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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2005.13599 | Carlos Coimbra-Araujo | C. H. Coimbra-Ara\'ujo and R. C. Anjos | Acceleration of charged particles from near-extremal rotating black
holes embedded in magnetic fields | 13 pages, 14 figures | null | 10.1088/1361-6382/abc189 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The aim of the present article is to evaluate the motion of charged test
particles in the vicinity of a near-extremal rotating black hole in the
presence of magnetic fields. Euler-Lagrange motion equations and effective
potential methods are used to characterize the motion out of the equatorial
plane. Such approach is of peculiar significance if it is considered, e.g.,
accretion processes onto rotating black holes. In general investigations
concerning accretion focus mostly on the simplest case of particles moving in
the equatorial plane. Here it will be considered that particles initially
moving around some particular orbit may be perturbed by a kick along the
$\theta$ direction, giving rise to other possible orbits. We confirm the
possibility that ultra high energy cosmic rays would be produced at the very
center of AGNs, for a specific range of magnetic field magnitudes, since it is
possible that ultra-high center-of-mass energies can be produced by particles
colliding near the horizon of fastly rotating black holes.
| [
{
"created": "Wed, 27 May 2020 19:09:56 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jun 2020 10:33:40 GMT",
"version": "v2"
}
] | 2021-02-03 | [
[
"Coimbra-Araújo",
"C. H.",
""
],
[
"Anjos",
"R. C.",
""
]
] | The aim of the present article is to evaluate the motion of charged test particles in the vicinity of a near-extremal rotating black hole in the presence of magnetic fields. Euler-Lagrange motion equations and effective potential methods are used to characterize the motion out of the equatorial plane. Such approach is of peculiar significance if it is considered, e.g., accretion processes onto rotating black holes. In general investigations concerning accretion focus mostly on the simplest case of particles moving in the equatorial plane. Here it will be considered that particles initially moving around some particular orbit may be perturbed by a kick along the $\theta$ direction, giving rise to other possible orbits. We confirm the possibility that ultra high energy cosmic rays would be produced at the very center of AGNs, for a specific range of magnetic field magnitudes, since it is possible that ultra-high center-of-mass energies can be produced by particles colliding near the horizon of fastly rotating black holes. |
1905.01793 | Yasusada Nambu | Yasusada Nambu, Sousuke Noda, Yuichiro Sakai | Wave Optics in Spacetimes with Compact Gravitating Object | 24 pages, accepted version in Phys. Rev. D | Phys. Rev. D 100, 064037 (2019) | 10.1103/PhysRevD.100.064037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the wave optics in spherically symmetric spacetimes:
Schwarzschild black hole, spherical star with a perfect absorbing surface, and
massless/massive Ellis wormholes. Assuming a point wave source, wave pattern
and power spectrums for scattering waves are obtained by solving the scalar
wave equation numerically. We found that the power spectrum at the observer in
the forward direction shows oscillations with two characteristic periods
determined by the interference effect associated with the photon sphere and the
diffraction effect due to the absorbing boundary condition inside of the photon
sphere.
| [
{
"created": "Mon, 6 May 2019 02:13:00 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Sep 2019 10:53:41 GMT",
"version": "v2"
}
] | 2019-09-25 | [
[
"Nambu",
"Yasusada",
""
],
[
"Noda",
"Sousuke",
""
],
[
"Sakai",
"Yuichiro",
""
]
] | We investigate the wave optics in spherically symmetric spacetimes: Schwarzschild black hole, spherical star with a perfect absorbing surface, and massless/massive Ellis wormholes. Assuming a point wave source, wave pattern and power spectrums for scattering waves are obtained by solving the scalar wave equation numerically. We found that the power spectrum at the observer in the forward direction shows oscillations with two characteristic periods determined by the interference effect associated with the photon sphere and the diffraction effect due to the absorbing boundary condition inside of the photon sphere. |
gr-qc/0607047 | Clifford M. Will | Emanuele Berti, Sai Iyer, Clifford M. Will (Washington University, St.
Louis) | Eccentricity content of binary black hole initial data | 5 pages, 5 figures, clarifications and minor corrections; version
submitted to Phys. Rev. D | Phys.Rev. D74 (2006) 061503 | 10.1103/PhysRevD.74.061503 | null | gr-qc | null | Using a post-Newtonian diagnostic tool developed by Mora and Will, we examine
numerically generated quasiequilibrium initial data sets that have been used in
recently successful numerical evolutions of binary black holes through plunge,
merger and ringdown. We show that a small but significant orbital eccentricity
is required to match post-Newtonian and quasiequilibrium calculations. If this
proves to be a real eccentricity, it could affect the fine details of the
subsequent numerical evolutions and the predicted gravitational waveforms.
| [
{
"created": "Tue, 11 Jul 2006 19:51:02 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Jul 2006 20:01:47 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Jul 2006 08:26:36 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Berti",
"Emanuele",
"",
"Washington University, St.\n Louis"
],
[
"Iyer",
"Sai",
"",
"Washington University, St.\n Louis"
],
[
"Will",
"Clifford M.",
"",
"Washington University, St.\n Louis"
]
] | Using a post-Newtonian diagnostic tool developed by Mora and Will, we examine numerically generated quasiequilibrium initial data sets that have been used in recently successful numerical evolutions of binary black holes through plunge, merger and ringdown. We show that a small but significant orbital eccentricity is required to match post-Newtonian and quasiequilibrium calculations. If this proves to be a real eccentricity, it could affect the fine details of the subsequent numerical evolutions and the predicted gravitational waveforms. |
gr-qc/0107038 | Spiros Cotsakis | Peter Leach, Spiros Cotsakis and John Miritzis | Symmetry, singularities and intregrability in complex dynamics VII:
Integrability Properties of FRW-Scalar Cosmologies | 22 pages, LaTeX | null | null | null | gr-qc | null | This paper considers some physically interesting cosmological dynamical
systems in the FRW-scalarfield category which are examined for integrability
according to the criterion of Painlev\'e. In the literature these systems have
been examined from the point of view of dynamical systems and the results from
the two disparate methods of analysis are compared. This allows some more
general comments to be made on the use of the Painlev\'e method in covariant
systems.
| [
{
"created": "Wed, 11 Jul 2001 06:16:35 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Leach",
"Peter",
""
],
[
"Cotsakis",
"Spiros",
""
],
[
"Miritzis",
"John",
""
]
] | This paper considers some physically interesting cosmological dynamical systems in the FRW-scalarfield category which are examined for integrability according to the criterion of Painlev\'e. In the literature these systems have been examined from the point of view of dynamical systems and the results from the two disparate methods of analysis are compared. This allows some more general comments to be made on the use of the Painlev\'e method in covariant systems. |
gr-qc/9307002 | Ted Jacobson | Ted Jacobson and Gungwon Kang | Conformal Invariance of Black Hole Temperature | 8 pages, plain LaTeX, NSF-ITP-93-91 | Class.Quant.Grav.10:L201-L206,1993 | 10.1088/0264-9381/10/11/002 | null | gr-qc hep-th | null | It is shown that the surface gravity and temperature of a stationary black
hole are invariant under conformal transformations of the metric that are the
identity at infinity. More precisely, we find a conformal invariant definition
of the surface gravity of a conformal Killing horizon that agrees with the
usual definition(s) for a true Killing horizon and is proportional to the
temperature as defined by Hawking radiation. This result is reconciled with the
intimate relation between the trace anomaly and the Hawking effect, despite the
{\it non}invariance of the trace anomaly under conformal transformations.
| [
{
"created": "Tue, 6 Jul 1993 23:38:00 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Jacobson",
"Ted",
""
],
[
"Kang",
"Gungwon",
""
]
] | It is shown that the surface gravity and temperature of a stationary black hole are invariant under conformal transformations of the metric that are the identity at infinity. More precisely, we find a conformal invariant definition of the surface gravity of a conformal Killing horizon that agrees with the usual definition(s) for a true Killing horizon and is proportional to the temperature as defined by Hawking radiation. This result is reconciled with the intimate relation between the trace anomaly and the Hawking effect, despite the {\it non}invariance of the trace anomaly under conformal transformations. |
2401.00091 | Valerio Faraoni | Valerio Faraoni and Carla Zeyn | Disforming scalar-tensor cosmology | 15 pages, latex. Added a section and an appendix on second order
disformal transformation, extra discussion, bibliography expanded. Matches
the version to appear in Phys. Rev. D | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Disformal transformations of Friedmann-Lema\^itre-Robertson-Walker and
Bianchi geometries are analyzed in the context of scalar-tensor gravity. Novel
aspects discussed explicitly are the $3+1$ splitting, the effective fluid
equivalent of the gravitational scalar, Bianchi models, stealth solutions, and
de Sitter solutions with non-constant scalar field (which are signatures of
scalar-tensor gravity). Both pure disformal transformations and more general
ones are discussed, including those containing higher derivatives of the scalar
field recently introduced in the literature.
| [
{
"created": "Fri, 29 Dec 2023 22:30:50 GMT",
"version": "v1"
},
{
"created": "Wed, 8 May 2024 00:28:18 GMT",
"version": "v2"
}
] | 2024-05-09 | [
[
"Faraoni",
"Valerio",
""
],
[
"Zeyn",
"Carla",
""
]
] | Disformal transformations of Friedmann-Lema\^itre-Robertson-Walker and Bianchi geometries are analyzed in the context of scalar-tensor gravity. Novel aspects discussed explicitly are the $3+1$ splitting, the effective fluid equivalent of the gravitational scalar, Bianchi models, stealth solutions, and de Sitter solutions with non-constant scalar field (which are signatures of scalar-tensor gravity). Both pure disformal transformations and more general ones are discussed, including those containing higher derivatives of the scalar field recently introduced in the literature. |
1911.06116 | Ignazio Ciufolini | Ignazio Ciufolini, Richard Matzner, Vahe Gurzadyan, Roger Penrose | A new laser-ranged satellite for General Relativity and space geodesy:
III. De Sitter effect and the LARES 2 space experiment | 9 pages | Eur. Phys. J. C, 77 12 (2017) 819 | 10.1140/epjc/s10052-017-5339-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In two previous papers we presented the LARES 2 space experiment aimed at a
very accurate test of frame-dragging and at other tests of fundamental physics
and measurements of space geodesy and geodynamics. We presented the error
sources of the LARES 2 experiment, its error budget and Monte Carlo simulations
and covariance analyses confirming an accuracy of a few parts in one thousand
in the test of frame-dragging. Here we discuss the impact of the orbital
perturbation known as the de Sitter effect, or geodetic precession, in the
error budget of the LARES 2 frame-dragging experiment. We show that the
uncertainty in the de Sitter effect has a negligible impact in the final error
budget because of the very accurate results now available for the test of the
de Sitter precession and because of its very nature. The total error budget in
the LARES 2 test of frame-dragging remains at a level of the order of 0.2%, as
determined in the first two papers of this series.
| [
{
"created": "Tue, 12 Nov 2019 10:22:35 GMT",
"version": "v1"
}
] | 2019-11-15 | [
[
"Ciufolini",
"Ignazio",
""
],
[
"Matzner",
"Richard",
""
],
[
"Gurzadyan",
"Vahe",
""
],
[
"Penrose",
"Roger",
""
]
] | In two previous papers we presented the LARES 2 space experiment aimed at a very accurate test of frame-dragging and at other tests of fundamental physics and measurements of space geodesy and geodynamics. We presented the error sources of the LARES 2 experiment, its error budget and Monte Carlo simulations and covariance analyses confirming an accuracy of a few parts in one thousand in the test of frame-dragging. Here we discuss the impact of the orbital perturbation known as the de Sitter effect, or geodetic precession, in the error budget of the LARES 2 frame-dragging experiment. We show that the uncertainty in the de Sitter effect has a negligible impact in the final error budget because of the very accurate results now available for the test of the de Sitter precession and because of its very nature. The total error budget in the LARES 2 test of frame-dragging remains at a level of the order of 0.2%, as determined in the first two papers of this series. |
1902.02871 | Gernot Hei{\ss}el | David Fajman and Gernot Hei{\ss}el | Kantowski-Sachs cosmology with Vlasov matter | 19 pages, 4 figures, 1 table | null | 10.1088/1361-6382/ab2425 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse the Kantowski-Sachs cosmologies with Vlasov matter of massive and
massless particles using dynamical systems analysis. We show that generic
solutions are past and future asymptotic to the non-flat locally rotationally
symmetric Kasner vacuum solution. Furthermore, we establish that solutions with
massive Vlasov matter behave like solutions with massless Vlasov matter towards
the singularities.
| [
{
"created": "Thu, 7 Feb 2019 22:37:14 GMT",
"version": "v1"
}
] | 2019-09-04 | [
[
"Fajman",
"David",
""
],
[
"Heißel",
"Gernot",
""
]
] | We analyse the Kantowski-Sachs cosmologies with Vlasov matter of massive and massless particles using dynamical systems analysis. We show that generic solutions are past and future asymptotic to the non-flat locally rotationally symmetric Kasner vacuum solution. Furthermore, we establish that solutions with massive Vlasov matter behave like solutions with massless Vlasov matter towards the singularities. |
gr-qc/0211002 | Dr. Anirudh Pradhan | Anirudh Pradhan and Hare Ram Pandey | Plane-Symmetric Inhomogeneous Bulk Viscous Cosmological Models with
Variable $\Lambda$ | 11 pages | Int.J.Mod.Phys.D12:941-952,2003 | 10.1142/S0218271803003359 | null | gr-qc | null | A plane-symmetric non-static cosmological model representing a bulk viscous
fluid distribution has been obtained which is inhomogeneous and anisotropic and
a particular case of which is gravitationally radiative. Without assuming any
{\it adhoc} law, we obtain a cosmological constant as a decreasing function of
time. The physical and geometric features of the models are also discussed.
| [
{
"created": "Fri, 1 Nov 2002 11:02:27 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Pradhan",
"Anirudh",
""
],
[
"Pandey",
"Hare Ram",
""
]
] | A plane-symmetric non-static cosmological model representing a bulk viscous fluid distribution has been obtained which is inhomogeneous and anisotropic and a particular case of which is gravitationally radiative. Without assuming any {\it adhoc} law, we obtain a cosmological constant as a decreasing function of time. The physical and geometric features of the models are also discussed. |
2204.08634 | Hing Tong Cho | Hing-Tong Cho, Jen-Tsung Hsiang and Bei-Lok Hu | Quantum Capacity and Vacuum Compressibility of Spacetime: Thermal Fields | 47 pages | Universe 8, 291 (2022) | null | null | gr-qc cond-mat.stat-mech hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | An important yet perplexing result from work in the 90s and 00s is the
near-unity value of the ratio of fluctuations in the vacuum energy density of
quantum fields to the mean in a collection of generic spacetimes. This was done
by way of calculating the noise kernels which are the correlators of the
stress-energy tensor of quantum fields. In this paper we revisit this issue via
a quantum thermodynamics approach, by calculating two quintessential
thermodynamic quantities: the heat capacity and the quantum compressibility of
some model geometries filled with a quantum field at high and low temperatures.
This is because heat capacity at constant volume gives a measure of the
fluctuations of the energy density to the mean. When this ratio approaches or
exceeds unity, the validity of the canonical distribution is called into
question. Likewise, a system's compressibility at constant pressure is a
criterion for the validity of grand canonical ensemble. We derive the free
energy density and, from it, obtain the expressions for these two thermodynamic
quantities for thermal and quantum fields in 2d Casimir space, 2d Einstein
cylinder and 4d ($S^1 \times S^3$ ) Einstein universe. To examine the
dependence on the dimensionality of space, for completeness, we have also
derived these thermodynamic quantities for the Einstein universes with
even-spatial dimensions: $S^1 \times S^2$ and $S^1 \times S^4$. With this array
of spacetimes we can investigate the thermodynamic stability of quantum matter
fields in them and make some qualitative observations on the compatibility
condition for the co-existence between quantum fields and spacetimes, a
fundamental issue in the quantum and gravitation conundrum.
| [
{
"created": "Tue, 19 Apr 2022 03:32:10 GMT",
"version": "v1"
}
] | 2023-01-10 | [
[
"Cho",
"Hing-Tong",
""
],
[
"Hsiang",
"Jen-Tsung",
""
],
[
"Hu",
"Bei-Lok",
""
]
] | An important yet perplexing result from work in the 90s and 00s is the near-unity value of the ratio of fluctuations in the vacuum energy density of quantum fields to the mean in a collection of generic spacetimes. This was done by way of calculating the noise kernels which are the correlators of the stress-energy tensor of quantum fields. In this paper we revisit this issue via a quantum thermodynamics approach, by calculating two quintessential thermodynamic quantities: the heat capacity and the quantum compressibility of some model geometries filled with a quantum field at high and low temperatures. This is because heat capacity at constant volume gives a measure of the fluctuations of the energy density to the mean. When this ratio approaches or exceeds unity, the validity of the canonical distribution is called into question. Likewise, a system's compressibility at constant pressure is a criterion for the validity of grand canonical ensemble. We derive the free energy density and, from it, obtain the expressions for these two thermodynamic quantities for thermal and quantum fields in 2d Casimir space, 2d Einstein cylinder and 4d ($S^1 \times S^3$ ) Einstein universe. To examine the dependence on the dimensionality of space, for completeness, we have also derived these thermodynamic quantities for the Einstein universes with even-spatial dimensions: $S^1 \times S^2$ and $S^1 \times S^4$. With this array of spacetimes we can investigate the thermodynamic stability of quantum matter fields in them and make some qualitative observations on the compatibility condition for the co-existence between quantum fields and spacetimes, a fundamental issue in the quantum and gravitation conundrum. |
2105.04887 | Sayan Kar | Rajendra Prasad Bhatt, Anushree Roy and Sayan Kar (IIT Kharagpur,
India) | Analog Raychaudhuri equation in mechanics | 21 pages, 9 figures, to appear in Resonance, Journal of Science
Education (Indian Academy of Sciences) | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Usually, in mechanics, we obtain the trajectory of a particle in a given
force field by solving Newton's second law with chosen initial conditions. In
contrast, through our work here, we first demonstrate how one may analyse the
behaviour of a suitably defined family of trajectories of a given mechanical
system. Such an approach leads us to develop a mechanics analog following the
well-known Raychaudhuri equation largely studied in Riemannian geometry and
general relativity. The idea of geodesic focusing, which is more familiar to a
relativist, appears to be analogous to the meeting of trajectories of a
mechanical system within a finite time. Applying our general results to the
case of simple pendula, we obtain relevant quantitative consequences.
Thereafter, we set up and perform a straightforward experiment based on a
system with two pendula. The experimental results on this system are found to
tally well with our proposed theoretical model. In summary, the simple theory,
as well as the related experiment, provides us with a way to understand the
essence of a fairly involved concept in advanced physics from an elementary
standpoint.
| [
{
"created": "Tue, 11 May 2021 09:18:58 GMT",
"version": "v1"
},
{
"created": "Thu, 19 May 2022 05:16:57 GMT",
"version": "v2"
}
] | 2022-05-20 | [
[
"Bhatt",
"Rajendra Prasad",
"",
"IIT Kharagpur,\n India"
],
[
"Roy",
"Anushree",
"",
"IIT Kharagpur,\n India"
],
[
"Kar",
"Sayan",
"",
"IIT Kharagpur,\n India"
]
] | Usually, in mechanics, we obtain the trajectory of a particle in a given force field by solving Newton's second law with chosen initial conditions. In contrast, through our work here, we first demonstrate how one may analyse the behaviour of a suitably defined family of trajectories of a given mechanical system. Such an approach leads us to develop a mechanics analog following the well-known Raychaudhuri equation largely studied in Riemannian geometry and general relativity. The idea of geodesic focusing, which is more familiar to a relativist, appears to be analogous to the meeting of trajectories of a mechanical system within a finite time. Applying our general results to the case of simple pendula, we obtain relevant quantitative consequences. Thereafter, we set up and perform a straightforward experiment based on a system with two pendula. The experimental results on this system are found to tally well with our proposed theoretical model. In summary, the simple theory, as well as the related experiment, provides us with a way to understand the essence of a fairly involved concept in advanced physics from an elementary standpoint. |
1306.4318 | Gavin Hartnett S | Gavin S. Hartnett and Jorge E. Santos | Non-Axisymmetric Instability of Rotating Black Holes in Higher
Dimensions | 5 pages, 2 figures, v2: minor revisions | null | 10.1103/PhysRevD.88.041505 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the scalar-gravitational quasi-normal modes of equal angular
momenta Myers-Perry black holes in odd dimensions. We find a new bar-mode
(non-axisymmetric) classical instability for $D \ge 7$. These black holes were
previously found to be unstable to axisymmetric perturbations for spins very
near extremality. The bar-mode instability we find sets in at much slower
spins, and is therefore the dominant instability of these black holes. This
instability has important consequences for the phase diagram of black holes in
higher dimensions.
| [
{
"created": "Tue, 18 Jun 2013 20:00:02 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Jun 2013 20:17:18 GMT",
"version": "v2"
}
] | 2013-09-04 | [
[
"Hartnett",
"Gavin S.",
""
],
[
"Santos",
"Jorge E.",
""
]
] | We calculate the scalar-gravitational quasi-normal modes of equal angular momenta Myers-Perry black holes in odd dimensions. We find a new bar-mode (non-axisymmetric) classical instability for $D \ge 7$. These black holes were previously found to be unstable to axisymmetric perturbations for spins very near extremality. The bar-mode instability we find sets in at much slower spins, and is therefore the dominant instability of these black holes. This instability has important consequences for the phase diagram of black holes in higher dimensions. |
1703.01409 | Vahid Kamali | Vahid Kamali, Spyros Basilakos, Ahmad Mehrabi, Meysam Motaharfar,
Erfan Massaeli | Tachyon warm inflation with the effects of Loop Quantum Cosmology in the
light of Planck 2015 | 11 pages, 4 figures, The paper has been accepted by IJMPD | null | 10.1142/S0218271818500566 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the observational signatures of quantum cosmology in the
Cosmic Microwave Background data provided by Planck collaboration. We apply the
warm inflationary paradigm with a tachyon scalar field to the loop quantum
cosmology. In this context, we first provide the basic cosmological functions
in terms of the tachyon field. We then obtain the slow-roll parameters and the
power spectrum of scalar and tensor fluctuations respectively. Finally, we
study the performance of various warm inflationary scenarios against the latest
Planck data and we find a family of models which are in agreement with the
observations.
| [
{
"created": "Sat, 4 Mar 2017 07:45:25 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Jan 2018 11:57:11 GMT",
"version": "v2"
}
] | 2018-04-25 | [
[
"Kamali",
"Vahid",
""
],
[
"Basilakos",
"Spyros",
""
],
[
"Mehrabi",
"Ahmad",
""
],
[
"Motaharfar",
"Meysam",
""
],
[
"Massaeli",
"Erfan",
""
]
] | We investigate the observational signatures of quantum cosmology in the Cosmic Microwave Background data provided by Planck collaboration. We apply the warm inflationary paradigm with a tachyon scalar field to the loop quantum cosmology. In this context, we first provide the basic cosmological functions in terms of the tachyon field. We then obtain the slow-roll parameters and the power spectrum of scalar and tensor fluctuations respectively. Finally, we study the performance of various warm inflationary scenarios against the latest Planck data and we find a family of models which are in agreement with the observations. |
1210.3860 | Bahram Mashhoon | C. Chicone and B. Mashhoon | Linearized Gravitational Waves in Nonlocal General Relativity | 30 pages, 1 figure; v2: slightly expanded and improved version | Phys. Rev. D 87, 064015 (2013) | 10.1103/PhysRevD.87.064015 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate gravitational radiation in the linear approximation within the
framework of the recent nonlocal generalization of Einstein's theory of
gravitation. In this theory, nonlocality can simulate dark matter; in fact, in
the Newtonian regime, we recover the phenomenological Tohline-Kuhn approach to
modified gravity. To account for the observational data regarding the rotation
curves of spiral galaxies, nonlocality is associated with a characteristic
length scale of order \lambda_0 = 10 kpc. It follows that in nonlocal gravity,
the treatment of extremely low-frequency (~ 10^{-12} Hz) gravitational waves
with wavelengths of order \lambda_0 would be quite different than in general
relativity. However, for radiation of frequency > 10^{-8} Hz, which is the
frequency range that is the focus of current observational searches, the
corresponding wavelengths are very small compared to \lambda_0. We find that in
this frequency regime the nonlocal deviations from general relativity
essentially average out and can be safely neglected in practice.
| [
{
"created": "Mon, 15 Oct 2012 00:04:53 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Mar 2013 23:38:01 GMT",
"version": "v2"
}
] | 2015-06-11 | [
[
"Chicone",
"C.",
""
],
[
"Mashhoon",
"B.",
""
]
] | We investigate gravitational radiation in the linear approximation within the framework of the recent nonlocal generalization of Einstein's theory of gravitation. In this theory, nonlocality can simulate dark matter; in fact, in the Newtonian regime, we recover the phenomenological Tohline-Kuhn approach to modified gravity. To account for the observational data regarding the rotation curves of spiral galaxies, nonlocality is associated with a characteristic length scale of order \lambda_0 = 10 kpc. It follows that in nonlocal gravity, the treatment of extremely low-frequency (~ 10^{-12} Hz) gravitational waves with wavelengths of order \lambda_0 would be quite different than in general relativity. However, for radiation of frequency > 10^{-8} Hz, which is the frequency range that is the focus of current observational searches, the corresponding wavelengths are very small compared to \lambda_0. We find that in this frequency regime the nonlocal deviations from general relativity essentially average out and can be safely neglected in practice. |
2311.08229 | Luca D'Onofrio | Luca D'Onofrio (1), Rosario De Rosa (15 and 2), Cristiano Palomba (1),
Paola Leaci (1 and 3), Ornella J. Piccinni (4), Valeria Sequino (15 and 2),
Luciano Errico (15 and 2), Lucia Trozzo (2), Jim Palfreyman (5), James W.
McKee (6 and 7), Bradley W. Meyers (8), Ingrid Stairs (9), Lucas Guillemot
(10 and 11), Ismael Cognard (10 and 11), Gilles Theureau (10, 11, and 12),
Michael J. Keith (13), Andrew Lyne (13), Chris Flynn (14), Ben Stappers (13)
((1) INFN, Sezione di Roma, (2) Universit\`a di Napoli "Federico II", (3)
Universit\`a di Roma "Sapienza", (4) Institut de Fisica d'Altes Energies
(IFAE), The Barcelona Institute of Science and Technology, Campus UAB (5)
University of Tasmania, (6) E.A. Milne Centre for Astrophysics, University of
Hull, Cottingham Road, Kingston-upon-Hull, (7) Centre of Excellence for Data
Science, Artificial Intelligence and Modelling (DAIM), University of Hull,
(8) International Centre for Radio Astronomy Research (ICRAR), Curtin
University, (9) Dept. of Physics and Astronomy, University of British
Columbia, (10) Laboratoire de Physique et Chimie de l'Environnement et de
l'Espace, Universit\'e d'Orl\'eans/CNRS, (11) Observatoire Radioastronomique
de Nancay, Observatoire de Paris, Universit\'e PSL, Universit\'e d'Orl\'eans,
CNRS, Nancay, France, (12) LUTH, Observatoire de Paris, PSL Research
University, Meudon, France, (13) Jodrell Bank Centre for Astrophysics,
Department of Physics and Astronomy, The University of Manchester, UK, (14)
OzGrav-Swinburne University of Technology, Australia, (15) INFN, Sezione di
Napoli) | Search for gravitational wave signals from known pulsars in LIGO-Virgo
O3 data using the 5n-vector ensemble method | null | Phys. Rev. D 108, 122002 , Published 4 December 2023 | 10.1103/PhysRevD.108.122002 | null | gr-qc physics.data-an | http://creativecommons.org/licenses/by/4.0/ | The 5n-vector ensemble method is a multiple test for the targeted search of
continuous gravitational waves from an ensemble of known pulsars. This method
can improve the detection probability combining the results from individually
undetectable pulsars if few signals are near the detection threshold. In this
paper, we apply the 5n-vector ensemble method to the O3 data set from the LIGO
and Virgo detectors considering an ensemble of 201 known pulsars. We find no
evidence for a signal from the ensemble and set a 95% credible upper limit on
the mean ellipticity assuming a common exponential distribution for the
pulsars' ellipticities. Using two independent hierarchical Bayesian procedures,
we find upper limits of $1.2 \times 10^{-9}$ and $2.5 \times 10^{-9}$ on the
mean ellipticity for the 201 analyzed pulsars.
| [
{
"created": "Tue, 14 Nov 2023 15:09:23 GMT",
"version": "v1"
}
] | 2024-01-04 | [
[
"D'Onofrio",
"Luca",
"",
"15 and 2"
],
[
"De Rosa",
"Rosario",
"",
"15 and 2"
],
[
"Palomba",
"Cristiano",
"",
"1 and 3"
],
[
"Leaci",
"Paola",
"",
"1 and 3"
],
[
"Piccinni",
"Ornella J.",
"",
"15 and 2"
],
[
"... | The 5n-vector ensemble method is a multiple test for the targeted search of continuous gravitational waves from an ensemble of known pulsars. This method can improve the detection probability combining the results from individually undetectable pulsars if few signals are near the detection threshold. In this paper, we apply the 5n-vector ensemble method to the O3 data set from the LIGO and Virgo detectors considering an ensemble of 201 known pulsars. We find no evidence for a signal from the ensemble and set a 95% credible upper limit on the mean ellipticity assuming a common exponential distribution for the pulsars' ellipticities. Using two independent hierarchical Bayesian procedures, we find upper limits of $1.2 \times 10^{-9}$ and $2.5 \times 10^{-9}$ on the mean ellipticity for the 201 analyzed pulsars. |
2310.09829 | Anas El Balali | Anas El Balali | Quantum Schwarzschild Black Hole Optical Aspects | 27 pages, 7 figures, Accepted for publication in Gravitation and
Cosmology | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | In this paper, we investigate the optical behaviors of a quantum
Schwarzschild black hole with a spacetime solution including a parameter
$\lambda$ that encodes its discretization. Concretly, we derive the effective
potential of such solution. In particular, we study the circular orbits around
the quantum black hole. Indeed, we find that the effective potential is
characterized by a minimum and a maximum yielding a double photon spheres
denoted by $r_{p_1}, r_{p_2}$ respectively. Then, we analyse the double shadow
behaviors as a function of the parameter $\lambda$ where we show that it
controles the shadow circular size. An inspection of the Innermost Stable
Circular Orbits (ISCO) shows that the radius $r_{ISCO}$ increases as a function
of $\lambda$. Besides, we find that such radius is equal to $6M$ for an angular
momentum $L=2\sqrt{3}$ independently of $\lambda$. A numerical analysis shows
that the photon sphere of radius $r_{p_1}$ generates a shadow with a radius
larger than $r_{ISCO}$. Thus, a truncation of the effective potential is
imposed to exclude such behavior. Finally, the $\lambda$-effect is inspect on
the deflection angle of such a black hole showing that it increases when higher
values of the parameter $\lambda$ are considered. However, such an increase is
limited by an upper bound given by $\frac{6 M}{b}$.
| [
{
"created": "Sun, 15 Oct 2023 13:25:08 GMT",
"version": "v1"
}
] | 2023-10-17 | [
[
"Balali",
"Anas El",
""
]
] | In this paper, we investigate the optical behaviors of a quantum Schwarzschild black hole with a spacetime solution including a parameter $\lambda$ that encodes its discretization. Concretly, we derive the effective potential of such solution. In particular, we study the circular orbits around the quantum black hole. Indeed, we find that the effective potential is characterized by a minimum and a maximum yielding a double photon spheres denoted by $r_{p_1}, r_{p_2}$ respectively. Then, we analyse the double shadow behaviors as a function of the parameter $\lambda$ where we show that it controles the shadow circular size. An inspection of the Innermost Stable Circular Orbits (ISCO) shows that the radius $r_{ISCO}$ increases as a function of $\lambda$. Besides, we find that such radius is equal to $6M$ for an angular momentum $L=2\sqrt{3}$ independently of $\lambda$. A numerical analysis shows that the photon sphere of radius $r_{p_1}$ generates a shadow with a radius larger than $r_{ISCO}$. Thus, a truncation of the effective potential is imposed to exclude such behavior. Finally, the $\lambda$-effect is inspect on the deflection angle of such a black hole showing that it increases when higher values of the parameter $\lambda$ are considered. However, such an increase is limited by an upper bound given by $\frac{6 M}{b}$. |
gr-qc/0302005 | Mahmut Hortacsu | M. Hortacsu, H. T. Ozcelik, B. Yapiskan | Properties of Solutions in 2+1 Dimensions | 16 pages, 1 figures, PlainTeX, Dedicated to Prof. Yavuz Nutku on his
60th birthday. References added | Gen.Rel.Grav. 35 (2003) 1209-1221 | 10.1023/A:1024445724029 | null | gr-qc | null | We solve the Einstein equations for the 2+1 dimensions with and without
scalar fields. We calculate the entropy, Hawking temperature and the emission
probabilities for these cases. We also compute the Newman-Penrose coefficients
for different solutions and compare them.
| [
{
"created": "Mon, 3 Feb 2003 10:56:59 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Feb 2003 12:38:26 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Hortacsu",
"M.",
""
],
[
"Ozcelik",
"H. T.",
""
],
[
"Yapiskan",
"B.",
""
]
] | We solve the Einstein equations for the 2+1 dimensions with and without scalar fields. We calculate the entropy, Hawking temperature and the emission probabilities for these cases. We also compute the Newman-Penrose coefficients for different solutions and compare them. |
1512.06252 | Marko Vojinovic | Aleksandar Mikovic, Marko Vojinovic | Categorical generalization of spinfoam models | Proceedings of the QQQ conference, Tallinn, Estonia, 2012. 10 pages | J. Phys.: Conf. Ser. 532, 012020 (2014) | 10.1088/1742-6596/532/1/012020 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a brief review of the problem of quantum gravity. After the
discussion of the nonrenormalizability of general relativity, we briefly
mention the main research directions which aim to resolve this problem. Our
attention then focuses on the approach of Loop Quantum Gravity, specifically
spinfoam models. These models have some issues concerning the semiclassical
limit and coupling of matter fields. The recent developments in category theory
provide us with the necessary formalism to introduce a new action for general
relativity and perform covariant quantization so that the issues of spinfoam
models are successfully resolved.
| [
{
"created": "Sat, 19 Dec 2015 14:06:24 GMT",
"version": "v1"
}
] | 2015-12-22 | [
[
"Mikovic",
"Aleksandar",
""
],
[
"Vojinovic",
"Marko",
""
]
] | We give a brief review of the problem of quantum gravity. After the discussion of the nonrenormalizability of general relativity, we briefly mention the main research directions which aim to resolve this problem. Our attention then focuses on the approach of Loop Quantum Gravity, specifically spinfoam models. These models have some issues concerning the semiclassical limit and coupling of matter fields. The recent developments in category theory provide us with the necessary formalism to introduce a new action for general relativity and perform covariant quantization so that the issues of spinfoam models are successfully resolved. |
1512.05729 | Matt Visser | Matt Visser (Victoria University of Wellington) | Buchert coarse-graining and the classical energy conditions | 6 Pages; contribution to the MG14 conference - Rome 2015; V2:
Significant changes. One key inequality now proved, (not on the basis of
usual averaging arguments), but on the basis of the Cauchy-Schwarz
inequality. The trace of the effective stress-energy can be non-zero and of
either sign. The effective stress-energy satisfies many of the classical
energy conditions | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | So-called "Buchert averaging" is actually a coarse-graining procedure, where
fine detail is "smeared out" due to limited spatio-temporal resolution. For
technical reasons, (to be explained herein), "averaging" is not really an
appropriate term, and I shall consistently describe the process as a
"coarse-graining". Because Einstein gravity is nonlinear the coarse-grained
Einstein tensor is typically not equal to the Einstein tensor of the
coarse-grained spacetime geometry. The discrepancy can be viewed as an
"effective" stress-energy. To keep otherwise messy technical issues firmly
under control, I shall work with conformal-FLRW (CFLRW) cosmologies. These
CFLRW-based models are particularly tractable, and are also particularly
attractive observationally: the CMB is not distorted. In this CFLRW context one
can prove some rigorous theorems regarding the interplay between Buchert
coarse-graining, tracelessness of the effective stress-energy, and the
classical energy conditions.
| [
{
"created": "Thu, 17 Dec 2015 19:20:37 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Jan 2016 19:01:16 GMT",
"version": "v2"
}
] | 2016-01-08 | [
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | So-called "Buchert averaging" is actually a coarse-graining procedure, where fine detail is "smeared out" due to limited spatio-temporal resolution. For technical reasons, (to be explained herein), "averaging" is not really an appropriate term, and I shall consistently describe the process as a "coarse-graining". Because Einstein gravity is nonlinear the coarse-grained Einstein tensor is typically not equal to the Einstein tensor of the coarse-grained spacetime geometry. The discrepancy can be viewed as an "effective" stress-energy. To keep otherwise messy technical issues firmly under control, I shall work with conformal-FLRW (CFLRW) cosmologies. These CFLRW-based models are particularly tractable, and are also particularly attractive observationally: the CMB is not distorted. In this CFLRW context one can prove some rigorous theorems regarding the interplay between Buchert coarse-graining, tracelessness of the effective stress-energy, and the classical energy conditions. |
1111.4228 | Mario Novello | M. Novello and E. Bittencourt | The gravitational mechanism to generate mass II | This is the further development of previous article (The
gravitational mechanism to generate mass, arXiv:1008.2371) which appeared in
Classical and Quantum Gravity 28 (2011) 035003 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With the eminent confirmation or disproof of the existence of Higgs boson by
experiments on the LHC it is time to analyze in a non-dogmatic way the
suggestions to understand the origin of the mass. Here we analyze the recent
proposal according to which gravity is what is really responsible for the
generation of mass of all bodies. The great novelty of such mechanism is that
the gravitational field acts merely as a catalyst, once the final expression of
the mass does not depend either on the intensity or on the particular
characteristics of the gravitational field.
| [
{
"created": "Wed, 16 Nov 2011 13:37:40 GMT",
"version": "v1"
}
] | 2011-11-21 | [
[
"Novello",
"M.",
""
],
[
"Bittencourt",
"E.",
""
]
] | With the eminent confirmation or disproof of the existence of Higgs boson by experiments on the LHC it is time to analyze in a non-dogmatic way the suggestions to understand the origin of the mass. Here we analyze the recent proposal according to which gravity is what is really responsible for the generation of mass of all bodies. The great novelty of such mechanism is that the gravitational field acts merely as a catalyst, once the final expression of the mass does not depend either on the intensity or on the particular characteristics of the gravitational field. |
2303.00139 | Vladimir Ivashchuk | V. D. Ivashchuk, K. K. Ernazarov and A. A. Kobtsev | Exact $(1 + 3 + 6)$-dimensional cosmological-type solutions in
gravitational model with Yang-Mills field, Gauss-Bonnet term and
$\Lambda$-term | 17 pages, 3 figures, LaTex, Revised version: 3 paragraphs are added
into Introduction, new references are included and few references
(self-citations) are omitted | Symmetry, 15 (4), 783 (2023) | 10.3390/sym15040783 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider $10$-dimensional gravitational model with $SO(6)$ Yang-Mills
field, Gauss-Bonnet term and $\Lambda$-term. We study so-called cosmological
type solutions defined on product manifold $M = R \times R^3 \times K$, where
$K$ is $6d$ Calabi-Yau manifold. By putting the gauge field 1-form to be
coinciding with 1-form spin connection on $K$, we obtain exact cosmological
solutions with exponential dependence of scale factors (upon $t$-variable),
governed by two non-coinciding Hubble-like parameters: $H >0$, $h$, obeying $ H
+ 2 h \neq 0$. We also present static analogs of these cosmological solutions
(for $H \neq 0$, $h \neq H$ and $ H + 2 h \neq 0$). The islands of stability
for both classes of solutions are outlined.
| [
{
"created": "Wed, 1 Mar 2023 00:12:49 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Mar 2023 20:56:05 GMT",
"version": "v2"
}
] | 2023-03-28 | [
[
"Ivashchuk",
"V. D.",
""
],
[
"Ernazarov",
"K. K.",
""
],
[
"Kobtsev",
"A. A.",
""
]
] | We consider $10$-dimensional gravitational model with $SO(6)$ Yang-Mills field, Gauss-Bonnet term and $\Lambda$-term. We study so-called cosmological type solutions defined on product manifold $M = R \times R^3 \times K$, where $K$ is $6d$ Calabi-Yau manifold. By putting the gauge field 1-form to be coinciding with 1-form spin connection on $K$, we obtain exact cosmological solutions with exponential dependence of scale factors (upon $t$-variable), governed by two non-coinciding Hubble-like parameters: $H >0$, $h$, obeying $ H + 2 h \neq 0$. We also present static analogs of these cosmological solutions (for $H \neq 0$, $h \neq H$ and $ H + 2 h \neq 0$). The islands of stability for both classes of solutions are outlined. |
1702.00095 | Alexander Tolish | David Garfinkle, Stefan Hollands, Akihiro Ishibashi, Alexander Tolish,
and Robert M. Wald | The Memory Effect for Particle Scattering in Even Spacetime Dimensions | 14 pages. Typos corrected, reference added, eq. (11) corrected and
clarified (results unchanged), arguments in secs. IV,V revised (results
unchanged) | Class. Quantum Grav. 34, 145015 (2017) | 10.1088/1361-6382/aa777b | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explicitly calculate the gravitational wave memory effect for classical
point particle sources in linearized gravity off of an even dimensional
Minkowski background. We show that there is no memory effect in $d>4$
dimensions, in agreement with the general analysis of Hollands, Ishibashi, and
Wald (2016).
| [
{
"created": "Wed, 1 Feb 2017 00:44:17 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Jun 2017 19:17:15 GMT",
"version": "v2"
}
] | 2017-07-04 | [
[
"Garfinkle",
"David",
""
],
[
"Hollands",
"Stefan",
""
],
[
"Ishibashi",
"Akihiro",
""
],
[
"Tolish",
"Alexander",
""
],
[
"Wald",
"Robert M.",
""
]
] | We explicitly calculate the gravitational wave memory effect for classical point particle sources in linearized gravity off of an even dimensional Minkowski background. We show that there is no memory effect in $d>4$ dimensions, in agreement with the general analysis of Hollands, Ishibashi, and Wald (2016). |
2006.13545 | Seiji Kawamura | Seiji Kawamura, Masaki Ando, Naoki Seto, Shuichi Sato, Mitsuru Musha,
Isao Kawano, Jun'ichi Yokoyama, Takahiro Tanaka, Kunihito Ioka, Tomotada
Akutsu, Takeshi Takashima, Kazuhiro Agatsuma, Akito Araya, Naoki Aritomi,
Hideki Asada, Takeshi Chiba, Satoshi Eguchi, Motohiro Enoki, Masa-Katsu
Fujimoto, Ryuichi Fujita, Toshifumi Futamase, Tomohiro Harada, Kazuhiro
Hayama, Yoshiaki Himemoto, Takashi Hiramatsu, Feng-Lei Hong, Mizuhiko
Hosokawa, Kiyotomo Ichiki, Satoshi Ikari, Hideki Ishihara, Tomohiro Ishikawa,
Yousuke Itoh, Takahiro Ito, Shoki Iwaguchi, Kiwamu Izumi, Nobuyuki Kanda,
Shinya Kanemura, Fumiko Kawazoe, Shiho Kobayashi, Kazunori Kohri, Yasufumi
Kojima, Keiko Kokeyama, Kei Kotake, Sachiko Kuroyanagi, Kei-ichi Maeda,
Shuhei Matsushita, Yuta Michimura, Taigen Morimoto, Shinji Mukohyama, Koji
Nagano, Shigeo Nagano, Takeo Naito, Kouji Nakamura, Takashi Nakamura,
Hiroyuki Nakano, Kenichi Nakao, Shinichi Nakasuka, Yoshinori Nakayama,
Kazuhiro Nakazawa, Atsushi Nishizawa, Masashi Ohkawa, Kenichi Oohara,
Norichika Sago, Motoyuki Saijo, Masaaki Sakagami, Shin-ichiro Sakai, Takashi
Sato, Masaru Shibata, Hisaaki Shinkai, Ayaka Shoda, Kentaro Somiya, Hajime
Sotani, Ryutaro Takahashi, Hirotaka Takahashi, Takamori Akiteru, Keisuke
Taniguchi, Atsushi Taruya, Kimio Tsubono, Shinji Tsujikawa, Akitoshi Ueda,
Ken-ichi Ueda, Izumi Watanabe, Kent Yagi, Rika Yamada, Shuichiro Yokoyama,
Chul-Moon Yoo, Zong-Hong Zhu | Current status of space gravitational wave antenna DECIGO and B-DECIGO | 10 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Deci-hertz Interferometer Gravitational Wave Observatory (DECIGO) is the
future Japanese space mission with a frequency band of 0.1 Hz to 10 Hz. DECIGO
aims at the detection of primordial gravitational waves, which could be
produced during the inflationary period right after the birth of the universe.
There are many other scientific objectives of DECIGO, including the direct
measurement of the acceleration of the expansion of the universe, and reliable
and accurate predictions of the timing and locations of neutron star/black hole
binary coalescences. DECIGO consists of four clusters of observatories placed
in the heliocentric orbit. Each cluster consists of three spacecraft, which
form three Fabry-Perot Michelson interferometers with an arm length of 1,000
km. Three clusters of DECIGO will be placed far from each other, and the fourth
cluster will be placed in the same position as one of the three clusters to
obtain the correlation signals for the detection of the primordial
gravitational waves. We plan to launch B-DECIGO, which is a scientific
pathfinder of DECIGO, before DECIGO in the 2030s to demonstrate the
technologies required for DECIGO, as well as to obtain fruitful scientific
results to further expand the multi-messenger astronomy.
| [
{
"created": "Wed, 24 Jun 2020 08:08:18 GMT",
"version": "v1"
}
] | 2020-06-25 | [
[
"Kawamura",
"Seiji",
""
],
[
"Ando",
"Masaki",
""
],
[
"Seto",
"Naoki",
""
],
[
"Sato",
"Shuichi",
""
],
[
"Musha",
"Mitsuru",
""
],
[
"Kawano",
"Isao",
""
],
[
"Yokoyama",
"Jun'ichi",
""
],
[
"Tana... | Deci-hertz Interferometer Gravitational Wave Observatory (DECIGO) is the future Japanese space mission with a frequency band of 0.1 Hz to 10 Hz. DECIGO aims at the detection of primordial gravitational waves, which could be produced during the inflationary period right after the birth of the universe. There are many other scientific objectives of DECIGO, including the direct measurement of the acceleration of the expansion of the universe, and reliable and accurate predictions of the timing and locations of neutron star/black hole binary coalescences. DECIGO consists of four clusters of observatories placed in the heliocentric orbit. Each cluster consists of three spacecraft, which form three Fabry-Perot Michelson interferometers with an arm length of 1,000 km. Three clusters of DECIGO will be placed far from each other, and the fourth cluster will be placed in the same position as one of the three clusters to obtain the correlation signals for the detection of the primordial gravitational waves. We plan to launch B-DECIGO, which is a scientific pathfinder of DECIGO, before DECIGO in the 2030s to demonstrate the technologies required for DECIGO, as well as to obtain fruitful scientific results to further expand the multi-messenger astronomy. |
gr-qc/0411110 | Carles Bona | C. Bona, T. Ledvinka, C. Palenzuela-Luque and M. Zacek | Constraint-preserving boundary conditions in the Z4 Numerical Relativity
formalism | Enhanced version, including a new Appendix on maximally dissipative
boundary conditions (12 pages, 5 figures) | Class.Quant.Grav. 22 (2005) 2615-2634 | 10.1088/0264-9381/22/13/007 | null | gr-qc | null | The constraint-preserving approach, which aim is to provide consistent
boundary conditions for Numerical Relativity simulations, is discussed in
parallel with other recent developments. The case of the Z4 system is
considered, and constraint-preserving boundary conditions of the Sommerfeld
type are provided. A necessary condition for the stability of the proposed
boundary conditions is obtained, which amounts to the requirement of a
symmetric ordering of space derivatives. This requirement is numerically seen
to be also sufficient in the absence of corners and edges. Maximally
dissipative boundary conditions are also implemented. In this case, a less
restrictive stability condition is obtained, which is shown numerically to be
also sufficient even in the presence of corners and edges.
| [
{
"created": "Tue, 23 Nov 2004 08:36:18 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Dec 2004 19:40:37 GMT",
"version": "v2"
},
{
"created": "Tue, 14 Jun 2005 08:53:18 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Bona",
"C.",
""
],
[
"Ledvinka",
"T.",
""
],
[
"Palenzuela-Luque",
"C.",
""
],
[
"Zacek",
"M.",
""
]
] | The constraint-preserving approach, which aim is to provide consistent boundary conditions for Numerical Relativity simulations, is discussed in parallel with other recent developments. The case of the Z4 system is considered, and constraint-preserving boundary conditions of the Sommerfeld type are provided. A necessary condition for the stability of the proposed boundary conditions is obtained, which amounts to the requirement of a symmetric ordering of space derivatives. This requirement is numerically seen to be also sufficient in the absence of corners and edges. Maximally dissipative boundary conditions are also implemented. In this case, a less restrictive stability condition is obtained, which is shown numerically to be also sufficient even in the presence of corners and edges. |
1107.4115 | M. C. Bertin | M. C. Bertin, B. M. Pimentel, C. E. Valc\'arcel, G. E. R. Zambrano | Hamilton-Jacobi formalism for Linearized Gravity | To be published in Classical and Quantum Gravity | Class.Quant.Grav.28:175015,2011 | 10.1088/0264-9381/28/17/175015 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study the theory of linearized gravity via the
Hamilton-Jacobi formalism. We make a brief review of this theory and its
Lagrangian description, as well as a review of the Hamilton-Jacobi approach for
singular systems. Then we apply this formalism to analyze the constraint
structure of the linearized gravity in instant and front-form dynamics.
| [
{
"created": "Wed, 20 Jul 2011 20:31:00 GMT",
"version": "v1"
}
] | 2011-08-22 | [
[
"Bertin",
"M. C.",
""
],
[
"Pimentel",
"B. M.",
""
],
[
"Valcárcel",
"C. E.",
""
],
[
"Zambrano",
"G. E. R.",
""
]
] | In this work we study the theory of linearized gravity via the Hamilton-Jacobi formalism. We make a brief review of this theory and its Lagrangian description, as well as a review of the Hamilton-Jacobi approach for singular systems. Then we apply this formalism to analyze the constraint structure of the linearized gravity in instant and front-form dynamics. |
gr-qc/0305006 | Tsutomu Kobayashi | Tsutomu Kobayashi, Hideaki Kudoh, Takahiro Tanaka | Primordial gravitational waves in inflationary braneworld | 16 pages, 4 figures, typos corrected | Phys.Rev. D68 (2003) 044025 | 10.1103/PhysRevD.68.044025 | KUNS-1842, YITP-03-23 | gr-qc hep-th | null | We study primordial gravitational waves from inflation in Randall-Sundrum
braneworld model. The effect of small change of the Hubble parameter during
inflation is investigated using a toy model given by connecting two de Sitter
branes. We analyze the power spectrum of final zero-mode gravitons, which is
generated from the vacuum fluctuations of both initial Kaluza-Klein modes and
zero-mode. The amplitude of fluctuations is confirmed to agree with the
four-dimensional one at low energies, whereas it is enhanced due to the
normalization factor of zero-mode at high energies. We show that the
five-dimensional spectrum can be well approximated by applying a simple mapping
to the four-dimensional fluctuation amplitude.
| [
{
"created": "Fri, 2 May 2003 10:43:25 GMT",
"version": "v1"
},
{
"created": "Sun, 11 May 2003 12:08:20 GMT",
"version": "v2"
},
{
"created": "Fri, 21 Nov 2003 12:17:37 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Kobayashi",
"Tsutomu",
""
],
[
"Kudoh",
"Hideaki",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | We study primordial gravitational waves from inflation in Randall-Sundrum braneworld model. The effect of small change of the Hubble parameter during inflation is investigated using a toy model given by connecting two de Sitter branes. We analyze the power spectrum of final zero-mode gravitons, which is generated from the vacuum fluctuations of both initial Kaluza-Klein modes and zero-mode. The amplitude of fluctuations is confirmed to agree with the four-dimensional one at low energies, whereas it is enhanced due to the normalization factor of zero-mode at high energies. We show that the five-dimensional spectrum can be well approximated by applying a simple mapping to the four-dimensional fluctuation amplitude. |
2301.10465 | Ryotaku Suzuki | Kenshin Isomura, Ryotaku Suzuki and Shinya Tomizawa | Particle motions around regular black holes | 19 pages, 8 figures; v2: analysis of photon orbits improved, refs
added, 21 pages; v3: published version, fixed minor typos, fixed figures, 20
pages | null | 10.1103/PhysRevD.107.084003 | TTI-MATHPHYS-19 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the bound orbits of massive/massless, neutral particles and
photons moving around regular black holes of Fan and Wang. For massive
particles, we show the existence of stable/unstable circular orbits and the
charge dependence of the radius of the innermost stable circular orbit.
Remarkably, we find an unstable circular orbit of photons inside the event
horizon. For massless particles and photons, we show that both stable and
unstable circular orbits can exist in a regular and horizonless spacetime with
a slight overcharge. Then, we also discuss the periapsis shift of massive
neutral particles orbiting around the black hole, and show that the charge
gives a negative correction to the shift for black holes with small
nonlinearity of electrodynamics.
| [
{
"created": "Wed, 25 Jan 2023 08:51:18 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Feb 2023 12:32:47 GMT",
"version": "v2"
},
{
"created": "Fri, 24 Mar 2023 06:06:37 GMT",
"version": "v3"
}
] | 2023-04-19 | [
[
"Isomura",
"Kenshin",
""
],
[
"Suzuki",
"Ryotaku",
""
],
[
"Tomizawa",
"Shinya",
""
]
] | We investigate the bound orbits of massive/massless, neutral particles and photons moving around regular black holes of Fan and Wang. For massive particles, we show the existence of stable/unstable circular orbits and the charge dependence of the radius of the innermost stable circular orbit. Remarkably, we find an unstable circular orbit of photons inside the event horizon. For massless particles and photons, we show that both stable and unstable circular orbits can exist in a regular and horizonless spacetime with a slight overcharge. Then, we also discuss the periapsis shift of massive neutral particles orbiting around the black hole, and show that the charge gives a negative correction to the shift for black holes with small nonlinearity of electrodynamics. |
gr-qc/0312008 | Jose Geraldo Pereira | R. Aldrovandi, J. G. Pereira, K. H. Vu | Selected Topics in Teleparallel Gravity | RevTeX4, 7 pages, 2 eps figures. Talk presented at the "24th National
Meeting of the Brazilian Physical Society", section Particles and Fields,
Caxambu MG, Brazil, from September/30 to October/04/2003 | Braz.J.Phys.34:1374-1380,2004 | null | null | gr-qc hep-th | null | Teleparallel gravity can be seen as a gauge theory for the translation group.
As such, its fundamental field is neither the tetrad nor the metric, but a
gauge potential assuming values in the Lie algebra of the translation group.
This gauge character makes of teleparallel gravity, despite its equivalence to
general relativity, a rather peculiar theory. A first important point is that
it does not rely on the universality of free fall, and consequently does not
require the equivalence principle to describe the gravitational interaction.
Another peculiarity is its similarity with Maxwell's theory, which allows an
Abelian nonintegrable phase factor approach, and consequently a global
formulation for gravitation. Application of these concepts to the motion of
spinless particles, as well as to the COW and gravitational Aharonov-Bohm
effects are presented and discussed.
| [
{
"created": "Mon, 1 Dec 2003 16:12:01 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Aldrovandi",
"R.",
""
],
[
"Pereira",
"J. G.",
""
],
[
"Vu",
"K. H.",
""
]
] | Teleparallel gravity can be seen as a gauge theory for the translation group. As such, its fundamental field is neither the tetrad nor the metric, but a gauge potential assuming values in the Lie algebra of the translation group. This gauge character makes of teleparallel gravity, despite its equivalence to general relativity, a rather peculiar theory. A first important point is that it does not rely on the universality of free fall, and consequently does not require the equivalence principle to describe the gravitational interaction. Another peculiarity is its similarity with Maxwell's theory, which allows an Abelian nonintegrable phase factor approach, and consequently a global formulation for gravitation. Application of these concepts to the motion of spinless particles, as well as to the COW and gravitational Aharonov-Bohm effects are presented and discussed. |
gr-qc/0007081 | Toshiharu Kawai | Toshiharu Kawai | Energy-momentum and angular momentum densities in gauge theories of
gravity | 18 pages | Phys.Rev. D62 (2000) 104014 | 10.1103/PhysRevD.62.104014 | null | gr-qc | null | In the $\bar{\mbox{\rm Poincar\'{e}}}$ gauge theory of gravity, which has
been formulated on the basis of a principal fiber bundle over the space-time
manifold having the covering group of the proper orthochronous Poincar\'{e}
group as the structure group, we examine the tensorial properties of the
dynamical energy-momentum density ${}^{G}{\mathbf T}_{k}{}^{\mu}$ and the ` `
spin" angular momentum density ${}^{G}{\mathbf S}_{kl}{}^{\mu}$ of the
gravitational field. They are both space-time vector densities, and transform
as tensors under {\em global} $SL(2,C)$- transformations. Under {\em local}
internal translation, ${}^{G}{\mathbf T}_{k}{}^{\mu}$ is invariant, while
${}^{G}{\mathbf S}_{kl}{}^{\mu}$ transforms inhomogeneously. The dynamical
energy-momentum density ${}^{M}{\mathbf T}_{k}{}^{\mu}$ and the ` ` spin"
angular momentum density ${}^{M}{\mathbf S}_{kl}{}^{\mu}$ of the matter field
are also examined, and they are known to be space-time vector densities and to
obey tensorial transformation rules under internal $\bar{\mbox{\rm
Poincar\'{e}}}$ gauge transformations. The corresponding discussions in
extended new general relativity which is obtained as a teleparallel limit of
$\bar{\mbox{\rm Poincar\'{e}}}$ gauge theory are also given, and
energy-momentum and ` ` spin" angular momentum densities are known to be well
behaved. Namely, they are all space-time vector densities, etc. In both
theories, integrations of these densities on a space-like surface give the
total energy-momentum and {\em total} (={\em spin}+{\em orbital}) angular
momentum for asymptotically flat space-time. The tensorial properties of
canonical energy-momentum and ` ` extended orbital angular momentum" densities
are also examined.
| [
{
"created": "Mon, 31 Jul 2000 04:28:07 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Sep 2000 02:40:57 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Kawai",
"Toshiharu",
""
]
] | In the $\bar{\mbox{\rm Poincar\'{e}}}$ gauge theory of gravity, which has been formulated on the basis of a principal fiber bundle over the space-time manifold having the covering group of the proper orthochronous Poincar\'{e} group as the structure group, we examine the tensorial properties of the dynamical energy-momentum density ${}^{G}{\mathbf T}_{k}{}^{\mu}$ and the ` ` spin" angular momentum density ${}^{G}{\mathbf S}_{kl}{}^{\mu}$ of the gravitational field. They are both space-time vector densities, and transform as tensors under {\em global} $SL(2,C)$- transformations. Under {\em local} internal translation, ${}^{G}{\mathbf T}_{k}{}^{\mu}$ is invariant, while ${}^{G}{\mathbf S}_{kl}{}^{\mu}$ transforms inhomogeneously. The dynamical energy-momentum density ${}^{M}{\mathbf T}_{k}{}^{\mu}$ and the ` ` spin" angular momentum density ${}^{M}{\mathbf S}_{kl}{}^{\mu}$ of the matter field are also examined, and they are known to be space-time vector densities and to obey tensorial transformation rules under internal $\bar{\mbox{\rm Poincar\'{e}}}$ gauge transformations. The corresponding discussions in extended new general relativity which is obtained as a teleparallel limit of $\bar{\mbox{\rm Poincar\'{e}}}$ gauge theory are also given, and energy-momentum and ` ` spin" angular momentum densities are known to be well behaved. Namely, they are all space-time vector densities, etc. In both theories, integrations of these densities on a space-like surface give the total energy-momentum and {\em total} (={\em spin}+{\em orbital}) angular momentum for asymptotically flat space-time. The tensorial properties of canonical energy-momentum and ` ` extended orbital angular momentum" densities are also examined. |
0704.2243 | Clifford M. Will | Thomas Mitchell and Clifford M. Will (Washington University, St.
Louis) | Post-Newtonian gravitational radiation and equations of motion via
direct integration of the relaxed Einstein equations. V. Evidence for the
strong equivalence principle to second post-Newtonian order | 14 pages, submitted to Phys. Rev. D; small changes to coincide with
published version | Phys.Rev.D75:124025,2007 | 10.1103/PhysRevD.75.124025 | null | gr-qc | null | Using post-Newtonian equations of motion for fluid bodies valid to the second
post-Newtonian order, we derive the equations of motion for binary systems with
finite-sized, non-spinning but arbitrarily shaped bodies. In particular we
study the contributions of the internal structure of the bodies (such as
self-gravity) that would diverge if the size of the bodies were to shrink to
zero. Using a set of virial relations accurate to the first post-Newtonian
order that reflect the stationarity of each body, and redefining the masses to
include 1PN and 2PN self-gravity terms, we demonstrate the complete
cancellation of a class of potentially divergent, structure-dependent terms
that scale as s^{-1} and s^{-5/2}, where s is the characteristic size of the
bodies. This is further evidence of the Strong Equivalence Principle, and
supports the use of post-Newtonian approximations to derive equations of motion
for strong-field bodies such as neutron stars and black holes. This extends
earlier work done by Kopeikin.
| [
{
"created": "Tue, 17 Apr 2007 21:51:04 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Jul 2007 13:48:45 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Mitchell",
"Thomas",
"",
"Washington University, St.\n Louis"
],
[
"Will",
"Clifford M.",
"",
"Washington University, St.\n Louis"
]
] | Using post-Newtonian equations of motion for fluid bodies valid to the second post-Newtonian order, we derive the equations of motion for binary systems with finite-sized, non-spinning but arbitrarily shaped bodies. In particular we study the contributions of the internal structure of the bodies (such as self-gravity) that would diverge if the size of the bodies were to shrink to zero. Using a set of virial relations accurate to the first post-Newtonian order that reflect the stationarity of each body, and redefining the masses to include 1PN and 2PN self-gravity terms, we demonstrate the complete cancellation of a class of potentially divergent, structure-dependent terms that scale as s^{-1} and s^{-5/2}, where s is the characteristic size of the bodies. This is further evidence of the Strong Equivalence Principle, and supports the use of post-Newtonian approximations to derive equations of motion for strong-field bodies such as neutron stars and black holes. This extends earlier work done by Kopeikin. |
gr-qc/0201041 | Sanjay M. Wagh | Sanjay M. Wagh | Classical formulation of Cosmic Censorship Hypothesis | Revtex4, No figures, Replaced to match submitted version, New
Discussion and reference added. Conclusions unchanged | null | null | null | gr-qc astro-ph hep-th physics.class-ph | null | Spacetimes admitting appropriate spatial homothetic Killing vectors are
called spatially homothetic spacetimes. Such spacetimes conform to the fact
that gravity has no length-scale for matter inhomogeneities. The matter density
for such spacetimes is (spatially) arbitrary and the matter generating the
spacetime admits {\it any} equation of state. Spatially homothetic spacetimes
necessarily possess energy-momentum fluxes. We first discuss spherically
symmetric and axially symmetric examples of such spacetimes that do not form
naked singularities for regular initial data. We then show that the Cosmic
Censorship Hypothesis is {\em equivalent} to the statement that gravity has no
length-scale for matter properties.
| [
{
"created": "Sun, 13 Jan 2002 03:40:05 GMT",
"version": "v1"
},
{
"created": "Sun, 3 Feb 2002 05:48:35 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Wagh",
"Sanjay M.",
""
]
] | Spacetimes admitting appropriate spatial homothetic Killing vectors are called spatially homothetic spacetimes. Such spacetimes conform to the fact that gravity has no length-scale for matter inhomogeneities. The matter density for such spacetimes is (spatially) arbitrary and the matter generating the spacetime admits {\it any} equation of state. Spatially homothetic spacetimes necessarily possess energy-momentum fluxes. We first discuss spherically symmetric and axially symmetric examples of such spacetimes that do not form naked singularities for regular initial data. We then show that the Cosmic Censorship Hypothesis is {\em equivalent} to the statement that gravity has no length-scale for matter properties. |
1805.05023 | Yun Soo Myung | Yun Soo Myung, De-Cheng Zou | Gregory-Laflamme instability of black hole in
Einstein-scalar-Gauss-Bonnet theories | 14 pages, 4 figures, version to appear in Physical Review D | Phys. Rev. D 98, 024030 (2018) | 10.1103/PhysRevD.98.024030 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the stability analysis of Schwarzschild black hole in
Einstein-scalar-Gauss-Bonnet (ESGB) theory because the instability of
Schwarzschild black hole without scalar hair implies the Gauss-Bonnet black
hole with scalar hair. The linearized scalar equation is compared to the
Lichnerowicz-Ricci tensor equation in the Einstein-Weyl gravity. It turns out
that the instability of Schwarzschild black hole in ESGB theory is interpreted
as not the tachyonic instability, but the Gregory-Laflamme instability of black
string. In the small mass regime of $1/\lambda<1.174/r_+$, the Schwarzschild
solution becomes unstable and a new branch of solution with scalar hair
bifurcates from the Schwarzschild one. This is very similar to finding a newly
non-Schwarzschild black hole in Einstein-Weyl gravity.
| [
{
"created": "Mon, 14 May 2018 06:31:39 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Jul 2018 23:57:28 GMT",
"version": "v2"
}
] | 2018-07-25 | [
[
"Myung",
"Yun Soo",
""
],
[
"Zou",
"De-Cheng",
""
]
] | We investigate the stability analysis of Schwarzschild black hole in Einstein-scalar-Gauss-Bonnet (ESGB) theory because the instability of Schwarzschild black hole without scalar hair implies the Gauss-Bonnet black hole with scalar hair. The linearized scalar equation is compared to the Lichnerowicz-Ricci tensor equation in the Einstein-Weyl gravity. It turns out that the instability of Schwarzschild black hole in ESGB theory is interpreted as not the tachyonic instability, but the Gregory-Laflamme instability of black string. In the small mass regime of $1/\lambda<1.174/r_+$, the Schwarzschild solution becomes unstable and a new branch of solution with scalar hair bifurcates from the Schwarzschild one. This is very similar to finding a newly non-Schwarzschild black hole in Einstein-Weyl gravity. |
gr-qc/9902031 | Manfred Requardt | Manfred Requardt | Space-Time as an Orderparameter Manifold in Random Networks and the
Emergence of Physical Points | 40 pages, Latex | null | null | null | gr-qc hep-th math-ph math.MP | null | In the following we are going to describe how macroscopic space-time is
supposed to emerge as an orderparameter manifold or superstructure floating in
a stochastic discrete network structure. As in preceeding work (mentioned
below), our analysis is based on the working philosophy that both physics and
the corresponding mathematics have to be genuinely discrete on the primordial
(Planck scale) level. This strategy is concretely implemented in the form of
cellular networks and random graphs. One of our main themes is the development
of the concept of physical (proto)points as densely entangled subcomplexes of
the network and their respective web, establishing something like
(proto)causality. It max perhaps be said that certain parts of our programme
are realisations of some old and qualitative ideas of Menger and more recent
ones sketched by Smolin a couple of years ago. We briefly indicate how this
two-story-concept of space-time can be used to encode the (at least in our
view) existing non-local aspects of quantum theory without violating
macroscopic space-time causality!
| [
{
"created": "Thu, 11 Feb 1999 09:57:15 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Requardt",
"Manfred",
""
]
] | In the following we are going to describe how macroscopic space-time is supposed to emerge as an orderparameter manifold or superstructure floating in a stochastic discrete network structure. As in preceeding work (mentioned below), our analysis is based on the working philosophy that both physics and the corresponding mathematics have to be genuinely discrete on the primordial (Planck scale) level. This strategy is concretely implemented in the form of cellular networks and random graphs. One of our main themes is the development of the concept of physical (proto)points as densely entangled subcomplexes of the network and their respective web, establishing something like (proto)causality. It max perhaps be said that certain parts of our programme are realisations of some old and qualitative ideas of Menger and more recent ones sketched by Smolin a couple of years ago. We briefly indicate how this two-story-concept of space-time can be used to encode the (at least in our view) existing non-local aspects of quantum theory without violating macroscopic space-time causality! |
1809.06192 | Astrid Eichhorn | Astrid Eichhorn, Sumati Surya and Fleur Versteegen | Induced Spatial Geometry from Causal Structure | 38 pages, 24 figures | null | 10.1088/1361-6382/ab114b | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the Hawking-King-McCarthy-Malament (HKMM) theorem and the
associated reconstruction of spacetime geometry from its causal structure
$(M,\prec)$ and local volume element $\epsilon$, we define a one-parameter
family of spatial distance functions on a Cauchy hypersurface $\Sigma$ using
only $(M,\prec)$ and $\epsilon$. The parameter corresponds to a "mesoscale"
cut-off which, when appropriately chosen, provides a distance function which
approximates the induced spatial distance function to leading order. This
admits a straightforward generalisation to the discrete analogue of a Cauchy
hypersurface in a causal set. For causal sets which are approximated by
continuum spacetimes, this distance function approaches the continuum induced
distance when the mesoscale is much smaller than the scale of the extrinsic
curvature of the hypersurface, but much larger than the discreteness scale. We
verify these expectations by performing extensive numerical simulations of
causal sets which are approximated by simple spacetime regions in 2 and 3
spacetime dimensions.
| [
{
"created": "Mon, 17 Sep 2018 13:34:01 GMT",
"version": "v1"
}
] | 2019-05-22 | [
[
"Eichhorn",
"Astrid",
""
],
[
"Surya",
"Sumati",
""
],
[
"Versteegen",
"Fleur",
""
]
] | Motivated by the Hawking-King-McCarthy-Malament (HKMM) theorem and the associated reconstruction of spacetime geometry from its causal structure $(M,\prec)$ and local volume element $\epsilon$, we define a one-parameter family of spatial distance functions on a Cauchy hypersurface $\Sigma$ using only $(M,\prec)$ and $\epsilon$. The parameter corresponds to a "mesoscale" cut-off which, when appropriately chosen, provides a distance function which approximates the induced spatial distance function to leading order. This admits a straightforward generalisation to the discrete analogue of a Cauchy hypersurface in a causal set. For causal sets which are approximated by continuum spacetimes, this distance function approaches the continuum induced distance when the mesoscale is much smaller than the scale of the extrinsic curvature of the hypersurface, but much larger than the discreteness scale. We verify these expectations by performing extensive numerical simulations of causal sets which are approximated by simple spacetime regions in 2 and 3 spacetime dimensions. |
gr-qc/0009012 | Lee Samuel Finn | Lee Samuel Finn and Soma Mukherjee | Data conditioning for gravitational wave detectors: A Kalman filter for
regressing suspension violin mode | REVTeX; 42 pages, incl. 14 figures, 4 tables | Phys.Rev.D63:062004,2001; Erratum-ibid.D67:109902,2003 | 10.1103/PhysRevD.63.062004 10.1103/PhysRevD.67.109902 | null | gr-qc | null | Interferometric gravitational wave detectors operate by sensing the
differential light travel time between free test masses. Correspondingly, they
are sensitive to anything that changes the physical distance between the test
masses, including physical motion of the masses themselves. In ground-based
detectors the test masses are suspended as pendula and, consequently, thermal
or other excitations of the suspension wires' violin modes lead to a strong,
albeit narrow-band, ``signal'' in the detector wave-band that can confound
attempts to observe gravitational waves.
Here we describe the design of a Kalman filter that determines the
time-dependent vibrational state of a detector's suspension ``violin'' modes
from the detector output. From the estimated state we can predict that
component of the detector output due to suspension excitations, thermal or
otherwise, and subtractively remove those disturbances from the detector
output. We demonstrate the filter's effectiveness both through numerical
simulations and application to real data taken on the LIGO 40 M prototype
detector.
| [
{
"created": "Tue, 5 Sep 2000 13:23:17 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Finn",
"Lee Samuel",
""
],
[
"Mukherjee",
"Soma",
""
]
] | Interferometric gravitational wave detectors operate by sensing the differential light travel time between free test masses. Correspondingly, they are sensitive to anything that changes the physical distance between the test masses, including physical motion of the masses themselves. In ground-based detectors the test masses are suspended as pendula and, consequently, thermal or other excitations of the suspension wires' violin modes lead to a strong, albeit narrow-band, ``signal'' in the detector wave-band that can confound attempts to observe gravitational waves. Here we describe the design of a Kalman filter that determines the time-dependent vibrational state of a detector's suspension ``violin'' modes from the detector output. From the estimated state we can predict that component of the detector output due to suspension excitations, thermal or otherwise, and subtractively remove those disturbances from the detector output. We demonstrate the filter's effectiveness both through numerical simulations and application to real data taken on the LIGO 40 M prototype detector. |
1012.2070 | Alexis Larranaga PhD | Alexis Larranaga, Sindy Mojica | Geometrothermodynamics of a Charged Black Hole of String Theory | 10 pages | Brazilian Journal of Physics 41,2: 154-158 (2011) | 10.1007/s13538-011-0015-4 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The thermodynamics of the Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS)
charged black hole from string theory is reformulated within the context of the
recently developed formalism of geometrothermodynamics. The geometry of the
space of equilibrium states is curved, but we show that the thermodynamic
curvature does not diverge when the black hole solution becomes a naked
singularity. This provides a counterexample to the conventional notion that a
thermodynamical curvature divergence signals the occurrence of a phase
transition.
| [
{
"created": "Thu, 9 Dec 2010 18:32:39 GMT",
"version": "v1"
}
] | 2011-09-02 | [
[
"Larranaga",
"Alexis",
""
],
[
"Mojica",
"Sindy",
""
]
] | The thermodynamics of the Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) charged black hole from string theory is reformulated within the context of the recently developed formalism of geometrothermodynamics. The geometry of the space of equilibrium states is curved, but we show that the thermodynamic curvature does not diverge when the black hole solution becomes a naked singularity. This provides a counterexample to the conventional notion that a thermodynamical curvature divergence signals the occurrence of a phase transition. |
0909.2223 | Carlos Coimbra-Araujo | P. S. Letelier and C. H. Coimbra-Araujo | Gravity with extra dimensions and dark matter interpretation:
Phenomenological example via Miyamoto-Nagai galaxy | 10 pages, 10 figures, submitted to Brazilian Journal of Physics | null | 10.1007/s13538-012-0059-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A configuration whose density profile coincides with the Newtonian potential
for spiral galaxies is constructed from a 4D isotropic metric plus extra
dimensional components. A Miyamoto-Nagai ansatz is used to solve Einstein
equations. The stable rotation curves of such system are computed and, without
fitting techniques, we recover with accuracy the observational data for flat or
not asymptotically flat galaxy rotation curves. The density profiles are
reconstructed and compared to that obtained from the Newtonian potential.
| [
{
"created": "Fri, 11 Sep 2009 17:34:55 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Sep 2011 10:40:54 GMT",
"version": "v2"
}
] | 2015-05-14 | [
[
"Letelier",
"P. S.",
""
],
[
"Coimbra-Araujo",
"C. H.",
""
]
] | A configuration whose density profile coincides with the Newtonian potential for spiral galaxies is constructed from a 4D isotropic metric plus extra dimensional components. A Miyamoto-Nagai ansatz is used to solve Einstein equations. The stable rotation curves of such system are computed and, without fitting techniques, we recover with accuracy the observational data for flat or not asymptotically flat galaxy rotation curves. The density profiles are reconstructed and compared to that obtained from the Newtonian potential. |
gr-qc/9801093 | G. Dautcourt | G. Dautcourt | On the Ultrarelativistic Limit of General Relativity | 9 pages, Latex, submitted to Acta Physica Polonica (Jadwisin
Conference Proceedings) | Acta Phys.Polon. B29 (1998) 1047-1055 | null | null | gr-qc | null | As is well-known, Newton's gravitational theory can be formulated as a
four-dimensional space-time theory and follows as singular limit from
Einstein's theory, if the velocity of light tends to the infinity. Here
'singular' stands for the fact, that the limiting geometrical structure differs
from a regular Riemannian space-time. Geometrically, the transition Einstein to
Newton can be viewed as an 'opening' of the light cones. This picture suggests
that there might be other singular limits of Einstein's theory: Let all light
cones shrink and ultimately become part of a congruence of singular world
lines. The limiting structure may be considered as a nullhypersurface embedded
in a five-dimensional spacetime. While the velocity of light tends to zero
here, all other velocities tend to the velocity of light. Thus one may speak of
an ultrarelativistic limit of General Relativity. The resulting theory is as
simple as Newton's gravitational theory, with the basic difference, that
Newton's elliptic differential equation is replaced by essentially ordinary
differential equations, with derivatives tangent to the generators of the
singular congruence. The Galilei group is replaced by the Carroll group
introduced by L\'evy-Leblond. We suggest to study near ultrarelativistic
situations with a perturbational approach starting from the singular structure,
similar to post-Newtonian expansions in the $c \to \infty$ case.
| [
{
"created": "Wed, 28 Jan 1998 21:16:38 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Dautcourt",
"G.",
""
]
] | As is well-known, Newton's gravitational theory can be formulated as a four-dimensional space-time theory and follows as singular limit from Einstein's theory, if the velocity of light tends to the infinity. Here 'singular' stands for the fact, that the limiting geometrical structure differs from a regular Riemannian space-time. Geometrically, the transition Einstein to Newton can be viewed as an 'opening' of the light cones. This picture suggests that there might be other singular limits of Einstein's theory: Let all light cones shrink and ultimately become part of a congruence of singular world lines. The limiting structure may be considered as a nullhypersurface embedded in a five-dimensional spacetime. While the velocity of light tends to zero here, all other velocities tend to the velocity of light. Thus one may speak of an ultrarelativistic limit of General Relativity. The resulting theory is as simple as Newton's gravitational theory, with the basic difference, that Newton's elliptic differential equation is replaced by essentially ordinary differential equations, with derivatives tangent to the generators of the singular congruence. The Galilei group is replaced by the Carroll group introduced by L\'evy-Leblond. We suggest to study near ultrarelativistic situations with a perturbational approach starting from the singular structure, similar to post-Newtonian expansions in the $c \to \infty$ case. |
1906.07033 | Sebastian Bramberger | Sebastian F. Bramberger, Mariam Chitishvili, George Lavrelashvili | Aspects of the negative mode problem in quantum tunneling with gravity | 16 pages, 8 figures | Phys. Rev. D 100, 125006 (2019) | 10.1103/PhysRevD.100.125006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some solutions describing vacuum decay exhibit a catastrophic instability.
This, so-called negative mode problem in quantum tunneling with gravity, was
discovered 34 years ago and in spite of the fact that in these years many
different groups worked on this topic, it has still not been resolved. Here, we
briefly summarize the current status of the problem and investigate properties
of the bounces, numerically and analytically for physically interesting
potentials. In the framework of the Hamiltonian approach we show that for
generic polynomial potentials the negative mode problem could arise at energies
much lower than the Planck mass, indicating that the negative mode problem is
not related to physics at the Planck scale. At the same time we find that for a
Higgs like potential, as it appears in the standard model, the problem does not
appear at realistic values of the potential's parameters but only at the Planck
scale.
| [
{
"created": "Mon, 17 Jun 2019 13:45:18 GMT",
"version": "v1"
}
] | 2019-12-11 | [
[
"Bramberger",
"Sebastian F.",
""
],
[
"Chitishvili",
"Mariam",
""
],
[
"Lavrelashvili",
"George",
""
]
] | Some solutions describing vacuum decay exhibit a catastrophic instability. This, so-called negative mode problem in quantum tunneling with gravity, was discovered 34 years ago and in spite of the fact that in these years many different groups worked on this topic, it has still not been resolved. Here, we briefly summarize the current status of the problem and investigate properties of the bounces, numerically and analytically for physically interesting potentials. In the framework of the Hamiltonian approach we show that for generic polynomial potentials the negative mode problem could arise at energies much lower than the Planck mass, indicating that the negative mode problem is not related to physics at the Planck scale. At the same time we find that for a Higgs like potential, as it appears in the standard model, the problem does not appear at realistic values of the potential's parameters but only at the Planck scale. |
1810.11785 | Matteo Luca Ruggiero | Matteo Luca Ruggiero, Angelo Tartaglia | Test of gravitomagnetism with satellites around the Earth | 6 pages, 3 figures; revised to match the version accepted for
publication in EPJP | Eur. Phys. J. Plus (2019) 134: 205 | 10.1140/epjp/i2019-12602-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We focus on the possibility of measuring the gravitomagnetic effects due to
the rotation of the Earth, by means of a space-based experiment that exploits
satellites in geostationary orbits. Due to the rotation of the Earth, there is
an asymmetry in the propagation of electromagnetic signals in opposite
directions along a closed path around the Earth. We work out the delays between
the two counter-propagating beams for a simple configuration, and suggest that
accurate time measurements could allow, in principle, to detect the
gravitomagnetic effect of the Earth
| [
{
"created": "Sun, 28 Oct 2018 09:35:12 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Jan 2019 18:26:22 GMT",
"version": "v2"
},
{
"created": "Sun, 3 Mar 2019 21:03:07 GMT",
"version": "v3"
}
] | 2019-05-21 | [
[
"Ruggiero",
"Matteo Luca",
""
],
[
"Tartaglia",
"Angelo",
""
]
] | We focus on the possibility of measuring the gravitomagnetic effects due to the rotation of the Earth, by means of a space-based experiment that exploits satellites in geostationary orbits. Due to the rotation of the Earth, there is an asymmetry in the propagation of electromagnetic signals in opposite directions along a closed path around the Earth. We work out the delays between the two counter-propagating beams for a simple configuration, and suggest that accurate time measurements could allow, in principle, to detect the gravitomagnetic effect of the Earth |
2402.11315 | Eric Ling | Gregory J. Galloway and Eric Ling | Rigidity aspects of Penrose's singularity theorem | 16 pages. v2: minor corrections/changes and expanded proof of Theorem
8 | null | null | CPH-GEOTOP-DNRF151; CF21-0680 | gr-qc math.DG | http://creativecommons.org/licenses/by/4.0/ | In this paper, we study rigidity aspects of Penrose's singularity theorem.
Specifically, we aim to answer the following question: if a spacetime satisfies
the hypotheses of Penrose's singularity theorem except with weakly trapped
surfaces instead of trapped surfaces, then what can be said about the global
spacetime structure if the spacetime is null geodesically complete? In this
setting, we show that we obtain a foliation of MOTS which generate totally
geodesic null hypersurfaces. Depending on our starting assumptions, we obtain
either local or global rigidity results. We apply our arguments to cosmological
spacetimes (i.e., spacetimes with compact Cauchy surfaces) and scenarios
involving topological censorship.
| [
{
"created": "Sat, 17 Feb 2024 16:00:21 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Apr 2024 15:20:10 GMT",
"version": "v2"
}
] | 2024-04-30 | [
[
"Galloway",
"Gregory J.",
""
],
[
"Ling",
"Eric",
""
]
] | In this paper, we study rigidity aspects of Penrose's singularity theorem. Specifically, we aim to answer the following question: if a spacetime satisfies the hypotheses of Penrose's singularity theorem except with weakly trapped surfaces instead of trapped surfaces, then what can be said about the global spacetime structure if the spacetime is null geodesically complete? In this setting, we show that we obtain a foliation of MOTS which generate totally geodesic null hypersurfaces. Depending on our starting assumptions, we obtain either local or global rigidity results. We apply our arguments to cosmological spacetimes (i.e., spacetimes with compact Cauchy surfaces) and scenarios involving topological censorship. |
gr-qc/9506074 | Robert Graham | Andras Csordas and Robert Graham | Hartle-Hawking state in supersymmetric minisuperspace | 11 pages, revtex | Phys.Lett. B373 (1996) 51-55 | 10.1016/0370-2693(96)00098-6 | null | gr-qc | null | The Hartle-Hawking `no-boundary' state is constructed explicitly for the
recently developed supersymmetric minisuperspace model with non-vanishing
fermion number.
| [
{
"created": "Thu, 29 Jun 1995 10:54:07 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Csordas",
"Andras",
""
],
[
"Graham",
"Robert",
""
]
] | The Hartle-Hawking `no-boundary' state is constructed explicitly for the recently developed supersymmetric minisuperspace model with non-vanishing fermion number. |
1802.03465 | Edward Anderson | Edward Anderson | Monopoles of Twelve Types in 3-Body Problems | 39 pages including 23 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider twelve different ways of modelling the 3-body problem in
dimension $\geq 2$. These can be viewed as models of classical and quantum
background independence. We show that a different type of monopole is realized
in each's relational space: a type of reduced configuration space. 8 cases
occur in 2-$d$, and 4 distinct ones in 3-$d$; these reflect counts of
non-equivalent subgroup actions of $S_3 \times C_2$ and $S_3$ respectively. The
$S_3$ acts on particle labels; the extra $C_2$ corresponds to the purely 2-$d$
option of whether or not to identify mirror images. The non-equivalent
realization is due to a suite of subgroup, orbit space and stratification
features.
Our 2-$d$ monopoles include 4 known ones: a realization of Dirac's monopole
in relational space rather than its more habitual setting of space, the 2-$d$
version of Iwai's monopole, and indistinguishable particle monopoles with and
without mirror image identification. The 4 new ones are indistinguishable under
a 2-particle label switch or under even permutations, in each case with
optional mirror image identification. Our 4 3-$d$ monopoles are 2 known ones:
the actual Iwai monopole and its already-announced indistinguishable-particles
counterpart, and 2 new ones: the two-particle label switch and even permutation
cases. All 4 3-$d$ cases are stratified. The three even-permutation cases are
orbifolds, two with boundary, the 3-$d$ case's boundary constituting a separate
stratum, giving a stratified orbifold. We document each of the 12 cases'
underlying shape space and relational space, and each monopole's Hopf
mathematics, global-section versus topological quantization dichotomy, Dirac
string positioning, and Chern integral concordance with topological
contributions form of Gauss--Bonnet Theorem.
| [
{
"created": "Fri, 9 Feb 2018 22:06:47 GMT",
"version": "v1"
}
] | 2018-02-13 | [
[
"Anderson",
"Edward",
""
]
] | We consider twelve different ways of modelling the 3-body problem in dimension $\geq 2$. These can be viewed as models of classical and quantum background independence. We show that a different type of monopole is realized in each's relational space: a type of reduced configuration space. 8 cases occur in 2-$d$, and 4 distinct ones in 3-$d$; these reflect counts of non-equivalent subgroup actions of $S_3 \times C_2$ and $S_3$ respectively. The $S_3$ acts on particle labels; the extra $C_2$ corresponds to the purely 2-$d$ option of whether or not to identify mirror images. The non-equivalent realization is due to a suite of subgroup, orbit space and stratification features. Our 2-$d$ monopoles include 4 known ones: a realization of Dirac's monopole in relational space rather than its more habitual setting of space, the 2-$d$ version of Iwai's monopole, and indistinguishable particle monopoles with and without mirror image identification. The 4 new ones are indistinguishable under a 2-particle label switch or under even permutations, in each case with optional mirror image identification. Our 4 3-$d$ monopoles are 2 known ones: the actual Iwai monopole and its already-announced indistinguishable-particles counterpart, and 2 new ones: the two-particle label switch and even permutation cases. All 4 3-$d$ cases are stratified. The three even-permutation cases are orbifolds, two with boundary, the 3-$d$ case's boundary constituting a separate stratum, giving a stratified orbifold. We document each of the 12 cases' underlying shape space and relational space, and each monopole's Hopf mathematics, global-section versus topological quantization dichotomy, Dirac string positioning, and Chern integral concordance with topological contributions form of Gauss--Bonnet Theorem. |
gr-qc/9405015 | Chopin Soo | Lee Smolin and Chopin Soo | The Chern-Simons Invariant as the Natural Time Variable for Classical
and Quantum Cosmology | 32 pages, gr-qc/9405015, CGPG-94/4-1 (revised and extended, Oct. 94) | Nucl.Phys.B449:289-316,1995 | 10.1016/0550-3213(95)00222-E | null | gr-qc hep-th | null | We propose that the Chern-Simons invariant of the Ashtekar-Sen connection is
the natural internal time coordinate for classical and quantum cosmology. The
reasons for this are a number of interesting properties of this functional,
which we describe here. 1)It is a function on the gauge and diffeomorphism
invariant configuration space, whose gradient is orthogonal to the two physical
degrees of freedom, in the metric defined by the Ashtekar formulation of
general relativity. 2)The imaginary part of the Chern-Simons form reduces in
the limit of small cosmological constant, $\Lambda$, and solutions close to
DeSitter spacetime, to the York extrinsic time coordinate. 3)Small matter-field
excitations of the Chern-Simons state satisfy, by virtue of the quantum
constraints, a functional Schroedinger equation in which the matter fields
evolve on a DeSitter background in the Chern-Simons time. We then n propose
this is the natural vacuum state of the theory for $\Lambda \neq 0$. 4)This
time coordinate is periodic on the configuration space of Euclideanized
spacetimes, due to the large gauge transformations, which means that physical
expectation values for all states in non-perturbative quantum gravity will
satisfy the $KMS$ condition, and may then be interpreted as thermal states.
5)Forms for the physical hamiltonians and inner product which support the
proposal are suggested, and a new action principle for general relativity, as a
geodesic principle on the connection superspace, is found.
| [
{
"created": "Fri, 6 May 1994 18:52:59 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Oct 1994 19:52:55 GMT",
"version": "v2"
}
] | 2011-07-19 | [
[
"Smolin",
"Lee",
""
],
[
"Soo",
"Chopin",
""
]
] | We propose that the Chern-Simons invariant of the Ashtekar-Sen connection is the natural internal time coordinate for classical and quantum cosmology. The reasons for this are a number of interesting properties of this functional, which we describe here. 1)It is a function on the gauge and diffeomorphism invariant configuration space, whose gradient is orthogonal to the two physical degrees of freedom, in the metric defined by the Ashtekar formulation of general relativity. 2)The imaginary part of the Chern-Simons form reduces in the limit of small cosmological constant, $\Lambda$, and solutions close to DeSitter spacetime, to the York extrinsic time coordinate. 3)Small matter-field excitations of the Chern-Simons state satisfy, by virtue of the quantum constraints, a functional Schroedinger equation in which the matter fields evolve on a DeSitter background in the Chern-Simons time. We then n propose this is the natural vacuum state of the theory for $\Lambda \neq 0$. 4)This time coordinate is periodic on the configuration space of Euclideanized spacetimes, due to the large gauge transformations, which means that physical expectation values for all states in non-perturbative quantum gravity will satisfy the $KMS$ condition, and may then be interpreted as thermal states. 5)Forms for the physical hamiltonians and inner product which support the proposal are suggested, and a new action principle for general relativity, as a geodesic principle on the connection superspace, is found. |
gr-qc/9307015 | Kristin Schleich | Kristin Schleich and Donald M. Witt | Generalized Sums over Histories for Quantum Gravity I. Smooth Conifolds | 81pp., plain TeX, To appear in Nucl. Phys. B | Nucl.Phys.B402:411-468,1993 | 10.1016/0550-3213(93)90649-A | null | gr-qc hep-th | null | This paper proposes to generalize the histories included in Euclidean
functional integrals from manifolds to a more general set of compact
topological spaces. This new set of spaces, called conifolds, includes
nonmanifold stationary points that arise naturally in a semiclasssical
evaluation of such integrals; additionally, it can be proven that sequences of
approximately Einstein manifolds and sequences of approximately Einstein
conifolds both converge to Einstein conifolds. Consequently, generalized
Euclidean functional integrals based on these conifold histories yield
semiclassical amplitudes for sequences of both manifold and conifold histories
that approach a stationary point of the Einstein action. Therefore sums over
conifold histories provide a useful and self-consistent starting point for
further study of topological effects in quantum gravity. Postscript figures
available via anonymous ftp at black-hole.physics.ubc.ca (137.82.43.40) in file
gen1.ps.
| [
{
"created": "Tue, 13 Jul 1993 22:38:00 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Schleich",
"Kristin",
""
],
[
"Witt",
"Donald M.",
""
]
] | This paper proposes to generalize the histories included in Euclidean functional integrals from manifolds to a more general set of compact topological spaces. This new set of spaces, called conifolds, includes nonmanifold stationary points that arise naturally in a semiclasssical evaluation of such integrals; additionally, it can be proven that sequences of approximately Einstein manifolds and sequences of approximately Einstein conifolds both converge to Einstein conifolds. Consequently, generalized Euclidean functional integrals based on these conifold histories yield semiclassical amplitudes for sequences of both manifold and conifold histories that approach a stationary point of the Einstein action. Therefore sums over conifold histories provide a useful and self-consistent starting point for further study of topological effects in quantum gravity. Postscript figures available via anonymous ftp at black-hole.physics.ubc.ca (137.82.43.40) in file gen1.ps. |
gr-qc/9803067 | Murat Ozer | A. A. Al-Nowaiser, Murat \"Ozer and M. O. Taha | A Non-Singular Universe in String Cosmology | RevTex, 10 pages, a new reference and related information is added | Int.J.Mod.Phys.D8:43-49,1999 | 10.1142/S0218271899000055 | null | gr-qc astro-ph hep-ph | null | We consider the low-energy effective string action in four dimensions
including the leading order-$\alpha'$ terms. An exact homogeneous solution is
obtained. It represents a non-singular expanding cosmological model in which
the tensor fields tend to vanish as $t\to \infty$. The scale factor $a(t)$ of
the very early universe in this model has the time dependence
$a(t)^2=a_0^2+t^2$. The violation of the strong energy condition of classical
General Relativity to avoid the initial singularity requires that the central
charge deficit of the theory be larger than a certain value. The significance
of this solution is discussed.
| [
{
"created": "Wed, 18 Mar 1998 19:19:07 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Mar 1998 14:11:37 GMT",
"version": "v2"
},
{
"created": "Sun, 22 Mar 1998 07:08:24 GMT",
"version": "v3"
}
] | 2014-11-17 | [
[
"Al-Nowaiser",
"A. A.",
""
],
[
"Özer",
"Murat",
""
],
[
"Taha",
"M. O.",
""
]
] | We consider the low-energy effective string action in four dimensions including the leading order-$\alpha'$ terms. An exact homogeneous solution is obtained. It represents a non-singular expanding cosmological model in which the tensor fields tend to vanish as $t\to \infty$. The scale factor $a(t)$ of the very early universe in this model has the time dependence $a(t)^2=a_0^2+t^2$. The violation of the strong energy condition of classical General Relativity to avoid the initial singularity requires that the central charge deficit of the theory be larger than a certain value. The significance of this solution is discussed. |
2002.03787 | Sunil Kumar Tripathy Dr. | S K Tripathy, B Mishra, Saibal Ray and Rikpratik Sengupta | Bouncing Models in an Extended Gravity Theory | 14 pages,13 figures | Chinese Journal of Physics 71 (2021) 610 | 10.1016/j.cjph.2021.03.026 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some bouncing models are investigated in the framework of an extended theory
of gravity. The extended gravity model is a simple extension of the General
Relativity where an additional matter geometry coupling is introduced to
account for the late time cosmic speed up phenomena. The dynamics of the models
are discussed in the background of a flat FRW universe. Some viable models are
reconstructed for specifically assumed bouncing scale factors. The behavior of
the models are found to be decided mostly by the parameters of the respective
models. The extended gravity based minimal matter-geometry coupling parameter
has a role to remove the omega singularity occurring at the bouncing epoch. It
is noted that the constructed models violate the energy conditions, however, in
some cases this violation leads to the evolution of the models in phantom
phase. The stability of the models are analyzed under linear homogeneous
perturbations and it is found that, near the bounce, the models show
instability but the perturbations decay out smoothly to provide stable models
at late times.
| [
{
"created": "Thu, 6 Feb 2020 11:03:42 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Sep 2020 17:05:21 GMT",
"version": "v2"
}
] | 2021-06-10 | [
[
"Tripathy",
"S K",
""
],
[
"Mishra",
"B",
""
],
[
"Ray",
"Saibal",
""
],
[
"Sengupta",
"Rikpratik",
""
]
] | Some bouncing models are investigated in the framework of an extended theory of gravity. The extended gravity model is a simple extension of the General Relativity where an additional matter geometry coupling is introduced to account for the late time cosmic speed up phenomena. The dynamics of the models are discussed in the background of a flat FRW universe. Some viable models are reconstructed for specifically assumed bouncing scale factors. The behavior of the models are found to be decided mostly by the parameters of the respective models. The extended gravity based minimal matter-geometry coupling parameter has a role to remove the omega singularity occurring at the bouncing epoch. It is noted that the constructed models violate the energy conditions, however, in some cases this violation leads to the evolution of the models in phantom phase. The stability of the models are analyzed under linear homogeneous perturbations and it is found that, near the bounce, the models show instability but the perturbations decay out smoothly to provide stable models at late times. |
gr-qc/0203008 | Ivan L. Zhogin | I. L. Zhogin | Trilinear generally covariant equations of AP | 8 pages, Latex. Corrected typos (e.g., in Eqs.(5), (26)) | Sov.Phys.J. 34 (1991) 105-110 | null | null | gr-qc | null | Field equations for n-frames h_a{}^\mu that are possible in the theory of
absolute parallelism (AP) are considered. The methods of compatibility (or
formal integrability) theory enable us to find the non-Lagrangian equation
having unusual kind of compatibility conditions, guaranteed by two (not one)
identities. This 'unique equation' was not noted explicitly in the
classification by Einstein and Mayer of compatible second order equations of
AP.
It is shown that some equations of AP (including 'unique equation') can be
written in a trilinear form that contains only the matrix of frame density (of
some weight) H_a{}^\mu and its derivatives and not inverse (coframe density)
matrix. The equations are still regular and involutive for degenerate but
finite matrices H_a{}^\mu if rank H_a{}^\mu > 1.
| [
{
"created": "Mon, 4 Mar 2002 06:25:22 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Sep 2002 09:48:01 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Zhogin",
"I. L.",
""
]
] | Field equations for n-frames h_a{}^\mu that are possible in the theory of absolute parallelism (AP) are considered. The methods of compatibility (or formal integrability) theory enable us to find the non-Lagrangian equation having unusual kind of compatibility conditions, guaranteed by two (not one) identities. This 'unique equation' was not noted explicitly in the classification by Einstein and Mayer of compatible second order equations of AP. It is shown that some equations of AP (including 'unique equation') can be written in a trilinear form that contains only the matrix of frame density (of some weight) H_a{}^\mu and its derivatives and not inverse (coframe density) matrix. The equations are still regular and involutive for degenerate but finite matrices H_a{}^\mu if rank H_a{}^\mu > 1. |
gr-qc/9403055 | Don N. Page | Sheldon Goldstein (Rutgers University) and Don N. Page (University of
Alberta) | Linearly Positive Histories: Probabilities for a Robust Family of
Sequences of Quantum Events | 8 pages, LaTeX. Shortened slightly to permit publication in Phys.
Rev. Lett. A paragraph after Eq. (21) was expanded | Phys.Rev.Lett.74:3715-3719,1995 | 10.1103/PhysRevLett.74.3715 | Alberta-Thy-43-93 | gr-qc hep-th | null | Nonnegative probabilities that obey the sum rules may be assigned to a much
wider family of sets of histories than decohering histories. The resulting {\it
linearly positive histories} avoid the highly restrictive decoherence
conditions and yet give the same probabilities when those conditions apply.
Thus linearly positive histories are a broad extension of decohering histories.
Moreover, the resulting theory is manifestly time-reversal invariant.
| [
{
"created": "Tue, 29 Mar 1994 22:59:58 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Sep 1994 20:09:38 GMT",
"version": "v2"
},
{
"created": "Fri, 3 Mar 1995 20:32:41 GMT",
"version": "v3"
}
] | 2014-11-17 | [
[
"Goldstein",
"Sheldon",
"",
"Rutgers University"
],
[
"Page",
"Don N.",
"",
"University of\n Alberta"
]
] | Nonnegative probabilities that obey the sum rules may be assigned to a much wider family of sets of histories than decohering histories. The resulting {\it linearly positive histories} avoid the highly restrictive decoherence conditions and yet give the same probabilities when those conditions apply. Thus linearly positive histories are a broad extension of decohering histories. Moreover, the resulting theory is manifestly time-reversal invariant. |
gr-qc/0107099 | Hideo Iguchi | Hideo Iguchi and Tomohiro Harada | Physical aspects of naked singularity explosion - How does a naked
singularity explode? -- | 18 pages, 16 figures | Class.Quant.Grav.18:3681-3700,2001 | 10.1088/0264-9381/18/17/319 | YITP-01-22, WU-AP/121/01 | gr-qc | null | The behaviors of quantum stress tensor for the scalar field on the classical
background of spherical dust collapse is studied. In the previous works
diverging flux of quantum radiation was predicted. We use the exact expressions
in a 2D model formulated by Barve et al. Our present results show that the back
reaction does not become important during the semiclassical phase. The
appearance of the naked singularity would not be affected by this quantum field
radiation. To predict whether the naked singularity explosion occurs or not we
need the theory of quantum gravity. We depict the generation of the diverging
flux inside the collapsing star. The quantum energy is gathered around the
center positively. This would be converted to the diverging flux along the
Cauchy horizon. The ingoing negative flux crosses the Cauchy horizon. The
intensity of it is divergent only at the central naked singularity. This
diverging negative ingoing flux is balanced with the outgoing positive
diverging flux which propagates along the Cauchy horizon. After the replacement
of the naked singularity to the practical high density region the instantaneous
diverging radiation would change to more milder one with finite duration.
| [
{
"created": "Tue, 31 Jul 2001 06:10:19 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Iguchi",
"Hideo",
""
],
[
"Harada",
"Tomohiro",
""
]
] | The behaviors of quantum stress tensor for the scalar field on the classical background of spherical dust collapse is studied. In the previous works diverging flux of quantum radiation was predicted. We use the exact expressions in a 2D model formulated by Barve et al. Our present results show that the back reaction does not become important during the semiclassical phase. The appearance of the naked singularity would not be affected by this quantum field radiation. To predict whether the naked singularity explosion occurs or not we need the theory of quantum gravity. We depict the generation of the diverging flux inside the collapsing star. The quantum energy is gathered around the center positively. This would be converted to the diverging flux along the Cauchy horizon. The ingoing negative flux crosses the Cauchy horizon. The intensity of it is divergent only at the central naked singularity. This diverging negative ingoing flux is balanced with the outgoing positive diverging flux which propagates along the Cauchy horizon. After the replacement of the naked singularity to the practical high density region the instantaneous diverging radiation would change to more milder one with finite duration. |
gr-qc/9805051 | Marc A. Pelath | M.A. Pelath, K.P. Tod, and Robert M. Wald | Trapped surfaces in prolate collapse in the Gibbons-Penrose construction | 22 pages, 6 figures | Class.Quant.Grav. 15 (1998) 3917-3934 | 10.1088/0264-9381/15/12/018 | null | gr-qc | null | We investigate existence and properties of trapped surfaces in two models of
collapsing null dust shells within the Gibbons-Penrose construction. In the
first model, the shell is initially a prolate spheroid, and the resulting
singularity forms at the ends first (relative to a natural time slicing by flat
hyperplanes), in analogy with behavior found in certain prolate collapse
examples considered by Shapiro and Teukolsky. We give an explicit example in
which trapped surfaces are present on the shell, but none exist prior to the
last flat slice, thereby explicitly showing that the absence of trapped
surfaces on a particular, natural slicing does not imply an absence of trapped
surfaces in the spacetime. We then examine a model considered by Barrabes,
Israel and Letelier (BIL) of a cylindrical shell of mass M and length L, with
hemispherical endcaps of mass m. We obtain a "phase diagram" for the presence
of trapped surfaces on the shell with respect to essential parameters $\lambda
\equiv M/L$ and $\mu \equiv m/M$. It is found that no trapped surfaces are
present on the shell when $\lambda$ or $\mu$ are sufficiently small. (We are
able only to search for trapped surfaces lying on the shell itself.) In the
limit $\lambda \to 0$, the existence or nonexistence of trapped surfaces lying
within the shell is seen to be in remarkably good accord with the hoop
conjecture.
| [
{
"created": "Wed, 13 May 1998 20:23:04 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Pelath",
"M. A.",
""
],
[
"Tod",
"K. P.",
""
],
[
"Wald",
"Robert M.",
""
]
] | We investigate existence and properties of trapped surfaces in two models of collapsing null dust shells within the Gibbons-Penrose construction. In the first model, the shell is initially a prolate spheroid, and the resulting singularity forms at the ends first (relative to a natural time slicing by flat hyperplanes), in analogy with behavior found in certain prolate collapse examples considered by Shapiro and Teukolsky. We give an explicit example in which trapped surfaces are present on the shell, but none exist prior to the last flat slice, thereby explicitly showing that the absence of trapped surfaces on a particular, natural slicing does not imply an absence of trapped surfaces in the spacetime. We then examine a model considered by Barrabes, Israel and Letelier (BIL) of a cylindrical shell of mass M and length L, with hemispherical endcaps of mass m. We obtain a "phase diagram" for the presence of trapped surfaces on the shell with respect to essential parameters $\lambda \equiv M/L$ and $\mu \equiv m/M$. It is found that no trapped surfaces are present on the shell when $\lambda$ or $\mu$ are sufficiently small. (We are able only to search for trapped surfaces lying on the shell itself.) In the limit $\lambda \to 0$, the existence or nonexistence of trapped surfaces lying within the shell is seen to be in remarkably good accord with the hoop conjecture. |
1606.00698 | Srijit Bhattacharjee | Srijit Bhattacharjee, Debaprasad Maity, and Rupak Mukherjee | Constraining scalar-Gauss-Bonnet Inflation by Reheating, Unitarity and
PLANCK | 22 pages, 12 Pdf figures; Modified version including updated analyses
compatible with the latest observational data. Almost matches with the
published version | Phys. Rev. D 95, 023514 (2017) | 10.1103/PhysRevD.95.023514 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the inflationary dynamics in detail for theories with Gauss-Bonnet
gravity coupled to scalar functions, in light of the Planck data. Considering
the chaotic inflationary scenario, we constrain the parameters of two models
involving inflaton-Gauss-Bonnet coupling by current Planck data. For non zero
inflaton-Gauss-Bonnet coupling $\beta$, an inflationary analysis provides us a
big cosmologically viable region in the space of $(m,\beta)$, where $m$ is the
mass of inflaton. However, we study further on constraining $\beta$ arising
from reheating considerations and unitarity of tree-level amplitude involving
we have studied the constraints on $\beta$ arising from reheating
considerations and unitarity of tree level amplitude involving $2$ graviton
$\rightarrow 2$ graviton ($h h\rightarrow hh$) scattering. Our analysis,
particularly on reheating significantly reduces the parameter space of
$(m,\beta)$ for all models. he quadratic Gauss-Bonnet coupling parameter turns
out to be more strongly constrained than that of the linear coupling. For the
linear Gauss-Bonnet coupling function, we obtain $\beta \lesssim 10^3$, with
the condition $\beta (m/M_P)^2 \simeq 10^{-4}$. However, study of the Higgs
inflation scenario in the presence of Gauss-Bonnet term turned out to be
strongly disfavored.
| [
{
"created": "Mon, 30 May 2016 15:04:22 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Jun 2016 12:32:44 GMT",
"version": "v2"
},
{
"created": "Mon, 6 Feb 2017 19:28:18 GMT",
"version": "v3"
}
] | 2017-02-08 | [
[
"Bhattacharjee",
"Srijit",
""
],
[
"Maity",
"Debaprasad",
""
],
[
"Mukherjee",
"Rupak",
""
]
] | We revisit the inflationary dynamics in detail for theories with Gauss-Bonnet gravity coupled to scalar functions, in light of the Planck data. Considering the chaotic inflationary scenario, we constrain the parameters of two models involving inflaton-Gauss-Bonnet coupling by current Planck data. For non zero inflaton-Gauss-Bonnet coupling $\beta$, an inflationary analysis provides us a big cosmologically viable region in the space of $(m,\beta)$, where $m$ is the mass of inflaton. However, we study further on constraining $\beta$ arising from reheating considerations and unitarity of tree-level amplitude involving we have studied the constraints on $\beta$ arising from reheating considerations and unitarity of tree level amplitude involving $2$ graviton $\rightarrow 2$ graviton ($h h\rightarrow hh$) scattering. Our analysis, particularly on reheating significantly reduces the parameter space of $(m,\beta)$ for all models. he quadratic Gauss-Bonnet coupling parameter turns out to be more strongly constrained than that of the linear coupling. For the linear Gauss-Bonnet coupling function, we obtain $\beta \lesssim 10^3$, with the condition $\beta (m/M_P)^2 \simeq 10^{-4}$. However, study of the Higgs inflation scenario in the presence of Gauss-Bonnet term turned out to be strongly disfavored. |
gr-qc/0602100 | Martin Bojowald | Martin Bojowald | Quantum Riemannian Geometry and Black Holes | 45 pages, 4 figures, chapter of "Trends in Quantum Gravity Research"
(Nova Science) | null | null | IGPG-06/2-2, AEI-2006-009 | gr-qc hep-th | null | Black Holes have always played a central role in investigations of quantum
gravity. This includes both conceptual issues such as the role of classical
singularities and information loss, and technical ones to probe the consistency
of candidate theories. Lacking a full theory of quantum gravity, such studies
had long been restricted to black hole models which include some aspects of
quantization. However, it is then not always clear whether the results are
consequences of quantum gravity per se or of the particular steps one had
undertaken to bring the system into a treatable form. Over a little more than
the last decade loop quantum gravity has emerged as a widely studied candidate
for quantum gravity, where it is now possible to introduce black hole models
within a quantum theory of gravity. This makes it possible to use only quantum
effects which are known to arise also in the full theory, but still work in a
rather simple and physically interesting context of black holes. Recent
developments have now led to the first physical results about non-rotating
quantum black holes obtained in this way. Restricting to the interior inside
the Schwarzschild horizon, the resulting quantum model is free of the classical
singularity, which is a consequence of discrete quantum geometry taking over
for the continuous classical space-time picture. This fact results in a change
of paradigm concerning the information loss problem. The horizon itself can
also be studied in the quantum theory by imposing horizon conditions at the
level of states. Thereby one can illustrate the nature of horizon degrees of
freedom and horizon fluctuations. All these developments allow us to study the
quantum dynamics explicitly and in detail which provides a rich ground to test
the consistency of the full theory.
| [
{
"created": "Fri, 24 Feb 2006 17:30:48 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bojowald",
"Martin",
""
]
] | Black Holes have always played a central role in investigations of quantum gravity. This includes both conceptual issues such as the role of classical singularities and information loss, and technical ones to probe the consistency of candidate theories. Lacking a full theory of quantum gravity, such studies had long been restricted to black hole models which include some aspects of quantization. However, it is then not always clear whether the results are consequences of quantum gravity per se or of the particular steps one had undertaken to bring the system into a treatable form. Over a little more than the last decade loop quantum gravity has emerged as a widely studied candidate for quantum gravity, where it is now possible to introduce black hole models within a quantum theory of gravity. This makes it possible to use only quantum effects which are known to arise also in the full theory, but still work in a rather simple and physically interesting context of black holes. Recent developments have now led to the first physical results about non-rotating quantum black holes obtained in this way. Restricting to the interior inside the Schwarzschild horizon, the resulting quantum model is free of the classical singularity, which is a consequence of discrete quantum geometry taking over for the continuous classical space-time picture. This fact results in a change of paradigm concerning the information loss problem. The horizon itself can also be studied in the quantum theory by imposing horizon conditions at the level of states. Thereby one can illustrate the nature of horizon degrees of freedom and horizon fluctuations. All these developments allow us to study the quantum dynamics explicitly and in detail which provides a rich ground to test the consistency of the full theory. |
gr-qc/0004075 | T. Damour | Thibault Damour and Alexander Vilenkin | Gravitational wave bursts from cosmic strings | 4 pages, revtex, 2 figures, submitted to Phys. Rev. Letters | Phys.Rev.Lett.85:3761-3764,2000 | 10.1103/PhysRevLett.85.3761 | IHES/P/00/32 | gr-qc astro-ph hep-ph hep-th | null | Cusps of cosmic strings emit strong beams of high-frequency gravitational
waves (GW). As a consequence of these beams, the stochastic ensemble of
gravitational waves generated by a cosmological network of oscillating loops is
strongly non Gaussian, and includes occasional sharp bursts that stand above
the rms GW background. These bursts might be detectable by the planned GW
detectors LIGO/VIRGO and LISA for string tensions as small as $G \mu \sim
10^{-13}$. The GW bursts discussed here might be accompanied by Gamma Ray
Bursts.
| [
{
"created": "Wed, 26 Apr 2000 09:47:22 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Damour",
"Thibault",
""
],
[
"Vilenkin",
"Alexander",
""
]
] | Cusps of cosmic strings emit strong beams of high-frequency gravitational waves (GW). As a consequence of these beams, the stochastic ensemble of gravitational waves generated by a cosmological network of oscillating loops is strongly non Gaussian, and includes occasional sharp bursts that stand above the rms GW background. These bursts might be detectable by the planned GW detectors LIGO/VIRGO and LISA for string tensions as small as $G \mu \sim 10^{-13}$. The GW bursts discussed here might be accompanied by Gamma Ray Bursts. |
2404.19268 | Diego Solano-Alfaro | Diego Solano-Alfaro and Francisco Frutos-Alfaro | Equatorial circular motion in a Kerr-like spacetime | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An study of the equatorial circular motion of photons and massive particles
around a rotating compact body like a neutron star is presented. For this goal,
we use an approximate Kerr-like metric with mass quadrupole as perturbation.
The effect of this deformation on the photon sphere, and the innermost stable
circular orbit, is determined via an effective potential. Furthermore, a
stability anaysis is shown, where we observed the same behavior of the
effective potential for co-rotating and counter-rotating particles. A
comparison with the results for the innermost stable circular orbit obtained
for the Hartle-Thorne spacetime is also presented.
| [
{
"created": "Tue, 30 Apr 2024 05:21:22 GMT",
"version": "v1"
}
] | 2024-05-01 | [
[
"Solano-Alfaro",
"Diego",
""
],
[
"Frutos-Alfaro",
"Francisco",
""
]
] | An study of the equatorial circular motion of photons and massive particles around a rotating compact body like a neutron star is presented. For this goal, we use an approximate Kerr-like metric with mass quadrupole as perturbation. The effect of this deformation on the photon sphere, and the innermost stable circular orbit, is determined via an effective potential. Furthermore, a stability anaysis is shown, where we observed the same behavior of the effective potential for co-rotating and counter-rotating particles. A comparison with the results for the innermost stable circular orbit obtained for the Hartle-Thorne spacetime is also presented. |
gr-qc/9604036 | Heinz-Dieter Conradi | Heinz-Dieter Conradi (RWTH-Aachen, Germany) | Tunneling of Macroscopic Universes | 10 pages, one eps-file includes, uses LaTeX2e | Int.J.Mod.Phys. D7 (1998) 189-200 | 10.1142/S0218271898000152 | PHITA 95/36 | gr-qc | null | The meaning of `tunneling' in a timeless theory such as quantum cosmology is
discussed. A recent suggestion of `tunneling' of the macroscopic universe at
the classical turning point is analyzed in an anisotropic and inhomogeneous toy
model. This `inhomogeneous tunneling' is a local process which cannot be
interpreted as a tunneling of the universe.
| [
{
"created": "Thu, 18 Apr 1996 15:48:18 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Conradi",
"Heinz-Dieter",
"",
"RWTH-Aachen, Germany"
]
] | The meaning of `tunneling' in a timeless theory such as quantum cosmology is discussed. A recent suggestion of `tunneling' of the macroscopic universe at the classical turning point is analyzed in an anisotropic and inhomogeneous toy model. This `inhomogeneous tunneling' is a local process which cannot be interpreted as a tunneling of the universe. |
1810.04153 | Philipp Hoehn | Philipp A Hoehn and Augustin Vanrietvelde | How to switch between relational quantum clocks | 26 pages + appendices. Written in a manner accessible to an audience
unacquainted with the problem of time and Hamiltonian constraints. A few
clarifications added. Matches published version | New J. Phys. 22 (2020) 123048 | 10.1088/1367-2630/abd1ac | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Every clock is a physical system and thereby ultimately quantum. A naturally
arising question is how to describe time evolution relative to quantum clocks
and, specifically, how the dynamics relative to different quantum clocks are
related. This is a pressing issue in view of the multiple choice problem of
time in quantum gravity, which posits that there is no distinguished choice of
internal clock in generic general relativistic systems and that different
choices lead to inequivalent quantum theories. Exploiting a recent approach to
switching quantum reference systems (arXiv:1809.00556, arXiv:1809:05093), we
exhibit a systematic method for switching between different clock choices in
the quantum theory. We illustrate it by means of the parametrized particle,
which, like gravity, features a Hamiltonian constraint. We explicitly switch
between the quantum evolution relative to the non-relativistic time variable
and that relative to the particle's position, which requires carefully
regularizing the zero-modes in the so-called time-of-arrival observable. While
this toy model is simple, our approach is general and directly amenable to
quantum cosmology. It proceeds by systematically linking the reduced quantum
theories relative to different clock choices via the clock-choice-neutral Dirac
quantized theory, in analogy to coordinate changes on a manifold. This method
suggests a new perspective on the multiple choice problem, indicating that it
is rather a multiple choice feature of a complete relational quantum theory,
taken as the conjunction of Dirac quantized and quantum deparametrized
theories. Precisely this conjunction permits one to consistently switch between
different temporal reference systems which is a prerequisite for a quantum
notion of general covariance. Finally, we show that quantum uncertainties lead
to discontinuity in the relational dynamics when switching clocks.
| [
{
"created": "Tue, 9 Oct 2018 17:48:19 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jul 2020 16:23:35 GMT",
"version": "v2"
},
{
"created": "Mon, 4 Jan 2021 15:43:33 GMT",
"version": "v3"
}
] | 2021-01-05 | [
[
"Hoehn",
"Philipp A",
""
],
[
"Vanrietvelde",
"Augustin",
""
]
] | Every clock is a physical system and thereby ultimately quantum. A naturally arising question is how to describe time evolution relative to quantum clocks and, specifically, how the dynamics relative to different quantum clocks are related. This is a pressing issue in view of the multiple choice problem of time in quantum gravity, which posits that there is no distinguished choice of internal clock in generic general relativistic systems and that different choices lead to inequivalent quantum theories. Exploiting a recent approach to switching quantum reference systems (arXiv:1809.00556, arXiv:1809:05093), we exhibit a systematic method for switching between different clock choices in the quantum theory. We illustrate it by means of the parametrized particle, which, like gravity, features a Hamiltonian constraint. We explicitly switch between the quantum evolution relative to the non-relativistic time variable and that relative to the particle's position, which requires carefully regularizing the zero-modes in the so-called time-of-arrival observable. While this toy model is simple, our approach is general and directly amenable to quantum cosmology. It proceeds by systematically linking the reduced quantum theories relative to different clock choices via the clock-choice-neutral Dirac quantized theory, in analogy to coordinate changes on a manifold. This method suggests a new perspective on the multiple choice problem, indicating that it is rather a multiple choice feature of a complete relational quantum theory, taken as the conjunction of Dirac quantized and quantum deparametrized theories. Precisely this conjunction permits one to consistently switch between different temporal reference systems which is a prerequisite for a quantum notion of general covariance. Finally, we show that quantum uncertainties lead to discontinuity in the relational dynamics when switching clocks. |
1604.01385 | David A. Craig | David A. Craig | The consistent histories approach to loop quantum cosmology | 31 pages, 4 pdf figures. Invited review for special issue of Int. J.
Mod. Phys. D on loop quantum cosmology. Typos corrected | Int. J. Mod. Phys. D25 1642009 (2016) | 10.1142/S0218271816420098 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the application of the consistent (or decoherent) histories
formulation of quantum theory to canonical loop quantum cosmology. Conventional
quantum theory relies crucially on "measurements" to convert unrealized quantum
potentialities into physical outcomes that can be assigned probabilities. In
the early universe and other physical contexts in which there are no observers
or measuring apparatus (or indeed, in any closed quantum system), what criteria
determine which alternative outcomes may be realized and what their
probabilities are? In the consistent histories formulation it is the vanishing
of interference between the branch wave functions describing alternative
histories -- as determined by the system's decoherence functional -- that
determines which alternatives may be assigned probabilities. We describe the
consistent histories formulation and how it may be applied to canonical loop
quantum cosmology, describing in detail the application to homogeneous and
isotropic cosmological models with scalar matter. We show how the theory may be
used to make definite physical predictions in the absence of "observers". As an
application, we demonstrate how the theory predicts that loop quantum models
"bounce" from large volume to large volume, while conventional
"Wheeler-DeWitt"-quantized universes are invariably singular. We also briefly
indicate the relation to other work.
| [
{
"created": "Tue, 5 Apr 2016 19:51:12 GMT",
"version": "v1"
},
{
"created": "Tue, 3 May 2016 15:55:05 GMT",
"version": "v2"
},
{
"created": "Mon, 6 Jun 2016 05:48:17 GMT",
"version": "v3"
}
] | 2016-06-30 | [
[
"Craig",
"David A.",
""
]
] | We review the application of the consistent (or decoherent) histories formulation of quantum theory to canonical loop quantum cosmology. Conventional quantum theory relies crucially on "measurements" to convert unrealized quantum potentialities into physical outcomes that can be assigned probabilities. In the early universe and other physical contexts in which there are no observers or measuring apparatus (or indeed, in any closed quantum system), what criteria determine which alternative outcomes may be realized and what their probabilities are? In the consistent histories formulation it is the vanishing of interference between the branch wave functions describing alternative histories -- as determined by the system's decoherence functional -- that determines which alternatives may be assigned probabilities. We describe the consistent histories formulation and how it may be applied to canonical loop quantum cosmology, describing in detail the application to homogeneous and isotropic cosmological models with scalar matter. We show how the theory may be used to make definite physical predictions in the absence of "observers". As an application, we demonstrate how the theory predicts that loop quantum models "bounce" from large volume to large volume, while conventional "Wheeler-DeWitt"-quantized universes are invariably singular. We also briefly indicate the relation to other work. |
1308.6289 | Sanved Kolekar | Sanved Kolekar and T. Padmanabhan | Indistinguishability of thermal and quantum fluctuations | v1. 4 pages, no figure, v2. minor clarification added, v3. accepted
for publication in CQG Fast Track Comm | Class. Quant. Grav. Fast Track Comm 32, 202001 (2015) | 10.1088/0264-9381/32/20/202001 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The existence of Davies-Unruh temperature in a uniformly accelerated frame
shows that quantum fluctuations of the inertial vacuum state appears as thermal
fluctuations in the accelerated frame. Hence thermodynamic experiments cannot
distinguish between phenomena occurring in a thermal bath of temperature T in
the inertial frame from those in a frame accelerating through inertial vacuum
with the acceleration $a=2\pi T$. We show that this indisguishability between
quantum fluctuations and thermal fluctuations goes far beyond the fluctuations
in the vacuum state. We show by an exact calculation, that the reduced density
matrix for a uniformly accelerated observer when the quantum field is in a
thermal state of temperature $T^\prime$ is symmetric between acceleration
temperature $T = a/(2\pi)$ and the thermal bath temperature $T^\prime$. Thus
thermal phenomena cannot distinguish whether (i) one is accelerating with $a =
2\pi T$ through a bath of temperature $T^\prime$ or (ii) accelerating with
$a=2\pi T^\prime$ through a bath of temperature T. This shows that thermal and
quantum fluctuations in an accelerated frame affect the observer in a symmetric
manner. The implications are discussed.
| [
{
"created": "Wed, 28 Aug 2013 20:00:30 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Sep 2013 00:25:21 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Aug 2015 16:02:06 GMT",
"version": "v3"
}
] | 2018-06-20 | [
[
"Kolekar",
"Sanved",
""
],
[
"Padmanabhan",
"T.",
""
]
] | The existence of Davies-Unruh temperature in a uniformly accelerated frame shows that quantum fluctuations of the inertial vacuum state appears as thermal fluctuations in the accelerated frame. Hence thermodynamic experiments cannot distinguish between phenomena occurring in a thermal bath of temperature T in the inertial frame from those in a frame accelerating through inertial vacuum with the acceleration $a=2\pi T$. We show that this indisguishability between quantum fluctuations and thermal fluctuations goes far beyond the fluctuations in the vacuum state. We show by an exact calculation, that the reduced density matrix for a uniformly accelerated observer when the quantum field is in a thermal state of temperature $T^\prime$ is symmetric between acceleration temperature $T = a/(2\pi)$ and the thermal bath temperature $T^\prime$. Thus thermal phenomena cannot distinguish whether (i) one is accelerating with $a = 2\pi T$ through a bath of temperature $T^\prime$ or (ii) accelerating with $a=2\pi T^\prime$ through a bath of temperature T. This shows that thermal and quantum fluctuations in an accelerated frame affect the observer in a symmetric manner. The implications are discussed. |
gr-qc/9304005 | Mark A. Miller | O. Bostrom, M. Miller, L. Smolin | A New Discretization of Classical and Quantum General Relativity | 25 pages, LaTeX (calculational errors corrected, revised conclusions) | null | null | Goteborg ITP 94-5, SU-GP-93-4-1, CGPG-94/3-3 | gr-qc hep-lat hep-th | null | We propose a new discrete approximation to the Einstein equations, based on
the Capovilla-Dell-Jacobson form of the action for the Ashtekar variables. This
formulation is analogous to the Regge calculus in that the curvature has
support on sets of measure zero. Both a Lagrangian and Hamiltonian formulation
are proposed and we report partial results about the constraint algebra of the
Hamiltonian formulation. We find that the discrete versions of the
diffeomorphism constraints do not commute with each other or with the
Hamiltonian constraint.
| [
{
"created": "Mon, 5 Apr 1993 13:51:34 GMT",
"version": "v1"
},
{
"created": "Tue, 10 May 1994 21:02:16 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Bostrom",
"O.",
""
],
[
"Miller",
"M.",
""
],
[
"Smolin",
"L.",
""
]
] | We propose a new discrete approximation to the Einstein equations, based on the Capovilla-Dell-Jacobson form of the action for the Ashtekar variables. This formulation is analogous to the Regge calculus in that the curvature has support on sets of measure zero. Both a Lagrangian and Hamiltonian formulation are proposed and we report partial results about the constraint algebra of the Hamiltonian formulation. We find that the discrete versions of the diffeomorphism constraints do not commute with each other or with the Hamiltonian constraint. |
0707.1608 | Roberto Giambo' | Roberto Giamb\'o, Sara Quintavalle | Dimensional dependence of naked singularity formation in spherical
gravitational collapse | 11 pages, to appear with minor modifications on Class. Quantum Grav | Class.Quant.Grav.25:145003,2008 | 10.1088/0264-9381/25/14/145003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The complete spectrum of the endstates - naked singularities, or blackholes -
of gravitational collapse is analyzed for a wide class of $N$-dimensional
spacetimes in spherical symmetry, which includes and generalizes the dust
solutions and the case of vanishing radial stresses. The final fate of the
collapse is shown to be fully determined by the local behavior of a single
scalar function and by the dimension $N$ of the spacetime. In particular, the
``critical'' behavior of the N=4 spacetimes, where a sort of phase transition
from black hole to naked singularity can occur, is still present if N=5 but
does not occur if $N > 5$, independently from the initial data of the collapse.
Physically, the results turn out to be related to the kinematical properties of
the considered solutions.
| [
{
"created": "Wed, 11 Jul 2007 13:04:18 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Jun 2008 17:12:52 GMT",
"version": "v2"
}
] | 2010-03-24 | [
[
"Giambó",
"Roberto",
""
],
[
"Quintavalle",
"Sara",
""
]
] | The complete spectrum of the endstates - naked singularities, or blackholes - of gravitational collapse is analyzed for a wide class of $N$-dimensional spacetimes in spherical symmetry, which includes and generalizes the dust solutions and the case of vanishing radial stresses. The final fate of the collapse is shown to be fully determined by the local behavior of a single scalar function and by the dimension $N$ of the spacetime. In particular, the ``critical'' behavior of the N=4 spacetimes, where a sort of phase transition from black hole to naked singularity can occur, is still present if N=5 but does not occur if $N > 5$, independently from the initial data of the collapse. Physically, the results turn out to be related to the kinematical properties of the considered solutions. |
1905.07638 | Oldrich Semerak | O. Semer\'ak, M. Basovn\'ik, P. Kotla\v{r}\'ik | Schwarzschild binary supported by an Appell ring | 20 pages, 17 figures | Physical Review D 99 (2019) 064050 | 10.1103/PhysRevD.99.064050 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We continue to study black holes subjected to strong sources of gravity,
again paying special attention to the behaviour of geometry in the black-hole
interior. After examining, in previous two papers, the deformation arising in
the Majumdar-Papapetrou binary of extremally charged black holes and that of a
Schwarzschild black hole due to a surrounding (Bach-Weyl) ring, we consider
here the system of two Schwarzschild-type black holes held apart by the Appell
ring. After verifying that such a configuration can be in a strut-free
equilibrium along certain lines in a parameter space, we compute several basic
geometric characteristics of the equilibrium configurations. Then, like in
previous papers, we calculate and visualize simple invariants determined by the
metric (lapse or, equivalently, potential), by its first derivatives
(gravitational acceleration) and by its second derivatives (Kretschmann
scalar). Extension into the black-hole interior is achieved along particular
null geodesics starting tangentially to the horizon. In contrast to the case
involving the Bach-Weyl ring, here each single black hole is placed
asymmetrically with respect to the equatorial plane (given by the Appell ring)
and the interior geometry is really deformed in a non-symmetrical way. Inside
the black holes, we again found regions of negative Kretschmann scalar in some
cases.
| [
{
"created": "Sat, 18 May 2019 20:13:58 GMT",
"version": "v1"
}
] | 2019-05-21 | [
[
"Semerák",
"O.",
""
],
[
"Basovník",
"M.",
""
],
[
"Kotlařík",
"P.",
""
]
] | We continue to study black holes subjected to strong sources of gravity, again paying special attention to the behaviour of geometry in the black-hole interior. After examining, in previous two papers, the deformation arising in the Majumdar-Papapetrou binary of extremally charged black holes and that of a Schwarzschild black hole due to a surrounding (Bach-Weyl) ring, we consider here the system of two Schwarzschild-type black holes held apart by the Appell ring. After verifying that such a configuration can be in a strut-free equilibrium along certain lines in a parameter space, we compute several basic geometric characteristics of the equilibrium configurations. Then, like in previous papers, we calculate and visualize simple invariants determined by the metric (lapse or, equivalently, potential), by its first derivatives (gravitational acceleration) and by its second derivatives (Kretschmann scalar). Extension into the black-hole interior is achieved along particular null geodesics starting tangentially to the horizon. In contrast to the case involving the Bach-Weyl ring, here each single black hole is placed asymmetrically with respect to the equatorial plane (given by the Appell ring) and the interior geometry is really deformed in a non-symmetrical way. Inside the black holes, we again found regions of negative Kretschmann scalar in some cases. |
gr-qc/9603060 | Philip Papadopoulos | Roberto Go'mez (1), Pablo Laguna (2), Philippos Papadopoulos (2) and
Jeff Winicour (1) ((1) University of Pittsburgh, (2) Penn State University) | Cauchy-characteristic Evolution of Einstein-Klein-Gordon Systems | Submitted to Phys. Rev. D, 16 pages, revtex, 7 figures available at
http://nr.astro.psu.edu:8080/preprints.html | Phys.Rev.D54:4719-4727,1996 | 10.1103/PhysRevD.54.4719 | CGPG-96/4-1 | gr-qc | null | A Cauchy-characteristic initial value problem for the Einstein-Klein-Gordon
system with spherical symmetry is presented. Initial data are specified on the
union of a space-like and null hypersurface. The development of the data is
obtained with the combination of a constrained Cauchy evolution in the interior
domain and a characteristic evolution in the exterior, asymptotically flat
region. The matching interface between the space-like and characteristic
foliations is constructed by imposing continuity conditions on metric,
extrinsic curvature and scalar field variables, ensuring smoothness across the
matching surface. The accuracy of the method is established for all ranges of
$M/R$, most notably, with a detailed comparison of invariant observables
against reference solutions obtained with a calibrated, global, null algorithm.
| [
{
"created": "Fri, 29 Mar 1996 21:15:36 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Go'mez",
"Roberto",
"",
"University of Pittsburgh"
],
[
"Laguna",
"Pablo",
"",
"Penn State University"
],
[
"Papadopoulos",
"Philippos",
"",
"Penn State University"
],
[
"Winicour",
"Jeff",
"",
"University of Pittsburgh"
]
] | A Cauchy-characteristic initial value problem for the Einstein-Klein-Gordon system with spherical symmetry is presented. Initial data are specified on the union of a space-like and null hypersurface. The development of the data is obtained with the combination of a constrained Cauchy evolution in the interior domain and a characteristic evolution in the exterior, asymptotically flat region. The matching interface between the space-like and characteristic foliations is constructed by imposing continuity conditions on metric, extrinsic curvature and scalar field variables, ensuring smoothness across the matching surface. The accuracy of the method is established for all ranges of $M/R$, most notably, with a detailed comparison of invariant observables against reference solutions obtained with a calibrated, global, null algorithm. |
0811.4484 | Grigory Vereshkov | Leonid Marochnik (1), Daniel Usikov, and Grigory Vereshkov (2) ((1)
University of Maryland, College Park, (2) Research Institute of Physics,
Southern Federal University) | Graviton, ghost and instanton condensation on horizon scale of the
Universe. Dark energy as a macroscopic effect of quantum gravity | 92 pp, 4 figs, REVTeX 4; v2: misprints corrected; some footnotes and
refs added | null | null | null | gr-qc astro-ph hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that cosmological acceleration, Dark Energy (DE) effect is a
consequence of the zero rest mass, conformal non-invariance of gravitons, and
1-loop finiteness of quantum gravity (QG). The effect is due to graviton-ghost
condensates arising from the interference of quantum coherent states. The
theory is constructed as follows: Faddeev-Popov-De Witt gauged path integral ->
factorization of classical and quantum variables -> transition to the 1-loop
approximation -> choice of ghost sector, satisfying 1-loop finiteness of the
theory off the mass shell. The Bogolyubov-Born-Green-Kirckwood-Yvon (BBGKY)
chain for the spectral function of gravitons renormalized by ghosts is used to
build a theory of gravitons in the isotropic Universe. We found three exact
solutions of the equations that describe virtual graviton and ghost condensates
as well as condensates of instanton fluctuations. Exact solutions correspond to
various condensates with different graviton-ghost compositions. The formalism
of the BBGKY chain takes into account the contribution of non-relativistic
matter in the formation of a common self-consistent gravitational field. It is
shown that the era of non-relativistic matter dominance must be replaced by an
era of dominance of graviton-ghost condensate. Pre-asymptotic state of DE is a
condensate of virtual gravitons and ghosts with a constant conformal
wavelength. The asymptotic state predicted by the theory is a graviton-ghost
condensate of constant physical wavelength in the De Sitter space. Such DE
phenomenon is presented in the form of the model that interpolates the exact
solutions of equations of 1-loop QG. Processing of observational DE data
extracted from the Hubble diagram for supernovae SNIa suggests that the
graviton-ghost condensate is an adequate variable component of DE.
| [
{
"created": "Thu, 27 Nov 2008 08:34:37 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Sep 2009 07:57:14 GMT",
"version": "v2"
}
] | 2009-09-07 | [
[
"Marochnik",
"Leonid",
""
],
[
"Usikov",
"Daniel",
""
],
[
"Vereshkov",
"Grigory",
""
]
] | We show that cosmological acceleration, Dark Energy (DE) effect is a consequence of the zero rest mass, conformal non-invariance of gravitons, and 1-loop finiteness of quantum gravity (QG). The effect is due to graviton-ghost condensates arising from the interference of quantum coherent states. The theory is constructed as follows: Faddeev-Popov-De Witt gauged path integral -> factorization of classical and quantum variables -> transition to the 1-loop approximation -> choice of ghost sector, satisfying 1-loop finiteness of the theory off the mass shell. The Bogolyubov-Born-Green-Kirckwood-Yvon (BBGKY) chain for the spectral function of gravitons renormalized by ghosts is used to build a theory of gravitons in the isotropic Universe. We found three exact solutions of the equations that describe virtual graviton and ghost condensates as well as condensates of instanton fluctuations. Exact solutions correspond to various condensates with different graviton-ghost compositions. The formalism of the BBGKY chain takes into account the contribution of non-relativistic matter in the formation of a common self-consistent gravitational field. It is shown that the era of non-relativistic matter dominance must be replaced by an era of dominance of graviton-ghost condensate. Pre-asymptotic state of DE is a condensate of virtual gravitons and ghosts with a constant conformal wavelength. The asymptotic state predicted by the theory is a graviton-ghost condensate of constant physical wavelength in the De Sitter space. Such DE phenomenon is presented in the form of the model that interpolates the exact solutions of equations of 1-loop QG. Processing of observational DE data extracted from the Hubble diagram for supernovae SNIa suggests that the graviton-ghost condensate is an adequate variable component of DE. |
1807.01379 | Gerard Clement | G\'erard Cl\'ement | Rotating magnetized black diholes | 25 pages, revised version published in Phys. Rev. D | Phys. Rev. D 98, 104003 (2018) | 10.1103/PhysRevD.98.104003 | LAPTH-020/18 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze a four-parameter class of asymptotically flat magnetized solutions
to the Einstein-Maxwell equations constructed by Manko et al., and show that
these represent systems of two co-rotating extreme black holes with equal
masses and electric charges, and opposite magnetic and NUT charges, connected
by a cosmic string. We discuss several three-parameter subclasses, and
determine in each case the parameter domain in which the ring singularity is
absent. We find a two-parameter subclass and a one-parameter subclass where the
conical singularity is also absent in the horizon co-rotating frame.
| [
{
"created": "Tue, 3 Jul 2018 21:50:32 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Nov 2018 13:15:48 GMT",
"version": "v2"
}
] | 2018-11-14 | [
[
"Clément",
"Gérard",
""
]
] | We analyze a four-parameter class of asymptotically flat magnetized solutions to the Einstein-Maxwell equations constructed by Manko et al., and show that these represent systems of two co-rotating extreme black holes with equal masses and electric charges, and opposite magnetic and NUT charges, connected by a cosmic string. We discuss several three-parameter subclasses, and determine in each case the parameter domain in which the ring singularity is absent. We find a two-parameter subclass and a one-parameter subclass where the conical singularity is also absent in the horizon co-rotating frame. |
1808.01372 | Jordan Wilson-Gerow | Jordan Wilson-Gerow, Colby DeLisle, Philip Stamp | A functional approach to soft graviton scattering and BMS charges | 20 pages, 4 figures | 2018 Class. Quantum Grav. 35 164001 | 10.1088/1361-6382/aacfef | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the interaction between a matter system and soft gravitons. We
use a functional eikonal expansion to deal with the infrared divergences, and
introduce a "composite generating functional" which allows us to calculate a
decoherence functional for the time evolution of the system. These techniques
allow us to formulate scattering problems in a way which deals consistently
with infrared effects, as well as being manifestly diffeomorphism invariant. We
show how the asymptotic form of the decoherence functional can be written in
terms of the infinitely many conserved charges associated with asymptotic BMS
symmetries, and allow us to address the question of how much information is
lost during the scattering.
| [
{
"created": "Fri, 3 Aug 2018 21:48:38 GMT",
"version": "v1"
}
] | 2018-08-07 | [
[
"Wilson-Gerow",
"Jordan",
""
],
[
"DeLisle",
"Colby",
""
],
[
"Stamp",
"Philip",
""
]
] | We consider the interaction between a matter system and soft gravitons. We use a functional eikonal expansion to deal with the infrared divergences, and introduce a "composite generating functional" which allows us to calculate a decoherence functional for the time evolution of the system. These techniques allow us to formulate scattering problems in a way which deals consistently with infrared effects, as well as being manifestly diffeomorphism invariant. We show how the asymptotic form of the decoherence functional can be written in terms of the infinitely many conserved charges associated with asymptotic BMS symmetries, and allow us to address the question of how much information is lost during the scattering. |
1004.0627 | Ahmad Sheykhi | Ahmad Sheykhi | Entropic Corrections to Friedmann Equations | 4 pages, the version appears in Phys. Rev. D | Phys.Rev.D81:104011,2010 | 10.1103/PhysRevD.81.104011 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | Recently, Verlinde discussed that gravity can be understood as an entropic
force caused by changes in the information associated with the positions of
material bodies. In the Verlinde's argument, the area law of the black hole
entropy plays a crucial role. However, the entropy-area relation can be
modified from the inclusion of quantum effects, motivated from the loop quantum
gravity. In this note, by employing this modified entropy-area relation, we
derive corrections to Newton's law of gravitation as well as modified Friedman
equations by adopting the viewpoint that gravity can be emerged as an entropic
force. Our study further supports the universality of the log correction and
provides a strong consistency check on Verlinde's model.
| [
{
"created": "Tue, 30 Mar 2010 08:33:38 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Apr 2010 07:14:24 GMT",
"version": "v2"
},
{
"created": "Sat, 10 Apr 2010 03:48:10 GMT",
"version": "v3"
},
{
"created": "Tue, 27 Apr 2010 04:37:04 GMT",
"version": "v4"
}
] | 2010-05-19 | [
[
"Sheykhi",
"Ahmad",
""
]
] | Recently, Verlinde discussed that gravity can be understood as an entropic force caused by changes in the information associated with the positions of material bodies. In the Verlinde's argument, the area law of the black hole entropy plays a crucial role. However, the entropy-area relation can be modified from the inclusion of quantum effects, motivated from the loop quantum gravity. In this note, by employing this modified entropy-area relation, we derive corrections to Newton's law of gravitation as well as modified Friedman equations by adopting the viewpoint that gravity can be emerged as an entropic force. Our study further supports the universality of the log correction and provides a strong consistency check on Verlinde's model. |
0902.0481 | Edvin Deadman | E. Deadman, J. M. Stewart | Numerical Relativity and Asymptotic Flatness | 24 pages, to be published in Classical and Quantum Gravity | Class.Quant.Grav.26:065008,2009 | 10.1088/0264-9381/26/6/065008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is highly plausible that the region of space-time far from an isolated
gravitating body is, in some sense, asymptotically Minkowskian. However
theoretical studies of the full nonlinear theory, initiated by Bondi et al.
(1962), Sachs (1962) and Newman & Unti (1962), rely on careful, clever,
a-priori choices of chart (and tetrad) and so are not readily accessible to the
numerical relativist, who chooses her/his chart on the basis of quite different
grounds. This paper seeks to close this gap. Starting from data available in a
typical numerical evolution, we construct a chart and tetrad which is,
asymptotically, sufficiently close to the theoretical ones, so that the key
concepts of Bondi news function, Bondi mass and its rate of decrease can be
estimated. In particular these esimates can be expressed in the numerical
relativist's chart as numerical relativity recipes.
| [
{
"created": "Tue, 3 Feb 2009 11:40:30 GMT",
"version": "v1"
}
] | 2009-09-30 | [
[
"Deadman",
"E.",
""
],
[
"Stewart",
"J. M.",
""
]
] | It is highly plausible that the region of space-time far from an isolated gravitating body is, in some sense, asymptotically Minkowskian. However theoretical studies of the full nonlinear theory, initiated by Bondi et al. (1962), Sachs (1962) and Newman & Unti (1962), rely on careful, clever, a-priori choices of chart (and tetrad) and so are not readily accessible to the numerical relativist, who chooses her/his chart on the basis of quite different grounds. This paper seeks to close this gap. Starting from data available in a typical numerical evolution, we construct a chart and tetrad which is, asymptotically, sufficiently close to the theoretical ones, so that the key concepts of Bondi news function, Bondi mass and its rate of decrease can be estimated. In particular these esimates can be expressed in the numerical relativist's chart as numerical relativity recipes. |
2012.14429 | Cl\'audio Gomes | Cl\'audio Gomes and Orfeu Bertolami | Stability Conditions for the Horndeski Scalar Field Gravity Model | 12 pages | null | 10.1088/1475-7516/2022/04/008 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We constrain the viable models of Horndeski gravity, written in its
equivalent Generalised Galileon version, by resorting to the Witten positive
energy theorem. We find that the free function $G_3(\phi, X)$ in the Lagrangian
is constrained to be a function solely of the scalar field, $G_3(\phi)$, and
relations among the free functions are found. Other criterion for stability are
also analysed, such as the attractiveness of gravity, the Dolgov-Kawasacki
instability and the energy conditions. Some applications for Cosmology are
discussed
| [
{
"created": "Sun, 27 Dec 2020 13:28:58 GMT",
"version": "v1"
}
] | 2022-04-12 | [
[
"Gomes",
"Cláudio",
""
],
[
"Bertolami",
"Orfeu",
""
]
] | We constrain the viable models of Horndeski gravity, written in its equivalent Generalised Galileon version, by resorting to the Witten positive energy theorem. We find that the free function $G_3(\phi, X)$ in the Lagrangian is constrained to be a function solely of the scalar field, $G_3(\phi)$, and relations among the free functions are found. Other criterion for stability are also analysed, such as the attractiveness of gravity, the Dolgov-Kawasacki instability and the energy conditions. Some applications for Cosmology are discussed |
1910.13329 | Bogeun Gwak | Bogeun Gwak | Weak Cosmic Censorship in Kerr-Sen Black Hole under Charged Scalar Field | 15 pages, 5 figures, published in JCAP | JCAP 03 (2020) 058 | 10.1088/1475-7516/2020/03/058 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the weak cosmic censorship conjecture for Kerr-Sen black
holes, which are solutions to the four-dimensional low-energy effective field
theory for the heterotic string theory, based on the scattering of a charged
scalar field. When the fluxes of the scalar field are assumed to transfer its
conserved quantities to the black hole, extremal and near-extremal black holes
cannot be over-spun and over-charged in their first-order variations, which is
sufficient to conclude that the weak cosmic censorship conjecture is valid for
Kerr-Sen black holes. We confirm our conclusion by relating it to the first,
second, and third laws of thermodynamics.
| [
{
"created": "Tue, 29 Oct 2019 15:48:28 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Mar 2020 23:33:28 GMT",
"version": "v2"
}
] | 2020-04-01 | [
[
"Gwak",
"Bogeun",
""
]
] | We investigate the weak cosmic censorship conjecture for Kerr-Sen black holes, which are solutions to the four-dimensional low-energy effective field theory for the heterotic string theory, based on the scattering of a charged scalar field. When the fluxes of the scalar field are assumed to transfer its conserved quantities to the black hole, extremal and near-extremal black holes cannot be over-spun and over-charged in their first-order variations, which is sufficient to conclude that the weak cosmic censorship conjecture is valid for Kerr-Sen black holes. We confirm our conclusion by relating it to the first, second, and third laws of thermodynamics. |
gr-qc/0104067 | Claus Laemmerzahl | Claus L\"ammerzahl, Hansj\"org Dittus, Achim Peters, Stephan Schiller | OPTIS - a satellite-based test of Special and General Relativity | To appear in Class. Quantum Grav | Class.Quant.Grav. 18 (2001) 2499-2508 | 10.1088/0264-9381/18/13/312 | null | gr-qc | null | A new satellite based test of Special and General Relativity is proposed. For
the Michelson-Morley experiment we expect an improvement of at least three
orders of magnitude, and for the Kennedy-Thorndike experiment an improvement of
more than one order of magnitude. Furthermore, an improvement by two orders of
the test of the universality of the gravitational red shift by comparison of an
atomic clock with an optical clock is projected.
The tests are based on ultrastable optical cavities, an atomic clock and a
comb generator.
| [
{
"created": "Fri, 20 Apr 2001 16:57:06 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Lämmerzahl",
"Claus",
""
],
[
"Dittus",
"Hansjörg",
""
],
[
"Peters",
"Achim",
""
],
[
"Schiller",
"Stephan",
""
]
] | A new satellite based test of Special and General Relativity is proposed. For the Michelson-Morley experiment we expect an improvement of at least three orders of magnitude, and for the Kennedy-Thorndike experiment an improvement of more than one order of magnitude. Furthermore, an improvement by two orders of the test of the universality of the gravitational red shift by comparison of an atomic clock with an optical clock is projected. The tests are based on ultrastable optical cavities, an atomic clock and a comb generator. |
2307.01055 | Yan Wang | Wen-Fan Feng, Tan Liu, Jie-Wen Chen, Yan Wang and Soumya D. Mohanty | Effects of spin-orbit coupling on gravitational waveforms from a
triaxial non-aligned neutron star in a binary system | 17 pages, 9 figures. Match the version accepted by PRD | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Spinning neutron stars (NSs) can emit continuous gravitational waves (GWs)
that carry a wealth of information about the compact object. If such a signal
is detected, it will provide us with new insight into the physical properties
of matter under extreme conditions. Future space-based GW detectors, such as
LISA and TianQin, can potentially detect some double NSs in tight binaries with
orbital periods shorter than 10 minutes. The possibility of a successful
directed search for continuous GWs from the spinning NS in such a binary system
identified by LISA/TianQin will be significantly increased with the proposed
next-generation ground-based GW observatories, such as Cosmic Explorer and
Einstein Telescope. Searching for continuous GWs from such a tight binary
system requires highly accurate waveform templates that account for the
interaction of the NS with its companion. In this spirit, we derive analytic
approximations that describe the GWs emitted by a triaxial non-aligned NS in a
binary system in which the effects of spin-orbit coupling have been
incorporated. The difference with the widely used waveform for the isolated NS
is estimated and the parameter estimation accuracy of an example signal using
Cosmic Explorer is calculated. For a typical tight double NS system with a
6~min orbital period, the angular frequency correction of the spinning NS in
this binary due to spin precession is $\sim 10^{-6}~{\rm Hz}$, which is in the
same order of magnitude as the angular frequency of orbital precession. The
fitting factor between the waveforms with and without spin precession will drop
to less than 0.97 after a few days ($\sim 10^5~{\rm s}$). We find that
spin-orbit coupling has the potential to improve the accuracy of parameter
estimation, especially for the binary inclination angle and spin precession
cone opening angle, by up to 3 orders of magnitude. (Abridged)
| [
{
"created": "Mon, 3 Jul 2023 14:35:16 GMT",
"version": "v1"
},
{
"created": "Sun, 10 Sep 2023 07:38:44 GMT",
"version": "v2"
}
] | 2023-09-12 | [
[
"Feng",
"Wen-Fan",
""
],
[
"Liu",
"Tan",
""
],
[
"Chen",
"Jie-Wen",
""
],
[
"Wang",
"Yan",
""
],
[
"Mohanty",
"Soumya D.",
""
]
] | Spinning neutron stars (NSs) can emit continuous gravitational waves (GWs) that carry a wealth of information about the compact object. If such a signal is detected, it will provide us with new insight into the physical properties of matter under extreme conditions. Future space-based GW detectors, such as LISA and TianQin, can potentially detect some double NSs in tight binaries with orbital periods shorter than 10 minutes. The possibility of a successful directed search for continuous GWs from the spinning NS in such a binary system identified by LISA/TianQin will be significantly increased with the proposed next-generation ground-based GW observatories, such as Cosmic Explorer and Einstein Telescope. Searching for continuous GWs from such a tight binary system requires highly accurate waveform templates that account for the interaction of the NS with its companion. In this spirit, we derive analytic approximations that describe the GWs emitted by a triaxial non-aligned NS in a binary system in which the effects of spin-orbit coupling have been incorporated. The difference with the widely used waveform for the isolated NS is estimated and the parameter estimation accuracy of an example signal using Cosmic Explorer is calculated. For a typical tight double NS system with a 6~min orbital period, the angular frequency correction of the spinning NS in this binary due to spin precession is $\sim 10^{-6}~{\rm Hz}$, which is in the same order of magnitude as the angular frequency of orbital precession. The fitting factor between the waveforms with and without spin precession will drop to less than 0.97 after a few days ($\sim 10^5~{\rm s}$). We find that spin-orbit coupling has the potential to improve the accuracy of parameter estimation, especially for the binary inclination angle and spin precession cone opening angle, by up to 3 orders of magnitude. (Abridged) |
1210.6807 | Laszlo Arpad Gergely | M\'arton T\'apai, Zolt\'an Keresztes, L\'aszl\'o \'Arp\'ad Gergely | Gravitational waveforms for black hole binaries with unequal masses | submitted to the proceedings of the conference on Relativity and
Gravitation: 100 Years after Einstein in Prague | Springer Proceedings in Physics 157, 455-458 (2014) | 10.1007/978-3-319-06761-2_65 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derived a post-Newtonian (PN) inspiral only gravitational waveform for
unequal mass, spinning black hole binaries. Towards the end of the inspiral the
larger spin dominates over the orbital angular momentum (while the smaller spin
is negligible), hence the name Spin-Dominated Waveforms (SDW). Such systems are
common sources for future gravitational wave detectors and during the inspiral
the largest amplitude waves are emitted exactly in its last part. The SDW
waveforms emerge as a double expansion in the PN parameter and the ratio of the
orbital angular momentum to the dominant spin.
| [
{
"created": "Thu, 25 Oct 2012 12:22:23 GMT",
"version": "v1"
}
] | 2014-09-12 | [
[
"Tápai",
"Márton",
""
],
[
"Keresztes",
"Zoltán",
""
],
[
"Gergely",
"László Árpád",
""
]
] | We derived a post-Newtonian (PN) inspiral only gravitational waveform for unequal mass, spinning black hole binaries. Towards the end of the inspiral the larger spin dominates over the orbital angular momentum (while the smaller spin is negligible), hence the name Spin-Dominated Waveforms (SDW). Such systems are common sources for future gravitational wave detectors and during the inspiral the largest amplitude waves are emitted exactly in its last part. The SDW waveforms emerge as a double expansion in the PN parameter and the ratio of the orbital angular momentum to the dominant spin. |
2105.02086 | Adrian Macquet | Adrian Macquet, Marie-Anne Bizouard, Eric Burns, Nelson Christensen,
Michael Coughlin, Zorawar Wadiasingh, George Younes | Search for Long-duration Gravitational-wave Signals Associated with
Magnetar Giant Flares | null | The Astrophysical Journal, 918:80 (7pp), 2021 September 10 | 10.3847/1538-4357/ac0efd | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Magnetar giant flares are rare and highly energetic phenomena observed in the
transient sky whose emission mechanisms are still not fully understood.
Depending on the nature of the excited modes of the magnetar, they are also
expected to emit gravitational waves, which may bring unique information about
the dynamics of the excitation. A few magnetar giant flares have been proposed
to be associated to short gamma-ray bursts. In this paper we revisit, with a
new gravitational-wave search algorithm, the possible emission of gravitational
waves from four magnetar giant flares within 5 Mpc. While no gravitational-wave
signals were observed, we discuss the future prospects of detecting signals
with more sensitive gravitational-wave detectors. We in particular show that
galactic magnetar giant flares that emit at least 1% of their electromagnetic
energy as gravitational waves could be detected during the planned observing
run of the LIGO and Virgo detectors at design sensitivity, with even better
prospects for third generation detectors.
| [
{
"created": "Wed, 5 May 2021 14:38:02 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Sep 2021 14:47:25 GMT",
"version": "v2"
}
] | 2021-09-14 | [
[
"Macquet",
"Adrian",
""
],
[
"Bizouard",
"Marie-Anne",
""
],
[
"Burns",
"Eric",
""
],
[
"Christensen",
"Nelson",
""
],
[
"Coughlin",
"Michael",
""
],
[
"Wadiasingh",
"Zorawar",
""
],
[
"Younes",
"George",
"... | Magnetar giant flares are rare and highly energetic phenomena observed in the transient sky whose emission mechanisms are still not fully understood. Depending on the nature of the excited modes of the magnetar, they are also expected to emit gravitational waves, which may bring unique information about the dynamics of the excitation. A few magnetar giant flares have been proposed to be associated to short gamma-ray bursts. In this paper we revisit, with a new gravitational-wave search algorithm, the possible emission of gravitational waves from four magnetar giant flares within 5 Mpc. While no gravitational-wave signals were observed, we discuss the future prospects of detecting signals with more sensitive gravitational-wave detectors. We in particular show that galactic magnetar giant flares that emit at least 1% of their electromagnetic energy as gravitational waves could be detected during the planned observing run of the LIGO and Virgo detectors at design sensitivity, with even better prospects for third generation detectors. |
1006.1830 | Ron Lenk | Ron Lenk | Classical Electron Model with QED Corrections | 6 pages, comments welcome | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we build a metric for a classical general relativistic
electron model with QED corrections. We calculate the stress-energy tensor for
the radiative corrections to the Coulomb potential in both the near-field and
far-field approximations. We solve the three field equations in both cases by
using a perturbative expansion to first order in alpha (the fine-structure
constant) while insisting that the usual (+, +, -, -) structure of the
stress-energy tensor is maintained. The resulting metric models a
(non-spinning) electron with a Coulomb potential with QED corrections, and
maintains masslessness of the photon to self-consistent order. The near-field
solution resembles the metric of a global monopole.
| [
{
"created": "Tue, 8 Jun 2010 17:26:22 GMT",
"version": "v1"
}
] | 2010-06-10 | [
[
"Lenk",
"Ron",
""
]
] | In this article we build a metric for a classical general relativistic electron model with QED corrections. We calculate the stress-energy tensor for the radiative corrections to the Coulomb potential in both the near-field and far-field approximations. We solve the three field equations in both cases by using a perturbative expansion to first order in alpha (the fine-structure constant) while insisting that the usual (+, +, -, -) structure of the stress-energy tensor is maintained. The resulting metric models a (non-spinning) electron with a Coulomb potential with QED corrections, and maintains masslessness of the photon to self-consistent order. The near-field solution resembles the metric of a global monopole. |
gr-qc/9509005 | null | E. Recami, F. Raciti, W.A. Rodrigues Jr., and V.T. Zanchin | Micro--universes and ``strong black holes'': a purely geometric approach
to elementary particles | standard latex file, using wspro.sty | null | null | null | gr-qc | null | We present here a panoramic view of our unified, bi--scale theory of
gravitational and strong interactions [which is mathematically analogous to the
last version of N.Rosen's bi--metric theory; and yields physical results
similar to strong gravity's]. This theory, developed during the last 15 years,
is purely geometrical in nature, adopting the methods of General Relativity for
the description of hadron structure and strong interactions. In particular,
hadrons are associated with `` strong black--holes'', from the external point
of view, and with ``micro--universes'', from the internal point of view. Among
the results herein presented, let us mention the derivation: (i) of confinement
and (ii) asymptotic freedom for the hadron constituents; (iii) of the Yukawa
behaviour for the strong potential at the static limit; (iv) of the strong
coupling ``constant'', and (v) of mesonic mass spectra.
| [
{
"created": "Mon, 4 Sep 1995 10:09:49 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"Recami",
"E.",
""
],
[
"Raciti",
"F.",
""
],
[
"Rodrigues",
"W. A.",
"Jr."
],
[
"Zanchin",
"V. T.",
""
]
] | We present here a panoramic view of our unified, bi--scale theory of gravitational and strong interactions [which is mathematically analogous to the last version of N.Rosen's bi--metric theory; and yields physical results similar to strong gravity's]. This theory, developed during the last 15 years, is purely geometrical in nature, adopting the methods of General Relativity for the description of hadron structure and strong interactions. In particular, hadrons are associated with `` strong black--holes'', from the external point of view, and with ``micro--universes'', from the internal point of view. Among the results herein presented, let us mention the derivation: (i) of confinement and (ii) asymptotic freedom for the hadron constituents; (iii) of the Yukawa behaviour for the strong potential at the static limit; (iv) of the strong coupling ``constant'', and (v) of mesonic mass spectra. |
1002.2329 | Lo\"ic Rolland | The Virgo collaboration: T. Accadia, F. Acernese, F. Antonucci, S.
Aoudia, K. G. Arun, P. Astone, G. Ballardin, F. Barone, M. Barsuglia, Th. S.
Bauer, M.G. Beker, A. Belletoile, S. Bigotta, S. Birindelli, M. Bitossi, M.
A. Bizouard, M. Blom, C. Boccara, F. Bondu, L. Bonelli, R. Bonnand, L. Bosi,
S. Braccini, C. Bradaschia, A. Brillet, V. Brisson, R. Budzynski, T. Bulik,
H. J. Bulten, D. Buskulic, C. Buy, G. Cagnoli, E. Calloni, E. Campagna, B.
Canuel, F. Carbognani, F. Cavalier, R. Cavalieri, G. Cella, E. Cesarini, E.
Chassande-Mottin, A. Chincarini, F. Cleva, E. Coccia, C. N. Colacino, J.
Colas, A. Colla, M. Colombini, A. Corsi, J.-P. Coulon, E. Cuoco, S.
D'Antonio, A. Dari, V. Dattilo, M. Davier, R. Day, R. De Rosa, M. del Prete,
L. Di Fiore, A. Di Lieto, M. Di Paolo Emilio, A. Di Virgilio, A. Dietz, M.
Drago, V. Fafone, I. Ferrante, F. Fidecaro, I. Fiori, R. Flaminio, J.-D.
Fournier, J. Franc, S. Frasca, F. Frasconi, A. Freise, M. Galimberti, L.
Gammaitoni, F. Garufi, G. Gemme, E. Genin, A. Gennai, A. Giazotto, R. Gouaty,
M. Granata, C. Greverie, G. M. Guidi, H. Heitmann, P. Hello, S. Hild, D.
Huet, P. Jaranowski, I. Kowalska, A. Krolak, N. Leroy, N. Letendre, T. G. F.
Li, M. Lorenzini, V. Loriette, G. Losurdo, J. M. Mackowski, E. Majorana, I.
Maksimovic, N. Man, M. Mantovani, F. Marchesoni, F. Marion, J. Marque, F.
Martelli, A. Masserot, C. Michel, L. Milano, Y. Minenkov, M. Mohan, J.
Moreau, N. Morgado, A. Morgia, S. Mosca, V. Moscatelli, B. Mours, I. Neri, F.
Nocera, G. Pagliaroli, L. Palladino, C. Palomba, F. Paoletti, S. Pardi, M.
Parisi, A. Pasqualetti, R. Passaquieti, D. Passuello, G. Persichetti, M.
Pichot, F. Piergiovanni, M. Pietka, L. Pinard, R. Poggiani, M. Prato, G. A.
Prodi, M. Punturo, P. Puppo, O. Rabaste, D. S. Rabeling, P. Rapagnani, V. Re,
T. Regimbau, F. Ricci, F. Robinet, A. Rocchi, L. Rolland, R. Romano, D.
Rosinska, P. Ruggi, B. Sassolas, D. Sentenac, R. Sturani, B. Swinkels, A.
Toncelli, M. Tonelli, O. Torre, E. Tournefier, F. Travasso, J. Trummer, G.
Vajente, J. F. J. van den Brand, S. van der Putten, M. Vavoulidis, G.
Vedovato, D. Verkindt, F. Vetrano, A. Vicere, J.-Y. Vinet, H. Vocca, M. Was,
M. Yvert | Virgo calibration and reconstruction of the gravitational wave strain
during VSR1 | 8 pages, 8 figures, proceedings of Amaldi 8 conference, to be
published in Journal of Physics Conference Series (JPCS). Second release:
correct typos | J.Phys.Conf.Ser.228:012015,2010 | 10.1088/1742-6596/228/1/012015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Virgo is a kilometer-length interferometer for gravitational waves detection
located near Pisa. Its first science run, VSR1, occured from May to October
2007. The aims of the calibration are to measure the detector sensitivity and
to reconstruct the time series of the gravitational wave strain h(t). The
absolute length calibration is based on an original non-linear reconstruction
of the differential arm length variations in free swinging Michelson
configurations. It uses the laser wavelength as length standard. This method is
used to calibrate the frequency dependent response of the Virgo mirror
actuators and derive the detector in-loop response and sensitivity within ~5%.
The principle of the strain reconstruction is highlighted and the h(t)
systematic errors are estimated. A photon calibrator is used to check the sign
of h(t). The reconstructed h(t) during VSR1 is valid from 10 Hz up to 10 kHz
with systematic errors estimated to 6% in amplitude. The phase error is
estimated to be 70 mrad below 1.9 kHz and 6 micro-seconds above.
| [
{
"created": "Thu, 11 Feb 2010 12:41:31 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Feb 2010 09:02:09 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"The Virgo collaboration",
"",
""
],
[
"Accadia",
"T.",
""
],
[
"Acernese",
"F.",
""
],
[
"Antonucci",
"F.",
""
],
[
"Aoudia",
"S.",
""
],
[
"Arun",
"K. G.",
""
],
[
"Astone",
"P.",
""
],
[
"Ballard... | Virgo is a kilometer-length interferometer for gravitational waves detection located near Pisa. Its first science run, VSR1, occured from May to October 2007. The aims of the calibration are to measure the detector sensitivity and to reconstruct the time series of the gravitational wave strain h(t). The absolute length calibration is based on an original non-linear reconstruction of the differential arm length variations in free swinging Michelson configurations. It uses the laser wavelength as length standard. This method is used to calibrate the frequency dependent response of the Virgo mirror actuators and derive the detector in-loop response and sensitivity within ~5%. The principle of the strain reconstruction is highlighted and the h(t) systematic errors are estimated. A photon calibrator is used to check the sign of h(t). The reconstructed h(t) during VSR1 is valid from 10 Hz up to 10 kHz with systematic errors estimated to 6% in amplitude. The phase error is estimated to be 70 mrad below 1.9 kHz and 6 micro-seconds above. |
2010.07330 | Alexandru Lupsasca | Delilah E. A. Gates, Shahar Hadar, Alexandru Lupsasca | Photon Emission from Circular Equatorial Kerr Orbiters | 24 pages, 10 figures. v2: expanded discussion | Phys. Rev. D 103, 044050 (2021) | 10.1103/PhysRevD.103.044050 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider monochromatic and isotropic photon emission from circular
equatorial Kerr orbiters. We derive analytic expressions for the photon escape
probability and the redshift-dependent total flux collected on the celestial
sphere as a function of emission radius and black hole parameters. These
calculations crucially involve the critical curve delineating the region of
photon escape from that of photon capture in each emitter's sky. This curve
generalizes to finite orbital radius the usual Kerr critical curve and displays
interesting features in the limit of high spin, which we investigate by
developing a perturbative expansion about extremality. Although the innermost
stable circular orbit appears to approach the event horizon for very rapidly
spinning black holes, we find in this regime that the photon escape probability
tends to $5/12+1/(\sqrt{5}\pi)\arctan\sqrt{5/3}\approx54.65\%$. We also obtain
a simple formula for the flux distribution received on the celestial sphere,
which is nonzero. This confirms that the near-horizon geometry of a high-spin
black hole is in principle observable. These results require us to introduce a
novel type of near-horizon double-scaling limit. We explain the dip observed in
the total flux at infinity as an imprint of the black hole: the black hole
"bite".
| [
{
"created": "Wed, 14 Oct 2020 18:01:37 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Nov 2020 22:31:12 GMT",
"version": "v2"
}
] | 2021-03-03 | [
[
"Gates",
"Delilah E. A.",
""
],
[
"Hadar",
"Shahar",
""
],
[
"Lupsasca",
"Alexandru",
""
]
] | We consider monochromatic and isotropic photon emission from circular equatorial Kerr orbiters. We derive analytic expressions for the photon escape probability and the redshift-dependent total flux collected on the celestial sphere as a function of emission radius and black hole parameters. These calculations crucially involve the critical curve delineating the region of photon escape from that of photon capture in each emitter's sky. This curve generalizes to finite orbital radius the usual Kerr critical curve and displays interesting features in the limit of high spin, which we investigate by developing a perturbative expansion about extremality. Although the innermost stable circular orbit appears to approach the event horizon for very rapidly spinning black holes, we find in this regime that the photon escape probability tends to $5/12+1/(\sqrt{5}\pi)\arctan\sqrt{5/3}\approx54.65\%$. We also obtain a simple formula for the flux distribution received on the celestial sphere, which is nonzero. This confirms that the near-horizon geometry of a high-spin black hole is in principle observable. These results require us to introduce a novel type of near-horizon double-scaling limit. We explain the dip observed in the total flux at infinity as an imprint of the black hole: the black hole "bite". |
gr-qc/0502083 | Jia Feng Chang | Jia-Feng Chang and You-Gen Shen | Neutrino Quasinormal Modes of a Kerr-Newman-de Sitter Black Hole | 25 pages, 13 figures | Nucl.Phys.B712:347-370,2005 | 10.1016/j.nuclphysb.2005.01.043 | null | gr-qc | null | Using the P\"{o}shl-Teller approximation, we evaluate the neutrino
quasinormal modes (QNMs) of a Kerr-Newman-de Sitter black hole. The result
shows that for a Kerr-Newman-de Sitter black hole, massless neutrino
perturbation of large $\Lambda$, positive $m$ and small value of $n$ will decay
slowly.
| [
{
"created": "Mon, 21 Feb 2005 09:52:29 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Feb 2005 07:14:55 GMT",
"version": "v2"
},
{
"created": "Sat, 26 Mar 2005 14:51:09 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Chang",
"Jia-Feng",
""
],
[
"Shen",
"You-Gen",
""
]
] | Using the P\"{o}shl-Teller approximation, we evaluate the neutrino quasinormal modes (QNMs) of a Kerr-Newman-de Sitter black hole. The result shows that for a Kerr-Newman-de Sitter black hole, massless neutrino perturbation of large $\Lambda$, positive $m$ and small value of $n$ will decay slowly. |
1706.06372 | Orfeu Bertolami | Hodjat Mariji, Orfeu Bertolami | Neutron Stars, Ungravity, and the I-Love-Q relation | 20 pages, 1 table, 7 figures. Version to match the one that appeared
in Physical Review D96 (2017) 084042 | Phys. Rev. D 96, 084042 (2017) | 10.1103/PhysRevD.96.084042 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we study neutron stars (NSs) in an ungravity (UG) inspired
model. We examine the UG effects on the static properties of the selected NSs,
in different mass and radius regimes, i.e., mini, moderate, and heavy NSs,
using a polytropic equation of state approach. Based on the observational data,
we obtain bounds on the characteristic length and scaling dimension of the UG
model. Furthermore, we obtain dynamic properties, such as inertial moment (I),
Love number (Love), and quadrupole moment (Q) of a slowly rotating NS in the
presence of the exterior gravity and ungravity fields. The UG model is also
examined with respect to the I-Love-Q universal relation.
| [
{
"created": "Tue, 20 Jun 2017 11:29:33 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Oct 2017 10:34:14 GMT",
"version": "v2"
}
] | 2017-10-25 | [
[
"Mariji",
"Hodjat",
""
],
[
"Bertolami",
"Orfeu",
""
]
] | In this work, we study neutron stars (NSs) in an ungravity (UG) inspired model. We examine the UG effects on the static properties of the selected NSs, in different mass and radius regimes, i.e., mini, moderate, and heavy NSs, using a polytropic equation of state approach. Based on the observational data, we obtain bounds on the characteristic length and scaling dimension of the UG model. Furthermore, we obtain dynamic properties, such as inertial moment (I), Love number (Love), and quadrupole moment (Q) of a slowly rotating NS in the presence of the exterior gravity and ungravity fields. The UG model is also examined with respect to the I-Love-Q universal relation. |
1501.00918 | Juan Calderon Bustillo | Juan Calder\'on Bustillo, Alejandro Boh\'e, Sascha Husa, Alicia M.
Sintes, Mark Hannam and Michael P\"urrer | Comparison of subdominant gravitational wave harmonics between
post-Newtonian and numerical relativity calculations and construction of
multi-mode hybrids | 19 pages, 13 Figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waveforms which describe the inspiral, merger and ringdown of
coalescing binaries are usually constructed by synthesising information from
perturbative descriptions, in particular post-Newtonian theory and black-hole
perturbation theory, with numerical solutions of the full Einstein equations.
In this paper we discuss the "glueing" of numerical and post-Newtonian
waveforms to produce hybrid waveforms which include subdominant spherical
harmonics ("higher order modes"), and focus in particular on the process of
consistently aligning the waveforms, which requires a comparison of both
descriptions and a discussion of their imprecisions. We restrict to the
non-precessing case, and illustrate the process using numerical waveforms of up
to mass ratio $q=18$ produced with the BAM code, and publicly available
waveforms from the SXS catalogue. The results also suggest new ways of
analysing finite radius errors in numerical simulations.
| [
{
"created": "Mon, 5 Jan 2015 16:47:15 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Feb 2015 13:51:22 GMT",
"version": "v2"
}
] | 2015-02-25 | [
[
"Bustillo",
"Juan Calderón",
""
],
[
"Bohé",
"Alejandro",
""
],
[
"Husa",
"Sascha",
""
],
[
"Sintes",
"Alicia M.",
""
],
[
"Hannam",
"Mark",
""
],
[
"Pürrer",
"Michael",
""
]
] | Gravitational waveforms which describe the inspiral, merger and ringdown of coalescing binaries are usually constructed by synthesising information from perturbative descriptions, in particular post-Newtonian theory and black-hole perturbation theory, with numerical solutions of the full Einstein equations. In this paper we discuss the "glueing" of numerical and post-Newtonian waveforms to produce hybrid waveforms which include subdominant spherical harmonics ("higher order modes"), and focus in particular on the process of consistently aligning the waveforms, which requires a comparison of both descriptions and a discussion of their imprecisions. We restrict to the non-precessing case, and illustrate the process using numerical waveforms of up to mass ratio $q=18$ produced with the BAM code, and publicly available waveforms from the SXS catalogue. The results also suggest new ways of analysing finite radius errors in numerical simulations. |
1807.02148 | M. B. Paranjape | J. Gamboa, F. Mendez, M. B. Paranjape, Benoit Sirois | The twin paradox: the role of acceleration | 16 pages, 5 figures | null | 10.1139/cjp-2018-0788 | UdeM-GPP-TH-18-263 | gr-qc physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The twin paradox, which evokes from the the idea that two twins may age
differently because of their relative motion, has been studied and explained
ever since it was first described in 1906, the year after special relativity
was invented. The question can be asked: "Is there anything more to say?" It
seems evident that acceleration has a role to play, however this role has
largely been brushed aside since it is not required in calculating, in a
preferred reference frame, the relative age difference of the twins. Indeed, if
one tries to calculate the age difference from the point of the view of the
twin that undergoes the acceleration, then the role of the acceleration is
crucial and cannot be dismissed. In the resolution of the twin paradox, the
role of the acceleration has been denigrated to the extent that it has been
treated as a red-herring. This is a mistake and shows a clear misunderstanding
of the twin paradox.
| [
{
"created": "Thu, 5 Jul 2018 18:46:43 GMT",
"version": "v1"
}
] | 2019-10-23 | [
[
"Gamboa",
"J.",
""
],
[
"Mendez",
"F.",
""
],
[
"Paranjape",
"M. B.",
""
],
[
"Sirois",
"Benoit",
""
]
] | The twin paradox, which evokes from the the idea that two twins may age differently because of their relative motion, has been studied and explained ever since it was first described in 1906, the year after special relativity was invented. The question can be asked: "Is there anything more to say?" It seems evident that acceleration has a role to play, however this role has largely been brushed aside since it is not required in calculating, in a preferred reference frame, the relative age difference of the twins. Indeed, if one tries to calculate the age difference from the point of the view of the twin that undergoes the acceleration, then the role of the acceleration is crucial and cannot be dismissed. In the resolution of the twin paradox, the role of the acceleration has been denigrated to the extent that it has been treated as a red-herring. This is a mistake and shows a clear misunderstanding of the twin paradox. |
1707.06415 | Handhika Ramadhan | Ilham Prasetyo and Handhika S. Ramadhan | Classical defects in higher-dimensional Einstein gravity coupled to
nonlinear $\sigma$-models | accepted for publication in the General Relativity and Gravitation | null | 10.1007/s10714-017-2278-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct solutions of higher-dimensional Einstein gravity coupled to
nonlinear $\sigma$-model with cosmological constant. The $\sigma$-model can be
perceived as exterior configuration of a spontaneously-broken $SO(D-1)$ global
higher-codimensional "monopole". Here we allow the kinetic term of the
$\sigma$-model to be noncanonical; in particular we specifically study a
quadratic-power-law type. This is some possible higher-dimensional
generalization of the Bariola-Vilenkin (BV) solutions with $k$-global monopole
studied recently. The solutions can be perceived as the exterior solution of a
black hole swallowing up noncanonical global defects. Even in the absence of
comological constant its surrounding spacetime is asymptotically non-flat; it
suffers from deficit solid angle. We discuss the corresponding horizons. For
$\Lambda>0$ in $4d$ there can exist three extremal conditions (the cold,
ultracold, and Nariai black holes), while in higher-than-four dimensions the
extremal black hole is only Nariai. For $\Lambda<0$ we only have black hole
solutions with one horizon, save for the $4d$ case where there can exist two
horizons. We give constraints on the mass and the symmetry-breaking scale for
the existence of all the extremal cases. In addition, we also obtain factorized
solutions, whose topology is the direct product of two-dimensional spaces of
constant curvature ($M_2$, $dS_2$, or $AdS_2$) with (D-2)-sphere. We study all
possible factorized channels.
| [
{
"created": "Thu, 20 Jul 2017 08:42:20 GMT",
"version": "v1"
}
] | 2017-08-30 | [
[
"Prasetyo",
"Ilham",
""
],
[
"Ramadhan",
"Handhika S.",
""
]
] | We construct solutions of higher-dimensional Einstein gravity coupled to nonlinear $\sigma$-model with cosmological constant. The $\sigma$-model can be perceived as exterior configuration of a spontaneously-broken $SO(D-1)$ global higher-codimensional "monopole". Here we allow the kinetic term of the $\sigma$-model to be noncanonical; in particular we specifically study a quadratic-power-law type. This is some possible higher-dimensional generalization of the Bariola-Vilenkin (BV) solutions with $k$-global monopole studied recently. The solutions can be perceived as the exterior solution of a black hole swallowing up noncanonical global defects. Even in the absence of comological constant its surrounding spacetime is asymptotically non-flat; it suffers from deficit solid angle. We discuss the corresponding horizons. For $\Lambda>0$ in $4d$ there can exist three extremal conditions (the cold, ultracold, and Nariai black holes), while in higher-than-four dimensions the extremal black hole is only Nariai. For $\Lambda<0$ we only have black hole solutions with one horizon, save for the $4d$ case where there can exist two horizons. We give constraints on the mass and the symmetry-breaking scale for the existence of all the extremal cases. In addition, we also obtain factorized solutions, whose topology is the direct product of two-dimensional spaces of constant curvature ($M_2$, $dS_2$, or $AdS_2$) with (D-2)-sphere. We study all possible factorized channels. |
0909.0274 | Martin Richarte MR | Luis P. Chimento, Monica Forte, and Martin G. Richarte | Crossing the phantom divide with k-essence in brane-worlds | 8 pages, 5 figures. The article was fully rewritten. References
added. Accepted for publication in MPLA (2010) | Mod.Phys.Lett.A25:2469-2481,2010 | 10.1142/S0217732310033797 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a flat 3-brane in presence of a linear $k$ field with nonzero
cosmological constant $\Lambda_{4}$. In this model the crossing of the phantom
divide (PD) occurs when the $k$-essence energy density becomes negative. We
show that in the high energy regime the effective equation of state has a
resemblance of a modified Chaplygin gas while in the low energy regime it
becomes linear. We find a scale factor that begins from a singularity and
evolves to a de Sitter stable stage while other solutions have a
super-accelerated regime and end with a big rip. We use the energy conditions
to show when the effective equation of state of the brane-universe crosses the
PD.
| [
{
"created": "Tue, 1 Sep 2009 20:21:00 GMT",
"version": "v1"
},
{
"created": "Sat, 5 Jun 2010 17:02:51 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"Chimento",
"Luis P.",
""
],
[
"Forte",
"Monica",
""
],
[
"Richarte",
"Martin G.",
""
]
] | We study a flat 3-brane in presence of a linear $k$ field with nonzero cosmological constant $\Lambda_{4}$. In this model the crossing of the phantom divide (PD) occurs when the $k$-essence energy density becomes negative. We show that in the high energy regime the effective equation of state has a resemblance of a modified Chaplygin gas while in the low energy regime it becomes linear. We find a scale factor that begins from a singularity and evolves to a de Sitter stable stage while other solutions have a super-accelerated regime and end with a big rip. We use the energy conditions to show when the effective equation of state of the brane-universe crosses the PD. |
gr-qc/9703039 | Sung S.-T. | S.-T. Sung | A Quantum Material Model of Static Schwarzschild Black Holes | 24 pages, Latex, 8 ps figures | null | null | null | gr-qc | null | A quantum-mechanical prescription of static Einstein field equation is
proposed in order to construct the matter-metric eigen-states in the interior
of a static Schwarzschild black hole where the signature of space-time is
chosen as (--++). The spectrum of the quantum states is identified to be the
integral multiples of the surface gravity. A statistical explanation of black
hole entropy is given and a quantisation rule for the masses of Schwarzschild
black holes is proposed.
| [
{
"created": "Sun, 16 Mar 1997 22:55:13 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sung",
"S. -T.",
""
]
] | A quantum-mechanical prescription of static Einstein field equation is proposed in order to construct the matter-metric eigen-states in the interior of a static Schwarzschild black hole where the signature of space-time is chosen as (--++). The spectrum of the quantum states is identified to be the integral multiples of the surface gravity. A statistical explanation of black hole entropy is given and a quantisation rule for the masses of Schwarzschild black holes is proposed. |
1304.5430 | Manuel Hohmann | Manuel Hohmann | Extensions of Lorentzian spacetime geometry: From Finsler to Cartan and
vice versa | 33 pages, no figures, journal version | Phys. Rev. D 87 (2013) 124034 | 10.1103/PhysRevD.87.124034 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We briefly review two recently developed extensions of the Lorentzian
geometry of spacetime and prove that they are in fact closely related. The
first is the concept of observer space, which generalizes the space of
Lorentzian observers, i.e., future unit timelike vectors, using Cartan
geometry. The second is the concept of Finsler spacetimes, which generalizes
the Lorentzian metric of general relativity to an observer-dependent Finsler
metric. We show that every Finsler spacetime possesses a well-defined observer
space that can naturally be equipped with a Cartan geometry. Conversely, we
derive conditions under which a Cartan geometry on observer space gives rise to
a Finsler spacetime. We further show that these two constructions complement
each other. We finally apply our constructions to two gravity theories,
MacDowell-Mansouri gravity on observer space and Finsler gravity, and translate
their actions from one geometry to the other.
| [
{
"created": "Fri, 19 Apr 2013 14:38:33 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Jun 2013 05:55:03 GMT",
"version": "v2"
}
] | 2013-06-28 | [
[
"Hohmann",
"Manuel",
""
]
] | We briefly review two recently developed extensions of the Lorentzian geometry of spacetime and prove that they are in fact closely related. The first is the concept of observer space, which generalizes the space of Lorentzian observers, i.e., future unit timelike vectors, using Cartan geometry. The second is the concept of Finsler spacetimes, which generalizes the Lorentzian metric of general relativity to an observer-dependent Finsler metric. We show that every Finsler spacetime possesses a well-defined observer space that can naturally be equipped with a Cartan geometry. Conversely, we derive conditions under which a Cartan geometry on observer space gives rise to a Finsler spacetime. We further show that these two constructions complement each other. We finally apply our constructions to two gravity theories, MacDowell-Mansouri gravity on observer space and Finsler gravity, and translate their actions from one geometry to the other. |
2306.17221 | Benjamin Leather | Benjamin Leather, Niels Warburton | Applying the effective-source approach to frequency-domain self-force
calculations for eccentric orbits | 23 pages, 16 figures; updated to reflect published version | Phys. Rev. D 108, 084045 (2023) | 10.1103/PhysRevD.108.084045 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Extreme mass-ratio inspirals (EMRIs) are expected to have considerable
eccentricity when emitting gravitational waves (GWs) in the LISA band.
Developing GW templates that remain phase accurate over these long inspirals
requires the use of second-order self-force theory and practical second-order
self-force calculations are now emerging for quasi-circular EMRIs. These
calculations rely on effective-source regularization techniques in the
frequency domain that presently are specialized to circular orbits. Here we
make a first step towards more generic second-order calculations by extending
the frequency domain effective-source approach to eccentric orbits. In order to
overcome the slow convergence of the Fourier sum over radial modes, we develop
a new extended effective-sources approach which builds upon the method of
extended particular solutions. To demonstrate our new computational technique
we apply it a toy scalar-field problem which is conceptually similar to the
gravitational case.
| [
{
"created": "Thu, 29 Jun 2023 18:00:03 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Oct 2023 11:44:16 GMT",
"version": "v2"
}
] | 2023-10-25 | [
[
"Leather",
"Benjamin",
""
],
[
"Warburton",
"Niels",
""
]
] | Extreme mass-ratio inspirals (EMRIs) are expected to have considerable eccentricity when emitting gravitational waves (GWs) in the LISA band. Developing GW templates that remain phase accurate over these long inspirals requires the use of second-order self-force theory and practical second-order self-force calculations are now emerging for quasi-circular EMRIs. These calculations rely on effective-source regularization techniques in the frequency domain that presently are specialized to circular orbits. Here we make a first step towards more generic second-order calculations by extending the frequency domain effective-source approach to eccentric orbits. In order to overcome the slow convergence of the Fourier sum over radial modes, we develop a new extended effective-sources approach which builds upon the method of extended particular solutions. To demonstrate our new computational technique we apply it a toy scalar-field problem which is conceptually similar to the gravitational case. |
2305.13984 | Asuka Ito | Asuka Ito, Kazunori Kohri, Kazunori Nakayama | Probing high frequency gravitational waves with pulsars | 7 pages, 2 figures | null | null | KEK-QUP-2023-0011, KEK-TH-2529, KEK-Cosmo-0314, TU-1192 | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study graviton-photon conversion in magnetosphere of a pulsar and explore
the possibility of detecting high frequency gravitational waves with pulsar
observations. It is shown that conversion of one polarization mode of photons
can be enhanced significantly due to strong magnetic fields around a pulsar. We
also constrain stochastic gravitational waves in frequency range of
$10^{8}-10^{9}\,$Hz and $10^{13}-10^{27}\,$Hz by using data of observations of
the Crab pulsar and the Geminga pulsar. Our method widely fills the gap among
existing high frequency gravitational wave experiments and boosts the frequency
frontier in gravitational wave observations.
| [
{
"created": "Tue, 23 May 2023 12:08:25 GMT",
"version": "v1"
}
] | 2023-05-24 | [
[
"Ito",
"Asuka",
""
],
[
"Kohri",
"Kazunori",
""
],
[
"Nakayama",
"Kazunori",
""
]
] | We study graviton-photon conversion in magnetosphere of a pulsar and explore the possibility of detecting high frequency gravitational waves with pulsar observations. It is shown that conversion of one polarization mode of photons can be enhanced significantly due to strong magnetic fields around a pulsar. We also constrain stochastic gravitational waves in frequency range of $10^{8}-10^{9}\,$Hz and $10^{13}-10^{27}\,$Hz by using data of observations of the Crab pulsar and the Geminga pulsar. Our method widely fills the gap among existing high frequency gravitational wave experiments and boosts the frequency frontier in gravitational wave observations. |
0708.3835 | Farhad Darabi | F. Darabi | A 5D non compact and non Ricci flat Kaluza-Klein Cosmology | 13 pages, major revision, published online in GRG | Gen. Relativ. Gravit 41: 497--504 (2009) | 10.1007/s10714-008-0685-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A model universe is proposed in the framework of 5-dimensional noncompact
Kaluza-Klein cosmology which is not Ricci flat. The 4D part as the
Robertson-Walker metric is coupled to conventional perfect fluid, and its
extra-dimensional part is coupled to a dark pressure through a scalar field. It
is shown that neither early inflation nor current acceleration of the 4D
universe would happen if the non-vacuum states of the scalar field would
contribute to 4D cosmology.
| [
{
"created": "Tue, 28 Aug 2007 19:13:05 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Jun 2008 18:08:14 GMT",
"version": "v2"
},
{
"created": "Wed, 10 Sep 2008 10:14:30 GMT",
"version": "v3"
}
] | 2009-05-03 | [
[
"Darabi",
"F.",
""
]
] | A model universe is proposed in the framework of 5-dimensional noncompact Kaluza-Klein cosmology which is not Ricci flat. The 4D part as the Robertson-Walker metric is coupled to conventional perfect fluid, and its extra-dimensional part is coupled to a dark pressure through a scalar field. It is shown that neither early inflation nor current acceleration of the 4D universe would happen if the non-vacuum states of the scalar field would contribute to 4D cosmology. |
gr-qc/0503058 | Ken-Ichi Nakao | Hiroyuki Nakano, Ken-ichi Nakao, Masahide Yamaguchi | Black Strings in Our World | 11pages, no figure | Phys.Rev. D71 (2005) 124013 | 10.1103/PhysRevD.71.124013 | OCU-PHYS-229, AP-GR-24 | gr-qc astro-ph hep-ph | null | The brane world scenario is a new approach to resolve the problem on how to
compactify the higher dimensional spacetime to our 4-dimensional world. One of
the remarkable features of this scenario is the higher dimensional effects in
classical gravitational interactions at short distances. Due to this feature,
there are black string solutions in our 4-dimensional world. In this paper,
assuming the simplest model of complex minimally coupled scalar field with the
local U(1) symmetry, we show a possibility of black-string formation by merging
processes of type I long cosmic strings in our 4-dimensional world. No fine
tuning for the parameters in the model might be necessary.
| [
{
"created": "Mon, 14 Mar 2005 03:45:19 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Nakano",
"Hiroyuki",
""
],
[
"Nakao",
"Ken-ichi",
""
],
[
"Yamaguchi",
"Masahide",
""
]
] | The brane world scenario is a new approach to resolve the problem on how to compactify the higher dimensional spacetime to our 4-dimensional world. One of the remarkable features of this scenario is the higher dimensional effects in classical gravitational interactions at short distances. Due to this feature, there are black string solutions in our 4-dimensional world. In this paper, assuming the simplest model of complex minimally coupled scalar field with the local U(1) symmetry, we show a possibility of black-string formation by merging processes of type I long cosmic strings in our 4-dimensional world. No fine tuning for the parameters in the model might be necessary. |
2404.11703 | Oscar Castillo Felisola Dr. | Oscar Castillo-Felisola and Bastian Grez and Gonzalo J. Olmo and Oscar
Orellana and Jos\'e Perdiguero G\'arate | Cosmological Solutions in Polynomial Affine Gravity with Torsion | EPJC format, 11 pages. v2: improved discussion, additional references | null | null | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | The Polynomial Affine Gravity is an alternative gravitational model, where
the interactions are mediated solely by the affine connection, instead of the
metric tensor. In this paper, we explore the space of solutions to the field
equations when the torsion fields are turned on, in a homogeneous and isotropic
(cosmological) scenario. We explore various metric structures that emerge in
the space of solutions.
| [
{
"created": "Wed, 17 Apr 2024 19:10:32 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Jun 2024 08:34:55 GMT",
"version": "v2"
}
] | 2024-06-05 | [
[
"Castillo-Felisola",
"Oscar",
""
],
[
"Grez",
"Bastian",
""
],
[
"Olmo",
"Gonzalo J.",
""
],
[
"Orellana",
"Oscar",
""
],
[
"Gárate",
"José Perdiguero",
""
]
] | The Polynomial Affine Gravity is an alternative gravitational model, where the interactions are mediated solely by the affine connection, instead of the metric tensor. In this paper, we explore the space of solutions to the field equations when the torsion fields are turned on, in a homogeneous and isotropic (cosmological) scenario. We explore various metric structures that emerge in the space of solutions. |
0801.4529 | Saibal Ray | A. A. Usmani, P. P.Ghosh, Utpal Mukhopadhyay, P. C. Ray and Saibal Ray | The dark energy equation of state | 4 Latex pages, 3 figures, To appear in Mon. Not. R. Astron. Soc. Lett | Mon.Not.Roy.Astron.Soc.Lett.386:L92-95,2008 | 10.1111/j.1745-3933.2008.00468.x | null | gr-qc astro-ph hep-th | null | We perform a study of cosmic evolution with an equation of state parameter
$\omega(t)=\omega_0+\omega_1(t\dot H/H)$ by selecting a phenomenological
$\Lambda$ model of the form, $\dot\Lambda\sim H^3$. This simple proposition
explains both linearly expanding and inflationary Universes with a single set
of equations. We notice that the inflation leads to a scaling in the equation
of state parameter, $\omega(t)$, and hence in equation of state. In this
approach, one of its two parameters have been pin pointed and the other have
been delineated. It has been possible to show a connection between dark energy
and Higgs-Boson.
| [
{
"created": "Tue, 29 Jan 2008 16:32:58 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Mar 2008 13:16:32 GMT",
"version": "v2"
}
] | 2009-11-13 | [
[
"Usmani",
"A. A.",
""
],
[
"Ghosh",
"P. P.",
""
],
[
"Mukhopadhyay",
"Utpal",
""
],
[
"Ray",
"P. C.",
""
],
[
"Ray",
"Saibal",
""
]
] | We perform a study of cosmic evolution with an equation of state parameter $\omega(t)=\omega_0+\omega_1(t\dot H/H)$ by selecting a phenomenological $\Lambda$ model of the form, $\dot\Lambda\sim H^3$. This simple proposition explains both linearly expanding and inflationary Universes with a single set of equations. We notice that the inflation leads to a scaling in the equation of state parameter, $\omega(t)$, and hence in equation of state. In this approach, one of its two parameters have been pin pointed and the other have been delineated. It has been possible to show a connection between dark energy and Higgs-Boson. |
2007.12462 | Cosimo Bambi | Bakhtiyor Narzilloev, Javlon Rayimbaev, Sanjar Shaymatov, Ahmadjon
Abdujabbarov, Bobomurat Ahmedov, Cosimo Bambi | Can the dynamics of test particles around charged stringy black holes
mimic the spin of Kerr black holes? | 17 pages, 15 figures | Phys. Rev. D 102, 044013 (2020) | 10.1103/PhysRevD.102.044013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the motion of electrically charged particles, magnetic monopoles,
and magnetic dipoles around electrically and magnetically charged stringy black
holes. From the analysis of the radius of the innermost stable circular orbit
(ISCO) of electrically charged particles, we show that the electric charge $Q$
of stringy black holes can mimic well the spin of Kerr black holes; the black
hole magnetic charge $Q_m$ can mimic spins up to $a_* \simeq 0.85$ for magnetic
dipoles; the magnetic charge parameter $g$ of a magnetic monopole can mimic
spins up to $a_* \simeq 0.8$. This is due to the destructive character of the
magnetic field and such a result excludes the existence of an appreciable black
hole magnetic charge in astrophysical black holes from the observation of
rapidly rotating objects with dimensionless spin up to $a_* \simeq 0.99$. We
then consider the magnetar SGR (PSR) J1745-2900 as a magnetic dipole orbiting
the supermassive black hole Sagittarius A* (Sgr A*). We show that Sgr A* may be
interpreted as a stringy black hole with magnetic charge $Q_{\rm m}/M \leq
0.4118$.
| [
{
"created": "Fri, 24 Jul 2020 11:50:41 GMT",
"version": "v1"
}
] | 2020-08-12 | [
[
"Narzilloev",
"Bakhtiyor",
""
],
[
"Rayimbaev",
"Javlon",
""
],
[
"Shaymatov",
"Sanjar",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
],
[
"Ahmedov",
"Bobomurat",
""
],
[
"Bambi",
"Cosimo",
""
]
] | We study the motion of electrically charged particles, magnetic monopoles, and magnetic dipoles around electrically and magnetically charged stringy black holes. From the analysis of the radius of the innermost stable circular orbit (ISCO) of electrically charged particles, we show that the electric charge $Q$ of stringy black holes can mimic well the spin of Kerr black holes; the black hole magnetic charge $Q_m$ can mimic spins up to $a_* \simeq 0.85$ for magnetic dipoles; the magnetic charge parameter $g$ of a magnetic monopole can mimic spins up to $a_* \simeq 0.8$. This is due to the destructive character of the magnetic field and such a result excludes the existence of an appreciable black hole magnetic charge in astrophysical black holes from the observation of rapidly rotating objects with dimensionless spin up to $a_* \simeq 0.99$. We then consider the magnetar SGR (PSR) J1745-2900 as a magnetic dipole orbiting the supermassive black hole Sagittarius A* (Sgr A*). We show that Sgr A* may be interpreted as a stringy black hole with magnetic charge $Q_{\rm m}/M \leq 0.4118$. |
gr-qc/0112006 | Victor M. Villalba | Victor M. Villalba, Walter Greiner | Creation of scalar and Dirac particles in the presence of a time varying
electric field in an anisotropic Bianchi I universe | 8 pages, REVTEX 3.0. to appear in Phys. Rev. D | Phys.Rev. D65 (2002) 025007 | 10.1103/PhysRevD.65.025007 | null | gr-qc hep-th | null | In this article we compute the density of scalar and Dirac particles created
by a cosmological anisotropic Bianchi type I universe in the presence of a time
varying electric field. We show that the particle distribution becomes thermal
when one neglects the electric interaction.
| [
{
"created": "Fri, 7 Dec 2001 17:56:27 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Villalba",
"Victor M.",
""
],
[
"Greiner",
"Walter",
""
]
] | In this article we compute the density of scalar and Dirac particles created by a cosmological anisotropic Bianchi type I universe in the presence of a time varying electric field. We show that the particle distribution becomes thermal when one neglects the electric interaction. |
2303.07769 | Kalin Staykov Dr. | Kalin V. Staykov, Daniela D. Doneva, Lavinia Heisenberg, Nikolaos
Stergioulas, Stoytcho S. Yazadjiev | Differentially rotating scalarized neutron stars with realistic
post-merger profile | 17 pages, 6 figures | null | 10.1103/PhysRevD.108.024058 | ET-0053A-23 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The merger remnant of a binary neutron star coalescence is initially strongly
differentially rotating. Some properties of these remnants can be accurately
modeled through building equilibrium neutron star models. In the present paper,
we study how a modification of general relativity, namely scalar-tensor theory
with a massive scalar field, will alter the picture. In contrast to previous
studies, we implement a realistic phenomenological differential rotational law
which allows for neutron star models to attain maximal angular velocity away
from the center. We find that solutions with much higher masses and angular
momenta exist in scalar-tensor theory compared to general relativity. They keep
their quasi-spherical energy-density distribution for significantly higher
values of the angular momentum before transitioning to quasi-toroidal models,
in contrast to pure general relativity. Constructing such neutron star
solutions is the first step to our final goal that is studying how
scalarization alters the stability and gravitational wave emission of
post-merger remnants.
| [
{
"created": "Tue, 14 Mar 2023 10:18:59 GMT",
"version": "v1"
}
] | 2023-08-02 | [
[
"Staykov",
"Kalin V.",
""
],
[
"Doneva",
"Daniela D.",
""
],
[
"Heisenberg",
"Lavinia",
""
],
[
"Stergioulas",
"Nikolaos",
""
],
[
"Yazadjiev",
"Stoytcho S.",
""
]
] | The merger remnant of a binary neutron star coalescence is initially strongly differentially rotating. Some properties of these remnants can be accurately modeled through building equilibrium neutron star models. In the present paper, we study how a modification of general relativity, namely scalar-tensor theory with a massive scalar field, will alter the picture. In contrast to previous studies, we implement a realistic phenomenological differential rotational law which allows for neutron star models to attain maximal angular velocity away from the center. We find that solutions with much higher masses and angular momenta exist in scalar-tensor theory compared to general relativity. They keep their quasi-spherical energy-density distribution for significantly higher values of the angular momentum before transitioning to quasi-toroidal models, in contrast to pure general relativity. Constructing such neutron star solutions is the first step to our final goal that is studying how scalarization alters the stability and gravitational wave emission of post-merger remnants. |
2212.02917 | Muzaffer Adak | Muzaffer Adak, Nese Ozdemir, Ozcan Sert | Scale invariant Einstein-Cartan theory in three dimensions | Accepted for publication in Eur. Phys. J. C | Eur. Phys. J. C 83 (2023)106 | 10.1140/epjc/s10052-023-11255-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We retreat the well-known Einstein-Cartan theory by slightly modifying the
covariant derivative of spinor field by investigating double cover of the
Lorentz group. We first write the Lagrangian consisting of the Einstein-Hilbert
term, Dirac term and a scalar field term in a non-Riemannian spacetime with
curvature and torsion. Then by solving the affine connection analytically we
reformulate the theory in the Riemannian spacetime in a self-consistent way.
Finally we discuss our results and give future perspectives on the subject.
| [
{
"created": "Tue, 6 Dec 2022 12:17:29 GMT",
"version": "v1"
},
{
"created": "Sat, 21 Jan 2023 18:56:16 GMT",
"version": "v2"
}
] | 2023-02-03 | [
[
"Adak",
"Muzaffer",
""
],
[
"Ozdemir",
"Nese",
""
],
[
"Sert",
"Ozcan",
""
]
] | We retreat the well-known Einstein-Cartan theory by slightly modifying the covariant derivative of spinor field by investigating double cover of the Lorentz group. We first write the Lagrangian consisting of the Einstein-Hilbert term, Dirac term and a scalar field term in a non-Riemannian spacetime with curvature and torsion. Then by solving the affine connection analytically we reformulate the theory in the Riemannian spacetime in a self-consistent way. Finally we discuss our results and give future perspectives on the subject. |
2402.03684 | Shuxun Tian | Changcheng Jing and Shuxun Tian and Zong-Hong Zhu | Early dark energy triggered by spacetime dynamics that encodes cosmic
radiation-matter transition | 9 pages, 7 figures, published in Phys. Rev. D | Phys. Rev. D 109, 044016 (2024) | 10.1103/PhysRevD.109.044016 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | Early dark energy (EDE), introduced at the epoch of matter-radiation equality
to alleviate the Hubble tension, has posed a new coincidence problem: why EDE
appears at matter-radiation equality when their physics are completely
unrelated? To solve this coincidence problem, we propose a new EDE model based
on scalar-tensor gravity with the idea that EDE is triggered by spacetime
dynamics that encodes cosmic radiation-matter transition. Our model can induce
EDE naturally at matter-radiation equality without unnatural parameter tuning.
Compared with other EDE models, a distinguishing feature of ours is that it can
also induce a new energy component during cosmic matter-dark energy transition.
This is testable with low-redshift observations.
| [
{
"created": "Tue, 6 Feb 2024 04:13:50 GMT",
"version": "v1"
}
] | 2024-02-07 | [
[
"Jing",
"Changcheng",
""
],
[
"Tian",
"Shuxun",
""
],
[
"Zhu",
"Zong-Hong",
""
]
] | Early dark energy (EDE), introduced at the epoch of matter-radiation equality to alleviate the Hubble tension, has posed a new coincidence problem: why EDE appears at matter-radiation equality when their physics are completely unrelated? To solve this coincidence problem, we propose a new EDE model based on scalar-tensor gravity with the idea that EDE is triggered by spacetime dynamics that encodes cosmic radiation-matter transition. Our model can induce EDE naturally at matter-radiation equality without unnatural parameter tuning. Compared with other EDE models, a distinguishing feature of ours is that it can also induce a new energy component during cosmic matter-dark energy transition. This is testable with low-redshift observations. |
1611.10074 | Mauro Pieroni | F. Cicciarella and M. Pieroni | Universality for quintessence | 21 pages + appendices, 23 figures | JCAP 1708 (2017) no.08, 010 | 10.1088/1475-7516/2017/08/010 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several recent works suggested the possibility of describing inflation by
means of a renormalization group equation. In this paper we discuss the
application of these methods to models of quintessence. In this framework a
period of exponential expansion corresponds to the slow evolution of the scalar
field in the neighborhood of a fixed point. A minimal set of universality
classes for models of quintessence is defined and the transition from a matter
dominated to quintessence dominated universe is studied. Models in which
quintessence is non-minimally coupled with gravity are also discussed. We show
that the formalism proves to be extremely convenient to describe quintessence
and moreover we find that in most of the models discussed in this work
quintessence naturally takes over ordinary matter.
| [
{
"created": "Wed, 30 Nov 2016 10:03:23 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Aug 2017 10:40:43 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Sep 2017 14:28:29 GMT",
"version": "v3"
}
] | 2017-09-08 | [
[
"Cicciarella",
"F.",
""
],
[
"Pieroni",
"M.",
""
]
] | Several recent works suggested the possibility of describing inflation by means of a renormalization group equation. In this paper we discuss the application of these methods to models of quintessence. In this framework a period of exponential expansion corresponds to the slow evolution of the scalar field in the neighborhood of a fixed point. A minimal set of universality classes for models of quintessence is defined and the transition from a matter dominated to quintessence dominated universe is studied. Models in which quintessence is non-minimally coupled with gravity are also discussed. We show that the formalism proves to be extremely convenient to describe quintessence and moreover we find that in most of the models discussed in this work quintessence naturally takes over ordinary matter. |
gr-qc/9405040 | Claus Kiefer | D. Giulini and C. Kiefer | Wheeler-Dewitt Metric and the Attractivity of Gravity | LATEX, 6pages, slightly corrected and enlarged version, to appear in
Phys. Lett. A | Phys.Lett. A193 (1994) 21-24 | 10.1016/0375-9601(94)00651-2 | null | gr-qc | null | We investigate the class of ultralocal metrics on the configuration space of
canonical gravity. It is described by a parameter $\alpha$, where $\alpha=0.5$
corresponds to general relativity.
For $\alpha$ less than a critical value the signature is positive definite,
while for all other values it is indefinite. We show that in the positive
definite case gravity becomes repulsive. From the primordial helium abundance
we find that $\alpha$ must lie between $0.4$ and $0.55$.
| [
{
"created": "Wed, 18 May 1994 14:23:09 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Sep 1994 07:38:24 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Giulini",
"D.",
""
],
[
"Kiefer",
"C.",
""
]
] | We investigate the class of ultralocal metrics on the configuration space of canonical gravity. It is described by a parameter $\alpha$, where $\alpha=0.5$ corresponds to general relativity. For $\alpha$ less than a critical value the signature is positive definite, while for all other values it is indefinite. We show that in the positive definite case gravity becomes repulsive. From the primordial helium abundance we find that $\alpha$ must lie between $0.4$ and $0.55$. |
gr-qc/0405008 | Michael Petri | Michael Petri | On the thermodynamic origin of the Hawking entropy and a measurement of
the Hawking temperature | 27 pages, 1 figure | null | null | null | gr-qc astro-ph hep-th | null | In the spherically symmetric case the Einstein field equations take on their
simplest form for a matter-density rho = 1 / (8 pi r^2), from which a radial
metric coefficient g_{rr} \propto r follows. The boundary of an object with
such an interior matter-density is situated slightly outside of its
gravitational radius. Its surface-redshift scales with z \propto \sqrt{r}, so
that any such large object is practically indistinguishable from a black hole,
as seen from exterior space-time. The interior matter has a well defined
temperature, T \propto 1 / \sqrt{r}. Under the assumption, that the interior
matter can be described as an ultra-relativistic gas, the object's total
entropy and its temperature at infinity can be calculated by microscopic
statistical thermodynamics. They are equal to the Hawking result up to a
possibly different constant factor. The simplest solution of the field
equations with rho = 1 / (8 pi r^2) is the so called holographic solution,
short "holostar". It has an interior string equation of state. The strings are
densely packed, explaining why the solution does not collapse to a singularity.
The holographic solution has been shown to be a very accurate model for the
universe as we see it today in Ref[7]. The factor relating the holostar's
temperature at infinity to the Hawking temperature can be expressed in terms
the holostar's interior (local) radiation temperature and its (local)
matter-density, allowing an experimental verification of the Hawking
temperature law. Using the recent experimental data for the CMBR-temperature
and the total matter-density in the universe measured by WMAP, the Hawking
formula is verified to an accuracy of 1%.
| [
{
"created": "Sun, 2 May 2004 19:04:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Petri",
"Michael",
""
]
] | In the spherically symmetric case the Einstein field equations take on their simplest form for a matter-density rho = 1 / (8 pi r^2), from which a radial metric coefficient g_{rr} \propto r follows. The boundary of an object with such an interior matter-density is situated slightly outside of its gravitational radius. Its surface-redshift scales with z \propto \sqrt{r}, so that any such large object is practically indistinguishable from a black hole, as seen from exterior space-time. The interior matter has a well defined temperature, T \propto 1 / \sqrt{r}. Under the assumption, that the interior matter can be described as an ultra-relativistic gas, the object's total entropy and its temperature at infinity can be calculated by microscopic statistical thermodynamics. They are equal to the Hawking result up to a possibly different constant factor. The simplest solution of the field equations with rho = 1 / (8 pi r^2) is the so called holographic solution, short "holostar". It has an interior string equation of state. The strings are densely packed, explaining why the solution does not collapse to a singularity. The holographic solution has been shown to be a very accurate model for the universe as we see it today in Ref[7]. The factor relating the holostar's temperature at infinity to the Hawking temperature can be expressed in terms the holostar's interior (local) radiation temperature and its (local) matter-density, allowing an experimental verification of the Hawking temperature law. Using the recent experimental data for the CMBR-temperature and the total matter-density in the universe measured by WMAP, the Hawking formula is verified to an accuracy of 1%. |
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