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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1502.02758 | Matt Visser | Matt Visser (Victoria University of Wellington) | Conformally Friedmann-Lemaitre-Robertson-Walker cosmologies | V1: 17 pages; V2: 20 pages. 5 references added. Additional comments
on local conformal flatness. New section and extra comments
comparing/contrasting with LTB, Swiss-cheese, and timescape cosmologies. No
physics changes. V3: Now 21 pages. 3 references added. Some additional
discussion regarding dynamics. No physics changes. This version accepted for
publication in Classical and Quantum Gravity | Classical and Quantum Gravity 32 (2015) 135007 | 10.1088/0264-9381/32/13/135007 | null | gr-qc astro-ph.CO astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a universe where, according to the standard cosmological models, some 97%
of the total mass-energy is still "missing in action" it behooves us to spend
at least a little effort critically assessing and exploring radical
alternatives. Among possible, (dare we say plausible), nonstandard but
superficially viable models, those spacetimes conformal to the standard
Friedmann-Lemaitre-Robertson-Walker class of cosmological models play a very
special role --- these models have the unique and important property of
permitting large non-perturbative geometric deviations from
Friedmann-Lemaitre-Robertson-Walker cosmology without unacceptably distorting
the cosmic microwave background. Performing a "cosmographic" analysis, (that
is, temporarily setting aside the Einstein equations, since the question of
whether or not the Einstein equations are valid on galactic and cosmological
scales is essentially the same question as whether or not dark matter/dark
energy actually exist), and using both supernova data and information about
galactic structure, one can nevertheless place some quite significant
observational constraints on any possible conformal mode --- however there is
still an extremely rich range of phenomenological possibilities for both
cosmologists and astrophysicists to explore.
| [
{
"created": "Tue, 10 Feb 2015 02:45:28 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Feb 2015 18:56:01 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Apr 2015 23:58:15 GMT",
"version": "v3"
}
] | 2017-11-28 | [
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | In a universe where, according to the standard cosmological models, some 97% of the total mass-energy is still "missing in action" it behooves us to spend at least a little effort critically assessing and exploring radical alternatives. Among possible, (dare we say plausible), nonstandard but superficially viable models, those spacetimes conformal to the standard Friedmann-Lemaitre-Robertson-Walker class of cosmological models play a very special role --- these models have the unique and important property of permitting large non-perturbative geometric deviations from Friedmann-Lemaitre-Robertson-Walker cosmology without unacceptably distorting the cosmic microwave background. Performing a "cosmographic" analysis, (that is, temporarily setting aside the Einstein equations, since the question of whether or not the Einstein equations are valid on galactic and cosmological scales is essentially the same question as whether or not dark matter/dark energy actually exist), and using both supernova data and information about galactic structure, one can nevertheless place some quite significant observational constraints on any possible conformal mode --- however there is still an extremely rich range of phenomenological possibilities for both cosmologists and astrophysicists to explore. |
1406.7421 | Cristina Blaga | C. Blaga | Circular time-like geodesics around a charged spherically symmetric
dilaton black hole | 8 pages, 6 figures | Automat. Comput. Appl. Math., 22(2013), 41-49 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note we examine the circular time-like geodesics near a spherically
symmetric dilaton black hole, described using the exact solution for a static
charged black hole found by Gibbons and Maeda and, independently, by Garfinkle,
Horowitz and Strominger. The existence and stability of the circular orbits are
analysed using the effective potential of a free material test particle moving
on time-like geodesic near this black hole. We determine the radius of the
innermost stable circular orbit, the radius of the shortest circular orbit and
compare our results with those obtained by other authors for specific values of
the parameters involved in our analysis.
| [
{
"created": "Sat, 28 Jun 2014 17:10:33 GMT",
"version": "v1"
}
] | 2014-07-01 | [
[
"Blaga",
"C.",
""
]
] | In this note we examine the circular time-like geodesics near a spherically symmetric dilaton black hole, described using the exact solution for a static charged black hole found by Gibbons and Maeda and, independently, by Garfinkle, Horowitz and Strominger. The existence and stability of the circular orbits are analysed using the effective potential of a free material test particle moving on time-like geodesic near this black hole. We determine the radius of the innermost stable circular orbit, the radius of the shortest circular orbit and compare our results with those obtained by other authors for specific values of the parameters involved in our analysis. |
2103.10473 | Ugo Moschella | Ugo Moschella, Mario Novello | New dynamical features of pure k-essential cosmologies | null | null | 10.1142/S0218271822500109 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We come back on the dynamical properties of k-essential cosmological models
and show how the interesting phenomenological features of those models are
related to the existence of boundaries in the phase surface. We focus our
attention to the branching points where the energy density has an extremum and
the effective speed of sound diverges. We discuss the behaviour of solutions of
a general class of cosmological models exhibiting such curves and give two
possible interpretations; the most interesting possibility regards the arrow of
time that is reversed in trespassing the branching curve. This study teaches to
us something new about general FLRW cosmologies where the fluids driving the
cosmic evolution have equations of state that are multivalued functions of the
energy density and other thermodynamical quantities.
| [
{
"created": "Thu, 18 Mar 2021 18:42:11 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Sep 2021 19:40:56 GMT",
"version": "v2"
}
] | 2022-03-14 | [
[
"Moschella",
"Ugo",
""
],
[
"Novello",
"Mario",
""
]
] | We come back on the dynamical properties of k-essential cosmological models and show how the interesting phenomenological features of those models are related to the existence of boundaries in the phase surface. We focus our attention to the branching points where the energy density has an extremum and the effective speed of sound diverges. We discuss the behaviour of solutions of a general class of cosmological models exhibiting such curves and give two possible interpretations; the most interesting possibility regards the arrow of time that is reversed in trespassing the branching curve. This study teaches to us something new about general FLRW cosmologies where the fluids driving the cosmic evolution have equations of state that are multivalued functions of the energy density and other thermodynamical quantities. |
gr-qc/9409020 | null | Oleg A. Fonarev | Exact Einstein-scalar field solutions for formation of black holes in a
cosmological setting | 25 pages, 2 figures | Class.Quant.Grav.12:1739-1752,1995 | 10.1088/0264-9381/12/7/016 | null | gr-qc astro-ph hep-th | null | We consider self-interacting scalar fields coupled to gravity. Two classes of
exact solutions to Einstein's equations are obtained: the first class
corresponds to the minimal coupling, the second one to the conformal coupling.
One of the solutions is shown to describe a formation of a black hole in a
cosmological setting. Some properties of this solution are described. There are
two kinds of event horizons: a black hole horizon and cosmological horizons.
The cosmological horizons are not smooth. There is a mild curvature
singularity, which affects extended bodies but allows geodesics to be extended.
It is also shown that there is a critical value for a parameter on which the
solution depends. Above the critical point, the black hole singularity is
hidden within a global black hole event horizon. Below the critical point, the
singularity appears to be naked. The relevance to cosmic censorship is
discussed.
| [
{
"created": "Sun, 11 Sep 1994 17:51:00 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Sep 1994 18:58:00 GMT",
"version": "v2"
},
{
"created": "Sun, 11 Sep 1994 19:27:00 GMT",
"version": "v3"
}
] | 2010-04-06 | [
[
"Fonarev",
"Oleg A.",
""
]
] | We consider self-interacting scalar fields coupled to gravity. Two classes of exact solutions to Einstein's equations are obtained: the first class corresponds to the minimal coupling, the second one to the conformal coupling. One of the solutions is shown to describe a formation of a black hole in a cosmological setting. Some properties of this solution are described. There are two kinds of event horizons: a black hole horizon and cosmological horizons. The cosmological horizons are not smooth. There is a mild curvature singularity, which affects extended bodies but allows geodesics to be extended. It is also shown that there is a critical value for a parameter on which the solution depends. Above the critical point, the black hole singularity is hidden within a global black hole event horizon. Below the critical point, the singularity appears to be naked. The relevance to cosmic censorship is discussed. |
gr-qc/0207028 | Roman A. Konoplya | R.A.Konoplya | Decay of charged scalar field around a black hole: quasinormal modes of
R-N, R-N-AdS and dilaton black holes | 10 pages, LaTeX, 4 figures, considerable changes made and wrong
interpretation of computations corrected | Phys.Rev. D66 (2002) 084007 | 10.1103/PhysRevD.66.084007 | null | gr-qc | null | It is well known that the charged scalar perturbations of the
Reissner-Nordstrom metric will decay slower at very late times than the neutral
ones, thereby dominating in the late time signal. We show that at the stage of
quasinormal ringing, on the contrary, the neutral perturbations will decay
slower for RN, RNAdS and dilaton black holes. The QN frequencies of the nearly
extreme RN black hole have the same imaginary parts (damping times) for charged
and neutral perturbations. An explanation of this fact is not clear but,
possibly, is connected with the Choptuik scaling.
| [
{
"created": "Thu, 4 Jul 2002 13:44:53 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jul 2002 14:51:38 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Jul 2002 14:36:48 GMT",
"version": "v3"
}
] | 2009-11-07 | [
[
"Konoplya",
"R. A.",
""
]
] | It is well known that the charged scalar perturbations of the Reissner-Nordstrom metric will decay slower at very late times than the neutral ones, thereby dominating in the late time signal. We show that at the stage of quasinormal ringing, on the contrary, the neutral perturbations will decay slower for RN, RNAdS and dilaton black holes. The QN frequencies of the nearly extreme RN black hole have the same imaginary parts (damping times) for charged and neutral perturbations. An explanation of this fact is not clear but, possibly, is connected with the Choptuik scaling. |
2205.07987 | Karl Daningburg | Karl Daningburg and Richard O'Shaughnessy | Cost Minimization in Acquisition for Gravitational Wave Surrogate
Modeling | 8 pages, 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave science is dependent upon expensive numerical simulations,
which provide the foundational understanding of binary merger radiation needed
to interpret observations of massive binary black holes. The high cost of these
simulations limits large-scale campaigns to explore the binary black hole
parameter space. Surrogate models have been developed to efficiently
interpolate between simulation results, but these models require a sufficiently
comprehensive sample to train on. Acquisition functions can be used to identify
points in the domain for simulation. We develop a new acquisition function
which accounts for the cost of simulating new points. We show that when applied
to a 3D domain of binary mass ratio and dimensionless spins, the accumulated
cost of simulation is reduced by a factor of about 10.
| [
{
"created": "Mon, 16 May 2022 20:57:59 GMT",
"version": "v1"
}
] | 2022-05-18 | [
[
"Daningburg",
"Karl",
""
],
[
"O'Shaughnessy",
"Richard",
""
]
] | Gravitational wave science is dependent upon expensive numerical simulations, which provide the foundational understanding of binary merger radiation needed to interpret observations of massive binary black holes. The high cost of these simulations limits large-scale campaigns to explore the binary black hole parameter space. Surrogate models have been developed to efficiently interpolate between simulation results, but these models require a sufficiently comprehensive sample to train on. Acquisition functions can be used to identify points in the domain for simulation. We develop a new acquisition function which accounts for the cost of simulating new points. We show that when applied to a 3D domain of binary mass ratio and dimensionless spins, the accumulated cost of simulation is reduced by a factor of about 10. |
gr-qc/0301103 | Masaru Shibata | Masaru Shibata (Univ. Tokyo) | Axisymmetric general relativistic hydrodynamics: Long-term evolution of
neutron stars and stellar collapse to neutron stars and black holes | 28 pages, to appear in PRD 67, 0440XX (2003) | Phys.Rev. D67 (2003) 024033 | 10.1103/PhysRevD.67.024033 | null | gr-qc astro-ph | null | We report a new implementation for axisymmetric simulation in full general
relativity. In this implementation, the Einstein equations are solved using the
Nakamura-Shibata formulation with the so-called cartoon method to impose an
axisymmetric boundary condition, and the general relativistic hydrodynamic
equations are solved using a high-resolution shock-capturing scheme based on an
approximate Riemann solver. As tests, we performed the following simulations:
(i) long-term evolution of non-rotating and rapidly rotating neutron stars,
(ii) long-term evolution of neutron stars of a high-amplitude damping
oscillation accompanied with shock formation, (iii) collapse of unstable
neutron stars to black holes, and (iv) stellar collapses to neutron stars. The
tests (i)--(iii) were carried out with the $\Gamma$-law equation of state, and
the test (iv) with a more realistic parametric equation of state for
high-density matter. We found that this new implementation works very well: It
is possible to perform the simulations for stable neutron stars for more than
10 dynamical time scales, to capture strong shocks formed at stellar core
collapses, and to accurately compute the mass of black holes formed after the
collapse and subsequent accretion. In conclusion, this implementation is robust
enough to apply to astrophysical problems such as stellar core collapse of
massive stars to a neutron star and black hole, phase transition of a neutron
star to a high-density star, and accretion-induced collapse of a neutron star
to a black hole. The result for the first simulation of stellar core collapse
to a neutron star started from a realistic initial condition is also presented.
| [
{
"created": "Fri, 24 Jan 2003 18:07:49 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Shibata",
"Masaru",
"",
"Univ. Tokyo"
]
] | We report a new implementation for axisymmetric simulation in full general relativity. In this implementation, the Einstein equations are solved using the Nakamura-Shibata formulation with the so-called cartoon method to impose an axisymmetric boundary condition, and the general relativistic hydrodynamic equations are solved using a high-resolution shock-capturing scheme based on an approximate Riemann solver. As tests, we performed the following simulations: (i) long-term evolution of non-rotating and rapidly rotating neutron stars, (ii) long-term evolution of neutron stars of a high-amplitude damping oscillation accompanied with shock formation, (iii) collapse of unstable neutron stars to black holes, and (iv) stellar collapses to neutron stars. The tests (i)--(iii) were carried out with the $\Gamma$-law equation of state, and the test (iv) with a more realistic parametric equation of state for high-density matter. We found that this new implementation works very well: It is possible to perform the simulations for stable neutron stars for more than 10 dynamical time scales, to capture strong shocks formed at stellar core collapses, and to accurately compute the mass of black holes formed after the collapse and subsequent accretion. In conclusion, this implementation is robust enough to apply to astrophysical problems such as stellar core collapse of massive stars to a neutron star and black hole, phase transition of a neutron star to a high-density star, and accretion-induced collapse of a neutron star to a black hole. The result for the first simulation of stellar core collapse to a neutron star started from a realistic initial condition is also presented. |
gr-qc/0605107 | Kouji Nakamura | Kouji Nakamura | Gauge-invariant Formulation of the Second-order Cosmological
Perturbations | 5 pages, no figure. RevTeX; short letter version of gr-qc/0605108;
some details of explanations are added | Phys.Rev. D74 (2006) 101301 | 10.1103/PhysRevD.74.101301 | null | gr-qc astro-ph hep-ph hep-th math-ph math.MP | null | Gauge invariant treatments of the second order cosmological perturbation in a
four dimensional homogeneous isotropic universe filled with the perfect fluid
are completely formulated without any gauge fixing. We derive all components of
the Einstein equations in the case where the first order vector and tensor
modes are negligible. These equations imply that the tensor and the vector mode
of the second order metric perturbations may be generated by the scalar-scalar
mode coupling of the linear order perturbations as the result of the non-linear
effects of the Einstein equations.
| [
{
"created": "Fri, 19 May 2006 06:17:04 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Sep 2006 08:33:46 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Nakamura",
"Kouji",
""
]
] | Gauge invariant treatments of the second order cosmological perturbation in a four dimensional homogeneous isotropic universe filled with the perfect fluid are completely formulated without any gauge fixing. We derive all components of the Einstein equations in the case where the first order vector and tensor modes are negligible. These equations imply that the tensor and the vector mode of the second order metric perturbations may be generated by the scalar-scalar mode coupling of the linear order perturbations as the result of the non-linear effects of the Einstein equations. |
2302.08104 | Subenoy Chakraborty | Santu Mondal, Roshni Bhaumik, Sourav Dutta, and Subenoy Chakraborty | Multiscalar field cosmological model and possible solutions using
Noether symmetry approach | 12 pages, 3 figures | null | 10.1142/S0217732321502461 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this work, a cosmological model is considered having two scalar fields
minimally coupled to gravity with a mixed kinetic term. The model is
characterized by the coupling function and the potential function which are
assumed to depend on one of the scalar fields. Instead of choosing these
functions phenomenologically here, they are evaluated assuming the existence of
Noether symmetry. By appropriate choice of a point transformation in the
augmented space, one of the variables in the Lagrangian becomes cyclic and the
evolution equations become much simpler to have solutions. Finally, the
solutions are analyzed from cosmological view point.
| [
{
"created": "Thu, 16 Feb 2023 06:07:54 GMT",
"version": "v1"
}
] | 2023-02-17 | [
[
"Mondal",
"Santu",
""
],
[
"Bhaumik",
"Roshni",
""
],
[
"Dutta",
"Sourav",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | In this work, a cosmological model is considered having two scalar fields minimally coupled to gravity with a mixed kinetic term. The model is characterized by the coupling function and the potential function which are assumed to depend on one of the scalar fields. Instead of choosing these functions phenomenologically here, they are evaluated assuming the existence of Noether symmetry. By appropriate choice of a point transformation in the augmented space, one of the variables in the Lagrangian becomes cyclic and the evolution equations become much simpler to have solutions. Finally, the solutions are analyzed from cosmological view point. |
1412.4189 | Bogeun Gwak | Wha-Keun Ahn, Bogeun Gwak, Bum-Hoon Lee, Wonwoo Lee | Instability of Black Holes with a Gauss-Bonnet Term | 20 pages, 10 figures, published version in EPJC | Eur. Phys. J. C75, no. 8, 372 (2015) | 10.1140/epjc/s10052-015-3568-5 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the fragmentation instability of hairy black holes in the
theory with a Gauss$-$Bonnet(GB) term in asymptotically flat spacetime. Our
approach is through the non-perturbative fragmentation instability. By this
approach, we investigate whether the initial black hole can be broken into two
black holes by comparing the entropy of the initial black hole with the sum of
those of two fragmented black holes. The relation between the black hole
instability and the GB coupling with dilaton hair are presented. We describe
the phase diagrams with respect to the mass of the black hole solutions and
coupling constants. We find that a perturbatively stable black hole can be
unstable under fragmentation.
| [
{
"created": "Sat, 13 Dec 2014 03:39:24 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Sep 2015 17:48:38 GMT",
"version": "v2"
}
] | 2016-02-15 | [
[
"Ahn",
"Wha-Keun",
""
],
[
"Gwak",
"Bogeun",
""
],
[
"Lee",
"Bum-Hoon",
""
],
[
"Lee",
"Wonwoo",
""
]
] | We investigate the fragmentation instability of hairy black holes in the theory with a Gauss$-$Bonnet(GB) term in asymptotically flat spacetime. Our approach is through the non-perturbative fragmentation instability. By this approach, we investigate whether the initial black hole can be broken into two black holes by comparing the entropy of the initial black hole with the sum of those of two fragmented black holes. The relation between the black hole instability and the GB coupling with dilaton hair are presented. We describe the phase diagrams with respect to the mass of the black hole solutions and coupling constants. We find that a perturbatively stable black hole can be unstable under fragmentation. |
2102.09776 | Muhammad Zubair Ali Moughal | Muhammad Zubair Ali Moughal | Generating spiky solutions of Einstein field equations with the Stephani
transformation | PhD thesis. arXiv admin note: text overlap with arXiv:gr-qc/0410126
by other authors | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The Geroch/Stephani transformation is a solution-generating transformation,
and may generate spiky solutions. The spikes in solutions generated so far are
either early-time permanent spikes or transient spikes. We want to generate a
solution with a late-time permanent spike. We achieve this by applying the
Stephani transformation with the rotational Killing vector field of the locally
rotationally symmetric Jacobs solution. The late-time permanent spike occurs
along the cylindrical axis. The generated solution also features a rich variety
of transient structures. We introduce a new technique to analyse these
structures. Our findings lead us to discover a transient behaviour, which we
call the overshoot transition.
| [
{
"created": "Fri, 19 Feb 2021 07:36:16 GMT",
"version": "v1"
}
] | 2021-02-22 | [
[
"Moughal",
"Muhammad Zubair Ali",
""
]
] | The Geroch/Stephani transformation is a solution-generating transformation, and may generate spiky solutions. The spikes in solutions generated so far are either early-time permanent spikes or transient spikes. We want to generate a solution with a late-time permanent spike. We achieve this by applying the Stephani transformation with the rotational Killing vector field of the locally rotationally symmetric Jacobs solution. The late-time permanent spike occurs along the cylindrical axis. The generated solution also features a rich variety of transient structures. We introduce a new technique to analyse these structures. Our findings lead us to discover a transient behaviour, which we call the overshoot transition. |
1602.07520 | Angnis Schmidt-May | Angnis Schmidt-May | Nonlinear interactions for massive spin-2 fields | to appear in the proceedings of the Corfu Summer Institute 2015
"School and Workshops on Elementary Particle Physics and Gravity", 16 pages | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a basic introduction to ghost-free nonlinear theories involving
massive spin-2 fields, focussing on bimetric theory. After motivating the
construction of such models from field theoretical considerations, we review
the linear theories for massive and massless spin-2 fluctuations propagating on
maximally symmetric backgrounds. The structure of general nonlinear spin-2
interactions is explained before we specialise to the ghost-free case. We
review the maximally symmetric solutions of bimetric theory, its mass spectrum
and the parameter limit which brings the theory close to general relativity.
Finally we discuss applications of bimetric theory to cosmology with particular
emphasis on the role of the general relativity limit.
| [
{
"created": "Wed, 24 Feb 2016 14:21:14 GMT",
"version": "v1"
}
] | 2016-02-25 | [
[
"Schmidt-May",
"Angnis",
""
]
] | We give a basic introduction to ghost-free nonlinear theories involving massive spin-2 fields, focussing on bimetric theory. After motivating the construction of such models from field theoretical considerations, we review the linear theories for massive and massless spin-2 fluctuations propagating on maximally symmetric backgrounds. The structure of general nonlinear spin-2 interactions is explained before we specialise to the ghost-free case. We review the maximally symmetric solutions of bimetric theory, its mass spectrum and the parameter limit which brings the theory close to general relativity. Finally we discuss applications of bimetric theory to cosmology with particular emphasis on the role of the general relativity limit. |
2211.03849 | Eva Politou | Eva Politou | A geometric framework for conservation laws along null hypersurfaces | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the general theory of local conservation laws for arbitrary partial
differential equations to provide a geometric framework for conservation laws
on characteristic null hypersurfaces. The operator of interest is the wave
operator on general four-dimensional Lorentzian manifolds restricted on a null
hypersurface.
| [
{
"created": "Mon, 7 Nov 2022 20:35:48 GMT",
"version": "v1"
}
] | 2022-11-09 | [
[
"Politou",
"Eva",
""
]
] | We use the general theory of local conservation laws for arbitrary partial differential equations to provide a geometric framework for conservation laws on characteristic null hypersurfaces. The operator of interest is the wave operator on general four-dimensional Lorentzian manifolds restricted on a null hypersurface. |
1407.5264 | Otari Sakhelashvili | Otari Sakhelashvili | Dimensional Reduction in 6D Standing Waves Braneworld | arXiv admin note: text overlap with arXiv:1202.1608 by other authors | International Journal of Modern Physics D Vol. 24, No. 1 (2015) | 10.1142/S0218271815500091 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We found cosmological solution of the 6D standing wave braneworld model
generated by gravity coupled to a massless scalar phantom-like field. By
obtaining a full exact solution of the model we found a novel dynamical
mechanism in which the anisotropic nature of the primordial metric gives rise
to expansion of three spatial brane dimensions and affectively reduction of
other spatial directions. This dynamical mechanism can be relevant for
dimensional reduction in string and other higher dimensional theories in the
attempt of getting a 4D isotropic expanding space-time.
| [
{
"created": "Sun, 20 Jul 2014 10:33:13 GMT",
"version": "v1"
}
] | 2014-11-24 | [
[
"Sakhelashvili",
"Otari",
""
]
] | We found cosmological solution of the 6D standing wave braneworld model generated by gravity coupled to a massless scalar phantom-like field. By obtaining a full exact solution of the model we found a novel dynamical mechanism in which the anisotropic nature of the primordial metric gives rise to expansion of three spatial brane dimensions and affectively reduction of other spatial directions. This dynamical mechanism can be relevant for dimensional reduction in string and other higher dimensional theories in the attempt of getting a 4D isotropic expanding space-time. |
1012.2245 | Ahmed Bouda | A.Bouda and A.Belabbas | A possible Reinterpretation of Einstein's Equations | 11 pages, no figures | Int.J.Theor.Phys.49(2010)2630-2639 | 10.1007/s10773-010-0454-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we first review Huei's formulation in which it is shown that
the linearized Einstein equations can be written in the same form as the
Maxwell equations. We eliminate some imperfections like the scalar potential
which is ill linked to the electric-type field, the Lorentz-type force which is
obtained with a time independence restriction and the undesired factor 4 which
appears in the magnetic-type part. Second, from these results and in the light
of a recent work by C.C. Barros, we propose an extension of the equivalence
principle and we suggest a new interpretation for Einstein's equations by
showing that the electromagnetic Maxwell equations can be derived from a new
version of Einstein's ones.
| [
{
"created": "Fri, 10 Dec 2010 12:13:12 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Bouda",
"A.",
""
],
[
"Belabbas",
"A.",
""
]
] | In this paper, we first review Huei's formulation in which it is shown that the linearized Einstein equations can be written in the same form as the Maxwell equations. We eliminate some imperfections like the scalar potential which is ill linked to the electric-type field, the Lorentz-type force which is obtained with a time independence restriction and the undesired factor 4 which appears in the magnetic-type part. Second, from these results and in the light of a recent work by C.C. Barros, we propose an extension of the equivalence principle and we suggest a new interpretation for Einstein's equations by showing that the electromagnetic Maxwell equations can be derived from a new version of Einstein's ones. |
1711.06727 | Klaus Liegener Dr | Thorsten Lang, Klaus Liegener, Thomas Thiemann | Hamiltonian Renormalisation II. Renormalisation Flow of 1+1 dimensional
free scalar fields: Derivation | 30 pages | Class.Quant.Grav. 35 (2018) no.24, 245012 | 10.1088/1361-6382/aaec54 | null | gr-qc hep-lat hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the companion paper we motivated a renormalisation flow on
Osterwalder-Schrader data (OS-data) consisting of 1. a Hilbert space, 2. a
cyclic vacuum and 3. a Hamiltonian annihilating that vacuum. As the name
suggests, the motivation was via the OS reconstruction theorem which allows to
reconstruct the OS data from an OS measure satisfying (a subset of) the OS
axioms, in particular reflection positivity. The guiding principle was to map
the usual Wilsonian path integral renormalisation flow onto a flow of the
corresponding OS data.
We showed that this induced flow on the OS data has an unwanted feature which
disqualifies the associated coarse grained Hamiltonians from being the
projections of a continuum Hamiltonian onto vectors in the coarse grained
Hilbert space. This motivated the definition of a direct Hamiltonian
renormalisation flow which follows the guiding principle but does not suffer
from the afore mentioned caveat.
In order to test our proposal, we apply it to the only known completely
solvable model, namely the case of free scalar quantum fields. In this paper we
focus on the Klein Gordon field in two spacetime dimensions and illustrate the
difference between the path integral induced and direct Hamiltonian flow.
Generalisations to more general models in higher dimensions will be discussed
in our companion papers.
| [
{
"created": "Thu, 16 Nov 2017 14:42:22 GMT",
"version": "v1"
},
{
"created": "Sat, 6 Jul 2019 15:37:13 GMT",
"version": "v2"
}
] | 2019-07-09 | [
[
"Lang",
"Thorsten",
""
],
[
"Liegener",
"Klaus",
""
],
[
"Thiemann",
"Thomas",
""
]
] | In the companion paper we motivated a renormalisation flow on Osterwalder-Schrader data (OS-data) consisting of 1. a Hilbert space, 2. a cyclic vacuum and 3. a Hamiltonian annihilating that vacuum. As the name suggests, the motivation was via the OS reconstruction theorem which allows to reconstruct the OS data from an OS measure satisfying (a subset of) the OS axioms, in particular reflection positivity. The guiding principle was to map the usual Wilsonian path integral renormalisation flow onto a flow of the corresponding OS data. We showed that this induced flow on the OS data has an unwanted feature which disqualifies the associated coarse grained Hamiltonians from being the projections of a continuum Hamiltonian onto vectors in the coarse grained Hilbert space. This motivated the definition of a direct Hamiltonian renormalisation flow which follows the guiding principle but does not suffer from the afore mentioned caveat. In order to test our proposal, we apply it to the only known completely solvable model, namely the case of free scalar quantum fields. In this paper we focus on the Klein Gordon field in two spacetime dimensions and illustrate the difference between the path integral induced and direct Hamiltonian flow. Generalisations to more general models in higher dimensions will be discussed in our companion papers. |
2204.02454 | Vasilis Oikonomou | V.K. Oikonomou, Ifigeneia Giannakoudi | $\mathcal{R}^2$ Quantum Corrected Scalar Field Inflation | NPB Accepted | null | 10.1016/j.nuclphysb.2022.115779 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | String theory enjoys an elevated role among quantum gravity theories, since
it seems to be the most consistent UV completion of general relativity and the
Standard Model. However, it is hard to verify the existence of this underlying
theory on terrestrial accelerators. One way to probe string theory is to study
its imprints on the low-energy effective inflationary Lagrangian, which are
quantified in terms of high energy correction terms. It is highly likely, thus,
to find higher order curvature terms combined with string moduli, that is
scalar fields, since both these types of interactions and matter fields appear
in string theory. In this work we aim to stress the probability that the
inflationary dynamics are controlled by the synergy of scalar fields and higher
order curvature terms. Specifically, we shall consider a well motivated quantum
corrected canonical scalar field theory, with the quantum corrections being of
the $\mathcal{R}^2$ type. The reason for choosing minimally coupled scalar
theory is basically because if scalar fields are evaluated in their vacuum
configuration, they will either be minimally coupled or conformally coupled.
Here we choose the former case, and the whole study shall be performed in the
string frame (Jordan frame), in contrast to similar studies in the literature
where the Einstein frame two scalar theory is considered. We derive the field
equations of the quantum-corrected theory at leading order and we present the
form the slow-roll indices obtain for the quantum corrected theory. We
exemplify our theoretical framework by using the quadratic inflation model, and
as we show, the $\mathcal{R}^2$ quantum corrected quadratic inflation model
produces a viable inflationary phenomenology, in contrast with the simple
quadratic inflation model.
| [
{
"created": "Tue, 5 Apr 2022 18:59:24 GMT",
"version": "v1"
}
] | 2022-04-27 | [
[
"Oikonomou",
"V. K.",
""
],
[
"Giannakoudi",
"Ifigeneia",
""
]
] | String theory enjoys an elevated role among quantum gravity theories, since it seems to be the most consistent UV completion of general relativity and the Standard Model. However, it is hard to verify the existence of this underlying theory on terrestrial accelerators. One way to probe string theory is to study its imprints on the low-energy effective inflationary Lagrangian, which are quantified in terms of high energy correction terms. It is highly likely, thus, to find higher order curvature terms combined with string moduli, that is scalar fields, since both these types of interactions and matter fields appear in string theory. In this work we aim to stress the probability that the inflationary dynamics are controlled by the synergy of scalar fields and higher order curvature terms. Specifically, we shall consider a well motivated quantum corrected canonical scalar field theory, with the quantum corrections being of the $\mathcal{R}^2$ type. The reason for choosing minimally coupled scalar theory is basically because if scalar fields are evaluated in their vacuum configuration, they will either be minimally coupled or conformally coupled. Here we choose the former case, and the whole study shall be performed in the string frame (Jordan frame), in contrast to similar studies in the literature where the Einstein frame two scalar theory is considered. We derive the field equations of the quantum-corrected theory at leading order and we present the form the slow-roll indices obtain for the quantum corrected theory. We exemplify our theoretical framework by using the quadratic inflation model, and as we show, the $\mathcal{R}^2$ quantum corrected quadratic inflation model produces a viable inflationary phenomenology, in contrast with the simple quadratic inflation model. |
1207.6030 | Marc-Thierry Jaekel | Marc-Thierry Jaekel, Brahim Lamine and Serge Reynaud | Phases and relativity in atomic gravimetry | 7 pages, 1 figure | Classical and Quantum Gravity 30, 6 (2013) 065006 | 10.1088/0264-9381/30/6/065006 | LPTENS 12/28 | gr-qc physics.atom-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The phase observable measured by an atomic gravimeter built up on stimulated
Raman transitions is discussed in a fully relativistic context. It is written
in terms of laser phases which are invariant under relativistic gauge
transformations. The dephasing is the sum of light and atomic contributions
which are connected to one another through their interplay with conservation
laws at the interaction vertices. In the case of a closed geometry, a compact
form of the dephasing is written in terms of a Legendre transform of the laser
phases. These general expressions are illustrated by discussing two techniques
used for compensating the Doppler shift, one corresponding to chirped
frequencies and the other one to ramped variations.
| [
{
"created": "Wed, 25 Jul 2012 15:32:28 GMT",
"version": "v1"
}
] | 2014-09-16 | [
[
"Jaekel",
"Marc-Thierry",
""
],
[
"Lamine",
"Brahim",
""
],
[
"Reynaud",
"Serge",
""
]
] | The phase observable measured by an atomic gravimeter built up on stimulated Raman transitions is discussed in a fully relativistic context. It is written in terms of laser phases which are invariant under relativistic gauge transformations. The dephasing is the sum of light and atomic contributions which are connected to one another through their interplay with conservation laws at the interaction vertices. In the case of a closed geometry, a compact form of the dephasing is written in terms of a Legendre transform of the laser phases. These general expressions are illustrated by discussing two techniques used for compensating the Doppler shift, one corresponding to chirped frequencies and the other one to ramped variations. |
1802.01635 | Fr\'ed\'eric Lamy | Fr\'ed\'eric Lamy, Eric Gourgoulhon, Thibaut Paumard, Fr\'ed\'eric H.
Vincent | Imaging a non-singular rotating black hole at the center of the Galaxy | 25 pages, 31 figures; v2: two figures and some clarifications added,
version published in CQG | Classical and Quantum Gravity, 2018, Volume 35, Number 11 | 10.1088/1361-6382/aabd97 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the rotating generalization of Hayward's non-singular black hole
previously studied in the literature is geodesically incomplete, and that its
straightforward extension leads to a singular spacetime. We present another
extension, which is devoid of any curvature singularity. The obtained metric
depends on three parameters and, depending on their values, yields an event
horizon or not. These two regimes, named respectively regular rotating Hayward
black hole and naked rotating wormhole, are studied both numerically and
analytically. In preparation for the upcoming results of the Event Horizon
Telescope, the images of an accretion torus around Sgr A*, the supermassive
object at the center of the Galaxy, are computed. These images contain, even in
the absence of a horizon, a central faint region which bears a resemblance to
the shadow of Kerr black holes and emphasizes the difficulty of claiming the
existence of an event horizon from the analysis of strong-field images. The
frequencies of the co- and contra-rotating orbits at the innermost stable
circular orbit (ISCO) in this geometry are also computed, in the hope that
quasi-periodic oscillations may permit to compare this model with Kerr's black
hole on observational grounds.
| [
{
"created": "Mon, 5 Feb 2018 20:23:43 GMT",
"version": "v1"
},
{
"created": "Sat, 12 May 2018 20:21:25 GMT",
"version": "v2"
}
] | 2018-05-15 | [
[
"Lamy",
"Frédéric",
""
],
[
"Gourgoulhon",
"Eric",
""
],
[
"Paumard",
"Thibaut",
""
],
[
"Vincent",
"Frédéric H.",
""
]
] | We show that the rotating generalization of Hayward's non-singular black hole previously studied in the literature is geodesically incomplete, and that its straightforward extension leads to a singular spacetime. We present another extension, which is devoid of any curvature singularity. The obtained metric depends on three parameters and, depending on their values, yields an event horizon or not. These two regimes, named respectively regular rotating Hayward black hole and naked rotating wormhole, are studied both numerically and analytically. In preparation for the upcoming results of the Event Horizon Telescope, the images of an accretion torus around Sgr A*, the supermassive object at the center of the Galaxy, are computed. These images contain, even in the absence of a horizon, a central faint region which bears a resemblance to the shadow of Kerr black holes and emphasizes the difficulty of claiming the existence of an event horizon from the analysis of strong-field images. The frequencies of the co- and contra-rotating orbits at the innermost stable circular orbit (ISCO) in this geometry are also computed, in the hope that quasi-periodic oscillations may permit to compare this model with Kerr's black hole on observational grounds. |
1107.2959 | Aaron Zimmerman | Aaron Zimmerman, David A. Nichols, and Fan Zhang | Classifying the Isolated Zeros of Asymptotic Gravitational Radiation by
Tendex and Vortex Lines | 10 pages, 10 figures. Changed to reflect published version, sign
errors fixed | Phys.Rev.D84:044037,2011 | 10.1103/PhysRevD.84.044037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new method to visualize the curvature of spacetime was recently proposed.
This method finds the eigenvectors of the "electric" and "magnetic" components
of the Weyl tensor and, in analogy to the field lines of electromagnetism, uses
the eigenvectors' integral curves to illustrate the spacetime curvature. Here
we use this approach, along with well-known topological properties of fields on
closed surfaces, to show that an arbitrary, radiating, asymptotically flat
spacetime must have points near null infinity where the gravitational radiation
vanishes. At the zeros of the gravitational radiation, the field of integral
curves develops singular features analogous to the critical points of a vector
field. We can, therefore, apply the topological classification of singular
points of unoriented lines as a method to describe the radiation field. We
provide examples of the structure of these points using linearized gravity and
discuss an application to the extreme-kick black-hole-binary merger.
| [
{
"created": "Thu, 14 Jul 2011 21:48:42 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Aug 2011 17:34:13 GMT",
"version": "v2"
}
] | 2011-09-08 | [
[
"Zimmerman",
"Aaron",
""
],
[
"Nichols",
"David A.",
""
],
[
"Zhang",
"Fan",
""
]
] | A new method to visualize the curvature of spacetime was recently proposed. This method finds the eigenvectors of the "electric" and "magnetic" components of the Weyl tensor and, in analogy to the field lines of electromagnetism, uses the eigenvectors' integral curves to illustrate the spacetime curvature. Here we use this approach, along with well-known topological properties of fields on closed surfaces, to show that an arbitrary, radiating, asymptotically flat spacetime must have points near null infinity where the gravitational radiation vanishes. At the zeros of the gravitational radiation, the field of integral curves develops singular features analogous to the critical points of a vector field. We can, therefore, apply the topological classification of singular points of unoriented lines as a method to describe the radiation field. We provide examples of the structure of these points using linearized gravity and discuss an application to the extreme-kick black-hole-binary merger. |
1606.01215 | Daniel Guariento | Daniel C. Guariento, Flavio Mercati | Self-gravitating fluid solutions of Shape Dynamics | 9 pages | Phys. Rev. D 94, 064023 (2016) | 10.1103/PhysRevD.94.064023 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Shape Dynamics is a 3D conformally invariant theory of gravity which
possesses a large set of solutions in common with General Relativity. When
looked closely, these solutions are found to behave in surprising ways, so in
order to probe the fitness of Shape Dynamics as a viable alternative to General
Relativity one must find and understand increasingly more complex, less
symmetrical exact solutions, on which to base perturbative studies and
numerical analyses in order to compare them with data. Spherically symmetric
exact solutions have been studied, but only in a static vacuum setup. In this
work we construct a class of time-dependent exact solutions of Shape Dynamics
from first principles, representing a central inhomogeneity in an evolving
cosmological environment. By assuming only a perfect fluid source in a
spherically symmetric geometry we show that this fully dynamic non-vacuum
solution satisfies in all generality the Hamiltonian structure of Shape
Dynamics. The simplest choice of solutions is shown to be a member of the
McVittie family.
| [
{
"created": "Fri, 3 Jun 2016 18:33:05 GMT",
"version": "v1"
}
] | 2016-09-14 | [
[
"Guariento",
"Daniel C.",
""
],
[
"Mercati",
"Flavio",
""
]
] | Shape Dynamics is a 3D conformally invariant theory of gravity which possesses a large set of solutions in common with General Relativity. When looked closely, these solutions are found to behave in surprising ways, so in order to probe the fitness of Shape Dynamics as a viable alternative to General Relativity one must find and understand increasingly more complex, less symmetrical exact solutions, on which to base perturbative studies and numerical analyses in order to compare them with data. Spherically symmetric exact solutions have been studied, but only in a static vacuum setup. In this work we construct a class of time-dependent exact solutions of Shape Dynamics from first principles, representing a central inhomogeneity in an evolving cosmological environment. By assuming only a perfect fluid source in a spherically symmetric geometry we show that this fully dynamic non-vacuum solution satisfies in all generality the Hamiltonian structure of Shape Dynamics. The simplest choice of solutions is shown to be a member of the McVittie family. |
gr-qc/0412080 | Roberto Gomez | Nigel T. Bishop, Roberto Gomez, Luis Lehner, Manoj Maharaj and Jeffrey
Winicour | On characteristic initial data for a star orbiting a black hole | 20 pages, 10 figures | Phys.Rev. D72 (2005) 024002 | 10.1103/PhysRevD.72.024002 | null | gr-qc | null | We take further steps in the development of the characteristic approach to
enable handling the physical problem of a compact self-gravitating object, such
as a neutron star, in close orbit around a black hole. We examine different
options for setting the initial data for this problem and, in order to shed
light on their physical relevance, we carry out short time evolution of this
data. To this end we express the matter part of the characteristic gravity code
so that the hydrodynamics are in conservation form. The resulting gravity plus
matter relativity code provides a starting point for more refined future
efforts at longer term evolution. In the present work we find that,
independently of the details of the initial gravitational data, the system
quickly flushes out spurious gravitational radiation and relaxes to a
quasi-equilibrium state with an approximate helical symmetry corresponding to
the circular orbit of the star.
| [
{
"created": "Thu, 16 Dec 2004 17:52:05 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bishop",
"Nigel T.",
""
],
[
"Gomez",
"Roberto",
""
],
[
"Lehner",
"Luis",
""
],
[
"Maharaj",
"Manoj",
""
],
[
"Winicour",
"Jeffrey",
""
]
] | We take further steps in the development of the characteristic approach to enable handling the physical problem of a compact self-gravitating object, such as a neutron star, in close orbit around a black hole. We examine different options for setting the initial data for this problem and, in order to shed light on their physical relevance, we carry out short time evolution of this data. To this end we express the matter part of the characteristic gravity code so that the hydrodynamics are in conservation form. The resulting gravity plus matter relativity code provides a starting point for more refined future efforts at longer term evolution. In the present work we find that, independently of the details of the initial gravitational data, the system quickly flushes out spurious gravitational radiation and relaxes to a quasi-equilibrium state with an approximate helical symmetry corresponding to the circular orbit of the star. |
1909.00018 | Filipe Mena | Paulo Luz and Filipe C. Mena | Singularity theorems and the inclusion of torsion in affine theories of
gravity | 15 pages | null | 10.1063/1.5126220 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend the scope of the Raychaudhuri-Komar singularity theorem of General
Relativity to affine theories of gravity with and without torsion. We first
generalize the existing focusing theorems using time-like and null congruences
of curves which are hypersurface orthogonal, showing how the presence of
torsion affects the formation of focal points in Lorentzian manifolds.
Considering the energy conservation on a given affine gravity theory, we prove
new singularity theorems for accelerated curves in the cases of Lorentzian
manifolds containing perfect fluids or scalar field matter sources.
| [
{
"created": "Fri, 30 Aug 2019 18:14:11 GMT",
"version": "v1"
}
] | 2020-02-19 | [
[
"Luz",
"Paulo",
""
],
[
"Mena",
"Filipe C.",
""
]
] | We extend the scope of the Raychaudhuri-Komar singularity theorem of General Relativity to affine theories of gravity with and without torsion. We first generalize the existing focusing theorems using time-like and null congruences of curves which are hypersurface orthogonal, showing how the presence of torsion affects the formation of focal points in Lorentzian manifolds. Considering the energy conservation on a given affine gravity theory, we prove new singularity theorems for accelerated curves in the cases of Lorentzian manifolds containing perfect fluids or scalar field matter sources. |
gr-qc/0002039 | Mauricio Bellini | Mauricio Bellini (Universidad Nacional de Mar del Plata) | Warm inflation with coupled thermal quantum fluctuations: a new
semiclassical approach | Version awared ``Honorable Montion'' by Gravity Research Foundation
(2000) Version to be published in Il Nuovo Cimento B | Nuovo Cim.B115:1241-1247,2000 | null | null | gr-qc | null | I consider a new semiclassical expansion for the inflaton field in the
framework of warm inflation scenario. The fluctuations of the matter field are
considered as thermally coupled with the particles of the thermal bath. This
coupling parameter depends on the temperature of the bath. The power spectrum
remains invariant under this new semiclassical expansion for the inflaton.
However, I find that the thermal component of the amplitude for the primordial
field fluctuations should be very small at the end of inflation.
| [
{
"created": "Thu, 10 Feb 2000 14:03:19 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Mar 2000 13:29:05 GMT",
"version": "v2"
},
{
"created": "Tue, 16 May 2000 14:45:46 GMT",
"version": "v3"
},
{
"created": "Wed, 25 Oct 2000 19:12:36 GMT",
"version": "v4"
}
] | 2010-11-11 | [
[
"Bellini",
"Mauricio",
"",
"Universidad Nacional de Mar del Plata"
]
] | I consider a new semiclassical expansion for the inflaton field in the framework of warm inflation scenario. The fluctuations of the matter field are considered as thermally coupled with the particles of the thermal bath. This coupling parameter depends on the temperature of the bath. The power spectrum remains invariant under this new semiclassical expansion for the inflaton. However, I find that the thermal component of the amplitude for the primordial field fluctuations should be very small at the end of inflation. |
gr-qc/0702081 | David Garfinkle | David Garfinkle | Matters of Gravity, The Newsletter of the Topical Group in Gravitation
of the American Physical Society, Volume 29, Winter 2007 | 30 pages, latex, 1 figure, items added to the "we hear that..."
section | null | null | null | gr-qc | null | GGR News:
- The View from the NSF, by Beverly Berger
- GGR Program at the APS meeting in Jacksonville we hear that..., by David
Garfinkle
- 100 years ago, by David Garfinkle
Research Briefs:
- The Double Pulsar, by Michael Kramer
- Theoretical Approaches to Cosmic Acceleration, by Mark Trodden
Conference Reports:
- Numerical Relativity-Data Analysis, by Patrick Brady
- Note on Numerical Relativity-Data Analysis, by Peter Saulson
- Unruh and Wald Fest, by Carsten Gundlach and David Garfinkle
- Will Fest, by Eric Poisson
- Brane-World Gravity, by Andrew Mennim
- Gravity and Theoretical Physics, by Marco Cavaglia
| [
{
"created": "Wed, 14 Feb 2007 21:30:48 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Feb 2007 19:38:17 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Garfinkle",
"David",
""
]
] | GGR News: - The View from the NSF, by Beverly Berger - GGR Program at the APS meeting in Jacksonville we hear that..., by David Garfinkle - 100 years ago, by David Garfinkle Research Briefs: - The Double Pulsar, by Michael Kramer - Theoretical Approaches to Cosmic Acceleration, by Mark Trodden Conference Reports: - Numerical Relativity-Data Analysis, by Patrick Brady - Note on Numerical Relativity-Data Analysis, by Peter Saulson - Unruh and Wald Fest, by Carsten Gundlach and David Garfinkle - Will Fest, by Eric Poisson - Brane-World Gravity, by Andrew Mennim - Gravity and Theoretical Physics, by Marco Cavaglia |
gr-qc/9409055 | Anton Kraemmer-Rebhan | H. Nachbagauer, A. K. Rebhan, D. J. Schwarz | Effects of weak self-interactions in a relativistic plasma on
cosmological perturbations | 11 pages, REVTEX, 4 postscript figures included by epsf.sty -
expanded version (more details on the resummation of thermal masses which is
required for the late-time damping behaviour) | Phys.Rev.D51:2504-2508,1995 | 10.1103/PhysRevD.51.2504 | DESY 94-165, ENSLAPP-A-487/94, TUW-94-18 | gr-qc astro-ph hep-ph | null | The exact solutions for linear cosmological perturbations which have been
obtained for collisionless relativistic matter within thermal field theory are
extended to a self-interacting case. The two-loop contributions of scalar
$\lambda\phi^4$ theory to the thermal graviton self-energy are evaluated, which
give the $O(\lambda)$ corrections in the perturbation equations. The changes
are found to be perturbative on scales comparable to or larger than the Hubble
horizon, but the determination of the large-time damping behavior of subhorizon
perturbations requires a resummation of thermally induced masses.
| [
{
"created": "Tue, 27 Sep 1994 14:26:08 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Nov 1994 16:41:48 GMT",
"version": "v2"
}
] | 2009-12-30 | [
[
"Nachbagauer",
"H.",
""
],
[
"Rebhan",
"A. K.",
""
],
[
"Schwarz",
"D. J.",
""
]
] | The exact solutions for linear cosmological perturbations which have been obtained for collisionless relativistic matter within thermal field theory are extended to a self-interacting case. The two-loop contributions of scalar $\lambda\phi^4$ theory to the thermal graviton self-energy are evaluated, which give the $O(\lambda)$ corrections in the perturbation equations. The changes are found to be perturbative on scales comparable to or larger than the Hubble horizon, but the determination of the large-time damping behavior of subhorizon perturbations requires a resummation of thermally induced masses. |
1408.6436 | Piyali Bhar | Piyali Bhar | Vaidya-Tikekar Type Superdense Star Admitting Conformal Motion in
Presence of Quintessence Field | 9 pages,13 figures | Eur. Phys. J. C (2015) 75:123 | 10.1140/epjc/s10052-015-3340-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To explain the reason of accelerated expansion of our universe dark energy is
a suitable candidate. Motivated by this concept in the present paper we have
obtained a new model of an anisotropic superdense star which admits conformal
motions in presence of quintessence field which is characterized by a parameter
$omega$ with omega lies in the range -1 to -1/3.The model has been developed by
choosing Vaidya-Titekar ansatz [P C Vaidya and R Tikekar (1982)J. Astrophys
.Astron. 3 325].Our model satisfy all the physical requirements.We have analyze
our result analytically as well as with the help of graphical representation.
| [
{
"created": "Tue, 26 Aug 2014 10:39:45 GMT",
"version": "v1"
}
] | 2015-03-24 | [
[
"Bhar",
"Piyali",
""
]
] | To explain the reason of accelerated expansion of our universe dark energy is a suitable candidate. Motivated by this concept in the present paper we have obtained a new model of an anisotropic superdense star which admits conformal motions in presence of quintessence field which is characterized by a parameter $omega$ with omega lies in the range -1 to -1/3.The model has been developed by choosing Vaidya-Titekar ansatz [P C Vaidya and R Tikekar (1982)J. Astrophys .Astron. 3 325].Our model satisfy all the physical requirements.We have analyze our result analytically as well as with the help of graphical representation. |
1408.6997 | Leonardo Fernandez-Jambrina | L. Fern\'andez-Jambrina | Grand Rip and Grand Bang/Crunch cosmological singularities | 19 pages, 2 figures. Typos amended | Phys. Rev. D 90, 064014 (2014) | 10.1103/PhysRevD.90.064014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present accelerated expansion of the universe has enriched the list of
possible scenarios for its fate, singular or not. In this paper a unifying
framework for analyzing such behaviors is proposed, based on generalized power
and asymptotic expansions of the barotropic index $w$, or equivalently of the
deceleration parameter $q$, in terms of the time coordinate. Besides well known
singular and non-singular future behaviors, other types of strong singularities
appear around the phantom divide in flat models, with features similar to those
of big rip or big bang/crunch, which we have dubbed grand rip and grand
bang/crunch respectively, since energy density and pressure diverge faster than
$t^{-2}$ in coordinate time. In addition to this, the scale factor does not
admit convergent generalized power series around these singularities with a
finite number of terms with negative powers.
| [
{
"created": "Fri, 29 Aug 2014 12:35:23 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Sep 2014 17:14:27 GMT",
"version": "v2"
},
{
"created": "Wed, 10 Sep 2014 20:20:38 GMT",
"version": "v3"
},
{
"created": "Mon, 26 Jan 2015 08:39:31 GMT",
"version": "v4"
},
{
"cr... | 2019-03-07 | [
[
"Fernández-Jambrina",
"L.",
""
]
] | The present accelerated expansion of the universe has enriched the list of possible scenarios for its fate, singular or not. In this paper a unifying framework for analyzing such behaviors is proposed, based on generalized power and asymptotic expansions of the barotropic index $w$, or equivalently of the deceleration parameter $q$, in terms of the time coordinate. Besides well known singular and non-singular future behaviors, other types of strong singularities appear around the phantom divide in flat models, with features similar to those of big rip or big bang/crunch, which we have dubbed grand rip and grand bang/crunch respectively, since energy density and pressure diverge faster than $t^{-2}$ in coordinate time. In addition to this, the scale factor does not admit convergent generalized power series around these singularities with a finite number of terms with negative powers. |
2103.00183 | Roberto Casadio | Roberto Casadio | Geometry and thermodynamics of coherent quantum black holes | LaTeX, 16 pages, 6 graphs in 4 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We present a quantum description of black holes given by coherent states of
gravitons sourced by a matter core. The expected behaviour in the weak-field
region outside the horizon is recovered, with arbitrarily good approximation,
but the classical central singularity is not resolved because the coherent
states may not contain modes of arbitrarily short wavelength and the matter
core must therefore have finite size. Ensuing quantum corrections both in the
interior and exterior are also estimated by assuming the mean-field
approximation holds everywhere. These deviations from the classical black hole
geometry can be viewed as quantum hair and lead to a quantum corrected horizon
radius and thermodynamics.
| [
{
"created": "Sat, 27 Feb 2021 10:46:48 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Apr 2021 14:45:46 GMT",
"version": "v2"
},
{
"created": "Sat, 4 Sep 2021 06:10:16 GMT",
"version": "v3"
},
{
"created": "Tue, 1 Mar 2022 17:52:23 GMT",
"version": "v4"
},
{
"cre... | 2022-09-09 | [
[
"Casadio",
"Roberto",
""
]
] | We present a quantum description of black holes given by coherent states of gravitons sourced by a matter core. The expected behaviour in the weak-field region outside the horizon is recovered, with arbitrarily good approximation, but the classical central singularity is not resolved because the coherent states may not contain modes of arbitrarily short wavelength and the matter core must therefore have finite size. Ensuing quantum corrections both in the interior and exterior are also estimated by assuming the mean-field approximation holds everywhere. These deviations from the classical black hole geometry can be viewed as quantum hair and lead to a quantum corrected horizon radius and thermodynamics. |
2009.14632 | Guo-Ping Li | Guo-Ping Li, Ke-Jian He and Bing-Bing Chen | Lorentz Violation, Quantum Tunneling and Information Conservation | 11 pages;4 figures;accepted by Chinese Physics C | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, by introducing a Lorentz-invariance-violation (LIV) class of
dispersion relations (DR) suppressed by the second power $(E/E_{QG})^2$, we
have investigated the effect of LIV on the Hawking radiation of the charged
Dirac particle via tunneling from a Reissner-Nordstr\"om(RN) black hole. We
first find the effect of LIV speeds up the black hole evaporation, leaving the
induced Hawking temperature very sensitive to the changes in the energy of the
radiation particle, but at the same energy level, insensitive to the changes in
the charge of the radiation particle. This provides a phenomenological evidence
for the LIV-DR as a candidate for describing the effect of quantum gravity.
Then, when the effect of LIV is included, we find the statistical correlations
with the Planck-scale corrections between the successive emissions can leak out
the information through the radiation. And, it turns out that the black hole
radiation as tunneling is an entropy conservation process, and no information
loss occurs during the radiation, where the interpretation for the entropy of
black hole is addressed. Finally, we conclude that black hole evaporation is
still an unitary process in the context of quantum gravity.
| [
{
"created": "Mon, 28 Sep 2020 02:33:15 GMT",
"version": "v1"
}
] | 2020-10-01 | [
[
"Li",
"Guo-Ping",
""
],
[
"He",
"Ke-Jian",
""
],
[
"Chen",
"Bing-Bing",
""
]
] | In this paper, by introducing a Lorentz-invariance-violation (LIV) class of dispersion relations (DR) suppressed by the second power $(E/E_{QG})^2$, we have investigated the effect of LIV on the Hawking radiation of the charged Dirac particle via tunneling from a Reissner-Nordstr\"om(RN) black hole. We first find the effect of LIV speeds up the black hole evaporation, leaving the induced Hawking temperature very sensitive to the changes in the energy of the radiation particle, but at the same energy level, insensitive to the changes in the charge of the radiation particle. This provides a phenomenological evidence for the LIV-DR as a candidate for describing the effect of quantum gravity. Then, when the effect of LIV is included, we find the statistical correlations with the Planck-scale corrections between the successive emissions can leak out the information through the radiation. And, it turns out that the black hole radiation as tunneling is an entropy conservation process, and no information loss occurs during the radiation, where the interpretation for the entropy of black hole is addressed. Finally, we conclude that black hole evaporation is still an unitary process in the context of quantum gravity. |
1209.2110 | Lajos Di\'osi | Lajos Di\'osi | Note on Possible Emergence Time of Newtonian Gravity | 2pp, essentially revised, clarified, concretized version accepted in
PLA | Phys.Lett. A377 (2013) 1782-1783 | 10.1016/j.physleta.2013.05.021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | If gravity were an emergent phenomenon, some relativistic as well as
non-relativistic speculations claim it is, then a certain emergence time scale
tau_? would characterize it. We argue that the available experimental evidences
have poor time resolution regarding how immediate the creation of Newton field
of accelerated mass sources is. Although the concrete theoretical model of
gravity's `laziness' is missing, the concept and the scale tau_? ~ 1ms, rooted
in an extrapolation of spontaneous wave function collapse theory, might be
tested directly in reachable experiments.
| [
{
"created": "Sun, 9 Sep 2012 11:31:28 GMT",
"version": "v1"
},
{
"created": "Sat, 11 May 2013 20:50:49 GMT",
"version": "v2"
}
] | 2014-11-19 | [
[
"Diósi",
"Lajos",
""
]
] | If gravity were an emergent phenomenon, some relativistic as well as non-relativistic speculations claim it is, then a certain emergence time scale tau_? would characterize it. We argue that the available experimental evidences have poor time resolution regarding how immediate the creation of Newton field of accelerated mass sources is. Although the concrete theoretical model of gravity's `laziness' is missing, the concept and the scale tau_? ~ 1ms, rooted in an extrapolation of spontaneous wave function collapse theory, might be tested directly in reachable experiments. |
1403.7482 | Etera R. Livine | Mait\'e Dupuis, Florian Girelli, Etera R. Livine | Deformed Spinor Networks for Loop Gravity: Towards Hyperbolic Twisted
Geometries | 15 pages, 4 figures | Gen.Rel.Grav. 46 (2014) 11 | 10.1007/s10714-014-1802-3 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of a canonical quantization of general relativity, one can
deform the loop gravity phase space on a graph by replacing the T*SU(2) phase
space attached to each edge by SL(2,C) seen as a phase space. This deformation
is supposed to encode the presence of a non-zero cosmological constant. Here we
show how to parametrize this phase space in terms of spinor variables, thus
obtaining deformed spinor networks for loop gravity, with a deformed action of
the gauge group SU(2) at the vertices. These are to be formally interpreted as
the generalization of loop gravity twisted geometries to a hyperbolic
curvature.
| [
{
"created": "Fri, 28 Mar 2014 18:49:12 GMT",
"version": "v1"
}
] | 2016-03-08 | [
[
"Dupuis",
"Maité",
""
],
[
"Girelli",
"Florian",
""
],
[
"Livine",
"Etera R.",
""
]
] | In the context of a canonical quantization of general relativity, one can deform the loop gravity phase space on a graph by replacing the T*SU(2) phase space attached to each edge by SL(2,C) seen as a phase space. This deformation is supposed to encode the presence of a non-zero cosmological constant. Here we show how to parametrize this phase space in terms of spinor variables, thus obtaining deformed spinor networks for loop gravity, with a deformed action of the gauge group SU(2) at the vertices. These are to be formally interpreted as the generalization of loop gravity twisted geometries to a hyperbolic curvature. |
gr-qc/0310106 | Sanjay Sarwe | Sanjay B. Sarwe and R. V. Saraykar | Stability of Naked Singularity arising in gravitational collapse of Type
I matter fields | 16 pages, no figure, Latex, submitted to Pramana | Pramana65:17-33,2005 | 10.1007/BF02704372 | null | gr-qc | null | Considering gravitational collapse of Type I matter fields, we prove that,
given an arbitrary $C^{2}$- mass function $\textit{M}(r,v)$ and a $C^{1}$-
function $h(r,v)$ (through the corresponding $C^{1}$- metric function
$\nu(t,r)$), there exist infinitely many choices of energy distribution
function $b(r)$ such that the `true' initial data ($\textit{M},h(r,v)$) leads
the collapse to the formation of naked singularity. We further prove that the
occurrence of such a naked singularity is stable with respect to small changes
in the initial data. We remark that though the initial data leading to both
black hole and naked singularity form a "big" subset of the true initial data
set, their occurrence is not generic. The terms `stability' and `genericity'
are appropriately defined following the theory of dynamical systems. The
particular case of radial pressure $p_{r}(r)$ has been illustrated in details
to get clear picture of how naked singularity is formed and how, it is stable
with respect to initial data.
| [
{
"created": "Wed, 22 Oct 2003 19:22:18 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Oct 2004 17:11:19 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Sarwe",
"Sanjay B.",
""
],
[
"Saraykar",
"R. V.",
""
]
] | Considering gravitational collapse of Type I matter fields, we prove that, given an arbitrary $C^{2}$- mass function $\textit{M}(r,v)$ and a $C^{1}$- function $h(r,v)$ (through the corresponding $C^{1}$- metric function $\nu(t,r)$), there exist infinitely many choices of energy distribution function $b(r)$ such that the `true' initial data ($\textit{M},h(r,v)$) leads the collapse to the formation of naked singularity. We further prove that the occurrence of such a naked singularity is stable with respect to small changes in the initial data. We remark that though the initial data leading to both black hole and naked singularity form a "big" subset of the true initial data set, their occurrence is not generic. The terms `stability' and `genericity' are appropriately defined following the theory of dynamical systems. The particular case of radial pressure $p_{r}(r)$ has been illustrated in details to get clear picture of how naked singularity is formed and how, it is stable with respect to initial data. |
0909.5688 | Benjamin Bahr | B. Bahr, B. Dittrich | Breaking and restoring of diffeomorphism symmetry in discrete gravity | to appear in the Proceedings of the XXV Max Born Symposium "The
Planck Scale", Wroclaw, 29 June - 3 July, 2009 | null | 10.1063/1.3284371 | null | gr-qc hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the fate of diffeomorphism symmetry in discrete gravity.
Diffeomorphism symmetry is typically broken by the discretization. This has
repercussions for the observable content and the canonical formulation of the
theory. It might however be possible to construct discrete actions, so--called
perfect actions, with exact symmetries and we will review first steps towards
this end.
| [
{
"created": "Wed, 30 Sep 2009 18:21:24 GMT",
"version": "v1"
}
] | 2015-05-14 | [
[
"Bahr",
"B.",
""
],
[
"Dittrich",
"B.",
""
]
] | We discuss the fate of diffeomorphism symmetry in discrete gravity. Diffeomorphism symmetry is typically broken by the discretization. This has repercussions for the observable content and the canonical formulation of the theory. It might however be possible to construct discrete actions, so--called perfect actions, with exact symmetries and we will review first steps towards this end. |
gr-qc/9211014 | Peter Peldan | Peter Peldan | Unification of Gravity and Yang-Mills Theory in (2+1)-Dimensions | 22pages | Nucl.Phys. B395 (1993) 239-262 | 10.1016/0550-3213(93)90216-C | ITP 92-49 | gr-qc hep-th | null | A gauge and diffeomorphism invariant theory in (2+1)-dimensions is presented
in both first and second order Lagrangian form as well as in a Hamiltonian
form. For gauge group $SO(1,2)$, the theory is shown to describe ordinary
Einstein gravity with a cosmological constant. With gauge group
$G^{tot}=SO(1,2)\otimes G^{YM}$, it is shown that the equations of motion for
the $G^{YM}$ fields are the Yang-Mills equations. It is also shown that for
weak $G^{YM}$ Yang-Mills fields, this theory agrees with the conventional
Einstein-Yang-Mills theory to lowest order in Yang-Mills fields. Explicit
static and rotation symmetric solutions to the Einstein-Maxwell theory are
studied both for the conventional coupling and for this unified theory. In the
electric solution to the unified theory, point charges are not allowed, the
charges must have spatial extensions.
| [
{
"created": "Tue, 10 Nov 1992 12:48:16 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Peldan",
"Peter",
""
]
] | A gauge and diffeomorphism invariant theory in (2+1)-dimensions is presented in both first and second order Lagrangian form as well as in a Hamiltonian form. For gauge group $SO(1,2)$, the theory is shown to describe ordinary Einstein gravity with a cosmological constant. With gauge group $G^{tot}=SO(1,2)\otimes G^{YM}$, it is shown that the equations of motion for the $G^{YM}$ fields are the Yang-Mills equations. It is also shown that for weak $G^{YM}$ Yang-Mills fields, this theory agrees with the conventional Einstein-Yang-Mills theory to lowest order in Yang-Mills fields. Explicit static and rotation symmetric solutions to the Einstein-Maxwell theory are studied both for the conventional coupling and for this unified theory. In the electric solution to the unified theory, point charges are not allowed, the charges must have spatial extensions. |
0806.0669 | Martin Reiris | Martin Reiris | On the asymptotic spectrum of the reduced volume in cosmological
solutions of the Einstein equations | 25 pages, 2 figures | null | 10.1007/s10714-008-0693-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Say S is a compact three-manifold with non-positive Yamabe invariant. We
prove that in any long time constant mean curvature Einstein flow over S,
having bounded C^{\alpha} space-time curvature at the cosmological scale, the
reduced volume (-k/3)^{3}Vol(g(k)) (g(k) is the evolving spatial three-metric
and k the mean curvature) decays monotonically towards the volume value of the
geometrization in which the cosmologically normalized flow decays. In more
basic terms, under the given assumptions, there is volume collapse in the
regions where the injectivity radius collapses (i.e. tends to zero) in the long
time. We conjecture that under the curvature assumption above the Thurston
geometrization is the unique global attractor. We validate it in some special
cases.
| [
{
"created": "Wed, 4 Jun 2008 01:03:52 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Reiris",
"Martin",
""
]
] | Say S is a compact three-manifold with non-positive Yamabe invariant. We prove that in any long time constant mean curvature Einstein flow over S, having bounded C^{\alpha} space-time curvature at the cosmological scale, the reduced volume (-k/3)^{3}Vol(g(k)) (g(k) is the evolving spatial three-metric and k the mean curvature) decays monotonically towards the volume value of the geometrization in which the cosmologically normalized flow decays. In more basic terms, under the given assumptions, there is volume collapse in the regions where the injectivity radius collapses (i.e. tends to zero) in the long time. We conjecture that under the curvature assumption above the Thurston geometrization is the unique global attractor. We validate it in some special cases. |
2110.04879 | Roberto Ivan Cabrera Munguia Dr. | I. Cabrera-Munguia | Metric for two unequal extreme Kerr-Newman black holes | 9 pages | Physics Letters B 826 (2022) 136895 | 10.1016/j.physletb.2022.136895 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the present paper, within the framework of stationary axisymmetric
spacetimes, binary systems composed of two unequal co- and counter-rotating
extreme Kerr-Newman black holes separated by a massless strut are reported. The
metric describing both configurations is introduced in a closed analytical form
in terms of five arbitrary parameters: the masses $M_{i}$, electric charges
$Q_{i}$, and a coordinate distance $R$. We obtain novel results from these
configurations; in particular, those related to the merging process.
| [
{
"created": "Sun, 10 Oct 2021 19:00:23 GMT",
"version": "v1"
}
] | 2022-02-01 | [
[
"Cabrera-Munguia",
"I.",
""
]
] | In the present paper, within the framework of stationary axisymmetric spacetimes, binary systems composed of two unequal co- and counter-rotating extreme Kerr-Newman black holes separated by a massless strut are reported. The metric describing both configurations is introduced in a closed analytical form in terms of five arbitrary parameters: the masses $M_{i}$, electric charges $Q_{i}$, and a coordinate distance $R$. We obtain novel results from these configurations; in particular, those related to the merging process. |
gr-qc/0204037 | Walter Simon | Walter Simon | Criteria for (in)finite extent of static perfect fluids | 17 pages, Latex | Lect.Notes Phys. 604 (2002) 223-238 | null | UWThPh-2000-56 | gr-qc | null | In Newton's and in Einstein's theory we give criteria on the equation of
state of a barotropic perfect fluid which guarantee that the corresponding
one-parameter family of static, spherically symmetric solutions has finite
extent. These criteria are closely related to ones which are known to ensure
finite or infinite extent of the fluid region if the assumption of spherical
symmetry is replaced by certain asymptotic falloff conditions on the solutions.
We improve this result by relaxing the asymptotic asumptions. Our conditions on
the equation of state are also related to (but less restrictive than) ones
under which it has been shown in Relativity that static, asymptotically flat
fluid solutions are spherically symmetric. We present all these results in a
unified way.
| [
{
"created": "Tue, 9 Apr 2002 18:07:16 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Simon",
"Walter",
""
]
] | In Newton's and in Einstein's theory we give criteria on the equation of state of a barotropic perfect fluid which guarantee that the corresponding one-parameter family of static, spherically symmetric solutions has finite extent. These criteria are closely related to ones which are known to ensure finite or infinite extent of the fluid region if the assumption of spherical symmetry is replaced by certain asymptotic falloff conditions on the solutions. We improve this result by relaxing the asymptotic asumptions. Our conditions on the equation of state are also related to (but less restrictive than) ones under which it has been shown in Relativity that static, asymptotically flat fluid solutions are spherically symmetric. We present all these results in a unified way. |
2208.10986 | Luis Herrera | L. Herrera | Non-static hyperbolicallly symmetric fluids | 12 pages revtex 4. Based on the conferences delivered at Gravitex
2021 Conference, Durban, South Africa, and 4th PU International Conference of
Gravitation and Cosmology, Lahore, Pakistan, in August 2021 and November 2021
respectively. To appear in Int. J. Mod. Phys. D. arXiv admin note: text
overlap with arXiv:2109.07758, arXiv:2110.01888 | Int. J. Mod. Phys. D 31, 2240001, (2022) | 10.1142/S0218271822400016 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We present the general properties of dynamic dissipative fluid distribution
endowed with hyperbolical symmetry. All the equations required for its analysis
are exhibited and used to contrast the behavior of the system with the
spherically symmetric case. Several exact solutions are exhibited and
prospective applications to astrophysical and cosmological scenarios are
discussed.
| [
{
"created": "Tue, 23 Aug 2022 14:08:38 GMT",
"version": "v1"
}
] | 2022-10-05 | [
[
"Herrera",
"L.",
""
]
] | We present the general properties of dynamic dissipative fluid distribution endowed with hyperbolical symmetry. All the equations required for its analysis are exhibited and used to contrast the behavior of the system with the spherically symmetric case. Several exact solutions are exhibited and prospective applications to astrophysical and cosmological scenarios are discussed. |
1207.1086 | Daniel Guariento | Daniel C. Guariento, Michele Fontanini, Alan M. da Silva, Elcio
Abdalla | Realistic fluids as source for dynamically accreting black holes in a
cosmological background | 5 pages, 2 figures. Updated references and minor changes to match the
version accepted for publishing in PRD | Phys. Rev. D 86, 124020 (2012) | 10.1103/PhysRevD.86.124020 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that a single imperfect fluid can be used as a source to obtain the
generalized McVittie metric as an exact solution to Einstein's equations. The
mass parameter in this metric varies with time thanks to a mechanism based on
the presence of a temperature gradient. This fully dynamical solution is
interpreted as an accreting black hole in an expanding universe if the metric
asymptotes to Schwarzschild-de Sitter at temporal infinity. We present a simple
but instructive example for the mass function and briefly discuss the structure
of the apparent horizons and the past singularity.
| [
{
"created": "Wed, 4 Jul 2012 19:17:12 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Nov 2012 18:40:40 GMT",
"version": "v2"
}
] | 2012-12-07 | [
[
"Guariento",
"Daniel C.",
""
],
[
"Fontanini",
"Michele",
""
],
[
"da Silva",
"Alan M.",
""
],
[
"Abdalla",
"Elcio",
""
]
] | We show that a single imperfect fluid can be used as a source to obtain the generalized McVittie metric as an exact solution to Einstein's equations. The mass parameter in this metric varies with time thanks to a mechanism based on the presence of a temperature gradient. This fully dynamical solution is interpreted as an accreting black hole in an expanding universe if the metric asymptotes to Schwarzschild-de Sitter at temporal infinity. We present a simple but instructive example for the mass function and briefly discuss the structure of the apparent horizons and the past singularity. |
gr-qc/9604055 | Jolien Creighton | K. C. K. Chan, J. D. E. Creighton, and R. B. Mann | Conserved masses in GHS Einstein and string black holes | 16 pages REVTeX with packages amsfonts and amssymb | Phys.Rev. D54 (1996) 3892-3899 | 10.1103/PhysRevD.54.3892 | WATPHYS TH-96/06 | gr-qc hep-th | null | We analyze the relationship between quasilocal masses calculated for
solutions of conformally related theories. We show that the ADM mass of a
static, spherically symmetric solution is conformally invariant (up to a
constant factor) only if the background action functional is conformally
invariant. Thus, the requirement of conformal invariance places restrictions on
the choice of reference spacetimes. We calculate the mass of the black hole
solutions obtained by Garfinkle, Horowitz, and Strominger (GHS) for both the
string and the Einstein metrics. In addition, the quasilocal thermodynamic
quantities in the string metrics are computed and discussed.
| [
{
"created": "Mon, 29 Apr 1996 18:55:29 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Chan",
"K. C. K.",
""
],
[
"Creighton",
"J. D. E.",
""
],
[
"Mann",
"R. B.",
""
]
] | We analyze the relationship between quasilocal masses calculated for solutions of conformally related theories. We show that the ADM mass of a static, spherically symmetric solution is conformally invariant (up to a constant factor) only if the background action functional is conformally invariant. Thus, the requirement of conformal invariance places restrictions on the choice of reference spacetimes. We calculate the mass of the black hole solutions obtained by Garfinkle, Horowitz, and Strominger (GHS) for both the string and the Einstein metrics. In addition, the quasilocal thermodynamic quantities in the string metrics are computed and discussed. |
2006.08583 | Fabrizio Di Giovanni | Fabrizio Di Giovanni, Saeed Fakhry, Nicolas Sanchis-Gual, Juan Carlos
Degollado, Jos\'e A. Font | Dynamical formation and stability of fermion-boson stars | 13 pages, 16 figures | Phys. Rev. D 102, 084063 (2020) | 10.1103/PhysRevD.102.084063 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitationally bound structures composed by fermions and scalar particles
known as fermion-boson stars are regular and static configurations obtained by
solving the coupled Einstein-Klein-Gordon-Euler (EKGE) system. In this work, we
discuss one possible scenario through which these fermion-boson stars may form
by solving numerically the EKGE system under the simplifying assumption of
spherical symmetry. Our initial configurations assume an already existing
neutron star surrounded by an accreting cloud of a massive and complex scalar
field. The results of our simulations show that once part of the initial scalar
field is expelled via gravitational cooling the system gradually oscillates
around an equilibrium configuration that is asymptotically consistent with a
static solution of the system. The formation of fermion-boson stars for large
positive values of the coupling constant in the self-interaction term of the
scalar-field potential reveal the presence of a node in the scalar field. This
suggests that a fermionic core may help stabilize configurations with nodes in
the bosonic sector, as happens for purely boson stars in which the ground state
and the first excited state coexist.
| [
{
"created": "Mon, 15 Jun 2020 17:49:17 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Jun 2020 07:31:56 GMT",
"version": "v2"
}
] | 2020-11-04 | [
[
"Di Giovanni",
"Fabrizio",
""
],
[
"Fakhry",
"Saeed",
""
],
[
"Sanchis-Gual",
"Nicolas",
""
],
[
"Degollado",
"Juan Carlos",
""
],
[
"Font",
"José A.",
""
]
] | Gravitationally bound structures composed by fermions and scalar particles known as fermion-boson stars are regular and static configurations obtained by solving the coupled Einstein-Klein-Gordon-Euler (EKGE) system. In this work, we discuss one possible scenario through which these fermion-boson stars may form by solving numerically the EKGE system under the simplifying assumption of spherical symmetry. Our initial configurations assume an already existing neutron star surrounded by an accreting cloud of a massive and complex scalar field. The results of our simulations show that once part of the initial scalar field is expelled via gravitational cooling the system gradually oscillates around an equilibrium configuration that is asymptotically consistent with a static solution of the system. The formation of fermion-boson stars for large positive values of the coupling constant in the self-interaction term of the scalar-field potential reveal the presence of a node in the scalar field. This suggests that a fermionic core may help stabilize configurations with nodes in the bosonic sector, as happens for purely boson stars in which the ground state and the first excited state coexist. |
1811.00390 | Saulo Pereira H | S.H. Pereira, M.E.S. Alves and T.M. Guimar\~aes | An unified cosmological evolution driven by a mass dimension one
fermionic field | 22 pages, 5 figures | Eur. Phys. J. C (2019) 79:543 | 10.1140/epjc/s10052-019-7036-5 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An unified cosmological model for an Universe filled with a mass dimension
one (MDO) fermionic field plus the standard matter fields is considered. After
a primordial quantum fluctuation the field slowly rolls down to the bottom of a
symmetry breaking potential, driving the Universe to an inflationary regime
that increases the scale factor for about 71 e-folds. After the end of
inflation, the field starts to oscillate and can transfer its energy to the
standard model particles through a reheating mechanism. Such a process is
briefly discussed in terms of the admissible couplings of the MDO field with
the electromagnetic and Higgs fields. We show that even if the field loses all
its kinetic energy during reheating, it can evolve as dark matter due a
gravitational coupling (of spinorial origin) with baryonic matter. Since the
field acquires a constant value at the bottom of the potential, a non-null,
although tiny, mass term acts as a dark energy component nowadays. Therefore,
we conclude that MDO fermionic field is a good candidate to drive the whole
evolution of the Universe, in such a way that the inflationary field, dark
matter and dark energy are described by different manifestations of a single
field.
| [
{
"created": "Mon, 29 Oct 2018 19:52:39 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Jun 2019 20:14:09 GMT",
"version": "v2"
}
] | 2019-07-02 | [
[
"Pereira",
"S. H.",
""
],
[
"Alves",
"M. E. S.",
""
],
[
"Guimarães",
"T. M.",
""
]
] | An unified cosmological model for an Universe filled with a mass dimension one (MDO) fermionic field plus the standard matter fields is considered. After a primordial quantum fluctuation the field slowly rolls down to the bottom of a symmetry breaking potential, driving the Universe to an inflationary regime that increases the scale factor for about 71 e-folds. After the end of inflation, the field starts to oscillate and can transfer its energy to the standard model particles through a reheating mechanism. Such a process is briefly discussed in terms of the admissible couplings of the MDO field with the electromagnetic and Higgs fields. We show that even if the field loses all its kinetic energy during reheating, it can evolve as dark matter due a gravitational coupling (of spinorial origin) with baryonic matter. Since the field acquires a constant value at the bottom of the potential, a non-null, although tiny, mass term acts as a dark energy component nowadays. Therefore, we conclude that MDO fermionic field is a good candidate to drive the whole evolution of the Universe, in such a way that the inflationary field, dark matter and dark energy are described by different manifestations of a single field. |
gr-qc/9806009 | Roland Steinbauer | Michael Kunzinger, Roland Steinbauer | A rigorous solution concept for geodesic and geodesic deviation
equations in impulsive gravitational waves | RevTeX, 9 pages, final version (minor corrections, references added) | J.Math.Phys. 40 (1999) 1479-1489 | 10.1063/1.532816 | UWThPh-1998-25 | gr-qc math-ph math.MP | null | The geodesic as well as the geodesic deviation equation for impulsive
gravitational waves involve highly singular products of distributions
$(\theta\de$, $\theta^2\de$, $\de^2$). A solution concept for these equations
based on embedding the distributional metric into the Colombeau algebra of
generalized functions is presented. Using a universal regularization procedure
we prove existence and uniqueness results and calculate the distributional
limits of these solutions explicitly. The obtained limits are regularization
independent and display the physically expected behavior.
| [
{
"created": "Wed, 3 Jun 1998 08:31:39 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Apr 1999 13:34:02 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Kunzinger",
"Michael",
""
],
[
"Steinbauer",
"Roland",
""
]
] | The geodesic as well as the geodesic deviation equation for impulsive gravitational waves involve highly singular products of distributions $(\theta\de$, $\theta^2\de$, $\de^2$). A solution concept for these equations based on embedding the distributional metric into the Colombeau algebra of generalized functions is presented. Using a universal regularization procedure we prove existence and uniqueness results and calculate the distributional limits of these solutions explicitly. The obtained limits are regularization independent and display the physically expected behavior. |
1201.2725 | T.G Zlosnik | H.F. Westman, T.G. Zlosnik | Gravitation and spatial conformal invariance | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well-known that General Relativity with positive cosmological constant
can be formulated as a gauge theory with a broken SO(1,4) symmetry. This
symmetry is broken by the presence of an internal space-like vector $V^A$,
$A=0,...,4$, with SO(1,3) as a residual invariance group. Attempts to ascribe
dynamics to the field $V^{A}$ have been made in the literature but so far with
limited success. Regardless of this issue we can take the view that $V^A$ might
actually vary across spacetime and in particular become null or time-like. In
this paper we will study the case where $V^A$ is null. This is shown to
correspond to a Lorentz violating modified theory of gravity. Using the
isomorphism between the de Sitter group and the spatial conformal group,
$SO(1,4)\simeq C(3)$, we show that the resulting gravitational field equations
are invariant under all the symmetries, but spatial translations, of the
conformal group C(3).
| [
{
"created": "Fri, 13 Jan 2012 01:49:21 GMT",
"version": "v1"
}
] | 2012-01-16 | [
[
"Westman",
"H. F.",
""
],
[
"Zlosnik",
"T. G.",
""
]
] | It is well-known that General Relativity with positive cosmological constant can be formulated as a gauge theory with a broken SO(1,4) symmetry. This symmetry is broken by the presence of an internal space-like vector $V^A$, $A=0,...,4$, with SO(1,3) as a residual invariance group. Attempts to ascribe dynamics to the field $V^{A}$ have been made in the literature but so far with limited success. Regardless of this issue we can take the view that $V^A$ might actually vary across spacetime and in particular become null or time-like. In this paper we will study the case where $V^A$ is null. This is shown to correspond to a Lorentz violating modified theory of gravity. Using the isomorphism between the de Sitter group and the spatial conformal group, $SO(1,4)\simeq C(3)$, we show that the resulting gravitational field equations are invariant under all the symmetries, but spatial translations, of the conformal group C(3). |
gr-qc/9706069 | Abhay Ashtekar | Abhay Ashtekar, Troy A. Schilling | Geometrical Formulation of Quantum Mechanics | 41 pages, ReVTeX | null | null | CGPG 97/6-1 | gr-qc hep-th quant-ph | null | States of a quantum mechanical system are represented by rays in a complex
Hilbert space. The space of rays has, naturally, the structure of a K\"ahler
manifold. This leads to a geometrical formulation of the postulates of quantum
mechanics which, although equivalent to the standard algebraic formulation, has
a very different appearance. In particular, states are now represented by
points of a symplectic manifold (which happens to have, in addition, a
compatible Riemannian metric), observables are represented by certain
real-valued functions on this space and the Schr\"odinger evolution is captured
by the symplectic flow generated by a Hamiltonian function. There is thus a
remarkable similarity with the standard symplectic formulation of classical
mechanics. Features---such as uncertainties and state vector reductions---which
are specific to quantum mechanics can also be formulated geometrically but now
refer to the Riemannian metric---a structure which is absent in classical
mechanics. The geometrical formulation sheds considerable light on a number of
issues such as the second quantization procedure, the role of coherent states
in semi-classical considerations and the WKB approximation. More importantly,
it suggests generalizations of quantum mechanics. The simplest among these are
equivalent to the dynamical generalizations that have appeared in the
literature. The geometrical reformulation provides a unified framework to
discuss these and to correct a misconception. Finally, it also suggests
directions in which more radical generalizations may be found.
| [
{
"created": "Mon, 23 Jun 1997 15:55:02 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Schilling",
"Troy A.",
""
]
] | States of a quantum mechanical system are represented by rays in a complex Hilbert space. The space of rays has, naturally, the structure of a K\"ahler manifold. This leads to a geometrical formulation of the postulates of quantum mechanics which, although equivalent to the standard algebraic formulation, has a very different appearance. In particular, states are now represented by points of a symplectic manifold (which happens to have, in addition, a compatible Riemannian metric), observables are represented by certain real-valued functions on this space and the Schr\"odinger evolution is captured by the symplectic flow generated by a Hamiltonian function. There is thus a remarkable similarity with the standard symplectic formulation of classical mechanics. Features---such as uncertainties and state vector reductions---which are specific to quantum mechanics can also be formulated geometrically but now refer to the Riemannian metric---a structure which is absent in classical mechanics. The geometrical formulation sheds considerable light on a number of issues such as the second quantization procedure, the role of coherent states in semi-classical considerations and the WKB approximation. More importantly, it suggests generalizations of quantum mechanics. The simplest among these are equivalent to the dynamical generalizations that have appeared in the literature. The geometrical reformulation provides a unified framework to discuss these and to correct a misconception. Finally, it also suggests directions in which more radical generalizations may be found. |
2301.06879 | Bayram Tekin | Zeynep Tugce Ozkarsligil, Bayram Tekin | Mass formulas for individual black holes in merging binaries | 9 pages, matches the published version | Eur. J. Phys. 45 025601 (2024) | 10.1088/1361-6404/ad1531 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give formulas for individual black hole masses in a merger, by using
Newtonian physics, in terms of the three measured quantities in the detector:
the initial wave frequency $f_1$, the maximum detected frequency (chirp
frequency) $f_2$, and the time elapse $\tau$ between these two frequencies.
Newtonian gravity provides an excellent pedagogical tool to understand the
basic features of gravitational wave observations, but it must be augmented
with the assumption of gravitational radiation from General Relativity for
accelerating masses as there is no gravitational wave in Newtonian gravity. The
simplest approach would be to consider a binary system of two non-spinning
masses (two black holes) circling their common center of mass. All the
computations can be done within Newtonian physics, but the General Relativistic
formula for the power carried by gravitational waves is required in this
scheme. It turns out there is a subtle point: for the consistency of this
simple, yet pedagogical computation, taking the lowest order power formula from
General Relativity leads to complex individual masses. Here we remedy this
problem and {suggest} a way to write down an average power formula coming from
perturbative General Relativity.
| [
{
"created": "Tue, 17 Jan 2023 13:37:15 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Mar 2023 11:31:53 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Jan 2024 14:22:54 GMT",
"version": "v3"
}
] | 2024-01-17 | [
[
"Ozkarsligil",
"Zeynep Tugce",
""
],
[
"Tekin",
"Bayram",
""
]
] | We give formulas for individual black hole masses in a merger, by using Newtonian physics, in terms of the three measured quantities in the detector: the initial wave frequency $f_1$, the maximum detected frequency (chirp frequency) $f_2$, and the time elapse $\tau$ between these two frequencies. Newtonian gravity provides an excellent pedagogical tool to understand the basic features of gravitational wave observations, but it must be augmented with the assumption of gravitational radiation from General Relativity for accelerating masses as there is no gravitational wave in Newtonian gravity. The simplest approach would be to consider a binary system of two non-spinning masses (two black holes) circling their common center of mass. All the computations can be done within Newtonian physics, but the General Relativistic formula for the power carried by gravitational waves is required in this scheme. It turns out there is a subtle point: for the consistency of this simple, yet pedagogical computation, taking the lowest order power formula from General Relativity leads to complex individual masses. Here we remedy this problem and {suggest} a way to write down an average power formula coming from perturbative General Relativity. |
gr-qc/0301005 | Georgii Alekseev | G.A.Alekseev | Characteristic initial value problems for integrable hyperbolic
reductions of Einstein's equations | 8 pages, RevTeX 4; as submitted to the Proceedings of the workshop
"Nonlinear Physics: Theory and Experiment. II" (Gallipili (Lecce), Italy,
27.06.2002 - 06.07.2002), World Scientific, Singapore | null | 10.1142/9789812704467_0003 | null | gr-qc hep-th nlin.SI | null | A unified general approach is presented for construction of solutions of the
characteristic initial value problems for various integrable hyperbolic
reductions of Einstein's equations for space-times with two commuting
isometries in General Relativity and in some string theory induced gravity
models. In all cases the associated linear systems of similar structures are
used, and their fundamental solutions admit an alternative representations by
two ``scattering'' matrices of a simple analytical structures on the spectral
plane. The condition of equivalence of these representations leads to the
linear ``integral evolution equations'' whose scalar kernels and right hand
sides are determined completely by the initial data for the fields specified on
the two initial characteristics. If the initial data for the fields are given,
all field components of the corresponding solution can be expressed in
quadratures in terms of a unique solution of these quasi - Fredholm integral
evolution equations.
| [
{
"created": "Thu, 2 Jan 2003 23:32:35 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Alekseev",
"G. A.",
""
]
] | A unified general approach is presented for construction of solutions of the characteristic initial value problems for various integrable hyperbolic reductions of Einstein's equations for space-times with two commuting isometries in General Relativity and in some string theory induced gravity models. In all cases the associated linear systems of similar structures are used, and their fundamental solutions admit an alternative representations by two ``scattering'' matrices of a simple analytical structures on the spectral plane. The condition of equivalence of these representations leads to the linear ``integral evolution equations'' whose scalar kernels and right hand sides are determined completely by the initial data for the fields specified on the two initial characteristics. If the initial data for the fields are given, all field components of the corresponding solution can be expressed in quadratures in terms of a unique solution of these quasi - Fredholm integral evolution equations. |
1903.10450 | Frans Klinkhamer | F.R. Klinkhamer | Regularized big bang singularity | 16 pages, 1 figure, v6: published version | Phys. Rev. D 100, 023536 (2019) | 10.1103/PhysRevD.100.023536 | KA-TP-04-2019 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following up on earlier work on the regularization of the singular
Schwarzschild solution, we now apply the same procedure to the singular
Friedmann solution. Specifically, we are able to remove the divergences of the
big bang singularity, at the price of introducing a 3-dimensional spacetime
defect with a vanishing determinant of the metric. This particular
regularization also suggests the existence of a "pre-big-bang" phase.
| [
{
"created": "Mon, 25 Mar 2019 16:35:26 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Mar 2019 17:19:19 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Apr 2019 17:38:00 GMT",
"version": "v3"
},
{
"created": "Tue, 7 May 2019 14:31:31 GMT",
"version": "v4"
},
{
"cre... | 2019-07-31 | [
[
"Klinkhamer",
"F. R.",
""
]
] | Following up on earlier work on the regularization of the singular Schwarzschild solution, we now apply the same procedure to the singular Friedmann solution. Specifically, we are able to remove the divergences of the big bang singularity, at the price of introducing a 3-dimensional spacetime defect with a vanishing determinant of the metric. This particular regularization also suggests the existence of a "pre-big-bang" phase. |
1402.5947 | Lorenzo Iorio | Lorenzo Iorio | Post-Newtonian direct and mixed orbital effects due to the oblateness of
the central body | LaTex2e, 60 pages, 93 references, no figures, 2 tables. Sign error
corrected in Eq. (98) | Int. J. Mod. Phys. D24 (2015) 1550067 | 10.1142/S0218271815500674 | null | gr-qc astro-ph.EP physics.geo-ph physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The orbital dynamics of a test particle moving in the non-spherically
symmetric field of a rotating oblate primary is impacted also by certain
indirect, mixed effects arising from the interplay of the different Newtonian
and post-Newtonian accelerations which induce known direct perturbations. We
systematically calculate the indirect gravitoelectromagnetic shifts per orbit
of the Keplerian orbital elements of the test particle arising from the
crossing among the first even zonal harmonic $J_2$ of the central body and the
post-Newtonian static and stationary components of its gravitational field. We
also work out the Newtonian shifts per orbit of order $J_2^2$, and the direct
post-Newtonian gravitoelectric effects of order $J_2 c^{-2}$ arising from the
equations of motion. In the case of both the indirect and direct
gravitoelectric $J_2 c^{-2}$ shifts, our calculation holds for an arbitrary
orientation of the symmetry axis of the central body. We yield numerical
estimates of their relative magnitudes for systems ranging from Earth
artificial satellites to stars orbiting supermassive black holes.
| [
{
"created": "Sat, 22 Feb 2014 15:20:18 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Mar 2014 15:33:10 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Aug 2014 14:15:03 GMT",
"version": "v3"
},
{
"created": "Mon, 23 Mar 2015 14:07:57 GMT",
"version": "v4"
},
{
"cr... | 2017-10-06 | [
[
"Iorio",
"Lorenzo",
""
]
] | The orbital dynamics of a test particle moving in the non-spherically symmetric field of a rotating oblate primary is impacted also by certain indirect, mixed effects arising from the interplay of the different Newtonian and post-Newtonian accelerations which induce known direct perturbations. We systematically calculate the indirect gravitoelectromagnetic shifts per orbit of the Keplerian orbital elements of the test particle arising from the crossing among the first even zonal harmonic $J_2$ of the central body and the post-Newtonian static and stationary components of its gravitational field. We also work out the Newtonian shifts per orbit of order $J_2^2$, and the direct post-Newtonian gravitoelectric effects of order $J_2 c^{-2}$ arising from the equations of motion. In the case of both the indirect and direct gravitoelectric $J_2 c^{-2}$ shifts, our calculation holds for an arbitrary orientation of the symmetry axis of the central body. We yield numerical estimates of their relative magnitudes for systems ranging from Earth artificial satellites to stars orbiting supermassive black holes. |
2305.10535 | Nawsad Ali | Nawsad Ali | Bulk Viscous Bianchi Type-V Cosmological Model with Time Function G and
Lambda | 18 pages, 6 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by-sa/4.0/ | In this paper we are to study homogeneous and anisotropic Bianchi type-V
universe in presence of bulk viscous fluid source of matter with time function
gravitational constant G and cosmological term lambda. The viscosity
coefficient is regarded as power function of matter density in the first case
whereas in other case it is considered as proportional to the scale of
expansion. Physical realistic solutions of the field equations are obtained by
using a fractional form of Hubble's parameter, which leads an early
deceleration and late time acceleration of the universe. Certain physical and
geometrical behaviors of the model are also studied.
| [
{
"created": "Wed, 19 Apr 2023 23:33:28 GMT",
"version": "v1"
}
] | 2023-05-19 | [
[
"Ali",
"Nawsad",
""
]
] | In this paper we are to study homogeneous and anisotropic Bianchi type-V universe in presence of bulk viscous fluid source of matter with time function gravitational constant G and cosmological term lambda. The viscosity coefficient is regarded as power function of matter density in the first case whereas in other case it is considered as proportional to the scale of expansion. Physical realistic solutions of the field equations are obtained by using a fractional form of Hubble's parameter, which leads an early deceleration and late time acceleration of the universe. Certain physical and geometrical behaviors of the model are also studied. |
1906.02921 | Subhajit Barman | Subhajit Barman and Gopal Sardar | Perturbative approach to the entanglement entropy and the area law in
Fock and polymer quantization | 12 pages, 7 figures, revtex4 | Phys. Rev. D 99, 125015 (2019) | 10.1103/PhysRevD.99.125015 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The area dependence of entanglement entropy of a free scalar field is often
understood in terms of coupled harmonic oscillators. In Schrodinger
quantization, the Gaussian nature of ground state wave-function for these
oscillators is sufficient to provide the exact form of the reduced density
matrix and its eigenvalues, thus giving the entanglement entropy. However, in
polymer quantization, the ground state is not Gaussian and the formalism which
can provide the exact analytical form of the reduced density matrix is not yet
known. In order to address this issue, here we treat the interaction between
two coupled harmonic oscillators in the perturbative approach and evaluate the
entanglement entropy in Schrodinger and polymer quantization. In contrary to
Schrodinger quantization, we show that in high frequency regime the
entanglement entropy decreases for polymer quantization keeping the ratio of
coupling strength to the square of individual oscillator frequency fixed.
Furthermore, for a free scalar field, we validate the area dependence of
entanglement entropy in Fock quantization and demonstrate that polymer
quantization produces a similar area law.
| [
{
"created": "Fri, 7 Jun 2019 06:31:17 GMT",
"version": "v1"
}
] | 2019-07-03 | [
[
"Barman",
"Subhajit",
""
],
[
"Sardar",
"Gopal",
""
]
] | The area dependence of entanglement entropy of a free scalar field is often understood in terms of coupled harmonic oscillators. In Schrodinger quantization, the Gaussian nature of ground state wave-function for these oscillators is sufficient to provide the exact form of the reduced density matrix and its eigenvalues, thus giving the entanglement entropy. However, in polymer quantization, the ground state is not Gaussian and the formalism which can provide the exact analytical form of the reduced density matrix is not yet known. In order to address this issue, here we treat the interaction between two coupled harmonic oscillators in the perturbative approach and evaluate the entanglement entropy in Schrodinger and polymer quantization. In contrary to Schrodinger quantization, we show that in high frequency regime the entanglement entropy decreases for polymer quantization keeping the ratio of coupling strength to the square of individual oscillator frequency fixed. Furthermore, for a free scalar field, we validate the area dependence of entanglement entropy in Fock quantization and demonstrate that polymer quantization produces a similar area law. |
gr-qc/9908049 | Hans-Juergen Schmidt | V. Dzhunushaliev, H.-J. Schmidt | New vacuum solutions of conformal Weyl gravity | 15 pages, LaTeX, no figures, submitted to J. Math. Phys | J.Math.Phys. 41 (2000) 3007-3015 | 10.1063/1.533287 | Preprint UNIPO-MATH-99-July-19 | gr-qc | null | The Bach equation, i.e., the vacuum field equation following from the
Lagrangian L=C_{ijkl}C^{ijkl}, will be completely solved for the case that the
metric is conformally related to the cartesian product of two 2-spaces; this
covers the spherically and the plane symmetric space-times as special subcases.
Contrary to other approaches, we make a covariant 2+2-decomposition of the
field equation, and so we are able to apply results from 2-dimensional gravity.
Finally, some cosmological solutions will be presented and discussed.
| [
{
"created": "Tue, 17 Aug 1999 15:07:17 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Dzhunushaliev",
"V.",
""
],
[
"Schmidt",
"H. -J.",
""
]
] | The Bach equation, i.e., the vacuum field equation following from the Lagrangian L=C_{ijkl}C^{ijkl}, will be completely solved for the case that the metric is conformally related to the cartesian product of two 2-spaces; this covers the spherically and the plane symmetric space-times as special subcases. Contrary to other approaches, we make a covariant 2+2-decomposition of the field equation, and so we are able to apply results from 2-dimensional gravity. Finally, some cosmological solutions will be presented and discussed. |
2106.07618 | Karan Fernandes | Karan Fernandes, Susovan Maity and Tapas K. Das | Dynamical analogue spacetimes in non-relativistic flows | 42 pages, 33 figures. arXiv admin note: text overlap with
arXiv:2005.14114 | null | 10.1103/PhysRevD.106.025020 | null | gr-qc astro-ph.HE physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Analogue gravity models describe linear fluctuations of fluids as a massless
scalar field propagating on stationary acoustic spacetimes constructed from the
background flow. In this paper, we establish that this paradigm generalizes to
arbitrary order nonlinear perturbations propagating on dynamical analogue
spacetimes. Our results hold for all inviscid, spherically symmetric and
barotropic non-relativistic flows in the presence of an external conservative
force. We demonstrate that such fluids always admit a dynamical description
governed by a coupled pair of wave and continuity equations. We provide an
iterative approach to solve these equations about any known stationary solution
to all orders in perturbation. In the process, we reveal that there exists a
dynamical acoustic spacetime on which fluctuations of the mass accretion rate
propagate. The dynamical acoustic spacetime is shown to have a well defined
causal structure and curvature. In addition, we find a classical fluctuation
relation for the acoustic horizon of the spacetime that admit scenarios wherein
the horizon can grow as well as recede, with the latter being a result with no
known analogue in black holes. As an example, we numerically investigate the
Bondi flow accreting solution subject to exponentially damped time dependent
perturbations. We find that second and higher order classical perturbations
possess an acoustic horizon that oscillates and changes to a new stable size at
late times. In particular, the case of a receding acoustic horizon is realized
through `low frequency' perturbations. We discuss our results in the context of
more general analogue models and its potential implications on astrophysical
accretion flows.
| [
{
"created": "Mon, 14 Jun 2021 17:21:54 GMT",
"version": "v1"
}
] | 2022-08-17 | [
[
"Fernandes",
"Karan",
""
],
[
"Maity",
"Susovan",
""
],
[
"Das",
"Tapas K.",
""
]
] | Analogue gravity models describe linear fluctuations of fluids as a massless scalar field propagating on stationary acoustic spacetimes constructed from the background flow. In this paper, we establish that this paradigm generalizes to arbitrary order nonlinear perturbations propagating on dynamical analogue spacetimes. Our results hold for all inviscid, spherically symmetric and barotropic non-relativistic flows in the presence of an external conservative force. We demonstrate that such fluids always admit a dynamical description governed by a coupled pair of wave and continuity equations. We provide an iterative approach to solve these equations about any known stationary solution to all orders in perturbation. In the process, we reveal that there exists a dynamical acoustic spacetime on which fluctuations of the mass accretion rate propagate. The dynamical acoustic spacetime is shown to have a well defined causal structure and curvature. In addition, we find a classical fluctuation relation for the acoustic horizon of the spacetime that admit scenarios wherein the horizon can grow as well as recede, with the latter being a result with no known analogue in black holes. As an example, we numerically investigate the Bondi flow accreting solution subject to exponentially damped time dependent perturbations. We find that second and higher order classical perturbations possess an acoustic horizon that oscillates and changes to a new stable size at late times. In particular, the case of a receding acoustic horizon is realized through `low frequency' perturbations. We discuss our results in the context of more general analogue models and its potential implications on astrophysical accretion flows. |
0807.4253 | Julio Cesar Fabris | John D. Barrow, Antonio B. Batista, Julio C. Fabris and M. J. S.
Houndjo | Quantum Particle Production at Sudden Singularities | Latex file, 13 pages, five figures in eps format. Extended
discussion, new appendix and added references | Phys.Rev.D78:123508,2008 | 10.1103/PhysRevD.78.123508 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the effects of quantum particle production on a classical
sudden singularity occurring at fine time in a Friedmann universe. We use an
exact solution to describe an initially radiation-dominated universe that
evolves into a sudden singularity at finite time. We calculate the density of
created particles exactly and find that it is generally much smaller than the
classical background density and pressure which produce the sudden singularity.
We conclude that, in the example studied, the quantum particle production does
not lead to the avoidance or modification to the sudden future singularity. We
argue that the effects of small residual anisotropies in the expansion will not
change these results and show how they can be related to studies of classical
particle production using a bulk viscosity. We conclude that we do not expect
to see significant observable effects from local sudden singularities on our
past light cone.
| [
{
"created": "Sat, 26 Jul 2008 20:08:44 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Aug 2008 12:10:51 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Nov 2008 14:44:30 GMT",
"version": "v3"
}
] | 2012-07-06 | [
[
"Barrow",
"John D.",
""
],
[
"Batista",
"Antonio B.",
""
],
[
"Fabris",
"Julio C.",
""
],
[
"Houndjo",
"M. J. S.",
""
]
] | We investigate the effects of quantum particle production on a classical sudden singularity occurring at fine time in a Friedmann universe. We use an exact solution to describe an initially radiation-dominated universe that evolves into a sudden singularity at finite time. We calculate the density of created particles exactly and find that it is generally much smaller than the classical background density and pressure which produce the sudden singularity. We conclude that, in the example studied, the quantum particle production does not lead to the avoidance or modification to the sudden future singularity. We argue that the effects of small residual anisotropies in the expansion will not change these results and show how they can be related to studies of classical particle production using a bulk viscosity. We conclude that we do not expect to see significant observable effects from local sudden singularities on our past light cone. |
2205.00556 | Maur\'icio Richartz | Pedro Henrique Croti Siqueira, Maur\'icio Richartz | Quasinormal modes, quasibound states, scalar clouds, and superradiant
instabilities of a Kerr-like black hole | v2: 13 pages, 11 figures. Matches published version | Phys. Rev. D 106, 024046 (2022) | 10.1103/PhysRevD.106.024046 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the continued fraction method to determine the eigenfrequencies
associated with a scalar field around a Kerr-like black hole. The Kerr-like
metric considered in this article is a subclass of the general parametrization
of axisymmetric black holes proposed by Konoplya, Rezzolla and Zhidenko. In
addition to its mass $M$ and specific angular momentum $a$, the black hole
depends on a third parameter $\eta$, called the deformation parameter. We
investigate how the deformation parameter affects the quasinormal modes and the
quasibound states of a massive scalar field around the black hole. In
particular, we compute the time scales associated with the superradiant
instabilities of the scalar field in such a spacetime. The properties of
stationary scalar clouds that could be formed by these instabilities are also
discussed.
| [
{
"created": "Sun, 1 May 2022 20:40:18 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Jul 2022 02:57:38 GMT",
"version": "v2"
}
] | 2022-07-27 | [
[
"Siqueira",
"Pedro Henrique Croti",
""
],
[
"Richartz",
"Maurício",
""
]
] | We use the continued fraction method to determine the eigenfrequencies associated with a scalar field around a Kerr-like black hole. The Kerr-like metric considered in this article is a subclass of the general parametrization of axisymmetric black holes proposed by Konoplya, Rezzolla and Zhidenko. In addition to its mass $M$ and specific angular momentum $a$, the black hole depends on a third parameter $\eta$, called the deformation parameter. We investigate how the deformation parameter affects the quasinormal modes and the quasibound states of a massive scalar field around the black hole. In particular, we compute the time scales associated with the superradiant instabilities of the scalar field in such a spacetime. The properties of stationary scalar clouds that could be formed by these instabilities are also discussed. |
2206.13944 | Ryosuke Urakawa | Ryosuke Urakawa, Takuya Tsuchiya and Gen Yoneda | On the stability of covariant BSSN formulation | 18 pages, 6 figures | null | 10.1088/1361-6382/ac7e16 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this study, we investigate the numerical stability of the covariant BSSN
(cBSSN) formulation proposed by Brown. We calculate the constraint
amplification factor (CAF), which is an eigenvalue of the coefficient matrix of
the evolution equations of the constraints on the cBSSN formulation and on some
adjusted formulations with constraints added to the evolution equations. The
adjusted formulations have a higher numerical stability than the cBSSN
formulation from the viewpoint of the CAF.
| [
{
"created": "Mon, 27 Jun 2022 00:00:52 GMT",
"version": "v1"
}
] | 2022-08-10 | [
[
"Urakawa",
"Ryosuke",
""
],
[
"Tsuchiya",
"Takuya",
""
],
[
"Yoneda",
"Gen",
""
]
] | In this study, we investigate the numerical stability of the covariant BSSN (cBSSN) formulation proposed by Brown. We calculate the constraint amplification factor (CAF), which is an eigenvalue of the coefficient matrix of the evolution equations of the constraints on the cBSSN formulation and on some adjusted formulations with constraints added to the evolution equations. The adjusted formulations have a higher numerical stability than the cBSSN formulation from the viewpoint of the CAF. |
1708.04609 | Dennis Philipp | Dennis Philipp, Florian W\"oske, Liliane Biskupek, Eva Hackmann,
Enrico Mai, Meike List, Claus L\"ammerzahl, Benny Rievers | Modeling approaches for precise relativistic orbits: Analytical,
Lie-series, and pN approximation | 15 pages, 5 figures; updated version with journal reference | Advances in Space Research, Volume 62, Issue 4, 2018, Pages
921-934 | 10.1016/j.asr.2018.05.020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Accurate orbit modeling plays a key role in contemporary and future space
missions such as GRACE and its successor GRACE-FO, GNSS, and altimetry
missions. To fully exploit the technological capabilities and correctly
interpret measurements, relativistic orbital effects need to be taken into
account. Within the theory of General Relativity, equations of motion for
freely falling test objects, such as satellites orbiting the Earth, are given
by the geodesic equation. We analyze and compare different solution methods in
a spherically symmetric background, i.e. for the Schwarzschild spacetime, as a
test bed. We investigate satellite orbits and use direct numerical orbit
integration as well as the semi-analytical Lie-series approach. The results are
compared to the exact analytical reference solution in terms of elliptic
functions. For a set of exemplary orbits, we determine the respective accuracy
of the different methods. Within the post-Newtonian approximation of General
Relativity, modified orbital equations are obtained by adding relativistic
corrections to the Newtonian equations of motion. We analyze the accuracy of
this approximation with respect to the general relativistic setting. Therefore,
we solve the post-Newtonian equation of motion using the eXtended High
Performance Satellite dynamics Simulator. For corresponding initial conditions,
we compare orbits in the Schwarzschild spacetime to those in its post-Newtonian
approximation. Moreover, we compare the magnitude of relativistic contributions
to several typical perturbations of satellite orbits due to, e.g., solar
radiation pressure, Earth's albedo, and atmospheric drag. This comparison is
done for our test scenarios and for a real GRACE orbit to highlight the
importance of relativistic effects in geodetic space missions.
| [
{
"created": "Tue, 15 Aug 2017 17:59:12 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Feb 2019 16:50:44 GMT",
"version": "v2"
}
] | 2019-02-20 | [
[
"Philipp",
"Dennis",
""
],
[
"Wöske",
"Florian",
""
],
[
"Biskupek",
"Liliane",
""
],
[
"Hackmann",
"Eva",
""
],
[
"Mai",
"Enrico",
""
],
[
"List",
"Meike",
""
],
[
"Lämmerzahl",
"Claus",
""
],
[
"R... | Accurate orbit modeling plays a key role in contemporary and future space missions such as GRACE and its successor GRACE-FO, GNSS, and altimetry missions. To fully exploit the technological capabilities and correctly interpret measurements, relativistic orbital effects need to be taken into account. Within the theory of General Relativity, equations of motion for freely falling test objects, such as satellites orbiting the Earth, are given by the geodesic equation. We analyze and compare different solution methods in a spherically symmetric background, i.e. for the Schwarzschild spacetime, as a test bed. We investigate satellite orbits and use direct numerical orbit integration as well as the semi-analytical Lie-series approach. The results are compared to the exact analytical reference solution in terms of elliptic functions. For a set of exemplary orbits, we determine the respective accuracy of the different methods. Within the post-Newtonian approximation of General Relativity, modified orbital equations are obtained by adding relativistic corrections to the Newtonian equations of motion. We analyze the accuracy of this approximation with respect to the general relativistic setting. Therefore, we solve the post-Newtonian equation of motion using the eXtended High Performance Satellite dynamics Simulator. For corresponding initial conditions, we compare orbits in the Schwarzschild spacetime to those in its post-Newtonian approximation. Moreover, we compare the magnitude of relativistic contributions to several typical perturbations of satellite orbits due to, e.g., solar radiation pressure, Earth's albedo, and atmospheric drag. This comparison is done for our test scenarios and for a real GRACE orbit to highlight the importance of relativistic effects in geodetic space missions. |
1601.07290 | Yasutaka Koga | Yasutaka Koga and Tomohiro Harada | The correspondence between sonic points of ideal photon gas accretion
and photon spheres | 9pages | Phys. Rev. D 94, 044053 (2016) | 10.1103/PhysRevD.94.044053 | RUP-16-5 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In an accretion of fluid, its velocity may transit from subsonic to
supersonic. The point at which such transition occurs is called sonic point and
often mathematically special. We consider a steady-state and spherically
symmetric accretion problem of ideal photon gas in general static spherically
symmetric spacetime neglecting back reaction. Our main result is that the EOS
of ideal photon gas leads to correspondence between its sonic point and the
photon sphere of the spacetime in general situations. Despite of the dependence
of the EOS on the dimension of spacetime, this correspondence holds for
spacetimes of arbitrary dimensions.
| [
{
"created": "Wed, 27 Jan 2016 08:48:06 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Sep 2016 10:36:56 GMT",
"version": "v2"
}
] | 2016-09-07 | [
[
"Koga",
"Yasutaka",
""
],
[
"Harada",
"Tomohiro",
""
]
] | In an accretion of fluid, its velocity may transit from subsonic to supersonic. The point at which such transition occurs is called sonic point and often mathematically special. We consider a steady-state and spherically symmetric accretion problem of ideal photon gas in general static spherically symmetric spacetime neglecting back reaction. Our main result is that the EOS of ideal photon gas leads to correspondence between its sonic point and the photon sphere of the spacetime in general situations. Despite of the dependence of the EOS on the dimension of spacetime, this correspondence holds for spacetimes of arbitrary dimensions. |
1903.09316 | Alesandro Santos A. F. Santos | W. D. R. Jesus and A. F. Santos | Ricci dark energy in bumblebee gravity model | 10 pages, 4 figures, accepted for publication in MPLA | null | 10.1142/S0217732319501712 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Ricci dark energy is a model inspired by the holographic dark energy
models with the dark energy density being proportional to Ricci scalar
curvature. Here this model is studied in the bumblebee gravity theory. It is a
gravitational theory that exhibit spontaneous Lorentz symmetry breaking. Then
the modified Friedmann equation is solved for two cases. In the first case the
coupling constant $\xi$ is equal to zero. And in the second case a solution in
the vacuum, where the bumblebee field becomes a constant that minimizes the
potential, is considered. The coupling constant controls the interaction
gravity-bumblebee.
| [
{
"created": "Tue, 19 Mar 2019 12:10:20 GMT",
"version": "v1"
}
] | 2019-08-07 | [
[
"Jesus",
"W. D. R.",
""
],
[
"Santos",
"A. F.",
""
]
] | The Ricci dark energy is a model inspired by the holographic dark energy models with the dark energy density being proportional to Ricci scalar curvature. Here this model is studied in the bumblebee gravity theory. It is a gravitational theory that exhibit spontaneous Lorentz symmetry breaking. Then the modified Friedmann equation is solved for two cases. In the first case the coupling constant $\xi$ is equal to zero. And in the second case a solution in the vacuum, where the bumblebee field becomes a constant that minimizes the potential, is considered. The coupling constant controls the interaction gravity-bumblebee. |
1212.6954 | Julio Cesar Fabris | Gabriel F. Silva, Oliver F. Piattella, Julio C. Fabris, Luciano
Casarini, Taislane O. Barbosa | Bouncing solutions in Rastall's theory with a barotropic fluid | Latex file, 14 pages, 1 figure in eps format. Typos corrected, one
reference added. Published version | Grav. Cosmol. 19 (2013) 156-162 | 10.1134/S0202289313030109 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Rastall's theory is a modification of Einstein's theory of gravity where the
covariant divergence of the stress-energy tensor is no more vanishing, but
proportional to the gradient of the Ricci scalar. The motivation of this theory
is to investigate a possible non-minimal coupling of the matter fields to
geometry which, being proportional to the curvature scalar, may represent an
effective description of quantum gravity effects. Non-conservation of the
stress-energy tensor, via Bianchi identities, implies new field equations which
have been recently used in a cosmological context, leading to some interesting
results. In this paper we adopt Rastall's theory to reproduce some features of
the effective Friedmann's equation emerging from loop quantum cosmology. We
determine a class of bouncing cosmological solutions and comment about the
possibility of employing these models as effective descriptions of the full
quantum theory.
| [
{
"created": "Mon, 31 Dec 2012 19:36:27 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Jan 2013 11:11:00 GMT",
"version": "v2"
},
{
"created": "Fri, 26 Sep 2014 22:09:51 GMT",
"version": "v3"
}
] | 2015-06-12 | [
[
"Silva",
"Gabriel F.",
""
],
[
"Piattella",
"Oliver F.",
""
],
[
"Fabris",
"Julio C.",
""
],
[
"Casarini",
"Luciano",
""
],
[
"Barbosa",
"Taislane O.",
""
]
] | Rastall's theory is a modification of Einstein's theory of gravity where the covariant divergence of the stress-energy tensor is no more vanishing, but proportional to the gradient of the Ricci scalar. The motivation of this theory is to investigate a possible non-minimal coupling of the matter fields to geometry which, being proportional to the curvature scalar, may represent an effective description of quantum gravity effects. Non-conservation of the stress-energy tensor, via Bianchi identities, implies new field equations which have been recently used in a cosmological context, leading to some interesting results. In this paper we adopt Rastall's theory to reproduce some features of the effective Friedmann's equation emerging from loop quantum cosmology. We determine a class of bouncing cosmological solutions and comment about the possibility of employing these models as effective descriptions of the full quantum theory. |
gr-qc/9508009 | null | A. Mikovic | Unitary Theory of Evaporating 2D Black Holes | LaTex file | Class.Quant.Grav.13:209-220,1996 | 10.1088/0264-9381/13/2/009 | Imperial/TP/94-95/50 | gr-qc hep-th | null | We study a manifestly unitary formulation of 2d dilaton quantum gravity based
on the reduced phase space quantization. The spacetime metric can be expanded
in a formal power series of the matter energy-momentum tensor operator. This
expansion can be used for calculating the quantum corrections to the classical
black hole metric by evaluating the expectation value of the metric operator in
an appropriate class of the physical states. When the normal ordering in the
metric operator is chosen to be with respect to Kruskal vacuum, the lowest
order semiclassical metric is exactly the one-loop effective action metric
discovered by Bose, Parker and Peleg. The corresponding semiclassical geometry
describes an evaporating black hole which ends up as a remnant. The calculation
of higher order corrections and implications for the black hole fate are
discussed.
| [
{
"created": "Fri, 4 Aug 1995 12:08:09 GMT",
"version": "v1"
}
] | 2009-01-16 | [
[
"Mikovic",
"A.",
""
]
] | We study a manifestly unitary formulation of 2d dilaton quantum gravity based on the reduced phase space quantization. The spacetime metric can be expanded in a formal power series of the matter energy-momentum tensor operator. This expansion can be used for calculating the quantum corrections to the classical black hole metric by evaluating the expectation value of the metric operator in an appropriate class of the physical states. When the normal ordering in the metric operator is chosen to be with respect to Kruskal vacuum, the lowest order semiclassical metric is exactly the one-loop effective action metric discovered by Bose, Parker and Peleg. The corresponding semiclassical geometry describes an evaporating black hole which ends up as a remnant. The calculation of higher order corrections and implications for the black hole fate are discussed. |
1304.0487 | Alexandru Ionescu | S. Alexakis, A. D. Ionescu, and S. Klainerman | Rigidity of stationary black holes with small angular momentum on the
horizon | Minor corrections, submitted version | Duke Math. J. 163, no. 14 (2014), 2603-2615 | 10.1215/00127094-2819517 | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove a black hole rigidity result for slowly rotating stationary
solutions of the Einstein vacuum equations. More precisely, we prove that the
domain of outer communications of a regular stationary vacuum is isometric to
the domain of outer communications of a Kerr solution, provided that the
stationary Killing vector-field $\T$ is small on the bifurcation sphere.
| [
{
"created": "Mon, 1 Apr 2013 21:41:56 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Apr 2013 21:19:41 GMT",
"version": "v2"
}
] | 2015-01-14 | [
[
"Alexakis",
"S.",
""
],
[
"Ionescu",
"A. D.",
""
],
[
"Klainerman",
"S.",
""
]
] | We prove a black hole rigidity result for slowly rotating stationary solutions of the Einstein vacuum equations. More precisely, we prove that the domain of outer communications of a regular stationary vacuum is isometric to the domain of outer communications of a Kerr solution, provided that the stationary Killing vector-field $\T$ is small on the bifurcation sphere. |
gr-qc/0702092 | Jose Carlos de Araujo | J. C. N. de Araujo and O. D. Miranda | A solution for galactic disks with Yukawian gravitational potential | 7 pages; 1 eps figure; to appear in General Relativity and
Gravitation | Gen.Rel.Grav.39:777-784,2007 | 10.1007/s10714-007-0420-8 | null | gr-qc astro-ph | null | We present a new solution for the rotation curves of galactic disks with
gravitational potential of the Yukawa type. We follow the technique employed by
Toomre in 1963 in the study of galactic disks in the Newtonian theory. This new
solution allows an easy comparison between the Newtonian solution and the
Yukawian one. Therefore, constraints on the parameters of theories of
gravitation can be imposed, which in the weak field limit reduce to Yukawian
potentials. We then apply our formulae to the study of rotation curves for a
zero-thickness exponential disk and compare it with the Newtonian case studied
by Freeman in 1970. As an application of the mathematical tool developed here,
we show that in any theory of gravity with a massive graviton (this means a
gravitational potential of the Yukawa type), a strong limit can be imposed on
the mass (m_g) of this particle. For example, in order to obtain a galactic
disk with a scale length of b ~ 10 kpc, we should have a massive graviton of
m_g << 10^{-59} g. This result is much more restrictive than those inferred
from solar system observations.
| [
{
"created": "Thu, 15 Feb 2007 18:34:55 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"de Araujo",
"J. C. N.",
""
],
[
"Miranda",
"O. D.",
""
]
] | We present a new solution for the rotation curves of galactic disks with gravitational potential of the Yukawa type. We follow the technique employed by Toomre in 1963 in the study of galactic disks in the Newtonian theory. This new solution allows an easy comparison between the Newtonian solution and the Yukawian one. Therefore, constraints on the parameters of theories of gravitation can be imposed, which in the weak field limit reduce to Yukawian potentials. We then apply our formulae to the study of rotation curves for a zero-thickness exponential disk and compare it with the Newtonian case studied by Freeman in 1970. As an application of the mathematical tool developed here, we show that in any theory of gravity with a massive graviton (this means a gravitational potential of the Yukawa type), a strong limit can be imposed on the mass (m_g) of this particle. For example, in order to obtain a galactic disk with a scale length of b ~ 10 kpc, we should have a massive graviton of m_g << 10^{-59} g. This result is much more restrictive than those inferred from solar system observations. |
1402.2534 | N Khusnutdinov | Nail Khusnutdinov | Self-interaction for particles in the wormhole space-times | Talk given in 8th Alexander Friedman International Seminar on
Gravitation and Cosmology, Rio de Janeiro, May 29-June 4, 2011 | Int. J. Mod. Phys. Conf. Series 3, 354-363 (2011) | 10.1142/S2010194511001450 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The self-energy and self-force for particles with electric and scalar charges
at rest in the space-time of massless and massive wormholes are considered. The
particle with electric charge is always attracted to wormhole throat for
arbitrary profile of the throat. The self-force for scalar particle shows
different behavior depending on the non-minimal coupling. The self-force for
massive scalar field is localized close to the throat of the wormhole.
| [
{
"created": "Tue, 11 Feb 2014 15:47:21 GMT",
"version": "v1"
}
] | 2014-02-12 | [
[
"Khusnutdinov",
"Nail",
""
]
] | The self-energy and self-force for particles with electric and scalar charges at rest in the space-time of massless and massive wormholes are considered. The particle with electric charge is always attracted to wormhole throat for arbitrary profile of the throat. The self-force for scalar particle shows different behavior depending on the non-minimal coupling. The self-force for massive scalar field is localized close to the throat of the wormhole. |
1907.13435 | Koray D\"uzta\c{s} | Koray D\"uzta\c{s} | Overspinning Kerr-MOG black holes by test fields and the third law of
black hole dynamics | Accepted to appear in EPJC | Eur. Phys. J. C (2020) 80:19 | 10.1140/epjc/s10052-020-7607-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We evaluate the validity of the weak form of the cosmic censorship conjecture
and the third law of black hole dynamics for Kerr-MOG black holes interacting
with scalar test fields. Ignoring backreaction effects, we first show that both
extremal and nearly extremal Kerr-MOG black holes can be overspun into naked
singularities by scalar test fields with a frequency slightly above the
superradiance limit. In addition, nearly extremal Kerr-Mog black holes can be
continuously driven to extremality by test fields. Next, we employ backreaction
effects based on the argument that the angular velocity of the event horizon
increases before the absorption of the test field. Incorporating the
backreaction effects, we derive that the weak form of the cosmic censorship and
the third law are both valid for Kerr-Mog black holes with a modification
parameter $\alpha \lesssim 0.03$, which includes the Kerr case with $\alpha=0$.
| [
{
"created": "Wed, 24 Jul 2019 23:06:46 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Jan 2020 07:36:40 GMT",
"version": "v2"
}
] | 2020-01-17 | [
[
"Düztaş",
"Koray",
""
]
] | We evaluate the validity of the weak form of the cosmic censorship conjecture and the third law of black hole dynamics for Kerr-MOG black holes interacting with scalar test fields. Ignoring backreaction effects, we first show that both extremal and nearly extremal Kerr-MOG black holes can be overspun into naked singularities by scalar test fields with a frequency slightly above the superradiance limit. In addition, nearly extremal Kerr-Mog black holes can be continuously driven to extremality by test fields. Next, we employ backreaction effects based on the argument that the angular velocity of the event horizon increases before the absorption of the test field. Incorporating the backreaction effects, we derive that the weak form of the cosmic censorship and the third law are both valid for Kerr-Mog black holes with a modification parameter $\alpha \lesssim 0.03$, which includes the Kerr case with $\alpha=0$. |
0807.2808 | Jorge Pullin | Rodolfo Gambini and Jorge Pullin | Emergent diffeomorphism invariance in a discrete loop quantum gravity
model | 12 pages, Revtex | Class.Quant.Grav.26:035002,2009 | 10.1088/0264-9381/26/3/035002 | LSU-REL-071708 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several approaches to the dynamics of loop quantum gravity involve
discretizing the equations of motion. The resulting discrete theories are known
to be problematic since the first class algebra of constraints of the continuum
theory becomes second class upon discretization. If one treats the second class
constraints properly, the resulting theories have very different dynamics and
number of degrees of freedom than those of the continuum theory. It is
therefore questionable how these theories could be considered a starting point
for quantization and the definition of a continuum theory through a continuum
limit. We show explicitly in a model that the {\em uniform discretizations}
approach to the quantization of constrained systems overcomes these
difficulties. We consider here a simple diffeomorphism invariant one
dimensional model and complete the quantization using {\em uniform
discretizations}. The model can be viewed as a spherically symmetric reduction
of the well known Husain--Kucha\v{r} model of diffeomorphism invariant theory.
We show that the correct quantum continuum limit can be satisfactorily
constructed for this model. This opens the possibility of treating 1+1
dimensional dynamical situations of great interest in quantum gravity taking
into account the full dynamics of the theory and preserving the space-time
covariance at a quantum level.
| [
{
"created": "Thu, 17 Jul 2008 15:32:36 GMT",
"version": "v1"
}
] | 2009-01-16 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | Several approaches to the dynamics of loop quantum gravity involve discretizing the equations of motion. The resulting discrete theories are known to be problematic since the first class algebra of constraints of the continuum theory becomes second class upon discretization. If one treats the second class constraints properly, the resulting theories have very different dynamics and number of degrees of freedom than those of the continuum theory. It is therefore questionable how these theories could be considered a starting point for quantization and the definition of a continuum theory through a continuum limit. We show explicitly in a model that the {\em uniform discretizations} approach to the quantization of constrained systems overcomes these difficulties. We consider here a simple diffeomorphism invariant one dimensional model and complete the quantization using {\em uniform discretizations}. The model can be viewed as a spherically symmetric reduction of the well known Husain--Kucha\v{r} model of diffeomorphism invariant theory. We show that the correct quantum continuum limit can be satisfactorily constructed for this model. This opens the possibility of treating 1+1 dimensional dynamical situations of great interest in quantum gravity taking into account the full dynamics of the theory and preserving the space-time covariance at a quantum level. |
0706.4008 | Ingemar Eriksson | Ingemar Eriksson | Conserved Matter Superenergy Currents for Orthogonally Transitive
Abelian G2 Isometry Groups | 15 pages | Class.Quant.Grav.24:4955-4968,2007 | 10.1088/0264-9381/24/20/004 | null | gr-qc | null | In a previous paper we showed that the electromagnetic superenergy tensor,
the Chevreton tensor, gives rise to a conserved current when there is a
hypersurface orthogonal Killing vector present. In addition, the current is
proportional to the Killing vector. The aim of this paper is to extend this
result to the case when we have a two-parameter Abelian isometry group that
acts orthogonally transitive on non-null surfaces. It is shown that for
four-dimensional Einstein-Maxwell theory with a source-free electromagnetic
field, the corresponding superenergy currents lie in the orbits of the group
and are conserved. A similar result is also shown to hold for the trace of the
Chevreton tensor and for the Bach tensor, and also in Einstein-Klein-Gordon
theory for the superenergy of the scalar field. This links up well with the
fact that the Bel tensor has these properties and the possibility of
constructing conserved mixed currents between the gravitational field and the
matter fields.
| [
{
"created": "Wed, 27 Jun 2007 12:07:22 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Eriksson",
"Ingemar",
""
]
] | In a previous paper we showed that the electromagnetic superenergy tensor, the Chevreton tensor, gives rise to a conserved current when there is a hypersurface orthogonal Killing vector present. In addition, the current is proportional to the Killing vector. The aim of this paper is to extend this result to the case when we have a two-parameter Abelian isometry group that acts orthogonally transitive on non-null surfaces. It is shown that for four-dimensional Einstein-Maxwell theory with a source-free electromagnetic field, the corresponding superenergy currents lie in the orbits of the group and are conserved. A similar result is also shown to hold for the trace of the Chevreton tensor and for the Bach tensor, and also in Einstein-Klein-Gordon theory for the superenergy of the scalar field. This links up well with the fact that the Bel tensor has these properties and the possibility of constructing conserved mixed currents between the gravitational field and the matter fields. |
2408.02251 | Gustav Holzegel | Olivier Graf and Gustav Holzegel | Linear Stability of Schwarzschild-Anti-de Sitter spacetimes I: The
system of gravitational perturbations | null | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is the main paper of a series establishing the linear stability of
Schwarzschild-Anti-de Sitter (AdS) black holes to gravitational perturbations.
Specifically, we prove that solutions to the linearisation of the Einstein
equations $\textrm{Ric}(g) = \Lambda g$ with $\Lambda<0$ around a
Schwarzschild-AdS metric arising from regular initial data and with standard
Dirichlet-type boundary conditions imposed at the conformal boundary (inherited
from fixing the conformal class of the non-linear metric) remain globally
uniformly bounded on the black hole exterior and in fact decay inverse
logarithmically in time to a linearised Kerr-AdS metric. The proof exploits a
hierarchical structure of the equations of linearised gravity in double null
gauge and crucially relies on boundedness and logarithmic decay results for the
Teukolsky system, which are independent results proven in Part II of the
series. Contrary to the asymptotically flat case, addition of a residual pure
gauge solution to the original solution is not required to prove decay of all
linearised null curvature and Ricci coefficients. One may however normalise the
solution at the conformal boundary to be in standard AdS-form by adding such a
pure gauge solution, which is constructed dynamically from the trace of the
original solution at the conformal boundary and quantitatively controlled by
initial data.
| [
{
"created": "Mon, 5 Aug 2024 05:51:50 GMT",
"version": "v1"
}
] | 2024-08-06 | [
[
"Graf",
"Olivier",
""
],
[
"Holzegel",
"Gustav",
""
]
] | This is the main paper of a series establishing the linear stability of Schwarzschild-Anti-de Sitter (AdS) black holes to gravitational perturbations. Specifically, we prove that solutions to the linearisation of the Einstein equations $\textrm{Ric}(g) = \Lambda g$ with $\Lambda<0$ around a Schwarzschild-AdS metric arising from regular initial data and with standard Dirichlet-type boundary conditions imposed at the conformal boundary (inherited from fixing the conformal class of the non-linear metric) remain globally uniformly bounded on the black hole exterior and in fact decay inverse logarithmically in time to a linearised Kerr-AdS metric. The proof exploits a hierarchical structure of the equations of linearised gravity in double null gauge and crucially relies on boundedness and logarithmic decay results for the Teukolsky system, which are independent results proven in Part II of the series. Contrary to the asymptotically flat case, addition of a residual pure gauge solution to the original solution is not required to prove decay of all linearised null curvature and Ricci coefficients. One may however normalise the solution at the conformal boundary to be in standard AdS-form by adding such a pure gauge solution, which is constructed dynamically from the trace of the original solution at the conformal boundary and quantitatively controlled by initial data. |
1202.6561 | Gunther Caspar | Gunther Caspar, Thomas Sch\"onenbach, Peter Otto Hess, Mirko Sch\"afer
and Walter Greiner | Pseudo-Complex General Relativity: Schwarzschild, Reissner-Nordstr\"om
and Kerr Solutions | null | International Journal of Modern Physics E Vol. 21, No. 2 (2012)
1250015 (39 pages) | 10.1142/S0218301312500152 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The pseudo-complex General Relativity (pc-GR) is further considered. A new
projection method is proposed. It is shown, that the pc-GR introduces
automatically terms into the system which can be interpreted as dark energy.
The modified pseudo-complex Schwarzschild solution is investigated. The dark
energy part is treated as a liquid and possible solutions are discussed. As a
consequence, the collapse of a large stellar mass into a singularity at $r=0$
is avoided and no event-horizon is formed. Thus, black holes don't exist. The
resulting object can be viewed as a gray star. It contains no singularity which
emphasizes, again, that it is not a black hole. The corrections implied by a
charged large mass object (Reissner- Nordstr\"om) and a rotating gray star
(Kerr) are presented. For the latter, a special solution is presented. Finally,
we will consider the orbital speed of a mass in a circular orbit and suggest a
possible experimental verification.
| [
{
"created": "Wed, 29 Feb 2012 14:52:44 GMT",
"version": "v1"
}
] | 2012-03-01 | [
[
"Caspar",
"Gunther",
""
],
[
"Schönenbach",
"Thomas",
""
],
[
"Hess",
"Peter Otto",
""
],
[
"Schäfer",
"Mirko",
""
],
[
"Greiner",
"Walter",
""
]
] | The pseudo-complex General Relativity (pc-GR) is further considered. A new projection method is proposed. It is shown, that the pc-GR introduces automatically terms into the system which can be interpreted as dark energy. The modified pseudo-complex Schwarzschild solution is investigated. The dark energy part is treated as a liquid and possible solutions are discussed. As a consequence, the collapse of a large stellar mass into a singularity at $r=0$ is avoided and no event-horizon is formed. Thus, black holes don't exist. The resulting object can be viewed as a gray star. It contains no singularity which emphasizes, again, that it is not a black hole. The corrections implied by a charged large mass object (Reissner- Nordstr\"om) and a rotating gray star (Kerr) are presented. For the latter, a special solution is presented. Finally, we will consider the orbital speed of a mass in a circular orbit and suggest a possible experimental verification. |
1310.8048 | Alexander Viznyuk | Alexander Viznyuk, Yuri Shtanov, Varun Sahni | A no-boundary proposal for braneworld perturbations | 28 pages, 1 figure | Phys. Rev. D 89, 083523 (2014) | 10.1103/PhysRevD.89.083523 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a novel approach to the problem of cosmological perturbations in a
braneworld model with induced gravity, which leads to a closed system of
equations on the brane. We focus on a spatially closed brane that bounds the
interior four-ball of the bulk space. The background cosmological evolution on
the brane is now described by the normal branch, and the boundary conditions in
the bulk become the regularity conditions for the metric everywhere inside the
four-ball. In this approach, there is no spatial infinity or any other boundary
in the bulk space since the spatial section is compact, hence, we term this
setup as a no-boundary proposal. Assuming that the bulk cosmological constant
is absent and employing the Mukohyama master variable, we argue that the
effects of nonlocality on brane perturbations may be ignored if the brane is
marginally closed. In this case, there arises a relation that closes the system
of equations for perturbations on the brane. Perturbations of pressureless
matter and dark radiation can now be described by a system of coupled
second-order differential equations. Remarkably, this system can be exactly
solved in the matter-dominated and de Sitter regimes. In this case, apart from
the usual growing and decaying modes, we find two additional modes that behave
monotonically on super-Hubble spatial scales and exhibit rapid oscillations
with decaying amplitude on sub-Hubble spatial scales.
| [
{
"created": "Wed, 30 Oct 2013 07:23:33 GMT",
"version": "v1"
}
] | 2014-04-23 | [
[
"Viznyuk",
"Alexander",
""
],
[
"Shtanov",
"Yuri",
""
],
[
"Sahni",
"Varun",
""
]
] | We propose a novel approach to the problem of cosmological perturbations in a braneworld model with induced gravity, which leads to a closed system of equations on the brane. We focus on a spatially closed brane that bounds the interior four-ball of the bulk space. The background cosmological evolution on the brane is now described by the normal branch, and the boundary conditions in the bulk become the regularity conditions for the metric everywhere inside the four-ball. In this approach, there is no spatial infinity or any other boundary in the bulk space since the spatial section is compact, hence, we term this setup as a no-boundary proposal. Assuming that the bulk cosmological constant is absent and employing the Mukohyama master variable, we argue that the effects of nonlocality on brane perturbations may be ignored if the brane is marginally closed. In this case, there arises a relation that closes the system of equations for perturbations on the brane. Perturbations of pressureless matter and dark radiation can now be described by a system of coupled second-order differential equations. Remarkably, this system can be exactly solved in the matter-dominated and de Sitter regimes. In this case, apart from the usual growing and decaying modes, we find two additional modes that behave monotonically on super-Hubble spatial scales and exhibit rapid oscillations with decaying amplitude on sub-Hubble spatial scales. |
gr-qc/0201013 | Monica Pierri-Galvao | M. Pierri | Hamiltonian and Volume Operators | Latex, 8 pages | null | null | null | gr-qc | null | 2+1 gravity coupled to a massless scalar field has an initial singularity
when the spatial slices are compact. The quantized model is used here to
investigate several issues of quantum gravity. The spectrum of the volume
operator is studied at the initial singularity. The energy spectrum is
obtained. Dynamics of the universe is also investigated.
| [
{
"created": "Fri, 4 Jan 2002 11:13:40 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pierri",
"M.",
""
]
] | 2+1 gravity coupled to a massless scalar field has an initial singularity when the spatial slices are compact. The quantized model is used here to investigate several issues of quantum gravity. The spectrum of the volume operator is studied at the initial singularity. The energy spectrum is obtained. Dynamics of the universe is also investigated. |
2101.04592 | Barry Wardell | Adam Pound and Barry Wardell | Black hole perturbation theory and gravitational self-force | 121 pages, 1 figure. Invited chapter for "Handbook of Gravitational
Wave Astronomy" (Eds. C. Bambi, S. Katsanevas, and K. Kokkotas; Springer,
Singapore, 2021). v4 typos corrected | null | 10.1007/978-981-15-4702-7_38-1 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Much of the success of gravitational-wave astronomy rests on perturbation
theory. Historically, perturbative analysis of gravitational-wave sources has
largely focused on post-Newtonian theory. However, strong-field perturbation
theory is essential in many cases such as the quasinormal ringdown following
the merger of a binary system, tidally perturbed compact objects, and
extreme-mass-ratio inspirals. In this review, motivated primarily by
small-mass-ratio binaries but not limited to them, we provide an overview of
essential methods in (i) black hole perturbation theory, (ii) orbital mechanics
in Kerr spacetime, and (iii) gravitational self-force theory. Our treatment of
black hole perturbation theory covers most common methods, including the
Teukolsky and Regge-Wheeler-Zerilli equations, methods of metric
reconstruction, and Lorenz-gauge formulations, presenting them in a new
consistent and self-contained form. Our treatment of orbital mechanics covers
quasi-Keplerian and action-angle descriptions of bound geodesics and
accelerated orbits, osculating geodesics, near-identity averaging
transformations, multiscale expansions, and orbital resonances. Our summary of
self-force theory's foundations is brief, covering the main ideas and results
of matched asymptotic expansions, local expansion methods, puncture schemes,
and point particle descriptions. We conclude by combining the above methods in
a multiscale expansion of the perturbative Einstein equations, leading to
adiabatic and post-adiabatic evolution schemes. Our presentation is intended
primarily as a reference for practitioners but includes a variety of new
results. In particular, we present the first complete post-adiabatic
waveform-generation framework for generic (nonresonant) orbits in Kerr.
| [
{
"created": "Tue, 12 Jan 2021 16:44:53 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Jun 2021 13:15:05 GMT",
"version": "v2"
},
{
"created": "Mon, 13 Sep 2021 22:23:54 GMT",
"version": "v3"
},
{
"created": "Thu, 25 Jan 2024 01:29:56 GMT",
"version": "v4"
}
] | 2024-01-26 | [
[
"Pound",
"Adam",
""
],
[
"Wardell",
"Barry",
""
]
] | Much of the success of gravitational-wave astronomy rests on perturbation theory. Historically, perturbative analysis of gravitational-wave sources has largely focused on post-Newtonian theory. However, strong-field perturbation theory is essential in many cases such as the quasinormal ringdown following the merger of a binary system, tidally perturbed compact objects, and extreme-mass-ratio inspirals. In this review, motivated primarily by small-mass-ratio binaries but not limited to them, we provide an overview of essential methods in (i) black hole perturbation theory, (ii) orbital mechanics in Kerr spacetime, and (iii) gravitational self-force theory. Our treatment of black hole perturbation theory covers most common methods, including the Teukolsky and Regge-Wheeler-Zerilli equations, methods of metric reconstruction, and Lorenz-gauge formulations, presenting them in a new consistent and self-contained form. Our treatment of orbital mechanics covers quasi-Keplerian and action-angle descriptions of bound geodesics and accelerated orbits, osculating geodesics, near-identity averaging transformations, multiscale expansions, and orbital resonances. Our summary of self-force theory's foundations is brief, covering the main ideas and results of matched asymptotic expansions, local expansion methods, puncture schemes, and point particle descriptions. We conclude by combining the above methods in a multiscale expansion of the perturbative Einstein equations, leading to adiabatic and post-adiabatic evolution schemes. Our presentation is intended primarily as a reference for practitioners but includes a variety of new results. In particular, we present the first complete post-adiabatic waveform-generation framework for generic (nonresonant) orbits in Kerr. |
0709.2925 | Leonardo Gualtieri | V. Ferrari, L. Gualtieri, S. Marassi | A new approach to the study of quasi-normal modes of rotating stars | 24 pages, 7 figures, submitted to Phys. Rev. D | Phys.Rev.D76:104033,2007 | 10.1103/PhysRevD.76.104033 | null | gr-qc astro-ph | null | We propose a new method to study the quasi-normal modes of rotating
relativistic stars. Oscillations are treated as perturbations in the frequency
domain of the stationary, axisymmetric background describing a rotating star.
The perturbed quantities are expanded in circular harmonics, and the resulting
2D-equations they satisfy are integrated using spectral methods in the
(r,theta)-plane. The asymptotic conditions at infinity, needed to find the mode
frequencies, are implemented by generalizing the standing wave boundary
condition commonly used in the non rotating case. As a test, the method is
applied to find the quasi-normal mode frequencies of a slowly rotating star.
| [
{
"created": "Tue, 18 Sep 2007 22:09:23 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ferrari",
"V.",
""
],
[
"Gualtieri",
"L.",
""
],
[
"Marassi",
"S.",
""
]
] | We propose a new method to study the quasi-normal modes of rotating relativistic stars. Oscillations are treated as perturbations in the frequency domain of the stationary, axisymmetric background describing a rotating star. The perturbed quantities are expanded in circular harmonics, and the resulting 2D-equations they satisfy are integrated using spectral methods in the (r,theta)-plane. The asymptotic conditions at infinity, needed to find the mode frequencies, are implemented by generalizing the standing wave boundary condition commonly used in the non rotating case. As a test, the method is applied to find the quasi-normal mode frequencies of a slowly rotating star. |
2011.09623 | Celia Escamilla-Rivera | N. M. Jim\'enez Cruz and Celia Escamilla-Rivera | Late-time and Big Bang nucleosynthesis constraints for generic modify
gravity surveys | 23 pages, 17 figures. Version accepted in EPJP | null | 10.1140/epjp/s13360-020-00950-3 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, a new generic parameterisation for $f(R)$ theories is
presented. Our proposal for a new equation of state can reproduce an
$f(R)$-like evolution that describes late and early time universe within
1-$\sigma$ C.L when we use a combination of distance ladder measurements based
on Cosmic Chronometers, Supernovae Ia, Baryon Acoustic Oscillation and finally,
Cosmic Microwave Background and Lyman-$\alpha$ forest. Indeed, a family of
$f(R)$ cosmological viable scenarios were extensively analysed in the light of
late-time measurements, were an Eos reaches a precision better than $99.2\%$
over the numerical solutions for the field equations of this theory. Moreover,
in this proposal we extended the study to find constraints at the very early
time that can satisfy the Big Bang Nucleosynthesis data on helium fraction,
$Y_{p}$. To perform this analysis, and with our generic $w_{f(R)}$ --which can
be seemed it at the same level as other parameterisations into the pipeline and
analysis of observational surveys-- we consider both background and linear
perturbations evolution and constrain beyond the standard $\Lambda$CDM six
cosmological parameters. While there are strong constraints at background on
the free parameters of our $w_{f(R)}$, we found that $f(R)$ background viable
models can set early constraints to the current Hubble constant $H_0$, which is
in agreement with CMB data, but when late-time model-independent measurements
are considered, $H_0$ is fully compatible with the $R^{H18}$ value. Finally, as
an extension of these results, our proposal is capable to distinguish between
$f(R)$ scenarios at both routes of the distance ladder showing a good approach
to modify gravity at this level.
| [
{
"created": "Thu, 19 Nov 2020 02:56:22 GMT",
"version": "v1"
}
] | 2020-11-20 | [
[
"Cruz",
"N. M. Jiménez",
""
],
[
"Escamilla-Rivera",
"Celia",
""
]
] | In this work, a new generic parameterisation for $f(R)$ theories is presented. Our proposal for a new equation of state can reproduce an $f(R)$-like evolution that describes late and early time universe within 1-$\sigma$ C.L when we use a combination of distance ladder measurements based on Cosmic Chronometers, Supernovae Ia, Baryon Acoustic Oscillation and finally, Cosmic Microwave Background and Lyman-$\alpha$ forest. Indeed, a family of $f(R)$ cosmological viable scenarios were extensively analysed in the light of late-time measurements, were an Eos reaches a precision better than $99.2\%$ over the numerical solutions for the field equations of this theory. Moreover, in this proposal we extended the study to find constraints at the very early time that can satisfy the Big Bang Nucleosynthesis data on helium fraction, $Y_{p}$. To perform this analysis, and with our generic $w_{f(R)}$ --which can be seemed it at the same level as other parameterisations into the pipeline and analysis of observational surveys-- we consider both background and linear perturbations evolution and constrain beyond the standard $\Lambda$CDM six cosmological parameters. While there are strong constraints at background on the free parameters of our $w_{f(R)}$, we found that $f(R)$ background viable models can set early constraints to the current Hubble constant $H_0$, which is in agreement with CMB data, but when late-time model-independent measurements are considered, $H_0$ is fully compatible with the $R^{H18}$ value. Finally, as an extension of these results, our proposal is capable to distinguish between $f(R)$ scenarios at both routes of the distance ladder showing a good approach to modify gravity at this level. |
2001.08491 | Ingemar Bengtsson | Ingemar Bengtsson | The Hawking energy on photon surfaces | 9 pages; improved by two referees | Gen. Relativ. Gravit. (2020) 52:52 | 10.1007/s10714-020-02703-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hawking energy has a monotonicity property under the inverse mean
curvature flow on totally umbilic hypersurfaces with constant scalar curvature
in Einstein spaces. It grows if the hypersurface is spacelike, and decreases if
it is timelike. Timelike examples include Minkowski and de Sitter hyperboloids,
and photon surfaces in Schwarzschild.
| [
{
"created": "Thu, 23 Jan 2020 13:18:23 GMT",
"version": "v1"
},
{
"created": "Fri, 22 May 2020 20:01:25 GMT",
"version": "v2"
}
] | 2020-06-23 | [
[
"Bengtsson",
"Ingemar",
""
]
] | The Hawking energy has a monotonicity property under the inverse mean curvature flow on totally umbilic hypersurfaces with constant scalar curvature in Einstein spaces. It grows if the hypersurface is spacelike, and decreases if it is timelike. Timelike examples include Minkowski and de Sitter hyperboloids, and photon surfaces in Schwarzschild. |
gr-qc/0312095 | Beverly K. Berger | Beverly K. Berger | Hunting Local Mixmaster Dynamics in Spatially Inhomogeneous Cosmologies | 17 pages, 5 figures. Contribution to CQG Special Issue "A Spacetime
Safari: Essays in Honour of Vincent Moncrief" | Class.Quant.Grav. 21 (2004) S81-S96 | 10.1088/0264-9381/21/3/006 | null | gr-qc | null | Heuristic arguments and numerical simulations support the Belinskii et al
(BKL) claim that the approach to the singularity in generic gravitational
collapse is characterized by local Mixmaster dynamics (LMD). Here, one way to
identify LMD in collapsing spatially inhomogeneous cosmologies is explored. By
writing the metric of one spacetime in the standard variables of another,
signatures for LMD may be found. Such signatures for the dynamics of spatially
homogeneous Mixmaster models in the variables of U(1)-symmetric cosmologies are
reviewed. Similar constructions for U(1)-symmetric spacetimes in terms of the
dynamics of generic $T^2$-symmetric spacetime are presented.
| [
{
"created": "Sat, 20 Dec 2003 22:24:44 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Berger",
"Beverly K.",
""
]
] | Heuristic arguments and numerical simulations support the Belinskii et al (BKL) claim that the approach to the singularity in generic gravitational collapse is characterized by local Mixmaster dynamics (LMD). Here, one way to identify LMD in collapsing spatially inhomogeneous cosmologies is explored. By writing the metric of one spacetime in the standard variables of another, signatures for LMD may be found. Such signatures for the dynamics of spatially homogeneous Mixmaster models in the variables of U(1)-symmetric cosmologies are reviewed. Similar constructions for U(1)-symmetric spacetimes in terms of the dynamics of generic $T^2$-symmetric spacetime are presented. |
gr-qc/9805067 | Dharam V. Ahluwalia | D. V. Ahluwalia | Can general-relativistic description of gravitation be considered
complete? | Essay Awarded "Honorable Mention" by Gravity Research Foundation
(1998). The answer to the question posed in the title is an experimentally
verifiable "no." | Mod.Phys.Lett.A13:1393-1400,1998 | 10.1142/S0217732398001455 | LA-UR-98-1159 | gr-qc astro-ph hep-ph hep-th quant-ph | null | The local galactic cluster, the Great attractor, embeds us in a dimensionless
gravitational potential of about - 3 x 10^{-5}. In the solar system this
potential is constant to about 1 part in 10^{11}. Consequently, planetary
orbits, which are determined by the gradient in the gravitational potential,
remain unaffected. However, this is not so for the recently introduced
flavor-oscillation clocks where the new redshift-inducing phases depend on the
gravitational potential itself. On these grounds, and by studying the
invariance properties of the gravitational phenomenon in the weak fields, we
argue that there exists an element of incompleteness in the
general-relativistic description of gravitation. An incompleteness-establishing
inequality is derived and an experiment is outlined to test the thesis
presented.
| [
{
"created": "Mon, 18 May 1998 15:36:47 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ahluwalia",
"D. V.",
""
]
] | The local galactic cluster, the Great attractor, embeds us in a dimensionless gravitational potential of about - 3 x 10^{-5}. In the solar system this potential is constant to about 1 part in 10^{11}. Consequently, planetary orbits, which are determined by the gradient in the gravitational potential, remain unaffected. However, this is not so for the recently introduced flavor-oscillation clocks where the new redshift-inducing phases depend on the gravitational potential itself. On these grounds, and by studying the invariance properties of the gravitational phenomenon in the weak fields, we argue that there exists an element of incompleteness in the general-relativistic description of gravitation. An incompleteness-establishing inequality is derived and an experiment is outlined to test the thesis presented. |
1309.5510 | Gines Perez Teruel | Gin\'es R. P\'erez Teruel | An alternative formulation of Classical Mechanics based on an analogy
with Thermodynamics | null | null | 10.1088/0143-0807/34/6/1589 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study new Legendre transforms in classical mechanics and investigate some
of their general properties. The behaviour of the new functions is analyzed
under coordinate transformations.When invariance under different kinds of
transformations are considered, the new formulation is found to be completly
equivalent to the usual Lagrangian formulation, recovering well established
results like the conservation of the angular momentum. Furthermore, a natural
generalization of the Poisson Bracket is found to be inherent to the formalism
introduced. On the other hand, we find that with a convenient redefinition of
the Lagrangian, $\mathcal{L}^{\prime}=-\mathcal{L}$, it is possible to
establish an exact one-to-one mathematical correspondence between the
thermodynamic potentials and the new potentials of classical mechanics
| [
{
"created": "Sat, 21 Sep 2013 18:24:20 GMT",
"version": "v1"
}
] | 2013-10-23 | [
[
"Teruel",
"Ginés R. Pérez",
""
]
] | We study new Legendre transforms in classical mechanics and investigate some of their general properties. The behaviour of the new functions is analyzed under coordinate transformations.When invariance under different kinds of transformations are considered, the new formulation is found to be completly equivalent to the usual Lagrangian formulation, recovering well established results like the conservation of the angular momentum. Furthermore, a natural generalization of the Poisson Bracket is found to be inherent to the formalism introduced. On the other hand, we find that with a convenient redefinition of the Lagrangian, $\mathcal{L}^{\prime}=-\mathcal{L}$, it is possible to establish an exact one-to-one mathematical correspondence between the thermodynamic potentials and the new potentials of classical mechanics |
gr-qc/9410002 | V. V. Zhytnikov | Vadim V. Zhytnikov and James M. Nester | Can Galactic Observations Be Explained by a Relativistic Gravity Theory? | 12p, REVTeX 3.0 | Phys.Rev.Lett. 73 (1994) 2950-2953 | 10.1103/PhysRevLett.73.2950 | null | gr-qc | null | We consider the possibility of an alternative gravity theory explaining the
dynamics of galactic systems without dark matter. From very general assumptions
about the structure of a relativistic gravity theory we derive a general
expression for the metric to order $(v/c)^2$. This allows us to compare the
predictions of the theory with various experimental data: the Newtonian limit,
light deflection and retardation, rotation of galaxies and gravitational
lensing. Our general conclusion is that the possibility for any gravity theory
to explain the behaviour of galaxies without dark matter is rather improbable.
| [
{
"created": "Tue, 4 Oct 1994 06:10:16 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Zhytnikov",
"Vadim V.",
""
],
[
"Nester",
"James M.",
""
]
] | We consider the possibility of an alternative gravity theory explaining the dynamics of galactic systems without dark matter. From very general assumptions about the structure of a relativistic gravity theory we derive a general expression for the metric to order $(v/c)^2$. This allows us to compare the predictions of the theory with various experimental data: the Newtonian limit, light deflection and retardation, rotation of galaxies and gravitational lensing. Our general conclusion is that the possibility for any gravity theory to explain the behaviour of galaxies without dark matter is rather improbable. |
1802.00885 | Michael Coughlin | Michael W. Coughlin, Alessio Cirone, Patrick Meyers, Sho Atsuta,
Valerio Boschi, Andrea Chincarini, Nelson L. Christensen, Rosario De Rosa,
Anamaria Effler, Irene Fiori, Mark Golkowski, Melissa Guidry, Jan Harms,
Kazuhiro Hayama, Yuu Kataoka, Jerzy Kubisz, Andrzej Kulak, Michael Laxen,
Andrew Matas, Janusz Mlynarczyk, Tsutomu Ogawa, Federico Paoletti, Jacobo
Salvador, Robert Schofield, Kentaro Somiya and Eric Thrane | Measurement and subtraction of Schumann resonances at gravitational-wave
interferometers | null | Phys. Rev. D 97, 102007 (2018) | 10.1103/PhysRevD.97.102007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Correlated magnetic noise from Schumann resonances threatens to contaminate
the observation of a stochastic gravitational-wave background in
interferometric detectors. In previous work, we reported on the first effort to
eliminate global correlated noise from the Schumann resonances using Wiener
filtering, demonstrating as much as a factor of two reduction in the coherence
between magnetometers on different continents. In this work, we present results
from dedicated magnetometer measurements at the Virgo and KAGRA sites, which
are the first results for subtraction using data from gravitational-wave
detector sites. We compare these measurements to a growing network of permanent
magnetometer stations, including at the LIGO sites. We show how dedicated
measurements can reduce coherence to a level consistent with uncorrelated
noise. We also show the effect of mutual magnetometer attraction, arguing that
magnetometers should be placed at least one meter from one another.
| [
{
"created": "Sat, 3 Feb 2018 00:30:54 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Feb 2018 01:27:36 GMT",
"version": "v2"
}
] | 2018-06-06 | [
[
"Coughlin",
"Michael W.",
""
],
[
"Cirone",
"Alessio",
""
],
[
"Meyers",
"Patrick",
""
],
[
"Atsuta",
"Sho",
""
],
[
"Boschi",
"Valerio",
""
],
[
"Chincarini",
"Andrea",
""
],
[
"Christensen",
"Nelson L.",
... | Correlated magnetic noise from Schumann resonances threatens to contaminate the observation of a stochastic gravitational-wave background in interferometric detectors. In previous work, we reported on the first effort to eliminate global correlated noise from the Schumann resonances using Wiener filtering, demonstrating as much as a factor of two reduction in the coherence between magnetometers on different continents. In this work, we present results from dedicated magnetometer measurements at the Virgo and KAGRA sites, which are the first results for subtraction using data from gravitational-wave detector sites. We compare these measurements to a growing network of permanent magnetometer stations, including at the LIGO sites. We show how dedicated measurements can reduce coherence to a level consistent with uncorrelated noise. We also show the effect of mutual magnetometer attraction, arguing that magnetometers should be placed at least one meter from one another. |
2306.10969 | Raja Solanki | Raja Solanki, Zinnat Hassan, P.K. Sahoo | Wormhole solutions in $f(R,L_m)$ gravity | Chinese Journal of Physics published version | Chinese Journal of Physics, 85 (2023) 74-88 | 10.1016/j.cjph.2023.06.005 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work, we intend to explore wormhole geometries in the framework of
$f(R,L_m)$ gravity. We derive the field equations for the generic $f(R,L_m)$
function by assuming the static and spherically symmetric Morris-Thorne
wormhole metric. Then we consider two non-linear $f(R,L_m)$ model,
specifically, $f(R,L_m)=\frac{R}{2}+L_m^\alpha$ and
$f(R,L_m)=\frac{R}{2}+(1+\lambda R)L_m$, where $\alpha$ and $\lambda$ are free
model parameters. We obtain the wormhole solutions by assuming three cases,
namely, a linear barotropic EoS, anisotropic EoS, and isotropic EoS
corresponding to model I. We observe that for both barotropic and anisotropic
cases, the corresponding wormhole solutions obey the flaring-out condition
under asymptotic background, while for the isotropic case, the shape function
does not follow the flatness condition. Also, we find that the null energy
condition exhibits negative behavior in the vicinity of the throat. Further, we
consider two different shape functions to investigate the behavior of model II.
We find some constraints on the model parameter for which the violation of the
null energy condition exhibits. Finally, we employ the volume integral
quantifier to calculate the amount of exotic matter required near the wormhole
throat for both models. We conclude that the modification of standard GR can
efficiently minimize the use of exotic matter and provide stable traversable
wormhole solutions.
| [
{
"created": "Mon, 19 Jun 2023 14:31:36 GMT",
"version": "v1"
}
] | 2023-08-01 | [
[
"Solanki",
"Raja",
""
],
[
"Hassan",
"Zinnat",
""
],
[
"Sahoo",
"P. K.",
""
]
] | In this work, we intend to explore wormhole geometries in the framework of $f(R,L_m)$ gravity. We derive the field equations for the generic $f(R,L_m)$ function by assuming the static and spherically symmetric Morris-Thorne wormhole metric. Then we consider two non-linear $f(R,L_m)$ model, specifically, $f(R,L_m)=\frac{R}{2}+L_m^\alpha$ and $f(R,L_m)=\frac{R}{2}+(1+\lambda R)L_m$, where $\alpha$ and $\lambda$ are free model parameters. We obtain the wormhole solutions by assuming three cases, namely, a linear barotropic EoS, anisotropic EoS, and isotropic EoS corresponding to model I. We observe that for both barotropic and anisotropic cases, the corresponding wormhole solutions obey the flaring-out condition under asymptotic background, while for the isotropic case, the shape function does not follow the flatness condition. Also, we find that the null energy condition exhibits negative behavior in the vicinity of the throat. Further, we consider two different shape functions to investigate the behavior of model II. We find some constraints on the model parameter for which the violation of the null energy condition exhibits. Finally, we employ the volume integral quantifier to calculate the amount of exotic matter required near the wormhole throat for both models. We conclude that the modification of standard GR can efficiently minimize the use of exotic matter and provide stable traversable wormhole solutions. |
0912.1393 | Muhammad Sharif | M. Sharif and M. Farasat Shamir | Plane Symmetric Solutions in f(R) Gravity | 10 pages, accepted for publication in Mod. Phys. Lett. A | Mod.Phys.Lett.A25:1281-1288,2010 | 10.1142/S0217732310032536 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The modified theories of gravity, especially the f(R) theory, have attracted
much attention in recent years. In this context, we explore static plane
symmetric vacuum solutions using the metric approach of this theory. The field
equations are solved using the assumption of constant scalar curvature which
may be zero or non-zero. We have found a total of three plane symmetric
solutions. The correspondence of these solutions with the well-known solutions
in General Relativity is given.
| [
{
"created": "Tue, 8 Dec 2009 03:09:30 GMT",
"version": "v1"
}
] | 2010-06-21 | [
[
"Sharif",
"M.",
""
],
[
"Shamir",
"M. Farasat",
""
]
] | The modified theories of gravity, especially the f(R) theory, have attracted much attention in recent years. In this context, we explore static plane symmetric vacuum solutions using the metric approach of this theory. The field equations are solved using the assumption of constant scalar curvature which may be zero or non-zero. We have found a total of three plane symmetric solutions. The correspondence of these solutions with the well-known solutions in General Relativity is given. |
gr-qc/0005077 | Mohammad Vahid Takook | M. V. Takook | Spin 1/2 Field Theory in the de Sitter space-time | 7 pages, Proceedings of the Group 21, 15-20 july 1996, Goslar,
Germany | null | null | null | gr-qc | null | A covariant quantization of the free spinor fields (s=1/2) in 4-dimensional
de Sitter (dS) space-time based on analyticity in the complexified
pseudo-Riemanian manifold is presented. We define the Wigthman two-point
function ${\cal W}(x,y)$, which satisfies the conditions of: a) positivity, b)
locality, c) covariance, and d) normal analyticity. Then the Hilbert space
structure and the field operators $\psi (f)$ are defined. A
coordinate-independent formula for the unsmeared field operator $\psi (x)$ is
also given.
| [
{
"created": "Wed, 17 May 2000 05:25:35 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Takook",
"M. V.",
""
]
] | A covariant quantization of the free spinor fields (s=1/2) in 4-dimensional de Sitter (dS) space-time based on analyticity in the complexified pseudo-Riemanian manifold is presented. We define the Wigthman two-point function ${\cal W}(x,y)$, which satisfies the conditions of: a) positivity, b) locality, c) covariance, and d) normal analyticity. Then the Hilbert space structure and the field operators $\psi (f)$ are defined. A coordinate-independent formula for the unsmeared field operator $\psi (x)$ is also given. |
1703.03958 | Luis Herrera | L. Herrera | The Gibbs paradox, the Landauer principle and the irreversibility
associated with tilted observers | 10 pages Latex. Invited contribution for the special issue "Advances
in Relativistic Statistical Mechanics" published in Entropy | Entropy, 19,110, (2017) | 10.3390/e19030110 | null | gr-qc astro-ph.CO physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known that, in the context of General Relativity, some spacetimes,
when described by a congruence of comoving observers, may consist in a
distribution of a perfect (non-dissipative) fluid, whereas the same spacetime
as seen by a "tilted"' (Lorentz-boosted) congruence of observers, may exhibit
the presence of dissipative processes. As we shall see, the appearence of
entropy producing processes are related to the tight dependence of entropy on
the specific congruence of observers. This fact is well illustrated by the
Gibbs paradox. The appearance of such dissipative processes, as required by the
Landauer principle, are necessary, in order to erase the different amount of
information stored by comoving observers, with respect to tilted ones.
| [
{
"created": "Sat, 11 Mar 2017 11:34:36 GMT",
"version": "v1"
}
] | 2017-03-14 | [
[
"Herrera",
"L.",
""
]
] | It is well known that, in the context of General Relativity, some spacetimes, when described by a congruence of comoving observers, may consist in a distribution of a perfect (non-dissipative) fluid, whereas the same spacetime as seen by a "tilted"' (Lorentz-boosted) congruence of observers, may exhibit the presence of dissipative processes. As we shall see, the appearence of entropy producing processes are related to the tight dependence of entropy on the specific congruence of observers. This fact is well illustrated by the Gibbs paradox. The appearance of such dissipative processes, as required by the Landauer principle, are necessary, in order to erase the different amount of information stored by comoving observers, with respect to tilted ones. |
gr-qc/0307045 | Dr. Anirudh Pradhan | Anirudh Pradhan and Abha Rai | Tilted Bianchi Type V Bulk Viscous Cosmological Models in General
Relativity | 14 pages | Astrophys.Space Sci. 291 (2004) 149-160 | 10.1023/B:astr.0000032069.58003.b4 | null | gr-qc | null | Conformally flat tilted Bianchi type V cosmological models in presence of a
bulk viscous fluid and heat flow are investigated. The coefficient of bulk
viscosity is assumed to be a power function of mass density. Some physical and
geometric aspects of the models are also discussed.
| [
{
"created": "Thu, 10 Jul 2003 04:15:34 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Pradhan",
"Anirudh",
""
],
[
"Rai",
"Abha",
""
]
] | Conformally flat tilted Bianchi type V cosmological models in presence of a bulk viscous fluid and heat flow are investigated. The coefficient of bulk viscosity is assumed to be a power function of mass density. Some physical and geometric aspects of the models are also discussed. |
2407.18410 | Igor Khavkine | Igor Khavkine, David McNutt, Lode Wylleman | IDEAL characterization of vacuum pp-waves | 47pp, tikz figures | null | null | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | An IDEAL characterization of a particular spacetime metric, $g_0$, consists
of a set of tensorial equations $T[g] = 0$ arising from expressions constructed
from the metric, $g$, its curvature tensor and its covariant derivatives and
which are satisfied if and only if $g$ is locally isometric to the original
metric $g_0$. Earlier applications of the IDEAL classification of spacetimes
relied on the construction of particular scalar polynomial curvature invariants
as an important step in the procedure.
In this paper we investigate the well-known class of vacuum pp-wave
spacetimes, where all scalar polynomial curvature invariants vanish, and
determine the applicability of an IDEAL classification for these spacetimes. We
consider a modification of the IDEAL approach which permits a corresponding
extension of the Stewart-Walker lemma. With this change, we are able to
construct invariants and IDEAL-ly classify all of the vacuum pp-wave solutions
which admit a two- or higher-dimensional isometry group, with the exception of
one case.
| [
{
"created": "Thu, 25 Jul 2024 21:47:25 GMT",
"version": "v1"
}
] | 2024-07-29 | [
[
"Khavkine",
"Igor",
""
],
[
"McNutt",
"David",
""
],
[
"Wylleman",
"Lode",
""
]
] | An IDEAL characterization of a particular spacetime metric, $g_0$, consists of a set of tensorial equations $T[g] = 0$ arising from expressions constructed from the metric, $g$, its curvature tensor and its covariant derivatives and which are satisfied if and only if $g$ is locally isometric to the original metric $g_0$. Earlier applications of the IDEAL classification of spacetimes relied on the construction of particular scalar polynomial curvature invariants as an important step in the procedure. In this paper we investigate the well-known class of vacuum pp-wave spacetimes, where all scalar polynomial curvature invariants vanish, and determine the applicability of an IDEAL classification for these spacetimes. We consider a modification of the IDEAL approach which permits a corresponding extension of the Stewart-Walker lemma. With this change, we are able to construct invariants and IDEAL-ly classify all of the vacuum pp-wave solutions which admit a two- or higher-dimensional isometry group, with the exception of one case. |
2312.06783 | Soumodeep Mitra | Soumodeep Mitra, Sumanta Chakraborty, Rodrigo Vicente, and Justin C.
Feng | Probing the quantum nature of black holes with ultra-light boson
environments | v2, 15 pages, 2 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Quantum black holes (BHs), thought of as an excited multilevel system, can be
effectively modelled by replacing an event horizon with a partially reflective
membrane. This emergent feature affects their interaction with hosting
environments, with the most pronounced effects happening for environments of
particles with mass~$m_{\rm p}\lesssim (10
M_{\odot}/M)\,10^{-11}\mathrm{\,eV/c^2}$, with~$M$ the BH mass. We show that
ultra-light bosons -- a viable dark matter candidate -- can be used to probe
the quantum nature of BHs. We derive analytical expressions for the accretion
rate and dynamical friction acting on exotic compact objects moving through an
ultra-light scalar field, which we then use to estimate the orbital de-phasing
in the inspiralling of different Laser Inteferometer Space Antenna (LISA)
binaries. Our results indicate that LISA may be able to discriminate quantum
from classical BHs.
| [
{
"created": "Mon, 11 Dec 2023 19:01:43 GMT",
"version": "v1"
},
{
"created": "Mon, 20 May 2024 04:35:28 GMT",
"version": "v2"
}
] | 2024-05-21 | [
[
"Mitra",
"Soumodeep",
""
],
[
"Chakraborty",
"Sumanta",
""
],
[
"Vicente",
"Rodrigo",
""
],
[
"Feng",
"Justin C.",
""
]
] | Quantum black holes (BHs), thought of as an excited multilevel system, can be effectively modelled by replacing an event horizon with a partially reflective membrane. This emergent feature affects their interaction with hosting environments, with the most pronounced effects happening for environments of particles with mass~$m_{\rm p}\lesssim (10 M_{\odot}/M)\,10^{-11}\mathrm{\,eV/c^2}$, with~$M$ the BH mass. We show that ultra-light bosons -- a viable dark matter candidate -- can be used to probe the quantum nature of BHs. We derive analytical expressions for the accretion rate and dynamical friction acting on exotic compact objects moving through an ultra-light scalar field, which we then use to estimate the orbital de-phasing in the inspiralling of different Laser Inteferometer Space Antenna (LISA) binaries. Our results indicate that LISA may be able to discriminate quantum from classical BHs. |
gr-qc/0111094 | Carlos Augusto Romero Filho | E. Anderson, F. Dahia, James E. Lidsey, and C. Romero | Embeddings in Spacetimes Sourced by Scalar Fields | RevTEX (11 pages)/ To appear in the Journal of Mathematical Physics | J.Math.Phys.44:5108-5119,2003 | 10.1063/1.1610237 | null | gr-qc | null | The extension of the Campbell-Magaard embedding theorem to general relativity
with minimally-coupled scalar fields is formulated and proven. The result is
applied to the case of a self-interacting scalar field for which new embeddings
are found, and to Brans-Dicke theory. The relationship between Campbell-Magaard
theorem and the general relativity, Cauchy and initial value problems is
outlined.
| [
{
"created": "Tue, 27 Nov 2001 18:23:41 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Sep 2003 17:15:41 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Anderson",
"E.",
""
],
[
"Dahia",
"F.",
""
],
[
"Lidsey",
"James E.",
""
],
[
"Romero",
"C.",
""
]
] | The extension of the Campbell-Magaard embedding theorem to general relativity with minimally-coupled scalar fields is formulated and proven. The result is applied to the case of a self-interacting scalar field for which new embeddings are found, and to Brans-Dicke theory. The relationship between Campbell-Magaard theorem and the general relativity, Cauchy and initial value problems is outlined. |
1708.07325 | Robert Owen | Robert Owen, Alex S. Fox, John A. Freiberg, Terrence Pierre Jacques | Black Hole Spin Axis in Numerical Relativity | 21 pages, 14 figures. Version 2 is a substantial revision, with a
much better treatment of rotation generators. Version 2 submitted to PRD | Phys. Rev. D 99, 084031 (2019) | 10.1103/PhysRevD.99.084031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Colliding black holes are systems of profound interest in both gravitational
wave astronomy and in gravitation theory, and a variety of methods have been
developed for modeling their dynamics in detail. The features of these dynamics
are determined by the masses of the holes and by the magnitudes and axes of
their spins. While masses and spin magnitudes can be defined in reasonably
unambiguous ways, the spin axis is a concept which despite great physical
importance is seriously undermined by the coordinate freedom of general
relativity. Despite a great wealth of detailed numerical simulations of generic
spinning black hole collisions, very little attention has gone into defining or
justifying the definitions of the spin axis used in the numerical relativity
literature. In this paper, we summarize and contrast the various spin direction
measures available in the SpEC code, including a comparison with a method
common in other codes, we explain why these measures have shown qualitatively
different nutation features than one would expect from post-Newtonian theory,
and we derive and implement new measures that give much better agreement.
| [
{
"created": "Thu, 24 Aug 2017 09:07:08 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Oct 2018 01:16:00 GMT",
"version": "v2"
}
] | 2019-04-24 | [
[
"Owen",
"Robert",
""
],
[
"Fox",
"Alex S.",
""
],
[
"Freiberg",
"John A.",
""
],
[
"Jacques",
"Terrence Pierre",
""
]
] | Colliding black holes are systems of profound interest in both gravitational wave astronomy and in gravitation theory, and a variety of methods have been developed for modeling their dynamics in detail. The features of these dynamics are determined by the masses of the holes and by the magnitudes and axes of their spins. While masses and spin magnitudes can be defined in reasonably unambiguous ways, the spin axis is a concept which despite great physical importance is seriously undermined by the coordinate freedom of general relativity. Despite a great wealth of detailed numerical simulations of generic spinning black hole collisions, very little attention has gone into defining or justifying the definitions of the spin axis used in the numerical relativity literature. In this paper, we summarize and contrast the various spin direction measures available in the SpEC code, including a comparison with a method common in other codes, we explain why these measures have shown qualitatively different nutation features than one would expect from post-Newtonian theory, and we derive and implement new measures that give much better agreement. |
2104.11343 | Robie Hennigar | Ivan Booth, Robie A. Hennigar, Daniel Pook-Kolb | Ultimate fate of apparent horizons during a binary black hole merger I:
Locating and understanding axisymmetric marginally outer trapped surfaces | 19 pages, 10 figures | null | 10.1103/PhysRevD.104.084083 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In classical numerical relativity, marginally outer trapped surfaces (MOTSs)
are the main tool to locate and characterize black holes. For five decades it
has been known that during a binary merger, a new outer horizon forms around
the initial apparent horizons of the individual holes once they are
sufficiently close together. However the ultimate fate of those initial
horizons has remained a subject of speculation. Recent axisymmetric studies
have shed new light on this process and this pair of papers essentially
completes that line of research: we resolve the key features of the
post-swallowing axisymmetric evolution of the initial horizons. This first
paper introduces a new shooting-method for finding axisymmetric MOTSs along
with a reinterpretation of the stability operator as the analogue of the Jacobi
equation for families of MOTSs. Here, these tools are used to study exact
solutions and initial data. In the sequel paper they are applied to black hole
mergers.
| [
{
"created": "Thu, 22 Apr 2021 22:57:18 GMT",
"version": "v1"
}
] | 2021-11-03 | [
[
"Booth",
"Ivan",
""
],
[
"Hennigar",
"Robie A.",
""
],
[
"Pook-Kolb",
"Daniel",
""
]
] | In classical numerical relativity, marginally outer trapped surfaces (MOTSs) are the main tool to locate and characterize black holes. For five decades it has been known that during a binary merger, a new outer horizon forms around the initial apparent horizons of the individual holes once they are sufficiently close together. However the ultimate fate of those initial horizons has remained a subject of speculation. Recent axisymmetric studies have shed new light on this process and this pair of papers essentially completes that line of research: we resolve the key features of the post-swallowing axisymmetric evolution of the initial horizons. This first paper introduces a new shooting-method for finding axisymmetric MOTSs along with a reinterpretation of the stability operator as the analogue of the Jacobi equation for families of MOTSs. Here, these tools are used to study exact solutions and initial data. In the sequel paper they are applied to black hole mergers. |
gr-qc/0104003 | Michael Heller | M. Heller, W. Sasin, Z. Odrzygozdz | Noncommutative regime of fundamental physics | LaTex, 38 pages | null | null | CGC 07/01 | gr-qc | null | We further develop a model unifying general relativity with quantum mechanics
proposed in our earlier papers (J. Math. Phys. 38, 5840 (1998); 41, 5168
(2000)). The model is based on a noncommutative algebra $A$ defined on a
groupoid $\Gamma = E \times G$ where $E$ is the total space of a fibre bundle
over space-time and $G$ a Lie group acting on $E$. In this paper, the algebra
$A$ is defined in such a way that the model works also if $G$ is a noncompact
group. Differential algebra based on derivations of this algebra is elaborated
which allows us to construct a "noncommutative general relativity". The left
regular representation of the algebra $A$ in a Hilbert space leads to the
quantum sector of our model. Its position and momentum representations are
discussed in some detail. It is shown that the model has correct correspondence
with the standard theories: with general relativity, by restricting the algebra
$A$ to a subset of its center; with quantum mechanics, by changing from the
groupoid $\Gamma $ to its algebroid; with classical mechanics, by changing from
the groupoid $\Gamma $ to its tangent groupoid. We also construct a
noncommutative Fock space based on the proposed model.
| [
{
"created": "Mon, 2 Apr 2001 09:37:41 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Heller",
"M.",
""
],
[
"Sasin",
"W.",
""
],
[
"Odrzygozdz",
"Z.",
""
]
] | We further develop a model unifying general relativity with quantum mechanics proposed in our earlier papers (J. Math. Phys. 38, 5840 (1998); 41, 5168 (2000)). The model is based on a noncommutative algebra $A$ defined on a groupoid $\Gamma = E \times G$ where $E$ is the total space of a fibre bundle over space-time and $G$ a Lie group acting on $E$. In this paper, the algebra $A$ is defined in such a way that the model works also if $G$ is a noncompact group. Differential algebra based on derivations of this algebra is elaborated which allows us to construct a "noncommutative general relativity". The left regular representation of the algebra $A$ in a Hilbert space leads to the quantum sector of our model. Its position and momentum representations are discussed in some detail. It is shown that the model has correct correspondence with the standard theories: with general relativity, by restricting the algebra $A$ to a subset of its center; with quantum mechanics, by changing from the groupoid $\Gamma $ to its algebroid; with classical mechanics, by changing from the groupoid $\Gamma $ to its tangent groupoid. We also construct a noncommutative Fock space based on the proposed model. |
2210.09265 | Yongqiang Wang | Shi-Xian Sun, Yong-Qiang Wang, Li Zhao | Chains of mini-boson stars | 15 pages, 5 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we re-investigate the stationary, soliton-like solutions in
the model of the Einstein gravity coupled to a free and complex scalar field,
which have been known as mini-boson stars. With numerical method, we find that
in addition to the usual single mini-boson star solution, there exist a novel
family of solutions interpreted as chains of boson stars, which is made of some
boson stars along the symmetry axis. We show the configuration of two types of
chains, including an even number of constituents and an odd number of
constituents. Furthermore, we also study the effect of the frequency of the
complex scalar field on the ADM mass $M$ and the $U(1)$ scalar charge $Q$. It
is interesting to note that the existence of chains of boson stars does not
require the introduction of a complex scalar field with self-interacting
potential.
| [
{
"created": "Mon, 17 Oct 2022 17:14:08 GMT",
"version": "v1"
}
] | 2022-10-18 | [
[
"Sun",
"Shi-Xian",
""
],
[
"Wang",
"Yong-Qiang",
""
],
[
"Zhao",
"Li",
""
]
] | In this paper, we re-investigate the stationary, soliton-like solutions in the model of the Einstein gravity coupled to a free and complex scalar field, which have been known as mini-boson stars. With numerical method, we find that in addition to the usual single mini-boson star solution, there exist a novel family of solutions interpreted as chains of boson stars, which is made of some boson stars along the symmetry axis. We show the configuration of two types of chains, including an even number of constituents and an odd number of constituents. Furthermore, we also study the effect of the frequency of the complex scalar field on the ADM mass $M$ and the $U(1)$ scalar charge $Q$. It is interesting to note that the existence of chains of boson stars does not require the introduction of a complex scalar field with self-interacting potential. |
1509.05357 | Alexei Deriglazov A | Alexei A. Deriglazov and Walberto Guzm\'an Ram\'irez | Mathisson-Papapetrou-Tulczyjew-Dixon (MPTD) equations in
ultra-relativistic regime and gravimagnetic moment | 5 pages, typos corrected, close to published version | International Journal of Modern Physics D Vol. 26 (2017) 1750047
(12 pages) | 10.1142/S021827181750047X | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Mathisson-Papapetrou-Tulczyjew-Dixon (MPTD) equations in the Lagrangian
formulation correspond to the minimal interaction of spin with gravity. Due to
the interaction, in the Lagrangian equations instead of the original metric $g$
emerges spin-dependent effective metric $G=g+h(S)$. So we need to decide, which
of them the MPTD particle sees as the space-time metric. We show that MPTD
equations, if considered with respect to original metric, have unsatisfactory
behavior: the acceleration in the direction of velocity grows up to infinity in
the ultra-relativistic limit. If considered with respect to $G$, the theory has
no this problem. But the metric now depends on spin, so there is no unique
space-time manifold for the Universe of spinning particles: each particle
probes his own three-dimensional geometry. This can be improved by adding a
non-minimal interaction of spin with gravity through gravimagnetic moment. The
modified MPTD equations with unit gravimagnetic moment have reasonable behavior
within the original metric.
| [
{
"created": "Thu, 17 Sep 2015 18:24:13 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Oct 2016 13:04:45 GMT",
"version": "v2"
}
] | 2016-11-10 | [
[
"Deriglazov",
"Alexei A.",
""
],
[
"Ramírez",
"Walberto Guzmán",
""
]
] | Mathisson-Papapetrou-Tulczyjew-Dixon (MPTD) equations in the Lagrangian formulation correspond to the minimal interaction of spin with gravity. Due to the interaction, in the Lagrangian equations instead of the original metric $g$ emerges spin-dependent effective metric $G=g+h(S)$. So we need to decide, which of them the MPTD particle sees as the space-time metric. We show that MPTD equations, if considered with respect to original metric, have unsatisfactory behavior: the acceleration in the direction of velocity grows up to infinity in the ultra-relativistic limit. If considered with respect to $G$, the theory has no this problem. But the metric now depends on spin, so there is no unique space-time manifold for the Universe of spinning particles: each particle probes his own three-dimensional geometry. This can be improved by adding a non-minimal interaction of spin with gravity through gravimagnetic moment. The modified MPTD equations with unit gravimagnetic moment have reasonable behavior within the original metric. |
gr-qc/9903090 | Doc. Ing. Jozef Sima DRSc. | Jozef Sima and Miroslav Sukenik | The expansive nondecelerative universe - Gravitational effects and their
manifestation in black holes evaporation and far-infrared spectra | 7 pages, AmsTex | null | null | SS-99-01 | gr-qc | null | The paper summarizes the background of Expensive Nondecelerative Universe
model and its main consequences for gravitation. Applying the Vaidya metrics,
the model allows for the localization and determination of the density and
quantity of gravitational energy created by a body with the mass m in the
distance r. The consequences are manifested both in a macrosystem (Hawking's
phenomenon of black holes evaporation) and microworld phenomenon (far-infrared
spectral properties)
| [
{
"created": "Wed, 24 Mar 1999 12:20:07 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sima",
"Jozef",
""
],
[
"Sukenik",
"Miroslav",
""
]
] | The paper summarizes the background of Expensive Nondecelerative Universe model and its main consequences for gravitation. Applying the Vaidya metrics, the model allows for the localization and determination of the density and quantity of gravitational energy created by a body with the mass m in the distance r. The consequences are manifested both in a macrosystem (Hawking's phenomenon of black holes evaporation) and microworld phenomenon (far-infrared spectral properties) |
0709.1630 | Paul Frampton | Paul Frampton | Comment on ``Can Black Holes be Torn Up by a Phantom in Cyclic
Cosmology?" by X. Zhang. arXiv:0708.1408 [gr-qc] | 3 pages latex | null | null | null | gr-qc | null | In a recently archived paper by Zhang\cite{Zhang}, it is claimed that before
turnaround in a cyclic model two unexpected events happen: (1) black holes
cease to contract and begin to expand; (2) separated causal patches start to
reconnect. We show that both conclusions are erroneous and result from the
author's choice of variables.
| [
{
"created": "Tue, 11 Sep 2007 13:59:49 GMT",
"version": "v1"
}
] | 2007-09-12 | [
[
"Frampton",
"Paul",
""
]
] | In a recently archived paper by Zhang\cite{Zhang}, it is claimed that before turnaround in a cyclic model two unexpected events happen: (1) black holes cease to contract and begin to expand; (2) separated causal patches start to reconnect. We show that both conclusions are erroneous and result from the author's choice of variables. |
gr-qc/9810025 | Dmitry Korotkin | M.V.Babich and D.A.Korotkin | Self-dual SU(2) invariant Einstein metrics and modular dependence of
theta-functions | Misprints corrected | Lett.Math.Phys. 46 (1998) 323-337 | null | AEI-088 | gr-qc math.DG nlin.SI | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We simplify Hitchin's description of SU(2)-invariant self-dual Einstein
metrics, making use of the tau-function of related four-pole Schlesinger
system.
| [
{
"created": "Wed, 7 Oct 1998 20:42:42 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Mar 2014 00:52:03 GMT",
"version": "v2"
},
{
"created": "Tue, 24 Oct 2023 15:16:41 GMT",
"version": "v3"
}
] | 2023-10-25 | [
[
"Babich",
"M. V.",
""
],
[
"Korotkin",
"D. A.",
""
]
] | We simplify Hitchin's description of SU(2)-invariant self-dual Einstein metrics, making use of the tau-function of related four-pole Schlesinger system. |
gr-qc/0504144 | Husnu Baysal | H. Baysal and I. Yilmaz | Timelike and Spacelike Ricci Collineation Vectors in String Fluid | 10 pages | null | null | null | gr-qc | null | We study the consequences of the existence of timelike and spacelike Ricci
collineation vectors (RCVs) for string fluid in the context of general
relativity. Necessary and sufficient conditions are derived for a space-time
with string fluid to admit a timelike RCV, parallel to $u^a$, and a spacelike
RCV, parallel to $n^a$. In these cases, some results obtained are discussed.
| [
{
"created": "Fri, 29 Apr 2005 12:38:15 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Baysal",
"H.",
""
],
[
"Yilmaz",
"I.",
""
]
] | We study the consequences of the existence of timelike and spacelike Ricci collineation vectors (RCVs) for string fluid in the context of general relativity. Necessary and sufficient conditions are derived for a space-time with string fluid to admit a timelike RCV, parallel to $u^a$, and a spacelike RCV, parallel to $n^a$. In these cases, some results obtained are discussed. |
1711.08380 | Carlos M. Sendra | Ernesto F. Eiroa, Carlos M. Sendra | Shadow cast by rotating braneworld black holes with a cosmological
constant | 12 pages, 4 figures; v2: minor changes | Eur. Phys. J. C (2018) 78:91 | 10.1140/epjc/s10052-018-5586-6 | null | gr-qc astro-ph.CO astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, we study the shadow produced by rotating black holes with a
tidal charge in a Randall-Sundrum braneworld model, with a cosmological
constant. We obtain the apparent shape and the corresponding observables for
different values of the tidal charge and the rotation parameter, and we analyze
the influence of the presence of the cosmological constant. We also discuss the
observational prospects for this optical effect.
| [
{
"created": "Wed, 22 Nov 2017 16:38:58 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Feb 2018 17:00:07 GMT",
"version": "v2"
}
] | 2018-02-02 | [
[
"Eiroa",
"Ernesto F.",
""
],
[
"Sendra",
"Carlos M.",
""
]
] | In this article, we study the shadow produced by rotating black holes with a tidal charge in a Randall-Sundrum braneworld model, with a cosmological constant. We obtain the apparent shape and the corresponding observables for different values of the tidal charge and the rotation parameter, and we analyze the influence of the presence of the cosmological constant. We also discuss the observational prospects for this optical effect. |
1501.07274 | Emanuele Berti | Emanuele Berti, Enrico Barausse, Vitor Cardoso, Leonardo Gualtieri,
Paolo Pani, Ulrich Sperhake, Leo C. Stein, Norbert Wex, Kent Yagi, Tessa
Baker, C. P. Burgess, Fl\'avio S. Coelho, Daniela Doneva, Antonio De Felice,
Pedro G. Ferreira, Paulo C. C. Freire, James Healy, Carlos Herdeiro, Michael
Horbatsch, Burkhard Kleihaus, Antoine Klein, Kostas Kokkotas, Jutta Kunz,
Pablo Laguna, Ryan N. Lang, Tjonnie G. F. Li, Tyson Littenberg, Andrew Matas,
Saeed Mirshekari, Hirotada Okawa, Eugen Radu, Richard O'Shaughnessy,
Bangalore S. Sathyaprakash, Chris Van Den Broeck, Hans A. Winther, Helvi
Witek, Mir Emad Aghili, Justin Alsing, Brett Bolen, Luca Bombelli, Sarah
Caudill, Liang Chen, Juan Carlos Degollado, Ryuichi Fujita, Caixia Gao,
Davide Gerosa, Saeed Kamali, Hector O. Silva, Jo\~ao G. Rosa, Laleh
Sadeghian, Marco Sampaio, Hajime Sotani, Miguel Zilhao | Testing General Relativity with Present and Future Astrophysical
Observations | 188 pages, 46 figures, 6 tables, 903 references. Matches version
published in Classical and Quantum Gravity. Supplementary data files
available at http://www.phy.olemiss.edu/~berti/research/ and
http://centra.tecnico.ulisboa.pt/network/grit/files/ | Class. Quantum Grav. 32, 243001 (2015) | 10.1088/0264-9381/32/24/243001 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One century after its formulation, Einstein's general relativity has made
remarkable predictions and turned out to be compatible with all experimental
tests. Most of these tests probe the theory in the weak-field regime, and there
are theoretical and experimental reasons to believe that general relativity
should be modified when gravitational fields are strong and spacetime curvature
is large. The best astrophysical laboratories to probe strong-field gravity are
black holes and neutron stars, whether isolated or in binary systems. We review
the motivations to consider extensions of general relativity. We present a
(necessarily incomplete) catalog of modified theories of gravity for which
strong-field predictions have been computed and contrasted to Einstein's
theory, and we summarize our current understanding of the structure and
dynamics of compact objects in these theories. We discuss current bounds on
modified gravity from binary pulsar and cosmological observations, and we
highlight the potential of future gravitational wave measurements to inform us
on the behavior of gravity in the strong-field regime.
| [
{
"created": "Wed, 28 Jan 2015 21:00:11 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Feb 2015 17:23:39 GMT",
"version": "v2"
},
{
"created": "Tue, 22 Sep 2015 23:43:01 GMT",
"version": "v3"
},
{
"created": "Wed, 2 Dec 2015 03:09:26 GMT",
"version": "v4"
}
] | 2015-12-03 | [
[
"Berti",
"Emanuele",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Gualtieri",
"Leonardo",
""
],
[
"Pani",
"Paolo",
""
],
[
"Sperhake",
"Ulrich",
""
],
[
"Stein",
"Leo C.",
""
],
[
... | One century after its formulation, Einstein's general relativity has made remarkable predictions and turned out to be compatible with all experimental tests. Most of these tests probe the theory in the weak-field regime, and there are theoretical and experimental reasons to believe that general relativity should be modified when gravitational fields are strong and spacetime curvature is large. The best astrophysical laboratories to probe strong-field gravity are black holes and neutron stars, whether isolated or in binary systems. We review the motivations to consider extensions of general relativity. We present a (necessarily incomplete) catalog of modified theories of gravity for which strong-field predictions have been computed and contrasted to Einstein's theory, and we summarize our current understanding of the structure and dynamics of compact objects in these theories. We discuss current bounds on modified gravity from binary pulsar and cosmological observations, and we highlight the potential of future gravitational wave measurements to inform us on the behavior of gravity in the strong-field regime. |
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