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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1505.06637 | Laszlo B. Szabados | L\'aszl\'o B Szabados, Paul Tod | A positive Bondi--type mass in asymptotically de Sitter spacetimes | 51 pages; typos corrected, one reference added; final version,
appearing in Class. Quantum Grav | null | 10.1088/0264-9381/32/20/205011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The general structure of the conformal boundary $\mathscr{I}^+$ of
asymptotically de Sitter spacetimes is investigated. First we show that
Penrose's quasi-local mass, associated with a cut ${\cal S}$ of the conformal
boundary, can be zero even in the presence of outgoing gravitational radiation.
On the other hand, following a Witten--type spinorial proof, we show that an
analogous expression based on the Nester--Witten form is finite only if the
Witten spinor field solves the 2-surface twistor equation on ${\cal S}$, and it
yields a positive functional on the 2-surface twistor space on ${\cal S}$,
provided the matter fields satisfy the dominant energy condition. Moreover,
this functional is vanishing if and only if the domain of dependence of the
spacelike hypersurface which intersects $\mathscr{I}^+$ in the cut ${\cal S}$
is locally isometric to the de Sitter spacetime. For non-contorted cuts this
functional yields an invariant analogous to the Bondi mass.
| [
{
"created": "Mon, 25 May 2015 14:17:05 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Aug 2015 12:36:53 GMT",
"version": "v2"
}
] | 2015-10-07 | [
[
"Szabados",
"László B",
""
],
[
"Tod",
"Paul",
""
]
] | The general structure of the conformal boundary $\mathscr{I}^+$ of asymptotically de Sitter spacetimes is investigated. First we show that Penrose's quasi-local mass, associated with a cut ${\cal S}$ of the conformal boundary, can be zero even in the presence of outgoing gravitational radiation. On the other hand, following a Witten--type spinorial proof, we show that an analogous expression based on the Nester--Witten form is finite only if the Witten spinor field solves the 2-surface twistor equation on ${\cal S}$, and it yields a positive functional on the 2-surface twistor space on ${\cal S}$, provided the matter fields satisfy the dominant energy condition. Moreover, this functional is vanishing if and only if the domain of dependence of the spacelike hypersurface which intersects $\mathscr{I}^+$ in the cut ${\cal S}$ is locally isometric to the de Sitter spacetime. For non-contorted cuts this functional yields an invariant analogous to the Bondi mass. |
gr-qc/0506121 | H.-J. Schmidt | H.-J. Schmidt | Einsteins Arbeiten in Bezug auf die moderne Kosmologie | 19 pages, LaTeX, in German language, submitted for publication,
English language title: Einstein's papers in relation to modern cosmology | Acta Historica Astronomiae 27 (2005) 108-124 | null | null | gr-qc | null | We comment on the paper [1] by Albert Einstein from 1918 to Willem De
Sitter's solution [2] of the Einstein field equation from today's point of
view. To this end, we start by describing the geometry of the De Sitter
space-time and present its importance for the inflationary cosmological model.
| [
{
"created": "Sat, 25 Jun 2005 15:22:32 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Schmidt",
"H. -J.",
""
]
] | We comment on the paper [1] by Albert Einstein from 1918 to Willem De Sitter's solution [2] of the Einstein field equation from today's point of view. To this end, we start by describing the geometry of the De Sitter space-time and present its importance for the inflationary cosmological model. |
1110.4504 | V. M. Mostepanenko | V. B. Bezerra, V. M. Mostepanenko, H. F. Mota, and C. Romero | Thermal Casimir effect for neutrino and electromagnetic fields in closed
Friedmann cosmological model | 23 pages, to appear in Phys. Rev. D | null | 10.1103/PhysRevD.84.104025 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the total internal energy, total energy density and pressure,
and the free energy for the neutrino and electromagnetic fields in Einstein and
closed Friedmann cosmological models. The Casimir contributions to all these
quantities are separated. The asymptotic expressions for both the total
internal energy and free energy, and for the Casimir contributions to them are
found in the limiting cases of low and high temperatures. It is shown that the
neutrino field does not possess a classical limit at high temperature. As for
the electromagnetic field, we demonstrate that the total internal energy has
the classical contribution and the Casimir internal energy goes to the
classical limit at high temperature. The respective Casimir free energy
contains both linear and logarithmic terms with respect to the temperature. The
total and Casimir entropies for the neutrino and electromagnetic fields at low
temperature are also calculated and shown to be in agreement with the Nernst
heat theorem.
| [
{
"created": "Thu, 20 Oct 2011 11:51:10 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Bezerra",
"V. B.",
""
],
[
"Mostepanenko",
"V. M.",
""
],
[
"Mota",
"H. F.",
""
],
[
"Romero",
"C.",
""
]
] | We calculate the total internal energy, total energy density and pressure, and the free energy for the neutrino and electromagnetic fields in Einstein and closed Friedmann cosmological models. The Casimir contributions to all these quantities are separated. The asymptotic expressions for both the total internal energy and free energy, and for the Casimir contributions to them are found in the limiting cases of low and high temperatures. It is shown that the neutrino field does not possess a classical limit at high temperature. As for the electromagnetic field, we demonstrate that the total internal energy has the classical contribution and the Casimir internal energy goes to the classical limit at high temperature. The respective Casimir free energy contains both linear and logarithmic terms with respect to the temperature. The total and Casimir entropies for the neutrino and electromagnetic fields at low temperature are also calculated and shown to be in agreement with the Nernst heat theorem. |
0705.0284 | Claudio Dappiaggi | C. Dappiaggi (Pavia U.) | Projecting Massive Scalar Fields to Null Infinity | 26 pages | Ann. Henri Poincare 9 (2008), 35-63 | 10.1007/s00023-007-0349-1 | null | gr-qc hep-th math-ph math.MP | null | It is known that, in an asymptotically flat spacetime, null infinity cannot
act as an initial-value surface for massive real scalar fields. Exploiting
tools proper of harmonic analysis on hyperboloids and global norm estimates for
the wave operator, we show that it is possible to circumvent such obstruction
at least in Minkowski spacetime. Hence we project norm-finite solutions of the
Klein-Gordon equation of motion in data on null infinity and, eventually, we
interpret them in terms of boundary free field theory.
| [
{
"created": "Wed, 2 May 2007 13:11:14 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Dappiaggi",
"C.",
"",
"Pavia U."
]
] | It is known that, in an asymptotically flat spacetime, null infinity cannot act as an initial-value surface for massive real scalar fields. Exploiting tools proper of harmonic analysis on hyperboloids and global norm estimates for the wave operator, we show that it is possible to circumvent such obstruction at least in Minkowski spacetime. Hence we project norm-finite solutions of the Klein-Gordon equation of motion in data on null infinity and, eventually, we interpret them in terms of boundary free field theory. |
2405.10777 | Amitabh Virmani | Harsh, Sk Jahanur Hoque, Sitender Pratap Kashyap, Amitabh Virmani | de Sitter Teukolsky waves | 45 pages, 2 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present de Sitter Teukolsky waves -- linearised quadrupolar gravitational
waves in the transverse-traceless gauge in de Sitter spacetime. In the
cosmological constant $\Lambda$ going to zero limit, our solutions match to
Teukolsky solutions. For non-zero $\Lambda$, we compare our solutions to the
wider literature, where different authors have constructed linearised
gravitational perturbations in de Sitter spacetime with varied motivations. For
de Sitter Teukolsky waves, we compute the energy flux across future timelike
infinity $\mathcal{I}^{+}$ and show that it is manifestly positive.
| [
{
"created": "Fri, 17 May 2024 13:38:49 GMT",
"version": "v1"
}
] | 2024-05-20 | [
[
"Harsh",
"",
""
],
[
"Hoque",
"Sk Jahanur",
""
],
[
"Kashyap",
"Sitender Pratap",
""
],
[
"Virmani",
"Amitabh",
""
]
] | We present de Sitter Teukolsky waves -- linearised quadrupolar gravitational waves in the transverse-traceless gauge in de Sitter spacetime. In the cosmological constant $\Lambda$ going to zero limit, our solutions match to Teukolsky solutions. For non-zero $\Lambda$, we compare our solutions to the wider literature, where different authors have constructed linearised gravitational perturbations in de Sitter spacetime with varied motivations. For de Sitter Teukolsky waves, we compute the energy flux across future timelike infinity $\mathcal{I}^{+}$ and show that it is manifestly positive. |
1003.4385 | Jose Luis Flores | J.L. Flores, S. Haesen, M. Ortega | New Examples of Marginally Trapped Surfaces and Tubes in Warped
Spacetimes | 20 pages | null | 10.1088/0264-9381/27/14/145021 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present paper we provide new examples of marginally trapped surfaces
and tubes in FLRW spacetimes by using a basic relation between these objects
and CMC surfaces in 3-manifolds. We also provide a new method to construct
marginally trapped surfaces in closed FLRW spacetimes, which is based on the
classical Hopf map. The utility of this method is illustrated by providing
marginally trapped surfaces crossing expanding and collapsing regions of a
closed FLRW spacetime. The approach introduced in this paper is also extended
to twisted spaces.
| [
{
"created": "Tue, 23 Mar 2010 11:46:10 GMT",
"version": "v1"
}
] | 2015-05-18 | [
[
"Flores",
"J. L.",
""
],
[
"Haesen",
"S.",
""
],
[
"Ortega",
"M.",
""
]
] | In the present paper we provide new examples of marginally trapped surfaces and tubes in FLRW spacetimes by using a basic relation between these objects and CMC surfaces in 3-manifolds. We also provide a new method to construct marginally trapped surfaces in closed FLRW spacetimes, which is based on the classical Hopf map. The utility of this method is illustrated by providing marginally trapped surfaces crossing expanding and collapsing regions of a closed FLRW spacetime. The approach introduced in this paper is also extended to twisted spaces. |
2407.10421 | Hong-Hao Zhang | Jian Ge, Lei Ming, Shi-Dong Liang, Hong-Hao Zhang, Tiberiu Harko | Constraining Weyl type f(Q,T) gravity with Big Bang Nucleosynthesis | 19 pages, 12 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The Weyl type $f(Q,T)$ modified gravity theory is an extension of the $f(Q)$
and $f(Q,T)$ type theories, where $T$ is the trace of the matter
energy-momentum tensor, and the scalar non-metricity $Q$ is represented in its
standard Weyl form, and it is fully determined by a vector field $\omega _\mu$.
The theory can give a good description of the observational data, and of the
evolution of the late-time Universe, including a geometric explanation of the
dark energy. In this work we investigate the Big Bang Nucleosynthesis (BBN)
constraints on several Weyl type $f(Q,T)$ gravity models. In particular, we
consider the corrections that Weyl type $f(Q,T)$ terms induce on the freeze-out
temperature $\mathcal{T}_f$, as compared to the standard $\Lambda$CDM results.
We analyze in detail three distinct cosmological models, corresponding to
specific choices of the functional form of $f(Q,T)$. The first model has a
simple linear additive structure in $Q$ and $T$, the second model is
multiplicative in $Q$ and $T$, while the third is additive in $T$ and the
exponential of $Q$. For each $f(Q,T)$ we consider first the cosmological
evolution in the radiation dominated era, and then we impose the observational
bound on $\left|\delta \mathcal{T}_f/ \mathcal{T}_f\right|$ to obtain
constraints on the model parameters from the primordial abundances of the light
elements such as helium-4, deuterium and lithium-7. The abundances of helium-4
and deuterium agree with theoretical predictions, however, the lithium problem,
even slightly alleviated, still persists for the considered Weyl type $f(Q,T)$
models. Generally, these models satisfy the BBN constraints, and thus they
represent viable cosmologies describing the entire dynamical time scale of the
evolution of the Universe.
| [
{
"created": "Mon, 15 Jul 2024 03:52:00 GMT",
"version": "v1"
}
] | 2024-07-16 | [
[
"Ge",
"Jian",
""
],
[
"Ming",
"Lei",
""
],
[
"Liang",
"Shi-Dong",
""
],
[
"Zhang",
"Hong-Hao",
""
],
[
"Harko",
"Tiberiu",
""
]
] | The Weyl type $f(Q,T)$ modified gravity theory is an extension of the $f(Q)$ and $f(Q,T)$ type theories, where $T$ is the trace of the matter energy-momentum tensor, and the scalar non-metricity $Q$ is represented in its standard Weyl form, and it is fully determined by a vector field $\omega _\mu$. The theory can give a good description of the observational data, and of the evolution of the late-time Universe, including a geometric explanation of the dark energy. In this work we investigate the Big Bang Nucleosynthesis (BBN) constraints on several Weyl type $f(Q,T)$ gravity models. In particular, we consider the corrections that Weyl type $f(Q,T)$ terms induce on the freeze-out temperature $\mathcal{T}_f$, as compared to the standard $\Lambda$CDM results. We analyze in detail three distinct cosmological models, corresponding to specific choices of the functional form of $f(Q,T)$. The first model has a simple linear additive structure in $Q$ and $T$, the second model is multiplicative in $Q$ and $T$, while the third is additive in $T$ and the exponential of $Q$. For each $f(Q,T)$ we consider first the cosmological evolution in the radiation dominated era, and then we impose the observational bound on $\left|\delta \mathcal{T}_f/ \mathcal{T}_f\right|$ to obtain constraints on the model parameters from the primordial abundances of the light elements such as helium-4, deuterium and lithium-7. The abundances of helium-4 and deuterium agree with theoretical predictions, however, the lithium problem, even slightly alleviated, still persists for the considered Weyl type $f(Q,T)$ models. Generally, these models satisfy the BBN constraints, and thus they represent viable cosmologies describing the entire dynamical time scale of the evolution of the Universe. |
2007.15300 | Pankaj Sheoran | Ricardo Becerril, Susana Valdez -Alvarado, Ulises Nucamendi, Pankaj
Sheoran, Manuel D\'avila | Mass parameter and the bounds on redshifts and blueshifts of photons
emitted from geodesic particle orbiting in the vicinity of regular black
holes | 23 pages, 19 figures, Major revision, title and context changed, App.
A added, new figures added, updated to match journal version | Phys. Rev. D 103, 084054 (2021) | 10.1103/PhysRevD.103.084054 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain the mass parameter for a class of static and spherically symmetric
regular black holes (BHs) (namely Bardeen, Hayward and
Ay\'{o}n-Beato-Garc\'{i}a BHs) which are solutions of Einstein's field
equations coupled to nonlinear electrodynamics (NED) in terms of redshifts and
blueshifts of photons emitted by geodesic particles (for instance, stars)
orbiting around these BHs. The motion of photons is not governed by null
geodesics for these type of spacetime geometries which reflects the direct
effects of the electrodynamic nonlinearities in the photon motion; hence, an
effective geometry needs to be constructed to study null trajectories [Phys.
Rev. D61, 045001 (2000)]. To achieve the above, we first study the constants of
motion from the analysis of the motion of both geodesic particles moving in
stable circular orbits and photons ejected from them and reaching a distant
observer (or detector) in the equatorial plane for the above mentioned regular
BHs. The relationship between red/blueshifts of photons and the regular BH
observables is presented. We also numerically find the bounds on the photon
shifts for these regular BH cases.
| [
{
"created": "Thu, 30 Jul 2020 08:25:05 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Jun 2021 15:29:14 GMT",
"version": "v2"
}
] | 2021-06-07 | [
[
"Becerril",
"Ricardo",
""
],
[
"-Alvarado",
"Susana Valdez",
""
],
[
"Nucamendi",
"Ulises",
""
],
[
"Sheoran",
"Pankaj",
""
],
[
"Dávila",
"Manuel",
""
]
] | We obtain the mass parameter for a class of static and spherically symmetric regular black holes (BHs) (namely Bardeen, Hayward and Ay\'{o}n-Beato-Garc\'{i}a BHs) which are solutions of Einstein's field equations coupled to nonlinear electrodynamics (NED) in terms of redshifts and blueshifts of photons emitted by geodesic particles (for instance, stars) orbiting around these BHs. The motion of photons is not governed by null geodesics for these type of spacetime geometries which reflects the direct effects of the electrodynamic nonlinearities in the photon motion; hence, an effective geometry needs to be constructed to study null trajectories [Phys. Rev. D61, 045001 (2000)]. To achieve the above, we first study the constants of motion from the analysis of the motion of both geodesic particles moving in stable circular orbits and photons ejected from them and reaching a distant observer (or detector) in the equatorial plane for the above mentioned regular BHs. The relationship between red/blueshifts of photons and the regular BH observables is presented. We also numerically find the bounds on the photon shifts for these regular BH cases. |
0707.1475 | Alfonso Garc\'ia-Parrado G\'omez-Lobo Dr. | Alfonso Garc\'ia-Parrado G\'omez-Lobo | Dynamical laws of superenergy in General Relativity | 27 pages, no figures. Typos corrected, section 9 suppressed and more
acknowledgments added. To appear in Classical and Quantum Gravity | Class.Quant.Grav.25:015006,2008 | 10.1088/0264-9381/25/1/015006 | null | gr-qc | null | The Bel and Bel-Robinson tensors were introduced nearly fifty years ago in an
attempt to generalize to gravitation the energy-momentum tensor of
electromagnetism. This generalization was successful from the mathematical
point of view because these tensors share mathematical properties which are
remarkably similar to those of the energy-momentum tensor of electromagnetism.
However, the physical role of these tensors in General Relativity has remained
obscure and no interpretation has achieved wide acceptance. In principle, they
cannot represent {\em energy} and the term {\em superenergy} has been coined
for the hypothetical physical magnitude lying behind them. In this work we try
to shed light on the true physical meaning of {\em superenergy} by following
the same procedure which enables us to give an interpretation of the
electromagnetic energy. This procedure consists in performing an orthogonal
splitting of the Bel and Bel-Robinson tensors and analysing the different parts
resulting from the splitting. In the electromagnetic case such splitting gives
rise to the electromagnetic {\em energy density}, the Poynting vector and the
electromagnetic stress tensor, each of them having a precise physical
interpretation which is deduced from the {\em dynamical laws} of
electromagnetism (Poynting theorem). The full orthogonal splitting of the Bel
and Bel-Robinson tensors is more complex but, as expected, similarities with
electromagnetism are present. Also the covariant divergence of the Bel tensor
is analogous to the covariant divergence of the electromagnetic energy-momentum
tensor and the orthogonal splitting of the former is found. The ensuing {\em
equations} are to the superenergy what the Poynting theorem is to
electromagnetism. See paper for full abstract.
| [
{
"created": "Tue, 10 Jul 2007 15:42:29 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Nov 2007 13:56:58 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Gómez-Lobo",
"Alfonso García-Parrado",
""
]
] | The Bel and Bel-Robinson tensors were introduced nearly fifty years ago in an attempt to generalize to gravitation the energy-momentum tensor of electromagnetism. This generalization was successful from the mathematical point of view because these tensors share mathematical properties which are remarkably similar to those of the energy-momentum tensor of electromagnetism. However, the physical role of these tensors in General Relativity has remained obscure and no interpretation has achieved wide acceptance. In principle, they cannot represent {\em energy} and the term {\em superenergy} has been coined for the hypothetical physical magnitude lying behind them. In this work we try to shed light on the true physical meaning of {\em superenergy} by following the same procedure which enables us to give an interpretation of the electromagnetic energy. This procedure consists in performing an orthogonal splitting of the Bel and Bel-Robinson tensors and analysing the different parts resulting from the splitting. In the electromagnetic case such splitting gives rise to the electromagnetic {\em energy density}, the Poynting vector and the electromagnetic stress tensor, each of them having a precise physical interpretation which is deduced from the {\em dynamical laws} of electromagnetism (Poynting theorem). The full orthogonal splitting of the Bel and Bel-Robinson tensors is more complex but, as expected, similarities with electromagnetism are present. Also the covariant divergence of the Bel tensor is analogous to the covariant divergence of the electromagnetic energy-momentum tensor and the orthogonal splitting of the former is found. The ensuing {\em equations} are to the superenergy what the Poynting theorem is to electromagnetism. See paper for full abstract. |
1001.1141 | James Burnett | Christian. G. Boehmer and James Burnett | Dark Spinors | 3 pages, 2 figures, submitted to the Proceedings of the Twelfth
Marcel Grossmann Meeting on General Relativity; minor corrections | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article will provide the reader with a short introduction to dark
spinors, which are ELKO spinors, eingenspinors of the charge conjugation
operator, applied to dark matter and dark energy.
| [
{
"created": "Thu, 7 Jan 2010 20:58:54 GMT",
"version": "v1"
},
{
"created": "Sat, 6 Feb 2010 12:37:43 GMT",
"version": "v2"
}
] | 2010-02-06 | [
[
"Boehmer",
"Christian. G.",
""
],
[
"Burnett",
"James",
""
]
] | This article will provide the reader with a short introduction to dark spinors, which are ELKO spinors, eingenspinors of the charge conjugation operator, applied to dark matter and dark energy. |
1302.5163 | V. G. Gurzadyan | I.Ciufolini, V.G.Gurzadyan, R.Penrose, A.Paolozzi | Geodesic motion in General Relativity: LARES in Earth's gravity | 4 pages, 1 image | in: Low Dimensional Physics and Gauge Principles, Matinyan
Festschrift, p.93, World Scientific, 2013 | 10.1142/9789814440349_0008 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | According to General Relativity, as distinct from Newtonian gravity, motion
under gravity is treated by a theory that deals, initially, only with test
particles. At the same time, satellite measurements deal with extended bodies.
We discuss the correspondence between geodesic motion in General Relativity and
the motion of an extended body by means of the Ehlers-Geroch theorem, and in
the context of the recently launched LAser RElativity Satellite (LARES). Being
possibly the highest mean density orbiting body in the Solar system, this
satellite provides the best realization of a test particle ever reached
experimentally and provides a unique possibility for testing the predictions of
General Relativity.
| [
{
"created": "Thu, 21 Feb 2013 02:57:25 GMT",
"version": "v1"
}
] | 2017-10-03 | [
[
"Ciufolini",
"I.",
""
],
[
"Gurzadyan",
"V. G.",
""
],
[
"Penrose",
"R.",
""
],
[
"Paolozzi",
"A.",
""
]
] | According to General Relativity, as distinct from Newtonian gravity, motion under gravity is treated by a theory that deals, initially, only with test particles. At the same time, satellite measurements deal with extended bodies. We discuss the correspondence between geodesic motion in General Relativity and the motion of an extended body by means of the Ehlers-Geroch theorem, and in the context of the recently launched LAser RElativity Satellite (LARES). Being possibly the highest mean density orbiting body in the Solar system, this satellite provides the best realization of a test particle ever reached experimentally and provides a unique possibility for testing the predictions of General Relativity. |
1712.02699 | Katharina Radermacher | Katharina Radermacher | Orthogonal Bianchi B stiff fluids close to the initial singularity | 29 pages, v2: minor typos, layout changes | null | null | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In our previous article [Rad16], we investigated the asymptotic behaviour of
orthogonal Bianchi class B perfect fluids close to the initial singularity and
proved the Strong Cosmic Censorship conjecture in this setting. In several of
the statements, the case of a stiff fluid had to be excluded. The present paper
fills this gap.
We work in expansion-normalised variables introduced by Hewitt-Wainwright and
find that solutions converge, but show a convergence behaviour very different
from the non-stiff case: All solutions tend to limit points in the
two-dimensional Jacobs set. A set of full measure, which is also a countable
intersection of open and dense sets in the state space, yields convergence to a
specific subset of the Jacobs set.
| [
{
"created": "Thu, 7 Dec 2017 16:31:40 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Dec 2017 21:38:11 GMT",
"version": "v2"
}
] | 2017-12-13 | [
[
"Radermacher",
"Katharina",
""
]
] | In our previous article [Rad16], we investigated the asymptotic behaviour of orthogonal Bianchi class B perfect fluids close to the initial singularity and proved the Strong Cosmic Censorship conjecture in this setting. In several of the statements, the case of a stiff fluid had to be excluded. The present paper fills this gap. We work in expansion-normalised variables introduced by Hewitt-Wainwright and find that solutions converge, but show a convergence behaviour very different from the non-stiff case: All solutions tend to limit points in the two-dimensional Jacobs set. A set of full measure, which is also a countable intersection of open and dense sets in the state space, yields convergence to a specific subset of the Jacobs set. |
gr-qc/0702112 | Kayll Lake | Kayll Lake | Scalar Polynomial Singularities in Power-Law Spacetimes | 7 pages revtex4 two figures extended discussion | Gen.Rel.Grav.40:1609-1617,2008 | 10.1007/s10714-007-0563-7 | null | gr-qc | null | Recently, Helliwell and Konkowski (\texttt{gr-qc/0701149}) have examined the
quantum "healing" of some classical singularities in certain power-law
spacetimes. Here I further examine classical properties of these spacetimes and
show that some of them contain naked strong curvature singularities.
| [
{
"created": "Tue, 20 Feb 2007 19:27:58 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Apr 2007 18:22:35 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Lake",
"Kayll",
""
]
] | Recently, Helliwell and Konkowski (\texttt{gr-qc/0701149}) have examined the quantum "healing" of some classical singularities in certain power-law spacetimes. Here I further examine classical properties of these spacetimes and show that some of them contain naked strong curvature singularities. |
gr-qc/0301127 | Florian Siebel | Florian Siebel (MPA), Jose A. Font (Valencia), Ewald Mueller (MPA),
Philippos Papadopoulos (Portsmouth) | Axisymmetric core collapse simulations using characteristic numerical
relativity | 17 pages, 18 figures, submitted to Phys. Rev. D | Phys.Rev. D67 (2003) 124018 | 10.1103/PhysRevD.67.124018 | null | gr-qc astro-ph | null | We present results from axisymmetric stellar core collapse simulations in
general relativity. Our hydrodynamics code has proved robust and accurate
enough to allow for a detailed analysis of the global dynamics of the collapse.
Contrary to traditional approaches based on the 3+1 formulation of the
gravitational field equations, our framework uses a foliation based on a family
of outgoing light cones, emanating from a regular center, and terminating at
future null infinity. Such a coordinate system is well adapted to the study of
interesting dynamical spacetimes in relativistic astrophysics such as stellar
core collapse and neutron star formation. Perhaps most importantly this
procedure allows for the unambiguous extraction of gravitational waves at
future null infinity without any approximation, along with the commonly used
quadrupole formalism for the gravitational wave extraction. Our results
concerning the gravitational wave signals show noticeable disagreement when
those are extracted by computing the Bondi news at future null infinity on the
one hand and by using the quadrupole formula on the other hand. We have strong
indication that for our setup the quadrupole formula on the null cone does not
lead to physical gravitational wave signals. The Bondi gravitational wave
signals extracted at infinity show typical oscillation frequencies of about 0.5
kHz.
| [
{
"created": "Fri, 31 Jan 2003 08:34:18 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Siebel",
"Florian",
"",
"MPA"
],
[
"Font",
"Jose A.",
"",
"Valencia"
],
[
"Mueller",
"Ewald",
"",
"MPA"
],
[
"Papadopoulos",
"Philippos",
"",
"Portsmouth"
]
] | We present results from axisymmetric stellar core collapse simulations in general relativity. Our hydrodynamics code has proved robust and accurate enough to allow for a detailed analysis of the global dynamics of the collapse. Contrary to traditional approaches based on the 3+1 formulation of the gravitational field equations, our framework uses a foliation based on a family of outgoing light cones, emanating from a regular center, and terminating at future null infinity. Such a coordinate system is well adapted to the study of interesting dynamical spacetimes in relativistic astrophysics such as stellar core collapse and neutron star formation. Perhaps most importantly this procedure allows for the unambiguous extraction of gravitational waves at future null infinity without any approximation, along with the commonly used quadrupole formalism for the gravitational wave extraction. Our results concerning the gravitational wave signals show noticeable disagreement when those are extracted by computing the Bondi news at future null infinity on the one hand and by using the quadrupole formula on the other hand. We have strong indication that for our setup the quadrupole formula on the null cone does not lead to physical gravitational wave signals. The Bondi gravitational wave signals extracted at infinity show typical oscillation frequencies of about 0.5 kHz. |
1512.08349 | Er-Dong Guo | Er-Dong Guo, Miao Li, and Jia-Rui Sun | CFT dual of charged AdS black hole in the large dimension limit | Latex, 18 pages, minor corrections and references added | null | 10.1142/S0218271816500851 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the dual CFT description of the $d+1$-dimensional
Reissner-Nordstr\"om-Anti de Sitter (RN-AdS$_{d+1}$) black hole in the large
dimension (large $d$) limit, both for the extremal and nonextremal cases. The
central charge of the dual CFT$_2$ (or chiral CFT$_1$) is calculated for the
near horizon near extremal geometry which possess an AdS$_2$ structure.
Besides, the $Q$-picture hidden conformal symmetry in the nonextremal
background can be naturally obtained by a probe charged scalar field in the
large $d$ limit, without the need to input the usual limits to probe the hidden
conformal symmetry. Furthermore, an new dual CFT description of the nonextremal
RN-AdS$_{d+1}$ black hole is found in the large $d$ limit and the duality is
analyzed by comparing the entropies, the absorption cross sections and the
retarded Green's functions obtained both from the gravity and the dual CFT
sides.
| [
{
"created": "Mon, 28 Dec 2015 08:57:12 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Mar 2016 14:36:47 GMT",
"version": "v2"
}
] | 2016-06-15 | [
[
"Guo",
"Er-Dong",
""
],
[
"Li",
"Miao",
""
],
[
"Sun",
"Jia-Rui",
""
]
] | We study the dual CFT description of the $d+1$-dimensional Reissner-Nordstr\"om-Anti de Sitter (RN-AdS$_{d+1}$) black hole in the large dimension (large $d$) limit, both for the extremal and nonextremal cases. The central charge of the dual CFT$_2$ (or chiral CFT$_1$) is calculated for the near horizon near extremal geometry which possess an AdS$_2$ structure. Besides, the $Q$-picture hidden conformal symmetry in the nonextremal background can be naturally obtained by a probe charged scalar field in the large $d$ limit, without the need to input the usual limits to probe the hidden conformal symmetry. Furthermore, an new dual CFT description of the nonextremal RN-AdS$_{d+1}$ black hole is found in the large $d$ limit and the duality is analyzed by comparing the entropies, the absorption cross sections and the retarded Green's functions obtained both from the gravity and the dual CFT sides. |
1903.01436 | Peter Horvathy | P.-M. Zhang, M. Cariglia, M. Elbistan, G. W. Gibbons, P. A. Horvathy | "Kepler Harmonies" and conformal symmetries | 13 pages, 1 figure. Dedicated to the memory of Christian Duval
(1947-2018) | null | 10.1016/j.physletb.2019.03.057 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Kepler's rescaling becomes, when "Eisenhart-Duval lifted" to $5$-dimensional
"Bargmann" gravitational wave spacetime, an ordinary spacetime symmetry for
motion along null geodesics, which are the lifts of Keplerian trajectories. The
lifted rescaling generates a well-behaved conserved Noether charge upstairs,
which takes an unconventional form when expressed in conventional terms. This
conserved quantity seems to have escaped attention so far. Applications include
the Virial Theorem and also Kepler's Third Law. The lifted Kepler rescaling is
a Chrono-Projective transformation. The results extend to celestial mechanics
and Newtonian Cosmology.
| [
{
"created": "Mon, 4 Mar 2019 18:58:01 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Mar 2019 18:37:25 GMT",
"version": "v2"
}
] | 2019-05-22 | [
[
"Zhang",
"P. -M.",
""
],
[
"Cariglia",
"M.",
""
],
[
"Elbistan",
"M.",
""
],
[
"Gibbons",
"G. W.",
""
],
[
"Horvathy",
"P. A.",
""
]
] | Kepler's rescaling becomes, when "Eisenhart-Duval lifted" to $5$-dimensional "Bargmann" gravitational wave spacetime, an ordinary spacetime symmetry for motion along null geodesics, which are the lifts of Keplerian trajectories. The lifted rescaling generates a well-behaved conserved Noether charge upstairs, which takes an unconventional form when expressed in conventional terms. This conserved quantity seems to have escaped attention so far. Applications include the Virial Theorem and also Kepler's Third Law. The lifted Kepler rescaling is a Chrono-Projective transformation. The results extend to celestial mechanics and Newtonian Cosmology. |
gr-qc/9901082 | Takahiro Tanaka | Takahiro Tanaka | The No-Negative Mode Theorem in False Vacuum Decay with Gravity | 14 pages, 8 postscript figures, added references, corrected some
typos | Nucl.Phys. B556 (1999) 373-396 | 10.1016/S0550-3213(99)00369-7 | OU-TAP 92 | gr-qc | null | The so-called negative mode problem in the path integral approach to the
false vacuum decay with the effect of gravity has been an unsolved problem.
Several years ago, we proposed a conjecture which is to be proved in order to
give a consistent solution to the negative mode problem. We called it the
``no-negative mode conjecture''. In the present paper, we give a proof of this
conjecture for rather general models. Recently, we also proposed the
``no-supercritical supercurvature mode conjecture'' that claims the absence of
supercritical supercurvature modes in the one-bubble open inflation model. In
the same paper, we clarified the equivalence between the ``no-negative mode
conjecture'' and the ``no-supercritical supercurvature mode conjecture''.
Hence, the latter is also proved at the same time when the former is proved.
| [
{
"created": "Thu, 28 Jan 1999 17:45:44 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Feb 1999 12:35:42 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Tanaka",
"Takahiro",
""
]
] | The so-called negative mode problem in the path integral approach to the false vacuum decay with the effect of gravity has been an unsolved problem. Several years ago, we proposed a conjecture which is to be proved in order to give a consistent solution to the negative mode problem. We called it the ``no-negative mode conjecture''. In the present paper, we give a proof of this conjecture for rather general models. Recently, we also proposed the ``no-supercritical supercurvature mode conjecture'' that claims the absence of supercritical supercurvature modes in the one-bubble open inflation model. In the same paper, we clarified the equivalence between the ``no-negative mode conjecture'' and the ``no-supercritical supercurvature mode conjecture''. Hence, the latter is also proved at the same time when the former is proved. |
2110.12813 | Mohammed Khalil | Mohammed Khalil | Gravitational spin-orbit dynamics at the fifth-and-a-half post-Newtonian
order | 19 pages, 1 figure, ancillary file. v2: minor improvements, matches
published version | null | 10.1103/PhysRevD.104.124015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Accurate waveform models are crucial for gravitational-wave data analysis,
and since spin has a significant effect on the binary dynamics, it is important
to improve the spin description in these models. In this paper, we derive the
spin-orbit (SO) coupling at the fifth-and-a-half post-Newtonian (5.5PN) order.
The method we use splits the conservative dynamics into local and
nonlocal-in-time parts, then relates the local-in-time part to gravitational
self-force results by exploiting the simple mass-ratio dependence of the
post-Minkowskian expansion of the scattering angle. We calculate the nonlocal
contribution to the 5.5PN SO dynamics to eighth order in the small-eccentricity
expansion for bound orbits, and to leading order in the large-eccentricity
expansion for unbound orbits. For the local contribution, we obtain all the
5.5PN SO coefficients from first-order self-force results for the redshift and
spin-precession invariants, except for one unknown that could be fixed in the
future by second-order self-force results. However, by incorporating our 5.5PN
results in the effective-one-body formalism and comparing its binding energy to
numerical relativity, we find that the remaining unknown has a small effect on
the SO dynamics, demonstrating an improvement in accuracy at that order.
| [
{
"created": "Mon, 25 Oct 2021 11:23:28 GMT",
"version": "v1"
},
{
"created": "Sat, 20 Nov 2021 14:09:22 GMT",
"version": "v2"
}
] | 2021-12-15 | [
[
"Khalil",
"Mohammed",
""
]
] | Accurate waveform models are crucial for gravitational-wave data analysis, and since spin has a significant effect on the binary dynamics, it is important to improve the spin description in these models. In this paper, we derive the spin-orbit (SO) coupling at the fifth-and-a-half post-Newtonian (5.5PN) order. The method we use splits the conservative dynamics into local and nonlocal-in-time parts, then relates the local-in-time part to gravitational self-force results by exploiting the simple mass-ratio dependence of the post-Minkowskian expansion of the scattering angle. We calculate the nonlocal contribution to the 5.5PN SO dynamics to eighth order in the small-eccentricity expansion for bound orbits, and to leading order in the large-eccentricity expansion for unbound orbits. For the local contribution, we obtain all the 5.5PN SO coefficients from first-order self-force results for the redshift and spin-precession invariants, except for one unknown that could be fixed in the future by second-order self-force results. However, by incorporating our 5.5PN results in the effective-one-body formalism and comparing its binding energy to numerical relativity, we find that the remaining unknown has a small effect on the SO dynamics, demonstrating an improvement in accuracy at that order. |
0901.2353 | Ramin G. Daghigh | Ramin G. Daghigh | The Highly Real Quasinormal Modes of Schwarzschild-Anti De Sitter Black
Holes | 9 pages, 1 figure | JHEP 0904:045,2009 | 10.1088/1126-6708/2009/04/045 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A recent investigation has led to the possibility of the existence of an
interesting region of the asymptotic quasinormal mode spectrum of
Schwarzschild-anti de Sitter black holes. In this asymptotic region, the real
part of quasinormal mode frequencies approaches infinity while the damping rate
approaches a finite value. These quasinormal mode frequencies were calculated
using an analytic technique based on the complex coordinate WKB method. In this
paper, we use a different analytic technique to calculate such quasinormal mode
frequencies. The results of this paper provide further support of the
possibility of the existence of these modes.
| [
{
"created": "Thu, 15 Jan 2009 21:41:37 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Mar 2009 03:25:55 GMT",
"version": "v2"
},
{
"created": "Tue, 14 Apr 2009 14:06:29 GMT",
"version": "v3"
}
] | 2010-04-14 | [
[
"Daghigh",
"Ramin G.",
""
]
] | A recent investigation has led to the possibility of the existence of an interesting region of the asymptotic quasinormal mode spectrum of Schwarzschild-anti de Sitter black holes. In this asymptotic region, the real part of quasinormal mode frequencies approaches infinity while the damping rate approaches a finite value. These quasinormal mode frequencies were calculated using an analytic technique based on the complex coordinate WKB method. In this paper, we use a different analytic technique to calculate such quasinormal mode frequencies. The results of this paper provide further support of the possibility of the existence of these modes. |
1612.04235 | Frans Klinkhamer | F.R. Klinkhamer, G.E. Volovik | More on cold dark matter from q-theory | 8 pages, v3: minor changes, references updated | null | null | KA-TP-40-2016 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the rapidly-oscillating part of a $q$-field in a cosmological
context and find that its energy density behaves in the same way as a
cold-dark-matter component, namely proportional to the inverse cube of the
cosmic scale factor.
| [
{
"created": "Mon, 12 Dec 2016 15:46:57 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Dec 2016 13:36:43 GMT",
"version": "v2"
},
{
"created": "Tue, 13 Nov 2018 14:40:14 GMT",
"version": "v3"
}
] | 2018-11-14 | [
[
"Klinkhamer",
"F. R.",
""
],
[
"Volovik",
"G. E.",
""
]
] | We consider the rapidly-oscillating part of a $q$-field in a cosmological context and find that its energy density behaves in the same way as a cold-dark-matter component, namely proportional to the inverse cube of the cosmic scale factor. |
1408.1105 | David Kubiznak | Aruna Rajagopal, David Kubiznak, Robert B. Mann | Van der Waals black hole | 4 pages, 1 figure v3: corrected statements about energy conditions | null | 10.1016/j.physletb.2014.08.054 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of extended phase space, where the negative cosmological
constant is treated as a thermodynamic pressure in the first law of black hole
thermodynamics, we find an asymptotically AdS metric whose thermodynamics
matches exactly that of the Van der Waals fluid. However, we show that as a
solution of Einstein's equations, the corresponding stress energy tensor does
not obey any of the energy conditions everywhere outside of the horizon.
| [
{
"created": "Tue, 5 Aug 2014 20:10:16 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Aug 2014 19:30:55 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Nov 2014 14:17:52 GMT",
"version": "v3"
}
] | 2015-06-22 | [
[
"Rajagopal",
"Aruna",
""
],
[
"Kubiznak",
"David",
""
],
[
"Mann",
"Robert B.",
""
]
] | In the context of extended phase space, where the negative cosmological constant is treated as a thermodynamic pressure in the first law of black hole thermodynamics, we find an asymptotically AdS metric whose thermodynamics matches exactly that of the Van der Waals fluid. However, we show that as a solution of Einstein's equations, the corresponding stress energy tensor does not obey any of the energy conditions everywhere outside of the horizon. |
1905.04602 | Celia Escamilla-Rivera | Celia Escamilla-Rivera and Salvatore Capozziello | Unveiling cosmography from the dark energy equation of state | 9 pages, 3 figures, 2 tables. Observational data analysis added.
Accepted for publication in IJMPD | International Journal of Modern Physics D (2019) | 10.1142/S0218271819501542 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Constraining the dark energy equation of state, $w_x(z)$, is one of the main
issues of current and future cosmological surveys. In practice, this requires
making assumptions about the evolution of $w_x$ with redshift $z$, which can be
manifested in a choice of a specific parametric form where the number of
cosmological parameters play an important role in the observed cosmic
acceleration. Since any attempt to constrain the EoS requires fixing some prior
in one form or the other, settling a method to constrain cosmological
parameters is of great importance. In this paper, we provide a straightforward
approach to show how cosmological tests can be improved via a parametric
methodology based on cosmography. Using Supernovae Type IA samplers we show how
by performing a statistical analysis of a specific dark energy parameterisation
can give directly the cosmographic parameters values.
| [
{
"created": "Sat, 11 May 2019 22:39:39 GMT",
"version": "v1"
},
{
"created": "Sat, 20 Jul 2019 06:32:33 GMT",
"version": "v2"
}
] | 2019-07-29 | [
[
"Escamilla-Rivera",
"Celia",
""
],
[
"Capozziello",
"Salvatore",
""
]
] | Constraining the dark energy equation of state, $w_x(z)$, is one of the main issues of current and future cosmological surveys. In practice, this requires making assumptions about the evolution of $w_x$ with redshift $z$, which can be manifested in a choice of a specific parametric form where the number of cosmological parameters play an important role in the observed cosmic acceleration. Since any attempt to constrain the EoS requires fixing some prior in one form or the other, settling a method to constrain cosmological parameters is of great importance. In this paper, we provide a straightforward approach to show how cosmological tests can be improved via a parametric methodology based on cosmography. Using Supernovae Type IA samplers we show how by performing a statistical analysis of a specific dark energy parameterisation can give directly the cosmographic parameters values. |
gr-qc/9806008 | Sharon Morsink | Sharon M. Morsink, Nikolaos Stergioulas and Steve R. Blattnig | Quasi-normal modes of rotating relativistic stars - neutral modes for
realistic equations of state | 12 pages, 5 figures, submitted to ApJ | Astrophys.J.510:854-861,1999 | 10.1086/306630 | WISC-MILW-98-TH-19 | gr-qc astro-ph | null | We compute zero-frequency (neutral) quasi-normal f-modes of fully
relativistic and rapidly rotating neutron stars, using several realistic
equations of state (EOSs) for neutron star matter. The zero-frequency modes
signal the onset of the gravitational radiation-driven instability. We find
that the l=m=2 (bar) f-mode is unstable for stars with gravitational mass as
low as 1.0 - 1.2 M_\odot, depending on the EOS. For 1.4 M_\odot neutron stars,
the bar mode becomes unstable at 83 % - 93 % of the maximum allowed rotation
rate. For a wide range of EOSs, the bar mode becomes unstable at a ratio of
rotational to gravitational energies T/W \sim 0.07-0.09 for 1.4 M_\odot stars
and T/W \sim 0.06 for maximum mass stars. This is to be contrasted with the
Newtonian value of T/W \sim 0.14. We construct the following empirical formula
for the critical value of T/W for the bar mode,
(T/W)_2 = 0.115 - 0.048 M / M_{max}^{sph}, which is insensitive to the EOS to
within 4 - 6 %. This formula yields an estimate for the neutral mode sequence
of the bar mode as a function only of the star's mass, M, given the maximum
allowed mass, M_{max}^{sph}, of a nonrotating neutron star. The recent
discovery of the fast millisecond pulsar in the supernova remnant N157B,
supports the suggestion that a fraction of proto-neutron stars are born in a
supernova collapse with very large initial angular momentum. Thus, in a
fraction of newly born neutron stars the instability is a promising source of
continuous gravitational waves. It could also play a major role in the
rotational evolution (through the emission of angular momentum) of merged
binary neutron stars, if their post-merger angular momentum exceeds the maximum
allowed to form a Kerr black hole.
| [
{
"created": "Mon, 1 Jun 1998 15:19:20 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Morsink",
"Sharon M.",
""
],
[
"Stergioulas",
"Nikolaos",
""
],
[
"Blattnig",
"Steve R.",
""
]
] | We compute zero-frequency (neutral) quasi-normal f-modes of fully relativistic and rapidly rotating neutron stars, using several realistic equations of state (EOSs) for neutron star matter. The zero-frequency modes signal the onset of the gravitational radiation-driven instability. We find that the l=m=2 (bar) f-mode is unstable for stars with gravitational mass as low as 1.0 - 1.2 M_\odot, depending on the EOS. For 1.4 M_\odot neutron stars, the bar mode becomes unstable at 83 % - 93 % of the maximum allowed rotation rate. For a wide range of EOSs, the bar mode becomes unstable at a ratio of rotational to gravitational energies T/W \sim 0.07-0.09 for 1.4 M_\odot stars and T/W \sim 0.06 for maximum mass stars. This is to be contrasted with the Newtonian value of T/W \sim 0.14. We construct the following empirical formula for the critical value of T/W for the bar mode, (T/W)_2 = 0.115 - 0.048 M / M_{max}^{sph}, which is insensitive to the EOS to within 4 - 6 %. This formula yields an estimate for the neutral mode sequence of the bar mode as a function only of the star's mass, M, given the maximum allowed mass, M_{max}^{sph}, of a nonrotating neutron star. The recent discovery of the fast millisecond pulsar in the supernova remnant N157B, supports the suggestion that a fraction of proto-neutron stars are born in a supernova collapse with very large initial angular momentum. Thus, in a fraction of newly born neutron stars the instability is a promising source of continuous gravitational waves. It could also play a major role in the rotational evolution (through the emission of angular momentum) of merged binary neutron stars, if their post-merger angular momentum exceeds the maximum allowed to form a Kerr black hole. |
gr-qc/9603014 | Giovanni Amelino | G. Amelino-Camelia | Limits on the Measurability of Space-time Distances in (the
Semi-classical Approximation of) Quantum Gravity | 9 pages, LaTex. (This paper precedes and is cited in the paper ``On
Local Observations in Quantum Gravity'', gr-qc/9603013) | Mod.Phys.Lett. A9 (1994) 3415-3422 | 10.1142/S0217732394003245 | INFN-NA-94/35 | gr-qc | null | By taking into account both quantum mechanical and general relativistic
effects, I derive an equation that describes some limitations on the
measurability of space-time distances. I then discuss possible features of
quantum gravity which are suggested by this equation.
| [
{
"created": "Mon, 11 Mar 1996 13:01:14 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Amelino-Camelia",
"G.",
""
]
] | By taking into account both quantum mechanical and general relativistic effects, I derive an equation that describes some limitations on the measurability of space-time distances. I then discuss possible features of quantum gravity which are suggested by this equation. |
0803.2377 | Shun-Pei Miao | Shun-Pei Miao and R. P. Woodard | A Simple Operator Check of the Effective Fermion Mode Function during
Inflation | 39 pages, no figuire.(1) New version has clarified the ultimate
motivation by adding sentences to the abstract and to the penultimate
paragraph of the introduction. (2) By combining a number of references and
equations we have managed to reduce the length by 2 pages | Class.Quant.Grav.25:145009,2008 | 10.1088/0264-9381/25/14/145009 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a relatively simple operator formalism which reproduces the
leading infrared logarithm of the one loop quantum gravitational correction to
the fermion mode function on a locally de Sitter background. This rule may
serve as the basis for an eventual stochastic formulation of quantum gravity
during inflation. Such a formalism would not only effect a vast simplification
in obtaining the leading powers of $\ln(a)$ at fixed loop orders, it would also
permit us to sum the series of leading logarithms. A potentially important
point is that our rule does not seem to be consistent with any simple infrared
truncation of the fields. Our analysis also highlights the importance of spin
as a gravitational interaction that persists even when kinetic energy has
redshifted to zero.
| [
{
"created": "Sun, 16 Mar 2008 23:45:25 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Jun 2008 14:21:20 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Miao",
"Shun-Pei",
""
],
[
"Woodard",
"R. P.",
""
]
] | We present a relatively simple operator formalism which reproduces the leading infrared logarithm of the one loop quantum gravitational correction to the fermion mode function on a locally de Sitter background. This rule may serve as the basis for an eventual stochastic formulation of quantum gravity during inflation. Such a formalism would not only effect a vast simplification in obtaining the leading powers of $\ln(a)$ at fixed loop orders, it would also permit us to sum the series of leading logarithms. A potentially important point is that our rule does not seem to be consistent with any simple infrared truncation of the fields. Our analysis also highlights the importance of spin as a gravitational interaction that persists even when kinetic energy has redshifted to zero. |
1303.0232 | Sante Carloni Dr | Francesco Biscani and Sante Carloni | A first-order secular theory for the post-Newtonian two-body problem
with spin -- I: The restricted case | 14 pages, 3 figures, Published in MNRAS | MNRAS (January 21, 2013) 428 (3): 2295-2310 | 10.1093/mnras/sts198 | null | gr-qc astro-ph.EP math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the relativistic restricted two-body problem with spin employing a
perturbation scheme based on Lie series. Starting from a post-Newtonian
expansion of the field equations, we develop a first-order secular theory that
reproduces well-known relativistic effects such as the precession of the
pericentre and the Lense-Thirring and geodetic effects. Additionally, our
theory takes into full account the complex interplay between the various
relativistic effects, and provides a new explicit solution of the averaged
equations of motion in terms of elliptic functions. Our analysis reveals the
presence of particular configurations for which non-periodical behaviour can
arise. The application of our results to real astrodynamical systems (such as
Mercury-like and pulsar planets) highlights the contribution of relativistic
effects to the long-term evolution of the spin and orbit of the secondary body.
| [
{
"created": "Fri, 1 Mar 2013 17:47:35 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Mar 2013 11:21:22 GMT",
"version": "v2"
}
] | 2013-03-14 | [
[
"Biscani",
"Francesco",
""
],
[
"Carloni",
"Sante",
""
]
] | We revisit the relativistic restricted two-body problem with spin employing a perturbation scheme based on Lie series. Starting from a post-Newtonian expansion of the field equations, we develop a first-order secular theory that reproduces well-known relativistic effects such as the precession of the pericentre and the Lense-Thirring and geodetic effects. Additionally, our theory takes into full account the complex interplay between the various relativistic effects, and provides a new explicit solution of the averaged equations of motion in terms of elliptic functions. Our analysis reveals the presence of particular configurations for which non-periodical behaviour can arise. The application of our results to real astrodynamical systems (such as Mercury-like and pulsar planets) highlights the contribution of relativistic effects to the long-term evolution of the spin and orbit of the secondary body. |
1007.0554 | Guoying Chee | Guoying Chee | Stability of de Sitter solutions sourced by dark spinors | 10 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmology of ELKO and Lorentz Invariant NSS has been investigated using
dynamical system method starting from the proposal of Boehmer et al
[arXiv:1003.3858]. Some different results have been obtained by a different
approach. The exact solutions described by fixed points of the dynamical system
and their stability have been discussed. Some stable solutions corresponding to
de Sitter universes have been obtained.
| [
{
"created": "Sun, 4 Jul 2010 14:24:19 GMT",
"version": "v1"
}
] | 2010-07-06 | [
[
"Chee",
"Guoying",
""
]
] | Cosmology of ELKO and Lorentz Invariant NSS has been investigated using dynamical system method starting from the proposal of Boehmer et al [arXiv:1003.3858]. Some different results have been obtained by a different approach. The exact solutions described by fixed points of the dynamical system and their stability have been discussed. Some stable solutions corresponding to de Sitter universes have been obtained. |
2103.06329 | Jos\'e Villanueva | Mohsen Fathi, Samuel Lepe and J.R. Villanueva | Adiabatic analysis of the rotating BTZ black hole | Accepted version | Eur. Phys. J. C 81 (2021) 6, 499 | 10.1140/epjc/s10052-021-09302-6 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we analyze some interesting features of the thermodynamics of
the rotating BTZ black hole from the Carath\'{e}odory axiomatic postulate, for
which, we exploit the appropriate Pfaffian form. The allowed adiabatic
transformations are then obtained by solving the corresponding Cauchy problem,
and are studied accordingly. Furthermore, we discuss the implications of our
approach, regarding the the second and third laws of black hole thermodynamics.
In particular, the merging of two extremal black holes is studied in detail.
| [
{
"created": "Wed, 10 Mar 2021 20:18:35 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Jul 2021 20:08:07 GMT",
"version": "v2"
}
] | 2021-08-03 | [
[
"Fathi",
"Mohsen",
""
],
[
"Lepe",
"Samuel",
""
],
[
"Villanueva",
"J. R.",
""
]
] | In this paper we analyze some interesting features of the thermodynamics of the rotating BTZ black hole from the Carath\'{e}odory axiomatic postulate, for which, we exploit the appropriate Pfaffian form. The allowed adiabatic transformations are then obtained by solving the corresponding Cauchy problem, and are studied accordingly. Furthermore, we discuss the implications of our approach, regarding the the second and third laws of black hole thermodynamics. In particular, the merging of two extremal black holes is studied in detail. |
gr-qc/0501012 | Mauro Bologna | J. C. Flores and M. Bologna | Anderson's localization in a random metric: applications to cosmology | 10 pages | null | null | null | gr-qc | null | It is considered an equation for the Lyapunov exponent $% \gamma $ in a
random metric for a scalar propagating wave field. At first order in frequency
this equation is solved explicitly. The localization length $L_{c}$ (reciprocal
of Re($\gamma $)) is obtained as function of the metric-fluctuation-distance
$\Delta R$ (function of disorder) and the frequency $\omega $ of the wave.
Explicitly, low-frequencies propagate longer than high, that is $L_{c}\omega
^{2}=C^{te}$. Direct applications with cosmological quantities like background
radiation microwave ($\lambda \sim 1/2\times 10^{-3}$ [m]) and the
Universe-length (`localization length' $L_{c}\sim 1.6\times 10^{25}$ [m])
permits to evaluate the metric-fluctuations-distance as $\Delta R\sim 10^{-35}$
[m], a number at order of the Planck's length.
| [
{
"created": "Wed, 5 Jan 2005 18:49:02 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Flores",
"J. C.",
""
],
[
"Bologna",
"M.",
""
]
] | It is considered an equation for the Lyapunov exponent $% \gamma $ in a random metric for a scalar propagating wave field. At first order in frequency this equation is solved explicitly. The localization length $L_{c}$ (reciprocal of Re($\gamma $)) is obtained as function of the metric-fluctuation-distance $\Delta R$ (function of disorder) and the frequency $\omega $ of the wave. Explicitly, low-frequencies propagate longer than high, that is $L_{c}\omega ^{2}=C^{te}$. Direct applications with cosmological quantities like background radiation microwave ($\lambda \sim 1/2\times 10^{-3}$ [m]) and the Universe-length (`localization length' $L_{c}\sim 1.6\times 10^{25}$ [m]) permits to evaluate the metric-fluctuations-distance as $\Delta R\sim 10^{-35}$ [m], a number at order of the Planck's length. |
2204.04010 | Mu-Tao Wang | Po-Ning Chen, Mu-Tao Wang, Ye-Kai Wang, and Shing-Tung Yau | Conserved quantities in general relativity -- the view from null
infinity | Contribution to the book in honor of Elliott Lieb's 90th birthday.
arXiv admin note: substantial text overlap with arXiv:2010.14059,
arXiv:2003.07732 | null | null | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In general relativity, an idealized distant observer is situated at future
null infinity where light rays emitted from the source approach. This article
concerns conserved quantities such as mass, energy-momentum, angular momentum,
and center of mass at future null infinity. The classical definitions of Bondi
mass at future null infinity ascertains the mass radiated away in gravitational
waves distinctively. However, the same question for other conserved quantities
such as angular momentum has been a subtle issue since the discovery of
"supertranslation ambiguity" in the 1960's. Recently, new definitions of
angular momentum and center of mass were proposed and proved to be free of such
ambiguity [12,14]. These new definitions arise as limits of the Chen-Wang-Yau
quasilocal conserved quantities, which are based on the theory of optimal
isometric embedding and quasilocal mass of Wang-Yau. It is the purpose of this
note to discuss these recent developments
| [
{
"created": "Fri, 8 Apr 2022 11:40:23 GMT",
"version": "v1"
}
] | 2022-04-11 | [
[
"Chen",
"Po-Ning",
""
],
[
"Wang",
"Mu-Tao",
""
],
[
"Wang",
"Ye-Kai",
""
],
[
"Yau",
"Shing-Tung",
""
]
] | In general relativity, an idealized distant observer is situated at future null infinity where light rays emitted from the source approach. This article concerns conserved quantities such as mass, energy-momentum, angular momentum, and center of mass at future null infinity. The classical definitions of Bondi mass at future null infinity ascertains the mass radiated away in gravitational waves distinctively. However, the same question for other conserved quantities such as angular momentum has been a subtle issue since the discovery of "supertranslation ambiguity" in the 1960's. Recently, new definitions of angular momentum and center of mass were proposed and proved to be free of such ambiguity [12,14]. These new definitions arise as limits of the Chen-Wang-Yau quasilocal conserved quantities, which are based on the theory of optimal isometric embedding and quasilocal mass of Wang-Yau. It is the purpose of this note to discuss these recent developments |
gr-qc/9712072 | Haret Rosu | H.C. Rosu | Cosmological Levinson theorem | one LaTex page | Nuovo Cim. B114 (1999) 113-114 | null | null | gr-qc | null | If at least some Wheeler-DeWitt solutions can be interpreted as zero-energy
resonances then the total s-wave cross section of the corresponding quantum
universes is infinite
| [
{
"created": "Tue, 16 Dec 1997 22:41:04 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Apr 1999 16:07:50 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Rosu",
"H. C.",
""
]
] | If at least some Wheeler-DeWitt solutions can be interpreted as zero-energy resonances then the total s-wave cross section of the corresponding quantum universes is infinite |
2304.04984 | Ram Brustein | Ram Brustein, A.J.M. Medved, Tom Shindelman | Defrosting frozen stars: spectrum of internal fluid modes | 36 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The frozen star model provides a classical description of a regularized black
hole and is based upon the idea that regularizing the singularity requires
deviations from the Schwarzschild geometry which extend over horizon-sized
scales, as well as maximally negative radial pressure as an equation of state.
The frozen star has also been shown to be ultra-stable against perturbations; a
feature that can be attributed to the equation of state and corresponds to this
model mimicking a black hole in the limit $\hbar\to 0$ or, equivalently, the
limit of infinite Newton's constant. Here, we ``defrost'' the frozen star by
allowing its radial pressure to be perturbatively less negative than maximal.
This modification to the equation of state is implemented by appropriately
deforming the background metric so as to allow the frozen star to mimic a
quantum black hole at finite $\hbar$ and Newton's constant. As a consequence,
the defrosted star acquires a non-trivial spectrum of oscillatory
perturbations. To show this, we first use the Cowling approximation to obtain
generic equations for the energy density and pressure perturbations of a
static, spherically symmetric background with an anisotropic fluid. The
particular setting of a deformed frozen star is then considered, for which the
dispersion relation is obtained to leading order in terms of the deviation from
maximal pressure. The current results compare favorably with those obtained
earlier for the collapsed polymer model, whose strongly non-classical interior
is argued to provide a microscopic description of the frozen and defrosted star
geometries.
| [
{
"created": "Tue, 11 Apr 2023 05:00:38 GMT",
"version": "v1"
}
] | 2023-04-12 | [
[
"Brustein",
"Ram",
""
],
[
"Medved",
"A. J. M.",
""
],
[
"Shindelman",
"Tom",
""
]
] | The frozen star model provides a classical description of a regularized black hole and is based upon the idea that regularizing the singularity requires deviations from the Schwarzschild geometry which extend over horizon-sized scales, as well as maximally negative radial pressure as an equation of state. The frozen star has also been shown to be ultra-stable against perturbations; a feature that can be attributed to the equation of state and corresponds to this model mimicking a black hole in the limit $\hbar\to 0$ or, equivalently, the limit of infinite Newton's constant. Here, we ``defrost'' the frozen star by allowing its radial pressure to be perturbatively less negative than maximal. This modification to the equation of state is implemented by appropriately deforming the background metric so as to allow the frozen star to mimic a quantum black hole at finite $\hbar$ and Newton's constant. As a consequence, the defrosted star acquires a non-trivial spectrum of oscillatory perturbations. To show this, we first use the Cowling approximation to obtain generic equations for the energy density and pressure perturbations of a static, spherically symmetric background with an anisotropic fluid. The particular setting of a deformed frozen star is then considered, for which the dispersion relation is obtained to leading order in terms of the deviation from maximal pressure. The current results compare favorably with those obtained earlier for the collapsed polymer model, whose strongly non-classical interior is argued to provide a microscopic description of the frozen and defrosted star geometries. |
gr-qc/9904062 | David P. Rideout | D. P. Rideout and R. D. Sorkin | A Classical Sequential Growth Dynamics for Causal Sets | 28 pages, 9 figures, LaTeX, added references and a footnote, minor
corrections | Phys.Rev.D61:024002,2000 | 10.1103/PhysRevD.61.024002 | SU-GP-99/4-1 | gr-qc hep-th | null | Starting from certain causality conditions and a discrete form of general
covariance, we derive a very general family of classically stochastic,
sequential growth dynamics for causal sets. The resulting theories provide a
relatively accessible ``half way house'' to full quantum gravity that possibly
contains the latter's classical limit (general relativity). Because they can be
expressed in terms of state models for an assembly of Ising spins living on the
relations of the causal set, these theories also illustrate how
non-gravitational matter can arise dynamically from the causal set without
having to be built in at the fundamental level. Additionally, our results bring
into focus some interpretive issues of importance for causal set dynamics, and
for quantum gravity more generally.
| [
{
"created": "Sun, 25 Apr 1999 05:11:09 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Aug 1999 16:46:07 GMT",
"version": "v2"
},
{
"created": "Sat, 26 Jun 2004 21:18:06 GMT",
"version": "v3"
}
] | 2011-05-05 | [
[
"Rideout",
"D. P.",
""
],
[
"Sorkin",
"R. D.",
""
]
] | Starting from certain causality conditions and a discrete form of general covariance, we derive a very general family of classically stochastic, sequential growth dynamics for causal sets. The resulting theories provide a relatively accessible ``half way house'' to full quantum gravity that possibly contains the latter's classical limit (general relativity). Because they can be expressed in terms of state models for an assembly of Ising spins living on the relations of the causal set, these theories also illustrate how non-gravitational matter can arise dynamically from the causal set without having to be built in at the fundamental level. Additionally, our results bring into focus some interpretive issues of importance for causal set dynamics, and for quantum gravity more generally. |
gr-qc/9903049 | Ali Shojai Baghini | Fatimah Shojai and Ali Shojai and Mehdi Golshani | Conformal Transformations and Quantum Gravity | 8 pages, RevTex | Mod.Phys.Lett. A13 (1998) 2725-2729 | 10.1142/S0217732398002898 | null | gr-qc | null | Recently\cite{BQG}, it was shown that quantum effects of matter could be
identified with the conformal degree of freedom of the space-time metric.
Accordingly, one can introduce quantum effects either by making a scale
transformation (i.e. changing the metric), or by making a conformal
transformation (i.e. changing all physical quantities). These two ways are
investigated and compared. Also, it is argued that, the ultimate formulation of
such a quantum gravity theory should be in the framework of the scalar-tensor
theories.
| [
{
"created": "Sat, 13 Mar 1999 13:10:13 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Shojai",
"Fatimah",
""
],
[
"Shojai",
"Ali",
""
],
[
"Golshani",
"Mehdi",
""
]
] | Recently\cite{BQG}, it was shown that quantum effects of matter could be identified with the conformal degree of freedom of the space-time metric. Accordingly, one can introduce quantum effects either by making a scale transformation (i.e. changing the metric), or by making a conformal transformation (i.e. changing all physical quantities). These two ways are investigated and compared. Also, it is argued that, the ultimate formulation of such a quantum gravity theory should be in the framework of the scalar-tensor theories. |
1911.01809 | Daniele Gregoris | Daniele Gregoris, Yen Chin Ong, Bin Wang | The Horizon of the McVittie Black Hole: On the Role of the Cosmic Fluid
Modeling | Matches published version | Eur. Phys. J. C (2020) 80:159 | 10.1140/epjc/s10052-020-7707-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the existence and time evolution of the
cosmological and event horizons in a McVittie universe whose expansion is
driven by the Redlich-Kwong, (Modified) Berthelot, Dieterici, and Peng-Robinson
fluids, respectively. The equations of state of these fluids are rich enough to
account for both exotic and regular, as well as ideal and non-ideal matter
contents of the universe. We show that the cosmological horizon is expanding,
while the event horizon is shrinking along the cosmic time evolution. The
former achieves larger size for regular types of matter, contrary to the
latter. The strength of interactions within the cosmic fluid are shown to play
a more important role in affecting the evolution of the event horizon, rather
than of the cosmological horizon in the case of a singularity-free universe.
While the cosmological horizon always exists during the time evolution, the
event horizon can exist only when a certain relationship between the
Hawking-Hayward quasi-local mass and the Hubble function is fulfilled. In this
manner, we can study the role played by the large-scale physics (cosmic
evolution) on the local scale physics (evolution of a black hole).
| [
{
"created": "Tue, 5 Nov 2019 14:37:20 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Mar 2020 18:18:46 GMT",
"version": "v2"
}
] | 2020-03-03 | [
[
"Gregoris",
"Daniele",
""
],
[
"Ong",
"Yen Chin",
""
],
[
"Wang",
"Bin",
""
]
] | In this paper, we investigate the existence and time evolution of the cosmological and event horizons in a McVittie universe whose expansion is driven by the Redlich-Kwong, (Modified) Berthelot, Dieterici, and Peng-Robinson fluids, respectively. The equations of state of these fluids are rich enough to account for both exotic and regular, as well as ideal and non-ideal matter contents of the universe. We show that the cosmological horizon is expanding, while the event horizon is shrinking along the cosmic time evolution. The former achieves larger size for regular types of matter, contrary to the latter. The strength of interactions within the cosmic fluid are shown to play a more important role in affecting the evolution of the event horizon, rather than of the cosmological horizon in the case of a singularity-free universe. While the cosmological horizon always exists during the time evolution, the event horizon can exist only when a certain relationship between the Hawking-Hayward quasi-local mass and the Hubble function is fulfilled. In this manner, we can study the role played by the large-scale physics (cosmic evolution) on the local scale physics (evolution of a black hole). |
gr-qc/9910075 | Wladimir Belayev | W. B. Belayev | Cosmological model in 5D: Stationarity, yes or no | 1 figure, 1 table, revised version of gr-qc/9903016, some types,
references on part numbers, one column, Earth rotation | null | null | CMS-99-10 | gr-qc astro-ph | null | The tired-light cosmology is considered in the framework of Kaluza-Klein
theory in 5D. The solution of the five-dimensional semi-classical Einstein
equations with nonzero five-dimensional energy-momentum tensor gives density of
matter in the Universe well conformed to the observations. Variation of the
light velocity and change of the rest energy and mass are interrelated.
Variation of the Planck constant and electron charge is determined from formula
for hydrogen spectral frequencies and observations of the fine-structure.
Physical constants variation presents as explanation of anomalous change of the
length of a received wave detected during radiometric analysis of Pioneer 10/11
spacecraft data. Contemporary measurements accuracy of the Microwave Cosmic
Background doesn't allow to determine tendency of its parameters change
permitting choice between stationary and expanding Universe's model.
| [
{
"created": "Fri, 22 Oct 1999 15:15:14 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Oct 1999 11:33:40 GMT",
"version": "v2"
},
{
"created": "Thu, 28 Oct 1999 15:13:45 GMT",
"version": "v3"
},
{
"created": "Fri, 29 Oct 1999 06:19:39 GMT",
"version": "v4"
},
{
"c... | 2007-05-23 | [
[
"Belayev",
"W. B.",
""
]
] | The tired-light cosmology is considered in the framework of Kaluza-Klein theory in 5D. The solution of the five-dimensional semi-classical Einstein equations with nonzero five-dimensional energy-momentum tensor gives density of matter in the Universe well conformed to the observations. Variation of the light velocity and change of the rest energy and mass are interrelated. Variation of the Planck constant and electron charge is determined from formula for hydrogen spectral frequencies and observations of the fine-structure. Physical constants variation presents as explanation of anomalous change of the length of a received wave detected during radiometric analysis of Pioneer 10/11 spacecraft data. Contemporary measurements accuracy of the Microwave Cosmic Background doesn't allow to determine tendency of its parameters change permitting choice between stationary and expanding Universe's model. |
gr-qc/9310028 | Dadhich | S.Mukherjee and N.K.Dadhich | Inhomogenous Chaotic Inflation | 12pages, Normal Tex | null | null | null | gr-qc | null | A chaotic model of the early universe within the framework of the
singularity-free solutions of Einstein's equation is suggested. The evolution
of our universe at its early stage, starting out as a small domain of the
parent universe, is governed by the dynamics of a classical scalar field $\phi$
. If in any such domain, larger than Planck length,$\dot \phi$ happens to be
very large,$\phi$ may develop a dominant inhomogeneous mode,leading to an
anisotropic inflation of the universe. The particle $\phi$ is coupled to other
particles, which are produced copiously after inflation and these thermalize
leading to a rather low temperature universe $(T \geq 10^{4} $ Gev). The
electroweak B+L Baryogenesis is assumed to account for the observed baryon
asymmetry. The universe now passes through a radiation-dominated phase, leading
eventually to a matter-dominated universe, which is isotropic and homogeneous.
The model does not depend on the details of Planck scale physics.
| [
{
"created": "Wed, 20 Oct 1993 17:44:07 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mukherjee",
"S.",
""
],
[
"Dadhich",
"N. K.",
""
]
] | A chaotic model of the early universe within the framework of the singularity-free solutions of Einstein's equation is suggested. The evolution of our universe at its early stage, starting out as a small domain of the parent universe, is governed by the dynamics of a classical scalar field $\phi$ . If in any such domain, larger than Planck length,$\dot \phi$ happens to be very large,$\phi$ may develop a dominant inhomogeneous mode,leading to an anisotropic inflation of the universe. The particle $\phi$ is coupled to other particles, which are produced copiously after inflation and these thermalize leading to a rather low temperature universe $(T \geq 10^{4} $ Gev). The electroweak B+L Baryogenesis is assumed to account for the observed baryon asymmetry. The universe now passes through a radiation-dominated phase, leading eventually to a matter-dominated universe, which is isotropic and homogeneous. The model does not depend on the details of Planck scale physics. |
1807.05871 | Salomeh Khoeini-Moghaddam | Salomeh Khoeini-Moghaddam, Farzan Momeni, Fatemeh Yousefabadi | Fermionic Tachyons as a Source of Dark Energy | 5 figures | New Astronomy 100 (2023) 101986 | 10.1016/j.newast.2022.101986 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A model for the universe on the basis of a self interacting fermionic tachyon
field is investigated here. It is shown that, devising a self interaction
potential of a proper form, the fermionic tachyon field is capable of producing
an accelerating expansion that at late time tends to a constant value which is
in consistence with the cosmological constant. This way the introduced
fermionic tachyon field can be interpreted as the source of dark energy.
| [
{
"created": "Fri, 13 Jul 2018 08:46:33 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Jun 2019 18:12:33 GMT",
"version": "v2"
},
{
"created": "Thu, 9 Feb 2023 06:46:59 GMT",
"version": "v3"
}
] | 2023-03-29 | [
[
"Khoeini-Moghaddam",
"Salomeh",
""
],
[
"Momeni",
"Farzan",
""
],
[
"Yousefabadi",
"Fatemeh",
""
]
] | A model for the universe on the basis of a self interacting fermionic tachyon field is investigated here. It is shown that, devising a self interaction potential of a proper form, the fermionic tachyon field is capable of producing an accelerating expansion that at late time tends to a constant value which is in consistence with the cosmological constant. This way the introduced fermionic tachyon field can be interpreted as the source of dark energy. |
1512.08490 | Korumilli Sravan Kumar | K. Sravan Kumar, Jo\~ao Marto, Paulo Vargas Moniz, Suratna Das | Gravitational waves in $\alpha-$attractors | 6 pages, 2 figures. Contribution to the proceedings of "The
Fourtheenth Marcel Grossmann Meeting on General Relativity", University of
Rome "La Sapienza", Rome, July 12-18, 2015, based on a talk delivered at the
ST4 parallel session | World Scientific, December 2017, The Fourteenth Marcel Grossmann
Meeting: pp. 4262-4267 | 10.1142/9789813226609_0571 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study inflation in the $\alpha-$attractor model under a non-slow-roll
dynamics with an ansatz proposed by Gong \& Sasaki \cite{Gong:2015ypa} of
assuming $N=N\left(\phi\right)$. Under this approach, we construct a class of
local shapes of inflaton potential that are different from the T-models. We
find this type of inflationary scenario predicts an attractor at
$n_{s}\sim0.967$ and $r\sim0.00055$. In our approach, the non-slow-roll
inflaton dynamics are related to the $\alpha-$parameter which is the curvature
of K\"ahler geometry in the SUGRA embedding of this model.
| [
{
"created": "Mon, 28 Dec 2015 19:51:29 GMT",
"version": "v1"
}
] | 2017-11-21 | [
[
"Kumar",
"K. Sravan",
""
],
[
"Marto",
"João",
""
],
[
"Moniz",
"Paulo Vargas",
""
],
[
"Das",
"Suratna",
""
]
] | We study inflation in the $\alpha-$attractor model under a non-slow-roll dynamics with an ansatz proposed by Gong \& Sasaki \cite{Gong:2015ypa} of assuming $N=N\left(\phi\right)$. Under this approach, we construct a class of local shapes of inflaton potential that are different from the T-models. We find this type of inflationary scenario predicts an attractor at $n_{s}\sim0.967$ and $r\sim0.00055$. In our approach, the non-slow-roll inflaton dynamics are related to the $\alpha-$parameter which is the curvature of K\"ahler geometry in the SUGRA embedding of this model. |
gr-qc/0102022 | Vitorio A. De Lorenci | V. A. De Lorenci and M. A. Souza (EFEI - Itajuba') | Electromagnetic wave propagation inside a material medium: an effective
geometry interpretation | REVTeX file, 6 pages. Version to appear in Phys. Lett. B | Phys.Lett. B512 (2001) 417-422 | 10.1016/S0370-2693(01)00588-3 | null | gr-qc | null | We present a method developed to deal with electromagnetic wave propagation
inside a material medium that reacts, in general, non-linearly to the field
strength. We work in the context of Maxwell' s theory in the low frequency
limit and obtain a geometrical representation of light paths for each case
presented. The isotropic case and artificial birefringence caused by an
external electric field are analyzed as an application of the formalism and the
effective geometry associated to the wave propagation is exhibited.
| [
{
"created": "Tue, 6 Feb 2001 13:51:52 GMT",
"version": "v1"
},
{
"created": "Mon, 7 May 2001 17:43:06 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"De Lorenci",
"V. A.",
"",
"EFEI - Itajuba'"
],
[
"Souza",
"M. A.",
"",
"EFEI - Itajuba'"
]
] | We present a method developed to deal with electromagnetic wave propagation inside a material medium that reacts, in general, non-linearly to the field strength. We work in the context of Maxwell' s theory in the low frequency limit and obtain a geometrical representation of light paths for each case presented. The isotropic case and artificial birefringence caused by an external electric field are analyzed as an application of the formalism and the effective geometry associated to the wave propagation is exhibited. |
gr-qc/0605068 | Subenoy Chakraborty | Tanwi Bandyopadhyay, Subenoy Chakraborty | Collapsing Inhomogeneous Dust Fluid in the Background of Dark Energy | 10 Pages, no figure | null | null | null | gr-qc | null | In the present work, gravitational collapse of an inhomogeneous spherical
star model, consisting of inhomogeneous dust fluid (dark matter) in the
background of dark energy is considered. The collapsing process is examined
first separately for both dark matter and dark energy and then under the
combined effect of dark matter and dark energy with or without interaction. The
dark energy is considered in the form of perfect fluid and both marginally and
non-marginally bound cases are considered for the collapsing model. Finally
dark energy in the form of anisotropic fluid is investigated and it is found to
be similar to ref. [12]
| [
{
"created": "Thu, 11 May 2006 12:02:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bandyopadhyay",
"Tanwi",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | In the present work, gravitational collapse of an inhomogeneous spherical star model, consisting of inhomogeneous dust fluid (dark matter) in the background of dark energy is considered. The collapsing process is examined first separately for both dark matter and dark energy and then under the combined effect of dark matter and dark energy with or without interaction. The dark energy is considered in the form of perfect fluid and both marginally and non-marginally bound cases are considered for the collapsing model. Finally dark energy in the form of anisotropic fluid is investigated and it is found to be similar to ref. [12] |
1710.06768 | Vakif K Onemli | G. Karakaya, V. K. Onemli | Quantum Effects of Mass on Scalar Field Correlations and Fluctuations
during Inflation | 50 pages, 4 figures | Phys. Rev. D 97, 123531 (2018) | 10.1103/PhysRevD.97.123531 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider an infrared truncated massive minimally coupled scalar field with
a quartic self-interaction in the locally de Sitter background of an inflating
universe. We compute the two-point correlation function of the scalar and the
mean squared fluctuations (variance) of the field variation analytically, at
tree, one- and two-loop order. The one-loop correlator at a fixed comoving
separation asymptotes to zero in the massive case but grows, at late times,
like $-\lambda\ln^2(a)$ in the massless limit, where $a$ is the cosmic scale
factor. For a fixed physical distance, on the other hand, it grows, at late
times, like $-\lambda\ln^3(a)$ in the massless limit. This growth is severely
suppressed in the massive case. In fact, the one-loop correlator asymptotes
effectively to zero for masses larger than half the expansion rate. We find out
also that the tree-order variance of field variation decreases when quantum
corrections are included. Hence, the actual effect that any local observer
perceives in the field strength as fluctuations happen does not deviate from
the average effect as much as the tree-order variance implies.
| [
{
"created": "Wed, 18 Oct 2017 15:08:02 GMT",
"version": "v1"
}
] | 2018-06-27 | [
[
"Karakaya",
"G.",
""
],
[
"Onemli",
"V. K.",
""
]
] | We consider an infrared truncated massive minimally coupled scalar field with a quartic self-interaction in the locally de Sitter background of an inflating universe. We compute the two-point correlation function of the scalar and the mean squared fluctuations (variance) of the field variation analytically, at tree, one- and two-loop order. The one-loop correlator at a fixed comoving separation asymptotes to zero in the massive case but grows, at late times, like $-\lambda\ln^2(a)$ in the massless limit, where $a$ is the cosmic scale factor. For a fixed physical distance, on the other hand, it grows, at late times, like $-\lambda\ln^3(a)$ in the massless limit. This growth is severely suppressed in the massive case. In fact, the one-loop correlator asymptotes effectively to zero for masses larger than half the expansion rate. We find out also that the tree-order variance of field variation decreases when quantum corrections are included. Hence, the actual effect that any local observer perceives in the field strength as fluctuations happen does not deviate from the average effect as much as the tree-order variance implies. |
gr-qc/9801065 | Conceicao Bento | M.C. Bento, O. Bertolami and N.J. Nunes (Departamento de Fisica,
Instituto Superior Tecnico, Lisbon, Portugal) | Primordial Density Fluctuations in a Dual Supergravity Cosmology | 13 pages, Latex, 3 figures (uses epsf.sty) | Phys.Lett. B427 (1998) 261-266 | 10.1016/S0370-2693(98)00218-4 | DF/IST-6.97 | gr-qc | null | We analyse the spectrum of energy density fluctuations of a dual supergravity
model where the dilaton and the moduli are stabilized and sucessful inflation
is achieved inside domain walls that separate different vacua of the theory.
Constraints on the parameters of the superpotential are derived from the
amplitude of the primordial energy density fluctuations as inferred from COBE
and it is shown that the scale dependence of the tensor perturbations nearly
vanishes.
| [
{
"created": "Tue, 20 Jan 1998 17:02:46 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Bento",
"M. C.",
"",
"Departamento de Fisica,\n Instituto Superior Tecnico, Lisbon, Portugal"
],
[
"Bertolami",
"O.",
"",
"Departamento de Fisica,\n Instituto Superior Tecnico, Lisbon, Portugal"
],
[
"Nunes",
"N. J.",
"",
"Departamento de Fisica,\n Insti... | We analyse the spectrum of energy density fluctuations of a dual supergravity model where the dilaton and the moduli are stabilized and sucessful inflation is achieved inside domain walls that separate different vacua of the theory. Constraints on the parameters of the superpotential are derived from the amplitude of the primordial energy density fluctuations as inferred from COBE and it is shown that the scale dependence of the tensor perturbations nearly vanishes. |
2309.13651 | Cristian Stelea | Cristian Stelea, Marina-Aura Dariescu and Ciprian Dariescu | Charged black holes with dark halos | 14 pages, 3 figures. v2. Matches the published version | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, Cardoso et al. constructed an exact solution of Einstein's
equations that describes a supermassive black hole immersed into a dark matter
halo. In this work use a solution-generating technique, which is a direct
generalization of some of the Ehlers-Harrison transformation in the Ehlers
formalism in order to construct in an exact analytical form the charged version
of the Cardoso et al. solution. We describe some of its physical properties
and, finally, we also present its magnetized version.
| [
{
"created": "Sun, 24 Sep 2023 14:34:21 GMT",
"version": "v1"
},
{
"created": "Sun, 12 May 2024 11:16:56 GMT",
"version": "v2"
}
] | 2024-05-14 | [
[
"Stelea",
"Cristian",
""
],
[
"Dariescu",
"Marina-Aura",
""
],
[
"Dariescu",
"Ciprian",
""
]
] | Recently, Cardoso et al. constructed an exact solution of Einstein's equations that describes a supermassive black hole immersed into a dark matter halo. In this work use a solution-generating technique, which is a direct generalization of some of the Ehlers-Harrison transformation in the Ehlers formalism in order to construct in an exact analytical form the charged version of the Cardoso et al. solution. We describe some of its physical properties and, finally, we also present its magnetized version. |
0707.0452 | Eyo Ita III | Eyo Eyo Ita III | Instanton representation of Plebanski gravity: IX. Hamiltonian
minisuperspace dynamics in undensitized momentum space variables | 18 pages. Background material for revised journal article | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we illustrate the dynamics of the instanton representation in
the description of vacuum GR in minisuperspace for undensitized variables. We
uncover a new class of general solutions in both the degenerate and the
nondegenerate sectors of the theory. Additionally, the individual sectors are
preserved under Hamiltonian evolution. Finally, we present an algorithm for
constructing general solutions by expansion about the isotropic sector.
| [
{
"created": "Tue, 3 Jul 2007 15:59:38 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Apr 2008 19:25:25 GMT",
"version": "v2"
},
{
"created": "Mon, 7 Apr 2008 08:28:44 GMT",
"version": "v3"
},
{
"created": "Fri, 31 Jul 2009 08:24:29 GMT",
"version": "v4"
},
{
"crea... | 2010-04-23 | [
[
"Ita",
"Eyo Eyo",
"III"
]
] | In this paper we illustrate the dynamics of the instanton representation in the description of vacuum GR in minisuperspace for undensitized variables. We uncover a new class of general solutions in both the degenerate and the nondegenerate sectors of the theory. Additionally, the individual sectors are preserved under Hamiltonian evolution. Finally, we present an algorithm for constructing general solutions by expansion about the isotropic sector. |
2207.02224 | Zachary Nasipak | Zachary Nasipak | Adiabatic evolution due to the conservative scalar self-force during
orbital resonances | 30 pages, 6 figures, 3 tables; Updated to reflect published version | Phys. Rev. D 106, 064042 (2022) | 10.1103/PhysRevD.106.064042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the scalar self-force experienced by a scalar point-charge
orbiting a Kerr black hole along $r\theta$-resonant geodesics. We use the
self-force to calculate the averaged rate of change of the charge's orbital
energy $\langle\dot{E}\rangle$, angular momentum $\langle\dot{L}_z\rangle$, and
Carter constant $\langle\dot{Q}\rangle$, which together capture the
leading-order adiabatic, secular evolution of the point-charge. Away from
resonances, only the dissipative (time anti-symmetric) components of the
self-force contribute to $\langle\dot{E}\rangle$, $\langle\dot{L}_z\rangle$,
and $\langle\dot{Q}\rangle$. We demonstrate, using a new numerical code, that
during $r\theta$ resonances conservative (time symmetric) scalar perturbations
also contribute to $\langle\dot{Q}\rangle$ and, thus, help drive the adiabatic
evolution of the orbit. Furthermore, we observe that the relative impact of
these conservative contributions to $\langle\dot{Q}\rangle$ is particularly
strong for eccentric 2:3 resonances. These results provide the first conclusive
numerical evidence that conservative scalar perturbations of Kerr spacetime are
non-integrable during $r\theta$ resonances.
| [
{
"created": "Tue, 5 Jul 2022 18:00:01 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Sep 2022 20:03:40 GMT",
"version": "v2"
}
] | 2022-09-27 | [
[
"Nasipak",
"Zachary",
""
]
] | We calculate the scalar self-force experienced by a scalar point-charge orbiting a Kerr black hole along $r\theta$-resonant geodesics. We use the self-force to calculate the averaged rate of change of the charge's orbital energy $\langle\dot{E}\rangle$, angular momentum $\langle\dot{L}_z\rangle$, and Carter constant $\langle\dot{Q}\rangle$, which together capture the leading-order adiabatic, secular evolution of the point-charge. Away from resonances, only the dissipative (time anti-symmetric) components of the self-force contribute to $\langle\dot{E}\rangle$, $\langle\dot{L}_z\rangle$, and $\langle\dot{Q}\rangle$. We demonstrate, using a new numerical code, that during $r\theta$ resonances conservative (time symmetric) scalar perturbations also contribute to $\langle\dot{Q}\rangle$ and, thus, help drive the adiabatic evolution of the orbit. Furthermore, we observe that the relative impact of these conservative contributions to $\langle\dot{Q}\rangle$ is particularly strong for eccentric 2:3 resonances. These results provide the first conclusive numerical evidence that conservative scalar perturbations of Kerr spacetime are non-integrable during $r\theta$ resonances. |
gr-qc/0508048 | Christian Fronsdal | Christian Fronsdal | Growth of a Black Hole | 12 pages, 2 figures, TeX file | J.Geom.Phys. 57 (2006) 167-176 | 10.1016/j.geomphys.2006.02.008 | null | gr-qc hep-th | null | This paper studies the interpretation of physics near a Schwarzschild black
hole. A scenario for creation and growth is proposed that avoids the conundrum
of information loss. In this picture the horizon recedes as it is approached
and has no physical reality. Radiation is likely to occur, but it cannot be
predicted.
| [
{
"created": "Thu, 11 Aug 2005 13:23:06 GMT",
"version": "v1"
}
] | 2014-05-27 | [
[
"Fronsdal",
"Christian",
""
]
] | This paper studies the interpretation of physics near a Schwarzschild black hole. A scenario for creation and growth is proposed that avoids the conundrum of information loss. In this picture the horizon recedes as it is approached and has no physical reality. Radiation is likely to occur, but it cannot be predicted. |
gr-qc/0110124 | Shinji Tsujikawa | Shinji Tsujikawa (Univ. of Tokyo) | Density perturbations in the Ekpyrotic Universe and string-inspired
generalizations | 5 pages, 3 figures, some discussions and references are added | Phys.Lett. B526 (2002) 179-185 | 10.1016/S0370-2693(01)01526-X | null | gr-qc astro-ph hep-ph hep-th | null | We study density perturbations in several cosmological models motivated by
string theory. The evolution and the spectra of curvature perturbations ${\cal
R}$ are analyzed in the Ekpyrotic scenario and nonsingular string cosmologies.
We find that these string-inspired models generally exhibit blue spectra in
contrast to standard slow-roll inflationary scenarios. We also clarify the
parameter range where ${\cal R}$ is enhanced on superhorizon scales.
| [
{
"created": "Wed, 31 Oct 2001 06:26:32 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Dec 2001 05:11:47 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Tsujikawa",
"Shinji",
"",
"Univ. of Tokyo"
]
] | We study density perturbations in several cosmological models motivated by string theory. The evolution and the spectra of curvature perturbations ${\cal R}$ are analyzed in the Ekpyrotic scenario and nonsingular string cosmologies. We find that these string-inspired models generally exhibit blue spectra in contrast to standard slow-roll inflationary scenarios. We also clarify the parameter range where ${\cal R}$ is enhanced on superhorizon scales. |
1503.05005 | Jose Geraldo Pereira | A. Araujo, H. Jennen, J. G. Pereira, A. C. Sampson, L. L. Savi | On the spacetime connecting two aeons in conformal cyclic cosmology | 15 pages. V2: presentation changes aiming at clarifying the text,
matches published version | Gen. Relativ. Grav. 47 (2015) 151 (17 pages) | 10.1007/s10714-015-1991-4 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As quotient spaces, Minkowski and de Sitter are fundamental,
non-gravitational spacetimes for the construction of physical theories. When
general relativity is constructed on a de Sitter spacetime, the usual
Riemannian structure is replaced by a more general structure called de
Sitter-Cartan geometry. In the contraction limit of an infinite cosmological
term, the de Sitter-Cartan spacetime reduces to a singular, flat, conformal
invariant four-dimensional cone spacetime, in which our ordinary notions of
time interval and space distance are absent. It is shown that such spacetime
satisfies all properties, including the Weyl curvature hypothesis, necessary to
play the role of the bridging spacetime connecting two aeons in Penrose's
conformal cyclic cosmology.
| [
{
"created": "Tue, 17 Mar 2015 11:48:05 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Nov 2015 09:52:26 GMT",
"version": "v2"
}
] | 2015-11-18 | [
[
"Araujo",
"A.",
""
],
[
"Jennen",
"H.",
""
],
[
"Pereira",
"J. G.",
""
],
[
"Sampson",
"A. C.",
""
],
[
"Savi",
"L. L.",
""
]
] | As quotient spaces, Minkowski and de Sitter are fundamental, non-gravitational spacetimes for the construction of physical theories. When general relativity is constructed on a de Sitter spacetime, the usual Riemannian structure is replaced by a more general structure called de Sitter-Cartan geometry. In the contraction limit of an infinite cosmological term, the de Sitter-Cartan spacetime reduces to a singular, flat, conformal invariant four-dimensional cone spacetime, in which our ordinary notions of time interval and space distance are absent. It is shown that such spacetime satisfies all properties, including the Weyl curvature hypothesis, necessary to play the role of the bridging spacetime connecting two aeons in Penrose's conformal cyclic cosmology. |
0801.3425 | Leonid Verozub V | Leonid V. Verozub | Geodesic-invariant equations of gravitation | Latex, 24 pages with 5 figures | AnnalenPhys.17:28-51,2008 | 10.1002/andp.200710278 | null | gr-qc astro-ph math-ph math.MP | null | Einstein's equations of gravitation are not invariant under geodesic
mappings, i. e. under a certain class of mappings of the Christoffel symbols
and the metric tensor which leave the geodesic equations in a given coordinate
system invariant. A theory in which geodesic mappings play the role of gauge
transformations is considered.
| [
{
"created": "Tue, 22 Jan 2008 18:28:19 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Jan 2008 22:52:41 GMT",
"version": "v2"
},
{
"created": "Mon, 4 Feb 2008 20:35:36 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Verozub",
"Leonid V.",
""
]
] | Einstein's equations of gravitation are not invariant under geodesic mappings, i. e. under a certain class of mappings of the Christoffel symbols and the metric tensor which leave the geodesic equations in a given coordinate system invariant. A theory in which geodesic mappings play the role of gauge transformations is considered. |
1908.09582 | Michael Maziashvili | Michael Maziashvili | Salecker-Wigner-Karolyhazy Gedankenexperiment in light of the
self-gravity | 11 pages | General Relativity and Gravitation 52, 70 (2020) | 10.1007/s10714-020-02722-x | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Gedankenexperiment mentioned in the title, the imprecision in space-time
measurement is related to the spreading of clock's wave-function with the
passage of time required for the measurement. Special relativity puts a bound
on the measurement time, it cannot be reduced arbitrarily as the signal used
for the measurement cannot propagate with speed greater than that of light. In
view of this reasoning, one is led to conclude that the clock should be heavy
enough to slow down its wave-function from spreading with time. However, the
general relativity puts an upper bound on clock's mass, since its size must
remain greater then the Schwarzschild radius associated to it. This way one
reaches a limit in length measurement. However, as is discussed below, an
additional insight into the question comes by taking into account
self-gravitational effects. As a result, the uncertainty in length measurement
is reduced to the Planck length.
| [
{
"created": "Mon, 26 Aug 2019 10:26:27 GMT",
"version": "v1"
}
] | 2020-07-15 | [
[
"Maziashvili",
"Michael",
""
]
] | In Gedankenexperiment mentioned in the title, the imprecision in space-time measurement is related to the spreading of clock's wave-function with the passage of time required for the measurement. Special relativity puts a bound on the measurement time, it cannot be reduced arbitrarily as the signal used for the measurement cannot propagate with speed greater than that of light. In view of this reasoning, one is led to conclude that the clock should be heavy enough to slow down its wave-function from spreading with time. However, the general relativity puts an upper bound on clock's mass, since its size must remain greater then the Schwarzschild radius associated to it. This way one reaches a limit in length measurement. However, as is discussed below, an additional insight into the question comes by taking into account self-gravitational effects. As a result, the uncertainty in length measurement is reduced to the Planck length. |
1812.10679 | Claus Kiefer | Claus Kiefer | Space and Time 62 Years after the Berne Conference | 15 pages, 4 figures, contribution to the conference: Thinking about
Space and Time: 100 Years of Applying and Interpreting General Relativity,
Berne, Switzerland, September 12-14, 2017, v2: minor changes, v3: again minor
changes, final version | null | null | null | gr-qc physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In 1955, an international conference took place in Berne at which the state
of relativity theory and its possible generalizations were presented and
critically discussed. I review the most important contributions to that
conference and put them into the perspective of today's knowledge about the
nature of space and time.
| [
{
"created": "Thu, 27 Dec 2018 10:02:52 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Jan 2019 14:49:47 GMT",
"version": "v2"
},
{
"created": "Mon, 31 Aug 2020 14:24:36 GMT",
"version": "v3"
}
] | 2020-09-01 | [
[
"Kiefer",
"Claus",
""
]
] | In 1955, an international conference took place in Berne at which the state of relativity theory and its possible generalizations were presented and critically discussed. I review the most important contributions to that conference and put them into the perspective of today's knowledge about the nature of space and time. |
2008.08301 | Shao-Wen Wei | Run Zhou, Yu-Xiao Liu, Shao-Wen Wei | Phase transition and microstructures of five-dimensional charged
Gauss-Bonnet-AdS black holes in the grand canonical ensemble | 16 pages and 8 figures | null | 10.1103/PhysRevD.102.124015 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the small-large black hole phase transition and
construct the Ruppeiner geometry for the five-dimensional charged
Gauss-Bonnet-AdS black hole in the grand canonical ensemble. By making use of
the equal area law, we obtain the analytical coexistence curve of the small and
large black holes. Then the phase diagrams are examined. We also calculate the
change of the thermodynamic volume during the small-large phase transition,
which indicates that there exists a sudden change among the black hole
microstructures. The corresponding normalized scalar curvature of the Ruppeiner
geometry is also calculated. Combing with the empirical observation of scalar
curvature, we find that for low electric potential, the attractive interaction
dominates among the microstructures, while a high electric potential produces
repulsive interactions. In the reduced parameter space, we observe that only
attractive interaction is allowed when the coexistence region is excluded. The
normalized scalar curvature also admits a critical exponent 2 and a universal
constant $-\frac{1}{8}$. In particular, the value of the normalized scalar
curvature keeps the same along the coexistence small and large black hole
curves. So in the grand canonical ensemble, the interaction can keep constant
at the phase transition where the black hole microstructures change. These
results disclose the intriguing microstructures for the charged AdS black hole
in the Gauss-Bonnet gravity.
| [
{
"created": "Wed, 19 Aug 2020 07:18:52 GMT",
"version": "v1"
}
] | 2020-12-09 | [
[
"Zhou",
"Run",
""
],
[
"Liu",
"Yu-Xiao",
""
],
[
"Wei",
"Shao-Wen",
""
]
] | In this paper, we study the small-large black hole phase transition and construct the Ruppeiner geometry for the five-dimensional charged Gauss-Bonnet-AdS black hole in the grand canonical ensemble. By making use of the equal area law, we obtain the analytical coexistence curve of the small and large black holes. Then the phase diagrams are examined. We also calculate the change of the thermodynamic volume during the small-large phase transition, which indicates that there exists a sudden change among the black hole microstructures. The corresponding normalized scalar curvature of the Ruppeiner geometry is also calculated. Combing with the empirical observation of scalar curvature, we find that for low electric potential, the attractive interaction dominates among the microstructures, while a high electric potential produces repulsive interactions. In the reduced parameter space, we observe that only attractive interaction is allowed when the coexistence region is excluded. The normalized scalar curvature also admits a critical exponent 2 and a universal constant $-\frac{1}{8}$. In particular, the value of the normalized scalar curvature keeps the same along the coexistence small and large black hole curves. So in the grand canonical ensemble, the interaction can keep constant at the phase transition where the black hole microstructures change. These results disclose the intriguing microstructures for the charged AdS black hole in the Gauss-Bonnet gravity. |
2009.05187 | Qing-Yu Cai | Dongshan He and Qing-yu Cai | Wheeler-DeWitt equation rejects quantum effects of grown-up universes as
a candidate for dark energy | Any comments are welcome! | Phys. Lett. B 809, 135747 (2020) | 10.1016/j.physletb.2020.135747 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the changes of quantum effects of a growing universe
by using Wheeler-DeWitt equation (WDWE) together with de Broglie-Bohm quantum
trajectory approach. From WDWE, we obtain the quantum modified Friedmann
equations which have additional terms called quantum potential compared to
standard Friedmann equations. The quantum potential governs the behavior of the
early universe, providing energy for inflation, while it decreases rapidly as
the universe grows. The quantum potential of the grown-up universe is much
smaller than that required for accelerating expansion. This indicates that
quantum effects of our universe cannot be treated as a candidate for dark
energy.
| [
{
"created": "Fri, 11 Sep 2020 01:18:16 GMT",
"version": "v1"
}
] | 2020-09-14 | [
[
"He",
"Dongshan",
""
],
[
"Cai",
"Qing-yu",
""
]
] | In this paper, we study the changes of quantum effects of a growing universe by using Wheeler-DeWitt equation (WDWE) together with de Broglie-Bohm quantum trajectory approach. From WDWE, we obtain the quantum modified Friedmann equations which have additional terms called quantum potential compared to standard Friedmann equations. The quantum potential governs the behavior of the early universe, providing energy for inflation, while it decreases rapidly as the universe grows. The quantum potential of the grown-up universe is much smaller than that required for accelerating expansion. This indicates that quantum effects of our universe cannot be treated as a candidate for dark energy. |
1506.08649 | Murli Manohar Verma Dr. | Murli Manohar Verma and Bal Krishna Yadav | Dynamics of $f(R)$ gravity models and asymmetry of time | 10 pages, 9 figures | International Journal of Modern Physics D, 27(2), 1850002,(2018) | 10.1142/S0218271818500025 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We solve the field equations of modified gravity for $f(R)$ model in metric
formalism. Further, we obtain the fixed points of the dynamical system in phase
space analysis of $f(R)$ models, both with and without the effects of
radiation. Stability of these points is studied against perturbations in a
smooth spatial background by applying the conditions on the eigenvalues of the
matrix obtained in the linearized first-order differential equations. Following
this, these fixed points are used for analysing the dynamics of the system
during the radiation, matter and acceleration dominated phases of the universe.
Certain linear and quadratic forms of $f(R)$ are determined from the
geometrical and physical considerations and the behaviour of the scale factor
is found for those forms. Further, we also determine the Hubble parameter
$H(t)$, Ricci scalar $R$ for these cosmic phases. We show the emergence of an
asymmetry of time from the dynamics of the scalar field exclusively owing to
the $f(R)$ gravity in the Einstein frame that may lead to an arrow of time at a
classical level.
| [
{
"created": "Sat, 13 Jun 2015 10:38:14 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Jul 2017 11:01:04 GMT",
"version": "v2"
}
] | 2018-01-26 | [
[
"Verma",
"Murli Manohar",
""
],
[
"Yadav",
"Bal Krishna",
""
]
] | We solve the field equations of modified gravity for $f(R)$ model in metric formalism. Further, we obtain the fixed points of the dynamical system in phase space analysis of $f(R)$ models, both with and without the effects of radiation. Stability of these points is studied against perturbations in a smooth spatial background by applying the conditions on the eigenvalues of the matrix obtained in the linearized first-order differential equations. Following this, these fixed points are used for analysing the dynamics of the system during the radiation, matter and acceleration dominated phases of the universe. Certain linear and quadratic forms of $f(R)$ are determined from the geometrical and physical considerations and the behaviour of the scale factor is found for those forms. Further, we also determine the Hubble parameter $H(t)$, Ricci scalar $R$ for these cosmic phases. We show the emergence of an asymmetry of time from the dynamics of the scalar field exclusively owing to the $f(R)$ gravity in the Einstein frame that may lead to an arrow of time at a classical level. |
1311.0735 | Peter Hogan | C. Barrab\`es and P. A. Hogan | Collision of Shock Waves in Einstein-Maxwell Theory with a Cosmological
Constant: A Special Solution | Latex file, 7 pages | Physical Review D88, 087501 (2013) | 10.1103/PhysRevD.88.087501 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Post-collision space-times of the Cartesian product form M'xM'', where M' and
M'' are two-dimensional manifolds, are known with M' and M'' having constant
curvatures of equal and opposite sign (for the collision of electromagnetic
shock waves) or of the same sign (for the collision of gravitational shock
waves). We construct here a new explicit post-collision solution of the
Einstein-Maxwell vacuum field equations with a cosmological constant for which
M' has constant (nonzero) curvature and M'' has zero curvature.
| [
{
"created": "Mon, 4 Nov 2013 15:42:27 GMT",
"version": "v1"
}
] | 2013-11-05 | [
[
"Barrabès",
"C.",
""
],
[
"Hogan",
"P. A.",
""
]
] | Post-collision space-times of the Cartesian product form M'xM'', where M' and M'' are two-dimensional manifolds, are known with M' and M'' having constant curvatures of equal and opposite sign (for the collision of electromagnetic shock waves) or of the same sign (for the collision of gravitational shock waves). We construct here a new explicit post-collision solution of the Einstein-Maxwell vacuum field equations with a cosmological constant for which M' has constant (nonzero) curvature and M'' has zero curvature. |
gr-qc/9401025 | null | Norman Cruz, Cristi\'an Mart\'inez and Leda Pe\~na | Geodesic Structure of the 2 + 1 Black Hole | 13 pages, RevTex 3.0, 7 figures (available upon request). Submitted
to Phys. Rev. D | Class.Quant.Grav.11:2731-2740,1994 | 10.1088/0264-9381/11/11/014 | null | gr-qc | null | Null and timelike geodesics around a 2+1 black hole are determined. Complete
geodesics of both types exist in the rotating black-hole background, but not in
the spinless case. Upper and lower bounds for the radial size of the orbits are
given in all cases and the possibility of passing from one black hole exterior
spacetime to another is discussed using the Penrose diagrams. An analysis of
particle motions by means of effective potentials and orbit graphs are also
included.
| [
{
"created": "Tue, 25 Jan 1994 17:02:48 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Cruz",
"Norman",
""
],
[
"Martínez",
"Cristián",
""
],
[
"Peña",
"Leda",
""
]
] | Null and timelike geodesics around a 2+1 black hole are determined. Complete geodesics of both types exist in the rotating black-hole background, but not in the spinless case. Upper and lower bounds for the radial size of the orbits are given in all cases and the possibility of passing from one black hole exterior spacetime to another is discussed using the Penrose diagrams. An analysis of particle motions by means of effective potentials and orbit graphs are also included. |
gr-qc/9510061 | null | G. Giachetta and G.Sardanashvily | Stress-Energy-Momentum Tensors in Lagrangian Field Theory. Part 1.
Superpotentials | 49 pp, LaTeX file | null | null | MPH/CAM/103/95 | gr-qc dg-ga hep-th math.DG | null | Differential conservation laws in Lagrangian field theory are usually related
to symmetries of a Lagrangian density and are obtained if the Lie derivative of
a Lagrangian density by a certain class of vector fields on a fiber bundle
vanishes. However, only two field models meet this property in fact. In gauge
theory of exact internal symmetries, the Lie derivative by vertical vector
fields corresponding to gauge transformations is equal to zero. The
corresponding N\"oether current is reduced to a superpotential that provides
invariance of the N\"oether conservation law under gauge transformations. In
the gravitation theory, we meet the phenomenon of "hidden energy". Only the
superpotential part of energy-momentum of gravity and matter is observed when
the general covariant transformations are exact. Other parts of energy-momentum
display themselves if the invariance under general covariance transformations
is broken, e.g., by a background world metric. In this case, the Lie
derivatives of Lagrangian densities by vector fields which call into play the
stress-energy-momentum tensors fail to be equal to zero in general. We base our
analysis of differential conservation laws on the canonical decomposition of
the Lie derivative of a Lagrangian density $L$ by a projectable vector field on
a bundle and with respect to different Lepagian equivalents of $L$. Different
Lepagian equivalents lead to conserved quantities which differ from each other
in superpotential terms. We have different stress-energy-momentum tensors
depending on different lifts of vector fields on a base onto a bundle.
Moreover, different solutions of the same Euler-Lagrange equations may require
different energy-momentum tensors. We show that different
stress-energy-momentum tensors differ from each other in N\"oether currents. As
| [
{
"created": "Mon, 30 Oct 1995 16:39:17 GMT",
"version": "v1"
}
] | 2008-02-03 | [
[
"Giachetta",
"G.",
""
],
[
"Sardanashvily",
"G.",
""
]
] | Differential conservation laws in Lagrangian field theory are usually related to symmetries of a Lagrangian density and are obtained if the Lie derivative of a Lagrangian density by a certain class of vector fields on a fiber bundle vanishes. However, only two field models meet this property in fact. In gauge theory of exact internal symmetries, the Lie derivative by vertical vector fields corresponding to gauge transformations is equal to zero. The corresponding N\"oether current is reduced to a superpotential that provides invariance of the N\"oether conservation law under gauge transformations. In the gravitation theory, we meet the phenomenon of "hidden energy". Only the superpotential part of energy-momentum of gravity and matter is observed when the general covariant transformations are exact. Other parts of energy-momentum display themselves if the invariance under general covariance transformations is broken, e.g., by a background world metric. In this case, the Lie derivatives of Lagrangian densities by vector fields which call into play the stress-energy-momentum tensors fail to be equal to zero in general. We base our analysis of differential conservation laws on the canonical decomposition of the Lie derivative of a Lagrangian density $L$ by a projectable vector field on a bundle and with respect to different Lepagian equivalents of $L$. Different Lepagian equivalents lead to conserved quantities which differ from each other in superpotential terms. We have different stress-energy-momentum tensors depending on different lifts of vector fields on a base onto a bundle. Moreover, different solutions of the same Euler-Lagrange equations may require different energy-momentum tensors. We show that different stress-energy-momentum tensors differ from each other in N\"oether currents. As |
gr-qc/9802027 | Arlen Anderson | Yvonne Choquet-Bruhat, James W. York, Jr., and Arlen Anderson | Curvature-based Hyperbolic Systems for General Relativity | 15 pp., LaTeX, to appear in the Proceedings of the Eighth Marcel
Grossmann Meeting on General Relativity, further citations added | null | null | IFP-UNC-523, TAR-UNC-065 | gr-qc | null | We review curvature-based hyperbolic forms of the evolution part of the
Cauchy problem of General Relativity that we have obtained recently. We
emphasize first order symmetrizable hyperbolic systems possessing only physical
characteristics.
| [
{
"created": "Thu, 12 Feb 1998 17:29:38 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Feb 1998 20:00:14 GMT",
"version": "v2"
}
] | 2012-08-27 | [
[
"Choquet-Bruhat",
"Yvonne",
""
],
[
"York,",
"James W.",
"Jr."
],
[
"Anderson",
"Arlen",
""
]
] | We review curvature-based hyperbolic forms of the evolution part of the Cauchy problem of General Relativity that we have obtained recently. We emphasize first order symmetrizable hyperbolic systems possessing only physical characteristics. |
0711.3641 | J. E. Horvath | Daniel C. Guariento, J. E. Horvath, P. S. Cust\'odio and J. A. de
Freitas Pacheco | Evolution of Primordial Black Holes in a radiation and phantom energy
environment | 6 pp, 2 figs., to appear in GRG | Gen.Rel.Grav.40:1593-1602,2008 | 10.1007/s10714-007-0562-8 | null | gr-qc | null | In this work we extend previous work on the evolution of a Primordial Black
Hole (PBH) to address the presence of a dark energy component with a
super-negative equation of state as a background, investigating the competition
between the radiation accretion, the Hawking evaporation and the phantom
accretion, the latter two causing a decrease on black hole mass. It is found
that there is an instant during the matter-dominated era after which the
radiation accretion becomes negligible compared to the phantom accretion. The
Hawking evaporation may become important again depending on a mass threshold.
The evaporation of PBHs is quite modified at late times by these effects, but
only if the Generalized Second Law of thermodynamics is violated.
| [
{
"created": "Thu, 22 Nov 2007 19:52:58 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Guariento",
"Daniel C.",
""
],
[
"Horvath",
"J. E.",
""
],
[
"Custódio",
"P. S.",
""
],
[
"Pacheco",
"J. A. de Freitas",
""
]
] | In this work we extend previous work on the evolution of a Primordial Black Hole (PBH) to address the presence of a dark energy component with a super-negative equation of state as a background, investigating the competition between the radiation accretion, the Hawking evaporation and the phantom accretion, the latter two causing a decrease on black hole mass. It is found that there is an instant during the matter-dominated era after which the radiation accretion becomes negligible compared to the phantom accretion. The Hawking evaporation may become important again depending on a mass threshold. The evaporation of PBHs is quite modified at late times by these effects, but only if the Generalized Second Law of thermodynamics is violated. |
0909.2159 | Kazuharu Bamba | Kazuharu Bamba, Chao-Qiang Geng, and Shinji Tsujikawa | Equilibrium thermodynamics in modified gravitational theories | 11 pages, 2 figures, version to appear in Physics Letters B, typos
corrected | Phys.Lett.B688:101-109,2010 | 10.1016/j.physletb.2010.03.070 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that it is possible to obtain a picture of equilibrium thermodynamics
on the apparent horizon in the expanding cosmological background for a wide
class of modified gravity theories with the Lagrangian density $f(R, \phi, X)$,
where $R$ is the Ricci scalar and $X$ is the kinetic energy of a scalar field
$\phi$. This comes from a suitable definition of an energy momentum tensor of
the "dark" component that respects to a local energy conservation in the Jordan
frame. In this framework the horizon entropy $S$ corresponding to equilibrium
thermodynamics is equal to a quarter of the horizon area $A$ in units of
gravitational constant $G$, as in Einstein gravity. For a flat cosmological
background with a decreasing Hubble parameter, $S$ globally increases with
time, as it happens for viable $f(R)$ inflation and dark energy models. We also
show that the equilibrium description in terms of the horizon entropy $S$ is
convenient because it takes into account the contribution of both the horizon
entropy $\hat{S}$ in non-equilibrium thermodynamics and an entropy production
term.
| [
{
"created": "Fri, 11 Sep 2009 12:53:02 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Mar 2010 16:10:38 GMT",
"version": "v2"
},
{
"created": "Thu, 22 Apr 2010 04:41:54 GMT",
"version": "v3"
}
] | 2010-10-12 | [
[
"Bamba",
"Kazuharu",
""
],
[
"Geng",
"Chao-Qiang",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | We show that it is possible to obtain a picture of equilibrium thermodynamics on the apparent horizon in the expanding cosmological background for a wide class of modified gravity theories with the Lagrangian density $f(R, \phi, X)$, where $R$ is the Ricci scalar and $X$ is the kinetic energy of a scalar field $\phi$. This comes from a suitable definition of an energy momentum tensor of the "dark" component that respects to a local energy conservation in the Jordan frame. In this framework the horizon entropy $S$ corresponding to equilibrium thermodynamics is equal to a quarter of the horizon area $A$ in units of gravitational constant $G$, as in Einstein gravity. For a flat cosmological background with a decreasing Hubble parameter, $S$ globally increases with time, as it happens for viable $f(R)$ inflation and dark energy models. We also show that the equilibrium description in terms of the horizon entropy $S$ is convenient because it takes into account the contribution of both the horizon entropy $\hat{S}$ in non-equilibrium thermodynamics and an entropy production term. |
gr-qc/0006027 | Gabriel Catren | Gabriel Catren, Rafael Ferraro | Quantization of the Taub cosmological model with extrinsic time | 17 pages, no figures; authors' names corrected | Phys.Rev. D63 (2001) 023502 | 10.1103/PhysRevD.63.023502 | null | gr-qc | null | The paper addresses the quantization of minisuperspace cosmological models,
with application to the Taub Model. By desparametrizing the model with an
extrinsic time, a formalism is developed in order to define a conserved
Schr\"{o}dinger inner product in the space of solutions of the Wheeler-De Witt
equation. A quantum version of classical canonical transformations is
introduced for connecting the solutions of the Wheeler-De Witt equation with
the wave functions of the desparametrized system. Once this correspondence is
established, boundary conditions on the space of solutions of the Wheeler-De
Witt equation are found to select the physical subspace. The question of
defining boundary conditions on the space of solutions of the Wheeler-De Witt
equation without having reduced the system is examined.
| [
{
"created": "Wed, 7 Jun 2000 15:40:34 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Jun 2000 20:01:40 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Catren",
"Gabriel",
""
],
[
"Ferraro",
"Rafael",
""
]
] | The paper addresses the quantization of minisuperspace cosmological models, with application to the Taub Model. By desparametrizing the model with an extrinsic time, a formalism is developed in order to define a conserved Schr\"{o}dinger inner product in the space of solutions of the Wheeler-De Witt equation. A quantum version of classical canonical transformations is introduced for connecting the solutions of the Wheeler-De Witt equation with the wave functions of the desparametrized system. Once this correspondence is established, boundary conditions on the space of solutions of the Wheeler-De Witt equation are found to select the physical subspace. The question of defining boundary conditions on the space of solutions of the Wheeler-De Witt equation without having reduced the system is examined. |
gr-qc/9911030 | Alejandro Jakubi | Luis P. Chimento, Alejandro S. Jakubi and Diego Pavon | Quintessence inhomogeneous cosmology | 8 pages, LaTeX 2.09. To appear in Proceedings of ERE-99 | null | null | null | gr-qc | null | The Einstein-Klein-Gordon field equations are solved in a inhomogeneous
shear-free universe containing a material fluid, a self-interacting scalar
field, a variable cosmological term, and a heat flux. A quintessence-dominated
scenario arises with a power-law accelerated expansion compatible with the
currently observed homogeneous universe.
| [
{
"created": "Tue, 9 Nov 1999 00:48:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Chimento",
"Luis P.",
""
],
[
"Jakubi",
"Alejandro S.",
""
],
[
"Pavon",
"Diego",
""
]
] | The Einstein-Klein-Gordon field equations are solved in a inhomogeneous shear-free universe containing a material fluid, a self-interacting scalar field, a variable cosmological term, and a heat flux. A quintessence-dominated scenario arises with a power-law accelerated expansion compatible with the currently observed homogeneous universe. |
gr-qc/9412026 | L. Hannibal | Ludger Hannibal | Dirac Theory in Space-Time without Torsion | 8 pp, LaTeX | null | null | OL-PHYS-TH2-12/94-1 | gr-qc | null | It is proven that the usual quadratic general-covariant Lagrangian for the
Dirac field leads to a symmetric, divergence-free energy-momentum tensor in the
standard Riemannian framework of space-time without torsion, provided the
tetrad field components are the only quantities related to gravitation that are
varied independently.
| [
{
"created": "Thu, 8 Dec 1994 17:19:15 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Dec 1994 09:33:29 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Hannibal",
"Ludger",
""
]
] | It is proven that the usual quadratic general-covariant Lagrangian for the Dirac field leads to a symmetric, divergence-free energy-momentum tensor in the standard Riemannian framework of space-time without torsion, provided the tetrad field components are the only quantities related to gravitation that are varied independently. |
0905.3762 | Marek Nowakowski | M. Nowakowski, I. Arraut | The Minimum and Maximum Temperature of Black Body Radiation | 7 pages, 1 figure | Mod.Phys.Lett.A24:2133-2137,2009 | 10.1142/S0217732309030679 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show, in different ways, that in the ubiquitous phenomenon of black body
radiation there exists a minimum and maximum temperature. These limiting values
are so small and large respectively, that they are of no practical use, except
in an extreme situation of black hole evaporation where they lead to maximum
and minimum mass.
| [
{
"created": "Fri, 22 May 2009 21:16:12 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Nowakowski",
"M.",
""
],
[
"Arraut",
"I.",
""
]
] | We show, in different ways, that in the ubiquitous phenomenon of black body radiation there exists a minimum and maximum temperature. These limiting values are so small and large respectively, that they are of no practical use, except in an extreme situation of black hole evaporation where they lead to maximum and minimum mass. |
1111.1148 | Thomas L. Wilson | Thomas L. Wilson | A New Strategy For Solving Two Cosmological Problems in Hadron Physics | 19 pages, 2 figures, 1 table | Journal of Modern Physics 4, No. 5 (2013) 686 | 10.4236/jmp.2013.45096 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new approach to solving two of the cosmological problems (CCPs) is proposed
by introducing the Abbott-Deser (AD) method for defining Killing charges in
asymptotic de Sitter space as the only consistent means for defining the
ground-state vacuum for the CCP. That granted, Einstein gravity will also need
to be modified at short-distance nuclear scales, using instead a nonminimally
coupled scalar-tensor theory of gravitation that provides for the existence of
QCD's two-phase vacuum having two different zero-point energy states as a
function of temperature. Einstein gravity alone cannot accomplish this. The
scalar field will be taken from bag theory in hadron physics, and the origin of
the bag constant B is accounted for by gravity's cosmological constant - noting
that the Higgs mechanism does not account for either the curved-space origin of
lambda or the mass of composite hadrons. A small Hubble-scale graviton mass
naturally appears external to the hadron bag, induced by lambda. This mass is
unobservable and gravitationally gauge-dependent. It is shown to be related to
the cosmological event horizon in asmyptotic de Sitter space.
| [
{
"created": "Fri, 4 Nov 2011 15:11:24 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Dec 2011 16:42:49 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Mar 2013 18:00:49 GMT",
"version": "v3"
}
] | 2013-05-31 | [
[
"Wilson",
"Thomas L.",
""
]
] | A new approach to solving two of the cosmological problems (CCPs) is proposed by introducing the Abbott-Deser (AD) method for defining Killing charges in asymptotic de Sitter space as the only consistent means for defining the ground-state vacuum for the CCP. That granted, Einstein gravity will also need to be modified at short-distance nuclear scales, using instead a nonminimally coupled scalar-tensor theory of gravitation that provides for the existence of QCD's two-phase vacuum having two different zero-point energy states as a function of temperature. Einstein gravity alone cannot accomplish this. The scalar field will be taken from bag theory in hadron physics, and the origin of the bag constant B is accounted for by gravity's cosmological constant - noting that the Higgs mechanism does not account for either the curved-space origin of lambda or the mass of composite hadrons. A small Hubble-scale graviton mass naturally appears external to the hadron bag, induced by lambda. This mass is unobservable and gravitationally gauge-dependent. It is shown to be related to the cosmological event horizon in asmyptotic de Sitter space. |
gr-qc/0412030 | Giovanni Montani | Giovanni Montani | Geometrization of the Gauge Connection within a Kaluza-Klein Theory | 10 pages, no figure, to appear on Int. Journ. Theor. Phys | Int.J.Theor.Phys. 44 (2005) 43-52 | 10.1007/s10773-005-1435-0 | null | gr-qc | null | Within the framework of a Kaluza-Klein theory, we provide the geometrization
of a generic (Abelian and non-Abelian) gauge coupling, which comes out by
choosing a suitable matter fields dependence on the extra-coordinates.
We start by the extension of the Nother theorem to a multidimensional
spacetime being the direct sum of a 4-dimensional Minkowski space and of a
compact homogeneous manifold (whose isometries reflect the gauge symmetry); we
show, how on such a ``vacuum'' configuration, the extra-dimensional components
of the field momentum correspond to the gauge charges. Then we analyze the
structure of a Dirac algebra as referred to a spacetime with the Kaluza-Klein
restrictions and, by splitting the corresponding free-field Lagrangian, we show
how the gauge coupling terms outcome.
| [
{
"created": "Tue, 7 Dec 2004 11:57:07 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Montani",
"Giovanni",
""
]
] | Within the framework of a Kaluza-Klein theory, we provide the geometrization of a generic (Abelian and non-Abelian) gauge coupling, which comes out by choosing a suitable matter fields dependence on the extra-coordinates. We start by the extension of the Nother theorem to a multidimensional spacetime being the direct sum of a 4-dimensional Minkowski space and of a compact homogeneous manifold (whose isometries reflect the gauge symmetry); we show, how on such a ``vacuum'' configuration, the extra-dimensional components of the field momentum correspond to the gauge charges. Then we analyze the structure of a Dirac algebra as referred to a spacetime with the Kaluza-Klein restrictions and, by splitting the corresponding free-field Lagrangian, we show how the gauge coupling terms outcome. |
1911.07837 | Barak Shoshany | Barak Shoshany | Spin Networks and Cosmic Strings in 3+1 Dimensions | 70 pages, 3 figures; updated to version published in Classical and
Quantum Gravity | Class. Quantum Grav. 37 (2020) 085019 | 10.1088/1361-6382/ab778e | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spin networks, the quantum states of discrete geometry in loop quantum
gravity, are directed graphs whose links are labeled by irreducible
representations of SU(2), or spins. Cosmic strings are 1-dimensional
topological defects carrying distributional curvature in an otherwise flat
spacetime. In this paper we prove that the classical phase space of spin
networks coupled to cosmic strings may obtained as a straightforward
discretization of general relativity in 3+1 spacetime dimensions. We decompose
the continuous spatial geometry into 3-dimensional cells, which are dual to a
spin network graph in a unique and well-defined way. Assuming that the geometry
may only be probed by holonomies (or Wilson loops) located on the spin network,
we truncate the geometry such that the cells become flat and the curvature is
concentrated at the edges of the cells, which we then interpret as a network of
cosmic strings. The discrete phase space thus describes a spin network coupled
to cosmic strings. This work proves that the relation between gravity and spin
networks exists not only at the quantum level, but already at the classical
level. Two appendices provide detailed derivations of the Ashtekar formulation
of gravity as a Yang-Mills theory and the distributional geometry of cosmic
strings in this formulation.
| [
{
"created": "Mon, 18 Nov 2019 18:58:29 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Apr 2020 19:35:27 GMT",
"version": "v2"
}
] | 2020-04-03 | [
[
"Shoshany",
"Barak",
""
]
] | Spin networks, the quantum states of discrete geometry in loop quantum gravity, are directed graphs whose links are labeled by irreducible representations of SU(2), or spins. Cosmic strings are 1-dimensional topological defects carrying distributional curvature in an otherwise flat spacetime. In this paper we prove that the classical phase space of spin networks coupled to cosmic strings may obtained as a straightforward discretization of general relativity in 3+1 spacetime dimensions. We decompose the continuous spatial geometry into 3-dimensional cells, which are dual to a spin network graph in a unique and well-defined way. Assuming that the geometry may only be probed by holonomies (or Wilson loops) located on the spin network, we truncate the geometry such that the cells become flat and the curvature is concentrated at the edges of the cells, which we then interpret as a network of cosmic strings. The discrete phase space thus describes a spin network coupled to cosmic strings. This work proves that the relation between gravity and spin networks exists not only at the quantum level, but already at the classical level. Two appendices provide detailed derivations of the Ashtekar formulation of gravity as a Yang-Mills theory and the distributional geometry of cosmic strings in this formulation. |
gr-qc/9907033 | Dr. Asher Yahalom | Hai Halevi | Unmissing the Missing Matter in Neo-Kaluza-Klein Universes | 12 pages | null | null | null | gr-qc | null | Uncompactified KK universes are so intrinsically connected to the otherwise
only empirically required "missing" Dark Matter (DM), that:
1) They yield a simple prediction which explains both the enigma of the
extra-dimensions' (XD) unobservability and the enigma of the present DM. The
two enigmas are "annihilated" into the hypothesis of "missing light", or better
of "photonland". This eliminates the very need to hypothesize/search/find
DM-candidates of exceptional/exotic properties to explain their darkness.
2) An early, spontaneous gravitational XD-collapse of their natural 5D-DM
replaces KK's compactification mechanisms and cylindricity condition, and
(partly?) eliminates the quandary of the radically insufficient density
fluctuations.
| [
{
"created": "Thu, 8 Jul 1999 05:22:54 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Jul 1999 14:46:44 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Halevi",
"Hai",
""
]
] | Uncompactified KK universes are so intrinsically connected to the otherwise only empirically required "missing" Dark Matter (DM), that: 1) They yield a simple prediction which explains both the enigma of the extra-dimensions' (XD) unobservability and the enigma of the present DM. The two enigmas are "annihilated" into the hypothesis of "missing light", or better of "photonland". This eliminates the very need to hypothesize/search/find DM-candidates of exceptional/exotic properties to explain their darkness. 2) An early, spontaneous gravitational XD-collapse of their natural 5D-DM replaces KK's compactification mechanisms and cylindricity condition, and (partly?) eliminates the quandary of the radically insufficient density fluctuations. |
1812.09161 | Sven Herrmann | Sven Herrmann, Felix Finke, Martin L\"ulf, Olga Kichakova, Dirk
Puetzfeld, Daniela Knickmann, Meike List, Benny Rievers, Gabriele Giorgi,
Christoph G\"unther, Hansj\"org Dittus, Roberto Prieto-Cerdeira, Florian
Dilssner, Francisco Gonzalez, Erik Sch\"onemann, Javier Ventura-Traveset,
Claus L\"ammerzahl | Test of the Gravitational Redshift with Galileo Satellites in an
Eccentric Orbit | 6 pages, 3 figures, published in Phys. Rev. Lett. 121, 231102 | Physical Review Letters, Vol. 121, Iss. 23, p. 231102, 7 December
2018 | 10.1103/PhysRevLett.121.231102 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On August 22, 2014, the satellites GSAT-0201 and GSAT-0202 of the European
GNSS Galileo were unintentionally launched into eccentric orbits. Unexpectedly,
this has become a fortunate scientific opportunity since the onboard hydrogen
masers allow for a sensitive test of the redshift predicted by the theory of
general relativity. In the present Letter we describe an analysis of
approximately three years of data from these satellites including three
different clocks. For one of these we determine the test parameter quantifying
a potential violation of the combined effects of the gravitational redshift and
the relativistic Doppler shift. The uncertainty of our result is reduced by
more than a factor 4 as compared to the values of Gravity Probe A obtained in
1976.
| [
{
"created": "Fri, 21 Dec 2018 14:51:17 GMT",
"version": "v1"
}
] | 2018-12-24 | [
[
"Herrmann",
"Sven",
""
],
[
"Finke",
"Felix",
""
],
[
"Lülf",
"Martin",
""
],
[
"Kichakova",
"Olga",
""
],
[
"Puetzfeld",
"Dirk",
""
],
[
"Knickmann",
"Daniela",
""
],
[
"List",
"Meike",
""
],
[
"Ri... | On August 22, 2014, the satellites GSAT-0201 and GSAT-0202 of the European GNSS Galileo were unintentionally launched into eccentric orbits. Unexpectedly, this has become a fortunate scientific opportunity since the onboard hydrogen masers allow for a sensitive test of the redshift predicted by the theory of general relativity. In the present Letter we describe an analysis of approximately three years of data from these satellites including three different clocks. For one of these we determine the test parameter quantifying a potential violation of the combined effects of the gravitational redshift and the relativistic Doppler shift. The uncertainty of our result is reduced by more than a factor 4 as compared to the values of Gravity Probe A obtained in 1976. |
1403.5706 | Everton Murilo Carvalho Abreu | Rafael da C. Nunes, Ed\'esio M. Barboza Jr., Everton M. C. Abreu and
Jorge Ananias Neto | Dark energy models through nonextensive Tsallis' statistics | 7 pages, two-column format | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The accelerated expansion of the Universe is one of the greatest challenges
of modern physics. One candidate to explain this phenomenon is a new field
called dark energy. In this work we have used the Tsallis nonextensive
statistical formulation of the Friedmann equation to explore the
Barboza-Alcaniz and Chevalier-Polarski-Linder parametric dark energy models and
the Wang-Meng and Dalal vacuum decay models. After that, we have discussed the
observational tests and the constraints concerning the Tsallis nonextensive
parameter.
| [
{
"created": "Sat, 22 Mar 2014 21:52:22 GMT",
"version": "v1"
}
] | 2014-03-25 | [
[
"Nunes",
"Rafael da C.",
""
],
[
"Barboza",
"Edésio M.",
"Jr."
],
[
"Abreu",
"Everton M. C.",
""
],
[
"Neto",
"Jorge Ananias",
""
]
] | The accelerated expansion of the Universe is one of the greatest challenges of modern physics. One candidate to explain this phenomenon is a new field called dark energy. In this work we have used the Tsallis nonextensive statistical formulation of the Friedmann equation to explore the Barboza-Alcaniz and Chevalier-Polarski-Linder parametric dark energy models and the Wang-Meng and Dalal vacuum decay models. After that, we have discussed the observational tests and the constraints concerning the Tsallis nonextensive parameter. |
1001.1243 | Mubasher Jamil | Mubasher Jamil and M. Umar Farooq | Phantom Wormholes in (2+1)-dimensions | 10 pages, 5 figures | Int.J.Theor.Phys.49:835-841,2010 | 10.1007/s10773-010-0263-z | arXiv:1001.1243v1 [gr-qc] | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have constructed a (2+1)-dimensional wormhole using
inhomogeneous and anisotropic distribution of phantom energy. We have
determined the exact form of the equation of state of phantom energy that
supports the wormhole structure. Interestingly, this equation of state is
linear but variable one and is dependent only on the radial parameter of the
model.
| [
{
"created": "Fri, 8 Jan 2010 11:38:30 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Jamil",
"Mubasher",
""
],
[
"Farooq",
"M. Umar",
""
]
] | In this paper, we have constructed a (2+1)-dimensional wormhole using inhomogeneous and anisotropic distribution of phantom energy. We have determined the exact form of the equation of state of phantom energy that supports the wormhole structure. Interestingly, this equation of state is linear but variable one and is dependent only on the radial parameter of the model. |
gr-qc/9503038 | Sardanashvily Gennadi | G. Sardanashvily (Moscow State University) | Stress-Energy-Momentum Tensors in Constraint Field Theories | 25 pp, LaTeX file | J.Math.Phys. 38 (1997) 847-866 | 10.1063/1.531873 | TP\95\043 | gr-qc dg-ga hep-th math.DG | null | One has not any conventional energy-momentum conservation law in Lagrangian
field theory, but relations involving different stress-energy-momentum tensors
associated with different connections. It is not obvious how to choose the true
energy-momentum tensor. This problem is solved in the framework of the
multimomentum Hamiltonian formalism which provides the adequate description of
constraint field systems. The goal is that, for different solutions of the same
constraint field model, one should choose different stress-energy-momentum
tensors in general. Gauge theory illustrates this result. The
stress-energy-momentum tensors of affine-metric gravity are examined.
| [
{
"created": "Wed, 22 Mar 1995 15:54:58 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Sardanashvily",
"G.",
"",
"Moscow State University"
]
] | One has not any conventional energy-momentum conservation law in Lagrangian field theory, but relations involving different stress-energy-momentum tensors associated with different connections. It is not obvious how to choose the true energy-momentum tensor. This problem is solved in the framework of the multimomentum Hamiltonian formalism which provides the adequate description of constraint field systems. The goal is that, for different solutions of the same constraint field model, one should choose different stress-energy-momentum tensors in general. Gauge theory illustrates this result. The stress-energy-momentum tensors of affine-metric gravity are examined. |
1608.02532 | Luis Cort\'es Barbado | Luis C. Barbado, Carlos Barcel\'o, Luis J. Garay and Gil Jannes | Hawking versus Unruh effects, or the difficulty of slowly crossing a
black hole horizon | Minor corrections to match the published version. 14 pages, 2 figures | null | 10.1007/JHEP10(2016)161 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When analyzing the perception of Hawking radiation by different observers,
the Hawking effect becomes mixed with the Unruh effect. The separation of both
effects is not always clear in the literature. Here we propose an
inconsistency-free interpretation of what constitutes a Hawking effect and what
an Unruh effect. An appropriate interpretation is important in order to
elucidate what sort of effects a detector might experience depending on its
trajectory and the state of the quantum field. Under simplifying assumptions we
introduce an analytic formula that separates these two effects. Armed with the
previous interpretation we argue that for a free-falling detector to cross the
horizon without experiencing high-energy effects, it is necessary that the
horizon crossing is not attempted at low velocities.
| [
{
"created": "Mon, 8 Aug 2016 17:53:42 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Aug 2016 14:59:35 GMT",
"version": "v2"
},
{
"created": "Mon, 28 Nov 2016 11:16:20 GMT",
"version": "v3"
}
] | 2016-11-29 | [
[
"Barbado",
"Luis C.",
""
],
[
"Barceló",
"Carlos",
""
],
[
"Garay",
"Luis J.",
""
],
[
"Jannes",
"Gil",
""
]
] | When analyzing the perception of Hawking radiation by different observers, the Hawking effect becomes mixed with the Unruh effect. The separation of both effects is not always clear in the literature. Here we propose an inconsistency-free interpretation of what constitutes a Hawking effect and what an Unruh effect. An appropriate interpretation is important in order to elucidate what sort of effects a detector might experience depending on its trajectory and the state of the quantum field. Under simplifying assumptions we introduce an analytic formula that separates these two effects. Armed with the previous interpretation we argue that for a free-falling detector to cross the horizon without experiencing high-energy effects, it is necessary that the horizon crossing is not attempted at low velocities. |
gr-qc/0306119 | Pantelis S. Apostolopoulos | Pantelis S. Apostolopoulos | Self-similar Bianchi models: I. Class A models | 14 pages, Latex; to appear in Classical and Quantum Gravity | Class.Quant.Grav. 20 (2003) 3371-3384 | 10.1088/0264-9381/20/15/307 | null | gr-qc | null | We present a study of Bianchi class A tilted cosmological models admitting a
proper homothetic vector field together with the restrictions, both at the
geometrical and dynamical level, imposed by the existence of the simply
transitive similarity group. The general solution of the symmetry equations and
the form of the homothetic vector field are given in terms of a set of
arbitrary integration constants. We apply the geometrical results for tilted
perfect fluids sources and give the general Bianchi II self-similar solution
and the form of the similarity vector field. In addition we show that
self-similar perfect fluid Bianchi VII$_0$ models and irrotational Bianchi
VI$_0$ models do not exist.
| [
{
"created": "Thu, 26 Jun 2003 17:40:00 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Apostolopoulos",
"Pantelis S.",
""
]
] | We present a study of Bianchi class A tilted cosmological models admitting a proper homothetic vector field together with the restrictions, both at the geometrical and dynamical level, imposed by the existence of the simply transitive similarity group. The general solution of the symmetry equations and the form of the homothetic vector field are given in terms of a set of arbitrary integration constants. We apply the geometrical results for tilted perfect fluids sources and give the general Bianchi II self-similar solution and the form of the similarity vector field. In addition we show that self-similar perfect fluid Bianchi VII$_0$ models and irrotational Bianchi VI$_0$ models do not exist. |
1202.2733 | Marc Diaz-Aguilo Mr. | Marc Diaz-Aguil\'o, Enrique Garc\'ia-Berro, Alberto Lobo | Inflight magnetic characterization of the test masses onboard LISA
Pathfinder | 12 pages, 7 figures, Physical Review D, accepted on Feb 6th, 2012 | null | 10.1103/PhysRevD.85.042004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | LISA Pathfinder is a science and technology demonstrator of the European
Space Agency within the framework of its LISA mission, the latter aiming to be
the first space-borne gravitational wave observatory. The payload of LISA
Pathfinder is the so-called LISA Technology Package, which is designed to
measure relative accelerations between two test masses in nominal free fall.
The diagnostics subsystem consists of several modules, one of which is the
magnetic diagnostics unit. Its main function is the assessment of the
differential acceleration noise between the test masses due to magnetic
effects. This subsystem is composed of two onboard coils intended to produce
controlled magnetic fields at the location of the test masses. These magnetic
fields couple with the remanent magnetic moment and susceptibility and produce
forces and torques on the test masses. These, in turn, produce kinematic
excursions of the test masses which are sensed by the onboard interferometer.
We prove that adequately processing these excursions, the magnetic properties
of the test masses can be estimated using classical multi-parameter estimation
techniques. Moreover, we show that special processing procedures to minimize
the effect of the multi channel cross-talks are needed. Finally, we demonstrate
that the quality of our estimates is frequency dependent. We also suggest that
using a multiple frequency experiment the global estimate can be obtained in
such a way that the results of the magnetic experiment are more reliable.
Finally, using our procedure we compute the the contribution of the magnetic
noise to the total proof-mass acceleration noise.
| [
{
"created": "Mon, 13 Feb 2012 13:57:24 GMT",
"version": "v1"
}
] | 2015-06-04 | [
[
"Diaz-Aguiló",
"Marc",
""
],
[
"García-Berro",
"Enrique",
""
],
[
"Lobo",
"Alberto",
""
]
] | LISA Pathfinder is a science and technology demonstrator of the European Space Agency within the framework of its LISA mission, the latter aiming to be the first space-borne gravitational wave observatory. The payload of LISA Pathfinder is the so-called LISA Technology Package, which is designed to measure relative accelerations between two test masses in nominal free fall. The diagnostics subsystem consists of several modules, one of which is the magnetic diagnostics unit. Its main function is the assessment of the differential acceleration noise between the test masses due to magnetic effects. This subsystem is composed of two onboard coils intended to produce controlled magnetic fields at the location of the test masses. These magnetic fields couple with the remanent magnetic moment and susceptibility and produce forces and torques on the test masses. These, in turn, produce kinematic excursions of the test masses which are sensed by the onboard interferometer. We prove that adequately processing these excursions, the magnetic properties of the test masses can be estimated using classical multi-parameter estimation techniques. Moreover, we show that special processing procedures to minimize the effect of the multi channel cross-talks are needed. Finally, we demonstrate that the quality of our estimates is frequency dependent. We also suggest that using a multiple frequency experiment the global estimate can be obtained in such a way that the results of the magnetic experiment are more reliable. Finally, using our procedure we compute the the contribution of the magnetic noise to the total proof-mass acceleration noise. |
2207.12403 | Farook Rahaman | Susmita Sarkar, Nayan Sarkar, Farook Rahaman and Y Aditya | Wormholes in $\kappa(R,T)$ gravity | 15 pages, 12 figures. Published in To Physics Journal Vol 2, page 7
(2019) | To Physics Journal Vol 2, page 7 (2019) | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The wormhole solution could be found by solving the Einstein field equations
with violating the null energy condition (NEC). We represent wormhole solutions
in $\kappa(R,T)$ gravity in two different ways. At first, we find the shape
function by considering a redshift function and linear equation of state
(EoS). The solution represents a wormhole for the real feasible matter. In the
second part, we consider four pairs of two redshift functions and two shape
functions and analyze the obtained solutions. Some of the models suggest that
for particular values of the parameters, the existence of wormholes are
supported by an arbitrarily small quantity of exotic matter.
| [
{
"created": "Sat, 23 Jul 2022 18:40:38 GMT",
"version": "v1"
}
] | 2022-07-27 | [
[
"Sarkar",
"Susmita",
""
],
[
"Sarkar",
"Nayan",
""
],
[
"Rahaman",
"Farook",
""
],
[
"Aditya",
"Y",
""
]
] | The wormhole solution could be found by solving the Einstein field equations with violating the null energy condition (NEC). We represent wormhole solutions in $\kappa(R,T)$ gravity in two different ways. At first, we find the shape function by considering a redshift function and linear equation of state (EoS). The solution represents a wormhole for the real feasible matter. In the second part, we consider four pairs of two redshift functions and two shape functions and analyze the obtained solutions. Some of the models suggest that for particular values of the parameters, the existence of wormholes are supported by an arbitrarily small quantity of exotic matter. |
1507.01787 | Thomas Adams Dr | T. Adams (for the LIGO Scientific Collaboration, and the Virgo
Collaboration) | Low latency search for compact binary coalescences using MBTA | 4 pages, 2 figures, To appear in Proceedings of the 50th Rencontres
de Moriond | null | null | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Multi-Band Template Analysis is a low-latency analysis pipeline for the
detection of gravitational waves to triggering electromagnetic follow up
observations. Coincident observation of gravitational waves and an
electromagnetic counterpart will allow us to develop a complete picture of
energetic astronomical events. We give an outline of the MBTA pipeline, as well
as the procedure for distributing gravitational wave candidate events to our
astronomical partners. We give some details of the recent work that has been
done to improve the MBTA pipeline and are now making preparations for the
advanced detector era.
| [
{
"created": "Tue, 7 Jul 2015 13:05:39 GMT",
"version": "v1"
}
] | 2019-08-15 | [
[
"Adams",
"T.",
"",
"for the LIGO Scientific Collaboration, and the Virgo\n Collaboration"
]
] | The Multi-Band Template Analysis is a low-latency analysis pipeline for the detection of gravitational waves to triggering electromagnetic follow up observations. Coincident observation of gravitational waves and an electromagnetic counterpart will allow us to develop a complete picture of energetic astronomical events. We give an outline of the MBTA pipeline, as well as the procedure for distributing gravitational wave candidate events to our astronomical partners. We give some details of the recent work that has been done to improve the MBTA pipeline and are now making preparations for the advanced detector era. |
1007.2546 | Florian Bauer | Florian Bauer | Filtering out the cosmological constant in the Palatini formalism of
modified gravity | 22 pages, 1 figure, discussion extended, references added, accepted
by Gen.Rel.Grav | Gen.Rel.Grav.43:1733-1757,2011 | 10.1007/s10714-011-1153-2 | ICCUB-10-048 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | According to theoretical physics the cosmological constant (CC) is expected
to be much larger in magnitude than other energy densities in the universe,
which is in stark contrast to the observed Big Bang evolution. We address this
old CC problem not by introducing an extremely fine-tuned counterterm, but in
the context of modified gravity in the Palatini formalism. In our model the
large CC term is filtered out, and it does not prevent a standard cosmological
evolution. We discuss the filter effect in the epochs of radiation and matter
domination as well as in the asymptotic de Sitter future. The final expansion
rate can be much lower than inferred from the large CC without using a
fine-tuned counterterm. Finally, we show that the CC filter works also in the
Kottler (Schwarzschild-de Sitter) metric describing a black hole environment
with a CC compatible to the future de Sitter cosmos.
| [
{
"created": "Thu, 15 Jul 2010 13:02:53 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Jan 2011 16:27:18 GMT",
"version": "v2"
}
] | 2011-05-10 | [
[
"Bauer",
"Florian",
""
]
] | According to theoretical physics the cosmological constant (CC) is expected to be much larger in magnitude than other energy densities in the universe, which is in stark contrast to the observed Big Bang evolution. We address this old CC problem not by introducing an extremely fine-tuned counterterm, but in the context of modified gravity in the Palatini formalism. In our model the large CC term is filtered out, and it does not prevent a standard cosmological evolution. We discuss the filter effect in the epochs of radiation and matter domination as well as in the asymptotic de Sitter future. The final expansion rate can be much lower than inferred from the large CC without using a fine-tuned counterterm. Finally, we show that the CC filter works also in the Kottler (Schwarzschild-de Sitter) metric describing a black hole environment with a CC compatible to the future de Sitter cosmos. |
1404.2727 | Vyacheslav Ivanovich Dokuchaev | V. A. Berezin and V. I. Dokuchaev | Neutral thin shell immersed into the Reissner-Nordstr\"om space-time | 70 pages, 60 figures | null | null | Preprint INR RAS 1383/2014 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Starting from Israel equations for the spherically symmetric thin shells we
introduce the effective potential and show how it can be used in constructing,
without further thorough investigation, the corresponding Carter-Penrose
diagrams describing clearly the global geometry of the composite space-time
manifolds. We demonstrate, how this new method works, by considering all
possible configurations for the neutral thin dust shell immersed into different
types of Reissner-Nordstr\"om electro-vacuum manifolds.
| [
{
"created": "Thu, 10 Apr 2014 08:20:44 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Berezin",
"V. A.",
""
],
[
"Dokuchaev",
"V. I.",
""
]
] | Starting from Israel equations for the spherically symmetric thin shells we introduce the effective potential and show how it can be used in constructing, without further thorough investigation, the corresponding Carter-Penrose diagrams describing clearly the global geometry of the composite space-time manifolds. We demonstrate, how this new method works, by considering all possible configurations for the neutral thin dust shell immersed into different types of Reissner-Nordstr\"om electro-vacuum manifolds. |
1412.5453 | Salvatore Capozziello | A. V. Astashenok, S. Capozziello, S. D. Odintsov | Nonperturbative models of quark stars in $f(R)$ gravity | 9 pages, 5 figures, accepted for publication in Phys. Lett. B | null | 10.1016/j.physletb.2015.01.030 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quark star models with realistic equation of state in nonperturbative $f(R)$
gravity are considered. The mass-radius relation for $f(R)=R+\alpha R^2$ model
is obtained. Considering scalar curvature $R$ as an independent function, one
can find out, for each value of central density, the unique value of central
curvature for which one has solutions with the required asymptotic
$R\rightarrow 0$ for $r\rightarrow\infty$. In another words, one needs a
fine-tuning for $R$ to achieve quark stars in $f(R)$ gravity. We consider also
the analogue description in corresponding scalar-tensor gravity. The
fine-tuning on $R$ is equivalent to the fine-tuning on the scalar field $\phi$
in this description. For distant observers, the gravitational mass of the star
increases with increasing $\alpha$ ($\alpha>0$) but the interpretation of this
fact depends on frame where we work. Considering directly $f(R)$ gravity, one
can say that increasing of mass occurs by the "gravitational sphere" outside
the star with some "effective mass". On the other hand, in scalar-tensor
theory, we also have a dilaton sphere (or "disphere") outside the star but its
contribution to gravitational mass for distant observer is negligible. We show
that it is possible to discriminate modified theories of gravity from General
Relativity due to the gravitational redshift of the thermal spectrum emerging
from the surface of the star.
| [
{
"created": "Wed, 17 Dec 2014 15:57:09 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Jan 2015 08:43:33 GMT",
"version": "v2"
}
] | 2015-06-23 | [
[
"Astashenok",
"A. V.",
""
],
[
"Capozziello",
"S.",
""
],
[
"Odintsov",
"S. D.",
""
]
] | Quark star models with realistic equation of state in nonperturbative $f(R)$ gravity are considered. The mass-radius relation for $f(R)=R+\alpha R^2$ model is obtained. Considering scalar curvature $R$ as an independent function, one can find out, for each value of central density, the unique value of central curvature for which one has solutions with the required asymptotic $R\rightarrow 0$ for $r\rightarrow\infty$. In another words, one needs a fine-tuning for $R$ to achieve quark stars in $f(R)$ gravity. We consider also the analogue description in corresponding scalar-tensor gravity. The fine-tuning on $R$ is equivalent to the fine-tuning on the scalar field $\phi$ in this description. For distant observers, the gravitational mass of the star increases with increasing $\alpha$ ($\alpha>0$) but the interpretation of this fact depends on frame where we work. Considering directly $f(R)$ gravity, one can say that increasing of mass occurs by the "gravitational sphere" outside the star with some "effective mass". On the other hand, in scalar-tensor theory, we also have a dilaton sphere (or "disphere") outside the star but its contribution to gravitational mass for distant observer is negligible. We show that it is possible to discriminate modified theories of gravity from General Relativity due to the gravitational redshift of the thermal spectrum emerging from the surface of the star. |
1704.06617 | Maria Skugoreva | Maria A. Skugoreva | Late-time power-law stages of cosmological evolution in teleparallel
gravity with nonminimal coupling | 14 pages, 7 figures, some clarifications and references added,
published version | Grav. Cosmol. 24 (1), 103-111 (2018) | 10.1134/S0202289318010139 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the Universe evolution at late-time stages in models of
teleparallel gravity with power-law nonminimal coupling and a decreasing
power-law potential of the scalar field $\phi$. New asymptotic solutions are
found analytically for these models in vacuum and with a perfect fluid.
Applying numerical integration, we show that the cosmological evolution leads
to these solutions for some region of the initial conditions, and these
asymptotic regimes are stable with respect to homogeneous variations of the
initial data. The physical sense of the results is discussed.
| [
{
"created": "Fri, 21 Apr 2017 16:16:06 GMT",
"version": "v1"
},
{
"created": "Fri, 4 May 2018 23:37:15 GMT",
"version": "v2"
}
] | 2018-05-08 | [
[
"Skugoreva",
"Maria A.",
""
]
] | We investigate the Universe evolution at late-time stages in models of teleparallel gravity with power-law nonminimal coupling and a decreasing power-law potential of the scalar field $\phi$. New asymptotic solutions are found analytically for these models in vacuum and with a perfect fluid. Applying numerical integration, we show that the cosmological evolution leads to these solutions for some region of the initial conditions, and these asymptotic regimes are stable with respect to homogeneous variations of the initial data. The physical sense of the results is discussed. |
1402.6511 | Leszek Soko{\l}owski | Leszek M. Soko{\l}owski and Zdzis{\l}aw A. Golda | The local and global geometrical aspects of the twin paradox in static
spacetimes: I. Three spherically symmetric spacetimes | 27 pages, 0 figures, typos corrected, version published in APP B | Acta Phys. Polon. B45 (2014) 1051-1075 | 10.5506/APhysPolB.45.1051 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate local and global properties of timelike geodesics in three
static spherically symmetric spacetimes. These properties are of its own
mathematical relevance and provide a solution of the physical `twin paradox'
problem. The latter means that we focus our studies on the search of the
longest timelike geodesics between two given points. Due to problems with
solving the geodesic deviation equation we restrict our investigations to
radial and circular (if exist) geodesics. On these curves we find general
Jacobi vector fields, determine by means of them sequences of conjugate points
and with the aid of the comoving coordinate system and the spherical symmetry
we determine the cut points. These notions identify segments of radial and
circular gepdesics which are locally or globally of maximal length. In de
Sitter spacetime all geodesics are globally maximal. In CAdS and
Bertotti--Robinson spacetimes the radial geodesics which infinitely many times
oscillate between antipodal points in the space contain infinite number of
equally separated conjugate points and there are no other cut points. Yet in
these two spacetimes each outgoing or ingoing radial geodesic which does not
cross the centre is globally of maximal length. Circular geodesics exist only
in CAdS spacetime and contain an infinite sequence of equally separated
conjugate points. The geodesic curves which intersect the circular ones at
these points may either belong to the two-surface $\theta=\pi/2$ or lie outside
it.
| [
{
"created": "Wed, 26 Feb 2014 12:21:43 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Jun 2014 07:58:50 GMT",
"version": "v2"
}
] | 2014-06-05 | [
[
"Sokołowski",
"Leszek M.",
""
],
[
"Golda",
"Zdzisław A.",
""
]
] | We investigate local and global properties of timelike geodesics in three static spherically symmetric spacetimes. These properties are of its own mathematical relevance and provide a solution of the physical `twin paradox' problem. The latter means that we focus our studies on the search of the longest timelike geodesics between two given points. Due to problems with solving the geodesic deviation equation we restrict our investigations to radial and circular (if exist) geodesics. On these curves we find general Jacobi vector fields, determine by means of them sequences of conjugate points and with the aid of the comoving coordinate system and the spherical symmetry we determine the cut points. These notions identify segments of radial and circular gepdesics which are locally or globally of maximal length. In de Sitter spacetime all geodesics are globally maximal. In CAdS and Bertotti--Robinson spacetimes the radial geodesics which infinitely many times oscillate between antipodal points in the space contain infinite number of equally separated conjugate points and there are no other cut points. Yet in these two spacetimes each outgoing or ingoing radial geodesic which does not cross the centre is globally of maximal length. Circular geodesics exist only in CAdS spacetime and contain an infinite sequence of equally separated conjugate points. The geodesic curves which intersect the circular ones at these points may either belong to the two-surface $\theta=\pi/2$ or lie outside it. |
1304.6290 | Giorgio Papini | Giorgio Papini | Fermion-antifermion mixing in gravitational fields | 5 pages | Modern Physics Letters A 28, No. 17 (2013) 1350071 | 10.1142/SO217732313500715 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Mixing of fermion and antifermion states occurs in gravitational
interactions, leading to non-conservation of fermion number above temperatures
determined by the particle masses. We study the evolution of a $f\,,\bar{f}$
system and calculate the cross sections for the reactions
$f\rightleftharpoons\bar{f}$. Their values are identical in both directions.
However, if $\bar{f}$ changes quickly into a lighter antiparticle, then the
reaction symmetry is broken, \emph{resulting in an increased production of
matter over antimatter}.
| [
{
"created": "Tue, 23 Apr 2013 14:05:02 GMT",
"version": "v1"
}
] | 2013-05-29 | [
[
"Papini",
"Giorgio",
""
]
] | Mixing of fermion and antifermion states occurs in gravitational interactions, leading to non-conservation of fermion number above temperatures determined by the particle masses. We study the evolution of a $f\,,\bar{f}$ system and calculate the cross sections for the reactions $f\rightleftharpoons\bar{f}$. Their values are identical in both directions. However, if $\bar{f}$ changes quickly into a lighter antiparticle, then the reaction symmetry is broken, \emph{resulting in an increased production of matter over antimatter}. |
2111.04768 | Nosratollah Jafari Sonbolabadi | Ahmad Shariati, Nosratollah Jafari | Modified Inertia as Nonconservative Newtonian Dynamics | 9 pages, 1 figure | Phys.Rev.D 104 (2021) 8, 084070 | 10.1103/PhysRevD.104.084070 | null | gr-qc astro-ph.CO astro-ph.GA hep-th | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Modified Newtonian dynamics by Milgrom is a paradigm for explaining the
rotation curves of spiral galaxies and various other large scale structures.
This paradigm includes several different theories. Here we present Milgrom's
modified inertia (MI) theory in terms of a simple and tractable
non-conservative Newtonian dynamics, which is useful in obtaining observable
predictions of MI. It is found that: 1) Modified inertia theory is equivalent
to a Newtonian theory, with a non-conservative gravitational field, and dark
matter density; 2) The tidal force in the equivalent Newtonian dynamics is
non-conservative, and its effect on a binary system in free fall in the
gravitational field of a spheroid is addressed. We also discuss attempts to
restore conservation in MI.
| [
{
"created": "Mon, 8 Nov 2021 19:03:13 GMT",
"version": "v1"
}
] | 2021-11-12 | [
[
"Shariati",
"Ahmad",
""
],
[
"Jafari",
"Nosratollah",
""
]
] | Modified Newtonian dynamics by Milgrom is a paradigm for explaining the rotation curves of spiral galaxies and various other large scale structures. This paradigm includes several different theories. Here we present Milgrom's modified inertia (MI) theory in terms of a simple and tractable non-conservative Newtonian dynamics, which is useful in obtaining observable predictions of MI. It is found that: 1) Modified inertia theory is equivalent to a Newtonian theory, with a non-conservative gravitational field, and dark matter density; 2) The tidal force in the equivalent Newtonian dynamics is non-conservative, and its effect on a binary system in free fall in the gravitational field of a spheroid is addressed. We also discuss attempts to restore conservation in MI. |
1908.08410 | Behnam Pourhassan | M. Rostami, J. Sadeghi, S. Miraboutalebi, A. A. Masoudi, and B.
Pourhassan | Charged accelerating AdS black hole of $f(R)$ gravity and the
Joule-Thomson expansion | 19 pages, 7 figures | Int.J.Geom.Meth.Mod.Phys. 17 (2020) 09, 2050136 | 10.1142/S0219887820501364 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, the thermodynamical properties and the phase transitions of
the charged accelerating anti-de Sitter (AdS) black holes are investigated in
the framework of the $f(R)$ gravity. By studying the conditions for the phase
transitions, it has been shown that the $P-V$ criticality and the van der Waals
like phase transitions can be achieved for $ T \approx T_{c} $. The
Joule-Thomson expansion effects are also examined for the charged accelerating
AdS black holes of the $f(R)$ gravity. Here, we derive the inversion
temperatures as well as the inversion curves. Then, we determine the position
of the reverse point for different values of mass $M$ and parameter $b$ for the
corresponding black hole. At this point, the Joule-Thompson coefficient is
zero. So, in such case, we can say that such point is very important for the
finding of cooling - heating regions. Finally, we calculate the ratio of
minimum inversion temperature and critical temperature for such black hole.
| [
{
"created": "Wed, 21 Aug 2019 08:35:45 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Aug 2019 06:28:17 GMT",
"version": "v2"
}
] | 2021-11-09 | [
[
"Rostami",
"M.",
""
],
[
"Sadeghi",
"J.",
""
],
[
"Miraboutalebi",
"S.",
""
],
[
"Masoudi",
"A. A.",
""
],
[
"Pourhassan",
"B.",
""
]
] | In this paper, the thermodynamical properties and the phase transitions of the charged accelerating anti-de Sitter (AdS) black holes are investigated in the framework of the $f(R)$ gravity. By studying the conditions for the phase transitions, it has been shown that the $P-V$ criticality and the van der Waals like phase transitions can be achieved for $ T \approx T_{c} $. The Joule-Thomson expansion effects are also examined for the charged accelerating AdS black holes of the $f(R)$ gravity. Here, we derive the inversion temperatures as well as the inversion curves. Then, we determine the position of the reverse point for different values of mass $M$ and parameter $b$ for the corresponding black hole. At this point, the Joule-Thompson coefficient is zero. So, in such case, we can say that such point is very important for the finding of cooling - heating regions. Finally, we calculate the ratio of minimum inversion temperature and critical temperature for such black hole. |
1907.03776 | Suprit Singh | Viqar Husain, Suprit Singh | Matter-Geometry entanglement in quantum cosmology | Important work. 7 Pages, 6 figures. Accepted for publication in CQG
Letters | null | 10.1088/1361-6382/ab9d97 | null | gr-qc hep-th physics.comp-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a study of the evolution of entanglement entropy of matter and
geometry in quantum cosmology. For a variety of Gaussian initial states and
their linear combinations, and with evolution defined with respect to a
relational time, we show numerically that (i) entanglement entropy increases
rapidly at very early times, and subsequently saturates to a constant non-zero
value, and (ii) that the saturation value of this entropy is a linear function
of the energy associated to the quantum state: $S_{\text{ent}}^\psi = \gamma
\langle \hat{H} \rangle_\psi$. These results suggest a remnant of quantum
entanglement in the macroscopic Universe from the era of the Big Bang,
independent of the initial state parameters, and a "First Law" associated with
matter-gravity entanglement entropy in quantum gravity.
| [
{
"created": "Mon, 8 Jul 2019 18:00:08 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Jul 2019 17:22:17 GMT",
"version": "v2"
},
{
"created": "Wed, 17 Jun 2020 22:57:12 GMT",
"version": "v3"
}
] | 2020-09-10 | [
[
"Husain",
"Viqar",
""
],
[
"Singh",
"Suprit",
""
]
] | We present a study of the evolution of entanglement entropy of matter and geometry in quantum cosmology. For a variety of Gaussian initial states and their linear combinations, and with evolution defined with respect to a relational time, we show numerically that (i) entanglement entropy increases rapidly at very early times, and subsequently saturates to a constant non-zero value, and (ii) that the saturation value of this entropy is a linear function of the energy associated to the quantum state: $S_{\text{ent}}^\psi = \gamma \langle \hat{H} \rangle_\psi$. These results suggest a remnant of quantum entanglement in the macroscopic Universe from the era of the Big Bang, independent of the initial state parameters, and a "First Law" associated with matter-gravity entanglement entropy in quantum gravity. |
1407.3420 | Soon-Tae Hong | Soon-Tae Hong | Photon size in higher dimensional phantom cosmology | 6 pages, 3 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study a higher dimensional cosmology with phantom field associated with a
negative kinetic term. Assuming that the universe possesses the phantom field
defined in $D$ dimensional spacetime, we investigate in detail the solutions
involved in the higher dimensional phantom cosmology, to explicitly predict
photon size and phantom field strength at present in nature. To be specific, we
find that the photon size decreases drastically at the early stage of the
universe after the Big Bang. Next we explicitly demonstrate the dependences of
the photon size, universe size and phantom field strength on the spacetime
dimensionality $D$. We observe that the size of the universe undergoes stiff
explosion with different types of slope depending on $D$. Moreover the scale
factor of the universe at present is shown to approach to a saturated value,
which is independent of $D$ and is the same as that in the $D=4$
Friedmann-Robertson-Walker cosmology. The photon size and phantom field
strength in the greater dimensionality are also shown to be larger and lower
than those in the smaller one, respectively. Next the photon size at present
$b_{*}$ in $D=5$ is numerically shown to be extremely small, namely
$b_{*}=6.08\times 10^{-216}$ cm, comparing to $b_{*}=1.56\times 10^{-63}$ cm in
$D=10$. In contrast, the phantom field strength at present $\sigma_{*}$ is
shown to be relatively large $\sigma_{*}=4.72\times 10^{24}$ (dyne$)^{1/2}$ in
$D=5$, comparing to $\sigma_{*}=1.39\times 10^{22}$ (dyne$)^{1/2}$ in $D=10$.
| [
{
"created": "Sat, 12 Jul 2014 23:19:28 GMT",
"version": "v1"
},
{
"created": "Sun, 5 Apr 2015 08:34:23 GMT",
"version": "v2"
},
{
"created": "Fri, 25 Jun 2021 06:49:23 GMT",
"version": "v3"
}
] | 2021-06-28 | [
[
"Hong",
"Soon-Tae",
""
]
] | We study a higher dimensional cosmology with phantom field associated with a negative kinetic term. Assuming that the universe possesses the phantom field defined in $D$ dimensional spacetime, we investigate in detail the solutions involved in the higher dimensional phantom cosmology, to explicitly predict photon size and phantom field strength at present in nature. To be specific, we find that the photon size decreases drastically at the early stage of the universe after the Big Bang. Next we explicitly demonstrate the dependences of the photon size, universe size and phantom field strength on the spacetime dimensionality $D$. We observe that the size of the universe undergoes stiff explosion with different types of slope depending on $D$. Moreover the scale factor of the universe at present is shown to approach to a saturated value, which is independent of $D$ and is the same as that in the $D=4$ Friedmann-Robertson-Walker cosmology. The photon size and phantom field strength in the greater dimensionality are also shown to be larger and lower than those in the smaller one, respectively. Next the photon size at present $b_{*}$ in $D=5$ is numerically shown to be extremely small, namely $b_{*}=6.08\times 10^{-216}$ cm, comparing to $b_{*}=1.56\times 10^{-63}$ cm in $D=10$. In contrast, the phantom field strength at present $\sigma_{*}$ is shown to be relatively large $\sigma_{*}=4.72\times 10^{24}$ (dyne$)^{1/2}$ in $D=5$, comparing to $\sigma_{*}=1.39\times 10^{22}$ (dyne$)^{1/2}$ in $D=10$. |
gr-qc/9507022 | Ken-ichi Nakao | Ken-ichi Nakao | On a Quasi-Local Energy Outside the Cosmological Horizon | 5 pages, uuencode compressed latex | null | null | KUNS-1352 | gr-qc | null | We investigate a quasi-local energy naturally introduced by Kodama's
prescription for a spherically symmetric space-time with a positive
cosmological constant $\Lambda$. We find that this quasi-local energy is well
behaved inside a cosmological horizon. However, when there is a scalar field
with a long enough Compton wavelength, the quasi-local energy diverges in the
course of its time evolution outside the cosmological horizon. This means that
the quasi-local energy has a meaning only inside the cosmological horizon.
| [
{
"created": "Tue, 11 Jul 1995 11:18:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Nakao",
"Ken-ichi",
""
]
] | We investigate a quasi-local energy naturally introduced by Kodama's prescription for a spherically symmetric space-time with a positive cosmological constant $\Lambda$. We find that this quasi-local energy is well behaved inside a cosmological horizon. However, when there is a scalar field with a long enough Compton wavelength, the quasi-local energy diverges in the course of its time evolution outside the cosmological horizon. This means that the quasi-local energy has a meaning only inside the cosmological horizon. |
0805.2813 | Sean A. Hayward | Sean A. Hayward | Energy of gravitational radiation in plane-symmetric space-times | 7 REVTeX4 pages | Phys.Rev.D78:044027,2008 | 10.1103/PhysRevD.78.044027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational radiation in plane-symmetric space-times can be encoded in a
complex potential, satisfying a non-linear wave equation. An effective energy
tensor for the radiation is given, taking a scalar-field form in terms of the
potential, entering the field equations in the same way as the matter energy
tensor. It reduces to the Isaacson energy tensor in the linearized,
high-frequency approximation. An energy conservation equation is derived for a
quasi-local energy, essentially the Hawking energy. A transverse pressure
exerted by interacting low-frequency gravitational radiation is predicted.
| [
{
"created": "Mon, 19 May 2008 08:43:46 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Hayward",
"Sean A.",
""
]
] | Gravitational radiation in plane-symmetric space-times can be encoded in a complex potential, satisfying a non-linear wave equation. An effective energy tensor for the radiation is given, taking a scalar-field form in terms of the potential, entering the field equations in the same way as the matter energy tensor. It reduces to the Isaacson energy tensor in the linearized, high-frequency approximation. An energy conservation equation is derived for a quasi-local energy, essentially the Hawking energy. A transverse pressure exerted by interacting low-frequency gravitational radiation is predicted. |
gr-qc/0608139 | Andrea Geralico | D. Bini, A. Geralico, R. Ruffini | On the equilibrium of a charged massive particle in the field of a
Reissner-Nordstr\"om black hole | 9 pages, els macros | Phys.Lett.A360:515-517,2007 | 10.1016/j.physleta.2006.09.028 | null | gr-qc astro-ph | null | The multiyear problem of a two-body system consisting of a
Reissner-Nordstr\"om black hole and a charged massive particle at rest is here
solved by an exact perturbative solution of the full Einstein-Maxwell system of
equations. The expressions of the metric and of the electromagnetic field,
including the effects of the electromagnetically induced gravitational
perturbation and of the gravitationally induced electromagnetic perturbation,
are presented in closed analytic formulas.
| [
{
"created": "Thu, 31 Aug 2006 13:40:33 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Bini",
"D.",
""
],
[
"Geralico",
"A.",
""
],
[
"Ruffini",
"R.",
""
]
] | The multiyear problem of a two-body system consisting of a Reissner-Nordstr\"om black hole and a charged massive particle at rest is here solved by an exact perturbative solution of the full Einstein-Maxwell system of equations. The expressions of the metric and of the electromagnetic field, including the effects of the electromagnetically induced gravitational perturbation and of the gravitationally induced electromagnetic perturbation, are presented in closed analytic formulas. |
1411.2854 | Marios Christodoulou | Marios Christodoulou and Carlo Rovelli | How big is a black hole? | 7 pages, 5 figures. References added | Phys. Rev. D 91, 064046 (2015) | 10.1103/PhysRevD.91.064046 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The 3d volume inside a spherical black hole can be defined by extending an
intrinsic flat-spacetime characterization of the volume inside a 2-sphere. For
a collapsed object, the volume grows with time since the collapse, reaching a
simple asymptotic form, which has a compelling geometrical interpretation.
Perhaps surprising, it is large. The result may have relevance for the
discussion on the information paradox.
| [
{
"created": "Tue, 11 Nov 2014 15:36:39 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Jan 2015 20:00:57 GMT",
"version": "v2"
},
{
"created": "Mon, 16 Mar 2015 18:56:28 GMT",
"version": "v3"
}
] | 2015-03-25 | [
[
"Christodoulou",
"Marios",
""
],
[
"Rovelli",
"Carlo",
""
]
] | The 3d volume inside a spherical black hole can be defined by extending an intrinsic flat-spacetime characterization of the volume inside a 2-sphere. For a collapsed object, the volume grows with time since the collapse, reaching a simple asymptotic form, which has a compelling geometrical interpretation. Perhaps surprising, it is large. The result may have relevance for the discussion on the information paradox. |
1906.05978 | Zack Carson | Zack Carson, Andrew W. Steiner, Kent Yagi | Future Prospects for Constraining Nuclear Matter Parameters with
Gravitational Waves | 16 pages, 17 figures; new citations, hybrid star discussion paragraph
added; Used conditional probability distributions on tidal deformability and
nuclear parameters, rather than the two-dimensional PDFs | Phys. Rev. D 100, 023012 (2019) | 10.1103/PhysRevD.100.023012 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational wave emission from the merging binary neutron star system
GW170817 arrived full of tidal information which can be used to probe the
fundamental ultra-dense nuclear physics residing in these stars. In previous
work, we used two-dimensional correlations between nuclear matter parameters
and tidal deformabilities of neutron stars applying specifically to GW170817 to
derive constraints on the former. Here, we extend this analysis by finding
similar correlations for varying chirp masses, the dominant determining factor
in the frequency evolution of the inspiral, such that one can apply the same
method to future detections. We estimate how accurately one can measure nuclear
parameters with future gravitational wave interferometers and show how such
measurements can be improved by combining multiple events. We find that bounds
on the nuclear parameters with future observations can improve from the current
one with GW170817 only by $\sim 30\%$ due to the existence of systematic errors
caused mainly by the remaining uncertainty in the equation of state near and
just above the nuclear saturation density. We show that such systematic errors
can be reduced by considering multidimensional correlations among nuclear
parameters and tidal deformabilities with various neutron star masses.
| [
{
"created": "Fri, 14 Jun 2019 01:24:20 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Jul 2019 13:38:51 GMT",
"version": "v2"
},
{
"created": "Tue, 22 Sep 2020 07:12:55 GMT",
"version": "v3"
}
] | 2020-09-23 | [
[
"Carson",
"Zack",
""
],
[
"Steiner",
"Andrew W.",
""
],
[
"Yagi",
"Kent",
""
]
] | The gravitational wave emission from the merging binary neutron star system GW170817 arrived full of tidal information which can be used to probe the fundamental ultra-dense nuclear physics residing in these stars. In previous work, we used two-dimensional correlations between nuclear matter parameters and tidal deformabilities of neutron stars applying specifically to GW170817 to derive constraints on the former. Here, we extend this analysis by finding similar correlations for varying chirp masses, the dominant determining factor in the frequency evolution of the inspiral, such that one can apply the same method to future detections. We estimate how accurately one can measure nuclear parameters with future gravitational wave interferometers and show how such measurements can be improved by combining multiple events. We find that bounds on the nuclear parameters with future observations can improve from the current one with GW170817 only by $\sim 30\%$ due to the existence of systematic errors caused mainly by the remaining uncertainty in the equation of state near and just above the nuclear saturation density. We show that such systematic errors can be reduced by considering multidimensional correlations among nuclear parameters and tidal deformabilities with various neutron star masses. |
1208.5756 | Andrei Lebed G | Andrei G. Lebed | Breakdown of the Equivalence between Passive Gravitational Mass and
Energy for a Quantum Body | Talk at the 13th Marcel Grossmann Meeting on General Relativity
(Stockholm, Sweden, 1-7 July 2012), to be published in the proceedings of the
Meeting | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that passive gravitational mass operator of a hydrogen atom in
the post-Newtonian approximation of the general relativity does not commute
with its energy operator, taken in the absence of gravitational field.
Nevertheless, the equivalence between the expectation values of passive
gravitational mass and energy is shown to survive at a macroscopic level for
stationary quantum states. Breakdown of the equivalence between passive
gravitational mass and energy at a microscopic level for stationary quantum
states can be experimentally detected by studying unusual electromagnetic
radiation, emitted by the atoms, supported and moved in the Earth gravitational
field with constant velocity using spacecraft or satellite.
| [
{
"created": "Mon, 27 Aug 2012 17:43:38 GMT",
"version": "v1"
}
] | 2012-08-29 | [
[
"Lebed",
"Andrei G.",
""
]
] | It is shown that passive gravitational mass operator of a hydrogen atom in the post-Newtonian approximation of the general relativity does not commute with its energy operator, taken in the absence of gravitational field. Nevertheless, the equivalence between the expectation values of passive gravitational mass and energy is shown to survive at a macroscopic level for stationary quantum states. Breakdown of the equivalence between passive gravitational mass and energy at a microscopic level for stationary quantum states can be experimentally detected by studying unusual electromagnetic radiation, emitted by the atoms, supported and moved in the Earth gravitational field with constant velocity using spacecraft or satellite. |
1107.3705 | Hayato Motohashi | Hayato Motohashi, Teruaki Suyama | Black hole perturbation in parity violating gravitational theories | 17 pages; v2: References and physical discussion added, results
unchanged, matches published version in PRD | Phys. Rev. D 84, 084041 (2011) | 10.1103/PhysRevD.84.084041 | RESCEU-27/11 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study linear perturbations around the static and spherically symmetric
spacetime for the gravitational theories whose Lagrangian depends on Ricci
scalar and the parity violating Chern-Simons term. By an explicit construction,
we show that Hamiltonian for the perturbation variables is not bounded from
below in general, suggesting that such a background spacetime is unstable
against perturbations. This gives a strong limit on a phenomenological
gravitational model which violates parity. We also provide a necessary and
sufficient condition for the theory to belong to a special class in which no
such instability occurs. For such theories, the number of propagating modes for
$\ell \ge 2$ is three, one from the odd and the other two from the even. Unlike
in the case of $f(R)$ theories, those modes are coupled each other, which can
be used as a distinctive feature to test the parity violating theories from
observations. All the modes propagate at the speed of light. No-ghost condition
and no-tachyon condition are the same as those in $f(R)$ theories. For the
dipole perturbations, the odd and the even modes completely decouple. The odd
mode gives a slowly-rotating BH solution whose metric is linearized in its
angular momentum. We provide an integral expression of such a solution. On the
other hand, the even mode propagates at the speed of light. For the monopole
perturbation, in addition to a mode which just shifts the mass of the
background BH, there is also one even mode that propagates at the speed of
light.
| [
{
"created": "Tue, 19 Jul 2011 13:00:08 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Dec 2011 04:53:48 GMT",
"version": "v2"
}
] | 2011-12-15 | [
[
"Motohashi",
"Hayato",
""
],
[
"Suyama",
"Teruaki",
""
]
] | We study linear perturbations around the static and spherically symmetric spacetime for the gravitational theories whose Lagrangian depends on Ricci scalar and the parity violating Chern-Simons term. By an explicit construction, we show that Hamiltonian for the perturbation variables is not bounded from below in general, suggesting that such a background spacetime is unstable against perturbations. This gives a strong limit on a phenomenological gravitational model which violates parity. We also provide a necessary and sufficient condition for the theory to belong to a special class in which no such instability occurs. For such theories, the number of propagating modes for $\ell \ge 2$ is three, one from the odd and the other two from the even. Unlike in the case of $f(R)$ theories, those modes are coupled each other, which can be used as a distinctive feature to test the parity violating theories from observations. All the modes propagate at the speed of light. No-ghost condition and no-tachyon condition are the same as those in $f(R)$ theories. For the dipole perturbations, the odd and the even modes completely decouple. The odd mode gives a slowly-rotating BH solution whose metric is linearized in its angular momentum. We provide an integral expression of such a solution. On the other hand, the even mode propagates at the speed of light. For the monopole perturbation, in addition to a mode which just shifts the mass of the background BH, there is also one even mode that propagates at the speed of light. |
1409.2115 | Qing-Yu Cai | Dongshan He and Qing-yu Cai | Inflation of small true vacuum bubble by quantization of
Einstein-Hilbert action | Final version | Science China 58, 079801 (2015) | 10.1007/s11433-015-5659-6 | null | gr-qc astro-ph.CO hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the quantization of the Einstein-Hilbert action for a small true
vacuum bubble without matter or scalar field. The quantization of action
induces an extra term of potential called quantum potential in Hamilton-Jacobi
equation, which gives expanding solutions including the exponential expansion
solutions of the scalar factor $a$ for the bubble. We show that exponential
expansion of the bubble continues with a short period (about a Planck time
$t_p$), no matter whether the bubble is closed, flat or open. The exponential
expansion ends spontaneously when the bubble becomes large, i.e., the scalar
factor $a$ of the bubble approaches a Planck length $l_p$. We show that it is
quantum potential of the small true vacuum bubble that plays the role of the
scalar field potential suggested in the slow-roll inflation model. With the
picture of quantum tunneling, we calculate particle creation rate during
inflation, which shows that particles created by inflation have the capability
of reheating the universe.
| [
{
"created": "Sun, 7 Sep 2014 13:02:42 GMT",
"version": "v1"
},
{
"created": "Sun, 29 Mar 2015 11:47:29 GMT",
"version": "v2"
}
] | 2015-03-31 | [
[
"He",
"Dongshan",
""
],
[
"Cai",
"Qing-yu",
""
]
] | We study the quantization of the Einstein-Hilbert action for a small true vacuum bubble without matter or scalar field. The quantization of action induces an extra term of potential called quantum potential in Hamilton-Jacobi equation, which gives expanding solutions including the exponential expansion solutions of the scalar factor $a$ for the bubble. We show that exponential expansion of the bubble continues with a short period (about a Planck time $t_p$), no matter whether the bubble is closed, flat or open. The exponential expansion ends spontaneously when the bubble becomes large, i.e., the scalar factor $a$ of the bubble approaches a Planck length $l_p$. We show that it is quantum potential of the small true vacuum bubble that plays the role of the scalar field potential suggested in the slow-roll inflation model. With the picture of quantum tunneling, we calculate particle creation rate during inflation, which shows that particles created by inflation have the capability of reheating the universe. |
gr-qc/9607011 | Fernando Barbero | J. F. Barbero G., A. Dominguez, T. Goldman and J. Perez-Mercader | Dynamical Critical Phenomena and Large Scale Structure of the Universe:
the Power Spectrum for Density Fluctuations | 13 pages with 2 encapsulated PostScript figures included, gzipped tar
format | null | 10.1209/epl/i1997-00296-0 | LAEFF-96/15 | gr-qc astro-ph | null | As is well known, structure formation in the Universe at times after
decoupling can be described by hydrodynamic equations. These are shown here to
be equivalent to a generalization of the stochastic Kardar--Parisi--Zhang
equation with time-- dependent viscosity in epochs of dissipation. As a
consequence of the Dynamical Critical Scaling induced by noise and
fluctuations, these equations describe the fractal behavior (with a scale
dependent fractal dimension) observed at the smaller scales for the
galaxy--to--galaxy correlation function and $also$ the Harrison--Zel'dovich
spectrum at decoupling. By a Renormalization Group calculation of the
two--point correlation function between galaxies in the presence of (i) the
expansion of the Universe and (ii) non--equilibrium, we can account, from first
principles, for the main features of the observed shape of the power spectrum.
| [
{
"created": "Thu, 4 Jul 1996 10:33:36 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"G.",
"J. F. Barbero",
""
],
[
"Dominguez",
"A.",
""
],
[
"Goldman",
"T.",
""
],
[
"Perez-Mercader",
"J.",
""
]
] | As is well known, structure formation in the Universe at times after decoupling can be described by hydrodynamic equations. These are shown here to be equivalent to a generalization of the stochastic Kardar--Parisi--Zhang equation with time-- dependent viscosity in epochs of dissipation. As a consequence of the Dynamical Critical Scaling induced by noise and fluctuations, these equations describe the fractal behavior (with a scale dependent fractal dimension) observed at the smaller scales for the galaxy--to--galaxy correlation function and $also$ the Harrison--Zel'dovich spectrum at decoupling. By a Renormalization Group calculation of the two--point correlation function between galaxies in the presence of (i) the expansion of the Universe and (ii) non--equilibrium, we can account, from first principles, for the main features of the observed shape of the power spectrum. |
2205.15207 | Phongpichit Channuie | Narakorn Kaewkhao (Prince Songkla U.), Phongpichit Channuie (Walailak
U.) | Adiabatic invariant approach on Friedmann cyclic universe | v1: 5 pages, no figure | Nucl.Phys.B 987 (2023) 116088 | 10.1016/j.nuclphysb.2023.116088 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Oscillating or cyclic models of the universe were inspired by Friedmann's
seminal paper of 1922. The model supposes a closed universe. In this work, we
study Friedmann closed universe using the adiabatic invariant approach. We
start revisiting the cosmological force proposed by N. Rosen and derive the
Lagrangian density from Rosen's concepts of cosmological force. Importantly, we
introduce the Noether gauge symmetry followed by the Rund-Traumann identity
(RTI) and adiabatic invariant approach to examine the cyclic models. We
consider a single component form of relativistic matter (stiff matter) at
$a(t=0)$ and $a(t=T)$, and surprisingly discover the world period is given by
$\sim 15.8$ Gy which is very close to that computed using the Friedmann's
formula for the cyclic universe.
| [
{
"created": "Mon, 30 May 2022 16:03:58 GMT",
"version": "v1"
}
] | 2023-01-24 | [
[
"Kaewkhao",
"Narakorn",
"",
"Prince Songkla U."
],
[
"Channuie",
"Phongpichit",
"",
"Walailak\n U."
]
] | Oscillating or cyclic models of the universe were inspired by Friedmann's seminal paper of 1922. The model supposes a closed universe. In this work, we study Friedmann closed universe using the adiabatic invariant approach. We start revisiting the cosmological force proposed by N. Rosen and derive the Lagrangian density from Rosen's concepts of cosmological force. Importantly, we introduce the Noether gauge symmetry followed by the Rund-Traumann identity (RTI) and adiabatic invariant approach to examine the cyclic models. We consider a single component form of relativistic matter (stiff matter) at $a(t=0)$ and $a(t=T)$, and surprisingly discover the world period is given by $\sim 15.8$ Gy which is very close to that computed using the Friedmann's formula for the cyclic universe. |
gr-qc/9412011 | Takahiro Tanaka | Kazuhiro Yamamoto, Takahiro Tanaka and Misao Sasaki | Particle Spectrum Created Through Bubble Nucleation | 14 pages, revtex file, 4 uuencoded compressed postscript figures
appended at the end | Phys.Rev.D51:2968-2978,1995 | 10.1103/PhysRevD.51.2968 | KUNS 1305 | gr-qc | null | Using the multi-dimensional wave function formalism, we investigate the
quantum state of a scalar field inside a true vacuum bubble nucleated through
false vacuum decay in flat spacetime. We developed a formalism which allows us
a mode-by-mode analysis. To demonstrate its advantage, we describe in detail
the evolution of the quantum state during the tunneling process in terms of
individual mode functions and interpret the result in the language of particle
creation. The spectrum of the created particles is examined based on quantum
field theory in the Milne universe.
| [
{
"created": "Sat, 3 Dec 1994 09:42:29 GMT",
"version": "v1"
}
] | 2009-10-09 | [
[
"Yamamoto",
"Kazuhiro",
""
],
[
"Tanaka",
"Takahiro",
""
],
[
"Sasaki",
"Misao",
""
]
] | Using the multi-dimensional wave function formalism, we investigate the quantum state of a scalar field inside a true vacuum bubble nucleated through false vacuum decay in flat spacetime. We developed a formalism which allows us a mode-by-mode analysis. To demonstrate its advantage, we describe in detail the evolution of the quantum state during the tunneling process in terms of individual mode functions and interpret the result in the language of particle creation. The spectrum of the created particles is examined based on quantum field theory in the Milne universe. |
1011.4249 | Alejandro Corichi | Alejandro Corichi and Asieh Karami | On the measure problem in slow roll inflation and loop quantum cosmology | 14 pages, 3 figures. Typos corrected, discussion expanded. Version to
be published in PRD | Phys.Rev.D83:104006,2011 | 10.1103/PhysRevD.83.104006 | IGC-11/2-2 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the measure problem in standard slow-roll inflationary models
from the perspective of loop quantum cosmology (LQC). Following recent results
by Ashtekar and Sloan, we study the probability of having enough e-foldings and
focus on its dependence on the quantum gravity scale, including the transition
of the theory to the limit where general relativity (GR) is recovered. Contrary
to the standard expectation, the probability of having enough inflation, that
is close to one in LQC, grows and tends to 1 as one approaches the GR limit. We
study the origin of the tension between these results with those by Gibbons and
Turok, and offer an explanation that brings these apparent contradictory
results into a coherent picture. As we show, the conflicting results stem from
different choices of initial conditions for the computation of probability. The
singularity free scenario of loop quantum cosmology offers a natural choice of
initial conditions, and suggests that enough inflation is generic.
| [
{
"created": "Thu, 18 Nov 2010 18:26:32 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Apr 2011 22:56:36 GMT",
"version": "v2"
}
] | 2011-05-12 | [
[
"Corichi",
"Alejandro",
""
],
[
"Karami",
"Asieh",
""
]
] | We consider the measure problem in standard slow-roll inflationary models from the perspective of loop quantum cosmology (LQC). Following recent results by Ashtekar and Sloan, we study the probability of having enough e-foldings and focus on its dependence on the quantum gravity scale, including the transition of the theory to the limit where general relativity (GR) is recovered. Contrary to the standard expectation, the probability of having enough inflation, that is close to one in LQC, grows and tends to 1 as one approaches the GR limit. We study the origin of the tension between these results with those by Gibbons and Turok, and offer an explanation that brings these apparent contradictory results into a coherent picture. As we show, the conflicting results stem from different choices of initial conditions for the computation of probability. The singularity free scenario of loop quantum cosmology offers a natural choice of initial conditions, and suggests that enough inflation is generic. |
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