id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0005120 | Diego M. Forni | Diego M. Forni, Mirta Iriondo and Carlos N. Kozameh | Null surfaces formulation in 3D | 15 pp., 4 figures, to appear in J. Math. Phys | J.Math.Phys. 41 (2000) 5517-5534 | 10.1063/1.533422 | null | gr-qc | null | The Null Surface Formulation of General Relativity is developed for 2+1
dimensional gravity. The geometrical meaning of the metricity condition is
analyzed and two approaches to the derivation of the field equations are
presented. One method makes explicit use of the conformal factor while the
other only uses conformal information. The resulting set of equations contain
the same geometrical meaning as the 4-D formulation without the technical
complexities of the higher dimensional analog. A canonical family of null
surfaces in this formulation, the light cone cuts of null infinity, are
constructed on asymptotically flat space times and some of their kinematical
aspects discussed. A particular example, which nevertheless contains most of
the generic features is explicitly constructed and analyzed, revealing the
behavior predicted in the full theory.
| [
{
"created": "Fri, 26 May 2000 22:13:26 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Forni",
"Diego M.",
""
],
[
"Iriondo",
"Mirta",
""
],
[
"Kozameh",
"Carlos N.",
""
]
] | The Null Surface Formulation of General Relativity is developed for 2+1 dimensional gravity. The geometrical meaning of the metricity condition is analyzed and two approaches to the derivation of the field equations are presented. One method makes explicit use of the conformal factor while the other only uses conformal information. The resulting set of equations contain the same geometrical meaning as the 4-D formulation without the technical complexities of the higher dimensional analog. A canonical family of null surfaces in this formulation, the light cone cuts of null infinity, are constructed on asymptotically flat space times and some of their kinematical aspects discussed. A particular example, which nevertheless contains most of the generic features is explicitly constructed and analyzed, revealing the behavior predicted in the full theory. |
1404.0006 | Adam Solomon | Yashar Akrami, Tomi S. Koivisto, Adam R. Solomon | The nature of spacetime in bigravity: two metrics or none? | 4 pages, no figures | Gen. Relativ. Gravit. 47 (2015) 1838 | 10.1007/s10714-014-1838-4 | NORDITA-2014-41 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The possibility of matter coupling to two metrics at once is considered. This
appears natural in the most general ghost-free, bimetric theory of gravity,
where it unlocks an additional symmetry with respect to the exchange of the
metrics. This double coupling, however, raises the problem of identifying the
observables of the theory. It is shown that if the two metrics couple minimally
to matter, then there is no physical metric to which all matter would
universally couple, and that moreover such an effective metric generically does
not exist even for an individual matter species. By studying point particle
dynamics, a resolution is suggested in the context of Finsler geometry.
| [
{
"created": "Mon, 31 Mar 2014 20:00:04 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Aug 2014 00:19:56 GMT",
"version": "v2"
}
] | 2015-11-10 | [
[
"Akrami",
"Yashar",
""
],
[
"Koivisto",
"Tomi S.",
""
],
[
"Solomon",
"Adam R.",
""
]
] | The possibility of matter coupling to two metrics at once is considered. This appears natural in the most general ghost-free, bimetric theory of gravity, where it unlocks an additional symmetry with respect to the exchange of the metrics. This double coupling, however, raises the problem of identifying the observables of the theory. It is shown that if the two metrics couple minimally to matter, then there is no physical metric to which all matter would universally couple, and that moreover such an effective metric generically does not exist even for an individual matter species. By studying point particle dynamics, a resolution is suggested in the context of Finsler geometry. |
1006.1169 | Subenoy Chakraborty | Subenoy Chakraborty, Ritabrata Biswas, Nairwita Mazumder | Unified First Law and Some Comments | 5 pages | Nuovo Cim.B125:1209-1214,2011 | 10.1393/ncb/i2010-10912-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this small article, unified first law has been analyzed and some results
have been deduced from it. The results have been presented in the form of
lemmas and some conclusions have been drawn from them.
| [
{
"created": "Mon, 7 Jun 2010 04:06:51 GMT",
"version": "v1"
}
] | 2011-04-12 | [
[
"Chakraborty",
"Subenoy",
""
],
[
"Biswas",
"Ritabrata",
""
],
[
"Mazumder",
"Nairwita",
""
]
] | In this small article, unified first law has been analyzed and some results have been deduced from it. The results have been presented in the form of lemmas and some conclusions have been drawn from them. |
gr-qc/0103021 | T. R. Mongan | T. R. Mongan | A simple quantum cosmology | To be published in General Relativity and Gravitation, August 2001 | Gen.Rel.Grav. 33 (2001) 1415-1424 | 10.1023/A:1012065826750 | null | gr-qc astro-ph hep-ph | null | A simple and surprisingly realistic model of the origin of the universe can
be developed using the Friedmann equation from general relativity, elementary
quantum mechanics, and the experimental values of h, c, G and the proton mass.
The model assumes there are N space dimensions (with N > 6) and the potential
constraining the radius r of the invisible N -3 compact dimensions varies as
r^4. In this model, the universe has zero total energy and is created from
nothing. There is no initial singularity. If space-time is eleven dimensional,
as required by M theory, the scalar field corresponding to the size of the
compact dimensions inflates the universe by about 26 orders of magnitude (60
e-folds). If the Hubble constant is 65 km/sec Mpc, the energy density of the
scalar field after inflation results in Omega-sub-Lambda = 0.68, in agreement
with recent astrophysical observations.
| [
{
"created": "Thu, 8 Mar 2001 00:27:05 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Mongan",
"T. R.",
""
]
] | A simple and surprisingly realistic model of the origin of the universe can be developed using the Friedmann equation from general relativity, elementary quantum mechanics, and the experimental values of h, c, G and the proton mass. The model assumes there are N space dimensions (with N > 6) and the potential constraining the radius r of the invisible N -3 compact dimensions varies as r^4. In this model, the universe has zero total energy and is created from nothing. There is no initial singularity. If space-time is eleven dimensional, as required by M theory, the scalar field corresponding to the size of the compact dimensions inflates the universe by about 26 orders of magnitude (60 e-folds). If the Hubble constant is 65 km/sec Mpc, the energy density of the scalar field after inflation results in Omega-sub-Lambda = 0.68, in agreement with recent astrophysical observations. |
1106.2411 | Muhammad Sharif | M. Sharif | The Pseudo-Newtonian Force and Potential of the Stringy Black Holes | 8 pages, accepted for publication in Romanian J. Physics | Rom. J. Phys. 56(2011)1035-1040 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is devoted to investigate the structure of the pseudo-Newtonian
force and potential of the stringy black holes. We discuss conditions for the
force character from an attractive to repulsive. It is also found that the
force will reach a maximum under certain conditions. Also, the ratio of mass
and charge is evaluated for the maximum force.
| [
{
"created": "Mon, 13 Jun 2011 10:36:07 GMT",
"version": "v1"
}
] | 2011-09-29 | [
[
"Sharif",
"M.",
""
]
] | This paper is devoted to investigate the structure of the pseudo-Newtonian force and potential of the stringy black holes. We discuss conditions for the force character from an attractive to repulsive. It is also found that the force will reach a maximum under certain conditions. Also, the ratio of mass and charge is evaluated for the maximum force. |
2202.05266 | Vishnu Jejjala | Vishnu Jejjala, Michael Kavic, Djordje Minic, Tatsu Takeuchi | First Principles Phenomenology of $H_0$ | 15 pages, 1 figure, LaTeX | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter we discuss infinite statistics and motivate its role in
quantum gravity. Then, we connect infinite statistics to a dynamical form of
dark energy, and we obtain an expression for the evolution of the Hubble
parameter that we compare to observation. The equation of state parameter
$w_{eff} < -1$ in this framework.
| [
{
"created": "Thu, 10 Feb 2022 18:59:59 GMT",
"version": "v1"
}
] | 2022-02-11 | [
[
"Jejjala",
"Vishnu",
""
],
[
"Kavic",
"Michael",
""
],
[
"Minic",
"Djordje",
""
],
[
"Takeuchi",
"Tatsu",
""
]
] | In this letter we discuss infinite statistics and motivate its role in quantum gravity. Then, we connect infinite statistics to a dynamical form of dark energy, and we obtain an expression for the evolution of the Hubble parameter that we compare to observation. The equation of state parameter $w_{eff} < -1$ in this framework. |
0902.0911 | Sergiu I. Vacaru | Sergiu I. Vacaru | Nonholomic Distributions and Gauge Models of Einstein Gravity | v4,latex2e, 39 pages, accepted for IJGMMP 7 (2010) | Int.J.Geom.Meth.Mod.Phys.7:215-246,2010 | null | null | gr-qc hep-th math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For (2+2)-dimensional nonholonomic distributions, the physical information
contained into a spacetime (pseudo) Riemannian metric can be encoded
equivalently into new types of geometric structures and linear connections
constructed as nonholonomic deformations of the Levi-Civita connection. Such
deformations and induced geometric/physical objects are completely determined
by a prescribed metric tensor. Reformulation of the Einstein equations in
nonholonomic variables (tetrads and new connections, for instance, with
constant coefficient curvatures and/or Yang-Mills like potentials) reveals
hidden geometric and rich quantum structures. It is shown how the Einstein
gravity theory can be re-defined equivalently as certain gauge models on
nonholonomic affine and/or de Sitter frame bundles. We speculate on possible
applications of the geometry of nonholonomic distributions with associated
nonlinear connections in classical and quantum gravity.
| [
{
"created": "Thu, 5 Feb 2009 20:16:56 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Feb 2009 21:53:30 GMT",
"version": "v2"
},
{
"created": "Tue, 17 Feb 2009 02:41:10 GMT",
"version": "v3"
},
{
"created": "Sat, 21 Nov 2009 20:35:36 GMT",
"version": "v4"
}
] | 2010-04-08 | [
[
"Vacaru",
"Sergiu I.",
""
]
] | For (2+2)-dimensional nonholonomic distributions, the physical information contained into a spacetime (pseudo) Riemannian metric can be encoded equivalently into new types of geometric structures and linear connections constructed as nonholonomic deformations of the Levi-Civita connection. Such deformations and induced geometric/physical objects are completely determined by a prescribed metric tensor. Reformulation of the Einstein equations in nonholonomic variables (tetrads and new connections, for instance, with constant coefficient curvatures and/or Yang-Mills like potentials) reveals hidden geometric and rich quantum structures. It is shown how the Einstein gravity theory can be re-defined equivalently as certain gauge models on nonholonomic affine and/or de Sitter frame bundles. We speculate on possible applications of the geometry of nonholonomic distributions with associated nonlinear connections in classical and quantum gravity. |
gr-qc/0611097 | Simone Speziale | Jonathan Hackett and Simone Speziale | Grasping rules and semiclassical limit of the geometry in the
Ponzano-Regge model | 18 pages, 1 figure | Class.Quant.Grav.24:1525-1546,2007 | 10.1088/0264-9381/24/6/010 | null | gr-qc | null | We show how the expectation values of geometrical quantities in 3d quantum
gravity can be explicitly computed using grasping rules. We compute the volume
of a labelled tetrahedron using the triple grasping. We show that the large
spin expansion of this value is dominated by the classical expression, and we
study the next to leading order quantum corrections.
| [
{
"created": "Fri, 17 Nov 2006 20:46:10 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Hackett",
"Jonathan",
""
],
[
"Speziale",
"Simone",
""
]
] | We show how the expectation values of geometrical quantities in 3d quantum gravity can be explicitly computed using grasping rules. We compute the volume of a labelled tetrahedron using the triple grasping. We show that the large spin expansion of this value is dominated by the classical expression, and we study the next to leading order quantum corrections. |
2107.05269 | Florencia Anabella Teppa Pannia | Florencia Anabella Teppa Pannia, Santiago Esteban Perez Bergliaffa and
Nelson Pinto-Neto | Particle Production in Accelerated Thin Bubbles | 14 pages, 3 figures | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We investigate the creation of scalar particles inside a region delimited by
a bubble which is expanding with non-zero acceleration. The bubble is modelled
as a thin shell and plays the role of a moving boundary, thus influencing the
fluctuations of the test scalar field inside it. Bubbles expanding in Minkowski
spacetime as well as those dividing two de Sitter spacetimes are explored in a
unified way. Our results for the Bogoliubov coefficient $\beta_k$ in the
adiabatic approximation show that in all cases the creation of scalar particles
decreases with the mass, and is much more significant in the case of nonzero
curvature. They also show that the dynamics of the bubble and its size are
relevant for particle creation, but in the dS-dS case the combination of both
effects leads to a behaviour different from that of Minkowski space-time, due
to the presence of a length scale (the Hubble radius of the internal geometry).
| [
{
"created": "Mon, 12 Jul 2021 09:04:15 GMT",
"version": "v1"
}
] | 2021-07-13 | [
[
"Pannia",
"Florencia Anabella Teppa",
""
],
[
"Bergliaffa",
"Santiago Esteban Perez",
""
],
[
"Pinto-Neto",
"Nelson",
""
]
] | We investigate the creation of scalar particles inside a region delimited by a bubble which is expanding with non-zero acceleration. The bubble is modelled as a thin shell and plays the role of a moving boundary, thus influencing the fluctuations of the test scalar field inside it. Bubbles expanding in Minkowski spacetime as well as those dividing two de Sitter spacetimes are explored in a unified way. Our results for the Bogoliubov coefficient $\beta_k$ in the adiabatic approximation show that in all cases the creation of scalar particles decreases with the mass, and is much more significant in the case of nonzero curvature. They also show that the dynamics of the bubble and its size are relevant for particle creation, but in the dS-dS case the combination of both effects leads to a behaviour different from that of Minkowski space-time, due to the presence of a length scale (the Hubble radius of the internal geometry). |
2305.07595 | Gustavo Brito | Gustavo P. de Brito, Astrid Eichhorn, Ludivine Fausten | Towards a bound on the Higgs mass in causal set quantum gravity | null | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the Standard Model of particle physics, the mass of the Higgs particle can
be linked to the scale at which the Standard Model breaks down due to a Landau
pole/triviality problem: for a Higgs mass somewhat higher than the measured
value, the Standard Model breaks down before the Planck scale. We take a first
step towards investigating this relation in the context of causal set quantum
gravity. We use a scalar-field propagator that carries the imprints of
spacetime discreteness in a modified ultraviolet behavior that depends on a
nonlocality scale. We investigate whether the modification can shift the scale
of the Landau pole in a scalar field theory with quartic interaction. We
discover that the modifications speed up the onset of the Landau pole
considerably, so that the scale of new physics occurs roughly at the
nonlocality scale. Our results call into question, whether a separation between
the nonlocality scale and the discreteness scale, which is postulated within
causal set quantum gravity, and which has been argued to give rise to
phenomenological consequences, is in fact achievable. Methodologically, our
paper is the first to apply continuum functional Renormalization Group
techniques in the context of a causal-set inspired setting.
| [
{
"created": "Fri, 12 May 2023 16:40:57 GMT",
"version": "v1"
}
] | 2023-05-15 | [
[
"de Brito",
"Gustavo P.",
""
],
[
"Eichhorn",
"Astrid",
""
],
[
"Fausten",
"Ludivine",
""
]
] | In the Standard Model of particle physics, the mass of the Higgs particle can be linked to the scale at which the Standard Model breaks down due to a Landau pole/triviality problem: for a Higgs mass somewhat higher than the measured value, the Standard Model breaks down before the Planck scale. We take a first step towards investigating this relation in the context of causal set quantum gravity. We use a scalar-field propagator that carries the imprints of spacetime discreteness in a modified ultraviolet behavior that depends on a nonlocality scale. We investigate whether the modification can shift the scale of the Landau pole in a scalar field theory with quartic interaction. We discover that the modifications speed up the onset of the Landau pole considerably, so that the scale of new physics occurs roughly at the nonlocality scale. Our results call into question, whether a separation between the nonlocality scale and the discreteness scale, which is postulated within causal set quantum gravity, and which has been argued to give rise to phenomenological consequences, is in fact achievable. Methodologically, our paper is the first to apply continuum functional Renormalization Group techniques in the context of a causal-set inspired setting. |
2001.01281 | Yannick Herfray | Yannick Herfray | Asymptotic Shear and the Intrinsic Conformal Geometry of Null-Infinity | This is the version accepted for publication: Extra references and
corrected a few typos | Journal of Mathematical Physics 61, 072502 (2020) | 10.1063/5.0003616 | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we propose a new geometrization of the radiative phase space
of asymptotically flat space-times: we show that the geometry induced on
null-infinity by the presence of gravitational waves can be understood to be a
generalisation of the tractor calculus of conformal manifolds adapted to the
case of degenerate conformal metrics. It follows that the whole formalism is,
by construction, manifestly conformally invariant. We first show that a choice
of asymptotic shear amounts to a choice of linear differential operator of
order two on the bundle of scales of null-infinity. We refer to these operators
as Poincar\'e operators. We then show that Poincar\'e operators are in
one-to-one correspondence with a particular class of tractor connections which
we call "null-normal" (they generalise the normal tractor connection of
conformal geometry). The tractor curvature encodes the presence of
gravitational waves and the non-uniqueness of flat null-normal tractor
connections correspond to the "degeneracy of gravity vacua" that has been
extensively discussed in the literature. This work thus brings back the
investigation of the radiative phase space of gravity to the study of (Cartan)
connections and associated bundles. This should allow, in particular, to
proliferate invariants of the phase space.
| [
{
"created": "Sun, 5 Jan 2020 18:08:59 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Jan 2020 19:45:19 GMT",
"version": "v2"
},
{
"created": "Thu, 27 Aug 2020 08:22:57 GMT",
"version": "v3"
}
] | 2020-08-28 | [
[
"Herfray",
"Yannick",
""
]
] | In this article we propose a new geometrization of the radiative phase space of asymptotically flat space-times: we show that the geometry induced on null-infinity by the presence of gravitational waves can be understood to be a generalisation of the tractor calculus of conformal manifolds adapted to the case of degenerate conformal metrics. It follows that the whole formalism is, by construction, manifestly conformally invariant. We first show that a choice of asymptotic shear amounts to a choice of linear differential operator of order two on the bundle of scales of null-infinity. We refer to these operators as Poincar\'e operators. We then show that Poincar\'e operators are in one-to-one correspondence with a particular class of tractor connections which we call "null-normal" (they generalise the normal tractor connection of conformal geometry). The tractor curvature encodes the presence of gravitational waves and the non-uniqueness of flat null-normal tractor connections correspond to the "degeneracy of gravity vacua" that has been extensively discussed in the literature. This work thus brings back the investigation of the radiative phase space of gravity to the study of (Cartan) connections and associated bundles. This should allow, in particular, to proliferate invariants of the phase space. |
0807.1640 | Francisco Lobo | Francisco S. N. Lobo | The dark side of gravity: Modified theories of gravity | 17 pages, invited chapter to appear in an edited collection 'Dark
Energy-Current Advances and Ideas' | Dark Energy-Current Advances and Ideas, 173-204 (2009), Research
Signpost, ISBN 978-81-308-0341-8 | null | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modern astrophysical and cosmological models are faced with two severe
theoretical difficulties, that can be summarized as the dark energy and the
dark matter problems. Relative to the former, it has been stated that cosmology
has entered a 'golden age', in which high-precision observational data have
confirmed with startling evidence that the Universe is undergoing a phase of
accelerated expansion. Several candidates, responsible for this expansion, have
been proposed in the literature, in particular, dark energy models and modified
gravity, amongst others. One is liable to ask: What is the so-called 'dark
energy' that is driving the acceleration of the universe? Is it a vacuum energy
or a dynamical field (''quintessence'')? Or is the acceleration due to
infra-red modifications of Einstein's theory of General Relativity? In the
context of dark matter, two observations, namely, the behavior of the galactic
rotation curves and the mass discrepancy in galactic clusters, suggest the
existence of a (non or weakly interacting) form of dark matter at galactic and
extra-galactic scales. It has also been proposed that modified gravity can
explain the galactic dynamics without the need of introducing dark matter. We
briefly review some of the modified theories of gravity that address these two
intriguing and exciting problems facing modern physics.
| [
{
"created": "Thu, 10 Jul 2008 12:59:04 GMT",
"version": "v1"
}
] | 2013-08-23 | [
[
"Lobo",
"Francisco S. N.",
""
]
] | Modern astrophysical and cosmological models are faced with two severe theoretical difficulties, that can be summarized as the dark energy and the dark matter problems. Relative to the former, it has been stated that cosmology has entered a 'golden age', in which high-precision observational data have confirmed with startling evidence that the Universe is undergoing a phase of accelerated expansion. Several candidates, responsible for this expansion, have been proposed in the literature, in particular, dark energy models and modified gravity, amongst others. One is liable to ask: What is the so-called 'dark energy' that is driving the acceleration of the universe? Is it a vacuum energy or a dynamical field (''quintessence'')? Or is the acceleration due to infra-red modifications of Einstein's theory of General Relativity? In the context of dark matter, two observations, namely, the behavior of the galactic rotation curves and the mass discrepancy in galactic clusters, suggest the existence of a (non or weakly interacting) form of dark matter at galactic and extra-galactic scales. It has also been proposed that modified gravity can explain the galactic dynamics without the need of introducing dark matter. We briefly review some of the modified theories of gravity that address these two intriguing and exciting problems facing modern physics. |
gr-qc/0212115 | Kazuyasu Shigemoto | M.Kenmoku and K.Shigemoto | Conservation of Energy in Black Holes and in Cosmology | 11 pages, talk given at 11th Theoretical and Experimental Problems of
General Relativity and Gravitation, Tomsk, Russia, July, 2002 | Grav.Cosmol. 9 (2003) 55-58 | null | null | gr-qc | null | We first review the various definition of the total energy in the
gravitational system. The naive definition has some defects, and we review how
to modify the definition of the total energy. Then we explicitly demonstrate
how to calculate the total energy of the system. Our example is the total
energy of a black hole in the expanding closed de Sitter universe in (2+1)
dimension. In general, we find that the contribution to the total energy comes
only from the singularity. Then we can calculate the total energy by evaluating
the contribution around the singularity.
| [
{
"created": "Fri, 27 Dec 2002 11:39:32 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kenmoku",
"M.",
""
],
[
"Shigemoto",
"K.",
""
]
] | We first review the various definition of the total energy in the gravitational system. The naive definition has some defects, and we review how to modify the definition of the total energy. Then we explicitly demonstrate how to calculate the total energy of the system. Our example is the total energy of a black hole in the expanding closed de Sitter universe in (2+1) dimension. In general, we find that the contribution to the total energy comes only from the singularity. Then we can calculate the total energy by evaluating the contribution around the singularity. |
1910.08008 | Matt Visser | Petarpa Boonserm, Tritos Ngampitipan, Alex Simpson, and Matt Visser | Decomposition of total stress-energy for the generalised Kiselev black
hole | 17 pages | Phys. Rev. D 101, 024022 (2020) | 10.1103/PhysRevD.101.024022 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate that the anisotropic stress-energy supporting the Kiselev
black hole can be mimicked by being split into a perfect fluid component plus
either an electromagnetic component or a scalar field component, thereby
quantifying the precise extent to which the Kiselev black hole fails to
represent a perfect fluid spacetime. The perfect fluid component carries either
an electric or a scalar charge, which then generates anisotropic
electromagnetic or scalar fields. This in turn generates anisotropic
contributions to the stress-energy. These in turn induce forces which partially
(in addition to the fluid pressure gradient) support the matter content against
gravity. This decomposition is carried out both for the original 1-component
Kiselev black hole and for the generalized N-component Kiselev black holes. We
also comment on the presence of energy condition violations (specifically for
the null energy condition --- NEC) for certain sub-classes of Kiselev black
holes.
| [
{
"created": "Thu, 17 Oct 2019 16:27:10 GMT",
"version": "v1"
}
] | 2020-01-15 | [
[
"Boonserm",
"Petarpa",
""
],
[
"Ngampitipan",
"Tritos",
""
],
[
"Simpson",
"Alex",
""
],
[
"Visser",
"Matt",
""
]
] | We demonstrate that the anisotropic stress-energy supporting the Kiselev black hole can be mimicked by being split into a perfect fluid component plus either an electromagnetic component or a scalar field component, thereby quantifying the precise extent to which the Kiselev black hole fails to represent a perfect fluid spacetime. The perfect fluid component carries either an electric or a scalar charge, which then generates anisotropic electromagnetic or scalar fields. This in turn generates anisotropic contributions to the stress-energy. These in turn induce forces which partially (in addition to the fluid pressure gradient) support the matter content against gravity. This decomposition is carried out both for the original 1-component Kiselev black hole and for the generalized N-component Kiselev black holes. We also comment on the presence of energy condition violations (specifically for the null energy condition --- NEC) for certain sub-classes of Kiselev black holes. |
2301.13263 | Bita Farsi | Ahmad Sheykhi, Bita Farsi | Growth of perturbations in higher dimensional Gauss-Bonnet FRW cosmology | 10 Pages, 11 figures. arXiv admin note: text overlap with
arXiv:2202.04118 | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We explore the influences of the higher order Gauss Bonnet (GB) correction
terms on the growth of perturbations at the early stage of a (n +
1)-dimensional Friedmann-Robertson-Walker (FRW) universe. Considering a
cosmological constant in the FRW background, we study the linear perturbations
by adopting the spherically symmetric collapse (SC) formalism. In light of the
modifications that appear in the field equations, we disclose the role of the
GB coupling constant {\alpha}, as well as the extra dimensions n > 3 on the
growth of perturbations. It, in essence, is done by defining a dimensionless
parameter \{beta}=(n-2)(n-3) \{alpha} H_0^2 in which H_0 is the Hubble
constant. We find that the matter density contrast starts growing at the early
stages of the universe and, as the universe expands, it grows faster compared
to the standard cosmology. Besides, in the framework of GB gravity, the growth
of matter perturbations in higher dimensions is faster than its standard
counterpart (n = 3). Further, in the presence of {\alpha}, the growth of
perturbations increases as it increases. This is an expected result, since the
higher order GB correction terms increase the strength of the gravity and thus
support the growth of perturbations. For the existing cosmological model, we
also investigate the behavior of quantities such as density abundance,
deceleration, and the jerk parameter. Finally, we study the imprint of the GB
parameter and the higher dimensions in the evolution of the mass function of
the dark matter halos.
| [
{
"created": "Mon, 30 Jan 2023 20:15:34 GMT",
"version": "v1"
},
{
"created": "Wed, 17 May 2023 05:56:02 GMT",
"version": "v2"
},
{
"created": "Sat, 12 Aug 2023 09:52:55 GMT",
"version": "v3"
}
] | 2023-08-15 | [
[
"Sheykhi",
"Ahmad",
""
],
[
"Farsi",
"Bita",
""
]
] | We explore the influences of the higher order Gauss Bonnet (GB) correction terms on the growth of perturbations at the early stage of a (n + 1)-dimensional Friedmann-Robertson-Walker (FRW) universe. Considering a cosmological constant in the FRW background, we study the linear perturbations by adopting the spherically symmetric collapse (SC) formalism. In light of the modifications that appear in the field equations, we disclose the role of the GB coupling constant {\alpha}, as well as the extra dimensions n > 3 on the growth of perturbations. It, in essence, is done by defining a dimensionless parameter \{beta}=(n-2)(n-3) \{alpha} H_0^2 in which H_0 is the Hubble constant. We find that the matter density contrast starts growing at the early stages of the universe and, as the universe expands, it grows faster compared to the standard cosmology. Besides, in the framework of GB gravity, the growth of matter perturbations in higher dimensions is faster than its standard counterpart (n = 3). Further, in the presence of {\alpha}, the growth of perturbations increases as it increases. This is an expected result, since the higher order GB correction terms increase the strength of the gravity and thus support the growth of perturbations. For the existing cosmological model, we also investigate the behavior of quantities such as density abundance, deceleration, and the jerk parameter. Finally, we study the imprint of the GB parameter and the higher dimensions in the evolution of the mass function of the dark matter halos. |
1005.5234 | Kazuharu Bamba | Kazuharu Bamba and Chao-Qiang Geng | Thermodynamics in $f(R)$ gravity in the Palatini formalism | 20 pages, no figure, accepted in JCAP | JCAP 1006:014,2010 | 10.1088/1475-7516/2010/06/014 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate thermodynamics of the apparent horizon in $f(R)$ gravity in
the Palatini formalism with non-equilibrium and equilibrium descriptions. We
demonstrate that it is more transparent to understand the horizon entropy in
the equilibrium framework than that in the non-equilibrium one. Furthermore, we
show that the second law of thermodynamics can be explicitly verified in both
phantom and non-phantom phases for the same temperature of the universe outside
and inside the apparent horizon.
| [
{
"created": "Fri, 28 May 2010 08:20:05 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Bamba",
"Kazuharu",
""
],
[
"Geng",
"Chao-Qiang",
""
]
] | We investigate thermodynamics of the apparent horizon in $f(R)$ gravity in the Palatini formalism with non-equilibrium and equilibrium descriptions. We demonstrate that it is more transparent to understand the horizon entropy in the equilibrium framework than that in the non-equilibrium one. Furthermore, we show that the second law of thermodynamics can be explicitly verified in both phantom and non-phantom phases for the same temperature of the universe outside and inside the apparent horizon. |
1607.00199 | K\'aroly Zolt\'an Csuk\'as | K\'aroly Zolt\'an Csuk\'as | Geometric inequalities in spherically symmetric spacetimes | 13 pages | Gen Relativ Gravit, 49: 94 (2017) | 10.1007/s10714-017-2256-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In geometric inequalities ADM mass plays more fundamental role than the
concept of quasi-local mass. This paper is to demonstrate that using the
quasi-local mass some new insights can be acquired. In spherically symmetric
spacetimes the Misner-Sharp mass and the concept of the Kodama vector field
provides an ideal setting to the investigations of geometric inequalities. We
applying the proposed new techniques to investigate the spacetimes containing
black hole or cosmological horizons but we shall also apply them in context of
normal bodies. Most of the previous investigations applied only the quasi-local
charges and the area. Our main point is to include the quasi-local mass in the
corresponding geometrical inequalities. This way we recover some known
relations but new inequalities are also derived.
| [
{
"created": "Fri, 1 Jul 2016 10:37:59 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Apr 2017 12:45:35 GMT",
"version": "v2"
}
] | 2017-06-28 | [
[
"Csukás",
"Károly Zoltán",
""
]
] | In geometric inequalities ADM mass plays more fundamental role than the concept of quasi-local mass. This paper is to demonstrate that using the quasi-local mass some new insights can be acquired. In spherically symmetric spacetimes the Misner-Sharp mass and the concept of the Kodama vector field provides an ideal setting to the investigations of geometric inequalities. We applying the proposed new techniques to investigate the spacetimes containing black hole or cosmological horizons but we shall also apply them in context of normal bodies. Most of the previous investigations applied only the quasi-local charges and the area. Our main point is to include the quasi-local mass in the corresponding geometrical inequalities. This way we recover some known relations but new inequalities are also derived. |
gr-qc/0102036 | null | M. Sharif (Hanyang University) | Energy and Momentum of a Class of Rotating Gravitational Waves | 11 pages, no figure, Latex | Int.J.Mod.Phys.A17:1175-1182,2002 | 10.1142/S0217751X02009655 | null | gr-qc | null | We calculate energy and momentum for a class of cylindrical rotating
gravitational waves using Einstein and Papapetrou's prescriptions. It is shown
that the results obtained are reduced to the special case of the cylindrical
gravitational waves already available in the literature.
| [
{
"created": "Fri, 9 Feb 2001 00:26:27 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Sharif",
"M.",
"",
"Hanyang University"
]
] | We calculate energy and momentum for a class of cylindrical rotating gravitational waves using Einstein and Papapetrou's prescriptions. It is shown that the results obtained are reduced to the special case of the cylindrical gravitational waves already available in the literature. |
gr-qc/9706073 | Sharon Morsink | John L. Friedman, Sharon M. Morsink | Axial instability of rotating relativistic stars | Latex, 18 pages. Equations 84 and 85 are corrected. Discussion of
timescales is corrected and updated | Astrophys.J. 502 (1998) 714-720 | 10.1086/305920 | null | gr-qc astro-ph | null | Perturbations of rotating relativistic stars can be classified by their
behavior under parity. For axial perturbations (r-modes), initial data with
negative canonical energy is found with angular dependence $e^{im\phi}$ for all
values of $m\geq 2$ and for arbitrarily slow rotation. This implies instability
(or marginal stability) of such perturbations for rotating perfect fluids. This
low $m$-instability is strikingly different from the instability to polar
perturbations, which sets in first for large values of $m$. The timescale for
the axial instability appears, for small angular velocity $\Omega$, to be
proportional to a high power of $\Omega$. As in the case of polar modes,
viscosity will again presumably enforce stability except for hot, rapidly
rotating neutron stars. This work complements Andersson's numerical
investigation of axial modes in slowly rotating stars.
| [
{
"created": "Mon, 23 Jun 1997 23:35:38 GMT",
"version": "v1"
},
{
"created": "Sun, 19 Oct 1997 23:08:29 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Jun 1998 14:21:00 GMT",
"version": "v3"
}
] | 2009-10-30 | [
[
"Friedman",
"John L.",
""
],
[
"Morsink",
"Sharon M.",
""
]
] | Perturbations of rotating relativistic stars can be classified by their behavior under parity. For axial perturbations (r-modes), initial data with negative canonical energy is found with angular dependence $e^{im\phi}$ for all values of $m\geq 2$ and for arbitrarily slow rotation. This implies instability (or marginal stability) of such perturbations for rotating perfect fluids. This low $m$-instability is strikingly different from the instability to polar perturbations, which sets in first for large values of $m$. The timescale for the axial instability appears, for small angular velocity $\Omega$, to be proportional to a high power of $\Omega$. As in the case of polar modes, viscosity will again presumably enforce stability except for hot, rapidly rotating neutron stars. This work complements Andersson's numerical investigation of axial modes in slowly rotating stars. |
gr-qc/0405035 | Philip D. Mannheim | Philip D. Mannheim (University of Connecticut) | The Work of Behram Kursunoglu | 8 pages, latex using ws-procs9x6.cls, talk presented at the 2003
Coral Gables conference | null | 10.1142/9789812701992_0053 | null | gr-qc | null | Talk presented at the 2003 Coral Gables conference in honor and appreciation
of the work of Professor Behram Kursunoglu, general relativist extraordinaire
and founder of the Coral Gables series of conferences, whose untimely death
occurred shortly before the 2003 conference.
| [
{
"created": "Thu, 6 May 2004 19:01:34 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Mannheim",
"Philip D.",
"",
"University of Connecticut"
]
] | Talk presented at the 2003 Coral Gables conference in honor and appreciation of the work of Professor Behram Kursunoglu, general relativist extraordinaire and founder of the Coral Gables series of conferences, whose untimely death occurred shortly before the 2003 conference. |
1804.08195 | Luca Buoninfante | Luca Buoninfante, Alexey S. Koshelev, Gaetano Lambiase, Jo\~ao Marto,
Anupam Mazumdar | Conformally-flat, non-singular static metric in infinite derivative
gravity | 24 pages. Revised version, stronger arguments presented for avoiding
singularity and event horizon | null | 10.1088/1475-7516/2018/06/014 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Einstein's theory of general relativity the vacuum solution yields a
blackhole with a curvature singularity, where there exists a point-like source
with a Dirac delta distribution which is introduced as a boundary condition in
the static case. It has been known for a while that ghost-free infinite
derivative theory of gravity can ameliorate such a singularity at least at the
level of linear perturbation around the Minkowski background. In this paper, we
will show that the Schwarzschild metric does not satisfy the boundary condition
at the origin within infinite derivative theory of gravity, since a Dirac delta
source is smeared out by non-local gravitational interaction. We will also show
that the spacetime metric becomes conformally-flat and singularity-free within
the non-local region, which can be also made devoid of an event horizon.
Furthermore, the scale of non-locality ought to be as large as that of the
Schwarzschild radius, in such a way that the gravitational potential in any
metric has to be always bounded by one, implying that gravity remains weak from
the infrared all the way up to the ultraviolet regime, in concurrence with the
results obtained in [arXiv:1707.00273]. The singular Schwarzschild blackhole
can now be potentially replaced by a non-singular compact object, whose core is
governed by the mass and the effective scale of non-locality.
| [
{
"created": "Sun, 22 Apr 2018 23:38:34 GMT",
"version": "v1"
},
{
"created": "Sat, 12 May 2018 17:06:26 GMT",
"version": "v2"
}
] | 2018-06-27 | [
[
"Buoninfante",
"Luca",
""
],
[
"Koshelev",
"Alexey S.",
""
],
[
"Lambiase",
"Gaetano",
""
],
[
"Marto",
"João",
""
],
[
"Mazumdar",
"Anupam",
""
]
] | In Einstein's theory of general relativity the vacuum solution yields a blackhole with a curvature singularity, where there exists a point-like source with a Dirac delta distribution which is introduced as a boundary condition in the static case. It has been known for a while that ghost-free infinite derivative theory of gravity can ameliorate such a singularity at least at the level of linear perturbation around the Minkowski background. In this paper, we will show that the Schwarzschild metric does not satisfy the boundary condition at the origin within infinite derivative theory of gravity, since a Dirac delta source is smeared out by non-local gravitational interaction. We will also show that the spacetime metric becomes conformally-flat and singularity-free within the non-local region, which can be also made devoid of an event horizon. Furthermore, the scale of non-locality ought to be as large as that of the Schwarzschild radius, in such a way that the gravitational potential in any metric has to be always bounded by one, implying that gravity remains weak from the infrared all the way up to the ultraviolet regime, in concurrence with the results obtained in [arXiv:1707.00273]. The singular Schwarzschild blackhole can now be potentially replaced by a non-singular compact object, whose core is governed by the mass and the effective scale of non-locality. |
gr-qc/9803091 | Aleksandr Zheltukhin | Semyon Pol'shin | Group Theoretical Examination of the Relativistic Wave Equations on
Curved Spaces. I.Basic Principles | 11 pages, LATEX, no figures, revised version | null | null | null | gr-qc | null | The basic principles of generalization of the group theoretical approach to
the relativistic wave equations on curved spaces are examined. The general
method of the determination of wave equations from the known symmetry group of
a symmetrical curved space is described. The method of obtaining the
symmetrical spaces in which invariant wave equations admit the limiting passage
to the relativistic wave equations on the flat (not necessarily real) spaces is
explained. Starting from the equations for massless particles and from the
Dirac equation in the Minkowski space, admissible real symmetrical spaces are
founded. The mentioned procedure is carried out also for the complex spaces. As
the basic point, the wave equations on the flat complex space are considered.
It is shown that the usual Dirac equation written down in the complex variables
does not lead to any curved space. By "decomposition" of the mentioned form of
the Dirac equation the equation leading to the space ${\Bbb C}{\Bbb P}^{n}$ and
being alternative to the usual Dirac equation on ${\Bbb C}^{n}$ is constructed.
| [
{
"created": "Fri, 27 Mar 1998 15:08:13 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Jul 1998 14:39:05 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Pol'shin",
"Semyon",
""
]
] | The basic principles of generalization of the group theoretical approach to the relativistic wave equations on curved spaces are examined. The general method of the determination of wave equations from the known symmetry group of a symmetrical curved space is described. The method of obtaining the symmetrical spaces in which invariant wave equations admit the limiting passage to the relativistic wave equations on the flat (not necessarily real) spaces is explained. Starting from the equations for massless particles and from the Dirac equation in the Minkowski space, admissible real symmetrical spaces are founded. The mentioned procedure is carried out also for the complex spaces. As the basic point, the wave equations on the flat complex space are considered. It is shown that the usual Dirac equation written down in the complex variables does not lead to any curved space. By "decomposition" of the mentioned form of the Dirac equation the equation leading to the space ${\Bbb C}{\Bbb P}^{n}$ and being alternative to the usual Dirac equation on ${\Bbb C}^{n}$ is constructed. |
1108.2813 | George E. A. Matsas | Jorge Castineiras, Emerson B. S. Correa, Luis C. B. Crispino, George
E. A. Matsas | Quantization of the Proca field in the Rindler wedge and the interaction
of uniformly accelerated currents with massive vector bosons from the Unruh
thermal bath | 5 pages, no figures | Phys.Rev.D84:025010,2011 | 10.1103/PhysRevD.84.025010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We canonically quantize the Proca field in the Rindler wedge and compute the
total response rate of a uniformly accelerated current interacting with massive
vector Rindler particles from the Unruh thermal bath. We explicitly verify that
the result obtained is exactly the same as the emission rate of massive vector
particles in the Minkowski vacuum as analyzed by inertial observers. Eventually
our results are interpreted in terms of the interaction of static electrons
coupled to $Z^0$ bosons present in Hawking radiation close to the event horizon
of a black hole.
| [
{
"created": "Sat, 13 Aug 2011 18:53:49 GMT",
"version": "v1"
}
] | 2011-11-10 | [
[
"Castineiras",
"Jorge",
""
],
[
"Correa",
"Emerson B. S.",
""
],
[
"Crispino",
"Luis C. B.",
""
],
[
"Matsas",
"George E. A.",
""
]
] | We canonically quantize the Proca field in the Rindler wedge and compute the total response rate of a uniformly accelerated current interacting with massive vector Rindler particles from the Unruh thermal bath. We explicitly verify that the result obtained is exactly the same as the emission rate of massive vector particles in the Minkowski vacuum as analyzed by inertial observers. Eventually our results are interpreted in terms of the interaction of static electrons coupled to $Z^0$ bosons present in Hawking radiation close to the event horizon of a black hole. |
2208.06869 | Job Furtado Neto | T. F. de Souza, A. C. A. Ramos, R. N. Costa Filho, J. Furtado | Generalized Ellis-Bronnikov graphene wormhole | 9 pages, 6 figures, two columns | null | null | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | In this paper, we investigate the spinless stationary Schr\"odinger equation
for the electron when it is permanently bound to a generalized Ellis-Bronnikov
graphene wormhole-like surface. The curvature gives rise to a geometric
potential affecting thus the electronic dynamics. The geometry of the
wormhole's shape is controlled by the parameter $n$ which assumes even values.
We discuss the role played by the parameter $n$ and the orbital angular
momentum on bound states and probability density for the electron.
| [
{
"created": "Sun, 14 Aug 2022 15:47:05 GMT",
"version": "v1"
}
] | 2022-08-16 | [
[
"de Souza",
"T. F.",
""
],
[
"Ramos",
"A. C. A.",
""
],
[
"Filho",
"R. N. Costa",
""
],
[
"Furtado",
"J.",
""
]
] | In this paper, we investigate the spinless stationary Schr\"odinger equation for the electron when it is permanently bound to a generalized Ellis-Bronnikov graphene wormhole-like surface. The curvature gives rise to a geometric potential affecting thus the electronic dynamics. The geometry of the wormhole's shape is controlled by the parameter $n$ which assumes even values. We discuss the role played by the parameter $n$ and the orbital angular momentum on bound states and probability density for the electron. |
1904.05791 | Vasiliy P. Neznamov | V.P.Neznamov, I.I.Safronov, V.Ye.Shemarulin | Stationary solutions of the second-order equation for fermions in
Kerr-Newman space-time | 47 pages, 2 figures, 6 tables | J. Exp. Theor. Phys. (2019) 128:64 | 10.1134/S1063776118120221 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When using the quantum mechanical second-order equation with the effective
potential of the Kerr-Newman (KN) field for fermions, results were obtained
that qualitatively differ from results obtained when using the Dirac equation.
In presence of two event horizons, existence of degenerate stationary bound
states was proved for charged and uncharged fermions with square integrable
wave functions vanishing on event horizons. The fermions in such states are
localized near the event horizons with the maxima of probability densities away
from the event horizons by fractions of the Compton wave length of fermions
versus the values of coupling constants, the values of angular and orbital
momenta $j,l$ and the value of the azimuthal quantum number $m_{\varphi}$. In
the case of extreme KN fields, absence of stationary bound states of fermions
was shown for any values of coupling constants. Existence of discrete energy
spectra was shown for charged and uncharged fermions in the field of naked KN
singularity at definite values of physical parameters. The KN naked singularity
poses no threat to cosmic censorship because of the regular behavior of the
effective potentials of the KN field in quantum mechanics with the second-order
equation.
| [
{
"created": "Wed, 10 Apr 2019 16:16:35 GMT",
"version": "v1"
}
] | 2019-04-12 | [
[
"Neznamov",
"V. P.",
""
],
[
"Safronov",
"I. I.",
""
],
[
"Shemarulin",
"V. Ye.",
""
]
] | When using the quantum mechanical second-order equation with the effective potential of the Kerr-Newman (KN) field for fermions, results were obtained that qualitatively differ from results obtained when using the Dirac equation. In presence of two event horizons, existence of degenerate stationary bound states was proved for charged and uncharged fermions with square integrable wave functions vanishing on event horizons. The fermions in such states are localized near the event horizons with the maxima of probability densities away from the event horizons by fractions of the Compton wave length of fermions versus the values of coupling constants, the values of angular and orbital momenta $j,l$ and the value of the azimuthal quantum number $m_{\varphi}$. In the case of extreme KN fields, absence of stationary bound states of fermions was shown for any values of coupling constants. Existence of discrete energy spectra was shown for charged and uncharged fermions in the field of naked KN singularity at definite values of physical parameters. The KN naked singularity poses no threat to cosmic censorship because of the regular behavior of the effective potentials of the KN field in quantum mechanics with the second-order equation. |
1108.5827 | Changjun Gao | Changjun Gao | Scalar Field, Four Dimensional Spacetime Volume and the Holographic Dark
Energy | 7 pages, 5 figures. References added and some typos corrected | Int. J. Mod. Phys. Conf. Ser. 10 (2012) 95-106 | 10.1142/S2010194512005806 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the cosmic evolution of a scalar field which is identified with
the four dimensional spacetime volume. Given a specific form for the Lagrangian
of the scalar field, a new holographic dark energy model is present. The energy
density of dark energy is reversely proportional to the square of the radius of
the cosmic null hypersurface which is present as a new infrared cutoff for the
Universe. We find this holographic dark energy belongs to the phantom dark
energy for some appropriate parameters in order to interpret the current
acceleration of the Universe.
| [
{
"created": "Tue, 30 Aug 2011 04:33:14 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Aug 2011 00:42:07 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Sep 2011 02:43:06 GMT",
"version": "v3"
},
{
"created": "Mon, 5 Sep 2011 07:07:25 GMT",
"version": "v4"
}
] | 2012-05-22 | [
[
"Gao",
"Changjun",
""
]
] | We explore the cosmic evolution of a scalar field which is identified with the four dimensional spacetime volume. Given a specific form for the Lagrangian of the scalar field, a new holographic dark energy model is present. The energy density of dark energy is reversely proportional to the square of the radius of the cosmic null hypersurface which is present as a new infrared cutoff for the Universe. We find this holographic dark energy belongs to the phantom dark energy for some appropriate parameters in order to interpret the current acceleration of the Universe. |
1002.3868 | Sante Carloni Dr | Sante Carloni | Covariant gauge invariant theory of Scalar Perturbations in
$f(R)$-gravity: a brief review | 23 pages, 12 figures, to appear on The Open Astronomy Journal | null | 10.2174/1874381101003010076 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I review the state of the art of the investigation on the structure formation
in $f(R)$-gravity based on the Covariant and Gauge Invariant approach to
perturbations. A critical analysis of the results, in particular the presence
of characteristic signature of these models, together with their meaning and
their implication is given.
| [
{
"created": "Sat, 20 Feb 2010 11:13:04 GMT",
"version": "v1"
}
] | 2015-05-18 | [
[
"Carloni",
"Sante",
""
]
] | I review the state of the art of the investigation on the structure formation in $f(R)$-gravity based on the Covariant and Gauge Invariant approach to perturbations. A critical analysis of the results, in particular the presence of characteristic signature of these models, together with their meaning and their implication is given. |
1003.5665 | T. Padmanabhan | T. Padmanabhan | Surface Density of Spacetime Degrees of Freedom from Equipartition Law
in theories of Gravity | v1: 20 pages; no figures. v2: Sec 4 added; 23 pages | Phys.Rev.D81:124040,2010 | 10.1103/PhysRevD.81.124040 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I show that the principle of equipartition, applied to area elements of a
surface which are in equilibrium at the local Davies-Unruh temperature, allows
one to determine the surface number density of the microscopic spacetime
degrees of freedom in any diffeomorphism invariant theory of gravity. The
entropy associated with these degrees of freedom matches with the Wald entropy
for the theory. This result also allows one to attribute an entropy density to
the spacetime in a natural manner. The field equations of the theory can then
be obtained by extremising this entropy. Moreover, when the microscopic degrees
of freedom are in local thermal equilibrium, the spacetime entropy of a bulk
region resides on its boundary.
| [
{
"created": "Mon, 29 Mar 2010 20:05:01 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Jun 2010 06:35:40 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"Padmanabhan",
"T.",
""
]
] | I show that the principle of equipartition, applied to area elements of a surface which are in equilibrium at the local Davies-Unruh temperature, allows one to determine the surface number density of the microscopic spacetime degrees of freedom in any diffeomorphism invariant theory of gravity. The entropy associated with these degrees of freedom matches with the Wald entropy for the theory. This result also allows one to attribute an entropy density to the spacetime in a natural manner. The field equations of the theory can then be obtained by extremising this entropy. Moreover, when the microscopic degrees of freedom are in local thermal equilibrium, the spacetime entropy of a bulk region resides on its boundary. |
2312.15452 | Junji Jia | Qianchuan Wang and Junji Jia | Periapsis shift in spherically symmetric spacetimes and effect of
electric interaction | 17 pages, 9 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The periapsis shift of charged test particles in arbitrary static and
spherically symmetric charged spacetimes are studied. Two perturbative methods,
the near-circular approximation and post-Newtonian methods, are developed, and
shown to be very accurate when the results are found to high orders. The former
method is more precise when the eccentricity $e$ of the orbit is small while
the latter works better when the orbit semilatus rectum $p$ is large. Results
from these two methods are shown to agree with each other when both $e$ is
small and $p$ is large. These results are then applied to the
Reissner-Nordstr\"om spacetime, the Einstein-Maxwell-dilation gravity and a
charged wormhole spacetime. The effects of various parameters on the periapsis
shift, especially that of the electrostatic interaction, are carefully studied.
The periapsis shift data of the solar-Mercury is then used to constrain the
charges of the Sun and Mercury, and the data of the Sgr A$^*$-S2 periapsis
shift is used to find, for the first time using this method, constraints about
the charges of Sgr A$^*$ and S2.
| [
{
"created": "Sun, 24 Dec 2023 10:18:10 GMT",
"version": "v1"
}
] | 2023-12-27 | [
[
"Wang",
"Qianchuan",
""
],
[
"Jia",
"Junji",
""
]
] | The periapsis shift of charged test particles in arbitrary static and spherically symmetric charged spacetimes are studied. Two perturbative methods, the near-circular approximation and post-Newtonian methods, are developed, and shown to be very accurate when the results are found to high orders. The former method is more precise when the eccentricity $e$ of the orbit is small while the latter works better when the orbit semilatus rectum $p$ is large. Results from these two methods are shown to agree with each other when both $e$ is small and $p$ is large. These results are then applied to the Reissner-Nordstr\"om spacetime, the Einstein-Maxwell-dilation gravity and a charged wormhole spacetime. The effects of various parameters on the periapsis shift, especially that of the electrostatic interaction, are carefully studied. The periapsis shift data of the solar-Mercury is then used to constrain the charges of the Sun and Mercury, and the data of the Sgr A$^*$-S2 periapsis shift is used to find, for the first time using this method, constraints about the charges of Sgr A$^*$ and S2. |
1001.4726 | Dmitri Vassiliev | Olga Chervova and Dmitri Vassiliev | The stationary Weyl equation and Cosserat elasticity | null | J.Phys.A43:335203,2010 | 10.1088/1751-8113/43/33/335203 | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The paper deals with the Weyl equation which is the massless Dirac equation.
We study the Weyl equation in the stationary setting, i.e. when the spinor
field oscillates harmonically in time. We suggest a new geometric
interpretation of the stationary Weyl equation, one which does not require the
use of spinors, Pauli matrices or covariant differentiation. We think of our
3-dimensional space as an elastic continuum and assume that material points of
this continuum can experience no displacements, only rotations. This framework
is a special case of the Cosserat theory of elasticity. Rotations of material
points of the space continuum are described mathematically by attaching to each
geometric point an orthonormal basis which gives a field of orthonormal bases
called the coframe. As the dynamical variables (unknowns) of our theory we
choose the coframe and a density. We choose a particular potential energy which
is conformally invariant and then incorporate time into our action in the
standard Newtonian way, by subtracting kinetic energy. The main result of our
paper is the theorem stating that in the stationary setting our model is
equivalent to a pair of Weyl equations. The crucial element of the proof is the
observation that our Lagrangian admits a factorization.
| [
{
"created": "Tue, 26 Jan 2010 15:41:31 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Chervova",
"Olga",
""
],
[
"Vassiliev",
"Dmitri",
""
]
] | The paper deals with the Weyl equation which is the massless Dirac equation. We study the Weyl equation in the stationary setting, i.e. when the spinor field oscillates harmonically in time. We suggest a new geometric interpretation of the stationary Weyl equation, one which does not require the use of spinors, Pauli matrices or covariant differentiation. We think of our 3-dimensional space as an elastic continuum and assume that material points of this continuum can experience no displacements, only rotations. This framework is a special case of the Cosserat theory of elasticity. Rotations of material points of the space continuum are described mathematically by attaching to each geometric point an orthonormal basis which gives a field of orthonormal bases called the coframe. As the dynamical variables (unknowns) of our theory we choose the coframe and a density. We choose a particular potential energy which is conformally invariant and then incorporate time into our action in the standard Newtonian way, by subtracting kinetic energy. The main result of our paper is the theorem stating that in the stationary setting our model is equivalent to a pair of Weyl equations. The crucial element of the proof is the observation that our Lagrangian admits a factorization. |
gr-qc/9801008 | F. J. Chinea | F. J. Chinea | New first integral for twisting type-N vacuum gravitational fields with
two non-commuting Killing vectors | 7 pages, LaTeX, uses ioplppt.sty and iopl12.sty; to be published in
Class. Quantum Grav | Class.Quant.Grav. 15 (1998) 367-371 | 10.1088/0264-9381/15/2/011 | null | gr-qc | null | A new first integral for the equations corresponding to twisting type-N
vacuum gravitational fields with two non-commuting Killing vectors is
introduced. A new reduction of the problem to a complex second-order ordinary
differential equation is given. Alternatively, the mentioned first integral can
be used in order to provide a first integral of the second-order complex
equation introduced in a previous treatment of the problem.
| [
{
"created": "Mon, 5 Jan 1998 22:18:47 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Chinea",
"F. J.",
""
]
] | A new first integral for the equations corresponding to twisting type-N vacuum gravitational fields with two non-commuting Killing vectors is introduced. A new reduction of the problem to a complex second-order ordinary differential equation is given. Alternatively, the mentioned first integral can be used in order to provide a first integral of the second-order complex equation introduced in a previous treatment of the problem. |
gr-qc/0510105 | Lorenzo Iorio | Lorenzo Iorio, Giuseppe Giudice | On the perspectives of testing the Dvali-Gabadadze-Porrati gravity model
with the outer planets of the Solar System | LaTex, 22 pages, 2 tables, 10 figures, 27 references. Reference [17]
added, reference [26] updated, caption of figures changed, small change in
section 1.2 | JCAP 0608:007,2006 | 10.1088/1475-7516/2006/08/007 | null | gr-qc astro-ph hep-ph physics.space-ph | null | The multidimensional braneworld gravity model by Dvali, Gabadadze and Porrati
was primarily put forth to explain the observed acceleration of the expansion
of the Universe without resorting to dark energy. One of the most intriguing
features of such a model is that it also predicts small effects on the orbital
motion of test particles which could be tested in such a way that local
measurements at Solar System scales would allow to get information on the
global properties of the Universe. Lue and Starkman derived a secular
extra-perihelion \omega precession of 5\times 10^-4 arcseconds per century,
while Iorio showed that the mean longitude \lambda is affected by a secular
precession of about 10^-3 arcseconds per century. Such effects depend only on
the eccentricities e of the orbits via second-order terms: they are, instead,
independent of their semimajor axes a. Up to now, the observational efforts
focused on the dynamics of the inner planets of the Solar System whose orbits
are the best known via radar ranging. Since the competing Newtonian and
Einsteinian effects like the precessions due to the solar quadrupole mass
moment J2, the gravitoelectric and gravitomagnetic part of the equations of
motion reduce with increasing distances, it would be possible to argue that an
analysis of the orbital dynamics of the outer planets of the Solar System, with
particular emphasis on Saturn because of the ongoing Cassini mission with its
precision ranging instrumentation, could be helpful in evidencing the predicted
new features of motion. In this note we investigate this possibility in view of
the latest results in the planetary ephemeris field. Unfortunately, the current
level of accuracy rules out this appealing possibility and it appears unlikely
that Cassini and GAIA will ameliorate the situation.
| [
{
"created": "Tue, 25 Oct 2005 12:58:07 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Jun 2006 14:50:00 GMT",
"version": "v2"
},
{
"created": "Mon, 31 Jul 2006 13:10:54 GMT",
"version": "v3"
}
] | 2010-01-27 | [
[
"Iorio",
"Lorenzo",
""
],
[
"Giudice",
"Giuseppe",
""
]
] | The multidimensional braneworld gravity model by Dvali, Gabadadze and Porrati was primarily put forth to explain the observed acceleration of the expansion of the Universe without resorting to dark energy. One of the most intriguing features of such a model is that it also predicts small effects on the orbital motion of test particles which could be tested in such a way that local measurements at Solar System scales would allow to get information on the global properties of the Universe. Lue and Starkman derived a secular extra-perihelion \omega precession of 5\times 10^-4 arcseconds per century, while Iorio showed that the mean longitude \lambda is affected by a secular precession of about 10^-3 arcseconds per century. Such effects depend only on the eccentricities e of the orbits via second-order terms: they are, instead, independent of their semimajor axes a. Up to now, the observational efforts focused on the dynamics of the inner planets of the Solar System whose orbits are the best known via radar ranging. Since the competing Newtonian and Einsteinian effects like the precessions due to the solar quadrupole mass moment J2, the gravitoelectric and gravitomagnetic part of the equations of motion reduce with increasing distances, it would be possible to argue that an analysis of the orbital dynamics of the outer planets of the Solar System, with particular emphasis on Saturn because of the ongoing Cassini mission with its precision ranging instrumentation, could be helpful in evidencing the predicted new features of motion. In this note we investigate this possibility in view of the latest results in the planetary ephemeris field. Unfortunately, the current level of accuracy rules out this appealing possibility and it appears unlikely that Cassini and GAIA will ameliorate the situation. |
1803.09872 | Dennis Lehmkuhl | Dennis Lehmkuhl | General Relativity as a Hybrid theory: The Genesis of Einstein's work on
the problem of motion | null | null | 10.1016/j.shpsb.2017.09.006 | null | gr-qc physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper I describe the genesis of Einstein's early work on the problem
of motion in general relativity (GR): the question of whether the motion of
matter subject to gravity can be derived directly from the Einstein field
equations. In addressing this question, Einstein himself always preferred the
vacuum approach to the problem: the attempt to derive geodesic motion of matter
from the vacuum Einstein equations. The paper first investigates why Einstein
was so skeptical of the energy-momentum tensor and its role in GR. Drawing on
hitherto unknown correspondence between Einstein and George Yuri Rainich, I
then show step by step how his work on the vacuum approach came about, and how
his quest for a unified field theory informed his interpretation of GR. I show
that Einstein saw GR as a hybrid theory from very early on: fundamental and
correct as far as gravity was concerned but phenomenological and effective in
how it accounted for matter. As a result, Einstein saw energy-momentum tensors
and singularities in GR as placeholders for a theory of matter not yet
delivered. The reason he preferred singularities was that he hoped that their
mathematical treatment would give a hint as to the sought after theory of
matter, a theory that would do justice to quantum features of matter.
| [
{
"created": "Tue, 27 Mar 2018 03:17:01 GMT",
"version": "v1"
}
] | 2018-03-28 | [
[
"Lehmkuhl",
"Dennis",
""
]
] | In this paper I describe the genesis of Einstein's early work on the problem of motion in general relativity (GR): the question of whether the motion of matter subject to gravity can be derived directly from the Einstein field equations. In addressing this question, Einstein himself always preferred the vacuum approach to the problem: the attempt to derive geodesic motion of matter from the vacuum Einstein equations. The paper first investigates why Einstein was so skeptical of the energy-momentum tensor and its role in GR. Drawing on hitherto unknown correspondence between Einstein and George Yuri Rainich, I then show step by step how his work on the vacuum approach came about, and how his quest for a unified field theory informed his interpretation of GR. I show that Einstein saw GR as a hybrid theory from very early on: fundamental and correct as far as gravity was concerned but phenomenological and effective in how it accounted for matter. As a result, Einstein saw energy-momentum tensors and singularities in GR as placeholders for a theory of matter not yet delivered. The reason he preferred singularities was that he hoped that their mathematical treatment would give a hint as to the sought after theory of matter, a theory that would do justice to quantum features of matter. |
gr-qc/0110095 | Kechkin O. V. | Oleg V. Kechkin | Generation of the bosonic string theory solutions from the stationary
Einstein fields via projection symmetry | 15 pages in LATEX | Phys.Lett.B523:323-330,2001 | 10.1016/S0370-2693(01)01350-8 | null | gr-qc | null | A new formalism for generation of solutions in the consistently truncated
low-energy bosonic string theory is developed. This formalism gives a
correspondence of the projection type between the theories toroidally
compactified from the diverse to three dimensions. Taking the stationary
Einstein-dilaton gravity as the theory with a lower dimension, we generate its
bosonic string theory extension and calculate the bosonic string theory
solution corresponding to the Kerr-NUT one modified by the presence of the
charged dilaton field.
| [
{
"created": "Tue, 23 Oct 2001 01:15:38 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Kechkin",
"Oleg V.",
""
]
] | A new formalism for generation of solutions in the consistently truncated low-energy bosonic string theory is developed. This formalism gives a correspondence of the projection type between the theories toroidally compactified from the diverse to three dimensions. Taking the stationary Einstein-dilaton gravity as the theory with a lower dimension, we generate its bosonic string theory extension and calculate the bosonic string theory solution corresponding to the Kerr-NUT one modified by the presence of the charged dilaton field. |
2407.20339 | Ippocratis Saltas Dr | Eugeny Babichev, Christos Charmousis, Benjamin Muntz, Antonio Padilla,
Ippocratis D. Saltas | Horndeski speed tests with scalar-photon couplings | 7 pages plus references | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit multi-messenger constraints from neutron star mergers on the speed
of propagation of gravitational and electromagnetic waves in Horndeski and
beyond Horndeski theories. By considering non-trivial couplings between the
dark energy field and the electromagnetic sector, the electromagnetic wave can
propagate through the cosmological background at non-unit speed, altering the
phenomenological constraints on its gravitational counterpart. In particular,
we show that recent models derived from a Kaluza-Klein compactification of
higher dimensional Horndeski models fall into a broader class of theories
disformally related to those whose gravitational waves propagate with unit
speed. This disformal equivalence can, however, be broken by the gravitational
couplings to other sectors with interesting phenomenological consequences. We
also consider higher order couplings between the scalar and the photon with
second order field equations, and show that they are not compatible with
constraints coming from multi-messenger speed tests and the decay of the
gravitational wave.
| [
{
"created": "Mon, 29 Jul 2024 18:00:12 GMT",
"version": "v1"
}
] | 2024-07-31 | [
[
"Babichev",
"Eugeny",
""
],
[
"Charmousis",
"Christos",
""
],
[
"Muntz",
"Benjamin",
""
],
[
"Padilla",
"Antonio",
""
],
[
"Saltas",
"Ippocratis D.",
""
]
] | We revisit multi-messenger constraints from neutron star mergers on the speed of propagation of gravitational and electromagnetic waves in Horndeski and beyond Horndeski theories. By considering non-trivial couplings between the dark energy field and the electromagnetic sector, the electromagnetic wave can propagate through the cosmological background at non-unit speed, altering the phenomenological constraints on its gravitational counterpart. In particular, we show that recent models derived from a Kaluza-Klein compactification of higher dimensional Horndeski models fall into a broader class of theories disformally related to those whose gravitational waves propagate with unit speed. This disformal equivalence can, however, be broken by the gravitational couplings to other sectors with interesting phenomenological consequences. We also consider higher order couplings between the scalar and the photon with second order field equations, and show that they are not compatible with constraints coming from multi-messenger speed tests and the decay of the gravitational wave. |
1506.08070 | Michael Feldman | Michael R. Feldman and John D. Anderson | On the possible onset of the Pioneer anomaly | 24+12 pages, 4 figures | Int. J. Mod. Phys. D24 (2015) 1550066 | 10.1142/S0218271815500662 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the possibility that the observed onset of the Pioneer anomaly
after Saturn encounter by Pioneer 11 is not necessarily due to mismodeling of
solar radiation pressure but instead reflects a physically relevant
characteristic of the anomaly itself. We employ the principles of a recently
proposed cosmological model termed "the theory of inertial centers" along with
an understanding of the fundamental assumptions taken by the Deep Space Network
(DSN) to attempt to model this sudden onset. Due to an ambiguity that arises
from the difference in the DSN definition of expected light-time with
light-time according to the theory of inertial centers, we are forced to adopt
a seemingly arbitrary convention to relate DSN-assumed clock-rates to physical
clock-rates for this model. We offer a possible reason for adopting the
convention employed in our analysis; however, we remain skeptical.
Nevertheless, with this convention, one finds that this theory is able to
replicate the previously reported Hubble-like behavior of the "clock
acceleration" for the Pioneer anomaly as well as the sudden onset of the
anomalous acceleration after Pioneer 11 Saturn encounter. While oscillatory
behavior with a yearly period is also predicted for the anomalous clock
accelerations of both Pioneer 10 and Pioneer 11, the predicted amplitude is an
order of magnitude too small when compared with that reported for Pioneer 10.
| [
{
"created": "Wed, 24 Jun 2015 09:52:42 GMT",
"version": "v1"
}
] | 2015-06-29 | [
[
"Feldman",
"Michael R.",
""
],
[
"Anderson",
"John D.",
""
]
] | We explore the possibility that the observed onset of the Pioneer anomaly after Saturn encounter by Pioneer 11 is not necessarily due to mismodeling of solar radiation pressure but instead reflects a physically relevant characteristic of the anomaly itself. We employ the principles of a recently proposed cosmological model termed "the theory of inertial centers" along with an understanding of the fundamental assumptions taken by the Deep Space Network (DSN) to attempt to model this sudden onset. Due to an ambiguity that arises from the difference in the DSN definition of expected light-time with light-time according to the theory of inertial centers, we are forced to adopt a seemingly arbitrary convention to relate DSN-assumed clock-rates to physical clock-rates for this model. We offer a possible reason for adopting the convention employed in our analysis; however, we remain skeptical. Nevertheless, with this convention, one finds that this theory is able to replicate the previously reported Hubble-like behavior of the "clock acceleration" for the Pioneer anomaly as well as the sudden onset of the anomalous acceleration after Pioneer 11 Saturn encounter. While oscillatory behavior with a yearly period is also predicted for the anomalous clock accelerations of both Pioneer 10 and Pioneer 11, the predicted amplitude is an order of magnitude too small when compared with that reported for Pioneer 10. |
1012.1443 | Ujjal Debnath | Piyali Bagchi Khatua and Ujjal Debnath | Role of Chameleon Field in Accelerating Universe | 10 pages, 8 figures | Astrophys.Space Sci.326:53-60,2010 | 10.1007/s10509-009-0207-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we have considered a model of the flat FRW universe filled with
cold dark matter and Chameleon field where the scale function is taken as, (i)
Intermediate Expansion and (ii) Logamediate Expansion. In the both cases we
find the expressions of Chameleon field, Chameleon potential, statefinder
parameters and slow-roll parameters. Also it has been shown that the potential
is always decreases with the chameleon field in both the scenarios. The nature
of slow-roll parameters have been shown diagrammatically.
| [
{
"created": "Tue, 7 Dec 2010 10:03:07 GMT",
"version": "v1"
}
] | 2011-09-30 | [
[
"Khatua",
"Piyali Bagchi",
""
],
[
"Debnath",
"Ujjal",
""
]
] | In this work, we have considered a model of the flat FRW universe filled with cold dark matter and Chameleon field where the scale function is taken as, (i) Intermediate Expansion and (ii) Logamediate Expansion. In the both cases we find the expressions of Chameleon field, Chameleon potential, statefinder parameters and slow-roll parameters. Also it has been shown that the potential is always decreases with the chameleon field in both the scenarios. The nature of slow-roll parameters have been shown diagrammatically. |
1709.08373 | Seramika Ariwahjoedi | Seramika Ariwahjoedi, Freddy P. Zen | (2+1) Regge Calculus: Discrete Curvatures, Bianchi Identity, and
Gauss-Codazzi Equation | 30 pages. 24 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The first results presented in our article are the clear definitions of both
intrinsic and extrinsic discrete curvatures in terms of holonomy and
plane-angle representation, a clear relation with their deficit angles, and
their clear geometrical interpretations in the first order discrete geometry.
The second results are the discrete version of Bianchi identity and
Gauss-Codazzi equation, together with their geometrical interpretations. It
turns out that the discrete Bianchi identity and Gauss-Codazzi equation, at
least in 3-dimension, could be derived from the dihedral angle formula of a
tetrahedron, while the dihedral angle relation itself is the spherical law of
cosine in disguise. Furthermore, the continuous infinitesimal curvature 2-form,
the standard Bianchi identity, and Gauss-Codazzi equation could be recovered in
the continuum limit.
| [
{
"created": "Mon, 25 Sep 2017 08:38:29 GMT",
"version": "v1"
}
] | 2017-09-26 | [
[
"Ariwahjoedi",
"Seramika",
""
],
[
"Zen",
"Freddy P.",
""
]
] | The first results presented in our article are the clear definitions of both intrinsic and extrinsic discrete curvatures in terms of holonomy and plane-angle representation, a clear relation with their deficit angles, and their clear geometrical interpretations in the first order discrete geometry. The second results are the discrete version of Bianchi identity and Gauss-Codazzi equation, together with their geometrical interpretations. It turns out that the discrete Bianchi identity and Gauss-Codazzi equation, at least in 3-dimension, could be derived from the dihedral angle formula of a tetrahedron, while the dihedral angle relation itself is the spherical law of cosine in disguise. Furthermore, the continuous infinitesimal curvature 2-form, the standard Bianchi identity, and Gauss-Codazzi equation could be recovered in the continuum limit. |
1009.0080 | Matt Visser | Jozef Skakala (Victoria University of Wellington) and Matt Visser
(Victoria University of Wellington) | Generic master equations for quasi-normal frequencies | 23 pages; V2: Minor additions, typos fixed. Matches published version | JHEP 1011:070,2010 | 10.1007/JHEP11(2010)070 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Generic master equations governing the highly-damped quasi-normal frequencies
[QNFs] of one-horizon, two-horizon, and even three-horizon spacetimes can be
obtained through either semi-analytic or monodromy techniques. While many
technical details differ, both between the semi-analytic and monodromy
approaches, and quite often among various authors seeking to apply the
monodromy technique, there is nevertheless widespread agreement regarding the
the general form of the QNF master equations. Within this class of generic
master equations we can establish some rather general results, relating the
existence of "families" of QNFs of the form omega_{a,n} = (offset)_a + i n
(gap) to the question of whether or not certain ratios of parameters are
rational or irrational.
| [
{
"created": "Wed, 1 Sep 2010 03:15:57 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Nov 2010 19:22:22 GMT",
"version": "v2"
}
] | 2010-11-26 | [
[
"Skakala",
"Jozef",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | Generic master equations governing the highly-damped quasi-normal frequencies [QNFs] of one-horizon, two-horizon, and even three-horizon spacetimes can be obtained through either semi-analytic or monodromy techniques. While many technical details differ, both between the semi-analytic and monodromy approaches, and quite often among various authors seeking to apply the monodromy technique, there is nevertheless widespread agreement regarding the the general form of the QNF master equations. Within this class of generic master equations we can establish some rather general results, relating the existence of "families" of QNFs of the form omega_{a,n} = (offset)_a + i n (gap) to the question of whether or not certain ratios of parameters are rational or irrational. |
1912.07278 | Xiangdong Zhang | Cong Zhang and Xiangdong Zhang | Quantum geometry and effective dynamics of Janis-Newman-Winicour
singularities | 17 pages,3 figures, references added. v3, accepted by PRD | Phys. Rev. D 101, 086002 (2020) | 10.1103/PhysRevD.101.086002 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspired by the recent proposal for the quantum effective dynamics of the
Schwarzschild spacetime given in \cite{AOS1}, we investigate the effective
dynamics of the loop quantized Janis-Newman-Winicour (JNW) spacetime which is
an extension of the Schwarzschild spacetime with an extra minimally coupled
massless scalar field. Two parameters are introduced in order to regularize the
Hamiltonian constraint in the quantum effective dynamics. These two parameters
are assumed to be Dirac observables when the effective dynamics is solved. By
carefully choosing appropriate conditions for these two parameters, we
completely determine them, and the resulted new effective description of the
JNW spacetime leads to a well behaved quantum dynamics which on one hand
resolves the classical singularities, and on the other hand, agrees with the
classical dynamics in the low curvature region.
| [
{
"created": "Mon, 16 Dec 2019 10:19:10 GMT",
"version": "v1"
},
{
"created": "Sat, 28 Dec 2019 05:50:39 GMT",
"version": "v2"
},
{
"created": "Tue, 31 Mar 2020 06:48:53 GMT",
"version": "v3"
}
] | 2020-04-07 | [
[
"Zhang",
"Cong",
""
],
[
"Zhang",
"Xiangdong",
""
]
] | Inspired by the recent proposal for the quantum effective dynamics of the Schwarzschild spacetime given in \cite{AOS1}, we investigate the effective dynamics of the loop quantized Janis-Newman-Winicour (JNW) spacetime which is an extension of the Schwarzschild spacetime with an extra minimally coupled massless scalar field. Two parameters are introduced in order to regularize the Hamiltonian constraint in the quantum effective dynamics. These two parameters are assumed to be Dirac observables when the effective dynamics is solved. By carefully choosing appropriate conditions for these two parameters, we completely determine them, and the resulted new effective description of the JNW spacetime leads to a well behaved quantum dynamics which on one hand resolves the classical singularities, and on the other hand, agrees with the classical dynamics in the low curvature region. |
2004.06214 | Burin Gumjudpai | Chonticha Kritpetch (IF Naresuan), Candrasyah Muhammad (IF Naresuan)
and Burin Gumjudpai (IF Naresuan and ThEP Center) | Holographic dark energy with non-minimal derivative coupling to gravity
effects | 12 pages, 12 figures | Physics of the Dark Universe, 30, 100712 (2020) | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Non-minimal derivative coupling (NMDC) to gravity in flat FLRW universe is
investigated in the scenario of holographic dark energy. Kinetic term is
coupled to the Einstein tensor under potential $V = (1/2)m^2 \phi^2$. The free
kinetic term is allowed to be canonical and phantom. Gravitational constant is
modified with the NMDC coupling. Holographic cutoff at Hubble horizon gives
modification to dark energy density. We evaluate dark energy equation of state
and the variation of gravitational constant of the theory such that the theory
can be constrained. It is found that positive NMDC coupling is favored rather
than the negative one. The model with purely NMDC theory and the potential is
favored with positive sub-Planckian NMDC coupling and decaying scalar field.
The canonical scalar field with positive NMDC coupling under the scalar
potential is also viable under some conditions that result in oscillating
scalar field. The phantom field case is not favored in this model since the
coupling and scalar mass are required to be super-Planckian while it is tightly
constrained by gravitational constant variation observations.
| [
{
"created": "Mon, 13 Apr 2020 21:54:38 GMT",
"version": "v1"
},
{
"created": "Sun, 19 Apr 2020 16:51:27 GMT",
"version": "v2"
},
{
"created": "Sat, 29 Aug 2020 20:09:36 GMT",
"version": "v3"
}
] | 2020-09-01 | [
[
"Kritpetch",
"Chonticha",
"",
"IF Naresuan"
],
[
"Muhammad",
"Candrasyah",
"",
"IF Naresuan"
],
[
"Gumjudpai",
"Burin",
"",
"IF Naresuan and ThEP Center"
]
] | Non-minimal derivative coupling (NMDC) to gravity in flat FLRW universe is investigated in the scenario of holographic dark energy. Kinetic term is coupled to the Einstein tensor under potential $V = (1/2)m^2 \phi^2$. The free kinetic term is allowed to be canonical and phantom. Gravitational constant is modified with the NMDC coupling. Holographic cutoff at Hubble horizon gives modification to dark energy density. We evaluate dark energy equation of state and the variation of gravitational constant of the theory such that the theory can be constrained. It is found that positive NMDC coupling is favored rather than the negative one. The model with purely NMDC theory and the potential is favored with positive sub-Planckian NMDC coupling and decaying scalar field. The canonical scalar field with positive NMDC coupling under the scalar potential is also viable under some conditions that result in oscillating scalar field. The phantom field case is not favored in this model since the coupling and scalar mass are required to be super-Planckian while it is tightly constrained by gravitational constant variation observations. |
2404.05464 | Mian Zhu | Shingo Akama and Mian Zhu | Parity violation in primordial tensor non-Gaussianities from matter
bounce cosmology | null | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been shown that primordial tensor non-Gaussianities from a cubic Weyl
action with a non-dynamical coupling are suppressed by the so-called slow-roll
parameter in a conventional framework of slow-roll inflation. In this paper, we
consider matter bounce cosmology in which the background spacetime is no longer
quasi-de Sitter, and hence one might expect that the matter bounce models could
predict non-suppressed non-Gaussianities. Nevertheless, we first show that the
corresponding non-Gaussian amplitudes from the cubic Weyl term with a
non-dynamical coupling are much smaller than those from the conventional
slow-roll inflation, in spite of the fact that there is no slow-roll
suppression. We then introduce a dynamical coupling that can boost the
magnitude of graviton cubic interactions and clarify that there is a parameter
region where the tensor non-Gaussianities can be enhanced and can potentially
be tested by cosmic microwave background experiments.
| [
{
"created": "Mon, 8 Apr 2024 12:42:02 GMT",
"version": "v1"
}
] | 2024-04-09 | [
[
"Akama",
"Shingo",
""
],
[
"Zhu",
"Mian",
""
]
] | It has been shown that primordial tensor non-Gaussianities from a cubic Weyl action with a non-dynamical coupling are suppressed by the so-called slow-roll parameter in a conventional framework of slow-roll inflation. In this paper, we consider matter bounce cosmology in which the background spacetime is no longer quasi-de Sitter, and hence one might expect that the matter bounce models could predict non-suppressed non-Gaussianities. Nevertheless, we first show that the corresponding non-Gaussian amplitudes from the cubic Weyl term with a non-dynamical coupling are much smaller than those from the conventional slow-roll inflation, in spite of the fact that there is no slow-roll suppression. We then introduce a dynamical coupling that can boost the magnitude of graviton cubic interactions and clarify that there is a parameter region where the tensor non-Gaussianities can be enhanced and can potentially be tested by cosmic microwave background experiments. |
gr-qc/9412070 | Joan Masso | Carles Bona, Joan Masso and Joan Stela | Numerical Black Holes: A Moving Grid Approach | 12 pages, LaTeX with RevTeX 3.0 macros, 4 uuencoded gz-compressed
postscript figures. Also available at http://jean-luc.ncsa.uiuc.edu/Papers/
To appear in Physical Review D | Phys.Rev. D51 (1995) 1639-1645 | 10.1103/PhysRevD.51.1639 | null | gr-qc | null | Spherically symmetric (1D) black-hole spacetimes are considered as a test for
numerical relativity. A finite difference code, based in the hyperbolic
structure of Einstein's equations with the harmonic slicing condition is
presented. Significant errors in the mass function are shown to arise from the
steep gradient zone behind the black hole horizon, which challenge the
Computational Fluid Dynamics numerical methods used in the code. The formalism
is extended to moving numerical grids, which are adapted to follow horizon
motion. The black hole exterior region can then be modeled with higher
accuracy.
| [
{
"created": "Thu, 22 Dec 1994 16:38:28 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Bona",
"Carles",
""
],
[
"Masso",
"Joan",
""
],
[
"Stela",
"Joan",
""
]
] | Spherically symmetric (1D) black-hole spacetimes are considered as a test for numerical relativity. A finite difference code, based in the hyperbolic structure of Einstein's equations with the harmonic slicing condition is presented. Significant errors in the mass function are shown to arise from the steep gradient zone behind the black hole horizon, which challenge the Computational Fluid Dynamics numerical methods used in the code. The formalism is extended to moving numerical grids, which are adapted to follow horizon motion. The black hole exterior region can then be modeled with higher accuracy. |
0708.1783 | Paul Davies | P. C. W. Davies | Constraints on the value of the fine structure constant from
gravitational thermodynamics | 6 pages, no figures, journal publication | Int.J.Theor.Phys.47:1949-1953,2008 | 10.1007/s10773-007-9638-1 | null | gr-qc | null | In this paper I show how the second law of thermodynamics, generalized to
include event horizon area, places interesting constraints on the value of the
fine structure constant. A simple analysis leads to the conclusion that
classical Dirac and point-like magnetic monopoles could be used to violate the
second law, and that GUT monopoles are inconsistent with minicharged particles.
| [
{
"created": "Mon, 13 Aug 2007 22:26:42 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Sep 2007 22:59:51 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Davies",
"P. C. W.",
""
]
] | In this paper I show how the second law of thermodynamics, generalized to include event horizon area, places interesting constraints on the value of the fine structure constant. A simple analysis leads to the conclusion that classical Dirac and point-like magnetic monopoles could be used to violate the second law, and that GUT monopoles are inconsistent with minicharged particles. |
gr-qc/0310029 | Yousuke Itoh | Yousuke Itoh | Equation of motion for relativistic compact binaries with the strong
field point particle limit: Third post-Newtonian order | 52 pages, no figure, Appendices B and D added. Phys. Rev. D in press | Phys.Rev. D69 (2004) 064018 | 10.1103/PhysRevD.69.064018 | null | gr-qc | null | An equation of motion for relativistic compact binaries is derived through
the third post-Newtonian (3 PN) approximation of general relativity. The strong
field point particle limit and multipole expansion of the stars are used to
solve iteratively the harmonically relaxed Einstein equations. We take into
account the Lorentz contraction on the multipole moments defined in our
previous works. We then derive a 3 PN acceleration of the binary orbital motion
of the two spherical compact stars based on a surface integral approach which
is a direct consequence of local energy momentum conservation. Our resulting
equation of motion admits a conserved energy (neglecting the 2.5 PN radiation
reaction effect), is Lorentz invariant and is unambiguous: there exist no
undetermined parameter reported in the previous works. We shall show that our 3
PN equation of motion agrees physically with the Blanchet and Faye 3 PN
equation of motion if $\lambda = - 1987/3080$, where $\lambda$ is the parameter
which is undetermined within their framework. This value of $\lambda$ is
consistent with the result of Damour, Jaranowski, and Sch\"afer who first
completed a 3 PN iteration of the ADM Hamiltonian in the ADMTT gauge using the
dimensional regularization.
| [
{
"created": "Sun, 5 Oct 2003 18:06:47 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Feb 2004 13:38:58 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Itoh",
"Yousuke",
""
]
] | An equation of motion for relativistic compact binaries is derived through the third post-Newtonian (3 PN) approximation of general relativity. The strong field point particle limit and multipole expansion of the stars are used to solve iteratively the harmonically relaxed Einstein equations. We take into account the Lorentz contraction on the multipole moments defined in our previous works. We then derive a 3 PN acceleration of the binary orbital motion of the two spherical compact stars based on a surface integral approach which is a direct consequence of local energy momentum conservation. Our resulting equation of motion admits a conserved energy (neglecting the 2.5 PN radiation reaction effect), is Lorentz invariant and is unambiguous: there exist no undetermined parameter reported in the previous works. We shall show that our 3 PN equation of motion agrees physically with the Blanchet and Faye 3 PN equation of motion if $\lambda = - 1987/3080$, where $\lambda$ is the parameter which is undetermined within their framework. This value of $\lambda$ is consistent with the result of Damour, Jaranowski, and Sch\"afer who first completed a 3 PN iteration of the ADM Hamiltonian in the ADMTT gauge using the dimensional regularization. |
1908.11073 | Nelson Christensen | Nelson Christensen | Implications of the binary coalescence events found in O1 and O2 for the
stochastic background of gravitational events | Contribution to the 2019 Gravitation session of the 54th Rencontres
de Moriond | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Advanced LIGO and Advanced Virgo detectors have commenced observations.
Gravitational waves from the merger of binary black hole systems and a binary
neutron star system have been observed. A major goal for LIGO and Virgo is to
detect or set limits on a stochastic background of gravitational waves. A
stochastic background of gravitational waves is expected to arise from a
superposition of a large number of unresolved cosmological and/or astrophysical
sources. A cosmologically produced background would carry unique signatures
from the earliest epochs in the evolution of the Universe. Similarly, an
astrophysical background would provide information about the astrophysical
sources that generated it. The observation of gravitational waves from compact
binary mergers implies that there will be a stochastic background from these
sources that could be observed by Advanced LIGO and Advanced Virgo in the
coming years. The LIGO and Virgo search for a stochastic background should
probe interesting regions of the parameter space for numerous astrophysical and
cosmological models. Presented here is an outline of LIGO and Virgo's search
strategies for a stochastic background of gravitational waves, including the
search for gravitational wave polarizations outside of what is predicted from
general relativity. Also discussed is how global electromagnetic noise (from
the Schumann resonances) could affect this search; possible strategies to
monitor and subtract this potential source of correlated noise in a the global
detector network are explained. The results from Advanced LIGO's observing runs
O1 and O2 will be presented, along with the implications of the gravitational
wave detections. The future goals for Advanced LIGO and Advanced Virgo will be
explained.
| [
{
"created": "Thu, 29 Aug 2019 07:06:44 GMT",
"version": "v1"
}
] | 2019-08-30 | [
[
"Christensen",
"Nelson",
""
]
] | The Advanced LIGO and Advanced Virgo detectors have commenced observations. Gravitational waves from the merger of binary black hole systems and a binary neutron star system have been observed. A major goal for LIGO and Virgo is to detect or set limits on a stochastic background of gravitational waves. A stochastic background of gravitational waves is expected to arise from a superposition of a large number of unresolved cosmological and/or astrophysical sources. A cosmologically produced background would carry unique signatures from the earliest epochs in the evolution of the Universe. Similarly, an astrophysical background would provide information about the astrophysical sources that generated it. The observation of gravitational waves from compact binary mergers implies that there will be a stochastic background from these sources that could be observed by Advanced LIGO and Advanced Virgo in the coming years. The LIGO and Virgo search for a stochastic background should probe interesting regions of the parameter space for numerous astrophysical and cosmological models. Presented here is an outline of LIGO and Virgo's search strategies for a stochastic background of gravitational waves, including the search for gravitational wave polarizations outside of what is predicted from general relativity. Also discussed is how global electromagnetic noise (from the Schumann resonances) could affect this search; possible strategies to monitor and subtract this potential source of correlated noise in a the global detector network are explained. The results from Advanced LIGO's observing runs O1 and O2 will be presented, along with the implications of the gravitational wave detections. The future goals for Advanced LIGO and Advanced Virgo will be explained. |
1706.03927 | Koray D\"uzta\c{s} | Koray D\"uzta\c{s} | Cosmic censorship and the third law of black hole dynamics | Final version to appear in Turkish Journal of Physics (Open access) | null | 10.3906/fiz-1802-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Israel's proof of the third law of black hole dynamics is based on the
semi-rigidity assumption which requires that the areas of the outermost trapped
surfaces are preserved. We argue that the condition that the area of the event
horizon should not decrease is necessary -but not sufficient- for the
semi-rigidity assumption to hold. It is known that the presence of a naked
singularity in the exterior region invalidates Hawking's proof of the area
theorem. In this sense, the third law assumes the validity of the strong form
of the cosmic censorship conjecture, contrary to general acceptance. Still, one
cannot guarantee that the semi-rigidity assumption holds. Therefore the current
proof is incomplete. Recent studies on the interactions of black holes with
fermionic fields imply a generic formation of naked singularities. The presence
of these singularities invalidates the laws of black hole dynamics and cosmic
censorship conjecture for the processes that satisfy the weak energy condition.
| [
{
"created": "Tue, 13 Jun 2017 07:19:12 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Oct 2017 09:00:17 GMT",
"version": "v2"
},
{
"created": "Fri, 18 May 2018 22:00:18 GMT",
"version": "v3"
}
] | 2018-05-22 | [
[
"Düztaş",
"Koray",
""
]
] | Israel's proof of the third law of black hole dynamics is based on the semi-rigidity assumption which requires that the areas of the outermost trapped surfaces are preserved. We argue that the condition that the area of the event horizon should not decrease is necessary -but not sufficient- for the semi-rigidity assumption to hold. It is known that the presence of a naked singularity in the exterior region invalidates Hawking's proof of the area theorem. In this sense, the third law assumes the validity of the strong form of the cosmic censorship conjecture, contrary to general acceptance. Still, one cannot guarantee that the semi-rigidity assumption holds. Therefore the current proof is incomplete. Recent studies on the interactions of black holes with fermionic fields imply a generic formation of naked singularities. The presence of these singularities invalidates the laws of black hole dynamics and cosmic censorship conjecture for the processes that satisfy the weak energy condition. |
2305.04065 | Bobby Eka Gunara | Tegar Ari Widianto, Ahmad Khoirul Falah, Agus Suroso, Husin Alatas,
and Bobby Eka Gunara | Some Cosmological Consequences of Higher Dimensional
Klein-Gordon-Rastall Theory | 40 pages, 32 figures, typos corrected, abstract and all section
revised as referee suggestion. Accepted in European Phys Jour C | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Using dynamical system analysis, we investigate some cosmological
consequences of Rastall gravity coupled to a scalar field (called the
Klein-Gordon-Rastall theory) with exponential scalar potential turned on in
higher dimensions. From the critical points of the autonomous equations, we can
determine the dominant components of the energy density in different cosmic
eras. We obtain a fixed point representing a scalar field-matter-dominated era
which corresponds to either a late-time or past-time attractor depending on the
parameters used. According to this point, the inflationary phase, corresponding
to past-time attractors, is given by unstable nodes, whilst the dark energy
era, corresponding to late-time attractors, is represented by stable nodes. In
the inflationary sector, power-law inflation can still occur in this
Klein-Gordon-Rastall cosmological model. On the other hand, in the late-time
sector, we find a nontrivial interplay between a scalar field with an
exponential potential and the non-conservative energy-momentum tensor of the
non-relativistic matter field (baryonic-dark matter) in curved spacetime plays
a role as the dark energy. Based on such features, the Klein-Gordon-Rastall
cosmology could be a promising candidate for describing both the early and
late-time universe.
| [
{
"created": "Sat, 6 May 2023 15:00:44 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Oct 2023 13:42:51 GMT",
"version": "v2"
}
] | 2023-10-25 | [
[
"Widianto",
"Tegar Ari",
""
],
[
"Falah",
"Ahmad Khoirul",
""
],
[
"Suroso",
"Agus",
""
],
[
"Alatas",
"Husin",
""
],
[
"Gunara",
"Bobby Eka",
""
]
] | Using dynamical system analysis, we investigate some cosmological consequences of Rastall gravity coupled to a scalar field (called the Klein-Gordon-Rastall theory) with exponential scalar potential turned on in higher dimensions. From the critical points of the autonomous equations, we can determine the dominant components of the energy density in different cosmic eras. We obtain a fixed point representing a scalar field-matter-dominated era which corresponds to either a late-time or past-time attractor depending on the parameters used. According to this point, the inflationary phase, corresponding to past-time attractors, is given by unstable nodes, whilst the dark energy era, corresponding to late-time attractors, is represented by stable nodes. In the inflationary sector, power-law inflation can still occur in this Klein-Gordon-Rastall cosmological model. On the other hand, in the late-time sector, we find a nontrivial interplay between a scalar field with an exponential potential and the non-conservative energy-momentum tensor of the non-relativistic matter field (baryonic-dark matter) in curved spacetime plays a role as the dark energy. Based on such features, the Klein-Gordon-Rastall cosmology could be a promising candidate for describing both the early and late-time universe. |
gr-qc/0412093 | Mauro Hueller | M. Hueller, M. Armano, L. Carbone, A. Cavalleri, R. Dolesi, C. D.
Hoyle, S. Vitale, W. J. Weber | Measuring the LISA test mass magnetic proprieties with a torsion
pendulum | 6 pages, 3 figures | Class.Quant.Grav. 22 (2005) S521-S526 | 10.1088/0264-9381/22/10/052 | null | gr-qc | null | Achieving the low frequency LISA sensitivity requires that the test masses
acting as the interferometer end mirrors are free-falling with an unprecedented
small degree of deviation. Magnetic disturbances, originating in the
interaction of the test mass with the environmental magnetic field, can
significantly deteriorate the LISA performance and can be parameterized through
the test mass remnant dipole moment $\vec{m}_r$ and the magnetic susceptibility
$\chi$. While the LISA test flight precursor LTP will investigate these effects
during the preliminary phases of the mission, the very stringent requirements
on the test mass magnetic cleanliness make ground-based characterization of its
magnetic proprieties paramount. We propose a torsion pendulum technique to
accurately measure on ground the magnetic proprieties of the LISA/LTP test
masses.
| [
{
"created": "Sun, 19 Dec 2004 20:44:39 GMT",
"version": "v1"
},
{
"created": "Mon, 2 May 2005 12:38:08 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Hueller",
"M.",
""
],
[
"Armano",
"M.",
""
],
[
"Carbone",
"L.",
""
],
[
"Cavalleri",
"A.",
""
],
[
"Dolesi",
"R.",
""
],
[
"Hoyle",
"C. D.",
""
],
[
"Vitale",
"S.",
""
],
[
"Weber",
"W. J.",
""
]
] | Achieving the low frequency LISA sensitivity requires that the test masses acting as the interferometer end mirrors are free-falling with an unprecedented small degree of deviation. Magnetic disturbances, originating in the interaction of the test mass with the environmental magnetic field, can significantly deteriorate the LISA performance and can be parameterized through the test mass remnant dipole moment $\vec{m}_r$ and the magnetic susceptibility $\chi$. While the LISA test flight precursor LTP will investigate these effects during the preliminary phases of the mission, the very stringent requirements on the test mass magnetic cleanliness make ground-based characterization of its magnetic proprieties paramount. We propose a torsion pendulum technique to accurately measure on ground the magnetic proprieties of the LISA/LTP test masses. |
gr-qc/0412024 | Pui Tang Leung | L. K. Tsui and P. T. Leung | Universality in Quasi-normal Modes of Neutron Stars | 16 pages, 9 figures | Mon.Not.Roy.Astron.Soc.357:1029-1037,2005 | 10.1111/j.1365-2966.2005.08710.x/abs/ | null | gr-qc | null | We study the universality in gravitational waves emitted from non-rotating
neutron stars characterized by different equations of state (EOS). We find that
the quasi-normal mode frequencies of such waves, including the $w$-modes and
the $f$-mode, display similar universal scaling behaviours that hold for most
EOS. Such behaviours are shown to stem from the mathematical structure of the
axial and the polar gravitational wave equations, and the fact that the mass
distribution function can be approximated by a cubic-quintic polynomial in
radius. As a benchmark for other realistic neutron stars, a simple model of
neutron stars is adopted here to reproduce the pulsation frequencies and the
generic scaling behaviours mentioned above with good accuracy.
| [
{
"created": "Mon, 6 Dec 2004 03:48:07 GMT",
"version": "v1"
}
] | 2011-05-23 | [
[
"Tsui",
"L. K.",
""
],
[
"Leung",
"P. T.",
""
]
] | We study the universality in gravitational waves emitted from non-rotating neutron stars characterized by different equations of state (EOS). We find that the quasi-normal mode frequencies of such waves, including the $w$-modes and the $f$-mode, display similar universal scaling behaviours that hold for most EOS. Such behaviours are shown to stem from the mathematical structure of the axial and the polar gravitational wave equations, and the fact that the mass distribution function can be approximated by a cubic-quintic polynomial in radius. As a benchmark for other realistic neutron stars, a simple model of neutron stars is adopted here to reproduce the pulsation frequencies and the generic scaling behaviours mentioned above with good accuracy. |
gr-qc/9808058 | Makoto Narita | Makoto Narita (Rikkyo University) | Rigid Singularity Theorem in Globally Hyperbolic Spacetimes | 3 pages, uses revtex.sty, to appear in Physical Review D | Phys.Rev. D58 (1998) 127501 | 10.1103/PhysRevD.58.127501 | null | gr-qc math-ph math.MP | null | We show the rigid singularity theorem, that is, a globally hyperbolic
spacetime satisfying the strong energy condition and containing past trapped
sets, either is timelike geodesically incomplete or splits isometrically as
space $\times$ time. This result is related to Yau's Lorentzian splitting
conjecture.
| [
{
"created": "Fri, 21 Aug 1998 12:30:04 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Narita",
"Makoto",
"",
"Rikkyo University"
]
] | We show the rigid singularity theorem, that is, a globally hyperbolic spacetime satisfying the strong energy condition and containing past trapped sets, either is timelike geodesically incomplete or splits isometrically as space $\times$ time. This result is related to Yau's Lorentzian splitting conjecture. |
1811.02458 | Israel Quiros | Israel Quiros, Roberto De Arcia | On local scale invariance and the questionable theoretical basis of the
conformal transformations' issue | 20 pag. no figures. Extended abstract, references added, new appendix
section added, minor changes to the text | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Here we follow the mainstream of thinking about physical equivalence of
different representations of a theory, regarded as the consequence of
invariance of the laws of physics -- represented by an action principle and the
derived motion equations -- under given transformations; be it coordinate,
gauge or conformal transformations. Accordingly the conformal transformations'
issue is discussed by invoking the assumed invariance of the laws of physics --
in particular the laws of gravity -- under conformal transformations of the
metric. It is shown that Brans-Dicke and scalar-tensor theories are not
well-suited to address physical equivalence of the conformal frames since the
corresponding laws of gravity are not invariant under the conformal
transformations or Weyl rescalings. The search for conformal symmetry leads us
to explore the physical consequences of Weyl-invariant theories of gravity,
that represent a natural arena where to discuss on physical equivalence of the
conformally related representations. We show that conformal invariance of the
action of a (supposedly conformal invariant) theory and of the derived motion
equations is not enough to ensure actual Weyl invariance. It is required, also,
that the underlying geometrical structure of the background spacetime be, at
least, Weyl-integrable. Otherwise, if assume (as usual) spacetimes of
(pseudo)Riemannian geometrical structure, the resulting -- apparently conformal
invariant -- theory is anomalous in that, only massless matter fields can be
consistently coupled. Gauge freedom, a distinctive feature of actually
Weyl-invariant theories of gravity, leads to very unusual consequences.
| [
{
"created": "Tue, 6 Nov 2018 16:09:24 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Nov 2018 04:04:47 GMT",
"version": "v2"
}
] | 2018-11-14 | [
[
"Quiros",
"Israel",
""
],
[
"De Arcia",
"Roberto",
""
]
] | Here we follow the mainstream of thinking about physical equivalence of different representations of a theory, regarded as the consequence of invariance of the laws of physics -- represented by an action principle and the derived motion equations -- under given transformations; be it coordinate, gauge or conformal transformations. Accordingly the conformal transformations' issue is discussed by invoking the assumed invariance of the laws of physics -- in particular the laws of gravity -- under conformal transformations of the metric. It is shown that Brans-Dicke and scalar-tensor theories are not well-suited to address physical equivalence of the conformal frames since the corresponding laws of gravity are not invariant under the conformal transformations or Weyl rescalings. The search for conformal symmetry leads us to explore the physical consequences of Weyl-invariant theories of gravity, that represent a natural arena where to discuss on physical equivalence of the conformally related representations. We show that conformal invariance of the action of a (supposedly conformal invariant) theory and of the derived motion equations is not enough to ensure actual Weyl invariance. It is required, also, that the underlying geometrical structure of the background spacetime be, at least, Weyl-integrable. Otherwise, if assume (as usual) spacetimes of (pseudo)Riemannian geometrical structure, the resulting -- apparently conformal invariant -- theory is anomalous in that, only massless matter fields can be consistently coupled. Gauge freedom, a distinctive feature of actually Weyl-invariant theories of gravity, leads to very unusual consequences. |
0905.0955 | Vjacheslav Dorofeev | A. A. Grib | Spontaneous breaking of symmetry of the gravitons of the long wave
spectrum in the early Universe | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that nonlinear terms in equations of gravitons on the background
of curved space-time of the expanding Universe can solve the problem of the
negative square of the effective mass formally arising in linear approximation
for gravitons. Similar to well known spontaneous breaking of symmetry in
Goldstone model one must take another vacuum so that nonzero vacuum expectation
value of the quantized graviton field leads to change of spectrum for
gravitons. There appears two graviton fields, one with the positive mass,
another with the zero mass. Energy density and the density of particles created
by gravitation of the expanding Universe are calculated for some special cases
of the scale factor. Numerical of result are obtained for the dust universe
case.
| [
{
"created": "Thu, 7 May 2009 06:22:38 GMT",
"version": "v1"
}
] | 2009-05-08 | [
[
"Grib",
"A. A.",
""
]
] | It is shown that nonlinear terms in equations of gravitons on the background of curved space-time of the expanding Universe can solve the problem of the negative square of the effective mass formally arising in linear approximation for gravitons. Similar to well known spontaneous breaking of symmetry in Goldstone model one must take another vacuum so that nonzero vacuum expectation value of the quantized graviton field leads to change of spectrum for gravitons. There appears two graviton fields, one with the positive mass, another with the zero mass. Energy density and the density of particles created by gravitation of the expanding Universe are calculated for some special cases of the scale factor. Numerical of result are obtained for the dust universe case. |
gr-qc/0612140 | Carlos A. R. Herdeiro | L. Filipe Costa, Carlos A. R. Herdeiro | A gravito-electromagnetic analogy based on tidal tensors | 30 pages, LaTeX; v2. 38 pages, Major rewritting including: i) a new
realisation of the proposed analogy giving a simple derivation of the
Papapetrou equation for a spinning particle; ii) an appendix with a
derivation of the generalised worldline deviation equation; iii) a detailed
discussion of main results; iv) more references; v) typos corrected | Phys.Rev.D78:024021,2008 | 10.1103/PhysRevD.78.024021 | null | gr-qc hep-th | null | We propose a new approach to a physical analogy between General Relativity
and Electromagnetism, based on tidal tensors of both theories. Using this
approach we write a covariant form for the gravitational analogues of the
Maxwell equations. The following realisations of the analogy are given. The
first one matches linearised gravitational tidal tensors to exact
electromagnetic tidal tensors in Minkwoski spacetime. The second one matches
exact magnetic gravitational tidal tensors for ultra-stationary metrics to
exact magnetic tidal tensors of electromagnetism in curved spaces. In the third
we show that our approach leads to two-step exact derivation of the Papapetrou
force on a gyroscope. We then establish a new proof for a class of tensor
identities that define invariants of the type $\vec{E}^2-\vec{B}^2$ and
$\vec{E}\cdot\vec{B}$, and we exhibit the invariants built from tidal tensors
in both gravity and electromagnetism. We contrast our approach with the two
gravito-electromagnetic analogies commonly found in the literature, and argue
that it sheds light on the debate about the limit of validity of one of the
analogies, and clarifies issues concerning the physical interpretation of the
other.
| [
{
"created": "Thu, 21 Dec 2006 20:28:54 GMT",
"version": "v1"
},
{
"created": "Mon, 21 May 2007 17:42:18 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Costa",
"L. Filipe",
""
],
[
"Herdeiro",
"Carlos A. R.",
""
]
] | We propose a new approach to a physical analogy between General Relativity and Electromagnetism, based on tidal tensors of both theories. Using this approach we write a covariant form for the gravitational analogues of the Maxwell equations. The following realisations of the analogy are given. The first one matches linearised gravitational tidal tensors to exact electromagnetic tidal tensors in Minkwoski spacetime. The second one matches exact magnetic gravitational tidal tensors for ultra-stationary metrics to exact magnetic tidal tensors of electromagnetism in curved spaces. In the third we show that our approach leads to two-step exact derivation of the Papapetrou force on a gyroscope. We then establish a new proof for a class of tensor identities that define invariants of the type $\vec{E}^2-\vec{B}^2$ and $\vec{E}\cdot\vec{B}$, and we exhibit the invariants built from tidal tensors in both gravity and electromagnetism. We contrast our approach with the two gravito-electromagnetic analogies commonly found in the literature, and argue that it sheds light on the debate about the limit of validity of one of the analogies, and clarifies issues concerning the physical interpretation of the other. |
2312.17129 | Sujoy Modak | Dhamar S. Astilla, Sujoy K. Modak and Enrique Salazar | Anisotropic particle creation from $T-$vacuum in the radiation dominated
universe | 16 pages, revtex two column, 3 figures | null | null | null | gr-qc astro-ph.CO hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | We further investigate novel features of the $T-$vacuum state, originally
defined in the context of quantum field theory in a (1+1) dimensional radiation
dominated universe [Modak, JHEP 12, 031 (2020)]. Here we extend the previous
work to a realistic (3+1) dimensional set up and show that $T-$vacuum causes an
\emph{anisotropic particle creation} in the radiation dominated early universe.
Unlike the Hawking or Unruh effect, where the particle content is thermal and
asymptotically defined, here it is non-thermal and time dependent. This novel
example of particle creation is interesting because these particles are
detected in the frame of physical/cosmological observers, who envision the
$T-$vacuum as a particle excited state, and therefore may eventually be
compared with observations.
| [
{
"created": "Thu, 28 Dec 2023 17:05:56 GMT",
"version": "v1"
}
] | 2023-12-29 | [
[
"Astilla",
"Dhamar S.",
""
],
[
"Modak",
"Sujoy K.",
""
],
[
"Salazar",
"Enrique",
""
]
] | We further investigate novel features of the $T-$vacuum state, originally defined in the context of quantum field theory in a (1+1) dimensional radiation dominated universe [Modak, JHEP 12, 031 (2020)]. Here we extend the previous work to a realistic (3+1) dimensional set up and show that $T-$vacuum causes an \emph{anisotropic particle creation} in the radiation dominated early universe. Unlike the Hawking or Unruh effect, where the particle content is thermal and asymptotically defined, here it is non-thermal and time dependent. This novel example of particle creation is interesting because these particles are detected in the frame of physical/cosmological observers, who envision the $T-$vacuum as a particle excited state, and therefore may eventually be compared with observations. |
1706.00507 | Vasilis Oikonomou | V.K. Oikonomou | Reheating in Constant-roll $F(R)$ Gravity | null | Mod. Phys. Lett. A32 (2017) 1750172 | 10.1142/S0217732317501723 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we address the reheating issue in the context of $F(R)$ gravity,
for theories that the inflationary era does not obey the slow-roll condition
but the constant-roll condition is assumed. As it is known, the reheating era
takes place after the end of the inflationary era, so we investigate the
implications of a constant-roll inflation era on the reheating era. We quantify
our considerations by calculating the reheating temperature for the
constant-roll $R^2$ model and we compare to the standard reheating temperature
in the context of $F(R)$ gravity. As we demonstrate, the new reheating
temperature may differ from the standard one, and in addition we show how the
reheating era may restrict the constant-roll era by constraining the
constant-roll parameter.
| [
{
"created": "Thu, 1 Jun 2017 22:05:41 GMT",
"version": "v1"
}
] | 2017-10-10 | [
[
"Oikonomou",
"V. K.",
""
]
] | In this work we address the reheating issue in the context of $F(R)$ gravity, for theories that the inflationary era does not obey the slow-roll condition but the constant-roll condition is assumed. As it is known, the reheating era takes place after the end of the inflationary era, so we investigate the implications of a constant-roll inflation era on the reheating era. We quantify our considerations by calculating the reheating temperature for the constant-roll $R^2$ model and we compare to the standard reheating temperature in the context of $F(R)$ gravity. As we demonstrate, the new reheating temperature may differ from the standard one, and in addition we show how the reheating era may restrict the constant-roll era by constraining the constant-roll parameter. |
1611.00208 | Bethan Cropp | Bethan Cropp | Strange Horizons: Understanding Causal Barriers Beyond General
Relativity | PhD Thesis, with minor corrections, submitted to SISSA in 2015, 152
pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This thesis explores two avenues into understanding the physics of black
holes and horizons beyond general relativity, via analogue models and Lorentz
violating theories. Analogue spacetimes have wildly different dynamics to
general relativity; this allows the possibility of non-Killing horizons in
stationary solutions. In the case of non-Killing horizons different definitions
of surface gravity are truly different quantities. This also has application to
modified theories of gravity, where there is no reason to expect all horizons
to be Killing horizons. In Lorentz violating theories, the situation becomes
even stranger, as Killing horizons are at best low energy barriers, but for
superluminal dispersion relations a true causal barrier, the universal horizon,
may be present. We investigate the nature of these universal horizons via a ray
tracing study, and delve into what happens near both the universal and Killing
horizons. From this study we determine the surface gravity of universal
horizons by the peeling properties of rays near the horizon and discuss
whether, and at what temperature these horizons radiate. Finally, we combine
our investigations of universal horizons and analogue spacetimes, and ask why
we have not seen a universal horizon in studies of analogue gravity.
| [
{
"created": "Tue, 1 Nov 2016 13:02:24 GMT",
"version": "v1"
}
] | 2016-11-02 | [
[
"Cropp",
"Bethan",
""
]
] | This thesis explores two avenues into understanding the physics of black holes and horizons beyond general relativity, via analogue models and Lorentz violating theories. Analogue spacetimes have wildly different dynamics to general relativity; this allows the possibility of non-Killing horizons in stationary solutions. In the case of non-Killing horizons different definitions of surface gravity are truly different quantities. This also has application to modified theories of gravity, where there is no reason to expect all horizons to be Killing horizons. In Lorentz violating theories, the situation becomes even stranger, as Killing horizons are at best low energy barriers, but for superluminal dispersion relations a true causal barrier, the universal horizon, may be present. We investigate the nature of these universal horizons via a ray tracing study, and delve into what happens near both the universal and Killing horizons. From this study we determine the surface gravity of universal horizons by the peeling properties of rays near the horizon and discuss whether, and at what temperature these horizons radiate. Finally, we combine our investigations of universal horizons and analogue spacetimes, and ask why we have not seen a universal horizon in studies of analogue gravity. |
0806.0628 | Eric Greenwood | Eric Greenwood and Dejan Stojkovic | Hawking radiation as seen by an infalling observer | Added analysis of the Hawking-like radiation as seen by an observer
in Eddington-Finkelstein coordinates. Accepted for publication in JHEP | JHEP 0909:058,2009 | 10.1088/1126-6708/2009/09/058 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate an important question of Hawking-like radiation as seen by an
infalling observer during gravitational collapse. Using the functional
Schrodinger formalism we are able to probe the time dependent regime which is
out of the reach of the standard approximations like the Bogolyubov method. We
calculate the occupation number of particles whose frequencies are measured in
the proper time of an infalling observer in two crucially different space-time
foliations: Schwarzschild and Eddington-Finkelstein. We demonstrate that the
distribution in Schwarzschild reference frame is not quite thermal, though it
becomes thermal once the horizon is crossed. We approximately fit the
temperature and find that the local temperature increases as the horizon is
approached, and diverges exactly at the horizon. In Eddington-Finkelstein
reference frame the temperature at the horizon is finite, since the observer in
that frame is not accelerated. These results are in agreement with what is
generically expected in the absence of backreaction. We also discuss some
subtleties related to the physical interpretation of the infinite local
temperature in Schwarzschild reference frame.
| [
{
"created": "Tue, 3 Jun 2008 20:03:19 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Sep 2009 21:18:07 GMT",
"version": "v2"
}
] | 2014-11-18 | [
[
"Greenwood",
"Eric",
""
],
[
"Stojkovic",
"Dejan",
""
]
] | We investigate an important question of Hawking-like radiation as seen by an infalling observer during gravitational collapse. Using the functional Schrodinger formalism we are able to probe the time dependent regime which is out of the reach of the standard approximations like the Bogolyubov method. We calculate the occupation number of particles whose frequencies are measured in the proper time of an infalling observer in two crucially different space-time foliations: Schwarzschild and Eddington-Finkelstein. We demonstrate that the distribution in Schwarzschild reference frame is not quite thermal, though it becomes thermal once the horizon is crossed. We approximately fit the temperature and find that the local temperature increases as the horizon is approached, and diverges exactly at the horizon. In Eddington-Finkelstein reference frame the temperature at the horizon is finite, since the observer in that frame is not accelerated. These results are in agreement with what is generically expected in the absence of backreaction. We also discuss some subtleties related to the physical interpretation of the infinite local temperature in Schwarzschild reference frame. |
1207.6024 | Surajit Chattopadhyay | Rahul Ghosh (Bhairab Ganguly College), Antonio Pasqua (University of
Trieste) and Surajit Chattopadhyay (Pailan College of Management and
Technology) | Generalized second law of thermodynamics in the emergent universe for
some viable models of f(T) gravity | 12 pages, 17 figures. arXiv admin note: text overlap with
arXiv:1201.2511 by other authors | Eur. Phys. J. Plus (2013) 128: 12 | 10.1140/epjp/i2013-13012-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present study is motivated by the study of reference [1], where the
generalized second law of thermodynamics has been investigated for a flat FRW
universe for two viable models of $f(T)$ gravity. In the present work, we have
considered a non-flat universe and accordingly studied the behaviors of
equation of state parameter and deceleration parameter. Subsequently, using the
first law of thermodynamics we derived the expressions for the time derivative
of the total entropy of a universe enveloped by apparent horizon. In the next
phase, with the choice of scale factor pertaining to an emergent universe we
have investigated the sign of the time derivatives of total entropy for three
viable models of $f(T)$ gravity.
| [
{
"created": "Tue, 24 Jul 2012 11:34:22 GMT",
"version": "v1"
},
{
"created": "Sat, 24 Nov 2012 15:57:46 GMT",
"version": "v2"
}
] | 2013-11-22 | [
[
"Ghosh",
"Rahul",
"",
"Bhairab Ganguly College"
],
[
"Pasqua",
"Antonio",
"",
"University of\n Trieste"
],
[
"Chattopadhyay",
"Surajit",
"",
"Pailan College of Management and\n Technology"
]
] | The present study is motivated by the study of reference [1], where the generalized second law of thermodynamics has been investigated for a flat FRW universe for two viable models of $f(T)$ gravity. In the present work, we have considered a non-flat universe and accordingly studied the behaviors of equation of state parameter and deceleration parameter. Subsequently, using the first law of thermodynamics we derived the expressions for the time derivative of the total entropy of a universe enveloped by apparent horizon. In the next phase, with the choice of scale factor pertaining to an emergent universe we have investigated the sign of the time derivatives of total entropy for three viable models of $f(T)$ gravity. |
2202.12415 | Justo Hernan Ospino Zu\~niga | J. Ospino, J.L. Hernandez-Pastora, L.A. Nunez | All analytic solutions for geodesic motion in axially symmetric
space-times | null | null | 10.1140/epjc/s10052-022-10544-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent observations of the orbits of star clusters around Sgr $A^\star$,
imaging of black holes and gravitational waveforms of merging compact objects
require a detailed understanding of the general relativistic geodesic motion.
We came up with a method to provide all the possible geodesics in an axially
symmetric space-time. The Kerr metric is explicitly worked out, recovering the
Schwarzschild geodesics in the static limit. We also found the most general
Killing tensor and its associated constant of motion for an axisymmetric
space-time. The relevance of these results is crucial to understanding the
different scenarios and the fundamental nature of the compact object at the
galactic center.
| [
{
"created": "Thu, 24 Feb 2022 23:14:07 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Mar 2022 21:04:09 GMT",
"version": "v2"
}
] | 2022-07-13 | [
[
"Ospino",
"J.",
""
],
[
"Hernandez-Pastora",
"J. L.",
""
],
[
"Nunez",
"L. A.",
""
]
] | Recent observations of the orbits of star clusters around Sgr $A^\star$, imaging of black holes and gravitational waveforms of merging compact objects require a detailed understanding of the general relativistic geodesic motion. We came up with a method to provide all the possible geodesics in an axially symmetric space-time. The Kerr metric is explicitly worked out, recovering the Schwarzschild geodesics in the static limit. We also found the most general Killing tensor and its associated constant of motion for an axisymmetric space-time. The relevance of these results is crucial to understanding the different scenarios and the fundamental nature of the compact object at the galactic center. |
1505.00214 | Paul Tod | Ron Kelly and Paul Tod | Penrose's quasi-local mass for asymptotically anti-de Sitter space-times | 7 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Penrose's quasi-local mass construction is carried through for two-surfaces
at infinity in asymptotically anti-de Sitter space-times. A modification of the
Witten argument is given to prove a positivity property of the resulting
conserved quantities.
[This work formed part of Ron Kelly's Oxford D.Phil. thesis, and the first
person pronoun refers to him. It appeared in hand-written form as
`Asymptotically anti-de Sitter space-times' in Twistor Newsletter 20 (1985)
pp11-23 (available at http://people.maths.ox.ac.uk/lmason/Tn/TN1-25), but is
appearing type-set for the first time here. Footnotes marked ${\bf{PT}}$ have
been added for this version by Paul Tod, in the hope of making this work
available to a wider audience.]
| [
{
"created": "Fri, 1 May 2015 16:33:25 GMT",
"version": "v1"
}
] | 2015-05-04 | [
[
"Kelly",
"Ron",
""
],
[
"Tod",
"Paul",
""
]
] | Penrose's quasi-local mass construction is carried through for two-surfaces at infinity in asymptotically anti-de Sitter space-times. A modification of the Witten argument is given to prove a positivity property of the resulting conserved quantities. [This work formed part of Ron Kelly's Oxford D.Phil. thesis, and the first person pronoun refers to him. It appeared in hand-written form as `Asymptotically anti-de Sitter space-times' in Twistor Newsletter 20 (1985) pp11-23 (available at http://people.maths.ox.ac.uk/lmason/Tn/TN1-25), but is appearing type-set for the first time here. Footnotes marked ${\bf{PT}}$ have been added for this version by Paul Tod, in the hope of making this work available to a wider audience.] |
1903.06376 | Akash Kumar Mishra | Akash K Mishra, Sumanta Chakraborty, Sudipta Sarkar | Understanding photon sphere and black hole shadow in dynamically
evolving spacetimes | 39 pages, Accepted in PRD | Phys. Rev. D 99, 104080 (2019) | 10.1103/PhysRevD.99.104080 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have derived the differential equation governing the evolution of the
photon sphere for dynamical black hole spacetimes with or without spherical
symmetry. Numerical solution of the same depicting evolution of the photon
sphere has been presented for Vaidya, Reissner-Nordstr\"{o}m-Vaidya and
de-Sitter Vaidya spacetimes. It has been pointed out that evolution of the
photon sphere depends crucially on the validity of the null energy condition by
the in-falling matter and may present an observational window to even test it
through black hole shadow. We have also presented the evolution of the photon
sphere for slowly rotating Kerr-Vaidya spacetime and associated structure of
black hole shadow. Finally, the effective graviton metric for
Einstein-Gauss-Bonnet gravity has been presented, and the graviton sphere has
been contrasted with the photon sphere in this context.
| [
{
"created": "Fri, 15 Mar 2019 06:02:40 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Jun 2019 04:56:49 GMT",
"version": "v2"
}
] | 2019-06-05 | [
[
"Mishra",
"Akash K",
""
],
[
"Chakraborty",
"Sumanta",
""
],
[
"Sarkar",
"Sudipta",
""
]
] | We have derived the differential equation governing the evolution of the photon sphere for dynamical black hole spacetimes with or without spherical symmetry. Numerical solution of the same depicting evolution of the photon sphere has been presented for Vaidya, Reissner-Nordstr\"{o}m-Vaidya and de-Sitter Vaidya spacetimes. It has been pointed out that evolution of the photon sphere depends crucially on the validity of the null energy condition by the in-falling matter and may present an observational window to even test it through black hole shadow. We have also presented the evolution of the photon sphere for slowly rotating Kerr-Vaidya spacetime and associated structure of black hole shadow. Finally, the effective graviton metric for Einstein-Gauss-Bonnet gravity has been presented, and the graviton sphere has been contrasted with the photon sphere in this context. |
gr-qc/9811016 | Fernando C. Lombardo | Mario Castagnino, Susana Landau, and Fernando C. Lombardo | Creation of unstable particles and decoherence in semiclassical
cosmology | latex file; 18 pages. Some changes have been added. To appear in Gen.
Rel. and Grav | Gen.Rel.Grav. 31 (1999) 1407-1422 | 10.1023/A:1026793212170 | null | gr-qc | null | We consider a simple cosmological model in order to show the importance of
unstable particle creation for the validity of the semiclassical approximation.
Using the mathematical structure of rigged Hilbert spaces we show that particle
creation is the seed of decoherence which enables the quantum to classical
transition.
| [
{
"created": "Wed, 4 Nov 1998 17:13:32 GMT",
"version": "v1"
},
{
"created": "Wed, 26 May 1999 13:48:15 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Castagnino",
"Mario",
""
],
[
"Landau",
"Susana",
""
],
[
"Lombardo",
"Fernando C.",
""
]
] | We consider a simple cosmological model in order to show the importance of unstable particle creation for the validity of the semiclassical approximation. Using the mathematical structure of rigged Hilbert spaces we show that particle creation is the seed of decoherence which enables the quantum to classical transition. |
1504.02455 | Emanuele Berti | Kostas Glampedakis, George Pappas, Hector O. Silva, Emanuele Berti | Post-Tolman-Oppenheimer-Volkoff formalism for relativistic stars | 25 pages, 11 figures, 1 table. Minor changes to match version
published in PRD | Phys. Rev. D 92, 024056 (2015) | 10.1103/PhysRevD.92.024056 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Besides their astrophysical interest, compact stars also provide an arena for
understanding the properties of theories of gravity that differ from Einstein's
general relativity. Numerous studies have shown that different modified
theories of gravity can modify the bulk properties (such as mass and radius) of
neutron stars for given assumptions on the microphysics. What is not usually
stressed though is the strong degeneracy in the predictions of these theories
for the stellar mass and radius. Motivated by this observation, in this paper
we take an alternative route and construct a stellar structure formalism which,
without adhering to any particular theory of gravity, describes in a simple
parametrized form the departure from compact stars in general relativity. This
"post-Tolman-Oppenheimer-Volkoff (TOV)" formalism for spherical static stars is
inspired by the well-known parametrized post-Newtonian theory, extended to
second post-Newtonian order by adding suitable correction terms to the fully
relativistic TOV equations. We show how neutron star properties are modified
within our formalism, paying special attention to the effect of each correction
term. We also show that the formalism is equivalent to general relativity with
an "effective" (gravity-modified) equation of state.
| [
{
"created": "Thu, 9 Apr 2015 19:46:41 GMT",
"version": "v1"
},
{
"created": "Sat, 1 Aug 2015 00:10:39 GMT",
"version": "v2"
}
] | 2015-08-05 | [
[
"Glampedakis",
"Kostas",
""
],
[
"Pappas",
"George",
""
],
[
"Silva",
"Hector O.",
""
],
[
"Berti",
"Emanuele",
""
]
] | Besides their astrophysical interest, compact stars also provide an arena for understanding the properties of theories of gravity that differ from Einstein's general relativity. Numerous studies have shown that different modified theories of gravity can modify the bulk properties (such as mass and radius) of neutron stars for given assumptions on the microphysics. What is not usually stressed though is the strong degeneracy in the predictions of these theories for the stellar mass and radius. Motivated by this observation, in this paper we take an alternative route and construct a stellar structure formalism which, without adhering to any particular theory of gravity, describes in a simple parametrized form the departure from compact stars in general relativity. This "post-Tolman-Oppenheimer-Volkoff (TOV)" formalism for spherical static stars is inspired by the well-known parametrized post-Newtonian theory, extended to second post-Newtonian order by adding suitable correction terms to the fully relativistic TOV equations. We show how neutron star properties are modified within our formalism, paying special attention to the effect of each correction term. We also show that the formalism is equivalent to general relativity with an "effective" (gravity-modified) equation of state. |
gr-qc/9808045 | Clive Wells | Clive G. Wells | Extending the Black Hole Uniqueness Theorems, II. Superstring Black
Holes | 18 pages, LaTeX (REVTeX) | null | null | DAMTP-1998-106 | gr-qc hep-th | null | We make use of an internal symmetry of a truncation of the bosonic sector of
the superstring and N=4 supergravity theories to write down an analogue of
Robinson's identity for the black holes of this theory. This allows us to prove
the uniqueness of a restricted class of black hole solutions. In particular, we
can apply the methods of the preceding paper to prove the uniqueness of a class
of accelerating black holes (the Stringy Ernst solution and Stringy C-metric)
which incorporate the possibility of the black hole accelerating within an
electromagnetic flux tube. These solutions and their associated uniqueness may
be useful in future instanton calculations.
| [
{
"created": "Mon, 17 Aug 1998 00:01:39 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Wells",
"Clive G.",
""
]
] | We make use of an internal symmetry of a truncation of the bosonic sector of the superstring and N=4 supergravity theories to write down an analogue of Robinson's identity for the black holes of this theory. This allows us to prove the uniqueness of a restricted class of black hole solutions. In particular, we can apply the methods of the preceding paper to prove the uniqueness of a class of accelerating black holes (the Stringy Ernst solution and Stringy C-metric) which incorporate the possibility of the black hole accelerating within an electromagnetic flux tube. These solutions and their associated uniqueness may be useful in future instanton calculations. |
0710.5671 | Jorma Louko | Jorma Louko, Alejandro Satz | Transition rate of the Unruh-DeWitt detector in curved spacetime | 27 pages, 1 figure. v3: Typos corrected. Published version | Class.Quant.Grav.25:055012, 2008 | 10.1088/0264-9381/25/5/055012 | null | gr-qc | null | We examine the Unruh-DeWitt particle detector coupled to a scalar field in an
arbitrary Hadamard state in four-dimensional curved spacetime. Using smooth
switching functions to turn on and off the interaction, we obtain a
regulator-free integral formula for the total excitation probability, and we
show that an instantaneous transition rate can be recovered in a suitable
limit. Previous results in Minkowski space are recovered as a special case. As
applications, we consider an inertial detector in the Rindler vacuum and a
detector at rest in a static Newtonian gravitational field. Gravitational
corrections to decay rates in atomic physics laboratory experiments on the
surface of the Earth are estimated to be suppressed by 42 orders of magnitude.
| [
{
"created": "Tue, 30 Oct 2007 15:11:53 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Nov 2007 17:17:47 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Feb 2008 12:13:12 GMT",
"version": "v3"
}
] | 2014-11-18 | [
[
"Louko",
"Jorma",
""
],
[
"Satz",
"Alejandro",
""
]
] | We examine the Unruh-DeWitt particle detector coupled to a scalar field in an arbitrary Hadamard state in four-dimensional curved spacetime. Using smooth switching functions to turn on and off the interaction, we obtain a regulator-free integral formula for the total excitation probability, and we show that an instantaneous transition rate can be recovered in a suitable limit. Previous results in Minkowski space are recovered as a special case. As applications, we consider an inertial detector in the Rindler vacuum and a detector at rest in a static Newtonian gravitational field. Gravitational corrections to decay rates in atomic physics laboratory experiments on the surface of the Earth are estimated to be suppressed by 42 orders of magnitude. |
1808.05834 | Ulrich Sperhake | William G. Cook, Diandian Wang, Ulrich Sperhake | Orbiting black-hole binaries and apparent horizons in higher dimensions | 24 pages, 3 Figures, 3 Tables; to match version published in CQG | null | 10.1088/1361-6382/aae995 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study gravitational wave emission and the structure and formation of
apparent horizons in orbiting black-hole binary systems in higher-dimensional
general relativity. For this purpose we present an apparent horizon finder for
use in higher dimensional numerical simulations and test the finder's accuracy
and consistency in single and binary black-hole spacetimes. The black-hole
binaries we model in $D=6$ dimensions complete up to about one orbit before
merging or scatter off each other without formation of a common horizon. In
agreement with the absence of stable circular geodesic orbits around
higher-dimensional black holes, we do not find binaries completing multiple
orbits without finetuning of the initial data. All binaries radiate about
$0.13\,\%$ to $0.2\,\%$ of the total mass-energy in gravitational waves, over
an order of magnitude below the radiated energy measured for four-dimensional
binaries. The low radiative efficiency is accompanied by relatively slow
dynamics of the binaries as expected from the more rapid falloff of the binding
gravitational force in higher dimensions.
| [
{
"created": "Fri, 17 Aug 2018 12:03:20 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Nov 2018 18:40:43 GMT",
"version": "v2"
}
] | 2018-11-19 | [
[
"Cook",
"William G.",
""
],
[
"Wang",
"Diandian",
""
],
[
"Sperhake",
"Ulrich",
""
]
] | We study gravitational wave emission and the structure and formation of apparent horizons in orbiting black-hole binary systems in higher-dimensional general relativity. For this purpose we present an apparent horizon finder for use in higher dimensional numerical simulations and test the finder's accuracy and consistency in single and binary black-hole spacetimes. The black-hole binaries we model in $D=6$ dimensions complete up to about one orbit before merging or scatter off each other without formation of a common horizon. In agreement with the absence of stable circular geodesic orbits around higher-dimensional black holes, we do not find binaries completing multiple orbits without finetuning of the initial data. All binaries radiate about $0.13\,\%$ to $0.2\,\%$ of the total mass-energy in gravitational waves, over an order of magnitude below the radiated energy measured for four-dimensional binaries. The low radiative efficiency is accompanied by relatively slow dynamics of the binaries as expected from the more rapid falloff of the binding gravitational force in higher dimensions. |
1906.08789 | Maria Okounkova | Maria Okounkova, Leo C. Stein, Mark A. Scheel, Saul A. Teukolsky | Numerical binary black hole collisions in dynamical Chern-Simons gravity | 13 pages (+ appendices), 15 figures | Phys. Rev. D 100, 104026 (2019) | 10.1103/PhysRevD.100.104026 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We produce the first numerical relativity binary black hole gravitational
waveforms in a higher-curvature theory beyond general relativity. In
particular, we study head-on collisions of binary black holes in order-reduced
dynamical Chern-Simons gravity. This is a precursor to producing
beyond-general-relativity waveforms for inspiraling binary black hole systems
that are useful for gravitational wave detection. Head-on collisions are
interesting in their own right, however, as they cleanly probe the quasi-normal
mode spectrum of the final black hole. We thus compute the leading-order
dynamical Chern-Simons modifications to the complex frequencies of the
post-merger gravitational radiation. We consider equal-mass systems, with equal
spins oriented along the axis of collision, resulting in remnant black holes
with spin. We find modifications to the complex frequencies of the quasi-normal
mode spectrum that behave as a power law with the spin of the remnant, and that
are not degenerate with the frequencies associated with a Kerr black hole of
any mass and spin. We discuss these results in the context of testing general
relativity with gravitational wave observations.
| [
{
"created": "Thu, 20 Jun 2019 18:00:22 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Nov 2019 14:34:14 GMT",
"version": "v2"
}
] | 2019-11-20 | [
[
"Okounkova",
"Maria",
""
],
[
"Stein",
"Leo C.",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Teukolsky",
"Saul A.",
""
]
] | We produce the first numerical relativity binary black hole gravitational waveforms in a higher-curvature theory beyond general relativity. In particular, we study head-on collisions of binary black holes in order-reduced dynamical Chern-Simons gravity. This is a precursor to producing beyond-general-relativity waveforms for inspiraling binary black hole systems that are useful for gravitational wave detection. Head-on collisions are interesting in their own right, however, as they cleanly probe the quasi-normal mode spectrum of the final black hole. We thus compute the leading-order dynamical Chern-Simons modifications to the complex frequencies of the post-merger gravitational radiation. We consider equal-mass systems, with equal spins oriented along the axis of collision, resulting in remnant black holes with spin. We find modifications to the complex frequencies of the quasi-normal mode spectrum that behave as a power law with the spin of the remnant, and that are not degenerate with the frequencies associated with a Kerr black hole of any mass and spin. We discuss these results in the context of testing general relativity with gravitational wave observations. |
1106.2413 | Muhammad Sharif | M. Sharif and Farida Khanum | Kaluza-Klein Cosmology With Modified Holographic Dark Energy | 13 pages, accepted for publication in Gen. Relativ. Gravit | Gen. Relativ. Gravit. 43(2011)2885-2894 | 10.1007/s10714-011-1211-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the compact Kaluza-Klein cosmology in which modified
holographic dark energy is interacting with dark matter. Using this scenario,
we evaluate equation of state parameter as well as equation of evolution of the
modified holographic dark energy. Further, it is shown that the generalized
second law of thermodynamics holds without any constraint.
| [
{
"created": "Mon, 13 Jun 2011 10:51:52 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Sharif",
"M.",
""
],
[
"Khanum",
"Farida",
""
]
] | We investigate the compact Kaluza-Klein cosmology in which modified holographic dark energy is interacting with dark matter. Using this scenario, we evaluate equation of state parameter as well as equation of evolution of the modified holographic dark energy. Further, it is shown that the generalized second law of thermodynamics holds without any constraint. |
2309.11168 | Saulo Soares De Albuquerque Filho | Saulo Albuquerque, Sebastian H. V\"olkel, Kostas D. Kokkotas, and
Valdir B. Bezerra | Inverse problem of analog gravity systems | 11 pages, 7 figures | Phys. Rev. D 108, 124053 (2023) | 10.1103/PhysRevD.108.124053 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Analog gravity models of black holes and exotic compact objects provide a
unique opportunity to study key properties of such systems in controlled
laboratory environments. In contrast to astrophysical systems, analog gravity
systems can be prepared carefully and their dynamical aspects thus investigated
in unprecedented ways. While gravitational wave scattering properties of
astrophysical compact objects are more connected to quasinormal modes,
laboratory experiments can also access the transmission and reflection
coefficients, which are otherwise mostly relevant for Hawking radiation related
phenomena. In this work, we report two distinct results. First, we outline a
semiclassical, nonparametric method that allows for the reconstruction of the
effective perturbation potential from the knowledge of transmission and
reflection coefficients for certain types of potentials in the Schr\"odinger
wave equation admitting resonant tunneling. Second, we show how to use our
method by applying it to an imperfect draining vortex, which has been suggested
as an analog of extreme compact objects. Although the inverse problem is, in
general, not unique, choosing physically motivated assumptions and requiring
the validity of semiclassical theory, we demonstrate that the method provides
efficient and accurate results.
| [
{
"created": "Wed, 20 Sep 2023 09:26:28 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Feb 2024 15:38:42 GMT",
"version": "v2"
}
] | 2024-02-12 | [
[
"Albuquerque",
"Saulo",
""
],
[
"Völkel",
"Sebastian H.",
""
],
[
"Kokkotas",
"Kostas D.",
""
],
[
"Bezerra",
"Valdir B.",
""
]
] | Analog gravity models of black holes and exotic compact objects provide a unique opportunity to study key properties of such systems in controlled laboratory environments. In contrast to astrophysical systems, analog gravity systems can be prepared carefully and their dynamical aspects thus investigated in unprecedented ways. While gravitational wave scattering properties of astrophysical compact objects are more connected to quasinormal modes, laboratory experiments can also access the transmission and reflection coefficients, which are otherwise mostly relevant for Hawking radiation related phenomena. In this work, we report two distinct results. First, we outline a semiclassical, nonparametric method that allows for the reconstruction of the effective perturbation potential from the knowledge of transmission and reflection coefficients for certain types of potentials in the Schr\"odinger wave equation admitting resonant tunneling. Second, we show how to use our method by applying it to an imperfect draining vortex, which has been suggested as an analog of extreme compact objects. Although the inverse problem is, in general, not unique, choosing physically motivated assumptions and requiring the validity of semiclassical theory, we demonstrate that the method provides efficient and accurate results. |
1308.5035 | Chikun Ding | Chikun Ding, Changqing Liu, Yuanyuan Xiao, Liqun Jiang and Rong-Gen
Cai | Strong gravitational lensing in a black-hole spacetime dominated by dark
energy | 11 pages, 5 figures, 3 tables, accepted by Phys. Rev. D. arXiv admin
note: substantial text overlap with arXiv:1012.1670, arXiv:1106.1974; and
text overlap with arXiv:1003.1429, arXiv:1102.0086 by other authors | Phys. Rev. D 88 104007 (2013) | 10.1103/PhysRevD.88.104007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the influence of phantom fields on strong field gravitational
lensing. Supposing that the gravitational field of the supermassive central
object of the Galaxy is described by a phantom black hole metric, we estimate
the numerical values of the coefficients and observations and find that the
influence of the phantom fields is somewhat similar to that of the electric
charge in a Reissner-Norstr\"{o}m black hole, i.e., the deflect angle and
angular separation increase with the phantom constant $b$. However, other
observations are contrary to the Reissner-Norstr\"{o}m case and show the
effects of dark energy, such as (i) compressing the usual black hole and more
powerfully attracting photons, (ii) making the relativistic Einstein ring
larger than that of the usual black hole, and (iii) not weakening the usual
relative magnitudes, which will facilitate observations.
| [
{
"created": "Fri, 23 Aug 2013 03:26:25 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Oct 2013 01:56:41 GMT",
"version": "v2"
}
] | 2013-11-14 | [
[
"Ding",
"Chikun",
""
],
[
"Liu",
"Changqing",
""
],
[
"Xiao",
"Yuanyuan",
""
],
[
"Jiang",
"Liqun",
""
],
[
"Cai",
"Rong-Gen",
""
]
] | We study the influence of phantom fields on strong field gravitational lensing. Supposing that the gravitational field of the supermassive central object of the Galaxy is described by a phantom black hole metric, we estimate the numerical values of the coefficients and observations and find that the influence of the phantom fields is somewhat similar to that of the electric charge in a Reissner-Norstr\"{o}m black hole, i.e., the deflect angle and angular separation increase with the phantom constant $b$. However, other observations are contrary to the Reissner-Norstr\"{o}m case and show the effects of dark energy, such as (i) compressing the usual black hole and more powerfully attracting photons, (ii) making the relativistic Einstein ring larger than that of the usual black hole, and (iii) not weakening the usual relative magnitudes, which will facilitate observations. |
2012.06162 | De-Cheng Zou | Chao-Ming Zhang, De-Cheng Zou, Ming Zhang | Triple points and phase diagrams of Born-Infeld AdS black holes in 4D
Einstein-Gauss-Bonnet gravity | null | Phys.Lett.B 811 (2020), 135955 | 10.1016/j.physletb.2020.135955 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By treating the cosmological constant as a thermodynamic pressure, we
investigate the thermodynamic behaviors of Born-Infeld AdS black hole in 4D
Einstein-Gauss-Bonnet (EGB) gravity. The result shows that the Van der Waals
like small/large black hole (SBH/LBH) phase transition always appears for any
positive parameters $\alpha$ and $\beta$. Moreover, we observe a new phenomenon
of small/intermediate/large black hole (SBH/IBH/LBH) phase transition with one
tricritical and two critical points in the available parameter region for
\alpha and \beta. This behavior is reminiscent of the solid/liquid/gas phase
transition.
| [
{
"created": "Fri, 11 Dec 2020 06:43:39 GMT",
"version": "v1"
}
] | 2020-12-14 | [
[
"Zhang",
"Chao-Ming",
""
],
[
"Zou",
"De-Cheng",
""
],
[
"Zhang",
"Ming",
""
]
] | By treating the cosmological constant as a thermodynamic pressure, we investigate the thermodynamic behaviors of Born-Infeld AdS black hole in 4D Einstein-Gauss-Bonnet (EGB) gravity. The result shows that the Van der Waals like small/large black hole (SBH/LBH) phase transition always appears for any positive parameters $\alpha$ and $\beta$. Moreover, we observe a new phenomenon of small/intermediate/large black hole (SBH/IBH/LBH) phase transition with one tricritical and two critical points in the available parameter region for \alpha and \beta. This behavior is reminiscent of the solid/liquid/gas phase transition. |
2201.06296 | Sven Zschocke | Sven Zschocke | Light propagation in 2PN approximation in the monopole and quadrupole
field of a body at rest: Initial value problem | 55 pages, 1 figure, 4 tables | Physical Review D 105 (2022) 024040 | 10.1103/PhysRevD.105.024040 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The light trajectory in the gravitational field of one body at rest with
monopole and quadrupole structure is determined in the second post-Newtonian
(2PN) approximation. The terms in the geodesic equation for light rays are
separated into time-independent tensorial coefficients and four kind of
time-dependent scalar functions. Accordingly, the first and second integration
of geodesic equation can be reduced in each case to only four kind of scalar
master integrals. These integrals can be solved in closed form by recurrence
relations. The 2PN terms of monopole and quadrupole contribute less than $1$
nano-arcsecond to the total light deflection. There are, however, enhanced
terms in the 2PN light deflection, both in case of monopole and quadrupole.
These enhanced 2PN terms are caused by the use of an impact vector which is
indispensable for modeling of real astrometric measurements. In case of grazing
light rays at Jupiter and Saturn, the enhanced 2PN terms, caused by the
quadrupole structure of the body, amount up to 0.95 micro-arcseconds and 0.29
micro-arcseconds, respectively. Thus, the 2PN quadrupole terms are relevant for
high-precision astrometry on the sub-micro-arcsecond scale of accuracy.
| [
{
"created": "Mon, 17 Jan 2022 09:27:30 GMT",
"version": "v1"
}
] | 2022-01-26 | [
[
"Zschocke",
"Sven",
""
]
] | The light trajectory in the gravitational field of one body at rest with monopole and quadrupole structure is determined in the second post-Newtonian (2PN) approximation. The terms in the geodesic equation for light rays are separated into time-independent tensorial coefficients and four kind of time-dependent scalar functions. Accordingly, the first and second integration of geodesic equation can be reduced in each case to only four kind of scalar master integrals. These integrals can be solved in closed form by recurrence relations. The 2PN terms of monopole and quadrupole contribute less than $1$ nano-arcsecond to the total light deflection. There are, however, enhanced terms in the 2PN light deflection, both in case of monopole and quadrupole. These enhanced 2PN terms are caused by the use of an impact vector which is indispensable for modeling of real astrometric measurements. In case of grazing light rays at Jupiter and Saturn, the enhanced 2PN terms, caused by the quadrupole structure of the body, amount up to 0.95 micro-arcseconds and 0.29 micro-arcseconds, respectively. Thus, the 2PN quadrupole terms are relevant for high-precision astrometry on the sub-micro-arcsecond scale of accuracy. |
2109.01149 | Antoine Leh\'ebel | Christos Charmousis, Antoine Leh\'ebel, Evangelos Smyrniotis, Nikolaos
Stergioulas | Astrophysical constraints on compact objects in 4D Einstein-Gauss-Bonnet
gravity | Virgo preprint number VIR-0918C-21, 30 pages, 9 figures; v2 contains
some corrections to the mass-radius relations, showing in particular that all
equations of state converge at high densities | null | 10.1088/1475-7516/2022/02/033 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the properties of compact objects in a particular 4D Horndeski
theory originating from higher dimensional Einstein-Gauss-Bonnet gravity.
Remarkably, an exact vacuum solution is known. This compact object differs from
general relativity mostly in the strong field regime. We discuss some
properties of black holes in this framework and investigate in detail the
properties of neutron stars, both static and in slow rotation. We find that for
relatively modest deviations from general relativity, the secondary object in
GW190814 is compatible with being a slowly-rotating neutron star, without
resorting to very stiff or exotic equations of state. Remarkably, the
equilibrium sequence of neutron stars matches asymptotically to the black hole
limit, completetly closing the mass gap between neutron stars and black holes
of same radius, although the stability of equilibrium solutions has yet to be
determined. As a consequence, there exists a universal endpoint for the neutron
star sequence, independent of the equation of state. In light of our results
and of current observational constraints, we discuss specific constraints on
the coupling constant that parametrizes deviations from general relativity in
this theory.
| [
{
"created": "Thu, 2 Sep 2021 18:00:03 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Feb 2022 15:01:53 GMT",
"version": "v2"
}
] | 2022-03-02 | [
[
"Charmousis",
"Christos",
""
],
[
"Lehébel",
"Antoine",
""
],
[
"Smyrniotis",
"Evangelos",
""
],
[
"Stergioulas",
"Nikolaos",
""
]
] | We study the properties of compact objects in a particular 4D Horndeski theory originating from higher dimensional Einstein-Gauss-Bonnet gravity. Remarkably, an exact vacuum solution is known. This compact object differs from general relativity mostly in the strong field regime. We discuss some properties of black holes in this framework and investigate in detail the properties of neutron stars, both static and in slow rotation. We find that for relatively modest deviations from general relativity, the secondary object in GW190814 is compatible with being a slowly-rotating neutron star, without resorting to very stiff or exotic equations of state. Remarkably, the equilibrium sequence of neutron stars matches asymptotically to the black hole limit, completetly closing the mass gap between neutron stars and black holes of same radius, although the stability of equilibrium solutions has yet to be determined. As a consequence, there exists a universal endpoint for the neutron star sequence, independent of the equation of state. In light of our results and of current observational constraints, we discuss specific constraints on the coupling constant that parametrizes deviations from general relativity in this theory. |
gr-qc/0304028 | Dmitri Vassiliev | Dmitri Vassiliev | Quadratic metric-affine gravity | 25 pages, LaTeX2e | Annalen Phys. 14 (2005) 231-252 | 10.1002/andp.200410118 | null | gr-qc math.DG | null | We consider spacetime to be a connected real 4-manifold equipped with a
Lorentzian metric and an affine connection. The 10 independent components of
the (symmetric) metric tensor and the 64 connection coefficients are the
unknowns of our theory. We introduce an action which is quadratic in curvature
and study the resulting system of Euler-Lagrange equations. In the first part
of the paper we look for Riemannian solutions, i.e. solutions whose connection
is Levi-Civita. We find two classes of Riemannian solutions: 1) Einstein
spaces, and 2) spacetimes with metric of a pp-wave and parallel Ricci
curvature. We prove that for a generic quadratic action these are the only
Riemannian solutions. In the second part of the paper we look for
non-Riemannian solutions. We define the notion of a "Weyl pseudoinstanton"
(metric compatible spacetime whose curvature is purely Weyl) and prove that a
Weyl pseudoinstanton is a solution of our field equations. Using the
pseudoinstanton approach we construct explicitly a non-Riemannian solution
which is a wave of torsion in Minkowski space. We discuss the possibility of
using this non-Riemannian solution as a mathematical model for the graviton or
the neutrino.
| [
{
"created": "Sun, 6 Apr 2003 23:22:36 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Vassiliev",
"Dmitri",
""
]
] | We consider spacetime to be a connected real 4-manifold equipped with a Lorentzian metric and an affine connection. The 10 independent components of the (symmetric) metric tensor and the 64 connection coefficients are the unknowns of our theory. We introduce an action which is quadratic in curvature and study the resulting system of Euler-Lagrange equations. In the first part of the paper we look for Riemannian solutions, i.e. solutions whose connection is Levi-Civita. We find two classes of Riemannian solutions: 1) Einstein spaces, and 2) spacetimes with metric of a pp-wave and parallel Ricci curvature. We prove that for a generic quadratic action these are the only Riemannian solutions. In the second part of the paper we look for non-Riemannian solutions. We define the notion of a "Weyl pseudoinstanton" (metric compatible spacetime whose curvature is purely Weyl) and prove that a Weyl pseudoinstanton is a solution of our field equations. Using the pseudoinstanton approach we construct explicitly a non-Riemannian solution which is a wave of torsion in Minkowski space. We discuss the possibility of using this non-Riemannian solution as a mathematical model for the graviton or the neutrino. |
gr-qc/0404054 | Olaf Dreyer | Olaf Dreyer | Relational Physics and Quantum Space | Essay submitted to the 2004 Gravity Research Foundation competition | null | null | null | gr-qc | null | In a purely relational theory there exists a tension between the relational
character of the theory and the existence of quantities like distance and
duration. We review this issue in the context of the Leibniz-Clarke
correspondence. We then address this conflict by showing that a purely
relational definition of length and time can be given, provided the dynamics of
the theory is known. We further show that in such a setting it is natural to
expect Lorentz transformations to describe the mapping between different
observers. We then comment on how these insights can be used to make progress
in the search for a theory of quantum gravity.
| [
{
"created": "Tue, 13 Apr 2004 01:18:22 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Dreyer",
"Olaf",
""
]
] | In a purely relational theory there exists a tension between the relational character of the theory and the existence of quantities like distance and duration. We review this issue in the context of the Leibniz-Clarke correspondence. We then address this conflict by showing that a purely relational definition of length and time can be given, provided the dynamics of the theory is known. We further show that in such a setting it is natural to expect Lorentz transformations to describe the mapping between different observers. We then comment on how these insights can be used to make progress in the search for a theory of quantum gravity. |
0908.3766 | John T. Whelan | John T. Whelan, Reinhard Prix, and Deepak Khurana | Searching for Galactic White Dwarf Binaries in Mock LISA Data using an
F-Statistic Template Bank | 29 pages, 11 figures; submitted to Classical and Quantum Gravity | Class.Quant.Grav.27:055010,2010 | 10.1088/0264-9381/27/5/055010 | LIGO-P080087-v5 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe an F-statistic search for continuous gravitational waves from
galactic white-dwarf binaries in simulated LISA Data. Our search method employs
a hierarchical template-grid based exploration of the parameter space. In the
first stage, candidate sources are identified in searches using different
simulated laser signal combinations (known as TDI variables). Since each source
generates a primary maximum near its true "Doppler parameters" (intrinsic
frequency and sky position) as well as numerous secondary maxima of the
F-statistic in Doppler parameter space, a search for multiple sources needs to
distinguish between true signals and secondary maxima associated with other,
"louder" signals. Our method does this by applying a coincidence test to reject
candidates which are not found at nearby parameter space positions in searches
using each of the three TDI variables. For signals surviving the coincidence
test, we perform a fully coherent search over a refined parameter grid to
provide an accurate parameter estimation for the final candidates. Suitably
tuned, the pipeline is able to extract 1989 true signals with only 5 false
alarms. The use of the rigid adiabatic approximation allows recovery of signal
parameters with errors comparable to statistical expectations, although there
is still some systematic excess with respect to statistical errors expected
from Gaussian noise. An experimental iterative pipeline with seven rounds of
signal subtraction and re-analysis of the residuals allows us to increase the
number of signals recovered to a total of 3419 with 29 false alarms.
| [
{
"created": "Wed, 26 Aug 2009 16:19:10 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Oct 2009 18:39:31 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Jan 2010 22:21:04 GMT",
"version": "v3"
}
] | 2010-02-19 | [
[
"Whelan",
"John T.",
""
],
[
"Prix",
"Reinhard",
""
],
[
"Khurana",
"Deepak",
""
]
] | We describe an F-statistic search for continuous gravitational waves from galactic white-dwarf binaries in simulated LISA Data. Our search method employs a hierarchical template-grid based exploration of the parameter space. In the first stage, candidate sources are identified in searches using different simulated laser signal combinations (known as TDI variables). Since each source generates a primary maximum near its true "Doppler parameters" (intrinsic frequency and sky position) as well as numerous secondary maxima of the F-statistic in Doppler parameter space, a search for multiple sources needs to distinguish between true signals and secondary maxima associated with other, "louder" signals. Our method does this by applying a coincidence test to reject candidates which are not found at nearby parameter space positions in searches using each of the three TDI variables. For signals surviving the coincidence test, we perform a fully coherent search over a refined parameter grid to provide an accurate parameter estimation for the final candidates. Suitably tuned, the pipeline is able to extract 1989 true signals with only 5 false alarms. The use of the rigid adiabatic approximation allows recovery of signal parameters with errors comparable to statistical expectations, although there is still some systematic excess with respect to statistical errors expected from Gaussian noise. An experimental iterative pipeline with seven rounds of signal subtraction and re-analysis of the residuals allows us to increase the number of signals recovered to a total of 3419 with 29 false alarms. |
gr-qc/0409053 | Yuan-Zhong Zhang | Kamal K. Nandi, Yuan-Zhong Zhang, and Nail G. Migranov | A Semiclassical ANEC Constraint On Classical Traversable Lorentzian
Wormholes | 9 pages, no figures | J. Nonlinear Phenomena in Complex Systems 9(2006)61-67 | null | null | gr-qc | null | The present article lies at the interface between gravity, a highly nonlinear
phenomenon, and quantum field theory. The nonlinear field equations of Einstein
permit the theoretical existence of classical wormholes. One of the fundamental
questions relates to the practical viability of such wormholes. One way to
answer this question is to assess if the total \emph{volume} of exotic matter
needed to maintain the wormhole is finite. Using this value as the lower bound,
we propose a modified semiclassical volume Averaged Null Energy Condition
(ANEC) constraint as a method of discarding many solutions as being possible
self-consistent wormhole solutions of semiclassical gravity. The proposed
constraint is consistent with known results. It turns out that a class of
Morris-Thorne wormholes can be ruled out on the basis of this constraint.
| [
{
"created": "Mon, 13 Sep 2004 08:59:36 GMT",
"version": "v1"
},
{
"created": "Sun, 29 May 2005 01:08:32 GMT",
"version": "v2"
},
{
"created": "Tue, 13 Jun 2006 04:02:15 GMT",
"version": "v3"
},
{
"created": "Fri, 16 Jun 2006 01:13:04 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Nandi",
"Kamal K.",
""
],
[
"Zhang",
"Yuan-Zhong",
""
],
[
"Migranov",
"Nail G.",
""
]
] | The present article lies at the interface between gravity, a highly nonlinear phenomenon, and quantum field theory. The nonlinear field equations of Einstein permit the theoretical existence of classical wormholes. One of the fundamental questions relates to the practical viability of such wormholes. One way to answer this question is to assess if the total \emph{volume} of exotic matter needed to maintain the wormhole is finite. Using this value as the lower bound, we propose a modified semiclassical volume Averaged Null Energy Condition (ANEC) constraint as a method of discarding many solutions as being possible self-consistent wormhole solutions of semiclassical gravity. The proposed constraint is consistent with known results. It turns out that a class of Morris-Thorne wormholes can be ruled out on the basis of this constraint. |
1210.0186 | Emil M. Prodanov | Rossen I. Ivanov and Emil M. Prodanov | Cyclic Universe with an Inflationary Phase from a Cosmological Model
with Real Gas Quintessence | 21 pages, 8 figures, to appear in Physical Review D | Physical Review D 86, 083536 (2012) | 10.1103/PhysRevD.86.083536 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Phase-plane stability analysis of a dynamical system describing the Universe
as a two-fraction fluid containing baryonic dust and real virial gas
quintessence is presented. Existence of a stable periodic solution experiencing
inflationary periods is shown. A van der Waals quintessence model is revisited
and cyclic Universe solution again found.
| [
{
"created": "Sun, 30 Sep 2012 11:05:24 GMT",
"version": "v1"
}
] | 2022-09-15 | [
[
"Ivanov",
"Rossen I.",
""
],
[
"Prodanov",
"Emil M.",
""
]
] | Phase-plane stability analysis of a dynamical system describing the Universe as a two-fraction fluid containing baryonic dust and real virial gas quintessence is presented. Existence of a stable periodic solution experiencing inflationary periods is shown. A van der Waals quintessence model is revisited and cyclic Universe solution again found. |
2007.05644 | Benaoumeur Bakhti | Benaoumeur Bakhti | D-dimensional self-gravitating lattice gas in general relativity | null | null | 10.1142/S0217751X21502171 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using a lattice equation of state combined with the D-dimensional
Tolman-Oppenheimer-Volkoff equation and the Friedmann equations, we investigate
the possibility of the formation of compact objects as well as the time
evolution of the scale factor and the density profile of a self-gravitating
material cluster. The numerical results show that in a $2+1$ dimensional
spacetime, the mass is independent of the central pressure. Hence, the
formation of only compact objects with a finite constant mass similar to the
white dwarf is possible. However, in a $3+1$ dimensional spacetime,
self-gravity leads to the formation of compact objects with a large gap of mass
and the corresponding phase diagram has the same structure as the one for
Neutron Star. The results also show that beyond certain critical central
pressure, the star is unstable against gravitational collapse, and it may end
in a black hole. Analysis of spacetimes of higher dimensions shows that gravity
has the stronger effect in $3+1$ dimensions. Numerical solutions of the
Friedmann equations show that the effect of the curvature of spacetime
increases with increasing temperature, but decreases with increasing
dimensionality beyond $D=3$.
| [
{
"created": "Fri, 10 Jul 2020 23:21:03 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Oct 2021 17:43:53 GMT",
"version": "v2"
}
] | 2021-12-01 | [
[
"Bakhti",
"Benaoumeur",
""
]
] | Using a lattice equation of state combined with the D-dimensional Tolman-Oppenheimer-Volkoff equation and the Friedmann equations, we investigate the possibility of the formation of compact objects as well as the time evolution of the scale factor and the density profile of a self-gravitating material cluster. The numerical results show that in a $2+1$ dimensional spacetime, the mass is independent of the central pressure. Hence, the formation of only compact objects with a finite constant mass similar to the white dwarf is possible. However, in a $3+1$ dimensional spacetime, self-gravity leads to the formation of compact objects with a large gap of mass and the corresponding phase diagram has the same structure as the one for Neutron Star. The results also show that beyond certain critical central pressure, the star is unstable against gravitational collapse, and it may end in a black hole. Analysis of spacetimes of higher dimensions shows that gravity has the stronger effect in $3+1$ dimensions. Numerical solutions of the Friedmann equations show that the effect of the curvature of spacetime increases with increasing temperature, but decreases with increasing dimensionality beyond $D=3$. |
gr-qc/9510045 | Robin W. Tucker | Pierre Teyssandier and Robin W Tucker | Gravity, Gauges and Clocks | 8 pages Plain Tex (No Figures), Classical and Quantum Gravity | Class.Quant.Grav. 13 (1996) 145-152 | 10.1088/0264-9381/13/1/013 | null | gr-qc | null | We discuss the definitions of standard clocks in theories of gravitation.
These definitions are motivated by the invariance of actions under different
gauge symmetries. We contrast the definition of a standard Weyl clock with that
of a clock in general relativity and argue that the historical criticisms of
theories based on non-metric compatible connections by Einstein, Pauli and
others must be considered in the context of Weyl's original gauge symmetry. We
argue that standard Einsteinian clocks can be defined in non-Riemannian
theories of gravitation by adopting the Weyl group as a local gauge symmetry
that {\it preserves the metric} and discuss the hypothesis that atomic clocks
may be adopted to measure proper time in the presence of non-Riemannian
gravitational fields. These ideas are illustrated in terms of a recently
developed model of gravitation based on a non-Riemannian space-time geometry.
| [
{
"created": "Mon, 23 Oct 1995 16:04:52 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Teyssandier",
"Pierre",
""
],
[
"Tucker",
"Robin W",
""
]
] | We discuss the definitions of standard clocks in theories of gravitation. These definitions are motivated by the invariance of actions under different gauge symmetries. We contrast the definition of a standard Weyl clock with that of a clock in general relativity and argue that the historical criticisms of theories based on non-metric compatible connections by Einstein, Pauli and others must be considered in the context of Weyl's original gauge symmetry. We argue that standard Einsteinian clocks can be defined in non-Riemannian theories of gravitation by adopting the Weyl group as a local gauge symmetry that {\it preserves the metric} and discuss the hypothesis that atomic clocks may be adopted to measure proper time in the presence of non-Riemannian gravitational fields. These ideas are illustrated in terms of a recently developed model of gravitation based on a non-Riemannian space-time geometry. |
1902.09199 | Enrico Barausse | Enrico Barausse | Black holes in General Relativity and beyond | 9 pages, 1 figure. Published in the proceedings of the conference
'Recent Progress in Relativistic Astrophysics', Shanghai, China, 6-8 May 2019 | null | 10.3390/proceedings2019017001 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent detections of gravitational waves from binary systems of black
holes are in remarkable agreement with the predictions of General Relativity.
In this pedagogical mini-review, I will go through the physics of the different
phases of the evolution of black hole binary systems, providing a qualitative
physical interpretation of each one of them. I will also briefly describe how
these phases would be modified if gravitation were described by a theory
extending or deforming General Relativity, or if the binary components turned
out to be more exotic compact objects than black holes.
| [
{
"created": "Mon, 25 Feb 2019 11:25:32 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Jun 2019 10:08:06 GMT",
"version": "v2"
}
] | 2021-11-24 | [
[
"Barausse",
"Enrico",
""
]
] | The recent detections of gravitational waves from binary systems of black holes are in remarkable agreement with the predictions of General Relativity. In this pedagogical mini-review, I will go through the physics of the different phases of the evolution of black hole binary systems, providing a qualitative physical interpretation of each one of them. I will also briefly describe how these phases would be modified if gravitation were described by a theory extending or deforming General Relativity, or if the binary components turned out to be more exotic compact objects than black holes. |
gr-qc/0207117 | G. S. Asanov | G.S. Asanov | Finslerian Post-Lorentzian Kinematic Transformations in
Anisotropic-Space Case | null | null | null | null | gr-qc | null | The Finslerian post-Lorentzian kinematic transformations can explicitly be
obtained under uni-directional breakdown of spatial isotropy, provided that the
requirement that the relativistic unit hypersurface (indicatrix or mass shell)
be a space of constant negative curvature is still fulfilled. The method
consists in evaluating respective Finslerian tetrads and then treating them as
the bases of inertial reference frames. The Transport Synchronization has
rigorously been proven, which opens up the ways proper to favour the concept of
one-way light velocity. Transition to the Hamiltonian treatment is
straightforward, so that the Finslerian transformation laws for momenta and
frequences, as well as due Finslerian corrections to Doppler effect, become
clear. An important common feature of the ordinary pseudo-Euclidean theory of
special relativity and of the Finslerian relativistic approach under study is
that they both endeavour to establish a universal prescription for applying the
theory to systems in differing states of motion.
| [
{
"created": "Tue, 30 Jul 2002 03:58:50 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Asanov",
"G. S.",
""
]
] | The Finslerian post-Lorentzian kinematic transformations can explicitly be obtained under uni-directional breakdown of spatial isotropy, provided that the requirement that the relativistic unit hypersurface (indicatrix or mass shell) be a space of constant negative curvature is still fulfilled. The method consists in evaluating respective Finslerian tetrads and then treating them as the bases of inertial reference frames. The Transport Synchronization has rigorously been proven, which opens up the ways proper to favour the concept of one-way light velocity. Transition to the Hamiltonian treatment is straightforward, so that the Finslerian transformation laws for momenta and frequences, as well as due Finslerian corrections to Doppler effect, become clear. An important common feature of the ordinary pseudo-Euclidean theory of special relativity and of the Finslerian relativistic approach under study is that they both endeavour to establish a universal prescription for applying the theory to systems in differing states of motion. |
gr-qc/0409119 | Tatyana P. Shestakova | T. P. Shestakova and C. Simeone | The problem of time and gauge invariance in the quantization of
cosmological models. II. Recent developments in the path integral approach | 13 pages, to be published in Grav. Cosmol. For the first part of the
paper, see gr-qc/0409114 | Grav.Cosmol. 10 (2004) 257-268 | null | null | gr-qc | null | The paper is the second part of the work devoted to the problem of time in
quantum cosmology. Here we consider in detail two approaches within the scope
of Feynman path integration scheme: The first, by Simeone and collaborators, is
gauge-invariant and lies within the unitary approach to a consistent
quantization of gravity. It is essentially based on the idea of
deparametrization (reduction to physical degrees of freedom) as a first step
before quantization. The other approach by Savchenko, Shestakova and Vereshkov
is rather radical. It is an attempt to take into account peculiarities of the
Universe as a system without asymptotic states that leads to the conclusion
that quantum geometrodynamics constructed for such a system is, in general, a
gauge-noninvariant theory. However, this theory is shown to be mathematically
consistent and the problem of time is solved in this theory in a natural way.
| [
{
"created": "Thu, 30 Sep 2004 09:15:56 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Shestakova",
"T. P.",
""
],
[
"Simeone",
"C.",
""
]
] | The paper is the second part of the work devoted to the problem of time in quantum cosmology. Here we consider in detail two approaches within the scope of Feynman path integration scheme: The first, by Simeone and collaborators, is gauge-invariant and lies within the unitary approach to a consistent quantization of gravity. It is essentially based on the idea of deparametrization (reduction to physical degrees of freedom) as a first step before quantization. The other approach by Savchenko, Shestakova and Vereshkov is rather radical. It is an attempt to take into account peculiarities of the Universe as a system without asymptotic states that leads to the conclusion that quantum geometrodynamics constructed for such a system is, in general, a gauge-noninvariant theory. However, this theory is shown to be mathematically consistent and the problem of time is solved in this theory in a natural way. |
gr-qc/0301105 | Miguel Alcubierre | Miguel Alcubierre, Ricardo Becerril, F. Siddhartha Guzman, Tonatiuh
Matos, Dario Nunez, L. Arturo Urena-Lopez | Numerical studies of Phi^2-Oscillatons | null | Class.Quant.Grav. 20 (2003) 2883-2904 | 10.1088/0264-9381/20/13/332 | null | gr-qc | null | We present an exhaustive analysis of the numerical evolution of the
Einstein-Klein-Gordon equations for the case of a real scalar field endowed
with a quadratic self-interaction potential. The self-gravitating equilibrium
configurations are called oscillatons and are close relatives of boson stars,
their complex counterparts. Unlike boson stars, for which the oscillations of
the two components of the complex scalar field are such that the spacetime
geometry remains static, oscillatons give rise to a geometry that is
time-dependent and oscillatory in nature. However, they can still be classified
into stable (S-branch) and unstable (U-branch) cases. We have found that
S-oscillatons are indeed stable configurations under small perturbations and
typically migrate to other S-profiles when perturbed strongly. On the other
hand, U-oscillatons are intrinsically unstable: they migrate to the S-branch if
their mass is decreased and collapse to black holes if their mass is increased
even by a small amount. The S-oscillatons can also be made to collapse to black
holes if enough mass is added to them, but such collapse can be efficiently
prevented by the gravitational cooling mechanism in the case of diluted
oscillatons.
| [
{
"created": "Fri, 24 Jan 2003 21:00:15 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Alcubierre",
"Miguel",
""
],
[
"Becerril",
"Ricardo",
""
],
[
"Guzman",
"F. Siddhartha",
""
],
[
"Matos",
"Tonatiuh",
""
],
[
"Nunez",
"Dario",
""
],
[
"Urena-Lopez",
"L. Arturo",
""
]
] | We present an exhaustive analysis of the numerical evolution of the Einstein-Klein-Gordon equations for the case of a real scalar field endowed with a quadratic self-interaction potential. The self-gravitating equilibrium configurations are called oscillatons and are close relatives of boson stars, their complex counterparts. Unlike boson stars, for which the oscillations of the two components of the complex scalar field are such that the spacetime geometry remains static, oscillatons give rise to a geometry that is time-dependent and oscillatory in nature. However, they can still be classified into stable (S-branch) and unstable (U-branch) cases. We have found that S-oscillatons are indeed stable configurations under small perturbations and typically migrate to other S-profiles when perturbed strongly. On the other hand, U-oscillatons are intrinsically unstable: they migrate to the S-branch if their mass is decreased and collapse to black holes if their mass is increased even by a small amount. The S-oscillatons can also be made to collapse to black holes if enough mass is added to them, but such collapse can be efficiently prevented by the gravitational cooling mechanism in the case of diluted oscillatons. |
1905.00409 | Matthew Mewes | Matthew Mewes | Signals for Lorentz violation in gravitational waves | 14 pages | Phys. Rev. D 99, 104062 (2019) | 10.1103/PhysRevD.99.104062 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lorentz violations in gravitational waves are investigated. Plane-wave
solutions for arbitrary gauge-invariant violations in linearized gravity are
constructed. Signatures of Lorentz violation include dispersion, birefringence,
and anisotropies. Modifications to waves from coalescing compact binaries and
to strain signals in gravitational-wave detectors are derived.
| [
{
"created": "Wed, 1 May 2019 17:49:52 GMT",
"version": "v1"
}
] | 2019-06-05 | [
[
"Mewes",
"Matthew",
""
]
] | Lorentz violations in gravitational waves are investigated. Plane-wave solutions for arbitrary gauge-invariant violations in linearized gravity are constructed. Signatures of Lorentz violation include dispersion, birefringence, and anisotropies. Modifications to waves from coalescing compact binaries and to strain signals in gravitational-wave detectors are derived. |
1709.02007 | Ian Hinder | Ian Hinder, Lawrence E. Kidder, Harald P. Pfeiffer | An eccentric binary black hole inspiral-merger-ringdown gravitational
waveform model from numerical relativity and post-Newtonian theory | null | Phys. Rev. D 98, 044015 (2018) | 10.1103/PhysRevD.98.044015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a prescription for computing gravitational waveforms for the
inspiral, merger and ringdown of non-spinning eccentric binary black hole
systems. The inspiral waveform is computed using the post-Newtonian expansion
and the merger waveform is computed by interpolating a small number of
quasi-circular NR waveforms. The use of circular merger waveforms is possible
because eccentric binaries circularize in the last few cycles before the
merger, which we demonstrate up to mass ratio $q = m_1/m_2 = 3$. The complete
model is calibrated to 23 numerical relativity (NR) simulations starting ~20
cycles before the merger with eccentricities $e_\text{ref} \le 0.08$ and mass
ratios $q \le 3$, where $e_\text{ref}$ is the eccentricity ~7 cycles before the
merger. The NR waveforms are long enough that they start above 30 Hz (10 Hz)
for BBH systems with total mass $M \ge 80 M_\odot$ ($230 M_\odot$). We find
that, for the sensitivity of advanced LIGO at the time of its first observing
run, the eccentric model has a faithfulness with NR of over 97% for systems
with total mass $M \ge 85 M_\odot$ across the parameter space ($e_\text{ref}
\le 0.08, q \le 3$). For systems with total mass $M \ge 70 M_\odot$, the
faithfulness is over 97% for $e_\text{ref} \lesssim 0.05$ and $q \le 3$. The NR
waveforms and the Mathematica code for the model are publicly available.
| [
{
"created": "Wed, 6 Sep 2017 21:27:58 GMT",
"version": "v1"
}
] | 2018-08-15 | [
[
"Hinder",
"Ian",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Pfeiffer",
"Harald P.",
""
]
] | We present a prescription for computing gravitational waveforms for the inspiral, merger and ringdown of non-spinning eccentric binary black hole systems. The inspiral waveform is computed using the post-Newtonian expansion and the merger waveform is computed by interpolating a small number of quasi-circular NR waveforms. The use of circular merger waveforms is possible because eccentric binaries circularize in the last few cycles before the merger, which we demonstrate up to mass ratio $q = m_1/m_2 = 3$. The complete model is calibrated to 23 numerical relativity (NR) simulations starting ~20 cycles before the merger with eccentricities $e_\text{ref} \le 0.08$ and mass ratios $q \le 3$, where $e_\text{ref}$ is the eccentricity ~7 cycles before the merger. The NR waveforms are long enough that they start above 30 Hz (10 Hz) for BBH systems with total mass $M \ge 80 M_\odot$ ($230 M_\odot$). We find that, for the sensitivity of advanced LIGO at the time of its first observing run, the eccentric model has a faithfulness with NR of over 97% for systems with total mass $M \ge 85 M_\odot$ across the parameter space ($e_\text{ref} \le 0.08, q \le 3$). For systems with total mass $M \ge 70 M_\odot$, the faithfulness is over 97% for $e_\text{ref} \lesssim 0.05$ and $q \le 3$. The NR waveforms and the Mathematica code for the model are publicly available. |
1911.13228 | Sergey Rubin | S.G. Rubin | Cosmology and matter induced branes | 23 pages, 2 figures | Symmetry 2020, 12(1), 45 | 10.3390/sym12010045 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The extra space paradigm plays a significant role in modern physics and in
cosmology as the specific case. In this review, the relation between the main
cosmological parameters - Planck mass and Cosmological constants - and a metric
of extra space is discussed. Matter distribution inside extra space and its
effect on the 4-dimensional observational parameters is of particular interest.
The ways to solve the Fine-tuning problem and the Hierarchy problem are
analyzed.
| [
{
"created": "Tue, 26 Nov 2019 07:04:41 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Dec 2019 06:43:34 GMT",
"version": "v2"
}
] | 2019-12-30 | [
[
"Rubin",
"S. G.",
""
]
] | The extra space paradigm plays a significant role in modern physics and in cosmology as the specific case. In this review, the relation between the main cosmological parameters - Planck mass and Cosmological constants - and a metric of extra space is discussed. Matter distribution inside extra space and its effect on the 4-dimensional observational parameters is of particular interest. The ways to solve the Fine-tuning problem and the Hierarchy problem are analyzed. |
1907.11949 | Flavio Bombacigno | Flavio Bombacigno, Fabio Moretti and Giovanni Montani | Scalar modes in extended hybrid metric-Palatini gravity: weak field
phenomenology | 14 pages, 1 figure. Comments are welcome | Phys. Rev. D 100, 124036 (2019) | 10.1103/PhysRevD.100.124036 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the nature of additional scalar degrees of freedom contained
in extended hybrid metric-Palatini gravity, outlining the emergence of two
coupled dynamical scalar modes. In particular, we discuss the weak field limit
of the theory, both in the static case and from a gravitational waves
perspective. In the first case, performing an analysis at the lowest order of
the post parameterized Newtonian (PPN) structure of the model, we stress the
settling of Yukawa corrections to the Newtonian potential. In this respect, we
show that one scalar field can have long range interactions and used in the
principle for mimicking dark matter effects. Concerning the gravitational waves
propagation, instead, we demonstrate that is possible to have well-defined
physical degrees of freedom, provided by suitable constraints on model
parameters. Moreover, the study of the geodesic deviation points out the
presence of breathing and longitudinal polarizations due to these novel scalar
waves, which on peculiar assumptions can give rise to beating phenomena during
their propagation.
| [
{
"created": "Sat, 27 Jul 2019 17:06:36 GMT",
"version": "v1"
},
{
"created": "Sun, 10 Nov 2019 20:25:49 GMT",
"version": "v2"
}
] | 2019-12-17 | [
[
"Bombacigno",
"Flavio",
""
],
[
"Moretti",
"Fabio",
""
],
[
"Montani",
"Giovanni",
""
]
] | We investigate the nature of additional scalar degrees of freedom contained in extended hybrid metric-Palatini gravity, outlining the emergence of two coupled dynamical scalar modes. In particular, we discuss the weak field limit of the theory, both in the static case and from a gravitational waves perspective. In the first case, performing an analysis at the lowest order of the post parameterized Newtonian (PPN) structure of the model, we stress the settling of Yukawa corrections to the Newtonian potential. In this respect, we show that one scalar field can have long range interactions and used in the principle for mimicking dark matter effects. Concerning the gravitational waves propagation, instead, we demonstrate that is possible to have well-defined physical degrees of freedom, provided by suitable constraints on model parameters. Moreover, the study of the geodesic deviation points out the presence of breathing and longitudinal polarizations due to these novel scalar waves, which on peculiar assumptions can give rise to beating phenomena during their propagation. |
0903.5319 | Barry Wardell | Marc Casals, Sam Dolan, Adrian Ottewill, Barry Wardell | Pade Approximants of the Green Function in Spherically Symmetric
Spacetimes | 19 pages, 12 figures | Phys.Rev.D79:124044,2009 | 10.1103/PhysRevD.79.124044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the scalar Green function for spherically symmetric spacetimes
expressed as a coordinate series expansion in the separation of the points. We
calculate the series expansion of the function $V(x,x')$ appearing in the
Hadamard parametrix of the scalar Green function to very high order. This
expansion is then used to investigate the convergence properties of the series
and to estimate its radius of convergence. Using the method of Pade
approximants, we show that the series can be extended beyond its radius of
convergence to within a short distance of the normal neighborhood boundary.
| [
{
"created": "Tue, 31 Mar 2009 18:39:06 GMT",
"version": "v1"
}
] | 2009-07-09 | [
[
"Casals",
"Marc",
""
],
[
"Dolan",
"Sam",
""
],
[
"Ottewill",
"Adrian",
""
],
[
"Wardell",
"Barry",
""
]
] | We investigate the scalar Green function for spherically symmetric spacetimes expressed as a coordinate series expansion in the separation of the points. We calculate the series expansion of the function $V(x,x')$ appearing in the Hadamard parametrix of the scalar Green function to very high order. This expansion is then used to investigate the convergence properties of the series and to estimate its radius of convergence. Using the method of Pade approximants, we show that the series can be extended beyond its radius of convergence to within a short distance of the normal neighborhood boundary. |
0803.3367 | Grigory Volovik | G.E. Volovik | On de Sitter radiation via quantum tunneling | 15 pages, no figures, IJMPD style, version submitted to IJMPD | Int. J. Mod. Phys. D 18 (2009) 1227-1241 | 10.1142/S0218271809015035 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss why the tunneling picture does not necessarily lead to Hawking
radiation from the de Sitter horizon. The experience with the condensed matter
analogs of event horizon suggests that the de Sitter vacuum is stable against
the Hawking radiation. On the other hand the detector immersed into the de
Sitter background will detect the radiation which looks as thermal with the
effective temperature twice larger than the Hawking temperature associated with
the cosmological horizon.
| [
{
"created": "Mon, 24 Mar 2008 06:47:42 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Mar 2008 20:53:21 GMT",
"version": "v2"
},
{
"created": "Tue, 1 Apr 2008 14:11:57 GMT",
"version": "v3"
},
{
"created": "Wed, 21 Jan 2009 18:52:15 GMT",
"version": "v4"
},
{
"created": "Sun, 25 Jan 2009 17:31:44 GMT",
"version": "v5"
},
{
"created": "Thu, 29 Jan 2009 14:00:58 GMT",
"version": "v6"
}
] | 2015-05-13 | [
[
"Volovik",
"G. E.",
""
]
] | We discuss why the tunneling picture does not necessarily lead to Hawking radiation from the de Sitter horizon. The experience with the condensed matter analogs of event horizon suggests that the de Sitter vacuum is stable against the Hawking radiation. On the other hand the detector immersed into the de Sitter background will detect the radiation which looks as thermal with the effective temperature twice larger than the Hawking temperature associated with the cosmological horizon. |
1904.01427 | Rocco D'Agostino | Salvatore Capozziello, Rocco D'Agostino, Orlando Luongo | Extended Gravity Cosmography | 82 pages, 35 figures. Accepted for publication in IJMPD | null | 10.1142/S0218271819300167 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmography can be considered as a sort of a model-independent approach to
tackle the dark energy/modified gravity problem. In this review, the success
and the shortcomings of the $\Lambda$CDM model, based on General Relativity and
standard model of particles, are discussed in view of the most recent
observational constraints. The motivations for considering extensions and
modifications of General Relativity are taken into account, with particular
attention to $f(R)$ and $f(T)$ theories of gravity where dynamics is
represented by curvature or torsion field respectively. The features of $f(R)$
models are explored in metric and Palatini formalisms. We discuss the
connection between $f(R)$ gravity and scalar-tensor theories highlighting the
role of conformal transformations in the Einstein and Jordan frames.
Cosmological dynamics of $f(R)$ models is investigated through the
corresponding viability criteria. Afterwards, the equivalent formulation of
General Relativity (Teleparallel Equivalent General Relativity) in terms of
torsion and its extension to $f(T)$ gravity is considered. Finally, the
cosmographic method is adopted to break the degeneracy among dark energy
models. A novel approach, built upon rational Pad\'e and Chebyshev polynomials,
is proposed to overcome limits of standard cosmography based on Taylor
expansion. The approach provides accurate model-independent approximations of
the Hubble flow. Numerical analyses, based on Monte Carlo Markov Chain
integration of cosmic data, are presented to bound coefficients of the
cosmographic series. These techniques are thus applied to reconstruct $f(R)$
and $f(T)$ functions and to frame the late-time expansion history of the
universe with no \emph{a priori} assumptions on its equation of state. A
comparison between the $\Lambda$CDM cosmological model with $f(R)$ and $f(T)$
models is reported.
| [
{
"created": "Mon, 1 Apr 2019 09:35:25 GMT",
"version": "v1"
}
] | 2019-04-09 | [
[
"Capozziello",
"Salvatore",
""
],
[
"D'Agostino",
"Rocco",
""
],
[
"Luongo",
"Orlando",
""
]
] | Cosmography can be considered as a sort of a model-independent approach to tackle the dark energy/modified gravity problem. In this review, the success and the shortcomings of the $\Lambda$CDM model, based on General Relativity and standard model of particles, are discussed in view of the most recent observational constraints. The motivations for considering extensions and modifications of General Relativity are taken into account, with particular attention to $f(R)$ and $f(T)$ theories of gravity where dynamics is represented by curvature or torsion field respectively. The features of $f(R)$ models are explored in metric and Palatini formalisms. We discuss the connection between $f(R)$ gravity and scalar-tensor theories highlighting the role of conformal transformations in the Einstein and Jordan frames. Cosmological dynamics of $f(R)$ models is investigated through the corresponding viability criteria. Afterwards, the equivalent formulation of General Relativity (Teleparallel Equivalent General Relativity) in terms of torsion and its extension to $f(T)$ gravity is considered. Finally, the cosmographic method is adopted to break the degeneracy among dark energy models. A novel approach, built upon rational Pad\'e and Chebyshev polynomials, is proposed to overcome limits of standard cosmography based on Taylor expansion. The approach provides accurate model-independent approximations of the Hubble flow. Numerical analyses, based on Monte Carlo Markov Chain integration of cosmic data, are presented to bound coefficients of the cosmographic series. These techniques are thus applied to reconstruct $f(R)$ and $f(T)$ functions and to frame the late-time expansion history of the universe with no \emph{a priori} assumptions on its equation of state. A comparison between the $\Lambda$CDM cosmological model with $f(R)$ and $f(T)$ models is reported. |
1701.05828 | Nathaniel Barlow | Nathaniel S. Barlow, Steven J. Weinstein, and Joshua A. Faber | An asymptotically consistent approximant for the equatorial bending
angle of light due to Kerr black holes | 16 pages, 7 figures, submitted to Classical and Quantum Gravity | Class. Quantum Grav. 34 (2017) 135017 | 10.1088/1361-6382/aa7538 | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by-sa/4.0/ | An accurate closed-form expression is provided to predict the bending angle
of light as a function of impact parameter for equatorial orbits around Kerr
black holes of arbitrary spin. This expression is constructed by assuring that
the weak- and strong-deflection limits are explicitly satisfied while
maintaining accuracy at intermediate values of impact parameter via the method
of asymptotic approximants (Barlow et al, 2016 Q. J. Mech. Appl. Math.,
doi=10.1093/qjmam/hbw014). To this end, the strong deflection limit for a
prograde orbit around an extremal black hole is examined, and the full
non-vanishing asymptotic behavior is determined. The derived approximant may be
an attractive alternative to computationally expensive elliptical integrals
used in black hole simulations.
| [
{
"created": "Fri, 20 Jan 2017 15:35:55 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jun 2017 20:24:33 GMT",
"version": "v2"
}
] | 2017-06-29 | [
[
"Barlow",
"Nathaniel S.",
""
],
[
"Weinstein",
"Steven J.",
""
],
[
"Faber",
"Joshua A.",
""
]
] | An accurate closed-form expression is provided to predict the bending angle of light as a function of impact parameter for equatorial orbits around Kerr black holes of arbitrary spin. This expression is constructed by assuring that the weak- and strong-deflection limits are explicitly satisfied while maintaining accuracy at intermediate values of impact parameter via the method of asymptotic approximants (Barlow et al, 2016 Q. J. Mech. Appl. Math., doi=10.1093/qjmam/hbw014). To this end, the strong deflection limit for a prograde orbit around an extremal black hole is examined, and the full non-vanishing asymptotic behavior is determined. The derived approximant may be an attractive alternative to computationally expensive elliptical integrals used in black hole simulations. |
1302.2610 | I. V. Kanatchikov | I.V. Kanatchikov | De Donder-Weyl Hamiltonian formulation and precanonical quantization of
vielbein gravity | 14 pages. v2 corrects small typos in (35) and the equation preceding
(12) | J. Phys.: Conf. Ser. 442 012041 (2013) | 10.1088/1742-6596/442/1/012041 | null | gr-qc hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The De Donder-Weyl (DW) covariant Hamiltonian formulation of Palatini
first-order Lagrangian of vielbein (tetrad) gravity and its precanonical
quantization are presented. No splitting into the space and time is required in
this formulation. Our recent generalization of Dirac brackets is used to treat
the second class primary constraints appearing in the DW Hamiltonian
formulation and to find the fundamental brackets. Quantization of the latter
yields the representation of vielbeins as differential operators with respect
to the spin connection coefficients, and the Dirac-like precanonical
Schr\"odinger equation on the space of spin connection coefficients and
space-time variables. The transition amplitudes on this space describe the
quantum geometry of space-time. We also discuss the Hilbert space of the
theory, the invariant measure on the spin connection coefficients, and point to
the possible quantum singularity avoidance built in in the natural choice of
the boundary conditions of the wave functions on the space of spin connection
coefficients.
| [
{
"created": "Mon, 11 Feb 2013 20:54:33 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jan 2015 16:16:59 GMT",
"version": "v2"
}
] | 2015-01-28 | [
[
"Kanatchikov",
"I. V.",
""
]
] | The De Donder-Weyl (DW) covariant Hamiltonian formulation of Palatini first-order Lagrangian of vielbein (tetrad) gravity and its precanonical quantization are presented. No splitting into the space and time is required in this formulation. Our recent generalization of Dirac brackets is used to treat the second class primary constraints appearing in the DW Hamiltonian formulation and to find the fundamental brackets. Quantization of the latter yields the representation of vielbeins as differential operators with respect to the spin connection coefficients, and the Dirac-like precanonical Schr\"odinger equation on the space of spin connection coefficients and space-time variables. The transition amplitudes on this space describe the quantum geometry of space-time. We also discuss the Hilbert space of the theory, the invariant measure on the spin connection coefficients, and point to the possible quantum singularity avoidance built in in the natural choice of the boundary conditions of the wave functions on the space of spin connection coefficients. |
2305.12113 | Nicolas Menicucci | Sundance O. Bilson-Thompson, Scott L. Todd, James Read, Valentina
Baccetti, Nicolas C. Menicucci | Tachyonic media in analogue models of special relativity | (v2) minor changes after peer review; (v1) 13 pages, 4 figures | Phys. Rev. D 108, 124020 (2023) | 10.1103/PhysRevD.108.124020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In sonic models of special relativity, the fact that the sonic medium
violates (ordinary) Lorentz symmetry is apparent to observers external to the
sonic medium but not to a class of observers existing within the medium itself.
We show that the situation is symmetric: internal observers will judge physics
in the external laboratory to violate their own sonic Lorentz symmetries. We
therefore treat all observers on an equal footing such that each is able to
retain a commitment to their own Lorentz symmetries. We then generalize beyond
the case of subsystem-environment decompositions to situations in which there
exist multiple phonon fields, all obeying Lorentz symmetries but with different
invariant speeds. In such cases, we argue that all observers have freedom to
choose which field is symmetry preserving, and so -- in a certain precise sense
-- which other fields are perceived as having an 'ether.' This choice is
influenced -- but not determined -- by a desire for simplicity in the
description of physical laws. Sending information faster than sound serves as a
model of tachyonic signalling to a distant receiver. Immutable causality of the
laboratory setup when perceived externally to a sonic medium manifests
internally through the confinement of the tachyons to an apparent ether (with a
rest frame), which we call a 'tachyonic medium,' thereby preventing tachyonic
exchange from emulating the scenario of a round-trip signal travelling into an
observer's past causal cone. The assignment of sonic-Lorentz-violating effects
to fields that obey 'photonic' Lorentz symmetries thus ensures that causality
associated with the 'sonic' Lorentz symmetries is preserved.
| [
{
"created": "Sat, 20 May 2023 06:24:09 GMT",
"version": "v1"
},
{
"created": "Sat, 9 Sep 2023 13:00:59 GMT",
"version": "v2"
}
] | 2024-02-07 | [
[
"Bilson-Thompson",
"Sundance O.",
""
],
[
"Todd",
"Scott L.",
""
],
[
"Read",
"James",
""
],
[
"Baccetti",
"Valentina",
""
],
[
"Menicucci",
"Nicolas C.",
""
]
] | In sonic models of special relativity, the fact that the sonic medium violates (ordinary) Lorentz symmetry is apparent to observers external to the sonic medium but not to a class of observers existing within the medium itself. We show that the situation is symmetric: internal observers will judge physics in the external laboratory to violate their own sonic Lorentz symmetries. We therefore treat all observers on an equal footing such that each is able to retain a commitment to their own Lorentz symmetries. We then generalize beyond the case of subsystem-environment decompositions to situations in which there exist multiple phonon fields, all obeying Lorentz symmetries but with different invariant speeds. In such cases, we argue that all observers have freedom to choose which field is symmetry preserving, and so -- in a certain precise sense -- which other fields are perceived as having an 'ether.' This choice is influenced -- but not determined -- by a desire for simplicity in the description of physical laws. Sending information faster than sound serves as a model of tachyonic signalling to a distant receiver. Immutable causality of the laboratory setup when perceived externally to a sonic medium manifests internally through the confinement of the tachyons to an apparent ether (with a rest frame), which we call a 'tachyonic medium,' thereby preventing tachyonic exchange from emulating the scenario of a round-trip signal travelling into an observer's past causal cone. The assignment of sonic-Lorentz-violating effects to fields that obey 'photonic' Lorentz symmetries thus ensures that causality associated with the 'sonic' Lorentz symmetries is preserved. |
1511.00636 | Christian Corda Prof. | Rishabh Jain, Burra G. Sidharth and Christian Corda | The Jeans theorem and the "Tolman-Oppenheimer-Volkov equation" in an
exact wave solution of R^2 gravity | Comments: 15 pages, the results of arXiv:1105.0147 have been
partially reviewed. Final version matching the one published in the Adv. High
En. Phys. Special Issue "Classical and Quantum Gravity and Its Applications"
Edited by S. Hossein Hendi and others | Adv. High. En. Phys. 2601741 (2016) | 10.1155/2016/2601741 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Corda, Mosquera Cuesta and Lorduy Gomez have shown that spherically symmetric
stationary states can be used as a model for galaxies in the framework of the
linearized R^2 gravity. Those states could represent a partial solution to the
Dark Matter Problem. Here we discuss an improvement of this work. In fact, as
the star density is a functional of the invariants of the associated Vlasov
equation, we show that any of these invariants is in its turn a functional of
the local energy and the angular momentum. As a consequence, the star density
depends only on these two integrals of the Vlasov system. This result is known
as the "Jeans theorem". In addition, we find an analogous of the historical
Tolman- Oppenheimer-Volkov equation for the system considered in this paper.
For the sake of completeness, in the final Section of the paper we consider two
additional models which argue that Dark Matter could not be an essential
element.
| [
{
"created": "Fri, 23 Oct 2015 21:08:24 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Nov 2015 08:06:14 GMT",
"version": "v2"
},
{
"created": "Mon, 13 Jun 2016 07:26:50 GMT",
"version": "v3"
},
{
"created": "Thu, 8 Sep 2016 14:21:21 GMT",
"version": "v4"
},
{
"created": "Thu, 13 Oct 2016 16:58:15 GMT",
"version": "v5"
}
] | 2016-10-17 | [
[
"Jain",
"Rishabh",
""
],
[
"Sidharth",
"Burra G.",
""
],
[
"Corda",
"Christian",
""
]
] | Corda, Mosquera Cuesta and Lorduy Gomez have shown that spherically symmetric stationary states can be used as a model for galaxies in the framework of the linearized R^2 gravity. Those states could represent a partial solution to the Dark Matter Problem. Here we discuss an improvement of this work. In fact, as the star density is a functional of the invariants of the associated Vlasov equation, we show that any of these invariants is in its turn a functional of the local energy and the angular momentum. As a consequence, the star density depends only on these two integrals of the Vlasov system. This result is known as the "Jeans theorem". In addition, we find an analogous of the historical Tolman- Oppenheimer-Volkov equation for the system considered in this paper. For the sake of completeness, in the final Section of the paper we consider two additional models which argue that Dark Matter could not be an essential element. |
1708.04698 | Valeri Frolov P | Valeri P. Frolov | Remarks on non-singular black holes | 10 pages, Extended version of the plenary talk given at a Joint
Meeting: 13th International Conference on Gravitation, Astrophysics, and
Cosmology 15th Italian-Korean Symposium on Relativistic Astrophysics, Seoul,
July 03--07, 2017 | null | 10.1051/epjconf/201816801001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We briefly discuss non-singular black hole models, with the main focus on the
properties of non-singular evaporating black holes. Such black holes possess an
apparent horizon, however the event horizon may be absent. In such a case, the
information from the black hole interior may reach the external observer after
the complete evaporation of the black hole. This model might be used for the
resolution of the information loss puzzle. However, as we demonstrate, in a
general case the quantum radiation emitted from the black hole interior,
calculated in the given black hole background, is very large. This outburst of
the radiation is exponentially large for models with the redshift function
$\alpha=1$. We show that it can be suppressed by including a non-trivial
redshift function. However, even this suppression is not enough to guarantee
self-consistency of the model. This problem is a manifestation of a general
problem, known as the "mass inflation". We briefly comment on possible ways to
overcome this problem in the models of non-singular evaporating black holes.
| [
{
"created": "Tue, 15 Aug 2017 21:51:23 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Aug 2017 20:02:29 GMT",
"version": "v2"
}
] | 2018-01-24 | [
[
"Frolov",
"Valeri P.",
""
]
] | We briefly discuss non-singular black hole models, with the main focus on the properties of non-singular evaporating black holes. Such black holes possess an apparent horizon, however the event horizon may be absent. In such a case, the information from the black hole interior may reach the external observer after the complete evaporation of the black hole. This model might be used for the resolution of the information loss puzzle. However, as we demonstrate, in a general case the quantum radiation emitted from the black hole interior, calculated in the given black hole background, is very large. This outburst of the radiation is exponentially large for models with the redshift function $\alpha=1$. We show that it can be suppressed by including a non-trivial redshift function. However, even this suppression is not enough to guarantee self-consistency of the model. This problem is a manifestation of a general problem, known as the "mass inflation". We briefly comment on possible ways to overcome this problem in the models of non-singular evaporating black holes. |
2205.09050 | Denis Dobkowski-Ry{\l}ko | Denis Dobkowski-Ry{\l}ko and Jerzy Lewandowski | A generalization of the quadruple formula for the energy of
gravitational radiation in de Sitter spacetime | 13+7 pages, 1 figure | null | 10.1103/PhysRevD.106.044047 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study gravitational radiation produced by time changing matter source in
de Sitter spacetime. We consider a cosmological Killing horizon instead of the
conformal boundary used in the radiation theory in the Minkowski spacetime. The
energy of the radiation passing through the horizon is derived. Our result
takes the form of a generalized quadruple formula expressed in terms of the
mass and pressure quadruple moments and is written explicitly up to the first
order in $\sqrt{\Lambda}$. The zeroth order term recovers the famous Einstein's
quadruple formula obtained for the perturbed Minkowski spacetime, whereas the
first order term is a new correction.
| [
{
"created": "Wed, 18 May 2022 16:34:25 GMT",
"version": "v1"
}
] | 2022-09-07 | [
[
"Dobkowski-Ryłko",
"Denis",
""
],
[
"Lewandowski",
"Jerzy",
""
]
] | We study gravitational radiation produced by time changing matter source in de Sitter spacetime. We consider a cosmological Killing horizon instead of the conformal boundary used in the radiation theory in the Minkowski spacetime. The energy of the radiation passing through the horizon is derived. Our result takes the form of a generalized quadruple formula expressed in terms of the mass and pressure quadruple moments and is written explicitly up to the first order in $\sqrt{\Lambda}$. The zeroth order term recovers the famous Einstein's quadruple formula obtained for the perturbed Minkowski spacetime, whereas the first order term is a new correction. |
1908.11258 | Giovanni Camelio | Giovanni Camelio, Tim Dietrich, Miguel Marques and Stephan Rosswog | Rotating neutron stars with non-barotropic thermal profile | 18 pages, 3 appendices, 2 tables, 9 figures. Accepted by PRD | Phys. Rev. D 100, 123001 (2019) | 10.1103/PhysRevD.100.123001 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Neutron stars provide an excellent laboratory for physics under the most
extreme conditions. Up to now, models of axisymmetric, stationary,
differentially rotating neutron stars were constructed under the strong
assumption of barotropicity, where a one-to-one relation between all
thermodynamic quantities exists. This implies that the specific angular
momentum of a matter element depends only on its angular velocity. The physical
conditions in the early stages of neutron stars, however, are determined by
their violent birth processes, typically a supernova or in some cases the
merger of two neutron stars, and detailed numerical models show that the
resulting stars are by no means barotropic. Here, we construct models for
stationary, differentially rotating, non-barotropic neutron stars, where the
equation of state and the specific angular momentum depend on more than one
independent variable. We show that the potential formulation of the
relativistic Euler equation can be extended to the non-barotropic case, which,
to the best of our knowledge, is a new result even for the Newtonian case. We
implement the new method into the XNS code and construct equilibrium
configurations for non-barotropic equations of state. We scrutinize the
resulting configurations by evolving them dynamically with the numerical
relativity code BAM, thereby demonstrating that the new method indeed produces
stationary, differentially rotating, non-barotropic neutron star
configurations.
| [
{
"created": "Thu, 29 Aug 2019 14:35:09 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Nov 2019 13:58:46 GMT",
"version": "v2"
}
] | 2019-12-11 | [
[
"Camelio",
"Giovanni",
""
],
[
"Dietrich",
"Tim",
""
],
[
"Marques",
"Miguel",
""
],
[
"Rosswog",
"Stephan",
""
]
] | Neutron stars provide an excellent laboratory for physics under the most extreme conditions. Up to now, models of axisymmetric, stationary, differentially rotating neutron stars were constructed under the strong assumption of barotropicity, where a one-to-one relation between all thermodynamic quantities exists. This implies that the specific angular momentum of a matter element depends only on its angular velocity. The physical conditions in the early stages of neutron stars, however, are determined by their violent birth processes, typically a supernova or in some cases the merger of two neutron stars, and detailed numerical models show that the resulting stars are by no means barotropic. Here, we construct models for stationary, differentially rotating, non-barotropic neutron stars, where the equation of state and the specific angular momentum depend on more than one independent variable. We show that the potential formulation of the relativistic Euler equation can be extended to the non-barotropic case, which, to the best of our knowledge, is a new result even for the Newtonian case. We implement the new method into the XNS code and construct equilibrium configurations for non-barotropic equations of state. We scrutinize the resulting configurations by evolving them dynamically with the numerical relativity code BAM, thereby demonstrating that the new method indeed produces stationary, differentially rotating, non-barotropic neutron star configurations. |
0905.3362 | Willians Barreto | W. Barreto | The Post-Quasistatic Approximation as a test bed for Numerical
Relativity | 4 pages; to appear as a Brief Report in Physical Review D | Phys.Rev.D79:107502,2009 | 10.1103/PhysRevD.79.107502 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that observers in the standard ADM 3+1 treatment of matter are
the same as the observers used in the matter treatment of Bondi: they are
comoving and local Minkowskian. Bondi's observers are the basis of the
post--quasitatic approximation (PQSA) to study a contracting distribution of
matter. This correspondence suggests the possibility of using the PQSA as a
test bed for Numerical Relativity. The treatment of matter by the PQSA and its
connection with the ADM 3+1 treatment are presented, for its practical use as a
calibration tool and as a test bed for numerical relativistic hydrodynamic
codes.
| [
{
"created": "Wed, 20 May 2009 17:41:46 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Barreto",
"W.",
""
]
] | It is shown that observers in the standard ADM 3+1 treatment of matter are the same as the observers used in the matter treatment of Bondi: they are comoving and local Minkowskian. Bondi's observers are the basis of the post--quasitatic approximation (PQSA) to study a contracting distribution of matter. This correspondence suggests the possibility of using the PQSA as a test bed for Numerical Relativity. The treatment of matter by the PQSA and its connection with the ADM 3+1 treatment are presented, for its practical use as a calibration tool and as a test bed for numerical relativistic hydrodynamic codes. |
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