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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2006.04618 | Joseph P Johnson | Joseph P Johnson and S. Shankaranarayanan | Cosmological perturbations in the interacting dark sector: Mapping
fields and fluids | 31 pages, 3 table, 8 figures | Phys. Rev. D 103, 023510 (2021) | 10.1103/PhysRevD.103.023510 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There is no unique way to describe the dark energy-dark matter interaction,
as we have little information about the nature and dynamics of the dark sector.
Hence, in many of the phenomenological dark matter fluid interaction models in
the literature, the interaction strength $Q_{\nu}$ in the dark sector is
introduced by hand. Demanding that the interaction strength $Q_{\nu}$ in the
dark sector must have a field theory description, we obtain a unique form of
interaction strength. We show the equivalence between the fields and fluids for
the $f(R,\chi)$ model where $f$ is an arbitrary, smooth function of $R$ and
classical scalar field $\chi$, which represents dark matter. Up to first order
in perturbations, we show that the one-to-one mapping between the
\emph{classical} field theory description and the phenomenological fluid
description of interacting dark energy and dark matter exists \emph{only} for
this unique form of interaction. We then classify the interacting dark energy
models considered in the literature into two categories based on the
field-theoretic description. We introduce a novel autonomous system and its
stability analysis for the general interacting dark sector. We show that the
dark-energy dominated epoch occurs earlier than the non-interacting systems for
a specific scalar field potential and a range of coupling strengths.
| [
{
"created": "Fri, 5 Jun 2020 17:14:50 GMT",
"version": "v1"
},
{
"created": "Sat, 19 Dec 2020 17:45:57 GMT",
"version": "v2"
}
] | 2021-01-13 | [
[
"Johnson",
"Joseph P",
""
],
[
"Shankaranarayanan",
"S.",
""
]
] | There is no unique way to describe the dark energy-dark matter interaction, as we have little information about the nature and dynamics of the dark sector. Hence, in many of the phenomenological dark matter fluid interaction models in the literature, the interaction strength $Q_{\nu}$ in the dark sector is introduced by hand. Demanding that the interaction strength $Q_{\nu}$ in the dark sector must have a field theory description, we obtain a unique form of interaction strength. We show the equivalence between the fields and fluids for the $f(R,\chi)$ model where $f$ is an arbitrary, smooth function of $R$ and classical scalar field $\chi$, which represents dark matter. Up to first order in perturbations, we show that the one-to-one mapping between the \emph{classical} field theory description and the phenomenological fluid description of interacting dark energy and dark matter exists \emph{only} for this unique form of interaction. We then classify the interacting dark energy models considered in the literature into two categories based on the field-theoretic description. We introduce a novel autonomous system and its stability analysis for the general interacting dark sector. We show that the dark-energy dominated epoch occurs earlier than the non-interacting systems for a specific scalar field potential and a range of coupling strengths. |
2202.00696 | V\'ictor Jaramillo | V\'ictor Jaramillo, Nicolas Sanchis-Gual, Juan Barranco, Argelia
Bernal, Juan Carlos Degollado, Carlos Herdeiro, Miguel Megevand, Dar\'io
N\'u\~nez | Head-on collisions of $\ell$-boson stars | 23 pages. Updated version with broader discussion, typos corrected
and new analyses and figures | null | 10.1103/PhysRevD.105.104057 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Fully non-linear numerical evolutions of the Einstein-(multi)--Klein-Gordon
equations are performed to study head-on collisions of $\ell$-boson stars.
Despite being spherically symmetric, $\ell$-boson stars have a (hidden) frame
of reference, used in defining their individual multipolar fields. To assess
the impact of their relative orientation, we perform simulations with different
angles between the axes of the two colliding stars. Additionally, two scenarios
are considered for the colliding stars: that they are composites of either the
same or different scalar fields. Despite some model-specific behaviours, the
simulations generically indicate that: 1) the collision of two sufficiently
(and equally) massive stars leads to black hole formation; 2) below a certain
mass threshold the end result of the evolution is a bound state of the
composite scalar fields, that neither disperses nor collapses into a black hole
within the simulation time; 3) this end product (generically) deviates from
spherical symmetry and the equipartition of the number of bosonic particles
between the different scalar fields composing the initial boson stars is lost,
albeit not dramatically. This last observation indicates, albeit without being
conclusive, that the end result of these collisions belongs to the previously
reported larger family of equilibrium multi-field boson stars, generically
non-spherical, and of which $\ell$-boson stars are a symmetry enhanced point.
We also extract and discuss the waveforms from the collisions studied.
| [
{
"created": "Tue, 1 Feb 2022 19:00:03 GMT",
"version": "v1"
},
{
"created": "Fri, 13 May 2022 16:41:46 GMT",
"version": "v2"
}
] | 2022-06-08 | [
[
"Jaramillo",
"Víctor",
""
],
[
"Sanchis-Gual",
"Nicolas",
""
],
[
"Barranco",
"Juan",
""
],
[
"Bernal",
"Argelia",
""
],
[
"Degollado",
"Juan Carlos",
""
],
[
"Herdeiro",
"Carlos",
""
],
[
"Megevand",
"Miguel",
""
],
[
"Núñez",
"Darío",
""
]
] | Fully non-linear numerical evolutions of the Einstein-(multi)--Klein-Gordon equations are performed to study head-on collisions of $\ell$-boson stars. Despite being spherically symmetric, $\ell$-boson stars have a (hidden) frame of reference, used in defining their individual multipolar fields. To assess the impact of their relative orientation, we perform simulations with different angles between the axes of the two colliding stars. Additionally, two scenarios are considered for the colliding stars: that they are composites of either the same or different scalar fields. Despite some model-specific behaviours, the simulations generically indicate that: 1) the collision of two sufficiently (and equally) massive stars leads to black hole formation; 2) below a certain mass threshold the end result of the evolution is a bound state of the composite scalar fields, that neither disperses nor collapses into a black hole within the simulation time; 3) this end product (generically) deviates from spherical symmetry and the equipartition of the number of bosonic particles between the different scalar fields composing the initial boson stars is lost, albeit not dramatically. This last observation indicates, albeit without being conclusive, that the end result of these collisions belongs to the previously reported larger family of equilibrium multi-field boson stars, generically non-spherical, and of which $\ell$-boson stars are a symmetry enhanced point. We also extract and discuss the waveforms from the collisions studied. |
gr-qc/0302093 | Steven D. Penn | Steven D. Penn, Peter H. Sneddon, Helena Armandula, Joseph C.
Betzwieser, Gianpietro Cagnoli, Jordan Camp, D. R. M. Crooks, Martin M.
Fejer, Andri M. Gretarsson, Gregory M. Harry, Jim Hough, Scott E.
Kittelberger, Michael J. Mortonson, Roger Route, Sheila Rowan, Christophoros
C. Vassiliou | Mechanical Loss in Tantala/Silica Dielectric Mirror Coatings | 8 pages, 6 figures, two figures are color | Class.Quant.Grav. 20 (2003) 2917-2928 | 10.1088/0264-9381/20/13/334 | null | gr-qc | null | Current interferometric gravitational wave detectors use test masses with
mirror coatings formed from multiple layers of dielectric materials, most
commonly alternating layers of SiO2 (silica) and Ta2O5 (tantala). However,
mechanical loss in the Ta2O5/SiO2 coatings may limit the design sensitivity for
advanced detectors. We have investigated sources of mechanical loss in the
Ta2O5/SiO2 coatings, including loss associated with the coating-substrate
interface, with the coating-layer interfaces, and with the bulk material. Our
results indicate that the loss is associated with the bulk coating materials
and that the loss of Ta2O5 is substantially larger than that of SiO2.
| [
{
"created": "Mon, 24 Feb 2003 17:12:09 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Penn",
"Steven D.",
""
],
[
"Sneddon",
"Peter H.",
""
],
[
"Armandula",
"Helena",
""
],
[
"Betzwieser",
"Joseph C.",
""
],
[
"Cagnoli",
"Gianpietro",
""
],
[
"Camp",
"Jordan",
""
],
[
"Crooks",
"D. R. M.",
""
],
[
"Fejer",
"Martin M.",
""
],
[
"Gretarsson",
"Andri M.",
""
],
[
"Harry",
"Gregory M.",
""
],
[
"Hough",
"Jim",
""
],
[
"Kittelberger",
"Scott E.",
""
],
[
"Mortonson",
"Michael J.",
""
],
[
"Route",
"Roger",
""
],
[
"Rowan",
"Sheila",
""
],
[
"Vassiliou",
"Christophoros C.",
""
]
] | Current interferometric gravitational wave detectors use test masses with mirror coatings formed from multiple layers of dielectric materials, most commonly alternating layers of SiO2 (silica) and Ta2O5 (tantala). However, mechanical loss in the Ta2O5/SiO2 coatings may limit the design sensitivity for advanced detectors. We have investigated sources of mechanical loss in the Ta2O5/SiO2 coatings, including loss associated with the coating-substrate interface, with the coating-layer interfaces, and with the bulk material. Our results indicate that the loss is associated with the bulk coating materials and that the loss of Ta2O5 is substantially larger than that of SiO2. |
0707.1671 | Sergey Kozyrev | S.M.Kozyrev | Comment about the "Gravity coupled to a scalar field in extra
dimensions" paper | null | null | null | null | gr-qc | null | Wehus and Ravndal have argued that in d + 1 dimensions the general solution
for gravity minimally coupled to a scalar field can not be explicitly written
in Schwarzschild coordinates. We contest these objections.
| [
{
"created": "Wed, 11 Jul 2007 17:42:15 GMT",
"version": "v1"
}
] | 2007-07-12 | [
[
"Kozyrev",
"S. M.",
""
]
] | Wehus and Ravndal have argued that in d + 1 dimensions the general solution for gravity minimally coupled to a scalar field can not be explicitly written in Schwarzschild coordinates. We contest these objections. |
1204.0419 | Simen Braeck | S. Braeck, O. Gron | A river model of space | 22 pages, 5 figures | Eur. Phys. J. Plus (2013) 128: 24 | 10.1140/epjp/i2013-13024-2 | null | gr-qc astro-ph.CO astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the theory of general relativity gravitational phenomena are usually
attributed to the curvature of four-dimensional spacetime. In this context we
are often confronted with the question of how the concept of ordinary physical
three-dimensional space fits into this picture. In this work we present a
simple and intuitive model of space for both the Schwarzschild spacetime and
the de Sitter spacetime in which physical space is defined as a specified set
of freely moving reference particles. Using a combination of orthonormal basis
fields and the usual formalism in a coordinate basis we calculate the physical
velocity field of these reference particles. Thus we obtain a vivid description
of space in which space behaves like a river flowing radially toward the
singularity in the Schwarzschild spacetime and radially toward infinity in the
de Sitter spacetime. We also consider the effect of the river of space upon
light rays and material particles and show that the river model of space
provides an intuitive explanation for the behavior of light and particles at
and beyond the event horizons associated with these spacetimes.
| [
{
"created": "Mon, 2 Apr 2012 14:31:03 GMT",
"version": "v1"
}
] | 2017-05-15 | [
[
"Braeck",
"S.",
""
],
[
"Gron",
"O.",
""
]
] | Within the theory of general relativity gravitational phenomena are usually attributed to the curvature of four-dimensional spacetime. In this context we are often confronted with the question of how the concept of ordinary physical three-dimensional space fits into this picture. In this work we present a simple and intuitive model of space for both the Schwarzschild spacetime and the de Sitter spacetime in which physical space is defined as a specified set of freely moving reference particles. Using a combination of orthonormal basis fields and the usual formalism in a coordinate basis we calculate the physical velocity field of these reference particles. Thus we obtain a vivid description of space in which space behaves like a river flowing radially toward the singularity in the Schwarzschild spacetime and radially toward infinity in the de Sitter spacetime. We also consider the effect of the river of space upon light rays and material particles and show that the river model of space provides an intuitive explanation for the behavior of light and particles at and beyond the event horizons associated with these spacetimes. |
2310.16357 | Andronikos Paliathanasis | Andronikos Paliathanasis | The Brans-Dicke field in Non-metricity gravity: Cosmological solutions
and Conformal transformations | 25 pages, 1 figure | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | We consider the Brans-Dicke theory in non-metricity gravity, which belongs to
the family of symmetric teleparallel scalar-tensor theories. Our focus lies in
exploring the implications of the conformal transformation, as we derive the
conformal equivalent theory in the Einstein frame, distinct from the minimally
coupled scalar field theory. The fundamental principle of the conformal
transformation suggests the mathematical equivalence of the related theories.
However, to thoroughly analyze the impact on physical variables, we investigate
the spatially flat Friedmann--Lema\^{\i}tre--Robertson--Walker geometry,
defining the connection in the non-coincidence gauge. We construct exact
solutions for the cosmological model in one frame and compare the physical
properties in the conformal related frame. Surprisingly, we find that the
general physical properties of the exact solutions remain invariant under the
conformal transformation. Finally, we construct, for the first time, an
analytic solution for the symmetric teleparallel scalar-tensor cosmology.
| [
{
"created": "Wed, 25 Oct 2023 04:37:00 GMT",
"version": "v1"
}
] | 2023-10-26 | [
[
"Paliathanasis",
"Andronikos",
""
]
] | We consider the Brans-Dicke theory in non-metricity gravity, which belongs to the family of symmetric teleparallel scalar-tensor theories. Our focus lies in exploring the implications of the conformal transformation, as we derive the conformal equivalent theory in the Einstein frame, distinct from the minimally coupled scalar field theory. The fundamental principle of the conformal transformation suggests the mathematical equivalence of the related theories. However, to thoroughly analyze the impact on physical variables, we investigate the spatially flat Friedmann--Lema\^{\i}tre--Robertson--Walker geometry, defining the connection in the non-coincidence gauge. We construct exact solutions for the cosmological model in one frame and compare the physical properties in the conformal related frame. Surprisingly, we find that the general physical properties of the exact solutions remain invariant under the conformal transformation. Finally, we construct, for the first time, an analytic solution for the symmetric teleparallel scalar-tensor cosmology. |
2406.17643 | Cameron Bunney | Cameron R. D. Bunney and Jorma Louko | Circular motion in (anti-)de Sitter spacetime: thermality versus finite
size | 18 pages: 10 pages + 8 pages appendices. 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Anti-de Sitter spacetime and the static patch of de Sitter spacetime are
arenas for investigating thermal and finite-size effects seen by an accelerated
quantum observer. We consider an Unruh-DeWitt detector in uniform circular
motion coupled to a conformal scalar field in $(2+1)$-dimensional de Sitter and
anti-de Sitter spacetimes in the limit of a small cosmological constant
$\Lambda$. In anti-de Sitter spacetime, where $\Lambda$ mimics spatial
confinement, we find that the resonance peaks in the detector's response
closely match those of a detector in Minkowski space with a cylindrical
boundary, but with curvature corrections, more significant when the field has
an ambient temperature. In the static patch of de Sitter spacetime, in the
Euclidean vacuum, we show that the leading curvature correction to the
detector's response is proportional to $\Lambda$, as in zero temperature
anti-de Sitter, whilst the temperature corrections decay exponentially as
$\Lambda \to 0$.
| [
{
"created": "Tue, 25 Jun 2024 15:34:19 GMT",
"version": "v1"
}
] | 2024-06-26 | [
[
"Bunney",
"Cameron R. D.",
""
],
[
"Louko",
"Jorma",
""
]
] | Anti-de Sitter spacetime and the static patch of de Sitter spacetime are arenas for investigating thermal and finite-size effects seen by an accelerated quantum observer. We consider an Unruh-DeWitt detector in uniform circular motion coupled to a conformal scalar field in $(2+1)$-dimensional de Sitter and anti-de Sitter spacetimes in the limit of a small cosmological constant $\Lambda$. In anti-de Sitter spacetime, where $\Lambda$ mimics spatial confinement, we find that the resonance peaks in the detector's response closely match those of a detector in Minkowski space with a cylindrical boundary, but with curvature corrections, more significant when the field has an ambient temperature. In the static patch of de Sitter spacetime, in the Euclidean vacuum, we show that the leading curvature correction to the detector's response is proportional to $\Lambda$, as in zero temperature anti-de Sitter, whilst the temperature corrections decay exponentially as $\Lambda \to 0$. |
0711.2441 | A. Joel Saavedra | Sergio del Campo, Ramon Herrera and Joel Saavedra | Open Inflationary Universes in Gauss-Bonnet Brane Cosmology | Revtex, 4 Figures. Accepted by Modern Physics Letters A | Mod.Phys.Lett.A23:1187-1197,2008 | 10.1142/S0217732308025784 | null | gr-qc hep-th | null | In this article, we study a type of one-field approach for open inflationary
universe scenario in the context of braneworld models with a Gauss-Bonnet
correction term. For a one-bubble universe model, we determine and characterize
the existence of the Coleman-De Lucia instanton together with the period of
inflation after tunneling has occurred. Our results are compared those
analogous obtained when the usual Einstein Theory of Gravitation is used.
| [
{
"created": "Thu, 15 Nov 2007 15:30:13 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"del Campo",
"Sergio",
""
],
[
"Herrera",
"Ramon",
""
],
[
"Saavedra",
"Joel",
""
]
] | In this article, we study a type of one-field approach for open inflationary universe scenario in the context of braneworld models with a Gauss-Bonnet correction term. For a one-bubble universe model, we determine and characterize the existence of the Coleman-De Lucia instanton together with the period of inflation after tunneling has occurred. Our results are compared those analogous obtained when the usual Einstein Theory of Gravitation is used. |
2207.07414 | Zhixiang Ren | Tianyu Zhao, Ruoxi Lyu, He Wang, Zhoujian Cao, Zhixiang Ren | Space-based gravitational wave signal detection and extraction with deep
neural network | 19 pages, 7 figures | Commun Phys 6, 212 (2023) | 10.1038/s42005-023-01334-6 | null | gr-qc cs.AI | http://creativecommons.org/licenses/by/4.0/ | Space-based gravitational wave (GW) detectors will be able to observe signals
from sources that are otherwise nearly impossible from current ground-based
detection. Consequently, the well established signal detection method, matched
filtering, will require a complex template bank, leading to a computational
cost that is too expensive in practice. Here, we develop a high-accuracy GW
signal detection and extraction method for all space-based GW sources. As a
proof of concept, we show that a science-driven and uniform multi-stage
self-attention-based deep neural network can identify synthetic signals that
are submerged in Gaussian noise. Our method exhibits a detection rate exceeding
99% in identifying signals from various sources, with the signal-to-noise ratio
at 50, at a false alarm rate of 1%. while obtaining at least 95% similarity
compared with target signals. We further demonstrate the interpretability and
strong generalization behavior for several extended scenarios.
| [
{
"created": "Fri, 15 Jul 2022 11:48:15 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jul 2022 06:28:05 GMT",
"version": "v2"
},
{
"created": "Wed, 16 Aug 2023 02:17:48 GMT",
"version": "v3"
}
] | 2023-08-17 | [
[
"Zhao",
"Tianyu",
""
],
[
"Lyu",
"Ruoxi",
""
],
[
"Wang",
"He",
""
],
[
"Cao",
"Zhoujian",
""
],
[
"Ren",
"Zhixiang",
""
]
] | Space-based gravitational wave (GW) detectors will be able to observe signals from sources that are otherwise nearly impossible from current ground-based detection. Consequently, the well established signal detection method, matched filtering, will require a complex template bank, leading to a computational cost that is too expensive in practice. Here, we develop a high-accuracy GW signal detection and extraction method for all space-based GW sources. As a proof of concept, we show that a science-driven and uniform multi-stage self-attention-based deep neural network can identify synthetic signals that are submerged in Gaussian noise. Our method exhibits a detection rate exceeding 99% in identifying signals from various sources, with the signal-to-noise ratio at 50, at a false alarm rate of 1%. while obtaining at least 95% similarity compared with target signals. We further demonstrate the interpretability and strong generalization behavior for several extended scenarios. |
0807.0112 | Luke Butcher | Luke M. Butcher, Anthony Lasenby, Michael Hobson | The physical significance of the Babak-Grishchuk gravitational
energy-momentum tensor | 10 pages. Submitted to Phys. Rev. D; acknowledgements adjusted | Phys.Rev.D78:064034,2008 | 10.1103/PhysRevD.78.064034 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the claim of Babak and Grishchuk [1] to have solved the problem of
localising the energy and momentum of the gravitational field. After
summarising Grishchuk's flat-space formulation of gravity, we demonstrate its
equivalence to General Relativity at the level of the action. Two important
transformations are described (diffeomorphisms applied to all fields, and
diffeomorphisms applied to the flat-space metric alone) and we argue that both
should be considered gauge transformations: they alter the mathematical
representation of a physical system, but not the system itself. By examining
the transformation properties of the Babak-Grishchuk gravitational
energy-momentum tensor under these gauge transformations (infinitesimal and
finite) we conclude that this object has no physical significance.
| [
{
"created": "Tue, 1 Jul 2008 11:03:34 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Jul 2008 14:37:15 GMT",
"version": "v2"
}
] | 2009-02-23 | [
[
"Butcher",
"Luke M.",
""
],
[
"Lasenby",
"Anthony",
""
],
[
"Hobson",
"Michael",
""
]
] | We examine the claim of Babak and Grishchuk [1] to have solved the problem of localising the energy and momentum of the gravitational field. After summarising Grishchuk's flat-space formulation of gravity, we demonstrate its equivalence to General Relativity at the level of the action. Two important transformations are described (diffeomorphisms applied to all fields, and diffeomorphisms applied to the flat-space metric alone) and we argue that both should be considered gauge transformations: they alter the mathematical representation of a physical system, but not the system itself. By examining the transformation properties of the Babak-Grishchuk gravitational energy-momentum tensor under these gauge transformations (infinitesimal and finite) we conclude that this object has no physical significance. |
1306.4964 | Jansen Formiga | J. B. Formiga | Equivalent teleparallel theories in diagonalizable spacetimes: Comment
on "Metric-affine approach to teleparallel gravity" | 7 pages | null | 10.1103/PhysRevD.88.068501 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known that the teleparallel equivalent of general relativity
yields the same vacuum solutions as general relativity does, which ensures that
this particular teleparallel model is in good agreement with experiments. A
less known result concerns the existence of a wider class of teleparallel
models which also admits these solutions when the spacetime is diagonalizable
by means of a coordinate change. However, it is stated in Ref. [Phys. Rev. D
67, 044016 (2003).] that the teleparallel equivalent of general relativity is
the only teleparallel model which admits black holes. To show that this
statement is not true, I prove the existence of this wider class by taking an
approach different from that of Ref. [Phys. Rev. D 19, 3524 (1979)].
| [
{
"created": "Thu, 20 Jun 2013 19:31:42 GMT",
"version": "v1"
}
] | 2013-10-02 | [
[
"Formiga",
"J. B.",
""
]
] | It is well known that the teleparallel equivalent of general relativity yields the same vacuum solutions as general relativity does, which ensures that this particular teleparallel model is in good agreement with experiments. A less known result concerns the existence of a wider class of teleparallel models which also admits these solutions when the spacetime is diagonalizable by means of a coordinate change. However, it is stated in Ref. [Phys. Rev. D 67, 044016 (2003).] that the teleparallel equivalent of general relativity is the only teleparallel model which admits black holes. To show that this statement is not true, I prove the existence of this wider class by taking an approach different from that of Ref. [Phys. Rev. D 19, 3524 (1979)]. |
2401.10771 | Avisikta Ghosh | Avisikta Ghosh | Study of Orbital Dynamics in Singular and Regular Naked Singularity
Space-times | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The universe is filled with various compact objects and the most attractive
of them are the black holes and singularity. But it is also known that at the
singularity density becomes so infinitely high that the present physics
knowledge breaks down. Thus, the singularity remains a flaw of the present
theories. Several methods have been exercised to resolve the singularity. One
such mathematical method is through conformal transformations. This paper deals
with regularizing a naked singularity space-time using conformal
transformations, further studying and comparing its time-like orbits with that
of the naked singularity space-time.
| [
{
"created": "Fri, 19 Jan 2024 15:42:07 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Apr 2024 07:46:16 GMT",
"version": "v2"
}
] | 2024-04-04 | [
[
"Ghosh",
"Avisikta",
""
]
] | The universe is filled with various compact objects and the most attractive of them are the black holes and singularity. But it is also known that at the singularity density becomes so infinitely high that the present physics knowledge breaks down. Thus, the singularity remains a flaw of the present theories. Several methods have been exercised to resolve the singularity. One such mathematical method is through conformal transformations. This paper deals with regularizing a naked singularity space-time using conformal transformations, further studying and comparing its time-like orbits with that of the naked singularity space-time. |
1412.7208 | Otakar Svitek | Petr Kaspar, Otakar Svitek | Averaging in LRS class II spacetimes | 3 figures, accepted in GRG | Gen. Rel. Grav. 47 (2015) 4 | 10.1007/s10714-014-1844-6 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | We generalize Buchert's averaged equations [Gen. Rel. Grav. 32, 105 (2000);
Gen. Rel. Grav. 33, 1381 (2001)] to LRS class II dust model in the sense that
all Einstein equations are averaged, not only the trace part. We derive the
relevant averaged equations and we investigate backreaction on expansion and
shear scalars in an approximate LTB model. Finally we propose a way to close
the system of averaged equations.
| [
{
"created": "Mon, 22 Dec 2014 23:28:32 GMT",
"version": "v1"
}
] | 2015-02-17 | [
[
"Kaspar",
"Petr",
""
],
[
"Svitek",
"Otakar",
""
]
] | We generalize Buchert's averaged equations [Gen. Rel. Grav. 32, 105 (2000); Gen. Rel. Grav. 33, 1381 (2001)] to LRS class II dust model in the sense that all Einstein equations are averaged, not only the trace part. We derive the relevant averaged equations and we investigate backreaction on expansion and shear scalars in an approximate LTB model. Finally we propose a way to close the system of averaged equations. |
gr-qc/0202096 | Harald P. Pfeiffer | Harald P. Pfeiffer, Lawrence E. Kidder, Mark A. Scheel, Saul A.
Teukolsky | A multidomain spectral method for solving elliptic equations | 31 pages, 8 figures | Comput.Phys.Commun. 152 (2003) 253-273 | 10.1016/S0010-4655(02)00847-0 | null | gr-qc | null | We present a new solver for coupled nonlinear elliptic partial differential
equations (PDEs). The solver is based on pseudo-spectral collocation with
domain decomposition and can handle one- to three-dimensional problems. It has
three distinct features. First, the combined problem of solving the PDE,
satisfying the boundary conditions, and matching between different subdomains
is cast into one set of equations readily accessible to standard linear and
nonlinear solvers. Second, touching as well as overlapping subdomains are
supported; both rectangular blocks with Chebyshev basis functions as well as
spherical shells with an expansion in spherical harmonics are implemented.
Third, the code is very flexible: The domain decomposition as well as the
distribution of collocation points in each domain can be chosen at run time,
and the solver is easily adaptable to new PDEs. The code has been used to solve
the equations of the initial value problem of general relativity and should be
useful in many other problems. We compare the new method to finite difference
codes and find it superior in both runtime and accuracy, at least for the
smooth problems considered here.
| [
{
"created": "Wed, 27 Feb 2002 14:59:18 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Pfeiffer",
"Harald P.",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Teukolsky",
"Saul A.",
""
]
] | We present a new solver for coupled nonlinear elliptic partial differential equations (PDEs). The solver is based on pseudo-spectral collocation with domain decomposition and can handle one- to three-dimensional problems. It has three distinct features. First, the combined problem of solving the PDE, satisfying the boundary conditions, and matching between different subdomains is cast into one set of equations readily accessible to standard linear and nonlinear solvers. Second, touching as well as overlapping subdomains are supported; both rectangular blocks with Chebyshev basis functions as well as spherical shells with an expansion in spherical harmonics are implemented. Third, the code is very flexible: The domain decomposition as well as the distribution of collocation points in each domain can be chosen at run time, and the solver is easily adaptable to new PDEs. The code has been used to solve the equations of the initial value problem of general relativity and should be useful in many other problems. We compare the new method to finite difference codes and find it superior in both runtime and accuracy, at least for the smooth problems considered here. |
1807.10287 | Naritaka Oshita | Naritaka Oshita and Niayesh Afshordi | Probing microstructure of black hole spacetimes with gravitational wave
echoes | 9 pages, 7 figures, accepted for publication in PRD | Phys. Rev. D 99, 044002 (2019) | 10.1103/PhysRevD.99.044002 | RESCEU-10/18 | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum nature of black hole horizons has been a subject of recent interest
and scrutiny. In particular, a near-horizon quantum violation of the
equivalence principle has been proposed as a resolution of the black hole
information paradox. Such a violation may lead to a modified dispersion
relation at high energies, which could become relevant due to the intense
gravitational blueshift experienced by ingoing gravitational waves. We
investigate the ringdown for a perturbed black hole with such a modified
dispersion relation and find that infalling gravitational waves are partially
reflected near the horizon. This results in the appearance of late-time ${\it
echoes}$ in the ringdown phase of black hole merger events, with similar
properties to those (arguably) seen in the Advanced LIGO observations. Current
measurements suggest a Lorentz-violation scale of $10^{13 \pm 2}$ GeV for
gravitational waves, with comparable dissipation and dispersion. Therefore, if
confirmed, black hole ringdown echoes probe the microstructure of horizons and
thus can test Lorentz-violating UV completions, such as in
Ho$\v{r}$ava-Lifshitz gravity.
| [
{
"created": "Thu, 26 Jul 2018 18:00:02 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Feb 2019 05:19:09 GMT",
"version": "v2"
}
] | 2019-02-14 | [
[
"Oshita",
"Naritaka",
""
],
[
"Afshordi",
"Niayesh",
""
]
] | Quantum nature of black hole horizons has been a subject of recent interest and scrutiny. In particular, a near-horizon quantum violation of the equivalence principle has been proposed as a resolution of the black hole information paradox. Such a violation may lead to a modified dispersion relation at high energies, which could become relevant due to the intense gravitational blueshift experienced by ingoing gravitational waves. We investigate the ringdown for a perturbed black hole with such a modified dispersion relation and find that infalling gravitational waves are partially reflected near the horizon. This results in the appearance of late-time ${\it echoes}$ in the ringdown phase of black hole merger events, with similar properties to those (arguably) seen in the Advanced LIGO observations. Current measurements suggest a Lorentz-violation scale of $10^{13 \pm 2}$ GeV for gravitational waves, with comparable dissipation and dispersion. Therefore, if confirmed, black hole ringdown echoes probe the microstructure of horizons and thus can test Lorentz-violating UV completions, such as in Ho$\v{r}$ava-Lifshitz gravity. |
1412.3657 | Christopher Moore | Christopher J. Moore and Jonathan R. Gair | Novel Method for Incorporating Model Uncertainties into Gravitational
Wave Parameter Estimates | 6 pages, 3 figures, accepted for publication in Physical Review
Letters | null | 10.1103/PhysRevLett.113.251101 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Posterior distributions on parameters computed from experimental data using
Bayesian techniques are only as accurate as the models used to construct them.
In many applications these models are incomplete, which both reduces the
prospects of detection and leads to a systematic error in the parameter
estimates. In the analysis of data from gravitational wave detectors, for
example, accurate waveform templates can be computed using numerical methods,
but the prohibitive cost of these simulations means this can only be done for a
small handful of parameters. In this work a novel method to fold model
uncertainties into data analysis is proposed; the waveform uncertainty is
analytically marginalised over using with a prior distribution constructed by
using Gaussian process regression to interpolate the waveform difference from a
small training set of accurate templates. The method is well motivated, easy to
implement, and no more computationally expensive than standard techniques. The
new method is shown to perform extremely well when applied to a toy problem.
While we use the application to gravitational wave data analysis to motivate
and illustrate the technique, it can be applied in any context where model
uncertainties exist.
| [
{
"created": "Thu, 11 Dec 2014 14:32:22 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Moore",
"Christopher J.",
""
],
[
"Gair",
"Jonathan R.",
""
]
] | Posterior distributions on parameters computed from experimental data using Bayesian techniques are only as accurate as the models used to construct them. In many applications these models are incomplete, which both reduces the prospects of detection and leads to a systematic error in the parameter estimates. In the analysis of data from gravitational wave detectors, for example, accurate waveform templates can be computed using numerical methods, but the prohibitive cost of these simulations means this can only be done for a small handful of parameters. In this work a novel method to fold model uncertainties into data analysis is proposed; the waveform uncertainty is analytically marginalised over using with a prior distribution constructed by using Gaussian process regression to interpolate the waveform difference from a small training set of accurate templates. The method is well motivated, easy to implement, and no more computationally expensive than standard techniques. The new method is shown to perform extremely well when applied to a toy problem. While we use the application to gravitational wave data analysis to motivate and illustrate the technique, it can be applied in any context where model uncertainties exist. |
gr-qc/0302102 | Y. Bisabr | Yousef Bisabr | Mach's Principle and Model for a Broken Symmetric Theory of Gravity | 9 pages, no figures | Int.J.Theor.Phys. 44 (2005) 283-291 | 10.1007/s10773-006-9033-3 | null | gr-qc | null | We investigate spontaneous symmetry breaking in a conformally invariant
gravitational model. In particular, we use a conformally invariant scalar
tensor theory as the vacuum sector of a gravitational model to examine the idea
that gravitational coupling may be the result of a spontaneous symmetry
breaking. In this model matter is taken to be coupled with a metric which is
different but conformally related to the metric appearing explicitly in the
vacuum sector. We show that after the spontaneous symmetry breaking the
resulting theory is consistent with Mach's principle in the sense that inertial
masses of particles have variable configurations in a cosmological context.
Moreover, our analysis allows to construct a mechanism in which the resulting
large vacuum energy density relaxes during evolution of the universe.
| [
{
"created": "Tue, 25 Feb 2003 20:05:58 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Mar 2004 20:49:27 GMT",
"version": "v2"
},
{
"created": "Tue, 6 Jul 2004 18:16:48 GMT",
"version": "v3"
}
] | 2015-06-25 | [
[
"Bisabr",
"Yousef",
""
]
] | We investigate spontaneous symmetry breaking in a conformally invariant gravitational model. In particular, we use a conformally invariant scalar tensor theory as the vacuum sector of a gravitational model to examine the idea that gravitational coupling may be the result of a spontaneous symmetry breaking. In this model matter is taken to be coupled with a metric which is different but conformally related to the metric appearing explicitly in the vacuum sector. We show that after the spontaneous symmetry breaking the resulting theory is consistent with Mach's principle in the sense that inertial masses of particles have variable configurations in a cosmological context. Moreover, our analysis allows to construct a mechanism in which the resulting large vacuum energy density relaxes during evolution of the universe. |
2310.17553 | Shaswata Chowdhury | Shaswata Chowdhury | Anisotropies and modified gravity theories in stellar and substellar
objects | This review article prepared for "Special Issue Metric-Affine Gravity
Tartu", 49 pages, 10 figures, 3 tables, version accepted to Int. J. of
Geometric Methods in Modern Physics (IJGMMP) | null | null | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In several classes of modified gravity theories, extra degrees of freedom are
not completely screened in the interiors of stellar and substellar objects. In
such theories, the hydrostatic equilibrium condition inside these objects is
altered. Moreover, the interior structures of these objects might have a small
pressure anisotropy induced by several physical phenomena, including rotation
and magnetic fields. All these effects, both individually and collectively,
induce changes in predicted stellar observables. Such changes have an impact on
different phases of the stellar life cycle, starting from its birth to its
death, covering almost all the branches of the Hertzsprung-Russell diagram. The
aim of this work is to systematically review the current literature on the
topic. We discuss the main results and constraints obtained on a class of
modified gravity theories.
| [
{
"created": "Thu, 26 Oct 2023 16:45:59 GMT",
"version": "v1"
}
] | 2023-10-27 | [
[
"Chowdhury",
"Shaswata",
""
]
] | In several classes of modified gravity theories, extra degrees of freedom are not completely screened in the interiors of stellar and substellar objects. In such theories, the hydrostatic equilibrium condition inside these objects is altered. Moreover, the interior structures of these objects might have a small pressure anisotropy induced by several physical phenomena, including rotation and magnetic fields. All these effects, both individually and collectively, induce changes in predicted stellar observables. Such changes have an impact on different phases of the stellar life cycle, starting from its birth to its death, covering almost all the branches of the Hertzsprung-Russell diagram. The aim of this work is to systematically review the current literature on the topic. We discuss the main results and constraints obtained on a class of modified gravity theories. |
gr-qc/0607134 | Hunter Monroe | Hunter Monroe | Topology and Closed Timelike Curves II: Causal structure | See companion paper by the same title | null | null | null | gr-qc astro-ph math.DG | null | Because no closed timelike curve (CTC) on a Lorentzian manifold can be
deformed to a point, any such manifold containing a CTC must have a topological
feature, to be called a timelike wormhole, that prevents the CTC from being
deformed to a point. If all wormholes have horizons, which typically seems to
be the case in space-times without exotic matter, then each CTC must transit
some timelike wormhole's horizon. Therefore, a Lorentzian manifold containing a
CTC may nevertheless be causally well behaving once its horizon's are deleted.
For instance, there may be a Cauchy-like surface through which every timelike
curve passes one and only once before crossing a horizon.
| [
{
"created": "Mon, 31 Jul 2006 04:30:09 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Aug 2006 12:17:28 GMT",
"version": "v2"
},
{
"created": "Sun, 3 Sep 2006 03:23:12 GMT",
"version": "v3"
},
{
"created": "Fri, 8 Sep 2006 12:46:39 GMT",
"version": "v4"
},
{
"created": "Thu, 14 Sep 2006 22:48:26 GMT",
"version": "v5"
}
] | 2007-05-23 | [
[
"Monroe",
"Hunter",
""
]
] | Because no closed timelike curve (CTC) on a Lorentzian manifold can be deformed to a point, any such manifold containing a CTC must have a topological feature, to be called a timelike wormhole, that prevents the CTC from being deformed to a point. If all wormholes have horizons, which typically seems to be the case in space-times without exotic matter, then each CTC must transit some timelike wormhole's horizon. Therefore, a Lorentzian manifold containing a CTC may nevertheless be causally well behaving once its horizon's are deleted. For instance, there may be a Cauchy-like surface through which every timelike curve passes one and only once before crossing a horizon. |
1302.5156 | Mir Faizal | Mir Faizal | Noncommutative Quantum Gravity | 11 pages, 0 figures, accepted for publication in Mod. Phys. Lett. A | Mod. Phys. Lett. A28: 1350034, 2013 | 10.1142/S021773231350034X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the BRST and anti-BRST symmetries for perturbative quantum gravity
in noncommutative spacetime. In this noncommutative perturbative quantum
gravity the sum of the classical Lagrangian density with a gauge fixing term
and a ghost term is shown to be invariant the noncommutative BRST and the
noncommutative anti-BRST transformations. We analyse the gauge fixing term and
the ghost term in both linear as well as non-linear gauges. We also discuss the
unitarity evolution of the theory and analyse the violation of unitarity of by
introduction of a bare mass term in the noncommutative BRST and the
noncommutative anti-BRST transformations.
| [
{
"created": "Thu, 21 Feb 2013 01:57:41 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Mar 2013 21:56:40 GMT",
"version": "v2"
}
] | 2015-06-15 | [
[
"Faizal",
"Mir",
""
]
] | We discuss the BRST and anti-BRST symmetries for perturbative quantum gravity in noncommutative spacetime. In this noncommutative perturbative quantum gravity the sum of the classical Lagrangian density with a gauge fixing term and a ghost term is shown to be invariant the noncommutative BRST and the noncommutative anti-BRST transformations. We analyse the gauge fixing term and the ghost term in both linear as well as non-linear gauges. We also discuss the unitarity evolution of the theory and analyse the violation of unitarity of by introduction of a bare mass term in the noncommutative BRST and the noncommutative anti-BRST transformations. |
1403.1865 | Laura Henderson | Laura J. Henderson (1), Robert B. Mann (1) and Sean Stotyn (2) ((1)
Department of Physics and Astronomy, University of Waterloo, (2) Department
of Physics and Astronomy, University of British Columbia) | Gauss-Bonnet Boson Stars with a Single Killing Vector | 46 pages, 17 figures | Phys. Rev. D 91, 024009 (2015) | 10.1103/PhysRevD.91.024009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct asymptotically anti-de Sitter boson stars in
Einstein-Gauss-Bonnet gravity coupled to a $\frac{D-1}{2}$-tuplet of complex
massless scalar fields both perturbatively and numerically in D=5,7,9,11
dimensions. These solutions possess just a single helical Killing symmetry due
to the choice of scalar fields. The energy density at the centre of the star
characterizes the solutions, and for each choice of the Gauss-Bonnet coupling
$\alpha$ we obtain a one parameter family of solutions. All solutions respect
the first law of thermodynamics; in the numerical case to within 1 part in
$10^6$. We describe the dependence of the angular velocity, mass, and angular
momentum of the boson stars on $\alpha$ and on the dimensionality. For D>5,
these quantities exhibit damped oscillations about finite central values as the
central energy density tends to infinity, where the amplitude of oscillation
increases nonlinearly with $\alpha$. In the limit of diverging central energy
density, the Kretschmann invariant at the centre of the boson star also
diverges. This is in contrast to the D=5 case, where the Kretschmann invariant
diverges at a finite value of the central energy density.
| [
{
"created": "Fri, 7 Mar 2014 20:52:14 GMT",
"version": "v1"
},
{
"created": "Tue, 27 May 2014 22:27:17 GMT",
"version": "v2"
}
] | 2015-01-14 | [
[
"Henderson",
"Laura J.",
""
],
[
"Mann",
"Robert B.",
""
],
[
"Stotyn",
"Sean",
""
]
] | We construct asymptotically anti-de Sitter boson stars in Einstein-Gauss-Bonnet gravity coupled to a $\frac{D-1}{2}$-tuplet of complex massless scalar fields both perturbatively and numerically in D=5,7,9,11 dimensions. These solutions possess just a single helical Killing symmetry due to the choice of scalar fields. The energy density at the centre of the star characterizes the solutions, and for each choice of the Gauss-Bonnet coupling $\alpha$ we obtain a one parameter family of solutions. All solutions respect the first law of thermodynamics; in the numerical case to within 1 part in $10^6$. We describe the dependence of the angular velocity, mass, and angular momentum of the boson stars on $\alpha$ and on the dimensionality. For D>5, these quantities exhibit damped oscillations about finite central values as the central energy density tends to infinity, where the amplitude of oscillation increases nonlinearly with $\alpha$. In the limit of diverging central energy density, the Kretschmann invariant at the centre of the boson star also diverges. This is in contrast to the D=5 case, where the Kretschmann invariant diverges at a finite value of the central energy density. |
gr-qc/0606105 | Sergio Dain | Sergio Dain | Proof of the angular momentum-mass inequality for axisymmetric black
holes | The statement before Eq. (17) in page 5 in the previous version is
incorrect. This mistake is corrected in the new version | J.Diff.Geom.79:33-67,2008 | null | null | gr-qc math-ph math.DG math.MP | null | We prove that extreme Kerr initial data set is a unique absolute minimum of
the total mass in a (physically relevant) class of vacuum, maximal,
asymptotically flat, axisymmetric data for Einstein equations with fixed
angular momentum. These data represent non-stationary, axially symmetric, black
holes. As a consequence, we obtain that any data in this class satisfy the
inequality $\sqrt{J} \leq m$, where $m$ and $J$ are the total mass and angular
momentum of the spacetime.
| [
{
"created": "Fri, 23 Jun 2006 16:58:15 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Dec 2006 17:48:42 GMT",
"version": "v2"
},
{
"created": "Tue, 8 May 2007 19:25:39 GMT",
"version": "v3"
}
] | 2008-12-18 | [
[
"Dain",
"Sergio",
""
]
] | We prove that extreme Kerr initial data set is a unique absolute minimum of the total mass in a (physically relevant) class of vacuum, maximal, asymptotically flat, axisymmetric data for Einstein equations with fixed angular momentum. These data represent non-stationary, axially symmetric, black holes. As a consequence, we obtain that any data in this class satisfy the inequality $\sqrt{J} \leq m$, where $m$ and $J$ are the total mass and angular momentum of the spacetime. |
1405.7363 | Nikolaos Batakis Professor | Nikolaos A. Batakis | First exact Geon found is a non-singular monopole, propagating as a
primordial gravitational pp-wave | 13 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Geons are particle-like electrovacua. The concept is well-defined, but it
still lacks a proper first example. Emerging as such is a self-confined exact
2-parameter pp-wave non-Dirac monopole {\cal G} with primordial Q/r^2 (r\geq
r_o) field plus higher moments. {\cal G} has effective mass,
independently-scaled NUT-like charge \kappa|Q|=2r_o as diameter, and spin.
{\cal G} {\em cannot} have actual {\sc em} charge $Q$ (by \partial{\cal G}=0),
Ricci-flat limits, nor spacetime or Dirac-string singularities, but Dirac's
quantization condition holds. {\cal G}/2, as an upgraded `Kerr-Newman'
alternative or {\cal S}_Q geon, carries actual charge Q confined by topology on
a round-S^2[r_o] physical singularity on \partial{\cal S}_Q\neq0. {\cal G} and
{\cal S}_Q offer exact analytic models in particle physics and cosmology,
notably for primordial gravitational waves, inflation, and pre-galactic
dynamics.
| [
{
"created": "Wed, 28 May 2014 18:04:08 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Jul 2014 08:22:35 GMT",
"version": "v2"
}
] | 2014-07-11 | [
[
"Batakis",
"Nikolaos A.",
""
]
] | Geons are particle-like electrovacua. The concept is well-defined, but it still lacks a proper first example. Emerging as such is a self-confined exact 2-parameter pp-wave non-Dirac monopole {\cal G} with primordial Q/r^2 (r\geq r_o) field plus higher moments. {\cal G} has effective mass, independently-scaled NUT-like charge \kappa|Q|=2r_o as diameter, and spin. {\cal G} {\em cannot} have actual {\sc em} charge $Q$ (by \partial{\cal G}=0), Ricci-flat limits, nor spacetime or Dirac-string singularities, but Dirac's quantization condition holds. {\cal G}/2, as an upgraded `Kerr-Newman' alternative or {\cal S}_Q geon, carries actual charge Q confined by topology on a round-S^2[r_o] physical singularity on \partial{\cal S}_Q\neq0. {\cal G} and {\cal S}_Q offer exact analytic models in particle physics and cosmology, notably for primordial gravitational waves, inflation, and pre-galactic dynamics. |
gr-qc/0103037 | Albert Roura | Esteban Calzetta, Albert Roura and Enric Verdaguer | Master equation for quantum Brownian motion derived by stochastic
methods | 10 pages, RevTeX. To appear in the proceedings of the 5th Peyresq
meeting | Int.J.Theor.Phys.40:2317,2001 | 10.1023/A:1012946523088 | null | gr-qc | null | The master equation for a linear open quantum system in a general environment
is derived using a stochastic approach. This is an alternative derivation to
that of Hu, Paz and Zhang, which was based on the direct computation of path
integrals, or to that of Halliwell and Yu, based on the evolution of the Wigner
function for a linear closed quantum system. We first show by using the
influence functinal formalism that the reduced Wigner function for the open
system coincides with a distribution function resulting from averaging both
over the initial conditions and the stochastic source of a formal Langevin
equation. The master equation for the reduced Wigner function can then be
deduced as a Fokker-Planck equation obtained from the formal Langevin equation.
| [
{
"created": "Mon, 12 Mar 2001 17:15:08 GMT",
"version": "v1"
}
] | 2011-08-04 | [
[
"Calzetta",
"Esteban",
""
],
[
"Roura",
"Albert",
""
],
[
"Verdaguer",
"Enric",
""
]
] | The master equation for a linear open quantum system in a general environment is derived using a stochastic approach. This is an alternative derivation to that of Hu, Paz and Zhang, which was based on the direct computation of path integrals, or to that of Halliwell and Yu, based on the evolution of the Wigner function for a linear closed quantum system. We first show by using the influence functinal formalism that the reduced Wigner function for the open system coincides with a distribution function resulting from averaging both over the initial conditions and the stochastic source of a formal Langevin equation. The master equation for the reduced Wigner function can then be deduced as a Fokker-Planck equation obtained from the formal Langevin equation. |
1108.4582 | Diana Kaminski | Diana Kaminski | AQV VI. A holonomy groupoid formulation | 27 pages, 1 figure | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The philosophy of the Loop Quantum Gravity approach is to construct the
canonical variables by using the duality of infinitesimal connections and
holonomies along loops. Based on this fundamental property for example the
holonomy-flux *-algebra has been formulated. A generalisation of the one-to-one
correspondence between infinitesimal objects: connections and curvature and
path based objects: holonomy maps and parallel transports is used to replace
the configuration space of the theory. This generalised duality is related to
the concept of path connections and holonomy groupoids, which originally has
been invented by Mackenzie and which is presented shortly in this article.
Finally these objects are used to propose some new algebras of quantum
variables for Loop Quantum Gravity.
| [
{
"created": "Fri, 19 Aug 2011 16:53:51 GMT",
"version": "v1"
}
] | 2011-08-24 | [
[
"Kaminski",
"Diana",
""
]
] | The philosophy of the Loop Quantum Gravity approach is to construct the canonical variables by using the duality of infinitesimal connections and holonomies along loops. Based on this fundamental property for example the holonomy-flux *-algebra has been formulated. A generalisation of the one-to-one correspondence between infinitesimal objects: connections and curvature and path based objects: holonomy maps and parallel transports is used to replace the configuration space of the theory. This generalised duality is related to the concept of path connections and holonomy groupoids, which originally has been invented by Mackenzie and which is presented shortly in this article. Finally these objects are used to propose some new algebras of quantum variables for Loop Quantum Gravity. |
2003.00764 | Reggie Pantig | Reggie C. Pantig, Emmanuel T. Rodulfo | Weak deflection angle of a dirty black hole | 6 pages, 1 figure; expressions in section 4 simplified thoroughly;
accepted for publication in Chinese Journal of Physics | Chin. J. Phys. (2020) 66; 691-702 | 10.1016/j.cjph.2020.06.015 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we present the weak deflection angle in a Schwarzschild black
hole of mass $m$ surrounded by the dark matter of mass $M$ and thickness
$\Delta r_{s}$. The Gauss-Bonnet theorem, formulated for asymptotic spacetimes,
is found to be ill-behaved in the third-order of $1/\Delta r_{s}$ for very
large $\Delta r_{s}$. Using the finite-distance for the radial locations of the
source and the receiver, we derived the expression for the weak deflection
angle up to the third-order of $1/\Delta r_{s}$ using Ishihara (\textit{et
al.}) method. The result showed that the required dark matter thickness is
$\sim2\sqrt{3mM}$ for the deviations in the weak deflection angle to occur.
Such thickness requirement is better by a factor of 2 as compared to the
deviations in the shadow radius ($\sim\sqrt{3mM}$). It implies that the use of
the weak deflection angle in detecting dark matter effects in one's galaxy is
better than using any deviations in the shadow radius.
| [
{
"created": "Mon, 2 Mar 2020 11:10:22 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Mar 2020 07:31:56 GMT",
"version": "v2"
},
{
"created": "Sun, 19 Jul 2020 02:55:01 GMT",
"version": "v3"
}
] | 2020-07-21 | [
[
"Pantig",
"Reggie C.",
""
],
[
"Rodulfo",
"Emmanuel T.",
""
]
] | In this paper, we present the weak deflection angle in a Schwarzschild black hole of mass $m$ surrounded by the dark matter of mass $M$ and thickness $\Delta r_{s}$. The Gauss-Bonnet theorem, formulated for asymptotic spacetimes, is found to be ill-behaved in the third-order of $1/\Delta r_{s}$ for very large $\Delta r_{s}$. Using the finite-distance for the radial locations of the source and the receiver, we derived the expression for the weak deflection angle up to the third-order of $1/\Delta r_{s}$ using Ishihara (\textit{et al.}) method. The result showed that the required dark matter thickness is $\sim2\sqrt{3mM}$ for the deviations in the weak deflection angle to occur. Such thickness requirement is better by a factor of 2 as compared to the deviations in the shadow radius ($\sim\sqrt{3mM}$). It implies that the use of the weak deflection angle in detecting dark matter effects in one's galaxy is better than using any deviations in the shadow radius. |
gr-qc/9603003 | B. Linet | B. Boisseau, C. Charmousis and B. Linet | Electrostatic self-force in a static weak gravitational field with
cylindrical symmetry | 11 pages, no figure, latex | Class. Quant. Grav. 13 (1996) 1797 | 10.1088/0264-9381/13/7/013 | null | gr-qc | null | We determine the electrostatic self-force at rest in an arbitrary static
metric with cylindrical symmetry in the linear approximation in the Newtonian
constant. In linearised Einstein theory, we express it in terms of the
components of the energy-momentum tensor.
| [
{
"created": "Mon, 4 Mar 1996 12:38:08 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Boisseau",
"B.",
""
],
[
"Charmousis",
"C.",
""
],
[
"Linet",
"B.",
""
]
] | We determine the electrostatic self-force at rest in an arbitrary static metric with cylindrical symmetry in the linear approximation in the Newtonian constant. In linearised Einstein theory, we express it in terms of the components of the energy-momentum tensor. |
2111.07329 | Suman Ghosh | Vivek Sharma and Suman Ghosh | Generalised Ellis-Bronnikov wormholes embedded in warped braneworld
background and energy conditions | 19+6 preprint pages | Eur. Phys. J. C (2021) 81:1004 | 10.1140/epjc/s10052-021-09789-z | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Ellis-Bronnikov (EB) wormholes require violation of null energy conditions at
the `throat'. This problem was cured by a simple modification of the `shape
function', which introduces a new parameter $m\ge 2$ ($m=2$ corresponds to the
EB model). This leads to a generalised (GEB) version. In this work, we consider
a model where the GEB wormhole geometry is embedded in a five dimensional
warped background. We studied the status of all the energy conditions in detail
for both EB and GEB embedding. We present our results analytically (wherever
possible) and graphically. Remarkably, the presence of decaying warp factor
leads to satisfaction of weak energy conditions even for the EB geometry, while
the status of all the other energy conditions are improved compared to the four
dimensional scenario. Besides inventing a new way to avoid the presence of
exotic matter, in order to form a wormhole passage, our work reveals yet
another advantage of having a warped extra dimension.
| [
{
"created": "Sun, 14 Nov 2021 12:21:08 GMT",
"version": "v1"
}
] | 2021-11-16 | [
[
"Sharma",
"Vivek",
""
],
[
"Ghosh",
"Suman",
""
]
] | Ellis-Bronnikov (EB) wormholes require violation of null energy conditions at the `throat'. This problem was cured by a simple modification of the `shape function', which introduces a new parameter $m\ge 2$ ($m=2$ corresponds to the EB model). This leads to a generalised (GEB) version. In this work, we consider a model where the GEB wormhole geometry is embedded in a five dimensional warped background. We studied the status of all the energy conditions in detail for both EB and GEB embedding. We present our results analytically (wherever possible) and graphically. Remarkably, the presence of decaying warp factor leads to satisfaction of weak energy conditions even for the EB geometry, while the status of all the other energy conditions are improved compared to the four dimensional scenario. Besides inventing a new way to avoid the presence of exotic matter, in order to form a wormhole passage, our work reveals yet another advantage of having a warped extra dimension. |
2307.09382 | Kuntal Pal | Kunal Pal, Kuntal Pal, and Tapobrata Sarkar | Geodesically completing regular black holes by the Simpson-Visser method | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Regular black holes are often geodesically incomplete when their extensions
to negative values of the radial coordinate are considered. Here, we propose to
use the Simpson-Visser method of regularising a singular spacetime, and apply
it to a regular solution that is geodesically incomplete, to construct a
geodesically complete regular solution. Our method is generic, and can be used
to cure geodesic incompleteness in any spherically symmetric static regular
solution, so that the resulting solution is symmetric in the radial coordinate.
As an example, we illustrate this procedure using a regular black hole solution
with an asymptotic Minkowski core. We study the structure of the resulting
metric, and show that it can represent a wormhole or a regular black hole with
a single or double horizon per side of the throat. Further, we construct a
source Lagrangian for which the geodesically complete spacetime is an exact
solution of the Einstein equations, and show that this consists of a phantom
scalar field and a nonlinear electromagnetic field. Finally, gravitational
lensing properties of the geodesically complete spacetime are briefly studied.
| [
{
"created": "Tue, 18 Jul 2023 16:02:39 GMT",
"version": "v1"
}
] | 2023-07-19 | [
[
"Pal",
"Kunal",
""
],
[
"Pal",
"Kuntal",
""
],
[
"Sarkar",
"Tapobrata",
""
]
] | Regular black holes are often geodesically incomplete when their extensions to negative values of the radial coordinate are considered. Here, we propose to use the Simpson-Visser method of regularising a singular spacetime, and apply it to a regular solution that is geodesically incomplete, to construct a geodesically complete regular solution. Our method is generic, and can be used to cure geodesic incompleteness in any spherically symmetric static regular solution, so that the resulting solution is symmetric in the radial coordinate. As an example, we illustrate this procedure using a regular black hole solution with an asymptotic Minkowski core. We study the structure of the resulting metric, and show that it can represent a wormhole or a regular black hole with a single or double horizon per side of the throat. Further, we construct a source Lagrangian for which the geodesically complete spacetime is an exact solution of the Einstein equations, and show that this consists of a phantom scalar field and a nonlinear electromagnetic field. Finally, gravitational lensing properties of the geodesically complete spacetime are briefly studied. |
0706.0129 | Szymon {\L}{\ke}ski | Jacek Jezierski, Jerzy Kijowski, Szymon Leski | Energy-minimizing two black holes initial data | Minor corrections, 2 references added | Phys.Rev.D76:024014,2007 | 10.1103/PhysRevD.76.024014 | null | gr-qc | null | An attempt to construct the ``ground state'' vacuum initial data for the
gravitational field surrounding two black holes is presented. The ground state
is defined as the gravitational initial data minimizing the ADM mass within the
class of data for which the masses of the holes and their distance are fixed.
To parameterize different geometric arrangements of the two holes (and,
therefore, their distance) we use an appropriately chosen scale factor. A
method for analyzing the variations of the ADM mass and the masses (areas) of
the horizons in terms of gravitational degrees of freedom is proposed. The
Misner initial data are analyzed in this context: it is shown that they do not
minimize the ADM mass.
| [
{
"created": "Fri, 1 Jun 2007 11:52:27 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Jul 2007 14:33:22 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Jezierski",
"Jacek",
""
],
[
"Kijowski",
"Jerzy",
""
],
[
"Leski",
"Szymon",
""
]
] | An attempt to construct the ``ground state'' vacuum initial data for the gravitational field surrounding two black holes is presented. The ground state is defined as the gravitational initial data minimizing the ADM mass within the class of data for which the masses of the holes and their distance are fixed. To parameterize different geometric arrangements of the two holes (and, therefore, their distance) we use an appropriately chosen scale factor. A method for analyzing the variations of the ADM mass and the masses (areas) of the horizons in terms of gravitational degrees of freedom is proposed. The Misner initial data are analyzed in this context: it is shown that they do not minimize the ADM mass. |
0904.4551 | Kenta Kiuchi | Kenta Kiuchi, Yuichiro Sekiguchi, Masaru Shibata, Keisuke Taniguchi | Longterm general relativistic simulation of binary neutron stars
collapsing to a black hole | 35 pages, 20 figures, accepted to PRD | Phys.Rev.D80:064037,2009 | 10.1103/PhysRevD.80.064037 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General relativistic simulations for the merger of binary neutron stars are
performed as an extension of a previous work\cite{Shibata:2006nm}. We prepare
binary neutron stars with a large initial orbital separation and employ the
moving-puncture formulation, which enables to follow merger and ringdown phases
for a long time, even after black hole formation. For modeling inspiraling
neutron stars, which should be composed of cold neutron stars, the
Akmal-Pandhalipande-Ravenhall (APR) equation of state (EOS) is adopted. After
the onset of the merger, the hybrid-type EOS is used; i.e., the cold and
thermal parts are given by the APR and $\Gamma$-law EOSs, respectively. Three
equal-mass binaries each with mass $1.4M_\odot,1.45M_\odot,1.5M_\odot$ and two
unequal-mass binaries with mass 1.3--$1.6M_\odot$, 1.35--$1.65M_\odot$ are
prepared. We focus primarily on the black hole formation case, and explore mass
and spin of the black hole, mass of disks which surround the black hole, and
gravitational waves emitted during the black hole formation. We find that (i)
for the systems of $m_0=2.9$--$3.0M_\odot$ and of mass ratio $\approx 0.8$, the
mass of disks which surround the formed black hole is 0.006--$0.02M_{\odot}$;
(ii) the spin of the formed black hole is $0.78 \pm 0.02$ when a black hole is
formed after the merger in the dynamical time scale. This value depends weakly
on the total mass and mass ratio, and is about 0.1 larger than that of a black
hole formed from nonspinning binary black holes; (iii) for the black-hole
formation case, Fourier spectrum shape of gravitational waves emitted in the
merger and ringdown phases has a universal qualitative feature irrespective of
the total mass and mass ratio, but quantitatively, the spectrum reflects the
parameters of the binary neutron stars.
| [
{
"created": "Wed, 29 Apr 2009 08:27:50 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Aug 2009 05:53:51 GMT",
"version": "v2"
}
] | 2009-11-06 | [
[
"Kiuchi",
"Kenta",
""
],
[
"Sekiguchi",
"Yuichiro",
""
],
[
"Shibata",
"Masaru",
""
],
[
"Taniguchi",
"Keisuke",
""
]
] | General relativistic simulations for the merger of binary neutron stars are performed as an extension of a previous work\cite{Shibata:2006nm}. We prepare binary neutron stars with a large initial orbital separation and employ the moving-puncture formulation, which enables to follow merger and ringdown phases for a long time, even after black hole formation. For modeling inspiraling neutron stars, which should be composed of cold neutron stars, the Akmal-Pandhalipande-Ravenhall (APR) equation of state (EOS) is adopted. After the onset of the merger, the hybrid-type EOS is used; i.e., the cold and thermal parts are given by the APR and $\Gamma$-law EOSs, respectively. Three equal-mass binaries each with mass $1.4M_\odot,1.45M_\odot,1.5M_\odot$ and two unequal-mass binaries with mass 1.3--$1.6M_\odot$, 1.35--$1.65M_\odot$ are prepared. We focus primarily on the black hole formation case, and explore mass and spin of the black hole, mass of disks which surround the black hole, and gravitational waves emitted during the black hole formation. We find that (i) for the systems of $m_0=2.9$--$3.0M_\odot$ and of mass ratio $\approx 0.8$, the mass of disks which surround the formed black hole is 0.006--$0.02M_{\odot}$; (ii) the spin of the formed black hole is $0.78 \pm 0.02$ when a black hole is formed after the merger in the dynamical time scale. This value depends weakly on the total mass and mass ratio, and is about 0.1 larger than that of a black hole formed from nonspinning binary black holes; (iii) for the black-hole formation case, Fourier spectrum shape of gravitational waves emitted in the merger and ringdown phases has a universal qualitative feature irrespective of the total mass and mass ratio, but quantitatively, the spectrum reflects the parameters of the binary neutron stars. |
gr-qc/0211015 | Pavlov | A. A. Grib, Yu. V. Pavlov | Cold dark matter and primordial superheavy particles | LaTeX, 5 pages, no figures | Int.J.Mod.Phys. A17 (2002) 4435-4440 | 10.1142/S0217751X02013514 | null | gr-qc hep-ph | null | The hypothesis that cold dark matter consists of primordial superheavy
particles, the decay of short lifetime component of which led to the observable
mass of matter while long living component survived up to modern times
manifesting its presence in high energetic cosmic rays particles is
investigated.
| [
{
"created": "Tue, 5 Nov 2002 07:23:05 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Grib",
"A. A.",
""
],
[
"Pavlov",
"Yu. V.",
""
]
] | The hypothesis that cold dark matter consists of primordial superheavy particles, the decay of short lifetime component of which led to the observable mass of matter while long living component survived up to modern times manifesting its presence in high energetic cosmic rays particles is investigated. |
2206.04505 | Poulami Dutta Roy | Poulami Dutta Roy, Sayan Kar (IIT Kharagpur) | Generalised Hayward spacetimes: Geometry, matter and scalar quasinormal
modes | 45 pages, 22 figures, 7 tables. Matches published version | null | 10.1103/PhysRevD.106.044028 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Bardeen's 1968 idea of a regular black hole spacetime was revived by Hayward
in 2006 through the construction of a new example of such a geometry. Later it
was realised by Neves and Saa, that a wider, two-parameter class exists, with
Bardeen and Hayward spacetimes as special cases. In this article, we revisit
and generalise the Hayward spacetime by applying the Damour-Solodukhin (DS)
prescription. Recalling the DS suggestion of a deformed Schwarzschild spacetime
where $g_{tt} = -\left (1-\frac{2M_1}{r}\right )$, $g_{rr} = \left
(1-\frac{2M_2}{r}\right )^{-1}$ and $M_1\neq M_2$, we propose a similar
deformation of the Hayward geometry. The $g_{tt}$ and $g_{rr}$ in the original
Hayward line element remain functionally the same, {\em albeit} mutations
introduced via differently valued metric parameters, following the DS idea.
This results in a plethora of spacetime geometries, known as well as new, and
including singular black holes, wormholes or regular black holes. We first
study the geometric features and matter content of each of such spacetimes in
some detail. Subsequently, we find the scalar quasinormal modes corresponding
to scalar wave propagation in these geometries. We investigate how the real and
imaginary parts of the quasinormal modes depend on the values and ranges of the
metric parameters used to classify the geometries. Finally, we argue how our
results on this family of spacetimes suggest their utility as black hole
mimickers.
| [
{
"created": "Thu, 9 Jun 2022 13:45:13 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Aug 2022 12:21:04 GMT",
"version": "v2"
}
] | 2022-08-15 | [
[
"Roy",
"Poulami Dutta",
"",
"IIT Kharagpur"
],
[
"Kar",
"Sayan",
"",
"IIT Kharagpur"
]
] | Bardeen's 1968 idea of a regular black hole spacetime was revived by Hayward in 2006 through the construction of a new example of such a geometry. Later it was realised by Neves and Saa, that a wider, two-parameter class exists, with Bardeen and Hayward spacetimes as special cases. In this article, we revisit and generalise the Hayward spacetime by applying the Damour-Solodukhin (DS) prescription. Recalling the DS suggestion of a deformed Schwarzschild spacetime where $g_{tt} = -\left (1-\frac{2M_1}{r}\right )$, $g_{rr} = \left (1-\frac{2M_2}{r}\right )^{-1}$ and $M_1\neq M_2$, we propose a similar deformation of the Hayward geometry. The $g_{tt}$ and $g_{rr}$ in the original Hayward line element remain functionally the same, {\em albeit} mutations introduced via differently valued metric parameters, following the DS idea. This results in a plethora of spacetime geometries, known as well as new, and including singular black holes, wormholes or regular black holes. We first study the geometric features and matter content of each of such spacetimes in some detail. Subsequently, we find the scalar quasinormal modes corresponding to scalar wave propagation in these geometries. We investigate how the real and imaginary parts of the quasinormal modes depend on the values and ranges of the metric parameters used to classify the geometries. Finally, we argue how our results on this family of spacetimes suggest their utility as black hole mimickers. |
gr-qc/0301029 | Stanislav Alexeyev | M. Pomazanov, V. Kolubasova, S. Alexeyev (Lomonosov Moscow State
University, Moscow, Russia) | The problem of singularities of higher order curvature corrections in
four dimensional string gravity | 11 pages, iop style, changes in motivation and discussion parts | null | null | null | gr-qc | null | The influence of higher order (stringly inspired) curvature corrections to
the classical General Relativity spherically symmetric solution is studied. In
string gravity these curvature corrections have a special form and can provide
a singular contribution to the field equations because they generate higher
derivatives of metric functions multiplied by a small parameter. Analytically
and numerically it is shown that sometimes in 4D string gravity the
Schwarzschild solution is not recovered when the string coupling constant
vanishes and limited number of higher order curvature corrections is
considered.
| [
{
"created": "Wed, 8 Jan 2003 20:11:00 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Jul 2003 13:32:30 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Pomazanov",
"M.",
"",
"Lomonosov Moscow State\n University, Moscow, Russia"
],
[
"Kolubasova",
"V.",
"",
"Lomonosov Moscow State\n University, Moscow, Russia"
],
[
"Alexeyev",
"S.",
"",
"Lomonosov Moscow State\n University, Moscow, Russia"
]
] | The influence of higher order (stringly inspired) curvature corrections to the classical General Relativity spherically symmetric solution is studied. In string gravity these curvature corrections have a special form and can provide a singular contribution to the field equations because they generate higher derivatives of metric functions multiplied by a small parameter. Analytically and numerically it is shown that sometimes in 4D string gravity the Schwarzschild solution is not recovered when the string coupling constant vanishes and limited number of higher order curvature corrections is considered. |
1104.3685 | Nikolaos Stergioulas | Nikolaos Stergioulas | An improved method for constructing models of self-gravitating tori
around black holes | 13 pages, 6 figures, accepted for publication in Int. J. Mod. Phys. D | Int.J.Mod.Phys.D20:1251-1263,2011 | 10.1142/S021827181101944X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General-relativistic models of self-gravitating tori around black holes are
constructed with a self-consistent-field method in compactified coordinates.
The numerical code is highly accurate and robust, allowing for the construction
of models that exactly fill their Roche lobe, when a cusp exists. As a first
application, we focus on self-consistent models with cusp, having different
values of constant specific angular momentum. Scaling all results with the mass
of the black hole, we find evidence that models with constant specific angular
momentum that can fill their Roche lobe are still limited by $l<4M_{\rm BH}$
(as is the case for models constructed in a fixed background metric) even for
heavy tori.
| [
{
"created": "Tue, 19 Apr 2011 09:26:41 GMT",
"version": "v1"
}
] | 2015-03-19 | [
[
"Stergioulas",
"Nikolaos",
""
]
] | General-relativistic models of self-gravitating tori around black holes are constructed with a self-consistent-field method in compactified coordinates. The numerical code is highly accurate and robust, allowing for the construction of models that exactly fill their Roche lobe, when a cusp exists. As a first application, we focus on self-consistent models with cusp, having different values of constant specific angular momentum. Scaling all results with the mass of the black hole, we find evidence that models with constant specific angular momentum that can fill their Roche lobe are still limited by $l<4M_{\rm BH}$ (as is the case for models constructed in a fixed background metric) even for heavy tori. |
0909.3214 | David Garfinkle | David Garfinkle | Matters of Gravity, The Newsletter of the Topical Group on Gravitation
of the American Physical Society, Volume 34, Fall 2009 | 20 pages, latex | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | GGR News:
New Matters of Gravity Correspondents, by David Garfinkle
we hear that..., by David Garfinkle
Research Briefs:
Numerical Relativity Studies of Black Hole Kicks, by Pablo Laguna
Conference Reports:
AbhayFest, by Chris Beetle
Eastern Gravity Meeting, by Jeff Winicour
Benasque Workshop on Gravity, by Roberto Emparan and Veronika Hubeny
Workshop on the Fluid-Gravity Correspondence, by Mukund Rangamani
| [
{
"created": "Thu, 17 Sep 2009 13:26:59 GMT",
"version": "v1"
}
] | 2016-09-08 | [
[
"Garfinkle",
"David",
""
]
] | GGR News: New Matters of Gravity Correspondents, by David Garfinkle we hear that..., by David Garfinkle Research Briefs: Numerical Relativity Studies of Black Hole Kicks, by Pablo Laguna Conference Reports: AbhayFest, by Chris Beetle Eastern Gravity Meeting, by Jeff Winicour Benasque Workshop on Gravity, by Roberto Emparan and Veronika Hubeny Workshop on the Fluid-Gravity Correspondence, by Mukund Rangamani |
1809.03307 | Muhammad Sharif | M. Sharif and Aisha Siddiqa | Curvature-Matter Coupling Effects on Axial Gravitational Waves | 17 pages, no figure, to appear in EPJC | Eur. Phys. J. C 78(2018)721 | 10.1140/epjc/s10052-018-6201-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the propagation of axial gravitational waves in
the background of the flat FRW universe in $f(R,T)$ theory. The field equations
are obtained for unperturbed as well as axially perturbed FRW metric. These
field equations are solved simultaneously to obtain the unknown perturbation
parameters. We find that the assumed perturbations can affect matter as well as
four-velocity. Moreover, ignoring the material perturbations we explicitly
obtain an expression for four-velocity. It is concluded that axial
gravitational waves in the curvature-matter coupling background can produce
cosmological rotation or have memory effect if the wave profile has a
discontinuity at the wavefront.
| [
{
"created": "Sat, 1 Sep 2018 02:32:14 GMT",
"version": "v1"
}
] | 2018-09-26 | [
[
"Sharif",
"M.",
""
],
[
"Siddiqa",
"Aisha",
""
]
] | In this paper, we investigate the propagation of axial gravitational waves in the background of the flat FRW universe in $f(R,T)$ theory. The field equations are obtained for unperturbed as well as axially perturbed FRW metric. These field equations are solved simultaneously to obtain the unknown perturbation parameters. We find that the assumed perturbations can affect matter as well as four-velocity. Moreover, ignoring the material perturbations we explicitly obtain an expression for four-velocity. It is concluded that axial gravitational waves in the curvature-matter coupling background can produce cosmological rotation or have memory effect if the wave profile has a discontinuity at the wavefront. |
1001.0241 | Sergei Rubin | S.G. Rubin | On the Origin of Gauge Symmetries and Fundamental Constants | 9 pages, minor corrections | JETP Vol. 109, No. 6, p. 961 (2009) | 10.1134/S1063776109120061 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A statistical mechanism is proposed for symmetrization of an extra space. The
conditions and rate of attainment of a symmetric configuration and, as a
consequence, the appearance of gauge invariance in low-energy physics is
discussed. It is shown that, under some conditions, this situation occurs only
after completion of the inflationary stage. The dependence of the constants
$\hbar$ and G on the geometry of the extra space and the initial parameters of
the Lagrangian of the gravitational field with higher derivatives are analyzed.
| [
{
"created": "Fri, 1 Jan 2010 15:52:50 GMT",
"version": "v1"
}
] | 2015-05-14 | [
[
"Rubin",
"S. G.",
""
]
] | A statistical mechanism is proposed for symmetrization of an extra space. The conditions and rate of attainment of a symmetric configuration and, as a consequence, the appearance of gauge invariance in low-energy physics is discussed. It is shown that, under some conditions, this situation occurs only after completion of the inflationary stage. The dependence of the constants $\hbar$ and G on the geometry of the extra space and the initial parameters of the Lagrangian of the gravitational field with higher derivatives are analyzed. |
2005.14061 | Abdulla Al Mamon | Abdulla Al Mamon, Subhajit Saha | Testing Lambert$W$ equation of state with observational Hubble parameter
data | 11 pages, 6 figures | New Astronomy 86, 101567 (2021) | 10.1016/j.newast.2020.101567 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the possibility that the Universe is driven by
a single dark fluid described by a Lambert $W$ equation of state parameter,
$w_{eff}$, which is essentially dependent on two parameters $\vartheta_{1}$ and
$\vartheta_{2}$ which need to be fixed from observations. We obtain the
constraints on these parameters using the latest 51 data points of $H(z)$
measurements, spanning the redshift range $0.07\leq z \leq 2.36$. The present
study shows that the Universe is indeed undergoing an accelerated expansion
phase following the decelerated one at the transition redshift,
$z_{t}=0.77\pm0.03$ ($1\sigma$) and is well consistent with the recent
observations. We also find that at low redshifts, $w_{eff}$ evolves only in the
quintessence regime ($-1<w_{eff}<-\frac{1}{3}$) within $1\sigma$ confidence
level. Its present value is found to be $-0.96\pm0.02$ ($1\sigma$). The fact
that the present value of $w_{eff}$ is very close to the Cosmological Constant
$\Lambda$ implies that our proposed equation of state parameter might serve as
a unification of dark matter and dark energy. Furthermore, we compare the
evolution of $H(z)$ for the model under consideration with that of the
$\Lambda$CDM model. Finally, we observe that for the best-fit case, the
differences between the two models are negligible at $z\sim 0.67$.
| [
{
"created": "Thu, 28 May 2020 14:53:14 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Jan 2021 07:23:21 GMT",
"version": "v2"
}
] | 2022-02-14 | [
[
"Mamon",
"Abdulla Al",
""
],
[
"Saha",
"Subhajit",
""
]
] | In this paper, we investigate the possibility that the Universe is driven by a single dark fluid described by a Lambert $W$ equation of state parameter, $w_{eff}$, which is essentially dependent on two parameters $\vartheta_{1}$ and $\vartheta_{2}$ which need to be fixed from observations. We obtain the constraints on these parameters using the latest 51 data points of $H(z)$ measurements, spanning the redshift range $0.07\leq z \leq 2.36$. The present study shows that the Universe is indeed undergoing an accelerated expansion phase following the decelerated one at the transition redshift, $z_{t}=0.77\pm0.03$ ($1\sigma$) and is well consistent with the recent observations. We also find that at low redshifts, $w_{eff}$ evolves only in the quintessence regime ($-1<w_{eff}<-\frac{1}{3}$) within $1\sigma$ confidence level. Its present value is found to be $-0.96\pm0.02$ ($1\sigma$). The fact that the present value of $w_{eff}$ is very close to the Cosmological Constant $\Lambda$ implies that our proposed equation of state parameter might serve as a unification of dark matter and dark energy. Furthermore, we compare the evolution of $H(z)$ for the model under consideration with that of the $\Lambda$CDM model. Finally, we observe that for the best-fit case, the differences between the two models are negligible at $z\sim 0.67$. |
gr-qc/0004026 | Dr G. A. Jaroszkiewicz | George Jaroszkiewicz (School of Mathematical Sciences, University of
Nottingham, UK) | Discrete spacetime: classical causality,prediction, retrodiction and the
mathematical arrow of time | 20 pages, 7 eps figures | null | null | null | gr-qc | null | A mathematical definition of classical causality over discrete spacetime
dynamics is formulated. The approach is background free and permits a
definition of causality in a precise way whenever the spacetime dynamics
permits. It gives a natural meaning to the concepts of cosmic time, spacelike
hypersurfaces and timelike or lightlike flows without assuming the notion of a
background metric. The concepts of causal propagators and the speed of
causality are discussed. In this approach the concepts of spacetime and
dynamics are linked in an essential and inseparable whole, with no meaning to
either on its own.
| [
{
"created": "Sat, 8 Apr 2000 21:17:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Jaroszkiewicz",
"George",
"",
"School of Mathematical Sciences, University of\n Nottingham, UK"
]
] | A mathematical definition of classical causality over discrete spacetime dynamics is formulated. The approach is background free and permits a definition of causality in a precise way whenever the spacetime dynamics permits. It gives a natural meaning to the concepts of cosmic time, spacelike hypersurfaces and timelike or lightlike flows without assuming the notion of a background metric. The concepts of causal propagators and the speed of causality are discussed. In this approach the concepts of spacetime and dynamics are linked in an essential and inseparable whole, with no meaning to either on its own. |
1808.06502 | Andrea Geralico | Donato Bini, Andrea Geralico | Hyperbolic-like elastic scattering of spinning particles by a
Schwarzschild black hole | 16 pages, 2 figures; published version. arXiv admin note: text
overlap with arXiv:1707.09814 | Gen. Relativ. Gravit. 49, 84 (2017) | 10.1007/s10714-017-2247-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The scattering of spinning test particles by a Schwarzschild black hole is
studied. The motion is described according to the Mathisson-Papapetrou-Dixon
model for extended bodies in a given gravitational background field. The
equatorial plane is taken as the orbital plane, the spin vector being
orthogonal to it with constant magnitude. The equations of motion are solved
analytically in closed form to first-order in spin and the solution is used to
compute corrections to the standard geodesic scattering angle as well as
capture cross section by the black hole.
| [
{
"created": "Fri, 17 Aug 2018 11:13:48 GMT",
"version": "v1"
}
] | 2018-08-21 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
]
] | The scattering of spinning test particles by a Schwarzschild black hole is studied. The motion is described according to the Mathisson-Papapetrou-Dixon model for extended bodies in a given gravitational background field. The equatorial plane is taken as the orbital plane, the spin vector being orthogonal to it with constant magnitude. The equations of motion are solved analytically in closed form to first-order in spin and the solution is used to compute corrections to the standard geodesic scattering angle as well as capture cross section by the black hole. |
1808.04506 | Peng Wang | Peng Wang, Houwen Wu and Haitang Yang | Thermodynamics and Phase Transitions of Nonlinear Electrodynamics Black
Holes in an Extended Phase Space | minor corrections, references added | null | 10.1088/1475-7516/2019/04/052 | CTP-SCU/2018003 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the thermodynamic behavior of nonlinear electrodynamics (NLED)
black holes in an extended phase space, which includes the cosmological
constant $\Lambda=-3/l^{2}$ and dimensionful couplings $a$ in NLED as
thermodynamic variables. For a generic NLED black hole with the charge $Q$, we
find that the Smarr relation is satisfied in the extended phase space, and the
state of equation can be written as $Tl=\tilde{T}\left( r_{+}/l,Q/l,al^{-c}
\right) $, where $\left[ a\right] =L^{c}$, and $T$ and $r_{+}$ are the
temperature and horizon radius of the black hole, respectively. For some values
of $Q/l$ and $al^{-c}$, the phase structure of the black hole is uniquely
determined. Focusing on Born-Infeld and iBorn-Infeld AdS black holes, we obtain
the corresponding phase diagrams in the $a/l^{2}$-$Q/l$ plane, which provides a
new viewpoint towards the black holes' phase structure and critical behavior.
For Born-Infeld black holes, the critical line and the region, where a
reentrant phase transition occurs, in the $a/l^{2}$-$Q/l$ plane are both finite
and terminate at $\left\{ \tilde{a}_{c}\text{, }\tilde{Q}_{c}\right\}
\simeq\left\{ 0.069\text{, }0.37\right\} $. However for iBorn-Infeld black
holes, the critical line and the reentrant phase transition region in the
$a/l^{2}$-$Q/l$ plane are semi-infinite and extend to $Q/l=\infty$. We also
examine thermal and electrical stabilities of Born-Infeld and iBorn-Infeld AdS
black holes.
| [
{
"created": "Tue, 14 Aug 2018 02:11:27 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Aug 2018 06:20:06 GMT",
"version": "v2"
}
] | 2019-05-08 | [
[
"Wang",
"Peng",
""
],
[
"Wu",
"Houwen",
""
],
[
"Yang",
"Haitang",
""
]
] | We investigate the thermodynamic behavior of nonlinear electrodynamics (NLED) black holes in an extended phase space, which includes the cosmological constant $\Lambda=-3/l^{2}$ and dimensionful couplings $a$ in NLED as thermodynamic variables. For a generic NLED black hole with the charge $Q$, we find that the Smarr relation is satisfied in the extended phase space, and the state of equation can be written as $Tl=\tilde{T}\left( r_{+}/l,Q/l,al^{-c} \right) $, where $\left[ a\right] =L^{c}$, and $T$ and $r_{+}$ are the temperature and horizon radius of the black hole, respectively. For some values of $Q/l$ and $al^{-c}$, the phase structure of the black hole is uniquely determined. Focusing on Born-Infeld and iBorn-Infeld AdS black holes, we obtain the corresponding phase diagrams in the $a/l^{2}$-$Q/l$ plane, which provides a new viewpoint towards the black holes' phase structure and critical behavior. For Born-Infeld black holes, the critical line and the region, where a reentrant phase transition occurs, in the $a/l^{2}$-$Q/l$ plane are both finite and terminate at $\left\{ \tilde{a}_{c}\text{, }\tilde{Q}_{c}\right\} \simeq\left\{ 0.069\text{, }0.37\right\} $. However for iBorn-Infeld black holes, the critical line and the reentrant phase transition region in the $a/l^{2}$-$Q/l$ plane are semi-infinite and extend to $Q/l=\infty$. We also examine thermal and electrical stabilities of Born-Infeld and iBorn-Infeld AdS black holes. |
1812.07727 | Sebastian Murk | Valentina Baccetti, Sebastian Murk, Daniel R. Terno | Black hole evaporation and semiclassical thin shell collapse | 10 pages, 4 figures. Published version. Fixed typographical error in
eq. 23 | Phys. Rev. D 100, 064054 (2019) | 10.1103/PhysRevD.100.064054 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In case of spherical symmetry, the assumptions of finite-time formation of a
trapped region and regularity of its boundary --- the apparent horizon --- are
sufficient to identify the form of the metric and energy-momentum tensor in its
vicinity. By comparison with the known results for quasistatic evaporation of
black holes, we complete the identification of their parameters. Consistency of
the Einstein equations allows only two possible types of higher-order terms in
the energy-momentum tensor. By using its local conservation, we provide a
method of calculation of the higher-order terms, explicitly determining the
leading-order regular corrections. Contraction of a spherically symmetric thin
dust shell is the simplest model of gravitational collapse. Nevertheless, the
inclusion of a collapse-triggered radiation in different extensions of this
model leads to apparent contradictions. Using our results, we resolve these
contradictions and show how gravitational collapse may be completed in finite
time according to a distant observer.
| [
{
"created": "Wed, 19 Dec 2018 01:51:40 GMT",
"version": "v1"
},
{
"created": "Fri, 24 May 2019 07:53:40 GMT",
"version": "v2"
},
{
"created": "Tue, 1 Oct 2019 06:40:55 GMT",
"version": "v3"
},
{
"created": "Fri, 10 Jan 2020 05:28:49 GMT",
"version": "v4"
}
] | 2020-01-13 | [
[
"Baccetti",
"Valentina",
""
],
[
"Murk",
"Sebastian",
""
],
[
"Terno",
"Daniel R.",
""
]
] | In case of spherical symmetry, the assumptions of finite-time formation of a trapped region and regularity of its boundary --- the apparent horizon --- are sufficient to identify the form of the metric and energy-momentum tensor in its vicinity. By comparison with the known results for quasistatic evaporation of black holes, we complete the identification of their parameters. Consistency of the Einstein equations allows only two possible types of higher-order terms in the energy-momentum tensor. By using its local conservation, we provide a method of calculation of the higher-order terms, explicitly determining the leading-order regular corrections. Contraction of a spherically symmetric thin dust shell is the simplest model of gravitational collapse. Nevertheless, the inclusion of a collapse-triggered radiation in different extensions of this model leads to apparent contradictions. Using our results, we resolve these contradictions and show how gravitational collapse may be completed in finite time according to a distant observer. |
0910.1279 | Huguet Eric | S. Faci, E. Huguet, J. Queva, J. Renaud | Conformally covariant quantization of Maxwell field in de Sitter space | v2 is is the definitive (improved compare to v1) version | Phys.Rev.D80:124005,2009 | 10.1103/PhysRevD.80.124005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, we quantize the Maxwell ("massless spin one") de Sitter
field in a conformally invariant gauge. This quantization is invariant under
the SO$_0(2,4)$ group and consequently under the de Sitter group. We obtain a
new de Sitter invariant two-points function which is very simple. Our method
relies on the one hand on a geometrical point of view which uses the
realization of Minkowski, de Sitter and anti-de Sitter spaces as intersections
of the null cone in $\setR^6$ and a moving plane, and on the other hand on a
canonical quantization scheme of the Gupta-Bleuler type.
| [
{
"created": "Wed, 7 Oct 2009 14:56:43 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Jan 2010 17:18:44 GMT",
"version": "v2"
}
] | 2010-01-11 | [
[
"Faci",
"S.",
""
],
[
"Huguet",
"E.",
""
],
[
"Queva",
"J.",
""
],
[
"Renaud",
"J.",
""
]
] | In this article, we quantize the Maxwell ("massless spin one") de Sitter field in a conformally invariant gauge. This quantization is invariant under the SO$_0(2,4)$ group and consequently under the de Sitter group. We obtain a new de Sitter invariant two-points function which is very simple. Our method relies on the one hand on a geometrical point of view which uses the realization of Minkowski, de Sitter and anti-de Sitter spaces as intersections of the null cone in $\setR^6$ and a moving plane, and on the other hand on a canonical quantization scheme of the Gupta-Bleuler type. |
gr-qc/9911095 | Robert M. Wald | Robert M. Wald and Andreas Zoupas | A General Definition of "Conserved Quantities" in General Relativity and
Other Theories of Gravity | 39 pages, no figures | Phys.Rev. D61 (2000) 084027 | 10.1103/PhysRevD.61.084027 | null | gr-qc hep-th | null | In general relativity, the notion of mass and other conserved quantities at
spatial infinity can be defined in a natural way via the Hamiltonian framework:
Each conserved quantity is associated with an asymptotic symmetry and the value
of the conserved quantity is defined to be the value of the Hamiltonian which
generates the canonical transformation on phase space corresponding to this
symmetry. However, such an approach cannot be employed to define `conserved
quantities' in a situation where symplectic current can be radiated away (such
as occurs at null infinity in general relativity) because there does not, in
general, exist a Hamiltonian which generates the given asymptotic symmetry.
(This fact is closely related to the fact that the desired `conserved
quantities' are not, in general, conserved!) In this paper we give a
prescription for defining `conserved quantities' by proposing a modification of
the equation that must be satisfied by a Hamiltonian. Our prescription is a
very general one, and is applicable to a very general class of asymptotic
conditions in arbitrary diffeomorphism covariant theories of gravity derivable
from a Lagrangian, although we have not investigated existence and uniqueness
issues in the most general contexts. In the case of general relativity with the
standard asymptotic conditions at null infinity, our prescription agrees with
the one proposed by Dray and Streubel from entirely different considerations.
| [
{
"created": "Wed, 24 Nov 1999 21:14:17 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Wald",
"Robert M.",
""
],
[
"Zoupas",
"Andreas",
""
]
] | In general relativity, the notion of mass and other conserved quantities at spatial infinity can be defined in a natural way via the Hamiltonian framework: Each conserved quantity is associated with an asymptotic symmetry and the value of the conserved quantity is defined to be the value of the Hamiltonian which generates the canonical transformation on phase space corresponding to this symmetry. However, such an approach cannot be employed to define `conserved quantities' in a situation where symplectic current can be radiated away (such as occurs at null infinity in general relativity) because there does not, in general, exist a Hamiltonian which generates the given asymptotic symmetry. (This fact is closely related to the fact that the desired `conserved quantities' are not, in general, conserved!) In this paper we give a prescription for defining `conserved quantities' by proposing a modification of the equation that must be satisfied by a Hamiltonian. Our prescription is a very general one, and is applicable to a very general class of asymptotic conditions in arbitrary diffeomorphism covariant theories of gravity derivable from a Lagrangian, although we have not investigated existence and uniqueness issues in the most general contexts. In the case of general relativity with the standard asymptotic conditions at null infinity, our prescription agrees with the one proposed by Dray and Streubel from entirely different considerations. |
0811.3860 | Matteo Luca Ruggiero | Matteo Luca Ruggiero, Lorenzo Iorio | Constraining Post-Newtonian f(R) Gravity in the Solar System | 28 pages, AASTeX macros, Contribution to "The Problems of Modern
Cosmology", special volume on the occasion of Prof. S.D. Odintsov's 50th
birthday. Editor: Prof. P. M. Lavrov, Tomsk State Pedagogical University | The Problems of Modern Cosmology, pages 261-272, Tomsk State
Pedagogical University (2009) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider some models of f(R) gravity that can be used to describe, in a
suitable weak-field limit, the gravitational field of the Sun. Using a
perturbative approach, we focus on the impact that the modifications of the
gravitational field, due to the non-linearity of the gravity Lagrangian, have
on the Solar System dynamics. We compare the theoretical predictions for the
precession of the longitude of the pericentre $\varpi$ of a test particle with
the corrections to the standard Newtonian-Einsteinian precessions of the
longitudes of perihelia of some planets of the Solar System recently estimated
by E.V. Pitjeva by fitting large data sets with various versions of the EPM
ephemerides.
| [
{
"created": "Mon, 24 Nov 2008 12:41:50 GMT",
"version": "v1"
}
] | 2009-03-17 | [
[
"Ruggiero",
"Matteo Luca",
""
],
[
"Iorio",
"Lorenzo",
""
]
] | We consider some models of f(R) gravity that can be used to describe, in a suitable weak-field limit, the gravitational field of the Sun. Using a perturbative approach, we focus on the impact that the modifications of the gravitational field, due to the non-linearity of the gravity Lagrangian, have on the Solar System dynamics. We compare the theoretical predictions for the precession of the longitude of the pericentre $\varpi$ of a test particle with the corrections to the standard Newtonian-Einsteinian precessions of the longitudes of perihelia of some planets of the Solar System recently estimated by E.V. Pitjeva by fitting large data sets with various versions of the EPM ephemerides. |
1408.5487 | Andrea Geralico | Donato Bini, Fernando de Felice, Andrea Geralico | Observer-dependent optical properties of stationary axisymmetric
spacetimes | 14 pages, 2 figures; published version | IJGMMP 11, 1450024 (2014) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The world lines of null particles admit arbitrary parametrizations. In the
presence of a family of observers one may introduce along a null world line an
extension of the so-called Cattaneo's relative standard time parameter (valid
for massive particles) which plays a special role. Another possibility is to
use the coordinate time itself as a parameter. The relation between relative
standard time and coordinate time allows for the introduction of an
observer-dependent optical path and associated refraction index. Both these
quantities are studied here working out explicit examples concerning familiar
null orbits and observers in black hole spacetimes.
| [
{
"created": "Sat, 23 Aug 2014 10:40:33 GMT",
"version": "v1"
}
] | 2014-08-26 | [
[
"Bini",
"Donato",
""
],
[
"de Felice",
"Fernando",
""
],
[
"Geralico",
"Andrea",
""
]
] | The world lines of null particles admit arbitrary parametrizations. In the presence of a family of observers one may introduce along a null world line an extension of the so-called Cattaneo's relative standard time parameter (valid for massive particles) which plays a special role. Another possibility is to use the coordinate time itself as a parameter. The relation between relative standard time and coordinate time allows for the introduction of an observer-dependent optical path and associated refraction index. Both these quantities are studied here working out explicit examples concerning familiar null orbits and observers in black hole spacetimes. |
gr-qc/9704051 | Dirk Kreimer | E.W.Mielke and D.Kreimer | Chiral Anomaly in Contorted Spacetimes | 17 pages, REVTEX | Gen.Rel.Grav.31:701-712,1999 | 10.1023/A:1026653314045 | MZ-TH/97-18 | gr-qc | null | The Dirac equation in Riemann-Cartan spacetimes with torsion is reconsidered.
As is well-known, only the axial covector torsion $A$, a one-form, couples to
massive Dirac fields. Using diagrammatic techniques, we show that besides the
familiar Riemannian term only the Pontrjagin type four-form $dA\wedge dA$ does
arise additionally in the chiral anomaly, but not the Nieh-Yan term $d ^* A$,
as has been claimed recently. Implications for cosmic strings in
Einstein-Cartan theory as well as for Ashtekar's canonical approach to quantum
gravity are discussed.
| [
{
"created": "Fri, 18 Apr 1997 11:20:22 GMT",
"version": "v1"
}
] | 2011-04-15 | [
[
"Mielke",
"E. W.",
""
],
[
"Kreimer",
"D.",
""
]
] | The Dirac equation in Riemann-Cartan spacetimes with torsion is reconsidered. As is well-known, only the axial covector torsion $A$, a one-form, couples to massive Dirac fields. Using diagrammatic techniques, we show that besides the familiar Riemannian term only the Pontrjagin type four-form $dA\wedge dA$ does arise additionally in the chiral anomaly, but not the Nieh-Yan term $d ^* A$, as has been claimed recently. Implications for cosmic strings in Einstein-Cartan theory as well as for Ashtekar's canonical approach to quantum gravity are discussed. |
0903.2902 | Kentaro Somiya | Kentaro Somiya and Kazuhiro Yamamoto | Coating thermal noise of a finite-size cylindrical mirror | 13 pages, 4 figures | Phys.Rev.D79:102004,2009 | 10.1103/PhysRevD.79.102004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Thermal noise of a mirror is one of the limiting noise sources in the high
precision measurement such as gravitational-wave detection, and the modeling of
thermal noise has been developed and refined over a decade. In this paper, we
present a derivation of coating thermal noise of a finite-size cylindrical
mirror based on the fluctuation-dissipation theorem. The result agrees to a
previous result with an infinite-size mirror in the limit of large thickness,
and also agrees to an independent result based on the mode expansion with a
thin-mirror approximation. Our study will play an important role not only to
accurately estimate the thermal-noise level of gravitational-wave detectors but
also to help analyzing thermal noise in quantum-measurement experiments with
lighter mirrors.
| [
{
"created": "Tue, 17 Mar 2009 05:23:11 GMT",
"version": "v1"
}
] | 2009-07-30 | [
[
"Somiya",
"Kentaro",
""
],
[
"Yamamoto",
"Kazuhiro",
""
]
] | Thermal noise of a mirror is one of the limiting noise sources in the high precision measurement such as gravitational-wave detection, and the modeling of thermal noise has been developed and refined over a decade. In this paper, we present a derivation of coating thermal noise of a finite-size cylindrical mirror based on the fluctuation-dissipation theorem. The result agrees to a previous result with an infinite-size mirror in the limit of large thickness, and also agrees to an independent result based on the mode expansion with a thin-mirror approximation. Our study will play an important role not only to accurately estimate the thermal-noise level of gravitational-wave detectors but also to help analyzing thermal noise in quantum-measurement experiments with lighter mirrors. |
2104.11529 | Joao Magueijo | Joao Magueijo | Cosmological time and the constants of nature | null | null | 10.1016/j.physletb.2021.136487 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We propose that cosmological time is {\it effectively} the conjugate of the
constants of nature. Different definitions of time arise, with the most
relevant related to the constant controlling the dynamics in each epoch. The
Hamiltonian constraint then becomes a Schrodinger equation. In the connection
representation, it is solved by monochromatic plane waves moving in a space
generalizing the Chern-Simons functional. Normalizable superpositions exist and
for factorizable coherent states we recover the classical limit and a seamless
handover between potentially disparate times. There is also a rich structure of
alternative states, including entangled constants, opening up the doors to new
phenomenology.
| [
{
"created": "Fri, 23 Apr 2021 10:39:03 GMT",
"version": "v1"
}
] | 2021-06-30 | [
[
"Magueijo",
"Joao",
""
]
] | We propose that cosmological time is {\it effectively} the conjugate of the constants of nature. Different definitions of time arise, with the most relevant related to the constant controlling the dynamics in each epoch. The Hamiltonian constraint then becomes a Schrodinger equation. In the connection representation, it is solved by monochromatic plane waves moving in a space generalizing the Chern-Simons functional. Normalizable superpositions exist and for factorizable coherent states we recover the classical limit and a seamless handover between potentially disparate times. There is also a rich structure of alternative states, including entangled constants, opening up the doors to new phenomenology. |
gr-qc/0201049 | Jean-Michel Alimi du Daec | A. Serna (U. Miguel Hernandez, Elche, Spain) J.-M. Alimi (LAEC,
Observatoire de Meudon, France), A. Navarro (Univ. de Murcia, Murcia, Spain) | Convergence of Scalar-Tensor theories toward General Relativity and
Primordial Nucleosynthesis | 20 Pages, 3 Figures, accepted for publication in Class. and Quantum
Gravity | Class.Quant.Grav. 19 (2002) 857-874 | 10.1088/0264-9381/19/5/302 | null | gr-qc astro-ph | null | In this paper, we analyze the conditions for convergence toward General
Relativity of scalar-tensor gravity theories defined by an arbitrary coupling
function $\alpha$ (in the Einstein frame). We show that, in general, the
evolution of the scalar field $(\phi)$ is governed by two opposite mechanisms:
an attraction mechanism which tends to drive scalar-tensor models toward
Einstein's theory, and a repulsion mechanism which has the contrary effect. The
attraction mechanism dominates the recent epochs of the universe evolution if,
and only if, the scalar field and its derivative satisfy certain boundary
conditions. Since these conditions for convergence toward general relativity
depend on the particular scalar-tensor theory used to describe the universe
evolution, the nucleosynthesis bounds on the present value of the coupling
function, $\alpha_0$, strongly differ from some theories to others. For
example, in theories defined by $\alpha \propto \mid\phi\mid$ analytical
estimates lead to very stringent nucleosynthesis bounds on $\alpha_0$
($\lesssim 10^{-19}$). By contrast, in scalar-tensor theories defined by
$\alpha \propto \phi$ much larger limits on $\alpha_0$ ($\lesssim 10^{-7}$) are
found.
| [
{
"created": "Tue, 15 Jan 2002 13:05:15 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Serna",
"A.",
"",
"U. Miguel Hernandez, Elche, Spain"
],
[
"Alimi",
"J. -M.",
"",
"LAEC,\n Observatoire de Meudon, France"
],
[
"Navarro",
"A.",
"",
"Univ. de Murcia, Murcia, Spain"
]
] | In this paper, we analyze the conditions for convergence toward General Relativity of scalar-tensor gravity theories defined by an arbitrary coupling function $\alpha$ (in the Einstein frame). We show that, in general, the evolution of the scalar field $(\phi)$ is governed by two opposite mechanisms: an attraction mechanism which tends to drive scalar-tensor models toward Einstein's theory, and a repulsion mechanism which has the contrary effect. The attraction mechanism dominates the recent epochs of the universe evolution if, and only if, the scalar field and its derivative satisfy certain boundary conditions. Since these conditions for convergence toward general relativity depend on the particular scalar-tensor theory used to describe the universe evolution, the nucleosynthesis bounds on the present value of the coupling function, $\alpha_0$, strongly differ from some theories to others. For example, in theories defined by $\alpha \propto \mid\phi\mid$ analytical estimates lead to very stringent nucleosynthesis bounds on $\alpha_0$ ($\lesssim 10^{-19}$). By contrast, in scalar-tensor theories defined by $\alpha \propto \phi$ much larger limits on $\alpha_0$ ($\lesssim 10^{-7}$) are found. |
gr-qc/0612116 | Albert V. Minkevich | A.V. Minkevich, A.S. Garkun and V.I. Kudin | Homogeneous isotropic cosmological models with pseudoscalar torsion
function in Poincare gauge theory of gravity and accelerating Universe | 8 pages, 2 figures; some misprints are corrected | Proc. of the 5th Intern. Conf. Boyai-Gauss-Lobachevsky:
Non-Euclidean Geometry in Modern Physics, Minsk, Belarus, Oct. 10-13, 2006,
p. 196-202 | null | null | gr-qc | null | The "dark energy" problem is investigated in the framework of the Poincare
gauge theory of gravity in 4-dimensional Riemann-Cartan space-time. By using
general expression for gravitational Lagrangian homogeneous isotropic
cosmological models with pseudoscalar torsion function are built and
investigated. It is shown that by certain restrictions on indefinite parameters
of gravitational Lagrangian the cosmological equations at asymptotics contain
effective cosmological constant and can lead to observable acceleration of
cosmological expansion. This effect has geometrical nature and is connected
with space-time torsion.
| [
{
"created": "Tue, 19 Dec 2006 16:36:41 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Jan 2007 11:24:12 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Minkevich",
"A. V.",
""
],
[
"Garkun",
"A. S.",
""
],
[
"Kudin",
"V. I.",
""
]
] | The "dark energy" problem is investigated in the framework of the Poincare gauge theory of gravity in 4-dimensional Riemann-Cartan space-time. By using general expression for gravitational Lagrangian homogeneous isotropic cosmological models with pseudoscalar torsion function are built and investigated. It is shown that by certain restrictions on indefinite parameters of gravitational Lagrangian the cosmological equations at asymptotics contain effective cosmological constant and can lead to observable acceleration of cosmological expansion. This effect has geometrical nature and is connected with space-time torsion. |
gr-qc/9907043 | Andrew P. Bilyard | Andrew P Billyard (Dalhousie University), Alan A Coley (Dalhousie
University) and James E Lidsey (University of London) | Qualitative Analysis of Early Universe Cosmologies | Submitted to Journal of Mathematical Physics, 18 pages, 4 figures,
uses package "graphicx" to insert figures | J.Math.Phys. 40 (1999) 5092 | 10.1063/1.533017 | Dal-99-06 | gr-qc hep-th | null | A qualitative analysis is presented for a class of homogeneous cosmologies
derived from the string effective action when a cosmological constant is
present in the matter sector of the theory. Such a term has significant effects
on the qualitative dynamics. For example, models exist which undergo a series
of oscillations between expanding and contracting phases due to the existence
of a heteroclinic cycle in the phase space. Particular analytical solutions
corresponding to the equilibrium points are also found.
| [
{
"created": "Sun, 11 Jul 1999 13:54:48 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Billyard",
"Andrew P",
"",
"Dalhousie University"
],
[
"Coley",
"Alan A",
"",
"Dalhousie\n University"
],
[
"Lidsey",
"James E",
"",
"University of London"
]
] | A qualitative analysis is presented for a class of homogeneous cosmologies derived from the string effective action when a cosmological constant is present in the matter sector of the theory. Such a term has significant effects on the qualitative dynamics. For example, models exist which undergo a series of oscillations between expanding and contracting phases due to the existence of a heteroclinic cycle in the phase space. Particular analytical solutions corresponding to the equilibrium points are also found. |
1206.5786 | Bal\'azs Mik\'oczi | Bal\'azs Mik\'oczi, Bence Kocsis, P\'eter Forg\'acs, M\'aty\'as
Vas\'uth | Parameter estimation for inspiraling eccentric compact binaries
including pericenter precession | 14 two-column pages, 12 figures, expanded version; contains the proof
corrections | Phys.Rev.D86:104027,2012 | 10.1103/PhysRevD.86.104027 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspiraling supermassive black hole binary systems with high orbital
eccentricity are important sources for space-based gravitational wave (GW)
observatories like the Laser Interferometer Space Antenna (LISA). Eccentricity
adds orbital harmonics to the Fourier transform of the GW signal and
relativistic pericenter precession leads to a three-way splitting of each
harmonic peak. We study the parameter estimation accuracy for such waveforms
with different initial eccentricity using the Fisher matrix method and a Monte
Carlo sampling of the initial binary orientation. The eccentricity improves the
parameter estimation by breaking degeneracies between different parameters. In
particular, we find that the source localization precision improves
significantly for higher-mass binaries due to eccentricity. The typical sky
position errors are $\sim1 $deg for a nonspinning, $10^7\,M_{\odot}$ equal-mass
binary at redshift $z=1$, if the initial eccentricity 1 yr before merger is
$e_0\sim 0.6$. Pericenter precession does not affect the source localization
accuracy significantly, but it does further improve the mass and eccentricity
estimation accuracy systematically by a factor of 3--10 for masses between
$10^6$ and $10^7\,M_{\odot}$ for $e_0 \sim 0.3$.
| [
{
"created": "Mon, 25 Jun 2012 19:54:58 GMT",
"version": "v1"
},
{
"created": "Sat, 17 Nov 2012 18:35:21 GMT",
"version": "v2"
}
] | 2013-05-30 | [
[
"Mikóczi",
"Balázs",
""
],
[
"Kocsis",
"Bence",
""
],
[
"Forgács",
"Péter",
""
],
[
"Vasúth",
"Mátyás",
""
]
] | Inspiraling supermassive black hole binary systems with high orbital eccentricity are important sources for space-based gravitational wave (GW) observatories like the Laser Interferometer Space Antenna (LISA). Eccentricity adds orbital harmonics to the Fourier transform of the GW signal and relativistic pericenter precession leads to a three-way splitting of each harmonic peak. We study the parameter estimation accuracy for such waveforms with different initial eccentricity using the Fisher matrix method and a Monte Carlo sampling of the initial binary orientation. The eccentricity improves the parameter estimation by breaking degeneracies between different parameters. In particular, we find that the source localization precision improves significantly for higher-mass binaries due to eccentricity. The typical sky position errors are $\sim1 $deg for a nonspinning, $10^7\,M_{\odot}$ equal-mass binary at redshift $z=1$, if the initial eccentricity 1 yr before merger is $e_0\sim 0.6$. Pericenter precession does not affect the source localization accuracy significantly, but it does further improve the mass and eccentricity estimation accuracy systematically by a factor of 3--10 for masses between $10^6$ and $10^7\,M_{\odot}$ for $e_0 \sim 0.3$. |
1704.02404 | Yuri Bonder | Yuri Bonder | An algorithm for quantum gravity phenomenology | For the proceedings of the XI Mexican School on Gravitation and
Mathematical Physics (Dec. 2016) | null | 10.1088/1742-6596/1030/1/012001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum gravity phenomenology is the strategy towards quantum gravity where
the priority is to make contact with experiments. Here I describe what I
consider to be the best procedure to do quantum gravity phenomenology. The key
step is to have a generic parametrization which allows one to perform
self-consistency checks and to deal with many different experiments. As an
example I describe the role that the Standard Model Extension has played when
looking for Lorentz violation.
| [
{
"created": "Fri, 7 Apr 2017 23:47:32 GMT",
"version": "v1"
}
] | 2018-08-01 | [
[
"Bonder",
"Yuri",
""
]
] | Quantum gravity phenomenology is the strategy towards quantum gravity where the priority is to make contact with experiments. Here I describe what I consider to be the best procedure to do quantum gravity phenomenology. The key step is to have a generic parametrization which allows one to perform self-consistency checks and to deal with many different experiments. As an example I describe the role that the Standard Model Extension has played when looking for Lorentz violation. |
1704.06539 | Shahab Shahidi | Zahra Haghani, Tiberiu Harko and Shahab Shahidi | The Maxwell-Chern-Simons gravity and its cosmological implications | 19 pages, 12 figures | Eur. Phys. J. C (2017) 77: 514 | 10.1140/epjc/s10052-017-5078-0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the cosmological implications of a gravitational theory
containing two vector fields coupled minimally to gravity as well as a
generalized Chern-Simons term that couples the two vector fields. One of the
vector fields is the usual Maxwell field, while the other is a constrained
vector field with constant norm included in the action via a Lagrange
multiplier. The theory admits a de Sitter type solution, with healthy
cosmological perturbations. We will show that there is 6 degrees of freedom
propagate on top of de Sitter space-time, two tensor polarizations and four
degrees of freedom related to two massless vector fields interacting with each
other via Chern-Simons interaction term. We also investigate in detail the
behavior of the geometric and physical parameters of a homogeneous and
anisotropic Bianchi type I Universe, by using both analytical and numerical
methods, by assuming that the matter content of the Universe can be described
by the stiff causal and pressureless dust fluid equations of state. The time
evolution of the Bianchi type I Universe strongly depends on the initial
conditions of the physical and geometrical quantities, as well as on the
numerical values of the model parameters. Two important observational
parameters, the mean anisotropy parameter, and the deceleration parameter, are
also studied in detail, and we show that independently of the matter equation
of state the cosmological evolution of the Bianchi type I Universe always ends
in an isotropic and exponentially accelerating, de Sitter type, phase.
| [
{
"created": "Fri, 21 Apr 2017 13:47:35 GMT",
"version": "v1"
}
] | 2017-08-09 | [
[
"Haghani",
"Zahra",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Shahidi",
"Shahab",
""
]
] | We consider the cosmological implications of a gravitational theory containing two vector fields coupled minimally to gravity as well as a generalized Chern-Simons term that couples the two vector fields. One of the vector fields is the usual Maxwell field, while the other is a constrained vector field with constant norm included in the action via a Lagrange multiplier. The theory admits a de Sitter type solution, with healthy cosmological perturbations. We will show that there is 6 degrees of freedom propagate on top of de Sitter space-time, two tensor polarizations and four degrees of freedom related to two massless vector fields interacting with each other via Chern-Simons interaction term. We also investigate in detail the behavior of the geometric and physical parameters of a homogeneous and anisotropic Bianchi type I Universe, by using both analytical and numerical methods, by assuming that the matter content of the Universe can be described by the stiff causal and pressureless dust fluid equations of state. The time evolution of the Bianchi type I Universe strongly depends on the initial conditions of the physical and geometrical quantities, as well as on the numerical values of the model parameters. Two important observational parameters, the mean anisotropy parameter, and the deceleration parameter, are also studied in detail, and we show that independently of the matter equation of state the cosmological evolution of the Bianchi type I Universe always ends in an isotropic and exponentially accelerating, de Sitter type, phase. |
2212.13961 | Martin Bojowald | Martin Bojowald and Artur Tsobanjan | An algebraic approach to the "frozen formalism" problem of time | 54 pages, one figure | Phys. Rev. D 107 (2023) 024003 | 10.1103/PhysRevD.107.024003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The long-standing problem of time in canonical quantum gravity is the source
of several conceptual and technical issues. Here, recent mathematical results
are used to provide a consistent algebraic formulation of dynamical symplectic
reduction that avoids difficult requirements such as the computation of a
complete set of Dirac observables or the construction of a physical Hilbert
space. In addition, the new algebraic treatment makes it possible to implement
a consistent realization of the gauge structure off the constraint surface. As
a consequence, previously unrecognized consistency conditions are imposed on
deparameterization -- the method traditionally used to unfreeze evolution in
completely constrained systems. A detailed discussion of how the new
formulation extends previous semiclassical results shows that an internal time
degree of freedom need not be semiclassical in order to define a consistent
quantum evolution.
| [
{
"created": "Wed, 28 Dec 2022 17:05:31 GMT",
"version": "v1"
}
] | 2023-01-04 | [
[
"Bojowald",
"Martin",
""
],
[
"Tsobanjan",
"Artur",
""
]
] | The long-standing problem of time in canonical quantum gravity is the source of several conceptual and technical issues. Here, recent mathematical results are used to provide a consistent algebraic formulation of dynamical symplectic reduction that avoids difficult requirements such as the computation of a complete set of Dirac observables or the construction of a physical Hilbert space. In addition, the new algebraic treatment makes it possible to implement a consistent realization of the gauge structure off the constraint surface. As a consequence, previously unrecognized consistency conditions are imposed on deparameterization -- the method traditionally used to unfreeze evolution in completely constrained systems. A detailed discussion of how the new formulation extends previous semiclassical results shows that an internal time degree of freedom need not be semiclassical in order to define a consistent quantum evolution. |
gr-qc/0012021 | Mauricio Bellini | Mauricio Bellini (IFM, Universidad Michoacana de San Nicolas de
Hidalgo) | Coarse-grained field wave function in stochastic inflation | to appear in Nuclear Physics B (version with some changes and some
references added) | Nucl.Phys. B604 (2001) 441-451 | 10.1016/S0550-3213(01)00196-1 | null | gr-qc astro-ph hep-ph hep-th | null | The wave function for the matter field fluctuations in the infrared sector is
studied within the framework of inflationary cosmology. These fluctuations are
described by a coarse-grained field which takes into account only the modes
with wavelength much bigger than the size of the Hubble horizon. The case of a
power-law expanding universe is considered and it is found that the relevant
phase-space remains coherent under certain circumstances. In this case the
classical stochastic treatment for matter field fluctuations is not valid,
however, for $p > 4.6$, the system loses its coherence and a classical
stochastic approximation is allowed.
| [
{
"created": "Tue, 5 Dec 2000 18:47:49 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Feb 2001 18:37:58 GMT",
"version": "v2"
},
{
"created": "Tue, 20 Feb 2001 23:32:25 GMT",
"version": "v3"
},
{
"created": "Tue, 10 Apr 2001 22:48:09 GMT",
"version": "v4"
}
] | 2009-10-31 | [
[
"Bellini",
"Mauricio",
"",
"IFM, Universidad Michoacana de San Nicolas de\n Hidalgo"
]
] | The wave function for the matter field fluctuations in the infrared sector is studied within the framework of inflationary cosmology. These fluctuations are described by a coarse-grained field which takes into account only the modes with wavelength much bigger than the size of the Hubble horizon. The case of a power-law expanding universe is considered and it is found that the relevant phase-space remains coherent under certain circumstances. In this case the classical stochastic treatment for matter field fluctuations is not valid, however, for $p > 4.6$, the system loses its coherence and a classical stochastic approximation is allowed. |
1908.05592 | Tao Zhou | Zonghai Li and Tao Zhou | Equivalence of Gibbons-Werner method to geodesics method in the study of
gravitational lensing | 7 pages, 1 figure, accepted for publication in Phys. Rev. D | Phys. Rev. D 101, 044043 (2020) | 10.1103/PhysRevD.101.044043 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Gibbons-Werner method where the Gauss-Bonnet theorem is applied to study
the gravitational deflection angle has received much attention recently. In
this paper, we study the equivalence of the Gibbons-Werner method to the
standard geodesics method, and it is shown that the geodesics method can be
derived with the Gibbons-Werner method, for asymptotically flat case. In the
geodesics method, the gravitational deflection angle of particle depends
entirely on the geodesic curvature of the particle ray in the Euclidean space.
The gravitational deflection of light in Kerr-Newman spacetime is calculated by
different technologies under the Gibbons-Werner framework, as an intuitive
example to show the equivalence.
| [
{
"created": "Thu, 15 Aug 2019 15:42:34 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Feb 2020 17:36:39 GMT",
"version": "v2"
}
] | 2020-02-24 | [
[
"Li",
"Zonghai",
""
],
[
"Zhou",
"Tao",
""
]
] | The Gibbons-Werner method where the Gauss-Bonnet theorem is applied to study the gravitational deflection angle has received much attention recently. In this paper, we study the equivalence of the Gibbons-Werner method to the standard geodesics method, and it is shown that the geodesics method can be derived with the Gibbons-Werner method, for asymptotically flat case. In the geodesics method, the gravitational deflection angle of particle depends entirely on the geodesic curvature of the particle ray in the Euclidean space. The gravitational deflection of light in Kerr-Newman spacetime is calculated by different technologies under the Gibbons-Werner framework, as an intuitive example to show the equivalence. |
1803.06486 | Yasutaka Koga | Yasutaka Koga, Tomohiro Harada | Rotating accretion flows in $D$ dimensions: sonic points, critical
points and photon spheres | 11 pages | Phys. Rev. D 98, 024018 (2018) | 10.1103/PhysRevD.98.024018 | RUP-18-9 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give the formulation and the general analysis of the rotational accretion
problem on $D$-dimensional spherical spacetime and investigate sonic points and
critical points. First, we construct the simple two-dimensional rotating
accretion flow model in general $D$-dimensional static spherically symmetric
spacetime and formulate the problem. The flow forms a two-dimensional disk
lying on the equatorial plane and the disk is assumed to be geometrically thin
and has uniform distribution in the polar angle directions. Analyzing the
critical point of the problem, we give the conditions for the critical point
and its classification explicitly and show the coincidence with the sonic point
for generic equation of state (EOS). Next, adopting the EOS of ideal photon gas
to the analysis, we reveal that there always exists a correspondence between
the sonic points and the photon spheres of the spacetime. Our main result is
that the sonic point of the rotating accretion flow of ideal photon gas must be
on (one of) the unstable photon sphere(s) of the spacetime in arbitrary
spacetime dimensions. This paper extends this correspondence for spherical
flows shown in the authors' previous work to rotating accretion disks.
| [
{
"created": "Sat, 17 Mar 2018 10:31:50 GMT",
"version": "v1"
}
] | 2018-07-18 | [
[
"Koga",
"Yasutaka",
""
],
[
"Harada",
"Tomohiro",
""
]
] | We give the formulation and the general analysis of the rotational accretion problem on $D$-dimensional spherical spacetime and investigate sonic points and critical points. First, we construct the simple two-dimensional rotating accretion flow model in general $D$-dimensional static spherically symmetric spacetime and formulate the problem. The flow forms a two-dimensional disk lying on the equatorial plane and the disk is assumed to be geometrically thin and has uniform distribution in the polar angle directions. Analyzing the critical point of the problem, we give the conditions for the critical point and its classification explicitly and show the coincidence with the sonic point for generic equation of state (EOS). Next, adopting the EOS of ideal photon gas to the analysis, we reveal that there always exists a correspondence between the sonic points and the photon spheres of the spacetime. Our main result is that the sonic point of the rotating accretion flow of ideal photon gas must be on (one of) the unstable photon sphere(s) of the spacetime in arbitrary spacetime dimensions. This paper extends this correspondence for spherical flows shown in the authors' previous work to rotating accretion disks. |
0912.0481 | Cyril Pitrou | Gilles Esposito-Farese, Cyril Pitrou, Jean-Philippe Uzan | Vector theories in cosmology | 17 pages, no figure | Phys.Rev.D81:063519,2010 | 10.1103/PhysRevD.81.063519 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article provides a general study of the Hamiltonian stability and the
hyperbolicity of vector field models involving both a general function of the
Faraday tensor and its dual, $f(F^2,F\tilde F)$, as well as a Proca potential
for the vector field, $V(A^2)$. In particular it is demonstrated that theories
involving only $f(F^2)$ do not satisfy the hyperbolicity conditions. It is then
shown that in this class of models, the cosmological dynamics always dilutes
the vector field. In the case of a nonminimal coupling to gravity, it is
established that theories involving $R f(A^2)$ or $Rf(F^2)$ are generically
pathologic. To finish, we exhibit a model where the vector field is not diluted
during the cosmological evolution, because of a nonminimal vector
field-curvature coupling which maintains second-order field equations. The
relevance of such models for cosmology is discussed.
| [
{
"created": "Wed, 2 Dec 2009 18:14:48 GMT",
"version": "v1"
}
] | 2010-04-29 | [
[
"Esposito-Farese",
"Gilles",
""
],
[
"Pitrou",
"Cyril",
""
],
[
"Uzan",
"Jean-Philippe",
""
]
] | This article provides a general study of the Hamiltonian stability and the hyperbolicity of vector field models involving both a general function of the Faraday tensor and its dual, $f(F^2,F\tilde F)$, as well as a Proca potential for the vector field, $V(A^2)$. In particular it is demonstrated that theories involving only $f(F^2)$ do not satisfy the hyperbolicity conditions. It is then shown that in this class of models, the cosmological dynamics always dilutes the vector field. In the case of a nonminimal coupling to gravity, it is established that theories involving $R f(A^2)$ or $Rf(F^2)$ are generically pathologic. To finish, we exhibit a model where the vector field is not diluted during the cosmological evolution, because of a nonminimal vector field-curvature coupling which maintains second-order field equations. The relevance of such models for cosmology is discussed. |
0805.3796 | Burin Gumjudpai | Burin Gumjudpai (DAMTP U. Cambridge and TPTP Naresuan U.) | Slow-roll, acceleration, the Big Rip and WKB approximation in NLS-type
formulation of scalar field cosmology | [7 pages, no figure, more reference added, accepted by JCAP] | JCAP 0809:028,2008 | 10.1088/1475-7516/2008/09/028 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Aspects of non-linear Schr\"{o}dinger-type (NLS) formulation of scalar
(phantom) field cosmology on slow-roll, acceleration, WKB approximation and Big
Rip singularity are presented. Slow-roll parameters for the curvature and
barotropic density terms are introduced. We reexpress all slow-roll parameters,
slow-roll conditions and acceleration condition in NLS form. WKB approximation
in the NLS formulation is also discussed when simplifying to linear case. Most
of the Schr\"{o}dinger potentials in NLS formulation are very slowly-varying,
hence WKB approximation is valid in the ranges. In the NLS form of Big Rip
singularity, two quantities are infinity in stead of three. We also found that
approaching the Big Rip, $w_{\rm eff}\to -1 + {2}/{3q}$, $(q<0)$ which is the
same as effective phantom equation of state in the flat case.
| [
{
"created": "Sat, 24 May 2008 21:18:57 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jul 2008 19:26:01 GMT",
"version": "v2"
},
{
"created": "Fri, 5 Sep 2008 18:25:04 GMT",
"version": "v3"
},
{
"created": "Thu, 25 Sep 2008 16:43:58 GMT",
"version": "v4"
},
{
"created": "Fri, 26 Sep 2008 11:09:15 GMT",
"version": "v5"
}
] | 2014-11-18 | [
[
"Gumjudpai",
"Burin",
"",
"DAMTP U. Cambridge and TPTP Naresuan U."
]
] | Aspects of non-linear Schr\"{o}dinger-type (NLS) formulation of scalar (phantom) field cosmology on slow-roll, acceleration, WKB approximation and Big Rip singularity are presented. Slow-roll parameters for the curvature and barotropic density terms are introduced. We reexpress all slow-roll parameters, slow-roll conditions and acceleration condition in NLS form. WKB approximation in the NLS formulation is also discussed when simplifying to linear case. Most of the Schr\"{o}dinger potentials in NLS formulation are very slowly-varying, hence WKB approximation is valid in the ranges. In the NLS form of Big Rip singularity, two quantities are infinity in stead of three. We also found that approaching the Big Rip, $w_{\rm eff}\to -1 + {2}/{3q}$, $(q<0)$ which is the same as effective phantom equation of state in the flat case. |
gr-qc/9607057 | Filipe de Moraes Paiva | M. F. A. da Silva, L. Herrera, F. M. Paiva, N. O. Santos | On the parameters of Lewis metric for the Lewis class | Latex | Class.Quant.Grav.12:111-118,1995 | 10.1088/0264-9381/12/1/009 | null | gr-qc | null | The physical and geometrical meaning of the four parameters of Lewis metric
for the Lewis class are investigated. Matching this spacetime to a completely
anisotropic, rigidly rotating, fluid cylinder, we obtain from the junction
conditions that the four parameters are related to the vorticity of the source.
Furthermore it is shown that one of the parameters must vanish if one wishes to
reduce the Lewis class to a locally static spacetime. Using the Cartan scalars
it is shown that the Lewis class does not include globally Minkowski as special
class, and that it is not locally equivalent to the Levi-Civita metric. Also it
is shown that, in contrast with the Weyl class, the parameter responsible for
the vorticity appears explicitly in the expression for the Cartan scalars.
Finally, to enhance our understanding of the Lewis class, we analyse the van
Stockum metric.
| [
{
"created": "Tue, 23 Jul 1996 17:34:18 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"da Silva",
"M. F. A.",
""
],
[
"Herrera",
"L.",
""
],
[
"Paiva",
"F. M.",
""
],
[
"Santos",
"N. O.",
""
]
] | The physical and geometrical meaning of the four parameters of Lewis metric for the Lewis class are investigated. Matching this spacetime to a completely anisotropic, rigidly rotating, fluid cylinder, we obtain from the junction conditions that the four parameters are related to the vorticity of the source. Furthermore it is shown that one of the parameters must vanish if one wishes to reduce the Lewis class to a locally static spacetime. Using the Cartan scalars it is shown that the Lewis class does not include globally Minkowski as special class, and that it is not locally equivalent to the Levi-Civita metric. Also it is shown that, in contrast with the Weyl class, the parameter responsible for the vorticity appears explicitly in the expression for the Cartan scalars. Finally, to enhance our understanding of the Lewis class, we analyse the van Stockum metric. |
1502.07691 | Xian Gao | Xian Gao | On covariant expansion of the gravitational St\"{u}ckelberg trick | 7 pages, double column, 1 figure | Phys. Rev. D 91, 094001 (2015) | 10.1103/PhysRevD.91.094001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new approach to expanding the "St\"{u}ckelbergized" fiducial metric in a
covariant manner is developed. The idea is to consider the curved 4-dimensional
space as a codimension-one hypersurface embedded in a 5-dimensional Minkowski
bulk, in which the 5-dimensional Goldstone modes can be defined as usual. After
solving one constraint among the five 5-dimensional Goldstone modes and
projecting onto the 4-dimensional hypersurface, we are able to express the
"St\"{u}ckelbergized" fiducial metric in terms of the 4-dimensional Goldstone
modes as well as 4-dimensional curvature quantities. We also compared the
results with expressions got using the Riemann Normal Coordinates (RNC) in Gao
et al [Phys. Rev. D90, 124073 (2014)] and find that, after a simple field
redefinition, results got in two approaches exactly coincide.
| [
{
"created": "Thu, 26 Feb 2015 19:38:41 GMT",
"version": "v1"
}
] | 2015-05-06 | [
[
"Gao",
"Xian",
""
]
] | A new approach to expanding the "St\"{u}ckelbergized" fiducial metric in a covariant manner is developed. The idea is to consider the curved 4-dimensional space as a codimension-one hypersurface embedded in a 5-dimensional Minkowski bulk, in which the 5-dimensional Goldstone modes can be defined as usual. After solving one constraint among the five 5-dimensional Goldstone modes and projecting onto the 4-dimensional hypersurface, we are able to express the "St\"{u}ckelbergized" fiducial metric in terms of the 4-dimensional Goldstone modes as well as 4-dimensional curvature quantities. We also compared the results with expressions got using the Riemann Normal Coordinates (RNC) in Gao et al [Phys. Rev. D90, 124073 (2014)] and find that, after a simple field redefinition, results got in two approaches exactly coincide. |
2104.05879 | Robert Bluhm | Robert Bluhm and Yumu Yang | Gravity with Explicit Diffeomorphism Breaking | null | Symmetry 2021, 13, 660 | 10.3390/sym13040660 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Modified theories of gravity that explicitly break diffeomorphism invariance
have been used for over a decade to explore open issues related to quantum
gravity, dark energy, and dark matter. At the same time, the Standard-Model
Extension (SME) has been widely used as a phenomenological framework in
investigations of spacetime symmetry breaking. Until recently, it was thought
that the SME was suitable only for theories with spontaneous spacetime symmetry
breaking due to consistency conditions stemming from the Bianchi identities.
However, it has recently been shown that, particularly with matter couplings
included, the consistency conditions can also be satisfied in theories with
explicit breaking. An overview of how this is achieved is presented, and two
examples are examined. The first is massive gravity, which includes a
nondynamical background tensor. The second is a model based on a low-energy
limit of Ho\v rava gravity, where spacetime has a physically preferred
foliation. In both cases, bounds on matter--gravity interactions that
explicitly break diffeomorphisms are obtained using the SME.
| [
{
"created": "Tue, 13 Apr 2021 00:58:01 GMT",
"version": "v1"
}
] | 2021-04-14 | [
[
"Bluhm",
"Robert",
""
],
[
"Yang",
"Yumu",
""
]
] | Modified theories of gravity that explicitly break diffeomorphism invariance have been used for over a decade to explore open issues related to quantum gravity, dark energy, and dark matter. At the same time, the Standard-Model Extension (SME) has been widely used as a phenomenological framework in investigations of spacetime symmetry breaking. Until recently, it was thought that the SME was suitable only for theories with spontaneous spacetime symmetry breaking due to consistency conditions stemming from the Bianchi identities. However, it has recently been shown that, particularly with matter couplings included, the consistency conditions can also be satisfied in theories with explicit breaking. An overview of how this is achieved is presented, and two examples are examined. The first is massive gravity, which includes a nondynamical background tensor. The second is a model based on a low-energy limit of Ho\v rava gravity, where spacetime has a physically preferred foliation. In both cases, bounds on matter--gravity interactions that explicitly break diffeomorphisms are obtained using the SME. |
0907.4002 | Atsushi Higuchi | Atsushi Higuchi, Yen Cheong Lee, Jack R. Nicholas | More on the covariant retarded Green's function for the electromagnetic
field in de Sitter spacetime | 4 pages, addendum to PRD 78, 084031 (2008) [arXiv:0808.0642] | Phys.Rev.D80:107502,2009 | 10.1103/PhysRevD.80.107502 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent paper (Phys. Rev. D78, 084031 (2008), arXiv:0808.0642, Ref. [1])
it was shown in examples that the covariant retarded Green's functions in
particular gauges for electromagnetism and linearized gravity can be used to
reproduce field configurations correctly in spite of the spacelike nature of
past infinity in de Sitter spacetime. In this paper we extend the work of Ref.
[1] concerning the electromagnetic field and show that the covariant retarded
Green's function with an arbitrary value of the gauge parameter reproduces the
electromagnetic field from two opposite charges at antipodal points of de
Sitter spacetime.
| [
{
"created": "Thu, 23 Jul 2009 08:53:51 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Aug 2009 16:35:00 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"Higuchi",
"Atsushi",
""
],
[
"Lee",
"Yen Cheong",
""
],
[
"Nicholas",
"Jack R.",
""
]
] | In a recent paper (Phys. Rev. D78, 084031 (2008), arXiv:0808.0642, Ref. [1]) it was shown in examples that the covariant retarded Green's functions in particular gauges for electromagnetism and linearized gravity can be used to reproduce field configurations correctly in spite of the spacelike nature of past infinity in de Sitter spacetime. In this paper we extend the work of Ref. [1] concerning the electromagnetic field and show that the covariant retarded Green's function with an arbitrary value of the gauge parameter reproduces the electromagnetic field from two opposite charges at antipodal points of de Sitter spacetime. |
gr-qc/0405069 | Alexander E. Shalyt-Margolin | A.E.Shalyt-Margolin | Pure States, Mixed States and Hawking Problem in Generalized Quantum
Mechanics | 12 pages,no figures,some corrections,new references | Mod.Phys.Lett. A19 (2004) 2037-2045 | 10.1142/S0217732304015312 | null | gr-qc | null | This paper is the continuation of a study into the information paradox
problem started by the author in his earlier works. As previously, the key
instrument is a deformed density matrix in quantum mechanics of the early
universe. It is assumed that the latter represents quantum mechanics with
fundamental length. It is demonstrated that the obtained results agree well
with the canonical viewpoint that in the processes involving black holes pure
states go to the mixed ones in the assumption that all measurements are
performed by the observer in a well-known quantum mechanics. Also it is shown
that high entropy for Planck remnants of black holes appearing in the
assumption of the Generalized Uncertainty Relations may be explained within the
scope of the density matrix entropy introduced by the author previously. It is
noted that the suggested paradigm is consistent with the Holographic Principle.
Because of this, a conjecture is made about the possibility for obtaining the
Generalized Uncertainty Relations from the covariant entropy bound at high
energies in the same way as R. Bousso has derived Heisenberg uncertainty
principle for the flat space.
| [
{
"created": "Thu, 13 May 2004 10:37:12 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Jul 2004 06:05:46 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Shalyt-Margolin",
"A. E.",
""
]
] | This paper is the continuation of a study into the information paradox problem started by the author in his earlier works. As previously, the key instrument is a deformed density matrix in quantum mechanics of the early universe. It is assumed that the latter represents quantum mechanics with fundamental length. It is demonstrated that the obtained results agree well with the canonical viewpoint that in the processes involving black holes pure states go to the mixed ones in the assumption that all measurements are performed by the observer in a well-known quantum mechanics. Also it is shown that high entropy for Planck remnants of black holes appearing in the assumption of the Generalized Uncertainty Relations may be explained within the scope of the density matrix entropy introduced by the author previously. It is noted that the suggested paradigm is consistent with the Holographic Principle. Because of this, a conjecture is made about the possibility for obtaining the Generalized Uncertainty Relations from the covariant entropy bound at high energies in the same way as R. Bousso has derived Heisenberg uncertainty principle for the flat space. |
1506.06071 | Marta Campigotto | M. Campigotto, L. Fatibene | Generally Covariant vs. Gauge Structure for Conformal Field Theories | 11 pages, comments are welcome | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce the natural lift of spacetime diffeomorphisms for conformal
gravity and discuss the physical equivalence between the natural and gauge
natural structure of the theory. Accordingly, we argue that conformal
transformations must be introduced as gauge transformations (affecting fields
but not spacetime point) and then discuss special structures implied by the
splitting of the conformal group.
| [
{
"created": "Fri, 19 Jun 2015 16:07:03 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Campigotto",
"M.",
""
],
[
"Fatibene",
"L.",
""
]
] | We introduce the natural lift of spacetime diffeomorphisms for conformal gravity and discuss the physical equivalence between the natural and gauge natural structure of the theory. Accordingly, we argue that conformal transformations must be introduced as gauge transformations (affecting fields but not spacetime point) and then discuss special structures implied by the splitting of the conformal group. |
1201.3820 | Luis Cort\'es Barbado | Luis C. Barbado, Carlos Barcel\'o and Luis J. Garay | Hawking radiation as perceived by different observers: An analytic
expression for the effective-temperature function | 10 pages, 1 figure | Class.Quant.Grav.29:075013,2012 | 10.1088/0264-9381/29/7/075013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Given a field vacuum state in a black hole spacetime, this state can be
analysed in terms of how it is perceived (in terms of particle content) by
different observers. This can be done by means of the effective-temperature
function introduced by Barcel\'o et al. in [1]. In Barbado et al. [2], this
function was analysed in a case by case basis for a number of interesting
situations. In this work, we find a general analytic expression for the
effective-temperature function which, apart from the vacuum state choice,
depends on the position, the local velocity and the acceleration of the
specific observer. We give a clear physical interpretation of the quantities
appearing in the expression, and illustrate its potentiality with a few
examples.
| [
{
"created": "Wed, 18 Jan 2012 15:16:29 GMT",
"version": "v1"
},
{
"created": "Sat, 24 Mar 2012 11:59:20 GMT",
"version": "v2"
}
] | 2016-11-26 | [
[
"Barbado",
"Luis C.",
""
],
[
"Barceló",
"Carlos",
""
],
[
"Garay",
"Luis J.",
""
]
] | Given a field vacuum state in a black hole spacetime, this state can be analysed in terms of how it is perceived (in terms of particle content) by different observers. This can be done by means of the effective-temperature function introduced by Barcel\'o et al. in [1]. In Barbado et al. [2], this function was analysed in a case by case basis for a number of interesting situations. In this work, we find a general analytic expression for the effective-temperature function which, apart from the vacuum state choice, depends on the position, the local velocity and the acceleration of the specific observer. We give a clear physical interpretation of the quantities appearing in the expression, and illustrate its potentiality with a few examples. |
1104.0442 | Kuiroukidis | Kostas Kleidis and Nicholas K. Spyrou | A conventional approach to the dark-energy concept | 15 pages, 2 figures | A&A 529, A26 (2011) | 10.1051/0004-6361/201016057 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by results implying that the constituents of dark matter (DM) might
be collisional, we consider a cosmological (toy-) model, in which the DM itself
possesses some sort of thermodynamic properties. In this case, not only can the
matter content of the Universe be treated as a classical gravitating fluid of
positive pressure, but, together with all its other physical characteristics,
the energy of this fluid's internal motions should be taken into account as a
source of the universal gravitational field. This form of energy can compensate
for the extra (dark) energy, needed to compromise spatial flatness, while the
post-recombination Universe remains ever-decelerating. At the same time (i.e.,
in the context of the collisional-DM approach), the theoretical curve
representing the distance modulus as a function of the cosmological redshift,
{\mu}(z), fits the Hubble diagram of a multi-used sample of supernova Ia events
quite accurately. A cosmological model filled with collisional DM could
accommodate the majority of the currently-available observational data
(including, also, those from baryon acoustic oscillations), without the need
for either any dark energy (DE) or the cosmological constant. However, as we
demonstrate, this is not the case for someone who, although living in a
Universe filled with self-interacting DM, insists on adopting the traditional,
collisionless-DM approach. From the point of view of this observer, the
cosmologically-distant light-emitting sources seem to lie farther (i.e., they
appear to be dimmer) than expected, while the Universe appears to be either
accelerating or decelerating, depending on the value of the cosmological
redshift. This picture, which, nowadays, represents the common perception in
observational cosmology, acquires a more conventional interpretation within the
context of the collisional-DM approach.
| [
{
"created": "Mon, 4 Apr 2011 00:22:16 GMT",
"version": "v1"
}
] | 2015-03-19 | [
[
"Kleidis",
"Kostas",
""
],
[
"Spyrou",
"Nicholas K.",
""
]
] | Motivated by results implying that the constituents of dark matter (DM) might be collisional, we consider a cosmological (toy-) model, in which the DM itself possesses some sort of thermodynamic properties. In this case, not only can the matter content of the Universe be treated as a classical gravitating fluid of positive pressure, but, together with all its other physical characteristics, the energy of this fluid's internal motions should be taken into account as a source of the universal gravitational field. This form of energy can compensate for the extra (dark) energy, needed to compromise spatial flatness, while the post-recombination Universe remains ever-decelerating. At the same time (i.e., in the context of the collisional-DM approach), the theoretical curve representing the distance modulus as a function of the cosmological redshift, {\mu}(z), fits the Hubble diagram of a multi-used sample of supernova Ia events quite accurately. A cosmological model filled with collisional DM could accommodate the majority of the currently-available observational data (including, also, those from baryon acoustic oscillations), without the need for either any dark energy (DE) or the cosmological constant. However, as we demonstrate, this is not the case for someone who, although living in a Universe filled with self-interacting DM, insists on adopting the traditional, collisionless-DM approach. From the point of view of this observer, the cosmologically-distant light-emitting sources seem to lie farther (i.e., they appear to be dimmer) than expected, while the Universe appears to be either accelerating or decelerating, depending on the value of the cosmological redshift. This picture, which, nowadays, represents the common perception in observational cosmology, acquires a more conventional interpretation within the context of the collisional-DM approach. |
1506.02422 | Luis Herrera | L. Herrera | Gravitational radiation within its source | Talk given at the International Conference on Relativistic
Astrophysics (through Skype), Lahore, February 2015. To appear in the
proceedings, to be published by Punjab University Press. 9 pages, Revtex-4 | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review a recently proposed framework for studying axially symmetric
dissipative fluids \cite{Ref1}. Some general results are discussed at the most
general level. We then proceed to analyze some particular cases. First, the
shear-free case is considered \cite{3}. We shall next discuss the perfect fluid
case under the geodesic condition, without impossing ab initio the shear--free
condition \cite{2}. Finally a dissipative, geodesic fluid \cite{4}, is analyzed
in some detail. We conclude by bringing out the attention to some open issues.
| [
{
"created": "Mon, 8 Jun 2015 09:48:38 GMT",
"version": "v1"
}
] | 2015-06-10 | [
[
"Herrera",
"L.",
""
]
] | We review a recently proposed framework for studying axially symmetric dissipative fluids \cite{Ref1}. Some general results are discussed at the most general level. We then proceed to analyze some particular cases. First, the shear-free case is considered \cite{3}. We shall next discuss the perfect fluid case under the geodesic condition, without impossing ab initio the shear--free condition \cite{2}. Finally a dissipative, geodesic fluid \cite{4}, is analyzed in some detail. We conclude by bringing out the attention to some open issues. |
2402.17799 | Subenoy Chakraborty | Subenoy Chakraborty and Madhukrishna Chakraborty | A Revisit to Classical and Quantum aspects of Raychaudhuri equation and
possible resolution of Singularity | 43 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this review, we provide a concrete overview of the Raychaudhuri equation,
Focusing theorem and Convergence conditions in a plethora of backgrounds and
discuss the consequences. We also present various classical and quantum
approaches suggested in the literature that could potentially mitigate the
initial big-bang singularity and the black-hole singularity.
| [
{
"created": "Tue, 27 Feb 2024 05:50:27 GMT",
"version": "v1"
}
] | 2024-02-29 | [
[
"Chakraborty",
"Subenoy",
""
],
[
"Chakraborty",
"Madhukrishna",
""
]
] | In this review, we provide a concrete overview of the Raychaudhuri equation, Focusing theorem and Convergence conditions in a plethora of backgrounds and discuss the consequences. We also present various classical and quantum approaches suggested in the literature that could potentially mitigate the initial big-bang singularity and the black-hole singularity. |
1701.01003 | Larry Ford | Jen-Tsung Hsiang, L. H. Ford, Kin-Wang Ng and Chun-Hsien Wu | Quantum Stress Tensor Fluctuations and Primordial Gravity Waves | 33 pages, 3 figures | Phys. Rev. D 95, 063524 (2017) | 10.1103/PhysRevD.95.063524 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the effect of the stress tensor of a quantum matter field, such as
the electromagnetic field, on the spectrum of primordial gravity waves expected
in inflationary cosmology. We find that the net effect is a small reduction in
the power spectrum, especially at higher frequencies, but which has a different
form from that described by the usual spectral index. Thus this effect has a
characteristic signature, and is in principle observable. The net effect is a
sum of two contributions, one of which is due to quantum fluctuations of the
matter field stress tensor. The other is a quantum correction to the graviton
field due to coupling to the expectation value of this stress tensor. Both
contributions are sensitive to initial conditions in the very early universe,
so this effect has the potential to act as a probe of these initial conditions.
| [
{
"created": "Wed, 4 Jan 2017 13:32:08 GMT",
"version": "v1"
}
] | 2017-04-05 | [
[
"Hsiang",
"Jen-Tsung",
""
],
[
"Ford",
"L. H.",
""
],
[
"Ng",
"Kin-Wang",
""
],
[
"Wu",
"Chun-Hsien",
""
]
] | We examine the effect of the stress tensor of a quantum matter field, such as the electromagnetic field, on the spectrum of primordial gravity waves expected in inflationary cosmology. We find that the net effect is a small reduction in the power spectrum, especially at higher frequencies, but which has a different form from that described by the usual spectral index. Thus this effect has a characteristic signature, and is in principle observable. The net effect is a sum of two contributions, one of which is due to quantum fluctuations of the matter field stress tensor. The other is a quantum correction to the graviton field due to coupling to the expectation value of this stress tensor. Both contributions are sensitive to initial conditions in the very early universe, so this effect has the potential to act as a probe of these initial conditions. |
1005.3108 | Morteza Mohseni | Morteza Mohseni | General relativistic spinning fluids with a modified projection tensor | Submitted to General Relativity and Gravitation | Gen.Rel.Grav.42:1727-1737,2010 | 10.1007/s10714-010-0943-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An energy-momentum tensor for general relativistic spinning fluids compatible
with Tulczyjew-type supplementary condition is derived from the variation of a
general Lagrangian with unspecified explicit form. This tensor is the sum of a
term containing the Belinfante-Rosenfeld tensor and a modified perfect-fluid
energy-momentum tensor in which the four-velocity is replaced by a unit
four-vector in the direction of fluid momentum. The equations of motion are
obtained and it is shown that they admit a Friedmann-Robertson-Walker
space-time as a solution.
| [
{
"created": "Tue, 18 May 2010 06:16:17 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Mohseni",
"Morteza",
""
]
] | An energy-momentum tensor for general relativistic spinning fluids compatible with Tulczyjew-type supplementary condition is derived from the variation of a general Lagrangian with unspecified explicit form. This tensor is the sum of a term containing the Belinfante-Rosenfeld tensor and a modified perfect-fluid energy-momentum tensor in which the four-velocity is replaced by a unit four-vector in the direction of fluid momentum. The equations of motion are obtained and it is shown that they admit a Friedmann-Robertson-Walker space-time as a solution. |
2104.11553 | Jie-Xiong Mo | Shan-Quan Lan, Jie-Xiong Mo, Gu-Qiang Li and Xiao-Bao Xu | Effects of dark energy on dynamic phase transition of charged AdS black
holes | 10pages, 6figures | null | 10.1103/PhysRevD.104.104032 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Searching for the effect of quintessence dark energy on the kinetics of black
hole phase transition, we investigate in detail the dynamic phase transition of
charged AdS black holes surrounded by quintessence in this paper. Based on the
Gibbs free energy landscape, we obtain the analytic expression of the
corresponding Gibbs free energy. As shown in $G_L-r_+$ curve at the phase
transition temperature, there exist double wells with the same depth, providing
further support on the finding in the former literature. By numerically solving
the Fokker-Planck equation with both the initial condition and reflecting
boundary condition imposed, we probe the probabilistic evolution of charged AdS
black holes surrounded by quintessence. The peak denoting the initial black
hole state gradually decreases while the other peak starts to grow from zero,
approaching to be a stationary distribution in the long time limit with two
peaks denoting the large and small black holes respectively. We also study the
first passage process of charged AdS black holes surrounded by quintessence and
discuss the relevant quantities. We resolve the Fokker-Planck equation by
adding the absorbing boundary condition for the intermediate transition state.
It is shown intuitively that the peaks located at the large (small) black hole
decay very rapidly, irrespective of the initial black hole state. In all the
procedures above, we have compared the cases with different choices of the
state parameter of quintessence dark energy $\omega_q$. The larger $\omega_q$
is, the faster the initial black hole state decays, showing the effect of
quintessence dark energy. To the best of our knowledge, it is the first probe
on the influence of dark energy on the dynamic phase transition of charged AdS
black hole.
| [
{
"created": "Fri, 23 Apr 2021 12:23:37 GMT",
"version": "v1"
}
] | 2021-11-24 | [
[
"Lan",
"Shan-Quan",
""
],
[
"Mo",
"Jie-Xiong",
""
],
[
"Li",
"Gu-Qiang",
""
],
[
"Xu",
"Xiao-Bao",
""
]
] | Searching for the effect of quintessence dark energy on the kinetics of black hole phase transition, we investigate in detail the dynamic phase transition of charged AdS black holes surrounded by quintessence in this paper. Based on the Gibbs free energy landscape, we obtain the analytic expression of the corresponding Gibbs free energy. As shown in $G_L-r_+$ curve at the phase transition temperature, there exist double wells with the same depth, providing further support on the finding in the former literature. By numerically solving the Fokker-Planck equation with both the initial condition and reflecting boundary condition imposed, we probe the probabilistic evolution of charged AdS black holes surrounded by quintessence. The peak denoting the initial black hole state gradually decreases while the other peak starts to grow from zero, approaching to be a stationary distribution in the long time limit with two peaks denoting the large and small black holes respectively. We also study the first passage process of charged AdS black holes surrounded by quintessence and discuss the relevant quantities. We resolve the Fokker-Planck equation by adding the absorbing boundary condition for the intermediate transition state. It is shown intuitively that the peaks located at the large (small) black hole decay very rapidly, irrespective of the initial black hole state. In all the procedures above, we have compared the cases with different choices of the state parameter of quintessence dark energy $\omega_q$. The larger $\omega_q$ is, the faster the initial black hole state decays, showing the effect of quintessence dark energy. To the best of our knowledge, it is the first probe on the influence of dark energy on the dynamic phase transition of charged AdS black hole. |
gr-qc/0306058 | Kleihaus | B. Kleihaus, J. Kunz, F. Navarro-Lerida | Rotating Dilaton Black Holes with Hair | 49 pages, 13 figures | Phys.Rev. D69 (2004) 064028 | 10.1103/PhysRevD.69.064028 | null | gr-qc hep-th | null | We consider stationary rotating black holes in SU(2) Einstein-Yang-Mills
theory, coupled to a dilaton. The black holes possess non-trivial non-Abelian
electric and magnetic fields outside their regular event horizon. While generic
solutions carry no non-Abelian magnetic charge, but non-Abelian electric
charge, the presence of the dilaton field allows also for rotating solutions
with no non-Abelian charge at all. As a consequence, these special solutions do
not exhibit the generic asymptotic non-integer power fall-off of the
non-Abelian gauge field functions. The rotating black hole solutions form
sequences, characterized by the winding number $n$ and the node number $k$ of
their gauge field functions, tending to embedded Abelian black holes. The
stationary non-Abelian black hole solutions satisfy a mass formula, similar to
the Smarr formula, where the dilaton charge enters instead of the magnetic
charge. Introducing a topological charge, we conjecture, that black hole
solutions in SU(2) Einstein-Yang-Mills-dilaton theory are uniquely
characterized by their mass, their angular momentum, their dilaton charge,
their non-Abelian electric charge, and their topological charge.
| [
{
"created": "Fri, 13 Jun 2003 15:15:16 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Kleihaus",
"B.",
""
],
[
"Kunz",
"J.",
""
],
[
"Navarro-Lerida",
"F.",
""
]
] | We consider stationary rotating black holes in SU(2) Einstein-Yang-Mills theory, coupled to a dilaton. The black holes possess non-trivial non-Abelian electric and magnetic fields outside their regular event horizon. While generic solutions carry no non-Abelian magnetic charge, but non-Abelian electric charge, the presence of the dilaton field allows also for rotating solutions with no non-Abelian charge at all. As a consequence, these special solutions do not exhibit the generic asymptotic non-integer power fall-off of the non-Abelian gauge field functions. The rotating black hole solutions form sequences, characterized by the winding number $n$ and the node number $k$ of their gauge field functions, tending to embedded Abelian black holes. The stationary non-Abelian black hole solutions satisfy a mass formula, similar to the Smarr formula, where the dilaton charge enters instead of the magnetic charge. Introducing a topological charge, we conjecture, that black hole solutions in SU(2) Einstein-Yang-Mills-dilaton theory are uniquely characterized by their mass, their angular momentum, their dilaton charge, their non-Abelian electric charge, and their topological charge. |
0907.2617 | Elisa Manrique | Elisa Manrique and Martin Reuter | Bimetric Truncations for Quantum Einstein Gravity and Asymptotic Safety | 48 pages, 5 figures | Annals Phys.325:785-815,2010 | 10.1016/j.aop.2009.11.009 | MZ-TH/09-17 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the average action approach to the quantization of gravity the fundamental
requirement of "background independence" is met by actually introducing a
background metric but leaving it completely arbitrary. The associated Wilsonian
renormalization group defines a coarse graining flow on a theory space of
functionals which, besides the dynamical metric, depend explicitly on the
background metric. All solutions to the truncated flow equations known to date
have a trivial background field dependence only, namely via the classical gauge
fixing term. In this paper we analyze a number of conceptual issues related to
the bimetric character of the gravitational average action and explore a first
nontrivial bimetric truncation in the simplified setting of conformally reduced
gravity. Possible implications for the Asymptotic Safety program and the
cosmological constant problem are discussed in detail.
| [
{
"created": "Wed, 15 Jul 2009 15:19:04 GMT",
"version": "v1"
}
] | 2010-03-02 | [
[
"Manrique",
"Elisa",
""
],
[
"Reuter",
"Martin",
""
]
] | In the average action approach to the quantization of gravity the fundamental requirement of "background independence" is met by actually introducing a background metric but leaving it completely arbitrary. The associated Wilsonian renormalization group defines a coarse graining flow on a theory space of functionals which, besides the dynamical metric, depend explicitly on the background metric. All solutions to the truncated flow equations known to date have a trivial background field dependence only, namely via the classical gauge fixing term. In this paper we analyze a number of conceptual issues related to the bimetric character of the gravitational average action and explore a first nontrivial bimetric truncation in the simplified setting of conformally reduced gravity. Possible implications for the Asymptotic Safety program and the cosmological constant problem are discussed in detail. |
gr-qc/0108055 | Daniel Finley | Daniel Finley (Univ. of New Mexico) | Equations for Complex-Valued, Twisting, Type N, Vacuum Solutions, with
one or two Killing/homothetic vectors | 7 pages, TeX file, from a talk at GR16, Durban, South Africa, July,
2001 | null | null | null | gr-qc | null | HH-spaces, i.e., complex spacetimes, of Petrov type NxN are determined by a
trio of pde's for two functions, lambda and a, of three independent variables
(and also two gauge functions, chosen to be two of the independent variables if
one prefers). As in common integrable systems, these form a second order,
linear system for lambda; howver, here the integrability conditions, involving
a, are more complicated than is common. Therefore, with the hope of finding new
solutions, these equations are now constrained to also admit both one and two
homothetic or Killing vectors. The case with one Killing and one homothetic
vector reduces these equations to two ode's for two unknown functions of the
one remaining variable.
In addition, we also describe in detail the explicit forms of the metric,
tetrad, connections, and curvature for twisting HH-spaces of Petrov type NxN,
modulo the determining equations. This simplifies considerably the process of
obtaining these details cleanly from earlier articles on the subject, thus
simplifying access to the research area.
| [
{
"created": "Thu, 23 Aug 2001 00:02:29 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Finley",
"Daniel",
"",
"Univ. of New Mexico"
]
] | HH-spaces, i.e., complex spacetimes, of Petrov type NxN are determined by a trio of pde's for two functions, lambda and a, of three independent variables (and also two gauge functions, chosen to be two of the independent variables if one prefers). As in common integrable systems, these form a second order, linear system for lambda; howver, here the integrability conditions, involving a, are more complicated than is common. Therefore, with the hope of finding new solutions, these equations are now constrained to also admit both one and two homothetic or Killing vectors. The case with one Killing and one homothetic vector reduces these equations to two ode's for two unknown functions of the one remaining variable. In addition, we also describe in detail the explicit forms of the metric, tetrad, connections, and curvature for twisting HH-spaces of Petrov type NxN, modulo the determining equations. This simplifies considerably the process of obtaining these details cleanly from earlier articles on the subject, thus simplifying access to the research area. |
1805.00804 | Fazlay Ahmed | Fazlay Ahmed, Muhammed Amir, Sushant G. Ghosh | Particle acceleration of two general particles in the background of
rotating Ay\'{o}n-Beato-Garc\'{i}a black holes | 17 pages, 6 figures | null | 10.1007/s10509-019-3498-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The rotating Ay\'{o}n-Beato-Garc\'{i}a (ABG) black holes, apart from mass
($M$) and rotation parameter ($a$), has an additional charge $Q$ and
encompassed the Kerr black hole as particular case when $Q=0$. We demonstrate
the ergoregions of rotating ABG black holes depend on both rotation parameter
$a$ and charge $Q$, and the area of the ergoregions increases with increase in
the values of $Q$, when compared with the Kerr black hole and the extremal
regular black hole changes with the value of $Q$. Ban{\~a}dos, Silk and West
(BSW) demonstrated that an extremal Kerr black hole can act as a particle
accelerator with arbitrarily high center-of-mass energy ($E_{CM}$) when the
collision takes place at any point in the ergoregion and thus in turn provides
a suitable framework for Plank-scale physics. We study the collision of two
general particles with different masses falling freely from rest in the
equatorial plane of a rotating ABG black hole near the event horizon and find
that the $E_{CM}$ of two colliding particles is arbitrarily high when one of
the particles take a critical value of angular momentum in the extremal case,
whereas for nonextremal case $E_{CM}$ for a pair of colliding particles is
generically divergent at the inner horizon, and explicitly studying the effect
of charge $Q$ on the $E_{CM}$ for ABG black hole. In particular, our results in
the limit $Q\rightarrow 0$ reduce exactly to \emph{vis-$\grave{a}$-vis} those
of the Kerr black hole.
| [
{
"created": "Wed, 2 May 2018 13:48:25 GMT",
"version": "v1"
}
] | 2019-01-23 | [
[
"Ahmed",
"Fazlay",
""
],
[
"Amir",
"Muhammed",
""
],
[
"Ghosh",
"Sushant G.",
""
]
] | The rotating Ay\'{o}n-Beato-Garc\'{i}a (ABG) black holes, apart from mass ($M$) and rotation parameter ($a$), has an additional charge $Q$ and encompassed the Kerr black hole as particular case when $Q=0$. We demonstrate the ergoregions of rotating ABG black holes depend on both rotation parameter $a$ and charge $Q$, and the area of the ergoregions increases with increase in the values of $Q$, when compared with the Kerr black hole and the extremal regular black hole changes with the value of $Q$. Ban{\~a}dos, Silk and West (BSW) demonstrated that an extremal Kerr black hole can act as a particle accelerator with arbitrarily high center-of-mass energy ($E_{CM}$) when the collision takes place at any point in the ergoregion and thus in turn provides a suitable framework for Plank-scale physics. We study the collision of two general particles with different masses falling freely from rest in the equatorial plane of a rotating ABG black hole near the event horizon and find that the $E_{CM}$ of two colliding particles is arbitrarily high when one of the particles take a critical value of angular momentum in the extremal case, whereas for nonextremal case $E_{CM}$ for a pair of colliding particles is generically divergent at the inner horizon, and explicitly studying the effect of charge $Q$ on the $E_{CM}$ for ABG black hole. In particular, our results in the limit $Q\rightarrow 0$ reduce exactly to \emph{vis-$\grave{a}$-vis} those of the Kerr black hole. |
1707.02860 | Yuri Pavlov | Yu. V. Pavlov, O. B. Zaslavskii | Number of revolutions of a particle around a black hole: Is it infinite
or finite? | 19 pages, 3 figures | Gen. Relativ. Gravit. (2018) 50: 14 | 10.1007/s10714-017-2333-5 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a particle falling into a rotating black hole. Such a particle
makes an infinite number of revolutions $n$ from the viewpoint of a remote
observer who uses the Boyer-Lindquist type of coordinates. We examine the
behavior of $n$ when it is measured with respect to a local reference frame
that also rotates due to dragging effect of spacetime. The crucial point
consists here in the observation that for a nonextremal black hole, the leading
contributions to $n$ from a particle itself and the reference frame have the
same form being in fact universal, so that divergences mutually cancel. As a
result, the relative number of revolutions turns out to be finite. For the
extremal black hole this is not so, $n$ can be infinite. Different choices of
the local reference frame are considered, the results turn out to be the same
qualitatively. For illustration, we discuss two explicit examples - rotation in
the flat spacetime and in the Kerr metric.
| [
{
"created": "Mon, 10 Jul 2017 13:49:10 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Jan 2018 16:07:05 GMT",
"version": "v2"
}
] | 2018-01-11 | [
[
"Pavlov",
"Yu. V.",
""
],
[
"Zaslavskii",
"O. B.",
""
]
] | We consider a particle falling into a rotating black hole. Such a particle makes an infinite number of revolutions $n$ from the viewpoint of a remote observer who uses the Boyer-Lindquist type of coordinates. We examine the behavior of $n$ when it is measured with respect to a local reference frame that also rotates due to dragging effect of spacetime. The crucial point consists here in the observation that for a nonextremal black hole, the leading contributions to $n$ from a particle itself and the reference frame have the same form being in fact universal, so that divergences mutually cancel. As a result, the relative number of revolutions turns out to be finite. For the extremal black hole this is not so, $n$ can be infinite. Different choices of the local reference frame are considered, the results turn out to be the same qualitatively. For illustration, we discuss two explicit examples - rotation in the flat spacetime and in the Kerr metric. |
1302.7234 | Norman G\"urlebeck | Norman G\"urlebeck | Source integrals of asymptotic multipole moments | 9 pages, 1 figure, contribution to the proceedings of the conference
"Relativity and Gravitation - 100 Years after Einstein in Prague", June
25-29, 2012, Prague | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive source integrals for multipole moments that describe the behaviour
of static and axially symmetric spacetimes close to spatial infinity. We assume
isolated non-singular sources but will not restrict the matter content
otherwise. Some future applications of these source integrals of the asymptotic
multipole moments are outlined as well.
| [
{
"created": "Thu, 28 Feb 2013 15:34:55 GMT",
"version": "v1"
}
] | 2013-03-01 | [
[
"Gürlebeck",
"Norman",
""
]
] | We derive source integrals for multipole moments that describe the behaviour of static and axially symmetric spacetimes close to spatial infinity. We assume isolated non-singular sources but will not restrict the matter content otherwise. Some future applications of these source integrals of the asymptotic multipole moments are outlined as well. |
gr-qc/9805086 | Hong-Yi Zhou | Hong-Yi Zhou(Tsinghua U.,Beijing) | An Implication of Ether Drift | 6 pages,2 postscript figures | null | null | null | gr-qc | null | The experimental results of the two-photon absorption(TPA) and
M\"{o}ssbauer-rotor(MR) for testing the isotropy of the speed of light are
explained in an ether drift model with a drift velocity of $\sim 10^{-3}c$.
Further tests of the ether drift assumption are suggested.
| [
{
"created": "Fri, 22 May 1998 08:46:47 GMT",
"version": "v1"
},
{
"created": "Mon, 25 May 1998 14:23:29 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Zhou",
"Hong-Yi",
"",
"Tsinghua U.,Beijing"
]
] | The experimental results of the two-photon absorption(TPA) and M\"{o}ssbauer-rotor(MR) for testing the isotropy of the speed of light are explained in an ether drift model with a drift velocity of $\sim 10^{-3}c$. Further tests of the ether drift assumption are suggested. |
1805.02330 | Jiliang Jing | Ruanjing Zhang, Jiliang Jing, Songbai Chen | Strong gravitational lensing for black hole with scalar charge in
massive gravity | 14 pages, 4 figures, 3 tables | Phys. Rev. D 95, (2017) 064054 | 10.1103/PhysRevD.95.064054 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the strong gravitational lensing for black hole with scalar
charge in massive gravity. We find that the scalar charge and the type of the
black hole significantly affect the radius of the photon sphere, deflection
angle, angular image position, angular image separation, relative
magnifications and time delay in strong gravitational lensing. Our results can
be reduced to that of the Schwarzschild and Reissner-Nordstr$\ddot{o}$m black
holes in some special cases.
| [
{
"created": "Mon, 7 May 2018 03:17:08 GMT",
"version": "v1"
}
] | 2018-05-16 | [
[
"Zhang",
"Ruanjing",
""
],
[
"Jing",
"Jiliang",
""
],
[
"Chen",
"Songbai",
""
]
] | We investigate the strong gravitational lensing for black hole with scalar charge in massive gravity. We find that the scalar charge and the type of the black hole significantly affect the radius of the photon sphere, deflection angle, angular image position, angular image separation, relative magnifications and time delay in strong gravitational lensing. Our results can be reduced to that of the Schwarzschild and Reissner-Nordstr$\ddot{o}$m black holes in some special cases. |
gr-qc/9605039 | Robert Mann | C. Alvarez and R.B. Mann | Testing the Equivalence Principle in the Quantum Regime | 6 pages, harvmac, Honorable mention in the Gravity Research
Foundation Essay Contest | Gen.Rel.Grav. 29 (1997) 245-250 | 10.1023/A:1010296229642 | WATPHYS-TH96/07 | gr-qc | null | We consider possible tests of the Einstein Equivalence Principle for physical
systems in which quantum-mechanical vacuum energies cannot be neglected.
Specific tests include a search for the manifestation of non-metric effects in
Lamb-shift transitions of Hydrogenic atoms and in anomalous magnetic moments of
massive leptons. We discuss how current experiments already set bounds on the
violation of the equivalence principle in this sector and how new
(high-precision) measurements of these quantities could provide further
information to this end.
| [
{
"created": "Fri, 17 May 1996 21:31:38 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Alvarez",
"C.",
""
],
[
"Mann",
"R. B.",
""
]
] | We consider possible tests of the Einstein Equivalence Principle for physical systems in which quantum-mechanical vacuum energies cannot be neglected. Specific tests include a search for the manifestation of non-metric effects in Lamb-shift transitions of Hydrogenic atoms and in anomalous magnetic moments of massive leptons. We discuss how current experiments already set bounds on the violation of the equivalence principle in this sector and how new (high-precision) measurements of these quantities could provide further information to this end. |
1611.00654 | Sourav Sur | Sourav Sur and Arshdeep Singh Bhatia | Weakly dynamic dark energy via metric-scalar couplings with torsion | 39 pages, 16 figures, 4 tables | JCAP 1707 (2017) 039 | 10.1088/1475-7516/2017/07/039 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the dynamical aspects of dark energy in the context of a
non-minimally coupled scalar field with curvature and torsion. Whereas the
scalar field acts as the source of the trace mode of torsion, a suitable
constraint on the torsion pseudo-trace provides a mass term for the scalar
field in the effective action. In the equivalent scalar-tensor framework, we
find explicit cosmological solutions representing dark energy in both Einstein
and Jordan frames. We demand the dynamical evolution of the dark energy to be
weak enough, so that the present-day values of the cosmological parameters
could be estimated keeping them within the confidence limits set for the
standard $\L$CDM model from recent observations. For such estimates, we examine
the variations of the effective matter density and the dark energy equation of
state parameters over different redshift ranges. In spite of being weakly
dynamic, the dark energy component differs significantly from the cosmological
constant, both in characteristics and features, for e.g. it interacts with the
cosmological (dust) fluid in the Einstein frame, and crosses the phantom
barrier in the Jordan frame. We also obtain the upper bounds on the torsion
mode parameters and the lower bound on the effective Brans-Dicke parameter. The
latter turns out to be fairly large, and in agreement with the local gravity
constraints, which therefore come in support of our analysis.
| [
{
"created": "Wed, 2 Nov 2016 15:41:24 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Feb 2017 15:47:39 GMT",
"version": "v2"
},
{
"created": "Thu, 17 Aug 2017 10:32:31 GMT",
"version": "v3"
}
] | 2017-08-18 | [
[
"Sur",
"Sourav",
""
],
[
"Bhatia",
"Arshdeep Singh",
""
]
] | We study the dynamical aspects of dark energy in the context of a non-minimally coupled scalar field with curvature and torsion. Whereas the scalar field acts as the source of the trace mode of torsion, a suitable constraint on the torsion pseudo-trace provides a mass term for the scalar field in the effective action. In the equivalent scalar-tensor framework, we find explicit cosmological solutions representing dark energy in both Einstein and Jordan frames. We demand the dynamical evolution of the dark energy to be weak enough, so that the present-day values of the cosmological parameters could be estimated keeping them within the confidence limits set for the standard $\L$CDM model from recent observations. For such estimates, we examine the variations of the effective matter density and the dark energy equation of state parameters over different redshift ranges. In spite of being weakly dynamic, the dark energy component differs significantly from the cosmological constant, both in characteristics and features, for e.g. it interacts with the cosmological (dust) fluid in the Einstein frame, and crosses the phantom barrier in the Jordan frame. We also obtain the upper bounds on the torsion mode parameters and the lower bound on the effective Brans-Dicke parameter. The latter turns out to be fairly large, and in agreement with the local gravity constraints, which therefore come in support of our analysis. |
2006.16652 | Mariano Cadoni | M. Cadoni, M. Tuveri, A. P. Sanna | Long-Range Quantum Gravity | 10 pages, no figure | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is a tantalising possibility that quantum gravity (QG) states remaining
coherent at astrophysical, galactic and cosmological scales could exist and
that they could play a crucial role in understanding macroscopic gravitational
effects. We explore, using only general principles of General Relativity,
quantum and statistical mechanics, the possibility of using long-range QG
states to describe black holes. In particular, we discuss in a critical way the
interplay between various aspects of long-range quantum gravity, such as the
holographic bound, classical and quantum criticality and the recently proposed
quantum thermal generalisation of Einstein's equivalence principle. We also
show how black hole thermodynamics can be easily explained in this framework.
| [
{
"created": "Tue, 30 Jun 2020 10:21:38 GMT",
"version": "v1"
}
] | 2020-07-01 | [
[
"Cadoni",
"M.",
""
],
[
"Tuveri",
"M.",
""
],
[
"Sanna",
"A. P.",
""
]
] | It is a tantalising possibility that quantum gravity (QG) states remaining coherent at astrophysical, galactic and cosmological scales could exist and that they could play a crucial role in understanding macroscopic gravitational effects. We explore, using only general principles of General Relativity, quantum and statistical mechanics, the possibility of using long-range QG states to describe black holes. In particular, we discuss in a critical way the interplay between various aspects of long-range quantum gravity, such as the holographic bound, classical and quantum criticality and the recently proposed quantum thermal generalisation of Einstein's equivalence principle. We also show how black hole thermodynamics can be easily explained in this framework. |
1003.3402 | Martin Scholtz | Jiri Bicak, Martin Scholtz, Paul Tod | On asymptotically flat solutions of Einstein's equations periodic in
time I. Vacuum and electrovacuum solutions | 25 pages, 2 figures, published in Class. Quant. Grav. | Classical and Quantum Gravity, Volume 27, Issue 5, 055007 (2010) | 10.1088/0264-9381/27/5/055007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By an argument similar to that of Gibbons and Stewart, but in a different
coordinate system and less restrictive gauge, we show that any
weakly-asymptotically-simple, analytic vacuum or electrovacuum solutions of the
Einstein equations which are periodic in time are necessarily stationary.
| [
{
"created": "Wed, 17 Mar 2010 16:11:55 GMT",
"version": "v1"
}
] | 2010-03-19 | [
[
"Bicak",
"Jiri",
""
],
[
"Scholtz",
"Martin",
""
],
[
"Tod",
"Paul",
""
]
] | By an argument similar to that of Gibbons and Stewart, but in a different coordinate system and less restrictive gauge, we show that any weakly-asymptotically-simple, analytic vacuum or electrovacuum solutions of the Einstein equations which are periodic in time are necessarily stationary. |
1302.1245 | Jian-Yang Zhu | Xiao Liu, Kui Xiao and Jian-Yang Zhu | Dynamical behaviors of FRW Universe containing a positive/negative
potential scalar field in loop quantum cosmology | 6 pages, 2 figures, accepted for publication in General Relativity
and Gravitation | Gen. Relativ. Gravit. 45, 1021 (2013) | 10.1007/s10714-013-1511-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamical behaviors of FRW Universe containing a posivive/negative
potential scalar field in loop quantum cosmology scenario are discussed. The
method of the phase-plane analysis is used to investigate the stability of the
Universe. It is found that the stability properties in this situation are quite
different from the classical cosmology case. For a positive potential scalar
field coupled with a barotropic fluid, the cosmological autonomous system has
five fixed points and one of them is stable if the adiabatic index $\gamma$
satisfies $0<\gamma<2$. This leads to the fact that the universe just have one
bounce point instead of the singularity which lies in the quantum dominated
area and it is caused by the quantum geometry effect. There are four fixed
points if one considers a scalar field with a negative potential, but none of
them is stable. Therefore, the universe has two kinds of bounce points, one is
caused by the quantum geometry effect and the other is caused by the negative
potential, the Universe may enter a classical re-collapse after the quantum
bounce. This hints that the spatially flat FRW Universe containing a negative
potential scalar field is cyclic.
| [
{
"created": "Wed, 6 Feb 2013 02:16:04 GMT",
"version": "v1"
}
] | 2014-02-03 | [
[
"Liu",
"Xiao",
""
],
[
"Xiao",
"Kui",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | The dynamical behaviors of FRW Universe containing a posivive/negative potential scalar field in loop quantum cosmology scenario are discussed. The method of the phase-plane analysis is used to investigate the stability of the Universe. It is found that the stability properties in this situation are quite different from the classical cosmology case. For a positive potential scalar field coupled with a barotropic fluid, the cosmological autonomous system has five fixed points and one of them is stable if the adiabatic index $\gamma$ satisfies $0<\gamma<2$. This leads to the fact that the universe just have one bounce point instead of the singularity which lies in the quantum dominated area and it is caused by the quantum geometry effect. There are four fixed points if one considers a scalar field with a negative potential, but none of them is stable. Therefore, the universe has two kinds of bounce points, one is caused by the quantum geometry effect and the other is caused by the negative potential, the Universe may enter a classical re-collapse after the quantum bounce. This hints that the spatially flat FRW Universe containing a negative potential scalar field is cyclic. |
gr-qc/9901009 | Kechkin Oleg V. | Oleg V. Kechkin | Charging Symmetries and Linearizing Potentials for Gravity Models with
Symplectic Symmetry | 12 pages in LaTex | Gen.Rel.Grav. 31 (1999) 1075-1086 | 10.1023/A:1026791817196 | null | gr-qc | null | In this paper we continue to study a class of four-dimensional gravity models
with n Abelian vector fields and Sp(2n)/U(n) coset of scalar fields. This class
contains General Relativity (n=0) and Einstein-Maxwell dilaton-axion theory
(n=1), which arizes in the low-energy limit of heterotic string theory. We
perform reduction of the model with arbitrary $n$ to three dimensions and study
the subgroup of non-gauge symmetries of the resulting theory. First, we find an
explicit form these symmetries using Ernst matrix potential formulation.
Second, we construct new matrix variable which linearly transforms under the
action of the non-gauge transformations. Finally, we establish one general
invariant of the non-gauge symmetry subgroup, which allow us to clarify this
subgroup structure.
| [
{
"created": "Tue, 5 Jan 1999 16:45:36 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Kechkin",
"Oleg V.",
""
]
] | In this paper we continue to study a class of four-dimensional gravity models with n Abelian vector fields and Sp(2n)/U(n) coset of scalar fields. This class contains General Relativity (n=0) and Einstein-Maxwell dilaton-axion theory (n=1), which arizes in the low-energy limit of heterotic string theory. We perform reduction of the model with arbitrary $n$ to three dimensions and study the subgroup of non-gauge symmetries of the resulting theory. First, we find an explicit form these symmetries using Ernst matrix potential formulation. Second, we construct new matrix variable which linearly transforms under the action of the non-gauge transformations. Finally, we establish one general invariant of the non-gauge symmetry subgroup, which allow us to clarify this subgroup structure. |
1504.03173 | Lorenzo Sebastiani | Shynaray Myrzakul, Ratbay Myrzakulov and Lorenzo Sebastiani | Inhomogeneous fluids for warm inflation | 11 pages, final version accepted in Astrophys.Space Sci | Astrophys.Space Sci. 357 (2015) 2, 168 | 10.1007/s10509-015-2397-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inhomogeneous fluid models for warm inflation are investigated. The
early-time acceleration is supported by inhomogeneous fluid whose coupling with
radiation leads to the radiation dominated era after inflation. Several
examples are analyzed, strong dissipation regime is discussed, and the
viability of the models respect to the last Planck data is verified.
| [
{
"created": "Fri, 10 Apr 2015 03:52:14 GMT",
"version": "v1"
},
{
"created": "Wed, 20 May 2015 07:01:25 GMT",
"version": "v2"
}
] | 2015-09-21 | [
[
"Myrzakul",
"Shynaray",
""
],
[
"Myrzakulov",
"Ratbay",
""
],
[
"Sebastiani",
"Lorenzo",
""
]
] | Inhomogeneous fluid models for warm inflation are investigated. The early-time acceleration is supported by inhomogeneous fluid whose coupling with radiation leads to the radiation dominated era after inflation. Several examples are analyzed, strong dissipation regime is discussed, and the viability of the models respect to the last Planck data is verified. |
2008.10090 | Tim Koslowski A | Alicia Castro, Tim Koslowski | Renormalization Group Approach to the Continuum Limit of Matrix Models
of Quantum Gravity with Preferred Foliation | 12 pages, 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This contribution is not intended as a review but, by suggestion of the
editors, as a glimpse ahead into the realm of dually weighted tensor models for
quantum gravity. This class of models allows one to consider a wider class of
quantum gravity models, in particular one can formulate state sum models of
spacetime with an intrinsic notion of foliation. The simplest one of these
models is the one proposed by Benedetti and Henson, which is a matrix model
formulation of two-dimensional Causal Dynamical Triangulations (CDT). In this
paper we apply the Functional Renormalization Group Equation (FRGE) to the
Benedetti-Henson model with the purpose of investigating the possible continuum
limits of this class of models. Possible continuum limits appear in this FRGE
approach as fixed points of the renormalization group flow where the size of
the matrix acts as the renormalization scale. Considering very small
truncations, we find fixed points that are compatible with analytically known
results for CDT in two dimensions. By studying the scheme dependence of our
results we find that precision results require larger truncations than the ones
considered in the present work. We conclude that our work suggests that the
FRGE is a useful exploratory tool for dually weighted matrix models. We thus
expect that the FRGE will be a useful exploratory tool for the investigation of
dually weighted tensor models for CDT in higher dimensions.
| [
{
"created": "Sun, 23 Aug 2020 18:33:26 GMT",
"version": "v1"
}
] | 2020-08-25 | [
[
"Castro",
"Alicia",
""
],
[
"Koslowski",
"Tim",
""
]
] | This contribution is not intended as a review but, by suggestion of the editors, as a glimpse ahead into the realm of dually weighted tensor models for quantum gravity. This class of models allows one to consider a wider class of quantum gravity models, in particular one can formulate state sum models of spacetime with an intrinsic notion of foliation. The simplest one of these models is the one proposed by Benedetti and Henson, which is a matrix model formulation of two-dimensional Causal Dynamical Triangulations (CDT). In this paper we apply the Functional Renormalization Group Equation (FRGE) to the Benedetti-Henson model with the purpose of investigating the possible continuum limits of this class of models. Possible continuum limits appear in this FRGE approach as fixed points of the renormalization group flow where the size of the matrix acts as the renormalization scale. Considering very small truncations, we find fixed points that are compatible with analytically known results for CDT in two dimensions. By studying the scheme dependence of our results we find that precision results require larger truncations than the ones considered in the present work. We conclude that our work suggests that the FRGE is a useful exploratory tool for dually weighted matrix models. We thus expect that the FRGE will be a useful exploratory tool for the investigation of dually weighted tensor models for CDT in higher dimensions. |
2308.04875 | Paul Frampton | Paul H. Frampton | Kerr-Newman and Electromagnetic acceleration | 7 pages LaTeX. A new Section 4 included; additional references added | null | null | null | gr-qc astro-ph.CO hep-ph | http://creativecommons.org/licenses/by/4.0/ | Previous discussions of charged dark matter neglected PBH spin and employed
the Reissner-Nordstrom metric. In Nature we expect the PBHs to possess spin
which require use of the technically more challenging Kerr-Newman metric. It is
shown that the use of K-N metric retains the principal properties already
obtained using the R-N metric, in particular the dominance of Coulomb repulsion
requires super-extremality and the presence of naked singularities. In this
sense, the spin of the PBHs is not an essential complication.
| [
{
"created": "Tue, 8 Aug 2023 17:53:42 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Feb 2024 15:10:04 GMT",
"version": "v2"
}
] | 2024-02-06 | [
[
"Frampton",
"Paul H.",
""
]
] | Previous discussions of charged dark matter neglected PBH spin and employed the Reissner-Nordstrom metric. In Nature we expect the PBHs to possess spin which require use of the technically more challenging Kerr-Newman metric. It is shown that the use of K-N metric retains the principal properties already obtained using the R-N metric, in particular the dominance of Coulomb repulsion requires super-extremality and the presence of naked singularities. In this sense, the spin of the PBHs is not an essential complication. |
2004.05121 | Francisco Lobo | Marzieh Peyravi, Nematollah Riazi, Francisco S. N. Lobo | Novel thick brane solutions with $U(1)$ symmetry breaking | 14 pages, 9 figures. Comments welcome. V2: discussion and references
added. Version to appear in Eur.Phys.J.C | Eur. Phys. J. C 81, 216 (2021) | 10.1140/epjc/s10052-021-08988-y | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, using two scalar fields ($\phi$, $\psi$) coupled to 4+1
dimensional gravity, we construct novel topological brane solutions through an
explicit $U(1)$ symmetry breaking term. The potential of this model is
constructed so that two distinct degenerate vacua in the $\phi$ field exist, in
analogy to the $\phi^{4}$ potential. Therefore, brane solutions appear due to
the vacuum structure of the $\phi$ field. However, the topology and vacuum
structure in the $\psi$ direction depends on the symmetry breaking parameter
$\beta^{2}$, which leads to different types of branes. As a result, one can
interpret the present model as a combination of a $\phi^{4}$ brane with an
auxiliary field, which leads to deviations from the $\phi^{4}$ system with the
brane achieving a richer internal structure. Furthermore, we analyse in detail
the behaviour of the superpotentials, the warp factors, the Ricci and
Kretschmann scalars and the Einstein tensor components. In addition to this, we
explore the stability of the brane in terms of the free parameters of the
model. The analysis presented here complements previous work and is
sufficiently novel to be interesting.
| [
{
"created": "Fri, 10 Apr 2020 17:06:48 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Feb 2021 16:24:50 GMT",
"version": "v2"
}
] | 2021-03-08 | [
[
"Peyravi",
"Marzieh",
""
],
[
"Riazi",
"Nematollah",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | In this work, using two scalar fields ($\phi$, $\psi$) coupled to 4+1 dimensional gravity, we construct novel topological brane solutions through an explicit $U(1)$ symmetry breaking term. The potential of this model is constructed so that two distinct degenerate vacua in the $\phi$ field exist, in analogy to the $\phi^{4}$ potential. Therefore, brane solutions appear due to the vacuum structure of the $\phi$ field. However, the topology and vacuum structure in the $\psi$ direction depends on the symmetry breaking parameter $\beta^{2}$, which leads to different types of branes. As a result, one can interpret the present model as a combination of a $\phi^{4}$ brane with an auxiliary field, which leads to deviations from the $\phi^{4}$ system with the brane achieving a richer internal structure. Furthermore, we analyse in detail the behaviour of the superpotentials, the warp factors, the Ricci and Kretschmann scalars and the Einstein tensor components. In addition to this, we explore the stability of the brane in terms of the free parameters of the model. The analysis presented here complements previous work and is sufficiently novel to be interesting. |
2102.08618 | Stefano Viaggiu | Stefano Viaggiu | The physical nature of the cosmological constant and the decoherence
scale in a renormalization-group approach | Accepted for publication in Int. J. Mod. Phys. D | IJMPD Vol. 30 Issue No. 06, Article No. 2150043, Year 2021 | 10.1142/S0218271821500437 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we consider the nature of the cosmological constant as due by
quantum fluctuations. Quantum fluctuations are generated at Planckian scales by
noncommutative effects and watered down at larger scales up to a decoherence
scale $L_D$ where classicality is reached. In particular, we formally depict
the presence of the scale at $L_D$ by adopting a renormalization group
approach. As a result, an analogy arises between the expression for the
observed cosmological constant $\overline{\Lambda}$ generated by quantum
fluctuations and the one expected by a renormalization group approach, provided
that the renormalization scale $\mu$ is suitably chosen. In this framework, the
decoherence scale $L_D$ is naturally identified with the value ${\mu}_D$, with
$\hbar{\mu}_D$ representing the minimum allowed particle-momentum for our
visible universe. Finally, by mimicking renormalization group approach, we
present a technique to formally obtain a non-trivial infrared (IR) fixed point
at $\mu=\mu_D$ in our model.
| [
{
"created": "Wed, 17 Feb 2021 07:45:31 GMT",
"version": "v1"
},
{
"created": "Fri, 7 May 2021 13:35:09 GMT",
"version": "v2"
}
] | 2021-05-10 | [
[
"Viaggiu",
"Stefano",
""
]
] | In this paper we consider the nature of the cosmological constant as due by quantum fluctuations. Quantum fluctuations are generated at Planckian scales by noncommutative effects and watered down at larger scales up to a decoherence scale $L_D$ where classicality is reached. In particular, we formally depict the presence of the scale at $L_D$ by adopting a renormalization group approach. As a result, an analogy arises between the expression for the observed cosmological constant $\overline{\Lambda}$ generated by quantum fluctuations and the one expected by a renormalization group approach, provided that the renormalization scale $\mu$ is suitably chosen. In this framework, the decoherence scale $L_D$ is naturally identified with the value ${\mu}_D$, with $\hbar{\mu}_D$ representing the minimum allowed particle-momentum for our visible universe. Finally, by mimicking renormalization group approach, we present a technique to formally obtain a non-trivial infrared (IR) fixed point at $\mu=\mu_D$ in our model. |
1611.07293 | Leandros Perivolaropoulos | Leandros Perivolaropoulos | Sub-millimeter Spatial Oscillations of Newton's Constant: Theoretical
Models and Laboratory Tests | 21 pages, 15 Figures. Published version (Phys. Rev. D 95, 084050,
2017). Typos corrected in eqs. (3.23), (3.34), (3.35). The Mathematica file
producing the Figures of the paper along with the data analysis is unchanged
and is publicly available at http://leandros.physics.uoi.gr/newt-oscil/ | Phys. Rev. D 95, 084050 (2017) | 10.1103/PhysRevD.95.084050 | null | gr-qc astro-ph.CO hep-ex hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the viability of sub-millimeter wavelength oscillating
deviations from the Newtonian potential at both the theoretical and the
experimental/observational level. At the theoretical level such deviations are
generic predictions in a wide range of extensions of General Relativity (GR)
including $f(R)$ theories, massive Brans-Dicke theories, compactified extra
dimension models and nonlocal extensions of GR. However, the range of
parameters associated with such oscillating deviations is usually connected
with instabilities. An exception emerges in nonlocal gravity theories where
oscillating deviations from Newtonian potential occur naturally on
sub-millimeter scales without instabilities. As an example of a model with
unstable Newtonian oscillations we review an $f(R)$ expansion around General
Relativity of the form $f(R)=R+\frac{1}{6 m^2} R^2$ with $m^2<0$ pointing out
possible stabilization mechanisms. As an example of a model with stable
Newtonian oscillations we discuss nonlocal gravity theories. If such
oscillations are realized in Nature on sub-millimeter scales, a signature is
expected in torsion balance experiments testing Newton's law. We search for
such a signature in the torsion balance data of the Washington experiment
(combined torque residuals) testing Newton's law at sub-millimeter scales. We
show that an oscillating residual ansatz with spatial wavelength $\lambda
\simeq 0.1mm$ provides a better fit to the data compared to the residual
Newtonian constant ansatz by $\Delta \chi^2 = -15$. Similar improved fits, also
occur in about $10\%$ of Monte Carlo realizations of Newtonian data. Thus, the
significance level of this improved fit is at a level of not more than
$2\sigma$. The energy scale corresponding to this best fit wavelength is
identical to the dark energy length scale $\lambda_{de} \equiv\sqrt[4]{\hbar
c/\rho_{ de}}\approx 0.1mm$.
| [
{
"created": "Tue, 22 Nov 2016 13:28:29 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Apr 2017 16:48:51 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Apr 2017 10:59:21 GMT",
"version": "v3"
}
] | 2017-05-10 | [
[
"Perivolaropoulos",
"Leandros",
""
]
] | We investigate the viability of sub-millimeter wavelength oscillating deviations from the Newtonian potential at both the theoretical and the experimental/observational level. At the theoretical level such deviations are generic predictions in a wide range of extensions of General Relativity (GR) including $f(R)$ theories, massive Brans-Dicke theories, compactified extra dimension models and nonlocal extensions of GR. However, the range of parameters associated with such oscillating deviations is usually connected with instabilities. An exception emerges in nonlocal gravity theories where oscillating deviations from Newtonian potential occur naturally on sub-millimeter scales without instabilities. As an example of a model with unstable Newtonian oscillations we review an $f(R)$ expansion around General Relativity of the form $f(R)=R+\frac{1}{6 m^2} R^2$ with $m^2<0$ pointing out possible stabilization mechanisms. As an example of a model with stable Newtonian oscillations we discuss nonlocal gravity theories. If such oscillations are realized in Nature on sub-millimeter scales, a signature is expected in torsion balance experiments testing Newton's law. We search for such a signature in the torsion balance data of the Washington experiment (combined torque residuals) testing Newton's law at sub-millimeter scales. We show that an oscillating residual ansatz with spatial wavelength $\lambda \simeq 0.1mm$ provides a better fit to the data compared to the residual Newtonian constant ansatz by $\Delta \chi^2 = -15$. Similar improved fits, also occur in about $10\%$ of Monte Carlo realizations of Newtonian data. Thus, the significance level of this improved fit is at a level of not more than $2\sigma$. The energy scale corresponding to this best fit wavelength is identical to the dark energy length scale $\lambda_{de} \equiv\sqrt[4]{\hbar c/\rho_{ de}}\approx 0.1mm$. |
1609.09461 | Venanzi Marta Miss | Giovanni Montani, Marta Venanzi | Bianchi I cosmology in the presence of a causally regularized viscous
fluid | null | null | 10.1140/epjc/s10052-017-5042-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the dynamics of a Bianchi I cosmology in the presence of a viscous
fluid, causally regularized according to the Lichnerowicz approach. We show how
the effect induced by shear viscosity is still able to produce a matter
creation phenomenon, meaning that also in the regularized theory we address,
the Universe is emerging from a singularity with a vanishing energy density
value. We discuss the structure of the singularity in the isotropic limit, when
bulk viscosity is the only retained contribution. We see that, as far as
viscosity is not a dominant effect, the dynamics of the isotropic Universe
possesses the usual inviscid power-law behavior but in correspondence of
aneffective equation of state, depending on the bulk viscosity coefficient.
Finally, we show that, in the limit of a strong non-thermodynamical equilibrium
of the Universe mimicked by a dominant contribution of the effective viscous
pressure, a power-law inflation behavior of the Universe appears, the
cosmological horizons are removed and a significant amount of entropy is
produced.
| [
{
"created": "Thu, 29 Sep 2016 18:54:52 GMT",
"version": "v1"
},
{
"created": "Sat, 1 Oct 2016 20:25:32 GMT",
"version": "v2"
},
{
"created": "Wed, 22 Feb 2017 16:26:17 GMT",
"version": "v3"
}
] | 2017-09-13 | [
[
"Montani",
"Giovanni",
""
],
[
"Venanzi",
"Marta",
""
]
] | We analyze the dynamics of a Bianchi I cosmology in the presence of a viscous fluid, causally regularized according to the Lichnerowicz approach. We show how the effect induced by shear viscosity is still able to produce a matter creation phenomenon, meaning that also in the regularized theory we address, the Universe is emerging from a singularity with a vanishing energy density value. We discuss the structure of the singularity in the isotropic limit, when bulk viscosity is the only retained contribution. We see that, as far as viscosity is not a dominant effect, the dynamics of the isotropic Universe possesses the usual inviscid power-law behavior but in correspondence of aneffective equation of state, depending on the bulk viscosity coefficient. Finally, we show that, in the limit of a strong non-thermodynamical equilibrium of the Universe mimicked by a dominant contribution of the effective viscous pressure, a power-law inflation behavior of the Universe appears, the cosmological horizons are removed and a significant amount of entropy is produced. |
gr-qc/0011091 | David Blaschke | D. Behnke, D. Blaschke, V. Pervushin, D. Proskurin, A. Zakharov | Cosmological Consequences of Conformal General Relativity | 12 pages, talk presented at "Hot Points in Astrophysics", JINR Dubna,
Russia, August 22-26, 2000 | null | null | MPG-VT-UR 210/00 | gr-qc | null | We consider cosmological consequences of a conformal-invariant unified theory
which is dynamically equivalent to general relativity and is given in a space
with the geometry of similarity. We show that the conformal-invariant theory
offers new explanations for to such problems as the arrow of time, initial
cosmic data, dark matter and accelerating evolution of the universe in the dust
stage.
| [
{
"created": "Sun, 26 Nov 2000 18:06:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Behnke",
"D.",
""
],
[
"Blaschke",
"D.",
""
],
[
"Pervushin",
"V.",
""
],
[
"Proskurin",
"D.",
""
],
[
"Zakharov",
"A.",
""
]
] | We consider cosmological consequences of a conformal-invariant unified theory which is dynamically equivalent to general relativity and is given in a space with the geometry of similarity. We show that the conformal-invariant theory offers new explanations for to such problems as the arrow of time, initial cosmic data, dark matter and accelerating evolution of the universe in the dust stage. |
2108.04858 | Alexander Zhidenko | M. S. Churilova, R. A. Konoplya, A. Zhidenko | Analytic formula for quasinormal modes in the near-extreme
Kerr-Newman-de Sitter spacetime governed by a non-P\"oschl-Teller potential | 9 pages | Phys. Rev. D 105, 084003 (2022) | 10.1103/PhysRevD.105.084003 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quasinormal modes of scalar, electromagnetic, and gravitational fields in the
extreme Schwarzschild-de Sitter background are known to be expressed in
analytic form as eigenvalues of the P\"oschl-Teller wavelike equation. We show
that perturbations of fermionic fields (given by Dirac and Rarita-Schwinger
equations) do not lead to the P\"oschl-Teller effective potential.
Nevertheless, using the Frobenius method we find quasinormal modes analytically
in this case as well. We write down the analytical formula for quasinormal
frequencies of the near-extreme Schwarzschild-de Sitter black holes, which is
valid for both bosonic and fermionic fields. We further extend the analysis to
the case of charged rotating black holes and find a general analytical formula
for quasinormal modes of the fields of various spin for the near extreme
Kerr-Newman-de Sitter spacetime.
| [
{
"created": "Tue, 10 Aug 2021 18:18:51 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Apr 2022 15:34:36 GMT",
"version": "v2"
}
] | 2022-04-07 | [
[
"Churilova",
"M. S.",
""
],
[
"Konoplya",
"R. A.",
""
],
[
"Zhidenko",
"A.",
""
]
] | Quasinormal modes of scalar, electromagnetic, and gravitational fields in the extreme Schwarzschild-de Sitter background are known to be expressed in analytic form as eigenvalues of the P\"oschl-Teller wavelike equation. We show that perturbations of fermionic fields (given by Dirac and Rarita-Schwinger equations) do not lead to the P\"oschl-Teller effective potential. Nevertheless, using the Frobenius method we find quasinormal modes analytically in this case as well. We write down the analytical formula for quasinormal frequencies of the near-extreme Schwarzschild-de Sitter black holes, which is valid for both bosonic and fermionic fields. We further extend the analysis to the case of charged rotating black holes and find a general analytical formula for quasinormal modes of the fields of various spin for the near extreme Kerr-Newman-de Sitter spacetime. |
gr-qc/0207086 | Etesi Gabor | Gabor Etesi (Renyi Institute, Hungary) | Note on a reformulation of the strong cosmic censor conjceture based on
computability | LaTeX, 9 pages, 1 eps-figure; minor typos corrected and journal
reference added | Phys.Lett. B550 (2002) 1-7 | 10.1016/S0370-2693(02)02966-0 | null | gr-qc | null | In this letter we provide a reformulation of the strong cosmic censor
conjecture taking into account recent results on Malament--Hogarth space-times.
We claim that the strong version of the cosmic censor conjecture can be
formulated by postulating that a physically relevant space-time is either
globally hyperbolic or possesses the Malament--Hogarth property. But it is
known that a Malament--Hogarth space-time in principle is capable for
performing non-Turing computations such as checking consistency of ZFC set
theory. In this way we get an intimate conjectured link between the cosmic
censorship scenario and computability theory.
| [
{
"created": "Mon, 22 Jul 2002 17:09:56 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Nov 2002 12:34:40 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Etesi",
"Gabor",
"",
"Renyi Institute, Hungary"
]
] | In this letter we provide a reformulation of the strong cosmic censor conjecture taking into account recent results on Malament--Hogarth space-times. We claim that the strong version of the cosmic censor conjecture can be formulated by postulating that a physically relevant space-time is either globally hyperbolic or possesses the Malament--Hogarth property. But it is known that a Malament--Hogarth space-time in principle is capable for performing non-Turing computations such as checking consistency of ZFC set theory. In this way we get an intimate conjectured link between the cosmic censorship scenario and computability theory. |
1107.5334 | Christian Corda cordac | Christian Corda | Effective temperature for black holes | 10 pages,accepted for publication in Journal of High Energy Physics.
Comments are welcome | Journal of High Energy Physics Volume 2011, Number 8, 101 | 10.1007/JHEP08(2011)101 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The physical interpretation of black hole's quasinormal modes is fundamental
for realizing unitary quantum gravity theory as black holes are considered
theoretical laboratories for testing models of such an ultimate theory and
their quasinormal modes are natural candidates for an interpretation in terms
of quantum levels. The spectrum of black hole's quasinormal modes can be
re-analysed by introducing a black hole's effective temperature which takes
into account the fact that, as shown by Parikh and Wilczek, the radiation
spectrum cannot be strictly thermal. This issue changes in a fundamental way
the physical understanding of such a spectrum and enables a re-examination of
various results in the literature which realizes important modifies on quantum
physics of black holes. In particular, the formula of the horizon's area
quantization and the number of quanta of area result modified becoming
functions of the quantum "overtone" number n. Consequently, the famous formula
of Bekenstein-Hawking entropy, its sub-leading corrections and the number of
microstates are also modified. Black hole's entropy results a function of the
quantum overtone number too. We emphasize that this is the first time that
black hole's entropy is directly connected with a quantum number. Previous
results in the literature are re-obtained in the limit n \to \infty.
| [
{
"created": "Tue, 26 Jul 2011 21:06:21 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jul 2011 14:11:56 GMT",
"version": "v2"
}
] | 2011-09-15 | [
[
"Corda",
"Christian",
""
]
] | The physical interpretation of black hole's quasinormal modes is fundamental for realizing unitary quantum gravity theory as black holes are considered theoretical laboratories for testing models of such an ultimate theory and their quasinormal modes are natural candidates for an interpretation in terms of quantum levels. The spectrum of black hole's quasinormal modes can be re-analysed by introducing a black hole's effective temperature which takes into account the fact that, as shown by Parikh and Wilczek, the radiation spectrum cannot be strictly thermal. This issue changes in a fundamental way the physical understanding of such a spectrum and enables a re-examination of various results in the literature which realizes important modifies on quantum physics of black holes. In particular, the formula of the horizon's area quantization and the number of quanta of area result modified becoming functions of the quantum "overtone" number n. Consequently, the famous formula of Bekenstein-Hawking entropy, its sub-leading corrections and the number of microstates are also modified. Black hole's entropy results a function of the quantum overtone number too. We emphasize that this is the first time that black hole's entropy is directly connected with a quantum number. Previous results in the literature are re-obtained in the limit n \to \infty. |
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