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/0208004 | Heiko Herrmann | Heiko J. Herrmann, G. Rueckner, W. Muschik, H.-H. v. Borzeszkowski | Spin Axioms in Relativistic Continuum Physics | 15 pages, dirac-electron example has been rewritten | Found.Phys. 34 (2004) 1005-1021 | 10.1023/B:FOOP.0000034226.19527.0e | null | gr-qc | null | The 24 components of the relativistic spin tensor consist of 3+3 basic spin
fields and 9+9 constitutive fields. Empirically only 3 basic spin fields and 9
constitutive fields are known. This empirem can be expressed by two spin
axioms, one of them identifying 3 spin fields, and the other one 9 constitutive
fields to each other. This identification by the spin axioms is
material-independent and does not mix basic spin fields with constitutive
properties. The approaches to the Weyssenhoff fluid and the Dirac-electron
fluid found in literature are discussed with regard to these spin axioms. The
conjecture is formulated, that another reduction from 6 to 3 basic spin fields
which does not obey the spin axioms introduces special material properties by
not allowed mixing of constitutive and basic fields.
| [
{
"created": "Fri, 2 Aug 2002 12:21:24 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Aug 2002 10:25:29 GMT",
"version": "v2"
}
] | 2013-07-23 | [
[
"Herrmann",
"Heiko J.",
""
],
[
"Rueckner",
"G.",
""
],
[
"Muschik",
"W.",
""
],
[
"Borzeszkowski",
"H. -H. v.",
""
]
] | The 24 components of the relativistic spin tensor consist of 3+3 basic spin fields and 9+9 constitutive fields. Empirically only 3 basic spin fields and 9 constitutive fields are known. This empirem can be expressed by two spin axioms, one of them identifying 3 spin fields, and the other one 9 constitutive fields to each other. This identification by the spin axioms is material-independent and does not mix basic spin fields with constitutive properties. The approaches to the Weyssenhoff fluid and the Dirac-electron fluid found in literature are discussed with regard to these spin axioms. The conjecture is formulated, that another reduction from 6 to 3 basic spin fields which does not obey the spin axioms introduces special material properties by not allowed mixing of constitutive and basic fields. |
1003.0352 | Antonino Marciano | Antonino Marciano | Towards inhomogeneous loop quantum cosmology: triangulating Bianchi IX
with perturbations | 4 pages. To appear in the proceedings of 12th Marcel Grossmann
Meeting on General Relativity (MG 12), Paris, France, 12-18 Jul 2009 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This brief article sums up results obtained in arXiv:0911.2653, which
develops a constrained SU(2) lattice gauge theory in the "dipole"
approximation. This is a further step toward the issue of a (inhomogeneous)
loop quantum cosmology and its merging into loop quantum gravity.
| [
{
"created": "Mon, 1 Mar 2010 14:06:57 GMT",
"version": "v1"
}
] | 2010-03-02 | [
[
"Marciano",
"Antonino",
""
]
] | This brief article sums up results obtained in arXiv:0911.2653, which develops a constrained SU(2) lattice gauge theory in the "dipole" approximation. This is a further step toward the issue of a (inhomogeneous) loop quantum cosmology and its merging into loop quantum gravity. |
0908.0283 | Dong-han Yeom | Jakob Hansen, Dong-il Hwang, Dong-han Yeom | Dynamics of false vacuum bubbles: beyond the thin shell approximation | 40 pages, 41 figures | JHEP 0911:016,2009 | 10.1088/1126-6708/2009/11/016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We numerically study the dynamics of false vacuum bubbles which are inside an
almost flat background; we assumed spherical symmetry and the size of the
bubble is smaller than the size of the background horizon. According to the
thin shell approximation and the null energy condition, if the bubble is
outside of a Schwarzschild black hole, unless we assume Farhi-Guth-Guven
tunneling, expanding and inflating solutions are impossible. In this paper, we
extend our method to beyond the thin shell approximation: we include the
dynamics of fields and assume that the transition layer between a true vacuum
and a false vacuum has non-zero thickness. If a shell has sufficiently low
energy, as expected from the thin shell approximation, it collapses (Type 1).
However, if the shell has sufficiently large energy, it tends to expand. Here,
via the field dynamics, field values of inside of the shell slowly roll down to
the true vacuum and hence the shell does not inflate (Type 2). If we add
sufficient exotic matters to regularize the curvature near the shell, inflation
may be possible without assuming Farhi-Guth-Guven tunneling. In this case, a
wormhole is dynamically generated around the shell (Type 3). By tuning our
simulation parameters, we could find transitions between Type 1 and Type 2, as
well as between Type 2 and Type 3. Between Type 2 and Type 3, we could find
another class of solutions (Type 4). Finally, we discuss the generation of a
bubble universe and the violation of unitarity. We conclude that the existence
of a certain combination of exotic matter fields violates unitarity.
| [
{
"created": "Mon, 3 Aug 2009 15:50:34 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Nov 2009 07:39:32 GMT",
"version": "v2"
}
] | 2010-04-30 | [
[
"Hansen",
"Jakob",
""
],
[
"Hwang",
"Dong-il",
""
],
[
"Yeom",
"Dong-han",
""
]
] | We numerically study the dynamics of false vacuum bubbles which are inside an almost flat background; we assumed spherical symmetry and the size of the bubble is smaller than the size of the background horizon. According to the thin shell approximation and the null energy condition, if the bubble is outside of a Schwarzschild black hole, unless we assume Farhi-Guth-Guven tunneling, expanding and inflating solutions are impossible. In this paper, we extend our method to beyond the thin shell approximation: we include the dynamics of fields and assume that the transition layer between a true vacuum and a false vacuum has non-zero thickness. If a shell has sufficiently low energy, as expected from the thin shell approximation, it collapses (Type 1). However, if the shell has sufficiently large energy, it tends to expand. Here, via the field dynamics, field values of inside of the shell slowly roll down to the true vacuum and hence the shell does not inflate (Type 2). If we add sufficient exotic matters to regularize the curvature near the shell, inflation may be possible without assuming Farhi-Guth-Guven tunneling. In this case, a wormhole is dynamically generated around the shell (Type 3). By tuning our simulation parameters, we could find transitions between Type 1 and Type 2, as well as between Type 2 and Type 3. Between Type 2 and Type 3, we could find another class of solutions (Type 4). Finally, we discuss the generation of a bubble universe and the violation of unitarity. We conclude that the existence of a certain combination of exotic matter fields violates unitarity. |
gr-qc/0102008 | David Langlois | David Langlois (IAP, Paris) | Superfluid neutron stars | 2 pages, "mprocl.sty" with LaTeX 2.09; contribution to the 9th Marcel
Grossmann Meeting (MG9), Rome, July 2000 | null | 10.1142/9789812777386_0338 | null | gr-qc | null | Neutron stars are believed to contain (neutron and proton) superfluids. I
will give a summary of a macroscopic description of the interior of neutron
stars, in a formulation which is general relativistic. I will also present
recent results on the oscillations of neutron stars, with superfluidity
explicitly taken into account, which leads in particular to the existence of a
new class of modes.
| [
{
"created": "Fri, 2 Feb 2001 13:23:27 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Langlois",
"David",
"",
"IAP, Paris"
]
] | Neutron stars are believed to contain (neutron and proton) superfluids. I will give a summary of a macroscopic description of the interior of neutron stars, in a formulation which is general relativistic. I will also present recent results on the oscillations of neutron stars, with superfluidity explicitly taken into account, which leads in particular to the existence of a new class of modes. |
gr-qc/0210099 | P. A. Hogan | P.A. Hogan, E.M. O'Shea | Shear-Free Gravitational Waves in an Anisotropic Universe | 32 pages, accepted for publication in Physical Review D | Phys.Rev. D66 (2002) 124016 | 10.1103/PhysRevD.66.124016 | null | gr-qc | null | We study gravitational waves propagating through an anisotropic Bianchi I
dust-filled universe (containing the Einstein-de-Sitter universe as a special
case). The waves are modeled as small perturbations of this background
cosmological model and we choose a family of null hypersurfaces in this
space-time to act as the histories of the wavefronts of the radiation. We find
that the perturbations we generate can describe pure gravitational radiation if
and only if the null hypersurfaces are shear-free. We calculate the
gauge-invariant small perturbations explicitly in this case. How these differ
from the corresponding perturbations when the background space-time is
isotropic is clearly exhibited.
| [
{
"created": "Tue, 29 Oct 2002 11:18:20 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Hogan",
"P. A.",
""
],
[
"O'Shea",
"E. M.",
""
]
] | We study gravitational waves propagating through an anisotropic Bianchi I dust-filled universe (containing the Einstein-de-Sitter universe as a special case). The waves are modeled as small perturbations of this background cosmological model and we choose a family of null hypersurfaces in this space-time to act as the histories of the wavefronts of the radiation. We find that the perturbations we generate can describe pure gravitational radiation if and only if the null hypersurfaces are shear-free. We calculate the gauge-invariant small perturbations explicitly in this case. How these differ from the corresponding perturbations when the background space-time is isotropic is clearly exhibited. |
1810.04102 | Yan Peng | Yan Peng | On instabilities of scalar hairy regular compact reflecting stars | 8 pages | JHEP10(2018)185 | 10.1007/JHEP10(2018)185 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the system constructed by charged scalar fields linearly coupled to
asymptotically flat horizonless compact reflecting stars. We obtain bounds on
the charge of the scalar field, below which the scalar hairy star is expected
to suffer from nonlinear instabilities. It means that scalar hairy regular
configurations are unstable for scalar fields of small charge. For the
highly-charged star, there are also bounds on radii of regular compact
reflecting stars. When the star radius is below the bound, the hairy star is
always unstable.
| [
{
"created": "Tue, 9 Oct 2018 16:20:28 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Oct 2018 08:36:31 GMT",
"version": "v2"
}
] | 2018-11-05 | [
[
"Peng",
"Yan",
""
]
] | We study the system constructed by charged scalar fields linearly coupled to asymptotically flat horizonless compact reflecting stars. We obtain bounds on the charge of the scalar field, below which the scalar hairy star is expected to suffer from nonlinear instabilities. It means that scalar hairy regular configurations are unstable for scalar fields of small charge. For the highly-charged star, there are also bounds on radii of regular compact reflecting stars. When the star radius is below the bound, the hairy star is always unstable. |
1709.03547 | Luca Guido Molinari | Carlo Alberto Mantica and Luca Guido Molinari | Shear and vorticity of perfect-fluid spacetimes and the shear-free
conjecture | 7 pages. In this version we added a brief presentation of the
"shear-free conjecture" with references | null | null | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain expressions for the shear and the vorticity tensors of
perfect-fluid spacetimes, in terms of the divergence of the Weyl tensor. For
such spacetimes, we prove that if the gradient of the energy density is
parallel to the velocity, then either the expansion rate is zero, or the
vorticity vanishes. This statement recalls the "shear-free conjecture" for a
perfect barotropic fluid: vanishing shear implies either vanishing expansion
rate or vanishing vorticity. Finally, we give a new condition for a perfect
fluid to be a Generalized Robinson-Walker spacetime.
| [
{
"created": "Mon, 11 Sep 2017 19:04:22 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Nov 2017 21:32:24 GMT",
"version": "v2"
}
] | 2017-11-21 | [
[
"Mantica",
"Carlo Alberto",
""
],
[
"Molinari",
"Luca Guido",
""
]
] | We obtain expressions for the shear and the vorticity tensors of perfect-fluid spacetimes, in terms of the divergence of the Weyl tensor. For such spacetimes, we prove that if the gradient of the energy density is parallel to the velocity, then either the expansion rate is zero, or the vorticity vanishes. This statement recalls the "shear-free conjecture" for a perfect barotropic fluid: vanishing shear implies either vanishing expansion rate or vanishing vorticity. Finally, we give a new condition for a perfect fluid to be a Generalized Robinson-Walker spacetime. |
2307.07263 | Marie-No\"elle C\'el\'erier | M.-N. C\'el\'erier | Interior spacetimes sourced by stationary differentially rotating
irrotational cylindrical fluids. II. Axial pressure | overlap with 2312.09263 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent series of papers new exact analytical solutions of Einstein
equations representing interior spacetimes sourced by stationary rigidly
rotating cylinders of fluids have been displayed. We have first considered a
fluid with an axially directed pressure C\'el\'erier, Phys. Rev. D 104, 064040
(2021), J. Math. Phys. 64, 032501 (2023), then a perfect fluid, J. Math. Phys.
64, 022501 (2023), followed by a fluid with an azimuthally directed pressure,
J. Math. Phys. 64, 042501 (2023), and finally a fluid where the anisotropic
pressure is radially oriented, J. Math. Phys. 64, 052502 (2023). This work is
being currently extended to the cases of differentially rotating irrotational
fluids. The results are presented in a new series of papers considering, in
turn, a perfect fluid source, arXiv:2305.11565 [gr-qc], and the same three
anisotropic pressure cases. Here, fluids with an axially directed pressure are
considered. A general method for generating new mathematical solutions to the
field equations is displayed and three classes are presented so as to exemplify
this recipe. Their mathematical and physical properties are analyzed. The first
class, named class A, whose other mathematical and physical properties
determine a standard configuration, is shown to exhibit a singular axis of
symmetry which can be considered as an awkward drawback. The second class,
class B, is free from such a singularity but appears to exhibit a negative
energy density which characterizes a rather exotic kind of matter. The third
class, class C, is the best behaved since it possesses the main properties
expected from spacetimes sourced by rather standard fluids. The three classes
are matched to an exterior Lewis-Weyl vacuum and the conditions for avoiding an
angular deficit are discussed. A comparison with the rigidly rotating fluid
case is provided.
| [
{
"created": "Fri, 14 Jul 2023 10:37:28 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Jul 2024 15:32:19 GMT",
"version": "v2"
}
] | 2024-07-08 | [
[
"Célérier",
"M. -N.",
""
]
] | In a recent series of papers new exact analytical solutions of Einstein equations representing interior spacetimes sourced by stationary rigidly rotating cylinders of fluids have been displayed. We have first considered a fluid with an axially directed pressure C\'el\'erier, Phys. Rev. D 104, 064040 (2021), J. Math. Phys. 64, 032501 (2023), then a perfect fluid, J. Math. Phys. 64, 022501 (2023), followed by a fluid with an azimuthally directed pressure, J. Math. Phys. 64, 042501 (2023), and finally a fluid where the anisotropic pressure is radially oriented, J. Math. Phys. 64, 052502 (2023). This work is being currently extended to the cases of differentially rotating irrotational fluids. The results are presented in a new series of papers considering, in turn, a perfect fluid source, arXiv:2305.11565 [gr-qc], and the same three anisotropic pressure cases. Here, fluids with an axially directed pressure are considered. A general method for generating new mathematical solutions to the field equations is displayed and three classes are presented so as to exemplify this recipe. Their mathematical and physical properties are analyzed. The first class, named class A, whose other mathematical and physical properties determine a standard configuration, is shown to exhibit a singular axis of symmetry which can be considered as an awkward drawback. The second class, class B, is free from such a singularity but appears to exhibit a negative energy density which characterizes a rather exotic kind of matter. The third class, class C, is the best behaved since it possesses the main properties expected from spacetimes sourced by rather standard fluids. The three classes are matched to an exterior Lewis-Weyl vacuum and the conditions for avoiding an angular deficit are discussed. A comparison with the rigidly rotating fluid case is provided. |
1410.0631 | Massimiliano Rinaldi | Massimiliano Rinaldi, Guido Cognola, Luciano Vanzo, Sergio Zerbini | Inflation in scale-invariant theories of gravity | Minor typos corrected. Version accepted for publication in PRD | Phys. Rev. D 91, 123527 (2015) | 10.1103/PhysRevD.91.123527 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Thanks to the Planck Collaboration, we know the value of the scalar spectral
index of primordial fluctuations with unprecedented precision. In addition, the
joint analysis of the data from Planck, BICEP2, and KEK has further constrained
the value of the tensor-to-scalar ratio $r$ so that chaotic inflationary
scenarios seem to be disfavoured. Inspired by these results, we look for a
model that yields a value of $r$ that is larger than the one predicted by the
Starobinsky model but is still within the new constraints. We show that purely
quadratic, renormalizable, and scale-invariant gravity, implemented by
loop-corrections, satisfies these requirements.
| [
{
"created": "Thu, 2 Oct 2014 18:14:18 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Oct 2014 14:09:59 GMT",
"version": "v2"
},
{
"created": "Wed, 11 Feb 2015 11:52:28 GMT",
"version": "v3"
},
{
"created": "Tue, 21 Apr 2015 11:26:24 GMT",
"version": "v4"
},
{
"created": "Fri, 12 Jun 2015 09:45:44 GMT",
"version": "v5"
}
] | 2015-06-24 | [
[
"Rinaldi",
"Massimiliano",
""
],
[
"Cognola",
"Guido",
""
],
[
"Vanzo",
"Luciano",
""
],
[
"Zerbini",
"Sergio",
""
]
] | Thanks to the Planck Collaboration, we know the value of the scalar spectral index of primordial fluctuations with unprecedented precision. In addition, the joint analysis of the data from Planck, BICEP2, and KEK has further constrained the value of the tensor-to-scalar ratio $r$ so that chaotic inflationary scenarios seem to be disfavoured. Inspired by these results, we look for a model that yields a value of $r$ that is larger than the one predicted by the Starobinsky model but is still within the new constraints. We show that purely quadratic, renormalizable, and scale-invariant gravity, implemented by loop-corrections, satisfies these requirements. |
gr-qc/0210024 | Gilad Gour | Gilad Gour | Algebraic approach to quantum black holes: logarithmic corrections to
black hole entropy | 15 pages, Revtex, to appear in Phys. Rev. D | Phys.Rev. D66 (2002) 104022 | 10.1103/PhysRevD.66.104022 | null | gr-qc hep-th quant-ph | null | The algebraic approach to black hole quantization requires the horizon area
eigenvalues to be equally spaced. As shown previously, for a neutral
non-rotating black hole, such eigenvalues must be $2^{n}$-fold degenerate if
one constructs the black hole stationary states by means of a pair of creation
operators subject to a specific algebra. We show that the algebra of these two
building blocks exhibits $U(2)\equiv U(1)\times SU(2)$ symmetry, where the area
operator generates the U(1) symmetry. The three generators of the SU(2)
symmetry represent a {\it global} quantum number (hyperspin) of the black hole,
and we show that this hyperspin must be zero. As a result, the degeneracy of
the $n$-th area eigenvalue is reduced to $2^{n}/n^{3/2}$ for large $n$, and
therefore, the logarithmic correction term $-3/2\log A$ should be added to the
Bekenstein-Hawking entropy. We also provide a heuristic approach explaining
this result, and an evidence for the existence of {\it two} building blocks.
| [
{
"created": "Tue, 8 Oct 2002 17:36:49 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Gour",
"Gilad",
""
]
] | The algebraic approach to black hole quantization requires the horizon area eigenvalues to be equally spaced. As shown previously, for a neutral non-rotating black hole, such eigenvalues must be $2^{n}$-fold degenerate if one constructs the black hole stationary states by means of a pair of creation operators subject to a specific algebra. We show that the algebra of these two building blocks exhibits $U(2)\equiv U(1)\times SU(2)$ symmetry, where the area operator generates the U(1) symmetry. The three generators of the SU(2) symmetry represent a {\it global} quantum number (hyperspin) of the black hole, and we show that this hyperspin must be zero. As a result, the degeneracy of the $n$-th area eigenvalue is reduced to $2^{n}/n^{3/2}$ for large $n$, and therefore, the logarithmic correction term $-3/2\log A$ should be added to the Bekenstein-Hawking entropy. We also provide a heuristic approach explaining this result, and an evidence for the existence of {\it two} building blocks. |
0902.4513 | Ivan L. Zhogin | I.L. Zhogin | One more fitting (D=5) of Supernovae redshifts | 5 pages, 3 figures; few paragraphs and four references are added | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Supernova Ia redshifts are fitted with a simple $5D$ model: the galaxies are
assumed to be enclosed in a giant $S^3$-spherical shell of significant
thickness, which expands (ultra)relativisticaly in Minkowski (1+4)$D$-space.
This model, as compared with the kinematic (1+3)$D$ Milne cosmological model
(which was reinvented by Prof Farley), goes in line with the Copernican
principle: any galaxy observes the same isotropic distribution of distant
galaxies and supernovae, as well as the same Hubble plot of SN Ia distance
modulus $\mu$ vs redshift $z$. A good fit is obtained (no free parameters); it
coincides with the Milne model (empty model) at low $z$, while shows some more
luminosity at high $z$, leading to 1% decrease in the true distance modulus
(and 50% increase in luminosity) at $z\sim2$.
The model proposed can be also interpreted as a sort of FLRW-model with the
scale factor $a(t)=t/t_0$; this could hardly be a solution of general
relativity (without inventing some super-dark energy with $w=-1/3$, a sort of
dark curvature); 5$D$ GR is also unsuitable -- it has no longitudinal
polarization. However, there still exists the other theory (with $D=5$ and no
singularities in solutions), the other game in the town, which seems to be able
to do the job.
| [
{
"created": "Thu, 26 Feb 2009 06:27:45 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Mar 2009 11:40:10 GMT",
"version": "v2"
},
{
"created": "Tue, 6 Sep 2022 12:36:15 GMT",
"version": "v3"
}
] | 2022-09-07 | [
[
"Zhogin",
"I. L.",
""
]
] | Supernova Ia redshifts are fitted with a simple $5D$ model: the galaxies are assumed to be enclosed in a giant $S^3$-spherical shell of significant thickness, which expands (ultra)relativisticaly in Minkowski (1+4)$D$-space. This model, as compared with the kinematic (1+3)$D$ Milne cosmological model (which was reinvented by Prof Farley), goes in line with the Copernican principle: any galaxy observes the same isotropic distribution of distant galaxies and supernovae, as well as the same Hubble plot of SN Ia distance modulus $\mu$ vs redshift $z$. A good fit is obtained (no free parameters); it coincides with the Milne model (empty model) at low $z$, while shows some more luminosity at high $z$, leading to 1% decrease in the true distance modulus (and 50% increase in luminosity) at $z\sim2$. The model proposed can be also interpreted as a sort of FLRW-model with the scale factor $a(t)=t/t_0$; this could hardly be a solution of general relativity (without inventing some super-dark energy with $w=-1/3$, a sort of dark curvature); 5$D$ GR is also unsuitable -- it has no longitudinal polarization. However, there still exists the other theory (with $D=5$ and no singularities in solutions), the other game in the town, which seems to be able to do the job. |
gr-qc/0409115 | L. C. Garcia de Andrade | L.C. Garcia de Anddrade | Irrotational vortex geometry of torsion loops | Latex file | null | null | null | gr-qc | null | The irrotational vortex geometry carachter of torsion loops is displayed by
showing that torsion loops and nonradial flow acoustic metrics are conformally
equivalent in $(1+1)$ dimensions while radial flow acoustic spacetime are
conformally related in $(2+1)$ dimensional spacetime. The analysis of
2-dimensional space allows us to express the fluid density in terms of the
parameters of torsion loop metric. These results lead us to conclude that the
acoustic metric of vortex flows is the gravitational analog of torsion loop
spacetime. Since no vorticity in the fluids is considered we do not make
explicit use of non-Riemannian geometry of vortex acoustics in classical
fluids. Acoustic nonradial flows are shown to exihibit a full analogy with
torsion loop metric.
| [
{
"created": "Wed, 29 Sep 2004 23:19:45 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Anddrade",
"L. C. Garcia",
""
]
] | The irrotational vortex geometry carachter of torsion loops is displayed by showing that torsion loops and nonradial flow acoustic metrics are conformally equivalent in $(1+1)$ dimensions while radial flow acoustic spacetime are conformally related in $(2+1)$ dimensional spacetime. The analysis of 2-dimensional space allows us to express the fluid density in terms of the parameters of torsion loop metric. These results lead us to conclude that the acoustic metric of vortex flows is the gravitational analog of torsion loop spacetime. Since no vorticity in the fluids is considered we do not make explicit use of non-Riemannian geometry of vortex acoustics in classical fluids. Acoustic nonradial flows are shown to exihibit a full analogy with torsion loop metric. |
gr-qc/0601039 | Maria Babiuc | Maria C. Babiuc, Bela Szilagyi, Jeffrey Winicour | Harmonic Initial-Boundary Evolution in General Relativity | 31 pages, 14 figures, submitted to Physical Review D | Phys.Rev.D73:064017,2006 | 10.1103/PhysRevD.73.064017 | null | gr-qc | null | Computational techniques which establish the stability of an
evolution-boundary algorithm for a model wave equation with shift are
incorporated into a well-posed version of the initial-boundary value problem
for gravitational theory in harmonic coordinates. The resulting algorithm is
implemented as a 3-dimensional numerical code which we demonstrate to provide
stable, convergent Cauchy evolution in gauge wave and shifted gauge wave
testbeds. Code performance is compared for Dirichlet, Neumann and Sommerfeld
boundary conditions and for boundary conditions which explicitly incorporate
constraint preservation. The results are used to assess strategies for
obtaining physically realistic boundary data by means of Cauchy-characteristic
matching.
| [
{
"created": "Tue, 10 Jan 2006 14:56:57 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Mar 2006 21:36:55 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Babiuc",
"Maria C.",
""
],
[
"Szilagyi",
"Bela",
""
],
[
"Winicour",
"Jeffrey",
""
]
] | Computational techniques which establish the stability of an evolution-boundary algorithm for a model wave equation with shift are incorporated into a well-posed version of the initial-boundary value problem for gravitational theory in harmonic coordinates. The resulting algorithm is implemented as a 3-dimensional numerical code which we demonstrate to provide stable, convergent Cauchy evolution in gauge wave and shifted gauge wave testbeds. Code performance is compared for Dirichlet, Neumann and Sommerfeld boundary conditions and for boundary conditions which explicitly incorporate constraint preservation. The results are used to assess strategies for obtaining physically realistic boundary data by means of Cauchy-characteristic matching. |
1909.11353 | Mikhail Iofa | Mikhail Z. Iofa | Black holes with supertranslation field, "large transformations" and
Israel theorem | 8 pages. Completely new discussion.Published version | Phys. Rev. D 102, 104008 (2020) | 10.1103/PhysRevD.102.104008 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An axial-symmetric vacuum solution of the Einstein equations containing a
supertranslation field diffeomorphic to the Schwarzschild solution is discussed
in the context of Israel theorem. The metric satisfies all conditions of the
Israel theorem, except for the condition on the form of the metric at spatial
infinity. Nevertheless, following the steps of the proof of the theorem we show
that the proof applies to the metric with supertranslation field and the
(transformed) metric used in the proof is spherically symmetric. We explain the
source of the seeming discrepancy connected with the use of "large"
transformations changing supertranslation field in the metric.
| [
{
"created": "Wed, 25 Sep 2019 09:04:20 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Nov 2020 11:07:26 GMT",
"version": "v2"
}
] | 2020-12-01 | [
[
"Iofa",
"Mikhail Z.",
""
]
] | An axial-symmetric vacuum solution of the Einstein equations containing a supertranslation field diffeomorphic to the Schwarzschild solution is discussed in the context of Israel theorem. The metric satisfies all conditions of the Israel theorem, except for the condition on the form of the metric at spatial infinity. Nevertheless, following the steps of the proof of the theorem we show that the proof applies to the metric with supertranslation field and the (transformed) metric used in the proof is spherically symmetric. We explain the source of the seeming discrepancy connected with the use of "large" transformations changing supertranslation field in the metric. |
0802.0942 | Francesco Cianfrani dr | Giovanni Montani, Francesco Cianfrani | General Relativity as Classical Limit of Evolutionary Quantum Gravity | 23 pages, to appear on Class. Quant. Grav | Class.Quant.Grav.25:065007,2008 | 10.1088/0264-9381/25/6/065007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the dynamics of the gravitational field when the covariance is
restricted to a synchronous gauge. In the spirit of the Noether theorem, we
determine the conservation law associated to the Lagrangian invariance and we
outline that a non-vanishing behavior of the Hamiltonian comes out. We then
interpret such resulting non-zero ``energy'' of the gravitational field in
terms of a dust fluid. This new matter contribution is co-moving to the slicing
and it accounts for the ``materialization'' of a synchronous reference from the
corresponding gauge condition. Further, we analyze the quantum dynamics of a
generic inhomogeneous Universe as described by this evolutionary scheme,
asymptotically to the singularity. We show how the phenomenology of such a
model overlaps the corresponding Wheeler-DeWitt picture. Finally, we study the
possibility of a Schr\"odinger dynamics of the gravitational field as a
consequence of the correspondence inferred between the ensemble dynamics of
stochastic systems and the WKB limit of their quantum evolution. We demonstrate
that the time dependence of the ensemble distribution is associated with the
first order correction in $\hbar$ to the WKB expansion of the energy spectrum.
| [
{
"created": "Thu, 7 Feb 2008 10:40:40 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Montani",
"Giovanni",
""
],
[
"Cianfrani",
"Francesco",
""
]
] | We analyze the dynamics of the gravitational field when the covariance is restricted to a synchronous gauge. In the spirit of the Noether theorem, we determine the conservation law associated to the Lagrangian invariance and we outline that a non-vanishing behavior of the Hamiltonian comes out. We then interpret such resulting non-zero ``energy'' of the gravitational field in terms of a dust fluid. This new matter contribution is co-moving to the slicing and it accounts for the ``materialization'' of a synchronous reference from the corresponding gauge condition. Further, we analyze the quantum dynamics of a generic inhomogeneous Universe as described by this evolutionary scheme, asymptotically to the singularity. We show how the phenomenology of such a model overlaps the corresponding Wheeler-DeWitt picture. Finally, we study the possibility of a Schr\"odinger dynamics of the gravitational field as a consequence of the correspondence inferred between the ensemble dynamics of stochastic systems and the WKB limit of their quantum evolution. We demonstrate that the time dependence of the ensemble distribution is associated with the first order correction in $\hbar$ to the WKB expansion of the energy spectrum. |
2305.18192 | Saeed Rastgoo | Angel Garcia-Chung, Matthew F. Carney, James B. Mertens, Aliasghar
Parvizi, Saeed Rastgoo, Yaser Tavakoli | Constraining the quantum gravity polymer scale using LIGO data | Invited contribution to "Focus issue on Quantum Gravity Phenomenology
in the Multi-Messenger Era: Challenges and Perspectives" in Classical and
Quantum Gravity, 18 pages, 6 figures, Part of the COST Action CA18108:
Quantum gravity phenomenology in the multi-messenger approach. V2: added
comments on polymer quantization & statistical method used. Minor
modification to plot colors. Published version | Class. Quantum Grav. 41 (2023) 1, 015011 | 10.1088/1361-6382/ad0db1 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first empirical constraints on the polymer scale describing
polymer quantized GWs propagating on a classical background. These constraints
are determined from the polymer-induced deviation from the classically
predicted propagation speed of GWs. We leverage posterior information on the
propagation speed of GWs from two previously reported sources: 1)
inter-detector arrival time delays for signals from the LIGO-Virgo
Collaboration's first gravitational-wave transient catalog, GWTC1, and 2) from
arrival time delays between GW signal GW170817 and its associated gamma-ray
burst GRB170817A. For pure-GW constraints, we find relatively uninformative
combined constraints of $\nu = 0.96\substack{+0.15 \\ -0.21} \times 10^{-53} \,
\rm{kg}^{1/2}$ and $\mu = 0.94\substack{+0.75 \\ -0.20} \times 10^{-48} \,
\rm{kg}^{1/2} \cdot s$ at the $90\%$ credible level for the two polymer
quantization schemes, where $\nu$ and $\mu$ refer to polymer parameters
associated to the polymer quantization schemes of propagating gravitational
degrees of freedom. For constraints from GW170817/GRB170817A, we report much
more stringent constraints of $\nu_{\mathrm{low}} =2.66\substack{+0.60 \\
-0.10}\times 10^{-56}$, $\nu_{\mathrm{high}} = 2.66\substack{+0.45 \\
-0.10}\times 10^{-56} $ and $\mu_{\mathrm{low}} = 2.84\substack{+0.64 \\
-0.11}\times 10^{-52}$, $\mu_{\mathrm{high}} = 2.76\substack{+0.46 \\
-0.11}\times 10^{-52}$ for both representations of polymer quantization and two
choices of spin prior indicated by the subscript. Additionally, we explore the
effect of varying the lag between emission of the GW and EM signals in the
multimessenger case.
| [
{
"created": "Mon, 29 May 2023 16:43:03 GMT",
"version": "v1"
},
{
"created": "Sun, 3 Dec 2023 01:42:24 GMT",
"version": "v2"
}
] | 2023-12-05 | [
[
"Garcia-Chung",
"Angel",
""
],
[
"Carney",
"Matthew F.",
""
],
[
"Mertens",
"James B.",
""
],
[
"Parvizi",
"Aliasghar",
""
],
[
"Rastgoo",
"Saeed",
""
],
[
"Tavakoli",
"Yaser",
""
]
] | We present the first empirical constraints on the polymer scale describing polymer quantized GWs propagating on a classical background. These constraints are determined from the polymer-induced deviation from the classically predicted propagation speed of GWs. We leverage posterior information on the propagation speed of GWs from two previously reported sources: 1) inter-detector arrival time delays for signals from the LIGO-Virgo Collaboration's first gravitational-wave transient catalog, GWTC1, and 2) from arrival time delays between GW signal GW170817 and its associated gamma-ray burst GRB170817A. For pure-GW constraints, we find relatively uninformative combined constraints of $\nu = 0.96\substack{+0.15 \\ -0.21} \times 10^{-53} \, \rm{kg}^{1/2}$ and $\mu = 0.94\substack{+0.75 \\ -0.20} \times 10^{-48} \, \rm{kg}^{1/2} \cdot s$ at the $90\%$ credible level for the two polymer quantization schemes, where $\nu$ and $\mu$ refer to polymer parameters associated to the polymer quantization schemes of propagating gravitational degrees of freedom. For constraints from GW170817/GRB170817A, we report much more stringent constraints of $\nu_{\mathrm{low}} =2.66\substack{+0.60 \\ -0.10}\times 10^{-56}$, $\nu_{\mathrm{high}} = 2.66\substack{+0.45 \\ -0.10}\times 10^{-56} $ and $\mu_{\mathrm{low}} = 2.84\substack{+0.64 \\ -0.11}\times 10^{-52}$, $\mu_{\mathrm{high}} = 2.76\substack{+0.46 \\ -0.11}\times 10^{-52}$ for both representations of polymer quantization and two choices of spin prior indicated by the subscript. Additionally, we explore the effect of varying the lag between emission of the GW and EM signals in the multimessenger case. |
1801.08838 | Paolo Valtancoli | Paolo Valtancoli | Ads spacetime in Lorentz covariant gauges | 9 pages, no figures | null | 10.1016/j.aop.2018.05.004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show how to generate the AdS spacetime metric in general Lorentz covariant
gauges. In particular we propose an iterative method for solving the Lorentz
gauge.
| [
{
"created": "Fri, 26 Jan 2018 15:09:49 GMT",
"version": "v1"
}
] | 2018-07-04 | [
[
"Valtancoli",
"Paolo",
""
]
] | We show how to generate the AdS spacetime metric in general Lorentz covariant gauges. In particular we propose an iterative method for solving the Lorentz gauge. |
1603.06769 | S. Sedigheh Hashemi | Nematollah Riazi and S. Sedigheh Hashemi | From Taub-NUT to Kaluza-Klein magnetic monopole | 7 pages, Contribution to the proceedings of the 9th Alexander
Friedmann International Seminar on Gravitation and Cosmology and 3rd
Satellite Symposium on the Casimir Effect, 22-26 June, 2015, St. Petersburg,
Russia, based on a talk. in International Journal of Modern Physics:
Conference Series, (2016) | null | 10.1142/S2010194516601216 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a Kaluza-Klien vacuum solution which closely resembles the
Taub-NUT magnetic monopole and we investigate its physical properties as viewed
from four space-time dimensions. We show that the Taub-NUT Kaluza-Klein vacuum
solution in five dimensions is a static magnetic monopole. We find that the
four dimensional matter properties do not obey the equation of state of
radiation and there is no event horizon. A comparison with the available
magnetic monopole solutions and the issue of vanishing and negative mass are
discussed.
| [
{
"created": "Tue, 22 Mar 2016 12:57:12 GMT",
"version": "v1"
}
] | 2016-04-20 | [
[
"Riazi",
"Nematollah",
""
],
[
"Hashemi",
"S. Sedigheh",
""
]
] | We present a Kaluza-Klien vacuum solution which closely resembles the Taub-NUT magnetic monopole and we investigate its physical properties as viewed from four space-time dimensions. We show that the Taub-NUT Kaluza-Klein vacuum solution in five dimensions is a static magnetic monopole. We find that the four dimensional matter properties do not obey the equation of state of radiation and there is no event horizon. A comparison with the available magnetic monopole solutions and the issue of vanishing and negative mass are discussed. |
1704.07720 | Hasan El Moumni | M. Chabab, H. El Moumni, S. Iraoui, K. Masmar, S. Zhizeh | More Insight into Microscopic Properties of RN-AdS Black Hole Surrounded
by Quintessence via an Alternative Extended Phase Space | 14 pages, 5 figures | International Journal of Geometric Methods in Modern Physics Vol.
15 (2018) 1850171 | 10.1142/S0219887818501712 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study the phase transition of the charged-AdS black hole
surrounded by quintessence via an alternative extended phase space defined by
the charge square $Q^2$ and her conjugate $\Psi$, a quantity proportional to
the inverse of horizon radius, while the cosmological constant is kept fixed.
The equation of state is derived under the form $Q^2=Q^2(T,\Psi)$ and the
critical behavior of such black hole analyzed. In addition, we explore the
connection between the microscopic structure and Ruppeiner geothermodynamics.
We also find that, at certain points of the phase space, the Ruppeiner
curvature is characterized by the presence of singularities that are
interpreted as phase transitions.
| [
{
"created": "Mon, 17 Apr 2017 14:01:08 GMT",
"version": "v1"
}
] | 2018-09-11 | [
[
"Chabab",
"M.",
""
],
[
"Moumni",
"H. El",
""
],
[
"Iraoui",
"S.",
""
],
[
"Masmar",
"K.",
""
],
[
"Zhizeh",
"S.",
""
]
] | In this work we study the phase transition of the charged-AdS black hole surrounded by quintessence via an alternative extended phase space defined by the charge square $Q^2$ and her conjugate $\Psi$, a quantity proportional to the inverse of horizon radius, while the cosmological constant is kept fixed. The equation of state is derived under the form $Q^2=Q^2(T,\Psi)$ and the critical behavior of such black hole analyzed. In addition, we explore the connection between the microscopic structure and Ruppeiner geothermodynamics. We also find that, at certain points of the phase space, the Ruppeiner curvature is characterized by the presence of singularities that are interpreted as phase transitions. |
2002.02044 | Michael Ross P | M.P. Ross, C.A. Hagedorn, E.A. Shaw, A.L. Lockwood, B.M. Iritani, J.G.
Lee, K. Venkateswara, and J. H. Gundlach | Limits on the Stochastic Gravitational Wave Background and Prospects for
Single Source Detection with GRACE Follow-On | null | Phys. Rev. D 101, 102004 (2020) | 10.1103/PhysRevD.101.102004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With a reinterpretation of recent results, the GRACE Follow-On mission can be
applied to gravitational wave astronomy. Existing GRACE Follow-On data
constrain the stochastic gravitational wave background to
$\Omega_{GW}<3.3\times10^{7}$ at 100 mHz. With a dedicated analysis, GRACE
Follow-On may be able to detect the inspiral of local neutron star binaries,
inspiral of subgalactic stellar-mass black hole binaries, or mergers of
intermediate-mass black hole binaries within the Milky Way.
| [
{
"created": "Thu, 6 Feb 2020 00:33:11 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Apr 2020 23:47:41 GMT",
"version": "v2"
},
{
"created": "Wed, 13 May 2020 20:57:08 GMT",
"version": "v3"
}
] | 2020-05-27 | [
[
"Ross",
"M. P.",
""
],
[
"Hagedorn",
"C. A.",
""
],
[
"Shaw",
"E. A.",
""
],
[
"Lockwood",
"A. L.",
""
],
[
"Iritani",
"B. M.",
""
],
[
"Lee",
"J. G.",
""
],
[
"Venkateswara",
"K.",
""
],
[
"Gundlach",
"J. H.",
""
]
] | With a reinterpretation of recent results, the GRACE Follow-On mission can be applied to gravitational wave astronomy. Existing GRACE Follow-On data constrain the stochastic gravitational wave background to $\Omega_{GW}<3.3\times10^{7}$ at 100 mHz. With a dedicated analysis, GRACE Follow-On may be able to detect the inspiral of local neutron star binaries, inspiral of subgalactic stellar-mass black hole binaries, or mergers of intermediate-mass black hole binaries within the Milky Way. |
gr-qc/0504080 | Rommel Guerrero | Rommel Guerrero, R. Omar Rodriguez, R. Ortiz, Rafael Torrealba | De Sitter and double irregular domain walls | 13 pages, 4 figures, added references, some equations corrected | Gen.Rel.Grav. 38 (2006) 845-855 | 10.1007/s10714-006-0297-y | null | gr-qc | null | A new method to obtain thick domain wall solutions to the coupled Einstein
scalar field system is presented. The procedure allows the construction of
irregular walls from well known ones, such that the spacetime associated to
them are physically different. As consequence of the approach, we obtain two
irregular geometries corresponding to thick domain walls with $dS$ expansion
and topological double kink embedded in $AdS$ spacetime. In particular, the
double brane can be derived from a fake superpotential.
| [
{
"created": "Mon, 18 Apr 2005 20:15:54 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Apr 2005 21:07:42 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Oct 2005 15:13:41 GMT",
"version": "v3"
},
{
"created": "Thu, 15 Mar 2007 22:13:00 GMT",
"version": "v4"
}
] | 2009-11-11 | [
[
"Guerrero",
"Rommel",
""
],
[
"Rodriguez",
"R. Omar",
""
],
[
"Ortiz",
"R.",
""
],
[
"Torrealba",
"Rafael",
""
]
] | A new method to obtain thick domain wall solutions to the coupled Einstein scalar field system is presented. The procedure allows the construction of irregular walls from well known ones, such that the spacetime associated to them are physically different. As consequence of the approach, we obtain two irregular geometries corresponding to thick domain walls with $dS$ expansion and topological double kink embedded in $AdS$ spacetime. In particular, the double brane can be derived from a fake superpotential. |
1101.2515 | Farook Rahaman | F.Rahaman, Peter K.F.Kuhfittig, K.Chakraborty, M.Kalam and D.Hossain | Modeling galactic halos with predominantly quintessential matter | 12 pages, 1 figure | Int.J.Theor.Phys.50:2655-2665,2011 | 10.1007/s10773-011-0761-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper discusses a new model for galactic dark matter by combining an
anisotropic pressure field corresponding to normal matter and a quintessence
dark energy field having a characteristic parameter $\omega_q$ such that
$-1<\omega_q< -\frac{1}{3}$. Stable stellar orbits together with an attractive
gravity exist only if $\omega_q$ is extremely close to $-\frac{1}{3}$, a result
consistent with the special case studied by Guzman et al. (2003). Less
exceptional forms of quintessence dark energy do not yield the desired stable
orbits and are therefore unsuitable for modeling dark matter.
| [
{
"created": "Thu, 13 Jan 2011 09:41:26 GMT",
"version": "v1"
}
] | 2011-07-15 | [
[
"Rahaman",
"F.",
""
],
[
"Kuhfittig",
"Peter K. F.",
""
],
[
"Chakraborty",
"K.",
""
],
[
"Kalam",
"M.",
""
],
[
"Hossain",
"D.",
""
]
] | This paper discusses a new model for galactic dark matter by combining an anisotropic pressure field corresponding to normal matter and a quintessence dark energy field having a characteristic parameter $\omega_q$ such that $-1<\omega_q< -\frac{1}{3}$. Stable stellar orbits together with an attractive gravity exist only if $\omega_q$ is extremely close to $-\frac{1}{3}$, a result consistent with the special case studied by Guzman et al. (2003). Less exceptional forms of quintessence dark energy do not yield the desired stable orbits and are therefore unsuitable for modeling dark matter. |
2210.03966 | Satoshi Matsumoto | S. Matsumoto | No-Go Theorems for Hairy Black Holes in Scalar- or
Vector-Tensor-Gauss-Bonnet Theory | 11 pages | null | 10.1088/1361-6382/ace94e | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we show a no-go theorem for static spherically symmetric black
holes with vector hair in Einstein-$\Lambda$-Vector-Tensor-Gauss-Bonnet theory
where a complex vector field non-minimally couples with Gauss-Bonnet invariant.
For this purpose, we expand metric functions and radial functions of a vector
field around the event horizon, and substitute the expansions into equations of
motion. Demanding that the equations of motion are satisfied in each order, we
show that the complex vector field vanishes on the event horizon. Moreover,
when the event horizon is degenerated, it is also implied that the complex
vector field vanishes on and outside the horizon.
| [
{
"created": "Sat, 8 Oct 2022 08:24:02 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Mar 2023 07:35:16 GMT",
"version": "v2"
}
] | 2023-08-16 | [
[
"Matsumoto",
"S.",
""
]
] | In this paper, we show a no-go theorem for static spherically symmetric black holes with vector hair in Einstein-$\Lambda$-Vector-Tensor-Gauss-Bonnet theory where a complex vector field non-minimally couples with Gauss-Bonnet invariant. For this purpose, we expand metric functions and radial functions of a vector field around the event horizon, and substitute the expansions into equations of motion. Demanding that the equations of motion are satisfied in each order, we show that the complex vector field vanishes on the event horizon. Moreover, when the event horizon is degenerated, it is also implied that the complex vector field vanishes on and outside the horizon. |
gr-qc/9712008 | Patricio Anibal Letelier | P.S. Letelier and W.M. Vieira | Chaos and Rotating Black Holes with Halos | 9 pages, 4 Postscript figures. Phys. Rev. D, in press | Phys.Rev.D56:8095-8098,1997 | 10.1103/PhysRevD.56.8095 | null | gr-qc | null | The occurrence of chaos for test particles moving around a slowly rotating
black hole with a dipolar halo is studied using Poincar\'e sections. We find a
novel effect, particles with angular momentum opposite to the black hole
rotation have larger chaotic regions in phase space than particles initially
moving in the same direction.
| [
{
"created": "Mon, 1 Dec 1997 18:10:45 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Letelier",
"P. S.",
""
],
[
"Vieira",
"W. M.",
""
]
] | The occurrence of chaos for test particles moving around a slowly rotating black hole with a dipolar halo is studied using Poincar\'e sections. We find a novel effect, particles with angular momentum opposite to the black hole rotation have larger chaotic regions in phase space than particles initially moving in the same direction. |
gr-qc/0608029 | Irina Radinschi | I. Radinschi and B. Ciobanu (Department of Physics, Gh. Asachi
Technical University, Iasi, Romania) | Weinberg Energy-Momentum Complex for a Stringy Black Hole Solution | 9 pages, LaTex | AIP Conf.Proc.895:329-332,2007 | 10.1063/1.2720445 | null | gr-qc | null | In our paper we compute the energy distribution of a magnetic stringy black
hole solution in the Weinberg prescription. The metric under consideration
describes the dual solution in the string frame that is known as the magnetic
stringy black hole solution. The metric is obtained by multiplying the electric
metric in the Einstein frame by a factor . The energy distribution depends on
the mass M and charge Q. Also, we make a discussion of the results and we
compare our result with those obtained in the Einstein and Landau and Lifshitz
prescriptions and investigate the connections between the expressions of the
energy obtained in these prescriptions.
| [
{
"created": "Fri, 4 Aug 2006 19:34:14 GMT",
"version": "v1"
},
{
"created": "Sun, 6 Aug 2006 09:54:05 GMT",
"version": "v2"
}
] | 2011-07-19 | [
[
"Radinschi",
"I.",
"",
"Department of Physics, Gh. Asachi\n Technical University, Iasi, Romania"
],
[
"Ciobanu",
"B.",
"",
"Department of Physics, Gh. Asachi\n Technical University, Iasi, Romania"
]
] | In our paper we compute the energy distribution of a magnetic stringy black hole solution in the Weinberg prescription. The metric under consideration describes the dual solution in the string frame that is known as the magnetic stringy black hole solution. The metric is obtained by multiplying the electric metric in the Einstein frame by a factor . The energy distribution depends on the mass M and charge Q. Also, we make a discussion of the results and we compare our result with those obtained in the Einstein and Landau and Lifshitz prescriptions and investigate the connections between the expressions of the energy obtained in these prescriptions. |
gr-qc/0312090 | Cristian R. Ghezzi | Cristian R. Ghezzi, Patricio S. Letelier | Numerical Simulation of General Relativistic Stellar Collapse | 3 pages, 4 figs., submitted to the Proceedings of the "X Marcel
Grossmann Meeting on General Relativity" in Rio de Janeiro, Brazil, July
20-26 (2003) | null | null | null | gr-qc | null | We present preliminar results and tests of a new general relativistic code to
simulate the hydrodynamic collapse of a 21 solar masses star. We have assumed
spherical symmetry and used the formalism of Misner and Sharp to construct a
finite-difference scheme to solve the Einstein's equations, energy-momentum
conservation equations and baryonic conservation equation. The code is similar
to the one originally developed by May and White (1967). Here we discuss the
capabilities of the code that make it well suited for numerical relativity on a
personal computer and some caveats based on the experiments we have made with
it.
| [
{
"created": "Fri, 19 Dec 2003 19:46:07 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ghezzi",
"Cristian R.",
""
],
[
"Letelier",
"Patricio S.",
""
]
] | We present preliminar results and tests of a new general relativistic code to simulate the hydrodynamic collapse of a 21 solar masses star. We have assumed spherical symmetry and used the formalism of Misner and Sharp to construct a finite-difference scheme to solve the Einstein's equations, energy-momentum conservation equations and baryonic conservation equation. The code is similar to the one originally developed by May and White (1967). Here we discuss the capabilities of the code that make it well suited for numerical relativity on a personal computer and some caveats based on the experiments we have made with it. |
gr-qc/0509053 | Hongwei Yu | Hongwei Yu and Shizhuan Lu | Spontaneous excitation of an accelerated atom in a spacetime with a
reflecting plane boundary | A few typographical errors corrected | Phys.Rev.D72:064022,2005; Erratum-ibid.D73:109901,2006 | 10.1103/PhysRevD.72.064022 10.1103/PhysRevD.73.109901 | null | gr-qc hep-th physics.atom-ph quant-ph | null | We study a two-level atom in interaction with a real massless scalar quantum
field in a spacetime with a reflecting boundary. The presence of the boundary
modifies the quantum fluctuations of the scalar field, which in turn modifies
the radiative properties of atoms. We calculate the rate of change of the mean
atomic energy of the atom for both inertial motion and uniform acceleration. It
is found that the modifications induced by the presence of a boundary make the
spontaneous radiation rate of an excited inertial atom to oscillate near the
boundary and this oscillatory behavior may offer a possible opportunity for
experimental tests for geometrical (boundary) effects in flat spacetime. While
for accelerated atoms, the transitions from ground states to excited states are
found to be possible even in vacuum due to changes in the vacuum fluctuations
induced by both the presence of the boundary and the acceleration of atoms, and
this can be regarded as an actual physical process underlying the Unruh effect.
| [
{
"created": "Thu, 15 Sep 2005 13:39:41 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Apr 2006 01:42:43 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Yu",
"Hongwei",
""
],
[
"Lu",
"Shizhuan",
""
]
] | We study a two-level atom in interaction with a real massless scalar quantum field in a spacetime with a reflecting boundary. The presence of the boundary modifies the quantum fluctuations of the scalar field, which in turn modifies the radiative properties of atoms. We calculate the rate of change of the mean atomic energy of the atom for both inertial motion and uniform acceleration. It is found that the modifications induced by the presence of a boundary make the spontaneous radiation rate of an excited inertial atom to oscillate near the boundary and this oscillatory behavior may offer a possible opportunity for experimental tests for geometrical (boundary) effects in flat spacetime. While for accelerated atoms, the transitions from ground states to excited states are found to be possible even in vacuum due to changes in the vacuum fluctuations induced by both the presence of the boundary and the acceleration of atoms, and this can be regarded as an actual physical process underlying the Unruh effect. |
1505.07462 | Emanuele Berti | Michael Horbatsch, Hector O. Silva, Davide Gerosa, Paolo Pani,
Emanuele Berti, Leonardo Gualtieri, Ulrich Sperhake | Tensor-multi-scalar theories: relativistic stars and 3+1 decomposition | 32 pages, 8 figures, 1 table, invited contribution to the Classical
and Quantum Gravity Focus Issue "Black holes and fundamental fields". v3:
version in press in CQG, with various improvements in response to the
referees' comments. In particular, the 3+1 decomposition now allows for
matter | Class. Quantum Grav. 32, 20, 204001 (2015) | 10.1088/0264-9381/32/20/204001 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational theories with multiple scalar fields coupled to the metric and
each other --- a natural extension of the well studied single-scalar-tensor
theories --- are interesting phenomenological frameworks to describe deviations
from general relativity in the strong-field regime. In these theories, the
$N$-tuple of scalar fields takes values in a coordinate patch of an
$N$-dimensional Riemannian target-space manifold whose properties are poorly
constrained by weak-field observations. Here we introduce for simplicity a
non-trivial model with two scalar fields and a maximally symmetric target-space
manifold. Within this model we present a preliminary investigation of
spontaneous scalarization for relativistic, perfect fluid stellar models in
spherical symmetry. We find that the scalarization threshold is determined by
the eigenvalues of a symmetric scalar-matter coupling matrix, and that the
properties of strongly scalarized stellar configurations additionally depend on
the target-space curvature radius. In preparation for numerical relativity
simulations, we also write down the $3+1$ decomposition of the field equations
for generic tensor-multi-scalar theories.
| [
{
"created": "Wed, 27 May 2015 20:00:59 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Jun 2015 17:53:51 GMT",
"version": "v2"
},
{
"created": "Sun, 6 Sep 2015 00:32:11 GMT",
"version": "v3"
}
] | 2016-05-02 | [
[
"Horbatsch",
"Michael",
""
],
[
"Silva",
"Hector O.",
""
],
[
"Gerosa",
"Davide",
""
],
[
"Pani",
"Paolo",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Gualtieri",
"Leonardo",
""
],
[
"Sperhake",
"Ulrich",
""
]
] | Gravitational theories with multiple scalar fields coupled to the metric and each other --- a natural extension of the well studied single-scalar-tensor theories --- are interesting phenomenological frameworks to describe deviations from general relativity in the strong-field regime. In these theories, the $N$-tuple of scalar fields takes values in a coordinate patch of an $N$-dimensional Riemannian target-space manifold whose properties are poorly constrained by weak-field observations. Here we introduce for simplicity a non-trivial model with two scalar fields and a maximally symmetric target-space manifold. Within this model we present a preliminary investigation of spontaneous scalarization for relativistic, perfect fluid stellar models in spherical symmetry. We find that the scalarization threshold is determined by the eigenvalues of a symmetric scalar-matter coupling matrix, and that the properties of strongly scalarized stellar configurations additionally depend on the target-space curvature radius. In preparation for numerical relativity simulations, we also write down the $3+1$ decomposition of the field equations for generic tensor-multi-scalar theories. |
2208.01872 | Laur J\"arv | Sebastian Bahamonde, Laur J\"arv | Coincident gauge for static spherical field configurations in symmetric
teleparallel gravity | 24 pages, version submitted to EPJC | Eur. Phys. J. C 82, 963 (2022) | 10.1140/epjc/s10052-022-10922-9 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In symmetric teleparallel gravities, where the independent connection is
characterized by nonmetricity while curvature and torsion are zero, it is
possible to find a coordinate system whereby the connection vanishes globally
and covariant derivatives reduce to partial derivatives -- the coincident
gauge. In this paper we derive general transformation rules into the coincident
gauge for spacetime configurations where the both the metric and connection are
static and spherically symmetric, and write out the respective form of the
coincident gauge metrics. Taking different options in fixing the freedom in the
connection allowed by the symmetry and the field equations, the Schwarzschild
metric in the coincident gauge can take for instance the Cartesian,
Kerr-Schild, and diagonal (isotropic-like) forms, while the BBMB black hole
metric in symmetric teleparallel scalar-tensor theory a certain diagonal form
fits the coincident gauge requirements but the Cartesian and Kerr-Schild forms
do not. Different connections imply different value for the boundary term which
could in principle be physically relevant, but simple arguments about the
coincident gauge do not seem to be sufficient to fix the connection uniquely.
As a byproduct of the investigation we also point out that only a particular
subset of static spherically symmetric connections has vanishing nonmetricity
in the Minkowski limit.
| [
{
"created": "Wed, 3 Aug 2022 06:52:50 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Oct 2022 09:48:36 GMT",
"version": "v2"
}
] | 2022-11-01 | [
[
"Bahamonde",
"Sebastian",
""
],
[
"Järv",
"Laur",
""
]
] | In symmetric teleparallel gravities, where the independent connection is characterized by nonmetricity while curvature and torsion are zero, it is possible to find a coordinate system whereby the connection vanishes globally and covariant derivatives reduce to partial derivatives -- the coincident gauge. In this paper we derive general transformation rules into the coincident gauge for spacetime configurations where the both the metric and connection are static and spherically symmetric, and write out the respective form of the coincident gauge metrics. Taking different options in fixing the freedom in the connection allowed by the symmetry and the field equations, the Schwarzschild metric in the coincident gauge can take for instance the Cartesian, Kerr-Schild, and diagonal (isotropic-like) forms, while the BBMB black hole metric in symmetric teleparallel scalar-tensor theory a certain diagonal form fits the coincident gauge requirements but the Cartesian and Kerr-Schild forms do not. Different connections imply different value for the boundary term which could in principle be physically relevant, but simple arguments about the coincident gauge do not seem to be sufficient to fix the connection uniquely. As a byproduct of the investigation we also point out that only a particular subset of static spherically symmetric connections has vanishing nonmetricity in the Minkowski limit. |
2311.15272 | Hossein Khodabakhshi | H. Khodabakhshi, F. Shojai and H. L\"u | Cosmological Time Crystals from Gauss-Bonnet Gravity in Four Dimensions | 24 pages, 8 figures, 2 tables | JCAP06(2024)002 | 10.1088/1475-7516/2024/06/002 | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | We investigate various cosmological aspects of a 4-Dimensional Gauss-Bonnet
Lagrangian, which is integrated into the Einstein Lagrangian with an arbitrary
sign, using the Friedman-Lema\^itre-Robertson-Walker (FLRW) metric. We consider
a general potential term, $V(a)$, that depends on the scale factor $a$, and we
analyze several scenarios by investigating the critical points of the dynamical
equations and stability conditions to understand how the universe's behavior is
affected by the Gauss-Bonnet term. Our research suggests that choosing the
negative sign, this integration allows for the spontaneous breaking of time
reflection symmetry. This can lead to the generation of a bounce universe even
with a normal matter sector, marking a significant departure from traditional
theories. Furthermore, we examine the possibility of a time-crystal universe,
showing that under certain circumstances, the theory might give rise to cyclic
universes.
| [
{
"created": "Sun, 26 Nov 2023 11:52:58 GMT",
"version": "v1"
},
{
"created": "Thu, 9 May 2024 17:49:26 GMT",
"version": "v2"
}
] | 2024-06-11 | [
[
"Khodabakhshi",
"H.",
""
],
[
"Shojai",
"F.",
""
],
[
"Lü",
"H.",
""
]
] | We investigate various cosmological aspects of a 4-Dimensional Gauss-Bonnet Lagrangian, which is integrated into the Einstein Lagrangian with an arbitrary sign, using the Friedman-Lema\^itre-Robertson-Walker (FLRW) metric. We consider a general potential term, $V(a)$, that depends on the scale factor $a$, and we analyze several scenarios by investigating the critical points of the dynamical equations and stability conditions to understand how the universe's behavior is affected by the Gauss-Bonnet term. Our research suggests that choosing the negative sign, this integration allows for the spontaneous breaking of time reflection symmetry. This can lead to the generation of a bounce universe even with a normal matter sector, marking a significant departure from traditional theories. Furthermore, we examine the possibility of a time-crystal universe, showing that under certain circumstances, the theory might give rise to cyclic universes. |
gr-qc/0602114 | John Klauder | John R. Klauder and J. Scott Little | Highly Irregular Quantum Constraints | 19 pages, latex | Class.Quant.Grav. 23 (2006) 3641 | 10.1088/0264-9381/23/10/025 | null | gr-qc hep-th math-ph math.MP | null | Motivated by a recent paper of Louko and Molgado, we consider a simple system
with a single classical constraint R(q)=0. If q_l denotes a generic solution to
R(q)=0, our examples include cases where R'(q_l)\ne 0 (regular constraint) and
R'(q_l)=0 (irregular constraint) of varying order as well as the case where
R(q)=0 for an interval, such as a \leq q \leq b. Quantization of irregular
constraints is normally not considered; however, using the projection operator
formalism we provide a satisfactory quantization which reduces to the
constrained classical system when \hbar \to 0. It is noteworthy that irregular
constraints change the observable aspects of a theory as compared to strictly
regular constraints.
| [
{
"created": "Mon, 27 Feb 2006 18:27:44 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Klauder",
"John R.",
""
],
[
"Little",
"J. Scott",
""
]
] | Motivated by a recent paper of Louko and Molgado, we consider a simple system with a single classical constraint R(q)=0. If q_l denotes a generic solution to R(q)=0, our examples include cases where R'(q_l)\ne 0 (regular constraint) and R'(q_l)=0 (irregular constraint) of varying order as well as the case where R(q)=0 for an interval, such as a \leq q \leq b. Quantization of irregular constraints is normally not considered; however, using the projection operator formalism we provide a satisfactory quantization which reduces to the constrained classical system when \hbar \to 0. It is noteworthy that irregular constraints change the observable aspects of a theory as compared to strictly regular constraints. |
0712.1520 | Miguel Sabido | W. Guzm\'an, M. Sabido and J. Socorro | Noncommutivity and Scalar Field Cosmology | 4 Pages, 2 figures, Revtex 4 | Phys.Rev.D76:087302,2007 | 10.1103/PhysRevD.76.087302 | null | gr-qc | null | In this work we extend and apply a previous proposal to study noncommutative
cosmology to the FRW cosmological background coupled to a scalar field, this is
done in classical and quantum scenarios. In both cases noncommutativity is
introduced in the gravitational field as well as in the scalar field through a
deformation of minisuperspace and are able to find exact solutions. Finally,
the effects of noncommutativity on the classical evolution are analyzed.
| [
{
"created": "Mon, 10 Dec 2007 15:54:43 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Guzmán",
"W.",
""
],
[
"Sabido",
"M.",
""
],
[
"Socorro",
"J.",
""
]
] | In this work we extend and apply a previous proposal to study noncommutative cosmology to the FRW cosmological background coupled to a scalar field, this is done in classical and quantum scenarios. In both cases noncommutativity is introduced in the gravitational field as well as in the scalar field through a deformation of minisuperspace and are able to find exact solutions. Finally, the effects of noncommutativity on the classical evolution are analyzed. |
1009.3745 | Azad Akhter Siddiqui Professor | Asghar Qadir and Azad A. Siddiqui | Asymptotic Behaviour of the Proper Length and Volume of the
Schwarzschild Singularity | 13 pages, 1 figure | Int.J.Mod.Phys.D18:397-404,2009 | 10.1142/S0218271809014510 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Though popular presentations give the Schwarzschild singularity as a point it
is known that it is spacelike and not timelike. Thus it has a "length" and is
not a "point". In fact, its length must necessarily be infinite. It has been
proved that the proper length of the Qadir-Wheeler suture model goes to
infinity [1], while its proper volume shrinks to zero, and the asymptotic
behaviour of the length and volume have been calculated. That model consists of
two Friedmann sections connected by a Schwarzschild "suture". The question
arises whether a similar analysis could provide the asymptotic behaviour of the
Schwarzschild black hole near the singularity. It is proved here that, unlike
the behaviour for the suture model, for the Schwarzschild essential singularity
$\Delta s$ $\thicksim $ $K^{1/3}\ln K$ and $V\thicksim $ $K^{-1}\ln K$, where
$K$ is the mean extrinsic curvature, or the York time.
| [
{
"created": "Mon, 20 Sep 2010 09:35:30 GMT",
"version": "v1"
}
] | 2010-11-26 | [
[
"Qadir",
"Asghar",
""
],
[
"Siddiqui",
"Azad A.",
""
]
] | Though popular presentations give the Schwarzschild singularity as a point it is known that it is spacelike and not timelike. Thus it has a "length" and is not a "point". In fact, its length must necessarily be infinite. It has been proved that the proper length of the Qadir-Wheeler suture model goes to infinity [1], while its proper volume shrinks to zero, and the asymptotic behaviour of the length and volume have been calculated. That model consists of two Friedmann sections connected by a Schwarzschild "suture". The question arises whether a similar analysis could provide the asymptotic behaviour of the Schwarzschild black hole near the singularity. It is proved here that, unlike the behaviour for the suture model, for the Schwarzschild essential singularity $\Delta s$ $\thicksim $ $K^{1/3}\ln K$ and $V\thicksim $ $K^{-1}\ln K$, where $K$ is the mean extrinsic curvature, or the York time. |
2309.00994 | Matteo Luca Ruggiero | Matteo Luca Ruggiero | Synchronization and Fundamental Time: a Connection between Relativity
and Quantum Mechanics | 11 pages; accepted for publication in Foundations of Physics | Foundations of Physics (2023) 53:83 | 10.1007/s10701-023-00724-8 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An interesting connection between special relativity and quantum mechanics
was put forward by Louis de Broglie, about 60 years ago, who focused on the
link between synchronization in a rotating frame and the quantization of the
angular momentum. Here we generalise his approach to curved spacetime, using
the gravitoelectromagnetic analogy, which can be applied to describe the weak
gravitational field around rotating sources, and give a new interpretation of
the results.
| [
{
"created": "Sat, 2 Sep 2023 17:30:20 GMT",
"version": "v1"
}
] | 2023-09-18 | [
[
"Ruggiero",
"Matteo Luca",
""
]
] | An interesting connection between special relativity and quantum mechanics was put forward by Louis de Broglie, about 60 years ago, who focused on the link between synchronization in a rotating frame and the quantization of the angular momentum. Here we generalise his approach to curved spacetime, using the gravitoelectromagnetic analogy, which can be applied to describe the weak gravitational field around rotating sources, and give a new interpretation of the results. |
gr-qc/0505153 | Viqar Husain | Viqar Husain and Oliver Winkler | How red is a quantum black hole? | 3 pages, essay for the Gravity Research Foundation | Int.J.Mod.Phys. D14 (2005) 2233-2238 | 10.1142/S0218271805007851 | null | gr-qc hep-th | null | Radiating black holes pose a number of puzzles for semiclassical and quantum
gravity. These include the transplanckian problem -- the nearly infinite
energies of Hawking particles created near the horizon, and the final state of
evaporation. A definitive resolution of these questions likely requires robust
inputs from quantum gravity. We argue that one such input is a quantum bound on
curvature. We show how this leads to an upper limit on the redshift of a
Hawking emitted particle, to a maximum temperature for a black hole, and to the
prediction of a Planck scale remnant.
| [
{
"created": "Mon, 30 May 2005 20:06:30 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Husain",
"Viqar",
""
],
[
"Winkler",
"Oliver",
""
]
] | Radiating black holes pose a number of puzzles for semiclassical and quantum gravity. These include the transplanckian problem -- the nearly infinite energies of Hawking particles created near the horizon, and the final state of evaporation. A definitive resolution of these questions likely requires robust inputs from quantum gravity. We argue that one such input is a quantum bound on curvature. We show how this leads to an upper limit on the redshift of a Hawking emitted particle, to a maximum temperature for a black hole, and to the prediction of a Planck scale remnant. |
1305.4631 | Anil Yadav dr | Ahmad T. Ali and Anil Kumar Yadav | Symmetry Group Analysis for perfect fluid Inhomogeneous Cosmological
Models in General Relativity | 13 pages | Int. J. Theor. Phys. 53: 2505 - 2519 (2014) | 10.1007/s10773-014-2049-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have searched the existence of the similarity solution for
plane symmetric inhomogeneous cosmological models in general relativity. The
matter source consists of perfect fluid with proportionality relation between
expansion scalar and shear scalar. The isovector fields of Einstein's field
equation for the models under consideration are derived. A new class of exact
solutions of Einstein's field equation have been obtained for inhomogeneous
space-time. The physical behaviors and geometric aspects of the derived models
have been discussed in detail.
| [
{
"created": "Mon, 20 May 2013 15:00:02 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Aug 2013 16:32:09 GMT",
"version": "v2"
}
] | 2014-07-14 | [
[
"Ali",
"Ahmad T.",
""
],
[
"Yadav",
"Anil Kumar",
""
]
] | In this paper, we have searched the existence of the similarity solution for plane symmetric inhomogeneous cosmological models in general relativity. The matter source consists of perfect fluid with proportionality relation between expansion scalar and shear scalar. The isovector fields of Einstein's field equation for the models under consideration are derived. A new class of exact solutions of Einstein's field equation have been obtained for inhomogeneous space-time. The physical behaviors and geometric aspects of the derived models have been discussed in detail. |
2311.02740 | Thanasis Karakasis | Dionysios P. Theodosopoulos, Thanasis Karakasis, George Koutsoumbas,
Eleftherios Papantonopoulos | Motion of particles around a magnetically charged Euler-Heisenberg black
hole with scalar hair and the Event Horizon Telescope | 38 pages, 23 figures, references added | null | 10.1140/epjc/s10052-024-12956-7 | null | gr-qc astro-ph.HE hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | We study the motion of uncharged particles and photons in the background of a
magnetically charged Euler-Heisenberg (EH) black hole (BH) with scalar hair.
The spacetime can be asymptotically (A)dS or flat. After investigating particle
motions around the BH and the behavior of the effective potential of the
particle radial motion, we determine the contribution of the BH parameters to
the geodesics. Photons follow null geodesics of an effective geometry induced
by the corrections of the EH non-linear electrodynamics. Thus, after
determining the effective geometry, we calculate the shadow of the BH. Upon
comparing the theoretically calculated BH shadow with the images of the shadows
of M87* and Sgr A* obtained by the Event Horizon Telescope collaboration, we
impose constraints on the BH parameters, namely the scalar hair ($\nu$), the
magnetic charge ($Q_{m}$) and the EH parameter ($\alpha$).
| [
{
"created": "Sun, 5 Nov 2023 19:09:27 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Nov 2023 13:18:49 GMT",
"version": "v2"
}
] | 2024-06-12 | [
[
"Theodosopoulos",
"Dionysios P.",
""
],
[
"Karakasis",
"Thanasis",
""
],
[
"Koutsoumbas",
"George",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
]
] | We study the motion of uncharged particles and photons in the background of a magnetically charged Euler-Heisenberg (EH) black hole (BH) with scalar hair. The spacetime can be asymptotically (A)dS or flat. After investigating particle motions around the BH and the behavior of the effective potential of the particle radial motion, we determine the contribution of the BH parameters to the geodesics. Photons follow null geodesics of an effective geometry induced by the corrections of the EH non-linear electrodynamics. Thus, after determining the effective geometry, we calculate the shadow of the BH. Upon comparing the theoretically calculated BH shadow with the images of the shadows of M87* and Sgr A* obtained by the Event Horizon Telescope collaboration, we impose constraints on the BH parameters, namely the scalar hair ($\nu$), the magnetic charge ($Q_{m}$) and the EH parameter ($\alpha$). |
1405.5077 | Abraham Harte | Abraham I. Harte | Motion in classical field theories and the foundations of the self-force
problem | 68 pages, 1 figure | null | 10.1007/978-3-319-18335-0_12 | null | gr-qc math-ph math.MP physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article serves as a pedagogical introduction to the problem of motion in
classical field theories. The primary focus is on self-interaction: How does an
object's own field affect its motion? General laws governing the self-force and
self-torque are derived using simple, non-perturbative arguments. The relevant
concepts are developed gradually by considering motion in a series of
increasingly complicated theories. Newtonian gravity is discussed first, then
Klein-Gordon theory, electromagnetism, and finally general relativity. Linear
and angular momenta as well as centers of mass are defined in each of these
cases. Multipole expansions for the force and torque are then derived to all
orders for arbitrarily self-interacting extended objects. These expansions are
found to be structurally identical to the laws of motion satisfied by extended
test bodies, except that all relevant fields are replaced by effective versions
which exclude the self-fields in a particular sense. Regularization methods
traditionally associated with self-interacting point particles arise as
straightforward perturbative limits of these (more fundamental) results.
Additionally, generic mechanisms are discussed which dynamically shift ---
i.e., renormalize --- the apparent multipole moments associated with
self-interacting extended bodies. Although this is primarily a synthesis of
earlier work, several new results and interpretations are included as well.
| [
{
"created": "Tue, 20 May 2014 13:28:29 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Aug 2015 16:50:54 GMT",
"version": "v2"
}
] | 2021-04-07 | [
[
"Harte",
"Abraham I.",
""
]
] | This article serves as a pedagogical introduction to the problem of motion in classical field theories. The primary focus is on self-interaction: How does an object's own field affect its motion? General laws governing the self-force and self-torque are derived using simple, non-perturbative arguments. The relevant concepts are developed gradually by considering motion in a series of increasingly complicated theories. Newtonian gravity is discussed first, then Klein-Gordon theory, electromagnetism, and finally general relativity. Linear and angular momenta as well as centers of mass are defined in each of these cases. Multipole expansions for the force and torque are then derived to all orders for arbitrarily self-interacting extended objects. These expansions are found to be structurally identical to the laws of motion satisfied by extended test bodies, except that all relevant fields are replaced by effective versions which exclude the self-fields in a particular sense. Regularization methods traditionally associated with self-interacting point particles arise as straightforward perturbative limits of these (more fundamental) results. Additionally, generic mechanisms are discussed which dynamically shift --- i.e., renormalize --- the apparent multipole moments associated with self-interacting extended bodies. Although this is primarily a synthesis of earlier work, several new results and interpretations are included as well. |
gr-qc/9910003 | Ion Cotaescu | Ion I. Cot\u{a}escu (The West University of Timi\c{s}oara, Romania) | Geometric models of (d+1)-dimensional relativistic rotating oscillators | 7 pages, Latex | J.Math.Phys. 41 (2000) 7290-7293 | 10.1063/1.1314894 | null | gr-qc | null | Geometric models of quantum relativistic rotating oscillators in arbitrary
dimensions are defined on backgrounds with deformed anti-de Sitter metrics. It
is shown that these models are analytically solvable, deriving the formulas of
the energy levels and corresponding normalized energy eigenfunctions. An
important property is that all these models have the same nonrelativistic
limit, namely the usual harmonic oscillator.
| [
{
"created": "Fri, 1 Oct 1999 13:07:59 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Cotăescu",
"Ion I.",
"",
"The West University of Timişoara, Romania"
]
] | Geometric models of quantum relativistic rotating oscillators in arbitrary dimensions are defined on backgrounds with deformed anti-de Sitter metrics. It is shown that these models are analytically solvable, deriving the formulas of the energy levels and corresponding normalized energy eigenfunctions. An important property is that all these models have the same nonrelativistic limit, namely the usual harmonic oscillator. |
0810.0505 | Niall \'O Murchadha | Niall O Murchadha | With commuting Killing vectors, the lapse and shift of one Killing
vector are constants along the other | The key result in this paper was previously discovered by Beig and
Chrusciel using a different approach. I add the appropriate reference and a
short discussion of their derivation | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Given an d-dimensional manifold with two commuting Killing vectors, together
with an d - 1 dimensional submanifold in which one of the Killing vectors lies,
then the lapse and shift of the second Killing vector, relative to this slice,
remain constant along the orbits of the `surface' Killing vector.
Alternatively, the six dot products that can be formed from the three vectors,
the two Killing vectors and the normal to the submanifold, are all constants
along the `surface' Killing vector.
| [
{
"created": "Thu, 2 Oct 2008 18:07:42 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Oct 2008 16:20:54 GMT",
"version": "v2"
}
] | 2008-10-09 | [
[
"Murchadha",
"Niall O",
""
]
] | Given an d-dimensional manifold with two commuting Killing vectors, together with an d - 1 dimensional submanifold in which one of the Killing vectors lies, then the lapse and shift of the second Killing vector, relative to this slice, remain constant along the orbits of the `surface' Killing vector. Alternatively, the six dot products that can be formed from the three vectors, the two Killing vectors and the normal to the submanifold, are all constants along the `surface' Killing vector. |
0907.4303 | Wen Zhao | W. Zhao, D. Baskaran, P. Coles | Detecting relics of a thermal gravitational wave background in the early
Universe | 9 pages, 4 figures, published version | Phys.Lett.B680:411-416,2009 | 10.1016/j.physletb.2009.09.018 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A thermal gravitational wave background can be produced in the early Universe
if a radiation dominated epoch precedes the usual inflationary stage. This
background provides a unique way to study the initial state of the Universe. We
discuss the imprint of this thermal spectra of gravitons on the cosmic
microwave background (CMB) power spectra, and its possible detection by CMB
observations. Assuming the inflationary stage is a pure de Sitter expansion we
find that, if the number of e-folds of inflation is smaller than 65, the signal
of this thermal spectrum can be detected by the observations of Planck and
PolarBear experiments, or the planned EPIC experiments. This bound can be even
looser if inflation-like stage is the sub-exponential.
| [
{
"created": "Fri, 24 Jul 2009 14:38:01 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Sep 2009 07:54:07 GMT",
"version": "v2"
},
{
"created": "Wed, 30 Sep 2009 08:39:21 GMT",
"version": "v3"
}
] | 2010-03-25 | [
[
"Zhao",
"W.",
""
],
[
"Baskaran",
"D.",
""
],
[
"Coles",
"P.",
""
]
] | A thermal gravitational wave background can be produced in the early Universe if a radiation dominated epoch precedes the usual inflationary stage. This background provides a unique way to study the initial state of the Universe. We discuss the imprint of this thermal spectra of gravitons on the cosmic microwave background (CMB) power spectra, and its possible detection by CMB observations. Assuming the inflationary stage is a pure de Sitter expansion we find that, if the number of e-folds of inflation is smaller than 65, the signal of this thermal spectrum can be detected by the observations of Planck and PolarBear experiments, or the planned EPIC experiments. This bound can be even looser if inflation-like stage is the sub-exponential. |
1603.07118 | Alfred Molina | Avas Khugaev, Naresh Dadhich and Alfred Molina | Higher dimensional generalization of Buchdahl-Vaidya-Tikekar model for
super compact star | 13 pages, 6 figures | Phys. Rev. D 94, 064065 (2016) | 10.1103/PhysRevD.94.064065 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain higher dimensional solutions for super compact star for the
Buchdahl-Vaidya-Tikekar metric ansatz. In particular, Vaidya and Tikekar
characterized the $3$-geometry by a parameter, $K$ which is related to the sign
of density gradient. It turns out that the key pressure isotropy equation
continues to have the same Gauss form, and hence $4$-dimensional solutions can
be taken over to higher dimensions with $K$ satisfying the relation, $K_n =
(K_4-n+4)/(n-3)$ where subscript refers to dimension of spacetime. Further
$K\geq0$ is required else density would have undesirable feature of increasing
with radius, and the equality indicates a constant density star described by
the Schwarzschild interior solution. This means for a given $K_4$, maximum
dimension could only be $n=K_4+4$, else $K_n$ will turn negative.
| [
{
"created": "Wed, 23 Mar 2016 10:19:57 GMT",
"version": "v1"
}
] | 2016-09-28 | [
[
"Khugaev",
"Avas",
""
],
[
"Dadhich",
"Naresh",
""
],
[
"Molina",
"Alfred",
""
]
] | We obtain higher dimensional solutions for super compact star for the Buchdahl-Vaidya-Tikekar metric ansatz. In particular, Vaidya and Tikekar characterized the $3$-geometry by a parameter, $K$ which is related to the sign of density gradient. It turns out that the key pressure isotropy equation continues to have the same Gauss form, and hence $4$-dimensional solutions can be taken over to higher dimensions with $K$ satisfying the relation, $K_n = (K_4-n+4)/(n-3)$ where subscript refers to dimension of spacetime. Further $K\geq0$ is required else density would have undesirable feature of increasing with radius, and the equality indicates a constant density star described by the Schwarzschild interior solution. This means for a given $K_4$, maximum dimension could only be $n=K_4+4$, else $K_n$ will turn negative. |
1810.00854 | Paul R. Anderson | Paul R. Anderson, Mathew J. Binkley, Jillian M. Bjerke, Paul W. Cauley | Black hole remnants may exist if Starobinsky inflation occurred | References added, a brief discussion relating to pair creation of
black holes added, sign of a higher derivative term corrected, minor changes
and corrections, 20 pages, 3 figures | Phys. Rev. D 98, 125011 (2018) | 10.1103/PhysRevD.98.125011 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Zero temperature black hole solutions to the semiclassical backreaction
equations are investigated. Evidence is provided that certain components of the
stress-energy tensors for free quantum fields at the horizon only depend on the
local geometry near the horizon. This allows the semiclassical backreaction
equations to be solved near the horizon. It is found that macroscopic uncharged
zero temperature black hole solutions to the equations may exist if the
coefficient of one of the higher derivative terms in the gravitational
Lagrangian is large enough and of the right sign for Starobinsky inflation to
have occurred in the early Universe.
| [
{
"created": "Mon, 1 Oct 2018 17:49:44 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Jan 2019 01:11:52 GMT",
"version": "v2"
}
] | 2019-01-29 | [
[
"Anderson",
"Paul R.",
""
],
[
"Binkley",
"Mathew J.",
""
],
[
"Bjerke",
"Jillian M.",
""
],
[
"Cauley",
"Paul W.",
""
]
] | Zero temperature black hole solutions to the semiclassical backreaction equations are investigated. Evidence is provided that certain components of the stress-energy tensors for free quantum fields at the horizon only depend on the local geometry near the horizon. This allows the semiclassical backreaction equations to be solved near the horizon. It is found that macroscopic uncharged zero temperature black hole solutions to the equations may exist if the coefficient of one of the higher derivative terms in the gravitational Lagrangian is large enough and of the right sign for Starobinsky inflation to have occurred in the early Universe. |
0812.5012 | Yuan K. Ha | Yuan K. Ha | Quantum Black Holes As Elementary Particles | Quantum black holes with a typical mass of 10^{-5} gm are
semiclassical objects. Like a heavy nucleus of an atom, they may subject to
the rules of quantum mechanics but not necessarily to the rules of quantum
field theory. 12 pages | null | null | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Are black holes elementary particles? Are they fermions or bosons? We
investigate the remarkable possibility that quantum black holes are the
smallest and heaviest elementary particles. We are able to construct various
fundamental quantum black holes: the spin-0, spin 1/2, spin-1, and the
Planck-charge cases, using the results in general relativity. Quantum black
holes in the neighborhood of the Galaxy could resolve the paradox posed by the
Greisen-Zatsepin-Kuzmin limit on the energy of cosmic rays from distant
sources. They could also play a role as dark matter in cosmology.
| [
{
"created": "Tue, 30 Dec 2008 19:20:51 GMT",
"version": "v1"
}
] | 2009-01-02 | [
[
"Ha",
"Yuan K.",
""
]
] | Are black holes elementary particles? Are they fermions or bosons? We investigate the remarkable possibility that quantum black holes are the smallest and heaviest elementary particles. We are able to construct various fundamental quantum black holes: the spin-0, spin 1/2, spin-1, and the Planck-charge cases, using the results in general relativity. Quantum black holes in the neighborhood of the Galaxy could resolve the paradox posed by the Greisen-Zatsepin-Kuzmin limit on the energy of cosmic rays from distant sources. They could also play a role as dark matter in cosmology. |
2304.05408 | Kimet Jusufi | Kimet Jusufi, Emmanuel Moulay, Jonas Mureika, Ahmed Farag Ali | Einstein-Rosen bridge from the minimal length | 9 pages, published in EPJC | Eur. Phys. J. C 83, 282 (2023) | 10.1140/epjc/s10052-023-11465-3 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use a string T-duality corrected pair of regular black holes to construct
an Einstein-Rosen (ER) bridge with the wormhole throat proportional to the
zero-point (Planck) length. This may be a geometric realization of quantum
entanglement for particle/antiparticle pairs. We point out that for an extreme
mass configuration consisting of a black hole pair, one can have an ER bridge
with a horizon area that coincides with the Bekenstein minimal area bound along
with a wormhole mass proportional to the Planck mass. This could be related to
gravitational self-completeness with quantum mechanical mass limits. We also
discuss the ER bridge for sub-Planckian mass horizonless wormholes and show
this admits a region of negative energy at the throat, which we posit to be
related to a particle of negative mass generated by quantum fluctuations or the
Casimir effect. We argue that Hawking radiation could be the best way for the
geometric realization of quantum entanglement for particle/antiparticle pairs
emitted by black holes. This sheds new light on the ER=EPR conjecture.
| [
{
"created": "Tue, 11 Apr 2023 16:11:13 GMT",
"version": "v1"
}
] | 2023-04-13 | [
[
"Jusufi",
"Kimet",
""
],
[
"Moulay",
"Emmanuel",
""
],
[
"Mureika",
"Jonas",
""
],
[
"Ali",
"Ahmed Farag",
""
]
] | We use a string T-duality corrected pair of regular black holes to construct an Einstein-Rosen (ER) bridge with the wormhole throat proportional to the zero-point (Planck) length. This may be a geometric realization of quantum entanglement for particle/antiparticle pairs. We point out that for an extreme mass configuration consisting of a black hole pair, one can have an ER bridge with a horizon area that coincides with the Bekenstein minimal area bound along with a wormhole mass proportional to the Planck mass. This could be related to gravitational self-completeness with quantum mechanical mass limits. We also discuss the ER bridge for sub-Planckian mass horizonless wormholes and show this admits a region of negative energy at the throat, which we posit to be related to a particle of negative mass generated by quantum fluctuations or the Casimir effect. We argue that Hawking radiation could be the best way for the geometric realization of quantum entanglement for particle/antiparticle pairs emitted by black holes. This sheds new light on the ER=EPR conjecture. |
gr-qc/0503030 | Miguel Alcubierre | Miguel Alcubierre | Are gauge shocks really shocks? | 7 pages, 5 figures, REVTEX 4. Revised version, including corrections
suggested by referees | Class.Quant.Grav. 22 (2005) 4071-4082 | 10.1088/0264-9381/22/19/017 | null | gr-qc | null | The existence of gauge pathologies associated with the Bona-Masso family of
generalized harmonic slicing conditions is proven for the case of simple 1+1
relativity. It is shown that these gauge pathologies are true shocks in the
sense that the characteristic lines associated with the propagation of the
gauge cross, which implies that the name ``gauge shock'' usually given to such
pathologies is indeed correct. These gauge shocks are associated with places
where the spatial hypersurfaces that determine the foliation of spacetime
become non-smooth.
| [
{
"created": "Tue, 8 Mar 2005 18:39:48 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Aug 2005 16:01:22 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Alcubierre",
"Miguel",
""
]
] | The existence of gauge pathologies associated with the Bona-Masso family of generalized harmonic slicing conditions is proven for the case of simple 1+1 relativity. It is shown that these gauge pathologies are true shocks in the sense that the characteristic lines associated with the propagation of the gauge cross, which implies that the name ``gauge shock'' usually given to such pathologies is indeed correct. These gauge shocks are associated with places where the spatial hypersurfaces that determine the foliation of spacetime become non-smooth. |
2404.03779 | Theodoros Papanikolaou | Theodoros Papanikolaou, Shreya Banerjee, Yi-Fu Cai, Salvatore
Capozziello, Emmanuel N. Saridakis | Primordial black holes and induced gravitational waves in non-singular
matter bouncing cosmology | Accepted at JCAP | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a novel model-independent generic mechanism for primordial black
hole formation within the context of non-singular matter bouncing cosmology. In
particular, considering a short duration transition from the matter contracting
phase to the Hot Big Bang expanding Universe, we find naturally enhanced
curvature perturbations on very small scales which can collapse and form
primordial black holes. Interestingly, the primordial black hole masses that we
find can lie within the observationally unconstrained asteroid-mass window,
potentially explaining the totality of dark matter. Remarkably, the enhanced
curvature perturbations, collapsing to primordial black holes, can induce as
well a stochastic gravitational-wave background, being potentially detectable
by future experiments, in particular by SKA, PTAs, LISA and ET, hence serving
as a new portal to probe the potential bouncing nature of the initial
conditions prevailed in the early Universe.
| [
{
"created": "Thu, 4 Apr 2024 19:51:16 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Apr 2024 15:20:21 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Jun 2024 17:01:43 GMT",
"version": "v3"
}
] | 2024-06-21 | [
[
"Papanikolaou",
"Theodoros",
""
],
[
"Banerjee",
"Shreya",
""
],
[
"Cai",
"Yi-Fu",
""
],
[
"Capozziello",
"Salvatore",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | We present a novel model-independent generic mechanism for primordial black hole formation within the context of non-singular matter bouncing cosmology. In particular, considering a short duration transition from the matter contracting phase to the Hot Big Bang expanding Universe, we find naturally enhanced curvature perturbations on very small scales which can collapse and form primordial black holes. Interestingly, the primordial black hole masses that we find can lie within the observationally unconstrained asteroid-mass window, potentially explaining the totality of dark matter. Remarkably, the enhanced curvature perturbations, collapsing to primordial black holes, can induce as well a stochastic gravitational-wave background, being potentially detectable by future experiments, in particular by SKA, PTAs, LISA and ET, hence serving as a new portal to probe the potential bouncing nature of the initial conditions prevailed in the early Universe. |
1209.3499 | Serge Parnovsky | Serge L. Parnovsky | Time-like singularities in General Relativity | 5 pages, accepted for publication in Herald of the University of
Kyiv, Astronomy | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the properties of naked time-like singularities in the General
Relativity and quantum effects in their vicinity. We demonstrate that only
line-like singularities can be formed by a collapse and are the only candidates
to break the Cosmic Censorship Principle.
| [
{
"created": "Sun, 16 Sep 2012 16:11:29 GMT",
"version": "v1"
}
] | 2012-09-18 | [
[
"Parnovsky",
"Serge L.",
""
]
] | We review the properties of naked time-like singularities in the General Relativity and quantum effects in their vicinity. We demonstrate that only line-like singularities can be formed by a collapse and are the only candidates to break the Cosmic Censorship Principle. |
2110.05657 | Alexander Simpson | Alex Simpson | From black-bounce to traversable wormhole, and beyond | V1: 20 pages, 4 figures, 73 references; MG16 Conference Proceedings,
2021. V2: Still 20 pages, 4 figures, now 76 references; MG16 Conference
Proceedings, 2021 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Key results from the literature pertaining to a class of nonsingular black
hole mimickers are explored. The family of candidate spacetimes is for now
labelled the `black-bounce' family, stemming from the original so-called
`Simpson--Visser' spacetime in static spherical symmetry. All model geometries
are analysed through the lens of standard general relativity, are globally free
from curvature singularities, pass all weak-field observational tests, and
smoothly interpolate between regular black holes and traversable wormholes. The
discourse is segregated along geometrical lines, with candidate spacetimes each
belonging to one of: static spherical symmetry, spherical symmetry with
dynamics, and stationary axisymmetry.
| [
{
"created": "Tue, 12 Oct 2021 00:29:41 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Oct 2021 01:45:49 GMT",
"version": "v2"
}
] | 2021-10-22 | [
[
"Simpson",
"Alex",
""
]
] | Key results from the literature pertaining to a class of nonsingular black hole mimickers are explored. The family of candidate spacetimes is for now labelled the `black-bounce' family, stemming from the original so-called `Simpson--Visser' spacetime in static spherical symmetry. All model geometries are analysed through the lens of standard general relativity, are globally free from curvature singularities, pass all weak-field observational tests, and smoothly interpolate between regular black holes and traversable wormholes. The discourse is segregated along geometrical lines, with candidate spacetimes each belonging to one of: static spherical symmetry, spherical symmetry with dynamics, and stationary axisymmetry. |
gr-qc/0511067 | J. Ponce de Leon | J. Ponce de Leon | Reinventing spacetime on a dynamical hypersurface | References added to the Introduction, and Abstract modified. Accepted
for publication in Mod. Phys. Lett. A | Mod. Phys. Lett. A, Vol. 21, No. 12 (2006) pp. 947-959. | 10.1142/S0217732306020214 | null | gr-qc | null | In braneworld models, Space-Time-Matter and other Kaluza-Klein theories, our
spacetime is devised as a four-dimensional hypersurface {\it orthogonal} to the
extra dimension in a five-dimensional bulk. We show that the FRW line element
can be "reinvented" on a dynamical four-dimensional hypersurface, which is {\it
not} orthogonal to the extra dimension, without any internal contradiction.
This hypersurface is selected by the requirement of continuity of the metric
and depends explicitly on the evolution of the extra dimension. The main
difference between the "conventional" FRW, on an orthogonal hypersurface, and
the new one is that the later contains higher-dimensional modifications to the
regular matter density and pressure in 4D. We compare the evolution of the
spacetime in these two interpretations. We find that a wealth of "new" physics
can be derived from a five-dimensional metric if it is interpreted on a
dynamical (non-orthogonal) 4D hypersurface. In particular, in the context of a
well-known cosmological metric in $5D$, we construct a FRW model which is
consistent with the late accelerated expansion of the universe, while fitting
simultaneously the observational data for the deceleration parameter. The model
predicts an effective equation of state for the universe, which is consistent
with observations.
| [
{
"created": "Sun, 13 Nov 2005 00:02:40 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Mar 2006 12:04:54 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"de Leon",
"J. Ponce",
""
]
] | In braneworld models, Space-Time-Matter and other Kaluza-Klein theories, our spacetime is devised as a four-dimensional hypersurface {\it orthogonal} to the extra dimension in a five-dimensional bulk. We show that the FRW line element can be "reinvented" on a dynamical four-dimensional hypersurface, which is {\it not} orthogonal to the extra dimension, without any internal contradiction. This hypersurface is selected by the requirement of continuity of the metric and depends explicitly on the evolution of the extra dimension. The main difference between the "conventional" FRW, on an orthogonal hypersurface, and the new one is that the later contains higher-dimensional modifications to the regular matter density and pressure in 4D. We compare the evolution of the spacetime in these two interpretations. We find that a wealth of "new" physics can be derived from a five-dimensional metric if it is interpreted on a dynamical (non-orthogonal) 4D hypersurface. In particular, in the context of a well-known cosmological metric in $5D$, we construct a FRW model which is consistent with the late accelerated expansion of the universe, while fitting simultaneously the observational data for the deceleration parameter. The model predicts an effective equation of state for the universe, which is consistent with observations. |
2110.05135 | Angelo Tartaglia | Angelo Tartaglia, Massimo Bassan, Giuseppe Pucacco, Valerio Ferroni,
Daniele Vetrugno | Dark gravitomagnetism with LISA and gravitational waves space detectors | 13, 2 figures, to be published in the Proceedings of the 16th Marcel
Grossmann meeting (2021) | null | null | null | gr-qc astro-ph.GA physics.space-ph | http://creativecommons.org/licenses/by/4.0/ | We present here the proposal to use the LISA interferometer for detecting the
gravito-magnetic field due to the rotation of the Milky Way, including the
contribution given by the dark matter halo. The galactic signal would be
superposed to the gravitomagnetic field of the Sun. The technique to be used is
based on the asymmetric propagation of light along the closed contour of the
space interferometer (Sagnac-like approach). Both principle and practical
aspects of the proposed experiment are discussed. The strategy for
disentangling the sought for signal from the kinematic terms due to proper
rotation and orbital motion is based on the time modulation of the time of
flight asymmetry. Such modulation will be originated by the annual oscillation
of the plane of the interferometer with respect to the galactic plane. Also the
effect of the gravitomagnetic field on the polarization of the electromagnetic
signals is presented as an in principle detectable phenomenon.
| [
{
"created": "Mon, 11 Oct 2021 10:28:33 GMT",
"version": "v1"
}
] | 2021-10-12 | [
[
"Tartaglia",
"Angelo",
""
],
[
"Bassan",
"Massimo",
""
],
[
"Pucacco",
"Giuseppe",
""
],
[
"Ferroni",
"Valerio",
""
],
[
"Vetrugno",
"Daniele",
""
]
] | We present here the proposal to use the LISA interferometer for detecting the gravito-magnetic field due to the rotation of the Milky Way, including the contribution given by the dark matter halo. The galactic signal would be superposed to the gravitomagnetic field of the Sun. The technique to be used is based on the asymmetric propagation of light along the closed contour of the space interferometer (Sagnac-like approach). Both principle and practical aspects of the proposed experiment are discussed. The strategy for disentangling the sought for signal from the kinematic terms due to proper rotation and orbital motion is based on the time modulation of the time of flight asymmetry. Such modulation will be originated by the annual oscillation of the plane of the interferometer with respect to the galactic plane. Also the effect of the gravitomagnetic field on the polarization of the electromagnetic signals is presented as an in principle detectable phenomenon. |
2303.16610 | Peng-Cheng Li | Tieguang Zi and Peng-Cheng Li | Probing the Tidal Deformability of the Central Object in an Extreme Mass
Ratio Inspiral with Analytic Kludge Waveforms | 12 pages, 4 figures,v2: minor changes, accepted by PRD | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop approximate ``analytic-kludge" waveforms to describe the inspiral
of a stellar-mass compact object into a supermassive compact object in an
extreme mass ratio inspiral (EMRI) scenario. The deformability of the
supermassive compact object is characterized by a dimensionless quantity called
the tidal Love number (TLN). Our analysis shows that, up to the leading order
of the mass ratio, the conservative dynamics of the EMRI are not affected by
tidal interaction, and the tidal effect is only present in the induced
quadrupole moment. We calculate the energy and angular momentum fluxes and
obtain leading order corrections to the orbital evolution equations. By
comparing the waveforms with and without tidal interaction, we demonstrate that
even a small TLN can produce significant differences in the waveforms, which
can be detected by space-borne detector LISA. Finally, using the Fisher
information matrix method, we perform parameter estimation for the TLN and find
that the precision can reach the level of $10^{-4}$ in suitable scenarios.
| [
{
"created": "Wed, 29 Mar 2023 11:49:18 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Jun 2023 01:44:04 GMT",
"version": "v2"
}
] | 2023-06-22 | [
[
"Zi",
"Tieguang",
""
],
[
"Li",
"Peng-Cheng",
""
]
] | We develop approximate ``analytic-kludge" waveforms to describe the inspiral of a stellar-mass compact object into a supermassive compact object in an extreme mass ratio inspiral (EMRI) scenario. The deformability of the supermassive compact object is characterized by a dimensionless quantity called the tidal Love number (TLN). Our analysis shows that, up to the leading order of the mass ratio, the conservative dynamics of the EMRI are not affected by tidal interaction, and the tidal effect is only present in the induced quadrupole moment. We calculate the energy and angular momentum fluxes and obtain leading order corrections to the orbital evolution equations. By comparing the waveforms with and without tidal interaction, we demonstrate that even a small TLN can produce significant differences in the waveforms, which can be detected by space-borne detector LISA. Finally, using the Fisher information matrix method, we perform parameter estimation for the TLN and find that the precision can reach the level of $10^{-4}$ in suitable scenarios. |
gr-qc/0605147 | Avtar Sehra | Avtar Singh Sehra | Quantum Modified Null Trajectories in Schwarzschild Spacetime | superluminal quantum modified photon propagation | null | null | null | gr-qc | null | The photon vacuum polarization effect in curved spacetime leads to
birefringence, i.e. the photon velocity becomes greater than (or less than) the
speed of light depending on its polarization. We investigate this phenomenon in
a Schwarzschild curved spacetime.
| [
{
"created": "Tue, 30 May 2006 16:32:47 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sehra",
"Avtar Singh",
""
]
] | The photon vacuum polarization effect in curved spacetime leads to birefringence, i.e. the photon velocity becomes greater than (or less than) the speed of light depending on its polarization. We investigate this phenomenon in a Schwarzschild curved spacetime. |
2402.05178 | David Pere\~n\'iguez Dr | David Pere\~niguez, Marina de Amicis, Richard Brito and Rodrigo
Panosso Macedo | Superradiant Instability of Magnetic Black Holes | 5+pages, 4+figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black hole superradiance has proven being very valuable in several realms of
gravitational physics, and holds a promising discovery potential. In this
paper, we show how it can sheed light on a long standing problem in physics,
the quest for magnetic monopoles in the Universe. Placing them in the interior
of primordial rotating black holes, which act as natural amplifiers, we show
that massive charged bosonic fields in their vicinity exhibit a superradiant
instability which surpasses significantly that of neutral Kerr black holes.
Strikingly, this is true for black holes containing an order-one number of
magnetic monopoles, or merely a single one, and possessing either low, moderate
or large values of angular momentum. In particular, the instability is
drastically faster than the radiative decay time of charged pions, thus making
it physically relevant. Furthermore, our analysis identifies the most unstable
modes as a class of monopole spheroidal harmonics, that we dub north and south
monopole modes, whose morphology is markedly different from the usual
superradiantly unstable modes since they extend along the rotational axis. We
conclude by discussing implications of our results for primordial magnetic
black holes, and their observational signatures as sources of cosmic rays and
high-frequency gravitational waves.
| [
{
"created": "Wed, 7 Feb 2024 19:00:03 GMT",
"version": "v1"
}
] | 2024-02-09 | [
[
"Pereñiguez",
"David",
""
],
[
"de Amicis",
"Marina",
""
],
[
"Brito",
"Richard",
""
],
[
"Macedo",
"Rodrigo Panosso",
""
]
] | Black hole superradiance has proven being very valuable in several realms of gravitational physics, and holds a promising discovery potential. In this paper, we show how it can sheed light on a long standing problem in physics, the quest for magnetic monopoles in the Universe. Placing them in the interior of primordial rotating black holes, which act as natural amplifiers, we show that massive charged bosonic fields in their vicinity exhibit a superradiant instability which surpasses significantly that of neutral Kerr black holes. Strikingly, this is true for black holes containing an order-one number of magnetic monopoles, or merely a single one, and possessing either low, moderate or large values of angular momentum. In particular, the instability is drastically faster than the radiative decay time of charged pions, thus making it physically relevant. Furthermore, our analysis identifies the most unstable modes as a class of monopole spheroidal harmonics, that we dub north and south monopole modes, whose morphology is markedly different from the usual superradiantly unstable modes since they extend along the rotational axis. We conclude by discussing implications of our results for primordial magnetic black holes, and their observational signatures as sources of cosmic rays and high-frequency gravitational waves. |
1803.02355 | Alessia Platania | Alfio Bonanno, Alessia Platania and Frank Saueressig | Cosmological bounds on the field content of asymptotically safe
gravity-matter models | 10 pages, 2 figures. V2: references added. Matches published version | null | 10.1016/j.physletb.2018.06.047 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the non-Gaussian fixed points (NGFPs) appearing in the renormalization
group flow of gravity and gravity-matter systems to construct models of
NGFP-driven inflation via a renormalization group improvement scheme. The
cosmological predictions of these models depend sensitively on the
characteristic properties of the NGFPs, including their position and stability
coefficients, which in turn are determined by the field content of the
underlying matter sector. We demonstrate that the NGFPs appearing in
gravity-matter systems where the matter content is close to the one of the
standard model of particle physics are the ones compatible with cosmological
data. Somewhat counterintuitively, the negative fixed point value of the
dimensionless cosmological constant is essential for these findings.
| [
{
"created": "Tue, 6 Mar 2018 19:00:00 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Aug 2018 16:34:07 GMT",
"version": "v2"
}
] | 2018-08-29 | [
[
"Bonanno",
"Alfio",
""
],
[
"Platania",
"Alessia",
""
],
[
"Saueressig",
"Frank",
""
]
] | We use the non-Gaussian fixed points (NGFPs) appearing in the renormalization group flow of gravity and gravity-matter systems to construct models of NGFP-driven inflation via a renormalization group improvement scheme. The cosmological predictions of these models depend sensitively on the characteristic properties of the NGFPs, including their position and stability coefficients, which in turn are determined by the field content of the underlying matter sector. We demonstrate that the NGFPs appearing in gravity-matter systems where the matter content is close to the one of the standard model of particle physics are the ones compatible with cosmological data. Somewhat counterintuitively, the negative fixed point value of the dimensionless cosmological constant is essential for these findings. |
gr-qc/0002037 | Paul Federbush | Paul Federbush (Univ. of Michigan) | On Schwarzschild-Like Solutions in Curvature-Quadratic Gravity | Now 5 explicit solutions! 6 pages LaTeX | null | null | null | gr-qc hep-th | null | Partial results are obtained for Schwarzschild- like solutions in a gravity
theory with action density (-g)^(1/2)[Rik^2+bR^2]. A seven parameter family of
implicit solutions is found. A number of explicit solutions are also exhibited.
| [
{
"created": "Wed, 9 Feb 2000 20:34:21 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Mar 2000 20:43:25 GMT",
"version": "v2"
},
{
"created": "Wed, 15 Mar 2000 13:34:13 GMT",
"version": "v3"
},
{
"created": "Thu, 16 Mar 2000 14:22:27 GMT",
"version": "v4"
},
{
"created": "Fri, 17 Mar 2000 14:59:38 GMT",
"version": "v5"
}
] | 2007-05-23 | [
[
"Federbush",
"Paul",
"",
"Univ. of Michigan"
]
] | Partial results are obtained for Schwarzschild- like solutions in a gravity theory with action density (-g)^(1/2)[Rik^2+bR^2]. A seven parameter family of implicit solutions is found. A number of explicit solutions are also exhibited. |
1006.3788 | Jonathan Thornburg | Jonathan Thornburg | Highly accurate and efficient self-force computations using time-domain
methods: Error estimates, validation, and optimization | 27 pages, 12 eps figures (10 of them color, but all are viewable ok
in black-and-white), uses RevTeX 4.1 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | If a small "particle" of mass $\mu M$ (with $\mu \ll 1$) orbits a
Schwarzschild or Kerr black hole of mass $M$, the particle is subject to an
$\O(\mu)$ radiation-reaction "self-force". Here I argue that it's valuable to
compute this self-force highly accurately (relative error of $\ltsim 10^{-6}$)
and efficiently, and I describe techniques for doing this and for obtaining and
validating error estimates for the computation. I use an
adaptive-mesh-refinement (AMR) time-domain numerical integration of the
perturbation equations in the Barack-Ori mode-sum regularization formalism;
this is efficient, yet allows easy generalization to arbitrary particle orbits.
I focus on the model problem of a scalar particle in a circular geodesic orbit
in Schwarzschild spacetime.
The mode-sum formalism gives the self-force as an infinite sum of regularized
spherical-harmonic modes $\sum_{\ell=0}^\infty F_{\ell,\reg}$, with
$F_{\ell,\reg}$ (and an "internal" error estimate) computed numerically for
$\ell \ltsim 30$ and estimated for larger~$\ell$ by fitting an asymptotic
"tail" series. Here I validate the internal error estimates for the individual
$F_{\ell,\reg}$ using a large set of numerical self-force computations of
widely-varying accuracies. I present numerical evidence that the actual
numerical errors in $F_{\ell,\reg}$ for different~$\ell$ are at most weakly
correlated, so the usual statistical error estimates are valid for computing
the self-force. I show that the tail fit is numerically ill-conditioned, but
this can be mostly alleviated by renormalizing the basis functions to have
similar magnitudes.
Using AMR, fixed mesh refinement, and extended-precision floating-point
arithmetic, I obtain the (contravariant) radial component of the self-force for
a particle in a circular geodesic orbit of areal radius $r = 10M$ to within
$1$~ppm relative error.
| [
{
"created": "Fri, 18 Jun 2010 19:54:32 GMT",
"version": "v1"
}
] | 2010-06-21 | [
[
"Thornburg",
"Jonathan",
""
]
] | If a small "particle" of mass $\mu M$ (with $\mu \ll 1$) orbits a Schwarzschild or Kerr black hole of mass $M$, the particle is subject to an $\O(\mu)$ radiation-reaction "self-force". Here I argue that it's valuable to compute this self-force highly accurately (relative error of $\ltsim 10^{-6}$) and efficiently, and I describe techniques for doing this and for obtaining and validating error estimates for the computation. I use an adaptive-mesh-refinement (AMR) time-domain numerical integration of the perturbation equations in the Barack-Ori mode-sum regularization formalism; this is efficient, yet allows easy generalization to arbitrary particle orbits. I focus on the model problem of a scalar particle in a circular geodesic orbit in Schwarzschild spacetime. The mode-sum formalism gives the self-force as an infinite sum of regularized spherical-harmonic modes $\sum_{\ell=0}^\infty F_{\ell,\reg}$, with $F_{\ell,\reg}$ (and an "internal" error estimate) computed numerically for $\ell \ltsim 30$ and estimated for larger~$\ell$ by fitting an asymptotic "tail" series. Here I validate the internal error estimates for the individual $F_{\ell,\reg}$ using a large set of numerical self-force computations of widely-varying accuracies. I present numerical evidence that the actual numerical errors in $F_{\ell,\reg}$ for different~$\ell$ are at most weakly correlated, so the usual statistical error estimates are valid for computing the self-force. I show that the tail fit is numerically ill-conditioned, but this can be mostly alleviated by renormalizing the basis functions to have similar magnitudes. Using AMR, fixed mesh refinement, and extended-precision floating-point arithmetic, I obtain the (contravariant) radial component of the self-force for a particle in a circular geodesic orbit of areal radius $r = 10M$ to within $1$~ppm relative error. |
0811.2237 | Aleksandar Rakic | Aleksandar Rakic and Dominik J. Schwarz | Newtonian Aspects of General Relativistic Galaxy Models | 7 pages, no figures, talk given at the XV National Conference of
Astronomers of Serbia, Belgrade, 2-5 October 2008 | null | null | BI-TP 2008/37 | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Many cosmological observations call for the existence of dark matter. The
most direct evidence for dark matter is inferred from the measured flatness of
galactic rotation curves. The latter is based on Newtonian gravity. Alternative
approaches to the rotation curve problem by means of general relativity have
recently been put forward. The class of models of interest is a subset of the
axially symmetric and stationary solutions of Einstein's equations with
rotating dust. As a step toward the understanding of general relativistic
galaxy models, we analyse rigidly as well as non-rigidly rotating
(Post-)Newtonian spacetimes. We find that the Newtonian limit of the considered
general relativistic galaxy model leads to Post-Newtonian terms in the metric.
| [
{
"created": "Thu, 13 Nov 2008 23:28:48 GMT",
"version": "v1"
}
] | 2008-11-19 | [
[
"Rakic",
"Aleksandar",
""
],
[
"Schwarz",
"Dominik J.",
""
]
] | Many cosmological observations call for the existence of dark matter. The most direct evidence for dark matter is inferred from the measured flatness of galactic rotation curves. The latter is based on Newtonian gravity. Alternative approaches to the rotation curve problem by means of general relativity have recently been put forward. The class of models of interest is a subset of the axially symmetric and stationary solutions of Einstein's equations with rotating dust. As a step toward the understanding of general relativistic galaxy models, we analyse rigidly as well as non-rigidly rotating (Post-)Newtonian spacetimes. We find that the Newtonian limit of the considered general relativistic galaxy model leads to Post-Newtonian terms in the metric. |
1409.3573 | Ippocratis Saltas Dr | Antonio Padilla and Ippocratis D. Saltas | A note on classical and quantum unimodular gravity | 5 pages; v2: Some clarifying comments added. Version to appear in
European Physical Journal C | null | 10.1140/epjc/s10052-015-3767-0 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss unimodular gravity at a classical level, and in terms of its
extension into the UV through an appropriate path integral representation.
Classically, unimodular gravity is simply a gauge fixed version of General
Relativity (GR), and as such it yields identical dynamics and physical
predictions. We clarify this and explain why there is no sense in which it can
"bring a new perspective" to the cosmological constant problem. The quantum
equivalence between unimodular gravity and GR is more of a subtle question, but
we present an argument that suggests one can always maintain the equivalence up
to arbitrarily high momenta. As a corollary to this, we argue that whenever
inequivalence is seen at the quantum level, that just means we have defined two
different quantum theories that happen to share a classical limit.
| [
{
"created": "Thu, 11 Sep 2014 20:00:06 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Nov 2015 01:19:35 GMT",
"version": "v2"
}
] | 2016-01-20 | [
[
"Padilla",
"Antonio",
""
],
[
"Saltas",
"Ippocratis D.",
""
]
] | We discuss unimodular gravity at a classical level, and in terms of its extension into the UV through an appropriate path integral representation. Classically, unimodular gravity is simply a gauge fixed version of General Relativity (GR), and as such it yields identical dynamics and physical predictions. We clarify this and explain why there is no sense in which it can "bring a new perspective" to the cosmological constant problem. The quantum equivalence between unimodular gravity and GR is more of a subtle question, but we present an argument that suggests one can always maintain the equivalence up to arbitrarily high momenta. As a corollary to this, we argue that whenever inequivalence is seen at the quantum level, that just means we have defined two different quantum theories that happen to share a classical limit. |
2004.05632 | Yerko V\'asquez | Almendra Arag\'on, Ram\'on B\'ecar, P. A. Gonz\'alez and Yerko
V\'asquez | Perturbative and nonperturbative quasinormal modes of 4D
Einstein-Gauss-Bonnet black holes | accepted for publication in EPJC | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the propagation of probe scalar fields in the background of 4D
Einstein-Gauss-Bonnet black holes with anti-de Sitter (AdS) asymptotics and
calculate the quasinormal modes. Mainly, we show that the quasinormal spectrum
consists of two different branches, a branch perturbative in the Gauss-Bonnet
coupling constant $\alpha$ and another branch nonperturbative in $\alpha$. The
perturbative branch consists of complex quasinormal frequencies that
approximate to the quasinormal frequencies of the Schwarzschild AdS black hole
in the limit of a null coupling constant. On the other hand, the
nonperturbative branch consists of purely imaginary frequencies and is
characterized by the growth of the imaginary part when $\alpha$ decreases,
diverging in the limit of null coupling constant, therefore they do not exist
for the Schwarzschild AdS black hole. Also, we find that the imaginary part of
the quasinormal frequencies is always negative for both branches; therefore,
the propagation of scalar fields is stable in this background.
| [
{
"created": "Sun, 12 Apr 2020 15:22:07 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Apr 2020 01:07:58 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Jul 2020 19:42:20 GMT",
"version": "v3"
}
] | 2020-07-31 | [
[
"Aragón",
"Almendra",
""
],
[
"Bécar",
"Ramón",
""
],
[
"González",
"P. A.",
""
],
[
"Vásquez",
"Yerko",
""
]
] | We study the propagation of probe scalar fields in the background of 4D Einstein-Gauss-Bonnet black holes with anti-de Sitter (AdS) asymptotics and calculate the quasinormal modes. Mainly, we show that the quasinormal spectrum consists of two different branches, a branch perturbative in the Gauss-Bonnet coupling constant $\alpha$ and another branch nonperturbative in $\alpha$. The perturbative branch consists of complex quasinormal frequencies that approximate to the quasinormal frequencies of the Schwarzschild AdS black hole in the limit of a null coupling constant. On the other hand, the nonperturbative branch consists of purely imaginary frequencies and is characterized by the growth of the imaginary part when $\alpha$ decreases, diverging in the limit of null coupling constant, therefore they do not exist for the Schwarzschild AdS black hole. Also, we find that the imaginary part of the quasinormal frequencies is always negative for both branches; therefore, the propagation of scalar fields is stable in this background. |
gr-qc/0201092 | Edward Anderson | Edward Anderson and Julian Barbour | Interacting vector fields in Relativity without Relativity | Replaced with final version accepted by Classical and Quantum Gravity
(14 pages, no figures) | Class.Quant.Grav. 19 (2002) 3249-3262 | 10.1088/0264-9381/19/12/309 | null | gr-qc | null | Barbour, Foster and \'{O} Murchadha have recently developed a new framework,
called here {\it{the 3-space approach}}, for the formulation of classical
bosonic dynamics. Neither time nor a locally Minkowskian structure of spacetime
are presupposed. Both arise as emergent features of the world from
geodesic-type dynamics on a space of 3-dimensional metric--matter
configurations. In fact gravity, the universal light cone and Abelian gauge
theory minimally coupled to gravity all arise naturally through a single common
mechanism. It yields relativity -- and more -- without presupposing relativity.
This paper completes the recovery of the presently known bosonic sector within
the 3-space approach. We show, for a rather general ansatz, that 3-vector
fields can interact among themselves only as Yang--Mills fields minimally
coupled to gravity.
| [
{
"created": "Tue, 29 Jan 2002 19:34:44 GMT",
"version": "v1"
},
{
"created": "Tue, 28 May 2002 16:30:56 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Anderson",
"Edward",
""
],
[
"Barbour",
"Julian",
""
]
] | Barbour, Foster and \'{O} Murchadha have recently developed a new framework, called here {\it{the 3-space approach}}, for the formulation of classical bosonic dynamics. Neither time nor a locally Minkowskian structure of spacetime are presupposed. Both arise as emergent features of the world from geodesic-type dynamics on a space of 3-dimensional metric--matter configurations. In fact gravity, the universal light cone and Abelian gauge theory minimally coupled to gravity all arise naturally through a single common mechanism. It yields relativity -- and more -- without presupposing relativity. This paper completes the recovery of the presently known bosonic sector within the 3-space approach. We show, for a rather general ansatz, that 3-vector fields can interact among themselves only as Yang--Mills fields minimally coupled to gravity. |
1502.05695 | David W. Tian | David Wenjie Tian, Ivan Booth | Lovelock-Brans-Dicke gravity | RevTex 13 pages. Minor changes are made to match the version
published in Classical and Quantum Gravity | Class. Quantum Grav. 33 (2016), 045001 | 10.1088/0264-9381/33/4/045001 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | According to Lovelock's theorem, the Hilbert-Einstein and the Lovelock
actions are indistinguishable from their field equations. However, they have
different scalar-tensor counterparts, which correspond to the Brans-Dicke and
the \emph{Lovelock-Brans-Dicke} (LBD) gravities, respectively. In this paper
the LBD model of alternative gravity with the Lagrangian density
$\mathscr{L}_{\text{LBD}}=\frac{1}{16\pi}\left[\phi\left( R
+\frac{a}{\sqrt{-g}}{}^*RR +
b\mathcal{G}\right)-\frac{\omega_{\text{L}}}{\phi}\nabla_\alpha \phi
\nabla^\alpha\phi \right]$ is developed, where ${}^*RR$ and $\mathcal{G}$
respectively denote the topological Chern-Pontryagin and Gauss-Bonnet
invariants. The field equation, the kinematical and dynamical wave equations,
and the constraint from energy-momentum conservation are all derived. It is
shown that, the LBD gravity reduces to general relativity in the limit
$\omega_{\text{L}}\to\infty$ unless the "topological balance condition" holds,
and in vacuum it can be conformally transformed into the dynamical Chern-Simons
gravity and the generalized Gauss-Bonnet dark energy with Horndeski-like or
Galileon-like kinetics. Moreover, the LBD gravity allows for the late-time
cosmic acceleration without dark energy. Finally, the LBD gravity is
generalized into the Lovelock-scalar-tensor gravity, and its equivalence to
fourth-order modified gravities is established. It is also emphasized that the
standard expressions for the contributions of generalized Gauss-Bonnet
dependence can be further simplified.
| [
{
"created": "Thu, 19 Feb 2015 20:42:25 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Mar 2015 19:43:54 GMT",
"version": "v2"
},
{
"created": "Mon, 27 Jul 2015 19:16:55 GMT",
"version": "v3"
},
{
"created": "Thu, 21 Jan 2016 17:55:42 GMT",
"version": "v4"
}
] | 2016-01-25 | [
[
"Tian",
"David Wenjie",
""
],
[
"Booth",
"Ivan",
""
]
] | According to Lovelock's theorem, the Hilbert-Einstein and the Lovelock actions are indistinguishable from their field equations. However, they have different scalar-tensor counterparts, which correspond to the Brans-Dicke and the \emph{Lovelock-Brans-Dicke} (LBD) gravities, respectively. In this paper the LBD model of alternative gravity with the Lagrangian density $\mathscr{L}_{\text{LBD}}=\frac{1}{16\pi}\left[\phi\left( R +\frac{a}{\sqrt{-g}}{}^*RR + b\mathcal{G}\right)-\frac{\omega_{\text{L}}}{\phi}\nabla_\alpha \phi \nabla^\alpha\phi \right]$ is developed, where ${}^*RR$ and $\mathcal{G}$ respectively denote the topological Chern-Pontryagin and Gauss-Bonnet invariants. The field equation, the kinematical and dynamical wave equations, and the constraint from energy-momentum conservation are all derived. It is shown that, the LBD gravity reduces to general relativity in the limit $\omega_{\text{L}}\to\infty$ unless the "topological balance condition" holds, and in vacuum it can be conformally transformed into the dynamical Chern-Simons gravity and the generalized Gauss-Bonnet dark energy with Horndeski-like or Galileon-like kinetics. Moreover, the LBD gravity allows for the late-time cosmic acceleration without dark energy. Finally, the LBD gravity is generalized into the Lovelock-scalar-tensor gravity, and its equivalence to fourth-order modified gravities is established. It is also emphasized that the standard expressions for the contributions of generalized Gauss-Bonnet dependence can be further simplified. |
2311.05352 | Jie Jiang | Hu Zhu and Jie Jiang | Generalized Covariant Entropy Bound in Einstein Gravity with Quadratic
Curvature Corrections | 7 pages | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | We explore the generalized covariant entropy bound in the theory where
Einstein gravity is perturbed by quadratic curvature terms, which can be viewed
as the first-order quantum correction to Einstein gravity. By replacing the
Bekenstein-Hawking entropy with the holographic entanglement entropy of this
theory and introducing two reasonable physical assumptions, we demonstrate that
the corresponding Generalized Covariant Entropy Bound is satisfied under a
first-order approximation of the perturbation from the quadratic curvature
terms. Our findings suggest that the entropy bound and the Generalized Second
Law of black holes are satisfied in the Einstein gravity under the first-order
perturbation from the quadratic curvature corrections, and they also imply that
the generalized covariant entropy bound may still hold even after considering
the quantum correction of gravity, but in this case, we may need to use
holographic entanglement entropy as the formula for gravitational entropy.
| [
{
"created": "Thu, 9 Nov 2023 13:24:12 GMT",
"version": "v1"
}
] | 2023-11-10 | [
[
"Zhu",
"Hu",
""
],
[
"Jiang",
"Jie",
""
]
] | We explore the generalized covariant entropy bound in the theory where Einstein gravity is perturbed by quadratic curvature terms, which can be viewed as the first-order quantum correction to Einstein gravity. By replacing the Bekenstein-Hawking entropy with the holographic entanglement entropy of this theory and introducing two reasonable physical assumptions, we demonstrate that the corresponding Generalized Covariant Entropy Bound is satisfied under a first-order approximation of the perturbation from the quadratic curvature terms. Our findings suggest that the entropy bound and the Generalized Second Law of black holes are satisfied in the Einstein gravity under the first-order perturbation from the quadratic curvature corrections, and they also imply that the generalized covariant entropy bound may still hold even after considering the quantum correction of gravity, but in this case, we may need to use holographic entanglement entropy as the formula for gravitational entropy. |
1109.2551 | Sigbjorn Hervik | Sigbjorn Hervik | A spacetime not characterised by its invariants is of aligned type II | 14pages, CQG to appear | Class. Quantum Grav. 28 (2011) 215009 | 10.1088/0264-9381/28/21/215009 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By using invariant theory we show that a (higher-dimensional) Lorentzian
metric that is not characterised by its invariants must be of aligned type II;
i.e., there exists a frame such that all the curvature tensors are
simultaneously of type II. This implies, using the boost-weight decomposition,
that for such a metric there exists a frame such that all positive boost-weight
components are zero. Indeed, we show a more general result, namely that any set
of tensors which is not characterised by its invariants, must be of aligned
type II. This result enables us to prove a number of related results, among
them the algebraic VSI conjecture.
| [
{
"created": "Mon, 12 Sep 2011 18:05:38 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Hervik",
"Sigbjorn",
""
]
] | By using invariant theory we show that a (higher-dimensional) Lorentzian metric that is not characterised by its invariants must be of aligned type II; i.e., there exists a frame such that all the curvature tensors are simultaneously of type II. This implies, using the boost-weight decomposition, that for such a metric there exists a frame such that all positive boost-weight components are zero. Indeed, we show a more general result, namely that any set of tensors which is not characterised by its invariants, must be of aligned type II. This result enables us to prove a number of related results, among them the algebraic VSI conjecture. |
1005.2600 | Israel Quiros | Israel Quiros, Eduardo Teste | Vacuum Structure of Cosmologically Viable Quadratic Modifications of
Gravity that are Functions of the Gauss-Bonnet Invariant | 10 pages, Latex, no figures. Discussion made more clear through the
use of new field variables. Several misprints and minor errors corrected.
References added. An error in an equation of a model of section V.C,
originated from a missprint in Ref. [19], corrected. Corresponding
computations and original comments replaced. Minor numerical misprints
corrected. Results unchanged | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a thorough study of the theoretical consistency of recently
proposed, viable, quadratic modifications of gravity that are functions of the
the Gauss-Bonnet invariant, regarding the stability of their perturbations
around vacuum, maximally symmetric spaces of constant curvature. We pay special
attention, in particular, to the investigation of pathological instabilities
associated with the occurrence of propagating spin-0 tachyon modes, and with
the development of a graviton ghost. The latter effect is associated with the
known "Ricci stability" issue, well studied in $f(R)$-theories. Within
quadratic modifications of gravity it is discussed for the first time. Special
attention is paid to the requirement of non-negativity of the effective
gravitational coupling, which warrants that the graviton is not a negative-norm
state. It is demonstrated that, several theories that pass the cosmological as
well as the solar system tests, have to be rule out on the basis of the
unavoidable character of these pathological instabilities.
| [
{
"created": "Fri, 14 May 2010 18:41:52 GMT",
"version": "v1"
},
{
"created": "Wed, 19 May 2010 20:12:17 GMT",
"version": "v2"
},
{
"created": "Fri, 21 May 2010 15:11:52 GMT",
"version": "v3"
},
{
"created": "Wed, 26 May 2010 17:05:32 GMT",
"version": "v4"
}
] | 2010-05-27 | [
[
"Quiros",
"Israel",
""
],
[
"Teste",
"Eduardo",
""
]
] | We perform a thorough study of the theoretical consistency of recently proposed, viable, quadratic modifications of gravity that are functions of the the Gauss-Bonnet invariant, regarding the stability of their perturbations around vacuum, maximally symmetric spaces of constant curvature. We pay special attention, in particular, to the investigation of pathological instabilities associated with the occurrence of propagating spin-0 tachyon modes, and with the development of a graviton ghost. The latter effect is associated with the known "Ricci stability" issue, well studied in $f(R)$-theories. Within quadratic modifications of gravity it is discussed for the first time. Special attention is paid to the requirement of non-negativity of the effective gravitational coupling, which warrants that the graviton is not a negative-norm state. It is demonstrated that, several theories that pass the cosmological as well as the solar system tests, have to be rule out on the basis of the unavoidable character of these pathological instabilities. |
2406.02101 | Xuefeng Feng | Xuefeng Feng, Huan Yang | Universal gravitational self-force for a point mass orbiting around a
compact star | 18 pages, 13 figures, 1 table, Comments are welcome | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we study the gravitational back-reaction (i.e., the
"self-force") of a point mass moving around a non-rotating, compact star on a
circular orbit. We find that the additional self-force, comparing with the case
with a point mass orbiting around a Schwarzschild black hole, can be well
characterized by an universal frequency-dependent function multiplied by the
(dynamical) tidal deformability of the compact star. This finding provides the
foundation for building the waveform model for an extreme mass-ratio inspiral
system around a star-like black hole mimicker, which is relevant for testing
General Relativity and exotic compact objects with space-borne gravitational
wave detectors.
| [
{
"created": "Tue, 4 Jun 2024 08:32:19 GMT",
"version": "v1"
}
] | 2024-06-05 | [
[
"Feng",
"Xuefeng",
""
],
[
"Yang",
"Huan",
""
]
] | In this work, we study the gravitational back-reaction (i.e., the "self-force") of a point mass moving around a non-rotating, compact star on a circular orbit. We find that the additional self-force, comparing with the case with a point mass orbiting around a Schwarzschild black hole, can be well characterized by an universal frequency-dependent function multiplied by the (dynamical) tidal deformability of the compact star. This finding provides the foundation for building the waveform model for an extreme mass-ratio inspiral system around a star-like black hole mimicker, which is relevant for testing General Relativity and exotic compact objects with space-borne gravitational wave detectors. |
2305.18048 | Diganta Bandopadhyay | Diganta Bandopadhyay and Christopher J. Moore | LISA stellar-mass black hole searches with semicoherent and
particle-swarm methods | 15 pages + appendices, 9 figures. Accepted in Physical Review D on 8
September 2023 | Phys. Rev. D 108, 084014 (2023) | 10.1103/PhysRevD.108.084014 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper considers the problem of searching for quiet, long-duration and
broadband gravitational wave signals, such as stellar-mass binary black hole
binaries, in mock LISA data. We propose a method that combines a semi-coherent
likelihood with the use of a particle swarm optimizer capable of efficiently
exploring a large parameter space. The semi-coherent analysis is used to widen
the peak of the likelihood distribution over parameter space, congealing
secondary peaks and thereby assisting in localizing the posterior bulk. An
iterative strategy is proposed, using particle swarm methods to initially
explore a wide, loosely-coherent likelihood and then progressively constraining
the signal to smaller regions in parameter space by increasing the level of
coherence. The properties of the semi-coherent likelihood are first
demonstrated using the well-studied binary neutron star signal GW170817. As a
proof of concept, the method is then successfully applied to a simplified
search for a stellar-mass binary black hole in zero-noise LISA data. Finally,
we conclude by discussing what remains to be done to develop this into a
fully-capable search and how the method might also be adapted to tackle the
EMRI search problem in LISA.
| [
{
"created": "Mon, 29 May 2023 12:26:49 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Oct 2023 14:25:28 GMT",
"version": "v2"
}
] | 2023-10-17 | [
[
"Bandopadhyay",
"Diganta",
""
],
[
"Moore",
"Christopher J.",
""
]
] | This paper considers the problem of searching for quiet, long-duration and broadband gravitational wave signals, such as stellar-mass binary black hole binaries, in mock LISA data. We propose a method that combines a semi-coherent likelihood with the use of a particle swarm optimizer capable of efficiently exploring a large parameter space. The semi-coherent analysis is used to widen the peak of the likelihood distribution over parameter space, congealing secondary peaks and thereby assisting in localizing the posterior bulk. An iterative strategy is proposed, using particle swarm methods to initially explore a wide, loosely-coherent likelihood and then progressively constraining the signal to smaller regions in parameter space by increasing the level of coherence. The properties of the semi-coherent likelihood are first demonstrated using the well-studied binary neutron star signal GW170817. As a proof of concept, the method is then successfully applied to a simplified search for a stellar-mass binary black hole in zero-noise LISA data. Finally, we conclude by discussing what remains to be done to develop this into a fully-capable search and how the method might also be adapted to tackle the EMRI search problem in LISA. |
gr-qc/0007002 | Jizong Lu | Xin-zhou Li and Jizong Lu | Global monopoles in the Brans-Dicke theory | Latex 6 pages, To be published in Phys. Rev. D | Phys.Rev. D62 (2000) 107501 | 10.1103/PhysRevD.62.107501 | null | gr-qc | null | A gravitating global monopole produces a repulsive grativational field
outside the core in addition to a solid angular deficit in the Brans-Dicke
theory. As a new feature, the angular deficit is dependent on the values of
\phi_{\infty} and \omega, where \phi_{\infty} is asymptotic value of scalar
field in space-like infinity and \omega is the Brans-Dicke parameter.
| [
{
"created": "Mon, 3 Jul 2000 02:59:38 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Li",
"Xin-zhou",
""
],
[
"Lu",
"Jizong",
""
]
] | A gravitating global monopole produces a repulsive grativational field outside the core in addition to a solid angular deficit in the Brans-Dicke theory. As a new feature, the angular deficit is dependent on the values of \phi_{\infty} and \omega, where \phi_{\infty} is asymptotic value of scalar field in space-like infinity and \omega is the Brans-Dicke parameter. |
1806.09333 | George Pappas Dr | Kostas Glampedakis and George Pappas | The modification of photon trapping orbits as a diagnostic of non-Kerr
spacetimes | 27 pages, 19 figures, changes and expanded discussion on several
topics, such as the off-equatorial photon rings and the loss of low
inclination photon trapping orbits, after the feedback from the referees | Phys. Rev. D 99, 124041 (2019) | 10.1103/PhysRevD.99.124041 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Photon circular orbits, an extreme case of light deflection, are among the
hallmarks of black holes and are known to play a central role in a variety of
phenomena related to these extreme objects. The very existence of such orbits
when motion is not confined in the equatorial plane, i.e. spherical orbits, is
indeed a special property of the separable Kerr metric and may not occur, for
instance, in the spacetime of other more speculative ultracompact objects. In
this paper we consider a general stationary-axisymmetric spacetime and examine
under what circumstances spherical or more general, variable-radius,
`spheroidal' non-equatorial photon orbits may exist with the ultimate goal of
using the modifications -- or even loss -- of photon trapping orbits as a
telltale of non-Kerr physics. In addressing this issue, we first derive a
general necessary condition for the existence of spherical/spheroidal orbits
and then go on to study photon trapping orbits in a variety of known non-Kerr
metrics (Johannsen, Johanssen-Psaltis, and Hartle-Thorne). The first of these
is an example of a separable spacetime which supports Kerr-like spherical
photon orbits. A more detailed analysis reveals a deeper connection between the
presence of spherical orbits and the separability of a metric (that is, the
existence of a third integral of motion). Specifically, a spacetime that does
not admit spherical orbits in any coordinates is necessarily non-separable. The
other two spacetimes considered here exhibit a clear non-Kerr behaviour by
having spherical photon orbits replaced by spheroidal ones. More importantly,
subject to the degree of deviation from Kerr, equatorial photon rings give
place to non-equatorial ones with an accompanying loss of low-inclination
spheroidal orbits. The implications of these results for the electromagnetic
and gravitational wave signature of non-Kerr objects are briefly discussed.
| [
{
"created": "Mon, 25 Jun 2018 09:01:55 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Apr 2019 15:03:05 GMT",
"version": "v2"
}
] | 2019-06-28 | [
[
"Glampedakis",
"Kostas",
""
],
[
"Pappas",
"George",
""
]
] | Photon circular orbits, an extreme case of light deflection, are among the hallmarks of black holes and are known to play a central role in a variety of phenomena related to these extreme objects. The very existence of such orbits when motion is not confined in the equatorial plane, i.e. spherical orbits, is indeed a special property of the separable Kerr metric and may not occur, for instance, in the spacetime of other more speculative ultracompact objects. In this paper we consider a general stationary-axisymmetric spacetime and examine under what circumstances spherical or more general, variable-radius, `spheroidal' non-equatorial photon orbits may exist with the ultimate goal of using the modifications -- or even loss -- of photon trapping orbits as a telltale of non-Kerr physics. In addressing this issue, we first derive a general necessary condition for the existence of spherical/spheroidal orbits and then go on to study photon trapping orbits in a variety of known non-Kerr metrics (Johannsen, Johanssen-Psaltis, and Hartle-Thorne). The first of these is an example of a separable spacetime which supports Kerr-like spherical photon orbits. A more detailed analysis reveals a deeper connection between the presence of spherical orbits and the separability of a metric (that is, the existence of a third integral of motion). Specifically, a spacetime that does not admit spherical orbits in any coordinates is necessarily non-separable. The other two spacetimes considered here exhibit a clear non-Kerr behaviour by having spherical photon orbits replaced by spheroidal ones. More importantly, subject to the degree of deviation from Kerr, equatorial photon rings give place to non-equatorial ones with an accompanying loss of low-inclination spheroidal orbits. The implications of these results for the electromagnetic and gravitational wave signature of non-Kerr objects are briefly discussed. |
0808.1035 | L. A. Glinka | L. A. Glinka | Global One-Dimensionality conjecture within Quantum General Relativity | 16 pages, no figures, to appear in Gravitation and Cosmology | Grav. Cosmol.16:7-15,2010 | 10.1134/S0202289310010020 | null | gr-qc hep-th math-ph math.MP quant-ph | http://creativecommons.org/licenses/by/3.0/ | The simple quantum gravity model, based on a new conjecture within the
canonically quantized 3+1 general relativity, is presented. The conjecture
states that matter fields are functionals of an embedding volume form only, and
reduces the quantum geometrodynamics. By dimensional reduction the resulting
theory is presented in the form of the Dirac equation, and application of the
Fock quantization with the diagonalization procedure yields construction of the
appropriate quantum field theory. The 1D wave function is derived, the
corresponding 3-dimensional manifolds are discussed, and physical scales are
associated with quantum correlations.
| [
{
"created": "Thu, 7 Aug 2008 18:48:08 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Aug 2008 09:46:31 GMT",
"version": "v2"
},
{
"created": "Sun, 24 Aug 2008 18:35:17 GMT",
"version": "v3"
},
{
"created": "Tue, 26 Aug 2008 12:14:52 GMT",
"version": "v4"
},
{
"created": "Tue, 30 Sep 2008 13:13:47 GMT",
"version": "v5"
},
{
"created": "Wed, 17 Jun 2009 08:06:40 GMT",
"version": "v6"
},
{
"created": "Wed, 17 Jun 2009 20:28:48 GMT",
"version": "v7"
}
] | 2010-05-27 | [
[
"Glinka",
"L. A.",
""
]
] | The simple quantum gravity model, based on a new conjecture within the canonically quantized 3+1 general relativity, is presented. The conjecture states that matter fields are functionals of an embedding volume form only, and reduces the quantum geometrodynamics. By dimensional reduction the resulting theory is presented in the form of the Dirac equation, and application of the Fock quantization with the diagonalization procedure yields construction of the appropriate quantum field theory. The 1D wave function is derived, the corresponding 3-dimensional manifolds are discussed, and physical scales are associated with quantum correlations. |
1310.7985 | Benjamin K Tippett | Benjamin K. Tippett, David Tsang | Traversable Achronal Retrograde Domains In Spacetime | 8 pages, If the contents of this are too technical for you visit
arXiv:1310.7983 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There are many spacetime geometries in general relativity which contain
closed timelike curves. A layperson might say that retrograde time travel is
possible in such spacetimes. To date no one has discovered a spacetime geometry
which emulates what a layperson would describe as a time machine.
The purpose of this paper is to propose such a space-time geometry. In our
geometry, a bubble of curvature travels along a closed trajectory. The inside
of the bubble is Rindler spacetime, and the exterior is Minkowski spacetime.
Accelerating observers inside of the bubble travel along closed timelike
curves. The walls of the bubble are generated with matter which violates the
classical energy conditions. We refer to such a bubble as a Traversable
Achronal Retrograde Domain In Spacetime.
| [
{
"created": "Tue, 29 Oct 2013 23:50:29 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Nov 2013 21:29:35 GMT",
"version": "v2"
}
] | 2013-11-06 | [
[
"Tippett",
"Benjamin K.",
""
],
[
"Tsang",
"David",
""
]
] | There are many spacetime geometries in general relativity which contain closed timelike curves. A layperson might say that retrograde time travel is possible in such spacetimes. To date no one has discovered a spacetime geometry which emulates what a layperson would describe as a time machine. The purpose of this paper is to propose such a space-time geometry. In our geometry, a bubble of curvature travels along a closed trajectory. The inside of the bubble is Rindler spacetime, and the exterior is Minkowski spacetime. Accelerating observers inside of the bubble travel along closed timelike curves. The walls of the bubble are generated with matter which violates the classical energy conditions. We refer to such a bubble as a Traversable Achronal Retrograde Domain In Spacetime. |
1202.5146 | Chongoh Lee | Chong Oh Lee | The holographic superconductors in higher-dimensional AdS soliton | LaTeX, 16 pages, 5 figures, typos corrected, one reference added,
version to appear in European Physical Journal C | null | 10.1140/epjc/s10052-012-2092-0 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | We explore the behaviors of the holographic superconductors at zero
temperature for a charged scalar field coupled to a Maxwell field in
higher-dimensional AdS soliton spacetime via analytical way. In the probe
limit, we obtain the critical chemical potentials increase linearly as a total
dimension $d$ grows up. We find that the critical exponent for condensation
operator is obtained as 1/2 independently of $d$, and the charge density is
linearly related to the chemical potential near the critical point.
Furthermore, we consider a slightly generalized setup the
Einstein-Power-Maxwell field theory, and find that the critical exponent for
condensation operator is given as $1/(4-2n)$ in terms of a power parameter $n$
of the Power-Maxwell field, and the charge density is proportional to the
chemical potential to the power of $1/(2-n)$.
| [
{
"created": "Thu, 23 Feb 2012 10:39:43 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Jul 2012 10:15:51 GMT",
"version": "v2"
},
{
"created": "Mon, 30 Jul 2012 19:23:46 GMT",
"version": "v3"
}
] | 2015-06-04 | [
[
"Lee",
"Chong Oh",
""
]
] | We explore the behaviors of the holographic superconductors at zero temperature for a charged scalar field coupled to a Maxwell field in higher-dimensional AdS soliton spacetime via analytical way. In the probe limit, we obtain the critical chemical potentials increase linearly as a total dimension $d$ grows up. We find that the critical exponent for condensation operator is obtained as 1/2 independently of $d$, and the charge density is linearly related to the chemical potential near the critical point. Furthermore, we consider a slightly generalized setup the Einstein-Power-Maxwell field theory, and find that the critical exponent for condensation operator is given as $1/(4-2n)$ in terms of a power parameter $n$ of the Power-Maxwell field, and the charge density is proportional to the chemical potential to the power of $1/(2-n)$. |
1410.4590 | Jorge Rocha | Rog\'erio Jorge, Ednilton S. de Oliveira and Jorge V. Rocha | Greybody factors for rotating black holes in higher dimensions | 39 pages, 17 figures; v2: updated references and minor corrections,
matches published version | Class. Quantum Grav. 32 (2015) 065008 | 10.1088/0264-9381/32/6/065008 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a thorough study of greybody factors for minimally-coupled scalar
fields propagating on the background of rotating black holes in higher (odd)
dimensions with all angular momenta set equal. For this special case, the
solution enjoys an enhanced symmetry, which translates into the advantageous
feature of being cohomogeneity-1, i.e., these backgrounds depend on a single
radial coordinate. Our analysis contemplates three distinct situations, with
the cosmological constant being zero, positive or negative. Using the technique
of matched asymptotic expansions we compute analytically the greybody factors
in the low-frequency regime, restricting to s-wave scattering. Our formulas
generalize those obtained previously in the literature for the static and
spherically symmetric case, with corrections arising from the change in the
horizon area due to rotation. It is also proven that, for this family of black
holes, the horizon area is a decreasing function of the spin parameter, without
regard of dimensionality and of cosmological constant. Through an improvement
on a calculation specific to the class of small black holes in anti-de Sitter
and not restricted to the usual low-frequency regime, we uncover a rich
structure of the greybody spectrum, more complex than previously reported but
also enjoying a certain degree of universality. We complement our low-frequency
analytic results with numerical computations valid over a wide range of
frequencies and extend them to higher angular momentum quantum numbers,
$\ell>0$. This allows us to probe the superradiant regime that is observed for
corotating wavefunctions. We point out that the maximum amplification factor
for intermediate-size black holes in anti-de Sitter can be surprisingly large.
| [
{
"created": "Thu, 16 Oct 2014 21:09:14 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Mar 2015 23:40:36 GMT",
"version": "v2"
}
] | 2015-03-06 | [
[
"Jorge",
"Rogério",
""
],
[
"de Oliveira",
"Ednilton S.",
""
],
[
"Rocha",
"Jorge V.",
""
]
] | We perform a thorough study of greybody factors for minimally-coupled scalar fields propagating on the background of rotating black holes in higher (odd) dimensions with all angular momenta set equal. For this special case, the solution enjoys an enhanced symmetry, which translates into the advantageous feature of being cohomogeneity-1, i.e., these backgrounds depend on a single radial coordinate. Our analysis contemplates three distinct situations, with the cosmological constant being zero, positive or negative. Using the technique of matched asymptotic expansions we compute analytically the greybody factors in the low-frequency regime, restricting to s-wave scattering. Our formulas generalize those obtained previously in the literature for the static and spherically symmetric case, with corrections arising from the change in the horizon area due to rotation. It is also proven that, for this family of black holes, the horizon area is a decreasing function of the spin parameter, without regard of dimensionality and of cosmological constant. Through an improvement on a calculation specific to the class of small black holes in anti-de Sitter and not restricted to the usual low-frequency regime, we uncover a rich structure of the greybody spectrum, more complex than previously reported but also enjoying a certain degree of universality. We complement our low-frequency analytic results with numerical computations valid over a wide range of frequencies and extend them to higher angular momentum quantum numbers, $\ell>0$. This allows us to probe the superradiant regime that is observed for corotating wavefunctions. We point out that the maximum amplification factor for intermediate-size black holes in anti-de Sitter can be surprisingly large. |
1911.04514 | Alexander Grant | B\'eatrice Bonga, Alexander M. Grant, Kartik Prabhu | Angular momentum at null infinity in Einstein-Maxwell theory | 43 pages; v2: fixed typos, matches published version | Phys. Rev. D 101, 044013 (2020) | 10.1103/PhysRevD.101.044013 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On Minkowski spacetime, the angular momentum flux through null infinity of
Maxwell fields, computed using the stress-energy tensor, depends not only on
the radiative degrees of freedom, but also on the Coulombic parts. However, the
angular momentum also can be computed using other conserved currents associated
with a Killing field, such as the Noether current and the canonical current.
The flux computed using these latter two currents is purely radiative. A
priori, it is not clear which of these is to be considered the true flux of
angular momentum for Maxwell fields. This situation carries over to Maxwell
fields on non-dynamical, asymptotically flat spacetimes for fluxes associated
with the Lorentz symmetries in the asymptotic Bondi-Metzner-Sachs (BMS)
algebra.
We investigate this question of angular momentum flux in the full
Einstein-Maxwell theory. Using the prescription of Wald and Zoupas, we compute
the charges associated with any BMS symmetry on cross-sections of null
infinity. The change of these charges along null infinity then provides a flux.
For Lorentz symmetries, the Maxwell fields contribute an additional term,
compared to the Wald-Zoupas charge in vacuum general relativity, to the charge
on a cross-section. With this additional term, the flux associated with Lorentz
symmetries, e.g., the angular momentum flux, is purely determined by the
radiative degrees of freedom of the gravitational and Maxwell fields. In fact,
the contribution to this flux by the Maxwell fields is given by the radiative
Noether current flux and not by the stress-energy flux.
| [
{
"created": "Mon, 11 Nov 2019 19:00:57 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Feb 2020 16:41:08 GMT",
"version": "v2"
}
] | 2020-02-17 | [
[
"Bonga",
"Béatrice",
""
],
[
"Grant",
"Alexander M.",
""
],
[
"Prabhu",
"Kartik",
""
]
] | On Minkowski spacetime, the angular momentum flux through null infinity of Maxwell fields, computed using the stress-energy tensor, depends not only on the radiative degrees of freedom, but also on the Coulombic parts. However, the angular momentum also can be computed using other conserved currents associated with a Killing field, such as the Noether current and the canonical current. The flux computed using these latter two currents is purely radiative. A priori, it is not clear which of these is to be considered the true flux of angular momentum for Maxwell fields. This situation carries over to Maxwell fields on non-dynamical, asymptotically flat spacetimes for fluxes associated with the Lorentz symmetries in the asymptotic Bondi-Metzner-Sachs (BMS) algebra. We investigate this question of angular momentum flux in the full Einstein-Maxwell theory. Using the prescription of Wald and Zoupas, we compute the charges associated with any BMS symmetry on cross-sections of null infinity. The change of these charges along null infinity then provides a flux. For Lorentz symmetries, the Maxwell fields contribute an additional term, compared to the Wald-Zoupas charge in vacuum general relativity, to the charge on a cross-section. With this additional term, the flux associated with Lorentz symmetries, e.g., the angular momentum flux, is purely determined by the radiative degrees of freedom of the gravitational and Maxwell fields. In fact, the contribution to this flux by the Maxwell fields is given by the radiative Noether current flux and not by the stress-energy flux. |
1605.06617 | Roberto Casadio | R. Casadio, A. Giugno, A. Giusti | Global and Local Horizon Quantum Mechanics | 13 pages, no figures. Added section about GUP and Hawking radiation.
Version accepted in GERG | null | 10.1007/s10714-017-2198-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Horizons are classical causal structures that arise in systems with sharply
defined energy and corresponding gravitational radius. A global gravitational
radius operator can be introduced for a static and spherically symmetric
quantum mechanical matter state by lifting the classical "Hamiltonian"
constraint that relates the gravitational radius to the ADM mass, thus giving
rise to a "horizon wave-function". This minisuperspace-like formalism is shown
here to be able to consistently describe also the local gravitational radius
related to the Misner-Sharp mass function of the quantum source, provided its
energy spectrum is determine by spatially localised modes.
| [
{
"created": "Sat, 21 May 2016 10:17:45 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Jan 2017 08:09:56 GMT",
"version": "v2"
}
] | 2017-02-08 | [
[
"Casadio",
"R.",
""
],
[
"Giugno",
"A.",
""
],
[
"Giusti",
"A.",
""
]
] | Horizons are classical causal structures that arise in systems with sharply defined energy and corresponding gravitational radius. A global gravitational radius operator can be introduced for a static and spherically symmetric quantum mechanical matter state by lifting the classical "Hamiltonian" constraint that relates the gravitational radius to the ADM mass, thus giving rise to a "horizon wave-function". This minisuperspace-like formalism is shown here to be able to consistently describe also the local gravitational radius related to the Misner-Sharp mass function of the quantum source, provided its energy spectrum is determine by spatially localised modes. |
2405.12685 | Crist\'obal Laporte | Jesse Daas, Cristobal Laporte, Frank Saueressig and Tim van Dijk | Rethinking the Effective Field Theory formulation of Gravity | 10 pages. Essay received Honorable Mention at the Gravity Research
Foundation 2024 Awards for Essays on Gravitation. v2: fixed typos and updated
to match published version | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General relativity is highly successful in explaining a wide range of
gravitational phenomena including the gravitational waves emitted by binary
systems and the shadows cast by supermassive black holes. From a modern
perspective the theory is not fundamental though, but constitutes the lowest
order term in an effective field theory description of the gravitational force.
As a consequence, the gravitational dynamics should receive corrections by
higher-derivative terms. This essay discusses structural aspects associated
with these corrections and summarizes their imprint on static, spherically
symmetric geometries. Along these lines, we critically reassess the common
practice of using local field redefinitions in order to simplify the dynamics
at the danger of shifting physics effects into sectors which are beyond the
approximation under consideration.
| [
{
"created": "Tue, 21 May 2024 11:19:51 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jul 2024 07:42:25 GMT",
"version": "v2"
}
] | 2024-07-26 | [
[
"Daas",
"Jesse",
""
],
[
"Laporte",
"Cristobal",
""
],
[
"Saueressig",
"Frank",
""
],
[
"van Dijk",
"Tim",
""
]
] | General relativity is highly successful in explaining a wide range of gravitational phenomena including the gravitational waves emitted by binary systems and the shadows cast by supermassive black holes. From a modern perspective the theory is not fundamental though, but constitutes the lowest order term in an effective field theory description of the gravitational force. As a consequence, the gravitational dynamics should receive corrections by higher-derivative terms. This essay discusses structural aspects associated with these corrections and summarizes their imprint on static, spherically symmetric geometries. Along these lines, we critically reassess the common practice of using local field redefinitions in order to simplify the dynamics at the danger of shifting physics effects into sectors which are beyond the approximation under consideration. |
gr-qc/9704031 | Stanislav Alexeyev | S.O. Alexeyev | Internal Structure of a Gauss-Bonnet Black Hole | 4 pages, LaTeX, gc-97.sty (included), 7 LaTeX figures (included) | Grav.Cosmol.3:161-164,1997 | null | null | gr-qc | null | Black holes are studied in the frames of superstring theory using a
non-trivial numerical integration method. A low energy string action containing
graviton, dilaton, Gauss-Bonnet and Maxwell contributions is considered.
Four-dimensional black hole solutions are studied inside and outside the event
horizon. The internal part of the solutions is shown to have a non-trivial
topology.
| [
{
"created": "Fri, 11 Apr 1997 14:55:40 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Alexeyev",
"S. O.",
""
]
] | Black holes are studied in the frames of superstring theory using a non-trivial numerical integration method. A low energy string action containing graviton, dilaton, Gauss-Bonnet and Maxwell contributions is considered. Four-dimensional black hole solutions are studied inside and outside the event horizon. The internal part of the solutions is shown to have a non-trivial topology. |
1903.01662 | Leonid Perlov | Leonid Perlov | SO(2,1) Connection in Timelike 3+1 Foliation | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce 3+1 timelike foliation of the four dimensional Lorentz manifold
to derive the 3+1 Sen-Ashtekar-Barbero-Immirzi formalism in case of $SO(2,1)$
rotation gauge group, which is possible due to the existence of the $so(2,1)$
algebra isomorphism to $R^3_{2,1}$ algebra with respect to the vector product.
We prove that the newly introduced flux and extrinsic curvature variables
preserve the symplectic structure of the original variables. We then introduce
the modified rotational constraint and succeed to write it as a Gauss
constraint of a newly obtained connection. The newly obtained connection is
slightly different from the classical 3+1 spacelike
Sen-Ashtekar-Barbero-Immirzi connection as it contains in addition the
Minkowski metric $\eta_{ij}$ as a coefficient. Our result has a very simple
form and clearly shows how $so(2,1)$ connection is different from $so(3)$ one.
Also it is the first time that the key-stone fact that makes the whole
formalism work in timelike 3+1 case, i.e. $so(2,1) \simeq R^3_{2,1}$
isomorphism and its relation to the $so(2,1)$ connection has been researched.
| [
{
"created": "Tue, 5 Mar 2019 04:32:01 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Mar 2019 18:41:13 GMT",
"version": "v2"
},
{
"created": "Wed, 15 May 2019 04:58:51 GMT",
"version": "v3"
},
{
"created": "Wed, 3 Jul 2019 23:42:00 GMT",
"version": "v4"
}
] | 2019-07-05 | [
[
"Perlov",
"Leonid",
""
]
] | We introduce 3+1 timelike foliation of the four dimensional Lorentz manifold to derive the 3+1 Sen-Ashtekar-Barbero-Immirzi formalism in case of $SO(2,1)$ rotation gauge group, which is possible due to the existence of the $so(2,1)$ algebra isomorphism to $R^3_{2,1}$ algebra with respect to the vector product. We prove that the newly introduced flux and extrinsic curvature variables preserve the symplectic structure of the original variables. We then introduce the modified rotational constraint and succeed to write it as a Gauss constraint of a newly obtained connection. The newly obtained connection is slightly different from the classical 3+1 spacelike Sen-Ashtekar-Barbero-Immirzi connection as it contains in addition the Minkowski metric $\eta_{ij}$ as a coefficient. Our result has a very simple form and clearly shows how $so(2,1)$ connection is different from $so(3)$ one. Also it is the first time that the key-stone fact that makes the whole formalism work in timelike 3+1 case, i.e. $so(2,1) \simeq R^3_{2,1}$ isomorphism and its relation to the $so(2,1)$ connection has been researched. |
1801.04539 | Stefano Ansoldi | S. Ansoldi, Z. Merali, E. I. Guendelman | From Black Holes to Baby Universes: Exploring the Possibility of
Creating a Cosmos in the Laboratory | To appear in the proceedings for the Bahamas Advanced Study Institute
and Conferences 2017, Stella Maris, the Bahamas, and the "Big Bang in a
Little Room" event, University of the Bahamas, Nassau, the Bahamas | Bulg. J. Phys. vol.45 no.2 (2018), pp. 203-220 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the essential features of baby-universe production, starting from
a description of black holes and wormholes, in terms of the causal structure of
spacetime, and following a qualitative review of the connection between vacuum
decay and inflation in early universe cosmology. Related open questions are
also addressed, especially in connection with the possibility that baby
universes could be formed within our present universe - either in a future
particle accelerator, or spontaneously.
| [
{
"created": "Sun, 14 Jan 2018 11:57:00 GMT",
"version": "v1"
}
] | 2018-09-24 | [
[
"Ansoldi",
"S.",
""
],
[
"Merali",
"Z.",
""
],
[
"Guendelman",
"E. I.",
""
]
] | We discuss the essential features of baby-universe production, starting from a description of black holes and wormholes, in terms of the causal structure of spacetime, and following a qualitative review of the connection between vacuum decay and inflation in early universe cosmology. Related open questions are also addressed, especially in connection with the possibility that baby universes could be formed within our present universe - either in a future particle accelerator, or spontaneously. |
1511.09125 | Israel Quiros | Roberto De Arcia, Tame Gonzalez, Genly Le\'on, Ulises Nucamendi,
Israel Quiros | Cubic Derivative Interactions and Asymptotic Dynamics of the Galileon
Vacuum | 16 pages, 12 eps figures | null | 10.1088/0264-9381/33/12/125036 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we apply the tools of the dynamical systems theory in order to
uncover the whole asymptotic structure of the vacuum interactions of a galileon
model with a cubic derivative interaction term. It is shown that, contrary to
what occurs in the presence of background matter, the galileon interactions of
vacuum appreciably modify the late-time cosmic dynamics. In particular, a local
late-time attractor representing phantom behavior arises which is inevitably
associated with a big rip singularity. It seems that the gravitational
interactions of the background matter with the galileon screen the effects of
the gravitational self-interactions of the galileon, thus erasing any potential
modification of the late-time dynamics by the galileon vacuum processes. Unlike
other galileon models inspired in the DGP scenario, self-accelerating solutions
do not arise in this model.
| [
{
"created": "Mon, 30 Nov 2015 01:06:03 GMT",
"version": "v1"
}
] | 2016-06-01 | [
[
"De Arcia",
"Roberto",
""
],
[
"Gonzalez",
"Tame",
""
],
[
"León",
"Genly",
""
],
[
"Nucamendi",
"Ulises",
""
],
[
"Quiros",
"Israel",
""
]
] | In this paper we apply the tools of the dynamical systems theory in order to uncover the whole asymptotic structure of the vacuum interactions of a galileon model with a cubic derivative interaction term. It is shown that, contrary to what occurs in the presence of background matter, the galileon interactions of vacuum appreciably modify the late-time cosmic dynamics. In particular, a local late-time attractor representing phantom behavior arises which is inevitably associated with a big rip singularity. It seems that the gravitational interactions of the background matter with the galileon screen the effects of the gravitational self-interactions of the galileon, thus erasing any potential modification of the late-time dynamics by the galileon vacuum processes. Unlike other galileon models inspired in the DGP scenario, self-accelerating solutions do not arise in this model. |
2212.10580 | Stefano Bondani | Stefano Bondani and Sergio Luigi Cacciatori | Non canonical polarizations of Gravitational Waves | 10 pages, 8 figures | Eur. Phys. J. C (2023) 83: 310 | 10.1140/epjc/s10052-023-11502-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We hereby propose an alternative and additional angle on the nature of
gravitational waves (GWs), postulating the theoretical and experimental
possibility that GWs carry a deformation of the time component of spacetime,
other than the spatial one. By explicitly working outside of the
transverse-traceless gauge, we propose how events with welldefined time
duration, when hit by a GW, would consequently be expected to show a difference
in their characteristic time, as measured from the rest frame of an outside
observer,whose clock is to remain unaffected by the GW. This constitutes a
theoretically viable way in the sense of detecting the passing of the wave
itself and may prove relevant as a standalone method for GWs detection other
than laser interferometers, or as well be implemented as a complementary but
independent system of signal triggering, improving the statistical significance
of existing methods. A simple but physically realistic scenario in which the
appropriate conditions for the generation and detection of GWs with time
dilation are met is presented, along with the conceptual design of an
experimental detector.
| [
{
"created": "Tue, 20 Dec 2022 19:00:04 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Jun 2023 09:00:46 GMT",
"version": "v2"
}
] | 2023-06-06 | [
[
"Bondani",
"Stefano",
""
],
[
"Cacciatori",
"Sergio Luigi",
""
]
] | We hereby propose an alternative and additional angle on the nature of gravitational waves (GWs), postulating the theoretical and experimental possibility that GWs carry a deformation of the time component of spacetime, other than the spatial one. By explicitly working outside of the transverse-traceless gauge, we propose how events with welldefined time duration, when hit by a GW, would consequently be expected to show a difference in their characteristic time, as measured from the rest frame of an outside observer,whose clock is to remain unaffected by the GW. This constitutes a theoretically viable way in the sense of detecting the passing of the wave itself and may prove relevant as a standalone method for GWs detection other than laser interferometers, or as well be implemented as a complementary but independent system of signal triggering, improving the statistical significance of existing methods. A simple but physically realistic scenario in which the appropriate conditions for the generation and detection of GWs with time dilation are met is presented, along with the conceptual design of an experimental detector. |
1003.5122 | Benny Walther | Christian Lubich, Benny Walther, Bernd Bruegmann | Symplectic Integration of Post-Newtonian Equations of Motion with Spin | 9 pages, 6 figures | Phys.Rev.D81:104025,2010 | 10.1103/PhysRevD.81.104025 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a non-canonically symplectic integration scheme tailored to
numerically computing the post-Newtonian motion of a spinning black-hole
binary. Using a splitting approach we combine the flows of orbital and spin
contributions. In the context of the splitting, it is possible to integrate the
individual terms of the spin-orbit and spin-spin Hamiltonians analytically,
exploiting the special structure of the underlying equations of motion. The
outcome is a symplectic, time-reversible integrator, which can be raised to
arbitrary order by composition. A fourth-order version is shown to give
excellent behavior concerning error growth and conservation of energy and
angular momentum in long-term simulations. Favorable properties of the
integrator are retained in the presence of weak dissipative forces due to
radiation damping in the full post-Newtonian equations.
| [
{
"created": "Fri, 26 Mar 2010 12:08:16 GMT",
"version": "v1"
}
] | 2010-05-25 | [
[
"Lubich",
"Christian",
""
],
[
"Walther",
"Benny",
""
],
[
"Bruegmann",
"Bernd",
""
]
] | We present a non-canonically symplectic integration scheme tailored to numerically computing the post-Newtonian motion of a spinning black-hole binary. Using a splitting approach we combine the flows of orbital and spin contributions. In the context of the splitting, it is possible to integrate the individual terms of the spin-orbit and spin-spin Hamiltonians analytically, exploiting the special structure of the underlying equations of motion. The outcome is a symplectic, time-reversible integrator, which can be raised to arbitrary order by composition. A fourth-order version is shown to give excellent behavior concerning error growth and conservation of energy and angular momentum in long-term simulations. Favorable properties of the integrator are retained in the presence of weak dissipative forces due to radiation damping in the full post-Newtonian equations. |
1502.02988 | Ranjan Sharma | Ranjan Sharma, Shyam Das and Ramesh Tikekar | A class of conformally flat solutions for systems undergoing radiative
gravitational collapse | To appear in Gen. Relativ. Grav | Gen. Relativ. Gravit (2015) 47:25 | 10.1007/s10714-015-1869-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a class of conformally flat solutions of the Einstein's field
equations for spherical systems undergoing gravitational collapse accompanied
with radial heat flux. The interior space-time of the collapsing matter is
chosen to be conformal to the Robertson-Walker space-time so that its Weyl
tensor vanishes identically. The conditions which ensure smooth matching of the
interior space-time of the collapsing system, across its boundary, with the
exterior space-time of a radiating star which is described by Vaidya metric
lead to an equation governing its overall subsequent evolution. New solutions
of this equation have been shown to provide physically viable models of
collapsing stars.
| [
{
"created": "Sun, 8 Feb 2015 19:23:01 GMT",
"version": "v1"
}
] | 2017-11-20 | [
[
"Sharma",
"Ranjan",
""
],
[
"Das",
"Shyam",
""
],
[
"Tikekar",
"Ramesh",
""
]
] | We present a class of conformally flat solutions of the Einstein's field equations for spherical systems undergoing gravitational collapse accompanied with radial heat flux. The interior space-time of the collapsing matter is chosen to be conformal to the Robertson-Walker space-time so that its Weyl tensor vanishes identically. The conditions which ensure smooth matching of the interior space-time of the collapsing system, across its boundary, with the exterior space-time of a radiating star which is described by Vaidya metric lead to an equation governing its overall subsequent evolution. New solutions of this equation have been shown to provide physically viable models of collapsing stars. |
gr-qc/9804059 | Joan Masso | Joan Masso, Edward Seidel, Wai-Mo Suen and Paul Walker | Event Horizons in Numerical Relativity II: Analyzing the Horizon | 23 double column pages including 28 figures. Higher quality figures
(big size!) available upon request (jmasso OR pwalker@aei-potsdam.mpg.de) | Phys.Rev. D59 (1999) 064015 | 10.1103/PhysRevD.59.064015 | null | gr-qc | null | We present techniques and methods for analyzing the dynamics of event
horizons in numerically constructed spacetimes. There are three classes of
analytical tools we have investigated. The first class consists of proper
geometrical measures of the horizon which allow us comparison with perturbation
theory and powerful global theorems. The second class involves the location and
study of horizon generators. The third class includes the induced horizon
2-metric in the generator comoving coordinates and a set of membrane-paradigm
like quantities. Applications to several distorted, rotating, and colliding
black hole spacetimes are provided as examples of these techniques.
| [
{
"created": "Thu, 23 Apr 1998 07:06:41 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Masso",
"Joan",
""
],
[
"Seidel",
"Edward",
""
],
[
"Suen",
"Wai-Mo",
""
],
[
"Walker",
"Paul",
""
]
] | We present techniques and methods for analyzing the dynamics of event horizons in numerically constructed spacetimes. There are three classes of analytical tools we have investigated. The first class consists of proper geometrical measures of the horizon which allow us comparison with perturbation theory and powerful global theorems. The second class involves the location and study of horizon generators. The third class includes the induced horizon 2-metric in the generator comoving coordinates and a set of membrane-paradigm like quantities. Applications to several distorted, rotating, and colliding black hole spacetimes are provided as examples of these techniques. |
2211.16825 | Jin Qiao | Jin Qiao, Zhao Li, Tao Zhu, Ran Ji, Guoliang Li, and Wen Zhao | Testing parity symmetry of gravity with gravitational waves | 22 pages, no figures | Front. Astron. Space Sci. 9, 1109086 (2023) | 10.3389/fspas.2022.1109086 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The examination of parity symmetry in gravitational interactions has drawn
increasing attention. Although Einstein's General Relativity is
parity-conserved, numerous theories of parity-violating (PV) gravity in
different frameworks have recently been proposed for different motivations. In
this review, we briefly summarize the recent progress of these theories, and
focus on the observable effects of PV terms in the gravitational waves (GWs),
which are mainly reflected in the difference between the left-hand and
right-hand polarization modes. We are primarily concerned with the implications
of these theories for GWs generated by the compact binary coalescences and the
primordial GWs generated in the early Universe. The deviation of GW waveforms
and/or primordial power spectrum can always be quantified by the energy scale
of parity violation of the theory. Applying the current and future GW
observation from laser interferometers and cosmic microwave background
radiation, the current and potential constraints on the PV energy scales are
presented, which indicates that the parity symmetry of gravity can be tested in
high energy scale in this new era of gravitational waves.
| [
{
"created": "Wed, 30 Nov 2022 08:49:25 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Dec 2022 13:42:03 GMT",
"version": "v2"
}
] | 2023-02-15 | [
[
"Qiao",
"Jin",
""
],
[
"Li",
"Zhao",
""
],
[
"Zhu",
"Tao",
""
],
[
"Ji",
"Ran",
""
],
[
"Li",
"Guoliang",
""
],
[
"Zhao",
"Wen",
""
]
] | The examination of parity symmetry in gravitational interactions has drawn increasing attention. Although Einstein's General Relativity is parity-conserved, numerous theories of parity-violating (PV) gravity in different frameworks have recently been proposed for different motivations. In this review, we briefly summarize the recent progress of these theories, and focus on the observable effects of PV terms in the gravitational waves (GWs), which are mainly reflected in the difference between the left-hand and right-hand polarization modes. We are primarily concerned with the implications of these theories for GWs generated by the compact binary coalescences and the primordial GWs generated in the early Universe. The deviation of GW waveforms and/or primordial power spectrum can always be quantified by the energy scale of parity violation of the theory. Applying the current and future GW observation from laser interferometers and cosmic microwave background radiation, the current and potential constraints on the PV energy scales are presented, which indicates that the parity symmetry of gravity can be tested in high energy scale in this new era of gravitational waves. |
1702.06036 | Laura Castell\'o Gomar | Laura Castell\'o Gomar, Daniel Mart\'in de Blas, Guillermo A. Mena
Marug\'an, and Javier Olmedo | Hybrid loop quantum cosmology and predictions for the cosmic microwave
background | 34 pages, 23 figures, 1 table; v2: revised and minor improvements
included | Phys. Rev. D 96, 103528 (2017) | 10.1103/PhysRevD.96.103528 | IGC-17|2-1 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the consequences of the hybrid quantization approach for
primordial perturbations in loop quantum cosmology, obtaining predictions for
the cosmic microwave background and comparing them with data collected by the
Planck mission. In this work, we complete previous studies about the scalar
perturbations and incorporate tensor modes. We compute their power spectrum for
a variety of vacuum states. We then analyze the tensor-to-scalar ratio and the
consistency relation between this quantity and the spectral index of the tensor
power spectrum. We also compute the temperature-temperature, electric-electric,
temperature-electric, and magnetic-magnetic correlation functions. Finally, we
discuss the effects of the quantum geometry in these correlation functions and
confront them with observations.
| [
{
"created": "Mon, 20 Feb 2017 16:01:19 GMT",
"version": "v1"
},
{
"created": "Tue, 30 May 2017 10:00:23 GMT",
"version": "v2"
}
] | 2017-11-29 | [
[
"Gomar",
"Laura Castelló",
""
],
[
"de Blas",
"Daniel Martín",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
],
[
"Olmedo",
"Javier",
""
]
] | We investigate the consequences of the hybrid quantization approach for primordial perturbations in loop quantum cosmology, obtaining predictions for the cosmic microwave background and comparing them with data collected by the Planck mission. In this work, we complete previous studies about the scalar perturbations and incorporate tensor modes. We compute their power spectrum for a variety of vacuum states. We then analyze the tensor-to-scalar ratio and the consistency relation between this quantity and the spectral index of the tensor power spectrum. We also compute the temperature-temperature, electric-electric, temperature-electric, and magnetic-magnetic correlation functions. Finally, we discuss the effects of the quantum geometry in these correlation functions and confront them with observations. |
gr-qc/0301032 | Maurizio Gasperini | M. Gasperini | Phenomenology of the relic dilaton background | 6 pages, latex, IOP style ecssm.sty included, to appear in Proc. of
the 15th SIGRAV Conference on General Relativity and Gravitational Physics | null | null | BA-TH/02-454 | gr-qc hep-th | null | We discuss the expected amplitude of a cosmic background of massive,
non-relativistic dilatons, and we report recent results about its possible
detection. This paper is a contracted version of a talk given at the 15th
SIGRAV Conference on "General Relativity and Gravitational Physics" (Villa
Mondragone, Roma, September 2002).
| [
{
"created": "Thu, 9 Jan 2003 18:38:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gasperini",
"M.",
""
]
] | We discuss the expected amplitude of a cosmic background of massive, non-relativistic dilatons, and we report recent results about its possible detection. This paper is a contracted version of a talk given at the 15th SIGRAV Conference on "General Relativity and Gravitational Physics" (Villa Mondragone, Roma, September 2002). |
gr-qc/9404057 | Renaud Parentani | S. Massar and R. Parentani | From Vacuum Fluctuations to Radiation: Accelerated Detectors and Black
Holes | definitive version, 39 pages and 5 figures available upon request
from S.M., ULB-TH 94/02 | null | null | null | gr-qc hep-th | null | The vacuum fluctuations that induce the transitions and the thermalisation of
a uniformly accelerated two level atom are studied in detail. Their energy
content is revealed through the weak measurement formalism of Aharonov et al.
It is shown that each time the detector makes a transition it radiates a
Minkowski photon. The same analysis is then applied to the conversion of vacuum
fluctuations into real quanta in the context of black hole radiation. Initially
these fluctuations are located around the light like geodesic that shall
generate the horizon and carry zero total energy. However upon exiting from the
star they break up into two pieces one of which gradually acquires positive
energy and becomes a Hawking quantum, the other, its ''partner", ends up in the
singularity. As time goes by the vacuum fluctuations generating Hawking quanta
have exponentially large energy densities. This implies that back reaction
effects are large.
| [
{
"created": "Thu, 28 Apr 1994 07:08:05 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Jun 1994 12:49:43 GMT",
"version": "v2"
}
] | 2009-09-25 | [
[
"Massar",
"S.",
""
],
[
"Parentani",
"R.",
""
]
] | The vacuum fluctuations that induce the transitions and the thermalisation of a uniformly accelerated two level atom are studied in detail. Their energy content is revealed through the weak measurement formalism of Aharonov et al. It is shown that each time the detector makes a transition it radiates a Minkowski photon. The same analysis is then applied to the conversion of vacuum fluctuations into real quanta in the context of black hole radiation. Initially these fluctuations are located around the light like geodesic that shall generate the horizon and carry zero total energy. However upon exiting from the star they break up into two pieces one of which gradually acquires positive energy and becomes a Hawking quantum, the other, its ''partner", ends up in the singularity. As time goes by the vacuum fluctuations generating Hawking quanta have exponentially large energy densities. This implies that back reaction effects are large. |
1810.06753 | Wei-Xiang Feng | Wei-Xiang Feng, Chao-Qiang Geng, Ling-Wei Luo | The Buchdahl Stability Bound in Eddington-inspired Born-Infeld Gravity | 13 pages, 2 figures, 1 table; references and a table added, typos
corrected, \kappa-energy condition defined; version published in Chinese
Physics C | Chin. Phys. C43, 083107 (2019) | 10.1088/1674-1137/43/8/083107 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give the Buchdahl stability bound in Eddington-inspired Born-Infeld (EiBI)
gravity. We show that this bound depends on an energy condition controlled by
the model parameter $\kappa$. From this bound, we can constrain $\kappa\lesssim
10^{8}\text{m}^2$ if a neutron star with a mass around $3M_{\odot}$ is observed
in the future. In addition, to avoid the potential pathologies in EiBI, a
\emph{Hagedorn-like} equation of state associated with $\kappa$ at the center
of a compact star is inevitable, which is similar to the Hagedorn temperature
in string theory.
| [
{
"created": "Mon, 15 Oct 2018 23:43:36 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Mar 2019 03:46:37 GMT",
"version": "v2"
},
{
"created": "Thu, 6 Jun 2019 03:45:08 GMT",
"version": "v3"
},
{
"created": "Fri, 19 Jul 2019 03:05:18 GMT",
"version": "v4"
}
] | 2019-07-22 | [
[
"Feng",
"Wei-Xiang",
""
],
[
"Geng",
"Chao-Qiang",
""
],
[
"Luo",
"Ling-Wei",
""
]
] | We give the Buchdahl stability bound in Eddington-inspired Born-Infeld (EiBI) gravity. We show that this bound depends on an energy condition controlled by the model parameter $\kappa$. From this bound, we can constrain $\kappa\lesssim 10^{8}\text{m}^2$ if a neutron star with a mass around $3M_{\odot}$ is observed in the future. In addition, to avoid the potential pathologies in EiBI, a \emph{Hagedorn-like} equation of state associated with $\kappa$ at the center of a compact star is inevitable, which is similar to the Hagedorn temperature in string theory. |
gr-qc/0509017 | Mikhail V. Gorbatenko | Mikhail V. Gorbatenko | On the Possibility to Explain "The Pioneer Anomaly" within the Framework
of Conformal Geometrodynamics | 15 pages, LaTeX2e | null | null | null | gr-qc | null | Einstein-Infeld-Hoffmann method is used to solve the problem of motion of two
bodies when the equations of general relativity are of the generalized form:
they have been reduced to a form invariant under conformal transformations. It
is proved that not only metric degrees of freedom, but also derivatives of
vector $A_{\alpha}$ appearing in the generalized equations can exert influence
on the motion of bodies in a certain space-time domain. This influence can
account for the recently observed anomalous acceleration of spacecrafts Pioneer
10, Pioneer 11. The impact of vector $A_{\alpha}$ on the motion of bodies is
interpreted as a consequence of viscosity in geometrodynamic continuum.
| [
{
"created": "Tue, 6 Sep 2005 15:52:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gorbatenko",
"Mikhail V.",
""
]
] | Einstein-Infeld-Hoffmann method is used to solve the problem of motion of two bodies when the equations of general relativity are of the generalized form: they have been reduced to a form invariant under conformal transformations. It is proved that not only metric degrees of freedom, but also derivatives of vector $A_{\alpha}$ appearing in the generalized equations can exert influence on the motion of bodies in a certain space-time domain. This influence can account for the recently observed anomalous acceleration of spacecrafts Pioneer 10, Pioneer 11. The impact of vector $A_{\alpha}$ on the motion of bodies is interpreted as a consequence of viscosity in geometrodynamic continuum. |
1007.4039 | Matt Visser | Jozef Skakala (Victoria University of Wellington) and Matt Visser
(Victoria University of Wellington) | Highly-damped quasi-normal frequencies for piecewise Eckart potentials | v1: 4 pages; letter-length summary of results reported in
considerably more detail in arXiv:1004.2539; v2: minor typos fixed in
equation (34); matches published version | Physical Review D81 (2010) 125023 | 10.1103/PhysRevD.81.125023 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Highly-damped quasi-normal frequencies are very often of the form omega_n =
(offset) + i n (gap). We investigate the genericity of this phenomenon by
considering a model potential that is piecewise Eckart (piecewise
Poeschl-Teller), and developing an analytic "quantization condition" for the
highly-damped quasi-normal frequencies. We find that this omega_n = (offset) +
i n (gap) behaviour is generic but not universal, with the controlling feature
being whether or not the ratio of the rates of exponential falloff in the two
asymptotic directions is a rational number. These observations are of direct
relevance to any physical situation where highly-damped quasi-normal modes
(damped modes) are important --- in particular (but not limited to) to black
hole physics, both theoretical and observational.
| [
{
"created": "Fri, 23 Jul 2010 03:58:40 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Sep 2010 06:18:24 GMT",
"version": "v2"
}
] | 2010-09-02 | [
[
"Skakala",
"Jozef",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | Highly-damped quasi-normal frequencies are very often of the form omega_n = (offset) + i n (gap). We investigate the genericity of this phenomenon by considering a model potential that is piecewise Eckart (piecewise Poeschl-Teller), and developing an analytic "quantization condition" for the highly-damped quasi-normal frequencies. We find that this omega_n = (offset) + i n (gap) behaviour is generic but not universal, with the controlling feature being whether or not the ratio of the rates of exponential falloff in the two asymptotic directions is a rational number. These observations are of direct relevance to any physical situation where highly-damped quasi-normal modes (damped modes) are important --- in particular (but not limited to) to black hole physics, both theoretical and observational. |
1110.6244 | Sumati Surya | Sumati Surya | Evidence for a Phase Transition in 2D Causal Set Quantum Gravity | 14 pages, 13 figures | null | 10.1088/0264-9381/29/13/132001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present evidence for a phase transition in a theory of 2D causal set
quantum gravity which contains a dimensionless non-locality parameter $\epsilon
\in (0,1]$. The transition is between a continuum phase and a crystalline
phase, characterised by a set of covariant observables. For a fixed size of the
causal set the transition temperature $\beta_c^{-1}$ decreases monotonotically
with $\epsilon$. The line of phase transitions in the $\beta_c^2$ v/s
$\epsilon$ plane asymptotes to the infinite temperature axis, suggesting that
the continuum phase survives the analytic continuation.
| [
{
"created": "Fri, 28 Oct 2011 04:28:47 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Surya",
"Sumati",
""
]
] | We present evidence for a phase transition in a theory of 2D causal set quantum gravity which contains a dimensionless non-locality parameter $\epsilon \in (0,1]$. The transition is between a continuum phase and a crystalline phase, characterised by a set of covariant observables. For a fixed size of the causal set the transition temperature $\beta_c^{-1}$ decreases monotonotically with $\epsilon$. The line of phase transitions in the $\beta_c^2$ v/s $\epsilon$ plane asymptotes to the infinite temperature axis, suggesting that the continuum phase survives the analytic continuation. |
1603.01569 | Henrique de Andrade Gomes | Henrique de A. Gomes | Local(ish) gravity theories in conformal superspace | 24 pages, 7 page appendix, 7 figures, Annals of Physics, June 2018 | null | 10.1016/j.aop.2018.05.014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by well-known obstacles to quantum gravity, I look for the most
general geometrodynamical symmetries compatible with a reduced physical
configuration space for metric gravity. I argue that they lead either to a
completely static Universe, or one embodying spatial conformal diffeomorphisms.
Demanding locality for an action compatible with these principles determines
the sort of terms one can add, both for the purely gravitational part as well
as matter couplings. The symmetries guarantee that there are two gravitational
propagating physical degrees of freedom (and no explicit
refoliation-invariance). The simplest such system has a geometric
interpretation as a geodesic model in infinite dimensional conformal
superspace. An approximate solution to the equations of motion corresponds to a
static Bianchi IX spatial ansatz. The unique coupling to electromagnetism
forces its propagation equations to be hyperbolic, enabling us to \"build" a
standard space-time causal structure. There are, however, deviations from the
standard Maxwell equations when space-time anisotropies become too large.
Regarding quantization, with the geometric interpretation and the lack of
refoliation invariance, the path integral treatment of the symmetries becomes
much less involved than the similar approaches to GR. The symmetries form an
(infinite-dimensional) Lie algebra, and no BFV treatment is necessary. We find
that the propagator around the flat solution has up to 6-th order spatial
derivatives, giving it plausible regularization properties as in
Horava-Lifschitz.
| [
{
"created": "Fri, 4 Mar 2016 18:57:57 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Aug 2017 23:21:51 GMT",
"version": "v2"
},
{
"created": "Sat, 4 Aug 2018 14:03:23 GMT",
"version": "v3"
}
] | 2018-08-07 | [
[
"Gomes",
"Henrique de A.",
""
]
] | Motivated by well-known obstacles to quantum gravity, I look for the most general geometrodynamical symmetries compatible with a reduced physical configuration space for metric gravity. I argue that they lead either to a completely static Universe, or one embodying spatial conformal diffeomorphisms. Demanding locality for an action compatible with these principles determines the sort of terms one can add, both for the purely gravitational part as well as matter couplings. The symmetries guarantee that there are two gravitational propagating physical degrees of freedom (and no explicit refoliation-invariance). The simplest such system has a geometric interpretation as a geodesic model in infinite dimensional conformal superspace. An approximate solution to the equations of motion corresponds to a static Bianchi IX spatial ansatz. The unique coupling to electromagnetism forces its propagation equations to be hyperbolic, enabling us to \"build" a standard space-time causal structure. There are, however, deviations from the standard Maxwell equations when space-time anisotropies become too large. Regarding quantization, with the geometric interpretation and the lack of refoliation invariance, the path integral treatment of the symmetries becomes much less involved than the similar approaches to GR. The symmetries form an (infinite-dimensional) Lie algebra, and no BFV treatment is necessary. We find that the propagator around the flat solution has up to 6-th order spatial derivatives, giving it plausible regularization properties as in Horava-Lifschitz. |
gr-qc/0410124 | Ruth Lazkoz | L. Fern\'andez-Jambrina and Ruth Lazkoz | Geodesic behavior of sudden future singularities | 3 pages, revtex, twocolumn | Phys.Rev. D70 (2004) 121503 | 10.1103/PhysRevD.70.121503 | null | gr-qc | null | In this paper we analyze the effect of recently proposed classes of sudden
future singularities on causal geodesics of FLRW spacetimes. Geodesics are
shown to be extendible and just the equations for geodesic deviation are
singular, although tidal forces are not strong enough to produce a Big Rip. For
the sake of completeness, we compare with the typical sudden future
singularities of phantom cosmologies.
| [
{
"created": "Tue, 26 Oct 2004 16:32:39 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jan 2005 11:43:32 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Fernández-Jambrina",
"L.",
""
],
[
"Lazkoz",
"Ruth",
""
]
] | In this paper we analyze the effect of recently proposed classes of sudden future singularities on causal geodesics of FLRW spacetimes. Geodesics are shown to be extendible and just the equations for geodesic deviation are singular, although tidal forces are not strong enough to produce a Big Rip. For the sake of completeness, we compare with the typical sudden future singularities of phantom cosmologies. |
1910.10856 | Nikolaos Stergioulas | Stamatis Vretinaris, Nikolaos Stergioulas and Andreas Bauswein | Empirical relations for gravitational-wave asteroseismology of binary
neutron star mergers | 26 pages, 16 figures | Phys. Rev. D 101, 084039 (2020) | 10.1103/PhysRevD.101.084039 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct new, multivariate empirical relations for measuring neutron star
radii and tidal deformabilities from the dominant gravitational wave frequency
in the post-merger phase of binary neutron star mergers. The relations
determine neutron star radii and tidal deformabilities for specific neutron
star masses with consistent accuracy and depend only on two observables: the
post-merger peak frequency $f_{\rm peak}$ and the chirp mass $M_{\rm chirp}$.
The former could be measured with good accuracy from gravitational waves
emitted in the post-merger phase using next-generation detectors, whereas the
latter is already obtained with good accuracy from the inspiral phase with
present-day detectors. Our main data set consists of a gravitational wave
catalogue obtained with CFC/SPH simulations. We also extract the $f_{\rm peak}$
frequency from the publicly available CoRe data set, obtained through
grid-based GRHD simulations and find good agreement between the extracted
frequencies of the two data sets. As a result, we can construct empirical
relations for the combined data sets. Furthermore, we investigate empirical
relations for two secondary peaks, $f_{2-0}$ and $f_{\rm spiral}$, and show
that these relations are distinct in the whole parameter space, in agreement
with a previously introduced spectral classification scheme. Finally, we show
that the spectral classification scheme can be reproduced using
machine-learning techniques.
| [
{
"created": "Thu, 24 Oct 2019 00:32:54 GMT",
"version": "v1"
}
] | 2020-04-29 | [
[
"Vretinaris",
"Stamatis",
""
],
[
"Stergioulas",
"Nikolaos",
""
],
[
"Bauswein",
"Andreas",
""
]
] | We construct new, multivariate empirical relations for measuring neutron star radii and tidal deformabilities from the dominant gravitational wave frequency in the post-merger phase of binary neutron star mergers. The relations determine neutron star radii and tidal deformabilities for specific neutron star masses with consistent accuracy and depend only on two observables: the post-merger peak frequency $f_{\rm peak}$ and the chirp mass $M_{\rm chirp}$. The former could be measured with good accuracy from gravitational waves emitted in the post-merger phase using next-generation detectors, whereas the latter is already obtained with good accuracy from the inspiral phase with present-day detectors. Our main data set consists of a gravitational wave catalogue obtained with CFC/SPH simulations. We also extract the $f_{\rm peak}$ frequency from the publicly available CoRe data set, obtained through grid-based GRHD simulations and find good agreement between the extracted frequencies of the two data sets. As a result, we can construct empirical relations for the combined data sets. Furthermore, we investigate empirical relations for two secondary peaks, $f_{2-0}$ and $f_{\rm spiral}$, and show that these relations are distinct in the whole parameter space, in agreement with a previously introduced spectral classification scheme. Finally, we show that the spectral classification scheme can be reproduced using machine-learning techniques. |
gr-qc/0312086 | Daniel Grumiller | H. Balasin and D. Grumiller | The ultrarelativistic limit of 2D dilaton gravity and its energy
momentum tensor | 20 pages, 3 eps-figures, v4: corrected typo in affiliation and 2
misprints in the text, added PACS numbers | Class.Quant.Grav. 21 (2004) 2859-2872 | 10.1088/0264-9381/21/12/006 | TUW-03-26, ESI 1423 | gr-qc hep-th | null | The ultrarelativistic limit of twodimensional dilaton gravity is presented
and its associated (anti-)selfdual energy momentum tensor is derived. It is
localized on a null line, although the line element remains twice
differentiable. Relations to the Aichelburg-Sexl spacetime and constant dilaton
vacua are pointed out. Geodesics are found to be smooth for minimally coupled
test particles but non-smooth -- with a finite jump in the acceleration -- for
test particles coupled non-minimally to the dilaton. Quantization on boosted
backgrounds is discussed; no anomalous trace of the energy momentum tensor
arises and the 1-loop flux component can be adjusted to be equal to the
classical flux of the shock wave.
| [
{
"created": "Thu, 18 Dec 2003 16:16:13 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Dec 2003 14:59:50 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Apr 2004 17:24:30 GMT",
"version": "v3"
},
{
"created": "Mon, 19 Apr 2004 13:40:00 GMT",
"version": "v4"
}
] | 2009-11-10 | [
[
"Balasin",
"H.",
""
],
[
"Grumiller",
"D.",
""
]
] | The ultrarelativistic limit of twodimensional dilaton gravity is presented and its associated (anti-)selfdual energy momentum tensor is derived. It is localized on a null line, although the line element remains twice differentiable. Relations to the Aichelburg-Sexl spacetime and constant dilaton vacua are pointed out. Geodesics are found to be smooth for minimally coupled test particles but non-smooth -- with a finite jump in the acceleration -- for test particles coupled non-minimally to the dilaton. Quantization on boosted backgrounds is discussed; no anomalous trace of the energy momentum tensor arises and the 1-loop flux component can be adjusted to be equal to the classical flux of the shock wave. |
1312.6683 | Oleksii Iegurnov | M.P. Korkina, O.O. Iegurnov | Matching of Stephani and de Sitter solutions on the hypersurface of
constant time | Accepted for publication in Visnyk Dnipropetrovskogo universytetu.
Fizyka. Radioelectronika. No2. Issue 20. V.21, 2013, 12 pages | Visnyk Dnipropetrovskogo universytetu. Fizyka. Radioelectronika.
No2. Issue 20. V.21, 2013 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The spherically symmetric solution for perfect fluid with homogeneous density
and inhomogeneous pressure has been considered. This solution is known as
Stephani solution. The matching of this solution and de Sitter solution has
been done on a hypersurface of constant time. The matching has been done for
general case and for particular cases (flat, closed, open universe). An
equality of the densities and a bound of the pressures have been shown on the
matching hypersurface. Also, restrictions on some arbitrary functions have been
found.
| [
{
"created": "Sat, 21 Dec 2013 14:42:35 GMT",
"version": "v1"
}
] | 2013-12-25 | [
[
"Korkina",
"M. P.",
""
],
[
"Iegurnov",
"O. O.",
""
]
] | The spherically symmetric solution for perfect fluid with homogeneous density and inhomogeneous pressure has been considered. This solution is known as Stephani solution. The matching of this solution and de Sitter solution has been done on a hypersurface of constant time. The matching has been done for general case and for particular cases (flat, closed, open universe). An equality of the densities and a bound of the pressures have been shown on the matching hypersurface. Also, restrictions on some arbitrary functions have been found. |
0907.4736 | Vladimir Kassandrov | Vladimir V. Kassandrov | On Hierarchy and Equivalence of Relativistic Equations for Massive
Fields | 7 pages, twocolumn. Problem of construction the hierarchy of
solutions in the massive case reformulated | Grav.Cosmol.14:53-59,2008 | 10.1134/S0202289308010076 | null | gr-qc hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A non-canonical correspondence of the complete sets of solutions to the Dirac
and Klein-Gordon free equations in Minkowski space-time is established. This
allows for a novel viewpoint on the relationship of relativistic equations for
different spins and on the origin of spinor transformations. In particular,
starting from a solution to the Dirac equation, one obtains a chain of other
solutions to both Dirac and Klein-Gordon equations. A comparison with the
massless case is performed, and examples of non-trivial singular solutions are
presented. A generalization to Riemannian space-time and inclusion of
interactions are briefly discussed.
| [
{
"created": "Mon, 27 Jul 2009 19:07:47 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Aug 2009 23:09:23 GMT",
"version": "v2"
}
] | 2010-11-23 | [
[
"Kassandrov",
"Vladimir V.",
""
]
] | A non-canonical correspondence of the complete sets of solutions to the Dirac and Klein-Gordon free equations in Minkowski space-time is established. This allows for a novel viewpoint on the relationship of relativistic equations for different spins and on the origin of spinor transformations. In particular, starting from a solution to the Dirac equation, one obtains a chain of other solutions to both Dirac and Klein-Gordon equations. A comparison with the massless case is performed, and examples of non-trivial singular solutions are presented. A generalization to Riemannian space-time and inclusion of interactions are briefly discussed. |
gr-qc/0408101 | Marc Henneaux | Marc Henneaux and Claudio Teitelboim | Duality in linearized gravity | 10 pages; introduction rewritten and references added | Phys.Rev. D71 (2005) 024018 | 10.1103/PhysRevD.71.024018 | null | gr-qc hep-th | null | We show that duality transformations of linearized gravity in four
dimensions, i.e., rotations of the linearized Riemann tensor and its dual into
each other, can be extended to the dynamical fields of the theory so as to be
symmetries of the action and not just symmetries of the equations of motion.
Our approach relies on the introduction of two "superpotentials", one for the
spatial components of the spin-2 field and the other for their canonically
conjugate momenta. These superpotentials are two-index, symmetric tensors. They
can be taken to be the basic dynamical fields and appear locally in the action.
They are simply rotated into each other under duality. In terms of the
superpotentials, the canonical generator of duality rotations is found to have
a Chern-Simons like structure, as in the Maxwell case.
| [
{
"created": "Tue, 31 Aug 2004 13:39:24 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Jan 2005 07:34:40 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Henneaux",
"Marc",
""
],
[
"Teitelboim",
"Claudio",
""
]
] | We show that duality transformations of linearized gravity in four dimensions, i.e., rotations of the linearized Riemann tensor and its dual into each other, can be extended to the dynamical fields of the theory so as to be symmetries of the action and not just symmetries of the equations of motion. Our approach relies on the introduction of two "superpotentials", one for the spatial components of the spin-2 field and the other for their canonically conjugate momenta. These superpotentials are two-index, symmetric tensors. They can be taken to be the basic dynamical fields and appear locally in the action. They are simply rotated into each other under duality. In terms of the superpotentials, the canonical generator of duality rotations is found to have a Chern-Simons like structure, as in the Maxwell case. |
gr-qc/9602043 | Steven Corley | S. Corley and T. Jacobson | Focusing and the Holographic Hypothesis | 8 pages, plain latex, 5 figures included using psfig | Phys.Rev.D53:6720-6724,1996 | 10.1103/PhysRevD.53.R6720 | THU-96/11 | gr-qc hep-th | null | The ``screen mapping" introduced by Susskind to implement 't Hooft's
holographic hypothesis is studied. For a single screen time, there are an
infinite number of images of a black hole event horizon, almost all of which
have smaller area on the screen than the horizon area. This is consistent with
the focusing equation because of the existence of focal points. However, the
{\it boundary} of the past (or future) of the screen obeys the area theorem,
and so always gives an expanding map to the screen, as required by the
holographic hypothesis. These considerations are illustrated with several
axisymmetric static black hole spacetimes.
| [
{
"created": "Thu, 22 Feb 1996 17:18:43 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Corley",
"S.",
""
],
[
"Jacobson",
"T.",
""
]
] | The ``screen mapping" introduced by Susskind to implement 't Hooft's holographic hypothesis is studied. For a single screen time, there are an infinite number of images of a black hole event horizon, almost all of which have smaller area on the screen than the horizon area. This is consistent with the focusing equation because of the existence of focal points. However, the {\it boundary} of the past (or future) of the screen obeys the area theorem, and so always gives an expanding map to the screen, as required by the holographic hypothesis. These considerations are illustrated with several axisymmetric static black hole spacetimes. |
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