comments, and some minor corrections. (87 pages, TeX
with harvmac.) | J.Statist.Phys. 82 (1996) 1575-1646 | 10.1007/BF02183396 | DAMTP/94-48, NI 94006 | gr-qc hep-th quant-ph | null | We review the consistent histories formulations of quantum mechanics
developed by Griffiths, Omn\`es and Gell-Mann and Hartle, and describe the
classification of consistent sets. We illustrate some general features of
consistent sets by a few simple lemmas and examples. We consider various
interpretations of the formalism, and examine the new problems which arise in
reconstructing the past and predicting the future. It is shown that Omn\`es'
characterisation of true statements --- statements which can be deduced
unconditionally in his interpretation --- is incorrect. We examine critically
Gell-Mann and Hartle's interpretation of the formalism, and in particular their
discussions of communication, prediction and retrodiction, and conclude that
their explanation of the apparent persistence of quasiclassicality relies on
assumptions about an as yet unknown theory of experience. Our overall
conclusion is that the consistent histories approach illustrates the need to
supplement quantum mechanics by some selection principle in order to produce a
fundamental theory capable of unconditional predictions.
| [
{
"created": "Thu, 22 Dec 1994 15:22:13 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jan 1996 19:35:25 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Dowker",
"Fay",
""
],
[
"Kent",
"Adrian",
""
]
] | We review the consistent histories formulations of quantum mechanics developed by Griffiths, Omn\`es and Gell-Mann and Hartle, and describe the classification of consistent sets. We illustrate some general features of consistent sets by a few simple lemmas and examples. We consider various interpretations of the formalism, and examine the new problems which arise in reconstructing the past and predicting the future. It is shown that Omn\`es' characterisation of true statements --- statements which can be deduced unconditionally in his interpretation --- is incorrect. We examine critically Gell-Mann and Hartle's interpretation of the formalism, and in particular their discussions of communication, prediction and retrodiction, and conclude that their explanation of the apparent persistence of quasiclassicality relies on assumptions about an as yet unknown theory of experience. Our overall conclusion is that the consistent histories approach illustrates the need to supplement quantum mechanics by some selection principle in order to produce a fundamental theory capable of unconditional predictions. |
gr-qc/0209107 | Lior M. Burko | Lior M.Burko and Gaurav Khanna | Radiative falloff in the background of rotating black hole | 5 pages, 4 Encapsulated PostScript figures; Accepted to Phys. Rev. D
(Rapid Communication) | Phys.Rev. D67 (2003) 081502 | 10.1103/PhysRevD.67.081502 | null | gr-qc | null | We study numerically the late-time tails of linearized fields with any spin
$s$ in the background of a spinning black hole. Our code is based on the
ingoing Kerr coordinates, which allow us to penetrate through the event
horizon. The late time tails are dominated by the mode with the least multipole
moment $\ell$ which is consistent with the equatorial symmetry of the initial
data and is equal to or greater than the least radiative mode with $s$ and the
azimuthal number $m$.
| [
{
"created": "Fri, 27 Sep 2002 17:44:58 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Mar 2003 20:05:36 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Burko",
"Lior M.",
""
],
[
"Khanna",
"Gaurav",
""
]
] | We study numerically the late-time tails of linearized fields with any spin $s$ in the background of a spinning black hole. Our code is based on the ingoing Kerr coordinates, which allow us to penetrate through the event horizon. The late time tails are dominated by the mode with the least multipole moment $\ell$ which is consistent with the equatorial symmetry of the initial data and is equal to or greater than the least radiative mode with $s$ and the azimuthal number $m$. |
2201.08287 | Dimitris Moustos | Dimitris Moustos | Uniformly accelerated Brownian oscillator in (2+1)D:
temperature-dependent dissipation and frequency shift | 8 pages, 1 figure, Appendix A was added, Updated to match the
published version | Phys. Lett. B 829, 137115 (2022) | 10.1016/j.physletb.2022.137115 | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | We consider an Unruh-DeWitt detector modeled as a harmonic oscillator that is
coupled to a massless quantum scalar field in the (2+1)-dimensional Minkowski
spacetime. We treat the detector as an open quantum system and employ a quantum
Langevin equation to describe its time evolution, with the field, which is
characterized by a frequency-independent spectral density, acting as a
stochastic force. We investigate a point-like detector moving with constant
acceleration through the Minkowski vacuum and an inertial one immersed in a
thermal reservoir at the Unruh temperature, exploring the implications of the
well-known non-equivalence between the two cases on their dynamics. We find
that both the accelerated detector's dissipation rate and the shift of its
frequency caused by the coupling to the field bath depend on the acceleration
temperature. Interestingly enough this is not only in contrast to the case of
inertial motion in a heat bath but also to any analogous quantum Brownian
motion model in open systems, where dissipation and frequency shifts are not
known to exhibit temperature dependencies. Nonetheless, we show that the
fluctuating-dissipation theorem still holds for the detector-field system and
in the weak-coupling limit an accelerated detector is driven at late times to a
thermal equilibrium state at the Unruh temperature.
| [
{
"created": "Thu, 20 Jan 2022 16:45:38 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Apr 2022 09:09:22 GMT",
"version": "v2"
}
] | 2022-04-28 | [
[
"Moustos",
"Dimitris",
""
]
] | We consider an Unruh-DeWitt detector modeled as a harmonic oscillator that is coupled to a massless quantum scalar field in the (2+1)-dimensional Minkowski spacetime. We treat the detector as an open quantum system and employ a quantum Langevin equation to describe its time evolution, with the field, which is characterized by a frequency-independent spectral density, acting as a stochastic force. We investigate a point-like detector moving with constant acceleration through the Minkowski vacuum and an inertial one immersed in a thermal reservoir at the Unruh temperature, exploring the implications of the well-known non-equivalence between the two cases on their dynamics. We find that both the accelerated detector's dissipation rate and the shift of its frequency caused by the coupling to the field bath depend on the acceleration temperature. Interestingly enough this is not only in contrast to the case of inertial motion in a heat bath but also to any analogous quantum Brownian motion model in open systems, where dissipation and frequency shifts are not known to exhibit temperature dependencies. Nonetheless, we show that the fluctuating-dissipation theorem still holds for the detector-field system and in the weak-coupling limit an accelerated detector is driven at late times to a thermal equilibrium state at the Unruh temperature. |
2304.12553 | Zhen Li | Zhen Li, Faqiang Yuan | Energy extraction via Comisso-Asenjo mechanism from rotating hairy black
hole | 8 pages, 8 figures. arXiv admin note: text overlap with
arXiv:2304.08831 | null | 10.1103/PhysRevD.108.024039 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was demonstrated by Comisso and Asenjo that the magnetic reconnection in
the ergosphere is a promising mechanism to extract energy from the rotating
Kerr black hole. In this work, we investigate the role of Comisso-Asenjo
mechanism in energy extraction from the newly suggested rotating hairy black
holes which have an extra hair due to the additional surrounding sources, such
as dark matter or dark energy. We examine how the hairy parameters
characterized the hair affect the magnetic reconnection process in addition to
other important variables of the Comisso-Asenjo process, including the
parameter spaces that permit energy extraction, the power, efficiency and power
ratios with respect to the Blandford-Znajek mechanism.
| [
{
"created": "Tue, 25 Apr 2023 03:41:41 GMT",
"version": "v1"
},
{
"created": "Thu, 4 May 2023 08:34:17 GMT",
"version": "v2"
}
] | 2023-08-02 | [
[
"Li",
"Zhen",
""
],
[
"Yuan",
"Faqiang",
""
]
] | It was demonstrated by Comisso and Asenjo that the magnetic reconnection in the ergosphere is a promising mechanism to extract energy from the rotating Kerr black hole. In this work, we investigate the role of Comisso-Asenjo mechanism in energy extraction from the newly suggested rotating hairy black holes which have an extra hair due to the additional surrounding sources, such as dark matter or dark energy. We examine how the hairy parameters characterized the hair affect the magnetic reconnection process in addition to other important variables of the Comisso-Asenjo process, including the parameter spaces that permit energy extraction, the power, efficiency and power ratios with respect to the Blandford-Znajek mechanism. |
1205.4417 | Domingo Louis-Martinez | Domingo J. Louis-Martinez | A relativistic action-at-a-distance description of gravitational
interactions? | null | null | 10.1103/PhysRevD.86.045009 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that certain aspects of gravitation may be described using a
relativistic action-at-a-distance formulation. The equations of motion of the
model presented are invariant under Lorentz transformations and agree with the
equations of Einstein's theory of General Relativity, at the first
Post-Newtonian approximation, for any number of interacting point masses.
| [
{
"created": "Sun, 20 May 2012 13:25:33 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Louis-Martinez",
"Domingo J.",
""
]
] | It is shown that certain aspects of gravitation may be described using a relativistic action-at-a-distance formulation. The equations of motion of the model presented are invariant under Lorentz transformations and agree with the equations of Einstein's theory of General Relativity, at the first Post-Newtonian approximation, for any number of interacting point masses. |
1306.5634 | Iver Brevik | Iver Brevik and {\O}yvind Gr{\o}n | Universe Models with Negative Bulk Viscosity | 7 pages latex, no figures, published electronically in Astrophys.
Space Sci | Astrophys. Space Sci. (2013) 347, 399 | 10.1007/s10509-013-1525-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The concept of negative temperatures has occasionally been used in connection
with quantum systems. A recent example of this sort is reported in the paper of
S. Braun et al. [Science 339,52 (2013)], where an attractively interacting
ensemble of ultracold atoms is investigated experimentally and found to
correspond to a negative-temperature system since the entropy decreases with
increasing energy at the high end of the energy spectrum. As the authors
suggest, it would be of interest to investigate whether a suitable
generalization of standard cosmological theory could be helpful, in order to
elucidate the observed accelerated expansion of the universe usually explained
in terms of a positive tensile stress (negative pressure). In the present note
we take up this basic idea and investigate a generalization of the standard
viscous cosmological theory, not by admitting negative temperatures but instead
by letting the bulk viscosity take negative values. Evidently, such an approach
breaks standard thermodynamics, but may actually be regarded to lead to the
same kind of bizarre consequences as the standard approach of admitting the
equation-of-state parameter w to be less than -1. In universe models dominated
by negative viscosity we find that the fluid's entropy decreases with time, as
one would expect. Moreover, we find that the fluid transition from the
quintessence region into the phantom region (thus passing the phantom divide
w=-1) can actually be reversed. Also in generalizations of the LCDM-universe
models with a fluid having negative bulk viscosity we find that the viscosity
decreases the expansion of the universe.
| [
{
"created": "Mon, 24 Jun 2013 14:03:09 GMT",
"version": "v1"
}
] | 2013-10-01 | [
[
"Brevik",
"Iver",
""
],
[
"Grøn",
"Øyvind",
""
]
] | The concept of negative temperatures has occasionally been used in connection with quantum systems. A recent example of this sort is reported in the paper of S. Braun et al. [Science 339,52 (2013)], where an attractively interacting ensemble of ultracold atoms is investigated experimentally and found to correspond to a negative-temperature system since the entropy decreases with increasing energy at the high end of the energy spectrum. As the authors suggest, it would be of interest to investigate whether a suitable generalization of standard cosmological theory could be helpful, in order to elucidate the observed accelerated expansion of the universe usually explained in terms of a positive tensile stress (negative pressure). In the present note we take up this basic idea and investigate a generalization of the standard viscous cosmological theory, not by admitting negative temperatures but instead by letting the bulk viscosity take negative values. Evidently, such an approach breaks standard thermodynamics, but may actually be regarded to lead to the same kind of bizarre consequences as the standard approach of admitting the equation-of-state parameter w to be less than -1. In universe models dominated by negative viscosity we find that the fluid's entropy decreases with time, as one would expect. Moreover, we find that the fluid transition from the quintessence region into the phantom region (thus passing the phantom divide w=-1) can actually be reversed. Also in generalizations of the LCDM-universe models with a fluid having negative bulk viscosity we find that the viscosity decreases the expansion of the universe. |
1901.04498 | William East | William E. East | Cosmic Censorship Upheld in Spheroidal Collapse of Collisionless Matter | 6 pages, 6 figures; revised to match PRL version, including expanded
results | Phys. Rev. Lett. 122, 231103 (2019) | 10.1103/PhysRevLett.122.231103 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the collapse of spheroidal configurations of collisionless particles
in full general relativity. This setup was originally considered by Shapiro and
Teukolsky (1991), where it was found that prolate configurations with a
sufficiently large semimajor axis gave rise to diverging curvature, but no
apparent horizon. This was taken as evidence for the formation of a naked
singularity, in violation of cosmic censorship. We revisit such configurations
using different coordinates/slicing, and considering a range of values for the
semimajor axis and eccentricity of the initial matter distribution, and find
that the final state in all cases studied is a black hole plus gravitational
radiation. Though initially distorted, the proper circumferences of the
apparent horizons that are found do not significantly exceed the hoop
conjecture bound. Configurations with a larger semimajor axis can produce
strong gravitational radiation, with luminosities up to $P_{\rm GW}\sim 2\times
10^{-3}c^5/G$.
| [
{
"created": "Mon, 14 Jan 2019 19:00:02 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Jun 2019 18:08:56 GMT",
"version": "v2"
}
] | 2019-06-18 | [
[
"East",
"William E.",
""
]
] | We study the collapse of spheroidal configurations of collisionless particles in full general relativity. This setup was originally considered by Shapiro and Teukolsky (1991), where it was found that prolate configurations with a sufficiently large semimajor axis gave rise to diverging curvature, but no apparent horizon. This was taken as evidence for the formation of a naked singularity, in violation of cosmic censorship. We revisit such configurations using different coordinates/slicing, and considering a range of values for the semimajor axis and eccentricity of the initial matter distribution, and find that the final state in all cases studied is a black hole plus gravitational radiation. Though initially distorted, the proper circumferences of the apparent horizons that are found do not significantly exceed the hoop conjecture bound. Configurations with a larger semimajor axis can produce strong gravitational radiation, with luminosities up to $P_{\rm GW}\sim 2\times 10^{-3}c^5/G$. |
2310.18686 | Gungwon Kang | Yeong-Bok Bae, Young-Hwan Hyun and Gungwon Kang | Ringdown gravitational waves from close scattering of two black holes | 6 pages,4 figures | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have numerically investigated close scattering processes of two black
holes (BHs). Our careful analysis shows for the first time a non-merging
ringdown gravitational wave coming from dynamical tidal deformations of
individual BHs during their close encounter. The ringdown wave frequencies turn
out to agree well with the quasi-normal ones of a single BH in perturbation
theory, despite its distinctive physical context from the merging case. Our
study shows a new type of gravitational waveform and opens up a new exploration
of strong gravitational interactions using BH encounters.
| [
{
"created": "Sat, 28 Oct 2023 12:01:08 GMT",
"version": "v1"
}
] | 2023-10-31 | [
[
"Bae",
"Yeong-Bok",
""
],
[
"Hyun",
"Young-Hwan",
""
],
[
"Kang",
"Gungwon",
""
]
] | We have numerically investigated close scattering processes of two black holes (BHs). Our careful analysis shows for the first time a non-merging ringdown gravitational wave coming from dynamical tidal deformations of individual BHs during their close encounter. The ringdown wave frequencies turn out to agree well with the quasi-normal ones of a single BH in perturbation theory, despite its distinctive physical context from the merging case. Our study shows a new type of gravitational waveform and opens up a new exploration of strong gravitational interactions using BH encounters. |
gr-qc/0608113 | Luca Baiotti | Luca Baiotti, Luciano Rezzolla | Challenging the paradigm of singularity excision in gravitational
collapse | 4 pages, 4 figures, accepted for publication on Phys. Rev. Lett | Phys.Rev.Lett. 97 (2006) 141101 | 10.1103/PhysRevLett.97.141101 | null | gr-qc astro-ph | null | A paradigm deeply rooted in modern numerical relativity calculations
prescribes the removal of those regions of the computational domain where a
physical singularity may develop. We here challenge this paradigm by performing
three-dimensional simulations of the collapse of uniformly rotating stars to
black holes without excision. We show that this choice, combined with suitable
gauge conditions and the use of minute numerical dissipation, improves
dramatically the long-term stability of the evolutions. In turn, this allows
for the calculation of the waveforms well beyond what previously possible,
providing information on the black-hole ringing and setting a new mark on the
present knowledge of the gravitational-wave emission from the stellar collapse
to a rotating black hole.
| [
{
"created": "Sat, 26 Aug 2006 11:40:59 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Oct 2006 17:23:27 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Baiotti",
"Luca",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | A paradigm deeply rooted in modern numerical relativity calculations prescribes the removal of those regions of the computational domain where a physical singularity may develop. We here challenge this paradigm by performing three-dimensional simulations of the collapse of uniformly rotating stars to black holes without excision. We show that this choice, combined with suitable gauge conditions and the use of minute numerical dissipation, improves dramatically the long-term stability of the evolutions. In turn, this allows for the calculation of the waveforms well beyond what previously possible, providing information on the black-hole ringing and setting a new mark on the present knowledge of the gravitational-wave emission from the stellar collapse to a rotating black hole. |
gr-qc/0102013 | Sean A. Hayward | Sean A. Hayward | Gravitational-wave dynamics and black-hole dynamics: second
quasi-spherical approximation | 16 revtex pages | Class.Quant.Grav. 18 (2001) 5561-5582 | 10.1088/0264-9381/18/24/316 | null | gr-qc | null | Gravitational radiation with roughly spherical wavefronts, produced by
roughly spherical black holes or other astrophysical objects, is described by
an approximation scheme. The first quasi-spherical approximation, describing
radiation propagation on a background, is generalized to include additional
non-linear effects, due to the radiation itself. The gravitational radiation is
locally defined and admits an energy tensor, satisfying all standard local
energy conditions and entering the truncated Einstein equations as an effective
energy tensor. This second quasi-spherical approximation thereby includes
gravitational radiation reaction, such as the back-reaction on the black hole.
With respect to a canonical flow of time, the combined energy-momentum of the
matter and gravitational radiation is covariantly conserved. The corresponding
Noether charge is a local gravitational mass-energy. Energy conservation is
formulated as a local first law relating the gradient of the gravitational mass
to work and energy-supply terms, including the energy flux of the gravitational
radiation. Zeroth, first and second laws of black-hole dynamics are given,
involving a dynamic surface gravity. Local gravitational-wave dynamics is
described by a non-linear wave equation. In terms of a complex gravitational-
radiation potential, the energy tensor has a scalar-field form and the wave
equation is an Ernst equation, holding independently at each spherical angle.
The strain to be measured by a distant detector is simply defined.
| [
{
"created": "Mon, 5 Feb 2001 07:20:47 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Hayward",
"Sean A.",
""
]
] | Gravitational radiation with roughly spherical wavefronts, produced by roughly spherical black holes or other astrophysical objects, is described by an approximation scheme. The first quasi-spherical approximation, describing radiation propagation on a background, is generalized to include additional non-linear effects, due to the radiation itself. The gravitational radiation is locally defined and admits an energy tensor, satisfying all standard local energy conditions and entering the truncated Einstein equations as an effective energy tensor. This second quasi-spherical approximation thereby includes gravitational radiation reaction, such as the back-reaction on the black hole. With respect to a canonical flow of time, the combined energy-momentum of the matter and gravitational radiation is covariantly conserved. The corresponding Noether charge is a local gravitational mass-energy. Energy conservation is formulated as a local first law relating the gradient of the gravitational mass to work and energy-supply terms, including the energy flux of the gravitational radiation. Zeroth, first and second laws of black-hole dynamics are given, involving a dynamic surface gravity. Local gravitational-wave dynamics is described by a non-linear wave equation. In terms of a complex gravitational- radiation potential, the energy tensor has a scalar-field form and the wave equation is an Ernst equation, holding independently at each spherical angle. The strain to be measured by a distant detector is simply defined. |
2405.08335 | Amee Bhatt | Amee Bhatt | A Comparative Study of Shadows of Magnetized and Non-Magnetized
Singularities | 6 pages, & figues | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by-nc-sa/4.0/ | The recent observations of the galactic center of the M87 galaxy have made
the field of observing black holes and calculating its shadow much more
intriguing. Approaching the question of calculating shadows, many
approximations are made in order to simplify the equations which makes the
considered case less realistic. Understanding the shadow of different
singularities under the influence of magnetic field is of more importance
astrophysically as the accreting matter around the singularity would generate
electromagnetic fields as it would be in plasma state due to the high tidal
effects. Here, we use Ernst technique to immerse spacetimes in uniform,
sourceless and asymptotic magnetic field. Later, we compare the effective
potential of null geodesics in magnetized and non-magnetized cases. This study
would be helpful in understanding the M87 shadow and the forthcoming image of
shadow of SagA*.
| [
{
"created": "Tue, 14 May 2024 06:13:22 GMT",
"version": "v1"
}
] | 2024-05-15 | [
[
"Bhatt",
"Amee",
""
]
] | The recent observations of the galactic center of the M87 galaxy have made the field of observing black holes and calculating its shadow much more intriguing. Approaching the question of calculating shadows, many approximations are made in order to simplify the equations which makes the considered case less realistic. Understanding the shadow of different singularities under the influence of magnetic field is of more importance astrophysically as the accreting matter around the singularity would generate electromagnetic fields as it would be in plasma state due to the high tidal effects. Here, we use Ernst technique to immerse spacetimes in uniform, sourceless and asymptotic magnetic field. Later, we compare the effective potential of null geodesics in magnetized and non-magnetized cases. This study would be helpful in understanding the M87 shadow and the forthcoming image of shadow of SagA*. |
gr-qc/0110104 | Allemandi Gianluca | G. Allemandi, M. Francaviglia, M. Raiteri | The First Law of Isolated Horizons via Noether Theorem | 29 pages | null | null | null | gr-qc | null | A general recipe proposed elsewhere to define, via Noether theorem, the
variation of energy for a natural field theory is applied to Einstein-Maxwell
theory. The electromagnetic field is analysed in the geometric framework of
natural bundles. Einstein-Maxwell theory turns then out to be natural rather
than gauge-natural. As a consequence of this assumption a correction term \a la
Regge-Teitelboim is needed to define the variation of energy, also for the pure
electromagnetic part of the Einstein-Maxwell Lagrangian. Integrability
conditions for the variational equation which defines the variation of energy
are analysed in relation with boundary conditions on physical data. As an
application the first law of thermodynamics for rigidly rotating horizons is
obtained.
| [
{
"created": "Wed, 24 Oct 2001 08:11:13 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Allemandi",
"G.",
""
],
[
"Francaviglia",
"M.",
""
],
[
"Raiteri",
"M.",
""
]
] | A general recipe proposed elsewhere to define, via Noether theorem, the variation of energy for a natural field theory is applied to Einstein-Maxwell theory. The electromagnetic field is analysed in the geometric framework of natural bundles. Einstein-Maxwell theory turns then out to be natural rather than gauge-natural. As a consequence of this assumption a correction term \a la Regge-Teitelboim is needed to define the variation of energy, also for the pure electromagnetic part of the Einstein-Maxwell Lagrangian. Integrability conditions for the variational equation which defines the variation of energy are analysed in relation with boundary conditions on physical data. As an application the first law of thermodynamics for rigidly rotating horizons is obtained. |
gr-qc/0206038 | J. Alberto Lobo | Alberto Lobo, Massimo Cerdonio, Alvaro Montero | Fake signals caused by heavy mass motions near a sensitive spherical
gravitational wave antenna | 10 pages, 4 EPS figures, LaTeX2e, IOP style files, submitted to CQG | Class.Quant.Grav. 19 (2002) 4845-4854 | 10.1088/0264-9381/19/19/304 | null | gr-qc | null | This paper analyses in quantitative detail the effect caused by a moving mass
on a spherical gravitational wave detector. This applies to situations where
heavy traffic or similar disturbances happen near the GW antenna. Such
disturbances result in quadrupole tidal stresses in the antenna mass, and they
therefore precisely fake a real gravitational signal. The study shows that
there always are characteristic frequencies, depending on the motion of the
external masses, at which the fake signals are most intense. It however appears
that, even at those frequencies, fake signals should be orders of magnitude
below the sensitivity curve of an optimised detector, in likely realistic
situations.
| [
{
"created": "Thu, 13 Jun 2002 17:22:37 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Lobo",
"Alberto",
""
],
[
"Cerdonio",
"Massimo",
""
],
[
"Montero",
"Alvaro",
""
]
] | This paper analyses in quantitative detail the effect caused by a moving mass on a spherical gravitational wave detector. This applies to situations where heavy traffic or similar disturbances happen near the GW antenna. Such disturbances result in quadrupole tidal stresses in the antenna mass, and they therefore precisely fake a real gravitational signal. The study shows that there always are characteristic frequencies, depending on the motion of the external masses, at which the fake signals are most intense. It however appears that, even at those frequencies, fake signals should be orders of magnitude below the sensitivity curve of an optimised detector, in likely realistic situations. |
gr-qc/0110013 | David Garfinkle | David Garfinkle | Harmonic coordinate method for simulating generic singularities | 5 pages, 4 figures, Revtex, discussion expanded, references added | Phys.Rev.D65:044029,2002 | 10.1103/PhysRevD.65.044029 | null | gr-qc | null | This paper presents both a numerical method for general relativity and an
application of that method. The method involves the use of harmonic coordinates
in a 3+1 code to evolve the Einstein equations with scalar field matter. In
such coordinates, the terms in Einstein's equations with the highest number of
derivatives take a form similar to that of the wave equation. The application
is an exploration of the generic approach to the singularity for this type of
matter. The preliminary results indicate that the dynamics as one approaches
the singularity is locally the dynamics of the Kasner spacetimes.
| [
{
"created": "Mon, 1 Oct 2001 19:48:44 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Jan 2002 00:38:08 GMT",
"version": "v2"
}
] | 2011-04-21 | [
[
"Garfinkle",
"David",
""
]
] | This paper presents both a numerical method for general relativity and an application of that method. The method involves the use of harmonic coordinates in a 3+1 code to evolve the Einstein equations with scalar field matter. In such coordinates, the terms in Einstein's equations with the highest number of derivatives take a form similar to that of the wave equation. The application is an exploration of the generic approach to the singularity for this type of matter. The preliminary results indicate that the dynamics as one approaches the singularity is locally the dynamics of the Kasner spacetimes. |
gr-qc/0203099 | Lorenzo Iorio | Lorenzo Iorio, David M. Lucchesi, I. Ciufolini | The LARES mission revisited: an alternative scenario | Latex2e, 20 pages, 6 figures, 5 tables. To appear on Classical and
Quantum Gravity | Class.Quant.Grav. 19 (2002) 4311-4326 | 10.1088/0264-9381/19/16/307 | null | gr-qc astro-ph physics.geo-ph physics.space-ph | null | A new proposal for the implementation of LARES mission is presented. In
particular, a new observable is proposed and alternative scenarios are
discussed.
| [
{
"created": "Wed, 27 Mar 2002 16:50:30 GMT",
"version": "v1"
},
{
"created": "Sun, 7 Apr 2002 17:10:30 GMT",
"version": "v2"
},
{
"created": "Wed, 8 May 2002 16:44:44 GMT",
"version": "v3"
},
{
"created": "Thu, 11 Jul 2002 13:56:59 GMT",
"version": "v4"
},
{
"cre... | 2007-05-23 | [
[
"Iorio",
"Lorenzo",
""
],
[
"Lucchesi",
"David M.",
""
],
[
"Ciufolini",
"I.",
""
]
] | A new proposal for the implementation of LARES mission is presented. In particular, a new observable is proposed and alternative scenarios are discussed. |
1707.04495 | S. I. Kruglov | S. I. Kruglov | Born--Infeld-type electrodynamics and magnetic black holes | 15 pages, 6 figures, corrected Eq. (26) and Fig. 6 | Annals Phys. 383 (2017) 550-559; Annals Phys. 434 (2021), 168625 | 10.1016/j.aop.2017.06.008 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate a Born--Infeld-type model of nonlinear electrodynamics,
possessing three parameters, coupled with general relativity. As a particular
case Born--Infeld electrodynamics is reproduced. There is no singularity of the
electric field at the centre of point-like charged particles and self-energy of
charges is finite in this model. The magnetized black hole is studied and
solutions are obtained. We demonstrate that for some parameters of the model
the black hole is regular. We find the asymptotic of the metric and mass
functions at $r\rightarrow\infty$ and $r\rightarrow 0$, and corrections to the
Reissner--Nordstr\"{o}m solution. Thermodynamics of black holes is
investigated. We calculate the Hawking temperature of black holes and show that
black holes are not stable and there are phase transitions in the model under
consideration.
| [
{
"created": "Wed, 12 Jul 2017 21:44:09 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Sep 2021 15:31:41 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Oct 2021 14:18:44 GMT",
"version": "v3"
}
] | 2021-10-22 | [
[
"Kruglov",
"S. I.",
""
]
] | We investigate a Born--Infeld-type model of nonlinear electrodynamics, possessing three parameters, coupled with general relativity. As a particular case Born--Infeld electrodynamics is reproduced. There is no singularity of the electric field at the centre of point-like charged particles and self-energy of charges is finite in this model. The magnetized black hole is studied and solutions are obtained. We demonstrate that for some parameters of the model the black hole is regular. We find the asymptotic of the metric and mass functions at $r\rightarrow\infty$ and $r\rightarrow 0$, and corrections to the Reissner--Nordstr\"{o}m solution. Thermodynamics of black holes is investigated. We calculate the Hawking temperature of black holes and show that black holes are not stable and there are phase transitions in the model under consideration. |
gr-qc/0312047 | Piotr Chrusciel | Hubert L. Bray, Piotr T. Chrusciel | The Penrose Inequality | 29 pages, latex2e, minor misprints corrected, final version to appear
in "The Einstein Equations and the Large Scale Behavior of Gravitational
Fields (50 years of the Cauchy problem in general relativity)", H. Friedrich
and P.T. Chruściel, Editors, Birkhaeuser, 2004 | null | null | Esi preprint 1390 | gr-qc math.DG | null | In 1973, R. Penrose presented an argument that the total mass of a space-time
which contains black holes with event horizons of total area $A$ should be at
least $\sqrt{A/16\pi}$. An important special case of this physical statement
translates into a very beautiful mathematical inequality in Riemannian geometry
known as the Riemannian Penrose inequality. This inequality was first
established by G. Huisken and T. Ilmanen in 1997 for a single black hole and
then by one of the authors (H.B.) in 1999 for any number of black holes. The
two approaches use two different geometric flow techniques and are described
here. We further present some background material concerning the problem at
hand, discuss some applications of Penrose-type inequalities, as well as the
open questions remaining.
| [
{
"created": "Mon, 8 Dec 2003 23:08:19 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Sep 2004 15:38:15 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Bray",
"Hubert L.",
""
],
[
"Chrusciel",
"Piotr T.",
""
]
] | In 1973, R. Penrose presented an argument that the total mass of a space-time which contains black holes with event horizons of total area $A$ should be at least $\sqrt{A/16\pi}$. An important special case of this physical statement translates into a very beautiful mathematical inequality in Riemannian geometry known as the Riemannian Penrose inequality. This inequality was first established by G. Huisken and T. Ilmanen in 1997 for a single black hole and then by one of the authors (H.B.) in 1999 for any number of black holes. The two approaches use two different geometric flow techniques and are described here. We further present some background material concerning the problem at hand, discuss some applications of Penrose-type inequalities, as well as the open questions remaining. |
2203.00524 | Alex Deich | Alexander Deich, Alejandro C\'ardenas-Avenda\~no, Nicolas Yunes | Chaos in Quadratic Gravity | 12 pages, 11 figures | null | 10.1103/PhysRevD.106.024040 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | While recent gravitational wave observations by LIGO and Virgo allow for
tests of general relativity in the extreme gravity regime, these observations
are still blind to a large swath of phenomena outside these instruments'
sensitivity curves. Future gravitational-wave detectors, such as LISA, will
enable probes of longer-duration and lower-frequency events. In particular,
LISA will enable the characterization of the non-linear dynamics of extreme
mass-ratio inspirals, when a small compact object falls into a supermassive
black hole. In this paper, we study the motion of test particles around
spinning black holes in two quadratic gravity theories: scalar Gauss-Bonnet and
dynamical Chern-Simons gravity. We show that geodesic trajectories around
rotating black holes in these theories are likely to not have a fourth constant
of the motion. In particular, we show that Poincar\'e sections of the orbital
phase space present chaotic features that will affect the inspiral of small
compact objects into supermassive black holes in these theories. Nevertheless,
the characteristic size of these chaotic features is tiny and their location in
parameter space is very close to the event horizon of the supermassive black
hole. Therefore, the detection of such chaotic features with LISA is likely
very challenging, at best.
| [
{
"created": "Tue, 1 Mar 2022 15:08:25 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jul 2022 19:32:05 GMT",
"version": "v2"
}
] | 2022-08-03 | [
[
"Deich",
"Alexander",
""
],
[
"Cárdenas-Avendaño",
"Alejandro",
""
],
[
"Yunes",
"Nicolas",
""
]
] | While recent gravitational wave observations by LIGO and Virgo allow for tests of general relativity in the extreme gravity regime, these observations are still blind to a large swath of phenomena outside these instruments' sensitivity curves. Future gravitational-wave detectors, such as LISA, will enable probes of longer-duration and lower-frequency events. In particular, LISA will enable the characterization of the non-linear dynamics of extreme mass-ratio inspirals, when a small compact object falls into a supermassive black hole. In this paper, we study the motion of test particles around spinning black holes in two quadratic gravity theories: scalar Gauss-Bonnet and dynamical Chern-Simons gravity. We show that geodesic trajectories around rotating black holes in these theories are likely to not have a fourth constant of the motion. In particular, we show that Poincar\'e sections of the orbital phase space present chaotic features that will affect the inspiral of small compact objects into supermassive black holes in these theories. Nevertheless, the characteristic size of these chaotic features is tiny and their location in parameter space is very close to the event horizon of the supermassive black hole. Therefore, the detection of such chaotic features with LISA is likely very challenging, at best. |
1007.3857 | Matteo Luca Ruggiero | Matteo Luca Ruggiero | Gravito-electromagnetic Aharonov-Bohm effect: some rotation effects
revised | 19 pages, 2 figures, in in Proceedings of Analysis, Manifolds and
Geometric Structures in Physics, International Conference in Honour of Y.
Choquet-Bruhat, June 2004, Isola d'Elba, Italy | Nuovo Cim. B119:893,2004 | 10.1393/ncb/i2004-10185-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By means of the description of the standard relative dynamics in terms of
gravito-electromagnetic fields, in the context of natural splitting, we
formally introduce the gravito-magnetic Aharonov-Bohm effect. Then, we
interpret the Sagnac effect as a gravito-magnetic Aharonov-Bohm effect and we
exploit this formalism for studying the General Relativistic corrections to the
Sagnac effect in stationary and axially symmetric geometries.
| [
{
"created": "Thu, 22 Jul 2010 11:26:46 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Ruggiero",
"Matteo Luca",
""
]
] | By means of the description of the standard relative dynamics in terms of gravito-electromagnetic fields, in the context of natural splitting, we formally introduce the gravito-magnetic Aharonov-Bohm effect. Then, we interpret the Sagnac effect as a gravito-magnetic Aharonov-Bohm effect and we exploit this formalism for studying the General Relativistic corrections to the Sagnac effect in stationary and axially symmetric geometries. |
1410.4657 | Taeyoon Moon | Yun Soo Myung and Taeyoon Moon | Cosmological three-coupled scalar theory for the dS/LCFT correspondence | 1+25 pages, 1 figure, version accepted for publication in JCAP | null | 10.1088/1475-7516/2015/01/033 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate cosmological perturbations generated during de Sitter
inflation in the three-coupled scalar theory. This theory is composed of three
coupled scalars ($\phi_p,p=1,2,3$) to give a sixth-order derivative scalar
theory for $\phi_3$, in addition to tensor. Recovering the power spectra
between scalars from the LCFT correlators in momentum space indicates that the
de Sitter/logarithmic conformal field theory (dS/LCFT) correspondence works in
the superhorizon limit. We use LCFT correlators derived from the dS/LCFT
differentiate dictionary to compare cosmological correlators (power spectra)
and find also LCFT correlators by making use of extrapolate dictionary. This is
because the former approach is more conventional than the latter. A bulk
version dual to the truncation process to find a unitary CFT in the LCFT
corresponds to selecting a physical field $\phi_2$ with positive norm
propagating on the dS spacetime.
| [
{
"created": "Fri, 17 Oct 2014 08:27:48 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Jan 2015 07:24:28 GMT",
"version": "v2"
}
] | 2015-06-23 | [
[
"Myung",
"Yun Soo",
""
],
[
"Moon",
"Taeyoon",
""
]
] | We investigate cosmological perturbations generated during de Sitter inflation in the three-coupled scalar theory. This theory is composed of three coupled scalars ($\phi_p,p=1,2,3$) to give a sixth-order derivative scalar theory for $\phi_3$, in addition to tensor. Recovering the power spectra between scalars from the LCFT correlators in momentum space indicates that the de Sitter/logarithmic conformal field theory (dS/LCFT) correspondence works in the superhorizon limit. We use LCFT correlators derived from the dS/LCFT differentiate dictionary to compare cosmological correlators (power spectra) and find also LCFT correlators by making use of extrapolate dictionary. This is because the former approach is more conventional than the latter. A bulk version dual to the truncation process to find a unitary CFT in the LCFT corresponds to selecting a physical field $\phi_2$ with positive norm propagating on the dS spacetime. |
1211.3202 | Shahar Hod | Shahar Hod | Stationary Scalar Clouds Around Rotating Black Holes | 5 pages | Physical Review D 86, 104026 (2012) | 10.1103/PhysRevD.86.104026 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by novel results in the theory of wave dynamics in black-hole
spacetimes, we analyze the dynamics of a massive scalar field surrounding a
rapidly rotating Kerr black hole. In particular, we report on the existence of
stationary (infinitely long-lived) regular field configurations in the
background of maximally rotating black holes. The effective height of these
scalar "clouds" above the central black hole is determined analytically. Our
results support the possible existence of stationary scalar field dark matter
distributions surrounding rapidly rotating black holes.
| [
{
"created": "Wed, 14 Nov 2012 04:32:07 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Nov 2012 06:23:58 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Hod",
"Shahar",
""
]
] | Motivated by novel results in the theory of wave dynamics in black-hole spacetimes, we analyze the dynamics of a massive scalar field surrounding a rapidly rotating Kerr black hole. In particular, we report on the existence of stationary (infinitely long-lived) regular field configurations in the background of maximally rotating black holes. The effective height of these scalar "clouds" above the central black hole is determined analytically. Our results support the possible existence of stationary scalar field dark matter distributions surrounding rapidly rotating black holes. |
1008.0695 | Muhammad Sharif | M. Sharif and Aisha Siddiqa | Dynamics of Charged Plane Symmetric Gravitational Collapse | 21 pages, accepted for publication Gen. Relativ. Grav | Gen.Rel.Grav.43:73-91,2011 | 10.1007/s10714-010-1071-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study dynamics of the charged plane symmetric gravitational
collapse. For this purpose, we discuss non-adiabatic flow of a viscous fluid
and deduce the results for adiabatic case. The Einstein and Maxwell field
equations are formulated for general plane symmetric spacetime in the interior.
Junction conditions between the interior and exterior regions are derived. For
the non-adiabatic case, the exterior is taken as plane symmetric charged Vaidya
spacetime while for the adiabatic case, it is described by plane
Reissner-Nordstr$\ddot{o}$m spacetime. Using Misner and Sharp formalism, we
obtain dynamical equations to investigate the effects of different forces over
the rate of collapse. In non-adiabatic case, a dynamical equation is joined
with transport equation of heat flux. Finally, a relation between the Weyl
tensor and energy density is found.
| [
{
"created": "Wed, 4 Aug 2010 04:53:31 GMT",
"version": "v1"
}
] | 2011-02-11 | [
[
"Sharif",
"M.",
""
],
[
"Siddiqa",
"Aisha",
""
]
] | In this paper, we study dynamics of the charged plane symmetric gravitational collapse. For this purpose, we discuss non-adiabatic flow of a viscous fluid and deduce the results for adiabatic case. The Einstein and Maxwell field equations are formulated for general plane symmetric spacetime in the interior. Junction conditions between the interior and exterior regions are derived. For the non-adiabatic case, the exterior is taken as plane symmetric charged Vaidya spacetime while for the adiabatic case, it is described by plane Reissner-Nordstr$\ddot{o}$m spacetime. Using Misner and Sharp formalism, we obtain dynamical equations to investigate the effects of different forces over the rate of collapse. In non-adiabatic case, a dynamical equation is joined with transport equation of heat flux. Finally, a relation between the Weyl tensor and energy density is found. |
1907.06168 | Miguel Cruz | Gilberto Aguilar-P\'erez, Miguel Cruz, Samuel Lepe and Israel
Moran-Rivera | Hairy black hole stability under odd parity perturbations in the
Einstein-Gauss-Bonnet model | 15 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Supported by the use of a regular scalar field we find a black hole solution
in the Einstein-Gauss-Bonnet model. From the obtained solution we can recover
the Schwarzschild black hole as in other works. Later, by implementing the odd
parity perturbations method we study the stability of the linearized equations
of motion of the model, we find the explicit form of the Regge-Wheeler
potential and we explore the condition of vanishing perturbations at the
horizon of the black hole. We test the stability of the obtained solution by
checking the positivity condition of the Regge-Wheeler potential. Finally, we
show that the stability of model depends on the value of a parameter introduced
in the profile for the scalar field.
| [
{
"created": "Sun, 14 Jul 2019 05:09:07 GMT",
"version": "v1"
}
] | 2019-07-16 | [
[
"Aguilar-Pérez",
"Gilberto",
""
],
[
"Cruz",
"Miguel",
""
],
[
"Lepe",
"Samuel",
""
],
[
"Moran-Rivera",
"Israel",
""
]
] | Supported by the use of a regular scalar field we find a black hole solution in the Einstein-Gauss-Bonnet model. From the obtained solution we can recover the Schwarzschild black hole as in other works. Later, by implementing the odd parity perturbations method we study the stability of the linearized equations of motion of the model, we find the explicit form of the Regge-Wheeler potential and we explore the condition of vanishing perturbations at the horizon of the black hole. We test the stability of the obtained solution by checking the positivity condition of the Regge-Wheeler potential. Finally, we show that the stability of model depends on the value of a parameter introduced in the profile for the scalar field. |
1702.04293 | Massimo Giovannini | Massimo Giovannini | Hypermagnetic knots and gravitational radiation at intermediate
frequencies | 19 pages, 2 figures; to appear in Classical and Quantum Gravity as a
regular article | Class. Quantum Grav. 34 (2017) 135010 | 10.1088/1361-6382/aa75c5 | CERN-PH-TH-2016-195 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The maximally gyrotropic configurations of the hypermagnetic field at the
electroweak epoch can induce a stochastic background of relic gravitational
waves with comoving frequencies ranging from the $\mu$Hz to the kHz. Using two
complementary approaches we construct a physical template family for the
emission of the gravitational radiation produced by the hypermagnetic knots.
The current constraints and the presumed sensitivities of the advanced
wide-band interferometers (both terrestrial and space-borne) are combined to
infer that the lack of observations at intermediate frequencies may invalidate
the premise of baryogenesis models based (directly or indirectly) on the
presence of gyrotropic configurations of the hypermagnetic field at the
electroweak epoch. Over the intermediate frequency range the spectral energy
density of the gravitational waves emitted by the hypermagnetic knots at the
electroweak scale can exceed the inflationary signal even by nine orders of
magnitude without affecting the standard bounds applicable on the stochastic
backgrounds of gravitational radiation. The signal of hypermagnetic knots can
be disambiguated, at least in principle, since the the produced gravitational
waves are polarized.
| [
{
"created": "Tue, 14 Feb 2017 17:07:11 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Jun 2017 15:41:39 GMT",
"version": "v2"
}
] | 2017-06-28 | [
[
"Giovannini",
"Massimo",
""
]
] | The maximally gyrotropic configurations of the hypermagnetic field at the electroweak epoch can induce a stochastic background of relic gravitational waves with comoving frequencies ranging from the $\mu$Hz to the kHz. Using two complementary approaches we construct a physical template family for the emission of the gravitational radiation produced by the hypermagnetic knots. The current constraints and the presumed sensitivities of the advanced wide-band interferometers (both terrestrial and space-borne) are combined to infer that the lack of observations at intermediate frequencies may invalidate the premise of baryogenesis models based (directly or indirectly) on the presence of gyrotropic configurations of the hypermagnetic field at the electroweak epoch. Over the intermediate frequency range the spectral energy density of the gravitational waves emitted by the hypermagnetic knots at the electroweak scale can exceed the inflationary signal even by nine orders of magnitude without affecting the standard bounds applicable on the stochastic backgrounds of gravitational radiation. The signal of hypermagnetic knots can be disambiguated, at least in principle, since the the produced gravitational waves are polarized. |
1408.3390 | Ernesto F. Eiroa | Ernesto F. Eiroa, Carlos M. Sendra | Strong deflection lensing by charged black holes in scalar-tensor
gravity | 12 pages, 3 figures; v2: improved version, new references added | Eur. Phys. J. C (2014) 74:3171 | 10.1140/epjc/s10052-014-3171-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine a class of charged black holes in scalar-tensor gravity as
gravitational lenses. We find the deflection angle in the strong deflection
limit, from which we obtain the positions and the magnifications of the
relativistic images. We compare our results with those corresponding to the
Reissner-Norstrom spacetime and we analyze the observational aspects in the
case of the Galactic supermassive black hole.
| [
{
"created": "Thu, 14 Aug 2014 19:07:34 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Nov 2014 19:31:43 GMT",
"version": "v2"
}
] | 2014-12-01 | [
[
"Eiroa",
"Ernesto F.",
""
],
[
"Sendra",
"Carlos M.",
""
]
] | We examine a class of charged black holes in scalar-tensor gravity as gravitational lenses. We find the deflection angle in the strong deflection limit, from which we obtain the positions and the magnifications of the relativistic images. We compare our results with those corresponding to the Reissner-Norstrom spacetime and we analyze the observational aspects in the case of the Galactic supermassive black hole. |
1512.02864 | Thomas Adams Dr | T Adams, D. Buskulic, V. Germain, G. M. Guidi, F. Marion, M. Montani,
B. Mours, F. Piergiovanni, G. Wang | Low-latency analysis pipeline for compact binary coalescences in the
advanced gravitational wave detector era | 18 pages, 10 figures | null | 10.1088/0264-9381/33/17/175012 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The multi-band template analysis (MBTA) pipeline is a low-latency coincident
analysis pipeline for the detection of gravitational waves (GWs) from compact
binary coalescences. MBTA runs with a low computational cost, and can identify
candidate GW events online with a sub-minute latency. The low computational
running cost of MBTA also makes it useful for data quality studies. Events
detected by MBTA online can be used to alert astronomical partners for
electromagnetic follow-up. We outline the current status of MBTA and give
details of recent pipeline upgrades and validation tests that were performed in
preparation for the first advanced detector observing period. The MBTA pipeline
is ready for the outset of the advanced detector era and the exciting prospects
it will bring.
| [
{
"created": "Wed, 9 Dec 2015 14:14:59 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Aug 2016 14:06:54 GMT",
"version": "v2"
}
] | 2016-08-24 | [
[
"Adams",
"T",
""
],
[
"Buskulic",
"D.",
""
],
[
"Germain",
"V.",
""
],
[
"Guidi",
"G. M.",
""
],
[
"Marion",
"F.",
""
],
[
"Montani",
"M.",
""
],
[
"Mours",
"B.",
""
],
[
"Piergiovanni",
"F.",
... | The multi-band template analysis (MBTA) pipeline is a low-latency coincident analysis pipeline for the detection of gravitational waves (GWs) from compact binary coalescences. MBTA runs with a low computational cost, and can identify candidate GW events online with a sub-minute latency. The low computational running cost of MBTA also makes it useful for data quality studies. Events detected by MBTA online can be used to alert astronomical partners for electromagnetic follow-up. We outline the current status of MBTA and give details of recent pipeline upgrades and validation tests that were performed in preparation for the first advanced detector observing period. The MBTA pipeline is ready for the outset of the advanced detector era and the exciting prospects it will bring. |
2001.03290 | Hideki Asada | Keita Takizawa, Toshiaki Ono, Hideki Asada | Gravitational deflection angle of light: Definition by an observer and
its application to an asymptotically nonflat spacetime | 9 pages, 7 figures; Figures 6 and 7 added, accepted by PRD | Phys. Rev. D 101, 104032 (2020) | 10.1103/PhysRevD.101.104032 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational deflection angle of light for an observer and source at
finite distance from a lens object has been studied by Ishihara et al. [Phys.
Rev. D, 94, 084015 (2016)], based on the Gauss-Bonnet theorem with using the
optical metric. Their approach to finite-distance cases is limited within an
asymptotically flat spacetime. By making several assumptions, we give an
interpretation of their definition from the observer's viewpoint: The observer
assumes the direction of a hypothetical light emission at the observer position
and makes a comparison between the fiducial emission direction and the
direction along the real light ray. The angle between the two directions at the
observer location can be interpreted as the deflection angle by Ishihara et al.
The present interpretation does not require the asymptotic flatness. Motivated
by this, we avoid such asymptotic regions to discuss another integral form of
the deflection angle of light. This form makes it clear that the proposed
deflection angle can be used not only for asymptotically flat spacetimes but
also for asymptotically nonflat ones. We examine the proposed deflection angle
in two models for the latter case; Kottler (Schwarzschild-de Sitter) solution
in general relativity and a spherical solution in Weyl conformal gravity.
Effects of finite distance on the light deflection in Weyl conformal gravity
result in an extra term in the deflection angle, which may be marginally
observable in a certain parameter region. On the other hand, those in Kottler
spacetime are beyond reach of the current technology.
| [
{
"created": "Fri, 10 Jan 2020 02:47:46 GMT",
"version": "v1"
},
{
"created": "Thu, 14 May 2020 04:50:04 GMT",
"version": "v2"
}
] | 2020-05-27 | [
[
"Takizawa",
"Keita",
""
],
[
"Ono",
"Toshiaki",
""
],
[
"Asada",
"Hideki",
""
]
] | The gravitational deflection angle of light for an observer and source at finite distance from a lens object has been studied by Ishihara et al. [Phys. Rev. D, 94, 084015 (2016)], based on the Gauss-Bonnet theorem with using the optical metric. Their approach to finite-distance cases is limited within an asymptotically flat spacetime. By making several assumptions, we give an interpretation of their definition from the observer's viewpoint: The observer assumes the direction of a hypothetical light emission at the observer position and makes a comparison between the fiducial emission direction and the direction along the real light ray. The angle between the two directions at the observer location can be interpreted as the deflection angle by Ishihara et al. The present interpretation does not require the asymptotic flatness. Motivated by this, we avoid such asymptotic regions to discuss another integral form of the deflection angle of light. This form makes it clear that the proposed deflection angle can be used not only for asymptotically flat spacetimes but also for asymptotically nonflat ones. We examine the proposed deflection angle in two models for the latter case; Kottler (Schwarzschild-de Sitter) solution in general relativity and a spherical solution in Weyl conformal gravity. Effects of finite distance on the light deflection in Weyl conformal gravity result in an extra term in the deflection angle, which may be marginally observable in a certain parameter region. On the other hand, those in Kottler spacetime are beyond reach of the current technology. |
gr-qc/9901053 | Hisaaki Shinkai | Gen Yoneda and Hisa-aki Shinkai | Constructing hyperbolic systems in the Ashtekar formulation of general
relativity | 15 pages, RevTeX, minor changes in Introduction. published as Int. J.
Mod. Phys. D 9 (2000) 13 | Int.J.Mod.Phys. D9 (2000) 13-34 | 10.1142/S0218271800000037 | null | gr-qc math-ph math.MP | null | Hyperbolic formulations of the equations of motion are essential technique
for proving the well-posedness of the Cauchy problem of a system, and are also
helpful for implementing stable long time evolution in numerical applications.
We, here, present three kinds of hyperbolic systems in the Ashtekar formulation
of general relativity for Lorentzian vacuum spacetime. We exhibit several (I)
weakly hyperbolic, (II) diagonalizable hyperbolic, and (III) symmetric
hyperbolic systems, with each their eigenvalues. We demonstrate that Ashtekar's
original equations form a weakly hyperbolic system. We discuss how gauge
conditions and reality conditions are constrained during each step toward
constructing a symmetric hyperbolic system.
| [
{
"created": "Tue, 19 Jan 1999 22:29:03 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Feb 1999 02:02:36 GMT",
"version": "v2"
},
{
"created": "Wed, 16 Jun 1999 15:32:17 GMT",
"version": "v3"
},
{
"created": "Mon, 1 May 2000 06:35:16 GMT",
"version": "v4"
}
] | 2009-10-31 | [
[
"Yoneda",
"Gen",
""
],
[
"Shinkai",
"Hisa-aki",
""
]
] | Hyperbolic formulations of the equations of motion are essential technique for proving the well-posedness of the Cauchy problem of a system, and are also helpful for implementing stable long time evolution in numerical applications. We, here, present three kinds of hyperbolic systems in the Ashtekar formulation of general relativity for Lorentzian vacuum spacetime. We exhibit several (I) weakly hyperbolic, (II) diagonalizable hyperbolic, and (III) symmetric hyperbolic systems, with each their eigenvalues. We demonstrate that Ashtekar's original equations form a weakly hyperbolic system. We discuss how gauge conditions and reality conditions are constrained during each step toward constructing a symmetric hyperbolic system. |
2011.12841 | Juliano Neves | R. V. Maluf, Juliano C. S. Neves | Black holes with a cosmological constant in bumblebee gravity | 11 pages, 5 figures. V3 with new comments on the bumblebee potential.
Published in Physical Review D | Phys. Rev. D 103, 044002 (2021) | 10.1103/PhysRevD.103.044002 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we present black hole solutions with a cosmological constant in
bumblebee gravity, which provides a mechanism for the Lorentz symmetry
violation by assuming a nonzero vacuum expectation value for the bumblebee
field. From the gravitational point of view, such solutions are spherically
symmetric black holes with an effective cosmological constant and are supported
by an anisotropic energy-momentum tensor, conceived of as the manifestation of
the bumblebee field in the spacetime geometry. Then we calculate the shadow
angular radius for the proposed black hole solution with a positive effective
cosmological constant. In particular, our results are the very first relation
between the bumblebee field and the shadow angular size.
| [
{
"created": "Wed, 25 Nov 2020 15:50:55 GMT",
"version": "v1"
},
{
"created": "Sun, 29 Nov 2020 15:47:19 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Feb 2021 16:38:29 GMT",
"version": "v3"
}
] | 2021-02-02 | [
[
"Maluf",
"R. V.",
""
],
[
"Neves",
"Juliano C. S.",
""
]
] | In this work, we present black hole solutions with a cosmological constant in bumblebee gravity, which provides a mechanism for the Lorentz symmetry violation by assuming a nonzero vacuum expectation value for the bumblebee field. From the gravitational point of view, such solutions are spherically symmetric black holes with an effective cosmological constant and are supported by an anisotropic energy-momentum tensor, conceived of as the manifestation of the bumblebee field in the spacetime geometry. Then we calculate the shadow angular radius for the proposed black hole solution with a positive effective cosmological constant. In particular, our results are the very first relation between the bumblebee field and the shadow angular size. |
1006.1850 | Khaled Saaidi | Kh. Saaidi, A. Mohammadi | Brane Cosmology for Vacuum and Cosmological Constant Bulk | 13 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the cosmology of a 3-brane universe, in a five dimensional space
time (Bulk). We present some solutions to the five-dimensional Einstein
equation, where a perfect fluid is confined to the 3-brane. We investigate the
evolution of brane for two models of bulk. We choose ordinary and modified
polytropic gas in brane and it is seen that these models have some new
features.
| [
{
"created": "Wed, 9 Jun 2010 16:21:22 GMT",
"version": "v1"
}
] | 2010-06-10 | [
[
"Saaidi",
"Kh.",
""
],
[
"Mohammadi",
"A.",
""
]
] | We consider the cosmology of a 3-brane universe, in a five dimensional space time (Bulk). We present some solutions to the five-dimensional Einstein equation, where a perfect fluid is confined to the 3-brane. We investigate the evolution of brane for two models of bulk. We choose ordinary and modified polytropic gas in brane and it is seen that these models have some new features. |
1608.02979 | Jos\'e Villanueva | Graeme Candlish, Marco Olivares, Constanza Osses and J.R. Villanueva | Photon paths in the hyperbolic topological black hole spacetime of
conformal Weyl gravity | 13 pages, 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we find analytical solutions to the null geodesics in the
hyperbolic topological black hole spacetime of conformal Weyl gravity in an
invariant $2$-plane given by the orbits of an azimuthal Killing vector. Exact
expressions for the (non-compact) horizons are found, which depend on the
cosmological constant and the coupling constants of conformal Weyl gravity. The
angular motion is examined qualitatively by means of an effective potential;
quantitatively, the equation of motion is solved in terms of the
$\wp$-Weierstra{\ss} elliptic function. Thus, we find the deflection angle for
photons without using any approximation, which is a novel result for this
topology.
| [
{
"created": "Tue, 9 Aug 2016 20:23:54 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Aug 2018 05:41:52 GMT",
"version": "v2"
}
] | 2018-08-24 | [
[
"Candlish",
"Graeme",
""
],
[
"Olivares",
"Marco",
""
],
[
"Osses",
"Constanza",
""
],
[
"Villanueva",
"J. R.",
""
]
] | In this work we find analytical solutions to the null geodesics in the hyperbolic topological black hole spacetime of conformal Weyl gravity in an invariant $2$-plane given by the orbits of an azimuthal Killing vector. Exact expressions for the (non-compact) horizons are found, which depend on the cosmological constant and the coupling constants of conformal Weyl gravity. The angular motion is examined qualitatively by means of an effective potential; quantitatively, the equation of motion is solved in terms of the $\wp$-Weierstra{\ss} elliptic function. Thus, we find the deflection angle for photons without using any approximation, which is a novel result for this topology. |
2408.06852 | Xiangdong Zhang | Yunlong Liu and Xiangdong Zhang | Analytic solutions for the motion of spinning particles near brane-world
black hole | 16 pages, 4 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The general motion of spinning test particles to the leading order
approximation of spin in the brane-world spacetime is investigated. Analytical
integrations for the equations of motion and linear shifts in orbital frequency
are obtained. As a result, we found that both the nodal precession and the
periastron precession become larger when the tidal charge $b$ of brane-world
spacetime becomes smaller. For the periastron precession, the effect is further
amplified as the spin increases. Our work can potentially be applied to the
study of gravitational waveforms of Extreme Mass Ratio Inspirals with spin in
brane-world spacetime.
| [
{
"created": "Tue, 13 Aug 2024 12:27:52 GMT",
"version": "v1"
}
] | 2024-08-14 | [
[
"Liu",
"Yunlong",
""
],
[
"Zhang",
"Xiangdong",
""
]
] | The general motion of spinning test particles to the leading order approximation of spin in the brane-world spacetime is investigated. Analytical integrations for the equations of motion and linear shifts in orbital frequency are obtained. As a result, we found that both the nodal precession and the periastron precession become larger when the tidal charge $b$ of brane-world spacetime becomes smaller. For the periastron precession, the effect is further amplified as the spin increases. Our work can potentially be applied to the study of gravitational waveforms of Extreme Mass Ratio Inspirals with spin in brane-world spacetime. |
gr-qc/0510085 | Dag {\O}stvang | Dag {\O}stvang | Metrically Stationary, Axially Symmetric, Isolated Systems in
Quasi-Metric Gravity | 20 pages; v3: somewhat extended; v4: accepted for publication in Acta
Physica Polonica B; v5: must have non-universal gravitational coupling; v6:
minor corrections; v7: rewritten with extended theory; v9: inconsistent
equation replaced (results unaffected) | Acta Phys.Polon.B39:1849-1868,2008 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational field exterior respectively interior to an axially
symmetric, metrically stationary, isolated spinning source made of perfect
fluid is examined within the quasi-metric framework. (A metrically stationary
system is defined as a system which is stationary except for the direct effects
of the global cosmic expansion on the space-time geometry.) Field equations are
set up and an attempt is made to find an approximate series solution for the
exterior part. However, the result is that no stationary solution corresponding
to a spinning source can exist when considering terms beyond a certain order in
small quantities. That is, except for metrically static systems, axially
symmetric systems must necessarily be non-stationary in quasi-metric gravity.
However, sufficiently weak, axially symmetric gravitational fields associated
with slowly rotating sources, may still be considered as stationary as an
excellent approximation.
Thus a truncated, approximately stationary solution is found for the exterior
field. To lowest order in small quantities, the gravito-magnetic part of the
found metric family corresponds with the Kerr metric in the metric
approximation. On the other hand, the gravito-electric part of the found metric
family also includes a tidal term characterized by the free quadrupole-moment
parameter $J_2$ describing the effect of source deformation due to the
rotation. This term has no counterpart in the Kerr metric. Finally, the
geodetic effect for a gyroscope in orbit is calculated. There is a correction
term, unfortunately barely too small to be detectable by Gravity Probe B, to
the standard expression.
| [
{
"created": "Wed, 19 Oct 2005 01:48:28 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Dec 2005 06:27:50 GMT",
"version": "v2"
},
{
"created": "Wed, 7 Mar 2007 22:58:30 GMT",
"version": "v3"
},
{
"created": "Wed, 7 May 2008 22:33:46 GMT",
"version": "v4"
},
{
"cre... | 2024-03-25 | [
[
"Østvang",
"Dag",
""
]
] | The gravitational field exterior respectively interior to an axially symmetric, metrically stationary, isolated spinning source made of perfect fluid is examined within the quasi-metric framework. (A metrically stationary system is defined as a system which is stationary except for the direct effects of the global cosmic expansion on the space-time geometry.) Field equations are set up and an attempt is made to find an approximate series solution for the exterior part. However, the result is that no stationary solution corresponding to a spinning source can exist when considering terms beyond a certain order in small quantities. That is, except for metrically static systems, axially symmetric systems must necessarily be non-stationary in quasi-metric gravity. However, sufficiently weak, axially symmetric gravitational fields associated with slowly rotating sources, may still be considered as stationary as an excellent approximation. Thus a truncated, approximately stationary solution is found for the exterior field. To lowest order in small quantities, the gravito-magnetic part of the found metric family corresponds with the Kerr metric in the metric approximation. On the other hand, the gravito-electric part of the found metric family also includes a tidal term characterized by the free quadrupole-moment parameter $J_2$ describing the effect of source deformation due to the rotation. This term has no counterpart in the Kerr metric. Finally, the geodetic effect for a gyroscope in orbit is calculated. There is a correction term, unfortunately barely too small to be detectable by Gravity Probe B, to the standard expression. |
gr-qc/0509052 | D. Bar | D. Bar | Gravitational wave holography | 19 pages, 2 figures. A few misprints were corrected | Int.J.Theor.Phys.46:503-517,2007 | 10.1007/s10773-006-9108-1 | null | gr-qc | null | We represent and discuss a theory of gravitational holography in which all
the involved waves; subject, reference and illuminator are gravitational waves
(GW). Although these waves are so weak that no terrestrial experimental
set-ups, even the large LIGO, VIRGO, GEO and TAMA facilities, were able up to
now to directly detect them they are, nevertheless, known under certain
conditions (such as very small wavelengths) to be almost indistinguishable (see
P. 962 in Ref. \cite{mtw}) from their analogue electromagnetic waves (EMW). We,
therefore theoretically, show, using the known methods of optical holography
and taking into account the very peculiar nature of GW, that it is also
possible to reconstruct subject gravitational waves.
| [
{
"created": "Wed, 14 Sep 2005 22:03:34 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Aug 2007 19:46:04 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bar",
"D.",
""
]
] | We represent and discuss a theory of gravitational holography in which all the involved waves; subject, reference and illuminator are gravitational waves (GW). Although these waves are so weak that no terrestrial experimental set-ups, even the large LIGO, VIRGO, GEO and TAMA facilities, were able up to now to directly detect them they are, nevertheless, known under certain conditions (such as very small wavelengths) to be almost indistinguishable (see P. 962 in Ref. \cite{mtw}) from their analogue electromagnetic waves (EMW). We, therefore theoretically, show, using the known methods of optical holography and taking into account the very peculiar nature of GW, that it is also possible to reconstruct subject gravitational waves. |
gr-qc/0208009 | Martin Snajdr | Martin Snajdr, Valeri Frolov and Jean-Pierre DeVilliers | Scattering of a Long Cosmic String by a Rotating Black Hole | 27 pages, 14 figures, to be published in Classical and Quantum
Gravity | Class.Quant.Grav. 19 (2002) 5987-6008 | 10.1088/0264-9381/19/23/308 | null | gr-qc | null | The scattering of a straight, infinitely long string by a rotating black hole
is considered. We assume that a string is moving with velocity v and that
initially the string is parallel to the axis of rotation of the black hole. We
demonstrate that as a result of scattering, the string is displaced in the
direction perpendicular to the velocity by an amount kappa(v,b), where b is the
impact parameter. The late-time solution is represented by a kink and
anti-kink, propagating in opposite directions at the speed of light, and
leaving behind them the string in a new ``phase''. We present the results of
the numerical study of the string scattering and their comparison with the
weak-field approximation, valid where the impact parameter is large, b/M >> 1,
and also with the scattering by a non-rotating black hole which was studied in
earlier works.
| [
{
"created": "Sat, 3 Aug 2002 02:52:23 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Oct 2002 07:36:55 GMT",
"version": "v2"
},
{
"created": "Sun, 3 Nov 2002 01:27:14 GMT",
"version": "v3"
}
] | 2016-08-31 | [
[
"Snajdr",
"Martin",
""
],
[
"Frolov",
"Valeri",
""
],
[
"DeVilliers",
"Jean-Pierre",
""
]
] | The scattering of a straight, infinitely long string by a rotating black hole is considered. We assume that a string is moving with velocity v and that initially the string is parallel to the axis of rotation of the black hole. We demonstrate that as a result of scattering, the string is displaced in the direction perpendicular to the velocity by an amount kappa(v,b), where b is the impact parameter. The late-time solution is represented by a kink and anti-kink, propagating in opposite directions at the speed of light, and leaving behind them the string in a new ``phase''. We present the results of the numerical study of the string scattering and their comparison with the weak-field approximation, valid where the impact parameter is large, b/M >> 1, and also with the scattering by a non-rotating black hole which was studied in earlier works. |
1311.0595 | George F. R. Ellis | George F R Ellis | On the paradox of Hawking radiation in a maximally extended
Schwarzschild solution | 26 pages, 7 figures, 2 tables. arXiv admin note: text overlap with
arXiv:1310.4771 | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper considers the effect of Hawking radiation on an eternal black hole
- that is. a maximally extended Schwarzschild solution. Symmetry considerations
that hold independent of the details of the emission mechanism show there is an
inconsistency in the claim that such a blackhole evaporates away in a finite
time. In essence: because the external domain is static, there is an infinite
time available for the process to take place, so whenever the evaporation
process is claimed to come to completion, it should have happened earlier. The
problem is identified to lie in the claim that the locus of emission of Hawking
radiation lies just outside the globally defined event horizon. Rather, the
emission domain must be mainly located inside the event horizon, so most of the
Hawking radiation ends up at this singularity rather than at infinity and the
black hole never evaporates away. This result supports a previous claim
[arXiv:1310.4771] that astrophysical black holes do not evaporate.
| [
{
"created": "Mon, 4 Nov 2013 06:58:47 GMT",
"version": "v1"
}
] | 2013-11-05 | [
[
"Ellis",
"George F R",
""
]
] | This paper considers the effect of Hawking radiation on an eternal black hole - that is. a maximally extended Schwarzschild solution. Symmetry considerations that hold independent of the details of the emission mechanism show there is an inconsistency in the claim that such a blackhole evaporates away in a finite time. In essence: because the external domain is static, there is an infinite time available for the process to take place, so whenever the evaporation process is claimed to come to completion, it should have happened earlier. The problem is identified to lie in the claim that the locus of emission of Hawking radiation lies just outside the globally defined event horizon. Rather, the emission domain must be mainly located inside the event horizon, so most of the Hawking radiation ends up at this singularity rather than at infinity and the black hole never evaporates away. This result supports a previous claim [arXiv:1310.4771] that astrophysical black holes do not evaporate. |
gr-qc/0612103 | Oleg Teryaev | A. J. Silenko and O. V. Teryaev | Equivalence principle and experimental tests of gravitational spin
effects | 12 pages, version to appear in Physical Review D | Phys.Rev.D76:061101,2007 | 10.1103/PhysRevD.76.061101 | null | gr-qc | null | We study the possibility of experimental testing the manifestations of
equivalence principle in spin-gravity interactions. We reconsider the earlier
experimental data and get the first experimental bound on anomalous
gravitomagnetic moment. The spin coupling to the Earth's rotation may also be
explored at the extensions of neutron EDM and g-2 experiments. The spin
coupling to the terrestrial gravity produces a considerable effect which may be
discovered at the planned deuteron EDM experiment. The Earth's rotation should
also be taken into account in optical experiments on a search for axionlike
particles.
| [
{
"created": "Sun, 17 Dec 2006 15:52:32 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Sep 2007 11:12:28 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Silenko",
"A. J.",
""
],
[
"Teryaev",
"O. V.",
""
]
] | We study the possibility of experimental testing the manifestations of equivalence principle in spin-gravity interactions. We reconsider the earlier experimental data and get the first experimental bound on anomalous gravitomagnetic moment. The spin coupling to the Earth's rotation may also be explored at the extensions of neutron EDM and g-2 experiments. The spin coupling to the terrestrial gravity produces a considerable effect which may be discovered at the planned deuteron EDM experiment. The Earth's rotation should also be taken into account in optical experiments on a search for axionlike particles. |
2101.08842 | Abolhassan Mohammadi | Abolhassan Mohammadi, N. Doustimotlagh, Tayeb Golanbari, Behrooz
Malakolkalami, Shahram Jalalzadeh | Null geodesic of Schwarzschild AdS with Gaussian matter distribution | 11 pages, 14 figures, typos and grammars corrections, References
added, Some typos corrected | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the best ways to understand the gravitation of a massive object is by
studying the photon's motion around it. We study the null geodesic of a regular
black hole in anti-de Sitter spacetime, including a Gaussian matter
distribution. Obtaining the effective potential and possible motions of the
photon are discussed for different energy levels. The nature of the effective
potential implies that the photon is prevented from reaching the black hole's
center. Different types of possible orbits are considered. A photon with
negative energy is trapped in a potential hole and has a back and forth motion
between two horizons of the metric. However, for specific values of positive
energy, the trapped photon still has a back and forth motion; however, it
crosses the horizons in every direction. The effective potential has an
unstable point outside the horizons, which indicates the possible circular
motion of the photon. The closest approach of the photon and the bending angle
are also investigated.
| [
{
"created": "Thu, 21 Jan 2021 20:32:30 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Feb 2021 15:14:07 GMT",
"version": "v2"
},
{
"created": "Mon, 20 Sep 2021 16:46:26 GMT",
"version": "v3"
}
] | 2021-09-21 | [
[
"Mohammadi",
"Abolhassan",
""
],
[
"Doustimotlagh",
"N.",
""
],
[
"Golanbari",
"Tayeb",
""
],
[
"Malakolkalami",
"Behrooz",
""
],
[
"Jalalzadeh",
"Shahram",
""
]
] | One of the best ways to understand the gravitation of a massive object is by studying the photon's motion around it. We study the null geodesic of a regular black hole in anti-de Sitter spacetime, including a Gaussian matter distribution. Obtaining the effective potential and possible motions of the photon are discussed for different energy levels. The nature of the effective potential implies that the photon is prevented from reaching the black hole's center. Different types of possible orbits are considered. A photon with negative energy is trapped in a potential hole and has a back and forth motion between two horizons of the metric. However, for specific values of positive energy, the trapped photon still has a back and forth motion; however, it crosses the horizons in every direction. The effective potential has an unstable point outside the horizons, which indicates the possible circular motion of the photon. The closest approach of the photon and the bending angle are also investigated. |
2303.04785 | Sergey Rubin | Polina Petriakova, Arkady A. Popov, Sergey G. Rubin | Flexible extra dimensions | 12 pages, 4 figures | null | 10.1140/epjc/s10052-023-11542-7 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This paper discusses the origin of the small parameters with the aim of
explaining the Hierarchy problem. The flexible extra dimensions are an
essential tool in the process by which physical parameters are formed. The
evolution of a multidimensional metric starts at the Planck scale and is
completed with the static extra-dimensional metric and the 4-dim de Sitter
space at high energies, where the exponential production of causally
disconnected universes begins. Quantum fluctuations independently distort the
metric within these universes, causing inflationary processes within them. Some
of these universes tend asymptotically towards states characterised by small
Hubble parameters. The effective parameter reduction applied to the Higgs
sector of the Standard Model is explained by the presence of small-amplitude
distributions of a scalar field in a fraction of these universes.
| [
{
"created": "Wed, 8 Mar 2023 18:32:47 GMT",
"version": "v1"
}
] | 2023-05-24 | [
[
"Petriakova",
"Polina",
""
],
[
"Popov",
"Arkady A.",
""
],
[
"Rubin",
"Sergey G.",
""
]
] | This paper discusses the origin of the small parameters with the aim of explaining the Hierarchy problem. The flexible extra dimensions are an essential tool in the process by which physical parameters are formed. The evolution of a multidimensional metric starts at the Planck scale and is completed with the static extra-dimensional metric and the 4-dim de Sitter space at high energies, where the exponential production of causally disconnected universes begins. Quantum fluctuations independently distort the metric within these universes, causing inflationary processes within them. Some of these universes tend asymptotically towards states characterised by small Hubble parameters. The effective parameter reduction applied to the Higgs sector of the Standard Model is explained by the presence of small-amplitude distributions of a scalar field in a fraction of these universes. |
1512.01451 | Ramil Izmailov | Amarjit Tamang, Alexander A. Potapov, Regina Lukmanova, Ramil Izmailov
and Kamal K. Nandi | On generalized wormhole in the Eddington inspired Born-Infeld (EiBI)
gravity | 20 pages, 3 figures | Class.Quant.Grav. 32(23) : 235028, 2015 | 10.1088/0264-9381/32/23/235028 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we wish to investigate certain observable effects in the
recently obtained wormhole solution of the EiBI theory, which generalizes the
zero mass Ellis-Bronnikov wormhole of general relativity. The solutions of EiBI
theory contain an extra parameter $\kappa$ having the inverse dimension of the
cosmological constant $\Lambda$, and is expected to modify various general
relativistic observables such as the masses of wormhole mouths, tidal forces
and light deflection. A remarkable result is that a non-zero $\kappa$ could
prevent the tidal forces in the geodesic orthonormal frame from becoming
arbitrarily large near a small throat radius $(r_0 \sim {0})$ contrary to what
happens near a small Schwarzschild horizon radius $(M \sim 0)$. The role of
$\kappa$ in the flare-out and energy conditions is also analysed, which reveals
that the energy conditions are violated. We show that the exotic matter in the
EiBI wormhole cannot be interpreted as phantom $({\omega}=(p_{r}/ \rho)<-1)$ or
ghost field ${\phi} $ of general relativity due to the fact that both $\rho$
and $p_{r}$ are negative for all $\kappa$.
| [
{
"created": "Thu, 3 Dec 2015 14:03:00 GMT",
"version": "v1"
}
] | 2015-12-07 | [
[
"Tamang",
"Amarjit",
""
],
[
"Potapov",
"Alexander A.",
""
],
[
"Lukmanova",
"Regina",
""
],
[
"Izmailov",
"Ramil",
""
],
[
"Nandi",
"Kamal K.",
""
]
] | In this paper, we wish to investigate certain observable effects in the recently obtained wormhole solution of the EiBI theory, which generalizes the zero mass Ellis-Bronnikov wormhole of general relativity. The solutions of EiBI theory contain an extra parameter $\kappa$ having the inverse dimension of the cosmological constant $\Lambda$, and is expected to modify various general relativistic observables such as the masses of wormhole mouths, tidal forces and light deflection. A remarkable result is that a non-zero $\kappa$ could prevent the tidal forces in the geodesic orthonormal frame from becoming arbitrarily large near a small throat radius $(r_0 \sim {0})$ contrary to what happens near a small Schwarzschild horizon radius $(M \sim 0)$. The role of $\kappa$ in the flare-out and energy conditions is also analysed, which reveals that the energy conditions are violated. We show that the exotic matter in the EiBI wormhole cannot be interpreted as phantom $({\omega}=(p_{r}/ \rho)<-1)$ or ghost field ${\phi} $ of general relativity due to the fact that both $\rho$ and $p_{r}$ are negative for all $\kappa$. |
2108.08085 | Wojciech Kami\'nski | Wojciech Kami\'nski | Well-posedness of the ambient metric equations and stability of even
dimensional asymptotically de Sitter spacetimes | 24 pages, minor corrections, references updated | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Vanishing of the Fefferman-Graham obstruction tensor was used by Andersson
and Chru{\'s}ciel to show stability of the asymptotically de Sitter spaces in
even dimensions. However, existing proofs of hyperbolicity of this equation
contain gaps. We show in this paper that it is indeed a well-posed hyperbolic
system with unique up to diffeomorphism and conformal transformations smooth
development for smooth Cauchy data. Our method applies also to equations
defined by various versions Graham-Jenne-Mason-Sparling operators. In
particular, we use one of these operators to propagate Gover's condition of
being almost conformally Einstein. This allows to study initial data also for
Cauchy surfaces which cross conformal boundary. As a by-product we show that on
globally hyperbolic manifolds one can always choose conformal factor such that
Branson Q-curvature vanishes.
| [
{
"created": "Wed, 18 Aug 2021 10:38:30 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Mar 2022 18:38:03 GMT",
"version": "v2"
}
] | 2022-03-02 | [
[
"Kamiński",
"Wojciech",
""
]
] | Vanishing of the Fefferman-Graham obstruction tensor was used by Andersson and Chru{\'s}ciel to show stability of the asymptotically de Sitter spaces in even dimensions. However, existing proofs of hyperbolicity of this equation contain gaps. We show in this paper that it is indeed a well-posed hyperbolic system with unique up to diffeomorphism and conformal transformations smooth development for smooth Cauchy data. Our method applies also to equations defined by various versions Graham-Jenne-Mason-Sparling operators. In particular, we use one of these operators to propagate Gover's condition of being almost conformally Einstein. This allows to study initial data also for Cauchy surfaces which cross conformal boundary. As a by-product we show that on globally hyperbolic manifolds one can always choose conformal factor such that Branson Q-curvature vanishes. |
2108.11960 | William C. C. Lima | Markus B. Fr\"ob and William C. C. Lima | Cosmological Perturbations and Invariant Observables in Geodesic
Lightcone Coordinates | 38 pages. Some discussions improved and typos corrected. Matches
published version | JCAP01(2022)034 | 10.1088/1475-7516/2022/01/034 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a recent approach to the construction of gauge-invariant
relational observables in gravity in the context of cosmological perturbation
theory. These observables are constructed using a field-dependent coordinate
system, which we take to be geodesic lightcone coordinates. We show that the
observables are gauge-independent in the fully non-linear theory, and that they
have the expected form when one adopts the geodesic lightcone gauge for the
metric. We give explicit expressions for the Sasaki-Mukhanov variable at linear
order, and the Hubble rate -- as measured both by geodesic observers and by
observers co-moving with the inflaton -- to second order. Moreover, we show
that the well-known linearised equations of motion for the Sasaki-Mukhanov
variable and the scalar constraint variables follow from the gauge-invariant
Einstein's equations.
| [
{
"created": "Thu, 26 Aug 2021 18:00:00 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Jan 2022 15:19:27 GMT",
"version": "v2"
}
] | 2022-01-20 | [
[
"Fröb",
"Markus B.",
""
],
[
"Lima",
"William C. C.",
""
]
] | We consider a recent approach to the construction of gauge-invariant relational observables in gravity in the context of cosmological perturbation theory. These observables are constructed using a field-dependent coordinate system, which we take to be geodesic lightcone coordinates. We show that the observables are gauge-independent in the fully non-linear theory, and that they have the expected form when one adopts the geodesic lightcone gauge for the metric. We give explicit expressions for the Sasaki-Mukhanov variable at linear order, and the Hubble rate -- as measured both by geodesic observers and by observers co-moving with the inflaton -- to second order. Moreover, we show that the well-known linearised equations of motion for the Sasaki-Mukhanov variable and the scalar constraint variables follow from the gauge-invariant Einstein's equations. |
2407.08208 | Hai-Shan Liu | Hai-Shan Liu and Lei Zhang | Scalarization of Taub-NUT Black Holes in Extended
scalar-tensor-Gauss-Bonnet Theory | 19 pages, 10 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Recently, scalarization of Schwarzschild black hole are extensively studied.
In this work, we explore the scalarization of Taub-NUT black hole. The theory
we consider is the extended scalar-tensor-Gauss-Bonnet theory, which admits
Ricci-flat Taub-NUT black hole as a solution. An analysis of probe scalar field
is carried out to identify the mass parameter and NUT parameter (m,n) where the
hairy black holes start to emerge. Then, we use shooting method to construct
the scalarized Taub-NUT black hole numerically. Being different from the
Schwarzschild case, there exists two branches of new hairy black holes which
are smoothly connected to each other. We calculate the entropy of scalarized
black holes and compare it with the entropy of scalar-free Taub-NUT black
holes, it turns out that the entropy of the new hairy black holes are larger
than that of scalar-free black holes. A novel phenomena emerges in this system
that the entropy of the black holes at the bifurcation point is constant for
positive mass parameter. We then conjecture a maximal entropy bound for all the
scalarized black hole whose mass parameter at the bifurcation point is greater
than zero.
| [
{
"created": "Thu, 11 Jul 2024 06:24:10 GMT",
"version": "v1"
}
] | 2024-07-12 | [
[
"Liu",
"Hai-Shan",
""
],
[
"Zhang",
"Lei",
""
]
] | Recently, scalarization of Schwarzschild black hole are extensively studied. In this work, we explore the scalarization of Taub-NUT black hole. The theory we consider is the extended scalar-tensor-Gauss-Bonnet theory, which admits Ricci-flat Taub-NUT black hole as a solution. An analysis of probe scalar field is carried out to identify the mass parameter and NUT parameter (m,n) where the hairy black holes start to emerge. Then, we use shooting method to construct the scalarized Taub-NUT black hole numerically. Being different from the Schwarzschild case, there exists two branches of new hairy black holes which are smoothly connected to each other. We calculate the entropy of scalarized black holes and compare it with the entropy of scalar-free Taub-NUT black holes, it turns out that the entropy of the new hairy black holes are larger than that of scalar-free black holes. A novel phenomena emerges in this system that the entropy of the black holes at the bifurcation point is constant for positive mass parameter. We then conjecture a maximal entropy bound for all the scalarized black hole whose mass parameter at the bifurcation point is greater than zero. |
1210.6877 | Madhavan Varadarajan | Madhavan Varadarajan | Towards an Anomaly-Free Quantum Dynamics for a Weak Coupling Limit of
Euclidean Gravity: Diffeomorphism Covariance | 56 pages, No figures | Phys.Rev. D87 (2013) 4, 044040 | 10.1103/PhysRevD.87.044040 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The G-->0 limit of Euclidean gravity introduced by Smolin is described by a
generally covariant U(1)xU(1)xU(1) gauge theory. In an earlier paper, Tomlin
and Varadarajan constructed the quantum Hamiltonian constraint of density
weight 4/3 for this U(1)xU(1)xU(1) theory so as to produce a non-trivial
anomaly free LQG-type representation of the Poisson bracket between a pair of
Hamiltonian constraints. These constructions involved a choice of regulating
coordinate patches. The use of these coordinate patches is in apparent conflict
with spatial diffeomorphism covariance. In this work we show how an appropriate
choice of coordinate patches together with suitable modifications of these
constructions results in the diffeomorphism covariance of the continuum limit
action of the Hamiltonian constraint operator, while preserving the anomaly
free property of the continuum limit action of its commutator.
| [
{
"created": "Thu, 25 Oct 2012 15:35:56 GMT",
"version": "v1"
}
] | 2015-01-30 | [
[
"Varadarajan",
"Madhavan",
""
]
] | The G-->0 limit of Euclidean gravity introduced by Smolin is described by a generally covariant U(1)xU(1)xU(1) gauge theory. In an earlier paper, Tomlin and Varadarajan constructed the quantum Hamiltonian constraint of density weight 4/3 for this U(1)xU(1)xU(1) theory so as to produce a non-trivial anomaly free LQG-type representation of the Poisson bracket between a pair of Hamiltonian constraints. These constructions involved a choice of regulating coordinate patches. The use of these coordinate patches is in apparent conflict with spatial diffeomorphism covariance. In this work we show how an appropriate choice of coordinate patches together with suitable modifications of these constructions results in the diffeomorphism covariance of the continuum limit action of the Hamiltonian constraint operator, while preserving the anomaly free property of the continuum limit action of its commutator. |
gr-qc/0511150 | J. Ponce de Leon | J. Ponce de Leon | An analytic model for the transition from decelerated to accelerated
cosmic expansion | The abstract and introduction are improved and the discussion section
is expanded. A number of references are added | Int.J.Mod.Phys.D15:1237-1257,2006 | 10.1142/S0218271806008929 | null | gr-qc | null | We consider the scenario where our observable universe is devised as a
dynamical four-dimensional hypersurface embedded in a five-dimensional bulk
spacetime, with a large extra dimension, which is the {\it generalization of
the flat FRW cosmological metric to five dimensions}. This scenario generates a
simple analytical model where different stages of the evolution of the universe
are approximated by distinct parameterizations of the {\it same} spacetime. In
this model the evolution from decelerated to accelerated expansion can be
interpreted as a "first-order" phase transition between two successive stages.
The dominant energy condition allows different parts of the universe to evolve,
from deceleration to acceleration, at different redshifts within a narrow era.
This picture corresponds to the creation of bubbles of new phase, in the middle
of the old one, typical of first-order phase transitions. Taking $\Omega_{m} =
0.3$ today, we find that the cross-over from deceleration to acceleration
occurs at $z \sim 1-1.5 $, regardless of the equation of state in the very
early universe. In the case of primordial radiation, the model predicts that
the deceleration parameter "jumps" from $q \sim + 1.5$ to $q \sim - 0.4$ at $z
\sim 1.17$. At the present time $q = - 0.55$ and the equation of state of the
universe is $w = p/\rho \sim - 0.7 $, in agreement with observations and some
theoretical predictions.
| [
{
"created": "Tue, 29 Nov 2005 04:17:04 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Dec 2005 00:23:48 GMT",
"version": "v2"
},
{
"created": "Thu, 16 Mar 2006 05:00:38 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"de Leon",
"J. Ponce",
""
]
] | We consider the scenario where our observable universe is devised as a dynamical four-dimensional hypersurface embedded in a five-dimensional bulk spacetime, with a large extra dimension, which is the {\it generalization of the flat FRW cosmological metric to five dimensions}. This scenario generates a simple analytical model where different stages of the evolution of the universe are approximated by distinct parameterizations of the {\it same} spacetime. In this model the evolution from decelerated to accelerated expansion can be interpreted as a "first-order" phase transition between two successive stages. The dominant energy condition allows different parts of the universe to evolve, from deceleration to acceleration, at different redshifts within a narrow era. This picture corresponds to the creation of bubbles of new phase, in the middle of the old one, typical of first-order phase transitions. Taking $\Omega_{m} = 0.3$ today, we find that the cross-over from deceleration to acceleration occurs at $z \sim 1-1.5 $, regardless of the equation of state in the very early universe. In the case of primordial radiation, the model predicts that the deceleration parameter "jumps" from $q \sim + 1.5$ to $q \sim - 0.4$ at $z \sim 1.17$. At the present time $q = - 0.55$ and the equation of state of the universe is $w = p/\rho \sim - 0.7 $, in agreement with observations and some theoretical predictions. |
gr-qc/0309069 | Tiberiu Harko | M. K. Mak, T. Harko | Quark stars admitting a one-parameter group of conformal motions | 5 pages, no figures, to appear in IJMPD | Int.J.Mod.Phys. D13 (2004) 149-156 | 10.1142/S0218271804004451 | null | gr-qc | null | An exact analytical solution describing the interior of a charged strange
quark star is found under the assumption of spherical symmetry and the
existence of a one-parameter group of conformal motions. The solution describes
a unique static charged configuration of quark matter with radius $R=9.46$ km
and total mass $M=2.86M_{\odot}$.
| [
{
"created": "Mon, 15 Sep 2003 06:01:39 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Jan 2004 03:13:13 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Mak",
"M. K.",
""
],
[
"Harko",
"T.",
""
]
] | An exact analytical solution describing the interior of a charged strange quark star is found under the assumption of spherical symmetry and the existence of a one-parameter group of conformal motions. The solution describes a unique static charged configuration of quark matter with radius $R=9.46$ km and total mass $M=2.86M_{\odot}$. |
1011.4538 | Gabriel Abreu | Gabriel Abreu (Victoria University of Wellington), Matt Visser
(Victoria University of Wellington) | Entropy bounds for uncollapsed matter | 4 pages. Prepared for the proceedings of the Spanish Relativity
meeting (ERE2010), Granada, Spain, 6-10 Sep 2010 | J.Phys.Conf.Ser.314:012035,2011 | 10.1088/1742-6596/314/1/012035 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In any static spacetime the quasilocal Tolman mass contained within a volume
can be reduced to a Gauss-like surface integral involving the flux of a
suitably defined generalized surface gravity. By introducing some basic
thermodynamics, and invoking the Unruh effect, one can then develop elementary
bounds on the quasilocal entropy that are very similar in spirit to the
holographic bound, and closely related to entanglement entropy.
| [
{
"created": "Fri, 19 Nov 2010 23:59:49 GMT",
"version": "v1"
}
] | 2011-09-28 | [
[
"Abreu",
"Gabriel",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | In any static spacetime the quasilocal Tolman mass contained within a volume can be reduced to a Gauss-like surface integral involving the flux of a suitably defined generalized surface gravity. By introducing some basic thermodynamics, and invoking the Unruh effect, one can then develop elementary bounds on the quasilocal entropy that are very similar in spirit to the holographic bound, and closely related to entanglement entropy. |
1407.2958 | Davood Momeni Dr | Surajit Chattopadhyay, Davood Momeni, Aziza Altaibayeva, Ratbay
Myrzakulov | Can Holographic dark energy increase the mass of the wormhole? | Replaced version, in "Astrophysics and Space Science".Replaced to
remove overlaps | Astrophys.Space Sci. 356 (2015) no.1, 195-204 | 10.1007/s10509-014-2204-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we have studied accretion of dark energy (DE) onto Morris-
Thorne wormhole with three different forms, namely, holographic dark energy,
holographic Ricci dark energy and modified holographic Ricci dark energy .
Considering the scale factor in power-law form we have observed that as the
holographic dark energy accretes onto wormhole, the mass of the wormhole is
decreasing. In the next phase we considered three parameterization schemes that
are able to get hold of quintessence as well as phantom phases. Without any
choice of scale factor we reconstructed Hubble parameter from conservation
equation and dark energy densities and subsequently got the mass of the
wormhole separately for accretion of the three dark energy candidates. It was
observed that if these dark energies accrete onto the wormhole, then for
quintessence stage, wormhole mass decreases up to a certain finite value and
then again increases to aggressively during phantom phase of the universe.
| [
{
"created": "Fri, 27 Jun 2014 12:59:16 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Nov 2014 14:20:07 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Nov 2014 04:25:15 GMT",
"version": "v3"
},
{
"created": "Wed, 26 Nov 2014 11:41:42 GMT",
"version": "v4"
}
] | 2018-10-09 | [
[
"Chattopadhyay",
"Surajit",
""
],
[
"Momeni",
"Davood",
""
],
[
"Altaibayeva",
"Aziza",
""
],
[
"Myrzakulov",
"Ratbay",
""
]
] | In this work, we have studied accretion of dark energy (DE) onto Morris- Thorne wormhole with three different forms, namely, holographic dark energy, holographic Ricci dark energy and modified holographic Ricci dark energy . Considering the scale factor in power-law form we have observed that as the holographic dark energy accretes onto wormhole, the mass of the wormhole is decreasing. In the next phase we considered three parameterization schemes that are able to get hold of quintessence as well as phantom phases. Without any choice of scale factor we reconstructed Hubble parameter from conservation equation and dark energy densities and subsequently got the mass of the wormhole separately for accretion of the three dark energy candidates. It was observed that if these dark energies accrete onto the wormhole, then for quintessence stage, wormhole mass decreases up to a certain finite value and then again increases to aggressively during phantom phase of the universe. |
gr-qc/9905096 | Daniel Augusto Turolla Vanzella | Daniel A.T. Vanzella and George E.A. Matsas | Search for semiclassical-gravity effects in relativistic stars | 10 pages (REVTEX) | Phys.Rev.D61:127303,2000 | 10.1103/PhysRevD.61.127303 | IFT-P.044/99 | gr-qc astro-ph hep-ph hep-th | null | We discuss the possible influence of gravity in the neutronization process,
$p^+ e^- \to n \nu_e$, which is particularly important as a cooling mechanism
of neutron stars. Our approach is semiclassical in the sense that leptonic
fields are quantized on a classical background spacetime, while neutrons and
protons are treated as excited and unexcited nucleon states, respectively. We
expect gravity to have some influence wherever the energy content carried by
the in-state is barely above the neutron mass. In this case the emitted
neutrinos would be soft enough to have a wavelength of the same order as the
space curvature radius.
| [
{
"created": "Tue, 25 May 1999 21:36:46 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Vanzella",
"Daniel A. T.",
""
],
[
"Matsas",
"George E. A.",
""
]
] | We discuss the possible influence of gravity in the neutronization process, $p^+ e^- \to n \nu_e$, which is particularly important as a cooling mechanism of neutron stars. Our approach is semiclassical in the sense that leptonic fields are quantized on a classical background spacetime, while neutrons and protons are treated as excited and unexcited nucleon states, respectively. We expect gravity to have some influence wherever the energy content carried by the in-state is barely above the neutron mass. In this case the emitted neutrinos would be soft enough to have a wavelength of the same order as the space curvature radius. |
0705.2440 | Alejandro Corichi | Alejandro Corichi, Jose A. Zapata | Quantum Structure of Geometry: Loopy and fuzzy? | 9 pages, no figures | Int.J.Mod.Phys.D17:445-451,2008 | 10.1142/S0218271808012115 | null | gr-qc | null | In any attempt to build a quantum theory of gravity, a central issue is to
unravel the structure of space-time at the smallest scale. Of particular
relevance is the possible definition of coordinate functions within the theory
and the study of their algebraic properties, such as non-commutativity. Here we
approach this issue from the perspective of loop quantum gravity and the
picture of quantum geometry that the formalism offers. In particular, as we
argue here, this emerging picture has two main elements: i) The nature of the
quantum geometry at Planck scale is one-dimensional, polymeric with quantized
geometrical quantities and; ii) Appropriately defined operators corresponding
to coordinates by means of intrinsic, relational, constructions become
non-commuting. This particular feature of the operators, that operationally
localize points on space, gives rise to an emerging geometry that is also, in a
precise sense, fuzzy.
| [
{
"created": "Wed, 16 May 2007 21:33:29 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Corichi",
"Alejandro",
""
],
[
"Zapata",
"Jose A.",
""
]
] | In any attempt to build a quantum theory of gravity, a central issue is to unravel the structure of space-time at the smallest scale. Of particular relevance is the possible definition of coordinate functions within the theory and the study of their algebraic properties, such as non-commutativity. Here we approach this issue from the perspective of loop quantum gravity and the picture of quantum geometry that the formalism offers. In particular, as we argue here, this emerging picture has two main elements: i) The nature of the quantum geometry at Planck scale is one-dimensional, polymeric with quantized geometrical quantities and; ii) Appropriately defined operators corresponding to coordinates by means of intrinsic, relational, constructions become non-commuting. This particular feature of the operators, that operationally localize points on space, gives rise to an emerging geometry that is also, in a precise sense, fuzzy. |
2008.03749 | Rance Solomon | Rance Solomon, Dejan Stojkovic | Generalizing weak gravity conjecture | null | Phys.Rev.D 102 (2020) 4, 046016 | 10.1103/PhysRevD.102.046016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The weak gravity conjecture implies the necessary existence of particles with
charge-to-mass ratio $q/m \geq 1$ so that the extremal charged black hole can
completely evaporate without leaving a dangerous stable extremal remnant while
simultaneously not revealing a naked singularity along the way. In other words,
this inequality ensures that the charge is emitted faster than the mass of a
black hole, which is in turn coincidentally consistent with the fact that
gravitational interaction for such parties is weaker than electromagnetic. To
extend this argument to non-extremal black holes, we solve the problem of a
charged shell of mass and charge ($m,q$) from a black hole with ($M,Q$). We
find a more general condition $q/m \geq Q/M$, which obviously reduces to the
weak gravity conjecture in the extremal limit, however it relaxes the condition
for complete evaporation of non-extremal black holes. This condition also
allows us to directly relate the particle content of the theory with the
spectrum of black hole states.
| [
{
"created": "Sun, 9 Aug 2020 15:36:23 GMT",
"version": "v1"
}
] | 2020-09-15 | [
[
"Solomon",
"Rance",
""
],
[
"Stojkovic",
"Dejan",
""
]
] | The weak gravity conjecture implies the necessary existence of particles with charge-to-mass ratio $q/m \geq 1$ so that the extremal charged black hole can completely evaporate without leaving a dangerous stable extremal remnant while simultaneously not revealing a naked singularity along the way. In other words, this inequality ensures that the charge is emitted faster than the mass of a black hole, which is in turn coincidentally consistent with the fact that gravitational interaction for such parties is weaker than electromagnetic. To extend this argument to non-extremal black holes, we solve the problem of a charged shell of mass and charge ($m,q$) from a black hole with ($M,Q$). We find a more general condition $q/m \geq Q/M$, which obviously reduces to the weak gravity conjecture in the extremal limit, however it relaxes the condition for complete evaporation of non-extremal black holes. This condition also allows us to directly relate the particle content of the theory with the spectrum of black hole states. |
1406.3916 | Tharanath R | R. Tharanath, Jishnu Suresh and V. C. Kuriakose | Phase transitions and Geometrothermodynamics of Regular black holes | 18 pages and 19 figures | null | 10.1007/s10714-015-1884-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the thermodynamics and state space geometry of regular
black hole solutions such as Bardeen black hole, Ay\'{o}n-Beato and Garc\'{i}a
black hole, Hayward black hole and Berej-Matyjasek-Trynieki-Wornowicz black
hole. We find that all these black holes show second order thermodynamic phase
transitions(SOTPT) by observing discontinuities in heat capacity-entropy graphs
as well as the cusp type double point in free energy-temperature graph. Using
the formulation of geometrothermodynamics we again find the singularities in
the heat capacity of the black holes by calculating the curvature scalar of the
Legendre invariant metric.
| [
{
"created": "Mon, 16 Jun 2014 06:47:53 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Tharanath",
"R.",
""
],
[
"Suresh",
"Jishnu",
""
],
[
"Kuriakose",
"V. C.",
""
]
] | In this paper we study the thermodynamics and state space geometry of regular black hole solutions such as Bardeen black hole, Ay\'{o}n-Beato and Garc\'{i}a black hole, Hayward black hole and Berej-Matyjasek-Trynieki-Wornowicz black hole. We find that all these black holes show second order thermodynamic phase transitions(SOTPT) by observing discontinuities in heat capacity-entropy graphs as well as the cusp type double point in free energy-temperature graph. Using the formulation of geometrothermodynamics we again find the singularities in the heat capacity of the black holes by calculating the curvature scalar of the Legendre invariant metric. |
2304.09163 | Shibesh Kumar Jas Pacif | Viraj Kalsariya and Shibesh Kumar Jas Pacif | Cosmo-dynamics of dark energy models resulting from a parametrization of
$H$ in $f(Q,T)$ gravity | 16 Pages, 26 Figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Our objective in this paper is to study the late-time behavior of the
universe in a model resulting from a parametrization of the Hubble parameter
($H$) in $f(Q,T)$ gravity. We have considered the flat
Friedmann-Lemaitre-Robertson-Walker (FLRW) as the background metric and
discussed the model in $f(Q,T)$ gravity, where $Q$ and $T$ are non-metricity
and the trace of the energy-momentum tensor respectively. The complicated field
equations are solved in a model-independent way by using a simple
parametrization of $H$. Some geometrical parameters and physical parameters for
the obtained model are calculated, and their cosmic evolution is described
through some graphical representation. The physical dynamics of the model are
discussed in some detail. Finally, we found the model's validity by checking
the energy conditions, kinematic behavior, and the speed of the sound for the
obtained models from the parametrization of $H$. The interesting results of the
models are compelling to the present scenario of late-time cosmic acceleration.
| [
{
"created": "Mon, 17 Apr 2023 14:43:23 GMT",
"version": "v1"
}
] | 2023-04-19 | [
[
"Kalsariya",
"Viraj",
""
],
[
"Pacif",
"Shibesh Kumar Jas",
""
]
] | Our objective in this paper is to study the late-time behavior of the universe in a model resulting from a parametrization of the Hubble parameter ($H$) in $f(Q,T)$ gravity. We have considered the flat Friedmann-Lemaitre-Robertson-Walker (FLRW) as the background metric and discussed the model in $f(Q,T)$ gravity, where $Q$ and $T$ are non-metricity and the trace of the energy-momentum tensor respectively. The complicated field equations are solved in a model-independent way by using a simple parametrization of $H$. Some geometrical parameters and physical parameters for the obtained model are calculated, and their cosmic evolution is described through some graphical representation. The physical dynamics of the model are discussed in some detail. Finally, we found the model's validity by checking the energy conditions, kinematic behavior, and the speed of the sound for the obtained models from the parametrization of $H$. The interesting results of the models are compelling to the present scenario of late-time cosmic acceleration. |
1508.03634 | Leo Singer | Leo P. Singer and Larry R. Price | Rapid Bayesian position reconstruction for gravitational-wave transients | 23 pages, 12 figures, published in Phys. Rev. D | Phys. Rev. D 93, 024013 (2016) | 10.1103/PhysRevD.93.024013 | LIGO-P1500009-v8 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the next few years, Advanced LIGO and Virgo should detect
gravitational waves from binary neutron star and neutron star-black hole
mergers. These sources are also predicted to power a broad array of
electromagnetic transients. Because the electromagnetic signatures can be faint
and fade rapidly, observing them hinges on rapidly inferring the sky location
from the gravitational-wave observations. Markov chain Monte Carlo methods for
gravitational-wave parameter estimation can take hours or more. We introduce
BAYESTAR, a rapid, Bayesian, non-Markov chain Monte Carlo sky localization
algorithm that takes just seconds to produce probability sky maps that are
comparable in accuracy to the full analysis. Prompt localizations from BAYESTAR
will make it possible to search electromagnetic counterparts of compact binary
mergers.
| [
{
"created": "Fri, 14 Aug 2015 20:05:01 GMT",
"version": "v1"
},
{
"created": "Sun, 27 Sep 2015 19:44:02 GMT",
"version": "v2"
},
{
"created": "Sat, 21 Nov 2015 06:46:50 GMT",
"version": "v3"
},
{
"created": "Mon, 7 Dec 2015 22:58:47 GMT",
"version": "v4"
},
{
"cr... | 2016-01-20 | [
[
"Singer",
"Leo P.",
""
],
[
"Price",
"Larry R.",
""
]
] | Within the next few years, Advanced LIGO and Virgo should detect gravitational waves from binary neutron star and neutron star-black hole mergers. These sources are also predicted to power a broad array of electromagnetic transients. Because the electromagnetic signatures can be faint and fade rapidly, observing them hinges on rapidly inferring the sky location from the gravitational-wave observations. Markov chain Monte Carlo methods for gravitational-wave parameter estimation can take hours or more. We introduce BAYESTAR, a rapid, Bayesian, non-Markov chain Monte Carlo sky localization algorithm that takes just seconds to produce probability sky maps that are comparable in accuracy to the full analysis. Prompt localizations from BAYESTAR will make it possible to search electromagnetic counterparts of compact binary mergers. |
2204.01879 | Kumar Shwetketu Virbhadra | K. S. Virbhadra | Distortions of images of Schwarzschild lensing | To appear in Physical Review D | Phys. Rev. D 106, 064038 (2022) | 10.1103/PhysRevD.106.064038 | null | gr-qc astro-ph.CO astro-ph.GA astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We model the supermassive dark object $M87^*$ as a Schwarzschild lens and
study the variations in tangential, radial, and total (the product of
tangential and radial) magnifications of images (primary, secondary, and
relativistic) against the changes in angular source position and the ratio of
lens-source to the observer-source distance. Further, we study the behavior of
partial derivatives (with respect to the angular source position) of total
magnifications of images against the angular source position. Finally, we model
supermassive dark objects at centers of 40 galaxies as Schwarzschild lenses and
study the variations in tangential, radial, and total magnifications of images
against the change in the ratio of mass of the lens to its distance. These
studies yield many nonintuitive results which are likely to be significant for
next generation Event Horizon Telescope observations. We {\em hypothesize} that
there exists a distortion parameter such that their signed sum of all images of
singular gravitational lensing of a source identically vanishes. We test this
with images of Schwarzschild lensing in weak and strong gravitational fields
and find that this esthetically appealing hypothesis succeeds with flying
colors.
| [
{
"created": "Mon, 4 Apr 2022 22:54:42 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Sep 2022 22:30:45 GMT",
"version": "v2"
}
] | 2022-09-23 | [
[
"Virbhadra",
"K. S.",
""
]
] | We model the supermassive dark object $M87^*$ as a Schwarzschild lens and study the variations in tangential, radial, and total (the product of tangential and radial) magnifications of images (primary, secondary, and relativistic) against the changes in angular source position and the ratio of lens-source to the observer-source distance. Further, we study the behavior of partial derivatives (with respect to the angular source position) of total magnifications of images against the angular source position. Finally, we model supermassive dark objects at centers of 40 galaxies as Schwarzschild lenses and study the variations in tangential, radial, and total magnifications of images against the change in the ratio of mass of the lens to its distance. These studies yield many nonintuitive results which are likely to be significant for next generation Event Horizon Telescope observations. We {\em hypothesize} that there exists a distortion parameter such that their signed sum of all images of singular gravitational lensing of a source identically vanishes. We test this with images of Schwarzschild lensing in weak and strong gravitational fields and find that this esthetically appealing hypothesis succeeds with flying colors. |
gr-qc/0512122 | Alexander Kamenshchik | M. Gaudin, V. Gorini, A. Kamenshchik, U. Moschella, V. Pasquier | Gravity of a static massless scalar field and a limiting
Schwarzschild-like geometry | 13 pages, 4 figures | Int.J.Mod.Phys. D15 (2006) 1387-1406 | 10.1142/S0218271806009121 | null | gr-qc | null | We study a set of static solutions of the Einstein equations in presence of a
massless scalar field and establish their connection to the Kantowski-Sachs
cosmological solutions based on some kind of duality transformations. The
physical properties of the limiting case of an empty hyperbolic spacetime
(pseudo-Schwarzschild geometry) are analyzed in some detail.
| [
{
"created": "Wed, 21 Dec 2005 14:10:06 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Gaudin",
"M.",
""
],
[
"Gorini",
"V.",
""
],
[
"Kamenshchik",
"A.",
""
],
[
"Moschella",
"U.",
""
],
[
"Pasquier",
"V.",
""
]
] | We study a set of static solutions of the Einstein equations in presence of a massless scalar field and establish their connection to the Kantowski-Sachs cosmological solutions based on some kind of duality transformations. The physical properties of the limiting case of an empty hyperbolic spacetime (pseudo-Schwarzschild geometry) are analyzed in some detail. |
gr-qc/9709004 | Michele Maggiore | Michele Maggiore | Massive string modes and non-singular pre-big-bang cosmology | 25 pages, Latex, 3 figures. Conceptual revisions. To be published in
Nucl. Phys. B | Nucl.Phys. B525 (1998) 413-431 | 10.1016/S0550-3213(98)00362-9 | CERN-TH/97-228 | gr-qc hep-th | null | Perturbative $\alpha '$ corrections to the low energy string effective action
have been recently found to have a potentially regularizing effect on the
singularity of the lowest order pre-big-bang solutions. Whether they actually
regularize it, however, cannot be determined working at any finite order in a
perturbative expansion in powers of the string constant $\alpha '$, because of
scheme dependence ambiguities. Physically, these corrections are dominated by
the integration over the first few massive string states. Very massive string
modes, instead, can have a regularizing effect which is non-perturbative in
$\alpha '$ and which basically comes from the fact that in a gravitational
field with Hubble constant $H$ they are produced with an effective Hawking
temperature $T=H/(2\pi)$, and an infinite production rate would occur if this
temperature exceeded the Hagedorn temperature. We discuss technical and
conceptual difficulties of this non-perturbative regularization mechanism.
| [
{
"created": "Tue, 2 Sep 1997 13:26:25 GMT",
"version": "v1"
},
{
"created": "Sat, 2 May 1998 13:00:29 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Maggiore",
"Michele",
""
]
] | Perturbative $\alpha '$ corrections to the low energy string effective action have been recently found to have a potentially regularizing effect on the singularity of the lowest order pre-big-bang solutions. Whether they actually regularize it, however, cannot be determined working at any finite order in a perturbative expansion in powers of the string constant $\alpha '$, because of scheme dependence ambiguities. Physically, these corrections are dominated by the integration over the first few massive string states. Very massive string modes, instead, can have a regularizing effect which is non-perturbative in $\alpha '$ and which basically comes from the fact that in a gravitational field with Hubble constant $H$ they are produced with an effective Hawking temperature $T=H/(2\pi)$, and an infinite production rate would occur if this temperature exceeded the Hagedorn temperature. We discuss technical and conceptual difficulties of this non-perturbative regularization mechanism. |
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