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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0702055 | Joe Polchinski | Joseph Polchinski and Jorge V. Rocha | Cosmic String Structure at the Gravitational Radiation Scale | 15 pages, 1 figure. v2, v3: small corrections, updated references | Phys.Rev.D75:123503,2007 | 10.1103/PhysRevD.75.123503 | null | gr-qc astro-ph hep-ph hep-th | null | We use our model of the small scale structure on cosmic strings to develop
further the result of Siemens, Olum, and Vilenkin that the gravitational
radiation length scale on cosmic strings is smaller than the previously assumed
$\Gamma G\mu t$. We discuss some of the properties of cosmic string loops at
this cutoff scale, and we argue that recent network simulations point to two
populations of cosmic string loops, one near the horizon scale and one near the
gravitational radiation cutoff.
| [
{
"created": "Fri, 9 Feb 2007 03:40:34 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Mar 2007 01:25:54 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Polchinski",
"Joseph",
""
],
[
"Rocha",
"Jorge V.",
""
]
] | We use our model of the small scale structure on cosmic strings to develop further the result of Siemens, Olum, and Vilenkin that the gravitational radiation length scale on cosmic strings is smaller than the previously assumed $\Gamma G\mu t$. We discuss some of the properties of cosmic string loops at this cutoff scale, and we argue that recent network simulations point to two populations of cosmic string loops, one near the horizon scale and one near the gravitational radiation cutoff. |
0811.1478 | Aleksandar Rakic | Aleksandar Rakic and Dominik J. Schwarz | General Relativistic Rotation Curves in a Post-Newtonian Light | 5 pages PoS style, no figures, talk given at the Identification of
Dark Matter conference (idm2008) Stockholm, 18-22 August 2008 | PoS idm2008:096,2008 | null | BI-TP 2008/36 | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The missing of a Keplerian fall-off in the observed galaxy rotation curves
represents classical evidence for the existence of dark matter on galactic
scales. There has been some recent activity concerning the potential of
modelling galactic systems with the help of general relativity. This was
motivated by claims that by the use of full general relativity dark matter
could be made superfluous. Here we focus on possible axisymmetric and
stationary solutions of Einstein's equations with rotating dust. After a short
review of the current debate we pursue the idea of approaching such
relativistic models in a Newtonian language. We analyse rigidly as well as
differentially rotating Newtonian and Post-Newtonian spacetimes and find that
it is necessary to incorporate a Post-Newtonian term in order to make physical
sense.
| [
{
"created": "Mon, 10 Nov 2008 14:26:07 GMT",
"version": "v1"
}
] | 2010-02-17 | [
[
"Rakic",
"Aleksandar",
""
],
[
"Schwarz",
"Dominik J.",
""
]
] | The missing of a Keplerian fall-off in the observed galaxy rotation curves represents classical evidence for the existence of dark matter on galactic scales. There has been some recent activity concerning the potential of modelling galactic systems with the help of general relativity. This was motivated by claims that by the use of full general relativity dark matter could be made superfluous. Here we focus on possible axisymmetric and stationary solutions of Einstein's equations with rotating dust. After a short review of the current debate we pursue the idea of approaching such relativistic models in a Newtonian language. We analyse rigidly as well as differentially rotating Newtonian and Post-Newtonian spacetimes and find that it is necessary to incorporate a Post-Newtonian term in order to make physical sense. |
gr-qc/9511060 | Richard Epp | Richard J. Epp | The Symplectic Structure of General Relativity in the Double-Null (2+2)
Formalism | 14 pages, LaTeX. Four figures available by FAX from
repp@dirac.ucdavis.edu | null | null | UCD-PHY-95-40 | gr-qc | null | In the (2+2) formulation of general relativity spacetime is foliated by a
two-parameter family of spacelike 2-surfaces (instead of the more usual
one-parameter family of spacelike 3-surfaces). In a partially gauge-fixed
setting (double-null gauge), I write down the symplectic structure of general
relativity in terms of intrinsic and extrinsic quantities associated with these
2-surfaces. This leads to an identification of the reduced phase space degrees
of freedom. In particular, I show that the two physical degrees of freedom of
general relativity are naturally encoded in a quantity closely related to the
twist of the pair of null normals to the 2-surfaces. By considering the
characteristic initial-value problem I establish a canonical transformation
between these and the more usually quoted conformal 2-metric (or shear) degrees
of freedom. (This paper is based on a talk given at the Fifth Midwest
Relativity Conference, Milwaukee, USA.)
| [
{
"created": "Wed, 22 Nov 1995 04:36:30 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"Epp",
"Richard J.",
""
]
] | In the (2+2) formulation of general relativity spacetime is foliated by a two-parameter family of spacelike 2-surfaces (instead of the more usual one-parameter family of spacelike 3-surfaces). In a partially gauge-fixed setting (double-null gauge), I write down the symplectic structure of general relativity in terms of intrinsic and extrinsic quantities associated with these 2-surfaces. This leads to an identification of the reduced phase space degrees of freedom. In particular, I show that the two physical degrees of freedom of general relativity are naturally encoded in a quantity closely related to the twist of the pair of null normals to the 2-surfaces. By considering the characteristic initial-value problem I establish a canonical transformation between these and the more usually quoted conformal 2-metric (or shear) degrees of freedom. (This paper is based on a talk given at the Fifth Midwest Relativity Conference, Milwaukee, USA.) |
0708.2690 | Muhammad Sharif | M. Sharif and Umber Sheikh | Effects of Schwarzschild Black Hole Horizon on Isothermal Plasma Wave
Dispersion | 23 pages, 8 figures accepted for publication in Gen. Relat. Grav | Gen.Rel.Grav.39:2095-2124,2007 | 10.1007/s10714-007-0505-4 | null | gr-qc astro-ph | null | The 3+1 GRMHD equations for Schwarzschild spacetime in Rindler coordinates
with isothermal state of plasma are formulated. We consider the cases of
non-rotating and rotating backgrounds with non-magnetized and magnetized
plasmas. For these cases, the perturbed form of these equations are linearized
and Fourier analyzed by introducing plane wave type solutions. The determinant
of these equations in each case leads to two dispersion relations which give
value of the wave number $k$. Using the wave number, we obtain information like
phase and group velocities etc. which help to discuss the nature of the waves
and their characteristics. These provide interesting information about the
black hole magnetosphere near the horizon. There are cases of normal and
anomalous dispersion. We find a case of normal dispersion of waves when the
plasma admits the properties of Veselago medium. Our results agree with those
of Mackay et al. according to which rotation of a black hole is required for
negative phase velocity propagation.
| [
{
"created": "Mon, 20 Aug 2007 12:42:08 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Sharif",
"M.",
""
],
[
"Sheikh",
"Umber",
""
]
] | The 3+1 GRMHD equations for Schwarzschild spacetime in Rindler coordinates with isothermal state of plasma are formulated. We consider the cases of non-rotating and rotating backgrounds with non-magnetized and magnetized plasmas. For these cases, the perturbed form of these equations are linearized and Fourier analyzed by introducing plane wave type solutions. The determinant of these equations in each case leads to two dispersion relations which give value of the wave number $k$. Using the wave number, we obtain information like phase and group velocities etc. which help to discuss the nature of the waves and their characteristics. These provide interesting information about the black hole magnetosphere near the horizon. There are cases of normal and anomalous dispersion. We find a case of normal dispersion of waves when the plasma admits the properties of Veselago medium. Our results agree with those of Mackay et al. according to which rotation of a black hole is required for negative phase velocity propagation. |
1810.00886 | Raimon Luna | Raimon Luna, Miguel Zilh\~ao, Vitor Cardoso, Jo\~ao L. Costa, Jos\'e
Nat\'ario | Strong cosmic censorship: The nonlinear story | 9 pages, 8 figures. v2: Matches published version | Phys. Rev. D 99, 064014 (2019) | 10.1103/PhysRevD.99.064014 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A satisfactory formulation of the laws of physics entails that the future
evolution of a physical system should be determined from appropriate initial
conditions. The existence of Cauchy horizons in solutions of the Einstein field
equations is therefore problematic, and expected to be an unstable artifact of
General Relativity. This is asserted by the Strong Cosmic Censorship
Conjecture, which was recently put into question by an analysis of the
linearized equations in the exterior of charged black holes in an expanding
universe. Here, we numerically evolve the nonlinear Einstein-Maxwell-scalar
field equations with a positive cosmological constant, under spherical
symmetry, and provide strong evidence that mass inflation indeed does not occur
in the near extremal regime. This shows that nonlinear effects might not
suffice to save the Strong Cosmic Censorship Conjecture.
| [
{
"created": "Mon, 1 Oct 2018 18:00:03 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Mar 2019 19:25:12 GMT",
"version": "v2"
}
] | 2019-03-27 | [
[
"Luna",
"Raimon",
""
],
[
"Zilhão",
"Miguel",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Costa",
"João L.",
""
],
[
"Natário",
"José",
""
]
] | A satisfactory formulation of the laws of physics entails that the future evolution of a physical system should be determined from appropriate initial conditions. The existence of Cauchy horizons in solutions of the Einstein field equations is therefore problematic, and expected to be an unstable artifact of General Relativity. This is asserted by the Strong Cosmic Censorship Conjecture, which was recently put into question by an analysis of the linearized equations in the exterior of charged black holes in an expanding universe. Here, we numerically evolve the nonlinear Einstein-Maxwell-scalar field equations with a positive cosmological constant, under spherical symmetry, and provide strong evidence that mass inflation indeed does not occur in the near extremal regime. This shows that nonlinear effects might not suffice to save the Strong Cosmic Censorship Conjecture. |
gr-qc/0401114 | Chris Van Den Broeck | Abhay Ashtekar, Jonathan Engle, Tomasz Pawlowski, and Chris Van Den
Broeck | Multipole Moments of Isolated Horizons | 25 pages, 1 figure. Minor typos corrected, reference added | Class.Quant.Grav. 21 (2004) 2549-2570 | 10.1088/0264-9381/21/11/003 | CGPG 2004-01/3 | gr-qc hep-th | null | To every axi-symmetric isolated horizon we associate two sets of numbers,
$M_n$ and $J_n$ with $n = 0, 1, 2, ...$, representing its mass and angular
momentum multipoles. They provide a diffeomorphism invariant characterization
of the horizon geometry. Physically, they can be thought of as the `source
multipoles' of black holes in equilibrium. These structures have a variety of
potential applications ranging from equations of motion of black holes and
numerical relativity to quantum gravity.
| [
{
"created": "Wed, 28 Jan 2004 19:21:13 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Oct 2004 18:19:40 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Engle",
"Jonathan",
""
],
[
"Pawlowski",
"Tomasz",
""
],
[
"Broeck",
"Chris Van Den",
""
]
] | To every axi-symmetric isolated horizon we associate two sets of numbers, $M_n$ and $J_n$ with $n = 0, 1, 2, ...$, representing its mass and angular momentum multipoles. They provide a diffeomorphism invariant characterization of the horizon geometry. Physically, they can be thought of as the `source multipoles' of black holes in equilibrium. These structures have a variety of potential applications ranging from equations of motion of black holes and numerical relativity to quantum gravity. |
2301.02534 | Luis Cesar Nunes Dos Santos | L. C. N. Santos, F. M. da Silva, C. E. Mota, I. P. Lobo, V. B. Bezerra | Kiselev black holes in $f(R,T)$ gravity | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain new exact solutions for the gravitational field equations in the
context of $f(R,T)$ gravity, thereby obtaining different classes of black holes
surrounded by fluids, taking into account some specific values of the parameter
of the equations of state, $w$. In order to obtain these solutions in the
context of $f(R,T)$ gravity, we consider viable particular choices of the
$f(R,T)$. Considering an anisotropic energy-momentum tensor, we write the field
equations with the required symmetries for this type of solution. Then, we
analyze the conditions of energy in a general way and also for particular
values of the parameter $w$ of the equation of state. In addition,
thermodynamic quantities, such as Hawking temperature and mass associated to
the horizons of solutions, are taken into account in our analysis.
| [
{
"created": "Thu, 5 Jan 2023 13:18:32 GMT",
"version": "v1"
}
] | 2023-01-09 | [
[
"Santos",
"L. C. N.",
""
],
[
"da Silva",
"F. M.",
""
],
[
"Mota",
"C. E.",
""
],
[
"Lobo",
"I. P.",
""
],
[
"Bezerra",
"V. B.",
""
]
] | We obtain new exact solutions for the gravitational field equations in the context of $f(R,T)$ gravity, thereby obtaining different classes of black holes surrounded by fluids, taking into account some specific values of the parameter of the equations of state, $w$. In order to obtain these solutions in the context of $f(R,T)$ gravity, we consider viable particular choices of the $f(R,T)$. Considering an anisotropic energy-momentum tensor, we write the field equations with the required symmetries for this type of solution. Then, we analyze the conditions of energy in a general way and also for particular values of the parameter $w$ of the equation of state. In addition, thermodynamic quantities, such as Hawking temperature and mass associated to the horizons of solutions, are taken into account in our analysis. |
2301.04826 | Srashti Goyal | Srashti Goyal and Aditya Vijaykumar and Jose Maria Ezquiaga and Miguel
Zumalacarregui | Probing lens-induced gravitational-wave birefringence as a test of
general relativity | 18 pages, 10 figures | Phys. Rev. D 108, 024052 2023 | 10.1103/PhysRevD.108.024052 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | Theories beyond general relativity (GR) modify the propagation of
gravitational waves (GWs). In some, inhomogeneities (aka. gravitational lenses)
allow interactions between the metric and additional fields to cause
lens-induced birefringence (LIB): a different speed of the two linear GW
polarisations ($+$ and $\times$). Inhomogeneities then act as non-isotropic
crystals, splitting the GW signal into two components whose relative time delay
depends on the theory and lens parameters. Here we study the observational
prospects for GW scrambling, i.e when the time delay between both GW
polarisations is smaller than the signal's duration and the waveform recorded
by a detector is distorted. We analyze the latest LIGO-Virgo-KAGRA catalog,
GWTC-3, and find no conclusive evidence for LIB. The highest log Bayes factor
that we find in favour of LIB is $3.21$ for GW$190521$, a particularly loud but
short event. However, when accounting for false alarms due to (Gaussian) noise
fluctuations, this evidence is below 1-$\sigma$. The tightest constraint on the
time delay is $<0.51$ ms (90% C.L.) from GW$200311\_115853$. From the
non-observation of GW scrambling, we constrain the optical depth for LIB,
accounting for the chance of randomly distributed lenses (eg. galaxies) along
the line of sight. Our LIB constraints on a (quartic) scalar-tensor Horndeski
theory are more stringent than solar system tests for a wide parameter range
and comparable to GW170817 in some limits. Interpreting GW190521 as an AGN
binary (i.e. taking an AGN flare as a counterpart) allows even more stringent
constraints. Our results demonstrate the potential and high sensitivity
achievable by tests of GR, based on GW lensing.
| [
{
"created": "Thu, 12 Jan 2023 06:07:35 GMT",
"version": "v1"
}
] | 2023-07-25 | [
[
"Goyal",
"Srashti",
""
],
[
"Vijaykumar",
"Aditya",
""
],
[
"Ezquiaga",
"Jose Maria",
""
],
[
"Zumalacarregui",
"Miguel",
""
]
] | Theories beyond general relativity (GR) modify the propagation of gravitational waves (GWs). In some, inhomogeneities (aka. gravitational lenses) allow interactions between the metric and additional fields to cause lens-induced birefringence (LIB): a different speed of the two linear GW polarisations ($+$ and $\times$). Inhomogeneities then act as non-isotropic crystals, splitting the GW signal into two components whose relative time delay depends on the theory and lens parameters. Here we study the observational prospects for GW scrambling, i.e when the time delay between both GW polarisations is smaller than the signal's duration and the waveform recorded by a detector is distorted. We analyze the latest LIGO-Virgo-KAGRA catalog, GWTC-3, and find no conclusive evidence for LIB. The highest log Bayes factor that we find in favour of LIB is $3.21$ for GW$190521$, a particularly loud but short event. However, when accounting for false alarms due to (Gaussian) noise fluctuations, this evidence is below 1-$\sigma$. The tightest constraint on the time delay is $<0.51$ ms (90% C.L.) from GW$200311\_115853$. From the non-observation of GW scrambling, we constrain the optical depth for LIB, accounting for the chance of randomly distributed lenses (eg. galaxies) along the line of sight. Our LIB constraints on a (quartic) scalar-tensor Horndeski theory are more stringent than solar system tests for a wide parameter range and comparable to GW170817 in some limits. Interpreting GW190521 as an AGN binary (i.e. taking an AGN flare as a counterpart) allows even more stringent constraints. Our results demonstrate the potential and high sensitivity achievable by tests of GR, based on GW lensing. |
2009.02579 | Hang Yu | Hang Yu and Yanbei Chen | Direct determination of supermassive black hole properties with
gravitational-wave radiation from surrounding stellar-mass black hole
binaries | 5 pages (main text excluding references), 5 figures; accepted for
publication in PRL | Phys. Rev. Lett. 126, 021101 (2021) | 10.1103/PhysRevLett.126.021101 | null | gr-qc astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A significant number of stellar-mass black-hole (BH) binaries may merge in
galactic nuclei or in the surrounding gas disks. With purposed space-borne
gravitational-wave observatories, we may use such a binary as a signal carrier
to probe modulations induced by a central supermassive BH (SMBH), which further
allows us to place constraints on the SMBH's properties. We show in particular
the de Sitter precession of the inner stellar-mass binary's orbital angular
momentum (AM) around the AM of the outer orbit will be detectable if the
precession period is comparable to the duration of observation, typically a few
years. Once detected, the precession can be combined with the Doppler shift
arising from the outer orbital motion to determine the mass of the SMBH and the
outer orbital separation individually and each with percent-level accuracy. If
we further assume a joint detection by space-borne and ground-based detectors,
the detectability threshold could be extended to a precession period of ~100
yr.
| [
{
"created": "Sat, 5 Sep 2020 18:20:23 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Dec 2020 21:41:56 GMT",
"version": "v2"
}
] | 2021-01-20 | [
[
"Yu",
"Hang",
""
],
[
"Chen",
"Yanbei",
""
]
] | A significant number of stellar-mass black-hole (BH) binaries may merge in galactic nuclei or in the surrounding gas disks. With purposed space-borne gravitational-wave observatories, we may use such a binary as a signal carrier to probe modulations induced by a central supermassive BH (SMBH), which further allows us to place constraints on the SMBH's properties. We show in particular the de Sitter precession of the inner stellar-mass binary's orbital angular momentum (AM) around the AM of the outer orbit will be detectable if the precession period is comparable to the duration of observation, typically a few years. Once detected, the precession can be combined with the Doppler shift arising from the outer orbital motion to determine the mass of the SMBH and the outer orbital separation individually and each with percent-level accuracy. If we further assume a joint detection by space-borne and ground-based detectors, the detectability threshold could be extended to a precession period of ~100 yr. |
gr-qc/0611042 | Sergey S. Kokarev | Sergey S. Kokarev and Vladimir G. Krechet | Time-dependent Spherically-symmetric 5-D Vacuum Solutions | null | Grav.Cosmol.2:99-106,1996 | null | null | gr-qc | null | Vacuum 5-D Einstein equations with spherical symmetry and t-dependence are
considered. For the case of separating variables several classes of exact
solutions are obtained. Effective matter, induced by geometrical scalar field
is analyzed.
| [
{
"created": "Mon, 6 Nov 2006 17:45:09 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kokarev",
"Sergey S.",
""
],
[
"Krechet",
"Vladimir G.",
""
]
] | Vacuum 5-D Einstein equations with spherical symmetry and t-dependence are considered. For the case of separating variables several classes of exact solutions are obtained. Effective matter, induced by geometrical scalar field is analyzed. |
2404.11984 | Subenoy Chakraborty | Ayanendu Dutta, Dhritimalya Roy, Subenoy Chakraborty | Particle motion around traversable wormholes: Possibility of closed
timelike geodesics | 12 pages, 7 figures, 1 table. Accepted in New Astronomy | New Astron. 111, 102236 (2024) | 10.1016/j.newast.2024.102236 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present work investigates the general wormhole solution in Einstein
gravity with an exponential shape function around an ultrastatic and a finite
redshift geometry. The geodesic motion around the wormholes is studied in which
the deflection angle of the orbiting photon sphere is found to be negative
after a certain region, indicating the presence of repulsive effect of gravity
in both the ultrastatic and finite redshift wormholes. Various unbounded and
bounded timelike trajectories are presented on the wormhole embedding diagrams,
in which some of the bound orbits involve intersection points that may lead to
causality violating geodesics. Another class of closed timelike geodesics are
obtained in the unstable circular trajectory that appeared at the wormhole
throat. Finally, the trajectories are classified in terms of the family of CTG
orbits.
| [
{
"created": "Thu, 18 Apr 2024 08:27:03 GMT",
"version": "v1"
}
] | 2024-06-06 | [
[
"Dutta",
"Ayanendu",
""
],
[
"Roy",
"Dhritimalya",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | The present work investigates the general wormhole solution in Einstein gravity with an exponential shape function around an ultrastatic and a finite redshift geometry. The geodesic motion around the wormholes is studied in which the deflection angle of the orbiting photon sphere is found to be negative after a certain region, indicating the presence of repulsive effect of gravity in both the ultrastatic and finite redshift wormholes. Various unbounded and bounded timelike trajectories are presented on the wormhole embedding diagrams, in which some of the bound orbits involve intersection points that may lead to causality violating geodesics. Another class of closed timelike geodesics are obtained in the unstable circular trajectory that appeared at the wormhole throat. Finally, the trajectories are classified in terms of the family of CTG orbits. |
2310.12463 | Benjamin Grace | Benjamin Grace, Karl Wette, Susan M. Scott, Ling Sun | Piecewise frequency model for searches for long-transient gravitational
waves from young neutron stars | 16 pages, 11 figures, 2 tables | Phys. Rev. D 108, 123045 (2023) | 10.1103/PhysRevD.108.123045 | LIGO-P2300314 | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we characterise the performance of a new search technique
designed to be sensitive to the remnants of binary neutron star systems.
Sensitivity estimates of the new method on simulated data are competitive
against those of other work. Previous searches for a gravitational-wave signal
from a possible neutron star remnant of the binary neutron star merger event
GW170817 have focused on short ($<500$~s) and long duration (2.5~hr -- 8~day)
signals. To date, no such post-merger signal has been detected. We introduce a
new piecewise model which has the flexibility to accurately follow
gravitational-wave signals which are rapidly evolving in frequency, such as
those which may be emitted from young neutron stars born from binary neutron
star mergers or supernovae. We investigate the sensitivity and computational
cost of this piecewise model when used in a fully coherent 1800-second
$\mathcal{F}$-statistic search on simulated data containing possible signals
from the GW170817 remnant. The sensitivity of the search using the piecewise
model is determined using simulated data, with noise consistent with the LIGO
second observing run. Across a 100--2000~Hz frequency band, the model achieves
a peak sensitivity of $h_{\text{rss}}^{50\%} = 4.4 \times 10^{-23}
\text{Hz}^{-1/2}$ at 200~Hz, competitive with other methods. The computational
cost of conducting the search, over a bank of $1.1 \times 10^{12}$ templates,
is estimated at 10 days running on 100 CPU's.
| [
{
"created": "Thu, 19 Oct 2023 04:44:28 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Dec 2023 05:38:18 GMT",
"version": "v2"
}
] | 2024-01-17 | [
[
"Grace",
"Benjamin",
""
],
[
"Wette",
"Karl",
""
],
[
"Scott",
"Susan M.",
""
],
[
"Sun",
"Ling",
""
]
] | In this work we characterise the performance of a new search technique designed to be sensitive to the remnants of binary neutron star systems. Sensitivity estimates of the new method on simulated data are competitive against those of other work. Previous searches for a gravitational-wave signal from a possible neutron star remnant of the binary neutron star merger event GW170817 have focused on short ($<500$~s) and long duration (2.5~hr -- 8~day) signals. To date, no such post-merger signal has been detected. We introduce a new piecewise model which has the flexibility to accurately follow gravitational-wave signals which are rapidly evolving in frequency, such as those which may be emitted from young neutron stars born from binary neutron star mergers or supernovae. We investigate the sensitivity and computational cost of this piecewise model when used in a fully coherent 1800-second $\mathcal{F}$-statistic search on simulated data containing possible signals from the GW170817 remnant. The sensitivity of the search using the piecewise model is determined using simulated data, with noise consistent with the LIGO second observing run. Across a 100--2000~Hz frequency band, the model achieves a peak sensitivity of $h_{\text{rss}}^{50\%} = 4.4 \times 10^{-23} \text{Hz}^{-1/2}$ at 200~Hz, competitive with other methods. The computational cost of conducting the search, over a bank of $1.1 \times 10^{12}$ templates, is estimated at 10 days running on 100 CPU's. |
gr-qc/9905076 | Gaspare Carbone | Gaspare Carbone, Mauro Carfora, Annalisa Marzuoli | Invariants of spin networks with boundary in Quantum Gravity and TQFT's | 9 pages | null | null | DFNT-T 9/99 SISSA 48/99/FM | gr-qc | null | The search for classical or quantum combinatorial invariants of compact
n-dimensional manifolds (n=3,4) plays a key role both in topological field
theories and in lattice quantum gravity. We present here a generalization of
the partition function proposed by Ponzano and Regge to the case of a compact
3-dimensional simplicial pair $(M^3, \partial M^3)$. The resulting state sum
$Z[(M^3, \partial M^3)]$ contains both Racah-Wigner 6j symbols associated with
tetrahedra and Wigner 3jm symbols associated with triangular faces lying in
$\partial M^3$. The analysis of the algebraic identities associated with the
combinatorial transformations involved in the proof of the topological
invariance makes it manifest a common structure underlying the 3-dimensional
models with empty and non empty boundaries respectively. The techniques
developed in the 3-dimensional case can be further extended in order to deal
with combinatorial models in n=2,4 and possibly to establish a hierarchy among
such models. As an example we derive here a 2-dimensional closed state sum
model including suitable sums of products of double 3jm symbols, each one of
them being associated with a triangle in the surface.
| [
{
"created": "Thu, 20 May 1999 13:02:56 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Carbone",
"Gaspare",
""
],
[
"Carfora",
"Mauro",
""
],
[
"Marzuoli",
"Annalisa",
""
]
] | The search for classical or quantum combinatorial invariants of compact n-dimensional manifolds (n=3,4) plays a key role both in topological field theories and in lattice quantum gravity. We present here a generalization of the partition function proposed by Ponzano and Regge to the case of a compact 3-dimensional simplicial pair $(M^3, \partial M^3)$. The resulting state sum $Z[(M^3, \partial M^3)]$ contains both Racah-Wigner 6j symbols associated with tetrahedra and Wigner 3jm symbols associated with triangular faces lying in $\partial M^3$. The analysis of the algebraic identities associated with the combinatorial transformations involved in the proof of the topological invariance makes it manifest a common structure underlying the 3-dimensional models with empty and non empty boundaries respectively. The techniques developed in the 3-dimensional case can be further extended in order to deal with combinatorial models in n=2,4 and possibly to establish a hierarchy among such models. As an example we derive here a 2-dimensional closed state sum model including suitable sums of products of double 3jm symbols, each one of them being associated with a triangle in the surface. |
2211.02601 | Riasat Ali | Rimsha Babar, Muhammad Asgher and Riasat Ali | Gravitational Analysis of Einstein-Non-Linear-Maxwell-Yukawa Black Hole
under the Effect of Newman-Janis Algorithm | 12 Pages, 8 figures, Published in Physica Scripta | Phys. Scr. (2022)97: 125201 | 10.1088/1402-4896/ac9863 | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | In this paper, we analyze the rotating Einstein-non-linear-Maxwell-Yukawa
black hole solution by Janis-Newman algorithmic rule and complex calculations.
We investigate the basic properties (i.e., Hawking radiation) for the
corresponding black hole solution. From the horizon structure of the black
hole, we discuss the graphical behavior of Hawking temperature $T_H$ and
analyze the effects of spin parameter (appears due to Newman-Janis approach) on
the $T_H$ of black hole. Furthermore, we investigate the corrected temperature
for rotating Einstein-non-linear-Maxwell-Yukawa black hole by using the vector
particles tunneling strategy which is based on Hamilton-Jacobi method. We
additionally study the graphical explanation of corrected $T_H$ through outer
horizon to investigate the physical and stable conditions of black hole.
Finally, we compute the corrected entropy and check that the effect of charged,
rotation and gravity on entropy.
| [
{
"created": "Fri, 4 Nov 2022 17:16:47 GMT",
"version": "v1"
}
] | 2022-11-07 | [
[
"Babar",
"Rimsha",
""
],
[
"Asgher",
"Muhammad",
""
],
[
"Ali",
"Riasat",
""
]
] | In this paper, we analyze the rotating Einstein-non-linear-Maxwell-Yukawa black hole solution by Janis-Newman algorithmic rule and complex calculations. We investigate the basic properties (i.e., Hawking radiation) for the corresponding black hole solution. From the horizon structure of the black hole, we discuss the graphical behavior of Hawking temperature $T_H$ and analyze the effects of spin parameter (appears due to Newman-Janis approach) on the $T_H$ of black hole. Furthermore, we investigate the corrected temperature for rotating Einstein-non-linear-Maxwell-Yukawa black hole by using the vector particles tunneling strategy which is based on Hamilton-Jacobi method. We additionally study the graphical explanation of corrected $T_H$ through outer horizon to investigate the physical and stable conditions of black hole. Finally, we compute the corrected entropy and check that the effect of charged, rotation and gravity on entropy. |
1706.08886 | Jose Edgar Madriz Aguilar | Jos\'e Edgar Madriz Aguilar, J. Zamarripa, A. Peraza and J. A. Licea | $\Lambda(t)$CDM and the present accelerating expansion of the universe
from 5D scalar vacuum | 8 pages. No figures. arXiv admin note: text overlap with
arXiv:0902.4736 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter we investigate some consequences of considering our 4D
observable universe as locally and isometrically embeded into a 5D spacetime,
where gravity is described by a Brans-Dicke theory in vacuum. Once we impose
the embeding conditions we obtain that gravity on the 4D spacetime is governed
by the Einstein field equations modified by an extra term that can play the
role of a dynamical cosmological constant. Two examples were studied. In the
first we derive a cosmological model of a universe filled only with a
cosmological constant. In the second we obtain a cosmological solution
describing a universe filled with matter, radiation and a dynamical
cosmological constant, in agree with observational data. Due to the 5D
geometrical origin for the dynamical cosmological constant we interpret that
the acceleration in the expansion is explained without the introduction of a
dark energy component. Moreover, all 4D matter sources are geometrically
induced in the same manner as it is usually done in the Wesson's induced matter
theory.
| [
{
"created": "Mon, 26 Jun 2017 14:10:22 GMT",
"version": "v1"
}
] | 2017-06-28 | [
[
"Aguilar",
"José Edgar Madriz",
""
],
[
"Zamarripa",
"J.",
""
],
[
"Peraza",
"A.",
""
],
[
"Licea",
"J. A.",
""
]
] | In this letter we investigate some consequences of considering our 4D observable universe as locally and isometrically embeded into a 5D spacetime, where gravity is described by a Brans-Dicke theory in vacuum. Once we impose the embeding conditions we obtain that gravity on the 4D spacetime is governed by the Einstein field equations modified by an extra term that can play the role of a dynamical cosmological constant. Two examples were studied. In the first we derive a cosmological model of a universe filled only with a cosmological constant. In the second we obtain a cosmological solution describing a universe filled with matter, radiation and a dynamical cosmological constant, in agree with observational data. Due to the 5D geometrical origin for the dynamical cosmological constant we interpret that the acceleration in the expansion is explained without the introduction of a dark energy component. Moreover, all 4D matter sources are geometrically induced in the same manner as it is usually done in the Wesson's induced matter theory. |
1605.07630 | Rajeev Kumar Jain | Alessandro Codello, Rajeev Kumar Jain | Leading Gravitational Corrections and a Unified Universe | 5 pages, 2 figures. This essay received "Honorable Mention" in the
2016 Gravity Research Foundation Awards for Essays on Gravitation. arXiv
admin note: substantial text overlap with arXiv:1603.00028 | Int. J. Mod. Phys. D 25, 1644023 (2016) | 10.1142/S0218271816440235 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Leading order gravitational corrections to the Einstein-Hilbert action can
lead to a consistent picture of the universe by unifying the epochs of
inflation and dark energy in a single framework. While the leading local
correction induces an inflationary phase in the early universe, the leading
non-local term leads to an accelerated expansion of the universe at the present
epoch. We argue that both the leading UV and IR terms can be obtained within
the framework of a covariant effective field theory of gravity. The
perturbative gravitational corrections therefore provide a fundamental basis
for understanding a possible connection between the two epochs.
| [
{
"created": "Tue, 24 May 2016 20:00:15 GMT",
"version": "v1"
}
] | 2016-10-27 | [
[
"Codello",
"Alessandro",
""
],
[
"Jain",
"Rajeev Kumar",
""
]
] | Leading order gravitational corrections to the Einstein-Hilbert action can lead to a consistent picture of the universe by unifying the epochs of inflation and dark energy in a single framework. While the leading local correction induces an inflationary phase in the early universe, the leading non-local term leads to an accelerated expansion of the universe at the present epoch. We argue that both the leading UV and IR terms can be obtained within the framework of a covariant effective field theory of gravity. The perturbative gravitational corrections therefore provide a fundamental basis for understanding a possible connection between the two epochs. |
2404.04649 | Faisal Javed | G. Mustafa, Faisal Javed, S. K. Maurya, Abdelghani Errehymy | New embedded wormhole solutions in Ricci inverse gravity | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter, we obtain two new embedded WH solutions by using the class-I
approach in the background of newly fourth-order Ricci inverse gravity. We show
that the combination of these newly calculated shape functions and Ricci
inverse gravity provides us with the possibility of obtaining traversable
wormholes. All the required wormhole properties are discussed, along with
flaring out and flatness conditions. The embedded diagrams within the scope of
upper and lower universes are provided under the effect of both newly
calculated embedded shape functions. All the energy conditions are explored
with valid and negative regions. The presence of exotic matter is confirmed due
to the negative region in all the energy conditions, specifically in the null
energy condition. The Doppler effect through the red-blue shifts function is
also discussed. Several key findings from the current research are described
that demonstrate the validity of these wormhole solutions in Ricci inverse
gravity.
| [
{
"created": "Sat, 6 Apr 2024 14:56:02 GMT",
"version": "v1"
}
] | 2024-04-09 | [
[
"Mustafa",
"G.",
""
],
[
"Javed",
"Faisal",
""
],
[
"Maurya",
"S. K.",
""
],
[
"Errehymy",
"Abdelghani",
""
]
] | In this letter, we obtain two new embedded WH solutions by using the class-I approach in the background of newly fourth-order Ricci inverse gravity. We show that the combination of these newly calculated shape functions and Ricci inverse gravity provides us with the possibility of obtaining traversable wormholes. All the required wormhole properties are discussed, along with flaring out and flatness conditions. The embedded diagrams within the scope of upper and lower universes are provided under the effect of both newly calculated embedded shape functions. All the energy conditions are explored with valid and negative regions. The presence of exotic matter is confirmed due to the negative region in all the energy conditions, specifically in the null energy condition. The Doppler effect through the red-blue shifts function is also discussed. Several key findings from the current research are described that demonstrate the validity of these wormhole solutions in Ricci inverse gravity. |
1108.0312 | Duncan Macleod | Duncan M. Macleod, Stephen Fairhurst, Brennan Hughey, Andrew P.
Lundgren, Larne Pekowsky, Jameson Rollins, Joshua R. Smith | Reducing the effect of seismic noise in LIGO searches by targeted veto
generation | 16 pages, 5 figures | Class.Quant.Grav., 29:055006, 2012 | 10.1088/0264-9381/29/5/055006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Laser Interferometer Gravitational-Wave Observatory forms part of the
international effort to detect and study gravitational waves of astrophysical
origin. One of the major obstacles for this project with the first generation
detectors was the effect of seismic noise on instrument sensitivity -
environmental disturbances causing motion of the interferometer optics,
coupling as noise in the gravitational wave data output. Typically transient
noise events have been identified by finding coincidence between noise in an
auxiliary data signal (with negligible sensitivity to gravitational waves) and
noise in the gravitational wave data, but attempts to include seismometer
readings in this scheme have proven ineffective. We present a new method of
generating a list of times of high seismic noise by tuning a gravitational wave
burst detection pipeline to the low frequency signature of these events. This
method has proven very effective at removing transients of seismic origin from
the gravitational wave (GW) data with only a small loss of analysable time. We
also present an outline for extending this method to other noise sources.
| [
{
"created": "Mon, 1 Aug 2011 13:41:27 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Aug 2011 12:50:44 GMT",
"version": "v2"
},
{
"created": "Wed, 20 Mar 2013 16:24:19 GMT",
"version": "v3"
}
] | 2013-03-21 | [
[
"Macleod",
"Duncan M.",
""
],
[
"Fairhurst",
"Stephen",
""
],
[
"Hughey",
"Brennan",
""
],
[
"Lundgren",
"Andrew P.",
""
],
[
"Pekowsky",
"Larne",
""
],
[
"Rollins",
"Jameson",
""
],
[
"Smith",
"Joshua R.",
... | The Laser Interferometer Gravitational-Wave Observatory forms part of the international effort to detect and study gravitational waves of astrophysical origin. One of the major obstacles for this project with the first generation detectors was the effect of seismic noise on instrument sensitivity - environmental disturbances causing motion of the interferometer optics, coupling as noise in the gravitational wave data output. Typically transient noise events have been identified by finding coincidence between noise in an auxiliary data signal (with negligible sensitivity to gravitational waves) and noise in the gravitational wave data, but attempts to include seismometer readings in this scheme have proven ineffective. We present a new method of generating a list of times of high seismic noise by tuning a gravitational wave burst detection pipeline to the low frequency signature of these events. This method has proven very effective at removing transients of seismic origin from the gravitational wave (GW) data with only a small loss of analysable time. We also present an outline for extending this method to other noise sources. |
1511.03755 | Cosimo Bambi | Cosimo Bambi, Alejandro Cardenas-Avendano, Gonzalo J. Olmo, D.
Rubiera-Garcia | Wormholes and nonsingular space-times in Palatini $f(R)$ gravity | 8 pages, 2 figures | Phys. Rev. D 93, 064016 (2016) | 10.1103/PhysRevD.93.064016 | IFIC/16-58 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reconsider the problem of $f(R)$ theories of gravity coupled to
Born-Infeld theory of electrodynamics formulated in a Palatini approach, where
metric and connection are independent fields. By studying electrovacuum
configurations in a static and spherically symmetric space-time, we find
solutions which reduce to their Reissner-Nordstr\"om counterparts at large
distances but undergo important non-perturbative modifications close to the
center. Our new analysis reveals that the point-like singularity is replaced by
a finite-size wormhole structure, which provides a geodesically complete and
thus nonsingular space-time, despite the existence of curvature divergences at
the wormhole throat. Implications of these results, in particular for the
cosmic censorship conjecture, are discussed.
| [
{
"created": "Thu, 12 Nov 2015 02:07:06 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Mar 2016 21:01:16 GMT",
"version": "v2"
}
] | 2016-07-25 | [
[
"Bambi",
"Cosimo",
""
],
[
"Cardenas-Avendano",
"Alejandro",
""
],
[
"Olmo",
"Gonzalo J.",
""
],
[
"Rubiera-Garcia",
"D.",
""
]
] | We reconsider the problem of $f(R)$ theories of gravity coupled to Born-Infeld theory of electrodynamics formulated in a Palatini approach, where metric and connection are independent fields. By studying electrovacuum configurations in a static and spherically symmetric space-time, we find solutions which reduce to their Reissner-Nordstr\"om counterparts at large distances but undergo important non-perturbative modifications close to the center. Our new analysis reveals that the point-like singularity is replaced by a finite-size wormhole structure, which provides a geodesically complete and thus nonsingular space-time, despite the existence of curvature divergences at the wormhole throat. Implications of these results, in particular for the cosmic censorship conjecture, are discussed. |
1807.05029 | Masashi Kimura | Masashi Kimura | Stability analysis of Schwarzschild black holes in dynamical
Chern-Simons gravity | 10 pages, accepted for publication in PRD | null | 10.1103/PhysRevD.98.024048 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dynamical Chern-Simons gravity has an interesting feature that the parity
violating term exists, and the coupling is determined by a dynamical scalar
field. When the spacetime has spherical symmetry, the parity violating term
vanishes, and then the metric of the Schwarzschild spacetime with vanishing
scalar field is an exact solution of dynamical Chern-Simons gravity. The effect
of the Chern-Simons coupling appears in the study of perturbation around the
Schwarzschild spacetime. Due to the parity violating term, the odd parity
metric perturbation and the perturbed scalar field are coupled, and the
perturbed field equations take the form of the coupled system of the
Schr\"odinger equations. We prove linear mode stability for a generic massive
scalar.
| [
{
"created": "Fri, 13 Jul 2018 12:10:12 GMT",
"version": "v1"
}
] | 2018-08-15 | [
[
"Kimura",
"Masashi",
""
]
] | Dynamical Chern-Simons gravity has an interesting feature that the parity violating term exists, and the coupling is determined by a dynamical scalar field. When the spacetime has spherical symmetry, the parity violating term vanishes, and then the metric of the Schwarzschild spacetime with vanishing scalar field is an exact solution of dynamical Chern-Simons gravity. The effect of the Chern-Simons coupling appears in the study of perturbation around the Schwarzschild spacetime. Due to the parity violating term, the odd parity metric perturbation and the perturbed scalar field are coupled, and the perturbed field equations take the form of the coupled system of the Schr\"odinger equations. We prove linear mode stability for a generic massive scalar. |
gr-qc/9703068 | Curt Cutler | Curt Cutler | Angular Resolution of the LISA Gravitational Wave Detector | 15 pages, 5 figures, RevTex 3.0 file | Phys.Rev. D57 (1998) 7089-7102 | 10.1103/PhysRevD.57.7089 | null | gr-qc | null | We calculate the angular resolution of the planned LISA detector, a
space-based laser interferometer for measuring low-frequency gravitational
waves from galactic and extragalactic sources. LISA is not a pointed
instrument; it is an all-sky monitor with a quadrupolar beam pattern. LISA will
measure simultaneously both polarization components of incoming gravitational
waves, so the data will consist of two time series. All physical properties of
the source, including its position, must be extracted from these time series.
LISA's angular resolution is therefore not a fixed quantity, but rather depends
on the type of signal and on how much other information must be extracted.
Information about the source position will be encoded in the measured signal in
three ways: 1) through the relative amplitudes and phases of the two
polarization components, 2) through the periodic Doppler shift imposed on the
signal by the detector's motion around the Sun, and 3) through the further
modulation of the signal caused by the detector's time-varying orientation. We
derive the basic formulae required to calculate the LISA's angular resolution
$\Delta \Omega_S$ for a given source. We then evaluate $\Delta \Omega_S$ for
two sources of particular interest: monchromatic sources and mergers of
supermassive black holes. For these two types of sources, we calculate (in the
high signal-to-noise approximation) the full variance-covariance matrix, which
gives the accuracy to which all source parameters can be measured. Since our
results on LISA's angular resolution depend mainly on gross features of the
detector geometry, orbit, and noise curve, we expect these results to be fairly
insensitive to modest changes in detector design that may occur between now and
launch. We also expect that our calculations could be easily modified to apply
to a modified design.
| [
{
"created": "Mon, 24 Mar 1997 21:34:25 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Cutler",
"Curt",
""
]
] | We calculate the angular resolution of the planned LISA detector, a space-based laser interferometer for measuring low-frequency gravitational waves from galactic and extragalactic sources. LISA is not a pointed instrument; it is an all-sky monitor with a quadrupolar beam pattern. LISA will measure simultaneously both polarization components of incoming gravitational waves, so the data will consist of two time series. All physical properties of the source, including its position, must be extracted from these time series. LISA's angular resolution is therefore not a fixed quantity, but rather depends on the type of signal and on how much other information must be extracted. Information about the source position will be encoded in the measured signal in three ways: 1) through the relative amplitudes and phases of the two polarization components, 2) through the periodic Doppler shift imposed on the signal by the detector's motion around the Sun, and 3) through the further modulation of the signal caused by the detector's time-varying orientation. We derive the basic formulae required to calculate the LISA's angular resolution $\Delta \Omega_S$ for a given source. We then evaluate $\Delta \Omega_S$ for two sources of particular interest: monchromatic sources and mergers of supermassive black holes. For these two types of sources, we calculate (in the high signal-to-noise approximation) the full variance-covariance matrix, which gives the accuracy to which all source parameters can be measured. Since our results on LISA's angular resolution depend mainly on gross features of the detector geometry, orbit, and noise curve, we expect these results to be fairly insensitive to modest changes in detector design that may occur between now and launch. We also expect that our calculations could be easily modified to apply to a modified design. |
2108.07801 | Ghulam Mustafa | G. Mustafa, Ibrar Hussain, Wu-Ming Liu | Quasi Periodic Oscillations of Test Particles and Red-Blue Shifts of the
Photons Emitted By the Charged Test Particles Orbiting the Charged Black Hole
in the Presence of Quintessence and Clouds of Strings | 20 pages, 14 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Here we examine the circular motion of test particles and photons in the
spacetime geometry of charged black hole surrounded by quintessence and clouds
of strings for the equation of state parameter $\omega_q=-2/3$. We observe that
there exist stable circular orbits in this geometry for very small values of
the quintessence and string cloud parameters, i.e., $0<\gamma<<1$ and
$0<\alpha<<1$. We observe that if the values of $\gamma$ and $\alpha$ increase,
the test particle can more easily escape the gravitational field of the black
hole. While the effect of the charge $Q$ of the black hole on the effective
potential is just opposite to that of the $\gamma$ and $\alpha$. Further, we
investigate the quasi-periodic oscillations of test particles near the stable
circular orbits. With the increasing values of $Q$, the stable circular orbits
get away from the central object; therefore, one can observe lower epicyclic
frequencies away from the central gravitating source with the increase in the
values of $Q$. The redshift parameter $z$ of the photons emitted by the charged
test particles moving in the stable circular orbits around the central source
increases with an increase in the parameter $\alpha$ and decreases with an
increase in the values of the charge $Q$. In the Banados-Silk-West (BSW)
process study, we note that the centre of mass-energy at the horizon of this
Riessner-Nordstrom black hole with quintessence and string clouds increases
indefinitely if the charge of one of the colliding particles attains its
critical value. For a better understanding of the study, we show the dependence
of the radii of the circular orbits, energy and angular momentum of the
particles, effective potential, effective force, quasi-periodic oscillations
and red-blue shifts of photons of the test particles in the circular orbits on
the parameters $\alpha$, $\gamma$ and $Q$ graphically.
| [
{
"created": "Mon, 16 Aug 2021 20:10:39 GMT",
"version": "v1"
}
] | 2021-08-19 | [
[
"Mustafa",
"G.",
""
],
[
"Hussain",
"Ibrar",
""
],
[
"Liu",
"Wu-Ming",
""
]
] | Here we examine the circular motion of test particles and photons in the spacetime geometry of charged black hole surrounded by quintessence and clouds of strings for the equation of state parameter $\omega_q=-2/3$. We observe that there exist stable circular orbits in this geometry for very small values of the quintessence and string cloud parameters, i.e., $0<\gamma<<1$ and $0<\alpha<<1$. We observe that if the values of $\gamma$ and $\alpha$ increase, the test particle can more easily escape the gravitational field of the black hole. While the effect of the charge $Q$ of the black hole on the effective potential is just opposite to that of the $\gamma$ and $\alpha$. Further, we investigate the quasi-periodic oscillations of test particles near the stable circular orbits. With the increasing values of $Q$, the stable circular orbits get away from the central object; therefore, one can observe lower epicyclic frequencies away from the central gravitating source with the increase in the values of $Q$. The redshift parameter $z$ of the photons emitted by the charged test particles moving in the stable circular orbits around the central source increases with an increase in the parameter $\alpha$ and decreases with an increase in the values of the charge $Q$. In the Banados-Silk-West (BSW) process study, we note that the centre of mass-energy at the horizon of this Riessner-Nordstrom black hole with quintessence and string clouds increases indefinitely if the charge of one of the colliding particles attains its critical value. For a better understanding of the study, we show the dependence of the radii of the circular orbits, energy and angular momentum of the particles, effective potential, effective force, quasi-periodic oscillations and red-blue shifts of photons of the test particles in the circular orbits on the parameters $\alpha$, $\gamma$ and $Q$ graphically. |
gr-qc/0603060 | Serguei Krasnikov | S. Krasnikov | Superluminal motion in (semi)classical relativity | Pedagogical review. In Russian | null | null | null | gr-qc astro-ph physics.space-ph | null | The possibility is discussed of superluminal motion of non-tachyonic (i.e.
moving with the instantaneous speed v<c) bodies within general relativity. It
is shown that in some occasions quantum field theory apparently prohibits such
motion, but not - to all appearance - in the general case.
| [
{
"created": "Wed, 15 Mar 2006 16:16:31 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Krasnikov",
"S.",
""
]
] | The possibility is discussed of superluminal motion of non-tachyonic (i.e. moving with the instantaneous speed v<c) bodies within general relativity. It is shown that in some occasions quantum field theory apparently prohibits such motion, but not - to all appearance - in the general case. |
gr-qc/9802071 | C. H. Woo | Shu-Yuan Chu | Is It Possible to Disentangle an Entangled Quantum State? | 5 pages; TeX | null | null | UCR HEP-T184 | gr-qc hep-ph hep-th quant-ph | null | Experimental tests of the suggestion that the generalization of Wheeler and
Feynman's time symmetric system is the dynamical basis underlying quantum
mechanics are considered. In a time-symmetric system, the instantaneous
correlations exhibited by two spatially separated particles in an entangled
state can be established through other particles, and can reveal advanced
interaction effects. In particular, the existence of advanced gravity waves may
be detectable through suitable arrangements at the Laser Interferometer
Gravitation- Wave Observatory.
| [
{
"created": "Fri, 27 Feb 1998 21:18:40 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Chu",
"Shu-Yuan",
""
]
] | Experimental tests of the suggestion that the generalization of Wheeler and Feynman's time symmetric system is the dynamical basis underlying quantum mechanics are considered. In a time-symmetric system, the instantaneous correlations exhibited by two spatially separated particles in an entangled state can be established through other particles, and can reveal advanced interaction effects. In particular, the existence of advanced gravity waves may be detectable through suitable arrangements at the Laser Interferometer Gravitation- Wave Observatory. |
2303.05986 | Sophie BIni | Sophie Bini, Gabriele Vedovato, Marco Drago, Francesco Salemi,
Giovanni Andrea Prodi | An autoencoder neural network integrated into gravitational-wave burst
searches to improve the rejection of noise transients | 19 pages, 7 figures, submitted to Classical and Quantum Gravity | null | 10.1088/1361-6382/acd981 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The gravitational-wave (GW) detector data are affected by short-lived
instrumental or terrestrial transients, called glitches, which can simulate GW
signals. Mitigation of glitches is particularly difficult for algorithms which
target generic sources of short-duration GW transients (GWT), and do not rely
on GW waveform models to distinguish astrophysical signals from noise, such as
Coherent WaveBurst (cWB). This work is part of the long-term effort to mitigate
transient noises in cWB, which led to the introduction of specific estimators,
and a machine-learning based signal-noise classification algorithm. Here, we
propose an autoencoder neural network, integrated into cWB, that learns
transient noises morphologies from GW time-series. We test its performance on
the glitch family known as blip. The resulting sensitivity to generic GWT and
binary black hole mergers significantly improves when tested on LIGO detectors
data from the last observation period (O3b). At false alarm rate of one event
per 50 years the sensitivity volume increases up to 30% for signal morphologies
similar to blip glitches. In perspective, this tool can adapt to classify
different transient noise classes that may affect future observing runs,
enhancing GWT searches.
| [
{
"created": "Fri, 10 Mar 2023 15:42:03 GMT",
"version": "v1"
}
] | 2023-06-21 | [
[
"Bini",
"Sophie",
""
],
[
"Vedovato",
"Gabriele",
""
],
[
"Drago",
"Marco",
""
],
[
"Salemi",
"Francesco",
""
],
[
"Prodi",
"Giovanni Andrea",
""
]
] | The gravitational-wave (GW) detector data are affected by short-lived instrumental or terrestrial transients, called glitches, which can simulate GW signals. Mitigation of glitches is particularly difficult for algorithms which target generic sources of short-duration GW transients (GWT), and do not rely on GW waveform models to distinguish astrophysical signals from noise, such as Coherent WaveBurst (cWB). This work is part of the long-term effort to mitigate transient noises in cWB, which led to the introduction of specific estimators, and a machine-learning based signal-noise classification algorithm. Here, we propose an autoencoder neural network, integrated into cWB, that learns transient noises morphologies from GW time-series. We test its performance on the glitch family known as blip. The resulting sensitivity to generic GWT and binary black hole mergers significantly improves when tested on LIGO detectors data from the last observation period (O3b). At false alarm rate of one event per 50 years the sensitivity volume increases up to 30% for signal morphologies similar to blip glitches. In perspective, this tool can adapt to classify different transient noise classes that may affect future observing runs, enhancing GWT searches. |
1103.6168 | Trevor W. Marshall | Trevor W. Marshall | Fields tell matter how to move | 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Starting from the Oppenheimer-Snyder solution for gravitational collapse, we
show by putting it into the harmonic coordinates, for which the distant Riemann
metric is galilean, that the final state of collapse for a collapsed star of
any mass, including the one thought to occupy the centre of our galaxy, has a
finite radius roughly equal to its Schwarzschild radius. By applying an
expression for the gravitational energy tensor, we are able to explain the
concentration of stellar material in a thin shell close to the surface, which
gives an explanation for why such a star does not undergo further collapse to a
black hole. The interior of the star is characterized by a low density of the
original stellar material, but, far from being empty, this region is occupied
by a very high density of gravitational energy; this density is negative and
the consequent repulsion is what produces the surface concentration of stellar
material.
| [
{
"created": "Thu, 31 Mar 2011 13:12:05 GMT",
"version": "v1"
}
] | 2011-04-01 | [
[
"Marshall",
"Trevor W.",
""
]
] | Starting from the Oppenheimer-Snyder solution for gravitational collapse, we show by putting it into the harmonic coordinates, for which the distant Riemann metric is galilean, that the final state of collapse for a collapsed star of any mass, including the one thought to occupy the centre of our galaxy, has a finite radius roughly equal to its Schwarzschild radius. By applying an expression for the gravitational energy tensor, we are able to explain the concentration of stellar material in a thin shell close to the surface, which gives an explanation for why such a star does not undergo further collapse to a black hole. The interior of the star is characterized by a low density of the original stellar material, but, far from being empty, this region is occupied by a very high density of gravitational energy; this density is negative and the consequent repulsion is what produces the surface concentration of stellar material. |
gr-qc/9704074 | Don Koks | Don Koks, B. L. Hu, Andrew Matacz, Alpan Raval | Thermal Particle Creation in Cosmological Spacetimes: A Stochastic
Approach | 17 pages, revtex (aps, eqsecnum), submitted to PRD, April 1997 | Phys.Rev.D56:4905-4915,1997; Erratum-ibid.D57:1317,1998 | 10.1103/PhysRevD.56.4905 10.1103/PhysRevD.57.1317 | UMDPP 96-116 | gr-qc | null | The stochastic method based on the influence functional formalism introduced
in an earlier paper to treat particle creation in near-uniformly accelerated
detectors and collapsing masses is applied here to treat thermal and
near-thermal radiance in certain types of cosmological expansions. It is
indicated how the appearance of thermal radiance in different cosmological
spacetimes and in the two apparently distinct classes of black hole and
cosmological spacetimes can be understood under a unifying conceptual and
methodological framework.
| [
{
"created": "Sun, 27 Apr 1997 03:48:00 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Koks",
"Don",
""
],
[
"Hu",
"B. L.",
""
],
[
"Matacz",
"Andrew",
""
],
[
"Raval",
"Alpan",
""
]
] | The stochastic method based on the influence functional formalism introduced in an earlier paper to treat particle creation in near-uniformly accelerated detectors and collapsing masses is applied here to treat thermal and near-thermal radiance in certain types of cosmological expansions. It is indicated how the appearance of thermal radiance in different cosmological spacetimes and in the two apparently distinct classes of black hole and cosmological spacetimes can be understood under a unifying conceptual and methodological framework. |
1003.3942 | Giovanni Amelino-Camelia | Giovanni Amelino-Camelia | Doubly-Special Relativity: Facts, Myths and Some Key Open Issues | This is the preprint version of a paper prepared for a special issue
"Feature Papers: Symmetry Concepts and Applications" of the journal Symmetry | null | 10.1142/9789814287333_0006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I report, emphasizing some key open issues and some aspects that are
particularly relevant for phenomenology, on the status of the development of
"doubly-special" relativistic ("DSR") theories with both an
observer-independent high-velocity scale and an observer-independent
small-length/large-momentum scale, possibly relevant for the
Planck-scale/quantum-gravity realm. I also give a true/false characterization
of the structure of these theories. In particular, I discuss a DSR scenario
without modification of the energy-momentum dispersion relation and without the
$\kappa$-Poincar\'e Hopf algebra, a scenario with deformed Poincar\'e
symmetries which is not a DSR scenario, some scenarios with both an invariant
length scale and an invariant velocity scale which are not DSR scenarios, and a
DSR scenario in which it is easy to verify that some observable relativistic
(but non-special-relativistic) features are insensitive to possible nonlinear
redefinitions of symmetry generators.
| [
{
"created": "Sat, 20 Mar 2010 17:33:30 GMT",
"version": "v1"
}
] | 2016-12-21 | [
[
"Amelino-Camelia",
"Giovanni",
""
]
] | I report, emphasizing some key open issues and some aspects that are particularly relevant for phenomenology, on the status of the development of "doubly-special" relativistic ("DSR") theories with both an observer-independent high-velocity scale and an observer-independent small-length/large-momentum scale, possibly relevant for the Planck-scale/quantum-gravity realm. I also give a true/false characterization of the structure of these theories. In particular, I discuss a DSR scenario without modification of the energy-momentum dispersion relation and without the $\kappa$-Poincar\'e Hopf algebra, a scenario with deformed Poincar\'e symmetries which is not a DSR scenario, some scenarios with both an invariant length scale and an invariant velocity scale which are not DSR scenarios, and a DSR scenario in which it is easy to verify that some observable relativistic (but non-special-relativistic) features are insensitive to possible nonlinear redefinitions of symmetry generators. |
1711.02273 | Rodolfo Casana R. Casana | R. Casana, A. Cavalcante, F. P. Poulis, E. B. Santos | An exact Schwarzschild-like solution in a bumblebee gravity model | 10 Latex2e pages | Phys. Rev. D 97, 104001 (2018) | 10.1103/PhysRevD.97.104001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have obtained an exact vacuum solution from a gravity sector contained in
the minimal standard-model extension. The theoretical model assumes a Riemann
spacetime coupled to the bumblebee field which is responsible for the
spontaneous Lorentz symmetry breaking. The solution achieved in a static and
spherically symmetric scenario establishes a Schwarzschild-like black hole. In
order to study the effects of the spontaneous Lorentz symmetry breaking, we
have investigated some classics tests including the advance of the perihelion,
bending of light and Shapiro's time-delay. Furthermore, we have computed some
upper-bounds from which the most stringent one attains a sensitivity at the
$10^{-13}$ level.
| [
{
"created": "Tue, 7 Nov 2017 03:46:30 GMT",
"version": "v1"
}
] | 2018-05-07 | [
[
"Casana",
"R.",
""
],
[
"Cavalcante",
"A.",
""
],
[
"Poulis",
"F. P.",
""
],
[
"Santos",
"E. B.",
""
]
] | We have obtained an exact vacuum solution from a gravity sector contained in the minimal standard-model extension. The theoretical model assumes a Riemann spacetime coupled to the bumblebee field which is responsible for the spontaneous Lorentz symmetry breaking. The solution achieved in a static and spherically symmetric scenario establishes a Schwarzschild-like black hole. In order to study the effects of the spontaneous Lorentz symmetry breaking, we have investigated some classics tests including the advance of the perihelion, bending of light and Shapiro's time-delay. Furthermore, we have computed some upper-bounds from which the most stringent one attains a sensitivity at the $10^{-13}$ level. |
2302.06140 | George Pappas Dr | Kostas Glampedakis and George Pappas | Is a black hole shadow a reliable test of the no-hair theorem? | Accepted for publication as a Regular Article in Physical Review D | Phys. Rev. D 107, 064001 (2023) | 10.1103/PhysRevD.107.064001 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Capturing the image of the shadow cast by the event horizon of an illuminated
black hole is, at the most basic level, an experiment of extreme light
deflection in a strongly curved spacetime. As such, the properties of an imaged
shadow can be used to probe the general relativistic Kerr nature of
astrophysical black holes. As an example of this prospect, it is commonly
asserted that a shadow can test the validity of the theory's famous `no hair
theorem' for the black hole's mass and spin multipole moments. In this paper,
we assess this statement by calculating the shadow's equatorial radius in
spacetimes with an arbitrary multipolar structure and within a slow rotation
approximation. We find that when moments higher than the quadrupole are taken
into account, the shadow acquires a high degree of degeneracy as a function of
the deviation from the Kerr multipole moments. The results of our analysis
suggest that dark objects with strongly non-Kerr multipolar structure could
nevertheless produce a Kerr-like shadow with its characteristic quasi-circular
shape.
| [
{
"created": "Mon, 13 Feb 2023 07:00:42 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Feb 2023 13:51:38 GMT",
"version": "v2"
}
] | 2023-03-14 | [
[
"Glampedakis",
"Kostas",
""
],
[
"Pappas",
"George",
""
]
] | Capturing the image of the shadow cast by the event horizon of an illuminated black hole is, at the most basic level, an experiment of extreme light deflection in a strongly curved spacetime. As such, the properties of an imaged shadow can be used to probe the general relativistic Kerr nature of astrophysical black holes. As an example of this prospect, it is commonly asserted that a shadow can test the validity of the theory's famous `no hair theorem' for the black hole's mass and spin multipole moments. In this paper, we assess this statement by calculating the shadow's equatorial radius in spacetimes with an arbitrary multipolar structure and within a slow rotation approximation. We find that when moments higher than the quadrupole are taken into account, the shadow acquires a high degree of degeneracy as a function of the deviation from the Kerr multipole moments. The results of our analysis suggest that dark objects with strongly non-Kerr multipolar structure could nevertheless produce a Kerr-like shadow with its characteristic quasi-circular shape. |
2104.13952 | Celio Muniz | G. Alencar, V. B. Bezerra and C. R. Muniz | Casimir Wormholes in (2+1) Dimensions with Applications to the Graphene | two figures, typos fixed | null | 10.1140/epjc/s10052-021-09734-0 | null | gr-qc cond-mat.other hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we show that wormholes in (2+1) dimensions (3-D) cannot be
sourced solely by both Casimir energy and tension, differently from what
happens in a 4-D scenario, in which case it has been shown recently, by the
direct computation of the exact shape and redshift functions of a wormhole
solution, that this is possible. We show that in a 3-D spacetime the same is
not true since the arising of at least an event horizon is inevitable. We do
the analysis for massive and massless fermions, as well as for scalar fields,
considering quasi-periodic boundary conditions and find that a possibility to
circumvent such a restriction is to introduce, besides the 3-D Casimir energy
density and tension, a cosmological constant, embedding the surface in a 4-D
manifold and applying a perpendicular weak magnetic field. This causes an
additional tension on it, which contributes to the formation of the wormhole.
Finally, we discuss the possibility of producing the condensed matter analogous
of this wormhole in a graphene sheet and analyze the electronic transport
through it.
| [
{
"created": "Wed, 28 Apr 2021 18:22:02 GMT",
"version": "v1"
},
{
"created": "Mon, 17 May 2021 12:58:20 GMT",
"version": "v2"
}
] | 2021-11-03 | [
[
"Alencar",
"G.",
""
],
[
"Bezerra",
"V. B.",
""
],
[
"Muniz",
"C. R.",
""
]
] | In this paper we show that wormholes in (2+1) dimensions (3-D) cannot be sourced solely by both Casimir energy and tension, differently from what happens in a 4-D scenario, in which case it has been shown recently, by the direct computation of the exact shape and redshift functions of a wormhole solution, that this is possible. We show that in a 3-D spacetime the same is not true since the arising of at least an event horizon is inevitable. We do the analysis for massive and massless fermions, as well as for scalar fields, considering quasi-periodic boundary conditions and find that a possibility to circumvent such a restriction is to introduce, besides the 3-D Casimir energy density and tension, a cosmological constant, embedding the surface in a 4-D manifold and applying a perpendicular weak magnetic field. This causes an additional tension on it, which contributes to the formation of the wormhole. Finally, we discuss the possibility of producing the condensed matter analogous of this wormhole in a graphene sheet and analyze the electronic transport through it. |
0705.3277 | Kevin E. Cahill | Kevin Cahill | Inflation in a Symmetric Vacuum | 4 pages | null | null | null | gr-qc | null | If in a finite universe, the tree-level vacuum is a symmetric superposition
of coherent states, in each of which the inflaton field assumes a different,
energy-minimizing mean value (vev), then the resulting energy is positive and
decreases exponentially as the volume of the universe increases. This effect
can drive inflation when that volume is small and explain part of dark energy
when it is big, but the effect is exceedingly tiny except at very early times.
| [
{
"created": "Wed, 23 May 2007 02:09:17 GMT",
"version": "v1"
}
] | 2007-05-24 | [
[
"Cahill",
"Kevin",
""
]
] | If in a finite universe, the tree-level vacuum is a symmetric superposition of coherent states, in each of which the inflaton field assumes a different, energy-minimizing mean value (vev), then the resulting energy is positive and decreases exponentially as the volume of the universe increases. This effect can drive inflation when that volume is small and explain part of dark energy when it is big, but the effect is exceedingly tiny except at very early times. |
2405.13087 | Soham Sen | Arpita Jana, Soham Sen, and Sunandan Gangopadhyay | Atom falling into a quantum corrected charged black hole and HBAR
entropy | 12 pages LATEX, comments are welcome | Phys. Rev. D 110 (2024) 026029 | 10.1103/PhysRevD.110.026029 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In an earlier analysis
\href{https://link.aps.org/doi/10.1103/PhysRevD.105.085007}{Phys. Rev. D 105
(2022) 085007}, we have explored the event of acceleration radiation for an
atom freely falling into the event horizon of a quantum-corrected Schwarzschild
black hole. We want to explore the acceleration-radiation when the atom is
freely falling into the event horizon of a charged quantum-corrected black
hole. We consider the quantum effects of the electromagnetic field along with
the gravitational field in an asymptotic safety regime. Introducing the quantum
improved Reisner-Nordstr\"{o}m metric, we have calculated the excitation
probability of a two-level atom freely falling into the event horizon of
quantum improved charged black hole. Recently, in the case of the braneworld
black hole (where the tidal charge has the same dimension as the square of the
charge of a Reissner-Nordstr\"{o}m black hole in natural units), we have
observed from the form of the transition probability that the temperature will
have no contribution in the first order of the tidal charge. We observe that
for a quantum corrected Reissner-Nordstr\"{o}m black hole, there is a
second-order contribution in the charge parameter in the temperature that can
be read off from the transition probability. Next, we calculate the HBAR
entropy in this thought experiment and show that this entropy has a leading
order Bekenstein-Hawking entropy term along with some higher order correction
terms involving logarithmic as well as fractional terms of the black hole area
due to infalling photons. We have finally investigated the validity of Wien's
displacement law and compared the critical value of the field wavelength with
the general Schwarzschild black hole and its corresponding quantum-corrected
case.
| [
{
"created": "Tue, 21 May 2024 10:51:40 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jul 2024 18:12:52 GMT",
"version": "v2"
}
] | 2024-07-31 | [
[
"Jana",
"Arpita",
""
],
[
"Sen",
"Soham",
""
],
[
"Gangopadhyay",
"Sunandan",
""
]
] | In an earlier analysis \href{https://link.aps.org/doi/10.1103/PhysRevD.105.085007}{Phys. Rev. D 105 (2022) 085007}, we have explored the event of acceleration radiation for an atom freely falling into the event horizon of a quantum-corrected Schwarzschild black hole. We want to explore the acceleration-radiation when the atom is freely falling into the event horizon of a charged quantum-corrected black hole. We consider the quantum effects of the electromagnetic field along with the gravitational field in an asymptotic safety regime. Introducing the quantum improved Reisner-Nordstr\"{o}m metric, we have calculated the excitation probability of a two-level atom freely falling into the event horizon of quantum improved charged black hole. Recently, in the case of the braneworld black hole (where the tidal charge has the same dimension as the square of the charge of a Reissner-Nordstr\"{o}m black hole in natural units), we have observed from the form of the transition probability that the temperature will have no contribution in the first order of the tidal charge. We observe that for a quantum corrected Reissner-Nordstr\"{o}m black hole, there is a second-order contribution in the charge parameter in the temperature that can be read off from the transition probability. Next, we calculate the HBAR entropy in this thought experiment and show that this entropy has a leading order Bekenstein-Hawking entropy term along with some higher order correction terms involving logarithmic as well as fractional terms of the black hole area due to infalling photons. We have finally investigated the validity of Wien's displacement law and compared the critical value of the field wavelength with the general Schwarzschild black hole and its corresponding quantum-corrected case. |
1507.01865 | M. Farasat Shamir | Adil Jhangeer, M. Farasat Shamir, Tayyaba Naz, Nazish Iftikhar | Classification of Cosmic Scale Factor via Noether Gauge Symmetries | 16 Pages | Int. J. Theor. Phys. 54(7): 2343-2353, 2015 | 10.1007/s10773-014-2456-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, a complete classification of Friedmann-Robertson-Walker (FRW)
spacetime by using approximate Noether approach is presented. Considered
spacetime is discussed for three different types of universe i.e. flat, open
and closed. Different forms of cosmic scale factor $a$ with respect to the
nature of the universe, which posses the nontrivial Noether gauge symmetries
(NGS) are reported. The perturbed Lagrangian corresponding to FRW metric in the
Noether equation is used to get Noether operators. For different types of
universe minimal and maximal set of Noether operators are reported. A list of
Noether operators are also computed which is not only independent from the
choice of the cosmic scale factor but also the choice type of universe.
Further, corresponding energy type first integral of motions are also
calculated.
| [
{
"created": "Mon, 6 Jul 2015 08:51:03 GMT",
"version": "v1"
}
] | 2015-07-08 | [
[
"Jhangeer",
"Adil",
""
],
[
"Shamir",
"M. Farasat",
""
],
[
"Naz",
"Tayyaba",
""
],
[
"Iftikhar",
"Nazish",
""
]
] | In this paper, a complete classification of Friedmann-Robertson-Walker (FRW) spacetime by using approximate Noether approach is presented. Considered spacetime is discussed for three different types of universe i.e. flat, open and closed. Different forms of cosmic scale factor $a$ with respect to the nature of the universe, which posses the nontrivial Noether gauge symmetries (NGS) are reported. The perturbed Lagrangian corresponding to FRW metric in the Noether equation is used to get Noether operators. For different types of universe minimal and maximal set of Noether operators are reported. A list of Noether operators are also computed which is not only independent from the choice of the cosmic scale factor but also the choice type of universe. Further, corresponding energy type first integral of motions are also calculated. |
2401.01354 | Bouzenada Abdelmalek . | Faizuddin Ahmed and Abdelmalek Bouzenada | Quantum dynamics of spin-0 particles in a cosmological space-time | 15 pages; 3 figures, published in NPB; arXiv admin note: text overlap
with arXiv:2312.06615, arXiv:2312.07629 | Nuclear Physics B 1000, 116490 (2024) | 10.1016/j.nuclphysb.2024.116490 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper, our focus is on investigating the impact of cosmological
constant on relativistic quantum systems comprising spin-0 scalar particles.
Our analysis centers around the Klein-Gordon equation, and we obtain both
approximate and exact analytical solutions for spin-0 particles of the quantum
system. Afterwards, we explore quantum oscillator fields by considering the
Klein-Gordon oscillator within the same space-time characterized by a
cosmological constant. We obtain an approximate expression for the energy
eigenvalue of the oscillator fields. In fact, the energy spectrum in both
scenarios are examined and show the influences of the cosmological constant and
geometry's topology. Our investigation is situated within the context of a
magnetic universe-a four-dimensional cosmological space-time recognized as the
Bonnor-Melvin universe
| [
{
"created": "Fri, 8 Dec 2023 19:44:35 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Apr 2024 10:07:02 GMT",
"version": "v2"
}
] | 2024-04-02 | [
[
"Ahmed",
"Faizuddin",
""
],
[
"Bouzenada",
"Abdelmalek",
""
]
] | In this paper, our focus is on investigating the impact of cosmological constant on relativistic quantum systems comprising spin-0 scalar particles. Our analysis centers around the Klein-Gordon equation, and we obtain both approximate and exact analytical solutions for spin-0 particles of the quantum system. Afterwards, we explore quantum oscillator fields by considering the Klein-Gordon oscillator within the same space-time characterized by a cosmological constant. We obtain an approximate expression for the energy eigenvalue of the oscillator fields. In fact, the energy spectrum in both scenarios are examined and show the influences of the cosmological constant and geometry's topology. Our investigation is situated within the context of a magnetic universe-a four-dimensional cosmological space-time recognized as the Bonnor-Melvin universe |
2404.07274 | Parthapratim Pradhan | Parthapratim Pradhan | Bekenstein-Hawking Entropy Products for NUT class of Black Holes in AdS
Space | Accepted in IJMPA | International Journal of Modern Physics A (2024) 2450044 | 10.1142/S0217751X24500441 | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | We derive the entropy product rule for
Taub-NUT~(Newman-Unti-Tamburino)-de~Sitter black hole~(BH) and
Taub-NUT--Anti-de~Sitter BH. We show that the entropy products in terms of both
the physical horizons are \emph{mass-independent}. Both \emph{perturbative}
approximation and \emph{direct} method have been considered. By introducing the
cosmological horizon we show that for Taub-NUT-de~Sitter BH, there exists a
mass-independent entropy functional relation in terms of three horizons namely
event horizon~(EH), Cauchy horizon~(CH) and cosmological horizon~(CHH) which
depends on cosmological parameter~($\Lambda$) and the NUT parameter~($N$). For
Taub-NUT-anti-de~Sitter BHs, we determine the mass-independent entropy
functional relations in terms of two physical horizons~(namely EH and CH) which
depends on only NUT parameter. Some-times some complicated functions of EH
entropy and CH entropy are also strictly mass-independent. This is plausible
only due to the new formalism developed in~\cite{wu}~[Phys. Rev. D 100,
101501(R)~(2019)] for NUT class of BHs. The formalism states that a generic
four-dimensional Taub-NUT spacetime should be described completely in terms of
three or four different types of thermodynamic hairs. They could be defined as
the Komar mass~($M=m$), the angular momentum~($J_{n}=mn$), the gravitomagnetic
charge ($N=n$), the dual~(magnetic) mass $(\tilde{M}=n)$. Finally, we could say
that this universality is mainly due to the presence of \emph{new conserved
charges $J_{N}=MN$} which is closely analogue to the Kerr-like angular momentum
$J=aM$.
| [
{
"created": "Wed, 10 Apr 2024 18:03:47 GMT",
"version": "v1"
}
] | 2024-06-04 | [
[
"Pradhan",
"Parthapratim",
""
]
] | We derive the entropy product rule for Taub-NUT~(Newman-Unti-Tamburino)-de~Sitter black hole~(BH) and Taub-NUT--Anti-de~Sitter BH. We show that the entropy products in terms of both the physical horizons are \emph{mass-independent}. Both \emph{perturbative} approximation and \emph{direct} method have been considered. By introducing the cosmological horizon we show that for Taub-NUT-de~Sitter BH, there exists a mass-independent entropy functional relation in terms of three horizons namely event horizon~(EH), Cauchy horizon~(CH) and cosmological horizon~(CHH) which depends on cosmological parameter~($\Lambda$) and the NUT parameter~($N$). For Taub-NUT-anti-de~Sitter BHs, we determine the mass-independent entropy functional relations in terms of two physical horizons~(namely EH and CH) which depends on only NUT parameter. Some-times some complicated functions of EH entropy and CH entropy are also strictly mass-independent. This is plausible only due to the new formalism developed in~\cite{wu}~[Phys. Rev. D 100, 101501(R)~(2019)] for NUT class of BHs. The formalism states that a generic four-dimensional Taub-NUT spacetime should be described completely in terms of three or four different types of thermodynamic hairs. They could be defined as the Komar mass~($M=m$), the angular momentum~($J_{n}=mn$), the gravitomagnetic charge ($N=n$), the dual~(magnetic) mass $(\tilde{M}=n)$. Finally, we could say that this universality is mainly due to the presence of \emph{new conserved charges $J_{N}=MN$} which is closely analogue to the Kerr-like angular momentum $J=aM$. |
0804.3323 | Neil J. Cornish | N. J. Cornish | Detection Strategies for Extreme Mass Ratio Inspirals | 10 pages, 4 figures, Updated for LISA 8 Symposium Proceedings | Class.Quant.Grav.28:094016,2011 | 10.1088/0264-9381/28/9/094016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The capture of compact stellar remnants by galactic black holes provides a
unique laboratory for exploring the near horizon geometry of the Kerr
spacetime, or possible departures from general relativity if the central cores
prove not to be black holes. The gravitational radiation produced by these
Extreme Mass Ratio Inspirals (EMRIs) encodes a detailed map of the black hole
geometry, and the detection and characterization of these signals is a major
scientific goal for the LISA mission. The waveforms produced are very complex,
and the signals need to be coherently tracked for hundreds to thousands of
cycles to produce a detection, making EMRI signals one of the most challenging
data analysis problems in all of gravitational wave astronomy. Estimates for
the number of templates required to perform an exhaustive grid-based
matched-filter search for these signals are astronomically large, and far out
of reach of current computational resources. Here I describe an alternative
approach that employs a hybrid between Genetic Algorithms and Markov Chain
Monte Carlo techniques, along with several time saving techniques for computing
the likelihood function. This approach has proven effective at the blind
extraction of relatively weak EMRI signals from simulated LISA data sets.
| [
{
"created": "Mon, 21 Apr 2008 14:30:45 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Aug 2008 17:56:28 GMT",
"version": "v2"
},
{
"created": "Sat, 16 Oct 2010 14:31:51 GMT",
"version": "v3"
}
] | 2011-04-22 | [
[
"Cornish",
"N. J.",
""
]
] | The capture of compact stellar remnants by galactic black holes provides a unique laboratory for exploring the near horizon geometry of the Kerr spacetime, or possible departures from general relativity if the central cores prove not to be black holes. The gravitational radiation produced by these Extreme Mass Ratio Inspirals (EMRIs) encodes a detailed map of the black hole geometry, and the detection and characterization of these signals is a major scientific goal for the LISA mission. The waveforms produced are very complex, and the signals need to be coherently tracked for hundreds to thousands of cycles to produce a detection, making EMRI signals one of the most challenging data analysis problems in all of gravitational wave astronomy. Estimates for the number of templates required to perform an exhaustive grid-based matched-filter search for these signals are astronomically large, and far out of reach of current computational resources. Here I describe an alternative approach that employs a hybrid between Genetic Algorithms and Markov Chain Monte Carlo techniques, along with several time saving techniques for computing the likelihood function. This approach has proven effective at the blind extraction of relatively weak EMRI signals from simulated LISA data sets. |
1501.01984 | Tsvi Piran | Elly Leiderschneider and Tsvi Piran | Super-Penrose collisions are inefficient - a Comment on: Black hole
fireworks: ultra-high-energy debris from super-Penrose collisions | null | null | null | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a paper posted on the arXiv a few weeks ago Berti, Brito and Cardoso
\cite{Berti+14} suggest that ultra-high-energy particles can emerge from
collisions in a black hole's ergosphere. This can happen if the process
involves a particle on an outgoing trajectory very close to the black hole.
Clearly such a particle cannot emerge from the black hole. It is argued
\cite{Berti+14} that this particle can arise in another collision. Thus the
process involves two collisions: one in which an outgoing particle is produced
extremely close to the horizon, and a second one in which energy is gained. The
real efficiency of this process should take into account, therefore, the energy
needed to produce the first particle. We show here that while this process is
kinematically possible, it requires a deposition of energy that is divergently
large compared with the energy of the escaping particle. Thus, in contradiction
to claims of infinitely high efficiencies, the efficiency of the combined
process is in fact extremely small, approaching zero for very high output
energies. Even under more general conditions than those considered in
\cite{Berti+14} the total energy gain never diverges, and is larger only by a
factor of a few than the energy gain of the original collisional Penrose
process that takes place between two infalling particles
\cite{Piran+75,PiranShaham77,Bejger+12}
| [
{
"created": "Thu, 8 Jan 2015 21:07:00 GMT",
"version": "v1"
}
] | 2015-01-13 | [
[
"Leiderschneider",
"Elly",
""
],
[
"Piran",
"Tsvi",
""
]
] | In a paper posted on the arXiv a few weeks ago Berti, Brito and Cardoso \cite{Berti+14} suggest that ultra-high-energy particles can emerge from collisions in a black hole's ergosphere. This can happen if the process involves a particle on an outgoing trajectory very close to the black hole. Clearly such a particle cannot emerge from the black hole. It is argued \cite{Berti+14} that this particle can arise in another collision. Thus the process involves two collisions: one in which an outgoing particle is produced extremely close to the horizon, and a second one in which energy is gained. The real efficiency of this process should take into account, therefore, the energy needed to produce the first particle. We show here that while this process is kinematically possible, it requires a deposition of energy that is divergently large compared with the energy of the escaping particle. Thus, in contradiction to claims of infinitely high efficiencies, the efficiency of the combined process is in fact extremely small, approaching zero for very high output energies. Even under more general conditions than those considered in \cite{Berti+14} the total energy gain never diverges, and is larger only by a factor of a few than the energy gain of the original collisional Penrose process that takes place between two infalling particles \cite{Piran+75,PiranShaham77,Bejger+12} |
gr-qc/9810035 | Shestakova Tatyana P. | V. A. Savchenko, T. P. Shestakova, G. M. Vereshkov | Quantum geometrodynamics in extended phase space - II. The Bianchi IX
model | LaTeX, 24 pages, A revised version: the comparison with the BFV
approach is given in details. For the first part of the paper, see
gr-qc/9809086 | Grav.Cosmol. 7 (2001) 102-116 | null | null | gr-qc | null | The mathematically correct approach to constructing quantum geometrodynamics
of a closed universe formulated in Part I is realized on the cosmological
Bianchi-IX model with scalar fields. The physical adequacy of the obtained
gauge-noninvariant theory to existing concepts about possible cosmological
scenarios is shown. It is demonstrated that the Wheeler-DeWitt quantum
geometrodynamics based on general quantum theoretical principles with
probability interpretation of a closed universe wave function does not exist.
The problem of the creation of the Universe is considered as a computational
problem of a quantum reduction of the singular state "Nothing" to one of
possible initial physical quantum states.
| [
{
"created": "Fri, 9 Oct 1998 12:11:17 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Nov 2000 11:24:29 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Savchenko",
"V. A.",
""
],
[
"Shestakova",
"T. P.",
""
],
[
"Vereshkov",
"G. M.",
""
]
] | The mathematically correct approach to constructing quantum geometrodynamics of a closed universe formulated in Part I is realized on the cosmological Bianchi-IX model with scalar fields. The physical adequacy of the obtained gauge-noninvariant theory to existing concepts about possible cosmological scenarios is shown. It is demonstrated that the Wheeler-DeWitt quantum geometrodynamics based on general quantum theoretical principles with probability interpretation of a closed universe wave function does not exist. The problem of the creation of the Universe is considered as a computational problem of a quantum reduction of the singular state "Nothing" to one of possible initial physical quantum states. |
gr-qc/0511141 | Eugeniu Popescu | R.B. Mann, E.M. Popescu | Scalar and tensorial topological matter coupled to (2+1)-dimensional
gravity:A.Classical theory and global charges | 40 pages | Class.Quant.Grav. 23 (2006) 3721-3746 | 10.1088/0264-9381/23/11/004 | null | gr-qc | null | We consider the coupling of scalar topological matter to (2+1)-dimensional
gravity. The matter fields consist of a 0-form scalar field and a 2-form tensor
field. We carry out a canonical analysis of the classical theory, investigating
its sectors and solutions. We show that the model admits both BTZ-like
black-hole solutions and homogeneous/inhomogeneous FRW cosmological
solutions.We also investigate the global charges associated with the model and
show that the algebra of charges is the extension of the Kac-Moody algebra for
the field-rigid gauge charges, and the Virasoro algebrafor the diffeomorphism
charges. Finally, we show that the model can be written as a generalized
Chern-Simons theory, opening the perspective for its formulation as a
generalized higher gauge theory.
| [
{
"created": "Sun, 27 Nov 2005 06:06:43 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Mann",
"R. B.",
""
],
[
"Popescu",
"E. M.",
""
]
] | We consider the coupling of scalar topological matter to (2+1)-dimensional gravity. The matter fields consist of a 0-form scalar field and a 2-form tensor field. We carry out a canonical analysis of the classical theory, investigating its sectors and solutions. We show that the model admits both BTZ-like black-hole solutions and homogeneous/inhomogeneous FRW cosmological solutions.We also investigate the global charges associated with the model and show that the algebra of charges is the extension of the Kac-Moody algebra for the field-rigid gauge charges, and the Virasoro algebrafor the diffeomorphism charges. Finally, we show that the model can be written as a generalized Chern-Simons theory, opening the perspective for its formulation as a generalized higher gauge theory. |
gr-qc/0602033 | Graham Woan | J. D. Romano and G. Woan | A principal component analysis for LISA -- the TDI connection | 7 pages, 3 figures, 1 table | Phys.Rev. D73 (2006) 102001 | 10.1103/PhysRevD.73.102001 | null | gr-qc | null | Data from the Laser Interferometer Space Antenna (LISA) is expected to be
dominated by frequency noise from its lasers. However the noise from any one
laser appears more than once in the data and there are combinations of the data
that are insensitive to this noise. These combinations, called time delay
interferometry (TDI) variables, have received careful study, and point the way
to how LISA data analysis may be performed. Here we approach the problem from
the direction of statistical inference, and show that these variables are a
direct consequence of a principal component analysis of the problem. We present
a formal analysis for a simple LISA model and show that there are eigenvectors
of the noise covariance matrix that do not depend on laser frequency noise.
Importantly, these orthogonal basis vectors correspond to linear combinations
of TDI variables. As a result we show that the likelihood function for source
parameters using LISA data can be based on TDI combinations of the data without
loss of information.
| [
{
"created": "Wed, 8 Feb 2006 18:04:22 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Romano",
"J. D.",
""
],
[
"Woan",
"G.",
""
]
] | Data from the Laser Interferometer Space Antenna (LISA) is expected to be dominated by frequency noise from its lasers. However the noise from any one laser appears more than once in the data and there are combinations of the data that are insensitive to this noise. These combinations, called time delay interferometry (TDI) variables, have received careful study, and point the way to how LISA data analysis may be performed. Here we approach the problem from the direction of statistical inference, and show that these variables are a direct consequence of a principal component analysis of the problem. We present a formal analysis for a simple LISA model and show that there are eigenvectors of the noise covariance matrix that do not depend on laser frequency noise. Importantly, these orthogonal basis vectors correspond to linear combinations of TDI variables. As a result we show that the likelihood function for source parameters using LISA data can be based on TDI combinations of the data without loss of information. |
0905.0178 | Andrey Shoom A | Shohreh Abdolrahimi, Valeri P. Frolov, and Andrey A. Shoom | Interior of a Charged Distorted Black Hole | 14 pages, 11 figures. References added, typos corrected. Some minor
changes in the text | Phys.Rev.D80:024011,2009 | 10.1103/PhysRevD.80.024011 | Alberta-Thy-07-09 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study interior of a charged, non-rotating distorted black hole. We
consider static and axisymmetric black holes, and focus on a special case when
an electrically charged distorted solution is obtained by the Harrison-Ernst
transformation from an uncharged one. We demonstrate that the Cauchy horizon of
such black hole remains regular, provided the distortion is regular at the
event horizon. The shape and the inner geometry of both the outer and inner
(Cauchy) horizons are studied. We demonstrate that there exists a duality
between the properties of the horizons. Proper time of a free fall of a test
particle moving in the interior of the distorted black hole along the symmetry
axis is calculated. We also study the property of the curvature in the inner
domain between the horizons. Simple relations between the 4D curvature
invariants and the Gaussian curvature of the outer and inner horizon surfaces
are found.
| [
{
"created": "Sat, 2 May 2009 06:22:11 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Jun 2009 00:11:33 GMT",
"version": "v2"
}
] | 2010-04-14 | [
[
"Abdolrahimi",
"Shohreh",
""
],
[
"Frolov",
"Valeri P.",
""
],
[
"Shoom",
"Andrey A.",
""
]
] | We study interior of a charged, non-rotating distorted black hole. We consider static and axisymmetric black holes, and focus on a special case when an electrically charged distorted solution is obtained by the Harrison-Ernst transformation from an uncharged one. We demonstrate that the Cauchy horizon of such black hole remains regular, provided the distortion is regular at the event horizon. The shape and the inner geometry of both the outer and inner (Cauchy) horizons are studied. We demonstrate that there exists a duality between the properties of the horizons. Proper time of a free fall of a test particle moving in the interior of the distorted black hole along the symmetry axis is calculated. We also study the property of the curvature in the inner domain between the horizons. Simple relations between the 4D curvature invariants and the Gaussian curvature of the outer and inner horizon surfaces are found. |
1204.4911 | Ricardo E. Gamboa Saravi | Ricardo E. Gamboa Saravi | Empty singularities in higher-dimensional Gravity | 13 pages | Int J Theor Phys (2012) 51:3062-3072 | 10.1007/s10773-012-1189-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the exact solution of Einstein's field equations consisting of a
($n+2$)-dimensional static and hyperplane symmetric thick slice of matter, with
constant and positive energy density $\rho$ and thickness $d$, surrounded by
two different vacua. We explicitly write down the pressure and the external
gravitational fields in terms of $\rho$ and $d$, the pressure is positive and
bounded, presenting a maximum at an asymmetrical position. And if
$\sqrt{\rho}\,d$ is small enough, the dominant energy condition is satisfied
all over the spacetime. We find that this solution presents many interesting
features. In particular, it has an empty singular boundary in one of the vacua.
| [
{
"created": "Sun, 22 Apr 2012 16:40:46 GMT",
"version": "v1"
}
] | 2012-08-21 | [
[
"Saravi",
"Ricardo E. Gamboa",
""
]
] | We study the exact solution of Einstein's field equations consisting of a ($n+2$)-dimensional static and hyperplane symmetric thick slice of matter, with constant and positive energy density $\rho$ and thickness $d$, surrounded by two different vacua. We explicitly write down the pressure and the external gravitational fields in terms of $\rho$ and $d$, the pressure is positive and bounded, presenting a maximum at an asymmetrical position. And if $\sqrt{\rho}\,d$ is small enough, the dominant energy condition is satisfied all over the spacetime. We find that this solution presents many interesting features. In particular, it has an empty singular boundary in one of the vacua. |
2307.08398 | Grigalius Taujanskas | Grigalius Taujanskas | Scattering of Maxwell potentials on curved spacetimes | 6 pages, extended abstract for arXiv:2211.14579, to appear in
Methusalem Lectures, Research Perspectives Ghent Analysis and PDE Center | null | 10.1007/978-3-031-48579-4_6 | null | gr-qc math.AP | http://creativecommons.org/licenses/by/4.0/ | We report on the recent construction of a scattering theory for Maxwell
potentials on curved spacetimes.
| [
{
"created": "Mon, 17 Jul 2023 11:31:04 GMT",
"version": "v1"
}
] | 2024-05-01 | [
[
"Taujanskas",
"Grigalius",
""
]
] | We report on the recent construction of a scattering theory for Maxwell potentials on curved spacetimes. |
1605.04332 | Casey Handmer | Casey J. Handmer, B\'ela Szil\'agyi, Jeffrey Winicour | Spectral Cauchy Characteristic Extraction of strain, news and
gravitational radiation flux | 30 pages, 17 figures | null | 10.1088/0264-9381/33/22/225007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new approach for the Cauchy-characteristic extraction of
gravitational radiation strain, news function, and the flux of the
energy-momentum, supermomentum and angular momentum associated with the
Bondi-Metzner-Sachs asymptotic symmetries. In Cauchy-characteristic extraction,
a characteristic evolution code takes numerical data on an inner worldtube
supplied by a Cauchy evolution code, and propagates it outwards to obtain the
space-time metric in a neighborhood of null infinity. The metric is first
determined in a scrambled form in terms of coordinates determined by the Cauchy
formalism. In prior treatments, the waveform is first extracted from this
metric and then transformed into an asymptotic inertial coordinate system. This
procedure provides the physically proper description of the waveform and the
radiated energy but it does not generalize to determine the flux of angular
momentum or supermomentum. Here we formulate and implement a new approach which
transforms the full metric into an asymptotic inertial frame and provides a
uniform treatment of all the radiation fluxes associated with the asymptotic
symmetries. Computations are performed and calibrated using the Spectral
Einstein Code (SpEC).
| [
{
"created": "Fri, 13 May 2016 21:05:56 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Jul 2016 06:34:01 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Sep 2016 04:59:12 GMT",
"version": "v3"
},
{
"created": "Fri, 7 Oct 2016 06:31:46 GMT",
"version": "v4"
}
] | 2016-11-23 | [
[
"Handmer",
"Casey J.",
""
],
[
"Szilágyi",
"Béla",
""
],
[
"Winicour",
"Jeffrey",
""
]
] | We present a new approach for the Cauchy-characteristic extraction of gravitational radiation strain, news function, and the flux of the energy-momentum, supermomentum and angular momentum associated with the Bondi-Metzner-Sachs asymptotic symmetries. In Cauchy-characteristic extraction, a characteristic evolution code takes numerical data on an inner worldtube supplied by a Cauchy evolution code, and propagates it outwards to obtain the space-time metric in a neighborhood of null infinity. The metric is first determined in a scrambled form in terms of coordinates determined by the Cauchy formalism. In prior treatments, the waveform is first extracted from this metric and then transformed into an asymptotic inertial coordinate system. This procedure provides the physically proper description of the waveform and the radiated energy but it does not generalize to determine the flux of angular momentum or supermomentum. Here we formulate and implement a new approach which transforms the full metric into an asymptotic inertial frame and provides a uniform treatment of all the radiation fluxes associated with the asymptotic symmetries. Computations are performed and calibrated using the Spectral Einstein Code (SpEC). |
gr-qc/0111079 | Gaston Giribet | Gaston Giribet, Claudio Simeone | Deparametrization and quantization of the Taub universe | 17 pages. Typos corrected | Int.J.Mod.Phys. A17 (2002) 2885-2896 | 10.1142/S0217751X02011370 | null | gr-qc | null | Previous analysis about the deparametrization and path integral quantization
of cosmological models are extended to models which do not admit an intrinsic
time. The formal expression for the transition amplitude is written down for
the Taub anisotropic universe with a clear notion of time. The relation
existing between the deparametrization associated to gauge fixation required in
the path integral approach and the procedure of reduction of the Wheeler-De
Witt equation is also studied.
| [
{
"created": "Fri, 23 Nov 2001 21:11:42 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Nov 2001 16:39:41 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Giribet",
"Gaston",
""
],
[
"Simeone",
"Claudio",
""
]
] | Previous analysis about the deparametrization and path integral quantization of cosmological models are extended to models which do not admit an intrinsic time. The formal expression for the transition amplitude is written down for the Taub anisotropic universe with a clear notion of time. The relation existing between the deparametrization associated to gauge fixation required in the path integral approach and the procedure of reduction of the Wheeler-De Witt equation is also studied. |
1411.7247 | Hossein Ghaffarnejad | Hossein Ghaffarnejad and Hassan Niad | Weak Gravitational lensing from regular Bardeen black holes | 20 pages, 7 figures with some revisions | International Journal Of Theoretical Physics (2015) | 10.1007/s10773-015-2787-8 | null | gr-qc astro-ph.GA hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we study weak gravitational lensing of regular Bardeen black
hole which has scalar charge $g$ and mass $m.$ We investigate the angular
position and magnification of non-relativistic images in two cases depending on
the presence or absence of photon sphere. Defining dimensionless charge
parameter $q=\frac{g}{2m}$ we seek to disappear photon sphere in the case of
$|q|>{24\sqrt5}/{125}$ for which the space time metric encounters strongly with
naked singularities. We specify the basic parameters of lensing in terms of
scalar charge by using the perturbative method and found that the parity of
images is different in two cases: (a) The strongly naked singularities is
present in the space time. (b) singularity of space time is weak or is
eliminated (the black hole lens).
| [
{
"created": "Mon, 24 Nov 2014 18:43:12 GMT",
"version": "v1"
},
{
"created": "Sat, 29 Nov 2014 07:17:50 GMT",
"version": "v2"
},
{
"created": "Sun, 22 Mar 2015 15:13:27 GMT",
"version": "v3"
},
{
"created": "Fri, 4 Sep 2015 07:03:42 GMT",
"version": "v4"
}
] | 2015-09-07 | [
[
"Ghaffarnejad",
"Hossein",
""
],
[
"Niad",
"Hassan",
""
]
] | In this article we study weak gravitational lensing of regular Bardeen black hole which has scalar charge $g$ and mass $m.$ We investigate the angular position and magnification of non-relativistic images in two cases depending on the presence or absence of photon sphere. Defining dimensionless charge parameter $q=\frac{g}{2m}$ we seek to disappear photon sphere in the case of $|q|>{24\sqrt5}/{125}$ for which the space time metric encounters strongly with naked singularities. We specify the basic parameters of lensing in terms of scalar charge by using the perturbative method and found that the parity of images is different in two cases: (a) The strongly naked singularities is present in the space time. (b) singularity of space time is weak or is eliminated (the black hole lens). |
gr-qc/0209053 | Santiago Esteban Perez Bergliaffa | M. Novello, S. E. Perez Bergliaffa, K. E. Hibberd | Analysis of static and spherically-symmetric solutions in NDL theory of
gravitation | RevTex4, 6 pages | Int.J.Mod.Phys. D13 (2004) 527-538 | 10.1142/S0218271804004608 | null | gr-qc | null | We investigate a static solution with spherical symmetry of a recently
proposed field theory of gravitation. In this so-called NDL theory, matter
interacts with gravity in accordance with the Weak Equivalence Principle, while
gravitons have a nonlinear self-interaction. It is shown that the predictions
of NDL agree with those of General Relativity in the three classic tests.
However, there are potential differences in the strong-field limit, which we
illustrate by proving that this theory does not allow the existence of static
and spherically symmetric black holes.
| [
{
"created": "Tue, 17 Sep 2002 14:29:32 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Novello",
"M.",
""
],
[
"Bergliaffa",
"S. E. Perez",
""
],
[
"Hibberd",
"K. E.",
""
]
] | We investigate a static solution with spherical symmetry of a recently proposed field theory of gravitation. In this so-called NDL theory, matter interacts with gravity in accordance with the Weak Equivalence Principle, while gravitons have a nonlinear self-interaction. It is shown that the predictions of NDL agree with those of General Relativity in the three classic tests. However, there are potential differences in the strong-field limit, which we illustrate by proving that this theory does not allow the existence of static and spherically symmetric black holes. |
1607.04148 | W.J. Handley | W.J. Handley, A.N. Lasenby, M.P. Hobson | Novel quantum initial conditions for inflation | 6 pages, 1 figure, Accepted by Physical Review D | null | 10.1103/PhysRevD.94.024041 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a novel approach for setting initial conditions on the mode
functions of the Mukhanov Sazaki equation. These conditions are motivated by
minimisation of the renormalised stress-energy tensor, and are valid for
setting a vacuum state even in a context where the spacetime is changing
rapidly. Moreover, these alternative conditions are potentially observationally
distinguishable. We apply this to the kinetically dominated universe, and
compare with the more traditional approach.
| [
{
"created": "Thu, 14 Jul 2016 14:28:13 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Jul 2016 14:10:40 GMT",
"version": "v2"
}
] | 2016-08-24 | [
[
"Handley",
"W. J.",
""
],
[
"Lasenby",
"A. N.",
""
],
[
"Hobson",
"M. P.",
""
]
] | We present a novel approach for setting initial conditions on the mode functions of the Mukhanov Sazaki equation. These conditions are motivated by minimisation of the renormalised stress-energy tensor, and are valid for setting a vacuum state even in a context where the spacetime is changing rapidly. Moreover, these alternative conditions are potentially observationally distinguishable. We apply this to the kinetically dominated universe, and compare with the more traditional approach. |
gr-qc/9806036 | Gabrielle Allen | Gabrielle Allen, Karen Camarda, Edward Seidel | Black Hole Spectroscopy: Determining Waveforms from 3D Excited Black
Holes | 4 pages, 5 figures, submitted to Phys. Rev. Lett | null | null | null | gr-qc | null | We present the first results for Cauchy nonlinear evolution of 3D,
nonaxisymmetric distorted black holes. We focus on the extraction and
verification of 3D waveforms determined by numerical relativity. We show that
the black hole evolution can be accurately followed through the ringdown
period, and comparing with a recently developed perturbative evolution
technique, we show that many waveforms in the black hole spectrum of modes,
such as l=2 and l=4, including weakly excited nonaxisymmetric modes with m not
zero, can be accurately evolved and extracted from the full nonlinear numerical
evolution. We also identify new physics contained in higher modes, due to
nonlinear effects. The implications for simulations related to gravitational
wave astronomy are discussed.
| [
{
"created": "Mon, 8 Jun 1998 12:09:40 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Allen",
"Gabrielle",
""
],
[
"Camarda",
"Karen",
""
],
[
"Seidel",
"Edward",
""
]
] | We present the first results for Cauchy nonlinear evolution of 3D, nonaxisymmetric distorted black holes. We focus on the extraction and verification of 3D waveforms determined by numerical relativity. We show that the black hole evolution can be accurately followed through the ringdown period, and comparing with a recently developed perturbative evolution technique, we show that many waveforms in the black hole spectrum of modes, such as l=2 and l=4, including weakly excited nonaxisymmetric modes with m not zero, can be accurately evolved and extracted from the full nonlinear numerical evolution. We also identify new physics contained in higher modes, due to nonlinear effects. The implications for simulations related to gravitational wave astronomy are discussed. |
1909.01047 | Jing Wang | Jing Wang | Quantum Corrections to Gravitational Potential of Scalarized Neutron
Star Binary | 10 pages, 6 figures | Eur. Phys. J. C (2019) 79:544 | 10.1140/epjc/s10052-019-7052-5 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the long-distance, low-energy, leading quantum corrections to
gravitational potential for scalarized neutron star (NS) binary systems, by
treating general relativity as an effective field theory. We neglect the
extended scales of two star components and treat them as heavy point particles,
which gravitationally interact with each other via the exchanges of both
gravitons and scalar particles, because of the settled scalar configurations
inside the stars. Accordingly, the gravitational potential includes both
Newtonian potential and scalar-modified Newtonian-like part. We, in the
non-relativistic limit, calculate the non-analytic corrections to the modified
gravitational potential directly from the sum of all exchanges of both
gravitons and scalar particles to one-loop order. The appropriate vertex rules
are extracted from the effective Lagrangian. Our calculations demonstrate that
either the graviton exchanges or the exchanges of scalar particles contribute
to both classical relativistic corrections and quantum corrections to the
gravitational potential of the scalarized NS binaries.
| [
{
"created": "Tue, 3 Sep 2019 10:32:10 GMT",
"version": "v1"
}
] | 2019-09-04 | [
[
"Wang",
"Jing",
""
]
] | We investigate the long-distance, low-energy, leading quantum corrections to gravitational potential for scalarized neutron star (NS) binary systems, by treating general relativity as an effective field theory. We neglect the extended scales of two star components and treat them as heavy point particles, which gravitationally interact with each other via the exchanges of both gravitons and scalar particles, because of the settled scalar configurations inside the stars. Accordingly, the gravitational potential includes both Newtonian potential and scalar-modified Newtonian-like part. We, in the non-relativistic limit, calculate the non-analytic corrections to the modified gravitational potential directly from the sum of all exchanges of both gravitons and scalar particles to one-loop order. The appropriate vertex rules are extracted from the effective Lagrangian. Our calculations demonstrate that either the graviton exchanges or the exchanges of scalar particles contribute to both classical relativistic corrections and quantum corrections to the gravitational potential of the scalarized NS binaries. |
2005.09607 | Anuradha Gupta | Anuradha Gupta, Sayantani Datta, Shilpa Kastha, Ssohrab Borhanian, K.
G. Arun, B. S. Sathyaprakash | Multiparameter tests of general relativity using multiband
gravitational-wave observations | 7 pages, 4 figures. v3: version published in PRL | Phys. Rev. Lett. 125, 201101 (2020) | 10.1103/PhysRevLett.125.201101 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this Letter we show that multiband observations of stellar-mass binary
black holes by the next generation of ground-based observatories (3G) and the
space-based Laser Interferometer Space Antenna (LISA) would facilitate a
comprehensive test of general relativity by simultaneously measuring all the
post-Newtonian (PN) coefficients. Multiband observations would measure most of
the known PN phasing coefficients to an accuracy below a few percent---two
orders-of-magnitude better than the best bounds achievable from even `golden'
binaries in the 3G or LISA bands. Such multiparameter bounds would play a
pivotal role in constraining the parameter space of modified theories of
gravity beyond general relativity.
| [
{
"created": "Tue, 19 May 2020 17:27:30 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Oct 2020 22:05:42 GMT",
"version": "v2"
},
{
"created": "Tue, 10 Nov 2020 19:14:13 GMT",
"version": "v3"
}
] | 2020-11-12 | [
[
"Gupta",
"Anuradha",
""
],
[
"Datta",
"Sayantani",
""
],
[
"Kastha",
"Shilpa",
""
],
[
"Borhanian",
"Ssohrab",
""
],
[
"Arun",
"K. G.",
""
],
[
"Sathyaprakash",
"B. S.",
""
]
] | In this Letter we show that multiband observations of stellar-mass binary black holes by the next generation of ground-based observatories (3G) and the space-based Laser Interferometer Space Antenna (LISA) would facilitate a comprehensive test of general relativity by simultaneously measuring all the post-Newtonian (PN) coefficients. Multiband observations would measure most of the known PN phasing coefficients to an accuracy below a few percent---two orders-of-magnitude better than the best bounds achievable from even `golden' binaries in the 3G or LISA bands. Such multiparameter bounds would play a pivotal role in constraining the parameter space of modified theories of gravity beyond general relativity. |
1706.04013 | Arianna Renzini | Arianna I. Renzini, Carlo R. Contaldi and Alan Heavens | Mapping weak lensing distortions in the Kerr metric | 16 pages, 11 figures | null | 10.1103/PhysRevD.95.124047 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Einstein's theory of General Relativity implies that energy, i.e. matter,
curves space-time and thus deforms lightlike geodesics, giving rise to
gravitational lensing. This phenomenon is well understood in the case of the
Schwarzschild metric, and has been accurately described in the past; however,
lensing in the Kerr space-time has received less attention in the literature
despite potential practical observational applications. In particular, lensing
in such space is not expressible as the gradient of a scalar potential and as
such is a source of curl-like signatures and an asymmetric shear pattern. In
this paper, we develop a differentiable lensing map in the Kerr metric,
reworking and extending previous approaches. By using standard tools of weak
gravitational lensing, we isolate and quantify the distortion that is uniquely
induced by the presence of angular momentum in the metric. We apply this
framework to the distortion induced by a Kerr-like foreground object on a
distribution of background of sources. We verify that the new unique lensing
signature is orders of magnitude below current observational bounds for a range
of lens configurations.
| [
{
"created": "Tue, 13 Jun 2017 11:40:02 GMT",
"version": "v1"
}
] | 2017-08-02 | [
[
"Renzini",
"Arianna I.",
""
],
[
"Contaldi",
"Carlo R.",
""
],
[
"Heavens",
"Alan",
""
]
] | Einstein's theory of General Relativity implies that energy, i.e. matter, curves space-time and thus deforms lightlike geodesics, giving rise to gravitational lensing. This phenomenon is well understood in the case of the Schwarzschild metric, and has been accurately described in the past; however, lensing in the Kerr space-time has received less attention in the literature despite potential practical observational applications. In particular, lensing in such space is not expressible as the gradient of a scalar potential and as such is a source of curl-like signatures and an asymmetric shear pattern. In this paper, we develop a differentiable lensing map in the Kerr metric, reworking and extending previous approaches. By using standard tools of weak gravitational lensing, we isolate and quantify the distortion that is uniquely induced by the presence of angular momentum in the metric. We apply this framework to the distortion induced by a Kerr-like foreground object on a distribution of background of sources. We verify that the new unique lensing signature is orders of magnitude below current observational bounds for a range of lens configurations. |
gr-qc/0409010 | Leor Barack | Leor Barack and Curt Cutler | Confusion Noise from LISA Capture Sources | 26 pages, 23 eps figures; Minor typographic corrections, version to
be published in PRD | Phys.Rev. D70 (2004) 122002 | 10.1103/PhysRevD.70.122002 | null | gr-qc astro-ph | null | Captures of compact objects (COs) by massive black holes (MBHs) in galactic
nuclei will be an important source for LISA, the space-based gravitational-wave
(GW) detector. However, a large fraction of captures will not be individually
resolvable--either because they are too distant, have unfavorable orientation,
or have too many years to go before final plunge--and so will constitute a
source of ``confusion noise,'' obscuring other types of sources. Here we
estimate the shape and overall magnitude of the spectrum of confusion noise
from CO captures. The overall magnitude depends on the capture rates, which are
rather uncertain, so we present results for a plausible range of rates. We show
that the impact of capture confusion noise on the total LISA noise curve ranges
from insignificant to modest, depending on these rates. Capture rates at the
high end of estimated ranges would raise LISA's overall (effective) noise level
by at most a factor \sim 2. While this slightly elevated noise level would
somewhat decrease LISA's sensitivity to other classes of sources, overall, this
would be a pleasant problem for LISA to have: It would also imply that
detection rates for CO captures were at nearly their maximum possible levels
(given LISA's baseline design). This paper includes several other results that
should be useful in further studies of LISA capture sources, including (i) a
calculation of the total GW energy output from generic inspirals into Kerr
MBHs, and (ii) an approximate GW energy spectrum for a typical capture.
| [
{
"created": "Thu, 2 Sep 2004 14:37:22 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Dec 2004 13:54:03 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Barack",
"Leor",
""
],
[
"Cutler",
"Curt",
""
]
] | Captures of compact objects (COs) by massive black holes (MBHs) in galactic nuclei will be an important source for LISA, the space-based gravitational-wave (GW) detector. However, a large fraction of captures will not be individually resolvable--either because they are too distant, have unfavorable orientation, or have too many years to go before final plunge--and so will constitute a source of ``confusion noise,'' obscuring other types of sources. Here we estimate the shape and overall magnitude of the spectrum of confusion noise from CO captures. The overall magnitude depends on the capture rates, which are rather uncertain, so we present results for a plausible range of rates. We show that the impact of capture confusion noise on the total LISA noise curve ranges from insignificant to modest, depending on these rates. Capture rates at the high end of estimated ranges would raise LISA's overall (effective) noise level by at most a factor \sim 2. While this slightly elevated noise level would somewhat decrease LISA's sensitivity to other classes of sources, overall, this would be a pleasant problem for LISA to have: It would also imply that detection rates for CO captures were at nearly their maximum possible levels (given LISA's baseline design). This paper includes several other results that should be useful in further studies of LISA capture sources, including (i) a calculation of the total GW energy output from generic inspirals into Kerr MBHs, and (ii) an approximate GW energy spectrum for a typical capture. |
1011.1982 | Puxun Wu | Zhengxiang Li, Puxun Wu and Hongwei Yu | Examining the cosmic acceleration with the latest Union2 supernova data | 17 pages, 6 figures; PLB in press | Phys.Lett.B695:1-8,2011 | 10.1016/j.physletb.2010.10.044 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this Letter, by reconstructing the $Om$ diagnostic and the deceleration
parameter $q$ from the latest Union2 Type Ia supernova sample with and without
the systematic error along with the baryon acoustic oscillation (BAO) and the
cosmic microwave background (CMB), we study the cosmic expanding history, using
the Chevallier-Polarski-Linder (CPL) parametrization. We obtain that Union2+BAO
favor an expansion with a decreasing of the acceleration at $z<0.3$. However,
once the CMB data is added in the analysis, the cosmic acceleration is found to
be still increasing, indicating a tension between low redshift data and high
redshift one. In order to reduce this tension significantly, two different
methods are considered and thus two different subsamples of Union2 are
selected. We then find that two different subsamples+BAO+CMB give completely
different results on the cosmic expanding history when the systematic error is
ignored, with one suggesting a decreasing cosmic acceleration, the other just
the opposite, although both of them alone with BAO support that the cosmic
acceleration is slowing down. However, once the systematic error is considered,
two different subsamples of Union2 along with BAO and CMB all favor an
increasing of the present cosmic acceleration. Therefore a clear-cut answer on
whether the cosmic acceleration is slowing down calls for more consistent data
and more reliable methods to analyze them.
| [
{
"created": "Tue, 9 Nov 2010 06:30:59 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Jan 2011 05:37:13 GMT",
"version": "v2"
}
] | 2015-03-17 | [
[
"Li",
"Zhengxiang",
""
],
[
"Wu",
"Puxun",
""
],
[
"Yu",
"Hongwei",
""
]
] | In this Letter, by reconstructing the $Om$ diagnostic and the deceleration parameter $q$ from the latest Union2 Type Ia supernova sample with and without the systematic error along with the baryon acoustic oscillation (BAO) and the cosmic microwave background (CMB), we study the cosmic expanding history, using the Chevallier-Polarski-Linder (CPL) parametrization. We obtain that Union2+BAO favor an expansion with a decreasing of the acceleration at $z<0.3$. However, once the CMB data is added in the analysis, the cosmic acceleration is found to be still increasing, indicating a tension between low redshift data and high redshift one. In order to reduce this tension significantly, two different methods are considered and thus two different subsamples of Union2 are selected. We then find that two different subsamples+BAO+CMB give completely different results on the cosmic expanding history when the systematic error is ignored, with one suggesting a decreasing cosmic acceleration, the other just the opposite, although both of them alone with BAO support that the cosmic acceleration is slowing down. However, once the systematic error is considered, two different subsamples of Union2 along with BAO and CMB all favor an increasing of the present cosmic acceleration. Therefore a clear-cut answer on whether the cosmic acceleration is slowing down calls for more consistent data and more reliable methods to analyze them. |
1508.04188 | Yun Soo Myung | Yun Soo Myung, Young-Jai Park | Scale-invariant power spectra from a Weyl-invariant scalar-tensor theory | 19 pages, no figures, version to appear in EPJC. arXiv admin note:
text overlap with arXiv:1407.0441 | Eur.Phys.J. C76 (2016) 79 | 10.1140/epjc/s10052-016-3924-0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain scale-invariant scalar and tensor power spectra from a
Weyl-invariant scalar-tensor theory in de Sitter spacetime. This implies that
the Weyl-invariance guarantees to implement the scale-invariance of power
spectrum in de Sitter spacetime. We establish a deep connection between the
Weyl-invariance of the action and scale-invariance of power spectrum in de
Sitter spacetime.
| [
{
"created": "Tue, 18 Aug 2015 01:26:43 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Feb 2016 01:34:40 GMT",
"version": "v2"
}
] | 2016-02-19 | [
[
"Myung",
"Yun Soo",
""
],
[
"Park",
"Young-Jai",
""
]
] | We obtain scale-invariant scalar and tensor power spectra from a Weyl-invariant scalar-tensor theory in de Sitter spacetime. This implies that the Weyl-invariance guarantees to implement the scale-invariance of power spectrum in de Sitter spacetime. We establish a deep connection between the Weyl-invariance of the action and scale-invariance of power spectrum in de Sitter spacetime. |
1911.05246 | Roman Konoplya | M. S. Churilova, R. A. Konoplya, A. Zhidenko | Arbitrarily long-lived quasinormal modes in a wormhole background | 7 pages, revtex, minor changes to match the version accepted for
publication in Physics Letters B | Phys. Lett. B802 (2020) 135207 | 10.1016/j.physletb.2020.135207 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Arbitrarily long lived modes, called quasi-resonances, are known to exist in
the spectrum of massive fields for a number of black-hole backgrounds at some
discrete values of mass of the field. Here we show that these modes also exist
in the background of wormholes, unless a wormhole has a constant red-shift
function, that is, tideless in the radial direction. The evidence of
quasi-resonances is supported by calculations in the frequency and time
domains, which are in a good concordance. At large masses of the field,
time-domain profiles of the absolute value of the wave function have peculiar
behavior: the long-lived modes dominate in the signal after a long period of
power-law tails.
| [
{
"created": "Wed, 13 Nov 2019 01:57:02 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Jan 2020 05:28:15 GMT",
"version": "v2"
}
] | 2020-01-28 | [
[
"Churilova",
"M. S.",
""
],
[
"Konoplya",
"R. A.",
""
],
[
"Zhidenko",
"A.",
""
]
] | Arbitrarily long lived modes, called quasi-resonances, are known to exist in the spectrum of massive fields for a number of black-hole backgrounds at some discrete values of mass of the field. Here we show that these modes also exist in the background of wormholes, unless a wormhole has a constant red-shift function, that is, tideless in the radial direction. The evidence of quasi-resonances is supported by calculations in the frequency and time domains, which are in a good concordance. At large masses of the field, time-domain profiles of the absolute value of the wave function have peculiar behavior: the long-lived modes dominate in the signal after a long period of power-law tails. |
1609.00848 | Vasilis Oikonomou | K. Kleidis, V.K. Oikonomou | Effects of Finite-time Singularities on Gravitational Waves | To appear in Astrophysics and Space Science | null | 10.1007/s10509-016-2914-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the impact of finite-time singularities on gravitational waves, in
the context of $F(R)$ gravity. We investigate which singularities are allowed
to occur during the inflationary era, when gravitational waves are considered,
and we discuss the quantitative implications of each allowed singularity. As we
show, only a pressure singularity, the so-called Type II and also a Type IV
singularity are allowed to occur during the inflationary era. In the case of a
Type II, the resulting amplitude of the gravitational wave is zero or almost
zero, hence this pressure singularity has a significant impact on the
primordial gravitational waves. The case of a Type IV singularity is more
interesting since as we show, the singularity has no effect on the amplitude of
the gravitational waves. Therefore, this result combined with the fact that the
Type IV singularity affects only the dynamics of inflation, leads to the
conclusion that the Universe passes smoothly through a Type IV singularity.
| [
{
"created": "Sat, 3 Sep 2016 18:16:39 GMT",
"version": "v1"
}
] | 2016-09-28 | [
[
"Kleidis",
"K.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | We analyze the impact of finite-time singularities on gravitational waves, in the context of $F(R)$ gravity. We investigate which singularities are allowed to occur during the inflationary era, when gravitational waves are considered, and we discuss the quantitative implications of each allowed singularity. As we show, only a pressure singularity, the so-called Type II and also a Type IV singularity are allowed to occur during the inflationary era. In the case of a Type II, the resulting amplitude of the gravitational wave is zero or almost zero, hence this pressure singularity has a significant impact on the primordial gravitational waves. The case of a Type IV singularity is more interesting since as we show, the singularity has no effect on the amplitude of the gravitational waves. Therefore, this result combined with the fact that the Type IV singularity affects only the dynamics of inflation, leads to the conclusion that the Universe passes smoothly through a Type IV singularity. |
2104.00544 | Behzad Eslam Panah | J. Sedaghat, S. M. Zebarjad, G. H. Bordbar, B. Eslam Panah, and R.
Moradi | Is the remnant of GW190425 a strange quark star? | 12 pages, 7 figures, 5 tables | Phys. Lett. B 833 (2022) 137388 | 10.1016/j.physletb.2022.137388 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This study investigates the effects of different QCD models on the structure
of strange quark stars (SQS). In these models, the running coupling constant
has a finite value in the infrared region of energy. By imposing some
constraints on the strange quark matter (SQM) and exploiting the analytic and
background perturbation theories, the equations of states for the SQM are
obtained. Then, the properties of SQSs in general relativity are evaluated. By
using component masses of GW190425 \cite{Abbott2020ApJL} as well as some
conversion relations between the baryonic mass and the gravitational mass, the
remnant mass of GW190425 is obtained. Our results for the maximum gravitational
mass of SQS are then compared with the remnant mass of GW190425. The results
indicate that the obtained maximum gravitational masses are comparable to the
remnant mass of GW190425. Therefore, it is proposed that the remnant mass of
GW190425 might be a SQS.
| [
{
"created": "Fri, 19 Mar 2021 07:30:18 GMT",
"version": "v1"
},
{
"created": "Sun, 19 Dec 2021 14:08:17 GMT",
"version": "v2"
},
{
"created": "Thu, 25 Aug 2022 21:21:38 GMT",
"version": "v3"
}
] | 2022-08-29 | [
[
"Sedaghat",
"J.",
""
],
[
"Zebarjad",
"S. M.",
""
],
[
"Bordbar",
"G. H.",
""
],
[
"Panah",
"B. Eslam",
""
],
[
"Moradi",
"R.",
""
]
] | This study investigates the effects of different QCD models on the structure of strange quark stars (SQS). In these models, the running coupling constant has a finite value in the infrared region of energy. By imposing some constraints on the strange quark matter (SQM) and exploiting the analytic and background perturbation theories, the equations of states for the SQM are obtained. Then, the properties of SQSs in general relativity are evaluated. By using component masses of GW190425 \cite{Abbott2020ApJL} as well as some conversion relations between the baryonic mass and the gravitational mass, the remnant mass of GW190425 is obtained. Our results for the maximum gravitational mass of SQS are then compared with the remnant mass of GW190425. The results indicate that the obtained maximum gravitational masses are comparable to the remnant mass of GW190425. Therefore, it is proposed that the remnant mass of GW190425 might be a SQS. |
gr-qc/0505023 | Jorge Pullin | Rodolfo Gambini and Jorge Pullin | Discrete space-time | 16 pages, RevTex, submitted to the volume "100 Years of Relativity -
Space-time Structure: Einstein and Beyond", A. Ashtekar, ed., to be published
by World Scientific. " | null | null | LSU-REL-050405 | gr-qc | null | We review recent efforts to construct gravitational theories on discrete
space-times, usually referred to as the ``consistent discretization'' approach.
The resulting theories are free of constraints at the canonical level and
therefore allow to tackle many problems that cannot be currently addressed in
continuum quantum gravity. In particular the theories imply a natural method
for resolving the big bang (and other types) of singularities and predict a
fundamental mechanism for decoherence of quantum states that might be relevant
to the black hole information paradox. At a classical level, the theories may
provide an attractive new path for the exploration of issues in numerical
relativity. Finally, the theories can make direct contact with several
kinematical results of continuum loop quantum gravity. We review in broad terms
several of these results and present in detail as an illustration the classical
treatment with this technique of the simple yet conceptually challenging model
of two oscillators with constant energy sum.
| [
{
"created": "Wed, 4 May 2005 17:01:20 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | We review recent efforts to construct gravitational theories on discrete space-times, usually referred to as the ``consistent discretization'' approach. The resulting theories are free of constraints at the canonical level and therefore allow to tackle many problems that cannot be currently addressed in continuum quantum gravity. In particular the theories imply a natural method for resolving the big bang (and other types) of singularities and predict a fundamental mechanism for decoherence of quantum states that might be relevant to the black hole information paradox. At a classical level, the theories may provide an attractive new path for the exploration of issues in numerical relativity. Finally, the theories can make direct contact with several kinematical results of continuum loop quantum gravity. We review in broad terms several of these results and present in detail as an illustration the classical treatment with this technique of the simple yet conceptually challenging model of two oscillators with constant energy sum. |
gr-qc/0606026 | Gerard Hooft 't | Gerard 't Hooft | The black hole horizon as a dynamical system | 16 pages, no figures. Presented at "Einstein's Legacy in the New
Millennium", Puri, India, 15-22 Dec. 2005. An extension of gr-qc/0504120 with
chapter added and small sign changes | Int.J.Mod.Phys. D15 (2006) 1587-1602 | 10.1142/S021827180600898X | ITP-UU-06/25, SPIN-06/21 | gr-qc | null | Interactions between outgoing Hawking particles and ingoing matter are
determined by gravitational forces and Standard Model interactions. In
particular the gravitational interactions are responsible for the unitarity of
the scattering against the horizon, as dictated by the holographic principle,
but the Standard Model interactions also contribute, and understanding their
effects is an important first step towards a complete understanding of the
horizon's dynamics. The relation between in- and outgoing states is described
in terms of an operator algebra. In this contribution, in which earlier results
are rederived and elaborated upon, we first describe the algebra induced on the
horizon by U(1) vector fields and scalar fields, including the case of an
Englert-Brout-Higgs mechanism, and a more careful consideration of the
transverse vector field components. We demonstrate that, unlike classical black
holes, the quantized black hole has on its horizon an imprint of its (recent)
past history, i.e., quantum hair. The relation between in- and outgoing states
depends on this imprint. As a first step towards the inclusion of non-Abelian
interactions, we then compute the effects of magnetic monopoles both in the
in-states and in the out-states. They completely modify, and indeed simplify,
our algebra.
| [
{
"created": "Tue, 6 Jun 2006 15:02:32 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Hooft",
"Gerard 't",
""
]
] | Interactions between outgoing Hawking particles and ingoing matter are determined by gravitational forces and Standard Model interactions. In particular the gravitational interactions are responsible for the unitarity of the scattering against the horizon, as dictated by the holographic principle, but the Standard Model interactions also contribute, and understanding their effects is an important first step towards a complete understanding of the horizon's dynamics. The relation between in- and outgoing states is described in terms of an operator algebra. In this contribution, in which earlier results are rederived and elaborated upon, we first describe the algebra induced on the horizon by U(1) vector fields and scalar fields, including the case of an Englert-Brout-Higgs mechanism, and a more careful consideration of the transverse vector field components. We demonstrate that, unlike classical black holes, the quantized black hole has on its horizon an imprint of its (recent) past history, i.e., quantum hair. The relation between in- and outgoing states depends on this imprint. As a first step towards the inclusion of non-Abelian interactions, we then compute the effects of magnetic monopoles both in the in-states and in the out-states. They completely modify, and indeed simplify, our algebra. |
gr-qc/0303033 | Stephen C. Anco | Stephen C. Anco | On multi-graviton and multi-gravitino gauge theories | 33 pages (latex) | Class.Quant.Grav.19:6445-6467,2002 | 10.1088/0264-9381/19/24/312 | null | gr-qc | null | This paper studies nonlinear deformations of the linear gauge theory of any
number of spin-2 and spin-3/2 fields with general formal multiplication rules
in place of standard Grassmann rules for manipulating the fields, in four
spacetime dimensions. General possibilities for multiplication rules and
coupling constants are simultaneously accommodated by regarding the set of
fields equivalently as a single algebra-valued spin-2 field and single
algebra-valued spin-3/2 field, where the underlying algebra is factorized into
a field-coupling part and an internal multiplication part. The condition that
there exist a gauge invariant Lagrangian (to within a divergence) for these
algebra-valued fields is used to derive determining equations whose solutions
give all allowed deformation terms, yielding nonlinear field equations and
nonabelian gauge symmetries, together with all allowed formal multiplication
rules as needed in the Lagrangian for demonstration of invariance under the
gauge symmetries and for derivation of the field equations. In the case of
spin-2 fields alone, the main result of this analysis is that all deformations
(without any higher derivatives than appear in the linear theory) are
equivalent to an algebra-valued Einstein gravity theory. By a systematic
examination of factorizations of the algebra, a novel type of nonlinear gauge
theory of two or more spin-2 fields is found, where the coupling for the fields
is based on structure constants of an anticommutative, anti-associative
algebra, and with formal multiplication rules that make the fields
anticommuting (while products obey anti-associativity). Supersymmetric
extensions of these results are obtained in the more general case when spin-3/2
fields are included.
| [
{
"created": "Sun, 9 Mar 2003 21:49:51 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Anco",
"Stephen C.",
""
]
] | This paper studies nonlinear deformations of the linear gauge theory of any number of spin-2 and spin-3/2 fields with general formal multiplication rules in place of standard Grassmann rules for manipulating the fields, in four spacetime dimensions. General possibilities for multiplication rules and coupling constants are simultaneously accommodated by regarding the set of fields equivalently as a single algebra-valued spin-2 field and single algebra-valued spin-3/2 field, where the underlying algebra is factorized into a field-coupling part and an internal multiplication part. The condition that there exist a gauge invariant Lagrangian (to within a divergence) for these algebra-valued fields is used to derive determining equations whose solutions give all allowed deformation terms, yielding nonlinear field equations and nonabelian gauge symmetries, together with all allowed formal multiplication rules as needed in the Lagrangian for demonstration of invariance under the gauge symmetries and for derivation of the field equations. In the case of spin-2 fields alone, the main result of this analysis is that all deformations (without any higher derivatives than appear in the linear theory) are equivalent to an algebra-valued Einstein gravity theory. By a systematic examination of factorizations of the algebra, a novel type of nonlinear gauge theory of two or more spin-2 fields is found, where the coupling for the fields is based on structure constants of an anticommutative, anti-associative algebra, and with formal multiplication rules that make the fields anticommuting (while products obey anti-associativity). Supersymmetric extensions of these results are obtained in the more general case when spin-3/2 fields are included. |
1505.04074 | Mingzhe Li | Mingzhe Li, Yicen Mou | Conformal invariant cosmological perturbations via the covariant
approach | 9 pages, the version to appear in JCAP | null | 10.1088/1475-7516/2015/10/037 | USTC-ICTS-15-04 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is known that some cosmological perturbations are conformal invariant.
This facilitates the studies of perturbations within some gravitational
theories alternative to general relativity, for example the scalar-tensor
theory, because it is possible to do equivalent analysis in a certain frame in
which the perturbation equations are simpler. In this paper we revisit the
problem of conformal invariances of cosmological perturbations in terms of the
covariant approach in which the perturbation variables have clear geometric and
physical meanings. We show that with this approach the conformal invariant
perturbations are easily identified.
| [
{
"created": "Fri, 15 May 2015 14:31:38 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Sep 2015 00:56:31 GMT",
"version": "v2"
}
] | 2015-10-21 | [
[
"Li",
"Mingzhe",
""
],
[
"Mou",
"Yicen",
""
]
] | It is known that some cosmological perturbations are conformal invariant. This facilitates the studies of perturbations within some gravitational theories alternative to general relativity, for example the scalar-tensor theory, because it is possible to do equivalent analysis in a certain frame in which the perturbation equations are simpler. In this paper we revisit the problem of conformal invariances of cosmological perturbations in terms of the covariant approach in which the perturbation variables have clear geometric and physical meanings. We show that with this approach the conformal invariant perturbations are easily identified. |
0705.3104 | Fang-Pei Chen | Fang-Pei Chen | The Dynamical Properties Derived from the More Generalized Lagrangian
Density for A Gravitational System | 31papes, no figure, submitted to GRG | null | null | null | gr-qc | null | The studies of the generalized Einstein Lagrangian densities without torsion
are extended to those of the more generalized Lagrangian densities with
torsion. The properties of the more generalized Lagrangian densities are
studied systematically and thoroughly. The dynamical laws of a gravitational
system such as the gravitational field equations, the conservation laws of the
energy-momentum tensor densities, the conservation laws of the spin densities
and the equations of motion for test particle are all derived from the
Lagrangian densities. The differences between the more generalized Lagrangian
densities and the generalized Einstein Lagrangian densities are discussed.
| [
{
"created": "Tue, 22 May 2007 08:02:32 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Chen",
"Fang-Pei",
""
]
] | The studies of the generalized Einstein Lagrangian densities without torsion are extended to those of the more generalized Lagrangian densities with torsion. The properties of the more generalized Lagrangian densities are studied systematically and thoroughly. The dynamical laws of a gravitational system such as the gravitational field equations, the conservation laws of the energy-momentum tensor densities, the conservation laws of the spin densities and the equations of motion for test particle are all derived from the Lagrangian densities. The differences between the more generalized Lagrangian densities and the generalized Einstein Lagrangian densities are discussed. |
1404.4492 | Alexander B. Balakin | Alexander B. Balakin and Timur Yu. Alpin | Extended axion electrodynamics: Anomalous dynamo-optical response
induced by gravitational pp-waves | 5 pages, based on talks on ICGAC-11, October, 1-5, 2013, Almaty | Gravitation and Cosmology, 20: 152 (2014) | 10.1134/S0202289314030037 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend the Einstein-Maxwell-axion theory including into the Lagrangian
cross-terms of the dynamo-optical type, which are quadratic in the Maxwell
tensor, linear in the covariant derivative of the macroscopic velocity
four-vector, and linear in the pseudoscalar (axion) field or its gradient
four-vector. We classify the new terms with respect to irreducible elements of
the covariant derivative of the macroscopic velocity four-vector of the
electromagnetically active medium: the expansion scalar, acceleration
four-vector, shear and vorticity tensors. Master equations of the extended
axion electrodynamics are used for the description of the response of an
axionically active electrodynamic system, induced by a pp-wave gravitational
background. We show that this response has a critical character, i.e., the
electric and magnetic fields, dynamo-optically coupled to the axions, grow
anomalously under the influence of the external pp-wave gravitational field.
| [
{
"created": "Thu, 17 Apr 2014 11:26:28 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Balakin",
"Alexander B.",
""
],
[
"Alpin",
"Timur Yu.",
""
]
] | We extend the Einstein-Maxwell-axion theory including into the Lagrangian cross-terms of the dynamo-optical type, which are quadratic in the Maxwell tensor, linear in the covariant derivative of the macroscopic velocity four-vector, and linear in the pseudoscalar (axion) field or its gradient four-vector. We classify the new terms with respect to irreducible elements of the covariant derivative of the macroscopic velocity four-vector of the electromagnetically active medium: the expansion scalar, acceleration four-vector, shear and vorticity tensors. Master equations of the extended axion electrodynamics are used for the description of the response of an axionically active electrodynamic system, induced by a pp-wave gravitational background. We show that this response has a critical character, i.e., the electric and magnetic fields, dynamo-optically coupled to the axions, grow anomalously under the influence of the external pp-wave gravitational field. |
1212.3169 | T. Damour | Thibault Damour | The General Relativistic Two Body Problem and the Effective One Body
Formalism | 41 pages, 4 figures, contribution to the proceedings of the
conference "Relativity and Gravitation - 100 years after Einstein in Prague",
Prague, 25-29 June 2012 | null | 10.1007/978-3-319-06349-2_5 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new analytical approach to the motion and radiation of (comparable mass)
binary systems has been introduced in 1999 under the name of Effective One Body
(EOB) formalism. We review the basic elements of this formalism, and discuss
some of its recent developments. Several recent comparisons between EOB
predictions and Numerical Relativity (NR) simulations have shown the aptitude
of the EOB formalism to provide accurate descriptions of the dynamics and
radiation of various binary systems (comprising black holes or neutron stars)
in regimes that are inaccessible to other analytical approaches (such as the
last orbits and the merger of comparable mass black holes). In synergy with NR
simulations, post-Newtonian (PN) theory and Gravitational Self-Force (GSF)
computations, the EOB formalism is likely to provide an efficient way of
computing the very many accurate template waveforms that are needed for
Gravitational Wave (GW) data analysis purposes.
| [
{
"created": "Thu, 13 Dec 2012 13:34:37 GMT",
"version": "v1"
}
] | 2015-05-27 | [
[
"Damour",
"Thibault",
""
]
] | A new analytical approach to the motion and radiation of (comparable mass) binary systems has been introduced in 1999 under the name of Effective One Body (EOB) formalism. We review the basic elements of this formalism, and discuss some of its recent developments. Several recent comparisons between EOB predictions and Numerical Relativity (NR) simulations have shown the aptitude of the EOB formalism to provide accurate descriptions of the dynamics and radiation of various binary systems (comprising black holes or neutron stars) in regimes that are inaccessible to other analytical approaches (such as the last orbits and the merger of comparable mass black holes). In synergy with NR simulations, post-Newtonian (PN) theory and Gravitational Self-Force (GSF) computations, the EOB formalism is likely to provide an efficient way of computing the very many accurate template waveforms that are needed for Gravitational Wave (GW) data analysis purposes. |
0706.0364 | Myungseok Yoon | Myungseok Yoon, Jihye Ha, and Wontae Kim | Entropy of Reissner-Nordstrom Black Holes with Minimal Length Revisited | 5 pages | Phys.Rev.D76:047501,2007 | 10.1103/PhysRevD.76.047501 | null | gr-qc | null | Based on the generalized uncertainty principle, we study the entropy of a
four-dimensional black hole by counting degrees of freedom near the horizon and
obtain the (finite) entropy proportional to the surface area at the horizon
without a cutoff introduced in the conventional brick-wall method.
| [
{
"created": "Mon, 4 Jun 2007 02:11:10 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Yoon",
"Myungseok",
""
],
[
"Ha",
"Jihye",
""
],
[
"Kim",
"Wontae",
""
]
] | Based on the generalized uncertainty principle, we study the entropy of a four-dimensional black hole by counting degrees of freedom near the horizon and obtain the (finite) entropy proportional to the surface area at the horizon without a cutoff introduced in the conventional brick-wall method. |
1910.10514 | Oleg Tsupko | G.S. Bisnovatyi-Kogan, O.Yu. Tsupko and V. Perlick | Shadow of black holes at local and cosmological distances | 14 pages, 16 figures; based on talk at the conference 'Multifrequency
Behaviour of High Energy Cosmic Sources - XIII - MULTIF2019'; see also our
previous papers arXiv:1804.04898, arXiv:1805.03311 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A brief illustrative discussion of the shadows of black holes at local and
cosmological distances is presented. Starting from definition of the term and
discussion of recent observations, we then investigate shadows at large,
cosmological distances. On a cosmological scale, the size of shadow observed by
comoving observer is expected to be affected by cosmic expansion. Exact
analytical solution for the shadow angular size of Schwarzschild black hole in
de Sitter universe was found. Additionally, an approximate method was
presented, based on using angular size redshift relation. This approach is
appropriate for general case of any multicomponent universe (with matter,
radiation and dark energy). It was shown, that supermassive black holes at
cosmological distances in universe with matter may give the shadow size
comparable with the shadow size in M87, and in the center of our Galaxy.
| [
{
"created": "Tue, 22 Oct 2019 15:30:30 GMT",
"version": "v1"
}
] | 2019-10-24 | [
[
"Bisnovatyi-Kogan",
"G. S.",
""
],
[
"Tsupko",
"O. Yu.",
""
],
[
"Perlick",
"V.",
""
]
] | A brief illustrative discussion of the shadows of black holes at local and cosmological distances is presented. Starting from definition of the term and discussion of recent observations, we then investigate shadows at large, cosmological distances. On a cosmological scale, the size of shadow observed by comoving observer is expected to be affected by cosmic expansion. Exact analytical solution for the shadow angular size of Schwarzschild black hole in de Sitter universe was found. Additionally, an approximate method was presented, based on using angular size redshift relation. This approach is appropriate for general case of any multicomponent universe (with matter, radiation and dark energy). It was shown, that supermassive black holes at cosmological distances in universe with matter may give the shadow size comparable with the shadow size in M87, and in the center of our Galaxy. |
gr-qc/0409030 | Christian Boehmer | Christian G. Boehmer | Static perfect fluid balls with given equation of state and cosmological
constant | 13 pages, LaTeX, 1 figure; new reference [7], submitted to the
Ukrainian Journal of Physics | Ukr.J.Phys. 50 (2005) 1219-1225 | null | TUW-04-28 | gr-qc math-ph math.MP | null | Static and spherically symmetric perfect fluid solutions of Einstein's field
equations with cosmological constant are analysed. After showing existence and
uniqueness of a regular solution at the centre the extension of this solution
is discussed. Then the existence of global solutions with given equation of
state and cosmological constant bounded by 4 pi rho_b, where rho_b is the
boundary density (given by the equation of state) of the perfect fluid ball, is
proved.
| [
{
"created": "Tue, 7 Sep 2004 15:09:01 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Sep 2004 12:24:00 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Boehmer",
"Christian G.",
""
]
] | Static and spherically symmetric perfect fluid solutions of Einstein's field equations with cosmological constant are analysed. After showing existence and uniqueness of a regular solution at the centre the extension of this solution is discussed. Then the existence of global solutions with given equation of state and cosmological constant bounded by 4 pi rho_b, where rho_b is the boundary density (given by the equation of state) of the perfect fluid ball, is proved. |
gr-qc/9710063 | Zoltan Perjes | L\'aszl\'o \'A. Gergely, Zolt\'an I. Perj\'es and M\'aty\'as Vas\'uth | Spin effects in gravitational radiation backreaction I. The
Lense-Thirring approximation | 11 pages, 1 figure | Phys.Rev. D57 (1998) 876-884 | 10.1103/PhysRevD.57.876 | null | gr-qc | null | The gravitational radiation backreaction effects are considered in the
Lense-Thirring approximation. New methods for parameterizing the orbit and for
averaging the instantaneous radiative losses are developed. To first order in
the spin S of the black hole, both in the absence and in the presence of
gravitational radiation, a complete description of the test-particle orbit is
given. This is achieved by two improvements over the existing descriptions.
First, by introducing new angle variables with a straightforward geometrical
meaning. Second, by finding a new parametrization of a generic orbit, which
assures that the integration over a radial period can be done in an especially
simple way, by applying the residue theorem. The instantaneous radiation losses
of the system are computed using the formulation of Blanchet, Damour and
Iyer(1989). All losses are given both in terms of the dynamical constants of
motion and the properly defined orbital elements $a,e,\iota$ and $\Psi_0$. The
radiative losses of the constants characterizing the Lense-Thirring motion,
when suitably converted, are in agreement with earlier results of Kidder, Will
and Wiseman(1993), Ryan(1996) and Shibata(1994). In addition, the radiative
losses of two slowly changing orbital elements $\Psi_0,\Phi_0$ are given in
order to complete the characterization of the orbit.
| [
{
"created": "Sat, 11 Oct 1997 12:10:39 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Gergely",
"László Á.",
""
],
[
"Perjés",
"Zoltán I.",
""
],
[
"Vasúth",
"Mátyás",
""
]
] | The gravitational radiation backreaction effects are considered in the Lense-Thirring approximation. New methods for parameterizing the orbit and for averaging the instantaneous radiative losses are developed. To first order in the spin S of the black hole, both in the absence and in the presence of gravitational radiation, a complete description of the test-particle orbit is given. This is achieved by two improvements over the existing descriptions. First, by introducing new angle variables with a straightforward geometrical meaning. Second, by finding a new parametrization of a generic orbit, which assures that the integration over a radial period can be done in an especially simple way, by applying the residue theorem. The instantaneous radiation losses of the system are computed using the formulation of Blanchet, Damour and Iyer(1989). All losses are given both in terms of the dynamical constants of motion and the properly defined orbital elements $a,e,\iota$ and $\Psi_0$. The radiative losses of the constants characterizing the Lense-Thirring motion, when suitably converted, are in agreement with earlier results of Kidder, Will and Wiseman(1993), Ryan(1996) and Shibata(1994). In addition, the radiative losses of two slowly changing orbital elements $\Psi_0,\Phi_0$ are given in order to complete the characterization of the orbit. |
1606.09619 | M. Alessandra Papa | The LIGO Scientific Collaboration and The Virgo Collaboration | Results of the deepest all-sky survey for continuous gravitational waves
on LIGO S6 data running on the Einstein@Home volunteer distributed computing
project | null | Phys. Rev. D 94, 102002 (2016) | 10.1103/PhysRevD.94.102002 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report results of a deep all-sky search for periodic gravitational waves
from isolated neutron stars in data from the S6 LIGO science run. The search
was possible thanks to the computing power provided by the volunteers of the
Einstein@Home distributed computing project. We find no significant signal
candidate and set the most stringent upper limits to date on the amplitude of
gravitational wave signals from the target population. At the frequency of best
strain sensitivity, between $170.5$ and $171$ Hz we set a 90% confidence upper
limit of ${5.5}^{-25}$, while at the high end of our frequency range, around
505 Hz, we achieve upper limits $\simeq {10}^{-24}$. At $230$ Hz we can exclude
sources with ellipticities greater than $10^{-6}$ within 100 pc of Earth with
fiducial value of the principal moment of inertia of $10^{38} \textrm{kg m}^2$.
If we assume a higher (lower) gravitational wave spindown we constrain farther
(closer) objects to higher (lower) ellipticities.
| [
{
"created": "Thu, 30 Jun 2016 19:19:06 GMT",
"version": "v1"
},
{
"created": "Sat, 2 Jul 2016 19:14:36 GMT",
"version": "v2"
}
] | 2016-11-23 | [
[
"The LIGO Scientific Collaboration",
"",
""
],
[
"The Virgo Collaboration",
"",
""
]
] | We report results of a deep all-sky search for periodic gravitational waves from isolated neutron stars in data from the S6 LIGO science run. The search was possible thanks to the computing power provided by the volunteers of the Einstein@Home distributed computing project. We find no significant signal candidate and set the most stringent upper limits to date on the amplitude of gravitational wave signals from the target population. At the frequency of best strain sensitivity, between $170.5$ and $171$ Hz we set a 90% confidence upper limit of ${5.5}^{-25}$, while at the high end of our frequency range, around 505 Hz, we achieve upper limits $\simeq {10}^{-24}$. At $230$ Hz we can exclude sources with ellipticities greater than $10^{-6}$ within 100 pc of Earth with fiducial value of the principal moment of inertia of $10^{38} \textrm{kg m}^2$. If we assume a higher (lower) gravitational wave spindown we constrain farther (closer) objects to higher (lower) ellipticities. |
gr-qc/9806010 | Bijan Saha | B. Saha | Scalar Field with Induced Nonlinearity: Regular Solutions and their
Stability | RevTex, 16 pages, 2 figures (drop.eps, inter.eps), submitted to
General Relativity and Gravitation | J.Theor.Math.Comput.Phys.2:15-26,1999 | null | null | gr-qc | null | Exact particle-like static, spherically and/or cylindrically symmetric
solutions to the equations of interacting scalar and electromagnetic field
system have been obtained within the scope of general relativity. In
particular, we considered Freedman-Robertson-Walker (FRW) space-time as an
external homogenous and isotropic gravitational field whereas the inhomogenous
and isotropic Universe is given by the G$\ddot o$del model. The solutions
obtained have been thoroughly studied for different types of interaction term.
It has been shown that in FRW space-time equations with different interaction
terms may have stable solutions while within the scope of G$\ddot o$del model
only the droplet-like configurations may be stable, if they are located in the
region where $g^{00}>0$.
| [
{
"created": "Wed, 3 Jun 1998 10:21:18 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Saha",
"B.",
""
]
] | Exact particle-like static, spherically and/or cylindrically symmetric solutions to the equations of interacting scalar and electromagnetic field system have been obtained within the scope of general relativity. In particular, we considered Freedman-Robertson-Walker (FRW) space-time as an external homogenous and isotropic gravitational field whereas the inhomogenous and isotropic Universe is given by the G$\ddot o$del model. The solutions obtained have been thoroughly studied for different types of interaction term. It has been shown that in FRW space-time equations with different interaction terms may have stable solutions while within the scope of G$\ddot o$del model only the droplet-like configurations may be stable, if they are located in the region where $g^{00}>0$. |
1801.05475 | Jaume Haro | Jaume de Haro and Supriya Pan | Note on bouncing backgrounds | Version accepted for publication on PRD | Phys. Rev. D 97, 103518 (2018) | 10.1103/PhysRevD.97.103518 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The theory of inflation is one of the fundamental and revolutionary
developments of modern cosmology that became able to explain many issues of
early universe in the context of the standard cosmological model (SCM).
However, the initial singularity of the universe, where physics is indefinite,
is still obscure in the combined `SCM+inflation' scenario. An alternative to
`SCM+inflation' without the initial singularity is thus always welcome, and
bouncing cosmology is an attempt of that. The current work is thus motivated to
investigate the bouncing solutions in modified gravity theories when the
background universe is described by the spatially flat
Friedmann-Lemaitre-Robertson-Walker (FLRW) geometry. We show that the simplest
way to obtain the bouncing cosmologies in such spacetime is to consider some
kind of Lagrangians whose gravitational sector depends only on the square of
the Hubble parameter of the FLRW universe. For these modified Lagrangians, the
corresponding Friedmann equation, a constraint in the dynamics of the universe,
depicts a curve in the phase space $(H,rho)$, where $H$ is the Hubble parameter
and $rho$ being the energy density of the universe. As a consequence, a
bouncing cosmology is obtained when this curve is closed and crosses the axis
$H = 0$ at least twice, and whose simplest particular example is the ellipse
depicting the well-known holonomy corrected Friedmann equation in Loop Quantum
Cosmology (LQC). Sometimes, a crucial point in such theories is the appearance
of the Ostrogradski instability at the perturbative level, however, fortunately
enough, in the present work as long as the linear level of perturbations is
concerned, this instability does not appear but such instability may appear at
the higher-order of perturbations.
| [
{
"created": "Tue, 16 Jan 2018 20:26:51 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Jan 2018 22:01:27 GMT",
"version": "v2"
},
{
"created": "Sat, 28 Apr 2018 07:13:20 GMT",
"version": "v3"
}
] | 2018-05-23 | [
[
"de Haro",
"Jaume",
""
],
[
"Pan",
"Supriya",
""
]
] | The theory of inflation is one of the fundamental and revolutionary developments of modern cosmology that became able to explain many issues of early universe in the context of the standard cosmological model (SCM). However, the initial singularity of the universe, where physics is indefinite, is still obscure in the combined `SCM+inflation' scenario. An alternative to `SCM+inflation' without the initial singularity is thus always welcome, and bouncing cosmology is an attempt of that. The current work is thus motivated to investigate the bouncing solutions in modified gravity theories when the background universe is described by the spatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) geometry. We show that the simplest way to obtain the bouncing cosmologies in such spacetime is to consider some kind of Lagrangians whose gravitational sector depends only on the square of the Hubble parameter of the FLRW universe. For these modified Lagrangians, the corresponding Friedmann equation, a constraint in the dynamics of the universe, depicts a curve in the phase space $(H,rho)$, where $H$ is the Hubble parameter and $rho$ being the energy density of the universe. As a consequence, a bouncing cosmology is obtained when this curve is closed and crosses the axis $H = 0$ at least twice, and whose simplest particular example is the ellipse depicting the well-known holonomy corrected Friedmann equation in Loop Quantum Cosmology (LQC). Sometimes, a crucial point in such theories is the appearance of the Ostrogradski instability at the perturbative level, however, fortunately enough, in the present work as long as the linear level of perturbations is concerned, this instability does not appear but such instability may appear at the higher-order of perturbations. |
gr-qc/0410016 | Harald P. Pfeiffer | Harald P. Pfeiffer, Lawrence E. Kidder, Mark A. Scheel, Deirdre
Shoemaker | Initial data for Einstein's equations with superposed gravitational
waves | Version accepted by PRD; added convergence plots, expanded
discussion. 9 pages, 9 figures | Phys.Rev. D71 (2005) 024020 | 10.1103/PhysRevD.71.024020 | null | gr-qc | null | A method is presented to construct initial data for Einstein's equations as a
superposition of a gravitational wave perturbation on an arbitrary stationary
background spacetime. The method combines the conformal thin sandwich formalism
with linear gravitational waves, and allows detailed control over
characteristics of the superposed gravitational wave like shape, location and
propagation direction. It is furthermore fully covariant with respect to
spatial coordinate changes and allows for very large amplitude of the
gravitational wave.
| [
{
"created": "Mon, 4 Oct 2004 22:14:30 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Feb 2005 17:17:22 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Pfeiffer",
"Harald P.",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Shoemaker",
"Deirdre",
""
]
] | A method is presented to construct initial data for Einstein's equations as a superposition of a gravitational wave perturbation on an arbitrary stationary background spacetime. The method combines the conformal thin sandwich formalism with linear gravitational waves, and allows detailed control over characteristics of the superposed gravitational wave like shape, location and propagation direction. It is furthermore fully covariant with respect to spatial coordinate changes and allows for very large amplitude of the gravitational wave. |
1206.3217 | Joel Franklin | S. Deser and J. Franklin | Symmetrically reduced Galileon equations and solutions | published version | Physical Review D 86, 047701 (2012) | 10.1103/PhysRevD.86.047701 | CALT 68-2876, BRX TH-657 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The maximally complicated arbitrary-dimensional "maximal" Galileon field
equations simplify dramatically for symmetric configurations. Thus, spherical
symmetry reduces the equations from the D- to the two-dimensional Monge-Ampere
equation, axial symmetry to its cubic extension etc. We can then obtain
explicit solutions, such as spherical or axial waves, and relate them to the
(known) general, but highly implicit, lower-D solutions.
| [
{
"created": "Thu, 14 Jun 2012 19:21:09 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Aug 2012 22:21:14 GMT",
"version": "v2"
}
] | 2012-08-24 | [
[
"Deser",
"S.",
""
],
[
"Franklin",
"J.",
""
]
] | The maximally complicated arbitrary-dimensional "maximal" Galileon field equations simplify dramatically for symmetric configurations. Thus, spherical symmetry reduces the equations from the D- to the two-dimensional Monge-Ampere equation, axial symmetry to its cubic extension etc. We can then obtain explicit solutions, such as spherical or axial waves, and relate them to the (known) general, but highly implicit, lower-D solutions. |
1202.2569 | Romualdo Tresguerres | Romualdo Tresguerres | Motion in gauge theories of gravity | 24 pages, 6 figures, revised version with minor changes | Int. J. Geom. Methods Mod. Phys., 10, 1250085 (2013) | 10.1142/S0219887812500855 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A description of motion is proposed, adapted to the composite bundle
interpretation of Poincar\'e Gauge Theory. Reference frames, relative positions
and time evolution are characterized in gauge-theoretical terms. The approach
is illustrated by an appropriate formulation of the familiar example of orbital
motion induced by Schwarzschild spacetime.
| [
{
"created": "Sun, 12 Feb 2012 20:53:24 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Sep 2012 17:31:34 GMT",
"version": "v2"
}
] | 2014-03-21 | [
[
"Tresguerres",
"Romualdo",
""
]
] | A description of motion is proposed, adapted to the composite bundle interpretation of Poincar\'e Gauge Theory. Reference frames, relative positions and time evolution are characterized in gauge-theoretical terms. The approach is illustrated by an appropriate formulation of the familiar example of orbital motion induced by Schwarzschild spacetime. |
gr-qc/0108034 | Seth A. Major | Seth A. Major and Kevin L. Setter | On the Universality of the Entropy-Area Relation | 6 pages | Class.Quant.Grav. 18 (2001) 5293-5298 | 10.1088/0264-9381/18/23/322 | null | gr-qc | null | We present an argument that, for a large class of possible dynamics, a
canonical quantization of gravity will satisfy the Bekenstein-Hawking
entropy-area relation. This result holds for temperatures low compared to the
Planck temperature and for boundaries with areas large compared to Planck area.
We also relate our description, in terms of a grand canonical ensemble, to
previous geometric entropy calculations using area ensembles.
| [
{
"created": "Sat, 11 Aug 2001 01:10:21 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Major",
"Seth A.",
""
],
[
"Setter",
"Kevin L.",
""
]
] | We present an argument that, for a large class of possible dynamics, a canonical quantization of gravity will satisfy the Bekenstein-Hawking entropy-area relation. This result holds for temperatures low compared to the Planck temperature and for boundaries with areas large compared to Planck area. We also relate our description, in terms of a grand canonical ensemble, to previous geometric entropy calculations using area ensembles. |
2404.10400 | Qihong Huang | Qihong Huang, He Huang, Bing Xu, Kaituo Zhang and Hao Chen | Phase space analysis of the evolution of the early universe in
Einstein-Cartan theory | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we perform the phase space analysis to investigate the
evolution of the early universe in Einstein-Cartan theory. By studying the
stability of critical points in dynamical system, it is found that there exist
two stable critical points which represent an expanding solution and an
Einstein static solution respectively. After analyzing the phase diagram of the
dynamical system, we find that there may exist a bouncing universe, an
oscillating universe or an Einstein static universe in the early time of
universe. In addition, by assuming that the early universe filled by the
radiation with $\omega= 1/3$ , the initial states of the early universe are
Einstein static universe or oscillating universe. When the equation of state
$\omega$ decreases with time, the universe can exit from the initial state and
evolve into an expanding phase.
| [
{
"created": "Tue, 16 Apr 2024 08:56:36 GMT",
"version": "v1"
}
] | 2024-04-17 | [
[
"Huang",
"Qihong",
""
],
[
"Huang",
"He",
""
],
[
"Xu",
"Bing",
""
],
[
"Zhang",
"Kaituo",
""
],
[
"Chen",
"Hao",
""
]
] | In this paper, we perform the phase space analysis to investigate the evolution of the early universe in Einstein-Cartan theory. By studying the stability of critical points in dynamical system, it is found that there exist two stable critical points which represent an expanding solution and an Einstein static solution respectively. After analyzing the phase diagram of the dynamical system, we find that there may exist a bouncing universe, an oscillating universe or an Einstein static universe in the early time of universe. In addition, by assuming that the early universe filled by the radiation with $\omega= 1/3$ , the initial states of the early universe are Einstein static universe or oscillating universe. When the equation of state $\omega$ decreases with time, the universe can exit from the initial state and evolve into an expanding phase. |
gr-qc/0607096 | Timothy Clifton | T. Clifton | Spherically Symmetric Solutions to Fourth-Order Theories of Gravity | 10 pages, published version | Class.Quant.Grav. 23 (2006) 7445 | 10.1088/0264-9381/23/24/015 | null | gr-qc | null | Gravitational theories generated from Lagrangians of the form f(R) are
considered. The spherically symmetric solutions to these equations are
discussed, paying particular attention to features that differ from the
standard Schwarzschild solution. The asymptotic form of solutions is described,
as is the lack of validity of Birkhoff's theorem. Exact solutions are presented
which illustrate these points and their stability and geodesics are
investigated.
| [
{
"created": "Sat, 22 Jul 2006 19:38:52 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Nov 2006 21:51:54 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Clifton",
"T.",
""
]
] | Gravitational theories generated from Lagrangians of the form f(R) are considered. The spherically symmetric solutions to these equations are discussed, paying particular attention to features that differ from the standard Schwarzschild solution. The asymptotic form of solutions is described, as is the lack of validity of Birkhoff's theorem. Exact solutions are presented which illustrate these points and their stability and geodesics are investigated. |
0910.3934 | Vladimir Belinski | V. A. Belinski | On Tunnelling Through the Black Hole Horizon | 21 pages, new section is added | Phys. Lett. A 376, 207 (2012) | 10.1016/j.physleta.2011.11.014 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown here that there is no way for particle creation to occur by
quantum tunneling through an infinitesimal neighborhood of the black hole
horizon. This result is a trivial consequence of the regularity of the horizon,
the equivalence principle and the general covariance of the relativistic theory
of gravity. Moreover, we also confirm the less trivial statement that no
particle creation by quantum tunneling through the black hole horizon is
possible independent of the size of the presupposed tunneling domain.
| [
{
"created": "Tue, 20 Oct 2009 18:31:05 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Jun 2012 16:41:06 GMT",
"version": "v2"
}
] | 2012-06-18 | [
[
"Belinski",
"V. A.",
""
]
] | It is shown here that there is no way for particle creation to occur by quantum tunneling through an infinitesimal neighborhood of the black hole horizon. This result is a trivial consequence of the regularity of the horizon, the equivalence principle and the general covariance of the relativistic theory of gravity. Moreover, we also confirm the less trivial statement that no particle creation by quantum tunneling through the black hole horizon is possible independent of the size of the presupposed tunneling domain. |
1608.06543 | Behzad Tahmasebzadeh | Behzad Tahmasebzadeh and Kayoomars Karami | Generalized Brans-Dicke inflation with a quartic potential | 13 pages, 6 figures | Nuclear Physics B 918 (2017) 1 | 10.1016/j.nuclphysb.2017.02.018 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the framework of Brans-Dicke gravity, we investigate inflation with
the quartic potential, $\lambda\varphi^4/4$, in the presence of generalized
Brans-Dicke parameter $\omega_{\rm GBD}(\varphi)$. We obtain the inflationary
observables containing the scalar spectral index, the tensor-to-scalar ratio,
the running of the scalar spectral index and the equilateral non-Gaussianity
parameter in terms of general form of the potential $U(\varphi)$ and
$\omega_{\rm GBD}(\varphi)$. For the quartic potential, our results show that
the predictions of the model are in well agreement with the Planck 2015 data
for the generalized Brans-Dicke parameters $\omega_{\rm
GBD}(\varphi)=\omega_0\varphi^{n}$ and $\omega_0e^{b\varphi}$. This is in
contrast with both the Einstein and standard Brans-Dicke gravity, in which the
result of quartic potential is disfavored by the Planck data.
| [
{
"created": "Sat, 20 Aug 2016 22:49:40 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Mar 2017 15:36:49 GMT",
"version": "v2"
}
] | 2017-03-14 | [
[
"Tahmasebzadeh",
"Behzad",
""
],
[
"Karami",
"Kayoomars",
""
]
] | Within the framework of Brans-Dicke gravity, we investigate inflation with the quartic potential, $\lambda\varphi^4/4$, in the presence of generalized Brans-Dicke parameter $\omega_{\rm GBD}(\varphi)$. We obtain the inflationary observables containing the scalar spectral index, the tensor-to-scalar ratio, the running of the scalar spectral index and the equilateral non-Gaussianity parameter in terms of general form of the potential $U(\varphi)$ and $\omega_{\rm GBD}(\varphi)$. For the quartic potential, our results show that the predictions of the model are in well agreement with the Planck 2015 data for the generalized Brans-Dicke parameters $\omega_{\rm GBD}(\varphi)=\omega_0\varphi^{n}$ and $\omega_0e^{b\varphi}$. This is in contrast with both the Einstein and standard Brans-Dicke gravity, in which the result of quartic potential is disfavored by the Planck data. |
1405.6998 | Seyed Hossein Hendi Dr. | Seyed Hossein Hendi and Ahmad Sheykhi | Charge rotating black string in gravitating nonlinear electromagnetic
fields | 11 pages, 3 eps figures | Physical Review D 88, 044044 (2013) | 10.1103/PhysRevD.88.044044 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a new class of charged rotating black string solutions coupled
to a nonlinear electromagnetic field in the background of anti-de Sitter
spaces. We consider two types of nonlinear electromagnetic field namely,
logarithmic and exponential forms. We investigate the geometric effects of
nonlinearity parameter and find that for large $r$, these solutions recover the
rotating back string solutions of Einstein-Maxwell theory. We calculate the
conserved and thermodynamic quantities of the rotating black string. We also
analyze thermodynamics of the spacetime and verify the validity of the first
law of thermodynamics for the obtained solutions.
| [
{
"created": "Sat, 24 May 2014 19:02:55 GMT",
"version": "v1"
}
] | 2014-05-28 | [
[
"Hendi",
"Seyed Hossein",
""
],
[
"Sheykhi",
"Ahmad",
""
]
] | We construct a new class of charged rotating black string solutions coupled to a nonlinear electromagnetic field in the background of anti-de Sitter spaces. We consider two types of nonlinear electromagnetic field namely, logarithmic and exponential forms. We investigate the geometric effects of nonlinearity parameter and find that for large $r$, these solutions recover the rotating back string solutions of Einstein-Maxwell theory. We calculate the conserved and thermodynamic quantities of the rotating black string. We also analyze thermodynamics of the spacetime and verify the validity of the first law of thermodynamics for the obtained solutions. |
gr-qc/0608018 | Robert M. Wald | Robert M. Wald | The History and Present Status of Quantum Field Theory in Curved
Spacetime | 15 pages, no figures; contribution to 7th International Conference on
the History of General Relativity | null | null | null | gr-qc hep-th | null | Quantum field theory in curved spacetime is a theory wherein matter is
treated fully in accord with the principles of quantum field theory, but
gravity is treated classically in accord with general relativity. It is not
expected to be an exact theory of nature, but it should provide a good
approximate description when the quantum effects of gravity itself do not play
a dominant role. A major impetus to the theory was provided by Hawking's
calculation of particle creation by black holes, showing that black holes
radiate as perfect black bodies. During the past 30 years, considerable
progress has been made in giving a mathematically rigorous formulation of
quantum field theory in curved spacetime. Major issues of principle with regard
to the formulation of the theory arise from the lack of Poincare symmetry and
the absence of a preferred vacuum state or preferred notion of ``particles''.
By the mid-1980's, it was understood how all of these difficulties could be
overcome for free (i.e., non-self-interacting) quantum fields by formulating
the theory via the algebraic approach and focusing attention on the local field
observables rather than a notion of ``particles''. However, these ideas, by
themselves, were not adequate for the formulation of interacting quantum field
theory, even at a perturbative level, since standard renormalization
prescriptions in Minkowski spacetime rely heavily on Poincare invariance and
the existence of a Poincare invariant vacuum state. However, during the past
decade, great progress has been made, mainly due to the importation into the
theory of the methods of ``microlocal analysis''. This article will describe
the historical development of the subject and describe some of the recent
progress.
| [
{
"created": "Thu, 3 Aug 2006 15:11:01 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Wald",
"Robert M.",
""
]
] | Quantum field theory in curved spacetime is a theory wherein matter is treated fully in accord with the principles of quantum field theory, but gravity is treated classically in accord with general relativity. It is not expected to be an exact theory of nature, but it should provide a good approximate description when the quantum effects of gravity itself do not play a dominant role. A major impetus to the theory was provided by Hawking's calculation of particle creation by black holes, showing that black holes radiate as perfect black bodies. During the past 30 years, considerable progress has been made in giving a mathematically rigorous formulation of quantum field theory in curved spacetime. Major issues of principle with regard to the formulation of the theory arise from the lack of Poincare symmetry and the absence of a preferred vacuum state or preferred notion of ``particles''. By the mid-1980's, it was understood how all of these difficulties could be overcome for free (i.e., non-self-interacting) quantum fields by formulating the theory via the algebraic approach and focusing attention on the local field observables rather than a notion of ``particles''. However, these ideas, by themselves, were not adequate for the formulation of interacting quantum field theory, even at a perturbative level, since standard renormalization prescriptions in Minkowski spacetime rely heavily on Poincare invariance and the existence of a Poincare invariant vacuum state. However, during the past decade, great progress has been made, mainly due to the importation into the theory of the methods of ``microlocal analysis''. This article will describe the historical development of the subject and describe some of the recent progress. |
1102.4863 | Daniela Doneva | Daniela D. Doneva, Ivan Zh. Stefanov, Stoytcho S. Yazadjiev | Solitons and Black Holes in a Generalized Skyrme Model with
Dilaton-Quarkonium field | 19 pages, 10 figures; v2: typos corrected, comments added | Phys.Rev.D83:124007,2011 | 10.1103/PhysRevD.83.124007 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Skyrme theory is among the viable effective theories which emerge from
low-energy limit of quantum chromodynamics. Many of its generalizations include
also a dilaton. Here we find new self-gravitating solutions, both solitons and
black holes, in a Generalized Skyrme Model (GSM) in which a dilaton is present.
The investigation of the properties of the solutions is done numerically. We
find that the introduction of the dilaton in the theory does not change the
picture qualitatively, only quantitatively. The model considered here has one
free parameter more than the Einstein-Skyrme model which comes from the
potential of the dilaton. We have applied also the turning point method to
establish that one of the black-hole branches of solutions is unstable. The
turning point method here is based on the first law of black-hole
thermodynamics a detailed derivation of which is given in the Appendix of the
paper.
| [
{
"created": "Wed, 23 Feb 2011 21:51:57 GMT",
"version": "v1"
},
{
"created": "Sat, 9 Jun 2012 20:00:36 GMT",
"version": "v2"
}
] | 2012-06-12 | [
[
"Doneva",
"Daniela D.",
""
],
[
"Stefanov",
"Ivan Zh.",
""
],
[
"Yazadjiev",
"Stoytcho S.",
""
]
] | Skyrme theory is among the viable effective theories which emerge from low-energy limit of quantum chromodynamics. Many of its generalizations include also a dilaton. Here we find new self-gravitating solutions, both solitons and black holes, in a Generalized Skyrme Model (GSM) in which a dilaton is present. The investigation of the properties of the solutions is done numerically. We find that the introduction of the dilaton in the theory does not change the picture qualitatively, only quantitatively. The model considered here has one free parameter more than the Einstein-Skyrme model which comes from the potential of the dilaton. We have applied also the turning point method to establish that one of the black-hole branches of solutions is unstable. The turning point method here is based on the first law of black-hole thermodynamics a detailed derivation of which is given in the Appendix of the paper. |
gr-qc/0510104 | Yuri Shtanov | Petr Tretyakov, Aleksey Toporensky, Yuri Shtanov, Varun Sahni | Quantum effects, soft singularities and the fate of the universe in a
braneworld cosmology | 19 pages, 3 figures, text slightly improved and references added.
Accepted for publication in Classical and Quantum Gravity | Class.Quant.Grav.23:3259-3274,2006 | 10.1088/0264-9381/23/10/001 | null | gr-qc astro-ph hep-ph | null | We examine a class of braneworld models in which the expanding universe
encounters a "quiescent" future singularity. At a quiescent singularity, the
energy density and pressure of the cosmic fluid as well as the Hubble parameter
remain finite while all derivatives of the Hubble parameter diverge (i.e.,
${\dot H}$, ${\ddot H}$, etc. $\to \infty$). Since the Kretschmann invariant
diverges ($R_{iklm}R^{iklm} \to \infty$) at the singularity, one expects
quantum effects to play an important role as the quiescent singularity is
approached. We explore the effects of vacuum polarization due to massless
conformally coupled fields near the singularity and show that these can either
cause the universe to recollapse or, else, lead to a softer singularity at
which $H$, ${\dot H}$, and ${\ddot H}$ remain finite while ${\dddot H}$ and
higher derivatives of the Hubble parameter diverge. An important aspect of the
quiescent singularity is that it is encountered in regions of low density,
which has obvious implications for a universe consisting of a cosmic web of
high and low density regions -- superclusters and voids. In addition to vacuum
polarization, the effects of quantum particle production of non-conformal
fields are also likely to be important. A preliminary examination shows that
intense particle production can lead to an accelerating universe whose Hubble
parameter shows oscillations about a constant value.
| [
{
"created": "Mon, 24 Oct 2005 09:33:03 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Mar 2006 22:41:03 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Tretyakov",
"Petr",
""
],
[
"Toporensky",
"Aleksey",
""
],
[
"Shtanov",
"Yuri",
""
],
[
"Sahni",
"Varun",
""
]
] | We examine a class of braneworld models in which the expanding universe encounters a "quiescent" future singularity. At a quiescent singularity, the energy density and pressure of the cosmic fluid as well as the Hubble parameter remain finite while all derivatives of the Hubble parameter diverge (i.e., ${\dot H}$, ${\ddot H}$, etc. $\to \infty$). Since the Kretschmann invariant diverges ($R_{iklm}R^{iklm} \to \infty$) at the singularity, one expects quantum effects to play an important role as the quiescent singularity is approached. We explore the effects of vacuum polarization due to massless conformally coupled fields near the singularity and show that these can either cause the universe to recollapse or, else, lead to a softer singularity at which $H$, ${\dot H}$, and ${\ddot H}$ remain finite while ${\dddot H}$ and higher derivatives of the Hubble parameter diverge. An important aspect of the quiescent singularity is that it is encountered in regions of low density, which has obvious implications for a universe consisting of a cosmic web of high and low density regions -- superclusters and voids. In addition to vacuum polarization, the effects of quantum particle production of non-conformal fields are also likely to be important. A preliminary examination shows that intense particle production can lead to an accelerating universe whose Hubble parameter shows oscillations about a constant value. |
2402.07482 | Marc Mars | Marc Mars | Hypersurface data: General properties and Birkhoff theorem in spherical
symmetry | 31 pages, no figures | Mediterranean Journal of Mathematics, Vol. 17, Art. num. 206
(2020) | 10.1007/s00009-020-01608-1 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The notions of (metric) hypersurface data were introduced in [Mars,2013] as a
tool to analyze, from an abstract viewpoint, hypersurfaces of arbitrary
signature in pseudo-riemannian manifolds. In this paper, general geometric
properties of these notions are studied. In particular, the properties of the
gauge group inherent to the geometric construction are analyzed and the metric
hypersurface connection and its corresponding curvature tensor are studied. The
results set up the stage for various potential applications. The particular but
relevant case of spherical symmetry is considered in detail. In particular, a
collection of gauge invariant quantities and a radial covariant derivative is
introduced, such that the constraint equations of the Einstein field equations
with matter can be written in a very compact form. The general solution of
these equations in the vacuum case and Lorentzian ambient signature is
obtained, and a generalization of the Birkhoff theorem to this abstract
hypersurface setting is derived.
| [
{
"created": "Mon, 12 Feb 2024 08:42:57 GMT",
"version": "v1"
}
] | 2024-02-13 | [
[
"Mars",
"Marc",
""
]
] | The notions of (metric) hypersurface data were introduced in [Mars,2013] as a tool to analyze, from an abstract viewpoint, hypersurfaces of arbitrary signature in pseudo-riemannian manifolds. In this paper, general geometric properties of these notions are studied. In particular, the properties of the gauge group inherent to the geometric construction are analyzed and the metric hypersurface connection and its corresponding curvature tensor are studied. The results set up the stage for various potential applications. The particular but relevant case of spherical symmetry is considered in detail. In particular, a collection of gauge invariant quantities and a radial covariant derivative is introduced, such that the constraint equations of the Einstein field equations with matter can be written in a very compact form. The general solution of these equations in the vacuum case and Lorentzian ambient signature is obtained, and a generalization of the Birkhoff theorem to this abstract hypersurface setting is derived. |
gr-qc/9707039 | Michael A. Clayton | M.A. Clayton | Canonical General Relativity: the Diffeomorphism constraints and Spatial
Frame Transformations | 12 pages; requires amsart, amssymb, amsmath; cleaned up slightly. To
appear in J. Math. Phys | J.Math.Phys. 39 (1998) 3805-3816 | 10.1063/1.532469 | CERN--TH/97--168 | gr-qc | null | Einstein's general relativity with both metric and vielbein treated as
independent fields is considered, demonstrating the existence of a consistent
variational principle and deriving a Hamiltonian formalism that treats the
spatial metric and spatial vielbein as canonical coordinates. This results in a
Hamiltonian in standard form that consists of Hamiltonian and momentum
constraints as well as constraints that generate spatial frame
transformations---all appearing as primary, first class constraints on phase
space. The formalism encompasses the standard coordinate frame and vielbein
approaches to general relativity, and the constraint algebra derived herein
reproduces known results in either limit.
| [
{
"created": "Wed, 16 Jul 1997 15:35:05 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Jan 1998 12:36:27 GMT",
"version": "v2"
},
{
"created": "Wed, 27 May 1998 12:33:35 GMT",
"version": "v3"
}
] | 2009-10-30 | [
[
"Clayton",
"M. A.",
""
]
] | Einstein's general relativity with both metric and vielbein treated as independent fields is considered, demonstrating the existence of a consistent variational principle and deriving a Hamiltonian formalism that treats the spatial metric and spatial vielbein as canonical coordinates. This results in a Hamiltonian in standard form that consists of Hamiltonian and momentum constraints as well as constraints that generate spatial frame transformations---all appearing as primary, first class constraints on phase space. The formalism encompasses the standard coordinate frame and vielbein approaches to general relativity, and the constraint algebra derived herein reproduces known results in either limit. |
2310.20302 | Diego S\'aez-Chill\'on G\'omez | Sergei D. Odintsov, Diego S\'aez-Chill\'on G\'omez, German S. Sharov | Exponential F(R) gravity with axion dark matter | 13 pages, 3 figures. To be published in Phys. Dark Universe | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmological evolution within the framework of exponential $F(R)$ gravity
is analysed by assuming two forms for dark matter: (a) a standard dust-like
fluid and (b) an axion scalar field. As shown in previous literature, an
axion-like field oscillates during the cosmological evolution but can play the
role of dark matter when approaching the minimum of its potential. Both
scenarios are confronted with recent observational data including the Pantheon
Type Ia supernovae, Hubble parameter estimations (Cosmic Chronometers), Baryon
Acoustic Oscillations and Cosmic Microwave Background distances. The models
show great possibilities in describing these observations when compared with
the $\Lambda$CDM model, supporting the viability of exponential $F(R)$ gravity.
The differences between both descriptions of dark matter is analysed.
| [
{
"created": "Tue, 31 Oct 2023 09:16:07 GMT",
"version": "v1"
}
] | 2023-11-01 | [
[
"Odintsov",
"Sergei D.",
""
],
[
"Gómez",
"Diego Sáez-Chillón",
""
],
[
"Sharov",
"German S.",
""
]
] | The cosmological evolution within the framework of exponential $F(R)$ gravity is analysed by assuming two forms for dark matter: (a) a standard dust-like fluid and (b) an axion scalar field. As shown in previous literature, an axion-like field oscillates during the cosmological evolution but can play the role of dark matter when approaching the minimum of its potential. Both scenarios are confronted with recent observational data including the Pantheon Type Ia supernovae, Hubble parameter estimations (Cosmic Chronometers), Baryon Acoustic Oscillations and Cosmic Microwave Background distances. The models show great possibilities in describing these observations when compared with the $\Lambda$CDM model, supporting the viability of exponential $F(R)$ gravity. The differences between both descriptions of dark matter is analysed. |
2207.12611 | Alexander Vikman | Pavel Jirou\v{s}ek, Keigo Shimada, Alexander Vikman and Masahide
Yamaguchi | Disforming to Conformal Symmetry | 18 pages + bibliography, no figures; V3: minor changes, updated
bibliography, published version | JCAP 11 (2022) 019 | 10.1088/1475-7516/2022/11/019 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We analyse the dynamical properties of disformally transformed theories of
gravity. We show that disformal transformation typically introduces novel
degrees of freedom, equivalent to the mimetic dark matter, which possesses a
Weyl-invariant formulation. We demonstrate that this phenomenon occurs in a
wider variety of disformal transformations than previously thought.
| [
{
"created": "Tue, 26 Jul 2022 02:26:29 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Aug 2022 13:59:32 GMT",
"version": "v2"
},
{
"created": "Fri, 11 Nov 2022 11:54:22 GMT",
"version": "v3"
}
] | 2022-11-14 | [
[
"Jiroušek",
"Pavel",
""
],
[
"Shimada",
"Keigo",
""
],
[
"Vikman",
"Alexander",
""
],
[
"Yamaguchi",
"Masahide",
""
]
] | We analyse the dynamical properties of disformally transformed theories of gravity. We show that disformal transformation typically introduces novel degrees of freedom, equivalent to the mimetic dark matter, which possesses a Weyl-invariant formulation. We demonstrate that this phenomenon occurs in a wider variety of disformal transformations than previously thought. |
1001.2395 | Otakar Svitek | Otakar Svitek | Existence of horizons in Robinson-Trautman spacetimes of arbitrary
dimension | to appear in proceedings of MGM12 Paris, France | null | 10.1142/9789814374552_0136 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the higher dimensional generalization of Penrose-Tod equation
describing past horizon in Robinson-Trautman spacetimes with a cosmological
constant and pure radiation. Results for D=4 dimensions are summarized.
Existence of its solutions in D>4 dimensions is proved using tools for
nonlinear elliptic partial differential equations.
| [
{
"created": "Thu, 14 Jan 2010 10:11:49 GMT",
"version": "v1"
}
] | 2016-11-15 | [
[
"Svitek",
"Otakar",
""
]
] | We derive the higher dimensional generalization of Penrose-Tod equation describing past horizon in Robinson-Trautman spacetimes with a cosmological constant and pure radiation. Results for D=4 dimensions are summarized. Existence of its solutions in D>4 dimensions is proved using tools for nonlinear elliptic partial differential equations. |
1312.6684 | Muhammad Jamil Amir | M. Jamil Amir and Saima Naheed | Spatially Homogeneous Rotating Solution in f(R) Gravity and Its Energy
Contents | 10 pages | Int. J. Theor. Phys. (2013)52: 1688-1695 | 10.1007/s10773-013-1489-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, the metric approach of $f(R)$ theory of gravity is used to
investigate the exact vacuum solutions of spatially homogeneous rotating
spacetimes. For this purpose, R is replaced by f(R) in the standard
Einstein-Hilbert action and the set of modified Einstein field equations reduce
to a single equation. We adopt the assumption of constant Ricci scalar which
maybe zero or non-zero. Moreover, the energy density of the non-trivial
solution has been evaluated by using the generalized Landau-Lifshitz
energy-momentum complex in the perspective of f(R) gravity for some appropriate
f(R) model, which turns out to be a constant quantity.
| [
{
"created": "Sun, 22 Dec 2013 06:59:37 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"Amir",
"M. Jamil",
""
],
[
"Naheed",
"Saima",
""
]
] | In this paper, the metric approach of $f(R)$ theory of gravity is used to investigate the exact vacuum solutions of spatially homogeneous rotating spacetimes. For this purpose, R is replaced by f(R) in the standard Einstein-Hilbert action and the set of modified Einstein field equations reduce to a single equation. We adopt the assumption of constant Ricci scalar which maybe zero or non-zero. Moreover, the energy density of the non-trivial solution has been evaluated by using the generalized Landau-Lifshitz energy-momentum complex in the perspective of f(R) gravity for some appropriate f(R) model, which turns out to be a constant quantity. |
1702.08381 | Stanislav Komarov | Alexander Gorbatsievich, Stanislav Komarov, Alexander Tarasenko | Optical appearance of a compact binary system in the neighbourhood of
supermassive black hole | 30 pages, 6 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Optical appearance of a compact binary star in the field of a supermassive
black hole is modeled in a strong field regime. Expressions for the redshift,
magnification coefficient and pulsar extinction time are derived.
By using the vierbein formalism we have derived equations of motion of
compact binary star in the external gravitational field. We have analysed both
the evolution of redshift of the optical ray from the usual star or white
dwarf, and the times of arrival of pulses of pulsar. The results are
illustrated by a calculation for a model binary system for the case of external
gravitational field of a Schwarzschild black hole. The obtained results can be
used for fitting timing data from the X-ray pulsars that moves in the
neighbourhood of the Galactic Center (Sgr A*).
| [
{
"created": "Mon, 27 Feb 2017 17:08:15 GMT",
"version": "v1"
}
] | 2017-02-28 | [
[
"Gorbatsievich",
"Alexander",
""
],
[
"Komarov",
"Stanislav",
""
],
[
"Tarasenko",
"Alexander",
""
]
] | Optical appearance of a compact binary star in the field of a supermassive black hole is modeled in a strong field regime. Expressions for the redshift, magnification coefficient and pulsar extinction time are derived. By using the vierbein formalism we have derived equations of motion of compact binary star in the external gravitational field. We have analysed both the evolution of redshift of the optical ray from the usual star or white dwarf, and the times of arrival of pulses of pulsar. The results are illustrated by a calculation for a model binary system for the case of external gravitational field of a Schwarzschild black hole. The obtained results can be used for fitting timing data from the X-ray pulsars that moves in the neighbourhood of the Galactic Center (Sgr A*). |
2204.07871 | Cl\'audio Gomes | Cl\'audio Gomes, Kamel Ourabah | Quantum kinetic theory of Jeans instability in non-minimal
matter-curvature coupling gravity | 13 pages, 2 figures, 3 plots | null | 10.1140/epjc/s10052-023-11184-9 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We present a quantum treatment of the Jeans gravitational instability in the
Newtonian limit of the non-minimal matter-curvature coupling gravity model. By
relying on Wigner functions, allowing for the representation of quantum states
in a classical phase space, we formulate a quantum kinetic treatment of this
problem, generalizing the classical kinetic approach [C. Gomes, Eur. Phys. J. C
80, 633 (2020)]. This allows us to study the interplay between non-minimal
matter-curvature coupling effects, quantum effects, and kinetic
(finite-temperature) effects, on the Jeans criterion. We study in detail
special cases of the model (general relativity, f(R) theories, pure non-minimal
coupling, etc.) and confront the model with the observed stability of Bok
globules.
| [
{
"created": "Sat, 16 Apr 2022 21:02:39 GMT",
"version": "v1"
}
] | 2023-01-23 | [
[
"Gomes",
"Cláudio",
""
],
[
"Ourabah",
"Kamel",
""
]
] | We present a quantum treatment of the Jeans gravitational instability in the Newtonian limit of the non-minimal matter-curvature coupling gravity model. By relying on Wigner functions, allowing for the representation of quantum states in a classical phase space, we formulate a quantum kinetic treatment of this problem, generalizing the classical kinetic approach [C. Gomes, Eur. Phys. J. C 80, 633 (2020)]. This allows us to study the interplay between non-minimal matter-curvature coupling effects, quantum effects, and kinetic (finite-temperature) effects, on the Jeans criterion. We study in detail special cases of the model (general relativity, f(R) theories, pure non-minimal coupling, etc.) and confront the model with the observed stability of Bok globules. |
1505.01791 | Otakar Svitek | T. Tahamtan, O. Svitek | Kundt spacetimes minimally coupled to scalar field | updated to published version | Eur. Phys. J. C 77 (2017) 384 | 10.1140/epjc/s10052-017-4945-z | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We derive an exact solution belonging to Kundt class of spacetimes both with
and without a cosmological constant that are minimally coupled to a free
massless scalar field. We show the algebraic type of these solutions and give
interpretation of the results. Subsequently, we look for solutions additionally
containing an electromagnetic field satisfying nonlinear field equations.
| [
{
"created": "Thu, 7 May 2015 17:56:31 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jan 2016 16:59:06 GMT",
"version": "v2"
},
{
"created": "Thu, 25 May 2017 16:56:47 GMT",
"version": "v3"
},
{
"created": "Fri, 16 Jun 2017 14:10:01 GMT",
"version": "v4"
}
] | 2017-06-19 | [
[
"Tahamtan",
"T.",
""
],
[
"Svitek",
"O.",
""
]
] | We derive an exact solution belonging to Kundt class of spacetimes both with and without a cosmological constant that are minimally coupled to a free massless scalar field. We show the algebraic type of these solutions and give interpretation of the results. Subsequently, we look for solutions additionally containing an electromagnetic field satisfying nonlinear field equations. |
1509.00911 | Aharon Davidson | Aharon Davidson, Ben Yellin | Is spacetime absolutely or just most probably Lorentzian? | 6 two column pages, 2 figures | Class. Quantum Grav. 33, 165009 (2016) | 10.1088/0264-9381/33/16/165009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Pre-gauging the cosmological scale factor $a(t)$ does not introduce
unphysical degrees of freedom into the exact FLRW classical solution. It seems
to lead, however, to a non-dynamical mini superspace. The missing ingredient, a
generalised momentum enjoying canonical Dirac (rather than Poisson) brackets
with the lapse function $n(t)$, calls for measure scaling which can be realised
by means of a scalar field. The latter is essential for establishing a
geometrical connection with the 5-dimensional Kaluza-Klein
Schwarzschild-deSitter black hole. Contrary to the Hartle-Hawking approach, (i)
The $t$-independent wave function $\psi(a)$ is traded for an explicit
$t$-dependent $\psi(n, t)$, (ii) The classical FLRW configuration does play a
major role in the structure of the 'most classical' cosmological wave packet,
and (iii) The non-singular Euclid/Lorentz crossovers get quantum mechanically
smeared.
| [
{
"created": "Thu, 3 Sep 2015 01:24:49 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jul 2016 17:28:19 GMT",
"version": "v2"
}
] | 2016-07-27 | [
[
"Davidson",
"Aharon",
""
],
[
"Yellin",
"Ben",
""
]
] | Pre-gauging the cosmological scale factor $a(t)$ does not introduce unphysical degrees of freedom into the exact FLRW classical solution. It seems to lead, however, to a non-dynamical mini superspace. The missing ingredient, a generalised momentum enjoying canonical Dirac (rather than Poisson) brackets with the lapse function $n(t)$, calls for measure scaling which can be realised by means of a scalar field. The latter is essential for establishing a geometrical connection with the 5-dimensional Kaluza-Klein Schwarzschild-deSitter black hole. Contrary to the Hartle-Hawking approach, (i) The $t$-independent wave function $\psi(a)$ is traded for an explicit $t$-dependent $\psi(n, t)$, (ii) The classical FLRW configuration does play a major role in the structure of the 'most classical' cosmological wave packet, and (iii) The non-singular Euclid/Lorentz crossovers get quantum mechanically smeared. |
gr-qc/9611064 | Chung-I. Kuo | Chung-I Kuo(Soochow University) | A Revised Proof of the Existence of Negative Energy Density in Quantum
Field Theory | 7 pages, RevTeX file, no figures, accepted by Nuovo Cimento IL | Nuovo Cim. B112 (1997) 629-632 | null | null | gr-qc | null | Negative energy density is unavoidable in the quantum theory of field. We
give a revised proof of the existence of negative energy density unambiguously
for a massless scalar field.
| [
{
"created": "Wed, 27 Nov 1996 08:39:50 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Jan 1997 06:24:29 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Kuo",
"Chung-I",
"",
"Soochow University"
]
] | Negative energy density is unavoidable in the quantum theory of field. We give a revised proof of the existence of negative energy density unambiguously for a massless scalar field. |
2106.12356 | Ying Wang | Xin Wu, Ying Wang, Wei Sun, Fuyao Liu | Construction of explicit symplectic integrators in general relativity.
IV. Kerr black holes | 12pages,12figures | null | 10.3847/1538-4357/abfc45 | null | gr-qc astro-ph.IM nlin.CD physics.comp-ph | http://creativecommons.org/licenses/by/4.0/ | In previous papers, explicit symplectic integrators were designed for
nonrotating black holes, such as a Schwarzschild black hole. However, they fail
to work in the Kerr spacetime because not all variables can be separable, or
not all splitting parts have analytical solutions as explicit functions of
proper time. To cope with this difficulty, we introduce a time transformation
function to the Hamiltonian of Kerr geometry so as to obtain a time-transformed
Hamiltonian consisting of five splitting parts, whose analytical solutions are
explicit functions of the new coordinate time. The chosen time transformation
function can cause time steps to be adaptive, but it is mainly used to
implement the desired splitting of the time transformed Hamiltonian. In this
manner, new explicit symplectic algorithms are easily available. Unlike Runge
Kutta integrators, the newly proposed algorithms exhibit good long term
behavior in the conservation of Hamiltonian quantities when appropriate fixed
coordinate time steps are considered. They are better than same order implicit
and explicit mixed symplectic algorithms and extended phase space explicit
symplectic like methods in computational efficiency. The proposed idea on the
construction of explicit symplectic integrators is suitable for not only the
Kerr metric but also many other relativistic problems, such as a Kerr black
hole immersed in a magnetic field, a Kerr Newman black hole with an external
magnetic field, axially symmetric core shell systems, and five dimensional
black ring metrics.
| [
{
"created": "Wed, 23 Jun 2021 12:48:41 GMT",
"version": "v1"
}
] | 2021-06-24 | [
[
"Wu",
"Xin",
""
],
[
"Wang",
"Ying",
""
],
[
"Sun",
"Wei",
""
],
[
"Liu",
"Fuyao",
""
]
] | In previous papers, explicit symplectic integrators were designed for nonrotating black holes, such as a Schwarzschild black hole. However, they fail to work in the Kerr spacetime because not all variables can be separable, or not all splitting parts have analytical solutions as explicit functions of proper time. To cope with this difficulty, we introduce a time transformation function to the Hamiltonian of Kerr geometry so as to obtain a time-transformed Hamiltonian consisting of five splitting parts, whose analytical solutions are explicit functions of the new coordinate time. The chosen time transformation function can cause time steps to be adaptive, but it is mainly used to implement the desired splitting of the time transformed Hamiltonian. In this manner, new explicit symplectic algorithms are easily available. Unlike Runge Kutta integrators, the newly proposed algorithms exhibit good long term behavior in the conservation of Hamiltonian quantities when appropriate fixed coordinate time steps are considered. They are better than same order implicit and explicit mixed symplectic algorithms and extended phase space explicit symplectic like methods in computational efficiency. The proposed idea on the construction of explicit symplectic integrators is suitable for not only the Kerr metric but also many other relativistic problems, such as a Kerr black hole immersed in a magnetic field, a Kerr Newman black hole with an external magnetic field, axially symmetric core shell systems, and five dimensional black ring metrics. |
1809.04992 | Damianos Iosifidis | Damianos Iosifidis, Christos G. Tsagas, Anastasios C. Petkou | The Raychaudhuri equation in spacetimes with torsion and non-metricity | Revised version. References added. To appear in PRD | Phys. Rev. D 98, 104037 (2018) | 10.1103/PhysRevD.98.104037 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce and develop the 1+3 covariant approach to relativity and
cosmology to spacetimes of arbitrary dimensions that have nonzero torsion and
do not satisfy the metricity condition. Focusing on timelike observers, we
identify and discuss the main differences between their kinematics and those of
their counterparts living in standard Riemannian spacetimes. At the centre of
our analysis lies the Raychaudhuri equation, which is the fundamental formula
monitoring the convergence/divergence, namely the collapse/expansion, of
timelike worldline congruences. To the best of our knowledge, we provide the
most general expression so far of the Raychaudhuri equation, with applications
to an extensive range of non-standard astrophysical and cosmological studies.
Assuming that metricity holds, but allowing for nonzero torsion, we recover the
results of analogous previous treatments. Focusing on non-metricity alone, we
identify a host of effects that depend on the nature of the timelike congruence
and on the type of the adopted non-metricity. We also demonstrate that in
spaces of high symmetry one can recover the pure-torsion results from their
pure non-metricity analogues, and vice-versa, via a simple ansatz between
torsion and non-metricity.
| [
{
"created": "Thu, 13 Sep 2018 14:42:22 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Nov 2018 14:16:50 GMT",
"version": "v2"
}
] | 2018-12-05 | [
[
"Iosifidis",
"Damianos",
""
],
[
"Tsagas",
"Christos G.",
""
],
[
"Petkou",
"Anastasios C.",
""
]
] | We introduce and develop the 1+3 covariant approach to relativity and cosmology to spacetimes of arbitrary dimensions that have nonzero torsion and do not satisfy the metricity condition. Focusing on timelike observers, we identify and discuss the main differences between their kinematics and those of their counterparts living in standard Riemannian spacetimes. At the centre of our analysis lies the Raychaudhuri equation, which is the fundamental formula monitoring the convergence/divergence, namely the collapse/expansion, of timelike worldline congruences. To the best of our knowledge, we provide the most general expression so far of the Raychaudhuri equation, with applications to an extensive range of non-standard astrophysical and cosmological studies. Assuming that metricity holds, but allowing for nonzero torsion, we recover the results of analogous previous treatments. Focusing on non-metricity alone, we identify a host of effects that depend on the nature of the timelike congruence and on the type of the adopted non-metricity. We also demonstrate that in spaces of high symmetry one can recover the pure-torsion results from their pure non-metricity analogues, and vice-versa, via a simple ansatz between torsion and non-metricity. |
0903.4124 | Nakia Carlevaro | Nakia Carlevaro, Orchidea Maria Lecian, Giovanni Montani | Fermion Dynamics by Internal and Space-Time Symmetries | 10 pages, no figure | Mod.Phys.Lett.A24:415-427,2009 | 10.1142/S0217732309030199 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This manuscript is devoted to introduce a gauge theory of the Lorentz Group
based on the ambiguity emerging in dealing with isometric
diffeo-morphism-induced Lorentz transformations. The behaviors under local
transformations of fermion fields and spin connections (assumed to be ordinary
world vectors) are analyzed in flat space-time and the role of the torsion
field, within the generalization to curved space-time, is briefly discussed.
The fermion dynamics is then analyzed including the new gauge fields and
assuming time-gauge. Stationary solutions of the problem are also analyzed in
the non-relativistic limit, to study the spinor structure of an hydrogen-like
atom.
| [
{
"created": "Tue, 24 Mar 2009 16:38:01 GMT",
"version": "v1"
}
] | 2014-11-18 | [
[
"Carlevaro",
"Nakia",
""
],
[
"Lecian",
"Orchidea Maria",
""
],
[
"Montani",
"Giovanni",
""
]
] | This manuscript is devoted to introduce a gauge theory of the Lorentz Group based on the ambiguity emerging in dealing with isometric diffeo-morphism-induced Lorentz transformations. The behaviors under local transformations of fermion fields and spin connections (assumed to be ordinary world vectors) are analyzed in flat space-time and the role of the torsion field, within the generalization to curved space-time, is briefly discussed. The fermion dynamics is then analyzed including the new gauge fields and assuming time-gauge. Stationary solutions of the problem are also analyzed in the non-relativistic limit, to study the spinor structure of an hydrogen-like atom. |
gr-qc/9512028 | Marcos Duarte Maia | E. M. Monte and M.D. Maia (Universidade de Bras\'ilia) | A Fundamental Theorem of Space-times | 12 pages, Latex | null | null | UnB/Mat/Fm-m495 | gr-qc | null | The fundamental theorem of submanifolds is adapted to space-times. It is
shown that the integrability conditions for the existence of submanifolds of a
pseudo-Euclidean space contain the Einstein and Yang-Mills equations.
| [
{
"created": "Thu, 14 Dec 1995 13:06:14 GMT",
"version": "v1"
}
] | 2016-08-15 | [
[
"Monte",
"E. M.",
"",
"Universidade de Brasília"
],
[
"Maia",
"M. D.",
"",
"Universidade de Brasília"
]
] | The fundamental theorem of submanifolds is adapted to space-times. It is shown that the integrability conditions for the existence of submanifolds of a pseudo-Euclidean space contain the Einstein and Yang-Mills equations. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.