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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2007.04123 | Carlos A. Batista da S. Filho | Thiago M. Mergulh\~ao and Carlos Batista | On the Equivalence of Spacetimes, the Cartan-Karlhede Algorithm | Didactic paper, intended to beginners on the field. 13 pages | Rev. Bras. Ensino F\'is. vol.42 (2020), e20200041 | 10.1590/1806-9126-rbef-2020-0041 | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known that in general relativity theory two spacetimes whose
metrics are related by a coordinate transformation are physically equivalent.
However, given two line elements, it is virtually impossible to implement the
most general coordinate transformation in order to check the equivalence of the
spacetimes. In this paper we present the so-called Cartan-Karlhede algorithm,
which provides a finite sequence of steps to decide whether or not two metrics
are equivalent. The point of this note is to illustrate the method through
several simple examples, so that the reader can learn the fundamentals and
details of the algorithm in practice.
| [
{
"created": "Wed, 8 Jul 2020 13:45:37 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Jul 2020 15:01:56 GMT",
"version": "v2"
}
] | 2020-08-03 | [
[
"Mergulhão",
"Thiago M.",
""
],
[
"Batista",
"Carlos",
""
]
] | It is well known that in general relativity theory two spacetimes whose metrics are related by a coordinate transformation are physically equivalent. However, given two line elements, it is virtually impossible to implement the most general coordinate transformation in order to check the equivalence of the spacetimes. In this paper we present the so-called Cartan-Karlhede algorithm, which provides a finite sequence of steps to decide whether or not two metrics are equivalent. The point of this note is to illustrate the method through several simple examples, so that the reader can learn the fundamentals and details of the algorithm in practice. |
2209.05608 | Maciej Maliborski | Jo\"el Kurzweil and Maciej Maliborski | Resonant Dynamics and the Instability of the Box Minkowski Model | 30 pages, 14 figures, v2: matches published version | null | 10.1103/PhysRevD.106.124020 | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the box Minkowski model [Phys. Rev. Lett. 109, 221101 (2012)] and
provide a strong argument that, subject to the Dirichlet boundary condition, it
is unstable toward black hole formation for arbitrarily small generic
perturbations. Using weakly nonlinear perturbation theory, we derive the
resonant system, which compared to systems with the anti-de Sitter asymptotics,
has extra resonant terms, and study its properties, including conserved
quantities. We find that the generic solution of the resonant system becomes
singular in finite time. Surprisingly, the additional resonant interactions do
not significantly affect the singular evolution. Furthermore, we find that the
interaction coefficients take a relatively simple form, making this a
particularly attractive toy model of turbulent gravitational instability.
| [
{
"created": "Mon, 12 Sep 2022 20:56:41 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Jan 2023 13:33:10 GMT",
"version": "v2"
}
] | 2023-01-11 | [
[
"Kurzweil",
"Joël",
""
],
[
"Maliborski",
"Maciej",
""
]
] | We revisit the box Minkowski model [Phys. Rev. Lett. 109, 221101 (2012)] and provide a strong argument that, subject to the Dirichlet boundary condition, it is unstable toward black hole formation for arbitrarily small generic perturbations. Using weakly nonlinear perturbation theory, we derive the resonant system, which compared to systems with the anti-de Sitter asymptotics, has extra resonant terms, and study its properties, including conserved quantities. We find that the generic solution of the resonant system becomes singular in finite time. Surprisingly, the additional resonant interactions do not significantly affect the singular evolution. Furthermore, we find that the interaction coefficients take a relatively simple form, making this a particularly attractive toy model of turbulent gravitational instability. |
gr-qc/0611032 | Dr. Anirudh Pradhan | Mahesh Kumar Yadav, Anju Rai and Anirudh Pradhan | Some Bianchi Type III String Cosmological Models with Bulk Viscosity | 12 pages, no figure. To appear in Int. J. Theor. Phys | Int.J.Theor.Phys.46:2677-2687,2007 | 10.1007/s10773-007-9381-7 | null | gr-qc | null | We investigate the integrability of cosmic strings in Bianchi III space-time
in presence of a bulk viscous fluid by applying a new technique. The behaviour
of the model is reduced to the solution of a single second order nonlinear
differential equation. We show that this equation admits an infinite family of
solutions. Some physical consequences from these results are also discussed.
| [
{
"created": "Sun, 5 Nov 2006 12:45:07 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Dec 2006 10:50:23 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Yadav",
"Mahesh Kumar",
""
],
[
"Rai",
"Anju",
""
],
[
"Pradhan",
"Anirudh",
""
]
] | We investigate the integrability of cosmic strings in Bianchi III space-time in presence of a bulk viscous fluid by applying a new technique. The behaviour of the model is reduced to the solution of a single second order nonlinear differential equation. We show that this equation admits an infinite family of solutions. Some physical consequences from these results are also discussed. |
1507.08194 | Dah-Wei Chiou | Steven Carlip, Dah-Wei Chiou, Wei-Tou Ni, Richard Woodard | Quantum Gravity: A Brief History of Ideas and Some Prospects | Invited review article. A few parts based on arXiv:1410.1486 and
arXiv:1412.4362. To appear in Int. J. Mod. Phys. D and in "One Hundred Years
of General Relativity: From Genesis and Empirical Foundations to
Gravitational Waves, Cosmology and Quantum Gravity," edited by Wei-Tou Ni
(World Scientific, Singapore, 2015) | Int. J. Mod. Phys. D, Vol. 24, No. 11 (2015) 1530028 | 10.1142/S0218271815300281 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a bird's-eye survey on the development of fundamental ideas of
quantum gravity, placing emphasis on perturbative approaches, string theory,
loop quantum gravity, and black hole thermodynamics. The early ideas at the
dawn of quantum gravity as well as the possible observations of quantum
gravitational effects in the foreseeable future are also briefly discussed.
| [
{
"created": "Wed, 29 Jul 2015 15:52:13 GMT",
"version": "v1"
}
] | 2016-02-03 | [
[
"Carlip",
"Steven",
""
],
[
"Chiou",
"Dah-Wei",
""
],
[
"Ni",
"Wei-Tou",
""
],
[
"Woodard",
"Richard",
""
]
] | We present a bird's-eye survey on the development of fundamental ideas of quantum gravity, placing emphasis on perturbative approaches, string theory, loop quantum gravity, and black hole thermodynamics. The early ideas at the dawn of quantum gravity as well as the possible observations of quantum gravitational effects in the foreseeable future are also briefly discussed. |
gr-qc/9501028 | Robert Bruce Mann | K.C.K. Chan and R.B. Mann | Exact Black Hole and Cosmological Solutions in a Two-Dimensional
Dilaton-Spectator Theory of Gravity | 34 pgs. Plain Tex, revised version contains some clarifying comments
concerning the relationship between the constants of integration and the
coupling constants. | Class.Quant.Grav.12:1609-1640,1995 | 10.1088/0264-9381/12/7/006 | WATPHYS TH-94/10 | gr-qc | null | Exact black hole and cosmological solutions are obtained for a special
two-dimensional dilaton-spectator ($\phi-\psi$) theory of gravity. We show how
in this context any desired spacetime behaviour can be determined by an
appropriate choice of a dilaton potential function $V(\phi)$ and a ``coupling
function'' $l(\phi)$ in the action. We illustrate several black hole solutions
as examples. In particular, asymptotically flat double- and multiple- horizon
black hole solutions are obtained. One solution bears an interesting
resemblance to the $2D$ string-theoretic black hole and contains the same
thermodynamic properties; another resembles the $4D$ Reissner-Nordstrom
solution. We find two characteristic features of all the black hole solutions.
First the coupling constants in $l(\phi)$ must be set equal to constants of
integration (typically the mass). Second, the spectator field $\psi$ and its
derivative $\psi^{'}$ both diverge at any event horizon. A test particle with
``spectator charge" ({\it i.e.} one coupled either to $\psi$ or $\psi^{'}$),
will therefore encounter an infinite tidal force at the horizon or an
``infinite potential barrier'' located outside the horizon respectively. We
also compute the Hawking temperature and entropy for our solutions. In $2D$
$FRW$ cosmology, two non-singular solutions which resemble two exact solutions
in $4D$ string-motivated cosmology are obtained. In addition, we construct a
singular model which describes the $4D$ standard non-inflationary big bang
cosmology ($big-bang\rightarrow radiation\rightarrow dust$). Motivated by the
similaritiesbetween $2D$ and $4D$ gravitational field equations in $FRW$
cosmology, we briefly discuss a special $4D$ dilaton-spectator action
constructed from the bosonic part of the low energy heterotic string action and
| [
{
"created": "Tue, 24 Jan 1995 14:11:36 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Mar 1995 14:40:48 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Chan",
"K. C. K.",
""
],
[
"Mann",
"R. B.",
""
]
] | Exact black hole and cosmological solutions are obtained for a special two-dimensional dilaton-spectator ($\phi-\psi$) theory of gravity. We show how in this context any desired spacetime behaviour can be determined by an appropriate choice of a dilaton potential function $V(\phi)$ and a ``coupling function'' $l(\phi)$ in the action. We illustrate several black hole solutions as examples. In particular, asymptotically flat double- and multiple- horizon black hole solutions are obtained. One solution bears an interesting resemblance to the $2D$ string-theoretic black hole and contains the same thermodynamic properties; another resembles the $4D$ Reissner-Nordstrom solution. We find two characteristic features of all the black hole solutions. First the coupling constants in $l(\phi)$ must be set equal to constants of integration (typically the mass). Second, the spectator field $\psi$ and its derivative $\psi^{'}$ both diverge at any event horizon. A test particle with ``spectator charge" ({\it i.e.} one coupled either to $\psi$ or $\psi^{'}$), will therefore encounter an infinite tidal force at the horizon or an ``infinite potential barrier'' located outside the horizon respectively. We also compute the Hawking temperature and entropy for our solutions. In $2D$ $FRW$ cosmology, two non-singular solutions which resemble two exact solutions in $4D$ string-motivated cosmology are obtained. In addition, we construct a singular model which describes the $4D$ standard non-inflationary big bang cosmology ($big-bang\rightarrow radiation\rightarrow dust$). Motivated by the similaritiesbetween $2D$ and $4D$ gravitational field equations in $FRW$ cosmology, we briefly discuss a special $4D$ dilaton-spectator action constructed from the bosonic part of the low energy heterotic string action and |
0910.3352 | Vladimir Dzhunushaliev | Vladimir Dzhunushaliev | Asymptotically flat gravitating spinor field solutions. Step 1 - the
statement of the problem and the comparison with confinement problem in QCD | 3 pages | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The situation with asymptotically flat gravitating spinor field solutions is
considered. It is supposed that the problem of constructing these solutions is
connected with confinement problem in quantum chromodynamics. It is argued that
in both cases we must use a nonperturbative quantum technique.
| [
{
"created": "Sun, 18 Oct 2009 04:57:43 GMT",
"version": "v1"
}
] | 2009-10-20 | [
[
"Dzhunushaliev",
"Vladimir",
""
]
] | The situation with asymptotically flat gravitating spinor field solutions is considered. It is supposed that the problem of constructing these solutions is connected with confinement problem in quantum chromodynamics. It is argued that in both cases we must use a nonperturbative quantum technique. |
1712.02668 | James Lucietti | Hari K. Kunduri, James Lucietti | No static bubbling spacetimes in higher dimensional Einstein-Maxwell
theory | 9 pages. v2: minor edits, references added | Class. Quantum Grav. 35 054003 (2018) | 10.1088/1361-6382/aaa744 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that any asymptotically flat static spacetime in higher dimensional
Einstein-Maxwell theory must have no magnetic field. This implies that there
are no static soliton spacetimes and completes the classification of static
non-extremal black holes in this theory. In particular, these results establish
that there are no asymptotically flat static spacetimes with non-trivial
topology, with or without a black hole, in Einstein-Maxwell theory.
| [
{
"created": "Thu, 7 Dec 2017 15:26:47 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Feb 2018 16:32:18 GMT",
"version": "v2"
}
] | 2018-02-02 | [
[
"Kunduri",
"Hari K.",
""
],
[
"Lucietti",
"James",
""
]
] | We prove that any asymptotically flat static spacetime in higher dimensional Einstein-Maxwell theory must have no magnetic field. This implies that there are no static soliton spacetimes and completes the classification of static non-extremal black holes in this theory. In particular, these results establish that there are no asymptotically flat static spacetimes with non-trivial topology, with or without a black hole, in Einstein-Maxwell theory. |
2311.01424 | Maria-Jose Guzman | Maria-Jose Guzman | The Hamiltonian constraint in the symmetric teleparallel equivalent of
general relativity | 12 pages, no figures; v2: crucial mistake corrected, updated
discussion, comments welcome | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | General relativity (GR) admits two alternative formulations with the same
dynamics attributing the gravitational phenomena to torsion or nonmetricity of
the manifold's connection. They lead, respectively, to the teleparallel
equivalent of general relativity (TEGR) and the symmetric teleparallel
equivalent of general relativity (STEGR). In this work, we focus on STEGR and
present its differences with the conventional, curvature-based GR. We exhibit
the 3+1 decomposition of the STEGR Lagrangian in the coincident gauge and
present the Hamiltonian, and the Hamiltonian and momenta constraints. For a
particular case of spherical symmetry, we explicitly show the differences in
the Hamiltonian between GR and STEGR, one of the few genuinely different
features of both formulations of gravity, and the repercussions it might
encompass to numerical relativity.
| [
{
"created": "Thu, 2 Nov 2023 17:38:52 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Apr 2024 16:28:34 GMT",
"version": "v2"
}
] | 2024-04-24 | [
[
"Guzman",
"Maria-Jose",
""
]
] | General relativity (GR) admits two alternative formulations with the same dynamics attributing the gravitational phenomena to torsion or nonmetricity of the manifold's connection. They lead, respectively, to the teleparallel equivalent of general relativity (TEGR) and the symmetric teleparallel equivalent of general relativity (STEGR). In this work, we focus on STEGR and present its differences with the conventional, curvature-based GR. We exhibit the 3+1 decomposition of the STEGR Lagrangian in the coincident gauge and present the Hamiltonian, and the Hamiltonian and momenta constraints. For a particular case of spherical symmetry, we explicitly show the differences in the Hamiltonian between GR and STEGR, one of the few genuinely different features of both formulations of gravity, and the repercussions it might encompass to numerical relativity. |
0904.1851 | Douglas A. Singleton | Merab Gogberashvili, Shynaray Myrzakul, and Douglas Singleton | Standing gravitational waves from domain walls | 4 pages two-column format, no figures, added discussion of physical
meaning of solution, added refernces, to be published PRD | Phys.Rev.D80:024040,2009 | 10.1103/PhysRevD.80.024040 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a plane symmetric, standing gravitational wave for a domain wall
plus a massless scalar field. The scalar field can be associated with a fluid
which has the properties of `stiff' matter, i.e. matter in which the speed of
sound equals the speed of light. Although domain walls are observationally
ruled out in the present era the solution has interesting features which might
shed light on the character of exact non-linear wave solutions to Einstein's
equations. Additionally this solution may act as a template for higher
dimensional 'brane-world' model standing waves.
| [
{
"created": "Sun, 12 Apr 2009 11:04:15 GMT",
"version": "v1"
},
{
"created": "Sun, 19 Jul 2009 09:40:16 GMT",
"version": "v2"
}
] | 2010-03-26 | [
[
"Gogberashvili",
"Merab",
""
],
[
"Myrzakul",
"Shynaray",
""
],
[
"Singleton",
"Douglas",
""
]
] | We construct a plane symmetric, standing gravitational wave for a domain wall plus a massless scalar field. The scalar field can be associated with a fluid which has the properties of `stiff' matter, i.e. matter in which the speed of sound equals the speed of light. Although domain walls are observationally ruled out in the present era the solution has interesting features which might shed light on the character of exact non-linear wave solutions to Einstein's equations. Additionally this solution may act as a template for higher dimensional 'brane-world' model standing waves. |
gr-qc/0111013 | David Wands | David Langlois (1), Kei-ichi Maeda (2) and David Wands (3) ((1) IAP,
(2) Waseda, (3) Portsmouth) | Conservation laws for collisions of branes (or shells) in general
relativity | 5 pages, revtex with epsf, 3 figures; revised version, minor changes,
to appear in Physical Review Letters | Phys.Rev.Lett. 88 (2002) 181301 | 10.1103/PhysRevLett.88.181301 | null | gr-qc astro-ph hep-th | null | We consider the collision of self-gravitating n-branes in a (n+2)-dimensional
spacetime. We show that there is a geometrical constraint which can be
expressed as a simple sum rule for angles characterizing Lorentz boosts between
branes and the intervening spacetime regions. This constraint can then be
re-interpreted as either energy or momentum conservation at the collision.
| [
{
"created": "Mon, 5 Nov 2001 14:33:02 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Apr 2002 09:06:24 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Langlois",
"David",
""
],
[
"Maeda",
"Kei-ichi",
""
],
[
"Wands",
"David",
""
]
] | We consider the collision of self-gravitating n-branes in a (n+2)-dimensional spacetime. We show that there is a geometrical constraint which can be expressed as a simple sum rule for angles characterizing Lorentz boosts between branes and the intervening spacetime regions. This constraint can then be re-interpreted as either energy or momentum conservation at the collision. |
1512.07095 | Runqiu Yang | Rong-Gen Cai and Run-Qiu Yang | Scaling Laws in Gravitational Collapse | 5 pages, 1 figure | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper presents two interesting scaling laws, which relate some critical
exponents in the critical behavior of spherically symmetric gravitational
collapses. These scaling laws are independent of the details of gravity theory
under consideration and share similar forms as those in thermodynamic and
geometrical phase transitions in condensed matter system. The properties of the
scaling laws are discussed and some numerical checks are given.
| [
{
"created": "Tue, 22 Dec 2015 14:15:32 GMT",
"version": "v1"
}
] | 2015-12-23 | [
[
"Cai",
"Rong-Gen",
""
],
[
"Yang",
"Run-Qiu",
""
]
] | This paper presents two interesting scaling laws, which relate some critical exponents in the critical behavior of spherically symmetric gravitational collapses. These scaling laws are independent of the details of gravity theory under consideration and share similar forms as those in thermodynamic and geometrical phase transitions in condensed matter system. The properties of the scaling laws are discussed and some numerical checks are given. |
gr-qc/9907092 | Stoytcho Yazadjiev | S.Yazadjiev | Newman-Janis method and rotating dilaton-axion black hole | 6 pages, latex | Gen.Rel.Grav.32:2345-2352,2000 | 10.1023/A:1002080003862 | SUTH 99-15 | gr-qc | null | It's shown that the rotating dilaton-axion black hole solution can be
obtained from GGHS static charged dilaton black hole solution via Newman-Janis
method.
| [
{
"created": "Wed, 28 Jul 1999 13:09:37 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Yazadjiev",
"S.",
""
]
] | It's shown that the rotating dilaton-axion black hole solution can be obtained from GGHS static charged dilaton black hole solution via Newman-Janis method. |
1704.02572 | Hamid Reza Sepangi | M. Honardoost, D. F. Mota, H. R. Sepangi | Symmetron with a non-minimal kinetic term | 12 pages, 4 figures, to appear in JCAP | JCAP 11 (2017) 018 | 10.1088/1475-7516/2017/11/018 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the compatibility of the Symmetron with dark energy by
introducing a non-minimal kinetic term associated with the Symmetron. In this
new model, the effect of the friction term appearing in the equation of motion
of the Symmetron field becomes more pronounced due to the non-minimal kinetic
term appearing in the action and, under specific conditions after symmetry
breaking, the universe experiences an accelerating phase which, in spite of the
large effective mass of the scalar field, lasts as long as the Hubble time
$H_{0}$.
| [
{
"created": "Sun, 9 Apr 2017 08:36:16 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Nov 2017 11:27:54 GMT",
"version": "v2"
}
] | 2017-11-29 | [
[
"Honardoost",
"M.",
""
],
[
"Mota",
"D. F.",
""
],
[
"Sepangi",
"H. R.",
""
]
] | We investigate the compatibility of the Symmetron with dark energy by introducing a non-minimal kinetic term associated with the Symmetron. In this new model, the effect of the friction term appearing in the equation of motion of the Symmetron field becomes more pronounced due to the non-minimal kinetic term appearing in the action and, under specific conditions after symmetry breaking, the universe experiences an accelerating phase which, in spite of the large effective mass of the scalar field, lasts as long as the Hubble time $H_{0}$. |
2208.09302 | Jaros{\l}aw Kopi\'nski | A. Rod Gover and Jaros{\l}aw Kopi\'nski | Higher fundamental forms of the conformal boundary of asymptotically de
Sitter spacetimes | 24 pages | Class. Quantum Grav. 40 015001 2023 | 10.1088/1361-6382/aca459 | null | gr-qc math.DG | http://creativecommons.org/licenses/by/4.0/ | We provide a partial characterization of the conformal infinity of
asymptotically de Sitter spacetimes by deriving constraints that relate the
asymptotics of the stress-energy tensor with conformal geometric data. The
latter is captured using recently defined objects, called higher conformal
fundamental forms. For the boundary hypersurface, these generalize to higher
order the trace-free part of the second form.
| [
{
"created": "Fri, 19 Aug 2022 12:30:20 GMT",
"version": "v1"
}
] | 2023-02-16 | [
[
"Gover",
"A. Rod",
""
],
[
"Kopiński",
"Jarosław",
""
]
] | We provide a partial characterization of the conformal infinity of asymptotically de Sitter spacetimes by deriving constraints that relate the asymptotics of the stress-energy tensor with conformal geometric data. The latter is captured using recently defined objects, called higher conformal fundamental forms. For the boundary hypersurface, these generalize to higher order the trace-free part of the second form. |
2305.13761 | Salih Kibaro\u{g}lu | Salih Kibaro\u{g}lu | Modified Friedmann Equations from Maxwell-Weyl Gauge Theory | 20 pages | Nucl. Phys. B 1006 (2024) 116634 | 10.1016/j.nuclphysb.2024.116634 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This study investigates the possibility of a homogeneous and isotropic
cosmological solution within the context of the Maxwell-Weyl gauge theory of
gravity. To achieve this, we utilize the Einstein-Yang-Mills theory as an
analogy and represent the Maxwell gauge field in terms of two time-dependent
scalar fields. We derive the modified Friedmann equations, integrating the
contributions from the Maxwell gauge fields and an effective cosmological
constant that depends on the Dirac scalar field. Our analysis reveals how these
modifications influence various cosmological scenarios, including power-law
evolution, de Sitter-like expansion, inflationary phases, non-singular bounce
cosmologies, and cyclic cosmologies.
| [
{
"created": "Tue, 23 May 2023 07:25:16 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Jul 2024 06:50:41 GMT",
"version": "v2"
}
] | 2024-07-26 | [
[
"Kibaroğlu",
"Salih",
""
]
] | This study investigates the possibility of a homogeneous and isotropic cosmological solution within the context of the Maxwell-Weyl gauge theory of gravity. To achieve this, we utilize the Einstein-Yang-Mills theory as an analogy and represent the Maxwell gauge field in terms of two time-dependent scalar fields. We derive the modified Friedmann equations, integrating the contributions from the Maxwell gauge fields and an effective cosmological constant that depends on the Dirac scalar field. Our analysis reveals how these modifications influence various cosmological scenarios, including power-law evolution, de Sitter-like expansion, inflationary phases, non-singular bounce cosmologies, and cyclic cosmologies. |
0805.2997 | Hector Calderon | Hector H. Calderon (Montana State University) | Quantum fields near phantom-energy `sudden' singularities | 6 pages RevTeX | Phys.Rev.D78:044041,2008 | 10.1103/PhysRevD.78.044041 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is committed to calculations near a type of future singularity
driven by phantom energy. At the singularities considered, the scale factor
remains finite but its derivative diverges. The general behavior of barotropic
phantom energy producing this singularity is calculated under the assumption
that near the singularity such fluid is the dominant contributor. We use the
semiclassical formula for renormalized stress tensors of conformally invariant
fields in conformally flat spacetimes and analyze the softening/enhancing of
the singularity due to quantum vacuum contributions. This dynamical analysis is
then compared to results from thermodynamical considerations. In both cases,
the vacuum states of quantized scalar and spinor fields strengthen the
accelerating expansion near the singularity whereas the vacuum states of vector
fields weaken it.
| [
{
"created": "Tue, 20 May 2008 03:18:52 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Calderon",
"Hector H.",
"",
"Montana State University"
]
] | This paper is committed to calculations near a type of future singularity driven by phantom energy. At the singularities considered, the scale factor remains finite but its derivative diverges. The general behavior of barotropic phantom energy producing this singularity is calculated under the assumption that near the singularity such fluid is the dominant contributor. We use the semiclassical formula for renormalized stress tensors of conformally invariant fields in conformally flat spacetimes and analyze the softening/enhancing of the singularity due to quantum vacuum contributions. This dynamical analysis is then compared to results from thermodynamical considerations. In both cases, the vacuum states of quantized scalar and spinor fields strengthen the accelerating expansion near the singularity whereas the vacuum states of vector fields weaken it. |
1905.06011 | Nathan Johnson-McDaniel | Tim Dietrich, Anuradha Samajdar, Sebastian Khan, Nathan K.
Johnson-McDaniel, Reetika Dudi, Wolfgang Tichy | Improving the NRTidal model for binary neutron star systems | Accepted manuscript | Phys. Rev. D 100, 044003 (2019) | 10.1103/PhysRevD.100.044003 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Accurate and fast gravitational waveform (GW) models are essential to extract
information about the properties of compact binary systems that generate GWs.
Building on previous work, we present an extension of the NRTidal model for
binary neutron star (BNS) waveforms. The upgrades are: (i) a new closed-form
expression for the tidal contribution to the GW phase which includes further
analytical knowledge and is calibrated to more accurate numerical relativity
data than previously available; (ii) a tidal correction to the GW amplitude;
(iii) an extension of the spin-sector incorporating equation-of-state-dependent
finite size effects at quadrupolar and octupolar order; these appear in the
spin-spin tail terms and cubic-in-spin terms, both at 3.5PN. We add the new
description to the precessing binary black hole waveform model IMRPhenomPv2 to
obtain a frequency-domain precessing binary neutron star model. In addition, we
extend the SEOBNRv4_ROM and IMRPhenomD aligned-spin binary black hole waveform
models with the improved tidal phase corrections. Focusing on the new
IMRPhenomPv2_NRTidalv2 approximant, we test the model by comparing with
numerical relativity waveforms as well as hybrid waveforms combining tidal
effective-one-body and numerical relativity data. We also check consistency
against a tidal effective-one-body model across large regions of the BNS
parameter space.
| [
{
"created": "Wed, 15 May 2019 08:05:10 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Jul 2019 10:05:00 GMT",
"version": "v2"
}
] | 2019-08-07 | [
[
"Dietrich",
"Tim",
""
],
[
"Samajdar",
"Anuradha",
""
],
[
"Khan",
"Sebastian",
""
],
[
"Johnson-McDaniel",
"Nathan K.",
""
],
[
"Dudi",
"Reetika",
""
],
[
"Tichy",
"Wolfgang",
""
]
] | Accurate and fast gravitational waveform (GW) models are essential to extract information about the properties of compact binary systems that generate GWs. Building on previous work, we present an extension of the NRTidal model for binary neutron star (BNS) waveforms. The upgrades are: (i) a new closed-form expression for the tidal contribution to the GW phase which includes further analytical knowledge and is calibrated to more accurate numerical relativity data than previously available; (ii) a tidal correction to the GW amplitude; (iii) an extension of the spin-sector incorporating equation-of-state-dependent finite size effects at quadrupolar and octupolar order; these appear in the spin-spin tail terms and cubic-in-spin terms, both at 3.5PN. We add the new description to the precessing binary black hole waveform model IMRPhenomPv2 to obtain a frequency-domain precessing binary neutron star model. In addition, we extend the SEOBNRv4_ROM and IMRPhenomD aligned-spin binary black hole waveform models with the improved tidal phase corrections. Focusing on the new IMRPhenomPv2_NRTidalv2 approximant, we test the model by comparing with numerical relativity waveforms as well as hybrid waveforms combining tidal effective-one-body and numerical relativity data. We also check consistency against a tidal effective-one-body model across large regions of the BNS parameter space. |
2407.15207 | Miguel Cruz | Miguel Cruz, Norman Cruz and Samuel Lepe | Thermodynamics inconsistencies in cosmological unimodular gravity models | 8 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study the thermodynamics of a cosmological unimodular gravity
model at late times by considering two different energy diffusion functions
that emerges in these scenarios, and that encodes the current for the
non-conservation of the energy-momentum tensor, usually termed as $Q(t)$.
Specifically, we discuss the barotropic and the continuous spontaneous
localization models as energy diffusion functions. The consistency conditions
demanded for the entropy of the system in terms of the cosmological parameters
of the model: positive production ($dS/dt>0$) and convexity condition
($d^{2}S/dt^{2} <0$), are investigated. We show that these conditions strongly
constraint the viavility of these models. Additionally, we comment about our
results and compare with those obtained in recent works where the restriction
of the parameters for these two diffusion models was implemented with the use
of cosmological data.
| [
{
"created": "Sun, 21 Jul 2024 16:13:28 GMT",
"version": "v1"
}
] | 2024-07-23 | [
[
"Cruz",
"Miguel",
""
],
[
"Cruz",
"Norman",
""
],
[
"Lepe",
"Samuel",
""
]
] | In this work we study the thermodynamics of a cosmological unimodular gravity model at late times by considering two different energy diffusion functions that emerges in these scenarios, and that encodes the current for the non-conservation of the energy-momentum tensor, usually termed as $Q(t)$. Specifically, we discuss the barotropic and the continuous spontaneous localization models as energy diffusion functions. The consistency conditions demanded for the entropy of the system in terms of the cosmological parameters of the model: positive production ($dS/dt>0$) and convexity condition ($d^{2}S/dt^{2} <0$), are investigated. We show that these conditions strongly constraint the viavility of these models. Additionally, we comment about our results and compare with those obtained in recent works where the restriction of the parameters for these two diffusion models was implemented with the use of cosmological data. |
2103.06718 | Katarina Martinovic | Katarina Martinovic, Charles Badger, Mairi Sakellariadou, Vuk Mandic | Searching for parity violation with the LIGO-Virgo-KAGRA network | 6 pages, 5 figures | Phys. Rev. D 104, 081101 (2021) | 10.1103/PhysRevD.104.L081101 | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | A stochastic gravitational wave background is expected to emerge from the
superposition of numerous gravitational wave sources of both astrophysical and
cosmological origin. A number of cosmological models can have a parity
violation, resulting in the generation of circularly polarised gravitational
waves. We present a method to search for parity violation in the gravitational
wave data. We first apply this method to the most recent, third, LIGO-Virgo
observing run. We then investigate the constraining power of future A+
LIGO-Virgo detectors, including KAGRA to the network, for a gravitational wave
background generated by early universe cosmological turbulence.
| [
{
"created": "Thu, 11 Mar 2021 15:04:15 GMT",
"version": "v1"
}
] | 2021-10-13 | [
[
"Martinovic",
"Katarina",
""
],
[
"Badger",
"Charles",
""
],
[
"Sakellariadou",
"Mairi",
""
],
[
"Mandic",
"Vuk",
""
]
] | A stochastic gravitational wave background is expected to emerge from the superposition of numerous gravitational wave sources of both astrophysical and cosmological origin. A number of cosmological models can have a parity violation, resulting in the generation of circularly polarised gravitational waves. We present a method to search for parity violation in the gravitational wave data. We first apply this method to the most recent, third, LIGO-Virgo observing run. We then investigate the constraining power of future A+ LIGO-Virgo detectors, including KAGRA to the network, for a gravitational wave background generated by early universe cosmological turbulence. |
2107.08519 | Ayan Mitra | Ayan Mitra, Vasilios Zarikas, Alfio Bonanno, Michael Good, Ertan
G\"udekli | Constraining the swiss-cheese IR-fixed point cosmology with cosmic
expansion | 12 pages, 6 figures. Accepted in Universe, MDPI | Universe 2021 | 10.3390/universe7080263 | 7(8):263 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent work, it has been proposed that the recent cosmic passage to a
cosmic acceleration era is the result of the existence of small anti-gravity
sources in each galaxy and clusters of galaxies. In particular, a swiss-cheese
cosmology model which relativistically integrates the contribution of all these
anti-gravity sources on galactic scale has been constructed assuming the
presence of an infrared fixed point for a scale dependent cosmological
constant. The derived cosmological expansion provides explanation for both the
fine tuning and the coincidence problem. The present work relaxes the previous
assumption on the running of the cosmological constant and allows for a generic
scaling around the infrared fixed point. Our analysis reveals in order to
produce a cosmic evolution consistent with the best $\Lambda$CDM model, the
IR-running of the cosmological constant is consistent with the presence of an
IR-fixed point.
| [
{
"created": "Sun, 18 Jul 2021 19:14:42 GMT",
"version": "v1"
}
] | 2021-07-27 | [
[
"Mitra",
"Ayan",
""
],
[
"Zarikas",
"Vasilios",
""
],
[
"Bonanno",
"Alfio",
""
],
[
"Good",
"Michael",
""
],
[
"Güdekli",
"Ertan",
""
]
] | In a recent work, it has been proposed that the recent cosmic passage to a cosmic acceleration era is the result of the existence of small anti-gravity sources in each galaxy and clusters of galaxies. In particular, a swiss-cheese cosmology model which relativistically integrates the contribution of all these anti-gravity sources on galactic scale has been constructed assuming the presence of an infrared fixed point for a scale dependent cosmological constant. The derived cosmological expansion provides explanation for both the fine tuning and the coincidence problem. The present work relaxes the previous assumption on the running of the cosmological constant and allows for a generic scaling around the infrared fixed point. Our analysis reveals in order to produce a cosmic evolution consistent with the best $\Lambda$CDM model, the IR-running of the cosmological constant is consistent with the presence of an IR-fixed point. |
gr-qc/0309094 | Stephane Fay | Stephane Fay | Isotropisation of Generalized Scalar-Tensor theory plus a massive scalar
field in the Bianchi type I model | 10 pages | Class.Quant.Grav. 18 (2001) 2887-2894 | 10.1088/0264-9381/18/15/304 | null | gr-qc | null | In this paper we study the isotropisation of a Generalized Scalar-Tensor
theory with a massive scalar field. We find it depends on a condition on the
Brans-Dicke coupling function and the potential and show that asymptotically
the metric functions always tend toward a power or exponential law of the
proper time. These results generalise and unify these of De Sitter in the case
of a cosmological constant and of Cooley and Kitada in the case of an
exponential potential.
| [
{
"created": "Fri, 19 Sep 2003 12:15:02 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Fay",
"Stephane",
""
]
] | In this paper we study the isotropisation of a Generalized Scalar-Tensor theory with a massive scalar field. We find it depends on a condition on the Brans-Dicke coupling function and the potential and show that asymptotically the metric functions always tend toward a power or exponential law of the proper time. These results generalise and unify these of De Sitter in the case of a cosmological constant and of Cooley and Kitada in the case of an exponential potential. |
gr-qc/0212019 | Jose Luis Rosales | J.L. Rosales | The Pioneer's acceleration anomaly and Hubble's constant | 8 pages, LaTex, minor changes for submission | null | null | null | gr-qc | null | The reported anomalous acceleration acting on the Pioneers spacecrafts could
be seen as a consequence of the existence of some local curvature in light
geodesics when using the coordinate speed of light in an expanding space-time.
The effect is related with the non synchronous character of the underlying
metric and therefore, planets closed orbits can not reveal it. It is shown that
the cosmic expansion rate -the Hubble parameter H- has been indeed detected.
Additionally, a relation for an existing annual term is obtained which depends
on the cosine of the ecliptic latitude of the spacecraft, suggestingan
heuristic analogy between the effect and Foucault's experiment - light rays
playing a similar role in the expanding space than Foucault's Pendulum does
while determining Earth's rotation. This statement could be seen as a benchmark
for future experiments.
| [
{
"created": "Wed, 4 Dec 2002 17:37:52 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Dec 2002 12:28:32 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Rosales",
"J. L.",
""
]
] | The reported anomalous acceleration acting on the Pioneers spacecrafts could be seen as a consequence of the existence of some local curvature in light geodesics when using the coordinate speed of light in an expanding space-time. The effect is related with the non synchronous character of the underlying metric and therefore, planets closed orbits can not reveal it. It is shown that the cosmic expansion rate -the Hubble parameter H- has been indeed detected. Additionally, a relation for an existing annual term is obtained which depends on the cosine of the ecliptic latitude of the spacecraft, suggestingan heuristic analogy between the effect and Foucault's experiment - light rays playing a similar role in the expanding space than Foucault's Pendulum does while determining Earth's rotation. This statement could be seen as a benchmark for future experiments. |
2112.05167 | Adrien Kuntz | Adrien Kuntz | Precession resonances in hierarchical triple systems | Version accepted for publication in PRD | null | 10.1103/PhysRevD.105.024017 | null | gr-qc astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a new kind of resonance occuring in relativistic three-body
hierarchical systems: the precession resonance, occuring when the relativistic
precession timescale of a binary equals the period of a distant perturber. We
find that, contrary to what most previous studies assume, it can lead to an
exponential increase of eccentricity of the binary even when relativistic
precession dominates the quadrupolar perturbation. The resonance may happen in
the observation band of LISA or change the eccentricity distribution of
triples. We discuss the physics of the resonance, showing that it mainly
depends on three parameters.
| [
{
"created": "Thu, 9 Dec 2021 19:00:04 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jan 2022 17:52:25 GMT",
"version": "v2"
}
] | 2022-01-06 | [
[
"Kuntz",
"Adrien",
""
]
] | We describe a new kind of resonance occuring in relativistic three-body hierarchical systems: the precession resonance, occuring when the relativistic precession timescale of a binary equals the period of a distant perturber. We find that, contrary to what most previous studies assume, it can lead to an exponential increase of eccentricity of the binary even when relativistic precession dominates the quadrupolar perturbation. The resonance may happen in the observation band of LISA or change the eccentricity distribution of triples. We discuss the physics of the resonance, showing that it mainly depends on three parameters. |
2008.04289 | Alesandro Santos | P. S. Ens and A. F. Santos | $f(R)$ gravity and Tsallis holographic dark energy | 14 pages, accepted for publication in EPL | null | 10.1209/0295-5075/131/40007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The $f(R)$ gravity theory is considered. It is a gravitational theory that
generalizes the Einstein-Hilbert action. In this context, a holographic dark
energy model is studied. Tsallis non-extensive entropy is used to introduce the
dark energy density based on the holographic principle. Then the Friedmann
equation, deceleration parameter, and equation of state for this model are
investigated.
| [
{
"created": "Mon, 10 Aug 2020 17:40:30 GMT",
"version": "v1"
}
] | 2020-12-02 | [
[
"Ens",
"P. S.",
""
],
[
"Santos",
"A. F.",
""
]
] | The $f(R)$ gravity theory is considered. It is a gravitational theory that generalizes the Einstein-Hilbert action. In this context, a holographic dark energy model is studied. Tsallis non-extensive entropy is used to introduce the dark energy density based on the holographic principle. Then the Friedmann equation, deceleration parameter, and equation of state for this model are investigated. |
1111.6575 | Stephane Houndjo Dr | M. Hamani Daouda, Manuel E. Rodrigues and M. J. S. Houndjo | Reconstruction of f(T) gravity according to holographic dark energy | 11 pages, Accepted for publication in EPJC | Euro. Phys. J. C 72, Number 2, 1893 (2012) | 10.1140/epjc/s10052-012-1893-5 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop the reconstruction of a model of $f(T)$ gravity according to the
holographic dark energy. $T$ is the torsion scalar and its initial value from
the Teleparallel gravity is imposed for fitting the initial value of the
function $f(T)$. The result shows a polynomial function for $f(T)$, and we also
observe that, when $\Omega_V\rightarrow 1$ at the future time, $\omega_V$ may
cross -1 for some values of the input parameter $b$. Another interesting aspect
of the obtained model is that it provides the unification of the dark matter
with the dark energy.
| [
{
"created": "Mon, 28 Nov 2011 20:43:32 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Jan 2012 20:07:39 GMT",
"version": "v2"
}
] | 2012-02-16 | [
[
"Daouda",
"M. Hamani",
""
],
[
"Rodrigues",
"Manuel E.",
""
],
[
"Houndjo",
"M. J. S.",
""
]
] | We develop the reconstruction of a model of $f(T)$ gravity according to the holographic dark energy. $T$ is the torsion scalar and its initial value from the Teleparallel gravity is imposed for fitting the initial value of the function $f(T)$. The result shows a polynomial function for $f(T)$, and we also observe that, when $\Omega_V\rightarrow 1$ at the future time, $\omega_V$ may cross -1 for some values of the input parameter $b$. Another interesting aspect of the obtained model is that it provides the unification of the dark matter with the dark energy. |
gr-qc/9702031 | Sergei Krasnikov | S. V. Krasnikov | A singularity-free WEC-respecting time machine | The final version. To be published in CQG. The proof is made more
detailed and a few minor errors are corrected | Class.Quant.Grav. 15 (1998) 997-1003 | 10.1088/0264-9381/15/4/020 | null | gr-qc | null | A time machine (TM) is constructed whose creating in contrast to all TMs
known so far requires neither singularities, nor violation of the weak energy
condition (WEC). The spacetime exterior to the TM closely resembles the
Friedmann universe.
| [
{
"created": "Sun, 16 Feb 1997 23:38:26 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Feb 1997 10:48:20 GMT",
"version": "v2"
},
{
"created": "Mon, 9 Mar 1998 17:10:56 GMT",
"version": "v3"
}
] | 2009-10-30 | [
[
"Krasnikov",
"S. V.",
""
]
] | A time machine (TM) is constructed whose creating in contrast to all TMs known so far requires neither singularities, nor violation of the weak energy condition (WEC). The spacetime exterior to the TM closely resembles the Friedmann universe. |
gr-qc/0610123 | Ernesto F. Eiroa | Cecilia Bejarano, Ernesto F. Eiroa, Claudio Simeone | Thin-shell wormholes associated with global cosmic strings | 7 pages; v2: minor changes. Accepted for publication in Physical
Review D | Phys.Rev.D75:027501,2007 | 10.1103/PhysRevD.75.027501 | null | gr-qc astro-ph | null | In this article we construct cylindrical thin-shell wormholes in the context
of global cosmic strings. We study the stability of static configurations under
perturbations preserving the symmetry and we find that the throat tends to
collapse or expand, depending only on the direction of the velocity
perturbation.
| [
{
"created": "Wed, 25 Oct 2006 19:18:25 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Dec 2006 18:13:09 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bejarano",
"Cecilia",
""
],
[
"Eiroa",
"Ernesto F.",
""
],
[
"Simeone",
"Claudio",
""
]
] | In this article we construct cylindrical thin-shell wormholes in the context of global cosmic strings. We study the stability of static configurations under perturbations preserving the symmetry and we find that the throat tends to collapse or expand, depending only on the direction of the velocity perturbation. |
1109.5612 | F. S. Guzman | F. S. Guzman | Toward restrictions on boson stars as black hole mimickers | Proceedings of the Spanish Relativity Meeting ERE 2010, 4 pages, 2
eps figures | J.Phys.Conf.Ser. 314:012085,2011 | 10.1088/1742-6596/314/1/012085 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The status of boson stars as black hole mimickers is presented. We focus on
the analysis of the emission spectrum of a simple accretion disk model. We
describe the free parameters that allow a boson star to become a black hole
mimicker and present an example of a particular astrophysical case.
| [
{
"created": "Mon, 26 Sep 2011 15:42:00 GMT",
"version": "v1"
}
] | 2011-09-27 | [
[
"Guzman",
"F. S.",
""
]
] | The status of boson stars as black hole mimickers is presented. We focus on the analysis of the emission spectrum of a simple accretion disk model. We describe the free parameters that allow a boson star to become a black hole mimicker and present an example of a particular astrophysical case. |
gr-qc/0305046 | Matteo Luca Ruggiero | Guido Rizzi, Matteo Luca Ruggiero | The Sagnac Phase Shift suggested by the Aharonov-Bohm effect for
relativistic matter beams | 18 pages, LaTeX, 2 EPS figures. To appear in General Relativity and
Gravitation | Gen.Rel.Grav. 35 (2003) 1745-1760 | 10.1023/A:1026053828421 | null | gr-qc | null | The phase shift due to the Sagnac Effect, for relativistic matter beams
counter-propagating in a rotating interferometer, is deduced on the bases of a
a formal analogy with the the Aharonov-Bohm effect. A procedure outlined by
Sakurai, in which non relativistic quantum mechanics and newtonian physics
appear together with some intrinsically relativistic elements, is generalized
to a fully relativistic context, using the Cattaneo's splitting technique. This
approach leads to an exact derivation, in a self-consistently relativistic way,
of the Sagnac effect. Sakurai's result is recovered in the first order
approximation.
| [
{
"created": "Tue, 13 May 2003 07:23:27 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Rizzi",
"Guido",
""
],
[
"Ruggiero",
"Matteo Luca",
""
]
] | The phase shift due to the Sagnac Effect, for relativistic matter beams counter-propagating in a rotating interferometer, is deduced on the bases of a a formal analogy with the the Aharonov-Bohm effect. A procedure outlined by Sakurai, in which non relativistic quantum mechanics and newtonian physics appear together with some intrinsically relativistic elements, is generalized to a fully relativistic context, using the Cattaneo's splitting technique. This approach leads to an exact derivation, in a self-consistently relativistic way, of the Sagnac effect. Sakurai's result is recovered in the first order approximation. |
2006.12550 | John W. Moffat | J. W. Moffat | Modified Gravity (MOG), Cosmology and Black Holes | 8 pages, no figures. Changes made to comply with published paper.
Paper accepted for publication by Journal of Cosmology and Astroparticle
Physics. Text corrected to match published paper | JCAP 02:017 (2021) | 10.1088/1475-7516/2021/02/017 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A covariant modified gravity (MOG) is formulated by adding to general
relativity two new degrees of freedom, a scalar field gravitational coupling
strength $G= 1/\chi$ and a gravitational spin 1 vector field $\phi_\mu$. The
$G$ is written as $G=G_N(1+\alpha)$ where $G_N$ is Newton's constant, and the
gravitational source charge for the vector field is $Q_g=\sqrt{\alpha G_N}M$,
where $M$ is the mass of a body. Cosmological solutions of the theory are
derived in a homogeneous and isotropic cosmology. Black holes in MOG are
stationary as the end product of gravitational collapse and are axisymmetric
solutions with spherical topology. It is shown that the scalar field $\chi$ is
constant everywhere for an isolated black hole with asymptotic flat boundary
condition. A consequence of this is that the scalar field loses its monopole
moment radiation.
| [
{
"created": "Mon, 22 Jun 2020 18:23:31 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jul 2020 19:25:09 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Dec 2020 17:12:56 GMT",
"version": "v3"
},
{
"created": "Wed, 10 Feb 2021 17:45:30 GMT",
"version": "v4"
}
] | 2021-02-17 | [
[
"Moffat",
"J. W.",
""
]
] | A covariant modified gravity (MOG) is formulated by adding to general relativity two new degrees of freedom, a scalar field gravitational coupling strength $G= 1/\chi$ and a gravitational spin 1 vector field $\phi_\mu$. The $G$ is written as $G=G_N(1+\alpha)$ where $G_N$ is Newton's constant, and the gravitational source charge for the vector field is $Q_g=\sqrt{\alpha G_N}M$, where $M$ is the mass of a body. Cosmological solutions of the theory are derived in a homogeneous and isotropic cosmology. Black holes in MOG are stationary as the end product of gravitational collapse and are axisymmetric solutions with spherical topology. It is shown that the scalar field $\chi$ is constant everywhere for an isolated black hole with asymptotic flat boundary condition. A consequence of this is that the scalar field loses its monopole moment radiation. |
gr-qc/0201054 | Marc Mars | Marc Mars, Jose M.M. Senovilla | Geometry of General Hypersurfaces in Spacetime: Junction Conditions | Latex, no figures | Class.Quant.Grav.10:1865-1897,1993 | 10.1088/0264-9381/10/9/026 | null | gr-qc | null | We study imbedded hypersurfaces in spacetime whose causal character is
allowed to change from point to point. Inherited geometrical structures on
these hypersurfaces are defined by two methods: first, the standard rigged
connection induced by a rigging vector (a vector not tangent to the
hypersurface anywhere); and a second, more physically adapted, where each
observer in spacetime induces a new type of connection that we call the rigged
metric connection. The generalisation of the Gauss and Codazzi equations are
also given. With the above machinery, we attack the problem of matching two
spacetimes across a general hypersurface. It is seen that the preliminary
junction conditions allowing for the correct definition of Einstein's equations
in the distributional sense reduce to the requirement that the first
fundamental form of the hypersurface be continuous. The Bianchi identities are
then proven to hold in the distributional sense. Next, we find the proper
junction conditions which forbid the appearance of singular parts in the
curvature. Finally, we derive the physical implications of the junction
conditions: only six independent discontinuities of the Riemann tensor are
allowed. These are six matter discontinuities at non-null points of the
hypersurface. For null points, the existence of two arbitrary discontinuities
of the Weyl tensor (together with four in the matter tensor) are also allowed.
| [
{
"created": "Wed, 16 Jan 2002 14:06:38 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Mars",
"Marc",
""
],
[
"Senovilla",
"Jose M. M.",
""
]
] | We study imbedded hypersurfaces in spacetime whose causal character is allowed to change from point to point. Inherited geometrical structures on these hypersurfaces are defined by two methods: first, the standard rigged connection induced by a rigging vector (a vector not tangent to the hypersurface anywhere); and a second, more physically adapted, where each observer in spacetime induces a new type of connection that we call the rigged metric connection. The generalisation of the Gauss and Codazzi equations are also given. With the above machinery, we attack the problem of matching two spacetimes across a general hypersurface. It is seen that the preliminary junction conditions allowing for the correct definition of Einstein's equations in the distributional sense reduce to the requirement that the first fundamental form of the hypersurface be continuous. The Bianchi identities are then proven to hold in the distributional sense. Next, we find the proper junction conditions which forbid the appearance of singular parts in the curvature. Finally, we derive the physical implications of the junction conditions: only six independent discontinuities of the Riemann tensor are allowed. These are six matter discontinuities at non-null points of the hypersurface. For null points, the existence of two arbitrary discontinuities of the Weyl tensor (together with four in the matter tensor) are also allowed. |
gr-qc/9903007 | Siming Liu | L.Hao, J.Wei, S.Liu | Relativistic Spheres | 8 pages revtex, 1 ps figure | null | null | null | gr-qc | null | By analyzing the Einstein's equations for the static sphere, we find that
there exists a non-singular static configuration whose radius can approach its
corresponding horizon size arbitrarily.
| [
{
"created": "Tue, 2 Mar 1999 10:20:13 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hao",
"L.",
""
],
[
"Wei",
"J.",
""
],
[
"Liu",
"S.",
""
]
] | By analyzing the Einstein's equations for the static sphere, we find that there exists a non-singular static configuration whose radius can approach its corresponding horizon size arbitrarily. |
0712.4143 | Karim Noui | Karim Noui, Alejandro Perez, Kevin Vandersloot | Cosmological Plebanski theory | 20 pages | Gen.Rel.Grav.41:2597-2618,2009 | 10.1007/s10714-009-0783-0 | null | gr-qc | null | We consider the cosmological symmetry reduction of the Plebanski action as a
toy-model to explore, in this simple framework, some issues related to loop
quantum gravity and spin-foam models. We make the classical analysis of the
model and perform both path integral and canonical quantizations. As for the
full theory, the reduced model admits two types of classical solutions:
topological and gravitational ones. The quantization mixes these two solutions,
which prevents the model to be equivalent to standard quantum cosmology.
Furthermore, the topological solution dominates at the classical limit. We also
study the effect of an Immirzi parameter in the model.
| [
{
"created": "Wed, 26 Dec 2007 19:46:30 GMT",
"version": "v1"
}
] | 2014-11-18 | [
[
"Noui",
"Karim",
""
],
[
"Perez",
"Alejandro",
""
],
[
"Vandersloot",
"Kevin",
""
]
] | We consider the cosmological symmetry reduction of the Plebanski action as a toy-model to explore, in this simple framework, some issues related to loop quantum gravity and spin-foam models. We make the classical analysis of the model and perform both path integral and canonical quantizations. As for the full theory, the reduced model admits two types of classical solutions: topological and gravitational ones. The quantization mixes these two solutions, which prevents the model to be equivalent to standard quantum cosmology. Furthermore, the topological solution dominates at the classical limit. We also study the effect of an Immirzi parameter in the model. |
1407.5114 | Mariam Bouhmadi-Lopez | Mariam Bouhmadi-Lopez, Che-Yu Chen, Pisin Chen | Cosmological singularities in Born-Infeld determinantal gravity | 6 pages, 2 figures, RevTex4-1. A minor change. Version accepted in
PRD | Phys. Rev. D 90, 123518 (2014) | 10.1103/PhysRevD.90.123518 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Born-Infeld determinantal gravity has been recently proposed as a way to
smooth the Big Bang singularity. This theory is formulated on the Weitzenbock
space-time and the teleparallel representation is used instead of the standard
Riemannian representation. We find that although this theory is shown to be
singularity-free for certain region of the parameter space in which the
divergence of the Hubble rate at the high energy regime is substituted by a
de-Sitter stage or a bounce in a Friedmann-Lemaitre-Robertson-Walker universe,
cosmological singularities such as Big Rip, Big Bang, Big Freeze, and Sudden
singularities can emerge in other regions of the configuration space of the
theory. We also show that all these singular events exist even though the
Universe is filled with a perfect fluid with a constant equation of state.
| [
{
"created": "Fri, 18 Jul 2014 20:42:24 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Nov 2014 19:14:07 GMT",
"version": "v2"
}
] | 2014-12-24 | [
[
"Bouhmadi-Lopez",
"Mariam",
""
],
[
"Chen",
"Che-Yu",
""
],
[
"Chen",
"Pisin",
""
]
] | The Born-Infeld determinantal gravity has been recently proposed as a way to smooth the Big Bang singularity. This theory is formulated on the Weitzenbock space-time and the teleparallel representation is used instead of the standard Riemannian representation. We find that although this theory is shown to be singularity-free for certain region of the parameter space in which the divergence of the Hubble rate at the high energy regime is substituted by a de-Sitter stage or a bounce in a Friedmann-Lemaitre-Robertson-Walker universe, cosmological singularities such as Big Rip, Big Bang, Big Freeze, and Sudden singularities can emerge in other regions of the configuration space of the theory. We also show that all these singular events exist even though the Universe is filled with a perfect fluid with a constant equation of state. |
gr-qc/0109038 | Patrick Peter | Patrick Peter (IAP) and Nelson Pinto-Neto (CBPF) | Has the Universe always expanded ? | 11 pages, LaTeX-ReVTeX, no figures, submitted to PRD | Phys.Rev. D65 (2002) 023513 | 10.1103/PhysRevD.65.023513 | null | gr-qc | null | We consider a cosmological setting for which the currently expanding era is
preceded by a contracting phase, that is, we assume the Universe experienced at
least one bounce. We show that scalar hydrodynamic perturbations lead to a
singular behavior of the Bardeen potential and/or its derivatives (i.e. the
curvature) for whatever Universe model for which the last bounce epoch can be
smoothly and causally joined to the radiation dominated era. Such a Universe
would be filled with non-linear perturbations long before nucleosynthesis, and
would thus be incompatible with observations. We therefore conclude that no
observable bounce could possibly have taken place in the early universe if
Einstein gravity together with hydrodynamical fluids is to describe its
evolution, and hence, under these conditions, that the Universe has always
expanded.
| [
{
"created": "Tue, 11 Sep 2001 16:35:10 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Peter",
"Patrick",
"",
"IAP"
],
[
"Pinto-Neto",
"Nelson",
"",
"CBPF"
]
] | We consider a cosmological setting for which the currently expanding era is preceded by a contracting phase, that is, we assume the Universe experienced at least one bounce. We show that scalar hydrodynamic perturbations lead to a singular behavior of the Bardeen potential and/or its derivatives (i.e. the curvature) for whatever Universe model for which the last bounce epoch can be smoothly and causally joined to the radiation dominated era. Such a Universe would be filled with non-linear perturbations long before nucleosynthesis, and would thus be incompatible with observations. We therefore conclude that no observable bounce could possibly have taken place in the early universe if Einstein gravity together with hydrodynamical fluids is to describe its evolution, and hence, under these conditions, that the Universe has always expanded. |
0903.2258 | David Reeb | Stephen D. H. Hsu, David Reeb | Black holes, information and decoherence | 7 pages, revtex; v2: added discussion of laboratory decoherence
experiments, minor changes, final version to be published in Phys. Rev. D | Phys.Rev.D79:124037,2009 | 10.1103/PhysRevD.79.124037 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the experimental capabilities required to test whether black
holes destroy information. We show that an experiment capable of illuminating
the information puzzle must necessarily be able to detect or manipulate
macroscopic superpositions (i.e., Everett branches). Hence, it could also
address the fundamental question of decoherence versus wavefunction collapse.
| [
{
"created": "Thu, 12 Mar 2009 20:01:05 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jun 2009 01:48:21 GMT",
"version": "v2"
}
] | 2009-07-09 | [
[
"Hsu",
"Stephen D. H.",
""
],
[
"Reeb",
"David",
""
]
] | We investigate the experimental capabilities required to test whether black holes destroy information. We show that an experiment capable of illuminating the information puzzle must necessarily be able to detect or manipulate macroscopic superpositions (i.e., Everett branches). Hence, it could also address the fundamental question of decoherence versus wavefunction collapse. |
0806.3052 | Eric Poisson | Stephanne Taylor and Eric Poisson | Nonrotating black hole in a post-Newtonian tidal environment | 27 pages, 1 figure | Phys.Rev.D78:084016,2008 | 10.1103/PhysRevD.78.084016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the motion and tidal dynamics of a nonrotating black hole placed
within a post-Newtonian external spacetime. The tidal perturbation created by
the external environment is treated as a small perturbation. At a large
distance from the black hole, the gravitational field of the external
distribution of matter is assumed to be sufficiently weak to be adequately
described by the (first) post-Newtonian approximation to general relativity.
There, the black hole is treated as a monopole contribution to the total
gravitational field. There exists an overlap in the domains of validity of each
description, and the black-hole and post-Newtonian metrics are matched in the
overlap. The matching procedure produces the equations of motion for the black
hole and the gravito-electric and gravito-magnetic tidal fields acting on the
black hole. We first calculate the equations of motion and tidal fields by
making no assumptions regarding the nature of the post-Newtonian environment;
this could contain a continuous distribution of matter or any number of
condensed bodies. We next specialize our discussion to a situation in which the
black hole is a member of a post-Newtonian two-body system. As an application
of our results, we examine the geometry of the deformed event horizon and
calculate the tidal heating of the black hole, the rate at which it acquires
mass as a result of its tidal interaction with the companion body.
| [
{
"created": "Wed, 18 Jun 2008 17:38:42 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Sep 2008 18:35:12 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Taylor",
"Stephanne",
""
],
[
"Poisson",
"Eric",
""
]
] | We examine the motion and tidal dynamics of a nonrotating black hole placed within a post-Newtonian external spacetime. The tidal perturbation created by the external environment is treated as a small perturbation. At a large distance from the black hole, the gravitational field of the external distribution of matter is assumed to be sufficiently weak to be adequately described by the (first) post-Newtonian approximation to general relativity. There, the black hole is treated as a monopole contribution to the total gravitational field. There exists an overlap in the domains of validity of each description, and the black-hole and post-Newtonian metrics are matched in the overlap. The matching procedure produces the equations of motion for the black hole and the gravito-electric and gravito-magnetic tidal fields acting on the black hole. We first calculate the equations of motion and tidal fields by making no assumptions regarding the nature of the post-Newtonian environment; this could contain a continuous distribution of matter or any number of condensed bodies. We next specialize our discussion to a situation in which the black hole is a member of a post-Newtonian two-body system. As an application of our results, we examine the geometry of the deformed event horizon and calculate the tidal heating of the black hole, the rate at which it acquires mass as a result of its tidal interaction with the companion body. |
gr-qc/0406049 | Vladimir Khatsymovsky | V.M. Khatsymovsky | Feynman path integral in area tensor Regge calculus and correspondence
principle | 9 pages, plain LaTeX | Phys.Lett. B601 (2004) 222-228 | 10.1016/j.physletb.2004.09.038 | null | gr-qc | null | The quantum measure in area tensor Regge calculus can be constructed in such
the way that it reduces to the Feynman path integral describing canonical
quantisation if the continuous limit along any of the coordinates is taken.
This construction does not necessarily mean that Lorentzian (Euclidean) measure
satisfies correspondence principle, that is, takes the form proportional to
$e^{iS}$ ($e^{-S}$) where $S$ is the action. Requirement to fit this principle
means some restriction on the action, or, in the context of representation of
the Regge action in terms of independent rotation matrices (connections),
restriction on such representation. We show that the representation based on
separate treatment of the selfdual and antiselfdual rotations allows to modify
the derivation and give sense to the conditionally convergent integrals to
implement both the canonical quantisation and correspondence principles. If
configurations are considered such that the measure is factorisable into the
product of independent measures on the separate areas (thus far it was just the
case in our analysis), the considered modification of the measure does not
effect the vacuum expectation values.
| [
{
"created": "Fri, 11 Jun 2004 15:31:08 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Khatsymovsky",
"V. M.",
""
]
] | The quantum measure in area tensor Regge calculus can be constructed in such the way that it reduces to the Feynman path integral describing canonical quantisation if the continuous limit along any of the coordinates is taken. This construction does not necessarily mean that Lorentzian (Euclidean) measure satisfies correspondence principle, that is, takes the form proportional to $e^{iS}$ ($e^{-S}$) where $S$ is the action. Requirement to fit this principle means some restriction on the action, or, in the context of representation of the Regge action in terms of independent rotation matrices (connections), restriction on such representation. We show that the representation based on separate treatment of the selfdual and antiselfdual rotations allows to modify the derivation and give sense to the conditionally convergent integrals to implement both the canonical quantisation and correspondence principles. If configurations are considered such that the measure is factorisable into the product of independent measures on the separate areas (thus far it was just the case in our analysis), the considered modification of the measure does not effect the vacuum expectation values. |
gr-qc/0008003 | Ana Nunes | Ana Nunes (U. Lisbon) and Jose P. Mimoso (U. Lisbon) | On the potentials yielding cosmological scaling solutions | RevTeX, 10 pages, no figures | Phys.Lett. B488 (2000) 423-427 | 10.1016/S0370-2693(00)00919-9 | CFNUL/2000-1 | gr-qc | null | In the present work we perform a phase-plane analysis of the complete
dynamical system corresponding to a flat FRW cosmological models with a perfect
fluid and a self-interacting scalar field and show that every positive and
monotonous potential which is asymptotically exponential yields a scaling
solution as a global attractor.
| [
{
"created": "Tue, 1 Aug 2000 16:39:32 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Aug 2000 20:56:07 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Nunes",
"Ana",
"",
"U. Lisbon"
],
[
"Mimoso",
"Jose P.",
"",
"U. Lisbon"
]
] | In the present work we perform a phase-plane analysis of the complete dynamical system corresponding to a flat FRW cosmological models with a perfect fluid and a self-interacting scalar field and show that every positive and monotonous potential which is asymptotically exponential yields a scaling solution as a global attractor. |
1712.00135 | Elena Giorgi | Elena Giorgi | Coupled gravitational and electromagnetic perturbations of
Reissner-Nordstr\"om spacetime in a polarized setting | null | null | null | null | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive a system of equations governing the coupled gravitational and
electromagnetic perturbations of Reissner-Nordstr\"om spacetime. The equations
are derived in the context of global non-linear stability of
Reissner-Nordstr\"om under axially symmetric polarized perturbations, as a
generalization of the recent work on non-linear stability of Schwarzschild
spacetime of Klainerman-Szeftel. The main result consists in deriving, through
a Chandrasekhar-type transformation, a gauge invariant quantity associated to
the electromagnetic tensor that verifies a Regge-Wheeler equation. In this
paper, we present the derivation of the main equations, postponing the
estimates of the non-linear system and the construction of the dynamical
spacetime to a later time.
| [
{
"created": "Fri, 1 Dec 2017 00:26:39 GMT",
"version": "v1"
}
] | 2017-12-04 | [
[
"Giorgi",
"Elena",
""
]
] | We derive a system of equations governing the coupled gravitational and electromagnetic perturbations of Reissner-Nordstr\"om spacetime. The equations are derived in the context of global non-linear stability of Reissner-Nordstr\"om under axially symmetric polarized perturbations, as a generalization of the recent work on non-linear stability of Schwarzschild spacetime of Klainerman-Szeftel. The main result consists in deriving, through a Chandrasekhar-type transformation, a gauge invariant quantity associated to the electromagnetic tensor that verifies a Regge-Wheeler equation. In this paper, we present the derivation of the main equations, postponing the estimates of the non-linear system and the construction of the dynamical spacetime to a later time. |
gr-qc/0610055 | Ozgur Delice | Ozgur Delice | Cylindrically symmetric, static strings with a cosmological constant in
Brans-Dicke theory | 8 pages, Revtex; Published version | Phys.Rev.D74:124001,2006 | 10.1103/PhysRevD.74.124001 | null | gr-qc hep-th | null | The static, cylindrically symmetric vacuum solutions with a cosmological
constant in the framework of the Brans-Dicke theory are investigated. Some of
these solutions admitting Lorentz boost invariance along the symmetry axis
correspond to local, straight cosmic strings with a cosmological constant. Some
physical properties of such solutions are studied. These strings apply
attractive or repulsive forces on the test particles. A smooth matching is also
performed with a recently introduced interior thick string solution with a
cosmological constant.
| [
{
"created": "Wed, 11 Oct 2006 13:30:52 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Oct 2006 12:50:59 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Dec 2006 01:55:19 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Delice",
"Ozgur",
""
]
] | The static, cylindrically symmetric vacuum solutions with a cosmological constant in the framework of the Brans-Dicke theory are investigated. Some of these solutions admitting Lorentz boost invariance along the symmetry axis correspond to local, straight cosmic strings with a cosmological constant. Some physical properties of such solutions are studied. These strings apply attractive or repulsive forces on the test particles. A smooth matching is also performed with a recently introduced interior thick string solution with a cosmological constant. |
1206.5517 | Frigyes Nemes Mr. | F. Nemes, B. Mik\'oczi | Perturbed Kepler-problem in general relativity with quaternions | 22 pages, 4 figures | Int. J. Mod. Phys. D 22, 1350040 (2013) | 10.1142/S0218271813500405 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The motion of binary star systems is re-examined in the presence of
perturbations from the theory of general relativity. The Kepler problem is
regularized and linearized with quaternions. In this way first order
perturbation results are derived.
| [
{
"created": "Sun, 24 Jun 2012 16:19:33 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Jul 2012 13:23:06 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Oct 2012 09:11:44 GMT",
"version": "v3"
}
] | 2013-07-09 | [
[
"Nemes",
"F.",
""
],
[
"Mikóczi",
"B.",
""
]
] | The motion of binary star systems is re-examined in the presence of perturbations from the theory of general relativity. The Kepler problem is regularized and linearized with quaternions. In this way first order perturbation results are derived. |
gr-qc/9410032 | Kawai | Toshiharu Kawai | Exotic black hole solution in teleparallel theory of (2+1)-dimensional
gravity | 11, ReVTeX | Prog.Theor.Phys. 94 (1995) 1169-1174 | 10.1143/PTP.94.1169 | null | gr-qc | null | A black hole solution in a teleparallel theory of (2+1)-dimensional gravity,
given in a previous paper, is examined. This solution is also a solution of the
three-dimensional vacuum Einstein equation with a vanishing cosmological
constant. Remarkable is the fact that this solution gives a black hole in a \lq
\lq flat-land" in the Einstein theory and a Newtonian limit. Coordinate
transformations to \lq \lq Minkowskian" coordinates, however, are singular not
only at the origin, but also on the event horizon. {\em In the
three-dimensional Einstein theory, vacuum regions of space-times can be locally
non-trivial}.
| [
{
"created": "Mon, 24 Oct 1994 10:00:15 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Kawai",
"Toshiharu",
""
]
] | A black hole solution in a teleparallel theory of (2+1)-dimensional gravity, given in a previous paper, is examined. This solution is also a solution of the three-dimensional vacuum Einstein equation with a vanishing cosmological constant. Remarkable is the fact that this solution gives a black hole in a \lq \lq flat-land" in the Einstein theory and a Newtonian limit. Coordinate transformations to \lq \lq Minkowskian" coordinates, however, are singular not only at the origin, but also on the event horizon. {\em In the three-dimensional Einstein theory, vacuum regions of space-times can be locally non-trivial}. |
2305.01268 | Xiangyun Fu fu | Min Wang, Xiangyun Fu, Bing Xu, Ying Yang, and Zhaoxia Chen | Testing the FLRW metric with the Hubble and transversal BAO measurements | Accepted by PRD | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The cosmological principle is one of the fundamental assumptions of the
standard model of Cosmology (SCM), and it allow us to describe cosmic distances
and clocks by using the Friedmann-Lema$\rm{\hat{{\i}}}$tre-Roberton-Walker
(FLRW) metric. Thus, it is essential to test the FLRW metric with cosmological
observations to verify the validity of the SCM. In this work, we perform tests
of the FLRW metric by comparing the observational comoving angles between the
Hubble $H(z)$ and angular Baryon Acoustic Oscillation (BAO) measurements. The
Gaussian process is employed to reconstruct the Hubble $H(z)$ measurements and
the angular diameter distance (ADD) from the transversal BAO data. A
non-parametric method is adopted to probe the possible deviations from the FLRW
metric at any redshift by comparing the comoving distances from the
reconstructed Hubble $H(z)$ measurements with the ADD reconstructed from the
transversal BAO data. Then, we propose two types of parameterizations for the
deviations from the FLRW metric, and test the FLRW metric by using the priors
of specific sound horizon scales. To avoid the bias caused by the prior of a
specific sound horizon scale, we perform the consistency test with a flat prior
of the sound horizon scale. We find that there a concordance between the FLRW
metric and the observational data by using parametric and non-parametric
methods, and the parameterizations can be employed to test the FLRW metric in a
new way independent of the sound horizon scale.
| [
{
"created": "Tue, 2 May 2023 09:05:14 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Oct 2023 07:25:06 GMT",
"version": "v2"
}
] | 2023-10-30 | [
[
"Wang",
"Min",
""
],
[
"Fu",
"Xiangyun",
""
],
[
"Xu",
"Bing",
""
],
[
"Yang",
"Ying",
""
],
[
"Chen",
"Zhaoxia",
""
]
] | The cosmological principle is one of the fundamental assumptions of the standard model of Cosmology (SCM), and it allow us to describe cosmic distances and clocks by using the Friedmann-Lema$\rm{\hat{{\i}}}$tre-Roberton-Walker (FLRW) metric. Thus, it is essential to test the FLRW metric with cosmological observations to verify the validity of the SCM. In this work, we perform tests of the FLRW metric by comparing the observational comoving angles between the Hubble $H(z)$ and angular Baryon Acoustic Oscillation (BAO) measurements. The Gaussian process is employed to reconstruct the Hubble $H(z)$ measurements and the angular diameter distance (ADD) from the transversal BAO data. A non-parametric method is adopted to probe the possible deviations from the FLRW metric at any redshift by comparing the comoving distances from the reconstructed Hubble $H(z)$ measurements with the ADD reconstructed from the transversal BAO data. Then, we propose two types of parameterizations for the deviations from the FLRW metric, and test the FLRW metric by using the priors of specific sound horizon scales. To avoid the bias caused by the prior of a specific sound horizon scale, we perform the consistency test with a flat prior of the sound horizon scale. We find that there a concordance between the FLRW metric and the observational data by using parametric and non-parametric methods, and the parameterizations can be employed to test the FLRW metric in a new way independent of the sound horizon scale. |
1501.06282 | Chopin Soo | Eyo Eyo Ita III, Chopin Soo, Hoi-Lai Yu | Intrinsic Time Quantum Geometrodynamics | 6 pages | Prog. Theor. Exp. Phys. (2015) 083E01 | 10.1093/ptep/ptv109 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum Geometrodynamics with intrinsic time development and momentric
variables is presented. An underlying SU(3) group structure at each spatial
point regulates the theory. The intrinsic time behavior of the theory is
analyzed, together with its ground state and primordial quantum fluctuations.
Cotton-York potential dominates at early times when the universe was small; the
ground state naturally resolves Penrose's Weyl Curvature Hypothesis, and
thermodynamic and gravitational `arrows of time' point in the same direction.
Ricci scalar potential corresponding to Einstein's General Relativity emerges
as a zero-point energy contribution. A new set of fundamental commutation
relations without Planck's constant emerges from the unification of Gravitation
and Quantum Mechanics.
| [
{
"created": "Mon, 26 Jan 2015 08:25:30 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Feb 2015 15:46:49 GMT",
"version": "v2"
}
] | 2015-08-12 | [
[
"Ita",
"Eyo Eyo",
"III"
],
[
"Soo",
"Chopin",
""
],
[
"Yu",
"Hoi-Lai",
""
]
] | Quantum Geometrodynamics with intrinsic time development and momentric variables is presented. An underlying SU(3) group structure at each spatial point regulates the theory. The intrinsic time behavior of the theory is analyzed, together with its ground state and primordial quantum fluctuations. Cotton-York potential dominates at early times when the universe was small; the ground state naturally resolves Penrose's Weyl Curvature Hypothesis, and thermodynamic and gravitational `arrows of time' point in the same direction. Ricci scalar potential corresponding to Einstein's General Relativity emerges as a zero-point energy contribution. A new set of fundamental commutation relations without Planck's constant emerges from the unification of Gravitation and Quantum Mechanics. |
0804.2502 | Jos\'e Wadih Maluf Dr. | J. W. Maluf and F. F. Faria | On the construction of Fermi-Walker transported frames | 16 pages, no figures | AnnalenPhys.17:326-335,2008 | 10.1002/andp.200810289 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider tetrad fields as reference frames adapted to observers that move
along arbitrary timelike trajectories in spacetime. By means of a local Lorentz
transformation we can transform these frames into Fermi-Walker transported
frames, which define a standard of non-rotation for accelerated observers. Here
we present a simple prescription for the construction of Fermi-Walker
transported frames out of an arbitrary set of tetrad fields.
| [
{
"created": "Tue, 15 Apr 2008 23:40:40 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Maluf",
"J. W.",
""
],
[
"Faria",
"F. F.",
""
]
] | We consider tetrad fields as reference frames adapted to observers that move along arbitrary timelike trajectories in spacetime. By means of a local Lorentz transformation we can transform these frames into Fermi-Walker transported frames, which define a standard of non-rotation for accelerated observers. Here we present a simple prescription for the construction of Fermi-Walker transported frames out of an arbitrary set of tetrad fields. |
2307.16534 | Kamal Hajian | Kamal Hajian | Single-rotating Five-dimensional Near-horizon Extremal Geometry in
General Relativity | 10 pages, published version | Phys.Rev.D 109 (2024) 4, 044040 | 10.1103/PhysRevD.109.044040 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The geometries with SL$(2,\mathbb{R})$ and some axial U$(1)$ isometries are
called ``near-horizon extremal geometries" and are found usually, but not
necessarily, in the near-horizon limit of the extremal black holes. We present
a new member of this family of solutions in five-dimensional Einstein-Hilbert
gravity that has only one nonzero angular momentum. In contrast with the
single-rotating Myers-Perry extremal black hole and its near-horizon geometry
in five dimensions, this solution may have a nonvanishing and finite entropy.
Although there is a uniqueness theorem that prohibits the existence of such
single-rotating near-horizon geometries in five-dimensional general relativity,
this solution has a curvature singularity at one of the poles, which breaks the
smoothness conditions in the theorem.
| [
{
"created": "Mon, 31 Jul 2023 10:00:25 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Feb 2024 08:39:27 GMT",
"version": "v2"
}
] | 2024-02-22 | [
[
"Hajian",
"Kamal",
""
]
] | The geometries with SL$(2,\mathbb{R})$ and some axial U$(1)$ isometries are called ``near-horizon extremal geometries" and are found usually, but not necessarily, in the near-horizon limit of the extremal black holes. We present a new member of this family of solutions in five-dimensional Einstein-Hilbert gravity that has only one nonzero angular momentum. In contrast with the single-rotating Myers-Perry extremal black hole and its near-horizon geometry in five dimensions, this solution may have a nonvanishing and finite entropy. Although there is a uniqueness theorem that prohibits the existence of such single-rotating near-horizon geometries in five-dimensional general relativity, this solution has a curvature singularity at one of the poles, which breaks the smoothness conditions in the theorem. |
2307.09079 | Tao Wang | Zhi-Shuo Qu, Towe Wang, Chao-Jun Feng | Reduced Kiselev black hole | 8 pages, 5 figures, references added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Kiselev model describes a black hole surrounded by a fluid with equations
of state $p_r/\rho=-1$ and $p_t/\rho=(3w+1)/2$ respectively in radial and
tangential directions. It has been extensively studied in the parameter region
$-1<w<-1/3$. If one rids off the black hole and turns to the region $-1/3<w<0$,
i.e. $p_t>0$, then a new horizon of black hole type will emerge. This case has
been mentioned in Kiselev's pioneer work but seldom investigated in the
literature. Referring to it as reduced Kiselev black hole, we revisit this case
with attention to its causal structure, thermodynamics, shadow cast and
weak-field limit. An alternative interpretation and extensions of the black
hole are also discussed.
| [
{
"created": "Tue, 18 Jul 2023 08:56:37 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Dec 2023 13:01:46 GMT",
"version": "v2"
}
] | 2023-12-27 | [
[
"Qu",
"Zhi-Shuo",
""
],
[
"Wang",
"Towe",
""
],
[
"Feng",
"Chao-Jun",
""
]
] | The Kiselev model describes a black hole surrounded by a fluid with equations of state $p_r/\rho=-1$ and $p_t/\rho=(3w+1)/2$ respectively in radial and tangential directions. It has been extensively studied in the parameter region $-1<w<-1/3$. If one rids off the black hole and turns to the region $-1/3<w<0$, i.e. $p_t>0$, then a new horizon of black hole type will emerge. This case has been mentioned in Kiselev's pioneer work but seldom investigated in the literature. Referring to it as reduced Kiselev black hole, we revisit this case with attention to its causal structure, thermodynamics, shadow cast and weak-field limit. An alternative interpretation and extensions of the black hole are also discussed. |
1405.2832 | Roberto Chan | R. Chan, M. F. A. da Silva, C. F. C. Brandt | Gravitational Collapse of an Imperfect Non Adiabatic Fluid | 25 pages, 16 figures, published in IJMPD | International Journal of Modern Physics D Vol. 23, No. 6 (2014)
1450056 | 10.1142/S0218271814500564 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the evolution of an anisotropic shear-free fluid with heat flux and
kinematic self-similarity of the second kind. We found a class of solution to
the Einstein field equations by assuming that the part of the tangential
pressure which is explicitly time dependent of the fluid is zero and that the
fluid moves along time-like geodesics. The energy conditions, geometrical and
physical properties of the solutions are studied. The energy conditions are all
satisfied at the beginning of the collapse but when the system approaches the
singularity the energy conditions are violated, allowing for the appearance of
an attractive phantom energy. We have found that, depending on the self-similar
parameter $\alpha$ and the geometrical radius, they may represent a naked
singularity. We speculate that the apparent horizon disappears due to the
emergence of exotic energy at the end of the collapse, or due to the
characteristics of null acceleration systems as shown by recent work.
| [
{
"created": "Mon, 12 May 2014 16:51:31 GMT",
"version": "v1"
}
] | 2014-05-13 | [
[
"Chan",
"R.",
""
],
[
"da Silva",
"M. F. A.",
""
],
[
"Brandt",
"C. F. C.",
""
]
] | We study the evolution of an anisotropic shear-free fluid with heat flux and kinematic self-similarity of the second kind. We found a class of solution to the Einstein field equations by assuming that the part of the tangential pressure which is explicitly time dependent of the fluid is zero and that the fluid moves along time-like geodesics. The energy conditions, geometrical and physical properties of the solutions are studied. The energy conditions are all satisfied at the beginning of the collapse but when the system approaches the singularity the energy conditions are violated, allowing for the appearance of an attractive phantom energy. We have found that, depending on the self-similar parameter $\alpha$ and the geometrical radius, they may represent a naked singularity. We speculate that the apparent horizon disappears due to the emergence of exotic energy at the end of the collapse, or due to the characteristics of null acceleration systems as shown by recent work. |
2102.06951 | Pardyumn Kumar Sahoo | Avik De, Tee-How Loo, Simran Arora and P.K. Sahoo | Energy conditions for a $(WRS)_4$ spacetime in $F(R)$-gravity | EPJP published version | Eur. Phys. J. Plus, 136(2) (2021) 218 | 10.1140/epjp/s13360-021-01216-2 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The objective of the present paper is to study 4-dimensional weakly Ricci
symmetric spacetimes $(WRS)_4$ with non-zero constant Ricci scalar. We prove
that such a $(WRS)_4$ satisfying $F(R)$-gravity field equations represents a
perfect fluid with vanishing vorticity. Some energy conditions are studied
under the current setting to constrain the functional form of $F(R)$. We
examine a couple of popular toy models in $F(R)$-gravity, $F(R)=e^{\alpha R}$
where $\alpha$ is constant and $F(R)=R-\beta \tanh(R)$, $\beta$ is a constant.
We also find that the equation of state parameter (EoS) in both models supports
the universe's accelerating behavior, i.e., $\omega=-1$. According to the
recently suggested observations of accelerated expansion, both cases define
that the null, weak, and dominant energy conditions justify their requirements
while the strong energy conditions violate them.
| [
{
"created": "Sat, 13 Feb 2021 16:02:33 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Mar 2021 05:25:59 GMT",
"version": "v2"
}
] | 2021-03-30 | [
[
"De",
"Avik",
""
],
[
"Loo",
"Tee-How",
""
],
[
"Arora",
"Simran",
""
],
[
"Sahoo",
"P. K.",
""
]
] | The objective of the present paper is to study 4-dimensional weakly Ricci symmetric spacetimes $(WRS)_4$ with non-zero constant Ricci scalar. We prove that such a $(WRS)_4$ satisfying $F(R)$-gravity field equations represents a perfect fluid with vanishing vorticity. Some energy conditions are studied under the current setting to constrain the functional form of $F(R)$. We examine a couple of popular toy models in $F(R)$-gravity, $F(R)=e^{\alpha R}$ where $\alpha$ is constant and $F(R)=R-\beta \tanh(R)$, $\beta$ is a constant. We also find that the equation of state parameter (EoS) in both models supports the universe's accelerating behavior, i.e., $\omega=-1$. According to the recently suggested observations of accelerated expansion, both cases define that the null, weak, and dominant energy conditions justify their requirements while the strong energy conditions violate them. |
1809.01078 | Dr. Sudhaker Upadhyay | Sudhaker Upadhyay, Seyed Hossein Hendi, Shahram Panahiyan and Behzad
Eslam Panah | Thermal fluctuations of charged black holes in gravity's rainbow | 19 pages, 16 captioned figures, accepted for publication in PTEP | Prog. Theor. Exp. Phys. 2018, 093E01 | 10.1093/ptep/pty093 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum fluctuation effects have an irrefutable role in high energy physics.
Such fluctuation can be often regarded as a correction of infrared (IR) limit.
In this paper, the effects of the first-order correction of entropy, caused by
thermal fluctuation, on the thermodynamics of charged black holes in gravity's
rainbow will be discussed. It will be shown that such correction has profound
contributions to high energy limit of thermodynamical quantities, stability
conditions of the black holes and interestingly has no effect on
thermodynamical phase transitions. The coupling between gravity's rainbow and
the first-order correction will be addressed. In addition, the measurement of
entropy as a function of fluctuation of temperature will be done and it will be
shown that de Sitter (dS) case enforces an upper limit on the values of
temperature and produces cyclic like diagrams. While for the anti-de Sitter
(AdS) case, a lower limit on the entropy is provided and although for special
cases a cyclic like behavior could be observed, no upper or lower limit exists
for the temperature. In addition, a comparison between non-correction and
correction included cases on the thermodynamical properties of solutions will
also be discussed and the effects of the first-order correction will be
highlighted. It will be shown that the first-order correction provides the
solutions with larger classes of thermal stability conditions which may result
into existence of a larger number of thermodynamical structures for the black
holes.
| [
{
"created": "Tue, 4 Sep 2018 16:36:23 GMT",
"version": "v1"
}
] | 2018-10-02 | [
[
"Upadhyay",
"Sudhaker",
""
],
[
"Hendi",
"Seyed Hossein",
""
],
[
"Panahiyan",
"Shahram",
""
],
[
"Panah",
"Behzad Eslam",
""
]
] | Quantum fluctuation effects have an irrefutable role in high energy physics. Such fluctuation can be often regarded as a correction of infrared (IR) limit. In this paper, the effects of the first-order correction of entropy, caused by thermal fluctuation, on the thermodynamics of charged black holes in gravity's rainbow will be discussed. It will be shown that such correction has profound contributions to high energy limit of thermodynamical quantities, stability conditions of the black holes and interestingly has no effect on thermodynamical phase transitions. The coupling between gravity's rainbow and the first-order correction will be addressed. In addition, the measurement of entropy as a function of fluctuation of temperature will be done and it will be shown that de Sitter (dS) case enforces an upper limit on the values of temperature and produces cyclic like diagrams. While for the anti-de Sitter (AdS) case, a lower limit on the entropy is provided and although for special cases a cyclic like behavior could be observed, no upper or lower limit exists for the temperature. In addition, a comparison between non-correction and correction included cases on the thermodynamical properties of solutions will also be discussed and the effects of the first-order correction will be highlighted. It will be shown that the first-order correction provides the solutions with larger classes of thermal stability conditions which may result into existence of a larger number of thermodynamical structures for the black holes. |
0912.3125 | Doreen M\"uller | Doreen Mueller, Bernd Bruegmann | Toward a dynamical shift condition for unequal mass black hole binary
simulations | 15 pages, submitted to CQG for NRDA 2009 conference proceedings | Class.Quant.Grav.27:114008,2010 | 10.1088/0264-9381/27/11/114008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Moving puncture simulations of black hole binaries rely on a specific gauge
choice that leads to approximately stationary coordinates near each black hole.
Part of the shift condition is a damping parameter, which has to be properly
chosen for stable evolutions. However, a constant damping parameter does not
account for the difference in mass in unequal mass binaries. We introduce a
position dependent shift damping that addresses this problem. Although the
coordinates change, the changes in the extracted gravitational waves are small.
| [
{
"created": "Wed, 16 Dec 2009 12:51:09 GMT",
"version": "v1"
}
] | 2010-05-25 | [
[
"Mueller",
"Doreen",
""
],
[
"Bruegmann",
"Bernd",
""
]
] | Moving puncture simulations of black hole binaries rely on a specific gauge choice that leads to approximately stationary coordinates near each black hole. Part of the shift condition is a damping parameter, which has to be properly chosen for stable evolutions. However, a constant damping parameter does not account for the difference in mass in unequal mass binaries. We introduce a position dependent shift damping that addresses this problem. Although the coordinates change, the changes in the extracted gravitational waves are small. |
1211.7183 | Luigi Ferraioli | Luigi Ferraioli, Edward K. Porter, Eric Plagnol | Bayesian Inference for LISA Pathfinder using Markov Chain Monte Carlo
Methods | null | null | null | null | gr-qc astro-ph.IM physics.data-an | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a parameter estimation procedure based on a Bayesian framework by
applying a Markov Chain Monte Carlo algorithm to the calibration of the
dynamical parameters of a space based gravitational wave detector. The method
is based on the Metropolis-Hastings algorithm and a two-stage annealing
treatment in order to ensure an effective exploration of the parameter space at
the beginning of the chain. We compare two versions of the algorithm with an
application to a LISA Pathfinder data analysis problem. The two algorithms
share the same heating strategy but with one moving in coordinate directions
using proposals from a multivariate Gaussian distribution, while the other uses
the natural logarithm of some parameters and proposes jumps in the eigen-space
of the Fisher Information matrix. The algorithm proposing jumps in the
eigen-space of the Fisher Information matrix demonstrates a higher acceptance
rate and a slightly better convergence towards the equilibrium parameter
distributions in the application to LISA Pathfinder data . For this experiment,
we return parameter values that are all within $\sim1\sigma$ of the injected
values. When we analyse the accuracy of our parameter estimation in terms of
the effect they have on the force-per-unit test mass noise estimate, we find
that the induced errors are three orders of magnitude less than the expected
experimental uncertainty in the power spectral density.
| [
{
"created": "Fri, 30 Nov 2012 08:40:08 GMT",
"version": "v1"
}
] | 2012-12-03 | [
[
"Ferraioli",
"Luigi",
""
],
[
"Porter",
"Edward K.",
""
],
[
"Plagnol",
"Eric",
""
]
] | We present a parameter estimation procedure based on a Bayesian framework by applying a Markov Chain Monte Carlo algorithm to the calibration of the dynamical parameters of a space based gravitational wave detector. The method is based on the Metropolis-Hastings algorithm and a two-stage annealing treatment in order to ensure an effective exploration of the parameter space at the beginning of the chain. We compare two versions of the algorithm with an application to a LISA Pathfinder data analysis problem. The two algorithms share the same heating strategy but with one moving in coordinate directions using proposals from a multivariate Gaussian distribution, while the other uses the natural logarithm of some parameters and proposes jumps in the eigen-space of the Fisher Information matrix. The algorithm proposing jumps in the eigen-space of the Fisher Information matrix demonstrates a higher acceptance rate and a slightly better convergence towards the equilibrium parameter distributions in the application to LISA Pathfinder data . For this experiment, we return parameter values that are all within $\sim1\sigma$ of the injected values. When we analyse the accuracy of our parameter estimation in terms of the effect they have on the force-per-unit test mass noise estimate, we find that the induced errors are three orders of magnitude less than the expected experimental uncertainty in the power spectral density. |
2112.08032 | Djeyrane-Sophie Erfani | Djeyrane-Sophie Erfani, Hossein Shojaie | Study of the de Sitter space-time and its behavior at infinity | null | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | The aim of this manuscript is to review the studies about de Sitter solution
and the null infinity of asymptotically flat and de Sitter space-times. Thus,
after introducing the de Sitter space-time, the symmetry group is described.
Also precise definitions of asymptotically flat and de Sitter space-times are
reviewed. Henceforth, the null infinities and the asymptotic symmetry groups of
these two space-times are considered, which lead to the Fefferman-Graham
approach and the Penrose-Newman formalism.
| [
{
"created": "Wed, 15 Dec 2021 10:51:50 GMT",
"version": "v1"
}
] | 2021-12-16 | [
[
"Erfani",
"Djeyrane-Sophie",
""
],
[
"Shojaie",
"Hossein",
""
]
] | The aim of this manuscript is to review the studies about de Sitter solution and the null infinity of asymptotically flat and de Sitter space-times. Thus, after introducing the de Sitter space-time, the symmetry group is described. Also precise definitions of asymptotically flat and de Sitter space-times are reviewed. Henceforth, the null infinities and the asymptotic symmetry groups of these two space-times are considered, which lead to the Fefferman-Graham approach and the Penrose-Newman formalism. |
gr-qc/0005062 | Alicia M. Sintes | A.M. Sintes, B.F. Schutz | Removal of interference from external coherent signals | Latex, 6 pages, 3 figures. Published in "Laser Interferometer Space
Antenna: Second international LISA symposium on gravitational waves". Edt. W.
Folkner; American Institute of Physics, pp. 135-140 (1998) | null | null | null | gr-qc | null | We present a technique that we call coherent line removal, for removing
external coherent interference from gravitational wave interferometer data. We
illustrate the usefulness of this technique applying it to the the data
produced by the Glasgow laser interferometer in 1996 and removing all those
lines corresponding to the electricity supply frequency and its harmonics. We
also find that this method seems to reduce the level of non-Gaussian noise
present in the interferometer and therefore, it can raise the sensitivity and
duty cycle of the detectors.
| [
{
"created": "Tue, 16 May 2000 13:24:25 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sintes",
"A. M.",
""
],
[
"Schutz",
"B. F.",
""
]
] | We present a technique that we call coherent line removal, for removing external coherent interference from gravitational wave interferometer data. We illustrate the usefulness of this technique applying it to the the data produced by the Glasgow laser interferometer in 1996 and removing all those lines corresponding to the electricity supply frequency and its harmonics. We also find that this method seems to reduce the level of non-Gaussian noise present in the interferometer and therefore, it can raise the sensitivity and duty cycle of the detectors. |
1909.03034 | Vicente Antunes | Vicente Antunes, Ignacio Bediaga, Mario Novello | Gravitational baryogenesis without CPT violation | 17 pages, minor corrections and some explanatory remarks to comply
with the referee report are included | JCAP 10 (2019) 076 | 10.1088/1475-7516/2019/10/076 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that in theories with nonminimal curvature-matter couplings up to
first order in the curvature, baryon number (B) conservation and CP are
automatically violated, provided that the curvature scalar and its gradient do
not vanish. Together with the associated gravitationally induced particle
creation in a cosmological framework, which is an essentially
out-of-equilibrium process, this implies that all of Sakharov's conditions are
satisfied in the simplest extension of General Relativity, without the need of
CPT violation. Here, derivatives of the curvature can be disregarded, thus
evading the potential problems associated with the Gravitational Baryogenesis
(GB) model in a cosmological context. Thanks to the particle creation pressure
and the trace anomaly, the curvature scalar is nonzero even in a
radiation-dominated Universe. Moreover, the trace anomaly or the energy density
of a massive scalar field can amplify the baryon asymmetry at very high
temperatures, even when the particle creation rate is very slow. As a result, a
baryon asymmetry compatible with observations and a huge CP violation can be
generated in the early Universe.
| [
{
"created": "Fri, 6 Sep 2019 17:40:12 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Sep 2019 17:55:07 GMT",
"version": "v2"
},
{
"created": "Tue, 1 Oct 2019 03:21:45 GMT",
"version": "v3"
},
{
"created": "Sun, 3 Nov 2019 23:04:21 GMT",
"version": "v4"
}
] | 2019-11-13 | [
[
"Antunes",
"Vicente",
""
],
[
"Bediaga",
"Ignacio",
""
],
[
"Novello",
"Mario",
""
]
] | We show that in theories with nonminimal curvature-matter couplings up to first order in the curvature, baryon number (B) conservation and CP are automatically violated, provided that the curvature scalar and its gradient do not vanish. Together with the associated gravitationally induced particle creation in a cosmological framework, which is an essentially out-of-equilibrium process, this implies that all of Sakharov's conditions are satisfied in the simplest extension of General Relativity, without the need of CPT violation. Here, derivatives of the curvature can be disregarded, thus evading the potential problems associated with the Gravitational Baryogenesis (GB) model in a cosmological context. Thanks to the particle creation pressure and the trace anomaly, the curvature scalar is nonzero even in a radiation-dominated Universe. Moreover, the trace anomaly or the energy density of a massive scalar field can amplify the baryon asymmetry at very high temperatures, even when the particle creation rate is very slow. As a result, a baryon asymmetry compatible with observations and a huge CP violation can be generated in the early Universe. |
1603.09693 | Peter Zimmerman | Samuel E. Gralla and Peter Zimmerman | Plasma Waves and Jets from Moving Conductors | 10 pages. v2 improvements | Phys. Rev. D 93, 123016 (2016) | 10.1103/PhysRevD.93.123016 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider force-free plasma waves launched by the motion of conducting
material through a magnetic field. We develop a spacetime-covariant formalism
for perturbations of a uniform magnetic field and show how the transverse
motion of a conducting fluid acts as a source. We show that fast-mode waves are
sourced by the compressibility of the fluid, with incompressible fluids
launching a pure-Alfv\'en outflow. Remarkably, this outflow can be written down
in closed form for an arbitrary time-dependent, nonaxisymmetric incompressible
flow. The instantaneous flow velocity is imprinted on the magnetic field and
transmitted away at the speed of light, carrying detailed information about the
conducting source at the time of emission. These results can be applied to
transients in pulsar outflows and to jets from neutron stars orbiting in the
magnetosphere of another compact object. We discuss jets from moving conductors
in some detail.
| [
{
"created": "Thu, 31 Mar 2016 17:28:53 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Jun 2016 23:24:13 GMT",
"version": "v2"
}
] | 2016-06-29 | [
[
"Gralla",
"Samuel E.",
""
],
[
"Zimmerman",
"Peter",
""
]
] | We consider force-free plasma waves launched by the motion of conducting material through a magnetic field. We develop a spacetime-covariant formalism for perturbations of a uniform magnetic field and show how the transverse motion of a conducting fluid acts as a source. We show that fast-mode waves are sourced by the compressibility of the fluid, with incompressible fluids launching a pure-Alfv\'en outflow. Remarkably, this outflow can be written down in closed form for an arbitrary time-dependent, nonaxisymmetric incompressible flow. The instantaneous flow velocity is imprinted on the magnetic field and transmitted away at the speed of light, carrying detailed information about the conducting source at the time of emission. These results can be applied to transients in pulsar outflows and to jets from neutron stars orbiting in the magnetosphere of another compact object. We discuss jets from moving conductors in some detail. |
1911.02030 | T. Padmanabhan | T. Padmanabhan | Geodesic distance: A descriptor of geometry and correlator of
pre-geometric density of spacetime events | ver 3: 18 pages; Appendix with details of the calculations added | null | 10.1142/S0217732320300086 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Classical geometry can be described either in terms of a metric tensor
$g_{ab}(x)$ or in terms of the geodesic distance $\sigma^2(x,x')$. Recent work,
however, has shown that the geodesic distance is better suited to describe the
quantum structure of spacetime. This is because one can incorporate some of the
key quantum effects by replacing $\sigma^2$ by another function $S[\sigma^2]$
such that $S[0]=L_0^2$ is non-zero. This allows one to introduce a
zero-point-length in the spacetime. I show that the geodesic distance can be an
emergent construct, arising in the form of a correlator
$S[\sigma^2(x,y)]=\langle J(x)J(y)\rangle$, of a pregeometric variable $J(x)$,
which, in turn, can be interpreted as the quantum density of spacetime events.
This approach also shows why null surfaces play a special role in the interface
of quantum theory and gravity. I describe several technical and conceptual
aspects of this construction and discuss some of its implications.
| [
{
"created": "Tue, 5 Nov 2019 19:00:03 GMT",
"version": "v1"
},
{
"created": "Sun, 23 Feb 2020 08:34:20 GMT",
"version": "v2"
},
{
"created": "Fri, 13 Mar 2020 07:33:57 GMT",
"version": "v3"
}
] | 2020-05-20 | [
[
"Padmanabhan",
"T.",
""
]
] | Classical geometry can be described either in terms of a metric tensor $g_{ab}(x)$ or in terms of the geodesic distance $\sigma^2(x,x')$. Recent work, however, has shown that the geodesic distance is better suited to describe the quantum structure of spacetime. This is because one can incorporate some of the key quantum effects by replacing $\sigma^2$ by another function $S[\sigma^2]$ such that $S[0]=L_0^2$ is non-zero. This allows one to introduce a zero-point-length in the spacetime. I show that the geodesic distance can be an emergent construct, arising in the form of a correlator $S[\sigma^2(x,y)]=\langle J(x)J(y)\rangle$, of a pregeometric variable $J(x)$, which, in turn, can be interpreted as the quantum density of spacetime events. This approach also shows why null surfaces play a special role in the interface of quantum theory and gravity. I describe several technical and conceptual aspects of this construction and discuss some of its implications. |
1101.4375 | Maciej Dunajski | Stephen Casey, Maciej Dunajski, Gary Gibbons, Claude Warnick | Optical Metrics and Projective Equivalence | 18 pages, two figures, final version, to appear in Physical Review D | Phys.Rev.D83:084047,2011 | 10.1103/PhysRevD.83.084047 | DAMTP-2011-23 | gr-qc hep-th math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Trajectories of light rays in a static spacetime are described by
unparametrised geodesics of the Riemannian optical metric associated with the
Lorentzian spacetime metric. We investigate the uniqueness of this structure
and demonstrate that two different observers, moving relative to one another,
who both see the universe as static may determine the geometry of the light
rays differently. More specifically, we classify Lorentzian metrics admitting
more than one hyper--surface orthogonal time--like Killing vector and analyze
the projective equivalence of the resulting optical metrics. These metrics are
shown to be projectively equivalent up to diffeomorphism if the static Killing
vectors generate a group $SL(2, \R)$, but not projectively equivalent in
general. We also consider the cosmological $C$--metrics in Einstein--Maxwell
theory and demonstrate that optical metrics corresponding to different values
of the cosmological constant are projectively equivalent.
| [
{
"created": "Sun, 23 Jan 2011 14:06:52 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Mar 2011 21:20:42 GMT",
"version": "v2"
}
] | 2011-05-12 | [
[
"Casey",
"Stephen",
""
],
[
"Dunajski",
"Maciej",
""
],
[
"Gibbons",
"Gary",
""
],
[
"Warnick",
"Claude",
""
]
] | Trajectories of light rays in a static spacetime are described by unparametrised geodesics of the Riemannian optical metric associated with the Lorentzian spacetime metric. We investigate the uniqueness of this structure and demonstrate that two different observers, moving relative to one another, who both see the universe as static may determine the geometry of the light rays differently. More specifically, we classify Lorentzian metrics admitting more than one hyper--surface orthogonal time--like Killing vector and analyze the projective equivalence of the resulting optical metrics. These metrics are shown to be projectively equivalent up to diffeomorphism if the static Killing vectors generate a group $SL(2, \R)$, but not projectively equivalent in general. We also consider the cosmological $C$--metrics in Einstein--Maxwell theory and demonstrate that optical metrics corresponding to different values of the cosmological constant are projectively equivalent. |
gr-qc/0106009 | Beverly K. Berger | Beverly K. Berger | Approach to the Singularity in Spatially Inhomogeneous Cosmologies | 17 pages, in Differential Equations and Mathematical Physics :
Proceedings of an International Conference Held at the University of Alabama
in Birmingham, ed. by R. Weikard, G. Weinstein (American Mathematical
Society, 2000) | null | null | null | gr-qc | null | A combination of analytic and numerical methods has yielded a clear
understanding of the approach to the singularity in spatially inhomogeneous
cosmologies. Strong support is found for the longstanding claim by Belinskii,
Khalatnikov, and Lifshitz that the collapse is dominated by local Kasner or
Mixmaster behavior. The Method of Consistent Potentials is used to establish
the consistency of asymptotic velocity term dominance (AVTD) (local Kasner
behavior) in that no terms in Einstein's equations will grow exponentially when
the VTD solution, obtained by neglecting all terms containing spatial
derivatives, is substituted into the full equations. When the VTD solution is
inconsistent, the exponential terms act dynamically as potentials either to
drive the system into a consistent AVTD regime or to maintain an oscillatory
approach to the singularity.
| [
{
"created": "Mon, 4 Jun 2001 17:42:45 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Berger",
"Beverly K.",
""
]
] | A combination of analytic and numerical methods has yielded a clear understanding of the approach to the singularity in spatially inhomogeneous cosmologies. Strong support is found for the longstanding claim by Belinskii, Khalatnikov, and Lifshitz that the collapse is dominated by local Kasner or Mixmaster behavior. The Method of Consistent Potentials is used to establish the consistency of asymptotic velocity term dominance (AVTD) (local Kasner behavior) in that no terms in Einstein's equations will grow exponentially when the VTD solution, obtained by neglecting all terms containing spatial derivatives, is substituted into the full equations. When the VTD solution is inconsistent, the exponential terms act dynamically as potentials either to drive the system into a consistent AVTD regime or to maintain an oscillatory approach to the singularity. |
2006.06006 | Jose Luis Bl\'azquez-Salcedo | Jose Luis Bl\'azquez-Salcedo, Daniela D. Doneva, Sarah Kahlen, Jutta
Kunz, Petya Nedkova and Stoytcho S. Yazadjiev | Polar quasinormal modes of the scalarized Einstein-Gauss-Bonnet black
holes | 25 pages, 10 figures | Phys. Rev. D 102, 024086 (2020) | 10.1103/PhysRevD.102.024086 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the polar quasinormal modes of spontaneously scalarized black holes
in Einstein-Gauss-Bonnet theory. In previous works we showed that a set of
nodeless solutions of the fundamental branch of the model studied in [1] are
stable under both radial [2] and axial perturbations [3]. Here we calculate the
polar quasinormal modes and show that this set of solutions is stable against
the polar perturbations as well. Thus for a certain region of the parameter
space the scalarized black holes are potentially stable physically interesting
objects. The spectrum of the polar quasinormal modes differs both
quantitatively and qualitatively from the Schwarzschild one which offers the
possibility to test the Gauss-Bonnet theory via the future gravitational wave
observations.
| [
{
"created": "Wed, 10 Jun 2020 18:00:14 GMT",
"version": "v1"
}
] | 2020-08-05 | [
[
"Blázquez-Salcedo",
"Jose Luis",
""
],
[
"Doneva",
"Daniela D.",
""
],
[
"Kahlen",
"Sarah",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Nedkova",
"Petya",
""
],
[
"Yazadjiev",
"Stoytcho S.",
""
]
] | We study the polar quasinormal modes of spontaneously scalarized black holes in Einstein-Gauss-Bonnet theory. In previous works we showed that a set of nodeless solutions of the fundamental branch of the model studied in [1] are stable under both radial [2] and axial perturbations [3]. Here we calculate the polar quasinormal modes and show that this set of solutions is stable against the polar perturbations as well. Thus for a certain region of the parameter space the scalarized black holes are potentially stable physically interesting objects. The spectrum of the polar quasinormal modes differs both quantitatively and qualitatively from the Schwarzschild one which offers the possibility to test the Gauss-Bonnet theory via the future gravitational wave observations. |
1705.01461 | \.I \c{C}a\u{g}r{\i} \.I\c{s}eri | Levent Akant, Birses Debir, \.I. \c{C}a\u{g}r{\i} \.I\c{s}eri | Non-relativistic Limit of Thermodynamics of Bose Field in a Static
Space-time and Bose-Einstein Condensation | Typos corrected | null | 10.1088/1361-6382/aaa0a7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the grand canonical thermodynamics of a noninteracting scalar
field in a static spacetime. We take the nonrelativistic limit of thermodynamic
quantities in a way that leaves the curved structure of the background geometry
intact. Using Mellin transform and heat kernel techniques we obtain asymptotic
expansions of thermodynamic quantities appropriate for the analysis of
Bose-Einstein condensation. We apply our results to investigate gravitational
effects on the Bose-Einstein condensation for a scalar field in a finite
volume. We also analyze the boundary effects on the depletion coefficient of
the scalar field.
| [
{
"created": "Tue, 2 May 2017 10:20:03 GMT",
"version": "v1"
},
{
"created": "Mon, 22 May 2017 09:52:32 GMT",
"version": "v2"
},
{
"created": "Fri, 11 Aug 2017 14:58:47 GMT",
"version": "v3"
},
{
"created": "Tue, 22 May 2018 22:15:19 GMT",
"version": "v4"
}
] | 2018-05-24 | [
[
"Akant",
"Levent",
""
],
[
"Debir",
"Birses",
""
],
[
"İşeri",
"İ. Çağrı",
""
]
] | We consider the grand canonical thermodynamics of a noninteracting scalar field in a static spacetime. We take the nonrelativistic limit of thermodynamic quantities in a way that leaves the curved structure of the background geometry intact. Using Mellin transform and heat kernel techniques we obtain asymptotic expansions of thermodynamic quantities appropriate for the analysis of Bose-Einstein condensation. We apply our results to investigate gravitational effects on the Bose-Einstein condensation for a scalar field in a finite volume. We also analyze the boundary effects on the depletion coefficient of the scalar field. |
1006.0811 | Zuyao Sun | Zu-Yao Sun, Chun-Xiao Yue, You-Gen Shen, Chang-Bo Sun | Dynamics of phantom model with O(N) symmetry in loop quantum cosmology | 9 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Many astrophysical data show that the expansion of our universe is
accelerating. In this paper, we study the model of phantom with O(N) symmetry
in background of loop quantum cosmology(LQC). We investigate the phase-space
stability of the corresponding autonomous system and find no stable node but
only 2 saddle points in the field of real numbers. The dynamics is similar to
the single-field phantom model in LQC[1]. The effect of O(N) symmetry just
influence the detail of the universe's evolution. This is a sharp contrast with
the result in general relativity, in which the dynamics of scalar fields models
with O$(N)$ symmetry are quite different from the single-field models[2][3][4].
| [
{
"created": "Fri, 4 Jun 2010 08:44:36 GMT",
"version": "v1"
}
] | 2010-06-07 | [
[
"Sun",
"Zu-Yao",
""
],
[
"Yue",
"Chun-Xiao",
""
],
[
"Shen",
"You-Gen",
""
],
[
"Sun",
"Chang-Bo",
""
]
] | Many astrophysical data show that the expansion of our universe is accelerating. In this paper, we study the model of phantom with O(N) symmetry in background of loop quantum cosmology(LQC). We investigate the phase-space stability of the corresponding autonomous system and find no stable node but only 2 saddle points in the field of real numbers. The dynamics is similar to the single-field phantom model in LQC[1]. The effect of O(N) symmetry just influence the detail of the universe's evolution. This is a sharp contrast with the result in general relativity, in which the dynamics of scalar fields models with O$(N)$ symmetry are quite different from the single-field models[2][3][4]. |
gr-qc/9605044 | Herbert Liebl | H. Liebl (Vienna, Tech. U.), D.V. Vassilevich and S. Alexandrov (St.
Petersburg University) | Hawking radiation and masses in generalized dilaton theories | 24 pages, 3 Postscript figures | Class.Quant.Grav. 14 (1997) 889-904 | 10.1088/0264-9381/14/4/007 | TUW-96-08 | gr-qc hep-th | null | A generalized dilaton action is considered of which the standard dilaton
black hole and spherically reduced gravity are particular cases. The
Arnowitt-Deser-Misner (ADM) and the Bondi-Sachs (BS) mass are calculated.
Special attention is paid to both the asymptotic conditions for the metric as
well as for the reference space-time. For the latter one we suggest a modified
expression thereby obtaining a new definition of energy. Depending on the
parameters of the model the Hawking radiation behaves like a positive or
negative power of the mass.
| [
{
"created": "Mon, 20 May 1996 17:16:00 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Liebl",
"H.",
"",
"Vienna, Tech. U."
],
[
"Vassilevich",
"D. V.",
"",
"St.\n Petersburg University"
],
[
"Alexandrov",
"S.",
"",
"St.\n Petersburg University"
]
] | A generalized dilaton action is considered of which the standard dilaton black hole and spherically reduced gravity are particular cases. The Arnowitt-Deser-Misner (ADM) and the Bondi-Sachs (BS) mass are calculated. Special attention is paid to both the asymptotic conditions for the metric as well as for the reference space-time. For the latter one we suggest a modified expression thereby obtaining a new definition of energy. Depending on the parameters of the model the Hawking radiation behaves like a positive or negative power of the mass. |
gr-qc/9706019 | Neven | Neven Bilic (Rudjer Boskovic Institute Zagreb), Raoul Viollier
(university of Cape Town) | Free Energy of Gravitating Fermions | 7 pages, LaTex | null | null | null | gr-qc | null | We study a system of self-gravitating massive fermions in the framework of
the general-relativistic Thomas-Fermi model. We postulate the free energy
functional and show that its extremization is equivalent to solving the
Einstein's field equations. A self-gravitating fermion gas we then describe by
a set of Thomas-Fermi type self-consistency equations.
| [
{
"created": "Mon, 9 Jun 1997 14:28:39 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bilic",
"Neven",
"",
"Rudjer Boskovic Institute Zagreb"
],
[
"Viollier",
"Raoul",
"",
"university of Cape Town"
]
] | We study a system of self-gravitating massive fermions in the framework of the general-relativistic Thomas-Fermi model. We postulate the free energy functional and show that its extremization is equivalent to solving the Einstein's field equations. A self-gravitating fermion gas we then describe by a set of Thomas-Fermi type self-consistency equations. |
1305.4231 | Lorenzo Sebastiani | L. Sebastiani, D. Momeni, R. Myrzakulov and S.D. Odintsov | The instabilities and (anti)-evaporation of Schwarzschild-de Sitter
black holes in modified gravity | 23 pages, 10 figures, last version, accepted for publication in PRD | Physical Review D, V.88, N10, 104022 (2013) [17 pages] | 10.1103/PhysRevD.88.104022 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the future evolution of Nariai black hole which is extremal
limit of Schwarzschild-de Sitter one in modified gravity. The perturbations
equations around Nariai black hole are derived in static and cosmological
patches for general $F(R)$-gravity. The analytical and numerical study of
several realistic $F(R)$-models shows the occurence of rich variety of
scenarios: instabilities, celebrated Hawking evaporation and anti-evaporation
of black hole. The realization of specific scenario depends on the model under
consideration. It is remarkable that the presence of such primordial black
holes at current universe may indicate towards the modified gravity which
supports the anti-evaporation as preferrable model. As some generalization we
extend the study of Nariai black hole evolution to modified Gauss-Bonnet
gravity. The corresponding perturbations equations turn out to be much more
complicated than in the case of $F(R)$ gravity. For specific example of
modified Gauss-Bonnet gravity we demonstrate that Nariai solution maybe stable.
| [
{
"created": "Sat, 18 May 2013 06:03:12 GMT",
"version": "v1"
},
{
"created": "Sat, 2 Nov 2013 08:43:21 GMT",
"version": "v2"
}
] | 2013-12-30 | [
[
"Sebastiani",
"L.",
""
],
[
"Momeni",
"D.",
""
],
[
"Myrzakulov",
"R.",
""
],
[
"Odintsov",
"S. D.",
""
]
] | We investigate the future evolution of Nariai black hole which is extremal limit of Schwarzschild-de Sitter one in modified gravity. The perturbations equations around Nariai black hole are derived in static and cosmological patches for general $F(R)$-gravity. The analytical and numerical study of several realistic $F(R)$-models shows the occurence of rich variety of scenarios: instabilities, celebrated Hawking evaporation and anti-evaporation of black hole. The realization of specific scenario depends on the model under consideration. It is remarkable that the presence of such primordial black holes at current universe may indicate towards the modified gravity which supports the anti-evaporation as preferrable model. As some generalization we extend the study of Nariai black hole evolution to modified Gauss-Bonnet gravity. The corresponding perturbations equations turn out to be much more complicated than in the case of $F(R)$ gravity. For specific example of modified Gauss-Bonnet gravity we demonstrate that Nariai solution maybe stable. |
gr-qc/9405044 | Ian Moss | Ian G. Moss and Stephen J. Poletti | Conformal anomalies on Einstein spaces with Boundary | 8 pages, NCL94-TP10, (ReVTeX) | Phys.Lett. B333 (1994) 326-330 | 10.1016/0370-2693(94)90150-3 | null | gr-qc hep-th | null | The anomalous rescaling for antisymmetric tensor fields, including gauge
bosons, and Dirac fermions on Einstein spaces with boundary has been prone to
errors and these are corrected here. The explicit calculations lead to some
interesting identities that indicate a deeper underlying structure.
| [
{
"created": "Sat, 21 May 1994 09:59:29 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Moss",
"Ian G.",
""
],
[
"Poletti",
"Stephen J.",
""
]
] | The anomalous rescaling for antisymmetric tensor fields, including gauge bosons, and Dirac fermions on Einstein spaces with boundary has been prone to errors and these are corrected here. The explicit calculations lead to some interesting identities that indicate a deeper underlying structure. |
1503.03407 | Ivan Agullo | Ivan Agullo and Abhay Ashtekar | Unitarity and ultraviolet regularity in cosmology | 30 pages, 0 figures. Version to be published in PRD | Phys. Rev. D91, 124010 (2015) | 10.1103/PhysRevD.91.124010 | LSU-REL-031115 | gr-qc hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum field theory in curved space-times is a well developed area in
mathematical physics which has had important phenomenological applications to
the very early universe. However, it is not commonly appreciated that on time
dependent space-times ---including the simplest cosmological models--- dynamics
of quantum fields is not unitary in the standard sense. This issue is first
explained with an explicit example and it is then shown that a generalized
notion of unitarity does hold. The generalized notion allows one to correctly
pass to the Schr\"odinger picture starting from the Heisenberg picture used in
the textbook treatments. Finally, we indicate how these considerations can be
extended from simple cosmological models to general globally hyperbolic
space-times
| [
{
"created": "Wed, 11 Mar 2015 16:30:54 GMT",
"version": "v1"
},
{
"created": "Wed, 13 May 2015 14:23:01 GMT",
"version": "v2"
}
] | 2015-07-27 | [
[
"Agullo",
"Ivan",
""
],
[
"Ashtekar",
"Abhay",
""
]
] | Quantum field theory in curved space-times is a well developed area in mathematical physics which has had important phenomenological applications to the very early universe. However, it is not commonly appreciated that on time dependent space-times ---including the simplest cosmological models--- dynamics of quantum fields is not unitary in the standard sense. This issue is first explained with an explicit example and it is then shown that a generalized notion of unitarity does hold. The generalized notion allows one to correctly pass to the Schr\"odinger picture starting from the Heisenberg picture used in the textbook treatments. Finally, we indicate how these considerations can be extended from simple cosmological models to general globally hyperbolic space-times |
gr-qc/9810085 | Jose Luis Rosales | Jose-Luis Rosales and Jose-Luis Sanchez-Gomez | The "Pioneer effect" as a manifestation of the cosmic expansion in the
solar system | null | null | null | null | gr-qc | null | It is proposed that the recently reported anomalous acceleration acting on
the Pioneers spacecrafts should be a consequence of the existence of some local
curvature in light geodesics when using the coordinate speed of light in an
expanding spacetime. This suggests taht this "Pioneer effect" is nothing else
but the detection of cosmological expansion in the solar system.
| [
{
"created": "Wed, 28 Oct 1998 12:36:27 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Oct 1998 17:58:44 GMT",
"version": "v2"
},
{
"created": "Mon, 24 May 1999 17:57:16 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Rosales",
"Jose-Luis",
""
],
[
"Sanchez-Gomez",
"Jose-Luis",
""
]
] | It is proposed that the recently reported anomalous acceleration acting on the Pioneers spacecrafts should be a consequence of the existence of some local curvature in light geodesics when using the coordinate speed of light in an expanding spacetime. This suggests taht this "Pioneer effect" is nothing else but the detection of cosmological expansion in the solar system. |
1903.07898 | Albino Perego Dr | Albino Perego, Sebastiano Bernuzzi and David Radice | Thermodynamics conditions of matter in neutron star mergers | 23 pages, 10 Figures, to be submitted to EPJA Topical Issue: The
first Neutron Star Merger Observation - Implications for Nuclear Physics.
Movies of the thermodynamical conditions available also on the youtube
channel https://www.youtube.com/channel/UChmn-JGNa9mfY5H5938jnig | null | 10.1140/epja/i2019-12810-7 | null | gr-qc astro-ph.HE nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Matter in neutron star collisions can reach densities up to few times the
nuclear saturation threshold and temperatures up to one hundred MeV.
Understanding the structure and composition of such matter requires many-body
nonperturbative calculations that are currently highly uncertain.Unique
constraints on the neutron star matter are provided by gravitational-wave
observations aided by numerical relativity simulations. In this work, we
explore the thermodynamical conditions of matter and radiation along the merger
dynamics. We consider 3 microphysical equation of state models and numerical
relativity simulations including an approximate neutrino transport scheme. The
neutron star cores collision and their multiple centrifugal bounces heat the
initially cold matter to several tens of MeV. Streams of hot matter with
initial densities $\sim1-2\rho_0$ move outwards and cool due to decompression
and neutrino emission. The merger can result in a neutron star remnant with
densities up to $3-5\rho_0$ and temperatures $\sim 50$~MeV. The highest
temperatures are confined in an approximately spherical annulus at densities
$\sim\rho_0$. Such temperatures favour positron-neutron capture at densities
$\sim\rho_0$, thus leading to a neutrino emission dominated by electron
antineutrinos. We study the impact of trapped neutrinos on the remnant matter's
pressure, electron fraction and temperature and find that it has a negligible
effect. Disks around neutron star or black hole remnant are neutron rich and
not isentropic, but they differ in size, entropy and lepton fraction depending
on the nature of the central object. In presence of a black hole, disks are
smaller and mostly transparent to neutrinos; in presence of a massive neutron
star, they are more massive, geometrically and optically thick.
| [
{
"created": "Tue, 19 Mar 2019 09:24:25 GMT",
"version": "v1"
}
] | 2019-09-04 | [
[
"Perego",
"Albino",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Radice",
"David",
""
]
] | Matter in neutron star collisions can reach densities up to few times the nuclear saturation threshold and temperatures up to one hundred MeV. Understanding the structure and composition of such matter requires many-body nonperturbative calculations that are currently highly uncertain.Unique constraints on the neutron star matter are provided by gravitational-wave observations aided by numerical relativity simulations. In this work, we explore the thermodynamical conditions of matter and radiation along the merger dynamics. We consider 3 microphysical equation of state models and numerical relativity simulations including an approximate neutrino transport scheme. The neutron star cores collision and their multiple centrifugal bounces heat the initially cold matter to several tens of MeV. Streams of hot matter with initial densities $\sim1-2\rho_0$ move outwards and cool due to decompression and neutrino emission. The merger can result in a neutron star remnant with densities up to $3-5\rho_0$ and temperatures $\sim 50$~MeV. The highest temperatures are confined in an approximately spherical annulus at densities $\sim\rho_0$. Such temperatures favour positron-neutron capture at densities $\sim\rho_0$, thus leading to a neutrino emission dominated by electron antineutrinos. We study the impact of trapped neutrinos on the remnant matter's pressure, electron fraction and temperature and find that it has a negligible effect. Disks around neutron star or black hole remnant are neutron rich and not isentropic, but they differ in size, entropy and lepton fraction depending on the nature of the central object. In presence of a black hole, disks are smaller and mostly transparent to neutrinos; in presence of a massive neutron star, they are more massive, geometrically and optically thick. |
gr-qc/0303057 | Luciano Rezzolla | Luciano Rezzolla | Linear and Nonlinear Dynamics of Relativistic Tori | Invited Talk at the 15th SIGRAV Conference, Frascati Sept. 2002; IOP
Conference Series, one reference added | null | null | null | gr-qc astro-ph | null | I present results of two-dimensional general relativistic hydrodynamical
simulations of constant specific angular momentum tori orbiting around a
Schwarzschild black hole. After introducing axisymmetric perturbations, these
objects either become unstable to the runaway instability or respond with
regular oscillations. The latter, in particular, are responsible for
quasi-periodic bursts of accretion onto the black hole as well as for the
emission of intense gravitational radiation, with signal-to-noise ratios at the
detector which are comparable or even larger than the typical ones expected in
stellar-core collapse.
| [
{
"created": "Fri, 14 Mar 2003 18:41:08 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Mar 2003 12:02:09 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Rezzolla",
"Luciano",
""
]
] | I present results of two-dimensional general relativistic hydrodynamical simulations of constant specific angular momentum tori orbiting around a Schwarzschild black hole. After introducing axisymmetric perturbations, these objects either become unstable to the runaway instability or respond with regular oscillations. The latter, in particular, are responsible for quasi-periodic bursts of accretion onto the black hole as well as for the emission of intense gravitational radiation, with signal-to-noise ratios at the detector which are comparable or even larger than the typical ones expected in stellar-core collapse. |
gr-qc/0003044 | Abeesham | A. Beesham and S. G. Ghosh | Naked Singularities in the Charged Vaidya-deSitter Spacetime | 8 pages, latex, no figures | Int.J.Mod.Phys. D12 (2003) 801-810 | 10.1142/S0218271803003220 | null | gr-qc | null | We study the occurrence of naked singularities in the spherically symmetric
collapse of a charged null fluid in an expanding deSitter background - a piece
of charged Vaidya-deSitter spacetime. The necessary conditions for the
formation of a naked singularity are found. The results for the uncharged
solutions can be recovered from our analysis.
| [
{
"created": "Fri, 10 Mar 2000 08:05:35 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Beesham",
"A.",
""
],
[
"Ghosh",
"S. G.",
""
]
] | We study the occurrence of naked singularities in the spherically symmetric collapse of a charged null fluid in an expanding deSitter background - a piece of charged Vaidya-deSitter spacetime. The necessary conditions for the formation of a naked singularity are found. The results for the uncharged solutions can be recovered from our analysis. |
1007.3189 | Nigel Bishop | P.J. van der Walt and N.T. Bishop | Observational cosmology using characteristic numerical relativity | null | Phys.Rev.D82:084001,2010 | 10.1103/PhysRevD.82.084001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The characteristic formalism in numerical relativity, which has been
developed to study gravitational waves, and the observer metric approach in
observational cosmology both make use of coordinate systems based on null
cones. In this paper, these coordinate systems are compared and it is then
demonstrated how characteristic numerical relativity can be used to investigate
problems in observational cosmology. In a numerical experiment using the
characteristic formalism, it is shown how the historical evolution of a LTB
universe compares to that of the $\Lambda$CDM model given identical
observational data on a local observer's past null cone. It is demonstrated
that, at an earlier epoch of the LTB model, the observational data would not be
consistent with that of the $\Lambda$CDM model.
| [
{
"created": "Mon, 19 Jul 2010 15:45:56 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"van der Walt",
"P. J.",
""
],
[
"Bishop",
"N. T.",
""
]
] | The characteristic formalism in numerical relativity, which has been developed to study gravitational waves, and the observer metric approach in observational cosmology both make use of coordinate systems based on null cones. In this paper, these coordinate systems are compared and it is then demonstrated how characteristic numerical relativity can be used to investigate problems in observational cosmology. In a numerical experiment using the characteristic formalism, it is shown how the historical evolution of a LTB universe compares to that of the $\Lambda$CDM model given identical observational data on a local observer's past null cone. It is demonstrated that, at an earlier epoch of the LTB model, the observational data would not be consistent with that of the $\Lambda$CDM model. |
1405.7907 | Sean Carroll | Sean M. Carroll and Charles T. Sebens | Many Worlds, the Born Rule, and Self-Locating Uncertainty | 15 pages. A version of this paper appears as a chapter in Quantum
Theory: A Two-Time Success Story, Yakir Aharonov Festschrift (2013), D.C.
Struppa, J.M. Tollaksen, eds. (Springer-Verlag), p. 157. This work is a
summary of a more comprehensive paper at http://arxiv.org/abs/arXiv:1405.7577 | null | 10.1007/978-88-470-5217-8_10 | CALT-68-2929 | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide a derivation of the Born Rule in the context of the Everett
(Many-Worlds) approach to quantum mechanics. Our argument is based on the idea
of self-locating uncertainty: in the period between the wave function branching
via decoherence and an observer registering the outcome of the measurement,
that observer can know the state of the universe precisely without knowing
which branch they are on. We show that there is a uniquely rational way to
apportion credence in such cases, which leads directly to the Born Rule. Our
analysis generalizes straightforwardly to cases of combined classical and
quantum self-locating uncertainty, as in the cosmological multiverse.
| [
{
"created": "Fri, 30 May 2014 16:19:05 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jun 2014 08:16:10 GMT",
"version": "v2"
},
{
"created": "Wed, 25 Mar 2015 16:31:04 GMT",
"version": "v3"
}
] | 2015-06-19 | [
[
"Carroll",
"Sean M.",
""
],
[
"Sebens",
"Charles T.",
""
]
] | We provide a derivation of the Born Rule in the context of the Everett (Many-Worlds) approach to quantum mechanics. Our argument is based on the idea of self-locating uncertainty: in the period between the wave function branching via decoherence and an observer registering the outcome of the measurement, that observer can know the state of the universe precisely without knowing which branch they are on. We show that there is a uniquely rational way to apportion credence in such cases, which leads directly to the Born Rule. Our analysis generalizes straightforwardly to cases of combined classical and quantum self-locating uncertainty, as in the cosmological multiverse. |
1612.01236 | Ivan Agullo | Ivan Agullo and Parampreet Singh | Loop Quantum Cosmology: A brief review | 47 pages, 3 figures. To appear as a chapter contribution for a volume
edited by A. Ashtekar and J. Pullin, to be published in the World Scientific
series "100 Years of General Relativity." | null | null | LSU-REL-12160416 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the last decade, progress on quantization of homogeneous cosmological
spacetimes using techniques of loop quantum gravity has led to insights on
various fundamental questions and has opened new avenues to explore Planck
scale physics. These include the problem of singularities and their possible
generic resolution, constructing viable non-singular models of the very early
universe, and bridging quantum gravity with cosmological observations. These
results, which emerge from an interplay of sophisticated analytical and
numerical techniques, has also led to valuable hints on loop quantization of
black hole and inhomogeneous spacetimes. In this review, we provide a summary
of this progress while focusing on concrete examples of the quantization
procedure and phenomenology of cosmological perturbations.
| [
{
"created": "Mon, 5 Dec 2016 03:26:24 GMT",
"version": "v1"
}
] | 2016-12-06 | [
[
"Agullo",
"Ivan",
""
],
[
"Singh",
"Parampreet",
""
]
] | In the last decade, progress on quantization of homogeneous cosmological spacetimes using techniques of loop quantum gravity has led to insights on various fundamental questions and has opened new avenues to explore Planck scale physics. These include the problem of singularities and their possible generic resolution, constructing viable non-singular models of the very early universe, and bridging quantum gravity with cosmological observations. These results, which emerge from an interplay of sophisticated analytical and numerical techniques, has also led to valuable hints on loop quantization of black hole and inhomogeneous spacetimes. In this review, we provide a summary of this progress while focusing on concrete examples of the quantization procedure and phenomenology of cosmological perturbations. |
1911.11513 | Ioannis Gialamas | Ioannis D. Gialamas and A. B. Lahanas | Reheating in $R^2$ Palatini inflationary models | 38 pages, 14 figures, pdflatex, text, figures and references added,
formulas updated | Phys. Rev. D 101, 084007 (2020) | 10.1103/PhysRevD.101.084007 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider $R^2$ inflation in the Palatini gravity assuming the existence of
scalar fields, coupled to gravity in the most general manner. These theories,
in the Einstein frame, and for one scalar field $h$, share common features with
$K$ - inflation models. We apply this formalism for the study of popular
inflationary models, whose potentials are monomials, $ V \sim h^{n} $, with $ n
$ a positive even integer. We also study the Higgs model non-minimally coupled
to gravity. Although these have been recently studied, in the framework of the
Palatini approach, we show that the scalar power spectrum severely constrains
these models. Although we do not propose a particular reheating mechanism, we
show that the quadratic $ \sim h^2$ and the Higgs model can survive these
constraints with a maximum reheating temperature as large as $ \sim 10^{15} \,
GeV$, when reheating is instantaneous. However, this can be only attained at
the cost of a delicate fine-tuning of couplings. Deviations from this
fine-tuned values can still yield predictions compatible with the cosmological
data, for couplings that lie in very tight range, giving lower reheating
temperatures.
| [
{
"created": "Tue, 26 Nov 2019 13:21:33 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Dec 2019 10:56:34 GMT",
"version": "v2"
},
{
"created": "Tue, 3 Mar 2020 12:32:51 GMT",
"version": "v3"
}
] | 2020-04-08 | [
[
"Gialamas",
"Ioannis D.",
""
],
[
"Lahanas",
"A. B.",
""
]
] | We consider $R^2$ inflation in the Palatini gravity assuming the existence of scalar fields, coupled to gravity in the most general manner. These theories, in the Einstein frame, and for one scalar field $h$, share common features with $K$ - inflation models. We apply this formalism for the study of popular inflationary models, whose potentials are monomials, $ V \sim h^{n} $, with $ n $ a positive even integer. We also study the Higgs model non-minimally coupled to gravity. Although these have been recently studied, in the framework of the Palatini approach, we show that the scalar power spectrum severely constrains these models. Although we do not propose a particular reheating mechanism, we show that the quadratic $ \sim h^2$ and the Higgs model can survive these constraints with a maximum reheating temperature as large as $ \sim 10^{15} \, GeV$, when reheating is instantaneous. However, this can be only attained at the cost of a delicate fine-tuning of couplings. Deviations from this fine-tuned values can still yield predictions compatible with the cosmological data, for couplings that lie in very tight range, giving lower reheating temperatures. |
1705.07361 | Anton Sheykin | S. A. Paston, E. N. Semenova, V. A. Franke, A. A. Sheykin | Algebra of Implicitly Defined Constraints for Gravity as the General
Form of Embedding Theory | 11 pages | Gravit. Cosmol. (2017) 23:1 | 10.1134/S0202289317010145 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the embedding theory, the approach to gravity proposed by Regge
and Teitelboim, in which 4D space-time is treated as a surface in
high-dimensional flat ambient space. In its general form, which does not
contain artificially imposed constraints, this theory can be viewed as an
extension of GR. In the present paper we study the canonical description of the
embedding theory in this general form. In this case, one of the natural
constraints cannot be written explicitly, in contrast to the case where
additional Einsteinian constraints are imposed. Nevertheless, it is possible to
calculate all Poisson brackets with this constraint. We prove that the algebra
of four emerging constraints is closed, i.e., all of them are first-class
constraints. The explicit form of this algebra is also obtained.
| [
{
"created": "Sat, 20 May 2017 21:54:40 GMT",
"version": "v1"
}
] | 2017-05-23 | [
[
"Paston",
"S. A.",
""
],
[
"Semenova",
"E. N.",
""
],
[
"Franke",
"V. A.",
""
],
[
"Sheykin",
"A. A.",
""
]
] | We consider the embedding theory, the approach to gravity proposed by Regge and Teitelboim, in which 4D space-time is treated as a surface in high-dimensional flat ambient space. In its general form, which does not contain artificially imposed constraints, this theory can be viewed as an extension of GR. In the present paper we study the canonical description of the embedding theory in this general form. In this case, one of the natural constraints cannot be written explicitly, in contrast to the case where additional Einsteinian constraints are imposed. Nevertheless, it is possible to calculate all Poisson brackets with this constraint. We prove that the algebra of four emerging constraints is closed, i.e., all of them are first-class constraints. The explicit form of this algebra is also obtained. |
1409.3476 | Jeremy Rekier | Jeremy Rekier and Isabel Cordero-Carrion and Andre Fuzfa | Fully relativistic nonlinear cosmological evolution in spherical
symmetry using the BSSN formalism | 11 pages, 12 figures | Phys. Rev. D 91, 024025 (2015) | 10.1103/PhysRevD.91.024025 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a fully relativistic numerical method for the study of
cosmological problems using the Baumgarte-Shapiro-Shibata-Nakamura formalism on
a dynamical Friedmann-Lema\^itre-Robertson-Walker background. This has many
potential applications including the study of the growth of structures beyond
the linear regime. We present one such application by reproducing the
Lema\^itre-Tolman-Bondi solution for the collapse of pressureless matter with
arbitrary lapse function. The regular and smooth numerical solution at the
center of coordinates proceeds in a natural way by relying on the Partially
Implicit Runge-Kutta algorithm described in Montero and Cordero-Carri\'on
[arXiv:1211.5930]. We generalize the usual radiative outer boundary condition
to the case of a dynamical background and show the stability and convergence
properties of the method in the study of pure gauge dynamics on a de Sitter
background.
| [
{
"created": "Thu, 11 Sep 2014 15:35:37 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Jan 2015 20:51:16 GMT",
"version": "v2"
}
] | 2015-01-22 | [
[
"Rekier",
"Jeremy",
""
],
[
"Cordero-Carrion",
"Isabel",
""
],
[
"Fuzfa",
"Andre",
""
]
] | We present a fully relativistic numerical method for the study of cosmological problems using the Baumgarte-Shapiro-Shibata-Nakamura formalism on a dynamical Friedmann-Lema\^itre-Robertson-Walker background. This has many potential applications including the study of the growth of structures beyond the linear regime. We present one such application by reproducing the Lema\^itre-Tolman-Bondi solution for the collapse of pressureless matter with arbitrary lapse function. The regular and smooth numerical solution at the center of coordinates proceeds in a natural way by relying on the Partially Implicit Runge-Kutta algorithm described in Montero and Cordero-Carri\'on [arXiv:1211.5930]. We generalize the usual radiative outer boundary condition to the case of a dynamical background and show the stability and convergence properties of the method in the study of pure gauge dynamics on a de Sitter background. |
2309.02359 | Abraham Harte | Abraham I. Harte, David Dwyer | Local symmetries as constraints on the motion of freely-falling extended
bodies | 25 pages, minor changes | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Different extended objects can fall in different ways, depending on their
internal structures. Some motions are nevertheless impossible, regardless of
internal structure. This paper derives universal constraints on extended-body
motion, both in Newtonian gravity and in general relativity. In both theories,
we identify a weak notion of "local symmetry" which precludes certain force and
torque combinations. Local symmetries imply that certain components of a body's
quadrupole moment cannot affect its motion. They also imply that some forces
arise only in combination with appropriate torques. Many of these symmetries
are shown to be determined by the algebraic structure of the tidal tensor. In
general relativity, we thus relate qualitative features of extended-body motion
to the Petrov type of the spacetime. Doing so shows that local symmetries are
in fact ubiquitous. In general relativity, there are at least two in all
algebraically-special spacetimes. Some of these are generated by Killing
vectors and some by conformal Killing-Yano tensors. However, many local
symmetries do not fall into either of these classes.
| [
{
"created": "Tue, 5 Sep 2023 16:20:14 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Sep 2023 15:07:00 GMT",
"version": "v2"
}
] | 2023-09-14 | [
[
"Harte",
"Abraham I.",
""
],
[
"Dwyer",
"David",
""
]
] | Different extended objects can fall in different ways, depending on their internal structures. Some motions are nevertheless impossible, regardless of internal structure. This paper derives universal constraints on extended-body motion, both in Newtonian gravity and in general relativity. In both theories, we identify a weak notion of "local symmetry" which precludes certain force and torque combinations. Local symmetries imply that certain components of a body's quadrupole moment cannot affect its motion. They also imply that some forces arise only in combination with appropriate torques. Many of these symmetries are shown to be determined by the algebraic structure of the tidal tensor. In general relativity, we thus relate qualitative features of extended-body motion to the Petrov type of the spacetime. Doing so shows that local symmetries are in fact ubiquitous. In general relativity, there are at least two in all algebraically-special spacetimes. Some of these are generated by Killing vectors and some by conformal Killing-Yano tensors. However, many local symmetries do not fall into either of these classes. |
gr-qc/0205006 | Myron Bander | Myron Bander | An explicit time variable for cosmology and the matter-vacuum energy
coincidence | 5 pages REVTEX4 | null | null | UCI-TR-2002-15 | gr-qc hep-ph hep-th | null | By allowing for non zero vacuum expectation values for some of the fields
that appear in the Hamiltonian constraint of canonical general relativity a
time variable, with usual properties, can be identified; the constraint plays
the role of the ordinary Hamiltonian. The energy eigenvalues contribute to the
variation of the scale parameter similarly to the way matter density does. For
a universe described by a superposition of eigenstates or by a thermodynamic
ensemble the dominant contribution comes from energy, or equivalently effective
matter density, of the same order as the vacuum energy (cosmological constant).
This may explain the observed ``coincidence'' of these two values.
| [
{
"created": "Wed, 1 May 2002 20:57:13 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bander",
"Myron",
""
]
] | By allowing for non zero vacuum expectation values for some of the fields that appear in the Hamiltonian constraint of canonical general relativity a time variable, with usual properties, can be identified; the constraint plays the role of the ordinary Hamiltonian. The energy eigenvalues contribute to the variation of the scale parameter similarly to the way matter density does. For a universe described by a superposition of eigenstates or by a thermodynamic ensemble the dominant contribution comes from energy, or equivalently effective matter density, of the same order as the vacuum energy (cosmological constant). This may explain the observed ``coincidence'' of these two values. |
gr-qc/0505152 | Peter Dimitris Rippis | Peter D. Rippis | Dynamics of radiation dominated branes: Vacuum dynamics from radiation | 12 pages, 1 fig., typos and reference corrected. Submitted for
publication | null | null | null | gr-qc astro-ph hep-th | null | I point out a symmetry, between equations of state for polytropic fluids, in
the equation of motion of a spherically symmetric singular shell embedded in
4-d and 5-d vacuum spacetimes. In particular the equation of motion of a shell
consisting of radiation has the same form as for a vacuum shell or domain wall.
| [
{
"created": "Mon, 30 May 2005 16:04:12 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jun 2005 12:59:23 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Rippis",
"Peter D.",
""
]
] | I point out a symmetry, between equations of state for polytropic fluids, in the equation of motion of a spherically symmetric singular shell embedded in 4-d and 5-d vacuum spacetimes. In particular the equation of motion of a shell consisting of radiation has the same form as for a vacuum shell or domain wall. |
1204.0869 | Valery Kiselev | V. V. Kiselev | CMBR anisotropy in the framework of cosmological extrapolation of MOND | 18 pages, 5 eps-figures, references and comments added | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A modified gravity involving a critical acceleration, as empirically
established at galactic scales and successfully tested by data on supernovae of
type Ia, can fit the measured multipole spectrum of anisotropy in the cosmic
microwave background radiation, so that a dark sector of Universe is
constructively mimicked as caused by the dynamics beyond the general
relativity. Physical consequences, verifiable predictions and falsifiable
issues are listed and discussed.
| [
{
"created": "Wed, 4 Apr 2012 05:35:36 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Jun 2012 06:25:54 GMT",
"version": "v2"
}
] | 2012-06-25 | [
[
"Kiselev",
"V. V.",
""
]
] | A modified gravity involving a critical acceleration, as empirically established at galactic scales and successfully tested by data on supernovae of type Ia, can fit the measured multipole spectrum of anisotropy in the cosmic microwave background radiation, so that a dark sector of Universe is constructively mimicked as caused by the dynamics beyond the general relativity. Physical consequences, verifiable predictions and falsifiable issues are listed and discussed. |
gr-qc/9909014 | Steven Carlip | S. Carlip | Kinetic Energy and the Equivalence Principle | 11 pages, LaTeX; pedagogical paper sent to archive at students'
request | Am.J.Phys.66:409-413,1998 | 10.1119/1.18885 | UCD-97-10 | gr-qc | null | According to the general theory of relativity, kinetic energy contributes to
gravitational mass. Surprisingly, the observational evidence for this
prediction does not seem to be discussed in the literature. I reanalyze
existing experimental data to test the equivalence principle for the kinetic
energy of atomic electrons, and show that fairly strong limits on possible
violations can be obtained. I discuss the relationship of this result to the
occasional claim that ``light falls with twice the acceleration of ordinary
matter.''
| [
{
"created": "Fri, 3 Sep 1999 20:25:38 GMT",
"version": "v1"
}
] | 2011-01-13 | [
[
"Carlip",
"S.",
""
]
] | According to the general theory of relativity, kinetic energy contributes to gravitational mass. Surprisingly, the observational evidence for this prediction does not seem to be discussed in the literature. I reanalyze existing experimental data to test the equivalence principle for the kinetic energy of atomic electrons, and show that fairly strong limits on possible violations can be obtained. I discuss the relationship of this result to the occasional claim that ``light falls with twice the acceleration of ordinary matter.'' |
1601.04040 | Ali \"Ovg\"un | I. Sakalli and A. \"Ovg\"un | Hawking Radiation of Mass Generating Particles From Dyonic Reissner
Nordstr\"{o}m Black Hole | 8 pages, Accepted for publication in Journal of Astrophysics and
Astronomy | J Astrophys Astron (2016) 37: 21 | 10.1007/s12036-016-9397-6 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hawking radiation is considered as a quantum tunneling process, which can
be studied in the framework of the Hamilton-Jacobi method. In this study, we
present the wave equation for a mass generating massive and charged scalar
particle (boson). In sequel, we analyze the quantum tunneling of these bosons
from a generic 4-dimensional spherically symmetric black hole. We apply the
Hamilton-Jacobi formalism to derive the radial integral solution for the
classically forbidden action which leads to the tunneling probability. To
support our arguments, we take the dyonic Reissner-Nordstr\"{o}m black hole as
a test background. Comparing the tunneling probability obtained with the
Boltzmann formula, we succeed to read the standard Hawking temperature of the
dyonic Reissner-Nordstr\"{o}m black hole.
| [
{
"created": "Fri, 15 Jan 2016 19:29:43 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Jun 2016 11:21:06 GMT",
"version": "v2"
}
] | 2016-08-23 | [
[
"Sakalli",
"I.",
""
],
[
"Övgün",
"A.",
""
]
] | The Hawking radiation is considered as a quantum tunneling process, which can be studied in the framework of the Hamilton-Jacobi method. In this study, we present the wave equation for a mass generating massive and charged scalar particle (boson). In sequel, we analyze the quantum tunneling of these bosons from a generic 4-dimensional spherically symmetric black hole. We apply the Hamilton-Jacobi formalism to derive the radial integral solution for the classically forbidden action which leads to the tunneling probability. To support our arguments, we take the dyonic Reissner-Nordstr\"{o}m black hole as a test background. Comparing the tunneling probability obtained with the Boltzmann formula, we succeed to read the standard Hawking temperature of the dyonic Reissner-Nordstr\"{o}m black hole. |
gr-qc/0002080 | Maurizio Gasperini | M. Gasperini | Birth of the Universe as anti-tunnelling from the string perturbative
vacuum | 11 pages, Latex, three figures included using epsfig. Essay written
for the 2000 Awards for Essays on Gravitation (Gravity Research Foundation,
Wellesley Hills, MA), and selected for Honorable Mention. One reference
added. To appear in Int. J. Mod. Phys. D | Int.J.Mod.Phys. D10 (2001) 15-24 | 10.1142/S0218271801000585 | BA-TH/99-367 | gr-qc hep-th | null | The decay of the string perturbative vacuum, if triggered by a suitable,
duality-breaking dilaton potential, can efficiently proceed via the parametric
amplification of the Wheeler-De Witt wave function in superspace, and can
appropriately describe the birth of our Universe as a quantum process of pair
production from the vacuum.
| [
{
"created": "Wed, 23 Feb 2000 14:00:50 GMT",
"version": "v1"
},
{
"created": "Wed, 17 May 2000 12:51:29 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Gasperini",
"M.",
""
]
] | The decay of the string perturbative vacuum, if triggered by a suitable, duality-breaking dilaton potential, can efficiently proceed via the parametric amplification of the Wheeler-De Witt wave function in superspace, and can appropriately describe the birth of our Universe as a quantum process of pair production from the vacuum. |
1606.00713 | Saibal Ray | Debabrata Deb, Sourav Roy Chowdhury, Saibal Ray, Farook Rahaman and
B.K. Guha | Relativistic model for anisotropic strange stars | 21 pages, 11 figures, 2 tables, Accepted in Annals of physics | null | 10.1016/j.aop.2017.10.010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, we attempt to find a singularity free solution of Einstein's
field equations for compact stellar objects, precisely strange (quark) stars,
considering Schwarzschild metric as the exterior spacetime. To this end, we
consider that the stellar object is spherically symmetric, static and
anisotropic in nature and follows the density profile given by Mak and Harko
(2002), which satisfies all the physical conditions. To investigate different
properties of the ultra-dense strange stars we have employed the MIT bag model
for the quark matter. Our investigation displays an interesting feature that
the anisotropy of compact stars increases with the radial coordinate and
attains its maximum value at the surface which seems an inherent property for
the singularity free anisotropic compact stellar objects. In this connection we
also perform several tests for physical features of the proposed model and show
that these are reasonably acceptable within certain range. Further, we find
that the model is consistent with the energy conditions and the compact stellar
structure is stable with the validity of the TOV equation and Herrera cracking
concept. For the masses bellow the maximum mass point in mass vs radius curve
the typical behavior achieved within the framework of general relativity. We
have calculated the maximum mass and radius of the strange stars for the three
finite values of bag constant $B_g$.
| [
{
"created": "Mon, 30 May 2016 12:47:58 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Oct 2017 11:21:23 GMT",
"version": "v2"
}
] | 2017-10-19 | [
[
"Deb",
"Debabrata",
""
],
[
"Chowdhury",
"Sourav Roy",
""
],
[
"Ray",
"Saibal",
""
],
[
"Rahaman",
"Farook",
""
],
[
"Guha",
"B. K.",
""
]
] | In this article, we attempt to find a singularity free solution of Einstein's field equations for compact stellar objects, precisely strange (quark) stars, considering Schwarzschild metric as the exterior spacetime. To this end, we consider that the stellar object is spherically symmetric, static and anisotropic in nature and follows the density profile given by Mak and Harko (2002), which satisfies all the physical conditions. To investigate different properties of the ultra-dense strange stars we have employed the MIT bag model for the quark matter. Our investigation displays an interesting feature that the anisotropy of compact stars increases with the radial coordinate and attains its maximum value at the surface which seems an inherent property for the singularity free anisotropic compact stellar objects. In this connection we also perform several tests for physical features of the proposed model and show that these are reasonably acceptable within certain range. Further, we find that the model is consistent with the energy conditions and the compact stellar structure is stable with the validity of the TOV equation and Herrera cracking concept. For the masses bellow the maximum mass point in mass vs radius curve the typical behavior achieved within the framework of general relativity. We have calculated the maximum mass and radius of the strange stars for the three finite values of bag constant $B_g$. |
2301.07657 | Julian Barbour | Julian Barbour | Gravity's Creative Core | 17 pages, 2 figures | null | null | null | gr-qc hep-th physics.hist-ph | http://creativecommons.org/licenses/by-nc-nd/4.0/ | I argue that the essence of gravity can be understood only in the context of
the universe and that unrecognised implicit retention of Newtonian absolute
scale and the impact of thermodynamics have obscured it. Typical attempts to
resolve the conflict between maximal matter entropy in the early universe and
the second law of thermodynamics illustrate my case. Rovelli, for example,
argues that the scale factor, and with it the overall state, was out of
equilibrium. He illustrates subsequent entropy-increasing interaction with
other degrees of freedom in two models: particles in a box interacting with a
piston initially out of equilibrium and Newtonian gravitating particles.
However, the piston's position and momentum, like the particles", are defined
relative to the box, while unobservable absolute space defines those of the
gravitating particles. Their representation using observable scale-invariant
variables shows that the box and gravitational statistics differ greatly: in
the latter a single degree of freedom, gravity's creative core, drives the
system in every solution from entropic-like disorder to ever increasing ordered
structure. Since in many ways such particles are a good approximation to
general relativity, this may also be true for our universe.
| [
{
"created": "Wed, 18 Jan 2023 17:03:39 GMT",
"version": "v1"
}
] | 2023-01-19 | [
[
"Barbour",
"Julian",
""
]
] | I argue that the essence of gravity can be understood only in the context of the universe and that unrecognised implicit retention of Newtonian absolute scale and the impact of thermodynamics have obscured it. Typical attempts to resolve the conflict between maximal matter entropy in the early universe and the second law of thermodynamics illustrate my case. Rovelli, for example, argues that the scale factor, and with it the overall state, was out of equilibrium. He illustrates subsequent entropy-increasing interaction with other degrees of freedom in two models: particles in a box interacting with a piston initially out of equilibrium and Newtonian gravitating particles. However, the piston's position and momentum, like the particles", are defined relative to the box, while unobservable absolute space defines those of the gravitating particles. Their representation using observable scale-invariant variables shows that the box and gravitational statistics differ greatly: in the latter a single degree of freedom, gravity's creative core, drives the system in every solution from entropic-like disorder to ever increasing ordered structure. Since in many ways such particles are a good approximation to general relativity, this may also be true for our universe. |
0809.1140 | Sini R | Sini R, V. C. Kuriakose | Quasinormal modes of RN black hole space time with cosmic string in a
Dirac field | 12 pages, 28 figures | Mod.Phys.Lett.A24:2025-2037,2009 | 10.1142/S0217732309030394 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We evaluate quasinormal mode frequencies for RN black hole space times with
cosmic string perturbed by a massless Dirac field, using P\"{o}schl-Teller
potential method. We find that only in the case of RN black hole having small
charge, the effect due to cosmic string will dominate when perturbed by a
negatively charged Dirac field, but if we are perturbing with positively
charged Dirac field decay will be less in the case of black hole having cosmic
string compared to the RN black hole without string
| [
{
"created": "Sat, 6 Sep 2008 06:56:42 GMT",
"version": "v1"
}
] | 2014-11-18 | [
[
"R",
"Sini",
""
],
[
"Kuriakose",
"V. C.",
""
]
] | We evaluate quasinormal mode frequencies for RN black hole space times with cosmic string perturbed by a massless Dirac field, using P\"{o}schl-Teller potential method. We find that only in the case of RN black hole having small charge, the effect due to cosmic string will dominate when perturbed by a negatively charged Dirac field, but if we are perturbing with positively charged Dirac field decay will be less in the case of black hole having cosmic string compared to the RN black hole without string |
2211.04059 | Maximilian Kraft | David Fajman and Maximilian Kraft | Recollapsing spacetimes with $\Lambda<0$ | 28 pages, 3 figures | null | 10.1088/1361-6382/acd97c | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | We show that any homogeneous initial data set with $\Lambda<0$ on a product
3-manifold of the orthogonal form $(F\times \mathbb
S^1,a_0^2dz^2+b_0^2\sigma^2,c_0dz^2+d_0\sigma)$, where $(F,\sigma)$ is a closed
2-surface of constant curvature and $a_0,..., d_0$ are suitable constants,
recollapses under the Einstein-flow with a negative cosmological constant and
forms crushing singularities at the big bang and the big crunch, respectively.
Towards certain singularities among those the Kretschmann scalar remains
bounded, hence these are not curvature singularities. We then show that the
presence of a massless scalar field causes the Kretschmann scalar to blow-up
towards both ends of spacetime for all solutions in the corresponding class. By
standard arguments this recollapsing behaviour extends to an open neighborhood
in the set of initial data sets and is in this sense generic close to the
homogeneous regime.
| [
{
"created": "Tue, 8 Nov 2022 07:38:12 GMT",
"version": "v1"
}
] | 2023-07-05 | [
[
"Fajman",
"David",
""
],
[
"Kraft",
"Maximilian",
""
]
] | We show that any homogeneous initial data set with $\Lambda<0$ on a product 3-manifold of the orthogonal form $(F\times \mathbb S^1,a_0^2dz^2+b_0^2\sigma^2,c_0dz^2+d_0\sigma)$, where $(F,\sigma)$ is a closed 2-surface of constant curvature and $a_0,..., d_0$ are suitable constants, recollapses under the Einstein-flow with a negative cosmological constant and forms crushing singularities at the big bang and the big crunch, respectively. Towards certain singularities among those the Kretschmann scalar remains bounded, hence these are not curvature singularities. We then show that the presence of a massless scalar field causes the Kretschmann scalar to blow-up towards both ends of spacetime for all solutions in the corresponding class. By standard arguments this recollapsing behaviour extends to an open neighborhood in the set of initial data sets and is in this sense generic close to the homogeneous regime. |
1108.3796 | Leandro Belo | L.R.A. Belo, E.P. Spaniol, J.A. de Deus and V.C. de Andrade | A look on the internal structure of Teleparallel Equivalent of General
Relativity | 13 pages | Adv. Studies Theor. Phys., 6, no. 7, 325 - 337 (2012) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the Dirac procedure to treat constraints dynamical sistems applied to
gravitation, as described in the context of Teleparallel Equivalent of General
Relativity (TEGR), we investigate, from the first class constraints, the gauge
transformations in the fundamental field: the components of tetrads. We have
shown that there is no an isotropy in physical space with respect to gauge
transformations, i.e., given an arbitrary gravitational field, coming from a
gauge transformation in the internal space, physical space reacts differently
in the spatial and temporal components. By making an appropriate choice, we
have found a gauge transformation for the components of tetrad field that
allows a direct analogy with the gauge transformations of the Yang-Mills
theory. In addition, to the asymptotically flat case in which the algebra index
is fixed, we recover the transformations of Electromagnetism. Moreover, still
considering the asymptotically flat case, the dependence of the gauge
transformation parameter in the space-time variables is periodic, just like in
the Electromagnetism. Furthermore, the gravitoelectric and gravitomagnetic
fields as have recently been defined, make sense since they allow a direct
relation with the momenta, which is analogous to what occurs in other gauge
theories.
| [
{
"created": "Thu, 18 Aug 2011 17:03:42 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Aug 2011 04:54:43 GMT",
"version": "v2"
},
{
"created": "Sun, 30 Sep 2012 00:12:11 GMT",
"version": "v3"
}
] | 2012-10-02 | [
[
"Belo",
"L. R. A.",
""
],
[
"Spaniol",
"E. P.",
""
],
[
"de Deus",
"J. A.",
""
],
[
"de Andrade",
"V. C.",
""
]
] | Using the Dirac procedure to treat constraints dynamical sistems applied to gravitation, as described in the context of Teleparallel Equivalent of General Relativity (TEGR), we investigate, from the first class constraints, the gauge transformations in the fundamental field: the components of tetrads. We have shown that there is no an isotropy in physical space with respect to gauge transformations, i.e., given an arbitrary gravitational field, coming from a gauge transformation in the internal space, physical space reacts differently in the spatial and temporal components. By making an appropriate choice, we have found a gauge transformation for the components of tetrad field that allows a direct analogy with the gauge transformations of the Yang-Mills theory. In addition, to the asymptotically flat case in which the algebra index is fixed, we recover the transformations of Electromagnetism. Moreover, still considering the asymptotically flat case, the dependence of the gauge transformation parameter in the space-time variables is periodic, just like in the Electromagnetism. Furthermore, the gravitoelectric and gravitomagnetic fields as have recently been defined, make sense since they allow a direct relation with the momenta, which is analogous to what occurs in other gauge theories. |
1011.0214 | Paul Wesson | Paul S. Wesson | The Embedding of General Relativity in Five-Dimensional Canonical Space:
A Short History and a Review of Recent Physical Progress | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Einstein theory can be embedded in Kaluza-Klein theory, and in particular all
4D vacuum solutions can be embedded in 5D (pure) canonical space where
spacetime is independent of the extra coordinate. The uniqueness of 5D
canonical space is quickly reproven, and its history and implications briefly
reviewed. For 4D anti-deSitter space, the 5D space involves a wave running
around spacetime, with an associated particle that has a local value of the
cosmological 'constant' proportional to the square of the mass.
| [
{
"created": "Sun, 31 Oct 2010 22:47:07 GMT",
"version": "v1"
}
] | 2010-11-02 | [
[
"Wesson",
"Paul S.",
""
]
] | Einstein theory can be embedded in Kaluza-Klein theory, and in particular all 4D vacuum solutions can be embedded in 5D (pure) canonical space where spacetime is independent of the extra coordinate. The uniqueness of 5D canonical space is quickly reproven, and its history and implications briefly reviewed. For 4D anti-deSitter space, the 5D space involves a wave running around spacetime, with an associated particle that has a local value of the cosmological 'constant' proportional to the square of the mass. |
0704.2889 | Marc Mars | Lars Andersson, Marc Mars, Walter Simon | Stability of marginally outer trapped surfaces and existence of
marginally outer trapped tubes | 33 pages, no figures, typos corrected, minor changes in presentation | null | null | null | gr-qc | null | The present work extends our short communication Phys. Rev. Lett. 95, 111102
(2005). For smooth marginally outer trapped surfaces (MOTS) in a smooth
spacetime we define stability with respect to variations along arbitrary
vectors v normal to the MOTS. After giving some introductory material about
linear non self-adjoint elliptic operators, we introduce the stability operator
L_v and we characterize stable MOTS in terms of sign conditions on the
principal eigenvalue of L_v. The main result shows that given a strictly stable
MOTS S contained in one leaf of a given reference foliation in a spacetime,
there is an open marginally outer trapped tube (MOTT), adapted to the reference
foliation, which contains S. We give conditions under which the MOTT can be
completed. Finally, we show that under standard energy conditions on the
spacetime, the MOTT must be either locally achronal, spacelike or null.
| [
{
"created": "Sun, 22 Apr 2007 15:13:38 GMT",
"version": "v1"
},
{
"created": "Tue, 22 May 2007 15:13:59 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Andersson",
"Lars",
""
],
[
"Mars",
"Marc",
""
],
[
"Simon",
"Walter",
""
]
] | The present work extends our short communication Phys. Rev. Lett. 95, 111102 (2005). For smooth marginally outer trapped surfaces (MOTS) in a smooth spacetime we define stability with respect to variations along arbitrary vectors v normal to the MOTS. After giving some introductory material about linear non self-adjoint elliptic operators, we introduce the stability operator L_v and we characterize stable MOTS in terms of sign conditions on the principal eigenvalue of L_v. The main result shows that given a strictly stable MOTS S contained in one leaf of a given reference foliation in a spacetime, there is an open marginally outer trapped tube (MOTT), adapted to the reference foliation, which contains S. We give conditions under which the MOTT can be completed. Finally, we show that under standard energy conditions on the spacetime, the MOTT must be either locally achronal, spacelike or null. |
2404.09374 | Gokhan Alkac | Gokhan Alkac, Mehmet Kemal Gumus, Mehmet Ali Olpak | Classical double copy in the black hole mini-superspace | Citation added | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We give a novel formulation of classical double copy in the mini-superspace
of static, spherically symmetric black holes where the map between the
solutions of general relativity and Maxwell's theory can be realized in
Boyer-Lindsquit coordinates. By employing the reduced action principle, we show
that the double copy structure can be generalized to Lovelock gravities and
quasi-topological gravities. However, the gravitational solutions are mapped to
the purely electric solutions of Maxwell's theory with a difference: instead of
a direct match between the Kerr-Schild scalar in the gravity side and the
scalar potential in the gauge theory side, the scalar potential becomes a
polynomial in the Kerr-Schild scalar, giving rise to a generalization of the
Kerr-Schild double copy. We calculate the Regge-Teitelboim surface charges and
prove that the mass of the black hole solution is identified with the electric
charge corresponding to the Coulomb part of the gauge theory solution in the
same way it does in the case of general relativity.
| [
{
"created": "Sun, 14 Apr 2024 22:55:49 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Apr 2024 09:44:37 GMT",
"version": "v2"
},
{
"created": "Fri, 19 Apr 2024 12:34:59 GMT",
"version": "v3"
}
] | 2024-04-22 | [
[
"Alkac",
"Gokhan",
""
],
[
"Gumus",
"Mehmet Kemal",
""
],
[
"Olpak",
"Mehmet Ali",
""
]
] | We give a novel formulation of classical double copy in the mini-superspace of static, spherically symmetric black holes where the map between the solutions of general relativity and Maxwell's theory can be realized in Boyer-Lindsquit coordinates. By employing the reduced action principle, we show that the double copy structure can be generalized to Lovelock gravities and quasi-topological gravities. However, the gravitational solutions are mapped to the purely electric solutions of Maxwell's theory with a difference: instead of a direct match between the Kerr-Schild scalar in the gravity side and the scalar potential in the gauge theory side, the scalar potential becomes a polynomial in the Kerr-Schild scalar, giving rise to a generalization of the Kerr-Schild double copy. We calculate the Regge-Teitelboim surface charges and prove that the mass of the black hole solution is identified with the electric charge corresponding to the Coulomb part of the gauge theory solution in the same way it does in the case of general relativity. |
1709.02083 | Nolene Naidu | NF Naidu, M Govender, S Thirukkanesh, SD Maharaj | Radiating fluid sphere immersed in an anisotropic atmosphere | 12 pages, 4 figures | Gen Relativ Gravit (2017) 49:95 | 10.1007/s10714-017-2258-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We model a radiating star undergoing dissipative gravitational collapse in
the form of radial heat flux. The exterior of the collapsing star is described
by the generalised Vaidya solution representing a mixture of null radiation and
strings. Our model generalises previously known results of constant string
density atmosphere to include inhomogeneities in the exterior spacetime. By
utilising a causal heat transport equation of the Maxwell-Cattaneo form we show
that relaxational effects are enhanced in the presence of inhomogeneities due
to the string density.
| [
{
"created": "Thu, 7 Sep 2017 05:59:58 GMT",
"version": "v1"
}
] | 2017-09-13 | [
[
"Naidu",
"NF",
""
],
[
"Govender",
"M",
""
],
[
"Thirukkanesh",
"S",
""
],
[
"Maharaj",
"SD",
""
]
] | We model a radiating star undergoing dissipative gravitational collapse in the form of radial heat flux. The exterior of the collapsing star is described by the generalised Vaidya solution representing a mixture of null radiation and strings. Our model generalises previously known results of constant string density atmosphere to include inhomogeneities in the exterior spacetime. By utilising a causal heat transport equation of the Maxwell-Cattaneo form we show that relaxational effects are enhanced in the presence of inhomogeneities due to the string density. |
1406.0401 | Alessandro Nagar | Thibault Damour and Alessandro Nagar | A new analytic representation of the ringdown waveform of coalescing
spinning black hole binaries | 7 pages, 7 figures. Results improved with respect to first version.
To appear in Phys. Rev. D | null | 10.1103/PhysRevD.90.024054 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new way of analyzing, and analytically representing, the
ringdown part of the gravitational wave signal emitted by coalescing black hole
binaries.By contrast with the usual {\it linear} decomposition of the
multipolar complex waveform $h(t)$ in a sum of quasi-normal modes, our
procedure relies on a {\it multiplicative} decomposition of $h(t)$ as the
product of the fundamental quasi-normal mode with a remaining time-dependent
complex factor whose amplitude and phase are separately fitted. As an
illustrative example, we apply our analysis and fitting procedure to the
ringdown part of a sample of sixteen $\ell=m=2$ equal-mass, spinning,
nonprecessing, numerical waveforms computed with the SP$_{\rm E}$C code,now
publicly available in the SXS catalogue. Our approach yields an efficient and
accurate way to represent the ringdown waveform, thereby offering a new way to
complete the analytical effective-one-body inspiral-plus-plunge waveform.
| [
{
"created": "Mon, 2 Jun 2014 14:58:43 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Jul 2014 15:35:59 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Damour",
"Thibault",
""
],
[
"Nagar",
"Alessandro",
""
]
] | We propose a new way of analyzing, and analytically representing, the ringdown part of the gravitational wave signal emitted by coalescing black hole binaries.By contrast with the usual {\it linear} decomposition of the multipolar complex waveform $h(t)$ in a sum of quasi-normal modes, our procedure relies on a {\it multiplicative} decomposition of $h(t)$ as the product of the fundamental quasi-normal mode with a remaining time-dependent complex factor whose amplitude and phase are separately fitted. As an illustrative example, we apply our analysis and fitting procedure to the ringdown part of a sample of sixteen $\ell=m=2$ equal-mass, spinning, nonprecessing, numerical waveforms computed with the SP$_{\rm E}$C code,now publicly available in the SXS catalogue. Our approach yields an efficient and accurate way to represent the ringdown waveform, thereby offering a new way to complete the analytical effective-one-body inspiral-plus-plunge waveform. |
gr-qc/9908015 | Zoltan Perjes | L\'aszl\'o \'A. Gergely, Zolt\'an I. Perj\'es and M\'aty\'as Vas\'uth | The true and eccentric anomaly parametrizations of the perturbed Kepler
motion | 19 pages, to appear in ApJ Suppl | Astrophys.J.Suppl. 126 (2000) 79-84 | 10.1086/313290 | null | gr-qc astro-ph | null | The true and eccentric anomaly parametrizations of the Kepler motion are
generalized to quasiperiodic orbits, by considering perturbations of the radial
part of the kinetic energy in a form of a series of negative powers of the
orbital radius. A toolchest of methods for averaging observables as functions
of the energy $E$ and angular momentum $L$ is developed. A broad range of
systems governed by the generic Brumberg force and recent applications in the
theory of gravitational radiation involve integrals of these functions over a
period of motion. These integrals are evaluated by using the residue theorem.
In the course of this work two important questions emerge: (1) When does the
true and eccentric anomaly parameter exist? (2) Under what circumstances and
why are the poles in the origin? The purpose of this paper is to find the
answer to these queries.
| [
{
"created": "Thu, 5 Aug 1999 11:32:38 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Gergely",
"László Á.",
""
],
[
"Perjés",
"Zoltán I.",
""
],
[
"Vasúth",
"Mátyás",
""
]
] | The true and eccentric anomaly parametrizations of the Kepler motion are generalized to quasiperiodic orbits, by considering perturbations of the radial part of the kinetic energy in a form of a series of negative powers of the orbital radius. A toolchest of methods for averaging observables as functions of the energy $E$ and angular momentum $L$ is developed. A broad range of systems governed by the generic Brumberg force and recent applications in the theory of gravitational radiation involve integrals of these functions over a period of motion. These integrals are evaluated by using the residue theorem. In the course of this work two important questions emerge: (1) When does the true and eccentric anomaly parameter exist? (2) Under what circumstances and why are the poles in the origin? The purpose of this paper is to find the answer to these queries. |
1207.6602 | Peter K.F. Kuhfittig | Peter K. F. Kuhfittig | Neutron star interiors and topology change | 7 pages, no figures | Advances in Mathematical Physics, vol. 2013, Article ID 630196, 4
pages, 2013 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quark matter is believed to exist in the center of neutron stars. A combined
model consisting of quark matter and ordinary matter is used to show that the
extreme conditions existing in the center could result in a topology change,
that is, in the formation of wormholes.
| [
{
"created": "Fri, 27 Jul 2012 17:22:03 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Jan 2013 15:17:57 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Mar 2013 17:17:57 GMT",
"version": "v3"
},
{
"created": "Fri, 29 Mar 2013 17:49:41 GMT",
"version": "v4"
},
{
"cr... | 2021-12-14 | [
[
"Kuhfittig",
"Peter K. F.",
""
]
] | Quark matter is believed to exist in the center of neutron stars. A combined model consisting of quark matter and ordinary matter is used to show that the extreme conditions existing in the center could result in a topology change, that is, in the formation of wormholes. |
1104.4706 | Vasily Borodikhin | V. N. Borodikhin | Vector Theory of Gravity: quantum and classical effects, renormalization | 16 pages, 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we make quantization of gravitation interaction within the
framework of a vector theory of gravitation for the first time. The work
demonstrates that this theory meets the requirement of renormalizability. Here
we consider some quantum effects, particularly graviton scattering on fermion
and corrections to the Newton's. Gravitational energy sign changing mechanism
and classical transition on small scale is discussed. It is shown that within
this theory black holes of Schwarzschield hole type can exist. Problem of dark
energy structure and acceleration of Universe expansion is investigated. We
also consider the behavior of binary pulsars in the vector theory of
gravitation.
| [
{
"created": "Mon, 25 Apr 2011 10:59:57 GMT",
"version": "v1"
},
{
"created": "Sat, 12 May 2012 05:23:05 GMT",
"version": "v2"
},
{
"created": "Fri, 26 Oct 2012 09:41:41 GMT",
"version": "v3"
}
] | 2012-10-29 | [
[
"Borodikhin",
"V. N.",
""
]
] | In this work, we make quantization of gravitation interaction within the framework of a vector theory of gravitation for the first time. The work demonstrates that this theory meets the requirement of renormalizability. Here we consider some quantum effects, particularly graviton scattering on fermion and corrections to the Newton's. Gravitational energy sign changing mechanism and classical transition on small scale is discussed. It is shown that within this theory black holes of Schwarzschield hole type can exist. Problem of dark energy structure and acceleration of Universe expansion is investigated. We also consider the behavior of binary pulsars in the vector theory of gravitation. |
2012.07392 | Callum Hunter | Callum Hunter | Effective Non-Minimal Quadratic Gravity and the Classical Cut-Off | 27 pages, 1 Figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we consider Quadratic Gravity as a low energy effective field
theory of some unknown UV-complete theory of gravity. Using the spin-2 ghost
pathology that occurs in Quadratic Gravity, we derive maximum value for the
classical cut-off of the low energy effective field theory in various
configurations. We then add on higher order, bottom-up, effective terms. At
each order we allow the introduction of non-minimally coupled scalar field
terms, and we calculate the vacuum expectation value of the theory under an
assumed $\mathbb{Z}_2$ symmetry breaking of the scalar field. This symmetry
breaking leads us to introduce a constant in the action which is required to
ensure that the physical spin-2 degree of freedom is massless in the flat space
approximation, an implicit assumption we make throughout the work. We then
consider the case in which we do not fine tune the introduced constant, which
leads to an (Anti-)de Sitter solution about which we can then expand. The sign
of the chosen cosmological constant is the major factor in determining whether
the geometry is de Sitter or Anti-de Sitter. Then expanding about this geometry
allows us to increase the theoretical classical cut-off as compared to the flat
space case by an amount that is proportional to the free cosmological constant
parameter.
| [
{
"created": "Mon, 14 Dec 2020 10:26:12 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Apr 2021 10:06:44 GMT",
"version": "v2"
}
] | 2021-04-08 | [
[
"Hunter",
"Callum",
""
]
] | In this paper we consider Quadratic Gravity as a low energy effective field theory of some unknown UV-complete theory of gravity. Using the spin-2 ghost pathology that occurs in Quadratic Gravity, we derive maximum value for the classical cut-off of the low energy effective field theory in various configurations. We then add on higher order, bottom-up, effective terms. At each order we allow the introduction of non-minimally coupled scalar field terms, and we calculate the vacuum expectation value of the theory under an assumed $\mathbb{Z}_2$ symmetry breaking of the scalar field. This symmetry breaking leads us to introduce a constant in the action which is required to ensure that the physical spin-2 degree of freedom is massless in the flat space approximation, an implicit assumption we make throughout the work. We then consider the case in which we do not fine tune the introduced constant, which leads to an (Anti-)de Sitter solution about which we can then expand. The sign of the chosen cosmological constant is the major factor in determining whether the geometry is de Sitter or Anti-de Sitter. Then expanding about this geometry allows us to increase the theoretical classical cut-off as compared to the flat space case by an amount that is proportional to the free cosmological constant parameter. |
1304.0457 | Vasileios Paschalidis | Vasileios Paschalidis, Zachariah B. Etienne, Roman Gold, Stuart L.
Shapiro | An efficient spectral interpolation routine for the TwoPunctures code | Link for downloading the Einstein Toolkit version:
http://webusers.physics.illinois.edu/~vpaschal/TwoPuncturesET/ Link for
downloading the standalone version:
http://webusers.physics.illinois.edu/~vpaschal/TwoPunctures_Standalone/ | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | TwoPunctures is perhaps the most widely-adopted code for generating binary
black hole "puncture" initial data and interpolating these (spectral) data onto
evolution grids. In typical usage, the bulk of this code's run time is spent in
its spectral interpolation routine. We announce a new publicly-available
spectral interpolation routine that improves the performance of the original
interpolation routine by a factor of ~100, yielding results consistent with the
original spectral interpolation routine to roundoff precision. This note serves
as a guide for installing this routine both in the original standalone
TwoPunctures code and the Einstein Toolkit supported version of this code.
| [
{
"created": "Mon, 1 Apr 2013 20:00:07 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Apr 2013 00:23:04 GMT",
"version": "v2"
}
] | 2013-04-05 | [
[
"Paschalidis",
"Vasileios",
""
],
[
"Etienne",
"Zachariah B.",
""
],
[
"Gold",
"Roman",
""
],
[
"Shapiro",
"Stuart L.",
""
]
] | TwoPunctures is perhaps the most widely-adopted code for generating binary black hole "puncture" initial data and interpolating these (spectral) data onto evolution grids. In typical usage, the bulk of this code's run time is spent in its spectral interpolation routine. We announce a new publicly-available spectral interpolation routine that improves the performance of the original interpolation routine by a factor of ~100, yielding results consistent with the original spectral interpolation routine to roundoff precision. This note serves as a guide for installing this routine both in the original standalone TwoPunctures code and the Einstein Toolkit supported version of this code. |
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