id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1210.2805 | Puxun Wu | Jun Chen, Puxun Wu, Hongwei Yu, and Zhengxiang Li | Is the Cosmic Transparency Spatially Homogeneous? | 10 pages, 1 figure. Accepted for publication in JCAP on Sept. 26 | null | 10.1088/1475-7516/2012/10/029 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the constraints on the cosmic opacity using the latest BAO and
Union2 SNIa data in this paper and find that the best fit values seem to
indicate that an opaque universe is preferred in redshift regions $0.20-0.35$,
$0.35-0.44$ and $0.60-0.73$, whereas, a transparent universe is favored in
redshift regions $0.106-0.20$, $0.44-0.57$and $0.57-0.60$. However, our result
is still consistent with a transparent universe at the 1$\sigma$ confidence
level, even though the best-fit cosmic opacity oscillates between zero and some
nonzero values as the redshift varies.
| [
{
"created": "Wed, 10 Oct 2012 05:08:31 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Chen",
"Jun",
""
],
[
"Wu",
"Puxun",
""
],
[
"Yu",
"Hongwei",
""
],
[
"Li",
"Zhengxiang",
""
]
] | We study the constraints on the cosmic opacity using the latest BAO and Union2 SNIa data in this paper and find that the best fit values seem to indicate that an opaque universe is preferred in redshift regions $0.20-0.35$, $0.35-0.44$ and $0.60-0.73$, whereas, a transparent universe is favored in redshift regions $0.106-0.20$, $0.44-0.57$and $0.57-0.60$. However, our result is still consistent with a transparent universe at the 1$\sigma$ confidence level, even though the best-fit cosmic opacity oscillates between zero and some nonzero values as the redshift varies. |
2403.15355 | Xian Gao | Zhi-Chao Wang, Xian Gao | Spatial covariant gravity with two degrees of freedom in the presence of
an auxiliary scalar field: perturbation analysis | 17 pages, no figure | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate a class of gravity theories respecting only spatial
covariance, termed spatially covariant gravity, in the presence of an auxiliary
scalar field. We examine the conditions on the Lagrangian required to eliminate
scalar degrees of freedom, allowing only two tensorial degrees of freedom to
propagate. Instead of strict constraint analysis, in this work, we employ the
perturbation method and focus on the necessary conditions to evade the scalar
mode at linear order in perturbations around a cosmological background.
Starting from a general action and solving the auxiliary perturbation variables
in terms of the would-be dynamical scalar mode, we derive the condition to
remove its kinetic term, thus ensuring that no scalar mode propagates. As an
application of the general condition, we study a polynomial-type Lagrangian as
a concrete example, in which all the monomials are spatially covariant scalars
containing two derivatives. We find that the auxiliary scalar field plays a
nontrivial role, and new terms in the Lagrangian are allowed. Our analysis
sheds light on constructing gravity theories with two degrees of freedom in the
extended framework of spatially covariant gravity.
| [
{
"created": "Fri, 22 Mar 2024 17:10:00 GMT",
"version": "v1"
}
] | 2024-03-25 | [
[
"Wang",
"Zhi-Chao",
""
],
[
"Gao",
"Xian",
""
]
] | We investigate a class of gravity theories respecting only spatial covariance, termed spatially covariant gravity, in the presence of an auxiliary scalar field. We examine the conditions on the Lagrangian required to eliminate scalar degrees of freedom, allowing only two tensorial degrees of freedom to propagate. Instead of strict constraint analysis, in this work, we employ the perturbation method and focus on the necessary conditions to evade the scalar mode at linear order in perturbations around a cosmological background. Starting from a general action and solving the auxiliary perturbation variables in terms of the would-be dynamical scalar mode, we derive the condition to remove its kinetic term, thus ensuring that no scalar mode propagates. As an application of the general condition, we study a polynomial-type Lagrangian as a concrete example, in which all the monomials are spatially covariant scalars containing two derivatives. We find that the auxiliary scalar field plays a nontrivial role, and new terms in the Lagrangian are allowed. Our analysis sheds light on constructing gravity theories with two degrees of freedom in the extended framework of spatially covariant gravity. |
1406.0358 | Manuel Tessmer | Manuel Tessmer and Gerhard Sch\"afer | Eccentric Motion of Spinning Compact Binaries | 15 pages, 1 figure | Phys. Rev. D 89, 104055 (2014) | 10.1103/PhysRevD.89.104055 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The equations of motion for spinning compact binaries on eccentric orbits are
treated perturbatively in powers of a fractional mass-difference ordering
parameter. The solution is valid through first order in the mass-difference
parameter. A canonical point transformation removes the leading order terms of
the spin-orbit Hamiltonian which induce a wiggling precession of the orbital
angular momentum around the conserved total angular momentum, a precession
which disappears in the case of equal masses or one single spin. Action-angle
variables are applied which make a canonical perturbation theory easily
treatable.
| [
{
"created": "Mon, 2 Jun 2014 13:21:04 GMT",
"version": "v1"
}
] | 2014-06-03 | [
[
"Tessmer",
"Manuel",
""
],
[
"Schäfer",
"Gerhard",
""
]
] | The equations of motion for spinning compact binaries on eccentric orbits are treated perturbatively in powers of a fractional mass-difference ordering parameter. The solution is valid through first order in the mass-difference parameter. A canonical point transformation removes the leading order terms of the spin-orbit Hamiltonian which induce a wiggling precession of the orbital angular momentum around the conserved total angular momentum, a precession which disappears in the case of equal masses or one single spin. Action-angle variables are applied which make a canonical perturbation theory easily treatable. |
2102.06213 | Ivica Smoli\'c | Ana Bokuli\'c, Tajron Juri\'c, Ivica Smoli\'c | Black hole thermodynamics in the presence of nonlinear electromagnetic
fields | 20 pages (two columns), 2 figures; ver.3: version accepted for
publication in Physical Review D (several additional technical comments and
references; one paragraph added to the "Discussion") | Phys. Rev. D 103, 124059 (2021) | 10.1103/PhysRevD.103.124059 | ZTF-EP-21-02; RBI-ThPhys-2021-6 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As the interaction between the black holes and highly energetic infalling
charged matter receives quantum corrections, the basic laws of black hole
mechanics have to be carefully rederived. Using the covariant phase space
formalism, we generalize the first law of black hole mechanics, both
"equilibrium state" and "physical process" versions, in the presence of
nonlinear electrodynamics fields, defined by Lagrangians depending on both
quadratic electromagnetic invariants, $F_{ab}F^{ab}$ and $F_{ab}\,{\star
F}^{ab}$. Derivation of this law demands a specific treatment of the Lagrangian
parameters, similar to embedding of the cosmological constant into
thermodynamic context. Furthermore, we discuss the validity of energy
conditions, several complementing proofs of the zeroth law of black hole
electrodynamics and some aspects of the recently generalized Smarr formula, its
(non-)linearity and relation to the first law.
| [
{
"created": "Thu, 11 Feb 2021 19:00:03 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Mar 2021 20:00:28 GMT",
"version": "v2"
},
{
"created": "Fri, 25 Jun 2021 19:45:10 GMT",
"version": "v3"
}
] | 2021-06-29 | [
[
"Bokulić",
"Ana",
""
],
[
"Jurić",
"Tajron",
""
],
[
"Smolić",
"Ivica",
""
]
] | As the interaction between the black holes and highly energetic infalling charged matter receives quantum corrections, the basic laws of black hole mechanics have to be carefully rederived. Using the covariant phase space formalism, we generalize the first law of black hole mechanics, both "equilibrium state" and "physical process" versions, in the presence of nonlinear electrodynamics fields, defined by Lagrangians depending on both quadratic electromagnetic invariants, $F_{ab}F^{ab}$ and $F_{ab}\,{\star F}^{ab}$. Derivation of this law demands a specific treatment of the Lagrangian parameters, similar to embedding of the cosmological constant into thermodynamic context. Furthermore, we discuss the validity of energy conditions, several complementing proofs of the zeroth law of black hole electrodynamics and some aspects of the recently generalized Smarr formula, its (non-)linearity and relation to the first law. |
2302.05173 | Stavros Venikoudis | F.P. Fronimos (Aristotle U., Thessaloniki), S.A. Venikoudis (Aristotle
U., Thessaloniki) | Inflationary phenomenology of non-minimally coupled
Einstein-Chern-Simons gravity | null | null | null | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work we investigate the inflationary era in the presence of a
canonical scalar field and Chern-Simons parity violating corrections. It was
also assumed that a non minimal coupling between curvature and the scalar field
is present. For the shake of completeness, the slow-roll and the constant-roll
scenarios were examined separately. In the context of this scalar-tensor
theory, inflation can be viable for both scenarios since the observational
indices take acceptable values according to the most recent Planck data.
Furthermore, the involvement of the Chern-Simons term has no effect on the
background equations, in contrast to the scalar function which couples with the
Ricci scalar and participates in the equations of motion. However, the
Chern-Simons term ensures the chirality of stochastic gravitational waves. A
blue-tilted tensor spectral index of primordial curvature perturbations can be
manifested since, tensor modes are strongly affected by the Chern-Simons term.
Lastly, the Swampland criteria and the Lyth-bound were examined in order to
distinguish the effective field theories towards the path of a consistent
M-theory.
| [
{
"created": "Fri, 10 Feb 2023 11:08:17 GMT",
"version": "v1"
}
] | 2023-02-13 | [
[
"Fronimos",
"F. P.",
"",
"Aristotle U., Thessaloniki"
],
[
"Venikoudis",
"S. A.",
"",
"Aristotle\n U., Thessaloniki"
]
] | In this work we investigate the inflationary era in the presence of a canonical scalar field and Chern-Simons parity violating corrections. It was also assumed that a non minimal coupling between curvature and the scalar field is present. For the shake of completeness, the slow-roll and the constant-roll scenarios were examined separately. In the context of this scalar-tensor theory, inflation can be viable for both scenarios since the observational indices take acceptable values according to the most recent Planck data. Furthermore, the involvement of the Chern-Simons term has no effect on the background equations, in contrast to the scalar function which couples with the Ricci scalar and participates in the equations of motion. However, the Chern-Simons term ensures the chirality of stochastic gravitational waves. A blue-tilted tensor spectral index of primordial curvature perturbations can be manifested since, tensor modes are strongly affected by the Chern-Simons term. Lastly, the Swampland criteria and the Lyth-bound were examined in order to distinguish the effective field theories towards the path of a consistent M-theory. |
1909.04411 | Tapobrata Sarkar | Sandip Chowdhury, Kunal Pal, Kuntal Pal, Tapobrata Sarkar | Collapse in $f(R)$ gravity and the method of $R$ matching | 19 Pages, 18 figures | null | 10.1140/epjc/s10052-020-08459-w | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Collapsing solutions in $f(R)$ gravity are restricted due to junction
conditions that demand continuity of the Ricci scalar and its normal derivative
across the time-like collapsing hypersurface. These are obtained via the method
of $R$-matching, which is ubiquitous in $f(R)$ collapse scenarios. In this
paper, we study spherically symmetric collapse with the modification term
$\alpha R^2$, and use $R$-matching to exemplify a class of new solutions. After
discussing some mathematical preliminaries by which we obtain an algebraic
relation between the shear and the anisotropy in these theories, we consider
two metric ansatzes. In the first, the collapsing metric is considered to be a
separable function of the co-moving radius and time, and the collapse is
shear-free, and in the second, a non-separable interior solution is considered,
that represents gravitational collapse with non-zero shear viscosity. We arrive
at novel solutions that indicate the formation of black holes or locally naked
singularities, while obeying all the necessary energy conditions. The separable
case allows for a simple analytic expression of the energy-momentum tensor,
that indicates the positivity of the pressures throughout collapse, and is
further used to study the heat flux evolution of the collapsing matter, whose
analytic solutions are presented under certain approximations. These clearly
highlight the role of modified gravity in the examples that we consider.
| [
{
"created": "Tue, 10 Sep 2019 11:19:19 GMT",
"version": "v1"
}
] | 2020-10-28 | [
[
"Chowdhury",
"Sandip",
""
],
[
"Pal",
"Kunal",
""
],
[
"Pal",
"Kuntal",
""
],
[
"Sarkar",
"Tapobrata",
""
]
] | Collapsing solutions in $f(R)$ gravity are restricted due to junction conditions that demand continuity of the Ricci scalar and its normal derivative across the time-like collapsing hypersurface. These are obtained via the method of $R$-matching, which is ubiquitous in $f(R)$ collapse scenarios. In this paper, we study spherically symmetric collapse with the modification term $\alpha R^2$, and use $R$-matching to exemplify a class of new solutions. After discussing some mathematical preliminaries by which we obtain an algebraic relation between the shear and the anisotropy in these theories, we consider two metric ansatzes. In the first, the collapsing metric is considered to be a separable function of the co-moving radius and time, and the collapse is shear-free, and in the second, a non-separable interior solution is considered, that represents gravitational collapse with non-zero shear viscosity. We arrive at novel solutions that indicate the formation of black holes or locally naked singularities, while obeying all the necessary energy conditions. The separable case allows for a simple analytic expression of the energy-momentum tensor, that indicates the positivity of the pressures throughout collapse, and is further used to study the heat flux evolution of the collapsing matter, whose analytic solutions are presented under certain approximations. These clearly highlight the role of modified gravity in the examples that we consider. |
2208.06899 | Marie-No\"elle C\'el\'erier | Marie-No\''elle C\'el\'erier (Observatoire de Paris) | Study of stationary rigidly rotating anisotropic cylindrical fluids with
new exact interior solutions of GR. 4. Radial pressure | 11 pages, 0 figures | null | 10.1063/5.0121169 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | This article belongs to a series where the influence of anisotropic pressure
on the gravitational properties of rigidly rotating fluids is studied using new
exactsolutions of GR constructed for the purpose. For mathematical
simplification, stationarity and cylindrical symmetry implying three Killing
vectors are considered. Moreover, two pressure components are set to vanish in
turn. In Papers 1 and 2 the pressure is axially directed, while it is azimuthal
in Paper 3. In present Paper 4, a radially directed pressure is considered.
Since a generic differential equation, split into three parts, emerges from the
field equations, three different classes of solutions can be considered. Two
could only be partially integrated. The other one, that is fully integrated,
yields a set of solutions with negative pressure. Physical processes where a
negative pressure is encountered are depicted and give a rather solid
foundation to this class of solutions. Moreover, these fully integrated
solutions satisfy the axisymmetry condition while they do not verify the
so-called "regularity condition". But, since their Kretschmann scalar does not
diverge on the axis, this feature must be considered as reporting a mere
coordinate singularity. Finally, the matching of these solutions to an exterior
appropriate vacuum enforce other constraints on the two constant parameters
defining each solution in the class. The results displayed here deserve to be
interpreted in the light of those depicted in the other four papers in the
series.
| [
{
"created": "Sun, 14 Aug 2022 18:59:37 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Aug 2023 08:09:55 GMT",
"version": "v2"
}
] | 2023-08-08 | [
[
"Célérier",
"Marie-No\\''elle",
"",
"Observatoire de Paris"
]
] | This article belongs to a series where the influence of anisotropic pressure on the gravitational properties of rigidly rotating fluids is studied using new exactsolutions of GR constructed for the purpose. For mathematical simplification, stationarity and cylindrical symmetry implying three Killing vectors are considered. Moreover, two pressure components are set to vanish in turn. In Papers 1 and 2 the pressure is axially directed, while it is azimuthal in Paper 3. In present Paper 4, a radially directed pressure is considered. Since a generic differential equation, split into three parts, emerges from the field equations, three different classes of solutions can be considered. Two could only be partially integrated. The other one, that is fully integrated, yields a set of solutions with negative pressure. Physical processes where a negative pressure is encountered are depicted and give a rather solid foundation to this class of solutions. Moreover, these fully integrated solutions satisfy the axisymmetry condition while they do not verify the so-called "regularity condition". But, since their Kretschmann scalar does not diverge on the axis, this feature must be considered as reporting a mere coordinate singularity. Finally, the matching of these solutions to an exterior appropriate vacuum enforce other constraints on the two constant parameters defining each solution in the class. The results displayed here deserve to be interpreted in the light of those depicted in the other four papers in the series. |
gr-qc/9804081 | Mikel Susperregi | Mikel Susperregi (QMW, London), Anupam Mazumdar (U. of Sussex) | Extended Inflation with an Exponential Potential | 6 pages, 2 figures | Phys.Rev.D58:083512,1998 | 10.1103/PhysRevD.58.083512 | null | gr-qc astro-ph | null | In this paper we investigate extended inflation with an exponential potential
$V(\sigma)= V_0 e^{-\kappa\sigma}$, which provides a simple cosmological
scenario where the distribution of the constants of Nature is mostly determined
by $\kappa$. In particular, we show that this theory predicts a uniform
distribution for the Planck mass at the end of inflation, for the entire
ensemble of universes that undergo stochastic inflation. Eternal inflation
takes place in this scenario for a broad family of initial conditions, all of
which lead up to the same value of the Planck mass at the end of inflation. The
predicted value of the Planck mass is consistent with the observed value within
a comfortable range of values of the parameters involved.
| [
{
"created": "Wed, 29 Apr 1998 16:44:09 GMT",
"version": "v1"
}
] | 2011-01-20 | [
[
"Susperregi",
"Mikel",
"",
"QMW, London"
],
[
"Mazumdar",
"Anupam",
"",
"U. of Sussex"
]
] | In this paper we investigate extended inflation with an exponential potential $V(\sigma)= V_0 e^{-\kappa\sigma}$, which provides a simple cosmological scenario where the distribution of the constants of Nature is mostly determined by $\kappa$. In particular, we show that this theory predicts a uniform distribution for the Planck mass at the end of inflation, for the entire ensemble of universes that undergo stochastic inflation. Eternal inflation takes place in this scenario for a broad family of initial conditions, all of which lead up to the same value of the Planck mass at the end of inflation. The predicted value of the Planck mass is consistent with the observed value within a comfortable range of values of the parameters involved. |
0810.5223 | Miodrag Krmar | Vladan Pankovic and Simo Ciganovic | A Simple Determination of the Thermodynamical Characteristics of the
Weakly Charged, Very Thin Black Ring | six pages, no figures | null | null | NS-Ph/18-08 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In our previous work we suggested a very simple, approximate formalism for
description of some basic (especially thermodynamical) characteristics of a
non-charged, rotating, very thin black ring. Here, in our new work,
generalizing our previous results, we suggest a very simple, approximate
description of some basic (especially thermodynamical) characteristics of a
weakly charged, rotating, very thin black ring. (Our formalism is not
theoretically dubious, since, at it is not hard to see, it can represent an
extreme simplification of a more accurate, e.g. Copeland-Lahiri, string
formalism for the black hole description.) Even if suggested formalism is,
generally speaking, phenomenological and rough, obtained final results,
unexpectedly, are non-trivial. Concretely, given formalism reproduces exactly
Bekenstein-Hawking entropy, Bekenstein quantization of the entropy or horizon
area and Hawking temperature of a weakly charged, rotating, very thin black
ring originally obtained earlier using more accurate analysis by Emparan,
Aestefanesei, Radu etc. (Conceptually it is similar to situation in Bohr's
atomic model where energy levels are determined practically exactly even if
electron motion is described roughly.) Our formalism is physically based on the
assumption that circumference of the horizon tube holds the natural (integer)
number of corresponding reduced Compton's wave length. (It is conceptually
similar to Bohr's quantization postulate in Bohr's atomic model interpreted by
de Broglie relation.) Also, we use, mathematically, practically only simple
algebraic equations.
| [
{
"created": "Wed, 29 Oct 2008 09:43:18 GMT",
"version": "v1"
}
] | 2008-10-30 | [
[
"Pankovic",
"Vladan",
""
],
[
"Ciganovic",
"Simo",
""
]
] | In our previous work we suggested a very simple, approximate formalism for description of some basic (especially thermodynamical) characteristics of a non-charged, rotating, very thin black ring. Here, in our new work, generalizing our previous results, we suggest a very simple, approximate description of some basic (especially thermodynamical) characteristics of a weakly charged, rotating, very thin black ring. (Our formalism is not theoretically dubious, since, at it is not hard to see, it can represent an extreme simplification of a more accurate, e.g. Copeland-Lahiri, string formalism for the black hole description.) Even if suggested formalism is, generally speaking, phenomenological and rough, obtained final results, unexpectedly, are non-trivial. Concretely, given formalism reproduces exactly Bekenstein-Hawking entropy, Bekenstein quantization of the entropy or horizon area and Hawking temperature of a weakly charged, rotating, very thin black ring originally obtained earlier using more accurate analysis by Emparan, Aestefanesei, Radu etc. (Conceptually it is similar to situation in Bohr's atomic model where energy levels are determined practically exactly even if electron motion is described roughly.) Our formalism is physically based on the assumption that circumference of the horizon tube holds the natural (integer) number of corresponding reduced Compton's wave length. (It is conceptually similar to Bohr's quantization postulate in Bohr's atomic model interpreted by de Broglie relation.) Also, we use, mathematically, practically only simple algebraic equations. |
1912.11851 | Cameron Bunney | Cameron R. D. Bunney and Gabriele Gradoni | Electromagnetism in Curved Spacetimes: Coupling of the Doppler and
Gravitational Redshifts | 11 pages, 4 figures; v4 typos corrected. In previous versions, the
emitted and observed frequencies were mislabelled in the section
"Gravitational Redshift." | null | 10.1109/MAP.2021.3099714 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the basic prerequisites of electromagnetism in flat spacetime and
provide the description of electromagnetism in terms of the Faraday tensor. We
generalise electromagnetic theory to a general relativistic setting,
introducing the Einstein field equations to describe the propagation of
electromagnetic radiation in curved space-time. We investigate gravitational
redshift and derive formulae for the combined effect of gravitational redshift
and the Doppler shift in curved spacetime.
| [
{
"created": "Thu, 26 Dec 2019 12:19:32 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Sep 2020 18:18:46 GMT",
"version": "v2"
},
{
"created": "Sun, 25 Apr 2021 20:53:46 GMT",
"version": "v3"
},
{
"created": "Thu, 12 Oct 2023 13:53:21 GMT",
"version": "v4"
}
] | 2023-10-13 | [
[
"Bunney",
"Cameron R. D.",
""
],
[
"Gradoni",
"Gabriele",
""
]
] | We present the basic prerequisites of electromagnetism in flat spacetime and provide the description of electromagnetism in terms of the Faraday tensor. We generalise electromagnetic theory to a general relativistic setting, introducing the Einstein field equations to describe the propagation of electromagnetic radiation in curved space-time. We investigate gravitational redshift and derive formulae for the combined effect of gravitational redshift and the Doppler shift in curved spacetime. |
0710.0435 | Shih-Yuin Lin | Shih-Yuin Lin and B. L. Hu | Entanglement, recoherence and information flow in an accelerated
detector - quantum field system: Implications for black hole information
issue | 16 pages, 12 figures; minor changes | Class.Quant.Grav.25:154004,2008 | 10.1088/0264-9381/25/15/154004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study an exactly solvable model where an uniformly accelerated detector is
linearly coupled to a massless scalar field initially in the Minkowski vacuum.
Using the exact correlation functions we show that as soon as the coupling is
switched on one can see information flowing from the detector to the field and
propagating with the radiation into null infinity. By expressing the reduced
density matrix of the detector in terms of the two-point functions, we
calculate the purity function in the detector and study the evolution of
quantum entanglement between the detector and the field. Only in the ultraweak
coupling regime could some degree of recoherence in the detector appear at late
times, but never in full restoration. We explicitly show that under the most
general conditions the detector never recovers its quantum coherence and the
entanglement between the detector and the field remains large at late times. To
the extent this model can be used as an analog to the system of a black hole
interacting with a quantum field, our result seems to suggest in the prevalent
non-Markovian regime, assuming unitarity for the combined system, that black
hole information is not lost but transferred to the quantum field degrees of
freedom. Our combined system will evolve into a highly entangled state between
a remnant of large area (in Bekenstein's black hole atom analog) without any
information of its initial state, and the quantum field, now imbued with
complex information content not-so-easily retrievable by a local observer.
| [
{
"created": "Tue, 2 Oct 2007 03:41:43 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Nov 2007 10:46:19 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Jul 2008 07:21:23 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Lin",
"Shih-Yuin",
""
],
[
"Hu",
"B. L.",
""
]
] | We study an exactly solvable model where an uniformly accelerated detector is linearly coupled to a massless scalar field initially in the Minkowski vacuum. Using the exact correlation functions we show that as soon as the coupling is switched on one can see information flowing from the detector to the field and propagating with the radiation into null infinity. By expressing the reduced density matrix of the detector in terms of the two-point functions, we calculate the purity function in the detector and study the evolution of quantum entanglement between the detector and the field. Only in the ultraweak coupling regime could some degree of recoherence in the detector appear at late times, but never in full restoration. We explicitly show that under the most general conditions the detector never recovers its quantum coherence and the entanglement between the detector and the field remains large at late times. To the extent this model can be used as an analog to the system of a black hole interacting with a quantum field, our result seems to suggest in the prevalent non-Markovian regime, assuming unitarity for the combined system, that black hole information is not lost but transferred to the quantum field degrees of freedom. Our combined system will evolve into a highly entangled state between a remnant of large area (in Bekenstein's black hole atom analog) without any information of its initial state, and the quantum field, now imbued with complex information content not-so-easily retrievable by a local observer. |
2302.11528 | Boran Yesilyurt | R. P. Woodard and B. Yesilyurt | Unfinished Business in A Nonlinear Sigma Model on de Sitter Background | 23 pages, 11 figures, uses LaTeX2e, Version 2 revised for publication
with 5 figures and length of 25 pages | JHEP 06 (2023) 206 | 10.1007/JHEP06(2023)206 | UFIFT-QG-23-03 | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Nonlinear sigma models on de Sitter background possess the same kind of
derivative interactions as gravity, and show the same sorts of large spacetime
logarithms in correlation functions and solutions to the effective field
equations. It was recently demonstrated that these logarithms can be resummed
by combining a variant of Starobinsky's stochastic formalism with a variant of
the renormalization group. This work considers one of these models and
completes two pieces of analysis which were left unfinished: the evolution of
the background at two loop order and the one loop beta function.
| [
{
"created": "Wed, 22 Feb 2023 18:09:39 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Jul 2023 02:43:04 GMT",
"version": "v2"
}
] | 2023-07-06 | [
[
"Woodard",
"R. P.",
""
],
[
"Yesilyurt",
"B.",
""
]
] | Nonlinear sigma models on de Sitter background possess the same kind of derivative interactions as gravity, and show the same sorts of large spacetime logarithms in correlation functions and solutions to the effective field equations. It was recently demonstrated that these logarithms can be resummed by combining a variant of Starobinsky's stochastic formalism with a variant of the renormalization group. This work considers one of these models and completes two pieces of analysis which were left unfinished: the evolution of the background at two loop order and the one loop beta function. |
0707.4513 | Simone Speziale | Bianca Dittrich, Laurent Freidel and Simone Speziale | Linearized dynamics from the 4-simplex Regge action | 16 (+9 Appendix) pages, 1 figure | Phys.Rev.D76:104020,2007 | 10.1103/PhysRevD.76.104020 | pi-qg-48 | gr-qc hep-lat | null | We study the relation between the hessian matrix of the riemannian Reggae
action on a 4-simplex and linearized quantum gravity. We give an explicit
formula for the hessian as a function of the geometry, and show that it has a
single zero mode. We then use a 3d lattice model to show that (i) the zero mode
is a remnant of the continuum diffeomorphism invariance, and (ii) we recover
the complete free graviton propagator in the continuum limit. The results help
clarify the structure of the boundary state needed in the recent calculations
of the graviton propagator in loop quantum gravity, and in particular its role
in fixing the gauge.
| [
{
"created": "Tue, 31 Jul 2007 00:28:40 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Dittrich",
"Bianca",
""
],
[
"Freidel",
"Laurent",
""
],
[
"Speziale",
"Simone",
""
]
] | We study the relation between the hessian matrix of the riemannian Reggae action on a 4-simplex and linearized quantum gravity. We give an explicit formula for the hessian as a function of the geometry, and show that it has a single zero mode. We then use a 3d lattice model to show that (i) the zero mode is a remnant of the continuum diffeomorphism invariance, and (ii) we recover the complete free graviton propagator in the continuum limit. The results help clarify the structure of the boundary state needed in the recent calculations of the graviton propagator in loop quantum gravity, and in particular its role in fixing the gauge. |
1712.00483 | Joel Berg\'e | Joel Berg\'e, Philippe Brax, Gilles M\'etris, Martin Pernot-Borr\`as,
Pierre Touboul, Jean-Philippe Uzan | MICROSCOPE mission: first constraints on the violation of the weak
equivalence principle by a light scalar dilaton | Matches publlished version. Supplemental material added | Phys. Rev. Lett. 120, 141101 (2018) | 10.1103/PhysRevLett.120.141101 | null | gr-qc astro-ph.CO hep-ex | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The existence of a light or massive scalar field with a coupling to matter
weaker than gravitational strength is a possible source of violation of the
weak equivalence principle. We use the first results on the E\"otv\"os
parameter by the MICROSCOPE experiment to set new constraints on such scalar
fields. For a massive scalar field of mass smaller than $10^{-12}$ eV (i.e.
range larger than a few $10^5$ m) we improve existing constraints by one order
of magnitude to $|\alpha|<10^{-11}$ if the scalar field couples to the baryon
number and to $|\alpha|<10^{-12}$ if the scalar field couples to the difference
between the baryon and the lepton numbers. We also consider a model describing
the coupling of a generic dilaton to the standard matter fields with five
parameters, for a light field: we find that for masses smaller than
$10^{-12}$eV, the constraints on the dilaton coupling parameters are improved
by one order of magnitude compared to previous equivalence principle tests.
| [
{
"created": "Fri, 1 Dec 2017 20:32:30 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Dec 2017 15:21:23 GMT",
"version": "v2"
},
{
"created": "Mon, 16 Apr 2018 21:04:43 GMT",
"version": "v3"
}
] | 2018-04-18 | [
[
"Bergé",
"Joel",
""
],
[
"Brax",
"Philippe",
""
],
[
"Métris",
"Gilles",
""
],
[
"Pernot-Borràs",
"Martin",
""
],
[
"Touboul",
"Pierre",
""
],
[
"Uzan",
"Jean-Philippe",
""
]
] | The existence of a light or massive scalar field with a coupling to matter weaker than gravitational strength is a possible source of violation of the weak equivalence principle. We use the first results on the E\"otv\"os parameter by the MICROSCOPE experiment to set new constraints on such scalar fields. For a massive scalar field of mass smaller than $10^{-12}$ eV (i.e. range larger than a few $10^5$ m) we improve existing constraints by one order of magnitude to $|\alpha|<10^{-11}$ if the scalar field couples to the baryon number and to $|\alpha|<10^{-12}$ if the scalar field couples to the difference between the baryon and the lepton numbers. We also consider a model describing the coupling of a generic dilaton to the standard matter fields with five parameters, for a light field: we find that for masses smaller than $10^{-12}$eV, the constraints on the dilaton coupling parameters are improved by one order of magnitude compared to previous equivalence principle tests. |
1306.6233 | Runqiu Yang | Rong-Gen Cai, Li-Ming Cao, Li Li, and Run-Qiu Yang | P-V criticality in the extended phase space of Gauss-Bonnet black holes
in AdS space | 23 pages,9 figures | null | 10.1007/JHEP09(2013)005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the $P-V$ criticality and phase transition in the extended phase
space of charged Gauss-Bonnet black holes in anti-de Sitter space, where the
cosmological constant appears as a dynamical pressure of the system and its
conjugate quantity is the thermodynamic volume of the black hole. The black
holes can have a Ricci flat ($k=0$), spherical ($k=1$), or hyperbolic ($k=-1$)
horizon. We find that for the Ricci flat and hyperbolic Gauss-Bonnet black
holes, no $P-V$ criticality and phase transition appear, while for the black
holes with a spherical horizon, even when the charge of the black hole is
absent, the $P-V$ criticality and the small black hole/large black hole phase
transition will appear, but it happens only in $d=5$ dimensions; when the
charge does not vanish, the $P-V$ criticality and the small black hole/large
phase transition always appear in $d=5$ dimensions; in the case of $d\ge 6$, to
have the $P-V$ criticality and the small black hole/large black hole phase
transition, there exists an upper bound for the parameter
$b=\widetilde{\alpha}|Q|^{-2/(d-3)}$, where $\tilde {\alpha}$ is the
Gauss-Bonnet coefficient and $Q$ is the charge of the black hole. We calculate
the critical exponents at the critical point and find that for all cases, they
are the same as those in the van der Waals liquid-gas system.
| [
{
"created": "Wed, 26 Jun 2013 13:24:52 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Jun 2013 03:22:35 GMT",
"version": "v2"
},
{
"created": "Thu, 4 Jul 2013 15:44:09 GMT",
"version": "v3"
},
{
"created": "Sat, 10 Aug 2013 02:25:29 GMT",
"version": "v4"
}
] | 2015-06-16 | [
[
"Cai",
"Rong-Gen",
""
],
[
"Cao",
"Li-Ming",
""
],
[
"Li",
"Li",
""
],
[
"Yang",
"Run-Qiu",
""
]
] | We study the $P-V$ criticality and phase transition in the extended phase space of charged Gauss-Bonnet black holes in anti-de Sitter space, where the cosmological constant appears as a dynamical pressure of the system and its conjugate quantity is the thermodynamic volume of the black hole. The black holes can have a Ricci flat ($k=0$), spherical ($k=1$), or hyperbolic ($k=-1$) horizon. We find that for the Ricci flat and hyperbolic Gauss-Bonnet black holes, no $P-V$ criticality and phase transition appear, while for the black holes with a spherical horizon, even when the charge of the black hole is absent, the $P-V$ criticality and the small black hole/large black hole phase transition will appear, but it happens only in $d=5$ dimensions; when the charge does not vanish, the $P-V$ criticality and the small black hole/large phase transition always appear in $d=5$ dimensions; in the case of $d\ge 6$, to have the $P-V$ criticality and the small black hole/large black hole phase transition, there exists an upper bound for the parameter $b=\widetilde{\alpha}|Q|^{-2/(d-3)}$, where $\tilde {\alpha}$ is the Gauss-Bonnet coefficient and $Q$ is the charge of the black hole. We calculate the critical exponents at the critical point and find that for all cases, they are the same as those in the van der Waals liquid-gas system. |
2203.07069 | Samuel Barroso Bellido | Samuel Barroso Bellido, Mariusz P. Dabrowski | Observational Imprints of Our Lost Twin Anti-Universe | 14 pages, 1 figure. To be published | null | 10.1140/epjc/s10052-022-10945-2 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider observational consequences of the entanglement between our
universe and a hypothetical twin anti-universe in the third quantization scheme
of the canonical quantum gravity. Based on our previous investigations we
select some special form of the interuniversal interaction which allows the
entanglement entropy of the pair of universes to diverge at some critical
points of their classical evolution. We find that the modification of the
cosmic microwave background (CMB) power spectrum due to the entanglement with
our twin anti-universe is enlarged for small modes $k$ and small multipole
numbers $l$ with the Planck constraint onto the interaction coupling constant
$\lambda_o\lesssim\mathcal{O}(10^{-56})$. Some other coupling functions which
allow more critical points are also briefly commented on in the context of
their observational effect on CMB and other observations.
| [
{
"created": "Fri, 11 Mar 2022 12:56:40 GMT",
"version": "v1"
}
] | 2022-11-08 | [
[
"Bellido",
"Samuel Barroso",
""
],
[
"Dabrowski",
"Mariusz P.",
""
]
] | We consider observational consequences of the entanglement between our universe and a hypothetical twin anti-universe in the third quantization scheme of the canonical quantum gravity. Based on our previous investigations we select some special form of the interuniversal interaction which allows the entanglement entropy of the pair of universes to diverge at some critical points of their classical evolution. We find that the modification of the cosmic microwave background (CMB) power spectrum due to the entanglement with our twin anti-universe is enlarged for small modes $k$ and small multipole numbers $l$ with the Planck constraint onto the interaction coupling constant $\lambda_o\lesssim\mathcal{O}(10^{-56})$. Some other coupling functions which allow more critical points are also briefly commented on in the context of their observational effect on CMB and other observations. |
gr-qc/9704037 | Raul Abramo | L.R. Abramo, R.H. Brandenberger, V.M. Mukhanov | The Energy-Momentum Tensor for Cosmological Perturbations | 29 pages, LaTex; to appear in Phys. Rev. D | Phys.Rev. D56 (1997) 3248-3257 | 10.1103/PhysRevD.56.3248 | BROWN-HET-1046 | gr-qc astro-ph hep-ph hep-th | null | We study the effective energy-momentum tensor (EMT) for cosmological
perturbations and formulate the gravitational back-reaction problem in a gauge
invariant manner. We analyze the explicit expressions for the EMT in the cases
of scalar metric fluctuations and of gravitational waves and derive the
resulting equations of state. The formalism is applied to investigate the
back-reaction effects in chaotic inflation. We find that for long wavelength
scalar and tensor perturbations, the effective energy density is negative and
thus counteracts any pre-existing cosmological constant. For scalar
perturbations during an epoch of inflation, the equation of state is de
Sitter-like.
| [
{
"created": "Mon, 14 Apr 1997 17:06:17 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Apr 1997 16:48:36 GMT",
"version": "v2"
},
{
"created": "Fri, 18 Apr 1997 22:22:21 GMT",
"version": "v3"
},
{
"created": "Thu, 24 Apr 1997 19:46:58 GMT",
"version": "v4"
},
{
"c... | 2009-10-30 | [
[
"Abramo",
"L. R.",
""
],
[
"Brandenberger",
"R. H.",
""
],
[
"Mukhanov",
"V. M.",
""
]
] | We study the effective energy-momentum tensor (EMT) for cosmological perturbations and formulate the gravitational back-reaction problem in a gauge invariant manner. We analyze the explicit expressions for the EMT in the cases of scalar metric fluctuations and of gravitational waves and derive the resulting equations of state. The formalism is applied to investigate the back-reaction effects in chaotic inflation. We find that for long wavelength scalar and tensor perturbations, the effective energy density is negative and thus counteracts any pre-existing cosmological constant. For scalar perturbations during an epoch of inflation, the equation of state is de Sitter-like. |
1901.03390 | Anto Sulaksono | A. B. Wahidin, A. Rahmansyah, and A. Sulaksono | Effect of Scalar Boson on Fermionic Dark Star | 27 pages,11 figures, accepted for publication in IJMPD | null | 10.1142/S0218271819500718 | null | gr-qc astro-ph.SR hep-ph nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The role of scalar boson exchange as a mediator of the fermionic dark
particle interaction and the mass of dark particle on the bulk properties of
fermionic dark stars including their moment of inertia and tidal deformability
are studied. We have found that the role of the attractive nature of the scalar
boson exchange and the fermionic dark particle mass can control the stiffness
of the fermionic dark star equation of state. By increasing the strength of
scalar boson coupling, the fermionic dark star becomes more compact. As a
consequence, if scalar boson exchange contribution is included the compactness
of a dark star can exceed $C$=0.22. We also compare the fermionic dark stars
moment of inertia and tidal deformability to those of neutron stars (with and
without hyperons in neutron star core) predicted by relativistic mean field
model. It is evidence that the properties of both types of stars are quite
different. We also have found that the universal I-Love relation in fermionic
dark stars is not affected by scalar boson exchange contribution and the
fermionic dark particle mass. Possible observations of fermionic dark stars are
also discussed.
| [
{
"created": "Thu, 3 Jan 2019 07:32:21 GMT",
"version": "v1"
}
] | 2019-03-27 | [
[
"Wahidin",
"A. B.",
""
],
[
"Rahmansyah",
"A.",
""
],
[
"Sulaksono",
"A.",
""
]
] | The role of scalar boson exchange as a mediator of the fermionic dark particle interaction and the mass of dark particle on the bulk properties of fermionic dark stars including their moment of inertia and tidal deformability are studied. We have found that the role of the attractive nature of the scalar boson exchange and the fermionic dark particle mass can control the stiffness of the fermionic dark star equation of state. By increasing the strength of scalar boson coupling, the fermionic dark star becomes more compact. As a consequence, if scalar boson exchange contribution is included the compactness of a dark star can exceed $C$=0.22. We also compare the fermionic dark stars moment of inertia and tidal deformability to those of neutron stars (with and without hyperons in neutron star core) predicted by relativistic mean field model. It is evidence that the properties of both types of stars are quite different. We also have found that the universal I-Love relation in fermionic dark stars is not affected by scalar boson exchange contribution and the fermionic dark particle mass. Possible observations of fermionic dark stars are also discussed. |
1612.03604 | Szymon Sikora | Szymon Sikora and Krzysztof G{\l}\'od | Example of an inhomogeneous cosmological model in the context of
backreaction | null | Phys. Rev. D 95, 063517 (2017) | 10.1103/PhysRevD.95.063517 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, we present an example of an inhomogeneous cosmological
model, which is inspired by the linear perturbation theory. The metric of this
model can be described as the Einstein-de Sitter background with a periodically
distributed dust overdensities. The model construction enables application of
the Green-Wald averaging scheme and the Buchert averaging technique
simultaneously. We compare the angular diameter distance function of the
considered model to the angular diameter distances corresponding to the average
space-times given by the Green-Wald and the Buchert frameworks respectively.
| [
{
"created": "Mon, 12 Dec 2016 10:41:11 GMT",
"version": "v1"
}
] | 2017-03-29 | [
[
"Sikora",
"Szymon",
""
],
[
"Głód",
"Krzysztof",
""
]
] | In this article, we present an example of an inhomogeneous cosmological model, which is inspired by the linear perturbation theory. The metric of this model can be described as the Einstein-de Sitter background with a periodically distributed dust overdensities. The model construction enables application of the Green-Wald averaging scheme and the Buchert averaging technique simultaneously. We compare the angular diameter distance function of the considered model to the angular diameter distances corresponding to the average space-times given by the Green-Wald and the Buchert frameworks respectively. |
1312.3462 | Tomi Koivisto | Tomi Sebastian Koivisto, Danielle Elizabeth Wills | Matters on a moving brane | 7 pages, 2 pictures. Received an Honorable Mention in the Gravity
Research Foundation Essay Contest 2013 | Int.J.Mod.Phys. D22 (2013) 1342024 | 10.1142/S0218271813420248 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A novel generalisation of the Dirac-Born-Infeld string scenario is described.
It is shown that matter residing on the moving brane is dark and has the
so-called disformal coupling to gravity. This gives rise to cosmologies where
dark matter stems from the oscillations of the open strings along the brane and
the transverse oscillations result in dark energy. Furthermore, due to a new
screening mechanism that conceals the fifth force from local experiments, one
may even entertain the possibility that the visible sector is also moving along
the extra dimensions.
| [
{
"created": "Thu, 12 Dec 2013 12:22:14 GMT",
"version": "v1"
}
] | 2013-12-18 | [
[
"Koivisto",
"Tomi Sebastian",
""
],
[
"Wills",
"Danielle Elizabeth",
""
]
] | A novel generalisation of the Dirac-Born-Infeld string scenario is described. It is shown that matter residing on the moving brane is dark and has the so-called disformal coupling to gravity. This gives rise to cosmologies where dark matter stems from the oscillations of the open strings along the brane and the transverse oscillations result in dark energy. Furthermore, due to a new screening mechanism that conceals the fifth force from local experiments, one may even entertain the possibility that the visible sector is also moving along the extra dimensions. |
1104.3494 | Marc Lilley | Marc Lilley, Larissa Lorenz, Sebastien Clesse | Observational signatures of a non-singular bouncing cosmology | 40 pages, 5 figures, typos corrected and reference added | JCAP06(2011)004 | 10.1088/1475-7516/2011/06/004 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a cosmological scenario in which inflation is preceded by a bounce.
In this scenario, the primordial singularity, one of the major shortcomings of
inflation, is replaced by a non-singular bounce, prior to which the universe
undergoes a phase of contraction. Our starting point is the bouncing cosmology
investigated in Falciano et al. (2008), which we complete by a detailed study
of the transfer of cosmological perturbations through the bounce and a
discussion of possible observational effects of bouncing cosmologies. We focus
on a symmetric bounce and compute the evolution of cosmological perturbations
during the contracting, bouncing and inflationary phases. We derive an
expression for the Mukhanov-Sasaki perturbation variable at the onset of the
inflationary phase that follows the bounce. Rather than being in the
Bunch-Davies vacuum, it is found to be in an excited state that depends on the
time scale of the bounce. We then show that this induces oscillations
superimposed on the nearly scale-invariant primordial spectra for scalar and
tensor perturbations. We discuss the effects of these oscillations in the
cosmic microwave background and in the matter power spectrum. We propose a new
way to indirectly measure the spatial curvature energy density parameter in the
context of this model.
| [
{
"created": "Mon, 18 Apr 2011 14:26:11 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Jun 2011 09:12:35 GMT",
"version": "v2"
}
] | 2015-05-27 | [
[
"Lilley",
"Marc",
""
],
[
"Lorenz",
"Larissa",
""
],
[
"Clesse",
"Sebastien",
""
]
] | We study a cosmological scenario in which inflation is preceded by a bounce. In this scenario, the primordial singularity, one of the major shortcomings of inflation, is replaced by a non-singular bounce, prior to which the universe undergoes a phase of contraction. Our starting point is the bouncing cosmology investigated in Falciano et al. (2008), which we complete by a detailed study of the transfer of cosmological perturbations through the bounce and a discussion of possible observational effects of bouncing cosmologies. We focus on a symmetric bounce and compute the evolution of cosmological perturbations during the contracting, bouncing and inflationary phases. We derive an expression for the Mukhanov-Sasaki perturbation variable at the onset of the inflationary phase that follows the bounce. Rather than being in the Bunch-Davies vacuum, it is found to be in an excited state that depends on the time scale of the bounce. We then show that this induces oscillations superimposed on the nearly scale-invariant primordial spectra for scalar and tensor perturbations. We discuss the effects of these oscillations in the cosmic microwave background and in the matter power spectrum. We propose a new way to indirectly measure the spatial curvature energy density parameter in the context of this model. |
gr-qc/9708071 | Hisaaki Shinkai | G. L. Comer (St. Louis Univ.) and Hisa-aki Shinkai (Washington Univ.,
St. Louis) | Generation of scalar-tensor gravity effects in equilibrium state boson
stars | 20 pages, RevTeX, 11 figures, to appear in Class. Quantum Grav.,
comments added, refs updated | Class.Quant.Grav. 15 (1998) 669-688 | 10.1088/0264-9381/15/3/016 | null | gr-qc | null | Boson stars in zero-, one-, and two-node equilibrium states are modeled
numerically within the framework of Scalar-Tensor Gravity. The complex scalar
field is taken to be both massive and self-interacting. Configurations are
formed in the case of a linear gravitational scalar coupling (the Brans-Dicke
case) and a quadratic coupling which has been used previously in a cosmological
context. The coupling parameters and asymptotic value for the gravitational
scalar field are chosen so that the known observational constraints on
Scalar-Tensor Gravity are satisfied. It is found that the constraints are so
restrictive that the field equations of General Relativity and Scalar-Tensor
gravity yield virtually identical solutions. We then use catastrophe theory to
determine the dynamically stable configurations. It is found that the maximum
mass allowed for a stable state in Scalar-Tensor gravity in the present
cosmological era is essentially unchanged from that of General Relativity. We
also construct boson star configurations appropriate to earlier cosmological
eras and find that the maximum mass for stable states is smaller than that
predicted by General Relativity, and the more so for earlier eras. However, our
results also show that if the cosmological era is early enough then only states
with positive binding energy can be constructed.
| [
{
"created": "Thu, 28 Aug 1997 21:26:54 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Dec 1997 20:46:50 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Comer",
"G. L.",
"",
"St. Louis Univ."
],
[
"Shinkai",
"Hisa-aki",
"",
"Washington Univ.,\n St. Louis"
]
] | Boson stars in zero-, one-, and two-node equilibrium states are modeled numerically within the framework of Scalar-Tensor Gravity. The complex scalar field is taken to be both massive and self-interacting. Configurations are formed in the case of a linear gravitational scalar coupling (the Brans-Dicke case) and a quadratic coupling which has been used previously in a cosmological context. The coupling parameters and asymptotic value for the gravitational scalar field are chosen so that the known observational constraints on Scalar-Tensor Gravity are satisfied. It is found that the constraints are so restrictive that the field equations of General Relativity and Scalar-Tensor gravity yield virtually identical solutions. We then use catastrophe theory to determine the dynamically stable configurations. It is found that the maximum mass allowed for a stable state in Scalar-Tensor gravity in the present cosmological era is essentially unchanged from that of General Relativity. We also construct boson star configurations appropriate to earlier cosmological eras and find that the maximum mass for stable states is smaller than that predicted by General Relativity, and the more so for earlier eras. However, our results also show that if the cosmological era is early enough then only states with positive binding energy can be constructed. |
1101.5034 | Mauricio Cataldo MC | Mauricio Cataldo, Paola Meza and Paul Minning | N-dimensional static and evolving Lorentzian wormholes with cosmological
constant | 10 pages, accepted for publication in Phys. Rev. D | Phys.Rev.D83:044050,2011 | 10.1103/PhysRevD.83.044050 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a family of static and evolving spherically symmetric Lorentzian
wormhole solutions in N+1 dimensional Einstein gravity. In general, for static
wormholes, we require that at least the radial pressure has a barotropic
equation of state of the form $p_r=\omega_r \rho$, where the state parameter
$\omega_r$ is constant. On the other hand, it is shown that in any dimension $N
\geq 3$, with $\phi(r)=\Lambda=0$ and anisotropic barotropic pressure with
constant state parameters, static wormhole configurations are always
asymptotically flat spacetimes, while in 2+1 gravity there are not only
asymptotically flat static wormholes and also more general ones. In this case,
the matter sustaining the three-dimensional wormhole may be only a pressureless
fluid. In the case of evolving wormholes with $N \geq 3$, the presence of a
cosmological constant leads to an expansion or contraction of the wormhole
configurations: for positive cosmological constant we have wormholes which
expand forever and, for negative cosmological constant we have wormholes which
expand to a maximum value and then recollapse. In the absence of a cosmological
constant the wormhole expands with constant velocity, i.e without acceleration
or deceleration. In 2+1 dimensions the expanding wormholes always have an
isotropic and homogeneous pressure, depending only on the time coordinate.
| [
{
"created": "Wed, 26 Jan 2011 11:48:01 GMT",
"version": "v1"
}
] | 2011-03-23 | [
[
"Cataldo",
"Mauricio",
""
],
[
"Meza",
"Paola",
""
],
[
"Minning",
"Paul",
""
]
] | We present a family of static and evolving spherically symmetric Lorentzian wormhole solutions in N+1 dimensional Einstein gravity. In general, for static wormholes, we require that at least the radial pressure has a barotropic equation of state of the form $p_r=\omega_r \rho$, where the state parameter $\omega_r$ is constant. On the other hand, it is shown that in any dimension $N \geq 3$, with $\phi(r)=\Lambda=0$ and anisotropic barotropic pressure with constant state parameters, static wormhole configurations are always asymptotically flat spacetimes, while in 2+1 gravity there are not only asymptotically flat static wormholes and also more general ones. In this case, the matter sustaining the three-dimensional wormhole may be only a pressureless fluid. In the case of evolving wormholes with $N \geq 3$, the presence of a cosmological constant leads to an expansion or contraction of the wormhole configurations: for positive cosmological constant we have wormholes which expand forever and, for negative cosmological constant we have wormholes which expand to a maximum value and then recollapse. In the absence of a cosmological constant the wormhole expands with constant velocity, i.e without acceleration or deceleration. In 2+1 dimensions the expanding wormholes always have an isotropic and homogeneous pressure, depending only on the time coordinate. |
1904.08617 | Mikica Kocic | Mikica Kocic, Francesco Torsello, Marcus H\"og\r{a}s and Edvard
Mortsell | Spherical dust collapse in bimetric relativity: Bimetric polytropes | 24 pages, 17 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a method for solving the constraint equations in the Hassan-Rosen
bimetric theory to determine the initial data for the gravitational collapse of
spherically symmetric dust. The setup leads to equations similar to those for a
polytropic fluid in general relativity, here called a generalized Lane-Emden
equation. Using a numerical code which solves the evolution equations in the
standard 3+1 form, we also obtain a short term development of the initial data
for these bimetric polytropes. The evolution highlights some important features
of the bimetric theory such as the interwoven and oscillating null cones
representing the essential nonbidiagonality in the dynamics of the two metrics.
The simulations are in the strong-field regime and show that, at least at an
early stage, the collapse of a dust cloud is similar to that in general
relativity, and with no instabilities, albeit with small oscillations in the
metric fields.
| [
{
"created": "Thu, 18 Apr 2019 07:40:54 GMT",
"version": "v1"
}
] | 2019-04-19 | [
[
"Kocic",
"Mikica",
""
],
[
"Torsello",
"Francesco",
""
],
[
"Högås",
"Marcus",
""
],
[
"Mortsell",
"Edvard",
""
]
] | We present a method for solving the constraint equations in the Hassan-Rosen bimetric theory to determine the initial data for the gravitational collapse of spherically symmetric dust. The setup leads to equations similar to those for a polytropic fluid in general relativity, here called a generalized Lane-Emden equation. Using a numerical code which solves the evolution equations in the standard 3+1 form, we also obtain a short term development of the initial data for these bimetric polytropes. The evolution highlights some important features of the bimetric theory such as the interwoven and oscillating null cones representing the essential nonbidiagonality in the dynamics of the two metrics. The simulations are in the strong-field regime and show that, at least at an early stage, the collapse of a dust cloud is similar to that in general relativity, and with no instabilities, albeit with small oscillations in the metric fields. |
1502.02929 | Behzad Eslam Panah | G. H. Bordbar, S. H. Hendi and B. Eslam Panah | Neutron stars in Einstein-$\Lambda$ gravity: the cosmological constant
effects | 14 pages, 10 figures, title changed, numerical solutions added,
references added | Eur. Phys. J. Plus. 131, 315 (2016) | 10.1140/epjp/i2016-16315-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Regarding a $d-$dimensional spherically symmetric line element in the context
of Einstein-$\Lambda$ gravity, the hydrostatic equilibrium equation of stars is
obtained. Then, by using the lowest order constrained variational (LOCV) method
with the AV$18$ potential and employing microscopic many body calculations in
the modern equation of state, the structure properties of neutron stars are
investigated. Regardless of cosmological point of view and considering
arbitrary positive and negative values of the cosmological constant, the
maximum mass of the neutron stars and their corresponding radius in
$4$-dimensions are computed. The results show that there is an upper limit for
the maximum mass of neutron star for positive cosmological constant ($M_{\max
}\leq 1.68M_{\odot }$). On the other hand, it is shown that the Einstein
gravity cannot explain the structure of neutron star with negative $\Lambda$.
Other properties of neutron stars such as; the Schwarzschild radius, average
density, compactness and Buchdahl- Bondi bound are studied. In addition, by
using the Buchdahl-Bondi bound for neutron stars, stability of these stars is
investigated. Finally, the dynamical stability is investigated and shown that
the neutron stars follow the dynamical stability in this gravity.
| [
{
"created": "Tue, 10 Feb 2015 15:00:39 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Jan 2016 18:23:42 GMT",
"version": "v2"
},
{
"created": "Thu, 26 Jan 2017 19:07:30 GMT",
"version": "v3"
}
] | 2017-01-30 | [
[
"Bordbar",
"G. H.",
""
],
[
"Hendi",
"S. H.",
""
],
[
"Panah",
"B. Eslam",
""
]
] | Regarding a $d-$dimensional spherically symmetric line element in the context of Einstein-$\Lambda$ gravity, the hydrostatic equilibrium equation of stars is obtained. Then, by using the lowest order constrained variational (LOCV) method with the AV$18$ potential and employing microscopic many body calculations in the modern equation of state, the structure properties of neutron stars are investigated. Regardless of cosmological point of view and considering arbitrary positive and negative values of the cosmological constant, the maximum mass of the neutron stars and their corresponding radius in $4$-dimensions are computed. The results show that there is an upper limit for the maximum mass of neutron star for positive cosmological constant ($M_{\max }\leq 1.68M_{\odot }$). On the other hand, it is shown that the Einstein gravity cannot explain the structure of neutron star with negative $\Lambda$. Other properties of neutron stars such as; the Schwarzschild radius, average density, compactness and Buchdahl- Bondi bound are studied. In addition, by using the Buchdahl-Bondi bound for neutron stars, stability of these stars is investigated. Finally, the dynamical stability is investigated and shown that the neutron stars follow the dynamical stability in this gravity. |
1707.04938 | Willians Barreto | W. Barreto, H. P. de Oliveira and B. Rodriguez-Mueller | Fixed mesh refinement in the characteristic formulation of General
Relativity | 14 papes, 7 figures. To appear in General Relativity and Gravitation | General Relativity and Gravitation 49: 107 (2017) | 10.1007/s10714-017-2273-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We implement a spatially fixed mesh refinement under spherical symmetry for
the characteristic formulation of General Relativity. The
Courant-Friedrich-Levy (CFL) condition lets us deploy an adaptive resolution in
(retarded-like) time, even for the nonlinear regime. As test cases, we
replicate the main features of the gravitational critical behavior and the
spacetime structure at null infinity using the Bondi mass and the News
function. Additionally, we obtain the global energy conservation for an extreme
situation, i.e. in the threshold of the black hole formation. In principle, the
calibrated code can be used in conjunction with an ADM 3+1 code to confirm the
critical behavior recently reported in the gravitational collapse of a massless
scalar field in an asymptotic anti-de Sitter spacetime. For the scenarios
studied, the fixed mesh refinement offers improved runtime and results
comparable to code without mesh refinement.
| [
{
"created": "Sun, 16 Jul 2017 19:45:30 GMT",
"version": "v1"
}
] | 2017-07-27 | [
[
"Barreto",
"W.",
""
],
[
"de Oliveira",
"H. P.",
""
],
[
"Rodriguez-Mueller",
"B.",
""
]
] | We implement a spatially fixed mesh refinement under spherical symmetry for the characteristic formulation of General Relativity. The Courant-Friedrich-Levy (CFL) condition lets us deploy an adaptive resolution in (retarded-like) time, even for the nonlinear regime. As test cases, we replicate the main features of the gravitational critical behavior and the spacetime structure at null infinity using the Bondi mass and the News function. Additionally, we obtain the global energy conservation for an extreme situation, i.e. in the threshold of the black hole formation. In principle, the calibrated code can be used in conjunction with an ADM 3+1 code to confirm the critical behavior recently reported in the gravitational collapse of a massless scalar field in an asymptotic anti-de Sitter spacetime. For the scenarios studied, the fixed mesh refinement offers improved runtime and results comparable to code without mesh refinement. |
gr-qc/0607051 | Barry Holstein | Barry R. Holstein | Quantum Corrections to the Reissner-Nordstrom and Kerr-Newman Metrics:
Spin 1 | 21 pages, 1 Figure | null | 10.1103/PhysRevD.74.084030 | null | gr-qc hep-ph hep-th | null | A previous evaluation of one-photon loop corrections to the energy-momentum
tensor has been extended to particles with unit spin and speculations are
presented concerning general properties of such forms.
| [
{
"created": "Wed, 12 Jul 2006 15:59:21 GMT",
"version": "v1"
}
] | 2013-05-29 | [
[
"Holstein",
"Barry R.",
""
]
] | A previous evaluation of one-photon loop corrections to the energy-momentum tensor has been extended to particles with unit spin and speculations are presented concerning general properties of such forms. |
1106.4627 | Subenoy Chakraborty | Nairwita Mazumder, Ritabrata Biswas, Subenoy Chakraborty | Interacting Holographic Dark Energy at the Ricci scale and Dynamical
system | 10 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we consider homogeneous and isotropic FRW model of the
universe, filled with interacting dark matter and dark energy. The dark matter
is chosen as usual in the form of dust while dark energy is holographic in
nature with IR cut off at the Ricci's length and it is in the form of a perfect
fluid with variable equation of state. We have chosen the interaction term of
the following two types: (i) a linear combination of the matter density of the
two fluids, (ii) a product of the two matter densities. For both the choices
the evolution equations are transformed to an autonomous system and the
corresponding critical points are analyzed. Finally, for the first choice of
the interaction term the evolution of the ratio of the energy densities has
been studied from the point of view of the present coincidence problem.
| [
{
"created": "Thu, 23 Jun 2011 05:10:07 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Oct 2011 18:15:56 GMT",
"version": "v2"
}
] | 2011-10-21 | [
[
"Mazumder",
"Nairwita",
""
],
[
"Biswas",
"Ritabrata",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | In this work, we consider homogeneous and isotropic FRW model of the universe, filled with interacting dark matter and dark energy. The dark matter is chosen as usual in the form of dust while dark energy is holographic in nature with IR cut off at the Ricci's length and it is in the form of a perfect fluid with variable equation of state. We have chosen the interaction term of the following two types: (i) a linear combination of the matter density of the two fluids, (ii) a product of the two matter densities. For both the choices the evolution equations are transformed to an autonomous system and the corresponding critical points are analyzed. Finally, for the first choice of the interaction term the evolution of the ratio of the energy densities has been studied from the point of view of the present coincidence problem. |
gr-qc/0511054 | Michael Maziashvili | Michael Maziashvili | Black hole remnants due to GUP or quantum gravity? | 3 pages | Phys.Lett.B635:232-234,2006 | 10.1016/j.physletb.2006.03.009 | null | gr-qc hep-ph hep-th | null | Based on the micro-black hole \emph{gedanken} experiment as well as on
general considerations of quantum mechanics and gravity the generalized
uncertainty principle (GUP) is analyzed by using the running Newton constant.
The result is used to decide between the GUP and quantum gravitational effects
as a possible mechanism leading to the black hole remnants of about Planck
mass.
| [
{
"created": "Thu, 10 Nov 2005 10:48:39 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Mar 2006 12:58:46 GMT",
"version": "v2"
}
] | 2010-11-05 | [
[
"Maziashvili",
"Michael",
""
]
] | Based on the micro-black hole \emph{gedanken} experiment as well as on general considerations of quantum mechanics and gravity the generalized uncertainty principle (GUP) is analyzed by using the running Newton constant. The result is used to decide between the GUP and quantum gravitational effects as a possible mechanism leading to the black hole remnants of about Planck mass. |
1802.08553 | Ritabrata Biswas | Sandip Dutta and Ritabrata Biswas | Dark Energy Accretion onto Van der Waal's Black Hole | 17 pages, 12 figures, Accepted for publication in Communications in
Theoretical Physics | null | 10.1088/0253-6102/71/2/209 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the most general static spherically symmetric black hole metric.
The accretion of the fluid flow around the Van der Waal's black hole is
investigated and we calculate the fluid's four-velocity, the critical point and
the speed of sound during the accretion process. We also analyze the nature of
the universe's density and the mass of the black hole during accretion of the
fluid flow. The density of the fluid flow is also taken into account. We
observe that the mass is related to redshift. We compare the accreting power of
the Van der Waal's black hole with Schwarzschild black hole for different
accreting fluid.
| [
{
"created": "Wed, 21 Feb 2018 11:53:06 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Jul 2018 10:50:19 GMT",
"version": "v2"
}
] | 2019-03-27 | [
[
"Dutta",
"Sandip",
""
],
[
"Biswas",
"Ritabrata",
""
]
] | We consider the most general static spherically symmetric black hole metric. The accretion of the fluid flow around the Van der Waal's black hole is investigated and we calculate the fluid's four-velocity, the critical point and the speed of sound during the accretion process. We also analyze the nature of the universe's density and the mass of the black hole during accretion of the fluid flow. The density of the fluid flow is also taken into account. We observe that the mass is related to redshift. We compare the accreting power of the Van der Waal's black hole with Schwarzschild black hole for different accreting fluid. |
2402.16163 | J\'unior Diniz Toniato | Mario Novello and J\'unior D. Toniato | An overview of field theories of gravity | 35 pages, 3 figures, to appear as chapter in "Tribute to Ruben
Aldrovandi", edited by F. Caruso, J.G. Pereira and A. Santoro (Editora
Livraria da F\'isica, S\~ao Paulo, 2024) | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the general relativity theory the basic ingredient to describe gravity is
the geometry, which interacts with all forms of matter and energy, and as such,
the metric could be interpreted as a true physical quantity. However the metric
is not matter nor energy, but instead it is a new dynamical variable that
Einstein introduced to describe gravity. In order to conciliate this approach
to the more traditional ones, physicists have tried to describe the main ideas
of GR in terms of standard conceptions of field theory. In this sense, curved
metrics are seen as a dynamical variable emerging from a more fundamental field
which lies upon a flat Minkowski spacetime. This was made by the hypothesis
that the metric tensor may be written as $g_{\mu\nu} = \eta_{\mu\nu} +
h_{\mu\nu}$ where the tensor $ h_{\mu\nu}$ was interpreted either in terms of a
spin-2 or constructed in terms of other fields. We review some proposals that
were suggested in the treatment of gravity in terms of scalar, spinor and
tensor fields configurations.
| [
{
"created": "Sun, 25 Feb 2024 18:00:08 GMT",
"version": "v1"
}
] | 2024-02-27 | [
[
"Novello",
"Mario",
""
],
[
"Toniato",
"Júnior D.",
""
]
] | In the general relativity theory the basic ingredient to describe gravity is the geometry, which interacts with all forms of matter and energy, and as such, the metric could be interpreted as a true physical quantity. However the metric is not matter nor energy, but instead it is a new dynamical variable that Einstein introduced to describe gravity. In order to conciliate this approach to the more traditional ones, physicists have tried to describe the main ideas of GR in terms of standard conceptions of field theory. In this sense, curved metrics are seen as a dynamical variable emerging from a more fundamental field which lies upon a flat Minkowski spacetime. This was made by the hypothesis that the metric tensor may be written as $g_{\mu\nu} = \eta_{\mu\nu} + h_{\mu\nu}$ where the tensor $ h_{\mu\nu}$ was interpreted either in terms of a spin-2 or constructed in terms of other fields. We review some proposals that were suggested in the treatment of gravity in terms of scalar, spinor and tensor fields configurations. |
1411.6410 | David Vitali | Mateusz Bawaj, Ciro Biancofiore, Michele Bonaldi, Federica Bonfigli,
Antonio Borrielli, Giovanni Di Giuseppe, Lorenzo Marconi, Francesco Marino,
Riccardo Natali, Antonio Pontin, Giovanni A. Prodi, Enrico Serra, David
Vitali, and Francesco Marin | Probing deformed commutators with macroscopic harmonic oscillators | 11 pages, 3 figures, reference added | Nature Communications 6, 7503 (2015) | 10.1038/ncomms8503 | null | gr-qc physics.optics quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A minimal observable length is a common feature of theories that aim to merge
quantum physics and gravity. Quantum mechanically, this concept is associated
to a nonzero minimal uncertainty in position measurements, which is encoded in
deformed commutation relations. In spite of increasing theoretical interest,
the subject suffers from the complete lack of dedicated experiments and bounds
to the deformation parameters are roughly extrapolated from indirect
measurements. As recently proposed, low-energy mechanical oscillators could
allow to reveal the effect of a modified commutator. Here we analyze the free
evolution of high quality factor micro- and nano-oscillators, spanning a wide
range of masses around the Planck mass $m_{\mathrm{P}}$ (${\approx
22\,\mu\mathrm{g}}$), and compare it with a model of deformed dynamics.
Previous limits to the parameters quantifying the commutator deformation are
substantially lowered.
| [
{
"created": "Mon, 24 Nov 2014 11:03:44 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Aug 2015 22:30:57 GMT",
"version": "v2"
},
{
"created": "Tue, 25 Aug 2015 14:55:25 GMT",
"version": "v3"
}
] | 2015-08-26 | [
[
"Bawaj",
"Mateusz",
""
],
[
"Biancofiore",
"Ciro",
""
],
[
"Bonaldi",
"Michele",
""
],
[
"Bonfigli",
"Federica",
""
],
[
"Borrielli",
"Antonio",
""
],
[
"Di Giuseppe",
"Giovanni",
""
],
[
"Marconi",
"Lorenzo",
... | A minimal observable length is a common feature of theories that aim to merge quantum physics and gravity. Quantum mechanically, this concept is associated to a nonzero minimal uncertainty in position measurements, which is encoded in deformed commutation relations. In spite of increasing theoretical interest, the subject suffers from the complete lack of dedicated experiments and bounds to the deformation parameters are roughly extrapolated from indirect measurements. As recently proposed, low-energy mechanical oscillators could allow to reveal the effect of a modified commutator. Here we analyze the free evolution of high quality factor micro- and nano-oscillators, spanning a wide range of masses around the Planck mass $m_{\mathrm{P}}$ (${\approx 22\,\mu\mathrm{g}}$), and compare it with a model of deformed dynamics. Previous limits to the parameters quantifying the commutator deformation are substantially lowered. |
1502.05875 | Tirthabir Biswas | Tirthabir Biswas, Riley Mayes and Colleen Lattyak | Perturbations in Bouncing and Cyclic Models, a General Study | 21 pages, 12 figures | Phys. Rev. D 93, 063505 (2016) | 10.1103/PhysRevD.93.063505 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Being able to reliably track perturbations across bounces and turnarounds in
cyclic and bouncing cosmology lies at the heart of being able to compare the
predictions of these models with the Cosmic Microwave Background observations.
This has been a challenging task due to the unknown nature of the physics
involved during the bounce as well as the technical challenge of matching
perturbations precisely between the expansion and contraction phases. In this
paper, we will present general techniques (analytical and numerical) that can
be applied to understand the physics of the fluctuations, especially those with
"long" wavelengths, and test its validity in some simple bouncing/cyclic toy
models where the physics is well understood. We will then apply our techniques
to more interesting cosmological models such as the bounce inflation and cyclic
inflation.
| [
{
"created": "Wed, 18 Feb 2015 00:14:27 GMT",
"version": "v1"
}
] | 2016-03-23 | [
[
"Biswas",
"Tirthabir",
""
],
[
"Mayes",
"Riley",
""
],
[
"Lattyak",
"Colleen",
""
]
] | Being able to reliably track perturbations across bounces and turnarounds in cyclic and bouncing cosmology lies at the heart of being able to compare the predictions of these models with the Cosmic Microwave Background observations. This has been a challenging task due to the unknown nature of the physics involved during the bounce as well as the technical challenge of matching perturbations precisely between the expansion and contraction phases. In this paper, we will present general techniques (analytical and numerical) that can be applied to understand the physics of the fluctuations, especially those with "long" wavelengths, and test its validity in some simple bouncing/cyclic toy models where the physics is well understood. We will then apply our techniques to more interesting cosmological models such as the bounce inflation and cyclic inflation. |
1405.4881 | Yuki Yokokura | Laurent Freidel, Yuki Yokokura | Non-equilibrium thermodynamics of gravitational screens | 30 pages, 3 figures. This is the published version in Classical and
Quantum Gravity. Typos are modified, references are added, discussions
(especially, of section 6) are clarified but the main results do not change | null | 10.1088/0264-9381/32/21/215002 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Einstein gravity equations projected on a timelike surface,
which represents the time evolution of what we call a gravitational screen. We
show that such a screen behaves like a viscous bubble with a surface tension
and an internal energy, and that the Einstein equations take the same forms as
non-equilibrium thermodynamic equations for a viscous bubble. We provide a
consistent dictionary between gravitational and thermodynamical variables. In
the non-viscous cases there are three thermodynamic equations which
characterize a bubble dynamics: These are the first law, the Marangoni flow
equation and the Young-Laplace equation. In all three equations the surface
tension plays a central role: In the first law it appears as a work term per
unit area, in the Marangoni flow its gradient drives a force, and in the
Young-Laplace equation it contributes to a pressure proportional to the surface
curvature. The gravity equations appear as a natural generalization of these
bubble equations when the bubble itself is viscous and dynamical. In
particular, it shows that the mechanism of entropy production for the viscous
bubble is mapped onto the production of gravitational waves. We also review the
relationship between surface tension and temperature, and discuss black-hole
thermodynamics.
| [
{
"created": "Mon, 19 May 2014 20:22:28 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Oct 2015 06:54:06 GMT",
"version": "v2"
}
] | 2015-10-07 | [
[
"Freidel",
"Laurent",
""
],
[
"Yokokura",
"Yuki",
""
]
] | We study the Einstein gravity equations projected on a timelike surface, which represents the time evolution of what we call a gravitational screen. We show that such a screen behaves like a viscous bubble with a surface tension and an internal energy, and that the Einstein equations take the same forms as non-equilibrium thermodynamic equations for a viscous bubble. We provide a consistent dictionary between gravitational and thermodynamical variables. In the non-viscous cases there are three thermodynamic equations which characterize a bubble dynamics: These are the first law, the Marangoni flow equation and the Young-Laplace equation. In all three equations the surface tension plays a central role: In the first law it appears as a work term per unit area, in the Marangoni flow its gradient drives a force, and in the Young-Laplace equation it contributes to a pressure proportional to the surface curvature. The gravity equations appear as a natural generalization of these bubble equations when the bubble itself is viscous and dynamical. In particular, it shows that the mechanism of entropy production for the viscous bubble is mapped onto the production of gravitational waves. We also review the relationship between surface tension and temperature, and discuss black-hole thermodynamics. |
0705.1570 | Andrey Shoom A | Valeri P. Frolov and Andrey A. Shoom | Interior of Distorted Black Holes | 12 pages, 16 figures | Phys.Rev.D76:064037,2007 | 10.1103/PhysRevD.76.064037 | null | gr-qc hep-th | null | We study the interior of distorted static axisymmetric black holes. We obtain
a general interior solution and study its asymptotics both near the horizon and
singularity. As a special example, we apply the obtained results to the case of
the so-called `caged' black holes.
| [
{
"created": "Fri, 11 May 2007 00:05:36 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Frolov",
"Valeri P.",
""
],
[
"Shoom",
"Andrey A.",
""
]
] | We study the interior of distorted static axisymmetric black holes. We obtain a general interior solution and study its asymptotics both near the horizon and singularity. As a special example, we apply the obtained results to the case of the so-called `caged' black holes. |
gr-qc/0610033 | Muhammad Sharif | M. Sharif and Zahid Ahmad | Gravitational Perfect Fluid Collapse With Cosmological Constant | LaTex 13 pages, accepted for publication in Mod. Phys. Lett. A | Mod.Phys.Lett.A22:1493-1502,2007;
Mod.Phys.Lett.A22:2947-2948(Addendum),2007 | 10.1142/S0217732307021834 10.1142/S0217732307025972 | null | gr-qc | null | In this paper, the effect of a positive cosmological constant on spherically
symmetric collapse with perfect fluid has been investigated. The matching
conditions between static exterior and non-static interior spacetimes are given
in the presence of a cosmological constant. We also study the apparent horizons
and their physical significance. It is concluded that the cosmological constant
slows down the collapse of matter and hence limit the size of the black hole.
This analysis gives the generalization of the dust case to the perfect fluid.
We recover the results of the dust case for $p=0$.
| [
{
"created": "Mon, 9 Oct 2006 03:02:33 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Sharif",
"M.",
""
],
[
"Ahmad",
"Zahid",
""
]
] | In this paper, the effect of a positive cosmological constant on spherically symmetric collapse with perfect fluid has been investigated. The matching conditions between static exterior and non-static interior spacetimes are given in the presence of a cosmological constant. We also study the apparent horizons and their physical significance. It is concluded that the cosmological constant slows down the collapse of matter and hence limit the size of the black hole. This analysis gives the generalization of the dust case to the perfect fluid. We recover the results of the dust case for $p=0$. |
1701.06662 | Kirill Bronnikov | Kirill A. Bronnikov, Julio C. Fabris, Oliver F. Piattella, Denis C.
Rodrigues, Edison C. Santos | Duality between k-essence and Rastall gravity | 10 pages, no figures. Two references added | Eur. Phys. J. C 77, 409 (2017) | 10.1140/epjc/s10052-017-4977-4 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The k-essence theory with a power-law function of $(\partial\phi)^2$ and
Rastall's non-conservative theory of gravity with a scalar field are shown to
have the same solutions for the metric under the assumption that both the
metric and the scalar fields depend on a single coordinate. This equivalence
(called k-R duality) holds for static configurations with various symmetries
(spherical, plane, cylindrical, etc.) and all homogeneous cosmologies. In the
presence of matter, Rastall's theory requires additional assumptions on how the
stress-energy tensor non-conservation is distributed between different
contributions. Two versions of such non-conservation are considered in the case
of isotropic spatially flat cosmological models with a perfect fluid: one (R1)
in which there is no coupling between the scalar field and the fluid, and
another (R2) in which the fluid separately obeys the usual conservation law. In
version R1 it is shown that k-R duality holds not only for the cosmological
models themselves but also for their adiabatic perturbations. In version R2,
among other results, a particular model is singled out that reproduces the same
cosmological expansion history as the standard $\Lambda$CDM model but predicts
different behaviors of small fluctuations in the k-essence and Rastall
frameworks.
| [
{
"created": "Mon, 23 Jan 2017 22:47:51 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Jan 2017 00:24:59 GMT",
"version": "v2"
}
] | 2017-09-19 | [
[
"Bronnikov",
"Kirill A.",
""
],
[
"Fabris",
"Julio C.",
""
],
[
"Piattella",
"Oliver F.",
""
],
[
"Rodrigues",
"Denis C.",
""
],
[
"Santos",
"Edison C.",
""
]
] | The k-essence theory with a power-law function of $(\partial\phi)^2$ and Rastall's non-conservative theory of gravity with a scalar field are shown to have the same solutions for the metric under the assumption that both the metric and the scalar fields depend on a single coordinate. This equivalence (called k-R duality) holds for static configurations with various symmetries (spherical, plane, cylindrical, etc.) and all homogeneous cosmologies. In the presence of matter, Rastall's theory requires additional assumptions on how the stress-energy tensor non-conservation is distributed between different contributions. Two versions of such non-conservation are considered in the case of isotropic spatially flat cosmological models with a perfect fluid: one (R1) in which there is no coupling between the scalar field and the fluid, and another (R2) in which the fluid separately obeys the usual conservation law. In version R1 it is shown that k-R duality holds not only for the cosmological models themselves but also for their adiabatic perturbations. In version R2, among other results, a particular model is singled out that reproduces the same cosmological expansion history as the standard $\Lambda$CDM model but predicts different behaviors of small fluctuations in the k-essence and Rastall frameworks. |
gr-qc/0207014 | Hongsu Kim | Hongsu Kim | Removal of Closed Timelike Curves in Kerr-Newman Spacetime | 14 pages, Revtex, Typos corrected | null | null | null | gr-qc astro-ph hep-th | null | A simple yet systematic new algorithm to investigate the global structure of
Kerr-Newman spacetime is suggested. Namely, the global structure of
\theta=const. timelike submanifolds of Kerr-Newman metric are studied by
introducing a new time coordinate slightly different from the usual
Boyer-Lindquist time coordinate. In addition, it is demonstrated that the
possible causality violation thus far regarded to occur near the ring
singularity via the development of closed timelike curves there is not really
an unavoidable pathology which has plagued the Kerr-Newman solution but simply
a gauge (coordinate) artifact as it disappears upon transforming from
Boyer-Lindquist to the new time coordinate. This last point appears to lend
support to the fact that, indeed, the Kerr-Newman spacetime is a legitimate
solution to represent the interior as well as the exterior regions of a
rotating, charged black hole spacetime.
| [
{
"created": "Tue, 2 Jul 2002 09:08:16 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Jul 2002 06:56:51 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Kim",
"Hongsu",
""
]
] | A simple yet systematic new algorithm to investigate the global structure of Kerr-Newman spacetime is suggested. Namely, the global structure of \theta=const. timelike submanifolds of Kerr-Newman metric are studied by introducing a new time coordinate slightly different from the usual Boyer-Lindquist time coordinate. In addition, it is demonstrated that the possible causality violation thus far regarded to occur near the ring singularity via the development of closed timelike curves there is not really an unavoidable pathology which has plagued the Kerr-Newman solution but simply a gauge (coordinate) artifact as it disappears upon transforming from Boyer-Lindquist to the new time coordinate. This last point appears to lend support to the fact that, indeed, the Kerr-Newman spacetime is a legitimate solution to represent the interior as well as the exterior regions of a rotating, charged black hole spacetime. |
gr-qc/9403012 | Ralph Scott | Raymond S. Puzio | The Gauss Map and 2+1 Gravity | null | Class.Quant.Grav.11:2667-2676,1994 | 10.1088/0264-9381/11/11/009 | null | gr-qc | null | We prove that the Gauss map of a surface of constant mean curvature embedded
in Minkowski space is harmonic. This fact will then be used to study 2+1
gravity for surfaces of genus higher than one. By considering the energy of the
Gauss map, a canonical transform between the ADM reduced variables and holonomy
variables can be constructed. This allows one to solve (in principle) for the
evolution in the ADM variables without having to explicitly solve the
constraints first.
| [
{
"created": "Fri, 4 Mar 1994 06:53:14 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Puzio",
"Raymond S.",
""
]
] | We prove that the Gauss map of a surface of constant mean curvature embedded in Minkowski space is harmonic. This fact will then be used to study 2+1 gravity for surfaces of genus higher than one. By considering the energy of the Gauss map, a canonical transform between the ADM reduced variables and holonomy variables can be constructed. This allows one to solve (in principle) for the evolution in the ADM variables without having to explicitly solve the constraints first. |
1004.3235 | Steinar Johannesen | Oyvind Gron and Steinar Johannesen | A spacetime with closed timelike geodesics everywhere | 7 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present article we find a new class of solutions of Einstein's field
equations. It describes stationary, cylindrically symmetric spacetimes with
closed timelike geodesics everywhere outside the symmetry axis. These
spacetimes contain a magnetic field parallel to the axis, a perfect fluid with
constant density and pressure, and Lorentz invariant vacuum with energy density
represented by a negative cosmological constant.
| [
{
"created": "Mon, 19 Apr 2010 15:44:38 GMT",
"version": "v1"
}
] | 2010-04-20 | [
[
"Gron",
"Oyvind",
""
],
[
"Johannesen",
"Steinar",
""
]
] | In the present article we find a new class of solutions of Einstein's field equations. It describes stationary, cylindrically symmetric spacetimes with closed timelike geodesics everywhere outside the symmetry axis. These spacetimes contain a magnetic field parallel to the axis, a perfect fluid with constant density and pressure, and Lorentz invariant vacuum with energy density represented by a negative cosmological constant. |
gr-qc/9801032 | Patrick R. Brady | Patrick R. Brady, Ian G. Moss and Robert C. Myers | Cosmic Censorship: As Strong As Ever | 4 pages RevTeX style, 1 figure included using epsfig | Phys.Rev.Lett. 80 (1998) 3432-3435 | 10.1103/PhysRevLett.80.3432 | NSF-ITP-98-001, GRP-490 | gr-qc | null | Spacetimes which have been considered counter-examples to strong cosmic
censorship are revisited. We demonstrate the classical instability of the
Cauchy horizon inside charged black holes embedded in de Sitter spacetime for
all values of the physical parameters. The relevant modes which maintain the
instability, in the regime which was previously considered stable, originate as
outgoing modes near to the black hole event horizon. This same mechanism is
also relevant for the instability of Cauchy horizons in other proposed
counter-examples of strong cosmic censorship.
| [
{
"created": "Mon, 12 Jan 1998 17:10:18 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Brady",
"Patrick R.",
""
],
[
"Moss",
"Ian G.",
""
],
[
"Myers",
"Robert C.",
""
]
] | Spacetimes which have been considered counter-examples to strong cosmic censorship are revisited. We demonstrate the classical instability of the Cauchy horizon inside charged black holes embedded in de Sitter spacetime for all values of the physical parameters. The relevant modes which maintain the instability, in the regime which was previously considered stable, originate as outgoing modes near to the black hole event horizon. This same mechanism is also relevant for the instability of Cauchy horizons in other proposed counter-examples of strong cosmic censorship. |
1102.5636 | Alexander Petrov Nikolaevich | A.N. Petrov | Noether and Belinfante corrected types of currents for perturbations in
the Einstein-Gauss-Bonnet gravity | 22 pages, no figures, version accepted to CQG | Class. Quantum Grav. 28 (2011) 215021 (17pp) | 10.1088/0264-9381/28/21/215021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of an arbitrary $D$-dimensional metric theory, perturbations
are considered on arbitrary backgrounds that are however solutions of the
theory. Conserved currents for perturbations are presented following two known
prescriptions: canonical N{\oe}ther theorem and Belinfante symmetrization rule.
Using generalized formulae, currents in the Einstein-Gauss-Bonnet (EGB) gravity
for arbitrary types of perturbations on arbitrary curved backgrounds (not only
vacuum) are constructed in an explicit covariant form. Special attention is
paid to the energy-momentum tensors for perturbations which are an important
part in the structure of the currents. We use the derived expressions for two
applied calculations: a) to present the energy density for weak flat
gravitational waves in $D$-dimensional EGB gravity; b) to construct the mass
flux for the Maeda-Dadhich-Molina 3D radiating black holes of a Kaluza-Klein
type in 6D EGB gravity.
| [
{
"created": "Mon, 28 Feb 2011 10:55:04 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Oct 2011 08:54:39 GMT",
"version": "v2"
}
] | 2015-05-27 | [
[
"Petrov",
"A. N.",
""
]
] | In the framework of an arbitrary $D$-dimensional metric theory, perturbations are considered on arbitrary backgrounds that are however solutions of the theory. Conserved currents for perturbations are presented following two known prescriptions: canonical N{\oe}ther theorem and Belinfante symmetrization rule. Using generalized formulae, currents in the Einstein-Gauss-Bonnet (EGB) gravity for arbitrary types of perturbations on arbitrary curved backgrounds (not only vacuum) are constructed in an explicit covariant form. Special attention is paid to the energy-momentum tensors for perturbations which are an important part in the structure of the currents. We use the derived expressions for two applied calculations: a) to present the energy density for weak flat gravitational waves in $D$-dimensional EGB gravity; b) to construct the mass flux for the Maeda-Dadhich-Molina 3D radiating black holes of a Kaluza-Klein type in 6D EGB gravity. |
1904.00384 | Gianluca Calcagni | Gianluca Calcagni, Sachiko Kuroyanagi, Sylvain Marsat, Mairi
Sakellariadou, Nicola Tamanini, Gianmassimo Tasinato | Gravitational-wave luminosity distance in quantum gravity | 6 pages, 1 figure. v2: discussion improved; v3: references updated | Phys. Lett. B 798 (2019) 135000 | 10.1016/j.physletb.2019.135000 | KCL-PH-TH/2019-30 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dimensional flow, the scale dependence of the dimensionality of spacetime, is
a feature shared by many theories of quantum gravity (QG). We present the first
study of the consequences of QG dimensional flow for the luminosity distance
scaling of gravitational waves in the frequency ranges of LIGO and LISA. We
find generic modifications with respect to the standard general-relativistic
scaling, largely independent of specific QG proposals. We constrain these
effects using two examples of multimessenger standard sirens, the binary
neutron-star merger GW170817 and a simulated supermassive black-hole merger
event detectable with LISA. We apply these constraints to various QG
candidates, finding that the quantum geometries of group field theory, spin
foams and loop quantum gravity can give rise to observable signals in the
gravitational-wave spin-2 sector. Our results complement and improve GW
propagation-speed bounds on modified dispersion relations. Under more
model-dependent assumptions, we also show that bounds on quantum geometry can
be strengthened by solar-system tests.
| [
{
"created": "Sun, 31 Mar 2019 11:31:22 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Jul 2019 08:21:49 GMT",
"version": "v2"
},
{
"created": "Fri, 11 Oct 2019 11:38:06 GMT",
"version": "v3"
}
] | 2019-10-14 | [
[
"Calcagni",
"Gianluca",
""
],
[
"Kuroyanagi",
"Sachiko",
""
],
[
"Marsat",
"Sylvain",
""
],
[
"Sakellariadou",
"Mairi",
""
],
[
"Tamanini",
"Nicola",
""
],
[
"Tasinato",
"Gianmassimo",
""
]
] | Dimensional flow, the scale dependence of the dimensionality of spacetime, is a feature shared by many theories of quantum gravity (QG). We present the first study of the consequences of QG dimensional flow for the luminosity distance scaling of gravitational waves in the frequency ranges of LIGO and LISA. We find generic modifications with respect to the standard general-relativistic scaling, largely independent of specific QG proposals. We constrain these effects using two examples of multimessenger standard sirens, the binary neutron-star merger GW170817 and a simulated supermassive black-hole merger event detectable with LISA. We apply these constraints to various QG candidates, finding that the quantum geometries of group field theory, spin foams and loop quantum gravity can give rise to observable signals in the gravitational-wave spin-2 sector. Our results complement and improve GW propagation-speed bounds on modified dispersion relations. Under more model-dependent assumptions, we also show that bounds on quantum geometry can be strengthened by solar-system tests. |
0910.3140 | Steven B. Giddings | Steven B. Giddings | Beyond the Planck scale | 11 pages, 1 figure. To appear in the proceedings of the XXV Max Born
Symposium, "The Planck Scale," Wroclaw, Poland | null | 10.1063/1.3284370 | CERN-PH-TH/2009-193 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I outline motivations for believing that important quantum gravity effects
lie beyond the Planck scale at both higher energies and longer distances and
times. These motivations arise in part from the study of ultra-high energy
scattering, and also from considerations in cosmology. I briefly summarize some
inferences about such ultra-planckian physics, and clues we might pursue
towards the principles of a more fundamental theory addressing the known
puzzles and paradoxes of quantum gravity.
| [
{
"created": "Fri, 16 Oct 2009 15:22:54 GMT",
"version": "v1"
}
] | 2015-05-14 | [
[
"Giddings",
"Steven B.",
""
]
] | I outline motivations for believing that important quantum gravity effects lie beyond the Planck scale at both higher energies and longer distances and times. These motivations arise in part from the study of ultra-high energy scattering, and also from considerations in cosmology. I briefly summarize some inferences about such ultra-planckian physics, and clues we might pursue towards the principles of a more fundamental theory addressing the known puzzles and paradoxes of quantum gravity. |
2203.16083 | Alexander B. Balakin | Alexander B. Balakin and Alexei S. Ilin | Self-interaction in a cosmic dark fluid: The four-kernel rheological
extension of the equations of state | 19 pages, 3 figures | Phys. Rev. D, 105, 103525 (2022) | 10.1103/PhysRevD.105.103525 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We establish a new self-consistent model of coupling between the cosmic dark
energy and dark matter in the framework of the rheological approach, which is
based on the representation of the equations of state in terms of integral
operators of the Volterra-type. We elaborate the so-called four-kernel model,
in the framework of which both the dark energy and dark matter pressures are
presented by two integrals containing the energy densities of the dark energy
and dark matter. For the Volterra operators, the kernels of which are
associated with the effects of fading memory, the corresponding isotropic
homogeneous cosmological model is shown to be exactly integrable. We consider
the classification of the model exact solutions, based on the analysis of roots
of the characteristic polynomial associated with the key equation of the
presented model. The scalars of the pressure and energy-density of the dark
energy and dark matter, the Hubble function and acceleration parameter are
presented explicitly as the functions of the dimensionless scale factor. The
scale factor as the function of the cosmological time is found in quadratures
and is described analytically, qualitatively and numerically. Asymptotic
analysis allowed us to classify the models with respect to behavior typical for
the Big Rip, Little Rip and Pseudo Rip (de Sitter type). Two intriguing exact
cosmological solutions are discussed, which describe the super-exponential
expansion and the symmetric bounce. New solutions are presented, which
correspond to the quasi-periodic behavior of the state functions of the dark
fluid and of the geometric characteristics of the Universe.
| [
{
"created": "Wed, 30 Mar 2022 06:23:56 GMT",
"version": "v1"
}
] | 2022-06-09 | [
[
"Balakin",
"Alexander B.",
""
],
[
"Ilin",
"Alexei S.",
""
]
] | We establish a new self-consistent model of coupling between the cosmic dark energy and dark matter in the framework of the rheological approach, which is based on the representation of the equations of state in terms of integral operators of the Volterra-type. We elaborate the so-called four-kernel model, in the framework of which both the dark energy and dark matter pressures are presented by two integrals containing the energy densities of the dark energy and dark matter. For the Volterra operators, the kernels of which are associated with the effects of fading memory, the corresponding isotropic homogeneous cosmological model is shown to be exactly integrable. We consider the classification of the model exact solutions, based on the analysis of roots of the characteristic polynomial associated with the key equation of the presented model. The scalars of the pressure and energy-density of the dark energy and dark matter, the Hubble function and acceleration parameter are presented explicitly as the functions of the dimensionless scale factor. The scale factor as the function of the cosmological time is found in quadratures and is described analytically, qualitatively and numerically. Asymptotic analysis allowed us to classify the models with respect to behavior typical for the Big Rip, Little Rip and Pseudo Rip (de Sitter type). Two intriguing exact cosmological solutions are discussed, which describe the super-exponential expansion and the symmetric bounce. New solutions are presented, which correspond to the quasi-periodic behavior of the state functions of the dark fluid and of the geometric characteristics of the Universe. |
2103.14663 | Simone Mastrogiovanni | S. Mastrogiovanni, K. Leyde, C. Karathanasis, E. Chassande-Mottin, D.
A. Steer, J. Gair, A. Ghosh, R. Gray, S. Mukherjee, S. Rinaldi | Cosmology in the dark: On the importance of source population models for
gravitational-wave cosmology | 20 pages, 12 figures | Phys. Rev. D 104, 062009 (2021) | 10.1103/PhysRevD.104.062009 | null | gr-qc astro-ph.CO astro-ph.SR | http://creativecommons.org/licenses/by/4.0/ | Knowledge of the shape of the mass spectrum of compact objects can be used to
help break the degeneracy between the mass and redshift of the gravitational
wave (GW) sources, and thus can be used to infer cosmological parameters in the
absence of redshift measurements obtained from electromagnetic observations. In
this paper, we study extensively different aspects of this approach, including
its computational limits and achievable accuracy. We focus on ground-based
detectors with current and future sensitivities, we first perform the analysis
of an extensive set of simulated data with a hierarchical Bayesian scheme
inferring population and cosmological parameters. We consider a population
model (power-law plus Gaussian) which exhibits characteristic scales (extremes
of the mass spectrum, presence of an accumulation point) that allows an
indirect estimate of the source redshift. Our analysis of this catalog
highlights and quantifies the tight interplay between source population and
cosmological parameters, as well as the influence of initial assumptions
(whether formulated on the source or cosmological parameters). We then validate
our results by an "end-to-end" analysis using simulated GW data and posterior
samples generated from Bayesian samplers used for GW parameter estimation, thus
mirroring the analysis chain used for observational data for the first time in
literature. Our results then lead us to re-examine the estimation of $H_0$
obtained with GWTC-1, and we show explicitly how population assumptions impact
the final $H_0$ result. Our results underline the importance of inferring
population and cosmological parameters jointly (and not separately as is often
assumed). The only exception, as we discuss, is if an electromagnetic
counterpart was to be observed for all the BBH events: then the population
assumptions have less impact on the estimation of cosmological parameters.
| [
{
"created": "Fri, 26 Mar 2021 18:03:48 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Jun 2021 12:05:04 GMT",
"version": "v2"
}
] | 2021-09-29 | [
[
"Mastrogiovanni",
"S.",
""
],
[
"Leyde",
"K.",
""
],
[
"Karathanasis",
"C.",
""
],
[
"Chassande-Mottin",
"E.",
""
],
[
"Steer",
"D. A.",
""
],
[
"Gair",
"J.",
""
],
[
"Ghosh",
"A.",
""
],
[
"Gray",
... | Knowledge of the shape of the mass spectrum of compact objects can be used to help break the degeneracy between the mass and redshift of the gravitational wave (GW) sources, and thus can be used to infer cosmological parameters in the absence of redshift measurements obtained from electromagnetic observations. In this paper, we study extensively different aspects of this approach, including its computational limits and achievable accuracy. We focus on ground-based detectors with current and future sensitivities, we first perform the analysis of an extensive set of simulated data with a hierarchical Bayesian scheme inferring population and cosmological parameters. We consider a population model (power-law plus Gaussian) which exhibits characteristic scales (extremes of the mass spectrum, presence of an accumulation point) that allows an indirect estimate of the source redshift. Our analysis of this catalog highlights and quantifies the tight interplay between source population and cosmological parameters, as well as the influence of initial assumptions (whether formulated on the source or cosmological parameters). We then validate our results by an "end-to-end" analysis using simulated GW data and posterior samples generated from Bayesian samplers used for GW parameter estimation, thus mirroring the analysis chain used for observational data for the first time in literature. Our results then lead us to re-examine the estimation of $H_0$ obtained with GWTC-1, and we show explicitly how population assumptions impact the final $H_0$ result. Our results underline the importance of inferring population and cosmological parameters jointly (and not separately as is often assumed). The only exception, as we discuss, is if an electromagnetic counterpart was to be observed for all the BBH events: then the population assumptions have less impact on the estimation of cosmological parameters. |
0710.4252 | Sam Dolan Dr | Sam R. Dolan | Scattering of Long-Wavelength Gravitational Waves | 7 pages, no figs. Minor changes made to match published version | Phys.Rev.D77:044004,2008 | 10.1103/PhysRevD.77.044004 | null | gr-qc astro-ph | null | We consider the scattering of a low-frequency gravitational wave by a massive
compact body in vacuum. We apply partial-wave methods to compute amplitudes for
the helicity-conserving and helicity-reversing contributions to the cross
section, accurate to first order in $M\omega$. Contrary to previous claims, we
find that the partial-wave cross section agrees with the cross section derived
via perturbation-theory methods.
| [
{
"created": "Tue, 23 Oct 2007 12:26:53 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Feb 2008 10:19:29 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Dolan",
"Sam R.",
""
]
] | We consider the scattering of a low-frequency gravitational wave by a massive compact body in vacuum. We apply partial-wave methods to compute amplitudes for the helicity-conserving and helicity-reversing contributions to the cross section, accurate to first order in $M\omega$. Contrary to previous claims, we find that the partial-wave cross section agrees with the cross section derived via perturbation-theory methods. |
1707.09651 | Antonin Coutant | Antonin Coutant, Silke Weinfurtner | Low frequency analogue Hawking radiation: The Korteweg-de Vries model | 23 pages, 5 figures. v2: typo corrected, references added | Phys. Rev. D 97, 025005 (2018) | 10.1103/PhysRevD.97.025005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive analytic expressions for the low-frequency properties of the
analogue Hawking radiation in a general weak-dispersive medium. A thermal
low-frequency part of the spectrum is expected even when dispersive effects
become significant. We consider the two most common class of weak-dispersive
media and investigate all possible anomalous scattering processes due
inhomogeneous background flows. We first argue that under minimal assumptions,
the scattering processes in near-critical flows are well described by a
linearized Korteweg-de Vries equation. Within our theoretical model greybody
factors are neglected, that is, the mode co-moving with the flow decouples from
the other ones. We also exhibit a flow example with an exact expression for the
effective temperature. We see that this temperature coincides with the Hawking
one only when the dispersive length scale is much smaller than the flow
gradient scale. We apply the same method in inhomogeneous flows without an
analogue horizon. In this case, the spectrum coefficients decrease with
decreasing frequencies. Our findings are in agreement with previous numerical
works, generalizing their findings to arbitrary flow profiles. Our analytical
expressions provide estimates to guide ongoing experimental efforts.
| [
{
"created": "Sun, 30 Jul 2017 17:52:34 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Jan 2018 17:22:18 GMT",
"version": "v2"
}
] | 2018-01-15 | [
[
"Coutant",
"Antonin",
""
],
[
"Weinfurtner",
"Silke",
""
]
] | We derive analytic expressions for the low-frequency properties of the analogue Hawking radiation in a general weak-dispersive medium. A thermal low-frequency part of the spectrum is expected even when dispersive effects become significant. We consider the two most common class of weak-dispersive media and investigate all possible anomalous scattering processes due inhomogeneous background flows. We first argue that under minimal assumptions, the scattering processes in near-critical flows are well described by a linearized Korteweg-de Vries equation. Within our theoretical model greybody factors are neglected, that is, the mode co-moving with the flow decouples from the other ones. We also exhibit a flow example with an exact expression for the effective temperature. We see that this temperature coincides with the Hawking one only when the dispersive length scale is much smaller than the flow gradient scale. We apply the same method in inhomogeneous flows without an analogue horizon. In this case, the spectrum coefficients decrease with decreasing frequencies. Our findings are in agreement with previous numerical works, generalizing their findings to arbitrary flow profiles. Our analytical expressions provide estimates to guide ongoing experimental efforts. |
2110.11273 | Maria-Jose Guzman | Alexey Golovnev, Maria-Jose Guzman | Lorentz symmetries and primary constraints in covariant teleparallel
gravity | 19 pages, no figures, comments welcome | Phys. Rev. D 104, 124074 (2021) | 10.1103/PhysRevD.104.124074 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | In this article we explore local Lorentz transformations in theories of
gravity based on the teleparallel formalism. For the teleparallel equivalent of
general relativity (TEGR), the spin connection plays no role in the equations
of motion, and therefore it is possible to simply put it equal to zero with no
change in physical quantities, and then the theory is formulated purely in
terms of the tetrad field which can be freely chosen in any way. In nonlinear
modifications of TEGR, this is a more intricate issue, and vanishing spin
connection is then the Weitzenb\"{o}ck gauge choice which imposes restrictions
on the choice of tetrad. This has led to considering the so-called covariant
formulation of $f(T)$ gravity. We examine the primary constraints arising when
passing to the Hamiltonian framework, and compute their algebra. We show that
the problems of local Lorentz symmetry breaking still appear in this
formulation, even if in a different disguise.
| [
{
"created": "Thu, 21 Oct 2021 17:01:07 GMT",
"version": "v1"
}
] | 2021-12-30 | [
[
"Golovnev",
"Alexey",
""
],
[
"Guzman",
"Maria-Jose",
""
]
] | In this article we explore local Lorentz transformations in theories of gravity based on the teleparallel formalism. For the teleparallel equivalent of general relativity (TEGR), the spin connection plays no role in the equations of motion, and therefore it is possible to simply put it equal to zero with no change in physical quantities, and then the theory is formulated purely in terms of the tetrad field which can be freely chosen in any way. In nonlinear modifications of TEGR, this is a more intricate issue, and vanishing spin connection is then the Weitzenb\"{o}ck gauge choice which imposes restrictions on the choice of tetrad. This has led to considering the so-called covariant formulation of $f(T)$ gravity. We examine the primary constraints arising when passing to the Hamiltonian framework, and compute their algebra. We show that the problems of local Lorentz symmetry breaking still appear in this formulation, even if in a different disguise. |
1412.8383 | Yen Chin Ong | Pisin Chen, Keisuke Izumi, James M. Nester, Yen Chin Ong | Remnant Symmetry, Propagation and Evolution in f(T) Gravity | Fixed typo. Version accepted by PRD | Phys. Rev. D 91, 064003 (2015) | 10.1103/PhysRevD.91.064003 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was recently argued that f(T) gravity could inherit "remnant symmetry"
from the full Lorentz group, despite the fact that the theory is not locally
Lorentz invariant. Confusion has arisen regarding the implication of this
result for the previous works, which established that f(T) gravity is
pathological due to superluminal propagation, local acausality, and non-unique
time evolution. We clarify that the existence of the "remnant group" does not
rid the theory of these various problems, but instead strongly supports it.
| [
{
"created": "Mon, 29 Dec 2014 16:32:32 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Jan 2015 16:54:52 GMT",
"version": "v2"
},
{
"created": "Fri, 6 Mar 2015 21:55:56 GMT",
"version": "v3"
}
] | 2015-03-11 | [
[
"Chen",
"Pisin",
""
],
[
"Izumi",
"Keisuke",
""
],
[
"Nester",
"James M.",
""
],
[
"Ong",
"Yen Chin",
""
]
] | It was recently argued that f(T) gravity could inherit "remnant symmetry" from the full Lorentz group, despite the fact that the theory is not locally Lorentz invariant. Confusion has arisen regarding the implication of this result for the previous works, which established that f(T) gravity is pathological due to superluminal propagation, local acausality, and non-unique time evolution. We clarify that the existence of the "remnant group" does not rid the theory of these various problems, but instead strongly supports it. |
1106.1864 | Pablo Laguna | Tanja Bode, Pablo Laguna and Richard A. Matzner | Super-Extremal Spinning Black Holes via Accretion | 11 pages, 10 figures | null | 10.1103/PhysRevD.84.064044 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A Kerr black hole with mass $M$ and angular momentum $J$ satisfies the
extremality inequality $|J| \le M^2$. In the presence of matter and/or
gravitational radiation, this bound needs to be reformulated in terms of local
measurements of the mass and the angular momentum directly associated with the
black hole. The isolated and dynamical horizon framework provides such
quasi-local characterization of black hole mass and angular momentum. With this
framework, it is possible in axisymmetry to reformulate the extremality limit
as $|J| \le 2\,M_H^2$, with $M_H$ the irreducible mass of the black hole
computed from its apparent horizon area and $J$ obtained using approximate
rotational Killing vectors on the apparent horizon. The $|J| \le 2\,M_H^2$
condition is also equivalent to requiring a non-negative black hole surface
gravity. We present numerical experiments of an accreting black hole that
temporarily violates this extremality inequality. The initial configuration
consists of a single, rotating black hole surrounded by a thick, shell cloud of
negative energy density. For these numerical experiments, we introduce a new
matter-without-matter evolution method.
| [
{
"created": "Thu, 9 Jun 2011 17:22:37 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Bode",
"Tanja",
""
],
[
"Laguna",
"Pablo",
""
],
[
"Matzner",
"Richard A.",
""
]
] | A Kerr black hole with mass $M$ and angular momentum $J$ satisfies the extremality inequality $|J| \le M^2$. In the presence of matter and/or gravitational radiation, this bound needs to be reformulated in terms of local measurements of the mass and the angular momentum directly associated with the black hole. The isolated and dynamical horizon framework provides such quasi-local characterization of black hole mass and angular momentum. With this framework, it is possible in axisymmetry to reformulate the extremality limit as $|J| \le 2\,M_H^2$, with $M_H$ the irreducible mass of the black hole computed from its apparent horizon area and $J$ obtained using approximate rotational Killing vectors on the apparent horizon. The $|J| \le 2\,M_H^2$ condition is also equivalent to requiring a non-negative black hole surface gravity. We present numerical experiments of an accreting black hole that temporarily violates this extremality inequality. The initial configuration consists of a single, rotating black hole surrounded by a thick, shell cloud of negative energy density. For these numerical experiments, we introduce a new matter-without-matter evolution method. |
gr-qc/9905008 | hamid Reza Sepangi | F. Darabi and H. R. Sepangi | On Signature Transition and Compactification in Kaluza-Klein Cosmology | 13 pages, 3 figures | Class.Quant.Grav. 16 (1999) 1565-1575 | 10.1088/0264-9381/16/5/307 | null | gr-qc hep-th | null | We consider an empty (4+1) dimensional Kaluza-Klein universe with a negative
cosmological constant and a Robertson-Walker type metric. It is shown that the
solutions to Einstein field equations have degenerate metric and exhibit
transitioins from a Euclidean to a Lorentzian domain. We then suggest a
mechanism, based on signature transition which leads to compactification of the
internal space in the Lorentzian region as $a \sim |\Lambda|^{1/2}$. With the
assumption of a very small value for the cosmological constant we find that the
size of the universe $R$ and the internal scale factor $a$ would be related
according to $Ra\sim 1$ in the Lorentzian region. The corresponding
Wheeler-DeWitt equation has exact solution in the mini-superspace giving rise
to a quantum state which peaks in the vicinity of the classical solutions
undergoing signature transition.
| [
{
"created": "Mon, 3 May 1999 14:21:59 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Darabi",
"F.",
""
],
[
"Sepangi",
"H. R.",
""
]
] | We consider an empty (4+1) dimensional Kaluza-Klein universe with a negative cosmological constant and a Robertson-Walker type metric. It is shown that the solutions to Einstein field equations have degenerate metric and exhibit transitioins from a Euclidean to a Lorentzian domain. We then suggest a mechanism, based on signature transition which leads to compactification of the internal space in the Lorentzian region as $a \sim |\Lambda|^{1/2}$. With the assumption of a very small value for the cosmological constant we find that the size of the universe $R$ and the internal scale factor $a$ would be related according to $Ra\sim 1$ in the Lorentzian region. The corresponding Wheeler-DeWitt equation has exact solution in the mini-superspace giving rise to a quantum state which peaks in the vicinity of the classical solutions undergoing signature transition. |
1906.08640 | Luis Herrera | L. Herrera, A. Di Prisco and J. Carot | Complexity of the Bondi metric | 7 pages Revtex-4. Published in Phys.Rev. D. arXiv admin note: text
overlap with arXiv:gr-qc/0511112 | Phys. Rev. D99, 124028, (2019) | 10.1103/PhysRevD.99.124028 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A recently introduced concept of complexity for relativistic fluids is
extended to the vacuum solutions represented by the Bondi metric. A complexity
hierarchy is established, ranging from the Minkowski spacetime (the simplest
one) to gravitationally radiating systems (the more complex). Particularly
interesting is the possibility to differentiate between natural non--radiative
(NNRS) and non--natural non--radiative (NNNRS) systems, the latter appearing to
be simpler than the former. The relationship between vorticity and the degree
of complexity is stressed.
| [
{
"created": "Wed, 19 Jun 2019 08:19:47 GMT",
"version": "v1"
}
] | 2019-07-17 | [
[
"Herrera",
"L.",
""
],
[
"Di Prisco",
"A.",
""
],
[
"Carot",
"J.",
""
]
] | A recently introduced concept of complexity for relativistic fluids is extended to the vacuum solutions represented by the Bondi metric. A complexity hierarchy is established, ranging from the Minkowski spacetime (the simplest one) to gravitationally radiating systems (the more complex). Particularly interesting is the possibility to differentiate between natural non--radiative (NNRS) and non--natural non--radiative (NNNRS) systems, the latter appearing to be simpler than the former. The relationship between vorticity and the degree of complexity is stressed. |
1509.04163 | Mariafelicia De Laurentis Professor | Salvatore Capozziello, Mariafelicia De Laurentis, Ruben Farinelli,
Sergei D. Odintsov | The Mass-Radius relation for Neutron Stars in $f(R)$ gravity | 10 pages, 6 figures, to appear in Phys. Rev. D | Phys. Rev. D 93, 023501 (2016) | 10.1103/PhysRevD.93.023501 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the Mass -Radius diagram for static neutron star models obtained
by the numerical solution of modified Tolman-Oppenheimer-Volkoff equations in
$f(R)$ gravity where the Lagrangians $f(R)=R+\alpha R^2 (1+\gamma R)$ and
$f(R)=R^{1+\epsilon }$ are adopted. Unlike the case of the perturbative
approach previously reported, the solutions are constrained by the presence of
an extra degree of freedom, coming from the trace of the field equations. In
particular, the stiffness of the equation of state determines an upper limit on
the central density $\rho_c$ above which the the positivity condition of
energy-matter tensor trace $T^{\rm m}=\rho - 3 p$ holds. In the case of
quadratic f(R)-gravity, we find higher masses and radii at lower central
densities with an inversion of the behavior around a pivoting $\rho_c$ which
depends on the choice of the equation of state. When considering the cubic
corrections, we find solutions converging to the required asymptotic behavior
of flat metric only for $\gamma < 0$. A similar analysis is performed for
$f(R)=R^{1+\epsilon }$ considering $\epsilon$ as the leading parameter. We work
strictly in the Jordan frame in order to consider matter minimally coupled with
respect to geometry. This fact allows us to avoid ambiguities that could emerge
in adopting the Einstein frame.
| [
{
"created": "Thu, 10 Sep 2015 23:55:40 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Sep 2015 19:24:10 GMT",
"version": "v2"
},
{
"created": "Mon, 30 Nov 2015 21:35:03 GMT",
"version": "v3"
}
] | 2016-01-13 | [
[
"Capozziello",
"Salvatore",
""
],
[
"De Laurentis",
"Mariafelicia",
""
],
[
"Farinelli",
"Ruben",
""
],
[
"Odintsov",
"Sergei D.",
""
]
] | We discuss the Mass -Radius diagram for static neutron star models obtained by the numerical solution of modified Tolman-Oppenheimer-Volkoff equations in $f(R)$ gravity where the Lagrangians $f(R)=R+\alpha R^2 (1+\gamma R)$ and $f(R)=R^{1+\epsilon }$ are adopted. Unlike the case of the perturbative approach previously reported, the solutions are constrained by the presence of an extra degree of freedom, coming from the trace of the field equations. In particular, the stiffness of the equation of state determines an upper limit on the central density $\rho_c$ above which the the positivity condition of energy-matter tensor trace $T^{\rm m}=\rho - 3 p$ holds. In the case of quadratic f(R)-gravity, we find higher masses and radii at lower central densities with an inversion of the behavior around a pivoting $\rho_c$ which depends on the choice of the equation of state. When considering the cubic corrections, we find solutions converging to the required asymptotic behavior of flat metric only for $\gamma < 0$. A similar analysis is performed for $f(R)=R^{1+\epsilon }$ considering $\epsilon$ as the leading parameter. We work strictly in the Jordan frame in order to consider matter minimally coupled with respect to geometry. This fact allows us to avoid ambiguities that could emerge in adopting the Einstein frame. |
2404.08375 | Lang Liu | Zu-Cheng Chen and Lang Liu | Detecting a Gravitational-Wave Background from Null Energy Condition
Violation: Prospects for Taiji | 23 pages, 5 figures. arXiv admin note: text overlap with
arXiv:2310.00411 | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The null energy condition (NEC) is a fundamental principle in general
relativity, and its violation could leave discernible signatures in
gravitational waves (GWs). A violation of the NEC during the primordial era
would imprint a blue-tilted spectrum on the stochastic gravitational wave
background (SGWB) at nanohertz frequencies, potentially accounting for the
recently detected signal by pulsar timing arrays. Remarkably, models of NEC
violation during inflation also predict a nearly scale-invariant GW spectrum in
the millihertz frequency range, which could be detectable by upcoming
space-based GW detectors such as Taiji. The observation of this distinctive
spectrum would provide compelling evidence for new physics beyond the standard
cosmological paradigm. In this study, we explore Taiji's ability to detect an
SGWB arising from NEC violation during inflation, considering various
foregrounds and noise sources, including an extragalactic foreground from
binary black hole mergers throughout the universe, a galactic foreground from
white dwarf binaries, and the intrinsic noise of the Taiji detector. Employing
comprehensive Bayesian parameter estimation techniques to analyze simulated
Taiji data, we demonstrate a remarkable precision improvement of three orders
of magnitude compared to the NANOGrav 15-year data set for measuring the tensor
power spectrum amplitude, $P_{T,2}$, during the second inflationary stage. This
substantial enhancement in measurement capabilities underscores Taiji's
potential as a powerful probe for investigating the NEC violation in the early
Universe.
| [
{
"created": "Fri, 12 Apr 2024 10:20:29 GMT",
"version": "v1"
}
] | 2024-04-15 | [
[
"Chen",
"Zu-Cheng",
""
],
[
"Liu",
"Lang",
""
]
] | The null energy condition (NEC) is a fundamental principle in general relativity, and its violation could leave discernible signatures in gravitational waves (GWs). A violation of the NEC during the primordial era would imprint a blue-tilted spectrum on the stochastic gravitational wave background (SGWB) at nanohertz frequencies, potentially accounting for the recently detected signal by pulsar timing arrays. Remarkably, models of NEC violation during inflation also predict a nearly scale-invariant GW spectrum in the millihertz frequency range, which could be detectable by upcoming space-based GW detectors such as Taiji. The observation of this distinctive spectrum would provide compelling evidence for new physics beyond the standard cosmological paradigm. In this study, we explore Taiji's ability to detect an SGWB arising from NEC violation during inflation, considering various foregrounds and noise sources, including an extragalactic foreground from binary black hole mergers throughout the universe, a galactic foreground from white dwarf binaries, and the intrinsic noise of the Taiji detector. Employing comprehensive Bayesian parameter estimation techniques to analyze simulated Taiji data, we demonstrate a remarkable precision improvement of three orders of magnitude compared to the NANOGrav 15-year data set for measuring the tensor power spectrum amplitude, $P_{T,2}$, during the second inflationary stage. This substantial enhancement in measurement capabilities underscores Taiji's potential as a powerful probe for investigating the NEC violation in the early Universe. |
1004.0773 | Roberto A. Sussman | Roberto A. Sussman and German Izquierdo | A dynamical systems study of the inhomogeneous Lambda-CDM model | Final version published in Classical and Quantum Gravity: 26 pages in
IOP LaTeX macro style, 9 pdf figures | Class. Quant. Grav. 28:045006,2011;
Class.Quant.Grav.28:045006,2011 | 10.1088/0264-9381/28/4/045006 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider spherically symmetric inhomogeneous dust models with a positive
cosmological constant, $\Lambda$, given by the Lemaitre-Tolman-Bondi metric.
These configurations provide a simple but useful generalization of the
Lambda-CDM model describing cold dark matter (CDM) and a Lambda term, which
seems to fit current cosmological observations. The dynamics of these models
can be fully described by scalar evolution equations that can be given in the
form of a proper dynamical system associated with a 4-dimensional phase space
whose critical points and invariant subspaces are examined and classified. The
phase space evolution of various configurations is studied in detail by means
of two 2-dimensional subspaces: a projection into the invariant homogeneous
subspace associated with Lambda-CDM solutions with FLRW metric, and a
projection into a subspace generated by suitably defined fluctuations that
convey the effects of inhomogeneity. We look at cases with perpetual expansion,
bouncing and loitering behavior, as well as configurations with "mixed"
kinematic patters, such as a collapsing region in an expanding background. In
all cases, phase space trajectories emerge from and converge to stable past and
future attractors in a qualitatively analogous way as in the case of the FLRW
limit. However, we can identify in both projections of the phase space various
qualitative features absent in the FLRW limit that can be useful in the
construction of toy models of astrophysical and cosmological inhomogeneities.
| [
{
"created": "Tue, 6 Apr 2010 05:15:13 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Feb 2011 00:55:56 GMT",
"version": "v2"
}
] | 2015-03-14 | [
[
"Sussman",
"Roberto A.",
""
],
[
"Izquierdo",
"German",
""
]
] | We consider spherically symmetric inhomogeneous dust models with a positive cosmological constant, $\Lambda$, given by the Lemaitre-Tolman-Bondi metric. These configurations provide a simple but useful generalization of the Lambda-CDM model describing cold dark matter (CDM) and a Lambda term, which seems to fit current cosmological observations. The dynamics of these models can be fully described by scalar evolution equations that can be given in the form of a proper dynamical system associated with a 4-dimensional phase space whose critical points and invariant subspaces are examined and classified. The phase space evolution of various configurations is studied in detail by means of two 2-dimensional subspaces: a projection into the invariant homogeneous subspace associated with Lambda-CDM solutions with FLRW metric, and a projection into a subspace generated by suitably defined fluctuations that convey the effects of inhomogeneity. We look at cases with perpetual expansion, bouncing and loitering behavior, as well as configurations with "mixed" kinematic patters, such as a collapsing region in an expanding background. In all cases, phase space trajectories emerge from and converge to stable past and future attractors in a qualitatively analogous way as in the case of the FLRW limit. However, we can identify in both projections of the phase space various qualitative features absent in the FLRW limit that can be useful in the construction of toy models of astrophysical and cosmological inhomogeneities. |
1708.04489 | Justin Feng | Justin C. Feng and Richard A. Matzner | The Weiss Variation of the Gravitational Action | 32 pages w/ 2 figures. Revised to match published version | Gen Relativ Gravit (2018) 50: 99 | 10.1007/s10714-018-2420-2 | UTTG-04-17 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Weiss variational principle in mechanics and classical field theory is a
variational principle which allows displacements of the boundary. We review the
Weiss variation in mechanics and classical field theory, and present a novel
geometric derivation of the Weiss variation for the gravitational action: the
Einstein-Hilbert action plus the Gibbons-Hawking-York boundary term. In
particular, we use the first and second variation of area formulas (we present
a derivation accessible to physicists in an appendix) to interpret and vary the
Gibbons-Hawking-York boundary term. The Weiss variation for the gravitational
action is in principle known to the Relativity community, but the variation of
area approach formalizes the derivation, and facilitates the discussion of time
evolution in General Relativity. A potentially useful feature of the formalism
presented in this article is that it avoids an explicit 3+1 decomposition in
the bulk spacetime.
| [
{
"created": "Mon, 14 Aug 2017 04:21:51 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Oct 2017 16:52:20 GMT",
"version": "v2"
},
{
"created": "Tue, 24 Jul 2018 14:53:41 GMT",
"version": "v3"
}
] | 2018-07-25 | [
[
"Feng",
"Justin C.",
""
],
[
"Matzner",
"Richard A.",
""
]
] | The Weiss variational principle in mechanics and classical field theory is a variational principle which allows displacements of the boundary. We review the Weiss variation in mechanics and classical field theory, and present a novel geometric derivation of the Weiss variation for the gravitational action: the Einstein-Hilbert action plus the Gibbons-Hawking-York boundary term. In particular, we use the first and second variation of area formulas (we present a derivation accessible to physicists in an appendix) to interpret and vary the Gibbons-Hawking-York boundary term. The Weiss variation for the gravitational action is in principle known to the Relativity community, but the variation of area approach formalizes the derivation, and facilitates the discussion of time evolution in General Relativity. A potentially useful feature of the formalism presented in this article is that it avoids an explicit 3+1 decomposition in the bulk spacetime. |
2305.11453 | Yu Shi | Dawei Wu, Ji-chong Yang, Yu Shi | Exact conditions for antiUnruh effect in (1+1)-dimensional spacetime | 16 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Exact conditions for antiUnruh effect in (1+1)-dimensional spacetime are
obtained. For detectors with Gaussian switching functions, the analytic results
are similar to previous ones, indicating that antiUnruh effect occurs when the
energy gap matches the characteristic time scale. However, this conclusion does
not hold for detectors with square wave switching functions, in which case the
condition turns out to depend on both the energy gap and the characteristic
time scale in some nontrivial way. We also show analytically that there is no
antiUnruh effect for detectors with Gaussian switching functions in
(3+1)-dimensional spacetime.
| [
{
"created": "Fri, 19 May 2023 06:18:45 GMT",
"version": "v1"
}
] | 2023-05-22 | [
[
"Wu",
"Dawei",
""
],
[
"Yang",
"Ji-chong",
""
],
[
"Shi",
"Yu",
""
]
] | Exact conditions for antiUnruh effect in (1+1)-dimensional spacetime are obtained. For detectors with Gaussian switching functions, the analytic results are similar to previous ones, indicating that antiUnruh effect occurs when the energy gap matches the characteristic time scale. However, this conclusion does not hold for detectors with square wave switching functions, in which case the condition turns out to depend on both the energy gap and the characteristic time scale in some nontrivial way. We also show analytically that there is no antiUnruh effect for detectors with Gaussian switching functions in (3+1)-dimensional spacetime. |
1711.01147 | Mohsen Fathi | Mohsen Fathi, Morteza Mohseni | Congruence Convergence in pp-wave Spacetime | 14 pages, 2 figures | Theor. Math. Phys. 195 (2), 729-744 (2018) | 10.1134/S0040577918050082 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We argue that the well-known geodesic completeness property of pp-waves, can
be disregarded once the geodesics are extracted as being extended along sets of
Brinkmann coordinates. This issue is investigated in the more general context
of congruence convergence and we show that the problem leads to diverse issues
for non-geodesic congruences. The discussion is mostly based on the null
congruence expansion and a generalized Raychaudhuri equation is also provided.
| [
{
"created": "Thu, 2 Nov 2017 04:14:49 GMT",
"version": "v1"
},
{
"created": "Sun, 22 Apr 2018 05:33:59 GMT",
"version": "v2"
}
] | 2018-04-24 | [
[
"Fathi",
"Mohsen",
""
],
[
"Mohseni",
"Morteza",
""
]
] | We argue that the well-known geodesic completeness property of pp-waves, can be disregarded once the geodesics are extracted as being extended along sets of Brinkmann coordinates. This issue is investigated in the more general context of congruence convergence and we show that the problem leads to diverse issues for non-geodesic congruences. The discussion is mostly based on the null congruence expansion and a generalized Raychaudhuri equation is also provided. |
1204.2868 | Edward Anderson | Edward Anderson | Approaching the Problem of Time with a Combined
Semiclassical-Records-Histories Scheme | An improved version of the text, and with various further references.
25 pages, 4 figures | Class. Quantum Grav. 29 235015 (2012) | 10.1088/0264-9381/29/23/235015 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I approach the Problem of Time and other foundations of Quantum Cosmology
using a combined histories, timeless and semiclassical approach. This approach
is along the lines pursued by Halliwell. It involves the timeless probabilities
for dynamical trajectories entering regions of configuration space, which are
computed within the semiclassical regime. Moreover, the objects that Halliwell
uses in this approach commute with the Hamiltonian constraint, H. This approach
has not hitherto been considered for models that also possess nontrivial linear
constraints, Lin. This paper carries this out for some concrete relational
particle models (RPM's). If there is also commutation with Lin - the Kuchar
observables condition - the constructed objects are Dirac observables.
Moreover, this paper shows that the problem of Kuchar observables is explicitly
resolved for 1- and 2-d RPM's. Then as a first route to Halliwell's approach
for nontrivial linear constraints that is also a construction of Dirac
observables, I consider theories for which Kuchar observables are formally
known, giving the relational triangle as an example. As a second route, I apply
an indirect method that generalizes both group-averaging and Barbour's best
matching. For conceptual clarity, my study involves the simpler case of
Halliwell 2003 sharp-edged window function. I leave the elsewise-improved
softened case of Halliwell 2009 for a subsequent Paper II. Finally, I provide
comments on Halliwell's approach and how well it fares as regards the various
facets of the Problem of Time and as an implementation of QM propositions.
| [
{
"created": "Fri, 13 Apr 2012 03:11:19 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Aug 2012 11:19:03 GMT",
"version": "v2"
}
] | 2015-06-04 | [
[
"Anderson",
"Edward",
""
]
] | I approach the Problem of Time and other foundations of Quantum Cosmology using a combined histories, timeless and semiclassical approach. This approach is along the lines pursued by Halliwell. It involves the timeless probabilities for dynamical trajectories entering regions of configuration space, which are computed within the semiclassical regime. Moreover, the objects that Halliwell uses in this approach commute with the Hamiltonian constraint, H. This approach has not hitherto been considered for models that also possess nontrivial linear constraints, Lin. This paper carries this out for some concrete relational particle models (RPM's). If there is also commutation with Lin - the Kuchar observables condition - the constructed objects are Dirac observables. Moreover, this paper shows that the problem of Kuchar observables is explicitly resolved for 1- and 2-d RPM's. Then as a first route to Halliwell's approach for nontrivial linear constraints that is also a construction of Dirac observables, I consider theories for which Kuchar observables are formally known, giving the relational triangle as an example. As a second route, I apply an indirect method that generalizes both group-averaging and Barbour's best matching. For conceptual clarity, my study involves the simpler case of Halliwell 2003 sharp-edged window function. I leave the elsewise-improved softened case of Halliwell 2009 for a subsequent Paper II. Finally, I provide comments on Halliwell's approach and how well it fares as regards the various facets of the Problem of Time and as an implementation of QM propositions. |
1812.02136 | Iarley P. Lobo Dr | Iarley P. Lobo, Michele Ronco | Rainbow-like Black Hole metric from Loop Quantum Gravity | 29 pages | Universe 4 (2018), no.12, 139 | 10.3390/universe4120139 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The hypersurface deformation algebra consists in a fruitful approach to
derive deformed solutions of general relativity based on symmetry
considerations with quantum gravity effects, whose linearization has been
recently demonstrated to be connected to the DSR program by the
$\kappa$-Poincar\'e symmetry. Based on this approach, we analyzed the solution
derived for the interior of a black hole and we found similarities with the, so
called, rainbow metrics, like a momentum-dependence of the metric functions.
Moreover, we derived an effective, time-dependent Planck length and compared
different regularization schemes.
| [
{
"created": "Wed, 5 Dec 2018 17:50:35 GMT",
"version": "v1"
}
] | 2018-12-06 | [
[
"Lobo",
"Iarley P.",
""
],
[
"Ronco",
"Michele",
""
]
] | The hypersurface deformation algebra consists in a fruitful approach to derive deformed solutions of general relativity based on symmetry considerations with quantum gravity effects, whose linearization has been recently demonstrated to be connected to the DSR program by the $\kappa$-Poincar\'e symmetry. Based on this approach, we analyzed the solution derived for the interior of a black hole and we found similarities with the, so called, rainbow metrics, like a momentum-dependence of the metric functions. Moreover, we derived an effective, time-dependent Planck length and compared different regularization schemes. |
gr-qc/0602037 | Joe Polchinski | Gary T. Horowitz and Joseph Polchinski | Gauge/gravity duality | To appear in "Towards quantum gravity", ed. Daniele Oriti, Cambridge
University Press. 20pgs; v2, v3: references updated | null | null | null | gr-qc hep-th | null | We review the emergence of gravity from gauge theory in the context of
AdS/CFT duality. We discuss the evidence for the duality, its lessons for
gravitational physics, generalizations, and open questions.
| [
{
"created": "Fri, 10 Feb 2006 02:03:56 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Mar 2006 05:27:19 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Apr 2006 00:34:09 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Horowitz",
"Gary T.",
""
],
[
"Polchinski",
"Joseph",
""
]
] | We review the emergence of gravity from gauge theory in the context of AdS/CFT duality. We discuss the evidence for the duality, its lessons for gravitational physics, generalizations, and open questions. |
0709.0726 | Jan-Peter Boernsen | Jan-Peter Boernsen, Anton E. M. van de Ven | Inducing the Lovelock action | 11 pages, 3 figures | null | null | null | gr-qc hep-th | null | We re-analyze a possible ambiguity in the application of dimensional
regularization to Einstein-Gauss-Bonnet gravity, arising from the way one
treats the Gauss-Bonnet term. It is demonstrated that the addition of such a
term to the action gives rise to a non-minimal graviton wave operator, but does
not produce new on shell divergences at one loop order in d=4. However, from a
d-dimensional perspective the Gauss-Bonnet term is shown to generate new
divergences in the form of the six-dimensional Euler density. The conjecture
that one would next produce the eight-dimensional Euler term is shown to be
false.
| [
{
"created": "Wed, 5 Sep 2007 19:43:23 GMT",
"version": "v1"
}
] | 2011-11-10 | [
[
"Boernsen",
"Jan-Peter",
""
],
[
"van de Ven",
"Anton E. M.",
""
]
] | We re-analyze a possible ambiguity in the application of dimensional regularization to Einstein-Gauss-Bonnet gravity, arising from the way one treats the Gauss-Bonnet term. It is demonstrated that the addition of such a term to the action gives rise to a non-minimal graviton wave operator, but does not produce new on shell divergences at one loop order in d=4. However, from a d-dimensional perspective the Gauss-Bonnet term is shown to generate new divergences in the form of the six-dimensional Euler density. The conjecture that one would next produce the eight-dimensional Euler term is shown to be false. |
1305.7204 | Dibyendu Panigrahi DP | D. Panigrahi, B. C. Paul and S. Chatterjee | Constraining Modified Chaplygin gas parameters | 15 pages, 9 figures | Gravitation and Cosmology, 2015, Vol. 21, pp. 83 | 10.1134/S0202289315010119 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the evolution of a FRW model fuelled by a modified Chaplygin
gas with an equation of state $p = A\rho -\frac{B}{\rho^\alpha}$. An attempt is
made here to constrain the free parameters of MCG model through the wellknown
contour plot technique using observational data. The permissible range of
values of the pair of free parameters are determined to study the viability of
cosmological models \emph{vis-a-vis} observational results. Aside from allowing
the desirable feature of \emph{flip} of the sign of deceleration parameter we
also find that the transition from the decelerating to the accelerating phase
occurs at relatively low value of redshift in accordance with the observational
prediction that the acceleration is a recent phenomenon. It is found that the
effective acoustic speed may become imaginary depending upon the initial
conditions signalling that perturbations associated with instability sets in
resulting in structure formation. As one considers more negative values of $A$
the \emph{flip} in sign is delayed resulting the density parameter to change
fast. Again it is found from the contour plot that compatibility with
observational results is admitted with a value of $A$ which is very near to
zero or a small negative number.
| [
{
"created": "Thu, 30 May 2013 18:54:31 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Jul 2014 20:04:42 GMT",
"version": "v2"
}
] | 2015-10-23 | [
[
"Panigrahi",
"D.",
""
],
[
"Paul",
"B. C.",
""
],
[
"Chatterjee",
"S.",
""
]
] | We investigate the evolution of a FRW model fuelled by a modified Chaplygin gas with an equation of state $p = A\rho -\frac{B}{\rho^\alpha}$. An attempt is made here to constrain the free parameters of MCG model through the wellknown contour plot technique using observational data. The permissible range of values of the pair of free parameters are determined to study the viability of cosmological models \emph{vis-a-vis} observational results. Aside from allowing the desirable feature of \emph{flip} of the sign of deceleration parameter we also find that the transition from the decelerating to the accelerating phase occurs at relatively low value of redshift in accordance with the observational prediction that the acceleration is a recent phenomenon. It is found that the effective acoustic speed may become imaginary depending upon the initial conditions signalling that perturbations associated with instability sets in resulting in structure formation. As one considers more negative values of $A$ the \emph{flip} in sign is delayed resulting the density parameter to change fast. Again it is found from the contour plot that compatibility with observational results is admitted with a value of $A$ which is very near to zero or a small negative number. |
gr-qc/0208090 | Olivier Sarbach | Claudia Moreno, Olivier Sarbach | Stability properties of black holes in self-gravitating nonlinear
electrodynamics | 15 pages, no figures | Phys.Rev. D67 (2003) 024028 | 10.1103/PhysRevD.67.024028 | null | gr-qc | null | We analyze the dynamical stability of black hole solutions in
self-gravitating nonlinear electrodynamics with respect to arbitrary linear
fluctuations of the metric and the electromagnetic field. In particular, we
derive simple conditions on the electromagnetic Lagrangian which imply linear
stability in the domain of outer communication. We show that these conditions
hold for several of the regular black hole solutions found by Ayon-Beato and
Garcia.
| [
{
"created": "Thu, 29 Aug 2002 18:41:38 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Moreno",
"Claudia",
""
],
[
"Sarbach",
"Olivier",
""
]
] | We analyze the dynamical stability of black hole solutions in self-gravitating nonlinear electrodynamics with respect to arbitrary linear fluctuations of the metric and the electromagnetic field. In particular, we derive simple conditions on the electromagnetic Lagrangian which imply linear stability in the domain of outer communication. We show that these conditions hold for several of the regular black hole solutions found by Ayon-Beato and Garcia. |
1509.07354 | Szilvia Karsai | Gergely G\'abor Barnaf\"oldi, Szilvia Karsai, B\'ela Luk\'acs, and
P\'eter P\'osfay | Testing a Possible Way of Geometrization of the Strong Interaction by a
Kaluza-Klein Star | 10 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Geometrization of the fundamental interactions has been extensively studied
during the century. The idea of introducing compactified spatial dimensions
originated by Kaluza and Klein. Following their approach, several model were
built representing quantum numbers (e.g. charges) as compactified space-time
dimensions. Such geometrized theoretical descriptions of the fundamental
interactions might lead us to get closer to the unification of the principle
theories.
Here, we apply a $3+1_C+1$ dimensional theory, which contains one extra
compactified spatial dimension $1_C$ in connection with the flavour quantum
number in Quantum Chromodynamics. Within our model the size of the $1_C$
dimension is proportional to the inverse mass-difference of the first low-mass
baryon states. We used this phenomena to apply in a compact star model -- a
natural laboratory for testing the theory of strong interaction and the
gravitational theory in parallel.
Our aim is to test the modification of the measurable macroscopical
parameters of a compact Kaluza-Klein star by varying the size of the
compactified extra dimension. Since larger the $R_C$ the smaller the mass
difference between the first spokes of the Kaluza-Klein ladder resulting
smaller-mass stars. Using the Tolman-Oppenheimer-Volkov equation, we
investigate the $M$-$R$ diagram and the dependence of the maximum mass of
compact stars. Besides testing the validity of our model we compare our results
to the existing observational data of pulsar properties for constraints.
| [
{
"created": "Thu, 10 Sep 2015 09:25:10 GMT",
"version": "v1"
}
] | 2015-09-25 | [
[
"Barnaföldi",
"Gergely Gábor",
""
],
[
"Karsai",
"Szilvia",
""
],
[
"Lukács",
"Béla",
""
],
[
"Pósfay",
"Péter",
""
]
] | Geometrization of the fundamental interactions has been extensively studied during the century. The idea of introducing compactified spatial dimensions originated by Kaluza and Klein. Following their approach, several model were built representing quantum numbers (e.g. charges) as compactified space-time dimensions. Such geometrized theoretical descriptions of the fundamental interactions might lead us to get closer to the unification of the principle theories. Here, we apply a $3+1_C+1$ dimensional theory, which contains one extra compactified spatial dimension $1_C$ in connection with the flavour quantum number in Quantum Chromodynamics. Within our model the size of the $1_C$ dimension is proportional to the inverse mass-difference of the first low-mass baryon states. We used this phenomena to apply in a compact star model -- a natural laboratory for testing the theory of strong interaction and the gravitational theory in parallel. Our aim is to test the modification of the measurable macroscopical parameters of a compact Kaluza-Klein star by varying the size of the compactified extra dimension. Since larger the $R_C$ the smaller the mass difference between the first spokes of the Kaluza-Klein ladder resulting smaller-mass stars. Using the Tolman-Oppenheimer-Volkov equation, we investigate the $M$-$R$ diagram and the dependence of the maximum mass of compact stars. Besides testing the validity of our model we compare our results to the existing observational data of pulsar properties for constraints. |
2407.09602 | Maximilian Dax | Maximilian Dax, Stephen R. Green, Jonathan Gair, Nihar Gupte, Michael
P\"urrer, Vivien Raymond, Jonas Wildberger, Jakob H. Macke, Alessandra
Buonanno, Bernhard Sch\"olkopf | Real-time gravitational-wave inference for binary neutron stars using
machine learning | 8+8 pages, 3+7 figures | null | null | LIGO-P2400294 | gr-qc astro-ph.IM cs.LG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Mergers of binary neutron stars (BNSs) emit signals in both the
gravitational-wave (GW) and electromagnetic (EM) spectra. Famously, the 2017
multi-messenger observation of GW170817 led to scientific discoveries across
cosmology, nuclear physics, and gravity. Central to these results were the sky
localization and distance obtained from GW data, which, in the case of
GW170817, helped to identify the associated EM transient, AT 2017gfo, 11 hours
after the GW signal. Fast analysis of GW data is critical for directing
time-sensitive EM observations; however, due to challenges arising from the
length and complexity of signals, it is often necessary to make approximations
that sacrifice accuracy. Here, we present a machine learning framework that
performs complete BNS inference in just one second without making any such
approximations. Our approach enhances multi-messenger observations by providing
(i) accurate localization even before the merger; (ii) improved localization
precision by $\sim30\%$ compared to approximate low-latency methods; and (iii)
detailed information on luminosity distance, inclination, and masses, which can
be used to prioritize expensive telescope time. Additionally, the flexibility
and reduced cost of our method open new opportunities for equation-of-state
studies. Finally, we demonstrate that our method scales to extremely long
signals, up to an hour in length, thus serving as a blueprint for data analysis
for next-generation ground- and space-based detectors.
| [
{
"created": "Fri, 12 Jul 2024 18:00:02 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Aug 2024 13:00:54 GMT",
"version": "v2"
}
] | 2024-08-05 | [
[
"Dax",
"Maximilian",
""
],
[
"Green",
"Stephen R.",
""
],
[
"Gair",
"Jonathan",
""
],
[
"Gupte",
"Nihar",
""
],
[
"Pürrer",
"Michael",
""
],
[
"Raymond",
"Vivien",
""
],
[
"Wildberger",
"Jonas",
""
],
[... | Mergers of binary neutron stars (BNSs) emit signals in both the gravitational-wave (GW) and electromagnetic (EM) spectra. Famously, the 2017 multi-messenger observation of GW170817 led to scientific discoveries across cosmology, nuclear physics, and gravity. Central to these results were the sky localization and distance obtained from GW data, which, in the case of GW170817, helped to identify the associated EM transient, AT 2017gfo, 11 hours after the GW signal. Fast analysis of GW data is critical for directing time-sensitive EM observations; however, due to challenges arising from the length and complexity of signals, it is often necessary to make approximations that sacrifice accuracy. Here, we present a machine learning framework that performs complete BNS inference in just one second without making any such approximations. Our approach enhances multi-messenger observations by providing (i) accurate localization even before the merger; (ii) improved localization precision by $\sim30\%$ compared to approximate low-latency methods; and (iii) detailed information on luminosity distance, inclination, and masses, which can be used to prioritize expensive telescope time. Additionally, the flexibility and reduced cost of our method open new opportunities for equation-of-state studies. Finally, we demonstrate that our method scales to extremely long signals, up to an hour in length, thus serving as a blueprint for data analysis for next-generation ground- and space-based detectors. |
2010.12194 | Ming Zhang | Ming Zhang and Jie Jiang | Shadows of the accelerating black holes | 7 pages, 5 captioned figures | Phys. Rev. D 103, 025005 (2021) | 10.1103/PhysRevD.103.025005 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | Due to the acceleration of the black hole, the circular orbits of the photons
will deviate from the equatorial plane and the property of the black hole
shadow will change. We find that the latitude of the circular orbit increases
with the increasing acceleration and then show that the observer's inclination
angles which make the shadow radius and the shadow distortion maximum increase
with the increasing acceleration for the accelerating Kerr black hole.
| [
{
"created": "Fri, 23 Oct 2020 06:52:56 GMT",
"version": "v1"
}
] | 2021-01-20 | [
[
"Zhang",
"Ming",
""
],
[
"Jiang",
"Jie",
""
]
] | Due to the acceleration of the black hole, the circular orbits of the photons will deviate from the equatorial plane and the property of the black hole shadow will change. We find that the latitude of the circular orbit increases with the increasing acceleration and then show that the observer's inclination angles which make the shadow radius and the shadow distortion maximum increase with the increasing acceleration for the accelerating Kerr black hole. |
gr-qc/0105019 | Anzhong Wang | C.F.C. Brandt, L.-M. Lin, J.F. Villas da Rocha and A.Z. Wang | Gravitational collapse of spherically symmetric perfect fluid with
kinematic self-similarity | Revtex, 12 figures | Int.J.Mod.Phys. D11 (2002) 155-186 | 10.1142/S0218271802001500 | null | gr-qc | null | Analytic spherically symmetric solutions of the Einstein field equations
coupled with a perfect fluid and with self-similarities of the zeroth, first
and second kinds, found recently by Benoit and Coley [Class. Quantum Grav. {\bf
15}, 2397 (1998)], are studied, and found that some of them represent
gravitational collapse. When the solutions have self-similarity of the first
(homothetic) kind, some of the solutions may represent critical collapse but in
the sense that now the "critical" solution separates the collapse that forms
black holes from the collapse that forms naked singularities. The formation of
such black holes always starts with a mass gap, although the "critical"
solution has homothetic self-similarity. The solutions with self-similarity of
the zeroth and second kinds seem irrelevant to critical collapse. Yet, it is
also found that the de Sitter solution is a particular case of the solutions
with self-similarity of the zeroth kind, and that the Schwarzschild solution is
a particular case of the solutions with self-similarity of the second kind with
the index $\alpha = 3/2$.
| [
{
"created": "Fri, 4 May 2001 17:13:55 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Brandt",
"C. F. C.",
""
],
[
"Lin",
"L. -M.",
""
],
[
"da Rocha",
"J. F. Villas",
""
],
[
"Wang",
"A. Z.",
""
]
] | Analytic spherically symmetric solutions of the Einstein field equations coupled with a perfect fluid and with self-similarities of the zeroth, first and second kinds, found recently by Benoit and Coley [Class. Quantum Grav. {\bf 15}, 2397 (1998)], are studied, and found that some of them represent gravitational collapse. When the solutions have self-similarity of the first (homothetic) kind, some of the solutions may represent critical collapse but in the sense that now the "critical" solution separates the collapse that forms black holes from the collapse that forms naked singularities. The formation of such black holes always starts with a mass gap, although the "critical" solution has homothetic self-similarity. The solutions with self-similarity of the zeroth and second kinds seem irrelevant to critical collapse. Yet, it is also found that the de Sitter solution is a particular case of the solutions with self-similarity of the zeroth kind, and that the Schwarzschild solution is a particular case of the solutions with self-similarity of the second kind with the index $\alpha = 3/2$. |
2405.03623 | Fernando Carneiro | F. L. Carneiro, S. C. Ulhoa and M. P. Lobo | On Reference Frames and Coordinate Transformations | 12 pages, 1 figure. A new reference has been added | Rev. Bras. Ensino Fis. v.46, p.e20240043, 2024 | 10.1590/1806-9126-RBEF-2024-0043 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This article explores the differences between frame and coordinate
transformations in relativistic theories. We highlight the key role of tetrad
fields in connecting spacetime and frame indices. Using Maxwell's
electrodynamics as an example, we show that Maxwell's equations are invariant
under coordinate transformations but exhibit covariant behavior under frame
transformations. We also analyze the energy-momentum of an electromagnetic
field in different frames, providing deeper insights into the implications of
different frames of reference and coordinate systems.
| [
{
"created": "Mon, 6 May 2024 16:41:13 GMT",
"version": "v1"
},
{
"created": "Tue, 14 May 2024 16:03:31 GMT",
"version": "v2"
}
] | 2024-05-15 | [
[
"Carneiro",
"F. L.",
""
],
[
"Ulhoa",
"S. C.",
""
],
[
"Lobo",
"M. P.",
""
]
] | This article explores the differences between frame and coordinate transformations in relativistic theories. We highlight the key role of tetrad fields in connecting spacetime and frame indices. Using Maxwell's electrodynamics as an example, we show that Maxwell's equations are invariant under coordinate transformations but exhibit covariant behavior under frame transformations. We also analyze the energy-momentum of an electromagnetic field in different frames, providing deeper insights into the implications of different frames of reference and coordinate systems. |
0807.0069 | Chih-Hung Wang | Chih-Hung Wang, Yu-Huei Wu | Inflation in $R + R^2$ Gravity with Torsion | 9 pages, LaTex; v2: separated into five sections, added more content
in Introduction and Conclusion, abstract and section 2 improved; v3: three
typos are corrected | Class.Quant.Grav.26:045016,2009 | 10.1088/0264-9381/26/4/045016 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/3.0/ | We examine an inflationary model in $R + R^2$ gravity with torsion, where
$R^2$ denotes five independent quadratic curvature invariants; it turns out
that only two free parameters remain in this model. We show that the behavior
of the scale factor $a(t)$ is determined by two scalar fields, axial torsion
$\chi(t)$ and the totally anti-symmetric curvature $E(t)$, which satisfy two
first-order differential equations. Considering $\dot{\chi}\approx 0$ during
inflation leads to a power-law inflation: $a \sim (t+ A)^p$ where $1< p \leq 2
$, and the constant $A$ is determined by the initial values of $E$, $\chi$ and
the two parameters. After the end of inflation, $\chi$ and $E$ will enter into
an oscillatory phase.
| [
{
"created": "Tue, 1 Jul 2008 05:36:19 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Dec 2008 13:59:00 GMT",
"version": "v2"
},
{
"created": "Fri, 6 Feb 2009 08:51:40 GMT",
"version": "v3"
}
] | 2009-02-12 | [
[
"Wang",
"Chih-Hung",
""
],
[
"Wu",
"Yu-Huei",
""
]
] | We examine an inflationary model in $R + R^2$ gravity with torsion, where $R^2$ denotes five independent quadratic curvature invariants; it turns out that only two free parameters remain in this model. We show that the behavior of the scale factor $a(t)$ is determined by two scalar fields, axial torsion $\chi(t)$ and the totally anti-symmetric curvature $E(t)$, which satisfy two first-order differential equations. Considering $\dot{\chi}\approx 0$ during inflation leads to a power-law inflation: $a \sim (t+ A)^p$ where $1< p \leq 2 $, and the constant $A$ is determined by the initial values of $E$, $\chi$ and the two parameters. After the end of inflation, $\chi$ and $E$ will enter into an oscillatory phase. |
1303.6056 | Tetsuya Shiromizu | Tetsuya Shiromizu, Kentaro Tanabe | Static spacetimes with/without black holes in dynamical Chern-Simons
gravity | 3 pages | null | 10.1103/PhysRevD.87.081504 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the static and asymptotically flat black hole spacetime is
unique to be Schwarzschild spacetime in the dynamical Chern-Simons gravity. In
addition, we show that the strictly static spacetimes should be the Minkowski
spacetime.
| [
{
"created": "Mon, 25 Mar 2013 09:13:17 GMT",
"version": "v1"
}
] | 2015-06-15 | [
[
"Shiromizu",
"Tetsuya",
""
],
[
"Tanabe",
"Kentaro",
""
]
] | We show that the static and asymptotically flat black hole spacetime is unique to be Schwarzschild spacetime in the dynamical Chern-Simons gravity. In addition, we show that the strictly static spacetimes should be the Minkowski spacetime. |
1201.2379 | Ilia Musco | Ilia Musco and John C. Miller | Primordial black hole formation in the early universe: critical
behaviour and self-similarity | 23 pages, 8 figures, new abstract, submitted to Classical and Quantum
Gravity. This new version of the paper has been completely rewritten with
respect the previous one, with several changes and substantial additional
work | Class. Quantum Grav. 30 145009 (2013) | 10.1088/0264-9381/30/14/145009 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following on after three previous papers discussing the formation of
primordial black holes during the radiative era of the early universe, we
present here a further investigation of the critical nature of the process
involved, aimed at making contact with some of the basic underlying ideas from
the literature on critical collapse. We focus on the intermediate state, which
we have found appearing in cases with perturbations close to the critical
limit, and examine the connection between this and the similarity solutions
which play a fundamental role in the standard picture of critical collapse. We
have derived a set of self-similar equations for the null-slicing form of the
metric which we are using for our numerical calculations, and have then
compared the results obtained by integrating these with the ones coming from
our simulations for collapse of cosmological perturbations within an expanding
universe. We find that the similarity solution is asymptotically approached in
a region which grows to cover both the contracting matter and part of the
semi-void which forms outside it. Our main interest is in the situation
relevant for primordial black hole formation in the radiative era of the early
universe, where the relation between the pressure $p$ and the energy density
$e$ can be reasonably approximated by an expression of the form $p = we$ with
$w=1/3$. However, we have also looked at other values of $w$, both because
these have been considered in previous literature and also because they can be
helpful for giving further insight into situations relevant for primordial
black hole formation. As in our previous work, we have started our simulations
with initial supra-horizon scale perturbations of a type which could have come
from inflation.
| [
{
"created": "Wed, 11 Jan 2012 19:03:42 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Apr 2013 16:48:15 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Apr 2013 19:25:38 GMT",
"version": "v3"
}
] | 2013-12-11 | [
[
"Musco",
"Ilia",
""
],
[
"Miller",
"John C.",
""
]
] | Following on after three previous papers discussing the formation of primordial black holes during the radiative era of the early universe, we present here a further investigation of the critical nature of the process involved, aimed at making contact with some of the basic underlying ideas from the literature on critical collapse. We focus on the intermediate state, which we have found appearing in cases with perturbations close to the critical limit, and examine the connection between this and the similarity solutions which play a fundamental role in the standard picture of critical collapse. We have derived a set of self-similar equations for the null-slicing form of the metric which we are using for our numerical calculations, and have then compared the results obtained by integrating these with the ones coming from our simulations for collapse of cosmological perturbations within an expanding universe. We find that the similarity solution is asymptotically approached in a region which grows to cover both the contracting matter and part of the semi-void which forms outside it. Our main interest is in the situation relevant for primordial black hole formation in the radiative era of the early universe, where the relation between the pressure $p$ and the energy density $e$ can be reasonably approximated by an expression of the form $p = we$ with $w=1/3$. However, we have also looked at other values of $w$, both because these have been considered in previous literature and also because they can be helpful for giving further insight into situations relevant for primordial black hole formation. As in our previous work, we have started our simulations with initial supra-horizon scale perturbations of a type which could have come from inflation. |
1001.5129 | Tanwi Ghosh | Tanwi Ghosh and Soumitra Sengupta | Strong gravitational lensing across dilaton anti-de Sitter black hole | 8 pages and 3 figures. Accepted in Physical Review D | Phys.Rev.D81:044013,2010 | 10.1103/PhysRevD.81.044013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we investigate gravitational lensing effect in strong field
region around a dilaton black holes in an anti de Sitter (ADS) space. We also
analyse the dependence of the radius of the photon sphere and deflection angle
on dilaton coupling and cosmological constant in this black hole space time.
Finally the values of minimum impact parameter, the separation between the
first and the other images as well as the ratio between the flux of the first
image and the flux coming from all the other images are determined to
characterize some possible distinct signatures of such black holes.
| [
{
"created": "Thu, 28 Jan 2010 08:57:06 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Feb 2010 06:02:49 GMT",
"version": "v2"
}
] | 2010-04-14 | [
[
"Ghosh",
"Tanwi",
""
],
[
"Sengupta",
"Soumitra",
""
]
] | In this work we investigate gravitational lensing effect in strong field region around a dilaton black holes in an anti de Sitter (ADS) space. We also analyse the dependence of the radius of the photon sphere and deflection angle on dilaton coupling and cosmological constant in this black hole space time. Finally the values of minimum impact parameter, the separation between the first and the other images as well as the ratio between the flux of the first image and the flux coming from all the other images are determined to characterize some possible distinct signatures of such black holes. |
2011.00816 | Tao Zhang | Tao Zhang, Fu-Wen Shu, Qing-Wen Tang and Dong-Hui Du | Constraints on Ho\v{r}ava-Lifshitz gravity from GRB 170817A | 21 pages, 2 tables. Accepted for publication in EPJC | Eur. Phys. J. C 80, 1062 (2020) | 10.1140/epjc/s10052-020-08626-z | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we focus on a toy model: (3+1)-dimensional Ho\v{r}ava-Lifshitz
gravity coupling with an anisotropic electromagnetic (EM) field which is
generated through a Kaluza-Klein reduction of a (4+1)-dimensional
Ho\v{r}ava-Lifshitz gravity. This model exhibits a remarkable feature that it
has the same velocity for both gravitational and electromagnetic waves. This
feature makes it possible to restrict the parameters of the theory from GRB
170817A. In this work we use this feature to discuss possible constraints on
the parameter $\beta$ in the theory, by analyzing the possible Lorentz
invariance violation effect of the GRB 170817A. This is achieved by analyzing
potential time delay of gamma-ray photons in this event. It turns out that it
places a stringent constraint on this parameter. In the most ideal case, it
gives $|1-\sqrt{\beta}|<(10^{-19}-10^{-18})$.
| [
{
"created": "Mon, 2 Nov 2020 08:35:40 GMT",
"version": "v1"
}
] | 2020-11-24 | [
[
"Zhang",
"Tao",
""
],
[
"Shu",
"Fu-Wen",
""
],
[
"Tang",
"Qing-Wen",
""
],
[
"Du",
"Dong-Hui",
""
]
] | In this work we focus on a toy model: (3+1)-dimensional Ho\v{r}ava-Lifshitz gravity coupling with an anisotropic electromagnetic (EM) field which is generated through a Kaluza-Klein reduction of a (4+1)-dimensional Ho\v{r}ava-Lifshitz gravity. This model exhibits a remarkable feature that it has the same velocity for both gravitational and electromagnetic waves. This feature makes it possible to restrict the parameters of the theory from GRB 170817A. In this work we use this feature to discuss possible constraints on the parameter $\beta$ in the theory, by analyzing the possible Lorentz invariance violation effect of the GRB 170817A. This is achieved by analyzing potential time delay of gamma-ray photons in this event. It turns out that it places a stringent constraint on this parameter. In the most ideal case, it gives $|1-\sqrt{\beta}|<(10^{-19}-10^{-18})$. |
2109.08748 | Maxence Corman | Maxence Corman, Abhirup Ghosh, Celia Escamilla-Rivera, Martin
A.Hendry, Sylvain Marsat and Nicola Tamanini | Constraining cosmological extra dimensions with gravitational wave
standard sirens: from theory to current and future multi-messenger
observations | 20 pages, 3 figures | null | 10.1103/PhysRevD.105.064061 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The propagation of gravitational waves (GWs) at cosmological distances offers
a new way to test the gravitational interaction at the largest scales. Many
modified theories of gravity, usually introduced to explain the observed
acceleration of the universe, can be probed in an alternative and complementary
manner with respect to standard electromagnetic (EM) observations. In this
paper we consider a homogeneous and isotropic cosmology with extra spatial
dimensions at large scales, which represents a simple phenomenological
prototype for extra-dimensional modified gravity cosmological models. By
assuming that gravity propagates through the higher-dimensional spacetime,
while photons are constrained to the usual four dimensions of general
relativity, we derive from first principles the relation between the luminosity
distance measured by GW detectors and the one inferred by EM observations. We
then use this relation to constrain the number of cosmological extra dimensions
with the binary neutron star event GW170817 and the binary black hole merger
GW190521. We further provide forecasts for the Laser Interferometer Space
Antenna (LISA) by simulating multi-messenger observations of massive black hole
binary (MBHB) mergers. This paper extends and updates previous analyses which
crucially neglected an additional redshift dependency in the GW-EM luminosity
distance relation which affects results obtained from multi-messenger GW events
at high redshift, in particular constraints expected from LISA MBHBs.
| [
{
"created": "Fri, 17 Sep 2021 20:07:43 GMT",
"version": "v1"
}
] | 2022-04-13 | [
[
"Corman",
"Maxence",
""
],
[
"Ghosh",
"Abhirup",
""
],
[
"Escamilla-Rivera",
"Celia",
""
],
[
"Hendry",
"Martin A.",
""
],
[
"Marsat",
"Sylvain",
""
],
[
"Tamanini",
"Nicola",
""
]
] | The propagation of gravitational waves (GWs) at cosmological distances offers a new way to test the gravitational interaction at the largest scales. Many modified theories of gravity, usually introduced to explain the observed acceleration of the universe, can be probed in an alternative and complementary manner with respect to standard electromagnetic (EM) observations. In this paper we consider a homogeneous and isotropic cosmology with extra spatial dimensions at large scales, which represents a simple phenomenological prototype for extra-dimensional modified gravity cosmological models. By assuming that gravity propagates through the higher-dimensional spacetime, while photons are constrained to the usual four dimensions of general relativity, we derive from first principles the relation between the luminosity distance measured by GW detectors and the one inferred by EM observations. We then use this relation to constrain the number of cosmological extra dimensions with the binary neutron star event GW170817 and the binary black hole merger GW190521. We further provide forecasts for the Laser Interferometer Space Antenna (LISA) by simulating multi-messenger observations of massive black hole binary (MBHB) mergers. This paper extends and updates previous analyses which crucially neglected an additional redshift dependency in the GW-EM luminosity distance relation which affects results obtained from multi-messenger GW events at high redshift, in particular constraints expected from LISA MBHBs. |
1711.05138 | Manuel Kraemer | Jo\~ao Morais, Mariam Bouhmadi-L\'opez, Manuel Kraemer, Salvador
Robles-P\'erez | Pre-inflation from the multiverse: Can it solve the quadrupole problem
in the cosmic microwave background? | 15 pages, 9 figures. Correction of typos, one figure added. Accepted
for publication in European Physical Journal C | Eur. Phys. J. C (2018) 78: 240 | 10.1140/epjc/s10052-018-5698-z | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze a quantized toy model of a universe undergoing eternal inflation
using a quantum-field-theoretical formulation of the Wheeler-DeWitt equation.
This so-called third quantization method leads to the picture that the
eternally inflating universe is converted to a multiverse in which
sub-universes are created and exhibit a distinctive phase in their evolution
before reaching an asymptotic de Sitter phase. From the perspective of one of
these sub-universes, we can thus analyze the pre-inflationary phase that arises
naturally. Assuming that our observable universe is represented by one of those
sub-universes, we calculate how this pre-inflationary phase influences the
power spectrum of the cosmic microwave background (CMB) anisotropies and
analyze whether it can explain the observed discrepancy of the power spectrum
on large scales, i.e. the quadrupole issue in the CMB. While the answer to this
question is negative in the specific model analyzed here, we point out a
possible resolution of this issue.
| [
{
"created": "Tue, 14 Nov 2017 15:16:29 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Mar 2018 18:48:31 GMT",
"version": "v2"
}
] | 2018-03-22 | [
[
"Morais",
"João",
""
],
[
"Bouhmadi-López",
"Mariam",
""
],
[
"Kraemer",
"Manuel",
""
],
[
"Robles-Pérez",
"Salvador",
""
]
] | We analyze a quantized toy model of a universe undergoing eternal inflation using a quantum-field-theoretical formulation of the Wheeler-DeWitt equation. This so-called third quantization method leads to the picture that the eternally inflating universe is converted to a multiverse in which sub-universes are created and exhibit a distinctive phase in their evolution before reaching an asymptotic de Sitter phase. From the perspective of one of these sub-universes, we can thus analyze the pre-inflationary phase that arises naturally. Assuming that our observable universe is represented by one of those sub-universes, we calculate how this pre-inflationary phase influences the power spectrum of the cosmic microwave background (CMB) anisotropies and analyze whether it can explain the observed discrepancy of the power spectrum on large scales, i.e. the quadrupole issue in the CMB. While the answer to this question is negative in the specific model analyzed here, we point out a possible resolution of this issue. |
1005.3001 | Gerry McKeon | D.G.C. McKeon | The Canonical Structure of the First Order Einstein-Hilbert Action | null | Int.J.Mod.Phys.A25:3453-3480,2010 | 10.1142/S0217751X10050093 | null | gr-qc hep-th | http://creativecommons.org/licenses/publicdomain/ | The Dirac constraint formalism is used to analyze the first order form of the
Einstein-Hilbert action in d > 2 dimensions. Unlike previous treatments, this
is done without eliminating fields at the outset by solving equations of motion
that are independent of time derivatives when they correspond to first class
constraints. As anticipated by the way in which the affine connection
transforms under a diffeomorphism, not only primary and secondary but also
tertiary first class constraints arise. These leave d(d - 3) degrees of freedom
in phase space. The gauge invariance of the action is discussed, with special
attention being paid to the gauge generators of Henneaux, Teitelboim and
Zanelli and of Castellani.
| [
{
"created": "Mon, 17 May 2010 19:15:14 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"McKeon",
"D. G. C.",
""
]
] | The Dirac constraint formalism is used to analyze the first order form of the Einstein-Hilbert action in d > 2 dimensions. Unlike previous treatments, this is done without eliminating fields at the outset by solving equations of motion that are independent of time derivatives when they correspond to first class constraints. As anticipated by the way in which the affine connection transforms under a diffeomorphism, not only primary and secondary but also tertiary first class constraints arise. These leave d(d - 3) degrees of freedom in phase space. The gauge invariance of the action is discussed, with special attention being paid to the gauge generators of Henneaux, Teitelboim and Zanelli and of Castellani. |
1706.08779 | Kofinas Georgios | Georgios Kofinas, Vasilios Zarikas | A solution of the dark energy and its coincidence problem based on local
antigravity sources without fine-tuning or new scales | 34 pages, 2 figures, version to app. in Phys. Rev. D | Phys. Rev. D 97, 123542 (2018) | 10.1103/PhysRevD.97.123542 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A novel idea is proposed for a natural solution of the dark energy and its
cosmic coincidence problem. The existence of local antigravity sources,
associated with astrophysical matter configurations distributed throughout the
universe, can lead to a recent cosmic acceleration effect. Various physical
theories can be compatible with this idea, but here, in order to test our
proposal, we focus on quantum originated spherically symmetric metrics matched
with the cosmological evolution through the simplest Swiss cheese model. In the
context of asymptotically safe gravity, we have explained the observed amount
of dark energy using Newton's constant, the galaxy or cluster length scales,
and dimensionless order one parameters predicted by the theory, without
fine-tuning or extra unproven energy scales. The interior modified
Schwarzschild-de Sitter metric allows us to approximately interpret this result
as that the standard cosmological constant is a composite quantity made of the
above parameters, instead of a fundamental one.
| [
{
"created": "Tue, 27 Jun 2017 11:07:46 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Jun 2018 08:00:59 GMT",
"version": "v2"
}
] | 2018-07-04 | [
[
"Kofinas",
"Georgios",
""
],
[
"Zarikas",
"Vasilios",
""
]
] | A novel idea is proposed for a natural solution of the dark energy and its cosmic coincidence problem. The existence of local antigravity sources, associated with astrophysical matter configurations distributed throughout the universe, can lead to a recent cosmic acceleration effect. Various physical theories can be compatible with this idea, but here, in order to test our proposal, we focus on quantum originated spherically symmetric metrics matched with the cosmological evolution through the simplest Swiss cheese model. In the context of asymptotically safe gravity, we have explained the observed amount of dark energy using Newton's constant, the galaxy or cluster length scales, and dimensionless order one parameters predicted by the theory, without fine-tuning or extra unproven energy scales. The interior modified Schwarzschild-de Sitter metric allows us to approximately interpret this result as that the standard cosmological constant is a composite quantity made of the above parameters, instead of a fundamental one. |
2211.00314 | Shoki Iwaguchi | Shoki Iwaguchi, Atsushi Nishizawa, Yanbei Chen, Yuki Kawasaki,
Tomohiro Ishikawa, Masaaki Kitaguchi, Yutaka Yamagata, Bin Wu, Ryuma Shimizu,
Kurumi Umemura, Kenji Tsuji, Hirohiko Shimizu, Yuta Michimura, and Seiji
Kawamura | Displacement-noise-free interferometeric gravitational-wave detector
using unidirectional neutrons with four speeds | null | null | 10.1016/j.physleta.2022.128581 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For further gravitational wave (GW) detections, it is significant to invent a
technique to reduce all kinds of mirror displacement noise dominant at low
frequencies for ground-based detectors. The neutron displacement-noise-free
interferometer (DFI) is one of the tools to reduce all the mirror displacement
noise at lower frequencies. In this paper, we describe a further simplified
configuration of a neutron DFI in terms of neutron incidence direction. In the
new configuration, neutrons enter the interferometer with unidirectional
incidence at four speeds as opposed to two bidirectional incidences of opposite
directions at two speeds as reported previously. This simplification of the
neutron DFI is significant for proof-of-principle experiments.
| [
{
"created": "Tue, 1 Nov 2022 07:47:56 GMT",
"version": "v1"
}
] | 2022-12-28 | [
[
"Iwaguchi",
"Shoki",
""
],
[
"Nishizawa",
"Atsushi",
""
],
[
"Chen",
"Yanbei",
""
],
[
"Kawasaki",
"Yuki",
""
],
[
"Ishikawa",
"Tomohiro",
""
],
[
"Kitaguchi",
"Masaaki",
""
],
[
"Yamagata",
"Yutaka",
""
... | For further gravitational wave (GW) detections, it is significant to invent a technique to reduce all kinds of mirror displacement noise dominant at low frequencies for ground-based detectors. The neutron displacement-noise-free interferometer (DFI) is one of the tools to reduce all the mirror displacement noise at lower frequencies. In this paper, we describe a further simplified configuration of a neutron DFI in terms of neutron incidence direction. In the new configuration, neutrons enter the interferometer with unidirectional incidence at four speeds as opposed to two bidirectional incidences of opposite directions at two speeds as reported previously. This simplification of the neutron DFI is significant for proof-of-principle experiments. |
2403.08661 | Francesco Becattini | F. Becattini, D. Roselli (University of Florence and INFN) | Negative pressure as a quantum effect in free-streaming in the
cosmological background | 28 pages, 15 figures | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a study of energy density and pressure of a free real scalar
quantum field after its decoupling from a thermal bath in the spatially flat
Friedman-Lemaitre-Robertson-Walker space-time by solving the Klein-Gordon
equation both analytically and numerically for different predetermined scale
factor functions $a(t)$. The energy density and pressure, defined by
subtracting the vacuum expectation values at the decoupling time, feature
corrections with respect to the classical free-streaming solution of the
relativistic Boltzmann equation. We show that if the expansion rate is
comparable or larger than $mc^2/\hbar$ or $KT_0/\hbar$ where $m$ is the mass
and $T_0$ the decoupling temperature, both energy density and pressure gets
strong quantum corrections which substantially modify their classical
dependence on the scale factor $a(t)$ and drive pressure to large negative
values. For a minimally coupled field with a very low mass in an expanding de
Sitter universe quantum corrections are dominant driving pressure and energy
density to become asymptotically constant with an equation of state
$p/\varepsilon \simeq -1$, thereby mimicking a cosmological constant. For a
minimally coupled massless field, quantum corrections are asymptotically
dominant for any accelerated expansion.
| [
{
"created": "Wed, 13 Mar 2024 16:15:20 GMT",
"version": "v1"
}
] | 2024-03-14 | [
[
"Becattini",
"F.",
"",
"University of Florence and INFN"
],
[
"Roselli",
"D.",
"",
"University of Florence and INFN"
]
] | We present a study of energy density and pressure of a free real scalar quantum field after its decoupling from a thermal bath in the spatially flat Friedman-Lemaitre-Robertson-Walker space-time by solving the Klein-Gordon equation both analytically and numerically for different predetermined scale factor functions $a(t)$. The energy density and pressure, defined by subtracting the vacuum expectation values at the decoupling time, feature corrections with respect to the classical free-streaming solution of the relativistic Boltzmann equation. We show that if the expansion rate is comparable or larger than $mc^2/\hbar$ or $KT_0/\hbar$ where $m$ is the mass and $T_0$ the decoupling temperature, both energy density and pressure gets strong quantum corrections which substantially modify their classical dependence on the scale factor $a(t)$ and drive pressure to large negative values. For a minimally coupled field with a very low mass in an expanding de Sitter universe quantum corrections are dominant driving pressure and energy density to become asymptotically constant with an equation of state $p/\varepsilon \simeq -1$, thereby mimicking a cosmological constant. For a minimally coupled massless field, quantum corrections are asymptotically dominant for any accelerated expansion. |
2405.15499 | Jose Wadih Maluf Dr. | J. W. Maluf, F. Lessa Carneiro, S. C. Ulhoa and J. F. da Rocha-Neto | Energy of Gravitational Radiation and the Background Energy of the
Space-Time | 24 pages, 12 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We address the issue of gravitational radiation in the context of the
Bondi-Sachs space-time, and consider the expression for the gravitational
energy of the radiation obtained in the realm of the teleparallel equivalent of
general relativity (TEGR). This expression is independent of the radial
distance (i.e., of powers of $1/r$) and depends exclusively on the functions
$c(u,\theta,\phi)$ and $d(u,\theta,\phi)$, which yield the news functions ($u$
is the retarded time, $u=t-r$). We investigate the mathematical and physical
features of this energy expression in the simpler framework of axial symmetry.
Once a burst of gravitational radiation takes place in a self gravitating
system, that leads to a loss of the Bondi mass, gravitational radiation is
emitted throughout the whole space-time. The existence and presence of this
radiation in the background structure of the space-time is consistent with the
analysis developed by Papapetrou, and Hallidy and Janis, who found no proof
that a gravitational system that emits a burst of gravitational radiation is
preceded and followed by two stationary gravitational field configurations,
namely, it seems that it is impossible for a gravitational system, which is
initially stationary, to return to a stationary state after emitting a burst of
axially symmetric gravitational radiation, in which case the space-time is not
even asymptotically stationary. Therefore, it is plausible that the
gravitational energy of radiation is present in the background structure of the
space-time, and this is the energy predicted in the TEGR. This analysis lead us
to conjecture that the noise detected in the large terrestrial gravitational
wave observatories is intrinsically related to the background gravitational
radiation.
| [
{
"created": "Fri, 24 May 2024 12:38:49 GMT",
"version": "v1"
}
] | 2024-05-27 | [
[
"Maluf",
"J. W.",
""
],
[
"Carneiro",
"F. Lessa",
""
],
[
"Ulhoa",
"S. C.",
""
],
[
"da Rocha-Neto",
"J. F.",
""
]
] | We address the issue of gravitational radiation in the context of the Bondi-Sachs space-time, and consider the expression for the gravitational energy of the radiation obtained in the realm of the teleparallel equivalent of general relativity (TEGR). This expression is independent of the radial distance (i.e., of powers of $1/r$) and depends exclusively on the functions $c(u,\theta,\phi)$ and $d(u,\theta,\phi)$, which yield the news functions ($u$ is the retarded time, $u=t-r$). We investigate the mathematical and physical features of this energy expression in the simpler framework of axial symmetry. Once a burst of gravitational radiation takes place in a self gravitating system, that leads to a loss of the Bondi mass, gravitational radiation is emitted throughout the whole space-time. The existence and presence of this radiation in the background structure of the space-time is consistent with the analysis developed by Papapetrou, and Hallidy and Janis, who found no proof that a gravitational system that emits a burst of gravitational radiation is preceded and followed by two stationary gravitational field configurations, namely, it seems that it is impossible for a gravitational system, which is initially stationary, to return to a stationary state after emitting a burst of axially symmetric gravitational radiation, in which case the space-time is not even asymptotically stationary. Therefore, it is plausible that the gravitational energy of radiation is present in the background structure of the space-time, and this is the energy predicted in the TEGR. This analysis lead us to conjecture that the noise detected in the large terrestrial gravitational wave observatories is intrinsically related to the background gravitational radiation. |
2402.02294 | Zhongmin Qian | Zhongmin Qian | Dirac operators and field equations of the gravitational field and
matter fields | 17 pages | null | null | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | Dirac operators on curved space-times are introduced with the help of a new
point-view that observers have to be included in the formulation of natural
laws. The class of Dirac operators are Lorentz invariant in the sense that the
transformation rule is specified under diffeomorphisms of the space-time which
preserve the time orientation and the gravitational field. Moreover these Dirac
operators, like the original Dirac's operator with the special relativity,
satisfy the Hamiltonian relation required by the general theory of relativity
up to a correction due to the setup of a reference frame. In order to
generalise (or discover) Dirac operators, which have been an important building
block in the quantum field theories (QFTs), to curved space-times, we bring
observers (which are elements of the principal orthonormal bundle over the
space-time with its structure group being the proper Lorentz group) into the
description of Fermion fields in the presence of a gravitational field. As a
consequence field equations combining the gravitational field and matter fields
may be formulated. This work suggests that observational effects (due to the
setup of references) in the presence of a strong gravitational field, i.e.
matter, may be unavoidable.
| [
{
"created": "Sat, 3 Feb 2024 23:17:02 GMT",
"version": "v1"
}
] | 2024-02-06 | [
[
"Qian",
"Zhongmin",
""
]
] | Dirac operators on curved space-times are introduced with the help of a new point-view that observers have to be included in the formulation of natural laws. The class of Dirac operators are Lorentz invariant in the sense that the transformation rule is specified under diffeomorphisms of the space-time which preserve the time orientation and the gravitational field. Moreover these Dirac operators, like the original Dirac's operator with the special relativity, satisfy the Hamiltonian relation required by the general theory of relativity up to a correction due to the setup of a reference frame. In order to generalise (or discover) Dirac operators, which have been an important building block in the quantum field theories (QFTs), to curved space-times, we bring observers (which are elements of the principal orthonormal bundle over the space-time with its structure group being the proper Lorentz group) into the description of Fermion fields in the presence of a gravitational field. As a consequence field equations combining the gravitational field and matter fields may be formulated. This work suggests that observational effects (due to the setup of references) in the presence of a strong gravitational field, i.e. matter, may be unavoidable. |
gr-qc/0011040 | Gyula Fodor | Gyula Fodor | Generating spherically symmetric static perfect fluid solutions | 17 pages | null | null | null | gr-qc | null | By a choice of new variables the pressure isotropy condition for spherically
symmetric static perfect fluid spacetimes can be made a quadratic algebraic
equation in one of the two functions appearing in it. Using the other variable
as a generating function, the pressure and the density of the fluid can be
expressed algebraically by the function and its derivatives. One of the
functions in the metric can also be expressed similarly, but to obtain the
other function, related to the redshift factor, one has to perform an integral.
Conditions on the generating function ensuring regularity and physicality near
the center are investiagted. Two everywhere physically well behaving example
solutions are generated, one representing a compact fluid body with a zero
pressure surface, the other an infinite sphere.
| [
{
"created": "Sun, 12 Nov 2000 05:36:26 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Fodor",
"Gyula",
""
]
] | By a choice of new variables the pressure isotropy condition for spherically symmetric static perfect fluid spacetimes can be made a quadratic algebraic equation in one of the two functions appearing in it. Using the other variable as a generating function, the pressure and the density of the fluid can be expressed algebraically by the function and its derivatives. One of the functions in the metric can also be expressed similarly, but to obtain the other function, related to the redshift factor, one has to perform an integral. Conditions on the generating function ensuring regularity and physicality near the center are investiagted. Two everywhere physically well behaving example solutions are generated, one representing a compact fluid body with a zero pressure surface, the other an infinite sphere. |
gr-qc/0206083 | Charles Torre | C. G. Torre | Quantum Dynamics of the Polarized Gowdy Model | 24 pages, some typos corrected | Phys.Rev.D66:084017,2002 | 10.1103/PhysRevD.66.084017 | null | gr-qc hep-th math-ph math.MP | null | The polarized Gowdy ${\bf T}^3$ vacuum spacetimes are characterized, modulo
gauge, by a ``point particle'' degree of freedom and a function $\phi$ that
satisfies a linear field equation and a non-linear constraint. The quantum
Gowdy model has been defined by using a representation for $\phi$ on a Fock
space $\cal F$. Using this quantum model, it has recently been shown that the
dynamical evolution determined by the linear field equation for $\phi$ is not
unitarily implemented on $\cal F$. In this paper: (1) We derive the classical
and quantum model using the ``covariant phase space'' formalism. (2) We show
that time evolution is not unitarily implemented even on the physical Hilbert
space of states ${\cal H} \subset {\cal F}$ defined by the quantum constraint.
(3) We show that the spatially smeared canonical coordinates and momenta as
well as the time-dependent Hamiltonian for $\phi$ are well-defined,
self-adjoint operators for all time, admitting the usual probability
interpretation despite the lack of unitary dynamics.
| [
{
"created": "Thu, 27 Jun 2002 17:30:50 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Jun 2002 17:15:11 GMT",
"version": "v2"
}
] | 2009-02-24 | [
[
"Torre",
"C. G.",
""
]
] | The polarized Gowdy ${\bf T}^3$ vacuum spacetimes are characterized, modulo gauge, by a ``point particle'' degree of freedom and a function $\phi$ that satisfies a linear field equation and a non-linear constraint. The quantum Gowdy model has been defined by using a representation for $\phi$ on a Fock space $\cal F$. Using this quantum model, it has recently been shown that the dynamical evolution determined by the linear field equation for $\phi$ is not unitarily implemented on $\cal F$. In this paper: (1) We derive the classical and quantum model using the ``covariant phase space'' formalism. (2) We show that time evolution is not unitarily implemented even on the physical Hilbert space of states ${\cal H} \subset {\cal F}$ defined by the quantum constraint. (3) We show that the spatially smeared canonical coordinates and momenta as well as the time-dependent Hamiltonian for $\phi$ are well-defined, self-adjoint operators for all time, admitting the usual probability interpretation despite the lack of unitary dynamics. |
gr-qc/9409003 | Mike Cassidy | M.J.Cassidy | Nonlinearity in Quantum Theory and Closed Timelike Curves | 17 pages plain TeX, DAMTP R/94/34 | Phys.Rev. D52 (1995) 5676-5680 | 10.1103/PhysRevD.52.5676 | null | gr-qc hep-th | null | We examine consequences of the density matrix approach to quantum theory in
the context of a model spacetime containing closed timelike curves and find
that in general, an initially pure state will evolve in a nonlinear way to a
mixed quantum state. CPT invariance and the implications of this nonlinearity
for the statistical interpretation of quantum theory are discussed.
| [
{
"created": "Fri, 2 Sep 1994 14:46:30 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Sep 1994 16:46:00 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Cassidy",
"M. J.",
""
]
] | We examine consequences of the density matrix approach to quantum theory in the context of a model spacetime containing closed timelike curves and find that in general, an initially pure state will evolve in a nonlinear way to a mixed quantum state. CPT invariance and the implications of this nonlinearity for the statistical interpretation of quantum theory are discussed. |
1904.00270 | Mohammad Nouri-Zonoz | A. Besharat, M. Miri and M. Nouri-Zonoz | Optical Aharonov-Bohm effect due to toroidal moment inspired by general
relativity | 18 pages, Replaced with the published version | J. Phys. Commun. 3 (2019) 115019 | 10.1088/2399-6528/ab582a | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the analogy between propagation of light rays in a stationary curved
spacetime and in a toroidal (meta-)material. After introducing a novel
gravitational analog of the index of refraction of a magneto-electric medium,
it is argued that light rays not only feel a Lorentz-like force in a
magneto-electric medium due to the non-vanishing curl of the toroidal moment,
but also there exists an optical analog of Aharonov-Bohm effect for the rays
traveling in a region with a curl-free toroidal moment. Experimental
realization of this effect could utilize either a multiferroic material or a
toroidal metamaterial.
| [
{
"created": "Sat, 30 Mar 2019 19:02:27 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Apr 2019 07:07:51 GMT",
"version": "v2"
},
{
"created": "Wed, 6 May 2020 22:13:31 GMT",
"version": "v3"
}
] | 2020-05-08 | [
[
"Besharat",
"A.",
""
],
[
"Miri",
"M.",
""
],
[
"Nouri-Zonoz",
"M.",
""
]
] | We study the analogy between propagation of light rays in a stationary curved spacetime and in a toroidal (meta-)material. After introducing a novel gravitational analog of the index of refraction of a magneto-electric medium, it is argued that light rays not only feel a Lorentz-like force in a magneto-electric medium due to the non-vanishing curl of the toroidal moment, but also there exists an optical analog of Aharonov-Bohm effect for the rays traveling in a region with a curl-free toroidal moment. Experimental realization of this effect could utilize either a multiferroic material or a toroidal metamaterial. |
2209.05475 | Gonzalo Morras | Gonzalo Morras, Jose Francisco Nu\~no Siles, Juan Garcia-Bellido,
Ester Ruiz Morales | The False Alarms induced by Gaussian Noise in Gravitational Wave
Detectors | 22 pages, 11 figures | Phys. Rev. D 107, 023027 (2023) | 10.1103/PhysRevD.107.023027 | IFT-UAM/CSIC-22-105 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gaussian noise is an irreducible component of the background in gravitational
wave (GW) detectors. Although stationary Gaussian noise is uncorrelated in
frequencies, we show that there is an important correlation in time when
looking at the matched filter signal to noise ratio (SNR) of a template, with a
typical autocorrelation time that depends on the template and the shape of the
noise power spectral density (PSD). Taking this correlation into account, we
compute from first principles the false alarm rate (FAR) of a template in
Gaussian noise, defined as the number of occurrences per unit time that the
template's matched filter SNR goes over a threshold $\rho$. We find that the
Gaussian FAR can be well approximated by the usual expression for uncorrelated
noise, if we replace the sampling rate by an effective sampling rate that
depends on the parameters of the template, the noise PSD and the threshold
$\rho$. This results in a minimum SNR threshold that has to be demanded to a
given GW trigger, if we want to keep events generated from Gaussian noise below
a certain FAR. We extend the formalism to multiple detectors and to the
analysis of GW events. We apply our method to the GW candidates added in the
GWTC-3 catalog, and discuss the possibility that GW200308\_173609 and
GW200322\_091133 could be generated by Gaussian noise fluctuations.
| [
{
"created": "Mon, 12 Sep 2022 17:59:03 GMT",
"version": "v1"
}
] | 2023-02-01 | [
[
"Morras",
"Gonzalo",
""
],
[
"Siles",
"Jose Francisco Nuño",
""
],
[
"Garcia-Bellido",
"Juan",
""
],
[
"Morales",
"Ester Ruiz",
""
]
] | Gaussian noise is an irreducible component of the background in gravitational wave (GW) detectors. Although stationary Gaussian noise is uncorrelated in frequencies, we show that there is an important correlation in time when looking at the matched filter signal to noise ratio (SNR) of a template, with a typical autocorrelation time that depends on the template and the shape of the noise power spectral density (PSD). Taking this correlation into account, we compute from first principles the false alarm rate (FAR) of a template in Gaussian noise, defined as the number of occurrences per unit time that the template's matched filter SNR goes over a threshold $\rho$. We find that the Gaussian FAR can be well approximated by the usual expression for uncorrelated noise, if we replace the sampling rate by an effective sampling rate that depends on the parameters of the template, the noise PSD and the threshold $\rho$. This results in a minimum SNR threshold that has to be demanded to a given GW trigger, if we want to keep events generated from Gaussian noise below a certain FAR. We extend the formalism to multiple detectors and to the analysis of GW events. We apply our method to the GW candidates added in the GWTC-3 catalog, and discuss the possibility that GW200308\_173609 and GW200322\_091133 could be generated by Gaussian noise fluctuations. |
2010.10674 | Mart\'in G. Richarte MR | J\'ulio C. Fabris, Mart\'in G. Richarte, Alberto Saa | Quasinormal modes and self-adjoint extensions of the Schroedinger
operator | & pages, 1 Figure. Accepted for its publication in Physical Review D | Phys. Rev. D 103, 045001 (2021) | 10.1103/PhysRevD.103.045001 | null | gr-qc hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit here the analytical continuation approach usually employed to
compute quasinormal modes (QNM) and frequencies of a given potential barrier
$V$ starting from the bounded states and respective eigenvalues of the
Schroedinger operator associated with the potential well corresponding to the
inverted potential $-V$. We consider an exactly soluble problem corresponding
to a potential barrier of the Poschl-Teller type with a well defined and
behaved QNM spectrum, but for which the associated Schroedinger operator $\cal
H$ obtained by analytical continuation fails to be self-adjoint. Although $\cal
H$ admits self-adjoint extensions, we show that the eigenstates corresponding
to the analytically continued QNM do not belong to any self-adjoint extension
domain and, consequently, they cannot be interpreted as authentic quantum
mechanical bounded states. Our result challenges the practical use of the this
type of method when $\cal H$ fails to be self-adjoint since, in such cases, we
would not have in advance any reasonable criterion to choose the initial
eigenstates of $\cal H$ which would correspond to the analytically continued
QNM.
| [
{
"created": "Tue, 20 Oct 2020 23:53:44 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Jan 2021 18:03:37 GMT",
"version": "v2"
}
] | 2021-02-09 | [
[
"Fabris",
"Júlio C.",
""
],
[
"Richarte",
"Martín G.",
""
],
[
"Saa",
"Alberto",
""
]
] | We revisit here the analytical continuation approach usually employed to compute quasinormal modes (QNM) and frequencies of a given potential barrier $V$ starting from the bounded states and respective eigenvalues of the Schroedinger operator associated with the potential well corresponding to the inverted potential $-V$. We consider an exactly soluble problem corresponding to a potential barrier of the Poschl-Teller type with a well defined and behaved QNM spectrum, but for which the associated Schroedinger operator $\cal H$ obtained by analytical continuation fails to be self-adjoint. Although $\cal H$ admits self-adjoint extensions, we show that the eigenstates corresponding to the analytically continued QNM do not belong to any self-adjoint extension domain and, consequently, they cannot be interpreted as authentic quantum mechanical bounded states. Our result challenges the practical use of the this type of method when $\cal H$ fails to be self-adjoint since, in such cases, we would not have in advance any reasonable criterion to choose the initial eigenstates of $\cal H$ which would correspond to the analytically continued QNM. |
gr-qc/0601138 | Juan Antonio Morales Lladosa | Juan Antonio Morales Lladosa | Coordinates and frames from the causal point of view | 5 pages, 1 figure, short communication in A Century of Relativity
Physics, Proceedings of the XXVIII Spanish Relativity Meeting ERE-2006, 6-10
September - Oviedo - Spain (AIP Conference Proceedings) | null | 10.1063/1.2218231 | null | gr-qc | null | Lorentzian frames may belong to one of the 199 causal classes. Of these
numerous causal classes, people are essentially aware only of two of them.
Nevertheless, other causal classes are present in some well-known solutions, or
present a strong interest in the physical construction of coordinate systems.
Here we show the unusual causal classes to which belong so familiar coordinate
systems as those of Lema{\^{\i}}tre, those of Eddington-Finkelstein, or those
of Bondi-Sachs. Also the causal classes associated to the Coll light
coordinates (four congruences of real geodetic null lines) and to the Coll
positioning systems (light signals broadcasted by four clocks) are analyzed.
The role that these results play in the comprehension and classification of
relativistic coordinate systems is emphasized.
| [
{
"created": "Tue, 31 Jan 2006 16:32:14 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Lladosa",
"Juan Antonio Morales",
""
]
] | Lorentzian frames may belong to one of the 199 causal classes. Of these numerous causal classes, people are essentially aware only of two of them. Nevertheless, other causal classes are present in some well-known solutions, or present a strong interest in the physical construction of coordinate systems. Here we show the unusual causal classes to which belong so familiar coordinate systems as those of Lema{\^{\i}}tre, those of Eddington-Finkelstein, or those of Bondi-Sachs. Also the causal classes associated to the Coll light coordinates (four congruences of real geodetic null lines) and to the Coll positioning systems (light signals broadcasted by four clocks) are analyzed. The role that these results play in the comprehension and classification of relativistic coordinate systems is emphasized. |
gr-qc/9308001 | Jorge Pullin | Octavio Obregon, Jorge Pullin and Michael P. Ryan | Bianchi Cosmologies: New Variables and a Hidden Supersymmetry | 15 Pages, RevTex, NSF-ITP-93-90 | Phys.Rev. D48 (1993) 5642-5647 | 10.1103/PhysRevD.48.5642 | null | gr-qc | null | We find a supersymmetrization of the Bianchi IX cosmology in terms of
Ashtekar's new variables. This provides a framework for connecting the recent
results of Graham and those of Ryan and Moncrief for quantum states of this
model. These states are also related with the states obtained particularizing
supergravity for a minisuperspace. Implications for the general theory are also
briefly discussed.
| [
{
"created": "Wed, 4 Aug 1993 14:41:52 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Obregon",
"Octavio",
""
],
[
"Pullin",
"Jorge",
""
],
[
"Ryan",
"Michael P.",
""
]
] | We find a supersymmetrization of the Bianchi IX cosmology in terms of Ashtekar's new variables. This provides a framework for connecting the recent results of Graham and those of Ryan and Moncrief for quantum states of this model. These states are also related with the states obtained particularizing supergravity for a minisuperspace. Implications for the general theory are also briefly discussed. |
gr-qc/9805009 | Claus Laemmerzahl | Claus L\"ammerzahl | Quantum Tests of the Foundations of General Relativity | Classical and Quantum Gravity 15, 13 (1998) | null | 10.1088/0264-9381/15/1/003 | null | gr-qc | null | The role of the equivalence principle in the context of non-relativistic
quantum mechanics and matter wave interferometry, especially atom beam
interferometry, will be discussed. A generalised form of the weak equivalence
principle which is capable of covering quantum phenomena too, will be proposed.
It is shown that this generalised equivalence principle is valid for matter
wave interferometry and for the dynamics of expectation values. In addition,
the use of this equivalence principle makes it possible to determine the
structure of the interaction of quantum systems with gravitational and inertial
fields. It is also shown that the path of the mean value of the position
operator in the case of gravitational interaction does fulfill this generalised
equivalence principle.
| [
{
"created": "Tue, 5 May 1998 09:50:36 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Lämmerzahl",
"Claus",
""
]
] | The role of the equivalence principle in the context of non-relativistic quantum mechanics and matter wave interferometry, especially atom beam interferometry, will be discussed. A generalised form of the weak equivalence principle which is capable of covering quantum phenomena too, will be proposed. It is shown that this generalised equivalence principle is valid for matter wave interferometry and for the dynamics of expectation values. In addition, the use of this equivalence principle makes it possible to determine the structure of the interaction of quantum systems with gravitational and inertial fields. It is also shown that the path of the mean value of the position operator in the case of gravitational interaction does fulfill this generalised equivalence principle. |
gr-qc/0512125 | David Delphenich | David Delphenich | Projective geometry and special relativity | 41 pages, 4 figures. Annalen der Physik (Leipzig) (2006), to be
published | Annalen Phys. 15 (2006) 216-246 | 10.1002/andp.200510179 | null | gr-qc | null | Some concepts of real and complex projective geometry are applied to the
fundamental physical notions that relate to Minkowski space and the Lorentz
group. In particular, it is shown that the transition from an infinite speed of
propagation for light waves to a finite one entails the replacement of a
hyperplane at infinity with a light cone and the replacement of an affine
hyperplane - or rest space - with a proper time hyperboloid. The transition
from the metric theory of electromagnetism to the pre-metric theory is
discussed in the context of complex projective geometry, and ultimately it is
proposed that the geometrical issues are more general than electromagnetism,
namely, they pertain to the transition from point mechanics to wave mechanics.
| [
{
"created": "Thu, 22 Dec 2005 00:40:29 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Delphenich",
"David",
""
]
] | Some concepts of real and complex projective geometry are applied to the fundamental physical notions that relate to Minkowski space and the Lorentz group. In particular, it is shown that the transition from an infinite speed of propagation for light waves to a finite one entails the replacement of a hyperplane at infinity with a light cone and the replacement of an affine hyperplane - or rest space - with a proper time hyperboloid. The transition from the metric theory of electromagnetism to the pre-metric theory is discussed in the context of complex projective geometry, and ultimately it is proposed that the geometrical issues are more general than electromagnetism, namely, they pertain to the transition from point mechanics to wave mechanics. |
2012.09193 | Sebasti\'an Bahamonde Dr | Sebastian Bahamonde, Jorge Gigante Valcarcel, Laur J\"arv, Christian
Pfeifer | Exploring Axial Symmetry in Modified Teleparallel Gravity | 26 pages, 1 figure. Matches published version in PRD | Phys. Rev. D 103, 044058 (2021) | 10.1103/PhysRevD.103.044058 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Axially symmetric spacetimes play an important role in the relativistic
description of rotating astrophysical objects like black holes, stars, etc. In
gravitational theories that venture beyond the usual Riemannian geometry by
allowing independent connection components, the notion of symmetry concerns,
not just the metric, but also the connection. As discovered recently, in
teleparallel geometries, axial symmetry can be realised in two branches, while
only one of these has a continuous spherically symmetric limit. In the current
paper, we consider a very generic $f(T,B,\phi,X)$ family of teleparallel
gravities, whose action depends on the torsion scalar $T$ and the boundary term
$B$, as well as a scalar field $\phi$ with its kinetic term $X$. As the field
equations can be decomposed into symmetric and antisymmetric (spin connection)
parts, we thoroughly analyse the antisymmetric equations and look for solutions
of axial spacetimes which could be used as ans\"atze to tackle the symmetric
part of the field equations. In particular, we find solutions corresponding to
a generalisation of the Taub-NUT metric, and the slowly rotating Kerr
spacetime. Since this work also concerns a wider issue of how to determine the
spin connection in teleparallel gravity, we also show that the method of
"turning off gravity" proposed in the literature, does not always produce a
solution to the antisymmetric equations.
| [
{
"created": "Wed, 16 Dec 2020 19:00:04 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Feb 2021 17:40:39 GMT",
"version": "v2"
}
] | 2021-02-26 | [
[
"Bahamonde",
"Sebastian",
""
],
[
"Valcarcel",
"Jorge Gigante",
""
],
[
"Järv",
"Laur",
""
],
[
"Pfeifer",
"Christian",
""
]
] | Axially symmetric spacetimes play an important role in the relativistic description of rotating astrophysical objects like black holes, stars, etc. In gravitational theories that venture beyond the usual Riemannian geometry by allowing independent connection components, the notion of symmetry concerns, not just the metric, but also the connection. As discovered recently, in teleparallel geometries, axial symmetry can be realised in two branches, while only one of these has a continuous spherically symmetric limit. In the current paper, we consider a very generic $f(T,B,\phi,X)$ family of teleparallel gravities, whose action depends on the torsion scalar $T$ and the boundary term $B$, as well as a scalar field $\phi$ with its kinetic term $X$. As the field equations can be decomposed into symmetric and antisymmetric (spin connection) parts, we thoroughly analyse the antisymmetric equations and look for solutions of axial spacetimes which could be used as ans\"atze to tackle the symmetric part of the field equations. In particular, we find solutions corresponding to a generalisation of the Taub-NUT metric, and the slowly rotating Kerr spacetime. Since this work also concerns a wider issue of how to determine the spin connection in teleparallel gravity, we also show that the method of "turning off gravity" proposed in the literature, does not always produce a solution to the antisymmetric equations. |
2212.13832 | Yeinzon Rodriguez Garcia | Jhan N. Martinez (1), Jose F. Rodriguez (1,2), Yeinzon Rodriguez
(1,3), Gabriel Gomez (4) ((1) Universidad Industrial de Santander, (2)
ICRANet, (3) Universidad Antonio Narino, (4) Universidad de Santiago de
Chile) | Particle-like solutions in the generalized SU(2) Proca theory | LaTeX file in RevTeX 4.1 style, 21 pages, 13 figures. v2: Minor
clarifications added. Conclusions unchanged. v3: Some other clarifications,
an appendix, and two figures added. Conclusions unchanged. Version published
in Journal of Cosmology and Astroparticle Physics | JCAP 2304: 032, 2023 | 10.1088/1475-7516/2023/04/032 | PI/UAN-2023-723FT | gr-qc astro-ph.SR hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The generalized SU(2) Proca theory is a vector-tensor modified gravity theory
where the action is invariant under both diffeomorphisms and global internal
transformations of the SU(2) group. This work constitutes the first approach to
investigate the physical properties of the theory at astrophysical scales. We
have found solutions that naturally generalize the particle-like solutions of
the Einstein-Yang-Mills equations, also known as gauge boson stars. Under the
requirement that the solutions must be static, asymptotically flat, and
globally regular, the t'Hooft-Polyakov magnetic monopole configuration for the
vector field rises as one viable possibility. The solutions have been obtained
analytically through asymptotic expansions and numerically by solving the
boundary value problem. We have found new features in the solutions such as
regions with negative effective energy density and imaginary effective charge.
We have also obtained a new kind of globally charged solutions for some region
in the parameter space of the theory. Furthermore, we have constructed
equilibrium sequences and found turning points in some cases. These results
hint towards the existence of stable solutions which are absent in the
Einstein-Yang-Mills case.
| [
{
"created": "Wed, 28 Dec 2022 14:34:00 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Jan 2023 22:37:45 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Apr 2023 14:37:30 GMT",
"version": "v3"
}
] | 2023-04-13 | [
[
"Martinez",
"Jhan N.",
""
],
[
"Rodriguez",
"Jose F.",
""
],
[
"Rodriguez",
"Yeinzon",
""
],
[
"Gomez",
"Gabriel",
""
]
] | The generalized SU(2) Proca theory is a vector-tensor modified gravity theory where the action is invariant under both diffeomorphisms and global internal transformations of the SU(2) group. This work constitutes the first approach to investigate the physical properties of the theory at astrophysical scales. We have found solutions that naturally generalize the particle-like solutions of the Einstein-Yang-Mills equations, also known as gauge boson stars. Under the requirement that the solutions must be static, asymptotically flat, and globally regular, the t'Hooft-Polyakov magnetic monopole configuration for the vector field rises as one viable possibility. The solutions have been obtained analytically through asymptotic expansions and numerically by solving the boundary value problem. We have found new features in the solutions such as regions with negative effective energy density and imaginary effective charge. We have also obtained a new kind of globally charged solutions for some region in the parameter space of the theory. Furthermore, we have constructed equilibrium sequences and found turning points in some cases. These results hint towards the existence of stable solutions which are absent in the Einstein-Yang-Mills case. |
1011.6466 | Theodore A. Jacobson | Isaac Carruthers and Ted Jacobson | Cosmic alignment of the aether | 7 pages, 2 figures; v.2: typos corrected, minor edits, version
published in PRD | Phys.Rev.D83:024034,2011 | 10.1103/PhysRevD.83.024034 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Einstein-aether theory and Horava gravity, a timelike unit vector is
coupled to the spacetime metric. It has previously been shown that in an
exponentially expanding homogeneous, isotropic background, small perturbations
of the vector relax back to the isotropic frame. Here we investigate large
deviations from isotropy, maintaining homogeneity. We find that, for generic
values of the coupling constants, the aether and metric relax to the isotropic
configuration if the initial aether hyperbolic boost angle and its time
derivative in units of the cosmological constant are less than something of
order unity. For larger angles or angle derivatives, the behavior is strongly
dependent on the values of the coupling constants. Generally there is runaway
behavior, in which the anisotropy increases with time, and/or singularities
occur.
| [
{
"created": "Tue, 30 Nov 2010 05:58:29 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Jan 2011 07:27:58 GMT",
"version": "v2"
}
] | 2011-03-07 | [
[
"Carruthers",
"Isaac",
""
],
[
"Jacobson",
"Ted",
""
]
] | In Einstein-aether theory and Horava gravity, a timelike unit vector is coupled to the spacetime metric. It has previously been shown that in an exponentially expanding homogeneous, isotropic background, small perturbations of the vector relax back to the isotropic frame. Here we investigate large deviations from isotropy, maintaining homogeneity. We find that, for generic values of the coupling constants, the aether and metric relax to the isotropic configuration if the initial aether hyperbolic boost angle and its time derivative in units of the cosmological constant are less than something of order unity. For larger angles or angle derivatives, the behavior is strongly dependent on the values of the coupling constants. Generally there is runaway behavior, in which the anisotropy increases with time, and/or singularities occur. |
gr-qc/0306006 | Erik Schnetter | Erik Schnetter | Finding apparent horizons and other two-surfaces of constant expansion | 21 pages, 8 figures; two references added | Class.Quant.Grav.20:4719-4737,2003 | 10.1088/0264-9381/20/22/001 | null | gr-qc | null | Apparent horizons are structures of spacelike hypersurfaces that can be
determined locally in time. Closed surfaces of constant expansion (CE surfaces)
are a generalisation of apparent horizons. I present an efficient method for
locating CE surfaces. This method uses an explicit representation of the
surface, allowing for arbitrary resolutions and, in principle, shapes. The CE
surface equation is then solved as a nonlinear elliptic equation.
It is reasonable to assume that CE surfaces foliate a spacelike hypersurface
outside of some interior region, thus defining an invariant (but still
slicing-dependent) radial coordinate. This can be used to determine gauge modes
and to compare time evolutions with different gauge conditions. CE surfaces
also provide an efficient way to find new apparent horizons as they appear e.g.
in binary black hole simulations.
| [
{
"created": "Mon, 2 Jun 2003 14:26:14 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Aug 2003 10:00:58 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Schnetter",
"Erik",
""
]
] | Apparent horizons are structures of spacelike hypersurfaces that can be determined locally in time. Closed surfaces of constant expansion (CE surfaces) are a generalisation of apparent horizons. I present an efficient method for locating CE surfaces. This method uses an explicit representation of the surface, allowing for arbitrary resolutions and, in principle, shapes. The CE surface equation is then solved as a nonlinear elliptic equation. It is reasonable to assume that CE surfaces foliate a spacelike hypersurface outside of some interior region, thus defining an invariant (but still slicing-dependent) radial coordinate. This can be used to determine gauge modes and to compare time evolutions with different gauge conditions. CE surfaces also provide an efficient way to find new apparent horizons as they appear e.g. in binary black hole simulations. |
1705.11098 | Vasilis Oikonomou | S. Nojiri, S.D. Odintsov, V.K. Oikonomou | Modified Gravity Theories on a Nutshell: Inflation, Bounce and Late-time
Evolution | Updated version, minor typos and corrected | null | 10.1016/j.physrep.2017.06.001 | Phys.Rept. 692 (2017) 1-104 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We systematically review some standard issues and also the latest
developments of modified gravity in cosmology, emphasizing on inflation,
bouncing cosmology and late-time acceleration era. Particularly, we present the
formalism of standard modified gravity theory representatives, like $F(R)$,
$F(\mathcal{G})$ and $F(T)$ gravity theories, but also several alternative
theoretical proposals which appeared in the literature during the last decade.
We emphasize on the formalism developed for these theories and we explain how
these theories can be considered as viable descriptions for our Universe. Using
these theories, we present how a viable inflationary era can be produced in the
context of these theories, with the viability being justified if compatibility
with the latest observational data is achieved. Also we demonstrate how
bouncing cosmologies can actually be described by these theories. Moreover, we
systematically discuss several qualitative features of the dark energy era by
using the modified gravity formalism, and also we critically discuss how a
unified description of inflation with dark energy era can be described by
solely using the modified gravity framework. Finally, we also discuss some
astrophysical solutions in the context of modified gravity, and several
qualitative features of these solutions. The aim of this review is to gather
the different modified gravity techniques and form a virtual modified gravity
"toolbox", which will contain all the necessary information on inflation, dark
energy and bouncing cosmologies in the context of the various forms of modified
gravity.
| [
{
"created": "Wed, 31 May 2017 13:41:52 GMT",
"version": "v1"
},
{
"created": "Sat, 6 Oct 2018 04:27:20 GMT",
"version": "v2"
},
{
"created": "Sun, 23 May 2021 13:57:25 GMT",
"version": "v3"
}
] | 2021-05-25 | [
[
"Nojiri",
"S.",
""
],
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | We systematically review some standard issues and also the latest developments of modified gravity in cosmology, emphasizing on inflation, bouncing cosmology and late-time acceleration era. Particularly, we present the formalism of standard modified gravity theory representatives, like $F(R)$, $F(\mathcal{G})$ and $F(T)$ gravity theories, but also several alternative theoretical proposals which appeared in the literature during the last decade. We emphasize on the formalism developed for these theories and we explain how these theories can be considered as viable descriptions for our Universe. Using these theories, we present how a viable inflationary era can be produced in the context of these theories, with the viability being justified if compatibility with the latest observational data is achieved. Also we demonstrate how bouncing cosmologies can actually be described by these theories. Moreover, we systematically discuss several qualitative features of the dark energy era by using the modified gravity formalism, and also we critically discuss how a unified description of inflation with dark energy era can be described by solely using the modified gravity framework. Finally, we also discuss some astrophysical solutions in the context of modified gravity, and several qualitative features of these solutions. The aim of this review is to gather the different modified gravity techniques and form a virtual modified gravity "toolbox", which will contain all the necessary information on inflation, dark energy and bouncing cosmologies in the context of the various forms of modified gravity. |
1906.03190 | Rittick Roy | Rittick Roy and Urjit A. Yajnik | Evolution of black hole shadow in the presence of ultralight bosons | New table added with improvement over previous model, version
published in Phys. Lett. B | null | 10.1016/j.physletb.2020.135284 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Kerr black holes coupled to quantized bosonic fields display a special
version of the Hawking effect, governed by the superradiance condition. This
leads to rapid growth of boson cloud through spontaneous creation, leading to
slowing down of the black hole, and detectable as growth of the black hole
shadow. This can be developed into a technique for searching or constraining
the existence of ultralight bosons. We study this phenomenon for spin-0 bosons
in the shadow of a black hole, with a detailed analysis of Sgr$A^*$, and put
estimates on the evolution time scales and subsequent change in the black hole
shadow features. Our study shows that there is a small window of parameters
where the increase of shadow of a supermassive black hole may be visible, but
only if the sensitivity of measurements increases from current 25 $\mu$as to
about 0.1 $\mu$as.
| [
{
"created": "Fri, 7 Jun 2019 15:54:02 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Feb 2020 07:34:37 GMT",
"version": "v2"
}
] | 2020-02-27 | [
[
"Roy",
"Rittick",
""
],
[
"Yajnik",
"Urjit A.",
""
]
] | Kerr black holes coupled to quantized bosonic fields display a special version of the Hawking effect, governed by the superradiance condition. This leads to rapid growth of boson cloud through spontaneous creation, leading to slowing down of the black hole, and detectable as growth of the black hole shadow. This can be developed into a technique for searching or constraining the existence of ultralight bosons. We study this phenomenon for spin-0 bosons in the shadow of a black hole, with a detailed analysis of Sgr$A^*$, and put estimates on the evolution time scales and subsequent change in the black hole shadow features. Our study shows that there is a small window of parameters where the increase of shadow of a supermassive black hole may be visible, but only if the sensitivity of measurements increases from current 25 $\mu$as to about 0.1 $\mu$as. |
1602.08104 | Steffen Gielen | Steffen Gielen, Lorenzo Sindoni | Quantum Cosmology from Group Field Theory Condensates: a Review | null | SIGMA 12 (2016), 082 | 10.3842/SIGMA.2016.082 | IMPERIAL-TP-2016-SG-1 | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by-sa/4.0/ | We give, in some detail, a critical overview over recent work towards
deriving a cosmological phenomenology from the fundamental quantum dynamics of
group field theory (GFT), based on the picture of a macroscopic universe as a
"condensate" of a large number of quanta of geometry which are given by
excitations of the GFT field over a "no-space" vacuum. We emphasise conceptual
foundations, relations to other research programmes in GFT and the wider
context of loop quantum gravity (LQG), and connections to the quantum physics
of real Bose-Einstein condensates. We show how to extract an effective dynamics
for GFT condensates from the microscopic GFT physics, and how to compare it
with predictions of more conventional quantum cosmology models, in particular
loop quantum cosmology (LQC). No detailed familiarity with the GFT formalism is
assumed.
| [
{
"created": "Thu, 25 Feb 2016 21:00:15 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Aug 2016 05:23:55 GMT",
"version": "v2"
}
] | 2016-08-19 | [
[
"Gielen",
"Steffen",
""
],
[
"Sindoni",
"Lorenzo",
""
]
] | We give, in some detail, a critical overview over recent work towards deriving a cosmological phenomenology from the fundamental quantum dynamics of group field theory (GFT), based on the picture of a macroscopic universe as a "condensate" of a large number of quanta of geometry which are given by excitations of the GFT field over a "no-space" vacuum. We emphasise conceptual foundations, relations to other research programmes in GFT and the wider context of loop quantum gravity (LQG), and connections to the quantum physics of real Bose-Einstein condensates. We show how to extract an effective dynamics for GFT condensates from the microscopic GFT physics, and how to compare it with predictions of more conventional quantum cosmology models, in particular loop quantum cosmology (LQC). No detailed familiarity with the GFT formalism is assumed. |
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