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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0705.3829 | Deirdre Shoemaker | Birjoo Vaishnav, Ian Hinder, Frank Herrmann, Deirdre Shoemaker | Matched Filtering of Numerical Relativity Templates of Spinning Binary
Black Holes | null | Phys.Rev.D76:084020,2007 | 10.1103/PhysRevD.76.084020 | null | gr-qc astro-ph | null | Tremendous progress has been made towards the solution of the
binary-black-hole problem in numerical relativity. The waveforms produced by
numerical relativity will play a role in gravitational wave detection as either
test-beds for analytic template banks or as template banks themselves. As the
parameter space explored by numerical relativity expands, the importance of
quantifying the effect that each parameter has on first the detection of
gravitational waves and then the parameter estimation of their sources
increases. In light of this, we present a study of equal-mass, spinning
binary-black-hole evolutions through matched filtering techniques commonly used
in data analysis. We study how the match between two numerical waveforms varies
with numerical resolution, initial angular momentum of the black holes and the
inclination angle between the source and the detector. This study is limited by
the fact that the spinning black-hole-binaries are oriented axially and the
waveforms only contain approximately two and a half orbits before merger. We
find that for detection purposes, spinning black holes require the inclusion of
the higher harmonics in addition to the dominant mode, a condition that becomes
more important as the black-hole-spins increase. In addition, we conduct a
preliminary investigation of how well a template of fixed spin and inclination
angle can detect target templates of arbitrary spin and inclination for the
axial case considered here.
| [
{
"created": "Fri, 25 May 2007 18:57:53 GMT",
"version": "v1"
},
{
"created": "Sun, 27 May 2007 18:36:30 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Vaishnav",
"Birjoo",
""
],
[
"Hinder",
"Ian",
""
],
[
"Herrmann",
"Frank",
""
],
[
"Shoemaker",
"Deirdre",
""
]
] | Tremendous progress has been made towards the solution of the binary-black-hole problem in numerical relativity. The waveforms produced by numerical relativity will play a role in gravitational wave detection as either test-beds for analytic template banks or as template banks themselves. As the parameter space explored by numerical relativity expands, the importance of quantifying the effect that each parameter has on first the detection of gravitational waves and then the parameter estimation of their sources increases. In light of this, we present a study of equal-mass, spinning binary-black-hole evolutions through matched filtering techniques commonly used in data analysis. We study how the match between two numerical waveforms varies with numerical resolution, initial angular momentum of the black holes and the inclination angle between the source and the detector. This study is limited by the fact that the spinning black-hole-binaries are oriented axially and the waveforms only contain approximately two and a half orbits before merger. We find that for detection purposes, spinning black holes require the inclusion of the higher harmonics in addition to the dominant mode, a condition that becomes more important as the black-hole-spins increase. In addition, we conduct a preliminary investigation of how well a template of fixed spin and inclination angle can detect target templates of arbitrary spin and inclination for the axial case considered here. |
1006.5412 | Anil Yadav dr | Anil Kumar Yadav, Farook Rahaman and Saibal Ray | Dark energy models with variable equation of state parameter | 8 pages, 6 figures | Int.J.Theor.Phys.50:871-881,2011 | 10.1007/s10773-010-0628-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dark energy models with variable equation of state parameter $\omega$ is
investigated by using law of variation of Hubble's parameter that yields the
constant value of deceleration parameter. The equation of state parameter
$\omega$ is found to be time dependent and its existing range for this model is
consistent with the recent observations of SN Ia data, SN Ia data (with CMBR
anisotropy) and galaxy clustering statistics. The physical significance of the
dark energy models has also been discussed.
| [
{
"created": "Mon, 28 Jun 2010 17:18:55 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Sep 2010 16:29:05 GMT",
"version": "v2"
}
] | 2011-02-01 | [
[
"Yadav",
"Anil Kumar",
""
],
[
"Rahaman",
"Farook",
""
],
[
"Ray",
"Saibal",
""
]
] | The dark energy models with variable equation of state parameter $\omega$ is investigated by using law of variation of Hubble's parameter that yields the constant value of deceleration parameter. The equation of state parameter $\omega$ is found to be time dependent and its existing range for this model is consistent with the recent observations of SN Ia data, SN Ia data (with CMBR anisotropy) and galaxy clustering statistics. The physical significance of the dark energy models has also been discussed. |
2401.15809 | Arthur Garnier | Arthur Garnier | Particle dynamics in spherically symmetric electro-vacuum instantons | null | null | 10.1140/epjc/s10052-024-12719-4 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we study the geodesic motion in spherically symmetric
electro-vacuum Euclidean solutions of the Einstein equation. There are two
kinds of such solutions: the Euclidean Reissner-Nordstr\"{o}m (ERN) metrics,
and the Bertotti-Robinson-like (BR) metrics, the latter having constant
Kretschmann scalar. First, we derive the motion equations for the ERN spacetime
and we generalize the results of Battista-Esposito, showing that all orbits in
as ERN spacetime are unbounded if and only if it has an event horizon. We also
obtain the Weierstrass form of the polar radial motion, providing an efficient
tool for numerical computations. We then study the angular deflection of orbits
in the Euclidean Schwarzschild spacetime which, in contrast to the Lorentzian
background, can be either positive or negative. We observe the presence of a
null and a maximal deflection rings for particles with velocity at infinity
$v>1$ and we give approximate values for their size when $v\gtrsim1$. For BR
spacetimes, we obtain analytic solutions for the radial motion in proper
length, involving (hyperbolic) trigonometric functions and we deduce that
orbits either exponentially go to the singularity or are periodic. Finally, we
apply the previous results and use algorithms related to Weierstrass' elliptic
functions to produce a Python code to plot orbits of the spacetimes ERN and BR,
and draw "shadows" of the first ones, as it was already done before for
classical black holes.
| [
{
"created": "Mon, 29 Jan 2024 00:12:32 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Apr 2024 15:53:19 GMT",
"version": "v2"
}
] | 2024-04-17 | [
[
"Garnier",
"Arthur",
""
]
] | In this paper, we study the geodesic motion in spherically symmetric electro-vacuum Euclidean solutions of the Einstein equation. There are two kinds of such solutions: the Euclidean Reissner-Nordstr\"{o}m (ERN) metrics, and the Bertotti-Robinson-like (BR) metrics, the latter having constant Kretschmann scalar. First, we derive the motion equations for the ERN spacetime and we generalize the results of Battista-Esposito, showing that all orbits in as ERN spacetime are unbounded if and only if it has an event horizon. We also obtain the Weierstrass form of the polar radial motion, providing an efficient tool for numerical computations. We then study the angular deflection of orbits in the Euclidean Schwarzschild spacetime which, in contrast to the Lorentzian background, can be either positive or negative. We observe the presence of a null and a maximal deflection rings for particles with velocity at infinity $v>1$ and we give approximate values for their size when $v\gtrsim1$. For BR spacetimes, we obtain analytic solutions for the radial motion in proper length, involving (hyperbolic) trigonometric functions and we deduce that orbits either exponentially go to the singularity or are periodic. Finally, we apply the previous results and use algorithms related to Weierstrass' elliptic functions to produce a Python code to plot orbits of the spacetimes ERN and BR, and draw "shadows" of the first ones, as it was already done before for classical black holes. |
2110.12941 | Alejandro Torres Forn\'e | Ainara Saiz-P\'erez, Alejandro Torres-Forn\'e, and Jos\'e A. Font | Classification of the core-collapse supernova explosion mechanism with
learned dictionaries | null | null | 10.1093/mnras/stac698 | null | gr-qc astro-ph.HE astro-ph.IM astro-ph.SR | http://creativecommons.org/licenses/by/4.0/ | Core-collapse supernovae (CCSN) are a prime source of gravitational waves.
Estimations of their typical frequencies make them perfect targets for the
current network of advanced, ground-based detectors. A successful detection
could potentially reveal the underlying explosion mechanism through the
analysis of the waveform. This has been illustrated using the SupernovaModel
Evidence Extractor (SMEE; Logue et al. (2012)), an algorithm based on
principal-component analysis and Bayesian model selection. Here, we present a
complementary approach to SMEE based on (supervised) dictionary-learning and
show that it is able to reconstruct and classify CCSN signals according to
their morphology. Our waveform signals are obtained from (a) two publicly
available catalogs built from numerical simulations of neutrino-driven (Mur)
and magneto-rotational (Dim) CCSN explosions and (b) from a third 'mock'
catalog of simulated sine-Gaussian (SG) waveforms. Those signals are injected
into coloured Gaussian noise to simulate the background noise of Advanced LIGO
in its broadband configuration and scaled to a freely-specifiable
signal-to-noise ratio (SNR). We show that our approach correctly classifies
signals from all three dictionaries. In particular, for SNR=15-20, we obtain
perfect matches for both Dim and SG signals and about 85% true classifications
for Mur signals. These results are comparable to those reported by SMEE for the
same CCSN signals when those are injected in only one LIGO detector. We discuss
the main limitations of our approach as well as possible improvements.
| [
{
"created": "Mon, 25 Oct 2021 13:22:08 GMT",
"version": "v1"
}
] | 2022-03-30 | [
[
"Saiz-Pérez",
"Ainara",
""
],
[
"Torres-Forné",
"Alejandro",
""
],
[
"Font",
"José A.",
""
]
] | Core-collapse supernovae (CCSN) are a prime source of gravitational waves. Estimations of their typical frequencies make them perfect targets for the current network of advanced, ground-based detectors. A successful detection could potentially reveal the underlying explosion mechanism through the analysis of the waveform. This has been illustrated using the SupernovaModel Evidence Extractor (SMEE; Logue et al. (2012)), an algorithm based on principal-component analysis and Bayesian model selection. Here, we present a complementary approach to SMEE based on (supervised) dictionary-learning and show that it is able to reconstruct and classify CCSN signals according to their morphology. Our waveform signals are obtained from (a) two publicly available catalogs built from numerical simulations of neutrino-driven (Mur) and magneto-rotational (Dim) CCSN explosions and (b) from a third 'mock' catalog of simulated sine-Gaussian (SG) waveforms. Those signals are injected into coloured Gaussian noise to simulate the background noise of Advanced LIGO in its broadband configuration and scaled to a freely-specifiable signal-to-noise ratio (SNR). We show that our approach correctly classifies signals from all three dictionaries. In particular, for SNR=15-20, we obtain perfect matches for both Dim and SG signals and about 85% true classifications for Mur signals. These results are comparable to those reported by SMEE for the same CCSN signals when those are injected in only one LIGO detector. We discuss the main limitations of our approach as well as possible improvements. |
2206.02813 | Alexandre Pombo | Carlos A.R. Herdeiro, Jo\~ao M.S. Oliveira, Alexandre M. Pombo, Eugen
Radu | Deconstructing scaling virial identities in General Relativity:
spherical symmetry and beyond | 14 pages | null | 10.1103/PhysRevD.106.024054 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Derrick-type virial identities, obtained via dilatation (scaling) arguments,
have a variety of applications in field theories. We deconstruct such virial
identities in relativistic gravity showing how they can be recast as
self-evident integrals of appropriate combinations of the equations of motion.
In spherical symmetry, the appropriate combination and gauge choice guarantee
the geometric part can be integrated out to yield a master form of the virial
identity as a non-trivial energy-momentum balance condition, valid for both
asymptotically flat black holes and self-gravitating solitons, for any matter
model. Specifying the matter model we recover previous results obtained via the
scaling procedure. We then discuss the more general case of stationary,
axi-symmetric, asymptotically flat black hole or solitonic solutions in General
Relativity, for which a master form for their virial identity is proposed, in a
specific gauge but regardless of the matter content. In the flat spacetime
limit, the master virial identity for both the spherical and axial cases
reduces to a balance condition for the principal pressures, discussed by Deser.
| [
{
"created": "Mon, 6 Jun 2022 18:00:03 GMT",
"version": "v1"
}
] | 2022-08-17 | [
[
"Herdeiro",
"Carlos A. R.",
""
],
[
"Oliveira",
"João M. S.",
""
],
[
"Pombo",
"Alexandre M.",
""
],
[
"Radu",
"Eugen",
""
]
] | Derrick-type virial identities, obtained via dilatation (scaling) arguments, have a variety of applications in field theories. We deconstruct such virial identities in relativistic gravity showing how they can be recast as self-evident integrals of appropriate combinations of the equations of motion. In spherical symmetry, the appropriate combination and gauge choice guarantee the geometric part can be integrated out to yield a master form of the virial identity as a non-trivial energy-momentum balance condition, valid for both asymptotically flat black holes and self-gravitating solitons, for any matter model. Specifying the matter model we recover previous results obtained via the scaling procedure. We then discuss the more general case of stationary, axi-symmetric, asymptotically flat black hole or solitonic solutions in General Relativity, for which a master form for their virial identity is proposed, in a specific gauge but regardless of the matter content. In the flat spacetime limit, the master virial identity for both the spherical and axial cases reduces to a balance condition for the principal pressures, discussed by Deser. |
gr-qc/0605122 | Ilia Musco | Alexander G. Polnarev (1), Ilia Musco (1). ((1)Astronomy Unit, Queen
Mary University of London) | Curvature profiles as initial conditions for primordial black hole
formation | 31 pages, submitted to Class. Quant. Grav. In this version many
changes: new results and discussions | Class.Quant.Grav.24:1405-1432,2007 | 10.1088/0264-9381/24/6/003 | null | gr-qc | null | This work is part of an ongoing research programme to study possible
Primordial Black Hole (PBH) formation during the radiation dominated era of the
early universe. Working within spherical symmetry, we specify an initial
configuration in terms of a curvature profile, which represents initial
conditions for the large amplitude metric perturbations, away from the
homogeneous Friedmann Robertson Walker model, which are required for PBH
formation. Using an asymptotic quasi-homogeneous solution, we relate the
curvature profile with the density and velocity fields, which at an early
enough time, when the length scale of the configuration is much larger than the
cosmological horizon, can be treated as small perturbations of the background
values. We present general analytic solutions for the density and velocity
profiles. These solutions enable us to consider in a self-consistent way the
formation of PBHs in a wide variety of cosmological situations with the
cosmological fluid being treated as an arbitrary mixture of different
components with different equations of state. We show that the analytical
solutions for the density and velocity profiles as functions of the initial
time are pure growing modes. We then use two different parametrisation for the
curvature profile and follow numerically the evolution of a range of initial
configuration.
| [
{
"created": "Wed, 24 May 2006 18:00:09 GMT",
"version": "v1"
},
{
"created": "Thu, 25 May 2006 19:55:26 GMT",
"version": "v2"
},
{
"created": "Tue, 30 May 2006 19:22:31 GMT",
"version": "v3"
},
{
"created": "Sun, 16 Jul 2006 22:03:51 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Polnarev",
"Alexander G.",
""
],
[
"Musco",
"Ilia",
""
],
[
".",
"",
""
]
] | This work is part of an ongoing research programme to study possible Primordial Black Hole (PBH) formation during the radiation dominated era of the early universe. Working within spherical symmetry, we specify an initial configuration in terms of a curvature profile, which represents initial conditions for the large amplitude metric perturbations, away from the homogeneous Friedmann Robertson Walker model, which are required for PBH formation. Using an asymptotic quasi-homogeneous solution, we relate the curvature profile with the density and velocity fields, which at an early enough time, when the length scale of the configuration is much larger than the cosmological horizon, can be treated as small perturbations of the background values. We present general analytic solutions for the density and velocity profiles. These solutions enable us to consider in a self-consistent way the formation of PBHs in a wide variety of cosmological situations with the cosmological fluid being treated as an arbitrary mixture of different components with different equations of state. We show that the analytical solutions for the density and velocity profiles as functions of the initial time are pure growing modes. We then use two different parametrisation for the curvature profile and follow numerically the evolution of a range of initial configuration. |
2010.12677 | Mu-Tao Wang | Mu-Tao Wang | Quasi-local mass and isometric embedding with reference to a static
spacetime | to appear in Advanced Studies in Pure Mathematics 85, 2020, The Role
of Metrics in the Theory of Partial Differential Equations | null | null | null | gr-qc math-ph math.AP math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The mathematical theory of isometric embedding is applied to study the notion
of quasilocal mass in general relativity. In particular, I shall report some
recent progress of quasilocal mass with reference to a cosmological spacetime,
such as the de Sitter or the Anti-de Sitter spacetime, or a blackhole
spacetime, such as the Schwarzschild spacetime. This article is based on joint
work with Po-Ning Chen, Ye-Kai Wang, and Shing-Tung Yau.
| [
{
"created": "Fri, 23 Oct 2020 21:30:22 GMT",
"version": "v1"
}
] | 2020-10-27 | [
[
"Wang",
"Mu-Tao",
""
]
] | The mathematical theory of isometric embedding is applied to study the notion of quasilocal mass in general relativity. In particular, I shall report some recent progress of quasilocal mass with reference to a cosmological spacetime, such as the de Sitter or the Anti-de Sitter spacetime, or a blackhole spacetime, such as the Schwarzschild spacetime. This article is based on joint work with Po-Ning Chen, Ye-Kai Wang, and Shing-Tung Yau. |
1307.6265 | Yun Soo Myung | Yun Soo Myung | Comment on Ricci dark energy in Chern-Simons modified gravity | 7 pages, 2 figures, version to appear in EPJC | null | 10.1140/epjc/s10052-013-2515-6 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit Ricci dark energy in Chern-Simons modified gravity. As far as the
cosmological evolution, this is nothing but the Ricci dark energy with a
minimally coupled scalar without potential which means that the role of
Chern-Simons term is suppressed. Using the equation of state parameter, this
model is similar to the modified Chaplygin gas model only when two are around
the de Sitter universe deriving by the cosmological constant in the future.
However, two past evolutions are different.
| [
{
"created": "Tue, 23 Jul 2013 23:13:34 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Myung",
"Yun Soo",
""
]
] | We revisit Ricci dark energy in Chern-Simons modified gravity. As far as the cosmological evolution, this is nothing but the Ricci dark energy with a minimally coupled scalar without potential which means that the role of Chern-Simons term is suppressed. Using the equation of state parameter, this model is similar to the modified Chaplygin gas model only when two are around the de Sitter universe deriving by the cosmological constant in the future. However, two past evolutions are different. |
gr-qc/0509113 | Sigbjorn Hervik | Alan Coley, Sigbjorn Hervik, Nicos Pelavas | On Spacetimes with Constant Scalar Invariants | 25 pages, 1 figure, v2: minor changes throughout | Class.Quant.Grav.23:3053-3074,2006 | 10.1088/0264-9381/23/9/018 | null | gr-qc hep-th math-ph math.MP | null | We study Lorentzian spacetimes for which all scalar invariants constructed
from the Riemann tensor and its covariant derivatives are constant ($CSI$
spacetimes). We obtain a number of general results in arbitrary dimensions. We
study and construct warped product $CSI$ spacetimes and higher-dimensional
Kundt $CSI$ spacetimes. We show how these spacetimes can be constructed from
locally homogeneous spaces and $VSI$ spacetimes. The results suggest a number
of conjectures. In particular, it is plausible that for $CSI$ spacetimes that
are not locally homogeneous the Weyl type is $II$, $III$, $N$ or $O$, with any
boost weight zero components being constant. We then consider the
four-dimensional $CSI$ spacetimes in more detail. We show that there are severe
constraints on these spacetimes, and we argue that it is plausible that they
are either locally homogeneous or that the spacetime necessarily belongs to the
Kundt class of $CSI$ spacetimes, all of which are constructed. The
four-dimensional results lend support to the conjectures in higher dimensions.
| [
{
"created": "Wed, 28 Sep 2005 16:44:29 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Apr 2006 16:20:35 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Coley",
"Alan",
""
],
[
"Hervik",
"Sigbjorn",
""
],
[
"Pelavas",
"Nicos",
""
]
] | We study Lorentzian spacetimes for which all scalar invariants constructed from the Riemann tensor and its covariant derivatives are constant ($CSI$ spacetimes). We obtain a number of general results in arbitrary dimensions. We study and construct warped product $CSI$ spacetimes and higher-dimensional Kundt $CSI$ spacetimes. We show how these spacetimes can be constructed from locally homogeneous spaces and $VSI$ spacetimes. The results suggest a number of conjectures. In particular, it is plausible that for $CSI$ spacetimes that are not locally homogeneous the Weyl type is $II$, $III$, $N$ or $O$, with any boost weight zero components being constant. We then consider the four-dimensional $CSI$ spacetimes in more detail. We show that there are severe constraints on these spacetimes, and we argue that it is plausible that they are either locally homogeneous or that the spacetime necessarily belongs to the Kundt class of $CSI$ spacetimes, all of which are constructed. The four-dimensional results lend support to the conjectures in higher dimensions. |
0907.1311 | Dennis Bessada | Dennis Bessada, William H. Kinney, Konstantinos Tzirakis | Inflationary potentials in DBI models | Minor changes, reference added. Version submitted to JCAP | JCAP 0909:031,2009 | 10.1088/1475-7516/2009/09/031 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study DBI inflation based upon a general model characterized by a
power-law flow parameter $\epsilon(\phi)\propto\phi^{\alpha}$ and speed of
sound $c_s(\phi)\propto\phi^{\beta}$, where $\alpha$ and $\beta$ are constants.
We show that in the slow-roll limit this general model gives rise to distinct
inflationary classes according to the relation between $\alpha$ and $\beta$ and
to the time evolution of the inflaton field, each one corresponding to a
specific potential; in particular, we find that the well-known canonical
polynomial (large- and small-field), hybrid and exponential potentials also
arise in this non-canonical model. We find that these non-canonical classes
have the same physical features as their canonical analogs, except for the fact
that the inflaton field evolves with varying speed of sound; also, we show that
a broad class of canonical and D-brane inflation models are particular cases of
this general non-canonical model. Next, we compare the predictions of
large-field polynomial models with the current observational data, showing that
models with low speed of sound have red-tilted scalar spectrum with low
tensor-to-scalar ratio, in good agreement with the observed values. These
models also show a correlation between large non-gaussianity with low tensor
amplitudes, which is a distinct signature of DBI inflation with large-field
polynomial potentials.
| [
{
"created": "Tue, 7 Jul 2009 22:12:54 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Aug 2009 17:22:02 GMT",
"version": "v2"
}
] | 2009-10-02 | [
[
"Bessada",
"Dennis",
""
],
[
"Kinney",
"William H.",
""
],
[
"Tzirakis",
"Konstantinos",
""
]
] | We study DBI inflation based upon a general model characterized by a power-law flow parameter $\epsilon(\phi)\propto\phi^{\alpha}$ and speed of sound $c_s(\phi)\propto\phi^{\beta}$, where $\alpha$ and $\beta$ are constants. We show that in the slow-roll limit this general model gives rise to distinct inflationary classes according to the relation between $\alpha$ and $\beta$ and to the time evolution of the inflaton field, each one corresponding to a specific potential; in particular, we find that the well-known canonical polynomial (large- and small-field), hybrid and exponential potentials also arise in this non-canonical model. We find that these non-canonical classes have the same physical features as their canonical analogs, except for the fact that the inflaton field evolves with varying speed of sound; also, we show that a broad class of canonical and D-brane inflation models are particular cases of this general non-canonical model. Next, we compare the predictions of large-field polynomial models with the current observational data, showing that models with low speed of sound have red-tilted scalar spectrum with low tensor-to-scalar ratio, in good agreement with the observed values. These models also show a correlation between large non-gaussianity with low tensor amplitudes, which is a distinct signature of DBI inflation with large-field polynomial potentials. |
2201.11804 | Mikhail Khlopunov | M. Khlopunov, D. V. Gal'tsov | Gravitational radiation from a binary system in odd-dimensional
spacetime | 47 pages, 1 figure | null | 10.1088/1475-7516/2022/04/014 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We explore possible manifestations of an odd number of extra dimensions in
gravitational radiation, which are associated with violation of Huygens'
principle in flat odd-dimensional spacetime. Our setup can be regarded as the
limit of an infinite compactification radius in ADD model and is not viable as
realistic cosmology, but it still may be useful as a simple analytically
solvable model catching certain features of more realistic scenarios. The model
consists of two point masses moving inside a flat three-dimensional brane,
embedded in a five-dimensional Minkowski space and interacting only through a
massless scalar field localized on the same brane, while gravitational
radiation is emitted into the bulk. This setup avoids the difficulties
associated with taking into account the gravitational stresses binding the
system, which require the cubic terms in the perturbative gravitational
Lagrangian, and permits to limit ourselves to linearized theory. We calculate
radiation in a linearized five-dimensional gravity generalizing the
Rohrlich-Teitelboim approach to extract the emitted part of the retarded
gravitational field. The source term consists of a local contribution from
point particles and a non-local contribution from scalar field stresses, which
is calculated using the DIRE approach to post-Newtonian expansions. In the
nonrelativistic limit, we find an analog of the quadrupole formula containing
an integral over the history of the particles' motion preceding the retarded
time. We also show that, for an observer on the brane, the radiation contains a
third polarization: the breathing mode.
| [
{
"created": "Thu, 27 Jan 2022 20:50:43 GMT",
"version": "v1"
}
] | 2022-04-20 | [
[
"Khlopunov",
"M.",
""
],
[
"Gal'tsov",
"D. V.",
""
]
] | We explore possible manifestations of an odd number of extra dimensions in gravitational radiation, which are associated with violation of Huygens' principle in flat odd-dimensional spacetime. Our setup can be regarded as the limit of an infinite compactification radius in ADD model and is not viable as realistic cosmology, but it still may be useful as a simple analytically solvable model catching certain features of more realistic scenarios. The model consists of two point masses moving inside a flat three-dimensional brane, embedded in a five-dimensional Minkowski space and interacting only through a massless scalar field localized on the same brane, while gravitational radiation is emitted into the bulk. This setup avoids the difficulties associated with taking into account the gravitational stresses binding the system, which require the cubic terms in the perturbative gravitational Lagrangian, and permits to limit ourselves to linearized theory. We calculate radiation in a linearized five-dimensional gravity generalizing the Rohrlich-Teitelboim approach to extract the emitted part of the retarded gravitational field. The source term consists of a local contribution from point particles and a non-local contribution from scalar field stresses, which is calculated using the DIRE approach to post-Newtonian expansions. In the nonrelativistic limit, we find an analog of the quadrupole formula containing an integral over the history of the particles' motion preceding the retarded time. We also show that, for an observer on the brane, the radiation contains a third polarization: the breathing mode. |
gr-qc/0206020 | Fay Dowker | Fay Dowker | Topology change in quantum gravity | LaTeX, 18 pages. Contribution to the proceedings of the Stephen
Hawking 60th birthday conference, Cambridge, January 2002 | null | null | null | gr-qc hep-th | null | A particular approach to topology change in quantum gravity is reviewed,
showing that several aspects of Stephen's work are intertwined with it in an
essential way. Speculations are made on possible implications for the causal
set approach to quantum gravity.
| [
{
"created": "Fri, 7 Jun 2002 11:31:56 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Dowker",
"Fay",
""
]
] | A particular approach to topology change in quantum gravity is reviewed, showing that several aspects of Stephen's work are intertwined with it in an essential way. Speculations are made on possible implications for the causal set approach to quantum gravity. |
2206.04608 | Gerard Hooft 't | Gerard t Hooft | Quantum clones inside black holes | 16 pages (incl. title page), 1 figure | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | A systematic procedure is proposed for better understanding the evolution
laws of black holes in terms of pure quantum states. We start with the two
opposed regions I and II in the Penrose diagram, and study the evolution of
matter in these regions, using the algebra derived earlier from the Shapiro
effect in quantum particles. Since this spacetime has two distinct asymptotic
regions, one must assume that there is a mechanism that reduces the number of
states. In earlier work we proposed that region II describes the angular
antipodes of region I, the `antipodal identification', but this eventually
leads to contradictions. Our much simpler proposal is now that all states
defined in region II are exact quantum clones of those in region I. This
indicates more precisely how to restore unitarity by making all quantum states
observable, and in addition suggests that generalisations towards other black
hole structures will be possible. An apparent complication is that the wave
function must evolve with a purely antisymmetric, imaginary-valued Hamiltonian,
but this complication can be well-understood in a realistic interpretation of
quantum mechanics.
| [
{
"created": "Thu, 9 Jun 2022 16:55:54 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Jun 2022 10:14:22 GMT",
"version": "v2"
},
{
"created": "Fri, 22 Jul 2022 16:48:43 GMT",
"version": "v3"
},
{
"created": "Thu, 8 Sep 2022 12:12:18 GMT",
"version": "v4"
}
] | 2022-09-09 | [
[
"Hooft",
"Gerard t",
""
]
] | A systematic procedure is proposed for better understanding the evolution laws of black holes in terms of pure quantum states. We start with the two opposed regions I and II in the Penrose diagram, and study the evolution of matter in these regions, using the algebra derived earlier from the Shapiro effect in quantum particles. Since this spacetime has two distinct asymptotic regions, one must assume that there is a mechanism that reduces the number of states. In earlier work we proposed that region II describes the angular antipodes of region I, the `antipodal identification', but this eventually leads to contradictions. Our much simpler proposal is now that all states defined in region II are exact quantum clones of those in region I. This indicates more precisely how to restore unitarity by making all quantum states observable, and in addition suggests that generalisations towards other black hole structures will be possible. An apparent complication is that the wave function must evolve with a purely antisymmetric, imaginary-valued Hamiltonian, but this complication can be well-understood in a realistic interpretation of quantum mechanics. |
gr-qc/9703047 | Peter Breitenlohner | Peter Breitenlohner (1), George Lavrelashvili (2) and Dieter Maison
(1) ((1) Max-Planck-Institut f\"ur Physik - Werner Heisenberg Institut -
Munich, (2) Institute for Theoretical Physics, University of Bern) | Mass inflation and chaotic behaviour inside hairy black holes | 22 pages, Latex, 5 figures (8 eps files) | Nucl.Phys.B524:427-443,1998 | 10.1016/S0550-3213(98)00177-1 | MPI-PhT/97-20 and BUTP-97/08 | gr-qc hep-th | null | We analyze the interior geometry of static, spherically symmetric black holes
of the Einstein-Yang-Mills-Higgs theory. Generically the solutions exhibit a
behaviour that may be described as ``mass inflation'', although with a
remarkable difference between the cases with and without a Higgs field. Without
Higgs field the YM field induces a kind of cyclic behaviour leading to repeated
cycles of mass inflation - taking the form of violent explosions - interrupted
by quiescent periods and subsequent approaches to an almost Cauchy horizon.
With the Higgs field no such cycles occur. In addition there are non-generic
families with a Schwarzschild resp. Reissner-Nordstr{\o}m type singularity at
r=0.
| [
{
"created": "Tue, 18 Mar 1997 17:21:29 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Breitenlohner",
"Peter",
""
],
[
"Lavrelashvili",
"George",
""
],
[
"Maison",
"Dieter",
""
]
] | We analyze the interior geometry of static, spherically symmetric black holes of the Einstein-Yang-Mills-Higgs theory. Generically the solutions exhibit a behaviour that may be described as ``mass inflation'', although with a remarkable difference between the cases with and without a Higgs field. Without Higgs field the YM field induces a kind of cyclic behaviour leading to repeated cycles of mass inflation - taking the form of violent explosions - interrupted by quiescent periods and subsequent approaches to an almost Cauchy horizon. With the Higgs field no such cycles occur. In addition there are non-generic families with a Schwarzschild resp. Reissner-Nordstr{\o}m type singularity at r=0. |
2201.00027 | Niayesh Afshordi | Randy S. Conklin, Niayesh Afshordi | Boltzmann Meets Lorentz: A Surrogate Model for Black Hole Echoes | 19 pages, 29 figures, comments are welcome | null | null | null | gr-qc astro-ph.CO astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | The existence of black hole horizons has not been strictly proven
observationally, and indeed it may not be possible to do so. However,
alternatives may be established by the observation of gravitational wave echoes
that probe possible near-horizon structure. These echoes are proposed to be
generated in exotic compact objects that are horizonless and feature a
partially reflecting "wall" inside their light rings, creating a cavity in
which gravitational perturbations may echo, while leaking out through the
angular momentum barrier with each pass. The characteristic signature of echoes
is a comb of nearly evenly spaced spectral resonances. While approximately
true, deviations from this simple picture can lead to severe observational
signal losses. In this paper, we explore such subtleties with the latest
results for echo sourcing and geometry. A physically motivated echo model is
then developed as a sum over Lorentzian spectral lines, parametrized by
functions of the horizon frame frequency and the size of the cavity. Our final
spectrum is a function of only the mass and spin of the black hole, as well as
the UV scale of the near-horizon physics. We then apply this model in a search
for echoes in the gravitational wave event with the loudest ringdown signal in
LIGO/Virgo, i.e. GW190521. We interpret our findings as a measurement of the
fractional energy in post-merger echoes equal to $E_{echoes} / E_{GR} = 8.9 \pm
4.5\%$, where the uncertainty range represents the 90% credible region. The
robustness of this result is tested against noise backgrounds and simulated
injections, and we find that a signal persists through modifications to the
model and changes in the data search.
| [
{
"created": "Fri, 31 Dec 2021 19:02:12 GMT",
"version": "v1"
}
] | 2022-01-04 | [
[
"Conklin",
"Randy S.",
""
],
[
"Afshordi",
"Niayesh",
""
]
] | The existence of black hole horizons has not been strictly proven observationally, and indeed it may not be possible to do so. However, alternatives may be established by the observation of gravitational wave echoes that probe possible near-horizon structure. These echoes are proposed to be generated in exotic compact objects that are horizonless and feature a partially reflecting "wall" inside their light rings, creating a cavity in which gravitational perturbations may echo, while leaking out through the angular momentum barrier with each pass. The characteristic signature of echoes is a comb of nearly evenly spaced spectral resonances. While approximately true, deviations from this simple picture can lead to severe observational signal losses. In this paper, we explore such subtleties with the latest results for echo sourcing and geometry. A physically motivated echo model is then developed as a sum over Lorentzian spectral lines, parametrized by functions of the horizon frame frequency and the size of the cavity. Our final spectrum is a function of only the mass and spin of the black hole, as well as the UV scale of the near-horizon physics. We then apply this model in a search for echoes in the gravitational wave event with the loudest ringdown signal in LIGO/Virgo, i.e. GW190521. We interpret our findings as a measurement of the fractional energy in post-merger echoes equal to $E_{echoes} / E_{GR} = 8.9 \pm 4.5\%$, where the uncertainty range represents the 90% credible region. The robustness of this result is tested against noise backgrounds and simulated injections, and we find that a signal persists through modifications to the model and changes in the data search. |
gr-qc/0701109 | Bruno Giacomazzo | B. Giacomazzo (1,2) and L. Rezzolla (1,3) ((1) Albert Einstein
Institute, Golm, Germany, (2) SISSA and INFN, Trieste, Italy, (3) Department
of Physics, Louisiana State University, USA) | WhiskyMHD: a new numerical code for general relativistic
magnetohydrodynamics | minor changes to match the published version | Class.Quant.Grav.24:S235-S258,2007 | 10.1088/0264-9381/24/12/S16 | null | gr-qc astro-ph | null | The accurate modelling of astrophysical scenarios involving compact objects
and magnetic fields, such as the collapse of rotating magnetized stars to black
holes or the phenomenology of gamma-ray bursts, requires the solution of the
Einstein equations together with those of general-relativistic
magnetohydrodynamics. We present a new numerical code developed to solve the
full set of general-relativistic magnetohydrodynamics equations in a dynamical
and arbitrary spacetime with high-resolution shock-capturing techniques on
domains with adaptive mesh refinements. After a discussion of the equations
solved and of the techniques employed, we present a series of testbeds carried
out to validate the code and assess its accuracy. Such tests range from the
solution of relativistic Riemann problems in flat spacetime, over to the
stationary accretion onto a Schwarzschild black hole and up to the evolution of
oscillating magnetized stars in equilibrium and constructed as consistent
solutions of the coupled Einstein-Maxwell equations.
| [
{
"created": "Fri, 19 Jan 2007 19:25:03 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jun 2007 09:17:57 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Giacomazzo",
"B.",
""
],
[
"Rezzolla",
"L.",
""
]
] | The accurate modelling of astrophysical scenarios involving compact objects and magnetic fields, such as the collapse of rotating magnetized stars to black holes or the phenomenology of gamma-ray bursts, requires the solution of the Einstein equations together with those of general-relativistic magnetohydrodynamics. We present a new numerical code developed to solve the full set of general-relativistic magnetohydrodynamics equations in a dynamical and arbitrary spacetime with high-resolution shock-capturing techniques on domains with adaptive mesh refinements. After a discussion of the equations solved and of the techniques employed, we present a series of testbeds carried out to validate the code and assess its accuracy. Such tests range from the solution of relativistic Riemann problems in flat spacetime, over to the stationary accretion onto a Schwarzschild black hole and up to the evolution of oscillating magnetized stars in equilibrium and constructed as consistent solutions of the coupled Einstein-Maxwell equations. |
1905.03237 | Rafael Nunes | Rafael C. Nunes, Marcio E. S. Alves, Jose C. N. de Araujo | Forecast constraints on $f(T)$ gravity with gravitational waves from
compact binary coalescences | 13 pages, 9 captioned figures. Version published in PRD | Phys. Rev. D 100, 064012 (2019) | 10.1103/PhysRevD.100.064012 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The direct detection of gravitational waves (GWs) opened a new chapter in the
modern cosmology to probe possible deviations from the general relativity (GR)
theory. In the present work, we investigate for the first time the modified GW
form propagation from the inspiraling of compact binary systems within the
context of $f(T)$ gravity in order to obtain new forecasts/constraints on the
free parameter of the theory. First, we show that the modified waveform differs
from the GR waveform essentially due to induced corrections on the GWs
amplitude. Then, we discuss the forecasts on the $f(T)$ gravity assuming
simulated sources of GWs as black hole binaries, neutron star binaries and
black hole - neutron star binary systems, which emit GWs in the frequency band
of the Advanced LIGO (aLIGO) interferometer and of the third generation
Einstein Telescope (ET). We show that GWs sources detected within the aLIGO
sensitivity can return estimates of the same order of magnitude of the current
cosmological observations. On the other hand, detection within the ET
sensitivity can improve by up to 2 orders of magnitude the current bound on the
$f(T)$ gravity. Therefore, the statistical accuracy that can be achieved by
future ground based GW observations, mainly with the ET detector (and planed
detectors with a similar sensitivity), can allow strong bounds on the free
parameter of the theory, and can be decisive to test the theory of gravitation.
| [
{
"created": "Wed, 8 May 2019 17:50:16 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Sep 2019 15:06:03 GMT",
"version": "v2"
}
] | 2019-09-16 | [
[
"Nunes",
"Rafael C.",
""
],
[
"Alves",
"Marcio E. S.",
""
],
[
"de Araujo",
"Jose C. N.",
""
]
] | The direct detection of gravitational waves (GWs) opened a new chapter in the modern cosmology to probe possible deviations from the general relativity (GR) theory. In the present work, we investigate for the first time the modified GW form propagation from the inspiraling of compact binary systems within the context of $f(T)$ gravity in order to obtain new forecasts/constraints on the free parameter of the theory. First, we show that the modified waveform differs from the GR waveform essentially due to induced corrections on the GWs amplitude. Then, we discuss the forecasts on the $f(T)$ gravity assuming simulated sources of GWs as black hole binaries, neutron star binaries and black hole - neutron star binary systems, which emit GWs in the frequency band of the Advanced LIGO (aLIGO) interferometer and of the third generation Einstein Telescope (ET). We show that GWs sources detected within the aLIGO sensitivity can return estimates of the same order of magnitude of the current cosmological observations. On the other hand, detection within the ET sensitivity can improve by up to 2 orders of magnitude the current bound on the $f(T)$ gravity. Therefore, the statistical accuracy that can be achieved by future ground based GW observations, mainly with the ET detector (and planed detectors with a similar sensitivity), can allow strong bounds on the free parameter of the theory, and can be decisive to test the theory of gravitation. |
gr-qc/0511097 | Andrew DeBenedictis | A. DeBenedictis, D. Horvat, S. Ilijic, S. Kloster, K. S. Viswanathan | Gravastar Solutions with Continuous Pressures and Equation of State | 19 pages, 9 figures. Latest version contains new and updated
references along with some clarifying remarks in the stability analysis | Class.Quant.Grav. 23 (2006) 2303-2316 | 10.1088/0264-9381/23/7/007 | null | gr-qc astro-ph hep-th | null | We study the gravitational vacuum star (gravastar) configuration as proposed
by other authors in a model where the interior de Sitter spacetime segment is
continuously extended to the exterior Schwarzschild spacetime. The multilayered
structure in previous papers is replaced by a continuous stress-energy tensor
at the price of introducing anisotropy in the (fluid) model of the gravastar.
Either with an ansatz for the equation of state connecting the radial $p_r$ and
tangential $p_t$ pressure or with a calculated equation of state with
non-homogeneous energy/fluid density, solutions are obtained which in all
aspects satisfy the conditions expected for an anisotropic gravastar. Certain
energy conditions have been shown to be obeyed and a polytropic equation of
state has been derived. Stability of the solution with respect to possible
axial perturbation is shown to hold.
| [
{
"created": "Thu, 17 Nov 2005 03:26:41 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Feb 2006 20:48:48 GMT",
"version": "v2"
},
{
"created": "Tue, 19 Jun 2007 16:18:29 GMT",
"version": "v3"
}
] | 2007-06-19 | [
[
"DeBenedictis",
"A.",
""
],
[
"Horvat",
"D.",
""
],
[
"Ilijic",
"S.",
""
],
[
"Kloster",
"S.",
""
],
[
"Viswanathan",
"K. S.",
""
]
] | We study the gravitational vacuum star (gravastar) configuration as proposed by other authors in a model where the interior de Sitter spacetime segment is continuously extended to the exterior Schwarzschild spacetime. The multilayered structure in previous papers is replaced by a continuous stress-energy tensor at the price of introducing anisotropy in the (fluid) model of the gravastar. Either with an ansatz for the equation of state connecting the radial $p_r$ and tangential $p_t$ pressure or with a calculated equation of state with non-homogeneous energy/fluid density, solutions are obtained which in all aspects satisfy the conditions expected for an anisotropic gravastar. Certain energy conditions have been shown to be obeyed and a polytropic equation of state has been derived. Stability of the solution with respect to possible axial perturbation is shown to hold. |
2103.06667 | Yan-Gang Miao | Xin-Chang Cai, Yan-Gang Miao | Connections between entropy surface density and microscopic property in
black holes | v1: 16 pages, 7 figures; v2: clarifications added and typos corrected | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a new microscopic quantity $\varepsilon $ that describes the
contribution of a single black hole molecule to black hole entropy and give a
key relation that this microscopic quantity is proportional to the macroscopic
quantity -- entropy surface density $\sigma_{S}$, thus connecting a microscopic
quantity to a macroscopic quantity of black holes. Such a connection provides a
new probe for understanding the black hole microstructure from the macroscopic
perspective. We also classify black holes in terms of entropy surface density.
When its entropy surface density is larger (smaller) than $1/4$, this type of
black holes is defined as strong (weak) Bekenstein-Hawking black holes, where
the black holes with $1/4$-entropy surface density are regarded as
Bekenstein-Hawking black holes. We compute the entropy surface density for four
models, where three of them are regular black holes -- the Bardeen black hole,
the Ay\'{o}n-Beato-Garc\'{\i}a black hole, and the Hayward black hole, and one
of them is a singular black hole -- the five-dimensional neutral Gauss-Bonnet
black hole. Under this scheme of classification, the Bardeen black hole, the
Ay\'{o}n-Beato-Garc\'{\i}a black hole, and the five-dimensional neutral
Gauss-Bonnet black hole belong to the type of strong Bekenstein-Hawking black
holes, but the Hayward black hole belongs to the type of weak
Bekenstein-Hawking black holes, and the four black holes approach to the
Bekenstein-Hawking black hole if their event horizon radii go to infinity. In
addition, we find interesting properties in phase transitions from the
viewpoint of entropy surface density, or equivalently from the viewpoint of a
single black hole molecule entropy, for the five-dimensional neutral
Gauss-Bonnet AdS black hole.
| [
{
"created": "Thu, 11 Mar 2021 13:45:31 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Mar 2021 10:34:16 GMT",
"version": "v2"
}
] | 2021-03-30 | [
[
"Cai",
"Xin-Chang",
""
],
[
"Miao",
"Yan-Gang",
""
]
] | We introduce a new microscopic quantity $\varepsilon $ that describes the contribution of a single black hole molecule to black hole entropy and give a key relation that this microscopic quantity is proportional to the macroscopic quantity -- entropy surface density $\sigma_{S}$, thus connecting a microscopic quantity to a macroscopic quantity of black holes. Such a connection provides a new probe for understanding the black hole microstructure from the macroscopic perspective. We also classify black holes in terms of entropy surface density. When its entropy surface density is larger (smaller) than $1/4$, this type of black holes is defined as strong (weak) Bekenstein-Hawking black holes, where the black holes with $1/4$-entropy surface density are regarded as Bekenstein-Hawking black holes. We compute the entropy surface density for four models, where three of them are regular black holes -- the Bardeen black hole, the Ay\'{o}n-Beato-Garc\'{\i}a black hole, and the Hayward black hole, and one of them is a singular black hole -- the five-dimensional neutral Gauss-Bonnet black hole. Under this scheme of classification, the Bardeen black hole, the Ay\'{o}n-Beato-Garc\'{\i}a black hole, and the five-dimensional neutral Gauss-Bonnet black hole belong to the type of strong Bekenstein-Hawking black holes, but the Hayward black hole belongs to the type of weak Bekenstein-Hawking black holes, and the four black holes approach to the Bekenstein-Hawking black hole if their event horizon radii go to infinity. In addition, we find interesting properties in phase transitions from the viewpoint of entropy surface density, or equivalently from the viewpoint of a single black hole molecule entropy, for the five-dimensional neutral Gauss-Bonnet AdS black hole. |
gr-qc/0608133 | Detlev Buchholz | Detlev Buchholz and Jan Schlemmer | Local Temperature in Curved Spacetime | 9 pages, no figures; minor changes in the exposition; version as to
appear in CQG | Class.Quant.Grav.24:F25-F31,2007 | 10.1088/0264-9381/24/7/F01 | null | gr-qc hep-th | null | A physically meaningful local concept of temperature is introduced in quantum
field theory on curved spacetime and applied to the example of a massless field
on de Sitter space. It turns out in this model that the equilibrium (Gibbs)
states which can be prepared by a geodesic observer have in general a varying
temperature distribution in the neighborhood of the geodesic and may not even
allow for a consistent thermal interpretation close to the horizon. This
result, which can be traced back to the Unruh effect, illustrates the failure
of a global notion of temperature in curved spacetime and reveals the need for
a local concept, as presented here.
| [
{
"created": "Wed, 30 Aug 2006 16:44:31 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Mar 2007 12:52:09 GMT",
"version": "v2"
}
] | 2010-11-02 | [
[
"Buchholz",
"Detlev",
""
],
[
"Schlemmer",
"Jan",
""
]
] | A physically meaningful local concept of temperature is introduced in quantum field theory on curved spacetime and applied to the example of a massless field on de Sitter space. It turns out in this model that the equilibrium (Gibbs) states which can be prepared by a geodesic observer have in general a varying temperature distribution in the neighborhood of the geodesic and may not even allow for a consistent thermal interpretation close to the horizon. This result, which can be traced back to the Unruh effect, illustrates the failure of a global notion of temperature in curved spacetime and reveals the need for a local concept, as presented here. |
1110.3288 | Cristhian Said Osorio Mayor | H. I. Arcos, C. S. O. Mayor, G. Otalora and J. G. Pereira | Spin-2 fields and helicity | 10 pages. V2: presentation changes and discussion added | Foundations of Physics, Volume 42, Number 10 (2012), 1339-1349 | 10.1007/s10701-012-9670-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By considering the irreducible representations of the Lorentz group, an
analysis of the different spin-2 waves is presented. In particular, the
question of the helicity is discussed. It is concluded that, although from the
point of view of representation theory there are no compelling reasons to
choose between spin-2 waves with helicity = + - 1 or helicity = + - 2,
consistency arguments of the ensuing field theories favor waves with helicity =
+ - 1.
| [
{
"created": "Fri, 14 Oct 2011 18:29:33 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Sep 2012 20:38:58 GMT",
"version": "v2"
}
] | 2012-09-05 | [
[
"Arcos",
"H. I.",
""
],
[
"Mayor",
"C. S. O.",
""
],
[
"Otalora",
"G.",
""
],
[
"Pereira",
"J. G.",
""
]
] | By considering the irreducible representations of the Lorentz group, an analysis of the different spin-2 waves is presented. In particular, the question of the helicity is discussed. It is concluded that, although from the point of view of representation theory there are no compelling reasons to choose between spin-2 waves with helicity = + - 1 or helicity = + - 2, consistency arguments of the ensuing field theories favor waves with helicity = + - 1. |
0801.4702 | Adolfo De Un\'anue | Adolfo De Un\'anue (1), Daniel Sudarsky (1) ((1) Instituto de Ciencias
Nucleares, Universidad Nacional Autonoma de Mexico, Ciudad de Mexico, Mexico) | Phenomenological analysis of quantum collapse as source of the seeds of
cosmic structure | 18 pages, 9 figures | Phys.Rev.D78:043510,2008 | 10.1103/PhysRevD.78.043510 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/3.0/ | The standard inflationary version of the origin of the cosmic structure as
the result of the quantum fluctuations during the early universe is less than
fully satisfactory as has been argued in [A. Perez, H. Sahlmann, and D.
Sudarsky, Class. Quantum Grav., 23, 2317, (2006)]. A proposal is made there of
a way to address the shortcomings by invoking a process similar to the collapse
of the quantum mechanical wave function of the various modes of the inflaton
field. This in turn was inspired on the ideas of R. Penrose about the role that
quantum gravity might play in bringing about such breakdown of the standard
unitary evolution of quantum mechanics. In this paper we study in some detail
the two schemes of collapse considered in the original work together with an
alternative scheme, which can be considered as "more natural" than the former
two. The new scheme, assumes that the collapse follows the correlations
indicated in the Wigner functional of the initial state. We end with
considerations regarding the degree to which the various schemes can be
expected to produce a spectrum that resembles the observed one.
| [
{
"created": "Wed, 30 Jan 2008 16:03:24 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Aug 2008 06:51:28 GMT",
"version": "v2"
}
] | 2012-05-30 | [
[
"De Unánue",
"Adolfo",
""
],
[
"Sudarsky",
"Daniel",
""
]
] | The standard inflationary version of the origin of the cosmic structure as the result of the quantum fluctuations during the early universe is less than fully satisfactory as has been argued in [A. Perez, H. Sahlmann, and D. Sudarsky, Class. Quantum Grav., 23, 2317, (2006)]. A proposal is made there of a way to address the shortcomings by invoking a process similar to the collapse of the quantum mechanical wave function of the various modes of the inflaton field. This in turn was inspired on the ideas of R. Penrose about the role that quantum gravity might play in bringing about such breakdown of the standard unitary evolution of quantum mechanics. In this paper we study in some detail the two schemes of collapse considered in the original work together with an alternative scheme, which can be considered as "more natural" than the former two. The new scheme, assumes that the collapse follows the correlations indicated in the Wigner functional of the initial state. We end with considerations regarding the degree to which the various schemes can be expected to produce a spectrum that resembles the observed one. |
1206.3015 | Luisa T. Buchman | Luisa T. Buchman, Harald P. Pfeiffer, Mark A. Scheel, and Bela
Szilagyi | Simulations of non-equal mass black hole binaries with spectral methods | corresponds to final published version | null | 10.1103/PhysRevD.86.084033 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper presents techniques and results for simulations of unequal mass,
non-spinning black hole binaries with pseudo-spectral methods. Specifically, we
develop an efficient root-finding procedure to ensure the black hole initial
data have the desired masses and spins, we extend the dual coordinate frame
method and eccentricity removal to asymmetric binaries. Furthermore, we
describe techniques to simulate mergers of unequal mass black holes. The second
part of the paper presents numerical simulations of non-spinning black hole
binaries with mass ratios 2, 3, 4 and 6, covering between 15 and 22 orbits,
merger and ringdown. We discuss the accuracy of these simulations, the
evolution of the (initially zero) black hole spins, and the remnant black hole
properties.
| [
{
"created": "Thu, 14 Jun 2012 06:16:36 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Oct 2012 00:55:40 GMT",
"version": "v2"
}
] | 2013-05-30 | [
[
"Buchman",
"Luisa T.",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Szilagyi",
"Bela",
""
]
] | This paper presents techniques and results for simulations of unequal mass, non-spinning black hole binaries with pseudo-spectral methods. Specifically, we develop an efficient root-finding procedure to ensure the black hole initial data have the desired masses and spins, we extend the dual coordinate frame method and eccentricity removal to asymmetric binaries. Furthermore, we describe techniques to simulate mergers of unequal mass black holes. The second part of the paper presents numerical simulations of non-spinning black hole binaries with mass ratios 2, 3, 4 and 6, covering between 15 and 22 orbits, merger and ringdown. We discuss the accuracy of these simulations, the evolution of the (initially zero) black hole spins, and the remnant black hole properties. |
gr-qc/0111001 | Leor Barack | Leor Barack, Yasushi Mino, Hiroyuki Nakano, Amos Ori, and Misao Sasaki | Calculating the gravitational self force in Schwarzschild spacetime | Final publication version. Note corrections to Eqs. (13-15) | Phys.Rev.Lett.88:091101,2002 | 10.1103/PhysRevLett.88.091101 | null | gr-qc | null | We present a practical method for calculating the local gravitational
self-force (often called ``radiation-reaction force'') for a pointlike particle
orbiting a Schwarzschild black hole. This is an implementation of the method of
{\it mode-sum regularization}, in which one first calculates the (finite)
contribution to the force due to each individual multipole mode of the
perturbation, and then applies a certain regularization procedure to the mode
sum. Here we give the values of all the ``regularization parameters'' required
for implementing this regularization procedure, for any geodesic orbit in
Schwarzschild spacetime.
| [
{
"created": "Thu, 1 Nov 2001 19:11:00 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Jan 2002 15:03:19 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Feb 2002 14:44:15 GMT",
"version": "v3"
}
] | 2009-10-09 | [
[
"Barack",
"Leor",
""
],
[
"Mino",
"Yasushi",
""
],
[
"Nakano",
"Hiroyuki",
""
],
[
"Ori",
"Amos",
""
],
[
"Sasaki",
"Misao",
""
]
] | We present a practical method for calculating the local gravitational self-force (often called ``radiation-reaction force'') for a pointlike particle orbiting a Schwarzschild black hole. This is an implementation of the method of {\it mode-sum regularization}, in which one first calculates the (finite) contribution to the force due to each individual multipole mode of the perturbation, and then applies a certain regularization procedure to the mode sum. Here we give the values of all the ``regularization parameters'' required for implementing this regularization procedure, for any geodesic orbit in Schwarzschild spacetime. |
1502.02985 | Andrea Maselli | Irene Milillo, Daniele Bertacca, Marco Bruni and Andrea Maselli | The missing link: a nonlinear post-Friedmann framework for small and
large scales | Small changes to match the version to appear on PRD | null | 10.1103/PhysRevD.92.023519 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a nonlinear post-Friedmann framework for structure formation,
generalizing to cosmology the weak-field (post-Minkowskian) approximation,
unifying the treatment of small and large scales. We consider a universe filled
with a pressureless fluid and a cosmological constant $\Lambda$, the theory of
gravity is Einstein's general relativity and the background is the standard
flat $\Lambda$CDM cosmological model.
We expand the metric and the energy-momentum tensor in powers of $1/c$,
keeping the matter density and peculiar velocity as exact fundamental
variables. We assume the Poisson gauge, including scalar and tensor modes up to
$1/c^4$ order and vector modes up to $1/c^5$ terms. Through a redefinition of
the scalar potentials as a resummation of the metric contributions at different
orders, we obtain a complete set of nonlinear equations, providing a unified
framework to study structure formation from small to superhorizon scales, from
the nonlinear Newtonian to the linear relativistic regime. We explicitly show
the validity of our scheme in the two limits: at leading order we recover the
fully nonlinear equations of Newtonian cosmology; when linearized, our
equations become those for scalar and vector modes of first-order relativistic
perturbation theory in the Poisson gauge. Tensor modes are nondynamical at the
$1/c^4$ order we consider: they are purely nonlinear and describe a distortion
of the spatial slices determined at this order by a constraint, quadratic in
the scalar and vector variables. The main results of our analysis are as
follows: (a) at leading order a purely Newtonian nonlinear energy current
sources a frame-dragging gravitomagnetic vector potential, and (b) in the
leading-order Newtonian regime and in the linear relativistic regime the two
scalar metric potentials are the same, while the nonlinearity of general
relativity makes them different.
| [
{
"created": "Tue, 10 Feb 2015 16:55:12 GMT",
"version": "v1"
},
{
"created": "Sat, 9 May 2015 18:28:25 GMT",
"version": "v2"
}
] | 2015-08-06 | [
[
"Milillo",
"Irene",
""
],
[
"Bertacca",
"Daniele",
""
],
[
"Bruni",
"Marco",
""
],
[
"Maselli",
"Andrea",
""
]
] | We present a nonlinear post-Friedmann framework for structure formation, generalizing to cosmology the weak-field (post-Minkowskian) approximation, unifying the treatment of small and large scales. We consider a universe filled with a pressureless fluid and a cosmological constant $\Lambda$, the theory of gravity is Einstein's general relativity and the background is the standard flat $\Lambda$CDM cosmological model. We expand the metric and the energy-momentum tensor in powers of $1/c$, keeping the matter density and peculiar velocity as exact fundamental variables. We assume the Poisson gauge, including scalar and tensor modes up to $1/c^4$ order and vector modes up to $1/c^5$ terms. Through a redefinition of the scalar potentials as a resummation of the metric contributions at different orders, we obtain a complete set of nonlinear equations, providing a unified framework to study structure formation from small to superhorizon scales, from the nonlinear Newtonian to the linear relativistic regime. We explicitly show the validity of our scheme in the two limits: at leading order we recover the fully nonlinear equations of Newtonian cosmology; when linearized, our equations become those for scalar and vector modes of first-order relativistic perturbation theory in the Poisson gauge. Tensor modes are nondynamical at the $1/c^4$ order we consider: they are purely nonlinear and describe a distortion of the spatial slices determined at this order by a constraint, quadratic in the scalar and vector variables. The main results of our analysis are as follows: (a) at leading order a purely Newtonian nonlinear energy current sources a frame-dragging gravitomagnetic vector potential, and (b) in the leading-order Newtonian regime and in the linear relativistic regime the two scalar metric potentials are the same, while the nonlinearity of general relativity makes them different. |
1708.07874 | Hamid Shabani | Hamid Shabani and Amir Hadi Ziaie | Bouncing cosmological solutions from f(R,T) gravity | 49 pages, 11 figures, one table | Eur. Phys. J. C 78:397 (2018) | 10.1140/epjc/s10052-018-5886-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study classical bouncing solutions in the context of $f({\sf
R},{\sf T})={\sf R}+h({\sf T})$ gravity in a flat {\sf FLRW} background using a
perfect fluid as the only matter content. Our investigation is based on
introducing an effective fluid through defining effective energy density and
pressure; we call this reformulation as the "effective picture". These
definitions have been already introduced to study the energy conditions in
$f({\sf R},{\sf T})$ gravity. We examine various models to which different
effective equations of state, corresponding to different $h({\sf T})$
functions, can be attributed. It is also discussed that one can link between an
assumed $f({\sf R},{\sf T})$ model in the effective picture and the theories
with generalized equation of state ({\sf EoS}). We obtain cosmological
scenarios exhibiting a nonsingular bounce before and after which the Universe
lives within a de-Sitter phase. We then proceed to find general solutions for
matter bounce and investigate their properties. We show that the properties of
bouncing solution in the effective picture of $f({\sf R},{\sf T})$ gravity are
as follows: for a specific form of the $f({\sf R,T})$ function, these solutions
are without any future singularities. Moreover, stability analysis of the
nonsingular solutions through matter density perturbations revealed that except
two of the models, the parameters of scalar-type perturbations for the other
ones have a slight transient fluctuation around the bounce point and damp to
zero or a finite value at late times. Hence these bouncing solutions are stable
against scalar-type perturbations. It is possible that all energy conditions be
respected by the real perfect fluid, however, the null and the strong energy
conditions can be violated by the effective fluid near the bounce event.
| [
{
"created": "Fri, 25 Aug 2017 20:17:49 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Nov 2017 09:22:14 GMT",
"version": "v2"
},
{
"created": "Tue, 2 Jan 2018 07:02:15 GMT",
"version": "v3"
},
{
"created": "Thu, 25 Jan 2018 21:04:55 GMT",
"version": "v4"
},
{
"cre... | 2018-06-05 | [
[
"Shabani",
"Hamid",
""
],
[
"Ziaie",
"Amir Hadi",
""
]
] | In this work we study classical bouncing solutions in the context of $f({\sf R},{\sf T})={\sf R}+h({\sf T})$ gravity in a flat {\sf FLRW} background using a perfect fluid as the only matter content. Our investigation is based on introducing an effective fluid through defining effective energy density and pressure; we call this reformulation as the "effective picture". These definitions have been already introduced to study the energy conditions in $f({\sf R},{\sf T})$ gravity. We examine various models to which different effective equations of state, corresponding to different $h({\sf T})$ functions, can be attributed. It is also discussed that one can link between an assumed $f({\sf R},{\sf T})$ model in the effective picture and the theories with generalized equation of state ({\sf EoS}). We obtain cosmological scenarios exhibiting a nonsingular bounce before and after which the Universe lives within a de-Sitter phase. We then proceed to find general solutions for matter bounce and investigate their properties. We show that the properties of bouncing solution in the effective picture of $f({\sf R},{\sf T})$ gravity are as follows: for a specific form of the $f({\sf R,T})$ function, these solutions are without any future singularities. Moreover, stability analysis of the nonsingular solutions through matter density perturbations revealed that except two of the models, the parameters of scalar-type perturbations for the other ones have a slight transient fluctuation around the bounce point and damp to zero or a finite value at late times. Hence these bouncing solutions are stable against scalar-type perturbations. It is possible that all energy conditions be respected by the real perfect fluid, however, the null and the strong energy conditions can be violated by the effective fluid near the bounce event. |
1502.01945 | Volker Perlick | Jonathan Gratus, Volker Perlick, Robin W.Tucker | On the self-force in Bopp-Podolsky electrodynamics | 30 pages, 6 figures; minor reformulations, some figures changed,
additional explanations added | J. Phys. A: Math. Theor. 48, 435401 (2015) | 10.1088/1751-8113/48/43/435401 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the classical vacuum Maxwell-Lorentz theory the self-force of a charged
point particle is infinite. This makes classical mass renormalization necessary
and, in the special relativistic domain, leads to the Abraham-Lorentz-Dirac
equation of motion possessing unphysical run-away and pre-acceleration
solutions. In this paper we investigate whether the higher-order modification
of classical vacuum electrodynamics suggested by Bopp, Lande, Thomas and
Podolsky in the 1940s, can provide a solution to this problem. Since the theory
is linear, Green-function techniques enable one to write the field of a charged
point particle on Minkowski spacetime as an integral over the particle's
history. By introducing the notion of timelike worldlines that are "bounded
away from the backward light-cone" we are able to prescribe criteria for the
convergence of such integrals. We also exhibit a timelike worldline yielding
singular fields on a lightlike hyperplane in spacetime. In this case the field
is mildly singular at the event where the particle crosses the hyperplane. Even
in the case when the Bopp-Podolsky field is bounded, it exhibits a directional
discontinuity as one approaches the point particle. We describe a procedure for
assigning a value to the field on the particle worldline which enables one to
define a finite Lorentz self-force. This is explicitly derived leading to an
integro-differential equation for the motion of the particle in an external
electromagnetic field. We conclude that any worldline solutions to this
equation belonging to the categories discussed in the paper have continuous
4-velocities.
| [
{
"created": "Fri, 6 Feb 2015 16:40:43 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Oct 2015 14:35:10 GMT",
"version": "v2"
}
] | 2015-10-12 | [
[
"Gratus",
"Jonathan",
""
],
[
"Perlick",
"Volker",
""
],
[
"Tucker",
"Robin W.",
""
]
] | In the classical vacuum Maxwell-Lorentz theory the self-force of a charged point particle is infinite. This makes classical mass renormalization necessary and, in the special relativistic domain, leads to the Abraham-Lorentz-Dirac equation of motion possessing unphysical run-away and pre-acceleration solutions. In this paper we investigate whether the higher-order modification of classical vacuum electrodynamics suggested by Bopp, Lande, Thomas and Podolsky in the 1940s, can provide a solution to this problem. Since the theory is linear, Green-function techniques enable one to write the field of a charged point particle on Minkowski spacetime as an integral over the particle's history. By introducing the notion of timelike worldlines that are "bounded away from the backward light-cone" we are able to prescribe criteria for the convergence of such integrals. We also exhibit a timelike worldline yielding singular fields on a lightlike hyperplane in spacetime. In this case the field is mildly singular at the event where the particle crosses the hyperplane. Even in the case when the Bopp-Podolsky field is bounded, it exhibits a directional discontinuity as one approaches the point particle. We describe a procedure for assigning a value to the field on the particle worldline which enables one to define a finite Lorentz self-force. This is explicitly derived leading to an integro-differential equation for the motion of the particle in an external electromagnetic field. We conclude that any worldline solutions to this equation belonging to the categories discussed in the paper have continuous 4-velocities. |
2408.01644 | Leandro Gomes G | Leandro G. Gomes, Marcelo A. C. Nogueira and Lucas Ruiz dos Santos | Einstein's equations constrained by homogeneous and isotropic expansion:
Initial value problems and applications | 18 pages; 3 figures | null | null | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | In this manuscript, we put forth a general scheme for defining initial value
problems from Einstein's equations of General Relativity constrained by
homogeneous and isotropic expansion. The cosmological models arising as
solutions are naturally interpreted as spatially homogeneous and isotropic on
``large scales". In order to show the well-posedness and applicability of such
a scheme, we specialize in a class of spacetimes filled with the general
homogeneous perfect fluid and inhomogeneous viscoelastic matter. We prove the
existence, uniqueness, and relative stability of solutions, and an additional
inequality for the energy density. As a consequence of our theorems, a new
mechanism of energy transfer appears involving the different components of
matter. A class of exact solutions is also obtained to exemplify the general
results.
| [
{
"created": "Sat, 3 Aug 2024 03:02:49 GMT",
"version": "v1"
}
] | 2024-08-06 | [
[
"Gomes",
"Leandro G.",
""
],
[
"Nogueira",
"Marcelo A. C.",
""
],
[
"Santos",
"Lucas Ruiz dos",
""
]
] | In this manuscript, we put forth a general scheme for defining initial value problems from Einstein's equations of General Relativity constrained by homogeneous and isotropic expansion. The cosmological models arising as solutions are naturally interpreted as spatially homogeneous and isotropic on ``large scales". In order to show the well-posedness and applicability of such a scheme, we specialize in a class of spacetimes filled with the general homogeneous perfect fluid and inhomogeneous viscoelastic matter. We prove the existence, uniqueness, and relative stability of solutions, and an additional inequality for the energy density. As a consequence of our theorems, a new mechanism of energy transfer appears involving the different components of matter. A class of exact solutions is also obtained to exemplify the general results. |
1101.0386 | Ujjal Debnath | Prabir Rudra, Ritabrata Biswas and Ujjal Debnath | Gravitational Collapse in Generalized Vaidya Space-Time for Lovelock
Gravity Theory | 11 pages | Astrophys.Space Sci.335:505-513,2011 | 10.1007/s10509-011-0759-x | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we have assumed the generalized Vaidya solution in Lovelock
theory of gravity in $(n+2)$-dimensions. It has been shown that Gauss-Bonnet
gravity, dimensionally continued Lovelock gravity and pure Lovelock gravity can
be constructed by suitable choice of parameters. We have investigated the
occurrence of singularities formed by the gravitational collapse in above three
particular forms of Lovelock theory of gravity. The dependence of the nature of
singularity on the existence of radial null geodesic for Vaidya space-time has
been specially considered. In all the three models, we have shown that the
nature of singularities (naked singularity or black hole) completely depend on
the parameters. Choices of various parameters are shown in tabular form. In
Gauss-Bonnet gravity theory, it can be concluded that the possibility of naked
singularity increases with increase in dimensions. In dimensionally continued
Lovelock gravity, the naked singularity is possible for odd dimensions for
several values of parameters. In pure Lovelock gravity, only black hole forms
due to the gravitational collapse for any values of parameters. It has been
shown that when accretion is taking place on a collapsing object, it is highly
unlikely to get a black hole. Finally on considering the phantom era in the
expanding universe it is observed that there is no possibility of formation of
a black hole if we are in the Gauss-Bonnet gravity considering the accreting
procedure upon a collapsing object.
| [
{
"created": "Sun, 2 Jan 2011 05:17:34 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Apr 2011 09:30:49 GMT",
"version": "v2"
}
] | 2011-09-12 | [
[
"Rudra",
"Prabir",
""
],
[
"Biswas",
"Ritabrata",
""
],
[
"Debnath",
"Ujjal",
""
]
] | In this work, we have assumed the generalized Vaidya solution in Lovelock theory of gravity in $(n+2)$-dimensions. It has been shown that Gauss-Bonnet gravity, dimensionally continued Lovelock gravity and pure Lovelock gravity can be constructed by suitable choice of parameters. We have investigated the occurrence of singularities formed by the gravitational collapse in above three particular forms of Lovelock theory of gravity. The dependence of the nature of singularity on the existence of radial null geodesic for Vaidya space-time has been specially considered. In all the three models, we have shown that the nature of singularities (naked singularity or black hole) completely depend on the parameters. Choices of various parameters are shown in tabular form. In Gauss-Bonnet gravity theory, it can be concluded that the possibility of naked singularity increases with increase in dimensions. In dimensionally continued Lovelock gravity, the naked singularity is possible for odd dimensions for several values of parameters. In pure Lovelock gravity, only black hole forms due to the gravitational collapse for any values of parameters. It has been shown that when accretion is taking place on a collapsing object, it is highly unlikely to get a black hole. Finally on considering the phantom era in the expanding universe it is observed that there is no possibility of formation of a black hole if we are in the Gauss-Bonnet gravity considering the accreting procedure upon a collapsing object. |
1009.4793 | Boris E. Meierovich | Boris E. Meierovich | Vector order parameter in general relativity. Covariant equations | null | Phys.Rev.D82:024004,2010 | 10.1103/PhysRevD.82.024004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Phase transitions with spontaneous symmetry breaking and vector order
parameter are considered in multidimensional theory of general relativity.
Covariant equations, describing the gravitational properties of topological
defects, are derived. The topological defects are classified in accordance with
the symmetry of the covariant derivative of the vector order parameter. The
abilities of the derived equations are demonstrated in application to the brane
world concept. New solutions of the Einstein equations with a transverse vector
order parameter are presented. In the vicinity of phase transition the
solutions are found analytically.
| [
{
"created": "Fri, 24 Sep 2010 10:17:48 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Meierovich",
"Boris E.",
""
]
] | Phase transitions with spontaneous symmetry breaking and vector order parameter are considered in multidimensional theory of general relativity. Covariant equations, describing the gravitational properties of topological defects, are derived. The topological defects are classified in accordance with the symmetry of the covariant derivative of the vector order parameter. The abilities of the derived equations are demonstrated in application to the brane world concept. New solutions of the Einstein equations with a transverse vector order parameter are presented. In the vicinity of phase transition the solutions are found analytically. |
gr-qc/0301130 | Karlucio Castello Branco | E. Abdalla, K. H. C. Castello-Branco and A. Lima-Santos | Area Quantization in Quasi-Extreme Black Holes | Final version to appear in Mod. Phys. Lett. A | Mod.Phys.Lett. A18 (2003) 1435-1440 | 10.1142/S0217732303011435 | null | gr-qc | null | We consider quasi-extreme Kerr and quasi-extreme Schwarzschild-de Sitter
black holes. From the known analytical expressions obtained for their
quasi-normal modes frequencies, we suggest an area quantization prescription
for those objects.
| [
{
"created": "Fri, 31 Jan 2003 20:42:36 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Feb 2003 18:28:18 GMT",
"version": "v2"
},
{
"created": "Tue, 4 Feb 2003 14:03:46 GMT",
"version": "v3"
},
{
"created": "Thu, 5 Jun 2003 17:58:30 GMT",
"version": "v4"
}
] | 2009-11-10 | [
[
"Abdalla",
"E.",
""
],
[
"Castello-Branco",
"K. H. C.",
""
],
[
"Lima-Santos",
"A.",
""
]
] | We consider quasi-extreme Kerr and quasi-extreme Schwarzschild-de Sitter black holes. From the known analytical expressions obtained for their quasi-normal modes frequencies, we suggest an area quantization prescription for those objects. |
1402.4434 | Vladim\'ir Balek | Vladim\'ir Balek, Matej \v{S}kovran | Effect of radiation-like solid on CMB anisotropies | 24 pages, 3 figures | Class. Quant. Grav. 32, 015015 (2015) | 10.1088/0264-9381/32/1/015015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the power in the lowest multipoles of CMB anisotropies in the
presence of radiation-like solid, a hypothetical new kind of radiation with
nonzero shear modulus. If only the ordinary Sachs-Wolfe effect is taken into
account, the shear modulus to energy density ratio must be in absolute value of
order $10^{-5}$ or less for the theory to be consistent with observations
within cosmic variance. With the integrated Sachs-Wolfe effect switched on, the
constraint is relaxed almost by two orders of magnitude.
| [
{
"created": "Tue, 18 Feb 2014 18:40:22 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Jan 2015 22:04:42 GMT",
"version": "v2"
}
] | 2015-06-18 | [
[
"Balek",
"Vladimír",
""
],
[
"Škovran",
"Matej",
""
]
] | We compute the power in the lowest multipoles of CMB anisotropies in the presence of radiation-like solid, a hypothetical new kind of radiation with nonzero shear modulus. If only the ordinary Sachs-Wolfe effect is taken into account, the shear modulus to energy density ratio must be in absolute value of order $10^{-5}$ or less for the theory to be consistent with observations within cosmic variance. With the integrated Sachs-Wolfe effect switched on, the constraint is relaxed almost by two orders of magnitude. |
2309.05420 | Bhaskar Biswas | Bhaskar Biswas, Evangelos Smyrniotis, Ioannis Liodis, and Nikolaos
Stergioulas | A Bayesian investigation of the neutron star equation-of-state vs.
gravity degeneracy | Comments are welcome! | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Despite its elegance, the theory of General Relativity is subject to
experimental, observational, and theoretical scrutiny to arrive at tighter
constraints or an alternative, more preferred theory. In alternative gravity
theories, the macroscopic properties of neutron stars, such as mass, radius,
tidal deformability, etc. are modified. This creates a degeneracy between the
uncertainties in the equation of state (EoS) and gravity since assuming a
different EoS can be mimicked by changing to a different theory of gravity. We
formulate a hierarchical Bayesian framework to simultaneously infer the EoS and
gravity parameters by combining multiple astrophysical observations. We test
this framework for a particular 4D Horndeski scalar-tensor theory originating
from higher-dimensional Einstein-Gauss-Bonnet gravity and a set of 20 realistic
EoS and place improved constraints on the coupling constant of the theory with
current observations. Assuming a large number of observations with upgraded or
third-generation detectors, we find that the $A+$ upgrade could place
interesting bounds on the coupling constant of the theory, whereas with the
LIGO Voyager upgrade or the third-generation detectors (Einstein Telescope and
Cosmic Explorer), the degeneracy between EoS and gravity could be resolved with
high confidence, even for small deviations from GR.
| [
{
"created": "Mon, 11 Sep 2023 12:40:26 GMT",
"version": "v1"
}
] | 2023-09-12 | [
[
"Biswas",
"Bhaskar",
""
],
[
"Smyrniotis",
"Evangelos",
""
],
[
"Liodis",
"Ioannis",
""
],
[
"Stergioulas",
"Nikolaos",
""
]
] | Despite its elegance, the theory of General Relativity is subject to experimental, observational, and theoretical scrutiny to arrive at tighter constraints or an alternative, more preferred theory. In alternative gravity theories, the macroscopic properties of neutron stars, such as mass, radius, tidal deformability, etc. are modified. This creates a degeneracy between the uncertainties in the equation of state (EoS) and gravity since assuming a different EoS can be mimicked by changing to a different theory of gravity. We formulate a hierarchical Bayesian framework to simultaneously infer the EoS and gravity parameters by combining multiple astrophysical observations. We test this framework for a particular 4D Horndeski scalar-tensor theory originating from higher-dimensional Einstein-Gauss-Bonnet gravity and a set of 20 realistic EoS and place improved constraints on the coupling constant of the theory with current observations. Assuming a large number of observations with upgraded or third-generation detectors, we find that the $A+$ upgrade could place interesting bounds on the coupling constant of the theory, whereas with the LIGO Voyager upgrade or the third-generation detectors (Einstein Telescope and Cosmic Explorer), the degeneracy between EoS and gravity could be resolved with high confidence, even for small deviations from GR. |
0810.1776 | Klein David | David Klein, Peter Collas | Timelike Killing Fields and Relativistic Statistical Mechanics | This version contains minor corrections, additional discussion, and
will appear in Classical and Quantum Gravity | Class.Quant.Grav.26:045018,2009 | 10.1088/0264-9381/26/4/045018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For spacetimes with timelike Killing fields, we introduce a
"Fermi-Walker-Killing" coordinate system and use it to prove a Liouville
Theorem for an appropriate volume element of phase space for a statistical
mechanical system of particles. We derive an exact relativistic formula for the
Helmholtz free energy of an ideal gas and compare it, for a class of
spacetimes, to its Newtonian analog, derived both independently and as the
Newtonian limit of our formula. We also find the relativistic thermodynamic
equation of state. Specific examples are given in Kerr spacetime.
| [
{
"created": "Thu, 9 Oct 2008 23:00:15 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Dec 2008 14:30:18 GMT",
"version": "v2"
}
] | 2009-02-12 | [
[
"Klein",
"David",
""
],
[
"Collas",
"Peter",
""
]
] | For spacetimes with timelike Killing fields, we introduce a "Fermi-Walker-Killing" coordinate system and use it to prove a Liouville Theorem for an appropriate volume element of phase space for a statistical mechanical system of particles. We derive an exact relativistic formula for the Helmholtz free energy of an ideal gas and compare it, for a class of spacetimes, to its Newtonian analog, derived both independently and as the Newtonian limit of our formula. We also find the relativistic thermodynamic equation of state. Specific examples are given in Kerr spacetime. |
1803.01171 | Didier Solis | Didier A. Solis | Global properties of asymptotically de Sitter and Anti de Sitter
spacetimes | 136 pages, 13 figures | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the first part of this work we show a uniqueness result for globally
hyperbolic spacetimes with a spacelike conformal boundary satisfying the vacuum
Einstein equations with positive cosmological constant. Then we present
applications of this result in the contexts of cosmic censorship and the
initial value problem in general relativity. Further extensions of this result
to non-vacuum solutions of the Einstein equations are also studied. On the
other hand, the second half of this thesis deals with spacetimes with timelike
boundary. We first develop the causal theory of such spacetimes and then use it
to prove a quasi-local version of the principle of topological censorship.
| [
{
"created": "Sat, 3 Mar 2018 14:23:09 GMT",
"version": "v1"
}
] | 2018-03-06 | [
[
"Solis",
"Didier A.",
""
]
] | In the first part of this work we show a uniqueness result for globally hyperbolic spacetimes with a spacelike conformal boundary satisfying the vacuum Einstein equations with positive cosmological constant. Then we present applications of this result in the contexts of cosmic censorship and the initial value problem in general relativity. Further extensions of this result to non-vacuum solutions of the Einstein equations are also studied. On the other hand, the second half of this thesis deals with spacetimes with timelike boundary. We first develop the causal theory of such spacetimes and then use it to prove a quasi-local version of the principle of topological censorship. |
1501.02636 | Luis Cort\'es Barbado | Luis C. Barbado | Hawking and Unruh radiation perception by different observers:
applications of the effective temperature function (in Spanish) | PhD Thesis of Luis Cort\'es Barbado, in Spanish. PhD supervisors:
Carlos Barcel\'o Ser\'on and Luis Javier Garay Elizondo. appears as Cort\'es
Barbado, L. Percepci\'on de las radiaciones Hawking y Unruh por distintos
observadores: aplicaciones de la funci\'on de temperatura efectiva. Granada:
Universidad de Granada, 2014. 164 p. [http://hdl.handle.net/10481/34102].
ISBN: 978-84-9083-062-8 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the perception of the radiation phenomena of Hawking radiation and
Unruh effect by using two main tools: the Unruh-DeWitt detectors and the
effective temperature function (ETF), this last tool based on Bogoliubov
transformations. Using the Unruh-DeWitt detectors we find an adiabatic
expansion of the detection properties along linear trajectories with slowly
varying acceleration in Minkowski, which allows us to calculate the spectrum
detected, finding the thermal spectrum as the zeroth order contribution. Using
the ETF we study the perception of Hawking radiation by observers following
radial trajectories outside a Schwarzschild black hole. One of the most
important results is that, in general, free-falling observers crossing the
event horizon do detect some radiation, even when the field is in the Unruh
vacuum state, due to a Doppler blue-shift that diverges at the horizon. We give
a general expression for the ETF, which has a clear interpretation in terms of
well-known physical phenomena. We discuss which contribution to the perception
comes from the radiation emitted by the black hole, and which contribution is
due to the Unruh effect caused by the movement of the observer. We conclude
that the Unruh effect is not only due to the observer's proper acceleration and
cannot even be defined locally, but is due to the observer's acceleration with
respect to the asymptotic region. We apply the ETF to the analysis of different
physical situations, in particular to a possible buoyancy scenario near the
horizon due to Hawking radiation pressure. Finally, we propose a non-stationary
vacuum state, which we call pulsating vacuum, for the radiation field outside a
stellar object hovering closely to form an event horizon. In this vacuum state,
we get nearly Hawking radiation emitted by the object, while avoiding the known
problems of the information paradox and the trans-planckian problem.
| [
{
"created": "Mon, 12 Jan 2015 13:28:11 GMT",
"version": "v1"
}
] | 2015-01-13 | [
[
"Barbado",
"Luis C.",
""
]
] | We study the perception of the radiation phenomena of Hawking radiation and Unruh effect by using two main tools: the Unruh-DeWitt detectors and the effective temperature function (ETF), this last tool based on Bogoliubov transformations. Using the Unruh-DeWitt detectors we find an adiabatic expansion of the detection properties along linear trajectories with slowly varying acceleration in Minkowski, which allows us to calculate the spectrum detected, finding the thermal spectrum as the zeroth order contribution. Using the ETF we study the perception of Hawking radiation by observers following radial trajectories outside a Schwarzschild black hole. One of the most important results is that, in general, free-falling observers crossing the event horizon do detect some radiation, even when the field is in the Unruh vacuum state, due to a Doppler blue-shift that diverges at the horizon. We give a general expression for the ETF, which has a clear interpretation in terms of well-known physical phenomena. We discuss which contribution to the perception comes from the radiation emitted by the black hole, and which contribution is due to the Unruh effect caused by the movement of the observer. We conclude that the Unruh effect is not only due to the observer's proper acceleration and cannot even be defined locally, but is due to the observer's acceleration with respect to the asymptotic region. We apply the ETF to the analysis of different physical situations, in particular to a possible buoyancy scenario near the horizon due to Hawking radiation pressure. Finally, we propose a non-stationary vacuum state, which we call pulsating vacuum, for the radiation field outside a stellar object hovering closely to form an event horizon. In this vacuum state, we get nearly Hawking radiation emitted by the object, while avoiding the known problems of the information paradox and the trans-planckian problem. |
1301.1237 | Branislav Cvetkovi\'c | Milutin Blagojevi\'c, Branislav Cvetkovi\'c, Olivera Miskovic, and
Rodrigo Olea | Holography in 3D AdS gravity with torsion | LATEX, 26 pages; v2, minor revisions | null | 10.1007/JHEP05(2013)103 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Basic aspects of the AdS/CFT correspondence are studied in the framework of
3-dimensional gravity with torsion. After choosing a consistent holographic
ansatz, we formulate an improved approach to the Noether--Ward identities for
the boundary theory. The method is applied first to the topological
Mielke--Baekler model, and then to the more interesting (parity-preserving)
3-dimensional gravity with propagating torsion. In both cases, we find the
finite holographic energy-momentum and spin currents and obtain the associated
(anomalous) Noether--Ward identities.
| [
{
"created": "Mon, 7 Jan 2013 15:51:41 GMT",
"version": "v1"
},
{
"created": "Mon, 6 May 2013 15:10:16 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Blagojević",
"Milutin",
""
],
[
"Cvetković",
"Branislav",
""
],
[
"Miskovic",
"Olivera",
""
],
[
"Olea",
"Rodrigo",
""
]
] | Basic aspects of the AdS/CFT correspondence are studied in the framework of 3-dimensional gravity with torsion. After choosing a consistent holographic ansatz, we formulate an improved approach to the Noether--Ward identities for the boundary theory. The method is applied first to the topological Mielke--Baekler model, and then to the more interesting (parity-preserving) 3-dimensional gravity with propagating torsion. In both cases, we find the finite holographic energy-momentum and spin currents and obtain the associated (anomalous) Noether--Ward identities. |
1911.00644 | Aar\'on Villanueva | Manuel Tiglio and Aar\'on Villanueva | On ab initio-based, free and closed-form expressions for gravitational
waves | 12 pages, 6 figures. Adding code for GWs and fix minor typos based on
journal reports. Accepted in Nature Scientific Reports | Scientific Reports 11, 5832 (2021) | 10.1038/s41598-021-85102-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a new approach for finding high accuracy, free and closed-form
expressions for the gravitational waves emitted by binary black hole collisions
from ab initio models. More precisely, our expressions are built from numerical
surrogate models based on supercomputer simulations of the Einstein equations,
which have been shown to be essentially indistinguishable from each other.
Distinct aspects of our approach are that: i) representations of the
gravitational waves can be explicitly written in a few lines, ii) these
representations are free-form yet still fast to search for and validate and
iii) there are no underlying physical approximations in the underlying model.
The key strategy is combining techniques from Artificial Intelligence and
Reduced Order Modeling for parameterized systems. Namely, symbolic regression
through genetic programming combined with sparse representations in parameter
space and the time domain using Reduced Basis and the Empirical Interpolation
Method enabling fast free-form symbolic searches and large-scale a posteriori
validations. As a proof of concept we present our results for the collision of
two black holes, initially without spin, and with an initial separation
corresponding to $25-31$ gravitational wave cycles before merger. The minimum
overlap, compared to ground truth solutions, is $99\%$. That is, $1\%$
difference between our closed-form expressions and supercomputer simulations;
this is considered for gravitational (GW) science more than the minimum
required due to experimental numerical errors which otherwise dominate. This
paper aims to contribute to the field of GWs in particular and Artificial
Intelligence in general.
| [
{
"created": "Sat, 2 Nov 2019 04:10:52 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Feb 2021 08:37:56 GMT",
"version": "v2"
},
{
"created": "Fri, 12 Mar 2021 14:12:19 GMT",
"version": "v3"
}
] | 2021-03-15 | [
[
"Tiglio",
"Manuel",
""
],
[
"Villanueva",
"Aarón",
""
]
] | We introduce a new approach for finding high accuracy, free and closed-form expressions for the gravitational waves emitted by binary black hole collisions from ab initio models. More precisely, our expressions are built from numerical surrogate models based on supercomputer simulations of the Einstein equations, which have been shown to be essentially indistinguishable from each other. Distinct aspects of our approach are that: i) representations of the gravitational waves can be explicitly written in a few lines, ii) these representations are free-form yet still fast to search for and validate and iii) there are no underlying physical approximations in the underlying model. The key strategy is combining techniques from Artificial Intelligence and Reduced Order Modeling for parameterized systems. Namely, symbolic regression through genetic programming combined with sparse representations in parameter space and the time domain using Reduced Basis and the Empirical Interpolation Method enabling fast free-form symbolic searches and large-scale a posteriori validations. As a proof of concept we present our results for the collision of two black holes, initially without spin, and with an initial separation corresponding to $25-31$ gravitational wave cycles before merger. The minimum overlap, compared to ground truth solutions, is $99\%$. That is, $1\%$ difference between our closed-form expressions and supercomputer simulations; this is considered for gravitational (GW) science more than the minimum required due to experimental numerical errors which otherwise dominate. This paper aims to contribute to the field of GWs in particular and Artificial Intelligence in general. |
1508.06364 | Ryotaro Kase | Antonio De Felice, Ryotaro Kase, Shinji Tsujikawa | Existence and disappearance of conical singularities in
Gleyzes-Langlois-Piazza-Vernizzi theories | 10 pages | Phys. Rev. D 92, 124060 (2015) | 10.1103/PhysRevD.92.124060 | YITP-15-72 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a class of Gleyzes-Langlois-Piazza-Vernizzi (GLPV) theories, we derive
both vacuum and interior Schwarzschild solutions under the condition that the
derivatives of a scalar field $\phi$ with respect to the radius $r$ vanish. If
the parameter $\alpha_{\rm H}$ characterizing the deviation from Horndeski
theories approaches a non-zero constant at the center of a spherically
symmetric body, we find that the conical singularity arises at $r=0$ with the
Ricci scalar given by $R=-2\alpha_{\rm H}/r^2$. This originates from violation
of the geometrical structure of four-dimensional curvature quantities. The
conical singularity can disappear for the models in which the parameter
$\alpha_{\rm H}$ vanishes in the limit that $r \to 0$. We propose explicit
models without the conical singularity by properly designing the classical
Lagrangian in such a way that the main contribution to $\alpha_{\rm H}$ comes
from the field derivative $\phi'(r)$ around $r=0$. We show that the extension
of covariant Galileons with a diatonic coupling allows for the recovery of
general relativistic behavior inside a so-called Vainshtein radius. In this
case, both the propagation of a fifth force and the deviation from Horndeski
theories are suppressed outside a compact body in such a way that the model is
compatible with local gravity experiments inside the solar system.
| [
{
"created": "Wed, 26 Aug 2015 04:49:16 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Dec 2015 06:48:31 GMT",
"version": "v2"
}
] | 2015-12-29 | [
[
"De Felice",
"Antonio",
""
],
[
"Kase",
"Ryotaro",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | In a class of Gleyzes-Langlois-Piazza-Vernizzi (GLPV) theories, we derive both vacuum and interior Schwarzschild solutions under the condition that the derivatives of a scalar field $\phi$ with respect to the radius $r$ vanish. If the parameter $\alpha_{\rm H}$ characterizing the deviation from Horndeski theories approaches a non-zero constant at the center of a spherically symmetric body, we find that the conical singularity arises at $r=0$ with the Ricci scalar given by $R=-2\alpha_{\rm H}/r^2$. This originates from violation of the geometrical structure of four-dimensional curvature quantities. The conical singularity can disappear for the models in which the parameter $\alpha_{\rm H}$ vanishes in the limit that $r \to 0$. We propose explicit models without the conical singularity by properly designing the classical Lagrangian in such a way that the main contribution to $\alpha_{\rm H}$ comes from the field derivative $\phi'(r)$ around $r=0$. We show that the extension of covariant Galileons with a diatonic coupling allows for the recovery of general relativistic behavior inside a so-called Vainshtein radius. In this case, both the propagation of a fifth force and the deviation from Horndeski theories are suppressed outside a compact body in such a way that the model is compatible with local gravity experiments inside the solar system. |
1908.00655 | Trevor Vincent | Trevor Vincent, Francois Foucart, Matthew D. Duez, Roland Haas,
Lawrence E. Kidder, Harald P. Pfeiffer and Mark A. Scheel | Unequal Mass Binary Neutron Star Simulations with Neutrino Transport:
Ejecta and Neutrino Emission | 23 pages, 15 figures | Phys. Rev. D 101, 044053 (2020) | 10.1103/PhysRevD.101.044053 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present twelve new simulations of unequal mass neutron star mergers. The
simulations were preformed with the SpEC code, and utilize nuclear-theory based
equations of state and a two-moment gray neutrino transport scheme with an
improved energy estimate based on evolving the number density. We model the
neutron stars with the SFHo, LS220 and DD2 equations of state (EOS) and we
study the neutrino and matter emission of all twelve models to search for
robust trends between binary parameters and emission characteristics. We find
that the total mass of the dynamical ejecta exceeds $0.01M_\odot$ only for SFHo
with weak dependence on the mass-ratio across all models. We find that the
ejecta have a broad electron fraction ($Y_e$) distribution ($\approx
0.06-0.48$), with mean $0.2$. $Y_e$ increases with neutrino irradiation over
time, but decreases with increasing binary asymmetry. We also find that the
models have ejecta with a broad asymptotic velocity distribution ($\approx
0.05-0.7c$). The average velocity lies in the range $0.2c - 0.3c$ and decreases
with binary asymmetry. Furthermore, we find that disk mass increases with
binary asymmetry and stiffness of the EOS. The $Y_e$ of the disk increases with
softness of the EOS. The strongest neutrino emission occurs for the models with
soft EOS. For (anti) electron neutrinos we find no significant dependence of
the magnitude or angular distribution or neutrino luminosity with mass-ratio.
The heavier neutrino species have a luminosity dependence on mass-ratio but an
angular distribution which does not change with mass-ratio.
| [
{
"created": "Thu, 1 Aug 2019 23:03:45 GMT",
"version": "v1"
}
] | 2020-03-04 | [
[
"Vincent",
"Trevor",
""
],
[
"Foucart",
"Francois",
""
],
[
"Duez",
"Matthew D.",
""
],
[
"Haas",
"Roland",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Scheel",
"Mark A.",
""
... | We present twelve new simulations of unequal mass neutron star mergers. The simulations were preformed with the SpEC code, and utilize nuclear-theory based equations of state and a two-moment gray neutrino transport scheme with an improved energy estimate based on evolving the number density. We model the neutron stars with the SFHo, LS220 and DD2 equations of state (EOS) and we study the neutrino and matter emission of all twelve models to search for robust trends between binary parameters and emission characteristics. We find that the total mass of the dynamical ejecta exceeds $0.01M_\odot$ only for SFHo with weak dependence on the mass-ratio across all models. We find that the ejecta have a broad electron fraction ($Y_e$) distribution ($\approx 0.06-0.48$), with mean $0.2$. $Y_e$ increases with neutrino irradiation over time, but decreases with increasing binary asymmetry. We also find that the models have ejecta with a broad asymptotic velocity distribution ($\approx 0.05-0.7c$). The average velocity lies in the range $0.2c - 0.3c$ and decreases with binary asymmetry. Furthermore, we find that disk mass increases with binary asymmetry and stiffness of the EOS. The $Y_e$ of the disk increases with softness of the EOS. The strongest neutrino emission occurs for the models with soft EOS. For (anti) electron neutrinos we find no significant dependence of the magnitude or angular distribution or neutrino luminosity with mass-ratio. The heavier neutrino species have a luminosity dependence on mass-ratio but an angular distribution which does not change with mass-ratio. |
gr-qc/9702021 | Domenico Giulini | Domenico Giulini | Determination and Reduction of Large Diffeomorphisms | 4 pages, Latex, macro espcrc2.sty. Contribution to the proceedings of
the second conference on Constrained Dynamics and Quantum Gravity, Santa
Margherita, Italy, 17-21 September 1996. To appear in Nucl. Phys. B Suppl | Nucl.Phys.Proc.Suppl. 57 (1997) 342-345 | 10.1016/S0920-5632(97)00369-1 | Freiburg, THEP-97/5 | gr-qc | null | Within the Hamiltonian formulation of diffeomorphism invariant theories we
address the problem of how to determine and how to reduce diffeomorphisms
outside the identity component.
| [
{
"created": "Tue, 11 Feb 1997 15:54:20 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Giulini",
"Domenico",
""
]
] | Within the Hamiltonian formulation of diffeomorphism invariant theories we address the problem of how to determine and how to reduce diffeomorphisms outside the identity component. |
gr-qc/0611050 | Matej Pavsic | Matej Pavsic | An Extra Structure of Spacetime: A Space of Points, Areas and Volumes | 13 pages; A talk presented at the XXIX Spanish Relativity Meeting ERE
2006, 4th-8th September 2006, Palma de Mallorca, Spain | J.Phys.Conf.Ser.66:012022,2007 | 10.1088/1742-6596/66/1/012022 | null | gr-qc | null | A theory in which points, lines, areas and volumes are on on the same footing
is investigated. All those geometric objects form a 16-dimensional manifold,
called C-space, which generalizes spacetime. In such higher dimensional space
fundamental interactions can be unified \` a la Kaluza-Klein. The ordinary,
4-dimensional, gravity and gauge fields are incorporated in the metric and spin
connection, whilst the conserved gauge charges are related to the isometries of
curved C-space. It is shown that a conserved generator of an isometry in
C-space contains a part with derivatives, which generalizes orbital angular
momentum, and a part with the generators of Clifford algebra, which generalizes
spin.
| [
{
"created": "Wed, 8 Nov 2006 10:17:40 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Pavsic",
"Matej",
""
]
] | A theory in which points, lines, areas and volumes are on on the same footing is investigated. All those geometric objects form a 16-dimensional manifold, called C-space, which generalizes spacetime. In such higher dimensional space fundamental interactions can be unified \` a la Kaluza-Klein. The ordinary, 4-dimensional, gravity and gauge fields are incorporated in the metric and spin connection, whilst the conserved gauge charges are related to the isometries of curved C-space. It is shown that a conserved generator of an isometry in C-space contains a part with derivatives, which generalizes orbital angular momentum, and a part with the generators of Clifford algebra, which generalizes spin. |
gr-qc/0608097 | Luciano Gottardi | Luciano Gottardi | Complete model of a spherical gravitational wave detector with
capacitive transducers. Calibration and sensitivity optimization | 23 pages, 20 figures, codes of the simulations are available on
request by contacting the author | Phys.Rev.D75:022002,2007 | 10.1103/PhysRevD.75.022002 | null | gr-qc | null | We report the results of a detailed numerical analysis of a real resonant
spherical gravitational wave antenna operating with six resonant two-mode
capacitive transducers read out by superconducting quantum interference devices
(SQUID) amplifiers. We derive a set of equations to describe the
electro-mechanical dynamics of the detector. The model takes into account the
effect of all the noise sources present in each transducer chain: the thermal
noise associated with the mechanical resonators, the thermal noise from the
superconducting impedance matching transformer, the back-action noise and the
additive current noise of the SQUID amplifier. Asymmetries in the detector
signal-to-noise ratio and bandwidth, coming from considering the transducers
not as point-like objects but as sensor with physically defined geometry and
dimension, are also investigated. We calculate the sensitivity for an
ultracryogenic, 30 ton, 2 meter in diameter, spherical detector with optimal
and non-optimal impedance matching of the electrical read-out scheme to the
mechanical modes. The results of the analysis is useful not only to optimize
existing smaller mass spherical detector like MiniGrail, in Leiden, but also as
a technological guideline for future massive detectors. Furthermore we
calculate the antenna patterns when the sphere operates with one, three and six
resonators. The sky coverage for two detectors based in The Netherlands and
Brasil and operating in coincidence is also estimated. Finally, we describe and
numerically verify a calibration and filtering procedure useful for diagnostic
and detection purposes in analogy with existing resonant bar detectors.
| [
{
"created": "Sun, 20 Aug 2006 19:44:16 GMT",
"version": "v1"
},
{
"created": "Tue, 1 May 2007 16:38:05 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Gottardi",
"Luciano",
""
]
] | We report the results of a detailed numerical analysis of a real resonant spherical gravitational wave antenna operating with six resonant two-mode capacitive transducers read out by superconducting quantum interference devices (SQUID) amplifiers. We derive a set of equations to describe the electro-mechanical dynamics of the detector. The model takes into account the effect of all the noise sources present in each transducer chain: the thermal noise associated with the mechanical resonators, the thermal noise from the superconducting impedance matching transformer, the back-action noise and the additive current noise of the SQUID amplifier. Asymmetries in the detector signal-to-noise ratio and bandwidth, coming from considering the transducers not as point-like objects but as sensor with physically defined geometry and dimension, are also investigated. We calculate the sensitivity for an ultracryogenic, 30 ton, 2 meter in diameter, spherical detector with optimal and non-optimal impedance matching of the electrical read-out scheme to the mechanical modes. The results of the analysis is useful not only to optimize existing smaller mass spherical detector like MiniGrail, in Leiden, but also as a technological guideline for future massive detectors. Furthermore we calculate the antenna patterns when the sphere operates with one, three and six resonators. The sky coverage for two detectors based in The Netherlands and Brasil and operating in coincidence is also estimated. Finally, we describe and numerically verify a calibration and filtering procedure useful for diagnostic and detection purposes in analogy with existing resonant bar detectors. |
1705.03265 | Andrea Addazi AndAdd | Andrea Addazi, Shin'ichi Nojiri, Sergei Odintsov | Evaporation and anti-evaporation instability of a Schwarzschild-de
Sitter braneworld: the case of five-dimensional F(R) gravity | 10 pages, version accepted (to appear) in PRD | Phys. Rev. D 95, 124020 (2017) | 10.1103/PhysRevD.95.124020 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the problem of a four-dimensional brane lying in the
five-dimensional degenerate Schwarzschild-de Sitter (Nariai) black hole, in
five-dimensional $F(R)$-gravity. We show that there cannot exist the brane in
the Nariai bulk space except the case that the brane tension vanishes. We
demonstrate that the five-dimensional Nariai bulk is unstable in a large region
of the parameter space. In particular, the Nariai bulk can have classical
(anti-)evaporation instabilities. The bulk instability back-reacts on the
four-dimensional brane, in case that the brane tension vanishes, and the
unstable modes propagate in their world-volume.
| [
{
"created": "Tue, 9 May 2017 10:37:26 GMT",
"version": "v1"
}
] | 2017-06-21 | [
[
"Addazi",
"Andrea",
""
],
[
"Nojiri",
"Shin'ichi",
""
],
[
"Odintsov",
"Sergei",
""
]
] | We study the problem of a four-dimensional brane lying in the five-dimensional degenerate Schwarzschild-de Sitter (Nariai) black hole, in five-dimensional $F(R)$-gravity. We show that there cannot exist the brane in the Nariai bulk space except the case that the brane tension vanishes. We demonstrate that the five-dimensional Nariai bulk is unstable in a large region of the parameter space. In particular, the Nariai bulk can have classical (anti-)evaporation instabilities. The bulk instability back-reacts on the four-dimensional brane, in case that the brane tension vanishes, and the unstable modes propagate in their world-volume. |
gr-qc/0305049 | Yuri N. Obukhov | Guillermo F. Rubilar, Yuri N. Obukhov, Friedrich W. Hehl | Torsion nonminimally coupled to the electromagnetic field and
birefringence | Revtex, 12 pages, no figures | Class.Quant.Grav. 20 (2003) L185-L192 | 10.1088/0264-9381/20/14/101 | null | gr-qc astro-ph hep-th | null | In conventional Maxwell--Lorentz electrodynamics, the propagation of light is
influenced by the metric, not, however, by the possible presence of a torsion
T. Still the light can feel torsion if the latter is coupled nonminimally to
the electromagnetic field F by means of a supplementary Lagrangian of the type
l^2 T^2 F^2 (l = coupling constant). Recently Preuss suggested a specific
nonminimal term of this nature. We evaluate the spacetime relation of Preuss in
the background of a general O(3)-symmetric torsion field and prove by
specifying the optical metric of spacetime that this can yield birefringence in
vacuum. Moreover, we show that the nonminimally coupled homogeneous and
isotropic torsion field in a Friedmann cosmos affects the speed of light.
| [
{
"created": "Tue, 13 May 2003 18:18:34 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Rubilar",
"Guillermo F.",
""
],
[
"Obukhov",
"Yuri N.",
""
],
[
"Hehl",
"Friedrich W.",
""
]
] | In conventional Maxwell--Lorentz electrodynamics, the propagation of light is influenced by the metric, not, however, by the possible presence of a torsion T. Still the light can feel torsion if the latter is coupled nonminimally to the electromagnetic field F by means of a supplementary Lagrangian of the type l^2 T^2 F^2 (l = coupling constant). Recently Preuss suggested a specific nonminimal term of this nature. We evaluate the spacetime relation of Preuss in the background of a general O(3)-symmetric torsion field and prove by specifying the optical metric of spacetime that this can yield birefringence in vacuum. Moreover, we show that the nonminimally coupled homogeneous and isotropic torsion field in a Friedmann cosmos affects the speed of light. |
2207.06007 | Pankaj Sheoran | Shobhit Giri, Pankaj Sheoran, Hemwati Nandan and Sanjar Shaymatov | Chaos motion and Periastron precession of spinning test particles moving
in the vicinage of a Schwarzschild black hole surrounded by a quintessence
matter field | 18 pages, 11 Captioned figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work, our main objective is to investigate the orbits of
spinning test particles around a Schwarzschild black hole under the influence
of a quintessence matter field (SQBH). We begin with the dynamics of the
spinning test particles around SQBH which is governed by the
Mathisson-Papapetrou-Dixon (MPD) equations under the pole-dipole approximation,
where the gravitational field and the higher multipoles of the particle are
neglected. Depending on the types of saddle points,the effective potential are
classified and the possibility of chaotic orbits is discussed. The inner most
stable circular orbits (ISCOs) of the spinning particle around SQBH are
addressed, as are the effects of the parameters $S$ (particles' spin) and
$\epsilon$ (equation of state parameter). Later, Periastron precession is
investigated up to the first-order spin correction for a spinning particle
moving in nearly circular orbits around SQBH. It is noted that the addition of
particle's spin revamps the results obtained for the non-spinning particles and
also articulates the some interesting observational properties of the SQBH.
Additionally, we discuss the ramifications of employing first-order spin
corrections for analysing ISCOs, as well as compare our results to the
Schwarzschild black hole to ensure that they are consistent in the limit when
equation of state parameter $\epsilon=-1/3$ and normalization factor $\alpha
\to 0$.
| [
{
"created": "Wed, 13 Jul 2022 07:26:55 GMT",
"version": "v1"
}
] | 2022-07-14 | [
[
"Giri",
"Shobhit",
""
],
[
"Sheoran",
"Pankaj",
""
],
[
"Nandan",
"Hemwati",
""
],
[
"Shaymatov",
"Sanjar",
""
]
] | In the present work, our main objective is to investigate the orbits of spinning test particles around a Schwarzschild black hole under the influence of a quintessence matter field (SQBH). We begin with the dynamics of the spinning test particles around SQBH which is governed by the Mathisson-Papapetrou-Dixon (MPD) equations under the pole-dipole approximation, where the gravitational field and the higher multipoles of the particle are neglected. Depending on the types of saddle points,the effective potential are classified and the possibility of chaotic orbits is discussed. The inner most stable circular orbits (ISCOs) of the spinning particle around SQBH are addressed, as are the effects of the parameters $S$ (particles' spin) and $\epsilon$ (equation of state parameter). Later, Periastron precession is investigated up to the first-order spin correction for a spinning particle moving in nearly circular orbits around SQBH. It is noted that the addition of particle's spin revamps the results obtained for the non-spinning particles and also articulates the some interesting observational properties of the SQBH. Additionally, we discuss the ramifications of employing first-order spin corrections for analysing ISCOs, as well as compare our results to the Schwarzschild black hole to ensure that they are consistent in the limit when equation of state parameter $\epsilon=-1/3$ and normalization factor $\alpha \to 0$. |
2309.08554 | Tomi Koivisto | D\'ebora Aguiar Gomes, Jose Beltr\'an Jim\'enez, Tomi S. Koivisto | General Parallel Cosmology | 17 pages + appendices and references, 1 table. Submitted v2: less
typos, more refs | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General (tele)parallel Relativity, G$_\parallel$R, is the relativistic
completion of Einstein's theories of gravity. The focus of this article is the
derivation of the homogeneous and isotropic solution in G$_\parallel$R. The
first-principles derivation, based on a non-trivial realisation of the
symmetry, supersedes and unifies previous constructions of Riemannian and
teleparallel cosmologies, and establishes the uniqueness of the physical
solution. The constitutive law and the form of the material and inertial source
currents is presented in the tensor (Palatini) formalism and adapted to the
cosmological background, which exhibits novel features absent in the previously
studied, static solutions to the theory. The results are contrasted with those
in some incomplete theories, such as sitting at the three corners of the
geometrical trinity and corresponding to particular reference frames in
G$_\parallel$R.
| [
{
"created": "Fri, 15 Sep 2023 17:20:35 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Oct 2023 15:31:24 GMT",
"version": "v2"
}
] | 2023-10-18 | [
[
"Gomes",
"Débora Aguiar",
""
],
[
"Jiménez",
"Jose Beltrán",
""
],
[
"Koivisto",
"Tomi S.",
""
]
] | General (tele)parallel Relativity, G$_\parallel$R, is the relativistic completion of Einstein's theories of gravity. The focus of this article is the derivation of the homogeneous and isotropic solution in G$_\parallel$R. The first-principles derivation, based on a non-trivial realisation of the symmetry, supersedes and unifies previous constructions of Riemannian and teleparallel cosmologies, and establishes the uniqueness of the physical solution. The constitutive law and the form of the material and inertial source currents is presented in the tensor (Palatini) formalism and adapted to the cosmological background, which exhibits novel features absent in the previously studied, static solutions to the theory. The results are contrasted with those in some incomplete theories, such as sitting at the three corners of the geometrical trinity and corresponding to particular reference frames in G$_\parallel$R. |
1702.06357 | Kourosh Nozari | Mohsen Khodadi, Kourosh Nozari and Anahita Hajizadeh | Some Astrophysical Aspects of a Schwarzschild Geometry Equipped with a
Minimal Measurable Length | 12 pages, 2 figures, Revised Version, to appear in PLB | Phys. Lett. B 770 (2017) 556 | 10.1016/j.physletb.2017.05.016 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By considering a deformation of the Schwarzschild metric in the presence of a
minimal measurable length which still respects the equivalence principle, we
study corrections to the standard general relativistic predictions for some
astrophysical phenomena such as stability of circular orbits of black hole
accretion disks, redshift of black hole accretion disks, gravitational tidal
forces and the geodetic drift rate. We use the \emph{Gravity Probe B} data to
see robustness of our results. Our analysis shows also that the relevant
deformation parameter $\varepsilon$ which has a geometric origin, plays the
same role as the charge to mass ratio, $\frac{e}{m}$ in the
Reissner-Nordstr\"{o}m metric.
| [
{
"created": "Tue, 21 Feb 2017 12:45:20 GMT",
"version": "v1"
},
{
"created": "Sun, 7 May 2017 13:50:52 GMT",
"version": "v2"
}
] | 2017-06-22 | [
[
"Khodadi",
"Mohsen",
""
],
[
"Nozari",
"Kourosh",
""
],
[
"Hajizadeh",
"Anahita",
""
]
] | By considering a deformation of the Schwarzschild metric in the presence of a minimal measurable length which still respects the equivalence principle, we study corrections to the standard general relativistic predictions for some astrophysical phenomena such as stability of circular orbits of black hole accretion disks, redshift of black hole accretion disks, gravitational tidal forces and the geodetic drift rate. We use the \emph{Gravity Probe B} data to see robustness of our results. Our analysis shows also that the relevant deformation parameter $\varepsilon$ which has a geometric origin, plays the same role as the charge to mass ratio, $\frac{e}{m}$ in the Reissner-Nordstr\"{o}m metric. |
2206.07111 | Ulrich Beckering Vinckers | Ulrich K. Beckering Vinckers, \'Alvaro de la Cruz-Dombriz, Ivan
Kol\'a\v{r}, Francisco J. Maldonado Torralba, Anupam Mazumdar | Ghost-free infinite-derivative dilaton gravity in two dimensions | 21 pages, 5 figures, version accepted for publication in PRD | Phys. Rev. D 106, 064037 (2022) | 10.1103/PhysRevD.106.064037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the ghost-free infinite-derivative extensions of the
Spherically-Reduced Gravity (SRG) and Callan-Giddings-Harvey-Strominger (CGHS)
theories in two space-time dimensions. For the case of SRG, we specify the
Schwarzschild-type gauge and diagonalise the quadratic action for field
perturbations after taking the background fields to be those of the flat-space
solution with a linear dilaton. Using the obtained diagonalisation, we
construct ghost-free infinite-derivative modifications of the SRG theory. In
the context of this modified SRG theory we derive a non-local modification of
the linearised spherically-reduced Schwarzschild solution. For the case of CGHS
gravity, we work in the conformal gauge and diagonalise the quadratic action
associated with this theory for a general background solution. Using these
results, we construct the ghost-free infinite-derivative modifications of the
CGHS theory and examine non-local modifications to the linearised CGHS
black-hole solution.
| [
{
"created": "Tue, 14 Jun 2022 18:53:10 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Sep 2022 10:50:30 GMT",
"version": "v2"
}
] | 2022-09-23 | [
[
"Vinckers",
"Ulrich K. Beckering",
""
],
[
"de la Cruz-Dombriz",
"Álvaro",
""
],
[
"Kolář",
"Ivan",
""
],
[
"Torralba",
"Francisco J. Maldonado",
""
],
[
"Mazumdar",
"Anupam",
""
]
] | We present the ghost-free infinite-derivative extensions of the Spherically-Reduced Gravity (SRG) and Callan-Giddings-Harvey-Strominger (CGHS) theories in two space-time dimensions. For the case of SRG, we specify the Schwarzschild-type gauge and diagonalise the quadratic action for field perturbations after taking the background fields to be those of the flat-space solution with a linear dilaton. Using the obtained diagonalisation, we construct ghost-free infinite-derivative modifications of the SRG theory. In the context of this modified SRG theory we derive a non-local modification of the linearised spherically-reduced Schwarzschild solution. For the case of CGHS gravity, we work in the conformal gauge and diagonalise the quadratic action associated with this theory for a general background solution. Using these results, we construct the ghost-free infinite-derivative modifications of the CGHS theory and examine non-local modifications to the linearised CGHS black-hole solution. |
2102.02215 | Shahar Hod | Shahar Hod | Stationary scalar clouds supported by rapidly-rotating acoustic black
holes in a photon-fluid model | 6 pages | Phys. Rev. D 103, 084003 (2021) | 10.1103/PhysRevD.103.084003 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | It has recently been proved that, in the presence of vortex flows, the
fluctuation dynamics of a rotating photon-fluid model is governed by the
Klein-Gordon equation of an effective massive scalar field in a
$(2+1)$-dimensional acoustic black-hole spacetime. Interestingly, it has been
demonstrated numerically that the rotating acoustic black hole, like the
familiar Kerr black-hole spacetime, may support spatially regular stationary
density fluctuations (linearized acoustic scalar `clouds') in its exterior
regions. In particular, it has been shown that the composed
rotating-acoustic-black-hole-stationary-scalar-field configurations of the
photon-fluid model exist in the narrow dimensionless regime
$\alpha\equiv\Omega_0/m\Omega_{\text{H}}\in(1,\alpha_{\text{max}})$ with
$\alpha_{\text{max}}\simeq 1.08$ [here $\Omega_{\text{H}}$ is the angular
velocity of the black-hole horizon and $\{\Omega_0,m\}$ are respectively the
effective proper mass and the azimuthal harmonic index of the acoustic scalar
field]. In the present paper we use analytical techniques in order to explore
the physical and mathematical properties of the acoustic scalar clouds of the
photon-fluid model in the regime $\Omega_{\text{H}}r_{\text{H}}\gg1$ of
rapidly-spinning central supporting acoustic black holes. In particular, we
derive a remarkably compact analytical formula for the discrete resonance
spectrum $\{\Omega_0(\Omega_{\text{H}},m;n)\}$ which characterizes the
stationary bound-state acoustic scalar clouds of the photon-fluid model.
Interestingly, it is proved that the critical (maximal) mass parameter
$\alpha_{\text{max}}$, which determines the regime of existence of the composed
acoustic-black-hole-stationary-bound-state-massive-scalar-field configurations,
is given by the exact dimensionless relation
$\alpha_{\text{max}}=\sqrt{{{32}\over{27}}}$.
| [
{
"created": "Wed, 3 Feb 2021 19:00:01 GMT",
"version": "v1"
}
] | 2021-04-07 | [
[
"Hod",
"Shahar",
""
]
] | It has recently been proved that, in the presence of vortex flows, the fluctuation dynamics of a rotating photon-fluid model is governed by the Klein-Gordon equation of an effective massive scalar field in a $(2+1)$-dimensional acoustic black-hole spacetime. Interestingly, it has been demonstrated numerically that the rotating acoustic black hole, like the familiar Kerr black-hole spacetime, may support spatially regular stationary density fluctuations (linearized acoustic scalar `clouds') in its exterior regions. In particular, it has been shown that the composed rotating-acoustic-black-hole-stationary-scalar-field configurations of the photon-fluid model exist in the narrow dimensionless regime $\alpha\equiv\Omega_0/m\Omega_{\text{H}}\in(1,\alpha_{\text{max}})$ with $\alpha_{\text{max}}\simeq 1.08$ [here $\Omega_{\text{H}}$ is the angular velocity of the black-hole horizon and $\{\Omega_0,m\}$ are respectively the effective proper mass and the azimuthal harmonic index of the acoustic scalar field]. In the present paper we use analytical techniques in order to explore the physical and mathematical properties of the acoustic scalar clouds of the photon-fluid model in the regime $\Omega_{\text{H}}r_{\text{H}}\gg1$ of rapidly-spinning central supporting acoustic black holes. In particular, we derive a remarkably compact analytical formula for the discrete resonance spectrum $\{\Omega_0(\Omega_{\text{H}},m;n)\}$ which characterizes the stationary bound-state acoustic scalar clouds of the photon-fluid model. Interestingly, it is proved that the critical (maximal) mass parameter $\alpha_{\text{max}}$, which determines the regime of existence of the composed acoustic-black-hole-stationary-bound-state-massive-scalar-field configurations, is given by the exact dimensionless relation $\alpha_{\text{max}}=\sqrt{{{32}\over{27}}}$. |
2205.03643 | Semra G\"urta\c{s} Do\u{g}an | Abdullah Guvendi, Semra Gurtas Dogan | Quasibound states for a scalar field under the influence of an external
magnetic field in the near-horizon geometry of the BTZ black hole with
torsion | null | Indian J Phys (2023) | 10.1007/s12648-023-02743-7 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We consider a charged scalar field under the effect of an external uniform
magnetic field in the near-horizon geometry of the Banados-Teitelboim-Zanelli
black hole with torsion and obtain quasi-stationary states of the system under
consideration through obtaining analytical solution of the corresponding
Klein-Gordon equation. We obtain the solution function of the equation and
accordingly we arrive at a complex spectra. We observe that the real
oscillation frequency of the modes and their decay time depends on the strength
of the external magnetic field besides the parameters of the geometric
background. We see that the amplitude of the real oscillation modes decreases
and the decay time of the modes becomes longer as the strength of the external
magnetic field increases. The results also indicate that the geometric
background is stable under such a perturbation field.
| [
{
"created": "Sat, 7 May 2022 12:34:54 GMT",
"version": "v1"
},
{
"created": "Sun, 29 May 2022 05:53:58 GMT",
"version": "v2"
},
{
"created": "Mon, 4 Jul 2022 17:17:45 GMT",
"version": "v3"
},
{
"created": "Tue, 15 Nov 2022 13:23:21 GMT",
"version": "v4"
}
] | 2023-05-25 | [
[
"Guvendi",
"Abdullah",
""
],
[
"Dogan",
"Semra Gurtas",
""
]
] | We consider a charged scalar field under the effect of an external uniform magnetic field in the near-horizon geometry of the Banados-Teitelboim-Zanelli black hole with torsion and obtain quasi-stationary states of the system under consideration through obtaining analytical solution of the corresponding Klein-Gordon equation. We obtain the solution function of the equation and accordingly we arrive at a complex spectra. We observe that the real oscillation frequency of the modes and their decay time depends on the strength of the external magnetic field besides the parameters of the geometric background. We see that the amplitude of the real oscillation modes decreases and the decay time of the modes becomes longer as the strength of the external magnetic field increases. The results also indicate that the geometric background is stable under such a perturbation field. |
gr-qc/0410053 | Robert Mann | Amjad Ashoorioon and Robert B. Mann | Generation of Cosmological Seed Magnetic Fields from Inflation with
Cutoff | Latex, 16 pages, 2 figures, 4 references added, minor corrections;
v4: more references added, boundary term written in a covariant form,
discussion regarding other gauge fields added, submitted to PRD; v5: matched
with the published version | Phys.Rev. D71 (2005) 103509 | 10.1103/PhysRevD.71.103509 | null | gr-qc astro-ph hep-th | null | Inflation has the potential to seed the galactic magnetic fields observed
today. However, there is an obstacle to the amplification of the quantum
fluctuations of the electromagnetic field during inflation: namely the
conformal invariance of electromagnetic theory on a conformally flat underlying
geometry. As the existence of a preferred minimal length breaks the conformal
invariance of the background geometry, it is plausible that this effect could
generate some electromagnetic field amplification. We show that this scenario
is equivalent to endowing the photon with a large negative mass during
inflation. This effective mass is negligibly small in a radiation and matter
dominated universe. Depending on the value of the free parameter of the theory,
we show that the seed required by the dynamo mechanism can be generated. We
also show that this mechanism can produce the requisite galactic magnetic field
without resorting to a dynamo mechanism.
| [
{
"created": "Tue, 12 Oct 2004 20:11:22 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Oct 2004 19:21:05 GMT",
"version": "v2"
},
{
"created": "Wed, 17 Nov 2004 18:04:44 GMT",
"version": "v3"
},
{
"created": "Fri, 15 Apr 2005 18:50:38 GMT",
"version": "v4"
},
{
"c... | 2007-05-23 | [
[
"Ashoorioon",
"Amjad",
""
],
[
"Mann",
"Robert B.",
""
]
] | Inflation has the potential to seed the galactic magnetic fields observed today. However, there is an obstacle to the amplification of the quantum fluctuations of the electromagnetic field during inflation: namely the conformal invariance of electromagnetic theory on a conformally flat underlying geometry. As the existence of a preferred minimal length breaks the conformal invariance of the background geometry, it is plausible that this effect could generate some electromagnetic field amplification. We show that this scenario is equivalent to endowing the photon with a large negative mass during inflation. This effective mass is negligibly small in a radiation and matter dominated universe. Depending on the value of the free parameter of the theory, we show that the seed required by the dynamo mechanism can be generated. We also show that this mechanism can produce the requisite galactic magnetic field without resorting to a dynamo mechanism. |
1306.1826 | Ignazio Ciufolini | Ignazio Ciufolini | Time travel, Clock Puzzles and Their Experimental Tests | To appear in the European Journal of Physics Web of Conf. (2013) | null | 10.1051/epjconf/20135801005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Is time travel possible? What is Einstein's theory of relativity
mathematically predicting in that regard? Is time travel related to the
so-called clock 'paradoxes' of relativity and if so how? Is there any accurate
experimental evidence of the phenomena regarding the different flow of time
predicted by General Relativity and is there any possible application of the
temporal phenomena predicted by relativity to our everyday life? Which temporal
phenomena are predicted in the vicinities of a rotating body and of a
mass-energy current, and do we have any experimental test of the occurrence of
these phenomena near a rotating body? In this paper, we address and answer some
of these questions.
| [
{
"created": "Fri, 7 Jun 2013 10:56:14 GMT",
"version": "v1"
}
] | 2017-03-22 | [
[
"Ciufolini",
"Ignazio",
""
]
] | Is time travel possible? What is Einstein's theory of relativity mathematically predicting in that regard? Is time travel related to the so-called clock 'paradoxes' of relativity and if so how? Is there any accurate experimental evidence of the phenomena regarding the different flow of time predicted by General Relativity and is there any possible application of the temporal phenomena predicted by relativity to our everyday life? Which temporal phenomena are predicted in the vicinities of a rotating body and of a mass-energy current, and do we have any experimental test of the occurrence of these phenomena near a rotating body? In this paper, we address and answer some of these questions. |
1212.4318 | Remo Garattini | Remo Garattini | Effects of Modified Dispersion Relations and Noncommutative Geometry on
the Cosmological Constant Computation | 8 Pages. Prepared for the Proceedings of the "Twelfth international
Symposium Frontiers of fundamental Physics FFP12", Udine 21-23.11.11 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute Zero Point Energy in a spherically symmetric background with the
help of the Wheeler-DeWitt equation. This last one is regarded as a
Sturm-Liouville problem with the cosmological constant considered as the
associated eigenvalue. The graviton contribution, at one loop is extracted with
the help of a variational approach together with Gaussian trial functionals.
The divergences handled with a zeta function regularization are compared with
the results obtained using a Noncommutative Geometry (NCG) and Modified
Dispersion Relations (MDR). In both NCG and MDR no renormalization scheme is
necessary to remove infinities in contrast to what happens in conventional
approaches. Effects on photon propagation are briefly discussed.
| [
{
"created": "Tue, 18 Dec 2012 11:42:36 GMT",
"version": "v1"
}
] | 2012-12-19 | [
[
"Garattini",
"Remo",
""
]
] | We compute Zero Point Energy in a spherically symmetric background with the help of the Wheeler-DeWitt equation. This last one is regarded as a Sturm-Liouville problem with the cosmological constant considered as the associated eigenvalue. The graviton contribution, at one loop is extracted with the help of a variational approach together with Gaussian trial functionals. The divergences handled with a zeta function regularization are compared with the results obtained using a Noncommutative Geometry (NCG) and Modified Dispersion Relations (MDR). In both NCG and MDR no renormalization scheme is necessary to remove infinities in contrast to what happens in conventional approaches. Effects on photon propagation are briefly discussed. |
gr-qc/0409003 | John J. Oh | Sung-Won Kim, Won Tae Kim, and John J. Oh | Decay Rate and Low-Energy Near-Horizon Dynamics of Acoustic Black Holes | 13pages, 3figures, RevTeX3, some minors corrected. version to appear
in PLB | Phys.Lett.B608:10-16,2005 | 10.1016/j.physletb.2005.01.012 | null | gr-qc hep-th | null | We study the low-energy dynamics of an acoustic black hole near the sonic
horizon. For the experimental test of black hole evaporation in the laboratory,
the decay rate (greybody factor) of the acoustic black hole (sonic hole) can be
calculated by the usual low-energy perturbation method. As a consequence, we
obtain the decay rate of the sonic horizon from the absorption and the
reflection coefficients. Moreover, we show that the thermal emission from the
sonic horizon is only proportional to a control parameter which describes the
velocity of the fluid.
| [
{
"created": "Wed, 1 Sep 2004 04:52:25 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Oct 2004 17:38:39 GMT",
"version": "v2"
},
{
"created": "Thu, 25 Nov 2004 20:31:01 GMT",
"version": "v3"
}
] | 2010-11-05 | [
[
"Kim",
"Sung-Won",
""
],
[
"Kim",
"Won Tae",
""
],
[
"Oh",
"John J.",
""
]
] | We study the low-energy dynamics of an acoustic black hole near the sonic horizon. For the experimental test of black hole evaporation in the laboratory, the decay rate (greybody factor) of the acoustic black hole (sonic hole) can be calculated by the usual low-energy perturbation method. As a consequence, we obtain the decay rate of the sonic horizon from the absorption and the reflection coefficients. Moreover, we show that the thermal emission from the sonic horizon is only proportional to a control parameter which describes the velocity of the fluid. |
2205.05891 | Shiraz Khan | Shiraz Khan, S. A. Mardan, M. A. Rehman | Development of complexity induced frameworks for charged cylindrical
polytropes | 21 pages, 6 figures | null | 10.1088/1475-7516/2022/07/023 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | The main theme of this work is the development of complexity induced
generalized frameworks for static cylindrical polytropes. We consider two
different definitions of generalized polytopes with charged anisotropic inner
fluid distribution. A new methodology based on complexity factor for the
generation of consistent sets of differential equations will be presented. We
conclude our work by carrying out graphical analysis of developed frameworks.
| [
{
"created": "Thu, 12 May 2022 06:05:19 GMT",
"version": "v1"
}
] | 2022-07-20 | [
[
"Khan",
"Shiraz",
""
],
[
"Mardan",
"S. A.",
""
],
[
"Rehman",
"M. A.",
""
]
] | The main theme of this work is the development of complexity induced generalized frameworks for static cylindrical polytropes. We consider two different definitions of generalized polytopes with charged anisotropic inner fluid distribution. A new methodology based on complexity factor for the generation of consistent sets of differential equations will be presented. We conclude our work by carrying out graphical analysis of developed frameworks. |
gr-qc/9809010 | Toru Tsuchida | Tooru Tsuchida, Kazuya Watanabe | Comment on the exterior solutions and their geometry in scalar-tensor
theories of gravity | 18 pages, 3 figures, Submitted to Progress of Theoretical Physics | Prog.Theor.Phys.101:73-90,1999 | 10.1143/PTP.101.73 | null | gr-qc | null | We study series of the stationary solutions with asymptotic flatness
properties in the Einstein-Maxwell-free scalar system because they are locally
equivalent with the exterior solutions in some class of the scalar-tensor
theories of gravity. First, we classify spherical exterior solutions into two
types of the solutions, an apparently black hole type solution and an
apparently worm hole type solution. The solutions contain three parameters, and
we clarify their physical significance. Second, we reduce the field equations
for the axisymmetric exterior solutions. We find that the reduced equations are
partially the same as the Ernst equations. As simple examples, we derive new
series of the static, axisymmetric exterior solutions, which correspond to
Voorhees's solutions. We then show a non-trivial relation between the spherical
exterior solutions and our new solutions. Finally, since null geodesics have
conformally invariant properties, we study the local geometry of the exterior
solutions by using the optical scalar equations and find some anomalous
behaviors of the null geodesics.
| [
{
"created": "Wed, 2 Sep 1998 14:16:53 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Sep 1998 09:56:02 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Tsuchida",
"Tooru",
""
],
[
"Watanabe",
"Kazuya",
""
]
] | We study series of the stationary solutions with asymptotic flatness properties in the Einstein-Maxwell-free scalar system because they are locally equivalent with the exterior solutions in some class of the scalar-tensor theories of gravity. First, we classify spherical exterior solutions into two types of the solutions, an apparently black hole type solution and an apparently worm hole type solution. The solutions contain three parameters, and we clarify their physical significance. Second, we reduce the field equations for the axisymmetric exterior solutions. We find that the reduced equations are partially the same as the Ernst equations. As simple examples, we derive new series of the static, axisymmetric exterior solutions, which correspond to Voorhees's solutions. We then show a non-trivial relation between the spherical exterior solutions and our new solutions. Finally, since null geodesics have conformally invariant properties, we study the local geometry of the exterior solutions by using the optical scalar equations and find some anomalous behaviors of the null geodesics. |
1312.4128 | Chen Songbai | LiYong Ji, Songbai Chen, Jiliang Jing | Strong gravitational lensing in a rotating Kaluza-Klein black hole with
squashed horizons | 20 pages; 7 figures. Accepted for publication in JHEP. arXiv admin
note: substantial text overlap with arXiv:1102.0086 | JHEP 03 (2014) 089 | 10.1007/JHEP03(2014)089 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have investigated the strong gravitational lensing in a rotating squashed
Kaluza-Klein (KK) black hole spacetime. Our result show that the strong
gravitational lensings in the rotating squashed KK black hole spacetime have
some distinct behaviors from those in the backgrounds of the four-dimensional
Kerr black hole and of the squashed KK G\"{o}del black hole. In the rotating
squashed KK black hole spacetime, the marginally circular photon radius
$\rho_{ps}$, the coefficient $\bar{a}$, $\bar{b}$, the deflection angle
$\alpha(\theta)$ in the $\phi$ direction and the corresponding observational
variables are independent of whether the photon goes with or against the
rotation of the background, which is different with those in the usual
four-dimensional Kerr black hole spacetime. Moreover, we also find that with
the increase of the scale of extra dimension $\rho_0$, the marginally circular
photon radius $\rho_{ps}$ and the angular position of the relativistic images
$\theta_\infty$ first decreases and then increases in the rotating squashed KK
black hole for fixed rotation parameter $b$, but in the squashed KK G\"{o}del
black hole they increase for the smaller global rotation parameter $j$ and
decrease for the larger one. In the extremely squashed case $\rho_0=0$, the
coefficient $\bar{a}$ in the rotating squashed KK black hole increases
monotonously with the rotation parameter, but in the squashed KK G\"{o}del
black hole it is a constant and independent of the global rotation of the
G\"{o}del Universe.
| [
{
"created": "Sun, 15 Dec 2013 09:50:39 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Feb 2014 04:01:09 GMT",
"version": "v2"
}
] | 2014-04-01 | [
[
"Ji",
"LiYong",
""
],
[
"Chen",
"Songbai",
""
],
[
"Jing",
"Jiliang",
""
]
] | We have investigated the strong gravitational lensing in a rotating squashed Kaluza-Klein (KK) black hole spacetime. Our result show that the strong gravitational lensings in the rotating squashed KK black hole spacetime have some distinct behaviors from those in the backgrounds of the four-dimensional Kerr black hole and of the squashed KK G\"{o}del black hole. In the rotating squashed KK black hole spacetime, the marginally circular photon radius $\rho_{ps}$, the coefficient $\bar{a}$, $\bar{b}$, the deflection angle $\alpha(\theta)$ in the $\phi$ direction and the corresponding observational variables are independent of whether the photon goes with or against the rotation of the background, which is different with those in the usual four-dimensional Kerr black hole spacetime. Moreover, we also find that with the increase of the scale of extra dimension $\rho_0$, the marginally circular photon radius $\rho_{ps}$ and the angular position of the relativistic images $\theta_\infty$ first decreases and then increases in the rotating squashed KK black hole for fixed rotation parameter $b$, but in the squashed KK G\"{o}del black hole they increase for the smaller global rotation parameter $j$ and decrease for the larger one. In the extremely squashed case $\rho_0=0$, the coefficient $\bar{a}$ in the rotating squashed KK black hole increases monotonously with the rotation parameter, but in the squashed KK G\"{o}del black hole it is a constant and independent of the global rotation of the G\"{o}del Universe. |
1001.3096 | Gaston Giribet | C. Garraffo, G. Giribet, E. Gravanis, S. Willison | Vacuum thin shell solutions in five-dimensional Lovelock gravity | 9 pages. This is an extended version of the authors' contribution to
the Proceedings of the Marcel Grossmann Meeting, held in Paris, 12-18 July
2009 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Junction conditions for vacuum solutions in five-dimensional
Einstein-Gauss-Bonnet gravity are studied. We focus on those cases where two
spherically symmetric regions of space-time are joined in such a way that the
induced stress tensor on the junction surface vanishes. So a spherical vacuum
shell, containing no matter, arises as a boundary between two regions of the
space-time. Such solutions are a generalized kind of spherically symmetric
empty space solutions, described by metric functions of the class $C^0$. New
global structures arise with surprising features. In particular, we show that
vacuum spherically symmetric wormholes do exist in this theory. These can be
regarded as gravitational solitons, which connect two asymptotically (Anti)
de-Sitter spaces with different masses and/or different effective cosmological
constants. We prove the existence of both static and dynamical solutions and
discuss their (in)stability under perturbations that preserve the symmetry.
This leads us to discuss a new type of instability that arises in
five-dimensional Lovelock theory of gravity for certain values of the coupling
of the Gauss-Bonnet term.
| [
{
"created": "Mon, 18 Jan 2010 18:23:28 GMT",
"version": "v1"
}
] | 2010-01-19 | [
[
"Garraffo",
"C.",
""
],
[
"Giribet",
"G.",
""
],
[
"Gravanis",
"E.",
""
],
[
"Willison",
"S.",
""
]
] | Junction conditions for vacuum solutions in five-dimensional Einstein-Gauss-Bonnet gravity are studied. We focus on those cases where two spherically symmetric regions of space-time are joined in such a way that the induced stress tensor on the junction surface vanishes. So a spherical vacuum shell, containing no matter, arises as a boundary between two regions of the space-time. Such solutions are a generalized kind of spherically symmetric empty space solutions, described by metric functions of the class $C^0$. New global structures arise with surprising features. In particular, we show that vacuum spherically symmetric wormholes do exist in this theory. These can be regarded as gravitational solitons, which connect two asymptotically (Anti) de-Sitter spaces with different masses and/or different effective cosmological constants. We prove the existence of both static and dynamical solutions and discuss their (in)stability under perturbations that preserve the symmetry. This leads us to discuss a new type of instability that arises in five-dimensional Lovelock theory of gravity for certain values of the coupling of the Gauss-Bonnet term. |
gr-qc/9906048 | Stoytcho Yazadjiev | S.Yazadjiev | Exact static solutions in four dimensional Einstein-Maxwell-Dilaton
gravity | 8 pages, latex | Int.J.Mod.Phys. D8 (1999) 635-643 | 10.1142/S0218271899000432 | SUTH 99-14 | gr-qc | null | Classes of exact static solutions in four-dimensional
Einstein-Maxwell-Dilaton gravity are found. Besides of the well-known solutions
previously found in the literature, new solutions are presented.It's shown that
spherically symmetric solutions, except the case of charged dilaton black hole,
represent globally naked strong curvature singularities.
| [
{
"created": "Tue, 15 Jun 1999 11:29:12 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Yazadjiev",
"S.",
""
]
] | Classes of exact static solutions in four-dimensional Einstein-Maxwell-Dilaton gravity are found. Besides of the well-known solutions previously found in the literature, new solutions are presented.It's shown that spherically symmetric solutions, except the case of charged dilaton black hole, represent globally naked strong curvature singularities. |
1907.00027 | Pablo Laguna | Kenny Higginbotham, Bhavesh Khamesra, Jame P. McInerney, Karan Jani,
Deirdre M. Shoemaker, Pablo Laguna | Coping with Junk Radiation in Binary Black Hole Simulations | 5 pages, 6 figures | Phys. Rev. D 100, 081501 (2019) | 10.1103/PhysRevD.100.081501 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spurious junk radiation in the initial data for binary black hole numerical
simulations has been an issue of concern. The radiation affects the masses and
spins of the black holes, modifying their orbital dynamics and thus potentially
compromising the accuracy of templates used in gravitational wave analysis. Our
study finds that junk radiation effects are localized to the vicinity of the
black holes. Using insights from single black hole simulations, we obtain
fitting formulas to estimate the changes from junk radiation on the mass and
spin magnitude of the black holes in binary systems. We demonstrate how these
fitting formulas could be used to adjust the initial masses and spin magnitudes
of the black holes, so the resulting binary has the desired parameters after
the junk radiation has left the computational domain. A comparison of waveforms
from raw simulations with those from simulations that have been adjusted for
junk radiation demonstrate that junk radiation could have an appreciable effect
on the templates for LIGO sources with SNRs above 30.
| [
{
"created": "Fri, 28 Jun 2019 18:29:22 GMT",
"version": "v1"
}
] | 2019-10-09 | [
[
"Higginbotham",
"Kenny",
""
],
[
"Khamesra",
"Bhavesh",
""
],
[
"McInerney",
"Jame P.",
""
],
[
"Jani",
"Karan",
""
],
[
"Shoemaker",
"Deirdre M.",
""
],
[
"Laguna",
"Pablo",
""
]
] | Spurious junk radiation in the initial data for binary black hole numerical simulations has been an issue of concern. The radiation affects the masses and spins of the black holes, modifying their orbital dynamics and thus potentially compromising the accuracy of templates used in gravitational wave analysis. Our study finds that junk radiation effects are localized to the vicinity of the black holes. Using insights from single black hole simulations, we obtain fitting formulas to estimate the changes from junk radiation on the mass and spin magnitude of the black holes in binary systems. We demonstrate how these fitting formulas could be used to adjust the initial masses and spin magnitudes of the black holes, so the resulting binary has the desired parameters after the junk radiation has left the computational domain. A comparison of waveforms from raw simulations with those from simulations that have been adjusted for junk radiation demonstrate that junk radiation could have an appreciable effect on the templates for LIGO sources with SNRs above 30. |
0906.1448 | Hideki Asada | Yuji Torigoe, Keisuke Hattori, Hideki Asada | Gravitational waveforms for 2- and 3-body gravitating systems | 11 pages, 4 figures, accepted for publication in PRL | Phys.Rev.Lett.102:251101,2009 | 10.1103/PhysRevLett.102.251101 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Different numbers of self-gravitating particles (in different types of
periodic motion) are most likely to generate very different shapes of
gravitational waves, some of which, however, can be accidentally almost the
same. One such example is a binary and a three-body system for Lagrange's
solution. To track the evolution of these similar waveforms, we define a chirp
mass to the triple system. Thereby, we show that the quadrupole waveforms
cannot distinguish the sources. It is suggested that waveforms with higher
$\ell$-th multipoles will be important for classification of them (with a
conjecture of $\ell \leq N$ for N particles).
| [
{
"created": "Mon, 8 Jun 2009 09:39:16 GMT",
"version": "v1"
}
] | 2009-07-22 | [
[
"Torigoe",
"Yuji",
""
],
[
"Hattori",
"Keisuke",
""
],
[
"Asada",
"Hideki",
""
]
] | Different numbers of self-gravitating particles (in different types of periodic motion) are most likely to generate very different shapes of gravitational waves, some of which, however, can be accidentally almost the same. One such example is a binary and a three-body system for Lagrange's solution. To track the evolution of these similar waveforms, we define a chirp mass to the triple system. Thereby, we show that the quadrupole waveforms cannot distinguish the sources. It is suggested that waveforms with higher $\ell$-th multipoles will be important for classification of them (with a conjecture of $\ell \leq N$ for N particles). |
gr-qc/0301060 | Roberto Gomez | Nigel T. Bishop, Roberto Gomez, Sascha Husa, Luis Lehner, Jeffrey
Winicour | A numerical relativistic model of a massive particle in orbit near a
Schwarzschild black hole | 12 pages, 9 figures, RevTeX4, to appear in Phys. Rev. D | Phys.Rev. D68 (2003) 084015 | 10.1103/PhysRevD.68.084015 | AEI-2003-006, NSF-KITP-03-55 | gr-qc | null | We present a method for computing the evolution of a spacetime containing a
massive particle and a black hole. The essential idea is that the gravitational
field is evolved using full numerical relativity, with the particle generating
a non-zero source term in the Einstein equations. The matter fields are not
evolved by hydrodynamic equations. Instead the particle is treated as a rigid
body whose center follows a geodesic. The necessary theoretical framework is
developed and then implemented in a computer code that uses the null-cone, or
characteristic, formulation of numerical relativity. The performance of the
code is illustrated in test runs, including a complete orbit (near r=9M) of a
Schwarzschild black hole.
| [
{
"created": "Thu, 16 Jan 2003 16:14:01 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Sep 2003 17:51:41 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Bishop",
"Nigel T.",
""
],
[
"Gomez",
"Roberto",
""
],
[
"Husa",
"Sascha",
""
],
[
"Lehner",
"Luis",
""
],
[
"Winicour",
"Jeffrey",
""
]
] | We present a method for computing the evolution of a spacetime containing a massive particle and a black hole. The essential idea is that the gravitational field is evolved using full numerical relativity, with the particle generating a non-zero source term in the Einstein equations. The matter fields are not evolved by hydrodynamic equations. Instead the particle is treated as a rigid body whose center follows a geodesic. The necessary theoretical framework is developed and then implemented in a computer code that uses the null-cone, or characteristic, formulation of numerical relativity. The performance of the code is illustrated in test runs, including a complete orbit (near r=9M) of a Schwarzschild black hole. |
2407.12946 | Ali Bleybel Dr. | Ali Bleybel | On the conformal group of a globally hyperbolic spacetime | null | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Groups of causal and conformal automorphisms of globally hyperbolic
spacetimes were studied.
In two dimensions, we prove that all globally hyperbolic spacetimes that are
directed and connected are causally isomorphic. We work out the consequences of
this fact and obtain a (partial) classification of the causal automorphism and
conformal groups of a two-dimensional globally hyperbolic space.
Finally, we present a generalization for locally conformally flat globally
hyperbolic spacetimes.
| [
{
"created": "Wed, 17 Jul 2024 18:24:12 GMT",
"version": "v1"
}
] | 2024-07-19 | [
[
"Bleybel",
"Ali",
""
]
] | The Groups of causal and conformal automorphisms of globally hyperbolic spacetimes were studied. In two dimensions, we prove that all globally hyperbolic spacetimes that are directed and connected are causally isomorphic. We work out the consequences of this fact and obtain a (partial) classification of the causal automorphism and conformal groups of a two-dimensional globally hyperbolic space. Finally, we present a generalization for locally conformally flat globally hyperbolic spacetimes. |
gr-qc/9807077 | Jorge Pullin | Reinaldo Gleiser, Carlos Nicasio, Richard Price and Jorge Pullin | Gravitational radiation from Schwarzschild black holes: the second order
perturbation formalism | 28 pages, no figures, RevTeX, final version to appear in Physics
Reports | Phys.Rept. 325 (2000) 41-81 | 10.1016/S0370-1573(99)00048-4 | CGPG-98/7-2 | gr-qc astro-ph | null | The perturbation theory of black holes has been useful recently for providing
estimates of gravitational radiation from black hole collisions. Second order
perturbation theory, relatively undeveloped until recently, has proved to be
important both for providing refined estimates and for indicating the range of
validity of perturbation theory. Here we present the second order formalism for
perturbations of Schwarzschild spacetimes. The emphasis is on practical methods
for carrying out second order computations of outgoing radiation. General
issues are illustrated throughout with examples from ``close-limit'' results,
perturbation calculations in which black holes start from small separation.
| [
{
"created": "Wed, 29 Jul 1998 05:10:41 GMT",
"version": "v1"
},
{
"created": "Fri, 7 May 1999 04:00:23 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Gleiser",
"Reinaldo",
""
],
[
"Nicasio",
"Carlos",
""
],
[
"Price",
"Richard",
""
],
[
"Pullin",
"Jorge",
""
]
] | The perturbation theory of black holes has been useful recently for providing estimates of gravitational radiation from black hole collisions. Second order perturbation theory, relatively undeveloped until recently, has proved to be important both for providing refined estimates and for indicating the range of validity of perturbation theory. Here we present the second order formalism for perturbations of Schwarzschild spacetimes. The emphasis is on practical methods for carrying out second order computations of outgoing radiation. General issues are illustrated throughout with examples from ``close-limit'' results, perturbation calculations in which black holes start from small separation. |
0806.0950 | Matt Visser | Jozef Skakala (Victoria University of Wellington), Matt Visser
(Victoria University of Wellington) | Pseudo-Finslerian spacetimes and multi-refringence | V1: 19 pages. V2: Now 30 pages. Title changed, discussion
considerably expanded and rearranged, references more than doubled. This
version accepted for publication in International Journal of Modern Physics
D. | Int.J.Mod.Phys.D19:1119-1146,2010 | 10.1142/S0218271810017172 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is reasonably well-known that birefringent crystal optics can to some
extent be described by the use of pseudo-Finslerian spacetimes (an extension of
pseudo-Riemannian spacetime). What is less commonly appreciated is that there
are two separate and quite disjoint pseudo-Finsler structures for the two
photon polarizations, and further, that there are separate tangent-space
pseudo-Finsler structures defined by the group velocity and co-tangent-space
pseudo-co-Finsler structures defined by the phase velocity. The
inter-connections between these four separate pseudo-Finsler structures are
rather subtle. One particular source of technical difficulty is the fact that
because physicists need to use pseudo-Finsler structures to describe
propagation of signals, there will be nonzero null vectors in both the tangent
and cotangent spaces -- this causes significant problems in that many of the
mathematical results normally obtained for "usual'' (Euclidean signature)
Finsler structures either do not apply, or require significant modifications to
their formulation. We shall first provide a few basic definitions, and then
present a tutorial outline of the relevant physics of birefringent optics,
explicitly demonstrating the interpretation in terms of pseudo-Finsler
spacetimes. We shall then discuss the tricky issues that arise when trying to
inter-relate the various pseudo-Finsler structures we encounter, and finish by
connecting these technical questions (which of course arise in what is a
physically a very well-understood situation) back to ongoing research into
possible extensions and modifications of general relativity.
| [
{
"created": "Thu, 5 Jun 2008 11:42:38 GMT",
"version": "v1"
},
{
"created": "Fri, 7 May 2010 22:43:39 GMT",
"version": "v2"
}
] | 2014-11-18 | [
[
"Skakala",
"Jozef",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | It is reasonably well-known that birefringent crystal optics can to some extent be described by the use of pseudo-Finslerian spacetimes (an extension of pseudo-Riemannian spacetime). What is less commonly appreciated is that there are two separate and quite disjoint pseudo-Finsler structures for the two photon polarizations, and further, that there are separate tangent-space pseudo-Finsler structures defined by the group velocity and co-tangent-space pseudo-co-Finsler structures defined by the phase velocity. The inter-connections between these four separate pseudo-Finsler structures are rather subtle. One particular source of technical difficulty is the fact that because physicists need to use pseudo-Finsler structures to describe propagation of signals, there will be nonzero null vectors in both the tangent and cotangent spaces -- this causes significant problems in that many of the mathematical results normally obtained for "usual'' (Euclidean signature) Finsler structures either do not apply, or require significant modifications to their formulation. We shall first provide a few basic definitions, and then present a tutorial outline of the relevant physics of birefringent optics, explicitly demonstrating the interpretation in terms of pseudo-Finsler spacetimes. We shall then discuss the tricky issues that arise when trying to inter-relate the various pseudo-Finsler structures we encounter, and finish by connecting these technical questions (which of course arise in what is a physically a very well-understood situation) back to ongoing research into possible extensions and modifications of general relativity. |
1902.05760 | Betti Hartmann | Yves Brihaye (Universite de Mons, Belgium) and Betti Hartmann
(IFSC/USP, Brazil) | Spontaneous scalarization of charged black holes at the approach to
extremality | 13 pages including 6 figures and one table | null | 10.1016/j.physletb.2019.03.043 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study static, spherically symmetric and electrically charged black hole
solutions in a quadratic Einstein-scalar-Gauss-Bonnet gravity model. Very
similar to the uncharged case, black holes undergo spontaneous scalarization
for sufficiently large scalar-tensor coupling $\gamma$ - a phenomenon
attributed to a tachyonic instability of the scalar field system. While in the
uncharged case, this effect is only possible for positive values of $\gamma$,
we show that for sufficiently large values of the electric charge $Q$ two
independent domains of existence in the $\gamma$-$Q$-plane appear: one for
positive $\gamma$ and one for negative $\gamma$. We demonstrate that this new
domain for negative $\gamma$ exists because of the fact that the near-horizon
geometry of a nearly extremally charged black hole is $AdS_2\times S^2$.This
new domain appears for electric charges larger than approximately 74$\%$ of the
extremal charge. For positive $\gamma$ we observe that a singularity with
diverging curvature invariants forms outside the horizon when approaching
extremality.
| [
{
"created": "Fri, 15 Feb 2019 10:37:59 GMT",
"version": "v1"
}
] | 2019-04-03 | [
[
"Brihaye",
"Yves",
"",
"Universite de Mons, Belgium"
],
[
"Hartmann",
"Betti",
"",
"IFSC/USP, Brazil"
]
] | We study static, spherically symmetric and electrically charged black hole solutions in a quadratic Einstein-scalar-Gauss-Bonnet gravity model. Very similar to the uncharged case, black holes undergo spontaneous scalarization for sufficiently large scalar-tensor coupling $\gamma$ - a phenomenon attributed to a tachyonic instability of the scalar field system. While in the uncharged case, this effect is only possible for positive values of $\gamma$, we show that for sufficiently large values of the electric charge $Q$ two independent domains of existence in the $\gamma$-$Q$-plane appear: one for positive $\gamma$ and one for negative $\gamma$. We demonstrate that this new domain for negative $\gamma$ exists because of the fact that the near-horizon geometry of a nearly extremally charged black hole is $AdS_2\times S^2$.This new domain appears for electric charges larger than approximately 74$\%$ of the extremal charge. For positive $\gamma$ we observe that a singularity with diverging curvature invariants forms outside the horizon when approaching extremality. |
2301.09768 | Tiziano Schiavone | Tiziano Schiavone, Giovanni Montani | Signature of $f\left(R\right)$ gravity via Lema\^itre-Tolman-Bondi
inhomogeneous perturbations | 31 pages, 5 figures, updated to match published version | EPJC 84, 490 (2024) | 10.1140/epjc/s10052-024-12842-2 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | We analyze inhomogeneous cosmological models in the local Universe, described
by the Lema\^itre-Tolman-Bondi (LTB) metric and developed using linear
perturbation theory on a homogeneous and isotropic Universe background.
Focusing on the different evolution of spherical symmetric inhomogeneities, we
compare the $\Lambda$LTB model, in which the cosmological constant $\Lambda$ is
included in the LTB formalism, with inhomogeneous cosmological models based on
$f\left(R\right)$ modified gravity theories viewed in the Jordan frame. We
solve the system of field equations for both inhomogeneous cosmological models
adopting the method of separation of variables: we integrate analytically the
radial profiles of local perturbations, while their time evolution requires a
numerical approach. The main result of the analysis concerns the different
radial profiles of local inhomogeneities due to the presence of a non-minimally
coupled scalar field in the Jordan frame of $f\left(R\right)$ gravity. While
radial perturbations follow a power-law in the $\Lambda$LTB model, Yukawa-like
contributions appear in the $f\left(R\right)$ theory. Interestingly, this
latter peculiar behavior of radial profile is not affected by the choice of the
$f\left(R\right)$ functional form. The numerical solution of time-dependent
perturbations exhibits a non-diverging profile. This work suggests that
investigations about local inhomogeneities in the late Universe may allow us to
discriminate if the present cosmic acceleration is caused by a cosmological
constant term or a modified gravity effect.
| [
{
"created": "Tue, 24 Jan 2023 00:38:27 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Jul 2023 18:39:54 GMT",
"version": "v2"
},
{
"created": "Wed, 10 Jan 2024 16:23:44 GMT",
"version": "v3"
},
{
"created": "Wed, 15 May 2024 17:34:05 GMT",
"version": "v4"
}
] | 2024-05-16 | [
[
"Schiavone",
"Tiziano",
""
],
[
"Montani",
"Giovanni",
""
]
] | We analyze inhomogeneous cosmological models in the local Universe, described by the Lema\^itre-Tolman-Bondi (LTB) metric and developed using linear perturbation theory on a homogeneous and isotropic Universe background. Focusing on the different evolution of spherical symmetric inhomogeneities, we compare the $\Lambda$LTB model, in which the cosmological constant $\Lambda$ is included in the LTB formalism, with inhomogeneous cosmological models based on $f\left(R\right)$ modified gravity theories viewed in the Jordan frame. We solve the system of field equations for both inhomogeneous cosmological models adopting the method of separation of variables: we integrate analytically the radial profiles of local perturbations, while their time evolution requires a numerical approach. The main result of the analysis concerns the different radial profiles of local inhomogeneities due to the presence of a non-minimally coupled scalar field in the Jordan frame of $f\left(R\right)$ gravity. While radial perturbations follow a power-law in the $\Lambda$LTB model, Yukawa-like contributions appear in the $f\left(R\right)$ theory. Interestingly, this latter peculiar behavior of radial profile is not affected by the choice of the $f\left(R\right)$ functional form. The numerical solution of time-dependent perturbations exhibits a non-diverging profile. This work suggests that investigations about local inhomogeneities in the late Universe may allow us to discriminate if the present cosmic acceleration is caused by a cosmological constant term or a modified gravity effect. |
2407.06926 | Som Dev Bishoyi | Som Dev Bishoyi, Subir Sabharwal and Gaurav Khanna | Non-Axisymmetric Gravitational "Hair" for Extremal Black Holes | 7 pages, 9 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Various generalizations of the scalar, axisymmetric Aretakis "horizon hair"
for extremal black holes have recently appeared in the literature. In this
paper, we present an expression for a non-axisymmetric Aretakis gravitational
charge and its potentially observable imprint at a finite distance from the
horizon (Ori-coefficient) in extremal Kerr black hole backgrounds. We offer
strong and robust numerical evidence for the existence of this hair and its
properties. Specifically, we consider the time evolution of horizon
penetrating, quadrupolar and (subdominant) octupolar gravitational
perturbations with compact support on extremal Kerr (EK) spacetime. We do this
by numerically solving the Teukolsky equation and determining the Aretakis
charge values on the horizon and at a finite distance from the black hole.
| [
{
"created": "Tue, 9 Jul 2024 15:03:24 GMT",
"version": "v1"
}
] | 2024-07-11 | [
[
"Bishoyi",
"Som Dev",
""
],
[
"Sabharwal",
"Subir",
""
],
[
"Khanna",
"Gaurav",
""
]
] | Various generalizations of the scalar, axisymmetric Aretakis "horizon hair" for extremal black holes have recently appeared in the literature. In this paper, we present an expression for a non-axisymmetric Aretakis gravitational charge and its potentially observable imprint at a finite distance from the horizon (Ori-coefficient) in extremal Kerr black hole backgrounds. We offer strong and robust numerical evidence for the existence of this hair and its properties. Specifically, we consider the time evolution of horizon penetrating, quadrupolar and (subdominant) octupolar gravitational perturbations with compact support on extremal Kerr (EK) spacetime. We do this by numerically solving the Teukolsky equation and determining the Aretakis charge values on the horizon and at a finite distance from the black hole. |
gr-qc/0501015 | Jakob Hansen | Jakob Hansen, Alexei Khokhlov and Igor Novikov | Physics of the interior of a spherical, charged black hole with a scalar
field | null | Phys.Rev. D71 (2005) 064013 | 10.1103/PhysRevD.71.064013 | null | gr-qc | null | We analyse the physics of nonlinear gravitational processes inside a
spherical charged black hole perturbed by a self-gravitating massless scalar
field. For this purpose we created an appropriate numerical code. Throughout
the paper, in addition to investigation of the properties of the mathematical
singularities where some curvature scalars are equal to infinity, we analyse
the properties of the physical singularities where the Kretschmann curvature
scalar is equal to the planckian value. Using a homogeneous approximation we
analyse the properties of the spacetime near a spacelike singularity in
spacetimes influenced by different matter contents namely a scalar field,
pressureless dust and matter with ultrarelativistic isotropic pressure. We also
carry out full nonlinear analyses of the scalar field and geometry of spacetime
inside black holes by means of an appropriate numerical code with adaptive mesh
refinement capabilities. We use this code to investigate the nonlinear effects
of gravitational focusing, mass inflation, matter squeeze, and these effects
dependence on the initial boundary conditions. It is demonstrated that the
position of the physical singularity inside a black hole is quite different
from the positions of the mathematical singularities. In the case of the
existence of a strong outgoing flux of the scalar field inside a black hole it
is possible to have the existence of two null singularities and one central
$r=0$ singularity simultaneously.
| [
{
"created": "Thu, 6 Jan 2005 13:44:24 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Hansen",
"Jakob",
""
],
[
"Khokhlov",
"Alexei",
""
],
[
"Novikov",
"Igor",
""
]
] | We analyse the physics of nonlinear gravitational processes inside a spherical charged black hole perturbed by a self-gravitating massless scalar field. For this purpose we created an appropriate numerical code. Throughout the paper, in addition to investigation of the properties of the mathematical singularities where some curvature scalars are equal to infinity, we analyse the properties of the physical singularities where the Kretschmann curvature scalar is equal to the planckian value. Using a homogeneous approximation we analyse the properties of the spacetime near a spacelike singularity in spacetimes influenced by different matter contents namely a scalar field, pressureless dust and matter with ultrarelativistic isotropic pressure. We also carry out full nonlinear analyses of the scalar field and geometry of spacetime inside black holes by means of an appropriate numerical code with adaptive mesh refinement capabilities. We use this code to investigate the nonlinear effects of gravitational focusing, mass inflation, matter squeeze, and these effects dependence on the initial boundary conditions. It is demonstrated that the position of the physical singularity inside a black hole is quite different from the positions of the mathematical singularities. In the case of the existence of a strong outgoing flux of the scalar field inside a black hole it is possible to have the existence of two null singularities and one central $r=0$ singularity simultaneously. |
2308.09974 | Jose Luis Flores | Ivan P. Costa e Silva, Jos\'e L. Flores, Benjam\'in Olea | On the existence of sections with constant surface gravity on null
hypersurfaces | 21 pages | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We identify, in spacetimes satisfying the null convergence condition, a
certain natural class of null hypersurfaces that admit null sections with
constant surface gravity. Our work is meant to offer complementary results to
previous work on null hypersurfaces of zero expansion arising from the study of
Cauchy and black hole horizons in general relativity.
| [
{
"created": "Sat, 19 Aug 2023 10:37:34 GMT",
"version": "v1"
}
] | 2023-08-22 | [
[
"Silva",
"Ivan P. Costa e",
""
],
[
"Flores",
"José L.",
""
],
[
"Olea",
"Benjamín",
""
]
] | We identify, in spacetimes satisfying the null convergence condition, a certain natural class of null hypersurfaces that admit null sections with constant surface gravity. Our work is meant to offer complementary results to previous work on null hypersurfaces of zero expansion arising from the study of Cauchy and black hole horizons in general relativity. |
1310.1602 | Yu-Huei Wu | Chih-Hung Wang and Yu-Huei Wu | Gravitational radiation and angular momentum flux from a spinning
dynamical black hole | JGRG 20, 2010/9/24, conference proceeding | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/3.0/ | A four-dimensional asymptotic expansion scheme is used to study the next
order effects of the nonlinearity near a spinning dynamical black hole. The
angular momentum flux and energy flux formula are then obtained by asymptotic
expansion and the compatibility of the coupling Newman-Penrose equations. After
constructing the reference frame in terms of the compatible constant spinors,
the energy-momentum flux is derived and it is related to the black hole area
growth. Directly from the flux formula of the spinning dynamical horizon, we
find that the physically reasonable condition on the positivity of the
gravitational energy flux yields that the shear will monotonically decrease
with time.
| [
{
"created": "Sun, 6 Oct 2013 16:56:08 GMT",
"version": "v1"
}
] | 2013-10-08 | [
[
"Wang",
"Chih-Hung",
""
],
[
"Wu",
"Yu-Huei",
""
]
] | A four-dimensional asymptotic expansion scheme is used to study the next order effects of the nonlinearity near a spinning dynamical black hole. The angular momentum flux and energy flux formula are then obtained by asymptotic expansion and the compatibility of the coupling Newman-Penrose equations. After constructing the reference frame in terms of the compatible constant spinors, the energy-momentum flux is derived and it is related to the black hole area growth. Directly from the flux formula of the spinning dynamical horizon, we find that the physically reasonable condition on the positivity of the gravitational energy flux yields that the shear will monotonically decrease with time. |
2302.09471 | Chi-Yong Lin | Yi-Ting Li, Chen-Yu Wang, Da-Shin Lee, and Chi-Yong Lin | Homoclinic orbits in Kerr-Newman black holes | 29 pages, 10 figures, revised version accepted for publication in
Physical Review D. arXiv admin note: text overlap with arXiv:2208.11906 | Physical Review D 108, 044010 (2023) | 10.1103/PhysRevD.108.044010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the exact solutions of the homoclinic orbits for the timelike
geodesics of the particle on the general nonequatorial orbits in the
Kerr-Newman black holes. The homoclinic orbit is the separatrix between bound
and plunging geodesics, a solution that asymptotes to an energetically bound,
unstable spherical orbit. The solutions are written in terms of the elliptical
integrals and the Jacobi elliptic functions of manifestly real functions of the
Mino time where we focus on the effect from the charge of the black hole to the
homoclinic orbits. The parameter space of the homoclinic solutions is explored.
The nonequatorial homoclinic orbits in Kerr cases can be obtained by setting
the charge of the black holes to be zero. The homoclinic orbits and the
associated phase portrait as a function of the radial position and its
derivation with respect to the Mino time are plotted using the analytical
solutions. In particular, the solutions can reduce to the zero azimuthal
angular moment homoclinic orbits for understanding the frame dragging effects
from the spin as well as the charge of the black hole. The implications of the
obtained results to observations are discussed.
| [
{
"created": "Sun, 19 Feb 2023 03:59:56 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Aug 2023 01:55:46 GMT",
"version": "v2"
}
] | 2023-08-11 | [
[
"Li",
"Yi-Ting",
""
],
[
"Wang",
"Chen-Yu",
""
],
[
"Lee",
"Da-Shin",
""
],
[
"Lin",
"Chi-Yong",
""
]
] | We present the exact solutions of the homoclinic orbits for the timelike geodesics of the particle on the general nonequatorial orbits in the Kerr-Newman black holes. The homoclinic orbit is the separatrix between bound and plunging geodesics, a solution that asymptotes to an energetically bound, unstable spherical orbit. The solutions are written in terms of the elliptical integrals and the Jacobi elliptic functions of manifestly real functions of the Mino time where we focus on the effect from the charge of the black hole to the homoclinic orbits. The parameter space of the homoclinic solutions is explored. The nonequatorial homoclinic orbits in Kerr cases can be obtained by setting the charge of the black holes to be zero. The homoclinic orbits and the associated phase portrait as a function of the radial position and its derivation with respect to the Mino time are plotted using the analytical solutions. In particular, the solutions can reduce to the zero azimuthal angular moment homoclinic orbits for understanding the frame dragging effects from the spin as well as the charge of the black hole. The implications of the obtained results to observations are discussed. |
2310.11278 | Metin Arik | Metin Arik, Tarik Tok | The Higgs Field in the closed FLRW universe | 20 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider SO(3) symmetric triplet of Higgs fields and SO(4) symmetric
complex doublet of Higgs fields in the closed FLRW universe. For these models,
Lagrangian densities provide effective potentials leading to spontaneous
symmetry breaking which gives cosmological expectation value of the Higgs field
and the Higgs mass. We find a relation which emerges between the size of the
FLRW universe and cosmological vacuum expectation value of the Higgs field.
| [
{
"created": "Tue, 17 Oct 2023 13:56:55 GMT",
"version": "v1"
}
] | 2023-10-18 | [
[
"Arik",
"Metin",
""
],
[
"Tok",
"Tarik",
""
]
] | We consider SO(3) symmetric triplet of Higgs fields and SO(4) symmetric complex doublet of Higgs fields in the closed FLRW universe. For these models, Lagrangian densities provide effective potentials leading to spontaneous symmetry breaking which gives cosmological expectation value of the Higgs field and the Higgs mass. We find a relation which emerges between the size of the FLRW universe and cosmological vacuum expectation value of the Higgs field. |
2105.06366 | Ajit Mehta | Ajit Kumar Mehta, Alessandra Buonanno, Jonathan Gair, M. Coleman
Miller, Ebraheem Farag, R. J. deBoer, M. Wiescher, F.X. Timmes | Observing intermediate-mass black holes and the upper--stellar-mass gap
with LIGO and Virgo | 29 pages, 18 figures | The Astrophysical Journal, Volume 924, Number 1 (2022) | 10.3847/1538-4357/ac3130 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Using ground-based gravitational-wave detectors, we probe the mass function
of intermediate-mass black holes (IMBHs) wherein we also include BHs in the
upper mass gap $\sim 60-130~M_\odot$. Employing the projected sensitivity of
the upcoming LIGO and Virgo fourth observing (O4) run, we perform Bayesian
analysis on quasi-circular non-precessing, spinning IMBH binaries (IMBHBs) with
total masses $50\mbox{--} 500\, M_\odot$, mass ratios 1.25, 4, and 10, and
dimensionless spins up to 0.95, and estimate the precision with which the
source-frame parameters can be measured. We find that, at $2\sigma$, the mass
of the heavier component of IMBHBs can be constrained with an uncertainty of
$\sim 10-40\%$ at a signal-to-noise ratio of $20$. Focusing on the stellar-mass
gap with new tabulations of the $^{12}\text{C}(\alpha, \gamma)^{16} \text{O}$
reaction rate and its uncertanties, we evolve massive helium core stars using
\MESA\, to establish the lower and upper edge of the mass gap as
$\simeq$\,59$^{+34}_{-13}$\,$M_{\odot}$ and
$\simeq$\,139$^{+30}_{-14}$\,$M_{\odot}$ respectively, where the error bars
give the mass range that follows from the $\pm 3\sigma$ uncertainty in the
$^{12}\text{C}(\alpha, \gamma) ^{16} \text{O}$ nuclear reaction rate. We find
that high resolution of the tabulated reaction rate and fine temporal
resolution are necessary to resolve the peak of the BH mass spectrum. We then
study IMBHBs with components lying in the mass gap and show that the O4 run
will be able to robustly identify most such systems. Finally, we re-analyse
GW190521 with a state-of-the-art aligned-spin waveform model, finding that the
primary mass lies in the mass gap with 90\% credibility.
| [
{
"created": "Thu, 13 May 2021 15:53:33 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Oct 2021 14:06:17 GMT",
"version": "v2"
}
] | 2022-01-25 | [
[
"Mehta",
"Ajit Kumar",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Gair",
"Jonathan",
""
],
[
"Miller",
"M. Coleman",
""
],
[
"Farag",
"Ebraheem",
""
],
[
"deBoer",
"R. J.",
""
],
[
"Wiescher",
"M.",
""
],... | Using ground-based gravitational-wave detectors, we probe the mass function of intermediate-mass black holes (IMBHs) wherein we also include BHs in the upper mass gap $\sim 60-130~M_\odot$. Employing the projected sensitivity of the upcoming LIGO and Virgo fourth observing (O4) run, we perform Bayesian analysis on quasi-circular non-precessing, spinning IMBH binaries (IMBHBs) with total masses $50\mbox{--} 500\, M_\odot$, mass ratios 1.25, 4, and 10, and dimensionless spins up to 0.95, and estimate the precision with which the source-frame parameters can be measured. We find that, at $2\sigma$, the mass of the heavier component of IMBHBs can be constrained with an uncertainty of $\sim 10-40\%$ at a signal-to-noise ratio of $20$. Focusing on the stellar-mass gap with new tabulations of the $^{12}\text{C}(\alpha, \gamma)^{16} \text{O}$ reaction rate and its uncertanties, we evolve massive helium core stars using \MESA\, to establish the lower and upper edge of the mass gap as $\simeq$\,59$^{+34}_{-13}$\,$M_{\odot}$ and $\simeq$\,139$^{+30}_{-14}$\,$M_{\odot}$ respectively, where the error bars give the mass range that follows from the $\pm 3\sigma$ uncertainty in the $^{12}\text{C}(\alpha, \gamma) ^{16} \text{O}$ nuclear reaction rate. We find that high resolution of the tabulated reaction rate and fine temporal resolution are necessary to resolve the peak of the BH mass spectrum. We then study IMBHBs with components lying in the mass gap and show that the O4 run will be able to robustly identify most such systems. Finally, we re-analyse GW190521 with a state-of-the-art aligned-spin waveform model, finding that the primary mass lies in the mass gap with 90\% credibility. |
2211.09579 | Maxim Khlopov | M.Yu. Khlopov and O.M. Lecian | Evolution and Possible Forms of Primordial Antimatter and Dark Matter
celestial objects | Prepared for Proceedings of XXV Bled Workshop "What comes beyond the
Standard models?" | null | null | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The structure and evolution of Primordial Antimatter domains and Dark matter
objects are analysed. Relativistic low-density antimatter domains are
described. The Relativistic FRW perfect-fluid solution is found for the
characterization of i) ultra-high density antimatter domains, ii) high-density
antimatter domains, and iii) dense anti-matter domains. The possible
sub-domains structures is analyzed. The structures evolved to the time of
galaxy formation are outlined. Comparison is given with other primordial
celestial objects. The features of antistars are outlined. In the case of WIMP
dark matter clumps, the mechanisms of their survival to the present time are
discussed. The cosmological features of neutrino clumping due to fifth force
are examined.
| [
{
"created": "Thu, 17 Nov 2022 15:10:21 GMT",
"version": "v1"
}
] | 2022-11-18 | [
[
"Khlopov",
"M. Yu.",
""
],
[
"Lecian",
"O. M.",
""
]
] | The structure and evolution of Primordial Antimatter domains and Dark matter objects are analysed. Relativistic low-density antimatter domains are described. The Relativistic FRW perfect-fluid solution is found for the characterization of i) ultra-high density antimatter domains, ii) high-density antimatter domains, and iii) dense anti-matter domains. The possible sub-domains structures is analyzed. The structures evolved to the time of galaxy formation are outlined. Comparison is given with other primordial celestial objects. The features of antistars are outlined. In the case of WIMP dark matter clumps, the mechanisms of their survival to the present time are discussed. The cosmological features of neutrino clumping due to fifth force are examined. |
0708.2469 | Hyeong-Chan Kim | Hyeong-Chan Kim and Jungjai Lee | Extraordinary vacuum black string solutions | 20 pages, 4 figures, add 2 references | Phys.Rev.D77:024012,2008 | 10.1103/PhysRevD.77.024012 | null | gr-qc hep-th | null | In addition to the boosted static solution there are two other classes of
stationary string-like solutions of the vacuum Einstein equation in
(4+1)-dimensions. Each class is characterized by three parameters of mass,
tension, and momentum flow along the fifth coordinate. We analyze the metric
properties of one of the two classes, which was previously assumed to be naked
singular, and show that the solution spectrum contains black string and
wormhole in addition to the known naked singularity as the momentum flow to
mass ratio increases. Interestingly, there does not exist new zero momentum
solution in these cases.
| [
{
"created": "Sat, 18 Aug 2007 11:18:14 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Dec 2007 03:03:51 GMT",
"version": "v2"
},
{
"created": "Mon, 14 Jan 2008 08:19:53 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Kim",
"Hyeong-Chan",
""
],
[
"Lee",
"Jungjai",
""
]
] | In addition to the boosted static solution there are two other classes of stationary string-like solutions of the vacuum Einstein equation in (4+1)-dimensions. Each class is characterized by three parameters of mass, tension, and momentum flow along the fifth coordinate. We analyze the metric properties of one of the two classes, which was previously assumed to be naked singular, and show that the solution spectrum contains black string and wormhole in addition to the known naked singularity as the momentum flow to mass ratio increases. Interestingly, there does not exist new zero momentum solution in these cases. |
1709.05851 | Przemyslaw Malkiewicz | Herv\'e Bergeron, Jean Pierre Gazeau and Przemys{\l}aw Ma{\l}kiewicz | Primordial gravitational waves in a quantum model of big bounce | 38 pages, 8 figures | JCAP 05 (2018) 057 | 10.1088/1475-7516/2018/05/057 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We quantise and solve the dynamics of gravitational waves in a quantum
Friedmann-Lemaitre-Robertson-Walker spacetime filled with perfect fluid. The
classical model is formulated canonically. The Hamiltonian constraint is
de-parametrised by setting a fluid variable as the internal clock. The obtained
reduced (i.e. physical) phase space is then quantised. Our quantisation
procedure is implemented in accordance with two different phase space
symmetries, namely, the Weyl-Heisenberg symmetry for the perturbation
variables, and the affine symmetry for the background variables. As an
appealing outcome, the initial singularity is removed and replaced with a
quantum bounce. The quantum model depends on a free parameter that is naturally
induced from quantisation and determines the scale of the bounce. We study the
dynamics of the quantised gravitational waves across the bounce through three
different methods ("thin-horizon", analytical and numerical) which give
consistent results and we determine the primordial power spectrum for the case
of radiation-dominated universe. Next, we use the instantaneous
radiation-matter transition transfer function to make approximate predictions
for late universe and constrain our model with LIGO and Planck data. We also
give an estimate of the quantum uncertainties in the present-day universe.
| [
{
"created": "Mon, 18 Sep 2017 10:33:07 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Apr 2018 10:33:57 GMT",
"version": "v2"
}
] | 2018-05-29 | [
[
"Bergeron",
"Hervé",
""
],
[
"Gazeau",
"Jean Pierre",
""
],
[
"Małkiewicz",
"Przemysław",
""
]
] | We quantise and solve the dynamics of gravitational waves in a quantum Friedmann-Lemaitre-Robertson-Walker spacetime filled with perfect fluid. The classical model is formulated canonically. The Hamiltonian constraint is de-parametrised by setting a fluid variable as the internal clock. The obtained reduced (i.e. physical) phase space is then quantised. Our quantisation procedure is implemented in accordance with two different phase space symmetries, namely, the Weyl-Heisenberg symmetry for the perturbation variables, and the affine symmetry for the background variables. As an appealing outcome, the initial singularity is removed and replaced with a quantum bounce. The quantum model depends on a free parameter that is naturally induced from quantisation and determines the scale of the bounce. We study the dynamics of the quantised gravitational waves across the bounce through three different methods ("thin-horizon", analytical and numerical) which give consistent results and we determine the primordial power spectrum for the case of radiation-dominated universe. Next, we use the instantaneous radiation-matter transition transfer function to make approximate predictions for late universe and constrain our model with LIGO and Planck data. We also give an estimate of the quantum uncertainties in the present-day universe. |
2207.13431 | Alejandro Jim\'enez-Cano | Adri\`a Delhom, Alejandro Jim\'enez-Cano and Francisco Jos\'e
Maldonado Torralba | Instabilities in field theories: Lecture notes with a view into modified
gravity | 53 pages, 2 figures, 2 tables. This text is an extended and polished
version of the lectures prepared for the course `Selected Topics in the
Theories of Gravity', given at the Institute of Physics (University of Tartu,
Estonia) in spring 2022 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modified theories of gravity usually present new degrees of freedom, as well
as higher order derivatives, wrong signs in certain terms and complicated
couplings already present in the Lagrangian from the beginning or originated by
the field redefinitions needed to reach an Einstein frame. As a consequence,
they are very prone to present dynamical instabilities that could spoil any
attempt to construct viable models within these frameworks. In these three
lectures we introduce the most common types of instabilities that appear in
field theory as well as some techniques to detect them, and supplement these
contents with several examples. The goal is to understand the implications of
having such pathological behaviors and the application of these notions to
modified theories of gravity.
| [
{
"created": "Wed, 27 Jul 2022 10:20:44 GMT",
"version": "v1"
}
] | 2022-07-28 | [
[
"Delhom",
"Adrià",
""
],
[
"Jiménez-Cano",
"Alejandro",
""
],
[
"Torralba",
"Francisco José Maldonado",
""
]
] | Modified theories of gravity usually present new degrees of freedom, as well as higher order derivatives, wrong signs in certain terms and complicated couplings already present in the Lagrangian from the beginning or originated by the field redefinitions needed to reach an Einstein frame. As a consequence, they are very prone to present dynamical instabilities that could spoil any attempt to construct viable models within these frameworks. In these three lectures we introduce the most common types of instabilities that appear in field theory as well as some techniques to detect them, and supplement these contents with several examples. The goal is to understand the implications of having such pathological behaviors and the application of these notions to modified theories of gravity. |
2101.01949 | Aurelien Barrau | Aur\'elien Barrau, L\'eonard Ferdinand, Killian Martineau, Cyril
Renevey | Closer look at white hole remnants | null | Phys. Rev. D 103, 043532 (2021) | 10.1103/PhysRevD.103.043532 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The idea that, after their evaporation, Planck-mass black holes might tunnel
into metastable white holes has recently been intensively studied. Those relics
have been considered as a dark matter candidate. We show that the model is
severely constrained and underline some possible detection paths. We also
investigate, in a more general setting, the way the initial black hole mass
spectrum would be distorted by both the bouncing effect and the Hawking
evaporation.
| [
{
"created": "Wed, 6 Jan 2021 10:18:18 GMT",
"version": "v1"
},
{
"created": "Sat, 13 Feb 2021 12:20:56 GMT",
"version": "v2"
}
] | 2021-03-03 | [
[
"Barrau",
"Aurélien",
""
],
[
"Ferdinand",
"Léonard",
""
],
[
"Martineau",
"Killian",
""
],
[
"Renevey",
"Cyril",
""
]
] | The idea that, after their evaporation, Planck-mass black holes might tunnel into metastable white holes has recently been intensively studied. Those relics have been considered as a dark matter candidate. We show that the model is severely constrained and underline some possible detection paths. We also investigate, in a more general setting, the way the initial black hole mass spectrum would be distorted by both the bouncing effect and the Hawking evaporation. |
1910.08487 | Gerasimos Rigopoulos | Tomislav Prokopec and Gerasimos Rigopoulos | $\Delta\mathcal{N}$ and the stochastic conveyor belt of Ultra Slow-Roll | v1: 28 pages, 5 figures; v2: small changes in text for
clarifications, results unchanged, matches version to be published in
Phys.Rev.D | Phys. Rev. D 104, 083505 (2021) | 10.1103/PhysRevD.104.083505 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse field fluctuations during an Ultra Slow-Roll phase in the
stochastic picture of inflation and the resulting non-Gaussian curvature
perturbation, fully including the gravitational backreaction of the field's
velocity. By working to leading order in a gradient expansion, we first
demonstrate that consistency with the momentum constraint of General Relativity
prevents the field velocity from having a stochastic source, reflecting the
existence of a single scalar dynamical degree of freedom on long wavelengths.
We then focus on a completely level potential surface, $V=V_0$, extending from
a specified exit point $\phi_{\rm e}$, where slow roll resumes or inflation
ends, to $\phi\rightarrow +\infty$. We compute the probability distribution in
the number of e-folds $\mathcal{N}$ required to reach $\phi_{\rm e}$ which
allows for the computation of the curvature perturbation. We find that, if the
field's initial velocity is high enough, all points eventually exit through
$\phi_{\rm e}$ and a finite curvature perturbation is generated. On the
contrary, if the initial velocity is low, some points enter an eternally
inflating regime despite the existence of $\phi_{\rm e}$. In that case the
probability distribution for $\mathcal{N}$, although normalizable, does not
possess finite moments, leading to a divergent curvature perturbation.
| [
{
"created": "Fri, 18 Oct 2019 16:11:58 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Sep 2021 20:45:38 GMT",
"version": "v2"
}
] | 2021-10-04 | [
[
"Prokopec",
"Tomislav",
""
],
[
"Rigopoulos",
"Gerasimos",
""
]
] | We analyse field fluctuations during an Ultra Slow-Roll phase in the stochastic picture of inflation and the resulting non-Gaussian curvature perturbation, fully including the gravitational backreaction of the field's velocity. By working to leading order in a gradient expansion, we first demonstrate that consistency with the momentum constraint of General Relativity prevents the field velocity from having a stochastic source, reflecting the existence of a single scalar dynamical degree of freedom on long wavelengths. We then focus on a completely level potential surface, $V=V_0$, extending from a specified exit point $\phi_{\rm e}$, where slow roll resumes or inflation ends, to $\phi\rightarrow +\infty$. We compute the probability distribution in the number of e-folds $\mathcal{N}$ required to reach $\phi_{\rm e}$ which allows for the computation of the curvature perturbation. We find that, if the field's initial velocity is high enough, all points eventually exit through $\phi_{\rm e}$ and a finite curvature perturbation is generated. On the contrary, if the initial velocity is low, some points enter an eternally inflating regime despite the existence of $\phi_{\rm e}$. In that case the probability distribution for $\mathcal{N}$, although normalizable, does not possess finite moments, leading to a divergent curvature perturbation. |
1408.4535 | Babak Vakili | B. Vakili, K. Nozari, V. Hosseinzadeh and M. A. Gorji | Bouncing scalar field cosmology in the polymeric minisuperspace picture | 11 pages, 2 figures, to appear in MPLA. (Although the main results in
this paper may be considered as a reproduction of the results of reference
16, we would like to draw the reader's attention to the method of "Polymeric
symplectic structure" from which the results are obtained.) | Mod. Phys. Lett. A 29 (2014) 1450169 | 10.1142/S0217732314501697 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a cosmological setup consisting of a FRW metric as the background
geometry with a massless scalar field in the framework of classical
polymerization of a given dynamical system. To do this, we first introduce the
polymeric representation of the quantum operators. We then extend the
corresponding process to reach a transformation which maps any classical
variable to its polymeric counterpart. It is shown that such a formalism has
also an analogue in terms of the symplectic structure, i.e., instead of
applying polymerization to the classical Hamiltonian to arrive its polymeric
form, one can use a new set of variables in terms of which Hamiltonian retains
its form but now the corresponding symplectic structure gets a new deformed
functional form. We show that these two methods are equivalent and by applying
of them to the scalar field FRW cosmology see that the resulting scale factor
exhibits a bouncing behavior from a contraction phase to an expanding era.
Since the replacing of the big bang singularity by a bouncing behavior is one
of the most important predictions of the quantum cosmological theories, we may
claim that our polymerized classical model brings with itself some signals from
quantum theory.
| [
{
"created": "Wed, 20 Aug 2014 06:19:52 GMT",
"version": "v1"
}
] | 2014-10-21 | [
[
"Vakili",
"B.",
""
],
[
"Nozari",
"K.",
""
],
[
"Hosseinzadeh",
"V.",
""
],
[
"Gorji",
"M. A.",
""
]
] | We study a cosmological setup consisting of a FRW metric as the background geometry with a massless scalar field in the framework of classical polymerization of a given dynamical system. To do this, we first introduce the polymeric representation of the quantum operators. We then extend the corresponding process to reach a transformation which maps any classical variable to its polymeric counterpart. It is shown that such a formalism has also an analogue in terms of the symplectic structure, i.e., instead of applying polymerization to the classical Hamiltonian to arrive its polymeric form, one can use a new set of variables in terms of which Hamiltonian retains its form but now the corresponding symplectic structure gets a new deformed functional form. We show that these two methods are equivalent and by applying of them to the scalar field FRW cosmology see that the resulting scale factor exhibits a bouncing behavior from a contraction phase to an expanding era. Since the replacing of the big bang singularity by a bouncing behavior is one of the most important predictions of the quantum cosmological theories, we may claim that our polymerized classical model brings with itself some signals from quantum theory. |
0908.2356 | Stephen Fairhurst | Stephen Fairhurst | Triangulation of gravitational wave sources with a network of detectors | 20 pages, 5 figures | New J.Phys.11:123006,2009; Erratum-ibid.13:069602,2011 | 10.1088/1367-2630/11/12/123006 10.1088/1367-2630/13/6/069602 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There is significant benefit to be gained by pursuing multi-messenger
astronomy with gravitational wave and electromagnetic observations. In order to
undertake electromagnetic follow-ups of gravitational wave signals, it will be
necessary to accurately localize them in the sky. Since gravitational wave
detectors are not inherently pointing instruments, localization will occur
primarily through triangulation with a network of detectors. We investigate the
expected timing accuracy for observed signals and the consequences for
localization. In addition, we discuss the effect of systematic uncertainties in
the waveform and calibration of the instruments on the localization of sources.
We provide illustrative results of timing and localization accuracy as well as
systematic effects for coalescing binary waveforms.
| [
{
"created": "Mon, 17 Aug 2009 13:34:23 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Dec 2009 14:01:30 GMT",
"version": "v2"
}
] | 2011-07-06 | [
[
"Fairhurst",
"Stephen",
""
]
] | There is significant benefit to be gained by pursuing multi-messenger astronomy with gravitational wave and electromagnetic observations. In order to undertake electromagnetic follow-ups of gravitational wave signals, it will be necessary to accurately localize them in the sky. Since gravitational wave detectors are not inherently pointing instruments, localization will occur primarily through triangulation with a network of detectors. We investigate the expected timing accuracy for observed signals and the consequences for localization. In addition, we discuss the effect of systematic uncertainties in the waveform and calibration of the instruments on the localization of sources. We provide illustrative results of timing and localization accuracy as well as systematic effects for coalescing binary waveforms. |
1503.02662 | Neil J. Cornish | Laura Sampson, Neil J. Cornish and Sean T. McWilliams | Constraining the Solution to the Last Parsec Problem with Pulsar Timing | 14 pages, 8 figures | null | 10.1103/PhysRevD.91.084055 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The detection of a stochastic gravitational-wave signal from the
superposition of many inspiraling supermassive black holes with pulsar timing
arrays (PTAs) is likely to occur within the next decade. With this detection
will come the opportunity to learn about the processes that drive
black-hole-binary systems toward merger through their effects on the
gravitational-wave spectrum. We use Bayesian methods to investigate the extent
to which effects other than gravitational-wave emission can be distinguished
using PTA observations. We show that, even in the absence of a detection, it is
possible to place interesting constraints on these dynamical effects for
conservative predictions of the population of tightly bound supermassive
black-hole binaries. For instance, if we assume a relatively weak signal
consistent with a low number of bound binaries and a low black-hole-mass to
galaxy-mass correlation, we still find that a non-detection by a simulated
array, with a sensitivity that should be reached in practice within a few
years, disfavors gravitational-wave-dominated evolution with an odds ratio of
$\sim$30:1. Such a finding would suggest either that all existing astrophysical
models for the population of tightly bound binaries are overly optimistic, or
else that some dynamical effect other than gravitational-wave emission is
actually dominating binary evolution even at the relatively high
frequencies/small orbital separations probed by PTAs.
| [
{
"created": "Mon, 9 Mar 2015 20:00:09 GMT",
"version": "v1"
}
] | 2015-06-24 | [
[
"Sampson",
"Laura",
""
],
[
"Cornish",
"Neil J.",
""
],
[
"McWilliams",
"Sean T.",
""
]
] | The detection of a stochastic gravitational-wave signal from the superposition of many inspiraling supermassive black holes with pulsar timing arrays (PTAs) is likely to occur within the next decade. With this detection will come the opportunity to learn about the processes that drive black-hole-binary systems toward merger through their effects on the gravitational-wave spectrum. We use Bayesian methods to investigate the extent to which effects other than gravitational-wave emission can be distinguished using PTA observations. We show that, even in the absence of a detection, it is possible to place interesting constraints on these dynamical effects for conservative predictions of the population of tightly bound supermassive black-hole binaries. For instance, if we assume a relatively weak signal consistent with a low number of bound binaries and a low black-hole-mass to galaxy-mass correlation, we still find that a non-detection by a simulated array, with a sensitivity that should be reached in practice within a few years, disfavors gravitational-wave-dominated evolution with an odds ratio of $\sim$30:1. Such a finding would suggest either that all existing astrophysical models for the population of tightly bound binaries are overly optimistic, or else that some dynamical effect other than gravitational-wave emission is actually dominating binary evolution even at the relatively high frequencies/small orbital separations probed by PTAs. |
1301.0698 | Yuri Pavlov | A. A. Grib and Yu. V. Pavlov | On the energy of particle collisions in the ergosphere of the rotating
black holes | 4 pages, 1 figure | EPL (Europhysics Letters) 101 (2013) 20004 | 10.1209/0295-5075/101/20004 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the energy in the centre of mass frame of colliding
particles in free fall at any point of the ergosphere of the rotating black
hole can grow without limit for fixed energy values on infinity. The effect
takes place for large negative values of the angular momentum of one of the
particles.
| [
{
"created": "Fri, 4 Jan 2013 10:31:58 GMT",
"version": "v1"
}
] | 2013-01-31 | [
[
"Grib",
"A. A.",
""
],
[
"Pavlov",
"Yu. V.",
""
]
] | It is shown that the energy in the centre of mass frame of colliding particles in free fall at any point of the ergosphere of the rotating black hole can grow without limit for fixed energy values on infinity. The effect takes place for large negative values of the angular momentum of one of the particles. |
1712.09852 | Philippe Brax | Philippe Brax and Mario Pitschmann | Exact Solutions to Non-Linear Symmetron Theory: One and Two Mirror
Systems | 14 pages, 6 figures | Phys. Rev. D 97, 064015 (2018) | 10.1103/PhysRevD.97.064015 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the exact analytical solutions to the symmetron field theory
equations in the presence of a one or two mirror system. The one dimensional
equations of motion are integrated exactly for both systems and their solutions
can be expressed in terms of Jacobi elliptic functions. Surprisingly, in the
case of two parallel mirrors the equations of motion generically provide not a
unique solution but a discrete set of solutions with increasing number of nodes
and energies. The solutions obtained herein can be applied to qBOUNCE
experiments, neutron interferometry and for the calculation of the symmetron
field induced "Casimir force" in the CANNEX experiment.
| [
{
"created": "Thu, 28 Dec 2017 13:31:09 GMT",
"version": "v1"
}
] | 2018-03-21 | [
[
"Brax",
"Philippe",
""
],
[
"Pitschmann",
"Mario",
""
]
] | We derive the exact analytical solutions to the symmetron field theory equations in the presence of a one or two mirror system. The one dimensional equations of motion are integrated exactly for both systems and their solutions can be expressed in terms of Jacobi elliptic functions. Surprisingly, in the case of two parallel mirrors the equations of motion generically provide not a unique solution but a discrete set of solutions with increasing number of nodes and energies. The solutions obtained herein can be applied to qBOUNCE experiments, neutron interferometry and for the calculation of the symmetron field induced "Casimir force" in the CANNEX experiment. |
1010.2057 | Qasem Exirifard | Qasem Exirifard | Triangular Ring Resonator: Direct measurement of the parity-odd
parameters of the photon sector of SME | ref. added, minor corrections, matches the published version | null | 10.1142/S0218271814500382 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce the the Triangular Ring (TR) resonator. We show that the
difference between the clockwise and anti-clockwise resonant frequencies of a
vacuum TR resonator is sensitive to the birefringence parity-odd parameters of
the photon's sector of the minimal Standard Model Extension (mSME): the
Standard Model plus all the perturbative parameters encoding the break the
Lorentz symmetry. We report that utilizing the current technology allows for
direct measurement of these parameters with a sensitivity of the parity even
ones and improves the best current resonator bounds by couple of orders of
magnitudes.
We note that designing an optical table that rotates perpendicular to the
gravitational equipotential surface (geoid) allows for direct measurement of
the constancy of the light speed at the vicinity of the earth in all directions
in particular perpendicular to the geoid. If this table could achieve the
precision of the ordinary tables, then it would improve the GPS bounds on the
constancy of the light speed perpendicular to geoid by about eight orders of
magnitude.
| [
{
"created": "Mon, 11 Oct 2010 10:27:13 GMT",
"version": "v1"
},
{
"created": "Sat, 13 Nov 2010 08:07:37 GMT",
"version": "v2"
},
{
"created": "Sun, 30 Jan 2011 14:39:37 GMT",
"version": "v3"
},
{
"created": "Thu, 14 Jul 2011 11:25:30 GMT",
"version": "v4"
},
{
"c... | 2015-03-17 | [
[
"Exirifard",
"Qasem",
""
]
] | We introduce the the Triangular Ring (TR) resonator. We show that the difference between the clockwise and anti-clockwise resonant frequencies of a vacuum TR resonator is sensitive to the birefringence parity-odd parameters of the photon's sector of the minimal Standard Model Extension (mSME): the Standard Model plus all the perturbative parameters encoding the break the Lorentz symmetry. We report that utilizing the current technology allows for direct measurement of these parameters with a sensitivity of the parity even ones and improves the best current resonator bounds by couple of orders of magnitudes. We note that designing an optical table that rotates perpendicular to the gravitational equipotential surface (geoid) allows for direct measurement of the constancy of the light speed at the vicinity of the earth in all directions in particular perpendicular to the geoid. If this table could achieve the precision of the ordinary tables, then it would improve the GPS bounds on the constancy of the light speed perpendicular to geoid by about eight orders of magnitude. |
gr-qc/9903044 | Heinz-Juergen Schmidt | H.-J. Schmidt, F. Homann (University of Osnabrueck) | Photon Stars | 10 pages, 5 figures, talk at the DPG Spring Meeting 1999 | Gen.Rel.Grav. 32 (2000) 919-931 | 10.1023/A:1001989125318 | null | gr-qc | null | We discuss numerical solutions of Einstein's field equation describing
static, spherically symmetric conglomerations of a photon gas. These equations
imply a back reaction of the metric on the energy density of the photon gas
according to Tolman's equation. The 3-fold of solutions corresponds to a class
of physically different solutions which is parameterized by only two
quantities, e.g. mass and surface temperature. The energy density is typically
concentrated on a shell because the center contains a repelling singularity,
which can, however, not be reached by timelike or null geodesics. The physical
relevance of these solutions is completely open, although their existence may
raise some doubts w.r. to the stability of black holes.
| [
{
"created": "Fri, 12 Mar 1999 13:56:21 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Schmidt",
"H. -J.",
"",
"University of Osnabrueck"
],
[
"Homann",
"F.",
"",
"University of Osnabrueck"
]
] | We discuss numerical solutions of Einstein's field equation describing static, spherically symmetric conglomerations of a photon gas. These equations imply a back reaction of the metric on the energy density of the photon gas according to Tolman's equation. The 3-fold of solutions corresponds to a class of physically different solutions which is parameterized by only two quantities, e.g. mass and surface temperature. The energy density is typically concentrated on a shell because the center contains a repelling singularity, which can, however, not be reached by timelike or null geodesics. The physical relevance of these solutions is completely open, although their existence may raise some doubts w.r. to the stability of black holes. |
2105.07890 | Jorge Armando Rueda | J. A. Rueda and R. Ruffini | The Quantum Emission of an Alive Black Hole | Third Award Winning Essay of the "Gravity Research Foundation 2021
awards for essays on Gravitation", to be published in a special issue of
IJMPD in October 2021. arXiv admin note: substantial text overlap with
arXiv:1911.07552 | null | 10.1142/S0218271821410030 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A long march of fifty years of successive theoretical progress and new
physics discovered using observations of gamma-ray bursts, has finally led to
the formulation of an efficient mechanism able to extract the rotational energy
of a Kerr black hole to power these most energetic astrophysical sources and
active galactic nuclei. We here present the salient features of this
long-sought mechanism, based on gravito-electrodynamics, and which represents
an authentic shift of paradigm of black holes as forever "alive" astrophysical
objects.
| [
{
"created": "Fri, 14 May 2021 07:51:28 GMT",
"version": "v1"
}
] | 2022-01-26 | [
[
"Rueda",
"J. A.",
""
],
[
"Ruffini",
"R.",
""
]
] | A long march of fifty years of successive theoretical progress and new physics discovered using observations of gamma-ray bursts, has finally led to the formulation of an efficient mechanism able to extract the rotational energy of a Kerr black hole to power these most energetic astrophysical sources and active galactic nuclei. We here present the salient features of this long-sought mechanism, based on gravito-electrodynamics, and which represents an authentic shift of paradigm of black holes as forever "alive" astrophysical objects. |
1003.1619 | Lorenzo Fatibene | L. Fatibene, M. Ferraris, M. Francaviglia | Extended Loop Quantum Gravity | 7 pages, few typos corrected | Class.Quant.Grav.27:185016,2010 | 10.1088/0264-9381/27/18/185016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss constraint structure of extended theories of gravitation (also
known as f(R) theories) in the vacuum selfdual formulation introduced in ref.
[1].
| [
{
"created": "Mon, 8 Mar 2010 13:26:46 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Mar 2010 17:25:16 GMT",
"version": "v2"
},
{
"created": "Thu, 18 Mar 2010 06:47:27 GMT",
"version": "v3"
}
] | 2015-03-13 | [
[
"Fatibene",
"L.",
""
],
[
"Ferraris",
"M.",
""
],
[
"Francaviglia",
"M.",
""
]
] | We discuss constraint structure of extended theories of gravitation (also known as f(R) theories) in the vacuum selfdual formulation introduced in ref. [1]. |
gr-qc/9805054 | Dan Baleanu | Dumitru Baleanu (Bogoliubov LPTh, Dubna, Russia) | Killing-Yano tensors and Nambu tensors | content enlarged and revised,10 pages LateX, no figures, accepted for
publication in Il Nuovo Cimento | null | null | null | gr-qc | null | We present the conditions when a Killing-Yano tensor becomes a Nambu tensor.
We have shown that in the flat space case all Killing-Yano tensors are Nambu
tensors.
In the case of Taub-NUT metric and Kerr-Newmann metric we found that a
Killing-Yano tensor of order two generate a Nambu tensor of order three.
| [
{
"created": "Thu, 14 May 1998 19:49:09 GMT",
"version": "v1"
},
{
"created": "Sat, 16 May 1998 20:37:10 GMT",
"version": "v2"
},
{
"created": "Sun, 15 Aug 1999 10:42:54 GMT",
"version": "v3"
},
{
"created": "Tue, 17 Aug 1999 18:38:17 GMT",
"version": "v4"
}
] | 2016-08-31 | [
[
"Baleanu",
"Dumitru",
"",
"Bogoliubov LPTh, Dubna, Russia"
]
] | We present the conditions when a Killing-Yano tensor becomes a Nambu tensor. We have shown that in the flat space case all Killing-Yano tensors are Nambu tensors. In the case of Taub-NUT metric and Kerr-Newmann metric we found that a Killing-Yano tensor of order two generate a Nambu tensor of order three. |
gr-qc/9808052 | Massimo Giovannini | Massimo Giovannini (University of Cambridge, DAMTP) | Magnetic Knots as The origin of Spikes in the Gravitational Waves
Backgrounds | Accepted for publication in Physical Review D, 20 pages in RevTex
style, 4 Encapsulated figures | Phys.Rev. D58 (1998) 124027 | 10.1103/PhysRevD.58.124027 | DAMTP-1998-107 | gr-qc astro-ph hep-ph hep-th | null | The dynamical symmetries of hot and electrically neutral plasmas in a highly
conducting medium suggest that, after the epoch of the electron-positron
annihilation, magnetohydrodynamical configurations carrying a net magnetic
helicity can be present. The simultaneous conservation of the magnetic flux and
helicity implies that the (divergence free) field lines will possess
inhomogeneous knot structures acting as source seeds in the evolution equations
of the scalar, vector and tensor fluctuations of the background geometry. We
give explicit examples of magnetic knot configurations with finite energy and
we compute the induced metric fluctuations. Since magnetic knots are
(conformally) coupled to gravity via the vertex dictated by the equivalence
principle, they can imprint spikes in the gravitational wave spectrum for
frequencies compatible with the typical scale of the knot corresponding, in our
examples, to a present frequency range of $10^{-11}$--$10^{-12}$ Hertz. At
lower frequencies the spectrum is power-suppressed and well below the COBE
limit. For smaller length scales (i.e. for larger frequencies) the spectrum is
exponentially suppressed and then irrelevant for the pulsar bounds. Depending
upon the number of knots of the configuration, the typical amplitude of the
gravitational wave logarithmic energy spectrum (in critical units) can be even
four orders of magnitude larger than the usual flat (inflationary) energy
spectrum generated thanks to the parametric amplification of the vacuum
fluctuations.
| [
{
"created": "Wed, 19 Aug 1998 22:29:19 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Giovannini",
"Massimo",
"",
"University of Cambridge, DAMTP"
]
] | The dynamical symmetries of hot and electrically neutral plasmas in a highly conducting medium suggest that, after the epoch of the electron-positron annihilation, magnetohydrodynamical configurations carrying a net magnetic helicity can be present. The simultaneous conservation of the magnetic flux and helicity implies that the (divergence free) field lines will possess inhomogeneous knot structures acting as source seeds in the evolution equations of the scalar, vector and tensor fluctuations of the background geometry. We give explicit examples of magnetic knot configurations with finite energy and we compute the induced metric fluctuations. Since magnetic knots are (conformally) coupled to gravity via the vertex dictated by the equivalence principle, they can imprint spikes in the gravitational wave spectrum for frequencies compatible with the typical scale of the knot corresponding, in our examples, to a present frequency range of $10^{-11}$--$10^{-12}$ Hertz. At lower frequencies the spectrum is power-suppressed and well below the COBE limit. For smaller length scales (i.e. for larger frequencies) the spectrum is exponentially suppressed and then irrelevant for the pulsar bounds. Depending upon the number of knots of the configuration, the typical amplitude of the gravitational wave logarithmic energy spectrum (in critical units) can be even four orders of magnitude larger than the usual flat (inflationary) energy spectrum generated thanks to the parametric amplification of the vacuum fluctuations. |
2208.00425 | Beatriz Elizaga Navascu\'es | Beatriz Elizaga Navascu\'es, Alejandro Garc\'ia-Quismondo, and
Guillermo A. Mena Marug\'an | Hamiltonian formulation and loop quantization of a recent extension of
the Kruskal spacetime | 18 pages | Phys. Rev. D 106, 043531 (2022) | 10.1103/PhysRevD.106.043531 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Hamiltonian formulation of the Ashtekar-Olmedo-Singh model for
the description of the interior geometry of non-rotating, uncharged black
holes. This model incorporates loop quantum effects through the introduction of
two regularization parameters. We consider an extended phase space formalism
proposed by the creators of the model that includes such parameters as
configuration variables, constrained to be functions of the black hole mass. We
generalize this restriction, allowing for an off-shell phase space dependence.
We then introduce a gauge fixing procedure and reduce the system, proving that
the reduced symplectic structure cannot reproduce the standard relativistic one
in terms of the densitized triad and the Ashtekar-Barbero connection. Actually,
the reduced structure precisely compensates the modifications that arise in the
Hamilton equations when the regularization parameters are treated as phase
space functions, rather than as numbers, attaining a consistent Hamiltonian
derivation of the dynamics. We then choose the extended phase space formalism
as starting point to address the loop quantization of the model. Taking the
definition of certain geometric operators as the only basic ingredient and
adopting prescriptions that have proven successful in loop quantum cosmology,
we construct a polymer representation of all the constraints and deduce the
formal expression of the physical states, assuming reasonable spectral
properties for the constraint operators. The physical states turn out to be
characterized by a wave function of the black hole mass with support on a very
specific set. We finally discuss conditions that guarantee the existence of
physical states in the region of large black hole masses. This is a first step
in the development of a new loop quantum theory of black holes.
| [
{
"created": "Sun, 31 Jul 2022 13:03:51 GMT",
"version": "v1"
}
] | 2022-09-07 | [
[
"Navascués",
"Beatriz Elizaga",
""
],
[
"García-Quismondo",
"Alejandro",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
]
] | We study the Hamiltonian formulation of the Ashtekar-Olmedo-Singh model for the description of the interior geometry of non-rotating, uncharged black holes. This model incorporates loop quantum effects through the introduction of two regularization parameters. We consider an extended phase space formalism proposed by the creators of the model that includes such parameters as configuration variables, constrained to be functions of the black hole mass. We generalize this restriction, allowing for an off-shell phase space dependence. We then introduce a gauge fixing procedure and reduce the system, proving that the reduced symplectic structure cannot reproduce the standard relativistic one in terms of the densitized triad and the Ashtekar-Barbero connection. Actually, the reduced structure precisely compensates the modifications that arise in the Hamilton equations when the regularization parameters are treated as phase space functions, rather than as numbers, attaining a consistent Hamiltonian derivation of the dynamics. We then choose the extended phase space formalism as starting point to address the loop quantization of the model. Taking the definition of certain geometric operators as the only basic ingredient and adopting prescriptions that have proven successful in loop quantum cosmology, we construct a polymer representation of all the constraints and deduce the formal expression of the physical states, assuming reasonable spectral properties for the constraint operators. The physical states turn out to be characterized by a wave function of the black hole mass with support on a very specific set. We finally discuss conditions that guarantee the existence of physical states in the region of large black hole masses. This is a first step in the development of a new loop quantum theory of black holes. |
2002.10264 | Haidar Sheikhahmadi | Haidar Sheikhahmadi | An exact solution for a force-free field electrodynamics accretion disk
surrounding a perturbed charged black hole | I appreciate any constructive comments and enlightening criticisms. 4
pages | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently the first real image of the supermassive black hole at the heart of
the galaxy M87 successfully has been captured. To explain the behavior of both
the observed powerful jets and the electromagnetic accretion disk the Blandford
Znajek mechanism, by the Event Horizon Telescope collaboration, has been
considered. To justify these phenomena we are seeking an exact solution for a
perturbed Rissner-Nordstrom black hole surrounded by a force-free field
electrodynamics accretion disk. Although a charged black hole is a toy model,
by tending the charge to zero one can obtain the results for a perturbed,
rotating, Schwarzschild one immediately. Finding an exact solution in regards
to the force-free field electrodynamics as a source for perturbations in
different classes of the black holes is may one of the open problems yet. Here
to find the solution, different Maxwell's scalars besides the energy-momentum
tensor in both tangent and bend backgrounds are calculated. In doing so, the
well known Newman-Penrose formalism is considered.
| [
{
"created": "Fri, 21 Feb 2020 13:36:05 GMT",
"version": "v1"
}
] | 2020-02-25 | [
[
"Sheikhahmadi",
"Haidar",
""
]
] | Recently the first real image of the supermassive black hole at the heart of the galaxy M87 successfully has been captured. To explain the behavior of both the observed powerful jets and the electromagnetic accretion disk the Blandford Znajek mechanism, by the Event Horizon Telescope collaboration, has been considered. To justify these phenomena we are seeking an exact solution for a perturbed Rissner-Nordstrom black hole surrounded by a force-free field electrodynamics accretion disk. Although a charged black hole is a toy model, by tending the charge to zero one can obtain the results for a perturbed, rotating, Schwarzschild one immediately. Finding an exact solution in regards to the force-free field electrodynamics as a source for perturbations in different classes of the black holes is may one of the open problems yet. Here to find the solution, different Maxwell's scalars besides the energy-momentum tensor in both tangent and bend backgrounds are calculated. In doing so, the well known Newman-Penrose formalism is considered. |
gr-qc/9311003 | Sergey Tertychniy | S.Tertychniy | Local Determination of the Light Deflection in the Sperically Symmetric
Static Gravitational Field | 23 pages including 2 figures, uuencoded compressed PostScript, no
local number | null | null | null | gr-qc | null | The new method of invariant definition of the measurable angle of light
deflection in the static central symmetric gravitational field is suggested.
The predicted pure gravitational contribution to the deflection angle slightly
differs from its classical estimate and one may hope that this discrepancy
could be experimentally detected in the near future. (uuencoded,compressed
PostScript, 23 p. inc. 2 fig.)
| [
{
"created": "Tue, 2 Nov 1993 19:23:49 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Tertychniy",
"S.",
""
]
] | The new method of invariant definition of the measurable angle of light deflection in the static central symmetric gravitational field is suggested. The predicted pure gravitational contribution to the deflection angle slightly differs from its classical estimate and one may hope that this discrepancy could be experimentally detected in the near future. (uuencoded,compressed PostScript, 23 p. inc. 2 fig.) |
2404.00407 | Ayesha Almas | Adnan Malik, Yonghui Xia, Ayesha Almas, M. Farasat Shamir | Anisotropic Spheres Via Embedding Approach in $f(R,\phi, X)$ Gravity | 20 pages, 21 figures | Eur. Phys. J. Plus 138 (2023) 1091 | 10.1140/epjp/s13360-023-04721-8 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this manuscript, we investigate the behavior of stellar structure through
embedding approach in $f(R, \phi, X)$ modified theory of gravity, where $R$
denotes the Ricci scalar, $\phi$ represents the scalar potential and $X$
indicates the kinetic potential. For this purpose, we consider the spherically
symmetric space-time with anisotropic fluid. We further choose three different
stars i.e. LMC X-4, Cen X-3, and EXO 1785-248 to demonstrate the behavior of
stellar structures. We further compare the Schwarzschild space-time as exterior
geometry with spherically symmetric space-time to calculate the values of
unknown parameters. In this regard, we investigate the graphical features of
stellar spheres such es energy density, pressure components, anisotropic
component, equation of state parameters, stability analysis and energy
conditions. Furthermore, we investigate some extra conditions such as mass
function, compactness factor and surface redshift respectively. Conclusively,
all the compact stars under observations are realistic, stable, and are free
from any physical or geometrical singularities. We find that the embedding
class one solution for anisotropic compact stars is viable and stable.
| [
{
"created": "Sat, 30 Mar 2024 16:24:09 GMT",
"version": "v1"
}
] | 2024-04-02 | [
[
"Malik",
"Adnan",
""
],
[
"Xia",
"Yonghui",
""
],
[
"Almas",
"Ayesha",
""
],
[
"Shamir",
"M. Farasat",
""
]
] | In this manuscript, we investigate the behavior of stellar structure through embedding approach in $f(R, \phi, X)$ modified theory of gravity, where $R$ denotes the Ricci scalar, $\phi$ represents the scalar potential and $X$ indicates the kinetic potential. For this purpose, we consider the spherically symmetric space-time with anisotropic fluid. We further choose three different stars i.e. LMC X-4, Cen X-3, and EXO 1785-248 to demonstrate the behavior of stellar structures. We further compare the Schwarzschild space-time as exterior geometry with spherically symmetric space-time to calculate the values of unknown parameters. In this regard, we investigate the graphical features of stellar spheres such es energy density, pressure components, anisotropic component, equation of state parameters, stability analysis and energy conditions. Furthermore, we investigate some extra conditions such as mass function, compactness factor and surface redshift respectively. Conclusively, all the compact stars under observations are realistic, stable, and are free from any physical or geometrical singularities. We find that the embedding class one solution for anisotropic compact stars is viable and stable. |
1101.4668 | Cynthia Trendafilova | Cynthia S. Trendafilova and Stephen A. Fulling | Static solutions of Einstein's equations with cylindrical symmetry | 16 pages, 5 figures, 3 tables; many literature citations removed from
main body; added historical section to put project into context and include
additional references | Eur. J. Phys. 32 (2011) 1663-1677 | 10.1088/0143-0807/32/6/020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In analogy with the standard derivation of the Schwarzschild solution, we
find all static, cylindrically symmetric solutions of the Einstein field
equations for vacuum. These include not only the well known cone solution,
which is locally flat, but others in which the metric coefficients are powers
of the radial coordinate and the space-time is curved. These solutions appear
in the literature, but in different forms, corresponding to different
definitions of the radial coordinate. Because all the vacuum solutions are
singular on the axis, we attempt to match them to "interior" solutions with
nonvanishing energy density and pressure. In addition to the well known "cosmic
string" solution joining on to the cone, we find some numerical solutions that
join on to the other exterior solutions.
| [
{
"created": "Mon, 24 Jan 2011 21:35:06 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Jun 2011 19:02:15 GMT",
"version": "v2"
},
{
"created": "Fri, 26 Aug 2011 18:06:41 GMT",
"version": "v3"
}
] | 2015-05-27 | [
[
"Trendafilova",
"Cynthia S.",
""
],
[
"Fulling",
"Stephen A.",
""
]
] | In analogy with the standard derivation of the Schwarzschild solution, we find all static, cylindrically symmetric solutions of the Einstein field equations for vacuum. These include not only the well known cone solution, which is locally flat, but others in which the metric coefficients are powers of the radial coordinate and the space-time is curved. These solutions appear in the literature, but in different forms, corresponding to different definitions of the radial coordinate. Because all the vacuum solutions are singular on the axis, we attempt to match them to "interior" solutions with nonvanishing energy density and pressure. In addition to the well known "cosmic string" solution joining on to the cone, we find some numerical solutions that join on to the other exterior solutions. |
1604.07253 | Scott Robertson | Scott Robertson, Florent Michel, Renaud Parentani | Scattering of gravity waves in subcritical flows over an obstacle | 21 pages, 17 figures | Phys. Rev. D 93, 124060 (2016) | 10.1103/PhysRevD.93.124060 | null | gr-qc physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We numerically study the scattering coefficients of linear water waves on
stationary flows above a localized obstacle. We compare the scattering on
trans- and subcritical flows, and then focus on the latter which have been used
in recent analog gravity experiments. The main difference concerns the
magnitude of the mode amplification: whereas transcritical flows display a
large amplification (which is generally in good agreement with the Hawking
prediction), this effect is heavily suppressed in subcritical flows. This is
due to the transmission across the obstacle for frequencies less than some
critical value. As a result, subcritical flows display high- and low-frequency
behaviors separated by a narrow band around the critical frequency. In the
low-frequency regime, transmission of long wavelengths is accompanied by
non-adiabatic scattering into short wavelengths, whose spectrum is
approximately linear in frequency. By contrast, in the high-frequency regime,
no simple description seems to exist. In particular, for obstacles similar to
those recently used, we observe that the upstream slope still affects the
scattering on the downstream side because of some residual transmission.
| [
{
"created": "Mon, 25 Apr 2016 13:43:15 GMT",
"version": "v1"
}
] | 2016-06-29 | [
[
"Robertson",
"Scott",
""
],
[
"Michel",
"Florent",
""
],
[
"Parentani",
"Renaud",
""
]
] | We numerically study the scattering coefficients of linear water waves on stationary flows above a localized obstacle. We compare the scattering on trans- and subcritical flows, and then focus on the latter which have been used in recent analog gravity experiments. The main difference concerns the magnitude of the mode amplification: whereas transcritical flows display a large amplification (which is generally in good agreement with the Hawking prediction), this effect is heavily suppressed in subcritical flows. This is due to the transmission across the obstacle for frequencies less than some critical value. As a result, subcritical flows display high- and low-frequency behaviors separated by a narrow band around the critical frequency. In the low-frequency regime, transmission of long wavelengths is accompanied by non-adiabatic scattering into short wavelengths, whose spectrum is approximately linear in frequency. By contrast, in the high-frequency regime, no simple description seems to exist. In particular, for obstacles similar to those recently used, we observe that the upstream slope still affects the scattering on the downstream side because of some residual transmission. |
gr-qc/9909038 | Bogdan Dimitrov | B.G. Dimitrov (JINR, Dubna) | A Modified Variational Principle in Relativistic Hydrodynamics. II.
Variations of the vector field and the projection tensor in the general case
and under definite assumptions | 31 pages, Latex, no figures | null | null | null | gr-qc | null | The purpose of the paper is to develop further a projection variational
approach in relativistic hydrodynamics. The approach, previously proposed in
[gr-qc/9908032], is based on the variation of the vector field and the
projection tensor (instead of the given metric tensor) and their first partial
derivatives. The previously proved property of non-commutativity of the
variation and the partial derivative in respect to the projection tensor has
been used to find all the variations. Subsequently, motivated by some analogy
with the well-known (3+1) ADM projection formalism, an assumption has been made
about a zero-covariant derivative of the projection tensor in respect to the
projection connection. The combination of the equations for the variations of
the projective tensor with covariant and contravariant indices has lead to the
derivation of an important and concisely written relation: the derivative of
the vector field length is equal to the ''twice'' projected along the vector
field initial Christoffell connection. The result is of interest due to the
following reasons: 1. It is a more general one and contains in itself a
well-known formulae in affine differential geometry for the so called
equiaffine connections (admitting covariantly conserved tensor fields), for
which the trace of the connection is equal to the gradient of the logarithm of
the vector field length. 2. The additional term is the projected (with the
projection tensor) initially given connection and accounts for the influence of
the reference system on the change of the vector field's length, measured in
this system. 3. The formulae has been obtained within the proposed formalism of
non-commuting variation and partial derivative.
| [
{
"created": "Sun, 12 Sep 1999 12:50:21 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Dimitrov",
"B. G.",
"",
"JINR, Dubna"
]
] | The purpose of the paper is to develop further a projection variational approach in relativistic hydrodynamics. The approach, previously proposed in [gr-qc/9908032], is based on the variation of the vector field and the projection tensor (instead of the given metric tensor) and their first partial derivatives. The previously proved property of non-commutativity of the variation and the partial derivative in respect to the projection tensor has been used to find all the variations. Subsequently, motivated by some analogy with the well-known (3+1) ADM projection formalism, an assumption has been made about a zero-covariant derivative of the projection tensor in respect to the projection connection. The combination of the equations for the variations of the projective tensor with covariant and contravariant indices has lead to the derivation of an important and concisely written relation: the derivative of the vector field length is equal to the ''twice'' projected along the vector field initial Christoffell connection. The result is of interest due to the following reasons: 1. It is a more general one and contains in itself a well-known formulae in affine differential geometry for the so called equiaffine connections (admitting covariantly conserved tensor fields), for which the trace of the connection is equal to the gradient of the logarithm of the vector field length. 2. The additional term is the projected (with the projection tensor) initially given connection and accounts for the influence of the reference system on the change of the vector field's length, measured in this system. 3. The formulae has been obtained within the proposed formalism of non-commuting variation and partial derivative. |
1508.07573 | Vladimir Khatsymovsky | V.M. Khatsymovsky | First order minisuperspace model for the Faddeev formulation of gravity | 12 pages, 1 figure, to appear in Mod. Phys. Lett. A | Mod. Phys. Lett. A, Vol. 30, No. 32 (2015) 1550172 | 10.1142/S0217732315501746 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Faddeev formulation of general relativity (GR) is considered where the metric
is composed of ten vector fields or a ten-dimensional tetrad. Upon partial use
of the field equations, this theory results in the usual GR.
Earlier we have proposed some minisuperspace model for the Faddeev
formulation where the tetrad fields are piecewise constant on the polytopes
like 4-simplices or, say, cuboids into which ${\rm I \hspace{-3pt} R}^4$ can be
decomposed.
Now we study some representation of this (discrete) theory, an analogue of
the Cartan-Weyl connection-type form of the Hilbert-Einstein action in the
usual continuum GR.
| [
{
"created": "Sun, 30 Aug 2015 13:56:31 GMT",
"version": "v1"
}
] | 2015-09-28 | [
[
"Khatsymovsky",
"V. M.",
""
]
] | Faddeev formulation of general relativity (GR) is considered where the metric is composed of ten vector fields or a ten-dimensional tetrad. Upon partial use of the field equations, this theory results in the usual GR. Earlier we have proposed some minisuperspace model for the Faddeev formulation where the tetrad fields are piecewise constant on the polytopes like 4-simplices or, say, cuboids into which ${\rm I \hspace{-3pt} R}^4$ can be decomposed. Now we study some representation of this (discrete) theory, an analogue of the Cartan-Weyl connection-type form of the Hilbert-Einstein action in the usual continuum GR. |
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