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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2107.06554 | Zheng-Wen Long | Yi Yang, Dong Liu, Zhaoyi Xu, Yujia Xing, Shurui Wu, Zheng-Wen Long | Echoes of novel black-bounce spacetimes | null | null | 10.1103/PhysRevD.104.104021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave echoes can be used as a significant observable to
understand the properties of black holes horizon. In addition, echoes would
also closely relate to the unique properties of compact objects. In this work
we study the evolution of electromagnetic field and scalar field under the
background of novel black-bounce spacetimes. Our results show an obvious echoes
signal that can characterize the properties of novel black-bounce spacetimes,
and a detailed analysis about the characteristics of the echoes signal is
given. By studying the quasinormal ringdown of the three states of novel
black-bounce spacetimes, including black holes in $0<a<2 M$, the one-way
wormhole in $a=2M$ and the traversable wormhole in $a>2 M$, we find that the
echoes signal only appears when $a>2M$ in this spacetime, but when the
parameter $a$ increases to a threshold, the echoes signal will be transformed
into a quasinormal ringdown of the two-way traversable wormhole.
| [
{
"created": "Wed, 14 Jul 2021 08:39:20 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jul 2021 13:08:48 GMT",
"version": "v2"
},
{
"created": "Thu, 28 Oct 2021 15:25:46 GMT",
"version": "v3"
}
] | 2021-11-10 | [
[
"Yang",
"Yi",
""
],
[
"Liu",
"Dong",
""
],
[
"Xu",
"Zhaoyi",
""
],
[
"Xing",
"Yujia",
""
],
[
"Wu",
"Shurui",
""
],
[
"Long",
"Zheng-Wen",
""
]
] | Gravitational wave echoes can be used as a significant observable to understand the properties of black holes horizon. In addition, echoes would also closely relate to the unique properties of compact objects. In this work we study the evolution of electromagnetic field and scalar field under the background of novel black-bounce spacetimes. Our results show an obvious echoes signal that can characterize the properties of novel black-bounce spacetimes, and a detailed analysis about the characteristics of the echoes signal is given. By studying the quasinormal ringdown of the three states of novel black-bounce spacetimes, including black holes in $0<a<2 M$, the one-way wormhole in $a=2M$ and the traversable wormhole in $a>2 M$, we find that the echoes signal only appears when $a>2M$ in this spacetime, but when the parameter $a$ increases to a threshold, the echoes signal will be transformed into a quasinormal ringdown of the two-way traversable wormhole. |
2408.04925 | Sahil Saini | Esteban Mato, Javier Olmedo and Sahil Saini | Spherically symmetric loop quantum gravity: Schwarzschild spacetimes
with a cosmological constant | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We provide a quantization of the Schwarzschild spacetime in the presence of a
cosmological constant, based on midisuperspace methods developed in the
spherically symmetric sector of loop quantum gravity, using in particular the
'improved dynamics' scheme. We include both the deSitter and anti-deSitter
cases. We find that the quantization puts a Planckian upper limit on the
possible values of a positive cosmological constant similar to the bounds
obtained earlier from studies of homogeneous spacetimes with a cosmological
constant. Using semiclassical physical states, we obtain the effective metric
and demonstrate the causal structure for various cases. Quantum gravity
modifications ensure that the singularity is replaced by a transition surface
in all the cases, where the curvature invariants approach mass-independent
Planckian bounds. Analysis of the effective stress-energy tensor shows that the
null energy condition is violated in the vicinity of the transition surface.
| [
{
"created": "Fri, 9 Aug 2024 08:12:22 GMT",
"version": "v1"
}
] | 2024-08-12 | [
[
"Mato",
"Esteban",
""
],
[
"Olmedo",
"Javier",
""
],
[
"Saini",
"Sahil",
""
]
] | We provide a quantization of the Schwarzschild spacetime in the presence of a cosmological constant, based on midisuperspace methods developed in the spherically symmetric sector of loop quantum gravity, using in particular the 'improved dynamics' scheme. We include both the deSitter and anti-deSitter cases. We find that the quantization puts a Planckian upper limit on the possible values of a positive cosmological constant similar to the bounds obtained earlier from studies of homogeneous spacetimes with a cosmological constant. Using semiclassical physical states, we obtain the effective metric and demonstrate the causal structure for various cases. Quantum gravity modifications ensure that the singularity is replaced by a transition surface in all the cases, where the curvature invariants approach mass-independent Planckian bounds. Analysis of the effective stress-energy tensor shows that the null energy condition is violated in the vicinity of the transition surface. |
gr-qc/0206009 | Fabio Scardigli | Fabio Scardigli | Analysis of a Shell System in General Relativity | PhD Thesis, 59 pages, University of Bern, December 2001 | null | null | null | gr-qc | null | This Thesis concerns a thin fluid shell embedded in its own gravitational
field. The starting point is a work of Hajicek and Kijowski, where the
hamiltonian formalism for shell(s) (with no symmetry) in Einstein gravity is
developed. An open problem at the end of that paper is to show how the
hamiltonian formalism defines a regular constrained system: the hamiltonian and
the constraints must be differentiable functionals on the phase space, so that
their Poisson Brackets are well defined objects. On the contrary, some
constraints at the shell result to be non differentiable functionals on the
phase space. This problem is tackled, in the present thesis, by following the
reduction procedure suggested by Teitelboim and Henneaux: the singular
constraints are solved and the solution is substituted back into the
hamiltonian. The resulting hamiltonian is shown to lead to equivalent dynamics,
without singular constraints. Besides, the final reduced system (hamiltonian
plus canonical constraints) is shown to be fully differentiable on the reduced
phase space.
| [
{
"created": "Mon, 3 Jun 2002 19:34:14 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Scardigli",
"Fabio",
""
]
] | This Thesis concerns a thin fluid shell embedded in its own gravitational field. The starting point is a work of Hajicek and Kijowski, where the hamiltonian formalism for shell(s) (with no symmetry) in Einstein gravity is developed. An open problem at the end of that paper is to show how the hamiltonian formalism defines a regular constrained system: the hamiltonian and the constraints must be differentiable functionals on the phase space, so that their Poisson Brackets are well defined objects. On the contrary, some constraints at the shell result to be non differentiable functionals on the phase space. This problem is tackled, in the present thesis, by following the reduction procedure suggested by Teitelboim and Henneaux: the singular constraints are solved and the solution is substituted back into the hamiltonian. The resulting hamiltonian is shown to lead to equivalent dynamics, without singular constraints. Besides, the final reduced system (hamiltonian plus canonical constraints) is shown to be fully differentiable on the reduced phase space. |
1201.5715 | Carlos F. Sopuerta | Carlos F. Sopuerta and Nicolas Yunes | Approximate Waveforms for Extreme-Mass-Ratio Inspirals: The Chimera
Scheme | 10 pages, 3 figures. LaTeX, JPCS style. Submitted to the proceedings
of the 9th Edoardo Amaldi Conference on Gravitational Waves, and the 2011
Numerical Relativity - Data Analysis (NRDA) meeting, held 10-15 July 2011 in
Cardiff, Wales, UK, July 10-15 2011 | null | 10.1088/1742-6596/363/1/012021 | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a new kludge scheme to model the dynamics of generic
extreme-mass-ratio inspirals (EMRIs; stellar compact objects spiraling into a
spinning supermassive black hole) and their gravitational-wave emission. The
Chimera scheme is a hybrid method that combines tools from different
approximation techniques in General Relativity: (i) A multipolar,
post-Minkowskian expansion for the far-zone metric perturbation (the
gravitational waveforms) and for the local prescription of the self-force; (ii)
a post-Newtonian expansion for the computation of the multipole moments in
terms of the trajectories; and (iii) a BH perturbation theory expansion when
treating the trajectories as a sequence of self-adjusting Kerr geodesics. The
EMRI trajectory is made out of Kerr geodesic fragments joined via the method of
osculating elements as dictated by the multipolar post-Minkowskian
radiation-reaction prescription. We implemented the proper coordinate mapping
between Boyer-Lindquist coordinates, associated with the Kerr geodesics, and
harmonic coordinates, associated with the multipolar post-Minkowskian
decomposition. The Chimera scheme is thus a combination of approximations that
can be used to model generic inspirals of systems with extreme to intermediate
mass ratios, and hence, it can provide valuable information for future
space-based gravitational-wave observatories, like LISA, and even for advanced
ground detectors. The local character in time of our multipolar
post-Minkowskian self-force makes this scheme amenable to study the possible
appearance of transient resonances in generic inspirals.
| [
{
"created": "Fri, 27 Jan 2012 08:08:05 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Sopuerta",
"Carlos F.",
""
],
[
"Yunes",
"Nicolas",
""
]
] | We describe a new kludge scheme to model the dynamics of generic extreme-mass-ratio inspirals (EMRIs; stellar compact objects spiraling into a spinning supermassive black hole) and their gravitational-wave emission. The Chimera scheme is a hybrid method that combines tools from different approximation techniques in General Relativity: (i) A multipolar, post-Minkowskian expansion for the far-zone metric perturbation (the gravitational waveforms) and for the local prescription of the self-force; (ii) a post-Newtonian expansion for the computation of the multipole moments in terms of the trajectories; and (iii) a BH perturbation theory expansion when treating the trajectories as a sequence of self-adjusting Kerr geodesics. The EMRI trajectory is made out of Kerr geodesic fragments joined via the method of osculating elements as dictated by the multipolar post-Minkowskian radiation-reaction prescription. We implemented the proper coordinate mapping between Boyer-Lindquist coordinates, associated with the Kerr geodesics, and harmonic coordinates, associated with the multipolar post-Minkowskian decomposition. The Chimera scheme is thus a combination of approximations that can be used to model generic inspirals of systems with extreme to intermediate mass ratios, and hence, it can provide valuable information for future space-based gravitational-wave observatories, like LISA, and even for advanced ground detectors. The local character in time of our multipolar post-Minkowskian self-force makes this scheme amenable to study the possible appearance of transient resonances in generic inspirals. |
gr-qc/0106039 | Chris Doran | Chris Doran and Anthony Lasenby | Perturbation Theory Calculation of the Black Hole Elastic Scattering
Cross Section | 11 latex pages, no figures | Phys.Rev. D66 (2002) 024006 | 10.1103/PhysRevD.66.024006 | null | gr-qc astro-ph | null | The differential cross section for scattering of a Dirac particle in a black
hole background is found. The result is the gravitational analog of the Mott
formula for scattering in a Coulomb background. The equivalence principle is
neatly embodied in the cross section, which depends only on the incident
velocity, and not the particle mass. The low angle limit agrees with classical
calculations based on the geodesic equation. The calculation employs a
well-defined iterative scheme which can be extended to higher orders. Repeating
the calculation in different gauges shows that our result for the cross section
is gauge-invariant and highlights the issues involved in setting up a sensible
iterative scheme.
| [
{
"created": "Mon, 11 Jun 2001 15:43:12 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Doran",
"Chris",
""
],
[
"Lasenby",
"Anthony",
""
]
] | The differential cross section for scattering of a Dirac particle in a black hole background is found. The result is the gravitational analog of the Mott formula for scattering in a Coulomb background. The equivalence principle is neatly embodied in the cross section, which depends only on the incident velocity, and not the particle mass. The low angle limit agrees with classical calculations based on the geodesic equation. The calculation employs a well-defined iterative scheme which can be extended to higher orders. Repeating the calculation in different gauges shows that our result for the cross section is gauge-invariant and highlights the issues involved in setting up a sensible iterative scheme. |
1706.05530 | Hui-Ling Li | Hui-Ling Li, Zhong-Wen Feng | Holographic Van der Waals phase transition of the higher dimensional
electrically charged hairy black hole | 9 pages, 6 figures, 3 tables | Eur. Phys. J. C 78 (2018) 49 | 10.1140/epjc/s10052-018-5515-8 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | With motivation by holography, employing black hole entropy, two point
connection function and entanglement entropy, we show that, for the higher
dimensional Anti-de Sitter charged hairy black hole in the fixed charged
ensemble, a Van der Waals-like phase transition can be observed. Furthermore,
based on the Maxwell's equal area construction, we check numerically the equal
area law for a first order phase transition in order to further characterize
the Van der Waals-like phase transition.
| [
{
"created": "Sat, 17 Jun 2017 13:01:54 GMT",
"version": "v1"
}
] | 2018-10-08 | [
[
"Li",
"Hui-Ling",
""
],
[
"Feng",
"Zhong-Wen",
""
]
] | With motivation by holography, employing black hole entropy, two point connection function and entanglement entropy, we show that, for the higher dimensional Anti-de Sitter charged hairy black hole in the fixed charged ensemble, a Van der Waals-like phase transition can be observed. Furthermore, based on the Maxwell's equal area construction, we check numerically the equal area law for a first order phase transition in order to further characterize the Van der Waals-like phase transition. |
gr-qc/9310020 | Joe Parry | J. Parry D. S. Salopek and J. M. Stewart | Solving the Hamilton-Jacobi Equation for General Relativity | 13 pages, RevTeX, DAMTP-R93/22 | Phys.Rev.D49:2872-2881,1994 | 10.1103/PhysRevD.49.2872 | null | gr-qc | null | We demonstrate a systematic method for solving the Hamilton-Jacobi equation
for general relativity with the inclusion of matter fields. The generating
functional is expanded in a series of spatial gradients. Each term is
manifestly invariant under reparameterizations of the spatial coordinates
(``gauge-invariant''). At each order we solve the Hamiltonian constraint using
a conformal transformation of the 3-metric as well as a line integral in
superspace. This gives a recursion relation for the generating functional which
then may be solved to arbitrary order simply by functionally differentiating
previous orders. At fourth order in spatial gradients, we demonstrate solutions
for irrotational dust as well as for a scalar field. We explicitly evolve the
3-metric to the same order. This method can be used to derive the Zel'dovich
approximation for general relativity.
| [
{
"created": "Tue, 12 Oct 1993 16:43:12 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Salopek",
"J. Parry D. S.",
""
],
[
"Stewart",
"J. M.",
""
]
] | We demonstrate a systematic method for solving the Hamilton-Jacobi equation for general relativity with the inclusion of matter fields. The generating functional is expanded in a series of spatial gradients. Each term is manifestly invariant under reparameterizations of the spatial coordinates (``gauge-invariant''). At each order we solve the Hamiltonian constraint using a conformal transformation of the 3-metric as well as a line integral in superspace. This gives a recursion relation for the generating functional which then may be solved to arbitrary order simply by functionally differentiating previous orders. At fourth order in spatial gradients, we demonstrate solutions for irrotational dust as well as for a scalar field. We explicitly evolve the 3-metric to the same order. This method can be used to derive the Zel'dovich approximation for general relativity. |
2403.10741 | Daniele Oriti | Daniele Oriti | Hydrodynamics on (mini)superspace, or a non-linear extension of quantum
cosmology | 31 pages; invited contribution to the collective volume "Time and
timelessness in fundamental physics and cosmology" (eds S. De Bianchi, M.
Forgione, L. Marongiu), to be published by Springer | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We outline the content and theoretical support for the proposal of
"hydrodynamics on (mini)superspace" (or a non-linear extension of quantum
cosmology) as an effective framework for quantum gravity in a cosmological
context. The basis for the proposal is a general correspondence between
hydrodynamics and cosmology, and a picture of the universe as a quantum gravity
condensate. The support comes from several directions. One is from mathematical
physics: the hydrodynamics of quantum fluids can be mapped to relativistic
cosmological dynamics, and both share the same conformal symmetries, which can
be unraveled via geometric methods in superspace. The second is that the
proposed framework is realized in quantum gravity formalisms like group field
theory, in which an emergent cosmological dynamics can be extracted from the
hydrodynamics of fundamental quantum simplices in a condensate phase. The same
proposal can be motivated from the idea of 3rd quantization of gravity and from
recent work on quantum cosmology, as an effective way of incorporating topology
changing processes or cosmological inhomogeneities, respectively. A key
conceptual ingredient is the relational understanding of space and time, which
makes superspace the natural arena for gravitational dynamics, as opposed to
the "spacetime" manifold, together with the general idea of emergent spacetime.
The proposal and the results supporting it suggest an exciting dialogue between
quantum gravity, the theory of quantum fluids and cosmology, as well as a new
direction for analogue gravity simulations in the lab.
| [
{
"created": "Sat, 16 Mar 2024 00:03:26 GMT",
"version": "v1"
}
] | 2024-03-19 | [
[
"Oriti",
"Daniele",
""
]
] | We outline the content and theoretical support for the proposal of "hydrodynamics on (mini)superspace" (or a non-linear extension of quantum cosmology) as an effective framework for quantum gravity in a cosmological context. The basis for the proposal is a general correspondence between hydrodynamics and cosmology, and a picture of the universe as a quantum gravity condensate. The support comes from several directions. One is from mathematical physics: the hydrodynamics of quantum fluids can be mapped to relativistic cosmological dynamics, and both share the same conformal symmetries, which can be unraveled via geometric methods in superspace. The second is that the proposed framework is realized in quantum gravity formalisms like group field theory, in which an emergent cosmological dynamics can be extracted from the hydrodynamics of fundamental quantum simplices in a condensate phase. The same proposal can be motivated from the idea of 3rd quantization of gravity and from recent work on quantum cosmology, as an effective way of incorporating topology changing processes or cosmological inhomogeneities, respectively. A key conceptual ingredient is the relational understanding of space and time, which makes superspace the natural arena for gravitational dynamics, as opposed to the "spacetime" manifold, together with the general idea of emergent spacetime. The proposal and the results supporting it suggest an exciting dialogue between quantum gravity, the theory of quantum fluids and cosmology, as well as a new direction for analogue gravity simulations in the lab. |
1602.04233 | Izzet Sakalli | I. Sakalli and O. A. Aslan | Absorption Cross-section and Decay Rate of Rotating Linear Dilaton Black
Holes | 18 pages and 2 figures | Astroparticle Physics 74, 73 (2016) | 10.1016/j.astropartphys.2015.10.005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analytically study the scalar perturbation of non-asymptotically flat
(NAF) rotating linear dilaton black holes (RLDBHs) in 4-dimensions. We show
that both radial and angular wave equations can be solved in terms of the
hypergeometric functions. The exact greybody factor (GF), the absorption
cross-section (ACS), and the decay rate (DR) for the massless scalar waves are
computed for these black holes (BHs). The results obtained for ACS and DR are
discussed through graphs.
| [
{
"created": "Fri, 12 Feb 2016 21:48:43 GMT",
"version": "v1"
}
] | 2016-02-16 | [
[
"Sakalli",
"I.",
""
],
[
"Aslan",
"O. A.",
""
]
] | We analytically study the scalar perturbation of non-asymptotically flat (NAF) rotating linear dilaton black holes (RLDBHs) in 4-dimensions. We show that both radial and angular wave equations can be solved in terms of the hypergeometric functions. The exact greybody factor (GF), the absorption cross-section (ACS), and the decay rate (DR) for the massless scalar waves are computed for these black holes (BHs). The results obtained for ACS and DR are discussed through graphs. |
1710.10052 | Paul Tod | Paul Tod | The St\"utzfunktion and the Cut Function | 10 pages. This is a corrected, revised and updated version of a paper
which originally appeared in Recent Advances in General Relativity, eds. A I
Janis and J R Porter, Einstein Studies vol. 4, Birkha\"user 1992 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I review some standard theory of convex bodies in $\mathbb{R}^3$ and rephrase
it in a formalism of Ted Newman to show the relation between the
St\"utzfunktion of the former theory and the cut function introduced by Ted.
This leads to a conjectured inequality for space-like two-spheres in Minkowski
space that generalises Minkowski's inequality and is implied by Penrose's
cosmic censorship hypothesis.
| [
{
"created": "Fri, 27 Oct 2017 09:53:18 GMT",
"version": "v1"
}
] | 2017-10-30 | [
[
"Tod",
"Paul",
""
]
] | I review some standard theory of convex bodies in $\mathbb{R}^3$ and rephrase it in a formalism of Ted Newman to show the relation between the St\"utzfunktion of the former theory and the cut function introduced by Ted. This leads to a conjectured inequality for space-like two-spheres in Minkowski space that generalises Minkowski's inequality and is implied by Penrose's cosmic censorship hypothesis. |
0807.1178 | Jeandrew Brink | Jeandrew Brink | Spacetime Encodings I- A Spacetime Reconstruction Problem | 5 pages, 2 figures | Phys.Rev.D78:102001,2008 | 10.1103/PhysRevD.78.102001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper explores features of an idealized mathematical machine (algorithm)
that would be capable of reconstructing the gravitational nature (the
multipolar structure or spacetime metric) of a compact object, by observing
gravitational radiation emitted by a small object that orbits and spirals into
it. An outline is given of the mathematical developments that must be carried
out in order to construct such a machine.
| [
{
"created": "Tue, 8 Jul 2008 06:43:15 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Brink",
"Jeandrew",
""
]
] | This paper explores features of an idealized mathematical machine (algorithm) that would be capable of reconstructing the gravitational nature (the multipolar structure or spacetime metric) of a compact object, by observing gravitational radiation emitted by a small object that orbits and spirals into it. An outline is given of the mathematical developments that must be carried out in order to construct such a machine. |
1708.02878 | Paul Klinger | Piotr T. Chru\'sciel, Erwann Delay, Paul Klinger, Andreas Kriegl,
Peter W. Michor, Armin Rainer | Non-singular spacetimes with a negative cosmological constant: V. Boson
stars | 21 pages, v2: journal accepted version | Letters in Mathematical Physics 108, 9 (September 2018), 2009-2030 | 10.1007/s11005-018-1062-3 | UWThPh-2017-23 | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove existence of large families of solutions of Einstein-complex scalar
field equations with a negative cosmological constant, with a stationary or
static metric and a time-periodic complex scalar field.
| [
{
"created": "Wed, 9 Aug 2017 15:28:14 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Feb 2018 11:49:58 GMT",
"version": "v2"
}
] | 2019-02-06 | [
[
"Chruściel",
"Piotr T.",
""
],
[
"Delay",
"Erwann",
""
],
[
"Klinger",
"Paul",
""
],
[
"Kriegl",
"Andreas",
""
],
[
"Michor",
"Peter W.",
""
],
[
"Rainer",
"Armin",
""
]
] | We prove existence of large families of solutions of Einstein-complex scalar field equations with a negative cosmological constant, with a stationary or static metric and a time-periodic complex scalar field. |
2311.06653 | Eduar Antonio Becerra Vergara | F. D. Lora-Clavijo, G. D. Prada-M\'endez, L. M. Becerra, E. A.
Becerra-Vergara | The $\textit{q}$-metric naked singularity: A viable explanation for the
nature of the central object in the Milky Way | Accepted for publication in Classical and Quantum Gravity | null | 10.1088/1361-6382/ad0b9e | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we investigate whether the compact object at the center of the
Milky Way is a naked singularity described by the $\textit{q}$-metric
spacetime. Our fitting of the astrometric and spectroscopic data for the S2
star implies that similarly to the Schwarzschild black hole, the
$\textit{q}$-metric naked singularity offers a satisfactory fit to the observed
measurements. Additionally, it is shown that the shadow produced by the naked
singularity is consistent with the shadow observed by the Event Horizon
Telescope collaboration for Sgr-A*. It is worth mentioning that the spatial
distribution of the S-stars favors the notion that the compact object at the
center of our Galaxy can be described by an almost static spacetime. Based on
these findings, the $\textit{q}$-metric naked singularity turns up as a
compelling candidate for further investigation.
| [
{
"created": "Sat, 11 Nov 2023 19:47:04 GMT",
"version": "v1"
}
] | 2023-11-14 | [
[
"Lora-Clavijo",
"F. D.",
""
],
[
"Prada-Méndez",
"G. D.",
""
],
[
"Becerra",
"L. M.",
""
],
[
"Becerra-Vergara",
"E. A.",
""
]
] | In this work, we investigate whether the compact object at the center of the Milky Way is a naked singularity described by the $\textit{q}$-metric spacetime. Our fitting of the astrometric and spectroscopic data for the S2 star implies that similarly to the Schwarzschild black hole, the $\textit{q}$-metric naked singularity offers a satisfactory fit to the observed measurements. Additionally, it is shown that the shadow produced by the naked singularity is consistent with the shadow observed by the Event Horizon Telescope collaboration for Sgr-A*. It is worth mentioning that the spatial distribution of the S-stars favors the notion that the compact object at the center of our Galaxy can be described by an almost static spacetime. Based on these findings, the $\textit{q}$-metric naked singularity turns up as a compelling candidate for further investigation. |
2007.06766 | Rodrigo Lipparelli Fernandez | Rodrigo L. Fernandez, Ribamar R. R. Reis and Sergio E. Jor\'as | Massive scalar wave packet emission by a charged Black Hole and Cosmic
Censorship Conjecture violation | 9 pages, 8 figures | Phys. Rev. D 102, 024049 (2020) | 10.1103/PhysRevD.102.024049 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the tunneling probability of a massive ($m_w$) uncharged scalar
packet out from a near-extremal, static charged black hole (with mass $M$ and
charge $Q\lesssim M$). We show that there is indeed a net probability that a
massive uncharged particle tunnels out from the black hole so that the final
state (with new mass $M'\equiv M-m_w < Q$) does violate the cosmic censorship
conjecture. Nevertheless, the typical time for such a black hole to discharge
(i.e, to absorb charge $-Q$ from its surroundings and then become neutral) is
much smaller than the tunneling time; therefore, the violation is never
attained in practice. Even for a completely isolated black hole (should it
exist), the standard time dilation near the horizon stretches the typical
violation time scale to unobservable values.
| [
{
"created": "Tue, 14 Jul 2020 01:56:56 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Jul 2020 19:02:22 GMT",
"version": "v2"
}
] | 2020-07-21 | [
[
"Fernandez",
"Rodrigo L.",
""
],
[
"Reis",
"Ribamar R. R.",
""
],
[
"Jorás",
"Sergio E.",
""
]
] | We study the tunneling probability of a massive ($m_w$) uncharged scalar packet out from a near-extremal, static charged black hole (with mass $M$ and charge $Q\lesssim M$). We show that there is indeed a net probability that a massive uncharged particle tunnels out from the black hole so that the final state (with new mass $M'\equiv M-m_w < Q$) does violate the cosmic censorship conjecture. Nevertheless, the typical time for such a black hole to discharge (i.e, to absorb charge $-Q$ from its surroundings and then become neutral) is much smaller than the tunneling time; therefore, the violation is never attained in practice. Even for a completely isolated black hole (should it exist), the standard time dilation near the horizon stretches the typical violation time scale to unobservable values. |
gr-qc/9807035 | Burkhard Kleihaus | B. Kleihaus (1), J. Kunz (2), A. Sood (2) and M. Wirschins (2) ((1)
NUI Maynooth, Ireland, (2) University Oldenburg, Germany) | Black Holes with Yang-Mills Hair | LaTeX using epsf, aipproc, 10 pages including 9 ps figures, Talk held
by Jutta Kunz at the Conference on Particles, Fields and Gravitation in Lodz,
Poland, April 1998 | null | 10.1063/1.57143 | null | gr-qc hep-th | null | In Einstein-Maxwell theory black holes are uniquely determined by their mass,
their charge and their angular momentum. This is no longer true in
Einstein-Yang-Mills theory. We discuss sequences of neutral and charged SU(N)
Einstein-Yang-Mills black holes, which are static spherically symmetric and
asymptotically flat, and which carry Yang-Mills hair. Furthermore, in
Einstein-Maxwell theory static black holes are spherically symmetric. We
demonstrate that, in contrast, SU(2) Einstein-Yang-Mills theory possesses a
sequence of black holes, which are static and only axially symmetric.
| [
{
"created": "Wed, 15 Jul 1998 12:06:17 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Kleihaus",
"B.",
""
],
[
"Kunz",
"J.",
""
],
[
"Sood",
"A.",
""
],
[
"Wirschins",
"M.",
""
]
] | In Einstein-Maxwell theory black holes are uniquely determined by their mass, their charge and their angular momentum. This is no longer true in Einstein-Yang-Mills theory. We discuss sequences of neutral and charged SU(N) Einstein-Yang-Mills black holes, which are static spherically symmetric and asymptotically flat, and which carry Yang-Mills hair. Furthermore, in Einstein-Maxwell theory static black holes are spherically symmetric. We demonstrate that, in contrast, SU(2) Einstein-Yang-Mills theory possesses a sequence of black holes, which are static and only axially symmetric. |
1407.6047 | Gergely Sz\'ekely | J. X. Madar\'asz, G. Sz\'ekely and M. Stannett | On the Possibility and Consequences of Negative Mass | 8 pages, 5 figures | null | null | null | gr-qc math-ph math.LO math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the possibility and consequences of the existence of particles
having negative relativistic masses, and show that their existence implies the
existence of faster- than-light particles (tachyons). Our proof requires only
two postulates concerning such particles: that it is possible for particles of
any (positive, negative or zero) relativistic mass to collide inelastically
with 'normal' (i.e. positive relativistic mass) particles, and that
four-momentum is conserved in such collisions.
| [
{
"created": "Tue, 22 Jul 2014 21:27:48 GMT",
"version": "v1"
}
] | 2014-07-24 | [
[
"Madarász",
"J. X.",
""
],
[
"Székely",
"G.",
""
],
[
"Stannett",
"M.",
""
]
] | We investigate the possibility and consequences of the existence of particles having negative relativistic masses, and show that their existence implies the existence of faster- than-light particles (tachyons). Our proof requires only two postulates concerning such particles: that it is possible for particles of any (positive, negative or zero) relativistic mass to collide inelastically with 'normal' (i.e. positive relativistic mass) particles, and that four-momentum is conserved in such collisions. |
gr-qc/0601119 | Ingemar Bengtsson | J. E. Aman, Ingemar Bengtsson and Narit Pidokrajt | Flat Information Geometries in Black Hole Thermodynamics | 14 pages, one figure. Dedicated to Rafael Sorkin's birthday | Gen.Rel.Grav.38:1305-1315,2006 | 10.1007/s10714-006-0306-1 | null | gr-qc | null | The Hessian of either the entropy or the energy function can be regarded as a
metric on a Gibbs surface. For two parameter families of asymptotically flat
black holes in arbitrary dimension one or the other of these metrics are flat,
and the state space is a flat wedge. The mathematical reason for this is traced
back to the scale invariance of the Einstein-Maxwell equations. The picture of
state space that we obtain makes some properties such as the occurence of
divergent specific heats transparent.
| [
{
"created": "Fri, 27 Jan 2006 12:59:53 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Aman",
"J. E.",
""
],
[
"Bengtsson",
"Ingemar",
""
],
[
"Pidokrajt",
"Narit",
""
]
] | The Hessian of either the entropy or the energy function can be regarded as a metric on a Gibbs surface. For two parameter families of asymptotically flat black holes in arbitrary dimension one or the other of these metrics are flat, and the state space is a flat wedge. The mathematical reason for this is traced back to the scale invariance of the Einstein-Maxwell equations. The picture of state space that we obtain makes some properties such as the occurence of divergent specific heats transparent. |
gr-qc/0306029 | Matteo Luca Ruggiero | Matteo Luca Ruggiero, Angelo Tartaglia | Einstein-Cartan theory as a theory of defects in space-time | 18 pages, 7 EPS figures, RevTeX4, to appear in the American Journal
of Physics, revised version with typos corrected | Am.J.Phys.71:1303-1313,2003 | 10.1119/1.1596176 | null | gr-qc | null | The Einstein-Cartan theory of gravitation and the classical theory of defects
in an elastic medium are presented and compared. The former is an extension of
general relativity and refers to four-dimensional space-time, while we
introduce the latter as a description of the equilibrium state of a
three-dimensional continuum. Despite these important differences, an analogy is
built on their common geometrical foundations, and it is shown that a
space-time with curvature and torsion can be considered as a state of a
four-dimensional continuum containing defects. This formal analogy is useful
for illustrating the geometrical concept of torsion by applying it to concrete
physical problems. Moreover, the presentation of these theories using a common
geometrical basis allows a deeper understanding of their foundations.
| [
{
"created": "Sat, 7 Jun 2003 09:45:53 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Jul 2003 12:02:34 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Ruggiero",
"Matteo Luca",
""
],
[
"Tartaglia",
"Angelo",
""
]
] | The Einstein-Cartan theory of gravitation and the classical theory of defects in an elastic medium are presented and compared. The former is an extension of general relativity and refers to four-dimensional space-time, while we introduce the latter as a description of the equilibrium state of a three-dimensional continuum. Despite these important differences, an analogy is built on their common geometrical foundations, and it is shown that a space-time with curvature and torsion can be considered as a state of a four-dimensional continuum containing defects. This formal analogy is useful for illustrating the geometrical concept of torsion by applying it to concrete physical problems. Moreover, the presentation of these theories using a common geometrical basis allows a deeper understanding of their foundations. |
0901.1569 | Jose Luis Jaramillo | Jos\'e Luis Jaramillo | Isolated Horizon structures in quasiequilibrium black hole initial data | 4 pages, no figures. Shortened presentation matching the published
version | Phys.Rev.D79:087506,2009 | 10.1103/PhysRevD.79.087506 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Isolated horizon conditions enforce the time invariance of both the intrinsic
and the extrinsic geometry of a (quasilocal) black hole horizon. Nonexpanding
horizons, only requiring the invariance of the intrinsic geometry, have been
successfully employed in the (excision) initial data of black holes in
instantaneous equilibrium. Here we propose the use of the full isolated horizon
structure when solving the elliptic system resulting from the complete set of
conformal 3+1 Einstein equations under a quasiequilibrium ansatz prescription.
We argue that a set of geometric inner boundary conditions for this extended
elliptic system then follows, determining the shape of the excision surface.
| [
{
"created": "Mon, 12 Jan 2009 13:08:13 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Apr 2009 09:59:14 GMT",
"version": "v2"
}
] | 2009-10-29 | [
[
"Jaramillo",
"José Luis",
""
]
] | Isolated horizon conditions enforce the time invariance of both the intrinsic and the extrinsic geometry of a (quasilocal) black hole horizon. Nonexpanding horizons, only requiring the invariance of the intrinsic geometry, have been successfully employed in the (excision) initial data of black holes in instantaneous equilibrium. Here we propose the use of the full isolated horizon structure when solving the elliptic system resulting from the complete set of conformal 3+1 Einstein equations under a quasiequilibrium ansatz prescription. We argue that a set of geometric inner boundary conditions for this extended elliptic system then follows, determining the shape of the excision surface. |
gr-qc/0601069 | Joseph Henson | Joe Henson | Constructing an interval of Minkowski space from a causal set | latex; 8 pages, one figure; accepted for publication in Classical and
Quantum Gravity Letters | Class.Quant.Grav.23:L29-L35,2006 | 10.1088/0264-9381/23/4/L02 | null | gr-qc | null | A criticism sometimes made of the causal set quantum gravity program is that
there is no practical scheme for identifying manifoldlike causal sets and
finding embeddings of them into manifolds. A computational method for
constructing an approximate embedding of a small manifoldlike causal set into
Minkowski space (or any spacetime that is approximately flat at short scales)
is given, and tested in the 2 dimensional case. This method can also be used to
determine how manifoldlike a causal set is, and conversely to define scales of
manifoldlikeness.
| [
{
"created": "Tue, 17 Jan 2006 15:34:36 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Henson",
"Joe",
""
]
] | A criticism sometimes made of the causal set quantum gravity program is that there is no practical scheme for identifying manifoldlike causal sets and finding embeddings of them into manifolds. A computational method for constructing an approximate embedding of a small manifoldlike causal set into Minkowski space (or any spacetime that is approximately flat at short scales) is given, and tested in the 2 dimensional case. This method can also be used to determine how manifoldlike a causal set is, and conversely to define scales of manifoldlikeness. |
1304.6542 | Natsuki Watanabe | Natsuki Watanabe | Domain wall in $f(R)$ gravity | 11 pages, no figure | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational impact inside and outside of a domain wall is studied in
the context of $f(R)$ gravity theory. The function $f(R)$ is found which
satisfies the stability conditions. Our results imply that the domain wall may
cause topological inflation.
| [
{
"created": "Wed, 24 Apr 2013 10:37:21 GMT",
"version": "v1"
}
] | 2013-04-25 | [
[
"Watanabe",
"Natsuki",
""
]
] | The gravitational impact inside and outside of a domain wall is studied in the context of $f(R)$ gravity theory. The function $f(R)$ is found which satisfies the stability conditions. Our results imply that the domain wall may cause topological inflation. |
1410.6710 | Prabir Rudra | Prabir Rudra (Asutosh College) | Coincidence Problem in f(T) Gravity Models | 14 pages, 15 figures (Revised form, Accepted for publication in
Astrophys. and Space Sci.) | null | 10.1007/s10509-015-2365-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this assignment we try to probe the role played by torsion in the current
scenario of coincidence and devise a set-up for its realization. In order to
model the scenario, the energy arising from the torsion component is considered
analogous to dark energy. An interaction between dark energy and dark matter is
considered, which is by far the best possible tool to realize the coincidence.
A set-up is designed and a constraint equation is obtained which screens the
models of \textit{f(T)} gravity that can successfully accommodate the
stationary scenario in its framework, from those which cannot. Due to the
absence of a universally accepted interaction term introduced by a fundamental
theory, the study is conducted over three different forms of chosen interaction
terms. As an illustration two widely known models of \textit{f(T)} gravity are
taken into consideration and used in the designed setup. The study reveals that
the realization of the coincidence scenario as well as the role played by
torsion in the current universe is a model dependent phenomenon. It is found
that the first model showed a considerable departure from the stationary
scenario. On the contrary the other four models are perfectly consistent with
our setup and generated a satisfactory stationary scenario, thus showing their
cosmological viability and their superiority over their counterparts. For the
third model (exponential model) it was seen that the cosmological coincidence
is realized only in the phantom regime. For the fourth (logarithmic model) and
the fifth models, we see that the the stationary scenario is attained for
negative interaction values. This shows that the direction of flow must be from
dark energy to dark matter unlike the previous models. Under such circumstances
the universe will return from the present energy dominated phase to a matter
dominated phase.
| [
{
"created": "Thu, 23 Oct 2014 07:06:24 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Apr 2015 11:14:13 GMT",
"version": "v2"
}
] | 2015-06-03 | [
[
"Rudra",
"Prabir",
"",
"Asutosh College"
]
] | In this assignment we try to probe the role played by torsion in the current scenario of coincidence and devise a set-up for its realization. In order to model the scenario, the energy arising from the torsion component is considered analogous to dark energy. An interaction between dark energy and dark matter is considered, which is by far the best possible tool to realize the coincidence. A set-up is designed and a constraint equation is obtained which screens the models of \textit{f(T)} gravity that can successfully accommodate the stationary scenario in its framework, from those which cannot. Due to the absence of a universally accepted interaction term introduced by a fundamental theory, the study is conducted over three different forms of chosen interaction terms. As an illustration two widely known models of \textit{f(T)} gravity are taken into consideration and used in the designed setup. The study reveals that the realization of the coincidence scenario as well as the role played by torsion in the current universe is a model dependent phenomenon. It is found that the first model showed a considerable departure from the stationary scenario. On the contrary the other four models are perfectly consistent with our setup and generated a satisfactory stationary scenario, thus showing their cosmological viability and their superiority over their counterparts. For the third model (exponential model) it was seen that the cosmological coincidence is realized only in the phantom regime. For the fourth (logarithmic model) and the fifth models, we see that the the stationary scenario is attained for negative interaction values. This shows that the direction of flow must be from dark energy to dark matter unlike the previous models. Under such circumstances the universe will return from the present energy dominated phase to a matter dominated phase. |
gr-qc/9810047 | G. R. Filewood | G. R. Filewood | Microtorsion | 18 pages | null | null | null | gr-qc | null | The problem of unification of electro-magnetism and gravitation in four
dimensions; some new ideas involving torsion. A metric consisting of a
combination of symmetric and anti-symmetric parts is postulated and, in the
framework of general covariance, used to derive the free-field electro-magnetic
stress-energy tensor and the source tensor.
| [
{
"created": "Wed, 14 Oct 1998 08:38:29 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Filewood",
"G. R.",
""
]
] | The problem of unification of electro-magnetism and gravitation in four dimensions; some new ideas involving torsion. A metric consisting of a combination of symmetric and anti-symmetric parts is postulated and, in the framework of general covariance, used to derive the free-field electro-magnetic stress-energy tensor and the source tensor. |
1503.02916 | Iver Brevik | Iver Brevik and Alexander Timoshkin | Inhomogeneous Dark Fluid and Dark Matter, Leading to a Bounce Cosmology | 13 pages, no figures. Mini-review, to appear in the MDPI journal
Universe | Universe 2015, 1, 24-37 | 10.3390/universe1010024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The purpose of this short review is to describe cosmological models with a
linear inhomogeneous time-dependent equation of state (EoS) for the dark
energy, when the dark fluid is coupled with dark matter. This may lead to a
bounce cosmology. We consider equivalent descriptions in terms of the EoS
parameters for an exponential, a power-law, or a double-exponential law for the
scale factor $a$. Stability issues are discussed by considering small
perturbations around the critical points for the bounce, in the early as well
as in the late, universe. The latter part of the paper is concerned with dark
energy coupled with dark matter in viscous fluid cosmology. We allow the bulk
viscosity $\zeta=\zeta(H,t)$ to be a function of the Hubble parameter and the
time, and consider the Little Rip, the Pseudo Rip, and the bounce universe.
Analytic expressions for characteristic properties of these cosmological models
are obtained.
| [
{
"created": "Tue, 10 Mar 2015 14:10:23 GMT",
"version": "v1"
}
] | 2015-03-17 | [
[
"Brevik",
"Iver",
""
],
[
"Timoshkin",
"Alexander",
""
]
] | The purpose of this short review is to describe cosmological models with a linear inhomogeneous time-dependent equation of state (EoS) for the dark energy, when the dark fluid is coupled with dark matter. This may lead to a bounce cosmology. We consider equivalent descriptions in terms of the EoS parameters for an exponential, a power-law, or a double-exponential law for the scale factor $a$. Stability issues are discussed by considering small perturbations around the critical points for the bounce, in the early as well as in the late, universe. The latter part of the paper is concerned with dark energy coupled with dark matter in viscous fluid cosmology. We allow the bulk viscosity $\zeta=\zeta(H,t)$ to be a function of the Hubble parameter and the time, and consider the Little Rip, the Pseudo Rip, and the bounce universe. Analytic expressions for characteristic properties of these cosmological models are obtained. |
1904.00963 | Aron Kovacs | \'Aron D. Kov\'acs | Well-posedness of cubic Horndeski theories | null | Phys. Rev. D 100, 024005 (2019) | 10.1103/PhysRevD.100.024005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the local well-posedness of the initial value problem for cubic
Horndeski theories. Three different strongly hyperbolic modifications of the
ADM formulation of the Einstein equations are extended to cubic Horndeski
theories in the weak field regime. In the first one, the equations of motion
are rewritten as a coupled elliptic-hyperbolic system of partial differential
equations. The second one is based on the BSSN formulation with a generalised
Bona-Mass\'o slicing (covering the 1+log slicing) and non-dynamical shift
vector. The third one is an extension of the CCZ4 formulation with a
generalised Bona-Mass\'o slicing (also covering the 1+log slicing) and a gamma
driver shift condition. This final formulation may be particularly suitable for
applications in non-linear numerical simulations.
| [
{
"created": "Mon, 1 Apr 2019 16:54:50 GMT",
"version": "v1"
}
] | 2019-07-17 | [
[
"Kovács",
"Áron D.",
""
]
] | We study the local well-posedness of the initial value problem for cubic Horndeski theories. Three different strongly hyperbolic modifications of the ADM formulation of the Einstein equations are extended to cubic Horndeski theories in the weak field regime. In the first one, the equations of motion are rewritten as a coupled elliptic-hyperbolic system of partial differential equations. The second one is based on the BSSN formulation with a generalised Bona-Mass\'o slicing (covering the 1+log slicing) and non-dynamical shift vector. The third one is an extension of the CCZ4 formulation with a generalised Bona-Mass\'o slicing (also covering the 1+log slicing) and a gamma driver shift condition. This final formulation may be particularly suitable for applications in non-linear numerical simulations. |
2110.09608 | Sashwat Tanay Mr | Gihyuk Cho, Sashwat Tanay, Achamveedu Gopakumar and Hyung Mok Lee | Generalized quasi-Keplerian solution for eccentric, non-spinning compact
binaries at 4PN order and the associated IMR waveform | 38 pages, 4 figures | Phys. Rev. D 105, 064010 (2022) | 10.1103/PhysRevD.105.064010 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive fourth post-Newtonian (4PN) contributions to the Keplerian-type
parametric solution associated with the conservative dynamics of eccentric,
non-spinning compact binaries. The solution has been computed while ignoring
certain zero-average, oscillatory terms arising due to 4PN tail effects. We
provide explicit expressions for the parametric solution and various orbital
elements in terms of the conserved energy, angular momentum and symmetric mass
ratio. Canonical perturbation theory (along with the technique of Pade
approximant) is used to incorporate the 4PN nonlocal-in-time tail effects
within the action-angles framework. We then employ the resulting solution to
obtain an updated inspiral-merger-ringdown (IMR) waveform that models the
coalescence of non-spinning, moderately eccentric black hole binaries,
influenced by arXiv:1709.02007. Our updated waveform is expected to be valid
over similar parameter range as the above reference. We also present a related
waveform which makes use of only the post-Newtonian equations and thus is valid
only for the inspiral stage. This waveform is expected to work for a much
larger range of eccentricity ($e_t \lesssim 0.85$) than our full IMR waveform
(which assumes circularization of the binaries close to merger). We finally
pursue preliminary data analysis studies to probe the importance of including
the 4PN contributions to the binary dynamics while constructing gravitational
waveform templates for eccentric mergers.
| [
{
"created": "Mon, 18 Oct 2021 20:11:20 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Mar 2022 23:06:54 GMT",
"version": "v2"
},
{
"created": "Sun, 17 Apr 2022 19:08:03 GMT",
"version": "v3"
}
] | 2022-04-19 | [
[
"Cho",
"Gihyuk",
""
],
[
"Tanay",
"Sashwat",
""
],
[
"Gopakumar",
"Achamveedu",
""
],
[
"Lee",
"Hyung Mok",
""
]
] | We derive fourth post-Newtonian (4PN) contributions to the Keplerian-type parametric solution associated with the conservative dynamics of eccentric, non-spinning compact binaries. The solution has been computed while ignoring certain zero-average, oscillatory terms arising due to 4PN tail effects. We provide explicit expressions for the parametric solution and various orbital elements in terms of the conserved energy, angular momentum and symmetric mass ratio. Canonical perturbation theory (along with the technique of Pade approximant) is used to incorporate the 4PN nonlocal-in-time tail effects within the action-angles framework. We then employ the resulting solution to obtain an updated inspiral-merger-ringdown (IMR) waveform that models the coalescence of non-spinning, moderately eccentric black hole binaries, influenced by arXiv:1709.02007. Our updated waveform is expected to be valid over similar parameter range as the above reference. We also present a related waveform which makes use of only the post-Newtonian equations and thus is valid only for the inspiral stage. This waveform is expected to work for a much larger range of eccentricity ($e_t \lesssim 0.85$) than our full IMR waveform (which assumes circularization of the binaries close to merger). We finally pursue preliminary data analysis studies to probe the importance of including the 4PN contributions to the binary dynamics while constructing gravitational waveform templates for eccentric mergers. |
gr-qc/9907019 | William A. Hiscock | Chad Clark, William A. Hiscock, and Shane L. Larson | Null geodesics in the Alcubierre warp drive spacetime: the view from the
bridge | 14 pages + 3 figures, REVTeX | Class.Quant.Grav. 16 (1999) 3965-3972 | 10.1088/0264-9381/16/12/313 | MSUPHY99.02 | gr-qc | null | The null geodesic equations in the Alcubierre warp drive spacetime are
numerically integrated to determine the angular deflection and redshift of
photons which propagate through the distortion of the ``warp drive'' bubble to
reach an observer at the origin of the warp effect. We find that for a starship
with an effective warp speed exceeding the speed of light, stars in the forward
hemisphere will appear closer to the direction of motion than they would to an
observer at rest. This aberration is qualitatively similar to that caused by
special relativity. Behind the starship, a conical region forms from within
which no signal can reach the starship, an effective ``horizon''. Conversely,
there is also an horizon-like structure in a conical region in front of the
starship, into which the starship cannot send a signal. These causal structures
are somewhat analogous to the Mach cones associated with supersonic fluid flow.
The existence of these structures suggests that the divergence of quantum
vacuum energy when the starship effectively exceeds the speed of light, first
discovered in two dimensions, will likely be present in four dimensions also,
and prevent any warp-drive starship from ever exceeding the effective speed of
light.
| [
{
"created": "Tue, 6 Jul 1999 18:53:33 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Clark",
"Chad",
""
],
[
"Hiscock",
"William A.",
""
],
[
"Larson",
"Shane L.",
""
]
] | The null geodesic equations in the Alcubierre warp drive spacetime are numerically integrated to determine the angular deflection and redshift of photons which propagate through the distortion of the ``warp drive'' bubble to reach an observer at the origin of the warp effect. We find that for a starship with an effective warp speed exceeding the speed of light, stars in the forward hemisphere will appear closer to the direction of motion than they would to an observer at rest. This aberration is qualitatively similar to that caused by special relativity. Behind the starship, a conical region forms from within which no signal can reach the starship, an effective ``horizon''. Conversely, there is also an horizon-like structure in a conical region in front of the starship, into which the starship cannot send a signal. These causal structures are somewhat analogous to the Mach cones associated with supersonic fluid flow. The existence of these structures suggests that the divergence of quantum vacuum energy when the starship effectively exceeds the speed of light, first discovered in two dimensions, will likely be present in four dimensions also, and prevent any warp-drive starship from ever exceeding the effective speed of light. |
gr-qc/9808065 | Dharam V. Ahluwalia | D. V. Ahluwalia (EFUAZ, Zacatecas) | On an incompleteness in the general-relativistic description of
gravitation | Based on a paper of the author published in Mod. Phys. Lett. A Vol.
13, #17 (1998) 1397-1400. Invited talk presented at the symposium to honor
Professor Mendel Sachs. To appear in the proceedings. For a popular version
see, Charles Seife, New Scientist 13 June 1998, p. 11 | null | null | EFUAZ FT-98-64 | gr-qc astro-ph hep-ph quant-ph | null | The recently introduced mechanism of flavor-oscillation clocks has been used
to emphasize observability of constant gravitational potentials and thereby to
question completeness of the theory of general relativity. An inequality has
been derived to experimentally test the thesis presented.
| [
{
"created": "Tue, 25 Aug 1998 17:22:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ahluwalia",
"D. V.",
"",
"EFUAZ, Zacatecas"
]
] | The recently introduced mechanism of flavor-oscillation clocks has been used to emphasize observability of constant gravitational potentials and thereby to question completeness of the theory of general relativity. An inequality has been derived to experimentally test the thesis presented. |
gr-qc/0304089 | Roy Maartens | Roy Maartens (Portsmouth) | Brane-world cosmological perturbations: a covariant approach | Based on a talk at the Brane-world Gravity Workshop, Yukawa
Institute, Jan 2002. 17 pages, 4 figures | Prog.Theor.Phys.Suppl.148:213-234,2003 | 10.1143/PTPS.148.213 | null | gr-qc astro-ph hep-th | null | The standard cosmological model, based on general relativity with an
inflationary era, is very effective in accounting for a broad range of observed
features of the universe. However, the ongoing puzzles about the nature of dark
matter and dark energy, together with the problem of a fundamental theoretical
framework for inflation, indicate that cosmology may be probing the limits of
validity of general relativity. The early universe provides a testing ground
for theories of gravity, since gravitational dynamics can lead to
characteristic imprints on the CMB and other cosmological observations.
Precision cosmology is in principle a means to constrain and possibly falsify
candidate quantum gravity theories like M theory. Generalized Randall-Sundrum
brane-worlds provide a phenomenological means to test aspects of M theory. I
outline the 1+3-covariant approach to cosmological perturbations in these
brane-worlds, and its application to CMB anisotropies.
| [
{
"created": "Wed, 23 Apr 2003 14:33:41 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Maartens",
"Roy",
"",
"Portsmouth"
]
] | The standard cosmological model, based on general relativity with an inflationary era, is very effective in accounting for a broad range of observed features of the universe. However, the ongoing puzzles about the nature of dark matter and dark energy, together with the problem of a fundamental theoretical framework for inflation, indicate that cosmology may be probing the limits of validity of general relativity. The early universe provides a testing ground for theories of gravity, since gravitational dynamics can lead to characteristic imprints on the CMB and other cosmological observations. Precision cosmology is in principle a means to constrain and possibly falsify candidate quantum gravity theories like M theory. Generalized Randall-Sundrum brane-worlds provide a phenomenological means to test aspects of M theory. I outline the 1+3-covariant approach to cosmological perturbations in these brane-worlds, and its application to CMB anisotropies. |
1903.05695 | Beatriz Elizaga Navascu\'es | Beatriz Elizaga Navascu\'es, Guillermo A. Mena Marug\'an and Thomas
Thiemann | Hamiltonian diagonalization in hybrid quantum cosmology | 22 pages, matches published version | Class. Quantum Grav. 36, 185010 (2019) | 10.1088/1361-6382/ab32af | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the possibility of selecting a natural vacuum state for scalar and
tensor gauge-invariant cosmological perturbations in the context of hybrid
quantum cosmology, by identifying those variables for the description of the
perturbations that display a dynamical behavior adapted to the evolution of the
entire cosmology. We make use of a canonical formulation of the whole of the
cosmological system in which the perturbative gauge-invariant degrees of
freedom are identified as canonical variables. Introducing background-dependent
linear canonical transformations on these perturbations and completing them for
the entire system, we are able to characterize a generic collection of
annihilation and creationlike variables that obey the dynamics dictated by a
respective collection of Hamiltonians. We then impose that such Hamiltonians
possess no self-interaction terms so that, in a Fock representation with normal
ordering, they act diagonally on the basis of $n$-particle states. This leads
to a semilinear first-order partial differential equation with respect to the
background for the coefficients that define the annihilation and creationlike
variables for all Fourier modes, as well as to a very precise ultraviolet
characterization of them. Such first-order equation contains, in the imaginary
part of its complex solutions, the complicated second-order field equation that
typically arises for the time-dependent frequency of the perturbations in the
context of quantum field theory in curved spacetimes. We check that the
asymptotic knowledge acquired allows one to select the standard vacua in
Minkowski and de Sitter spacetimes. Finally, we discuss the relation of our
vacuum and the standard adiabatic vacua, and check that our asymptotic
characterization of variables with a diagonal Hamiltonian displays the
properties that would be desirable for an adiabatic state of infinite order.
| [
{
"created": "Wed, 13 Mar 2019 19:38:14 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Sep 2019 07:44:44 GMT",
"version": "v2"
}
] | 2020-07-07 | [
[
"Navascués",
"Beatriz Elizaga",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
],
[
"Thiemann",
"Thomas",
""
]
] | We explore the possibility of selecting a natural vacuum state for scalar and tensor gauge-invariant cosmological perturbations in the context of hybrid quantum cosmology, by identifying those variables for the description of the perturbations that display a dynamical behavior adapted to the evolution of the entire cosmology. We make use of a canonical formulation of the whole of the cosmological system in which the perturbative gauge-invariant degrees of freedom are identified as canonical variables. Introducing background-dependent linear canonical transformations on these perturbations and completing them for the entire system, we are able to characterize a generic collection of annihilation and creationlike variables that obey the dynamics dictated by a respective collection of Hamiltonians. We then impose that such Hamiltonians possess no self-interaction terms so that, in a Fock representation with normal ordering, they act diagonally on the basis of $n$-particle states. This leads to a semilinear first-order partial differential equation with respect to the background for the coefficients that define the annihilation and creationlike variables for all Fourier modes, as well as to a very precise ultraviolet characterization of them. Such first-order equation contains, in the imaginary part of its complex solutions, the complicated second-order field equation that typically arises for the time-dependent frequency of the perturbations in the context of quantum field theory in curved spacetimes. We check that the asymptotic knowledge acquired allows one to select the standard vacua in Minkowski and de Sitter spacetimes. Finally, we discuss the relation of our vacuum and the standard adiabatic vacua, and check that our asymptotic characterization of variables with a diagonal Hamiltonian displays the properties that would be desirable for an adiabatic state of infinite order. |
2203.09917 | Abhishek Chowdhuri | Abhishek Chowdhuri, Arpan Bhattacharyya | Study of eccentric binaries in Horndeski theory | 35 Pages, 1 figures, section 8 updated and more discussions regarding
the rate of energy and angular-momentum flux added, several consistency
checks of our results are added, a figure showing the variation of the
semi-major axis of the orbit of the binary as a function of eccentricity
added, discussion updated, references added, Minor typos corrected in Eq.
(7.22)& (A.2), title slightly changed | Phys.Rev.D 106 (2022) 6, 064046 | 10.1103/PhysRevD.106.064046 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the orbital evolution of eccentric binary systems in Horndeski
gravity. This particular theory provides a testbed to give insightful
comparisons with data. We compute the rate of energy loss and the rate of
change of angular momentum for the binaries by calculating the multipole
moments of the radiation fields. We have used appropriate parameters for the
eccentric binaries to compute the decay rates of its orbital eccentricity and
semi-major axis. We then compare this decay rate with that of GR.
| [
{
"created": "Fri, 18 Mar 2022 12:53:16 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Sep 2022 16:49:21 GMT",
"version": "v2"
},
{
"created": "Tue, 27 Sep 2022 08:10:40 GMT",
"version": "v3"
}
] | 2022-09-28 | [
[
"Chowdhuri",
"Abhishek",
""
],
[
"Bhattacharyya",
"Arpan",
""
]
] | We study the orbital evolution of eccentric binary systems in Horndeski gravity. This particular theory provides a testbed to give insightful comparisons with data. We compute the rate of energy loss and the rate of change of angular momentum for the binaries by calculating the multipole moments of the radiation fields. We have used appropriate parameters for the eccentric binaries to compute the decay rates of its orbital eccentricity and semi-major axis. We then compare this decay rate with that of GR. |
0902.1859 | Andreas Kleinw\"achter | Robert Filter and Andreas Kleinw\"achter | On the multipole moments of a rigidly rotating fluid body | 5 pages, 4 figures, to appear in Annalen der Physik | Annalen Phys.18:102-106,2009 | 10.1002/andp.200910337 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on numerical simulations and analytical calculations we formulate a new
conjecture concerning the multipole moments of a rigidly rotating fluid body in
equilibrium. The conjecture implies that the exterior region of such a fluid is
not described by the Kerr metric.
| [
{
"created": "Wed, 11 Feb 2009 12:10:53 GMT",
"version": "v1"
}
] | 2009-09-28 | [
[
"Filter",
"Robert",
""
],
[
"Kleinwächter",
"Andreas",
""
]
] | Based on numerical simulations and analytical calculations we formulate a new conjecture concerning the multipole moments of a rigidly rotating fluid body in equilibrium. The conjecture implies that the exterior region of such a fluid is not described by the Kerr metric. |
0805.2926 | Bahram Mashhoon | Bahram Mashhoon | Nonlocal Special Relativity | 35 pages, invited paper to appear in the Minkowski issue of Annalen
der Physik | Annalen Phys.17:705-727, 2008 | 10.1002/andp.200810308 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the special theory of relativity, Lorentz invariance is extended in
Minkowski spacetime from ideal inertial observers to actual observers by means
of the hypothesis of locality, which postulates that accelerated observers are
always pointwise inertial. A critical examination of the locality assumption
reveals its domain of validity: it is true for pointwise coincidences, but is
in conflict with wave-particle duality. To remedy this situation, a nonlocal
theory of accelerated systems is presented that reduces to the standard theory
in the limit of small accelerations. Some of the main consequences of nonlocal
special relativity are briefly outlined.
| [
{
"created": "Mon, 19 May 2008 19:00:21 GMT",
"version": "v1"
}
] | 2009-11-18 | [
[
"Mashhoon",
"Bahram",
""
]
] | In the special theory of relativity, Lorentz invariance is extended in Minkowski spacetime from ideal inertial observers to actual observers by means of the hypothesis of locality, which postulates that accelerated observers are always pointwise inertial. A critical examination of the locality assumption reveals its domain of validity: it is true for pointwise coincidences, but is in conflict with wave-particle duality. To remedy this situation, a nonlocal theory of accelerated systems is presented that reduces to the standard theory in the limit of small accelerations. Some of the main consequences of nonlocal special relativity are briefly outlined. |
2307.06674 | Krishnakanta Bhattacharya | Krishnakanta Bhattacharya and Kazuharu Bamba | Boundary terms and Brown-York quasi-local parameters for scalar-tensor
theory: a study on both timelike and null hypersurfaces | 36 Pages, Version accepted for publication in Physical Review D | Phys. Rev. D 109 (2024), 064026 | 10.1103/PhysRevD.109.064026 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Boundary term and Brown-York (BY) formalism, which is based on the
Hamilton-Jacobi principle, are complimentary of each other as the gravitational
actions are not, usually, well-posed. In scalar-tensor theory, which is an
important alternative to GR, it has been shown that this complementarity
becomes even more crucial in establishing the equivalence of the BY quasi-local
parameters in the two frames which are conformally connected. Furthermore,
Brown-York tensor and the corresponding quasi-local parameters are important
from two important yet different aspects of gravitational theories: black hole
thermodynamics and fluid-gravity correspondence. The investigation suggests
that while the two frames are equivalent from the thermodynamic viewpoints,
they are not equivalent from the perspective of fluid-gravity analogy or the
membrane paradigm. In addition, the null boundary term and null Brown-York
formalism are the recent developments (so far obtained only for GR) which is
non-trivial owing to the degeneracy of the null surface. In the present
analysis these are extended for scalar-tensor theory. The present analysis also
suggests that, regarding the equivalence (or inequivalence) of the two frame,
the null formalism draws the same inferences as of the timelike case, which in
turn establishes the consistency of the newly developed null Brown-York
formalism.
| [
{
"created": "Thu, 13 Jul 2023 10:49:31 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Feb 2024 23:07:27 GMT",
"version": "v2"
}
] | 2024-03-12 | [
[
"Bhattacharya",
"Krishnakanta",
""
],
[
"Bamba",
"Kazuharu",
""
]
] | Boundary term and Brown-York (BY) formalism, which is based on the Hamilton-Jacobi principle, are complimentary of each other as the gravitational actions are not, usually, well-posed. In scalar-tensor theory, which is an important alternative to GR, it has been shown that this complementarity becomes even more crucial in establishing the equivalence of the BY quasi-local parameters in the two frames which are conformally connected. Furthermore, Brown-York tensor and the corresponding quasi-local parameters are important from two important yet different aspects of gravitational theories: black hole thermodynamics and fluid-gravity correspondence. The investigation suggests that while the two frames are equivalent from the thermodynamic viewpoints, they are not equivalent from the perspective of fluid-gravity analogy or the membrane paradigm. In addition, the null boundary term and null Brown-York formalism are the recent developments (so far obtained only for GR) which is non-trivial owing to the degeneracy of the null surface. In the present analysis these are extended for scalar-tensor theory. The present analysis also suggests that, regarding the equivalence (or inequivalence) of the two frame, the null formalism draws the same inferences as of the timelike case, which in turn establishes the consistency of the newly developed null Brown-York formalism. |
0906.2042 | Seiju Ohashi | Seiju Ohashi, Tetsuya Shiromizu, Sumio Yamada | The Riemannian Penrose inequality and a virtual gravitational collapse | 4pages, minor changes, accepted for publication in Physical Review D | Phys.Rev.D80:047501,2009 | 10.1103/PhysRevD.80.047501 | null | gr-qc astro-ph.CO hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reinterpret the proof of the Riemannian Penrose inequality by H. Bray. The
modified argument turns out to have a nice feature so that the flow of
Riemannian metrics appearing Bray's proof gives a Lorentzian metric of a
spacetime. We also discuss a possible extension of our approach to charged
black holes.
| [
{
"created": "Thu, 11 Jun 2009 04:54:47 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Jul 2009 04:39:42 GMT",
"version": "v2"
}
] | 2010-02-25 | [
[
"Ohashi",
"Seiju",
""
],
[
"Shiromizu",
"Tetsuya",
""
],
[
"Yamada",
"Sumio",
""
]
] | We reinterpret the proof of the Riemannian Penrose inequality by H. Bray. The modified argument turns out to have a nice feature so that the flow of Riemannian metrics appearing Bray's proof gives a Lorentzian metric of a spacetime. We also discuss a possible extension of our approach to charged black holes. |
2008.09774 | Jie Jiang | Xin-Yang Wang and Jie Jiang | Investigating the Linearized Second Law in Horndeski Gravity | 6 pages | Phys. Rev. D 102, 084020 (2020) | 10.1103/PhysRevD.102.084020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Since the entropy of stationary black holes in Horndeski gravity will be
modified by the non-minimally coupling scalar field, a significant issue of
whether the Wald entropy still obeys the linearized second law of black hole
thermodynamics can be proposed. To investigate this issue, a physical process
that the black hole in Horndeski gravity is perturbed by the accreting matter
fields and finally settles down to a stationary state is considered. According
to the two assumptions that there is a regular bifurcation surface in the
background spacetime and that the matter fields always satisfy the null energy
condition, one can show that the Wald entropy monotonically increases along the
future event horizon under the linear order approximation without any specific
expression of the metric. It illustrates that the Wald entropy of black holes
in Horndeski gravitational theory still obeys the requirement of the linearized
second law. Our work strengthens the physical explanation of Wald entropy in
Horndeski gravity and takes a step towards studying the area increase theorem
in the gravitational theories with non-minimal coupled matter fields.
| [
{
"created": "Sat, 22 Aug 2020 07:59:17 GMT",
"version": "v1"
}
] | 2020-10-12 | [
[
"Wang",
"Xin-Yang",
""
],
[
"Jiang",
"Jie",
""
]
] | Since the entropy of stationary black holes in Horndeski gravity will be modified by the non-minimally coupling scalar field, a significant issue of whether the Wald entropy still obeys the linearized second law of black hole thermodynamics can be proposed. To investigate this issue, a physical process that the black hole in Horndeski gravity is perturbed by the accreting matter fields and finally settles down to a stationary state is considered. According to the two assumptions that there is a regular bifurcation surface in the background spacetime and that the matter fields always satisfy the null energy condition, one can show that the Wald entropy monotonically increases along the future event horizon under the linear order approximation without any specific expression of the metric. It illustrates that the Wald entropy of black holes in Horndeski gravitational theory still obeys the requirement of the linearized second law. Our work strengthens the physical explanation of Wald entropy in Horndeski gravity and takes a step towards studying the area increase theorem in the gravitational theories with non-minimal coupled matter fields. |
0901.1955 | Ahmed Youssef | Jean-Pierre Gazeau (APC), Ahmed Youssef (APC) | A discrete nonetheless remarkable brick in de Sitter: the "massless
minimally coupled field" | Proceedings of the XXVII Colloquium on Group Theoretical Methods in
Physics, Yerevan, August 2008 | Phys.Atom.Nucl.73:222-229,2010 | 10.1134/S1063778810020031 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Over the last ten years interest in the physics of de Sitter spacetime has
been growing very fast. Besides the supposed existence of a "de sitterian
period" in inflation theories, the observational evidence of an acceleration of
the universe expansion (interpreted as a positive cosmological constant or a
"dark energy" or some form of "quintessence") has triggered a lot of attention
in the physics community. A specific de sitterian field called "massless
minimally coupled field" (mmc) plays a fundamental role in inflation models and
in the construction of the de sitterian gravitational field. A covariant
quantization of the mmc field, `a la Krein-Gupta-Bleuler was proposed in [1].
In this talk, we will review this construction and explain the relevance of
such a field in the construction of a massless spin 2 field in de Sitter
space-time.
| [
{
"created": "Wed, 14 Jan 2009 09:05:27 GMT",
"version": "v1"
}
] | 2014-11-18 | [
[
"Gazeau",
"Jean-Pierre",
"",
"APC"
],
[
"Youssef",
"Ahmed",
"",
"APC"
]
] | Over the last ten years interest in the physics of de Sitter spacetime has been growing very fast. Besides the supposed existence of a "de sitterian period" in inflation theories, the observational evidence of an acceleration of the universe expansion (interpreted as a positive cosmological constant or a "dark energy" or some form of "quintessence") has triggered a lot of attention in the physics community. A specific de sitterian field called "massless minimally coupled field" (mmc) plays a fundamental role in inflation models and in the construction of the de sitterian gravitational field. A covariant quantization of the mmc field, `a la Krein-Gupta-Bleuler was proposed in [1]. In this talk, we will review this construction and explain the relevance of such a field in the construction of a massless spin 2 field in de Sitter space-time. |
gr-qc/9703081 | Soumya Mohanty | Soumya D. Mohanty (IUCAA, Pune, India) | Hierarchical search strategy for the detection of gravitational waves
from coalescing binaries: Extension to post-Newtonian wave forms | 30 page RevTeX file and 17 figures (postscript). Submitted to PRD Feb
21, 1997 | Phys.Rev.D57:630-658,1998 | 10.1103/PhysRevD.57.630 | IUCAA preprint # 15/97 | gr-qc | null | The detection of gravitational waves from coalescing compact binaries would
be a computationally intensive process if a single bank of template wave forms
(i.e., a one step search) is used. In an earlier paper we had presented a
detection strategy, called a two step search}, that utilizes a hierarchy of
template banks. It was shown that in the simple case of a family of Newtonian
signals, an on-line two step search was about 8 times faster than an on-line
one step search (for initial LIGO). In this paper we extend the two step search
to the more realistic case of zero spin 1.5 post-Newtonian wave forms. We also
present formulas for detection and false alarm probabilities which take
statistical correlations into account. We find that for the case of a 1.5
post-Newtonian family of templates and signals, an on-line two step search
requires about 1/21 the computing power that would be required for the
corresponding on-line one step search. This reduction is achieved when signals
having strength S = 10.34 are required to be detected with a probability of
0.95, at an average of one false event per year, and the noise power spectral
density used is that of advanced LIGO. For initial LIGO, the reduction achieved
in computing power is about 1/27 for S = 9.98 and the same probabilities for
detection and false alarm as above.
| [
{
"created": "Thu, 27 Mar 1997 11:11:39 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Mohanty",
"Soumya D.",
"",
"IUCAA, Pune, India"
]
] | The detection of gravitational waves from coalescing compact binaries would be a computationally intensive process if a single bank of template wave forms (i.e., a one step search) is used. In an earlier paper we had presented a detection strategy, called a two step search}, that utilizes a hierarchy of template banks. It was shown that in the simple case of a family of Newtonian signals, an on-line two step search was about 8 times faster than an on-line one step search (for initial LIGO). In this paper we extend the two step search to the more realistic case of zero spin 1.5 post-Newtonian wave forms. We also present formulas for detection and false alarm probabilities which take statistical correlations into account. We find that for the case of a 1.5 post-Newtonian family of templates and signals, an on-line two step search requires about 1/21 the computing power that would be required for the corresponding on-line one step search. This reduction is achieved when signals having strength S = 10.34 are required to be detected with a probability of 0.95, at an average of one false event per year, and the noise power spectral density used is that of advanced LIGO. For initial LIGO, the reduction achieved in computing power is about 1/27 for S = 9.98 and the same probabilities for detection and false alarm as above. |
1508.03820 | Arick Shao | Gustav Holzegel, Arick Shao | Unique continuation from infinity in asymptotically Anti-de Sitter
spacetimes | 50 pages, minor edits from referee comments | null | 10.1007/s00220-016-2576-0 | null | gr-qc hep-th math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the unique continuation properties of asymptotically Anti-de
Sitter spacetimes by studying Klein-Gordon-type equations $\Box_g \phi + \sigma
\phi = \mathcal{G} ( \phi, \partial \phi )$, $\sigma \in \mathbb{R}$, on a
large class of such spacetimes. Our main result establishes that if $\phi$
vanishes to sufficiently high order (depending on $\sigma$) on a sufficiently
long time interval along the conformal boundary $\mathcal{I}$, then the
solution necessarily vanishes in a neighborhood of $\mathcal{I}$. In
particular, in the $\sigma$-range where Dirichlet and Neumann conditions are
possible on $\mathcal{I}$ for the forward problem, we prove uniqueness if both
these conditions are imposed. The length of the time interval can be related to
the refocusing time of null geodesics on these backgrounds and is expected to
be sharp. Some global applications as well a uniqueness result for
gravitational perturbations are also discussed. The proof is based on novel
Carleman estimates established in this setting.
| [
{
"created": "Sun, 16 Aug 2015 12:33:55 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Aug 2016 14:29:07 GMT",
"version": "v2"
}
] | 2016-09-14 | [
[
"Holzegel",
"Gustav",
""
],
[
"Shao",
"Arick",
""
]
] | We consider the unique continuation properties of asymptotically Anti-de Sitter spacetimes by studying Klein-Gordon-type equations $\Box_g \phi + \sigma \phi = \mathcal{G} ( \phi, \partial \phi )$, $\sigma \in \mathbb{R}$, on a large class of such spacetimes. Our main result establishes that if $\phi$ vanishes to sufficiently high order (depending on $\sigma$) on a sufficiently long time interval along the conformal boundary $\mathcal{I}$, then the solution necessarily vanishes in a neighborhood of $\mathcal{I}$. In particular, in the $\sigma$-range where Dirichlet and Neumann conditions are possible on $\mathcal{I}$ for the forward problem, we prove uniqueness if both these conditions are imposed. The length of the time interval can be related to the refocusing time of null geodesics on these backgrounds and is expected to be sharp. Some global applications as well a uniqueness result for gravitational perturbations are also discussed. The proof is based on novel Carleman estimates established in this setting. |
1712.09474 | Parampreet Singh | Sahil Saini, Parampreet Singh | Generic absence of strong singularities in loop quantum Bianchi-IX
spacetimes | 23 pages | null | 10.1088/1361-6382/aaad79 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the generic resolution of strong singularities in loop quantized
effective Bianchi-IX spacetime in two different quantizations - the connection
operator based `A' quantization and the extrinsic curvature based `K'
quantization. We show that in the effective spacetime description with
arbitrary matter content, it is necessary to include inverse triad corrections
to resolve all the strong singularities in the `A' quantization. Whereas in the
`K' quantization these results can be obtained without including inverse triad
corrections. Under these conditions, the energy density, expansion and shear
scalars for both of the quantization prescriptions are bounded. Notably, both
the quantizations can result in potentially curvature divergent events if
matter content allows divergences in the partial derivatives of the energy
density with respect to the triad variables at a finite energy density. Such
events are found to be weak curvature singularities beyond which geodesics can
be extended in the effective spacetime. Our results show that all potential
strong curvature singularities of the classical theory are forbidden in
Bianchi-IX spacetime in loop quantum cosmology and geodesic evolution never
breaks down for such events.
| [
{
"created": "Wed, 27 Dec 2017 01:35:08 GMT",
"version": "v1"
}
] | 2018-03-14 | [
[
"Saini",
"Sahil",
""
],
[
"Singh",
"Parampreet",
""
]
] | We study the generic resolution of strong singularities in loop quantized effective Bianchi-IX spacetime in two different quantizations - the connection operator based `A' quantization and the extrinsic curvature based `K' quantization. We show that in the effective spacetime description with arbitrary matter content, it is necessary to include inverse triad corrections to resolve all the strong singularities in the `A' quantization. Whereas in the `K' quantization these results can be obtained without including inverse triad corrections. Under these conditions, the energy density, expansion and shear scalars for both of the quantization prescriptions are bounded. Notably, both the quantizations can result in potentially curvature divergent events if matter content allows divergences in the partial derivatives of the energy density with respect to the triad variables at a finite energy density. Such events are found to be weak curvature singularities beyond which geodesics can be extended in the effective spacetime. Our results show that all potential strong curvature singularities of the classical theory are forbidden in Bianchi-IX spacetime in loop quantum cosmology and geodesic evolution never breaks down for such events. |
1306.6486 | Emma Jakobsson | Ingemar Bengtsson, Emma Jakobsson, Jos\'e M. M. Senovilla | Trapped surfaces in Oppenheimer-Snyder black holes | 34 pages, 7 figures | Phys. Rev. D 88 (2013) 064012 | 10.1103/PhysRevD.88.064012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Oppenheimer-Snyder solution models a homogeneous round dust cloud
collapsing to a black hole. Inside its event horizon there is a region through
which trapped surfaces pass. We try to determine exactly where the boundary of
this region meets the centre of the cloud. We present explicit examples of the
relevant trapped (topological) spheres; they extend into the exterior vacuum
region, and are carefully matched at the junction between the cloud and the
vacuum.
| [
{
"created": "Thu, 27 Jun 2013 13:03:46 GMT",
"version": "v1"
}
] | 2013-09-17 | [
[
"Bengtsson",
"Ingemar",
""
],
[
"Jakobsson",
"Emma",
""
],
[
"Senovilla",
"José M. M.",
""
]
] | The Oppenheimer-Snyder solution models a homogeneous round dust cloud collapsing to a black hole. Inside its event horizon there is a region through which trapped surfaces pass. We try to determine exactly where the boundary of this region meets the centre of the cloud. We present explicit examples of the relevant trapped (topological) spheres; they extend into the exterior vacuum region, and are carefully matched at the junction between the cloud and the vacuum. |
2106.10242 | Zhengcheng Gu | Tianyao Fang and Zheng-Cheng Gu | Topological gravity in 3+1D and a possible origin of dark matte | 24 pages, comments and suggestions are welcome | null | null | null | gr-qc cond-mat.str-el math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | Dark matter is one of the deepest mystery of the universe. So far there is no
natural explanation why the dark matter should exist and even dominate the
universe. In this paper, we begin with a 3+1D topological gravity theory which
is super renormalizable with vanishing beta functions, then we argue that
Einstein gravity can emerge by condensing loop-like excitation from the
underlying topological gravity theory. In the meanwhile, the uncondensed
loop-like excitations serves as a natural candidate of dark matter and a
generalized Einstein equation can be derived in the presence of
loop-source(dark matter) background. Surprisingly, we find that such kind of
dark matter will not contribute to scalar curvature, however, it will become a
source of torsion. Finally, we derive the generalized Einstein equation in the
presence of Dirac field. Very different from the usual Einstein-Carton theory,
our theory further predicts that any type of normal matter, including Dirac
field will not produce torsion. All these unique predictions can be tested by
future experiments. Our framework suggests that topological invariant principle
might play a more profound role than the well-known general covariance
principle, especially towards understanding the nature of dark matter and
quantum gravity in 3+1D.
| [
{
"created": "Fri, 18 Jun 2021 17:08:33 GMT",
"version": "v1"
}
] | 2021-06-21 | [
[
"Fang",
"Tianyao",
""
],
[
"Gu",
"Zheng-Cheng",
""
]
] | Dark matter is one of the deepest mystery of the universe. So far there is no natural explanation why the dark matter should exist and even dominate the universe. In this paper, we begin with a 3+1D topological gravity theory which is super renormalizable with vanishing beta functions, then we argue that Einstein gravity can emerge by condensing loop-like excitation from the underlying topological gravity theory. In the meanwhile, the uncondensed loop-like excitations serves as a natural candidate of dark matter and a generalized Einstein equation can be derived in the presence of loop-source(dark matter) background. Surprisingly, we find that such kind of dark matter will not contribute to scalar curvature, however, it will become a source of torsion. Finally, we derive the generalized Einstein equation in the presence of Dirac field. Very different from the usual Einstein-Carton theory, our theory further predicts that any type of normal matter, including Dirac field will not produce torsion. All these unique predictions can be tested by future experiments. Our framework suggests that topological invariant principle might play a more profound role than the well-known general covariance principle, especially towards understanding the nature of dark matter and quantum gravity in 3+1D. |
1811.07786 | Enrico Barausse | Oscar Ramos and Enrico Barausse | Constraints on Ho\v{r}ava gravity from binary black hole observations | 18 pages, 4 figures; typos corrected and one reference added in
version 2, to match published version; v3: typo in eq 17b corrected in
erratum (typo does not propagate, results unchanged) | Phys. Rev. D 99, 024034 (2019) | 10.1103/PhysRevD.99.024034 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Ho\v{r}ava gravity breaks Lorentz symmetry by introducing a preferred
spacetime foliation, which is defined by a timelike dynamical scalar field, the
khronon. The presence of this preferred foliation makes black hole solutions
more complicated than in General Relativity, with the appearance of multiple
distinct event horizons: a matter horizon for light/matter fields, a spin-0
horizon for the scalar excitations of the khronon, a spin-2 horizon for
tensorial gravitational waves, and even, at least in spherical symmetry, a
universal horizon for instantaneously propagating modes appearing in the
ultraviolet. We study how black hole solutions in Ho\v{r}ava gravity change
when the black hole is allowed to move with low velocity relative to the
preferred foliation. These slowly moving solutions are a crucial ingredient to
compute black hole "sensitivities" and predict gravitational wave emission (and
in particular dipolar radiation) from the inspiral of binary black hole
systems. We find that for generic values of the theory's three dimensionless
coupling constants, slowly moving black holes present curvature singularities
at the universal horizon. Singularities at the spin-0 horizon also arise unless
one waives the requirement of asymptotic flatness at spatial infinity.
Nevertheless, we have verified that at least in a one-dimensional subset of the
(three-dimensional) parameter space of the theory's coupling constants, slowly
moving black holes are regular everywhere, even though they coincide with the
general relativistic ones (thus implying in particular the absence of dipolar
gravitational radiation). Remarkably, this subset of the parameter space
essentially coincides with the one selected by the recent constraints from
GW170817 and by solar system tests.
| [
{
"created": "Mon, 19 Nov 2018 16:38:15 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Jan 2019 17:18:45 GMT",
"version": "v2"
},
{
"created": "Mon, 6 Sep 2021 09:03:49 GMT",
"version": "v3"
}
] | 2021-09-07 | [
[
"Ramos",
"Oscar",
""
],
[
"Barausse",
"Enrico",
""
]
] | Ho\v{r}ava gravity breaks Lorentz symmetry by introducing a preferred spacetime foliation, which is defined by a timelike dynamical scalar field, the khronon. The presence of this preferred foliation makes black hole solutions more complicated than in General Relativity, with the appearance of multiple distinct event horizons: a matter horizon for light/matter fields, a spin-0 horizon for the scalar excitations of the khronon, a spin-2 horizon for tensorial gravitational waves, and even, at least in spherical symmetry, a universal horizon for instantaneously propagating modes appearing in the ultraviolet. We study how black hole solutions in Ho\v{r}ava gravity change when the black hole is allowed to move with low velocity relative to the preferred foliation. These slowly moving solutions are a crucial ingredient to compute black hole "sensitivities" and predict gravitational wave emission (and in particular dipolar radiation) from the inspiral of binary black hole systems. We find that for generic values of the theory's three dimensionless coupling constants, slowly moving black holes present curvature singularities at the universal horizon. Singularities at the spin-0 horizon also arise unless one waives the requirement of asymptotic flatness at spatial infinity. Nevertheless, we have verified that at least in a one-dimensional subset of the (three-dimensional) parameter space of the theory's coupling constants, slowly moving black holes are regular everywhere, even though they coincide with the general relativistic ones (thus implying in particular the absence of dipolar gravitational radiation). Remarkably, this subset of the parameter space essentially coincides with the one selected by the recent constraints from GW170817 and by solar system tests. |
1807.09214 | Donato Bini | Kjell Rosquist, Donato Bini, Bahram Mashhoon | Twisted Gravitational Waves of Petrov Type D | 22 pages, RevTex macros; v2: typos corrected, matches published
version | Phys. Rev. D 98, 064039 (2018) | 10.1103/PhysRevD.98.064039 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Twisted gravitational waves (TGWs) are nonplanar unidirectional Ricci-flat
solutions of general relativity. Thus far only TGWs of Petrov type \emph{II}
are implicitly known that depend on a solution of a partial differential
equation and have wave fronts with negative Gaussian curvature. A special
Petrov type \emph{D} class of such solutions that depends on an arbitrary
function is explicitly studied in this paper and its Killing vectors are worked
out. Moreover, we concentrate on two solutions of this class, namely, the
Harrison solution and a simpler solution we call the $w$-metric and determine
their Penrose plane-wave limits. The corresponding transition from a nonplanar
TGW to a plane gravitational wave is elucidated.
| [
{
"created": "Tue, 24 Jul 2018 16:24:12 GMT",
"version": "v1"
},
{
"created": "Sun, 23 Sep 2018 13:32:50 GMT",
"version": "v2"
}
] | 2018-09-25 | [
[
"Rosquist",
"Kjell",
""
],
[
"Bini",
"Donato",
""
],
[
"Mashhoon",
"Bahram",
""
]
] | Twisted gravitational waves (TGWs) are nonplanar unidirectional Ricci-flat solutions of general relativity. Thus far only TGWs of Petrov type \emph{II} are implicitly known that depend on a solution of a partial differential equation and have wave fronts with negative Gaussian curvature. A special Petrov type \emph{D} class of such solutions that depends on an arbitrary function is explicitly studied in this paper and its Killing vectors are worked out. Moreover, we concentrate on two solutions of this class, namely, the Harrison solution and a simpler solution we call the $w$-metric and determine their Penrose plane-wave limits. The corresponding transition from a nonplanar TGW to a plane gravitational wave is elucidated. |
gr-qc/0606129 | George Sparling | George Sparling | The structure of cosmic time | 39 pages | null | null | null | gr-qc | null | Following the approach of Julien Lesgourgues [astro-ph/0409426], we analyze
the mathematical structure of the time co-ordinate of present day cosmological
models, where these models include a cosmological constant term to account for
the observed acceleration of the universe: we find that in all cases, except
for a set of measure zero in the parameter space, the time is given by an
(abelian) integral on a torus; the imaginary period of this integral then gives
a natural periodicity in imaginary time for the universe; following Stephen
Hawking, this periodicity may be interpreted either as giving a fundamental
mass scale for the universe, or (using Planck's constant) a fundamental
temperature, or both. The precise structure that emerges suggests that the
structure of time can be regarded as an order parameter arising perhaps in a
phase transition in the early universe; one might hope that this structure
would be predictable in any fundamental theory.
| [
{
"created": "Thu, 29 Jun 2006 19:19:15 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sparling",
"George",
""
]
] | Following the approach of Julien Lesgourgues [astro-ph/0409426], we analyze the mathematical structure of the time co-ordinate of present day cosmological models, where these models include a cosmological constant term to account for the observed acceleration of the universe: we find that in all cases, except for a set of measure zero in the parameter space, the time is given by an (abelian) integral on a torus; the imaginary period of this integral then gives a natural periodicity in imaginary time for the universe; following Stephen Hawking, this periodicity may be interpreted either as giving a fundamental mass scale for the universe, or (using Planck's constant) a fundamental temperature, or both. The precise structure that emerges suggests that the structure of time can be regarded as an order parameter arising perhaps in a phase transition in the early universe; one might hope that this structure would be predictable in any fundamental theory. |
1510.04713 | Mengjie Wang | Mengjie Wang, Carlos Herdeiro, Marco O. P. Sampaio | Maxwell perturbations on asymptotically anti-de Sitter spacetimes:
Generic boundary conditions and a new branch of quasinormal modes | v2. Slight revision of the paper's title and other minor changes | Phys. Rev. D 92, 124006 (2015) | 10.1103/PhysRevD.92.124006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Perturbations of asymptotically Anti-de-Sitter (AdS) spacetimes are often
considered by imposing field vanishing boundary conditions (BCs) at the AdS
boundary. Such BCs, of Dirichlet-type, imply a vanishing energy flux at the
boundary, but the converse is, generically, not true. Regarding AdS as a
gravitational box, we consider vanishing energy flux (VEF) BCs as a more
fundamental physical requirement and we show that these BCs can lead to a new
branch of modes. As a concrete example, we consider Maxwell perturbations on
Kerr-AdS black holes in the Teukolsky formalism, but our formulation applies
also for other spin fields. Imposing VEF BCs, we find a set of two Robin BCs,
even for Schwarzschild-AdS black holes. The Robin BCs on the Teukolsky
variables can be used to study quasinormal modes, superradiant instabilities
and vector clouds. As a first application, we consider here the quasinormal
modes of Schwarzschild-AdS black holes. We find that one of the Robin BCs
yields the quasinormal spectrum reported in the literature, while the other one
unveils a new branch for the quasinormal spectrum.
| [
{
"created": "Thu, 15 Oct 2015 20:38:20 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Dec 2015 23:24:10 GMT",
"version": "v2"
}
] | 2015-12-04 | [
[
"Wang",
"Mengjie",
""
],
[
"Herdeiro",
"Carlos",
""
],
[
"Sampaio",
"Marco O. P.",
""
]
] | Perturbations of asymptotically Anti-de-Sitter (AdS) spacetimes are often considered by imposing field vanishing boundary conditions (BCs) at the AdS boundary. Such BCs, of Dirichlet-type, imply a vanishing energy flux at the boundary, but the converse is, generically, not true. Regarding AdS as a gravitational box, we consider vanishing energy flux (VEF) BCs as a more fundamental physical requirement and we show that these BCs can lead to a new branch of modes. As a concrete example, we consider Maxwell perturbations on Kerr-AdS black holes in the Teukolsky formalism, but our formulation applies also for other spin fields. Imposing VEF BCs, we find a set of two Robin BCs, even for Schwarzschild-AdS black holes. The Robin BCs on the Teukolsky variables can be used to study quasinormal modes, superradiant instabilities and vector clouds. As a first application, we consider here the quasinormal modes of Schwarzschild-AdS black holes. We find that one of the Robin BCs yields the quasinormal spectrum reported in the literature, while the other one unveils a new branch for the quasinormal spectrum. |
1806.04253 | Paolo Pani | Adriano Testa and Paolo Pani | Analytical template for gravitational-wave echoes: signal
characterization and prospects of detection with current and future
interferometers | v3: 13+4 pages, 11 figures, 4 appendices; matches the PRD version
with a new plot and extended results. v2 (submitted version): 12 pages + 4
appendices; 9 figures. Further discussion and new appendix with template for
localized sources at generic position. Template and waveforms available at
https://www.darkgra.org/gw-echo-catalogue.html | Phys. Rev. D 98, 044018 (2018) | 10.1103/PhysRevD.98.044018 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational-wave echoes in the post-merger ringdown phase are under intense
scrutiny as probes of near-horizon quantum structures and as signatures of
exotic states of matter in ultracompact stars. We present an analytical
template that describes the ringdown and the echo signal for nonspinning
objects in terms of two physical parameters: the reflectivity and the redshift
at the surface of the object. We characterize the properties of the template
and adopt it in a preliminary parameter estimation with current (aLIGO) and
future (Cosmic Explorer, Einstein Telescope, LISA) gravitational-wave
detectors. For fixed signal-to-noise ratio in the post-merger phase, the
constraints on the model parameters depend only mildly on the details of the
detector sensitivity curve, but depend strongly on the reflectivity. Our
analysis suggests that it might be possible to detect or rule out Planckian
corrections at the horizon scale for perfectly-reflecting ultracompact objects
at $5\sigma$ confidence level with Advanced LIGO/Virgo. On the other hand,
signal-to-noise ratios in the ringdown phase equal to $\approx 100$ (as
achievable with future interferometers) might allow us to probe near-horizon
quantum structures with reflectivity $\gtrsim30\%$ ($\gtrsim85\%$) at $2\sigma$
($3\sigma$) level.
| [
{
"created": "Mon, 11 Jun 2018 21:44:28 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Jun 2018 14:38:44 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Sep 2018 13:28:21 GMT",
"version": "v3"
}
] | 2018-09-18 | [
[
"Testa",
"Adriano",
""
],
[
"Pani",
"Paolo",
""
]
] | Gravitational-wave echoes in the post-merger ringdown phase are under intense scrutiny as probes of near-horizon quantum structures and as signatures of exotic states of matter in ultracompact stars. We present an analytical template that describes the ringdown and the echo signal for nonspinning objects in terms of two physical parameters: the reflectivity and the redshift at the surface of the object. We characterize the properties of the template and adopt it in a preliminary parameter estimation with current (aLIGO) and future (Cosmic Explorer, Einstein Telescope, LISA) gravitational-wave detectors. For fixed signal-to-noise ratio in the post-merger phase, the constraints on the model parameters depend only mildly on the details of the detector sensitivity curve, but depend strongly on the reflectivity. Our analysis suggests that it might be possible to detect or rule out Planckian corrections at the horizon scale for perfectly-reflecting ultracompact objects at $5\sigma$ confidence level with Advanced LIGO/Virgo. On the other hand, signal-to-noise ratios in the ringdown phase equal to $\approx 100$ (as achievable with future interferometers) might allow us to probe near-horizon quantum structures with reflectivity $\gtrsim30\%$ ($\gtrsim85\%$) at $2\sigma$ ($3\sigma$) level. |
2204.02435 | Cenalo Vaz | Cenalo Vaz | Quantum Collapse of a Thin Shell Revisited | 14 pages, no figures. To appear in Phys. Rev. D | null | 10.1103/PhysRevD.105.086020 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | There are several possible choices of the time parameter for the canonical
description of a self-gravitating thin shell, but quantum thories built on
different time parameters lead to unitarily inequivalent descriptions. We
compare the quantum collapse of a thin dust shell in two different times {\it
viz.,} the time coordinate in the interior of the shell (originally addressed
in \cite{hajicek92a}) and the time coordinate of the comoving observer (proper
time). In each case, we obtain exact solutions to the Wheeler-DeWitt equation
requiring only a finite and well behaved $U(1)$ current. The two quantum
theories are complementary and each highlights the role played by the Planck
mass: stationary states of positive energy in interior time exist only if the
shell rest mass in smaller than the Planck mass. In proper time they exist only
when the shell rest mass is {\it greater} than the Planck mass. In coordinate
time there are both scattering states and bound states with a well defined
energy spectrum. In the proper time description there are only bound states,
whose spectrum we determine.
| [
{
"created": "Tue, 5 Apr 2022 18:27:16 GMT",
"version": "v1"
}
] | 2022-05-04 | [
[
"Vaz",
"Cenalo",
""
]
] | There are several possible choices of the time parameter for the canonical description of a self-gravitating thin shell, but quantum thories built on different time parameters lead to unitarily inequivalent descriptions. We compare the quantum collapse of a thin dust shell in two different times {\it viz.,} the time coordinate in the interior of the shell (originally addressed in \cite{hajicek92a}) and the time coordinate of the comoving observer (proper time). In each case, we obtain exact solutions to the Wheeler-DeWitt equation requiring only a finite and well behaved $U(1)$ current. The two quantum theories are complementary and each highlights the role played by the Planck mass: stationary states of positive energy in interior time exist only if the shell rest mass in smaller than the Planck mass. In proper time they exist only when the shell rest mass is {\it greater} than the Planck mass. In coordinate time there are both scattering states and bound states with a well defined energy spectrum. In the proper time description there are only bound states, whose spectrum we determine. |
2302.12609 | Bernard J. Carr | B. J. Carr | The Generalized Uncertainty Principle and Higher Dimensions: Linking
Black Holes and Elementary Particles | 17 pages, 5 figures | Frontiers in Astronomy and Space Sciences 9:1008221 (2022) | 10.3389/fspas.2022.1008221 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes play an important role in linking microphysics with macrophysics,
with those of the Planck mass ($M_P \sim10^{-5}$g) featuring in any theory of
quantum gravity. In particular, the Compton-Schwarzschild correspondence posits
a smooth transition between the Compton wavelength ($R_C \propto 1/M$) below
the Planck mass and the Schwarzschild radius ($R_{\rm S} \propto M$) above it.
The duality between $R_{\rm C}$ and $R_{\rm S}$ implies a form of the
Generalized Uncertainty Principle (GUP) and suggests that elementary particles
may be sub-Planckian black holes. The simplest possibility is that the ADM mass
has the form $M + \beta M_P^2/M$ for some constant $\beta$ and this model can
be extended to charged and rotating black holes, clearly relevant to elementary
particles. Another possibility is that sub-Planckian black holes may arise in
loop quantum gravity and this explicitly links black holes and elementary
particles. Higher dimensions may modify both proposals. If there are $n$ extra
dimensions, all with the same compactification scale, one expects $R_{\rm S}
\propto M^{1/(1+n)}$ below this scale but $R_{\rm C}$ depends on the form of
the higher-dimensional wave-function. If it is spherically symmetric, then
$R_{\rm C} \propto M^{-1}$, so duality is broken and the Planck mass is
reduced, allowing the possibility of TeV quantum gravity. If the wave-function
is pancaked in the extra dimensions, $R_{\rm C} \propto M^{-1/(1+n)}$ and so
duality is preserved but the Planck mass is unchanged.
| [
{
"created": "Fri, 24 Feb 2023 12:51:41 GMT",
"version": "v1"
}
] | 2023-02-27 | [
[
"Carr",
"B. J.",
""
]
] | Black holes play an important role in linking microphysics with macrophysics, with those of the Planck mass ($M_P \sim10^{-5}$g) featuring in any theory of quantum gravity. In particular, the Compton-Schwarzschild correspondence posits a smooth transition between the Compton wavelength ($R_C \propto 1/M$) below the Planck mass and the Schwarzschild radius ($R_{\rm S} \propto M$) above it. The duality between $R_{\rm C}$ and $R_{\rm S}$ implies a form of the Generalized Uncertainty Principle (GUP) and suggests that elementary particles may be sub-Planckian black holes. The simplest possibility is that the ADM mass has the form $M + \beta M_P^2/M$ for some constant $\beta$ and this model can be extended to charged and rotating black holes, clearly relevant to elementary particles. Another possibility is that sub-Planckian black holes may arise in loop quantum gravity and this explicitly links black holes and elementary particles. Higher dimensions may modify both proposals. If there are $n$ extra dimensions, all with the same compactification scale, one expects $R_{\rm S} \propto M^{1/(1+n)}$ below this scale but $R_{\rm C}$ depends on the form of the higher-dimensional wave-function. If it is spherically symmetric, then $R_{\rm C} \propto M^{-1}$, so duality is broken and the Planck mass is reduced, allowing the possibility of TeV quantum gravity. If the wave-function is pancaked in the extra dimensions, $R_{\rm C} \propto M^{-1/(1+n)}$ and so duality is preserved but the Planck mass is unchanged. |
gr-qc/9411028 | Franz Embacher | Franz Embacher | The trace left by signature-change-induced compactification | 15 pages, LaTeX, no figures | Class.Quant.Grav.12:1723-1732,1995 | 10.1088/0264-9381/12/7/014 | UWThPh-1994-55 | gr-qc | null | Recently, it has been shown that an infinite succession of classical
signature changes (''signature oscillations'') can compactify and stabilize
internal dimensions, and simultaneously leads, after a coarse graining type of
average procedure, to an effective (''physical'') space-time geometry
displaying the usual Lorentzian metric signature. Here, we consider a minimally
coupled scalar field on such an oscillating background and study its effective
dynamics. It turns out that the resulting field equation in four dimensions
contains a coupling to some non-metric structure, the imprint of the
''microscopic'' signature oscillations on the effective properties of matter.
In a multidimensional FRW model, this structure is identical to a massive
scalar field evolving in its homogeneous mode.
| [
{
"created": "Fri, 11 Nov 1994 11:17:00 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Embacher",
"Franz",
""
]
] | Recently, it has been shown that an infinite succession of classical signature changes (''signature oscillations'') can compactify and stabilize internal dimensions, and simultaneously leads, after a coarse graining type of average procedure, to an effective (''physical'') space-time geometry displaying the usual Lorentzian metric signature. Here, we consider a minimally coupled scalar field on such an oscillating background and study its effective dynamics. It turns out that the resulting field equation in four dimensions contains a coupling to some non-metric structure, the imprint of the ''microscopic'' signature oscillations on the effective properties of matter. In a multidimensional FRW model, this structure is identical to a massive scalar field evolving in its homogeneous mode. |
gr-qc/0605057 | Llu\'is Bel | Ll. Bel | A look inside the theory of the linear approximation | 14 pages, typos corrected, section replaced | null | null | null | gr-qc | null | We introduce in the framework of the linear approximation of General
relativity a natural distinction between General gauge transformations
generated by any vector field and those Special ones for which this vector
field is a gradient. This allows to introduce geometrical objects that are not
invariant under General gauge transformations but they are under Special ones.
We develop then a formalism that strengthens the analogy of the formalisms of
the electromagnetic and the gravitational theories in a Special relativity
framework. We are thus able to define the energy-momentum tensor of the
gravitational field and to fully analyze the gravitational field of isolated
point masses or continuous distributions of them obtained by linear
superpositions.
| [
{
"created": "Wed, 10 May 2006 11:19:51 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Feb 2007 08:41:54 GMT",
"version": "v2"
},
{
"created": "Sat, 23 Jun 2007 17:06:55 GMT",
"version": "v3"
}
] | 2007-06-23 | [
[
"Bel",
"Ll.",
""
]
] | We introduce in the framework of the linear approximation of General relativity a natural distinction between General gauge transformations generated by any vector field and those Special ones for which this vector field is a gradient. This allows to introduce geometrical objects that are not invariant under General gauge transformations but they are under Special ones. We develop then a formalism that strengthens the analogy of the formalisms of the electromagnetic and the gravitational theories in a Special relativity framework. We are thus able to define the energy-momentum tensor of the gravitational field and to fully analyze the gravitational field of isolated point masses or continuous distributions of them obtained by linear superpositions. |
gr-qc/9607063 | Alberto Carlini | A. Carlini and I.D. Novikov | Time machines and the Principle of Self-Consistency as a consequence of
the Principle of Stationary Action (II): the Cauchy problem for a
self-interacting relativistic particle | 39 pages, latex file | Int.J.Mod.Phys. D5 (1996) 445-480 | 10.1142/S021827189600028X | TIT/HEP-338/COSMO-75 | gr-qc hep-th | null | We consider the action principle to derive the classical, relativistic motion
of a self-interacting particle in a 4-D Lorentzian spacetime containing a
wormhole and which allows the existence of closed time-like curves. In
particular, we study the case of a pointlike particle subject to a
`hard-sphere' self-interaction potential and which can traverse the wormhole an
arbitrary number of times, and show that the only possible trajectories for
which the classical action is stationary are those which are globally
self-consistent. Generically, the multiplicity of these trajectories (defined
as the number of self-consistent solutions to the equations of motion beginning
with given Cauchy data) is finite, and it becomes infinite if certain
constraints on the same initial data are satisfied. This confirms the previous
conclusions (for a non-relativistic model) by Echeverria, Klinkhammer and
Thorne that the Cauchy initial value problem in the presence of a wormhole
`time machine' is classically `ill-posed' (far too many solutions). Our results
further extend the recent claim by Novikov et al. that the `Principle of
self-consistency' is a natural consequence of the `Principle of minimal
action.'
| [
{
"created": "Wed, 24 Jul 1996 14:54:25 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Carlini",
"A.",
""
],
[
"Novikov",
"I. D.",
""
]
] | We consider the action principle to derive the classical, relativistic motion of a self-interacting particle in a 4-D Lorentzian spacetime containing a wormhole and which allows the existence of closed time-like curves. In particular, we study the case of a pointlike particle subject to a `hard-sphere' self-interaction potential and which can traverse the wormhole an arbitrary number of times, and show that the only possible trajectories for which the classical action is stationary are those which are globally self-consistent. Generically, the multiplicity of these trajectories (defined as the number of self-consistent solutions to the equations of motion beginning with given Cauchy data) is finite, and it becomes infinite if certain constraints on the same initial data are satisfied. This confirms the previous conclusions (for a non-relativistic model) by Echeverria, Klinkhammer and Thorne that the Cauchy initial value problem in the presence of a wormhole `time machine' is classically `ill-posed' (far too many solutions). Our results further extend the recent claim by Novikov et al. that the `Principle of self-consistency' is a natural consequence of the `Principle of minimal action.' |
2112.02584 | Vasilis Oikonomou | S.D. Odintsov, V.K. Oikonomou | Pre-Inflationary Bounce Effects on Primordial Gravitational Waves of
$f(R)$ Gravity | PLB Accepted | null | 10.1016/j.physletb.2021.136817 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we shall study a possible pre-inflationary scenario for our
Universe and how this might be realized by $f(R)$ gravity. Specifically, we
shall introduce a scenario in which the Universe in the pre-inflationary era
contracts until it reaches a minimum magnitude, and subsequently expands,
slowly entering a slow-roll quasi-de Sitter inflationary era. This
pre-inflationary bounce avoids the cosmic singularity, and for the eras before
and after the quasi-de Sitter inflationary stage, approximately satisfies the
string theory motivated scale factor duality $a(t)=a^{-1}(-t)$. We investigate
which approximate forms of $f(R)$ can realize such a non-singular
pre-inflationary scenario, the quasi-de Sitter patch of which is described by
an $R^2$ gravity, thus the exit from inflation is guaranteed. Furthermore,
since in string theory pre-Big Bang scenarios lead to an overall amplification
of the gravitational wave energy spectrum, we examine in detail this
perspective for the $f(R)$ gravity generating this pre-inflationary
non-singular bounce. As we show, in the $f(R)$ gravity case, the energy
spectrum of the primordial gravitational waves background is also amplified,
however the drawback is that the amplification is too small to be detected by
future high frequency interferometers. Thus we conclude that, as in the case of
single scalar field theories, $f(R)$ gravity cannot produce detectable
stochastic gravitational waves and a synergistic theory of scalars and higher
order curvature terms might be needed.
| [
{
"created": "Sun, 5 Dec 2021 14:35:16 GMT",
"version": "v1"
}
] | 2022-01-05 | [
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | In this work we shall study a possible pre-inflationary scenario for our Universe and how this might be realized by $f(R)$ gravity. Specifically, we shall introduce a scenario in which the Universe in the pre-inflationary era contracts until it reaches a minimum magnitude, and subsequently expands, slowly entering a slow-roll quasi-de Sitter inflationary era. This pre-inflationary bounce avoids the cosmic singularity, and for the eras before and after the quasi-de Sitter inflationary stage, approximately satisfies the string theory motivated scale factor duality $a(t)=a^{-1}(-t)$. We investigate which approximate forms of $f(R)$ can realize such a non-singular pre-inflationary scenario, the quasi-de Sitter patch of which is described by an $R^2$ gravity, thus the exit from inflation is guaranteed. Furthermore, since in string theory pre-Big Bang scenarios lead to an overall amplification of the gravitational wave energy spectrum, we examine in detail this perspective for the $f(R)$ gravity generating this pre-inflationary non-singular bounce. As we show, in the $f(R)$ gravity case, the energy spectrum of the primordial gravitational waves background is also amplified, however the drawback is that the amplification is too small to be detected by future high frequency interferometers. Thus we conclude that, as in the case of single scalar field theories, $f(R)$ gravity cannot produce detectable stochastic gravitational waves and a synergistic theory of scalars and higher order curvature terms might be needed. |
1408.3449 | M.A.M. Souza | Jamilton Rodrigues and Marcos Souza | Getting inflationary models using the deformation method | 6 pages, 2 figures | Phys. Scr. 90 (2015) 045301 | 10.1088/0031-8949/90/4/045301 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we show that the dynamics associated with slow-roll models of
inflation can be investigated through a method called deformation procedure.
Using the latter, we explicitly derive an expression linking two slow-roll
inflationary potentials, applying the resulting framework to show how to
construct an eternal inflation from chaotic inflation, or even, a natural
inflation from hilltop inflation, easily.
| [
{
"created": "Fri, 15 Aug 2014 00:31:18 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Mar 2015 14:53:50 GMT",
"version": "v2"
}
] | 2015-03-19 | [
[
"Rodrigues",
"Jamilton",
""
],
[
"Souza",
"Marcos",
""
]
] | In this paper we show that the dynamics associated with slow-roll models of inflation can be investigated through a method called deformation procedure. Using the latter, we explicitly derive an expression linking two slow-roll inflationary potentials, applying the resulting framework to show how to construct an eternal inflation from chaotic inflation, or even, a natural inflation from hilltop inflation, easily. |
1003.1386 | Chris Van Den Broeck | Chris Van Den Broeck | Compact binary coalescence and the science case for Einstein Telescope | 3 pages, 6 eps figures. (Very) brief summary of a talk given at the
12th Marcel Grossmann meeting; to appear in the Proceedings | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Einstein Telescope (ET) is a possible third generation ground-based
gravitational wave observatory for which a design study is currently being
carried out. A brief (and non-exhaustive) overview is given of ET's projected
capabilities regarding astrophysics and cosmology through observations of
inspiraling and coalescing compact binaries. In particular, ET would give us
unprecedented insight into the mass function of neutron stars and black holes,
the internal structure of neutron stars, the evolution of coalescence rates
over cosmological timescales, and the geometry and dynamics of the Universe as
a whole.
| [
{
"created": "Sat, 6 Mar 2010 14:19:05 GMT",
"version": "v1"
}
] | 2010-03-09 | [
[
"Broeck",
"Chris Van Den",
""
]
] | Einstein Telescope (ET) is a possible third generation ground-based gravitational wave observatory for which a design study is currently being carried out. A brief (and non-exhaustive) overview is given of ET's projected capabilities regarding astrophysics and cosmology through observations of inspiraling and coalescing compact binaries. In particular, ET would give us unprecedented insight into the mass function of neutron stars and black holes, the internal structure of neutron stars, the evolution of coalescence rates over cosmological timescales, and the geometry and dynamics of the Universe as a whole. |
1702.01162 | Salvatore Capozziello | S. Capozziello, M. Capriolo, M. Transirico | The gravitational energy-momentum pseudo-tensor of Higher-Order Theories
of Gravity | 23 pages, to be published in Annalen der Physik | null | 10.1002/andp.201600376 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the gravitational energy momentum tensor $\tau^{\eta}_{\alpha}$ for
a general Lagrangian of any order $L=L\left(g_{\mu\nu}, g_{\mu\nu,i_{1}},
g_{\mu\nu,i_{1}i_{2}},g_{\mu\nu,i_{1}i_{2}i_{3}},\cdots,
g_{\mu\nu,i_{1}i_{2}i_{3}\cdots i_{n}}\right)$ and in particular for a
Lagrangian such as $L_{g}=(\overline{R}+a_{0}R^{2}+\sum_{k=1}^{p}
a_{k}R\Box^{k}R)\sqrt{-g}$. We prove that this tensor, in general, is not
covariant but only affine, then it is a pseudo-tensor. Furthermore, the
pseudo-tensor $\tau^{\eta}_{\alpha}$ is calculated in the weak field limit up
to a first non-vanishing term of order $h^{2}$ where $h$ is the metric
perturbation. The average value of the pseudo-tensor over a suitable spacetime
domain is obtained. Finally we calculate the power per unit solid angle
$\Omega$ carried by a gravitational wave in a direction $\hat{x}$ for a fixed
wave number $\mathbf{k}$ under a suitable gauge. These results are useful in
view of searching for further modes of gravitational radiation beyond the
standard two modes of General Relativity and to deal with nonlocal theories of
gravity where terms involving $\Box R$ are present. The general aim of the
approach is to deal with theories of any order under the same standard of
Landau pseudo-tensor.
| [
{
"created": "Fri, 3 Feb 2017 21:14:50 GMT",
"version": "v1"
}
] | 2017-05-24 | [
[
"Capozziello",
"S.",
""
],
[
"Capriolo",
"M.",
""
],
[
"Transirico",
"M.",
""
]
] | We derive the gravitational energy momentum tensor $\tau^{\eta}_{\alpha}$ for a general Lagrangian of any order $L=L\left(g_{\mu\nu}, g_{\mu\nu,i_{1}}, g_{\mu\nu,i_{1}i_{2}},g_{\mu\nu,i_{1}i_{2}i_{3}},\cdots, g_{\mu\nu,i_{1}i_{2}i_{3}\cdots i_{n}}\right)$ and in particular for a Lagrangian such as $L_{g}=(\overline{R}+a_{0}R^{2}+\sum_{k=1}^{p} a_{k}R\Box^{k}R)\sqrt{-g}$. We prove that this tensor, in general, is not covariant but only affine, then it is a pseudo-tensor. Furthermore, the pseudo-tensor $\tau^{\eta}_{\alpha}$ is calculated in the weak field limit up to a first non-vanishing term of order $h^{2}$ where $h$ is the metric perturbation. The average value of the pseudo-tensor over a suitable spacetime domain is obtained. Finally we calculate the power per unit solid angle $\Omega$ carried by a gravitational wave in a direction $\hat{x}$ for a fixed wave number $\mathbf{k}$ under a suitable gauge. These results are useful in view of searching for further modes of gravitational radiation beyond the standard two modes of General Relativity and to deal with nonlocal theories of gravity where terms involving $\Box R$ are present. The general aim of the approach is to deal with theories of any order under the same standard of Landau pseudo-tensor. |
1807.04212 | Diego Carranza | Diego A. Carranza and Juan A. Valiente Kroon | Construction of anti-de Sitter-like spacetimes using the metric
conformal Einstein field equations: the vacuum case | 29 pages, 1 figure | Class. Quantum Grav. 35, 245006 (2018) | 10.1088/1361-6382/aaeb54 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We make use of the metric version of the conformal Einstein field equations
to construct anti-de Sitter-like spacetimes by means of a suitably posed
initial-boundary value problem. The evolution system associated to this
initial-boundary value problem consists of a set of conformal wave equations
for a number of conformal fields and the conformal metric. This formulation
makes use of generalised wave coordinates and allows the free specification of
the Ricci scalar of the conformal metric via a conformal gauge source function.
We consider Dirichlet boundary conditions for the evolution equations at the
conformal boundary and show that these boundary conditions can, in turn, be
constructed from the 3-dimensional Lorentzian metric of the conformal boundary
and a linear combination of the incoming and outgoing radiation as measured by
certain components of the Weyl tensor. To show that a solution to the conformal
evolution equations implies a solution to the Einstein field equations we also
provide a discussion of the propagation of the constraints for this
initial-boundary value problem. The existence of local solutions to the
initial-boundary value problem in a neighbourhood of the corner where the
initial hypersurface and the conformal boundary intersect is subject to
compatibility conditions between the initial and boundary data. The
construction described is amenable to numerical implementation and should allow
the systematic exploration of boundary conditions.
| [
{
"created": "Wed, 11 Jul 2018 15:57:15 GMT",
"version": "v1"
}
] | 2018-12-19 | [
[
"Carranza",
"Diego A.",
""
],
[
"Kroon",
"Juan A. Valiente",
""
]
] | We make use of the metric version of the conformal Einstein field equations to construct anti-de Sitter-like spacetimes by means of a suitably posed initial-boundary value problem. The evolution system associated to this initial-boundary value problem consists of a set of conformal wave equations for a number of conformal fields and the conformal metric. This formulation makes use of generalised wave coordinates and allows the free specification of the Ricci scalar of the conformal metric via a conformal gauge source function. We consider Dirichlet boundary conditions for the evolution equations at the conformal boundary and show that these boundary conditions can, in turn, be constructed from the 3-dimensional Lorentzian metric of the conformal boundary and a linear combination of the incoming and outgoing radiation as measured by certain components of the Weyl tensor. To show that a solution to the conformal evolution equations implies a solution to the Einstein field equations we also provide a discussion of the propagation of the constraints for this initial-boundary value problem. The existence of local solutions to the initial-boundary value problem in a neighbourhood of the corner where the initial hypersurface and the conformal boundary intersect is subject to compatibility conditions between the initial and boundary data. The construction described is amenable to numerical implementation and should allow the systematic exploration of boundary conditions. |
1112.0821 | Kouji Nakamura | Kouji Nakamura | Short note on construction of gauge-invariant variables of linear metric
perturbations on an arbitrary background spacetime | 4 pages, no figures, jgrg21.sty is used. Prepared for the proceedings
of the International Conference JGRG21 (2011, Sendai, Japan) | null | null | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An outline of a proof of the decomposition of linear metric perturbations
into gauge-invariant and gauge-variant parts on an arbitrary background
spacetime which admits ADM decomposition is briefly discussed. We explicitly
construct the gauge-invariant and gauge-variant parts of the linear metric
perturbations based on some assumptions. This implies that we can develop the
higher-order gauge-invariant perturbation theory on an arbitrary background
spacetime.
| [
{
"created": "Mon, 5 Dec 2011 02:05:54 GMT",
"version": "v1"
}
] | 2011-12-06 | [
[
"Nakamura",
"Kouji",
""
]
] | An outline of a proof of the decomposition of linear metric perturbations into gauge-invariant and gauge-variant parts on an arbitrary background spacetime which admits ADM decomposition is briefly discussed. We explicitly construct the gauge-invariant and gauge-variant parts of the linear metric perturbations based on some assumptions. This implies that we can develop the higher-order gauge-invariant perturbation theory on an arbitrary background spacetime. |
0905.1244 | Salvatore Capozziello | S. Capozziello, V.I. Man'ko, G. Marmo, C. Stornaiolo | A tomographic description for classical and quantum cosmological
perturbations | 12 pages | null | 10.1088/0031-8949/80/04/045901 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Classical and quantum perturbations can be described in terms of marginal
distribution functions in the framework of tomographic cosmology. In
particular, the so called Radon transformation and the mode-parametric quantum
oscillator description can give rise to links between quantum and classical
regimes. The approach results a natural scheme to discuss the transition from
the quantum to the classical perturbations and then it could be a workable
scheme to connect primordial fluctuations with the today observed large scale
structure.
| [
{
"created": "Fri, 8 May 2009 12:43:27 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Capozziello",
"S.",
""
],
[
"Man'ko",
"V. I.",
""
],
[
"Marmo",
"G.",
""
],
[
"Stornaiolo",
"C.",
""
]
] | Classical and quantum perturbations can be described in terms of marginal distribution functions in the framework of tomographic cosmology. In particular, the so called Radon transformation and the mode-parametric quantum oscillator description can give rise to links between quantum and classical regimes. The approach results a natural scheme to discuss the transition from the quantum to the classical perturbations and then it could be a workable scheme to connect primordial fluctuations with the today observed large scale structure. |
gr-qc/0302033 | Laszlo B. Szabados | Laszlo B. Szabados | On the roots of the Poincare structure of asymptotically flat spacetimes | 34 pages, plain TEX, misleading notations changed, discussion
improved and corrected, appearing in Class. Quantum Grav | Class.Quant.Grav. 20 (2003) 2627-2662 | 10.1088/0264-9381/20/13/312 | null | gr-qc | null | The analysis of vacuum general relativity by R. Beig and N. O Murchadha (Ann.
Phys. vol 174, 463 (1987)) is extended in numerous ways. The weakest possible
power-type fall-off conditions for the energy-momentum tensor, the metric, the
extrinsic curvature, the lapse and the shift are determined, which, together
with the parity conditions, are preserved by the energy-momentum conservation
and the evolution equations. The algebra of the asymptotic Killing vectors,
defined with respect to a foliation of the spacetime, is shown to be the
Lorentz Lie algebra for slow fall-off of the metric, but it is the Poincare
algebra for 1/r or faster fall-off. It is shown that the applicability of the
symplectic formalism already requires the 1/r (or faster) fall-off of the
metric. The connection between the Poisson algebra of the Beig-O Murchadha
Hamiltonians and the asymptotic Killing vectors is clarified. The value H[K^a]
of their Hamiltonian is shown to be conserved in time if K^a is an asymptotic
Killing vector defined with respect to the constant time slices. The angular
momentum and centre-of-mass, defined by the value of H[K^a] for asymptotic
rotation-boost Killing vectors K^a, are shown to be finite only for 1/r or
faster fall-off of the metric. Our center-of-mass expression is the difference
of that of Beig and O Murchadha and the spatial momentum times the coordinate
time. The spatial angular momentum and this centre-of-mass form a Lorentz
tensor, which transforms in the correct way under Poincare transformations.
| [
{
"created": "Mon, 10 Feb 2003 15:45:12 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Apr 2003 15:43:15 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Szabados",
"Laszlo B.",
""
]
] | The analysis of vacuum general relativity by R. Beig and N. O Murchadha (Ann. Phys. vol 174, 463 (1987)) is extended in numerous ways. The weakest possible power-type fall-off conditions for the energy-momentum tensor, the metric, the extrinsic curvature, the lapse and the shift are determined, which, together with the parity conditions, are preserved by the energy-momentum conservation and the evolution equations. The algebra of the asymptotic Killing vectors, defined with respect to a foliation of the spacetime, is shown to be the Lorentz Lie algebra for slow fall-off of the metric, but it is the Poincare algebra for 1/r or faster fall-off. It is shown that the applicability of the symplectic formalism already requires the 1/r (or faster) fall-off of the metric. The connection between the Poisson algebra of the Beig-O Murchadha Hamiltonians and the asymptotic Killing vectors is clarified. The value H[K^a] of their Hamiltonian is shown to be conserved in time if K^a is an asymptotic Killing vector defined with respect to the constant time slices. The angular momentum and centre-of-mass, defined by the value of H[K^a] for asymptotic rotation-boost Killing vectors K^a, are shown to be finite only for 1/r or faster fall-off of the metric. Our center-of-mass expression is the difference of that of Beig and O Murchadha and the spatial momentum times the coordinate time. The spatial angular momentum and this centre-of-mass form a Lorentz tensor, which transforms in the correct way under Poincare transformations. |
1404.1802 | Jacob D. Bekenstein | Jacob D. Bekenstein | Optimizing entropy bounds for macroscopic systems | 13 pages, 2 figures, LaTeX | Phys. Rev. E 89, 052137 (2014) | 10.1103/PhysRevE.89.052137 | null | gr-qc hep-th physics.chem-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The universal bound on specific entropy was originally inferred from black
hole thermodynamics. We here show from classical thermodynamics alone that for
a system at fixed volume or fixed pressure, the ratio of entropy to
nonrelativistic energy has a unique maximum $(S/E)_\mathrm{max}$. A simple
argument from quantum dynamics allows one to set a model--independent upper
bound on $(S/E)_\mathrm{max}$ which is usually much tighter than the universal
bound. We illustrate with two examples.
| [
{
"created": "Mon, 7 Apr 2014 14:45:23 GMT",
"version": "v1"
},
{
"created": "Wed, 28 May 2014 11:18:51 GMT",
"version": "v2"
}
] | 2014-05-29 | [
[
"Bekenstein",
"Jacob D.",
""
]
] | The universal bound on specific entropy was originally inferred from black hole thermodynamics. We here show from classical thermodynamics alone that for a system at fixed volume or fixed pressure, the ratio of entropy to nonrelativistic energy has a unique maximum $(S/E)_\mathrm{max}$. A simple argument from quantum dynamics allows one to set a model--independent upper bound on $(S/E)_\mathrm{max}$ which is usually much tighter than the universal bound. We illustrate with two examples. |
2211.10733 | Roman Ilin | R.V. Ilin, S.A. Paston | Dual models for p-form mimetic gravity and their connection to perfect
fluids consisting of (p+1)-branes | 9 pages, published version | Phys. Lett. B 841 (2023) 137952 | 10.1016/j.physletb.2023.137952 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose an approach that allows one to reformulate $n$-dimensional
$p$-form mimetic gravity (including usual mimetic gravity as particular case $p
= 0$) as nonlinear $(n-p-1)$-form electrodynamics via electric-magnetic
duality. The resulting dual Lagrangian density is just the square root of the
ordinary quadratic Lagrangian density of $(n-p-1)$-form electrodynamics. By
applying field transformation in the action, we show that for the arbitrary $p$
this dual theory transforms into the $(p+1)$-brane fluid: the model of the
stack of the parallel $(p+1)$-dimensional branes foliating physical spacetime.
As the structure of the field transformations depends on $p$, the sets of
solutions in these models are related differently. We prove, that for $p = 0$
and $p = n-2$ dual mimetic models describe usual particle fluid with the
potential flow and to the $(n-1)$-brane fluid respectively. For other values of
$p$ not all mimetic solutions behave like that, in general, so we restrict
ourselves only to the case $n = 4$, $p = 1$. In this case, we show, that
mimetic formulation is dual to the well-known Nielsen-Olesen theory of "dual
strings" and discuss the criterion indicating whether its solutions behave like
string fluid. The cosmological solutions for these models in are also
discussed.
| [
{
"created": "Sat, 19 Nov 2022 15:58:59 GMT",
"version": "v1"
},
{
"created": "Mon, 15 May 2023 22:48:41 GMT",
"version": "v2"
}
] | 2023-05-17 | [
[
"Ilin",
"R. V.",
""
],
[
"Paston",
"S. A.",
""
]
] | We propose an approach that allows one to reformulate $n$-dimensional $p$-form mimetic gravity (including usual mimetic gravity as particular case $p = 0$) as nonlinear $(n-p-1)$-form electrodynamics via electric-magnetic duality. The resulting dual Lagrangian density is just the square root of the ordinary quadratic Lagrangian density of $(n-p-1)$-form electrodynamics. By applying field transformation in the action, we show that for the arbitrary $p$ this dual theory transforms into the $(p+1)$-brane fluid: the model of the stack of the parallel $(p+1)$-dimensional branes foliating physical spacetime. As the structure of the field transformations depends on $p$, the sets of solutions in these models are related differently. We prove, that for $p = 0$ and $p = n-2$ dual mimetic models describe usual particle fluid with the potential flow and to the $(n-1)$-brane fluid respectively. For other values of $p$ not all mimetic solutions behave like that, in general, so we restrict ourselves only to the case $n = 4$, $p = 1$. In this case, we show, that mimetic formulation is dual to the well-known Nielsen-Olesen theory of "dual strings" and discuss the criterion indicating whether its solutions behave like string fluid. The cosmological solutions for these models in are also discussed. |
2006.08398 | Lorenzo Resca Dr. | Lorenzo Gallerani Resca | Cosmological Mass of the Photon and Dark Energy as its Bose-Einstein
Condensate in de Sitter Space | null | Indian J Phys 97 605 2023 | 10.1007/s12648-022-02395-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I develop a physical picture of dark energy (DE) based on fundamental
principles and constants of quantum mechanics (QM) and general relativity (GR)
theories. It derives from a conjecture of non-zero masses for nearly
standard-model photons, based on QM localization at a cosmological scale. Dark
energy is associated with de Sitter space and that has a fundamentally
invariant event horizon. I conceive of DE as a Bose-Einstein condensate (BEC)
of cosmologically massive photons and I estimate fundamentally the binding
energy per particle originating from an effectively attractive QM potential in
that BEC. Since massive photons may stand at rest in a de Sitter universe with
flat spatial geometry, I solve the time-independent Schroedinger equation for a
non-relativistic attractive spherical-well potential self-confining at the de
Sitter horizon. The minimal critical potential depth that binds a particle
state at the top of that well, combined with the prototypical condition of dark
energy-pressure relation in the standard flat $\Lambda$-CDM model, provides an
estimate of the photon mass, $m_g$. That is supported by an independent
calculation of the vacuum energy of the BEC in a de Sitter static metric with
coordinate-time slicing. These estimates provide compatible accounts of dark
energy condensation, bridging a chasm between nuclear and cosmological scales.
Most notably, I consider a system of cosmological units, or `$g$-units,' that
complements the fundamental system of Planck units in various ways. The
geometric mean of Planck and $g$-mass turns out to be remarkably close to
current estimates of neutrino masses, suggesting that even masses of the
lightest known fermions may be deeply related to both GR and QM fundamental
constants $\Lambda$, $G$, $c$ and $h$. I finally relate the fine structure
constant to $m_g$ and a Coulomb potential confined within a corresponding
cosmological horizon.
| [
{
"created": "Mon, 15 Jun 2020 13:41:02 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Aug 2021 23:17:42 GMT",
"version": "v10"
},
{
"created": "Fri, 3 Sep 2021 02:27:28 GMT",
"version": "v11"
},
{
"created": "Wed, 29 Dec 2021 23:42:49 GMT",
"version": "v12"
},
{
"... | 2023-02-23 | [
[
"Resca",
"Lorenzo Gallerani",
""
]
] | I develop a physical picture of dark energy (DE) based on fundamental principles and constants of quantum mechanics (QM) and general relativity (GR) theories. It derives from a conjecture of non-zero masses for nearly standard-model photons, based on QM localization at a cosmological scale. Dark energy is associated with de Sitter space and that has a fundamentally invariant event horizon. I conceive of DE as a Bose-Einstein condensate (BEC) of cosmologically massive photons and I estimate fundamentally the binding energy per particle originating from an effectively attractive QM potential in that BEC. Since massive photons may stand at rest in a de Sitter universe with flat spatial geometry, I solve the time-independent Schroedinger equation for a non-relativistic attractive spherical-well potential self-confining at the de Sitter horizon. The minimal critical potential depth that binds a particle state at the top of that well, combined with the prototypical condition of dark energy-pressure relation in the standard flat $\Lambda$-CDM model, provides an estimate of the photon mass, $m_g$. That is supported by an independent calculation of the vacuum energy of the BEC in a de Sitter static metric with coordinate-time slicing. These estimates provide compatible accounts of dark energy condensation, bridging a chasm between nuclear and cosmological scales. Most notably, I consider a system of cosmological units, or `$g$-units,' that complements the fundamental system of Planck units in various ways. The geometric mean of Planck and $g$-mass turns out to be remarkably close to current estimates of neutrino masses, suggesting that even masses of the lightest known fermions may be deeply related to both GR and QM fundamental constants $\Lambda$, $G$, $c$ and $h$. I finally relate the fine structure constant to $m_g$ and a Coulomb potential confined within a corresponding cosmological horizon. |
1011.6280 | Peter Phillips | Peter R. Phillips | Conformal cosmology with a positive effective gravitational constant | null | null | 10.1111/j.1365-2966.2011.19408.x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The conformal cosmological model presented by Mannheim predicts a negative
value for the effective gravitational constant, G. It also involves a scalar
field, S, which is treated classically. In this paper we point out that a
classical treatment of S is inappropriate, because the Hamiltonian is
non-Hermitean, and the theory must be developed in the way pioneered by Bender
and others. When this is done, we arrive at a Hamiltonian with an energy
spectrum that is bounded below, and also a G that is positive. The resulting
theory closely resembles the conventional cosmology based on Einstein
relativity.
| [
{
"created": "Mon, 29 Nov 2010 16:31:36 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Phillips",
"Peter R.",
""
]
] | The conformal cosmological model presented by Mannheim predicts a negative value for the effective gravitational constant, G. It also involves a scalar field, S, which is treated classically. In this paper we point out that a classical treatment of S is inappropriate, because the Hamiltonian is non-Hermitean, and the theory must be developed in the way pioneered by Bender and others. When this is done, we arrive at a Hamiltonian with an energy spectrum that is bounded below, and also a G that is positive. The resulting theory closely resembles the conventional cosmology based on Einstein relativity. |
gr-qc/0005046 | Gyq | Guoying Chee and Yanhua Jia | Self-Dual Conformal Supergravity and the Hamiltonian Formulation | null | Gen.Rel.Grav. 33 (2001) 1953-1972 | 10.1023/A:1013098909922 | null | gr-qc | null | In terms of Dirac matrices the self-dual and anti-self-dual decomposition of
a conformal supergravity is given and a self-dual conformal supergravity theory
is developed as a connection dynamic theory in which the basic dynamic variabes
include the self-dual spin connection i.e. the Ashtekar connection rather than
the triad. The Hamiltonian formulation and the constraints are obtained by
using the Dirac-Bergmann algorithm.
PACS numbers: 04.20.Cv, 04.20.Fy,04.65.+e
| [
{
"created": "Sat, 13 May 2000 07:56:48 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Chee",
"Guoying",
""
],
[
"Jia",
"Yanhua",
""
]
] | In terms of Dirac matrices the self-dual and anti-self-dual decomposition of a conformal supergravity is given and a self-dual conformal supergravity theory is developed as a connection dynamic theory in which the basic dynamic variabes include the self-dual spin connection i.e. the Ashtekar connection rather than the triad. The Hamiltonian formulation and the constraints are obtained by using the Dirac-Bergmann algorithm. PACS numbers: 04.20.Cv, 04.20.Fy,04.65.+e |
2308.15604 | Robert Conte | Robert Conte (ENS Paris-Saclay) | On a dynamical system linked to the BKL scenario | 9 pages, to appear, Physica scripta | null | null | null | gr-qc nlin.SI | http://creativecommons.org/licenses/by/4.0/ | We consider the six-dimensional dynamical system in three components
introduced by Ryan to describe the scenario of Belinskii, Khalatnikov and
Lifshitz to the cosmological singularity when the spatial metric tensor is not
diagonal. Despite its nonintegrability, recently proven by Goldstein and
Piechocki, the three four-dimensional systems defined by canceling one of the
three components happen to be integrable. We express their general solution as
a rational function of, respectively, two exponential functions, a third
Painlev\'e function, two exponential functions.
| [
{
"created": "Tue, 29 Aug 2023 19:53:57 GMT",
"version": "v1"
}
] | 2023-08-31 | [
[
"Conte",
"Robert",
"",
"ENS Paris-Saclay"
]
] | We consider the six-dimensional dynamical system in three components introduced by Ryan to describe the scenario of Belinskii, Khalatnikov and Lifshitz to the cosmological singularity when the spatial metric tensor is not diagonal. Despite its nonintegrability, recently proven by Goldstein and Piechocki, the three four-dimensional systems defined by canceling one of the three components happen to be integrable. We express their general solution as a rational function of, respectively, two exponential functions, a third Painlev\'e function, two exponential functions. |
2012.14423 | Manuel Hohmann | Manuel Hohmann and Christian Pfeifer | Teleparallel axions and cosmology | 16 pages, 4 figures; journal version | Eur.Phys.J. C81 (2021) no.4, 376 | 10.1140/epjc/s10052-021-09165-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the most general teleparallel theory of gravity whose action is a
linear combination of the five scalar invariants which are quadratic in the
torsion tensor. Since two of these invariants possess odd parity, they
naturally allow for a coupling to pseudo-scalar fields, thus yielding a
Lagrangian which is even under parity transformations. In analogy to similar
fields in gauge theories, we call these pseudo-scalar fields \emph{teleparallel
axions}. For the most general coupling of a single axion field, we derive the
cosmological field equations. We find that for a family of cosmologically
symmetric teleparallel geometries, which possess non-vanishing axial torsion,
the axion coupling contributes to the cosmological dynamics in the early
universe. Most remarkably, this contribution is also present when the axion is
coupled to the teleparallel equivalent of general relativity, hence allowing
for a canonical coupling of a pseudo-scalar to general relativity. For this
case we schematically present the influence of the axion coupling on the fixed
points in the cosmological dynamics understood as dynamical system. Finally, we
display possible generalizations and similar extensions in other geometric
frameworks to model gravity.
| [
{
"created": "Mon, 28 Dec 2020 18:59:00 GMT",
"version": "v1"
},
{
"created": "Sat, 8 May 2021 21:05:45 GMT",
"version": "v2"
}
] | 2021-05-11 | [
[
"Hohmann",
"Manuel",
""
],
[
"Pfeifer",
"Christian",
""
]
] | We consider the most general teleparallel theory of gravity whose action is a linear combination of the five scalar invariants which are quadratic in the torsion tensor. Since two of these invariants possess odd parity, they naturally allow for a coupling to pseudo-scalar fields, thus yielding a Lagrangian which is even under parity transformations. In analogy to similar fields in gauge theories, we call these pseudo-scalar fields \emph{teleparallel axions}. For the most general coupling of a single axion field, we derive the cosmological field equations. We find that for a family of cosmologically symmetric teleparallel geometries, which possess non-vanishing axial torsion, the axion coupling contributes to the cosmological dynamics in the early universe. Most remarkably, this contribution is also present when the axion is coupled to the teleparallel equivalent of general relativity, hence allowing for a canonical coupling of a pseudo-scalar to general relativity. For this case we schematically present the influence of the axion coupling on the fixed points in the cosmological dynamics understood as dynamical system. Finally, we display possible generalizations and similar extensions in other geometric frameworks to model gravity. |
2006.12162 | Bjoern S. Schmekel | Bjoern S. Schmekel | Note on the Conservation of Quasi-Local Energy in an Expanding Universe | 3 pages, 1 figure | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Whether energy is conserved in a universe which keeps expanding is an
intriguing question. It is tempting to argue that the total energy within the
universe would have to increase as the universe expands. Upon more detailed
inspection the question is a lot harder to settle since defining what is meant
by energy or even what is meant by energy being conserved is a difficult
problem in general relativity. Using the definition of quasi-local energy
provided by Brown and York we try to answer the question in which sense the
total energy in an expanding (or collapsing) universe is conserved.
| [
{
"created": "Mon, 22 Jun 2020 11:46:53 GMT",
"version": "v1"
}
] | 2020-06-23 | [
[
"Schmekel",
"Bjoern S.",
""
]
] | Whether energy is conserved in a universe which keeps expanding is an intriguing question. It is tempting to argue that the total energy within the universe would have to increase as the universe expands. Upon more detailed inspection the question is a lot harder to settle since defining what is meant by energy or even what is meant by energy being conserved is a difficult problem in general relativity. Using the definition of quasi-local energy provided by Brown and York we try to answer the question in which sense the total energy in an expanding (or collapsing) universe is conserved. |
0708.2360 | Demosthenes Kazanas | Manasse R. Mbonye and Demosthenes Kazanas | Can gravitational collapse sustain singularity-free trapped surfaces? | 17 pages, 3 figures, accepted for publication in International
Journal of Modern Physics D | Int.J.Mod.Phys.D17:165-177,2008 | 10.1142/S0218271808011924 | null | gr-qc astro-ph hep-th | null | In singularity generating spacetimes both the out-going and in-going
expansions of null geodesic congruences $\theta ^{+}$ and $\theta ^{-}$ should
become increasingly negative without bound, inside the horizon. This behavior
leads to geodetic incompleteness which in turn predicts the existence of a
singularity. In this work we inquire on whether, in gravitational collapse,
spacetime can sustain singularity-free trapped surfaces, in the sense that such
a spacetime remains geodetically complete. As a test case, we consider a well
known solution of the Einstien Field Equations which is Schwarzschild-like at
large distances and consists of a fluid with a $p=-\rho $ equation of state
near $r=0$. By following both the expansion parameters $\theta ^{+}$ and
$\theta ^{-}$ across the horizon and into the black hole we find that both
$\theta ^{+}$ and $\theta ^{+}\theta ^{-}$ have turning points inside the
trapped region. Further, we find that deep inside the black hole there is a
region $0\leq r<r_{0}$ (that includes the black hole center) which is not
trapped. Thus the trapped region is bounded both from outside and inside. The
spacetime is geodetically complete, a result which violates a condition for
singularity formation. It is inferred that in general if gravitational collapse
were to proceed with a $p=-\rho $ fluid formation, the resulting black hole may
be singularity-free.
| [
{
"created": "Fri, 17 Aug 2007 12:59:31 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Mbonye",
"Manasse R.",
""
],
[
"Kazanas",
"Demosthenes",
""
]
] | In singularity generating spacetimes both the out-going and in-going expansions of null geodesic congruences $\theta ^{+}$ and $\theta ^{-}$ should become increasingly negative without bound, inside the horizon. This behavior leads to geodetic incompleteness which in turn predicts the existence of a singularity. In this work we inquire on whether, in gravitational collapse, spacetime can sustain singularity-free trapped surfaces, in the sense that such a spacetime remains geodetically complete. As a test case, we consider a well known solution of the Einstien Field Equations which is Schwarzschild-like at large distances and consists of a fluid with a $p=-\rho $ equation of state near $r=0$. By following both the expansion parameters $\theta ^{+}$ and $\theta ^{-}$ across the horizon and into the black hole we find that both $\theta ^{+}$ and $\theta ^{+}\theta ^{-}$ have turning points inside the trapped region. Further, we find that deep inside the black hole there is a region $0\leq r<r_{0}$ (that includes the black hole center) which is not trapped. Thus the trapped region is bounded both from outside and inside. The spacetime is geodetically complete, a result which violates a condition for singularity formation. It is inferred that in general if gravitational collapse were to proceed with a $p=-\rho $ fluid formation, the resulting black hole may be singularity-free. |
gr-qc/0504110 | Edward Malec | Edward Malec and Grzegorz Wylezek | The Huygens principle and cosmological gravitational waves in the
Regge-Wheeler gauge | 4 pages | Class.Quant.Grav. 22 (2005) 3549-3554 | 10.1088/0264-9381/22/17/013 | null | gr-qc astro-ph | null | We study the propagation of axial gravitational waves in Friedman universes.
The evolution equation is obtained in the Regge-Wheeler gauge. The
gravitational waves obey the Huygens principle in the radiation dominated era,
but in the matter dominated universe their propagation depends on their
wavelengths, with the scale fixed essentially by the Hubble radius. Short waves
practically satisfy the Huygens principle while long waves can backscatter off
the curvature of a spacetime.
| [
{
"created": "Fri, 22 Apr 2005 14:37:21 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Apr 2005 14:33:17 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Malec",
"Edward",
""
],
[
"Wylezek",
"Grzegorz",
""
]
] | We study the propagation of axial gravitational waves in Friedman universes. The evolution equation is obtained in the Regge-Wheeler gauge. The gravitational waves obey the Huygens principle in the radiation dominated era, but in the matter dominated universe their propagation depends on their wavelengths, with the scale fixed essentially by the Hubble radius. Short waves practically satisfy the Huygens principle while long waves can backscatter off the curvature of a spacetime. |
1003.4112 | Paulo M. S\'a | Paulo M. S\'a and Alfredo B. Henriques | Gravitational wave generation in hybrid quintessential inflationary
models | 10 pages, 11 figures, one reference added | Phys.Rev.D81:124043,2010 | 10.1103/PhysRevD.81.124043 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the generation of gravitational waves in the hybrid
quintessential inflationary model. The full gravitational-wave energy spectrum
is calculated using the method of continuous Bogoliubov coefficients. The
post-inflationary kination period, characteristic of quintessential
inflationary models, leaves a clear signature on the spectrum, namely, a peak
at high frequencies. The maximum of the peak is firmly located at the MHz-GHz
region of the spectrum and corresponds to $\Omega_{GW} \simeq 10^{-12}$. This
peak is substantially smaller than the one appearing in the gravitational-wave
energy spectrum of the original quintessential inflationary model, therefore
avoiding any conflict with the nucleosynthesis constraint on
$\Omega_\Omega_{GW}$.
| [
{
"created": "Mon, 22 Mar 2010 10:19:35 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Jul 2010 09:29:30 GMT",
"version": "v2"
}
] | 2015-03-13 | [
[
"Sá",
"Paulo M.",
""
],
[
"Henriques",
"Alfredo B.",
""
]
] | We investigate the generation of gravitational waves in the hybrid quintessential inflationary model. The full gravitational-wave energy spectrum is calculated using the method of continuous Bogoliubov coefficients. The post-inflationary kination period, characteristic of quintessential inflationary models, leaves a clear signature on the spectrum, namely, a peak at high frequencies. The maximum of the peak is firmly located at the MHz-GHz region of the spectrum and corresponds to $\Omega_{GW} \simeq 10^{-12}$. This peak is substantially smaller than the one appearing in the gravitational-wave energy spectrum of the original quintessential inflationary model, therefore avoiding any conflict with the nucleosynthesis constraint on $\Omega_\Omega_{GW}$. |
1611.07529 | Patricia Schmidt | Chad R. Galley, Patricia Schmidt | Fast and efficient evaluation of gravitational waveforms via
reduced-order spline interpolation | 28 pages, 13 figures | null | null | LIGO-P1600064 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Numerical simulations of merging black hole binaries produce the most
accurate gravitational waveforms. The availability of hundreds of these
numerical relativity (NR) waveforms, often containing many higher spherical
harmonic modes, allows one to study many aspects of gravitational waves.
Amongst these are the response of data analysis pipelines, the calibration of
semi-analytical models, the building of reduced-order surrogates, the
estimation of the parameters of detected gravitational waves, and the
composition of public catalogs of NR waveform data. The large number of
generated NR waveforms consequently requires efficient data storage and
handling, especially since many more waveforms will be generated at an
increased rate in the forthcoming years. In addition, gravitational wave data
analyses often require the NR waveforms to be interpolated and uniformly
resampled at high sampling rates. Previously, this resulted in very large data
files (up to $\sim$ several GB) in memory-intensive operations, which is
unfeasible when confronted with hundreds of multi-modal NR waveforms. To handle
these challenges, we present a simple and efficient method to significantly
\emph{compress} the original waveform data sets while accurately reproducing
the original data via spline interpolation. The method is generically
applicable to relatively smooth, one-dimensional datasets and uses a greedy
algorithm to determine the most relevant subset of the full data such that a
spline interpolant of a specified polynomial degree will represent the original
data to within a requested point-wise tolerance. We find significant
compression of the original NR data sets presented here. These compressed data
sets can then be evaluated fast and efficiently and resampled as desired.
| [
{
"created": "Tue, 22 Nov 2016 21:00:04 GMT",
"version": "v1"
}
] | 2016-11-24 | [
[
"Galley",
"Chad R.",
""
],
[
"Schmidt",
"Patricia",
""
]
] | Numerical simulations of merging black hole binaries produce the most accurate gravitational waveforms. The availability of hundreds of these numerical relativity (NR) waveforms, often containing many higher spherical harmonic modes, allows one to study many aspects of gravitational waves. Amongst these are the response of data analysis pipelines, the calibration of semi-analytical models, the building of reduced-order surrogates, the estimation of the parameters of detected gravitational waves, and the composition of public catalogs of NR waveform data. The large number of generated NR waveforms consequently requires efficient data storage and handling, especially since many more waveforms will be generated at an increased rate in the forthcoming years. In addition, gravitational wave data analyses often require the NR waveforms to be interpolated and uniformly resampled at high sampling rates. Previously, this resulted in very large data files (up to $\sim$ several GB) in memory-intensive operations, which is unfeasible when confronted with hundreds of multi-modal NR waveforms. To handle these challenges, we present a simple and efficient method to significantly \emph{compress} the original waveform data sets while accurately reproducing the original data via spline interpolation. The method is generically applicable to relatively smooth, one-dimensional datasets and uses a greedy algorithm to determine the most relevant subset of the full data such that a spline interpolant of a specified polynomial degree will represent the original data to within a requested point-wise tolerance. We find significant compression of the original NR data sets presented here. These compressed data sets can then be evaluated fast and efficiently and resampled as desired. |
1010.4262 | Douglas Shaw | Douglas J. Shaw and John D. Barrow | A Testable Solution of the Cosmological Constant and Coincidence
Problems | 31 pages, 4 figures; v2: version accepted by Phys. Rev. D | Phys.Rev.D83:043518,2011 | 10.1103/PhysRevD.83.043518 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new solution to the cosmological constant (CC) and coincidence
problems in which the observed value of the CC, $\Lambda$, is linked to other
observable properties of the universe. This is achieved by promoting the CC
from a parameter which must to specified, to a field which can take many
possible values. The observed value of Lambda ~ 1/(9.3 Gyrs)^2$ (approximately
10^(-120) in Planck units) is determined by a new constraint equation which
follows from the application of a causally restricted variation principle. When
applied to our visible universe, the model makes a testable prediction for the
dimensionless spatial curvature of Omega_k0 = -0.0056 s_b/0.5; where s_b ~ 1/2
is a QCD parameter. Requiring that a classical history exist, our model
determines the probability of observing a given Lambda. The observed CC value,
which we successfully predict, is typical within our model even before the
effects of anthropic selection are included. When anthropic selection effects
are accounted for, we find that the observed coincidence between t_Lambda =
Lambda^(-1/2) and the age of the universe, t_U, is a typical occurrence in our
model. In contrast to multiverse explanations of the CC problems, our solution
is independent of the choice of a prior weighting of different $\Lambda$-values
and does not rely on anthropic selection effects. Our model includes no
unnatural small parameters and does not require the introduction of new
dynamical scalar fields or modifications to general relativity, and it can be
tested by astronomical observations in the near future.
| [
{
"created": "Wed, 20 Oct 2010 18:02:49 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Feb 2011 09:32:08 GMT",
"version": "v2"
}
] | 2015-03-17 | [
[
"Shaw",
"Douglas J.",
""
],
[
"Barrow",
"John D.",
""
]
] | We present a new solution to the cosmological constant (CC) and coincidence problems in which the observed value of the CC, $\Lambda$, is linked to other observable properties of the universe. This is achieved by promoting the CC from a parameter which must to specified, to a field which can take many possible values. The observed value of Lambda ~ 1/(9.3 Gyrs)^2$ (approximately 10^(-120) in Planck units) is determined by a new constraint equation which follows from the application of a causally restricted variation principle. When applied to our visible universe, the model makes a testable prediction for the dimensionless spatial curvature of Omega_k0 = -0.0056 s_b/0.5; where s_b ~ 1/2 is a QCD parameter. Requiring that a classical history exist, our model determines the probability of observing a given Lambda. The observed CC value, which we successfully predict, is typical within our model even before the effects of anthropic selection are included. When anthropic selection effects are accounted for, we find that the observed coincidence between t_Lambda = Lambda^(-1/2) and the age of the universe, t_U, is a typical occurrence in our model. In contrast to multiverse explanations of the CC problems, our solution is independent of the choice of a prior weighting of different $\Lambda$-values and does not rely on anthropic selection effects. Our model includes no unnatural small parameters and does not require the introduction of new dynamical scalar fields or modifications to general relativity, and it can be tested by astronomical observations in the near future. |
0806.0682 | Jose Ademir Sales Lima | S. H. Pereira and J. A. S. Lima | On Phantom Thermodynamics | 14 pages, no figures, text revised | Phys.Lett.B669:266-270,2008 | 10.1016/j.physletb.2008.10.006 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The thermodynamic properties of dark energy fluids described by an equation
of state parameter $\omega=p/\rho$ are rediscussed in the context of FRW type
geometries. Contrarily to previous claims, it is argued here that the phantom
regime $\omega<-1$ is not physically possible since that both the temperature
and the entropy of every physical fluids must be always positive definite. This
means that one cannot appeal to negative temperature in order to save the
phantom dark energy hypothesis as has been recently done in the literature.
Such a result remains true as long as the chemical potential is zero. However,
if the phantom fluid is endowed with a non-null chemical potential, the phantom
field hypothesis becomes thermodynamically consistent, that is, there are
macroscopic equilibrium states with $T>0$ and $S>0$ in the course of the
Universe expansion. Further, the negative value of the chemical potential
resulting from the entropy constraint ($S>0$) suggests a bosonic massless
nature to the phantom particles.
| [
{
"created": "Wed, 4 Jun 2008 03:20:14 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Oct 2008 17:37:51 GMT",
"version": "v2"
}
] | 2014-11-18 | [
[
"Pereira",
"S. H.",
""
],
[
"Lima",
"J. A. S.",
""
]
] | The thermodynamic properties of dark energy fluids described by an equation of state parameter $\omega=p/\rho$ are rediscussed in the context of FRW type geometries. Contrarily to previous claims, it is argued here that the phantom regime $\omega<-1$ is not physically possible since that both the temperature and the entropy of every physical fluids must be always positive definite. This means that one cannot appeal to negative temperature in order to save the phantom dark energy hypothesis as has been recently done in the literature. Such a result remains true as long as the chemical potential is zero. However, if the phantom fluid is endowed with a non-null chemical potential, the phantom field hypothesis becomes thermodynamically consistent, that is, there are macroscopic equilibrium states with $T>0$ and $S>0$ in the course of the Universe expansion. Further, the negative value of the chemical potential resulting from the entropy constraint ($S>0$) suggests a bosonic massless nature to the phantom particles. |
gr-qc/0011019 | Spiros Cotsakis | John Miritzis, Peter Leach and Spiros Cotsakis | Symmetry, Singularities and Integrability in Complex Dynamics IV:
Painleve Integrability of Isotropic Cosmologies | 9 pp, latex, gc style, to appear in Grav.Cosm | Grav.Cosmol. 6 (2000) 282-290 | null | null | gr-qc | null | We apply the results of singularity analysis to the isotropic cosmological
models in general relativity and string theory with a variety of matter terms.
For some of these models the standard Painlev\'{e} test is sufficient to
demonstrate integrability or nonintegrability in the sense of Painlev\'{e}. For
others of these models it is necessary to use a less algorithmic procedure.
| [
{
"created": "Mon, 6 Nov 2000 17:57:59 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Miritzis",
"John",
""
],
[
"Leach",
"Peter",
""
],
[
"Cotsakis",
"Spiros",
""
]
] | We apply the results of singularity analysis to the isotropic cosmological models in general relativity and string theory with a variety of matter terms. For some of these models the standard Painlev\'{e} test is sufficient to demonstrate integrability or nonintegrability in the sense of Painlev\'{e}. For others of these models it is necessary to use a less algorithmic procedure. |
1502.05388 | Ian Jubb | Michel Buck, Fay Dowker, Ian Jubb and Sumati Surya | Boundary Terms for Causal Sets | null | Class.Quant.Grav. 32 (2015) 20, 205004 | 10.1088/0264-9381/32/20/205004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a family of boundary terms for the action of a causal set with a
spacelike boundary. We show that in the continuum limit one recovers the
Gibbons-Hawking-York boundary term in the mean. We also calculate the continuum
limit of the mean causal set action for an Alexandrov interval in flat
spacetime. We find that it is equal to the volume of the codimension-2
intersection of the two light-cone boundaries of the interval.
| [
{
"created": "Wed, 18 Feb 2015 20:57:12 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Oct 2015 09:53:34 GMT",
"version": "v2"
}
] | 2015-10-30 | [
[
"Buck",
"Michel",
""
],
[
"Dowker",
"Fay",
""
],
[
"Jubb",
"Ian",
""
],
[
"Surya",
"Sumati",
""
]
] | We propose a family of boundary terms for the action of a causal set with a spacelike boundary. We show that in the continuum limit one recovers the Gibbons-Hawking-York boundary term in the mean. We also calculate the continuum limit of the mean causal set action for an Alexandrov interval in flat spacetime. We find that it is equal to the volume of the codimension-2 intersection of the two light-cone boundaries of the interval. |
2312.11899 | Hiroaki Tahara | Hiroaki W. H. Tahara, Kazufumi Takahashi, Masato Minamitsuji, Hayato
Motohashi | Exact solution for rotating black holes in parity-violating gravity | 19 pages, 8 figures | Progress of Theoretical and Experimental Physics, Volume 2024,
Issue 5, May 2024, 053E02 | 10.1093/ptep/ptae046 | RUP-23-26, YITP-23-147 | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has recently been pointed out that one can construct invertible conformal
transformations with a parity-violating conformal factor, which can be employed
to generate a novel class of parity-violating ghost-free metric theories from
general relativity. We obtain exact solutions for rotating black holes in such
theories by performing the conformal transformation on the Kerr solution in
general relativity, which we dub conformal Kerr solutions. We explore the
geodesic motion of a test particle in the conformal Kerr spacetime. While null
geodesics remain the same as those in the Kerr spacetime, timelike geodesics
exhibit interesting differences due to an effective external force caused by
the parity-violating conformal factor.
| [
{
"created": "Tue, 19 Dec 2023 06:50:28 GMT",
"version": "v1"
},
{
"created": "Mon, 20 May 2024 12:44:13 GMT",
"version": "v2"
}
] | 2024-05-21 | [
[
"Tahara",
"Hiroaki W. H.",
""
],
[
"Takahashi",
"Kazufumi",
""
],
[
"Minamitsuji",
"Masato",
""
],
[
"Motohashi",
"Hayato",
""
]
] | It has recently been pointed out that one can construct invertible conformal transformations with a parity-violating conformal factor, which can be employed to generate a novel class of parity-violating ghost-free metric theories from general relativity. We obtain exact solutions for rotating black holes in such theories by performing the conformal transformation on the Kerr solution in general relativity, which we dub conformal Kerr solutions. We explore the geodesic motion of a test particle in the conformal Kerr spacetime. While null geodesics remain the same as those in the Kerr spacetime, timelike geodesics exhibit interesting differences due to an effective external force caused by the parity-violating conformal factor. |
0906.1047 | Andreas Albrecht | Andreas Albrecht | de Sitter equilibrium as a fundamental framework for cosmology | 14 pages including 2 figures. In the proceedings of the DICE2008
conference, Thomas Elze ed. (IOP 2009) V2: Typos fixed in Eqns. 1, 10, 13, 18
and 20. No other changes | null | 10.1088/1742-6596/174/1/012006 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmology might turn out to be the study of fluctuations around a "de Sitter
equilibrium" state. In this article I review the basic ideas and the attractive
features of this framework, and respond to a number common questions raised
about the de Sitter equilibrium picture. I show that this framework does not
suffer from the "Boltzmann Brain" problem, and relate this cosmological picture
to recent work on the "clock ambiguity".
| [
{
"created": "Fri, 5 Jun 2009 07:26:39 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Aug 2010 13:29:20 GMT",
"version": "v2"
}
] | 2015-05-13 | [
[
"Albrecht",
"Andreas",
""
]
] | Cosmology might turn out to be the study of fluctuations around a "de Sitter equilibrium" state. In this article I review the basic ideas and the attractive features of this framework, and respond to a number common questions raised about the de Sitter equilibrium picture. I show that this framework does not suffer from the "Boltzmann Brain" problem, and relate this cosmological picture to recent work on the "clock ambiguity". |
gr-qc/9901037 | Omar Benhar | O. Benhar, E. Berti and V. Ferrari | The imprint of the equation of state on the axial w-modes of oscillating
neutron stars | 9 pages, 7 figures, mn.sty | Mon.Not.Roy.Astron.Soc. 310 (1999) 797-803 | 10.1046/j.1365-8711.1999.02983.x | null | gr-qc nucl-th | null | We discuss the dependence of the pulsation frequencies of the axial
quasi-normal modes of a nonrotating neutron star upon the equation of state
describing the star interior. The continued fraction method has been used to
compute the complex frequencies for a set of equations of state based on
different physical assumptions and spanning a wide range of stiffness. The
numerical results show that the detection of axial gravitational waves would
allow to discriminate between the models underlying the different equation of
states, thus providing relevant information on both the structure of neutron
star matter and the nature of the hadronic interactions.
| [
{
"created": "Wed, 13 Jan 1999 14:00:40 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Benhar",
"O.",
""
],
[
"Berti",
"E.",
""
],
[
"Ferrari",
"V.",
""
]
] | We discuss the dependence of the pulsation frequencies of the axial quasi-normal modes of a nonrotating neutron star upon the equation of state describing the star interior. The continued fraction method has been used to compute the complex frequencies for a set of equations of state based on different physical assumptions and spanning a wide range of stiffness. The numerical results show that the detection of axial gravitational waves would allow to discriminate between the models underlying the different equation of states, thus providing relevant information on both the structure of neutron star matter and the nature of the hadronic interactions. |
gr-qc/9711075 | Dharam V. Ahluwalia | D. V. Ahluwalia (Los Alamos) | Three Quantum Aspects of Gravity | Invited paper to appear in the Festscrift celebrating 90th birthday
of Professor Ta-You Wu | Chin.J.Phys.35:804-808,1997 | null | LA-UR-97-4809 | gr-qc | null | It is argued that (a) In the quantum realm test-particle masses have
non-trivial observability which induces a non-geometric element in gravity, (b)
Any theory of quantum gravity, on fundamental grounds, must contain an element
of non-locality that makes position measurements non-commutative, and (c) The
classical notion of free fall does not readily generalize to the quantum
regime.
| [
{
"created": "Tue, 25 Nov 1997 23:15:35 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ahluwalia",
"D. V.",
"",
"Los Alamos"
]
] | It is argued that (a) In the quantum realm test-particle masses have non-trivial observability which induces a non-geometric element in gravity, (b) Any theory of quantum gravity, on fundamental grounds, must contain an element of non-locality that makes position measurements non-commutative, and (c) The classical notion of free fall does not readily generalize to the quantum regime. |
gr-qc/9601040 | Charles Hellaby | Charles Hellaby and Tevian dray | Reply Comment: Comparison of Approaches to Classical Signature Change | 10 pages, latex, no figures. Replying to - "Comment on `Failure of
Standard Conservation Laws at a Classical Change of Signature'", S.A.
Hayward, Phys. Rev. D52, 7331-7332 (1995) (gr-qc/9606045) | Phys.Rev. D52 (1995) 7333-7339 | 10.1103/PhysRevD.52.7333 | null | gr-qc | null | We contrast the two approaches to ``classical" signature change used by
Hayward with the one used by us (Hellaby and Dray). There is (as yet) no
rigorous derivation of appropriate distributional field equations. Hayward's
distributional approach is based on a postulated modified form of the field
equations. We make an alternative postulate. We point out an important
difference between two possible philosophies of signature change --- ours is
strictly classical, while Hayward's Lagrangian approach adopts what amounts to
an imaginary proper ``time" on one side of the signature change, as is
explicitly done in quantum cosmology. We also explain why we chose to use the
Darmois-Israel type junction conditions, rather than the Lichnerowicz type
junction conditions favoured by Hayward. We show that the difference in results
is entirely explained by the difference in philosophy (imaginary versus real
Euclidean ``time"), and not by the difference in approach to junction
conditions (Lichnerowicz with specific coordinates versus Darmois with general
coordinates).
| [
{
"created": "Thu, 25 Jan 1996 18:21:04 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Hellaby",
"Charles",
""
],
[
"dray",
"Tevian",
""
]
] | We contrast the two approaches to ``classical" signature change used by Hayward with the one used by us (Hellaby and Dray). There is (as yet) no rigorous derivation of appropriate distributional field equations. Hayward's distributional approach is based on a postulated modified form of the field equations. We make an alternative postulate. We point out an important difference between two possible philosophies of signature change --- ours is strictly classical, while Hayward's Lagrangian approach adopts what amounts to an imaginary proper ``time" on one side of the signature change, as is explicitly done in quantum cosmology. We also explain why we chose to use the Darmois-Israel type junction conditions, rather than the Lichnerowicz type junction conditions favoured by Hayward. We show that the difference in results is entirely explained by the difference in philosophy (imaginary versus real Euclidean ``time"), and not by the difference in approach to junction conditions (Lichnerowicz with specific coordinates versus Darmois with general coordinates). |
gr-qc/0212128 | D. V. Ahluwalia | D. V. Ahluwalia-Khalilova | Operational indistinguishabilty of doubly special relativities from
special relativity | 8 pages [This paper is no longer being pursued for publication. Its
essential, and updated, content is now available in Sec. 2 of D. V.
Ahluwalia-Khalilova, A freely falling frame at the interface of gravitational
and quantum realms, Class. Quant. Grav. 22 (2005) 1433-1450.] | null | null | null | gr-qc hep-ph hep-th | null | We argue that existing doubly special relativities may not be operationally
distinguishable from the special relativity. In the process we point out that
some of the phenomenologically motivated modifications of dispersion relations,
and arrived conclusions, must be reconsidered. Finally, we reflect on the
possible conceptual issues that arise in quest for a theory of spacetime with
two invariant scales.
| [
{
"created": "Tue, 31 Dec 2002 12:49:45 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Jun 2003 16:42:18 GMT",
"version": "v2"
},
{
"created": "Wed, 10 Aug 2005 01:37:58 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Ahluwalia-Khalilova",
"D. V.",
""
]
] | We argue that existing doubly special relativities may not be operationally distinguishable from the special relativity. In the process we point out that some of the phenomenologically motivated modifications of dispersion relations, and arrived conclusions, must be reconsidered. Finally, we reflect on the possible conceptual issues that arise in quest for a theory of spacetime with two invariant scales. |
1511.06083 | Kazufumi Takahashi | Kazufumi Takahashi, Teruaki Suyama, Tsutomu Kobayashi | Universal instability of hairy black holes in Lovelock-Galileon theories
in D dimensions | 14 pages; matches published version | Phys. Rev. D 93, 064068 (2016) | 10.1103/PhysRevD.93.064068 | RESCEU-32/15, RUP-15-27 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze spherically symmetric black hole solutions with time-dependent
scalar hair in a class of Lovelock-Galileon theories, which are the
scalar-tensor theories with second-order field equations in arbitrary
dimensions. We first show that known black hole solutions in five dimensions
are always plagued by the ghost/gradient instability in the vicinity of the
horizon. We then generalize such black hole solutions to higher dimensions and
show that the same instability found in five dimensions appears universally in
any number of dimensions.
| [
{
"created": "Thu, 19 Nov 2015 07:46:54 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Mar 2016 02:03:08 GMT",
"version": "v2"
}
] | 2016-04-06 | [
[
"Takahashi",
"Kazufumi",
""
],
[
"Suyama",
"Teruaki",
""
],
[
"Kobayashi",
"Tsutomu",
""
]
] | We analyze spherically symmetric black hole solutions with time-dependent scalar hair in a class of Lovelock-Galileon theories, which are the scalar-tensor theories with second-order field equations in arbitrary dimensions. We first show that known black hole solutions in five dimensions are always plagued by the ghost/gradient instability in the vicinity of the horizon. We then generalize such black hole solutions to higher dimensions and show that the same instability found in five dimensions appears universally in any number of dimensions. |
1606.09186 | Andrea Dapor | Mehdi Assanioussi, Andrea Dapor | Rainbow metric from quantum gravity: anisotropic cosmology | 14 pages, 1 figure | Phys. Rev. D 95, 063513 (2017) | 10.1103/PhysRevD.95.063513 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we present a construction of effective cosmological models
which describe the propagation of a massive quantum scalar field on a quantum
anisotropic cosmological spacetime. Each obtained effective model is
represented by a rainbow metric in which particles of distinct momenta
propagate on different classical geometries. Our analysis shows that upon
certain assumptions and conditions on the parameters determining such
anisotropic models, we surprisingly obtain a unique deformation parameter
$\beta$ in the modified dispersion relation of the modes. Hence inducing an
isotropic deformation despite the general starting considerations. We then
ensure the recovery of the dispersion relation realized in the isotropic case,
studied in [arXiv:1412.6000], when some proper symmetry constraints are
imposed, and we estimate the value of the deformation parameter for this case
in loop quantum cosmology context.
| [
{
"created": "Wed, 29 Jun 2016 17:08:13 GMT",
"version": "v1"
}
] | 2017-03-21 | [
[
"Assanioussi",
"Mehdi",
""
],
[
"Dapor",
"Andrea",
""
]
] | In this paper we present a construction of effective cosmological models which describe the propagation of a massive quantum scalar field on a quantum anisotropic cosmological spacetime. Each obtained effective model is represented by a rainbow metric in which particles of distinct momenta propagate on different classical geometries. Our analysis shows that upon certain assumptions and conditions on the parameters determining such anisotropic models, we surprisingly obtain a unique deformation parameter $\beta$ in the modified dispersion relation of the modes. Hence inducing an isotropic deformation despite the general starting considerations. We then ensure the recovery of the dispersion relation realized in the isotropic case, studied in [arXiv:1412.6000], when some proper symmetry constraints are imposed, and we estimate the value of the deformation parameter for this case in loop quantum cosmology context. |
1105.0988 | Naresh Dadhich | Naresh Dadhich | Universal features of gravity and higher dimensions | 7 pages, revtex, Plenary lecture in 13th Regional Conference on
Mathematical Physics held on Oct. 23-31, 2010 at Antalaya, Turkey, To appear
in Proceedings of the Conference | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study some universal features of gravity in higher dimensions and by
universal we mean a feature that remains true in all dimensions $\geq4$. They
include: (a) the gravitational dynamics always follows from the Bianchi
derivative of a homogeneous polynomial in Riemann curvature and it thereby
characterizes the Lovelock polynomial action, (b) all the $\Lambda$-vacuum
solutions of the Einstein-Lovelock as well as pure Lovelock equation have the
same asymptotic limit agreeing with the $d$ dimensional Einstein solution and
(c) gravity inside a uniform density sphere is independent of the spacetime
dimension and it is always given by the Schwarzschild interior solution.
| [
{
"created": "Thu, 5 May 2011 06:30:35 GMT",
"version": "v1"
}
] | 2011-05-06 | [
[
"Dadhich",
"Naresh",
""
]
] | We study some universal features of gravity in higher dimensions and by universal we mean a feature that remains true in all dimensions $\geq4$. They include: (a) the gravitational dynamics always follows from the Bianchi derivative of a homogeneous polynomial in Riemann curvature and it thereby characterizes the Lovelock polynomial action, (b) all the $\Lambda$-vacuum solutions of the Einstein-Lovelock as well as pure Lovelock equation have the same asymptotic limit agreeing with the $d$ dimensional Einstein solution and (c) gravity inside a uniform density sphere is independent of the spacetime dimension and it is always given by the Schwarzschild interior solution. |
gr-qc/0505149 | Ilya Mandel | Ilya Mandel | The geometry of a naked singularity created by standing waves near a
Schwarzschild horizon, and its application to the binary black hole problem | 12 pages, 6 figures | Phys.Rev. D72 (2005) 084025 | 10.1103/PhysRevD.72.084025 | null | gr-qc | null | The most promising way to compute the gravitational waves emitted by binary
black holes (BBHs) in their last dozen orbits, where post-Newtonian techniques
fail, is a quasistationary approximation introduced by Detweiler and being
pursued by Price and others. In this approximation the outgoing gravitational
waves at infinity and downgoing gravitational waves at the holes' horizons are
replaced by standing waves so as to guarantee that the spacetime has a helical
Killing vector field. Because the horizon generators will not, in general, be
tidally locked to the holes' orbital motion, the standing waves will destroy
the horizons, converting the black holes into naked singularities that resemble
black holes down to near the horizon radius. This paper uses a spherically
symmetric, scalar-field model problem to explore in detail the following BBH
issues: (i) The destruction of a horizon by the standing waves. (ii) The
accuracy with which the resulting naked singularity resembles a black hole.
(iii) The conversion of the standing-wave spacetime (with a destroyed horizon)
into a spacetime with downgoing waves by the addition of a ``radiation-reaction
field''. (iv) The accuracy with which the resulting downgoing waves agree with
the downgoing waves of a true black-hole spacetime (with horizon). The model
problem used to study these issues consists of a Schwarzschild black hole
endowed with spherical standing waves of a scalar field. It is found that the
spacetime metric of the singular, standing-wave spacetime, and its
radiation-reaction-field-constructed downgoing waves are quite close to those
for a Schwarzschild black hole with downgoing waves -- sufficiently close to
make the BBH quasistationary approximation look promising for
non-tidally-locked black holes.
| [
{
"created": "Mon, 30 May 2005 06:52:38 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Mandel",
"Ilya",
""
]
] | The most promising way to compute the gravitational waves emitted by binary black holes (BBHs) in their last dozen orbits, where post-Newtonian techniques fail, is a quasistationary approximation introduced by Detweiler and being pursued by Price and others. In this approximation the outgoing gravitational waves at infinity and downgoing gravitational waves at the holes' horizons are replaced by standing waves so as to guarantee that the spacetime has a helical Killing vector field. Because the horizon generators will not, in general, be tidally locked to the holes' orbital motion, the standing waves will destroy the horizons, converting the black holes into naked singularities that resemble black holes down to near the horizon radius. This paper uses a spherically symmetric, scalar-field model problem to explore in detail the following BBH issues: (i) The destruction of a horizon by the standing waves. (ii) The accuracy with which the resulting naked singularity resembles a black hole. (iii) The conversion of the standing-wave spacetime (with a destroyed horizon) into a spacetime with downgoing waves by the addition of a ``radiation-reaction field''. (iv) The accuracy with which the resulting downgoing waves agree with the downgoing waves of a true black-hole spacetime (with horizon). The model problem used to study these issues consists of a Schwarzschild black hole endowed with spherical standing waves of a scalar field. It is found that the spacetime metric of the singular, standing-wave spacetime, and its radiation-reaction-field-constructed downgoing waves are quite close to those for a Schwarzschild black hole with downgoing waves -- sufficiently close to make the BBH quasistationary approximation look promising for non-tidally-locked black holes. |
2401.02448 | Archie Cable | Archie Cable | A second-order stochastic effective theory for the long-distance
behaviour of scalar fields in de Sitter spacetime | PhD Thesis | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This thesis introduces an effective theory for the long-distance behaviour of
scalar fields in de Sitter spacetime, known as the second-order stochastic
theory, with the aim of computing scalar correlation functions that are useful
in inflationary cosmology.
| [
{
"created": "Wed, 3 Jan 2024 11:30:51 GMT",
"version": "v1"
}
] | 2024-01-08 | [
[
"Cable",
"Archie",
""
]
] | This thesis introduces an effective theory for the long-distance behaviour of scalar fields in de Sitter spacetime, known as the second-order stochastic theory, with the aim of computing scalar correlation functions that are useful in inflationary cosmology. |
2107.05111 | Oleksandr Stashko | O. S. Stashko, V. I. Zhdanov, A. N. Alexandrov | Thin accretion discs around spherically symmetric configurations with
nonlinear scalar fields | null | Phys. Rev. D 104, 104055 (2021) | 10.1103/PhysRevD.104.104055 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study stable circular orbits (SCO) around static spherically symmetric
configuration of General Relativity with a non-linear scalar field (SF). The
configurations are described by solutions of the Einstein-SF equations with
monomial SF potential $V(\phi)=|\phi|^{2n}$, $n>2$, under the conditions of the
asymptotic flatness and behavior of SF $\phi\sim 1/r$ at spatial infinity. We
proved that under these conditions the solution exists and is uniquely defined
by the configuration mass $M>0$ and scalar "charge" $Q$. The solutions and the
space-time geodesics have been investigated numerically in the range $n\le40$,
$|Q|\le 60$, $M\le60$. We focus on how nonlinearity of the field affects
properties of SCO distributions (SCOD), which in turn affect topological form
of the thin accretion disk around the configuration. Maps are presented showing
the location of possible SCOD types for different $M,Q,n$. We found many
differences from the Fisher-Janis-Newman-Winicour metric (FJNW) dealing with
the linear SF, though basic qualitative properties of the configurations have
much in common with the FJNW case. For some values of $n$, a topologically new
SCOD type was discovered that is not available for the FJNW metric. All images
of accretion disks have a dark spot in the center (mimicking an ordinary black
hole), either because there is no SCO near the center or because of the strong
deflection of photon trajectories near the singularity.
| [
{
"created": "Sun, 11 Jul 2021 18:52:34 GMT",
"version": "v1"
}
] | 2022-09-07 | [
[
"Stashko",
"O. S.",
""
],
[
"Zhdanov",
"V. I.",
""
],
[
"Alexandrov",
"A. N.",
""
]
] | We study stable circular orbits (SCO) around static spherically symmetric configuration of General Relativity with a non-linear scalar field (SF). The configurations are described by solutions of the Einstein-SF equations with monomial SF potential $V(\phi)=|\phi|^{2n}$, $n>2$, under the conditions of the asymptotic flatness and behavior of SF $\phi\sim 1/r$ at spatial infinity. We proved that under these conditions the solution exists and is uniquely defined by the configuration mass $M>0$ and scalar "charge" $Q$. The solutions and the space-time geodesics have been investigated numerically in the range $n\le40$, $|Q|\le 60$, $M\le60$. We focus on how nonlinearity of the field affects properties of SCO distributions (SCOD), which in turn affect topological form of the thin accretion disk around the configuration. Maps are presented showing the location of possible SCOD types for different $M,Q,n$. We found many differences from the Fisher-Janis-Newman-Winicour metric (FJNW) dealing with the linear SF, though basic qualitative properties of the configurations have much in common with the FJNW case. For some values of $n$, a topologically new SCOD type was discovered that is not available for the FJNW metric. All images of accretion disks have a dark spot in the center (mimicking an ordinary black hole), either because there is no SCO near the center or because of the strong deflection of photon trajectories near the singularity. |
2207.01273 | Alfredo Bautista | A. Bautista, A. Ibort, J. Lafuente, R. Low | A conformal boundary for space-times based on light-like geodesics: the
3-dimensional case | 28 pages, 5 figures | Journal of Mathematical Physics, 58, 022503 (2017) | 10.1063/1.4976506 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new causal boundary, which we will term the $l$-boundary, inspired by the
geometry of the space of light rays and invariant by conformal diffeomorphisms
for space-times of any dimension $m\geq 3$, proposed by one of the authors
(R.J. Low, The space of null geodesics (and a new causal boundary), Lecture
Notes in Physics, 692, Springer, 2006, 35--50) is analyzed in detail for
space-times of dimension 3. Under some natural assumptions it is shown that the
completed space-time becomes a smooth manifold with boundary and its relation
with Geroch-Kronheimer-Penrose causal boundary is discussed. A number of
examples illustrating the properties of this new causal boundary as well as a
discussion on the obtained results will be provided.
| [
{
"created": "Mon, 4 Jul 2022 09:06:23 GMT",
"version": "v1"
}
] | 2022-07-05 | [
[
"Bautista",
"A.",
""
],
[
"Ibort",
"A.",
""
],
[
"Lafuente",
"J.",
""
],
[
"Low",
"R.",
""
]
] | A new causal boundary, which we will term the $l$-boundary, inspired by the geometry of the space of light rays and invariant by conformal diffeomorphisms for space-times of any dimension $m\geq 3$, proposed by one of the authors (R.J. Low, The space of null geodesics (and a new causal boundary), Lecture Notes in Physics, 692, Springer, 2006, 35--50) is analyzed in detail for space-times of dimension 3. Under some natural assumptions it is shown that the completed space-time becomes a smooth manifold with boundary and its relation with Geroch-Kronheimer-Penrose causal boundary is discussed. A number of examples illustrating the properties of this new causal boundary as well as a discussion on the obtained results will be provided. |
gr-qc/9303023 | null | Luca Amendola, Diego Bellisai and Franco Occhionero, Rome Astronomical
Observatory | Inflationary Attractors and Perturbation Spectra in Generally Coupled
Gravity | to appear in Phys. Rev. D, 10 pages, 4 figures available (also by
fax), LATEX, OAR 93/4 | Phys.Rev. D47 (1993) 4267-4272 | 10.1103/PhysRevD.47.4267 | null | gr-qc astro-ph | null | A generic outcome of theories with scalar-tensor coupling is the existence of
inflationary attractors, either power-law or de Sitter. The fluctuations
arising during this phase are Gaussian and their spectrum depends on the
wavenumber $k$ according to the power-law $k^{1/(1-p)}$, where $p$ is the
inflationary power-law exponent. We investigate to which extent these
properties depend on the coupling function and on the potential. We find the
class of models in which viable attractors exist. Within this class, we find
that the cosmic expansion and the scaling of the fluctuation spectrum are
independent of the coupling function. Further, the analytical solution of the
Fokker-Planck equation shows that the deviations from Gaussianity are
negligible.
| [
{
"created": "Fri, 19 Mar 1993 15:01:00 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Amendola",
"Luca",
""
],
[
"Bellisai",
"Diego",
""
],
[
"Occhionero",
"Franco",
""
],
[
"Observatory",
"Rome Astronomical",
""
]
] | A generic outcome of theories with scalar-tensor coupling is the existence of inflationary attractors, either power-law or de Sitter. The fluctuations arising during this phase are Gaussian and their spectrum depends on the wavenumber $k$ according to the power-law $k^{1/(1-p)}$, where $p$ is the inflationary power-law exponent. We investigate to which extent these properties depend on the coupling function and on the potential. We find the class of models in which viable attractors exist. Within this class, we find that the cosmic expansion and the scaling of the fluctuation spectrum are independent of the coupling function. Further, the analytical solution of the Fokker-Planck equation shows that the deviations from Gaussianity are negligible. |
1809.07448 | Yisong Yang Professor | Chenmei Xu, Yisong Yang | Determination of Bending Angle of Light Deflection Subject to Possible
Weak and Strong Quantum Gravity Effects | 18 pages. Modification and improvement are made to the previous
version. Title is modified. To appear | International Journal of Modern Physics A 35 (2020) 2050188 | 10.1142/S0217751X20501882 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Explicit expressions for the bending angle of light deflection arising from
phenomenologically deformed black-hole metrics, subject to possible weak and
strong quantum gravity effects, respectively, are obtained, by a highly
effective method. The accuracy and effectiveness of these expressions are then
illustrated by numerically solving the differential equation governing the
deflection angle directly in the weak quantum effect situation.
| [
{
"created": "Thu, 20 Sep 2018 01:59:26 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Sep 2018 18:15:54 GMT",
"version": "v2"
},
{
"created": "Fri, 8 Feb 2019 03:46:20 GMT",
"version": "v3"
},
{
"created": "Thu, 8 Oct 2020 16:15:17 GMT",
"version": "v4"
}
] | 2021-01-13 | [
[
"Xu",
"Chenmei",
""
],
[
"Yang",
"Yisong",
""
]
] | Explicit expressions for the bending angle of light deflection arising from phenomenologically deformed black-hole metrics, subject to possible weak and strong quantum gravity effects, respectively, are obtained, by a highly effective method. The accuracy and effectiveness of these expressions are then illustrated by numerically solving the differential equation governing the deflection angle directly in the weak quantum effect situation. |
2307.13040 | Sara Fernandez Uria | Martin Bojowald, David Brizuela, Paula Calizaya Cabrera and Sara F.
Uria | Reduction of primordial chaos by generic quantum effects | 11 pages, 2 figures, accepted for publication as a letter in Physical
Review D | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | According to general relativity, the generic early-universe dynamics is
chaotic. Various quantum-gravity effects have been suggested that may change
this behavior in different ways. Here, it is shown how key mathematical
properties of the classical dynamics can be extended to evolving quantum states
using quasiclassical methods, making it possible to apply the established
dynamical-systems approach to chaos even to quantum evolution. As a result, it
is found that quantum fluctuations contribute to the reduction of the
primordial chaos in early-universe models.
| [
{
"created": "Mon, 24 Jul 2023 18:00:07 GMT",
"version": "v1"
}
] | 2023-07-26 | [
[
"Bojowald",
"Martin",
""
],
[
"Brizuela",
"David",
""
],
[
"Cabrera",
"Paula Calizaya",
""
],
[
"Uria",
"Sara F.",
""
]
] | According to general relativity, the generic early-universe dynamics is chaotic. Various quantum-gravity effects have been suggested that may change this behavior in different ways. Here, it is shown how key mathematical properties of the classical dynamics can be extended to evolving quantum states using quasiclassical methods, making it possible to apply the established dynamical-systems approach to chaos even to quantum evolution. As a result, it is found that quantum fluctuations contribute to the reduction of the primordial chaos in early-universe models. |
2208.07230 | Bruce Allen | Bruce Allen and Joseph D. Romano | Hellings and Downs correlation of an arbitrary set of pulsars | Final published version. Note that the arXiv version of the Abstract
has been shortened to fit arXiv requirements | Phys. Rev. D 108, 043026 (2023) | 10.1103/PhysRevD.108.043026 | null | gr-qc astro-ph.CO astro-ph.HE astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | Pulsar timing arrays (PTAs) detect gravitational waves (GWs) via the
correlations they induce in the arrival times of pulses from different pulsars.
We assume that the GWs are described by a Gaussian ensemble. The mean
correlation $h^2 \mu_{\rm u}(\gamma)$ as a function of the angle $\gamma$
between the directions to two pulsars was predicted by Hellings and Downs (HD)
in 1983. The variance $\sigma^2_{\rm tot}(\gamma)$ in this correlation was
recently calculated by Allen[11] for a single noise-free pulsar pair at angle
$\gamma$, which shows that after averaging over many pairs, the variance
reduces to an intrinsic cosmic variance $\sigma^2_{\rm cos}(\gamma)$. Here, we
extend this to an $arbitrary$ set of pulsars at specific sky locations, with
pulsar pairs binned by $\gamma$. We derive the linear combination of
pulsar-pair correlations which is the optimal estimator of the HD correlation
for each bin, illustrating our methods with plots of the expected range of
variation away from the HD curve, for the sets of pulsars monitored by three
active PTA collaborations. We compute the variance of and the covariance
between these binned estimates, and show that these reduce to the cosmic
variance and covariance $s(\gamma,\gamma')$ respectively, in the many-pulsar
limit. The likely fluctuations away from the HD curve $\mu_{\rm u}(\gamma)$ are
strongly correlated/anticorrelated in the three angular regions where $\mu_{\rm
u}(\gamma)$ is successively positive, negative, and positive. We also construct
the optimal estimator of the squared strain $h^2$. When there are very many
pulsar pairs, this determines $h^2$ with arbitrary precision because PTAs probe
an infinite set of GW modes. To assess observed deviations away from the HD
curve, we characterize several $\chi^2$ goodness-of-fit statistics. We also
show how pulsar noise and measurement noise can be included.
| [
{
"created": "Mon, 15 Aug 2022 14:40:29 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Nov 2022 18:06:07 GMT",
"version": "v2"
},
{
"created": "Wed, 16 Nov 2022 17:39:49 GMT",
"version": "v3"
},
{
"created": "Wed, 5 Apr 2023 16:39:37 GMT",
"version": "v4"
},
{
"cre... | 2023-08-25 | [
[
"Allen",
"Bruce",
""
],
[
"Romano",
"Joseph D.",
""
]
] | Pulsar timing arrays (PTAs) detect gravitational waves (GWs) via the correlations they induce in the arrival times of pulses from different pulsars. We assume that the GWs are described by a Gaussian ensemble. The mean correlation $h^2 \mu_{\rm u}(\gamma)$ as a function of the angle $\gamma$ between the directions to two pulsars was predicted by Hellings and Downs (HD) in 1983. The variance $\sigma^2_{\rm tot}(\gamma)$ in this correlation was recently calculated by Allen[11] for a single noise-free pulsar pair at angle $\gamma$, which shows that after averaging over many pairs, the variance reduces to an intrinsic cosmic variance $\sigma^2_{\rm cos}(\gamma)$. Here, we extend this to an $arbitrary$ set of pulsars at specific sky locations, with pulsar pairs binned by $\gamma$. We derive the linear combination of pulsar-pair correlations which is the optimal estimator of the HD correlation for each bin, illustrating our methods with plots of the expected range of variation away from the HD curve, for the sets of pulsars monitored by three active PTA collaborations. We compute the variance of and the covariance between these binned estimates, and show that these reduce to the cosmic variance and covariance $s(\gamma,\gamma')$ respectively, in the many-pulsar limit. The likely fluctuations away from the HD curve $\mu_{\rm u}(\gamma)$ are strongly correlated/anticorrelated in the three angular regions where $\mu_{\rm u}(\gamma)$ is successively positive, negative, and positive. We also construct the optimal estimator of the squared strain $h^2$. When there are very many pulsar pairs, this determines $h^2$ with arbitrary precision because PTAs probe an infinite set of GW modes. To assess observed deviations away from the HD curve, we characterize several $\chi^2$ goodness-of-fit statistics. We also show how pulsar noise and measurement noise can be included. |
gr-qc/9811058 | David Coule | D.H. Coule | Varying c cosmology and Planck value constraints | extended version | Mod.Phys.Lett. A14 (1999) 2437-2446 | 10.1142/S0217732399002534 | null | gr-qc | null | It has been suggested that by increasing the speed of light during the early
universe various cosmological problems of standard big bang cosmology can be
overcome, without requiring an inflationary phase. However, we find that as the
Planck length and Planck time are then made correspondingly smaller, and
together with the need that the universe should not re-enter a Planck epoch,
the higher $c$ models have very limited ability to resolve such problems. For a
constantly decreasing $c$ the universe will quickly becomes quantum
gravitationally dominated as time increases: the opposite to standard cosmology
where quantum behaviour is only ascribed to early times.
| [
{
"created": "Tue, 17 Nov 1998 15:53:36 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Jun 1999 13:39:34 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Coule",
"D. H.",
""
]
] | It has been suggested that by increasing the speed of light during the early universe various cosmological problems of standard big bang cosmology can be overcome, without requiring an inflationary phase. However, we find that as the Planck length and Planck time are then made correspondingly smaller, and together with the need that the universe should not re-enter a Planck epoch, the higher $c$ models have very limited ability to resolve such problems. For a constantly decreasing $c$ the universe will quickly becomes quantum gravitationally dominated as time increases: the opposite to standard cosmology where quantum behaviour is only ascribed to early times. |
1507.00251 | Thuan Vo Van | Vo Van Thuan | From Microscopic Gravitational Waves to the Quantum Indeterminism | 7 pages, vhepu14 text-form | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on an extended space-time symmetry a new attempt to search for links
between general relativity and quantum mechanics is proposed. A simplified
cylindrical model of gravitational geometrical dynamics leads to a microscopic
geodesic description of strongly curved extradimensional space-time which
implies a duality between an emission law of microscopic gravitational waves
and the quantum mechanical equations of free elementary particles.
Consequently, the Heisenberg indeterminism would originate from the time-space
curvatures.
| [
{
"created": "Tue, 30 Jun 2015 03:40:26 GMT",
"version": "v1"
}
] | 2015-07-02 | [
[
"Van Thuan",
"Vo",
""
]
] | Based on an extended space-time symmetry a new attempt to search for links between general relativity and quantum mechanics is proposed. A simplified cylindrical model of gravitational geometrical dynamics leads to a microscopic geodesic description of strongly curved extradimensional space-time which implies a duality between an emission law of microscopic gravitational waves and the quantum mechanical equations of free elementary particles. Consequently, the Heisenberg indeterminism would originate from the time-space curvatures. |
1607.05251 | Michael Holst | Michael Holst, Olivier Sarbach, Manuel Tiglio, Michele Vallisneri | The Emergence of Gravitational Wave Science: 100 Years of Development of
Mathematical Theory, Detectors, Numerical Algorithms, and Data Analysis Tools | 41 pages, 5 figures. To appear in Bulletin of the American
Mathematical Society | null | null | null | gr-qc physics.comp-ph physics.data-an physics.hist-ph physics.ins-det | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On September 14, 2015, the newly upgraded Laser Interferometer
Gravitational-wave Observatory (LIGO) recorded a loud gravitational-wave (GW)
signal, emitted a billion light-years away by a coalescing binary of two
stellar-mass black holes. The detection was announced in February 2016, in time
for the hundredth anniversary of Einstein's prediction of GWs within the theory
of general relativity (GR). The signal represents the first direct detection of
GWs, the first observation of a black-hole binary, and the first test of GR in
its strong-field, high-velocity, nonlinear regime. In the remainder of its
first observing run, LIGO observed two more signals from black-hole binaries,
one moderately loud, another at the boundary of statistical significance. The
detections mark the end of a decades-long quest, and the beginning of GW
astronomy: finally, we are able to probe the unseen, electromagnetically dark
Universe by listening to it. In this article, we present a short historical
overview of GW science: this young discipline combines GR, arguably the
crowning achievement of classical physics, with record-setting, ultra-low-noise
laser interferometry, and with some of the most powerful developments in the
theory of differential geometry, partial differential equations,
high-performance computation, numerical analysis, signal processing,
statistical inference, and data science. Our emphasis is on the synergy between
these disciplines, and how mathematics, broadly understood, has historically
played, and continues to play, a crucial role in the development of GW science.
We focus on black holes, which are very pure mathematical solutions of
Einstein's gravitational-field equations that are nevertheless realized in
Nature, and that provided the first observed signals.
| [
{
"created": "Mon, 18 Jul 2016 19:39:23 GMT",
"version": "v1"
}
] | 2016-07-19 | [
[
"Holst",
"Michael",
""
],
[
"Sarbach",
"Olivier",
""
],
[
"Tiglio",
"Manuel",
""
],
[
"Vallisneri",
"Michele",
""
]
] | On September 14, 2015, the newly upgraded Laser Interferometer Gravitational-wave Observatory (LIGO) recorded a loud gravitational-wave (GW) signal, emitted a billion light-years away by a coalescing binary of two stellar-mass black holes. The detection was announced in February 2016, in time for the hundredth anniversary of Einstein's prediction of GWs within the theory of general relativity (GR). The signal represents the first direct detection of GWs, the first observation of a black-hole binary, and the first test of GR in its strong-field, high-velocity, nonlinear regime. In the remainder of its first observing run, LIGO observed two more signals from black-hole binaries, one moderately loud, another at the boundary of statistical significance. The detections mark the end of a decades-long quest, and the beginning of GW astronomy: finally, we are able to probe the unseen, electromagnetically dark Universe by listening to it. In this article, we present a short historical overview of GW science: this young discipline combines GR, arguably the crowning achievement of classical physics, with record-setting, ultra-low-noise laser interferometry, and with some of the most powerful developments in the theory of differential geometry, partial differential equations, high-performance computation, numerical analysis, signal processing, statistical inference, and data science. Our emphasis is on the synergy between these disciplines, and how mathematics, broadly understood, has historically played, and continues to play, a crucial role in the development of GW science. We focus on black holes, which are very pure mathematical solutions of Einstein's gravitational-field equations that are nevertheless realized in Nature, and that provided the first observed signals. |
1312.5976 | Claus Kiefer | Mariam Bouhmadi-Lopez, Claus Kiefer, Manuel Kraemer | Resolution of type IV singularities in quantum cosmology | 10 pages, 4 figures, clarifications included | Phys. Rev. D 89, 064016 (2014) | 10.1103/PhysRevD.89.064016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the fate of classical type IV singularities in quantum cosmology.
The framework is Wheeler-DeWitt quantization applied to homogeneous and
isotropic universes with a perfect fluid described by a generalized Chaplygin
gas. Such a fluid can be dynamically realized by a scalar field. We treat the
cases of a standard scalar field with positive kinetic energy and of a scalar
field with negative energy (phantom field). We first present the classical
solutions. We then discuss in detail the Wheeler-DeWitt equation for these
models. We are able to give analytic solutions for a special case and to draw
conclusions for the general case. Adopting the criterion that singularities are
avoided if the wave function vanishes in the region of the classical
singularity, we find that type IV singularities are avoided only for particular
solutions of the Wheeler-DeWitt equation. We compare this result with earlier
results found for other types of singularities.
| [
{
"created": "Fri, 20 Dec 2013 15:00:16 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Feb 2014 15:40:42 GMT",
"version": "v2"
}
] | 2014-03-12 | [
[
"Bouhmadi-Lopez",
"Mariam",
""
],
[
"Kiefer",
"Claus",
""
],
[
"Kraemer",
"Manuel",
""
]
] | We discuss the fate of classical type IV singularities in quantum cosmology. The framework is Wheeler-DeWitt quantization applied to homogeneous and isotropic universes with a perfect fluid described by a generalized Chaplygin gas. Such a fluid can be dynamically realized by a scalar field. We treat the cases of a standard scalar field with positive kinetic energy and of a scalar field with negative energy (phantom field). We first present the classical solutions. We then discuss in detail the Wheeler-DeWitt equation for these models. We are able to give analytic solutions for a special case and to draw conclusions for the general case. Adopting the criterion that singularities are avoided if the wave function vanishes in the region of the classical singularity, we find that type IV singularities are avoided only for particular solutions of the Wheeler-DeWitt equation. We compare this result with earlier results found for other types of singularities. |
1109.4119 | Philip D. Mannheim | Philip D. Mannheim | Cosmological Perturbations in Conformal Gravity | 43 pages. Final version. To appear in Phys. Rev. D | null | 10.1103/PhysRevD.85.124008 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first steps needed for an analysis of the perturbations that
occur in the cosmology associated with the conformal gravity theory. We discuss
the implications of conformal invariance for perturbative coordinate gauge
choices, and show that in the conformal theory the trace of the metric
fluctuation kinematically decouples from the first-order gravitational
fluctuation equations. We determine the equations that describe first-order
metric fluctuations around the illustrative conformally flat de Sitter
background. Via a conformal transformation we show that such fluctuations can
be constructed from fluctuations around a flat background, even though the
fluctuations themselves are associated with a perturbative geometry that is not
itself conformal to flat. We extend the analysis to fluctuations around other
cosmologically relevant backgrounds, such as the conformally-flat
Robertson-Walker background, and find tensor fluctuations that grow far more
rapidly than those that occur in the analogous standard case. We comment on
some recent work by 't Hooft and by Maldacena on deriving conformal gravity
from Einstein gravity or vice versa. We show that while the standard gravity
tensor fluctuations around a de Sitter background are also fluctuation
solutions in the conformal theory, in the conformal case they do not carry
energy.
| [
{
"created": "Mon, 19 Sep 2011 18:37:29 GMT",
"version": "v1"
},
{
"created": "Thu, 31 May 2012 17:54:06 GMT",
"version": "v2"
}
] | 2013-05-30 | [
[
"Mannheim",
"Philip D.",
""
]
] | We present the first steps needed for an analysis of the perturbations that occur in the cosmology associated with the conformal gravity theory. We discuss the implications of conformal invariance for perturbative coordinate gauge choices, and show that in the conformal theory the trace of the metric fluctuation kinematically decouples from the first-order gravitational fluctuation equations. We determine the equations that describe first-order metric fluctuations around the illustrative conformally flat de Sitter background. Via a conformal transformation we show that such fluctuations can be constructed from fluctuations around a flat background, even though the fluctuations themselves are associated with a perturbative geometry that is not itself conformal to flat. We extend the analysis to fluctuations around other cosmologically relevant backgrounds, such as the conformally-flat Robertson-Walker background, and find tensor fluctuations that grow far more rapidly than those that occur in the analogous standard case. We comment on some recent work by 't Hooft and by Maldacena on deriving conformal gravity from Einstein gravity or vice versa. We show that while the standard gravity tensor fluctuations around a de Sitter background are also fluctuation solutions in the conformal theory, in the conformal case they do not carry energy. |
0805.4399 | Davide Batic | Davide Batic and Manuel Sandoval | The hypergeneralized Heun equation in QFT in curved space-times | 8 pages | null | 10.2478/s11534-009-0107-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we show for the first time the role played by the
hypergeneralized Heun equation (HHE) in the context of Quantum Field Theory in
curved space-times. More precisely, we find suitable transformations relating
the separated radial and angular parts of a massive Dirac equation in the
Kerr-Newman-deSitter metric to a HHE.
| [
{
"created": "Wed, 28 May 2008 18:36:50 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Batic",
"Davide",
""
],
[
"Sandoval",
"Manuel",
""
]
] | In this article we show for the first time the role played by the hypergeneralized Heun equation (HHE) in the context of Quantum Field Theory in curved space-times. More precisely, we find suitable transformations relating the separated radial and angular parts of a massive Dirac equation in the Kerr-Newman-deSitter metric to a HHE. |
2405.03736 | Ajit Mohan Srivastava | Ajit M. Srivastava | Percolating Cosmic String loops from evaporating primordial black holes | 8 pages. arXiv admin note: substantial text overlap with
arXiv:hep-ph/0611253 | Phys. Lett. B Volume 853, June 2024, 138683 | 10.1016/j.physletb.2024.138683 | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | The Pulsar timing data from NANOGrav Collaboration has regenerated interest
in the possibility of observing stochastic gravitational wave background
arising from cosmic strings. In the standard theory, the cosmic string network
forms during spontaneous symmetry breaking (SSB) phase transition in the whole
universe via the so called Kibble mechanism. This scenario would not be
possible, e.g., in models of low energy inflation, where the reheat temperature
is much lower than the energy scale of cosmic strings. We point out a very
different possibility, where a network of even high energy scale cosmic strings
can form when the temperature of the Universe is much lower. We consider local
heating of plasma in the early universe by evaporating primordial black holes
(PBHs). It is known that for suitable masses of PBHs, their Hawking radiation
may re-heat the surrounding plasma to high temperatures, restoring certain
symmetries {\it locally} which are broken at the ambient temperature at that
stage. Expansion of the hot plasma cools it so that the {\it locally restored
symmetry} is spontaneously broken again. If this SSB supports formation of
cosmic strings, then string loops will form in this region around the PBH.
Further, resulting temperature gradients lead to pressure gradients such that
plasma develops radial flow with the string loops getting stretched as they get
dragged by the flow. For a finite density of PBHs of suitable masses, one will
get local hot spots, each one contributing to expanding cosmic string loops.
For suitable PBH density, the loops from different regions may intersect.
Intercommutation of strings can then lead to percolation, leading to the
possibility of formation of infinite string network, even when the entire
universe never goes through the respective SSB phase transition.
| [
{
"created": "Mon, 6 May 2024 15:53:27 GMT",
"version": "v1"
}
] | 2024-05-08 | [
[
"Srivastava",
"Ajit M.",
""
]
] | The Pulsar timing data from NANOGrav Collaboration has regenerated interest in the possibility of observing stochastic gravitational wave background arising from cosmic strings. In the standard theory, the cosmic string network forms during spontaneous symmetry breaking (SSB) phase transition in the whole universe via the so called Kibble mechanism. This scenario would not be possible, e.g., in models of low energy inflation, where the reheat temperature is much lower than the energy scale of cosmic strings. We point out a very different possibility, where a network of even high energy scale cosmic strings can form when the temperature of the Universe is much lower. We consider local heating of plasma in the early universe by evaporating primordial black holes (PBHs). It is known that for suitable masses of PBHs, their Hawking radiation may re-heat the surrounding plasma to high temperatures, restoring certain symmetries {\it locally} which are broken at the ambient temperature at that stage. Expansion of the hot plasma cools it so that the {\it locally restored symmetry} is spontaneously broken again. If this SSB supports formation of cosmic strings, then string loops will form in this region around the PBH. Further, resulting temperature gradients lead to pressure gradients such that plasma develops radial flow with the string loops getting stretched as they get dragged by the flow. For a finite density of PBHs of suitable masses, one will get local hot spots, each one contributing to expanding cosmic string loops. For suitable PBH density, the loops from different regions may intersect. Intercommutation of strings can then lead to percolation, leading to the possibility of formation of infinite string network, even when the entire universe never goes through the respective SSB phase transition. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.