id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9709046 | Andrzej Krolak | John K. Beem and Andrzej Krolak | Cauchy Horizon Endpoints and Differentiability | 16 pages, Latex | null | 10.1063/1.532610 | null | gr-qc | null | Cauchy horizons are shown to be differentiable at endpoints where only a
single null generator leaves the horizon. A Cauchy horizon fails to have any
null generator endpoints on a given open subset iff it is differentiable on the
open subset and also iff the horizon is (at least) of class C^1 on the open
subset. Given the null convergence condition, a compact horizon which is of
class C^2 almost everywhere has no endpoints and is (at least) of class C^1 at
all points.
| [
{
"created": "Thu, 18 Sep 1997 08:55:54 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Beem",
"John K.",
""
],
[
"Krolak",
"Andrzej",
""
]
] | Cauchy horizons are shown to be differentiable at endpoints where only a single null generator leaves the horizon. A Cauchy horizon fails to have any null generator endpoints on a given open subset iff it is differentiable on the open subset and also iff the horizon is (at least) of class C^1 on the open subset. Given the null convergence condition, a compact horizon which is of class C^2 almost everywhere has no endpoints and is (at least) of class C^1 at all points. |
1308.6747 | Muhammad Sharif | M. Sharif and Rabia Saleem | Statefinder Diagnostic for Dark Energy Models in Bianchi I Universe | 24 pages, 19 figures | Int. J. Mod. Phys. D 21(2012)1250046 | 10.1142/S0218271812500460 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the statefinder, the deceleration and equation
of state parameters when universe is composed of generalized holographic dark
energy or generalized Ricci dark energy for Bianchi I universe model. These
parameters are found for both interacting as well as non-interacting scenarios
of generalized holographic or generalized Ricci dark energy with dark matter
and generalized Chaplygin gas. We explore these parameters graphically for
different situations. It is concluded that these models represent accelerated
expansion of the universe.
| [
{
"created": "Thu, 29 Aug 2013 02:48:23 GMT",
"version": "v1"
}
] | 2015-06-17 | [
[
"Sharif",
"M.",
""
],
[
"Saleem",
"Rabia",
""
]
] | In this paper, we investigate the statefinder, the deceleration and equation of state parameters when universe is composed of generalized holographic dark energy or generalized Ricci dark energy for Bianchi I universe model. These parameters are found for both interacting as well as non-interacting scenarios of generalized holographic or generalized Ricci dark energy with dark matter and generalized Chaplygin gas. We explore these parameters graphically for different situations. It is concluded that these models represent accelerated expansion of the universe. |
gr-qc/0410146 | Tomasz Pawlowski | Jerzy Lewandowski, Tomasz Pawlowski | Quasi-local rotating black holes in higher dimension: geometry | 32 pages, RevTex4 | Class.Quant.Grav. 22 (2005) 1573-1598 | 10.1088/0264-9381/22/9/007 | null | gr-qc hep-th | null | With a help of a generalized Raychaudhuri equation non-expanding null
surfaces are studied in arbitrarily dimensional case. The definition and basic
properties of non-expanding and isolated horizons known in the literature in
the 4 and 3 dimensional cases are generalized. A local description of horizon's
geometry is provided. The Zeroth Law of black hole thermodynamics is derived.
The constraints have a similar structure to that of the 4 dimensional spacetime
case. The geometry of a vacuum isolated horizon is determined by the induced
metric and the rotation 1-form potential, local generalizations of the area and
the angular momentum typically used in the stationary black hole solutions
case.
| [
{
"created": "Thu, 28 Oct 2004 21:13:15 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Lewandowski",
"Jerzy",
""
],
[
"Pawlowski",
"Tomasz",
""
]
] | With a help of a generalized Raychaudhuri equation non-expanding null surfaces are studied in arbitrarily dimensional case. The definition and basic properties of non-expanding and isolated horizons known in the literature in the 4 and 3 dimensional cases are generalized. A local description of horizon's geometry is provided. The Zeroth Law of black hole thermodynamics is derived. The constraints have a similar structure to that of the 4 dimensional spacetime case. The geometry of a vacuum isolated horizon is determined by the induced metric and the rotation 1-form potential, local generalizations of the area and the angular momentum typically used in the stationary black hole solutions case. |
0804.0572 | Irene Milillo | Irene Milillo, Massimiliano Lattanzi, Giovanni Montani | On the coupling between spinning particles and cosmological
gravitational waves | 4 pages, to appear in Proceedings of the II Stueckelberg Workshop -
Int. J. Mod. Phys. A | Int.J.Mod.Phys.A23:1278-1281,2008 | 10.1142/S0217751X08040226 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The influence of spin in a system of classical particles on the propagation
of gravitational waves is analyzed in the cosmological context of primordial
thermal equilibrium. On a flat Friedmann-Robertson-Walker metric, when the
precession is neglected, there is no contribution due to the spin to the
distribution function of the particles. Adding a small tensor perturbation to
the background metric, we study if a coupling between gravitational waves and
spin exists that can modify the evolution of the distribution function, leading
to new terms in the anisotropic stress, and then to a new source for
gravitational waves. In the chosen gauge, the final result is that, in the
absence of other kind of perturbations, there is no coupling between spin and
gravitational waves.
| [
{
"created": "Thu, 3 Apr 2008 17:12:00 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Milillo",
"Irene",
""
],
[
"Lattanzi",
"Massimiliano",
""
],
[
"Montani",
"Giovanni",
""
]
] | The influence of spin in a system of classical particles on the propagation of gravitational waves is analyzed in the cosmological context of primordial thermal equilibrium. On a flat Friedmann-Robertson-Walker metric, when the precession is neglected, there is no contribution due to the spin to the distribution function of the particles. Adding a small tensor perturbation to the background metric, we study if a coupling between gravitational waves and spin exists that can modify the evolution of the distribution function, leading to new terms in the anisotropic stress, and then to a new source for gravitational waves. In the chosen gauge, the final result is that, in the absence of other kind of perturbations, there is no coupling between spin and gravitational waves. |
gr-qc/0601044 | David Mattingly | David Mattingly | On horizon constraints and Hawking radiation | null | null | null | null | gr-qc | null | Questions about black holes in quantum gravity generally presuppose the
presence of a horizon. Recently Carlip has shown that enforcing an initial data
surface to be a horizon leads to the correct form for the Bekenstein-Hawking
entropy of the black hole. Requiring a horizon also constitutes fixed
background geometry, which generically leads to non-conservation of the matter
stress tensor at the horizon. In this work, I show that the generated matter
energy flux for a Schwarzschild black hole is in agreement with the first law
of black hole thermodynamics, $8 \pi G \Delta Q = \kappa \Delta A$.
| [
{
"created": "Wed, 11 Jan 2006 20:48:50 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mattingly",
"David",
""
]
] | Questions about black holes in quantum gravity generally presuppose the presence of a horizon. Recently Carlip has shown that enforcing an initial data surface to be a horizon leads to the correct form for the Bekenstein-Hawking entropy of the black hole. Requiring a horizon also constitutes fixed background geometry, which generically leads to non-conservation of the matter stress tensor at the horizon. In this work, I show that the generated matter energy flux for a Schwarzschild black hole is in agreement with the first law of black hole thermodynamics, $8 \pi G \Delta Q = \kappa \Delta A$. |
gr-qc/0209101 | Shane L. Larson | Curt Cutler (AEI), William A. Hiscock (Montana State) and Shane L.
Larson (Caltech) | LISA, binary stars, and the mass of the graviton | ReVTeX 4, 6 pages, 1 figure, submitted to Phys Rev D | Phys.Rev. D67 (2003) 024015 | 10.1103/PhysRevD.67.024015 | null | gr-qc astro-ph | null | We extend and improve earlier estimates of the ability of the proposed LISA
(Laser Interferometer Space Antenna) gravitational wave detector to place upper
bounds on the graviton mass, m_g, by comparing the arrival times of
gravitational and electromagnetic signals from binary star systems. We show
that the best possible limit on m_g obtainable this way is ~ 50 times better
than the current limit set by Solar System measurements. Among currently known,
well-understood binaries, 4U1820-30 is the best for this purpose; LISA
observations of 4U1820-30 should yield a limit ~ 3-4 times better than the
present Solar System bound. AM CVn-type binaries offer the prospect of
improving the limit by a factor of 10, if such systems can be better understood
by the time of the LISA mission. We briefly discuss the likelihood that radio
and optical searches during the next decade will yield binaries that more
closely approach the best possible case.
| [
{
"created": "Thu, 26 Sep 2002 17:30:13 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Cutler",
"Curt",
"",
"AEI"
],
[
"Hiscock",
"William A.",
"",
"Montana State"
],
[
"Larson",
"Shane L.",
"",
"Caltech"
]
] | We extend and improve earlier estimates of the ability of the proposed LISA (Laser Interferometer Space Antenna) gravitational wave detector to place upper bounds on the graviton mass, m_g, by comparing the arrival times of gravitational and electromagnetic signals from binary star systems. We show that the best possible limit on m_g obtainable this way is ~ 50 times better than the current limit set by Solar System measurements. Among currently known, well-understood binaries, 4U1820-30 is the best for this purpose; LISA observations of 4U1820-30 should yield a limit ~ 3-4 times better than the present Solar System bound. AM CVn-type binaries offer the prospect of improving the limit by a factor of 10, if such systems can be better understood by the time of the LISA mission. We briefly discuss the likelihood that radio and optical searches during the next decade will yield binaries that more closely approach the best possible case. |
2302.07999 | Alberto Escalante | Alberto Escalante (Puebla U., Inst. Fis.), P. Fernando Oca\~na
Garc\'ia (Puebla U., Inst. Fis.) | Hamiltonian analysis for new massive gravity | null | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | A detailed canonical analysis for three-dimensional massive gravity is
performed. The construction of the fundamental Dirac brackets, the complete
structure of the constraints and the counting of the physical degrees of
freedom are reported. In addition, it is shown that the extended Hamiltonian is
healed from Orstrogradki's instabilities.
| [
{
"created": "Thu, 16 Feb 2023 00:15:54 GMT",
"version": "v1"
},
{
"created": "Tue, 9 May 2023 01:31:01 GMT",
"version": "v2"
}
] | 2023-05-10 | [
[
"Escalante",
"Alberto",
"",
"Puebla U., Inst. Fis."
],
[
"García",
"P. Fernando Ocaña",
"",
"Puebla U., Inst. Fis."
]
] | A detailed canonical analysis for three-dimensional massive gravity is performed. The construction of the fundamental Dirac brackets, the complete structure of the constraints and the counting of the physical degrees of freedom are reported. In addition, it is shown that the extended Hamiltonian is healed from Orstrogradki's instabilities. |
2010.13628 | Rajendra Gupta | Rajendra P. Gupta | Varying physical constants and the lithium problem | 8 pages, 2 figures, thoroughly revised as published with typos
corrected. Critical comments welcomed | Astroparticle Physics (2021) 129, 102578 | 10.1016/j.astropartphys.2021.102578 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have used the recently published varying physical constants (VPC) approach
to resolve the primordial lithium abundance problem. The value of the ratio of
$7Li$ to hydrogen $7Li/H=1.400(\pm 0.023){\times}10^{-10}$ we have calculated
using this approach is about four times lower than that estimated using the
standard lambda cold dark matter (${\Lambda}$CDM) cosmological model, and is
consistent with the most agreed observational value of $1.6(\pm
0.3){\times}10^{-10}$. In the VPC approach Einstein equations are modified to
include the variation of the speed of light $c$, gravitational constant $G$ and
cosmological constant ${\Lambda}$ using the Einstein-Hilbert action.
Application of this approach to cosmology naturally leads to the variation of
the Plank constant $\hbar$ and the Boltzmann constant $k_B$ as well. They
approach fixed values at the scale factor $a\ll 1$: $c=c_0/e$, $G=G_0/e^3$,
$\hbar=\hbar_0/e$ and $k_B=k_{B0}/e^{5/4}$, where $e$ is the Euler's number
(=2.7183). Since the VPC cosmology reduces to the same form as the
${\Lambda}$CDM cosmology at very small scale factors, we could use an existing
Big-Bang nucleosynthesis (BBN) code AlterBBN with the above changes to
calculate the light element abundances under the VPC cosmology. Among other
abundances we have calculated at baryon to photon ratio
${\eta}=6.1{\times}10^{-10}$ are: $4He/H =0.2478 (\pm 0.041)$, $D/H =2.453(\pm
0.041){\times}10^{-5}$ and $3 He/H=2.940(\pm 0.049){\times}10^{-5}$.
| [
{
"created": "Fri, 23 Oct 2020 16:13:47 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jan 2021 16:53:35 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Mar 2022 01:15:39 GMT",
"version": "v3"
}
] | 2022-03-25 | [
[
"Gupta",
"Rajendra P.",
""
]
] | We have used the recently published varying physical constants (VPC) approach to resolve the primordial lithium abundance problem. The value of the ratio of $7Li$ to hydrogen $7Li/H=1.400(\pm 0.023){\times}10^{-10}$ we have calculated using this approach is about four times lower than that estimated using the standard lambda cold dark matter (${\Lambda}$CDM) cosmological model, and is consistent with the most agreed observational value of $1.6(\pm 0.3){\times}10^{-10}$. In the VPC approach Einstein equations are modified to include the variation of the speed of light $c$, gravitational constant $G$ and cosmological constant ${\Lambda}$ using the Einstein-Hilbert action. Application of this approach to cosmology naturally leads to the variation of the Plank constant $\hbar$ and the Boltzmann constant $k_B$ as well. They approach fixed values at the scale factor $a\ll 1$: $c=c_0/e$, $G=G_0/e^3$, $\hbar=\hbar_0/e$ and $k_B=k_{B0}/e^{5/4}$, where $e$ is the Euler's number (=2.7183). Since the VPC cosmology reduces to the same form as the ${\Lambda}$CDM cosmology at very small scale factors, we could use an existing Big-Bang nucleosynthesis (BBN) code AlterBBN with the above changes to calculate the light element abundances under the VPC cosmology. Among other abundances we have calculated at baryon to photon ratio ${\eta}=6.1{\times}10^{-10}$ are: $4He/H =0.2478 (\pm 0.041)$, $D/H =2.453(\pm 0.041){\times}10^{-5}$ and $3 He/H=2.940(\pm 0.049){\times}10^{-5}$. |
2303.18111 | Kristina Giesel | Kristina Giesel and Hongguang Liu | Dynamically implementing the $\overline{\mu}$-scheme in cosmological and
spherically symmetric models in an extended phase space model | 16 pages + appendix, accepted by universe, contribution to the
special issue "Loop Quantum Gravity: A Themed Issue in Honor of Prof. Abhay
Ashtekar" | Universe 2023, 9(4), 176 | 10.3390/universe9040176 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider an extended phase space formulation for cosmological and
spherically symmetric models in which the choice of a given
$\overline{\mu}$-scheme can be implemented dynamically. These models are
constructed in the context of the relational formalism by using a canonical
transformation on the extended phase space which provides a Kucha\v{r}
decomposition of the extended phase space. The resulting model can be
understood as a gauge-unfixed model of a given $\overline{\mu}$-scheme. We use
this formalism to investigate the restrictions to the allowed
$\overline{\mu}$-scheme from this perspective and discuss the differences in
the cosmological and spherically symmetric case. This method can be useful, for
example, to obtain a $\overline{\mu}$-scheme in a top-down derivation from full
LQG to symmetry reduced effective models, where for some models only the
$\mu_0$-scheme has been obtained so far.
| [
{
"created": "Fri, 31 Mar 2023 14:58:55 GMT",
"version": "v1"
}
] | 2023-04-04 | [
[
"Giesel",
"Kristina",
""
],
[
"Liu",
"Hongguang",
""
]
] | We consider an extended phase space formulation for cosmological and spherically symmetric models in which the choice of a given $\overline{\mu}$-scheme can be implemented dynamically. These models are constructed in the context of the relational formalism by using a canonical transformation on the extended phase space which provides a Kucha\v{r} decomposition of the extended phase space. The resulting model can be understood as a gauge-unfixed model of a given $\overline{\mu}$-scheme. We use this formalism to investigate the restrictions to the allowed $\overline{\mu}$-scheme from this perspective and discuss the differences in the cosmological and spherically symmetric case. This method can be useful, for example, to obtain a $\overline{\mu}$-scheme in a top-down derivation from full LQG to symmetry reduced effective models, where for some models only the $\mu_0$-scheme has been obtained so far. |
1504.03062 | Kiyoshi Shiraishi | Takuya Maki and Kiyoshi Shiraishi | Exact solutions for gravitational collapse with a dilaton field in
arbitrary dimensions | 15 pages, 2 eps figures | Classical and Quantum Gravity 12, No. 1, pp. 159-172 (1995) | 10.1088/0264-9381/12/1/014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present time-dependent analytic solutions to the Einstein equations
coupled with a dilaton (scalar) field. The background geometry for the
solutions is a product of an N-dimensional spherically symmetric space and a
d-dimensional flat space. We discuss the global properties of the spacetime.
| [
{
"created": "Mon, 13 Apr 2015 04:36:44 GMT",
"version": "v1"
},
{
"created": "Sat, 6 Apr 2019 02:49:23 GMT",
"version": "v2"
}
] | 2019-04-09 | [
[
"Maki",
"Takuya",
""
],
[
"Shiraishi",
"Kiyoshi",
""
]
] | We present time-dependent analytic solutions to the Einstein equations coupled with a dilaton (scalar) field. The background geometry for the solutions is a product of an N-dimensional spherically symmetric space and a d-dimensional flat space. We discuss the global properties of the spacetime. |
2102.06734 | Rita Teixeira da Costa | Rita Teixeira da Costa, Marc Casals | The Teukolsky--Starobinsky constants: facts and fictions | 17 pages, 4 figures | Classical and Quantum Gravity, 38:165016 (2020) | 10.1088/1361-6382/ac11a8 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Teukolsky Master Equation describes the dynamics of massless fields with
spin on a Kerr black hole. Under separation of variables, spin-reversal for
this equation is accomplished through the so-called Teukolsky--Starobinsky
identities. These identities are associated to the so-called
Teukolsky--Starobinsky constants, which are spin-dependent.
We collect some properties of the Teukolsky--Starobinsky constants and dispel
some myths present in the literature. We show that, contrary to popular belief,
these constants can be negative for spin larger than 2. Such fields thus
exhibit a novel form of energy amplification which occurs for non-superradiant
frequencies.
| [
{
"created": "Fri, 12 Feb 2021 19:33:41 GMT",
"version": "v1"
}
] | 2021-08-20 | [
[
"da Costa",
"Rita Teixeira",
""
],
[
"Casals",
"Marc",
""
]
] | The Teukolsky Master Equation describes the dynamics of massless fields with spin on a Kerr black hole. Under separation of variables, spin-reversal for this equation is accomplished through the so-called Teukolsky--Starobinsky identities. These identities are associated to the so-called Teukolsky--Starobinsky constants, which are spin-dependent. We collect some properties of the Teukolsky--Starobinsky constants and dispel some myths present in the literature. We show that, contrary to popular belief, these constants can be negative for spin larger than 2. Such fields thus exhibit a novel form of energy amplification which occurs for non-superradiant frequencies. |
gr-qc/9310029 | null | J\"urgen Audretsch and Karl-Peter Marzlin | Ramsey fringes in atomic interferometry: measurability of the influence
of space-time curvature | 28 pages, Preprint KONS-RGKU-94/02, RevTeX 2.1 The description of the
proposed experiment has been substantially changed. Instead of the space-time
curvature of the earth we now consider the curvature caused by two
laboratory-sized lead blocks. (Pictures are not changed) | Phys.Rev. A50 (1994) 2080 | 10.1103/PhysRevA.50.2080 | null | gr-qc | null | The influence od space-time curvature on quantum matter which can be
theoretically described by covariant wave equations has not been experimentally
established yet. In this paper we analyse in detail the suitability of the
Ramsey atom beam interferometer for the measurement of the phase shift caused
by the Riemannian curvature of the earth. It appears that the detection should
be possible with minor modifications of existing devices within the near
future. The paper is divided into two parts. The first one is concerned with
the derivation of general relativistic correction terms to the Pauli equation
starting from the fully covariant Dirac equation and their physical
interpretation. The inertial effects of acceleration and rotation are included.
In the second part we calculate the phase shift as seen in a laboratory resting
on the rotating earth and examine various possibilities to enlarge the
sensitivity of the apparatus to space-time curvature. Some remarks on the
Lense-Thirring effect and on gravitational waves are made. Since the two parts
may be more or less interesting for physicists with different research fields
they are written in such a way that each one may be read without much reference
to the other one.
| [
{
"created": "Thu, 21 Oct 1993 14:52:37 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Feb 1994 13:07:17 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Audretsch",
"Jürgen",
""
],
[
"Marzlin",
"Karl-Peter",
""
]
] | The influence od space-time curvature on quantum matter which can be theoretically described by covariant wave equations has not been experimentally established yet. In this paper we analyse in detail the suitability of the Ramsey atom beam interferometer for the measurement of the phase shift caused by the Riemannian curvature of the earth. It appears that the detection should be possible with minor modifications of existing devices within the near future. The paper is divided into two parts. The first one is concerned with the derivation of general relativistic correction terms to the Pauli equation starting from the fully covariant Dirac equation and their physical interpretation. The inertial effects of acceleration and rotation are included. In the second part we calculate the phase shift as seen in a laboratory resting on the rotating earth and examine various possibilities to enlarge the sensitivity of the apparatus to space-time curvature. Some remarks on the Lense-Thirring effect and on gravitational waves are made. Since the two parts may be more or less interesting for physicists with different research fields they are written in such a way that each one may be read without much reference to the other one. |
2210.05998 | Jorge Gigante Valcarcel | Sebastian Bahamonde, Johann Chevrier, Jorge Gigante Valcarcel | New black hole solutions with a dynamical traceless nonmetricity tensor
in Metric-Affine Gravity | 21 pages, 0 figures, minor changes, references added. It matches the
version published in JCAP | JCAP02(2023)018 | 10.1088/1475-7516/2023/02/018 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of Metric-Affine Gravity, the existing correspondence
between the Einstein tensor and the energy-momentum tensor of matter provided
by General Relativity is extended towards a post-Riemannian description in
terms of the torsion and nonmetricity fields, which are sourced by the spin,
dilation and shear currents of matter. In this work, we focus on the dynamical
role of the traceless part of the nonmetricity tensor and its intrinsic
connection with shears, defining a model which encloses a new black hole
solution endowed with shear charges. We show that the extension in the presence
of dynamical torsion and Weyl vector leads to the broadest family of static and
spherically symmetric black hole solutions with spin, dilation and shear
charges in Metric-Affine Gravity so far.
| [
{
"created": "Wed, 12 Oct 2022 08:07:01 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Feb 2023 08:04:58 GMT",
"version": "v2"
}
] | 2023-02-10 | [
[
"Bahamonde",
"Sebastian",
""
],
[
"Chevrier",
"Johann",
""
],
[
"Valcarcel",
"Jorge Gigante",
""
]
] | In the framework of Metric-Affine Gravity, the existing correspondence between the Einstein tensor and the energy-momentum tensor of matter provided by General Relativity is extended towards a post-Riemannian description in terms of the torsion and nonmetricity fields, which are sourced by the spin, dilation and shear currents of matter. In this work, we focus on the dynamical role of the traceless part of the nonmetricity tensor and its intrinsic connection with shears, defining a model which encloses a new black hole solution endowed with shear charges. We show that the extension in the presence of dynamical torsion and Weyl vector leads to the broadest family of static and spherically symmetric black hole solutions with spin, dilation and shear charges in Metric-Affine Gravity so far. |
2308.05544 | Yi Yang | Yi Yang, Dong Liu, Ali \"Ovg\"un, Gaetano Lambiase, and Zheng-Wen Long | Black hole surrounded by the pseudo-isothermal dark matter halo | null | Eur. Phys. J. C (2024) 84:63 | 10.1140/epjc/s10052-024-12412-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The abundance of dark matter in the actual universe motivates us to construct
the black hole spacetime enveloped by dark matter. In this paper, we derive a
new spherically symmetric black hole surrounded by the pseudo-isothermal dark
matter halo, and then explore the effects of the pseudo-isothermal halo profile
on a rotating black hole at the M87 galactic center, aiming to achieve a black
hole solution that aligns with those found in the real universe. Using the
Newman-Janis method, we derive a rotating black hole solution encompassed by
the pseudo-isothermal halo, which is consistent with observations of actual
black holes that are believed to possess spin. Our investigation focuses on the
impact of the pseudo-isothermal halo on the black hole event horizon, time-like
and null orbits, as well as the black hole shadow. We find that as the spin
parameter $a$ increases, the interval between the inner event horizon and the
outer event horizon of the rotating black hole surrounded by the
pseudo-isothermal halo in M87 diminishes. This leads to the formation of an
extreme black hole. The presence of dark matter, however, has minimal effect on
the event horizon. Moreover, in the M87 as the spin parameter $a$ increases,
the black hole shadow deviates increasingly from a standard circle, with larger
spin parameters causing more pronounced distortion relative to the standard
circle. Surprisingly, we observe that the dark matter density has very little
influence on the shadow of the black hole surrounded by the pseudo-isothermal
halo in the M87. This study contributes to a deeper understanding of black hole
structures and the role of dark matter in the universe.
| [
{
"created": "Thu, 10 Aug 2023 12:53:47 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Aug 2023 13:52:43 GMT",
"version": "v2"
},
{
"created": "Wed, 24 Jan 2024 15:45:12 GMT",
"version": "v3"
}
] | 2024-01-29 | [
[
"Yang",
"Yi",
""
],
[
"Liu",
"Dong",
""
],
[
"Övgün",
"Ali",
""
],
[
"Lambiase",
"Gaetano",
""
],
[
"Long",
"Zheng-Wen",
""
]
] | The abundance of dark matter in the actual universe motivates us to construct the black hole spacetime enveloped by dark matter. In this paper, we derive a new spherically symmetric black hole surrounded by the pseudo-isothermal dark matter halo, and then explore the effects of the pseudo-isothermal halo profile on a rotating black hole at the M87 galactic center, aiming to achieve a black hole solution that aligns with those found in the real universe. Using the Newman-Janis method, we derive a rotating black hole solution encompassed by the pseudo-isothermal halo, which is consistent with observations of actual black holes that are believed to possess spin. Our investigation focuses on the impact of the pseudo-isothermal halo on the black hole event horizon, time-like and null orbits, as well as the black hole shadow. We find that as the spin parameter $a$ increases, the interval between the inner event horizon and the outer event horizon of the rotating black hole surrounded by the pseudo-isothermal halo in M87 diminishes. This leads to the formation of an extreme black hole. The presence of dark matter, however, has minimal effect on the event horizon. Moreover, in the M87 as the spin parameter $a$ increases, the black hole shadow deviates increasingly from a standard circle, with larger spin parameters causing more pronounced distortion relative to the standard circle. Surprisingly, we observe that the dark matter density has very little influence on the shadow of the black hole surrounded by the pseudo-isothermal halo in the M87. This study contributes to a deeper understanding of black hole structures and the role of dark matter in the universe. |
gr-qc/9806082 | Fernando Kokubun | F. Kokubun | Gravitational Waves from The Newtonian plus H\'enon-Heiles System | 10 pages, RevTex, three PS figures, to be published in Phys.Lett. A | Phys.Lett. A245 (1998) 358-362 | 10.1016/S0375-9601(98)00470-8 | null | gr-qc | null | In this work we analyze the emission of gravitational waves from a
gravitational system described by a Newtonian term plus a H\'enon-Heiles term.
The main concern is to analyze how the inclusion of the Newtonian term changes
the emission of gravitational waves, considering its emission in the chaotic
and regular regime.
| [
{
"created": "Fri, 19 Jun 1998 23:48:53 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Kokubun",
"F.",
""
]
] | In this work we analyze the emission of gravitational waves from a gravitational system described by a Newtonian term plus a H\'enon-Heiles term. The main concern is to analyze how the inclusion of the Newtonian term changes the emission of gravitational waves, considering its emission in the chaotic and regular regime. |
2210.14968 | Dirk Puetzfeld | Peter A. Hogan, Dirk Puetzfeld | Colliding Plane Fronted Waves and a Gravito--Electromagnetic Searchlight | 7 pages, 2 figures | Phys. Rev. D 106, 124043 (2022) | 10.1103/PhysRevD.106.124043 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a formulation of Einstein--Maxwell vacuum fields due to plane
fronted electromagnetic waves sharing their wave fronts with gravitational
waves. This is based on a recent geometrical reconstruction of plane fronted
wave fields by the authors which clearly identifies the cases in which the wave
fronts collide or do not collide. In the former case our construction suggests
an explicit example of a searchlight beam, accompanied by gravitational
radiation, which sweeps across the sky. This gravito--electromagnetic
searchlight and its properties are described in detail.
| [
{
"created": "Wed, 26 Oct 2022 18:24:26 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Dec 2022 15:54:13 GMT",
"version": "v2"
}
] | 2023-01-02 | [
[
"Hogan",
"Peter A.",
""
],
[
"Puetzfeld",
"Dirk",
""
]
] | We present a formulation of Einstein--Maxwell vacuum fields due to plane fronted electromagnetic waves sharing their wave fronts with gravitational waves. This is based on a recent geometrical reconstruction of plane fronted wave fields by the authors which clearly identifies the cases in which the wave fronts collide or do not collide. In the former case our construction suggests an explicit example of a searchlight beam, accompanied by gravitational radiation, which sweeps across the sky. This gravito--electromagnetic searchlight and its properties are described in detail. |
1108.0829 | Tomasz Pawlowski | Guillermo A. Mena Marugan, Javier Olmedo, Tomasz Pawlowski | Prescriptions in Loop Quantum Cosmology: A comparative analysis | 18 pages, 6 figures, RevTex4-1 + BibTex | null | 10.1103/PhysRevD.84.064012 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Various prescriptions proposed in the literature to attain the polymeric
quantization of a homogeneous and isotropic flat spacetime coupled to a
massless scalar field are carefully analyzed in order to discuss their
differences. A detailed numerical analysis confirms that, for states which are
not deep in the quantum realm, the expectation values and dispersions of some
natural observables of interest in cosmology are qualitatively the same for all
the considered prescriptions. On the contrary, the amplitude of the wave
functions of those states differs considerably at the bounce epoch for these
prescriptions. This difference cannot be absorbed by a change of
representation. Finally, the prescriptions with simpler superselection sectors
are clearly more efficient from the numerical point of view.
| [
{
"created": "Wed, 3 Aug 2011 12:34:36 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Marugan",
"Guillermo A. Mena",
""
],
[
"Olmedo",
"Javier",
""
],
[
"Pawlowski",
"Tomasz",
""
]
] | Various prescriptions proposed in the literature to attain the polymeric quantization of a homogeneous and isotropic flat spacetime coupled to a massless scalar field are carefully analyzed in order to discuss their differences. A detailed numerical analysis confirms that, for states which are not deep in the quantum realm, the expectation values and dispersions of some natural observables of interest in cosmology are qualitatively the same for all the considered prescriptions. On the contrary, the amplitude of the wave functions of those states differs considerably at the bounce epoch for these prescriptions. This difference cannot be absorbed by a change of representation. Finally, the prescriptions with simpler superselection sectors are clearly more efficient from the numerical point of view. |
1410.2528 | Valery Kiselev | Ja.V. Balitsky, V.V. Kiselev | Inflaton as a pseudo-Goldstone boson of vacuum energy shift symmetry | 11 pages; calculations, comments, 2 figures and references added | JCAP 1504 (2015) 032 | 10.1088/1475-7516/2015/04/032 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The exact symmetry induced by the global shift of energy scale for the
cosmological constant in the action of matter fields is spontaneously broken by
setting the density of real vacuum energy and explicitly broken by the gravity
that means the existence of Nambu--Goldstone boson, which transforms into the
pseudo-Goldstone boson due to the gravity. We identify this boson with the
inflaton in the Einstein frame of action for the fields, while the breaking is
induced by a non-minimal interaction of boson with the scalar curvature in the
Jordan frame. The role of Galilean symmetry of field equation is emphasized in
the procedure of fixing some terms in the bare action.
| [
{
"created": "Thu, 25 Sep 2014 06:42:37 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Dec 2014 07:01:42 GMT",
"version": "v2"
},
{
"created": "Fri, 20 Feb 2015 08:07:02 GMT",
"version": "v3"
}
] | 2019-11-28 | [
[
"Balitsky",
"Ja. V.",
""
],
[
"Kiselev",
"V. V.",
""
]
] | The exact symmetry induced by the global shift of energy scale for the cosmological constant in the action of matter fields is spontaneously broken by setting the density of real vacuum energy and explicitly broken by the gravity that means the existence of Nambu--Goldstone boson, which transforms into the pseudo-Goldstone boson due to the gravity. We identify this boson with the inflaton in the Einstein frame of action for the fields, while the breaking is induced by a non-minimal interaction of boson with the scalar curvature in the Jordan frame. The role of Galilean symmetry of field equation is emphasized in the procedure of fixing some terms in the bare action. |
gr-qc/9811064 | Martin Goliath | Martin Goliath, Ulf S Nilsson, and Claes Uggla | Spatially self-similar spherically symmetric perfect-fluid models | 21 pages, 6 eps-figures | Class.Quant.Grav. 15 (1998) 167 | 10.1088/0264-9381/15/1/012 | null | gr-qc | null | Einstein's field equations for spatially self-similar spherically symmetric
perfect-fluid models are investigated. The field equations are rewritten as a
first-order system of autonomous differential equations. Dimensionless
variables are chosen in such a way that the number of equations in the coupled
system is reduced as far as possible and so that the reduced phase space
becomes compact and regular. The system is subsequently analysed qualitatively
with the theory of dynamical systems.
| [
{
"created": "Thu, 19 Nov 1998 13:44:35 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Goliath",
"Martin",
""
],
[
"Nilsson",
"Ulf S",
""
],
[
"Uggla",
"Claes",
""
]
] | Einstein's field equations for spatially self-similar spherically symmetric perfect-fluid models are investigated. The field equations are rewritten as a first-order system of autonomous differential equations. Dimensionless variables are chosen in such a way that the number of equations in the coupled system is reduced as far as possible and so that the reduced phase space becomes compact and regular. The system is subsequently analysed qualitatively with the theory of dynamical systems. |
1808.07083 | James T. Wheeler | James T Wheeler | General relativity as a biconformal gauge theory | 56 pages | Nucl.Phys. B (2019) 114624 | 10.1016/j.nuclphysb.2019.114624 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We consider the conformal group of a space of dim n=p+q, with SO(p,q) metric.
The quotient of this group by its homogeneous Weyl subgroup gives a principal
fiber bundle with 2n-dim base manifold and Weyl fibers. The Cartan
generalization to a curved 2n-dim geometry admits an action functional linear
in the curvatures. Because symmetry is maintained between the translations and
the special conformal transformations in the construction, these spaces are
called biconformal; this same symmetry gives biconformal spaces overlapping
structures with double field theories, including manifest T duality. We
establish that biconformal geometry is a form of double field theory, showing
how general relativity with integrable local scale invariance arises from its
field equations. While we discuss the relationship between biconformal
geometries and the double field theories of T-dual string theories, our
principal interest is the study of the gravity theory. We show that vanishing
torsion and vanishing co-torsion solutions to the field equations overconstrain
the system, implying a trivial biconformal space. Wih co-torsion unconstrained,
we show that (1) the torsion-free solutions are foliated by copies of an n-dim
Lie group, (2) torsion-free solutions generically describe locally
scale-invariant general relativity with symmetric, divergence-free sources on
either the co-tangent bundle of n-dim (p,q)-spacetime or the torus of double
field theory, and (3) torsion-free solutions admit a subclass of spacetimes
with n-dim non-abelian Lie symmetry. These latter cases include the possibility
of a gravity-electroweak unification. It is notable that the field equations
reduce all curvature components to dependence only on the solder form of an
n-dim Lagrangian submanifold, despite the increased number of curvature
components and doubled number of initial independent variables.
| [
{
"created": "Tue, 21 Aug 2018 18:52:28 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Apr 2019 18:29:09 GMT",
"version": "v2"
}
] | 2019-05-03 | [
[
"Wheeler",
"James T",
""
]
] | We consider the conformal group of a space of dim n=p+q, with SO(p,q) metric. The quotient of this group by its homogeneous Weyl subgroup gives a principal fiber bundle with 2n-dim base manifold and Weyl fibers. The Cartan generalization to a curved 2n-dim geometry admits an action functional linear in the curvatures. Because symmetry is maintained between the translations and the special conformal transformations in the construction, these spaces are called biconformal; this same symmetry gives biconformal spaces overlapping structures with double field theories, including manifest T duality. We establish that biconformal geometry is a form of double field theory, showing how general relativity with integrable local scale invariance arises from its field equations. While we discuss the relationship between biconformal geometries and the double field theories of T-dual string theories, our principal interest is the study of the gravity theory. We show that vanishing torsion and vanishing co-torsion solutions to the field equations overconstrain the system, implying a trivial biconformal space. Wih co-torsion unconstrained, we show that (1) the torsion-free solutions are foliated by copies of an n-dim Lie group, (2) torsion-free solutions generically describe locally scale-invariant general relativity with symmetric, divergence-free sources on either the co-tangent bundle of n-dim (p,q)-spacetime or the torus of double field theory, and (3) torsion-free solutions admit a subclass of spacetimes with n-dim non-abelian Lie symmetry. These latter cases include the possibility of a gravity-electroweak unification. It is notable that the field equations reduce all curvature components to dependence only on the solder form of an n-dim Lagrangian submanifold, despite the increased number of curvature components and doubled number of initial independent variables. |
1912.04306 | Kieran Finn | Kieran Finn | Initial Conditions of Inflation in a Bianchi I Universe | 5 pages 1 figure | Phys. Rev. D 101, 063512 (2020) | 10.1103/PhysRevD.101.063512 | MAN/HEP/2019/012 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the initial conditions of inflation in a Bianchi~I universe
that is homogeneous but not isotropic. We use the Eisenhart lift to describe
such a theory geometrically as geodesics on a field space manifold. We
construct the phase-space manifold of the theory by considering the tangent
bundle of the field space and equipping it with a natural metric. We find that
the total volume of this manifold is finite for a wide class of inflationary
models. We therefore take the initial conditions to be uniformly distributed
over it in accordance with Laplace's principle of indifference. This results in
a normalisable, reparametrisation invariant measure on the set of initial
conditions of inflation in a Bianchi~I universe. We find that this measure
favours an initial state in which the inflaton field is at or near its minimum,
with a mild preference for some initial anisotropy. Since inflation requires an
initial field value with a large displacement from its minimum, we therefore
conclude that the theory of inflation requires finely tuned initial conditions.
| [
{
"created": "Mon, 9 Dec 2019 19:00:11 GMT",
"version": "v1"
}
] | 2020-03-18 | [
[
"Finn",
"Kieran",
""
]
] | We investigate the initial conditions of inflation in a Bianchi~I universe that is homogeneous but not isotropic. We use the Eisenhart lift to describe such a theory geometrically as geodesics on a field space manifold. We construct the phase-space manifold of the theory by considering the tangent bundle of the field space and equipping it with a natural metric. We find that the total volume of this manifold is finite for a wide class of inflationary models. We therefore take the initial conditions to be uniformly distributed over it in accordance with Laplace's principle of indifference. This results in a normalisable, reparametrisation invariant measure on the set of initial conditions of inflation in a Bianchi~I universe. We find that this measure favours an initial state in which the inflaton field is at or near its minimum, with a mild preference for some initial anisotropy. Since inflation requires an initial field value with a large displacement from its minimum, we therefore conclude that the theory of inflation requires finely tuned initial conditions. |
2301.11204 | N. Merve Uzun | Ozgur Akarsu, N. Merve Uzun | Cosmological models in scale-independent energy-momentum squared gravity | 11 pages, 1 figure and no tables; matches the version published in
Physics of the Dark Universe | Phys. Dark Univ. 40, 101194 (2023) | 10.1016/j.dark.2023.101194 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scale-independent EMSG is a particular model of energy-momentum squared
gravity (EMSG) in which the new terms in the Einstein field equations arising
from the EMSG theory enter with the same power as the usual terms from
Einstein-Hilbert part of the action. However, the model violates the local
energy-momentum conservation and matter-current conservation in general and
hence, permits a process of matter creation/annihilation in an expanding
universe. Consequently, the scale factor dependencies of the energy densities
are modified by the dimensionless model parameter $\alpha$. We revisit some
nostalgias such as static universes and de Sitter/steady state universes. We
reproduce the original ones, moreover, present some novelties, e.g., a
spatially flat static universe, de Sitter expansion by negative vacuum energy,
steady state universes in the presence of arbitrary fluids with constant
equation of state (EoS) parameter other than dust, etc. We also investigate the
possible dynamics of dust dominated and radiation dominated universes.
Depending on the value of $\alpha$, dust/radiation dominated universe exhibits
power-law accelerated/decelerated expansion, corresponds to a steady state
model or may end in a big rip. In the framework of anisotropic cosmology, we
reproduce Barrow's quiescent universe in the presence of stiff fluid and extend
it to fluids with arbitrary constant EoS parameter. We also relax the condition
for isotropic initial singularity (big bang) owing to that EMSG effectively
allows ultra-stiff EoS parameters.
| [
{
"created": "Thu, 26 Jan 2023 16:26:52 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Feb 2023 09:17:16 GMT",
"version": "v2"
}
] | 2023-02-24 | [
[
"Akarsu",
"Ozgur",
""
],
[
"Uzun",
"N. Merve",
""
]
] | Scale-independent EMSG is a particular model of energy-momentum squared gravity (EMSG) in which the new terms in the Einstein field equations arising from the EMSG theory enter with the same power as the usual terms from Einstein-Hilbert part of the action. However, the model violates the local energy-momentum conservation and matter-current conservation in general and hence, permits a process of matter creation/annihilation in an expanding universe. Consequently, the scale factor dependencies of the energy densities are modified by the dimensionless model parameter $\alpha$. We revisit some nostalgias such as static universes and de Sitter/steady state universes. We reproduce the original ones, moreover, present some novelties, e.g., a spatially flat static universe, de Sitter expansion by negative vacuum energy, steady state universes in the presence of arbitrary fluids with constant equation of state (EoS) parameter other than dust, etc. We also investigate the possible dynamics of dust dominated and radiation dominated universes. Depending on the value of $\alpha$, dust/radiation dominated universe exhibits power-law accelerated/decelerated expansion, corresponds to a steady state model or may end in a big rip. In the framework of anisotropic cosmology, we reproduce Barrow's quiescent universe in the presence of stiff fluid and extend it to fluids with arbitrary constant EoS parameter. We also relax the condition for isotropic initial singularity (big bang) owing to that EMSG effectively allows ultra-stiff EoS parameters. |
1708.01344 | Taishi Ikeda | Taishi Ikeda, Chul-Moon Yoo, Vitor Cardoso | Self-gravitating oscillons and new critical behavior | 24 figures | Phys. Rev. D 96, 064047 (2017) | 10.1103/PhysRevD.96.064047 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamical evolution of self-interacting scalars is of paramount
importance in cosmological settings, and can teach us about the content of
Einstein's equations. In flat space, nonlinear scalar field theories can give
rise to localized, non-singular, time-dependent, long-lived solutions called
{\it oscillons}. Here, we discuss the effects of gravity on the properties and
formation of these structures, described by a scalar field with a double well
potential. We show that oscillons continue to exist even when gravity is turned
on, and we conjecture that there exists a sequence of critical solutions with
infinite lifetime. Our results suggest that a new type of critical behavior
appears in this theory, characterized by modulations of the lifetime of the
oscillon around the scaling law and the modulations of the amplitude of the
critical solutions.
| [
{
"created": "Fri, 4 Aug 2017 01:26:13 GMT",
"version": "v1"
}
] | 2017-10-04 | [
[
"Ikeda",
"Taishi",
""
],
[
"Yoo",
"Chul-Moon",
""
],
[
"Cardoso",
"Vitor",
""
]
] | The dynamical evolution of self-interacting scalars is of paramount importance in cosmological settings, and can teach us about the content of Einstein's equations. In flat space, nonlinear scalar field theories can give rise to localized, non-singular, time-dependent, long-lived solutions called {\it oscillons}. Here, we discuss the effects of gravity on the properties and formation of these structures, described by a scalar field with a double well potential. We show that oscillons continue to exist even when gravity is turned on, and we conjecture that there exists a sequence of critical solutions with infinite lifetime. Our results suggest that a new type of critical behavior appears in this theory, characterized by modulations of the lifetime of the oscillon around the scaling law and the modulations of the amplitude of the critical solutions. |
2012.11859 | Tomohiro Ishikawa | Tomohiro Ishikawa, Shoki Iwaguchi, Yuta Michimura, Masaki Ando, Rika
Yamada, Izumi Watanabe, Koji Nagano, Tomotada Akutsu, Kentaro Komori, Mitsuru
Musha, Takeo Naito, Taigen Morimoto, Seiji Kawamura | Improvement of the target sensitivity in DECIGO by optimizing its
parameters for quantum noise including the effect of diffraction loss | 13 pages, 12 figures | null | 10.3390/galaxies9010014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | DECIGO is the future Japanese gravitational wave detector in outer space. We
previously set the default design parameters to provide a good target
sensitivity to detect the primordial gravitational waves (GWs). However, the
updated upper limit of the primordial GWs by the Planck observations motivated
us for further optimization of the target sensitivity. Previously, we had not
considered optical diffraction loss due to the very long cavity length. In this
paper, we optimize various DECIGO parameters by maximizing the signal-to-noise
ratio (SNR), for the primordial GWs to quantum noise including the effects of
diffraction loss. We evaluated the power spectrum density for one cluster in
DECIGO utilizing the quantum noise of one differential Fabry-Perot
interferometer. Then we calculated the SNR by correlating two clusters in the
same position. We performed the optimization for two cases: the constant
mirror-thickness case and the constant mirror-mass case. As a result, we
obtained the SNR dependence on the mirror radius, which also determines various
DECIGO parameters. This result is the first step toward optimizing the DECIGO
design by considering the practical constraints on the mirror dimension and
implementing other noise sources.
| [
{
"created": "Tue, 22 Dec 2020 07:05:50 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Mar 2021 07:48:35 GMT",
"version": "v2"
}
] | 2021-03-10 | [
[
"Ishikawa",
"Tomohiro",
""
],
[
"Iwaguchi",
"Shoki",
""
],
[
"Michimura",
"Yuta",
""
],
[
"Ando",
"Masaki",
""
],
[
"Yamada",
"Rika",
""
],
[
"Watanabe",
"Izumi",
""
],
[
"Nagano",
"Koji",
""
],
[
"Akutsu",
"Tomotada",
""
],
[
"Komori",
"Kentaro",
""
],
[
"Musha",
"Mitsuru",
""
],
[
"Naito",
"Takeo",
""
],
[
"Morimoto",
"Taigen",
""
],
[
"Kawamura",
"Seiji",
""
]
] | DECIGO is the future Japanese gravitational wave detector in outer space. We previously set the default design parameters to provide a good target sensitivity to detect the primordial gravitational waves (GWs). However, the updated upper limit of the primordial GWs by the Planck observations motivated us for further optimization of the target sensitivity. Previously, we had not considered optical diffraction loss due to the very long cavity length. In this paper, we optimize various DECIGO parameters by maximizing the signal-to-noise ratio (SNR), for the primordial GWs to quantum noise including the effects of diffraction loss. We evaluated the power spectrum density for one cluster in DECIGO utilizing the quantum noise of one differential Fabry-Perot interferometer. Then we calculated the SNR by correlating two clusters in the same position. We performed the optimization for two cases: the constant mirror-thickness case and the constant mirror-mass case. As a result, we obtained the SNR dependence on the mirror radius, which also determines various DECIGO parameters. This result is the first step toward optimizing the DECIGO design by considering the practical constraints on the mirror dimension and implementing other noise sources. |
2301.10036 | Daniel Brito de Freitas | C. V. da Silva, M. M. F. Nepomuceno and D. B. de Freitas | Multiscale structure of the gravitational wave signal from GW150914
based on the nonextensivity $q$-triplet | 7 pages, 6 figures | null | 10.1209/0295-5075/acbc94 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the first gravitational wave, GW150914, detected by advanced LIGO
and constructed from the data of measurement of strain relative deformation of
the fabric of spacetime. We show that the time series from the gravitational
wave obeys Tsallis's $q$-Gaussian distribution as a probability density and its
dynamics evolve of the three associated Tsallis' indices named $q$-triplet.
This fact strongly suggests that these black hole merger systems behave in a
non-extensive manner. Furthermore, our results point out that the entropic
indexes obtained as a function of frequency are useful statistical parameters
to determine the dominant frequency when black hole coalescence is achieved.
| [
{
"created": "Tue, 24 Jan 2023 14:25:38 GMT",
"version": "v1"
}
] | 2023-03-15 | [
[
"da Silva",
"C. V.",
""
],
[
"Nepomuceno",
"M. M. F.",
""
],
[
"de Freitas",
"D. B.",
""
]
] | We study the first gravitational wave, GW150914, detected by advanced LIGO and constructed from the data of measurement of strain relative deformation of the fabric of spacetime. We show that the time series from the gravitational wave obeys Tsallis's $q$-Gaussian distribution as a probability density and its dynamics evolve of the three associated Tsallis' indices named $q$-triplet. This fact strongly suggests that these black hole merger systems behave in a non-extensive manner. Furthermore, our results point out that the entropic indexes obtained as a function of frequency are useful statistical parameters to determine the dominant frequency when black hole coalescence is achieved. |
gr-qc/0002010 | Sukanta Bose | Sukanta Bose, Archana Pai, and Sanjeev Dhurandhar | Detection of gravitational waves from inspiraling compact binaries using
a network of interferometric detectors | 6 pages, RevTeX. Based on talk given at GWDAW-99, Rome | Int.J.Mod.Phys. D9 (2000) 325-329 | 10.1142/S0218271800000360 | IUCAA-2/2000 | gr-qc astro-ph | null | We formulate the data analysis problem for the detection of the Newtonian
waveform from an inspiraling compact-binary by a network of arbitrarily
oriented and arbitrarily distributed laser interferometric gravitational wave
detectors. We obtain for the first time the relation between the optimal
statistic and the magnitude of the network correlation vector, which is
constructed from the matched network-filter. This generalizes the calculation
reported in an earlier work (gr-qc/9906064), where the detectors are taken to
be coincident.
| [
{
"created": "Wed, 2 Feb 2000 18:32:03 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Bose",
"Sukanta",
""
],
[
"Pai",
"Archana",
""
],
[
"Dhurandhar",
"Sanjeev",
""
]
] | We formulate the data analysis problem for the detection of the Newtonian waveform from an inspiraling compact-binary by a network of arbitrarily oriented and arbitrarily distributed laser interferometric gravitational wave detectors. We obtain for the first time the relation between the optimal statistic and the magnitude of the network correlation vector, which is constructed from the matched network-filter. This generalizes the calculation reported in an earlier work (gr-qc/9906064), where the detectors are taken to be coincident. |
gr-qc/9801025 | Sergey V. Sushkov | Sergey V. Sushkov | Particle Creation Near the Chronology Horizon | 6 pages, RevTeX, one postscript figure. Presented in the GR15,
December, 1997, IUCAA, Pune. Submitted to Phys.Rev.D | Phys.Rev. D58 (1998) 044006 | 10.1103/PhysRevD.58.044006 | KGPU-97-01 | gr-qc | null | We investigate the phenomenon of particle creation of the massless scalar
field in the model of spacetime in which, depending on the model's parameter
$\aout$, the chronology horizon could be formed. The model represents a
two-dimensional curved spacetime with the topology $R^1 \times S^1$ which is
asymptotically flat in the past and in the future. The spacetime is globally
hyperbolic and has no causal pathologies if $\aout<1$, and closed timelike
curves appear in the spacetime if $\aout\ge 1$. We obtain the spectrum of
created particles in the case $\aout<1$. In the limit $\aout \to 1$ this
spectrum gives the number of particles created into mode $n$ near the
chronology horizon. The main result we have obtained is that the number of
scalar particles created into each mode as well as the full number of particles
remain finite at the moment of forming of the chronology horizon.
| [
{
"created": "Fri, 9 Jan 1998 14:52:22 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Sushkov",
"Sergey V.",
""
]
] | We investigate the phenomenon of particle creation of the massless scalar field in the model of spacetime in which, depending on the model's parameter $\aout$, the chronology horizon could be formed. The model represents a two-dimensional curved spacetime with the topology $R^1 \times S^1$ which is asymptotically flat in the past and in the future. The spacetime is globally hyperbolic and has no causal pathologies if $\aout<1$, and closed timelike curves appear in the spacetime if $\aout\ge 1$. We obtain the spectrum of created particles in the case $\aout<1$. In the limit $\aout \to 1$ this spectrum gives the number of particles created into mode $n$ near the chronology horizon. The main result we have obtained is that the number of scalar particles created into each mode as well as the full number of particles remain finite at the moment of forming of the chronology horizon. |
2201.02112 | Quentin Vigneron | Quentin Vigneron | On non-Euclidean Newtonian theories and their cosmological backreaction | Published in Classical and Quantum Gravity | null | 10.1088/1361-6382/ac7a87 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | Constructing an extension of Newton's theory which is defined on a
non-Euclidean topology (in the sense of Thurston's decomposition), called a
non-Euclidean Newtonian theory, corresponding to the zeroth order of a
non-relativistic limit of general relativity is an important step in the study
of the backreaction problem in cosmology and might be a powerful tool to study
the influence of global topology on structure formation. After giving a precise
mathematical definition of such a theory, based on the concept of Galilean
manifolds, we propose two such extensions, for spherical or hyperbolic
topologies, using a minimal modification of the Newton-Cartan equations.
However as for now we do not seek to justify this modification from general
relativity. The first proposition features a non-zero cosmological
backreaction, but the presence of gravitomagnetism and the impossibility of
performing exact $N$-body calculations make this theory difficult to be
interpreted as a Newtonian-like theory. The second proposition features no
backreaction, exact $N$-body calculation is possible and no gravitomagnetism
appears. In absence of a justification from general relativity, we argue that
this non-Euclidean Newtonian theory should be the one to be considered, and
could be used to study the influence of topology on structure formation via
$N$-body simulations. For this purpose we give the mass point gravitational
field in $\mathbb{S}^3$.
| [
{
"created": "Thu, 6 Jan 2022 15:49:10 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Jun 2022 08:43:42 GMT",
"version": "v2"
}
] | 2022-06-23 | [
[
"Vigneron",
"Quentin",
""
]
] | Constructing an extension of Newton's theory which is defined on a non-Euclidean topology (in the sense of Thurston's decomposition), called a non-Euclidean Newtonian theory, corresponding to the zeroth order of a non-relativistic limit of general relativity is an important step in the study of the backreaction problem in cosmology and might be a powerful tool to study the influence of global topology on structure formation. After giving a precise mathematical definition of such a theory, based on the concept of Galilean manifolds, we propose two such extensions, for spherical or hyperbolic topologies, using a minimal modification of the Newton-Cartan equations. However as for now we do not seek to justify this modification from general relativity. The first proposition features a non-zero cosmological backreaction, but the presence of gravitomagnetism and the impossibility of performing exact $N$-body calculations make this theory difficult to be interpreted as a Newtonian-like theory. The second proposition features no backreaction, exact $N$-body calculation is possible and no gravitomagnetism appears. In absence of a justification from general relativity, we argue that this non-Euclidean Newtonian theory should be the one to be considered, and could be used to study the influence of topology on structure formation via $N$-body simulations. For this purpose we give the mass point gravitational field in $\mathbb{S}^3$. |
1310.2144 | Ujjal Debnath | Ujjal Debnath | Constraining the Parameters of Modified Chaplygin Gas in Einstein-Aether
Gravity | 16 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1206.0507, arXiv:1304.6713 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have assumed FRW model of the universe in Einstein-Aether gravity filled
with dark matter and Modified Chaplygin gas (MCG) type dark energy. We present
the Hubble parameter in terms of some unknown parameters and observational
parameters with the redshift z. From observed Hubble data (OHD) set (12
points), we have obtained the bounds of the arbitrary parameters (A,B) of MCG
by minimizing the \chi^{2} test. Next due to joint analysis of BAO and CMB
observations, we have also obtained the best fit values and the bounds of the
parameters (A,B) by fixing some other parameters. We have also taken type Ia
supernovae data set (union 2 data set with 557 data points). Next due to joint
analysis with SNe, we have obtained the best fit values of parameters. The
best-fit values and bounds of the parameters are obtained by 66%, 90% and 99%
confidence levels for OHD, OHD+BAO, OHD+BAO+CMB and OHD+BAO+CMB+SNe joint
analysis. The distance modulus \mu(z) against redshift z for our theoretical
MCG model in Einstein-Aether gravity have been tested for the best fit values
of the parameters and the observed SNe Ia union2 data sample.
| [
{
"created": "Sun, 6 Oct 2013 13:23:36 GMT",
"version": "v1"
}
] | 2013-10-09 | [
[
"Debnath",
"Ujjal",
""
]
] | We have assumed FRW model of the universe in Einstein-Aether gravity filled with dark matter and Modified Chaplygin gas (MCG) type dark energy. We present the Hubble parameter in terms of some unknown parameters and observational parameters with the redshift z. From observed Hubble data (OHD) set (12 points), we have obtained the bounds of the arbitrary parameters (A,B) of MCG by minimizing the \chi^{2} test. Next due to joint analysis of BAO and CMB observations, we have also obtained the best fit values and the bounds of the parameters (A,B) by fixing some other parameters. We have also taken type Ia supernovae data set (union 2 data set with 557 data points). Next due to joint analysis with SNe, we have obtained the best fit values of parameters. The best-fit values and bounds of the parameters are obtained by 66%, 90% and 99% confidence levels for OHD, OHD+BAO, OHD+BAO+CMB and OHD+BAO+CMB+SNe joint analysis. The distance modulus \mu(z) against redshift z for our theoretical MCG model in Einstein-Aether gravity have been tested for the best fit values of the parameters and the observed SNe Ia union2 data sample. |
1609.08373 | Sebasti\'an Bahamonde | Sebastian Bahamonde, M. Zubair, G. Abbas | Thermodynamics and cosmological reconstruction in $f(T,B)$ gravity | Accepted for publication in Physics of the Dark Universe. Some
notations and definitions have been changed but the conclusions are the same | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, it was formulated a teleparallel theory called $f(T,B)$ gravity
which connects both $f(T)$ and $f(R)$ under suitable limits. In this theory,
the function in the action is assumed to depend on the torsion scalar $T$ and
also on a boundary term related with the divergence of torsion,
$B=2\nabla_{\mu}T^{\mu}$. In this work, we study different features of a flat
Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) cosmology in this theory. First,
we show that the FLRW equations can be transformed to the form of Clausius
relation $\hat{T}_hS_{\rm eff}=-dE+WdV$, where $\hat{T}_h$ is the horizon
temperature and $S_{\rm eff}$ is the entropy which contains contributions both
from horizon entropy and an additional entropy term introduced due to the
non-equilibrium. We also formulate the constraint for the validity of the
generalised second law of thermodynamics (GSLT). Additionally, using a
cosmological reconstruction technique, we show that both $f(T,B)$ and $-T+F(B)$
gravity can mimic power-law, de-Sitter and $\Lambda$CDM models. Finally, we
formulate the perturbed evolution equations and analyse the stability of some
important cosmological solutions.
| [
{
"created": "Tue, 27 Sep 2016 12:21:47 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Dec 2017 15:12:29 GMT",
"version": "v2"
}
] | 2017-12-19 | [
[
"Bahamonde",
"Sebastian",
""
],
[
"Zubair",
"M.",
""
],
[
"Abbas",
"G.",
""
]
] | Recently, it was formulated a teleparallel theory called $f(T,B)$ gravity which connects both $f(T)$ and $f(R)$ under suitable limits. In this theory, the function in the action is assumed to depend on the torsion scalar $T$ and also on a boundary term related with the divergence of torsion, $B=2\nabla_{\mu}T^{\mu}$. In this work, we study different features of a flat Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) cosmology in this theory. First, we show that the FLRW equations can be transformed to the form of Clausius relation $\hat{T}_hS_{\rm eff}=-dE+WdV$, where $\hat{T}_h$ is the horizon temperature and $S_{\rm eff}$ is the entropy which contains contributions both from horizon entropy and an additional entropy term introduced due to the non-equilibrium. We also formulate the constraint for the validity of the generalised second law of thermodynamics (GSLT). Additionally, using a cosmological reconstruction technique, we show that both $f(T,B)$ and $-T+F(B)$ gravity can mimic power-law, de-Sitter and $\Lambda$CDM models. Finally, we formulate the perturbed evolution equations and analyse the stability of some important cosmological solutions. |
1911.04380 | Emil M. Prodanov | Rossen I. Ivanov and Emil M. Prodanov | On the Cosmological Models with Matter Creation | 19 pages, 1 figure, to appear in European Physical Journal C | European Physical Journal C (2019) 79:118 | 10.1140/epjc/s10052-019-7475-z | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The matter creation model of Prigogine--G\'eh\'eniau--Gunzig--Nardone is
revisited in terms of a redefined creation pressure which does not lead to
irreversible adiabatic evolution at constant specific entropy. With the
resulting freedom to choose a particular gas process, a flat FRWL cosmological
model is proposed based on three input characteristics: (i) a perfect fluid
comprising of an ideal gas, (ii) a quasi-adiabatic polytropic process, and
(iii) a particular rate of particle creation. Such model leads to the
description of the late-time acceleration of the expanding Universe with a
natural transition from decelerating to accelerating regime. Only the Friedmann
equations and the laws of thermodynamics are used and no assumptions of dark
energy component is made. The model also allows the explicit determination as
functions of time of all variables, including the entropy, the non-conserved
specific entropy and the time the accelerating phase begins. A form of
correspondence with the dark energy models (quintessence, in particular) is
established via the $Om$ diagnostics. Parallels with the concordance
cosmological $\Lambda$CDM model for the matter-dominated epoch and the present
epoch of accelerated expansion are also established via slight modifications of
both models.
| [
{
"created": "Mon, 11 Nov 2019 16:45:29 GMT",
"version": "v1"
}
] | 2022-09-15 | [
[
"Ivanov",
"Rossen I.",
""
],
[
"Prodanov",
"Emil M.",
""
]
] | The matter creation model of Prigogine--G\'eh\'eniau--Gunzig--Nardone is revisited in terms of a redefined creation pressure which does not lead to irreversible adiabatic evolution at constant specific entropy. With the resulting freedom to choose a particular gas process, a flat FRWL cosmological model is proposed based on three input characteristics: (i) a perfect fluid comprising of an ideal gas, (ii) a quasi-adiabatic polytropic process, and (iii) a particular rate of particle creation. Such model leads to the description of the late-time acceleration of the expanding Universe with a natural transition from decelerating to accelerating regime. Only the Friedmann equations and the laws of thermodynamics are used and no assumptions of dark energy component is made. The model also allows the explicit determination as functions of time of all variables, including the entropy, the non-conserved specific entropy and the time the accelerating phase begins. A form of correspondence with the dark energy models (quintessence, in particular) is established via the $Om$ diagnostics. Parallels with the concordance cosmological $\Lambda$CDM model for the matter-dominated epoch and the present epoch of accelerated expansion are also established via slight modifications of both models. |
2305.02013 | Alexander B. Balakin | Alexander B. Balakin and Anna O. Efremova | Dynamic aether as a trigger for spontaneous spinorization in early
Universe | 12 pages, 4 figures | Universe. 2023, 9, 481 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of the Einstein-Dirac-aether theory we consider a
phenomenological model of the spontaneous growth of the fermion number, which
is triggered by the dynamic aether. The trigger version of spinorization of the
early Universe is associated with two mechanisms: the first one is the aetheric
regulation of behavior of the spinor field; the second mechanism can be related
to a self-similarity of internal interactions in the spinor field. The dynamic
aether is designed to switch on and switch off the self-similar mechanism of
the spinor field evolution; from the mathematical point of view, the key of
such a guidance is made of the scalar of expansion of the aether flow,
proportional to the Hubble function in the isotropic cosmological model. Two
phenomenological parameters of the presented model are shown to be considered
as factors predetermining the total number of fermions born in the early
Universe.
| [
{
"created": "Wed, 3 May 2023 10:05:00 GMT",
"version": "v1"
}
] | 2023-11-15 | [
[
"Balakin",
"Alexander B.",
""
],
[
"Efremova",
"Anna O.",
""
]
] | In the framework of the Einstein-Dirac-aether theory we consider a phenomenological model of the spontaneous growth of the fermion number, which is triggered by the dynamic aether. The trigger version of spinorization of the early Universe is associated with two mechanisms: the first one is the aetheric regulation of behavior of the spinor field; the second mechanism can be related to a self-similarity of internal interactions in the spinor field. The dynamic aether is designed to switch on and switch off the self-similar mechanism of the spinor field evolution; from the mathematical point of view, the key of such a guidance is made of the scalar of expansion of the aether flow, proportional to the Hubble function in the isotropic cosmological model. Two phenomenological parameters of the presented model are shown to be considered as factors predetermining the total number of fermions born in the early Universe. |
1511.05790 | Przemyslaw Malkiewicz | Herve Bergeron, Ewa Czuchry, Jean-Pierre Gazeau and Przemyslaw
Malkiewicz | Nonadiabatic bounce and an inflationary phase in the quantum mixmaster
universe | 32 pages, 9 figures | Phys. Rev. D 93, 124053 (2016) | 10.1103/PhysRevD.93.124053 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following our previous paper, Bergeron et al, Smooth quantum dynamics of the
mixmaster universe, Phys. Rev. D 92, 061302(R) (2015), concerning the
quantization of the vacuum Bianchi IX model and the Born-Huang-Oppenheimer
framework, we present a further analysis of the dynamical properties of the
model. Consistently with the deep quantum regime, we implement the harmonic
approximation of the anisotropy potential. We thus obtain manageable dynamical
equations. We study the quantum anisotropic oscillations during the bouncing
phase of the universe. Neglecting the backreaction from transitions between
quantum anisotropy states we obtain analytical results. In particular, we
identify a parameter which is associated with dynamical properties of the
quantum model and describes a sort of phase transition. Once the parameter
exceeds its critical value, the Born-Huang-Oppenheimer approximation breaks
down. The application of the present result to a simple model of the Universe
indicates that the parameter indeed exceeds its critical value and that there
takes place a huge production of anisotropy at the bounce. This in turn must
lead to a sustained phase of accelerated expansion, an inflationary phase. The
quantitative inclusion of backreaction shall be examined in a follow-up paper
based on the vibronic approach.
| [
{
"created": "Wed, 18 Nov 2015 14:12:04 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Jun 2016 18:21:28 GMT",
"version": "v2"
}
] | 2016-06-29 | [
[
"Bergeron",
"Herve",
""
],
[
"Czuchry",
"Ewa",
""
],
[
"Gazeau",
"Jean-Pierre",
""
],
[
"Malkiewicz",
"Przemyslaw",
""
]
] | Following our previous paper, Bergeron et al, Smooth quantum dynamics of the mixmaster universe, Phys. Rev. D 92, 061302(R) (2015), concerning the quantization of the vacuum Bianchi IX model and the Born-Huang-Oppenheimer framework, we present a further analysis of the dynamical properties of the model. Consistently with the deep quantum regime, we implement the harmonic approximation of the anisotropy potential. We thus obtain manageable dynamical equations. We study the quantum anisotropic oscillations during the bouncing phase of the universe. Neglecting the backreaction from transitions between quantum anisotropy states we obtain analytical results. In particular, we identify a parameter which is associated with dynamical properties of the quantum model and describes a sort of phase transition. Once the parameter exceeds its critical value, the Born-Huang-Oppenheimer approximation breaks down. The application of the present result to a simple model of the Universe indicates that the parameter indeed exceeds its critical value and that there takes place a huge production of anisotropy at the bounce. This in turn must lead to a sustained phase of accelerated expansion, an inflationary phase. The quantitative inclusion of backreaction shall be examined in a follow-up paper based on the vibronic approach. |
gr-qc/9904057 | null | Thibault Damour | Experimental Tests of Relativistic Gravity | 10 pages, latex, uses espcrc2.sty, invited talk at the 1998 Texas
Symposium (to appear in Nucl. Phys. B (Proceedings Supplement)) | Nucl.Phys.Proc.Suppl. 80 (2000) 41-50 | 10.1016/S0920-5632(99)00828-2 | IHES/P/99/31 | gr-qc | null | The confrontation between Einstein's gravitation theory and experimental
results, notably binary pulsar data, is summarized and its significance
discussed. Experiment and theory agree at the 10^{-3} level or better. All the
basic structures of Einstein's theory (coupling of gravity to matter;
propagation and self-interaction of the gravitational field, including in
strong-field conditions) have been verified. However, the theoretical
possibility that scalar couplings be naturally driven toward zero by the
cosmological expansion suggests that the present agreement between Einstein's
theory and experiment might be compatible with the existence of a long-range
scalar contribution to gravity (such as the dilaton field, or a moduli field,
of string theory). This provides a new theoretical paradigm, and new
motivations for improving the experimental tests of gravity.
| [
{
"created": "Thu, 22 Apr 1999 13:34:07 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Damour",
"Thibault",
""
]
] | The confrontation between Einstein's gravitation theory and experimental results, notably binary pulsar data, is summarized and its significance discussed. Experiment and theory agree at the 10^{-3} level or better. All the basic structures of Einstein's theory (coupling of gravity to matter; propagation and self-interaction of the gravitational field, including in strong-field conditions) have been verified. However, the theoretical possibility that scalar couplings be naturally driven toward zero by the cosmological expansion suggests that the present agreement between Einstein's theory and experiment might be compatible with the existence of a long-range scalar contribution to gravity (such as the dilaton field, or a moduli field, of string theory). This provides a new theoretical paradigm, and new motivations for improving the experimental tests of gravity. |
2210.05216 | Simon Jacobsson | Simon Jacobsson and Thomas B\"ackdahl | Second order symmetry operators for the massive Dirac equation | 16 pages | 2023 Class. Quantum Grav. 40 045009 | 10.1088/1361-6382/acb3a9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Employing the covariant language of two-spinors, we find what conditions a
curved Lorentzian spacetime must satisfy for existence of a second order
symmetry operator for the massive Dirac equation. The conditions are formulated
as existence of a set of Killing spinors satisfying a set of covariant linear
differential equations. Using these Killing spinors, we then state the most
general form of such an operator. Partial results for the zeroth and first
order are presented and interpreted as well. Computer algebra tools from the
Mathematica package suite xAct were used for the calculations.
| [
{
"created": "Tue, 11 Oct 2022 07:32:52 GMT",
"version": "v1"
}
] | 2023-02-02 | [
[
"Jacobsson",
"Simon",
""
],
[
"Bäckdahl",
"Thomas",
""
]
] | Employing the covariant language of two-spinors, we find what conditions a curved Lorentzian spacetime must satisfy for existence of a second order symmetry operator for the massive Dirac equation. The conditions are formulated as existence of a set of Killing spinors satisfying a set of covariant linear differential equations. Using these Killing spinors, we then state the most general form of such an operator. Partial results for the zeroth and first order are presented and interpreted as well. Computer algebra tools from the Mathematica package suite xAct were used for the calculations. |
1505.04189 | Carlos A. R. Herdeiro | Carlos A. R. Herdeiro and Eugen Radu | How fast can a black hole rotate? | 10 pages, 2 figures, Essay written for the Gravity Research
Foundation 2015 Awards for Essays on Gravitation and selected for Honorable
Mention | null | 10.1142/S0218271815440228 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Kerr black holes have their angular momentum, $J$, bounded by their mass,
$M$: $Jc\leqslant GM^2$. There are, however, known black hole solutions
violating this Kerr bound. We propose a very simple universal bound on the
rotation, rather than on the angular momentum, of four-dimensional, stationary
and axisymmetric, asymptotically flat black holes, given in terms of an
appropriately defined horizon linear velocity, $v_H$. The $v_H$ bound is simply
that $v_H$ cannot exceed the velocity of light. We verify the $v_H$ bound for
known black hole solutions, including some that violate the Kerr bound, and
conjecture that only extremal Kerr black holes saturate the $v_H$ bound.
| [
{
"created": "Fri, 15 May 2015 20:00:17 GMT",
"version": "v1"
}
] | 2015-12-09 | [
[
"Herdeiro",
"Carlos A. R.",
""
],
[
"Radu",
"Eugen",
""
]
] | Kerr black holes have their angular momentum, $J$, bounded by their mass, $M$: $Jc\leqslant GM^2$. There are, however, known black hole solutions violating this Kerr bound. We propose a very simple universal bound on the rotation, rather than on the angular momentum, of four-dimensional, stationary and axisymmetric, asymptotically flat black holes, given in terms of an appropriately defined horizon linear velocity, $v_H$. The $v_H$ bound is simply that $v_H$ cannot exceed the velocity of light. We verify the $v_H$ bound for known black hole solutions, including some that violate the Kerr bound, and conjecture that only extremal Kerr black holes saturate the $v_H$ bound. |
2007.08049 | Fabao Gao | Fabao Gao and Jaume Llibre | Global dynamics of the Horava-Lifshitz cosmological model in a non-flat
universe with non-zero cosmological constant | 60 pages, 34 figures | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When the cosmological constant is non-zero the dynamics of the cosmological
model based on Horava-Lifshitz gravity in a non-flat universe is characterized
by using the qualitative theory of differential equations.
| [
{
"created": "Thu, 16 Jul 2020 00:41:11 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Oct 2021 15:34:48 GMT",
"version": "v2"
}
] | 2021-10-19 | [
[
"Gao",
"Fabao",
""
],
[
"Llibre",
"Jaume",
""
]
] | When the cosmological constant is non-zero the dynamics of the cosmological model based on Horava-Lifshitz gravity in a non-flat universe is characterized by using the qualitative theory of differential equations. |
0807.0945 | Narayan Banerjee | Narayan Banerjee and Koyel Ganguly | Generalised scalar-tensor theory and the cosmic acceleration | Typos (author's name!)corrected | Int.J.Mod.Phys.D18:445-451,2009 | 10.1142/S0218271809014479 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper it has been shown that a simple functional form of
$\omega(\phi)$ in a generalised scalar tensor theory can drive the present
cosmic acceleration without any quintessence field or the cosmological constant
$\Lambda$. Furthermore, it ensures a smooth transition from a decelerated to an
accelerated phase of expansion in the matter dominated regime.
| [
{
"created": "Mon, 7 Jul 2008 05:21:14 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jul 2008 05:16:42 GMT",
"version": "v2"
}
] | 2009-07-22 | [
[
"Banerjee",
"Narayan",
""
],
[
"Ganguly",
"Koyel",
""
]
] | In this paper it has been shown that a simple functional form of $\omega(\phi)$ in a generalised scalar tensor theory can drive the present cosmic acceleration without any quintessence field or the cosmological constant $\Lambda$. Furthermore, it ensures a smooth transition from a decelerated to an accelerated phase of expansion in the matter dominated regime. |
2203.11495 | Paritosh Verma | Paritosh Verma | Radiation from a Classical Harmonic Oscillator | null | null | null | null | gr-qc physics.class-ph | http://creativecommons.org/licenses/by/4.0/ | This article presents the calculation of gravitational and electromagnetic
radiation emitted from a classical simple harmonic oscillator (SHO). Here we
show only the selected formulae and apply them to a toy problem without
rigorous derivation. First, we calculate the explicit expressions for the
gravitational waves polarizations and then obtain the power radiated away in
gravitational waves using Brans-Dicke theory (BD). We also calculate the
electromagnetic dipole and quadrupole power emitted by the SHO and compare them
with their gravitational counterparts.
| [
{
"created": "Tue, 22 Mar 2022 07:09:39 GMT",
"version": "v1"
}
] | 2022-03-23 | [
[
"Verma",
"Paritosh",
""
]
] | This article presents the calculation of gravitational and electromagnetic radiation emitted from a classical simple harmonic oscillator (SHO). Here we show only the selected formulae and apply them to a toy problem without rigorous derivation. First, we calculate the explicit expressions for the gravitational waves polarizations and then obtain the power radiated away in gravitational waves using Brans-Dicke theory (BD). We also calculate the electromagnetic dipole and quadrupole power emitted by the SHO and compare them with their gravitational counterparts. |
1701.01296 | Stefan Palenta | Stefan Palenta and Reinhard Meinel | A continuous Riemann-Hilbert problem for colliding plane gravitational
waves | 34 pages, 9 figures, section 7 and appendix added | Class.Quant.Grav.34:195011,2017 | 10.1088/1361-6382/aa88dd | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the foundations of a new solution technique for the characteristic
initial value problem (IVP) of colliding plane gravitational waves. It has
extensive similarities to the approach of Alekseev and Griffiths in 2001, but
we use an inverse scattering method with a Riemann-Hilbert problem (RHP), which
allows for a transformation to a continuous RHP with a solution given in terms
of integral equations for non-singular functions. Ambiguities in this procedure
lead to the construction of a family of spacetimes containing the solution to
the IVP. Therefore the described technique also serves as an interesting
solution generating method. The procedure is exemplified by extending the
Szekeres class of colliding wave spacetimes with 2 additional real parameters.
The obtained solution seems to feature a limiting case of a new type of
impulsive waves, which are circularly polarised.
| [
{
"created": "Thu, 5 Jan 2017 12:45:33 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Jan 2017 16:32:12 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Jul 2017 11:44:07 GMT",
"version": "v3"
},
{
"created": "Mon, 22 Jan 2018 16:24:42 GMT",
"version": "v4"
}
] | 2018-01-23 | [
[
"Palenta",
"Stefan",
""
],
[
"Meinel",
"Reinhard",
""
]
] | We present the foundations of a new solution technique for the characteristic initial value problem (IVP) of colliding plane gravitational waves. It has extensive similarities to the approach of Alekseev and Griffiths in 2001, but we use an inverse scattering method with a Riemann-Hilbert problem (RHP), which allows for a transformation to a continuous RHP with a solution given in terms of integral equations for non-singular functions. Ambiguities in this procedure lead to the construction of a family of spacetimes containing the solution to the IVP. Therefore the described technique also serves as an interesting solution generating method. The procedure is exemplified by extending the Szekeres class of colliding wave spacetimes with 2 additional real parameters. The obtained solution seems to feature a limiting case of a new type of impulsive waves, which are circularly polarised. |
1807.09558 | Jiacheng Ding | Jia-Cheng Ding, Ping Li, Cong Li, Qi-Qi Fan, Jian-Bo Deng | The evolution of universe in the two-scalar theory | 19 pages,1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We generalize f(R,T) gravity into the two-scalar theory that includes two
independent scalar fields by the variational method, and we derive its field
equations in Einstein frame using conformal transformation. Based on Friedmann
equations and Raychaudhuri equation, with a consideration of the cosmic content
as its perfect-fluid form, a further discussion leads us to an accelerated
expanding condition of universe. In the two-scalar theory, universe has two
states which are the accelerated expansion and decelerated contraction, and it
has three stages during its evolution. The first and third stages are in the
accelerated expanding state, and the second stage is in the decelerated
contracting state. The third stage represents the present universe and it tends
to become a dust universe.
| [
{
"created": "Wed, 25 Jul 2018 12:54:11 GMT",
"version": "v1"
}
] | 2018-07-26 | [
[
"Ding",
"Jia-Cheng",
""
],
[
"Li",
"Ping",
""
],
[
"Li",
"Cong",
""
],
[
"Fan",
"Qi-Qi",
""
],
[
"Deng",
"Jian-Bo",
""
]
] | We generalize f(R,T) gravity into the two-scalar theory that includes two independent scalar fields by the variational method, and we derive its field equations in Einstein frame using conformal transformation. Based on Friedmann equations and Raychaudhuri equation, with a consideration of the cosmic content as its perfect-fluid form, a further discussion leads us to an accelerated expanding condition of universe. In the two-scalar theory, universe has two states which are the accelerated expansion and decelerated contraction, and it has three stages during its evolution. The first and third stages are in the accelerated expanding state, and the second stage is in the decelerated contracting state. The third stage represents the present universe and it tends to become a dust universe. |
2012.03965 | Eric Linder | Eric V. Linder, Stephen Appleby | An Expansion of Well Tempered Gravity | 7 pages | JCAP 2103, 074 (2021) | 10.1088/1475-7516/2021/03/074 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | When faced with two nigh intractable problems in cosmology -- how to remove
the original cosmological constant problem and how to parametrize modified
gravity to explain current cosmic acceleration -- we can make progress by
counterposing them. The well tempered solution to the cosmological constant
through degenerate scalar field dynamics also relates disparate Horndeski
gravity terms, making them contrapuntal. We derive the connection between the
kinetic term $K$ and braiding term $G_3$ for shift symmetric theories
(including the running Planck mass $G_4$), extending previous work on monomial
or binomial dependence to polynomials of arbitrary finite degree. We also
exhibit an example for an infinite series expansion. This contrapuntal
condition greatly reduces the number of parameters needed to test modified
gravity against cosmological observations, for these "golden" theories of
gravity.
| [
{
"created": "Mon, 7 Dec 2020 19:00:02 GMT",
"version": "v1"
}
] | 2021-04-06 | [
[
"Linder",
"Eric V.",
""
],
[
"Appleby",
"Stephen",
""
]
] | When faced with two nigh intractable problems in cosmology -- how to remove the original cosmological constant problem and how to parametrize modified gravity to explain current cosmic acceleration -- we can make progress by counterposing them. The well tempered solution to the cosmological constant through degenerate scalar field dynamics also relates disparate Horndeski gravity terms, making them contrapuntal. We derive the connection between the kinetic term $K$ and braiding term $G_3$ for shift symmetric theories (including the running Planck mass $G_4$), extending previous work on monomial or binomial dependence to polynomials of arbitrary finite degree. We also exhibit an example for an infinite series expansion. This contrapuntal condition greatly reduces the number of parameters needed to test modified gravity against cosmological observations, for these "golden" theories of gravity. |
2303.02464 | Tiberiu Harko | Teodora Matei, Tiberiu Harko, Gabriela Mocanu | Dark matter and radiation production during warm inflation in a curved
Universe-an irreversible thermodynamic approach | 17 pages, 5 figures, accepted for publication in the Romanian
Astronomical Journal | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the creation of dark matter particles as a result of the decay
of the scalar field in the framework of warm inflationary models, by using the
irreversible thermodynamics of open systems with matter creation/annihilation.
We consider the scalar fields, radiation and dark matter as an interacting
three component cosmological fluid in a homogeneous and isotropic
Friedmann-Lemaitre-Robertson-Walker (FLRW) Universe, in the presence of the
curvature terms. The thermodynamics of open systems as applied together with
the gravitational field equations to the three component cosmological fluid
leads to a generalization of the elementary scalar field-radiation interaction
model, which is the theoretical basis of warm inflationary models. Moreover,
the decay (creation) pressures describing matter production are explicitly
considered as parts of the cosmological fluid energy-momentum tensor. A
specific theoretical model, describing coherently oscillating scalar waves, is
considered. In particular, we investigate the role of the curvature terms in
the dynamical evolution of the early Universe, by considering numerical
solutions of the gravitational field equations. Our results indicate that
despite the fact that the Universe becomes flat at the end of the inflationary
era, the curvature terms, if present, may still play an important role in the
very first stages of the evolution of the Universe.
| [
{
"created": "Sat, 4 Mar 2023 17:49:01 GMT",
"version": "v1"
}
] | 2023-03-07 | [
[
"Matei",
"Teodora",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Mocanu",
"Gabriela",
""
]
] | We investigate the creation of dark matter particles as a result of the decay of the scalar field in the framework of warm inflationary models, by using the irreversible thermodynamics of open systems with matter creation/annihilation. We consider the scalar fields, radiation and dark matter as an interacting three component cosmological fluid in a homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker (FLRW) Universe, in the presence of the curvature terms. The thermodynamics of open systems as applied together with the gravitational field equations to the three component cosmological fluid leads to a generalization of the elementary scalar field-radiation interaction model, which is the theoretical basis of warm inflationary models. Moreover, the decay (creation) pressures describing matter production are explicitly considered as parts of the cosmological fluid energy-momentum tensor. A specific theoretical model, describing coherently oscillating scalar waves, is considered. In particular, we investigate the role of the curvature terms in the dynamical evolution of the early Universe, by considering numerical solutions of the gravitational field equations. Our results indicate that despite the fact that the Universe becomes flat at the end of the inflationary era, the curvature terms, if present, may still play an important role in the very first stages of the evolution of the Universe. |
1908.00037 | Carlos A. R. Herdeiro | Pedro G. S. Fernandes, Carlos A. R. Herdeiro, Alexandre M. Pombo,
Eugen Radu, Nicolas Sanchis-Gual | Charged black holes with axionic-type couplings: classes of solutions
and dynamical scalarisation | 23 pages, 13 figures | Phys. Rev. D 100, 084045 (2019) | 10.1103/PhysRevD.100.084045 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider an augmented Einstein-Maxwell-scalar model including an
axionic-type coupling between the scalar and electromagnetic field. We study
dyonic black hole solutions in this model. For the canonical axionic coupling
emerging from high energy physics, all charged black holes have axion hair. We
present their domain of existence and investigate some physical properties. For
other axionic-type couplings, two classes of black hole solutions may co-exist
in the model: scalar-free Reissner-Nordstr\"om black holes and scalarised black
holes. We show that in some region of the parameter space, the scalar-free
solutions are unstable. Then, there is non-uniqueness since new scalarised
black hole solutions with the same global charges also exist, which are
entropically preferred over the scalar-free solutions and, moreover, emerge
dynamically from the instability of the former.
| [
{
"created": "Wed, 31 Jul 2019 18:28:47 GMT",
"version": "v1"
}
] | 2019-10-30 | [
[
"Fernandes",
"Pedro G. S.",
""
],
[
"Herdeiro",
"Carlos A. R.",
""
],
[
"Pombo",
"Alexandre M.",
""
],
[
"Radu",
"Eugen",
""
],
[
"Sanchis-Gual",
"Nicolas",
""
]
] | We consider an augmented Einstein-Maxwell-scalar model including an axionic-type coupling between the scalar and electromagnetic field. We study dyonic black hole solutions in this model. For the canonical axionic coupling emerging from high energy physics, all charged black holes have axion hair. We present their domain of existence and investigate some physical properties. For other axionic-type couplings, two classes of black hole solutions may co-exist in the model: scalar-free Reissner-Nordstr\"om black holes and scalarised black holes. We show that in some region of the parameter space, the scalar-free solutions are unstable. Then, there is non-uniqueness since new scalarised black hole solutions with the same global charges also exist, which are entropically preferred over the scalar-free solutions and, moreover, emerge dynamically from the instability of the former. |
1812.04350 | Wen-Biao Han | Shu-Cheng Yang, Wen-Biao Han, Shuo Xin, Chen Zhang | Testing dispersion of gravitational waves from eccentric
extreme-mass-ratio inspirals | 15 pages, 7 figures | Int. J. Mod. Phys. D, 28, 1950166, 2019 | 10.1142/S0218271819501669 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In general relativity, there is no dispersion in gravitational waves, while
some modified gravity theories predict dispersion phenomena in the propagation
of gravitational waves. In this paper, we demonstrate that this dispersion will
induce an observable deviation of waveforms if the orbits have large
eccentricities. The mechanism is that the waveform modes with different
frequencies will be emitted at the same time due to the existence of
eccentricity. During the propagation, because of the dispersion, the arrival
time of different modes will be different, then produce the deviation and
dephasing of waveforms compared with general relativity. This kind of
dispersion phenomena related with extreme-mass-ratio inspirals could be
observed by space-borne detectors, and the constraint on the graviton mass
could be improved . Moreover, we find that the dispersion effect may also be
constrained by ground detectors better than the current result if a highly
eccentric intermediate-mass-ratio inspirals be observed.
| [
{
"created": "Tue, 11 Dec 2018 12:21:51 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Jan 2020 13:25:18 GMT",
"version": "v2"
}
] | 2020-01-17 | [
[
"Yang",
"Shu-Cheng",
""
],
[
"Han",
"Wen-Biao",
""
],
[
"Xin",
"Shuo",
""
],
[
"Zhang",
"Chen",
""
]
] | In general relativity, there is no dispersion in gravitational waves, while some modified gravity theories predict dispersion phenomena in the propagation of gravitational waves. In this paper, we demonstrate that this dispersion will induce an observable deviation of waveforms if the orbits have large eccentricities. The mechanism is that the waveform modes with different frequencies will be emitted at the same time due to the existence of eccentricity. During the propagation, because of the dispersion, the arrival time of different modes will be different, then produce the deviation and dephasing of waveforms compared with general relativity. This kind of dispersion phenomena related with extreme-mass-ratio inspirals could be observed by space-borne detectors, and the constraint on the graviton mass could be improved . Moreover, we find that the dispersion effect may also be constrained by ground detectors better than the current result if a highly eccentric intermediate-mass-ratio inspirals be observed. |
2204.09891 | Yakov Shlapentokh-Rothman | Yakov Shlapentokh-Rothman | Naked Singularities for the Einstein Vacuum Equations: The Interior
Solution | 166 pages, 5 figures | null | null | null | gr-qc math-ph math.AP math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a previous work [I. Rodnianski and Y. Shlapentokh-Rothman, Naked
Singularities for the Einstein Vacuum Equations: The Exterior Solution,
arXiv:1912.08478] we constructed solutions to the Einstein vacuum equations in
3+1 dimensions which corresponded to the exterior region of a naked
singularity. In this work we construct solutions which correspond to the
interior region and show that the two solutions may be glued together to
produce a naked singularity. Fundamental to our construction is the novel type
of self-similarity for the Einstein vacuum equations that we introduced in our
previous work and also the study of a new class of quasilinear PDE's of mixed
degenerate elliptic-hyperbolic type.
| [
{
"created": "Thu, 21 Apr 2022 05:34:24 GMT",
"version": "v1"
}
] | 2022-04-22 | [
[
"Shlapentokh-Rothman",
"Yakov",
""
]
] | In a previous work [I. Rodnianski and Y. Shlapentokh-Rothman, Naked Singularities for the Einstein Vacuum Equations: The Exterior Solution, arXiv:1912.08478] we constructed solutions to the Einstein vacuum equations in 3+1 dimensions which corresponded to the exterior region of a naked singularity. In this work we construct solutions which correspond to the interior region and show that the two solutions may be glued together to produce a naked singularity. Fundamental to our construction is the novel type of self-similarity for the Einstein vacuum equations that we introduced in our previous work and also the study of a new class of quasilinear PDE's of mixed degenerate elliptic-hyperbolic type. |
gr-qc/9906114 | Lorenzo Fatibene | L. Fatibene, M. Ferraris, M. Francaviglia, M. Raiteri | The Entropy of Taub-Bolt Solution | null | Annals Phys. 284 (2000) 197-214 | 10.1006/aphy.2000.6062 | null | gr-qc | null | A geometrical framework for the definition of entropy in General Relativity
via Noether theorem is briefly recalled and the entropy of Taub-Bolt Euclidean
solutions of Einstein equations is then obtained as an application. The
computed entropy agrees with previously known results, obtained by statistical
methods. It was generally believed that the entropy of Taub-Bolt solution could
not be computed via Noether theorem, due to the particular structure of
singularities of this solution. We show here that this is not true. The Misner
string singularity is, in fact, considered and its contribution to the entropy
is analyzed. As a result, in our framework entropy does not obey the
"one-quarter area law" and it is not directly related to horizons, as sometimes
erroneously suggested in current literature on the subject.
| [
{
"created": "Tue, 29 Jun 1999 07:34:44 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Fatibene",
"L.",
""
],
[
"Ferraris",
"M.",
""
],
[
"Francaviglia",
"M.",
""
],
[
"Raiteri",
"M.",
""
]
] | A geometrical framework for the definition of entropy in General Relativity via Noether theorem is briefly recalled and the entropy of Taub-Bolt Euclidean solutions of Einstein equations is then obtained as an application. The computed entropy agrees with previously known results, obtained by statistical methods. It was generally believed that the entropy of Taub-Bolt solution could not be computed via Noether theorem, due to the particular structure of singularities of this solution. We show here that this is not true. The Misner string singularity is, in fact, considered and its contribution to the entropy is analyzed. As a result, in our framework entropy does not obey the "one-quarter area law" and it is not directly related to horizons, as sometimes erroneously suggested in current literature on the subject. |
1212.1930 | Christopher Coleman-Smith | C. E. Coleman-Smith, B. Muller | A "Helium Atom" of Space: Dynamical Instability of the Isochoric
Pentahedron | 20 Pages, 19 Figures. Updated to submitted version, minor edits | null | 10.1103/PhysRevD.87.044047 | null | gr-qc hep-th nlin.CD | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an analysis of the dynamics of the equifacial pentahedron on the
Kapovich-Millson phase space under a volume preserving Hamiltonian. The
classical dynamics of polyhedra under such a Hamiltonian may arise from the
classical limit of the node volume operators in loop quantum gravity. The
pentahedron is the simplest nontrivial polyhedron for which the dynamics may be
chaotic. We consider the distribution of polyhedral configurations throughout
the space and find indications that the borders between certain configurations
act as separatrices. We examine the local stability of trajectories within this
phase space and find that locally unstable regions dominate although extended
stable regions are present. Canonical and microcanonical estimates of the
Kolmogorov-Sinai entropy suggest that the pentahedron is a strongly chaotic
system. The presence of chaos is further suggested by calculations of
intermediate time Lyapunov exponents which saturate to non zero values.
| [
{
"created": "Sun, 9 Dec 2012 22:49:38 GMT",
"version": "v1"
},
{
"created": "Sun, 6 Jan 2013 00:57:02 GMT",
"version": "v2"
}
] | 2013-03-14 | [
[
"Coleman-Smith",
"C. E.",
""
],
[
"Muller",
"B.",
""
]
] | We present an analysis of the dynamics of the equifacial pentahedron on the Kapovich-Millson phase space under a volume preserving Hamiltonian. The classical dynamics of polyhedra under such a Hamiltonian may arise from the classical limit of the node volume operators in loop quantum gravity. The pentahedron is the simplest nontrivial polyhedron for which the dynamics may be chaotic. We consider the distribution of polyhedral configurations throughout the space and find indications that the borders between certain configurations act as separatrices. We examine the local stability of trajectories within this phase space and find that locally unstable regions dominate although extended stable regions are present. Canonical and microcanonical estimates of the Kolmogorov-Sinai entropy suggest that the pentahedron is a strongly chaotic system. The presence of chaos is further suggested by calculations of intermediate time Lyapunov exponents which saturate to non zero values. |
1001.3951 | Christian Corda cordac | Lorenzo Iorio and Christian Corda | Gravitomagnetism and gravitational waves | To appear in the Special Issue of The Open Astronomy Journal "The Big
Challenge of Gravitational Waves, a New Window into the Universe", Editors
Christian Corda, Herman J. Mosquera Cuesta, Oswaldo Miranda and Theodore
Simos | The Open Astronomy Journal, 2011, 4, (Suppl 1-M5) 84-97 | 10.2174/1874381101004010084 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After extensively reviewing general relativistic gravitomagnetism, both
historically and phenomenologically, we review in detail the so-called magnetic
components of gravitational waves (GWs), which have to be taken into account in
the context of the total response functions of interferometers for GWs
propagating from arbitrary directions. Following the more recent approaches of
this important issue, the analysis of such magnetic components will be reviewed
in both of standard General Theory of Relativity (GTR) and Scalar Tensor
Gravity. Thus, we show in detail that such a magnetic component becomes
particularly important in the high-frequency portion of the range of ground
based interferometers for GWs which arises from the two different theories of
gravity. Our reviewed results show that if one neglects the magnetic
contribution to the gravitational field of a GW, approximately 15% of the
potential observable signal could, in principle, be lost.
| [
{
"created": "Fri, 22 Jan 2010 10:17:38 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Feb 2010 11:09:34 GMT",
"version": "v2"
}
] | 2011-08-25 | [
[
"Iorio",
"Lorenzo",
""
],
[
"Corda",
"Christian",
""
]
] | After extensively reviewing general relativistic gravitomagnetism, both historically and phenomenologically, we review in detail the so-called magnetic components of gravitational waves (GWs), which have to be taken into account in the context of the total response functions of interferometers for GWs propagating from arbitrary directions. Following the more recent approaches of this important issue, the analysis of such magnetic components will be reviewed in both of standard General Theory of Relativity (GTR) and Scalar Tensor Gravity. Thus, we show in detail that such a magnetic component becomes particularly important in the high-frequency portion of the range of ground based interferometers for GWs which arises from the two different theories of gravity. Our reviewed results show that if one neglects the magnetic contribution to the gravitational field of a GW, approximately 15% of the potential observable signal could, in principle, be lost. |
2206.00656 | Arun Rana | Asha B Modan, Sukanta Panda, Arun Rana | Imprints of Anisotropy on the Power Spectrum in Matter Dominated
Bouncing Universe as Background | 12 pages, 3 figures, added new references and few typos corrected | null | 10.1140/epjc/s10052-022-10867-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we aim to investigate the effects of the anisotropy on the
scale-invariant power spectrum considering the matter-dominated collapsing
universe as background and look for the deviations from this scale invariance.
Having set up this background, we consider a massless scalar field and work out
the correlations, first by using the perturbative approach in which the
anisotropic background is approximated with an effective isotropic metric
represented by the metric of matter dominated collapsing universe, second by
directly solving the field equation numerically, and then obtain the power
spectrum for the range of modes which are of cosmological interest. Using both
techniques, we get an upper bound on the deviation in the power spectrum from
the scale invariance. We also work out the power spectrum for much smaller
modes and look at whether it is possible to explain the observed anomalies in
CMB via the matter bounce scenario.
| [
{
"created": "Wed, 1 Jun 2022 17:47:48 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Jun 2022 06:52:16 GMT",
"version": "v2"
}
] | 2022-10-26 | [
[
"Modan",
"Asha B",
""
],
[
"Panda",
"Sukanta",
""
],
[
"Rana",
"Arun",
""
]
] | In this paper, we aim to investigate the effects of the anisotropy on the scale-invariant power spectrum considering the matter-dominated collapsing universe as background and look for the deviations from this scale invariance. Having set up this background, we consider a massless scalar field and work out the correlations, first by using the perturbative approach in which the anisotropic background is approximated with an effective isotropic metric represented by the metric of matter dominated collapsing universe, second by directly solving the field equation numerically, and then obtain the power spectrum for the range of modes which are of cosmological interest. Using both techniques, we get an upper bound on the deviation in the power spectrum from the scale invariance. We also work out the power spectrum for much smaller modes and look at whether it is possible to explain the observed anomalies in CMB via the matter bounce scenario. |
1101.2841 | Gonzalo Olmo | Gonzalo J. Olmo | Palatini Actions and Quantum Gravity Phenomenology | 16 pages, 1 figure. Enlarged version with examples that explicitly
show how the "soccer ball problem" is solved in this scenario. References
added and several small changes here and there to match with the published
version | null | 10.1088/1475-7516/2011/10/018 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that an invariant an universal length scale can be consistently
introduced in a generally covariant theory through the gravitational sector
using the Palatini approach. The resulting theory is able to capture different
aspects of quantum gravity phenomenology in a single framework. In particular,
it is found that in this theory field excitations propagating with different
energy-densities perceive different background metrics, which is a fundamental
characteristic of the DSR and Rainbow Gravity approaches. We illustrate these
properties with a particular gravitational model and explicitly show how the
{\it soccer ball problem} is avoided in this framework. The isotropic and
anisotropic cosmologies of this model also avoid the big bang singularity by
means of a big bounce.
| [
{
"created": "Fri, 14 Jan 2011 15:30:31 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Oct 2011 17:32:58 GMT",
"version": "v2"
}
] | 2015-05-27 | [
[
"Olmo",
"Gonzalo J.",
""
]
] | We show that an invariant an universal length scale can be consistently introduced in a generally covariant theory through the gravitational sector using the Palatini approach. The resulting theory is able to capture different aspects of quantum gravity phenomenology in a single framework. In particular, it is found that in this theory field excitations propagating with different energy-densities perceive different background metrics, which is a fundamental characteristic of the DSR and Rainbow Gravity approaches. We illustrate these properties with a particular gravitational model and explicitly show how the {\it soccer ball problem} is avoided in this framework. The isotropic and anisotropic cosmologies of this model also avoid the big bang singularity by means of a big bounce. |
1204.0589 | J. Ponce de Leon | J. Ponce de Leon | Cosmological model with variable equations of state for matter and dark
energy | null | Published in Class.Quant.Grav. 29 (2012) 135009 | 10.1088/0264-9381/29/13/135009 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a cosmological model which is physically reasonable,
mathematically tractable, and extends the study of CDM models to the case where
the equations of state (EoS) for matter and dark energy (DE) vary with time. It
is based on the assumptions of (i) flatness, (ii) validity of general
relativity, (iii) the presence of a DE component that varies between two
asymptotic values, (iv) the matter of the universe smoothly evolves from an
initial radiation stage - or a barotropic perfect fluid - to a phase where it
behaves as cosmological dust at late times. The model approximates the CDM ones
for small $z$ but significantly differ from them for large $z$. We focus our
attention on how the evolving EoS for matter and DE can modify the CDM
paradigm. We discuss a number of physical scenarios. One of them includes, as a
particular case, the so-called generalized Chaplygin gas models where DE
evolves from non-relativistic dust. Another kind of models shows that the
current accelerated expansion is compatible with a DE that behaves like
pressureless dust at late times. We also find that a universe with variable DE
can go from decelerated to accelerated expansion, and vice versa, several
times.
| [
{
"created": "Tue, 3 Apr 2012 03:51:58 GMT",
"version": "v1"
}
] | 2012-06-14 | [
[
"de Leon",
"J. Ponce",
""
]
] | We construct a cosmological model which is physically reasonable, mathematically tractable, and extends the study of CDM models to the case where the equations of state (EoS) for matter and dark energy (DE) vary with time. It is based on the assumptions of (i) flatness, (ii) validity of general relativity, (iii) the presence of a DE component that varies between two asymptotic values, (iv) the matter of the universe smoothly evolves from an initial radiation stage - or a barotropic perfect fluid - to a phase where it behaves as cosmological dust at late times. The model approximates the CDM ones for small $z$ but significantly differ from them for large $z$. We focus our attention on how the evolving EoS for matter and DE can modify the CDM paradigm. We discuss a number of physical scenarios. One of them includes, as a particular case, the so-called generalized Chaplygin gas models where DE evolves from non-relativistic dust. Another kind of models shows that the current accelerated expansion is compatible with a DE that behaves like pressureless dust at late times. We also find that a universe with variable DE can go from decelerated to accelerated expansion, and vice versa, several times. |
1606.02826 | Muxin Han | Muxin Han, Mingyi Zhang | On Spinfoams Near a Classical Curvature Singularity | 17 pages, 1 figure, minor modifications | Phys. Rev. D 94, 104075 (2016) | 10.1103/PhysRevD.94.104075 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the technique of spinfoam to study the space-time which,
classically, contains a curvature singularity. We derive from the full
covariant Loop Quantum Gravity (LQG) that the region near curvature singularity
has to be of strong quantum gravity effect. We show that the spinfoam
configuration describing the near-singularity region has to be of small spins
$j$, in order that its contribution to the full spinfoam amplitude is
nontrivial. The spinfoams in low and high curvature regions of the space-time
may be viewed as in two different {phases} of covariant LQG. There should be a
phase transition as the space-time described by spinfoam becomes more and more
curved. A candidate of order parameter is proposed for understanding the phase
transition. Moreover, we also analyze the spin-spin correlation function of
spinfoam, and show the correlation is of long-range in the low curvature phase.
This work is a first step toward understanding the physics of black hole and
early universe from the full covariant LQG theory.
| [
{
"created": "Thu, 9 Jun 2016 05:17:53 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Jan 2017 21:33:13 GMT",
"version": "v2"
}
] | 2017-01-24 | [
[
"Han",
"Muxin",
""
],
[
"Zhang",
"Mingyi",
""
]
] | We apply the technique of spinfoam to study the space-time which, classically, contains a curvature singularity. We derive from the full covariant Loop Quantum Gravity (LQG) that the region near curvature singularity has to be of strong quantum gravity effect. We show that the spinfoam configuration describing the near-singularity region has to be of small spins $j$, in order that its contribution to the full spinfoam amplitude is nontrivial. The spinfoams in low and high curvature regions of the space-time may be viewed as in two different {phases} of covariant LQG. There should be a phase transition as the space-time described by spinfoam becomes more and more curved. A candidate of order parameter is proposed for understanding the phase transition. Moreover, we also analyze the spin-spin correlation function of spinfoam, and show the correlation is of long-range in the low curvature phase. This work is a first step toward understanding the physics of black hole and early universe from the full covariant LQG theory. |
gr-qc/0308055 | Marsha Weaver | Marsha Weaver | On the area of the symmetry orbits in $T^2$ symmetric spacetimes with
Vlasov matter | 27 pages, version 2 minor changes and corrections | Class.Quant.Grav. 21 (2004) 1079-1098 | 10.1088/0264-9381/21/4/023 | null | gr-qc | null | This paper treats the global existence question for a collection of general
relativistic collisionless particles, all having the same mass. The spacetimes
considered are globally hyperbolic, with Cauchy surface a 3-torus. Furthermore,
the spacetimes considered are isometrically invariant under a two-dimensional
group action, the orbits of which are spacelike 2-tori. It is known from
previous work that the area of the group orbits serves as a global time
coordinate. In the present work it is shown that the area takes on all positive
values in the maximal Cauchy development.
| [
{
"created": "Sun, 17 Aug 2003 23:57:09 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Feb 2004 04:56:02 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Weaver",
"Marsha",
""
]
] | This paper treats the global existence question for a collection of general relativistic collisionless particles, all having the same mass. The spacetimes considered are globally hyperbolic, with Cauchy surface a 3-torus. Furthermore, the spacetimes considered are isometrically invariant under a two-dimensional group action, the orbits of which are spacelike 2-tori. It is known from previous work that the area of the group orbits serves as a global time coordinate. In the present work it is shown that the area takes on all positive values in the maximal Cauchy development. |
1405.1612 | Christos Charmousis | Christos Charmousis | From Lovelock to Horndeski's generalised scalar-tensor theory | Lecture notes from the 7th Aegean summer school "Beyond Einstein's
theory of gravity". No figures, 31 pages, some references and remarks added,
some of the typos present corrected | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review and discuss some recent progress in Lovelock and Horndeski theories
modifying Einstein's General Relativity. Using as our guide the uniqueness
properties of these modified gravity theories we then discuss how Kaluza-Klein
reduction of Lovelock theory can lead to effective scalar-tensor actions
including several important terms of Horndeski theory. We show how this can be
put to practical use by mapping analytic black hole solutions of one theory to
the other. We then elaborate on the subset of Horndeski theory that has
self-tuning properties and review a generic method giving scalar-tensor black
hole solutions.
| [
{
"created": "Wed, 7 May 2014 14:18:38 GMT",
"version": "v1"
},
{
"created": "Thu, 15 May 2014 14:20:22 GMT",
"version": "v2"
}
] | 2014-05-16 | [
[
"Charmousis",
"Christos",
""
]
] | We review and discuss some recent progress in Lovelock and Horndeski theories modifying Einstein's General Relativity. Using as our guide the uniqueness properties of these modified gravity theories we then discuss how Kaluza-Klein reduction of Lovelock theory can lead to effective scalar-tensor actions including several important terms of Horndeski theory. We show how this can be put to practical use by mapping analytic black hole solutions of one theory to the other. We then elaborate on the subset of Horndeski theory that has self-tuning properties and review a generic method giving scalar-tensor black hole solutions. |
2207.11848 | Youka Kaku | Youka Kaku, Shin'ya Maeda, Yasusada Nambu, Yuki Osawa | Quantumness of gravity in harmonically trapped particles | 21 pages, accepted version in PRD | null | 10.1103/PhysRevD.106.126005 | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | This study investigates the quantumness of gravity under the setup of the
atomic interferometry from the viewpoint of mass-energy equivalence. We
evaluated interference visibility considering a particle with internal energy
levels in a harmonic trapping potential. As per the result, for a spatially
superposed gravitational source mass, interference visibility exhibits collapse
and revival behavior, which implies that an initial separable internal state
evolves to the entangled state with respect to the degrees of freedom of the
center of mass, the internal energy levels, and the external source state. In
particular, it does not exhibit revival behavior when gravity is treated as a
quantum interaction, while it revives with a finite period for a semiclassical
treatment of gravity. We also examined the temporal behavior of entanglement
negativity and found that the nonrevival behavior of visibility reflects the
creation of the entanglement between the internal energy state and the external
source state which is uniquely induced by the quantum interaction of gravity in
accordance with the weak equivalence principle.
| [
{
"created": "Sun, 24 Jul 2022 23:36:35 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Dec 2022 06:53:51 GMT",
"version": "v2"
}
] | 2022-12-16 | [
[
"Kaku",
"Youka",
""
],
[
"Maeda",
"Shin'ya",
""
],
[
"Nambu",
"Yasusada",
""
],
[
"Osawa",
"Yuki",
""
]
] | This study investigates the quantumness of gravity under the setup of the atomic interferometry from the viewpoint of mass-energy equivalence. We evaluated interference visibility considering a particle with internal energy levels in a harmonic trapping potential. As per the result, for a spatially superposed gravitational source mass, interference visibility exhibits collapse and revival behavior, which implies that an initial separable internal state evolves to the entangled state with respect to the degrees of freedom of the center of mass, the internal energy levels, and the external source state. In particular, it does not exhibit revival behavior when gravity is treated as a quantum interaction, while it revives with a finite period for a semiclassical treatment of gravity. We also examined the temporal behavior of entanglement negativity and found that the nonrevival behavior of visibility reflects the creation of the entanglement between the internal energy state and the external source state which is uniquely induced by the quantum interaction of gravity in accordance with the weak equivalence principle. |
1512.03412 | Abraao Capistrano | A.J.S Capistrano, L.A. Cabral | Implications on the cosmic coincidence by a dynamical extrinsic
curvature | 3 figures | Classical and Quantum Gravity, v. 33, p. 245006, 2016 | 10.1088/0264-9381/33/24/245006 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we apply the smooth deformation concept in order to obtain a
modification of Friedmann equations. It is shown that the cosmic coincidence
can be at least alleviated using the dynamical properties of the extrinsic
curvature. We investigate the transition from nucleosynthesis to the
coincidence era obtaining a very small variation of the ratio
$r=\frac{\rho_{m}}{\rho_{ext}}$, that compares the matter energy density to
extrinsic energy density, compatible with the known behavior of the
deceleration parameter. We also show that the calculated "equivalence" redshift
matches the transition redshift from a deceleration to accelerated phase and
the coincidence ceases to be. The dynamics on $r$ is also studied based on
Hubble parameter observations as the latest Baryons Acoustic
Oscillations/Cosmic Microwave Background Radiation (BAO/CMBR) + SNIa.
| [
{
"created": "Wed, 9 Dec 2015 15:29:26 GMT",
"version": "v1"
}
] | 2017-04-06 | [
[
"Capistrano",
"A. J. S",
""
],
[
"Cabral",
"L. A.",
""
]
] | In this work, we apply the smooth deformation concept in order to obtain a modification of Friedmann equations. It is shown that the cosmic coincidence can be at least alleviated using the dynamical properties of the extrinsic curvature. We investigate the transition from nucleosynthesis to the coincidence era obtaining a very small variation of the ratio $r=\frac{\rho_{m}}{\rho_{ext}}$, that compares the matter energy density to extrinsic energy density, compatible with the known behavior of the deceleration parameter. We also show that the calculated "equivalence" redshift matches the transition redshift from a deceleration to accelerated phase and the coincidence ceases to be. The dynamics on $r$ is also studied based on Hubble parameter observations as the latest Baryons Acoustic Oscillations/Cosmic Microwave Background Radiation (BAO/CMBR) + SNIa. |
1804.07305 | Julian Georg | Julian Georg and Carl Rosenzweig | Can Cosmology Provide a Test of Quantum Mechanics? | null | null | 10.1088/1475-7516/2020/01/028 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inflation predicts that quantum fluctuations determine the large scale
structure of the Universe. This raises the striking possibility that quantum
mechanics, developed to describe nature at short distances, can be tested by
studying nature at its most immense -- cosmology. We illustrate the potential
of such a test by adapting the simplest form of the inflationary paradigm. A
nonlinear generalization of quantum mechanics modifies predictions for the
cosmological power spectrum. If we assume that the nonlinear parameter $b$ is a
comoving quantity observational cosmology, within the context of single field
inflation, is sufficiently precise to place a stringent limit, $b\leq 3\times
10^{-37}$ eV, on the current, physical size of the nonlinear term.
| [
{
"created": "Thu, 19 Apr 2018 18:00:02 GMT",
"version": "v1"
},
{
"created": "Wed, 6 May 2020 15:24:39 GMT",
"version": "v2"
}
] | 2020-05-07 | [
[
"Georg",
"Julian",
""
],
[
"Rosenzweig",
"Carl",
""
]
] | Inflation predicts that quantum fluctuations determine the large scale structure of the Universe. This raises the striking possibility that quantum mechanics, developed to describe nature at short distances, can be tested by studying nature at its most immense -- cosmology. We illustrate the potential of such a test by adapting the simplest form of the inflationary paradigm. A nonlinear generalization of quantum mechanics modifies predictions for the cosmological power spectrum. If we assume that the nonlinear parameter $b$ is a comoving quantity observational cosmology, within the context of single field inflation, is sufficiently precise to place a stringent limit, $b\leq 3\times 10^{-37}$ eV, on the current, physical size of the nonlinear term. |
2106.02247 | Sebasti\'an N\'ajera Valencia | Sebasti\'an N\'ajera, Aram Aguilar, Celia Escamilla-Rivera, Roberto A.
Sussman | The first non-static inhomogeneous exact solution in $f(T,B)$ gravity | 5 pages | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | We examine in this paper the possibility of finding exact solutions for
Teleparallel Gravity (TG) of the type of spherically symmetric Lema\^\i
tre-Tolman-Bondi (LTB) dust models. We apply to the LTB metric, as obtained
from the Schwarzschild solution in General Relativity, the formalism of
Teleparallel Gravity in its extension to $f(T,B)$ models. An exact LTB solution
is obtained that is compatible with a specific $f(T,B)$ model that seems to be
appropriate to fit observations when applied to standard spatially flat
Robertson-Walker geometry.
| [
{
"created": "Fri, 4 Jun 2021 04:27:04 GMT",
"version": "v1"
}
] | 2021-06-07 | [
[
"Nájera",
"Sebastián",
""
],
[
"Aguilar",
"Aram",
""
],
[
"Escamilla-Rivera",
"Celia",
""
],
[
"Sussman",
"Roberto A.",
""
]
] | We examine in this paper the possibility of finding exact solutions for Teleparallel Gravity (TG) of the type of spherically symmetric Lema\^\i tre-Tolman-Bondi (LTB) dust models. We apply to the LTB metric, as obtained from the Schwarzschild solution in General Relativity, the formalism of Teleparallel Gravity in its extension to $f(T,B)$ models. An exact LTB solution is obtained that is compatible with a specific $f(T,B)$ model that seems to be appropriate to fit observations when applied to standard spatially flat Robertson-Walker geometry. |
2111.11634 | Kazufumi Takahashi | Kazufumi Takahashi, Hayato Motohashi, Masato Minamitsuji | Invertible disformal transformations with higher derivatives | 14 pages | Phys. Rev. D 105, 024015 (2022) | 10.1103/PhysRevD.105.024015 | YITP-21-137 | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We consider a higher-derivative generalization of disformal transformations
in $D$-dimensional spacetime and clarify the conditions under which they form a
group with respect to the matrix product and the functional composition. These
conditions allow us to systematically construct the inverse transformation in a
fully covariant manner. Applying the invertible generalized disformal
transformation to known ghost-free scalar-tensor theories, we obtain a novel
class of ghost-free scalar-tensor theories, whose action contains the third- or
higher-order derivatives of the scalar field as well as nontrivial higher-order
derivative couplings to the curvature tensor.
| [
{
"created": "Tue, 23 Nov 2021 03:32:10 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jan 2022 00:43:01 GMT",
"version": "v2"
}
] | 2022-01-06 | [
[
"Takahashi",
"Kazufumi",
""
],
[
"Motohashi",
"Hayato",
""
],
[
"Minamitsuji",
"Masato",
""
]
] | We consider a higher-derivative generalization of disformal transformations in $D$-dimensional spacetime and clarify the conditions under which they form a group with respect to the matrix product and the functional composition. These conditions allow us to systematically construct the inverse transformation in a fully covariant manner. Applying the invertible generalized disformal transformation to known ghost-free scalar-tensor theories, we obtain a novel class of ghost-free scalar-tensor theories, whose action contains the third- or higher-order derivatives of the scalar field as well as nontrivial higher-order derivative couplings to the curvature tensor. |
1210.7204 | Alex Venditti | Alex Venditti and Charles Dyer | Choosing a vacuum state in a spherical spacetime with a conformal
Killing vector | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the problem of picking a physically motivated vacuum state on a
spherically symmetric spacetime with an extra conformal Killing vector, as
opposed to an extra Killing vector as in the Schwarzschild case. Considering a
conformal symmetry instead of a symmetry allows us to consider spacetimes that
are dynamical and not static (like Schwarzschild). The extra conformal symmetry
allows us to calculate the response of particle detectors however. We look at
the specific example of a self-similar LTB spacetime that represents a
spherically symmetric but inhomogeneous cosmology. We remark that the above
procedure might be applied to a spherically symmetric collapse solution that
represents black hole formation so that one can calculate the detailed spectrum
of Hawking radiation during a collapse.
| [
{
"created": "Fri, 26 Oct 2012 17:42:04 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Apr 2013 14:48:35 GMT",
"version": "v2"
},
{
"created": "Thu, 6 Mar 2014 03:55:25 GMT",
"version": "v3"
}
] | 2014-03-07 | [
[
"Venditti",
"Alex",
""
],
[
"Dyer",
"Charles",
""
]
] | We consider the problem of picking a physically motivated vacuum state on a spherically symmetric spacetime with an extra conformal Killing vector, as opposed to an extra Killing vector as in the Schwarzschild case. Considering a conformal symmetry instead of a symmetry allows us to consider spacetimes that are dynamical and not static (like Schwarzschild). The extra conformal symmetry allows us to calculate the response of particle detectors however. We look at the specific example of a self-similar LTB spacetime that represents a spherically symmetric but inhomogeneous cosmology. We remark that the above procedure might be applied to a spherically symmetric collapse solution that represents black hole formation so that one can calculate the detailed spectrum of Hawking radiation during a collapse. |
2304.14273 | Dr. Sudhaker Upadhyay | Sudhaker Upadhyay | Bouncing universe for deformed non-minimally coupled inflation model | 15 pages, 4 figures, published in Journal of Holography Applications
in Physics | JHAP 3, Winter 2023, 57 | 10.22128/jhap.2023.651.1038 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we consider a non-minimally coupled gravity model to study the
bouncing universe. The holographic principle has various effects on the
bouncing universe. We choose some suitable new variables and achieve the new
Hamiltonian and Lagrangian which have harmonic oscillator form. The
corresponding Lagrangian is deformed by non-commutative geometry. In order to
have a solution for the bouncing universe we specify the potential in the
equation state. In that case, we draw the equation of state in terms of time
and show that the equation of state crosses $-1$. Such bouncing behavior leads
us to apply some conditions on $\theta$ and $\beta$ from non-commutative
geometry. Here, we can also check the system's stability due to the deformation
of the non-minimally coupled gravity model. In order to examine the stability
of the system we obtain the variation of pressure with respect to density
energy. Also, we draw the variation of pressure with respect to energy density
and show the stability condition.
| [
{
"created": "Wed, 26 Apr 2023 15:13:41 GMT",
"version": "v1"
}
] | 2023-04-28 | [
[
"Upadhyay",
"Sudhaker",
""
]
] | In this paper, we consider a non-minimally coupled gravity model to study the bouncing universe. The holographic principle has various effects on the bouncing universe. We choose some suitable new variables and achieve the new Hamiltonian and Lagrangian which have harmonic oscillator form. The corresponding Lagrangian is deformed by non-commutative geometry. In order to have a solution for the bouncing universe we specify the potential in the equation state. In that case, we draw the equation of state in terms of time and show that the equation of state crosses $-1$. Such bouncing behavior leads us to apply some conditions on $\theta$ and $\beta$ from non-commutative geometry. Here, we can also check the system's stability due to the deformation of the non-minimally coupled gravity model. In order to examine the stability of the system we obtain the variation of pressure with respect to density energy. Also, we draw the variation of pressure with respect to energy density and show the stability condition. |
2304.12147 | Subhayan Maity | Subhayan Maity, Manojit Das | A complete, continuous and non-singular expansion of the Universe under
stimulated creation -annihilation process of the real scalar Bosons: An
introduction to the existence of the Anti Universe and Parallel Universe | The authors want to entertain strong criticism and comments on this
article from the community | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The general theory of relativity is the most popular theory to describe the
dynamics of a system (especially the Universe) under gravity. In this
framework, the solution of the Einstein field equation under curved space-time
yields the cosmic evolution equation. Besides the evolutionary dynamics of the
Universe may also be obtained from the other aspects like thermodynamics,
classical Lagrangian dynamics, symmetry analysis(Noether, Lie ) etc. This paper
presents a new approach to understanding the evolution of the Universe by
quantizing the cosmic fluid under gravity. While the general theory of
relativity is commonly used to describe the dynamics of the Universe, this
paper explores some other aspects of cosmic evolution from the particle
creation-annihilation mechanism of the cosmic fluid. The model suggests that
the Universe and Anti-Universe can coexist, and that there may be a parallel
system (CPT-invariant) of the Universe and Anti-Universe, all of which are
created through the adiabatic particle creation-annihilation mechanism of a
modified real scalar field acting as the cosmic fluid. This work provides a
different approach to obtaining the cosmic evolution equation from the quantum
field theory. Also the consequence of the quantization of the cosmic fluid
addresses the non-singular origin of the Universe and its continuous complete
evolution. Keywords : Evolution of the Universe, Quantum field theory,
Cosmology.
| [
{
"created": "Mon, 24 Apr 2023 14:57:35 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Apr 2023 15:12:05 GMT",
"version": "v2"
},
{
"created": "Thu, 1 Feb 2024 08:37:30 GMT",
"version": "v3"
},
{
"created": "Sun, 4 Feb 2024 09:01:00 GMT",
"version": "v4"
}
] | 2024-02-06 | [
[
"Maity",
"Subhayan",
""
],
[
"Das",
"Manojit",
""
]
] | The general theory of relativity is the most popular theory to describe the dynamics of a system (especially the Universe) under gravity. In this framework, the solution of the Einstein field equation under curved space-time yields the cosmic evolution equation. Besides the evolutionary dynamics of the Universe may also be obtained from the other aspects like thermodynamics, classical Lagrangian dynamics, symmetry analysis(Noether, Lie ) etc. This paper presents a new approach to understanding the evolution of the Universe by quantizing the cosmic fluid under gravity. While the general theory of relativity is commonly used to describe the dynamics of the Universe, this paper explores some other aspects of cosmic evolution from the particle creation-annihilation mechanism of the cosmic fluid. The model suggests that the Universe and Anti-Universe can coexist, and that there may be a parallel system (CPT-invariant) of the Universe and Anti-Universe, all of which are created through the adiabatic particle creation-annihilation mechanism of a modified real scalar field acting as the cosmic fluid. This work provides a different approach to obtaining the cosmic evolution equation from the quantum field theory. Also the consequence of the quantization of the cosmic fluid addresses the non-singular origin of the Universe and its continuous complete evolution. Keywords : Evolution of the Universe, Quantum field theory, Cosmology. |
gr-qc/0510042 | T. P. Singh | T. P. Singh (Tata Institute of Fundamental Research, Mumbai) | Quantum mechanics without spacetime: a case for noncommutative geometry | 35 pages, based on an invited talk given at QTS-4 [Fourth
International Conference on Quantum Theory and Symmetries], Varna, Bulgaria,
15-21 August, 2005 | Bulg.J.Phys.33:217,2006 | null | null | gr-qc hep-th quant-ph | null | Quantum mechanics in its presently known formulation requires an external
classical time for its description. A classical spacetime manifold and a
classical spacetime metric are produced by classical matter fields. In the
absence of such classical matter fields, quantum mechanics should be formulated
without reference to a classical time. If such a new formulation exists, it
follows as a consequence that standard linear quantum mechanics is a limiting
case of an underlying non-linear quantum theory. A possible approach to the new
formulation is through the use of noncommuting spacetime coordinates in
noncommutative differential geometry. Here, the non-linear theory is described
by a non-linear Schrodinger equation which belongs to the Doebner-Goldin class
of equations, discovered some years ago. This mass-dependent non-linearity is
significant when particle masses are comparable to Planck mass, and negligible
otherwise. Such a non-linearity is in principle detectable through experimental
tests of quantum mechanics for mesoscopic systems, and is a valuable empirical
probe of theories of quantum gravity. We also briefly remark on the possible
connection our approach could have with loop quantum gravity and string theory.
| [
{
"created": "Sun, 9 Oct 2005 09:32:58 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Singh",
"T. P.",
"",
"Tata Institute of Fundamental Research, Mumbai"
]
] | Quantum mechanics in its presently known formulation requires an external classical time for its description. A classical spacetime manifold and a classical spacetime metric are produced by classical matter fields. In the absence of such classical matter fields, quantum mechanics should be formulated without reference to a classical time. If such a new formulation exists, it follows as a consequence that standard linear quantum mechanics is a limiting case of an underlying non-linear quantum theory. A possible approach to the new formulation is through the use of noncommuting spacetime coordinates in noncommutative differential geometry. Here, the non-linear theory is described by a non-linear Schrodinger equation which belongs to the Doebner-Goldin class of equations, discovered some years ago. This mass-dependent non-linearity is significant when particle masses are comparable to Planck mass, and negligible otherwise. Such a non-linearity is in principle detectable through experimental tests of quantum mechanics for mesoscopic systems, and is a valuable empirical probe of theories of quantum gravity. We also briefly remark on the possible connection our approach could have with loop quantum gravity and string theory. |
gr-qc/0510029 | Peter D'Eath | A.N.St.J.Farley and P.D.D'Eath | Quantum Amplitudes in Black-Hole Evaporation II. Spin-0 Amplitude | null | null | null | null | gr-qc | null | This work on spin-0 amplitudes in black-hole evaporation is based on the
underlying results and methods outlined in our first paper, "I. Complex
Approach". The main result here, and the model calculation for work on all
higher spins, as described in several further papers, is the computation of the
quantum amplitude (rather than merely the probability) for a given slightly
anisotropic configuration of a scalar field $\phi$ on a space-like hypersurface
$\Sigma_F$ at a very late time $T$. For simplicity, one may take the initial
data for gravity and the massless scalar field at an initial surface $\Sigma_I$
to be spherically symmetric. This applies to perturbations of
spherically-symmetric collapse to a black hole, starting from a diffuse,
nearly-stationary configuration, where the bosonic part of the Lagrangian
consists of Einstein gravity and the massless scalar field. As in Paper I,
Feynman's $+i\epsilon$ approach is taken; this involves a rotation into the
complex: $T\to {\mid}T{\mid} \exp (-i\theta)$, with $0<\theta\leq\pi/2$. A
complex solution of the classical boundary-value problem is expected to exist,
provided $\theta>0$; although for $\theta =0$ (Lorentzian time-separation), the
classical boundary-value problem is badly posed. Once the amplitude is found
for $\theta>0$, one can take the limit $\theta\to 0_+$ to find the Lorentzian
amplitude. The paper also includes a discussion of adiabatic solutions of the
scalar wave equation, needed for the spin-0 calculation.
| [
{
"created": "Fri, 7 Oct 2005 16:29:53 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Farley",
"A. N. St. J.",
""
],
[
"D'Eath",
"P. D.",
""
]
] | This work on spin-0 amplitudes in black-hole evaporation is based on the underlying results and methods outlined in our first paper, "I. Complex Approach". The main result here, and the model calculation for work on all higher spins, as described in several further papers, is the computation of the quantum amplitude (rather than merely the probability) for a given slightly anisotropic configuration of a scalar field $\phi$ on a space-like hypersurface $\Sigma_F$ at a very late time $T$. For simplicity, one may take the initial data for gravity and the massless scalar field at an initial surface $\Sigma_I$ to be spherically symmetric. This applies to perturbations of spherically-symmetric collapse to a black hole, starting from a diffuse, nearly-stationary configuration, where the bosonic part of the Lagrangian consists of Einstein gravity and the massless scalar field. As in Paper I, Feynman's $+i\epsilon$ approach is taken; this involves a rotation into the complex: $T\to {\mid}T{\mid} \exp (-i\theta)$, with $0<\theta\leq\pi/2$. A complex solution of the classical boundary-value problem is expected to exist, provided $\theta>0$; although for $\theta =0$ (Lorentzian time-separation), the classical boundary-value problem is badly posed. Once the amplitude is found for $\theta>0$, one can take the limit $\theta\to 0_+$ to find the Lorentzian amplitude. The paper also includes a discussion of adiabatic solutions of the scalar wave equation, needed for the spin-0 calculation. |
2112.06359 | Nobuyoshi Komatsu | Nobuyoshi Komatsu | Energy stored on a cosmological horizon and its thermodynamic
fluctuations in holographic equipartition law | Final version accepted for publication in PRD. Typos are corrected
and references are updated. [12 pages, 1 figure] | Phys. Rev. D 105, 043534 (2022) | 10.1103/PhysRevD.105.043534 | null | gr-qc astro-ph.CO hep-ph | http://creativecommons.org/licenses/by/4.0/ | Our Universe is expected to finally approach a de Sitter universe whose
horizon is considered to be in thermal equilibrium. In the present article,
both the energy stored on the horizon and its thermodynamic fluctuations are
examined through the holographic equipartition law. First, it is confirmed that
a flat Friedmann--Robertson--Walker universe approaches a de Sitter universe,
using a cosmological model close to lambda cold dark matter ($\Lambda$CDM)
models. Then, based on the holographic equipartition law, the energy density of
the Hubble volume is calculated from the energy on the Hubble horizon of a de
Sitter universe. The energy density for a de Sitter universe is constant and
the order of the energy density is consistent with the order of that for the
observed cosmological constant. Second, thermodynamic fluctuations of energy on
the horizon are examined, assuming stable fluctuations around thermal
equilibrium states. A standard formulation of the fluctuations for a canonical
ensemble is applied to the Hubble horizon of a de Sitter universe. The
thermodynamic fluctuations of the energy are found to be a universal constant
corresponding to the Planck energy, regardless of the Hubble parameter. In
contrast, the relative fluctuations of the energy can be characterized by the
ratio of the one-degree-of-freedom energy to the Planck energy. At the present
time, the order of the relative fluctuations should be within the range of a
discrepancy derived from a discussion of the cosmological constant problem,
namely a range approximately from $10^{-60}$ to $10^{-123}$. The present
results may imply that the energy stored on the Hubble horizon is related to a
kind of effective dark energy, whereas the energy that can be `maximally'
stored on the horizon may behave as if it were a kind of effective vacuum-like
energy in an extended holographic equipartition law.
| [
{
"created": "Mon, 13 Dec 2021 00:18:59 GMT",
"version": "v1"
},
{
"created": "Sat, 19 Feb 2022 04:28:20 GMT",
"version": "v2"
}
] | 2022-02-25 | [
[
"Komatsu",
"Nobuyoshi",
""
]
] | Our Universe is expected to finally approach a de Sitter universe whose horizon is considered to be in thermal equilibrium. In the present article, both the energy stored on the horizon and its thermodynamic fluctuations are examined through the holographic equipartition law. First, it is confirmed that a flat Friedmann--Robertson--Walker universe approaches a de Sitter universe, using a cosmological model close to lambda cold dark matter ($\Lambda$CDM) models. Then, based on the holographic equipartition law, the energy density of the Hubble volume is calculated from the energy on the Hubble horizon of a de Sitter universe. The energy density for a de Sitter universe is constant and the order of the energy density is consistent with the order of that for the observed cosmological constant. Second, thermodynamic fluctuations of energy on the horizon are examined, assuming stable fluctuations around thermal equilibrium states. A standard formulation of the fluctuations for a canonical ensemble is applied to the Hubble horizon of a de Sitter universe. The thermodynamic fluctuations of the energy are found to be a universal constant corresponding to the Planck energy, regardless of the Hubble parameter. In contrast, the relative fluctuations of the energy can be characterized by the ratio of the one-degree-of-freedom energy to the Planck energy. At the present time, the order of the relative fluctuations should be within the range of a discrepancy derived from a discussion of the cosmological constant problem, namely a range approximately from $10^{-60}$ to $10^{-123}$. The present results may imply that the energy stored on the Hubble horizon is related to a kind of effective dark energy, whereas the energy that can be `maximally' stored on the horizon may behave as if it were a kind of effective vacuum-like energy in an extended holographic equipartition law. |
1911.10818 | Alessandro Nagar | Piero Rettegno, Fabio Martinetti, Alessandro Nagar, Donato Bini,
Gunnar Riemenschneider, and Thibault Damour | Comparing Effective One Body Hamiltonians for spin-aligned coalescing
binaries | 23 pages, 13 figures. Submitted to Phys. Rev. D | Phys. Rev. D 101, 104027 (2020) | 10.1103/PhysRevD.101.104027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | TEOBResumS and SEOBNRv4 are the two existing semi-analytical gravitational
waveform models for spin-aligned coalescing black hole binaries based on the
effective-one-body approach.They are informed by numerical relativity
simulations and provide the relative dynamics and waveforms from early inspiral
to plunge, merger and ringdown The central building block of each model is the
EOB resummed Hamiltonian.The two models implement different Hamiltonians that
are both deformations of the Hamiltonian of a test spinning black hole moving
around a Kerr black hole.Here we analytically compare, element by element, the
two Hamiltonians. In particular: we illustrate that one can introduce a
centrifugal radius SEOBNRv4, so to rewrite the Hamiltonian in a more compact
form that is analogous to the one of TEOBResumS.The latter centrifugal radius
cannot, however, be identified with the one used in TEOBResumS because the two
models differ in their ways of incorporating spin effects in their respective
deformations of the background Kerr Hamiltonian. We performed extensive
comparisons between the energetics corresponding to the two Hamiltonians using
gauge-invariant quantities. Finally, as an exploratory investigation, we apply
the post-adiabatic approximation to the newly rewritten SEOBNRv4 Hamiltonian,
illustrating that it is possible to generate long-inspiral waveforms with
negligible computational cost.
| [
{
"created": "Mon, 25 Nov 2019 10:33:20 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Nov 2019 13:50:38 GMT",
"version": "v2"
}
] | 2020-05-20 | [
[
"Rettegno",
"Piero",
""
],
[
"Martinetti",
"Fabio",
""
],
[
"Nagar",
"Alessandro",
""
],
[
"Bini",
"Donato",
""
],
[
"Riemenschneider",
"Gunnar",
""
],
[
"Damour",
"Thibault",
""
]
] | TEOBResumS and SEOBNRv4 are the two existing semi-analytical gravitational waveform models for spin-aligned coalescing black hole binaries based on the effective-one-body approach.They are informed by numerical relativity simulations and provide the relative dynamics and waveforms from early inspiral to plunge, merger and ringdown The central building block of each model is the EOB resummed Hamiltonian.The two models implement different Hamiltonians that are both deformations of the Hamiltonian of a test spinning black hole moving around a Kerr black hole.Here we analytically compare, element by element, the two Hamiltonians. In particular: we illustrate that one can introduce a centrifugal radius SEOBNRv4, so to rewrite the Hamiltonian in a more compact form that is analogous to the one of TEOBResumS.The latter centrifugal radius cannot, however, be identified with the one used in TEOBResumS because the two models differ in their ways of incorporating spin effects in their respective deformations of the background Kerr Hamiltonian. We performed extensive comparisons between the energetics corresponding to the two Hamiltonians using gauge-invariant quantities. Finally, as an exploratory investigation, we apply the post-adiabatic approximation to the newly rewritten SEOBNRv4 Hamiltonian, illustrating that it is possible to generate long-inspiral waveforms with negligible computational cost. |
1209.1385 | Subhajit Saha | Subhajit Saha and Subenoy Chakraborty | A redefinition of Hawking temperature on the event horizon:
Thermodynamical equilibrium | 10 pages | Physics Letters B 717, 319 (2012) | 10.1016/j.physletb.2012.09.065 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we have used the recently introduced redefined Hawking
temperature on the event horizon and investigated whether the generalised
second law of thermodynamics (GSLT) and thermodynamic equilibrium holds for
both the event and the apparent horizons. Here we have considered FRW universe
and examined the GSLT and thermodynamic equilibrium with three examples.
Finally, we have concluded that from the thermodynamic viewpoint, the universe
bounded by the event horizon is more realistic than that by the apparent
horizon at least for some examples.
| [
{
"created": "Thu, 6 Sep 2012 10:37:05 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Sep 2012 09:34:51 GMT",
"version": "v2"
},
{
"created": "Sun, 12 Jul 2015 16:58:31 GMT",
"version": "v3"
}
] | 2016-05-04 | [
[
"Saha",
"Subhajit",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | In this article we have used the recently introduced redefined Hawking temperature on the event horizon and investigated whether the generalised second law of thermodynamics (GSLT) and thermodynamic equilibrium holds for both the event and the apparent horizons. Here we have considered FRW universe and examined the GSLT and thermodynamic equilibrium with three examples. Finally, we have concluded that from the thermodynamic viewpoint, the universe bounded by the event horizon is more realistic than that by the apparent horizon at least for some examples. |
2310.04157 | Andrea Geralico | Davide Astesiano, Donato Bini, Andrea Geralico, Matteo Luca Ruggiero | Particle motion in a rotating dust spacetime: the Bonnor solution | 11 pages, 5 figures (10 eps files); v2: new Section IV added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the geometrical properties, spectral classification,
geodesics, and causal structure of the Bonnor's spacetime [Journal of Physics A
Math. Gen., \textbf{10}, 1673 (1977)], i.e., a stationary axisymmetric solution
with a rotating dust as a source. This spacetime has a directional singularity
at the origin of the coordinates (related to the diverging vorticity field of
the fluid there), which is surrounded by a toroidal region where closed
timelike curves (CTCs) are allowed, leading to chronology violations. We use
the effective potential approach to provide a classification of the different
kind of geodesic orbits on the symmetry plane as well as to study the
helical-like motion aroud the symmetry axis on a cylinder with constant radius.
In the former case we find that as a general feature for positive values of the
angular momentum test particles released from a fixed space point and directed
towards the singularity are repelled and scattered back as soon as they
approach the CTC boundary, without reaching the central singularity. In
contrast, for negative values of the angular momentum there exist conditions in
the parameter space for which particles are allowed to enter the pathological
region. Finally, as a more realistic mechanism, we study accelerated orbits
undergoing friction forces due to the interaction with the background fluid,
which may also act in order to prevent particles from approaching the CTC
region.
| [
{
"created": "Fri, 6 Oct 2023 11:11:31 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Feb 2024 17:34:12 GMT",
"version": "v2"
}
] | 2024-02-28 | [
[
"Astesiano",
"Davide",
""
],
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
],
[
"Ruggiero",
"Matteo Luca",
""
]
] | We investigate the geometrical properties, spectral classification, geodesics, and causal structure of the Bonnor's spacetime [Journal of Physics A Math. Gen., \textbf{10}, 1673 (1977)], i.e., a stationary axisymmetric solution with a rotating dust as a source. This spacetime has a directional singularity at the origin of the coordinates (related to the diverging vorticity field of the fluid there), which is surrounded by a toroidal region where closed timelike curves (CTCs) are allowed, leading to chronology violations. We use the effective potential approach to provide a classification of the different kind of geodesic orbits on the symmetry plane as well as to study the helical-like motion aroud the symmetry axis on a cylinder with constant radius. In the former case we find that as a general feature for positive values of the angular momentum test particles released from a fixed space point and directed towards the singularity are repelled and scattered back as soon as they approach the CTC boundary, without reaching the central singularity. In contrast, for negative values of the angular momentum there exist conditions in the parameter space for which particles are allowed to enter the pathological region. Finally, as a more realistic mechanism, we study accelerated orbits undergoing friction forces due to the interaction with the background fluid, which may also act in order to prevent particles from approaching the CTC region. |
1702.03626 | Xiangyun Fu fu | Xiangyun Fu and Pengcheng Li | Testing the Distance-Duality Relation from Strong Gravitational Lensing,
Type Ia Supernovae and Gamma-Ray Bursts Data up to redshift $z\sim3.6$ | 18pages and 5figures | null | 10.1142/S0218271817500973 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we perform a cosmological model-independent test of the cosmic
distance-duality relation (CDDR) in terms of the ratio of angular diameter
distance (ADD) $D=D_{\rm A}^{\rm sl}/D_{\rm A}^{\,\rm s}$ from strong
gravitational lensing (SGL) and the ratio of luminosity distance (LD)
$D^\ast=D_{\rm L}^{\,\rm l}/D_{\rm L}^{\,\rm s}$ obtained from the joint of
type Ia supernovae (SNIa) Union2.1 compilation and the latest Gamma-Ray Bursts
(GRBs) data, where the superscripts s and l correspond to the redshifts
$z_{\,\rm s}$ and $z_{\,\rm l}$ at the source and lens from SGL samples. The
purpose of combining GRB data with SNIa compilation is to test CDDR in a wider
redshift range. The LD associated with the redshits of the observed ADD, is
obtained through two cosmological model-independent methods, namely, method A:
binning the SNIa+GRBs data, and method B: reconstructing the function of DL by
combining the Crossing Statistic with the smoothing method. We find that CDDR
is compatible with the observations at $1\sigma$ confidence level for the power
law model which is assumed to describe the mass distribution of lensing systems
with method B in a wider redshift range.
| [
{
"created": "Mon, 13 Feb 2017 04:29:11 GMT",
"version": "v1"
}
] | 2017-07-26 | [
[
"Fu",
"Xiangyun",
""
],
[
"Li",
"Pengcheng",
""
]
] | In this paper, we perform a cosmological model-independent test of the cosmic distance-duality relation (CDDR) in terms of the ratio of angular diameter distance (ADD) $D=D_{\rm A}^{\rm sl}/D_{\rm A}^{\,\rm s}$ from strong gravitational lensing (SGL) and the ratio of luminosity distance (LD) $D^\ast=D_{\rm L}^{\,\rm l}/D_{\rm L}^{\,\rm s}$ obtained from the joint of type Ia supernovae (SNIa) Union2.1 compilation and the latest Gamma-Ray Bursts (GRBs) data, where the superscripts s and l correspond to the redshifts $z_{\,\rm s}$ and $z_{\,\rm l}$ at the source and lens from SGL samples. The purpose of combining GRB data with SNIa compilation is to test CDDR in a wider redshift range. The LD associated with the redshits of the observed ADD, is obtained through two cosmological model-independent methods, namely, method A: binning the SNIa+GRBs data, and method B: reconstructing the function of DL by combining the Crossing Statistic with the smoothing method. We find that CDDR is compatible with the observations at $1\sigma$ confidence level for the power law model which is assumed to describe the mass distribution of lensing systems with method B in a wider redshift range. |
gr-qc/0307098 | Christopher J. Fewster | C.J. Fewster and B. Mistry | Quantum Weak Energy Inequalities for the Dirac field in Flat Spacetime | 8 pages, REVTeX4, version to appear in Phys Rev D | Phys.Rev.D68:105010,2003 | 10.1103/PhysRevD.68.105010 | null | gr-qc hep-th | null | Quantum Weak Energy Inequalities (QWEIs) have been established for a variety
of quantum field theories in both flat and curved spacetimes. Dirac fields are
known (by a result of Fewster and Verch) to satisfy QWEIs under very general
circumstances. However this result does not provide an explicit formula for the
QWEI bound, so its magnitude has not previously been determined. In this paper
we present a new and explicit QWEI bound for Dirac fields of arbitrary mass in
four-dimensional Minkowski space. We follow the methods employed by Fewster and
Eveson for the scalar field, modified to take account of anticommutation
relations. A key ingredient is an identity for Fourier transforms established
by Fewster and Verch. We also compare our QWEI with those previously obtained
for scalar and spin-1 fields.
| [
{
"created": "Wed, 23 Jul 2003 10:52:18 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Sep 2003 15:00:05 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Fewster",
"C. J.",
""
],
[
"Mistry",
"B.",
""
]
] | Quantum Weak Energy Inequalities (QWEIs) have been established for a variety of quantum field theories in both flat and curved spacetimes. Dirac fields are known (by a result of Fewster and Verch) to satisfy QWEIs under very general circumstances. However this result does not provide an explicit formula for the QWEI bound, so its magnitude has not previously been determined. In this paper we present a new and explicit QWEI bound for Dirac fields of arbitrary mass in four-dimensional Minkowski space. We follow the methods employed by Fewster and Eveson for the scalar field, modified to take account of anticommutation relations. A key ingredient is an identity for Fourier transforms established by Fewster and Verch. We also compare our QWEI with those previously obtained for scalar and spin-1 fields. |
gr-qc/0207023 | Dr. Anirudh Pradhan | Anirudh Pradhan and Aotemshi I | Bulk Viscous Solutions to the Field Equations and the Deceleration
Parameter-Revisited | Latex 15 pages, submitted to IJMPD | Int.J.Mod.Phys.D11:1419-1434,2002 | 10.1142/S0218271802002402 | null | gr-qc | null | We utilise a form for the Hubble parameter to generate a number of solutions
to the Einstein field equations with variable cosmological constant and
variable gravitational constant in the presence of a bulk viscous fluid. The
Hubble law utilised yields a constant value for the deceleration parameter. A
new class of solutions is presented in the Robertson-Walker spacetimes. The
coefficient of bulk viscosity is assumed to be a power function of the mass
density. For a class of solutions, the deceleration parameter is negative which
is consistent with the supernovae Ia observations.
| [
{
"created": "Thu, 4 Jul 2002 12:41:49 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Pradhan",
"Anirudh",
""
],
[
"I",
"Aotemshi",
""
]
] | We utilise a form for the Hubble parameter to generate a number of solutions to the Einstein field equations with variable cosmological constant and variable gravitational constant in the presence of a bulk viscous fluid. The Hubble law utilised yields a constant value for the deceleration parameter. A new class of solutions is presented in the Robertson-Walker spacetimes. The coefficient of bulk viscosity is assumed to be a power function of the mass density. For a class of solutions, the deceleration parameter is negative which is consistent with the supernovae Ia observations. |
1506.08062 | Seyed Hossein Hendi Dr. | Seyed Hossein Hendi and Mir Faizal | Black Holes in Gauss-Bonnet Gravity's Rainbow | 12 pages with 26 figures, Accepted for publication in PRD | Phys. Rev. D 92, 044027 (2015) | 10.1103/PhysRevD.92.044027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we will generalize the Gauss-Bonnet gravity to an energy
dependent Gauss-Bonnet theory of gravity, which we shall call as the
Gauss-Bonnet gravity's rainbow. We will also couple this theory to a Maxwell's
theory. We will analyze black hole solutions in this energy dependent
Gauss-Bonnet gravity's rainbow. We will calculate the modifications to the
thermodynamics of black holes in the Gauss-Bonnet's gravity's rainbow. We will
demonstrate that even though the thermodynamics of the black holes get modified
in the Gauss-Bonnet gravity's rainbow, the first law of thermodynamics still
holds for this modified thermodynamics. We will also comment on the thermal
stability of the black hole solutions in this theory.
| [
{
"created": "Sat, 20 Jun 2015 12:16:07 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Aug 2015 08:57:34 GMT",
"version": "v2"
}
] | 2015-08-26 | [
[
"Hendi",
"Seyed Hossein",
""
],
[
"Faizal",
"Mir",
""
]
] | In this paper, we will generalize the Gauss-Bonnet gravity to an energy dependent Gauss-Bonnet theory of gravity, which we shall call as the Gauss-Bonnet gravity's rainbow. We will also couple this theory to a Maxwell's theory. We will analyze black hole solutions in this energy dependent Gauss-Bonnet gravity's rainbow. We will calculate the modifications to the thermodynamics of black holes in the Gauss-Bonnet's gravity's rainbow. We will demonstrate that even though the thermodynamics of the black holes get modified in the Gauss-Bonnet gravity's rainbow, the first law of thermodynamics still holds for this modified thermodynamics. We will also comment on the thermal stability of the black hole solutions in this theory. |
1312.0535 | Rafe Mazzeo | James Dilts, James Isenberg, Rafe Mazzeo, Caleb Meier | Non-CMC solutions of the Einstein constraint equations on asymptotically
Euclidean manifolds | 8 pages | null | 10.1088/0264-9381/31/6/065001 | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note we prove two existence theorems for the Einstein constraint
equations on asymptotically Euclidean manifolds. The first is for arbitrary
mean curvature functions with restrictions on the size of the
transverse-traceless data and the non-gravitational field data, while the
second assumes a near-CMC condition, with no other restrictions.
| [
{
"created": "Mon, 2 Dec 2013 18:11:05 GMT",
"version": "v1"
}
] | 2014-03-05 | [
[
"Dilts",
"James",
""
],
[
"Isenberg",
"James",
""
],
[
"Mazzeo",
"Rafe",
""
],
[
"Meier",
"Caleb",
""
]
] | In this note we prove two existence theorems for the Einstein constraint equations on asymptotically Euclidean manifolds. The first is for arbitrary mean curvature functions with restrictions on the size of the transverse-traceless data and the non-gravitational field data, while the second assumes a near-CMC condition, with no other restrictions. |
2108.11144 | Jaume Haro | Jaume de Haro and Llibert Arest\'e Sal\'o | A review of Quintessential Inflation | Invited review in the special issue "Latest Developments in the Quest
for the Unification of Cosmic Inflation and Dark Energy" of Galaxies | null | 10.3390/galaxies9040073 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We compute numerically the reheating temperature due to the gravitational
production of conformally coupled superheavy particles during the phase
transition from the end of inflation to the beginning of kination in two
different Quintessential Inflation (QI) scenarios, namely Lorentzian
Quintessential Inflation (LQI) and $\alpha$-attractors in the context of
Quintessential Inflation ($\alpha$-QI). Once these superheavy particles have
been created, they must decay into lighter ones to form a relativistic plasma,
whose energy density will eventually dominate the one of the inflaton field in
order to reheat after inflation our universe with a very high temperature, in
both cases greater than $10^7$ GeV, contrary to the usual belief that heavy
masses suppress the particle production and, thus, lead to an inefficient
reheating temperature. Finally, we will show that the over-production of
Gravitational Waves (GWs) during this phase transition, when one deals with our
models, does not disturb the Big Bang Nucleosynthesis (BBN) success.
| [
{
"created": "Wed, 25 Aug 2021 09:41:33 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Sep 2021 16:23:23 GMT",
"version": "v2"
}
] | 2023-01-03 | [
[
"de Haro",
"Jaume",
""
],
[
"Saló",
"Llibert Aresté",
""
]
] | We compute numerically the reheating temperature due to the gravitational production of conformally coupled superheavy particles during the phase transition from the end of inflation to the beginning of kination in two different Quintessential Inflation (QI) scenarios, namely Lorentzian Quintessential Inflation (LQI) and $\alpha$-attractors in the context of Quintessential Inflation ($\alpha$-QI). Once these superheavy particles have been created, they must decay into lighter ones to form a relativistic plasma, whose energy density will eventually dominate the one of the inflaton field in order to reheat after inflation our universe with a very high temperature, in both cases greater than $10^7$ GeV, contrary to the usual belief that heavy masses suppress the particle production and, thus, lead to an inefficient reheating temperature. Finally, we will show that the over-production of Gravitational Waves (GWs) during this phase transition, when one deals with our models, does not disturb the Big Bang Nucleosynthesis (BBN) success. |
1402.0202 | Bibhas Majhi Ranjan | Wontae Kim, Bibhas Ranjan Majhi | Free-fall energy density and flux in the Schwarzschild black hole | Published version | IJMPA 30, (2015) 1550053 | 10.1142/S0217751X15500530 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the four-dimensional background of Schwarzschild black hole, we
investigate the energy densities and fluxes in the freely falling frames for
the Boulware, Unruh, and Israel-Hartle-Hawking states. In particular, we study
their behaviors near the horizon and asymptotic spatial infinity by using the
trace anomaly of a conformally invariant scalar field. In the Boulware state,
both the energy density and flux are negative divergent when the observer is
dropped at the horizon, and asymptotically vanish. In the Unruh state, the
energy density is also negative divergent at the horizon while it is positive
finite asymptotically. The flux in the Unruh state is always positive and
divergent at the horizon. In the Israel-Hartle-Hawking state, the energy
density depends on the angular motion of free fall, and fluxes vanish at the
horizon and the spatial infinity. Finally, we discuss the role of the negative
energy density near the horizon in the evaporating black hole.
| [
{
"created": "Sun, 2 Feb 2014 15:23:09 GMT",
"version": "v1"
},
{
"created": "Sat, 2 May 2015 14:20:04 GMT",
"version": "v2"
}
] | 2015-05-05 | [
[
"Kim",
"Wontae",
""
],
[
"Majhi",
"Bibhas Ranjan",
""
]
] | In the four-dimensional background of Schwarzschild black hole, we investigate the energy densities and fluxes in the freely falling frames for the Boulware, Unruh, and Israel-Hartle-Hawking states. In particular, we study their behaviors near the horizon and asymptotic spatial infinity by using the trace anomaly of a conformally invariant scalar field. In the Boulware state, both the energy density and flux are negative divergent when the observer is dropped at the horizon, and asymptotically vanish. In the Unruh state, the energy density is also negative divergent at the horizon while it is positive finite asymptotically. The flux in the Unruh state is always positive and divergent at the horizon. In the Israel-Hartle-Hawking state, the energy density depends on the angular motion of free fall, and fluxes vanish at the horizon and the spatial infinity. Finally, we discuss the role of the negative energy density near the horizon in the evaporating black hole. |
1001.1252 | Hossein Farajollahi | Hossein Farajollahi, Arvin Ravanpak | On the Dynamics of Bianchi IX cosmological models | 11 pages, 1 figure | Int J Theor Phy, 48, 12, 3345-3352, 2009 | 10.1007/s10773-009-0137-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A cosmological description of the universe is proposed in the context of
Hamiltonian formulation of a Bianchi IX cosmology minimally coupled to a
massless scalar field. The classical and quantum results are studied with
special attention to the case of closed Friedmann-Robertson-Walker model.
| [
{
"created": "Fri, 8 Jan 2010 12:19:58 GMT",
"version": "v1"
}
] | 2015-05-14 | [
[
"Farajollahi",
"Hossein",
""
],
[
"Ravanpak",
"Arvin",
""
]
] | A cosmological description of the universe is proposed in the context of Hamiltonian formulation of a Bianchi IX cosmology minimally coupled to a massless scalar field. The classical and quantum results are studied with special attention to the case of closed Friedmann-Robertson-Walker model. |
gr-qc/0011007 | Sawa Manoff | Sawa Manoff | Conformal derivative and conformal transports over spaces with
contravariant and covariant affine connections and metrics | 17 pages, LaTeX | Int.J.Mod.Phys. A15 (2000) 679-695 | 10.1142/S0217751X00000343 | null | gr-qc | null | Transports preserving the angle between two contravariant vector fields but
changing their lengths proportional to their own lengths are introduced as
''conformal'' transports and investigated over spaces with contravariant and
covariant affine connections (whose components differ not only by sign) and
metrics. They are more general than the Fermi-Walker transports. In an
analogous way as in the case of Fermi-Walker transports a conformal covariant
differential operator and its conformal derivative are defined and considered
over the above mentioned spaces. Different special types of conformal
transports are determined inducing also Fermi-Walker transports for orthogonal
vector fields as special cases. Conditions under which the length of a non-null
contravariant vector field could swing as a homogeneous harmonic oscillator are
established. The results obtained regardless of any concrete field
(gravitational) theory could have direct applications in such types of
theories.
PACS numbers: 04.90.+e; 04.50.+h; 12.10.Gq; 02.40.Vh
| [
{
"created": "Fri, 3 Nov 2000 07:39:07 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Manoff",
"Sawa",
""
]
] | Transports preserving the angle between two contravariant vector fields but changing their lengths proportional to their own lengths are introduced as ''conformal'' transports and investigated over spaces with contravariant and covariant affine connections (whose components differ not only by sign) and metrics. They are more general than the Fermi-Walker transports. In an analogous way as in the case of Fermi-Walker transports a conformal covariant differential operator and its conformal derivative are defined and considered over the above mentioned spaces. Different special types of conformal transports are determined inducing also Fermi-Walker transports for orthogonal vector fields as special cases. Conditions under which the length of a non-null contravariant vector field could swing as a homogeneous harmonic oscillator are established. The results obtained regardless of any concrete field (gravitational) theory could have direct applications in such types of theories. PACS numbers: 04.90.+e; 04.50.+h; 12.10.Gq; 02.40.Vh |
gr-qc/9404025 | null | A. Casher and F. Englert | Entropy Generation in Quantum Gravity and Black Hole Remnants | 26 pages, ULB-TH 7/93 6 figures not included available on request
from F. E. Published in ``String Theory, Quantum Gravity and the Unification
of the Fundamental Interactions'', World Scientific 1993, and to be published
in the ``International Conference on Fundamental Aspects of Quantum Theory''
in Honor of Y. Aharonov's 60th birthday. (problem with truncation of long
lines) | null | null | null | gr-qc hep-th | null | The area entropy $A/4$ and the related Hawking temperature in the presence of
event horizons are rederived, for de Sitter and black hole topologies, as a
consequence of a tunneling of the wave functional associated to the classical
coupled matter and gravitational fields. The extension of the wave functional
outside the barrier provides a reservoir of quantum states which allows for an
additive constant to $A/4$. While, in a semi-classical analysis, this gives no
new information in the de Sitter case, it yields an infinite constant in the
black hole case. Evaporating black holes would then leave residual ``planckons"
- Planckian remnants with infinite degeneracy. Generic planckons can neither
decay into, nor be directly formed from, ordinary matter in a finite time. Such
opening at the Planck scale of an infinite Hilbert space is expected to provide
the ultraviolet cutoff required to render the theory finite in the sector of
large scale physics.
| [
{
"created": "Wed, 13 Apr 1994 13:43:09 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Apr 1994 13:03:31 GMT",
"version": "v2"
}
] | 2009-09-25 | [
[
"Casher",
"A.",
""
],
[
"Englert",
"F.",
""
]
] | The area entropy $A/4$ and the related Hawking temperature in the presence of event horizons are rederived, for de Sitter and black hole topologies, as a consequence of a tunneling of the wave functional associated to the classical coupled matter and gravitational fields. The extension of the wave functional outside the barrier provides a reservoir of quantum states which allows for an additive constant to $A/4$. While, in a semi-classical analysis, this gives no new information in the de Sitter case, it yields an infinite constant in the black hole case. Evaporating black holes would then leave residual ``planckons" - Planckian remnants with infinite degeneracy. Generic planckons can neither decay into, nor be directly formed from, ordinary matter in a finite time. Such opening at the Planck scale of an infinite Hilbert space is expected to provide the ultraviolet cutoff required to render the theory finite in the sector of large scale physics. |
1602.05071 | Erico Goulart | E. Goulart | Nonlinear electrodynamics is skilled with knots | 5 pages, 1 figure | null | 10.1209/0295-5075/115/10004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The aims of this letter are three-fold: First is to show that nonlinear
generalizations of electrodynamics support various types of knotted solutions
in vacuum. The solutions are universal in the sense that they do not depend on
the specific Lagrangian density, at least if the latter gives rise to a
well-posed theory. Second is to describe the interaction between probe waves
and knotted background configurations. We show that the qualitative behaviour
of this interaction may be described in terms of Robinson congruences, which
appear explicitly in the causal structure of the theory. Finally, we argue that
optical arrangements endowed with intense background fields could be the
natural place to look for the knots experimentally.
| [
{
"created": "Tue, 16 Feb 2016 16:11:24 GMT",
"version": "v1"
}
] | 2016-08-24 | [
[
"Goulart",
"E.",
""
]
] | The aims of this letter are three-fold: First is to show that nonlinear generalizations of electrodynamics support various types of knotted solutions in vacuum. The solutions are universal in the sense that they do not depend on the specific Lagrangian density, at least if the latter gives rise to a well-posed theory. Second is to describe the interaction between probe waves and knotted background configurations. We show that the qualitative behaviour of this interaction may be described in terms of Robinson congruences, which appear explicitly in the causal structure of the theory. Finally, we argue that optical arrangements endowed with intense background fields could be the natural place to look for the knots experimentally. |
1604.03543 | Pierre Fleury | Pierre Fleury | On the time delay between ultra-relativistic particles | 5 pages, 1 figure, v2 matches published version | Physics Letters B 760 (2016) 350-353 | 10.1016/j.physletb.2016.07.010 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The time delay between the receptions of ultra-relativistic particles emitted
simultaneously is a useful observable for both fundamental physics and
cosmology. The expression of the delay when the particles travel through an
arbitrary spacetime has been derived recently by Fanizza et al., using a
particular coordinate system and self-consistent assumptions. The present
article shows that this formula enjoys a simple physical interpretation: the
relative velocity between two ultra-relativistic particles is constant. This
result reveals an interesting kinematical property of general relativity,
namely that the tidal forces experienced by ultra-relativistic particles in the
direction of their motion are much smaller than those experienced orthogonally
to their motion.
| [
{
"created": "Tue, 12 Apr 2016 19:55:12 GMT",
"version": "v1"
},
{
"created": "Sat, 16 Jul 2016 10:46:33 GMT",
"version": "v2"
}
] | 2016-07-19 | [
[
"Fleury",
"Pierre",
""
]
] | The time delay between the receptions of ultra-relativistic particles emitted simultaneously is a useful observable for both fundamental physics and cosmology. The expression of the delay when the particles travel through an arbitrary spacetime has been derived recently by Fanizza et al., using a particular coordinate system and self-consistent assumptions. The present article shows that this formula enjoys a simple physical interpretation: the relative velocity between two ultra-relativistic particles is constant. This result reveals an interesting kinematical property of general relativity, namely that the tidal forces experienced by ultra-relativistic particles in the direction of their motion are much smaller than those experienced orthogonally to their motion. |
1408.6561 | S. I. Kruglov | S. I. Kruglov | Black hole emission of vector particles in (1+1) dimensions | 13 pages, 2 figures | Int. J. Mod. Phys. A Vol. 29 (2014), 1450118 | 10.1142/S0217751X14501188 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the radiation of spin-1 particles by black holes in (1+1)
dimensions within the Proca equation. The process is considered as quantum
tunnelling of bosons through an event horizon. It is shown that the emission
temperature for the Schwarzschild background geometry is the same as the
Hawking temperature corresponding to scalar particles emission. We also obtain
the radiation temperatures for the de Sitter, Rindler and Schwarzschild-de
Sitter space-times. In a particular case when two horizons in Schwarzschild-de
Sitter space-time coincides the Nariai temperature is recovered. The
thermodynamical entropy of a black hole is calculated for Schwarzschild-de
Sitter space-time having two horizons.
| [
{
"created": "Wed, 13 Aug 2014 00:17:46 GMT",
"version": "v1"
}
] | 2014-08-29 | [
[
"Kruglov",
"S. I.",
""
]
] | We investigate the radiation of spin-1 particles by black holes in (1+1) dimensions within the Proca equation. The process is considered as quantum tunnelling of bosons through an event horizon. It is shown that the emission temperature for the Schwarzschild background geometry is the same as the Hawking temperature corresponding to scalar particles emission. We also obtain the radiation temperatures for the de Sitter, Rindler and Schwarzschild-de Sitter space-times. In a particular case when two horizons in Schwarzschild-de Sitter space-time coincides the Nariai temperature is recovered. The thermodynamical entropy of a black hole is calculated for Schwarzschild-de Sitter space-time having two horizons. |
2205.12195 | Pisin Chen | AnaBHEL Collaboration: Pisin Chen, Gerard Mourou, Marc Besancon, Yuji
Fukuda, Jean-Francois Glicenstein, Jiwoo Nam, Ching-En Lin, Kuan-Nan Lin,
Shu-Xiao Liu, Yung-Kun Liu, Masaki Kando, Kotaro Kondo, Stathes Paganis,
Alexander Pirozhkov, Hideaki Takabe, Boris Tuchming, Wei-Po Wang, Naoki
Watamura, Jonathan Wheeler, Hsin-Yeh Wu | AnaBHEL (Analog Black Hole Evaporation via Lasers) Experiment: Concept,
Design, and Status | 18 pages, 26 figures | null | null | null | gr-qc hep-ex physics.optics physics.plasm-ph quant-ph | http://creativecommons.org/licenses/by/4.0/ | Accelerating relativistic mirror has long been recognized as a viable setting
where the physics mimics that of black hole Hawking radiation. In 2017, Chen
and Mourou proposed a novel method to realize such a system by traversing an
ultra-intense laser through a plasma target with a decreasing density. An
international AnaBHEL (Analog Black Hole Evaporation via Lasers) Collaboration
has been formed with the objectives of observing the analog Hawking radiation
and shedding light on the information loss paradox. To reach these goals, we
plan to first verify the dynamics of the flying plasma mirror and to
characterize the correspondence between the plasma density gradient and the
trajectory of the accelerating plasma mirror. We will then attempt to detect
the analog Hawking radiation photons and measure the entanglement between the
Hawking photons and their "partner particles". In this paper, we describe our
vision and strategy of AnaBHEL using the Apollon laser as a reference, and we
report on the progress of our R&D of the key components in this experiment,
including the supersonic gas jet with a graded density profile, and the
superconducting nanowire single-photon Hawking detector. In parallel to these
hardware efforts, we performed computer simulations to estimate the potential
backgrounds, and derive analytic expressions for modifications to the blackbody
spectrum of Hawking radiation for a perfectly reflecting, point mirror, due to
the semit-ransparency and finite-size effects specific to flying plasma
mirrors. Based on this more realistic radiation spectrum, we estimate the
Hawking photon yield to guide the design of the AnaBHEL experiment, which
appears to be achievable.
| [
{
"created": "Tue, 24 May 2022 16:49:43 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Jun 2022 16:53:48 GMT",
"version": "v2"
},
{
"created": "Fri, 10 Jun 2022 14:52:05 GMT",
"version": "v3"
}
] | 2022-06-13 | [
[
"AnaBHEL Collaboration",
"",
""
],
[
"Chen",
"Pisin",
""
],
[
"Mourou",
"Gerard",
""
],
[
"Besancon",
"Marc",
""
],
[
"Fukuda",
"Yuji",
""
],
[
"Glicenstein",
"Jean-Francois",
""
],
[
"Nam",
"Jiwoo",
""
],
[
"Lin",
"Ching-En",
""
],
[
"Lin",
"Kuan-Nan",
""
],
[
"Liu",
"Shu-Xiao",
""
],
[
"Liu",
"Yung-Kun",
""
],
[
"Kando",
"Masaki",
""
],
[
"Kondo",
"Kotaro",
""
],
[
"Paganis",
"Stathes",
""
],
[
"Pirozhkov",
"Alexander",
""
],
[
"Takabe",
"Hideaki",
""
],
[
"Tuchming",
"Boris",
""
],
[
"Wang",
"Wei-Po",
""
],
[
"Watamura",
"Naoki",
""
],
[
"Wheeler",
"Jonathan",
""
],
[
"Wu",
"Hsin-Yeh",
""
]
] | Accelerating relativistic mirror has long been recognized as a viable setting where the physics mimics that of black hole Hawking radiation. In 2017, Chen and Mourou proposed a novel method to realize such a system by traversing an ultra-intense laser through a plasma target with a decreasing density. An international AnaBHEL (Analog Black Hole Evaporation via Lasers) Collaboration has been formed with the objectives of observing the analog Hawking radiation and shedding light on the information loss paradox. To reach these goals, we plan to first verify the dynamics of the flying plasma mirror and to characterize the correspondence between the plasma density gradient and the trajectory of the accelerating plasma mirror. We will then attempt to detect the analog Hawking radiation photons and measure the entanglement between the Hawking photons and their "partner particles". In this paper, we describe our vision and strategy of AnaBHEL using the Apollon laser as a reference, and we report on the progress of our R&D of the key components in this experiment, including the supersonic gas jet with a graded density profile, and the superconducting nanowire single-photon Hawking detector. In parallel to these hardware efforts, we performed computer simulations to estimate the potential backgrounds, and derive analytic expressions for modifications to the blackbody spectrum of Hawking radiation for a perfectly reflecting, point mirror, due to the semit-ransparency and finite-size effects specific to flying plasma mirrors. Based on this more realistic radiation spectrum, we estimate the Hawking photon yield to guide the design of the AnaBHEL experiment, which appears to be achievable. |
1711.04933 | Francisco Turrubiates Dr. | Ruben Cordero, Hugo Garcia-Compean and Francisco J. Turrubiates | A phase space description of the FLRW quantum cosmology in Ho$\check{\rm
r}$ava-Lifshitz type gravity | 34 pages, 18 figures (Figures, comments and references added. Typos
corrected) | General Relativity and Gravitation (2019) 51:138 | 10.1007/s10714-019-2627-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum cosmology of the Friedmann-Lema\^{i}tre-Robertson-Walker model with
cosmological constant in the Ho$\check{\rm r}$ava-Lifshitz type gravity is
studied in the phase space by means of the Wigner function. The modification of
the usual general relativity description by the Ho$\check{\rm r}$ava-Lifshitz
type gravity induces a new scenario for the origin of the Universe with an
embryonic era where the Universe can exist classically before the tunneling
process takes place and which gives rise to the current evolution of the
Universe. The Wigner functions corresponding to the Hartle-Hawking, Vilenkin
and Linde boundary conditions are obtained by means of numerical calculations.
In particular three cases were studied for the potential of the Wheeler-DeWitt
equation: tunneling barrier with and without embryonic era and when the
potential barrier is not present. The quantum behavior of these three cases are
analyzed using the Wigner function for the three boundary conditions
considered.
| [
{
"created": "Tue, 14 Nov 2017 03:44:10 GMT",
"version": "v1"
},
{
"created": "Sat, 20 Jul 2019 05:59:04 GMT",
"version": "v2"
},
{
"created": "Sat, 2 Nov 2019 07:09:36 GMT",
"version": "v3"
}
] | 2019-11-05 | [
[
"Cordero",
"Ruben",
""
],
[
"Garcia-Compean",
"Hugo",
""
],
[
"Turrubiates",
"Francisco J.",
""
]
] | Quantum cosmology of the Friedmann-Lema\^{i}tre-Robertson-Walker model with cosmological constant in the Ho$\check{\rm r}$ava-Lifshitz type gravity is studied in the phase space by means of the Wigner function. The modification of the usual general relativity description by the Ho$\check{\rm r}$ava-Lifshitz type gravity induces a new scenario for the origin of the Universe with an embryonic era where the Universe can exist classically before the tunneling process takes place and which gives rise to the current evolution of the Universe. The Wigner functions corresponding to the Hartle-Hawking, Vilenkin and Linde boundary conditions are obtained by means of numerical calculations. In particular three cases were studied for the potential of the Wheeler-DeWitt equation: tunneling barrier with and without embryonic era and when the potential barrier is not present. The quantum behavior of these three cases are analyzed using the Wigner function for the three boundary conditions considered. |
1408.5264 | Andrea Geralico | Donato Bini, Mariateresa Crosta, Fernando de Felice, Andrea Geralico,
Alberto Vecchiato | The Erez-Rosen metric and the role of the quadrupole on light
propagation | 24 pages, 8 figures; published version | Class. Quantum Grav. 30, 045009 (2013) | 10.1088/0264-9381/30/4/045009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational field of a static body with quadrupole moment is described
by an exact solution found by Erez and Rosen. Here we investigate the role of
the quadrupole in the motion, deflection and lensing of a light ray in the
above metric. The standard lensing observables like image positions and
magnification have been explicitly obtained in the weak field and small
quadrupole limit. In this limit the spacetime metric appears as the natural
generalization to quadrupole corrections of the metric form adopted also in
current astrometric models. Hence, the corresponding analytical solution of the
inverse ray tracing problem as well as the consistency with other approaches
are also discussed.
| [
{
"created": "Fri, 22 Aug 2014 11:00:17 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Bini",
"Donato",
""
],
[
"Crosta",
"Mariateresa",
""
],
[
"de Felice",
"Fernando",
""
],
[
"Geralico",
"Andrea",
""
],
[
"Vecchiato",
"Alberto",
""
]
] | The gravitational field of a static body with quadrupole moment is described by an exact solution found by Erez and Rosen. Here we investigate the role of the quadrupole in the motion, deflection and lensing of a light ray in the above metric. The standard lensing observables like image positions and magnification have been explicitly obtained in the weak field and small quadrupole limit. In this limit the spacetime metric appears as the natural generalization to quadrupole corrections of the metric form adopted also in current astrometric models. Hence, the corresponding analytical solution of the inverse ray tracing problem as well as the consistency with other approaches are also discussed. |
2406.18205 | Philip Semr\'en | Philip Semr\'en | Cosmological Particle Creation Using an Equal-Time Wigner Formalism | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known that the expansion of the universe can create particles.
However, due to ambiguities when defining particles during the expansion, there
are still debates about how to choose vacuum and particle states. To clarify
how particles are produced in an expanding universe, we study the creation of
real scalar particles in flat FLRW spacetimes by using a recently developed
equal-time Wigner formalism. By comparing this quantum kinetic formalism with
the standard Bogoliubov approach, we make a natural definition of a particle
number in terms of kinetic phase-space functions, which we then compare with
common adiabatic particle numbers. With inspiration from flat spacetime QED, we
perform numerical calculations and discuss the interpretation of the particle
numbers in terms of a hypothetical switch-off in the expansion rate. Finally,
we consider how this interpretation is affected by regularization.
| [
{
"created": "Wed, 26 Jun 2024 09:37:36 GMT",
"version": "v1"
}
] | 2024-06-27 | [
[
"Semrén",
"Philip",
""
]
] | It is well known that the expansion of the universe can create particles. However, due to ambiguities when defining particles during the expansion, there are still debates about how to choose vacuum and particle states. To clarify how particles are produced in an expanding universe, we study the creation of real scalar particles in flat FLRW spacetimes by using a recently developed equal-time Wigner formalism. By comparing this quantum kinetic formalism with the standard Bogoliubov approach, we make a natural definition of a particle number in terms of kinetic phase-space functions, which we then compare with common adiabatic particle numbers. With inspiration from flat spacetime QED, we perform numerical calculations and discuss the interpretation of the particle numbers in terms of a hypothetical switch-off in the expansion rate. Finally, we consider how this interpretation is affected by regularization. |
1708.08004 | Tiberiu Harko | Juntong Su, Tiberiu Harko, Shi-Dong Liang | Irreversible thermodynamic description of dark matter and radiation
creation during inflationary reheating | 23 pages, 8 figures, accepted for publication in Advances in High
Energy Physics | Advances in High Energy Physics, Volume 2017, Article ID 7650238
(2017) | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the matter creation processes during the reheating period at
the end of inflation in the early Universe, by using the irreversible
thermodynamic of open systems. The matter content of the Universe is assumed to
consist of the inflationary scalar field, which, through its decay, generates
relativistic matter, and pressureless dark matter, respectively. At the early
stages of reheating the inflationary scalar field transfers its energy to the
newly created matter particles, with the field energy decreasing to near zero.
The general equations governing the irreversible matter creation during
reheating are obtained by combining the thermodynamics description of the
matter creation and the gravitational field equations. A dimensionless form of
the general system of the reheating equations is also introduced. The role of
the different inflationary scalar field potentials is analyzed by using
analytical and numerical methods, and the evolution of the matter and scalar
field densities, as well as of the cosmological parameters during reheating,
are obtained. Typically, the values of the energy densities of relativistic
matter and dark matter reach their maximum when the Universe is reheated up to
the reheating temperature, which is determined for each case, as a function of
the scalar field decay width, the scalar field particle mass, and of the
cosmological parameters. An interesting result is that particle production
leads to the acceleration of the Universe during the reheating phase, with the
deceleration parameter showing a complex dynamics. Once the energy density of
the scalar field becomes negligible with respect to the matter densities, the
expansion of the Universe decelerates, and inflation has a graceful exit after
reheating.
| [
{
"created": "Sat, 26 Aug 2017 18:14:26 GMT",
"version": "v1"
}
] | 2018-10-09 | [
[
"Su",
"Juntong",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Liang",
"Shi-Dong",
""
]
] | We investigate the matter creation processes during the reheating period at the end of inflation in the early Universe, by using the irreversible thermodynamic of open systems. The matter content of the Universe is assumed to consist of the inflationary scalar field, which, through its decay, generates relativistic matter, and pressureless dark matter, respectively. At the early stages of reheating the inflationary scalar field transfers its energy to the newly created matter particles, with the field energy decreasing to near zero. The general equations governing the irreversible matter creation during reheating are obtained by combining the thermodynamics description of the matter creation and the gravitational field equations. A dimensionless form of the general system of the reheating equations is also introduced. The role of the different inflationary scalar field potentials is analyzed by using analytical and numerical methods, and the evolution of the matter and scalar field densities, as well as of the cosmological parameters during reheating, are obtained. Typically, the values of the energy densities of relativistic matter and dark matter reach their maximum when the Universe is reheated up to the reheating temperature, which is determined for each case, as a function of the scalar field decay width, the scalar field particle mass, and of the cosmological parameters. An interesting result is that particle production leads to the acceleration of the Universe during the reheating phase, with the deceleration parameter showing a complex dynamics. Once the energy density of the scalar field becomes negligible with respect to the matter densities, the expansion of the Universe decelerates, and inflation has a graceful exit after reheating. |
1406.5224 | Stephen Taylor | Stephen Taylor, Justin Ellis, Jonathan Gair | Accelerated Bayesian model-selection and parameter-estimation in
continuous gravitational-wave searches with pulsar-timing arrays | 17 pages, 10 figures, 1 table. Minor changes to reflect published
version | Phys. Rev. D 90, 104028 (2014) | 10.1103/PhysRevD.90.104028 | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe several new techniques which accelerate Bayesian searches for
continuous gravitational-wave emission from supermassive black-hole binaries
using pulsar timing arrays. These techniques mitigate the problematic increase
of search-dimensionality with the size of the pulsar array which arises from
having to include an extra parameter per pulsar as the array is expanded. This
extra parameter corresponds to searching over the phase of the
gravitational-wave as it propagates past each pulsar so that we can coherently
include the pulsar-term in our search strategies. Our techniques make the
analysis tractable with powerful evidence-evaluation packages like MultiNest.
We find good agreement of our techniques with the parameter-estimation and
Bayes factor evaluation performed with full signal templates, and conclude that
these techniques make excellent first-cut tools for detection and
characterisation of continuous gravitational-wave signals with pulsar timing
arrays. Crucially, at low to moderate signal-to-noise ratios the factor by
which the analysis is sped up can be > 100, permitting rigorous programs of
systematic injection and recovery of signals to establish robust detection
criteria within a Bayesian formalism.
| [
{
"created": "Thu, 19 Jun 2014 21:40:47 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Nov 2014 23:25:54 GMT",
"version": "v2"
}
] | 2014-11-25 | [
[
"Taylor",
"Stephen",
""
],
[
"Ellis",
"Justin",
""
],
[
"Gair",
"Jonathan",
""
]
] | We describe several new techniques which accelerate Bayesian searches for continuous gravitational-wave emission from supermassive black-hole binaries using pulsar timing arrays. These techniques mitigate the problematic increase of search-dimensionality with the size of the pulsar array which arises from having to include an extra parameter per pulsar as the array is expanded. This extra parameter corresponds to searching over the phase of the gravitational-wave as it propagates past each pulsar so that we can coherently include the pulsar-term in our search strategies. Our techniques make the analysis tractable with powerful evidence-evaluation packages like MultiNest. We find good agreement of our techniques with the parameter-estimation and Bayes factor evaluation performed with full signal templates, and conclude that these techniques make excellent first-cut tools for detection and characterisation of continuous gravitational-wave signals with pulsar timing arrays. Crucially, at low to moderate signal-to-noise ratios the factor by which the analysis is sped up can be > 100, permitting rigorous programs of systematic injection and recovery of signals to establish robust detection criteria within a Bayesian formalism. |
1108.6301 | Dawood Kothawala Dr. | Dawood Kothawala | Box of Ideal Gas in Free Fall | 5 pages, no figures; abstract abridged and an appendix added
outlining some relevant mathematical steps; accepted in Phys. Lett. B | Phys. Lett. B 720: 410-413 (2013) | 10.1016/j.physletb.2013.02.035 | null | gr-qc cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the \textit{quantum} partition function of non-relativistic, ideal
gas in a (non-cubical) box falling freely in arbitrary curved spacetime with
centre 4-velocity u^a. When perturbed energy eigenvalues are properly taken
into account, we find that corrections to various thermodynamic quantities
include a very specific, sub-dominant term which is independent of
\textit{kinematic} details such as box dimensions and mass of particles. This
term is characterized by the dimensionless quantity, \Xi=R_00 \Lambda^2, where
R_00=R_ab u^a u^b and \Lambda=\beta \hbar c, and, quite intriguingly, produces
Euler relation of homogeneity two between entropy and energy -- a relation
familiar from black hole thermodynamics.
| [
{
"created": "Wed, 31 Aug 2011 17:54:22 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Feb 2013 11:23:37 GMT",
"version": "v2"
}
] | 2013-03-12 | [
[
"Kothawala",
"Dawood",
""
]
] | We study the \textit{quantum} partition function of non-relativistic, ideal gas in a (non-cubical) box falling freely in arbitrary curved spacetime with centre 4-velocity u^a. When perturbed energy eigenvalues are properly taken into account, we find that corrections to various thermodynamic quantities include a very specific, sub-dominant term which is independent of \textit{kinematic} details such as box dimensions and mass of particles. This term is characterized by the dimensionless quantity, \Xi=R_00 \Lambda^2, where R_00=R_ab u^a u^b and \Lambda=\beta \hbar c, and, quite intriguingly, produces Euler relation of homogeneity two between entropy and energy -- a relation familiar from black hole thermodynamics. |
gr-qc/0305080 | Thomas Thiemann | Thomas Thiemann | The Phoenix Project: Master Constraint Programme for Loop Quantum
Gravity | LATEX, uses AMSTEX | Class.Quant.Grav.23:2211-2248,2006 | 10.1088/0264-9381/23/7/002 | AEI-2003-047, PI-2003-003 | gr-qc hep-th math-ph math.MP quant-ph | null | The Hamiltonian constraint remains the major unsolved problem in Loop Quantum
Gravity (LQG). Seven years ago a mathematically consistent candidate
Hamiltonian constraint has been proposed but there are still several unsettled
questions which concern the algebra of commutators among smeared Hamiltonian
constraints which must be faced in order to make progress. In this paper we
propose a solution to this set of problems based on the so-called {\bf Master
Constraint} which combines the smeared Hamiltonian constraints for all smearing
functions into a single constraint. If certain mathematical conditions, which
still have to be proved, hold, then not only the problems with the commutator
algebra could disappear, also chances are good that one can control the
solution space and the (quantum) Dirac observables of LQG. Even a decision on
whether the theory has the correct classical limit and a connection with the
path integral (or spin foam) formulation could be in reach. While these are
exciting possibilities, we should warn the reader from the outset that, since
the proposal is, to the best of our knowledge, completely new and has been
barely tested in solvable models, there might be caveats which we are presently
unaware of and render the whole {\bf Master Constraint Programme} obsolete.
Thus, this paper should really be viewed as a proposal only, rather than a
presentation of hard results, which however we intend to supply in future
submissions.
| [
{
"created": "Wed, 21 May 2003 16:07:14 GMT",
"version": "v1"
}
] | 2011-07-18 | [
[
"Thiemann",
"Thomas",
""
]
] | The Hamiltonian constraint remains the major unsolved problem in Loop Quantum Gravity (LQG). Seven years ago a mathematically consistent candidate Hamiltonian constraint has been proposed but there are still several unsettled questions which concern the algebra of commutators among smeared Hamiltonian constraints which must be faced in order to make progress. In this paper we propose a solution to this set of problems based on the so-called {\bf Master Constraint} which combines the smeared Hamiltonian constraints for all smearing functions into a single constraint. If certain mathematical conditions, which still have to be proved, hold, then not only the problems with the commutator algebra could disappear, also chances are good that one can control the solution space and the (quantum) Dirac observables of LQG. Even a decision on whether the theory has the correct classical limit and a connection with the path integral (or spin foam) formulation could be in reach. While these are exciting possibilities, we should warn the reader from the outset that, since the proposal is, to the best of our knowledge, completely new and has been barely tested in solvable models, there might be caveats which we are presently unaware of and render the whole {\bf Master Constraint Programme} obsolete. Thus, this paper should really be viewed as a proposal only, rather than a presentation of hard results, which however we intend to supply in future submissions. |
1605.08976 | Saheb Soroushfar | Saheb Soroushfar, Reza Saffari, Sobhan Kazempour, Saskia Grunau, Jutta
Kunz | Detailed study of geodesics in the Kerr-Newman-(A)dS spactime and the
rotating charged black hole spacetime in $f(R)$ gravity | 35 pages,3 table,24 figures, Accepted for publication in Physical
Review D. arXiv admin note: text overlap with arXiv:1605.08975,
arXiv:1601.03143 | Phys. Rev. D 94, 024052 (2016) | 10.1103/PhysRevD.94.024052 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a detailed study of the geodesic equations in the spacetime of the
static and rotating charged black hole corresponding to the Kerr-Newman-(A)dS
spacetime. We derive the equations of motion for test particles and light rays
and present their solutions in terms of the Weierstrass $\wp$, $\zeta$ and
$\sigma$ functions as well as the Kleinian $\sigma$ function. With the help of
parametric diagrams and effective potentials we analyze the geodesic motion and
classify the possible orbit types. This spacetime is also a solution of $f(R)$
gravity with a constant curvature scalar.
| [
{
"created": "Sun, 29 May 2016 08:11:58 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Jul 2016 10:49:04 GMT",
"version": "v2"
}
] | 2016-08-02 | [
[
"Soroushfar",
"Saheb",
""
],
[
"Saffari",
"Reza",
""
],
[
"Kazempour",
"Sobhan",
""
],
[
"Grunau",
"Saskia",
""
],
[
"Kunz",
"Jutta",
""
]
] | We perform a detailed study of the geodesic equations in the spacetime of the static and rotating charged black hole corresponding to the Kerr-Newman-(A)dS spacetime. We derive the equations of motion for test particles and light rays and present their solutions in terms of the Weierstrass $\wp$, $\zeta$ and $\sigma$ functions as well as the Kleinian $\sigma$ function. With the help of parametric diagrams and effective potentials we analyze the geodesic motion and classify the possible orbit types. This spacetime is also a solution of $f(R)$ gravity with a constant curvature scalar. |
gr-qc/9701036 | William Krivan | W. Krivan, P. Laguna, P. Papadopoulos | Dynamics of spin-2 fields in Kerr background geometries | 3 pages LaTeX using sprocl.sty, 1 figure, to appear in: Proceedings
of the 18th Texas Symposium on Relativistic Astrophysics (eds Olinto, Frieman
and Schramm, World Scientific) | null | null | null | gr-qc | null | We have developed a numerical method for evolving perturbations of rotating
black holes. Solutions are obtained by integrating the Teukolsky equation
written as a first-order in time, coupled system of equations, in a form that
explicitly exhibits the radial characteristic directions. We follow the
propagation of generic initial data through the burst, quasi-normal ringing and
power-law tail phases. Future results may help to clarify the role of black
hole angular momentum on signals produced during the final stages of black hole
coalescence.
| [
{
"created": "Wed, 15 Jan 1997 16:14:47 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Krivan",
"W.",
""
],
[
"Laguna",
"P.",
""
],
[
"Papadopoulos",
"P.",
""
]
] | We have developed a numerical method for evolving perturbations of rotating black holes. Solutions are obtained by integrating the Teukolsky equation written as a first-order in time, coupled system of equations, in a form that explicitly exhibits the radial characteristic directions. We follow the propagation of generic initial data through the burst, quasi-normal ringing and power-law tail phases. Future results may help to clarify the role of black hole angular momentum on signals produced during the final stages of black hole coalescence. |
2308.05291 | Caiyu Liu | Caiyu Liu, Xin Wu | Effects of coupling constants on chaos of charged particles in the
$Einstein-\AE$ ther theory | 19 pages, 10 figures | null | 10.3390/universe9080365 | null | gr-qc astro-ph.GA | http://creativecommons.org/licenses/by/4.0/ | There are two free coupling parameters $c_{13}$ and $c_{14}$ in the
Einstein-\AE ther metric describing a non-rotating black hole. This metric is
the Reissner-Nordstr\"{o}m black hole solution when $0\leq 2c_{13}<c_{14}<2$,
but it is not for $0\leq c_{14}<2c_{13}<2$. When the black hole is immersed in
an external asymptotically uniform magnetic field, the Hamiltonian system
describing the motion of charged particles around the black hole is not
integrable. However, the Hamiltonian allows for the construction of explicit
symplectic integrators. The proposed fourth-order explicit symplectic scheme is
used to investigate the dynamics of charged particles because it exhibits
excellent long-term performance in conserving the Hamiltonian. No universal
rule can be given to the dependence of regular and chaotic dynamics on varying
one or two parameters $c_{13}$ and $c_{14}$ in the two cases of $0\leq
2c_{13}<c_{14}<2$ and $0\leq c_{14}<2c_{13}<2$. The distributions of order and
chaos in the binary parameter space $(c_{13},c_{14})$ rely on different
combinations of the other parameters and the initial conditions.
| [
{
"created": "Thu, 10 Aug 2023 02:13:42 GMT",
"version": "v1"
}
] | 2023-08-11 | [
[
"Liu",
"Caiyu",
""
],
[
"Wu",
"Xin",
""
]
] | There are two free coupling parameters $c_{13}$ and $c_{14}$ in the Einstein-\AE ther metric describing a non-rotating black hole. This metric is the Reissner-Nordstr\"{o}m black hole solution when $0\leq 2c_{13}<c_{14}<2$, but it is not for $0\leq c_{14}<2c_{13}<2$. When the black hole is immersed in an external asymptotically uniform magnetic field, the Hamiltonian system describing the motion of charged particles around the black hole is not integrable. However, the Hamiltonian allows for the construction of explicit symplectic integrators. The proposed fourth-order explicit symplectic scheme is used to investigate the dynamics of charged particles because it exhibits excellent long-term performance in conserving the Hamiltonian. No universal rule can be given to the dependence of regular and chaotic dynamics on varying one or two parameters $c_{13}$ and $c_{14}$ in the two cases of $0\leq 2c_{13}<c_{14}<2$ and $0\leq c_{14}<2c_{13}<2$. The distributions of order and chaos in the binary parameter space $(c_{13},c_{14})$ rely on different combinations of the other parameters and the initial conditions. |
gr-qc/0504116 | Wei-Tou Ni | Wei-Tou Ni | Empirical Foundations of Relativistic Gravity | 18 pages; International Journal of Modern Physics D, in press (World
Scientific, 2005); 100 Years of Gravity and Accelerated Frames--The Deepest
Insights of Einstein and Yang-Mills (Ed. J. P. Hsu and D. Fine, in press,
World Scientific, 2005) | Int.J.Mod.Phys.D14:901-922,2005 | 10.1142/S0218271805007139 | PMO-A-025 | gr-qc astro-ph hep-ph | null | In 1859, Le Verrier discovered the mercury perihelion advance anomaly. This
anomaly turned out to be the first relativistic-gravity effect observed. During
the 141 years to 2000, the precisions of laboratory and space experiments, and
astrophysical and cosmological observations on relativistic gravity have been
improved by 3 orders of magnitude. In 1999, we envisaged a 3-6 order
improvement in the next 30 years in all directions of tests of relativistic
gravity. In 2000, the interferometric gravitational wave detectors began their
runs to accumulate data. In 2003, the measurement of relativistic Shapiro
time-delay of the Cassini spacecraft determined the relativistic-gravity
parameter gammaγ with a 1.5-order improvement. In October 2004, Ciufolini
and Pavlis reported a measurement of the Lense-Thirring effect on the LAGEOS
and LAGEOS2 satellites to 10 percent of the value predicted by general
relativity. In April 2004, Gravity Probe B was launched and has been
accumulating science data for more than 170 days now. MICROSCOPE is on its way
for a 2007 launch to test Galileo equivalence principle to 10-15. STEP
(Satellite Test of Equivalence Principle), and ASTROD (Astrodynamical Space
Test of Relativity using Optical Devices) are in the good planning stage.
Various astrophysical tests and cosmological tests of relativistic gravity will
reach precision and ultra-precision stages. Clock tests and atomic
interferometry tests of relativistic gravity will reach an ever-increasing
precision. These will give revived interest and development both in
experimental and theoretical aspects of gravity, and may lead to answers to
some profound questions of gravity and the cosmos.
| [
{
"created": "Sun, 24 Apr 2005 06:22:21 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Ni",
"Wei-Tou",
""
]
] | In 1859, Le Verrier discovered the mercury perihelion advance anomaly. This anomaly turned out to be the first relativistic-gravity effect observed. During the 141 years to 2000, the precisions of laboratory and space experiments, and astrophysical and cosmological observations on relativistic gravity have been improved by 3 orders of magnitude. In 1999, we envisaged a 3-6 order improvement in the next 30 years in all directions of tests of relativistic gravity. In 2000, the interferometric gravitational wave detectors began their runs to accumulate data. In 2003, the measurement of relativistic Shapiro time-delay of the Cassini spacecraft determined the relativistic-gravity parameter gammaγ with a 1.5-order improvement. In October 2004, Ciufolini and Pavlis reported a measurement of the Lense-Thirring effect on the LAGEOS and LAGEOS2 satellites to 10 percent of the value predicted by general relativity. In April 2004, Gravity Probe B was launched and has been accumulating science data for more than 170 days now. MICROSCOPE is on its way for a 2007 launch to test Galileo equivalence principle to 10-15. STEP (Satellite Test of Equivalence Principle), and ASTROD (Astrodynamical Space Test of Relativity using Optical Devices) are in the good planning stage. Various astrophysical tests and cosmological tests of relativistic gravity will reach precision and ultra-precision stages. Clock tests and atomic interferometry tests of relativistic gravity will reach an ever-increasing precision. These will give revived interest and development both in experimental and theoretical aspects of gravity, and may lead to answers to some profound questions of gravity and the cosmos. |
1707.07675 | Ra\'ila Andr\'e | Ra\'ila Andr\'e and Gilberto M. Kremer | Stellar structure model in hydrostatic equilibrium in the context of
$f(\mathcal{R})$-gravity | 8 pages, 1 figure Manuscript accepted for publication in Research in
Astronomy and Astrophysics | null | null | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we present a stellar structure model from
$f(\mathcal{R})$-gravity point of view capable to describe some classes of
stars (White Dwarfs, Brown Dwarfs, Neutron stars, Red Giants and the Sun). This
model was based on $f(\mathcal{R})$-gravity field equations for
$f(\mathcal{R})= \mathcal{R}+ f_2 \mathcal{R}^2$, hydrostatic equilibrium
equation and a polytropic equation of state. We compared the results obtained
with those found by the Newtonian theory. It has been observed that in these
systems, where high curvature regimes emerge, stellar structure equations
undergo modifications. Despite the simplicity of this model, the results were
satisfactory. The estimated values of pressure, density and temperature of the
stars are within those determined by observations. This
$f(\mathcal{R})$-gravity model has been proved to be necessary to describe
stars with strong fields such as White Dwarfs, Neutron stars and Brown Dwarfs,
while stars with weaker fields, such as Red Giants and the Sun, were best
described by the Newtonian theory.
| [
{
"created": "Mon, 24 Jul 2017 10:21:17 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Aug 2017 10:59:04 GMT",
"version": "v2"
}
] | 2017-08-30 | [
[
"André",
"Raíla",
""
],
[
"Kremer",
"Gilberto M.",
""
]
] | In this work we present a stellar structure model from $f(\mathcal{R})$-gravity point of view capable to describe some classes of stars (White Dwarfs, Brown Dwarfs, Neutron stars, Red Giants and the Sun). This model was based on $f(\mathcal{R})$-gravity field equations for $f(\mathcal{R})= \mathcal{R}+ f_2 \mathcal{R}^2$, hydrostatic equilibrium equation and a polytropic equation of state. We compared the results obtained with those found by the Newtonian theory. It has been observed that in these systems, where high curvature regimes emerge, stellar structure equations undergo modifications. Despite the simplicity of this model, the results were satisfactory. The estimated values of pressure, density and temperature of the stars are within those determined by observations. This $f(\mathcal{R})$-gravity model has been proved to be necessary to describe stars with strong fields such as White Dwarfs, Neutron stars and Brown Dwarfs, while stars with weaker fields, such as Red Giants and the Sun, were best described by the Newtonian theory. |
gr-qc/0309073 | Maria J. Pareja | M. J. Pareja | Relativistic stars in differential rotation: bounds on the dragging rate
and on the rotational energy | 23 pages, no figures, LaTeX. Submitted to J. Math. Phys | J.Math.Phys. 45 (2004) 677-695 | 10.1063/1.1636515 | null | gr-qc | null | For general relativistic equilibrium stellar models (stationary axisymmetric
asymptotically flat and convection-free) with differential rotation, it is
shown that for a wide class of rotation laws the distribution of angular
velocity of the fluid has a sign, say "positive", and then both the dragging
rate and the angular momentum density are positive. In addition, the "mean
value" (with respect to an intrinsic density) of the dragging rate is shown to
be less than the mean value of the fluid angular velocity (in full general,
without having to restrict the rotation law, nor the uniformity in sign of the
fluid angular velocity); this inequality yields the positivity and an upper
bound of the total rotational energy.
| [
{
"created": "Tue, 16 Sep 2003 07:42:25 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Pareja",
"M. J.",
""
]
] | For general relativistic equilibrium stellar models (stationary axisymmetric asymptotically flat and convection-free) with differential rotation, it is shown that for a wide class of rotation laws the distribution of angular velocity of the fluid has a sign, say "positive", and then both the dragging rate and the angular momentum density are positive. In addition, the "mean value" (with respect to an intrinsic density) of the dragging rate is shown to be less than the mean value of the fluid angular velocity (in full general, without having to restrict the rotation law, nor the uniformity in sign of the fluid angular velocity); this inequality yields the positivity and an upper bound of the total rotational energy. |
1209.5081 | Robert Milson | Robert Milson, David McNutt, Alan Coley | Invariant classification of vacuum PP-waves | null | null | 10.1063/1.4791691 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We solve the equivalence problem for vacuum PP-wave spacetimes by employing
the Karlhede algorithm. Our main result is a suite of Cartan invariants that
allows for the complete invariant classification of the vacuum pp-waves. In
particular, we derive the invariant characterization of the G2 and G3
sub-classes in terms of these invariants. It is known [Collins91] that the
invariant classification of vacuum pp-waves requires at most the fourth order
covariant derivative of the curvature tensor, but no specific examples
requiring the fourth order were known. Using our comprehensive classification,
we prove that the q<=4 bound is sharp and explicitly describe all such maximal
order solutions.
| [
{
"created": "Sun, 23 Sep 2012 16:15:09 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Milson",
"Robert",
""
],
[
"McNutt",
"David",
""
],
[
"Coley",
"Alan",
""
]
] | We solve the equivalence problem for vacuum PP-wave spacetimes by employing the Karlhede algorithm. Our main result is a suite of Cartan invariants that allows for the complete invariant classification of the vacuum pp-waves. In particular, we derive the invariant characterization of the G2 and G3 sub-classes in terms of these invariants. It is known [Collins91] that the invariant classification of vacuum pp-waves requires at most the fourth order covariant derivative of the curvature tensor, but no specific examples requiring the fourth order were known. Using our comprehensive classification, we prove that the q<=4 bound is sharp and explicitly describe all such maximal order solutions. |
gr-qc/0002019 | Stefano Liberati | S. Liberati, T. Rothman, S. Sonego | Nonthermal nature of incipient extremal black holes | 13 pages, 2 epsf figures, RevTeX 3. Minor changes, version published
in PRD | Phys.Rev. D62 (2000) 024005 | 10.1103/PhysRevD.62.024005 | SISSA-Ref. 8/2000/A | gr-qc | null | We examine particle production from spherical bodies collapsing into extremal
Reissner-Nordstr\"om black holes. Kruskal coordinates become ill-defined in the
extremal case, but we are able to find a simple generalization of them that is
good in this limit. The extension allows us to calculate the late-time
worldline of the center of the collapsing star, thus establishing a
correspondence with a uniformly accelerated mirror in Minkowski spacetime. The
spectrum of created particles associated with such uniform acceleration is
nonthermal, indicating that a temperature is not defined. Moreover, the
spectrum contains a constant that depends on the history of the collapsing
object. At first sight this points to a violation of the no-hair theorems;
however, the expectation value of the stress-energy-momentum tensor is zero and
its variance vanishes as a power law at late times. Hence, both the no-hair
theorems and the cosmic censorship conjecture are preserved. The power-law
decay of the variance is in distinction to the exponential fall-off of a
nonextremal black hole. Therefore, although the vanishing of the stress
tensor's expectation value is consistent with a thermal state at zero
temperature, the incipient black hole does not behave as a thermal object at
any time and cannot be regarded as the thermodynamic limit of a nonextremal
black hole, regardless of the fact that the final product of collapse is
quiescent.
| [
{
"created": "Thu, 3 Feb 2000 17:50:36 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Jul 2000 17:05:36 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Liberati",
"S.",
""
],
[
"Rothman",
"T.",
""
],
[
"Sonego",
"S.",
""
]
] | We examine particle production from spherical bodies collapsing into extremal Reissner-Nordstr\"om black holes. Kruskal coordinates become ill-defined in the extremal case, but we are able to find a simple generalization of them that is good in this limit. The extension allows us to calculate the late-time worldline of the center of the collapsing star, thus establishing a correspondence with a uniformly accelerated mirror in Minkowski spacetime. The spectrum of created particles associated with such uniform acceleration is nonthermal, indicating that a temperature is not defined. Moreover, the spectrum contains a constant that depends on the history of the collapsing object. At first sight this points to a violation of the no-hair theorems; however, the expectation value of the stress-energy-momentum tensor is zero and its variance vanishes as a power law at late times. Hence, both the no-hair theorems and the cosmic censorship conjecture are preserved. The power-law decay of the variance is in distinction to the exponential fall-off of a nonextremal black hole. Therefore, although the vanishing of the stress tensor's expectation value is consistent with a thermal state at zero temperature, the incipient black hole does not behave as a thermal object at any time and cannot be regarded as the thermodynamic limit of a nonextremal black hole, regardless of the fact that the final product of collapse is quiescent. |
2307.15147 | Edisom S. Moreira Jr. | E. S. Moreira Jr | Boundary effects on the thermal stability of a black hole at the centre
of a conducting spherical shell | 10 pages, no figures. This version, except for stylistic changes,
fits with the published version in PRD | Phys. Rev. D 108, 105018 (2023) | 10.1103/PhysRevD.108.105018 | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | This paper reports calculations and analysis of the effects of a perfect
conducting wall of a very large spherical shell on the stable thermodynamic
equilibrium of a black hole sitting at the centre of the shell which is filled
with Electromagnetic blackbody radiation. A parallel is drawn with the case
where electromagnetic is replaced by scalar blackbody radiation with Dirichlet
or Neumann boundary conditions on the wall. It is found that the value of the
shell radius above which only blackbody radiation remains in stable
thermodynamic equilibrium can be considerably affected by vacuum polarization
due to the presence of the wall.
| [
{
"created": "Thu, 27 Jul 2023 18:48:25 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Oct 2023 11:36:31 GMT",
"version": "v2"
}
] | 2023-12-01 | [
[
"Moreira",
"E. S.",
"Jr"
]
] | This paper reports calculations and analysis of the effects of a perfect conducting wall of a very large spherical shell on the stable thermodynamic equilibrium of a black hole sitting at the centre of the shell which is filled with Electromagnetic blackbody radiation. A parallel is drawn with the case where electromagnetic is replaced by scalar blackbody radiation with Dirichlet or Neumann boundary conditions on the wall. It is found that the value of the shell radius above which only blackbody radiation remains in stable thermodynamic equilibrium can be considerably affected by vacuum polarization due to the presence of the wall. |
gr-qc/0411078 | Michael P\"urrer | Michael P\"urrer, Sascha Husa, Peter C. Aichelburg | News from Critical Collapse: Bondi Mass, Tails and Quasinormal Modes | 17 pages, 13 figures, uses RevTeX4, changed order of figures and
corrected references to match PRD version | Phys.Rev.D71:104005,2005 | 10.1103/PhysRevD.71.104005 | UWThPh-2004-33 | gr-qc | null | We discuss critical gravitational collapse on the threshold of apparent
horizon formation as a model both for the discussion of global aspects of
critical collapse and for numerical studies in a compactified context. For our
matter model we choose a self-gravitating massless scalar field in spherical
symmetry, which has been studied extensively in the critical collapse
literature. Our evolution system is based on Bondi coordinates, the mass
function is used as an evolution variable to ensure regularity at null
infinity. We compute radiation quantities like the Bondi mass and news function
and find that they reflect the DSS behavior. Surprisingly, the period of
radiation at null infinity is related to the formal result for the leading
quasi-normal mode of a black hole with rapidly decreasing mass. Furthermore,
our investigations shed some light on global versus local issues in critical
collapse, and the validity and usefulness of the concept of null infinity when
predicting detector signals.
| [
{
"created": "Mon, 15 Nov 2004 22:40:34 GMT",
"version": "v1"
},
{
"created": "Mon, 9 May 2005 15:11:32 GMT",
"version": "v2"
}
] | 2010-05-12 | [
[
"Pürrer",
"Michael",
""
],
[
"Husa",
"Sascha",
""
],
[
"Aichelburg",
"Peter C.",
""
]
] | We discuss critical gravitational collapse on the threshold of apparent horizon formation as a model both for the discussion of global aspects of critical collapse and for numerical studies in a compactified context. For our matter model we choose a self-gravitating massless scalar field in spherical symmetry, which has been studied extensively in the critical collapse literature. Our evolution system is based on Bondi coordinates, the mass function is used as an evolution variable to ensure regularity at null infinity. We compute radiation quantities like the Bondi mass and news function and find that they reflect the DSS behavior. Surprisingly, the period of radiation at null infinity is related to the formal result for the leading quasi-normal mode of a black hole with rapidly decreasing mass. Furthermore, our investigations shed some light on global versus local issues in critical collapse, and the validity and usefulness of the concept of null infinity when predicting detector signals. |
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