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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1807.06098 | Marcin Kisielowski PhD | Marcin Kisielowski, Jerzy Lewandowski | Spin-foam model for gravity coupled to massless scalar field | 35 pages, 6 figures | null | 10.1088/1361-6382/aafcc0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A spin-foam model is derived from the canonical model of Loop Quantum Gravity
coupled to a massless scalar field. We generalized to the full theory the
scheme first proposed in the context of Loop Quantum Cosmology by Ashtekar,
Campiglia and Henderson, later developed by Henderson, Rovelli, Vidotto and
Wilson-Ewing.
| [
{
"created": "Mon, 16 Jul 2018 20:41:24 GMT",
"version": "v1"
}
] | 2019-05-22 | [
[
"Kisielowski",
"Marcin",
""
],
[
"Lewandowski",
"Jerzy",
""
]
] | A spin-foam model is derived from the canonical model of Loop Quantum Gravity coupled to a massless scalar field. We generalized to the full theory the scheme first proposed in the context of Loop Quantum Cosmology by Ashtekar, Campiglia and Henderson, later developed by Henderson, Rovelli, Vidotto and Wilson-Ewing. |
gr-qc/9304036 | Henri Waelbrock | Luis Urrutia and N. Morales | The Cayley-Hamilton theorem for supermatrices | ICN-UNAM-93-06, 34 pages | null | 10.1088/0305-4470/27/6/022 | null | gr-qc | null | Starting from the expression for the superdeterminant of (xI-M), where M is
an arbitrary supermatrix, we propose a definition for the corresponding
characteristic polynomial and we prove that each supermatrix satisfies its
characteristic equation. Depending upon the factorization properties of the
basic polynomials whose ratio defines the above mentioned determinant we are
able to construct polynomials of lower degree which are also shown to be
annihilated by the supermatrix. Some particular cases and examples are
considered.
| [
{
"created": "Thu, 22 Apr 1993 19:46:29 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Urrutia",
"Luis",
""
],
[
"Morales",
"N.",
""
]
] | Starting from the expression for the superdeterminant of (xI-M), where M is an arbitrary supermatrix, we propose a definition for the corresponding characteristic polynomial and we prove that each supermatrix satisfies its characteristic equation. Depending upon the factorization properties of the basic polynomials whose ratio defines the above mentioned determinant we are able to construct polynomials of lower degree which are also shown to be annihilated by the supermatrix. Some particular cases and examples are considered. |
2312.04352 | Daniel Mayerson | Jef Heynen, Daniel R. Mayerson | Gravitational Multipoles in Five Dimensions | 25 pages + appendices | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We define gravitational mass and current multipoles for five-dimensional,
stationary, and asymptotically flat vacuum metrics. We do this by generalizing
Thorne's asymptotically Cartesian and mass-centered (ACMC) coordinate formalism
to five dimensions, and prove that the multipoles defined in this way are
unambiguously well-defined. Further, these two towers of multipole tensors, in
the case of biaxial symmetry, reduce to a tower of mass multipoles $M_\ell$,
and two separate towers of current or angular momentum multipoles
$S^{(1)}_\ell, S^{(2)}_\ell$. We apply our formalism to a few examples, in
particular Myers-Perry black holes, black rings, and smooth multicentered
geometries.
| [
{
"created": "Thu, 7 Dec 2023 15:17:16 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Apr 2024 17:30:22 GMT",
"version": "v2"
}
] | 2024-04-03 | [
[
"Heynen",
"Jef",
""
],
[
"Mayerson",
"Daniel R.",
""
]
] | We define gravitational mass and current multipoles for five-dimensional, stationary, and asymptotically flat vacuum metrics. We do this by generalizing Thorne's asymptotically Cartesian and mass-centered (ACMC) coordinate formalism to five dimensions, and prove that the multipoles defined in this way are unambiguously well-defined. Further, these two towers of multipole tensors, in the case of biaxial symmetry, reduce to a tower of mass multipoles $M_\ell$, and two separate towers of current or angular momentum multipoles $S^{(1)}_\ell, S^{(2)}_\ell$. We apply our formalism to a few examples, in particular Myers-Perry black holes, black rings, and smooth multicentered geometries. |
gr-qc/0103056 | Bernard S. Kay | Bernard S. Kay (York) | Application of linear hyperbolic PDE to linear quantum fields in curved
spacetimes: especially black holes, time machines and a new semi-local vacuum
concept | Talk at Journe'es E'quations aux de'rive'es partielles, Nantes, 5-9
June, 2000. 19 pages, 6 eps figures. Style file edpa.cls supplied. Requires
latexsym, amssymb, epsf | Journe'es E'quations aux de'rive'es partielles, Nantes, 5 au 9
juin 2000, GDR 1151 (CNRS) pp. IX-1 to IX-19 (Also available at
http://www.math.sciences.univ-nantes.fr/edpa/2000/html) | null | null | gr-qc | null | Several situations of physical importance may be modelled by linear quantum
fields propagating in fixed spacetime-dependent classical background fields.
For example, the quantum Dirac field in a strong and/or time-dependent external
electromagnetic field accounts for the creation of electron-positron pairs out
of the vacuum. Also, the theory of linear quantum fields propagating on a given
background curved spacetime is the appropriate framework for the derivation of
black-hole evaporation (Hawking effect) and for studying the question whether
or not it is possible in principle to manufacture a time-machine. It is a
well-established metatheorem that any question concerning such a linear quantum
field may be reduced to a definite question concerning the corresponding
classical field theory (i.e. linear hyperbolic PDE with non-constant
coefficients describing the background in question) -- albeit not necessarily a
question which would have arisen naturally in a purely classical context. The
focus in this talk will be on the covariant Klein-Gordon equation in a fixed
curved background, although we shall draw on analogies with other background
field problems and with the time-dependent harmonic oscillator. The aim is to
give a sketch-impression of the whole subject of Quantum Field Theory in Curved
Spacetime, focussing on work with which the author has been personally
involved, and also to mention some ideas and work-in-progress by the author and
collaborators towards a new "semi-local" vacuum construction for this subject.
A further aim is to introduce, and set into context, some recent advances in
our understanding of the general structure of quantum fields in curved
spacetimes which rely on classical results from microlocal analysis.
| [
{
"created": "Thu, 15 Mar 2001 19:56:55 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kay",
"Bernard S.",
"",
"York"
]
] | Several situations of physical importance may be modelled by linear quantum fields propagating in fixed spacetime-dependent classical background fields. For example, the quantum Dirac field in a strong and/or time-dependent external electromagnetic field accounts for the creation of electron-positron pairs out of the vacuum. Also, the theory of linear quantum fields propagating on a given background curved spacetime is the appropriate framework for the derivation of black-hole evaporation (Hawking effect) and for studying the question whether or not it is possible in principle to manufacture a time-machine. It is a well-established metatheorem that any question concerning such a linear quantum field may be reduced to a definite question concerning the corresponding classical field theory (i.e. linear hyperbolic PDE with non-constant coefficients describing the background in question) -- albeit not necessarily a question which would have arisen naturally in a purely classical context. The focus in this talk will be on the covariant Klein-Gordon equation in a fixed curved background, although we shall draw on analogies with other background field problems and with the time-dependent harmonic oscillator. The aim is to give a sketch-impression of the whole subject of Quantum Field Theory in Curved Spacetime, focussing on work with which the author has been personally involved, and also to mention some ideas and work-in-progress by the author and collaborators towards a new "semi-local" vacuum construction for this subject. A further aim is to introduce, and set into context, some recent advances in our understanding of the general structure of quantum fields in curved spacetimes which rely on classical results from microlocal analysis. |
gr-qc/0407073 | Ghanashyam Date | Ghanashyam Date and Golam Mortuza Hossain | Effective Hamiltonian for Isotropic Loop Quantum Cosmology | 18 pages, revtex4, one figure. In version 2, only e-print archive
numbers are corrected. In this final version minor typos are corrected and an
extra para of explanation added in the discussion. To appear in Class.
Quantum Grav | Class.Quant.Grav. 21 (2004) 4941-4953 | 10.1088/0264-9381/21/21/012 | IMSc/2004/07/27 | gr-qc astro-ph hep-th | null | For a class of solutions of the fundamental difference equation of isotropic
loop quantum cosmology, the difference equation can be replaced by a
differential equation valid for {\em all} values of the triad variable. The
differential equation admits a `unique' non-singular continuation through
vanishing triad. A WKB approximation for the solutions leads to an effective
continuum Hamiltonian. The effective dynamics is also non-singular (no big bang
singularity) and approximates the classical dynamics for large volumes. The
effective evolution is thus a more reliable model for further phenomenological
implications of the small volume effects.
| [
{
"created": "Mon, 19 Jul 2004 14:09:42 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Jul 2004 04:02:47 GMT",
"version": "v2"
},
{
"created": "Mon, 4 Oct 2004 11:58:02 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Date",
"Ghanashyam",
""
],
[
"Hossain",
"Golam Mortuza",
""
]
] | For a class of solutions of the fundamental difference equation of isotropic loop quantum cosmology, the difference equation can be replaced by a differential equation valid for {\em all} values of the triad variable. The differential equation admits a `unique' non-singular continuation through vanishing triad. A WKB approximation for the solutions leads to an effective continuum Hamiltonian. The effective dynamics is also non-singular (no big bang singularity) and approximates the classical dynamics for large volumes. The effective evolution is thus a more reliable model for further phenomenological implications of the small volume effects. |
1603.05302 | Rafael Nunes | Rafael C. Nunes | Connecting inflation with late cosmic acceleration by particle
production | 8 pages, 5 figures, Published version in International Journal of
Modern Physics D | Int. J. Mod. Phys. D, Vol. 25, No. 6 (2016) 1650067 | 10.1142/S021827181650067X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A continuous process of creation of particles is investigated as a possible
connection between the inflationary stage with late cosmic acceleration. In
this model, the inflationary era occurs due to a continuous and fast process of
creation of relativistic particles, and the recent accelerating phase is driven
by the non-relativistic matter creation from the gravitational field acting on
the quantum vacuum, which finally results in an effective equation of state
less than $-1$. Thus, explaining recent results in favor of a phantom dynamics
without the need of any modifications in the gravity theory has been proposed.
Finally, we confront the model with recent observational data of type Ia
Supernova, history of the Hubble parameter, baryon acoustic oscillations, and
the cosmic microwave background.
| [
{
"created": "Wed, 16 Mar 2016 22:31:56 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Apr 2016 13:10:04 GMT",
"version": "v2"
}
] | 2016-04-27 | [
[
"Nunes",
"Rafael C.",
""
]
] | A continuous process of creation of particles is investigated as a possible connection between the inflationary stage with late cosmic acceleration. In this model, the inflationary era occurs due to a continuous and fast process of creation of relativistic particles, and the recent accelerating phase is driven by the non-relativistic matter creation from the gravitational field acting on the quantum vacuum, which finally results in an effective equation of state less than $-1$. Thus, explaining recent results in favor of a phantom dynamics without the need of any modifications in the gravity theory has been proposed. Finally, we confront the model with recent observational data of type Ia Supernova, history of the Hubble parameter, baryon acoustic oscillations, and the cosmic microwave background. |
gr-qc/9911104 | Carlo Ungarelli | C. Ungarelli and A. Vecchio | Are pre-big-bang models falsifiable by gravitational wave experiments? | 4 pages, two eps figures, uses aipproc2.sty. To appear in the
Proceedings of the Third Edoardo Amaldi Conference | null | 10.1063/1.1291845 | null | gr-qc | null | One of the most interesting predictions of string-inspired cosmological
models is the presence of a stochastic background of relic gravitational waves
in the frequency band accessible to Earth-based detectors. Here we consider a
``minimal'' class of string cosmology models and explore whether they are
falsifiable by gravitational wave observations. In particular, we show that,
the detectability of the signal depends crucially on the actual values of the
model parameters. This feature will enable laser interferometers -- starting
from the second generation of detectors -- to place stringent constraints on
the theory for a fairly large range of the free parameters of the model.
| [
{
"created": "Fri, 26 Nov 1999 11:03:43 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Ungarelli",
"C.",
""
],
[
"Vecchio",
"A.",
""
]
] | One of the most interesting predictions of string-inspired cosmological models is the presence of a stochastic background of relic gravitational waves in the frequency band accessible to Earth-based detectors. Here we consider a ``minimal'' class of string cosmology models and explore whether they are falsifiable by gravitational wave observations. In particular, we show that, the detectability of the signal depends crucially on the actual values of the model parameters. This feature will enable laser interferometers -- starting from the second generation of detectors -- to place stringent constraints on the theory for a fairly large range of the free parameters of the model. |
0909.4862 | Weijia Li | Yi Ling, Wei-Jia Li, Jian-Pin Wu | Bouncing universe from a modified dispersion relation | 12 pages, no figure; references added, version published in JCAP | JCAP 0911:016,2009 | 10.1088/1475-7516/2009/11/016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we argue that modified Friedmann equations with a bounce
solution can be derived from a modified dispersion relation by employing a
thermodynamical description of general relativity on the apparent horizon.
| [
{
"created": "Mon, 28 Sep 2009 02:23:50 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Nov 2009 03:28:16 GMT",
"version": "v2"
}
] | 2010-04-30 | [
[
"Ling",
"Yi",
""
],
[
"Li",
"Wei-Jia",
""
],
[
"Wu",
"Jian-Pin",
""
]
] | In this paper we argue that modified Friedmann equations with a bounce solution can be derived from a modified dispersion relation by employing a thermodynamical description of general relativity on the apparent horizon. |
1305.4073 | Norman G\"urlebeck | Norman G\"urlebeck and David Petroff | A Generalized Family of Post-Newtonian Dedekind Ellipsoids | 23 pages, 17 figures; changes in v2: first paragraph in introduction
added, minor changes to agree with published version | Astrophys. J. 777:60 (2013) | 10.1088/0004-637X/777/1/60 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive a family of Post-Newtonian (PN) Dedekind ellipsoids to first order.
They describe non-axially symmetric, homogeneous, and rotating figures of
equilibrium. The sequence of the Newtonian Dedekind ellipsoids allows for an
axially symmetric limit in which a uniformly rotating Maclaurin spheroid is
recovered. However, the approach taken by Chandrasekhar & Elbert (1974) to find
the PN Dedekind ellipsoids excludes such a limit. In G\"urlebeck & Petroff
(2010), we considered an extension to their work that permits a limit of 1 PN
Maclaurin ellipsoids. Here we further detail the sequence and demonstrate that
a choice of parameters exists with which the singularity formerly found in
Chandrasekhar & Elbert (1974) along the sequence of PN Dedekind ellipsoids is
removed.
| [
{
"created": "Fri, 17 May 2013 13:33:43 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Nov 2013 14:18:58 GMT",
"version": "v2"
}
] | 2013-12-02 | [
[
"Gürlebeck",
"Norman",
""
],
[
"Petroff",
"David",
""
]
] | We derive a family of Post-Newtonian (PN) Dedekind ellipsoids to first order. They describe non-axially symmetric, homogeneous, and rotating figures of equilibrium. The sequence of the Newtonian Dedekind ellipsoids allows for an axially symmetric limit in which a uniformly rotating Maclaurin spheroid is recovered. However, the approach taken by Chandrasekhar & Elbert (1974) to find the PN Dedekind ellipsoids excludes such a limit. In G\"urlebeck & Petroff (2010), we considered an extension to their work that permits a limit of 1 PN Maclaurin ellipsoids. Here we further detail the sequence and demonstrate that a choice of parameters exists with which the singularity formerly found in Chandrasekhar & Elbert (1974) along the sequence of PN Dedekind ellipsoids is removed. |
1412.5689 | Ryuichi Fujita | Ryuichi Fujita | Gravitational Waves from a Particle in Circular Orbits around a Rotating
Black Hole to the 11th Post-Newtonian Order | 31 pages, additional datafiles are available at
http://www2.yukawa.kyoto-u.ac.jp/~misao/BHPC/calcs.html | Prog. Theor. Exp. Phys. 2015, Issue 3, 033E01 (2015) | 10.1093/ptep/ptv012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the energy flux of the gravitational waves radiated by a particle
of mass $\m$ in circular orbits around a rotating black hole of mass $M$ up to
the 11th post-Newtonian order (11PN), i.e. $v^{22}$ beyond the leading
Newtonian approximation where $v$ is the orbital velocity of the particle. By
comparing the PN results for the energy flux with high precision numerical
results in black hole perturbation theory, we find the region of validity in
the PN approximation becomes larger with increasing PN orders. If one requires
the relative error of the energy flux in the PN approximation to be less than
$10^{-5}$, the energy flux at 11PN (4PN) can be used for $v\lessapprox 0.33$
($v\lessapprox 0.13$). The region of validity can be further extended to
$v\lessapprox 0.4$ if one applies a resummation method to the energy flux at
11PN. We then compare the orbital phase during two-year inspiral from the PN
results with the high precision numerical results. We find that for late
(early) inspirals when $q\le 0.3$ ($q\le 0.9$), where $q$ is the dimensionless
spin parameter of the black hole, the difference in the phase is less than 1
($10^{-4}$) rads and hence these inspirals may be detected in the data analysis
for space detectors such as eLISA/NGO by the PN templates. We also compute the
energy flux radiated into the event horizon for a particle in circular orbits
around a non-rotating black hole at 22.5PN, i.e. $v^{45}$ beyond the leading
Newtonian approximation, which is comparable to the PN order derived in our
previous work for the energy flux to infinity at 22PN.
| [
{
"created": "Thu, 18 Dec 2014 00:30:03 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Mar 2015 07:42:17 GMT",
"version": "v2"
}
] | 2015-03-27 | [
[
"Fujita",
"Ryuichi",
""
]
] | We compute the energy flux of the gravitational waves radiated by a particle of mass $\m$ in circular orbits around a rotating black hole of mass $M$ up to the 11th post-Newtonian order (11PN), i.e. $v^{22}$ beyond the leading Newtonian approximation where $v$ is the orbital velocity of the particle. By comparing the PN results for the energy flux with high precision numerical results in black hole perturbation theory, we find the region of validity in the PN approximation becomes larger with increasing PN orders. If one requires the relative error of the energy flux in the PN approximation to be less than $10^{-5}$, the energy flux at 11PN (4PN) can be used for $v\lessapprox 0.33$ ($v\lessapprox 0.13$). The region of validity can be further extended to $v\lessapprox 0.4$ if one applies a resummation method to the energy flux at 11PN. We then compare the orbital phase during two-year inspiral from the PN results with the high precision numerical results. We find that for late (early) inspirals when $q\le 0.3$ ($q\le 0.9$), where $q$ is the dimensionless spin parameter of the black hole, the difference in the phase is less than 1 ($10^{-4}$) rads and hence these inspirals may be detected in the data analysis for space detectors such as eLISA/NGO by the PN templates. We also compute the energy flux radiated into the event horizon for a particle in circular orbits around a non-rotating black hole at 22.5PN, i.e. $v^{45}$ beyond the leading Newtonian approximation, which is comparable to the PN order derived in our previous work for the energy flux to infinity at 22PN. |
gr-qc/9903099 | Andrzej Krolak | Andrzej Krolak | Data Analysis for Continuous Gravitational-Wave Signals | 5 pages, 1 figure, LaTex, Moriond.sty macro | null | null | null | gr-qc | null | The main problem that we will face in the data analysis for continuous
gravitational-wave sources is processing of a very long time series and a very
large parameter space. We present a number of analytic and numerical tools that
can be useful in such a data analysis. These consist of methods to calculate
false alarm probabilities, use of probabilistic algorithms, application of
signal splitting, and accurate estimation of parameters by means of
optimization algorithms.
| [
{
"created": "Sun, 28 Mar 1999 08:22:45 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Krolak",
"Andrzej",
""
]
] | The main problem that we will face in the data analysis for continuous gravitational-wave sources is processing of a very long time series and a very large parameter space. We present a number of analytic and numerical tools that can be useful in such a data analysis. These consist of methods to calculate false alarm probabilities, use of probabilistic algorithms, application of signal splitting, and accurate estimation of parameters by means of optimization algorithms. |
1012.5582 | Yurii Ignatyev | Yu.G.Ignatyev, V.Yu.Shulikovsky | The Relativistic kinetics of gravitational waves collisional damping in
hot Universe | 7 pages, 1 table, 18 references | Gravitation & Cosmology, vol. 12, 2006, p. 1-7 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The article is a translation of authors paper printed earlier in the
inaccessible edition and summarizing the results of research of gravitational
waves damping problem in the cosmologic plasma due to the different
interactions of elementary particles.
| [
{
"created": "Mon, 27 Dec 2010 09:47:20 GMT",
"version": "v1"
}
] | 2010-12-30 | [
[
"Ignatyev",
"Yu. G.",
""
],
[
"Shulikovsky",
"V. Yu.",
""
]
] | The article is a translation of authors paper printed earlier in the inaccessible edition and summarizing the results of research of gravitational waves damping problem in the cosmologic plasma due to the different interactions of elementary particles. |
1406.6938 | Martin Reiris | Martin Reiris | On the shape of bodies in General Relativistic regimes | 20 pages, 3 figures | null | 10.1007/s10714-014-1777-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The analysis of axisymmetric spacetimes, dynamical or stationary, is usually
made in the reduced space. We prove here a stability property of the quo- tient
space and use it together with minimal surface techniques to constraint the
shape of General Relativistic bodies in terms of their energy and rotation.
These constraints are different in nature to the mechanical limitations that a
particular material body can have and which can forbid, for instance, rotation
faster than a certain rate, (after which the body falls apart). The relations
we are describing instead are fundamental and hold for all bodies, albeit they
are useful only in General Relativistic regimes. For Neutron stars they are
close to be optimal, and, although precise models for these stars display
tighter con- straints, our results are significative in that they do not depend
on the equation of state.
| [
{
"created": "Thu, 26 Jun 2014 16:30:02 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Reiris",
"Martin",
""
]
] | The analysis of axisymmetric spacetimes, dynamical or stationary, is usually made in the reduced space. We prove here a stability property of the quo- tient space and use it together with minimal surface techniques to constraint the shape of General Relativistic bodies in terms of their energy and rotation. These constraints are different in nature to the mechanical limitations that a particular material body can have and which can forbid, for instance, rotation faster than a certain rate, (after which the body falls apart). The relations we are describing instead are fundamental and hold for all bodies, albeit they are useful only in General Relativistic regimes. For Neutron stars they are close to be optimal, and, although precise models for these stars display tighter con- straints, our results are significative in that they do not depend on the equation of state. |
0802.0028 | Farhad Darabi | F.Darabi | Accelerating universe with time variation of $G$ and $\Lambda$ | 22 pages | Astrophys. Space. Sci. 338, 171 (2012) | 10.1007/s10509-011-0901-9 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a gravitational model in which scale transformations play the key
role in obtaining dynamical $G$ and $\Lambda$. We take a scale non-invariant
gravitational action with a cosmological constant and a gravitational coupling
constant. Then, by a scale transformation, through a dilaton field, we obtain a
new action containing cosmological and gravitational coupling terms which are
dynamically dependent on the dilaton field with Higgs type potential. The
vacuum expectation value of this dilaton field, through spontaneous symmetry
breaking on the basis of anthropic principle, determines the time variations of
$G$ and $\Lambda$. The relevance of these time variations to the current
acceleration of the universe, coincidence problem, Mach's cosmological
coincidence and those problems of standard cosmology addressed by inflationary
models, are discussed. The current acceleration of the universe is shown to be
a result of phase transition from radiation toward matter dominated eras. No
real coincidence problem between matter and vacuum energy densities exists in
this model and this apparent coincidence together with Mach's cosmological
coincidence are shown to be simple consequences of a new kind of scale factor
dependence of the energy momentum density as $\rho \sim a^{-4}$. This model
also provides the possibility for a super fast expansion of the scale factor at
very early universe by introducing exotic type matter like cosmic strings.
| [
{
"created": "Thu, 31 Jan 2008 22:49:12 GMT",
"version": "v1"
},
{
"created": "Sun, 1 Jun 2008 11:44:11 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Mar 2014 14:06:37 GMT",
"version": "v3"
}
] | 2015-05-13 | [
[
"Darabi",
"F.",
""
]
] | We study a gravitational model in which scale transformations play the key role in obtaining dynamical $G$ and $\Lambda$. We take a scale non-invariant gravitational action with a cosmological constant and a gravitational coupling constant. Then, by a scale transformation, through a dilaton field, we obtain a new action containing cosmological and gravitational coupling terms which are dynamically dependent on the dilaton field with Higgs type potential. The vacuum expectation value of this dilaton field, through spontaneous symmetry breaking on the basis of anthropic principle, determines the time variations of $G$ and $\Lambda$. The relevance of these time variations to the current acceleration of the universe, coincidence problem, Mach's cosmological coincidence and those problems of standard cosmology addressed by inflationary models, are discussed. The current acceleration of the universe is shown to be a result of phase transition from radiation toward matter dominated eras. No real coincidence problem between matter and vacuum energy densities exists in this model and this apparent coincidence together with Mach's cosmological coincidence are shown to be simple consequences of a new kind of scale factor dependence of the energy momentum density as $\rho \sim a^{-4}$. This model also provides the possibility for a super fast expansion of the scale factor at very early universe by introducing exotic type matter like cosmic strings. |
1702.07016 | Subenoy Chakraborty | Sanjukta Chakraborty and Subenoy Chakraborty | A study of charged cylindrical Gravitational collapse with dissipative
fluid | 11 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present works deals with gravitational collapse of cylindrical viscous
heat conducting anisotropic fluid following the work of Misner and Sharp. Using
Darmois matching conditions, the dynamical equations are derived and the effect
of charge and dissipative quantities over the cylindrical collapse are
analyzed. Finally, using the Miller-Israel-Steward causal thermodynamic theory,
the transport equation for heat flux are derived and its influence on
collapsing system has been studied.
| [
{
"created": "Mon, 20 Feb 2017 09:49:36 GMT",
"version": "v1"
}
] | 2017-02-24 | [
[
"Chakraborty",
"Sanjukta",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | The present works deals with gravitational collapse of cylindrical viscous heat conducting anisotropic fluid following the work of Misner and Sharp. Using Darmois matching conditions, the dynamical equations are derived and the effect of charge and dissipative quantities over the cylindrical collapse are analyzed. Finally, using the Miller-Israel-Steward causal thermodynamic theory, the transport equation for heat flux are derived and its influence on collapsing system has been studied. |
gr-qc/0404090 | Jerzy Matyjasek | Jerzy Matyjasek and O. B. Zaslavskii | Extremal limit for charged and rotating 2+1-dimensional black holes and
Bertotti-Robinson geometry | Presentation simplified. To appear in CQG | Class.Quant.Grav. 21 (2004) 4283 | 10.1088/0264-9381/21/17/014 | null | gr-qc hep-th | null | We consider 2+1--dimensional analogues of the Bertotti-Robinson (BR)
spacetimes in the sense that the coefficient at the angular part is a constant.
We show that such BR-like solutions are either pure static or uncharged
rotating. We trace the origin of the inconsistency between a charge and
rotation, considering the BR-like spacetime as a result of the limiting
transition of a non-extremal black hole to the extremal state. We also find
that the quasilocal energy and angular momentum of such BR-like spacetimes
calculated within the boundary $l=const$ ($l$ is the proper distance) are
constants independent of the position of the boundary.
| [
{
"created": "Wed, 21 Apr 2004 12:12:48 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Apr 2004 12:59:03 GMT",
"version": "v2"
},
{
"created": "Wed, 14 Jul 2004 10:57:05 GMT",
"version": "v3"
}
] | 2015-06-25 | [
[
"Matyjasek",
"Jerzy",
""
],
[
"Zaslavskii",
"O. B.",
""
]
] | We consider 2+1--dimensional analogues of the Bertotti-Robinson (BR) spacetimes in the sense that the coefficient at the angular part is a constant. We show that such BR-like solutions are either pure static or uncharged rotating. We trace the origin of the inconsistency between a charge and rotation, considering the BR-like spacetime as a result of the limiting transition of a non-extremal black hole to the extremal state. We also find that the quasilocal energy and angular momentum of such BR-like spacetimes calculated within the boundary $l=const$ ($l$ is the proper distance) are constants independent of the position of the boundary. |
1310.2756 | J. Brian Pitts | J. Brian Pitts | A First Class Constraint Generates Not a Gauge Transformation, But a Bad
Physical Change: The Case of Electromagnetism | null | Annals of Physics 351 (2014), pp. 382-406 | 10.1016/j.aop.2014.08.014 | null | gr-qc hep-th physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Dirac-Bergmann constrained dynamics, a first-class constraint typically
does not _alone_ generate a gauge transformation. Each first-class constraint
in Maxwell's theory generates a change in the electric field E by an arbitrary
gradient, spoiling Gauss's law. The secondary constraint p^i,_i=0 still holds,
but being a function of derivatives of momenta (mere auxiliary fields), it is
not directly about the observable electric field (a function of derivatives of
A), which couples to charge. Only a special combination of the two first-class
constraints, the Anderson-Bergmann-Castellani gauge generator G, leaves E
unchanged. Likewise only that combination leaves the canonical action
invariant---an argument independent of observables. If one uses a first-class
constraint to generate instead a canonical transformation, one partly strips
the canonical coordinates of physical meaning as electromagnetic potentials,
vindicating the Anderson-Bergmann Lagrangian orientation of interesting
canonical transformations. The need to keep gauge-invariant q,t-dH/dp=-E-p=0
supports using the gauge generator and primary Hamiltonian rather than the
separate first-class constraints and the extended Hamiltonian.
Partly paralleling Pons's criticism, it is shown that Dirac's proof that a
first-class primary constraint generates a gauge transformation, by comparing
evolutions from _identical_ initial data, cancels out and hence fails to detect
the alterations made to the initial state. It also neglects the arbitrary
coordinates multiplying the secondary constraints _inside_ the canonical
Hamiltonian. Thus the gauge-generating property has been ascribed to the
primaries alone.
Hence the Dirac conjecture about secondary first-class constraints as
generating gauge transformations rests upon a false presupposition about
primary first-class constraints. Clarity about electromagnetism help with GR.
| [
{
"created": "Thu, 10 Oct 2013 10:22:19 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Oct 2014 19:05:02 GMT",
"version": "v2"
}
] | 2014-10-10 | [
[
"Pitts",
"J. Brian",
""
]
] | In Dirac-Bergmann constrained dynamics, a first-class constraint typically does not _alone_ generate a gauge transformation. Each first-class constraint in Maxwell's theory generates a change in the electric field E by an arbitrary gradient, spoiling Gauss's law. The secondary constraint p^i,_i=0 still holds, but being a function of derivatives of momenta (mere auxiliary fields), it is not directly about the observable electric field (a function of derivatives of A), which couples to charge. Only a special combination of the two first-class constraints, the Anderson-Bergmann-Castellani gauge generator G, leaves E unchanged. Likewise only that combination leaves the canonical action invariant---an argument independent of observables. If one uses a first-class constraint to generate instead a canonical transformation, one partly strips the canonical coordinates of physical meaning as electromagnetic potentials, vindicating the Anderson-Bergmann Lagrangian orientation of interesting canonical transformations. The need to keep gauge-invariant q,t-dH/dp=-E-p=0 supports using the gauge generator and primary Hamiltonian rather than the separate first-class constraints and the extended Hamiltonian. Partly paralleling Pons's criticism, it is shown that Dirac's proof that a first-class primary constraint generates a gauge transformation, by comparing evolutions from _identical_ initial data, cancels out and hence fails to detect the alterations made to the initial state. It also neglects the arbitrary coordinates multiplying the secondary constraints _inside_ the canonical Hamiltonian. Thus the gauge-generating property has been ascribed to the primaries alone. Hence the Dirac conjecture about secondary first-class constraints as generating gauge transformations rests upon a false presupposition about primary first-class constraints. Clarity about electromagnetism help with GR. |
0709.0657 | Leonardo Gualtieri | V. Ferrari, L. Gualtieri | Quasi-Normal Modes and Gravitational Wave Astronomy | 25 pages, 7 figures, to appear on Gen. Rel. Grav | Gen.Rel.Grav.40:945-970,2008 | 10.1007/s10714-007-0585-1 | null | gr-qc astro-ph | null | We review the main results obtained in the literature on quasi-normal modes
of compact stars and black holes, in the light of recent exciting developments
of gravitational wave detectors. Quasi-normal modes are a fundamental feature
of the gravitational signal emitted by compact objects in many astrophysical
processes; we will show that their eigenfrequencies encode interesting
information on the nature and on the inner structure of the emitting source and
we will discuss whether we are ready for a gravitational wave asteroseismology.
| [
{
"created": "Wed, 5 Sep 2007 14:01:37 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jan 2008 14:09:17 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Ferrari",
"V.",
""
],
[
"Gualtieri",
"L.",
""
]
] | We review the main results obtained in the literature on quasi-normal modes of compact stars and black holes, in the light of recent exciting developments of gravitational wave detectors. Quasi-normal modes are a fundamental feature of the gravitational signal emitted by compact objects in many astrophysical processes; we will show that their eigenfrequencies encode interesting information on the nature and on the inner structure of the emitting source and we will discuss whether we are ready for a gravitational wave asteroseismology. |
2212.08554 | Manuel Tiglio | Franco Cerino, J. Andr\'es Diaz-Pace, Manuel Tiglio | An automated parameter domain decomposition approach for gravitational
wave surrogates using hp-greedy refinement | 16 pages, code available from authors upon request | null | null | null | gr-qc cs.LG math.RT | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce hp-greedy, a refinement approach for building gravitational wave
surrogates as an extension of the standard reduced basis framework. Our
proposal is data-driven, with a domain decomposition of the parameter space,
local reduced basis, and a binary tree as the resulting structure, which are
obtained in an automated way. When compared to the standard global reduced
basis approach, the numerical simulations of our proposal show three salient
features: i) representations of lower dimension with no loss of accuracy, ii) a
significantly higher accuracy for a fixed maximum dimensionality of the basis,
in some cases by orders of magnitude, and iii) results that depend on the
reduced basis seed choice used by the refinement algorithm. We first illustrate
the key parts of our approach with a toy model and then present a more
realistic use case of gravitational waves emitted by the collision of two
spinning, non-precessing black holes. We discuss performance aspects of
hp-greedy, such as overfitting with respect to the depth of the tree structure,
and other hyperparameter dependences. As two direct applications of the
proposed hp-greedy refinement, we envision: i) a further acceleration of
statistical inference, which might be complementary to focused reduced-order
quadratures, and ii) the search of gravitational waves through clustering and
nearest neighbors.
| [
{
"created": "Fri, 16 Dec 2022 16:12:51 GMT",
"version": "v1"
}
] | 2022-12-19 | [
[
"Cerino",
"Franco",
""
],
[
"Diaz-Pace",
"J. Andrés",
""
],
[
"Tiglio",
"Manuel",
""
]
] | We introduce hp-greedy, a refinement approach for building gravitational wave surrogates as an extension of the standard reduced basis framework. Our proposal is data-driven, with a domain decomposition of the parameter space, local reduced basis, and a binary tree as the resulting structure, which are obtained in an automated way. When compared to the standard global reduced basis approach, the numerical simulations of our proposal show three salient features: i) representations of lower dimension with no loss of accuracy, ii) a significantly higher accuracy for a fixed maximum dimensionality of the basis, in some cases by orders of magnitude, and iii) results that depend on the reduced basis seed choice used by the refinement algorithm. We first illustrate the key parts of our approach with a toy model and then present a more realistic use case of gravitational waves emitted by the collision of two spinning, non-precessing black holes. We discuss performance aspects of hp-greedy, such as overfitting with respect to the depth of the tree structure, and other hyperparameter dependences. As two direct applications of the proposed hp-greedy refinement, we envision: i) a further acceleration of statistical inference, which might be complementary to focused reduced-order quadratures, and ii) the search of gravitational waves through clustering and nearest neighbors. |
1310.1574 | Fatimah Shojai | F. Shojai and A. Shojai | Notes on the compatibility of type Ia supernovae data and varying--$G$
cosmology | null | Phys. Scr. 88, 055902, 2013 | 10.1088/0031-8949/88/05/055902 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Observational data for type Ia supernovae, shows that the expansion of the
universe is accelerated. This accelerated expansion can be described by a
cosmological constant or by dark energy models like quintessence. An
interesting question may be raised here. Is it possible to describe the
accelerated expansion of universe using varying--$G$ cosmological models? Here
we shall show that the price for having accelerated expansion in
slow--varying--$G$ models (in which the dynamical terms of $G$ are ignored) is
to have highly non--conserved matter and also that it is in contradiction with
other data.
| [
{
"created": "Sun, 6 Oct 2013 11:23:00 GMT",
"version": "v1"
}
] | 2015-06-17 | [
[
"Shojai",
"F.",
""
],
[
"Shojai",
"A.",
""
]
] | Observational data for type Ia supernovae, shows that the expansion of the universe is accelerated. This accelerated expansion can be described by a cosmological constant or by dark energy models like quintessence. An interesting question may be raised here. Is it possible to describe the accelerated expansion of universe using varying--$G$ cosmological models? Here we shall show that the price for having accelerated expansion in slow--varying--$G$ models (in which the dynamical terms of $G$ are ignored) is to have highly non--conserved matter and also that it is in contradiction with other data. |
gr-qc/9308021 | null | Nenad Manojlovi\'c and Bill Spence | Integrals of Motion in the Two Killing Vector Reduction of General
Relativity | 20 pages, plain TeX, SU-GP-93/7-8, UM-P-93/77 | Nucl.Phys.B423:243-259,1994 | 10.1016/0550-3213(94)90572-X | null | gr-qc | null | We apply the inverse scattering method to the midi-superspace models that are
characterized by a two-parameter Abelian group of motions with two spacelike
Killing vectors. We present a formulation that simplifies the construction of
the soliton solutions of Belinski\v i and Zakharov. Furthermore, it enables us
to obtain the zero curvature formulation for these models. Using this, and
imposing periodic boundary conditions corresponding to the Gowdy models when
the spatial topology is a three torus $T ^3$, we show that the equation of
motion for the monodromy matrix is an evolution equation of the Heisenberg
type. Consequently, the eigenvalues of the monodromy matrix are the generating
functionals for the integrals of motion. Furthermore, we utilise a suitable
formulation of the transition matrix to obtain explicit expressions for the
integrals of motion. This involves recursion relations which arise in solving
an equation of Riccati type. In the case when the two Killing vectors are
hypersurface orthogonal the integrals of motion have a particularly simple
form.
| [
{
"created": "Fri, 20 Aug 1993 20:58:00 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Manojlović",
"Nenad",
""
],
[
"Spence",
"Bill",
""
]
] | We apply the inverse scattering method to the midi-superspace models that are characterized by a two-parameter Abelian group of motions with two spacelike Killing vectors. We present a formulation that simplifies the construction of the soliton solutions of Belinski\v i and Zakharov. Furthermore, it enables us to obtain the zero curvature formulation for these models. Using this, and imposing periodic boundary conditions corresponding to the Gowdy models when the spatial topology is a three torus $T ^3$, we show that the equation of motion for the monodromy matrix is an evolution equation of the Heisenberg type. Consequently, the eigenvalues of the monodromy matrix are the generating functionals for the integrals of motion. Furthermore, we utilise a suitable formulation of the transition matrix to obtain explicit expressions for the integrals of motion. This involves recursion relations which arise in solving an equation of Riccati type. In the case when the two Killing vectors are hypersurface orthogonal the integrals of motion have a particularly simple form. |
gr-qc/0110046 | T. Padmanabhan | T.Padmanabhan | Combining general relativity and quantum theory: points of conflict and
contact | Invited Talk at "The Early Universe and Cosmological Observations: a
Critical Review", UCT, Cape Town, 23-25 July,2001; to appear in
Class.Quan.Grav | Class.Quant.Grav.19:3551-3566,2002 | 10.1088/0264-9381/19/13/312 | preprint IUCAA-44/2001 | gr-qc astro-ph hep-th | null | The issues related to bringing together the principles of general relativity
and quantum theory are discussed. After briefly summarising the points of
conflict between the two formalisms I focus on four specific themes in which
some contact has been established in the past between GR and quantum field
theory: (i) The role of planck length in the microstructure of spacetime (ii)
The role of quantum effects in cosmology and origin of the universe (iii) The
thermodynamics of spacetimes with horizons and especially the concept of
entropy related to spacetime geometry (iv) The problem of the cosmological
constant.
| [
{
"created": "Tue, 9 Oct 2001 07:11:51 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Padmanabhan",
"T.",
""
]
] | The issues related to bringing together the principles of general relativity and quantum theory are discussed. After briefly summarising the points of conflict between the two formalisms I focus on four specific themes in which some contact has been established in the past between GR and quantum field theory: (i) The role of planck length in the microstructure of spacetime (ii) The role of quantum effects in cosmology and origin of the universe (iii) The thermodynamics of spacetimes with horizons and especially the concept of entropy related to spacetime geometry (iv) The problem of the cosmological constant. |
gr-qc/9810070 | Pawel Nurowski | Pawel Nurowski, Lane Hughston, David Robinson | Extension of bundles of null directions | LaTex file, accepted in CQG | Class.Quant.Grav. 16 (1999) 255-279 | 10.1088/0264-9381/16/1/019 | null | gr-qc | null | The geometry of P, the bundle of null directions over an Einstein space-time,
is studied. The full set of invariants of the natural G-structure on P is
constructed using the Cartan method of equivalence. This leads to an extension
of P which is an elliptic fibration over the space-time. Examples are given
which show that such an extension, although natural, is not unique. A
reinterpretation of the Petrov classification in terms of the fibres of an
extension of P is presented.
| [
{
"created": "Wed, 21 Oct 1998 19:35:46 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Nurowski",
"Pawel",
""
],
[
"Hughston",
"Lane",
""
],
[
"Robinson",
"David",
""
]
] | The geometry of P, the bundle of null directions over an Einstein space-time, is studied. The full set of invariants of the natural G-structure on P is constructed using the Cartan method of equivalence. This leads to an extension of P which is an elliptic fibration over the space-time. Examples are given which show that such an extension, although natural, is not unique. A reinterpretation of the Petrov classification in terms of the fibres of an extension of P is presented. |
2111.11844 | Gaoping Long | Gaoping Long, Yongge Ma | The effective dynamics of weak coupling loop quantum gravity | null | null | 10.1103/PhysRevD.105.044043 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | By taking the limit that Newton's Gravitational constant tends to zero, the
weak coupling loop quantum gravity can be formulated as a $U(1)^3$ gauge theory
instead of the original $SU(2)$ gauge theory. In this paper, a parametrization
of the $SU(2)$ holonomy-flux variables by the $U(1)^3$ holonomy-flux variables
is introduced, and the Hamiltonian operator based on this parametrization is
obtained for the weak coupling loop quantum gravity. It is shown that the
effective dynamics obtained from the coherent state path integrals in $U(1)^3$
and $SU(2)$ loop quantum gravity respectively are consistent to each other in
the weak coupling limit, provided that the expectation values of the
Hamiltonian operators on the coherent states in these two theories coincide
with their classical expressions respectively.
| [
{
"created": "Tue, 23 Nov 2021 13:16:26 GMT",
"version": "v1"
}
] | 2022-03-09 | [
[
"Long",
"Gaoping",
""
],
[
"Ma",
"Yongge",
""
]
] | By taking the limit that Newton's Gravitational constant tends to zero, the weak coupling loop quantum gravity can be formulated as a $U(1)^3$ gauge theory instead of the original $SU(2)$ gauge theory. In this paper, a parametrization of the $SU(2)$ holonomy-flux variables by the $U(1)^3$ holonomy-flux variables is introduced, and the Hamiltonian operator based on this parametrization is obtained for the weak coupling loop quantum gravity. It is shown that the effective dynamics obtained from the coherent state path integrals in $U(1)^3$ and $SU(2)$ loop quantum gravity respectively are consistent to each other in the weak coupling limit, provided that the expectation values of the Hamiltonian operators on the coherent states in these two theories coincide with their classical expressions respectively. |
1506.01572 | Eva Hackmann | Eva Hackmann and Claus L\"ammerzahl | Analytical solutions for geodesics in black hole spacetimes | 8 pages; based on the contribution to the "Karl Schwarzschild Meeting
2013" in Frankfurt, Germany. arXiv admin note: substantial text overlap with
arXiv:1506.00807 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the analytical solution methods for the geodesic equations in
Kerr-Newman-Taub-NUT-de Sitter spacetimes and its subclasses in terms of
elliptic and hyperelliptic functions. A short guide to corresponding literature
for general timelike and lightlike motion is also presented.
| [
{
"created": "Thu, 4 Jun 2015 13:05:53 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Hackmann",
"Eva",
""
],
[
"Lämmerzahl",
"Claus",
""
]
] | We review the analytical solution methods for the geodesic equations in Kerr-Newman-Taub-NUT-de Sitter spacetimes and its subclasses in terms of elliptic and hyperelliptic functions. A short guide to corresponding literature for general timelike and lightlike motion is also presented. |
2112.14281 | Maxim Eingorn | M. Eingorn, N. O'Briant, K. Arzu, M. Brilenkov, A. Zhuk | Gravitational potentials and forces in the Lattice Universe: a slab | This is a preprint of an article published in the European Physical
Journal Plus. The final authenticated version is available online at:
https://doi.org/10.1140/epjp/s13360-021-01139-y | Eur. Phys. J. Plus 136, 205 (2021) | 10.1140/epjp/s13360-021-01139-y | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We study the effect of the slab topology $T\times R\times R$ of the Universe
on the form of gravitational potentials and forces created by point-like
masses. We obtain two alternative forms of solutions: one is based on the
Fourier series expansion of the delta function using the periodical property
along the toroidal dimension, and another one is derived by direct summation of
solutions of the Helmholtz equation for the source particle and all its images.
The latter one takes the form of the sum of Yukawa-type potentials. We
demonstrate that for the present Universe the latter solution is preferable for
numerical calculations since it requires less terms of the series to achieve
the necessary precision.
| [
{
"created": "Tue, 28 Dec 2021 19:40:29 GMT",
"version": "v1"
}
] | 2021-12-30 | [
[
"Eingorn",
"M.",
""
],
[
"O'Briant",
"N.",
""
],
[
"Arzu",
"K.",
""
],
[
"Brilenkov",
"M.",
""
],
[
"Zhuk",
"A.",
""
]
] | We study the effect of the slab topology $T\times R\times R$ of the Universe on the form of gravitational potentials and forces created by point-like masses. We obtain two alternative forms of solutions: one is based on the Fourier series expansion of the delta function using the periodical property along the toroidal dimension, and another one is derived by direct summation of solutions of the Helmholtz equation for the source particle and all its images. The latter one takes the form of the sum of Yukawa-type potentials. We demonstrate that for the present Universe the latter solution is preferable for numerical calculations since it requires less terms of the series to achieve the necessary precision. |
2106.06696 | Slava G. Turyshev | Slava G. Turyshev, Viktor T. Toth | Gravitational lensing by an extended mass distribution | 22 pages, 5 figures | Phys. Rev. D 104, 044013 (2021) | 10.1103/PhysRevD.104.044013 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We continue our investigation of the optical properties of the solar
gravitational lens (SGL). We treat the Sun as an extended axisymmetric body and
model its gravitational field using zonal harmonics. We consider a point source
that is positioned at a large but finite distance from the Sun and, using our
new angular eikonal method, we established the electro-magnetic (EM) field on
the image plane in the focal region behind the SGL and derive the SGL's impulse
response in the form of its point-spread function (PSF). The expression that we
derive describes the extended Sun in all regions of interest, including the
regions of strong and weak interference and the region of geometric optics. The
result is in the form of a single integral with respect to the azimuthal angle
of the impact parameter, covering all lensing regimes of the SGL. The same
expression can be used to describe gravitational lensing by a compact
axisymmetric mass distribution, characterized by small deviations from
spherical symmetry. It is valid in all lensing regimes. We also derive results
that describe the intensity of light observed by an imaging telescope in the
focal region. We present results of numerical simulations showing the view by a
telescope that moves in the image plane toward the optical axis. We consider
imaging of both point and extended sources. We show that while point sources
yield a number of distinct images consistent with the caustics due to zonal
harmonics of a particular order (e.g., Einstein cross), extended sources always
result in the formation of an Einstein ring. These results represent the most
comprehensive wave-theoretical treatment of gravitational lensing in the weak
gravitational field of a compact axisymmetric gravitating object.
| [
{
"created": "Sat, 12 Jun 2021 06:21:57 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Aug 2021 15:52:38 GMT",
"version": "v2"
}
] | 2021-08-06 | [
[
"Turyshev",
"Slava G.",
""
],
[
"Toth",
"Viktor T.",
""
]
] | We continue our investigation of the optical properties of the solar gravitational lens (SGL). We treat the Sun as an extended axisymmetric body and model its gravitational field using zonal harmonics. We consider a point source that is positioned at a large but finite distance from the Sun and, using our new angular eikonal method, we established the electro-magnetic (EM) field on the image plane in the focal region behind the SGL and derive the SGL's impulse response in the form of its point-spread function (PSF). The expression that we derive describes the extended Sun in all regions of interest, including the regions of strong and weak interference and the region of geometric optics. The result is in the form of a single integral with respect to the azimuthal angle of the impact parameter, covering all lensing regimes of the SGL. The same expression can be used to describe gravitational lensing by a compact axisymmetric mass distribution, characterized by small deviations from spherical symmetry. It is valid in all lensing regimes. We also derive results that describe the intensity of light observed by an imaging telescope in the focal region. We present results of numerical simulations showing the view by a telescope that moves in the image plane toward the optical axis. We consider imaging of both point and extended sources. We show that while point sources yield a number of distinct images consistent with the caustics due to zonal harmonics of a particular order (e.g., Einstein cross), extended sources always result in the formation of an Einstein ring. These results represent the most comprehensive wave-theoretical treatment of gravitational lensing in the weak gravitational field of a compact axisymmetric gravitating object. |
1903.03778 | Bobir Toshmatov | Bobir Toshmatov, Zden\v{e}k Stuchl\'ik, Bobomurat Ahmedov, Daniele
Malafarina | Relaxations of perturbations of spacetimes in general relativity coupled
to nonlinear electrodynamics | 9 pages, 4 figures, 1 table | Phys. Rev. D 99, 064043 (2019) | 10.1103/PhysRevD.99.064043 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Three well known exact regular solutions of general relativity (GR) coupled
to nonlinear electrodynamics (NED), namely the Maxwellian, Bardeen and Hayward
regular spacetimes, which can describe either a regular black hole or a
geometry without horizons, have been considered. Relaxation times for the
scalar, electromagnetic (EM) and gravitational perturbations of black holes
(BHs) and no-horizon spacetimes have been estimated in comparison with the ones
of the Schwarzschild and Reissner-Nordstr\"{o}m (RN) spacetimes. It has been
shown that the considered geometries in GR coupled to the NED have never
vanishing circular photon orbits and on account of this fact these spacetimes
always oscillate the EM perturbations with quasinormal frequencies (QNFs).
Moreover we have shown that the EM perturbations in the eikonal regime can be a
powerful tool to confirm that (i) the light rays do not follow null geodesics
in the NED by the relaxation rates; (ii) if the underlying solution has a
correct weak field limit to the Maxwell electrodynamics (LED) by the angular
velocity of the circular photon orbit.
| [
{
"created": "Sat, 9 Mar 2019 10:52:18 GMT",
"version": "v1"
}
] | 2019-03-29 | [
[
"Toshmatov",
"Bobir",
""
],
[
"Stuchlík",
"Zdeněk",
""
],
[
"Ahmedov",
"Bobomurat",
""
],
[
"Malafarina",
"Daniele",
""
]
] | Three well known exact regular solutions of general relativity (GR) coupled to nonlinear electrodynamics (NED), namely the Maxwellian, Bardeen and Hayward regular spacetimes, which can describe either a regular black hole or a geometry without horizons, have been considered. Relaxation times for the scalar, electromagnetic (EM) and gravitational perturbations of black holes (BHs) and no-horizon spacetimes have been estimated in comparison with the ones of the Schwarzschild and Reissner-Nordstr\"{o}m (RN) spacetimes. It has been shown that the considered geometries in GR coupled to the NED have never vanishing circular photon orbits and on account of this fact these spacetimes always oscillate the EM perturbations with quasinormal frequencies (QNFs). Moreover we have shown that the EM perturbations in the eikonal regime can be a powerful tool to confirm that (i) the light rays do not follow null geodesics in the NED by the relaxation rates; (ii) if the underlying solution has a correct weak field limit to the Maxwell electrodynamics (LED) by the angular velocity of the circular photon orbit. |
1906.01927 | Run-Qiu Yang | Run-Qiu Yang, Hui Liu, Shining Zhu, Le Luo and Rong-Gen Cai | Simulating quantum field theory in curved spacetime with quantum
many-body systems | 9 pages, 3 figures, published version | Phys. Rev. Research 2, 023107 (2020) | 10.1103/PhysRevResearch.2.023107 | null | gr-qc cond-mat.stat-mech hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper proposes a new general framework to build a one-to-one
correspondence between quantum field theories in static 1+1 dimensional curved
spacetime and quantum many-body systems. We show that a massless scalar field
in an arbitrary 2-dimensional static spacetime is always equivalent to a
site-dependent bosonic hopping model, while a massless Dirac field is
equivalent to a site-dependent free Hubbard model or a site-dependent isotropic
XY model. A possible experimental realization for such a correspondence in
trapped ions system is suggested. As applications of the analogue gravity
model, we show that they can be used to simulate Hawking radiation of black
hole and to study its entanglement. We also show in the analogue model that
black holes are most chaotic systems and the fastest scramblers in nature. We
also offer a concrete example about how to get some insights about quantum
many-body systems from back hole physics.
| [
{
"created": "Wed, 5 Jun 2019 10:35:53 GMT",
"version": "v1"
},
{
"created": "Tue, 5 May 2020 09:14:31 GMT",
"version": "v2"
}
] | 2020-05-06 | [
[
"Yang",
"Run-Qiu",
""
],
[
"Liu",
"Hui",
""
],
[
"Zhu",
"Shining",
""
],
[
"Luo",
"Le",
""
],
[
"Cai",
"Rong-Gen",
""
]
] | This paper proposes a new general framework to build a one-to-one correspondence between quantum field theories in static 1+1 dimensional curved spacetime and quantum many-body systems. We show that a massless scalar field in an arbitrary 2-dimensional static spacetime is always equivalent to a site-dependent bosonic hopping model, while a massless Dirac field is equivalent to a site-dependent free Hubbard model or a site-dependent isotropic XY model. A possible experimental realization for such a correspondence in trapped ions system is suggested. As applications of the analogue gravity model, we show that they can be used to simulate Hawking radiation of black hole and to study its entanglement. We also show in the analogue model that black holes are most chaotic systems and the fastest scramblers in nature. We also offer a concrete example about how to get some insights about quantum many-body systems from back hole physics. |
1803.00014 | Alberto Diez-Tejedor | Alberto Diez-Tejedor, Francisco Flores, Gustavo Niz | Horndeski dark matter and beyond | 11 pages, no figures. To appear in Phys. Rev. D | Phys. Rev. D 97, 123524 (2018) | 10.1103/PhysRevD.97.123524 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Starting from the Gleyzes-Langlois-Piazza-Vernizzi action, we derive the most
general effective theory that is invariant under internal shifts and a
$\mathbb{Z}_2$ mirror symmetry in the scalar sector. Contrary to what one may
think, this model presents a dark matter tracker previous to the dark energy
domination. We show that, in an empty universe and to linear order in
perturbations, the scalar mode clusters in exactly the same way as standard
nonrelativistic cold dark matter. This also holds for the subsector of the
theory where the speed of propagation of gravitational waves equals that of
light, in agreement with the recent multimessenger observation. However, the
inclusion of standard model particles introduces nontrivial couplings of the
gravitational scalar mode to baryons, modifying their clustering properties. We
argue that no arrangement of the parameters of the model can reduce the extra
scalar to precisely behave as cold dark matter.
| [
{
"created": "Wed, 28 Feb 2018 19:00:02 GMT",
"version": "v1"
},
{
"created": "Sun, 10 Jun 2018 21:43:12 GMT",
"version": "v2"
}
] | 2018-06-20 | [
[
"Diez-Tejedor",
"Alberto",
""
],
[
"Flores",
"Francisco",
""
],
[
"Niz",
"Gustavo",
""
]
] | Starting from the Gleyzes-Langlois-Piazza-Vernizzi action, we derive the most general effective theory that is invariant under internal shifts and a $\mathbb{Z}_2$ mirror symmetry in the scalar sector. Contrary to what one may think, this model presents a dark matter tracker previous to the dark energy domination. We show that, in an empty universe and to linear order in perturbations, the scalar mode clusters in exactly the same way as standard nonrelativistic cold dark matter. This also holds for the subsector of the theory where the speed of propagation of gravitational waves equals that of light, in agreement with the recent multimessenger observation. However, the inclusion of standard model particles introduces nontrivial couplings of the gravitational scalar mode to baryons, modifying their clustering properties. We argue that no arrangement of the parameters of the model can reduce the extra scalar to precisely behave as cold dark matter. |
1308.1917 | Miguel Socolovsky | O. Brauer, E. Kirchuk, L. Raviola and M. Socolovsky | Entropy of a Rindler Observer | 5 pages, 2 figures | null | 10.1007/s10773-013-1813-y | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the entropy of a Rindler particle-detector (observer) in the
presence of a quantum field in the Minkowski vacuum state; due to the Unruh
effect, the observer is immersed in a thermal bath at a temperature
proportional to its proper acceleration.
| [
{
"created": "Thu, 8 Aug 2013 18:08:06 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Brauer",
"O.",
""
],
[
"Kirchuk",
"E.",
""
],
[
"Raviola",
"L.",
""
],
[
"Socolovsky",
"M.",
""
]
] | We compute the entropy of a Rindler particle-detector (observer) in the presence of a quantum field in the Minkowski vacuum state; due to the Unruh effect, the observer is immersed in a thermal bath at a temperature proportional to its proper acceleration. |
2401.01440 | Pablo Laguna | Nirmal Patel, Aycin Aykutalp, Pablo Laguna | Calculating Quasi-Normal Modes of Schwarzschild Black Holes with Physics
Informed Neural Networks | 20 pages, 6 figures | null | null | null | gr-qc physics.comp-ph | http://creativecommons.org/licenses/by/4.0/ | Machine learning, particularly neural networks, has rapidly permeated most
activities and work where data has a story to tell. Recently, deep learning has
started to be used for solving differential equations with input from physics,
also known as Physics Informed Neural Networks (PINNs). We present a study
showing the efficacy of PINNs for solving the Zerilli and the Regge-Wheeler
equations in the time domain to calculate the quasi-normal oscillation modes of
a Schwarzschild black hole. We compare the extracted modes with those obtained
with finite difference methods. Although the PINN results are competitive, with
a few percent differences in the quasi-normal modes estimates relative to those
computed with finite difference methods, the real power of PINNs will emerge
when applied to large dimensionality problems.
| [
{
"created": "Tue, 2 Jan 2024 21:34:50 GMT",
"version": "v1"
}
] | 2024-01-04 | [
[
"Patel",
"Nirmal",
""
],
[
"Aykutalp",
"Aycin",
""
],
[
"Laguna",
"Pablo",
""
]
] | Machine learning, particularly neural networks, has rapidly permeated most activities and work where data has a story to tell. Recently, deep learning has started to be used for solving differential equations with input from physics, also known as Physics Informed Neural Networks (PINNs). We present a study showing the efficacy of PINNs for solving the Zerilli and the Regge-Wheeler equations in the time domain to calculate the quasi-normal oscillation modes of a Schwarzschild black hole. We compare the extracted modes with those obtained with finite difference methods. Although the PINN results are competitive, with a few percent differences in the quasi-normal modes estimates relative to those computed with finite difference methods, the real power of PINNs will emerge when applied to large dimensionality problems. |
1607.03003 | Jiro Matsumoto | Jiro Matsumoto | Scalar field dark energy with a minimal coupling in a spherically
symmetric background | 15 pages, 3 figures; v2: equations corrected and a figure added,
conclusions are changed a little, v3: references added, explanations
expanded, version to appear in IJMPD | Int. J. Mod. Phys. D, 27, 1750173 (2018) | 10.1142/S0218271817501735 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dark energy models and modified gravity theories have been actively studied
and the behaviors in the solar system have been also carefully investigated in
a part of the models. However, the isotropic solutions of the field equations
in the simple models of dark energy, e.g. quintessence model without matter
coupling, have not been well investigated. One of the reason would be the
nonlinearity of the field equations. In this paper, a method to evaluate the
solution of the field equations is constructed, and it is shown that there is a
model that can easily pass the solar system tests, whereas, there is also a
model that is constrained from the solar system tests.
| [
{
"created": "Mon, 11 Jul 2016 15:35:41 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Aug 2016 14:48:32 GMT",
"version": "v2"
},
{
"created": "Wed, 9 Aug 2017 05:12:15 GMT",
"version": "v3"
}
] | 2018-01-24 | [
[
"Matsumoto",
"Jiro",
""
]
] | Dark energy models and modified gravity theories have been actively studied and the behaviors in the solar system have been also carefully investigated in a part of the models. However, the isotropic solutions of the field equations in the simple models of dark energy, e.g. quintessence model without matter coupling, have not been well investigated. One of the reason would be the nonlinearity of the field equations. In this paper, a method to evaluate the solution of the field equations is constructed, and it is shown that there is a model that can easily pass the solar system tests, whereas, there is also a model that is constrained from the solar system tests. |
gr-qc/9708050 | Beverly K. Berger | Beverly K. Berger, David Garfinkle, Vincent Moncrief | Comment on ``The Gowdy $T^3$ Cosmologies Revisited'' | 3 pages, Revtex, 0 figures | null | null | null | gr-qc | null | A standard and reasonable definition of asymptotic velocity term dominance
(AVTD) shows that the numerical study by Hern and Stewart (gr-qc/9708038)
confirms previous results that generic Gowdy cosmologies on $T^3 \times R$ have
an AVTD singularity.
| [
{
"created": "Thu, 21 Aug 1997 11:32:46 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Berger",
"Beverly K.",
""
],
[
"Garfinkle",
"David",
""
],
[
"Moncrief",
"Vincent",
""
]
] | A standard and reasonable definition of asymptotic velocity term dominance (AVTD) shows that the numerical study by Hern and Stewart (gr-qc/9708038) confirms previous results that generic Gowdy cosmologies on $T^3 \times R$ have an AVTD singularity. |
gr-qc/0410117 | Nelson Pinto-Neto | Nelson Pinto-Neto | The Bohm Interpretation of Quantum Cosmology | 28 pages, 1 figure, contribution to the James Cushing festschrift to
appear in Foundations of Physics | Found.Phys.35:577-603,2005 | 10.1007/s10701-004-2012-8 | null | gr-qc | null | I make a review on the aplications of the Bohm-De Broglie interpretation of
quantum mechanics to quantum cosmology. In the framework of minisuperspaces
models, I show how quantum cosmological effects in Bohm's view can avoid the
initial singularity, isotropize the Universe, and even be a cause for the
present observed acceleration of the Universe. In the general case, we
enumerate the possible structures of quantum space and time.
| [
{
"created": "Fri, 22 Oct 2004 20:38:28 GMT",
"version": "v1"
}
] | 2011-08-04 | [
[
"Pinto-Neto",
"Nelson",
""
]
] | I make a review on the aplications of the Bohm-De Broglie interpretation of quantum mechanics to quantum cosmology. In the framework of minisuperspaces models, I show how quantum cosmological effects in Bohm's view can avoid the initial singularity, isotropize the Universe, and even be a cause for the present observed acceleration of the Universe. In the general case, we enumerate the possible structures of quantum space and time. |
1705.08315 | Mauricio Bellini | Mauricio Bellini (IFIMAR - CONICET and UNMdP) | Origin of time before inflation from a topological phase transition | Version accepted in Physics of the Dark Universe. arXiv admin note:
substantial text overlap with arXiv:1610.07979 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the origin of the universe (or pre-inflation) by suggesting that the
primordial space-time in the universe suffered a global topological phase
transition, from a 4D Euclidean manifold to an asymptotic 4D hyperbolic one. We
introduce a complex time, $\tau$, such that its real part becomes dominant
after started the topological phase transition. Before the big bang, $\tau$ is
a space-like coordinate, so that can be considered as a reversal variable.
After the phase transition is converted in a causal variable. The formalism
solves in a natural manner the quantum to classical transition of the
geometrical relativistic quantum fluctuations: $\sigma$, which has a geometric
origin.
| [
{
"created": "Mon, 22 May 2017 15:22:36 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Jun 2017 02:29:17 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Jul 2017 22:27:28 GMT",
"version": "v3"
}
] | 2017-07-21 | [
[
"Bellini",
"Mauricio",
"",
"IFIMAR - CONICET and UNMdP"
]
] | We study the origin of the universe (or pre-inflation) by suggesting that the primordial space-time in the universe suffered a global topological phase transition, from a 4D Euclidean manifold to an asymptotic 4D hyperbolic one. We introduce a complex time, $\tau$, such that its real part becomes dominant after started the topological phase transition. Before the big bang, $\tau$ is a space-like coordinate, so that can be considered as a reversal variable. After the phase transition is converted in a causal variable. The formalism solves in a natural manner the quantum to classical transition of the geometrical relativistic quantum fluctuations: $\sigma$, which has a geometric origin. |
1202.6189 | Pedro Castelo Ferreira Dr. | P. Castelo Ferreira | Constraining an Expanding Locally Anisotropic metric from the Pioneer
anomaly | 22 pages; 6 figures; based on arXiv:1102.2061 with updated estimative
for Pioneer anomaly | Advances in Space Research 51 (2013) 1266-1277 | 10.1016/j.asr.2012.11.004 | null | gr-qc astro-ph.EP hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is discussed the possibility of a fine-tuneable contribution to the two
way Doppler acceleration either towards, either outwards the Sun for
heliocentric distances above 20 AU by considering a background described by an
Expanding Locally Anisotropic (ELA) metric. This metric encodes both the
standard local Schwarzschild gravitational effects and the cosmological
Universe expansion effects allowing simultaneously to fine-tune other
gravitational effects at intermediate scales, which may be tentatively
interpreted as a covariant parameterization of either cold dark matter either
gravitational interaction corrections. Are derived bounds for the ELA metric
functional parameter by considering the bounds on the deviation from standard
General Relativity imposed by the current updated limits for the Pioneer
anomaly, taking in consideration both the natural outgassing and on-board
radiation pressure, resulting in an average Doppler acceleration outwards the
Sun of a_p = +0.4^{+2.1}_{-2.0} x 10^{-10} (m/s^2). It is also computed the
mass-energy density for the ELA metric within the bounds obtained and are
discussed the respective contributions to the cosmological mass-energy density
which, for compatibility with the Lambda-CDM model, are included in
Omega_{CDM}.
| [
{
"created": "Tue, 28 Feb 2012 11:55:03 GMT",
"version": "v1"
}
] | 2017-11-30 | [
[
"Ferreira",
"P. Castelo",
""
]
] | It is discussed the possibility of a fine-tuneable contribution to the two way Doppler acceleration either towards, either outwards the Sun for heliocentric distances above 20 AU by considering a background described by an Expanding Locally Anisotropic (ELA) metric. This metric encodes both the standard local Schwarzschild gravitational effects and the cosmological Universe expansion effects allowing simultaneously to fine-tune other gravitational effects at intermediate scales, which may be tentatively interpreted as a covariant parameterization of either cold dark matter either gravitational interaction corrections. Are derived bounds for the ELA metric functional parameter by considering the bounds on the deviation from standard General Relativity imposed by the current updated limits for the Pioneer anomaly, taking in consideration both the natural outgassing and on-board radiation pressure, resulting in an average Doppler acceleration outwards the Sun of a_p = +0.4^{+2.1}_{-2.0} x 10^{-10} (m/s^2). It is also computed the mass-energy density for the ELA metric within the bounds obtained and are discussed the respective contributions to the cosmological mass-energy density which, for compatibility with the Lambda-CDM model, are included in Omega_{CDM}. |
1702.01882 | Subinoy Das | Prolay Krishna Chanda, Subinoy Das | Static structure of chameleon dark Matter as an explanation of dwarf
spheroidal galactic core | 8 pages, 5 figures, References added and typos corrected, accepted in
PRD | Phys. Rev. D 95, 083008 (2017) | 10.1103/PhysRevD.95.083008 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a novel mechanism which explains cored dark matter density profile
in recently observed dark matter rich dwarf spheroidal galaxies. In our
scenario, dark matter particle mass decreases gradually as function of distance
towards the center of a dwarf galaxy due to its interaction with a chameleon
scalar. At closer distance towards galactic center the strength of attractive
scalar fifth force becomes much stronger than gravity and is balanced by the
Fermi pressure of dark matter cloud, thus an equilibrium static configuration
of dark matter halo is obtained. Like the case of soliton star or fermion
Q-star, the stability of the dark matter halo is obtained as the scalar
achieves a static profile and reaches an asymptotic value away from the
galactic center. For simple scalar-dark matter interaction and quadratic scalar
self interaction potential, we show that dark matter behaves exactly like cold
dark matter (CDM) beyond few $\rm{kpc}$ away from galactic center but at closer
distance it becomes lighter and fermi pressure cannot be ignored anymore. Using
Thomas-Fermi approximation, we numerically solve the radial static profile of
the scalar field, fermion mass and dark matter energy density as a function of
distance. We find that for fifth force mediated by an ultra light scalar, it is
possible to obtain a flattened dark matter density profile towards galactic
center. In our scenario, the fifth force can be neglected at distance $ r \geq
1\, \rm{kpc}$ from galactic center and dark matter can be simply treated as
heavy non-relativistic particles beyond this distance, thus reproducing the
success of CDM at large scales.
| [
{
"created": "Tue, 7 Feb 2017 05:11:47 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Apr 2017 12:35:21 GMT",
"version": "v2"
}
] | 2017-04-26 | [
[
"Chanda",
"Prolay Krishna",
""
],
[
"Das",
"Subinoy",
""
]
] | We propose a novel mechanism which explains cored dark matter density profile in recently observed dark matter rich dwarf spheroidal galaxies. In our scenario, dark matter particle mass decreases gradually as function of distance towards the center of a dwarf galaxy due to its interaction with a chameleon scalar. At closer distance towards galactic center the strength of attractive scalar fifth force becomes much stronger than gravity and is balanced by the Fermi pressure of dark matter cloud, thus an equilibrium static configuration of dark matter halo is obtained. Like the case of soliton star or fermion Q-star, the stability of the dark matter halo is obtained as the scalar achieves a static profile and reaches an asymptotic value away from the galactic center. For simple scalar-dark matter interaction and quadratic scalar self interaction potential, we show that dark matter behaves exactly like cold dark matter (CDM) beyond few $\rm{kpc}$ away from galactic center but at closer distance it becomes lighter and fermi pressure cannot be ignored anymore. Using Thomas-Fermi approximation, we numerically solve the radial static profile of the scalar field, fermion mass and dark matter energy density as a function of distance. We find that for fifth force mediated by an ultra light scalar, it is possible to obtain a flattened dark matter density profile towards galactic center. In our scenario, the fifth force can be neglected at distance $ r \geq 1\, \rm{kpc}$ from galactic center and dark matter can be simply treated as heavy non-relativistic particles beyond this distance, thus reproducing the success of CDM at large scales. |
1804.09206 | Robert J. Scherrer | Robert J. Scherrer | Dark energy with $w \rightarrow -1$: Asymptotic $\Lambda$ versus
pseudo-$\Lambda$ | 7 pages, no figures, references added | Phys. Rev. D 97, 123521 (2018) | 10.1103/PhysRevD.97.123521 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | If the dark energy density asymptotically approaches a nonzero constant,
$\rho_{DE} \rightarrow \rho_0$, then its equation of state parameter $w$
necessarily approaches $-1$. The converse is not true; dark energy with $w
\rightarrow -1$ can correspond to either $\rho_{DE} \rightarrow \rho_0$ or
$\rho_{DE} \rightarrow 0$. This provides a natural division of models with $w
\rightarrow -1$ into two distinct classes: asymptotic $\Lambda$ ($\rho_{DE}
\rightarrow \rho_0$) and pseudo-$\Lambda$ ($\rho_{DE} \rightarrow 0$). We
delineate the boundary between these two classes of models in terms of the
behavior of $w(a)$, $\rho_{DE}(a)$, and $a(t)$. We examine barotropic and
quintessence realizations of both types of models. Barotropic models with
positive squared sound speed and $w \rightarrow -1$ are always asymptotically
$\Lambda$; they can never produce pseudo-$\Lambda$ behavior. Quintessence
models can correspond to either asymptotic $\Lambda$ or pseudo-$\Lambda$
evolution, but the latter is impossible when the expansion is dominated by a
background barotropic fluid. We show that the distinction between asymptotic
$\Lambda$ and pseudo-$\Lambda$ models for $w> -1$ is mathematically dual to the
distinction between pseudo-rip and big/little rip models when $w < -1$.
| [
{
"created": "Tue, 24 Apr 2018 18:39:44 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Apr 2018 19:21:39 GMT",
"version": "v2"
}
] | 2018-06-20 | [
[
"Scherrer",
"Robert J.",
""
]
] | If the dark energy density asymptotically approaches a nonzero constant, $\rho_{DE} \rightarrow \rho_0$, then its equation of state parameter $w$ necessarily approaches $-1$. The converse is not true; dark energy with $w \rightarrow -1$ can correspond to either $\rho_{DE} \rightarrow \rho_0$ or $\rho_{DE} \rightarrow 0$. This provides a natural division of models with $w \rightarrow -1$ into two distinct classes: asymptotic $\Lambda$ ($\rho_{DE} \rightarrow \rho_0$) and pseudo-$\Lambda$ ($\rho_{DE} \rightarrow 0$). We delineate the boundary between these two classes of models in terms of the behavior of $w(a)$, $\rho_{DE}(a)$, and $a(t)$. We examine barotropic and quintessence realizations of both types of models. Barotropic models with positive squared sound speed and $w \rightarrow -1$ are always asymptotically $\Lambda$; they can never produce pseudo-$\Lambda$ behavior. Quintessence models can correspond to either asymptotic $\Lambda$ or pseudo-$\Lambda$ evolution, but the latter is impossible when the expansion is dominated by a background barotropic fluid. We show that the distinction between asymptotic $\Lambda$ and pseudo-$\Lambda$ models for $w> -1$ is mathematically dual to the distinction between pseudo-rip and big/little rip models when $w < -1$. |
2212.14065 | Parampreet Singh | Meysam Motaharfar, Parampreet Singh | Tunneling wavefunction proposal with loop quantum geometry effects | 19 pages, 6 figures. Expanded discussion on validity of effective
approach. References added. Published version in PRD | Phys. Rev. D 107, 066026 (2023) | 10.1103/PhysRevD.107.066026 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Vilenkin's tunneling wavefunction proposal our expanding universe is born
via a tunneling through a barrier from nothing at the zero scale factor. We
explore the viability of this proposal for the spatially closed FLRW model with
a positive cosmological constant including quantum gravity modifications in the
Planck regime. Our setting is the effective spacetime description of loop
quantum cosmology (LQC) which is known to replace the big bang singularity with
a bounce due to the holonomy modifications. Due to the bounce, the barrier
potential of the Wheeler-DeWitt theory is replaced by a step like potential
which makes the tunneling proposal incompatible. But for a complete picture of
singularity resolution, inverse scale factor modifications from quantum
geometry must be included which play an important role at very small scale
factors in the spatially closed models. We show that with inclusion of inverse
scale factor modifications the resulting potential is again a barrier
potential. The universe at the vanishing scale factor is dynamically
non-singular and in an Einstein static like phase. We show that quantum
geometric effects in LQC provide a non-singular completion of Vilenkin's
tunneling proposal. We also find that quantum geometric effects result in a
possibility of a tunneling to a quantum cyclic universe albeit for a very large
value of cosmological constant determined by the quantum geometry.
| [
{
"created": "Wed, 28 Dec 2022 19:04:51 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Apr 2023 18:22:41 GMT",
"version": "v2"
}
] | 2023-04-17 | [
[
"Motaharfar",
"Meysam",
""
],
[
"Singh",
"Parampreet",
""
]
] | In Vilenkin's tunneling wavefunction proposal our expanding universe is born via a tunneling through a barrier from nothing at the zero scale factor. We explore the viability of this proposal for the spatially closed FLRW model with a positive cosmological constant including quantum gravity modifications in the Planck regime. Our setting is the effective spacetime description of loop quantum cosmology (LQC) which is known to replace the big bang singularity with a bounce due to the holonomy modifications. Due to the bounce, the barrier potential of the Wheeler-DeWitt theory is replaced by a step like potential which makes the tunneling proposal incompatible. But for a complete picture of singularity resolution, inverse scale factor modifications from quantum geometry must be included which play an important role at very small scale factors in the spatially closed models. We show that with inclusion of inverse scale factor modifications the resulting potential is again a barrier potential. The universe at the vanishing scale factor is dynamically non-singular and in an Einstein static like phase. We show that quantum geometric effects in LQC provide a non-singular completion of Vilenkin's tunneling proposal. We also find that quantum geometric effects result in a possibility of a tunneling to a quantum cyclic universe albeit for a very large value of cosmological constant determined by the quantum geometry. |
1706.02070 | Hisa-aki Shinkai | Hisa-aki Shinkai, Takashi Torii | Nonlinear Dynamics in the Einstein-Gauss-Bonnet gravity | 14 pages, 10 figures, Fig.10 replaced, to be published in Phys. Rev.
D. (Aug, 2017) | Phys. Rev. D 96, 044009 (2017) | 10.1103/PhysRevD.96.044009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We numerically investigated how the nonlinear dynamics depends on the
dimensionality and on the higher-order curvature corrections in the form of
Gauss-Bonnet (GB) terms. We especially monitored the processes of appearances
of a singularity (or black hole) in two models: (i) a perturbed wormhole throat
in spherically symmetric space-time, and (ii) colliding scalar pulses in
plane-symmetric space-time. We used a dual-null formulation for evolving the
field equations, which enables us to locate the trapping horizons directly, and
also enables us to follow close to the large-curvature region due to its causal
integrating scheme. We observed that the fate of a perturbed wormhole is either
a black hole or an expanding throat depending on the total energy of the
structure, and its threshold depends on the coupling constant of the GB terms
($\alpha_{\rm GB}$). We also observed that a collision of large scalar pulses
will produce a large-curvature region, of which the magnitude also depends on
$\alpha_{\rm GB}$. For both models, the normal corrections ($\alpha_{\rm
GB}>0$) work for avoiding the appearance of singularity, although it is
inevitable. We also found that in the critical situation for forming a black
hole, the existence of the trapped region in the Einstein-GB gravity does not
directly indicate the formation of a black hole.
| [
{
"created": "Wed, 7 Jun 2017 07:25:32 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Jun 2017 03:13:23 GMT",
"version": "v2"
},
{
"created": "Mon, 31 Jul 2017 13:07:57 GMT",
"version": "v3"
}
] | 2017-08-16 | [
[
"Shinkai",
"Hisa-aki",
""
],
[
"Torii",
"Takashi",
""
]
] | We numerically investigated how the nonlinear dynamics depends on the dimensionality and on the higher-order curvature corrections in the form of Gauss-Bonnet (GB) terms. We especially monitored the processes of appearances of a singularity (or black hole) in two models: (i) a perturbed wormhole throat in spherically symmetric space-time, and (ii) colliding scalar pulses in plane-symmetric space-time. We used a dual-null formulation for evolving the field equations, which enables us to locate the trapping horizons directly, and also enables us to follow close to the large-curvature region due to its causal integrating scheme. We observed that the fate of a perturbed wormhole is either a black hole or an expanding throat depending on the total energy of the structure, and its threshold depends on the coupling constant of the GB terms ($\alpha_{\rm GB}$). We also observed that a collision of large scalar pulses will produce a large-curvature region, of which the magnitude also depends on $\alpha_{\rm GB}$. For both models, the normal corrections ($\alpha_{\rm GB}>0$) work for avoiding the appearance of singularity, although it is inevitable. We also found that in the critical situation for forming a black hole, the existence of the trapped region in the Einstein-GB gravity does not directly indicate the formation of a black hole. |
1912.02922 | Barak Shoshany | Barak Shoshany | At the Corner of Space and Time | 162 pages, 11 figures, PhD thesis; corrected minor typos and updated
references | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a rigorous piecewise-flat discretization of classical general
relativity in the first-order formulation, in both 2+1 and 3+1 dimensions,
carefully keeping track of curvature and torsion via holonomies. We show that
the resulting phase space is precisely that of spin networks, the quantum
states of discrete spacetime in loop quantum gravity, with additional degrees
of freedom called edge modes, which control the gluing between cells. This work
establishes, for the first time, a rigorous proof of the equivalence between
spin networks and piecewise-flat geometries with curvature and torsion degrees
of freedom. In addition, it demonstrates that careful consideration of edge
modes is crucial both for the purpose of this proof and for future work in the
field of loop quantum gravity. It also shows that spin networks have a dual
description related to teleparallel gravity, where gravity is encoded in
torsion instead of curvature degrees of freedom. Finally, it sets the stage for
collaboration between the loop quantum gravity community and theoretical
physicists working on edge modes from other perspectives, such as quantum
electrodynamics, non-abelian gauge theories, and classical gravity.
| [
{
"created": "Thu, 5 Dec 2019 23:41:03 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Apr 2020 19:42:43 GMT",
"version": "v2"
}
] | 2020-04-03 | [
[
"Shoshany",
"Barak",
""
]
] | We perform a rigorous piecewise-flat discretization of classical general relativity in the first-order formulation, in both 2+1 and 3+1 dimensions, carefully keeping track of curvature and torsion via holonomies. We show that the resulting phase space is precisely that of spin networks, the quantum states of discrete spacetime in loop quantum gravity, with additional degrees of freedom called edge modes, which control the gluing between cells. This work establishes, for the first time, a rigorous proof of the equivalence between spin networks and piecewise-flat geometries with curvature and torsion degrees of freedom. In addition, it demonstrates that careful consideration of edge modes is crucial both for the purpose of this proof and for future work in the field of loop quantum gravity. It also shows that spin networks have a dual description related to teleparallel gravity, where gravity is encoded in torsion instead of curvature degrees of freedom. Finally, it sets the stage for collaboration between the loop quantum gravity community and theoretical physicists working on edge modes from other perspectives, such as quantum electrodynamics, non-abelian gauge theories, and classical gravity. |
1004.4537 | Salvatore Vitale | Salvatore Vitale and Michele Zanolin | Parameter estimation from Gravitational waves generated by non-spinning
binary black holes with laser interferometers: beyond the Fisher information | null | Phys.Rev.D82:124065,2010 | 10.1103/PhysRevD.82.124065 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we apply to gravitational waves from non-spinning binary
systems a recently intro- duced frequentist methodology to calculate
analytically the error for a maximum likelihood estimate (MLE) of physical
parameters. While existing literature focuses on using the Cramer Rao Lower
bound (CRLB) and Monte Carlo simulations, we use a power expansion of the bias
and covariance in inverse powers of the signal to noise ratio. The use of
higher order derivatives of the likelihood function in the expansions makes the
prediction also sensitive to the secondary lobes of the MLE probability
distribution. We discuss conditions for validity of the CRLB and predict new
features in regions of the parameter space currently not explored. For example,
we see how the bias can become the most important contributor to the
parameters' errors for high mass systems (200M and above).
| [
{
"created": "Mon, 26 Apr 2010 14:23:15 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Jun 2010 07:43:24 GMT",
"version": "v2"
},
{
"created": "Tue, 29 Jun 2010 13:43:04 GMT",
"version": "v3"
},
{
"created": "Tue, 2 Nov 2010 10:16:50 GMT",
"version": "v4"
},
{
"created": "Fri, 12 Nov 2010 19:12:09 GMT",
"version": "v5"
}
] | 2011-02-02 | [
[
"Vitale",
"Salvatore",
""
],
[
"Zanolin",
"Michele",
""
]
] | In this paper we apply to gravitational waves from non-spinning binary systems a recently intro- duced frequentist methodology to calculate analytically the error for a maximum likelihood estimate (MLE) of physical parameters. While existing literature focuses on using the Cramer Rao Lower bound (CRLB) and Monte Carlo simulations, we use a power expansion of the bias and covariance in inverse powers of the signal to noise ratio. The use of higher order derivatives of the likelihood function in the expansions makes the prediction also sensitive to the secondary lobes of the MLE probability distribution. We discuss conditions for validity of the CRLB and predict new features in regions of the parameter space currently not explored. For example, we see how the bias can become the most important contributor to the parameters' errors for high mass systems (200M and above). |
1505.06546 | Fangyu Li | Fangyu Li and Hao Wen and Zhenyun Fang and Lianfu Wei and Yiwen Wang
and Miao Zhang | Quasi-B-mode generated by high-frequency gravitational waves and
corresponding perturbative photon fluxes | 22 pages, 6 figures, research article | Nuclear Physics B 911 (2016) 500-516 | 10.1016/j.nuclphysb.2016.08.009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Interaction of very low-frequency primordial(relic) gravitational waves(GWs)
to cosmic microwave background(CMB) can generate B-mode polarization. Here, for
the first time we point out that the electromagnetic(EM) response to
high-frequency GWs(HFGWs) would produce quasi-B-mode distribution of the
perturbative photon fluxes, and study the duality and high complementarity
between such two B-modes. Based on this quasi-B-mode in HFGWs, it is shown that
the distinguishing and observing of HFGWs from the braneworld would be quite
possible due to their large amplitude, higher frequency and very different
physical behaviors between the perturbative photon fluxes and background
photons, and the measurement of relic HFGWs may also be possible though face to
enormous challenge.
| [
{
"created": "Mon, 25 May 2015 05:51:34 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Jun 2015 07:20:31 GMT",
"version": "v2"
},
{
"created": "Tue, 20 Oct 2015 03:29:53 GMT",
"version": "v3"
},
{
"created": "Tue, 11 Oct 2016 17:13:59 GMT",
"version": "v4"
},
{
"created": "Sat, 15 Apr 2017 17:01:13 GMT",
"version": "v5"
}
] | 2017-04-18 | [
[
"Li",
"Fangyu",
""
],
[
"Wen",
"Hao",
""
],
[
"Fang",
"Zhenyun",
""
],
[
"Wei",
"Lianfu",
""
],
[
"Wang",
"Yiwen",
""
],
[
"Zhang",
"Miao",
""
]
] | Interaction of very low-frequency primordial(relic) gravitational waves(GWs) to cosmic microwave background(CMB) can generate B-mode polarization. Here, for the first time we point out that the electromagnetic(EM) response to high-frequency GWs(HFGWs) would produce quasi-B-mode distribution of the perturbative photon fluxes, and study the duality and high complementarity between such two B-modes. Based on this quasi-B-mode in HFGWs, it is shown that the distinguishing and observing of HFGWs from the braneworld would be quite possible due to their large amplitude, higher frequency and very different physical behaviors between the perturbative photon fluxes and background photons, and the measurement of relic HFGWs may also be possible though face to enormous challenge. |
2007.02666 | Ramil Izmailov N | K.K. Nandi, R.N. Izmailov, G.M. Garipova, R.R. Volotskova and A.A.
Potapov | On the Hoop conjecture in Einstein gravity coupled to nonlinear
electrodynamics | 7 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The famous hoop conjecture by Thorne has been claimed to be\ violated in
curved spacetimes coupled to linear electrodynamics. Hod \cite{Hod:2018} has
recently refuted this claim by clarifying the status and validity of the
conjecture appropriately interpreting the gravitational mass parameter $M$.
However, it turns out that partial violations of the conjecture might seemingly
occur also in the well known regular curved spacetimes of gravity coupled to
\textit{nonlinear electrodynamic}s. Using the interpretation of $M$ in a
generic form accommodating nonlinear electrodynamic coupling, we illustrate a
novel extension that the hoop conjecture is \textit{not} violated even in such
curved spacetimes. We introduce a Hod function summarizing the hoop conjecture
and find that it surprisingly encapsulates the transition regimes between
"horizon and no horizon" across the critical values determined essentially by
the concerned curved geometries.
| [
{
"created": "Mon, 6 Jul 2020 11:55:00 GMT",
"version": "v1"
}
] | 2020-07-07 | [
[
"Nandi",
"K. K.",
""
],
[
"Izmailov",
"R. N.",
""
],
[
"Garipova",
"G. M.",
""
],
[
"Volotskova",
"R. R.",
""
],
[
"Potapov",
"A. A.",
""
]
] | The famous hoop conjecture by Thorne has been claimed to be\ violated in curved spacetimes coupled to linear electrodynamics. Hod \cite{Hod:2018} has recently refuted this claim by clarifying the status and validity of the conjecture appropriately interpreting the gravitational mass parameter $M$. However, it turns out that partial violations of the conjecture might seemingly occur also in the well known regular curved spacetimes of gravity coupled to \textit{nonlinear electrodynamic}s. Using the interpretation of $M$ in a generic form accommodating nonlinear electrodynamic coupling, we illustrate a novel extension that the hoop conjecture is \textit{not} violated even in such curved spacetimes. We introduce a Hod function summarizing the hoop conjecture and find that it surprisingly encapsulates the transition regimes between "horizon and no horizon" across the critical values determined essentially by the concerned curved geometries. |
2103.05490 | Timothy Anson | Timothy Anson, Eugeny Babichev and Christos Charmousis | Deformed black hole in Sagittarius A | 24 pages, 1 figure; v3: reference added, matches published version | Phys. Rev. D 103, 124035 (2021) | 10.1103/PhysRevD.103.124035 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the post-Newtonian orbit of stars around a deformed Kerr black
hole. The deformation we consider is a class of disformal transformations of a
nontrivial Kerr solution in scalar-tensor theory which are labeled via the
disformal parameter $D$. We study different limits of the disformal parameter,
and compare the trajectories of stars orbiting a black hole to the case of the
Kerr spacetime in general relativity, up to 2PN order. Our findings show that
for generic nonzero $D$, the no-hair theorem of general relativity is violated,
in the sense that the black hole's quadrupole $Q$ is not determined by its mass
$M$ and angular momentum $J$ through the relation $Q=-J^2/M$. Limiting values
of $D$ provide examples of simple and exact noncircular metric solutions,
whereas in a particular limit, where $1+D$ is small but finite, we obtain a
leading correction to the Schwarzschild precession due to disformality. In this
case, the disformal parameter is constrained using the recent measurement of
the pericenter precession of the star S2 by the GRAVITY Collaboration.
| [
{
"created": "Tue, 9 Mar 2021 15:24:16 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Mar 2021 11:42:14 GMT",
"version": "v2"
},
{
"created": "Mon, 14 Jun 2021 15:40:13 GMT",
"version": "v3"
}
] | 2021-06-15 | [
[
"Anson",
"Timothy",
""
],
[
"Babichev",
"Eugeny",
""
],
[
"Charmousis",
"Christos",
""
]
] | We analyze the post-Newtonian orbit of stars around a deformed Kerr black hole. The deformation we consider is a class of disformal transformations of a nontrivial Kerr solution in scalar-tensor theory which are labeled via the disformal parameter $D$. We study different limits of the disformal parameter, and compare the trajectories of stars orbiting a black hole to the case of the Kerr spacetime in general relativity, up to 2PN order. Our findings show that for generic nonzero $D$, the no-hair theorem of general relativity is violated, in the sense that the black hole's quadrupole $Q$ is not determined by its mass $M$ and angular momentum $J$ through the relation $Q=-J^2/M$. Limiting values of $D$ provide examples of simple and exact noncircular metric solutions, whereas in a particular limit, where $1+D$ is small but finite, we obtain a leading correction to the Schwarzschild precession due to disformality. In this case, the disformal parameter is constrained using the recent measurement of the pericenter precession of the star S2 by the GRAVITY Collaboration. |
1604.01396 | Macarena Lagos | Macarena Lagos, Tessa Baker, Pedro G. Ferreira, Johannes Noller | A general theory of linear cosmological perturbations: scalar-tensor and
vector-tensor theories | Two code packages (xIST and COPPER) are published with this paper and
can be downloaded from https://github.com/noller/xIST. Final version with
minor changes | null | 10.1088/1475-7516/2016/08/007 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a method for parametrizing linear cosmological perturbations of
theories of gravity, around homogeneous and isotropic backgrounds. The method
is sufficiently general and systematic that it can be applied to theories with
any degrees of freedom (DoFs) and arbitrary gauge symmetries. In this paper, we
focus on scalar-tensor and vector-tensor theories, invariant under linear
coordinate transformations. In the case of scalar-tensor theories, we use our
framework to recover the simple parametrizations of linearized Horndeski and
"Beyond Horndeski" theories, and also find higher-derivative corrections. In
the case of vector-tensor theories, we first construct the most general
quadratic action for perturbations that leads to second-order equations of
motion, which propagates two scalar DoFs. Then we specialize to the case in
which the vector field is time-like (\`a la Einstein-Aether gravity), where the
theory only propagates one scalar DoF. As a result, we identify the complete
forms of the quadratic actions for perturbations, and the number of free
parameters that need to be defined, to cosmologically characterize these two
broad classes of theories.
| [
{
"created": "Tue, 5 Apr 2016 15:10:33 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jul 2016 10:19:10 GMT",
"version": "v2"
}
] | 2016-08-17 | [
[
"Lagos",
"Macarena",
""
],
[
"Baker",
"Tessa",
""
],
[
"Ferreira",
"Pedro G.",
""
],
[
"Noller",
"Johannes",
""
]
] | We present a method for parametrizing linear cosmological perturbations of theories of gravity, around homogeneous and isotropic backgrounds. The method is sufficiently general and systematic that it can be applied to theories with any degrees of freedom (DoFs) and arbitrary gauge symmetries. In this paper, we focus on scalar-tensor and vector-tensor theories, invariant under linear coordinate transformations. In the case of scalar-tensor theories, we use our framework to recover the simple parametrizations of linearized Horndeski and "Beyond Horndeski" theories, and also find higher-derivative corrections. In the case of vector-tensor theories, we first construct the most general quadratic action for perturbations that leads to second-order equations of motion, which propagates two scalar DoFs. Then we specialize to the case in which the vector field is time-like (\`a la Einstein-Aether gravity), where the theory only propagates one scalar DoF. As a result, we identify the complete forms of the quadratic actions for perturbations, and the number of free parameters that need to be defined, to cosmologically characterize these two broad classes of theories. |
2011.12969 | Christian Pfeifer | Sjors Heefer and Christian Pfeifer and Andrea Fuster | Randers pp-waves | 11 pagers, updated to journal version | Phys. Rev. D 104, 024007 (2021) | 10.1103/PhysRevD.104.024007 | null | gr-qc hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study Randers spacetimes of Berwald type and analyze Pfeifer
and Wohlfarth's vacuum field equation of Finsler gravity for this class. We
show that in this case the field equation is equivalent to the vanishing of the
Finsler Ricci tensor, analogously to Einstein gravity. This implies that the
considered vacuum field equation and Rutz's equation coincide in this scenario.
We also construct all exact solutions of Berwald-Randers type to vacuum Finsler
gravity, which turn out to be composed of a CCNV (covariantly constant null
vector) Lorentzian spacetime, commonly known as pp-wave, and a 1-form given by
the pp-wave distinguished null vector. We therefore refer to the found
solutions as Randers pp-waves.
| [
{
"created": "Wed, 25 Nov 2020 19:00:02 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Jul 2021 14:38:23 GMT",
"version": "v2"
},
{
"created": "Fri, 19 May 2023 11:58:56 GMT",
"version": "v3"
}
] | 2023-05-22 | [
[
"Heefer",
"Sjors",
""
],
[
"Pfeifer",
"Christian",
""
],
[
"Fuster",
"Andrea",
""
]
] | In this work we study Randers spacetimes of Berwald type and analyze Pfeifer and Wohlfarth's vacuum field equation of Finsler gravity for this class. We show that in this case the field equation is equivalent to the vanishing of the Finsler Ricci tensor, analogously to Einstein gravity. This implies that the considered vacuum field equation and Rutz's equation coincide in this scenario. We also construct all exact solutions of Berwald-Randers type to vacuum Finsler gravity, which turn out to be composed of a CCNV (covariantly constant null vector) Lorentzian spacetime, commonly known as pp-wave, and a 1-form given by the pp-wave distinguished null vector. We therefore refer to the found solutions as Randers pp-waves. |
1611.02789 | Jian-Yang Zhu | Zhi-Peng Peng, Jia-Ning Yu, Xiao-Min Zhang and Jian-Yang Zhu | Consistency of warm k-inflation | 8 pages. Accepted for publication as a Regular Article in Physical
Review D | Phys. Rev. D 94, 103531 (2016) | 10.1103/PhysRevD.94.103531 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend the k-inflation which is a type of kinetically driven inflationary
model under the standard inflationary scenario to a possible warm inflationary
scenario. The dynamical equations of this warm k-inflation model are obtained.
We rewrite the slow-roll parameters which are different from the usual
potential driven inflationary models and perform a linear stability analysis to
give the proper slow-roll conditions in the warm k-inflation. Two cases, a
power-law kinetic function and an exponential kinetic function, are studied,
when the dissipative coefficient $\Gamma=\Gamma_0$ and $\Gamma=\Gamma(\phi)$,
respectively. A proper number of e-folds is obtained in both concrete cases of
warm k-inflation. We find a constant dissipative coefficient
($\Gamma=\Gamma_0$) is not a workable choice for these two cases while the two
cases with $\Gamma=\Gamma(\phi)$ are self-consistent warm inflationary models.
| [
{
"created": "Wed, 9 Nov 2016 01:14:26 GMT",
"version": "v1"
}
] | 2016-12-06 | [
[
"Peng",
"Zhi-Peng",
""
],
[
"Yu",
"Jia-Ning",
""
],
[
"Zhang",
"Xiao-Min",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | We extend the k-inflation which is a type of kinetically driven inflationary model under the standard inflationary scenario to a possible warm inflationary scenario. The dynamical equations of this warm k-inflation model are obtained. We rewrite the slow-roll parameters which are different from the usual potential driven inflationary models and perform a linear stability analysis to give the proper slow-roll conditions in the warm k-inflation. Two cases, a power-law kinetic function and an exponential kinetic function, are studied, when the dissipative coefficient $\Gamma=\Gamma_0$ and $\Gamma=\Gamma(\phi)$, respectively. A proper number of e-folds is obtained in both concrete cases of warm k-inflation. We find a constant dissipative coefficient ($\Gamma=\Gamma_0$) is not a workable choice for these two cases while the two cases with $\Gamma=\Gamma(\phi)$ are self-consistent warm inflationary models. |
gr-qc/0602029 | Filimonova Irina V | S.S. Gershtein, A.A. Logunov and M.A.Mestvirishvili | Self-restriction of Gravitational Field and its Role in the Universe | 52 p | null | null | null | gr-qc | null | It is shown in the article that according to the Relativistic Theory of
Gravitation the gravitational field providing slowing down of the time rate
nevertheless stops itself this slowing down in strong fields. So a physical
tendency of this field to self-restriction of the gravitational potential is
demonstrated. This property of the field leads to a stopping of the collapse of
massive bodies and to the cyclic evolution of the homogeneous and isotropic
Universe.
| [
{
"created": "Wed, 8 Feb 2006 10:18:53 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Feb 2006 12:22:52 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Gershtein",
"S. S.",
""
],
[
"Logunov",
"A. A.",
""
],
[
"Mestvirishvili",
"M. A.",
""
]
] | It is shown in the article that according to the Relativistic Theory of Gravitation the gravitational field providing slowing down of the time rate nevertheless stops itself this slowing down in strong fields. So a physical tendency of this field to self-restriction of the gravitational potential is demonstrated. This property of the field leads to a stopping of the collapse of massive bodies and to the cyclic evolution of the homogeneous and isotropic Universe. |
1011.2881 | Pavel Krtous | Jindrich Dolansky, Pavel Krtous | Billiard in the space with a time machine | 13 pages, 16 figures | Phys.Rev.D82:124056,2010 | 10.1103/PhysRevD.82.124056 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a system of an elastic ball moving in the non-relativistic spacetime
with a nontrivial causal structure produced by a wormhole-based time machine.
For such a system it is possible to formulate a simple model of the so-called
`grandfather paradox': for certain `paradoxical' initial conditions the
standard straight trajectory of the ball would self-collide inconsistently. We
analyze globally consistent solutions of local equations of motion, namely, we
find all trajectories with one self-collision. It is demonstrated that all
standard initial conditions have a consistent evolution, including those
`paradoxical' ones, for which the inconsistent collision-free trajectory is
superseded by a special consistent self-colliding trajectory. Moreover, it is
shown that for a wide class of initial conditions more than one globally
consistent evolution exist. The nontrivial causal structure thus breaks the
uniqueness of the classical theory even for locally deterministic physical
laws.
| [
{
"created": "Fri, 12 Nov 2010 11:22:10 GMT",
"version": "v1"
}
] | 2011-01-20 | [
[
"Dolansky",
"Jindrich",
""
],
[
"Krtous",
"Pavel",
""
]
] | We study a system of an elastic ball moving in the non-relativistic spacetime with a nontrivial causal structure produced by a wormhole-based time machine. For such a system it is possible to formulate a simple model of the so-called `grandfather paradox': for certain `paradoxical' initial conditions the standard straight trajectory of the ball would self-collide inconsistently. We analyze globally consistent solutions of local equations of motion, namely, we find all trajectories with one self-collision. It is demonstrated that all standard initial conditions have a consistent evolution, including those `paradoxical' ones, for which the inconsistent collision-free trajectory is superseded by a special consistent self-colliding trajectory. Moreover, it is shown that for a wide class of initial conditions more than one globally consistent evolution exist. The nontrivial causal structure thus breaks the uniqueness of the classical theory even for locally deterministic physical laws. |
gr-qc/0503115 | Xu Lixin | Feng Luo, Hongya Liu | Brane Formation and Cosmological Constraint on the Number of Extra
Dimensions | 11 pages, no figures. To appear in IJTP | Int.J.Theor.Phys. 44 (2005) 1441-1450 | 10.1007/s10773-005-4778-2 | null | gr-qc astro-ph hep-th | null | Special relativity is generalized to extra dimensions and quantized energy
levels of particles are obtained. By calculating the probability of particles'
motion in extra dimensions at high temperature of the early universe, it is
proposed that the branes may have not existed since the very beginning of the
universe, but formed later. Meanwhile, before the formation, particles of the
universe may have filled in the whole bulk, not just on the branes. This
scenario differs from that in the standard big bang cosmology in which all
particles are assumed to be in the 4D spacetime. So, in brane models, whether
our universe began from a 4D big bang singularity is questionable. A
cosmological constraint on the number of extra dimensions is also given which
favors $N\geq 7$.
| [
{
"created": "Wed, 30 Mar 2005 00:27:41 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Luo",
"Feng",
""
],
[
"Liu",
"Hongya",
""
]
] | Special relativity is generalized to extra dimensions and quantized energy levels of particles are obtained. By calculating the probability of particles' motion in extra dimensions at high temperature of the early universe, it is proposed that the branes may have not existed since the very beginning of the universe, but formed later. Meanwhile, before the formation, particles of the universe may have filled in the whole bulk, not just on the branes. This scenario differs from that in the standard big bang cosmology in which all particles are assumed to be in the 4D spacetime. So, in brane models, whether our universe began from a 4D big bang singularity is questionable. A cosmological constraint on the number of extra dimensions is also given which favors $N\geq 7$. |
gr-qc/9707009 | Hans Kastrup | H.A. Kastrup (RWTH Aachen) | Canonical Quantum Statistics of an Isolated Schwarzschild Black Hole
with a Spectrum E_n = sigma sqrt{n} E_P | 14 pages, LaTeX A brief note added which refers to previous work
where the imaginary part of the partition function is related to metastable
states of the system | Phys.Lett. B413 (1997) 267-273 | 10.1016/S0370-2693(97)01121-0 | PITHA 97/18 | gr-qc hep-th | null | Many authors - beginning with Bekenstein - have suggested that the energy
levels E_n of a quantized isolated Schwarzschild black hole have the form E_n =
sigma sqrt{n} E_P, n=1,2,..., sigma =O(1), with degeneracies g^n. In the
present paper properties of a system with such a spectrum, considered as a
quantum canonical ensemble, are discussed: Its canonical partition function
Z(g,beta=1/kT), defined as a series for g<1, obeys the 1-dimensional heat
equation. It may be extended to values g>1 by means of an integral
representation which reveals a cut of Z(g,beta) in the complex g-plane from g=1
to infinity. Approaching the cut from above yields a real and an imaginary part
of Z. Very surprisingly, it is the (explicitly known) imaginary part which
gives the expected thermodynamical properties of Schwarzschild black holes:
Identifying the internal energy U with the rest energy Mc^2 requires beta to
have the value (in natural units) beta = 2M(lng/sigma^2)[1+O(1/M^2)], (4pi
sigma^2=lng gives Hawking's beta_H), and yields the entropy S=[lng/(4pi
sigma^2)] A/4 + O(lnA), where A is the area of the horizon.
| [
{
"created": "Thu, 3 Jul 1997 18:51:08 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Aug 1997 14:20:09 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Kastrup",
"H. A.",
"",
"RWTH Aachen"
]
] | Many authors - beginning with Bekenstein - have suggested that the energy levels E_n of a quantized isolated Schwarzschild black hole have the form E_n = sigma sqrt{n} E_P, n=1,2,..., sigma =O(1), with degeneracies g^n. In the present paper properties of a system with such a spectrum, considered as a quantum canonical ensemble, are discussed: Its canonical partition function Z(g,beta=1/kT), defined as a series for g<1, obeys the 1-dimensional heat equation. It may be extended to values g>1 by means of an integral representation which reveals a cut of Z(g,beta) in the complex g-plane from g=1 to infinity. Approaching the cut from above yields a real and an imaginary part of Z. Very surprisingly, it is the (explicitly known) imaginary part which gives the expected thermodynamical properties of Schwarzschild black holes: Identifying the internal energy U with the rest energy Mc^2 requires beta to have the value (in natural units) beta = 2M(lng/sigma^2)[1+O(1/M^2)], (4pi sigma^2=lng gives Hawking's beta_H), and yields the entropy S=[lng/(4pi sigma^2)] A/4 + O(lnA), where A is the area of the horizon. |
2211.17065 | Leihua Liu | Ke Gao, Lei-Hua Liu, Mian Zhu | Microlensing effects of wormholes associated to blackhole spacetimes | Match the publication version | Phys.Dark Univ. 41 (2023) 101254 | 10.1016/j.dark.2023.101254 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | In this paper, we investigate the microlensing effects of wormholes
associated to black hole spacetimes. Specifically, we work on three typical
wormholes (WH): Schwarzschild WH, Kerr WH, and RN WH, as well as their
blackhole correspondences. We evaluate the deflection angle upon the second
order under weak field approximation using Gauss-Bonnet theorem. Then, we study
their magnification with numerics.We find that a Kerr WH could lead to multi
peaks in the magnification with certain parameters in the prograde case, while
a Kerr BH predicts one peak. Therefore, the multi-peak feature of can be used
to distinguish the Kerr WH from other compact objects. We also find that the
magnification of RN BH will be one peak compared to RN WH, in which the
magnification of RN WH is negative in some situations. For other cases, the
behavior of magnification from wormholes and their corresponding blackholes is
similar. Our result may shed new light on exploring compact objects through the
microlensing effect.
| [
{
"created": "Wed, 30 Nov 2022 15:17:31 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Dec 2022 15:42:59 GMT",
"version": "v2"
},
{
"created": "Mon, 13 Feb 2023 14:17:34 GMT",
"version": "v3"
},
{
"created": "Thu, 8 Jun 2023 12:56:05 GMT",
"version": "v4"
}
] | 2023-06-09 | [
[
"Gao",
"Ke",
""
],
[
"Liu",
"Lei-Hua",
""
],
[
"Zhu",
"Mian",
""
]
] | In this paper, we investigate the microlensing effects of wormholes associated to black hole spacetimes. Specifically, we work on three typical wormholes (WH): Schwarzschild WH, Kerr WH, and RN WH, as well as their blackhole correspondences. We evaluate the deflection angle upon the second order under weak field approximation using Gauss-Bonnet theorem. Then, we study their magnification with numerics.We find that a Kerr WH could lead to multi peaks in the magnification with certain parameters in the prograde case, while a Kerr BH predicts one peak. Therefore, the multi-peak feature of can be used to distinguish the Kerr WH from other compact objects. We also find that the magnification of RN BH will be one peak compared to RN WH, in which the magnification of RN WH is negative in some situations. For other cases, the behavior of magnification from wormholes and their corresponding blackholes is similar. Our result may shed new light on exploring compact objects through the microlensing effect. |
1101.3168 | Torsten Asselmeyer-Maluga | T. Asselmeyer-Maluga and C.H. Brans | Gravitational sources induced by exotic smoothness | 17 pages, 8 figures, 5 appendices | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we construct a coordinate atlas in an exotic $\mathbb{R}^{4}$
using Bizaca's construction. The main source for such an atlas is the handle
body decomposition of a Casson handle, which of course is an infinite, but
periodic, process. The immersion of the end-periodic manifold into
$\mathbb{R}^{4}$ is directly related to the exoticness of the $\mathbb{R}^{4}$
and also gives rise naturally to a spinor field. Thus we obtain the interesting
result that the simplest exotic $\mathbb{R}^{4}$ generates an extra spinor
field by exoticness.
| [
{
"created": "Mon, 17 Jan 2011 10:18:13 GMT",
"version": "v1"
}
] | 2011-01-18 | [
[
"Asselmeyer-Maluga",
"T.",
""
],
[
"Brans",
"C. H.",
""
]
] | In this paper we construct a coordinate atlas in an exotic $\mathbb{R}^{4}$ using Bizaca's construction. The main source for such an atlas is the handle body decomposition of a Casson handle, which of course is an infinite, but periodic, process. The immersion of the end-periodic manifold into $\mathbb{R}^{4}$ is directly related to the exoticness of the $\mathbb{R}^{4}$ and also gives rise naturally to a spinor field. Thus we obtain the interesting result that the simplest exotic $\mathbb{R}^{4}$ generates an extra spinor field by exoticness. |
gr-qc/0604061 | Dmitriy Pak | Sang-Woo Kim, D.G. Pak | Torsion as a dynamic degree of freedom of quantum gravity | 13 pages, reduced final version | Class.Quant.Grav.25:065011,2008 | 10.1088/0264-9381/25/6/065011 | SNUTP-06-009 | gr-qc | null | The gauge approach to gravity based on the local Lorentz group with a general
independent affine connection A_{\mu cd} is developed. We consider SO(1,3)
gauge theory with a Lagrangian quadratic in curvature as a simple model of
quantum gravity. The torsion is proposed to represent a dynamic degree of
freedom of quantum gravity at scales above the Planckian energy. The
Einstein-Hilbert theory is induced as an effective theory due to quantum
corrections of torsion via generating a stable gravito-magnetic condensate. We
conjecture that torsion possesses an intrinsic quantum nature and can be
confined. A minimal Abelian projection for the Lorentz gauge model has been
constructed, and an effective theory of the cosmic knot at the Planckian scale
is proposed.
| [
{
"created": "Thu, 13 Apr 2006 12:20:10 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jul 2006 07:09:21 GMT",
"version": "v2"
},
{
"created": "Wed, 5 Mar 2008 06:19:18 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Kim",
"Sang-Woo",
""
],
[
"Pak",
"D. G.",
""
]
] | The gauge approach to gravity based on the local Lorentz group with a general independent affine connection A_{\mu cd} is developed. We consider SO(1,3) gauge theory with a Lagrangian quadratic in curvature as a simple model of quantum gravity. The torsion is proposed to represent a dynamic degree of freedom of quantum gravity at scales above the Planckian energy. The Einstein-Hilbert theory is induced as an effective theory due to quantum corrections of torsion via generating a stable gravito-magnetic condensate. We conjecture that torsion possesses an intrinsic quantum nature and can be confined. A minimal Abelian projection for the Lorentz gauge model has been constructed, and an effective theory of the cosmic knot at the Planckian scale is proposed. |
1501.01174 | Chiara Caprini | Chiara Caprini | Stochastic background of gravitational waves from cosmological sources | Proceedings of LISA Symposium X, accepted for publication in Journal
of Physics: Conference Series. Typos corrected, two references added | null | 10.1088/1742-6596/610/1/012004 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves (GW) can constitute a unique probe of the primordial
universe. In many cases, the characteristic frequency of the emitted GW is
directly related to the energy scale at which the GW source is operating in the
early universe. Consequently, different GW detectors can probe different energy
scales in the evolution of the universe. After a general introduction on the
properties of a GW stochastic background of primordial origin, some examples of
cosmological sources are presented, which may lead to observable GW signals.
| [
{
"created": "Tue, 6 Jan 2015 13:36:50 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Jan 2015 14:02:18 GMT",
"version": "v2"
}
] | 2015-06-11 | [
[
"Caprini",
"Chiara",
""
]
] | Gravitational waves (GW) can constitute a unique probe of the primordial universe. In many cases, the characteristic frequency of the emitted GW is directly related to the energy scale at which the GW source is operating in the early universe. Consequently, different GW detectors can probe different energy scales in the evolution of the universe. After a general introduction on the properties of a GW stochastic background of primordial origin, some examples of cosmological sources are presented, which may lead to observable GW signals. |
1503.04698 | Christof Wetterich | C. Wetterich | Can observations look back to the beginning of inflation? | additional example and references, 5 pages | null | 10.1016/j.physletb.2016.01.027 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmic microwave background can measure the inflaton potential only if
inflation lasts sufficiently long before the time of horizon crossing of
observable fluctuations, such that non-linear effects in the time evolution of
Green's functions lead to a loss of memory of initial conditions for the
ultraviolet tail of the spectrum. Within a derivative expansion of the quantum
effective action for an interacting scalar field we discuss the most general
solution for the correlation function, including arbitrary pure and mixed
quantum states. In this approximation no loss of memory occurs - cosmic
microwave observations see the initial spectrum at the beginning of inflation,
processed only mildly by the scale-violating effects at horizon crossing
induced by the inflaton potential.
| [
{
"created": "Mon, 16 Mar 2015 15:59:08 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Sep 2015 12:32:47 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Jan 2016 10:41:12 GMT",
"version": "v3"
}
] | 2016-01-20 | [
[
"Wetterich",
"C.",
""
]
] | The cosmic microwave background can measure the inflaton potential only if inflation lasts sufficiently long before the time of horizon crossing of observable fluctuations, such that non-linear effects in the time evolution of Green's functions lead to a loss of memory of initial conditions for the ultraviolet tail of the spectrum. Within a derivative expansion of the quantum effective action for an interacting scalar field we discuss the most general solution for the correlation function, including arbitrary pure and mixed quantum states. In this approximation no loss of memory occurs - cosmic microwave observations see the initial spectrum at the beginning of inflation, processed only mildly by the scale-violating effects at horizon crossing induced by the inflaton potential. |
0708.1396 | Jonn Miritzis | J. Miritzis | Oscillatory behavior of closed isotropic models in second order gravity
theory | 16 pages, 3 figures. With some minor improvements. To appear in
General Relativity and Gravitation | Gen.Rel.Grav.41:49-65,2009 | 10.1007/s10714-008-0651-3 | null | gr-qc | null | Homogeneous and isotropic models are studied in the Jordan frame of the
second order gravity theory. The late time evolution of the models is analysed
with the methods of the dynamical systems. The normal form of the dynamical
system has periodic solutions for a large set of initial conditions. This
implies that an initially expanding closed isotropic universe may exhibit
oscillatory behaviour.
| [
{
"created": "Fri, 10 Aug 2007 10:33:22 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Mar 2008 09:09:28 GMT",
"version": "v2"
}
] | 2009-01-16 | [
[
"Miritzis",
"J.",
""
]
] | Homogeneous and isotropic models are studied in the Jordan frame of the second order gravity theory. The late time evolution of the models is analysed with the methods of the dynamical systems. The normal form of the dynamical system has periodic solutions for a large set of initial conditions. This implies that an initially expanding closed isotropic universe may exhibit oscillatory behaviour. |
1107.1830 | Michael Hohensee | Michael A. Hohensee and Holger Mueller | Significance of the Compton frequency in atom interferometry | Submitted to the Proceedings of the 46th Rencontres de Moriond.
Gravitational Waves and Experimental Gravity. 20-27 March 2011, La Thuile,
Aosta valley, Italy | null | null | null | gr-qc hep-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent realization that atom interferometers (AIs) can be used to test
the gravitational redshift tests has proven to be controversial in some
quarters. Here, we address the issues raised against the interpretation of AIs
as redshift tests, reaffirming the fact that Mueller et al. [Nature 463, 926
(2010)] indeed report a gravitational redshift test.
| [
{
"created": "Sun, 10 Jul 2011 04:08:58 GMT",
"version": "v1"
}
] | 2011-07-12 | [
[
"Hohensee",
"Michael A.",
""
],
[
"Mueller",
"Holger",
""
]
] | The recent realization that atom interferometers (AIs) can be used to test the gravitational redshift tests has proven to be controversial in some quarters. Here, we address the issues raised against the interpretation of AIs as redshift tests, reaffirming the fact that Mueller et al. [Nature 463, 926 (2010)] indeed report a gravitational redshift test. |
1010.3589 | Hossein Farajollahi | Hossein Farajollahi, Amin Salehi | Attractors, Statefinders and Observational Measurement for Chameleonic
Brans--Dicke Cosmology | 28 pages, 38 figures | JCAP 1011:006,2010 | 10.1088/1475-7516/2010/11/006 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate chameleonic Brans--Dicke model applied to the FRW universes. A
framework to study stability and attractor solutions in the phase space is
developed for the model. We show that depending on the matter field and
stability conditions, it is possible to realize phantom-like behavior without
introducing phantom filed in the model while the stability is fulfilled and
phantom crossing occurs. The statefinder parameters to the model for different
kinds of matter interacting with the chameleon scalar field are studied. We
also compare our model with present day observations.
| [
{
"created": "Mon, 18 Oct 2010 13:15:52 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Oct 2010 01:08:55 GMT",
"version": "v2"
},
{
"created": "Wed, 3 Nov 2010 05:29:43 GMT",
"version": "v3"
},
{
"created": "Wed, 8 Jun 2011 07:05:36 GMT",
"version": "v4"
}
] | 2011-06-09 | [
[
"Farajollahi",
"Hossein",
""
],
[
"Salehi",
"Amin",
""
]
] | We investigate chameleonic Brans--Dicke model applied to the FRW universes. A framework to study stability and attractor solutions in the phase space is developed for the model. We show that depending on the matter field and stability conditions, it is possible to realize phantom-like behavior without introducing phantom filed in the model while the stability is fulfilled and phantom crossing occurs. The statefinder parameters to the model for different kinds of matter interacting with the chameleon scalar field are studied. We also compare our model with present day observations. |
2202.10063 | Simone Albanesi | Simone Albanesi, Alessandro Nagar, Sebastiano Bernuzzi, Andrea
Placidi, and Marta Orselli | Assessment of Effective-One-Body Radiation Reactions for Generic Planar
Orbits | 23 pages, 15 figures, Phys. Rev. D 105, 104031 | null | 10.1103/PhysRevD.105.104031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we assess the performances of different analytical
prescriptions for the effective-one-body (EOB) radiation reaction along generic
planar orbits using exact numerical result in the test-mass limit. We consider
three prescriptions put forward in the recent literature: (i) the quasicircular
prescription (QC), (ii) the QC with second post-Newtonian (2PN) order
noncircular corrections (QC2PN), and (iii) the QC corrected by the noncircular
Newtonian prefactor (NCN). The analytical fluxes are then compared against the
exact fluxes that are computed by solving the Teukolsky equation with a
test-mass source in geodesic motion. We find that the NCN prescription is the
most accurate for both eccentric and hyperbolic orbits and it is in robust
agreement also for large values of the eccentricity. This result carries over
to the comparable masses, as we discuss for a numerical-relativity (NR) case
study. We also demonstrate that, while the EOB/NR waveform unfaithfulness is a
necessary check for the precision of EOB models, the direct comparison of
EOB/NR fluxes is a more stringent and informative test to select the best
prescription. Finally, we propose an improved radiation reaction, NCN2PN, that
includes noncircular 2PN corrections, in resummed form, as a further
multiplicative contribution and that is valid for any mass ratio.
| [
{
"created": "Mon, 21 Feb 2022 09:23:01 GMT",
"version": "v1"
},
{
"created": "Thu, 19 May 2022 10:51:51 GMT",
"version": "v2"
}
] | 2022-05-20 | [
[
"Albanesi",
"Simone",
""
],
[
"Nagar",
"Alessandro",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Placidi",
"Andrea",
""
],
[
"Orselli",
"Marta",
""
]
] | In this paper we assess the performances of different analytical prescriptions for the effective-one-body (EOB) radiation reaction along generic planar orbits using exact numerical result in the test-mass limit. We consider three prescriptions put forward in the recent literature: (i) the quasicircular prescription (QC), (ii) the QC with second post-Newtonian (2PN) order noncircular corrections (QC2PN), and (iii) the QC corrected by the noncircular Newtonian prefactor (NCN). The analytical fluxes are then compared against the exact fluxes that are computed by solving the Teukolsky equation with a test-mass source in geodesic motion. We find that the NCN prescription is the most accurate for both eccentric and hyperbolic orbits and it is in robust agreement also for large values of the eccentricity. This result carries over to the comparable masses, as we discuss for a numerical-relativity (NR) case study. We also demonstrate that, while the EOB/NR waveform unfaithfulness is a necessary check for the precision of EOB models, the direct comparison of EOB/NR fluxes is a more stringent and informative test to select the best prescription. Finally, we propose an improved radiation reaction, NCN2PN, that includes noncircular 2PN corrections, in resummed form, as a further multiplicative contribution and that is valid for any mass ratio. |
gr-qc/9703077 | Claus Laemmerzahl | Reinhard Meinel | The rigidly rotating disk of dust and its black hole limit | 14 pages, LaTex, includes 1 figure, To appear in A.Garcia et al.
(eds.): Recent Developments in Gravitation and Mathematical Physics,
Proceedings of the 2nd Mexican School | A. Garcia et al. (eds.): Recent Developments in Gravitation and
Mathematical Physics, Science Network Publishing, Konstanz 1998 | null | null | gr-qc | null | The exact global solution of the Einstein equations [Neugebauer & Meinel,
Phys. Rev. Lett. 75 (1995) 3046] describing a rigidly rotating,
self-gravitating disk is discussed. The underlying matter model is a perfect
fluid in the limit of vanishing pressure. The solution represents the
general-relativistic analogue of the classical Maclaurin disk. It was derived
by applying solution techniques from soliton theory to the axisymmetric,
stationary vacuum Einstein equations. In contrast to the Newtonian solution,
there exists an upper limit for the total mass of the disk - if the angular
momentum is fixed. At this limit, a transition to a rotating black hole, i.e.,
to the Kerr solution occurs. Another limiting procedure leads to an interesting
cosmological solution. These results prove conjectures formulated by Bardeen
and Wagoner more than twenty-five years ago.
| [
{
"created": "Wed, 26 Mar 1997 12:24:56 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Meinel",
"Reinhard",
""
]
] | The exact global solution of the Einstein equations [Neugebauer & Meinel, Phys. Rev. Lett. 75 (1995) 3046] describing a rigidly rotating, self-gravitating disk is discussed. The underlying matter model is a perfect fluid in the limit of vanishing pressure. The solution represents the general-relativistic analogue of the classical Maclaurin disk. It was derived by applying solution techniques from soliton theory to the axisymmetric, stationary vacuum Einstein equations. In contrast to the Newtonian solution, there exists an upper limit for the total mass of the disk - if the angular momentum is fixed. At this limit, a transition to a rotating black hole, i.e., to the Kerr solution occurs. Another limiting procedure leads to an interesting cosmological solution. These results prove conjectures formulated by Bardeen and Wagoner more than twenty-five years ago. |
0905.2010 | J. Ponce de Leon | J. Ponce de Leon | Effective spacetime from multi-dimensional gravity | A typo in Eq. (24) is fixed | Grav.Cosmol.15:345-352,2009 | 10.1134/S0202289309040100 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the effective spacetimes in lower dimensions that can be extracted
from a multidimensional generalization of the Schwarzschild-Tangherlini
spacetimes derived by Fadeev, Ivashchuk and Melnikov ({\it Phys. Lett,} {\bf A
161} (1991) 98). The higher-dimensional spacetime has $D = (4 + n + m)$
dimensions, where $n$ and $m$ are the number of "internal" and "external" extra
dimensions, respectively. We analyze the effective $(4 + n)$ spacetime obtained
after dimensional reduction of the $m$ external dimensions. We find that when
the $m$ extra dimensions are compact (i) the physics in lower dimensions is
independent of $m$ and the character of the singularities in higher dimensions,
and (ii) the total gravitational mass $M$ of the effective matter distribution
is less than the Schwarzshild mass. In contrast, when the $m$ extra dimensions
are large this is not so; the physics in $(4 + n)$ does explicitly depend on
$m$, as well as on the nature of the singularities in high dimensions, and the
mass of the effective matter distribution (with the exception of wormhole-like
distributions) is bigger than the Schwarzshild mass. These results may be
relevant to observations for an experimental/observational test of the theory.
| [
{
"created": "Wed, 13 May 2009 04:24:08 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Nov 2009 07:27:00 GMT",
"version": "v2"
}
] | 2010-04-14 | [
[
"de Leon",
"J. Ponce",
""
]
] | We study the effective spacetimes in lower dimensions that can be extracted from a multidimensional generalization of the Schwarzschild-Tangherlini spacetimes derived by Fadeev, Ivashchuk and Melnikov ({\it Phys. Lett,} {\bf A 161} (1991) 98). The higher-dimensional spacetime has $D = (4 + n + m)$ dimensions, where $n$ and $m$ are the number of "internal" and "external" extra dimensions, respectively. We analyze the effective $(4 + n)$ spacetime obtained after dimensional reduction of the $m$ external dimensions. We find that when the $m$ extra dimensions are compact (i) the physics in lower dimensions is independent of $m$ and the character of the singularities in higher dimensions, and (ii) the total gravitational mass $M$ of the effective matter distribution is less than the Schwarzshild mass. In contrast, when the $m$ extra dimensions are large this is not so; the physics in $(4 + n)$ does explicitly depend on $m$, as well as on the nature of the singularities in high dimensions, and the mass of the effective matter distribution (with the exception of wormhole-like distributions) is bigger than the Schwarzshild mass. These results may be relevant to observations for an experimental/observational test of the theory. |
0804.0874 | David Maxwell | David Maxwell | A class of solutions of the vacuum Einstein constraint equations with
freely specified mean curvature | 21 pages | null | null | null | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a sufficient condition, with no restrictions on the mean curvature,
under which the conformal method can be used to generate solutions of the
vacuum Einstein constraint equations on compact manifolds. The condition
requires a so-called global supersolution but does not require a global
subsolution. As a consequence, we construct a class of solutions of the vacuum
Einstein constraint equations with freely specified mean curvature, extending a
recent result of Holst, Nagy, and Tsogtgerel [HNT07] which constructed similar
solutions in the presence of matter. We give a second proof of this result
showing that vacuum solutions can be obtained as a limit of [HNT07] non-vacuum
solutions. Our principal existence theorem is of independent interest in the
near-CMC case, where it simplifies previously known hypotheses required for
existence.
| [
{
"created": "Sat, 5 Apr 2008 21:59:18 GMT",
"version": "v1"
}
] | 2008-04-08 | [
[
"Maxwell",
"David",
""
]
] | We give a sufficient condition, with no restrictions on the mean curvature, under which the conformal method can be used to generate solutions of the vacuum Einstein constraint equations on compact manifolds. The condition requires a so-called global supersolution but does not require a global subsolution. As a consequence, we construct a class of solutions of the vacuum Einstein constraint equations with freely specified mean curvature, extending a recent result of Holst, Nagy, and Tsogtgerel [HNT07] which constructed similar solutions in the presence of matter. We give a second proof of this result showing that vacuum solutions can be obtained as a limit of [HNT07] non-vacuum solutions. Our principal existence theorem is of independent interest in the near-CMC case, where it simplifies previously known hypotheses required for existence. |
gr-qc/9903057 | L. L. Salcedo | L. L. Salcedo | On the uniqueness of the expected stress-energy tensor in renormalizable
field theories | RevTex, 4 pages, no figures. Minor additions and title changed. To
appear in Physical Review D | Phys.Rev. D60 (1999) 107502 | 10.1103/PhysRevD.60.107502 | ugr-dfm-5/98 | gr-qc hep-th | null | It is argued that the ambiguity introduced by the renormalization in the
effective action of a four-dimensional renormalizable quantum field theory is
at most a local polynomial action of canonical dimension four. The allowed
ambiguity in the expected stress-energy tensor of a massive scalar field is
severely restricted by this fact.
| [
{
"created": "Mon, 15 Mar 1999 11:52:17 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Sep 1999 14:20:21 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Salcedo",
"L. L.",
""
]
] | It is argued that the ambiguity introduced by the renormalization in the effective action of a four-dimensional renormalizable quantum field theory is at most a local polynomial action of canonical dimension four. The allowed ambiguity in the expected stress-energy tensor of a massive scalar field is severely restricted by this fact. |
2407.20131 | Emanuele Berti | Yiqiu Yang, Zhan-Feng Mai, Run-Qiu Yang, Lijing Shao, Emanuele Berti | Spectral instability of black holes: relating the frequency domain to
the time domain | 18 pages, 8 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent work has shown that the quasinormal mode spectrum of black holes is
unstable under small perturbations (of order $\epsilon$) of the radial
potential, while the early time-domain ringdown waveform is only marginally
affected. In this paper we provide further insight into the apparent tension
between the frequency-domain and the time-domain descriptions by analyzing the
scattering properties of the problem. In the frequency domain, we study
analytically the solutions corresponding to the perturbed potential. We show
that there are two qualitatively different classes of instabilities, and that
both Schwarzschild and Kerr black holes are affected by what we call a "Type
II" instability, i.e., an exponential migration of the mode frequencies away
from their unperturbed value as the perturbing "bump" moves away from the peak
of the unperturbed potential. In the time domain, we elucidate the effect of
the spectral instability in terms of the causal structure of the Green's
function. By using an equivalent scattering problem we confirm analytically
(and show numerically) that the deviation from the unperturbed waveform in the
early ringdown stage is proportional to $\epsilon$ when
$\epsilon\lesssim10^{-2}$.
| [
{
"created": "Mon, 29 Jul 2024 16:00:04 GMT",
"version": "v1"
}
] | 2024-07-30 | [
[
"Yang",
"Yiqiu",
""
],
[
"Mai",
"Zhan-Feng",
""
],
[
"Yang",
"Run-Qiu",
""
],
[
"Shao",
"Lijing",
""
],
[
"Berti",
"Emanuele",
""
]
] | Recent work has shown that the quasinormal mode spectrum of black holes is unstable under small perturbations (of order $\epsilon$) of the radial potential, while the early time-domain ringdown waveform is only marginally affected. In this paper we provide further insight into the apparent tension between the frequency-domain and the time-domain descriptions by analyzing the scattering properties of the problem. In the frequency domain, we study analytically the solutions corresponding to the perturbed potential. We show that there are two qualitatively different classes of instabilities, and that both Schwarzschild and Kerr black holes are affected by what we call a "Type II" instability, i.e., an exponential migration of the mode frequencies away from their unperturbed value as the perturbing "bump" moves away from the peak of the unperturbed potential. In the time domain, we elucidate the effect of the spectral instability in terms of the causal structure of the Green's function. By using an equivalent scattering problem we confirm analytically (and show numerically) that the deviation from the unperturbed waveform in the early ringdown stage is proportional to $\epsilon$ when $\epsilon\lesssim10^{-2}$. |
2306.04661 | Jose Tarciso Junior | Jos\'e Tarciso S. S. Junior and Manuel E. Rodrigues | Coincident f(Q) gravity: black holes, regular black holes and black
bounces | 30 pages, 1 figure | The European Physical Journal C 83, 475 (2023) | 10.1140/epjc/s10052-023-11660-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we will use the coincident gauge to investigate new solutions
of the f(Q) theory applied in the context of black holes, regular black holes,
and the black-bounce spacetime. For each of these approaches, we compute the
linear solutions and the solutions with the constraint that the non-metricity
scalar is zero. We also analyze the geodesics of each solution to interpret
whether the spacetime is extensible or not, find the Kretschmann scalar to
determine the regularity along spacetime, and in the context of regular black
holes and black-bounce, we calculate the energy conditions. In the latter
black-bounce case we realize that the null energy condition $(NEC)$,
specifically the $NEC_1=WEC_1=SEC_1\leftrightarrow \rho+p_{r}\geq 0$, is
satisfied outside the event horizon.
| [
{
"created": "Wed, 7 Jun 2023 02:17:47 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Jun 2023 16:50:55 GMT",
"version": "v2"
}
] | 2023-06-14 | [
[
"Junior",
"José Tarciso S. S.",
""
],
[
"Rodrigues",
"Manuel E.",
""
]
] | In this paper, we will use the coincident gauge to investigate new solutions of the f(Q) theory applied in the context of black holes, regular black holes, and the black-bounce spacetime. For each of these approaches, we compute the linear solutions and the solutions with the constraint that the non-metricity scalar is zero. We also analyze the geodesics of each solution to interpret whether the spacetime is extensible or not, find the Kretschmann scalar to determine the regularity along spacetime, and in the context of regular black holes and black-bounce, we calculate the energy conditions. In the latter black-bounce case we realize that the null energy condition $(NEC)$, specifically the $NEC_1=WEC_1=SEC_1\leftrightarrow \rho+p_{r}\geq 0$, is satisfied outside the event horizon. |
1803.07965 | Tim Dietrich | Tim Dietrich, Sebastiano Bernuzzi, Bernd Bruegmann, Wolfgang Tichy | High-resolution numerical relativity simulations of spinning binary
neutron star mergers | published as proceeding for the 26th Euromicro International
Conference on Parallel, Distributed, and Network-Based Processing. PDP 2018
IEEE Catalog Number: CFP18169 | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent detection of gravitational waves and electromagnetic counterparts
emitted during and after the collision of two neutron stars marks a
breakthrough in the field of multi-messenger astronomy. Numerical relativity
simulations are the only tool to describe the binary's merger dynamics in the
regime when speeds are largest and gravity is strongest. In this work we report
state-of-the-art binary neutron star simulations for irrotational
(non-spinning) and spinning configurations. The main use of these simulations
is to model the gravitational-wave signal. Key numerical requirements are the
understanding of the convergence properties of the numerical data and a
detailed error budget. The simulations have been performed on different HPC
clusters, they use multiple grid resolutions, and are based on eccentricity
reduced quasi-circular initial data. We obtain convergent waveforms with phase
errors of 0.5-1.5 rad accumulated over approximately 12 orbits to merger. The
waveforms have been used for the construction of a phenomenological waveform
model which has been applied for the analysis of the recent binary neutron star
detection. Additionally, we show that the data can also be used to test other
state-of-the-art semi-analytical waveform models.
| [
{
"created": "Wed, 21 Mar 2018 15:28:55 GMT",
"version": "v1"
}
] | 2018-03-22 | [
[
"Dietrich",
"Tim",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Bruegmann",
"Bernd",
""
],
[
"Tichy",
"Wolfgang",
""
]
] | The recent detection of gravitational waves and electromagnetic counterparts emitted during and after the collision of two neutron stars marks a breakthrough in the field of multi-messenger astronomy. Numerical relativity simulations are the only tool to describe the binary's merger dynamics in the regime when speeds are largest and gravity is strongest. In this work we report state-of-the-art binary neutron star simulations for irrotational (non-spinning) and spinning configurations. The main use of these simulations is to model the gravitational-wave signal. Key numerical requirements are the understanding of the convergence properties of the numerical data and a detailed error budget. The simulations have been performed on different HPC clusters, they use multiple grid resolutions, and are based on eccentricity reduced quasi-circular initial data. We obtain convergent waveforms with phase errors of 0.5-1.5 rad accumulated over approximately 12 orbits to merger. The waveforms have been used for the construction of a phenomenological waveform model which has been applied for the analysis of the recent binary neutron star detection. Additionally, we show that the data can also be used to test other state-of-the-art semi-analytical waveform models. |
gr-qc/0107078 | Pavel Krtous | Jiri Bicak and Pavel Krtous | Accelerated sources in de Sitter spacetime and the insufficiency of
retarded fields | 36 pages, 5 figures, LaTex2e; minor misprints corrected, one
reference added and some terminology changed | Phys.Rev.D64:124020,2001 | 10.1103/PhysRevD.64.124020 | null | gr-qc | null | The scalar and electromagnetic fields produced by the geodesic and uniformly
accelerated discrete charges in de Sitter spacetime are constructed by
employing the conformal relation between de Sitter and Minkowski space.
A special attention is paid to new effects arising in spacetimes which, like
de Sitter space, have spacelike conformal infinities. Under the presence of
particle and event horizons, purely retarded fields (appropriately defined)
become necessarily singular or even cannot be constructed at the "creation
light cones" -- future light cones of the "points" at which the sources "enter"
the universe. We construct smooth (outside the sources) fields involving both
retarded and advanced effects, and analyze the fields in detail in case of (i)
scalar monopoles, (ii) electromagnetic monopoles, and (iii) electromagnetic
rigid and geodesic dipoles.
| [
{
"created": "Tue, 24 Jul 2001 12:29:21 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Feb 2002 20:12:56 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Bicak",
"Jiri",
""
],
[
"Krtous",
"Pavel",
""
]
] | The scalar and electromagnetic fields produced by the geodesic and uniformly accelerated discrete charges in de Sitter spacetime are constructed by employing the conformal relation between de Sitter and Minkowski space. A special attention is paid to new effects arising in spacetimes which, like de Sitter space, have spacelike conformal infinities. Under the presence of particle and event horizons, purely retarded fields (appropriately defined) become necessarily singular or even cannot be constructed at the "creation light cones" -- future light cones of the "points" at which the sources "enter" the universe. We construct smooth (outside the sources) fields involving both retarded and advanced effects, and analyze the fields in detail in case of (i) scalar monopoles, (ii) electromagnetic monopoles, and (iii) electromagnetic rigid and geodesic dipoles. |
2403.11770 | Jinbo Yang | Xiao-Ping Rao, Hyat Huang and Jinbo Yang | Hairy Black Holes with Arbitrary Small Areas | 26 pages, 7 figures and 1 table. Comments are welcome | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtained new hairy black hole solutions in Einstein-scalar theory,
including asymptotic flat, de Sitter and anti-de Sitter black holes. The theory
is inspired by Ref. [1], where traversable wormhole solutions from an
Einstein-phantom scalar theory are constructed. In this work, we found new
black hole solutions in an Einstein-normal scalar theory. Comparing with
Schwarzschild metric, the hairy black holes have two interesting properties: i)
the areas of the black holes are always smaller than the same mass
Schwarzschild black holes; ii) A naked singularity with positive mass arises
when the black hole mass decreases. The energy conditions for the black holes
and naked singularities are checked. We found that, as hairy black holes, the
null energy condition(NEC) and the strong energy condition(SEC) are hold, while
the weak energy condition(WEC) is violated in the vicinity of black hole
horizon. The naked singularity respects to all three energy conditions. We also
investigate the quasinormal modes(QNMs) of the hairy black holes by a test
scalar field. The results indicate that one can distinguish hairy black holes
with the same mass Schwarzschilid black hole by their QNM spectra.
| [
{
"created": "Mon, 18 Mar 2024 13:28:54 GMT",
"version": "v1"
}
] | 2024-03-19 | [
[
"Rao",
"Xiao-Ping",
""
],
[
"Huang",
"Hyat",
""
],
[
"Yang",
"Jinbo",
""
]
] | We obtained new hairy black hole solutions in Einstein-scalar theory, including asymptotic flat, de Sitter and anti-de Sitter black holes. The theory is inspired by Ref. [1], where traversable wormhole solutions from an Einstein-phantom scalar theory are constructed. In this work, we found new black hole solutions in an Einstein-normal scalar theory. Comparing with Schwarzschild metric, the hairy black holes have two interesting properties: i) the areas of the black holes are always smaller than the same mass Schwarzschild black holes; ii) A naked singularity with positive mass arises when the black hole mass decreases. The energy conditions for the black holes and naked singularities are checked. We found that, as hairy black holes, the null energy condition(NEC) and the strong energy condition(SEC) are hold, while the weak energy condition(WEC) is violated in the vicinity of black hole horizon. The naked singularity respects to all three energy conditions. We also investigate the quasinormal modes(QNMs) of the hairy black holes by a test scalar field. The results indicate that one can distinguish hairy black holes with the same mass Schwarzschilid black hole by their QNM spectra. |
2005.05130 | Lokesh Mishra | Lokesh Mishra | Theories of Massive Gravity in 2+1 Dimensions | MScThesis (154 pages, University of Freiburg) (v2 same as v1; removed
obsolete tex pakages) | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This thesis is dedicated to the study of theories of massive gravity. The
formulation of higher spin gauge field theories, along with a Chern-Simons (CS)
like term for fields of higher spins is presented. Through this setup, general
features of theories describing massless/massive fields of higher spin in
arbitrary dimensions is discussed. In 2+1 dimensions, the existence of multiple
mass-generating mechanisms i.e. metric-based masses and topological masses,
offers the possibility for gauge bosons to acquire mixed masses. This scenario
is first introduced in a theory of photons where both Proca mass term and CS
mass term is simultaneously present. The mass-mixing which occurs in this
theory is further analysed through the St\"uckelberg formalism. Motivated by
these results, a theory of massive gravity where gravitons obtain masses from
both Fierz-Pauli mass term and CS mass term is studied. This theory allows for
3 propagating massive graviton modes, and their masses have undergone
considerable mixing. This mass-mixing is made explicit through a St\"uckelberg
analysis. The bimetric theory of gravity is a non-trivial generalization of the
theory of General Relativity. This theory provides a consistent non-linear
theory of massive gravity which is studied in detail. In this thesis, the
bimetric theory of gravity is extended in 2+1 dimensiosn to the theory of
Topologically Massive Bimetric Gravity (TMBG). In the theory of TMBG, the
mass-mixing which arises from the interaction of the two metrics and their
corresponding CS terms occurs at the nonlinear stage itself. For the version of
TMBG studied in this thesis, the linearized theory shows that there are 3
massive graviton modes, which corresponds to the same 3 modes found earlier.
Finally, quantum loop corrections to the graviton propagator from massive
photons (which acquire mass from both CS and Proca mechanism) is calculated.
| [
{
"created": "Fri, 8 May 2020 12:42:03 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Jan 2021 16:11:11 GMT",
"version": "v2"
}
] | 2021-01-26 | [
[
"Mishra",
"Lokesh",
""
]
] | This thesis is dedicated to the study of theories of massive gravity. The formulation of higher spin gauge field theories, along with a Chern-Simons (CS) like term for fields of higher spins is presented. Through this setup, general features of theories describing massless/massive fields of higher spin in arbitrary dimensions is discussed. In 2+1 dimensions, the existence of multiple mass-generating mechanisms i.e. metric-based masses and topological masses, offers the possibility for gauge bosons to acquire mixed masses. This scenario is first introduced in a theory of photons where both Proca mass term and CS mass term is simultaneously present. The mass-mixing which occurs in this theory is further analysed through the St\"uckelberg formalism. Motivated by these results, a theory of massive gravity where gravitons obtain masses from both Fierz-Pauli mass term and CS mass term is studied. This theory allows for 3 propagating massive graviton modes, and their masses have undergone considerable mixing. This mass-mixing is made explicit through a St\"uckelberg analysis. The bimetric theory of gravity is a non-trivial generalization of the theory of General Relativity. This theory provides a consistent non-linear theory of massive gravity which is studied in detail. In this thesis, the bimetric theory of gravity is extended in 2+1 dimensiosn to the theory of Topologically Massive Bimetric Gravity (TMBG). In the theory of TMBG, the mass-mixing which arises from the interaction of the two metrics and their corresponding CS terms occurs at the nonlinear stage itself. For the version of TMBG studied in this thesis, the linearized theory shows that there are 3 massive graviton modes, which corresponds to the same 3 modes found earlier. Finally, quantum loop corrections to the graviton propagator from massive photons (which acquire mass from both CS and Proca mechanism) is calculated. |
2205.06534 | Michel Duneau | Michel Duneau | Weyl locally integrable conformal gravity, rotation curves and cosmic
filaments | 12 pages, 8 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Weyl's conformal theory of gravity is an extension of Einstein's theory of
general relativity which associates metrics with 1-forms . In the case of
locally integrable (closed non-exact) 1-forms the spacetime manifolds are no
more simply connected. The Weil connections yield curvature tensors which
satisfy the basic properties of Riemann curvature tensors. The Ricci tensors
are symmetric, conformally invariant, and the Einstein tensors computed with
the Weyl connections implicate a cosmological term replacing the cosmological
constant by a function of spacetime, and a shear stress tensor. A toy model
based on the Schwarzschild metric is presented where the associated 1-form is
proportional to $d\varphi$ in Schwarzschild coordinates. This implies a
singularity on the whole z-axis and it generates a torque effect on geodesics.
According to initial conditions planar geodesics show almost constant
velocities independently of r. In the free case spin effects occur in the
neighbourhood of the singularity which are comparable to recent observations
concerning cosmic filaments.
| [
{
"created": "Fri, 13 May 2022 09:46:01 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jun 2022 08:25:33 GMT",
"version": "v2"
}
] | 2022-06-09 | [
[
"Duneau",
"Michel",
""
]
] | Weyl's conformal theory of gravity is an extension of Einstein's theory of general relativity which associates metrics with 1-forms . In the case of locally integrable (closed non-exact) 1-forms the spacetime manifolds are no more simply connected. The Weil connections yield curvature tensors which satisfy the basic properties of Riemann curvature tensors. The Ricci tensors are symmetric, conformally invariant, and the Einstein tensors computed with the Weyl connections implicate a cosmological term replacing the cosmological constant by a function of spacetime, and a shear stress tensor. A toy model based on the Schwarzschild metric is presented where the associated 1-form is proportional to $d\varphi$ in Schwarzschild coordinates. This implies a singularity on the whole z-axis and it generates a torque effect on geodesics. According to initial conditions planar geodesics show almost constant velocities independently of r. In the free case spin effects occur in the neighbourhood of the singularity which are comparable to recent observations concerning cosmic filaments. |
gr-qc/0612002 | Gonzalo Olmo | Gonzalo J. Olmo | Violation of the Equivalence Principle in Modified Theories of Gravity | 4 pages, references and small comments added, to appear in
Phys.Rev.Lett | Phys.Rev.Lett.98:061101,2007 | 10.1103/PhysRevLett.98.061101 | null | gr-qc astro-ph hep-th | null | We study modified theories of gravity of the f(R) type in Palatini formalism.
For a generic f(R) lagrangian, we show that the metric can be solved as the
product of a scalar function times a rank-two tensor (or auxiliary metric). The
scalar function is sensitive to the local energy-momentum density. The
auxiliary metric satisfies a set of equations very similar to Einstein's
equations and, for weak sources, it can be approximated by the Minkowski
metric. According to this, the metric coupled to the matter strongly departs
from the Minkowskian one in the neighbourhood of any microscopic physical
system. As a consequence, new gravitationally-induced interactions arise and
lead to observable effects at microscopic and macroscopic scales. In
particular, test body trajectories experience self-accelerations which depend
on the internal structure and composition of the body. These facts make very
unlikely the viability of Palatini f(R) models designed to change the late-time
cosmic evolution.
| [
{
"created": "Thu, 30 Nov 2006 21:51:21 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jan 2007 10:35:43 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Olmo",
"Gonzalo J.",
""
]
] | We study modified theories of gravity of the f(R) type in Palatini formalism. For a generic f(R) lagrangian, we show that the metric can be solved as the product of a scalar function times a rank-two tensor (or auxiliary metric). The scalar function is sensitive to the local energy-momentum density. The auxiliary metric satisfies a set of equations very similar to Einstein's equations and, for weak sources, it can be approximated by the Minkowski metric. According to this, the metric coupled to the matter strongly departs from the Minkowskian one in the neighbourhood of any microscopic physical system. As a consequence, new gravitationally-induced interactions arise and lead to observable effects at microscopic and macroscopic scales. In particular, test body trajectories experience self-accelerations which depend on the internal structure and composition of the body. These facts make very unlikely the viability of Palatini f(R) models designed to change the late-time cosmic evolution. |
gr-qc/0406030 | Albert V. Minkevich | Albert V. Minkevich | Non-Singular Cosmology and Gauge Theories of Gravitation | LaTeX2e, 16 pages | null | 10.1142/9789812702296_0003 | null | gr-qc | null | The resolution of the problem of cosmological singularity in the framework of
gauge theories of gravitation is discussed. Generalized cosmological Friedmann
equations for homogeneous isotropic models filled by interacting scalar fields
and usual gravitating matter are deduced. It is shown that generic feature of
cosmological models of flat, open and closed type is their regular bouncing
character.
| [
{
"created": "Tue, 8 Jun 2004 15:25:48 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Minkevich",
"Albert V.",
""
]
] | The resolution of the problem of cosmological singularity in the framework of gauge theories of gravitation is discussed. Generalized cosmological Friedmann equations for homogeneous isotropic models filled by interacting scalar fields and usual gravitating matter are deduced. It is shown that generic feature of cosmological models of flat, open and closed type is their regular bouncing character. |
gr-qc/0701075 | Hamid Reza Sepangi | B. Vakili, N. Khosravi and H. R. Sepangi | Bianchi spacetimes in noncommutative phase-space | 19 pages, 2 figures, to appear in Class. Quantum Grav | Class.Quant.Grav.24:931-949,2007 | 10.1088/0264-9381/24/4/013 | null | gr-qc | null | The effects of noncommutativity in the phase-space of the classical and
quantum cosmology of Bianchi models are investigated. Exact solutions in both
commutative and noncommutative cases are presented and compared. Further, the
Noether symmetries of the Bianchi class A spacetimes are studied in both cases
and similarities and differences are discussed.
| [
{
"created": "Sun, 14 Jan 2007 15:21:57 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Vakili",
"B.",
""
],
[
"Khosravi",
"N.",
""
],
[
"Sepangi",
"H. R.",
""
]
] | The effects of noncommutativity in the phase-space of the classical and quantum cosmology of Bianchi models are investigated. Exact solutions in both commutative and noncommutative cases are presented and compared. Further, the Noether symmetries of the Bianchi class A spacetimes are studied in both cases and similarities and differences are discussed. |
2107.01487 | Lili He | Lili He, Hans Lindblad | Masses at null infinity for Einstein's equations in harmonic coordinates | 31 pages. Added references. Typo corrected | null | null | null | gr-qc math-ph math.AP math.MP | http://creativecommons.org/licenses/by/4.0/ | In this work we give a complete picture of how to in a direct simple way
define the mass at null infinity in harmonic coordinates in three different
ways that we show satisfy the Bondi mass loss law. The first and second way
involve only the limit of metric (Trautman mass) respectively the null second
fundamental forms along asymptotically characteristic surfaces (asymptotic
Hawking mass) that only depend on the ADM mass. The last in an original way
involves construction of special characteristic coordinates at null infinity
(Bondi mass). The results here rely on asymptotics of the metric derived in
[24].
| [
{
"created": "Sat, 3 Jul 2021 20:01:13 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Apr 2022 19:07:18 GMT",
"version": "v2"
}
] | 2022-04-20 | [
[
"He",
"Lili",
""
],
[
"Lindblad",
"Hans",
""
]
] | In this work we give a complete picture of how to in a direct simple way define the mass at null infinity in harmonic coordinates in three different ways that we show satisfy the Bondi mass loss law. The first and second way involve only the limit of metric (Trautman mass) respectively the null second fundamental forms along asymptotically characteristic surfaces (asymptotic Hawking mass) that only depend on the ADM mass. The last in an original way involves construction of special characteristic coordinates at null infinity (Bondi mass). The results here rely on asymptotics of the metric derived in [24]. |
gr-qc/0110114 | Stefan Davids | Stefan Davids | A State Sum Model for (2+1) Lorentzian Quantum Gravity | 129 pages | null | null | null | gr-qc | null | A state sum model based on the group SU(1,1) is defined. Investigations of
its geometry and asymptotics suggest it is a good candidate for modelling (2+1)
Lorentzian quantum gravity.
| [
{
"created": "Fri, 26 Oct 2001 16:55:18 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"Davids",
"Stefan",
""
]
] | A state sum model based on the group SU(1,1) is defined. Investigations of its geometry and asymptotics suggest it is a good candidate for modelling (2+1) Lorentzian quantum gravity. |
2406.08078 | Reggie Pantig | Nikko John Leo S. Lobos, Anele M. Ncube, Reggie C. Pantig, and Alan S.
Cornell | Analyzing the effect of higher dimensions on the black hole silhouette,
deflection angles, and PINN approximated quasinormal modes | 16 pages, 13 figures, 2 tables. Comments are welcome | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the impact of higher dimensions on the properties of
Schwarzschild-Tangherlini black holes, focusing on the photonsphere, black hole
shadow, deflection angles, and quasinormal modes (QNMs). We find that these
properties diminish as the dimensionality ($n$) of the black hole increases.
Analysis of the shadow radius measured by the Event Horizon Telescope suggests
non-integer dimensions around $n\lessgtr4$. We derive an analytic formula for
the weak field deflection angle, highlighting the need for advanced sensitive
detection devices to observe lensed images influenced by higher dimensions. Our
study of QNMs using physics-informed neural networks and the WKB method reveals
a convergence towards known relationships between QNM frequencies and
photon-sphere orbit frequencies. Despite the energetic nature of perturbing
fields in higher dimensions, their damping increases. This suggests a complex
interplay between dimensionality and the dynamics of black hole phenomena.
| [
{
"created": "Wed, 12 Jun 2024 10:57:18 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Jun 2024 12:01:13 GMT",
"version": "v2"
}
] | 2024-06-24 | [
[
"Lobos",
"Nikko John Leo S.",
""
],
[
"Ncube",
"Anele M.",
""
],
[
"Pantig",
"Reggie C.",
""
],
[
"Cornell",
"Alan S.",
""
]
] | We investigate the impact of higher dimensions on the properties of Schwarzschild-Tangherlini black holes, focusing on the photonsphere, black hole shadow, deflection angles, and quasinormal modes (QNMs). We find that these properties diminish as the dimensionality ($n$) of the black hole increases. Analysis of the shadow radius measured by the Event Horizon Telescope suggests non-integer dimensions around $n\lessgtr4$. We derive an analytic formula for the weak field deflection angle, highlighting the need for advanced sensitive detection devices to observe lensed images influenced by higher dimensions. Our study of QNMs using physics-informed neural networks and the WKB method reveals a convergence towards known relationships between QNM frequencies and photon-sphere orbit frequencies. Despite the energetic nature of perturbing fields in higher dimensions, their damping increases. This suggests a complex interplay between dimensionality and the dynamics of black hole phenomena. |
0809.0273 | Piotr Jaranowski | P.Astone, M.Bassan, P.Bonifazi, K.M.Borkowski, R.J.Budzy\'nski,
A.Chincarini, E.Coccia, S.D'Antonio, M.Di Paolo Emilio, V.Fafone, S.Frasca,
S.Foffa, G.Giordano, P.Jaranowski, W.Kondracki, A.Kr\'olak, M.Maggiore,
A.Marini, Y.Minenkov, I.Modena, G.Modestino, A.Moleti, G.V.Pallottino,
C.Palomba, R.Parodi, M.Pietka, G.Pizzella, H.J.Pletsch, L.Quintieri, F.Ricci,
A.Rocchi, F.Ronga, R.Sturani, R.Terenzi, R.Vaccarone, M.Visco | All-sky search of NAUTILUS data | LaTeX, 12 pages | Class.Quant.Grav.25:184012,2008 | 10.1088/0264-9381/25/18/184012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A search for periodic gravitational-wave signals from isolated neutron stars
in the NAUTILUS detector data is presented. We have analyzed half a year of
data over the frequency band $<922.2; 923.2>$ Hz, the spindown range
$<-1.463\times10^{-8}; 0>$ Hz/s and over the entire sky. We have divided the
data into 2 day stretches and we have analyzed each stretch coherently using
matched filtering. We have imposed a low threshold for the optimal detection
statistic to obtain a set of candidates that are further examined for
coincidences among various data stretches. For some candidates we have also
investigated the change of the signal-to-noise ratio when we increase the
observation time from two to four days. Our analysis has not revealed any
gravitational-wave signals. Therefore we have imposed upper limits on the
dimensionless gravitational-wave amplitude over the parameter space that we
have searched. Depending on frequency, our upper limit ranges from $3.4 \times
10^{-23}$ to $1.3 \times 10^{-22}$. We have attempted a statistical
verification of the hypotheses leading to our conclusions. We estimate that our
upper limit is accurate to within 18%.
| [
{
"created": "Mon, 1 Sep 2008 15:45:11 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Astone",
"P.",
""
],
[
"Bassan",
"M.",
""
],
[
"Bonifazi",
"P.",
""
],
[
"Borkowski",
"K. M.",
""
],
[
"Budzyński",
"R. J.",
""
],
[
"Chincarini",
"A.",
""
],
[
"Coccia",
"E.",
""
],
[
"D'Antonio",
"S.",
""
],
[
"Emilio",
"M. Di Paolo",
""
],
[
"Fafone",
"V.",
""
],
[
"Frasca",
"S.",
""
],
[
"Foffa",
"S.",
""
],
[
"Giordano",
"G.",
""
],
[
"Jaranowski",
"P.",
""
],
[
"Kondracki",
"W.",
""
],
[
"Królak",
"A.",
""
],
[
"Maggiore",
"M.",
""
],
[
"Marini",
"A.",
""
],
[
"Minenkov",
"Y.",
""
],
[
"Modena",
"I.",
""
],
[
"Modestino",
"G.",
""
],
[
"Moleti",
"A.",
""
],
[
"Pallottino",
"G. V.",
""
],
[
"Palomba",
"C.",
""
],
[
"Parodi",
"R.",
""
],
[
"Pietka",
"M.",
""
],
[
"Pizzella",
"G.",
""
],
[
"Pletsch",
"H. J.",
""
],
[
"Quintieri",
"L.",
""
],
[
"Ricci",
"F.",
""
],
[
"Rocchi",
"A.",
""
],
[
"Ronga",
"F.",
""
],
[
"Sturani",
"R.",
""
],
[
"Terenzi",
"R.",
""
],
[
"Vaccarone",
"R.",
""
],
[
"Visco",
"M.",
""
]
] | A search for periodic gravitational-wave signals from isolated neutron stars in the NAUTILUS detector data is presented. We have analyzed half a year of data over the frequency band $<922.2; 923.2>$ Hz, the spindown range $<-1.463\times10^{-8}; 0>$ Hz/s and over the entire sky. We have divided the data into 2 day stretches and we have analyzed each stretch coherently using matched filtering. We have imposed a low threshold for the optimal detection statistic to obtain a set of candidates that are further examined for coincidences among various data stretches. For some candidates we have also investigated the change of the signal-to-noise ratio when we increase the observation time from two to four days. Our analysis has not revealed any gravitational-wave signals. Therefore we have imposed upper limits on the dimensionless gravitational-wave amplitude over the parameter space that we have searched. Depending on frequency, our upper limit ranges from $3.4 \times 10^{-23}$ to $1.3 \times 10^{-22}$. We have attempted a statistical verification of the hypotheses leading to our conclusions. We estimate that our upper limit is accurate to within 18%. |
2312.03860 | Charlie Hoy | Josu C. Aurrekoetxea, Charlie Hoy and Mark Hannam | Revisiting the cosmic string origin of GW190521 | 6 pages, 3 figures. Matches version published in PRL | null | null | LIGO-P2300425 | gr-qc astro-ph.CO astro-ph.HE hep-ph | http://creativecommons.org/licenses/by/4.0/ | For the first time we analyse gravitational-wave strain data using waveforms
constructed from strong gravity simulations of cosmic string loops collapsing
to Schwarzschild black holes; a previously unconsidered source. Since the
expected signal is dominated by a black-hole ringdown, it can mimic the
observed gravitational waves from high-mass binary black hole mergers. To
illustrate this, we consider GW190521, a short duration gravitational-wave
event observed in the third LIGO--Virgo--KAGRA observing run. We show that
describing this event as a collapsing cosmic string loop is favoured over
previous cosmic string analyses by an approximate log Bayes factor of $22$. The
binary black hole hypothesis is still preferred, mostly because the cosmic
string remnant is non-spinning. It remains an open question whether a spinning
remnant could form from loops with angular momentum, but if possible, it would
likely bring into contention the binary black hole preference. Finally, we
suggest that searches for ringdown-only waveforms would be a viable approach
for identifying collapsing cosmic string events and estimating their event
rate. This work opens up an important new direction for the cosmic-string and
gravitational-wave communities.
| [
{
"created": "Wed, 6 Dec 2023 19:15:56 GMT",
"version": "v1"
},
{
"created": "Fri, 10 May 2024 12:05:35 GMT",
"version": "v2"
}
] | 2024-05-13 | [
[
"Aurrekoetxea",
"Josu C.",
""
],
[
"Hoy",
"Charlie",
""
],
[
"Hannam",
"Mark",
""
]
] | For the first time we analyse gravitational-wave strain data using waveforms constructed from strong gravity simulations of cosmic string loops collapsing to Schwarzschild black holes; a previously unconsidered source. Since the expected signal is dominated by a black-hole ringdown, it can mimic the observed gravitational waves from high-mass binary black hole mergers. To illustrate this, we consider GW190521, a short duration gravitational-wave event observed in the third LIGO--Virgo--KAGRA observing run. We show that describing this event as a collapsing cosmic string loop is favoured over previous cosmic string analyses by an approximate log Bayes factor of $22$. The binary black hole hypothesis is still preferred, mostly because the cosmic string remnant is non-spinning. It remains an open question whether a spinning remnant could form from loops with angular momentum, but if possible, it would likely bring into contention the binary black hole preference. Finally, we suggest that searches for ringdown-only waveforms would be a viable approach for identifying collapsing cosmic string events and estimating their event rate. This work opens up an important new direction for the cosmic-string and gravitational-wave communities. |
gr-qc/0112040 | Alan D. Rendall | Alan D. Rendall | Cosmological models and centre manifold theory | 17 pages | Gen.Rel.Grav. 34 (2002) 1277-1294 | 10.1023/A:1019734703162 | AEI-2001-144 | gr-qc | null | Centre manifold theory is applied to some dynamical systems arising from
spatially homogeneous cosmological models. Detailed information is obtained
concerning the late-time behaviour of solutions of the Einstein equations of
Bianchi type III with collisionless matter. In addition some statements in the
literature on solutions of the Einstein equations coupled to a massive scalar
field are proved rigorously.
| [
{
"created": "Mon, 17 Dec 2001 14:03:17 GMT",
"version": "v1"
}
] | 2021-10-20 | [
[
"Rendall",
"Alan D.",
""
]
] | Centre manifold theory is applied to some dynamical systems arising from spatially homogeneous cosmological models. Detailed information is obtained concerning the late-time behaviour of solutions of the Einstein equations of Bianchi type III with collisionless matter. In addition some statements in the literature on solutions of the Einstein equations coupled to a massive scalar field are proved rigorously. |
gr-qc/0609073 | Celine Cattoen | Celine Cattoen (Victoria University of Wellington) and Matt Visser
(Victoria University of Wellington) | Generalized Puisieux series expansion for cosmological milestones | 3 pages, using World Scientific templates, conference proceedings for
MG11 Berlin, July 2006, to be published by World Scientific | null | null | null | gr-qc | null | We use generalized Puisieux series expansions to determine the behaviour of
the scale factor in the vicinity of typical cosmological milestones occurring
in a FRW universe. We describe some of the consequences of this generalized
Puisieux series expansion on other physical observables.
| [
{
"created": "Wed, 20 Sep 2006 00:20:18 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Cattoen",
"Celine",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | We use generalized Puisieux series expansions to determine the behaviour of the scale factor in the vicinity of typical cosmological milestones occurring in a FRW universe. We describe some of the consequences of this generalized Puisieux series expansion on other physical observables. |
gr-qc/0507139 | Guillermo A. Mena Marugan | Jeronimo Cortez and Guillermo A. Mena Marugan | Feasibility of a Unitary Quantum Dynamics in the Gowdy $T^3$
Cosmological Model | 12 pages, version accepted for publication in Physical Review D | Phys.Rev. D72 (2005) 064020 | 10.1103/PhysRevD.72.064020 | null | gr-qc | null | It has been pointed out that it is impossible to obtain a unitary
implementation of the dynamics for the polarized Gowdy $T^{3}$ cosmologies in
an otherwise satisfactory, nonperturbative canonical quantization proposed for
these spacetimes. By introducing suitable techniques to deal with
deparametrized models in cosmology that possess an explicit time dependence (as
it is the case for the toroidal Gowdy model), we present in this paper a
detailed analysis about the roots of this failure of unitarity. We investigate
the impediments to a unitary implementation of the evolution by considering
modifications to the dynamics. These modifications may be regarded as
perturbations. We show in a precise manner why and where unitary
implementability fails in our system, and prove that the obstructions are
extremely sensitive to modifications in the Hamiltonian that dictates the time
evolution of the symmetry-reduced model. We are able to characterize to a
certain extent how far the model is from unitarity. Moreover, we demonstrate
that the dynamics can actually be approximated as much as one wants by means of
unitary transformations.
| [
{
"created": "Fri, 29 Jul 2005 16:14:06 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Sep 2005 12:45:27 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Cortez",
"Jeronimo",
""
],
[
"Marugan",
"Guillermo A. Mena",
""
]
] | It has been pointed out that it is impossible to obtain a unitary implementation of the dynamics for the polarized Gowdy $T^{3}$ cosmologies in an otherwise satisfactory, nonperturbative canonical quantization proposed for these spacetimes. By introducing suitable techniques to deal with deparametrized models in cosmology that possess an explicit time dependence (as it is the case for the toroidal Gowdy model), we present in this paper a detailed analysis about the roots of this failure of unitarity. We investigate the impediments to a unitary implementation of the evolution by considering modifications to the dynamics. These modifications may be regarded as perturbations. We show in a precise manner why and where unitary implementability fails in our system, and prove that the obstructions are extremely sensitive to modifications in the Hamiltonian that dictates the time evolution of the symmetry-reduced model. We are able to characterize to a certain extent how far the model is from unitarity. Moreover, we demonstrate that the dynamics can actually be approximated as much as one wants by means of unitary transformations. |
0908.3680 | Matthew DePies | Matthew R Depies | Gravitational Waves and Light Cosmic Strings | 129 pages, 18 figures, PhD dissertation | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave signatures from cosmic strings are analyzed numerically.
Cosmic string networks form during phase transistions in the early universe and
these networks of long cosmic strings break into loops that radiate energy in
the form of gravitational waves until they decay. The gravitational waves come
in the form of harmonic modes from individual string loops, a "confusion noise"
from galactic loops, and a stochastic background of gravitational waves from a
network of loops. In this study string loops of larger size $\alpha$ and lower
string tensions $G\mu$ (where $\mu$ is the mass per unit length of the string)
are investigated than in previous studies. Several detectors are currently
searching for gravitational waves and a space based satellite, the Laser
Interferometer Space Antenna (LISA), is in the final stages of pre-flight. The
results for large loop sizes ($\alpha=0.1$) put an upper limit of about
$G\mu<10^{-9}$ and indicate that gravitational waves from string loops down to
$G\mu \approx 10^{-20}$ could be detectabe by LISA. The string tension is
related to the energy scale of the phase transition and the Planck mass via
$G\mu = \Lambda_s^2 / m_{pl}^2$, so the limits on $G\mu$ set the energy scale
of any phase transition to $\Lambda_s < 10^{-4.5} m_{pl}$. Our results indicate
that loops may form a significant gravitational wave signal, even for string
tensions too low to have larger cosmological effects.
| [
{
"created": "Tue, 25 Aug 2009 20:11:35 GMT",
"version": "v1"
}
] | 2009-09-30 | [
[
"Depies",
"Matthew R",
""
]
] | Gravitational wave signatures from cosmic strings are analyzed numerically. Cosmic string networks form during phase transistions in the early universe and these networks of long cosmic strings break into loops that radiate energy in the form of gravitational waves until they decay. The gravitational waves come in the form of harmonic modes from individual string loops, a "confusion noise" from galactic loops, and a stochastic background of gravitational waves from a network of loops. In this study string loops of larger size $\alpha$ and lower string tensions $G\mu$ (where $\mu$ is the mass per unit length of the string) are investigated than in previous studies. Several detectors are currently searching for gravitational waves and a space based satellite, the Laser Interferometer Space Antenna (LISA), is in the final stages of pre-flight. The results for large loop sizes ($\alpha=0.1$) put an upper limit of about $G\mu<10^{-9}$ and indicate that gravitational waves from string loops down to $G\mu \approx 10^{-20}$ could be detectabe by LISA. The string tension is related to the energy scale of the phase transition and the Planck mass via $G\mu = \Lambda_s^2 / m_{pl}^2$, so the limits on $G\mu$ set the energy scale of any phase transition to $\Lambda_s < 10^{-4.5} m_{pl}$. Our results indicate that loops may form a significant gravitational wave signal, even for string tensions too low to have larger cosmological effects. |
1006.0388 | Hanno Sahlmann | Hanno Sahlmann | On loop quantum gravity kinematics with non-degenerate spatial
background | 13 pages, 2 figures. v2: Some clarifications added, typos removed.
Virtually identical with published version | Class. Quant Grav.27:225007, 2010 | 10.1088/0264-9381/27/22/225007 | KA-TP-14-2010 | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a remarkable paper, T. Koslowski introduced kinematical representations
for loop quantum gravity in which there is a non-degenerate spatial background
metric present. He also considered their properties, and showed that Gauss and
diffeomorphism constraints can be implemented. With the present article, we
streamline and extend his treatment. In particular, we show that the standard
regularization of the geometric operators leads to well defined operators in
the new representations, and we work out their properties fully. We also give
details on the implementation of the constraints. All of this is done in such a
way as to show that the standard representation is a particular (and in some
ways exceptional) case of the more general constructions. This does not mean
that these new representations are as fundamental as the standard one. Rather,
we believe they might be useful to find some form of effective theory of loop
quantum gravity on large scales.
| [
{
"created": "Wed, 2 Jun 2010 14:20:25 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Oct 2010 03:59:52 GMT",
"version": "v2"
}
] | 2010-10-27 | [
[
"Sahlmann",
"Hanno",
""
]
] | In a remarkable paper, T. Koslowski introduced kinematical representations for loop quantum gravity in which there is a non-degenerate spatial background metric present. He also considered their properties, and showed that Gauss and diffeomorphism constraints can be implemented. With the present article, we streamline and extend his treatment. In particular, we show that the standard regularization of the geometric operators leads to well defined operators in the new representations, and we work out their properties fully. We also give details on the implementation of the constraints. All of this is done in such a way as to show that the standard representation is a particular (and in some ways exceptional) case of the more general constructions. This does not mean that these new representations are as fundamental as the standard one. Rather, we believe they might be useful to find some form of effective theory of loop quantum gravity on large scales. |
1211.5180 | Jian-Yang Zhu | Xiao Liu, Fei Huang and Jian-Yang Zhu | Path Integral of Bianchi I models in Loop Quantum Cosmology | 11 pages,revised version, accepted for publication in Class. Quantum
Grav | Class. Quantum Grav. 30 (2013) 065010 | 10.1088/0264-9381/30/6/065010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A path integral formulation of the Bianchi I models containing a massless
scalar field in loop quantum cosmology is constructed. Following the strategy
used in the homogenous and isotropic case, the calculation is extended to the
simplest non-isotropic models according to the $\bar{\mu}$ and
$\bar{\mu}^{\prime}$ scheme. It is proved from the path integral angle that the
quantum dynamic lacks the full invariance with respect to fiducial cell scaling
in the $\bar{\mu}$ scheme, but it does not in the $\bar{\mu}^{\prime}$ scheme.
The investigation affirms the equivalence of the canonical approach and the
path integral approach in loop quantum cosmology.
| [
{
"created": "Thu, 22 Nov 2012 01:21:24 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Feb 2013 12:42:00 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Liu",
"Xiao",
""
],
[
"Huang",
"Fei",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | A path integral formulation of the Bianchi I models containing a massless scalar field in loop quantum cosmology is constructed. Following the strategy used in the homogenous and isotropic case, the calculation is extended to the simplest non-isotropic models according to the $\bar{\mu}$ and $\bar{\mu}^{\prime}$ scheme. It is proved from the path integral angle that the quantum dynamic lacks the full invariance with respect to fiducial cell scaling in the $\bar{\mu}$ scheme, but it does not in the $\bar{\mu}^{\prime}$ scheme. The investigation affirms the equivalence of the canonical approach and the path integral approach in loop quantum cosmology. |
0803.1481 | Adellane Sousa | A. A. Sousa, R. B. Pereira and A. C. Silva | Energy and Angular Momentum Densities in a Godel-Type Universe in the
Teleparallel Geometry | 20 pages, no figures. Revised in view of Referee's comments. Version
to appear in the Gravitation and Cosmology | Grav.Cosmol.16:25-33,2010 | 10.1134/S0202289310010044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main scope of this research consists in evaluating the energy-momentum
(gravitational field plus matter) and gravitational angular momentum densities
in the universe with global rotation, considering the Godel-Obukhov metric. For
this, we use the Hamiltonian formalism of the Teleparallel Equivalent of
General Relativity (TEGR), which is justified for presenting covariant
expressions for the considered quantities. We found that the total energy
density calculated by the TEGR method is in agreement with the results reported
by other authors in the literature using pseudotensors. The result found for
the angular momentum density depends on the rotational parameter as expected.
We also show explicitly the equivalence among the field equations of the TEGR
and Einstein equations (RG), considering a perfect fluid and Godel-Obukhov
metric.
| [
{
"created": "Mon, 10 Mar 2008 19:49:49 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Mar 2008 20:06:31 GMT",
"version": "v2"
},
{
"created": "Mon, 7 Dec 2009 14:56:14 GMT",
"version": "v3"
}
] | 2010-03-19 | [
[
"Sousa",
"A. A.",
""
],
[
"Pereira",
"R. B.",
""
],
[
"Silva",
"A. C.",
""
]
] | The main scope of this research consists in evaluating the energy-momentum (gravitational field plus matter) and gravitational angular momentum densities in the universe with global rotation, considering the Godel-Obukhov metric. For this, we use the Hamiltonian formalism of the Teleparallel Equivalent of General Relativity (TEGR), which is justified for presenting covariant expressions for the considered quantities. We found that the total energy density calculated by the TEGR method is in agreement with the results reported by other authors in the literature using pseudotensors. The result found for the angular momentum density depends on the rotational parameter as expected. We also show explicitly the equivalence among the field equations of the TEGR and Einstein equations (RG), considering a perfect fluid and Godel-Obukhov metric. |
2203.08460 | Mehdi Shokri | Jafar Sadeghi, Saeed Noori Gashti and Mehdi Shokri | Anisotropic constant-roll inflationary scenario with complex
quintessence field and swampland conjectures | 18 pages, 2 figures | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/publicdomain/zero/1.0/ | In this paper, with the presence of swampland conjecture, we use the complex
form of a scalar field and investigate the anisotropic constant-roll of an
inflationary scenario. Recently, the complex quintessence field has been used
to describe the accelerating expansion of the universe which has had
interesting results connecting with various conditions. Therefore, the
Lagrangian density of the quintessence field leads to obtaining the equations
of the complex scalar field. Also, we use the anisotropic constant-roll
conditions and the field equation and calculate the exact solutions for some
cosmology parameters such as Hubble parameter and potential. Using the exact
solution of potential and refined swampland conditions, we plot some figures.
In that case, the figures lead us to have challenges between three concepts as
complex quintessence, anisotropic constant-roll conditions, and swampland
conjectures. Then we discuss their compatibility and incompatibility with
corresponding results. Finally, we will analyze the complex quintessence in
examining the inflationary scenario.
| [
{
"created": "Wed, 16 Mar 2022 08:37:31 GMT",
"version": "v1"
}
] | 2022-03-17 | [
[
"Sadeghi",
"Jafar",
""
],
[
"Gashti",
"Saeed Noori",
""
],
[
"Shokri",
"Mehdi",
""
]
] | In this paper, with the presence of swampland conjecture, we use the complex form of a scalar field and investigate the anisotropic constant-roll of an inflationary scenario. Recently, the complex quintessence field has been used to describe the accelerating expansion of the universe which has had interesting results connecting with various conditions. Therefore, the Lagrangian density of the quintessence field leads to obtaining the equations of the complex scalar field. Also, we use the anisotropic constant-roll conditions and the field equation and calculate the exact solutions for some cosmology parameters such as Hubble parameter and potential. Using the exact solution of potential and refined swampland conditions, we plot some figures. In that case, the figures lead us to have challenges between three concepts as complex quintessence, anisotropic constant-roll conditions, and swampland conjectures. Then we discuss their compatibility and incompatibility with corresponding results. Finally, we will analyze the complex quintessence in examining the inflationary scenario. |
2206.15187 | Lijing Shao | Lijing Shao | Radio Pulsars as a Laboratory for Strong-field Gravity Tests | 16 pages, 4 figures; Invited contribution to the forthcoming book
"Modified and Quantum Gravity - From theory to experimental searches on all
scales", Springer Nature, (Eds) Claus L\"ammerzahl and Christian Pfeifer | Lecture Notes in Physics 1017 (2023) 385 | 10.1007/978-3-031-31520-6_12 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | General relativity offers a classical description to gravitation and
spacetime, and is a cornerstone for modern physics. It has passed a number of
empirical tests with flying colours, mostly in the weak-gravity regimes, but
nowadays also in the strong-gravity regimes. Radio pulsars provide one of the
earliest extrasolar laboratories for gravity tests. They, in possession of
strongly self-gravitating bodies, i.e. neutron stars, are playing a unique role
in the studies of strong-field gravity. Radio timing of binary pulsars enables
very precise measurements of system parameters, and the pulsar timing
technology is extremely sensitive to various types of changes in the orbital
dynamics. If an alternative gravity theory causes modifications to binary
orbital evolution with respect to general relativity, the theory prediction can
be confronted with timing results. In this chapter, we review the basic
concepts in using radio pulsars for strong-field gravity tests, with the aid of
some recent examples in this regard, including tests of gravitational dipolar
radiation, massive gravity theories, and the strong equivalence principle. With
more sensitive radio telescopes coming online, pulsars are to provide even more
dedicated tests of strong gravity in the near future.
| [
{
"created": "Thu, 30 Jun 2022 10:54:43 GMT",
"version": "v1"
}
] | 2023-10-06 | [
[
"Shao",
"Lijing",
""
]
] | General relativity offers a classical description to gravitation and spacetime, and is a cornerstone for modern physics. It has passed a number of empirical tests with flying colours, mostly in the weak-gravity regimes, but nowadays also in the strong-gravity regimes. Radio pulsars provide one of the earliest extrasolar laboratories for gravity tests. They, in possession of strongly self-gravitating bodies, i.e. neutron stars, are playing a unique role in the studies of strong-field gravity. Radio timing of binary pulsars enables very precise measurements of system parameters, and the pulsar timing technology is extremely sensitive to various types of changes in the orbital dynamics. If an alternative gravity theory causes modifications to binary orbital evolution with respect to general relativity, the theory prediction can be confronted with timing results. In this chapter, we review the basic concepts in using radio pulsars for strong-field gravity tests, with the aid of some recent examples in this regard, including tests of gravitational dipolar radiation, massive gravity theories, and the strong equivalence principle. With more sensitive radio telescopes coming online, pulsars are to provide even more dedicated tests of strong gravity in the near future. |
2010.11452 | Paulo Jos\'e Ferreira Porf\'irio da Silva | C. Furtado, J. R. Nascimento, A. Yu. Petrov, P. J. Porf\'irio and A.
R. Soares | Strong gravitational lensing in a spacetime with topological charge
within the Eddington-inspired Born-Infeld gravity | 20 pages, 5 figures | Phys. Rev. D 103, 044047 (2021) | 10.1103/PhysRevD.103.044047 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we calculate the angular deflection of light in the strong field
limit in two spacetimes which were previously studied within the
Eddington-inspired Born-Infeld gravity (EiBI), namely, a black hole and a
wormhole, both with topological charge. We show that the presence of the
parameters characterizing EiBI and the topological charge promote significant
changes in the angular deflection of light with respect to that one obtained in
Schwarzschild spacetime. Using the expression for angular deflection in the
strong field limit, we calculate the position and magnification of the
respective relativistic images.
| [
{
"created": "Thu, 22 Oct 2020 05:26:23 GMT",
"version": "v1"
},
{
"created": "Sat, 24 Oct 2020 06:57:41 GMT",
"version": "v2"
}
] | 2021-02-26 | [
[
"Furtado",
"C.",
""
],
[
"Nascimento",
"J. R.",
""
],
[
"Petrov",
"A. Yu.",
""
],
[
"Porfírio",
"P. J.",
""
],
[
"Soares",
"A. R.",
""
]
] | In this work we calculate the angular deflection of light in the strong field limit in two spacetimes which were previously studied within the Eddington-inspired Born-Infeld gravity (EiBI), namely, a black hole and a wormhole, both with topological charge. We show that the presence of the parameters characterizing EiBI and the topological charge promote significant changes in the angular deflection of light with respect to that one obtained in Schwarzschild spacetime. Using the expression for angular deflection in the strong field limit, we calculate the position and magnification of the respective relativistic images. |
1202.1271 | Ivano Dami\~ao Soares | R. F. Aranha, I. Dami\~ao Soares and E. V. Tonini | Gravitational Wave Recoil and Kick Processes in the Merger of Two
Colliding Black Holes: The Non Head-on Case | 11 pages, 7 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine numerically the process of gravitational wave recoil in the merger
of two black holes in non head-on collision, in the realm of Robinson-Trautman
spacetimes. Characteristic initial data for the system are constructed, and the
evolution covers the post-merger phase up to the final configuration of the
remnant black hole. The net momentum flux carried out by gravitational waves
and the associated impulses are evaluated. Our analysis is based on the
Bondi-Sachs conservation laws for the energy momentum of the system. The net
kick velocity $V_{k}$ imparted to the merged system by the total gravitational
wave impulse is also evaluated. Typically for a non head-on collision the net
momentum flux carried out by gravitational waves is nonzero for equal-mass
colliding black holes. The distribution of $V_{k}$ as a function of the
symmetric mass ratio $\eta$ is well fitted by a modified Fitchett
$\eta$-scaling law, the additional parameter modifying the law being a measure
of the nonzero gravitational wave momentum flux for equal-mass initial black
holes. For an initial infalling velocity $v/c \simeq 0.462$ of the colliding
black holes, and incidence angle of collision $\rho_0=21^{o}$, we obtain a
maximum $V_{k} \sim 121 {\rm km/s}$ located at $\eta \simeq 0.226$. For initial
equal-mass black holes ($\eta=0.25$) we obtain $V_{k} \sim 107 {\rm km/s}$.
Based on the integrated Bondi-Sachs momentum conservation law we discuss a
possible definition of the center-of-mass velocity of the binary merged system
and show that -- in an appropriate inertial frame -- it approaches
asymptotically the net kick velocity, which is the velocity of the remnant
black hole in this inertial frame. For larger values of $v/c$ we obtain
substantially larger values of the net kick velocity, e.g., for $v/c \simeq
0.604$ a maximum $V_{k} \sim 610 {\rm km/s}$ is obtained.
| [
{
"created": "Mon, 6 Feb 2012 20:49:57 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Feb 2012 21:03:31 GMT",
"version": "v2"
}
] | 2012-02-16 | [
[
"Aranha",
"R. F.",
""
],
[
"Soares",
"I. Damião",
""
],
[
"Tonini",
"E. V.",
""
]
] | We examine numerically the process of gravitational wave recoil in the merger of two black holes in non head-on collision, in the realm of Robinson-Trautman spacetimes. Characteristic initial data for the system are constructed, and the evolution covers the post-merger phase up to the final configuration of the remnant black hole. The net momentum flux carried out by gravitational waves and the associated impulses are evaluated. Our analysis is based on the Bondi-Sachs conservation laws for the energy momentum of the system. The net kick velocity $V_{k}$ imparted to the merged system by the total gravitational wave impulse is also evaluated. Typically for a non head-on collision the net momentum flux carried out by gravitational waves is nonzero for equal-mass colliding black holes. The distribution of $V_{k}$ as a function of the symmetric mass ratio $\eta$ is well fitted by a modified Fitchett $\eta$-scaling law, the additional parameter modifying the law being a measure of the nonzero gravitational wave momentum flux for equal-mass initial black holes. For an initial infalling velocity $v/c \simeq 0.462$ of the colliding black holes, and incidence angle of collision $\rho_0=21^{o}$, we obtain a maximum $V_{k} \sim 121 {\rm km/s}$ located at $\eta \simeq 0.226$. For initial equal-mass black holes ($\eta=0.25$) we obtain $V_{k} \sim 107 {\rm km/s}$. Based on the integrated Bondi-Sachs momentum conservation law we discuss a possible definition of the center-of-mass velocity of the binary merged system and show that -- in an appropriate inertial frame -- it approaches asymptotically the net kick velocity, which is the velocity of the remnant black hole in this inertial frame. For larger values of $v/c$ we obtain substantially larger values of the net kick velocity, e.g., for $v/c \simeq 0.604$ a maximum $V_{k} \sim 610 {\rm km/s}$ is obtained. |
1808.06630 | Savitri V. Iyer | S. V. Iyer | Frame-dragging induced asymmetry in the bending of light near a Kerr
black hole | 6 pages, 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The deflection of light's trajectory has been studied in many different
spacetime geometries in weak and strong gravity, including the special cases of
spherically symmetric static and spinning black holes. It is also well known
that the rotation of massive objects results in the dragging of inertial frames
in the spacetime geometry. We present here a discussion of the asymmetry that
appears explicitly in the exact analytical expression for the bending angle of
light on the equatorial plane of the spinning, or Kerr, black hole.
| [
{
"created": "Mon, 20 Aug 2018 18:06:13 GMT",
"version": "v1"
}
] | 2018-08-22 | [
[
"Iyer",
"S. V.",
""
]
] | The deflection of light's trajectory has been studied in many different spacetime geometries in weak and strong gravity, including the special cases of spherically symmetric static and spinning black holes. It is also well known that the rotation of massive objects results in the dragging of inertial frames in the spacetime geometry. We present here a discussion of the asymmetry that appears explicitly in the exact analytical expression for the bending angle of light on the equatorial plane of the spinning, or Kerr, black hole. |
gr-qc/0105057 | Anatoli Vankov | Anatoli Vankov (Physics Department, Eastern Illinois University, USA) | Proposal of Experimental Test of General Relativity Theory | 28 pages | null | null | null | gr-qc | null | On the basis of the relativistic mass-energy concept we found that a proper
mass of a test particle in a gravitational field depends on a potential energy,
hence, a freely falling particle has a varying proper mass. Consequently, a
multitude of freely falling reference frames cannot be regarded as a multitude
of equivalent inertial reference frames. There is a class of experiments, in
which an inner observer can distinguish between the state of free fall in a
gravitational field and the state of free space by detecting the effect of a
proper mass variation. If so, a demonstration of a violation of the Equivalence
Principle is possible. It is shown that a variant of the classical
Pound-Rebka-Snider experiment on a photon frequency shift in a gravitational
field, if conducted in a freely falling laboratory, would be such a test.
Abbreviation: SRT- the Special Relativity Theory, GRT- the General Relativity
Theory, EP - the Equivalence Principle, PRS - the Pound-Rebka-Snider
(experiment)
| [
{
"created": "Thu, 17 May 2001 13:48:06 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Vankov",
"Anatoli",
"",
"Physics Department, Eastern Illinois University, USA"
]
] | On the basis of the relativistic mass-energy concept we found that a proper mass of a test particle in a gravitational field depends on a potential energy, hence, a freely falling particle has a varying proper mass. Consequently, a multitude of freely falling reference frames cannot be regarded as a multitude of equivalent inertial reference frames. There is a class of experiments, in which an inner observer can distinguish between the state of free fall in a gravitational field and the state of free space by detecting the effect of a proper mass variation. If so, a demonstration of a violation of the Equivalence Principle is possible. It is shown that a variant of the classical Pound-Rebka-Snider experiment on a photon frequency shift in a gravitational field, if conducted in a freely falling laboratory, would be such a test. Abbreviation: SRT- the Special Relativity Theory, GRT- the General Relativity Theory, EP - the Equivalence Principle, PRS - the Pound-Rebka-Snider (experiment) |
gr-qc/9403008 | Luis J. Garay | Luis J. Garay | Quantum gravity and minimum length | 23 pages, RevTeX, few minor changes, published version | Int.J.Mod.Phys. A10 (1995) 145-166 | 10.1142/S0217751X95000085 | Imperial/TP/93-94/20 | gr-qc hep-th | null | The existence of a fundamental scale, a lower bound to any output of a
position measurement, seems to be a model-independent feature of quantum
gravity. In fact, different approaches to this theory lead to this result. The
key ingredients for the appearance of this minimum length are quantum
mechanics, special relativity and general relativity. As a consequence,
classical notions such as causality or distance between events cannot be
expected to be applicable at this scale. They must be replaced by some other,
yet unknown, structure.
| [
{
"created": "Wed, 2 Mar 1994 15:50:51 GMT",
"version": "v1"
},
{
"created": "Tue, 9 May 1995 09:39:08 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Garay",
"Luis J.",
""
]
] | The existence of a fundamental scale, a lower bound to any output of a position measurement, seems to be a model-independent feature of quantum gravity. In fact, different approaches to this theory lead to this result. The key ingredients for the appearance of this minimum length are quantum mechanics, special relativity and general relativity. As a consequence, classical notions such as causality or distance between events cannot be expected to be applicable at this scale. They must be replaced by some other, yet unknown, structure. |
2112.13349 | Neven Bili\'c | Neven Bilic | Analog Schwarzschild-like geometry in fluids with external pressure | 20 pages, comments added, a few issues clarified, conclusions
expanded, typos corrected, results unchanged, to appear in Phys. Rev. D | null | 10.1103/PhysRevD.105.064052 | RBI-ThPhys-2022-3 | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We study acoustic geometry in fluids with external pressure. In particular,
we examine the conditions under which the acoustic metric mimics a
Schwarzschild-like metric. We demonstrate that it is possible to mimic a
Schwarzschild-like geometry in a consistent way only in the framework of
relativistic acoustic geometry.
| [
{
"created": "Sun, 26 Dec 2021 10:35:51 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Mar 2022 10:19:19 GMT",
"version": "v2"
}
] | 2022-04-06 | [
[
"Bilic",
"Neven",
""
]
] | We study acoustic geometry in fluids with external pressure. In particular, we examine the conditions under which the acoustic metric mimics a Schwarzschild-like metric. We demonstrate that it is possible to mimic a Schwarzschild-like geometry in a consistent way only in the framework of relativistic acoustic geometry. |
gr-qc/9311007 | null | S.Carlip and J.E.Nelson | Equivalent Quantisations of (2+1)-Dimensional Gravity | 7 pages, Plain Tex, DFTT 67/93, UCD-93-33 | Phys.Lett.B324:299-302,1994 | 10.1016/0370-2693(94)90197-X | null | gr-qc hep-th | null | For spacetimes with the topology $\IR\!\times\!T^2$, the action of
(2+1)-dimensional gravity with negative cosmological constant $\La$ is written
uniquely in terms of the time-independent traces of holonomies around two
intersecting noncontractible paths on $T^2$. The holonomy parameters are
related to the moduli on slices of constant mean curvature by a time-dependent
canonical transformation which introduces an effective Hamiltonian. The
quantisation of the two classically equivalent formulations differs by terms of
order $O(\hbar^3)$, negligible for small $|\La|$.
| [
{
"created": "Fri, 5 Nov 1993 08:39:42 GMT",
"version": "v1"
}
] | 2010-04-28 | [
[
"Carlip",
"S.",
""
],
[
"Nelson",
"J. E.",
""
]
] | For spacetimes with the topology $\IR\!\times\!T^2$, the action of (2+1)-dimensional gravity with negative cosmological constant $\La$ is written uniquely in terms of the time-independent traces of holonomies around two intersecting noncontractible paths on $T^2$. The holonomy parameters are related to the moduli on slices of constant mean curvature by a time-dependent canonical transformation which introduces an effective Hamiltonian. The quantisation of the two classically equivalent formulations differs by terms of order $O(\hbar^3)$, negligible for small $|\La|$. |
gr-qc/0401021 | Dr Mayeul Arminjon | Mayeul Arminjon | Ether theory of gravitation: why and how? | Standard LaTeX, 60 pages. Invited contribution to the book ``Ether,
Spacetime and Cosmology" (M. C. Duffy, ed.), to appear at Hadronic Press. v2:
minor improvements, new refs., post-scriptum summarizing later work | Ether, space-time and cosmology, Vol. 1: Modern ether concepts,
relativity and geometry (M. C. Duffy and J. Levy, Eds.), PD Publications,
Liverpool, UK (2008), pp. 139-201. ISBN: 1 873 694 10 5 | null | null | gr-qc | null | Gravitation might make a preferred frame appear, and with it a clear
space/time separation--the latter being, a priori, needed by quantum mechanics
(QM) in curved space-time. Several models of gravitation with an ether are
discussed: they assume metrical effects in an heterogeneous ether and/or a
Lorentz-symmetry breaking. One scalar model, starting from a semi-heuristic
view of gravity as a pressure force, is detailed. It has been developed to a
complete theory including continuum dynamics, cosmology, and links with
electromagnetism and QM. To test the theory, an asymptotic scheme of
post-Newtonian approximation has been built. That version of the theory which
is discussed here predicts an internal-structure effect, even at the
point-particle limit. The same might happen also in general relativity (GR) in
some gauges, if one would use a similar scheme. Adjusting the equations of
planetary motion on an ephemeris leaves a residual difference with it; one
should adjust the equations using primary observations. The same effects on
light rays are predicted as with GR, and a similar energy loss applies to
binary pulsars.
| [
{
"created": "Wed, 7 Jan 2004 13:20:27 GMT",
"version": "v1"
},
{
"created": "Thu, 31 May 2007 15:10:07 GMT",
"version": "v2"
}
] | 2008-04-07 | [
[
"Arminjon",
"Mayeul",
""
]
] | Gravitation might make a preferred frame appear, and with it a clear space/time separation--the latter being, a priori, needed by quantum mechanics (QM) in curved space-time. Several models of gravitation with an ether are discussed: they assume metrical effects in an heterogeneous ether and/or a Lorentz-symmetry breaking. One scalar model, starting from a semi-heuristic view of gravity as a pressure force, is detailed. It has been developed to a complete theory including continuum dynamics, cosmology, and links with electromagnetism and QM. To test the theory, an asymptotic scheme of post-Newtonian approximation has been built. That version of the theory which is discussed here predicts an internal-structure effect, even at the point-particle limit. The same might happen also in general relativity (GR) in some gauges, if one would use a similar scheme. Adjusting the equations of planetary motion on an ephemeris leaves a residual difference with it; one should adjust the equations using primary observations. The same effects on light rays are predicted as with GR, and a similar energy loss applies to binary pulsars. |
gr-qc/0401083 | Francisco Lobo | Francisco S.N. Lobo | Thin shells around traversable wormholes | 17 pages, 13 figures, Revtex4. Talk delivered at the APCTP Winter
School and Workshop: Quantum Gravity, Black Holes and Wormholes, POSTECH,
Pohang School of Environmental Engineering, South Korea, 11-14 Dec. 2003 | null | null | null | gr-qc | null | Applying the Darmois-Israel thin shell formalism, we construct static and
dynamic thin shells around traversable wormholes. Firstly, by applying the
cut-and-paste technique we apply a linearized stability analysis to thin-shell
wormholes in the presence of a generic cosmological constant. We find that for
large positive values of the cosmological constant, i.e., the Schwarzschild-de
Sitter solution, the regions of stability significantly increase relatively to
the Schwarzschild case, analyzed by Poisson and Visser. Secondly, we construct
static thin shell solutions by matching an interior wormhole solution to a
vacuum exterior solution at a junction surface. In the spirit of minimizing the
usage of exotic matter we analyze the domains in which the weak and null energy
conditions are satisfied at the junction surface. The characteristics and
several physical properties of the surface stresses are explored, namely, we
determine regions where the sign of tangential surface pressure is positive and
negative (surface tension). An equation governing the behavior of the radial
pressure across the junction surface is deduced. Specific dimensions of the
wormhole, namely, the throat radius and the junction interface radius, are
found by taking into account the traversability conditions, and estimates for
the traversal time and velocity are also determined.
| [
{
"created": "Sun, 18 Jan 2004 19:23:08 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Lobo",
"Francisco S. N.",
""
]
] | Applying the Darmois-Israel thin shell formalism, we construct static and dynamic thin shells around traversable wormholes. Firstly, by applying the cut-and-paste technique we apply a linearized stability analysis to thin-shell wormholes in the presence of a generic cosmological constant. We find that for large positive values of the cosmological constant, i.e., the Schwarzschild-de Sitter solution, the regions of stability significantly increase relatively to the Schwarzschild case, analyzed by Poisson and Visser. Secondly, we construct static thin shell solutions by matching an interior wormhole solution to a vacuum exterior solution at a junction surface. In the spirit of minimizing the usage of exotic matter we analyze the domains in which the weak and null energy conditions are satisfied at the junction surface. The characteristics and several physical properties of the surface stresses are explored, namely, we determine regions where the sign of tangential surface pressure is positive and negative (surface tension). An equation governing the behavior of the radial pressure across the junction surface is deduced. Specific dimensions of the wormhole, namely, the throat radius and the junction interface radius, are found by taking into account the traversability conditions, and estimates for the traversal time and velocity are also determined. |
2305.15326 | Jos\'e Jaime Terente D\'iaz | Jos\'e Jaime Terente D\'iaz and Mindaugas Kar\v{c}iauskas | Comoving curvature perturbation in Jordan and Einstein frames | 23 pages | Phys. Rev. D 108, 083535 (2023) | 10.1103/PhysRevD.108.083535 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of $F(\phi)R$ models of gravity, the conformal invariance of
the curvature perturbation on uniform-field slices has been already
demonstrated in several publications. In this work we study the curvature
perturbation $\mathcal{R}$ defined on hypersurfaces that comove with the
effective fluid whose energy-momentum tensor is covariantly conserved. We
derive the expressions of $\mathcal{R}$ at first order in perturbations in the
Jordan and Einstein frames and relate the two. Generically $\mathcal{R}$ is not
conformally invariant, but it is on sufficiently large scales during slow-roll
inflation. Using our results we also rederive the expressions for inflation
observables in the Jordan frame.
| [
{
"created": "Wed, 24 May 2023 16:42:01 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Aug 2023 12:34:55 GMT",
"version": "v2"
}
] | 2023-11-01 | [
[
"Díaz",
"José Jaime Terente",
""
],
[
"Karčiauskas",
"Mindaugas",
""
]
] | In the context of $F(\phi)R$ models of gravity, the conformal invariance of the curvature perturbation on uniform-field slices has been already demonstrated in several publications. In this work we study the curvature perturbation $\mathcal{R}$ defined on hypersurfaces that comove with the effective fluid whose energy-momentum tensor is covariantly conserved. We derive the expressions of $\mathcal{R}$ at first order in perturbations in the Jordan and Einstein frames and relate the two. Generically $\mathcal{R}$ is not conformally invariant, but it is on sufficiently large scales during slow-roll inflation. Using our results we also rederive the expressions for inflation observables in the Jordan frame. |
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