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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1106.3879 | Todd Oliynyk | Lars Andersson, Todd A. Oliynyk, and Bernd G. Schmidt | Dynamical elastic bodies in Newtonian gravity | null | Class. Quantum Grav. 28 (2011) 235006 (35pp) | 10.1088/0264-9381/28/23/235006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Well-posedness for the initial value problem for a self-gravitating elastic
body with free boundary in Newtonian gravity is proved. In the material frame,
the Euler-Lagrange equation becomes, assuming suitable constitutive properties
for the elastic material, a fully non-linear elliptic-hyperbolic system with
boundary conditions of Neumann type. For systems of this type, the initial data
must satisfy compatibility conditions in order to achieve regular solutions.
Given a relaxed reference configuration and a sufficiently small Newton's
constant, a neigborhood of initial data satisfying the compatibility conditions
is constructed.
| [
{
"created": "Mon, 20 Jun 2011 12:22:17 GMT",
"version": "v1"
}
] | 2012-06-28 | [
[
"Andersson",
"Lars",
""
],
[
"Oliynyk",
"Todd A.",
""
],
[
"Schmidt",
"Bernd G.",
""
]
] | Well-posedness for the initial value problem for a self-gravitating elastic body with free boundary in Newtonian gravity is proved. In the material frame, the Euler-Lagrange equation becomes, assuming suitable constitutive properties for the elastic material, a fully non-linear elliptic-hyperbolic system with boundary conditions of Neumann type. For systems of this type, the initial data must satisfy compatibility conditions in order to achieve regular solutions. Given a relaxed reference configuration and a sufficiently small Newton's constant, a neigborhood of initial data satisfying the compatibility conditions is constructed. |
2005.04693 | Aurelien Barrau | Aur\'elien Barrau | A pure general relativistic non-singular bouncing origin for the
Universe | null | null | 10.1140/epjc/s10052-020-8158-5 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter, we argue that the past of the Universe, extrapolated from
standard physics and measured cosmological parameters, might be a non-singular
bounce. We also show that, in this framework, quite stringent constraints can
be put on the reheating temperature and number of inflationary e-folds,
basically fixing $T_{RH}\sim T_{GUT}$ and $N\sim 70$. We draw some conclusions
about the shape of the inflaton potential and raise the "naturalness" issue in
this context. Finally, we argue that this could open a very specific window on
the "pre big bounce" universe.
| [
{
"created": "Sun, 10 May 2020 15:19:04 GMT",
"version": "v1"
},
{
"created": "Tue, 12 May 2020 18:39:41 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Jun 2020 07:19:58 GMT",
"version": "v3"
},
{
"created": "Fri, 26 Jun 2020 17:38:27 GMT",
"version": "v4"
}
] | 2020-07-15 | [
[
"Barrau",
"Aurélien",
""
]
] | In this letter, we argue that the past of the Universe, extrapolated from standard physics and measured cosmological parameters, might be a non-singular bounce. We also show that, in this framework, quite stringent constraints can be put on the reheating temperature and number of inflationary e-folds, basically fixing $T_{RH}\sim T_{GUT}$ and $N\sim 70$. We draw some conclusions about the shape of the inflaton potential and raise the "naturalness" issue in this context. Finally, we argue that this could open a very specific window on the "pre big bounce" universe. |
gr-qc/0404128 | Achamveedu Gopakumar | Thibault Damour, Achamveedu Gopakumar and Bala R. Iyer | Phasing of gravitational waves from inspiralling eccentric binaries | 49 pages, 6 figures, high quality figures upon request | Phys.Rev. D70 (2004) 064028 | 10.1103/PhysRevD.70.064028 | null | gr-qc astro-ph | null | We provide a method for analytically constructing high-accuracy templates for
the gravitational wave signals emitted by compact binaries moving in
inspiralling eccentric orbits. By contrast to the simpler problem of modeling
the gravitational wave signals emitted by inspiralling {\it circular} orbits,
which contain only two different time scales, namely those associated with the
orbital motion and the radiation reaction, the case of {\it inspiralling
eccentric} orbits involves {\it three different time scales}: orbital period,
periastron precession and radiation-reaction time scales. By using an improved
`method of variation of constants', we show how to combine these three time
scales, without making the usual approximation of treating the radiative time
scale as an adiabatic process. We explicitly implement our method at the 2.5PN
post-Newtonian accuracy. Our final results can be viewed as computing new
`post-adiabatic' short period contributions to the orbital phasing, or
equivalently, new short-period contributions to the gravitational wave
polarizations, $h_{+,\times}$, that should be explicitly added to the
`post-Newtonian' expansion for $h_{+,\times}$, if one treats radiative effects
on the orbital phasing of the latter in the usual adiabatic approximation. Our
results should be of importance both for the LIGO/VIRGO/GEO network of ground
based interferometric gravitational wave detectors (especially if Kozai
oscillations turn out to be significant in globular cluster triplets), and for
the future space-based interferometer LISA.
| [
{
"created": "Fri, 30 Apr 2004 14:01:31 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Damour",
"Thibault",
""
],
[
"Gopakumar",
"Achamveedu",
""
],
[
"Iyer",
"Bala R.",
""
]
] | We provide a method for analytically constructing high-accuracy templates for the gravitational wave signals emitted by compact binaries moving in inspiralling eccentric orbits. By contrast to the simpler problem of modeling the gravitational wave signals emitted by inspiralling {\it circular} orbits, which contain only two different time scales, namely those associated with the orbital motion and the radiation reaction, the case of {\it inspiralling eccentric} orbits involves {\it three different time scales}: orbital period, periastron precession and radiation-reaction time scales. By using an improved `method of variation of constants', we show how to combine these three time scales, without making the usual approximation of treating the radiative time scale as an adiabatic process. We explicitly implement our method at the 2.5PN post-Newtonian accuracy. Our final results can be viewed as computing new `post-adiabatic' short period contributions to the orbital phasing, or equivalently, new short-period contributions to the gravitational wave polarizations, $h_{+,\times}$, that should be explicitly added to the `post-Newtonian' expansion for $h_{+,\times}$, if one treats radiative effects on the orbital phasing of the latter in the usual adiabatic approximation. Our results should be of importance both for the LIGO/VIRGO/GEO network of ground based interferometric gravitational wave detectors (especially if Kozai oscillations turn out to be significant in globular cluster triplets), and for the future space-based interferometer LISA. |
0809.4352 | Anthony van Eysden | C. A. van Eysden and A. Melatos | Gravitational radiation from pulsar glitches | 28 pages | Class.Quant.Grav.25:225020,2008 | 10.1088/0264-9381/25/22/225020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The nonaxisymmetric Ekman flow excited inside a neutron star following a
rotational glitch is calculated analytically including stratification and
compressibility. For the largest glitches, the gravitational wave strain
produced by the hydrodynamic mass quadrupole moment approaches the sensitivity
range of advanced long-baseline interferometers. It is shown that the
viscosity, compressibility, and orientation of the star can be inferred in
principle from the width and amplitude ratios of the Fourier peaks (at the spin
frequency and its first harmonic) observed in the gravitational wave spectrum
in the plus and cross polarizations. These transport coefficients constrain the
equation of state of bulk nuclear matter, because they depend sensitively on
the degree of superfluidity.
| [
{
"created": "Thu, 25 Sep 2008 10:02:16 GMT",
"version": "v1"
}
] | 2010-04-15 | [
[
"van Eysden",
"C. A.",
""
],
[
"Melatos",
"A.",
""
]
] | The nonaxisymmetric Ekman flow excited inside a neutron star following a rotational glitch is calculated analytically including stratification and compressibility. For the largest glitches, the gravitational wave strain produced by the hydrodynamic mass quadrupole moment approaches the sensitivity range of advanced long-baseline interferometers. It is shown that the viscosity, compressibility, and orientation of the star can be inferred in principle from the width and amplitude ratios of the Fourier peaks (at the spin frequency and its first harmonic) observed in the gravitational wave spectrum in the plus and cross polarizations. These transport coefficients constrain the equation of state of bulk nuclear matter, because they depend sensitively on the degree of superfluidity. |
1203.0523 | Orfeu Bertolami | Orfeu Bertolami, Ricardo Zambujal Ferreira | Traversable Wormholes and Time Machines in non-minimally coupled
curvature-matter $f(R)$ theories | Revtex4, 7 pages. Version to match the one to appear in Physical
Review D | null | 10.1103/PhysRevD.85.104050 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain traversable wormhole and time machine solutions of the field
equations of an alternative of gravity with non-minimally curvature-matter
coupling. Our solutions exhibit a non-trivial redshift function and allow for
matter that satisfy the dominant energy condition.
| [
{
"created": "Fri, 2 Mar 2012 17:13:46 GMT",
"version": "v1"
},
{
"created": "Wed, 30 May 2012 18:01:14 GMT",
"version": "v2"
}
] | 2013-05-30 | [
[
"Bertolami",
"Orfeu",
""
],
[
"Ferreira",
"Ricardo Zambujal",
""
]
] | We obtain traversable wormhole and time machine solutions of the field equations of an alternative of gravity with non-minimally curvature-matter coupling. Our solutions exhibit a non-trivial redshift function and allow for matter that satisfy the dominant energy condition. |
2312.06757 | Vincent S. H. Lee | Vincent S. H. Lee, Kathryn M. Zurek, Yanbei Chen | Astronomical Image Blurring from Transversely Correlated Quantum Gravity
Fluctuations | 11 pages, 4 figures, v2: updated to match journal version,
conclusions unchanged | Phys.Rev.D 109 (2024) 8, 084005 | 10.1103/PhysRevD.109.084005 | CALT-TH-2022-039 | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum fluctuations in spacetime can, in some cases, lead to distortion in
astronomical images of faraway objects. In particular, a stochastic model of
quantum gravity predicts an accumulated fluctuation in the path length $\Delta
L$ with variance $\langle \Delta L^2\rangle\sim l_pL$ over a distance $L$,
similar to a random walk, and assuming no spatial correlation above length
$l_p$; it has been argued that such an effect is ruled out by observation of
sharp images from distant stars. However, in other theories, such as the
pixellon (modeled on the Verlinde-Zurek (VZ) effect), quantum fluctuations can
still accumulate as in the random walk model while simultaneously having large
distance correlations in the fluctuations. Using renormalization by analytic
continuation, we derive the correlation transverse to the light propagation,
and show that image distortion effects in the pixellon model are strongly
suppressed in comparison to the random walk model, thus evading all existing
and future constraints. We also find that the diffraction of light rays does
not lead to qualitative changes in the blurring effect.
| [
{
"created": "Mon, 11 Dec 2023 19:00:01 GMT",
"version": "v1"
},
{
"created": "Mon, 13 May 2024 20:10:02 GMT",
"version": "v2"
},
{
"created": "Wed, 22 May 2024 22:39:36 GMT",
"version": "v3"
}
] | 2024-05-24 | [
[
"Lee",
"Vincent S. H.",
""
],
[
"Zurek",
"Kathryn M.",
""
],
[
"Chen",
"Yanbei",
""
]
] | Quantum fluctuations in spacetime can, in some cases, lead to distortion in astronomical images of faraway objects. In particular, a stochastic model of quantum gravity predicts an accumulated fluctuation in the path length $\Delta L$ with variance $\langle \Delta L^2\rangle\sim l_pL$ over a distance $L$, similar to a random walk, and assuming no spatial correlation above length $l_p$; it has been argued that such an effect is ruled out by observation of sharp images from distant stars. However, in other theories, such as the pixellon (modeled on the Verlinde-Zurek (VZ) effect), quantum fluctuations can still accumulate as in the random walk model while simultaneously having large distance correlations in the fluctuations. Using renormalization by analytic continuation, we derive the correlation transverse to the light propagation, and show that image distortion effects in the pixellon model are strongly suppressed in comparison to the random walk model, thus evading all existing and future constraints. We also find that the diffraction of light rays does not lead to qualitative changes in the blurring effect. |
1812.07647 | Saurya Das | Saurya Das, Rajat K. Bhaduri | On the quantum origin of a small positive cosmological constant | 3 pages, revtex | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that Dark Matter consisting of ultralight bosons in a Bose-Einstein
condensate induces, via its quantum potential, a small positive cosmological
constant which matches the observed value. This explains its origin and why the
densities of Dark Matter and Dark Energy are approximately equal.
| [
{
"created": "Tue, 18 Dec 2018 21:27:55 GMT",
"version": "v1"
}
] | 2018-12-31 | [
[
"Das",
"Saurya",
""
],
[
"Bhaduri",
"Rajat K.",
""
]
] | We show that Dark Matter consisting of ultralight bosons in a Bose-Einstein condensate induces, via its quantum potential, a small positive cosmological constant which matches the observed value. This explains its origin and why the densities of Dark Matter and Dark Energy are approximately equal. |
gr-qc/0309058 | Leonid Grishchuk P. | D. Baskaran and L. P. Grishchuk | Components of the gravitational force in the field of a gravitational
wave | prints to 29 pages including 9 figures, new title, additional
explanations and references in response to referee's comments, to be
published in Class. Quant. Grav | Class.Quant.Grav. 21 (2004) 4041-4062 | 10.1088/0264-9381/21/17/003 | null | gr-qc astro-ph hep-th | null | Gravitational waves bring about the relative motion of free test masses. The
detailed knowledge of this motion is important conceptually and practically,
because the mirrors of laser interferometric detectors of gravitational waves
are essentially free test masses. There exists an analogy between the motion of
free masses in the field of a gravitational wave and the motion of free charges
in the field of an electromagnetic wave. In particular, a gravitational wave
drives the masses in the plane of the wave-front and also, to a smaller extent,
back and forth in the direction of the wave's propagation. To describe this
motion, we introduce the notion of `electric' and `magnetic' components of the
gravitational force. This analogy is not perfect, but it reflects some
important features of the phenomenon. Using different methods, we demonstrate
the presence and importance of what we call the `magnetic' component of motion
of free masses. It contributes to the variation of distance between a pair of
particles. We explicitely derive the full response function of a 2-arm laser
interferometer to a gravitational wave of arbitrary polarization. We give a
convenient description of the response function in terms of the spin-weighted
spherical harmonics. We show that the previously ignored `magnetic' component
may provide a correction of up to 10 %, or so, to the usual `electric'
component of the response function. The `magnetic' contribution must be taken
into account in the data analysis, if the parameters of the radiating system
are not to be mis-estimated.
| [
{
"created": "Thu, 11 Sep 2003 14:00:39 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Jul 2004 15:17:30 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Baskaran",
"D.",
""
],
[
"Grishchuk",
"L. P.",
""
]
] | Gravitational waves bring about the relative motion of free test masses. The detailed knowledge of this motion is important conceptually and practically, because the mirrors of laser interferometric detectors of gravitational waves are essentially free test masses. There exists an analogy between the motion of free masses in the field of a gravitational wave and the motion of free charges in the field of an electromagnetic wave. In particular, a gravitational wave drives the masses in the plane of the wave-front and also, to a smaller extent, back and forth in the direction of the wave's propagation. To describe this motion, we introduce the notion of `electric' and `magnetic' components of the gravitational force. This analogy is not perfect, but it reflects some important features of the phenomenon. Using different methods, we demonstrate the presence and importance of what we call the `magnetic' component of motion of free masses. It contributes to the variation of distance between a pair of particles. We explicitely derive the full response function of a 2-arm laser interferometer to a gravitational wave of arbitrary polarization. We give a convenient description of the response function in terms of the spin-weighted spherical harmonics. We show that the previously ignored `magnetic' component may provide a correction of up to 10 %, or so, to the usual `electric' component of the response function. The `magnetic' contribution must be taken into account in the data analysis, if the parameters of the radiating system are not to be mis-estimated. |
2405.05936 | Rodrigo Maier | Filipe Cattete Alves, Rodrigo Maier | Scalar Perturbations in Nonsingular Universes from Interacting Vacuum | null | Class. Quantum Grav. 41 125007 2024 | 10.1088/1361-6382/ad494d | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we examine the stability of scalar perturbations in nonsingular
models which emerge from an interacting vacuum component. The analysis
developed in this paper relies on two phenomenological choices for the energy
exchange between a nonrelativistic fluid and a vacuum component. In both
scenarios it can be shown that closed models may furnish nonsingular orbits of
physical interest in phase space once a decelerated past era is connected to a
graceful exit to late-time acceleration. Regarding such configurations as
background spacetimes we introduce scalar perturbations in order to examine the
stability of these models in a high energy domain. We explicitly show that the
vacuum perturbation is not an independent variable and diverges as dynamics
approaches the bounce. This feature assigns a rather unstable signature to the
dynamics making the choices for the energy transfer ill defined at least for
nonsingular configurations at the bounce scale.
| [
{
"created": "Thu, 9 May 2024 17:21:17 GMT",
"version": "v1"
},
{
"created": "Thu, 23 May 2024 16:04:33 GMT",
"version": "v2"
}
] | 2024-05-24 | [
[
"Alves",
"Filipe Cattete",
""
],
[
"Maier",
"Rodrigo",
""
]
] | In this paper we examine the stability of scalar perturbations in nonsingular models which emerge from an interacting vacuum component. The analysis developed in this paper relies on two phenomenological choices for the energy exchange between a nonrelativistic fluid and a vacuum component. In both scenarios it can be shown that closed models may furnish nonsingular orbits of physical interest in phase space once a decelerated past era is connected to a graceful exit to late-time acceleration. Regarding such configurations as background spacetimes we introduce scalar perturbations in order to examine the stability of these models in a high energy domain. We explicitly show that the vacuum perturbation is not an independent variable and diverges as dynamics approaches the bounce. This feature assigns a rather unstable signature to the dynamics making the choices for the energy transfer ill defined at least for nonsingular configurations at the bounce scale. |
1810.02825 | Antonios Tsokaros A. | Antonios Tsokaros, K\=oji Ury\=u, Stuart L. Shapiro | Complete initial value spacetimes containing black holes in general
relativity: Application to black hole-disk systems | 6 pages | Phys. Rev. D 99, 041501 (2019) | 10.1103/PhysRevD.99.041501 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new initial data formulation to solve the full set of Einstein
equations for spacetimes that contain a black hole under general conditions.
The method can be used to construct complete initial data for spacetimes (the
full metric) that contain a black hole. Contrary to most current studies the
formulation requires minimal assumptions. For example, rather than imposing the
form of the spatial conformal metric we impose 3 gauge conditions adapted to
the coordinates describing the system under consideration. For stationary,
axisymmetric spacetimes our method yields Kerr-Schild black holes in vacuum and
rotating equilibrium neutron stars. We demonstrate the power of our new method
by solving for the first time the whole system of Einstein equations for a
nonaxisymmetric, self-gravitating torus in the presence of a black hole. The
black hole has dimensionless spin $J_{\rm bh}/M_{\rm bh}^2=0.9918$, a rotation
axis tilted at a $30^\circ$ angle with respect to the angular momentum of the
disk, and a mass of $\sim 1/5$ of the disk.
| [
{
"created": "Fri, 5 Oct 2018 18:00:02 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Feb 2019 06:46:25 GMT",
"version": "v2"
}
] | 2019-03-06 | [
[
"Tsokaros",
"Antonios",
""
],
[
"Uryū",
"Kōji",
""
],
[
"Shapiro",
"Stuart L.",
""
]
] | We present a new initial data formulation to solve the full set of Einstein equations for spacetimes that contain a black hole under general conditions. The method can be used to construct complete initial data for spacetimes (the full metric) that contain a black hole. Contrary to most current studies the formulation requires minimal assumptions. For example, rather than imposing the form of the spatial conformal metric we impose 3 gauge conditions adapted to the coordinates describing the system under consideration. For stationary, axisymmetric spacetimes our method yields Kerr-Schild black holes in vacuum and rotating equilibrium neutron stars. We demonstrate the power of our new method by solving for the first time the whole system of Einstein equations for a nonaxisymmetric, self-gravitating torus in the presence of a black hole. The black hole has dimensionless spin $J_{\rm bh}/M_{\rm bh}^2=0.9918$, a rotation axis tilted at a $30^\circ$ angle with respect to the angular momentum of the disk, and a mass of $\sim 1/5$ of the disk. |
2112.07726 | Pierre-Henri Chavanis | Pierre-Henri Chavanis | Predictive model of fermionic dark matter halos with a quantum core and
an isothermal atmosphere | null | null | 10.1103/PhysRevD.106.043538 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a thermodynamical model of fermionic dark matter halos at finite
temperature. Statistical equilibrium states may be justified by a process of
violent collisionless relaxation in the sense of Lynden-Bell or from a
collisional relaxation of nongravitational origin if the fermions are
self-interacting. The most probable state (maximum entropy state) generically
has a "core-halo" structure with a quantum core (fermion ball) surrounded by an
isothermal atmosphere. The quantum core is equivalent to a polytrope of index
$n=3/2$. The Pauli exclusion principle creates a quantum pressure that prevents
gravitational collapse and solves the core-cusp problem of the cold dark matter
model. The isothermal atmosphere (which is similar to the NFW profile of cold
dark matter) accounts for the flat rotation curves of the galaxies at large
distances. We numerically solve the equation of hydrostatic equilibrium with
the Fermi-Dirac equation of state and determine the density profiles and
rotation curves of fermionic dark matter halos.
| [
{
"created": "Tue, 14 Dec 2021 20:08:32 GMT",
"version": "v1"
}
] | 2022-09-07 | [
[
"Chavanis",
"Pierre-Henri",
""
]
] | We develop a thermodynamical model of fermionic dark matter halos at finite temperature. Statistical equilibrium states may be justified by a process of violent collisionless relaxation in the sense of Lynden-Bell or from a collisional relaxation of nongravitational origin if the fermions are self-interacting. The most probable state (maximum entropy state) generically has a "core-halo" structure with a quantum core (fermion ball) surrounded by an isothermal atmosphere. The quantum core is equivalent to a polytrope of index $n=3/2$. The Pauli exclusion principle creates a quantum pressure that prevents gravitational collapse and solves the core-cusp problem of the cold dark matter model. The isothermal atmosphere (which is similar to the NFW profile of cold dark matter) accounts for the flat rotation curves of the galaxies at large distances. We numerically solve the equation of hydrostatic equilibrium with the Fermi-Dirac equation of state and determine the density profiles and rotation curves of fermionic dark matter halos. |
0809.0274 | Eleanor Knox | Eleanor Knox | Flavour-Oscillation Clocks and the Geometricity of General Relativity | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I look at the 'flavour-oscillation clocks' proposed by D.V. Ahluwalia, and
two arguments of his suggesting that such clocks might behave in a way that
threatens the geometricity of general relativity (GR). The first argument
states that the behaviour of these clocks in the vicinity of a rotating
gravitational source implies a non-geometric element of gravity. I argue that
the phenomenon is best seen as an instance of violation of the 'clock
hypothesis', and therefore does not threaten the geometrical nature of
gravitation. Ahluwalia's second argument, for the 'incompleteness' of general
relativity, involves the idea that flavour-oscillation clocks can detect
constant gravitational potentials. I argue that the purported
'incompleteness-establishing' result is in fact one that applies to all clocks.
It is entirely derivable from GR, does not result in the observability of the
potential, and is not at odds with any of GR's foundations.
| [
{
"created": "Mon, 1 Sep 2008 15:46:15 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Jun 2009 15:45:27 GMT",
"version": "v2"
}
] | 2009-06-16 | [
[
"Knox",
"Eleanor",
""
]
] | I look at the 'flavour-oscillation clocks' proposed by D.V. Ahluwalia, and two arguments of his suggesting that such clocks might behave in a way that threatens the geometricity of general relativity (GR). The first argument states that the behaviour of these clocks in the vicinity of a rotating gravitational source implies a non-geometric element of gravity. I argue that the phenomenon is best seen as an instance of violation of the 'clock hypothesis', and therefore does not threaten the geometrical nature of gravitation. Ahluwalia's second argument, for the 'incompleteness' of general relativity, involves the idea that flavour-oscillation clocks can detect constant gravitational potentials. I argue that the purported 'incompleteness-establishing' result is in fact one that applies to all clocks. It is entirely derivable from GR, does not result in the observability of the potential, and is not at odds with any of GR's foundations. |
1802.00177 | Avirup Ghosh | C. Fairoos, Avirup Ghosh, Sudipta Sarkar | Black Hole Entropy production and Transport coefficients in Lovelock
Gravity | 8 pages, no figures, expanded version accepted for publication in
PRD, references added, few typos corrected | Phys. Rev. D 98, 024036 (2018) | 10.1103/PhysRevD.98.024036 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the entropy evolution of black holes in Lovelock gravity by
formulating a thermodynamic generalization of null Raychaudhuri equation. We
show that the similarity between the expressions of entropy change of the black
hole horizon due to perturbation and that of a fluid, which is out of
equilibrium, transcends beyond general relativity to the Lovelock class of
theories. Exploiting this analogy we find that the shear and bulk viscosities
for the black holes in Lovelock theories exactly match with those obtained in
the membrane paradigm and also from holographic considerations.
| [
{
"created": "Thu, 1 Feb 2018 07:19:42 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Jun 2018 05:54:35 GMT",
"version": "v2"
},
{
"created": "Tue, 26 Jun 2018 17:25:07 GMT",
"version": "v3"
}
] | 2018-07-25 | [
[
"Fairoos",
"C.",
""
],
[
"Ghosh",
"Avirup",
""
],
[
"Sarkar",
"Sudipta",
""
]
] | We study the entropy evolution of black holes in Lovelock gravity by formulating a thermodynamic generalization of null Raychaudhuri equation. We show that the similarity between the expressions of entropy change of the black hole horizon due to perturbation and that of a fluid, which is out of equilibrium, transcends beyond general relativity to the Lovelock class of theories. Exploiting this analogy we find that the shear and bulk viscosities for the black holes in Lovelock theories exactly match with those obtained in the membrane paradigm and also from holographic considerations. |
2109.14258 | Anirban Saha Dr. | Sk. Moinuddin, Pradip Mukherjee, Anirban Saha, Amit Singha Roy | Energy momentum tensor of a non-minimally coupled scalar from the
equivalence of the Einstein and Jordan frames | 13 pages, laTex, no figure | Eur. Phys. J. C 83, 446 (2023) | 10.1140/epjc/s10052-023-11619-3 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Unlike the minimally coupled gravity theory where matter is coupled with
gravity in such a manner so that one can differentiate the matter and gravity
sector uniquely, the non-minimally coupled theories (NMCT) are distinguished by
the intermingling of two. As a consequence of this the calculation of the
energy momentum tensor (EMT) in NMCT is beset with an arbitrariness. In this
paper we provide an algorithm based on the well known equivalence between
Jordan frame and Einstein frame formulations which enables us to construct the
EMT for NMCT in a unique way.
| [
{
"created": "Wed, 29 Sep 2021 08:03:14 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Jun 2023 09:10:54 GMT",
"version": "v2"
}
] | 2023-06-02 | [
[
"Moinuddin",
"Sk.",
""
],
[
"Mukherjee",
"Pradip",
""
],
[
"Saha",
"Anirban",
""
],
[
"Roy",
"Amit Singha",
""
]
] | Unlike the minimally coupled gravity theory where matter is coupled with gravity in such a manner so that one can differentiate the matter and gravity sector uniquely, the non-minimally coupled theories (NMCT) are distinguished by the intermingling of two. As a consequence of this the calculation of the energy momentum tensor (EMT) in NMCT is beset with an arbitrariness. In this paper we provide an algorithm based on the well known equivalence between Jordan frame and Einstein frame formulations which enables us to construct the EMT for NMCT in a unique way. |
1607.08879 | Jose Navarro-Salas | I. Agullo, A. del Rio, J. Navarro-Salas | Electromagnetic duality anomaly in curved spacetimes | 5 pages. Typos corrected. Some points clarified. To appear in Phys.
Rev. Lett | Phys. Rev. Lett. 118, 111301 (2017) | 10.1103/PhysRevLett.118.111301 | null | gr-qc hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The source-free Maxwell action is invariant under electric-magnetic duality
rotations in arbitrary spacetimes. This leads to a conserved classical Noether
charge. We show that this conservation law is broken at the quantum level in
presence of a background classical gravitational field with a non-trivial
Chern-Pontryagin invariant, in a parallel way to the chiral anomaly for
massless Dirac fermions. Among the physical consequences, the net polarization
of the quantum electromagnetic field is not conserved.
| [
{
"created": "Fri, 29 Jul 2016 18:12:22 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Mar 2017 07:56:32 GMT",
"version": "v2"
}
] | 2017-03-22 | [
[
"Agullo",
"I.",
""
],
[
"del Rio",
"A.",
""
],
[
"Navarro-Salas",
"J.",
""
]
] | The source-free Maxwell action is invariant under electric-magnetic duality rotations in arbitrary spacetimes. This leads to a conserved classical Noether charge. We show that this conservation law is broken at the quantum level in presence of a background classical gravitational field with a non-trivial Chern-Pontryagin invariant, in a parallel way to the chiral anomaly for massless Dirac fermions. Among the physical consequences, the net polarization of the quantum electromagnetic field is not conserved. |
1912.12806 | Adel Rahman | Adel A. Rahman and Robert M. Wald | Black Hole Memory | 23 pages. v2: references and minor clarifications added; version
accepted for publication in PRD | Phys. Rev. D 101, 124010 (2020) | 10.1103/PhysRevD.101.124010 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The memory effect at null infinity, $\mathcal{I}^+$, can be defined in terms
of the permanent relative displacement of test particles (at leading order in
$1/r$) resulting from the passage of a burst of gravitational radiation. In
$D=4$ spacetime dimensions, the memory effect can be characterized by the
supertranslation relating the "good cuts" of $\mathcal{I}^+$ in the stationary
eras at early and late retarded times. It also can be characterized in terms of
charges and fluxes associated with supertranslations. Black hole event horizons
are in many ways analogous to $\mathcal{I}^+$. We consider here analogous
definitions of memory for a black hole, assuming that the black hole is
approximately stationary at early and late advanced times, so that its event
horizon is described by a Killing horizon (assumed nonextremal) at early and
late times. We give prescriptions for defining preferred foliations of
nonextremal Killing horizons. We give a definition of the memory tensor for a
black hole in terms of the "permanent relative displacement" of the null
geodesic generators of the event horizon between the early and late time
stationary eras. We show that preferred foliations of the event horizon in the
early and late time eras are related by a Chandrasekaran-Flanagan-Prabhu (CFP)
supertranslation. However, we find that the memory tensor for a black hole
horizon does not appear to be related to the CFP symmetries or their charges
and fluxes in a manner similar to that occurring at $\mathcal{I}^+$.
| [
{
"created": "Mon, 30 Dec 2019 04:11:51 GMT",
"version": "v1"
},
{
"created": "Tue, 5 May 2020 00:16:12 GMT",
"version": "v2"
}
] | 2020-07-01 | [
[
"Rahman",
"Adel A.",
""
],
[
"Wald",
"Robert M.",
""
]
] | The memory effect at null infinity, $\mathcal{I}^+$, can be defined in terms of the permanent relative displacement of test particles (at leading order in $1/r$) resulting from the passage of a burst of gravitational radiation. In $D=4$ spacetime dimensions, the memory effect can be characterized by the supertranslation relating the "good cuts" of $\mathcal{I}^+$ in the stationary eras at early and late retarded times. It also can be characterized in terms of charges and fluxes associated with supertranslations. Black hole event horizons are in many ways analogous to $\mathcal{I}^+$. We consider here analogous definitions of memory for a black hole, assuming that the black hole is approximately stationary at early and late advanced times, so that its event horizon is described by a Killing horizon (assumed nonextremal) at early and late times. We give prescriptions for defining preferred foliations of nonextremal Killing horizons. We give a definition of the memory tensor for a black hole in terms of the "permanent relative displacement" of the null geodesic generators of the event horizon between the early and late time stationary eras. We show that preferred foliations of the event horizon in the early and late time eras are related by a Chandrasekaran-Flanagan-Prabhu (CFP) supertranslation. However, we find that the memory tensor for a black hole horizon does not appear to be related to the CFP symmetries or their charges and fluxes in a manner similar to that occurring at $\mathcal{I}^+$. |
1811.08744 | Gregorio Carullo | Gregorio Carullo, Gunnar Riemenschneider, Ka Wa Tsang, Alessandro
Nagar, Walter Del Pozzo | GW150914 peak frequency: a novel consistency test of strong-field
General Relativity | 7 pages, 2 figures | Classical and Quantum Gravity 36 105009 (2019) | 10.1088/1361-6382/ab185e | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a novel test of General Relativity in the strong-field regime of
a binary black hole coalescence. Combining information coming from Numerical
Relativity simulations of coalescing black hole binaries with a Bayesian
reconstruction of the gravitational wave signal detected in LIGO-Virgo
interferometric data, allows one to test theoretical predictions for the
instantaneous gravitational wave frequency measured at the peak of the
gravitational wave signal amplitude. We present the construction of such a test
and apply it on the first gravitational wave event detected by the LIGO and
Virgo Collaborations, GW150914. The $p$-value obtained is $p=0.48$, to be
contrasted with an expected value of $p=0.5$, so that no signs of violations
from General Relativity were detected.
| [
{
"created": "Wed, 21 Nov 2018 14:15:51 GMT",
"version": "v1"
},
{
"created": "Thu, 2 May 2019 14:28:02 GMT",
"version": "v2"
}
] | 2019-05-03 | [
[
"Carullo",
"Gregorio",
""
],
[
"Riemenschneider",
"Gunnar",
""
],
[
"Tsang",
"Ka Wa",
""
],
[
"Nagar",
"Alessandro",
""
],
[
"Del Pozzo",
"Walter",
""
]
] | We introduce a novel test of General Relativity in the strong-field regime of a binary black hole coalescence. Combining information coming from Numerical Relativity simulations of coalescing black hole binaries with a Bayesian reconstruction of the gravitational wave signal detected in LIGO-Virgo interferometric data, allows one to test theoretical predictions for the instantaneous gravitational wave frequency measured at the peak of the gravitational wave signal amplitude. We present the construction of such a test and apply it on the first gravitational wave event detected by the LIGO and Virgo Collaborations, GW150914. The $p$-value obtained is $p=0.48$, to be contrasted with an expected value of $p=0.5$, so that no signs of violations from General Relativity were detected. |
1603.03312 | Joao Magueijo | Niayesh Afshordi and Joao Magueijo | The critical geometry of a thermal big bang | null | Phys. Rev. D 94, 101301 (2016) | 10.1103/PhysRevD.94.101301 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the space of scalar-tensor theories containing two
non-conformalmetrics, and find a discontinuity pointing to a "critical"
cosmological solution. Due to the different maximal speeds of propagation for
matter and gravity,the cosmological fluctuations start off inside the horizon
even without inflation, and will more naturally have a thermal origin (since
there is never vacuum domination). The critical model makes an unambiguous,
non-tuned prediction for the spectral index of the scalar fluctuations: $n_S=
0.96478(64)$. Considering also that no gravitational waves are produced, we
have unveiled the most predictive model on offer. The model has a simple
geometrical interpretation as a probe 3-brane embedded in an $EAdS_2\times E_3$
geometry.
| [
{
"created": "Wed, 9 Mar 2016 18:31:02 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Nov 2016 11:00:52 GMT",
"version": "v2"
}
] | 2016-11-23 | [
[
"Afshordi",
"Niayesh",
""
],
[
"Magueijo",
"Joao",
""
]
] | We explore the space of scalar-tensor theories containing two non-conformalmetrics, and find a discontinuity pointing to a "critical" cosmological solution. Due to the different maximal speeds of propagation for matter and gravity,the cosmological fluctuations start off inside the horizon even without inflation, and will more naturally have a thermal origin (since there is never vacuum domination). The critical model makes an unambiguous, non-tuned prediction for the spectral index of the scalar fluctuations: $n_S= 0.96478(64)$. Considering also that no gravitational waves are produced, we have unveiled the most predictive model on offer. The model has a simple geometrical interpretation as a probe 3-brane embedded in an $EAdS_2\times E_3$ geometry. |
gr-qc/9508028 | Stephen R. Lau | Stephen R. Lau (Technische Universitaet Wien) | On the Canonical Reduction of Spherically Symmetric Gravity | Revtex, 35 pages, no figures | Class.Quant.Grav.13:1541-1570,1996 | 10.1088/0264-9381/13/6/020 | TUW-95-21. Revised version contains (1) much improved notation, (2)
several repaired minus signs, (3) new references, and (4) some extra
discussion devoted to previously overlooked points concerning this work and
its main reference. To appear in Classical and Quantum Gravity | gr-qc | null | In a thorough paper Kuchar has examined the canonical reduction of the most
general action functional describing the geometrodynamics of the maximally
extended Schwarzschild geometry. This reduction yields the true degrees of
freedom for (vacuum) spherically symmetric general relativity. The essential
technical ingredient in Kuchar's analysis is a canonical transformation to a
certain chart on the gravitational phase space which features the Schwarzschild
mass parameter $M_{S}$, expressed in terms of what are essentially
Arnowitt-Deser-Misner variables, as a canonical coordinate. In this paper we
discuss the geometric interpretation of Kuchar's canonical transformation in
terms of the theory of quasilocal energy-momentum in general relativity given
by Brown and York. We find Kuchar's transformation to be a ``sphere-dependent
boost to the rest frame," where the ``rest frame'' is defined by vanishing
quasilocal momentum. Furthermore, our formalism is general enough to cover the
case of (vacuum) two-dimensional dilaton gravity. Therefore, besides reviewing
Kucha\v{r}'s original work for Schwarzschild black holes from the framework of
hyperbolic geometry, we present new results concerning the canonical reduction
of Witten-black-hole geometrodynamics.
| [
{
"created": "Fri, 11 Aug 1995 13:42:13 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Aug 1995 17:19:08 GMT",
"version": "v2"
},
{
"created": "Wed, 14 Feb 1996 19:05:43 GMT",
"version": "v3"
}
] | 2010-11-19 | [
[
"Lau",
"Stephen R.",
"",
"Technische Universitaet Wien"
]
] | In a thorough paper Kuchar has examined the canonical reduction of the most general action functional describing the geometrodynamics of the maximally extended Schwarzschild geometry. This reduction yields the true degrees of freedom for (vacuum) spherically symmetric general relativity. The essential technical ingredient in Kuchar's analysis is a canonical transformation to a certain chart on the gravitational phase space which features the Schwarzschild mass parameter $M_{S}$, expressed in terms of what are essentially Arnowitt-Deser-Misner variables, as a canonical coordinate. In this paper we discuss the geometric interpretation of Kuchar's canonical transformation in terms of the theory of quasilocal energy-momentum in general relativity given by Brown and York. We find Kuchar's transformation to be a ``sphere-dependent boost to the rest frame," where the ``rest frame'' is defined by vanishing quasilocal momentum. Furthermore, our formalism is general enough to cover the case of (vacuum) two-dimensional dilaton gravity. Therefore, besides reviewing Kucha\v{r}'s original work for Schwarzschild black holes from the framework of hyperbolic geometry, we present new results concerning the canonical reduction of Witten-black-hole geometrodynamics. |
0803.1052 | Helmut Friedrich | Helmut Friedrich | Families of conformally related asymptotically flat, static vacuum data | 18 pages | Class.Quant.Grav.25:135012,2008 | 10.1088/0264-9381/25/13/135012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Extending the results of an earlier article we give a complete description of
the asymptotically flat, conformally non-flat, static vacuum data which admit
non-trivial, asymptotically smooth conformal mappings onto other such data.
These data form a 3-parameter family which decomposes into 1-parameter families
of data which are conformal to each other. The data and the associated static
vacuum solutions are given explicitly in terms of elliptic and, in a special
case, elementary functions.
| [
{
"created": "Fri, 7 Mar 2008 10:39:29 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Friedrich",
"Helmut",
""
]
] | Extending the results of an earlier article we give a complete description of the asymptotically flat, conformally non-flat, static vacuum data which admit non-trivial, asymptotically smooth conformal mappings onto other such data. These data form a 3-parameter family which decomposes into 1-parameter families of data which are conformal to each other. The data and the associated static vacuum solutions are given explicitly in terms of elliptic and, in a special case, elementary functions. |
1603.01853 | Andrea Addazi AndAdd | Andrea Addazi and Antonino Marciano and Stephon Alexander | A Unified picture of Dark Matter and Dark Energy from Invisible QCD | arXiv admin note: text overlap with arXiv:1602.06557 | null | null | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been shown in a companion paper that the late time acceleration of the
universe can be accounted for by an extension of the QCD color to a $SU(3)$
invisible sector (IQCD). In this work we discuss a unified framework such the
scale of dark chiral-breaking dictates both the accelerated expansion of the
universe, and the origin of dark matter. We find that the strong and
gravitational dynamics of dark quarks and gluons evolve to eventually form
exotic dark stars. We discuss the dynamical complexity of these dark compact
objects in light of dark big bang nucleosynthesis. We argue how IQCD favors a
halo composed of very compact dark neutron stars, strange/quark stars and black
holes, with masses $M_{MACHO}< 10^{-7}M_{\odot}$. This avoids limit from MACHO
and EROS collaborations as well as limit from clusters. We also discuss
possible phenomenological implications in dark matter searches. We argue that
dark supernovae and dark binaries can emit very peculiar gravitational waves
signal testable by the LIGO/VIRGO collaboration and future projects dedicated
to these aspects.
| [
{
"created": "Sun, 6 Mar 2016 18:25:14 GMT",
"version": "v1"
}
] | 2016-03-16 | [
[
"Addazi",
"Andrea",
""
],
[
"Marciano",
"Antonino",
""
],
[
"Alexander",
"Stephon",
""
]
] | It has been shown in a companion paper that the late time acceleration of the universe can be accounted for by an extension of the QCD color to a $SU(3)$ invisible sector (IQCD). In this work we discuss a unified framework such the scale of dark chiral-breaking dictates both the accelerated expansion of the universe, and the origin of dark matter. We find that the strong and gravitational dynamics of dark quarks and gluons evolve to eventually form exotic dark stars. We discuss the dynamical complexity of these dark compact objects in light of dark big bang nucleosynthesis. We argue how IQCD favors a halo composed of very compact dark neutron stars, strange/quark stars and black holes, with masses $M_{MACHO}< 10^{-7}M_{\odot}$. This avoids limit from MACHO and EROS collaborations as well as limit from clusters. We also discuss possible phenomenological implications in dark matter searches. We argue that dark supernovae and dark binaries can emit very peculiar gravitational waves signal testable by the LIGO/VIRGO collaboration and future projects dedicated to these aspects. |
gr-qc/9707055 | null | Vladimir S. Mashkevich (Institute of Physics, Kiev) | Conservative Model of Black Hole and Lifting of the Information Loss
Paradox | 8 pages, LATEX 2.09 | null | null | IP 10/97 | gr-qc hep-th | null | The conservative model of a black hole is advanced. The model incorporates
conservation laws such as those of baryon and lepton numbers, which lifts the
information loss paradox. A scenario of black hole evaporation is considered.
Keywords: entropy, emission, radiation, universe, chemical potential
| [
{
"created": "Sat, 26 Jul 1997 23:28:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mashkevich",
"Vladimir S.",
"",
"Institute of Physics, Kiev"
]
] | The conservative model of a black hole is advanced. The model incorporates conservation laws such as those of baryon and lepton numbers, which lifts the information loss paradox. A scenario of black hole evaporation is considered. Keywords: entropy, emission, radiation, universe, chemical potential |
1207.3043 | Kuantay Boshkayev | Kuantay Boshkayev, Hernando Quevedo and Remo Ruffini | Gravitational field of compact objects in general relativity | 15 pages, published in Phys. Rev. D.:
http://prd.aps.org/pdf/PRD/v86/i6/e064043 | Physical Review D 86, 064043 (2012) | 10.1103/PhysRevD.86.064043 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study some exact and approximate solutions of Einstein's equations that
can be used to describe the gravitational field of astrophysical compact
objects in the limiting case of slow rotation and slight deformation. First, we
show that none of the standard models obtained by using Fock's method can be
used as an interior source for the approximate exterior Kerr solution. We then
use Fock's method to derive a generalized interior solution, and also an
exterior solution that turns out to be equivalent to the exterior Hartle-Thorne
approximate solution that, in turn, is equivalent to an approximate limiting
case of the exact Quevedo-Mashhoon solution. As a result we obtain an analytic
approximate solution that describes the interior and exterior gravitational
field of a slowly rotating and slightly deformed astrophysical object.
| [
{
"created": "Thu, 12 Jul 2012 18:10:13 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Oct 2012 18:23:09 GMT",
"version": "v2"
}
] | 2012-10-08 | [
[
"Boshkayev",
"Kuantay",
""
],
[
"Quevedo",
"Hernando",
""
],
[
"Ruffini",
"Remo",
""
]
] | We study some exact and approximate solutions of Einstein's equations that can be used to describe the gravitational field of astrophysical compact objects in the limiting case of slow rotation and slight deformation. First, we show that none of the standard models obtained by using Fock's method can be used as an interior source for the approximate exterior Kerr solution. We then use Fock's method to derive a generalized interior solution, and also an exterior solution that turns out to be equivalent to the exterior Hartle-Thorne approximate solution that, in turn, is equivalent to an approximate limiting case of the exact Quevedo-Mashhoon solution. As a result we obtain an analytic approximate solution that describes the interior and exterior gravitational field of a slowly rotating and slightly deformed astrophysical object. |
gr-qc/9705015 | Gungwong Kang | Gungwon Kang | Quantum Ergoregion Instability | 10 pages, latex, one epsfig, to appear in the Proceedings of the
APCTP Winter School on Duality of String Theory, Korea, Feb. 17-28, 1997; a
brief version of gr-qc/9701040 with slightly different presentation | null | 10.1142/9789814447287_0014 | null | gr-qc | null | We have shown that, as in the case of black holes, an ergosphere itself with
no event horizon inside can evaporate spontaneously, giving energy radiation to
spatial infinity until the ergoregion disappears. However, the feature of his
quantum ergoregion instability is very much different from black hole
radiation. It is rather analogous to a laser amplification. This analysis is
based on the canonical quantization of a neutral scalar field in the presence
of unstable modes characterized by complex frequencies in a simple model for a
rapidly rotating star.
| [
{
"created": "Fri, 9 May 1997 07:05:56 GMT",
"version": "v1"
}
] | 2016-11-03 | [
[
"Kang",
"Gungwon",
""
]
] | We have shown that, as in the case of black holes, an ergosphere itself with no event horizon inside can evaporate spontaneously, giving energy radiation to spatial infinity until the ergoregion disappears. However, the feature of his quantum ergoregion instability is very much different from black hole radiation. It is rather analogous to a laser amplification. This analysis is based on the canonical quantization of a neutral scalar field in the presence of unstable modes characterized by complex frequencies in a simple model for a rapidly rotating star. |
1810.01232 | Charles Wang | Charles H.-T. Wang, Daniel P. F. Rodrigues | Closing the gaps in quantum space and time: Conformally augmented gauge
structure of gravitation | 35 pages (8 pages main text, 27 pages supplementary material);
Published version | Phys. Rev. D 98, 124041 (2018) | 10.1103/PhysRevD.98.124041 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new framework of loop quantization that assimilates conformal and scale
invariance is constructed and is found to be applicable to a large class of
physically important theories of gravity and gravity-matter systems. They
include general relativity and scale-invariant scalar-tensor and dilaton
theories. Consequently, matter to be coupled to such theories is restricted to
be conformal or scale invariant. Standard model-type systems naturally fall
into this category. The new loop quantization follows from a novel conformally
generalized Holst action principle. In contrast to standard loop quantum
gravity, the resulting quantum geometry is not beset by the Immirzi ambiguity
and has no definitive area gaps within the considered large class of theories
of gravitation. As an additional feature, the scale invariance gives rise to a
conserved Weyl current and we discuss briefly its possible implication on the
problem of time in quantum gravity.
| [
{
"created": "Tue, 2 Oct 2018 13:34:43 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Dec 2018 15:00:38 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Dec 2018 17:16:04 GMT",
"version": "v3"
}
] | 2019-01-02 | [
[
"Wang",
"Charles H. -T.",
""
],
[
"Rodrigues",
"Daniel P. F.",
""
]
] | A new framework of loop quantization that assimilates conformal and scale invariance is constructed and is found to be applicable to a large class of physically important theories of gravity and gravity-matter systems. They include general relativity and scale-invariant scalar-tensor and dilaton theories. Consequently, matter to be coupled to such theories is restricted to be conformal or scale invariant. Standard model-type systems naturally fall into this category. The new loop quantization follows from a novel conformally generalized Holst action principle. In contrast to standard loop quantum gravity, the resulting quantum geometry is not beset by the Immirzi ambiguity and has no definitive area gaps within the considered large class of theories of gravitation. As an additional feature, the scale invariance gives rise to a conserved Weyl current and we discuss briefly its possible implication on the problem of time in quantum gravity. |
1706.03884 | Wen-Biao Han | Ran Cheng, Wen-Biao Han | Accurate recalibated waveforms for extreme-mass-ratio inspirals in
effective-one-body frame | 22, 10 tables, 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | How to calculate the gravitational waves (GWs) of
Extreme-mass-ratio-inspirals (EMRIs) in a highly accurate and efficient way
still keeps a challenge. In this paper, we present a so-called fully
recalibrated waveforms for EMRIs with high accuracy. Based on the numerical
data by solving the Teukolsky equations, we recalibrate all mass-ratio
independent coefficients of the factorized waveforms which are used in the
effective-one-body (EOB) models. Due to these new coefficients, the precision
of waveforms is improved enormously, and is much higher than the original forms
and at the same time higher than other existing calibration models. We believe
our model will play an important role in the waveform-template construction of
the space-based GW detectors.
| [
{
"created": "Tue, 13 Jun 2017 01:19:36 GMT",
"version": "v1"
}
] | 2017-06-14 | [
[
"Cheng",
"Ran",
""
],
[
"Han",
"Wen-Biao",
""
]
] | How to calculate the gravitational waves (GWs) of Extreme-mass-ratio-inspirals (EMRIs) in a highly accurate and efficient way still keeps a challenge. In this paper, we present a so-called fully recalibrated waveforms for EMRIs with high accuracy. Based on the numerical data by solving the Teukolsky equations, we recalibrate all mass-ratio independent coefficients of the factorized waveforms which are used in the effective-one-body (EOB) models. Due to these new coefficients, the precision of waveforms is improved enormously, and is much higher than the original forms and at the same time higher than other existing calibration models. We believe our model will play an important role in the waveform-template construction of the space-based GW detectors. |
1609.09781 | Ivan Debono | Ivan Debono and George F. Smoot | General Relativity and Cosmology: Unsolved Questions and Future
Directions | 82 pages, 8 figures | Universe. 2016; 2(4):23 | 10.3390/universe2040023 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For the last 100 years, General Relativity (GR) has taken over the
gravitational theory mantle held by Newtonian Gravity for the previous 200
years. This article reviews the status of GR in terms of its self-consistency,
completeness, and the evidence provided by observations, which have allowed GR
to remain the champion of gravitational theories against several other classes
of competing theories. We pay particular attention to the role of GR and
gravity in cosmology, one of the areas in which one gravity dominates and new
phenomena and effects challenge the orthodoxy. We also review other areas where
there are likely conflicts pointing to the need to replace or revise GR to
represent correctly observations and consistent theoretical framework.
Observations have long been key both to the theoretical liveliness and
viability of GR. We conclude with a discussion of the likely developments over
the next 100 years.
| [
{
"created": "Wed, 28 Sep 2016 11:23:55 GMT",
"version": "v1"
}
] | 2016-10-03 | [
[
"Debono",
"Ivan",
""
],
[
"Smoot",
"George F.",
""
]
] | For the last 100 years, General Relativity (GR) has taken over the gravitational theory mantle held by Newtonian Gravity for the previous 200 years. This article reviews the status of GR in terms of its self-consistency, completeness, and the evidence provided by observations, which have allowed GR to remain the champion of gravitational theories against several other classes of competing theories. We pay particular attention to the role of GR and gravity in cosmology, one of the areas in which one gravity dominates and new phenomena and effects challenge the orthodoxy. We also review other areas where there are likely conflicts pointing to the need to replace or revise GR to represent correctly observations and consistent theoretical framework. Observations have long been key both to the theoretical liveliness and viability of GR. We conclude with a discussion of the likely developments over the next 100 years. |
1011.0814 | Valentin Gladush | Valentin D. Gladush and Alexander I. Petrusenko | On the effective actions for the spherical charged dust shell in General
Relativity | 16 pages | Acta Phys. Pol. B 43, 3 (2012) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A simple and direct, based on the equations of motion, derivation of the
variational principle and effective actions for a spherical charged dust shell
in general relativity is offered. This principle is based on the relativistic
version of the D{\AE}Alembert principle of virtual displacements and leads to
the effective actions for the shell, which describe the shell from the point of
view of the exterior or interior stationary observers. Herewith, sides of the
shell are considered independently, in the coordinates of the interior or
exterior region of the shell. Canonical variables for a charged dust shell are
built. It is shown that the conditions of isometry of the sides of the shell
lead to the Hamiltonian constraint on these interior and exterior dynamical
systems. Special cases of the \^ohollow\"o and \^oscreening\"o shells are
briefly considered, as well as a family of the concentric charged dust shells.
| [
{
"created": "Wed, 3 Nov 2010 08:03:39 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Dec 2010 13:07:13 GMT",
"version": "v2"
},
{
"created": "Tue, 7 May 2013 08:50:25 GMT",
"version": "v3"
}
] | 2013-05-08 | [
[
"Gladush",
"Valentin D.",
""
],
[
"Petrusenko",
"Alexander I.",
""
]
] | A simple and direct, based on the equations of motion, derivation of the variational principle and effective actions for a spherical charged dust shell in general relativity is offered. This principle is based on the relativistic version of the D{\AE}Alembert principle of virtual displacements and leads to the effective actions for the shell, which describe the shell from the point of view of the exterior or interior stationary observers. Herewith, sides of the shell are considered independently, in the coordinates of the interior or exterior region of the shell. Canonical variables for a charged dust shell are built. It is shown that the conditions of isometry of the sides of the shell lead to the Hamiltonian constraint on these interior and exterior dynamical systems. Special cases of the \^ohollow\"o and \^oscreening\"o shells are briefly considered, as well as a family of the concentric charged dust shells. |
2407.16916 | Chikun Ding | Chikun Ding, Changqing Liu, Yuehua Xiao and Jun Chen | Phantom black holes and wormholes in Einstein-bumblebee gravity | 14 pages, 2 tables | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper we study Einstein-bumblebee gravity theory minimally coupled
with external matter -- a phantom/non-phantom(conventional) scalar field, find
that these scalar fields can affect the black hole solutions, i.e., giving a
hair to a black hole. In this model, the contents of the scalar field and the
forms of its potential are completely determined by the black hole spacetime.
The constant bumblebee field $b_\mu$ affects a spacetime via the coupling
constant $\ell$ and its motion equations. If $\ell>-1$, the phantom field is
admissible and the conventional scalar field is forbidden; if $\ell<-1$, the
phantom field is forbidden and the conventional scalar field is admissible.
When the bumblebee potential is quadratic, we obtain a wormhole solution
asymptotically to Ellis wormhole, it can be called Ellis-bumblebee-phantom
(EPB) wormhole which is regular everywhere and has no singularity. An
Schwarzschild-like wormhole with naked singularity and an asymptotic flat
phantom black hole solutions are also obtained. When the bumblebee potential is
linear, we derive a phantom (anti-)de-Sitter (dS/AdS) black hole solution which
can be asymptotic to Schwarzschild dS/AdS black hole. The phantom potential and
the Lagrange-multiplier $\lambda$ behave as a cosmological constant $\Lambda$.
| [
{
"created": "Wed, 24 Jul 2024 00:27:08 GMT",
"version": "v1"
}
] | 2024-07-25 | [
[
"Ding",
"Chikun",
""
],
[
"Liu",
"Changqing",
""
],
[
"Xiao",
"Yuehua",
""
],
[
"Chen",
"Jun",
""
]
] | In this paper we study Einstein-bumblebee gravity theory minimally coupled with external matter -- a phantom/non-phantom(conventional) scalar field, find that these scalar fields can affect the black hole solutions, i.e., giving a hair to a black hole. In this model, the contents of the scalar field and the forms of its potential are completely determined by the black hole spacetime. The constant bumblebee field $b_\mu$ affects a spacetime via the coupling constant $\ell$ and its motion equations. If $\ell>-1$, the phantom field is admissible and the conventional scalar field is forbidden; if $\ell<-1$, the phantom field is forbidden and the conventional scalar field is admissible. When the bumblebee potential is quadratic, we obtain a wormhole solution asymptotically to Ellis wormhole, it can be called Ellis-bumblebee-phantom (EPB) wormhole which is regular everywhere and has no singularity. An Schwarzschild-like wormhole with naked singularity and an asymptotic flat phantom black hole solutions are also obtained. When the bumblebee potential is linear, we derive a phantom (anti-)de-Sitter (dS/AdS) black hole solution which can be asymptotic to Schwarzschild dS/AdS black hole. The phantom potential and the Lagrange-multiplier $\lambda$ behave as a cosmological constant $\Lambda$. |
1906.04360 | Pedro Ca\~nate Casseres | Pedro Ca\~nate, Nora Breton and Leonardo Ortiz | (2+1)-dimensional Static Cyclic Symmetric Traversable Wormhole:
Quasinormal Modes and Causality | 18 pages, 6 figures, Minor changes | null | 10.1088/1361-6382/ab6859 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study a static cyclic symmetric traversable wormhole in
$(2+1)-$dimensional gravity coupled to nonlinear electrodynamics in anti-de
Sitter spacetime. The solution is characterized by three parameters: mass $M$,
cosmological constant $\Lambda$ and one electromagnetic parameter,
$q_{\alpha}$. The causality of this spacetime is studied, determining its
maximal extension and constructing then the corresponding Kruskal-Szekeres and
Penrose diagrams. The quasinormal modes (QNMs) that result from considering a
massive scalar test field in the wormhole background are determined by solving
in exact form the Klein-Gordon equation; the effective potential resembles the
one of a harmonic oscillator shifted from its equilibrium position and,
consequently, the QNMs have a pure point spectrum.
| [
{
"created": "Tue, 11 Jun 2019 02:44:27 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Oct 2019 14:21:32 GMT",
"version": "v2"
}
] | 2020-04-08 | [
[
"Cañate",
"Pedro",
""
],
[
"Breton",
"Nora",
""
],
[
"Ortiz",
"Leonardo",
""
]
] | In this paper we study a static cyclic symmetric traversable wormhole in $(2+1)-$dimensional gravity coupled to nonlinear electrodynamics in anti-de Sitter spacetime. The solution is characterized by three parameters: mass $M$, cosmological constant $\Lambda$ and one electromagnetic parameter, $q_{\alpha}$. The causality of this spacetime is studied, determining its maximal extension and constructing then the corresponding Kruskal-Szekeres and Penrose diagrams. The quasinormal modes (QNMs) that result from considering a massive scalar test field in the wormhole background are determined by solving in exact form the Klein-Gordon equation; the effective potential resembles the one of a harmonic oscillator shifted from its equilibrium position and, consequently, the QNMs have a pure point spectrum. |
2107.03283 | Mehdi Shokri | M. Shokri, J. Sadeghi and M. R. Setare | Constant-roll inflation from a fermionic field | 7 pages, 2 figures | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/publicdomain/zero/1.0/ | We study the inflationary period driven by a fermionic field which is
non-minimally coupled to gravity in the context of the constant-roll approach.
We consider the model for a specific form of coupling and perform the
corresponding inflationary analysis. By comparing the result with the Planck
observations coming from CMB anisotropies, we find the observational
constraints on the parameters space of the model and also the predictions the
model. We find that the values of $r$ and $n_{s}$ for $-1.5<\beta\leq-0.9$ are
in good agreement with the observations when $|\xi|=0.1$ and $N=60$.
| [
{
"created": "Mon, 28 Jun 2021 06:37:37 GMT",
"version": "v1"
}
] | 2021-07-08 | [
[
"Shokri",
"M.",
""
],
[
"Sadeghi",
"J.",
""
],
[
"Setare",
"M. R.",
""
]
] | We study the inflationary period driven by a fermionic field which is non-minimally coupled to gravity in the context of the constant-roll approach. We consider the model for a specific form of coupling and perform the corresponding inflationary analysis. By comparing the result with the Planck observations coming from CMB anisotropies, we find the observational constraints on the parameters space of the model and also the predictions the model. We find that the values of $r$ and $n_{s}$ for $-1.5<\beta\leq-0.9$ are in good agreement with the observations when $|\xi|=0.1$ and $N=60$. |
1803.06368 | Dario Bettoni | Luca Amendola, Dario Bettoni, Guillem Dom\`enech, Adalto R. Gomes | Doppelg\"anger dark energy: modified gravity with non-universal
couplings after GW170817 | 27 pages, no figures, published version, updated references | null | 10.1088/1475-7516/2018/06/029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational Wave (GW) astronomy severely narrowed down the theoretical
space for scalar-tensor theories. We propose a new class of attractor models
for Horndeski action in which GWs propagate at the speed of light in the nearby
universe but not in the past. To do so we derive new solutions to the
interacting dark sector in which the ratio of dark energy and dark matter
remains constant, which we refer to as doppelg\"anger dark energy (DDE). We
then remove the interaction between dark matter and dark energy by a suitable
change of variables. The accelerated expansion that (we) baryons observe is due
to a conformal coupling to the dark energy scalar field. We show how in this
context it is possible to find a non trivial subset of solutions in which GWs
propagate at the speed of light only at low red-shifts. The model is an
attractor, thus reaching the limit $c_{T}\to1$ relatively fast. However, the
effect of baryons turns out to be non-negligible and severely constrains the
form of the Lagrangian. In passing, we found that in the simplest DDE models
the no-ghost conditions for perturbations require a non-universal coupling to
gravity. In the end, we comment on possible ways to solve the lack of matter
domination stage for DDE models.
| [
{
"created": "Fri, 16 Mar 2018 18:34:57 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Jun 2018 15:07:23 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Feb 2019 11:22:52 GMT",
"version": "v3"
}
] | 2019-02-18 | [
[
"Amendola",
"Luca",
""
],
[
"Bettoni",
"Dario",
""
],
[
"Domènech",
"Guillem",
""
],
[
"Gomes",
"Adalto R.",
""
]
] | Gravitational Wave (GW) astronomy severely narrowed down the theoretical space for scalar-tensor theories. We propose a new class of attractor models for Horndeski action in which GWs propagate at the speed of light in the nearby universe but not in the past. To do so we derive new solutions to the interacting dark sector in which the ratio of dark energy and dark matter remains constant, which we refer to as doppelg\"anger dark energy (DDE). We then remove the interaction between dark matter and dark energy by a suitable change of variables. The accelerated expansion that (we) baryons observe is due to a conformal coupling to the dark energy scalar field. We show how in this context it is possible to find a non trivial subset of solutions in which GWs propagate at the speed of light only at low red-shifts. The model is an attractor, thus reaching the limit $c_{T}\to1$ relatively fast. However, the effect of baryons turns out to be non-negligible and severely constrains the form of the Lagrangian. In passing, we found that in the simplest DDE models the no-ghost conditions for perturbations require a non-universal coupling to gravity. In the end, we comment on possible ways to solve the lack of matter domination stage for DDE models. |
gr-qc/9804019 | Enzo Leguizamon | Mirta S. Iriondo, Enzo O. Leguizamon and Oscar A. Reula | On the dynamics of Einstein's equations in the Ashtekar formulation | 29 pages (published version) | Adv.Theor.Math.Phys.2:1075-1103,1998 | null | null | gr-qc | null | We study the dynamics of Einstein's equations in Ashtekar's variables from
the point of view of the theory of hyperbolic systems of evolution equations.
We extend previous results and show that by a suitable modification of the
Hamiltonian vector flow outside the sub-manifold of real and constrained
solutions, a symmetric hyperbolic system is obtained for any fixed choice of
lapse-shift pair, without assuming the solution to be a priori real. We notice
that the evolution system is block diagonal in the pair $(\sigma^a,A_b)$, and
provide explicit and very simple formulae for the eigenvector-eigenvalue pairs
in terms of an orthonormal tetrad with one of its components pointing along the
propagation direction. We also analyze the constraint equations and find that
when viewed as functions of the extended phase space they form a symmetric
hyperbolic system on their own. We also provide simple formulae for its
eigenvectors-eigenvalues pairs.
| [
{
"created": "Mon, 6 Apr 1998 19:56:58 GMT",
"version": "v1"
},
{
"created": "Fri, 8 May 1998 14:22:10 GMT",
"version": "v2"
},
{
"created": "Fri, 29 May 1998 22:47:06 GMT",
"version": "v3"
},
{
"created": "Wed, 31 Mar 1999 22:37:47 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Iriondo",
"Mirta S.",
""
],
[
"Leguizamon",
"Enzo O.",
""
],
[
"Reula",
"Oscar A.",
""
]
] | We study the dynamics of Einstein's equations in Ashtekar's variables from the point of view of the theory of hyperbolic systems of evolution equations. We extend previous results and show that by a suitable modification of the Hamiltonian vector flow outside the sub-manifold of real and constrained solutions, a symmetric hyperbolic system is obtained for any fixed choice of lapse-shift pair, without assuming the solution to be a priori real. We notice that the evolution system is block diagonal in the pair $(\sigma^a,A_b)$, and provide explicit and very simple formulae for the eigenvector-eigenvalue pairs in terms of an orthonormal tetrad with one of its components pointing along the propagation direction. We also analyze the constraint equations and find that when viewed as functions of the extended phase space they form a symmetric hyperbolic system on their own. We also provide simple formulae for its eigenvectors-eigenvalues pairs. |
gr-qc/9805044 | David I. Santiago | David I. Santiago, Dimitri Kalligas, and Robert V. Wagoner | Scalar-Tensor Cosmologies and their Late Time Evolution | 23 pages, no figures. Submitted for publicatiom in Phys. Rev, D15 | Phys.Rev.D58:124005,1998 | 10.1103/PhysRevD.58.124005 | null | gr-qc astro-ph | null | We study the asymptotic behavior at late times of Friedmann-Robertson-Walker
(uniform density) cosmological models within scalar-tensor theories of gravity.
Particularly, we analyze the late time behavior in the present (matter
dominated) epoch of the universe. The result of Damour and Nordtvedt that for a
massless scalar in a flat cosmology the Universe evolves towards a state
indistinguishable from general relativity is generalized. We first study a
massless scalar field in an open universe. It is found that, while the universe
tends to approach a state with less scalar contribution to gravity, the
attractor mechanism is not effective enough to drive the theory towards a final
state indistinguishable from general relativity. For the self-interacting case
it is found that the scalar field potential dominates the late time behavior.
In most cases this makes the attractor mechanism effective, thus resulting in a
theory of gravity with vanishingly small scalar contribution even for the open
Universe.
| [
{
"created": "Wed, 13 May 1998 07:49:41 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Santiago",
"David I.",
""
],
[
"Kalligas",
"Dimitri",
""
],
[
"Wagoner",
"Robert V.",
""
]
] | We study the asymptotic behavior at late times of Friedmann-Robertson-Walker (uniform density) cosmological models within scalar-tensor theories of gravity. Particularly, we analyze the late time behavior in the present (matter dominated) epoch of the universe. The result of Damour and Nordtvedt that for a massless scalar in a flat cosmology the Universe evolves towards a state indistinguishable from general relativity is generalized. We first study a massless scalar field in an open universe. It is found that, while the universe tends to approach a state with less scalar contribution to gravity, the attractor mechanism is not effective enough to drive the theory towards a final state indistinguishable from general relativity. For the self-interacting case it is found that the scalar field potential dominates the late time behavior. In most cases this makes the attractor mechanism effective, thus resulting in a theory of gravity with vanishingly small scalar contribution even for the open Universe. |
1311.4024 | Narayan Banerjee | Ankan Mukherjee and Narayan Banerjee | A Reconstruction of Quintessence Dark Energy | null | Eur. Phys. J. Plus (2015) 130: 201 | 10.1140/epjp/i2015-15201-7 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With a parametric form of the equation of state parameter of dark energy, a
quintessence potential has been reconstructed. The potential is found to be a
generalization of a double exponential potential. The constraints on the
parameters are obtained by maximum likelihood analysis using observational
Hubble data, type Ia supernova data, baryon acoustic oscillation data and the
CMB shift parameter data. Th emodel shows preference towards the phantom
behaviour of dark energy.
| [
{
"created": "Sat, 16 Nov 2013 06:30:45 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Jan 2016 09:23:38 GMT",
"version": "v2"
}
] | 2016-01-20 | [
[
"Mukherjee",
"Ankan",
""
],
[
"Banerjee",
"Narayan",
""
]
] | With a parametric form of the equation of state parameter of dark energy, a quintessence potential has been reconstructed. The potential is found to be a generalization of a double exponential potential. The constraints on the parameters are obtained by maximum likelihood analysis using observational Hubble data, type Ia supernova data, baryon acoustic oscillation data and the CMB shift parameter data. Th emodel shows preference towards the phantom behaviour of dark energy. |
1211.4376 | Igor Tanatarov | I. V. Tanatarov and O. B. Zaslavskii | What happens to Petrov classification on horizons of axisymmetric dirty
black holes | 41 pages. Expanded motivation for considering both FO and OO frames,
clarified exposition and improved terminilogy, added section on different
singular boosts | J. Math. Phys. 55, 022502 (2014) | 10.1063/1.4865995 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider axisymmetric stationary dirty black holes with regular
non-extremal or extremal horizons, and compute their on-horizon Petrov types.
The Petrov type (PT) in the frame of the observer crossing the horizon can be
different from that formally obtained in the usual (but singular in the horizon
limit) frame of an observer on a circular orbit. We call this entity the
boosted Petrov type (BPT), as the corresponding frame is obtained by a singular
boost from the regular one. The PT off-horizon can be more general than PT
on-horizon and that can be more general than the BPT on horizon. This is valid
for all regular metrics, irrespective of the extremality of the horizon. We
analyze and classify the possible relations between the three characteristics
and discuss the nature and features of the underlying singular boost. The three
Petrov types can be the same only for space-times of PT D and O off-horizon.
The mutual alignment of principal null directions and the generator in the
vicinity of the horizon is studied in detail. As an example, we also analyze a
special class of metrics with utra-extremal horizons (for which the regularity
conditions look different from the general case) and compare their off-horizon
and on-horizon algebraic structure in both frames.
| [
{
"created": "Mon, 19 Nov 2012 11:58:05 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Apr 2013 20:48:26 GMT",
"version": "v2"
},
{
"created": "Thu, 29 Aug 2013 13:01:26 GMT",
"version": "v3"
}
] | 2014-02-28 | [
[
"Tanatarov",
"I. V.",
""
],
[
"Zaslavskii",
"O. B.",
""
]
] | We consider axisymmetric stationary dirty black holes with regular non-extremal or extremal horizons, and compute their on-horizon Petrov types. The Petrov type (PT) in the frame of the observer crossing the horizon can be different from that formally obtained in the usual (but singular in the horizon limit) frame of an observer on a circular orbit. We call this entity the boosted Petrov type (BPT), as the corresponding frame is obtained by a singular boost from the regular one. The PT off-horizon can be more general than PT on-horizon and that can be more general than the BPT on horizon. This is valid for all regular metrics, irrespective of the extremality of the horizon. We analyze and classify the possible relations between the three characteristics and discuss the nature and features of the underlying singular boost. The three Petrov types can be the same only for space-times of PT D and O off-horizon. The mutual alignment of principal null directions and the generator in the vicinity of the horizon is studied in detail. As an example, we also analyze a special class of metrics with utra-extremal horizons (for which the regularity conditions look different from the general case) and compare their off-horizon and on-horizon algebraic structure in both frames. |
2406.18225 | Christopher Reyes | Christopher Reyes, Jeremy Sakstein | Neutron Stars in Aether Scalar-Tensor Theory | 10 pages, 3 figures | null | null | null | gr-qc astro-ph.CO astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Aether Scalar-Tensor theory is a modification of general relativity proposed
to explain galactic and cosmological mass discrepancies conventionally
attributed to dark matter. The theory is able to fit the cosmic microwave
background and the linear matter power spectrum without dark matter. In this
work, we derive the Tolman-Oppenheimer-Volkoff equation in this theory and
solve it for realistic nuclear equations of state to predict the mass-radius
relation of neutron stars. We find solutions that are compatible with all
current observations of neutron stars.
| [
{
"created": "Wed, 26 Jun 2024 10:14:47 GMT",
"version": "v1"
}
] | 2024-06-27 | [
[
"Reyes",
"Christopher",
""
],
[
"Sakstein",
"Jeremy",
""
]
] | Aether Scalar-Tensor theory is a modification of general relativity proposed to explain galactic and cosmological mass discrepancies conventionally attributed to dark matter. The theory is able to fit the cosmic microwave background and the linear matter power spectrum without dark matter. In this work, we derive the Tolman-Oppenheimer-Volkoff equation in this theory and solve it for realistic nuclear equations of state to predict the mass-radius relation of neutron stars. We find solutions that are compatible with all current observations of neutron stars. |
gr-qc/9807042 | Petr Hajicek | P. Hajicek | Black hole interacting with matter as a simple dynamical system | Latex, no figures, 26 pages | J.Math.Phys. 40 (1999) 318-339 | 10.1063/1.532774 | null | gr-qc | null | Recently, a variational principle has been derived from Einstein-Hilbert and
a matter Lagrangian for the spherically symmetric system of a dust shell and a
black hole. The so-called physical region of the phase space, which contains
all physically meaningful states of the system defined by the variational
principle, is specified; it has a complicated boundary. The principle is then
transformed to new variables that remove some problems of the original
formalism: the whole phase space is covered (in particular, the variables are
regular at all horizons), the constraint has a polynomial form, and the
constraint equation is uniquely solvable for two of the three conserved
momenta. The solutions for the momenta are written down explicitly. The
symmetry group of the system is studied. The equations of motion are derived
from the transformed principle and are shown to be equivalent to the previous
ones. Some lower-dimensional systems are constructed by exclusion of cyclic
variables, and some of their properties are found.
| [
{
"created": "Thu, 16 Jul 1998 13:40:54 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Hajicek",
"P.",
""
]
] | Recently, a variational principle has been derived from Einstein-Hilbert and a matter Lagrangian for the spherically symmetric system of a dust shell and a black hole. The so-called physical region of the phase space, which contains all physically meaningful states of the system defined by the variational principle, is specified; it has a complicated boundary. The principle is then transformed to new variables that remove some problems of the original formalism: the whole phase space is covered (in particular, the variables are regular at all horizons), the constraint has a polynomial form, and the constraint equation is uniquely solvable for two of the three conserved momenta. The solutions for the momenta are written down explicitly. The symmetry group of the system is studied. The equations of motion are derived from the transformed principle and are shown to be equivalent to the previous ones. Some lower-dimensional systems are constructed by exclusion of cyclic variables, and some of their properties are found. |
1612.06378 | Giulia Gubitosi | Francesco Brighenti, Giulia Gubitosi, Joao Magueijo | Primordial perturbations in a rainbow universe with running Newton
constant | 7 pages, 2 figures | Phys. Rev. D 95, 063534 (2017) | 10.1103/PhysRevD.95.063534 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the spectral index of primordial perturbations in a rainbow
universe. We allow the Newton constant $G$ to run at (super-)Planckian energies
and we consider both vacuum and thermal perturbations. If the rainbow metric is
the one associated to a generalized Horava-Lifshitz dispersion relation, we
find that only when $G$ tends asymptotically to zero can one match the observed
value of the spectral index and solve the horizon problem, both for vacuum and
thermal perturbations. For vacuum fluctuations the observational constraints
imply that the primordial universe expansion can be both accelerating or
decelerating, while in the case of thermal perturbations only decelerating
expansion is allowed.
| [
{
"created": "Mon, 19 Dec 2016 18:31:49 GMT",
"version": "v1"
}
] | 2017-04-05 | [
[
"Brighenti",
"Francesco",
""
],
[
"Gubitosi",
"Giulia",
""
],
[
"Magueijo",
"Joao",
""
]
] | We compute the spectral index of primordial perturbations in a rainbow universe. We allow the Newton constant $G$ to run at (super-)Planckian energies and we consider both vacuum and thermal perturbations. If the rainbow metric is the one associated to a generalized Horava-Lifshitz dispersion relation, we find that only when $G$ tends asymptotically to zero can one match the observed value of the spectral index and solve the horizon problem, both for vacuum and thermal perturbations. For vacuum fluctuations the observational constraints imply that the primordial universe expansion can be both accelerating or decelerating, while in the case of thermal perturbations only decelerating expansion is allowed. |
0809.0629 | Erich Gaertig | Erich Gaertig and Kostas D. Kokkotas | Oscillations of rapidly rotating relativistic stars | this article will be published in Physical Review D | Phys.Rev.D78:064063,2008 | 10.1103/PhysRevD.78.064063 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Non-axisymmetric oscillations of rapidly rotating relativistic stars are
studied using the Cowling approximation. The oscillation spectra have been
estimated by Fourier transforming the evolution equations describing the
perturbations. This is the first study of its kind and provides information on
the effect of fast rotation on the oscillation spectra while it offers the
possibility in studying the complete problem by including spacetime
perturbations. Our study includes both axisymmetric and non-axisymmetric
perturbations and provides limits for the onset of the secular bar mode
rotational instability. We also present approximate formulae for the dependence
of the oscillation spectrum from rotation. The results suggest that it is
possible to extract the relativistic star's parameters from the observed
gravitational wave spectrum.
| [
{
"created": "Wed, 3 Sep 2008 14:08:59 GMT",
"version": "v1"
}
] | 2009-09-29 | [
[
"Gaertig",
"Erich",
""
],
[
"Kokkotas",
"Kostas D.",
""
]
] | Non-axisymmetric oscillations of rapidly rotating relativistic stars are studied using the Cowling approximation. The oscillation spectra have been estimated by Fourier transforming the evolution equations describing the perturbations. This is the first study of its kind and provides information on the effect of fast rotation on the oscillation spectra while it offers the possibility in studying the complete problem by including spacetime perturbations. Our study includes both axisymmetric and non-axisymmetric perturbations and provides limits for the onset of the secular bar mode rotational instability. We also present approximate formulae for the dependence of the oscillation spectrum from rotation. The results suggest that it is possible to extract the relativistic star's parameters from the observed gravitational wave spectrum. |
0912.4255 | Pinkesh Patel | P. Patel, X. Siemens, R. Dupuis, J. Betzwieser | Implementation of barycentric resampling for continuous wave searches in
gravitational wave data | 10 pages, 3 figures | Phys.Rev.D81:084032,2010 | 10.1103/PhysRevD.81.084032 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe an efficient implementation of a coherent statistic for
continuous gravitational wave searches from neutron stars. The algorithm works
by transforming the data taken by a gravitational wave detector from a moving
Earth bound frame to one that sits at the Solar System barycenter. Many
practical difficulties arise in the implementation of this algorithm, some of
which have not been discussed previously. These difficulties include
constraints of small computer memory, discreteness of the data, losses due to
interpolation and gaps in real data. This implementation is considerably more
efficient than previous implementations of these kinds of searches on Laser
Interferometer Gravitational Wave (LIGO) detector data.
| [
{
"created": "Mon, 21 Dec 2009 20:59:53 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Jan 2010 00:40:40 GMT",
"version": "v2"
}
] | 2010-05-12 | [
[
"Patel",
"P.",
""
],
[
"Siemens",
"X.",
""
],
[
"Dupuis",
"R.",
""
],
[
"Betzwieser",
"J.",
""
]
] | We describe an efficient implementation of a coherent statistic for continuous gravitational wave searches from neutron stars. The algorithm works by transforming the data taken by a gravitational wave detector from a moving Earth bound frame to one that sits at the Solar System barycenter. Many practical difficulties arise in the implementation of this algorithm, some of which have not been discussed previously. These difficulties include constraints of small computer memory, discreteness of the data, losses due to interpolation and gaps in real data. This implementation is considerably more efficient than previous implementations of these kinds of searches on Laser Interferometer Gravitational Wave (LIGO) detector data. |
1808.06188 | Salvatore Capozziello | Salvatore Capozziello, Mohsen Khodadi, and Gaetano Lambiase | The quark chemical potential of QCD phase transition and the stochastic
background of gravitational waves | 12 pages, 4 figures, to appear in Phys. Lett. B | Phys.Lett. B789 (2019) 626-633 | 10.1016/j.physletb.2019.01.004 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The detection of stochastic background of gravitational waves (GWs), produced
by cosmological phase transitions (PTs), is of fundamental importance because
allows to probe the physics related to PT energy scales. Motivated by the
decisive role of non-zero quark chemical potential towards understanding
physics in the core of neutron stars, quark stars and heavy-ion collisions, in
this paper we qualitatively explore the stochastic background of GW spectrum
generated by a cosmological source such as high-density QCD first order PT
during the early Universe. Specifically, we calculate the frequency peak
$f_{peak}$ redshifted at today time and the fractional energy density
$\Omega_{gw}h^2$ in light of equation-of-state improved by the finite quark
(baryon) chemical potential (we consider an effective three flavor chiral
quarks model of QCD). Our calculations reveal a striking increase in $f_{peak}$
and $\Omega_{gw}h^2$ due to the quark chemical potential, which means to
improve the chances of detection, in possible future observations (in
particular SKA/PTA experiments), of the stochastic background of GWs from QCD
first order PT. Even if the improvements could be weak, by updating the
sensitivity of relevant detectors in the future, we can still remain hopeful.
Concerning the phenomenological contribution of QCD equation-of-state, and in
particular the possibility to detect a stochastic GW signal, we further show
that the role of the quark chemical potential is model-dependent. This feature
allows to discriminate among possible QCD effective models depending on their
capability to shed light on the dynamic of QCD-PT through future observations
of primordial GWs. In this perspective, the results are indeed encouraging to
employ the GWs to study the QCD PT in high density strong interaction matter.
| [
{
"created": "Sun, 19 Aug 2018 08:53:43 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Aug 2018 18:01:11 GMT",
"version": "v2"
},
{
"created": "Sat, 20 Oct 2018 14:41:47 GMT",
"version": "v3"
},
{
"created": "Sun, 6 Jan 2019 08:53:26 GMT",
"version": "v4"
}
] | 2019-01-23 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Khodadi",
"Mohsen",
""
],
[
"Lambiase",
"Gaetano",
""
]
] | The detection of stochastic background of gravitational waves (GWs), produced by cosmological phase transitions (PTs), is of fundamental importance because allows to probe the physics related to PT energy scales. Motivated by the decisive role of non-zero quark chemical potential towards understanding physics in the core of neutron stars, quark stars and heavy-ion collisions, in this paper we qualitatively explore the stochastic background of GW spectrum generated by a cosmological source such as high-density QCD first order PT during the early Universe. Specifically, we calculate the frequency peak $f_{peak}$ redshifted at today time and the fractional energy density $\Omega_{gw}h^2$ in light of equation-of-state improved by the finite quark (baryon) chemical potential (we consider an effective three flavor chiral quarks model of QCD). Our calculations reveal a striking increase in $f_{peak}$ and $\Omega_{gw}h^2$ due to the quark chemical potential, which means to improve the chances of detection, in possible future observations (in particular SKA/PTA experiments), of the stochastic background of GWs from QCD first order PT. Even if the improvements could be weak, by updating the sensitivity of relevant detectors in the future, we can still remain hopeful. Concerning the phenomenological contribution of QCD equation-of-state, and in particular the possibility to detect a stochastic GW signal, we further show that the role of the quark chemical potential is model-dependent. This feature allows to discriminate among possible QCD effective models depending on their capability to shed light on the dynamic of QCD-PT through future observations of primordial GWs. In this perspective, the results are indeed encouraging to employ the GWs to study the QCD PT in high density strong interaction matter. |
1702.07744 | Marko Vojinovic | Nikola Paunkovic and Marko Vojinovic | Gauge protected entanglement between gravity and matter | v4: published version, 30 pages | Class. Quant. Grav. 35, 185015 (2018) | 10.1088/1361-6382/aad7f1 | null | gr-qc hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that gravity and matter fields are generically entangled, as a
consequence of the local Poincar\'e symmetry. First, we present a general
argument, applicable to any particular theory of quantum gravity with matter,
by performing the analysis in the abstract nonperturbative canonical framework,
demonstrating the nonseparability of the scalar constraint, thus promoting the
entangled states as the physical ones. Also, within the covariant framework, we
show explicitly that the Hartle-Hawking state in the Regge model of quantum
gravity is necessarily entangled. Our result is potentially relevant for the
quantum-to-classical transition, taken within the framework of the decoherence
programme: due to the gauge symmetry requirements, the matter does not
decohere, it is by default decohered by gravity. Generically, entanglement is a
consequence of interaction. This new entanglement could potentially, in form of
an "effective interaction", bring about corrections to the weak equivalence
principle, further confirming that spacetime as a smooth four-dimensional
manifold is an emergent phenomenon. Finally, the existence of the
gauge-protected entanglement between gravity and matter could be seen as a
criterion for a plausible theory of quantum gravity, and in the case of
perturbative quantisation approaches, a confirmation of the persistence of the
manifestly broken gauge symmetry.
| [
{
"created": "Fri, 24 Feb 2017 20:09:13 GMT",
"version": "v1"
},
{
"created": "Wed, 3 May 2017 11:35:17 GMT",
"version": "v2"
},
{
"created": "Thu, 27 Jul 2017 16:03:17 GMT",
"version": "v3"
},
{
"created": "Wed, 29 Aug 2018 22:29:13 GMT",
"version": "v4"
}
] | 2018-08-31 | [
[
"Paunkovic",
"Nikola",
""
],
[
"Vojinovic",
"Marko",
""
]
] | We show that gravity and matter fields are generically entangled, as a consequence of the local Poincar\'e symmetry. First, we present a general argument, applicable to any particular theory of quantum gravity with matter, by performing the analysis in the abstract nonperturbative canonical framework, demonstrating the nonseparability of the scalar constraint, thus promoting the entangled states as the physical ones. Also, within the covariant framework, we show explicitly that the Hartle-Hawking state in the Regge model of quantum gravity is necessarily entangled. Our result is potentially relevant for the quantum-to-classical transition, taken within the framework of the decoherence programme: due to the gauge symmetry requirements, the matter does not decohere, it is by default decohered by gravity. Generically, entanglement is a consequence of interaction. This new entanglement could potentially, in form of an "effective interaction", bring about corrections to the weak equivalence principle, further confirming that spacetime as a smooth four-dimensional manifold is an emergent phenomenon. Finally, the existence of the gauge-protected entanglement between gravity and matter could be seen as a criterion for a plausible theory of quantum gravity, and in the case of perturbative quantisation approaches, a confirmation of the persistence of the manifestly broken gauge symmetry. |
0904.0982 | Alexandru Ionescu | S. Alexakis, A. D. Ionescu, S. Klainerman | Uniqueness of smooth stationary black holes in vacuum: small
perturbations of the Kerr spaces | null | Commun.Math.Phys.299:89-127,2010 | 10.1007/s00220-010-1072-1 | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that a regular stationary black-hole solution of the Einstein vacuum
equations which is "close" to some Kerr solution is, in fact, isometric to that
Kerr solution.
| [
{
"created": "Mon, 6 Apr 2009 18:15:02 GMT",
"version": "v1"
}
] | 2014-11-18 | [
[
"Alexakis",
"S.",
""
],
[
"Ionescu",
"A. D.",
""
],
[
"Klainerman",
"S.",
""
]
] | We prove that a regular stationary black-hole solution of the Einstein vacuum equations which is "close" to some Kerr solution is, in fact, isometric to that Kerr solution. |
1612.04179 | Yi Zhong | Yi Zhong and Emilio Elizalde | De Sitter and power-law solutions in some models of modified gravity | 10 pages | Mod. Phys. Lett. A 31, 1650221 (2016) | 10.1142/S0217732316502217 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspired by some recent works of Lovelock Brans-Dicke gravity and mimetic
gravity, cosmology solutions in extensions of these two modified gravities are
investigated. A non-local term is added to the Lovelock Brans-Dicke action and
Gauss-Bonnet terms to the mimetic action,correspondingly. De Sitter and power
scale factor solutions are then obtained in both theories. They can provide
natural new approaches to a more accurate description of the unverse evolution.
| [
{
"created": "Tue, 13 Dec 2016 13:58:22 GMT",
"version": "v1"
}
] | 2016-12-14 | [
[
"Zhong",
"Yi",
""
],
[
"Elizalde",
"Emilio",
""
]
] | Inspired by some recent works of Lovelock Brans-Dicke gravity and mimetic gravity, cosmology solutions in extensions of these two modified gravities are investigated. A non-local term is added to the Lovelock Brans-Dicke action and Gauss-Bonnet terms to the mimetic action,correspondingly. De Sitter and power scale factor solutions are then obtained in both theories. They can provide natural new approaches to a more accurate description of the unverse evolution. |
1403.4529 | Jaume Haro | Jaume de Haro | How can holonomy corrections be introduced in $f(R)$ gravity? | null | EPL 107 29001 (2014) | 10.1209/0295-5075/107/29001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the introduction of holonomy corrections in $f(R)$ gravity. We will
show that there are infinitely many ways, as many as canonical transformations,
to introduce this kind of corrections, depending on the canonical variables
(two coordinates and its conjugate momenta) used to obtain the Hamiltonian. In
each case, these corrections lead, at effective level, to different modified
holonomy corrected Friedmann equations in $f(R)$ gravity, which are in practice
analytically unworkable, i.e. only numerical analysis can be used to understand
its dynamics. Finally, we give arguments in favour of one preferred set of
variables, the one that conformally maps $f(R)$ to Einstein gravity, because
for these variables the dynamics of the system has a clear physical meaning:
the same as in standard Loop Quantum Cosmology, where the effective dynamics of
a system can be analytically studied.
| [
{
"created": "Tue, 18 Mar 2014 16:41:49 GMT",
"version": "v1"
}
] | 2014-09-03 | [
[
"de Haro",
"Jaume",
""
]
] | We study the introduction of holonomy corrections in $f(R)$ gravity. We will show that there are infinitely many ways, as many as canonical transformations, to introduce this kind of corrections, depending on the canonical variables (two coordinates and its conjugate momenta) used to obtain the Hamiltonian. In each case, these corrections lead, at effective level, to different modified holonomy corrected Friedmann equations in $f(R)$ gravity, which are in practice analytically unworkable, i.e. only numerical analysis can be used to understand its dynamics. Finally, we give arguments in favour of one preferred set of variables, the one that conformally maps $f(R)$ to Einstein gravity, because for these variables the dynamics of the system has a clear physical meaning: the same as in standard Loop Quantum Cosmology, where the effective dynamics of a system can be analytically studied. |
2305.19517 | Gabriel Menezes | Gabriel Menezes | Quantum gravity phenomenology from the perspective of quantum general
relativity and quadratic gravity | 18 pages, 1 figure, invited contribution to Classical and Quantum
Gravity Focus Issue: "Quantum Gravity Phenomenology in the Multi-Messenger
Era: Challenges and Perspectives"; v.2: Some text modifications, one figure
added, typos fixed and references added. This version has 19 pages, 2
figures. Published version | Class. Quantum Grav. 40 (2023) 235007 | 10.1088/1361-6382/acfb6d | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Multi-messenger astronomy provides us with the possibility of discovering
phenomenological signatures of quantum-gravity effects. This should be of
paramount importance in the pursuit of an elusive quantum theory for the
gravitational interactions. Here we discuss feasible explorations within the
effective field theory treatment of general relativity. By exploring current
techniques borrowed from modern amplitude methods, we calculate leading quantum
corrections to the classical radiated momentum and spectral waveforms. The
lessons drawn from these low-energy results are that phenomenological
applications in gravitational-wave physics can be discussed in line with the
effective field theory approach. In turn, we also examine possible
phenomenological surveys from the perspective of a UV completion for quantum
gravity which employs the metric as the fundamental dynamical variable, namely
quadratic gravity. Being more specific, by resorting to the eikonal
approximation, we compute the leading-order time delay/advance in the
scattering of light by a heavy object and find a possible significant deviation
from the standard general-relativity prediction. This allows us to probe causal
uncertainty due to quantum fluctuations of the gravitational field as a genuine
prediction from Planck-scale physics.
| [
{
"created": "Wed, 31 May 2023 03:01:01 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Dec 2023 02:39:40 GMT",
"version": "v2"
}
] | 2023-12-25 | [
[
"Menezes",
"Gabriel",
""
]
] | Multi-messenger astronomy provides us with the possibility of discovering phenomenological signatures of quantum-gravity effects. This should be of paramount importance in the pursuit of an elusive quantum theory for the gravitational interactions. Here we discuss feasible explorations within the effective field theory treatment of general relativity. By exploring current techniques borrowed from modern amplitude methods, we calculate leading quantum corrections to the classical radiated momentum and spectral waveforms. The lessons drawn from these low-energy results are that phenomenological applications in gravitational-wave physics can be discussed in line with the effective field theory approach. In turn, we also examine possible phenomenological surveys from the perspective of a UV completion for quantum gravity which employs the metric as the fundamental dynamical variable, namely quadratic gravity. Being more specific, by resorting to the eikonal approximation, we compute the leading-order time delay/advance in the scattering of light by a heavy object and find a possible significant deviation from the standard general-relativity prediction. This allows us to probe causal uncertainty due to quantum fluctuations of the gravitational field as a genuine prediction from Planck-scale physics. |
1901.00977 | Kiyoshi Shiraishi | Kiyoshi Shiraishi, Takuya Maki | Vacuum polarization near asymptotically anti-de Sitter black holes in
odd dimensions | 12 pages, 3 figures | Class.Quant.Grav. 11 (1994) 1687-1696 | 10.1088/0264-9381/11/7/009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, Ba\~nados, Teitelboim and Zanelli obtained spherically symmetric
black hole solutions in a particular class of Einstein--Lovelock gravity. We
derive the propagator in an exact form for a conformal scalar field in the
asymptotically anti-de Sitter black hole spacetime so as to study the quantum
effects of the scalar fields. We treat the cases in odd dimensions in this
paper. We calculate the vacuum expectation value of $\langle\varphi^2\rangle$
and show its dependence on the radial coordinate for the five-dimensional case
as an example.
| [
{
"created": "Fri, 4 Jan 2019 03:58:56 GMT",
"version": "v1"
}
] | 2019-02-05 | [
[
"Shiraishi",
"Kiyoshi",
""
],
[
"Maki",
"Takuya",
""
]
] | Recently, Ba\~nados, Teitelboim and Zanelli obtained spherically symmetric black hole solutions in a particular class of Einstein--Lovelock gravity. We derive the propagator in an exact form for a conformal scalar field in the asymptotically anti-de Sitter black hole spacetime so as to study the quantum effects of the scalar fields. We treat the cases in odd dimensions in this paper. We calculate the vacuum expectation value of $\langle\varphi^2\rangle$ and show its dependence on the radial coordinate for the five-dimensional case as an example. |
1211.0431 | Christoph Solveen | Christoph Solveen | Local Thermal Equilibrium and KMS states in Curved Spacetime | 13 pages; to appear in Class. Quant. Grav | Class. Quantum Grav. 29 (2012) 245015 | 10.1088/0264-9381/29/24/245015 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On the example of a free massless and conformally coupled scalar field, it is
argued that in quantum field theory in curved spacetimes with time-like Killing
field, the corresponding KMS states (generalized Gibbs ensembles) at parameter
\beta>0 need not possess a definite temperature in the sense of the zeroth law.
In fact, these states, although passive in the sense of the second law, are not
always in local thermal equilibrium (LTE). A criterion characterizing LTE
states with sharp local temperature is discussed. Moreover, a proposal is made
for fixing the renormalization freedom of composite fields which serve as
"thermal observables" and a new definition of the thermal energy of LTE states
is introduced. Based on these results a general relation between the local
temperature and the parameter \beta\ is established for KMS states in (Anti) de
Sitter spacetime.
| [
{
"created": "Fri, 2 Nov 2012 12:03:36 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Solveen",
"Christoph",
""
]
] | On the example of a free massless and conformally coupled scalar field, it is argued that in quantum field theory in curved spacetimes with time-like Killing field, the corresponding KMS states (generalized Gibbs ensembles) at parameter \beta>0 need not possess a definite temperature in the sense of the zeroth law. In fact, these states, although passive in the sense of the second law, are not always in local thermal equilibrium (LTE). A criterion characterizing LTE states with sharp local temperature is discussed. Moreover, a proposal is made for fixing the renormalization freedom of composite fields which serve as "thermal observables" and a new definition of the thermal energy of LTE states is introduced. Based on these results a general relation between the local temperature and the parameter \beta\ is established for KMS states in (Anti) de Sitter spacetime. |
2203.08723 | P. B. Covas | P. B. Covas, R. Prix | Improved short-segment detection statistic for continuous gravitational
waves | 11 pages | null | 10.1103/PhysRevD.105.124007 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Continuous gravitational waves represent one of the long-sought types of
signals that have yet to be detected. Due to their small amplitude, long
observational datasets (months-years) have to be analyzed together, thereby
vastly increasing the computational cost of these searches. All-sky searches
face the most severe computational obstacles, especially searches for sources
in unknown binary systems, which need to break the data into very short
segments in order to be computationally feasible. In this paper, we present a
new detection statistic that improves sensitivity by up to 19% compared to the
standard $\mathcal{F}$-statistic for segments shorter than a few hours.
| [
{
"created": "Wed, 16 Mar 2022 16:16:16 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Apr 2022 15:32:28 GMT",
"version": "v2"
}
] | 2022-06-22 | [
[
"Covas",
"P. B.",
""
],
[
"Prix",
"R.",
""
]
] | Continuous gravitational waves represent one of the long-sought types of signals that have yet to be detected. Due to their small amplitude, long observational datasets (months-years) have to be analyzed together, thereby vastly increasing the computational cost of these searches. All-sky searches face the most severe computational obstacles, especially searches for sources in unknown binary systems, which need to break the data into very short segments in order to be computationally feasible. In this paper, we present a new detection statistic that improves sensitivity by up to 19% compared to the standard $\mathcal{F}$-statistic for segments shorter than a few hours. |
1304.7331 | Daniele Malafarina | Pankaj S. Joshi, Daniele Malafarina, Ramesh Narayan | Distinguishing black holes from naked singularities through their
accretion disk properties | 18 pages, 5 figures, replaced with published version | Class. Quantum Grav. 31 015002 (2014) | 10.1088/0264-9381/31/1/015002 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that, in principle, a slowly evolving gravitationally collapsing
perfect fluid cloud can asymptotically settle to a static spherically symmetric
equilibrium configuration with a naked singularity at the center. We consider
one such asymptotic final configuration with a finite outer radius, and
construct a toy model in which it is matched to a Schwarzschild exterior
geometry. We examine the properties of circular orbits in this model. We then
investigate observational signatures of a thermal accretion disk in this
spacetime, comparing them with the signatures expected for a disk around a
black hole of the same mass. Several notable differences emerge. A disk around
the naked singularity is much more luminous than one around an equivalent black
hole. Also, the disk around the naked singularity has a spectrum with a high
frequency power law segment that carries a major fraction of the total
luminosity. Thus, at least some naked singularities can, in principle, be
distinguished observationally from black holes of the same mass. We discuss
possible implications of these results.
| [
{
"created": "Sat, 27 Apr 2013 06:21:23 GMT",
"version": "v1"
},
{
"created": "Tue, 6 May 2014 03:52:48 GMT",
"version": "v2"
}
] | 2015-06-15 | [
[
"Joshi",
"Pankaj S.",
""
],
[
"Malafarina",
"Daniele",
""
],
[
"Narayan",
"Ramesh",
""
]
] | We show that, in principle, a slowly evolving gravitationally collapsing perfect fluid cloud can asymptotically settle to a static spherically symmetric equilibrium configuration with a naked singularity at the center. We consider one such asymptotic final configuration with a finite outer radius, and construct a toy model in which it is matched to a Schwarzschild exterior geometry. We examine the properties of circular orbits in this model. We then investigate observational signatures of a thermal accretion disk in this spacetime, comparing them with the signatures expected for a disk around a black hole of the same mass. Several notable differences emerge. A disk around the naked singularity is much more luminous than one around an equivalent black hole. Also, the disk around the naked singularity has a spectrum with a high frequency power law segment that carries a major fraction of the total luminosity. Thus, at least some naked singularities can, in principle, be distinguished observationally from black holes of the same mass. We discuss possible implications of these results. |
2007.14312 | Bibhas Majhi Ranjan | Surojit Dalui, Bibhas Ranjan Majhi | Near horizon local instability and quantum thermality | Comments added, to appear in Phys. Rev. D | Phys. Rev. D 102, 124047 (2020) | 10.1103/PhysRevD.102.124047 | null | gr-qc hep-th nlin.CD physics.class-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit our previous proposed conjecture -- horizon creates a local
instability which acts as the source of quantum temperature of black hole. It
is found that a chargesless massless particle moving along the null trajectory
in Eddington-Finkelstein (EF) coordinates feels instability in the vicinity of
the horizon. Such instability is observer independent for this particle motion.
Moreover, an observer associated to EF coordinates finds the local Hamiltonian
as $xp$ where $p$ is the canonical momentum corresponding the coordinate $x$.
Finally, using this Hamiltonian we notice that at the quantum level this class
of observers feel the horizon as thermal object with temperature is given by
the Hawking expression. We provide this by using various techniques in quantum
mechanics and thereby bolstered our earlier claim -- the automatic local
instability can be a mechanism for emerging horizon as a thermal object. In
this process, the present analysis provides another set of coordinates (namely
EF frame), in addition to our earlier Painleve ones, in which the null
trajectory of the massless particle is governed by $xp$ type Hamiltonian in
near the horizon regime.
| [
{
"created": "Tue, 28 Jul 2020 15:34:03 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Dec 2020 02:54:40 GMT",
"version": "v2"
}
] | 2020-12-29 | [
[
"Dalui",
"Surojit",
""
],
[
"Majhi",
"Bibhas Ranjan",
""
]
] | We revisit our previous proposed conjecture -- horizon creates a local instability which acts as the source of quantum temperature of black hole. It is found that a chargesless massless particle moving along the null trajectory in Eddington-Finkelstein (EF) coordinates feels instability in the vicinity of the horizon. Such instability is observer independent for this particle motion. Moreover, an observer associated to EF coordinates finds the local Hamiltonian as $xp$ where $p$ is the canonical momentum corresponding the coordinate $x$. Finally, using this Hamiltonian we notice that at the quantum level this class of observers feel the horizon as thermal object with temperature is given by the Hawking expression. We provide this by using various techniques in quantum mechanics and thereby bolstered our earlier claim -- the automatic local instability can be a mechanism for emerging horizon as a thermal object. In this process, the present analysis provides another set of coordinates (namely EF frame), in addition to our earlier Painleve ones, in which the null trajectory of the massless particle is governed by $xp$ type Hamiltonian in near the horizon regime. |
1302.1354 | Bijan Saha Dr. | Bijan Saha | Nonlinear Spinor Fields in Bianchi type-I spacetime reexamined | 19 pages, 3 figures. arXiv admin note: substantial text overlap with
arXiv:1103.2890 | Int. J. Theor. Phys. 53 (2014) 1109 - 1129 | 10.1007/s10773-013-1906-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The specific behavior of spinor field in curve space-time with the exception
of FRW model almost always gives rise to non-trivial non-diagonal components of
the energy-momentum tensor. This non-triviality of non-diagonal components of
the energy-momentum tensor imposes some severe restrictions either on the
spinor field or on the metric functions. In this paper within the scope of an
anisotropic Bianchi type-I Universe we study the role of spinor field in the
evolution of the Universe. It is found that there exist two possibilities. In
one scenario the initially anisotropic Universe evolves into an isotropic one
asymptotically, but in this case the spinor field itself undergoes some severe
restrictions. In the second scenario the isotropization takes places almost at
the beginning of the process.
| [
{
"created": "Wed, 6 Feb 2013 13:16:33 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Dec 2013 11:25:05 GMT",
"version": "v2"
}
] | 2015-05-01 | [
[
"Saha",
"Bijan",
""
]
] | The specific behavior of spinor field in curve space-time with the exception of FRW model almost always gives rise to non-trivial non-diagonal components of the energy-momentum tensor. This non-triviality of non-diagonal components of the energy-momentum tensor imposes some severe restrictions either on the spinor field or on the metric functions. In this paper within the scope of an anisotropic Bianchi type-I Universe we study the role of spinor field in the evolution of the Universe. It is found that there exist two possibilities. In one scenario the initially anisotropic Universe evolves into an isotropic one asymptotically, but in this case the spinor field itself undergoes some severe restrictions. In the second scenario the isotropization takes places almost at the beginning of the process. |
1704.07840 | Jose' P. S. Lemos | Jos\'e P. S. Lemos, Vilson T. Zanchin | Plethora of relativistic charged spheres: The full spectrum of
Guilfoyle's static, electrically charged spherical solutions | 23 pages, 4 figures | Physical Review D 95, 104040 (2017) | 10.1103/PhysRevD.95.104040 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that Guilfoyle's exact solutions of the Einstein-Maxwell equations
for spherical symmetric static electrically charged matter with a
Reissner-Nordstr\"om exterior possess a bewildering plethora of different types
of solutions. For the parameter space of the solutions we use two normalized
variables, $q^2/R^2$ and $r_0/R$, where $q$ is the total electric charge, $r_0$
is the radius of the object, and $R$ is a length representing the square root
of the inverse energy density of the matter. The two other parameters, the mass
$m$ and the Guilfoyle parameter $a$, both dependent on $q$, $r_0$ and $R$, are
analyzed in detail. The full parameter space of solutions $q^2/R^2\times r_0/R$
is explored with the corresponding types of solutions being identified and
analyzed. The different types of solutions are regular charged stars, including
charged dust stars and stars saturating the Buchdahl-Andr\'easson bound,
quasiblack holes, regular charged black holes with a de Sitter core, regular
black holes with a core of phantom charged matter, other exotic regular black
holes, Schwarzschild stars, Schwarzschild black holes, Kasner spacetimes,
pointlike and planar naked singularities, and the Minkowski spacetime. Allowing
for $q^2<0$, in which case it is not possible to interpret $q$ as electric
charge, also yields new solutions, some of which are interesting and regular,
others are singular. Some of these types of solutions as well as the matter
properties have been previously found and studied, here the full spectrum being
presented in a unified manner.
| [
{
"created": "Tue, 25 Apr 2017 18:00:40 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Sep 2020 18:28:54 GMT",
"version": "v2"
}
] | 2020-09-18 | [
[
"Lemos",
"José P. S.",
""
],
[
"Zanchin",
"Vilson T.",
""
]
] | We show that Guilfoyle's exact solutions of the Einstein-Maxwell equations for spherical symmetric static electrically charged matter with a Reissner-Nordstr\"om exterior possess a bewildering plethora of different types of solutions. For the parameter space of the solutions we use two normalized variables, $q^2/R^2$ and $r_0/R$, where $q$ is the total electric charge, $r_0$ is the radius of the object, and $R$ is a length representing the square root of the inverse energy density of the matter. The two other parameters, the mass $m$ and the Guilfoyle parameter $a$, both dependent on $q$, $r_0$ and $R$, are analyzed in detail. The full parameter space of solutions $q^2/R^2\times r_0/R$ is explored with the corresponding types of solutions being identified and analyzed. The different types of solutions are regular charged stars, including charged dust stars and stars saturating the Buchdahl-Andr\'easson bound, quasiblack holes, regular charged black holes with a de Sitter core, regular black holes with a core of phantom charged matter, other exotic regular black holes, Schwarzschild stars, Schwarzschild black holes, Kasner spacetimes, pointlike and planar naked singularities, and the Minkowski spacetime. Allowing for $q^2<0$, in which case it is not possible to interpret $q$ as electric charge, also yields new solutions, some of which are interesting and regular, others are singular. Some of these types of solutions as well as the matter properties have been previously found and studied, here the full spectrum being presented in a unified manner. |
2312.04855 | Seiya Sasaoka | Seiya Sasaoka, Naoki Koyama, Diego Dominguez, Yusuke Sakai, Kentaro
Somiya, Yuto Omae, Hirotaka Takahashi | Comparative study of 1D and 2D convolutional neural network models with
attribution analysis for gravitational wave detection from compact binary
coalescences | 12 pages, 9 figures | Phys. Rev. D 109, 043011 (2024) | 10.1103/PhysRevD.109.043011 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent advancements in gravitational wave astronomy have seen the application
of convolutional neural networks (CNNs) in signal detection from compact binary
coalescences. This study presents a comparative analysis of two CNN
architectures: one-dimensional (1D) and two-dimensional (2D) along with an
ensemble model combining both. We trained these models to detect gravitational
wave signals from binary black hole (BBH) mergers, neutron star-black hole
(NSBH) mergers, and binary neutron star (BNS) mergers within real detector
noise. Our investigation entailed a comprehensive evaluation of the detection
performance of each model type across different signal classes. To understand
the models' decision-making processes, we employed feature map visualization
and attribution analysis. The findings revealed that while the 1D model showed
superior performance in detecting BBH signals, the 2D model excelled in
identifying NSBH and BNS signals. Notably, the ensemble model outperformed both
individual models across all signal types, demonstrating enhanced detection
capabilities. Additionally, input feature visualization indicated distinct
areas of focus in the data for the 1D and 2D models, emphasizing the
effectiveness of their combination.
| [
{
"created": "Fri, 8 Dec 2023 06:23:02 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Jan 2024 13:43:00 GMT",
"version": "v2"
}
] | 2024-02-08 | [
[
"Sasaoka",
"Seiya",
""
],
[
"Koyama",
"Naoki",
""
],
[
"Dominguez",
"Diego",
""
],
[
"Sakai",
"Yusuke",
""
],
[
"Somiya",
"Kentaro",
""
],
[
"Omae",
"Yuto",
""
],
[
"Takahashi",
"Hirotaka",
""
]
] | Recent advancements in gravitational wave astronomy have seen the application of convolutional neural networks (CNNs) in signal detection from compact binary coalescences. This study presents a comparative analysis of two CNN architectures: one-dimensional (1D) and two-dimensional (2D) along with an ensemble model combining both. We trained these models to detect gravitational wave signals from binary black hole (BBH) mergers, neutron star-black hole (NSBH) mergers, and binary neutron star (BNS) mergers within real detector noise. Our investigation entailed a comprehensive evaluation of the detection performance of each model type across different signal classes. To understand the models' decision-making processes, we employed feature map visualization and attribution analysis. The findings revealed that while the 1D model showed superior performance in detecting BBH signals, the 2D model excelled in identifying NSBH and BNS signals. Notably, the ensemble model outperformed both individual models across all signal types, demonstrating enhanced detection capabilities. Additionally, input feature visualization indicated distinct areas of focus in the data for the 1D and 2D models, emphasizing the effectiveness of their combination. |
gr-qc/0405021 | Sanjay Jhingan | J. Ibanez and S. Jhingan | Renormalization Group approach to Inhomogeneous Cosmology | 9 pages, minor corrections | Phys.Rev. D70 (2004) 063507 | 10.1103/PhysRevD.70.063507 | null | gr-qc | null | Soliton solutions are recovered as scale-invariant asymptotic states of
vacuum inhomogeneous cosmologies using renormalization group method. The
stability analysis of these states is also given.
| [
{
"created": "Wed, 5 May 2004 15:26:17 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Sep 2004 07:45:06 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Ibanez",
"J.",
""
],
[
"Jhingan",
"S.",
""
]
] | Soliton solutions are recovered as scale-invariant asymptotic states of vacuum inhomogeneous cosmologies using renormalization group method. The stability analysis of these states is also given. |
1002.1210 | Yuri Shtanov | Kirill Krasnov and Yuri Shtanov | Cosmological perturbations in a family of deformations of general
relativity | 45 pages, version published in JCAP; minor changes, one section moved
to the appendix | JCAP 06 (2010) 006 | 10.1088/1475-7516/2010/06/006 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study linear cosmological perturbations in a previously introduced family
of deformations of general relativity characterized by the absence of new
degrees of freedom. The homogeneous and isotropic background in this class of
theories is unmodified and is described by the usual Friedmann equations. The
theory of cosmological perturbations is modified and the relevant deformation
parameter has the dimension of length. Gravitational perturbations of the
scalar type can be described by a certain relativistic potential related to the
matter perturbations just as in general relativity. A system of differential
equations describing the evolution of this potential and of the stress-energy
density perturbations is obtained. We find that the evolution of scalar
perturbations proceeds with a modified effective time-dependent speed of sound,
which, contrary to the case of general relativity, does not vanish even at the
matter-dominated stage. In a broad range of values of the length parameter
controlling the deformation, a specific transition from the regime of modified
gravity to the regime of general relativity in the evolution of scalar
perturbations takes place during the radiation domination. In this case, the
resulting power spectrum of perturbations in radiation and dark matter is
suppressed on the comoving spatial scales that enter the Hubble radius before
this transition. We estimate the bounds on the deformation parameter for which
this suppression does not lead to observable consequences. Evolution of scalar
perturbations at the inflationary stage is modified but very slightly and the
primordial spectrum generated during inflation is not noticeably different from
the one obtained in general relativity.
| [
{
"created": "Fri, 5 Feb 2010 12:15:13 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Jun 2010 14:45:22 GMT",
"version": "v2"
}
] | 2010-06-08 | [
[
"Krasnov",
"Kirill",
""
],
[
"Shtanov",
"Yuri",
""
]
] | We study linear cosmological perturbations in a previously introduced family of deformations of general relativity characterized by the absence of new degrees of freedom. The homogeneous and isotropic background in this class of theories is unmodified and is described by the usual Friedmann equations. The theory of cosmological perturbations is modified and the relevant deformation parameter has the dimension of length. Gravitational perturbations of the scalar type can be described by a certain relativistic potential related to the matter perturbations just as in general relativity. A system of differential equations describing the evolution of this potential and of the stress-energy density perturbations is obtained. We find that the evolution of scalar perturbations proceeds with a modified effective time-dependent speed of sound, which, contrary to the case of general relativity, does not vanish even at the matter-dominated stage. In a broad range of values of the length parameter controlling the deformation, a specific transition from the regime of modified gravity to the regime of general relativity in the evolution of scalar perturbations takes place during the radiation domination. In this case, the resulting power spectrum of perturbations in radiation and dark matter is suppressed on the comoving spatial scales that enter the Hubble radius before this transition. We estimate the bounds on the deformation parameter for which this suppression does not lead to observable consequences. Evolution of scalar perturbations at the inflationary stage is modified but very slightly and the primordial spectrum generated during inflation is not noticeably different from the one obtained in general relativity. |
2205.06585 | Grigory Volovik | G.E. Volovik | Double Hawking temperature: from black hole to de Sitter | 6 pages, no figures. arXiv admin note: text overlap with
arXiv:2108.00419 | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The double Hawking temperature $T=2T_H$ appears in some approaches to the
Hawking radiation, when the radiation is considered in terms of the quantum
tunneling. We consider the origin of such temperature for the black hole
horizon and also for the cosmological horizon in de Sitter spacetime. In case
the black hole horizon, there are two contributions to the tunneling process of
radiation, each being governed by the temperature $T=2T_H$. These processes are
coherently combined to produce the radiation with the Hawking temperature
$T_H$. This can be traditionally interpreted as the pair creation of two
entangled particles, of which one goes towards the centre of the black hole,
while the other one escapes from the black hole. In case of the cosmological
horizon, the temperature $T=2T_H$ is physical. While the creation of the
entangled pair is described by the Hawking temperature, the de Sitter spacetime
allows for the another process, in which only single (non-entangled) particle
inside the cosmological horizon is created. This process is characterized by
the local temperature $T=2T_H$. Such single particle process takes place also
outside the black hole horizon, but it is exponentially suppressed.
| [
{
"created": "Thu, 12 May 2022 15:15:16 GMT",
"version": "v1"
},
{
"created": "Tue, 17 May 2022 15:22:33 GMT",
"version": "v2"
},
{
"created": "Mon, 23 May 2022 09:56:33 GMT",
"version": "v3"
},
{
"created": "Sat, 18 Jun 2022 15:31:16 GMT",
"version": "v4"
},
{
"c... | 2022-11-01 | [
[
"Volovik",
"G. E.",
""
]
] | The double Hawking temperature $T=2T_H$ appears in some approaches to the Hawking radiation, when the radiation is considered in terms of the quantum tunneling. We consider the origin of such temperature for the black hole horizon and also for the cosmological horizon in de Sitter spacetime. In case the black hole horizon, there are two contributions to the tunneling process of radiation, each being governed by the temperature $T=2T_H$. These processes are coherently combined to produce the radiation with the Hawking temperature $T_H$. This can be traditionally interpreted as the pair creation of two entangled particles, of which one goes towards the centre of the black hole, while the other one escapes from the black hole. In case of the cosmological horizon, the temperature $T=2T_H$ is physical. While the creation of the entangled pair is described by the Hawking temperature, the de Sitter spacetime allows for the another process, in which only single (non-entangled) particle inside the cosmological horizon is created. This process is characterized by the local temperature $T=2T_H$. Such single particle process takes place also outside the black hole horizon, but it is exponentially suppressed. |
gr-qc/9710050 | Francis Vendrell | F. Vendrell and M.E. Ortiz | Covariant path integrals and black holes | 5 pages, Revtex, 1 figure. To appear in the proceedings of the Eighth
Marcel Grossmann Meeting on General Relativity. (Jerusalem, Israel, June
1997) | null | null | Imperial/TP/97-98/2 | gr-qc | null | The thermal nature of the propagator in a collapsed black-hole spacetime is
shown to follow from the non-trivial topology of the configuration space in
tortoise coordinates by using the path integral formalism.
| [
{
"created": "Wed, 8 Oct 1997 13:07:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Vendrell",
"F.",
""
],
[
"Ortiz",
"M. E.",
""
]
] | The thermal nature of the propagator in a collapsed black-hole spacetime is shown to follow from the non-trivial topology of the configuration space in tortoise coordinates by using the path integral formalism. |
2007.03400 | Yujie Tan | Xiao-Yu Lu, Yu-Jie Tan, and Cheng-Gang Shao | Sensitivity functions for space-borne gravitational wave detectors | null | null | 10.1103/PhysRevD.100.044042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Time-delay interferometry is put forward to improve the signal-to-noise ratio
of space-borne gravitational wave detectors by canceling the large laser phase
noise with different combinations of measured data. Based on the Michelson data
combination, the sensitivity function of the detector can be obtained by
averaging the all-sky wave source positions. At present, there are two main
methods to encode gravitational wave signal into detector. One is to adapt
gravitational wave polarization angle depending on the arm orientation in the
gravitational wave frame, and the other is to divide the gravitational wave
signal into plus and cross polarizations in the detector frame. Although there
are some attempts using the first method to provide the analytical expression
of sensitivity function, only a semianalytical one could be obtained. Here,
starting with the second method, we demonstrate the equivalence of both
methods. First time to obtain the full analytical expression of sensitivity
function, which provides a fast and accurate mean to evaluate and compare the
performance of different space-borne detectors, such as LISA and TianQin.
| [
{
"created": "Tue, 7 Jul 2020 13:09:01 GMT",
"version": "v1"
}
] | 2020-07-08 | [
[
"Lu",
"Xiao-Yu",
""
],
[
"Tan",
"Yu-Jie",
""
],
[
"Shao",
"Cheng-Gang",
""
]
] | Time-delay interferometry is put forward to improve the signal-to-noise ratio of space-borne gravitational wave detectors by canceling the large laser phase noise with different combinations of measured data. Based on the Michelson data combination, the sensitivity function of the detector can be obtained by averaging the all-sky wave source positions. At present, there are two main methods to encode gravitational wave signal into detector. One is to adapt gravitational wave polarization angle depending on the arm orientation in the gravitational wave frame, and the other is to divide the gravitational wave signal into plus and cross polarizations in the detector frame. Although there are some attempts using the first method to provide the analytical expression of sensitivity function, only a semianalytical one could be obtained. Here, starting with the second method, we demonstrate the equivalence of both methods. First time to obtain the full analytical expression of sensitivity function, which provides a fast and accurate mean to evaluate and compare the performance of different space-borne detectors, such as LISA and TianQin. |
gr-qc/0702148 | Bogus{\l}aw Broda | Bogus{\l}aw Broda, Piotr Bronowski, Marcin Ostrowski and Micha{\l}
Szanecki | Quantization of four-dimensional Abelian gravity | Minor changes, additional symmetry discussed. 5 pages, 2 columns,
REVTeX 4 | Phys.Lett.B655:178-182,2007 | 10.1016/j.physletb.2007.08.067 | null | gr-qc hep-th | null | An abelian version of standard general relativity in the Cartan-Palatini
gauge-like formulation in four dimensions has been introduced. Traditional
canonical analysis utilizing similarities to the akin Husain-Kuchar SU(2)
version of gravity has been performed. The model has been next quantized in the
canonical path-integral Faddeev-Popov formalism yielding abelian BF theory.
| [
{
"created": "Wed, 28 Feb 2007 15:30:12 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Aug 2007 09:54:00 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Broda",
"Bogusław",
""
],
[
"Bronowski",
"Piotr",
""
],
[
"Ostrowski",
"Marcin",
""
],
[
"Szanecki",
"Michał",
""
]
] | An abelian version of standard general relativity in the Cartan-Palatini gauge-like formulation in four dimensions has been introduced. Traditional canonical analysis utilizing similarities to the akin Husain-Kuchar SU(2) version of gravity has been performed. The model has been next quantized in the canonical path-integral Faddeev-Popov formalism yielding abelian BF theory. |
gr-qc/0511082 | David Garfinkle | David Garfinkle | The need for dark matter in galaxies | null | Class.Quant.Grav. 23 (2006) 1391 | 10.1088/0264-9381/23/4/N01 | null | gr-qc astro-ph | null | Cooperstock and Tieu have proposed a model to account for galactic rotation
curves without invoking dark matter. I argue that no model of this type can
work.
| [
{
"created": "Tue, 15 Nov 2005 22:21:25 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Garfinkle",
"David",
""
]
] | Cooperstock and Tieu have proposed a model to account for galactic rotation curves without invoking dark matter. I argue that no model of this type can work. |
gr-qc/0104022 | Angelo Tartaglia | A. Tartaglia, M. L. Ruggiero | Testing gravitomagnetism on the Earth | LATEX, 8 pages, 1 eps figure | null | null | null | gr-qc | null | The paper contains a proposed experiment for testing the gravitomagnetic
effect on the propagation of light around a rotating mass. The idea is to use a
rotating spherical laboratory-scale shell, around which two mutually orthogonal
lightguides are wound acting as the arms of an interferometer. Numerical
estimates show that time of flight differences between the equatorial and polar
guides could be in the order of $\sim 10^{-20}$ s, actually detectable with
sensitivity perfectly comparable with those expected in gravitational wave
detection experiments.
| [
{
"created": "Sat, 7 Apr 2001 16:59:18 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Apr 2001 08:09:02 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Tartaglia",
"A.",
""
],
[
"Ruggiero",
"M. L.",
""
]
] | The paper contains a proposed experiment for testing the gravitomagnetic effect on the propagation of light around a rotating mass. The idea is to use a rotating spherical laboratory-scale shell, around which two mutually orthogonal lightguides are wound acting as the arms of an interferometer. Numerical estimates show that time of flight differences between the equatorial and polar guides could be in the order of $\sim 10^{-20}$ s, actually detectable with sensitivity perfectly comparable with those expected in gravitational wave detection experiments. |
gr-qc/9808021 | Victor Berezin | A. Yu. Neronov (Moscow State University) | Quasiclassical mass spectrum of the black hole model with
selfgravitating dust shell | 35 pages, 8 figures, to appear in Phys. Rev. D | Phys.Rev. D59 (1999) 044023 | 10.1103/PhysRevD.59.044023 | INR - 0530/98 | gr-qc | null | We consider a quantum mechanical black hole model introduced in {\it
Phys.Rev.}, {\bf D57}, 1118 (1998) that consists of the selfgravitating dust
shell. The Schroedinger equation for this model is a finite difference equation
with the shift of the argument along the imaginary axis. Solving this equation
in quasiclassical limit in complex domain leads to quantization conditions that
define discrete quasiclassical mass spectrum. One of the quantization
conditions is Bohr-Sommerfeld condition for the bound motion of the shell. The
other comes from the requirement that the wave function is unambiguously
defined on the Riemannian surface on which the coefficients of Schroedinger
equation are regular. The second quantization condition remains valid for the
unbound motion of the shell as well, and in the case of a collapsing null-dust
shell leads to $m\sim\sqrt{k}$ spectrum.
| [
{
"created": "Fri, 7 Aug 1998 14:56:06 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Neronov",
"A. Yu.",
"",
"Moscow State University"
]
] | We consider a quantum mechanical black hole model introduced in {\it Phys.Rev.}, {\bf D57}, 1118 (1998) that consists of the selfgravitating dust shell. The Schroedinger equation for this model is a finite difference equation with the shift of the argument along the imaginary axis. Solving this equation in quasiclassical limit in complex domain leads to quantization conditions that define discrete quasiclassical mass spectrum. One of the quantization conditions is Bohr-Sommerfeld condition for the bound motion of the shell. The other comes from the requirement that the wave function is unambiguously defined on the Riemannian surface on which the coefficients of Schroedinger equation are regular. The second quantization condition remains valid for the unbound motion of the shell as well, and in the case of a collapsing null-dust shell leads to $m\sim\sqrt{k}$ spectrum. |
1508.00312 | Yongwan Gim | Yongwan Gim and Wontae Kim | A Quantal Tolman Temperature | 5 pages, 1 figure, version to appear in EPJC | Eur. Phys. J. C75 (2015) 549 | 10.1140/epjc/s10052-015-3765-2 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The conventional Tolman temperature based on the assumption of the traceless
condition of energy-momentum tensor for matter fields is infinite at the
horizon if Hawking radiation is involved. However, we note that the temperature
associated with Hawking radiation is of relevance to the trace anomaly, which
means that the traceless condition should be released. So, a trace
anomaly-induced Stefan-Boltzmann law is newly derived by employing the first
law of thermodynamics and the property of the temperature independence of the
trace anomaly. Then, the Tolman temperature is quantum-mechanically generalized
according to the anomaly-induced Stefan-Boltzmann law. In an exactly soluble
model, we show that the Tolman factor does not appear in the generalized Tolman
temperature which is eventually finite everywhere, in particular, vanishing at
the horizon. It turns out that the equivalence principle survives at the
horizon with the help of the quantum principle, and some puzzles related to the
Tolman temperature are also resolved.
| [
{
"created": "Mon, 3 Aug 2015 04:46:44 GMT",
"version": "v1"
},
{
"created": "Sun, 29 Nov 2015 23:58:32 GMT",
"version": "v2"
}
] | 2015-12-01 | [
[
"Gim",
"Yongwan",
""
],
[
"Kim",
"Wontae",
""
]
] | The conventional Tolman temperature based on the assumption of the traceless condition of energy-momentum tensor for matter fields is infinite at the horizon if Hawking radiation is involved. However, we note that the temperature associated with Hawking radiation is of relevance to the trace anomaly, which means that the traceless condition should be released. So, a trace anomaly-induced Stefan-Boltzmann law is newly derived by employing the first law of thermodynamics and the property of the temperature independence of the trace anomaly. Then, the Tolman temperature is quantum-mechanically generalized according to the anomaly-induced Stefan-Boltzmann law. In an exactly soluble model, we show that the Tolman factor does not appear in the generalized Tolman temperature which is eventually finite everywhere, in particular, vanishing at the horizon. It turns out that the equivalence principle survives at the horizon with the help of the quantum principle, and some puzzles related to the Tolman temperature are also resolved. |
1207.4594 | Matej Pavsic | Matej Pav\v{s}i\v{c} | Wheeler-DeWitt Equation in Five Dimensions and Modified QED | 14 pages | null | 10.1016/j.physletb.2012.09.034 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the ADM splitting of the Einstein-Hilbert action in five
dimensions in the presence of matter that can be either a "point particle", or
a set of scalar fields. The Hamiltonian, being a linear superposition of
constraints, is equal to zero. Upon quantization, we obtain the Schr\"odinger
equation for a wave functional, \Psi, that depends on the matter degrees of
freedom, and on the 5D gravity degrees of freedom. After the Kaluza-Klein
splitting, the functional Schr\"odinger equation decomposes so that it contains
a part due to 4D gravity, a part due to electrodynamics, and a part due to
matter. Depending on choice of the matter term, we obtain two different
versions of a modified quantum electrodynamics. In one version, time
automatically appears, and there is no problem with infinite vacuum energy
density of matter fields, whereas in the other version such problems exist.
| [
{
"created": "Thu, 19 Jul 2012 09:40:45 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Pavšič",
"Matej",
""
]
] | We consider the ADM splitting of the Einstein-Hilbert action in five dimensions in the presence of matter that can be either a "point particle", or a set of scalar fields. The Hamiltonian, being a linear superposition of constraints, is equal to zero. Upon quantization, we obtain the Schr\"odinger equation for a wave functional, \Psi, that depends on the matter degrees of freedom, and on the 5D gravity degrees of freedom. After the Kaluza-Klein splitting, the functional Schr\"odinger equation decomposes so that it contains a part due to 4D gravity, a part due to electrodynamics, and a part due to matter. Depending on choice of the matter term, we obtain two different versions of a modified quantum electrodynamics. In one version, time automatically appears, and there is no problem with infinite vacuum energy density of matter fields, whereas in the other version such problems exist. |
2209.10469 | Takuya Katagiri | Takuya Katagiri, Masashi Kimura, Hiroyuki Nakano, Kazuyuki Omukai | Vanishing Love of Black Holes in General Relativity: From Spacetime
Conformal Symmetry of a Two-dimensional Reduced Geometry | 41 pages, v2: added discussion on the result of the Kerr black hole
in terms of the Teukolsky equation, v3: minor corrections, accepted for
publication in PRD | null | 10.1103/PhysRevD.107.124030 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We study the underlying structure of the vanishing of the Love numbers of
both Schwarzschild and Kerr black holes in terms of spacetime conformal
symmetry in a unified manner for the static spin-$s$ fields. The perturbations
can be reduced with the harmonic decomposition to a set of infinite static
scalar fields in a two-dimensional anti-de Sitter spacetime~$({\rm AdS}_2)$. In
the reduced system, each scalar field is paired with another, implying that all
multipole modes of the perturbation can be regarded as symmetric partners,
which can be understood from the property of the supersymmetry algebra. The
generator of the supersymmetric structure is constructed from a closed
conformal Killing vector field of ${\rm AdS}_2$. The associated conserved
quantity allows one to show no static response, i.e., vanishing of the Love and
dissipation numbers. We also discuss the vanishing Love numbers of the Kerr
black hole with the nonzero dissipation numbers for the non-axisymmetric
perturbations in terms of a radial constant found in a parallel manner as the
axisymmetric field case even though the interpretation for the structure is
controversial. The symmetric structure corresponds to the ``ladder'' symmetry
in Hui et al. [JCAP 01, no.01, 032 (2022)] although the geometrical origin is
different. Our ladder operator includes the generators of hidden symmetries in
previous works.
| [
{
"created": "Wed, 21 Sep 2022 16:11:02 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Oct 2022 14:48:42 GMT",
"version": "v2"
},
{
"created": "Tue, 6 Jun 2023 11:02:12 GMT",
"version": "v3"
}
] | 2023-06-28 | [
[
"Katagiri",
"Takuya",
""
],
[
"Kimura",
"Masashi",
""
],
[
"Nakano",
"Hiroyuki",
""
],
[
"Omukai",
"Kazuyuki",
""
]
] | We study the underlying structure of the vanishing of the Love numbers of both Schwarzschild and Kerr black holes in terms of spacetime conformal symmetry in a unified manner for the static spin-$s$ fields. The perturbations can be reduced with the harmonic decomposition to a set of infinite static scalar fields in a two-dimensional anti-de Sitter spacetime~$({\rm AdS}_2)$. In the reduced system, each scalar field is paired with another, implying that all multipole modes of the perturbation can be regarded as symmetric partners, which can be understood from the property of the supersymmetry algebra. The generator of the supersymmetric structure is constructed from a closed conformal Killing vector field of ${\rm AdS}_2$. The associated conserved quantity allows one to show no static response, i.e., vanishing of the Love and dissipation numbers. We also discuss the vanishing Love numbers of the Kerr black hole with the nonzero dissipation numbers for the non-axisymmetric perturbations in terms of a radial constant found in a parallel manner as the axisymmetric field case even though the interpretation for the structure is controversial. The symmetric structure corresponds to the ``ladder'' symmetry in Hui et al. [JCAP 01, no.01, 032 (2022)] although the geometrical origin is different. Our ladder operator includes the generators of hidden symmetries in previous works. |
1806.09151 | Bijan Saha Dr. | Bijan Saha | Spinor fields in spherically symmetric space-time | 9 pages, 5 figures | The European Physical Journal Plus 133, 461 (2018) | 10.1140/epjp/i2018-12273-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the scope of a spherically symmetric space-time we study the role of a
nonlinear spinor field in the formation of different configurations with
spherical symmetries. The presence of the non-diagonal components of
energy-momentum tensor of the spinor field leads to some severe restrictions on
the spinor field itself. Since spinor field is the source of the gravitational
one, the metric functions also changes in accordance with it. The system as a
whole possesses solutions only in case of some additional conditions on metric
functions.
| [
{
"created": "Sun, 24 Jun 2018 14:16:52 GMT",
"version": "v1"
}
] | 2018-12-31 | [
[
"Saha",
"Bijan",
""
]
] | Within the scope of a spherically symmetric space-time we study the role of a nonlinear spinor field in the formation of different configurations with spherical symmetries. The presence of the non-diagonal components of energy-momentum tensor of the spinor field leads to some severe restrictions on the spinor field itself. Since spinor field is the source of the gravitational one, the metric functions also changes in accordance with it. The system as a whole possesses solutions only in case of some additional conditions on metric functions. |
2402.16484 | Shunichiro Kinoshita | Shunichiro Kinoshita | On geometrical origin of Kodama vector | 10 pages; v2: minor changes, appendix B and references added | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | It has been known that warped product spacetimes such as spherically
symmetric ones admit the Kodama vector. This vector provides a locally
conserved current made by contraction of the Einstein tensor, even though there
is no Killing vector. In addition, a quasilocal mass, Birkhoff's theorem and
various properties are closely related to the Kodama vector. Recently, it is
shown that the notion of the Kodama vector can be extended to three-dimensional
axisymmetric spacetimes even if the spacetimes are not warped product. This
implies that warped product may not be a necessary condition for a spacetime to
admit the Kodama vector. We show properties of the Kodama vector originate from
the conformal Killing-Yano two-form. In particular, the well-known spacetimes
that admit the Kodama vector have a closed conformal Killing-Yano two-form.
Furthermore, we show the Kodama vector provides local conserved currents for
each order of the Lovelock tensor as well as the Einstein tensor.
| [
{
"created": "Mon, 26 Feb 2024 11:04:09 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Mar 2024 11:08:37 GMT",
"version": "v2"
}
] | 2024-03-13 | [
[
"Kinoshita",
"Shunichiro",
""
]
] | It has been known that warped product spacetimes such as spherically symmetric ones admit the Kodama vector. This vector provides a locally conserved current made by contraction of the Einstein tensor, even though there is no Killing vector. In addition, a quasilocal mass, Birkhoff's theorem and various properties are closely related to the Kodama vector. Recently, it is shown that the notion of the Kodama vector can be extended to three-dimensional axisymmetric spacetimes even if the spacetimes are not warped product. This implies that warped product may not be a necessary condition for a spacetime to admit the Kodama vector. We show properties of the Kodama vector originate from the conformal Killing-Yano two-form. In particular, the well-known spacetimes that admit the Kodama vector have a closed conformal Killing-Yano two-form. Furthermore, we show the Kodama vector provides local conserved currents for each order of the Lovelock tensor as well as the Einstein tensor. |
gr-qc/0406053 | Vilson T. Zanchin | Antares Kleber, Jos\'e P. S. Lemos, Vilson T. Zanchin | Thick shells and stars in Majumdar-Papapetrou general relativity | 16 pages, 3 figures; minor changes, added references | Grav.Cosmol. 11 (2005) 269-276 | null | null | gr-qc | null | The Majumdar-Papapetrou system is the subset of the Einstein-Maxwell-charged
dust matter theory, when the charge of each particle is equal to its mass.
Solutions for this system are less difficult to find, in general one does not
need even to impose any spatial symmetry a priori. For instance, any number of
extreme Reissner-Nordstrom solutions (which in vacuum reduce to extreme
Reissner-Nordstrom black holes) located at will is a solution. In matter one
can also find solutions with some ease. Here we find an exact solution of the
Majumdar-Papapetrou system, a spherically symmetric charged thick shell, with
mass m, outer radius r_o, and inner radius r_i. This solution consists of three
regions, an inner Minkowski region, a middle region with extreme charged dust
matter, and an outer Reissner-Nordstrom region. The matching of the regions,
obeying the usual junction conditions for boundary surfaces, is continuous. For
vanishing inner radius, one obtains a Bonnor star, whereas for vanishing
thickness, one obtains an infinitesimally thin shell. For sufficiently high
mass of the thick shell or sufficiently small outer radius, it forms an extreme
Reissner-Nordstrom quasi-black hole, i.e., a star whose gravitational
properties are virtually indistinguishable from a true extreme black hole. This
quasi-black hole has no hair and has a naked horizon, meaning that the Riemann
tensor at the horizon on an infalling probe diverges. At the critical value,
when the mass is equal to the outer radius, m=r_o, there is no smooth manifold.
Above the critical value when m>r_o there is no solution, the shell collapses
into a singularity. Systems with m< r_o are neutrally stable. Many of these
properties are similar to those of gravitational monopoles.
| [
{
"created": "Sun, 13 Jun 2004 21:39:22 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Dec 2005 20:56:22 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Kleber",
"Antares",
""
],
[
"Lemos",
"José P. S.",
""
],
[
"Zanchin",
"Vilson T.",
""
]
] | The Majumdar-Papapetrou system is the subset of the Einstein-Maxwell-charged dust matter theory, when the charge of each particle is equal to its mass. Solutions for this system are less difficult to find, in general one does not need even to impose any spatial symmetry a priori. For instance, any number of extreme Reissner-Nordstrom solutions (which in vacuum reduce to extreme Reissner-Nordstrom black holes) located at will is a solution. In matter one can also find solutions with some ease. Here we find an exact solution of the Majumdar-Papapetrou system, a spherically symmetric charged thick shell, with mass m, outer radius r_o, and inner radius r_i. This solution consists of three regions, an inner Minkowski region, a middle region with extreme charged dust matter, and an outer Reissner-Nordstrom region. The matching of the regions, obeying the usual junction conditions for boundary surfaces, is continuous. For vanishing inner radius, one obtains a Bonnor star, whereas for vanishing thickness, one obtains an infinitesimally thin shell. For sufficiently high mass of the thick shell or sufficiently small outer radius, it forms an extreme Reissner-Nordstrom quasi-black hole, i.e., a star whose gravitational properties are virtually indistinguishable from a true extreme black hole. This quasi-black hole has no hair and has a naked horizon, meaning that the Riemann tensor at the horizon on an infalling probe diverges. At the critical value, when the mass is equal to the outer radius, m=r_o, there is no smooth manifold. Above the critical value when m>r_o there is no solution, the shell collapses into a singularity. Systems with m< r_o are neutrally stable. Many of these properties are similar to those of gravitational monopoles. |
0712.2144 | Martin Zofka | M. Zofka, J. Bicak | Cylindrical spacetimes with a cosmological constant and their sources | 15 pages, 2 figures | Class.Quant.Grav.25:015011,2008 | 10.1088/0264-9381/25/1/015011 | null | gr-qc | null | We review and investigate some basic properties of static, cylindrically
symmetric spacetimes with non-zero cosmological constant, find non-singular
sheet sources of these spacetimes and discuss their characteristics, and
clarify their relation to the 4D black-string solutions.
| [
{
"created": "Thu, 13 Dec 2007 12:54:51 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Zofka",
"M.",
""
],
[
"Bicak",
"J.",
""
]
] | We review and investigate some basic properties of static, cylindrically symmetric spacetimes with non-zero cosmological constant, find non-singular sheet sources of these spacetimes and discuss their characteristics, and clarify their relation to the 4D black-string solutions. |
gr-qc/0307056 | Naresh Dadhich | Aseem Paranjape and Naresh Dadhich | Embedding Diagrams for the Reissner-Nordstr\"om spacetime | RevTex4, 4 pages and 4 eps figures | Gen.Rel.Grav. 36 (2004) 1189-1195 | 10.1023/B:GERG.0000018285.39500.ed | null | gr-qc | null | We consider embedding diagrams for the Reissner-Nordstr\"om spacetime. We
embed the $(r-t)$ and $(r-\phi)$ planes into 3-Minkowski/Euclidean space and
discuss the relation between the diagrams and the corresponding curvature
scalar of the 2-metrics
| [
{
"created": "Fri, 11 Jul 2003 04:40:34 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Paranjape",
"Aseem",
""
],
[
"Dadhich",
"Naresh",
""
]
] | We consider embedding diagrams for the Reissner-Nordstr\"om spacetime. We embed the $(r-t)$ and $(r-\phi)$ planes into 3-Minkowski/Euclidean space and discuss the relation between the diagrams and the corresponding curvature scalar of the 2-metrics |
gr-qc/0205022 | L. Raul Abramo | L. Raul Abramo (USP, Brazil), L. Brenig and E. Gunzig (ULB, Belgium) | On the stability of gravity in the presence of a non-minimally coupled
scalar field | References and some clarifications added; 11 pages, 1 figure;
submitted to Physics Letters B | Phys.Lett. B549 (2002) 13-19 | 10.1016/S0370-2693(02)02898-8 | null | gr-qc astro-ph hep-th | null | We show that Einstein's gravity coupled to a non-minimally coupled scalar
field is stable even for high values of the scalar field, when the sign of the
Einstein-Hilbert action is reversed. We also discuss inflationary solutions and
a possible new mechanism of reheating.
| [
{
"created": "Mon, 6 May 2002 21:26:14 GMT",
"version": "v1"
},
{
"created": "Wed, 29 May 2002 17:23:17 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Abramo",
"L. Raul",
"",
"USP, Brazil"
],
[
"Brenig",
"L.",
"",
"ULB, Belgium"
],
[
"Gunzig",
"E.",
"",
"ULB, Belgium"
]
] | We show that Einstein's gravity coupled to a non-minimally coupled scalar field is stable even for high values of the scalar field, when the sign of the Einstein-Hilbert action is reversed. We also discuss inflationary solutions and a possible new mechanism of reheating. |
1706.01056 | Fethi M. Ramazanoglu | Fethi M. Ramazano\u{g}lu | Spontaneous growth of vector fields in gravity | 5 pages, 2 figures | Phys. Rev. D 96, 064009 (2017) | 10.1103/PhysRevD.96.064009 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the spontaneous scalarization scenario in scalar-tensor theories
is a specific case of a more general phenomenon. The key fact is that the
instability causing the spontaneous growth in scalars is due to the nonminimal
coupling in the theory, and not related to the nature of the scalar. Another
field with the same form of coupling undergoes spontaneous growth as well. We
explicitly demonstrate this idea for vectors, naming it "spontaneous
vectorization", and study spherically symmetric neutron stars in such a theory.
We also comment on other tensor fields the idea can be applied, naming the
general mechanism "spontaneous tensorization".
| [
{
"created": "Sun, 4 Jun 2017 11:15:33 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Oct 2017 22:26:36 GMT",
"version": "v2"
}
] | 2017-10-10 | [
[
"Ramazanoğlu",
"Fethi M.",
""
]
] | We show that the spontaneous scalarization scenario in scalar-tensor theories is a specific case of a more general phenomenon. The key fact is that the instability causing the spontaneous growth in scalars is due to the nonminimal coupling in the theory, and not related to the nature of the scalar. Another field with the same form of coupling undergoes spontaneous growth as well. We explicitly demonstrate this idea for vectors, naming it "spontaneous vectorization", and study spherically symmetric neutron stars in such a theory. We also comment on other tensor fields the idea can be applied, naming the general mechanism "spontaneous tensorization". |
2009.01066 | Juan Calderon Bustillo | Juan Calder\'on Bustillo, Nicolas Sanchis-Gual, Alejandro
Torres-Forn\'e, Jos\'e A. Font | Confusing Head-On Collisions with Precessing Intermediate-Mass Binary
Black Hole Mergers | 10 pages, 9 Figures. Version accepted in Phys. Rev. Lett. Includes
Supplementary Material | Phys. Rev. Lett. 126, 201101 (2021) | 10.1103/PhysRevLett.126.201101 | LIGO-P1900363 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report a degeneracy between the gravitational-wave signals from
quasi-circular precessing black-hole mergers and those from extremely eccentric
mergers, namely head-on collisions. Performing model selection on numerically
simulated signals of head-on collisions using models for quasi-circular
binaries we find that, for signal-to-noise ratios of 15 and 25, typical of
Advanced LIGO observations, head-on mergers with respective total masses of
$M\in (125,300)M_\odot$ and $M\in (200,440)M_\odot$ would be identified as
precessing quasi-circular intermediate-mass black hole binaries, located at a
much larger distance. Ruling out the head-on scenario would require to perform
model selection using currently nonexistent waveform models for head-on
collisions, together with the application of astrophysically motivated priors
on the (rare) occurrence of those events. We show that in situations where
standard parameter inference of compact binaries may report component masses
inside (outside) the pair-instability supernova gap, the true object may be a
head-on merger with masses outside (inside) this gap. We briefly discuss the
potential implications of these findings for the recent gravitational-wave
detection GW190521, which we analyse in detail in [Phys. Rev. Lett. 126,
081101].
| [
{
"created": "Wed, 2 Sep 2020 13:40:02 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Apr 2021 08:50:24 GMT",
"version": "v2"
},
{
"created": "Mon, 17 May 2021 23:14:07 GMT",
"version": "v3"
}
] | 2021-05-19 | [
[
"Bustillo",
"Juan Calderón",
""
],
[
"Sanchis-Gual",
"Nicolas",
""
],
[
"Torres-Forné",
"Alejandro",
""
],
[
"Font",
"José A.",
""
]
] | We report a degeneracy between the gravitational-wave signals from quasi-circular precessing black-hole mergers and those from extremely eccentric mergers, namely head-on collisions. Performing model selection on numerically simulated signals of head-on collisions using models for quasi-circular binaries we find that, for signal-to-noise ratios of 15 and 25, typical of Advanced LIGO observations, head-on mergers with respective total masses of $M\in (125,300)M_\odot$ and $M\in (200,440)M_\odot$ would be identified as precessing quasi-circular intermediate-mass black hole binaries, located at a much larger distance. Ruling out the head-on scenario would require to perform model selection using currently nonexistent waveform models for head-on collisions, together with the application of astrophysically motivated priors on the (rare) occurrence of those events. We show that in situations where standard parameter inference of compact binaries may report component masses inside (outside) the pair-instability supernova gap, the true object may be a head-on merger with masses outside (inside) this gap. We briefly discuss the potential implications of these findings for the recent gravitational-wave detection GW190521, which we analyse in detail in [Phys. Rev. Lett. 126, 081101]. |
2307.05459 | Sam C. Collingbourne | Sam C. Collingbourne | Coercivity Properties of the Canonical Energy in Double Null Gauge | 31 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the canonical energy associated with solutions to the
linearised vacuum Einstein equation on a stationary spacetime. The main result
of this paper establishes, in the context of the $4$-dimensional Schwarzschild
exterior, a direct correspondence between the conservation law satisfied by the
canonical energy and the conservation laws deduced by Holzegel for
gravitational perturbations in double null gauge. Since the latter exhibit
useful coercivity properties (leading to energy and pointwise boundedness
statements) we obtain coercivity results for the canonical energy in the double
null gauge as a corollary. More generally, the correspondence suggests a
systematic way to uncover coercivity properties in the conservation laws for
the canonical energy on Kerr.
| [
{
"created": "Tue, 11 Jul 2023 17:47:37 GMT",
"version": "v1"
}
] | 2023-07-12 | [
[
"Collingbourne",
"Sam C.",
""
]
] | In this paper, we study the canonical energy associated with solutions to the linearised vacuum Einstein equation on a stationary spacetime. The main result of this paper establishes, in the context of the $4$-dimensional Schwarzschild exterior, a direct correspondence between the conservation law satisfied by the canonical energy and the conservation laws deduced by Holzegel for gravitational perturbations in double null gauge. Since the latter exhibit useful coercivity properties (leading to energy and pointwise boundedness statements) we obtain coercivity results for the canonical energy in the double null gauge as a corollary. More generally, the correspondence suggests a systematic way to uncover coercivity properties in the conservation laws for the canonical energy on Kerr. |
0811.2846 | Hideki Ishihara | Kouji Ogawa, Hideki Ishihara, Hiroshi Kozaki, and Hiroyuki Nakano | Perturbations of Spacetime around a Stationary Rotating Cosmic String | 30 pages, 6 figures; Minor corrections, references added, published
version in Physical Review D | Phys.Rev.D79:063501,2009 | 10.1103/PhysRevD.79.063501 | OCU-PHYS 307, AP-GR 64 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the metric perturbations around a stationary rotating Nambu-Goto
string in Minkowski spacetime. By solving the linearized Einstein equations, we
study the effects of azimuthal frame-dragging around the rotation axis and
linear frame-dragging along the rotation axis, the Newtonian logarithmic
potential, and the angular deficit around the string as the potential mode. We
also investigate gravitational waves propagating off the string and propagating
along the string, and show that the stationary rotating string emits
gravitational waves toward the directions specified by discrete angles from the
rotation axis. Waveforms, polarizations, and amplitudes which depend on the
direction are shown explicitly.
| [
{
"created": "Tue, 18 Nov 2008 07:13:47 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Feb 2009 03:14:50 GMT",
"version": "v2"
}
] | 2009-11-06 | [
[
"Ogawa",
"Kouji",
""
],
[
"Ishihara",
"Hideki",
""
],
[
"Kozaki",
"Hiroshi",
""
],
[
"Nakano",
"Hiroyuki",
""
]
] | We consider the metric perturbations around a stationary rotating Nambu-Goto string in Minkowski spacetime. By solving the linearized Einstein equations, we study the effects of azimuthal frame-dragging around the rotation axis and linear frame-dragging along the rotation axis, the Newtonian logarithmic potential, and the angular deficit around the string as the potential mode. We also investigate gravitational waves propagating off the string and propagating along the string, and show that the stationary rotating string emits gravitational waves toward the directions specified by discrete angles from the rotation axis. Waveforms, polarizations, and amplitudes which depend on the direction are shown explicitly. |
2104.04834 | Reinaldo Gleiser | Reinaldo J. Gleiser | Linear perturbations of the Linet-Tian metrics with a positive
cosmological constant | 33 pages, 6 figures | null | 10.1088/1361-6382/ac2133 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Linet-Tian metrics are solutions of the Einstein equations with a
cosmological constant, $\Lambda$, that can be positive or negative. The linear
instability of these metrics in the case $\Lambda <0$, has already been
established. In the case $\Lambda>0$, it was found in a recent analysis that
the perturbation equations admit unstable modes. The analysis was based on the
construction of a gauge invariant function of the metric perturbation
coefficients, called here $W(y)$. This function satisfied a linear second order
equation that could be used to set up a boundary value problem determining the
allowed, real or purely imaginary frequencies for the perturbations.
Nevertheless, the relation of these solutions to the full spectrum of
perturbations, and, therefore, to the evolution of arbitrary perturbations,
remained open. In this paper we consider again the perturbations of the
Linet-Tian metric with $\Lambda >0$, and show, using a form of the Darboux
transformation, that one can associate with the perturbation equations a self
adjoint problem that provides a solution to the completeness and spectrum of
the perturbations. This is also used to construct the explicit relation between
the solutions of the gauge invariant equation for $W(y)$, and the evolution of
arbitrary initial data, thus solving the problem that remained open in the
previous study. Numerical methods are then used to confirm the existence of
unstable modes as a part of the complete spectrum of the perturbations, thus
establishing the linear gravitational instability of the Linet-Tian metrics
with $\Lambda >0$.
| [
{
"created": "Sat, 10 Apr 2021 18:37:25 GMT",
"version": "v1"
}
] | 2021-10-27 | [
[
"Gleiser",
"Reinaldo J.",
""
]
] | The Linet-Tian metrics are solutions of the Einstein equations with a cosmological constant, $\Lambda$, that can be positive or negative. The linear instability of these metrics in the case $\Lambda <0$, has already been established. In the case $\Lambda>0$, it was found in a recent analysis that the perturbation equations admit unstable modes. The analysis was based on the construction of a gauge invariant function of the metric perturbation coefficients, called here $W(y)$. This function satisfied a linear second order equation that could be used to set up a boundary value problem determining the allowed, real or purely imaginary frequencies for the perturbations. Nevertheless, the relation of these solutions to the full spectrum of perturbations, and, therefore, to the evolution of arbitrary perturbations, remained open. In this paper we consider again the perturbations of the Linet-Tian metric with $\Lambda >0$, and show, using a form of the Darboux transformation, that one can associate with the perturbation equations a self adjoint problem that provides a solution to the completeness and spectrum of the perturbations. This is also used to construct the explicit relation between the solutions of the gauge invariant equation for $W(y)$, and the evolution of arbitrary initial data, thus solving the problem that remained open in the previous study. Numerical methods are then used to confirm the existence of unstable modes as a part of the complete spectrum of the perturbations, thus establishing the linear gravitational instability of the Linet-Tian metrics with $\Lambda >0$. |
gr-qc/0201011 | Jiri Bicak | Jiri Bicak | Exact solutions and their interpretation | 18 pages. To be published in: Proceedings of the 16th International
Conference on General Relativity and Gravitation, Durban, 15 - 21 July, 2001,
eds. N.T. Bishop and S.D. Maharaj, World Scientific | null | 10.1142/9789812776556_0017 | null | gr-qc | null | This is the account of the workshop Exact solutions and their interpretation
at the 16-th International Conference on General Relativity and Gravitation
held in Durban, July 15-21, 2001. Work reported in 32 oral contributions
spanned a wide variety of topics, ranging from exact radiative spacetimes to
cosmological solutions. Two invited review talks, on the role of exact
solutions in string theory and in cosmology, are also described.
| [
{
"created": "Thu, 3 Jan 2002 22:19:10 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Bicak",
"Jiri",
""
]
] | This is the account of the workshop Exact solutions and their interpretation at the 16-th International Conference on General Relativity and Gravitation held in Durban, July 15-21, 2001. Work reported in 32 oral contributions spanned a wide variety of topics, ranging from exact radiative spacetimes to cosmological solutions. Two invited review talks, on the role of exact solutions in string theory and in cosmology, are also described. |
1503.01636 | Jan Ambjorn | J. Ambjorn, A. Goerlich, J. Jurkiewicz and H. Zhang | The microscopic structure of 2D CDT coupled to matter | 14 pages,lot of figures | null | 10.1016/j.physletb.2015.05.026 | null | gr-qc hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that for 1+1 dimensional Causal Dynamical Triangulations (CDT)
coupled to 4 massive scalar fields one can construct an effective transfer
matrix if the masses squared is larger than or equal to 0.05. The properties of
this transfer matrix can explain why CDT coupled to matter can behave
completely different from "pure" CDT. We identify the important critical
exponent in the effective action, which may determine the universality class of
the model.
| [
{
"created": "Thu, 5 Mar 2015 13:57:16 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Ambjorn",
"J.",
""
],
[
"Goerlich",
"A.",
""
],
[
"Jurkiewicz",
"J.",
""
],
[
"Zhang",
"H.",
""
]
] | We show that for 1+1 dimensional Causal Dynamical Triangulations (CDT) coupled to 4 massive scalar fields one can construct an effective transfer matrix if the masses squared is larger than or equal to 0.05. The properties of this transfer matrix can explain why CDT coupled to matter can behave completely different from "pure" CDT. We identify the important critical exponent in the effective action, which may determine the universality class of the model. |
gr-qc/0002068 | Roberto Scipioni | Roberto Scipioni | On the triviality of certain non-Riemannian models of gravitation | 12 pages, Latex, final version for Physics Letters A | Phys.Lett. A269 (2000) 263-268 | 10.1016/S0375-9601(00)00268-1 | null | gr-qc | null | We prove in the Tucker-Wang approach to non-Riemannian Gravity that a general
homogeneous Lagrangian density in the general connection with order of
homogeneity of at least two, gives no contribution to the generalised Einstein
equations. Using this result other important cases are also considered.
| [
{
"created": "Sat, 19 Feb 2000 00:14:26 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Apr 2000 00:54:54 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Scipioni",
"Roberto",
""
]
] | We prove in the Tucker-Wang approach to non-Riemannian Gravity that a general homogeneous Lagrangian density in the general connection with order of homogeneity of at least two, gives no contribution to the generalised Einstein equations. Using this result other important cases are also considered. |
1108.5857 | Israel Quiros | Israel Quiros, Ricardo Garcia-Salcedo, Jose Edgar Madriz Aguilar,
Tonatiuh Matos | The conformal transformation's controversy: what are we missing? | 17 pages, no figures. version accepted by General Relativity and
Gravitation journal | General Relativity and Gravitation: Volume 45, Issue 2 (2013),
Page 489-518 | 10.1007/s10714-012-1484-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An alternative interpretation of the conformal transformations of the metric
is discussed according to which the latter can be viewed as a mapping among
Riemannian and Weyl-integrable spaces. A novel aspect of the conformal
transformation's issue is then revealed: these transformations relate
complementary geometrical pictures of a same physical reality, so that, the
question about which is the physical conformal frame, does not arise. In
addition, arguments are given which point out that, unless a clear statement of
what is understood by "equivalence of frames" is made, the issue is a semantic
one. For definiteness, an intuitively "natural" statement of conformal
equivalence is given, which is associated with conformal invariance of the
field equations. Under this particular reading, equivalence can take place only
if the metric is defined up to a conformal equivalence class. A concrete
example of a conformal-invariant theory of gravity is then explored. Since
Brans-Dicke theory is not conformally invariant, then the Jordan's and
Einstein's frames of the theory are not equivalent. Otherwise, in view of the
alternative approach proposed here, these frames represent complementary
geometrical descriptions of a same phenomenon. The different points of view
existing in the literature are critically scrutinized on the light of the new
arguments.
| [
{
"created": "Tue, 30 Aug 2011 07:41:16 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Dec 2011 05:54:54 GMT",
"version": "v2"
},
{
"created": "Mon, 16 Apr 2012 06:00:18 GMT",
"version": "v3"
},
{
"created": "Mon, 5 Nov 2012 14:30:34 GMT",
"version": "v4"
}
] | 2013-01-29 | [
[
"Quiros",
"Israel",
""
],
[
"Garcia-Salcedo",
"Ricardo",
""
],
[
"Aguilar",
"Jose Edgar Madriz",
""
],
[
"Matos",
"Tonatiuh",
""
]
] | An alternative interpretation of the conformal transformations of the metric is discussed according to which the latter can be viewed as a mapping among Riemannian and Weyl-integrable spaces. A novel aspect of the conformal transformation's issue is then revealed: these transformations relate complementary geometrical pictures of a same physical reality, so that, the question about which is the physical conformal frame, does not arise. In addition, arguments are given which point out that, unless a clear statement of what is understood by "equivalence of frames" is made, the issue is a semantic one. For definiteness, an intuitively "natural" statement of conformal equivalence is given, which is associated with conformal invariance of the field equations. Under this particular reading, equivalence can take place only if the metric is defined up to a conformal equivalence class. A concrete example of a conformal-invariant theory of gravity is then explored. Since Brans-Dicke theory is not conformally invariant, then the Jordan's and Einstein's frames of the theory are not equivalent. Otherwise, in view of the alternative approach proposed here, these frames represent complementary geometrical descriptions of a same phenomenon. The different points of view existing in the literature are critically scrutinized on the light of the new arguments. |
0905.1103 | Ricardo Garcia-Salcedo | Ricardo Garcia-Salcedo, Tame Gonzalez, Claudia Moreno and Israel
Quiros | Dynamics of FRW Universes Sourced by Non-Linear Electrodynamics | 8 pages, 10 figures, pdf file, tex file | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the dynamical systems tools to study the (linear) dynamics of
Friedmann-Robertson-Walker universes that are fuelled by non-linear
electrodynamics. We focus, mainly, in two particular models. In the first model
the cosmic evolution is fuelled by cold dark matter, a cosmological constant
and a non-linear electrodynamics field. In the second case non-singular
cosmology and late-time accelerated expansion are unified in a model where the
Einstein's field equations are sourced only by cold dark matter and a
non-linear electrodynamics field. It is shown that, in contrast to previous
claims, the cosmological effects coming from the non-linear electrodynamics
field are not as generic as though. In fact, critical points in the phase space
that could be associated with non-linear electrodynamic effects are not found.
| [
{
"created": "Thu, 7 May 2009 19:15:59 GMT",
"version": "v1"
}
] | 2009-05-08 | [
[
"Garcia-Salcedo",
"Ricardo",
""
],
[
"Gonzalez",
"Tame",
""
],
[
"Moreno",
"Claudia",
""
],
[
"Quiros",
"Israel",
""
]
] | We apply the dynamical systems tools to study the (linear) dynamics of Friedmann-Robertson-Walker universes that are fuelled by non-linear electrodynamics. We focus, mainly, in two particular models. In the first model the cosmic evolution is fuelled by cold dark matter, a cosmological constant and a non-linear electrodynamics field. In the second case non-singular cosmology and late-time accelerated expansion are unified in a model where the Einstein's field equations are sourced only by cold dark matter and a non-linear electrodynamics field. It is shown that, in contrast to previous claims, the cosmological effects coming from the non-linear electrodynamics field are not as generic as though. In fact, critical points in the phase space that could be associated with non-linear electrodynamic effects are not found. |
2405.04797 | Lakhan V. Jaybhaye | Lakhan V. Jaybhaye, Raja Solanki, P.K. Sahoo | Bouncing cosmological models in $f(R,L_m)$ gravity | Physica Scripta published version | Physics Scripta 99 (2024) 065031 | 10.1088/1402-4896/ad4838 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | This article explores matter bounce non-singular cosmology in $f(R,L_m)$
gravity. We consider two non-linear $f(R,L_m)$ functional forms, specifically,
$f(R,L_m) = \frac{R}{2} + \lambda R^2 + \alpha L_m$ and $f(R,L_m) = \frac{R}{2}
+ L_m ^\beta + \gamma$ representing a minimal coupling case. We derive the
corresponding Friedmann-like equations for both the assumed models in the FLRW
background, and then we present the impact of the model parameters along with
the parameter of bouncing scale factor on the equation of state parameter,
pressure, and the energy density. In addition, we examine the dynamical
behavior of cosmographic parameters such as jerk, lerk, and snap parameters.
Further, we find that the violation of the null energy condition along with the
strong energy condition depicts the non-singular accelerating behavior,
corresponding to both assumed non-linear $f(R,L_m)$ functions. Lastly, we
present the behavior of the adiabatic speed of sound to examine the viability
of the considered cosmological bouncing scenario.
| [
{
"created": "Wed, 8 May 2024 04:10:53 GMT",
"version": "v1"
}
] | 2024-05-17 | [
[
"Jaybhaye",
"Lakhan V.",
""
],
[
"Solanki",
"Raja",
""
],
[
"Sahoo",
"P. K.",
""
]
] | This article explores matter bounce non-singular cosmology in $f(R,L_m)$ gravity. We consider two non-linear $f(R,L_m)$ functional forms, specifically, $f(R,L_m) = \frac{R}{2} + \lambda R^2 + \alpha L_m$ and $f(R,L_m) = \frac{R}{2} + L_m ^\beta + \gamma$ representing a minimal coupling case. We derive the corresponding Friedmann-like equations for both the assumed models in the FLRW background, and then we present the impact of the model parameters along with the parameter of bouncing scale factor on the equation of state parameter, pressure, and the energy density. In addition, we examine the dynamical behavior of cosmographic parameters such as jerk, lerk, and snap parameters. Further, we find that the violation of the null energy condition along with the strong energy condition depicts the non-singular accelerating behavior, corresponding to both assumed non-linear $f(R,L_m)$ functions. Lastly, we present the behavior of the adiabatic speed of sound to examine the viability of the considered cosmological bouncing scenario. |
2206.02799 | Grigory Volovik | G.E. Volovik | Particle creation: Schwinger + Unruh + Hawking | 5 pages, no figures, accepted in JETP Letters | null | 10.1134/S0021364022601968 | null | gr-qc cond-mat.other hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the interconnection between the Schwinger pair creation in
electric field, Hawking radiation and particle creation in the Unruh effect.
All three processes can be described in terms of the entropy and temperature.
These thermodynamic like processes can be combined. We consider the combined
process of creation of charged and electrically neutral particles in the
electric field, which combine the Schwinger and Unruh effects. We also consider
the creation of the charged black and white holes in electric field, which
combines the Schwinger effect and the black hole entropy. The combined
processes obey the sum rules for the entropy and for the inverse temperature.
Some contributions to the entropy and to the temperature are negative, which
reflects the quantum entanglement between the created objects.
| [
{
"created": "Mon, 6 Jun 2022 17:55:34 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Jun 2022 17:59:05 GMT",
"version": "v2"
},
{
"created": "Sat, 3 Sep 2022 07:17:27 GMT",
"version": "v3"
},
{
"created": "Tue, 20 Sep 2022 23:06:04 GMT",
"version": "v4"
}
] | 2022-11-09 | [
[
"Volovik",
"G. E.",
""
]
] | We discuss the interconnection between the Schwinger pair creation in electric field, Hawking radiation and particle creation in the Unruh effect. All three processes can be described in terms of the entropy and temperature. These thermodynamic like processes can be combined. We consider the combined process of creation of charged and electrically neutral particles in the electric field, which combine the Schwinger and Unruh effects. We also consider the creation of the charged black and white holes in electric field, which combines the Schwinger effect and the black hole entropy. The combined processes obey the sum rules for the entropy and for the inverse temperature. Some contributions to the entropy and to the temperature are negative, which reflects the quantum entanglement between the created objects. |
2212.06837 | Pierre Heidmann | Pierre Heidmann, Ibrahima Bah and Emanuele Berti | Imaging Topological Solitons: the Microstructure Behind the Shadow | 15 pages and 6 figures, v2: typos corrected, v3: minor changes and
published version | null | 10.1103/PhysRevD.107.084042 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study photon geodesics in topological solitons that have the same
asymptotic properties as Schwarzschild black holes. These are coherent states
in string theory corresponding to pure deformations of spacetime through the
dynamics of compact extra dimensions. We compare these solutions with
Schwarzschild black holes by computing null geodesics, deriving Lyapunov
exponents, and imaging their geometries as seen by a distant observer. We show
that topological solitons are remarkably similar to black holes in apparent
size and scattering properties, while being smooth and horizonless. Incoming
photons experience very high redshift, inducing phenomenological horizon-like
behaviors from the point of view of photon scattering. Thus, they provide a
compelling case for real-world gravitational solitons and topological
alternatives to black holes from string theory.
| [
{
"created": "Tue, 13 Dec 2022 19:00:00 GMT",
"version": "v1"
},
{
"created": "Sat, 17 Dec 2022 07:51:27 GMT",
"version": "v2"
},
{
"created": "Thu, 1 Jun 2023 08:12:02 GMT",
"version": "v3"
}
] | 2023-06-02 | [
[
"Heidmann",
"Pierre",
""
],
[
"Bah",
"Ibrahima",
""
],
[
"Berti",
"Emanuele",
""
]
] | We study photon geodesics in topological solitons that have the same asymptotic properties as Schwarzschild black holes. These are coherent states in string theory corresponding to pure deformations of spacetime through the dynamics of compact extra dimensions. We compare these solutions with Schwarzschild black holes by computing null geodesics, deriving Lyapunov exponents, and imaging their geometries as seen by a distant observer. We show that topological solitons are remarkably similar to black holes in apparent size and scattering properties, while being smooth and horizonless. Incoming photons experience very high redshift, inducing phenomenological horizon-like behaviors from the point of view of photon scattering. Thus, they provide a compelling case for real-world gravitational solitons and topological alternatives to black holes from string theory. |
1812.02686 | Burkhard Kleihaus | Guillermo A. Gonzalez, Burkhard Kleihaus, Jutta Kunz and Sindy Mojica | Innermost stable circular orbits of neutron stars in
dilatonic-Einstein-Gauss-Bonnet theory | 14 pages, 11 figues | Phys. Rev. D 99, 024041 (2019) | 10.1103/PhysRevD.99.024041 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The innermost stable circular orbits (ISCOs) around rapidly rotating neutron
stars are studied in dilatonic Einstein-Gauss-Bonnet theory. Universal
relations for properly scaled ISCO properties are extended from General
Relativity to dilatonic Einstein-Gauss-Bonnet theory and additional relations
are obtained.
| [
{
"created": "Thu, 6 Dec 2018 17:54:53 GMT",
"version": "v1"
}
] | 2019-02-06 | [
[
"Gonzalez",
"Guillermo A.",
""
],
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Mojica",
"Sindy",
""
]
] | The innermost stable circular orbits (ISCOs) around rapidly rotating neutron stars are studied in dilatonic Einstein-Gauss-Bonnet theory. Universal relations for properly scaled ISCO properties are extended from General Relativity to dilatonic Einstein-Gauss-Bonnet theory and additional relations are obtained. |
1507.01795 | Arun Kumar Pandey | Arun Kumar Pandey, Jitesh R. Bhatt | Primordial Generation of Magnetic Fields | 7 pages. To appear in the proceedings of XXI DAE-BRNS High Energy
Physics Symposium, IIT Guwahati, India, December 2014 | null | 10.1007/978-3-319-25619-1_62 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reexamine generation of the primordial magnetic fields, at temperature
$T>80$TeV, by applying a consistent kinetic theory framework which is suitably
modified to take the quantum anomaly into account. The modified kinetic
equation can reproduce the known quantum field theoretic results upto the
leading orders. We show that our results qualitatively matches with the earlier
results obtained using heuristic arguments. The modified kinetic theory can
give the instabilities responsible for generation of the magnetic field due to
chiral imbalance in two distinct regimes: a) when the collisions play a
dominant role and b) when the primordial plasma can be regarded as
collisionless. We argue that the instability developing in the collisional
regime can dominate over the instability in the collisionless regime.
| [
{
"created": "Tue, 7 Jul 2015 13:24:23 GMT",
"version": "v1"
}
] | 2016-09-01 | [
[
"Pandey",
"Arun Kumar",
""
],
[
"Bhatt",
"Jitesh R.",
""
]
] | We reexamine generation of the primordial magnetic fields, at temperature $T>80$TeV, by applying a consistent kinetic theory framework which is suitably modified to take the quantum anomaly into account. The modified kinetic equation can reproduce the known quantum field theoretic results upto the leading orders. We show that our results qualitatively matches with the earlier results obtained using heuristic arguments. The modified kinetic theory can give the instabilities responsible for generation of the magnetic field due to chiral imbalance in two distinct regimes: a) when the collisions play a dominant role and b) when the primordial plasma can be regarded as collisionless. We argue that the instability developing in the collisional regime can dominate over the instability in the collisionless regime. |
gr-qc/9805074 | C. Anastopoulos | C. Anastopoulos | Classicality via hydrodynamics in quantum field theory | 17 pages, LATEX | null | null | University of Barcelona Preprint | gr-qc hep-th | null | Motivated by the consistent histories approach to quantum mechanics, we
examine a simple model of hydrodynamic coarse-graining for a scalar field. It
consists in averaging the field over spatial regions of size L and constructing
the evolution equation for the coarse grained quantities, thus identifying
dissipation and noise.
| [
{
"created": "Tue, 19 May 1998 16:11:43 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Anastopoulos",
"C.",
""
]
] | Motivated by the consistent histories approach to quantum mechanics, we examine a simple model of hydrodynamic coarse-graining for a scalar field. It consists in averaging the field over spatial regions of size L and constructing the evolution equation for the coarse grained quantities, thus identifying dissipation and noise. |
2310.14375 | Rakshak Adhikari | Rakshak Adhikari, Govind Menon, Mikhail V. Medvedev | Non-null and Force-Free Electromagnetic Configurations in Kerr Geometry | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Force-Free Electrodynamics (FFE) is known to describe the highly magnetized
plasma around pulsars and astrophysical black holes. The equations describing
FFE are highly non-linear and the task of finding a well-defined analytical
solution has been unyielding. However, FFE can also be understood in terms of
2-dimensional foliations of the ambient 4-dimensional spacetime. The study of
the foliations can provide significant insights into the structure of the
force-free fields and such foliations can be exploited to generate new null and
non-null solutions. In this paper, we present several nonnull solutions to the
FFE equations in the Kerr spacetime obtained by applying the aforementioned
methods of non-null foliations.
| [
{
"created": "Sun, 22 Oct 2023 18:02:44 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Dec 2023 02:43:50 GMT",
"version": "v2"
}
] | 2023-12-14 | [
[
"Adhikari",
"Rakshak",
""
],
[
"Menon",
"Govind",
""
],
[
"Medvedev",
"Mikhail V.",
""
]
] | Force-Free Electrodynamics (FFE) is known to describe the highly magnetized plasma around pulsars and astrophysical black holes. The equations describing FFE are highly non-linear and the task of finding a well-defined analytical solution has been unyielding. However, FFE can also be understood in terms of 2-dimensional foliations of the ambient 4-dimensional spacetime. The study of the foliations can provide significant insights into the structure of the force-free fields and such foliations can be exploited to generate new null and non-null solutions. In this paper, we present several nonnull solutions to the FFE equations in the Kerr spacetime obtained by applying the aforementioned methods of non-null foliations. |
1701.06893 | Maaneli Derakhshani | Maaneli Derakhshani | Semiclassical Newtonian Field Theories Based On Stochastic Mechanics I | 40 pages (33 pages excluding references), no figures, LaTeX | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is the first in a two-part series in which we extend non-relativistic
stochastic mechanics, in the ZSM formulation [1, 2], to semiclassical Newtonian
gravity (ZSM-Newton) and semiclassical Newtonian electrodynamics (ZSM-Coulomb),
under the assumption that the gravitational and electromagnetic fields are
fundamentally classical (i.e., not independently quantized fields). Our key
findings are: (1) a derivation of the usual $N$-particle Schr{\"o}dinger
equation for many particles interacting through operator-valued gravitational
or Coulomb potentials, and (2) recovery of the `single-body'
Schr{\"o}dinger-Newton and Schr{\"o}dinger-Coulomb equations as mean-field
equations valid for systems of gravitationally and electrostatically
interacting identical particles, respectively, in the weak-coupling large N
limit. We also compare ZSM-Newton/Coulomb to semiclassical Newtonian
gravity/electrodynamics approaches based on standard quantum theory, dynamical
collapse theories, and the de Broglie-Bohm theory.
| [
{
"created": "Tue, 17 Jan 2017 18:00:39 GMT",
"version": "v1"
}
] | 2017-01-25 | [
[
"Derakhshani",
"Maaneli",
""
]
] | This is the first in a two-part series in which we extend non-relativistic stochastic mechanics, in the ZSM formulation [1, 2], to semiclassical Newtonian gravity (ZSM-Newton) and semiclassical Newtonian electrodynamics (ZSM-Coulomb), under the assumption that the gravitational and electromagnetic fields are fundamentally classical (i.e., not independently quantized fields). Our key findings are: (1) a derivation of the usual $N$-particle Schr{\"o}dinger equation for many particles interacting through operator-valued gravitational or Coulomb potentials, and (2) recovery of the `single-body' Schr{\"o}dinger-Newton and Schr{\"o}dinger-Coulomb equations as mean-field equations valid for systems of gravitationally and electrostatically interacting identical particles, respectively, in the weak-coupling large N limit. We also compare ZSM-Newton/Coulomb to semiclassical Newtonian gravity/electrodynamics approaches based on standard quantum theory, dynamical collapse theories, and the de Broglie-Bohm theory. |
2011.01982 | Bekir Can L\"utf\"uo\u{g}lu | B. Hamil and B. C. L\"utf\"uo\u{g}lu | Effect of the modified Heisenberg algebra on the Black hole
thermodynamics | 11 pages, 7 figures | EPL 133 30003 (2021) | 10.1209/0295-5075/133/30003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter, we introduce two new forms of uncertainty relations by
extending the usual Heisenberg algebra with higher terms. Within these
scenarios, at first, we study on the Unruh temperature. We find that the Unruh
temperature increases in one of the new forms while it decreases in the other
form. Next, we explore the thermodynamic properties of a Schwarzschild black
hole by relying on these two new forms of the Heisenberg uncertainty relation.
We present the modifications in the mass-temperature, specific heat, and
entropy functions of the black hole according to the extension parameters.
| [
{
"created": "Tue, 3 Nov 2020 19:57:31 GMT",
"version": "v1"
}
] | 2021-04-13 | [
[
"Hamil",
"B.",
""
],
[
"Lütfüoğlu",
"B. C.",
""
]
] | In this letter, we introduce two new forms of uncertainty relations by extending the usual Heisenberg algebra with higher terms. Within these scenarios, at first, we study on the Unruh temperature. We find that the Unruh temperature increases in one of the new forms while it decreases in the other form. Next, we explore the thermodynamic properties of a Schwarzschild black hole by relying on these two new forms of the Heisenberg uncertainty relation. We present the modifications in the mass-temperature, specific heat, and entropy functions of the black hole according to the extension parameters. |
1204.4918 | Eduardo Martin-Martinez | Eduardo Martin-Martinez and Nicolas C. Menicucci | Cosmological quantum entanglement | 23 pages, 2 figures. v2 Added journal reference and minor changes to
match the published version | Class. Quantum Grav. 29 224003 (2012) | 10.1088/0264-9381/29/22/224003 | null | gr-qc astro-ph.CO quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review recent literature on the connection between quantum entanglement
and cosmology, with an emphasis on the context of expanding universes. We
discuss recent theoretical results reporting on the production of entanglement
in quantum fields due to the expansion of the underlying spacetime. We explore
how these results are affected by the statistics of the field (bosonic or
fermionic), the type of expansion (de Sitter or asymptotically stationary), and
the coupling to spacetime curvature (conformal or minimal). We then consider
the extraction of entanglement from a quantum field by coupling to local
detectors and how this procedure can be used to distinguish curvature from
heating by their entanglement signature. We review the role played by quantum
fluctuations in the early universe in nucleating the formation of galaxies and
other cosmic structures through their conversion into classical density
anisotropies during and after inflation. We report on current literature
attempting to account for this transition in a rigorous way and discuss the
importance of entanglement and decoherence in this process. We conclude with
some prospects for further theoretical and experimental research in this area.
These include extensions of current theoretical efforts, possible future
observational pursuits, and experimental analogues that emulate these cosmic
effects in a laboratory setting.
| [
{
"created": "Sun, 22 Apr 2012 17:31:16 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Oct 2012 03:01:58 GMT",
"version": "v2"
}
] | 2015-03-20 | [
[
"Martin-Martinez",
"Eduardo",
""
],
[
"Menicucci",
"Nicolas C.",
""
]
] | We review recent literature on the connection between quantum entanglement and cosmology, with an emphasis on the context of expanding universes. We discuss recent theoretical results reporting on the production of entanglement in quantum fields due to the expansion of the underlying spacetime. We explore how these results are affected by the statistics of the field (bosonic or fermionic), the type of expansion (de Sitter or asymptotically stationary), and the coupling to spacetime curvature (conformal or minimal). We then consider the extraction of entanglement from a quantum field by coupling to local detectors and how this procedure can be used to distinguish curvature from heating by their entanglement signature. We review the role played by quantum fluctuations in the early universe in nucleating the formation of galaxies and other cosmic structures through their conversion into classical density anisotropies during and after inflation. We report on current literature attempting to account for this transition in a rigorous way and discuss the importance of entanglement and decoherence in this process. We conclude with some prospects for further theoretical and experimental research in this area. These include extensions of current theoretical efforts, possible future observational pursuits, and experimental analogues that emulate these cosmic effects in a laboratory setting. |
1302.6186 | Morgan Le Delliou | Jos\'e P. Mimoso, Morgan Le Delliou and Filipe C. Mena | Local conditions separating expansion from collapse in spherically
symmetric models with anisotropic pressures | 15pp, 2 figs. RevTeX 4.1, corrected typo in acknowledgements | null | 10.1103/PhysRevD.88.043501 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate spherically symmetric spacetimes with an anisotropic fluid and
discuss the existence and stability of a dividing shell separating expanding
and collapsing regions. We resort to a 3+1 splitting and obtain gauge invariant
conditions relating intrinsic spacetimes quantities to properties of the matter
source. We find that the dividing shell is defined by a generalization of the
Tolman-Oppenheimer-Volkoff equilibrium condition. The latter establishes a
balance between the pressure gradients, both isotropic and anisotropic, and the
strength of the fields induced by the Misner-Sharp mass inside the separating
shell and by the pressure fluxes. This defines a local equilibrium condition,
but conveys also a non-local character given the definition of the Misner-Sharp
mass. By the same token, it is also a generalized thermodynamical equation of
state as usually interpreted for the perfect fluid case, which now has the
novel feature of involving both the isotropic and the anisotropic stress. We
have cast the governing equations in terms of local, gauge invariant quantities
which are revealing of the role played by the anisotropic pressures and
inhomogeneous electric part of the Weyl tensor. We analyse a particular
solution with dust and radiation that provides an illustration of our
conditions. In addition, our gauge invariant formalism not only encompasses the
cracking process from Herrera and coworkers but also reveals transparently the
interplay and importance of the shear and of the anisotropic stresses.
| [
{
"created": "Mon, 25 Feb 2013 18:41:31 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Mar 2013 19:00:55 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Mar 2013 16:01:19 GMT",
"version": "v3"
}
] | 2015-06-15 | [
[
"Mimoso",
"José P.",
""
],
[
"Delliou",
"Morgan Le",
""
],
[
"Mena",
"Filipe C.",
""
]
] | We investigate spherically symmetric spacetimes with an anisotropic fluid and discuss the existence and stability of a dividing shell separating expanding and collapsing regions. We resort to a 3+1 splitting and obtain gauge invariant conditions relating intrinsic spacetimes quantities to properties of the matter source. We find that the dividing shell is defined by a generalization of the Tolman-Oppenheimer-Volkoff equilibrium condition. The latter establishes a balance between the pressure gradients, both isotropic and anisotropic, and the strength of the fields induced by the Misner-Sharp mass inside the separating shell and by the pressure fluxes. This defines a local equilibrium condition, but conveys also a non-local character given the definition of the Misner-Sharp mass. By the same token, it is also a generalized thermodynamical equation of state as usually interpreted for the perfect fluid case, which now has the novel feature of involving both the isotropic and the anisotropic stress. We have cast the governing equations in terms of local, gauge invariant quantities which are revealing of the role played by the anisotropic pressures and inhomogeneous electric part of the Weyl tensor. We analyse a particular solution with dust and radiation that provides an illustration of our conditions. In addition, our gauge invariant formalism not only encompasses the cracking process from Herrera and coworkers but also reveals transparently the interplay and importance of the shear and of the anisotropic stresses. |
1804.02010 | Oldrich Semerak | P. Kotla\v{r}\'ik, O. Semer\'ak, P. \v{C}\'i\v{z}ek | Schwarzschild black hole encircled by a rotating thin disc: Properties
of perturbative solution | 14 pages, 7 figures | Physical Review D 97 (2018) 084006 | 10.1103/PhysRevD.97.084006 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In ApJ (1974), Will solved the perturbation of a Schwarzschild black hole due
to a slowly rotating light concentric thin ring, using Green's functions
expressed as infinite-sum expansions in multipoles and in the small mass and
rotational parameters. In a previous paper (ApJS 2017, Paper I), we expressed
the Green functions in closed form containing elliptic integrals, leaving just
summation over the mass expansion. Such a form is more practical for numerical
evaluation, but mainly for generalizing the problem to extended sources where
the Green functions have to be integrated over the source. We exemplified the
method by computing explicitly the first-order perturbation due to a slowly
rotating thin disc lying between two finite radii. After finding basic
parameters of the system -- mass and angular momentum of the black hole and of
the disc -- we now add further properties, namely those which reveal how the
disc gravity influences geometry of the black-hole horizon and those of
circular equatorial geodesics (specifically, radii of the photon, marginally
bound and marginally stable orbits). We also realize that, in the linear order,
no ergosphere occurs and the central singularity remains point-like, and check
the implications of natural physical requirements (energy conditions and
subluminal restriction on orbital speed) for the single-stream as well as
counter-rotating double-stream interpretations of the disc.
| [
{
"created": "Thu, 5 Apr 2018 18:18:37 GMT",
"version": "v1"
}
] | 2018-04-09 | [
[
"Kotlařík",
"P.",
""
],
[
"Semerák",
"O.",
""
],
[
"Čížek",
"P.",
""
]
] | In ApJ (1974), Will solved the perturbation of a Schwarzschild black hole due to a slowly rotating light concentric thin ring, using Green's functions expressed as infinite-sum expansions in multipoles and in the small mass and rotational parameters. In a previous paper (ApJS 2017, Paper I), we expressed the Green functions in closed form containing elliptic integrals, leaving just summation over the mass expansion. Such a form is more practical for numerical evaluation, but mainly for generalizing the problem to extended sources where the Green functions have to be integrated over the source. We exemplified the method by computing explicitly the first-order perturbation due to a slowly rotating thin disc lying between two finite radii. After finding basic parameters of the system -- mass and angular momentum of the black hole and of the disc -- we now add further properties, namely those which reveal how the disc gravity influences geometry of the black-hole horizon and those of circular equatorial geodesics (specifically, radii of the photon, marginally bound and marginally stable orbits). We also realize that, in the linear order, no ergosphere occurs and the central singularity remains point-like, and check the implications of natural physical requirements (energy conditions and subluminal restriction on orbital speed) for the single-stream as well as counter-rotating double-stream interpretations of the disc. |
2105.04145 | Umananda Dev Goswami | Jyatsnasree Bora and Umananda Dev Goswami | Radial oscillations and gravitational wave echoes of strange stars with
nonvanishing lambda | 15 pages, 10 figures | Astroparticle Physics 143 (2022) 102744 | 10.1016/j.astropartphys.2022.102744 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study the effect of the cosmological constant on radial oscillations and
gravitational wave echoes (GWEs) of non-rotating strange stars. To depict
strange star configurations we used two forms of equations of state (EoSs),
viz., the MIT Bag model EoS and the linear EoS. By taking a range of positive
and negative values of cosmological constant, the corresponding mass-radius
relationships for these stars have been calculated. For this purpose, first we
solved the Tolman-Oppenheimer-Volkoff (TOV) equations with a non-zero
cosmological constant and then we solved the pressure and radial perturbation
equations arising due to radial oscillations. The eigenfrequencies of the
fundamental $f$-mode and first 22 pressure $p$-modes are calculated for each of
these EoSs. Again considering the remnant of the GW170817 event as a strange
star, the echo frequencies emitted by such stars in presence of the
cosmological constant are computed. From these numerical calculations, we have
inferred relations between cosmological constant and mode frequency, structural
parameters, GWE frequencies of strange stars. Our results show that for strange
stars, the effective range of cosmological constant is $10^{-15}\,
\mbox{cm}^{-2} \le\,\Lambda\, \le 3\times 10^{-13}\, \mbox{cm}^{-2}$.
| [
{
"created": "Mon, 10 May 2021 06:57:32 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Jun 2022 12:33:30 GMT",
"version": "v2"
}
] | 2022-06-23 | [
[
"Bora",
"Jyatsnasree",
""
],
[
"Goswami",
"Umananda Dev",
""
]
] | We study the effect of the cosmological constant on radial oscillations and gravitational wave echoes (GWEs) of non-rotating strange stars. To depict strange star configurations we used two forms of equations of state (EoSs), viz., the MIT Bag model EoS and the linear EoS. By taking a range of positive and negative values of cosmological constant, the corresponding mass-radius relationships for these stars have been calculated. For this purpose, first we solved the Tolman-Oppenheimer-Volkoff (TOV) equations with a non-zero cosmological constant and then we solved the pressure and radial perturbation equations arising due to radial oscillations. The eigenfrequencies of the fundamental $f$-mode and first 22 pressure $p$-modes are calculated for each of these EoSs. Again considering the remnant of the GW170817 event as a strange star, the echo frequencies emitted by such stars in presence of the cosmological constant are computed. From these numerical calculations, we have inferred relations between cosmological constant and mode frequency, structural parameters, GWE frequencies of strange stars. Our results show that for strange stars, the effective range of cosmological constant is $10^{-15}\, \mbox{cm}^{-2} \le\,\Lambda\, \le 3\times 10^{-13}\, \mbox{cm}^{-2}$. |
gr-qc/0310131 | Jos\'e Wadih Maluf | A. A. Sousa and J. W. Maluf | Gravitomagnetic effect and spin-torsion coupling | 20 pages, no figures, accepted for publication in Gen. Rel. Grav | Gen.Rel.Grav. 36 (2004) 967-982 | 10.1023/B:GERG.0000018084.58267.b9 | null | gr-qc | null | We study the gravitomagnetic effect in the context of absolute parallelism
with the use of a modified geodesic equation via a free parameter b. We
calculate the time difference in two atomic clocks orbiting the Earth in
opposite directions and find a small correction due to the coupling between the
torsion of the spacetime and the internal structure of atomic clocks measured
by the free parameter.
| [
{
"created": "Thu, 30 Oct 2003 17:49:48 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Sousa",
"A. A.",
""
],
[
"Maluf",
"J. W.",
""
]
] | We study the gravitomagnetic effect in the context of absolute parallelism with the use of a modified geodesic equation via a free parameter b. We calculate the time difference in two atomic clocks orbiting the Earth in opposite directions and find a small correction due to the coupling between the torsion of the spacetime and the internal structure of atomic clocks measured by the free parameter. |
1310.7921 | Parthapratim Pradhan | Parthapratim Pradhan | Area Products and Mass Formula for Kerr-Newman-Taub-NUT Space-time | Accepted for publication in Modern Physics Letters A | Modern Physics Letters A, Vol. 30, No. 35 (2015) 1550170 | 10.1142/S0217732315501709 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive area product, entropy product, area sum and entropy sum of the
event horizon and Cauchy horizons for
Kerr-Newman-Taub-NUT(Newman-Unti-Tamburino) black hole in four dimensional
\emph{Lorentzian geometry}. We observe that these thermodynamic products are
\emph{not} universal(mass-independence) for this black hole(BH), whereas for
Kerr-Newman(KN) BH such products are universal (mass-independence). We also
examine the entropy sum and area sum. It is shown that they all are depends on
mass, charge and NUT parameter of the back ground space-time. Thus we can
conclude that the universal(mass-independence) behaviour of area product and
entropy product, area sum and entropy sum for Kerr-Newman-Taub-NUT(KNTN) BH
fails and which is also quite different from KN BH. We further show that the
KNTN BH do not possess \emph{first law of BH thermodynamics } and \emph
{Smarr-Gibbs-Duhem } relations, and that such relations are unlikely in the KN
case. The failure of these aforementioned features are due to presence of the
non-trivial NUT charge which makes the space-time to be asymptotically
non-flat, in contrast with KN BH. The another reason of the failure is that
Lorentzian KNTN geometry contains \emph{Dirac-Misner type singularity}, which
is a manifestation of a non-trivial topological twist of the manifold. The BH
\emph{mass formula} and \emph{Christodoulou-Ruffini mass formula} for KNTN
black holes are also derived. Finally, we compute the area bound which is just
Penrose like inequality for event horizon. From area bound we derive entropy
bound. These thermodynamic products on the multi horizon playing a crucial role
in BH thermodynamics to understand the microscopic nature of BH entropy.
| [
{
"created": "Tue, 29 Oct 2013 18:54:03 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Aug 2014 10:50:20 GMT",
"version": "v2"
},
{
"created": "Thu, 16 Jul 2015 05:43:04 GMT",
"version": "v3"
}
] | 2015-09-15 | [
[
"Pradhan",
"Parthapratim",
""
]
] | We derive area product, entropy product, area sum and entropy sum of the event horizon and Cauchy horizons for Kerr-Newman-Taub-NUT(Newman-Unti-Tamburino) black hole in four dimensional \emph{Lorentzian geometry}. We observe that these thermodynamic products are \emph{not} universal(mass-independence) for this black hole(BH), whereas for Kerr-Newman(KN) BH such products are universal (mass-independence). We also examine the entropy sum and area sum. It is shown that they all are depends on mass, charge and NUT parameter of the back ground space-time. Thus we can conclude that the universal(mass-independence) behaviour of area product and entropy product, area sum and entropy sum for Kerr-Newman-Taub-NUT(KNTN) BH fails and which is also quite different from KN BH. We further show that the KNTN BH do not possess \emph{first law of BH thermodynamics } and \emph {Smarr-Gibbs-Duhem } relations, and that such relations are unlikely in the KN case. The failure of these aforementioned features are due to presence of the non-trivial NUT charge which makes the space-time to be asymptotically non-flat, in contrast with KN BH. The another reason of the failure is that Lorentzian KNTN geometry contains \emph{Dirac-Misner type singularity}, which is a manifestation of a non-trivial topological twist of the manifold. The BH \emph{mass formula} and \emph{Christodoulou-Ruffini mass formula} for KNTN black holes are also derived. Finally, we compute the area bound which is just Penrose like inequality for event horizon. From area bound we derive entropy bound. These thermodynamic products on the multi horizon playing a crucial role in BH thermodynamics to understand the microscopic nature of BH entropy. |
gr-qc/0504131 | Aleksandar Mikovic | A. Mikovic | Tetrade Spin Foam Model | 13 pages | null | null | null | gr-qc | null | We propose a spin foam model of four-dimensional quantum gravity which is
based on the integration of the tetrads in the path integral for the Palatini
action of General Relativity. In the Euclidian gravity case we show that the
model can be understood as a modification of the Barrett-Crane spin foam model.
Fermionic matter can be coupled by using the path integral with sources for the
tetrads and the spin connection, and the corresponding state sum is based on a
spin foam where both the edges and the faces are colored independently with the
irreducible representations of the spacetime rotations group.
| [
{
"created": "Tue, 26 Apr 2005 14:12:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mikovic",
"A.",
""
]
] | We propose a spin foam model of four-dimensional quantum gravity which is based on the integration of the tetrads in the path integral for the Palatini action of General Relativity. In the Euclidian gravity case we show that the model can be understood as a modification of the Barrett-Crane spin foam model. Fermionic matter can be coupled by using the path integral with sources for the tetrads and the spin connection, and the corresponding state sum is based on a spin foam where both the edges and the faces are colored independently with the irreducible representations of the spacetime rotations group. |
1312.7112 | Alexey Smirnov | Alexey L. Smirnov | Interacting thin shells in the interior of a Reissner-Nordstrom black
hole | 24 pages, 7 figures, minor typos corrected | Gen.Rel.Grav. 46 (2014) 3, 1676 | 10.1007/s10714-014-1676-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we consider some applications of the extended
Dray-t'Hooft-Redmount relation. In particular, using this relation, we study
geometries of interacting thin shells near the future Cauchy horizon of a
Reissner-Nordstrom black hole.
| [
{
"created": "Thu, 26 Dec 2013 14:23:58 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Nov 2014 09:18:27 GMT",
"version": "v2"
}
] | 2014-11-26 | [
[
"Smirnov",
"Alexey L.",
""
]
] | In this paper we consider some applications of the extended Dray-t'Hooft-Redmount relation. In particular, using this relation, we study geometries of interacting thin shells near the future Cauchy horizon of a Reissner-Nordstrom black hole. |
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