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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1602.04559
|
Sandipan Sengupta
|
Romesh K. Kaul and Sandipan Sengupta
|
Degenerate spacetimes in first order gravity
|
Identical with the journal version
|
Phys. Rev. D 93, 084026 (2016)
|
10.1103/PhysRevD.93.084026
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present a systematic framework to obtain the most general solutions of the
equations of motion in first order gravity theory with degenerate tetrads.
There are many possible solutions. Generically, these exhibit non-vanishing
torsion even in the absence of any matter coupling. These solutions are shown
to contain a special set of eight configurations which are associated with the
homogeneous model three-geometries of Thurston.
|
[
{
"created": "Mon, 15 Feb 2016 04:26:37 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Apr 2016 03:07:25 GMT",
"version": "v2"
}
] |
2016-04-26
|
[
[
"Kaul",
"Romesh K.",
""
],
[
"Sengupta",
"Sandipan",
""
]
] |
We present a systematic framework to obtain the most general solutions of the equations of motion in first order gravity theory with degenerate tetrads. There are many possible solutions. Generically, these exhibit non-vanishing torsion even in the absence of any matter coupling. These solutions are shown to contain a special set of eight configurations which are associated with the homogeneous model three-geometries of Thurston.
|
gr-qc/0012110
|
Sascha Husa
|
Sascha Husa, Manuela Campanelli, Roberto Gomez, Jeffrey Winicour and
Yosef Zlochower
|
Colliding black holes from a null point of view: the close limit
|
2 pages, contribution to the 9th Marcel Grossmann meeting (MG9),
Rome, July 2000
| null | null | null |
gr-qc
| null |
We present a characteristic algorithm for computing the perturbations of a
Schwarzschild spacetime by means of solving the Teukolsky equations. Our
methods and results are expected to have direct bearing on the study of binary
black holes presently underway using a fully {\em nonlinear} characteristic
code \cite{Gomez98a}.
|
[
{
"created": "Fri, 29 Dec 2000 17:23:47 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Husa",
"Sascha",
""
],
[
"Campanelli",
"Manuela",
""
],
[
"Gomez",
"Roberto",
""
],
[
"Winicour",
"Jeffrey",
""
],
[
"Zlochower",
"Yosef",
""
]
] |
We present a characteristic algorithm for computing the perturbations of a Schwarzschild spacetime by means of solving the Teukolsky equations. Our methods and results are expected to have direct bearing on the study of binary black holes presently underway using a fully {\em nonlinear} characteristic code \cite{Gomez98a}.
|
gr-qc/0307111
|
Ruth Lazkoz
|
L.P. Chimento and Ruth Lazkoz
|
Constructing Phantom Cosmologies from Standard Scalar Field Universes
|
3 pages, revtex4, new title and minor changes in the main text and
references to match published version
|
Phys.Rev.Lett. 91 (2003) 211301
|
10.1103/PhysRevLett.91.211301
| null |
gr-qc
| null |
We illustrate how form-invariance transformations can be used for
constructing phantom cosmologies from standard scalar field universes. First,
we discuss how to relate two flat Friedmann-Robertson-Walker cosmologies with
different barotropic indexes $\gamma$ and $\bar \gamma$. Then, we consider the
particular case $\bar \gamma=-\gamma$, and we show that if the matter content
is interpreted in terms of self-interacting scalar fields, then the
corresponding transformation provides the link between a standard and a phantom
cosmology. After that, we illustrate the method by considering models with
exponential potentials. Finally, we also show that the mentioned duality
persists even if the typical braneworld modifications to the Friedmann equation
are considered.
|
[
{
"created": "Mon, 28 Jul 2003 14:05:42 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Jan 2004 09:29:36 GMT",
"version": "v2"
}
] |
2009-11-10
|
[
[
"Chimento",
"L. P.",
""
],
[
"Lazkoz",
"Ruth",
""
]
] |
We illustrate how form-invariance transformations can be used for constructing phantom cosmologies from standard scalar field universes. First, we discuss how to relate two flat Friedmann-Robertson-Walker cosmologies with different barotropic indexes $\gamma$ and $\bar \gamma$. Then, we consider the particular case $\bar \gamma=-\gamma$, and we show that if the matter content is interpreted in terms of self-interacting scalar fields, then the corresponding transformation provides the link between a standard and a phantom cosmology. After that, we illustrate the method by considering models with exponential potentials. Finally, we also show that the mentioned duality persists even if the typical braneworld modifications to the Friedmann equation are considered.
|
1603.03521
|
Wei Li
|
Jie An and Baorong Chang and Lixin Xu
|
Cosmic Constraints to wCDM Model from Strong Gravitational Lensing
|
6 pages, 2 figures
| null |
10.1088/0256-307X/33/7/079801
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we study the cosmic constraint to $w$CDM model via $118$
strong gravitational lensing systems which are complied from SLACS, BELLS, LSD
and SL2S surveys, where the ratio between two angular diameter distances
$D^{obs} = D_A(z_l,z_s)/D_A(0,z_s)$ is taken as a cosmic observable. To obtain
this ratio, we adopt two strong lensing models: one is the singular isothermal
sphere model (SIS), the other one is the power-law density profile (PLP) model.
Via the Markov Chain Mote Carlo method, the posterior distribution of the
cosmological model parameters space is obtained. The results show that the
cosmological model parameters are not sensitive to the parameterized forms of
the power-law index $\gamma$. Furthermore, the PLP model gives a relative
tighter constraint to the cosmological parameters than that of the SIS model.
The predicted value of $\Omega_m=0.31^{+0.44}_{-0.24}$ by SIS model is
compatible with that obtained by {\it Planck}2015: $\Omega_{m}=0.313\pm0.013$.
However, the value of $\Omega_m=0.15^{+0.13}_{-0.11}$ based on the PLP model is
smaller and has $1.25\sigma$ tension with that obtained by {\it Planck}2015
result. This discrepancy maybe come from the systematic errors.
|
[
{
"created": "Fri, 11 Mar 2016 05:05:50 GMT",
"version": "v1"
}
] |
2017-03-15
|
[
[
"An",
"Jie",
""
],
[
"Chang",
"Baorong",
""
],
[
"Xu",
"Lixin",
""
]
] |
In this paper, we study the cosmic constraint to $w$CDM model via $118$ strong gravitational lensing systems which are complied from SLACS, BELLS, LSD and SL2S surveys, where the ratio between two angular diameter distances $D^{obs} = D_A(z_l,z_s)/D_A(0,z_s)$ is taken as a cosmic observable. To obtain this ratio, we adopt two strong lensing models: one is the singular isothermal sphere model (SIS), the other one is the power-law density profile (PLP) model. Via the Markov Chain Mote Carlo method, the posterior distribution of the cosmological model parameters space is obtained. The results show that the cosmological model parameters are not sensitive to the parameterized forms of the power-law index $\gamma$. Furthermore, the PLP model gives a relative tighter constraint to the cosmological parameters than that of the SIS model. The predicted value of $\Omega_m=0.31^{+0.44}_{-0.24}$ by SIS model is compatible with that obtained by {\it Planck}2015: $\Omega_{m}=0.313\pm0.013$. However, the value of $\Omega_m=0.15^{+0.13}_{-0.11}$ based on the PLP model is smaller and has $1.25\sigma$ tension with that obtained by {\it Planck}2015 result. This discrepancy maybe come from the systematic errors.
|
gr-qc/9401030
|
Milan Mijic
|
Milan Mijic
|
Stochastic Dynamics of Coarse-Grained Quantum Fields in Inflationary
Universe
|
23 pages, Very Plain TeX
|
Phys.Rev. D49 (1994) 6434-6441
|
10.1103/PhysRevD.49.6434
| null |
gr-qc
| null |
It is shown how coarse-graining of quantum field ^M theory in de Sitter space
leads to the emergence of a classical ^M stochastic description as an effective
theory in the infra-red regime. ^M The quantum state of the coarse-grained
scalar field is found to be a highly^M squeezed coherent state, whose center
performs a random walk on a^M bundle of classical trajectories.^M
|
[
{
"created": "Wed, 26 Jan 1994 03:47:18 GMT",
"version": "v1"
}
] |
2009-10-22
|
[
[
"Mijic",
"Milan",
""
]
] |
It is shown how coarse-graining of quantum field ^M theory in de Sitter space leads to the emergence of a classical ^M stochastic description as an effective theory in the infra-red regime. ^M The quantum state of the coarse-grained scalar field is found to be a highly^M squeezed coherent state, whose center performs a random walk on a^M bundle of classical trajectories.^M
|
2102.09578
|
Parampreet Singh
|
Meysam Motaharfar, Parampreet Singh
|
On the role of dissipative effects in the quantum gravitational onset of
warm Starobinsky inflation in a closed universe
|
19 pages, 12 figures. Discussion revised. References added. To appear
in Phys. Rev. D
| null |
10.1103/PhysRevD.104.106006
| null |
gr-qc astro-ph.CO
|
http://creativecommons.org/licenses/by/4.0/
|
A problematic feature of low energy scale inflationary models, such as
Starobinsky inflation, in a spatially closed universe is the occurrence of a
recollapse and a big crunch singularity before inflation can even set in. In a
recent work it was shown that this problem can be successfully resolved in loop
quantum cosmology for a large class of initial conditions due to a non-singular
cyclic evolution and a hysteresis-like phenomena. However, for certain highly
unfavorable initial conditions the onset of inflation was still difficult to
obtain. In this work, we explore the role of dissipative particle production,
which is typical in warm inflation scenario, in the above setting. We find that
entropy production sourced by such dissipative effects makes hysteresis-like
phenomena stronger. As a result, the onset of inflation is quick in general
including for highly unfavorable initial conditions where it fails or is
significantly delayed in the absence of dissipative effects. We
phenomenologically consider three warm inflation scenarios with distinct forms
of dissipation coefficient, and from dynamical solutions and phase space
portraits find that the phase space of favorable initial conditions turns out
to be much larger than in cold inflation.
|
[
{
"created": "Thu, 18 Feb 2021 19:00:29 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Oct 2021 23:18:10 GMT",
"version": "v2"
}
] |
2021-11-24
|
[
[
"Motaharfar",
"Meysam",
""
],
[
"Singh",
"Parampreet",
""
]
] |
A problematic feature of low energy scale inflationary models, such as Starobinsky inflation, in a spatially closed universe is the occurrence of a recollapse and a big crunch singularity before inflation can even set in. In a recent work it was shown that this problem can be successfully resolved in loop quantum cosmology for a large class of initial conditions due to a non-singular cyclic evolution and a hysteresis-like phenomena. However, for certain highly unfavorable initial conditions the onset of inflation was still difficult to obtain. In this work, we explore the role of dissipative particle production, which is typical in warm inflation scenario, in the above setting. We find that entropy production sourced by such dissipative effects makes hysteresis-like phenomena stronger. As a result, the onset of inflation is quick in general including for highly unfavorable initial conditions where it fails or is significantly delayed in the absence of dissipative effects. We phenomenologically consider three warm inflation scenarios with distinct forms of dissipation coefficient, and from dynamical solutions and phase space portraits find that the phase space of favorable initial conditions turns out to be much larger than in cold inflation.
|
gr-qc/0007013
|
Hod Shahar
|
Shahar Hod
|
Black-hole radiation, the fundamental area unit, and the spectrum of
particle species
|
4 pages
|
Phys.Rev. D61 (2000) 124016
|
10.1103/PhysRevD.61.124016
| null |
gr-qc hep-th quant-ph
| null |
Bekenstein and Mukhanov have put forward the idea that, in a quantum theory
of gravity a black hole should have a discrete mass spectrum with a concomitant
{\it discrete} line emission. We note that a direct consequence of this
intriguing prediction is that, compared with blackbody radiation, black-hole
radiance is {\it less} entropic. We calculate the ratio of entropy emission
rate from a quantum black hole to the rate of black-hole entropy decrease, a
quantity which, according to the generalized second law (GSL) of
thermodynamics, should be larger than unity. Implications of our results for
the GSL, for the value of the fundamental area unit in quantum gravity, and for
the spectrum of massless particles in nature are discussed.
|
[
{
"created": "Mon, 10 Jul 2000 07:51:23 GMT",
"version": "v1"
}
] |
2009-10-31
|
[
[
"Hod",
"Shahar",
""
]
] |
Bekenstein and Mukhanov have put forward the idea that, in a quantum theory of gravity a black hole should have a discrete mass spectrum with a concomitant {\it discrete} line emission. We note that a direct consequence of this intriguing prediction is that, compared with blackbody radiation, black-hole radiance is {\it less} entropic. We calculate the ratio of entropy emission rate from a quantum black hole to the rate of black-hole entropy decrease, a quantity which, according to the generalized second law (GSL) of thermodynamics, should be larger than unity. Implications of our results for the GSL, for the value of the fundamental area unit in quantum gravity, and for the spectrum of massless particles in nature are discussed.
|
1506.08512
|
B. S. Ratanpal
|
B. S. Ratanpal, V. O. Thomas and D. M. Pandya
|
Anisotropic Star on Pseudo-Spheroidal Spacetime
|
19 pages, 8 figures, 1 table
|
Astrophys Space Sci (2016) 361:65
|
10.1007/s10509-016-2652-0
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A new class of exact solutions of Einstein's field equations representing
anisotropic distribution of matter on pseudo-spheroidal spacetime is obtained.
The parameters appearing in the model are restricted through physical
requirements of the model. It is found that the models given in the present
work is compatible with observational data of a wide variety of compact objects
like 4U 1820-30, PSR J1903+327, 4U 1608-52, Vela X-1, PSR J1614-2230, SMC X-4,
Cen X-3. A particular model of pulsar PSR J1614-2230 is studied in detail and
found that it satisfies all physical requirements needed for physically
acceptable model.
|
[
{
"created": "Mon, 29 Jun 2015 05:40:37 GMT",
"version": "v1"
}
] |
2016-04-06
|
[
[
"Ratanpal",
"B. S.",
""
],
[
"Thomas",
"V. O.",
""
],
[
"Pandya",
"D. M.",
""
]
] |
A new class of exact solutions of Einstein's field equations representing anisotropic distribution of matter on pseudo-spheroidal spacetime is obtained. The parameters appearing in the model are restricted through physical requirements of the model. It is found that the models given in the present work is compatible with observational data of a wide variety of compact objects like 4U 1820-30, PSR J1903+327, 4U 1608-52, Vela X-1, PSR J1614-2230, SMC X-4, Cen X-3. A particular model of pulsar PSR J1614-2230 is studied in detail and found that it satisfies all physical requirements needed for physically acceptable model.
|
0803.3456
|
Steven Carlip
|
S. Carlip
|
Is Quantum Gravity Necessary?
|
based on a talk given at Peyresq Physics 11, to appear in Class.
Quant. Grav
|
Class.Quant.Grav.25:154010,2008
|
10.1088/0264-9381/25/15/154010
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In view of the enormous difficulties we seem to face in quantizing general
relativity, we should perhaps consider the possibility that gravity is a
fundamentally classical interaction. Theoretical arguments against such mixed
classical-quantum models are strong, but not conclusive, and the question is
ultimately one for experiment. I review some work in progress on the
possibility of experimental tests, exploiting the nonlinearity of the
classical-quantum coupling, that could help settle this question.
|
[
{
"created": "Mon, 24 Mar 2008 20:13:49 GMT",
"version": "v1"
}
] |
2010-04-28
|
[
[
"Carlip",
"S.",
""
]
] |
In view of the enormous difficulties we seem to face in quantizing general relativity, we should perhaps consider the possibility that gravity is a fundamentally classical interaction. Theoretical arguments against such mixed classical-quantum models are strong, but not conclusive, and the question is ultimately one for experiment. I review some work in progress on the possibility of experimental tests, exploiting the nonlinearity of the classical-quantum coupling, that could help settle this question.
|
gr-qc/9809070
|
Jonathan Katz
|
J. I. Katz (Washington U., St. Louis)
|
Comment on ``Indication, from Pioneer 10/11, Galileo and Ulysses Data,
of an Apparent Anomalous, Weak, Long-Range Acceleration''
|
4pp, Revtex, recoil force now calculated numerically from Pioneer
engineering data, conclusions unchanged
|
Phys.Rev.Lett. 83 (1999) 1892
|
10.1103/PhysRevLett.83.1892
| null |
gr-qc astro-ph
| null |
The reported anomalous acceleration may be explained as the recoil of
radiated waste RTG heat scattered by the back of the high gain antenna.
|
[
{
"created": "Thu, 24 Sep 1998 15:16:26 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Oct 1998 21:00:29 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Dec 1998 21:00:30 GMT",
"version": "v3"
}
] |
2009-10-31
|
[
[
"Katz",
"J. I.",
"",
"Washington U., St. Louis"
]
] |
The reported anomalous acceleration may be explained as the recoil of radiated waste RTG heat scattered by the back of the high gain antenna.
|
gr-qc/0601032
|
Philip D. Mannheim
|
Philip D. Mannheim (University of Connecticut)
|
Gauge Invariant Treatment of the Energy Carried by a Gravitational Wave
|
13 pages, revtex4. Final version. To appear in Phys. Rev. D
|
Phys.Rev. D74 (2006) 024019
|
10.1103/PhysRevD.74.024019
| null |
gr-qc astro-ph hep-th
| null |
Even though the energy carried by a gravitational wave is not itself gauge
invariant, the interaction with a gravitational antenna of the gravitational
wave which carries that energy is. It therefore has to be possible to make some
statements which involve the energy which are in fact gauge invariant, and it
is the objective of this paper to provide them. In order to develop a gauge
invariant treatment of the issues involved, we construct a specific action for
gravitational fluctuations which is gauge invariant to second perturbative
order. Then, via variation of this action, we obtain an energy-momentum tensor
for perturbative gravitational fluctuations around a general curved background
whose covariant conservation condition is also fully gauge invariant to second
order. Contraction of this energy-momentum tensor with a Killing vector of the
background conveniently allows us to convert this covariant conservation
condition into an ordinary conservation condition which is also gauge invariant
through second order. Then, via spatial integration we are able to obtain a
relation involving the time derivative of the total energy of the fluctuation
and its asymptotic spatial momentum flux which is also completely gauge
invariant through second order. It is only in making the simplification of
setting the asymptotic momentum flux to zero that one would actually lose
manifest gauge invariance, with only invariance under those particular gauge
transformations which leave the asymptotic momentum flux zero then remaining.
However, if one works in an arbitrary gauge where the asymptotic momentum flux
is non-zero, the gravitational wave will then deliver both energy and momentum
to a gravitational antenna in a completely gauge invariant manner, no matter
how badly behaved at infinity the gauge function might be.
|
[
{
"created": "Mon, 9 Jan 2006 16:20:14 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Jan 2006 13:09:03 GMT",
"version": "v2"
},
{
"created": "Thu, 29 Jun 2006 18:57:25 GMT",
"version": "v3"
}
] |
2009-11-11
|
[
[
"Mannheim",
"Philip D.",
"",
"University of Connecticut"
]
] |
Even though the energy carried by a gravitational wave is not itself gauge invariant, the interaction with a gravitational antenna of the gravitational wave which carries that energy is. It therefore has to be possible to make some statements which involve the energy which are in fact gauge invariant, and it is the objective of this paper to provide them. In order to develop a gauge invariant treatment of the issues involved, we construct a specific action for gravitational fluctuations which is gauge invariant to second perturbative order. Then, via variation of this action, we obtain an energy-momentum tensor for perturbative gravitational fluctuations around a general curved background whose covariant conservation condition is also fully gauge invariant to second order. Contraction of this energy-momentum tensor with a Killing vector of the background conveniently allows us to convert this covariant conservation condition into an ordinary conservation condition which is also gauge invariant through second order. Then, via spatial integration we are able to obtain a relation involving the time derivative of the total energy of the fluctuation and its asymptotic spatial momentum flux which is also completely gauge invariant through second order. It is only in making the simplification of setting the asymptotic momentum flux to zero that one would actually lose manifest gauge invariance, with only invariance under those particular gauge transformations which leave the asymptotic momentum flux zero then remaining. However, if one works in an arbitrary gauge where the asymptotic momentum flux is non-zero, the gravitational wave will then deliver both energy and momentum to a gravitational antenna in a completely gauge invariant manner, no matter how badly behaved at infinity the gauge function might be.
|
gr-qc/0211084
|
Joan Centrella
|
Joan M. Centrella
|
Resource Letter GrW-1: Gravitational Waves
|
AAPT/AJP Resource Letter, American Journal of Physics, in press, 9
pages, 97 references
|
Am.J.Phys. 71 (2003) 520-525
|
10.1119/1.1543555
| null |
gr-qc astro-ph
| null |
This Resource Letter provides a guide to the literature on the physics and
astrophysics of gravitational waves. Journals, books, reports, archives, and
websites are provided as basic resources and for current research frontiers in
detectors, data analysis, and astrophysical source modeling.
|
[
{
"created": "Mon, 25 Nov 2002 21:21:17 GMT",
"version": "v1"
}
] |
2009-11-07
|
[
[
"Centrella",
"Joan M.",
""
]
] |
This Resource Letter provides a guide to the literature on the physics and astrophysics of gravitational waves. Journals, books, reports, archives, and websites are provided as basic resources and for current research frontiers in detectors, data analysis, and astrophysical source modeling.
|
1111.7127
|
Igor Khavkine
|
Igor Khavkine
|
Quantum astrometric observables I: time delay in classical and quantum
gravity
|
revtex4-1, 21 pages, 7 figures (published version); added journal ref
|
Phys. Rev. D 85, 124014 (2012)
|
10.1103/PhysRevD.85.124014
|
ITP-UU-10/02; SPIN-10-02
|
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A class of diffeomorphism invariant, physical observables, so-called
astrometric observables, is introduced. A particularly simple example, the time
delay, which expresses the difference between two initially synchronized proper
time clocks in relative inertial motion, is analyzed in detail. It is found to
satisfy some interesting inequalities related to the causal structure of
classical Lorentzian spacetimes. Thus it can serve as a probe of causal
structure and in particular of violations of causality. A quantum model of this
observable as well as the calculation of its variance due to vacuum
fluctuations in quantum linearized gravity are sketched. The question of
whether the causal inequalities are still satisfied by quantized gravity, which
is pertinent to the nature of causality in quantum gravity, is raised, but it
is shown that perturbative calculations cannot provide a definite answer. Some
potential applications of astrometric observables in quantum gravity are
discussed.
|
[
{
"created": "Wed, 30 Nov 2011 11:21:58 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Jun 2012 14:07:48 GMT",
"version": "v2"
}
] |
2012-06-26
|
[
[
"Khavkine",
"Igor",
""
]
] |
A class of diffeomorphism invariant, physical observables, so-called astrometric observables, is introduced. A particularly simple example, the time delay, which expresses the difference between two initially synchronized proper time clocks in relative inertial motion, is analyzed in detail. It is found to satisfy some interesting inequalities related to the causal structure of classical Lorentzian spacetimes. Thus it can serve as a probe of causal structure and in particular of violations of causality. A quantum model of this observable as well as the calculation of its variance due to vacuum fluctuations in quantum linearized gravity are sketched. The question of whether the causal inequalities are still satisfied by quantized gravity, which is pertinent to the nature of causality in quantum gravity, is raised, but it is shown that perturbative calculations cannot provide a definite answer. Some potential applications of astrometric observables in quantum gravity are discussed.
|
1008.3619
|
Marco Mamone-Capria
|
Marco Mamone-Capria
|
Spatial Directions, Anisotropy and Special Relativity
|
24 pages, 2 figures. Final enlarged and slightly corrected version.
Keywords: relativity, very special relativity, spatial isotropy, reciprocity,
differential aging; Foundations of Physics, 2011
|
Found.Phys.41:1375-1397,2011
|
10.1007/s10701-011-9554-3
| null |
gr-qc math-ph math.DG math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The concept of an objective spatial direction in special relativity is
investigated and theories assuming light-speed isotropy while accepting the
existence of a privileged spatial direction are classified. A natural
generalization of the proper time principle is introduced which makes it
possible to devise experimental tests of spatial isotropy. Several common
misunderstandings in the relativistic literature concerning the role of spatial
isotropy are clarified.
|
[
{
"created": "Sat, 21 Aug 2010 09:40:25 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Feb 2011 18:04:57 GMT",
"version": "v2"
},
{
"created": "Tue, 22 Feb 2011 17:58:22 GMT",
"version": "v3"
},
{
"created": "Fri, 20 May 2011 09:36:05 GMT",
"version": "v4"
}
] |
2011-06-30
|
[
[
"Mamone-Capria",
"Marco",
""
]
] |
The concept of an objective spatial direction in special relativity is investigated and theories assuming light-speed isotropy while accepting the existence of a privileged spatial direction are classified. A natural generalization of the proper time principle is introduced which makes it possible to devise experimental tests of spatial isotropy. Several common misunderstandings in the relativistic literature concerning the role of spatial isotropy are clarified.
|
2206.02783
|
Bivudutta Mishra Dr.
|
A.S. Agrawal, B. Mishra, P.K. Agrawal
|
Matter Bounce Scenario in Extended Symmetric Teleparallel Gravity
|
10 pages, 6 figures
|
Eur. Phys. J. C (2023) 83:113
|
10.1140/epjc/s10052-023-11266-8
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we have shown the matter bounce scenario of the Universe in an
extended symmetric teleparallel gravity, the f(Q) gravity. Motivated from the
bouncing scenario and loop quantum cosmology (LQC), the form of the function
$f(Q)$ has been obtained at the backdrop of Friedmann-Lemaitre-Robertson Walker
(FLRW) space time. Considering the background cosmology dominated by dust
fluid, the e-folding parameter has been expressed, which contains the
nonmetricity term. Since the slow roll criterion in the bouncing context is not
valid, we used a conformal equivalence between f(Q) and scalar-tensor model to
apply the bottom-up reconstruction technique in the bouncing model. The
dynamics of the model has been studied through the phase space analysis, where
both the stable and unstable nodes are obtained. Also, the stability analysis
has been performed with the first order scalar perturbation of the Hubble
parameter and matter energy density to verify the stability of the model.
|
[
{
"created": "Sat, 4 Jun 2022 05:59:37 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Feb 2023 06:08:02 GMT",
"version": "v2"
}
] |
2023-02-06
|
[
[
"Agrawal",
"A. S.",
""
],
[
"Mishra",
"B.",
""
],
[
"Agrawal",
"P. K.",
""
]
] |
In this paper, we have shown the matter bounce scenario of the Universe in an extended symmetric teleparallel gravity, the f(Q) gravity. Motivated from the bouncing scenario and loop quantum cosmology (LQC), the form of the function $f(Q)$ has been obtained at the backdrop of Friedmann-Lemaitre-Robertson Walker (FLRW) space time. Considering the background cosmology dominated by dust fluid, the e-folding parameter has been expressed, which contains the nonmetricity term. Since the slow roll criterion in the bouncing context is not valid, we used a conformal equivalence between f(Q) and scalar-tensor model to apply the bottom-up reconstruction technique in the bouncing model. The dynamics of the model has been studied through the phase space analysis, where both the stable and unstable nodes are obtained. Also, the stability analysis has been performed with the first order scalar perturbation of the Hubble parameter and matter energy density to verify the stability of the model.
|
2203.14696
|
Branislav Cvetkovi\'c
|
Milutin Blagojevi\'c and Branislav Cvetkovi\'c
|
Entropy of Kerr--Newman--AdS black holes with torsion
|
LaTex, 17 pages
| null |
10.1103/PhysRevD.105.104014
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The canonical approach to black hole entropy in Poincar\'e gauge theory
without matter is extended to include Maxwell field as a matter source. The new
formalism is used to calculate asymptotic charges and entropy of
Kerr--Newmann--AdS black holes with torsion. The result implies that the first
law, with a nontrivial contribution of the Maxwell field, takes the same form
as in general relativity.
|
[
{
"created": "Thu, 24 Mar 2022 21:18:25 GMT",
"version": "v1"
}
] |
2022-05-25
|
[
[
"Blagojević",
"Milutin",
""
],
[
"Cvetković",
"Branislav",
""
]
] |
The canonical approach to black hole entropy in Poincar\'e gauge theory without matter is extended to include Maxwell field as a matter source. The new formalism is used to calculate asymptotic charges and entropy of Kerr--Newmann--AdS black holes with torsion. The result implies that the first law, with a nontrivial contribution of the Maxwell field, takes the same form as in general relativity.
|
2311.02118
|
Claudio Nassif Cruz
|
Cl\'audio Nassif Cruz and A. C. Amaro de Faria Jr
|
A brief review of a modified relativity that explains cosmological
constant
|
15 pages, 2 figures. arXiv admin note: substantial text overlap with
arXiv:2303.14120
|
Reviews in Physics 11 (2023) 100088
|
10.1016/j.revip.2023.100088
| null |
gr-qc
|
http://creativecommons.org/publicdomain/zero/1.0/
|
The present review aims to show that a modified space-time with an invariant
minimum speed provides a relation with Weyl geometry in the Newtonian
approximation of weak-field. The deformed Special Relativity so-called
Symmetrical Special Relativity (SSR) has an invariant minimum speed $V$, which
is associated with a preferred reference frame $S_V$ for representing the
vacuum energy, thus leading to the cosmological constant ($\Lambda$). The
equation of state (EOS) of vacuum energy for $\Lambda$, i.e.,
$\rho_{\Lambda}=\epsilon=-p$ emerges naturally from such space-time, where $p$
is the pressure and $\rho_{\Lambda}=\epsilon$ is the vacuum energy density.
With the aim of establishing a relationship between $V$ and $\Lambda$ in the
modified metric of the space-time, we should consider a dark spherical universe
with Hubble radius $R_H$, having a very low value of $\epsilon$ that governs
the accelerated expansion of universe. In doing this, we aim to show that
SSR-metric has an equivalence with a de-Sitter (dS)-metric ($\Lambda>0$). On
the other hand, according to the Boomerang experiment that reveals a slightly
accelerated expansion of the universe, SSR leads to a dS-metric with an
approximation for $\Lambda<<1$ close to a flat space-time, which is in the
$\Lambda CDM$ scenario where the space is quasi-flat, so that
$\Omega_{m}+\Omega_{\Lambda}\approx 1$. We have $\Omega{cdm}\approx 23\%$ by
representing dark cold matter, $\Omega_m\approx 27\%$ for matter and
$\Omega_{\Lambda}\approx 73\%$ for the vacuum energy. Thus, the theory is
adjusted for the redshift $z=1$. This corresponds to the time $\tau_0$ of
transition between gravity and anti-gravity, leading to a slight acceleration
of expansion related to a tiny value of $\Lambda$, i.e., we find
$\Lambda_0=1.934\times 10^{-35}s^{-2}$. This result is in agreement with
observations.
|
[
{
"created": "Fri, 3 Nov 2023 03:37:15 GMT",
"version": "v1"
}
] |
2023-11-07
|
[
[
"Cruz",
"Cláudio Nassif",
""
],
[
"Faria",
"A. C. Amaro de",
"Jr"
]
] |
The present review aims to show that a modified space-time with an invariant minimum speed provides a relation with Weyl geometry in the Newtonian approximation of weak-field. The deformed Special Relativity so-called Symmetrical Special Relativity (SSR) has an invariant minimum speed $V$, which is associated with a preferred reference frame $S_V$ for representing the vacuum energy, thus leading to the cosmological constant ($\Lambda$). The equation of state (EOS) of vacuum energy for $\Lambda$, i.e., $\rho_{\Lambda}=\epsilon=-p$ emerges naturally from such space-time, where $p$ is the pressure and $\rho_{\Lambda}=\epsilon$ is the vacuum energy density. With the aim of establishing a relationship between $V$ and $\Lambda$ in the modified metric of the space-time, we should consider a dark spherical universe with Hubble radius $R_H$, having a very low value of $\epsilon$ that governs the accelerated expansion of universe. In doing this, we aim to show that SSR-metric has an equivalence with a de-Sitter (dS)-metric ($\Lambda>0$). On the other hand, according to the Boomerang experiment that reveals a slightly accelerated expansion of the universe, SSR leads to a dS-metric with an approximation for $\Lambda<<1$ close to a flat space-time, which is in the $\Lambda CDM$ scenario where the space is quasi-flat, so that $\Omega_{m}+\Omega_{\Lambda}\approx 1$. We have $\Omega{cdm}\approx 23\%$ by representing dark cold matter, $\Omega_m\approx 27\%$ for matter and $\Omega_{\Lambda}\approx 73\%$ for the vacuum energy. Thus, the theory is adjusted for the redshift $z=1$. This corresponds to the time $\tau_0$ of transition between gravity and anti-gravity, leading to a slight acceleration of expansion related to a tiny value of $\Lambda$, i.e., we find $\Lambda_0=1.934\times 10^{-35}s^{-2}$. This result is in agreement with observations.
|
1311.6087
|
Alan Parry
|
Alan R. Parry
|
Wave Dark Matter and Dwarf Spheroidal Galaxies
|
This is a posting of my PhD thesis. 143 pages, 27 figures, 3 tables.
Alan R. Parry, "Wave Dark Matter and Dwarf Spheroidal Galaxies", PhD Thesis,
Duke University, Durham, NC (March 2013)
| null | null | null |
gr-qc math.DG
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We explore a model of dark matter called wave dark matter (also known as
scalar field dark matter and boson stars) which has recently been motivated by
a new geometric perspective by Bray. Wave dark matter describes dark matter as
a scalar field which satisfies the Einstein-Klein-Gordon equations. These
equations rely on a fundamental constant $\Upsilon$ (also known as the "mass
term" of the Klein-Gordon equation). Specifically, in this dissertation, we
study spherically symmetric wave dark matter and compare these results with
observations of dwarf spheroidal galaxies as a first attempt to compare the
implications of the theory of wave dark matter with actual observations of dark
matter. This includes finding a first estimate of the fundamental constant
$\Upsilon$. The majority of this thesis has also been presented by the author
in three separate shorter papers with arXiv reference codes [arXiv:1210.5269
[gr-qc]], [arXiv:1212.6426 [gr-qc]], [arXiv:1301.0255 [astro-ph.GA]]; note that
[arXiv:1301.0255 [astro-ph.GA]], and hence part of Chapter 4, represents joint
work with Hubert Bray.
|
[
{
"created": "Sun, 24 Nov 2013 06:46:31 GMT",
"version": "v1"
}
] |
2013-11-26
|
[
[
"Parry",
"Alan R.",
""
]
] |
We explore a model of dark matter called wave dark matter (also known as scalar field dark matter and boson stars) which has recently been motivated by a new geometric perspective by Bray. Wave dark matter describes dark matter as a scalar field which satisfies the Einstein-Klein-Gordon equations. These equations rely on a fundamental constant $\Upsilon$ (also known as the "mass term" of the Klein-Gordon equation). Specifically, in this dissertation, we study spherically symmetric wave dark matter and compare these results with observations of dwarf spheroidal galaxies as a first attempt to compare the implications of the theory of wave dark matter with actual observations of dark matter. This includes finding a first estimate of the fundamental constant $\Upsilon$. The majority of this thesis has also been presented by the author in three separate shorter papers with arXiv reference codes [arXiv:1210.5269 [gr-qc]], [arXiv:1212.6426 [gr-qc]], [arXiv:1301.0255 [astro-ph.GA]]; note that [arXiv:1301.0255 [astro-ph.GA]], and hence part of Chapter 4, represents joint work with Hubert Bray.
|
1402.5935
|
Emmanuil Saridakis
|
A. Paliathanasis (Athens U.), S. Basilakos (RCAAM, Academy of Athens),
E.N. Saridakis (Natl. Tech. U., Athens and Valparaiso U., Catolica), S.
Capozziello (Naples U. and INFN, Naples), K. Atazadeh, F. Darabi (Azarbaijan
U. of Tarbiat Moallem), M. Tsamparlis (Athens U.)
|
New Schwarzschild-like solutions in f(T) gravity through Noether
symmetries
|
10 pages, to appear in Phys. Rev. D
|
Phys. Rev. D 89, 104042 (2014)
|
10.1103/PhysRevD.89.104042
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Spherically symmetric solutions for f(T) gravity models are derived by the so
called Noether Symmetry Approach. First, we present a full set of Noether
symmetries for some minisuperspace models. Then, we compute analytical
solutions and find that spherically symmetric solutions in f(T) gravity can be
recast in terms of Schwarzschild-like solutions modified by a distortion
function depending on a characteristic radius. The obtained solutions are more
general than those obtained by the usual solution methods.
|
[
{
"created": "Mon, 24 Feb 2014 20:17:47 GMT",
"version": "v1"
},
{
"created": "Sun, 11 May 2014 08:01:14 GMT",
"version": "v2"
}
] |
2014-05-28
|
[
[
"Paliathanasis",
"A.",
"",
"Athens U."
],
[
"Basilakos",
"S.",
"",
"RCAAM, Academy of Athens"
],
[
"Saridakis",
"E. N.",
"",
"Natl. Tech. U., Athens and Valparaiso U., Catolica"
],
[
"Capozziello",
"S.",
"",
"Naples U. and INFN, Naples"
],
[
"Atazadeh",
"K.",
"",
"Azarbaijan\n U. of Tarbiat Moallem"
],
[
"Darabi",
"F.",
"",
"Azarbaijan\n U. of Tarbiat Moallem"
],
[
"Tsamparlis",
"M.",
"",
"Athens U."
]
] |
Spherically symmetric solutions for f(T) gravity models are derived by the so called Noether Symmetry Approach. First, we present a full set of Noether symmetries for some minisuperspace models. Then, we compute analytical solutions and find that spherically symmetric solutions in f(T) gravity can be recast in terms of Schwarzschild-like solutions modified by a distortion function depending on a characteristic radius. The obtained solutions are more general than those obtained by the usual solution methods.
|
2004.12074
|
Xiao-Xiong Zeng
|
Xiao-Xiong Zeng, Hai-Qing Zhang, Hongbao Zhang
|
Shadows and photon spheres with spherical accretions in the
four-dimensional Gauss-Bonnet black hole
|
published version
|
Eur. Phys. J. C (2020) 80:872
|
10.1140/epjc/s10052-020-08449-y
| null |
gr-qc hep-th
|
http://creativecommons.org/publicdomain/zero/1.0/
|
We investigate the shadows and photon spheres of the four-dimensional
Gauss-Bonnet black hole with the static and infalling spherical accretions. We
show that for both cases, the shadow and photon sphere are always present. The
radii of the shadow and photon sphere are independent of the profiles of
accretion for a fixed Gauss-Bonnet constant, implying that the shadow is a
signature of the spacetime geometry and it is hardly influenced by accretion in
this case. Because of the Doppler effect, the shadow of the infalling accretion
is found to be darker than that of the static one. We also investigate the
effect of the Gauss-Bonnet constant on the shadow and photon sphere, and find
that the larger the Gauss-Bonnet constant is, the smaller the radii of the
shadow and photon sphere will be. In particular, the observed specific
intensity increases with the increasing of the Gauss-Bonnet constant.
|
[
{
"created": "Sat, 25 Apr 2020 07:45:05 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Apr 2020 07:51:27 GMT",
"version": "v2"
},
{
"created": "Mon, 13 Jul 2020 12:13:21 GMT",
"version": "v3"
},
{
"created": "Sat, 26 Sep 2020 11:06:19 GMT",
"version": "v4"
}
] |
2020-10-28
|
[
[
"Zeng",
"Xiao-Xiong",
""
],
[
"Zhang",
"Hai-Qing",
""
],
[
"Zhang",
"Hongbao",
""
]
] |
We investigate the shadows and photon spheres of the four-dimensional Gauss-Bonnet black hole with the static and infalling spherical accretions. We show that for both cases, the shadow and photon sphere are always present. The radii of the shadow and photon sphere are independent of the profiles of accretion for a fixed Gauss-Bonnet constant, implying that the shadow is a signature of the spacetime geometry and it is hardly influenced by accretion in this case. Because of the Doppler effect, the shadow of the infalling accretion is found to be darker than that of the static one. We also investigate the effect of the Gauss-Bonnet constant on the shadow and photon sphere, and find that the larger the Gauss-Bonnet constant is, the smaller the radii of the shadow and photon sphere will be. In particular, the observed specific intensity increases with the increasing of the Gauss-Bonnet constant.
|
0808.0404
|
Sushil Srivastava
|
S.K.Srivastava
|
Varying Gravitational Constant as Well as Cosmology from the Early
Inflation to Late Acceleration and Future Universe
|
31pages
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Here, cosmology is obtained from the variable gravitational constant $ G
\propto \phi^{-2}$ with $ \phi(x) $ being a scalar and its fluctuations around
the ground state. The gravitational action contains Einstein-Hilbert like term
with variable $ G $, kinetic energy and self-interaction potential for $
\phi(x) $. Two phase transitions take place in this model. The first one takes
place at the GUT (grand unified theory) scale $ \sim 2.45 \times 10^{14}{\rm
GeV} $, when the early universe exits the inflationay phase and the second one
at the electro-weak scale. Spontaneous symmetry breaking takes place around
this scale As a consequence, variable $ G $ acquires constant value $G_N$ (the
Newtonian gravitational constant).The standard model of cosmology is obtained
in the post-second phase transition era. Interestingly, the dark matter and
quintessence dark energy are created from the gravitational sector as a
combined effect of the linear term of scalar curvature and $ \phi(x) $ without
using non-linear terms of curvature or any other matter fields. It is
interesting to find that fluctuations in $ \phi(x) $ cause the phantom dark
energy after the second phase transition, which grows later in the expanding
universe. It is also found that the phantom era is free from big-rip
singularity.
|
[
{
"created": "Mon, 4 Aug 2008 09:28:14 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Sep 2008 01:03:29 GMT",
"version": "v2"
}
] |
2008-09-19
|
[
[
"Srivastava",
"S. K.",
""
]
] |
Here, cosmology is obtained from the variable gravitational constant $ G \propto \phi^{-2}$ with $ \phi(x) $ being a scalar and its fluctuations around the ground state. The gravitational action contains Einstein-Hilbert like term with variable $ G $, kinetic energy and self-interaction potential for $ \phi(x) $. Two phase transitions take place in this model. The first one takes place at the GUT (grand unified theory) scale $ \sim 2.45 \times 10^{14}{\rm GeV} $, when the early universe exits the inflationay phase and the second one at the electro-weak scale. Spontaneous symmetry breaking takes place around this scale As a consequence, variable $ G $ acquires constant value $G_N$ (the Newtonian gravitational constant).The standard model of cosmology is obtained in the post-second phase transition era. Interestingly, the dark matter and quintessence dark energy are created from the gravitational sector as a combined effect of the linear term of scalar curvature and $ \phi(x) $ without using non-linear terms of curvature or any other matter fields. It is interesting to find that fluctuations in $ \phi(x) $ cause the phantom dark energy after the second phase transition, which grows later in the expanding universe. It is also found that the phantom era is free from big-rip singularity.
|
1911.08316
|
Muhammad Sharif
|
M. Sharif and Arfa Waseem
|
Charged Gravastars with Conformal Motion in f(R,T) Gravity
|
21 pages, 5 figures
|
Astrophys. Space Sci. 364(2019)189
|
10.1007/s10509-019-3680-3
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
This paper studies the effects of charge on a peculiar stellar object,
recognized as gravastar, under the influence of $f(R,T)$ gravity by considering
the conjecture of Mazur and Mottola in general relativity. The gravastar is
also known as an alternative to a black hole and is expressed by three distinct
domains named as (i) the interior domain, (ii) the intermediate shell and (iii)
the exterior domain. We analyze these domains for a specific $f(R,T)$ gravity
model conceding the conformal Killing vectors. In the interior domain, we
assume that pressure is equal to negative energy density which leads to the
existence of repulsive force on the spherical shell. The intermediate shell
consists of ultra-relativistic plasma and pressure which shows a direct
relation with energy density and counterbalances the repulsive force applied by
the interior domain. The exterior vacuum spherical domain is taken to be the de
Sitter spacetime illustrated by the Reissner-Nordstr\"{o}m metric. We conclude
that non-singular solutions of charged gravastar with various physical
properties such as length, energy, entropy and equation of state parameter are
physically consistent.
|
[
{
"created": "Mon, 18 Nov 2019 07:16:58 GMT",
"version": "v1"
}
] |
2019-11-27
|
[
[
"Sharif",
"M.",
""
],
[
"Waseem",
"Arfa",
""
]
] |
This paper studies the effects of charge on a peculiar stellar object, recognized as gravastar, under the influence of $f(R,T)$ gravity by considering the conjecture of Mazur and Mottola in general relativity. The gravastar is also known as an alternative to a black hole and is expressed by three distinct domains named as (i) the interior domain, (ii) the intermediate shell and (iii) the exterior domain. We analyze these domains for a specific $f(R,T)$ gravity model conceding the conformal Killing vectors. In the interior domain, we assume that pressure is equal to negative energy density which leads to the existence of repulsive force on the spherical shell. The intermediate shell consists of ultra-relativistic plasma and pressure which shows a direct relation with energy density and counterbalances the repulsive force applied by the interior domain. The exterior vacuum spherical domain is taken to be the de Sitter spacetime illustrated by the Reissner-Nordstr\"{o}m metric. We conclude that non-singular solutions of charged gravastar with various physical properties such as length, energy, entropy and equation of state parameter are physically consistent.
|
gr-qc/0204072
|
Mariam Bouhmadi-Lopez
|
M. Bouhmadi-Lopez, L. J. Garay and P. F. Gonzalez-Diaz
|
Quantum behavior of FRW radiation-filled universes
|
RevTeX 4, 16 pages, 2 figures
|
Phys.Rev. D66 (2002) 083504
|
10.1103/PhysRevD.66.083504
| null |
gr-qc
| null |
We study the quantum vacuum fluctuations around closed
Friedmann-Robertson-Walker (FRW) radiation-filled universes with nonvanishing
cosmological constant. These vacuum fluctuations are represented by a
conformally coupled massive scalar field and are treated in the lowest order of
perturbation theory. In the semiclassical approximation, the perturbations are
governed by differential equations which, properly linearized, become
generalized Lame equations. The wave function thus obtained must satisfy
appropriate regularity conditions which ensure its finiteness for every field
configuration. We apply these results to asymptotically anti de-Sitter
Euclidean wormhole spacetimes and show that there is no catastrophic particle
creation in the Euclidean region, which would lead to divergences of the wave
function.
|
[
{
"created": "Tue, 23 Apr 2002 09:45:29 GMT",
"version": "v1"
}
] |
2009-11-07
|
[
[
"Bouhmadi-Lopez",
"M.",
""
],
[
"Garay",
"L. J.",
""
],
[
"Gonzalez-Diaz",
"P. F.",
""
]
] |
We study the quantum vacuum fluctuations around closed Friedmann-Robertson-Walker (FRW) radiation-filled universes with nonvanishing cosmological constant. These vacuum fluctuations are represented by a conformally coupled massive scalar field and are treated in the lowest order of perturbation theory. In the semiclassical approximation, the perturbations are governed by differential equations which, properly linearized, become generalized Lame equations. The wave function thus obtained must satisfy appropriate regularity conditions which ensure its finiteness for every field configuration. We apply these results to asymptotically anti de-Sitter Euclidean wormhole spacetimes and show that there is no catastrophic particle creation in the Euclidean region, which would lead to divergences of the wave function.
|
gr-qc/0006105
|
Yee J. Ng
|
Y. Jack Ng (University of North Carolina at Chapel Hill)
|
From computation to black holes and space-time foam
|
A misidentification of computer speeds is corrected. Our results for
black hole computation now agree with those given by S. Lloyd. All other
conclusions remain unchanged
|
Phys.Rev.Lett. 86 (2001) 2946; Erratum-ibid. 88 (2002) 139902
|
10.1103/PhysRevLett.86.2946
| null |
gr-qc astro-ph hep-ph hep-th quant-ph
| null |
We show that quantum mechanics and general relativity limit the speed
$\tilde{\nu}$ of a simple computer (such as a black hole) and its memory space
$I$ to $\tilde{\nu}^2 I^{-1} \lsim t_P^{-2}$, where $t_P$ is the Planck time.
We also show that the life-time of a simple clock and its precision are
similarly limited. These bounds and the holographic bound originate from the
same physics that governs the quantum fluctuations of space-time. We further
show that these physical bounds are realized for black holes, yielding the
correct Hawking black hole lifetime, and that space-time undergoes much larger
quantum fluctuations than conventional wisdom claims -- almost within range of
detection with modern gravitational-wave interferometers.
|
[
{
"created": "Thu, 29 Jun 2000 16:40:42 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Jul 2000 22:01:16 GMT",
"version": "v2"
},
{
"created": "Sun, 15 Oct 2000 19:11:42 GMT",
"version": "v3"
},
{
"created": "Thu, 8 Feb 2001 21:27:14 GMT",
"version": "v4"
},
{
"created": "Fri, 30 Mar 2001 22:54:47 GMT",
"version": "v5"
}
] |
2009-10-31
|
[
[
"Ng",
"Y. Jack",
"",
"University of North Carolina at Chapel Hill"
]
] |
We show that quantum mechanics and general relativity limit the speed $\tilde{\nu}$ of a simple computer (such as a black hole) and its memory space $I$ to $\tilde{\nu}^2 I^{-1} \lsim t_P^{-2}$, where $t_P$ is the Planck time. We also show that the life-time of a simple clock and its precision are similarly limited. These bounds and the holographic bound originate from the same physics that governs the quantum fluctuations of space-time. We further show that these physical bounds are realized for black holes, yielding the correct Hawking black hole lifetime, and that space-time undergoes much larger quantum fluctuations than conventional wisdom claims -- almost within range of detection with modern gravitational-wave interferometers.
|
2305.04969
|
Han Yan
|
Han Yan, Xian Chen, Alejandro Torres-Orjuela
|
Calculating the Gravitational Waves Emitted from High-speed Sources
|
9 pages, 2 figures. Accepted by PRD
|
Phys. Rev. D 107, 103044 (2023)
|
10.1103/PhysRevD.107.103044
| null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The possibility of forming gravitational-wave sources with high
center-of-mass (c.m.) velocities in the vicinity of supermassive black holes
requires us to develop a method of deriving the waveform in the observer's
frame. Here we show that in the limit where the c.m. velocity is high but the
relative velocities of the components of the source are small, we can solve the
problem by directly integrating the relaxed Einstein field equation. In
particular, we expand the result into multipole components which can be
conveniently calculated given the orbit of the source in the observer's frame.
Our numerical calculations using arbitrary c.m. velocities show that the result
is consistent with the Lorentz transformation of GWs to the leading order of
the radiation field. Moreover, we show an example of using this method to
calculate the waveform of a scattering event between the high-speed ($\sim
0.1c$) stellar objects embedded in the accretion disk of an active galactic
nucleus. Our multipole-expansion method not only has advantages in analyzing
the results from stellar-dynamical models but also provides new insight into
the multipole properties of the GWs emitted from a high-speed source.
|
[
{
"created": "Mon, 8 May 2023 18:03:27 GMT",
"version": "v1"
}
] |
2023-07-07
|
[
[
"Yan",
"Han",
""
],
[
"Chen",
"Xian",
""
],
[
"Torres-Orjuela",
"Alejandro",
""
]
] |
The possibility of forming gravitational-wave sources with high center-of-mass (c.m.) velocities in the vicinity of supermassive black holes requires us to develop a method of deriving the waveform in the observer's frame. Here we show that in the limit where the c.m. velocity is high but the relative velocities of the components of the source are small, we can solve the problem by directly integrating the relaxed Einstein field equation. In particular, we expand the result into multipole components which can be conveniently calculated given the orbit of the source in the observer's frame. Our numerical calculations using arbitrary c.m. velocities show that the result is consistent with the Lorentz transformation of GWs to the leading order of the radiation field. Moreover, we show an example of using this method to calculate the waveform of a scattering event between the high-speed ($\sim 0.1c$) stellar objects embedded in the accretion disk of an active galactic nucleus. Our multipole-expansion method not only has advantages in analyzing the results from stellar-dynamical models but also provides new insight into the multipole properties of the GWs emitted from a high-speed source.
|
1612.09309
|
David Wiltshire
|
Alan A. Coley, David L. Wiltshire
|
What is General Relativity?
|
18 pages. Invited article for Physica Scripta Focus issue on 21st
Century Frontiers. v2: Appendix amended, references added. v3: Small
corrections, references added, matches published version
|
Phys. Scripta 92 (2017) 053001
|
10.1088/1402-4896/aa6857
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
General relativity is a set of physical and geometric principles, which lead
to a set of (Einstein) field equations that determine the gravitational field,
and to the geodesic equations that describe light propagation and the motion of
particles on the background. But open questions remain, including: What is the
scale on which matter and geometry are dynamically coupled in the Einstein
equations? Are the field equations valid on small and large scales? What is the
largest scale on which matter can be coarse grained while following a geodesic
of a solution to Einstein's equations? We address these questions. If the field
equations are causal evolution equations, whose average on cosmological scales
is not an exact solution of the Einstein equations, then some simplifying
physical principle is required to explain the statistical homogeneity of the
late epoch Universe. Such a principle may have its origin in the dynamical
coupling between matter and geometry at the quantum level in the early
Universe. This possibility is hinted at by diverse approaches to quantum
gravity which find a dynamical reduction to two effective dimensions at high
energies on one hand, and by cosmological observations which are beginning to
strongly restrict the class of viable inflationary phenomenologies on the
other. We suggest that the foundational principles of general relativity will
play a central role in reformulating the theory of spacetime structure to meet
the challenges of cosmology in the 21st century.
|
[
{
"created": "Thu, 29 Dec 2016 21:17:32 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Jan 2017 18:54:38 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Apr 2017 14:04:36 GMT",
"version": "v3"
}
] |
2017-04-19
|
[
[
"Coley",
"Alan A.",
""
],
[
"Wiltshire",
"David L.",
""
]
] |
General relativity is a set of physical and geometric principles, which lead to a set of (Einstein) field equations that determine the gravitational field, and to the geodesic equations that describe light propagation and the motion of particles on the background. But open questions remain, including: What is the scale on which matter and geometry are dynamically coupled in the Einstein equations? Are the field equations valid on small and large scales? What is the largest scale on which matter can be coarse grained while following a geodesic of a solution to Einstein's equations? We address these questions. If the field equations are causal evolution equations, whose average on cosmological scales is not an exact solution of the Einstein equations, then some simplifying physical principle is required to explain the statistical homogeneity of the late epoch Universe. Such a principle may have its origin in the dynamical coupling between matter and geometry at the quantum level in the early Universe. This possibility is hinted at by diverse approaches to quantum gravity which find a dynamical reduction to two effective dimensions at high energies on one hand, and by cosmological observations which are beginning to strongly restrict the class of viable inflationary phenomenologies on the other. We suggest that the foundational principles of general relativity will play a central role in reformulating the theory of spacetime structure to meet the challenges of cosmology in the 21st century.
|
gr-qc/0110096
|
Kechkin O. V.
|
A. Herrera-Aguilar, Oleg V. Kechkin
|
Kalb--Ramond dipole solution in low-energy bosonic string theory
|
14 pages in LATEX
|
Gen.Rel.Grav.34:1331-1344,2002
|
10.1023/A:1020078132237
| null |
gr-qc
| null |
We construct a new solution subspace for the bosonic string theory toroidally
compactified to 3 dimensions. This subspace corresponds to the complex harmonic
scalar field coupled to the effective 3--dimensional gravity. We calculate a
class of the asymptotically flat and free of the Dirac string peculiarity
solutions which describes a Kalb--Ramond dipole source with the generally
nontrivial dilaton charge.
|
[
{
"created": "Tue, 23 Oct 2001 01:57:30 GMT",
"version": "v1"
}
] |
2010-11-19
|
[
[
"Herrera-Aguilar",
"A.",
""
],
[
"Kechkin",
"Oleg V.",
""
]
] |
We construct a new solution subspace for the bosonic string theory toroidally compactified to 3 dimensions. This subspace corresponds to the complex harmonic scalar field coupled to the effective 3--dimensional gravity. We calculate a class of the asymptotically flat and free of the Dirac string peculiarity solutions which describes a Kalb--Ramond dipole source with the generally nontrivial dilaton charge.
|
1507.03949
|
Ali \"Ovg\"un
|
A. \"Ovg\"un and I. Sakalli
|
On a Particular Thin-shell Wormhole
|
9 pages, accepted for publication in TMPh (Theoretical and
Mathematical Physics)
|
I. Theor Math Phys (2017) 190: 120
|
10.1134/S004057791701010X
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, using a black hole with scalar hair, we construct a scalar
thin-shell wormhole (TSW) in 2+1 dimensions by applying the Visser's famous cut
and paste technique. The surface stress, which is concentrated at the wormhole
throat is determined by using the Darmois-Israel formalism. By employing the
various gas models, we study the stability analysis of the TSW. The region of
stability is changed by tuning the parameters of "l" and "u". It is observed
that the obtained particular TSW originated from the black hole with scalar
hair could be more stable with particular $l$ parameter, however it still needs
exotic matter.
|
[
{
"created": "Tue, 14 Jul 2015 17:44:10 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jul 2015 08:10:49 GMT",
"version": "v2"
},
{
"created": "Wed, 25 Nov 2015 12:27:47 GMT",
"version": "v3"
},
{
"created": "Thu, 19 May 2016 13:18:35 GMT",
"version": "v4"
}
] |
2017-02-14
|
[
[
"Övgün",
"A.",
""
],
[
"Sakalli",
"I.",
""
]
] |
In this paper, using a black hole with scalar hair, we construct a scalar thin-shell wormhole (TSW) in 2+1 dimensions by applying the Visser's famous cut and paste technique. The surface stress, which is concentrated at the wormhole throat is determined by using the Darmois-Israel formalism. By employing the various gas models, we study the stability analysis of the TSW. The region of stability is changed by tuning the parameters of "l" and "u". It is observed that the obtained particular TSW originated from the black hole with scalar hair could be more stable with particular $l$ parameter, however it still needs exotic matter.
|
1404.4311
|
Kazuharu Bamba
|
Kazuharu Bamba, Guido Cognola, Sergei D. Odintsov and Sergio Zerbini
|
One-loop Modified Gravity in de Sitter Universe, Quantum Corrected
Inflation, and its Confrontation with the Planck Result
|
21 pages, no figure, several references added
|
Phys. Rev. D 90, 023525 (2014)
|
10.1103/PhysRevD.90.023525
|
OCHA-PP-322
|
gr-qc astro-ph.CO hep-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Motivated by issues on inflation, a generalized modified gravity model is
investigated, where the model Lagrangian is described by a smooth function
$f(R, K, \phi)$ of the Ricci scalar $R$, the kinetic term $K$ of a scalar field
$\phi$. In particular, the one-loop effective action in the de Sitter
background is examined on-shell as well as off-shell in the Landau gauge. In
addition, the on-shell quantum equivalence of $f(R)$ gravity in the Jordan and
Einstein frames is explicitly demonstrated. Furthermore, we present
applications related to the stability of the de Sitter solutions and the
one-loop quantum correction to inflation in quantum-corrected $R^2$ gravity. It
is shown that for a certain range of parameters, the spectral index of the
curvature perturbations can be consistent with the Planck analysis, but the
tensor-to-scalar ratio is smaller than the minimum value within the 1 $\sigma$
error range of the BICEP2 result.
|
[
{
"created": "Wed, 16 Apr 2014 16:59:13 GMT",
"version": "v1"
},
{
"created": "Thu, 22 May 2014 06:11:36 GMT",
"version": "v2"
}
] |
2014-07-23
|
[
[
"Bamba",
"Kazuharu",
""
],
[
"Cognola",
"Guido",
""
],
[
"Odintsov",
"Sergei D.",
""
],
[
"Zerbini",
"Sergio",
""
]
] |
Motivated by issues on inflation, a generalized modified gravity model is investigated, where the model Lagrangian is described by a smooth function $f(R, K, \phi)$ of the Ricci scalar $R$, the kinetic term $K$ of a scalar field $\phi$. In particular, the one-loop effective action in the de Sitter background is examined on-shell as well as off-shell in the Landau gauge. In addition, the on-shell quantum equivalence of $f(R)$ gravity in the Jordan and Einstein frames is explicitly demonstrated. Furthermore, we present applications related to the stability of the de Sitter solutions and the one-loop quantum correction to inflation in quantum-corrected $R^2$ gravity. It is shown that for a certain range of parameters, the spectral index of the curvature perturbations can be consistent with the Planck analysis, but the tensor-to-scalar ratio is smaller than the minimum value within the 1 $\sigma$ error range of the BICEP2 result.
|
1609.06544
|
Luis Granda
|
L. N. Granda and E. Loaiza
|
Phase space analysis for a scalar-tensor model with kinetic and
Gauss-Bonnet couplings
|
17 pages, 9 figures, accepted in PRD
| null |
10.1103/PhysRevD.94.063528
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the phase space for an scalar-tensor string inspired model of dark
energy with non minimal kinetic and Gauss Bonnet couplings. The form of the
scalar potential and of the coupling terms is of the exponential type, which
give rise to appealing cosmological solutions. The critical points describe a
variety of cosmological scenarios that go from matter or radiation dominated
universe to dark energy dominated universe. There were found trajectories in
the phase space departing from unstable or saddle fixed points and arriving to
the stable scalar field dominated point corresponding to late-time accelerated
expansion.
|
[
{
"created": "Wed, 21 Sep 2016 13:11:16 GMT",
"version": "v1"
}
] |
2016-10-12
|
[
[
"Granda",
"L. N.",
""
],
[
"Loaiza",
"E.",
""
]
] |
We study the phase space for an scalar-tensor string inspired model of dark energy with non minimal kinetic and Gauss Bonnet couplings. The form of the scalar potential and of the coupling terms is of the exponential type, which give rise to appealing cosmological solutions. The critical points describe a variety of cosmological scenarios that go from matter or radiation dominated universe to dark energy dominated universe. There were found trajectories in the phase space departing from unstable or saddle fixed points and arriving to the stable scalar field dominated point corresponding to late-time accelerated expansion.
|
1609.07904
|
Beatriz Elizaga Navascu\'es
|
Jer\'onimo Cortez, Beatriz Elizaga Navascu\'es, Mercedes
Mart\'in-Benito, Guillermo A. Mena Marug\'an, Jos\'e M. Velhinho
|
Dirac fields in flat FLRW cosmology: Uniqueness of the Fock quantization
|
19 pages, submitted for publication to Annals of Physics
| null |
10.1016/j.aop.2016.11.005
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We address the issue of the infinite ambiguity that affects the construction
of a Fock quantization of a Dirac field propagating in a cosmological spacetime
with flat compact sections. In particular, we discuss a physical criterion that
restricts to a unique possibility (up to unitary equivalence) the infinite set
of available vacua. We prove that this desired uniqueness is guaranteed, for
any possible choice of spin structure on the spatial sections, if we impose two
conditions. The first one is that the symmetries of the classical system must
be implemented quantum mechanically, so that the vacuum is invariant under the
symmetry transformations. The second and more important condition is that the
constructed theory must have a quantum dynamics that is implementable as a
(non-trivial) unitary operator in Fock space. Actually, this unitarity of the
quantum dynamics leads us to identify as explicitly time dependent some very
specific contributions of the Dirac field. In doing that, we essentially
characterize the part of the dynamics governed by the Dirac equation that is
unitarily implementable. The uniqueness of the Fock vacuum is attained then
once a physically motivated convention for the concepts of particles and
antiparticles is fixed.
|
[
{
"created": "Mon, 26 Sep 2016 09:44:09 GMT",
"version": "v1"
}
] |
2017-03-08
|
[
[
"Cortez",
"Jerónimo",
""
],
[
"Navascués",
"Beatriz Elizaga",
""
],
[
"Martín-Benito",
"Mercedes",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
],
[
"Velhinho",
"José M.",
""
]
] |
We address the issue of the infinite ambiguity that affects the construction of a Fock quantization of a Dirac field propagating in a cosmological spacetime with flat compact sections. In particular, we discuss a physical criterion that restricts to a unique possibility (up to unitary equivalence) the infinite set of available vacua. We prove that this desired uniqueness is guaranteed, for any possible choice of spin structure on the spatial sections, if we impose two conditions. The first one is that the symmetries of the classical system must be implemented quantum mechanically, so that the vacuum is invariant under the symmetry transformations. The second and more important condition is that the constructed theory must have a quantum dynamics that is implementable as a (non-trivial) unitary operator in Fock space. Actually, this unitarity of the quantum dynamics leads us to identify as explicitly time dependent some very specific contributions of the Dirac field. In doing that, we essentially characterize the part of the dynamics governed by the Dirac equation that is unitarily implementable. The uniqueness of the Fock vacuum is attained then once a physically motivated convention for the concepts of particles and antiparticles is fixed.
|
2207.10089
|
Nuno M. Santos
|
Nuno M. Santos, Carlos. A. R. Herdeiro, Eugen Radu
|
A little hair can make a big difference: thermodynamic stability of
quasi-bald asymptotically-flat black holes
|
11 pages, 4 figures. Comments are welcome
|
Phys. Rev. D 106 (2022) 12
|
10.1103/PhysRevD.106.124005
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The local thermodynamic stability of a black hole (BH) in the canonical
ensemble is defined by the positivity of the specific heat at constant global
charges. Schwarzschild BHs in thermodynamic equilibrium with an energy
reservoir are always unstable against small fluctuations of energy, whereas
sufficiently near-extremal Reissner-Nordstr\"{o}m/Kerr BHs are stable. One
could expect that asymptotically-flat hairy BHs branching off from such stable
phases would also be, by continuity, locally thermodynamically stable for
vanishingly little hair. We show this is not the case in some models, including
scalarized BHs bifurcating from Reissner-Nordstr\"{o}m and spinning BHs with
synchronized hair bifurcating from Kerr. Specifically, it is found that
quasi-bald BHs are locally thermodynamically unstable in the canonical ensemble
for all global charges and regardless of being dynamically and entropically
preferred over bald ones at fixed global charges.
|
[
{
"created": "Wed, 20 Jul 2022 18:00:00 GMT",
"version": "v1"
}
] |
2024-03-29
|
[
[
"Santos",
"Nuno M.",
""
],
[
"Herdeiro",
"Carlos. A. R.",
""
],
[
"Radu",
"Eugen",
""
]
] |
The local thermodynamic stability of a black hole (BH) in the canonical ensemble is defined by the positivity of the specific heat at constant global charges. Schwarzschild BHs in thermodynamic equilibrium with an energy reservoir are always unstable against small fluctuations of energy, whereas sufficiently near-extremal Reissner-Nordstr\"{o}m/Kerr BHs are stable. One could expect that asymptotically-flat hairy BHs branching off from such stable phases would also be, by continuity, locally thermodynamically stable for vanishingly little hair. We show this is not the case in some models, including scalarized BHs bifurcating from Reissner-Nordstr\"{o}m and spinning BHs with synchronized hair bifurcating from Kerr. Specifically, it is found that quasi-bald BHs are locally thermodynamically unstable in the canonical ensemble for all global charges and regardless of being dynamically and entropically preferred over bald ones at fixed global charges.
|
1412.1803
|
Mark A. Scheel
|
Mark A. Scheel, Matthew Giesler, Daniel A. Hemberger, Geoffrey
Lovelace, Kevin Kuper, Michael Boyle, Bela Szilagyi, Lawrence E. Kidder
|
Improved methods for simulating nearly extremal binary black holes
|
18 pages, 18 figures
| null |
10.1088/0264-9381/32/10/105009
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Astrophysical black holes could be nearly extremal (that is, rotating nearly
as fast as possible); therefore, nearly extremal black holes could be among the
binaries that current and future gravitational-wave observatories will detect.
Predicting the gravitational waves emitted by merging black holes requires
numerical-relativity simulations, but these simulations are especially
challenging when one or both holes have mass $m$ and spin $S$ exceeding the
Bowen-York limit of $S/m^2=0.93$. We present improved methods that enable us to
simulate merging, nearly extremal black holes more robustly and more
efficiently. We use these methods to simulate an unequal-mass, precessing
binary black hole coalescence, where the larger black hole has $S/m^2=0.99$. We
also use these methods to simulate a non-precessing binary black hole
coalescence, where both black holes have $S/m^2=0.994$, nearly reaching the
Novikov-Thorne upper bound for holes spun up by thin accretion disks. We
demonstrate numerical convergence and estimate the numerical errors of the
waveforms; we compare numerical waveforms from our simulations with
post-Newtonian and effective-one-body waveforms; we compare the evolution of
the black-hole masses and spins with analytic predictions; and we explore the
effect of increasing spin magnitude on the orbital dynamics (the so-called
"orbital hangup" effect).
|
[
{
"created": "Thu, 4 Dec 2014 20:34:08 GMT",
"version": "v1"
}
] |
2015-05-20
|
[
[
"Scheel",
"Mark A.",
""
],
[
"Giesler",
"Matthew",
""
],
[
"Hemberger",
"Daniel A.",
""
],
[
"Lovelace",
"Geoffrey",
""
],
[
"Kuper",
"Kevin",
""
],
[
"Boyle",
"Michael",
""
],
[
"Szilagyi",
"Bela",
""
],
[
"Kidder",
"Lawrence E.",
""
]
] |
Astrophysical black holes could be nearly extremal (that is, rotating nearly as fast as possible); therefore, nearly extremal black holes could be among the binaries that current and future gravitational-wave observatories will detect. Predicting the gravitational waves emitted by merging black holes requires numerical-relativity simulations, but these simulations are especially challenging when one or both holes have mass $m$ and spin $S$ exceeding the Bowen-York limit of $S/m^2=0.93$. We present improved methods that enable us to simulate merging, nearly extremal black holes more robustly and more efficiently. We use these methods to simulate an unequal-mass, precessing binary black hole coalescence, where the larger black hole has $S/m^2=0.99$. We also use these methods to simulate a non-precessing binary black hole coalescence, where both black holes have $S/m^2=0.994$, nearly reaching the Novikov-Thorne upper bound for holes spun up by thin accretion disks. We demonstrate numerical convergence and estimate the numerical errors of the waveforms; we compare numerical waveforms from our simulations with post-Newtonian and effective-one-body waveforms; we compare the evolution of the black-hole masses and spins with analytic predictions; and we explore the effect of increasing spin magnitude on the orbital dynamics (the so-called "orbital hangup" effect).
|
2012.01838
|
Daniel Sobral Blanco
|
Daniel Sobral-Blanco and Lucas Lombriser
|
Exploring the self-tuning of the cosmological constant from Planck mass
variation
|
15 pages, 1 figure. V3 version accepted for publication at CQG
| null | null | null |
gr-qc astro-ph.CO hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
Recently, the variation of the Planck mass in the General Relativistic
Einstein-Hilbert action was proposed as a self-tuning mechanism of the
cosmological constant, preventing Standard Model vacuum energy from freely
gravitating and enabling an estimation of the magnitude of its observed value.
We explore here new aspects of this proposal. We first develop an equivalent
Einstein-frame formalism to the current Jordan-frame formulation of the
mechanism and use this to highlight similarities and differences of self-tuning
to the sequestering mechanism. We then show how with an extension of the local
self-tuning action by a coupled Gauss-Bonnet term and a companion four-form
field strength, graviton loops can be prevented from incapacitating the
degravitation of the Standard Model vacuum energy. For certain cases, we
furthermore find that this extension can be recast as a Horndeski scalar-tensor
theory and be embedded in the conventional local self-tuning formalism. We then
explore the possibility of a unification of inflation with self-tuning. The
resulting equations can alternatively be used to motivate a multiverse
interpretation. In this context, we revisit the coincidence problem and provide
an estimation for the probability of the emergence of intelligent life in our
Universe as a function of cosmic age, inferred from star and terrestrial planet
formation processes. We conclude that we live at a very typical epoch, where we
should expect the energy densities of the cosmological constant and matter to
be of comparable size. For a dimensionless quantity to compare the emergence of
life throughout the cosmic history of different universes in an anthropic
analysis of the multiverse, we choose the order of magnitude difference of the
evolving horizon size of a universe to the size of its proton as the basic
building block of atoms, molecules, and eventually life. (abridged)
|
[
{
"created": "Thu, 3 Dec 2020 11:13:59 GMT",
"version": "v1"
},
{
"created": "Wed, 26 May 2021 09:35:08 GMT",
"version": "v2"
},
{
"created": "Sun, 31 Oct 2021 11:23:20 GMT",
"version": "v3"
}
] |
2021-11-02
|
[
[
"Sobral-Blanco",
"Daniel",
""
],
[
"Lombriser",
"Lucas",
""
]
] |
Recently, the variation of the Planck mass in the General Relativistic Einstein-Hilbert action was proposed as a self-tuning mechanism of the cosmological constant, preventing Standard Model vacuum energy from freely gravitating and enabling an estimation of the magnitude of its observed value. We explore here new aspects of this proposal. We first develop an equivalent Einstein-frame formalism to the current Jordan-frame formulation of the mechanism and use this to highlight similarities and differences of self-tuning to the sequestering mechanism. We then show how with an extension of the local self-tuning action by a coupled Gauss-Bonnet term and a companion four-form field strength, graviton loops can be prevented from incapacitating the degravitation of the Standard Model vacuum energy. For certain cases, we furthermore find that this extension can be recast as a Horndeski scalar-tensor theory and be embedded in the conventional local self-tuning formalism. We then explore the possibility of a unification of inflation with self-tuning. The resulting equations can alternatively be used to motivate a multiverse interpretation. In this context, we revisit the coincidence problem and provide an estimation for the probability of the emergence of intelligent life in our Universe as a function of cosmic age, inferred from star and terrestrial planet formation processes. We conclude that we live at a very typical epoch, where we should expect the energy densities of the cosmological constant and matter to be of comparable size. For a dimensionless quantity to compare the emergence of life throughout the cosmic history of different universes in an anthropic analysis of the multiverse, we choose the order of magnitude difference of the evolving horizon size of a universe to the size of its proton as the basic building block of atoms, molecules, and eventually life. (abridged)
|
2303.07873
|
Przemyslaw Malkiewicz
|
Herve Bergeron, Jaime de Cabo Martin, Jean-Pierre Gazeau and
Przemyslaw Malkiewicz
|
Can a quantum mixmaster universe undergo a spontaneous inflationary
phase?
|
15 pages, 6 figures
|
Phys. Rev. D 108, 043534 (2023)
| null | null |
gr-qc quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study a semiclassical model of the mixmaster universe. We first derive the
quantum model and then introduce its semiclassical approximation. We employ a
general integral quantization method that respects the symmetries of the model
given by the affine and the Weyl-Heisenberg groups, and can produce a wide
class of quantum models. The semiclassical approximation is based on the
coherent states. The semiclassical dynamics is complex and cannot be solved by
analytical methods. We focus on a key qualitative feature of the dynamics,
namely, we investigate whether the primordial anisotropic universe can undergo
a spontaneous inflationary phase driven by the anisotropic energy combined with
semiclassical corrections. The answer to this question provides a useful
perspective on the inflationary paradigm as well as on alternative bouncing
models.
|
[
{
"created": "Tue, 14 Mar 2023 13:06:02 GMT",
"version": "v1"
},
{
"created": "Sat, 2 Sep 2023 05:25:52 GMT",
"version": "v2"
}
] |
2023-09-06
|
[
[
"Bergeron",
"Herve",
""
],
[
"Martin",
"Jaime de Cabo",
""
],
[
"Gazeau",
"Jean-Pierre",
""
],
[
"Malkiewicz",
"Przemyslaw",
""
]
] |
We study a semiclassical model of the mixmaster universe. We first derive the quantum model and then introduce its semiclassical approximation. We employ a general integral quantization method that respects the symmetries of the model given by the affine and the Weyl-Heisenberg groups, and can produce a wide class of quantum models. The semiclassical approximation is based on the coherent states. The semiclassical dynamics is complex and cannot be solved by analytical methods. We focus on a key qualitative feature of the dynamics, namely, we investigate whether the primordial anisotropic universe can undergo a spontaneous inflationary phase driven by the anisotropic energy combined with semiclassical corrections. The answer to this question provides a useful perspective on the inflationary paradigm as well as on alternative bouncing models.
|
1706.01243
|
Adrien Bourgoin
|
Adrien Bourgoin, Aur\'elien Hees, Christophe Le Poncin-Lafitte,
S\'ebastien Bouquillon, G\'erard Francou and Marie-Christine Angonin
|
Constraints on Lorentz symmetry violations with Lunar Laser Ranging
| null | null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present new constraints on Lorentz symmetry (LS) violations with lunar
laser ranging (LLR). Those constraints are derived in the standard-model
extension (SME) framework aiming at parameterizing any LS deviations in all
sectors of physics. We restrict ourself to two sectors namely the pure
gravitational sector of the minimal SME and the gravity-matter coupling. We
describe the adopted method and compare our results to previous analysis based
on theoretical grounds. This work constitutes the first direct experimental
determination of the SME coefficients using LLR measurements.
|
[
{
"created": "Mon, 5 Jun 2017 09:07:50 GMT",
"version": "v1"
}
] |
2017-06-06
|
[
[
"Bourgoin",
"Adrien",
""
],
[
"Hees",
"Aurélien",
""
],
[
"Poncin-Lafitte",
"Christophe Le",
""
],
[
"Bouquillon",
"Sébastien",
""
],
[
"Francou",
"Gérard",
""
],
[
"Angonin",
"Marie-Christine",
""
]
] |
We present new constraints on Lorentz symmetry (LS) violations with lunar laser ranging (LLR). Those constraints are derived in the standard-model extension (SME) framework aiming at parameterizing any LS deviations in all sectors of physics. We restrict ourself to two sectors namely the pure gravitational sector of the minimal SME and the gravity-matter coupling. We describe the adopted method and compare our results to previous analysis based on theoretical grounds. This work constitutes the first direct experimental determination of the SME coefficients using LLR measurements.
|
gr-qc/0406089
|
G. S. Bisnovatyi-Kogan
|
G.S. Bisnovatyi-Kogan and V.N.Rudenko
|
Very high frequency gravitational wave background in the universe
|
14 pages
|
Class.Quant.Grav.21:3347-3359,2004
|
10.1088/0264-9381/21/14/001
| null |
gr-qc astro-ph
| null |
Astrophysical sources of high frequency gravitational radiation are
considered in association with a new interest to very sensitive HFGW receivers
required for the laboratory GW Hertz experiment. A special attention is paid to
the phenomenon of primordial black holes evaporation. They act like black body
to all kinds of radiation, including gravitons, and, therefore, emit an
equilibrium spectrum of gravitons during its evaporation. Limit on the density
of high frequency gravitons in the Universe is obtained, and possibilities of
their detection are briefly discussed.
|
[
{
"created": "Tue, 22 Jun 2004 11:35:28 GMT",
"version": "v1"
}
] |
2011-08-11
|
[
[
"Bisnovatyi-Kogan",
"G. S.",
""
],
[
"Rudenko",
"V. N.",
""
]
] |
Astrophysical sources of high frequency gravitational radiation are considered in association with a new interest to very sensitive HFGW receivers required for the laboratory GW Hertz experiment. A special attention is paid to the phenomenon of primordial black holes evaporation. They act like black body to all kinds of radiation, including gravitons, and, therefore, emit an equilibrium spectrum of gravitons during its evaporation. Limit on the density of high frequency gravitons in the Universe is obtained, and possibilities of their detection are briefly discussed.
|
2004.03141
|
Minyong Guo
|
Cheng-Yong Zhang, Shao-Jun Zhang, Peng-Cheng Li and Minyong Guo
|
Superradiance and stability of the novel 4D charged
Einstein-Gauss-Bonnet black hole
|
21 pages, 6 figures, references added
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We investigated the superradiance and stability of the novel 4D charged
Einstein-Gauss-Bonnet black hole which is recently inspired by Glavan and Lin
[Phys. Rev. Lett. 124, 081301 (2020)]. We found that the positive Gauss-Bonnet
coupling consant $\alpha$ enhances the superradiance, while the negative
$\alpha$ suppresses it. The condition for superradiant instability is proved.
We also worked out the quasinormal modes (QNMs) of the charged
Einstein-Gauss-Bonnet black hole and found that the real part of all the QNMs
live beyond the superradiance condition and the imaginary parts are all
negative. Therefore this black hole is superradiant stable. When $\alpha$ makes
the black hole extremal, there are normal modes.
|
[
{
"created": "Tue, 7 Apr 2020 05:57:34 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Apr 2020 11:56:16 GMT",
"version": "v2"
}
] |
2020-04-10
|
[
[
"Zhang",
"Cheng-Yong",
""
],
[
"Zhang",
"Shao-Jun",
""
],
[
"Li",
"Peng-Cheng",
""
],
[
"Guo",
"Minyong",
""
]
] |
We investigated the superradiance and stability of the novel 4D charged Einstein-Gauss-Bonnet black hole which is recently inspired by Glavan and Lin [Phys. Rev. Lett. 124, 081301 (2020)]. We found that the positive Gauss-Bonnet coupling consant $\alpha$ enhances the superradiance, while the negative $\alpha$ suppresses it. The condition for superradiant instability is proved. We also worked out the quasinormal modes (QNMs) of the charged Einstein-Gauss-Bonnet black hole and found that the real part of all the QNMs live beyond the superradiance condition and the imaginary parts are all negative. Therefore this black hole is superradiant stable. When $\alpha$ makes the black hole extremal, there are normal modes.
|
2203.07594
|
Umananda Dev Goswami
|
Dhruba Jyoti Gogoi and Umananda Dev Goswami
|
Quasinormal Modes and Hawking Radiation Sparsity of GUP corrected Black
Holes in Bumblebee Gravity with Topological Defects
|
40 pages, 23 figures
|
JCAP 06 (2022) 029
|
10.1088/1475-7516/2022/06/029
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We have obtained the Generalized Uncertainty Principle (GUP) corrected de
Sitter and anti-de Sitter black hole solutions in bumblebee gravity with a
topological defect. We have calculated the scalar, electromagnetic and
gravitational quasinormal modes for the both vanishing and non-vanishing
effective cosmological constant using Pad\'e averaged sixth order WKB
approximation method. Apart from this, the time evolutions for all three
perturbations are studied, and quasinormal modes are calculated using the time
domain profile. We found that the first order and second order GUP parameters
$\alpha$ and $\beta$, respectively have opposite impacts on the quasinormal
modes. The study also finds that the presence of a global monopole can decrease
the quasinormal frequencies and the decay rate significantly. On the other
hand, Lorentz symmetry violation has noticeable impacts on the quasinormal
frequencies and the decay rate. We have studied the greybody factors, power
spectrum and sparsity of the black hole with the vanishing effective
cosmological constant for all the three perturbations. The presence of Lorentz
symmetry breaking and the GUP parameter $\alpha$ decrease, while other GUP
parameter $\beta$ and the presence of global monopole increase the probability
of Hawking radiation to reach the spatial infinity. The presence of Lorentz
violation can make the black holes less sparse, while the presence of a global
monopole can increase the sparsity of the black holes. Moreover, we have seen
that the black hole area quantization rule is modified by the presence of
Lorentz symmetry breaking.
|
[
{
"created": "Tue, 15 Mar 2022 01:47:46 GMT",
"version": "v1"
},
{
"created": "Sat, 2 Jul 2022 11:05:44 GMT",
"version": "v2"
}
] |
2022-07-06
|
[
[
"Gogoi",
"Dhruba Jyoti",
""
],
[
"Goswami",
"Umananda Dev",
""
]
] |
We have obtained the Generalized Uncertainty Principle (GUP) corrected de Sitter and anti-de Sitter black hole solutions in bumblebee gravity with a topological defect. We have calculated the scalar, electromagnetic and gravitational quasinormal modes for the both vanishing and non-vanishing effective cosmological constant using Pad\'e averaged sixth order WKB approximation method. Apart from this, the time evolutions for all three perturbations are studied, and quasinormal modes are calculated using the time domain profile. We found that the first order and second order GUP parameters $\alpha$ and $\beta$, respectively have opposite impacts on the quasinormal modes. The study also finds that the presence of a global monopole can decrease the quasinormal frequencies and the decay rate significantly. On the other hand, Lorentz symmetry violation has noticeable impacts on the quasinormal frequencies and the decay rate. We have studied the greybody factors, power spectrum and sparsity of the black hole with the vanishing effective cosmological constant for all the three perturbations. The presence of Lorentz symmetry breaking and the GUP parameter $\alpha$ decrease, while other GUP parameter $\beta$ and the presence of global monopole increase the probability of Hawking radiation to reach the spatial infinity. The presence of Lorentz violation can make the black holes less sparse, while the presence of a global monopole can increase the sparsity of the black holes. Moreover, we have seen that the black hole area quantization rule is modified by the presence of Lorentz symmetry breaking.
|
2301.08055
|
Shibendu Gupta Choudhury
|
Shibendu Gupta Choudhury
|
Application of the Raychaudhuri Equation in Gravitational Systems
|
Thesis accepted for the award of PhD degree of IISER Kolkata,
December 2022
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The works reported in this thesis primarily address the application of the
Raychaudhuri equation in two intriguing problems in gravitational physics.
These problems still lack universally accepted explanations. The first problem
is related to the existence of spacetime singularities. We aim to find possible
escape routes from these problematic singularities at the classical level. The
second problem is associated with the late time accelerated expansion of the
Universe. In this context, our goal is to find a possible explanation of this
phenomenon without assuming the presence of any exotic contribution to the
stress-energy tensor.
|
[
{
"created": "Thu, 19 Jan 2023 13:04:49 GMT",
"version": "v1"
}
] |
2023-01-20
|
[
[
"Choudhury",
"Shibendu Gupta",
""
]
] |
The works reported in this thesis primarily address the application of the Raychaudhuri equation in two intriguing problems in gravitational physics. These problems still lack universally accepted explanations. The first problem is related to the existence of spacetime singularities. We aim to find possible escape routes from these problematic singularities at the classical level. The second problem is associated with the late time accelerated expansion of the Universe. In this context, our goal is to find a possible explanation of this phenomenon without assuming the presence of any exotic contribution to the stress-energy tensor.
|
0906.1098
|
David Kofro\v{n}
|
Jiri Bicak, David Kofron
|
Accelerating electromagnetic magic field from the C-metric
|
22 pages, 5 figures
|
Gen.Rel.Grav.41:1981-2001,2009
|
10.1007/s10714-009-0816-8
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Various aspects of the C-metric representing two rotating charged black holes
accelerated in opposite directions are summarized and its limits are
considered. A particular attention is paid to the special-relativistic limit in
which the electromagnetic field becomes the "magic field" of two oppositely
accelerated rotating charged relativistic discs. When the acceleration vanishes
the usual electromagnetic magic field of the Kerr-Newman black hole with
gravitational constant set to zero arises. Properties of the accelerated discs
and the fields produced are studied and illustrated graphically. The charges at
the rim of the accelerated discs move along spiral trajectories with the speed
of light. If the magic field has some deeper connection with the field of the
Dirac electron, as is sometimes conjectured because of the same gyromagnetic
ratio, the "accelerating magic field" represents the electromagnetic field of a
uniformly accelerated spinning electron. It generalizes the classical Born's
solution for two uniformly accelerated monopole charges.
|
[
{
"created": "Fri, 5 Jun 2009 11:53:32 GMT",
"version": "v1"
}
] |
2009-09-28
|
[
[
"Bicak",
"Jiri",
""
],
[
"Kofron",
"David",
""
]
] |
Various aspects of the C-metric representing two rotating charged black holes accelerated in opposite directions are summarized and its limits are considered. A particular attention is paid to the special-relativistic limit in which the electromagnetic field becomes the "magic field" of two oppositely accelerated rotating charged relativistic discs. When the acceleration vanishes the usual electromagnetic magic field of the Kerr-Newman black hole with gravitational constant set to zero arises. Properties of the accelerated discs and the fields produced are studied and illustrated graphically. The charges at the rim of the accelerated discs move along spiral trajectories with the speed of light. If the magic field has some deeper connection with the field of the Dirac electron, as is sometimes conjectured because of the same gyromagnetic ratio, the "accelerating magic field" represents the electromagnetic field of a uniformly accelerated spinning electron. It generalizes the classical Born's solution for two uniformly accelerated monopole charges.
|
2009.03402
|
Mohsen Fathi
|
Mohsen Fathi, J.R. Villanueva
|
The role of elliptic integrals in calculating the gravitational lensing
of a charged Weyl black hole surrounded by plasma
|
19 pages, 14 figures
|
Vestnik KRAUNC. Fiz.-mat. nauki., 36: 3, 167-190 (2021)
|
10.26117/2079-6641-2021-36-3-165-188
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we mainly aim at highlighting the importance of
(hyper-)elliptic integrals in the study of gravitational effects caused by
strongly gravitating systems. For this, we study the application of elliptic
integrals in calculating the light deflection as it passes a plasmic medium,
surrounding a charged Weyl black hole. To proceed with this, we consider two
specific algebraic ansatzes for the plasmic refractive index, and we
characterize the photon sphere for each of the cases. This will be used further
to calculate the angular diameter of the corresponding black hole shadow. We
show that the complexity of the refractive index expressions, can result in
substantially different types of dependencies of the light behavior on the
spacetime parameters.
|
[
{
"created": "Mon, 7 Sep 2020 20:19:23 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Nov 2020 16:21:51 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Oct 2021 13:38:47 GMT",
"version": "v3"
}
] |
2021-11-23
|
[
[
"Fathi",
"Mohsen",
""
],
[
"Villanueva",
"J. R.",
""
]
] |
In this paper, we mainly aim at highlighting the importance of (hyper-)elliptic integrals in the study of gravitational effects caused by strongly gravitating systems. For this, we study the application of elliptic integrals in calculating the light deflection as it passes a plasmic medium, surrounding a charged Weyl black hole. To proceed with this, we consider two specific algebraic ansatzes for the plasmic refractive index, and we characterize the photon sphere for each of the cases. This will be used further to calculate the angular diameter of the corresponding black hole shadow. We show that the complexity of the refractive index expressions, can result in substantially different types of dependencies of the light behavior on the spacetime parameters.
|
gr-qc/0105024
|
M. B. Altaie
|
M.B.Altaie
|
Quantum black hole inflation
|
18 pages, Latex
| null | null | null |
gr-qc
| null |
In this paper we follow a new approach for particle creation by a localized
strong gravitational field. The approach is based on a definition of the
physical vacuum drawn from Heisenberg uncertainty principle. Using the fact
that the gravitational field red-shifts the frequency modes of the vacuum, a
condition on the minimum stregth of the gravitational field required to achieve
real particle creation is derived. Application of this requirement on a
Schwartzchid black hole resulted in deducing an upper limit on the region,
outside the event horizon, where real particles can be created. Using this
regional upper limit, and considering particle creation by black holes as a
consequence of the Casimir effect, with the assumption that the created quanta
are to be added to the initial energy, we deduce a natural power law for the
development of the event horizon, and consequently a logarithmic law for the
area spectrum of an inflating black hole. Application of the results on a
cosmological model shows that if we start with a Planck-dimensional black hole,
then through the process of particle creation we end up with a universe having
the presently estimated critical density. Such a universe will be in a state of
eternal inflation.
|
[
{
"created": "Mon, 7 May 2001 14:03:01 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Altaie",
"M. B.",
""
]
] |
In this paper we follow a new approach for particle creation by a localized strong gravitational field. The approach is based on a definition of the physical vacuum drawn from Heisenberg uncertainty principle. Using the fact that the gravitational field red-shifts the frequency modes of the vacuum, a condition on the minimum stregth of the gravitational field required to achieve real particle creation is derived. Application of this requirement on a Schwartzchid black hole resulted in deducing an upper limit on the region, outside the event horizon, where real particles can be created. Using this regional upper limit, and considering particle creation by black holes as a consequence of the Casimir effect, with the assumption that the created quanta are to be added to the initial energy, we deduce a natural power law for the development of the event horizon, and consequently a logarithmic law for the area spectrum of an inflating black hole. Application of the results on a cosmological model shows that if we start with a Planck-dimensional black hole, then through the process of particle creation we end up with a universe having the presently estimated critical density. Such a universe will be in a state of eternal inflation.
|
0903.0143
|
Luiz C L Botelho
|
Luiz C L Botelho
|
Light Deflection on de-Sitter Space
|
9lho In order to protest against that stupid and ruthless decision of
arxiv moderation in not allow me to submit unplished articles in arxiv
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the light deflection on de-Sitter Space with negative cosmological
constant
|
[
{
"created": "Sun, 1 Mar 2009 20:57:56 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jul 2012 20:27:46 GMT",
"version": "v2"
}
] |
2012-07-04
|
[
[
"Botelho",
"Luiz C L",
""
]
] |
We study the light deflection on de-Sitter Space with negative cosmological constant
|
gr-qc/0412113
|
Ilya Lvovich Shapiro
|
D.F. Carneiro, E.A. Freiras, B. Gon\c{c}alves, A.G. de Lima, and I.L.
Shapiro (Universidade Federal de Juiz de Fora, MG, Brazil)
|
On Useful Conformal Tranformations In General Relativity
|
17 pages, LaTeX. Several misprints and mistakes in formulas
corrected, one derivation simplified and one reference added
|
Grav.Cosmol. 10 (2004) 305-312
| null |
DF-UFJF/2004-10
|
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
Local conformal transformations are known as a useful tool in various
applications of the gravitational theory, especially in cosmology. We describe
some new aspects of these transformations, in particular using them for
derivation of Einstein equations for the cosmological and Schwarzschild
metrics. Furthermore, the conformal transformation is applied for the
dimensional reduction of the Gauss-Bonnet topological invariant in $d=4$ to the
spaces of lower dimensions.
|
[
{
"created": "Wed, 22 Dec 2004 12:34:12 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Jun 2023 18:25:38 GMT",
"version": "v2"
}
] |
2023-06-05
|
[
[
"Carneiro",
"D. F.",
"",
"Universidade Federal de Juiz de Fora, MG, Brazil"
],
[
"Freiras",
"E. A.",
"",
"Universidade Federal de Juiz de Fora, MG, Brazil"
],
[
"Gonçalves",
"B.",
"",
"Universidade Federal de Juiz de Fora, MG, Brazil"
],
[
"de Lima",
"A. G.",
"",
"Universidade Federal de Juiz de Fora, MG, Brazil"
],
[
"Shapiro",
"I. L.",
"",
"Universidade Federal de Juiz de Fora, MG, Brazil"
]
] |
Local conformal transformations are known as a useful tool in various applications of the gravitational theory, especially in cosmology. We describe some new aspects of these transformations, in particular using them for derivation of Einstein equations for the cosmological and Schwarzschild metrics. Furthermore, the conformal transformation is applied for the dimensional reduction of the Gauss-Bonnet topological invariant in $d=4$ to the spaces of lower dimensions.
|
2101.02223
|
Jakub Bilski
|
Jakub Bilski
|
Lattice classical cosmology
|
4 pages
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
This article presents the lattice-smeared gravity phase space reduction
defined by the cosmological gauge-fixing conditions. These conditions are
specified to reduce the SU(2) symmetry and the spatial diffeomorphism
invariance of the loop quantum gravity's Fock space, known as the spin network.
The internal symmetry is fixed to the Abelian case and the diffeomorphism
invariance is simultaneously reduced to spatial translations. The unification
of the results of the related gauge fixing conditions leads to the gauge
generators correlation. Consequently, these conditions become solvable by
constant variables; hence the reduced constraints become globally satisfied and
vanish identically. By rigorously satisfying the reduced gauge symmetries, the
resulting cosmological model is precisely the limit of the gravitational theory
expressed in terms of holonomies and fluxes. Moreover, the obtained Hamiltonian
constraint is finite (without any cut-off introduction) and as rigorous as an
approximation of a Lie group by its representation. Furthermore, it has the
form of the sum over elementary cuboidal cells. Finally, the simple structure
of its homogeneities and anisotropies should allow to describe the quantum
cosmological evolution of the Universe in terms of transition amplitudes,
instead of using perturbative approximations.
|
[
{
"created": "Wed, 6 Jan 2021 19:00:11 GMT",
"version": "v1"
},
{
"created": "Wed, 26 May 2021 20:53:34 GMT",
"version": "v2"
}
] |
2021-05-28
|
[
[
"Bilski",
"Jakub",
""
]
] |
This article presents the lattice-smeared gravity phase space reduction defined by the cosmological gauge-fixing conditions. These conditions are specified to reduce the SU(2) symmetry and the spatial diffeomorphism invariance of the loop quantum gravity's Fock space, known as the spin network. The internal symmetry is fixed to the Abelian case and the diffeomorphism invariance is simultaneously reduced to spatial translations. The unification of the results of the related gauge fixing conditions leads to the gauge generators correlation. Consequently, these conditions become solvable by constant variables; hence the reduced constraints become globally satisfied and vanish identically. By rigorously satisfying the reduced gauge symmetries, the resulting cosmological model is precisely the limit of the gravitational theory expressed in terms of holonomies and fluxes. Moreover, the obtained Hamiltonian constraint is finite (without any cut-off introduction) and as rigorous as an approximation of a Lie group by its representation. Furthermore, it has the form of the sum over elementary cuboidal cells. Finally, the simple structure of its homogeneities and anisotropies should allow to describe the quantum cosmological evolution of the Universe in terms of transition amplitudes, instead of using perturbative approximations.
|
2207.03474
|
Boris Kruglikov
|
Boris Kruglikov, Wijnand Steneker
|
Killing Tensors in Koutras-McIntosh Spacetimes
| null | null |
10.1088/1361-6382/ac9509
| null |
gr-qc math-ph math.DG math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The Koutras-McIntosh family of metrics include conformally flat pp-waves and
the Wils metric. It appeared in a paper of 1996 by Koutras-McIntosh as an
example of a pure radiation spacetime without scalar curvature invariants or
infinitesimal symmetries. Here we demonstrate that these metrics have no
"hidden symmetries", by which we mean Killing tensors of low degrees. For the
particular case of Wils metrics we show the nonexistence of Killing tensors up
to degree 6.
The technique we use is the geometric theory of overdetermined PDEs and the
Cartan prolongation-projection method. Application of those allows to prove the
nonexistence of polynomial in momenta integrals for the equation of geodesics
in a mathematical rigorous way. Using the same technique we can completely
classify all lower degree Killing tensors and, in particular, prove that for
generic pp-waves all Killing tensors of degree 3 and 4 are reducible.
|
[
{
"created": "Thu, 7 Jul 2022 17:55:57 GMT",
"version": "v1"
}
] |
2022-12-07
|
[
[
"Kruglikov",
"Boris",
""
],
[
"Steneker",
"Wijnand",
""
]
] |
The Koutras-McIntosh family of metrics include conformally flat pp-waves and the Wils metric. It appeared in a paper of 1996 by Koutras-McIntosh as an example of a pure radiation spacetime without scalar curvature invariants or infinitesimal symmetries. Here we demonstrate that these metrics have no "hidden symmetries", by which we mean Killing tensors of low degrees. For the particular case of Wils metrics we show the nonexistence of Killing tensors up to degree 6. The technique we use is the geometric theory of overdetermined PDEs and the Cartan prolongation-projection method. Application of those allows to prove the nonexistence of polynomial in momenta integrals for the equation of geodesics in a mathematical rigorous way. Using the same technique we can completely classify all lower degree Killing tensors and, in particular, prove that for generic pp-waves all Killing tensors of degree 3 and 4 are reducible.
|
0901.2400
|
Lau Loi So
|
Lau Loi So and James M. Nester
|
New positive small vacuum region gravitational energy expressions
|
4 pages
|
Phys.Rev.D79:084028,2009
|
10.1103/PhysRevD.79.084028
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We construct an infinite number of new holonomic quasi-local gravitational
energy-momentum density pseudotensors with good limits asymptotically and in
small regions, both materially and in vacuum. For small vacuum regions they are
all a positive multiple of the Bel-Robinson tensor and consequently have
positive energy.
|
[
{
"created": "Fri, 16 Jan 2009 06:15:31 GMT",
"version": "v1"
}
] |
2010-04-14
|
[
[
"So",
"Lau Loi",
""
],
[
"Nester",
"James M.",
""
]
] |
We construct an infinite number of new holonomic quasi-local gravitational energy-momentum density pseudotensors with good limits asymptotically and in small regions, both materially and in vacuum. For small vacuum regions they are all a positive multiple of the Bel-Robinson tensor and consequently have positive energy.
|
1507.00901
|
Ujjal Debnath
|
Ujjal Debnath
|
Entropy Bound of Horizons for Accelerating, Rotating and Charged
Plebanski-Demianski Black Hole
|
6 pages
| null |
10.1016/j.aop.2016.06.014
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We first review the accelerating, rotating and charged Plebanski-Demianski
(PD) black hole, which includes the Kerr-Newman rotating black hole and the
Taub-NUT spacetime. The main feature of this black hole is that it has 4
horizons like event horizon, Cauchy horizon and two accelerating horizons. In
the non-extremal case, the surface area, entropy, surface gravity, temperature,
angular velocity, Komar energy and irreducible mass on the event horizon and
Cauchy horizon are presented for PD black hole. The entropy product,
temperature product, Komar energy product and irreducible mass product are
found for event horizon and Cauchy horizon. Also their sums are also found for
both horizons. All these relations are found to be depend on mass of the PD
black hole and other parameters. So all the products are not universal for PD
black hole. The entropy and area bounds for two horizons are investigated. Also
we found the Christodoulou-Ruffini mass for extremal PD black hole. Finally,
using first law of thermodynamics, we also found the Smarr relation for PD
black hole.
|
[
{
"created": "Thu, 2 Jul 2015 13:00:53 GMT",
"version": "v1"
}
] |
2016-08-03
|
[
[
"Debnath",
"Ujjal",
""
]
] |
We first review the accelerating, rotating and charged Plebanski-Demianski (PD) black hole, which includes the Kerr-Newman rotating black hole and the Taub-NUT spacetime. The main feature of this black hole is that it has 4 horizons like event horizon, Cauchy horizon and two accelerating horizons. In the non-extremal case, the surface area, entropy, surface gravity, temperature, angular velocity, Komar energy and irreducible mass on the event horizon and Cauchy horizon are presented for PD black hole. The entropy product, temperature product, Komar energy product and irreducible mass product are found for event horizon and Cauchy horizon. Also their sums are also found for both horizons. All these relations are found to be depend on mass of the PD black hole and other parameters. So all the products are not universal for PD black hole. The entropy and area bounds for two horizons are investigated. Also we found the Christodoulou-Ruffini mass for extremal PD black hole. Finally, using first law of thermodynamics, we also found the Smarr relation for PD black hole.
|
1806.01648
|
Wolfgang Muschik
|
Wolfgang Muschik
|
Entropy Identity inducing Non-Equilibrium Thermodynamics of Relativistic
Multi-Component Systems and their Newtonian Limits
|
arXiv admin note: text overlap with arXiv:1701.04103
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Non-equilibrium and equilibrium thermodynamics of an interacting component in
a special-relativistic multi-component system is discussed by use of an entropy
identity. The special case of the corresponding free component is considered.
Equilibrium conditions and especially the multi-component Killing relation of
the 4-temperature are discussed. Two axioms characterize the mixture:
additivity of the energy momentum tensors and of the 4-entropies of the
components generating those of the mixture. The resulting quantities of a
component and of the mixture, energy, energy flux, momentum flux, stress
tensor, entropy, entropy flux, supply and production and their Newtonian limits
in zeroth approximation are derived.
|
[
{
"created": "Sun, 3 Jun 2018 09:25:56 GMT",
"version": "v1"
}
] |
2018-06-06
|
[
[
"Muschik",
"Wolfgang",
""
]
] |
Non-equilibrium and equilibrium thermodynamics of an interacting component in a special-relativistic multi-component system is discussed by use of an entropy identity. The special case of the corresponding free component is considered. Equilibrium conditions and especially the multi-component Killing relation of the 4-temperature are discussed. Two axioms characterize the mixture: additivity of the energy momentum tensors and of the 4-entropies of the components generating those of the mixture. The resulting quantities of a component and of the mixture, energy, energy flux, momentum flux, stress tensor, entropy, entropy flux, supply and production and their Newtonian limits in zeroth approximation are derived.
|
1612.05856
|
Deng Wang
|
Deng Wang
|
Model-independent traversable wormholes from baryon acoustic
oscillations
|
Minor revision. Published in Physics of the Dark Universe
| null |
10.1016/j.dark.2023.101306
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we investigate the model-independent traversable wormholes
from baryon acoustic oscillations. Firstly, we place the statistical
constraints on the average dark energy equation of state $\omega_{av}$ by only
using BAO data. Subsequently, two specific wormhole solutions are obtained,
i.e, the cases of the constant redshift function and a special choice for the
shape function. For the first case, we analyze the traversabilities of the
wormhole configuration, and for the second case, we find that one can construct
theoretically a traversable wormhole with infinitesimal amounts of average null
energy condition violating phantom fluid. Furthermore, we perform the stability
analysis for the first case, and find that the stable equilibrium
configurations may increase for increasing values of the throat radius of the
wormhole in the cases of a positive and a negative surface energy density. It
is worth noting that the obtained wormhole solutions are static and spherically
symmetrical metric, and that we assume $\omega_{av}$ to be a constant between
different redshifts when placing constraints, hence, these wormhole solutions
can be interpreted as stable and static phantom wormholes configurations at
some certain redshift which lies in the range [0.32, 2.34].
|
[
{
"created": "Sun, 18 Dec 2016 04:59:28 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Aug 2023 17:31:23 GMT",
"version": "v2"
}
] |
2023-08-07
|
[
[
"Wang",
"Deng",
""
]
] |
In this paper, we investigate the model-independent traversable wormholes from baryon acoustic oscillations. Firstly, we place the statistical constraints on the average dark energy equation of state $\omega_{av}$ by only using BAO data. Subsequently, two specific wormhole solutions are obtained, i.e, the cases of the constant redshift function and a special choice for the shape function. For the first case, we analyze the traversabilities of the wormhole configuration, and for the second case, we find that one can construct theoretically a traversable wormhole with infinitesimal amounts of average null energy condition violating phantom fluid. Furthermore, we perform the stability analysis for the first case, and find that the stable equilibrium configurations may increase for increasing values of the throat radius of the wormhole in the cases of a positive and a negative surface energy density. It is worth noting that the obtained wormhole solutions are static and spherically symmetrical metric, and that we assume $\omega_{av}$ to be a constant between different redshifts when placing constraints, hence, these wormhole solutions can be interpreted as stable and static phantom wormholes configurations at some certain redshift which lies in the range [0.32, 2.34].
|
0706.4413
|
Mayeul Arminjon
|
Mayeul Arminjon
|
Quantum wave equations in curved space-time from wave mechanics
|
3 pages in 12pt LaTeX. Text of a talk given at the conference
"Symmetry and Perturbation Theory", 2-9 June 2007, Otranto (Italy). Submitted
to the Proceedings (G. Gaeta and Raff. Vitolo, eds, World Scientific)
| null |
10.1142/9789812776174_0031
| null |
gr-qc
| null |
Alternative versions of the Klein-Gordon and Dirac equations in a curved
spacetime are got by applying directly the classical-quantum correspondence.
|
[
{
"created": "Fri, 29 Jun 2007 14:00:36 GMT",
"version": "v1"
}
] |
2016-11-23
|
[
[
"Arminjon",
"Mayeul",
""
]
] |
Alternative versions of the Klein-Gordon and Dirac equations in a curved spacetime are got by applying directly the classical-quantum correspondence.
|
2012.09245
|
Vinicius Medeiros Gomes Da Silveira
|
V. M. G. Silveira, C. A. Z. Vasconcellos, E. G. S. Luna and D.
Hadjimichef
|
Matter-antimatter asymmetry and non-inertial effects
|
15 pages, 1 table, 4 figures
|
J. High Energy Phys. 2021, 285 (2021)
|
10.1007/JHEP03(2021)285
| null |
gr-qc hep-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We investigate non-inertial effects on $CP$-violating processes using a
model, based on the framework of quantum field theory in curved spacetimes,
devised to account for the decay of accelerated particles. We show that the
$CP$ violation parameter for the decay of accelerated kaons into two pions
decreases very slightly as very high accelerations are achieved, implying
decreased asymmetry between matter and antimatter in this regime. We discuss
the relationship between these results and cosmological processes surrounding
matter-antimatter asymmetry and argue that, due to the connection between
non-inertial and thermal phenomena established by the Unruh effect, this kind
of computation may prove useful in furthering the understanding of
thermodynamical effects in curved spacetimes.
|
[
{
"created": "Wed, 16 Dec 2020 20:19:52 GMT",
"version": "v1"
}
] |
2021-04-13
|
[
[
"Silveira",
"V. M. G.",
""
],
[
"Vasconcellos",
"C. A. Z.",
""
],
[
"Luna",
"E. G. S.",
""
],
[
"Hadjimichef",
"D.",
""
]
] |
We investigate non-inertial effects on $CP$-violating processes using a model, based on the framework of quantum field theory in curved spacetimes, devised to account for the decay of accelerated particles. We show that the $CP$ violation parameter for the decay of accelerated kaons into two pions decreases very slightly as very high accelerations are achieved, implying decreased asymmetry between matter and antimatter in this regime. We discuss the relationship between these results and cosmological processes surrounding matter-antimatter asymmetry and argue that, due to the connection between non-inertial and thermal phenomena established by the Unruh effect, this kind of computation may prove useful in furthering the understanding of thermodynamical effects in curved spacetimes.
|
2407.21380
|
Azwar Sutiono
|
Azwar Sutiono, Agus Suroso, Freddy Permana Zen
|
Dynamical System Analysis Of Chameleon Mechanism in Brans-Dicke
Scalar-Tensor Model
|
22 pages, 5 figures, Published in International Journal of
Theoretical Physics, Volume 63, article number 187, (2024)
|
Int. J. Theor. Phys. 63, 187 (2024)
|
10.1007/s10773-024-05726-4
| null |
gr-qc hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
We investigated the stability of the chameleon screening mechanism in the
Brans-Dicke scalar-tensor model. We define a constraint on the Brans-Dicke
parameter $\omega_{BD}^*$ identifying two stability groups,
$\omega_{BD}>\omega_{BD}^*$ and $0<\omega_{BD}<\omega_{BD}^*$. The first group
achieves stability with both appropriate eigenvalues and a density profile
consistent with dark energy dominance. The second exhibits eigenvalue stability
but contradicts conditions for a stable universe. We explore the impact of
variations in the scalar field potential and matter coupling by analyzing
different parameter sets. Each unique set of parameters results in a distinct
$\omega_{BD}^*$. Dynamic analysis reveals that stability is achieved when the
scalar field dominates, highlighting the importance of the kinetic and
potential terms while minimizing the influence of matter density. In high
matter density regions, the scalar field's negligible presence aligns with
standard gravitational behavior, whereas in low matter density regions, the
scalar field grows exponentially, driving dark energy and cosmic acceleration.
|
[
{
"created": "Wed, 31 Jul 2024 07:11:38 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Aug 2024 10:04:17 GMT",
"version": "v2"
}
] |
2024-08-06
|
[
[
"Sutiono",
"Azwar",
""
],
[
"Suroso",
"Agus",
""
],
[
"Zen",
"Freddy Permana",
""
]
] |
We investigated the stability of the chameleon screening mechanism in the Brans-Dicke scalar-tensor model. We define a constraint on the Brans-Dicke parameter $\omega_{BD}^*$ identifying two stability groups, $\omega_{BD}>\omega_{BD}^*$ and $0<\omega_{BD}<\omega_{BD}^*$. The first group achieves stability with both appropriate eigenvalues and a density profile consistent with dark energy dominance. The second exhibits eigenvalue stability but contradicts conditions for a stable universe. We explore the impact of variations in the scalar field potential and matter coupling by analyzing different parameter sets. Each unique set of parameters results in a distinct $\omega_{BD}^*$. Dynamic analysis reveals that stability is achieved when the scalar field dominates, highlighting the importance of the kinetic and potential terms while minimizing the influence of matter density. In high matter density regions, the scalar field's negligible presence aligns with standard gravitational behavior, whereas in low matter density regions, the scalar field grows exponentially, driving dark energy and cosmic acceleration.
|
2106.07121
|
James Quach Dr
|
Salman Sajad Wani, James Q. Quach, Mir Faizal
|
Time Fisher Information associated with Fluctuations in Quantum Geometry
|
12 pages
|
Europhys. Lett. 139, 6, 62002 (2022)
| null | null |
gr-qc quant-ph
|
http://creativecommons.org/licenses/by/4.0/
|
As time is not an observable, we use Fisher information (FI) to address the
problem of time. We show that the Hamiltonian constraint operator cannot be
used to analyze any quantum process for quantum geometries that are associated
with time-reparametrization invariant classical geometries. This is because the
Hamiltonian constraint does not contain FI about time. We demonstrate that
although the Hamiltonian operator is the generator of time, the Hamiltonian
constraint operator can not observe the change that arises through the passage
of time. This means that the problem of time is inescapably problematic in the
associated quantum gravitational theories. Although we explicitly derive these
results on the world-sheet of bosonic strings, we argue that it holds in
general. We also identify an operator on the world-sheet which contains FI
about time in a string theoretical processes. Motivated by this observation, we
propose that a criteria for a meaningful operator of any quantum gravitational
process, is that it should contain non-vanishing FI about time.
|
[
{
"created": "Mon, 14 Jun 2021 00:56:41 GMT",
"version": "v1"
}
] |
2022-09-27
|
[
[
"Wani",
"Salman Sajad",
""
],
[
"Quach",
"James Q.",
""
],
[
"Faizal",
"Mir",
""
]
] |
As time is not an observable, we use Fisher information (FI) to address the problem of time. We show that the Hamiltonian constraint operator cannot be used to analyze any quantum process for quantum geometries that are associated with time-reparametrization invariant classical geometries. This is because the Hamiltonian constraint does not contain FI about time. We demonstrate that although the Hamiltonian operator is the generator of time, the Hamiltonian constraint operator can not observe the change that arises through the passage of time. This means that the problem of time is inescapably problematic in the associated quantum gravitational theories. Although we explicitly derive these results on the world-sheet of bosonic strings, we argue that it holds in general. We also identify an operator on the world-sheet which contains FI about time in a string theoretical processes. Motivated by this observation, we propose that a criteria for a meaningful operator of any quantum gravitational process, is that it should contain non-vanishing FI about time.
|
0910.1307
|
Norman Cruz
|
Norman Cruz, Samuel Lepe, and Francisco Pena
|
The coincidence problem in the scenario of dark energy interacting with
two fluids
|
14 pages
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A cosmological model of dark energy interacting with dark matter and another
general component of the universe is considered. The evolution equations for
coincidence parameters r and s, which represent the ratios between the dark
energy and the matter and the other cosmic fluid, respectively, are analyzed in
terms of the stability of stationary solutions. The obtained general results
allow to shed some light on the coincidence problem and in the equations of
state of the three interacting fluids, due to the constraints imposes by the
stability of the solutions. We found that for an interaction proportional to
the sum of the DE density and the third fluid density, the hypothetical fluid
must have positive pressure, which leads naturally to a cosmological scenario
with radiation, unparticle or even some form of warm DM as the third
interacting fluid.
|
[
{
"created": "Wed, 7 Oct 2009 16:27:22 GMT",
"version": "v1"
}
] |
2009-10-08
|
[
[
"Cruz",
"Norman",
""
],
[
"Lepe",
"Samuel",
""
],
[
"Pena",
"Francisco",
""
]
] |
A cosmological model of dark energy interacting with dark matter and another general component of the universe is considered. The evolution equations for coincidence parameters r and s, which represent the ratios between the dark energy and the matter and the other cosmic fluid, respectively, are analyzed in terms of the stability of stationary solutions. The obtained general results allow to shed some light on the coincidence problem and in the equations of state of the three interacting fluids, due to the constraints imposes by the stability of the solutions. We found that for an interaction proportional to the sum of the DE density and the third fluid density, the hypothetical fluid must have positive pressure, which leads naturally to a cosmological scenario with radiation, unparticle or even some form of warm DM as the third interacting fluid.
|
1003.2786
|
Rong-Jia Yang
|
Xiang-Ting Gao and Rong-Jia Yang
|
Geometrical diagnostic for purely kinetic k-essence dark energy
|
4 pages, 4 figures, to appear in PLB, minimal errors are corrected
|
Phys.Lett.B687:99-102,2010
|
10.1016/j.physletb.2010.03.047
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Geometrical diagnostic, involving the statefinder $\{r,s\}$ and $Om(x)$, is
widely used to discriminate different dark energy models. We apply the
statefinder $\{r,s\}$ and $Om(x)$ to purely kinetic k-essence dark energy model
with Dirac-Born-Infeld-like Lagrangian which can be considered as scalar field
realizations of Chaplygin gas. We plot the evolution trajectories of this model
in the statefinder parameter-planes and $Om(x)$ parameter-plane. We find that
the statefinder $\{r,s\}$ and $Om(x)$ fail to distinguish purely kinetic
k-essence model from $\Lambda$CDM model at 68.3% confidence level for $z\ll 1$.
|
[
{
"created": "Sun, 14 Mar 2010 13:17:35 GMT",
"version": "v1"
},
{
"created": "Sun, 21 Mar 2010 12:38:44 GMT",
"version": "v2"
}
] |
2010-04-30
|
[
[
"Gao",
"Xiang-Ting",
""
],
[
"Yang",
"Rong-Jia",
""
]
] |
Geometrical diagnostic, involving the statefinder $\{r,s\}$ and $Om(x)$, is widely used to discriminate different dark energy models. We apply the statefinder $\{r,s\}$ and $Om(x)$ to purely kinetic k-essence dark energy model with Dirac-Born-Infeld-like Lagrangian which can be considered as scalar field realizations of Chaplygin gas. We plot the evolution trajectories of this model in the statefinder parameter-planes and $Om(x)$ parameter-plane. We find that the statefinder $\{r,s\}$ and $Om(x)$ fail to distinguish purely kinetic k-essence model from $\Lambda$CDM model at 68.3% confidence level for $z\ll 1$.
|
1704.00388
|
Stephen Adler
|
Stephen L. Adler
|
Implications of a frame dependent gravitational effective action for
perturbations on the Robertson-Walker Metric
|
Latex, 18 pages; v3 has typos corrected, revision of Sec. 5, added
Appendices D and E; v5 is final published version
|
International Journal of Modern Physics D 26 (2017) 1750159
|
10.1142/S0218271817501590
| null |
gr-qc astro-ph.CO hep-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In earlier work we showed that a frame dependent effective action motivated
by the postulates of three-space general coordinate invariance and Weyl scaling
invariance exactly mimics a cosmological constant in Robertson-Walker (RW)
spacetimes. Here we study the implications of this effective action for small
fluctuations around a spatially flat RW background geometry. The equations for
the conserving extension of the modified stress-energy tensor can be integrated
in closed form, and involve only the metric perturbation $h_{00}$. Hence the
equations for tensor and vector perturbations are unmodified, but there are
Hubble scale additions to the scalar perturbation equations, which nonetheless
admit no propagating wave solutions. Consequently, there are no modifications
to standard gravitational wave propagation theory, but there may be observable
implications for cosmology. We give a self-contained discussion, including an
analysis of the restricted class of gauge transformations that act when a frame
dependent effective action is present.
|
[
{
"created": "Sun, 2 Apr 2017 23:33:24 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Apr 2017 21:15:12 GMT",
"version": "v2"
},
{
"created": "Wed, 31 May 2017 16:34:42 GMT",
"version": "v3"
},
{
"created": "Sat, 8 Jul 2017 17:59:24 GMT",
"version": "v4"
},
{
"created": "Thu, 27 Jul 2017 23:27:44 GMT",
"version": "v5"
}
] |
2018-01-10
|
[
[
"Adler",
"Stephen L.",
""
]
] |
In earlier work we showed that a frame dependent effective action motivated by the postulates of three-space general coordinate invariance and Weyl scaling invariance exactly mimics a cosmological constant in Robertson-Walker (RW) spacetimes. Here we study the implications of this effective action for small fluctuations around a spatially flat RW background geometry. The equations for the conserving extension of the modified stress-energy tensor can be integrated in closed form, and involve only the metric perturbation $h_{00}$. Hence the equations for tensor and vector perturbations are unmodified, but there are Hubble scale additions to the scalar perturbation equations, which nonetheless admit no propagating wave solutions. Consequently, there are no modifications to standard gravitational wave propagation theory, but there may be observable implications for cosmology. We give a self-contained discussion, including an analysis of the restricted class of gauge transformations that act when a frame dependent effective action is present.
|
1203.5867
|
Hongwei Yu
|
Wenting Zhou, Hongwei Yu
|
Spontaneous excitation of a static multilevel atom coupled with
electromagnetic vacuum fluctuations in Schwarzschild spacetime
|
21 pages, no figures
|
Class. Quantum Grav. 29 (2012) 085003
|
10.1088/0264-9381/29/8/085003
| null |
gr-qc physics.atom-ph quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the spontaneous excitation of a radially polarized static multilevel
atom outside a spherically symmetric black hole in multi-polar interaction with
quantum electromagnetic fluctuations in the Boulware, Unruh and Hartle-Hawking
vacuum states. We find that spontaneous excitation does not occur in the
Boulware vacuum, and, in contrast to the scalar field case, spontaneous
emission rate is not well-behaved at the event horizon as result of the blow-up
of the proper acceleration of the static atom. However, spontaneous excitation
can take place both in the Unruh and the Hartle-Hawking vacua as if there were
thermal radiation from the black hole. Distinctive features in contrast to the
scalar field case are the existence of a term proportional to the proper
acceleration squared in the rate of change of the mean atomic energy in the
Unruh and the Hartle-Hawking vacuums and the structural similarity in the
spontaneous excitation rate between the static atoms outside a black hole and
uniformly accelerated ones in a flat space with a reflecting boundary, which is
particularly dramatic at the event horizon where a complete equivalence exists.
|
[
{
"created": "Tue, 27 Mar 2012 04:19:54 GMT",
"version": "v1"
}
] |
2012-03-28
|
[
[
"Zhou",
"Wenting",
""
],
[
"Yu",
"Hongwei",
""
]
] |
We study the spontaneous excitation of a radially polarized static multilevel atom outside a spherically symmetric black hole in multi-polar interaction with quantum electromagnetic fluctuations in the Boulware, Unruh and Hartle-Hawking vacuum states. We find that spontaneous excitation does not occur in the Boulware vacuum, and, in contrast to the scalar field case, spontaneous emission rate is not well-behaved at the event horizon as result of the blow-up of the proper acceleration of the static atom. However, spontaneous excitation can take place both in the Unruh and the Hartle-Hawking vacua as if there were thermal radiation from the black hole. Distinctive features in contrast to the scalar field case are the existence of a term proportional to the proper acceleration squared in the rate of change of the mean atomic energy in the Unruh and the Hartle-Hawking vacuums and the structural similarity in the spontaneous excitation rate between the static atoms outside a black hole and uniformly accelerated ones in a flat space with a reflecting boundary, which is particularly dramatic at the event horizon where a complete equivalence exists.
|
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