id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1909.03832 | Muhammad Asad Saeed Asad | Muhammad Asad Saeed, Ifra Noureen | Effect of Electromagnetism upon the Collapse of Cylindrical Symmetric
Stars in f(R; T) Gravity | 15 Pages, we want to make some fundamental changes in this work and
re-submit it soon | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By the end of the evaluation of this research artifact, readers would be able
to describe the effect of conducted plasma on evolution of stellar objects. In
this script, we have analyzed the stability of charged cylindrically symmetric
stellar objects in the context of f(R; T) theory of gravity. We have fabricated
field equations and their conforming dynamical equations and then we have used
perturbation scheme for additional analysis. Adiabatic index {\Gamma} has been
used to sort inequalities in the Newtonian and the post Newtonian regimes. At
the end we caught some extra limitations due to which we have concluded that
effect of charge on star upsurges its instability
| [
{
"created": "Fri, 6 Sep 2019 14:06:34 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Oct 2019 11:56:34 GMT",
"version": "v2"
}
] | 2019-10-28 | [
[
"Saeed",
"Muhammad Asad",
""
],
[
"Noureen",
"Ifra",
""
]
] | By the end of the evaluation of this research artifact, readers would be able to describe the effect of conducted plasma on evolution of stellar objects. In this script, we have analyzed the stability of charged cylindrically symmetric stellar objects in the context of f(R; T) theory of gravity. We have fabricated field equations and their conforming dynamical equations and then we have used perturbation scheme for additional analysis. Adiabatic index {\Gamma} has been used to sort inequalities in the Newtonian and the post Newtonian regimes. At the end we caught some extra limitations due to which we have concluded that effect of charge on star upsurges its instability |
1711.06321 | Mohd Shahalam | Abhineet Agarwal, R. Myrzakulov, S. K. J. Pacif, M. Shahalam | Cosmic acceleration from coupling of baryonic and dark matter
components: Analysis and diagnostics | 15 pages, 5 figures | International Journal of Modern Physics D, 28 (2019) 1950083 | 10.1142/S0218271819500834 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we examine a scenario in which late-time cosmic acceleration
might arise due to the coupling between baryonic matter and dark matter without
the presence of extra degrees of freedom. In this case, one can obtain
late-time acceleration in Jordan frame and not in Einstein frame. We consider
two different forms of parametrization of the coupling function, and put
constraints on the model parameters by using an integrated datasets of Hubble
parameter, Type Ia supernova and baryon acoustic oscillations. The models under
consideration are consistent with the observations. In addition, we perform the
statefinder and $Om$ diagnostics, and show that the models exhibit a
distinctive behavior due to the phantom characteristic in future which is a
generic feature of the underlying scenario.
| [
{
"created": "Mon, 13 Nov 2017 09:37:45 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Apr 2019 05:17:34 GMT",
"version": "v2"
}
] | 2022-07-20 | [
[
"Agarwal",
"Abhineet",
""
],
[
"Myrzakulov",
"R.",
""
],
[
"Pacif",
"S. K. J.",
""
],
[
"Shahalam",
"M.",
""
]
] | In this paper, we examine a scenario in which late-time cosmic acceleration might arise due to the coupling between baryonic matter and dark matter without the presence of extra degrees of freedom. In this case, one can obtain late-time acceleration in Jordan frame and not in Einstein frame. We consider two different forms of parametrization of the coupling function, and put constraints on the model parameters by using an integrated datasets of Hubble parameter, Type Ia supernova and baryon acoustic oscillations. The models under consideration are consistent with the observations. In addition, we perform the statefinder and $Om$ diagnostics, and show that the models exhibit a distinctive behavior due to the phantom characteristic in future which is a generic feature of the underlying scenario. |
1209.3565 | Sujoy Modak | Sujoy Kumar Modak | Thermodynamics of Black Holes: Semi-Classical Approaches and Beyond | Ph.D. thesis, 152 pages (including the front matter) ; Supervisor:
Rabin Banerjee ; Institution: S.N. Bose National Centre for Basic Sciences,
Kolkata, India ; Degree awarded on August 24, 2012 from University of
Calcutta, Kolkata, India | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This thesis is focussed to study various aspects of black hole physics. Our
approach is a semi-classical type, where the spacetime geometry of black holes
is considered to be classical but the fields moving in the background are
quantum in nature. Some notable facets of this thesis are the following. We
start by looking into the issue of generalized Smarr mass formula for arbitrary
dimensional black holes in Einstein-Maxwell gravity. We derive this formula for
these black holes and also demonstrate that such a formula can be expressed in
the form of a dimension independent identity $K_{\chi^{\mu}}=2ST$ (where the
l.h.s is the Komar conserved charge corresponding to the null Killing vector
$\chi^{\mu}$ and in the r.h.s $S, T$ are the semi-classical entropy and
temperature of a black hole) defined at the black hole event horizon. We
highlight the role of exact differentials in computations involving black hole
thermodynamics. Some results like the first law of black hole thermodynamics
and semi-classical entropy are obtained without using the laws of black hole
mechanics as usually done. The blackbody (Hawking) radiation spectrum for
higher dimensional black holes is computed by using a density matrix technique
of tunneling mechanism by considering both event and cosmological horizons. We
also provide the modifications to the semi-classical Hawking temperature and
Bekenstein-Hawking entropy due to various effects. These modifications are
mainly found due to higher order (in $\hbar$) effects to the WKB ansatz used
for the quantum tunneling formalism and non-commutative gravity inspired
effects. Finally, in we discuss phase transition phenomena in black holes. We
formulate a new methodology based on Clausius-Clapeyron and Ehrenfest's
equations to exhibit and classify phase transitions in black holes in analogy
to what is done in standard thermodynamics.
| [
{
"created": "Mon, 17 Sep 2012 07:37:55 GMT",
"version": "v1"
}
] | 2012-09-18 | [
[
"Modak",
"Sujoy Kumar",
""
]
] | This thesis is focussed to study various aspects of black hole physics. Our approach is a semi-classical type, where the spacetime geometry of black holes is considered to be classical but the fields moving in the background are quantum in nature. Some notable facets of this thesis are the following. We start by looking into the issue of generalized Smarr mass formula for arbitrary dimensional black holes in Einstein-Maxwell gravity. We derive this formula for these black holes and also demonstrate that such a formula can be expressed in the form of a dimension independent identity $K_{\chi^{\mu}}=2ST$ (where the l.h.s is the Komar conserved charge corresponding to the null Killing vector $\chi^{\mu}$ and in the r.h.s $S, T$ are the semi-classical entropy and temperature of a black hole) defined at the black hole event horizon. We highlight the role of exact differentials in computations involving black hole thermodynamics. Some results like the first law of black hole thermodynamics and semi-classical entropy are obtained without using the laws of black hole mechanics as usually done. The blackbody (Hawking) radiation spectrum for higher dimensional black holes is computed by using a density matrix technique of tunneling mechanism by considering both event and cosmological horizons. We also provide the modifications to the semi-classical Hawking temperature and Bekenstein-Hawking entropy due to various effects. These modifications are mainly found due to higher order (in $\hbar$) effects to the WKB ansatz used for the quantum tunneling formalism and non-commutative gravity inspired effects. Finally, in we discuss phase transition phenomena in black holes. We formulate a new methodology based on Clausius-Clapeyron and Ehrenfest's equations to exhibit and classify phase transitions in black holes in analogy to what is done in standard thermodynamics. |
2305.00401 | Dana Jones | Dana Jones, Ling Sun, Nils Siemonsen, William E. East, Susan M. Scott,
Karl Wette | Methods and prospects for gravitational wave searches targeting
ultralight vector boson clouds around known black holes | 21 pages, 12 figures | null | 10.1103/PhysRevD.108.064001 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Ultralight bosons are predicted in many extensions to the Standard Model and
are popular dark matter candidates. The black hole superradiance mechanism
allows for these particles to be probed using only their gravitational
interaction. In this scenario, an ultralight boson cloud may form spontaneously
around a spinning black hole and extract a non-negligible fraction of the black
hole's mass. These oscillating clouds produce quasi-monochromatic,
long-duration gravitational waves that may be detectable by ground-based or
space-based gravitational wave detectors. We discuss the capability of a new
long-duration signal tracking method, based on a hidden Markov model, to detect
gravitational wave signals generated by ultralight vector boson clouds,
including cases where the signal frequency evolution timescale is much shorter
than that of a typical continuous wave signal. We quantify the detection
horizon distances for vector boson clouds with current- and next-generation
ground-based detectors. We demonstrate that vector clouds hosted by black holes
with mass $\gtrsim 60 M_{\odot}$ and spin $\gtrsim 0.6$ are within the reach of
current-generation detectors up to a luminosity distance of $\sim 1$ Gpc. This
search method enables one to target vector boson clouds around remnant black
holes from compact binary mergers detected by gravitational-wave detectors. We
discuss the impact of the sky localization of the merger events and demonstrate
that a typical remnant black hole reasonably well-localized by the current
generation detector network is accessible in a follow-up search.
| [
{
"created": "Sun, 30 Apr 2023 05:58:24 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Aug 2023 01:29:22 GMT",
"version": "v2"
}
] | 2023-10-26 | [
[
"Jones",
"Dana",
""
],
[
"Sun",
"Ling",
""
],
[
"Siemonsen",
"Nils",
""
],
[
"East",
"William E.",
""
],
[
"Scott",
"Susan M.",
""
],
[
"Wette",
"Karl",
""
]
] | Ultralight bosons are predicted in many extensions to the Standard Model and are popular dark matter candidates. The black hole superradiance mechanism allows for these particles to be probed using only their gravitational interaction. In this scenario, an ultralight boson cloud may form spontaneously around a spinning black hole and extract a non-negligible fraction of the black hole's mass. These oscillating clouds produce quasi-monochromatic, long-duration gravitational waves that may be detectable by ground-based or space-based gravitational wave detectors. We discuss the capability of a new long-duration signal tracking method, based on a hidden Markov model, to detect gravitational wave signals generated by ultralight vector boson clouds, including cases where the signal frequency evolution timescale is much shorter than that of a typical continuous wave signal. We quantify the detection horizon distances for vector boson clouds with current- and next-generation ground-based detectors. We demonstrate that vector clouds hosted by black holes with mass $\gtrsim 60 M_{\odot}$ and spin $\gtrsim 0.6$ are within the reach of current-generation detectors up to a luminosity distance of $\sim 1$ Gpc. This search method enables one to target vector boson clouds around remnant black holes from compact binary mergers detected by gravitational-wave detectors. We discuss the impact of the sky localization of the merger events and demonstrate that a typical remnant black hole reasonably well-localized by the current generation detector network is accessible in a follow-up search. |
2003.02257 | Tiberiu Harko | Tiberiu Harko, Haidar Sheikhahmadi | Irreversible thermodynamical description of warm inflationary
cosmological models | 33 pages, 22 figures, accepted for publication in Physics of the Dark
Universe | Physics of the Dark Universe 28, 100521 (2020) | 10.1016/j.dark.2020.100521 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the interaction between scalar fields and radiation in the
framework of warm inflationary models by using the irreversible thermodynamics
of open systems with matter creation/annihilation. We consider the scalar
fields and radiation as an interacting two component cosmological fluid in a
homogeneous, spatially flat and isotropic Friedmann-Robertson-Walker (FRW)
Universe. The thermodynamics of open systems as applied together with the
gravitational field equations to the two component cosmological fluid leads to
a generalization of the elementary scalar field-radiation interaction model,
which is the theoretical basis of warm inflationary models, with the decay
(creation) pressures explicitly considered as parts of the cosmological fluid
energy-momentum tensor. Specific models describing coherently oscillating
scalar waves, scalar fields with a constant potential, and scalar fields with a
Higgs type potential are considered in detail. For each case exact and
numerical solutions of the gravitational field equations with scalar
field-radiation interaction are obtained, and they show the transition from an
accelerating inflationary phase to a decelerating one. The theoretical
predictions of the warm inflationary scenario with irreversible matter creation
are also compared in detail with the Planck 2018 observational data, and
constraints on the free parameters of the model are obtained.
| [
{
"created": "Wed, 4 Mar 2020 18:54:45 GMT",
"version": "v1"
}
] | 2020-05-19 | [
[
"Harko",
"Tiberiu",
""
],
[
"Sheikhahmadi",
"Haidar",
""
]
] | We investigate the interaction between scalar fields and radiation in the framework of warm inflationary models by using the irreversible thermodynamics of open systems with matter creation/annihilation. We consider the scalar fields and radiation as an interacting two component cosmological fluid in a homogeneous, spatially flat and isotropic Friedmann-Robertson-Walker (FRW) Universe. The thermodynamics of open systems as applied together with the gravitational field equations to the two component cosmological fluid leads to a generalization of the elementary scalar field-radiation interaction model, which is the theoretical basis of warm inflationary models, with the decay (creation) pressures explicitly considered as parts of the cosmological fluid energy-momentum tensor. Specific models describing coherently oscillating scalar waves, scalar fields with a constant potential, and scalar fields with a Higgs type potential are considered in detail. For each case exact and numerical solutions of the gravitational field equations with scalar field-radiation interaction are obtained, and they show the transition from an accelerating inflationary phase to a decelerating one. The theoretical predictions of the warm inflationary scenario with irreversible matter creation are also compared in detail with the Planck 2018 observational data, and constraints on the free parameters of the model are obtained. |
1507.00922 | Christian Pfeifer | Leonardo Barcaroli, Lukas K. Brunkhorst, Giulia Gubitosi, Niccol\'o
Loret, Christian Pfeifer | Hamilton geometry: Phase space geometry from modified dispersion
relations | 32 pages, section on quantisation of the theory added, comments on
additin of momenta on curved momentum spaces extended | Phys. Rev. D 92, 084053 (2015) | 10.1103/PhysRevD.92.084053 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe the Hamilton geometry of the phase space of particles whose
motion is characterised by general dispersion relations. In this framework
spacetime and momentum space are naturally curved and intertwined, allowing for
a simultaneous description of both spacetime curvature and non-trivial momentum
space geometry. We consider as explicit examples two models for Planck-scale
modified dispersion relations, inspired from the $q$-de Sitter and
$\kappa$-Poincar\'e quantum groups. In the first case we find the expressions
for the momentum and position dependent curvature of spacetime and momentum
space, while for the second case the manifold is flat and only the momentum
space possesses a nonzero, momentum dependent curvature. In contrast, for a
dispersion relation that is induced by a spacetime metric, as in General
Relativity, the Hamilton geometry yields a flat momentum space and the usual
curved spacetime geometry with only position dependent geometric objects.
| [
{
"created": "Fri, 3 Jul 2015 14:35:23 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Oct 2015 11:02:42 GMT",
"version": "v2"
}
] | 2015-11-04 | [
[
"Barcaroli",
"Leonardo",
""
],
[
"Brunkhorst",
"Lukas K.",
""
],
[
"Gubitosi",
"Giulia",
""
],
[
"Loret",
"Niccoló",
""
],
[
"Pfeifer",
"Christian",
""
]
] | We describe the Hamilton geometry of the phase space of particles whose motion is characterised by general dispersion relations. In this framework spacetime and momentum space are naturally curved and intertwined, allowing for a simultaneous description of both spacetime curvature and non-trivial momentum space geometry. We consider as explicit examples two models for Planck-scale modified dispersion relations, inspired from the $q$-de Sitter and $\kappa$-Poincar\'e quantum groups. In the first case we find the expressions for the momentum and position dependent curvature of spacetime and momentum space, while for the second case the manifold is flat and only the momentum space possesses a nonzero, momentum dependent curvature. In contrast, for a dispersion relation that is induced by a spacetime metric, as in General Relativity, the Hamilton geometry yields a flat momentum space and the usual curved spacetime geometry with only position dependent geometric objects. |
1902.01895 | Pankaj Saha | Debaprasad Maity and Pankaj Saha | Minimal plateau inflationary cosmologies and constraints from reheating | 27 pages, 8 figures. Matches Published version. (This work supersedes
the work: arXiv:1610.00173 [astro-ph.CO]) | Class. Quantum Grav. 36 045010 (2019) | 10.1088/1361-6382/ab0038 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With the growing consensus on simple power law inflation models not being
favored by the PLANCK observations, dynamics for the non-standard inflation
gain significant interest in the recent past. In this paper, we analyze in
detail a class of supergravity inspired phenomenological inflationary models
with non-polynomial potential based on Maity (Nucl.Phys. B919 (2017) 560), and
compare the model predictions with the currently most favored Starobinsky and
its generalized $\alpha$-attractor models in the ($n_s$ , $r$) plane
constrained by PLANCK. Importantly for a wide range of parameter space, our
model provides successful inflation in the sub-Planckian regime. We also have
performed model independent analysis of reheating in terms of the effective
equation of state parameter. In particular, we consider two stages of reheating
dynamics with generalized inflaton equation of state in the initial and
relativistic equation of state in the later phase. Finally, we show how our
generalized reheating analysis constrains the inflation models under
consideration
| [
{
"created": "Tue, 5 Feb 2019 20:14:05 GMT",
"version": "v1"
}
] | 2019-03-08 | [
[
"Maity",
"Debaprasad",
""
],
[
"Saha",
"Pankaj",
""
]
] | With the growing consensus on simple power law inflation models not being favored by the PLANCK observations, dynamics for the non-standard inflation gain significant interest in the recent past. In this paper, we analyze in detail a class of supergravity inspired phenomenological inflationary models with non-polynomial potential based on Maity (Nucl.Phys. B919 (2017) 560), and compare the model predictions with the currently most favored Starobinsky and its generalized $\alpha$-attractor models in the ($n_s$ , $r$) plane constrained by PLANCK. Importantly for a wide range of parameter space, our model provides successful inflation in the sub-Planckian regime. We also have performed model independent analysis of reheating in terms of the effective equation of state parameter. In particular, we consider two stages of reheating dynamics with generalized inflaton equation of state in the initial and relativistic equation of state in the later phase. Finally, we show how our generalized reheating analysis constrains the inflation models under consideration |
1403.0186 | Mohammad Reza Setare | M. R. Setare, V. Kamali | Warm-Intermediate Inflationary Universe Model with Viscous Pressure in
High Dissipative Regime | 17 pages, 4 figures, accepted for publication in General Relativity
and Gravitation. arXiv admin note: substantial text overlap with
arXiv:1312.2832, arXiv:1302.0493 | null | 10.1007/s10714-014-1698-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Warm inflation model with bulk viscous pressure in the context of
"intermediate inflation" where the cosmological scale factor expands as
$a(t)=a_0\exp(At^f)$, is studied. The characteristics of this model in
slow-roll approximation and in high dissipative regime are presented in two
cases: 1- Dissipative parameter $\Gamma$ as a function of scalar field $\phi$
and bulk viscous coefficient $\zeta$ as a function of energy density $\rho$. 2-
$\Gamma$ and $\zeta$ are constant parameters. Scalar, tensor perturbations and
spectral indices for this scenario are obtained. The cosmological parameters
appearing in the present model are constrained by recent observational data
(WMAP7).
| [
{
"created": "Sun, 2 Mar 2014 10:33:33 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"Setare",
"M. R.",
""
],
[
"Kamali",
"V.",
""
]
] | Warm inflation model with bulk viscous pressure in the context of "intermediate inflation" where the cosmological scale factor expands as $a(t)=a_0\exp(At^f)$, is studied. The characteristics of this model in slow-roll approximation and in high dissipative regime are presented in two cases: 1- Dissipative parameter $\Gamma$ as a function of scalar field $\phi$ and bulk viscous coefficient $\zeta$ as a function of energy density $\rho$. 2- $\Gamma$ and $\zeta$ are constant parameters. Scalar, tensor perturbations and spectral indices for this scenario are obtained. The cosmological parameters appearing in the present model are constrained by recent observational data (WMAP7). |
2407.12087 | Suddhasattwa Brahma | Idrus Husin Belfaqih, Martin Bojowald, Suddhasattwa Brahma and Erick
I. Duque | Black holes in effective loop quantum gravity: Covariant holonomy
modifications | 84+2 pages, 7 figures (all at the end of the draft); comments welcome | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Emergent modified gravity provides a covariant, effective framework for
obtaining spherically symmetric black hole solutions in models of loop quantum
gravity with scale-dependent holonomy modifications. Exact solutions for vacuum
black holes in the presence of a cosmological constant are derived here and
analyzed in four different gauges, explicitly related to one another by
standard coordinate transformations. The global structure is obtained by gluing
space-time regions corresponding to the gauge choices, reconstructing a
non-singular wormhole space-time for an arbitrary scale-dependent holonomy
parameter. This outcome demonstrates the robustness of black-hole models with
covariant holonomy modifications under quantization ambiguities. Compared with
previous constructions, full covariance of the resulting space-time models as
derived here implies subtle new effects and leads to a novel understanding of
the parameters in holonomy modifications, distinguishing a constant holonomy
length from a possibly scale-dependent function that may change coefficients of
holonomy terms. New physical results are obtained for instance in the context
of a non-trivial zero-mass limit of holonomy-modified space-times. The
existence of a consistent effective space-time structure implies various novel
aspects of a net gravitational stress-energy and related thermodynamical
properties.
| [
{
"created": "Tue, 16 Jul 2024 18:00:03 GMT",
"version": "v1"
}
] | 2024-07-18 | [
[
"Belfaqih",
"Idrus Husin",
""
],
[
"Bojowald",
"Martin",
""
],
[
"Brahma",
"Suddhasattwa",
""
],
[
"Duque",
"Erick I.",
""
]
] | Emergent modified gravity provides a covariant, effective framework for obtaining spherically symmetric black hole solutions in models of loop quantum gravity with scale-dependent holonomy modifications. Exact solutions for vacuum black holes in the presence of a cosmological constant are derived here and analyzed in four different gauges, explicitly related to one another by standard coordinate transformations. The global structure is obtained by gluing space-time regions corresponding to the gauge choices, reconstructing a non-singular wormhole space-time for an arbitrary scale-dependent holonomy parameter. This outcome demonstrates the robustness of black-hole models with covariant holonomy modifications under quantization ambiguities. Compared with previous constructions, full covariance of the resulting space-time models as derived here implies subtle new effects and leads to a novel understanding of the parameters in holonomy modifications, distinguishing a constant holonomy length from a possibly scale-dependent function that may change coefficients of holonomy terms. New physical results are obtained for instance in the context of a non-trivial zero-mass limit of holonomy-modified space-times. The existence of a consistent effective space-time structure implies various novel aspects of a net gravitational stress-energy and related thermodynamical properties. |
gr-qc/0405044 | Patrick Brady | Patrick R. Brady, Jolien D. E. Creighton, and Alan G. Wiseman | Upper limits on gravitational-wave signals based on loudest events | 8 pages, 1 figure | Class.Quant.Grav. 21 (2004) S1775-S1782 | 10.1088/0264-9381/21/20/020 | null | gr-qc | null | Searches for gravitational-wave bursts have often focused on the loudest
event(s) in searching for detections and in determining upper limits on
astrophysical populations. Typical upper limits have been reported on event
rates and event amplitudes which can then be translated into constraints on
astrophysical populations. We describe the mathematical construction of such
upper limits.
| [
{
"created": "Fri, 7 May 2004 20:19:53 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Brady",
"Patrick R.",
""
],
[
"Creighton",
"Jolien D. E.",
""
],
[
"Wiseman",
"Alan G.",
""
]
] | Searches for gravitational-wave bursts have often focused on the loudest event(s) in searching for detections and in determining upper limits on astrophysical populations. Typical upper limits have been reported on event rates and event amplitudes which can then be translated into constraints on astrophysical populations. We describe the mathematical construction of such upper limits. |
1511.02424 | Magd Elias Kahil | Magd E. Kahil | Stability of Stellar Systems Orbiting SgrA* | A talk presented at the Fifth Gammov International Conference on
Astronomy, Astrophysics , Cosmology and Astrobiology held in Odessa Ukraine,
August 16-23 | null | null | null | gr-qc astro-ph.GA astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Path equations of different orbiting objects in the presence of very strong
gravitational fields are essential to examine the impact of its gravitational
effect on the stability of each system. Implementing an analogous method, used
to examine the stability of planetary systems by solving the geodesic deviation
equations to obtain a finite value of the magnitude of its corresponding
deviation vectors. Thus, in order to know whether a system is stable or not,
the solution of corresponding deviation equations may give an indication about
the status of the stability for orbiting systems.Accordingly, two questions
must be addressed based on the status of stability of stellar objects orbiting
super-massive black holes in the galactic center.
1. Would the deviation equations play the same relevant role of orbiting
planetary systems for massive spinning objects such as neutron stars or black
holes? 2. What type of field theory which describes such a strong gravitational
field ?
| [
{
"created": "Sun, 8 Nov 2015 01:33:30 GMT",
"version": "v1"
}
] | 2015-11-11 | [
[
"Kahil",
"Magd E.",
""
]
] | Path equations of different orbiting objects in the presence of very strong gravitational fields are essential to examine the impact of its gravitational effect on the stability of each system. Implementing an analogous method, used to examine the stability of planetary systems by solving the geodesic deviation equations to obtain a finite value of the magnitude of its corresponding deviation vectors. Thus, in order to know whether a system is stable or not, the solution of corresponding deviation equations may give an indication about the status of the stability for orbiting systems.Accordingly, two questions must be addressed based on the status of stability of stellar objects orbiting super-massive black holes in the galactic center. 1. Would the deviation equations play the same relevant role of orbiting planetary systems for massive spinning objects such as neutron stars or black holes? 2. What type of field theory which describes such a strong gravitational field ? |
2306.02950 | Alesandro Santos | S. C. Ulhoa, A. F. Santos, E. P. Spaniol and Faqir C. Khanna | On Thermodynamics of Kerr Black Hole | 15 pages, 04 figures, accepted for publication in Annalen der Physik | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The gravitational Stefan-Boltzmann law is considered for the Kerr black hole
in the weak-field limit. The energy-momentum tensor predicted by
Teleparallelism Equivalent to General Relativity (TEGR) is used in the Thermo
Field Dynamics (TFD) formalism to thermalize the field. A temperature-dependent
gravitational pressure is obtained. Regions of divergent heat capacity are
observed. According to Landau theory, it allows the existence of distinct
phases around the Kerr black hole.
| [
{
"created": "Mon, 5 Jun 2023 15:15:38 GMT",
"version": "v1"
}
] | 2023-06-06 | [
[
"Ulhoa",
"S. C.",
""
],
[
"Santos",
"A. F.",
""
],
[
"Spaniol",
"E. P.",
""
],
[
"Khanna",
"Faqir C.",
""
]
] | The gravitational Stefan-Boltzmann law is considered for the Kerr black hole in the weak-field limit. The energy-momentum tensor predicted by Teleparallelism Equivalent to General Relativity (TEGR) is used in the Thermo Field Dynamics (TFD) formalism to thermalize the field. A temperature-dependent gravitational pressure is obtained. Regions of divergent heat capacity are observed. According to Landau theory, it allows the existence of distinct phases around the Kerr black hole. |
gr-qc/9706021 | Urjit A Yajnik | U. A. Yajnik and K. Narayan (Indian Institute of Technology, Bombay) | Canonical Quantization Inside the Schwarzschild Black Hole | 8 pages, LaTex. Title altered. One reference added. A few typos esp.
eq.(7),(38) corrected. To appear in Class.Q.Grav | Class.Quant.Grav. 15 (1998) 1315-1321 | 10.1088/0264-9381/15/5/013 | null | gr-qc hep-ph | null | We propose a scheme for quantizing a scalar field over the Schwarzschild
manifold including the interior of the horizon. On the exterior, the timelike
Killing vector and on the horizon the isometry corresponding to restricted
Lorentz boosts can be used to enforce the spectral condition. For the interior
we appeal to the need for CPT invariance to construct an explicitly positive
definite operator which allows identification of positive and negative
frequencies. This operator is the translation operator corresponding to the
inexorable propagation to smaller radii as expected from the classical metric.
We also propose an expression for the propagator in the interior and express it
as a mode sum.
| [
{
"created": "Mon, 9 Jun 1997 10:18:53 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Jan 1998 12:07:30 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Yajnik",
"U. A.",
"",
"Indian Institute of Technology, Bombay"
],
[
"Narayan",
"K.",
"",
"Indian Institute of Technology, Bombay"
]
] | We propose a scheme for quantizing a scalar field over the Schwarzschild manifold including the interior of the horizon. On the exterior, the timelike Killing vector and on the horizon the isometry corresponding to restricted Lorentz boosts can be used to enforce the spectral condition. For the interior we appeal to the need for CPT invariance to construct an explicitly positive definite operator which allows identification of positive and negative frequencies. This operator is the translation operator corresponding to the inexorable propagation to smaller radii as expected from the classical metric. We also propose an expression for the propagator in the interior and express it as a mode sum. |
gr-qc/0504073 | Akinbo Ojo Dr | Akinbo Ojo | On a thermodynamic basis for inflationary cosmology | Arguments sharpened. Certain aspects elaborated in more detail and
some areas clarified in response to referees' comments. 35 pages, no figures | null | null | null | gr-qc | null | Modifying the standard hot big bang model of cosmology with an inflationary
event has been very successful in resolving most of the outstanding
cosmological problems. The various inflationary mechanisms proposed depend on
the production of expansion from exotic phenomena, false vacuum, scalar fields
or other exotic particle behaviour within an environment of astronomically high
energy, making such proposals relatively inaccessible for verification by
experimental tests. Though descriptive of how space has been expanding, the
models do not give a complete and consistent mathematical or physical
explanation that compels space appearance and propels its expansion. Here we
describe another mechanism for achieving exponential inflation based
substantially on already tested physics and equations, particularly the
thermodynamic equation, dS = dE/T and relate this to the creation event.
| [
{
"created": "Sat, 16 Apr 2005 16:51:30 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Aug 2005 19:33:17 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Ojo",
"Akinbo",
""
]
] | Modifying the standard hot big bang model of cosmology with an inflationary event has been very successful in resolving most of the outstanding cosmological problems. The various inflationary mechanisms proposed depend on the production of expansion from exotic phenomena, false vacuum, scalar fields or other exotic particle behaviour within an environment of astronomically high energy, making such proposals relatively inaccessible for verification by experimental tests. Though descriptive of how space has been expanding, the models do not give a complete and consistent mathematical or physical explanation that compels space appearance and propels its expansion. Here we describe another mechanism for achieving exponential inflation based substantially on already tested physics and equations, particularly the thermodynamic equation, dS = dE/T and relate this to the creation event. |
1206.5121 | Farhad Darabi | K. Zeynali, F. Darabi, H. Motavalli | Black hole thermodynamics and modified GUP consistent with doubly
special relativity | 13 pages, 6 figures, minor revision, references added | Mod. Phys. Lett. A, Vol. 27, No. 39 (2012) 1250227 | 10.1142/S0217732312502276 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the black hole thermodynamics and obtain the correction terms for
temperature, entropy, and heat capacity of the Schwarzschild black hole,
resulting from the commutation relations in the framework of {\it Modified
Generalized Uncertainty Principle} suggested by {\it Doubly Special
Relativity}.
| [
{
"created": "Fri, 22 Jun 2012 11:57:14 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Dec 2012 06:19:19 GMT",
"version": "v2"
}
] | 2015-06-05 | [
[
"Zeynali",
"K.",
""
],
[
"Darabi",
"F.",
""
],
[
"Motavalli",
"H.",
""
]
] | We study the black hole thermodynamics and obtain the correction terms for temperature, entropy, and heat capacity of the Schwarzschild black hole, resulting from the commutation relations in the framework of {\it Modified Generalized Uncertainty Principle} suggested by {\it Doubly Special Relativity}. |
1708.03451 | Yun Soo Myung | Yun Soo Myung | Renormalizability and Newtonian potential in scale-invariant gravity | 9 pages, no figures, version to appear in IJMPD | null | 10.1142/S0218271818501055 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There is a conjecture that renormalizable higher-derivative gravity has a
finite classical potential at the origin. In this work we show clearly that the
scale-invariant gravity (SIG) satisfies the conjecture. This gravity produces
the better-behaved $1/k^4$ UV behavior as needed for renormalizability. It
turns out that the SIG has the linear classical potential of $V\propto r$ and
it is a UV complete theory.
| [
{
"created": "Fri, 11 Aug 2017 07:02:34 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Apr 2018 23:00:15 GMT",
"version": "v2"
}
] | 2018-09-12 | [
[
"Myung",
"Yun Soo",
""
]
] | There is a conjecture that renormalizable higher-derivative gravity has a finite classical potential at the origin. In this work we show clearly that the scale-invariant gravity (SIG) satisfies the conjecture. This gravity produces the better-behaved $1/k^4$ UV behavior as needed for renormalizability. It turns out that the SIG has the linear classical potential of $V\propto r$ and it is a UV complete theory. |
2010.04848 | Tousif Islam | Tousif Islam, Scott E. Field, Carl-Johan Haster and Rory Smith | Improved analysis of GW190412 with a precessing numerical relativity
surrogate waveform model | 15 pages, 4 figures; Matches the accepted version in PRD | Phys. Rev. D 103, 104027 (2021) | 10.1103/PhysRevD.103.104027 | LIGO Document Number DCC-P2000384 | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent observation of GW190412, the first high-mass ratio binary
black-hole (BBH) merger, by the LIGO-Virgo Collaboration (LVC) provides a
unique opportunity to probe the impact of subdominant harmonics and precession
effects encoded in a gravitational wave signal. We present refined estimates of
source parameters for GW190412 using \texttt{NRSur7dq4}, a recently developed
numerical relativity waveform surrogate model that includes all $\ell \leq 4$
spin-weighted spherical harmonic modes as well as the full physical effects of
precession. We compare our results with two different variants of
phenomenological precessing BBH waveform models, \texttt{IMRPhenomPv3HM} and
\texttt{IMRPhenomXPHM}, as well as to the LVC results. Our results are broadly
in agreement with \texttt{IMRPhenomXPHM} results and the reported LVC analysis
compiled with the \texttt{SEOBNRv4PHM} waveform model, but in tension with
\texttt{IMRPhenomPv3HM}. Using the \texttt{NRSur7dq4} model, we provide a
tighter constraint on the mass-ratio ($0.26^{+0.08}_{-0.06}$) as compared to
the LVC estimate of $0.28^{+0.13}_{-0.07}$ (both reported as median values
withs 90\% credible intervals). We also constrain the binary to be more
face-on, and find a broader posterior for the spin precession parameter. We
further find that even though $\ell=4$ harmonic modes have negligible
signal-to-noise ratio, omission of these modes will influence the estimated
posterior distribution of several source parameters including chirp mass,
effective inspiral spin, luminosity distance, and inclination. We also find
that commonly used model approximations, such as neglecting the asymmetric
modes (which are generically excited during precession), have negligible impact
on parameter recovery for moderate SNR-events similar to GW190412.
| [
{
"created": "Fri, 9 Oct 2020 23:38:30 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Apr 2021 23:59:27 GMT",
"version": "v2"
}
] | 2021-05-19 | [
[
"Islam",
"Tousif",
""
],
[
"Field",
"Scott E.",
""
],
[
"Haster",
"Carl-Johan",
""
],
[
"Smith",
"Rory",
""
]
] | The recent observation of GW190412, the first high-mass ratio binary black-hole (BBH) merger, by the LIGO-Virgo Collaboration (LVC) provides a unique opportunity to probe the impact of subdominant harmonics and precession effects encoded in a gravitational wave signal. We present refined estimates of source parameters for GW190412 using \texttt{NRSur7dq4}, a recently developed numerical relativity waveform surrogate model that includes all $\ell \leq 4$ spin-weighted spherical harmonic modes as well as the full physical effects of precession. We compare our results with two different variants of phenomenological precessing BBH waveform models, \texttt{IMRPhenomPv3HM} and \texttt{IMRPhenomXPHM}, as well as to the LVC results. Our results are broadly in agreement with \texttt{IMRPhenomXPHM} results and the reported LVC analysis compiled with the \texttt{SEOBNRv4PHM} waveform model, but in tension with \texttt{IMRPhenomPv3HM}. Using the \texttt{NRSur7dq4} model, we provide a tighter constraint on the mass-ratio ($0.26^{+0.08}_{-0.06}$) as compared to the LVC estimate of $0.28^{+0.13}_{-0.07}$ (both reported as median values withs 90\% credible intervals). We also constrain the binary to be more face-on, and find a broader posterior for the spin precession parameter. We further find that even though $\ell=4$ harmonic modes have negligible signal-to-noise ratio, omission of these modes will influence the estimated posterior distribution of several source parameters including chirp mass, effective inspiral spin, luminosity distance, and inclination. We also find that commonly used model approximations, such as neglecting the asymmetric modes (which are generically excited during precession), have negligible impact on parameter recovery for moderate SNR-events similar to GW190412. |
1509.07027 | Davood Momeni Dr | Antonio Pasqua, Surajit Chattopadhyay, Davood Momeni, Muhammad Raza,
Ratbay Myrzakulov, Mir Faizal | Cosmological reconstruction and {\it Om} diagnostic analysis of
Einstein-Aether Theory | 47 pages, 9 figures, 5 tables,Major Rvised version | JCAP04(2017)015 | 10.1088/1475-7516/2017/04/015 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we will analyse the cosmological models in Einstein-aether
gravity, which is a modified theory of gravity in which a time-like vector
field breaks the Lorentz symmetry. We will use this formalism to analyse
different cosmological models with different behavior of the scale factor. In
this analysis, we will use a certain functional dependence of the dark energy
on the Hubble parameter. It will be demonstrated that the aether vector field
has a non-trivial effect on these cosmological models. We will also perform the
\emph{Om} diagnostic in Einstein-aether gravity. Thus, we will fit parameters
of the cosmological models using recent observational data.
| [
{
"created": "Wed, 23 Sep 2015 15:19:50 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Oct 2015 03:41:13 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Mar 2016 15:33:39 GMT",
"version": "v3"
},
{
"created": "Wed, 9 Nov 2016 14:37:06 GMT",
"version": "v4"
}
] | 2017-04-19 | [
[
"Pasqua",
"Antonio",
""
],
[
"Chattopadhyay",
"Surajit",
""
],
[
"Momeni",
"Davood",
""
],
[
"Raza",
"Muhammad",
""
],
[
"Myrzakulov",
"Ratbay",
""
],
[
"Faizal",
"Mir",
""
]
] | In this paper, we will analyse the cosmological models in Einstein-aether gravity, which is a modified theory of gravity in which a time-like vector field breaks the Lorentz symmetry. We will use this formalism to analyse different cosmological models with different behavior of the scale factor. In this analysis, we will use a certain functional dependence of the dark energy on the Hubble parameter. It will be demonstrated that the aether vector field has a non-trivial effect on these cosmological models. We will also perform the \emph{Om} diagnostic in Einstein-aether gravity. Thus, we will fit parameters of the cosmological models using recent observational data. |
1812.11148 | David McNutt | S. Hervik and D. McNutt | Locally Homogeneous Kundt Triples and CSI Metrics | 17 pages | Classical and Quantum Gravity, 36, 185013 (2019) | 10.1088/1361-6382/ab3296 | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A pseudo-Riemannian manifold is called CSI if all scalar polynomial
invariants constructed from the curvature tensor and its covariant derivatives
are constant. In the Lorentzian case, the CSI spacetimes have been studied
extensively due to their application to gravity theories. It is conjectured
that a CSI spacetime is either locally homogeneous or belongs to the subclass
of degenerate Kundt metrics. Independent of this conjecture, any CSI spacetime
can be related to a particular locally homogeneous degenerate Kundt metric
sharing the same scalar polynomial curvature invariants. In this paper we will
invariantly classify the entire subclass of locally homogeneous CSI Kundt
spacetimes which are of alignment type {\bf D} to all orders and show that any
other CSI Kundt metric can be constructed from them.
| [
{
"created": "Fri, 28 Dec 2018 18:21:59 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Aug 2019 09:21:24 GMT",
"version": "v2"
}
] | 2019-08-29 | [
[
"Hervik",
"S.",
""
],
[
"McNutt",
"D.",
""
]
] | A pseudo-Riemannian manifold is called CSI if all scalar polynomial invariants constructed from the curvature tensor and its covariant derivatives are constant. In the Lorentzian case, the CSI spacetimes have been studied extensively due to their application to gravity theories. It is conjectured that a CSI spacetime is either locally homogeneous or belongs to the subclass of degenerate Kundt metrics. Independent of this conjecture, any CSI spacetime can be related to a particular locally homogeneous degenerate Kundt metric sharing the same scalar polynomial curvature invariants. In this paper we will invariantly classify the entire subclass of locally homogeneous CSI Kundt spacetimes which are of alignment type {\bf D} to all orders and show that any other CSI Kundt metric can be constructed from them. |
1808.07392 | Xiao-Mei Kuang | Adolfo Cisterna, Shi-Qian Hu, Xiao-Mei Kuang | Joule-Thomson expansion in AdS black holes with momentum relaxation | 21 pages, 9 figures; Published version | Physics Letters B 797 (2019) 134883 | 10.1016/j.physletb.2019.134883 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The inner structure of realistic materials make them exhibit momentum
relaxation. In this paper we study the holographic version of the Joule-Thomson
effect on AdS black holes in which translational invariance is broken by two
methods: First by considering planar black holes in general relativity
supported by axion scalar fields with a linear dependence on the horizon
coordinates and secondly by considering black holes in massive gravity models
in which momentum relaxation is obtained by breaking the bulk diffeomorphism
invariance of the theory. In contrast with black holes studied so far, for both
theories it is possible to obtain inversion curves with two branches
reproducing the behavior of Van der Wall fluids. Moreover in the specific case
of the massive gravity model we show that black holes can heat up when crossing
the inversion curve.
| [
{
"created": "Wed, 22 Aug 2018 14:51:21 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Aug 2019 23:57:27 GMT",
"version": "v2"
}
] | 2019-08-29 | [
[
"Cisterna",
"Adolfo",
""
],
[
"Hu",
"Shi-Qian",
""
],
[
"Kuang",
"Xiao-Mei",
""
]
] | The inner structure of realistic materials make them exhibit momentum relaxation. In this paper we study the holographic version of the Joule-Thomson effect on AdS black holes in which translational invariance is broken by two methods: First by considering planar black holes in general relativity supported by axion scalar fields with a linear dependence on the horizon coordinates and secondly by considering black holes in massive gravity models in which momentum relaxation is obtained by breaking the bulk diffeomorphism invariance of the theory. In contrast with black holes studied so far, for both theories it is possible to obtain inversion curves with two branches reproducing the behavior of Van der Wall fluids. Moreover in the specific case of the massive gravity model we show that black holes can heat up when crossing the inversion curve. |
1711.04704 | Alexander Rudenko S. | A.D. Dolgov, S.I. Godunov, A.S. Rudenko | Evolution of thick domain walls in inflationary and $p=w\rho$ universe | 15 pages, 9 figures | Eur. Phys. J. C 78 (2018) no.10, 855 | 10.1140/epjc/s10052-018-6350-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the evolution of thick domain walls in the different models of
cosmological inflation, in the matter-dominated and radiation-dominated
universe, or more generally in the universe with the equation of state
$p=w\rho$. We have found that the domain wall evolution crucially depends on
the time-dependent parameter $C(t)=1/(H(t)\delta_0)^2$, where $H(t)$ is the
Hubble parameter and $\delta_0$ is the thickness of the wall in flat
space-time. For $C(t)>2$ the physical thickness of the wall, $a(t)\delta(t)$,
tends with time to $\delta_0$, which is microscopically small. Otherwise, when
$C(t) \leq 2$, the wall steadily expands and can grow up to a cosmologically
large size.
| [
{
"created": "Mon, 13 Nov 2017 17:01:29 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Aug 2018 14:48:16 GMT",
"version": "v2"
}
] | 2018-11-02 | [
[
"Dolgov",
"A. D.",
""
],
[
"Godunov",
"S. I.",
""
],
[
"Rudenko",
"A. S.",
""
]
] | We study the evolution of thick domain walls in the different models of cosmological inflation, in the matter-dominated and radiation-dominated universe, or more generally in the universe with the equation of state $p=w\rho$. We have found that the domain wall evolution crucially depends on the time-dependent parameter $C(t)=1/(H(t)\delta_0)^2$, where $H(t)$ is the Hubble parameter and $\delta_0$ is the thickness of the wall in flat space-time. For $C(t)>2$ the physical thickness of the wall, $a(t)\delta(t)$, tends with time to $\delta_0$, which is microscopically small. Otherwise, when $C(t) \leq 2$, the wall steadily expands and can grow up to a cosmologically large size. |
gr-qc/0304087 | Hans Stephani | Hans Stephani | LaPlace, Weimar, Schiller and the birth of black hole theory | 12 pages | null | null | null | gr-qc | null | From the original papers an interesting and surprising connection is
established between LaPlace and his early discovery that black holes may occur
in nature, and a poem by Schiller.
| [
{
"created": "Wed, 23 Apr 2003 10:00:35 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Stephani",
"Hans",
""
]
] | From the original papers an interesting and surprising connection is established between LaPlace and his early discovery that black holes may occur in nature, and a poem by Schiller. |
1309.1320 | Vladimir Dzhunushaliev | Vladimir Dzhunushaliev and Vladimir Folomeev | Kaluza-Klein wormholes with the compactified fifth dimension | 6 pages, 3 figures | Mod. Phys. Lett. A, Vol. 29, No. 4 (2014) 1450025 | 10.1142/S0217732314500254 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider wormhole solutions in five-dimensional Kaluza-Klein gravity in
the presence of a massless ghost four-dimensional scalar field. The system
possesses two types of topological nontriviality connected with the presence of
the scalar field and of a magnetic charge. Mathematically, the presence of the
charge appears in the fact that the $S^3$ part of a spacetime metric is the
Hopf bundle $S^3 \rightarrow S^2$ with fibre $S^1$. We show that the fifth
dimension spanned on the sphere $S^1$ is compactified in the sense that
asymptotically, at large distances from the throat, the size of $S^1$ is equal
to some constant, the value of which can be chosen to lie, say, in the Planck
region. Then, from the four-dimensional point of view, such a wormhole contains
a radial magnetic (monopole) field, and an asymptotic four-dimensional observer
sees a wormhole with the compactified fifth dimension.
| [
{
"created": "Thu, 5 Sep 2013 11:49:11 GMT",
"version": "v1"
}
] | 2014-03-14 | [
[
"Dzhunushaliev",
"Vladimir",
""
],
[
"Folomeev",
"Vladimir",
""
]
] | We consider wormhole solutions in five-dimensional Kaluza-Klein gravity in the presence of a massless ghost four-dimensional scalar field. The system possesses two types of topological nontriviality connected with the presence of the scalar field and of a magnetic charge. Mathematically, the presence of the charge appears in the fact that the $S^3$ part of a spacetime metric is the Hopf bundle $S^3 \rightarrow S^2$ with fibre $S^1$. We show that the fifth dimension spanned on the sphere $S^1$ is compactified in the sense that asymptotically, at large distances from the throat, the size of $S^1$ is equal to some constant, the value of which can be chosen to lie, say, in the Planck region. Then, from the four-dimensional point of view, such a wormhole contains a radial magnetic (monopole) field, and an asymptotic four-dimensional observer sees a wormhole with the compactified fifth dimension. |
gr-qc/0001029 | Takeshi Chiba | Takeshi Chiba | Scalar-Tensor Gravity in Two 3-brane System | 8 pages, discussion expanded, references added | Phys.Rev.D62:021502,2000 | 10.1103/PhysRevD.62.021502 | UTAP-360 | gr-qc hep-th | null | We derive the low-energy effective action of four-dimensional gravity in the
Randall-Sundrum scenario in which two 3-branes of opposite tension reside in a
five-dimensional spacetime. The dimensional reduction with the Ansatz for the
radion field by Charmousis et al., which solves five-dimensional linearized
field equations, results in a class of scalar-tensor gravity theories. In the
limit of vanishing radion fluctuations, the effective action reduces to the
Brans-Dicke gravity in accord with the results of Garriga and Tanaka:
Brans-Dicke gravity with the corresponding Brans-Dicke parameter $0< \omega <
\infty$ (for positive tension brane) and $-3/2< \omega <0$ (for negative
tension brane). In general the gravity induced a brane belongs to a class of
scalar-tensor gravity with the Brans-Dicke parameter which is a function of the
interval and the radion. In particular, gravity on a positive tension brane
contains an attractor mechanism toward the Einstein gravity.
| [
{
"created": "Tue, 11 Jan 2000 11:36:20 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Jun 2000 03:42:53 GMT",
"version": "v2"
}
] | 2009-12-30 | [
[
"Chiba",
"Takeshi",
""
]
] | We derive the low-energy effective action of four-dimensional gravity in the Randall-Sundrum scenario in which two 3-branes of opposite tension reside in a five-dimensional spacetime. The dimensional reduction with the Ansatz for the radion field by Charmousis et al., which solves five-dimensional linearized field equations, results in a class of scalar-tensor gravity theories. In the limit of vanishing radion fluctuations, the effective action reduces to the Brans-Dicke gravity in accord with the results of Garriga and Tanaka: Brans-Dicke gravity with the corresponding Brans-Dicke parameter $0< \omega < \infty$ (for positive tension brane) and $-3/2< \omega <0$ (for negative tension brane). In general the gravity induced a brane belongs to a class of scalar-tensor gravity with the Brans-Dicke parameter which is a function of the interval and the radion. In particular, gravity on a positive tension brane contains an attractor mechanism toward the Einstein gravity. |
1311.0872 | Kent Yagi | Kent Yagi | Multipole Love Relations | 22 pages, 18 figures; universal relations for magnetic tidal
deformability corrected | Phys. Rev. D 89, 043011 (2014) | 10.1103/PhysRevD.89.043011 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational-wave observations in the near future may allow us to measure
tidal deformabilities of neutron stars, which leads us to the understanding of
physics at nuclear density. In principle, the gravitational waveform depends on
various tidal parameters, which correlate strongly. Therefore, it would be
useful if one can express such tidal parameters with a single parameter. Here,
we report on universal relations among various $\ell$-th (dimensionless)
electric, magnetic and shape tidal deformabilities in neutron stars and quark
stars that do not depend sensitively on the equation of state. Such relations
allow us to break the degeneracy among the tidal parameters. In this paper, we
focus on gravitational waves from non-spinning neutron-star binary inspirals.
We first derive the leading contribution of the $\ell$-th electric and $\ell=2$
magnetic tidal deformabilities to the gravitational-wave phase, which enters at
$2\ell +1$ and $6$ post-Newtonian orders relative to the leading Newtonian one
respectively. We then calculate the useful number of gravitational-wave cycles
and show that not only the $\ell=2$ but also $\ell=3$ electric tidal
deformabilities are important for parameter estimation with third-generation
gravitational-wave detectors such as LIGO III and Einstein Telescope. Although
the correlation between the $\ell=2$ and $\ell=3$ electric tidal
deformabilities deteriorate the measurement accuracy of the former
deformability parameter, one can increase its measurement accuracy
significantly by using the universal relation. We provide a fitting formula for
the LIGO III noise curve in the Appendix.
| [
{
"created": "Mon, 4 Nov 2013 21:00:02 GMT",
"version": "v1"
},
{
"created": "Sat, 9 Nov 2013 01:22:42 GMT",
"version": "v2"
},
{
"created": "Fri, 4 May 2018 21:57:08 GMT",
"version": "v3"
},
{
"created": "Mon, 4 Jun 2018 19:33:40 GMT",
"version": "v4"
}
] | 2018-06-06 | [
[
"Yagi",
"Kent",
""
]
] | Gravitational-wave observations in the near future may allow us to measure tidal deformabilities of neutron stars, which leads us to the understanding of physics at nuclear density. In principle, the gravitational waveform depends on various tidal parameters, which correlate strongly. Therefore, it would be useful if one can express such tidal parameters with a single parameter. Here, we report on universal relations among various $\ell$-th (dimensionless) electric, magnetic and shape tidal deformabilities in neutron stars and quark stars that do not depend sensitively on the equation of state. Such relations allow us to break the degeneracy among the tidal parameters. In this paper, we focus on gravitational waves from non-spinning neutron-star binary inspirals. We first derive the leading contribution of the $\ell$-th electric and $\ell=2$ magnetic tidal deformabilities to the gravitational-wave phase, which enters at $2\ell +1$ and $6$ post-Newtonian orders relative to the leading Newtonian one respectively. We then calculate the useful number of gravitational-wave cycles and show that not only the $\ell=2$ but also $\ell=3$ electric tidal deformabilities are important for parameter estimation with third-generation gravitational-wave detectors such as LIGO III and Einstein Telescope. Although the correlation between the $\ell=2$ and $\ell=3$ electric tidal deformabilities deteriorate the measurement accuracy of the former deformability parameter, one can increase its measurement accuracy significantly by using the universal relation. We provide a fitting formula for the LIGO III noise curve in the Appendix. |
1309.7206 | Torsten Asselmeyer-Maluga | T. Asselmeyer-Maluga and J. Krol | Decoherence in quantum cosmology and the cosmological constant | 8 pages, 1 figure, accepted in MPLA | Mod. Phys. Lett. A 28 (2013) 1350158 | 10.1142/S0217732313501587 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a spacetime having the topology of $S^{3}\times\mathbb{R}$ but
with a different smoothness structure. The initial state of the cosmos in our
model is identified with a wildly embedded 3-sphere (or a fractal space). In
previous work we showed that a wild embedding is obtained by a quantization of
a usual (or tame) embedding. Then a wild embedding can be identified with a
(geometrical) quantum state. During a decoherence process this wild 3-sphere is
changed to a homology 3-sphere. We are able to calculate the decoherence time
for this process. After the formation of the homology 3-sphere, we obtain a
spacetime with an accelerated expansion enforced by a cosmological constant.
The calculation of this cosmological constant gives a qualitative agreement
with the current measured value.
| [
{
"created": "Fri, 27 Sep 2013 11:11:45 GMT",
"version": "v1"
}
] | 2013-09-30 | [
[
"Asselmeyer-Maluga",
"T.",
""
],
[
"Krol",
"J.",
""
]
] | We discuss a spacetime having the topology of $S^{3}\times\mathbb{R}$ but with a different smoothness structure. The initial state of the cosmos in our model is identified with a wildly embedded 3-sphere (or a fractal space). In previous work we showed that a wild embedding is obtained by a quantization of a usual (or tame) embedding. Then a wild embedding can be identified with a (geometrical) quantum state. During a decoherence process this wild 3-sphere is changed to a homology 3-sphere. We are able to calculate the decoherence time for this process. After the formation of the homology 3-sphere, we obtain a spacetime with an accelerated expansion enforced by a cosmological constant. The calculation of this cosmological constant gives a qualitative agreement with the current measured value. |
1212.2623 | I-Sheng Yang | Lam Hui, Sean T. McWilliams, and I-Sheng Yang | Binary Systems as Resonance Detectors for Gravitational Waves | 8 pages, 1 figure. version 2, clarified several points thanks to
private communications with Marc Kamionkowski | null | 10.1103/PhysRevD.87.084009 | null | gr-qc astro-ph.CO astro-ph.GA astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves at suitable frequencies can resonantly interact with a
binary system, inducing changes to its orbit. A stochastic gravitational-wave
background causes the orbital elements of the binary to execute a classic
random walk, with the variance of orbital elements growing with time. The lack
of such a random walk in binaries that have been monitored with high precision
over long time-scales can thus be used to place an upper bound on the
gravitational-wave background. Using periastron time data from the Hulse-Taylor
binary pulsar spanning ~30 years, we obtain a bound of h_c < 7.9*10^(-14) at
~10^(-4) Hz, where h_c is the strain amplitude per logarithmic frequency
interval. Our constraint complements those from pulsar timing arrays, which
probe much lower frequencies, and ground-based gravitational-wave observations,
which probe much higher frequencies. Interesting sources in our frequency band,
which overlaps the lower sensitive frequencies of proposed space-based
observatories, include white-dwarf/supermassive black-hole binaries in the
early/late stages of inspiral, and TeV scale preheating or phase transitions.
The bound improves as (time span)^(-2) and (sampling rate)^(-1/2). The
Hulse-Taylor constraint can be improved to ~3.8*10^(-15) with a suitable
observational campaign over the next decade. Our approach can also be applied
to other binaries, including (with suitable care) the Earth-Moon system, to
obtain constraints at different frequencies. The observation of additional
binary pulsars with the SKA could reach a sensitivity of h_c ~ 3*10^(-17).
| [
{
"created": "Tue, 11 Dec 2012 20:50:31 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Mar 2013 07:38:45 GMT",
"version": "v2"
}
] | 2013-05-27 | [
[
"Hui",
"Lam",
""
],
[
"McWilliams",
"Sean T.",
""
],
[
"Yang",
"I-Sheng",
""
]
] | Gravitational waves at suitable frequencies can resonantly interact with a binary system, inducing changes to its orbit. A stochastic gravitational-wave background causes the orbital elements of the binary to execute a classic random walk, with the variance of orbital elements growing with time. The lack of such a random walk in binaries that have been monitored with high precision over long time-scales can thus be used to place an upper bound on the gravitational-wave background. Using periastron time data from the Hulse-Taylor binary pulsar spanning ~30 years, we obtain a bound of h_c < 7.9*10^(-14) at ~10^(-4) Hz, where h_c is the strain amplitude per logarithmic frequency interval. Our constraint complements those from pulsar timing arrays, which probe much lower frequencies, and ground-based gravitational-wave observations, which probe much higher frequencies. Interesting sources in our frequency band, which overlaps the lower sensitive frequencies of proposed space-based observatories, include white-dwarf/supermassive black-hole binaries in the early/late stages of inspiral, and TeV scale preheating or phase transitions. The bound improves as (time span)^(-2) and (sampling rate)^(-1/2). The Hulse-Taylor constraint can be improved to ~3.8*10^(-15) with a suitable observational campaign over the next decade. Our approach can also be applied to other binaries, including (with suitable care) the Earth-Moon system, to obtain constraints at different frequencies. The observation of additional binary pulsars with the SKA could reach a sensitivity of h_c ~ 3*10^(-17). |
gr-qc/9609027 | Lee Samuel Finn | Lee Samuel Finn (Northwestern University) | Gravitational radiation sources for acoustic detectors | 11 pages, LaTeX type, sprocl.sty, to appear in the proceedings of
OMNI-1: The first international workshop for an omnidirectional
gravitational-wave observatory | null | null | null | gr-qc astro-ph | null | When completed, the gravitational wave detectors now proposed or under
construction will provide us with a perspective on the Universe fundamentally
different from any we have come to know. With this new perspective comes the
hope that new insights and understandings of Nature will emerge. The proposed
acoustic detectors, with spherical geometries and operating at millikelvin
temperatures, are particularly well-suited to study gravitational radiation in
the 1--3 KHz band. In this brief report I review some sources of particular
interest for these detectors.
| [
{
"created": "Wed, 11 Sep 1996 13:49:08 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Finn",
"Lee Samuel",
"",
"Northwestern University"
]
] | When completed, the gravitational wave detectors now proposed or under construction will provide us with a perspective on the Universe fundamentally different from any we have come to know. With this new perspective comes the hope that new insights and understandings of Nature will emerge. The proposed acoustic detectors, with spherical geometries and operating at millikelvin temperatures, are particularly well-suited to study gravitational radiation in the 1--3 KHz band. In this brief report I review some sources of particular interest for these detectors. |
2105.11511 | Saeed Rastgoo | Keagan Blanchette, Saurya Das, Saeed Rastgoo | Effective GUP-modified Raychaudhuri equation and black hole singularity:
four models | 26 pages, 6 figures; v2: matches JHEP published version | J. High Energ. Phys. 2021, 62 (2021) | 10.1007/JHEP09(2021)062 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The classical Raychaudhuri equation predicts the formation of conjugate
points for a congruence of geodesics, in a finite proper time. This in
conjunction with the Hawking-Penrose singularity theorems predicts the
incompleteness of geodesics and thereby the singular nature of practically all
spacetimes. We compute the generic corrections to the Raychaudhuri equation in
the interior of a Schwarzschild black hole, arising from modifications to the
algebra inspired by the generalized uncertainty principle (GUP) theories. Then
we study four specific models of GUP, compute their effective dynamics as well
as their expansion and its rate of change using the Raychaudhuri equation. We
show that the modification from GUP in two of these models, where such
modifications are dependent of the configuration variables, lead to finite
Kretchmann scalar, expansion and its rate, hence implying the resolution of the
singularity. However, the other two models for which the modifications depend
on the momenta still retain their singularities even in the effective regime.
| [
{
"created": "Mon, 24 May 2021 19:33:37 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Sep 2021 18:31:35 GMT",
"version": "v2"
}
] | 2021-09-16 | [
[
"Blanchette",
"Keagan",
""
],
[
"Das",
"Saurya",
""
],
[
"Rastgoo",
"Saeed",
""
]
] | The classical Raychaudhuri equation predicts the formation of conjugate points for a congruence of geodesics, in a finite proper time. This in conjunction with the Hawking-Penrose singularity theorems predicts the incompleteness of geodesics and thereby the singular nature of practically all spacetimes. We compute the generic corrections to the Raychaudhuri equation in the interior of a Schwarzschild black hole, arising from modifications to the algebra inspired by the generalized uncertainty principle (GUP) theories. Then we study four specific models of GUP, compute their effective dynamics as well as their expansion and its rate of change using the Raychaudhuri equation. We show that the modification from GUP in two of these models, where such modifications are dependent of the configuration variables, lead to finite Kretchmann scalar, expansion and its rate, hence implying the resolution of the singularity. However, the other two models for which the modifications depend on the momenta still retain their singularities even in the effective regime. |
1112.5253 | Matt Visser | Prado Martin-Moruno (Victoria University of Wellington), Nadiezhda
Montelongo Garcia (CINVESTAV, IPN, Universidade de Lisboa), Francisco S. N.
Lobo (Universidade de Lisboa), and Matt Visser (Victoria University of
Wellington) | Generic thin-shell gravastars | V1: 39 pages, 9 figures; V2: 40 pages, 9 figures. References added,
some discussion added, some typos fixed. Identical to published version.
arXiv admin note: text overlap with arXiv:1112.2057 | JCAP 03 (2012) 034 | 10.1088/1475-7516/2012/03/034 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct generic spherically symmetric thin-shell gravastars by using the
cut-and-paste procedure. We take considerable effort to make the analysis as
general and unified as practicable; investigating both the internal physics of
the transition layer and its interaction with "external forces" arising due to
interactions between the transition layer and the bulk spacetime. Furthermore,
we discuss both the dynamic and static situations. In particular, we consider
"bounded excursion" dynamical configurations, and probe the stability of static
configurations. For gravastars there is always a particularly compelling
configuration in which the surface energy density is zero, while surface
tension is nonzero.
| [
{
"created": "Thu, 22 Dec 2011 09:18:57 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Mar 2012 03:55:50 GMT",
"version": "v2"
}
] | 2012-08-15 | [
[
"Martin-Moruno",
"Prado",
"",
"Victoria University of Wellington"
],
[
"Garcia",
"Nadiezhda Montelongo",
"",
"CINVESTAV, IPN, Universidade de Lisboa"
],
[
"Lobo",
"Francisco S. N.",
"",
"Universidade de Lisboa"
],
[
"Visser",
"Matt",
"",
... | We construct generic spherically symmetric thin-shell gravastars by using the cut-and-paste procedure. We take considerable effort to make the analysis as general and unified as practicable; investigating both the internal physics of the transition layer and its interaction with "external forces" arising due to interactions between the transition layer and the bulk spacetime. Furthermore, we discuss both the dynamic and static situations. In particular, we consider "bounded excursion" dynamical configurations, and probe the stability of static configurations. For gravastars there is always a particularly compelling configuration in which the surface energy density is zero, while surface tension is nonzero. |
2111.06767 | Nils Leif Vu | Nils L. Vu, Harald P. Pfeiffer, Gabriel S. Bonilla, Nils Deppe,
Fran\c{c}ois H\'ebert, Lawrence E. Kidder, Geoffrey Lovelace, Jordan Moxon,
Mark A. Scheel, Saul A. Teukolsky, William Throwe, Nikolas A. Wittek, Tom
W{\l}odarczyk | A scalable elliptic solver with task-based parallelism for the SpECTRE
numerical relativity code | 25 pages, 20 figures, published version. Results are reproducible
with the ancillary input files | Phys. Rev. D 105, 084027 (2022) | 10.1103/PhysRevD.105.084027 | null | gr-qc physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Elliptic partial differential equations must be solved numerically for many
problems in numerical relativity, such as initial data for every simulation of
merging black holes and neutron stars. Existing elliptic solvers can take
multiple days to solve these problems at high resolution and when matter is
involved, because they are either hard to parallelize or require a large amount
of computational resources. Here we present a new solver for linear and
nonlinear elliptic problems that is designed to scale with resolution and to
parallelize on computing clusters. To achieve this we employ a discontinuous
Galerkin discretization, an iterative multigrid-Schwarz preconditioned
Newton-Krylov algorithm, and a task-based parallelism paradigm. To accelerate
convergence of the elliptic solver we have developed novel
subdomain-preconditioning techniques. We find that our multigrid-Schwarz
preconditioned elliptic solves achieve iteration counts that are independent of
resolution, and our task-based parallel programs scale over 200 million degrees
of freedom to at least a few thousand cores. Our new code solves a classic
initial data problem for binary black holes faster than the spectral code SpEC
when distributed to only eight cores, and in a fraction of the time on more
cores. It is publicly accessible in the next-generation SpECTRE numerical
relativity code. Our results pave the way for highly parallel elliptic solves
in numerical relativity and beyond.
| [
{
"created": "Fri, 12 Nov 2021 15:23:45 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Apr 2022 15:18:07 GMT",
"version": "v2"
}
] | 2022-04-19 | [
[
"Vu",
"Nils L.",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Bonilla",
"Gabriel S.",
""
],
[
"Deppe",
"Nils",
""
],
[
"Hébert",
"François",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Lovelace",
"Geoffrey",
""
... | Elliptic partial differential equations must be solved numerically for many problems in numerical relativity, such as initial data for every simulation of merging black holes and neutron stars. Existing elliptic solvers can take multiple days to solve these problems at high resolution and when matter is involved, because they are either hard to parallelize or require a large amount of computational resources. Here we present a new solver for linear and nonlinear elliptic problems that is designed to scale with resolution and to parallelize on computing clusters. To achieve this we employ a discontinuous Galerkin discretization, an iterative multigrid-Schwarz preconditioned Newton-Krylov algorithm, and a task-based parallelism paradigm. To accelerate convergence of the elliptic solver we have developed novel subdomain-preconditioning techniques. We find that our multigrid-Schwarz preconditioned elliptic solves achieve iteration counts that are independent of resolution, and our task-based parallel programs scale over 200 million degrees of freedom to at least a few thousand cores. Our new code solves a classic initial data problem for binary black holes faster than the spectral code SpEC when distributed to only eight cores, and in a fraction of the time on more cores. It is publicly accessible in the next-generation SpECTRE numerical relativity code. Our results pave the way for highly parallel elliptic solves in numerical relativity and beyond. |
2006.03540 | Paul Abel | Derek J. Raine, Paul G. Abel | Quantum Optics of an Oscillator Falling into a Black Hole | 28 pages, 1 figure | null | 10.1088/1361-6382/abc8c8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a quantum optics treatment of the near horizon behaviour of a
quantum oscillator freely-falling into a pre-existing Schwarzschild black hole.
We use Painleve-Gullstrand coordinates to define a global vacuum state. In
contrast to an accelerated oscillator in the Minkowski vacuum, where there is
no radiation beyond an initial transient, we find that the oscillator radiates
positive energy to to infinity and negative energy into the black hole as it
attempts to come into equilibrium with the ambient vacuum. We discuss the
relationship of the model to Hawking radiation.
| [
{
"created": "Fri, 5 Jun 2020 16:28:04 GMT",
"version": "v1"
}
] | 2021-02-03 | [
[
"Raine",
"Derek J.",
""
],
[
"Abel",
"Paul G.",
""
]
] | We present a quantum optics treatment of the near horizon behaviour of a quantum oscillator freely-falling into a pre-existing Schwarzschild black hole. We use Painleve-Gullstrand coordinates to define a global vacuum state. In contrast to an accelerated oscillator in the Minkowski vacuum, where there is no radiation beyond an initial transient, we find that the oscillator radiates positive energy to to infinity and negative energy into the black hole as it attempts to come into equilibrium with the ambient vacuum. We discuss the relationship of the model to Hawking radiation. |
1712.04813 | Przemyslaw Malkiewicz | Przemys{\l}aw Ma{\l}kiewicz, Artur Miroszewski, Herv\'e Bergeron | Quantum phase space trajectories with application to quantum cosmology | 11 pages, 4 figures, the new version contains improved discussions | Phys. Rev. D 98, 026030 (2018) | 10.1103/PhysRevD.98.026030 | null | gr-qc math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop an approach to quantum dynamics based on quantum phase space
trajectories. The latter are built from a unitary irreducible representation of
the symmetry group of the respective classical phase space. We use a quantum
action functional to derive the basic equations. In principle, our formulation
is equivalent to the Hilbert space formulation. However, the former allows for
consistent truncations to reduced phase spaces in which approximate quantum
dynamics can be derived. We believe that our approach can be very useful in the
domain of quantum cosmology and therefore, we use the cosmological phase space
example to establish the basic equations of this formalism.
| [
{
"created": "Wed, 13 Dec 2017 15:16:30 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Mar 2018 09:26:02 GMT",
"version": "v2"
}
] | 2018-08-08 | [
[
"Małkiewicz",
"Przemysław",
""
],
[
"Miroszewski",
"Artur",
""
],
[
"Bergeron",
"Hervé",
""
]
] | We develop an approach to quantum dynamics based on quantum phase space trajectories. The latter are built from a unitary irreducible representation of the symmetry group of the respective classical phase space. We use a quantum action functional to derive the basic equations. In principle, our formulation is equivalent to the Hilbert space formulation. However, the former allows for consistent truncations to reduced phase spaces in which approximate quantum dynamics can be derived. We believe that our approach can be very useful in the domain of quantum cosmology and therefore, we use the cosmological phase space example to establish the basic equations of this formalism. |
gr-qc/0410051 | Riccardo Sturani | Orestis Malaspinas and Riccardo Sturani (U. of Geneva) | Detecting a stochastic background of gravitational waves by correlating
n detectors | 12 pages, version accepted by Class. & Quant. Grav | Class.Quant.Grav. 23 (2006) 319-328 | 10.1088/0264-9381/23/2/003 | null | gr-qc | null | We discuss the optimal detection strategy for a stochastic background of
gravitational waves in the case n detectors are available. In literature so
far, only two cases have been considered: 2- and n-point correlators. We
generalize these analysises to m-point correlators (with m<n) built out of the
n detector signals, obtaining the result that the optimal choice is to combine
2-point correlators. Correlating n detectors in this optimal way will improve
the (suitably defined) signal-to-noise ratio with respect to the n=2 case by a
factor equal to the fourth root of n(n-1)/2. Finally we give an estimation of
how this could improve the sensitivity for a network of multi-mode spherical
antennas.
| [
{
"created": "Tue, 12 Oct 2004 14:06:12 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Nov 2005 14:17:21 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Malaspinas",
"Orestis",
"",
"U. of Geneva"
],
[
"Sturani",
"Riccardo",
"",
"U. of Geneva"
]
] | We discuss the optimal detection strategy for a stochastic background of gravitational waves in the case n detectors are available. In literature so far, only two cases have been considered: 2- and n-point correlators. We generalize these analysises to m-point correlators (with m<n) built out of the n detector signals, obtaining the result that the optimal choice is to combine 2-point correlators. Correlating n detectors in this optimal way will improve the (suitably defined) signal-to-noise ratio with respect to the n=2 case by a factor equal to the fourth root of n(n-1)/2. Finally we give an estimation of how this could improve the sensitivity for a network of multi-mode spherical antennas. |
1808.10206 | Alexander Silenko | Alexander J. Silenko and Yury A. Tsalkou | Quasi-uniform gravitational field of a disk revisited | 32 pages | null | 10.1142/S0217751X19502282 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the quasi-uniform gravitational field of a disk in the
weak-field approximation and demonstrate an inappropriateness of preceding
results. The Riemann tensor of this field is determined. The nonexistence of
the uniform gravitational field is proven without the use of the weak-field
approximation. The previously found difference between equations of motion for
the momentum and spin in the accelerated frame and in the quasi-uniform
gravitational field also takes place for the disk. However, it does not violate
the Einstein equivalence principle because of the nonexistence of the uniform
gravitational field.
| [
{
"created": "Thu, 30 Aug 2018 10:14:03 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Nov 2019 17:19:09 GMT",
"version": "v2"
}
] | 2020-01-29 | [
[
"Silenko",
"Alexander J.",
""
],
[
"Tsalkou",
"Yury A.",
""
]
] | We calculate the quasi-uniform gravitational field of a disk in the weak-field approximation and demonstrate an inappropriateness of preceding results. The Riemann tensor of this field is determined. The nonexistence of the uniform gravitational field is proven without the use of the weak-field approximation. The previously found difference between equations of motion for the momentum and spin in the accelerated frame and in the quasi-uniform gravitational field also takes place for the disk. However, it does not violate the Einstein equivalence principle because of the nonexistence of the uniform gravitational field. |
1507.03714 | Roldao da Rocha | R. T. Cavalcanti, Roldao da Rocha | Dark Spinors Hawking Radiation in String Theory Black Holes | 11 pages, improved version, to appear in AHEP | Adv.High Energy Phys. 2016 (2016) 4681902 | 10.1155/2016/4681902 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hawking radiation spectrum of Kerr-Sen axion-dilaton black holes is
derived, in the context of dark spinors tunnelling across the horizon. Since a
black hole has a well defined temperature, it should radiate in principle all
the standard model particles, similar to a black body at that temperature. We
investigate the tunnelling of mass dimension one spin-1/2 dark fermions, that
are beyond the standard model and are prime candidates to the dark matter.
Their interactions with the standard model matter and gauge fields are
suppressed by at least one power of unification scale, being restricted just to
the Higgs field and to the graviton likewise. The tunnelling method for the
emission and absorption of mass dimension one particles across the event
horizon of Kerr-Sen axion-dilaton black holes is shown here to provide further
evidence for the universality of black hole radiation, further encompassing
particles beyond the standard model.
| [
{
"created": "Tue, 14 Jul 2015 03:54:52 GMT",
"version": "v1"
},
{
"created": "Sun, 10 Jan 2016 21:56:14 GMT",
"version": "v2"
}
] | 2016-01-14 | [
[
"Cavalcanti",
"R. T.",
""
],
[
"da Rocha",
"Roldao",
""
]
] | The Hawking radiation spectrum of Kerr-Sen axion-dilaton black holes is derived, in the context of dark spinors tunnelling across the horizon. Since a black hole has a well defined temperature, it should radiate in principle all the standard model particles, similar to a black body at that temperature. We investigate the tunnelling of mass dimension one spin-1/2 dark fermions, that are beyond the standard model and are prime candidates to the dark matter. Their interactions with the standard model matter and gauge fields are suppressed by at least one power of unification scale, being restricted just to the Higgs field and to the graviton likewise. The tunnelling method for the emission and absorption of mass dimension one particles across the event horizon of Kerr-Sen axion-dilaton black holes is shown here to provide further evidence for the universality of black hole radiation, further encompassing particles beyond the standard model. |
2207.02564 | Bart{\l}omiej Kiczek | Bartlomiej Kiczek and Marek Rogatko | Static axionlike dark matter clouds around magnetized rotating wormholes
-- probe limit case | null | Eur. Phys. J. C 82, 586 (2022) | 10.1140/epjc/s10052-022-10545-0 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The problem of the distribution of axionlike particle, being the model of
dark matter, in the nearby of rotating wormholes has been investigated
numerically. In the model in question the axion scalar is non-trivially coupled
to the Maxwell gauge field. We consider two toy models of rotating wormholes
embedded in magnetic field, Kerr-like and Teo rotating wormholes. Moreover one
assumes that the matter fields will not backreact on the wormhole spacetimes,
i.e., we shall study the problem in the probe limit case. We point out the
differences in the distribution of dark matter comparing to the location of it
in the vicinity of rotating magnetized black holes.
| [
{
"created": "Wed, 6 Jul 2022 10:23:09 GMT",
"version": "v1"
}
] | 2022-07-07 | [
[
"Kiczek",
"Bartlomiej",
""
],
[
"Rogatko",
"Marek",
""
]
] | The problem of the distribution of axionlike particle, being the model of dark matter, in the nearby of rotating wormholes has been investigated numerically. In the model in question the axion scalar is non-trivially coupled to the Maxwell gauge field. We consider two toy models of rotating wormholes embedded in magnetic field, Kerr-like and Teo rotating wormholes. Moreover one assumes that the matter fields will not backreact on the wormhole spacetimes, i.e., we shall study the problem in the probe limit case. We point out the differences in the distribution of dark matter comparing to the location of it in the vicinity of rotating magnetized black holes. |
1605.06011 | Paul G.N. de Vegvar | P. G. N. de Vegvar | Commutative deformations of general relativity: nonlocality, causality,
and dark matter | 47 pages including references, 0 figures, 0 tables Various
typos/omissions corrected | The Europhysical Jornal C, 77(1) 1-26, January 30, 2016 | 10.1140/epjc/s10052-017-4605-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hopf algebra methods are applied to study Drinfeld twists of
(3+1)-diffeomorphisms and deformed general relativity on \emph{commutative}
manifolds. A classical nonlocality length scale is produced above which
microcausality emerges. Matter fields are utilized to generate self-consistent
Abelian Drinfeld twists in a background independent manner and their continuous
and discrete symmetries are examined. There is negligible experimental effect
on the standard model of particles. While baryonic twist producing matter would
begin to behave acausally for rest masses above $\sim1-10$ TeV, other
possibilities are viable dark matter candidates or a right handed neutrino.
First order deformed Maxwell equations are derived and yield immeasurably small
cosmological dispersion and produce a propagation horizon only for photons at
or above Planck energies. This model incorporates dark matter without any
appeal to extra dimensions, supersymmetry, strings, grand unified theories,
mirror worlds, or modifications of Newtonian dynamics.
| [
{
"created": "Mon, 16 May 2016 02:25:15 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Nov 2016 18:36:40 GMT",
"version": "v2"
},
{
"created": "Sun, 11 Dec 2016 02:26:34 GMT",
"version": "v3"
},
{
"created": "Sun, 1 Jan 2017 20:47:13 GMT",
"version": "v4"
}
] | 2017-03-08 | [
[
"de Vegvar",
"P. G. N.",
""
]
] | Hopf algebra methods are applied to study Drinfeld twists of (3+1)-diffeomorphisms and deformed general relativity on \emph{commutative} manifolds. A classical nonlocality length scale is produced above which microcausality emerges. Matter fields are utilized to generate self-consistent Abelian Drinfeld twists in a background independent manner and their continuous and discrete symmetries are examined. There is negligible experimental effect on the standard model of particles. While baryonic twist producing matter would begin to behave acausally for rest masses above $\sim1-10$ TeV, other possibilities are viable dark matter candidates or a right handed neutrino. First order deformed Maxwell equations are derived and yield immeasurably small cosmological dispersion and produce a propagation horizon only for photons at or above Planck energies. This model incorporates dark matter without any appeal to extra dimensions, supersymmetry, strings, grand unified theories, mirror worlds, or modifications of Newtonian dynamics. |
gr-qc/0302032 | Simonetta Frittelli | Simonetta Frittelli (Duquesne University) and Roberto Gomez
(Pittsburgh Supercomputing Center) | Boundary conditions for hyperbolic formulations of the Einstein
equations | 15 pages; text added and typesetting errors corrected; to appear in
Classical and Quantum Gravity | Class.Quant.Grav.20:2379-2392,2003 | 10.1088/0264-9381/20/11/327 | null | gr-qc | null | In regards to the initial-boundary value problem of the Einstein equations,
we argue that the projection of the Einstein equations along the normal to the
boundary yields necessary and appropriate boundary conditions for a wide class
of equivalent formulations. We explicitly show that this is so for the
Einstein-Christoffel formulation of the Einstein equations in the case of
spherical symmetry.
| [
{
"created": "Mon, 10 Feb 2003 14:54:47 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Apr 2003 19:13:07 GMT",
"version": "v2"
}
] | 2011-07-19 | [
[
"Frittelli",
"Simonetta",
"",
"Duquesne University"
],
[
"Gomez",
"Roberto",
"",
"Pittsburgh Supercomputing Center"
]
] | In regards to the initial-boundary value problem of the Einstein equations, we argue that the projection of the Einstein equations along the normal to the boundary yields necessary and appropriate boundary conditions for a wide class of equivalent formulations. We explicitly show that this is so for the Einstein-Christoffel formulation of the Einstein equations in the case of spherical symmetry. |
gr-qc/9602005 | null | A. Chamorro and K. S. Virbhadra | Energy of a spherically symmetric charged dilaton black hole | 3 pages, LaTex, Published in "Inhomogeneous Cosmological Models",
(Eds. A Molina and J M M Senovilla, World Scientific, Singapore 1995), Pages
230-232 | null | null | null | gr-qc astro-ph hep-th | null | The energy associated with a static and spherically symmetric charged dilaton
black hole is obtained for arbitrary value of the coupling parameter (which
regulates the strength of the coupling of the dilaton to the Maxwell field)
$\beta$. The energy distribution depends on $\beta$, whereas the total energy
is independent of this and is given by the mass parameter of the black hole.
| [
{
"created": "Fri, 2 Feb 1996 08:37:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Chamorro",
"A.",
""
],
[
"Virbhadra",
"K. S.",
""
]
] | The energy associated with a static and spherically symmetric charged dilaton black hole is obtained for arbitrary value of the coupling parameter (which regulates the strength of the coupling of the dilaton to the Maxwell field) $\beta$. The energy distribution depends on $\beta$, whereas the total energy is independent of this and is given by the mass parameter of the black hole. |
1302.7170 | Chul-Moon Yoo | Chul-Moon Yoo, Tomohiro Harada and Naoki Tsukamoto | Wave Effect in Gravitational Lensing by the Ellis Wormhole | 18 pages, 8 figures | null | 10.1103/PhysRevD.87.084045 | YITP-13-15, RUP-13-3 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose the use of modulated spectra of astronomical sources due to
gravitational lensing to probe Ellis wormholes. The modulation factor due to
gravitational lensing by the Ellis wormhole is calculated. Within the
geometrical optics approximation, the normal point mass lens and the Ellis
wormhole are indistinguishable unless we know the source's unlensed luminosity.
This degeneracy is resolved with the significant wave effect in the low
frequency domain if we take the deviation from the geometrical optics into
account. We can roughly estimate the upper bound for the number density of
Ellis wormholes as $n\lesssim 10^{-9}\{AU}^{-3}$ with throat radius $a\sim1\cm$
from the existing femto-lensing analysis for compact objects.
| [
{
"created": "Thu, 28 Feb 2013 12:31:02 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Mar 2013 12:26:12 GMT",
"version": "v2"
}
] | 2013-04-24 | [
[
"Yoo",
"Chul-Moon",
""
],
[
"Harada",
"Tomohiro",
""
],
[
"Tsukamoto",
"Naoki",
""
]
] | We propose the use of modulated spectra of astronomical sources due to gravitational lensing to probe Ellis wormholes. The modulation factor due to gravitational lensing by the Ellis wormhole is calculated. Within the geometrical optics approximation, the normal point mass lens and the Ellis wormhole are indistinguishable unless we know the source's unlensed luminosity. This degeneracy is resolved with the significant wave effect in the low frequency domain if we take the deviation from the geometrical optics into account. We can roughly estimate the upper bound for the number density of Ellis wormholes as $n\lesssim 10^{-9}\{AU}^{-3}$ with throat radius $a\sim1\cm$ from the existing femto-lensing analysis for compact objects. |
1005.4102 | Xin-Zhou Li | Ping Xi, Xi-chen Ao and Xin-zhou Li | A simple derivation of level spacing of quasinormal frequencies for a
black hole with a deficit solid angle and quintessence-like matter | 6 pages, Accepted for publication in Astrophysics & Space Science | Astrophys.Space Sci.330:273-278,2010 | 10.1007/s10509-010-0410-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate analytically the level space of the imaginary
part of quasinormal frequencies for a black hole with a deficit solid angle and
quintessence-like matter by the Padmanabhan's method \cite{Padmanabhan}.
Padmanabhan presented a method to study analytically the imaginary part of
quasinormal frequencies for a class of spherically symmetric spacetimes
including Schwarzschild-de Sitter black holes which has an evenly spaced
structure. The results show that the level space of scalar and gravitational
quasinormal frequencies for this kind of black holes only depend on the surface
gravity of black-hole horizon in the range of -1 < w < -1/3, respectively . We
also extend the range of $w$ to $w \leq -1$, the results of which are similar
to that in -1 < w < -1/3 case. Particularly, a black hole with a deficit solid
angle in accelerating universe will be a Schwarzschild-de Sitter black hole,
fixing $w = -1$ and $\epsilon^2 = 0$. And a black hole with a deficit solid
angle in the accelerating universe will be a Schwarzschild black hole,when
$\rho_0 = 0$ and $\epsilon^2 = 0$. In this paper, $w$ is the parameter of state
equation, $\epsilon^2$ is a parameter relating to a deficit solid angle and
$\rho_0$ is the density of static spherically symmetrical quintessence-like
matter at $r = 1$.
| [
{
"created": "Sat, 22 May 2010 03:26:11 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Nov 2010 01:56:33 GMT",
"version": "v2"
}
] | 2010-11-05 | [
[
"Xi",
"Ping",
""
],
[
"Ao",
"Xi-chen",
""
],
[
"Li",
"Xin-zhou",
""
]
] | In this paper, we investigate analytically the level space of the imaginary part of quasinormal frequencies for a black hole with a deficit solid angle and quintessence-like matter by the Padmanabhan's method \cite{Padmanabhan}. Padmanabhan presented a method to study analytically the imaginary part of quasinormal frequencies for a class of spherically symmetric spacetimes including Schwarzschild-de Sitter black holes which has an evenly spaced structure. The results show that the level space of scalar and gravitational quasinormal frequencies for this kind of black holes only depend on the surface gravity of black-hole horizon in the range of -1 < w < -1/3, respectively . We also extend the range of $w$ to $w \leq -1$, the results of which are similar to that in -1 < w < -1/3 case. Particularly, a black hole with a deficit solid angle in accelerating universe will be a Schwarzschild-de Sitter black hole, fixing $w = -1$ and $\epsilon^2 = 0$. And a black hole with a deficit solid angle in the accelerating universe will be a Schwarzschild black hole,when $\rho_0 = 0$ and $\epsilon^2 = 0$. In this paper, $w$ is the parameter of state equation, $\epsilon^2$ is a parameter relating to a deficit solid angle and $\rho_0$ is the density of static spherically symmetrical quintessence-like matter at $r = 1$. |
2101.04496 | Sujay Kr. Biswas | Goutam Mandal, Soumya Chakraborty, Sudip Mishra and Sujay Kr. Biswas | A study of interacting scalar field model from the perspective of the
dynamical systems theory | 29 pages, 10 captioned figures. Title changed. The paper is revised
thoroughly. The version is published in The Physics of the Dark Universe | Phys.Dark Univ. 40 (2023) 101210 | 10.1016/j.dark.2023.101210 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, considering the background dynamics of flat
Friedmann-Lemaitre-Robertson-Walker(FLRW) model of the universe, we investigate
a scalar field model as dark energy candidate which interacting with the
pressure-less dust as dark matter from dynamical systems perspective. From
phenomenological vantage point two interaction terms are chosen: one depends on
Hubble parameter $H$ and other is local, independent of Hubble parameter. In
interaction model 1, the scalar field potential as well as the coupling are
considered to be in the form of inverse square and accordingly a
two-dimensional autonomous system is obtained. On the other hand, Interaction
model 2 comprises with the potential as well as coupling of scalar field which
are considered in form of exponential function of scalar field ($\phi$) and as
a result of which a four-dimensional autonomous system is achieved. We study
two systems separately and come by several critical points in 2D system as well
as in 4D system. We have derived sound speed and the classical stability
conditions. Furthermore, for 2D autonomous system we analyzed the stability of
some critical points at infinity. From this autonomous system, we obtain scalar
field dominated solutions representing late time accelerated evolution of the
universe that does not elucidate the coincidence problem. Late time scaling
solutions are also realized by the accelerated expansion of the universe which
evolves in quintessence era that alleviates the coincidence problem
successfully. From the analysis of 4D system, we obtain non-hyperbolic sets of
critical points which are analyzed by the center manifold theory. In this
model, the de Sitter like solutions represent the transient evolution of the
universe.
| [
{
"created": "Sat, 9 Jan 2021 15:45:38 GMT",
"version": "v1"
},
{
"created": "Wed, 24 May 2023 13:21:04 GMT",
"version": "v2"
}
] | 2023-05-25 | [
[
"Mandal",
"Goutam",
""
],
[
"Chakraborty",
"Soumya",
""
],
[
"Mishra",
"Sudip",
""
],
[
"Biswas",
"Sujay Kr.",
""
]
] | In this work, considering the background dynamics of flat Friedmann-Lemaitre-Robertson-Walker(FLRW) model of the universe, we investigate a scalar field model as dark energy candidate which interacting with the pressure-less dust as dark matter from dynamical systems perspective. From phenomenological vantage point two interaction terms are chosen: one depends on Hubble parameter $H$ and other is local, independent of Hubble parameter. In interaction model 1, the scalar field potential as well as the coupling are considered to be in the form of inverse square and accordingly a two-dimensional autonomous system is obtained. On the other hand, Interaction model 2 comprises with the potential as well as coupling of scalar field which are considered in form of exponential function of scalar field ($\phi$) and as a result of which a four-dimensional autonomous system is achieved. We study two systems separately and come by several critical points in 2D system as well as in 4D system. We have derived sound speed and the classical stability conditions. Furthermore, for 2D autonomous system we analyzed the stability of some critical points at infinity. From this autonomous system, we obtain scalar field dominated solutions representing late time accelerated evolution of the universe that does not elucidate the coincidence problem. Late time scaling solutions are also realized by the accelerated expansion of the universe which evolves in quintessence era that alleviates the coincidence problem successfully. From the analysis of 4D system, we obtain non-hyperbolic sets of critical points which are analyzed by the center manifold theory. In this model, the de Sitter like solutions represent the transient evolution of the universe. |
2309.14061 | Daiki Watarai | Daiki Watarai, Atsushi Nishizawa, Kipp Cannon | Physically consistent gravitational waveform for capturing beyond
general relativity effects in the compact object merger phase | 21 pages, 10 figures | null | null | RESCEU-21/23 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The merger phase of compact binary coalescences is the strongest gravity
regime that can be observed. To test the validity of general relativity (GR) in
strong gravitational fields, we propose a gravitational waveform parameterized
for deviations from GR in the dynamical and nonlinear regime of gravity. Our
fundamental idea is that perturbative modifications to a GR waveform can
capture possible deviations in the merger phase that are difficult to model in
a specific theory of gravity. One of notable points is that our waveform is
physically consistent in the sense that the additional radiative losses of
energy and angular momentum associated with beyond-GR modifications are
included. Our prescription to ensure physical consistency in the whole
coalescence process is expected to be applicable to any deviation from the
standard model of compact binary coalescence, such as the extended models of
gravity or the environmental effects of compact objects, as long as
perturbative modifications are considered. Based on the Fisher analysis and the
compatibility with Einstein-dilaton Gauss-Bonnet waveforms, we show that our
parameterization is a physically-consistent minimal one that captures the
deviations in the nonlinear regime.
| [
{
"created": "Mon, 25 Sep 2023 11:53:59 GMT",
"version": "v1"
}
] | 2023-09-26 | [
[
"Watarai",
"Daiki",
""
],
[
"Nishizawa",
"Atsushi",
""
],
[
"Cannon",
"Kipp",
""
]
] | The merger phase of compact binary coalescences is the strongest gravity regime that can be observed. To test the validity of general relativity (GR) in strong gravitational fields, we propose a gravitational waveform parameterized for deviations from GR in the dynamical and nonlinear regime of gravity. Our fundamental idea is that perturbative modifications to a GR waveform can capture possible deviations in the merger phase that are difficult to model in a specific theory of gravity. One of notable points is that our waveform is physically consistent in the sense that the additional radiative losses of energy and angular momentum associated with beyond-GR modifications are included. Our prescription to ensure physical consistency in the whole coalescence process is expected to be applicable to any deviation from the standard model of compact binary coalescence, such as the extended models of gravity or the environmental effects of compact objects, as long as perturbative modifications are considered. Based on the Fisher analysis and the compatibility with Einstein-dilaton Gauss-Bonnet waveforms, we show that our parameterization is a physically-consistent minimal one that captures the deviations in the nonlinear regime. |
1806.07160 | Paul Frampton | P.H. Frampton | Cyclic Cosmology and Holographic Entanglement Entropy | 8 pages LaTex. Talk at Conference on Particle and Cosmology, Nanyang
Technological University, Singapore. March 5-9, 2018 | null | 10.1142/S0217751X18440281 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | No abstract prepared.
| [
{
"created": "Tue, 19 Jun 2018 11:29:03 GMT",
"version": "v1"
}
] | 2018-12-05 | [
[
"Frampton",
"P. H.",
""
]
] | No abstract prepared. |
1509.02481 | Ott Vilson | Ott Vilson | Some remarks concerning invariant quantities in scalar-tensor gravity | 16 pages, Advances in Applied Clifford Algebras 2015 | Adv. Appl. Clifford Algebras 27, 321-332 (2017) | 10.1007/s00006-015-0567-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The aim of the current paper is to clarify some aspects of the formalism used
for describing the scalar-tensor gravity characterized by four arbitrary local
functionals of the scalar field. We recall the objects that are invariant with
respect to a spacetime point under the local Weyl rescaling of the metric and
under the scalar field redefinition. We phrase and prove a theorem that allows
to link such an object to each quantity in a theory where two out of the four
arbitrary local functionals of the scalar field are specified in a suitable
manner. Based on these results we phrase and reason the existence of the so
called translation rules.
| [
{
"created": "Tue, 8 Sep 2015 18:18:10 GMT",
"version": "v1"
}
] | 2017-06-13 | [
[
"Vilson",
"Ott",
""
]
] | The aim of the current paper is to clarify some aspects of the formalism used for describing the scalar-tensor gravity characterized by four arbitrary local functionals of the scalar field. We recall the objects that are invariant with respect to a spacetime point under the local Weyl rescaling of the metric and under the scalar field redefinition. We phrase and prove a theorem that allows to link such an object to each quantity in a theory where two out of the four arbitrary local functionals of the scalar field are specified in a suitable manner. Based on these results we phrase and reason the existence of the so called translation rules. |
gr-qc/0606064 | Piotr T. Chru\'sciel | Piotr T. Chrusciel, Daniel Maerten, Paul Tod | Rigid upper bounds for the angular momentum and centre of mass of
non-singular asymptotically anti-de Sitter space-times | improvements in the presentation; some statements corrected | JHEP 0611 (2006) 084 | 10.1088/1126-6708/2006/11/084 | AEI-2006-041 | gr-qc hep-th | null | We prove upper bounds on angular momentum and centre of mass in terms of the
Hamiltonian mass and cosmological constant for non-singular asymptotically
anti-de Sitter initial data sets satisfying the dominant energy condition. We
work in all space-dimensions larger than or equal to three, and allow a large
class of asymptotic backgrounds, with spherical and non-spherical conformal
infinities; in the latter case, a spin-structure compatibility condition is
imposed. We give a large class of non-trivial examples saturating the
inequality. We analyse exhaustively the borderline case in space-time dimension
four: for spherical cross-sections of Scri, equality together with completeness
occurs only in anti-de Sitter space-time. On the other hand, in the toroidal
case, regular non-trivial initial data sets saturating the bound exist.
| [
{
"created": "Wed, 14 Jun 2006 21:53:25 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Nov 2006 13:22:52 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Chrusciel",
"Piotr T.",
""
],
[
"Maerten",
"Daniel",
""
],
[
"Tod",
"Paul",
""
]
] | We prove upper bounds on angular momentum and centre of mass in terms of the Hamiltonian mass and cosmological constant for non-singular asymptotically anti-de Sitter initial data sets satisfying the dominant energy condition. We work in all space-dimensions larger than or equal to three, and allow a large class of asymptotic backgrounds, with spherical and non-spherical conformal infinities; in the latter case, a spin-structure compatibility condition is imposed. We give a large class of non-trivial examples saturating the inequality. We analyse exhaustively the borderline case in space-time dimension four: for spherical cross-sections of Scri, equality together with completeness occurs only in anti-de Sitter space-time. On the other hand, in the toroidal case, regular non-trivial initial data sets saturating the bound exist. |
1512.02639 | Kent Yagi | Kent Yagi and Nicolas Yunes | Binary Love Relations | 10 pages, 4 figures; fitting formulas added, accepted to CQG Letter | null | 10.1088/0264-9381/33/13/13LT01 | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When in a tight binary, the mutual tidal deformations of neutron stars
imprint onto observables, encoding information about their internal structure
at supranuclear densities and gravity in the extreme-gravity regime.
Gravitational wave observations of their late binary inspiral may serve as a
tool to extract the individual tidal deformabilities, but this is made
difficult by degeneracies between them in the gravitational wave model. We here
resolve this problem by discovering approximately universal relations between
dimensionless combinations of the individual tidal deformabilities. We show
that these relations break degeneracies in the gravitational wave model,
allowing for the accurate extraction of both deformabilities. Such measurements
can be used to better differentiate between equation-of-state models, and
improve tests of General Relativity and cosmology.
| [
{
"created": "Tue, 8 Dec 2015 21:00:04 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Jun 2016 17:57:29 GMT",
"version": "v2"
}
] | 2016-06-22 | [
[
"Yagi",
"Kent",
""
],
[
"Yunes",
"Nicolas",
""
]
] | When in a tight binary, the mutual tidal deformations of neutron stars imprint onto observables, encoding information about their internal structure at supranuclear densities and gravity in the extreme-gravity regime. Gravitational wave observations of their late binary inspiral may serve as a tool to extract the individual tidal deformabilities, but this is made difficult by degeneracies between them in the gravitational wave model. We here resolve this problem by discovering approximately universal relations between dimensionless combinations of the individual tidal deformabilities. We show that these relations break degeneracies in the gravitational wave model, allowing for the accurate extraction of both deformabilities. Such measurements can be used to better differentiate between equation-of-state models, and improve tests of General Relativity and cosmology. |
1006.0192 | Adriano Contillo | Alfio Bonanno, Adriano Contillo, Roberto Percacci | Inflationary solutions in asymptotically safe f(R) theories | 25 pages, 6 figures; accepted for publication in Clas.Quant.Grav | Class.Quant.Grav.28:145026,2011 | 10.1088/0264-9381/28/14/145026 | PI-QG-185 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the existence of inflationary solutions in a class of
renormalization group improved polynomial f(R) theories, which have been
studied recently in the context of the asymptotic safety scenario for quantum
gravity. These theories seem to possess a nontrivial ultraviolet fixed point,
where the dimensionful couplings scale according to their canonical
dimensionality. Assuming that the cutoff is proportional to the Hubble
parameter, we obtain modified Friedmann equations which admit both power law
and exponential solutions. We establish that for sufficiently high order
polynomial the solutions are reliable, in the sense that considering still
higher order polynomials is very unlikely to change the solution.
| [
{
"created": "Tue, 1 Jun 2010 17:32:18 GMT",
"version": "v1"
},
{
"created": "Fri, 27 May 2011 13:21:57 GMT",
"version": "v2"
}
] | 2011-06-24 | [
[
"Bonanno",
"Alfio",
""
],
[
"Contillo",
"Adriano",
""
],
[
"Percacci",
"Roberto",
""
]
] | We discuss the existence of inflationary solutions in a class of renormalization group improved polynomial f(R) theories, which have been studied recently in the context of the asymptotic safety scenario for quantum gravity. These theories seem to possess a nontrivial ultraviolet fixed point, where the dimensionful couplings scale according to their canonical dimensionality. Assuming that the cutoff is proportional to the Hubble parameter, we obtain modified Friedmann equations which admit both power law and exponential solutions. We establish that for sufficiently high order polynomial the solutions are reliable, in the sense that considering still higher order polynomials is very unlikely to change the solution. |
2203.00413 | Mouhssine Koussour | M. Koussour, S. H. Shekh, A. Hanin, Z. Sakhi, S. R. Bhoyer and M.
Bennai | Flat FLRW Universe in logarithmic symmetric teleparallel gravity with
observational constraints | CQG accepted version | Classical and Quantum Gravity (2022) | 10.1088/1361-6382/ac8c7d | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the homogeneous and isotropic flat FLRW
Universe in the logarithmic form of $f\left( Q\right) $ gravity, where $% Q $
is the non-metricity scalar, specifically, $f\left( Q\right) =\alpha +\beta
\log \left( Q\right) $, where $\alpha $ and $\beta $ are free model parameters.
In this study, we consider a parametrization of the Hubble parameter as
$H\left( z\right) =\eta \left[ (z+1)^{-\gamma }+1\right] $, where $\gamma $ and
$\eta $ are model/free parameters which are constrained by an $R^{2}$-test from
57 points of the Hubble datasets in the redshift range $0.07<z<2.36$. Further,
we investigate the physical properties of the model. We analyze the energy
conditions to check the compatibility of the model. We found the SEC is
violated for the logarithmic form of $f\left( Q\right) $ gravity due to the
reality that the Universe in an accelerating phase. Finally, we discuss some
important cosmological parameters in this context to compare our model with
dark energy models such as jerk parameter and statefinder parameters.
| [
{
"created": "Sun, 27 Feb 2022 17:25:54 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Aug 2022 20:29:20 GMT",
"version": "v2"
}
] | 2022-08-30 | [
[
"Koussour",
"M.",
""
],
[
"Shekh",
"S. H.",
""
],
[
"Hanin",
"A.",
""
],
[
"Sakhi",
"Z.",
""
],
[
"Bhoyer",
"S. R.",
""
],
[
"Bennai",
"M.",
""
]
] | In this paper, we investigate the homogeneous and isotropic flat FLRW Universe in the logarithmic form of $f\left( Q\right) $ gravity, where $% Q $ is the non-metricity scalar, specifically, $f\left( Q\right) =\alpha +\beta \log \left( Q\right) $, where $\alpha $ and $\beta $ are free model parameters. In this study, we consider a parametrization of the Hubble parameter as $H\left( z\right) =\eta \left[ (z+1)^{-\gamma }+1\right] $, where $\gamma $ and $\eta $ are model/free parameters which are constrained by an $R^{2}$-test from 57 points of the Hubble datasets in the redshift range $0.07<z<2.36$. Further, we investigate the physical properties of the model. We analyze the energy conditions to check the compatibility of the model. We found the SEC is violated for the logarithmic form of $f\left( Q\right) $ gravity due to the reality that the Universe in an accelerating phase. Finally, we discuss some important cosmological parameters in this context to compare our model with dark energy models such as jerk parameter and statefinder parameters. |
1108.5991 | Jonathan Halliwell | J.J.Halliwell | Decoherent Histories Analysis of Minisuperspace Quantum Cosmology | To appear in Proceedings of the 2010 DICE Conference | J. Phys.: Conf. Ser.. 306: 012023 (2011) | 10.1088/1742-6596/306/1/012023 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent results on the decoherent histories quantization of simple
cosmological models (minisuperspace models) are described. The most important
issue is the construction, from the wave function, of a probability
distribution answering various questions of physical interest, such as the
probability of the system entering a given region of configuration space at any
stage in its entire history. A standard but heuristic procedure is to use the
flux of (components of) the wave function in a WKB approximation as the
probability. This gives sensible semiclassical results but lacks an underlying
operator formalism. Here, we supply the underlying formalism by deriving
probability distributions linked to the Wheeler-DeWitt equation using the
decoherent histories approach to quantum theory, building on the generalized
quantum mechanics formalism developed by Hartle. The key step is the
construction of class operators characterizing questions of physical interest.
Taking advantage of a recent decoherent histories analysis of the arrival time
problem in non-relativistic quantum mechanics, we show that the appropriate
class operators in quantum cosmology are readily constructed using a complex
potential. The class operator for not entering a region of configuration space
is given by the $S$-matrix for scattering off a complex potential localized in
that region. We thus derive the class operators for entering one or more
regions in configuration space. The class operators commute with the
Hamiltonian, have a sensible classical limit and are closely related to an
intersection number operator. The corresponding probabilities coincide, in a
semiclassical approximation, with standard heuristic procedures.
| [
{
"created": "Tue, 30 Aug 2011 15:55:04 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Halliwell",
"J. J.",
""
]
] | Recent results on the decoherent histories quantization of simple cosmological models (minisuperspace models) are described. The most important issue is the construction, from the wave function, of a probability distribution answering various questions of physical interest, such as the probability of the system entering a given region of configuration space at any stage in its entire history. A standard but heuristic procedure is to use the flux of (components of) the wave function in a WKB approximation as the probability. This gives sensible semiclassical results but lacks an underlying operator formalism. Here, we supply the underlying formalism by deriving probability distributions linked to the Wheeler-DeWitt equation using the decoherent histories approach to quantum theory, building on the generalized quantum mechanics formalism developed by Hartle. The key step is the construction of class operators characterizing questions of physical interest. Taking advantage of a recent decoherent histories analysis of the arrival time problem in non-relativistic quantum mechanics, we show that the appropriate class operators in quantum cosmology are readily constructed using a complex potential. The class operator for not entering a region of configuration space is given by the $S$-matrix for scattering off a complex potential localized in that region. We thus derive the class operators for entering one or more regions in configuration space. The class operators commute with the Hamiltonian, have a sensible classical limit and are closely related to an intersection number operator. The corresponding probabilities coincide, in a semiclassical approximation, with standard heuristic procedures. |
1208.0531 | Arman Shokrollahi | Arman Shokrollahi | Free Motion of a Dirac Particle with a Minimum Uncertainty in Position | 14 pages . . . accepted for publication in Reports on Mathematical
Physics. arXiv admin note: text overlap with arXiv:1103.1015,arXiv:1103.3805
by different authors | null | 10.1016/S0034-4877(13)60009-9 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we present a covariant, relativistic noncommutative algebra
which includes two small deformation parameters. Using this algebra, we obtain
a generalized uncertainty principle which predicts a minimal observable length
in measure of space-time distances. Then, we introduce a new representation for
coordinate and momentum operators which leads to a generalized Dirac equation.
The solutions of the generalized Dirac equation for a free particle will be
explicitly obtained. We also obtain the modified fermionic propagator for a
free Dirac particle.
| [
{
"created": "Thu, 2 Aug 2012 16:22:02 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Aug 2012 15:38:28 GMT",
"version": "v2"
}
] | 2013-04-18 | [
[
"Shokrollahi",
"Arman",
""
]
] | In this paper, we present a covariant, relativistic noncommutative algebra which includes two small deformation parameters. Using this algebra, we obtain a generalized uncertainty principle which predicts a minimal observable length in measure of space-time distances. Then, we introduce a new representation for coordinate and momentum operators which leads to a generalized Dirac equation. The solutions of the generalized Dirac equation for a free particle will be explicitly obtained. We also obtain the modified fermionic propagator for a free Dirac particle. |
gr-qc/9303021 | null | Isidore Hauser and Frederick J. Ernst | Non-Analytic Extension of the Kinnersley-Chitre Group for Colliding
Plane Gravitational Waves. I | 65, FJE-93-001 | null | null | null | gr-qc | null | A program is outlined concerning the set of all solutions of the hyperbolic
Ernst equation on a two-dimensional manifold whose underlying topological space
is the same as the domain of all Ernst potentials for colliding plane
gravitational wave pairs. The aim of the program is to construct and apply a
non-trivial extension of the group of Kinnersley-Chitre transformations. This
is to be done by employing the formalism of a homogeneous Hilbert problem. In
this first paper of a series, the aforementioned program is completely carried
out for the collinear polarization case.
| [
{
"created": "Wed, 17 Mar 1993 15:37:09 GMT",
"version": "v1"
},
{
"created": "Sat, 20 Mar 1993 15:04:41 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Hauser",
"Isidore",
""
],
[
"Ernst",
"Frederick J.",
""
]
] | A program is outlined concerning the set of all solutions of the hyperbolic Ernst equation on a two-dimensional manifold whose underlying topological space is the same as the domain of all Ernst potentials for colliding plane gravitational wave pairs. The aim of the program is to construct and apply a non-trivial extension of the group of Kinnersley-Chitre transformations. This is to be done by employing the formalism of a homogeneous Hilbert problem. In this first paper of a series, the aforementioned program is completely carried out for the collinear polarization case. |
gr-qc/0204079 | Renaud Parentani | Renaud Parentani | What did we learn from studying acoustic black holes ? | 6 pages, Proceedings of the ``Journees Relativistes'' Dublin, Sept.
2001 | Int.J.Mod.Phys. A17 (2002) 2721-2726 | 10.1142/S0217751X02011679 | null | gr-qc | null | The study of acoustic black holes has been undertaken to provide new insights
about the role of high frequencies in black hole evaporation. Because of the
infinite gravitational redshift from the event horizon, Hawking quanta emerge
from configurations which possessed ultra high (trans-Planckian) frequencies.
Therefore Hawking radiation cannot be derived within the framework of a low
energy effective theory; and in all derivations there are some assumptions
concerning Planck scale physics. The analogy with condensed matter physics was
thus introduced to see if the asymptotic properties of the Hawking phonons
emitted by an acoustic black hole, namely stationarity and thermality, are
sensitive to the high frequency physics which stems from the granular character
of matter and which is governed by a non-linear dispersion relation. In 1995
Unruh showed that they are not sensitive in this respect, in spite of the fact
that phonon propagation near the (acoustic) horizon drastically differs from
that of photons. In 2000 the same analogy was used to establish the robustness
of the spectrum of primordial density fluctuations in inflationary models. This
analogy is currently stimulating research for experimenting Hawking radiation.
Finally it could also be a useful guide for going beyond the semi-classical
description of black hole evaporation.
| [
{
"created": "Fri, 26 Apr 2002 10:02:27 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Parentani",
"Renaud",
""
]
] | The study of acoustic black holes has been undertaken to provide new insights about the role of high frequencies in black hole evaporation. Because of the infinite gravitational redshift from the event horizon, Hawking quanta emerge from configurations which possessed ultra high (trans-Planckian) frequencies. Therefore Hawking radiation cannot be derived within the framework of a low energy effective theory; and in all derivations there are some assumptions concerning Planck scale physics. The analogy with condensed matter physics was thus introduced to see if the asymptotic properties of the Hawking phonons emitted by an acoustic black hole, namely stationarity and thermality, are sensitive to the high frequency physics which stems from the granular character of matter and which is governed by a non-linear dispersion relation. In 1995 Unruh showed that they are not sensitive in this respect, in spite of the fact that phonon propagation near the (acoustic) horizon drastically differs from that of photons. In 2000 the same analogy was used to establish the robustness of the spectrum of primordial density fluctuations in inflationary models. This analogy is currently stimulating research for experimenting Hawking radiation. Finally it could also be a useful guide for going beyond the semi-classical description of black hole evaporation. |
2207.03266 | J\'er\'emy Auffinger | J\'er\'emy Auffinger, Alexandre Arbey | Beyond the Standard Model with BlackHawk v2.0 | 8 pages, 4 figures, contribution to CompTools 2021. arXiv admin note:
text overlap with arXiv:2108.02737 | PoS (CompTools2021) 017 | null | null | gr-qc astro-ph.CO hep-ph | http://creativecommons.org/licenses/by/4.0/ | We present the new version of BlackHawk v2.0. BlackHawk is a public code
designed to compute the Hawking radiation spectra of (primordial) black holes.
In the version 2.0, we have added several non-standard BH metrics: charged,
higher dimensional and polymerized black holes, in addition to the usual
rotating (Kerr) BHs. BlackHawk also embeds some additional scripts and
numerical tables that can prove useful in e.g. dark matter studies. We describe
these new features and provide some examples of the capabilities of the code. A
tutorial for BlackHawk is available on the TOOLS2021 website:
https://indico.cern.ch/event/1076291/contributions/4609967/
| [
{
"created": "Thu, 7 Jul 2022 12:39:21 GMT",
"version": "v1"
}
] | 2022-07-08 | [
[
"Auffinger",
"Jérémy",
""
],
[
"Arbey",
"Alexandre",
""
]
] | We present the new version of BlackHawk v2.0. BlackHawk is a public code designed to compute the Hawking radiation spectra of (primordial) black holes. In the version 2.0, we have added several non-standard BH metrics: charged, higher dimensional and polymerized black holes, in addition to the usual rotating (Kerr) BHs. BlackHawk also embeds some additional scripts and numerical tables that can prove useful in e.g. dark matter studies. We describe these new features and provide some examples of the capabilities of the code. A tutorial for BlackHawk is available on the TOOLS2021 website: https://indico.cern.ch/event/1076291/contributions/4609967/ |
gr-qc/9404001 | Charles Hellaby | Charles Hellaby and Tevian Dray | Failure of Standard Conservation Laws at a Classical Change of Signature | 15pp, figures available on request from Charles Hellaby at
cwh@maths.uct.ac.za | Phys.Rev. D49 (1994) 5096-5104 | 10.1103/PhysRevD.49.5096 | University of Cape Town Preprint UCT 1994 | gr-qc | null | The Divergence Theorem as usually stated cannot be applied across a change of
signature unless it is re-expressed to allow for a finite source term on the
signature change surface. Consequently all conservation laws must also be
`modified', and therefore insistence on conservation of matter across such a
surface cannot be physically justified. The Darmois junction conditions
normally ensure conservation of matter via Israel's identities for the jump in
the energy-momentum density, but not when the signature changes. Modified
identities are derived for this jump when a signature change occurs, and the
resulting surface effects in the conservation laws are calculated. In general,
physical vector fields experience a jump in at least one component, and a
source term may therefore appear in the corresponding conservation law. Thus
current is also not conserved. These surface effects are a consequence of the
change in the character of physical law. The only way to recover standard
conservation laws is to impose restrictions that no realistic cosmological
model can satisfy.
| [
{
"created": "Sat, 2 Apr 1994 10:52:26 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Hellaby",
"Charles",
""
],
[
"Dray",
"Tevian",
""
]
] | The Divergence Theorem as usually stated cannot be applied across a change of signature unless it is re-expressed to allow for a finite source term on the signature change surface. Consequently all conservation laws must also be `modified', and therefore insistence on conservation of matter across such a surface cannot be physically justified. The Darmois junction conditions normally ensure conservation of matter via Israel's identities for the jump in the energy-momentum density, but not when the signature changes. Modified identities are derived for this jump when a signature change occurs, and the resulting surface effects in the conservation laws are calculated. In general, physical vector fields experience a jump in at least one component, and a source term may therefore appear in the corresponding conservation law. Thus current is also not conserved. These surface effects are a consequence of the change in the character of physical law. The only way to recover standard conservation laws is to impose restrictions that no realistic cosmological model can satisfy. |
2204.03048 | Pedro Jose Pompeia P. J. Pompeia | R. R. Cuzinatto, M. de Montigny, P. J. Pompeia | Non-commutativity and non-inertial effects on a scalar field in a cosmic
string space-time. Part 1: Klein-Gordon oscillator | 31 pages, 4 figures, 2 tables | Class. Quantum Grav. 39 (2022) 075006 | 10.1088/1361-6382/ac51bb | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse the Klein-Gordon oscillator in a cosmic string space-time and
study the effects stemming from the rotating frame and non-commutativity in
momentum space. We show that the latter mimics a constant magnetic field,
imparting physical interpretation to the setup. The field equation for the
scalar field is solved via separations of variables, and we obtain quantization
of energy and angular momentum. The space-time metric is non-degenerate as long
as the particle is confined within a hard-wall, whose position depends on the
rotation frame velocity and the string mass parameter. We investigate the
energy quantization both for a finite hard-wall (numerical evaluation) and in
the limit of an infinite hard-wall (analytical treatment). We stress the effect
of non-commutativity upon the energy quantization in each case.
| [
{
"created": "Wed, 6 Apr 2022 19:20:47 GMT",
"version": "v1"
}
] | 2022-04-08 | [
[
"Cuzinatto",
"R. R.",
""
],
[
"de Montigny",
"M.",
""
],
[
"Pompeia",
"P. J.",
""
]
] | We analyse the Klein-Gordon oscillator in a cosmic string space-time and study the effects stemming from the rotating frame and non-commutativity in momentum space. We show that the latter mimics a constant magnetic field, imparting physical interpretation to the setup. The field equation for the scalar field is solved via separations of variables, and we obtain quantization of energy and angular momentum. The space-time metric is non-degenerate as long as the particle is confined within a hard-wall, whose position depends on the rotation frame velocity and the string mass parameter. We investigate the energy quantization both for a finite hard-wall (numerical evaluation) and in the limit of an infinite hard-wall (analytical treatment). We stress the effect of non-commutativity upon the energy quantization in each case. |
1412.7643 | Andrea Geralico | Donato Bini, Andrea Geralico | Effect of an arbitrary spin orientation on the quadrupolar structure of
an extended body in a Schwarzschild spacetime | 15 pages, 3 figures; revised version matching the published one | Phys. Rev. D 91, 104036 (2015) | 10.1103/PhysRevD.91.104036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The influence of an arbitrary spin orientation on the quadrupolar structure
of an extended body moving in a Schwarzschild spacetime is investigated. The
body dynamics is described by the Mathisson-Papapetrou-Dixon model, without any
restriction on the motion or simplifying assumption on the associated spin
vector and quadrupole tensor, generalizing previous works. The equations of
motion are solved analytically in the limit of small values of the
characteristic length scales associated with the spin and quadrupole variables
with respect to the characteristic length of the background curvature. The
solution provides all corrections to the circular geodesic on the equatorial
plane taken as the reference trajectory due to both dipolar and quadrupolar
structure of the body as well as the conditions which the nonvanishing
components of the quadrupole tensor must fulfill in order that the problem be
self-consistent.
| [
{
"created": "Wed, 24 Dec 2014 11:06:47 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Sep 2015 10:59:22 GMT",
"version": "v2"
}
] | 2015-09-17 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
]
] | The influence of an arbitrary spin orientation on the quadrupolar structure of an extended body moving in a Schwarzschild spacetime is investigated. The body dynamics is described by the Mathisson-Papapetrou-Dixon model, without any restriction on the motion or simplifying assumption on the associated spin vector and quadrupole tensor, generalizing previous works. The equations of motion are solved analytically in the limit of small values of the characteristic length scales associated with the spin and quadrupole variables with respect to the characteristic length of the background curvature. The solution provides all corrections to the circular geodesic on the equatorial plane taken as the reference trajectory due to both dipolar and quadrupolar structure of the body as well as the conditions which the nonvanishing components of the quadrupole tensor must fulfill in order that the problem be self-consistent. |
1106.4203 | Jan Steinhoff | Jan Steinhoff | Canonical Formulation of Spin in General Relativity | 59 pages. Dissertation, Friedrich-Schiller-Universit\"at, Jena, 2010.
This thesis was submitted in June 2010. Cite as Ann. Phys. (Berlin) 523:296
(2011) | Ann. Phys. (Berlin) 523:296 (2011) | 10.1002/andp.201000178 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present thesis aims at an extension of the canonical formalism of
Arnowitt, Deser, and Misner from self-gravitating point-masses to objects with
spin. This would allow interesting applications, e.g., within the
post-Newtonian (PN) approximation. The extension succeeded via an action
approach to linear order in the single spins of the objects without restriction
to any further approximation. An order-by-order construction within the PN
approximation is possible and performed to the formal 3.5PN order as a
verification. In principle both approaches are applicable to higher orders in
spin. The PN next-to-leading order spin(1)-spin(1) level was tackled, modeling
the spin-induced quadrupole deformation by a single parameter. All
spin-dependent Hamiltonians for rapidly rotating bodies up to and including 3PN
are calculated.
| [
{
"created": "Tue, 21 Jun 2011 13:45:40 GMT",
"version": "v1"
}
] | 2011-06-22 | [
[
"Steinhoff",
"Jan",
""
]
] | The present thesis aims at an extension of the canonical formalism of Arnowitt, Deser, and Misner from self-gravitating point-masses to objects with spin. This would allow interesting applications, e.g., within the post-Newtonian (PN) approximation. The extension succeeded via an action approach to linear order in the single spins of the objects without restriction to any further approximation. An order-by-order construction within the PN approximation is possible and performed to the formal 3.5PN order as a verification. In principle both approaches are applicable to higher orders in spin. The PN next-to-leading order spin(1)-spin(1) level was tackled, modeling the spin-induced quadrupole deformation by a single parameter. All spin-dependent Hamiltonians for rapidly rotating bodies up to and including 3PN are calculated. |
1706.07790 | Heba Sami | Heba Sami, Neo Namane, Joseph Ntahompagaze, Maye Elmardi and Amare
Abebe | Reconstructing f(R) Gravity from a Chaplygin Scalar Field in de Sitter
Spacetimes | 20 pages, 10 figures | null | 10.1142/S0219887818500275 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a reconstruction technique for models of $f(R)$ gravity from the
Chaplygin scalar field in flat de Sitter spacetimes. Exploiting the equivalence
between $f(R)$ gravity and scalar-tensor theories, and treating the Chaplygin
gas as a scalar field model in a universe without conventional matter forms,
the Lagrangian densities for the $f(R)$ action are derived. Exact $f(R)$ models
and corresponding scalar field potentials are obtained for asymptotically de
Sitter spacetimes in early and late cosmological expansion histories. It is
shown that the reconstructed $f(R)$ models all have General Relativity as a
limiting solution.
| [
{
"created": "Fri, 23 Jun 2017 17:53:44 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Jun 2017 13:32:01 GMT",
"version": "v2"
}
] | 2018-02-14 | [
[
"Sami",
"Heba",
""
],
[
"Namane",
"Neo",
""
],
[
"Ntahompagaze",
"Joseph",
""
],
[
"Elmardi",
"Maye",
""
],
[
"Abebe",
"Amare",
""
]
] | We present a reconstruction technique for models of $f(R)$ gravity from the Chaplygin scalar field in flat de Sitter spacetimes. Exploiting the equivalence between $f(R)$ gravity and scalar-tensor theories, and treating the Chaplygin gas as a scalar field model in a universe without conventional matter forms, the Lagrangian densities for the $f(R)$ action are derived. Exact $f(R)$ models and corresponding scalar field potentials are obtained for asymptotically de Sitter spacetimes in early and late cosmological expansion histories. It is shown that the reconstructed $f(R)$ models all have General Relativity as a limiting solution. |
gr-qc/9902046 | Scott M. Hitchcock | Scott Hitchcock | Quantum Clocks and the Origin of Time in Complex Systems | 17 pages, LaTeX file, Revised and updated | null | null | MSUCL-1123 | gr-qc | null | The origin and nature of time in complex systems is explored using quantum
(or 'Feynman') clocks and the signals produced by them. Networks of these
clocks provide the basis for the evolution of complex systems. The general
concept of 'time' is translated into the 'lifetimes' of these unstable
configurations of matter. 'Temporal phase transitions' mark the emergence of
classical properties such as irreversibility, entropy, and thermodynamic arrows
of time. It is proposed that the creation of the universe can be modeled as a
quantum clock. Keywords: the problem of time, the arrow of time, time
asymmetry, the many-body problem, cellular networks, complexity, the
Wheeler-DeWitt equation, quantum cosmology, and instantons.
| [
{
"created": "Tue, 16 Feb 1999 18:05:30 GMT",
"version": "v1"
},
{
"created": "Sat, 20 Feb 1999 21:06:51 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Hitchcock",
"Scott",
""
]
] | The origin and nature of time in complex systems is explored using quantum (or 'Feynman') clocks and the signals produced by them. Networks of these clocks provide the basis for the evolution of complex systems. The general concept of 'time' is translated into the 'lifetimes' of these unstable configurations of matter. 'Temporal phase transitions' mark the emergence of classical properties such as irreversibility, entropy, and thermodynamic arrows of time. It is proposed that the creation of the universe can be modeled as a quantum clock. Keywords: the problem of time, the arrow of time, time asymmetry, the many-body problem, cellular networks, complexity, the Wheeler-DeWitt equation, quantum cosmology, and instantons. |
2211.05664 | Serge Parnovsky | S L Parnovsky | The Big Bang could be anisotropic. The case of Bianchi I model | 15 pages, no figures | null | 10.1088/1361-6382/acd7c2 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider an evolution of anisotropic cosmological model on the example of
the Bianchi type I homogeneous universe. It is filled by the mixture of matter
and dark energy with an arbitrary barotropic equation of state (EoS). The
general solution for this case is found and analyzed. A complete list of
possible future singularities for this model is given. Some new solution were
obtained for a particular EoSs, e.g. for the Bianchi type I {\Lambda}CDM
homogeneous model. It is shown that all special cases corresponding to
different EoSs have common properties, provided that now or at another moment
of time the Universe is expanding, and the density of the mixture is positive.
Then the evolution always begins with an anisotropic "Big Bang" which happened
a finite time ago. After that the universe is constantly expanding and, in all
cases, with rare exceptions, becomes more isotropic. A particularly strong
isotropization is associated with the epoch of inflation. After its completion,
the expansion of the universe becomes almost isotropic, and this case cannot be
distinguished from isotropic by astronomical observations. This fact allows us
to consider an anisotropic cosmological model as a possible candidate for the
description of the observed Universe despite the isotropic pattern of
expansion.
| [
{
"created": "Thu, 10 Nov 2022 15:59:19 GMT",
"version": "v1"
}
] | 2023-06-14 | [
[
"Parnovsky",
"S L",
""
]
] | We consider an evolution of anisotropic cosmological model on the example of the Bianchi type I homogeneous universe. It is filled by the mixture of matter and dark energy with an arbitrary barotropic equation of state (EoS). The general solution for this case is found and analyzed. A complete list of possible future singularities for this model is given. Some new solution were obtained for a particular EoSs, e.g. for the Bianchi type I {\Lambda}CDM homogeneous model. It is shown that all special cases corresponding to different EoSs have common properties, provided that now or at another moment of time the Universe is expanding, and the density of the mixture is positive. Then the evolution always begins with an anisotropic "Big Bang" which happened a finite time ago. After that the universe is constantly expanding and, in all cases, with rare exceptions, becomes more isotropic. A particularly strong isotropization is associated with the epoch of inflation. After its completion, the expansion of the universe becomes almost isotropic, and this case cannot be distinguished from isotropic by astronomical observations. This fact allows us to consider an anisotropic cosmological model as a possible candidate for the description of the observed Universe despite the isotropic pattern of expansion. |
2111.14138 | Xiao-Min Zhang | Xiao-Min Zhang, Kai Li, Yi-Fu Guo, Peng-Cheng Chu. He Liu and
Jian-Yang Zhu | Two models unifying warm inflation with dark matter and dark energy | 8 pages, 0 figures | Physical Review D 104, 103513 (2021) | 10.1103/PhysRevD.104.103513 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Two models that unify warm inflation with dark matter and dark energy are
proposed. In the models, a single scalar field is responsible for the early
expansion of the universe through the process of dissipative warm inflation and
then acts as both dark matter and dark energy in subsequent stages. The first
model is based on a noncanonical field with the Lagrangian density
$\mathcal{L}=F(X)-V(\phi)$, where the potential is dominant at the slow-roll
inflationary epoch and negligible in subsequent stages. The second model takes
advantage of a $k$-essence Lagrangian density having the coupled form
$\mathcal{L}=F(X)V(\phi)$. For both models, equations of the evolution for the
fields and observational constraints are presented, and an evolution law
describing how the energy density $\rho$ and state parameter $w$ scale with the
scale factor $a$ is obtained.
| [
{
"created": "Sun, 28 Nov 2021 13:35:03 GMT",
"version": "v1"
}
] | 2021-11-30 | [
[
"Zhang",
"Xiao-Min",
""
],
[
"Li",
"Kai",
""
],
[
"Guo",
"Yi-Fu",
""
],
[
"Liu",
"Peng-Cheng Chu. He",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | Two models that unify warm inflation with dark matter and dark energy are proposed. In the models, a single scalar field is responsible for the early expansion of the universe through the process of dissipative warm inflation and then acts as both dark matter and dark energy in subsequent stages. The first model is based on a noncanonical field with the Lagrangian density $\mathcal{L}=F(X)-V(\phi)$, where the potential is dominant at the slow-roll inflationary epoch and negligible in subsequent stages. The second model takes advantage of a $k$-essence Lagrangian density having the coupled form $\mathcal{L}=F(X)V(\phi)$. For both models, equations of the evolution for the fields and observational constraints are presented, and an evolution law describing how the energy density $\rho$ and state parameter $w$ scale with the scale factor $a$ is obtained. |
gr-qc/0506032 | Vicente Jos\'e Bol\'os | Vicente J. Bolos | Intrinsic definitions of "relative velocity" in general relativity | 29 pages, 12 figures. New proofs in special relativity and a new open
problem in general relativity (see Remark 5.2). An Appendix has been added,
studying the relative velocities in Schwarzschild, with new figures. Some
spelling erros fixed | Commun.Math.Phys.273:217-236,2007 | 10.1007/s00220-007-0248-9 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Given two observers, we define the "relative velocity" of one observer with
respect to the other in four different ways. All four definitions are given
intrinsically, i.e. independently of any coordinate system. Two of them are
given in the framework of spacelike simultaneity and, analogously, the other
two are given in the framework of observed (lightlike) simultaneity. Properties
and physical interpretations are discussed. Finally, we study relations between
them in special relativity, and we give some examples in Schwarzschild and
Robertson-Walker spacetimes.
| [
{
"created": "Mon, 6 Jun 2005 08:34:24 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jul 2006 10:43:03 GMT",
"version": "v2"
},
{
"created": "Fri, 24 Nov 2006 11:34:06 GMT",
"version": "v3"
},
{
"created": "Thu, 7 Apr 2011 09:50:17 GMT",
"version": "v4"
},
{
"cre... | 2011-08-05 | [
[
"Bolos",
"Vicente J.",
""
]
] | Given two observers, we define the "relative velocity" of one observer with respect to the other in four different ways. All four definitions are given intrinsically, i.e. independently of any coordinate system. Two of them are given in the framework of spacelike simultaneity and, analogously, the other two are given in the framework of observed (lightlike) simultaneity. Properties and physical interpretations are discussed. Finally, we study relations between them in special relativity, and we give some examples in Schwarzschild and Robertson-Walker spacetimes. |
1009.5174 | Byeong-soo Park | B. S. Park and D. G. Pak | Quantum Gravity Model in the framework of Weyl-Cartan geometry | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Weyl vector fields which can play an important role in quantum
gravity. The metric obtains its dynamical content after dynamical symmetry
breaking in the phase of the effective Einstein gravity which is induced by
quantum Weyl corrections. In low energy regime with scalar field there is a
relation between the Weyl vector fields and the torsion fields. If this
condition is given to Weyl vector fields and torsions, then the Lagrangian
becomes like Maxwell type.
| [
{
"created": "Mon, 27 Sep 2010 07:30:20 GMT",
"version": "v1"
}
] | 2010-09-28 | [
[
"Park",
"B. S.",
""
],
[
"Pak",
"D. G.",
""
]
] | We study the Weyl vector fields which can play an important role in quantum gravity. The metric obtains its dynamical content after dynamical symmetry breaking in the phase of the effective Einstein gravity which is induced by quantum Weyl corrections. In low energy regime with scalar field there is a relation between the Weyl vector fields and the torsion fields. If this condition is given to Weyl vector fields and torsions, then the Lagrangian becomes like Maxwell type. |
1601.01257 | Ondrej Kop\'a\v{c}ek | Ond\v{r}ej Kop\'a\v{c}ek and Vladim\'ir Karas | Effective potential of particles in the oblique black hole magnetosphere | 6 pages, 2 figures; to appear in the Proceedings of the "14th Marcel
Grossmann Meeting" (Rome, July 12 - 18, 2015) | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dynamics of charged matter in the oblique black hole magnetosphere is
investigated. In particular, we adopt a model consisting of a rotating black
hole embedded in the external large-scale magnetic field that is inclined
arbitrarily with respect to the rotation axis. Breaking the axial symmetry
appears to have profound consequences regarding the dynamics of particles and
it also poses some methodological difficulties. In this contribution we discuss
the applicability of the method of effective potential for the non-axisymmetric
model and show that it may only be applied in the appropriate reference frame.
| [
{
"created": "Sun, 3 Jan 2016 19:19:44 GMT",
"version": "v1"
}
] | 2016-01-07 | [
[
"Kopáček",
"Ondřej",
""
],
[
"Karas",
"Vladimír",
""
]
] | Dynamics of charged matter in the oblique black hole magnetosphere is investigated. In particular, we adopt a model consisting of a rotating black hole embedded in the external large-scale magnetic field that is inclined arbitrarily with respect to the rotation axis. Breaking the axial symmetry appears to have profound consequences regarding the dynamics of particles and it also poses some methodological difficulties. In this contribution we discuss the applicability of the method of effective potential for the non-axisymmetric model and show that it may only be applied in the appropriate reference frame. |
gr-qc/9708062 | Jeong-Young Ji | Rong-Gen Cai, Jeong-Young Ji and Kwang-Sup Soh | Action and entropy of black holes in spacetimes with a cosmological
constant | Revtex, 13 pages, no figures | Class.Quant.Grav.15:2783-2793,1998 | 10.1088/0264-9381/15/9/023 | null | gr-qc | null | In the Euclidean path integral approach, we calculate the actions and the
entropies for the Reissner-Nordstr\"om-de Sitter solutions. When the
temperatures of black hole and cosmological horizons are equal, the entropy is
the sum of one-quarter areas of black hole and cosmological horizons; when the
inner and outer black hole horizons coincide, the entropy is only one-quarter
area of cosmological horizon; and the entropy vanishes when the two black hole
horizons and cosmological horizon coincide. We also calculate the Euler numbers
of the corresponding Euclidean manifolds, and discuss the relationship between
the entropy of instanton and the Euler number.
| [
{
"created": "Tue, 26 Aug 1997 09:28:33 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Oct 1998 11:17:25 GMT",
"version": "v2"
}
] | 2011-04-15 | [
[
"Cai",
"Rong-Gen",
""
],
[
"Ji",
"Jeong-Young",
""
],
[
"Soh",
"Kwang-Sup",
""
]
] | In the Euclidean path integral approach, we calculate the actions and the entropies for the Reissner-Nordstr\"om-de Sitter solutions. When the temperatures of black hole and cosmological horizons are equal, the entropy is the sum of one-quarter areas of black hole and cosmological horizons; when the inner and outer black hole horizons coincide, the entropy is only one-quarter area of cosmological horizon; and the entropy vanishes when the two black hole horizons and cosmological horizon coincide. We also calculate the Euler numbers of the corresponding Euclidean manifolds, and discuss the relationship between the entropy of instanton and the Euler number. |
2003.02549 | Richard Woodard | D. Glavan (Louvain), S. P. Miao (NCKU), T. Prokopec (Utrecht) and R.
P. Woodard (Florida) | Single Graviton Loop Contribution to the Self-Mass of a Massless,
Conformally Coupled Scalar on de Sitter Background | 26 pages, 1 figure, uses LaTeX 2e. Version 2 revised slightly for
publication | Phys. Rev. D 101, 106016 (2020) | 10.1103/PhysRevD.101.106016 | UFIFT-QG-20-02, CP3-20-10 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use a simplified formalism to re-compute the single graviton loop
contribution to the self-mass of a massless, conformally coupled scalar on de
Sitter background which was originally made by Boran, Kahya and Park [1-3]. Our
result resolves the problem with the flat space correspondence limit that was
pointed out by Fr\"ob [4]. We discuss how this computation will be used in a
long-term project to purge the linearized effective field equation of gauge
dependence.
| [
{
"created": "Thu, 5 Mar 2020 11:55:41 GMT",
"version": "v1"
},
{
"created": "Sat, 16 May 2020 10:15:09 GMT",
"version": "v2"
}
] | 2020-05-20 | [
[
"Glavan",
"D.",
"",
"Louvain"
],
[
"Miao",
"S. P.",
"",
"NCKU"
],
[
"Prokopec",
"T.",
"",
"Utrecht"
],
[
"Woodard",
"R. P.",
"",
"Florida"
]
] | We use a simplified formalism to re-compute the single graviton loop contribution to the self-mass of a massless, conformally coupled scalar on de Sitter background which was originally made by Boran, Kahya and Park [1-3]. Our result resolves the problem with the flat space correspondence limit that was pointed out by Fr\"ob [4]. We discuss how this computation will be used in a long-term project to purge the linearized effective field equation of gauge dependence. |
1904.02168 | Ramon Masachs | Matthew Choptuik, Ramon Masachs, Benson Way | Multi-oscillating Boson Stars | 5 pages, 5 figures | Phys. Rev. Lett. 123, 131101 (2019) | 10.1103/PhysRevLett.123.131101 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose that stable boson stars generically fall within an
infinite-parameter family of solutions that oscillate on any number of
non-commensurate frequencies. We numerically construct two-frequency solutions
and explore their parameter space. These solutions merge with the standard
boson star family in the limit where the non-dominating frequencies are turned
off. We find that for a fixed energy, these two-frequency solutions can differ
considerably in size from standard boson stars.
| [
{
"created": "Wed, 3 Apr 2019 18:00:05 GMT",
"version": "v1"
}
] | 2019-10-02 | [
[
"Choptuik",
"Matthew",
""
],
[
"Masachs",
"Ramon",
""
],
[
"Way",
"Benson",
""
]
] | We propose that stable boson stars generically fall within an infinite-parameter family of solutions that oscillate on any number of non-commensurate frequencies. We numerically construct two-frequency solutions and explore their parameter space. These solutions merge with the standard boson star family in the limit where the non-dominating frequencies are turned off. We find that for a fixed energy, these two-frequency solutions can differ considerably in size from standard boson stars. |
2301.12611 | Richard Woodard | S. Katuwal (U. Florida) and R. P. Woodard (U. Florida) | Perturbative Quantum Gravity Induced Scalar Coupling to Electromagnetism | 7 pages, no figures, uses LaTeX2e. Version 2 slightly revised for
publication | Phys. Lett. B842 (2023) 137966 | 10.1016/j.physletb.2023.137966 | UFIFT-QG-23-01 | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Physicists working on atom interferometers are interested in scalar couplings
to electromagnetism of dimensions 5 and 6 which might be induced by quantum
gravity. There is a widespread belief that such couplings can only be induced
by conjectured non-perturbative effects, resulting in unknown coupling
strengths. In this letter we exhibit a completely perturbative mechanism
through which quantum gravity induces dimension six couplings with precisely
calculable coefficients.
| [
{
"created": "Mon, 30 Jan 2023 02:09:55 GMT",
"version": "v1"
},
{
"created": "Fri, 26 May 2023 12:38:48 GMT",
"version": "v2"
}
] | 2023-05-29 | [
[
"Katuwal",
"S.",
"",
"U. Florida"
],
[
"Woodard",
"R. P.",
"",
"U. Florida"
]
] | Physicists working on atom interferometers are interested in scalar couplings to electromagnetism of dimensions 5 and 6 which might be induced by quantum gravity. There is a widespread belief that such couplings can only be induced by conjectured non-perturbative effects, resulting in unknown coupling strengths. In this letter we exhibit a completely perturbative mechanism through which quantum gravity induces dimension six couplings with precisely calculable coefficients. |
0806.4815 | Dr. Anirudh Pradhan | Anirudh Pradhan and Priya Mathur | Inhomogeneous Perfect Fluid Universe with Electromagnetic Field in Lyra
Geometry | 22 pages, no figure, minor corrections | Fizika B18: 243-264, 2009 | 10.1007/s10509-009-0015-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new class of cylindrically symmetric inhomogeneous cosmological models for
perfect fluid distribution with electromagnetic field is obtained in the
context of Lyra's geometry. We have obtained two types of solutions by
considering the uniform as well as time dependent displacement field. The
source of the magnetic field is due to an electric current produced along the
z-axis. Only $F_{12}$ is a non-vanishing component of electromagnetic field
tensor. To get the deterministic solution, it has been assumed that the
expansion $\theta$ in the model is proportional to the shear $\sigma$. It has
been found that the solutions are consistent with the recent observations of
type Ia supernovae and the displacement vector $\beta(t)$ affects entropy.
Physical and geometric aspects of the models are also discussed in presence and
absence of magnetic field.
| [
{
"created": "Mon, 30 Jun 2008 07:41:08 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Aug 2008 11:52:23 GMT",
"version": "v2"
}
] | 2010-04-15 | [
[
"Pradhan",
"Anirudh",
""
],
[
"Mathur",
"Priya",
""
]
] | A new class of cylindrically symmetric inhomogeneous cosmological models for perfect fluid distribution with electromagnetic field is obtained in the context of Lyra's geometry. We have obtained two types of solutions by considering the uniform as well as time dependent displacement field. The source of the magnetic field is due to an electric current produced along the z-axis. Only $F_{12}$ is a non-vanishing component of electromagnetic field tensor. To get the deterministic solution, it has been assumed that the expansion $\theta$ in the model is proportional to the shear $\sigma$. It has been found that the solutions are consistent with the recent observations of type Ia supernovae and the displacement vector $\beta(t)$ affects entropy. Physical and geometric aspects of the models are also discussed in presence and absence of magnetic field. |
gr-qc/0104046 | Grigori Volovik | G.E. Volovik | Vacuum in quantum liquids and in general relativity | LaTeX, 53 pages, no figures, prepared for Proceedings of the Workshop
`Analog models for general relativity', Rio, October 2000 | Artificial Black Holes, eds. M. Novello, M. Visser and G. Volovik,
World Scientific, 2002, pp. 127--177 | null | null | gr-qc cond-mat hep-ph | null | Quantum liquids, in which an effective Lorentzian metric and thus some kind
of gravity gradually arise in the low-energy corner, are the objects where the
problems related to the quantum vacuum can be investigated in detail. In
particular, they provide the possible solution of the cosmological constant
problem: why the vacuum energy is by 120 orders of magnitude smaller than the
estimation from the relativistic quantum field theory. The almost complete
cancellation of the cosmological constant does not require any fine tuning and
comes from the fundamental ``trans-Planckian'' physics of quantum liquids. The
remaining vacuum energy is generated by the perturbations of quantum vacuum
caused by matter (quasiparticles), curvature, and other possible sources, such
as smooth component -- the quintessence. This provides the possible solution of
another cosmological constant problem: why the present cosmological constant is
on the order of the present matter density of the Universe. We discuss here
some properties of the quantum vacuum in quantum liquids: the vacuum energy
under different conditions; excitations above the vacuum state and the
effective acoustic metric for them provided by the motion of the vacuum;
Casimir effect, etc.
| [
{
"created": "Sun, 15 Apr 2001 09:37:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Volovik",
"G. E.",
""
]
] | Quantum liquids, in which an effective Lorentzian metric and thus some kind of gravity gradually arise in the low-energy corner, are the objects where the problems related to the quantum vacuum can be investigated in detail. In particular, they provide the possible solution of the cosmological constant problem: why the vacuum energy is by 120 orders of magnitude smaller than the estimation from the relativistic quantum field theory. The almost complete cancellation of the cosmological constant does not require any fine tuning and comes from the fundamental ``trans-Planckian'' physics of quantum liquids. The remaining vacuum energy is generated by the perturbations of quantum vacuum caused by matter (quasiparticles), curvature, and other possible sources, such as smooth component -- the quintessence. This provides the possible solution of another cosmological constant problem: why the present cosmological constant is on the order of the present matter density of the Universe. We discuss here some properties of the quantum vacuum in quantum liquids: the vacuum energy under different conditions; excitations above the vacuum state and the effective acoustic metric for them provided by the motion of the vacuum; Casimir effect, etc. |
2208.09488 | William East | William E. East and Frans Pretorius | Binary neutron star mergers in Einstein-scalar-Gauss-Bonnet gravity | 12 pages, 10 figures; revised to match PRD version | Phys. Rev. D 106, 104055 (2022) | 10.1103/PhysRevD.106.104055 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Binary neutron star mergers, which can lead to less massive black holes
relative to other known astrophysical channels, have the potential to probe
modifications to general relativity that arise at smaller curvature scales
compared to more massive compact object binaries. As a representative example
of this, here we study binary neutron star mergers in shift-symmetric
Einstein-scalar-Gauss-Bonnet gravity using evolutions of the full,
nonperturbative evolution equations. We find that the impact on the inspiral is
small, even at large values of the modified gravity coupling (as expected, as
neutron stars do not have scalar charge in this theory). However, postmerger
there can be strong scalar effects, including radiation. When a black hole
forms, it develops scalar charge, impacting the ringdown gravitational wave
signal. In cases where a longer-lived remnant star persists postmerger, we find
that the oscillations of the star source levels of scalar radiation similar to
the black hole formation cases. In remnant stars, we further find that at
coupling values comparable to the maximum value for which black hole solutions
of the same mass exist, there is significant nonlinear enhancement in the
scalar field, which if sufficiently large leads to a breakdown in the
evolution, seemingly due to loss of hyperbolicity of the underlying equations.
| [
{
"created": "Fri, 19 Aug 2022 18:00:02 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Nov 2022 16:25:31 GMT",
"version": "v2"
}
] | 2022-11-29 | [
[
"East",
"William E.",
""
],
[
"Pretorius",
"Frans",
""
]
] | Binary neutron star mergers, which can lead to less massive black holes relative to other known astrophysical channels, have the potential to probe modifications to general relativity that arise at smaller curvature scales compared to more massive compact object binaries. As a representative example of this, here we study binary neutron star mergers in shift-symmetric Einstein-scalar-Gauss-Bonnet gravity using evolutions of the full, nonperturbative evolution equations. We find that the impact on the inspiral is small, even at large values of the modified gravity coupling (as expected, as neutron stars do not have scalar charge in this theory). However, postmerger there can be strong scalar effects, including radiation. When a black hole forms, it develops scalar charge, impacting the ringdown gravitational wave signal. In cases where a longer-lived remnant star persists postmerger, we find that the oscillations of the star source levels of scalar radiation similar to the black hole formation cases. In remnant stars, we further find that at coupling values comparable to the maximum value for which black hole solutions of the same mass exist, there is significant nonlinear enhancement in the scalar field, which if sufficiently large leads to a breakdown in the evolution, seemingly due to loss of hyperbolicity of the underlying equations. |
0908.2957 | Viktor G. Czinner | Viktor G. Czinner and Antonino Flachi | Curvature corrections and topology change transition in brane-black hole
systems: A perturbative approach | 17 pages, 8 figures; several corrections made, substantial new
material added, the title has been changed | Phys. Rev. D 80, 104017 (2009) | 10.1103/PhysRevD.80.104017 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider curvature corrections to static, axisymmetric Dirac-Nambu-Goto
membranes embedded into a spherically symmetric black hole spacetime with
arbitrary number of dimensions. Since the next to leading order corrections in
the effective brane action are quadratic in the brane thickness l, we adopt a
linear perturbation approach in l^2. The perturbations are general in the sense
that they are not restricted to the Rindler zone nor to the near-critical
solutions of the unperturbed system. As a result, an unexpected asymmetry in
the perturbed system is found. In configurations, where the brane does not
cross the black hole horizon, the perturbative approach does not lead to
regular solutions if the number of the brane's spacetime dimensions D>3. This
condition, however, does not hold for the horizon crossing solutions.
Consequently we argue that the presented perturbative approach breaks down for
subcritical type solutions near the axis of the system for D>3. Nevertheless,
we can discuss topology-changing phase transitions in cases when D=2 or 3, i.e.
when the brane is a 1-dimensional string or a 2-dimensional sheet,
respectively. For the general case, a different, non-perturbative approach
should be sought. Based on the energy properties of those branes that are
quasi-statically evolved from the equatorial configuration, we illustrate the
results of the phase transition in the case of a D=3 brane. It is found that
small thickness perturbations do not modify the order of the transition, i.e.
it remains first order just as in the case of vanishing thickness.
| [
{
"created": "Thu, 20 Aug 2009 16:25:12 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Nov 2009 06:30:12 GMT",
"version": "v2"
}
] | 2009-11-15 | [
[
"Czinner",
"Viktor G.",
""
],
[
"Flachi",
"Antonino",
""
]
] | We consider curvature corrections to static, axisymmetric Dirac-Nambu-Goto membranes embedded into a spherically symmetric black hole spacetime with arbitrary number of dimensions. Since the next to leading order corrections in the effective brane action are quadratic in the brane thickness l, we adopt a linear perturbation approach in l^2. The perturbations are general in the sense that they are not restricted to the Rindler zone nor to the near-critical solutions of the unperturbed system. As a result, an unexpected asymmetry in the perturbed system is found. In configurations, where the brane does not cross the black hole horizon, the perturbative approach does not lead to regular solutions if the number of the brane's spacetime dimensions D>3. This condition, however, does not hold for the horizon crossing solutions. Consequently we argue that the presented perturbative approach breaks down for subcritical type solutions near the axis of the system for D>3. Nevertheless, we can discuss topology-changing phase transitions in cases when D=2 or 3, i.e. when the brane is a 1-dimensional string or a 2-dimensional sheet, respectively. For the general case, a different, non-perturbative approach should be sought. Based on the energy properties of those branes that are quasi-statically evolved from the equatorial configuration, we illustrate the results of the phase transition in the case of a D=3 brane. It is found that small thickness perturbations do not modify the order of the transition, i.e. it remains first order just as in the case of vanishing thickness. |
gr-qc/9901020 | David Hochberg | David Hochberg (LAEFF,Spain) and Matt Visser (Washington University) | General Dynamic Wormholes and Violation of the Null Energy Condition | Invited talk delivered at the Advanced School on Cosmology and
Particle Physics, Peniscola, Spain 22-28 June 1998. 10 pages using Springer
style files | null | null | null | gr-qc | null | Although wormholes can be treated as topological objects in spacetime and
from a global point-of-view, a precise definition of what a wormhole throat is
and where it can be located can be developed and treated entirely in terms of
local geometry. This has the advantage of being free from unnecesary technical
assumptions about asymptotic flatness, and other global properties of the
spacetime containing the wormhole. We discuss our recent work proving that the
violation of the null energy condition (NEC) is a generic feature of all
wormholes, whether they be time-dependent or static, and demonstrate that
time-dependent wormholes have two throats, one for each direction through the
wormhole, which coalesce only in the static limit.
| [
{
"created": "Thu, 7 Jan 1999 18:16:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hochberg",
"David",
"",
"LAEFF,Spain"
],
[
"Visser",
"Matt",
"",
"Washington University"
]
] | Although wormholes can be treated as topological objects in spacetime and from a global point-of-view, a precise definition of what a wormhole throat is and where it can be located can be developed and treated entirely in terms of local geometry. This has the advantage of being free from unnecesary technical assumptions about asymptotic flatness, and other global properties of the spacetime containing the wormhole. We discuss our recent work proving that the violation of the null energy condition (NEC) is a generic feature of all wormholes, whether they be time-dependent or static, and demonstrate that time-dependent wormholes have two throats, one for each direction through the wormhole, which coalesce only in the static limit. |
gr-qc/9502045 | Luanne Neumann | G.F. Chew | Weak Classical-Gravity Source in Standpoint Cosmology | 11 pages, uses math_macros.tex, latex | null | null | LBL-36809 | gr-qc | null | Guided by a linearized approximation to Einstein theory, an interim
prescription for ``weak source of gravity'' - - in ``particle'' energy-momentum
distributed along standpoint light cone - - is formulated for (classical)
standpoint cosmology.
| [
{
"created": "Tue, 28 Feb 1995 22:45:46 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Chew",
"G. F.",
""
]
] | Guided by a linearized approximation to Einstein theory, an interim prescription for ``weak source of gravity'' - - in ``particle'' energy-momentum distributed along standpoint light cone - - is formulated for (classical) standpoint cosmology. |
1004.0679 | Abraham Harte | Samuel E. Gralla, Abraham I. Harte, Robert M. Wald | Bobbing and Kicks in Electromagnetism and Gravity | 22 pages, 1 figure, minor reference changes and fixed typos | Phys.Rev.D81:104012,2010 | 10.1103/PhysRevD.81.104012 | null | gr-qc physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study systems analogous to binary black holes with spin in order to gain
some insight into the origin and nature of "bobbing" motion and "kicks" that
occur in this system. Our basic tool is a general formalism for describing the
motion of extended test bodies in an external electromagnetic field in curved
spacetime and possibly subject to other forces. We first show that bobbing of
exactly the type as observed in numerical simulations of the binary black hole
system occurs in a simple system consisting of two spinning balls connected by
an elastic band in flat spacetime. This bobbing may be understood as arising
from the difference between a spinning body's "lab frame centroid" and its true
center of mass, and is purely "kinematical" in the sense that it will appear
regardless of the forces holding two spinning bodies in orbit. Next, we develop
precise rules for relating the motion of charged bodies in a stationary
external electromagnetic field in flat spacetime with the motion of bodies in a
weakly curved stationary spacetime. We then consider the system consisting of
two orbiting charges with magnetic dipole moment and spin at a level of
approximation corresponding to 1.5 post-Newtonian order. Here we find that
considerable amounts of momentum are exchanged between the bodies and the
electromagnetic field; however, the bodies store this momentum entirely as
"hidden" mechanical momentum, so that the interchange does not give rise to any
net bobbing. The net bobbing that does occur is due solely to the kinematical
spin effect, and we therefore argue that the net bobbing of the electromagnetic
binary is not associated with possible kicks. We believe that this conclusion
holds in the gravitational case as well.
| [
{
"created": "Mon, 5 Apr 2010 18:40:02 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Apr 2010 22:43:34 GMT",
"version": "v2"
},
{
"created": "Tue, 27 Apr 2010 17:52:58 GMT",
"version": "v3"
}
] | 2010-05-25 | [
[
"Gralla",
"Samuel E.",
""
],
[
"Harte",
"Abraham I.",
""
],
[
"Wald",
"Robert M.",
""
]
] | We study systems analogous to binary black holes with spin in order to gain some insight into the origin and nature of "bobbing" motion and "kicks" that occur in this system. Our basic tool is a general formalism for describing the motion of extended test bodies in an external electromagnetic field in curved spacetime and possibly subject to other forces. We first show that bobbing of exactly the type as observed in numerical simulations of the binary black hole system occurs in a simple system consisting of two spinning balls connected by an elastic band in flat spacetime. This bobbing may be understood as arising from the difference between a spinning body's "lab frame centroid" and its true center of mass, and is purely "kinematical" in the sense that it will appear regardless of the forces holding two spinning bodies in orbit. Next, we develop precise rules for relating the motion of charged bodies in a stationary external electromagnetic field in flat spacetime with the motion of bodies in a weakly curved stationary spacetime. We then consider the system consisting of two orbiting charges with magnetic dipole moment and spin at a level of approximation corresponding to 1.5 post-Newtonian order. Here we find that considerable amounts of momentum are exchanged between the bodies and the electromagnetic field; however, the bodies store this momentum entirely as "hidden" mechanical momentum, so that the interchange does not give rise to any net bobbing. The net bobbing that does occur is due solely to the kinematical spin effect, and we therefore argue that the net bobbing of the electromagnetic binary is not associated with possible kicks. We believe that this conclusion holds in the gravitational case as well. |
1404.5946 | Franco Albareti | F. D. Albareti, J. A. R. Cembranos and A. L. Maroto | Vacuum energy as dark matter | 13 pages, 6 figures. Version published in PRD | Phys. Rev. D 90, 123509 (2014) | 10.1103/PhysRevD.90.123509 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the vacuum energy of massive quantum fields in an expanding
universe. We define a conserved renormalized energy-momentum tensor by means of
a comoving cutoff regularization. Using exact solutions for de Sitter
space-time, we show that in a certain range of mass and renormalization scales
there is a contribution to the vacuum energy density that scales as
nonrelativistic matter and that such a contribution becomes dominant at late
times. By means of the WKB approximation, we find that these results can be
extended to arbitrary Robertson-Walker geometries. We study the range of
parameters in which the vacuum energy density would be compatible with current
limits on dark matter abundance. Finally, by calculating the vacuum energy in a
perturbed Robertson-Walker background, we obtain the speed of sound of density
perturbations and show that the vacuum energy density contrast can grow on
sub-Hubble scales as in standard cold dark matter scenarios.
| [
{
"created": "Wed, 23 Apr 2014 08:44:05 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Dec 2014 21:22:22 GMT",
"version": "v2"
}
] | 2014-12-10 | [
[
"Albareti",
"F. D.",
""
],
[
"Cembranos",
"J. A. R.",
""
],
[
"Maroto",
"A. L.",
""
]
] | We consider the vacuum energy of massive quantum fields in an expanding universe. We define a conserved renormalized energy-momentum tensor by means of a comoving cutoff regularization. Using exact solutions for de Sitter space-time, we show that in a certain range of mass and renormalization scales there is a contribution to the vacuum energy density that scales as nonrelativistic matter and that such a contribution becomes dominant at late times. By means of the WKB approximation, we find that these results can be extended to arbitrary Robertson-Walker geometries. We study the range of parameters in which the vacuum energy density would be compatible with current limits on dark matter abundance. Finally, by calculating the vacuum energy in a perturbed Robertson-Walker background, we obtain the speed of sound of density perturbations and show that the vacuum energy density contrast can grow on sub-Hubble scales as in standard cold dark matter scenarios. |
gr-qc/0512020 | Sergey Kozyrev | Sergey Kozyrev | Exact Vacuum Solutions of Jordan, Brans-Dicke Field Equations | null | null | null | null | gr-qc | null | We present the static spherically symmetric vacuum solutions of the Jordan,
Brans-Dicke field equations. The new solutions are obtained by considering a
polar Gaussian, isothermal and radial hyperbolic metrics.
| [
{
"created": "Sun, 4 Dec 2005 12:28:45 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kozyrev",
"Sergey",
""
]
] | We present the static spherically symmetric vacuum solutions of the Jordan, Brans-Dicke field equations. The new solutions are obtained by considering a polar Gaussian, isothermal and radial hyperbolic metrics. |
0808.0871 | Anatoliy Prykarpatsky | Nikolai N. Bogolubov Jr., Anatoliy K. Prykarpatsky and Ufuk Taneri | The Vacuum Structure, Special Relativity Theory and Quantum Mechanics
Revisited: A Field Theory-No-Geometry Approach | 17 pages, Available at: \texttt{http://publications.ictp.it}}\hfill
IC/2008/ | Theor.Math.Phys.160:1079-1095,2009; Teor.Mat.Fiz.160:249-269,2009 | 10.1007/s11232-009-0101-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main fundamental principles characterizing the vacuum field structure are
formulated, the modeling of the related vacuum medium and charged point
particle dynamics by means of devised field theoretic tools are analyzed. The
Maxwell electrodynamic theory is revisited and newly derived from the suggested
vacuum field structure principles, the classical special relativity theory
relationship between the energy and the corresponding point particle mass is
revisited and newly obtained. The Lorentz force expression with respect to
arbitrary non-inertial reference frames is revisited and discussed in detail,
some new interpretations of relations between the special relativity theory and
quantum mechanics are presented. The famous quantum-mechanical Schr\"{o}dinger
type equations for a relativistic point particle in the external potential and
magnetic fields within the quasiclassical approximation as the Planck constant
$\hbar \to 0$ and the light velocity $c\to \infty$ are obtained.
| [
{
"created": "Wed, 6 Aug 2008 19:03:59 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Aug 2008 14:51:40 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Aug 2008 16:41:23 GMT",
"version": "v3"
},
{
"created": "Sun, 24 Aug 2008 09:04:39 GMT",
"version": "v4"
},
{
"cre... | 2010-01-26 | [
[
"Bogolubov",
"Nikolai N.",
"Jr."
],
[
"Prykarpatsky",
"Anatoliy K.",
""
],
[
"Taneri",
"Ufuk",
""
]
] | The main fundamental principles characterizing the vacuum field structure are formulated, the modeling of the related vacuum medium and charged point particle dynamics by means of devised field theoretic tools are analyzed. The Maxwell electrodynamic theory is revisited and newly derived from the suggested vacuum field structure principles, the classical special relativity theory relationship between the energy and the corresponding point particle mass is revisited and newly obtained. The Lorentz force expression with respect to arbitrary non-inertial reference frames is revisited and discussed in detail, some new interpretations of relations between the special relativity theory and quantum mechanics are presented. The famous quantum-mechanical Schr\"{o}dinger type equations for a relativistic point particle in the external potential and magnetic fields within the quasiclassical approximation as the Planck constant $\hbar \to 0$ and the light velocity $c\to \infty$ are obtained. |
1908.09650 | Alice Waterhouse | Alice Waterhouse | The $\phi^4$ kink on a wormhole spacetime | 20 pages, 9 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The soliton resolution conjecture states that solutions to solitonic
equations with generic initial data should, after some non--linear behaviour,
eventually resolve into a finite number of solitons plus a radiative term. This
conjecture is intimately tied to soliton stability, which has been investigated
for a number of solitonic equations, including that of $\phi^4$ theory on
$\mathbb{R}^{1,1}$. We study a modification of this theory on a $3+1$
dimensional wormhole spacetime which has a spherical throat of radius $a$, with
a focus on the stability properties of the modified kink. In particular, we
prove that the modified kink is linearly stable, and compare its discrete
spectrum to that of the $\phi^4$ kink on $\mathbb{R}^{1,1}$. We also study the
resonant coupling between the discrete modes and the continuous spectrum for
small but non--linear perturbations. Some numerical and analytical evidence for
asymptotic stability is presented for the range of $a$ where the kink has
exactly one discrete mode.
| [
{
"created": "Fri, 23 Aug 2019 14:45:18 GMT",
"version": "v1"
}
] | 2019-08-27 | [
[
"Waterhouse",
"Alice",
""
]
] | The soliton resolution conjecture states that solutions to solitonic equations with generic initial data should, after some non--linear behaviour, eventually resolve into a finite number of solitons plus a radiative term. This conjecture is intimately tied to soliton stability, which has been investigated for a number of solitonic equations, including that of $\phi^4$ theory on $\mathbb{R}^{1,1}$. We study a modification of this theory on a $3+1$ dimensional wormhole spacetime which has a spherical throat of radius $a$, with a focus on the stability properties of the modified kink. In particular, we prove that the modified kink is linearly stable, and compare its discrete spectrum to that of the $\phi^4$ kink on $\mathbb{R}^{1,1}$. We also study the resonant coupling between the discrete modes and the continuous spectrum for small but non--linear perturbations. Some numerical and analytical evidence for asymptotic stability is presented for the range of $a$ where the kink has exactly one discrete mode. |
1612.00861 | Tomislav Prokopec | Lei-Hua Liu and Tomislav Prokopec | Gravitational microlensing in Verlinde's emergent gravity | 19 pages, 2 figures | null | 10.1016/j.physletb.2017.03.061 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose gravitational microlensing as a way of testing the emergent
gravity theory recently proposed by Eric Verlinde~\cite{Verlinde:2016toy}. We
consider two limiting cases: the dark mass of maximally anisotropic pressures
(Case I) and of isotropic pressures (Case II). Our analysis of perihelion
advancement of a planet shows that only Case I yields a viable theory. In this
case the metric outside a star of mass $M_*$ can be modeled by that of a
point-like global monopole whose mass is $M_*$ and a deficit angle $\Delta =
\sqrt{(2GH_0M_*)/(3c^3)}$, where $H_0$ is the Hubble rate and $G$ the Newton
constant. This deficit angle can be used to test the theory since light
exhibits additional bending around stars given by, $\alpha_D\approx
-\pi\Delta/2$. This angle is independent on the distance from the star and it
affects equally light and massive particles. The effect is too small to be
measurable today, but should be within reach of the next generation of high
resolution telescopes. Finally we note that the advancement of periastron of a
planet orbiting around a star or black hole, which equals $\pi\Delta$ per
period, can be also used to test the theory.
| [
{
"created": "Thu, 1 Dec 2016 16:48:38 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Jan 2017 17:31:02 GMT",
"version": "v2"
}
] | 2017-04-05 | [
[
"Liu",
"Lei-Hua",
""
],
[
"Prokopec",
"Tomislav",
""
]
] | We propose gravitational microlensing as a way of testing the emergent gravity theory recently proposed by Eric Verlinde~\cite{Verlinde:2016toy}. We consider two limiting cases: the dark mass of maximally anisotropic pressures (Case I) and of isotropic pressures (Case II). Our analysis of perihelion advancement of a planet shows that only Case I yields a viable theory. In this case the metric outside a star of mass $M_*$ can be modeled by that of a point-like global monopole whose mass is $M_*$ and a deficit angle $\Delta = \sqrt{(2GH_0M_*)/(3c^3)}$, where $H_0$ is the Hubble rate and $G$ the Newton constant. This deficit angle can be used to test the theory since light exhibits additional bending around stars given by, $\alpha_D\approx -\pi\Delta/2$. This angle is independent on the distance from the star and it affects equally light and massive particles. The effect is too small to be measurable today, but should be within reach of the next generation of high resolution telescopes. Finally we note that the advancement of periastron of a planet orbiting around a star or black hole, which equals $\pi\Delta$ per period, can be also used to test the theory. |
1504.07774 | Mehdi Eshaghi | Mehdi Eshaghi, Nematollah Riazi and Ahmad Kiasatpour | Bulk Viscosity and Particle Creation in the Inflationary Cosmology | 5 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study particle creation in the presence of bulk viscosity of cosmic fluid
in the early universe within the framework of open thermodynamical systems.
Since the first-order theory of non-equilibrium thermodynamics is non-causal
and unstable, we try to solve the bulk viscosity equation of the cosmic fluid
with particle creation through the full causal theory. By adopting an
appropriate function for particle creation rate of "Creation of Cold Dark
Matter" model, we obtain analytical solutions which do not suffer from the
initial singularity and are in agreement with equivalent solutions of
Lambda-CDM model. We constrain the free parameter of particle creation in our
model based on recent Planck data. It is also found that the inflationary
solution is driven by bulk viscosity with or without particle creation.
| [
{
"created": "Wed, 29 Apr 2015 08:55:49 GMT",
"version": "v1"
}
] | 2015-04-30 | [
[
"Eshaghi",
"Mehdi",
""
],
[
"Riazi",
"Nematollah",
""
],
[
"Kiasatpour",
"Ahmad",
""
]
] | We study particle creation in the presence of bulk viscosity of cosmic fluid in the early universe within the framework of open thermodynamical systems. Since the first-order theory of non-equilibrium thermodynamics is non-causal and unstable, we try to solve the bulk viscosity equation of the cosmic fluid with particle creation through the full causal theory. By adopting an appropriate function for particle creation rate of "Creation of Cold Dark Matter" model, we obtain analytical solutions which do not suffer from the initial singularity and are in agreement with equivalent solutions of Lambda-CDM model. We constrain the free parameter of particle creation in our model based on recent Planck data. It is also found that the inflationary solution is driven by bulk viscosity with or without particle creation. |
2207.11147 | Yongqiang Wang | Chen Liang, Ji-Rong Ren, Shi-Xian Sun, Yong-Qiang Wang | Dirac-boson stars | 26 pages, 12 figures | null | 10.1007/JHEP02(2023)249 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we construct \textit{Dirac-boson stars} (DBSs) model composed
of a scalar field and two Dirac fields. The scalar field and both Dirac fields
are in the ground state. We consider the solution families of the DBSs for the
synchronized frequency $\tilde{\omega}$ and the nonsynchronized frequency
$\tilde{\omega}_D$ cases, respectively. We find several different solutions
when the Dirac mass $\tilde{\mu}_D$ and scalar field frequency
$\tilde{\omega}_S$ are taken in some particular ranges. In contrast, no similar
case has been found in previous studies of multistate boson stars. Moreover, we
discuss the characteristics of each type of solution family of the DBSs and
present the relationship between the ADM mass $M$ of the DBSs and the
synchronized frequency $\tilde{\omega}$ or the nonsynchronized frequency
$\tilde{\omega}_D$. Finally, we calculate the binding energy $E_B$ of the DBSs
and investigate the relationship of $E_B$ with the synchronized frequency
$\tilde{\omega}$ or the nonsynchronized frequency $\tilde{\omega}_D$.
| [
{
"created": "Fri, 22 Jul 2022 15:41:06 GMT",
"version": "v1"
}
] | 2023-03-22 | [
[
"Liang",
"Chen",
""
],
[
"Ren",
"Ji-Rong",
""
],
[
"Sun",
"Shi-Xian",
""
],
[
"Wang",
"Yong-Qiang",
""
]
] | In this paper, we construct \textit{Dirac-boson stars} (DBSs) model composed of a scalar field and two Dirac fields. The scalar field and both Dirac fields are in the ground state. We consider the solution families of the DBSs for the synchronized frequency $\tilde{\omega}$ and the nonsynchronized frequency $\tilde{\omega}_D$ cases, respectively. We find several different solutions when the Dirac mass $\tilde{\mu}_D$ and scalar field frequency $\tilde{\omega}_S$ are taken in some particular ranges. In contrast, no similar case has been found in previous studies of multistate boson stars. Moreover, we discuss the characteristics of each type of solution family of the DBSs and present the relationship between the ADM mass $M$ of the DBSs and the synchronized frequency $\tilde{\omega}$ or the nonsynchronized frequency $\tilde{\omega}_D$. Finally, we calculate the binding energy $E_B$ of the DBSs and investigate the relationship of $E_B$ with the synchronized frequency $\tilde{\omega}$ or the nonsynchronized frequency $\tilde{\omega}_D$. |
gr-qc/0610159 | Philip Tillman Mr. | P. Tillman | Deformation Quantization: From Quantum Mechanics to Quantum Field Theory | null | null | null | null | gr-qc | null | The aim of this paper is to give a basic overview of Deformation Quantization
(DQ) to physicists. A summary is given here of some of the key developments
over the past thirty years in the context of physics, from quantum mechanics to
quantum field theory. Also, we discuss some of the conceptual advantages of DQ
and how DQ may be related to algebraic quantum field theory. Additionally, our
previous results are summarized which includes the construction of the Fedosov
star-product on dS/AdS. One of the goals of these results was to verify that DQ
gave the same results as previous analyses of these spaces. Another was to
verify that the formal series used in the conventional treatment converged by
obtaining exact and nonperturbative results for these spaces.
| [
{
"created": "Tue, 31 Oct 2006 17:07:54 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Oct 2006 22:23:16 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Tillman",
"P.",
""
]
] | The aim of this paper is to give a basic overview of Deformation Quantization (DQ) to physicists. A summary is given here of some of the key developments over the past thirty years in the context of physics, from quantum mechanics to quantum field theory. Also, we discuss some of the conceptual advantages of DQ and how DQ may be related to algebraic quantum field theory. Additionally, our previous results are summarized which includes the construction of the Fedosov star-product on dS/AdS. One of the goals of these results was to verify that DQ gave the same results as previous analyses of these spaces. Another was to verify that the formal series used in the conventional treatment converged by obtaining exact and nonperturbative results for these spaces. |
1910.03067 | Luis L\'opez | J.C. Olvera and L. A. L\'opez | Scattering and absorption sections of nonlinear electromagnetic black
holes | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The expression of the impact parameter, in the analysis for classical and
semiclassical scattering cross sections for black holes, is obtained with
nonlinear electrodynamics (NLED) while the absorption section is studied with
the sinc approximation in the eikonal limit considering NLED. As an
illustration, we calculate the classical and semiclassical scattering as well
as the absorption sections for three black holes under NLED, the regular
magnetic Bardeen and Bronnikov black holes and the singular Euler-Heisenberg
black hole. All are compared with the sections of their linear electromagnetic
counterpart, the Reissner-Nordstrom (RN) black hole. The comparison shows how
NLED affects the sections as well as the variation with respect to the
Reissner-Nordstrom sections, in some cases these variations are small.
| [
{
"created": "Mon, 7 Oct 2019 20:16:39 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Jan 2020 18:39:16 GMT",
"version": "v2"
}
] | 2020-01-29 | [
[
"Olvera",
"J. C.",
""
],
[
"López",
"L. A.",
""
]
] | The expression of the impact parameter, in the analysis for classical and semiclassical scattering cross sections for black holes, is obtained with nonlinear electrodynamics (NLED) while the absorption section is studied with the sinc approximation in the eikonal limit considering NLED. As an illustration, we calculate the classical and semiclassical scattering as well as the absorption sections for three black holes under NLED, the regular magnetic Bardeen and Bronnikov black holes and the singular Euler-Heisenberg black hole. All are compared with the sections of their linear electromagnetic counterpart, the Reissner-Nordstrom (RN) black hole. The comparison shows how NLED affects the sections as well as the variation with respect to the Reissner-Nordstrom sections, in some cases these variations are small. |
gr-qc/0110068 | Viqar Husain | Viqar Husain, Asghar Qadir and Azad A. Siddiqui | Note on flat foliations of spherically symmetric spacetimes | 4 pages, to appear in PRD, reference added, typos corrected | Phys.Rev. D65 (2002) 027501 | 10.1103/PhysRevD.65.027501 | null | gr-qc | null | It is known that spherically symmetric spacetimes admit flat spacelike
foliations. We point out a simple method of seeing this result via the
Hamiltonian constraints of general relativity. The method yields explicit
formulas for the extrinsic curvatures of the slicings.
| [
{
"created": "Sun, 14 Oct 2001 22:46:03 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Nov 2001 19:33:02 GMT",
"version": "v2"
},
{
"created": "Sat, 20 Apr 2002 18:38:23 GMT",
"version": "v3"
}
] | 2016-08-31 | [
[
"Husain",
"Viqar",
""
],
[
"Qadir",
"Asghar",
""
],
[
"Siddiqui",
"Azad A.",
""
]
] | It is known that spherically symmetric spacetimes admit flat spacelike foliations. We point out a simple method of seeing this result via the Hamiltonian constraints of general relativity. The method yields explicit formulas for the extrinsic curvatures of the slicings. |
1405.2629 | Roberto Ivan Cabrera Munguia | I. Cabrera-Munguia, Claus L\"ammerzahl, L. A. L\'opez, Alfredo
Mac\'ias | Generalized black diholes | 8 pages, 3 figures, 1 table; accepted in Phys. Rev. D | Phys.Rev.D90:024013,2014 | 10.1103/PhysRevD.90.024013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A 5-parametric exact solution, describing a binary system composed of
identical counter-rotating black holes endowed with opposite electromagnetic
charges, is constructed. The addition of the angular momentum parameter to the
static Emparan-Teo dihole model introduces magnetic charges into this two-body
system. The solution can be considered as an extended model for describing
generalized black diholes as dyons. We derive the explicit functional form of
the horizon half-length parameter $\sigma$ as a function of the Komar
parameters: Komar mass $M$, electric/magnetic charge $Q_{E }/ Q_{B}$, angular
momentum $J$, and a coordinate distance $R$, where the parameters $(M, J, Q_E,
Q_B, R)$ characterize the upper constituent of the system, while $(M, -J, -Q_E,
-Q_B, R)$ are associated with the lower one. The addition of magnetic charges
enhances the standard Smarr mass formula in order to take into account their
contribution to the mass. The solution contains, as particular cases, two
solutions already discussed in the literature.
| [
{
"created": "Mon, 12 May 2014 05:21:56 GMT",
"version": "v1"
}
] | 2014-07-10 | [
[
"Cabrera-Munguia",
"I.",
""
],
[
"Lämmerzahl",
"Claus",
""
],
[
"López",
"L. A.",
""
],
[
"Macías",
"Alfredo",
""
]
] | A 5-parametric exact solution, describing a binary system composed of identical counter-rotating black holes endowed with opposite electromagnetic charges, is constructed. The addition of the angular momentum parameter to the static Emparan-Teo dihole model introduces magnetic charges into this two-body system. The solution can be considered as an extended model for describing generalized black diholes as dyons. We derive the explicit functional form of the horizon half-length parameter $\sigma$ as a function of the Komar parameters: Komar mass $M$, electric/magnetic charge $Q_{E }/ Q_{B}$, angular momentum $J$, and a coordinate distance $R$, where the parameters $(M, J, Q_E, Q_B, R)$ characterize the upper constituent of the system, while $(M, -J, -Q_E, -Q_B, R)$ are associated with the lower one. The addition of magnetic charges enhances the standard Smarr mass formula in order to take into account their contribution to the mass. The solution contains, as particular cases, two solutions already discussed in the literature. |
1203.4258 | Michael P\"urrer | Michael P\"urrer, Sascha Husa, Mark Hannam | An efficient iterative method to reduce eccentricity in
numerical-relativity simulations of compact binary inspiral | 24 pages, 25 figures, pdflatex; v2: minor changes | Phys. Rev. D 85, 124051 (2012) | 10.1103/PhysRevD.85.124051 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new iterative method to reduce eccentricity in black-hole-binary
simulations. Given a good first estimate of low-eccentricity starting momenta,
we evolve puncture initial data for ~4 orbits and construct improved initial
parameters by comparing the inspiral with post-Newtonian calculations. Our
method is the first to be applied directly to the gravitational-wave (GW)
signal, rather than the orbital motion. The GW signal is in general less
contaminated by gauge effects, which, in moving-puncture simulations, limit
orbital-motion-based measurements of the eccentricity to an uncertainty of
$\Delta e \sim 0.002$, making it difficult to reduce the eccentricity below
this value. Our new method can reach eccentricities below $10^{-3}$ in one or
two iteration steps; we find that this is well below the requirements for GW
astronomy in the advanced detector era. Our method can be readily adapted to
any compact-binary simulation with GW emission, including black-hole-binary
simulations that use alternative approaches, and neutron-star-binary
simulations. We also comment on the differences in eccentricity estimates based
on the strain $h$, and the Newman-Penrose scalar $\Psi_4$.
| [
{
"created": "Mon, 19 Mar 2012 20:53:27 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Apr 2012 14:04:03 GMT",
"version": "v2"
}
] | 2012-07-23 | [
[
"Pürrer",
"Michael",
""
],
[
"Husa",
"Sascha",
""
],
[
"Hannam",
"Mark",
""
]
] | We present a new iterative method to reduce eccentricity in black-hole-binary simulations. Given a good first estimate of low-eccentricity starting momenta, we evolve puncture initial data for ~4 orbits and construct improved initial parameters by comparing the inspiral with post-Newtonian calculations. Our method is the first to be applied directly to the gravitational-wave (GW) signal, rather than the orbital motion. The GW signal is in general less contaminated by gauge effects, which, in moving-puncture simulations, limit orbital-motion-based measurements of the eccentricity to an uncertainty of $\Delta e \sim 0.002$, making it difficult to reduce the eccentricity below this value. Our new method can reach eccentricities below $10^{-3}$ in one or two iteration steps; we find that this is well below the requirements for GW astronomy in the advanced detector era. Our method can be readily adapted to any compact-binary simulation with GW emission, including black-hole-binary simulations that use alternative approaches, and neutron-star-binary simulations. We also comment on the differences in eccentricity estimates based on the strain $h$, and the Newman-Penrose scalar $\Psi_4$. |
1509.05059 | Edesio Barboza Jr | Rafael C. Nunes, Ed\'esio M. Barboza Jr., Everton M. C. Abreu and
Jorge Ananias Neto | Probing the cosmological viability of non-gaussian statistics | 14 pages, 1 figure. arXiv admin note: text overlap with
arXiv:1503.05874, arXiv:1403.5706 | null | 10.1088/1475-7516/2016/08/051 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on the relationship between thermodynamics and gravity we propose, with
the aid of Verlinde's formalism, an alternative interpretation of the dynamical
evolution of the Friedmann-Robertson-Walker Universe. This description takes
into account the entropy and temperature intrinsic to the horizon of the
universe due to the information holographically stored there through
non-gaussian statistical theories proposed by Tsallis and Kaniadakis. The
effect of these non-gaussian statistics in the cosmological context is change
the strength of the gravitational constant. In this paper, we consider the
$w$CDM model modified by the non-gaussian statistics and investigate the
compatibility of these non-gaussian modification with the cosmological
observations. In order to analyze in which extend the cosmological data
constrain these non-extensive statistics, we use type Ia supernovae, baryon
acoustic oscillations, Hubble expansion rate function and the linear growth of
matter density perturbations data.
| [
{
"created": "Wed, 16 Sep 2015 20:43:12 GMT",
"version": "v1"
},
{
"created": "Wed, 25 May 2016 20:34:05 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Nunes",
"Rafael C.",
""
],
[
"Barboza",
"Edésio M.",
"Jr."
],
[
"Abreu",
"Everton M. C.",
""
],
[
"Neto",
"Jorge Ananias",
""
]
] | Based on the relationship between thermodynamics and gravity we propose, with the aid of Verlinde's formalism, an alternative interpretation of the dynamical evolution of the Friedmann-Robertson-Walker Universe. This description takes into account the entropy and temperature intrinsic to the horizon of the universe due to the information holographically stored there through non-gaussian statistical theories proposed by Tsallis and Kaniadakis. The effect of these non-gaussian statistics in the cosmological context is change the strength of the gravitational constant. In this paper, we consider the $w$CDM model modified by the non-gaussian statistics and investigate the compatibility of these non-gaussian modification with the cosmological observations. In order to analyze in which extend the cosmological data constrain these non-extensive statistics, we use type Ia supernovae, baryon acoustic oscillations, Hubble expansion rate function and the linear growth of matter density perturbations data. |
1605.01186 | Parthapratim Pradhan | Parthapratim Pradhan | Thermodynamic Properties of Kehagias-Sfetsos Black Hole \& KS/CFT
Correspondence | Version accepted in EPL | EPL (Europhysics Letters), Volume 120, Number 4, 2018 | 10.1209/0295-5075/120/40006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We speculate on various thermodynamic features of the inner
horizon~(${\mathcal H}^{-}$) and outer horizons~(${\mathcal H}^{+}$) of
Kehagias-Sfetsos~(KS) black hole~(BH) in the background of Ho\v{r}ava Lifshitz
gravity. We compute particularly the \emph{area product, area sum, area minus
and area division} of the BH horizons. We find that they all are \emph{not}
showing universal behavior whereas the product is a universal quantity~
[Pradhan P., \textit{Phys. Lett. B}, {\bf 747} (2015) {64}]. Based on these
relations, we derive the area bound of all horizons. From the area bound we
derive the entropy bound and irreducible mass bound for all the
horizons~(${\mathcal H}^{\pm}$). We also observe that the \emph{First law} of
BH thermodynamics and \emph {Smarr-Gibbs-Duhem } relations do not hold for this
BH. The underlying reason behind this failure due to the scale invariance of
the coupling constant. Moreover, we compute the
\emph{Cosmic-Censorship-Inequality} for this BH which gives the lower bound for
the total mass of the spacetime and it is supported by cosmic cencorship
conjecture. Finally, we discuss the KS/CFT~(Conformal Field Theory)
correspondence via a thermodynamic procedure.
| [
{
"created": "Wed, 4 May 2016 08:55:51 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Oct 2016 07:41:39 GMT",
"version": "v2"
},
{
"created": "Tue, 6 Mar 2018 07:49:50 GMT",
"version": "v3"
}
] | 2018-03-07 | [
[
"Pradhan",
"Parthapratim",
""
]
] | We speculate on various thermodynamic features of the inner horizon~(${\mathcal H}^{-}$) and outer horizons~(${\mathcal H}^{+}$) of Kehagias-Sfetsos~(KS) black hole~(BH) in the background of Ho\v{r}ava Lifshitz gravity. We compute particularly the \emph{area product, area sum, area minus and area division} of the BH horizons. We find that they all are \emph{not} showing universal behavior whereas the product is a universal quantity~ [Pradhan P., \textit{Phys. Lett. B}, {\bf 747} (2015) {64}]. Based on these relations, we derive the area bound of all horizons. From the area bound we derive the entropy bound and irreducible mass bound for all the horizons~(${\mathcal H}^{\pm}$). We also observe that the \emph{First law} of BH thermodynamics and \emph {Smarr-Gibbs-Duhem } relations do not hold for this BH. The underlying reason behind this failure due to the scale invariance of the coupling constant. Moreover, we compute the \emph{Cosmic-Censorship-Inequality} for this BH which gives the lower bound for the total mass of the spacetime and it is supported by cosmic cencorship conjecture. Finally, we discuss the KS/CFT~(Conformal Field Theory) correspondence via a thermodynamic procedure. |
2303.04463 | Erik Jensko | Christian G. Boehmer, Erik Jensko, Ruth Lazkoz | Dynamical systems analysis of $f(Q)$ gravity | 12 pages, 3 figures. Accepted for publication in Universe special
issue Modified Gravity Approaches to the Tensions of $\Lambda$CDM | Universe 9 (2023) 4, 166 | 10.3390/universe9040166 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modified gravity theories can be used for the description of homogeneous and
isotropic cosmological models through the corresponding field equations. These
can be cast into systems of autonomous differential equations because of their
sole dependence on a well chosen time variable, be it the cosmological time, or
an alternative. For that reason a dynamical systems approach offers a reliable
route to study those equations. Through a model independent set of variables we
are able to study all $f(Q)$ modified gravity models. The drawback of the
procedure is a more complicated constraint equation. However, it allows the
dynamical system to be formulated in fewer dimensions than using other
approaches. We focus on a recent model of interest, the power-exponential
model, and generalise the fluid content of the model.
| [
{
"created": "Wed, 8 Mar 2023 09:27:44 GMT",
"version": "v1"
}
] | 2024-04-08 | [
[
"Boehmer",
"Christian G.",
""
],
[
"Jensko",
"Erik",
""
],
[
"Lazkoz",
"Ruth",
""
]
] | Modified gravity theories can be used for the description of homogeneous and isotropic cosmological models through the corresponding field equations. These can be cast into systems of autonomous differential equations because of their sole dependence on a well chosen time variable, be it the cosmological time, or an alternative. For that reason a dynamical systems approach offers a reliable route to study those equations. Through a model independent set of variables we are able to study all $f(Q)$ modified gravity models. The drawback of the procedure is a more complicated constraint equation. However, it allows the dynamical system to be formulated in fewer dimensions than using other approaches. We focus on a recent model of interest, the power-exponential model, and generalise the fluid content of the model. |
1411.4828 | Vakhid Gani | Vakhid A. Gani, Alexander E. Dmitriev, Sergey G. Rubin | Deformed compact extra space as dark matter candidate | 12 pages, 5 figures; V2: some changes to match version published in
IJMPD | Int. J. Mod. Phys. D 24, 1545001 (2015) | 10.1142/S0218271815450017 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We elaborate the possibility for a deformed extra space to be considered as
the dark matter candidate. To perform calculations a class of two-dimensional
extra metrics was considered in the framework of the multidimensional gravity.
It was shown that there exists a family of stationary metrics of the extra
space possessing point-like defect. Estimation of cross section of scattering
of a particle of the ordinary matter on a spatial domain with deformed extra
space is in agreement with the observational constraints.
| [
{
"created": "Tue, 18 Nov 2014 12:55:33 GMT",
"version": "v1"
},
{
"created": "Sat, 19 Sep 2015 15:55:36 GMT",
"version": "v2"
}
] | 2016-11-24 | [
[
"Gani",
"Vakhid A.",
""
],
[
"Dmitriev",
"Alexander E.",
""
],
[
"Rubin",
"Sergey G.",
""
]
] | We elaborate the possibility for a deformed extra space to be considered as the dark matter candidate. To perform calculations a class of two-dimensional extra metrics was considered in the framework of the multidimensional gravity. It was shown that there exists a family of stationary metrics of the extra space possessing point-like defect. Estimation of cross section of scattering of a particle of the ordinary matter on a spatial domain with deformed extra space is in agreement with the observational constraints. |
1904.10023 | Joao Paulo Manoel Pitelli | J. P. M. Pitelli | Comment on "Hadamard states for a scalar field in anti-de Sitter
spacetime with arbitrary boundary conditions" | 3 pages | Phys. Rev. D 99, 108701 (2019) | 10.1103/PhysRevD.99.108701 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent paper (Phys. Rev. D 94, 125016 (2016)), the authors argued that
the singularities of the two-point functions on the Poincar\'e domain of the
$n$-dimensional anti-de Sitter spacetime ($\text{PAdS}_n$) have the Hadamard
form, regardless of which (Robin) boundary condition is chosen at the conformal
boundary. However, the argument used to prove this statement was based on an
incorrect expression for the two-point function $G^{+}(x,x')$, which was
obtained by demanding $\text{AdS}$ invariance for the vacuum state. In this
comment I show that their argument works only for Dirichlet and Neumann
boundary conditions and that the full $\text{AdS}$ symmetry cannot be respected
by nontrivial Robin conditions (i.e., those which are neither Dirichlet nor
Neumann). By studying the conformal scalar field on $\text{PAdS}_2$, I find the
correct expression for $G^{+}(x,x')$ and show that, notwithstanding this
problem, it still have the Hadamard form.
| [
{
"created": "Mon, 22 Apr 2019 18:41:45 GMT",
"version": "v1"
}
] | 2019-06-05 | [
[
"Pitelli",
"J. P. M.",
""
]
] | In a recent paper (Phys. Rev. D 94, 125016 (2016)), the authors argued that the singularities of the two-point functions on the Poincar\'e domain of the $n$-dimensional anti-de Sitter spacetime ($\text{PAdS}_n$) have the Hadamard form, regardless of which (Robin) boundary condition is chosen at the conformal boundary. However, the argument used to prove this statement was based on an incorrect expression for the two-point function $G^{+}(x,x')$, which was obtained by demanding $\text{AdS}$ invariance for the vacuum state. In this comment I show that their argument works only for Dirichlet and Neumann boundary conditions and that the full $\text{AdS}$ symmetry cannot be respected by nontrivial Robin conditions (i.e., those which are neither Dirichlet nor Neumann). By studying the conformal scalar field on $\text{PAdS}_2$, I find the correct expression for $G^{+}(x,x')$ and show that, notwithstanding this problem, it still have the Hadamard form. |
1803.02317 | Kimet Jusufi | Kimet Jusufi | Conical Morris-Thorne Wormholes with a Global Monopole Charge | 8 pages, 4 figures, accepted for publication in Physical Review D | Phys. Rev. D 98, 044016 (2018) | 10.1103/PhysRevD.98.044016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we have established an asymptotically conical Morris-Thorne
wormhole solution supported by anisotropic matter fluid and a global monopole
charge in the framework of a $1+3$ dimensional gravity minimally coupled to a
triplet of scalar fields $\phi^a$, resulting from the breaking of a global
$O(3)$ symmetry. For the anisotropic matter fluid we have considered the
equation of state (EoS) given by $\mathcal{P}_r=\omega \rho$, with a
consequence $\omega<-1$, implying a so-called phantom energy at the throat of
the wormhole which violates the energy conditions. In addition, we study the
weak gravitational lensing effect using the Gauss-Bonnet theorem (GBT) applied
to the wormhole optical geometry. We show that the total deflection angle
consists of a term given by $4\pi^2 \eta^2 $, which is independent from the
impact parameter $b$, and an additional term which depends on the radius of the
wormhole throat $b_0$ as well as the dimensionless constant $\zeta$.
| [
{
"created": "Tue, 6 Mar 2018 18:08:23 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Jul 2018 08:21:02 GMT",
"version": "v2"
}
] | 2018-08-15 | [
[
"Jusufi",
"Kimet",
""
]
] | In this paper we have established an asymptotically conical Morris-Thorne wormhole solution supported by anisotropic matter fluid and a global monopole charge in the framework of a $1+3$ dimensional gravity minimally coupled to a triplet of scalar fields $\phi^a$, resulting from the breaking of a global $O(3)$ symmetry. For the anisotropic matter fluid we have considered the equation of state (EoS) given by $\mathcal{P}_r=\omega \rho$, with a consequence $\omega<-1$, implying a so-called phantom energy at the throat of the wormhole which violates the energy conditions. In addition, we study the weak gravitational lensing effect using the Gauss-Bonnet theorem (GBT) applied to the wormhole optical geometry. We show that the total deflection angle consists of a term given by $4\pi^2 \eta^2 $, which is independent from the impact parameter $b$, and an additional term which depends on the radius of the wormhole throat $b_0$ as well as the dimensionless constant $\zeta$. |
1101.2789 | Roberto Tauraso | Riccardo March, Giovanni Bellettini, Roberto Tauraso, Simone
Dell'Agnello | Constraining spacetime torsion with the Moon and Mercury | null | Phys.Rev.D83:104008,2011 | 10.1103/PhysRevD.83.104008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report a search for new gravitational physics phenomena based on
Einstein-Cartan theory of General Relativity including spacetime torsion.
Starting from the parametrized torsion framework of Mao, Tegmark, Guth and
Cabi, we analyze the motion of test bodies in the presence of torsion, and in
particular we compute the corrections to the perihelion advance and to the
orbital geodetic precession of a satellite. We describe the torsion field by
means of three parameters, and we make use of the autoparallel trajectories,
which in general may differ from geodesics when torsion is present. We derive
the equations of motion of a test body in a spherically symmetric field, and
the equations of motion of a satellite in the gravitational field of the Sun
and the Earth. We calculate the secular variations of the longitudes of the
node and of the pericenter of the satellite. The computed secular variations
show how the corrections to the perihelion advance and to the orbital de Sitter
effect depend on the torsion parameters. All computations are performed under
the assumptions of weak field and slow motion. To test our predictions, we use
the measurements of the Moon geodetic precession from lunar laser ranging data,
and the measurements of Mercury's perihelion advance from planetary radar
ranging data. These measurements are then used to constrain suitable linear
combinations of the torsion parameters.
| [
{
"created": "Fri, 14 Jan 2011 12:40:05 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Mar 2011 15:43:01 GMT",
"version": "v2"
}
] | 2011-05-13 | [
[
"March",
"Riccardo",
""
],
[
"Bellettini",
"Giovanni",
""
],
[
"Tauraso",
"Roberto",
""
],
[
"Dell'Agnello",
"Simone",
""
]
] | We report a search for new gravitational physics phenomena based on Einstein-Cartan theory of General Relativity including spacetime torsion. Starting from the parametrized torsion framework of Mao, Tegmark, Guth and Cabi, we analyze the motion of test bodies in the presence of torsion, and in particular we compute the corrections to the perihelion advance and to the orbital geodetic precession of a satellite. We describe the torsion field by means of three parameters, and we make use of the autoparallel trajectories, which in general may differ from geodesics when torsion is present. We derive the equations of motion of a test body in a spherically symmetric field, and the equations of motion of a satellite in the gravitational field of the Sun and the Earth. We calculate the secular variations of the longitudes of the node and of the pericenter of the satellite. The computed secular variations show how the corrections to the perihelion advance and to the orbital de Sitter effect depend on the torsion parameters. All computations are performed under the assumptions of weak field and slow motion. To test our predictions, we use the measurements of the Moon geodetic precession from lunar laser ranging data, and the measurements of Mercury's perihelion advance from planetary radar ranging data. These measurements are then used to constrain suitable linear combinations of the torsion parameters. |
gr-qc/9909045 | Tekin Dereli | Tekin Dereli, Yuri N. Obukhov (METU, Ankara) | On the universality of low-energy string model | 11 pages, LATEX, no figures | Class.Quant.Grav. 17 (2000) 219-225 | 10.1088/0264-9381/17/1/315 | null | gr-qc | null | The low-energy (bosonic "heterotic") string theory is interpreted as a
universal limit of the Kaluza-Klein reduction when the dimension of an internal
space goes to infinity. We show that such an approach is helpful in obtaining
classical solutions of the string model. As a particular application, we obtain
new exact static solutions for the two-dimensional effective string model. They
turn out to be in agreement with the generalized no-hair conjecture, in
complete analogy with the four and higher dimensional Einstein theory of
gravity.
| [
{
"created": "Wed, 15 Sep 1999 09:17:02 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Dereli",
"Tekin",
"",
"METU, Ankara"
],
[
"Obukhov",
"Yuri N.",
"",
"METU, Ankara"
]
] | The low-energy (bosonic "heterotic") string theory is interpreted as a universal limit of the Kaluza-Klein reduction when the dimension of an internal space goes to infinity. We show that such an approach is helpful in obtaining classical solutions of the string model. As a particular application, we obtain new exact static solutions for the two-dimensional effective string model. They turn out to be in agreement with the generalized no-hair conjecture, in complete analogy with the four and higher dimensional Einstein theory of gravity. |
1710.06641 | Bo Wang | Bo Wang, Yang Zhang | Second-order cosmological perturbations. I. Produced by scalar-scalar
coupling in synchronous gauge | 65 pages, 0 figures. There are modifications in some terms in
Eq.(B.3) and Eq.(B.7) in this updated version, which are zero for the MD
stage yet nonvanishing for a general stage. We also fix a typo in Eq.(13) in
this updated version | Phys. Rev. D 96, 103522 (2017) | 10.1103/PhysRevD.96.103522 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a systematic study of the 2nd order scalar, vector and tensor
metric perturbations in the Einstein-de Sitter Universe in synchronous
coordinates. For the scalar-scalar coupling between 1st order perturbations, we
decompose the 2nd order perturbed Einstein equation into the respective field
equations of 2nd order scalar, vector, and tensor perturbations, and obtain
their solutions with general initial conditions. In particular, the decaying
modes of solution are included, the 2nd order vector is generated even the 1st
order vector is absent, and the solution of 2nd order tensor corrects that in
literature. We perform general synchronous-to-synchronous gauge transformations
up to 2nd order generated by a 1st order vector field $\xi^{(1)\mu}$ and a 2nd
order $\xi^{(2)\mu}$. All the residual gauge modes of 2nd order metric
perturbations and density contrast are found, and their number is substantially
reduced when the transformed 3-velocity of dust is set be zero. Moreover, we
show that only $\xi^{(2)\mu}$ is effective in carrying out 2nd order
transformations that we consider, because $\xi^{(1)\mu}$ has been used in
obtaining the 1st order perturbations. Holding the 1st order perturbations
fixed, the transformations by $\xi^{(2)\mu}$ on the 2nd order perturbations
have the same structure as those by $\xi^{(1)\mu}$ on the 1st order
perturbations.
| [
{
"created": "Wed, 18 Oct 2017 09:31:05 GMT",
"version": "v1"
},
{
"created": "Sun, 3 Feb 2019 14:54:33 GMT",
"version": "v10"
},
{
"created": "Sun, 22 Oct 2017 04:52:45 GMT",
"version": "v2"
},
{
"created": "Mon, 20 Nov 2017 12:32:25 GMT",
"version": "v3"
},
{
"c... | 2019-02-05 | [
[
"Wang",
"Bo",
""
],
[
"Zhang",
"Yang",
""
]
] | We present a systematic study of the 2nd order scalar, vector and tensor metric perturbations in the Einstein-de Sitter Universe in synchronous coordinates. For the scalar-scalar coupling between 1st order perturbations, we decompose the 2nd order perturbed Einstein equation into the respective field equations of 2nd order scalar, vector, and tensor perturbations, and obtain their solutions with general initial conditions. In particular, the decaying modes of solution are included, the 2nd order vector is generated even the 1st order vector is absent, and the solution of 2nd order tensor corrects that in literature. We perform general synchronous-to-synchronous gauge transformations up to 2nd order generated by a 1st order vector field $\xi^{(1)\mu}$ and a 2nd order $\xi^{(2)\mu}$. All the residual gauge modes of 2nd order metric perturbations and density contrast are found, and their number is substantially reduced when the transformed 3-velocity of dust is set be zero. Moreover, we show that only $\xi^{(2)\mu}$ is effective in carrying out 2nd order transformations that we consider, because $\xi^{(1)\mu}$ has been used in obtaining the 1st order perturbations. Holding the 1st order perturbations fixed, the transformations by $\xi^{(2)\mu}$ on the 2nd order perturbations have the same structure as those by $\xi^{(1)\mu}$ on the 1st order perturbations. |
1007.1948 | Abdelhafid Bounames | Hemza Azri and A. Bounames | Geometrical Origin of the Cosmological Constant | 15 pages, LaTeX, Published version, General Relativity and
Gravitation (2012), Online First | General Relativity and Gravitation, 44(10), 2547-2561(2012) | 10.1007/s10714-012-1413-9 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the description of the space-time of general relativity as a
diagonal four dimensional submanifold immersed in an eight dimensional
hypercomplex manifold, in torsionless case, leads to a geometrical origin of
the cosmological constant. The cosmological constant appears naturally in the
new field equations and its expression is given as the norm of a four-vector
$U$, i.e., ${\Lambda}=6g_{{\mu}{\nu}}U^{{\mu}}U^{{\nu}}$ and where U can be
determined from the Bianchi identities. Consequently, the cosmological constant
is space-time dependent, a Lorentz invariant scalar, and may be positive,
negative or null. The resulting energy momentum tensor of the dark energy
depends on the cosmological constant and its first derivative with respect to
the metric. As an application, we obtain the spherical solution for the field
equations. In cosmology, the modified Friedmann equations are proposed and a
condition on ${\Lambda}$ for an accelerating universe is deduced. For a
particular case of the vector $U$, we find a decaying cosmological constant
${\Lambda}\propto a(t)^{-6{\alpha}}$.
| [
{
"created": "Mon, 12 Jul 2010 17:28:14 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Sep 2010 01:42:53 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Nov 2011 09:00:50 GMT",
"version": "v3"
},
{
"created": "Mon, 6 Aug 2012 13:11:16 GMT",
"version": "v4"
},
{
"cre... | 2016-10-31 | [
[
"Azri",
"Hemza",
""
],
[
"Bounames",
"A.",
""
]
] | We show that the description of the space-time of general relativity as a diagonal four dimensional submanifold immersed in an eight dimensional hypercomplex manifold, in torsionless case, leads to a geometrical origin of the cosmological constant. The cosmological constant appears naturally in the new field equations and its expression is given as the norm of a four-vector $U$, i.e., ${\Lambda}=6g_{{\mu}{\nu}}U^{{\mu}}U^{{\nu}}$ and where U can be determined from the Bianchi identities. Consequently, the cosmological constant is space-time dependent, a Lorentz invariant scalar, and may be positive, negative or null. The resulting energy momentum tensor of the dark energy depends on the cosmological constant and its first derivative with respect to the metric. As an application, we obtain the spherical solution for the field equations. In cosmology, the modified Friedmann equations are proposed and a condition on ${\Lambda}$ for an accelerating universe is deduced. For a particular case of the vector $U$, we find a decaying cosmological constant ${\Lambda}\propto a(t)^{-6{\alpha}}$. |
gr-qc/9803030 | Anjan Ananda Sen. | A.A.Sen | Non static local string in Brans-Dicke theory | 7 pages LateX format, No figure, submitted to Phys.Rev.D | Pramana 55:369-374,2000 | 10.1007/s12043-000-0066-5 | null | gr-qc | null | A recent investigation shows that a local gauge string with a
phenomenological energy momentum tensor, as prescribed by Vilenkin, is
inconsistent in Brans-Dicke theory. In this work, it has been shown that such a
string is indeed consistent if one introduces time dependences in the metric. A
set of solutions of full nonlinear Einstein's equations for the interior region
of such a string are presented.
| [
{
"created": "Mon, 9 Mar 1998 12:50:20 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Sen",
"A. A.",
""
]
] | A recent investigation shows that a local gauge string with a phenomenological energy momentum tensor, as prescribed by Vilenkin, is inconsistent in Brans-Dicke theory. In this work, it has been shown that such a string is indeed consistent if one introduces time dependences in the metric. A set of solutions of full nonlinear Einstein's equations for the interior region of such a string are presented. |
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