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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2005.01310 | Shaoqi Hou | Shaoqi Hou, Zong-Hong Zhu | Gravitational memory effects and Bondi-Metzner-Sachs symmetries in
scalar-tensor theories | 29 pages, 2 figures. Add discussions on KK reduction, and soft
theorems. Feynman diagrams were fixed. Correct typos | JHEP 01 (2021) 083 | 10.1007/JHEP01(2021)083 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The relation between gravitational memory effects and Bondi-Metzner-Sachs
symmetry of the asymptotically flat spacetimes is studied in the scalar-tensor
theory. For this purpose, the solutions to the equations of motion near the
future null infinity are obtained in the generalized Bondi-Sachs coordinates
with a suitable determinant condition. It turns out that the
Bondi-Metzner-Sachs group is also a semi-direct product of an infinitesimal
dimensional supertranslation group and the Lorentz group as in general
relativity. There are also degenerate vacua in both the tensor and the scalar
sectors in the scalar-tensor theory. The supertranslation relates the vacua in
the tensor sector, while in the scalar sector, it is the Lorentz transformation
that transforms the vacua to each other. So there are the tensor memory effect
similar to the one in general relativity, and the scalar memory effect, which
is new. The evolution equations for the Bondi mass and angular momentum aspects
suggest that the null energy fluxes and the angular momentum fluxes across the
null infinity induce the transition among the vacua in the tensor and the
scalar sectors, respectively.
| [
{
"created": "Mon, 4 May 2020 08:12:28 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Aug 2020 06:54:27 GMT",
"version": "v2"
},
{
"created": "Fri, 14 Aug 2020 01:34:23 GMT",
"version": "v3"
},
{
"created": "Sun, 23 Aug 2020 07:29:54 GMT",
"version": "v4"
}
] | 2021-01-19 | [
[
"Hou",
"Shaoqi",
""
],
[
"Zhu",
"Zong-Hong",
""
]
] | The relation between gravitational memory effects and Bondi-Metzner-Sachs symmetry of the asymptotically flat spacetimes is studied in the scalar-tensor theory. For this purpose, the solutions to the equations of motion near the future null infinity are obtained in the generalized Bondi-Sachs coordinates with a suitable determinant condition. It turns out that the Bondi-Metzner-Sachs group is also a semi-direct product of an infinitesimal dimensional supertranslation group and the Lorentz group as in general relativity. There are also degenerate vacua in both the tensor and the scalar sectors in the scalar-tensor theory. The supertranslation relates the vacua in the tensor sector, while in the scalar sector, it is the Lorentz transformation that transforms the vacua to each other. So there are the tensor memory effect similar to the one in general relativity, and the scalar memory effect, which is new. The evolution equations for the Bondi mass and angular momentum aspects suggest that the null energy fluxes and the angular momentum fluxes across the null infinity induce the transition among the vacua in the tensor and the scalar sectors, respectively. |
1803.04904 | Kirill Bronnikov | S.V. Bolokhov and K.A. Bronnikov | On cosmology in nonlinear multidimensional gravity with multiple factor
spaces | 8 pages, 2 figures | Grav. Cosmol. 24, 154-160 (2018) | 10.1134/S0202289318020044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the scope of multidimensional Kaluza--Klein gravity with nonlinear
curvature terms and two spherical extra spaces of dimensions $m$ and $n$, we
study the properties of an effective action for the scale factors of the extra
dimensions. Dimensional reduction leads to an effective 4D multiscalar-tensor
theory. Based on qualitative estimates of the Casimir energy contribution on a
physically reasonable length scale, we demonstrate the existence of such sets
of initial parameters of the theory in the case $m=n$ that provide a minimum of
the effective potential that yield a fine-tuned value of the effective 4D
cosmological constant. The corresponding size of extra dimensions depends of
which conformal frame is interpreted as the observational one: it is about
three orders of magnitude larger than the standard Planck length if we adhere
to the Einstein frame, but it is $n$-dependent in the Jordan frame, and its
invisibility requirement restricts the total dimension to values $D = 4+2n \leq
20$.
| [
{
"created": "Tue, 13 Mar 2018 15:57:11 GMT",
"version": "v1"
}
] | 2020-10-20 | [
[
"Bolokhov",
"S. V.",
""
],
[
"Bronnikov",
"K. A.",
""
]
] | Within the scope of multidimensional Kaluza--Klein gravity with nonlinear curvature terms and two spherical extra spaces of dimensions $m$ and $n$, we study the properties of an effective action for the scale factors of the extra dimensions. Dimensional reduction leads to an effective 4D multiscalar-tensor theory. Based on qualitative estimates of the Casimir energy contribution on a physically reasonable length scale, we demonstrate the existence of such sets of initial parameters of the theory in the case $m=n$ that provide a minimum of the effective potential that yield a fine-tuned value of the effective 4D cosmological constant. The corresponding size of extra dimensions depends of which conformal frame is interpreted as the observational one: it is about three orders of magnitude larger than the standard Planck length if we adhere to the Einstein frame, but it is $n$-dependent in the Jordan frame, and its invisibility requirement restricts the total dimension to values $D = 4+2n \leq 20$. |
1404.6284 | Rory Smith | Priscilla Canizares, Scott E. Field, Jonathan Gair, Vivien Raymond,
Rory Smith and Manuel Tiglio | Accelerated gravitational-wave parameter estimation with reduced order
modeling | To appear in Physical Review Letters | Phys. Rev. Lett. 114, 071104 (2015) | 10.1103/PhysRevLett.114.071104 | LIGO-P1400038 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inferring the astrophysical parameters of coalescing compact binaries is a
key science goal of the upcoming advanced LIGO-Virgo gravitational-wave
detector network and, more generally, gravitational-wave astronomy. However,
current parameter estimation approaches for such scenarios can lead to
computationally intractable problems in practice. Therefore there is a pressing
need for new, fast and accurate Bayesian inference techniques. In this letter
we demonstrate that a reduced order modeling approach enables rapid parameter
estimation studies. By implementing a reduced order quadrature scheme within
the LIGO Algorithm Library, we show that Bayesian inference on the
9-dimensional parameter space of non-spinning binary neutron star inspirals can
be sped up by a factor of 30 for the early advanced detectors' configurations.
This speed-up will increase to about $150$ as the detectors improve their
low-frequency limit to 10Hz, reducing to hours analyses which would otherwise
take months to complete. Although these results focus on gravitational
detectors, the techniques are broadly applicable to any experiment where fast
Bayesian analysis is desirable.
| [
{
"created": "Thu, 24 Apr 2014 22:37:01 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jan 2015 23:59:16 GMT",
"version": "v2"
}
] | 2015-03-05 | [
[
"Canizares",
"Priscilla",
""
],
[
"Field",
"Scott E.",
""
],
[
"Gair",
"Jonathan",
""
],
[
"Raymond",
"Vivien",
""
],
[
"Smith",
"Rory",
""
],
[
"Tiglio",
"Manuel",
""
]
] | Inferring the astrophysical parameters of coalescing compact binaries is a key science goal of the upcoming advanced LIGO-Virgo gravitational-wave detector network and, more generally, gravitational-wave astronomy. However, current parameter estimation approaches for such scenarios can lead to computationally intractable problems in practice. Therefore there is a pressing need for new, fast and accurate Bayesian inference techniques. In this letter we demonstrate that a reduced order modeling approach enables rapid parameter estimation studies. By implementing a reduced order quadrature scheme within the LIGO Algorithm Library, we show that Bayesian inference on the 9-dimensional parameter space of non-spinning binary neutron star inspirals can be sped up by a factor of 30 for the early advanced detectors' configurations. This speed-up will increase to about $150$ as the detectors improve their low-frequency limit to 10Hz, reducing to hours analyses which would otherwise take months to complete. Although these results focus on gravitational detectors, the techniques are broadly applicable to any experiment where fast Bayesian analysis is desirable. |
0910.1627 | Guillermo A. Gonzalez | Camilo Akimushkin, Javier Ramos-Caro and Guillermo A. Gonz\'alez | Axially Symmetric Post-Newtonian Stellar Systems | 13 pages, 4 figures, to be published at Rev.Integr.Temas Mat | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a method to obtain self-consistent, axially symmetric, thin
disklike stellar models in the first post-Newtonian (1PN) approximation. The
models obtained are fully analytical and corresponds to the post-Newtonian
generalizations of classical ones. By introducing in the field equations
provided by the 1PN approximation a known distribution function (DF)
corresponding to a Newtonian model, two fundamental equations determining the
1PN corrections are obtained, which are solved using the Hunter method. The
rotation curves of the 1PN-corrected models differs from the classical ones
and, for the generalized Kalnajs discs, the 1PN corrections are clearly
appreciable with values of the mass and radius of a typical galaxy. On the
other hand, the relativistic mass correction can be ignored for all models.
| [
{
"created": "Thu, 8 Oct 2009 22:32:39 GMT",
"version": "v1"
}
] | 2009-10-12 | [
[
"Akimushkin",
"Camilo",
""
],
[
"Ramos-Caro",
"Javier",
""
],
[
"González",
"Guillermo A.",
""
]
] | We introduce a method to obtain self-consistent, axially symmetric, thin disklike stellar models in the first post-Newtonian (1PN) approximation. The models obtained are fully analytical and corresponds to the post-Newtonian generalizations of classical ones. By introducing in the field equations provided by the 1PN approximation a known distribution function (DF) corresponding to a Newtonian model, two fundamental equations determining the 1PN corrections are obtained, which are solved using the Hunter method. The rotation curves of the 1PN-corrected models differs from the classical ones and, for the generalized Kalnajs discs, the 1PN corrections are clearly appreciable with values of the mass and radius of a typical galaxy. On the other hand, the relativistic mass correction can be ignored for all models. |
2103.02382 | Gamal G.L. Nashed | G.G.L. Nashed and Shin'ichi Nojiri | Specific neutral and charged black holes in $f(R)$ gravitational theory | LaTeX 18 pages, 16 figures, several revisions | Phys. Rev. D 104, 124054 (2021) | 10.1103/PhysRevD.104.124054 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | With the successes of $f(R)$ theory as a neutral modification of Einstein's
general relativity (GR), we continue our study in this field and attempt to
find general %natural { neutral} and charged black hole (BH) solutions. In the
previous papers \cite{Nashed:2020mnp,Nashed:2020tbp}, we applied the field
equation of the $f(R)$ gravity to a spherically symmetric space-time
$ds^2=-U(r)dt^2+\frac{dr^2}{V(r)}+r^2 \left( d\theta^2+\sin^2\theta d\phi^2
\right)$ with unequal metric potentials $U(r)$ and $V(r)$ and with/without
electric charge. {Then we have obtained equations which include all the
possible static solutions with spherical symmetry.} To ensure the closed form
of system of the resulting differential equations in order to obtain specific
solutions, we assumed the derivative of the $f(R)$ with respect to the scalar
curvature $R$ to have a form %$F_1(r)=\frac{df(R(r))}{dR(r)} \propto
%{\color{red} 1 +} %\frac{c}{r^n}$ but in case $n>2$, the resulting black hole
solutions with/without charge do not %generate asymptotically GR BH solutions
in the limit $c\rightarrow 0$ which means that the only case that can generate
GR BHs is $n=2$. %In this paper, we assume another form, i.e., $F_1(r)
{=\frac{df(R(r))}{dR(r)} } = 1-\frac{F_0-\left(n-3\right)}{r^n}$ with a
constant $F_0$ and show that we can generate asymptotically GR BH solutions for
$n>2$ but we show that the $n=2$ case is not allowed. This form of $F_1(r)$
could be the most acceptable physical form that we can generate from it
physical metric potentials that can have a well-known asymptotic form and we
obtain the metric of the Einstein general relativity in the limit of $F_0\to
n-3$. We show that the form of the electric charge depends on $n$ and that
$n\neq 2$.}
| [
{
"created": "Wed, 3 Mar 2021 13:12:22 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Apr 2021 11:55:56 GMT",
"version": "v2"
},
{
"created": "Tue, 25 May 2021 14:32:55 GMT",
"version": "v3"
},
{
"created": "Tue, 29 Jun 2021 12:07:25 GMT",
"version": "v4"
},
{
"cr... | 2021-12-21 | [
[
"Nashed",
"G. G. L.",
""
],
[
"Nojiri",
"Shin'ichi",
""
]
] | With the successes of $f(R)$ theory as a neutral modification of Einstein's general relativity (GR), we continue our study in this field and attempt to find general %natural { neutral} and charged black hole (BH) solutions. In the previous papers \cite{Nashed:2020mnp,Nashed:2020tbp}, we applied the field equation of the $f(R)$ gravity to a spherically symmetric space-time $ds^2=-U(r)dt^2+\frac{dr^2}{V(r)}+r^2 \left( d\theta^2+\sin^2\theta d\phi^2 \right)$ with unequal metric potentials $U(r)$ and $V(r)$ and with/without electric charge. {Then we have obtained equations which include all the possible static solutions with spherical symmetry.} To ensure the closed form of system of the resulting differential equations in order to obtain specific solutions, we assumed the derivative of the $f(R)$ with respect to the scalar curvature $R$ to have a form %$F_1(r)=\frac{df(R(r))}{dR(r)} \propto %{\color{red} 1 +} %\frac{c}{r^n}$ but in case $n>2$, the resulting black hole solutions with/without charge do not %generate asymptotically GR BH solutions in the limit $c\rightarrow 0$ which means that the only case that can generate GR BHs is $n=2$. %In this paper, we assume another form, i.e., $F_1(r) {=\frac{df(R(r))}{dR(r)} } = 1-\frac{F_0-\left(n-3\right)}{r^n}$ with a constant $F_0$ and show that we can generate asymptotically GR BH solutions for $n>2$ but we show that the $n=2$ case is not allowed. This form of $F_1(r)$ could be the most acceptable physical form that we can generate from it physical metric potentials that can have a well-known asymptotic form and we obtain the metric of the Einstein general relativity in the limit of $F_0\to n-3$. We show that the form of the electric charge depends on $n$ and that $n\neq 2$.} |
2305.10533 | Philip Lynch PhD | Philip Lynch, Maarten van de Meent, Niels Warburton | Self-forced inspirals with spin-orbit precession | 25 pages, 9 figures, published in Physical Review D | Phys. Rev. D 109, 084072 (2024) | 10.1103/PhysRevD.109.084072 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We develop the first model for extreme mass-ratio inspirals (EMRIs) with
misaligned angular momentum and primary spin, and zero eccentricity -- also
known as quasi-spherical inspirals -- evolving under the influence of the
first-order in mass ratio gravitational self-force. The forcing terms are
provided by an efficient spectral interpolation of the first-order
gravitational self-force in the outgoing radiation gauge. In order to speed up
the calculation of the inspiral we apply a near-identity (averaging)
transformation to eliminate all dependence of the orbital phases from the
equations of motion while maintaining all secular effects of the first-order
gravitational self-force at post-adiabatic order. The resulting solutions are
defined with respect to `Mino time' so we perform a second averaging
transformation so the inspiral is parametrized in terms of Boyer-Lindquist
time, which is more convenient of LISA data analysis. We also perform a similar
analysis using the two-timescale expansion and find that using either approach
yields self-forced inspirals that can be evolved to sub-radian accuracy in less
than a second. The dominant contribution to the inspiral phase comes from the
adiabatic contributions and so we further refine our self-force model using
information from gravitational wave flux calculations. The significant
dephasing we observe between the lower and higher accuracy models highlights
the importance of accurately capturing adiabatic contributions to the phase
evolution.
| [
{
"created": "Wed, 17 May 2023 19:37:07 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Jun 2024 08:43:29 GMT",
"version": "v2"
}
] | 2024-06-05 | [
[
"Lynch",
"Philip",
""
],
[
"van de Meent",
"Maarten",
""
],
[
"Warburton",
"Niels",
""
]
] | We develop the first model for extreme mass-ratio inspirals (EMRIs) with misaligned angular momentum and primary spin, and zero eccentricity -- also known as quasi-spherical inspirals -- evolving under the influence of the first-order in mass ratio gravitational self-force. The forcing terms are provided by an efficient spectral interpolation of the first-order gravitational self-force in the outgoing radiation gauge. In order to speed up the calculation of the inspiral we apply a near-identity (averaging) transformation to eliminate all dependence of the orbital phases from the equations of motion while maintaining all secular effects of the first-order gravitational self-force at post-adiabatic order. The resulting solutions are defined with respect to `Mino time' so we perform a second averaging transformation so the inspiral is parametrized in terms of Boyer-Lindquist time, which is more convenient of LISA data analysis. We also perform a similar analysis using the two-timescale expansion and find that using either approach yields self-forced inspirals that can be evolved to sub-radian accuracy in less than a second. The dominant contribution to the inspiral phase comes from the adiabatic contributions and so we further refine our self-force model using information from gravitational wave flux calculations. The significant dephasing we observe between the lower and higher accuracy models highlights the importance of accurately capturing adiabatic contributions to the phase evolution. |
2203.03639 | Mouhssine Koussour | M. Koussour, S. H. Shekh, M. Govender and M. Bennai | Thermodynamical aspects of Bianchi type-I Universe in quadratic form of
$f\left( Q\right) $ gravity and observational constraints | Journal of High Energy Astrophysics accepted version | Journal of High Energy Astrophysics 37 (2023): 15-24 | 10.1016/j.jheap.2022.11.002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we discuss the Bianchi type-I cosmological model in the
framework of symmetric teleparallel gravity say $f(Q)$ gravity in which the
non-metricity term $Q$ is responsible for the gravitational interaction. We
consider a special form of the $f\left( Q\right) $ function which can be cast
as $f\left( Q\right) =\lambda Q^{n}$, where $\lambda $ and $n$ both are the
dynamical model parameters. Such a choice can be viewed as a hybrid scale
factor that leads to a relation between cosmic time and redshift as $% t=\left(
\frac{\alpha t_{0}}{\beta }\right) W\left[ \frac{\beta }{\alpha }e^{%
\frac{\beta -\ln \left( 1+z\right) }{\alpha }}\right] $ which describes a $%
\Lambda $CDM model of the Universe with the expansion evolving from
decelerating to an acceleration phase. The best values for the model parameters
i.e. $\alpha $ and $\beta $ that would accord with the most current
observational datasets are then estimated. We make use of 57 points from the
Hubble dataset, 1048 points from the supernovae of type Ia dataset and 6 points
from the BAO dataset. We use the Markov Chain Monte Carlo (MCMC) technique in
conjunction with Bayesian analysis and the likelihood function. Further, we
study the validity of our model with the investigation of the thermodynamical
quantities, energy conditions along with some physical variables such as the
EoS, and jerk parameters. Next, our results are discussed in light of current
observational data and trends.
| [
{
"created": "Mon, 7 Mar 2022 13:49:21 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Aug 2022 07:06:09 GMT",
"version": "v2"
},
{
"created": "Tue, 29 Nov 2022 18:04:08 GMT",
"version": "v3"
}
] | 2023-04-05 | [
[
"Koussour",
"M.",
""
],
[
"Shekh",
"S. H.",
""
],
[
"Govender",
"M.",
""
],
[
"Bennai",
"M.",
""
]
] | In this paper, we discuss the Bianchi type-I cosmological model in the framework of symmetric teleparallel gravity say $f(Q)$ gravity in which the non-metricity term $Q$ is responsible for the gravitational interaction. We consider a special form of the $f\left( Q\right) $ function which can be cast as $f\left( Q\right) =\lambda Q^{n}$, where $\lambda $ and $n$ both are the dynamical model parameters. Such a choice can be viewed as a hybrid scale factor that leads to a relation between cosmic time and redshift as $% t=\left( \frac{\alpha t_{0}}{\beta }\right) W\left[ \frac{\beta }{\alpha }e^{% \frac{\beta -\ln \left( 1+z\right) }{\alpha }}\right] $ which describes a $% \Lambda $CDM model of the Universe with the expansion evolving from decelerating to an acceleration phase. The best values for the model parameters i.e. $\alpha $ and $\beta $ that would accord with the most current observational datasets are then estimated. We make use of 57 points from the Hubble dataset, 1048 points from the supernovae of type Ia dataset and 6 points from the BAO dataset. We use the Markov Chain Monte Carlo (MCMC) technique in conjunction with Bayesian analysis and the likelihood function. Further, we study the validity of our model with the investigation of the thermodynamical quantities, energy conditions along with some physical variables such as the EoS, and jerk parameters. Next, our results are discussed in light of current observational data and trends. |
1211.6184 | Prayush Kumar | Duncan A. Brown, Prayush Kumar, Alexander H. Nitz | Template banks to search for low-mass binary black holes in advanced
gravitational-wave detectors | 12 pages, 10 figures | Phys. Rev. D 87, 082004 (2013) | 10.1103/PhysRevD.87.082004 | LIGO Document P1200099 | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Coalescing binary black holes (BBHs) are among the most likely sources for
the Laser Interferometer Gravitational-wave Observatory (LIGO) and its
international partners Virgo and KAGRA. Optimal searches for BBHs require
accurate waveforms for the signal model and effectual template banks that cover
the mass space of interest. We investigate the ability of the second-order
post-Newtonian TaylorF2 hexagonal template placement metric to construct an
effectual template bank, if the template waveforms used are effective one body
waveforms tuned to numerical relativity (EOBNRv2). We find that by combining
the existing TaylorF2 placement metric with EOBNRv2 waveforms, we can construct
an effectual search for BBHs with component masses in the range 3 Msolar <=
m_1, m_2 <= 25 Msolar. We also show that the (computationally less expensive)
TaylorF2 post-Newtonian waveforms can be used in place of EOBNRv2 waveforms
when M <~ 11.4 Msolar. Finally, we investigate the effect of modes other than
the dominant l = m = 2 mode in BBH searches. We find that for systems with
(m_1/m_2)<= 1.68 or inclination angle: \iota <= 0.31 or \iota >= 2.68 radians,
there is no significant loss in the total possible signal-to-noise ratio due to
neglecting modes other than l = m = 2 in the template waveforms. For a source
population uniformly distributed in spacial volume, over the entire sampled
region of the component-mass space, the loss in detection rate (averaged over a
uniform distribution of inclination angle and sky-location/polarization
angles), remains below ~11%. For binaries with high mass-ratios \textit{and}
0.31 <= \iota <= 2.68, including higher order modes could increase the
signal-to-noise ratio by as much as 8% in Advanced LIGO. Our results can be
used to construct matched-filter searches in Advanced LIGO and Advanced Virgo.
| [
{
"created": "Tue, 27 Nov 2012 02:34:48 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Mar 2013 21:51:19 GMT",
"version": "v2"
}
] | 2013-12-10 | [
[
"Brown",
"Duncan A.",
""
],
[
"Kumar",
"Prayush",
""
],
[
"Nitz",
"Alexander H.",
""
]
] | Coalescing binary black holes (BBHs) are among the most likely sources for the Laser Interferometer Gravitational-wave Observatory (LIGO) and its international partners Virgo and KAGRA. Optimal searches for BBHs require accurate waveforms for the signal model and effectual template banks that cover the mass space of interest. We investigate the ability of the second-order post-Newtonian TaylorF2 hexagonal template placement metric to construct an effectual template bank, if the template waveforms used are effective one body waveforms tuned to numerical relativity (EOBNRv2). We find that by combining the existing TaylorF2 placement metric with EOBNRv2 waveforms, we can construct an effectual search for BBHs with component masses in the range 3 Msolar <= m_1, m_2 <= 25 Msolar. We also show that the (computationally less expensive) TaylorF2 post-Newtonian waveforms can be used in place of EOBNRv2 waveforms when M <~ 11.4 Msolar. Finally, we investigate the effect of modes other than the dominant l = m = 2 mode in BBH searches. We find that for systems with (m_1/m_2)<= 1.68 or inclination angle: \iota <= 0.31 or \iota >= 2.68 radians, there is no significant loss in the total possible signal-to-noise ratio due to neglecting modes other than l = m = 2 in the template waveforms. For a source population uniformly distributed in spacial volume, over the entire sampled region of the component-mass space, the loss in detection rate (averaged over a uniform distribution of inclination angle and sky-location/polarization angles), remains below ~11%. For binaries with high mass-ratios \textit{and} 0.31 <= \iota <= 2.68, including higher order modes could increase the signal-to-noise ratio by as much as 8% in Advanced LIGO. Our results can be used to construct matched-filter searches in Advanced LIGO and Advanced Virgo. |
gr-qc/0512091 | Robert Bartnik | Robert Bartnik and Jim Isenberg | Spherically symmetric dynamical horizons | latex, 19 pages, no figures | Class.Quant.Grav.23:2559-2570,2006 | 10.1088/0264-9381/23/7/020 | NI05079 | gr-qc | null | We determine sufficient and necessary conditions for a spherically symmetric
initial data set to satisfy the dynamical horizon conditions in the spacetime
development. The constraint equations reduce to a single second order linear
master equation, which leads to a systematic construction of all spherically
symmetric dynamical horizons (SSDH) satisfying certain boundedness conditions.
We also find necessary and sufficient conditions for a given spherically
symmetric spacetime to contain a SSDH.
| [
{
"created": "Thu, 15 Dec 2005 14:04:27 GMT",
"version": "v1"
}
] | 2011-04-21 | [
[
"Bartnik",
"Robert",
""
],
[
"Isenberg",
"Jim",
""
]
] | We determine sufficient and necessary conditions for a spherically symmetric initial data set to satisfy the dynamical horizon conditions in the spacetime development. The constraint equations reduce to a single second order linear master equation, which leads to a systematic construction of all spherically symmetric dynamical horizons (SSDH) satisfying certain boundedness conditions. We also find necessary and sufficient conditions for a given spherically symmetric spacetime to contain a SSDH. |
2005.09182 | Mohammad Walid AlMasri | M. W. AlMasri | Restoring Classical Energy Conditions At Microscopic Level | Revised version, 19 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | We propose a mechanism for restoring classical energy conditions at quantized
level based on quantum inequalities and quantum interest conjecture. More
concretely, we assume for each quantum state in our visible universe to have
anti-state trapped at quantum gravity scale (or true vacuum in inflation
terminology). The proposed mechanism answers many outstanding questions related
to the arrow of time problem, possible interpretation of the weakness of
gravity and hierarchy problem, the probabilistic nature of quantum mechanics,
matter-antimatter asymmetry. Moreover, the proposed mechanism gives a strong
endorsement to inflation as a possible solution of flatness and horizon
problems.
| [
{
"created": "Mon, 18 May 2020 15:23:23 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Jun 2020 18:24:02 GMT",
"version": "v2"
},
{
"created": "Mon, 14 Sep 2020 16:51:22 GMT",
"version": "v3"
},
{
"created": "Sun, 6 Dec 2020 03:32:02 GMT",
"version": "v4"
},
{
"cr... | 2021-12-30 | [
[
"AlMasri",
"M. W.",
""
]
] | We propose a mechanism for restoring classical energy conditions at quantized level based on quantum inequalities and quantum interest conjecture. More concretely, we assume for each quantum state in our visible universe to have anti-state trapped at quantum gravity scale (or true vacuum in inflation terminology). The proposed mechanism answers many outstanding questions related to the arrow of time problem, possible interpretation of the weakness of gravity and hierarchy problem, the probabilistic nature of quantum mechanics, matter-antimatter asymmetry. Moreover, the proposed mechanism gives a strong endorsement to inflation as a possible solution of flatness and horizon problems. |
0803.3953 | Ragab Gad | M. Abdel-Megied and Ragab M. Gad | M{\o}ller's Energy in the Kantowski-Sachs Space-time | 7 pages and no figures | Adv.High Energy Phys.2010:379473,2010 | 10.1155/2010/379473 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a counter example to paper \cite{P71} and show that the result
obtained is correct for a class of metric but not general. We calculate the
total energy of the Kantowski-Sachs space-time by using the energy-momentum
definitions of M{\o}ller in the theory of general relativity and the tetrad
theory of gravity.
| [
{
"created": "Thu, 27 Mar 2008 15:17:11 GMT",
"version": "v1"
}
] | 2015-02-06 | [
[
"Abdel-Megied",
"M.",
""
],
[
"Gad",
"Ragab M.",
""
]
] | We present a counter example to paper \cite{P71} and show that the result obtained is correct for a class of metric but not general. We calculate the total energy of the Kantowski-Sachs space-time by using the energy-momentum definitions of M{\o}ller in the theory of general relativity and the tetrad theory of gravity. |
1111.1125 | Maite Dupuis | Mait\'e Dupuis, Etera R. Livine | Holomorphic Simplicity Constraints for 4d Riemannian Spinfoam Models | 4 pages. Proceedings of Loops'11, Madrid. To appear in Journal of
Physics: Conference Series (JPCS) | null | 10.1088/1742-6596/360/1/012046 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Starting from the reformulation of the classical phase space of Loop Quantum
Gravity in terms of spinor variables and spinor networks, we build coherent
spin network states and show how to use them to write the spinfoam path
integral for topological BF theory in terms of Gaussian integrals in the
spinors. Finally, we use this framework to revisit the simplicity constraints
reducing topological BF theory to 4d Riemannian gravity. These holomorphic
simplicity constraints lead us to a new spinfoam model for quantum gravity
whose amplitudes are defined as the evaluation of the coherent spin networks.
| [
{
"created": "Fri, 4 Nov 2011 13:33:37 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Dupuis",
"Maité",
""
],
[
"Livine",
"Etera R.",
""
]
] | Starting from the reformulation of the classical phase space of Loop Quantum Gravity in terms of spinor variables and spinor networks, we build coherent spin network states and show how to use them to write the spinfoam path integral for topological BF theory in terms of Gaussian integrals in the spinors. Finally, we use this framework to revisit the simplicity constraints reducing topological BF theory to 4d Riemannian gravity. These holomorphic simplicity constraints lead us to a new spinfoam model for quantum gravity whose amplitudes are defined as the evaluation of the coherent spin networks. |
gr-qc/0610063 | Zsolt Horv\'ath | Zsolt Horv\'ath, Zolt\'an Kov\'acs | Canonical theory of the Kantowski-Sachs cosmological models | 6 pages, in Proceedings of the FIKUT4 Conference | Publ.Astron.Dep.Eotvos Univ., PADEU 17, 229-234 (2006) | null | null | gr-qc | null | We briefly discuss the Hamiltonian formalism of Kantowski-Sachs space-times
with vacuum, anisotropic fluid and two cross-streaming radiation field sources.
For these models a cosmological time is introduced. New constraints are found
in which the fluid momenta are separated from the rest of the variables. In
consequence their Poisson brackets give an Abelian algebra.
| [
{
"created": "Thu, 12 Oct 2006 11:39:55 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Horváth",
"Zsolt",
""
],
[
"Kovács",
"Zoltán",
""
]
] | We briefly discuss the Hamiltonian formalism of Kantowski-Sachs space-times with vacuum, anisotropic fluid and two cross-streaming radiation field sources. For these models a cosmological time is introduced. New constraints are found in which the fluid momenta are separated from the rest of the variables. In consequence their Poisson brackets give an Abelian algebra. |
gr-qc/9905060 | Brendan S. Guilfoyle | Brendan S. Guilfoyle | Weyl-type Fields with Geodesic Lines of Force | 13 pages, RevTex | J.Math.Phys. 40 (1999) 2032-2045 | 10.1063/1.532849 | null | gr-qc | null | The static electrogravitational equations are studied and it is shown that an
aligned type D metric which has a Weyl-type relationship between the
gravitational and electric potential has shearfree geodesic lines of force. All
such fields are then found and turn out to be the fields of a charged sphere,
charged infinite rod and charged infinite plate. A further solution is also
found with shearing geodesic lines of force. This new solution can have $m>|e|$
or $m<|e|$, but cannot be in the Majumdar-Papapetrou class (in which $m =
|e|$). It is algebraically general and has flat equipotential surfaces.
| [
{
"created": "Tue, 18 May 1999 09:55:16 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Guilfoyle",
"Brendan S.",
""
]
] | The static electrogravitational equations are studied and it is shown that an aligned type D metric which has a Weyl-type relationship between the gravitational and electric potential has shearfree geodesic lines of force. All such fields are then found and turn out to be the fields of a charged sphere, charged infinite rod and charged infinite plate. A further solution is also found with shearing geodesic lines of force. This new solution can have $m>|e|$ or $m<|e|$, but cannot be in the Majumdar-Papapetrou class (in which $m = |e|$). It is algebraically general and has flat equipotential surfaces. |
gr-qc/9904016 | Warren G. Anderson | Warren G. Anderson (University of Wisconsin - Milwaukee), Werner
Israel (University of Victoria) | Quantum Flux from a Moving Spherical Mirror | 13 pages, 2 figures, RevTex, submitted to Phys. Rev. D | Phys. Rev. D 60, 084003 (1999) | 10.1103/PhysRevD.60.084003 | WISC-MILW-99-TH-02 | gr-qc | null | We calculate the flux from a spherical mirror which is expanding or
contracting with nearly uniform acceleration. We find that the flux at an
exterior point (which could in principle be a functional of the mirror's past
history) is actually found to be a local function, depending on the first and
second time derivatives of acceleration at the retarded time.
| [
{
"created": "Tue, 6 Apr 1999 16:47:22 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Apr 1999 20:10:05 GMT",
"version": "v2"
}
] | 2016-08-25 | [
[
"Anderson",
"Warren G.",
"",
"University of Wisconsin - Milwaukee"
],
[
"Israel",
"Werner",
"",
"University of Victoria"
]
] | We calculate the flux from a spherical mirror which is expanding or contracting with nearly uniform acceleration. We find that the flux at an exterior point (which could in principle be a functional of the mirror's past history) is actually found to be a local function, depending on the first and second time derivatives of acceleration at the retarded time. |
gr-qc/0012112 | David Blaschke | Danilo Behnke, David Blaschke, Victor Pervushin, Denis Proskurin | Conformal Cosmology and Supernova Data | 9 pages revtex, 1 figure, Contribution to the Proceedings of the
workshop "Quark Matter in Astro- and Particle Physics", Rostock, Nov 27 - 29,
2000, Eds: D. Blaschke, G. Burau, S.M. Schmidt | null | null | MPG-VT-UR 211/00 | gr-qc | null | We define the cosmological parameters $H_{c,0}$, $\Omega_{m,c}$ and
$\Omega_{\Lambda, c}$ within the Conformal Cosmology as obtained by the
homogeneous approximation to the conformal-invariant generalization of
Einstein's General Relativity theory. We present the definitions of the age of
the universe and of the luminosity distance in the context of this approach. A
possible explanation of the recent data from distant supernovae Ia without a
cosmological constant is presented.
| [
{
"created": "Fri, 29 Dec 2000 22:17:43 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Behnke",
"Danilo",
""
],
[
"Blaschke",
"David",
""
],
[
"Pervushin",
"Victor",
""
],
[
"Proskurin",
"Denis",
""
]
] | We define the cosmological parameters $H_{c,0}$, $\Omega_{m,c}$ and $\Omega_{\Lambda, c}$ within the Conformal Cosmology as obtained by the homogeneous approximation to the conformal-invariant generalization of Einstein's General Relativity theory. We present the definitions of the age of the universe and of the luminosity distance in the context of this approach. A possible explanation of the recent data from distant supernovae Ia without a cosmological constant is presented. |
1103.1703 | Arianto | Arianto, F.P. Zen, S. Feranie, I P. Widyatmika, and B.E. Gunara | Kaluza-Klein brane cosmology with a bulk scalar field | 11 pages, one section added, accepted for publication in PRD | Phys.Rev.D84:044008,2011 | 10.1103/PhysRevD.84.044008 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The brane-world cosmological model in higher-dimensional spacetime with a
bulk scalar field is investigated. We derive the $(4+n)$-dimensional
gravitational field equations for the scalar field on the $(3+n)$-brane in a
$(5+n)$-dimensional bulk with Einstein gravity plus a self-interacting scalar
field. The $(4+n)$-dimensional gravitational field equations can be formulated
to standard form with the extra component. Using this formalism we study the
Kaluza-Klein brane cosmology. We derive the Friedmann equation and a possible
energy leak out of the brane into the bulk. We present some exact solutions
corresponding to vacuum brane and matter on the brane.
| [
{
"created": "Wed, 9 Mar 2011 05:23:18 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Jun 2011 03:54:42 GMT",
"version": "v2"
}
] | 2011-08-12 | [
[
"Arianto",
"",
""
],
[
"Zen",
"F. P.",
""
],
[
"Feranie",
"S.",
""
],
[
"Widyatmika",
"I P.",
""
],
[
"Gunara",
"B. E.",
""
]
] | The brane-world cosmological model in higher-dimensional spacetime with a bulk scalar field is investigated. We derive the $(4+n)$-dimensional gravitational field equations for the scalar field on the $(3+n)$-brane in a $(5+n)$-dimensional bulk with Einstein gravity plus a self-interacting scalar field. The $(4+n)$-dimensional gravitational field equations can be formulated to standard form with the extra component. Using this formalism we study the Kaluza-Klein brane cosmology. We derive the Friedmann equation and a possible energy leak out of the brane into the bulk. We present some exact solutions corresponding to vacuum brane and matter on the brane. |
2302.04923 | Wei-Chen Lin | Wei-Chen Lin, Dejan Stojkovic and Dong-han Yeom | Trouble with the Penrose diagram in spacetimes connected via a spacelike
thin shell | Revised version. An Appendix has been added. 31 pages, 11 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, we point out the issue of the first junction condition in
the Penrose diagram constructed by cutting and pasting analytically known
metrics with spherical symmetry by a static spacelike thin shell. We
demonstrate this issue by using two examples -- the generalized black-to-white
hole bounce with mass difference and the Schwarzschild-to-de Sitter transition.
The goal is to construct the corresponding Penrose diagrams without any
explicit or implicit illness at the thin shell. To accomplish this, we find
that two coordinate transformations are required unless a special condition is
met. The first transformation serves as the removal of the unwanted area while
the second one reconciles the two different coordinate systems on two sides of
the shell by removing an implicit discontinuity in the Penrose diagram of this
type. However, the second transformation brings a different kind of coordinate
singularity back to the event horizon. This coordinate singularity either
creates a degeneracy such that all four-vectors are in 45$\degree$, or a
degeneracy such that timelike vectors are parallel to the event horizon in the
resulting Penrose diagram. We give geometric explanations for the discontinuity
and this special type of coordinate singularity. We further show that no static
conformal coordinates can cover all of the event horizons without having
coordinate singularity at some of them. Lastly, we draw a comparison to the
Reissner-Nordstr{\"o}m solution.
| [
{
"created": "Thu, 9 Feb 2023 20:38:12 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Jun 2023 08:17:46 GMT",
"version": "v2"
}
] | 2023-06-30 | [
[
"Lin",
"Wei-Chen",
""
],
[
"Stojkovic",
"Dejan",
""
],
[
"Yeom",
"Dong-han",
""
]
] | In this article, we point out the issue of the first junction condition in the Penrose diagram constructed by cutting and pasting analytically known metrics with spherical symmetry by a static spacelike thin shell. We demonstrate this issue by using two examples -- the generalized black-to-white hole bounce with mass difference and the Schwarzschild-to-de Sitter transition. The goal is to construct the corresponding Penrose diagrams without any explicit or implicit illness at the thin shell. To accomplish this, we find that two coordinate transformations are required unless a special condition is met. The first transformation serves as the removal of the unwanted area while the second one reconciles the two different coordinate systems on two sides of the shell by removing an implicit discontinuity in the Penrose diagram of this type. However, the second transformation brings a different kind of coordinate singularity back to the event horizon. This coordinate singularity either creates a degeneracy such that all four-vectors are in 45$\degree$, or a degeneracy such that timelike vectors are parallel to the event horizon in the resulting Penrose diagram. We give geometric explanations for the discontinuity and this special type of coordinate singularity. We further show that no static conformal coordinates can cover all of the event horizons without having coordinate singularity at some of them. Lastly, we draw a comparison to the Reissner-Nordstr{\"o}m solution. |
1511.01162 | Matt Visser | Ana Alonso-Serrano (Victoria University of Wellington) and Matt Visser
(Victoria University of Wellington) | On burning a lump of coal | 11 pages | Physics Letters B757 (2016) 383-386 | 10.1016/j.physletb.2016.04.023 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Burning something, (e.g. the proverbial lump of coal, or an encyclopaedia for
that matter), in a blackbody furnace leads to an approximately Planck emission
spectrum with an average entropy/information transfer of approximately $3.9 \pm
2.5$ bits per emitted photon. This quantitative and qualitative result depends
only on the underlying unitarity of the quantum physics of burning, combined
with the statistical mechanics of blackbody radiation. The fact that the
utterly standard and unitarity preserving process of burning something (in
fact, burning anything) nevertheless *has* an associated entropy/information
budget, and the quantitative *size* of that entropy/information budget, is a
severely under-appreciated feature of standard quantum statistical physics.
| [
{
"created": "Tue, 3 Nov 2015 23:50:14 GMT",
"version": "v1"
}
] | 2017-11-28 | [
[
"Alonso-Serrano",
"Ana",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | Burning something, (e.g. the proverbial lump of coal, or an encyclopaedia for that matter), in a blackbody furnace leads to an approximately Planck emission spectrum with an average entropy/information transfer of approximately $3.9 \pm 2.5$ bits per emitted photon. This quantitative and qualitative result depends only on the underlying unitarity of the quantum physics of burning, combined with the statistical mechanics of blackbody radiation. The fact that the utterly standard and unitarity preserving process of burning something (in fact, burning anything) nevertheless *has* an associated entropy/information budget, and the quantitative *size* of that entropy/information budget, is a severely under-appreciated feature of standard quantum statistical physics. |
2312.02292 | Grigory Volovik | G.E. Volovik | Thermodynamics and decay of de Sitter vacuum | 33 pages, published in Symmetry. The short version
arXiv:2312.02292v8, "de Sitter local thermodynamics in f(R) gravity", was
published in JETP Letters DOI: 10.1134/S0021364024600526 | Symmetry 16, 763 (2024) | 10.3390/sym16060763 | null | gr-qc cond-mat.other | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the consequences of unique symmetry of de Sitter spacetime, which
is invariant under the modified translations, ${\bf r}\rightarrow {\bf r}
-e^{Ht}{\bf a}$, where $H$ is the Hubble parameter. Due to this symmetry, all
the comoving observers at any point of the de Sitter space perceive the de
Sitter environment as the thermal bath with temperature $T=H/\pi$, which is
twice larger than the Gibbons-Hawking temperature of the cosmological horizon.
This leads to the heat exchange between gravity and matter, and to instability
of de Sitter state towards the creation of matter, its further heating, and
finally to the decay of the de Sitter state. The temperature $T=H/\pi$
determines different processes in the de Sitter environment, which are not
possible in Minkowski vacuum, such as the process of ionization of an atom.
This temperature also determines the local entropy of the de Sitter vacuum
state, and this allows us to calculate the total entropy inside the
cosmological horizon. The result reproduces the Gibbons-Hawking area law, which
is related to the cosmological horizon, $S_{\rm hor}=4\pi KA$, where
$K=1/(16\pi G)$. This supports the holographic properties of the cosmological
event horizon. We extend the consideration of the local thermodynamics of the
de Sitter state using the $f({\cal R})$ gravity. In this thermodynamics, the
Ricci scalar curvature ${\cal R}$ and the effective gravitational coupling $K$
are thermodynamically conjugate variables. The holographic connection between
the bulk entropy of the Hubble volume and the surface entropy of the
cosmological horizon remains the same. Such connection takes place only in the
$3+1$ spacetime, where there is the special symmetry due to which the variables
$K$ and ${\cal R}$ have the same dimensionality. We also consider the lessons
from the de Sitter symmetry for the thermodynamics of black and white holes.
| [
{
"created": "Mon, 4 Dec 2023 19:13:35 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Apr 2024 14:14:36 GMT",
"version": "v10"
},
{
"created": "Mon, 15 Apr 2024 09:16:48 GMT",
"version": "v11"
},
{
"created": "Mon, 22 Apr 2024 14:14:00 GMT",
"version": "v12"
},
{
"... | 2024-06-25 | [
[
"Volovik",
"G. E.",
""
]
] | We discuss the consequences of unique symmetry of de Sitter spacetime, which is invariant under the modified translations, ${\bf r}\rightarrow {\bf r} -e^{Ht}{\bf a}$, where $H$ is the Hubble parameter. Due to this symmetry, all the comoving observers at any point of the de Sitter space perceive the de Sitter environment as the thermal bath with temperature $T=H/\pi$, which is twice larger than the Gibbons-Hawking temperature of the cosmological horizon. This leads to the heat exchange between gravity and matter, and to instability of de Sitter state towards the creation of matter, its further heating, and finally to the decay of the de Sitter state. The temperature $T=H/\pi$ determines different processes in the de Sitter environment, which are not possible in Minkowski vacuum, such as the process of ionization of an atom. This temperature also determines the local entropy of the de Sitter vacuum state, and this allows us to calculate the total entropy inside the cosmological horizon. The result reproduces the Gibbons-Hawking area law, which is related to the cosmological horizon, $S_{\rm hor}=4\pi KA$, where $K=1/(16\pi G)$. This supports the holographic properties of the cosmological event horizon. We extend the consideration of the local thermodynamics of the de Sitter state using the $f({\cal R})$ gravity. In this thermodynamics, the Ricci scalar curvature ${\cal R}$ and the effective gravitational coupling $K$ are thermodynamically conjugate variables. The holographic connection between the bulk entropy of the Hubble volume and the surface entropy of the cosmological horizon remains the same. Such connection takes place only in the $3+1$ spacetime, where there is the special symmetry due to which the variables $K$ and ${\cal R}$ have the same dimensionality. We also consider the lessons from the de Sitter symmetry for the thermodynamics of black and white holes. |
2401.10871 | Sergey Chernov | S.V. Chernov | Shadows and photon rings of binary black holes | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper we present the images of binary black holes using the
Majumdar-Papapetrou multiblack hole solution, depending on the parameters of
the problem: the mass of black holes, the distance between them, and the
inclination of the observer. The images consists of a shadows and photon rings.
We find that a photon ring structure appears between black holes. The
trajectories of the photons are calculated.
| [
{
"created": "Fri, 19 Jan 2024 18:28:18 GMT",
"version": "v1"
}
] | 2024-01-22 | [
[
"Chernov",
"S. V.",
""
]
] | In this paper we present the images of binary black holes using the Majumdar-Papapetrou multiblack hole solution, depending on the parameters of the problem: the mass of black holes, the distance between them, and the inclination of the observer. The images consists of a shadows and photon rings. We find that a photon ring structure appears between black holes. The trajectories of the photons are calculated. |
1704.01400 | Christian Nwachioma | Christian Nwachioma and Farida Tahir | Path Equations In Absolute Parallelism Space | 16 pages, 3 figures. Version 2: argument improved, typos corrected, a
diagram removed | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Riemannian and Absolute Parallelism (AP) geometries are discussed. A lavish
treatment of path equations in the AP-space using the Bazanski-type Lagrangian
is presented; We write down an expression that is absolutely conserved along a
curve in the AP-space and show that it gives the same path equations as
obtained using the conventional Lagrangian formalism. We attribute physical
interpretations to the resultant path equations and we show that the
spin-torsion interaction is an inherent property of the AP-space.
| [
{
"created": "Wed, 5 Apr 2017 13:18:57 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Apr 2017 16:44:33 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Apr 2017 03:38:21 GMT",
"version": "v3"
}
] | 2017-04-19 | [
[
"Nwachioma",
"Christian",
""
],
[
"Tahir",
"Farida",
""
]
] | Riemannian and Absolute Parallelism (AP) geometries are discussed. A lavish treatment of path equations in the AP-space using the Bazanski-type Lagrangian is presented; We write down an expression that is absolutely conserved along a curve in the AP-space and show that it gives the same path equations as obtained using the conventional Lagrangian formalism. We attribute physical interpretations to the resultant path equations and we show that the spin-torsion interaction is an inherent property of the AP-space. |
gr-qc/0610017 | Tim Koslowski A | Tim Koslowski | Physical Diffeomorphisms in Loop Quantum Gravity | 25 pages, 2 figures, LaTeX | null | null | null | gr-qc | null | We investigate the action of diffeomorphisms in the context of Hamiltonian
Gravity. By considering how the diffeomorphism-invariant Hilbert space of Loop
Quantum Gravity should be constructed, we formulate a physical principle by
demanding, that the gauge-invariant Hilbert space is a completion of gauge-
(i.e. diffeomorphism-)orbits of the classical (configuration) variables,
explaining which extensions of the group of diffeomorphisms must be implemented
in the quantum theory. It turns out, that these are at least a subgroup of the
stratified analytic diffeomorphisms. Factoring these stratified diffeomorphisms
out, we obtain that the orbits of graphs under this group are just labelled by
their knot classes, which in turn form a countable set. Thus, using a physical
argument, we construct a separable Hilbert space for diffeomorphism invariant
Loop Quantum Gravity, that has a spin-knot basis, which is labelled by a
countable set consisting of the combination of knot-classes and spin quantum
numbers. It is important to notice, that this set of diffeomorphism leaves the
set of piecewise analytic edges invariant, which ensures, that one can
construct flux-operators and the associated Weyl-operators. A note on the
implications for the treatment of the Gauss- and the Hamilton-constraint of
Loop Quantum Gravity concludes our discussion.
| [
{
"created": "Thu, 5 Oct 2006 10:04:57 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Koslowski",
"Tim",
""
]
] | We investigate the action of diffeomorphisms in the context of Hamiltonian Gravity. By considering how the diffeomorphism-invariant Hilbert space of Loop Quantum Gravity should be constructed, we formulate a physical principle by demanding, that the gauge-invariant Hilbert space is a completion of gauge- (i.e. diffeomorphism-)orbits of the classical (configuration) variables, explaining which extensions of the group of diffeomorphisms must be implemented in the quantum theory. It turns out, that these are at least a subgroup of the stratified analytic diffeomorphisms. Factoring these stratified diffeomorphisms out, we obtain that the orbits of graphs under this group are just labelled by their knot classes, which in turn form a countable set. Thus, using a physical argument, we construct a separable Hilbert space for diffeomorphism invariant Loop Quantum Gravity, that has a spin-knot basis, which is labelled by a countable set consisting of the combination of knot-classes and spin quantum numbers. It is important to notice, that this set of diffeomorphism leaves the set of piecewise analytic edges invariant, which ensures, that one can construct flux-operators and the associated Weyl-operators. A note on the implications for the treatment of the Gauss- and the Hamilton-constraint of Loop Quantum Gravity concludes our discussion. |
1808.04832 | Oscar J. C. Dias | Oscar J.C. Dias, Harvey S. Reall and Jorge E. Santos | Strong cosmic censorship for charged de Sitter black holes with a
charged scalar field | 27 pages, 12 figures. v2: i) minor improvements of a few discussions;
ii) checked that, when overlap occurs, our numerical results agree with those
of arXiv:1808.03635 | null | 10.1088/1361-6382/aafcf2 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been shown recently that the strong cosmic censorship conjecture is
violated by near-extremal Reissner-Nordstr\"om-de Sitter black holes. We
investigate whether the introduction of a charged scalar field can rescue
strong cosmic censorship. We find that such a field improves the situation but
there is always a neighbourhood of extremality in which strong cosmic
censorship is violated by perturbations arising from smooth initial data.
| [
{
"created": "Tue, 14 Aug 2018 18:02:07 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Aug 2018 18:00:34 GMT",
"version": "v2"
}
] | 2019-02-13 | [
[
"Dias",
"Oscar J. C.",
""
],
[
"Reall",
"Harvey S.",
""
],
[
"Santos",
"Jorge E.",
""
]
] | It has been shown recently that the strong cosmic censorship conjecture is violated by near-extremal Reissner-Nordstr\"om-de Sitter black holes. We investigate whether the introduction of a charged scalar field can rescue strong cosmic censorship. We find that such a field improves the situation but there is always a neighbourhood of extremality in which strong cosmic censorship is violated by perturbations arising from smooth initial data. |
1201.4151 | Gianluca Calcagni | Gianluca Calcagni, Steffen Gielen, Daniele Oriti | Group field cosmology: a cosmological field theory of quantum geometry | 14 pages, 2 figures. v2: minor typos corrected, references added | Class. Quantum Grav. 29 (2012) 105005 | 10.1088/0264-9381/29/10/105005 | AEI-2011-099; pi-qg-255 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following the idea of a field quantization of gravity as realized in group
field theory, we construct a minisuperspace model where the wavefunction of
canonical quantum cosmology (either Wheeler-DeWitt or loop quantum cosmology)
is promoted to a field, the coordinates are minisuperspace variables, the
kinetic operator is the Hamiltonian constraint operator, and the action
features a nonlinear and possibly nonlocal interaction term. We discuss
free-field classical solutions, the quantum propagator, and a mean-field
approximation linearizing the equation of motion and augmenting the Hamiltonian
constraint by an effective term mixing gravitational and matter variables.
Depending on the choice of interaction, this can reproduce, for example, a
cosmological constant, a scalar-field potential, or a curvature contribution.
| [
{
"created": "Thu, 19 Jan 2012 19:25:20 GMT",
"version": "v1"
},
{
"created": "Tue, 1 May 2012 09:55:30 GMT",
"version": "v2"
}
] | 2012-05-02 | [
[
"Calcagni",
"Gianluca",
""
],
[
"Gielen",
"Steffen",
""
],
[
"Oriti",
"Daniele",
""
]
] | Following the idea of a field quantization of gravity as realized in group field theory, we construct a minisuperspace model where the wavefunction of canonical quantum cosmology (either Wheeler-DeWitt or loop quantum cosmology) is promoted to a field, the coordinates are minisuperspace variables, the kinetic operator is the Hamiltonian constraint operator, and the action features a nonlinear and possibly nonlocal interaction term. We discuss free-field classical solutions, the quantum propagator, and a mean-field approximation linearizing the equation of motion and augmenting the Hamiltonian constraint by an effective term mixing gravitational and matter variables. Depending on the choice of interaction, this can reproduce, for example, a cosmological constant, a scalar-field potential, or a curvature contribution. |
1404.0946 | Jorge L. Cervantes-Cota | Josue De-Santiago and Jorge L. Cervantes-Cota | Phase space analysis of the F (X) - V (\phi) scalar field Lagrangian and
scaling solutions in flat cosmology | 7 pages, 1 figure | J.Phys.Conf.Ser. 485 (2014) 012017 | 10.1088/1742-6596/485/1/012017 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review a system of autonomous differential equations developed in our
previous work [1] describing a flat cosmology filled with a barotropic fluid
and a scalar field with a modified kinetic term of the form L=F(X)-V(phi). We
analyze the critical points and summarize the conditions to obtain scaling
solutions. We consider a set of transformations and show that they leave
invariant the equations of motion for the systems in which the scaling solution
is obtained, allowing to reduce the number of degrees of freedom.
| [
{
"created": "Wed, 2 Apr 2014 17:32:51 GMT",
"version": "v1"
}
] | 2014-04-04 | [
[
"De-Santiago",
"Josue",
""
],
[
"Cervantes-Cota",
"Jorge L.",
""
]
] | We review a system of autonomous differential equations developed in our previous work [1] describing a flat cosmology filled with a barotropic fluid and a scalar field with a modified kinetic term of the form L=F(X)-V(phi). We analyze the critical points and summarize the conditions to obtain scaling solutions. We consider a set of transformations and show that they leave invariant the equations of motion for the systems in which the scaling solution is obtained, allowing to reduce the number of degrees of freedom. |
gr-qc/0411092 | Robert Beig | Robert Beig | Concepts of Hyperbolicity and Relativistic Continuum Mechanics | 12 pages, uses svmult.cls style file, expanded version of lecture
given at 319th WE-Heraeus Seminar on "Mathematical Relativity: New Ideas and
Developments" | Lect.Notes Phys. 692 (2006) 101-116 | 10.1007/11550259_5 | null | gr-qc | null | After a short introduction to the characteristic geometry underlying weakly
hyperbolic systems of partial differential equations we review the notion of
symmetric hyperbolicity of first-order systems and that of regular
hyperbolicity of second-order systems. Numerous examples are provided, mainly
taken from nonrelativistic and relativistic continuum mechanics.
| [
{
"created": "Thu, 18 Nov 2004 11:07:23 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Apr 2005 07:07:36 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Beig",
"Robert",
""
]
] | After a short introduction to the characteristic geometry underlying weakly hyperbolic systems of partial differential equations we review the notion of symmetric hyperbolicity of first-order systems and that of regular hyperbolicity of second-order systems. Numerous examples are provided, mainly taken from nonrelativistic and relativistic continuum mechanics. |
2009.08655 | Maxim Makukov | Maxim Makukov and Eduard Mychelkin | Triple path to the exponential metric | Accepted in Foundations of Physics | null | 10.1007/s10701-020-00384-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The exponential Papapetrou metric induced by scalar field conforms to
observational data not worse than the vacuum Schwarzschild solution. Here, we
analyze the origin of this metric as a peculiar space-time within a wide class
of scalar and antiscalar solutions of the Einstein equations parameterized by
scalar charge. Generalizing the three families of static solutions obtained by
Fisher (1948), Janis, Newman & Winicour (1968), and Xanthopoulos & Zannias
(1989), we prove that all three reduce to the same exponential metric provided
that scalar charge is equal to central mass, thereby suggesting the universal
character of such background scalar field.
| [
{
"created": "Fri, 18 Sep 2020 06:57:07 GMT",
"version": "v1"
}
] | 2020-09-21 | [
[
"Makukov",
"Maxim",
""
],
[
"Mychelkin",
"Eduard",
""
]
] | The exponential Papapetrou metric induced by scalar field conforms to observational data not worse than the vacuum Schwarzschild solution. Here, we analyze the origin of this metric as a peculiar space-time within a wide class of scalar and antiscalar solutions of the Einstein equations parameterized by scalar charge. Generalizing the three families of static solutions obtained by Fisher (1948), Janis, Newman & Winicour (1968), and Xanthopoulos & Zannias (1989), we prove that all three reduce to the same exponential metric provided that scalar charge is equal to central mass, thereby suggesting the universal character of such background scalar field. |
gr-qc/0311072 | Fangyu Li | Fang-Yu Li, Zhang-Han Wu, Yi Zhang | The Coupling of a Linearized Gravitational Wave to Electromagnetic
Fields and Relevant Noise Issues | 8 pages, 1 figure | Chin.Phys.Lett. 20 (2003) 1917 | 10.1088/0256-307X/20/11/004 | null | gr-qc | null | According to electrodynamical equations in curved spacetime we consider the
coupling of a linearized weak gravitational wave (GW) to a Gaussian beam
passing through a static magnetic field. It is found that unlike the properties
of the "left-circular" and "right-circular" waves of the tangential
perturbative photon fluxes in the cylindrical polar coordinates, the resultant
effect of the tangential and radial perturbations can produce the unique
nonvanishing photon flux propagating along the direction of the electric field
of the Gaussian beam. This result might provide a larger detecting space for
the high-frequency GWs in GHz band. Moreover, we also discuss the relevant
noise issues.
| [
{
"created": "Fri, 21 Nov 2003 08:51:02 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Li",
"Fang-Yu",
""
],
[
"Wu",
"Zhang-Han",
""
],
[
"Zhang",
"Yi",
""
]
] | According to electrodynamical equations in curved spacetime we consider the coupling of a linearized weak gravitational wave (GW) to a Gaussian beam passing through a static magnetic field. It is found that unlike the properties of the "left-circular" and "right-circular" waves of the tangential perturbative photon fluxes in the cylindrical polar coordinates, the resultant effect of the tangential and radial perturbations can produce the unique nonvanishing photon flux propagating along the direction of the electric field of the Gaussian beam. This result might provide a larger detecting space for the high-frequency GWs in GHz band. Moreover, we also discuss the relevant noise issues. |
0709.4604 | Olivier Minazzoli | Olivier Minazzoli, Bertrand Chauvineau | Relativistic analysis of an earth-satellite time transfer | 4 pages, conference | SF2A-2007: Proceedings of the Annual meeting of the French Society
of Astronomy and Astrophysics held in Grenoble, France, July 2-6, 2007, Eds.:
J. Bouvier, A. Chalabaev, and C. Charbonnel, p.106 | null | null | gr-qc | null | Analytical treatment of time transfer problem for Earth-Satellite system is
presented. The development was made in a complete relativistic framework. In
accordance with modern clock precision and for low altitude orbits, we neglect
the other bodies and consider only the 1/c^2 Earth potential developed up to
the J_2 term in spherical harmonics.
| [
{
"created": "Fri, 28 Sep 2007 12:49:51 GMT",
"version": "v1"
}
] | 2010-02-03 | [
[
"Minazzoli",
"Olivier",
""
],
[
"Chauvineau",
"Bertrand",
""
]
] | Analytical treatment of time transfer problem for Earth-Satellite system is presented. The development was made in a complete relativistic framework. In accordance with modern clock precision and for low altitude orbits, we neglect the other bodies and consider only the 1/c^2 Earth potential developed up to the J_2 term in spherical harmonics. |
2103.10920 | Vladimir Ivashchuk | A.N. Malybayev, K.A. Boshkayev, V.D. Ivashchuk | Quasinormal modes in the field of a dyon-like dilatonic black hole | 13 pages, 5 (double) figures, LaTex. Subsection 3.3 is extended; two
typos in formulas (22) and (30) are eliminated; 2 figures and 3 references
are added; a paragraph in Sec. 1 and Remark on page 10 are added; several
phrases are modified. To be published in EPJC | null | 10.1140/epjc/s10052-021-09252-z | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quasinormal modes of massless test scalar field in the background of
gravitational field for a non-extremal dilatonic dyonic black hole are
explored. The dyon-like black hole solution is considered in the gravitational
$4d$ model involving two scalar fields and two 2-forms. It is governed by two
2-dimensional dilatonic coupling vectors $\vec{\lambda}_i$ obeying
$\vec{\lambda}_i (\vec{\lambda}_1 + \vec{\lambda}_2) > 0$, $i =1,2$. The first
law of black hole thermodynamics is given and the Smarr relation is verified.
Quasinormal modes for a massless scalar (test) field in the eikonal
approximation are obtained and analysed. These modes depend upon a
dimensionless parameter $a$ ($0 < a \leq 2$) which is a function of
$\vec{\lambda}_i$. For limiting strong ($a = +0$) and weak ($a = 2$) coupling
cases, they coincide with the well-known results for the Schwarzschild and
Reissner-Nordstr\"om solutions. It is shown that the Hod conjecture, connecting
the damping rate and the Hawking temperature, is satisfied for $0 < a \leq 1$
and all allowed values of parameters.
| [
{
"created": "Fri, 19 Mar 2021 17:28:28 GMT",
"version": "v1"
},
{
"created": "Mon, 17 May 2021 13:58:28 GMT",
"version": "v2"
}
] | 2021-06-16 | [
[
"Malybayev",
"A. N.",
""
],
[
"Boshkayev",
"K. A.",
""
],
[
"Ivashchuk",
"V. D.",
""
]
] | Quasinormal modes of massless test scalar field in the background of gravitational field for a non-extremal dilatonic dyonic black hole are explored. The dyon-like black hole solution is considered in the gravitational $4d$ model involving two scalar fields and two 2-forms. It is governed by two 2-dimensional dilatonic coupling vectors $\vec{\lambda}_i$ obeying $\vec{\lambda}_i (\vec{\lambda}_1 + \vec{\lambda}_2) > 0$, $i =1,2$. The first law of black hole thermodynamics is given and the Smarr relation is verified. Quasinormal modes for a massless scalar (test) field in the eikonal approximation are obtained and analysed. These modes depend upon a dimensionless parameter $a$ ($0 < a \leq 2$) which is a function of $\vec{\lambda}_i$. For limiting strong ($a = +0$) and weak ($a = 2$) coupling cases, they coincide with the well-known results for the Schwarzschild and Reissner-Nordstr\"om solutions. It is shown that the Hod conjecture, connecting the damping rate and the Hawking temperature, is satisfied for $0 < a \leq 1$ and all allowed values of parameters. |
0704.0145 | Ghanashyam Date | Ghanashyam Date | Singularity Resolution in Isotropic Loop Quantum Cosmology: Recent
Developments | 24 pages, no figures. | null | null | IMSc/2007/03/2 | gr-qc | null | Since the past Iagrg meeting in December 2004, new developments in loop
quantum cosmology have taken place, especially with regards to the resolution
of the Big Bang singularity in the isotropic models. The singularity resolution
issue has been discussed in terms of physical quantities (expectation values of
Dirac observables) and there is also an ``improved'' quantization of the
Hamiltonian constraint. These developments are briefly discussed.
This is an expanded version of the review talk given at the
24$^{\mathrm{th}}$ IAGRG meeting in February 2007.
| [
{
"created": "Mon, 2 Apr 2007 08:56:47 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Date",
"Ghanashyam",
""
]
] | Since the past Iagrg meeting in December 2004, new developments in loop quantum cosmology have taken place, especially with regards to the resolution of the Big Bang singularity in the isotropic models. The singularity resolution issue has been discussed in terms of physical quantities (expectation values of Dirac observables) and there is also an ``improved'' quantization of the Hamiltonian constraint. These developments are briefly discussed. This is an expanded version of the review talk given at the 24$^{\mathrm{th}}$ IAGRG meeting in February 2007. |
gr-qc/9801100 | Jose Geraldo Pereira | R. Aldrovandi, A.L. Barbosa, L.C.B. Crispino and J.G. Pereira (IFT -
UNESP / Sao Paulo) | Non-Relativistic Spacetimes with Cosmological Constant | 15 pages, RevTeX, no figures, major changes in the presentation which
includes a new title and a whole new emphasis, version to appear in Clas.
Quant. Grav | Class.Quant.Grav. 16 (1999) 495-506 | 10.1088/0264-9381/16/2/013 | IFT-P.001/99 | gr-qc | null | Recent data on supernovae favor high values of the cosmological constant.
Spacetimes with a cosmological constant have non-relativistic kinematics quite
different from Galilean kinematics. De Sitter spacetimes, vacuum solutions of
Einstein's equations with a cosmological constant, reduce in the
non-relativistic limit to Newton-Hooke spacetimes, which are non-metric
homogeneous spacetimes with non-vanishing curvature. The whole non-relativistic
kinematics would then be modified, with possible consequences to cosmology, and
in particular to the missing-mass problem.
| [
{
"created": "Thu, 29 Jan 1998 15:53:08 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Jan 1999 15:19:05 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Aldrovandi",
"R.",
"",
"IFT -\n UNESP / Sao Paulo"
],
[
"Barbosa",
"A. L.",
"",
"IFT -\n UNESP / Sao Paulo"
],
[
"Crispino",
"L. C. B.",
"",
"IFT -\n UNESP / Sao Paulo"
],
[
"Pereira",
"J. G.",
"",
"IFT -\n UNESP / Sao Paulo"
]
] | Recent data on supernovae favor high values of the cosmological constant. Spacetimes with a cosmological constant have non-relativistic kinematics quite different from Galilean kinematics. De Sitter spacetimes, vacuum solutions of Einstein's equations with a cosmological constant, reduce in the non-relativistic limit to Newton-Hooke spacetimes, which are non-metric homogeneous spacetimes with non-vanishing curvature. The whole non-relativistic kinematics would then be modified, with possible consequences to cosmology, and in particular to the missing-mass problem. |
2210.07516 | Tomohiro Harada | Tomohiro Harada, Takahisa Igata, Hiromi Saida and Yohsuke Takamori | General formulae for the periapsis shift of a quasi-circular orbit in
static spherically symmetric spacetimes and the active gravitational mass
density | 25 pages, minor revision, discussion expanded, accepted for
publication in the International Journal of Modern Physics D | International Journal of Modern Physics D Vol. 32, No. 15 (2023)
2350098 (20 pages) | 10.1142/S0218271823500980 | RUP-22-21 | gr-qc astro-ph.GA astro-ph.HE astro-ph.SR hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the periapsis shift of a quasi-circular orbit in general static
spherically symmetric spacetimes. We derive two formulae in full order with
respect to the gravitational field, one in terms of the gravitational mass $m$
and the Einstein tensor and the other in terms of the orbital angular velocity
and the Einstein tensor. These formulae reproduce the well-known ones for the
forward shift in the Schwarzschild spacetime. In a general case, the shift
deviates from that in the vacuum spacetime due to a particular combination of
the components of the Einstein tensor at the radius $r$ of the orbit. The
formulae give a backward shift due to the extended-mass effect in Newtonian
gravity. In general relativity, in the weak-field and diffuse regime, the
active gravitational mass density, $\rho_{A}=(\epsilon+p_{r}+2p_{t})/c^{2}$,
plays an important role, where $\epsilon$, $p_{r}$, and $p_{t}$ are the energy
density, the radial stress, and the tangential stress of the matter field,
respectively. We show that the shift is backward if $\rho_{A}$ is beyond a
critical value $\rho_{c}\simeq 2.8\times 10^{-15} \mbox{g}/\mbox{cm}^{3}
(m/M_{\odot})^{2}(r/\mbox{au})^{-4}$, while a forward shift greater than that
in the vacuum spacetime instead implies $\rho_{A}<0$, i.e., the violation of
the strong energy condition, and thereby provides evidence for dark energy. We
obtain new observational constraints on $\rho_{A}$ in the Solar System and the
Galactic Centre.
| [
{
"created": "Fri, 14 Oct 2022 04:55:40 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Feb 2023 13:17:02 GMT",
"version": "v2"
},
{
"created": "Tue, 27 Jun 2023 01:12:46 GMT",
"version": "v3"
},
{
"created": "Thu, 19 Oct 2023 14:12:00 GMT",
"version": "v4"
},
{
"c... | 2024-01-09 | [
[
"Harada",
"Tomohiro",
""
],
[
"Igata",
"Takahisa",
""
],
[
"Saida",
"Hiromi",
""
],
[
"Takamori",
"Yohsuke",
""
]
] | We study the periapsis shift of a quasi-circular orbit in general static spherically symmetric spacetimes. We derive two formulae in full order with respect to the gravitational field, one in terms of the gravitational mass $m$ and the Einstein tensor and the other in terms of the orbital angular velocity and the Einstein tensor. These formulae reproduce the well-known ones for the forward shift in the Schwarzschild spacetime. In a general case, the shift deviates from that in the vacuum spacetime due to a particular combination of the components of the Einstein tensor at the radius $r$ of the orbit. The formulae give a backward shift due to the extended-mass effect in Newtonian gravity. In general relativity, in the weak-field and diffuse regime, the active gravitational mass density, $\rho_{A}=(\epsilon+p_{r}+2p_{t})/c^{2}$, plays an important role, where $\epsilon$, $p_{r}$, and $p_{t}$ are the energy density, the radial stress, and the tangential stress of the matter field, respectively. We show that the shift is backward if $\rho_{A}$ is beyond a critical value $\rho_{c}\simeq 2.8\times 10^{-15} \mbox{g}/\mbox{cm}^{3} (m/M_{\odot})^{2}(r/\mbox{au})^{-4}$, while a forward shift greater than that in the vacuum spacetime instead implies $\rho_{A}<0$, i.e., the violation of the strong energy condition, and thereby provides evidence for dark energy. We obtain new observational constraints on $\rho_{A}$ in the Solar System and the Galactic Centre. |
gr-qc/0407056 | Mariana Kirchbach | G. D. Acosta, M. Kirchbach | Massive Gauge Fields and the Planck Scale | Affiliation of first author updated; Reference [13] updated; Typos in
Refs. [15], [19] corrected | Found.Phys.Lett. 18 (2005) 157-170 | 10.1007/s10702-005-3959-1 | null | gr-qc | null | The present work is devoted to massive gauge fields in special relativity
with two fundamental constants-the velocity of light, and the Planck length, so
called doubly special relativity (DSR). The two invariant scales are accounted
for by properly modified boost parameters. Within above framework we construct
the vector potential as the (1/2,0)x(0,1/2) direct product, build the
associated field strength tensor together with the Dirac spinors and use them
to calculate various observables as functions of the Planck length.
| [
{
"created": "Wed, 14 Jul 2004 20:10:01 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Nov 2004 17:40:08 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Acosta",
"G. D.",
""
],
[
"Kirchbach",
"M.",
""
]
] | The present work is devoted to massive gauge fields in special relativity with two fundamental constants-the velocity of light, and the Planck length, so called doubly special relativity (DSR). The two invariant scales are accounted for by properly modified boost parameters. Within above framework we construct the vector potential as the (1/2,0)x(0,1/2) direct product, build the associated field strength tensor together with the Dirac spinors and use them to calculate various observables as functions of the Planck length. |
1912.13449 | Alexander Grant | \'Eanna \'E. Flanagan, Alexander M. Grant, Abraham I. Harte, David A.
Nichols | Persistent gravitational wave observables: Nonlinear plane wave
spacetimes | 24 pages, 1 figure, 1 table; v2: fixed typos, matches published
version | Phys. Rev. D 101, 104033 (2020) | 10.1103/PhysRevD.101.104033 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the first paper in this series, we introduced "persistent gravitational
wave observables" as a framework for generalizing the gravitational wave memory
effect. These observables are nonlocal in time and nonzero in the presence of
gravitational radiation. We defined three specific examples of persistent
observables: a generalization of geodesic deviation that allowed for arbitrary
acceleration, a holonomy observable involving a closed curve, and an observable
that can be measured using a spinning test particle. For linearized plane
waves, we showed that our observables could be determined just from one, two,
and three time integrals of the Riemann tensor along a central worldline, when
the observers follow geodesics. In this paper, we compute these three
persistent observables in nonlinear plane wave spacetimes, and we find that the
fully nonlinear observables contain effects that differ qualitatively from the
effects present in the observables at linear order. Many parts of these
observables can be determined from two functions, the transverse Jacobi
propagators, and their derivatives (for geodesic observers). These functions,
at linear order in the spacetime curvature, reduce to the one, two, and three
time integrals of the Riemann tensor mentioned above.
| [
{
"created": "Tue, 31 Dec 2019 17:43:23 GMT",
"version": "v1"
},
{
"created": "Tue, 19 May 2020 12:07:10 GMT",
"version": "v2"
}
] | 2020-05-20 | [
[
"Flanagan",
"Éanna É.",
""
],
[
"Grant",
"Alexander M.",
""
],
[
"Harte",
"Abraham I.",
""
],
[
"Nichols",
"David A.",
""
]
] | In the first paper in this series, we introduced "persistent gravitational wave observables" as a framework for generalizing the gravitational wave memory effect. These observables are nonlocal in time and nonzero in the presence of gravitational radiation. We defined three specific examples of persistent observables: a generalization of geodesic deviation that allowed for arbitrary acceleration, a holonomy observable involving a closed curve, and an observable that can be measured using a spinning test particle. For linearized plane waves, we showed that our observables could be determined just from one, two, and three time integrals of the Riemann tensor along a central worldline, when the observers follow geodesics. In this paper, we compute these three persistent observables in nonlinear plane wave spacetimes, and we find that the fully nonlinear observables contain effects that differ qualitatively from the effects present in the observables at linear order. Many parts of these observables can be determined from two functions, the transverse Jacobi propagators, and their derivatives (for geodesic observers). These functions, at linear order in the spacetime curvature, reduce to the one, two, and three time integrals of the Riemann tensor mentioned above. |
1806.03684 | S. M. M. Rasouli | S. M. M. Rasouli and Paulo Vargas Moniz | Extended anisotropic models in noncompact Kaluza-Klein theory | 19 pages, 4 figures | Class. Quantum Grav. 36 (2019) 075010 | 10.1088/1361-6382/ab0987 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, new exact solutions for locally rotational symmetric (LRS)
space-times are obtained within the modified Brans-Dicke theory (MBDT) (Rasouli
et al 2014 Class. Quantum Grav. 31 115002). Specifically, extended
five-dimensional (5D) versions of Kantowski-Sachs, LRS Bianchi type I and
Bianchi type III are investigated in the context of the standard Brans-Dicke
theory. We subsequently extract their corresponding dynamics on a 4D
hypersurface. Our results are discussed regarding others obtained in the
standard Brans-Dicke theory, induced-matter theory and general relativity.
Moreover, we comment on the evolution of the scale factor of the extra spatial
dimension, which is of interest in Kaluza-Klein frameworks.
| [
{
"created": "Sun, 10 Jun 2018 16:42:56 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Aug 2018 02:04:30 GMT",
"version": "v2"
},
{
"created": "Sat, 16 Mar 2019 13:43:32 GMT",
"version": "v3"
}
] | 2019-05-22 | [
[
"Rasouli",
"S. M. M.",
""
],
[
"Moniz",
"Paulo Vargas",
""
]
] | In this paper, new exact solutions for locally rotational symmetric (LRS) space-times are obtained within the modified Brans-Dicke theory (MBDT) (Rasouli et al 2014 Class. Quantum Grav. 31 115002). Specifically, extended five-dimensional (5D) versions of Kantowski-Sachs, LRS Bianchi type I and Bianchi type III are investigated in the context of the standard Brans-Dicke theory. We subsequently extract their corresponding dynamics on a 4D hypersurface. Our results are discussed regarding others obtained in the standard Brans-Dicke theory, induced-matter theory and general relativity. Moreover, we comment on the evolution of the scale factor of the extra spatial dimension, which is of interest in Kaluza-Klein frameworks. |
1603.07750 | Parthapratim Pradhan | Parthapratim Pradhan | $P-V$ Criticality of Conformal Gravity Holography in Four Dimensions | Accepted in MPLA, Modern Physics Letters A, 2018 | null | 10.1142/S021773231850030X | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | {We examine the critical behaviour i. e. $P-V$ criticality of conformal
gravity~(CG) in an extended phase space in which the cosmological constant
should be interpreted as a thermodynamic pressure and the corresponding
conjugate quantity as a thermodynamic volume.} The main potential point of
interest in CG is that there exists a {non-trivial} \emph{Rindler parameter
($a$)} in the {spacetime geometry. This geometric parameter has an important
role to construct a model for gravity at large distances where the parameter
"$a$" actually originates}. We also investigate the effect of the said
parameter on the {black hole~(BH) \emph{thermodynamic} equation of state,
critical constants, Reverse Isoperimetric Inequality,} {first law of
thermodynamics, Hawking-Page phase transition and Gibbs free energy} for this
BH. We speculate that due to the presence of the said parameter, there has been
a deformation {in the shape} of {the} isotherms in the $P-V$ diagram in
comparison with {the} charged-AdS~(anti de-Sitter) BH and {the} chargeless-AdS
BH. Interestingly, we find {that} the \emph{critical ratio} for this BH is
$\rho_{c} = \frac{P_{c} v_{c}}{T_{c}}=
\frac{\sqrt{3}}{2}\left(3\sqrt{2}-2\sqrt{3}\right)$, which is greater than the
charged AdS BH and Schwarzschild-AdS BH {i.e.}
$\rho_{c}^{CG}:\rho_{c}^{Sch-AdS}:\rho_{c}^{RN-AdS} = 0.67:0.50:0.37$. The
symbols are defined in the main work. Moreover, we observe that \emph{{the}
critical ratio {has a constant value}} and {it is} independent of the
{non-trivial} \emph{Rindler parameter ($a$)}. Finally, we derive {the}
\emph{reduced equation of state} in terms of {the} \emph{reduced temperature},
{the} \emph{reduced volume} and {the} \emph{reduced pressure} respectively.
| [
{
"created": "Thu, 24 Mar 2016 20:49:55 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jun 2016 07:44:33 GMT",
"version": "v2"
},
{
"created": "Sat, 17 Feb 2018 10:50:54 GMT",
"version": "v3"
}
] | 2018-02-20 | [
[
"Pradhan",
"Parthapratim",
""
]
] | {We examine the critical behaviour i. e. $P-V$ criticality of conformal gravity~(CG) in an extended phase space in which the cosmological constant should be interpreted as a thermodynamic pressure and the corresponding conjugate quantity as a thermodynamic volume.} The main potential point of interest in CG is that there exists a {non-trivial} \emph{Rindler parameter ($a$)} in the {spacetime geometry. This geometric parameter has an important role to construct a model for gravity at large distances where the parameter "$a$" actually originates}. We also investigate the effect of the said parameter on the {black hole~(BH) \emph{thermodynamic} equation of state, critical constants, Reverse Isoperimetric Inequality,} {first law of thermodynamics, Hawking-Page phase transition and Gibbs free energy} for this BH. We speculate that due to the presence of the said parameter, there has been a deformation {in the shape} of {the} isotherms in the $P-V$ diagram in comparison with {the} charged-AdS~(anti de-Sitter) BH and {the} chargeless-AdS BH. Interestingly, we find {that} the \emph{critical ratio} for this BH is $\rho_{c} = \frac{P_{c} v_{c}}{T_{c}}= \frac{\sqrt{3}}{2}\left(3\sqrt{2}-2\sqrt{3}\right)$, which is greater than the charged AdS BH and Schwarzschild-AdS BH {i.e.} $\rho_{c}^{CG}:\rho_{c}^{Sch-AdS}:\rho_{c}^{RN-AdS} = 0.67:0.50:0.37$. The symbols are defined in the main work. Moreover, we observe that \emph{{the} critical ratio {has a constant value}} and {it is} independent of the {non-trivial} \emph{Rindler parameter ($a$)}. Finally, we derive {the} \emph{reduced equation of state} in terms of {the} \emph{reduced temperature}, {the} \emph{reduced volume} and {the} \emph{reduced pressure} respectively. |
2206.10387 | Hamed Hadi | H. Hadi, F. Darabi, K.Atazadeh | Quantum time in near-horizon region of a black hole | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The understanding of time and dynamics can be elucidated by examining the
concept of entanglement in quantum theory. This particular perspective on time
is referred to as the timeless approach, which posits that the universe exists
in a fixed state where two separate subsystems, namely the "clock" and the
"rest," are entangled. By selecting an appropriate observable for the clock,
the state of the rest of the universe evolves unitarily in relation to the
variable that labels the clock observable's eigenstates, which is then
interpreted as time. This intriguing model, initially introduced by Page and
Wootters, has also been applied to the context of curved spacetime. In this
study, we explore various uncertainties pertaining to the dynamics of the rest
of the universe within a curved spacetime, including ambiguities related to the
clock, the system's time evolution, the flow of time, and the recording of its
history. Our investigation is primarily focused on the near horizon region of a
black hole, as the peculiar behavior of quantum effects in this area allows for
a thorough examination of the timeless depiction proposed by Page and Wootters
in describing the system's dynamics within curved spacetime. This analysis may
be valuable for quantum gravity projects that align with the approach put forth
by Page and Wootters. It is worth noting that the application of the Page and
Wootters approach in this particular region results in a distinct clock without
any ambiguity. However, the other aforementioned issues, unlike those resolved
in the realm of quantum mechanics, persist in this region.
| [
{
"created": "Fri, 17 Jun 2022 13:37:45 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Dec 2023 12:12:13 GMT",
"version": "v2"
}
] | 2023-12-07 | [
[
"Hadi",
"H.",
""
],
[
"Darabi",
"F.",
""
],
[
"Atazadeh",
"K.",
""
]
] | The understanding of time and dynamics can be elucidated by examining the concept of entanglement in quantum theory. This particular perspective on time is referred to as the timeless approach, which posits that the universe exists in a fixed state where two separate subsystems, namely the "clock" and the "rest," are entangled. By selecting an appropriate observable for the clock, the state of the rest of the universe evolves unitarily in relation to the variable that labels the clock observable's eigenstates, which is then interpreted as time. This intriguing model, initially introduced by Page and Wootters, has also been applied to the context of curved spacetime. In this study, we explore various uncertainties pertaining to the dynamics of the rest of the universe within a curved spacetime, including ambiguities related to the clock, the system's time evolution, the flow of time, and the recording of its history. Our investigation is primarily focused on the near horizon region of a black hole, as the peculiar behavior of quantum effects in this area allows for a thorough examination of the timeless depiction proposed by Page and Wootters in describing the system's dynamics within curved spacetime. This analysis may be valuable for quantum gravity projects that align with the approach put forth by Page and Wootters. It is worth noting that the application of the Page and Wootters approach in this particular region results in a distinct clock without any ambiguity. However, the other aforementioned issues, unlike those resolved in the realm of quantum mechanics, persist in this region. |
1807.03270 | Guilherme de Berredo-Peixoto | G. de Berredo-Peixoto | Non-metricities, torsion and fermions | 13 pages, LaTeX, no figures. Second version: I added some new
references for completeness | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I investigate the general extension of Einstein's gravity by considering the
third rank non-metricity tensor and the torsion tensor. The minimal coupling to
Dirac fields faces an ambiguity coming from a severe arbitrariness of the
Fock-Ivanenko coefficients. This arbitrariness is fed in part by the covariant
derivative of Dirac matrices, which is not completely determined as well. It is
remarkable that this feature is not exclusive to the non-metricity case: it
happens also for gravity with torsion alone. Nevertheless, theory in vacuum is
well defined and non-trivial, where torsion is the source of non-metricity or
vice-versa. I point also to the existence of two independent non-metricities.
| [
{
"created": "Mon, 9 Jul 2018 16:53:29 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Aug 2018 14:38:36 GMT",
"version": "v2"
}
] | 2018-08-07 | [
[
"de Berredo-Peixoto",
"G.",
""
]
] | I investigate the general extension of Einstein's gravity by considering the third rank non-metricity tensor and the torsion tensor. The minimal coupling to Dirac fields faces an ambiguity coming from a severe arbitrariness of the Fock-Ivanenko coefficients. This arbitrariness is fed in part by the covariant derivative of Dirac matrices, which is not completely determined as well. It is remarkable that this feature is not exclusive to the non-metricity case: it happens also for gravity with torsion alone. Nevertheless, theory in vacuum is well defined and non-trivial, where torsion is the source of non-metricity or vice-versa. I point also to the existence of two independent non-metricities. |
gr-qc/0203046 | W. B. Bonnor | W.B.Bonnor | Interaction between a stationary electric charge and a stationary
magnetic dipole | 11 pages, LaTeX | Class.Quant.Grav. 18 (2001) 2853 | 10.1088/0264-9381/18/15/301 | null | gr-qc | null | Using Einstein-Maxwell theory I investigate the gravitational field generated
by an electric charge and a magnetic dipole, both held in fixed positions, but
spinning with prescribed angular momenta. There is a conical singularity
between them representing a strut balancing the gravitational attraction of
their masses. However, there is in general another singularity, which I call a
torsion singularity. I interpret this as a couple needed to maintain the spins
at their prescribed values. It vanishes when the parameters obey a certain
formula.
A conclusion of the work is that the charge and the magnet must spin relative
to one another unless constrained by a couple.
| [
{
"created": "Wed, 13 Mar 2002 13:49:56 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Bonnor",
"W. B.",
""
]
] | Using Einstein-Maxwell theory I investigate the gravitational field generated by an electric charge and a magnetic dipole, both held in fixed positions, but spinning with prescribed angular momenta. There is a conical singularity between them representing a strut balancing the gravitational attraction of their masses. However, there is in general another singularity, which I call a torsion singularity. I interpret this as a couple needed to maintain the spins at their prescribed values. It vanishes when the parameters obey a certain formula. A conclusion of the work is that the charge and the magnet must spin relative to one another unless constrained by a couple. |
2010.02237 | Pierre Christian | Pierre Christian and Chi-kwan Chan | FANTASY: User-Friendly Symplectic Geodesic Integrator for Arbitrary
Metrics with Automatic Differentiation | Minor typos corrected, matches accepted version | null | 10.3847/1538-4357/abdc28 | null | gr-qc astro-ph.HE physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present FANTASY (Finally A Numerical Trajectory Algorithm both
Straightforward and sYmplectic), a user-friendly, open-source symplectic
geodesic integrator written in Python. FANTASY is designed to work
"out-of-the-box" and does not require anything from the user aside from the
metric and the initial conditions for the geodesics. FANTASY efficiently
computes derivatives up to machine precision using automatic differentiation,
allowing the integration of geodesics in arbitrary space(times) without the
need for the user to manually input Christoffel symbols or any other metric
derivatives. Further, FANTASY utilizes a Hamiltonian integration scheme that
doubles the phase space, where two copies of the particle phase space are
evolved together. This technique allows for an integration scheme that is both
explicit and symplectic, even when the Hamiltonian is not separable. FANTASY
comes prebuilt with second and fourth order schemes, and is easily extendible
to higher order schemes. FANTASY also includes an automatic Jacobian calculator
that allows for coordinate transformations to be done automatically.
| [
{
"created": "Mon, 5 Oct 2020 18:00:12 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Jan 2021 02:57:30 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Jan 2021 00:13:17 GMT",
"version": "v3"
},
{
"created": "Tue, 9 Feb 2021 23:05:23 GMT",
"version": "v4"
}
] | 2021-03-17 | [
[
"Christian",
"Pierre",
""
],
[
"Chan",
"Chi-kwan",
""
]
] | We present FANTASY (Finally A Numerical Trajectory Algorithm both Straightforward and sYmplectic), a user-friendly, open-source symplectic geodesic integrator written in Python. FANTASY is designed to work "out-of-the-box" and does not require anything from the user aside from the metric and the initial conditions for the geodesics. FANTASY efficiently computes derivatives up to machine precision using automatic differentiation, allowing the integration of geodesics in arbitrary space(times) without the need for the user to manually input Christoffel symbols or any other metric derivatives. Further, FANTASY utilizes a Hamiltonian integration scheme that doubles the phase space, where two copies of the particle phase space are evolved together. This technique allows for an integration scheme that is both explicit and symplectic, even when the Hamiltonian is not separable. FANTASY comes prebuilt with second and fourth order schemes, and is easily extendible to higher order schemes. FANTASY also includes an automatic Jacobian calculator that allows for coordinate transformations to be done automatically. |
1908.03416 | Emil Zeuthen | Emil Zeuthen and Eugene S. Polzik and Farid Ya. Khalili | Gravitational wave detection beyond the standard quantum limit using a
negative-mass spin system and virtual rigidity | Minor typos fixed, minor editing; 12 pages, 5 figures | Phys. Rev. D 100, 062004 (2019) | 10.1103/PhysRevD.100.062004 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave detectors (GWDs), which have brought about a new era in
astronomy, have reached such a level of maturity that further improvement
necessitates quantum-noise-evading techniques. Numerous proposals to this end
have been discussed in the literature, e.g., invoking frequency-dependent
squeezing or replacing the current Michelson interferometer topology by that of
the quantum speedmeter. Recently, a proposal based on the linking of a standard
interferometer to a negative-mass spin system via entangled light has offered
an unintrusive and small-scale new approach to quantum noise evasion in GWDs
[Phys. Rev. Lett. $\mathbf{121}$, 031101 (2018)]. The solution proposed therein
does not require modifications to the highly refined core optics of the present
GWD design and, when compared to previous proposals, is less prone to losses
and imperfections of the interferometer. In the present article, we refine this
scheme to an extent that the requirements on the auxiliary spin system are
feasible with state-of-the-art implementations. This is accomplished by
matching the effective (rather than intrinsic) susceptibilities of the
interferometer and spin system using the virtual rigidity concept, which, in
terms of implementation, requires only suitable choices of the various
homodyne, probe, and squeezing phases.
| [
{
"created": "Fri, 9 Aug 2019 11:24:15 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Sep 2019 19:38:00 GMT",
"version": "v2"
}
] | 2019-09-26 | [
[
"Zeuthen",
"Emil",
""
],
[
"Polzik",
"Eugene S.",
""
],
[
"Khalili",
"Farid Ya.",
""
]
] | Gravitational wave detectors (GWDs), which have brought about a new era in astronomy, have reached such a level of maturity that further improvement necessitates quantum-noise-evading techniques. Numerous proposals to this end have been discussed in the literature, e.g., invoking frequency-dependent squeezing or replacing the current Michelson interferometer topology by that of the quantum speedmeter. Recently, a proposal based on the linking of a standard interferometer to a negative-mass spin system via entangled light has offered an unintrusive and small-scale new approach to quantum noise evasion in GWDs [Phys. Rev. Lett. $\mathbf{121}$, 031101 (2018)]. The solution proposed therein does not require modifications to the highly refined core optics of the present GWD design and, when compared to previous proposals, is less prone to losses and imperfections of the interferometer. In the present article, we refine this scheme to an extent that the requirements on the auxiliary spin system are feasible with state-of-the-art implementations. This is accomplished by matching the effective (rather than intrinsic) susceptibilities of the interferometer and spin system using the virtual rigidity concept, which, in terms of implementation, requires only suitable choices of the various homodyne, probe, and squeezing phases. |
2008.12069 | Nils Andersson | N. Andersson and G.L.C. Comer | Relativistic fluid dynamics: physics for many different scales | Update of invited review for Living Reviews in Relativity, original
version from 2007. Substantial revision just under 250 pages with about 450
references. Comments welcome | null | 10.1007/s41114-021-00031-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The relativistic fluid is a highly successful model used to describe the
dynamics of many-particle systems moving at high velocities and/or in strong
gravity. It takes as input physics from microscopic scales and yields as output
predictions of bulk, macroscopic motion. By inverting the process-e.g., drawing
on astrophysical observations-an understanding of relativistic features can
lead to insight into physics on the microscopic scale. Relativistic fluids have
been used to model systems as "small" as colliding heavy ions in laboratory
experiments, and as large as the Universe itself, with "intermediate" sized
objects like neutron stars being considered along the way. The purpose of this
review is to discuss the mathematical and theoretical physics underpinnings of
the relativistic (multi-) fluid model. We focus on the variational principle
approach championed by Brandon Carter and collaborators, in which a crucial
element is to distinguish the momenta that are conjugate to the particle number
density currents. This approach differs from the "standard" text-book
derivation of the equations of motion from the divergence of the stress-energy
tensor in that one explicitly obtains the relativistic Euler equation as an
"integrability" condition on the relativistic vorticity. We discuss the
conservation laws and the equations of motion in detail, and provide a number
of (in our opinion) interesting and relevant applications of the general
theory. The formalism provides a foundation for complex models, e.g., including
electromagnetism, superfluidity and elasticity-all of which are relevant for
state of the art neutron-star modelling.
| [
{
"created": "Thu, 27 Aug 2020 11:56:23 GMT",
"version": "v1"
}
] | 2021-07-07 | [
[
"Andersson",
"N.",
""
],
[
"Comer",
"G. L. C.",
""
]
] | The relativistic fluid is a highly successful model used to describe the dynamics of many-particle systems moving at high velocities and/or in strong gravity. It takes as input physics from microscopic scales and yields as output predictions of bulk, macroscopic motion. By inverting the process-e.g., drawing on astrophysical observations-an understanding of relativistic features can lead to insight into physics on the microscopic scale. Relativistic fluids have been used to model systems as "small" as colliding heavy ions in laboratory experiments, and as large as the Universe itself, with "intermediate" sized objects like neutron stars being considered along the way. The purpose of this review is to discuss the mathematical and theoretical physics underpinnings of the relativistic (multi-) fluid model. We focus on the variational principle approach championed by Brandon Carter and collaborators, in which a crucial element is to distinguish the momenta that are conjugate to the particle number density currents. This approach differs from the "standard" text-book derivation of the equations of motion from the divergence of the stress-energy tensor in that one explicitly obtains the relativistic Euler equation as an "integrability" condition on the relativistic vorticity. We discuss the conservation laws and the equations of motion in detail, and provide a number of (in our opinion) interesting and relevant applications of the general theory. The formalism provides a foundation for complex models, e.g., including electromagnetism, superfluidity and elasticity-all of which are relevant for state of the art neutron-star modelling. |
1901.07310 | Zi-Yu Tang | Zi-Yu Tang, Yen Chin Ong, Bin Wang, Eleftherios Papantonopoulos | General Black Hole Solutions in (2+1)-dimensions with a Scalar Field
Non-Minimally Coupled to Gravity | To be published in PRD | Phys. Rev. D 100, 024003 (2019) | 10.1103/PhysRevD.100.024003 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss black hole solutions in (2+1)-dimensions with a scalar field
non-minimally coupled to Einstein's gravity in the presence of a cosmological
constant and a self-interacting scalar potential. Without specifying the form
of the potential, we find a general solution of the field equations, which
includes all the known asymptotically anti-de Sitter (AdS) black hole solutions
in (2+1)-dimensions as special cases once values of the coupling constants are
chosen appropriately. In addition, we obtain numerically new black hole
solutions and for some specific choices of the coupling constants we derive new
exact AdS black hole solutions. We also discuss the possibility of obtaining
asymptotically de Sitter black hole solutions with or without an
electromagnetic field.
| [
{
"created": "Tue, 22 Jan 2019 14:10:46 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jun 2019 04:40:52 GMT",
"version": "v2"
}
] | 2019-07-17 | [
[
"Tang",
"Zi-Yu",
""
],
[
"Ong",
"Yen Chin",
""
],
[
"Wang",
"Bin",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
]
] | We discuss black hole solutions in (2+1)-dimensions with a scalar field non-minimally coupled to Einstein's gravity in the presence of a cosmological constant and a self-interacting scalar potential. Without specifying the form of the potential, we find a general solution of the field equations, which includes all the known asymptotically anti-de Sitter (AdS) black hole solutions in (2+1)-dimensions as special cases once values of the coupling constants are chosen appropriately. In addition, we obtain numerically new black hole solutions and for some specific choices of the coupling constants we derive new exact AdS black hole solutions. We also discuss the possibility of obtaining asymptotically de Sitter black hole solutions with or without an electromagnetic field. |
1905.08113 | Wytler Cordeiro dos Santos | Wytler Cordeiro dos Santos | Introduction to Gauge Theory of Gravitation | 23 pages | e-Boletim da F\'isica - SSN:2318-8901 eBFIS77244(2019) | 10.26512/e-bfis.v8i1.23241 | v. 8 n. 1 (2019): VII EFRAS | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The fundamental interactions of nature, the electroweak and the quantum
chromodynamics, are described in the Standard Model by the Gauge Theory under
internal symmetries that maintain the invariance of the functional action. The
fundamental interaction of gravitation is very well described by Einstein's
General Relativity in a Riemannian spacetime metric, but General Relativity has
been over time a gravitational field theory apart from the Standard Model. The
theory of Gauge allows under symmetries of the group of Poincar\'e to impose
invariances in the functional of the action of the spinor field that result in
the gravitational interaction with the fermions. In this approach the
gravitational field, besides being described by the equation similar to General
Relativity, also brings a spin-gravitational interaction in a Riemann-Cartan
spacetime.
| [
{
"created": "Mon, 20 May 2019 13:49:21 GMT",
"version": "v1"
}
] | 2019-05-21 | [
[
"Santos",
"Wytler Cordeiro dos",
""
]
] | The fundamental interactions of nature, the electroweak and the quantum chromodynamics, are described in the Standard Model by the Gauge Theory under internal symmetries that maintain the invariance of the functional action. The fundamental interaction of gravitation is very well described by Einstein's General Relativity in a Riemannian spacetime metric, but General Relativity has been over time a gravitational field theory apart from the Standard Model. The theory of Gauge allows under symmetries of the group of Poincar\'e to impose invariances in the functional of the action of the spinor field that result in the gravitational interaction with the fermions. In this approach the gravitational field, besides being described by the equation similar to General Relativity, also brings a spin-gravitational interaction in a Riemann-Cartan spacetime. |
2301.02267 | Costantino Pacilio | Costantino Pacilio, Swetha Bhagwat | Identifying modified theories of gravity using binary black-hole
ringdowns | v1: 14 pages, 4 figures. v2: matches published version | null | 10.1103/PhysRevD.107.083021 | null | gr-qc astro-ph.HE hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Black-hole spectroscopy, that is, measuring the characteristic frequencies
and damping times of different modes in a black-hole ringdown, is a powerful
probe for testing deviations from the general theory of relativity (GR). In
this work, we present a comprehensive study on its ability to identify
deviations from the spectrum of a Kerr black hole in GR. Specifically, we
investigate the performance of black hole spectroscopy on a diverse set of
theoretically motivated as well as phenomenologically modified spectra. We find
that while the signal-to-noise ratio $\rho_{\rm RD}$ in the ringdown required
to identify a modification to the GR Kerr black hole spectrum depends on the
details of the modifications, a modification that introduces $\sim 1 \%$ shift
in the fundamental mode frequencies can typically be distinguished with
$\rho_{\rm RD} \in [150,500]$. This range of $\rho_{\rm RD}$ is feasible with
the next-generation detectors, showing a promising science case for black hole
spectroscopy.
| [
{
"created": "Thu, 5 Jan 2023 19:01:09 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Apr 2023 17:09:56 GMT",
"version": "v2"
}
] | 2023-04-14 | [
[
"Pacilio",
"Costantino",
""
],
[
"Bhagwat",
"Swetha",
""
]
] | Black-hole spectroscopy, that is, measuring the characteristic frequencies and damping times of different modes in a black-hole ringdown, is a powerful probe for testing deviations from the general theory of relativity (GR). In this work, we present a comprehensive study on its ability to identify deviations from the spectrum of a Kerr black hole in GR. Specifically, we investigate the performance of black hole spectroscopy on a diverse set of theoretically motivated as well as phenomenologically modified spectra. We find that while the signal-to-noise ratio $\rho_{\rm RD}$ in the ringdown required to identify a modification to the GR Kerr black hole spectrum depends on the details of the modifications, a modification that introduces $\sim 1 \%$ shift in the fundamental mode frequencies can typically be distinguished with $\rho_{\rm RD} \in [150,500]$. This range of $\rho_{\rm RD}$ is feasible with the next-generation detectors, showing a promising science case for black hole spectroscopy. |
2006.07913 | Yu-Xiao Liu | Zi-Chao Lin, Ke Yang, Shao-Wen Wei, Yong-Qiang Wang, Yu-Xiao Liu | Equivalence of solutions between the four-dimensional novel and
regularized EGB theories in a cylindrically symmetric spacetime | 20 pages, 9 figures, published version | Eur. Phys. J. C 80, 1033 (2020) | 10.1140/epjc/s10052-020-08612-5 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, a novel four-dimensional Einstein-Gauss-Bonnet (EGB) theory was
presented to bypass the Lovelock's theorem and to give nontrivial effects on
the four-dimensional local gravity. The main mechanism is to introduce a
redefinition $\alpha\rightarrow\alpha/(D-4)$ and to take the limit
$D\rightarrow4$. However, this theory does not have standard four-dimensional
field equations. Some regularization procedures are then proposed to address
this problem [arXiv:2003.11552, arXiv:2003.12771, arXiv:2004.08362,
arXiv:2004.09472, arXiv:2004.10716]. The resultant regularized four-dimensional
EGB theory has the same on-shell action as the original theory. Thus it is
expected that the novel four-dimensional EGB theory is equivalent to its
regularized version. However, the equivalence of these two theories is
symmetry-dependent. In this paper, we test the equivalence in a cylindrically
symmetric spacetime. The well-defined field equations of the two theories are
obtained, with which our follow-up analysis shows that they are equivalent in
such spacetime. Cylindrical cosmic strings are then considered as specific
examples of the metric. Three sets of solutions are obtained and the
corresponding string mass densities are evaluated. The results reveal how the
Gauss-Bonnet term in four dimensions contributes to the string geometry in the
new theory.
| [
{
"created": "Sun, 14 Jun 2020 14:24:23 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Nov 2020 08:35:04 GMT",
"version": "v2"
}
] | 2020-11-19 | [
[
"Lin",
"Zi-Chao",
""
],
[
"Yang",
"Ke",
""
],
[
"Wei",
"Shao-Wen",
""
],
[
"Wang",
"Yong-Qiang",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | Recently, a novel four-dimensional Einstein-Gauss-Bonnet (EGB) theory was presented to bypass the Lovelock's theorem and to give nontrivial effects on the four-dimensional local gravity. The main mechanism is to introduce a redefinition $\alpha\rightarrow\alpha/(D-4)$ and to take the limit $D\rightarrow4$. However, this theory does not have standard four-dimensional field equations. Some regularization procedures are then proposed to address this problem [arXiv:2003.11552, arXiv:2003.12771, arXiv:2004.08362, arXiv:2004.09472, arXiv:2004.10716]. The resultant regularized four-dimensional EGB theory has the same on-shell action as the original theory. Thus it is expected that the novel four-dimensional EGB theory is equivalent to its regularized version. However, the equivalence of these two theories is symmetry-dependent. In this paper, we test the equivalence in a cylindrically symmetric spacetime. The well-defined field equations of the two theories are obtained, with which our follow-up analysis shows that they are equivalent in such spacetime. Cylindrical cosmic strings are then considered as specific examples of the metric. Three sets of solutions are obtained and the corresponding string mass densities are evaluated. The results reveal how the Gauss-Bonnet term in four dimensions contributes to the string geometry in the new theory. |
1307.0172 | Houwen Wu | Deyou Chen, Houwen Wu, Haitang Yang | Observing remnants by fermions' tunneling | V2, 14 pages, typos corrected, version to appear in JCAP | JCAP 1403 (2014) 036 | 10.1088/1475-7516/2014/03/036 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The standard Hawking formula predicts the complete evaporation of black
holes. In this paper, we introduce effects of quantum gravity into fermions'
tunneling from Reissner-Nordstrom and Kerr black holes. The quantum gravity
effects slow down the increase of Hawking temperatures. This property naturally
leads to a residue mass in black hole evaporation. The corrected temperatures
are affected by the quantum numbers of emitted fermions. Meanwhile, the
temperature of the Kerr black hole is a function of $\theta$ due to the
rotation.
| [
{
"created": "Sun, 30 Jun 2013 02:39:18 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Mar 2014 16:05:25 GMT",
"version": "v2"
}
] | 2014-10-27 | [
[
"Chen",
"Deyou",
""
],
[
"Wu",
"Houwen",
""
],
[
"Yang",
"Haitang",
""
]
] | The standard Hawking formula predicts the complete evaporation of black holes. In this paper, we introduce effects of quantum gravity into fermions' tunneling from Reissner-Nordstrom and Kerr black holes. The quantum gravity effects slow down the increase of Hawking temperatures. This property naturally leads to a residue mass in black hole evaporation. The corrected temperatures are affected by the quantum numbers of emitted fermions. Meanwhile, the temperature of the Kerr black hole is a function of $\theta$ due to the rotation. |
1310.2384 | Florent Robinet | J. Aasi, J. Abadie, B. P. Abbott, R. Abbott, T. Abbott, M. R.
Abernathy, T. Accadia, F. Acernese, C. Adams, T. Adams, R. X. Adhikari, C.
Affeldt, M. Agathos, N. Aggarwal, O. D. Aguiar, P. Ajith, B. Allen, A.
Allocca, E. Amador Ceron, D. Amariutei, R. A. Anderson, S. B. Anderson, W. G.
Anderson, K. Arai, M. C. Araya, C. Arceneaux, J. Areeda, S. Ast, S. M. Aston,
P. Astone, P. Aufmuth, C. Aulbert, L. Austin, B. E. Aylott, S. Babak, P. T.
Baker, G. Ballardin, S. W. Ballmer, J. C. Barayoga, D. Barker, S. H. Barnum,
F. Barone, B. Barr, L. Barsotti, M. Barsuglia, M. A. Barton, I. Bartos, R.
Bassiri, A. Basti, J. Batch, J. Bauchrowitz, Th. S. Bauer, M. Bebronne, B.
Behnke, M. Bejger, M.G. Beker, A. S. Bell, C. Bell, I. Belopolski, G.
Bergmann, J. M. Berliner, D. Bersanetti, A. Bertolini, D. Bessis, J.
Betzwieser, P. T. Beyersdorf, T. Bhadbhade, I. A. Bilenko, G. Billingsley, J.
Birch, M. Bitossi, M. A. Bizouard, E. Black, J. K. Blackburn, L. Blackburn,
D. Blair, M. Blom, O. Bock, T. P. Bodiya, M. Boer, C. Bogan, C. Bond, F.
Bondu, L. Bonelli, R. Bonnand, R. Bork, M. Born, V. Boschi, S. Bose, L. Bosi,
J. Bowers, C. Bradaschia, P. R. Brady, V. B. Braginsky, M. Branchesi, C. A.
Brannen, J. E. Brau, J. Breyer, T. Briant, D. O. Bridges, A. Brillet, M.
Brinkmann, V. Brisson, M. Britzger, A. F. Brooks, D. A. Brown, D. D. Brown,
F. Br\"uckner, T. Bulik, H. J. Bulten, A. Buonanno, D. Buskulic, C. Buy, R.
L. Byer, L. Cadonati, G. Cagnoli, J. Calder\'on Bustillo, E. Calloni, J. B.
Camp, P. Campsie, K. C. Cannon, B. Canuel, J. Cao, C. D. Capano, F.
Carbognani, L. Carbone, S. Caride, A. Castiglia, S. Caudill, M. Cavagli\'a,
F. Cavalier, R. Cavalieri, G. Cella, C. Cepeda, E. Cesarini, R. Chakraborty,
T. Chalermsongsak, S. Chao, P. Charlton, E. Chassande-Mottin, X. Chen, Y.
Chen, A. Chincarini, A. Chiummo, H. S. Cho, J. Chow, N. Christensen, Q. Chu,
S. S. Y. Chua, S. Chung, G. Ciani, F. Clara, D. E. Clark, J. A. Clark, F.
Cleva, E. Coccia, P.-F. Cohadon, A. Colla, M. Colombini, M. Constancio Jr.,
A. Conte, R. Conte, D. Cook, T. R. Corbitt, M. Cordier, N. Cornish, A. Corsi,
C. A. Costa, M. W. Coughlin, J.-P. Coulon, S. Countryman, P. Couvares, D. M.
Coward, M. Cowart, D. C. Coyne, K. Craig, J. D. E. Creighton, T. D.
Creighton, S. G. Crowder, A. Cumming, L. Cunningham, E. Cuoco, K. Dahl, T.
Dal Canton, M. Damjanic, S. L. Danilishin, S. D'Antonio, K. Danzmann, V.
Dattilo, B. Daudert, H. Daveloza, M. Davier, G. S. Davies, E. J. Daw, R. Day,
T. Dayanga, R. De Rosa, G. Debreczeni, J. Degallaix, W. Del Pozzo, E.
Deleeuw, S. Del\'eglise, T. Denker, T. Dent, H. Dereli, V. Dergachev, R.
DeRosa, R. DeSalvo, S. Dhurandhar, L. Di Fiore, A. Di Lieto, I. Di Palma, A.
Di Virgilio, M. D\'iaz, A. Dietz, K. Dmitry, F. Donovan, K. L. Dooley, S.
Doravari, M. Drago, R. W. P. Drever, J. C. Driggers, Z. Du, J.-C. Dumas, S.
Dwyer, T. Eberle, M. Edwards, A. Effler, P. Ehrens, J. Eichholz, S. S.
Eikenberry, G. Endr\"oczi, R. Essick, T. Etzel, K. Evans, M. Evans, T. Evans,
M. Factourovich, V. Fafone, S. Fairhurst, Q. Fang, S. Farinon, B. Farr, W.
Farr, M. Favata, D. Fazi, H. Fehrmann, D. Feldbaum, I. Ferrante, F. Ferrini,
F. Fidecaro, L. S. Finn, I. Fiori, R. Fisher, R. Flaminio, E. Foley, S.
Foley, E. Forsi, N. Fotopoulos, J.-D. Fournier, S. Franco, S. Frasca, F.
Frasconi, M. Frede, M. Frei, Z. Frei, A. Freise, R. Frey, T. T. Fricke, P.
Fritschel, V. V. Frolov, M.-K. Fujimoto, P. Fulda, M. Fyffe, J. Gair, L.
Gammaitoni, J. Garcia, F. Garufi, N. Gehrels, G. Gemme, E. Genin, A. Gennai,
L. Gergely, S. Ghosh, J. A. Giaime, S. Giampanis, K. D. Giardina, A.
Giazotto, S. Gil-Casanova, C. Gill, J. Gleason, E. Goetz, R. Goetz, L.
Gondan, G. Gonz\'alez, N. Gordon, M. L. Gorodetsky, S. Gossan, S. Go{\ss}ler,
R. Gouaty, C. Graef, P. B. Graff, M. Granata, A. Grant, S. Gras, C. Gray, R.
J. S. Greenhalgh, A. M. Gretarsson, C. Griffo, P. Groot, H. Grote, K. Grover,
S. Grunewald, G. M. Guidi, C. Guido, K. E. Gushwa, E. K. Gustafson, R.
Gustafson, B. Hall, E. Hall, D. Hammer, G. Hammond, M. Hanke, J. Hanks, C.
Hanna, J. Hanson, J. Harms, G. M. Harry, I. W. Harry, E. D. Harstad, M. T.
Hartman, K. Haughian, K. Hayama, J. Heefner, A. Heidmann, M. Heintze, H.
Heitmann, P. Hello, G. Hemming, M. Hendry, I. S. Heng, A. W. Heptonstall, M.
Heurs, S. Hild, D. Hoak, K. A. Hodge, K. Holt, M. Holtrop, T. Hong, S.
Hooper, T. Horrom, D. J. Hosken, J. Hough, E. J. Howell, Y. Hu, Z. Hua, V.
Huang, E. A. Huerta, B. Hughey, S. Husa, S. H. Huttner, M. Huynh, T.
Huynh-Dinh, J. Iafrate, D. R. Ingram, R. Inta, T. Isogai, A. Ivanov, B. R.
Iyer, K. Izumi, M. Jacobson, E. James, H. Jang, Y. J. Jang, P. Jaranowski, F.
Jim\'enez-Forteza, W. W. Johnson, D. Jones, D. I. Jones, R. Jones, R.J.G.
Jonker, L. Ju, Haris K, P. Kalmus, V. Kalogera, S. Kandhasamy, G. Kang, J. B.
Kanner, M. Kasprzack, R. Kasturi, E. Katsavounidis, W. Katzman, H. Kaufer, K.
Kaufman, K. Kawabe, S. Kawamura, F. Kawazoe, F. K\'ef\'elian, D. Keitel, D.
B. Kelley, W. Kells, D. G. Keppel, A. Khalaidovski, F. Y. Khalili, E. A.
Khazanov, B. K. Kim, C. Kim, K. Kim, N. Kim, W. Kim, Y.-M. Kim, E. J. King,
P. J. King, D. L. Kinzel, J. S. Kissel, S. Klimenko, J. Kline, S.
Koehlenbeck, K. Kokeyama, V. Kondrashov, S. Koranda, W. Z. Korth, I.
Kowalska, D. Kozak, A. Kremin, V. Kringel, A. Kr\'olak, C. Kucharczyk, S.
Kudla, G. Kuehn, A. Kumar, P. Kumar, R. Kumar, R. Kurdyumov, P. Kwee, M.
Landry, B. Lantz, S. Larson, P. D. Lasky, C. Lawrie, A. Lazzarini, A. Le
Roux, P. Leaci, E. O. Lebigot, C.-H. Lee, H. K. Lee, H. M. Lee, J. Lee, J.
Lee, M. Leonardi, J. R. Leong, N. Leroy, N. Letendre, B. Levine, J. B. Lewis,
V. Lhuillier, T. G. F. Li, A. C. Lin, T. B. Littenberg, V. Litvine, F. Liu,
H. Liu, Y. Liu, Z. Liu, D. Lloyd, N. A. Lockerbie, V. Lockett, D. Lodhia, K.
Loew, J. Logue, A. L. Lombardi, M. Lorenzini, V. Loriette, M. Lormand, G.
Losurdo, J. Lough, J. Luan, M. J. Lubinski, H. L\"uck, A. P. Lundgren, J.
Macarthur, E. Macdonald, B. Machenschalk, M. MacInnis, D. M. Macleod, F.
Magana-Sandoval, M. Mageswaran, K. Mailand, E. Majorana, I. Maksimovic, V.
Malvezzi, N. Man, G. M. Manca, I. Mandel, V. Mandic, V. Mangano, M.
Mantovani, F. Marchesoni, F. Marion, S. M\'arka, Z. M\'arka, A. Markosyan, E.
Maros, J. Marque, F. Martelli, I. W. Martin, R. M. Martin, L. Martinelli, D.
Martynov, J. N. Marx, K. Mason, A. Masserot, T. J. Massinger, F. Matichard,
L. Matone, R. A. Matzner, N. Mavalvala, G. May, N. Mazumder, G. Mazzolo, R.
McCarthy, D. E. McClelland, S. C. McGuire, G. McIntyre, J. McIver, D.
Meacher, G. D. Meadors, M. Mehmet, J. Meidam, T. Meier, A. Melatos, G.
Mendell, R. A. Mercer, S. Meshkov, C. Messenger, M. S. Meyer, H. Miao, C.
Michel, E. E. Mikhailov, L. Milano, J. Miller, Y. Minenkov, C. M. F.
Mingarelli, S. Mitra, V. P. Mitrofanov, G. Mitselmakher, R. Mittleman, B.
Moe, M. Mohan, S. R. P. Mohapatra, F. Mokler, D. Moraru, G. Moreno, N.
Morgado, T. Mori, S. R. Morriss, K. Mossavi, B. Mours, C. M. Mow-Lowry, C. L.
Mueller, G. Mueller, S. Mukherjee, A. Mullavey, J. Munch, D. Murphy, P. G.
Murray, A. Mytidis, M. F. Nagy, D. Nanda Kumar, I. Nardecchia, T. Nash, L.
Naticchioni, R. Nayak, V. Necula, G. Nelemans, I. Neri, M. Neri, G. Newton,
T. Nguyen, E. Nishida, A. Nishizawa, A. Nitz, F. Nocera, D. Nolting, M. E.
Normandin, L. K. Nuttall, E. Ochsner, J. O'Dell, E. Oelker, G. H. Ogin, J. J.
Oh, S. H. Oh, F. Ohme, P. Oppermann, B. O'Reilly, W. Ortega Larcher, R.
O'Shaughnessy, C. Osthelder, C. D. Ott, D. J. Ottaway, R. S. Ottens, J. Ou,
H. Overmier, B. J. Owen, C. Padilla, A. Pai, C. Palomba, Y. Pan, C. Pankow,
F. Paoletti, R. Paoletti, M. A. Papa, H. Paris, A. Pasqualetti, R.
Passaquieti, D. Passuello, M. Pedraza, P. Peiris, S. Penn, A. Perreca, M.
Phelps, M. Pichot, M. Pickenpack, F. Piergiovanni, V. Pierro, L. Pinard, B.
Pindor, I. M. Pinto, M. Pitkin, J. Poeld, R. Poggiani, V. Poole, C. Poux, V.
Predoi, T. Prestegard, L. R. Price, M. Prijatelj, M. Principe, S. Privitera,
R. Prix, G. A. Prodi, L. Prokhorov, O. Puncken, M. Punturo, P. Puppo, V.
Quetschke, E. Quintero, R. Quitzow-James, F. J. Raab, D. S. Rabeling, I.
R\'acz, H. Radkins, P. Raffai, S. Raja, G. Rajalakshmi, M. Rakhmanov, C.
Ramet, P. Rapagnani, V. Raymond, V. Re, C. M. Reed, T. Reed, T. Regimbau, S.
Reid, D. H. Reitze, F. Ricci, R. Riesen, K. Riles, N. A. Robertson, F.
Robinet, A. Rocchi, S. Roddy, C. Rodriguez, M. Rodruck, C. Roever, L.
Rolland, J. G. Rollins, R. Romano, G. Romanov, J. H. Romie, D. Rosi\'nska, S.
Rowan, A. R\"udiger, P. Ruggi, K. Ryan, F. Salemi, L. Sammut, V. Sandberg, J.
Sanders, V. Sannibale, I. Santiago-Prieto, E. Saracco, B. Sassolas, B. S.
Sathyaprakash, P. R. Saulson, R. Savage, R. Schilling, R. Schnabel, R. M. S.
Schofield, E. Schreiber, D. Schuette, B. Schulz, B. F. Schutz, P. Schwinberg,
J. Scott, S. M. Scott, F. Seifert, D. Sellers, A. S. Sengupta, D. Sentenac,
A. Sergeev, D. Shaddock, S. Shah, M. S. Shahriar, M. Shaltev, B. Shapiro, P.
Shawhan, D. H. Shoemaker, T. L. Sidery, K. Siellez, X. Siemens, D. Sigg, D.
Simakov, A. Singer, L. Singer, A. M. Sintes, G. R. Skelton, B. J. J.
Slagmolen, J. Slutsky, J. R. Smith, M. R. Smith, R. J. E. Smith, N. D.
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A. Staley, E. Steinert, J. Steinlechner, S. Steinlechner, S. Steplewski, D.
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Stroeer, R. Sturani, A. L. Stuver, T. Z. Summerscales, S. Susmithan, P. J.
Sutton, B. Swinkels, G. Szeifert, M. Tacca, D. Talukder, L. Tang, D. B.
Tanner, S. P. Tarabrin, R. Taylor, A. P. M. ter Braack, M. P.
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Thrane, V. Tiwari, K. V. Tokmakov, C. Tomlinson, A. Toncelli, M. Tonelli, O.
Torre, C. V. Torres, C. I. Torrie, F. Travasso, G. Traylor, M. Tse, D.
Ugolini, C. S. Unnikrishnan, H. Vahlbruch, G. Vajente, M. Vallisneri, J. F.
J. van den Brand, C. Van Den Broeck, S. van der Putten, M. V. van der Sluys,
J. van Heijningen, A. A. van Veggel, S. Vass, M. Vas\'uth, R. Vaulin, A.
Vecchio, G. Vedovato, J. Veitch, P. J. Veitch, K. Venkateswara, D. Verkindt,
S. Verma, F. Vetrano, A. Vicer\'e, R. Vincent-Finley, J.-Y. Vinet, S. Vitale,
B. Vlcek, T. Vo, H. Vocca, C. Vorvick, W. D. Vousden, D. Vrinceanu, S. P.
Vyachanin, A. Wade, L. Wade, M. Wade, S. J. Waldman, M. Walker, L. Wallace,
Y. Wan, J. Wang, M. Wang, X. Wang, A. Wanner, R. L. Ward, M. Was, B. Weaver,
L.-W. Wei, M. Weinert, A. J. Weinstein, R. Weiss, T. Welborn, L. Wen, P.
Wessels, M. West, T. Westphal, K. Wette, J. T. Whelan, S. E. Whitcomb, D. J.
White, B. F. Whiting, S. Wibowo, K. Wiesner, C. Wilkinson, L. Williams, R.
Williams, T. Williams, J. L. Willis, B. Willke, M. Wimmer, L. Winkelmann, W.
Winkler, C. C. Wipf, H. Wittel, G. Woan, J. Worden, J. Yablon, I. Yakushin,
H. Yamamoto, C. C. Yancey, H. Yang, D. Yeaton-Massey, S. Yoshida, H. Yum, M.
Yvert, A. Zadro\.zny, M. Zanolin, J.-P. Zendri, F. Zhang, L. Zhang, C. Zhao,
H. Zhu, X. J. Zhu, N. Zotov, M. E. Zucker, J. Zweizig | Constraints on cosmic strings from the LIGO-Virgo gravitational-wave
detectors | null | Phys. Rev. Lett. 112, 131101 (2014) | 10.1103/PhysRevLett.112.131101 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmic strings can give rise to a large variety of interesting astrophysical
phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by
cusps are a promising observational signature. In this Letter we present a
search for GWs from cosmic string cusps in data collected by the LIGO and Virgo
gravitational wave detectors between 2005 and 2010, with over 625 days of live
time. We find no evidence of GW signals from cosmic strings. From this result,
we derive new constraints on cosmic string parameters, which complement and
improve existing limits from previous searches for a stochastic background of
GWs from cosmic microwave background measurements and pulsar timing data. In
particular, if the size of loops is given by the gravitational backreaction
scale, we place upper limits on the string tension $G\mu$ below $10^{-8}$ in
some regions of the cosmic string parameter space.
| [
{
"created": "Wed, 9 Oct 2013 07:41:30 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Apr 2014 06:37:24 GMT",
"version": "v2"
}
] | 2014-04-08 | [
[
"Aasi",
"J.",
""
],
[
"Abadie",
"J.",
""
],
[
"Abbott",
"B. P.",
""
],
[
"Abbott",
"R.",
""
],
[
"Abbott",
"T.",
""
],
[
"Abernathy",
"M. R.",
""
],
[
"Accadia",
"T.",
""
],
[
"Acernese",
"F.",
... | Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension $G\mu$ below $10^{-8}$ in some regions of the cosmic string parameter space. |
1111.5434 | Kiyoshi Shiraishi | Nahomi Kan (Yamaguchi Junior College), Koichro Kobayashi and Kiyoshi
Shiraishi (Yamaguchi University) | Einstein Universe under Deconstruction: the case with degenerate
fermions | 4 pages, 1 eps figure. To appear in the Proceedings of 21st Workshop
in General Relativity and Gravitation in Japan (JGRG21), held in Sakura Hall,
Katahira Campus, Tohoku University, Sendai, Japan (26 - 29 September 2011) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study self-consistent static solutions for an Einstein universe in a
graph-based induced gravity. In the generalization of the deconstruction model
based on the graph, the eigenvalues of the graph Laplacian and the adjacent
matrix gives the mass spectrum the particles. Thus we can easily control UV
divergences at one-loop level in such a model. We use the calculation method
with the spectrum distribution function of the graph and search for the static
solution supported by the degenerate pressure of the fermion (at zero
temperature). The report is based on arXiv:1110.5697.
| [
{
"created": "Wed, 23 Nov 2011 09:04:26 GMT",
"version": "v1"
}
] | 2011-11-24 | [
[
"Kan",
"Nahomi",
"",
"Yamaguchi Junior College"
],
[
"Kobayashi",
"Koichro",
"",
"Yamaguchi University"
],
[
"Shiraishi",
"Kiyoshi",
"",
"Yamaguchi University"
]
] | We study self-consistent static solutions for an Einstein universe in a graph-based induced gravity. In the generalization of the deconstruction model based on the graph, the eigenvalues of the graph Laplacian and the adjacent matrix gives the mass spectrum the particles. Thus we can easily control UV divergences at one-loop level in such a model. We use the calculation method with the spectrum distribution function of the graph and search for the static solution supported by the degenerate pressure of the fermion (at zero temperature). The report is based on arXiv:1110.5697. |
1104.0152 | Anjan Ananda Sen | N. Chandrachani Devi, Sudhakar Panda, Anjan A Sen | Solar System Constraints on Scalar Tensor Theories with Non-Standard
Action | 7 pages, Revtex style, two eps figures, revised version, accepted for
publication in Physical Review D | null | 10.1103/PhysRevD.84.063521 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the Post-Newtonian parameter (PPN),$\gamma$, for scalar-tensor
gravity theory when the action functional for the scalar field is a
non-standard one, namely the Dirac-Born-Infeld (DBI) type action, used in the
literature for a tachyon field. We investigate two different cases (Linear and
conformal couplings) when the scalar field is non-minimally coupled to gravity
via the scalar curvature. We find that the PPN parameter $\gamma$, which
measures the amount of space curvature per unit rest mass, becomes a function
of the effective mass of the scalar field. Using this PPN parameter, we
calculate the time delay $\Delta\tau$ for the signal to travel the round trip
distance bertween a ground based antenna and a reflector placed in a spacecraft
which is produced due to the grvitational field of Sun. We use this
$\Delta\tau$ to compare our result with that obtained by the Cassini mission
and derive the constraints on the model parameters.
| [
{
"created": "Fri, 1 Apr 2011 12:15:47 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Apr 2011 12:24:41 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Aug 2011 04:42:05 GMT",
"version": "v3"
}
] | 2015-05-27 | [
[
"Devi",
"N. Chandrachani",
""
],
[
"Panda",
"Sudhakar",
""
],
[
"Sen",
"Anjan A",
""
]
] | We compute the Post-Newtonian parameter (PPN),$\gamma$, for scalar-tensor gravity theory when the action functional for the scalar field is a non-standard one, namely the Dirac-Born-Infeld (DBI) type action, used in the literature for a tachyon field. We investigate two different cases (Linear and conformal couplings) when the scalar field is non-minimally coupled to gravity via the scalar curvature. We find that the PPN parameter $\gamma$, which measures the amount of space curvature per unit rest mass, becomes a function of the effective mass of the scalar field. Using this PPN parameter, we calculate the time delay $\Delta\tau$ for the signal to travel the round trip distance bertween a ground based antenna and a reflector placed in a spacecraft which is produced due to the grvitational field of Sun. We use this $\Delta\tau$ to compare our result with that obtained by the Cassini mission and derive the constraints on the model parameters. |
1203.5407 | Luis Cort\'es Barbado | Luis C. Barbado, Carlos Barcel\'o, Luis J. Garay | Hawking radiation as perceived by different observers (ERE2011
proceedings) | Proccedings of the Spanish Relativity Meeting 2011. 4 pages, 4
figures | AIP Conf. Proc. 1458 (2012), pp. 363-366 | 10.1063/1.4734435 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the perception of Hawking radiation by different observers outside a
black hole. The analysis is done in terms of an effective-temperature function
that varies along the trajectory of each observer. The vacuum state of the
radiation field is chosen to be non-stationary, so as to mimic the switching-on
of Hawking radiation that would appear in a real black hole collapse. We
analyse how this vacuum is perceived by observers staying at a fixed radius, by
observers coming in free-fall from radial infinity at different times, and by
observers in free-fall released from finite radial positions. Results found
have a compelling physical interpretation. One main result, at first
unexpected, is that in general free-falling observers do perceive particle
emission by the black hole when crossing the event horizon. This happens
because of a diverging Doppler shift at the event horizon.
| [
{
"created": "Sat, 24 Mar 2012 11:48:04 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Oct 2012 08:51:55 GMT",
"version": "v2"
}
] | 2012-10-02 | [
[
"Barbado",
"Luis C.",
""
],
[
"Barceló",
"Carlos",
""
],
[
"Garay",
"Luis J.",
""
]
] | We study the perception of Hawking radiation by different observers outside a black hole. The analysis is done in terms of an effective-temperature function that varies along the trajectory of each observer. The vacuum state of the radiation field is chosen to be non-stationary, so as to mimic the switching-on of Hawking radiation that would appear in a real black hole collapse. We analyse how this vacuum is perceived by observers staying at a fixed radius, by observers coming in free-fall from radial infinity at different times, and by observers in free-fall released from finite radial positions. Results found have a compelling physical interpretation. One main result, at first unexpected, is that in general free-falling observers do perceive particle emission by the black hole when crossing the event horizon. This happens because of a diverging Doppler shift at the event horizon. |
1509.03725 | Diego Pavon | Pedro C. Ferreira and Diego Pavon | Thermodynamics of nonsingular bouncing universes | 12 pages, 3 figures. Version published in the European Physical
Journal C | Eur. Phys. J. C (2016) 76:37 | 10.1140/epjc/s10052-016-3886-2 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Homogeneous and isotropic, nonsingular, bouncing world models are designed to
evade the initial singularity at the beginning of the cosmic expansion. Here,
we study the thermodynamics of the subset of these models governed by general
relativity. Considering the entropy of matter, radiation and that the entropy
of the apparent horizon is proportional to its area, we argue that these models
do not respect the generalised second law of thermodynamics, also away from the
bounce.
| [
{
"created": "Sat, 12 Sep 2015 09:32:12 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Nov 2015 14:23:01 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Dec 2015 10:28:46 GMT",
"version": "v3"
},
{
"created": "Fri, 5 Feb 2016 11:45:13 GMT",
"version": "v4"
}
] | 2016-03-09 | [
[
"Ferreira",
"Pedro C.",
""
],
[
"Pavon",
"Diego",
""
]
] | Homogeneous and isotropic, nonsingular, bouncing world models are designed to evade the initial singularity at the beginning of the cosmic expansion. Here, we study the thermodynamics of the subset of these models governed by general relativity. Considering the entropy of matter, radiation and that the entropy of the apparent horizon is proportional to its area, we argue that these models do not respect the generalised second law of thermodynamics, also away from the bounce. |
1909.12251 | Maria Okounkova | Maria Okounkova | Stability of rotating black holes in Einstein dilaton Gauss-Bonnet
gravity | 4 pages, 5 figures | Phys. Rev. D 100, 124054 (2019) | 10.1103/PhysRevD.100.124054 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In order to perform model-dependent tests of general relativity with
gravitational wave observations, we must have access to numerical relativity
binary black hole waveforms in theories beyond general relativity (GR). In this
study, we focus on order-reduced Einstein dilaton Gauss-Bonnet gravity (EDGB),
a higher curvature beyond-GR theory with motivations in string theory. The
stability of single, rotating black holes in EDGB is unknown, but is a
necessary condition for being able to simulate binary black hole systems
(especially the early-inspiral and late ringdown stages) in EDGB. We thus
investigate the stability of rotating black holes in order-reduced EDGB. We
evolve the leading-order EDGB scalar field and EDGB spacetime metric
deformation on a rotating black hole background, for a variety of spins. We
find that the EDGB metric deformation exhibits linear growth, but that this
level of growth exponentially converges to zero with numerical resolution.
Thus, we conclude that rotating black holes in EDGB are numerically stable to
leading-order, thus satisfying our necessary condition for performing binary
black hole simulations in EDGB.
| [
{
"created": "Thu, 26 Sep 2019 16:57:32 GMT",
"version": "v1"
}
] | 2020-01-01 | [
[
"Okounkova",
"Maria",
""
]
] | In order to perform model-dependent tests of general relativity with gravitational wave observations, we must have access to numerical relativity binary black hole waveforms in theories beyond general relativity (GR). In this study, we focus on order-reduced Einstein dilaton Gauss-Bonnet gravity (EDGB), a higher curvature beyond-GR theory with motivations in string theory. The stability of single, rotating black holes in EDGB is unknown, but is a necessary condition for being able to simulate binary black hole systems (especially the early-inspiral and late ringdown stages) in EDGB. We thus investigate the stability of rotating black holes in order-reduced EDGB. We evolve the leading-order EDGB scalar field and EDGB spacetime metric deformation on a rotating black hole background, for a variety of spins. We find that the EDGB metric deformation exhibits linear growth, but that this level of growth exponentially converges to zero with numerical resolution. Thus, we conclude that rotating black holes in EDGB are numerically stable to leading-order, thus satisfying our necessary condition for performing binary black hole simulations in EDGB. |
1512.05331 | Andrzej Banburski | Andrzej Banburski and Lin-Qing Chen | A simpler way of imposing simplicity constraints | 16 pages | Phys. Rev. D 94, 104003 (2016) | 10.1103/PhysRevD.94.104003 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate a way of imposing simplicity constraints in a holomorphic Spin
Foam model that we recently introduced. Rather than imposing the constraints on
the boundary spin network, as is usually done, one can impose the constraints
directly on the Spin Foam propagator. We find that the two approaches have the
same leading asymptotic behaviour, with differences appearing at higher order.
This allows us to obtain a model that greatly simplifies calculations, but
still has Regge Calculus as its semi-classical limit.
| [
{
"created": "Wed, 16 Dec 2015 20:53:50 GMT",
"version": "v1"
}
] | 2016-11-09 | [
[
"Banburski",
"Andrzej",
""
],
[
"Chen",
"Lin-Qing",
""
]
] | We investigate a way of imposing simplicity constraints in a holomorphic Spin Foam model that we recently introduced. Rather than imposing the constraints on the boundary spin network, as is usually done, one can impose the constraints directly on the Spin Foam propagator. We find that the two approaches have the same leading asymptotic behaviour, with differences appearing at higher order. This allows us to obtain a model that greatly simplifies calculations, but still has Regge Calculus as its semi-classical limit. |
gr-qc/9511049 | Thomas Thiemann | Thomas Thiemann | An account of transforms on \bar {{\cal A}/{\cal G}} | 19 pages, Latex, Contribution to the Workshop ``Recent mathematical
developments in classical and quantum gravity, Sintra, Portugal 1995 | Acta Cosmologica 21:145-167,1996 | null | CGPG-95/11-3, HUTMP-95/B-347 | gr-qc hep-th | null | In this article we summarize and describe the recently found transforms for
theories of connections modulo gauge transformations associated with compact
gauge groups. Specifically, we put into a coherent picture the so-called loop
transform, the inverse loop transform, the coherent state transform and finally
the Wick rotation transform which is the appropriate transform that
incorporates the correct reality conditions of quantum gravity when formulated
as a dynamical theory of connections while preserving the simple algebraic form
of the Hamiltonian constraint.
| [
{
"created": "Thu, 16 Nov 1995 23:56:19 GMT",
"version": "v1"
}
] | 2011-04-15 | [
[
"Thiemann",
"Thomas",
""
]
] | In this article we summarize and describe the recently found transforms for theories of connections modulo gauge transformations associated with compact gauge groups. Specifically, we put into a coherent picture the so-called loop transform, the inverse loop transform, the coherent state transform and finally the Wick rotation transform which is the appropriate transform that incorporates the correct reality conditions of quantum gravity when formulated as a dynamical theory of connections while preserving the simple algebraic form of the Hamiltonian constraint. |
1912.05674 | Rohan Raha | Rohan Raha | Euclidean quantum gravity for Kerr-Newman Spacetimes | arXiv admin note: text overlap with arXiv:gr-qc/9903089 by other
authors | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is very important to calculate the amount of radiation from a black hole
as the radiation from a black hole contributes to its entropy. In this paper I
have calculated the Entropy of a black hole from the action. I have used path
integral formalism to calculate the second order perturbation of the metric in
the action for a generalized Kerr-Newman metric.
| [
{
"created": "Wed, 11 Dec 2019 22:31:04 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Jan 2020 19:24:28 GMT",
"version": "v2"
}
] | 2020-01-07 | [
[
"Raha",
"Rohan",
""
]
] | It is very important to calculate the amount of radiation from a black hole as the radiation from a black hole contributes to its entropy. In this paper I have calculated the Entropy of a black hole from the action. I have used path integral formalism to calculate the second order perturbation of the metric in the action for a generalized Kerr-Newman metric. |
gr-qc/0405066 | Nikolaos Mavromatos | John Ellis, Nikolaos E. Mavromatos and Michael Westmuckett | A supersymmetric D-brane Model of Space-Time Foam | 33 pages, latex, five figures | Phys.Rev.D70:044036,2004 | 10.1103/PhysRevD.70.044036 | CERN-PH-TH/2004-074 | gr-qc hep-ph hep-th | null | We present a supersymmetric model of space-time foam with two stacks of eight
D8-branes with equal string tensions, separated by a single bulk dimension
containing D0-brane particles that represent quantum fluctuations in the
space-time foam. The ground state configuration with static D-branes has zero
vacuum energy. However, gravitons and other closed-string states propagating
through the bulk may interact with the D0-particles, causing them to recoil and
the vacuum energy to become non zero. This provides a possible origin of dark
energy. Recoil also distorts the background metric felt by energetic massless
string states, which travel at less than the usual (low-energy) velocity of
light. On the other hand, the propagation of chiral matter anchored on the D8
branes is not affected by such space-time foam effects.
| [
{
"created": "Wed, 12 May 2004 19:19:37 GMT",
"version": "v1"
}
] | 2009-09-11 | [
[
"Ellis",
"John",
""
],
[
"Mavromatos",
"Nikolaos E.",
""
],
[
"Westmuckett",
"Michael",
""
]
] | We present a supersymmetric model of space-time foam with two stacks of eight D8-branes with equal string tensions, separated by a single bulk dimension containing D0-brane particles that represent quantum fluctuations in the space-time foam. The ground state configuration with static D-branes has zero vacuum energy. However, gravitons and other closed-string states propagating through the bulk may interact with the D0-particles, causing them to recoil and the vacuum energy to become non zero. This provides a possible origin of dark energy. Recoil also distorts the background metric felt by energetic massless string states, which travel at less than the usual (low-energy) velocity of light. On the other hand, the propagation of chiral matter anchored on the D8 branes is not affected by such space-time foam effects. |
2103.03245 | V. G. Gurzadyan | M.Samsonyan, A.A.Kocharyan, A.Stepanian, V.G.Gurzadyan | Cosmic voids and induced hyperbolicity. II. Sensitivity to void/wall
scales | 6 pages, 3 figs; Eur. Phys. J. Plus (in press); published version | Eur. Phys. J. Plus 136, 350 (2021) | 10.1140/epjp/s13360-021-01310-5 | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | Cosmic voids as typical under-density regions in the large scale Universe are
known for their hyperbolic properties as an ability to deviate the photon
beams. The under-density then is acting as the negative curvature in the
hyperbolic spaces. The hyperbolicity of voids has to lead to distortion in the
statistical analysis at galactic surveys. We reveal the sensitivity of the
hyperbolicity and hence of the distortion with respect to the ratio of
void/wall scales which are observable parameters. This provides a principal
possibility to use the distortion in the galactic surveys in revealing the
line-of sight number of cosmic voids and their characteristic scales.
| [
{
"created": "Thu, 4 Mar 2021 03:07:05 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Mar 2021 03:37:06 GMT",
"version": "v2"
}
] | 2021-04-07 | [
[
"Samsonyan",
"M.",
""
],
[
"Kocharyan",
"A. A.",
""
],
[
"Stepanian",
"A.",
""
],
[
"Gurzadyan",
"V. G.",
""
]
] | Cosmic voids as typical under-density regions in the large scale Universe are known for their hyperbolic properties as an ability to deviate the photon beams. The under-density then is acting as the negative curvature in the hyperbolic spaces. The hyperbolicity of voids has to lead to distortion in the statistical analysis at galactic surveys. We reveal the sensitivity of the hyperbolicity and hence of the distortion with respect to the ratio of void/wall scales which are observable parameters. This provides a principal possibility to use the distortion in the galactic surveys in revealing the line-of sight number of cosmic voids and their characteristic scales. |
0905.2572 | Pia Astone | Sergio Frasca, Pia Astone | Robust estimation of the parameters of a disturbed non-stationary
Gaussian process | 10 pages; Presented to the GWDAW13 workshop, Jan 2009 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A typical problem in the detection of the gravitational waves in the data of
gravitational antennas is the non-stationarity of the Gaussian noise (and so
the varying sensitivity) and the presence of big impulsive disturbances. In
such conditions the estimation of the standard deviation of the Gaussian
process done with a classical estimator applied after a "rough" cleaning of the
big pulses often gives poor results. We propose a method based on a matched
filter applied to an AR histogram of the absolute value of the data
| [
{
"created": "Fri, 15 May 2009 15:49:36 GMT",
"version": "v1"
}
] | 2009-05-18 | [
[
"Frasca",
"Sergio",
""
],
[
"Astone",
"Pia",
""
]
] | A typical problem in the detection of the gravitational waves in the data of gravitational antennas is the non-stationarity of the Gaussian noise (and so the varying sensitivity) and the presence of big impulsive disturbances. In such conditions the estimation of the standard deviation of the Gaussian process done with a classical estimator applied after a "rough" cleaning of the big pulses often gives poor results. We propose a method based on a matched filter applied to an AR histogram of the absolute value of the data |
1807.10360 | Nadiezha Montelongo Garcia | Gabino Estevez Delgado, Joaquin Estevez Delgado, Nadiezhda Montelongo
Garcia, Modesto Pineda Duran | A perfect fluid model for compact stars | 7 pages, 4 figures | null | 10.1139/cjp-2018-0497 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of Einstein's the theory of general relativity we present a
new interior solution with a perfect fluid, this is constructed from the
proposal of a gravitational redshift factor. The geometry is regular and its
density and pressure are monotonic decrescent functions, furthermore the sound
speed is smaller than the light speed and monotonic crescent. The solution
depends on a parameter $w \in (0, 2.0375509325]$ related to the compactness of
the star $u = GM/c^2 R$, the maximum value $u = 0.2660858316$ which allow to
describe compact stars like quark stars or neutron stars. Although there is a
diversity of stars for which the model can be used, we only apply this solution
to describe the interior of a neutron star PSR J0348$+$0432. According to the
observations, it is known that its mass $M = (2.01 \pm 0.04)M_{\odot}$ and its
radius is between 12.062Km and 12.957Km, so the value of the compactness is in
the range $u \in [0.2244845, 0.2509338]$. In addition to the decreasing
behavior of the mentioned pressure and density functions, the results are
consistent with the density values range typical of neutron stars and the
maximal central density of the star result to be 1.283818 $\times 10^{18}
Kg/m^{3}$.
| [
{
"created": "Thu, 26 Jul 2018 20:49:29 GMT",
"version": "v1"
}
] | 2019-10-02 | [
[
"Delgado",
"Gabino Estevez",
""
],
[
"Delgado",
"Joaquin Estevez",
""
],
[
"Garcia",
"Nadiezhda Montelongo",
""
],
[
"Duran",
"Modesto Pineda",
""
]
] | In the framework of Einstein's the theory of general relativity we present a new interior solution with a perfect fluid, this is constructed from the proposal of a gravitational redshift factor. The geometry is regular and its density and pressure are monotonic decrescent functions, furthermore the sound speed is smaller than the light speed and monotonic crescent. The solution depends on a parameter $w \in (0, 2.0375509325]$ related to the compactness of the star $u = GM/c^2 R$, the maximum value $u = 0.2660858316$ which allow to describe compact stars like quark stars or neutron stars. Although there is a diversity of stars for which the model can be used, we only apply this solution to describe the interior of a neutron star PSR J0348$+$0432. According to the observations, it is known that its mass $M = (2.01 \pm 0.04)M_{\odot}$ and its radius is between 12.062Km and 12.957Km, so the value of the compactness is in the range $u \in [0.2244845, 0.2509338]$. In addition to the decreasing behavior of the mentioned pressure and density functions, the results are consistent with the density values range typical of neutron stars and the maximal central density of the star result to be 1.283818 $\times 10^{18} Kg/m^{3}$. |
gr-qc/9911118 | Marco Zagermann | Othmar Brodbeck and Marco Zagermann | Dimensionally Reduced Gravity, Hermitian Symmetric Spaces and the
Ashtekar Variables | 20 pages, no figures, Latex2e | Class.Quant.Grav. 17 (2000) 2749-2764 | 10.1088/0264-9381/17/14/310 | PSU-TH-223 | gr-qc hep-th | null | Dimensional reductions of various higher dimensional (super)gravity theories
lead to effectively two-dimensional field theories described by gravity coupled
G/H nonlinear sigma-models. We show that a new set of complexified variables
can be introduced when G/H is a Hermitian symmetric space. This generalizes an
earlier construction that grew out of the Ashtekar formulation of two Killing
vector reduced pure 4d general relativity. Apart from giving some new insights
into dimensional reductions of higher dimensional (super)gravity theories,
these Ashtekar-type variables offer several technical advantages in the context
of the exact quantization of these models. As an application, an infinite set
of conserved charges is constructed. Our results might serve as a starting
point for probing the quantum equivalence of the Ashtekar and the metric
formalism within a non-trivial midi-superspace model of quantum gravity.
| [
{
"created": "Mon, 29 Nov 1999 20:24:12 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Brodbeck",
"Othmar",
""
],
[
"Zagermann",
"Marco",
""
]
] | Dimensional reductions of various higher dimensional (super)gravity theories lead to effectively two-dimensional field theories described by gravity coupled G/H nonlinear sigma-models. We show that a new set of complexified variables can be introduced when G/H is a Hermitian symmetric space. This generalizes an earlier construction that grew out of the Ashtekar formulation of two Killing vector reduced pure 4d general relativity. Apart from giving some new insights into dimensional reductions of higher dimensional (super)gravity theories, these Ashtekar-type variables offer several technical advantages in the context of the exact quantization of these models. As an application, an infinite set of conserved charges is constructed. Our results might serve as a starting point for probing the quantum equivalence of the Ashtekar and the metric formalism within a non-trivial midi-superspace model of quantum gravity. |
2101.00415 | A. C. Khunt | A. C. Khunt, V. O. Thomas, P. C. Vinodkumar | Distinct Classes of Compact Stars Based On Geometrically Deduced
Equations of State | 19 pages, 8 figures | null | 10.1142/S0218271821500292 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We have computed the properties of compact objects like neutron stars based
on equation of state (EOS) deduced from a core-envelope model of superdense
stars. Such superdense stars have been studied by solving the Einstein's
equation based on pseudo-spheroidal and spherically symmetric space-time
geometry. The computed star properties are compared with those obtained based
on nuclear matter equations of state. From the mass-radius ($M-R$) relationship
obtained here, we are able to classify compact stars in three categories: (i)
highly compact self -bound stars that represents exotic matter compositions
with radius lying below 9 km (ii) normal neutron stars with radius between 9 to
12 km and (iii) soft matter neutron stars having radius lying between 12 to 20
km. Other properties such as Keplerian frequency, surface gravity and surface
gravitational redshift are also computed for all the three types. The present
work would be useful for the study of highly compact neutron like stars having
exotic matter compositions.
| [
{
"created": "Sat, 2 Jan 2021 10:27:01 GMT",
"version": "v1"
}
] | 2021-04-21 | [
[
"Khunt",
"A. C.",
""
],
[
"Thomas",
"V. O.",
""
],
[
"Vinodkumar",
"P. C.",
""
]
] | We have computed the properties of compact objects like neutron stars based on equation of state (EOS) deduced from a core-envelope model of superdense stars. Such superdense stars have been studied by solving the Einstein's equation based on pseudo-spheroidal and spherically symmetric space-time geometry. The computed star properties are compared with those obtained based on nuclear matter equations of state. From the mass-radius ($M-R$) relationship obtained here, we are able to classify compact stars in three categories: (i) highly compact self -bound stars that represents exotic matter compositions with radius lying below 9 km (ii) normal neutron stars with radius between 9 to 12 km and (iii) soft matter neutron stars having radius lying between 12 to 20 km. Other properties such as Keplerian frequency, surface gravity and surface gravitational redshift are also computed for all the three types. The present work would be useful for the study of highly compact neutron like stars having exotic matter compositions. |
gr-qc/0611044 | Stefan Hollands | Stefan Hollands and Donald Marolf | Asymptotic generators of fermionic charges and boundary conditions
preserving supersymmetry | 45 pages, Latex, no figures, v2: extended discussion of positive
energy theorem and explicit form of fermionic generators, references added | Class.Quant.Grav.24:2301-2332,2007 | 10.1088/0264-9381/24/9/010 | null | gr-qc hep-th | null | We use a covariant phase space formalism to give a general prescription for
defining Hamiltonian generators of bosonic and fermionic symmetries in
diffeomorphism invariant theories, such as supergravities. A simple and general
criterion is derived for a choice of boundary condition to lead to conserved
generators of the symmetries on the phase space. In particular, this provides a
criterion for the preservation of supersymmetries. For bosonic symmetries
corresponding to diffeomorphisms, our prescription coincides with the method of
Wald et al.
We then illustrate these methods in the case of certain supergravity theories
in $d=4$. In minimal AdS supergravity, the boundary conditions such that the
supercharges exist as Hamiltonian generators of supersymmetry transformations
are unique within the usual framework in which the boundary metric is fixed. In
extended ${\mathcal N}=4$ AdS supergravity, or more generally in the presence
of chiral matter superfields, we find that there exist many boundary conditions
preserving ${\mathcal N}=1$ supersymmetry for which corresponding generators
exist. These choices are shown to correspond to a choice of certain arbitrary
boundary ``superpotentials,'' for suitably defined ``boundary superfields.'' We
also derive corresponding formulae for the conserved bosonic charges, such as
energy, in those theories, and we argue that energy is always positive, for any
supersymmetry-preserving boundary conditions. We finally comment on the
relevance and interpretation of our results within the AdS-CFT correspondence.
| [
{
"created": "Tue, 7 Nov 2006 08:04:42 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Dec 2006 14:27:01 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Hollands",
"Stefan",
""
],
[
"Marolf",
"Donald",
""
]
] | We use a covariant phase space formalism to give a general prescription for defining Hamiltonian generators of bosonic and fermionic symmetries in diffeomorphism invariant theories, such as supergravities. A simple and general criterion is derived for a choice of boundary condition to lead to conserved generators of the symmetries on the phase space. In particular, this provides a criterion for the preservation of supersymmetries. For bosonic symmetries corresponding to diffeomorphisms, our prescription coincides with the method of Wald et al. We then illustrate these methods in the case of certain supergravity theories in $d=4$. In minimal AdS supergravity, the boundary conditions such that the supercharges exist as Hamiltonian generators of supersymmetry transformations are unique within the usual framework in which the boundary metric is fixed. In extended ${\mathcal N}=4$ AdS supergravity, or more generally in the presence of chiral matter superfields, we find that there exist many boundary conditions preserving ${\mathcal N}=1$ supersymmetry for which corresponding generators exist. These choices are shown to correspond to a choice of certain arbitrary boundary ``superpotentials,'' for suitably defined ``boundary superfields.'' We also derive corresponding formulae for the conserved bosonic charges, such as energy, in those theories, and we argue that energy is always positive, for any supersymmetry-preserving boundary conditions. We finally comment on the relevance and interpretation of our results within the AdS-CFT correspondence. |
2405.01003 | Maur\'icio Richartz | Maur\'icio Richartz, Jo\~ao Lu\'is Rosa, Emanuele Berti | Bounds on the mass of superradiantly unstable scalar fields around Kerr
black holes | 8 pages, 7 figures. v2: typos corrected, reference added | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we compute numerical bounds on the mass $\mu$ of superradiantly
unstable scalar fields in a Kerr black hole background using the continued
fraction method. We show that the normalized upper bound on the mass $\mu$
increases with the angular momentum number $\ell$ and the azimuthal number $m$,
approaching the most stringent analytical bound known to date when $\ell=m \gg
1$. We also provide an analytical fit to the numerically determined mass bound
as a function of the dimensionless spin parameter $a/M$ of the black hole with
an accuracy of the order $0.1\%$ for the fundamental mode with $\ell=m=1$, and
of the order $1\%$ for higher-order modes (up to $\ell=m=20$). We argue that
this analytical fit is particularly useful in astrophysical scenarios, since
the lowest $\ell=m$ modes are capable of producing the strongest observable
imprints of superradiance.
| [
{
"created": "Thu, 2 May 2024 05:02:13 GMT",
"version": "v1"
},
{
"created": "Mon, 6 May 2024 14:47:47 GMT",
"version": "v2"
}
] | 2024-05-07 | [
[
"Richartz",
"Maurício",
""
],
[
"Rosa",
"João Luís",
""
],
[
"Berti",
"Emanuele",
""
]
] | In this work we compute numerical bounds on the mass $\mu$ of superradiantly unstable scalar fields in a Kerr black hole background using the continued fraction method. We show that the normalized upper bound on the mass $\mu$ increases with the angular momentum number $\ell$ and the azimuthal number $m$, approaching the most stringent analytical bound known to date when $\ell=m \gg 1$. We also provide an analytical fit to the numerically determined mass bound as a function of the dimensionless spin parameter $a/M$ of the black hole with an accuracy of the order $0.1\%$ for the fundamental mode with $\ell=m=1$, and of the order $1\%$ for higher-order modes (up to $\ell=m=20$). We argue that this analytical fit is particularly useful in astrophysical scenarios, since the lowest $\ell=m$ modes are capable of producing the strongest observable imprints of superradiance. |
gr-qc/0607068 | Madhavan Varadarajan | Madhavan Varadarajan | Dirac Quantization of Parametrized Field Theory | 33 pages | Phys.Rev.D75:044018,2007 | 10.1103/PhysRevD.75.044018 | null | gr-qc | null | Parametrized field theory (PFT) is free field theory on flat spacetime in a
diffeomorphism invariant disguise. It describes field evolution on arbitrary
foliations of the flat spacetime instead of only the usual flat ones, by
treating the `embedding variables' which describe the foliation as dynamical
variables to be varied in the action in addition to the scalar field. A formal
Dirac quantization turns the constraints of PFT into functional Schrodinger
equations which describe evolution of quantum states from an arbitrary Cauchy
slice to an infinitesimally nearby one.This formal Schrodinger picture- based
quantization is unitarily equivalent to the standard Heisenberg picture based
Fock quantization of the free scalar field if scalar field evolution along
arbitrary foliations is unitarily implemented on the Fock space. Torre and
Varadarajan (TV) showed that for generic foliations emanating from a flat
initial slice in spacetimes of dimension greater than 2, evolution is not
unitarily implemented, thus implying an obstruction to Dirac quantization.
We construct a Dirac quantization of PFT,unitarily equivalent to the standard
Fock quantization, using techniques from Loop Quantum Gravity (LQG) which are
powerful enough to super-cede the no- go implications of the TV results. The
key features of our quantization include an LQG type representation for the
embedding variables, embedding dependent Fock spaces for the scalar field, an
anomaly free representation of (a generalization of) the finite transformations
generated by the constraints and group averaging techniques. The difference
between 2 and higher dimensions is that in the latter, only finite gauge
transformations are defined in the quantum theory, not the infinitesimal ones.
| [
{
"created": "Tue, 18 Jul 2006 08:45:28 GMT",
"version": "v1"
}
] | 2015-01-30 | [
[
"Varadarajan",
"Madhavan",
""
]
] | Parametrized field theory (PFT) is free field theory on flat spacetime in a diffeomorphism invariant disguise. It describes field evolution on arbitrary foliations of the flat spacetime instead of only the usual flat ones, by treating the `embedding variables' which describe the foliation as dynamical variables to be varied in the action in addition to the scalar field. A formal Dirac quantization turns the constraints of PFT into functional Schrodinger equations which describe evolution of quantum states from an arbitrary Cauchy slice to an infinitesimally nearby one.This formal Schrodinger picture- based quantization is unitarily equivalent to the standard Heisenberg picture based Fock quantization of the free scalar field if scalar field evolution along arbitrary foliations is unitarily implemented on the Fock space. Torre and Varadarajan (TV) showed that for generic foliations emanating from a flat initial slice in spacetimes of dimension greater than 2, evolution is not unitarily implemented, thus implying an obstruction to Dirac quantization. We construct a Dirac quantization of PFT,unitarily equivalent to the standard Fock quantization, using techniques from Loop Quantum Gravity (LQG) which are powerful enough to super-cede the no- go implications of the TV results. The key features of our quantization include an LQG type representation for the embedding variables, embedding dependent Fock spaces for the scalar field, an anomaly free representation of (a generalization of) the finite transformations generated by the constraints and group averaging techniques. The difference between 2 and higher dimensions is that in the latter, only finite gauge transformations are defined in the quantum theory, not the infinitesimal ones. |
gr-qc/9610020 | Alberto Carlini | A. Carlini and J. Greensite | The mass shell of the universe | plain latex file, 25 pags | Phys.Rev. D55 (1997) 3514-3524 | 10.1103/PhysRevD.55.3514 | TIT/HEP-346/COSMO-79 | gr-qc hep-th | null | The classical field equations of general relativity can be expressed as a
single geodesic equation, describing the free fall of a point particle in
superspace. Based on this formulation, a ``worldline'' quantization of gravity,
analogous to the Feynman-Schwinger treatment of particle propagation, is
proposed, and a hidden mass-shell parameter is identified. We consider the
effective action for the supermetric, which would be induced at one loop. In
certain minisuperspace models, we find that this effective action is stationary
for vanishing cosmological constant.
| [
{
"created": "Sat, 12 Oct 1996 07:48:29 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Carlini",
"A.",
""
],
[
"Greensite",
"J.",
""
]
] | The classical field equations of general relativity can be expressed as a single geodesic equation, describing the free fall of a point particle in superspace. Based on this formulation, a ``worldline'' quantization of gravity, analogous to the Feynman-Schwinger treatment of particle propagation, is proposed, and a hidden mass-shell parameter is identified. We consider the effective action for the supermetric, which would be induced at one loop. In certain minisuperspace models, we find that this effective action is stationary for vanishing cosmological constant. |
gr-qc/9603004 | Lee Samuel Finn | Lee Samuel Finn (Physics and Astronomy Department, Northwestern
University) | A numerical approach to binary black hole coalescence | 20 pages (including two figures) LaTeX w/amssymb, amsbsy, epsf and
sprocl (available from http://www.wspc.co.uk/wspc/index.html) macro packages.
A written version of the plenary lecture by the same name delivered at GR14.
To appear in proceedings of the GR14 conference | null | null | null | gr-qc | null | The nature of binary black hole coalescence is the final, uncharted frontier
of the relativistic Kepler problem. In the United States, binary black hole
coalescence has been identified as a computational ``Grand Challenge'' whose
solution is the object of a coordinated effort, just reaching its half-way
point, by more than two-score researchers at nearly a dozen institutions. In
this report I highlight what I see as the most serious problems standing
between us and a general computational solution to the problem of binary black
hole coalescence:
* the computational burden associated of the problem based on reasonable
extrapolations of present-day computing algorithms and near-term hardware
developments;
* some of the computational issues associated with those estimates, and how,
through the use of different or more sophisticated computational algorithms we
might reduce the expected burden; and
* some of the physical problems associated with the development of a
numerical solution of the field equations for a binary black hole system, with
particular attention to work going on in, or in association with, the Grand
Challenge.
| [
{
"created": "Tue, 5 Mar 1996 19:33:04 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Finn",
"Lee Samuel",
"",
"Physics and Astronomy Department, Northwestern\n University"
]
] | The nature of binary black hole coalescence is the final, uncharted frontier of the relativistic Kepler problem. In the United States, binary black hole coalescence has been identified as a computational ``Grand Challenge'' whose solution is the object of a coordinated effort, just reaching its half-way point, by more than two-score researchers at nearly a dozen institutions. In this report I highlight what I see as the most serious problems standing between us and a general computational solution to the problem of binary black hole coalescence: * the computational burden associated of the problem based on reasonable extrapolations of present-day computing algorithms and near-term hardware developments; * some of the computational issues associated with those estimates, and how, through the use of different or more sophisticated computational algorithms we might reduce the expected burden; and * some of the physical problems associated with the development of a numerical solution of the field equations for a binary black hole system, with particular attention to work going on in, or in association with, the Grand Challenge. |
1102.4919 | Rakesh Tibrewala | T.R. Govindarajan and Rakesh Tibrewala | Novel black hole bound states and entropy | 13 pages, 3 figures, approximate formula for energy spectrum added at
the end of section 2.1 along with additional minor changes to comply with the
version accepted in PRD | Phys. Rev. D 83, 124045 (2011) | 10.1103/PhysRevD.83.124045 | IMSC/2011/2/3 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We solve for the spectrum of the Laplacian as a Hamiltonian on
$\mathbb{R}^{2}-\mathbb{D}$ and in $\mathbb{R}^{3}-\mathbb{B}$. A
self-adjointness analysis with $\partial\mathbb{D}$ and $\partial\mathbb{B}$ as
the boundary for the two cases shows that a general class of boundary
conditions for which the Hamiltonian operator is essentially self-adjoint are
of the mixed (Robin) type. With this class of boundary conditions we obtain
"bound state" solutions for the Schroedinger equation. Interestingly, these
solutions are all localized near the boundary. We further show that the number
of bound states is finite and is in fact proportional to the perimeter or area
of the removed \emph{disc} or \emph{ball}. We then argue that similar
considerations should hold for static black hole backgrounds with the horizon
treated as the boundary.
| [
{
"created": "Thu, 24 Feb 2011 07:38:19 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Apr 2011 17:40:10 GMT",
"version": "v2"
},
{
"created": "Mon, 27 Jun 2011 05:21:24 GMT",
"version": "v3"
}
] | 2013-05-29 | [
[
"Govindarajan",
"T. R.",
""
],
[
"Tibrewala",
"Rakesh",
""
]
] | We solve for the spectrum of the Laplacian as a Hamiltonian on $\mathbb{R}^{2}-\mathbb{D}$ and in $\mathbb{R}^{3}-\mathbb{B}$. A self-adjointness analysis with $\partial\mathbb{D}$ and $\partial\mathbb{B}$ as the boundary for the two cases shows that a general class of boundary conditions for which the Hamiltonian operator is essentially self-adjoint are of the mixed (Robin) type. With this class of boundary conditions we obtain "bound state" solutions for the Schroedinger equation. Interestingly, these solutions are all localized near the boundary. We further show that the number of bound states is finite and is in fact proportional to the perimeter or area of the removed \emph{disc} or \emph{ball}. We then argue that similar considerations should hold for static black hole backgrounds with the horizon treated as the boundary. |
gr-qc/9410044 | Wai Suen | E.S.C. Ching, P.T. Leung, W.M. Suen and K. Young | Late Time Tail of Wave Propagation on Curved Spacetime | 11 pages, WUGRAV-94-12 | Phys.Rev.Lett. 74 (1995) 2414-2417 | 10.1103/PhysRevLett.74.2414 | null | gr-qc | null | The late time behavior of waves propagating on a general curved spacetime is
studied. The late time tail is not necessarily an inverse power of time. Our
work extends, places in context, and provides understanding for the known
results for the Schwarzschild spacetime. Analytic and numerical results are in
excellent agreement.
| [
{
"created": "Sun, 30 Oct 1994 00:44:59 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Ching",
"E. S. C.",
""
],
[
"Leung",
"P. T.",
""
],
[
"Suen",
"W. M.",
""
],
[
"Young",
"K.",
""
]
] | The late time behavior of waves propagating on a general curved spacetime is studied. The late time tail is not necessarily an inverse power of time. Our work extends, places in context, and provides understanding for the known results for the Schwarzschild spacetime. Analytic and numerical results are in excellent agreement. |
gr-qc/9904047 | Marco Cavagli\`a | Marco Cavaglia (AEI Potsdam) | The Birkhoff theorem for topologically massive gravity | 7 pages, no figures, LaTeX | Grav.Cosmol. 5 (1999) 101-103 | null | null | gr-qc | null | We derive the general $\Sigma_2\times S$ solution of topologically massive
gravity in vacuum and in presence of a cosmological constant. The field
equations reduce to three-dimensional Einstein equations and the solution has
constant Ricci tensor. We briefly discuss the emergence of non-Ricci flat
solutions when spin is introduced.
| [
{
"created": "Mon, 19 Apr 1999 15:58:10 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Cavaglia",
"Marco",
"",
"AEI Potsdam"
]
] | We derive the general $\Sigma_2\times S$ solution of topologically massive gravity in vacuum and in presence of a cosmological constant. The field equations reduce to three-dimensional Einstein equations and the solution has constant Ricci tensor. We briefly discuss the emergence of non-Ricci flat solutions when spin is introduced. |
1506.07809 | Sourav Bhattacharya | Sourav Bhattacharya | A note on entropy of de Sitter black holes | v2, 16pp; added references and discussions, results unchanged | Eur. Phys. J. C (2016) 76:112 | 10.1140/epjc/s10052-016-3955-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A de Sitter black hole or a black hole spacetime endowed with a positive
cosmological constant has two Killing horizons -- a black hole and a
cosmological event horizon surrounding it. It is natural to expect that the
total Bekenstein-Hawking entropy of such spacetimes should be the sum of the
two horizons' areas. In this work we apply the recently developed formalism
using the Gibbons-Hawking-York boundary term and the near horizon symmetries to
derive the total entropy of such two horizon spacetimes. We construct a
suitable general geometric set up for general stationary axisymmetric
spacetimes with two or more than two commuting Killing vector fields in an
arbitrary spacetime dimensions. This framework helps us to deal with both the
horizons in an equal footing. We show that in order to obtain the total entropy
of such spacetimes, the near horizon mode functions for the diffeomorphism
generating vector fields have to be restricted in a certain manner, compared to
the single horizon spacetimes. We next discuss specific known exact solutions
belonging to the Kerr-Newman- or the Plebanski-Demianski-de Sitter families to
show that they fall into the category of our general framework. We end with a
sketch of further possible extensions of this work.
| [
{
"created": "Thu, 25 Jun 2015 16:33:55 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Mar 2016 04:47:27 GMT",
"version": "v2"
}
] | 2016-03-08 | [
[
"Bhattacharya",
"Sourav",
""
]
] | A de Sitter black hole or a black hole spacetime endowed with a positive cosmological constant has two Killing horizons -- a black hole and a cosmological event horizon surrounding it. It is natural to expect that the total Bekenstein-Hawking entropy of such spacetimes should be the sum of the two horizons' areas. In this work we apply the recently developed formalism using the Gibbons-Hawking-York boundary term and the near horizon symmetries to derive the total entropy of such two horizon spacetimes. We construct a suitable general geometric set up for general stationary axisymmetric spacetimes with two or more than two commuting Killing vector fields in an arbitrary spacetime dimensions. This framework helps us to deal with both the horizons in an equal footing. We show that in order to obtain the total entropy of such spacetimes, the near horizon mode functions for the diffeomorphism generating vector fields have to be restricted in a certain manner, compared to the single horizon spacetimes. We next discuss specific known exact solutions belonging to the Kerr-Newman- or the Plebanski-Demianski-de Sitter families to show that they fall into the category of our general framework. We end with a sketch of further possible extensions of this work. |
1007.1561 | Christodoulakis Theodosios | Petros A. Terzis, T. Christodoulakis | Lie algebra automorphisms as Lie point symmetries and the solution space
for Bianchi Type I, II, IV, V vacuum geometries | LaTeX source file, 37 pages, no figures. Accepted to CQG. arXiv admin
note: substantial text overlap with arXiv:0803.3710, arXiv:gr-qc/0410123 | Class. Quantum Grav. (2012) 29 235007 | 10.1088/0264-9381/29/23/235007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lie group symmetry analysis for systems of coupled, nonlinear ordinary
differential equations is performed in order to obtain the entire solution
space to Einstein's field equations for vacuum Bianchi spacetime geometries.
The symmetries used are the automorphisms of the Lie algebra of the
corresponding three-dimensional isometry group acting on the hyper-surfaces of
simultaneity for each Bianchi Type, as well as the scaling and the time
reparametrization symmetry. A detailed application of the method is presented
for Bianchi Type IV. The result is the acquisition of the general solution of
Type IV in terms of sixth Painleve transcendent PVI, along with the known
pp-wave solution. For Bianchi Types I, II, V the known entire solution space is
attained and very briefly listed, along with two new Type V solutions of
Euclidean and neutral signature and a Type I pp-wave metric.
| [
{
"created": "Fri, 9 Jul 2010 11:21:31 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Oct 2012 10:37:12 GMT",
"version": "v2"
}
] | 2013-11-20 | [
[
"Terzis",
"Petros A.",
""
],
[
"Christodoulakis",
"T.",
""
]
] | Lie group symmetry analysis for systems of coupled, nonlinear ordinary differential equations is performed in order to obtain the entire solution space to Einstein's field equations for vacuum Bianchi spacetime geometries. The symmetries used are the automorphisms of the Lie algebra of the corresponding three-dimensional isometry group acting on the hyper-surfaces of simultaneity for each Bianchi Type, as well as the scaling and the time reparametrization symmetry. A detailed application of the method is presented for Bianchi Type IV. The result is the acquisition of the general solution of Type IV in terms of sixth Painleve transcendent PVI, along with the known pp-wave solution. For Bianchi Types I, II, V the known entire solution space is attained and very briefly listed, along with two new Type V solutions of Euclidean and neutral signature and a Type I pp-wave metric. |
1911.09745 | Chiara Mingarelli | Chiara M. F. Mingarelli, Stephen R. Taylor, B. S. Sathyaprakash, Will
M. Farr | Understanding $\Omega_\mathrm{gw}(f)$ in Gravitational Wave Experiments | 9 pages, 1 figure | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we provide a comprehensive derivation of the energy density in
the stochastic gravitational-wave background $\Omega_\mathrm{gw}(f)$, and show
how this quantity is measured in ground-based detectors such as Laser
Interferometer Gravitational-Wave Observatory (LIGO), space-based Laser
Interferometer Space Antenna (LISA), and Pulsar Timing Arrays. By definition
$\Omega_\mathrm{gw}(f) \propto S_h(f)$ -- the power spectral density (PSD) of
the Fourier modes of the gravitational-wave background. However, this is often
confused with the PSD of the strain signal, which we call $S_\mathrm{gw}(f)$,
and is a detector-dependent quantity. This has led to confusing definitions of
$\Omega_\mathrm{gw}(f)$ in the literature which differ by factors of up to 5
when written in a detector-dependent way. In addition to clarifying this
confusion, formulas presented in this paper facilitate easy comparison of
results from different detector groups, and how to convert from one measure of
the strength of the background (or an upper limit) to another. Our codes are
public and on GitHub.
| [
{
"created": "Thu, 21 Nov 2019 20:58:08 GMT",
"version": "v1"
}
] | 2019-11-25 | [
[
"Mingarelli",
"Chiara M. F.",
""
],
[
"Taylor",
"Stephen R.",
""
],
[
"Sathyaprakash",
"B. S.",
""
],
[
"Farr",
"Will M.",
""
]
] | In this paper we provide a comprehensive derivation of the energy density in the stochastic gravitational-wave background $\Omega_\mathrm{gw}(f)$, and show how this quantity is measured in ground-based detectors such as Laser Interferometer Gravitational-Wave Observatory (LIGO), space-based Laser Interferometer Space Antenna (LISA), and Pulsar Timing Arrays. By definition $\Omega_\mathrm{gw}(f) \propto S_h(f)$ -- the power spectral density (PSD) of the Fourier modes of the gravitational-wave background. However, this is often confused with the PSD of the strain signal, which we call $S_\mathrm{gw}(f)$, and is a detector-dependent quantity. This has led to confusing definitions of $\Omega_\mathrm{gw}(f)$ in the literature which differ by factors of up to 5 when written in a detector-dependent way. In addition to clarifying this confusion, formulas presented in this paper facilitate easy comparison of results from different detector groups, and how to convert from one measure of the strength of the background (or an upper limit) to another. Our codes are public and on GitHub. |
2107.12822 | Andrew Melatos | A. Melatos, P. Clearwater, S. Suvorova, L. Sun, W. Moran, R. J. Evans | Hidden Markov model tracking of continuous gravitational waves from a
neutron star with wandering spin. III. Rotational phase tracking | 33 pages, 16 figures, accepted for publication in Physical Review D | null | 10.1103/PhysRevD.104.042003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A hidden Markov model (HMM) solved recursively by the Viterbi algorithm can
be configured to search for persistent, quasimonochromatic gravitational
radiation from an isolated or accreting neutron star, whose rotational
frequency is unknown and wanders stochastically. Here an existing HMM analysis
pipeline is generalized to track rotational phase and frequency simultaneously,
by modeling the intra-step rotational evolution according to a phase-wrapped
Ornstein-Uhlenbeck process, and by calculating the emission probability using a
phase-sensitive version of the Bayesian matched filter known as the
$\mathcal{B}$-statistic. The generalized algorithm tracks signals from isolated
and binary sources with characteristic wave strain $h_0 \geq 1.3\times
10^{-26}$ in Gaussian noise with amplitude spectral density $4\times
10^{-24}\,{\rm Hz^{-1/2}}$, for a simulated observation composed of $N_T=37$
data segments, each $T_{\rm drift}=10\,{\rm days}$ long, the typical duration
of a search for the low-mass X-ray binary (LMXB) Sco X$-$1 with the Laser
Interferometer Gravitational Wave Observatory (LIGO). It is equally sensitive
to isolated and binary sources and $\approx 1.5$ times more sensitive than the
previous pipeline. Receiver operating characteristic curves and errors in the
recovered parameters are presented for a range of practical $h_0$ and $N_T$
values. The generalized algorithm successfully detects every available
synthetic signal in Stage I of the Sco X$-$1 Mock Data Challenge convened by
the LIGO Scientific Collaboration, recovering the frequency and orbital
semimajor axis with accuracies of better than $9.5\times 10^{-7}\,{\rm Hz}$ and
$1.6\times 10^{-3}\,{\rm lt\,s}$ respectively. The Viterbi solver runs in
$\approx 2\times 10^3$ CPU-hr for an isolated source and $\sim 10^5$ CPU-hr for
a LMXB source in a typical, broadband ($0.5$-${\rm kHz}$) search.
| [
{
"created": "Tue, 27 Jul 2021 13:42:41 GMT",
"version": "v1"
}
] | 2021-09-01 | [
[
"Melatos",
"A.",
""
],
[
"Clearwater",
"P.",
""
],
[
"Suvorova",
"S.",
""
],
[
"Sun",
"L.",
""
],
[
"Moran",
"W.",
""
],
[
"Evans",
"R. J.",
""
]
] | A hidden Markov model (HMM) solved recursively by the Viterbi algorithm can be configured to search for persistent, quasimonochromatic gravitational radiation from an isolated or accreting neutron star, whose rotational frequency is unknown and wanders stochastically. Here an existing HMM analysis pipeline is generalized to track rotational phase and frequency simultaneously, by modeling the intra-step rotational evolution according to a phase-wrapped Ornstein-Uhlenbeck process, and by calculating the emission probability using a phase-sensitive version of the Bayesian matched filter known as the $\mathcal{B}$-statistic. The generalized algorithm tracks signals from isolated and binary sources with characteristic wave strain $h_0 \geq 1.3\times 10^{-26}$ in Gaussian noise with amplitude spectral density $4\times 10^{-24}\,{\rm Hz^{-1/2}}$, for a simulated observation composed of $N_T=37$ data segments, each $T_{\rm drift}=10\,{\rm days}$ long, the typical duration of a search for the low-mass X-ray binary (LMXB) Sco X$-$1 with the Laser Interferometer Gravitational Wave Observatory (LIGO). It is equally sensitive to isolated and binary sources and $\approx 1.5$ times more sensitive than the previous pipeline. Receiver operating characteristic curves and errors in the recovered parameters are presented for a range of practical $h_0$ and $N_T$ values. The generalized algorithm successfully detects every available synthetic signal in Stage I of the Sco X$-$1 Mock Data Challenge convened by the LIGO Scientific Collaboration, recovering the frequency and orbital semimajor axis with accuracies of better than $9.5\times 10^{-7}\,{\rm Hz}$ and $1.6\times 10^{-3}\,{\rm lt\,s}$ respectively. The Viterbi solver runs in $\approx 2\times 10^3$ CPU-hr for an isolated source and $\sim 10^5$ CPU-hr for a LMXB source in a typical, broadband ($0.5$-${\rm kHz}$) search. |
2309.05106 | Adriano Rocha Soares | A. R. Soares, C. F. S. Pereira, R. L. L. Vit\'oria | Holonomy corrected Schwarzschild black hole lensing | null | null | 10.1103/PhysRevD.108.124024 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the present work, we theoretically investigate gravitational lensing in
the spacetime of a holonomy corrected Schwarzschild black hole. Analytical
expressions for the light deflection angle are obtained in both the weak field
limit and the strong field limit. Furthermore, we analyze observables, such as
relativistic images and magnifications, and compare the results with those
expected in a Schwarzschild spacetime. We discuss the possibilities and
difficulties of investigating such a solution in practice.
| [
{
"created": "Sun, 10 Sep 2023 18:28:12 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Nov 2023 23:12:55 GMT",
"version": "v2"
}
] | 2024-08-07 | [
[
"Soares",
"A. R.",
""
],
[
"Pereira",
"C. F. S.",
""
],
[
"Vitória",
"R. L. L.",
""
]
] | In the present work, we theoretically investigate gravitational lensing in the spacetime of a holonomy corrected Schwarzschild black hole. Analytical expressions for the light deflection angle are obtained in both the weak field limit and the strong field limit. Furthermore, we analyze observables, such as relativistic images and magnifications, and compare the results with those expected in a Schwarzschild spacetime. We discuss the possibilities and difficulties of investigating such a solution in practice. |
gr-qc/0612183 | Elcio Abdalla | Elcio Abdalla and Davi Giugno | Shedding Some New Lights upon the Stellar Quasi-Normal Modes | 30 pages, figures included | null | null | null | gr-qc | null | In the current paper we present some new data on the issue of quasi-normal
modes (QNMs) of uniform, neutron and quark stars. These questions have already
been addressed in the literature before, but we have found some interesting
features that have not been discussed so far. We have increased the range of
frequency values for the scalar and axial perturbations of such stars and made
a comparison between such QNMs and those of the very well-known Schwarzschild
black holes. Also addressed in this work was the interesting feature of
competing modes, which appear not only for uniform stars, but for quark stars
as well.
| [
{
"created": "Fri, 29 Dec 2006 13:38:27 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Abdalla",
"Elcio",
""
],
[
"Giugno",
"Davi",
""
]
] | In the current paper we present some new data on the issue of quasi-normal modes (QNMs) of uniform, neutron and quark stars. These questions have already been addressed in the literature before, but we have found some interesting features that have not been discussed so far. We have increased the range of frequency values for the scalar and axial perturbations of such stars and made a comparison between such QNMs and those of the very well-known Schwarzschild black holes. Also addressed in this work was the interesting feature of competing modes, which appear not only for uniform stars, but for quark stars as well. |
1801.03272 | Md. Wali Hossain | Md. Wali Hossain | Quintessential inflation: A unified scenario of inflation and dark
energy | 5 pages, 5 figures, Based on the talk given at the Joint
International Conference of ICGAC-XIII and IK-15 on Gravitation, Astrophysics
and Cosmology held at Ewha Womans University, Seoul, Korea (July 3-7, 2017),
Published in EPJ Web of Conferences | EPJ Web of Conferences 168, 04007 (2018) | 10.1051/epjconf/201816804007 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quintessential inflation unifies inflation and late time acceleration by a
single scalar field. Such a scenario, with canonical and non-canonical scalar
fields, has been discussed . The scalar field behaves as an inflaton field
during inflation and as a quintessence field during late time. Also the
predictions of the models has been compared with the recent Planck data.
| [
{
"created": "Wed, 10 Jan 2018 08:46:21 GMT",
"version": "v1"
}
] | 2018-01-11 | [
[
"Hossain",
"Md. Wali",
""
]
] | Quintessential inflation unifies inflation and late time acceleration by a single scalar field. Such a scenario, with canonical and non-canonical scalar fields, has been discussed . The scalar field behaves as an inflaton field during inflation and as a quintessence field during late time. Also the predictions of the models has been compared with the recent Planck data. |
1212.5772 | Kourosh Nozari | Kourosh Nozari, A. Behboodi and S. Akhshabi | Braneworld Teleparallel Gravity | 7 pages, no figure | Phys. Lett. B, 723, 201 (2013) | 10.1016/j.physletb.2013.04.058 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the gravity in the context of a braneworld teleparallel scenario.
The geometrical setup is assumed to be Randall-Sundrum II model where a single
positive tension brane is embedded in an infinite AdS bulk. We derive the
equivalent of Gauss-Codacci equations in teleparallel gravity and junction
conditions in this setup. Using these results we derive the induced
teleparallel field equations on the brane. We show that compared to general
relativity, the induced field equations in teleparallel gravity contain two
extra terms arising from the extra degrees of freedom in the teleparallel
Lagrangian. The term carrying the effects of the bulk to the brane is also
calculated and its implications are discussed.
| [
{
"created": "Sun, 23 Dec 2012 08:54:47 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Nozari",
"Kourosh",
""
],
[
"Behboodi",
"A.",
""
],
[
"Akhshabi",
"S.",
""
]
] | We study the gravity in the context of a braneworld teleparallel scenario. The geometrical setup is assumed to be Randall-Sundrum II model where a single positive tension brane is embedded in an infinite AdS bulk. We derive the equivalent of Gauss-Codacci equations in teleparallel gravity and junction conditions in this setup. Using these results we derive the induced teleparallel field equations on the brane. We show that compared to general relativity, the induced field equations in teleparallel gravity contain two extra terms arising from the extra degrees of freedom in the teleparallel Lagrangian. The term carrying the effects of the bulk to the brane is also calculated and its implications are discussed. |
2108.13026 | Yohsuke Takamori | Yohsuke Takamori, Atsushi Naruko, Yusuke Sakurai, Keitaro Takahashi,
Daisuke Yamauchi, Chul-Moon Yoo | Testing the Non-circularity of the Spacetime around Sagittarius A* with
Orbiting Pulsars | 14 pages, 9 figures, 2 tables, accepted for publication in PASJ,
replaced with the accepted manuscript | null | 10.1093/pasj/psac003 | YITP-21-48 | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A disformal Kerr black hole solution is a rotating black hole solution in a
modified gravity theory which breaks the circular condition of spacetime
differently from the case of the Kerr spacetime. In this paper, assuming that
Sagittarius A* (Sgr A*) is a disformal Kerr black hole, we examine the
potential to test the spacetime geometry with a hypothetical pulsar whose
orbital elements are similar to those of the S2/S0-2 star. By numerically
solving the equations of motion for the pulsar and photons emitted from it, we
calculate the apparent position of the pulsar and the time of arrival (TOA) of
the emitted pulse signals. Our analysis shows that the magnitude of the
difference in the TOAs reaches the order of $10\>{\rm ms}$ if the deviation
from the Kerr spacetime is significant. The time difference is mainly caused by
the non-circularity of the spacetime at the $1.5$ post-Newtonian order. The
accuracy of the TOA measurement by a future radio telescope named the Square
Kilometer Array (SKA) is between about $0.1\>{\rm ms}$ and $10\>{\rm ms}$ for a
normal pulsar. Thus, we expect that the SKA can distinguish the disformal Kerr
black hole from the Kerr black hole through the non-circularity of the
spacetime around Sgr A*.
| [
{
"created": "Mon, 30 Aug 2021 07:28:32 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Jan 2022 02:04:11 GMT",
"version": "v2"
}
] | 2022-03-14 | [
[
"Takamori",
"Yohsuke",
""
],
[
"Naruko",
"Atsushi",
""
],
[
"Sakurai",
"Yusuke",
""
],
[
"Takahashi",
"Keitaro",
""
],
[
"Yamauchi",
"Daisuke",
""
],
[
"Yoo",
"Chul-Moon",
""
]
] | A disformal Kerr black hole solution is a rotating black hole solution in a modified gravity theory which breaks the circular condition of spacetime differently from the case of the Kerr spacetime. In this paper, assuming that Sagittarius A* (Sgr A*) is a disformal Kerr black hole, we examine the potential to test the spacetime geometry with a hypothetical pulsar whose orbital elements are similar to those of the S2/S0-2 star. By numerically solving the equations of motion for the pulsar and photons emitted from it, we calculate the apparent position of the pulsar and the time of arrival (TOA) of the emitted pulse signals. Our analysis shows that the magnitude of the difference in the TOAs reaches the order of $10\>{\rm ms}$ if the deviation from the Kerr spacetime is significant. The time difference is mainly caused by the non-circularity of the spacetime at the $1.5$ post-Newtonian order. The accuracy of the TOA measurement by a future radio telescope named the Square Kilometer Array (SKA) is between about $0.1\>{\rm ms}$ and $10\>{\rm ms}$ for a normal pulsar. Thus, we expect that the SKA can distinguish the disformal Kerr black hole from the Kerr black hole through the non-circularity of the spacetime around Sgr A*. |
gr-qc/0505016 | Robin Zegers | Robin Zegers | Birkhoff's theorem in Lovelock gravity | 5 pages | J.Math.Phys.46:072502,2005 | 10.1063/1.1960798 | LPT 05-30 | gr-qc hep-th | null | We show that the generic solutions of the Lovelock equations with spherical,
planar or hyperbolic symmetry are locally isometric to the corresponding static
Lovelock black hole. As a consequence, these solutions are locally static: they
admit an additional Killing vector that can either be space-like or time-like,
depending on the position. This result also holds in the presence of an abelian
gauge field, in which case the solutions are locally isometric to a charged
static black hole.
| [
{
"created": "Tue, 3 May 2005 08:59:14 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Zegers",
"Robin",
""
]
] | We show that the generic solutions of the Lovelock equations with spherical, planar or hyperbolic symmetry are locally isometric to the corresponding static Lovelock black hole. As a consequence, these solutions are locally static: they admit an additional Killing vector that can either be space-like or time-like, depending on the position. This result also holds in the presence of an abelian gauge field, in which case the solutions are locally isometric to a charged static black hole. |
0908.3113 | S Habib Mazharimousavi | S. Habib Mazharimousavi, M. Halilsoy, I. Sakalli and O. Gurtug | Dilatonic interpolation between Reissner-Nordstrom and Bertotti-Robinson
spacetimes with physical consequences | 27 pages, 4 figures, to appear in CQG. | Class.Quant.Grav.27:105005,2010 | 10.1088/0264-9381/27/10/105005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a general class of static, spherically symmetric, non-asymptotically
flat and asymptotically non-(anti) de Sitter black hole solutions in
Einstein-Maxwell-Dilaton (EMD) theory of gravity in 4-dimensions. In this
general study we couple a magnetic Maxwell field with a general dilaton
potential, while double Liouville-type potentials are coupled with the gravity.
We show that the dilatonic parameters play the key role in switching between
the Bertotti-Robinson and Reissner-Nordstr\"om spacetimes. We study the
stability of such black holes under a linear radial perturbation, and in this
sense we find exceptional cases that the EMD black holes are unstable. In
continuation we give a detailed study of the spin-weighted harmonics in
dilatonic Hawking radiation spectrum and compare our results with the
previously known ones. Finally, we investigate the status of resulting naked
singularities of our general solution when probed with quantum test particles.
| [
{
"created": "Fri, 21 Aug 2009 12:47:15 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Mar 2010 12:00:55 GMT",
"version": "v2"
}
] | 2010-04-22 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"M.",
""
],
[
"Sakalli",
"I.",
""
],
[
"Gurtug",
"O.",
""
]
] | We give a general class of static, spherically symmetric, non-asymptotically flat and asymptotically non-(anti) de Sitter black hole solutions in Einstein-Maxwell-Dilaton (EMD) theory of gravity in 4-dimensions. In this general study we couple a magnetic Maxwell field with a general dilaton potential, while double Liouville-type potentials are coupled with the gravity. We show that the dilatonic parameters play the key role in switching between the Bertotti-Robinson and Reissner-Nordstr\"om spacetimes. We study the stability of such black holes under a linear radial perturbation, and in this sense we find exceptional cases that the EMD black holes are unstable. In continuation we give a detailed study of the spin-weighted harmonics in dilatonic Hawking radiation spectrum and compare our results with the previously known ones. Finally, we investigate the status of resulting naked singularities of our general solution when probed with quantum test particles. |
1803.00585 | Kentaro Komori | Kentaro Komori, Yutaro Enomoto, Hiroki Takeda, Yuta Michimura, Kentaro
Somiya, Masaki Ando, Stefan W. Ballmer | A Direct Approach for the Fluctuation-Dissipation Theorem under
Non-Equilibrium Steady-State Conditions | 8 pages, 6 figures | Phys. Rev. D 97, 102001 (2018) | 10.1103/PhysRevD.97.102001 | null | gr-qc physics.ins-det | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The test mass suspensions of cryogenic gravitational-wave detectors such as
the KAGRA project are tasked with extracting the heat deposited on the optics.
Thus these suspensions have a non-uniform temperature, requiring the
calculation of thermal noise in non-equilibrium conditions. While it is not
possible to describe the whole suspension system with one temperature, the
local temperature anywhere in the system is still well defined. We therefore
generalize the application of the fluctuation-dissipation theorem to mechanical
systems, pioneered by Saulson and Levin, to non-equilibrium conditions in which
a temperature can only be defined locally. The result is intuitive in the sense
that the temperature-averaging relevant for the thermal noise in the observed
degree of freedom is given by averaging the temperature field, weighted by the
dissipation density associated with that particular degree of freedom. After
proving this theorem we apply the result to examples of increasing complexity:
a simple spring, the bending of a pendulum suspension fiber, as well as a model
of the KAGRA cryogenic suspension. We conclude by outlining the application to
non-equilibrium thermo-elastic noise.
| [
{
"created": "Thu, 1 Mar 2018 19:03:05 GMT",
"version": "v1"
}
] | 2018-05-09 | [
[
"Komori",
"Kentaro",
""
],
[
"Enomoto",
"Yutaro",
""
],
[
"Takeda",
"Hiroki",
""
],
[
"Michimura",
"Yuta",
""
],
[
"Somiya",
"Kentaro",
""
],
[
"Ando",
"Masaki",
""
],
[
"Ballmer",
"Stefan W.",
""
]
] | The test mass suspensions of cryogenic gravitational-wave detectors such as the KAGRA project are tasked with extracting the heat deposited on the optics. Thus these suspensions have a non-uniform temperature, requiring the calculation of thermal noise in non-equilibrium conditions. While it is not possible to describe the whole suspension system with one temperature, the local temperature anywhere in the system is still well defined. We therefore generalize the application of the fluctuation-dissipation theorem to mechanical systems, pioneered by Saulson and Levin, to non-equilibrium conditions in which a temperature can only be defined locally. The result is intuitive in the sense that the temperature-averaging relevant for the thermal noise in the observed degree of freedom is given by averaging the temperature field, weighted by the dissipation density associated with that particular degree of freedom. After proving this theorem we apply the result to examples of increasing complexity: a simple spring, the bending of a pendulum suspension fiber, as well as a model of the KAGRA cryogenic suspension. We conclude by outlining the application to non-equilibrium thermo-elastic noise. |
1709.08942 | Georgios Lukes Gerakopoulos | Georgios Lukes-Gerakopoulos | Time parameterizations and spin supplementary conditions of the
Mathisson-Papapetrou-Dixon equations | 7 pages, 3 figures | Phys. Rev. D 96, 104023 (2017) | 10.1103/PhysRevD.96.104023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The implications of two different time constraints on the
Mathisson-Papapetrou-Dixon (MPD) equations are discussed under three spin
supplementary conditions (SSC). For this reason the MPD equations are revisited
without specifying the affine parameter and several relations are reintroduced
in their general form. The latter allows to investigate the consequences of
combining the Mathisson-Pirani (MP) SSC, the Tulczyjew-Dixon (TD) SSC and the
Ohashi-Kyrian-Semer\'{a}k (OKS) SSC with two affine parameter types: the proper
time on one hand and the parameterizations introduced in [Gen. Rel. Grav. 8,
197 (1977)] on the other. For the MP SSC and the TD SSC it is shown that
quantities that are constant of motion for the one affine parameter are not for
the other, while for the OKS SSC it is shown that the two affine parameters are
the same. To clarify the relation between the two affine parameters in the case
of the TD SSC the MPD equations are evolved and discussed.
| [
{
"created": "Tue, 26 Sep 2017 11:12:29 GMT",
"version": "v1"
}
] | 2017-11-17 | [
[
"Lukes-Gerakopoulos",
"Georgios",
""
]
] | The implications of two different time constraints on the Mathisson-Papapetrou-Dixon (MPD) equations are discussed under three spin supplementary conditions (SSC). For this reason the MPD equations are revisited without specifying the affine parameter and several relations are reintroduced in their general form. The latter allows to investigate the consequences of combining the Mathisson-Pirani (MP) SSC, the Tulczyjew-Dixon (TD) SSC and the Ohashi-Kyrian-Semer\'{a}k (OKS) SSC with two affine parameter types: the proper time on one hand and the parameterizations introduced in [Gen. Rel. Grav. 8, 197 (1977)] on the other. For the MP SSC and the TD SSC it is shown that quantities that are constant of motion for the one affine parameter are not for the other, while for the OKS SSC it is shown that the two affine parameters are the same. To clarify the relation between the two affine parameters in the case of the TD SSC the MPD equations are evolved and discussed. |
1411.4689 | Roland Steinbauer | Michael Kunzinger, Roland Steinbauer, Milena Stojkovic, James A.
Vickers | Hawking's singularity theorem for $C^{1,1}$-metrics | 19 pages, LaTeX; v2: corrected Lemma 4.2; v3: typos corrected, final
version | Classical Quantum Gravity 32 (2015), no. 7, 075012, 19 pp | 10.1088/0264-9381/32/7/075012 | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide a detailed proof of Hawking's singularity theorem in the
regularity class $C^{1,1}$, i.e., for spacetime metrics possessing locally
Lipschitz continuous first derivatives. The proof uses recent results in
$C^{1,1}$-causality theory and is based on regularisation techniques adapted to
the causal structure.
| [
{
"created": "Mon, 17 Nov 2014 22:46:42 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Jan 2015 12:38:27 GMT",
"version": "v2"
},
{
"created": "Thu, 5 Mar 2015 11:39:14 GMT",
"version": "v3"
}
] | 2016-09-15 | [
[
"Kunzinger",
"Michael",
""
],
[
"Steinbauer",
"Roland",
""
],
[
"Stojkovic",
"Milena",
""
],
[
"Vickers",
"James A.",
""
]
] | We provide a detailed proof of Hawking's singularity theorem in the regularity class $C^{1,1}$, i.e., for spacetime metrics possessing locally Lipschitz continuous first derivatives. The proof uses recent results in $C^{1,1}$-causality theory and is based on regularisation techniques adapted to the causal structure. |
2002.01745 | Anton Sheykin | A. A. Sheykin, D. P. Solovyev, V. V. Sukhanov, S. A. Paston | Modifications of gravity via differential transformations of field
variables | 18 pages | Symmetry 2020, 12(2), 240 | 10.3390/sym12020240 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss field theories appearing as a result of applying field
transformations with derivatives (differential field transformations, DFT) to a
known theory. We begin with some simple examples of DFTs to see the basic
properties of the procedure. In this process the dynamics of the theory might
either change or conserve. After that we concentrate on the theories of gravity
which appear as a result of various DFT applied to general relativity, namely
the mimetic gravity and Regge-Teitelboim embedding theory. We review main
results related to the extension of dynamics in these theories, as well as the
possibility to write down the action of a theory after DFT as the action of the
original theory before DFT plus an additional term. Such a term usually
contains some constraints with Lagrange multipliers and can be interpreted as
an action of additional matter, which might be of use in cosmological
applications, e.g. for the explanation of the effects of dark matter.
| [
{
"created": "Wed, 5 Feb 2020 12:09:58 GMT",
"version": "v1"
}
] | 2020-02-06 | [
[
"Sheykin",
"A. A.",
""
],
[
"Solovyev",
"D. P.",
""
],
[
"Sukhanov",
"V. V.",
""
],
[
"Paston",
"S. A.",
""
]
] | We discuss field theories appearing as a result of applying field transformations with derivatives (differential field transformations, DFT) to a known theory. We begin with some simple examples of DFTs to see the basic properties of the procedure. In this process the dynamics of the theory might either change or conserve. After that we concentrate on the theories of gravity which appear as a result of various DFT applied to general relativity, namely the mimetic gravity and Regge-Teitelboim embedding theory. We review main results related to the extension of dynamics in these theories, as well as the possibility to write down the action of a theory after DFT as the action of the original theory before DFT plus an additional term. Such a term usually contains some constraints with Lagrange multipliers and can be interpreted as an action of additional matter, which might be of use in cosmological applications, e.g. for the explanation of the effects of dark matter. |
0909.1267 | Francisco Lobo | Tiberiu Harko, Zolt\'an Kov\'acs, Francisco S. N. Lobo | Thin accretion disk signatures in dynamical Chern-Simons modified
gravity | 12 pages, 24 figures. V2: 10 pages, 13 figures, significant changes,
matches published version | Class.Quant.Grav.27:105010,2010 | 10.1088/0264-9381/27/10/105010 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A promising extension of general relativity is Chern-Simons (CS) modified
gravity, in which the Einstein-Hilbert action is modified by adding a
parity-violating CS term, which couples to gravity via a scalar field. In this
work, we consider the interesting, yet relatively unexplored, dynamical
formulation of CS modified gravity, where the CS coupling field is treated as a
dynamical field, endowed with its own stress-energy tensor and evolution
equation. We consider the possibility of observationally testing dynamical CS
modified gravity by using the accretion disk properties around slowly-rotating
black holes. The energy flux, temperature distribution, the emission spectrum
as well as the energy conversion efficiency are obtained, and compared to the
standard general relativistic Kerr solution. It is shown that the Kerr black
hole provide a more efficient engine for the transformation of the energy of
the accreting mass into radiation than their slowly-rotating counterparts in CS
modified gravity. Specific signatures appear in the electromagnetic spectrum,
thus leading to the possibility of directly testing CS modified gravity by
using astrophysical observations of the emission spectra from accretion disks.
| [
{
"created": "Mon, 7 Sep 2009 15:00:32 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Apr 2010 21:58:37 GMT",
"version": "v2"
}
] | 2010-04-23 | [
[
"Harko",
"Tiberiu",
""
],
[
"Kovács",
"Zoltán",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | A promising extension of general relativity is Chern-Simons (CS) modified gravity, in which the Einstein-Hilbert action is modified by adding a parity-violating CS term, which couples to gravity via a scalar field. In this work, we consider the interesting, yet relatively unexplored, dynamical formulation of CS modified gravity, where the CS coupling field is treated as a dynamical field, endowed with its own stress-energy tensor and evolution equation. We consider the possibility of observationally testing dynamical CS modified gravity by using the accretion disk properties around slowly-rotating black holes. The energy flux, temperature distribution, the emission spectrum as well as the energy conversion efficiency are obtained, and compared to the standard general relativistic Kerr solution. It is shown that the Kerr black hole provide a more efficient engine for the transformation of the energy of the accreting mass into radiation than their slowly-rotating counterparts in CS modified gravity. Specific signatures appear in the electromagnetic spectrum, thus leading to the possibility of directly testing CS modified gravity by using astrophysical observations of the emission spectra from accretion disks. |
gr-qc/0301117 | Dr G. A. Jaroszkiewicz | Jon Eakins and George Jaroszkiewicz | The origin of causal set structure in the quantum universe | Updated version with four new figures | null | null | null | gr-qc quant-ph | null | We discuss the origin of causal set structure and the emergence of classical
space and time in the universe. Given that the universe is a closed
self-referential quantum automaton with a quantum register consisting of a vast
number of elementary quantum subregisters, we find two distinct but intimately
related causal sets. One of these is associated with the factorization and
entanglement properties of states of the universe and encodes phenomena such as
quantum correlations and violations of Bell-type inqualities. The concepts of
separations and entanglements of states are used to show how state reduction
dynamics generates the familial relationships which gives this causal set
structure. The other causal set structure is generated by the factorization
properties of the observables (the Hermitian operators) over the quantum
register. The concept of skeleton sets of operators is used to show how the
factorization properties of these operators could generate the classical causal
set structures associated with Einstein locality.
| [
{
"created": "Tue, 28 Jan 2003 17:22:05 GMT",
"version": "v1"
},
{
"created": "Sat, 13 Dec 2003 17:27:58 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Eakins",
"Jon",
""
],
[
"Jaroszkiewicz",
"George",
""
]
] | We discuss the origin of causal set structure and the emergence of classical space and time in the universe. Given that the universe is a closed self-referential quantum automaton with a quantum register consisting of a vast number of elementary quantum subregisters, we find two distinct but intimately related causal sets. One of these is associated with the factorization and entanglement properties of states of the universe and encodes phenomena such as quantum correlations and violations of Bell-type inqualities. The concepts of separations and entanglements of states are used to show how state reduction dynamics generates the familial relationships which gives this causal set structure. The other causal set structure is generated by the factorization properties of the observables (the Hermitian operators) over the quantum register. The concept of skeleton sets of operators is used to show how the factorization properties of these operators could generate the classical causal set structures associated with Einstein locality. |
1312.6929 | Kirill Bronnikov | K.A. Bronnikov, L.N. Lipatova, I.D. Novikov, A.A. Shatskiy | Example of a stable wormhole in general relativity | 6 pages, no figures | Grav. Cosmol. 19 (4), 269-274 (2013) | 10.1134/S0202289313040038 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a static, spherically symmetric wormhole model whose metric
coincides with that of the so-called Ellis wormhole but the material source of
gravity consists of a perfect fluid with negative density and a source-free
radial electric or magnetic field. For a certain class of fluid equations of
state, it has been shown that this wormhole model is linearly stable under both
spherically symmetric perturbations and axial perturbations of arbitrary
multipolarity. A similar behavior is predicted for polar nonspherical
perturbations. It thus seems to be the first example of a stable wormhole model
in the framework of general relativity (at least without invoking phantom thin
shells as wormhole sources).
| [
{
"created": "Wed, 25 Dec 2013 06:16:24 GMT",
"version": "v1"
}
] | 2013-12-30 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Lipatova",
"L. N.",
""
],
[
"Novikov",
"I. D.",
""
],
[
"Shatskiy",
"A. A.",
""
]
] | We study a static, spherically symmetric wormhole model whose metric coincides with that of the so-called Ellis wormhole but the material source of gravity consists of a perfect fluid with negative density and a source-free radial electric or magnetic field. For a certain class of fluid equations of state, it has been shown that this wormhole model is linearly stable under both spherically symmetric perturbations and axial perturbations of arbitrary multipolarity. A similar behavior is predicted for polar nonspherical perturbations. It thus seems to be the first example of a stable wormhole model in the framework of general relativity (at least without invoking phantom thin shells as wormhole sources). |
1303.4752 | Norbert Bodendorfer | Norbert Bodendorfer, Yasha Neiman | Imaginary action, spinfoam asymptotics and the 'transplanckian' regime
of loop quantum gravity | 23 pages, 5 figures; v2: journal version, section 3 rewritten, minor
clarifications | Class. Quantum Grav. 30 (2013) 195018 | 10.1088/0264-9381/30/19/195018 | IGC-13/3-2 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was recently noted that the on-shell Einstein-Hilbert action with
York-Gibbons-Hawking boundary term has an imaginary part, proportional to the
area of the codimension-2 surfaces on which the boundary normal becomes null.
We discuss the extension of this result to first-order formulations of gravity.
As a side effect, we settle the issue of the Holst modification vs. the
Nieh-Yan density by demanding a variational principle with suitable boundary
conditions. We then set out to find the imaginary action in the large-spin
4-simplex limit of the Lorentzian EPRL/FK spinfoam. It turns out that the
spinfoam's effective action indeed has the correct imaginary part, but only if
the Barbero-Immirzi parameter is set to +/- i after the quantum calculation. We
point out an agreement between this effective action and a recent black hole
state-counting calculation in the same limit. Finally, we propose that the
large-spin limit of loop quantum gravity can be viewed as a high-energy
'transplanckian' regime.
| [
{
"created": "Tue, 19 Mar 2013 20:16:26 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Sep 2013 12:40:12 GMT",
"version": "v2"
}
] | 2013-09-13 | [
[
"Bodendorfer",
"Norbert",
""
],
[
"Neiman",
"Yasha",
""
]
] | It was recently noted that the on-shell Einstein-Hilbert action with York-Gibbons-Hawking boundary term has an imaginary part, proportional to the area of the codimension-2 surfaces on which the boundary normal becomes null. We discuss the extension of this result to first-order formulations of gravity. As a side effect, we settle the issue of the Holst modification vs. the Nieh-Yan density by demanding a variational principle with suitable boundary conditions. We then set out to find the imaginary action in the large-spin 4-simplex limit of the Lorentzian EPRL/FK spinfoam. It turns out that the spinfoam's effective action indeed has the correct imaginary part, but only if the Barbero-Immirzi parameter is set to +/- i after the quantum calculation. We point out an agreement between this effective action and a recent black hole state-counting calculation in the same limit. Finally, we propose that the large-spin limit of loop quantum gravity can be viewed as a high-energy 'transplanckian' regime. |
1101.4382 | Luis Cort\'es Barbado | Luis C. Barbado, Carlos Barcel\'o and Luis J. Garay | Hawking radiation as perceived by different observers | 33 pages, 18 figures | Class.Quant.Grav.28:125021,2011 | 10.1088/0264-9381/28/12/125021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use a method recently introduced in Barcel\'o et al (2011 Phys. Rev. D 83
41501), to analyse Hawking radiation in a Schwarzschild black hole as perceived
by different observers in the system. The method is based on the introduction
of an 'effective temperature' function that varies with time. First we
introduce a non-stationary vacuum state for a quantum scalar field, which
interpolates between the Boulware vacuum state at early times and the Unruh
vacuum state at late times. In this way we mimic the process of switching on
Hawking radiation in realistic collapse scenarios. Then, we analyse this vacuum
state from the perspective of static observers at different radial positions,
observers undergoing a free-fall trajectory from infinity and observers
standing at rest at a radial distance and then released to fall freely towards
the horizon. The physical image that emerges from these analyses is rather rich
and compelling. Among many other results, we find that generic freely-falling
observers do not perceive vacuum when crossing the horizon, but an effective
temperature a few times larger than the one that they perceived when it started
to free-fall. We explain this phenomenon as due to a diverging Doppler effect
at horizon crossing.
| [
{
"created": "Sun, 23 Jan 2011 16:22:53 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Jul 2011 07:54:52 GMT",
"version": "v2"
}
] | 2015-03-17 | [
[
"Barbado",
"Luis C.",
""
],
[
"Barceló",
"Carlos",
""
],
[
"Garay",
"Luis J.",
""
]
] | We use a method recently introduced in Barcel\'o et al (2011 Phys. Rev. D 83 41501), to analyse Hawking radiation in a Schwarzschild black hole as perceived by different observers in the system. The method is based on the introduction of an 'effective temperature' function that varies with time. First we introduce a non-stationary vacuum state for a quantum scalar field, which interpolates between the Boulware vacuum state at early times and the Unruh vacuum state at late times. In this way we mimic the process of switching on Hawking radiation in realistic collapse scenarios. Then, we analyse this vacuum state from the perspective of static observers at different radial positions, observers undergoing a free-fall trajectory from infinity and observers standing at rest at a radial distance and then released to fall freely towards the horizon. The physical image that emerges from these analyses is rather rich and compelling. Among many other results, we find that generic freely-falling observers do not perceive vacuum when crossing the horizon, but an effective temperature a few times larger than the one that they perceived when it started to free-fall. We explain this phenomenon as due to a diverging Doppler effect at horizon crossing. |
1106.3278 | Alexandre Le Tiec | Alexandre Le Tiec, Abdul H. Mrou\'e, Leor Barack, Alessandra Buonanno,
Harald P. Pfeiffer, Norichika Sago, Andrea Taracchini | Periastron Advance in Black-Hole Binaries | 5 pages, 3 figures; v2: new abstract, updated figures correcting
minor error, added references, minor changes to match published version; to
appear in Phys. Rev. Lett | Phys.Rev.Lett.107:141101,2011 | 10.1103/PhysRevLett.107.141101 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The general relativistic (Mercury-type) periastron advance is calculated here
for the first time with exquisite precision in full general relativity. We use
accurate numerical relativity simulations of spinless black hole binaries with
mass ratios 1/8 < m1/m2 < 1 and compare with the predictions of several
analytic approximation schemes. We find the effective-one-body model to be
remarkably accurate, and, surprisingly, so also the predictions of self-force
theory [replacing m1/m2 --> m1m2/(m1+m2)^2]. Our results can inform a universal
analytic model of the two-body dynamics, crucial for ongoing and future
gravitational-wave searches.
| [
{
"created": "Thu, 16 Jun 2011 17:04:14 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Sep 2011 19:30:14 GMT",
"version": "v2"
}
] | 2013-08-26 | [
[
"Tiec",
"Alexandre Le",
""
],
[
"Mroué",
"Abdul H.",
""
],
[
"Barack",
"Leor",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Sago",
"Norichika",
""
],
[
"Taracchini",
"Andrea",
... | The general relativistic (Mercury-type) periastron advance is calculated here for the first time with exquisite precision in full general relativity. We use accurate numerical relativity simulations of spinless black hole binaries with mass ratios 1/8 < m1/m2 < 1 and compare with the predictions of several analytic approximation schemes. We find the effective-one-body model to be remarkably accurate, and, surprisingly, so also the predictions of self-force theory [replacing m1/m2 --> m1m2/(m1+m2)^2]. Our results can inform a universal analytic model of the two-body dynamics, crucial for ongoing and future gravitational-wave searches. |
gr-qc/9705034 | Serge Droz | Serge Droz and Eric Poisson | Gravitational waves from inspiraling compact binaries: Second
post-Newtonian waveforms as search templates | LaTeX, one eps figure. Hires and color versions are available from
http://jovian.physics.uoguelph.ca/~droz/uni/papers/search.html | Phys.Rev.D56:4449-4454,1997 | 10.1103/PhysRevD.56.4449 | null | gr-qc | null | We ascertain the effectiveness of the second post-Newtonian approximation to
the gravitational waves emitted during the adiabatic inspiral of a compact
binary system as templates for signal searches with kilometer-scale
interferometric detectors. The reference signal is obtained by solving the
Teukolsky equation for a small mass moving on a circular orbit around a large
nonrotating black hole. Fitting factors computed from this signal and these
templates, for various types of binary systems, are all above the 90% mark.
According to Apostolatos' criterion, second post-Newtonian waveforms should
make acceptably effective search templates.
| [
{
"created": "Tue, 13 May 1997 21:05:45 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Droz",
"Serge",
""
],
[
"Poisson",
"Eric",
""
]
] | We ascertain the effectiveness of the second post-Newtonian approximation to the gravitational waves emitted during the adiabatic inspiral of a compact binary system as templates for signal searches with kilometer-scale interferometric detectors. The reference signal is obtained by solving the Teukolsky equation for a small mass moving on a circular orbit around a large nonrotating black hole. Fitting factors computed from this signal and these templates, for various types of binary systems, are all above the 90% mark. According to Apostolatos' criterion, second post-Newtonian waveforms should make acceptably effective search templates. |
2111.14794 | Thanasis Giannakopoulos | Thanasis Giannakopoulos, Nigel T. Bishop, David Hilditch, Denis
Pollney, Miguel Zilhao | Gauge structure of the Einstein field equations in Bondi-like
coordinates | 23 pages, 3 figures, ancillary files, data and more supplemental
material at 10.5281/zenodo.5618007, updated to match published version | Phys. Rev. D 105, 084055 (2022) | 10.1103/PhysRevD.105.084055 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The characteristic initial (boundary) value problem has numerous applications
in general relativity (GR) involving numerical studies, and is often formulated
using Bondi-like coordinates. Recently it was shown that several prototype
formulations of this type are only weakly hyperbolic. Presently we examine the
root cause of this result. In a linear analysis we identify the gauge,
constraint and physical blocks in the principal part of the Einstein field
equations in such a gauge, and show that the subsystem related to the gauge
variables is only weakly hyperbolic. Weak hyperbolicity of the full system
follows as a consequence in many cases. We demonstrate this explicitly in
specific examples, and thus argue that Bondi-like gauges result in weakly
hyperbolic free evolution systems under quite general conditions. Consequently
the characteristic initial (boundary) value problem of GR in these gauges is
rendered ill-posed in the simplest norms one would like to employ. The
possibility of finding good alternative norms, in which well-posedness is
achieved, is discussed. So motivated, we present numerical convergence tests
with an implementation of full GR which demonstrate the effect of weak
hyperbolicity in practice.
| [
{
"created": "Mon, 29 Nov 2021 18:48:01 GMT",
"version": "v1"
},
{
"created": "Mon, 2 May 2022 10:16:12 GMT",
"version": "v2"
}
] | 2022-05-03 | [
[
"Giannakopoulos",
"Thanasis",
""
],
[
"Bishop",
"Nigel T.",
""
],
[
"Hilditch",
"David",
""
],
[
"Pollney",
"Denis",
""
],
[
"Zilhao",
"Miguel",
""
]
] | The characteristic initial (boundary) value problem has numerous applications in general relativity (GR) involving numerical studies, and is often formulated using Bondi-like coordinates. Recently it was shown that several prototype formulations of this type are only weakly hyperbolic. Presently we examine the root cause of this result. In a linear analysis we identify the gauge, constraint and physical blocks in the principal part of the Einstein field equations in such a gauge, and show that the subsystem related to the gauge variables is only weakly hyperbolic. Weak hyperbolicity of the full system follows as a consequence in many cases. We demonstrate this explicitly in specific examples, and thus argue that Bondi-like gauges result in weakly hyperbolic free evolution systems under quite general conditions. Consequently the characteristic initial (boundary) value problem of GR in these gauges is rendered ill-posed in the simplest norms one would like to employ. The possibility of finding good alternative norms, in which well-posedness is achieved, is discussed. So motivated, we present numerical convergence tests with an implementation of full GR which demonstrate the effect of weak hyperbolicity in practice. |
gr-qc/9809075 | Rainer Kuehne | R. W. Kuhne | Remark on ``Indication, from Pioneer 10/11, Galileo, and Ulysses Data,
of an Apparent Anomalous, Weak, Long-Range Acceleration'' | 1 page, no figures, Revtex | null | null | null | gr-qc | null | Recently, Anderson et al. presented possible evidence for an anomalous
acceleration acting on spacecrafts. Furthermore, the motions of several planets
and comets are known to experience unexplained disturbances. A transneptunian
comet or asteroid belt might be the common origin of these anomalies.
| [
{
"created": "Mon, 28 Sep 1998 07:20:01 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kuhne",
"R. W.",
""
]
] | Recently, Anderson et al. presented possible evidence for an anomalous acceleration acting on spacecrafts. Furthermore, the motions of several planets and comets are known to experience unexplained disturbances. A transneptunian comet or asteroid belt might be the common origin of these anomalies. |
0811.1178 | Petros Wallden Dr | David Rideout and Petros Wallden | Emergent Continuum Spacetime from a Random, Discrete, Partial Order | 8 pages, 2 figures, based on talk by P. Wallden at the NEB XIII
conference | J.Phys.Conf.Ser.189:012045,2009 | 10.1088/1742-6596/189/1/012045 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There are several indications (from different approaches) that Spacetime at
the Plank Scale could be discrete. One approach to Quantum Gravity that takes
this most seriously is the Causal Sets Approach. In this approach spacetime is
fundamentally a discrete, random, partially ordered set (where the partial
order is the causal relation). In this contribution, we examine how timelike
and spacelike distances arise from a causal set (in the case that the causal
set is approximated by Minkowski spacetime), and how one can use this to obtain
geometrical information (such as lengths of curves) for the general case, where
the causal set could be approximated by some curved spacetime.
| [
{
"created": "Fri, 7 Nov 2008 17:04:53 GMT",
"version": "v1"
}
] | 2009-11-05 | [
[
"Rideout",
"David",
""
],
[
"Wallden",
"Petros",
""
]
] | There are several indications (from different approaches) that Spacetime at the Plank Scale could be discrete. One approach to Quantum Gravity that takes this most seriously is the Causal Sets Approach. In this approach spacetime is fundamentally a discrete, random, partially ordered set (where the partial order is the causal relation). In this contribution, we examine how timelike and spacelike distances arise from a causal set (in the case that the causal set is approximated by Minkowski spacetime), and how one can use this to obtain geometrical information (such as lengths of curves) for the general case, where the causal set could be approximated by some curved spacetime. |
gr-qc/0311054 | Tomas Liko | Tomas Liko, James M. Overduin, Paul S. Wesson | Astrophysical Implications of Higher-Dimensional Gravity | 23 pages, 2 figures; to appear in Space Science Reviews; v3: typos
corrected and minor changes to text, expanded derivation of fundamental mode
added | Space Sci.Rev.110:337-357,2004 | 10.1023/B:SPAC.0000023441.20373.6d | null | gr-qc | null | We review the implications of modern higher-dimensional theories of gravity
for astrophysics and cosmology. In particular, we discuss the latest
developments of space-time-matter theory in connection with dark matter,
particle dynamics and the cosmological constant, as well as related aspects of
quantum theory. There are also more immediate tests of extra dimensions,
notably involving perturbations of the cosmic 3K microwave background and the
precession of a supercooled gyroscope in Earth orbit. We also outline some
general features of embeddings, and include pictures of the big bang as viewed
from a higher dimension.
| [
{
"created": "Mon, 17 Nov 2003 19:32:30 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Nov 2003 21:39:08 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Apr 2005 02:20:55 GMT",
"version": "v3"
}
] | 2011-07-19 | [
[
"Liko",
"Tomas",
""
],
[
"Overduin",
"James M.",
""
],
[
"Wesson",
"Paul S.",
""
]
] | We review the implications of modern higher-dimensional theories of gravity for astrophysics and cosmology. In particular, we discuss the latest developments of space-time-matter theory in connection with dark matter, particle dynamics and the cosmological constant, as well as related aspects of quantum theory. There are also more immediate tests of extra dimensions, notably involving perturbations of the cosmic 3K microwave background and the precession of a supercooled gyroscope in Earth orbit. We also outline some general features of embeddings, and include pictures of the big bang as viewed from a higher dimension. |
2010.00986 | Emmanuil Saridakis | John D. Barrow, Spyros Basilakos, Emmanuel N. Saridakis | Big Bang Nucleosynthesis constraints on Barrow entropy | 6 pages, 1 figure | Phys.Lett.B 815 (2021) 136134 | 10.1016/j.physletb.2021.136134 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use Big Bang Nucleosynthesis (BBN) data in order to impose constraints on
the exponent of Barrow entropy. The latter is an extended entropy relation
arising from the incorporation of quantum-gravitational effects on the
black-hole structure, parameterized effectively by the new parameter $\Delta$.
When considered in a cosmological framework and under the light of the
gravity-thermodynamics conjecture, Barrow entropy leads to modified
cosmological scenarios whose Friedmann equations contain extra terms. We
perform a detailed analysis of the BBN era and we calculate the deviation of
the freeze-out temperature comparing to the result of standard cosmology. We
use the observationally determined bound on $ |\frac{\delta {T}_f}{{T}_f}|$ in
order to extract the upper bound on $\Delta$. As we find, the Barrow exponent
should be inside the bound $\Delta\lesssim 1.4\times 10^{-4}$ in order not to
spoil the BBN epoch, which shows that the deformation from standard
Bekenstein-Hawking expression should be small as expected.
| [
{
"created": "Fri, 2 Oct 2020 13:31:20 GMT",
"version": "v1"
}
] | 2021-02-19 | [
[
"Barrow",
"John D.",
""
],
[
"Basilakos",
"Spyros",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | We use Big Bang Nucleosynthesis (BBN) data in order to impose constraints on the exponent of Barrow entropy. The latter is an extended entropy relation arising from the incorporation of quantum-gravitational effects on the black-hole structure, parameterized effectively by the new parameter $\Delta$. When considered in a cosmological framework and under the light of the gravity-thermodynamics conjecture, Barrow entropy leads to modified cosmological scenarios whose Friedmann equations contain extra terms. We perform a detailed analysis of the BBN era and we calculate the deviation of the freeze-out temperature comparing to the result of standard cosmology. We use the observationally determined bound on $ |\frac{\delta {T}_f}{{T}_f}|$ in order to extract the upper bound on $\Delta$. As we find, the Barrow exponent should be inside the bound $\Delta\lesssim 1.4\times 10^{-4}$ in order not to spoil the BBN epoch, which shows that the deformation from standard Bekenstein-Hawking expression should be small as expected. |
1411.1935 | Golam Mortuza Hossain | Golam Mortuza Hossain and Gopal Sardar | Absence of Unruh effect in polymer quantization | 6 pages, 1 figure; v2 with improved discussions and notation; several
new references added; published in CQG with a slightly different title but
the same results | Class.Quant.Grav.33:245016,2016 | 10.1088/0264-9381/33/24/245016 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Unruh effect is a landmark prediction of standard quantum field theory in
which Fock vacuum state appears as a thermal state with respect to an uniformly
accelerating observer. Given its dependence on trans-Planckian modes, Unruh
effect is often considered as an arena for exploring a candidate theory of
quantum gravity. Here we show that Unruh effect disappears if, instead of using
Fock quantization, one uses polymer quantization or loop quantization, the
quantization method used in loop quantum gravity. Secondly, the polymer vacuum
state remains a vacuum state even for the accelerating observer in the sense
that expectation value of number density operator in it remains zero. Finally,
if experimental measurement of Unruh effect is ever possible then it may be
used either to verify or rule out a theory of quantum gravity.
| [
{
"created": "Fri, 7 Nov 2014 14:38:47 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Dec 2016 05:39:21 GMT",
"version": "v2"
}
] | 2016-12-07 | [
[
"Hossain",
"Golam Mortuza",
""
],
[
"Sardar",
"Gopal",
""
]
] | Unruh effect is a landmark prediction of standard quantum field theory in which Fock vacuum state appears as a thermal state with respect to an uniformly accelerating observer. Given its dependence on trans-Planckian modes, Unruh effect is often considered as an arena for exploring a candidate theory of quantum gravity. Here we show that Unruh effect disappears if, instead of using Fock quantization, one uses polymer quantization or loop quantization, the quantization method used in loop quantum gravity. Secondly, the polymer vacuum state remains a vacuum state even for the accelerating observer in the sense that expectation value of number density operator in it remains zero. Finally, if experimental measurement of Unruh effect is ever possible then it may be used either to verify or rule out a theory of quantum gravity. |
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