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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1609.06794 | Antonino Flachi | Antonino Flachi, Gon\c{c}alo M. Quinta, Jos\'e P. S. Lemos | Black Hole Quantum Vacuum Polarization in Higher Dimensions | 14 pages, 2 Figures | Phys. Rev. D 94, 105001 (2016) | 10.1103/PhysRevD.94.105001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The goal of this paper is to extend to higher dimensionality the methods and
computations of vacuum polarization effects in black hole spacetimes. We focus
our attention on the case of five dimensional Schwarzschild-Tangherlini black
holes, for which we adapt the general method initially developed by Candelas
and later refined by Anderson and others. We make use of point splitting
regularization and of the WKB approximation to extract the divergences occuring
in the coincidence limit of the Green function and, after calculating the
counter-terms using the Schwinger - De Witt expansion, we explicitly prove the
cancellation of the divergences and the regularity of the vacuum polarization
once counter-terms are added up. We finally handle numerically the renormalized
expression of the vacuum polarization. As a check on the method we also prove
the regularity of the vacuum polarization in the six dimensional case in the
large mass limit.
| [
{
"created": "Thu, 22 Sep 2016 01:25:20 GMT",
"version": "v1"
}
] | 2016-11-09 | [
[
"Flachi",
"Antonino",
""
],
[
"Quinta",
"Gonçalo M.",
""
],
[
"Lemos",
"José P. S.",
""
]
] | The goal of this paper is to extend to higher dimensionality the methods and computations of vacuum polarization effects in black hole spacetimes. We focus our attention on the case of five dimensional Schwarzschild-Tangherlini black holes, for which we adapt the general method initially developed by Candelas and later refined by Anderson and others. We make use of point splitting regularization and of the WKB approximation to extract the divergences occuring in the coincidence limit of the Green function and, after calculating the counter-terms using the Schwinger - De Witt expansion, we explicitly prove the cancellation of the divergences and the regularity of the vacuum polarization once counter-terms are added up. We finally handle numerically the renormalized expression of the vacuum polarization. As a check on the method we also prove the regularity of the vacuum polarization in the six dimensional case in the large mass limit. |
0905.0247 | Mahmood Roshan | Mahmood Roshan and Fatimah Shojai | Tracking $f(R)$ cosmology | 2 figures. To appear in Phys. Rev. D | Phys.Rev.D79:103510,2009 | 10.1103/PhysRevD.79.103510 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Metric $f(R)$ gravity theories are conformally equivalent to models of
quintessence in which matter is coupled to dark energy. We derive a condition
for stable tracker solution for metric $f(R)$ gravity in the Einstein frame. We
find that tracker solutions with $-0.361<\omega_{\varphi}<1$ exist if
$0<\Gamma<0.217$ and $\frac{d}{dt} \ln f'(\tilde{R})>0$, where
$\Gamma=\frac{V_{\varphi\varphi}V}{V_{\varphi}^{2}}$ is dimensionless function,
$\omega_{\varphi}$ is the equation of state parameter of the scalar field and
$\tilde{R}$ refers to Jordan frame's curvature scalar. Also, we show that there
exists $f(\tilde{R})$ gravity models which have tracking behavior in the
Einstein frame and so the curvature of space time is decreasing with time while
they lead to the solutions in the Jordan frame that the curvature of space time
can be increasing with time.
| [
{
"created": "Sun, 3 May 2009 07:11:10 GMT",
"version": "v1"
}
] | 2010-04-14 | [
[
"Roshan",
"Mahmood",
""
],
[
"Shojai",
"Fatimah",
""
]
] | Metric $f(R)$ gravity theories are conformally equivalent to models of quintessence in which matter is coupled to dark energy. We derive a condition for stable tracker solution for metric $f(R)$ gravity in the Einstein frame. We find that tracker solutions with $-0.361<\omega_{\varphi}<1$ exist if $0<\Gamma<0.217$ and $\frac{d}{dt} \ln f'(\tilde{R})>0$, where $\Gamma=\frac{V_{\varphi\varphi}V}{V_{\varphi}^{2}}$ is dimensionless function, $\omega_{\varphi}$ is the equation of state parameter of the scalar field and $\tilde{R}$ refers to Jordan frame's curvature scalar. Also, we show that there exists $f(\tilde{R})$ gravity models which have tracking behavior in the Einstein frame and so the curvature of space time is decreasing with time while they lead to the solutions in the Jordan frame that the curvature of space time can be increasing with time. |
1207.1049 | Babak Vakili | B. Vakili and M. A. Gorji | Thermostatistics with minimal length uncertainty relation | 16 pages, 1 figure, minor changes | JSTAT (2012) P10013 | null | null | gr-qc cond-mat.stat-mech quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Existence of minimal length is suggested in any quantum theory of gravity
such as string theory, double special relativity and black hole physics. One
way to impose minimal length is deforming Heisenberg algebra in phase space
which is called Generalized Uncertainty Principle (GUP). In this paper, we
develop statistical mechanics in GUP framework. Our method is quite general and
does not need to fix the generalized coordinates and momenta. We define general
transformation in phase space which transforms usual Heisenberg algebra to a
deformed one. In this method, quantum gravity effects only acts on the
structure of phase space and we relate these effects to the density of states.
We find an interesting phenomenon in Maxwell-Boltzmann statistics which has not
a classical analogy. We show that there is an upper bound for the number of
excited particles in the limit of high temperature which implies to the
condensation. Also we study modification of Bose-Einstein condensation and the
completely degenerate gas.
| [
{
"created": "Wed, 4 Jul 2012 16:19:41 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Oct 2012 16:32:33 GMT",
"version": "v2"
}
] | 2012-10-18 | [
[
"Vakili",
"B.",
""
],
[
"Gorji",
"M. A.",
""
]
] | Existence of minimal length is suggested in any quantum theory of gravity such as string theory, double special relativity and black hole physics. One way to impose minimal length is deforming Heisenberg algebra in phase space which is called Generalized Uncertainty Principle (GUP). In this paper, we develop statistical mechanics in GUP framework. Our method is quite general and does not need to fix the generalized coordinates and momenta. We define general transformation in phase space which transforms usual Heisenberg algebra to a deformed one. In this method, quantum gravity effects only acts on the structure of phase space and we relate these effects to the density of states. We find an interesting phenomenon in Maxwell-Boltzmann statistics which has not a classical analogy. We show that there is an upper bound for the number of excited particles in the limit of high temperature which implies to the condensation. Also we study modification of Bose-Einstein condensation and the completely degenerate gas. |
1812.05595 | Pasquale Bosso | Pasquale Bosso, Saurya Das | Lorentz invariant mass and length scales | 10 pages | Int.J.Mod.Phys. D, Vol. 28, No. 04, 1950068 (2019) | 10.1142/S0218271819500688 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the standard Lorentz transformations admit an invariant mass
(length) scale, such as the Planck scale. In other words, the frame
independence of such scale is built-in within those transformations, and one
does not need to invoke the principle of relativity for their invariance. This
automatically ensures the frame-independence of the spectrum of geometrical
operators in quantum gravity. Furthermore, we show that the above predicts a
small but measurable difference between the inertial and gravitational mass of
any object, regardless of its size or whether it is elementary or composite.
| [
{
"created": "Thu, 13 Dec 2018 18:59:46 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Jan 2019 23:54:39 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Apr 2019 17:48:53 GMT",
"version": "v3"
}
] | 2019-04-17 | [
[
"Bosso",
"Pasquale",
""
],
[
"Das",
"Saurya",
""
]
] | We show that the standard Lorentz transformations admit an invariant mass (length) scale, such as the Planck scale. In other words, the frame independence of such scale is built-in within those transformations, and one does not need to invoke the principle of relativity for their invariance. This automatically ensures the frame-independence of the spectrum of geometrical operators in quantum gravity. Furthermore, we show that the above predicts a small but measurable difference between the inertial and gravitational mass of any object, regardless of its size or whether it is elementary or composite. |
2107.12163 | Riasat Ali | Riasat Ali, Rimsha Babar, Muhammad Asgher, Syed Asif Ali Shah | Gravity Effects on Hawking Radiation from Charged Black Strings in
Rastall Theory | 10 pages, 4 figures, version accepted for publication in Annals of
Physics | null | 10.1016/j.aop.2021.168572 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The Rastall theory of gravity is the generalized form of the Einstein theory
which describes the conservation law of energy and momentum tensor. In our
work, we compute the charged black strings solution in the background of
Rastall theory by applying the Newman-Janis approach. After computing the
charged black strings solution in the background of Rastall theory, we study
the thermodynamical property (i.e., Hawking temperature) for the charged black
strings. Furthermore, we investigate the graphical representation of Hawking
temperature via event horizon to check the stability conditions of charged
black strings under the influence of Rastall theory. Moreover, we examine the
modified Hawking temperature for charged black strings in Rastall theory by
taking into account the quantum gravity effects. We also discuss the physical
state of charged black strings under the effects of quantum gravity and spin
parameter (appears due to Rastall theory in charged black strings solution).
| [
{
"created": "Mon, 26 Jul 2021 12:30:43 GMT",
"version": "v1"
}
] | 2021-08-25 | [
[
"Ali",
"Riasat",
""
],
[
"Babar",
"Rimsha",
""
],
[
"Asgher",
"Muhammad",
""
],
[
"Shah",
"Syed Asif Ali",
""
]
] | The Rastall theory of gravity is the generalized form of the Einstein theory which describes the conservation law of energy and momentum tensor. In our work, we compute the charged black strings solution in the background of Rastall theory by applying the Newman-Janis approach. After computing the charged black strings solution in the background of Rastall theory, we study the thermodynamical property (i.e., Hawking temperature) for the charged black strings. Furthermore, we investigate the graphical representation of Hawking temperature via event horizon to check the stability conditions of charged black strings under the influence of Rastall theory. Moreover, we examine the modified Hawking temperature for charged black strings in Rastall theory by taking into account the quantum gravity effects. We also discuss the physical state of charged black strings under the effects of quantum gravity and spin parameter (appears due to Rastall theory in charged black strings solution). |
1905.10162 | Jorge Ovalle | L. Gabbanelli, J. Ovalle, A. Sotomayor, Z. Stuchlik, R. Casadio | A causal Schwarzschild-de Sitter interior solution by gravitational
decoupling | 15 pages, 6 figures | null | 10.1140/epjc/s10052-019-7022-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We employ the minimal geometric deformation approach to gravitational
decoupling (MGD- decoupling) in order to build an exact anisotropic version of
the Schwarzschild interior solution in a space-time with cosmological constant.
Contrary to the well-known Schwarzschild interior, the matter density in the
new solution is not uniform and possesses subluminal sound speed. It therefore
satisfies all standard physical requirements for a candidate astrophysical
object.
| [
{
"created": "Fri, 24 May 2019 11:42:52 GMT",
"version": "v1"
}
] | 2019-06-26 | [
[
"Gabbanelli",
"L.",
""
],
[
"Ovalle",
"J.",
""
],
[
"Sotomayor",
"A.",
""
],
[
"Stuchlik",
"Z.",
""
],
[
"Casadio",
"R.",
""
]
] | We employ the minimal geometric deformation approach to gravitational decoupling (MGD- decoupling) in order to build an exact anisotropic version of the Schwarzschild interior solution in a space-time with cosmological constant. Contrary to the well-known Schwarzschild interior, the matter density in the new solution is not uniform and possesses subluminal sound speed. It therefore satisfies all standard physical requirements for a candidate astrophysical object. |
gr-qc/0404040 | Guihua Tian | Liao Liu, Zheng Zhao | Could the Gravitons Have Rest Masses? | null | null | null | null | gr-qc | null | If the cosmological constant $\Lambda $ can not be neglected, we will show in
this short report, that graviton should have a rest mass $m_g=\sqrt{2\Lambda
}=\sqrt{2\Lambda}\hbar c^{-1}$ different from zero.
| [
{
"created": "Fri, 9 Apr 2004 06:13:18 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Liu",
"Liao",
""
],
[
"Zhao",
"Zheng",
""
]
] | If the cosmological constant $\Lambda $ can not be neglected, we will show in this short report, that graviton should have a rest mass $m_g=\sqrt{2\Lambda }=\sqrt{2\Lambda}\hbar c^{-1}$ different from zero. |
1302.0466 | Mohamad Atazadeh | K. Atazadeh, F. Darabi | Energy conditions in $f(R,G)$ gravity | 10 pages, 6 figures. arXiv admin note: text overlap with
arXiv:1011.4159, arXiv:1012.0953 by other authors | Gen. Relativ. Gravit. (2014) 46:1664 | 10.1007/s10714-014-1664-8 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/3.0/ | Modified gravity is one of the most favorable candidates for explaining the
current accelerating expansion of the Universe. In this regard, we study the
viability of an alternative gravitational theory, namely $f(R,G)$, by imposing
energy conditions. We consider two forms of $f(R,G)$, commonly discussed in the
literature, which account for the stability of cosmological solutions. We
construct the inequalities obtained by energy conditions and specifically apply
the weak energy condition using the recent estimated values of the Hubble,
deceleration, jerk and snap parameters to probe the viability of the
above-mentioned forms of $f(R, G)$.
| [
{
"created": "Sun, 3 Feb 2013 08:51:10 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Jan 2014 05:01:10 GMT",
"version": "v2"
},
{
"created": "Wed, 22 Jan 2014 19:43:31 GMT",
"version": "v3"
},
{
"created": "Wed, 29 Jan 2014 20:16:08 GMT",
"version": "v4"
}
] | 2014-01-30 | [
[
"Atazadeh",
"K.",
""
],
[
"Darabi",
"F.",
""
]
] | Modified gravity is one of the most favorable candidates for explaining the current accelerating expansion of the Universe. In this regard, we study the viability of an alternative gravitational theory, namely $f(R,G)$, by imposing energy conditions. We consider two forms of $f(R,G)$, commonly discussed in the literature, which account for the stability of cosmological solutions. We construct the inequalities obtained by energy conditions and specifically apply the weak energy condition using the recent estimated values of the Hubble, deceleration, jerk and snap parameters to probe the viability of the above-mentioned forms of $f(R, G)$. |
gr-qc/0406040 | Jian Qi Shen | Jian Qi Shen | A note: graviton spin, gravitomagnetic fields and self-interaction of
non-inertial frame of reference | 8 pages, 0 figure, Latex. It is a supplement to the paper: Purely
gravitational generalization of spin-rotation couplings, J.Q. Shen, Phys.
Rev. D vol.70: 067501 (2004) | null | null | null | gr-qc | null | Three weak gravitational effects associated with the gravitomagnetic fields
are taken into account in this paper: (i) we discuss the background Lorentz
transformation and gauge transformation in a linearized gravity theory, and
obtain the expression for the spin of gravitational field by using the
canonical procedure and Noether theorem; (ii) we point out that by using the
coordinate transformation from the fixed frame to the rotating frame, it is
found that the nature of Mashhoon's spin-rotation coupling is in fact an
interaction between the gravitomagnetic moment of a spinning particle and the
gravitomagnetic fields. The fact that the rotational angular velocity of a
rotating frame can be viewed as a gravitomagnetic field is demonstrated; (iii)
a purely gravitational generalization of Mashhoon's spin-rotation coupling,
i.e., the interaction of the graviton spin with the gravitomagnetic fields is
actually a self-interaction of the spacetime (gravitational fields). In the
present paper, we will show that this self-interaction will also arise in a
non-inertial frame of reference itself: specifically, a rotating frame that
experiences a fluctuation of its rotational frequency (i.e., the change in the
rotational angular frequency) will undergo a weak self-interaction. The
self-interaction of the rotating frame, which can also be called the
self-interaction of the spacetime of the rotating frame, is just the
non-inertial generalization of the interaction of the graviton spin with the
gravitomagnetic fields.
| [
{
"created": "Thu, 10 Jun 2004 11:16:40 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Aug 2004 07:33:11 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Shen",
"Jian Qi",
""
]
] | Three weak gravitational effects associated with the gravitomagnetic fields are taken into account in this paper: (i) we discuss the background Lorentz transformation and gauge transformation in a linearized gravity theory, and obtain the expression for the spin of gravitational field by using the canonical procedure and Noether theorem; (ii) we point out that by using the coordinate transformation from the fixed frame to the rotating frame, it is found that the nature of Mashhoon's spin-rotation coupling is in fact an interaction between the gravitomagnetic moment of a spinning particle and the gravitomagnetic fields. The fact that the rotational angular velocity of a rotating frame can be viewed as a gravitomagnetic field is demonstrated; (iii) a purely gravitational generalization of Mashhoon's spin-rotation coupling, i.e., the interaction of the graviton spin with the gravitomagnetic fields is actually a self-interaction of the spacetime (gravitational fields). In the present paper, we will show that this self-interaction will also arise in a non-inertial frame of reference itself: specifically, a rotating frame that experiences a fluctuation of its rotational frequency (i.e., the change in the rotational angular frequency) will undergo a weak self-interaction. The self-interaction of the rotating frame, which can also be called the self-interaction of the spacetime of the rotating frame, is just the non-inertial generalization of the interaction of the graviton spin with the gravitomagnetic fields. |
gr-qc/0610131 | Alessandro Nagar | Alessandro Nagar, Olindo Zanotti, Jose A. Font, Luciano Rezzolla | On the accretion-induced QNM excitation of a Schwarzschild black hole | 15 pages, 12 figures, revised version. To appear in Phys. Rev. D | Phys.Rev.D75:044016,2007 | 10.1103/PhysRevD.75.044016 | null | gr-qc astro-ph | null | By combining the numerical solution of the nonlinear hydrodynamics equations
with the solution of the linear inhomogeneous Zerilli-Moncrief and
Regge-Wheeler equations we investigate the properties of the gravitational
radiation emitted during the axisymmetric accretion of matter onto a
Schwarzschild black hole. The matter models considered include quadrupolar dust
shells and thick accretion disks, permitting us to simulate situations which
may be encountered at the end stages of stellar gravitational collapse or
binary neutron star merger. We focus on the interference pattern appearing in
the energy spectra of the emitted gravitational waves and on the amount of
excitation of the quasi-normal modes of the accreting black hole. We show that,
quite generically in the presence of accretion, the black hole ringdown is not
a simple superposition of quasi-normal modes, although the fundamental mode is
usually present and often dominates the gravitational-wave signal. We interpret
this as due to backscattering of waves off the non-exponentially decaying part
of the black-hole potential and to the finite spatial extension of the
accreting matter. Our results suggest that the black-hole QNM contributions to
the full gravitational-wave signal should be extremely small and possibly not
detectable in generic astrophysical scenarios involving the accretion of
extended distributions of matter.
| [
{
"created": "Thu, 26 Oct 2006 23:40:37 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Feb 2007 10:42:19 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Nagar",
"Alessandro",
""
],
[
"Zanotti",
"Olindo",
""
],
[
"Font",
"Jose A.",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | By combining the numerical solution of the nonlinear hydrodynamics equations with the solution of the linear inhomogeneous Zerilli-Moncrief and Regge-Wheeler equations we investigate the properties of the gravitational radiation emitted during the axisymmetric accretion of matter onto a Schwarzschild black hole. The matter models considered include quadrupolar dust shells and thick accretion disks, permitting us to simulate situations which may be encountered at the end stages of stellar gravitational collapse or binary neutron star merger. We focus on the interference pattern appearing in the energy spectra of the emitted gravitational waves and on the amount of excitation of the quasi-normal modes of the accreting black hole. We show that, quite generically in the presence of accretion, the black hole ringdown is not a simple superposition of quasi-normal modes, although the fundamental mode is usually present and often dominates the gravitational-wave signal. We interpret this as due to backscattering of waves off the non-exponentially decaying part of the black-hole potential and to the finite spatial extension of the accreting matter. Our results suggest that the black-hole QNM contributions to the full gravitational-wave signal should be extremely small and possibly not detectable in generic astrophysical scenarios involving the accretion of extended distributions of matter. |
gr-qc/9701061 | Ali Mostafazadeh | Ali Mostafazadeh | Exact Semiclassical Evolutions in Relativistic and Nonrelativistic
Scalar Quantum Mechanics and Quantum Cosmology | Few minor corrections | Nucl.Phys. B509 (1998) 529-555 | 10.1016/S0550-3213(97)00617-2 | University of Alberta preprint no: Thy -97 | gr-qc hep-th quant-ph | null | The necessary and sufficient conditions for the exactness of the
semiclassical approximation for the solution of the Schr\"odinger and
Klein-Gordon equations are obtained. It is shown that the existence of an exact
semiclassical solution of the Schr\"odinger equation determines both the
semiclassical wave function and the interaction potential uniquely up to the
choice of the boundary conditions. This result also holds for the Klein-Gordon
equation. Its implications for the solution of the Wheeler-DeWitt equation for
the FRW scalar field minisuperspace models are discussed. In particular, exact
semiclassical solutions of the Wheeler-DeWitt equation for the case of massless
scalar field and exponential matter potentials are constructed. The existence
of exact semiclassical solutions for polynomial matter potentials of the form
$\lambda\phi^{2p}$ is also analyzed. It is shown that for p=1, 2 and 3,
right-going semiclassical solutions do not exist. A generalized semiclassical
perturbation expansion is also developed which is quite different from the
traditional $\hbar$ and $M_p^{-1}$-expansions.
| [
{
"created": "Tue, 28 Jan 1997 19:58:29 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Jan 1997 20:22:49 GMT",
"version": "v2"
},
{
"created": "Tue, 24 Jun 1997 20:14:23 GMT",
"version": "v3"
}
] | 2009-10-30 | [
[
"Mostafazadeh",
"Ali",
""
]
] | The necessary and sufficient conditions for the exactness of the semiclassical approximation for the solution of the Schr\"odinger and Klein-Gordon equations are obtained. It is shown that the existence of an exact semiclassical solution of the Schr\"odinger equation determines both the semiclassical wave function and the interaction potential uniquely up to the choice of the boundary conditions. This result also holds for the Klein-Gordon equation. Its implications for the solution of the Wheeler-DeWitt equation for the FRW scalar field minisuperspace models are discussed. In particular, exact semiclassical solutions of the Wheeler-DeWitt equation for the case of massless scalar field and exponential matter potentials are constructed. The existence of exact semiclassical solutions for polynomial matter potentials of the form $\lambda\phi^{2p}$ is also analyzed. It is shown that for p=1, 2 and 3, right-going semiclassical solutions do not exist. A generalized semiclassical perturbation expansion is also developed which is quite different from the traditional $\hbar$ and $M_p^{-1}$-expansions. |
gr-qc/0507083 | Slava G. Turyshev | James G. Williams, Slava G. Turyshev, and Dale H. Boggs | Lunar Laser Ranging Tests of the Equivalence Principle with the Earth
and Moon | 50 pages, 18 figures, 4 tables | Int.J.Mod.Phys.D18:1129-1175,2009 | 10.1142/S021827180901500X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A primary objective of the Lunar Laser Ranging (LLR) experiment is to provide
precise observations of the lunar orbit that contribute to a wide range of
science investigations. Time series of the highly accurate measurements of the
distance between the Earth and Moon provide unique information used to
determine whether, in accordance with the Equivalence Principle (EP), both of
these celestial bodies are falling towards the Sun at the same rate, despite
their different masses, compositions, and gravitational self-energies. Current
LLR solutions give $(-1.0 \pm 1.4) \times 10^{-13}$ for any possible inequality
in the ratios of the gravitational and inertial masses for the Earth and Moon,
$\Delta(M_G/M_I)$. This result, in combination with laboratory experiments on
the weak equivalence principle, yields a strong equivalence principle (SEP)
test of $\Delta(M_G/M_I)_{\tt SEP} = (-2.0 \pm 2.0) \times 10^{-13}$. Such an
accurate result allows other tests of gravitational theories. The result of the
SEP test translates into a value for the corresponding SEP violation parameter
$\eta$ of $(4.4 \pm 4.5)\times10^{-4}$, where $\eta = 4\beta -\gamma -3$ and
both $\gamma$ and $\beta$ are parametrized post-Newtonian (PPN) parameters. The
PPN parameter $\beta$ is determined to be $\beta - 1 = (1.2 \pm 1.1) \times
10^{-4}$. Focusing on the tests of the EP, we discuss the existing data, and
characterize the modeling and data analysis techniques. The robustness of the
LLR solutions is demonstrated with several different approaches that are
presented in the text. We emphasize that near-term improvements in the LLR
ranging accuracy will further advance the research of relativistic gravity in
the solar system, and, most notably, will continue to provide highly accurate
tests of the Equivalence Principle.
| [
{
"created": "Tue, 19 Jul 2005 07:05:34 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Jan 2009 07:32:05 GMT",
"version": "v2"
}
] | 2009-07-24 | [
[
"Williams",
"James G.",
""
],
[
"Turyshev",
"Slava G.",
""
],
[
"Boggs",
"Dale H.",
""
]
] | A primary objective of the Lunar Laser Ranging (LLR) experiment is to provide precise observations of the lunar orbit that contribute to a wide range of science investigations. Time series of the highly accurate measurements of the distance between the Earth and Moon provide unique information used to determine whether, in accordance with the Equivalence Principle (EP), both of these celestial bodies are falling towards the Sun at the same rate, despite their different masses, compositions, and gravitational self-energies. Current LLR solutions give $(-1.0 \pm 1.4) \times 10^{-13}$ for any possible inequality in the ratios of the gravitational and inertial masses for the Earth and Moon, $\Delta(M_G/M_I)$. This result, in combination with laboratory experiments on the weak equivalence principle, yields a strong equivalence principle (SEP) test of $\Delta(M_G/M_I)_{\tt SEP} = (-2.0 \pm 2.0) \times 10^{-13}$. Such an accurate result allows other tests of gravitational theories. The result of the SEP test translates into a value for the corresponding SEP violation parameter $\eta$ of $(4.4 \pm 4.5)\times10^{-4}$, where $\eta = 4\beta -\gamma -3$ and both $\gamma$ and $\beta$ are parametrized post-Newtonian (PPN) parameters. The PPN parameter $\beta$ is determined to be $\beta - 1 = (1.2 \pm 1.1) \times 10^{-4}$. Focusing on the tests of the EP, we discuss the existing data, and characterize the modeling and data analysis techniques. The robustness of the LLR solutions is demonstrated with several different approaches that are presented in the text. We emphasize that near-term improvements in the LLR ranging accuracy will further advance the research of relativistic gravity in the solar system, and, most notably, will continue to provide highly accurate tests of the Equivalence Principle. |
2310.00210 | Hiroki Matsui | Hiroki Matsui, Shinji Mukohyama | Hartle-Hawking No-boundary Proposal and Ho\v{r}ava-Lifshitz Gravity | 19 pages, 16 figures, v2: final published version | Phys. Rev. D 109, 023504 (2024) | 10.1103/PhysRevD.109.023504 | YITP-23-123, IPMU23-0035 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Hartle-Hawking no-boundary proposal in the framework of
Ho\v{r}ava-Lifshitz gravity. The former is a prominent hypothesis that
describes the quantum creation of the universe, while the latter is a potential
theory of quantum gravity that ensures renormalizability and unitarity, at
least in the so-called projectable version. For simplicity, we focus on a
global universe composed of a set of local universes each of which is closed,
homogeneous and isotropic. Although applying the no-boundary proposal to
Ho\v{r}ava-Lifshitz gravity is not straightforward, we demonstrate that the
proposal can be formulated within the Ho\v{r}ava-Lifshitz gravity utilizing the
Lorentzian path integral formulation of quantum gravity. In projectable
Ho\v{r}ava-Lifshitz gravity, the no-boundary wave function of the global
universe inevitably contains entanglement between different local universes
induced by ``dark matter as integration constant''. On the other hand, in the
non-projectable version, the no-boundary wave function of the global universe
is simply the direct product of wave functions of each local universe. We then
discuss how the no-boundary wave function is formulated under Dirichlet and
Robin boundary conditions. For the Dirichlet boundary condition, we point out
that its on-shell action diverges due to higher-dimensional operators, but this
problem can in principle be ameliorated by taking into account the
renormalization group flow. However, utilizing the Picard-Lefschetz theory to
identify the relevant critical points and performing the complex lapse
integration, we find that only the tunneling wave function can be obtained, as
in the case of general relativity. On the other hand, for the Robin boundary
condition with a particular imaginary Hubble expansion rate at the initial
hypersurface, the no-boundary wave function can be achieved in the
Ho\v{r}ava-Lifshitz gravity.
| [
{
"created": "Sat, 30 Sep 2023 01:19:04 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Jan 2024 04:52:36 GMT",
"version": "v2"
}
] | 2024-01-05 | [
[
"Matsui",
"Hiroki",
""
],
[
"Mukohyama",
"Shinji",
""
]
] | We study the Hartle-Hawking no-boundary proposal in the framework of Ho\v{r}ava-Lifshitz gravity. The former is a prominent hypothesis that describes the quantum creation of the universe, while the latter is a potential theory of quantum gravity that ensures renormalizability and unitarity, at least in the so-called projectable version. For simplicity, we focus on a global universe composed of a set of local universes each of which is closed, homogeneous and isotropic. Although applying the no-boundary proposal to Ho\v{r}ava-Lifshitz gravity is not straightforward, we demonstrate that the proposal can be formulated within the Ho\v{r}ava-Lifshitz gravity utilizing the Lorentzian path integral formulation of quantum gravity. In projectable Ho\v{r}ava-Lifshitz gravity, the no-boundary wave function of the global universe inevitably contains entanglement between different local universes induced by ``dark matter as integration constant''. On the other hand, in the non-projectable version, the no-boundary wave function of the global universe is simply the direct product of wave functions of each local universe. We then discuss how the no-boundary wave function is formulated under Dirichlet and Robin boundary conditions. For the Dirichlet boundary condition, we point out that its on-shell action diverges due to higher-dimensional operators, but this problem can in principle be ameliorated by taking into account the renormalization group flow. However, utilizing the Picard-Lefschetz theory to identify the relevant critical points and performing the complex lapse integration, we find that only the tunneling wave function can be obtained, as in the case of general relativity. On the other hand, for the Robin boundary condition with a particular imaginary Hubble expansion rate at the initial hypersurface, the no-boundary wave function can be achieved in the Ho\v{r}ava-Lifshitz gravity. |
gr-qc/0406097 | Claus Kiefer | Claus Kiefer | Hawking temperature from quasi-normal modes | 7 pages | Class.Quant.Grav. 21 (2004) L123 | 10.1088/0264-9381/21/17/L02 | null | gr-qc | null | A perturbed black hole has characteristic frequencies (quasi-normal modes).
Here I apply a quantum measurement analysis of the quasi-normal mode frequency
in the limit of high damping. It turns out that a measurement of this mode
necessarily adds noise to it. For a Schwarzschild black hole, this corresponds
exactly to the Hawking temperature. The situation for other black holes is
briefly discussed.
| [
{
"created": "Thu, 24 Jun 2004 08:30:05 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Kiefer",
"Claus",
""
]
] | A perturbed black hole has characteristic frequencies (quasi-normal modes). Here I apply a quantum measurement analysis of the quasi-normal mode frequency in the limit of high damping. It turns out that a measurement of this mode necessarily adds noise to it. For a Schwarzschild black hole, this corresponds exactly to the Hawking temperature. The situation for other black holes is briefly discussed. |
1003.1027 | Spiros Cotsakis | John D. Barrow, S. Cotsakis, A. Tsokaros | The Construction of Sudden Cosmological Singularities | 3 pages, prd style | null | 10.1142/9789814374552_0325 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Solutions of the Friedmann-Lemaitre cosmological equations of general
relativity have been found with finite-time singularities that are everywhere
regular, have regular Hubble expansion rate, and obey the strong-energy
conditions but possess pressure and acceleration singularities at finite time
that are not associated with geodesic incompleteness. We show how these
solutions with sudden singularities can be constructed using fractional series
methods and find the limiting form of the equation of state on approach to the
singularity.
| [
{
"created": "Thu, 4 Mar 2010 12:23:30 GMT",
"version": "v1"
}
] | 2016-11-15 | [
[
"Barrow",
"John D.",
""
],
[
"Cotsakis",
"S.",
""
],
[
"Tsokaros",
"A.",
""
]
] | Solutions of the Friedmann-Lemaitre cosmological equations of general relativity have been found with finite-time singularities that are everywhere regular, have regular Hubble expansion rate, and obey the strong-energy conditions but possess pressure and acceleration singularities at finite time that are not associated with geodesic incompleteness. We show how these solutions with sudden singularities can be constructed using fractional series methods and find the limiting form of the equation of state on approach to the singularity. |
2108.09407 | Ya-Peng Hu | Haximjan Abdusattar, Shi-Bei Kong, Wen-Long You, Hongsheng Zhang and
Ya-Peng Hu | First Principle Study of Gravitational Pressure and Thermodynamics of
FRW Universe | Some new footnotes added, and version published in JHEP | JHEP12(2022)168 | 10.1007/JHEP12(2022)168 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We make a first principle study of gravitational pressure in cosmic
thermodynamics. The pressure is directly derived from the unified first law, in
fact the Einstein field equation in spherically symmetric spacetime. By using
this pressure, we obtain the thermodynamics for the FRW universe, especially
presenting the gravitational equation of state for the FRW spacetime itself,
i.e. $P=P(R_A, T)$ for the first time. Furthermore, we study the Joule-Thomson
expansion as an application of the thermodynamic equation of state to find the
cooling-heating property of the FRW universe. We demonstrate that there is an
inversion temperature for a FRW universe if its enthalpy ${\cal H}$ is
negative. These investigations shed insights on the evolution of our universe
in view of thermodynamics.
| [
{
"created": "Sat, 21 Aug 2021 00:44:58 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Mar 2022 16:14:05 GMT",
"version": "v2"
},
{
"created": "Wed, 5 Oct 2022 15:26:48 GMT",
"version": "v3"
},
{
"created": "Thu, 29 Dec 2022 16:51:54 GMT",
"version": "v4"
}
] | 2023-01-18 | [
[
"Abdusattar",
"Haximjan",
""
],
[
"Kong",
"Shi-Bei",
""
],
[
"You",
"Wen-Long",
""
],
[
"Zhang",
"Hongsheng",
""
],
[
"Hu",
"Ya-Peng",
""
]
] | We make a first principle study of gravitational pressure in cosmic thermodynamics. The pressure is directly derived from the unified first law, in fact the Einstein field equation in spherically symmetric spacetime. By using this pressure, we obtain the thermodynamics for the FRW universe, especially presenting the gravitational equation of state for the FRW spacetime itself, i.e. $P=P(R_A, T)$ for the first time. Furthermore, we study the Joule-Thomson expansion as an application of the thermodynamic equation of state to find the cooling-heating property of the FRW universe. We demonstrate that there is an inversion temperature for a FRW universe if its enthalpy ${\cal H}$ is negative. These investigations shed insights on the evolution of our universe in view of thermodynamics. |
1006.1936 | Valerio Faraoni | Valerio Faraoni and Andres F. Zambrano Moreno (Bishop's University) | Are stealth scalar fields stable? | 10 pages, 1 table, no figures, to appear in Phys. Rev, D | Phys.Rev.D81:124050,2010 | 10.1103/PhysRevD.81.124050 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Non-gravitating (stealth) scalar fields associated with Minkowski space in
scalar-tensor gravity are examined. Analytical solutions for both non-minimally
coupled scalar field theory and for Brans-Dicke gravity are studied and their
stability with respect to tensor perturbations is assessed using a covariant
and gauge-invariant formalism developed for alternative gravity. For
Brans-Dicke solutions, the stability with respect to homogeneous perturbations
is also studied. There are regions of parameter space corresponding to
stability and other regions corresponding to instability.
| [
{
"created": "Thu, 10 Jun 2010 01:42:20 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
],
[
"Moreno",
"Andres F. Zambrano",
"",
"Bishop's University"
]
] | Non-gravitating (stealth) scalar fields associated with Minkowski space in scalar-tensor gravity are examined. Analytical solutions for both non-minimally coupled scalar field theory and for Brans-Dicke gravity are studied and their stability with respect to tensor perturbations is assessed using a covariant and gauge-invariant formalism developed for alternative gravity. For Brans-Dicke solutions, the stability with respect to homogeneous perturbations is also studied. There are regions of parameter space corresponding to stability and other regions corresponding to instability. |
1808.00801 | Ping Li | Ping-Li, Jia-Cheng Ding, Qi-Qi Fan, Xian-Ru Hu and Jian-Bo Deng | The Varying Speed of Light in Eddington-inspired Born-Infield Gravity
with Rainbow Metric | 20 pages, 5 Figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we proposed that at each point of spacetime, in addition to
the Riemannian metric tensor which describes the geometry of spacetime and the
gravitational field, there is an rainbow metric tensor which shows the geometry
of spacetime depends on the energy of the test particle. Because
Eddington-inspired Born-Infield(EiBI) gravity can be seen as a special
bi-metric gravity, we research a varying speed of light theory for a bi-metric
gravity corresponding to EiBI gravity. For FRW universe, we find the energy of
test particle will increase with rising energy density of universe. We also
research the varying speed of light for three different kinds of rainbow
functions and find the sign of parameter $\kappa$ would influence the trend of
spend of light.
| [
{
"created": "Thu, 2 Aug 2018 13:27:06 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Aug 2018 02:38:32 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Sep 2018 07:18:35 GMT",
"version": "v3"
},
{
"created": "Tue, 18 Sep 2018 01:50:17 GMT",
"version": "v4"
},
{
"cre... | 2019-05-15 | [
[
"Ping-Li",
"",
""
],
[
"Ding",
"Jia-Cheng",
""
],
[
"Fan",
"Qi-Qi",
""
],
[
"Hu",
"Xian-Ru",
""
],
[
"Deng",
"Jian-Bo",
""
]
] | In this paper, we proposed that at each point of spacetime, in addition to the Riemannian metric tensor which describes the geometry of spacetime and the gravitational field, there is an rainbow metric tensor which shows the geometry of spacetime depends on the energy of the test particle. Because Eddington-inspired Born-Infield(EiBI) gravity can be seen as a special bi-metric gravity, we research a varying speed of light theory for a bi-metric gravity corresponding to EiBI gravity. For FRW universe, we find the energy of test particle will increase with rising energy density of universe. We also research the varying speed of light for three different kinds of rainbow functions and find the sign of parameter $\kappa$ would influence the trend of spend of light. |
gr-qc/0505051 | Peter Leifer | P. Leifer and L.P. Horwitz | Field Equations of the CP(N-1) Affine Gauge Theory | LATEX, 20 pages, 6 figures | null | null | null | gr-qc | null | A non-linear relativistic 4D field model of a quantum particle which emerges
from the internal dynamics in the quantum phase space $CP(N-1)$ is proposed. In
this model there is no distinction between `particle' and its `surrounding
field', and the space-time manifold emerges from the description of the quantum
state. The quantum observables of the `quantum particle field' are described in
terms of the affine parallel transport of the local dynamical variables in
$CP(N-1)$.
| [
{
"created": "Wed, 11 May 2005 15:58:22 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jul 2006 07:02:11 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Leifer",
"P.",
""
],
[
"Horwitz",
"L. P.",
""
]
] | A non-linear relativistic 4D field model of a quantum particle which emerges from the internal dynamics in the quantum phase space $CP(N-1)$ is proposed. In this model there is no distinction between `particle' and its `surrounding field', and the space-time manifold emerges from the description of the quantum state. The quantum observables of the `quantum particle field' are described in terms of the affine parallel transport of the local dynamical variables in $CP(N-1)$. |
2211.10464 | Laura Olivia Villegas Olvera | Laura O. Villegas, Eduardo Ramirez-Codiz, V\'ictor Jaramillo, Juan
Carlos Degollado, Claudia Moreno, Dar\'io N\'u\~nez and Fernando J.
Romero-Cruz | Determination of the angular momentum of the Kerr black hole from
equatorial geodesic motion | 24 pages | null | 10.1088/1475-7516/2023/08/007 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a method to determine the angular momentum of a black hole, based
on observations of the trajectories of the bodies in the Kerr space-time. We
use the Hamilton equations to describe the dynamics of a particle and present
results for equatorial trajectories, obtaining an algebraic equation for the
magnitude of the black hole's angular momentum. We tailor a numerical code to
solve the dynamical equations and use it to generate synthetic data. We apply
the method in some representative examples, obtaining the parameters of the
trajectories as well as the black hole's angular momentum in good agreement
with the input data.
| [
{
"created": "Fri, 18 Nov 2022 19:04:47 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Mar 2023 05:41:42 GMT",
"version": "v2"
}
] | 2023-08-16 | [
[
"Villegas",
"Laura O.",
""
],
[
"Ramirez-Codiz",
"Eduardo",
""
],
[
"Jaramillo",
"Víctor",
""
],
[
"Degollado",
"Juan Carlos",
""
],
[
"Moreno",
"Claudia",
""
],
[
"Núñez",
"Darío",
""
],
[
"Romero-Cruz",
"Fern... | We present a method to determine the angular momentum of a black hole, based on observations of the trajectories of the bodies in the Kerr space-time. We use the Hamilton equations to describe the dynamics of a particle and present results for equatorial trajectories, obtaining an algebraic equation for the magnitude of the black hole's angular momentum. We tailor a numerical code to solve the dynamical equations and use it to generate synthetic data. We apply the method in some representative examples, obtaining the parameters of the trajectories as well as the black hole's angular momentum in good agreement with the input data. |
1404.0228 | Jakub Mielczarek Ph.D. | Jakub Mielczarek | Big Bang as a critical point | Essay written for the Gravity Research Foundation 2014 Awards for
Essays on Gravitation | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This essay addresses the issue of gravitational phase transitions in the
early universe. We suggest that a second order phase transition observed in the
Causal Dynamical Triangulations approach to quantum gravity may have a
cosmological relevance. The phase transition interpolates between a
non-geometric crumpled phase of gravity, and an extended phase with classical
properties. Transitions of this kind have been postulated earlier in the
context of geometrogenesis in Quantum Graphity. We show that critical behavior
may also be associated with a signature change event in Loop Quantum Cosmology.
In both cases, classical spacetime originates at the critical point associated
with a second order phase transition.
| [
{
"created": "Tue, 1 Apr 2014 13:18:32 GMT",
"version": "v1"
}
] | 2014-04-02 | [
[
"Mielczarek",
"Jakub",
""
]
] | This essay addresses the issue of gravitational phase transitions in the early universe. We suggest that a second order phase transition observed in the Causal Dynamical Triangulations approach to quantum gravity may have a cosmological relevance. The phase transition interpolates between a non-geometric crumpled phase of gravity, and an extended phase with classical properties. Transitions of this kind have been postulated earlier in the context of geometrogenesis in Quantum Graphity. We show that critical behavior may also be associated with a signature change event in Loop Quantum Cosmology. In both cases, classical spacetime originates at the critical point associated with a second order phase transition. |
1706.00459 | Chris Kavanagh | Chris Kavanagh, Donato Bini, Thibault Damour, Seth Hopper, Adrian C.
Ottewill, Barry Wardell | Spin-orbit precession along eccentric orbits for extreme mass ratio
black hole binaries and its effective-one-body transcription | null | Phys. Rev. D 96, 064012 (2017) | 10.1103/PhysRevD.96.064012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we present an analytical gravitational self-force calculation of
the spin-orbit precession along an eccentric orbit around a Schwarzschild black
hole, following closely the recent prescription of Akcay, Dempsey, and Dolan.
We then transcribe this quantity within the Effective-One-Body (EOB) formalism,
thereby determining several new, linear-in-mass-ratio, contributions in the
post-Newtonian expansion of the spin-orbit couplings entering the EOB
Hamiltonian. Namely, we determine the second gyro-gravitomagnetic ratio
$g_{S_*}(r,p_r,p_{\phi})$ up to order $p_r^2/r^4$ included.
| [
{
"created": "Thu, 1 Jun 2017 19:02:41 GMT",
"version": "v1"
}
] | 2017-09-20 | [
[
"Kavanagh",
"Chris",
""
],
[
"Bini",
"Donato",
""
],
[
"Damour",
"Thibault",
""
],
[
"Hopper",
"Seth",
""
],
[
"Ottewill",
"Adrian C.",
""
],
[
"Wardell",
"Barry",
""
]
] | In this work we present an analytical gravitational self-force calculation of the spin-orbit precession along an eccentric orbit around a Schwarzschild black hole, following closely the recent prescription of Akcay, Dempsey, and Dolan. We then transcribe this quantity within the Effective-One-Body (EOB) formalism, thereby determining several new, linear-in-mass-ratio, contributions in the post-Newtonian expansion of the spin-orbit couplings entering the EOB Hamiltonian. Namely, we determine the second gyro-gravitomagnetic ratio $g_{S_*}(r,p_r,p_{\phi})$ up to order $p_r^2/r^4$ included. |
1209.1945 | Chandrachur Chakraborty | Chandrachur Chakraborty, Partha Pratim Pradhan | Lense-Thirring Precession in Pleba\'nski-Demia\'nski spacetimes | 9 pages, Some special modifications are made | Eur. Phys. J. C (2013) 73:2536 | 10.1140/epjc/s10052-013-2536-1 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An exact expression of Lense-Thirring precession rate is derived for
non-extremal and extremal Pleba\'nski-Demia\'nski spacetimes. This formula is
used to find the exact Lense-Thirring precession rate in various axisymmetric
spacetimes, like: Kerr, Kerr-Newman, Kerr-de Sitter etc. We also show, if the
Kerr parameter vanishes in Pleba\'nski-Demia\'nski(PD) spacetime, the
Lense-Thirring precession does not vanish due to the existence of NUT charge.
To derive the LT precession rate in extremal Pleba\'nski-Demia\'nski we first
derive the general extremal condition for PD spacetimes. This general result
could be applied to get the extremal limit in any stationary and axisymmetric
spacetimes.
| [
{
"created": "Mon, 10 Sep 2012 11:14:57 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Apr 2013 16:49:12 GMT",
"version": "v2"
}
] | 2013-09-02 | [
[
"Chakraborty",
"Chandrachur",
""
],
[
"Pradhan",
"Partha Pratim",
""
]
] | An exact expression of Lense-Thirring precession rate is derived for non-extremal and extremal Pleba\'nski-Demia\'nski spacetimes. This formula is used to find the exact Lense-Thirring precession rate in various axisymmetric spacetimes, like: Kerr, Kerr-Newman, Kerr-de Sitter etc. We also show, if the Kerr parameter vanishes in Pleba\'nski-Demia\'nski(PD) spacetime, the Lense-Thirring precession does not vanish due to the existence of NUT charge. To derive the LT precession rate in extremal Pleba\'nski-Demia\'nski we first derive the general extremal condition for PD spacetimes. This general result could be applied to get the extremal limit in any stationary and axisymmetric spacetimes. |
1702.05630 | Cl\'ement Stahl | Cl\'ement Stahl | On early and late phases of acceleration of the expansion of the
universe | 172 pages, 38 figures, 9 tables, PhD thesis succesfully defended on
the 23rd january 2017 in Sapienza University of Rome, advisor R. Ruffini,
partially adapted from arXiv:1507.01401, arXiv:1507.01686, Int.J.Mod.Phys.
D25 (2016) no.06, 1650066, arXiv:1602.06556, arXiv:1602.09090,
arXiv:1603.07166, arXiv:1702.03185. Updated version available on the author's
website | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This thesis tackles the vast question of generating accelerated periods of
expansion of the universe. Models loosely related were developed in the early
and late universe. In the early universe, generalizations of the Schwinger
effect were developed in curved (de Sitter) space and some backreaction effects
were estimated. In the late universe, a fractal model was developed and
confronted to supernovae data. This relies on the idea of an accelerated
expanding universe being nothing but a mirage due to inhomogeneities disposed
in a fractal (in this particular model) way. Finally a model of interacting
energy based on an Einstein-Cartan gravitational theory was phenomenologically
investigated.
| [
{
"created": "Sat, 18 Feb 2017 16:33:08 GMT",
"version": "v1"
}
] | 2017-02-21 | [
[
"Stahl",
"Clément",
""
]
] | This thesis tackles the vast question of generating accelerated periods of expansion of the universe. Models loosely related were developed in the early and late universe. In the early universe, generalizations of the Schwinger effect were developed in curved (de Sitter) space and some backreaction effects were estimated. In the late universe, a fractal model was developed and confronted to supernovae data. This relies on the idea of an accelerated expanding universe being nothing but a mirage due to inhomogeneities disposed in a fractal (in this particular model) way. Finally a model of interacting energy based on an Einstein-Cartan gravitational theory was phenomenologically investigated. |
1204.5060 | Mohammad Reza Tanhayi Ahari | M. Fathi, M. Tanhayi-Ahari, M. R. Tanhayi and F. Tavakoli | Radiation effects on particle's trajectory in the linear level | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we first obtain the linear form of the scalar self-force and
then, the effect of self-force on the particle's trajectory is considered. In
de Sitter space-time, within the classical approach, we consider this effect.
Finally, some limits for the problem are presented.
| [
{
"created": "Mon, 23 Apr 2012 13:22:44 GMT",
"version": "v1"
}
] | 2012-04-24 | [
[
"Fathi",
"M.",
""
],
[
"Tanhayi-Ahari",
"M.",
""
],
[
"Tanhayi",
"M. R.",
""
],
[
"Tavakoli",
"F.",
""
]
] | In this work, we first obtain the linear form of the scalar self-force and then, the effect of self-force on the particle's trajectory is considered. In de Sitter space-time, within the classical approach, we consider this effect. Finally, some limits for the problem are presented. |
1903.10370 | Krishnakanta Bhattacharya | Krishnakanta Bhattacharya and Bibhas Ranjan Majhi | Thermogeometric study of van der Waals like phase transition in black
holes: an alternative approach | A few comments added, to appear in Phys. Lett. B | Physics Letters B 802 (2020) 135224 | 10.1016/j.physletb.2020.135224 | null | gr-qc cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well-known that the non-extremal anti-de-Sitter (AdS) black holes show
various van der Waals type criticalities, such as the $P-V$, $T-S$, $Y-X$,
$Q^2-\Psi$ etc. In these cases, the phase space diagram of the relevant
quantities are similar in behaviour to the isotherms on $P-V$ diagram for the
usual van der Waals gas system. The existing thermogeometric descriptions of
these criticalities for the black holes deal with the whole thermogeometric
manifold and its curvature. However, while observing the criticality, one only
notices the behaviour of the relevant phase space variables and keep all other
thermodynamic quantities as fixed. Therefore it is quite natural to investigate
the geometrical behaviour of the induced metric, defined by these constant
macroscopic variables, corresponding to the whole manifold of the
thermogeometry. Using geometrothermodynamics (GTD), we precisely address this
issue. It is observed that the extrinsic curvature of this induced metric also
diverges at the critical point. This provides an alternative but important
aspect of the thermogeometric description of phase transition of black holes.
The entire formalism in this paper is very general as it is valid for any
arbitrary black hole which shows the van der Waals type phase transition.
| [
{
"created": "Mon, 25 Mar 2019 14:40:01 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Jan 2020 15:03:52 GMT",
"version": "v2"
}
] | 2020-01-23 | [
[
"Bhattacharya",
"Krishnakanta",
""
],
[
"Majhi",
"Bibhas Ranjan",
""
]
] | It is well-known that the non-extremal anti-de-Sitter (AdS) black holes show various van der Waals type criticalities, such as the $P-V$, $T-S$, $Y-X$, $Q^2-\Psi$ etc. In these cases, the phase space diagram of the relevant quantities are similar in behaviour to the isotherms on $P-V$ diagram for the usual van der Waals gas system. The existing thermogeometric descriptions of these criticalities for the black holes deal with the whole thermogeometric manifold and its curvature. However, while observing the criticality, one only notices the behaviour of the relevant phase space variables and keep all other thermodynamic quantities as fixed. Therefore it is quite natural to investigate the geometrical behaviour of the induced metric, defined by these constant macroscopic variables, corresponding to the whole manifold of the thermogeometry. Using geometrothermodynamics (GTD), we precisely address this issue. It is observed that the extrinsic curvature of this induced metric also diverges at the critical point. This provides an alternative but important aspect of the thermogeometric description of phase transition of black holes. The entire formalism in this paper is very general as it is valid for any arbitrary black hole which shows the van der Waals type phase transition. |
2001.00027 | Run-Qiu Yang | Run-Qiu Yang and H. Lu | Universal bounds on the size of a black hole | Match the published version | Eur. Phys. J. C 80, 949 (2020) | 10.1140/epjc/s10052-020-08521-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For static black holes in Einstein gravity, if matter fields satisfy a few
general conditions, we conjecture that three characteristic parameters about
the spatial size of black holes, namely the outermost photon sphere area
$A_{\mathrm{ph,out}}$, the corresponding shadow area $A_{\mathrm{sh,out}}$ and
the horizon area $A_{\mathcal{H}}$ satisfy a series of universal inequalities
$9A_{\mathcal{H}}/4\leq A_{\mathrm{ph,out}}\leq A_{\mathrm{sh,out}}/3\leq 36\pi
M^2$, where $M$ is the ADM mass. We present a complete proof in the spherically
symmetric case and some pieces of evidence to support it in general static
cases. We also discuss the properties of the photon spheres in general static
spacetimes and show that, similar to horizon, photon spheres are also conformal
invariant structures of the spacetimes.
| [
{
"created": "Tue, 31 Dec 2019 19:00:03 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Jan 2020 12:10:43 GMT",
"version": "v2"
},
{
"created": "Sun, 18 Oct 2020 07:52:15 GMT",
"version": "v3"
}
] | 2020-10-20 | [
[
"Yang",
"Run-Qiu",
""
],
[
"Lu",
"H.",
""
]
] | For static black holes in Einstein gravity, if matter fields satisfy a few general conditions, we conjecture that three characteristic parameters about the spatial size of black holes, namely the outermost photon sphere area $A_{\mathrm{ph,out}}$, the corresponding shadow area $A_{\mathrm{sh,out}}$ and the horizon area $A_{\mathcal{H}}$ satisfy a series of universal inequalities $9A_{\mathcal{H}}/4\leq A_{\mathrm{ph,out}}\leq A_{\mathrm{sh,out}}/3\leq 36\pi M^2$, where $M$ is the ADM mass. We present a complete proof in the spherically symmetric case and some pieces of evidence to support it in general static cases. We also discuss the properties of the photon spheres in general static spacetimes and show that, similar to horizon, photon spheres are also conformal invariant structures of the spacetimes. |
1905.09468 | Muhammad Sharif | M. Sharif and Saadia Mumtaz | Phase Space Analysis for Anisotropic Universe with Nonlinear Bulk
Viscosity | 13 pages, 6 figures. arXiv admin note: text overlap with
arXiv:1702.04716 | Gen. Relativ. Gravit. 50(2018)63 | 10.1007/s10714-018-2384-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we discuss the phase space analysis of locally rotationally
symmetric Bianchi type I universe model by taking a noninteracting mixture of
dust like and viscous radiation like fluid whose viscous pressure satisfies a
nonlinear version of the Israel-Stewart transport equation. An autonomous
system of equations is established by defining normalized dimensionless
variables. In order to investigate the stability of the system, we evaluate
corresponding critical points for different values of the parameters. We also
compute the power-law scale factor whose behavior indicates different phases of
the universe model. It is found that our analysis does not provide a complete
immune from fine-tuning because the exponentially expanding solution occurs
only for a a particular range of parameters. We conclude that stable solutions
exist in the presence of nonlinear model for bulk viscosity with different
choices of the constant parameter $m$ for anisotropic universe.
| [
{
"created": "Tue, 21 May 2019 03:57:37 GMT",
"version": "v1"
}
] | 2019-05-29 | [
[
"Sharif",
"M.",
""
],
[
"Mumtaz",
"Saadia",
""
]
] | In this paper, we discuss the phase space analysis of locally rotationally symmetric Bianchi type I universe model by taking a noninteracting mixture of dust like and viscous radiation like fluid whose viscous pressure satisfies a nonlinear version of the Israel-Stewart transport equation. An autonomous system of equations is established by defining normalized dimensionless variables. In order to investigate the stability of the system, we evaluate corresponding critical points for different values of the parameters. We also compute the power-law scale factor whose behavior indicates different phases of the universe model. It is found that our analysis does not provide a complete immune from fine-tuning because the exponentially expanding solution occurs only for a a particular range of parameters. We conclude that stable solutions exist in the presence of nonlinear model for bulk viscosity with different choices of the constant parameter $m$ for anisotropic universe. |
1810.03008 | Cristian Stelea | Cristian Stelea, Marina-Aura Dariescu and Ciprian Dariescu | New bound of the mass-to-radius ratio for electrically charged stars | 9 pages, 1 figure | Phys. Rev. D 98, 124022 (2018) | 10.1103/PhysRevD.98.124022 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using a general solution-generating technique for electrically charged
relativistic stars with spherical symmetry, we derive a new bound on the
mass-radius ratio. This compactness bound is based on the already established
bounds for uncharged interior solutions and it will provide the corresponding
generalizations in presence of the electric charge.
| [
{
"created": "Sat, 6 Oct 2018 14:59:56 GMT",
"version": "v1"
}
] | 2018-12-26 | [
[
"Stelea",
"Cristian",
""
],
[
"Dariescu",
"Marina-Aura",
""
],
[
"Dariescu",
"Ciprian",
""
]
] | Using a general solution-generating technique for electrically charged relativistic stars with spherical symmetry, we derive a new bound on the mass-radius ratio. This compactness bound is based on the already established bounds for uncharged interior solutions and it will provide the corresponding generalizations in presence of the electric charge. |
1605.01383 | Alejandro Corichi | Alejandro Corichi and Asieh Karami | Loop quantum cosmology of Bianchi IX: Inclusion of inverse triad
corrections | 18 pages, 2 figures. Prepared for the special issue on Loop Quantum
Cosmology of the International Journal of Modern Physics D | Int.J.Mod.Phys. D25 (2016) no.08, 1642011 | 10.1142/S0218271816420116 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the loop quantization of the (diagonal) Bianchi type IX
cosmological model. We explore different quantization prescriptions that extend
the work of Wilson-Ewing and Singh. In particular, we study two different ways
of implementing the so-called inverse triad corrections. We construct the
corresponding Hamiltonian constraint operators and show that the singularity is
formally resolved. We find the effective equations associated with the
different quantization prescriptions, and study the relation with the isotropic
$k$=1 model that, classically, is contained within the Bianchi IX model. We use
geometrically defined scalar observables to explore the physical implications
of each of these theories. This is the first part in a series of papers
analyzing different aspects of the Bianchi IX model, with inverse corrections,
within loop quantum cosmology.
| [
{
"created": "Wed, 4 May 2016 19:09:08 GMT",
"version": "v1"
}
] | 2020-06-18 | [
[
"Corichi",
"Alejandro",
""
],
[
"Karami",
"Asieh",
""
]
] | We consider the loop quantization of the (diagonal) Bianchi type IX cosmological model. We explore different quantization prescriptions that extend the work of Wilson-Ewing and Singh. In particular, we study two different ways of implementing the so-called inverse triad corrections. We construct the corresponding Hamiltonian constraint operators and show that the singularity is formally resolved. We find the effective equations associated with the different quantization prescriptions, and study the relation with the isotropic $k$=1 model that, classically, is contained within the Bianchi IX model. We use geometrically defined scalar observables to explore the physical implications of each of these theories. This is the first part in a series of papers analyzing different aspects of the Bianchi IX model, with inverse corrections, within loop quantum cosmology. |
1602.08110 | Roberto Oliveri | M. Astorino, G. Comp\`ere, R. Oliveri, N. Vandevoorde | Mass of Kerr-Newman Black Holes in an external magnetic field | 21 pages; v2 matches published version | Phys. Rev. D 94, 024019 (2016) | 10.1103/PhysRevD.94.024019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The explicit solution for a Kerr-Newman black hole immersed in an external
magnetic field, sometimes called the Melvin-Kerr-Newman black hole, has been
derived by Ernst and Wild in 1976. In this paper, we clarify the first law and
Smarr formula for black holes in a magnetic field. We then define the unique
mass which is integrable and reduces to the Kerr-Newman mass in the absence of
magnetic field. This defines the thermodynamic potentials of the black hole.
Quite strikingly, the mass coincides with the standard Christodoulou-Ruffini
mass of a black hole as a function of the entropy, angular momentum and
electric charge.
| [
{
"created": "Thu, 25 Feb 2016 21:05:07 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Jul 2016 08:30:06 GMT",
"version": "v2"
}
] | 2016-07-13 | [
[
"Astorino",
"M.",
""
],
[
"Compère",
"G.",
""
],
[
"Oliveri",
"R.",
""
],
[
"Vandevoorde",
"N.",
""
]
] | The explicit solution for a Kerr-Newman black hole immersed in an external magnetic field, sometimes called the Melvin-Kerr-Newman black hole, has been derived by Ernst and Wild in 1976. In this paper, we clarify the first law and Smarr formula for black holes in a magnetic field. We then define the unique mass which is integrable and reduces to the Kerr-Newman mass in the absence of magnetic field. This defines the thermodynamic potentials of the black hole. Quite strikingly, the mass coincides with the standard Christodoulou-Ruffini mass of a black hole as a function of the entropy, angular momentum and electric charge. |
gr-qc/0507119 | Filimonova Irina V | E.Babichev, V.Dokuchaev and Y.Eroshenko | Black hole mass decreasing due to phantom energy accretion | Plenary talk presented at Workshop on High Energy Physics&Field
Theory (Protvino, Russia, 2004) | null | null | HEPFT/2004/3 | gr-qc | null | Solution for a stationary spherically symmetric accretion of the relativistic
perfect fluid with an equation of state p(rho) onto the Schwarzschild black
hole is presented. This solution is a generalization of Michel solution and
applicable to the problem of dark energy accretion. It is shown that accretion
of phantom energy is accompanied with the gradual decrease of the black hole
mass. Masses of all black holes tend to zero in the phantom energy universe
approaching to the Big Rip.
| [
{
"created": "Thu, 28 Jul 2005 11:24:10 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Babichev",
"E.",
""
],
[
"Dokuchaev",
"V.",
""
],
[
"Eroshenko",
"Y.",
""
]
] | Solution for a stationary spherically symmetric accretion of the relativistic perfect fluid with an equation of state p(rho) onto the Schwarzschild black hole is presented. This solution is a generalization of Michel solution and applicable to the problem of dark energy accretion. It is shown that accretion of phantom energy is accompanied with the gradual decrease of the black hole mass. Masses of all black holes tend to zero in the phantom energy universe approaching to the Big Rip. |
1907.00740 | Juan Antonio Nieto | J. A. Nieto | Generalized Elko Theory | Latex, 13 pages, published online in Modern Physics Letters A | null | 10.1142/S0217732319502110 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By using a totally antisymmetric spinor field we generalize Elko theory. We
compare our proposed theory with traditional totally antisymmetric spinor field
theory based on the Dirac equation. As an application of our formalism we
comment about the possibility to link our generalized Elko theory with
matroids, qubits and surreal numbers.
| [
{
"created": "Thu, 27 Jun 2019 19:03:39 GMT",
"version": "v1"
}
] | 2019-07-02 | [
[
"Nieto",
"J. A.",
""
]
] | By using a totally antisymmetric spinor field we generalize Elko theory. We compare our proposed theory with traditional totally antisymmetric spinor field theory based on the Dirac equation. As an application of our formalism we comment about the possibility to link our generalized Elko theory with matroids, qubits and surreal numbers. |
0909.1882 | Henrique de Andrade Gomes | John W. Barrett, Richard J. Dowdall, Winston J. Fairbairn, Henrique
Gomes, Frank Hellmann | A Summary of the asymptotic analysis for the EPRL amplitude | 8pages, Proceedings for Planck Scale 2009, talk given by Henrique
Gomes | null | 10.1063/1.3284398 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the basic steps in building the asymptotic analysis of the
Euclidean sector of new spin foam models using coherent states, for Immirzi
parameter less than one. We focus on conceptual issues and by so doing omit
peripheral proofs and the original discussion on spin structures.
| [
{
"created": "Thu, 10 Sep 2009 18:24:13 GMT",
"version": "v1"
}
] | 2015-05-14 | [
[
"Barrett",
"John W.",
""
],
[
"Dowdall",
"Richard J.",
""
],
[
"Fairbairn",
"Winston J.",
""
],
[
"Gomes",
"Henrique",
""
],
[
"Hellmann",
"Frank",
""
]
] | We review the basic steps in building the asymptotic analysis of the Euclidean sector of new spin foam models using coherent states, for Immirzi parameter less than one. We focus on conceptual issues and by so doing omit peripheral proofs and the original discussion on spin structures. |
gr-qc/9211007 | Ctirad Klimcik | C. Klim\v{c}\'ik and P. Koln\'ik | D=3: Singularities in Gravitational Scattering of Scalar Waves | 22 pages, 5 figures upon request, LaTeX | Class.Quant.Grav.10:1367-1382,1993 | 10.1088/0264-9381/10/7/013 | PRA-HEP-91/8 | gr-qc | null | Family of exact spacetimes of D=3 Einstein gravity interacting with massless
scalar field is obtained by suitable dimensional reduction of a class of D=4
plane-symmetric Einstein vacua. These D=3 spacetimes describe collisions of
line-fronted asymptotically null excitations and are generically singular to
the future. The solution for the scalar field can be decomposed into the
Fourier-Bessel modes around the background solitons. The criteria of regularity
of incoming waves are found. It is shown that the appearance of the scalar
curvature singularities need not stem from singularities of incoming waves.
Moreover, in distinction to D=4 case, for all solutions with regular incoming
waves the final singularities are inevitable.
| [
{
"created": "Wed, 4 Nov 1992 09:11:32 GMT",
"version": "v1"
}
] | 2016-08-14 | [
[
"Klimčík",
"C.",
""
],
[
"Kolník",
"P.",
""
]
] | Family of exact spacetimes of D=3 Einstein gravity interacting with massless scalar field is obtained by suitable dimensional reduction of a class of D=4 plane-symmetric Einstein vacua. These D=3 spacetimes describe collisions of line-fronted asymptotically null excitations and are generically singular to the future. The solution for the scalar field can be decomposed into the Fourier-Bessel modes around the background solitons. The criteria of regularity of incoming waves are found. It is shown that the appearance of the scalar curvature singularities need not stem from singularities of incoming waves. Moreover, in distinction to D=4 case, for all solutions with regular incoming waves the final singularities are inevitable. |
2109.10940 | Rajesh Karmakar | Rajesh Karmakar, Debaprasad Maity | Ringing Black Hole is Superradiant: Ultra-light Scalar Field | A new section has been added on obsevables effects. Also, few typos
are corrected and some references have been added. Accepted for publication
in Phys. Rev. D | null | 10.1103/PhysRevD.105.104045 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Superradiance has been studied quite extensively in the context of static
(charged) and rotating black hole spacetime. In this paper, we report for the
first time that for a minimally coupled scalar field, the absorption
cross-section of a Schwarzschild black hole in its ring down phase can be
superradiant. Our present result opens up an intriguing possibility of
observing the black hole merging phenomena through other fundamental fields.
| [
{
"created": "Wed, 22 Sep 2021 18:04:31 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Sep 2021 14:24:37 GMT",
"version": "v2"
},
{
"created": "Mon, 16 May 2022 15:21:02 GMT",
"version": "v3"
}
] | 2022-06-01 | [
[
"Karmakar",
"Rajesh",
""
],
[
"Maity",
"Debaprasad",
""
]
] | Superradiance has been studied quite extensively in the context of static (charged) and rotating black hole spacetime. In this paper, we report for the first time that for a minimally coupled scalar field, the absorption cross-section of a Schwarzschild black hole in its ring down phase can be superradiant. Our present result opens up an intriguing possibility of observing the black hole merging phenomena through other fundamental fields. |
1607.00972 | Luca Fabbri | Luca Fabbri | Torsion Gravity for Dirac Fields | 7 pages | Int.J.Geom.Meth.Mod.Phys.:14,1750037(2017) | 10.1142/S0219887817500372 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we will take into account the most complete back-ground with
torsion and curvature, providing the most exhaustive coupling for the Dirac
field: we will discuss the integrability of the interaction of the matter field
and the reduction of the matter field equations.
| [
{
"created": "Mon, 4 Jul 2016 17:45:30 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Jan 2017 01:33:45 GMT",
"version": "v2"
},
{
"created": "Mon, 22 May 2017 15:21:27 GMT",
"version": "v3"
}
] | 2017-05-23 | [
[
"Fabbri",
"Luca",
""
]
] | In this article we will take into account the most complete back-ground with torsion and curvature, providing the most exhaustive coupling for the Dirac field: we will discuss the integrability of the interaction of the matter field and the reduction of the matter field equations. |
1901.07615 | F. S. Guzman | J. A. Gonzalez, F. S. Guzman | Classification of a black hole spin out of its shadow using support
vector machines | 6 pages, 5 figures. Accepted for publication in Phys. Rev. D | Phys. Rev. D 99, 103002 (2019) | 10.1103/PhysRevD.99.103002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use Support Vector Machines (SVMs) to classify the spin of a black hole.
The SVMs are trained and tested with a catalog of numerically generated images
of black holes, assuming disk and spherical matter models with monochromatic
emission with wavelength of 4mm. We determine the accuracy of the SVM to
classify the spin in terms of the image resolution, for which we consider three
resolutions of $16^2,~32^2$ and $64^2$ pixels. Our approach is applied to the
specific mass of the Supermassive Black Hole (SMBH) at the center of the Milky
Way. Our findings are that when the distribution is a thin disk, the accuracy
in the classification resists even the coarsest resolution with accuracy over
90\%, whereas for the spherical distribution it drops below 80\% for low and
intermediate resolutions. The results show how the distribution of matter, the
angle of vision and the image resolution influence the ease to determine the
black hole spin.
| [
{
"created": "Tue, 22 Jan 2019 21:19:53 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Apr 2019 16:02:05 GMT",
"version": "v2"
},
{
"created": "Tue, 9 Apr 2019 16:38:23 GMT",
"version": "v3"
}
] | 2019-05-22 | [
[
"Gonzalez",
"J. A.",
""
],
[
"Guzman",
"F. S.",
""
]
] | We use Support Vector Machines (SVMs) to classify the spin of a black hole. The SVMs are trained and tested with a catalog of numerically generated images of black holes, assuming disk and spherical matter models with monochromatic emission with wavelength of 4mm. We determine the accuracy of the SVM to classify the spin in terms of the image resolution, for which we consider three resolutions of $16^2,~32^2$ and $64^2$ pixels. Our approach is applied to the specific mass of the Supermassive Black Hole (SMBH) at the center of the Milky Way. Our findings are that when the distribution is a thin disk, the accuracy in the classification resists even the coarsest resolution with accuracy over 90\%, whereas for the spherical distribution it drops below 80\% for low and intermediate resolutions. The results show how the distribution of matter, the angle of vision and the image resolution influence the ease to determine the black hole spin. |
1906.05309 | Vladimir Strokov N. | Vladimir N. Strokov, Shant Khlghatyan | The Orbital Lense-Thirring Precession in a Strong Field | 23 pages, 6 figures, 2 tables, typeset in arxiv-style; accepted for
publication in General Relativity and Gravitation | Gen Relativ Gravit (2019) 51: 82 | 10.1007/s10714-019-2563-9 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the exact evolution of the orbital angular momentum of a massive
particle in the gravitational field of a Kerr black hole. We show analytically
that, for a wide class of orbits, the angular momentum's hodograph is always
close to a circle. This applies to both bounded and unbounded orbits that do
not end up in the black hole. Deviations from the circular shape do not exceed
$\approx10\%$ and $\approx7\%$ for bounded and unbounded orbits, respectively.
We also find that nutation provides an accurate approximation for those
deviations, which fits the exact curve within $\sim 0.01\%$ for the orbits of
maximal deviation. Remarkably, the more the deviation, the better the nutation
approximates it. Thus, we demonstrate that the orbital Lense-Thirring
precession, originally obtained in the weak-field limit, is also a valid
description in the general case of (almost) arbitrary exact orbits. As a
by-product, we also derive the parameters of unstable spherical timelike orbits
as a function of their radii and arbitrary rotation parameter $a$ and Carter's
constant $Q$. We verify our results numerically for all the kinds of orbits
studied.
| [
{
"created": "Wed, 12 Jun 2019 18:01:08 GMT",
"version": "v1"
}
] | 2019-07-11 | [
[
"Strokov",
"Vladimir N.",
""
],
[
"Khlghatyan",
"Shant",
""
]
] | We study the exact evolution of the orbital angular momentum of a massive particle in the gravitational field of a Kerr black hole. We show analytically that, for a wide class of orbits, the angular momentum's hodograph is always close to a circle. This applies to both bounded and unbounded orbits that do not end up in the black hole. Deviations from the circular shape do not exceed $\approx10\%$ and $\approx7\%$ for bounded and unbounded orbits, respectively. We also find that nutation provides an accurate approximation for those deviations, which fits the exact curve within $\sim 0.01\%$ for the orbits of maximal deviation. Remarkably, the more the deviation, the better the nutation approximates it. Thus, we demonstrate that the orbital Lense-Thirring precession, originally obtained in the weak-field limit, is also a valid description in the general case of (almost) arbitrary exact orbits. As a by-product, we also derive the parameters of unstable spherical timelike orbits as a function of their radii and arbitrary rotation parameter $a$ and Carter's constant $Q$. We verify our results numerically for all the kinds of orbits studied. |
2403.17151 | Bahram Mashhoon | Bahram Mashhoon | Rotational Doppler Effect and Spin-Rotation Coupling | 29 pages | null | null | null | gr-qc physics.optics | http://creativecommons.org/licenses/by/4.0/ | The Rotational Doppler Effect (RDE) involves both the orbital angular
momentum of electromagnetic radiation as well as its helicity. The RDE
phenomena associated with photon helicity go beyond the standard theory of
relativity. The purpose of this paper is to elucidate the theoretical basis of
the helicity-dependent RDE in terms of the general phenomenon of spin-rotation
coupling. The physical implications of this coupling are briefly pointed out
and the nonlocal theory of rotating observers is described. For an observer
rotating uniformly about the direction of incidence of a plane wave of definite
helicity, the nonlocally measured amplitude of the wave is larger (smaller) if
the observer rotates in the same (opposite) sense as the electromagnetic field.
The implications of the nonlocal helicity dependence of the measured amplitude
of the radiation are briefly discussed.
| [
{
"created": "Mon, 25 Mar 2024 19:59:37 GMT",
"version": "v1"
}
] | 2024-03-27 | [
[
"Mashhoon",
"Bahram",
""
]
] | The Rotational Doppler Effect (RDE) involves both the orbital angular momentum of electromagnetic radiation as well as its helicity. The RDE phenomena associated with photon helicity go beyond the standard theory of relativity. The purpose of this paper is to elucidate the theoretical basis of the helicity-dependent RDE in terms of the general phenomenon of spin-rotation coupling. The physical implications of this coupling are briefly pointed out and the nonlocal theory of rotating observers is described. For an observer rotating uniformly about the direction of incidence of a plane wave of definite helicity, the nonlocally measured amplitude of the wave is larger (smaller) if the observer rotates in the same (opposite) sense as the electromagnetic field. The implications of the nonlocal helicity dependence of the measured amplitude of the radiation are briefly discussed. |
gr-qc/9911105 | Osvaldo M. Moreschi | Osvaldo M. Moreschi | Cosmic implications on thermodynamics and the explanation of the so
called horizon problem | 4 pages, 1 figure | null | null | null | gr-qc | null | We show that there are implications on thermodynamics that come from the
existence of the initial cosmic singularity. At present time this is more a
conceptual change than an observable one. However at very early cosmic times
there is a big difference between the actual behavior of thermodynamic
quantities and the behavior assumed in the standard cosmological model. We
present the discussion of two systems: an ideal monatomic gas at present, and a
photon gas at the early Universe. We show the striking result that the entropy
density goes to zero as the cosmic time goes to zero. This in turn, provides an
explanation for the so called horizon problem.
| [
{
"created": "Fri, 26 Nov 1999 12:57:59 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Nov 1999 12:46:56 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Moreschi",
"Osvaldo M.",
""
]
] | We show that there are implications on thermodynamics that come from the existence of the initial cosmic singularity. At present time this is more a conceptual change than an observable one. However at very early cosmic times there is a big difference between the actual behavior of thermodynamic quantities and the behavior assumed in the standard cosmological model. We present the discussion of two systems: an ideal monatomic gas at present, and a photon gas at the early Universe. We show the striking result that the entropy density goes to zero as the cosmic time goes to zero. This in turn, provides an explanation for the so called horizon problem. |
1305.7468 | Tim-Torben Paetz | Piotr T. Chru\'sciel, Tim-Torben Paetz | KIDs like cones | 32 pages; improvement of theorem 1.2; short appendix on Fuchsian ODEs
added; section 3.3 and an appendix related to it added, which give a useful
application of our analysis to bifurcate horizons | Class. Quantum Grav. 30 (2013) 235036 | 10.1088/0264-9381/30/23/235036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze vacuum Killing Initial Data on characteristic Cauchy surfaces. A
general theorem on existence of Killing vectors in the domain of dependence is
proved, and some special cases are analyzed in detail, including the case of
bifurcate Killing horizons.
| [
{
"created": "Fri, 31 May 2013 16:00:07 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Oct 2013 10:36:34 GMT",
"version": "v2"
}
] | 2015-06-16 | [
[
"Chruściel",
"Piotr T.",
""
],
[
"Paetz",
"Tim-Torben",
""
]
] | We analyze vacuum Killing Initial Data on characteristic Cauchy surfaces. A general theorem on existence of Killing vectors in the domain of dependence is proved, and some special cases are analyzed in detail, including the case of bifurcate Killing horizons. |
1703.03920 | Gang Ren | Gang Ren and Yi-Shi Duan | Extended Theory of Harmonic Maps Connects General Relativity to Chaos
and Quantum Mechanism | 8 page, no figures | null | 10.1016/j.chaos.2017.07.004 | null | gr-qc hep-th math-ph math.MP nlin.CD quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General relativity and quantum mechanism are two separate rules of modern
physics explaining how nature works. Both theories are accurate, but the direct
connection between two theories was not yet clarified. Recently, researchers
blur the line between classical and quantum physics by connecting chaos and
entanglement. Here, we showed the early reported extended HM theory that
included the general relativity can also be used to recover the classic chaos
equations and even the Schrodinger equation in quantum physics, suggesting the
extended theory of harmonic maps may act as a universal theory of physics.
| [
{
"created": "Sat, 11 Mar 2017 07:28:32 GMT",
"version": "v1"
}
] | 2017-10-11 | [
[
"Ren",
"Gang",
""
],
[
"Duan",
"Yi-Shi",
""
]
] | General relativity and quantum mechanism are two separate rules of modern physics explaining how nature works. Both theories are accurate, but the direct connection between two theories was not yet clarified. Recently, researchers blur the line between classical and quantum physics by connecting chaos and entanglement. Here, we showed the early reported extended HM theory that included the general relativity can also be used to recover the classic chaos equations and even the Schrodinger equation in quantum physics, suggesting the extended theory of harmonic maps may act as a universal theory of physics. |
gr-qc/0602056 | Georgios Kraniotis | G. V. Kraniotis | Periapsis and gravitomagnetic precessions of stellar orbits in Kerr and
Kerr-de Sitter black hole spacetimes | LaTeX file, 46 pages, typos fixed, substantial changes, version
published in Classical and Quantum Gravity, Vol 24 (2007) 1775-1808 | Class. Quantum Grav. 24 (2007) 1775-1808 | 10.1088/0264-9381/24/7/007 | MIFP-06-05 | gr-qc astro-ph | null | The exact solution for the motion of a test particle in a non-spherical polar
orbit around a Kerr black hole is derived. Exact novel expressions for frame
dragging (Lense-Thirring effect), periapsis advance and the orbital period are
produced. The resulting formulae, are expressed in terms of Appell's first
hypergeometric function $F_1$, Jacobi's amplitude function, and Appell's $F_1$
and Gau$\ss$ hypergeometric function respectively. The exact expression for
frame dragging is applied for the calculation of the Lense-Thirring effect for
the orbits of S-stars in the central arcsecond of our Galaxy assuming that the
galactic centre is a Kerr black hole, for various values of the Kerr parameter
including those supported by recent observations. In addition, we apply our
solutions for the calculation of frame dragging and periapsis advance for
stellar non-spherical polar orbits in regions of strong gravitational field
close to the event horizon of the galactic black hole, e.g. for orbits in the
central milliarcsecond of our galaxy. Such orbits are the target of the GRAVITY
experiment. We provide examples with orbital periods in the range of 100min -
54 days. Detection of such stellar orbits will allow the possibility of
measuring the relativistic effect of periapsis advance with high precision at
the strong field realm of general relativity. Further, an exact expression for
the orbital period of a test particle in a non-circular equatorial motion
around a Kerr black hole is produced. We also derive exact expressions for the
periapsis advance and the orbital period for a test particle in a non-circular
equatorial motion in the Kerr field in the presence of the cosmological
constant in terms of Lauricella's fourth hypergeometric function $F_D$.
| [
{
"created": "Wed, 15 Feb 2006 18:53:25 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Apr 2006 17:37:58 GMT",
"version": "v2"
},
{
"created": "Thu, 28 Sep 2006 18:59:22 GMT",
"version": "v3"
},
{
"created": "Thu, 29 Mar 2007 08:30:26 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Kraniotis",
"G. V.",
""
]
] | The exact solution for the motion of a test particle in a non-spherical polar orbit around a Kerr black hole is derived. Exact novel expressions for frame dragging (Lense-Thirring effect), periapsis advance and the orbital period are produced. The resulting formulae, are expressed in terms of Appell's first hypergeometric function $F_1$, Jacobi's amplitude function, and Appell's $F_1$ and Gau$\ss$ hypergeometric function respectively. The exact expression for frame dragging is applied for the calculation of the Lense-Thirring effect for the orbits of S-stars in the central arcsecond of our Galaxy assuming that the galactic centre is a Kerr black hole, for various values of the Kerr parameter including those supported by recent observations. In addition, we apply our solutions for the calculation of frame dragging and periapsis advance for stellar non-spherical polar orbits in regions of strong gravitational field close to the event horizon of the galactic black hole, e.g. for orbits in the central milliarcsecond of our galaxy. Such orbits are the target of the GRAVITY experiment. We provide examples with orbital periods in the range of 100min - 54 days. Detection of such stellar orbits will allow the possibility of measuring the relativistic effect of periapsis advance with high precision at the strong field realm of general relativity. Further, an exact expression for the orbital period of a test particle in a non-circular equatorial motion around a Kerr black hole is produced. We also derive exact expressions for the periapsis advance and the orbital period for a test particle in a non-circular equatorial motion in the Kerr field in the presence of the cosmological constant in terms of Lauricella's fourth hypergeometric function $F_D$. |
0805.0568 | Charmousis | Christos Charmousis | Higher order gravity theories and their black hole solutions | 44 pages, 2 figures, To appear in the proceedings of the 4th Aegean
Summer School on Black Holes, 17-22 September 2007, Mytilene, Island of
Lesvos, Greece | Lect.Notes Phys.769:299-346,2009 | 10.1007/978-3-540-88460-6_8 | LPT-08-42 | gr-qc astro-ph hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a particular higher order gravity theory, Lovelock theory, that
generalises in higher dimensions, general relativity. After briefly motivating
modifications of gravity, we will introduce the theory in question and we will
argue that it is a unique, mathematically sensible, and physically interesting
extension of general relativity. We will see, by using the formalism of
differential forms, the relation of Lovelock gravity to differential geometry
and topology of even dimensional manifolds. We will then discuss a generic
staticity theorem, which will give us the charged static black hole solutions.
We will examine their asymptotic behavior, analyse their horizon structure and
briefly their thermodynamics. We will then examine the distributional matching
conditions for Lovelock theory. We will see how induced 4 dimensional
Einstein-Hilbert terms result on the brane geometry from the higher order
Lovelock terms. With the junction conditions at hand, we will go back to the
black hole solutions and give applications for braneworlds: perturbations of
codimension 1 braneworlds and the exact solution for braneworld cosmology as
well as the determination of maximally symmetric codimension 2 braneworlds. In
both cases, the staticity theorem evoked beforehand will give us the general
solution for braneworld cosmology in codimension 1 and maximal symmetry warped
branes of codimension 2. We will then end with a discussion of the simplest
Kaluza-Klein reduction of Lovelock theory to a 4 dimensional
vector-scalar-tensor theory which has the unique property of retaining second
order field equations. We will conclude by listing some open problems and
common difficulties.
| [
{
"created": "Mon, 5 May 2008 16:40:26 GMT",
"version": "v1"
}
] | 2009-01-28 | [
[
"Charmousis",
"Christos",
""
]
] | We discuss a particular higher order gravity theory, Lovelock theory, that generalises in higher dimensions, general relativity. After briefly motivating modifications of gravity, we will introduce the theory in question and we will argue that it is a unique, mathematically sensible, and physically interesting extension of general relativity. We will see, by using the formalism of differential forms, the relation of Lovelock gravity to differential geometry and topology of even dimensional manifolds. We will then discuss a generic staticity theorem, which will give us the charged static black hole solutions. We will examine their asymptotic behavior, analyse their horizon structure and briefly their thermodynamics. We will then examine the distributional matching conditions for Lovelock theory. We will see how induced 4 dimensional Einstein-Hilbert terms result on the brane geometry from the higher order Lovelock terms. With the junction conditions at hand, we will go back to the black hole solutions and give applications for braneworlds: perturbations of codimension 1 braneworlds and the exact solution for braneworld cosmology as well as the determination of maximally symmetric codimension 2 braneworlds. In both cases, the staticity theorem evoked beforehand will give us the general solution for braneworld cosmology in codimension 1 and maximal symmetry warped branes of codimension 2. We will then end with a discussion of the simplest Kaluza-Klein reduction of Lovelock theory to a 4 dimensional vector-scalar-tensor theory which has the unique property of retaining second order field equations. We will conclude by listing some open problems and common difficulties. |
2207.03183 | Wei-Chen Lin | Deog Ki Hong, Wei-Chen Lin, Dong-han Yeom | Trouble with geodesics in black-to-white hole bouncing scenarios | 18 pages, 7 figures. (V2: Matching the version accepted by PRD. New
references added.) | null | 10.1103/PhysRevD.106.104011 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By utilizing the thin shell approximation, we investigate the behavior of
radial timelike geodesics in a black hole to white hole bouncing scenario with
a mass (de-)amplification relation. We show that those geodesics lose energy
after crossing the transition surface if the white hole mass is less than the
black hole mass and vice versa. That is, the bounded timelike radial geodesics
become closer to the event horizon in the mass decreasing direction. We then
show that by tracing a finite amount of bouncing cycles along the mass
decreasing direction, all bounded radial geodesics can be squeezed into the
range of the stretched horizon while the black hole and white hole are still
massive. Those highly squeezed geodesics are problematic since there exists a
Planck-scale blueshift between them and the regular infalling trajectories. We
also discuss the possible implication and rescues.
| [
{
"created": "Thu, 7 Jul 2022 09:23:46 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Nov 2022 06:02:02 GMT",
"version": "v2"
}
] | 2022-11-16 | [
[
"Hong",
"Deog Ki",
""
],
[
"Lin",
"Wei-Chen",
""
],
[
"Yeom",
"Dong-han",
""
]
] | By utilizing the thin shell approximation, we investigate the behavior of radial timelike geodesics in a black hole to white hole bouncing scenario with a mass (de-)amplification relation. We show that those geodesics lose energy after crossing the transition surface if the white hole mass is less than the black hole mass and vice versa. That is, the bounded timelike radial geodesics become closer to the event horizon in the mass decreasing direction. We then show that by tracing a finite amount of bouncing cycles along the mass decreasing direction, all bounded radial geodesics can be squeezed into the range of the stretched horizon while the black hole and white hole are still massive. Those highly squeezed geodesics are problematic since there exists a Planck-scale blueshift between them and the regular infalling trajectories. We also discuss the possible implication and rescues. |
1006.2983 | Bijan Saha | Yu.P. Rybakov, G.N. Shikin, Yu.A. Popov and Bijan Saha | Scalar field in cosmology: Potential for isotropization and inflation | 10 pages | Int.J.Theor.Phys.50 (2011) 3421 - 3431 | 10.1007/s10773-011-0847-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The important role of scalar field in cosmology was noticed by a number of
authors. Due to the fact that the scalar field possesses zero spin, it was
basically considered in isotropic cosmological models. If considered in an
anisotropic model, the linear scalar field does not lead to isotropization of
expansion process. One needs to introduce scalar field with nonlinear potential
for the isotropization process to take place. In this paper the general form of
scalar field potentials leading to the asymptotic isotropization in case of
Bianchi type-I cosmological model, and inflationary regime in case of isotropic
space-time is obtained. In doing so we solved both direct and inverse problem,
where by direct problem we mean to find metric functions and scalar field for
the given potential, whereas, the inverse problem means to find the potential
and scalar field for the given metric function. The scalar field potentials
leading to the inflation and isotropization were found both for harmonic and
proper synchronic time.
| [
{
"created": "Tue, 15 Jun 2010 13:31:59 GMT",
"version": "v1"
}
] | 2015-05-01 | [
[
"Rybakov",
"Yu. P.",
""
],
[
"Shikin",
"G. N.",
""
],
[
"Popov",
"Yu. A.",
""
],
[
"Saha",
"Bijan",
""
]
] | The important role of scalar field in cosmology was noticed by a number of authors. Due to the fact that the scalar field possesses zero spin, it was basically considered in isotropic cosmological models. If considered in an anisotropic model, the linear scalar field does not lead to isotropization of expansion process. One needs to introduce scalar field with nonlinear potential for the isotropization process to take place. In this paper the general form of scalar field potentials leading to the asymptotic isotropization in case of Bianchi type-I cosmological model, and inflationary regime in case of isotropic space-time is obtained. In doing so we solved both direct and inverse problem, where by direct problem we mean to find metric functions and scalar field for the given potential, whereas, the inverse problem means to find the potential and scalar field for the given metric function. The scalar field potentials leading to the inflation and isotropization were found both for harmonic and proper synchronic time. |
gr-qc/9912009 | Bernd Bruegmann | Bernd Bruegmann | Numerical Relativity in 3+1 Dimensions | 23 pages, 5 figures, review talk for Journees Relativistes 1999 | AnnalenPhys.9:227-246,2000 | 10.1002/(SICI)1521-3889(200005)9:3/5<227::AID-ANDP227>3.0.CO;2-D | AEI-1999-40 | gr-qc | null | Numerical relativity is finally approaching a state where the evolution of
rather general (3+1)-dimensional data sets can be computed in order to solve
the Einstein equations. After a general introduction, three topics of current
interest are briefly reviewed: binary black hole mergers, the evolution of
strong gravitational waves, and shift conditions for neutron star binaries.
| [
{
"created": "Thu, 2 Dec 1999 14:39:09 GMT",
"version": "v1"
}
] | 2017-09-27 | [
[
"Bruegmann",
"Bernd",
""
]
] | Numerical relativity is finally approaching a state where the evolution of rather general (3+1)-dimensional data sets can be computed in order to solve the Einstein equations. After a general introduction, three topics of current interest are briefly reviewed: binary black hole mergers, the evolution of strong gravitational waves, and shift conditions for neutron star binaries. |
1904.11602 | Oliver Janssen | Oliver Janssen, Jonathan J. Halliwell and Thomas Hertog | The no-boundary proposal in biaxial Bianchi IX minisuperspace | 49+29 pages, 19 figures | Phys. Rev. D 99, 123531 (2019) | 10.1103/PhysRevD.99.123531 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We implement the no-boundary proposal for the wave function of the universe
in an exactly solvable Bianchi IX minisuperspace model with two scale factors.
We extend our earlier work (Phys. Rev. Lett. 121, 081302, 2018 /
arXiv:1804.01102) to include the contribution from the $\mathbb{C}\text{P}^2
\setminus B^4$ topology. The resulting wave function yields normalizable
probabilities and thus fits into a predictive framework for semiclassical
quantum cosmology. We find that the amplitude is low for large anisotropies. In
the isotropic limit the usual Hartle-Hawking wave function for the de Sitter
minisuperspace model is recovered. Inhomogeneous perturbations in an extended
minisuperspace are shown to be initially in their ground state. We also
demonstrate that the precise mathematical implementation of the no-boundary
proposal as a functional integral in minisuperspace depends on detailed aspects
of the model, including the choice of gauge-fixing. This shows in particular
that the choice of contour cannot be fundamental, adding weight to the recent
proposal that the semiclassical no-boundary wave function should be defined
solely in terms of a collection of saddle points. We adopt this approach in
most of this paper. Finally we show that the semiclassical tunneling wave
function of the universe is essentially equal to the no-boundary state in this
particular minisuperspace model, at least in the subset of the classical domain
where the former is known.
| [
{
"created": "Thu, 25 Apr 2019 21:46:22 GMT",
"version": "v1"
}
] | 2019-07-03 | [
[
"Janssen",
"Oliver",
""
],
[
"Halliwell",
"Jonathan J.",
""
],
[
"Hertog",
"Thomas",
""
]
] | We implement the no-boundary proposal for the wave function of the universe in an exactly solvable Bianchi IX minisuperspace model with two scale factors. We extend our earlier work (Phys. Rev. Lett. 121, 081302, 2018 / arXiv:1804.01102) to include the contribution from the $\mathbb{C}\text{P}^2 \setminus B^4$ topology. The resulting wave function yields normalizable probabilities and thus fits into a predictive framework for semiclassical quantum cosmology. We find that the amplitude is low for large anisotropies. In the isotropic limit the usual Hartle-Hawking wave function for the de Sitter minisuperspace model is recovered. Inhomogeneous perturbations in an extended minisuperspace are shown to be initially in their ground state. We also demonstrate that the precise mathematical implementation of the no-boundary proposal as a functional integral in minisuperspace depends on detailed aspects of the model, including the choice of gauge-fixing. This shows in particular that the choice of contour cannot be fundamental, adding weight to the recent proposal that the semiclassical no-boundary wave function should be defined solely in terms of a collection of saddle points. We adopt this approach in most of this paper. Finally we show that the semiclassical tunneling wave function of the universe is essentially equal to the no-boundary state in this particular minisuperspace model, at least in the subset of the classical domain where the former is known. |
0808.1764 | David Garrison | David Garrison | Did Gravitational Waves Affect the Evolution of the Universe? | 14 pages, 1 figure | null | 10.1063/1.3183526 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As Cosmologists struggle to understand the evolution of our universe, an
often over-looked element is the affect of gravitational radiation on the
primordial plasma field. This appears to be due to the inaccurate approximation
of the primordial plasma field as a simple hydrodynamic fluid, therefore
neglecting the full dynamics of the magneto-fluid. In this paper, we show how
gravitational waves may have had a significant impact on the evolution of our
universe. While more work is needed, the author hopes to eventually develop a
large-scale simulation of structure formation in the early universe, which
takes the interactions of scalar perturbations, gravitational waves, magnetic
fields and a dynamic plasma field into account.
| [
{
"created": "Wed, 13 Aug 2008 01:01:23 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Jan 2009 23:16:41 GMT",
"version": "v2"
}
] | 2015-05-13 | [
[
"Garrison",
"David",
""
]
] | As Cosmologists struggle to understand the evolution of our universe, an often over-looked element is the affect of gravitational radiation on the primordial plasma field. This appears to be due to the inaccurate approximation of the primordial plasma field as a simple hydrodynamic fluid, therefore neglecting the full dynamics of the magneto-fluid. In this paper, we show how gravitational waves may have had a significant impact on the evolution of our universe. While more work is needed, the author hopes to eventually develop a large-scale simulation of structure formation in the early universe, which takes the interactions of scalar perturbations, gravitational waves, magnetic fields and a dynamic plasma field into account. |
1404.4046 | Herman Telkamp | Herman Telkamp | A relational approach to the Mach-Einstein question | Received honorable mention GRF 2013 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Mach's principle is incompatible with general relativity (GR), it has not
condensed into an established theory and suffers from inconsistencies. Yet, the
problem is that Mach's principle is a consequence of Berkeley's notions, which
are as good as irrefutable for their ontological nature. Moreover, the observed
coincidence of the "preferred inertial frame" and the frame attached to the
"fixed stars" is essentially Machian, while this coincidence is anomalous to
both GR and Newtonian physics. Another issue is that GR needs dark energy to
explain the accelerating expansion of the universe, while acceleration of
receding masses is inherent to the Machian principle. So GR and Mach's
principle question each other, while neither one can be falsified easily. This
suggest that both are valid in their particular domain. A relational theory may
reconcile the two, since it can cover both.
| [
{
"created": "Tue, 15 Apr 2014 18:35:01 GMT",
"version": "v1"
}
] | 2014-04-17 | [
[
"Telkamp",
"Herman",
""
]
] | Mach's principle is incompatible with general relativity (GR), it has not condensed into an established theory and suffers from inconsistencies. Yet, the problem is that Mach's principle is a consequence of Berkeley's notions, which are as good as irrefutable for their ontological nature. Moreover, the observed coincidence of the "preferred inertial frame" and the frame attached to the "fixed stars" is essentially Machian, while this coincidence is anomalous to both GR and Newtonian physics. Another issue is that GR needs dark energy to explain the accelerating expansion of the universe, while acceleration of receding masses is inherent to the Machian principle. So GR and Mach's principle question each other, while neither one can be falsified easily. This suggest that both are valid in their particular domain. A relational theory may reconcile the two, since it can cover both. |
0704.2881 | Daisuke Tatsumi | Daisuke Tatsumi, Ryutaro Takahashi, Koji Arai, Noriyasu Nakagawa,
Kazuhiro Agatsuma, Toshitaka Yamazaki, Mitsuhiro Fukushima, Masa-Katsu
Fujimoto, Akiteru Takamori, Alessandro Bertolini, Virginio Sannibale,
Riccardo DeSalvo, Szabolcs Marka, Masaki Ando, Kimio Tsubono, Tomomi Akutsu,
Kazuhiro Yamamoto, Hideki Ishitsuka, Takashi Uchiyama, Shinji Miyoki,
Masatake Ohashi, Kazuaki Kuroda, Norichika Awaya, Nobuyuki Kanda, Akito
Araya, Souichi Telada, Takayuki Tomaru, Tomiyoshi Haruyama, Akira Yamamoto,
Nobuaki Sato, Toshitaka Suzuki and Takakazu Shintomi | Current status of Japanese detectors | 6 pages, 5 figures, Proceedings of GWDAW-11 | Class.Quant.Grav.24:S399-S404,2007 | 10.1088/0264-9381/24/19/S03 | null | gr-qc | null | Current status of TAMA and CLIO detectors in Japan is reported in this
article. These two interferometric gravitational-wave detectors are being
developed for the large cryogenic gravitational wave telescope (LCGT) which is
a future plan for detecting gravitational wave signals at least once per year.
TAMA300 is being upgraded to improve the sensitivity in low frequency region
after the last observation experiment in 2004. To reduce the seismic noises, we
are installing new seismic isolation system, which is called TAMA Seismic
Attenuation System, for the four test masses. We confirmed stable mass locks of
a cavity and improvements of length and angular fluctuations by using two SASs.
We are currently optimizing the performance of the third and fourth SASs. We
continue TAMA300 operation and R&D studies for LCGT. Next data taking in the
summer of 2007 is planned.
CLIO is a 100-m baseline length prototype detector for LCGT to investigate
interferometer performance in cryogenic condition. The key features of CLIO are
that it locates Kamioka underground site for low seismic noise level, and
adopts cryogenic Sapphire mirrors for low thermal noise level. The first
operation of the cryogenic interferometer was successfully demonstrated in
February of 2006. Current sensitivity at room temperature is close to the
target sensitivity within a factor of 4. Several observation experiments at
room temperature have been done. Once the displacement noise reaches at thermal
noise level of room temperature, its improvement by cooling test mass mirrors
should be demonstrated.
| [
{
"created": "Sun, 22 Apr 2007 13:25:17 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Tatsumi",
"Daisuke",
""
],
[
"Takahashi",
"Ryutaro",
""
],
[
"Arai",
"Koji",
""
],
[
"Nakagawa",
"Noriyasu",
""
],
[
"Agatsuma",
"Kazuhiro",
""
],
[
"Yamazaki",
"Toshitaka",
""
],
[
"Fukushima",
"Mitsuhiro",
... | Current status of TAMA and CLIO detectors in Japan is reported in this article. These two interferometric gravitational-wave detectors are being developed for the large cryogenic gravitational wave telescope (LCGT) which is a future plan for detecting gravitational wave signals at least once per year. TAMA300 is being upgraded to improve the sensitivity in low frequency region after the last observation experiment in 2004. To reduce the seismic noises, we are installing new seismic isolation system, which is called TAMA Seismic Attenuation System, for the four test masses. We confirmed stable mass locks of a cavity and improvements of length and angular fluctuations by using two SASs. We are currently optimizing the performance of the third and fourth SASs. We continue TAMA300 operation and R&D studies for LCGT. Next data taking in the summer of 2007 is planned. CLIO is a 100-m baseline length prototype detector for LCGT to investigate interferometer performance in cryogenic condition. The key features of CLIO are that it locates Kamioka underground site for low seismic noise level, and adopts cryogenic Sapphire mirrors for low thermal noise level. The first operation of the cryogenic interferometer was successfully demonstrated in February of 2006. Current sensitivity at room temperature is close to the target sensitivity within a factor of 4. Several observation experiments at room temperature have been done. Once the displacement noise reaches at thermal noise level of room temperature, its improvement by cooling test mass mirrors should be demonstrated. |
1110.2159 | Kaca Bradonjic | Ka\'ca Bradonji\'c and John Stachel | Unimodular conformal and projective relativity | 6 pages. To appear in EPL. Abstract shortened. Equation typos fixed.
Two references added since v1 | EPL 97(1) (2012) 10001 | 10.1209/0295-5075/97/10001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We outline unimodular conformal and projective relativity (UCPR), an
extension of unimodular relativity in which the conformal and projective
structures play central roles. Under $SL(4,\mathbb{R})$ symmetry group, the
pseudo-Riemannian metric naturally decomposes into a four-volume element and a
conformal metric; and the affine connection decomposes into a one-form and a
trace-free projective connection. In UCPR, these four space-time structures are
treated as independent fields that have clear physical interpretations. A
Palatini-type variational principle for the usual general relativity Lagrangian
leads to a breakup of the Einstein field equations and the compatibility
conditions between the metric and connection. We indicate how new gravitational
theories may be generated by modifications of this Lagrangian and discuss two
such cases. Finally, we discuss possible physical consequences of our results
for quantum gravity.
| [
{
"created": "Mon, 10 Oct 2011 19:45:27 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Oct 2011 19:50:14 GMT",
"version": "v2"
},
{
"created": "Wed, 23 Nov 2011 19:10:48 GMT",
"version": "v3"
}
] | 2013-07-17 | [
[
"Bradonjić",
"Kaća",
""
],
[
"Stachel",
"John",
""
]
] | We outline unimodular conformal and projective relativity (UCPR), an extension of unimodular relativity in which the conformal and projective structures play central roles. Under $SL(4,\mathbb{R})$ symmetry group, the pseudo-Riemannian metric naturally decomposes into a four-volume element and a conformal metric; and the affine connection decomposes into a one-form and a trace-free projective connection. In UCPR, these four space-time structures are treated as independent fields that have clear physical interpretations. A Palatini-type variational principle for the usual general relativity Lagrangian leads to a breakup of the Einstein field equations and the compatibility conditions between the metric and connection. We indicate how new gravitational theories may be generated by modifications of this Lagrangian and discuss two such cases. Finally, we discuss possible physical consequences of our results for quantum gravity. |
2005.03771 | Vasil Todorinov | Pasquale Bosso, Saurya Das and Vasil Todorinov | Quantum field theory with the generalized uncertainty principle I:
scalar electrodynamics | Submitted to Annals o Physics | Annals of Physics Volume 422, November 2020, 168319 | 10.1016/j.aop.2020.168319 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, the authors presented a covariant extension of the Generalized
Uncertainty Principle (GUP) with a Lorentz invariant minimum length. This opens
the way for constructing and exploring the observable consequences of minimum
length in Relativistic Quantum Field Theories. In particular, we compute
quantum gravity corrections to high energy scattering experiments, which may
provide the much needed window of testing minimum length and quantum gravity
theories in the laboratory. To this end, we formulate the Lagrangian of Quantum
Electrodynamics for a complex scalar fields from the GUP modified minimally
coupled Klein-Gordon equation and write down its Feynman rules. We then
calculate the Relativistic Generalized Uncertainty Principle corrections to a
Quantum Electrodynamics scattering amplitude and discuss its implications.
| [
{
"created": "Thu, 7 May 2020 21:29:48 GMT",
"version": "v1"
}
] | 2021-08-12 | [
[
"Bosso",
"Pasquale",
""
],
[
"Das",
"Saurya",
""
],
[
"Todorinov",
"Vasil",
""
]
] | Recently, the authors presented a covariant extension of the Generalized Uncertainty Principle (GUP) with a Lorentz invariant minimum length. This opens the way for constructing and exploring the observable consequences of minimum length in Relativistic Quantum Field Theories. In particular, we compute quantum gravity corrections to high energy scattering experiments, which may provide the much needed window of testing minimum length and quantum gravity theories in the laboratory. To this end, we formulate the Lagrangian of Quantum Electrodynamics for a complex scalar fields from the GUP modified minimally coupled Klein-Gordon equation and write down its Feynman rules. We then calculate the Relativistic Generalized Uncertainty Principle corrections to a Quantum Electrodynamics scattering amplitude and discuss its implications. |
gr-qc/0604049 | Marco Valerio Battisti | Marco Valerio Battisti and Giovanni Montani | Evolutionary Quantum Dynamics of a Generic Universe | 7 pages, to appear on Phys. Lett. B | Phys.Lett. B637 (2006) 203-209 | 10.1016/j.physletb.2006.04.016 | null | gr-qc astro-ph | null | The implications of an Evolutionary Quantum Gravity are addressed in view of
formulating a new dark matter candidate. We consider a Schr\"odinger dynamics
for the gravitational field associated to a generic cosmological model and then
we solve the corresponding eigenvalues problem, inferring its phenomenological
issue for the actual Universe. The spectrum of the super-Hamiltonian is
determined including a free inflaton field, the ultrarelativistic thermal bath
and a perfect gas into the dynamics. We show that, when a Planckian cut-off is
imposed in the theory and the classical limit of the ground state is taken,
then a dark matter contribution can not arise because its critical parameter
$\Omega_{dm}$ is negligible today when the appropriate cosmological
implementation of the model is provided. Thus, we show that, from a
phenomenological point of view, an Evolutionary Quantum Cosmology overlaps the
Wheeler-DeWitt approach and therefore it can be inferred as appropriate to
describe early stages of the Universe without significant traces on the later
evolution. Finally, we provide indications that the horizon paradox can be
solved in the Planck era by the morphology of the Universe wave function.
| [
{
"created": "Mon, 10 Apr 2006 16:23:42 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Sep 2007 09:22:32 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Battisti",
"Marco Valerio",
""
],
[
"Montani",
"Giovanni",
""
]
] | The implications of an Evolutionary Quantum Gravity are addressed in view of formulating a new dark matter candidate. We consider a Schr\"odinger dynamics for the gravitational field associated to a generic cosmological model and then we solve the corresponding eigenvalues problem, inferring its phenomenological issue for the actual Universe. The spectrum of the super-Hamiltonian is determined including a free inflaton field, the ultrarelativistic thermal bath and a perfect gas into the dynamics. We show that, when a Planckian cut-off is imposed in the theory and the classical limit of the ground state is taken, then a dark matter contribution can not arise because its critical parameter $\Omega_{dm}$ is negligible today when the appropriate cosmological implementation of the model is provided. Thus, we show that, from a phenomenological point of view, an Evolutionary Quantum Cosmology overlaps the Wheeler-DeWitt approach and therefore it can be inferred as appropriate to describe early stages of the Universe without significant traces on the later evolution. Finally, we provide indications that the horizon paradox can be solved in the Planck era by the morphology of the Universe wave function. |
1408.3062 | Sujoy Modak PhD | Sujoy K. Modak, Leonardo Ort\'iz, Igor Pe\~na and Daniel Sudarsky | Non-Paradoxical Loss of Information in Black Hole Evaporation in a
Quantum Collapse Model | slightly expanded to improve on clarity and completeness, 11 pages, 3
figures, to appear in Physical Review D. arXiv admin note: text overlap with
arXiv:1406.4898 | Physical Review D, 91, 124009 (2015) | 10.1103/PhysRevD.91.124009 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a novel approach to address the black hole information paradox
(BHIP). The idea is based on adapting, to the situation at hand, the modified
versions of quantum theory involving spontaneous stochastic dynamical collapse
of quantum states, which have been considered in attempts to deal with
shortcomings of the standard Copenhagen interpretation of quantum mechanics, in
particular, the issue known as "the measurement problem". The new basic
hypothesis is that the modified quantum behavior is enhanced in the region of
high curvature so that the information encoded in the initial quantum state of
the matter fields is rapidly erased as the black hole singularity is
approached. We show that in this manner the complete evaporation of the black
hole via Hawking radiation can be understood as involving no paradox.
Calculations are performed using a modified version of quantum theory known as
"Continuous Spontaneous Localization" (CSL), which was originally developed in
the context of many particle non-relativistic quantum mechanics. We use a
version of CSL tailored to quantum field theory and applied in the context of
the two dimensional Callan-Giddings-Harvey-Strominger (CGHS) model. Although
the role of quantum gravity in this picture is restricted to the resolution of
the singularity, related studies suggest that there might be further
connections.
| [
{
"created": "Wed, 13 Aug 2014 17:41:06 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Aug 2014 20:57:42 GMT",
"version": "v2"
},
{
"created": "Mon, 18 May 2015 17:28:34 GMT",
"version": "v3"
}
] | 2015-06-05 | [
[
"Modak",
"Sujoy K.",
""
],
[
"Ortíz",
"Leonardo",
""
],
[
"Peña",
"Igor",
""
],
[
"Sudarsky",
"Daniel",
""
]
] | We consider a novel approach to address the black hole information paradox (BHIP). The idea is based on adapting, to the situation at hand, the modified versions of quantum theory involving spontaneous stochastic dynamical collapse of quantum states, which have been considered in attempts to deal with shortcomings of the standard Copenhagen interpretation of quantum mechanics, in particular, the issue known as "the measurement problem". The new basic hypothesis is that the modified quantum behavior is enhanced in the region of high curvature so that the information encoded in the initial quantum state of the matter fields is rapidly erased as the black hole singularity is approached. We show that in this manner the complete evaporation of the black hole via Hawking radiation can be understood as involving no paradox. Calculations are performed using a modified version of quantum theory known as "Continuous Spontaneous Localization" (CSL), which was originally developed in the context of many particle non-relativistic quantum mechanics. We use a version of CSL tailored to quantum field theory and applied in the context of the two dimensional Callan-Giddings-Harvey-Strominger (CGHS) model. Although the role of quantum gravity in this picture is restricted to the resolution of the singularity, related studies suggest that there might be further connections. |
0801.4671 | Tatyana P. Shestakova | T. P. Shestakova | Quantum cosmological solutions: their dependence on the choice of gauge
conditions and physical interpretation | 11 pages, 6 figures, talk presented at the International Conference
"Physical Interpretations of Relativity Theory - PIRT-2007" (Bauman
University, Moscow, July 2007) | Physical Interpretations of Relativity Theory: Proceedings of
International Meeting (Moscow, 2 - 5 July 2007), eds by M. C. Duffy, V. O.
Gladyshev, A. N. Morozov and P. Rowlands, Moscow, 2007, P. 104 - 112 | null | null | gr-qc | null | In "extended phase space" approach to quantum geometrodynamics numerical
solutions to Schrodinger equation corresponding to various choice of gauge
conditions are obtained for the simplest isotropic model. The "extended phase
space" approach belongs to those appeared in the last decade in which, as a
result of fixing a reference frame, the Wheeler - DeWitt static picture of the
world is replaced by evolutionary quantum geometrodynamics. Some aspects of
this approach were discussed at two previous PIRT meetings. We are interested
in the part of the wave function depending on physical degrees of freedom.
Three gauge conditions having a clear physical meaning are considered. They are
the conformal time gauge, the gauge producing the appearance of Lambda-term in
the Einstein equations, and the one covering the two previous cases as
asymptotic limits. The interpretation and discussion of the obtained solutions
is given.
| [
{
"created": "Wed, 30 Jan 2008 13:15:47 GMT",
"version": "v1"
}
] | 2008-01-31 | [
[
"Shestakova",
"T. P.",
""
]
] | In "extended phase space" approach to quantum geometrodynamics numerical solutions to Schrodinger equation corresponding to various choice of gauge conditions are obtained for the simplest isotropic model. The "extended phase space" approach belongs to those appeared in the last decade in which, as a result of fixing a reference frame, the Wheeler - DeWitt static picture of the world is replaced by evolutionary quantum geometrodynamics. Some aspects of this approach were discussed at two previous PIRT meetings. We are interested in the part of the wave function depending on physical degrees of freedom. Three gauge conditions having a clear physical meaning are considered. They are the conformal time gauge, the gauge producing the appearance of Lambda-term in the Einstein equations, and the one covering the two previous cases as asymptotic limits. The interpretation and discussion of the obtained solutions is given. |
gr-qc/9805087 | Henk van Elst | Henk van Elst and George F R Ellis (University of Cape Town) | Quasi-Newtonian dust cosmologies | 25 pages, LaTeX 2.09 (10pt), to appear in Classical and Quantum
Gravity, Vol. 15 (1998) | Class.Quant.Grav. 15 (1998) 3545-3573 | 10.1088/0264-9381/15/11/017 | UCT--98001 | gr-qc astro-ph | null | Exact dynamical equations for a generic dust matter source field in a
cosmological context are formulated with respect to a non-comoving
Newtonian-like timelike reference congruence and investigated for internal
consistency. On the basis of a lapse function $N$ (the relativistic
acceleration scalar potential) which evolves along the reference congruence
according to $\dot{N} = \alpha \Theta N$ ($\alpha = {const}$), we find that
consistency of the quasi-Newtonian dynamical equations is not attained at the
first derivative level. We then proceed to show that a self-consistent set can
be obtained by linearising the dynamical equations about a (non-comoving) FLRW
background. In this case, on properly accounting for the first-order momentum
density relating to the non-relativistic peculiar motion of the matter,
additional source terms arise in the evolution and constraint equations
describing small-amplitude energy density fluctuations that do not appear in
similar gravitational instability scenarios in the standard literature.
| [
{
"created": "Fri, 22 May 1998 15:30:22 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Sep 1998 14:21:04 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"van Elst",
"Henk",
"",
"University of Cape Town"
],
[
"Ellis",
"George F R",
"",
"University of Cape Town"
]
] | Exact dynamical equations for a generic dust matter source field in a cosmological context are formulated with respect to a non-comoving Newtonian-like timelike reference congruence and investigated for internal consistency. On the basis of a lapse function $N$ (the relativistic acceleration scalar potential) which evolves along the reference congruence according to $\dot{N} = \alpha \Theta N$ ($\alpha = {const}$), we find that consistency of the quasi-Newtonian dynamical equations is not attained at the first derivative level. We then proceed to show that a self-consistent set can be obtained by linearising the dynamical equations about a (non-comoving) FLRW background. In this case, on properly accounting for the first-order momentum density relating to the non-relativistic peculiar motion of the matter, additional source terms arise in the evolution and constraint equations describing small-amplitude energy density fluctuations that do not appear in similar gravitational instability scenarios in the standard literature. |
1708.00426 | Hee-Suk Cho | Hee-Suk Cho and Chang-Hwan Lee | Gravitational Wave Searches for Aligned-Spin Binary Neutron Stars Using
Nonspinning Templates | 4 pages, 2 figures | null | 10.3938/jkps.72.1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study gravitational wave searches for merging binary neutron stars (NSs).
We use nonspinning template waveforms towards the signals emitted from
aligned-spin NS-NS binaries, in which the spins of the NSs are aligned with the
orbital angular momentum. We use the TaylorF2 waveform model, which can
generate inspiral waveforms emitted from aligned-spin compact binaries. We
employ the single effective spin parameter $\chi_{\rm eff}$ to represent the
effect of two component spins ($\chi_1, \chi_2$) on the wave function. For a
target system, we choose a binary consisting of the same component masses of
$1.4 M_{\odot}$ and consider the spins up to $\chi_i= 0.4$, We investigate
fitting factors of the nonspinning templates to evaluate their efficiency in
gravitational wave searches for the aligned-spin NS-NS binaries. We find that
the templates can achieve the fitting factors exceeding $0.97$ only for the
signals in the range of $-0.2 \lesssim \chi_{\rm eff} \lesssim 0$. Therefore,
we demonstrate the necessity of using aligned-spin templates not to lose the
signals outside that range. We also show how much the recovered total mass can
be biased from the true value depending on the spin of the signal.
| [
{
"created": "Tue, 1 Aug 2017 17:23:08 GMT",
"version": "v1"
}
] | 2018-02-14 | [
[
"Cho",
"Hee-Suk",
""
],
[
"Lee",
"Chang-Hwan",
""
]
] | We study gravitational wave searches for merging binary neutron stars (NSs). We use nonspinning template waveforms towards the signals emitted from aligned-spin NS-NS binaries, in which the spins of the NSs are aligned with the orbital angular momentum. We use the TaylorF2 waveform model, which can generate inspiral waveforms emitted from aligned-spin compact binaries. We employ the single effective spin parameter $\chi_{\rm eff}$ to represent the effect of two component spins ($\chi_1, \chi_2$) on the wave function. For a target system, we choose a binary consisting of the same component masses of $1.4 M_{\odot}$ and consider the spins up to $\chi_i= 0.4$, We investigate fitting factors of the nonspinning templates to evaluate their efficiency in gravitational wave searches for the aligned-spin NS-NS binaries. We find that the templates can achieve the fitting factors exceeding $0.97$ only for the signals in the range of $-0.2 \lesssim \chi_{\rm eff} \lesssim 0$. Therefore, we demonstrate the necessity of using aligned-spin templates not to lose the signals outside that range. We also show how much the recovered total mass can be biased from the true value depending on the spin of the signal. |
2303.07562 | Hyerim Noh | Jai-chan Hwang and Hyerim Noh | Definition of electric and magnetic fields in curved spacetime | 6 pages, no figure, published version in Annals of Physics | null | 10.1016/j.aop.2023.169332 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Defining the electric and magnetic field vectors in curved spacetime requires
a proper choice of the observer's frame four-vector. Related literature shows
that this fundamental issue in physics still needs to be properly resolved. In
recent literature on using electromagnetic means to detect gravitational waves,
an ad hoc definition based on regarding $F_{ab}$ with two covariant indices as
the special relativistic one is popular. We show that by assigning physical
fields to tensor components in that way, one cannot identify the frame
four-vector allowing such a choice, thus failing to properly define the
external charge and current densities in that frame. We propose the normal
frame as the proper one. In this frame, the weak gravity corrections appear as
the effective polarizations and magnetizations in both the homogeneous and
inhomogeneous parts of Maxwell equations.
| [
{
"created": "Tue, 14 Mar 2023 01:02:48 GMT",
"version": "v1"
},
{
"created": "Sat, 6 May 2023 12:00:41 GMT",
"version": "v2"
}
] | 2023-05-24 | [
[
"Hwang",
"Jai-chan",
""
],
[
"Noh",
"Hyerim",
""
]
] | Defining the electric and magnetic field vectors in curved spacetime requires a proper choice of the observer's frame four-vector. Related literature shows that this fundamental issue in physics still needs to be properly resolved. In recent literature on using electromagnetic means to detect gravitational waves, an ad hoc definition based on regarding $F_{ab}$ with two covariant indices as the special relativistic one is popular. We show that by assigning physical fields to tensor components in that way, one cannot identify the frame four-vector allowing such a choice, thus failing to properly define the external charge and current densities in that frame. We propose the normal frame as the proper one. In this frame, the weak gravity corrections appear as the effective polarizations and magnetizations in both the homogeneous and inhomogeneous parts of Maxwell equations. |
0707.4362 | Guillermo A. Mena Marugan | Pablo Galan, Luis J. Garay, Guillermo A. Mena Marugan | Quantum time uncertainty in Schwarzschild-anti-de Sitter black holes | 10 pages, version published in Physical Review D | Phys.Rev.D76:044014,2007 | 10.1103/PhysRevD.76.044014 | null | gr-qc | null | The combined action of gravity and quantum mechanics gives rise to a minimum
time uncertainty in the lowest order approximation of a perturbative scheme, in
which quantum effects are regarded as corrections to the classical spacetime
geometry. From the nonperturbative point of view, both gravity and quantum
mechanics are treated on equal footing in a description that already contains
all possible backreaction effects as those above in a nonlinear manner. In this
paper, the existence or not of such minimum time uncertainty is analyzed in the
context of Schwarzschild-anti-de Sitter black holes using the isolated horizon
formalism. We show that from a perturbative point of view, a nonzero time
uncertainty is generically present owing to the energy scale introduced by the
cosmological constant, while in a quantization scheme that includes
nonperturbatively the effects of that scale, an arbitrarily high time
resolution can be reached.
| [
{
"created": "Mon, 30 Jul 2007 09:28:22 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Aug 2007 10:31:28 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Galan",
"Pablo",
""
],
[
"Garay",
"Luis J.",
""
],
[
"Marugan",
"Guillermo A. Mena",
""
]
] | The combined action of gravity and quantum mechanics gives rise to a minimum time uncertainty in the lowest order approximation of a perturbative scheme, in which quantum effects are regarded as corrections to the classical spacetime geometry. From the nonperturbative point of view, both gravity and quantum mechanics are treated on equal footing in a description that already contains all possible backreaction effects as those above in a nonlinear manner. In this paper, the existence or not of such minimum time uncertainty is analyzed in the context of Schwarzschild-anti-de Sitter black holes using the isolated horizon formalism. We show that from a perturbative point of view, a nonzero time uncertainty is generically present owing to the energy scale introduced by the cosmological constant, while in a quantization scheme that includes nonperturbatively the effects of that scale, an arbitrarily high time resolution can be reached. |
gr-qc/0406016 | Yuri Obukhov | Yu.N. Obukhov, T. Vargas | Goedel type solution in teleparallel gravity | Revtex, 15 pages, no figures, to appear in Phys. Lett. A | Phys.Lett. A327 (2004) 365-373 | 10.1016/j.physleta.2004.06.003 | null | gr-qc | null | The stationary cosmological model without closed timelike curves of G\"odel
type is obtained for the ideal dust matter source within the framework of the
teleparallel gravity. For a specific choice of the teleparallel gravity
parameters, this solution reproduces the causality violating stationary G\"odel
solution in general relativity, in accordance with the teleparallel equivalent
of general relativity. The relation between the axial-vector torsion and the
cosmic vorticity is clarified.
| [
{
"created": "Fri, 4 Jun 2004 13:33:38 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Obukhov",
"Yu. N.",
""
],
[
"Vargas",
"T.",
""
]
] | The stationary cosmological model without closed timelike curves of G\"odel type is obtained for the ideal dust matter source within the framework of the teleparallel gravity. For a specific choice of the teleparallel gravity parameters, this solution reproduces the causality violating stationary G\"odel solution in general relativity, in accordance with the teleparallel equivalent of general relativity. The relation between the axial-vector torsion and the cosmic vorticity is clarified. |
2004.06635 | James B. Hartle | James B. Hartle and Kristen Schleich | The Conformal Rotation in Linearised Gravity | A pre-arXiv paper posted for betterr accessibility, 20 pages, revtex4 | in Quantum Field Theory and Quantum Statistics (edited by I. A.
Batalin, C. J. Isham and G. A. Vilkovisky), Adam Hilger, Bristol, (1987 | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the quantum mechanics of Einstein gravity linearised about flat
spacetime. The two transverse-traceless components of the metric perturbation
are the true physical degrees of freedom. They appear in the quantum theory as
free quantum fields. Like the full Einstein action, the Euclidean action for
linearised gravity is unbounded below. It is therefore not possible to use that
action to represent the ground state wave function as a Euclidian functional
integral over exp{[-(action) /\hbar]}. However, it is possible to represent the
ground state as a Euclidian integral over the (deparametrised) action involving
only the true physical degrees of freedom. Starting from this integral
representation of the ground state and using the techniques of Faddeev and
Popov we show how to construct a Euclidean functional integral for the ground
state wave function. The integral explicitly exhibits the theory's gauge
symmetry, locality, and O(4) invariance. The conformal factor appears naturally
rotated into the complex plane. Other representations of the ground state are
exhibited.
| [
{
"created": "Tue, 14 Apr 2020 16:24:06 GMT",
"version": "v1"
}
] | 2020-04-15 | [
[
"Hartle",
"James B.",
""
],
[
"Schleich",
"Kristen",
""
]
] | We consider the quantum mechanics of Einstein gravity linearised about flat spacetime. The two transverse-traceless components of the metric perturbation are the true physical degrees of freedom. They appear in the quantum theory as free quantum fields. Like the full Einstein action, the Euclidean action for linearised gravity is unbounded below. It is therefore not possible to use that action to represent the ground state wave function as a Euclidian functional integral over exp{[-(action) /\hbar]}. However, it is possible to represent the ground state as a Euclidian integral over the (deparametrised) action involving only the true physical degrees of freedom. Starting from this integral representation of the ground state and using the techniques of Faddeev and Popov we show how to construct a Euclidean functional integral for the ground state wave function. The integral explicitly exhibits the theory's gauge symmetry, locality, and O(4) invariance. The conformal factor appears naturally rotated into the complex plane. Other representations of the ground state are exhibited. |
1912.03770 | Adamantia Zampeli | Adamantia Zampeli | Emergence of classicality from an inhomogeneous quantum universe | Prepared for the proceedings of the 2nd Domodossola summer school | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a short account of the quantisation of the Szekeres spacetime by
considering the symmetries of a reduced action principle. This is an
alternative approach than the one followed in the literature for the study of
inhomogeneities, which is usually based on perturbations of an inhomogeneous
field on the spacetime background. Here, we examine the emergence of
classicality with an exact inhomogeneous solution. We check whether the two
criteria for classicality are satisfied, that is the correlations on the phase
space and decoherence. We verify that these two properties indeed hold, thus
the classical behaviour emerges from our considerations. We comment on the
connection between the emergence of an inhomogeneous spacetime and the current
cosmological observations of a highly homogeneous universe at large scales.
| [
{
"created": "Sun, 8 Dec 2019 21:55:00 GMT",
"version": "v1"
}
] | 2019-12-10 | [
[
"Zampeli",
"Adamantia",
""
]
] | We give a short account of the quantisation of the Szekeres spacetime by considering the symmetries of a reduced action principle. This is an alternative approach than the one followed in the literature for the study of inhomogeneities, which is usually based on perturbations of an inhomogeneous field on the spacetime background. Here, we examine the emergence of classicality with an exact inhomogeneous solution. We check whether the two criteria for classicality are satisfied, that is the correlations on the phase space and decoherence. We verify that these two properties indeed hold, thus the classical behaviour emerges from our considerations. We comment on the connection between the emergence of an inhomogeneous spacetime and the current cosmological observations of a highly homogeneous universe at large scales. |
gr-qc/0607059 | Gianluca Calcagni | Gianluca Calcagni, Marina Cortes | Inflationary scalar spectrum in loop quantum cosmology | 29 pages, 2 figures. v2: typos corrected, discussion improved and
extended, new section added. Conclusions are unchanged | Class.Quant.Grav. 24 (2007) 829-854 | 10.1088/0264-9381/24/4/005 | null | gr-qc astro-ph hep-th | null | In the context of loop quantum cosmology, we consider an inflationary era
driven by a canonical scalar field and occurring in the semiclassical regime,
where spacetime is a continuum but quantum gravitational effects are important.
The spectral amplitude and index of scalar perturbations on an unperturbed de
Sitter background are computed at lowest order in the slow-roll parameters. The
scalar spectrum can be blue-tilted and far from scale invariance, and tuning of
the quantization ambiguities is necessary for agreement with observations. The
results are extended to a generalized quantization scheme including those
proposed in the literature. Quantization of the matter field at sub-horizon
scales can provide a consistency check of such schemes.
| [
{
"created": "Fri, 14 Jul 2006 18:23:43 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Jul 2006 19:52:50 GMT",
"version": "v2"
},
{
"created": "Thu, 18 Jan 2007 10:35:29 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Calcagni",
"Gianluca",
""
],
[
"Cortes",
"Marina",
""
]
] | In the context of loop quantum cosmology, we consider an inflationary era driven by a canonical scalar field and occurring in the semiclassical regime, where spacetime is a continuum but quantum gravitational effects are important. The spectral amplitude and index of scalar perturbations on an unperturbed de Sitter background are computed at lowest order in the slow-roll parameters. The scalar spectrum can be blue-tilted and far from scale invariance, and tuning of the quantization ambiguities is necessary for agreement with observations. The results are extended to a generalized quantization scheme including those proposed in the literature. Quantization of the matter field at sub-horizon scales can provide a consistency check of such schemes. |
gr-qc/9810087 | Philip Mannheim | Philip D. Mannheim (University of Connecticut) | The equivalence principle in classical mechanics and quantum mechanics | LaTeX, 21 pages. Expanded Final Version. To appear in "Contemporary
Fundamental Problems", Ed. Valeri Dvoeglazov (Nova Science Publishers),
Spring 2000 | null | null | null | gr-qc | null | We discuss our understanding of the equivalence principle in both classical
mechanics and quantum mechanics. We show that not only does the equivalence
principle hold for the trajectories of quantum particles in a background
gravitational field, but also that it is only because of this that the
equivalence principle is even to be expected to hold for classical particles at
all.
| [
{
"created": "Thu, 29 Oct 1998 19:19:22 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Apr 2000 20:34:40 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Mannheim",
"Philip D.",
"",
"University of Connecticut"
]
] | We discuss our understanding of the equivalence principle in both classical mechanics and quantum mechanics. We show that not only does the equivalence principle hold for the trajectories of quantum particles in a background gravitational field, but also that it is only because of this that the equivalence principle is even to be expected to hold for classical particles at all. |
0807.2990 | Wlodzimierz Piechocki | Przemyslaw Malkiewicz and Wlodzimierz Piechocki | Excited states of a string in a time dependent orbifold | Version accepted for publication in Class. Quantum Grav | Class.Quant.Grav.26:015008,2009 | 10.1088/0264-9381/26/1/015008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present analytical results on the propagation of a classical string in
non-zero modes through the singularity of the compactified Milne space. We
restrict our analysis to a string winding around the compact dimension of
spacetime. The compact dimension undergoes contraction to a point followed by
re-expansion. We demonstrate that the classical dynamics of the string in
excited states is non-singular in the entire spacetime.
| [
{
"created": "Fri, 18 Jul 2008 15:25:00 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Oct 2008 11:07:42 GMT",
"version": "v2"
},
{
"created": "Sat, 8 Nov 2008 08:52:17 GMT",
"version": "v3"
}
] | 2008-12-25 | [
[
"Malkiewicz",
"Przemyslaw",
""
],
[
"Piechocki",
"Wlodzimierz",
""
]
] | We present analytical results on the propagation of a classical string in non-zero modes through the singularity of the compactified Milne space. We restrict our analysis to a string winding around the compact dimension of spacetime. The compact dimension undergoes contraction to a point followed by re-expansion. We demonstrate that the classical dynamics of the string in excited states is non-singular in the entire spacetime. |
2010.04040 | Gilberto Medeiros Kremer | Gilberto M. Kremer and Leandro C. Mehret | Post-Newtonian Spherically Symmetrical Accretion | To appear in PRD | Phys. Rev. D 104, 024056 (2021) | 10.1103/PhysRevD.104.024056 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The objetive of this work is to investigate the influence of the corrections
to the spherical symmetrical accretion of an infinity gas cloud characterized
by a polytropic equation into a massive object due to the post-Newtonian
approximation.The post-Newtonian corrections to the critical values of the flow
velocity, sound velocity and radial distance are obtained from the system of
hydrodynamics equations in spherical coordinates. The critical point in the
post-Newtonian approximation accretion does not correspond to the transonic
point like in Newtonian theory. An equation for the Mach number was obtained as
a function of a dimensionless radial coordinate. It was considered that the
ratio of the sound velocity far the massive body and the speed of light was of
order $a_\infty/c=10^{-2}$. The analysis of the solution led to following
results: the Mach number for the Newtonian and post-Newtonian accretion have
practically the same values for radial distances of order of the critical
radial distance; by decreasing the radial distance the Mach number for the
Newtonian accretion is bigger than the one for the post-Newtonian accretion;
the Mach number increases by decreasing the ratio of the specific heats; the
difference between the Newtonian and post-Newtonian Mach numbers when the ratio
$a_\infty/c\ll10^{-2}$ is insignificant. The effect of the correction terms in
post-Newtonian Bernoulli equation is more perceptive for the lowest values of
the radial distance, and the solutions for $a_\infty/c>10^{-2}$ does not lead
to a continuous inflow and outflow velocity at the critical point. A comparison
of the solutions with those that follow from a relativistic Bernoulli equation
shows that the dependence of the Mach number with the radial distance of the
former is bigger than the post-Newtonian ones.
| [
{
"created": "Thu, 8 Oct 2020 15:08:07 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Jun 2021 20:42:57 GMT",
"version": "v2"
}
] | 2021-07-28 | [
[
"Kremer",
"Gilberto M.",
""
],
[
"Mehret",
"Leandro C.",
""
]
] | The objetive of this work is to investigate the influence of the corrections to the spherical symmetrical accretion of an infinity gas cloud characterized by a polytropic equation into a massive object due to the post-Newtonian approximation.The post-Newtonian corrections to the critical values of the flow velocity, sound velocity and radial distance are obtained from the system of hydrodynamics equations in spherical coordinates. The critical point in the post-Newtonian approximation accretion does not correspond to the transonic point like in Newtonian theory. An equation for the Mach number was obtained as a function of a dimensionless radial coordinate. It was considered that the ratio of the sound velocity far the massive body and the speed of light was of order $a_\infty/c=10^{-2}$. The analysis of the solution led to following results: the Mach number for the Newtonian and post-Newtonian accretion have practically the same values for radial distances of order of the critical radial distance; by decreasing the radial distance the Mach number for the Newtonian accretion is bigger than the one for the post-Newtonian accretion; the Mach number increases by decreasing the ratio of the specific heats; the difference between the Newtonian and post-Newtonian Mach numbers when the ratio $a_\infty/c\ll10^{-2}$ is insignificant. The effect of the correction terms in post-Newtonian Bernoulli equation is more perceptive for the lowest values of the radial distance, and the solutions for $a_\infty/c>10^{-2}$ does not lead to a continuous inflow and outflow velocity at the critical point. A comparison of the solutions with those that follow from a relativistic Bernoulli equation shows that the dependence of the Mach number with the radial distance of the former is bigger than the post-Newtonian ones. |
0808.2101 | Sunil Maharaj | S. S. Rajah, S.D. Maharaj | A Riccati equation in radiative stellar collapse | 13 pages, To appear in J. Math. Phys | J.Math.Phys.49:012501,2008 | 10.1063/1.2832628 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We model the behaviour of a relativistic spherically symmetric shearing fluid
undergoing gravitational collapse with heat flux. It is demonstrated that the
governing equation for the gravitational behaviour is a Riccati equation. We
show that the Riccati equation admits two classes of new solutions in closed
form. We regain particular models, obtained in previous investigations, as
special cases. A significant feature of our solutions is the general spatial
dependence in the metric functions which allows for a wider study of the
physical features of the model, such as the behaviour of the causal temperature
in inhomogeneous spacetimes.
| [
{
"created": "Fri, 15 Aug 2008 06:53:21 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Rajah",
"S. S.",
""
],
[
"Maharaj",
"S. D.",
""
]
] | We model the behaviour of a relativistic spherically symmetric shearing fluid undergoing gravitational collapse with heat flux. It is demonstrated that the governing equation for the gravitational behaviour is a Riccati equation. We show that the Riccati equation admits two classes of new solutions in closed form. We regain particular models, obtained in previous investigations, as special cases. A significant feature of our solutions is the general spatial dependence in the metric functions which allows for a wider study of the physical features of the model, such as the behaviour of the causal temperature in inhomogeneous spacetimes. |
0909.1589 | David Kubiznak | David Kubiznak | Black hole spacetimes with Killing-Yano symmetries | 6 pages, no figures, prepared for the proceedings of the ICMP 09,
v2:upgraded references | null | 10.1142/9789814304634_0052 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a brief overview of black hole spacetimes admitting Killing-Yano
tensors. In vacuum these include Kerr-NUT-(A)dS metrics and certain black brane
solutions. In the presence of matter fields, (conformal) Killing-Yano
symmetries are known to exist for the Plebanski-Demianski solution and
(trivially) for any spacetime with spherical symmetry. Special attention is
devoted to generalized Killing-Yano tensors of black holes in minimal gauged
supergravity. Several aspects directly related to the existence of Killing-Yano
tensors, such as the Kerr-Schild form, algebraic type of spacetimes, and
separability of field equations, are also briefly discussed.
| [
{
"created": "Tue, 8 Sep 2009 22:26:23 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Nov 2009 16:27:11 GMT",
"version": "v2"
}
] | 2017-08-23 | [
[
"Kubiznak",
"David",
""
]
] | We present a brief overview of black hole spacetimes admitting Killing-Yano tensors. In vacuum these include Kerr-NUT-(A)dS metrics and certain black brane solutions. In the presence of matter fields, (conformal) Killing-Yano symmetries are known to exist for the Plebanski-Demianski solution and (trivially) for any spacetime with spherical symmetry. Special attention is devoted to generalized Killing-Yano tensors of black holes in minimal gauged supergravity. Several aspects directly related to the existence of Killing-Yano tensors, such as the Kerr-Schild form, algebraic type of spacetimes, and separability of field equations, are also briefly discussed. |
1504.05356 | Roberto Casadio | Roberto Casadio, Andrea Giugno, Alessio Orlandi | Thermal corpuscular black holes | PDFLaTeX, 15 pages, 2 figure. Version to appear in PRD | Phys. Rev. D 91, 124069 (2015) | 10.1103/PhysRevD.91.124069 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the corpuscular model of an evaporating black hole consisting of a
specific quantum state for a large number $N$ of self-confined bosons. The
single-particle spectrum contains a discrete ground state of energy $m$
(corresponding to toy gravitons forming the black hole), and a gapless
continuous spectrum (to accommodate for the Hawking radiation with energy
$\omega>m$). Each constituent is in a superposition of the ground state and a
Planckian distribution at the expected Hawking temperature in the continuum. We
first find that, assuming the Hawking radiation is the leading effect of the
internal scatterings, the corresponding $N$-particle state can be collectively
described by a single-particle wave-function given by a superposition of a
total ground state with energy $M=N\,m$ and a Planckian distribution for $E>M$
at the same Hawking temperature. From this collective state, we compute the
partition function and obtain an entropy which reproduces the usual area law
with a logarithmic correction precisely related with the Hawking component. By
means of the horizon wave-function for the system, we finally show the
backreaction of modes with $\omega>m$ reduces the Hawking flux. Both
corrections, to the entropy and to the Hawking flux, suggest the evaporation
properly stops for vanishing mass, if the black hole is in this particular
quantum state.
| [
{
"created": "Tue, 21 Apr 2015 09:37:18 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Jun 2015 06:36:53 GMT",
"version": "v2"
}
] | 2015-07-01 | [
[
"Casadio",
"Roberto",
""
],
[
"Giugno",
"Andrea",
""
],
[
"Orlandi",
"Alessio",
""
]
] | We study the corpuscular model of an evaporating black hole consisting of a specific quantum state for a large number $N$ of self-confined bosons. The single-particle spectrum contains a discrete ground state of energy $m$ (corresponding to toy gravitons forming the black hole), and a gapless continuous spectrum (to accommodate for the Hawking radiation with energy $\omega>m$). Each constituent is in a superposition of the ground state and a Planckian distribution at the expected Hawking temperature in the continuum. We first find that, assuming the Hawking radiation is the leading effect of the internal scatterings, the corresponding $N$-particle state can be collectively described by a single-particle wave-function given by a superposition of a total ground state with energy $M=N\,m$ and a Planckian distribution for $E>M$ at the same Hawking temperature. From this collective state, we compute the partition function and obtain an entropy which reproduces the usual area law with a logarithmic correction precisely related with the Hawking component. By means of the horizon wave-function for the system, we finally show the backreaction of modes with $\omega>m$ reduces the Hawking flux. Both corrections, to the entropy and to the Hawking flux, suggest the evaporation properly stops for vanishing mass, if the black hole is in this particular quantum state. |
0903.2670 | Mohammad Vahid Takook | M.V. Takook and M.R. Tanhayi | Linear Weyl Gravity in de Sitter Universe | 13 pages, some details added, typos corrected, reference added | JHEP 1012:044,2010 | 10.1007/JHEP12(2010)044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we obtain the linear Weyl gravity in de Sitter background. Its
linear form in five-dimensional ambient space notation has also been obtained.
From the group theoretical point of view, we show that this conformal invariant
fourth order theory in its linear form does not transform as an unitary
irreducible representation of the de Sitter group.
| [
{
"created": "Sun, 15 Mar 2009 21:53:21 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Sep 2010 07:26:52 GMT",
"version": "v2"
}
] | 2010-12-23 | [
[
"Takook",
"M. V.",
""
],
[
"Tanhayi",
"M. R.",
""
]
] | In this paper we obtain the linear Weyl gravity in de Sitter background. Its linear form in five-dimensional ambient space notation has also been obtained. From the group theoretical point of view, we show that this conformal invariant fourth order theory in its linear form does not transform as an unitary irreducible representation of the de Sitter group. |
2311.04602 | Bobir Toshmatov | Bobir Toshmatov and Bobomurat Ahmedov | Tidal forces in parametrized spacetime: Rezzolla-Zhidenko
parametrization | 13 pages, 13 figures | Phys. Rev. D 108, 084035 (2023) | 10.1103/PhysRevD.108.084035 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | We investigate the tidal forces exerted by a spherically symmetric static
parametrized black hole. Our analysis reveals that the radial and angular
components of the tidal forces exerted by the black hole can exhibit both
positive and negative values near the black hole, depending on matters of the
spacetime parameters. Unlike the scenario with the Schwarzschild black hole,
where the radial tidal force (angular tidal force) is always stretching
(compressing) and becomes infinite at the center of the spacetime, the
parametrized black hole allows for finite and compressing (stretching) forces
within the event horizon. Additionally, we derive the geodesic deviation
equations for a particle in free fall and proceed to solve them through
numerical methods. Our analysis demonstrates that the spacetime parameters
$\epsilon$ and $a_1$ exhibit contrasting influences on the magnitudes of the
physical quantities associated with tidal effects.
| [
{
"created": "Wed, 8 Nov 2023 11:07:53 GMT",
"version": "v1"
}
] | 2023-11-09 | [
[
"Toshmatov",
"Bobir",
""
],
[
"Ahmedov",
"Bobomurat",
""
]
] | We investigate the tidal forces exerted by a spherically symmetric static parametrized black hole. Our analysis reveals that the radial and angular components of the tidal forces exerted by the black hole can exhibit both positive and negative values near the black hole, depending on matters of the spacetime parameters. Unlike the scenario with the Schwarzschild black hole, where the radial tidal force (angular tidal force) is always stretching (compressing) and becomes infinite at the center of the spacetime, the parametrized black hole allows for finite and compressing (stretching) forces within the event horizon. Additionally, we derive the geodesic deviation equations for a particle in free fall and proceed to solve them through numerical methods. Our analysis demonstrates that the spacetime parameters $\epsilon$ and $a_1$ exhibit contrasting influences on the magnitudes of the physical quantities associated with tidal effects. |
2201.06489 | Arnab Sarkar | Shashank S. Pandey, Arnab Sarkar, Amna Ali, and A. S. Majumdar | Effect of inhomogeneities on the propagation of gravitational waves from
binaries of compact objects | 8 pages, 5 figures | JCAP06(2022)021 | 10.1088/1475-7516/2022/06/021 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the propagation of gravitational waves in the late time Universe
with the presence of structure. Before detection, gravitational waves emitted
from distant sources have to traverse through regions of spacetime which are
far from smooth and homogeneous. We investigate the effect of inhomogeneities
on the observables associated with the gravitational wave sources. In
particular, we evaluate the impact of inhomogeneities on gravitational wave
propagation by employing Buchert's framework of averaging. In context of a toy
model within the above framework, it is first shown how the redshift versus
distance relation gets affected through the averaging process. We then study
the variation of the redshift dependent part of the observed gravitational wave
amplitude for different combination of our model parameters. We show that the
variation of the gravitational wave amplitude with respect to redshift can
deviate significantly compared to that in the $\Lambda$CDM-model. Our result
signifies the importance of local inhomogeneities on precision measurements of
parameters of gravitational wave sources.
| [
{
"created": "Mon, 17 Jan 2022 16:01:36 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Jan 2022 16:30:36 GMT",
"version": "v2"
},
{
"created": "Sat, 23 Apr 2022 14:47:10 GMT",
"version": "v3"
},
{
"created": "Fri, 24 Jun 2022 16:00:23 GMT",
"version": "v4"
}
] | 2022-06-27 | [
[
"Pandey",
"Shashank S.",
""
],
[
"Sarkar",
"Arnab",
""
],
[
"Ali",
"Amna",
""
],
[
"Majumdar",
"A. S.",
""
]
] | We consider the propagation of gravitational waves in the late time Universe with the presence of structure. Before detection, gravitational waves emitted from distant sources have to traverse through regions of spacetime which are far from smooth and homogeneous. We investigate the effect of inhomogeneities on the observables associated with the gravitational wave sources. In particular, we evaluate the impact of inhomogeneities on gravitational wave propagation by employing Buchert's framework of averaging. In context of a toy model within the above framework, it is first shown how the redshift versus distance relation gets affected through the averaging process. We then study the variation of the redshift dependent part of the observed gravitational wave amplitude for different combination of our model parameters. We show that the variation of the gravitational wave amplitude with respect to redshift can deviate significantly compared to that in the $\Lambda$CDM-model. Our result signifies the importance of local inhomogeneities on precision measurements of parameters of gravitational wave sources. |
1310.5335 | Mart\'in G. Richarte MR | Luis P. Chimento, Mart\'in G. Richarte, and Iv\'an E. S\'anchez
Garc\'ia | Interacting dark sector with variable vacuum energy | 5 pages,3 figures, 2 tables.
(http://prd.aps.org/abstract/PRD/v88/i8/e087301) | Phys. Rev. D 88, 087301 (2013) | 10.1103/PhysRevD.88.087301 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine a cosmological scenario where dark matter is coupled to a variable
vacuum energy while baryons and photons are two decoupled components for a
spatially flat Friedmann-Robertson-Walker spacetime. We apply the $\chi^{2}$
method to the updated observational Hubble data for constraining the
cosmological parameters and analyze the amount of dark energy in the radiation
era. We show that our model fulfills the severe bound of $\Omega_{x}(z\simeq
1100)<0.009$ at the $2\sigma$ level, so it is consistent with the recent
analysis that includes cosmic microwave background anisotropy measurements from
the Planck survey, the Atacama Cosmology Telescope, and the South Pole
Telescope along with the future constraints achievable by the Euclid and CMBPol
experiments, and fulfills the stringent bound $\Omega_{x}(z\simeq
10^{10})<0.04$ at the $2\sigma$ level in the big-bang nucleosynthesis epoch.
| [
{
"created": "Sun, 20 Oct 2013 14:56:40 GMT",
"version": "v1"
}
] | 2016-04-01 | [
[
"Chimento",
"Luis P.",
""
],
[
"Richarte",
"Martín G.",
""
],
[
"García",
"Iván E. Sánchez",
""
]
] | We examine a cosmological scenario where dark matter is coupled to a variable vacuum energy while baryons and photons are two decoupled components for a spatially flat Friedmann-Robertson-Walker spacetime. We apply the $\chi^{2}$ method to the updated observational Hubble data for constraining the cosmological parameters and analyze the amount of dark energy in the radiation era. We show that our model fulfills the severe bound of $\Omega_{x}(z\simeq 1100)<0.009$ at the $2\sigma$ level, so it is consistent with the recent analysis that includes cosmic microwave background anisotropy measurements from the Planck survey, the Atacama Cosmology Telescope, and the South Pole Telescope along with the future constraints achievable by the Euclid and CMBPol experiments, and fulfills the stringent bound $\Omega_{x}(z\simeq 10^{10})<0.04$ at the $2\sigma$ level in the big-bang nucleosynthesis epoch. |
0902.3416 | Alejandro Perez | Danilo Jimenez Rezende, and Alejandro Perez | 4d Lorentzian Holst action with topological terms | null | Phys.Rev.D79:064026,2009 | 10.1103/PhysRevD.79.064026 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Hamiltonian formulation of the general first order action of
general relativity compatible with local Lorentz invariance and background
independence. The most general simplectic structure (compatible with
diffeomorphism invariance and local Lorentz transformations) is obtained by
adding to the Holst action the Pontriagin, Euler and Nieh-Yan invariants with
independent coupling constants. We perform a detailed canonical analysis of
this general formulation (in the time gauge) exploring the structure of the
phase space in terms of connection variables. We explain the relationship of
these topological terms, and the effect of large SU(2) gauge transformations in
quantum theories of gravity defined in terms of the Ashtekar-Barbero
connection.
| [
{
"created": "Thu, 19 Feb 2009 17:20:26 GMT",
"version": "v1"
}
] | 2010-01-15 | [
[
"Rezende",
"Danilo Jimenez",
""
],
[
"Perez",
"Alejandro",
""
]
] | We study the Hamiltonian formulation of the general first order action of general relativity compatible with local Lorentz invariance and background independence. The most general simplectic structure (compatible with diffeomorphism invariance and local Lorentz transformations) is obtained by adding to the Holst action the Pontriagin, Euler and Nieh-Yan invariants with independent coupling constants. We perform a detailed canonical analysis of this general formulation (in the time gauge) exploring the structure of the phase space in terms of connection variables. We explain the relationship of these topological terms, and the effect of large SU(2) gauge transformations in quantum theories of gravity defined in terms of the Ashtekar-Barbero connection. |
1708.00271 | Hugo Ferreira | Francesco Bussola, Claudio Dappiaggi, Hugo R. C. Ferreira, Igor
Khavkine | Ground state for a massive scalar field in BTZ spacetime with Robin
boundary conditions | 17 pages, 3 figures | Phys. Rev. D 96, 105016 (2017) | 10.1103/PhysRevD.96.105016 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a real, massive scalar field in BTZ spacetime, a 2+1-dimensional
black hole solution of the Einstein's field equations with a negative
cosmological constant. First, we analyze the space of classical solutions in a
mode decomposition and we characterize the collection of all admissible
boundary conditions of Robin type which can be imposed at infinity. Secondly,
we investigate whether, for a given boundary condition, there exists a ground
state by constructing explicitly its two-point function. We demonstrate that
for a subclass of the boundary conditions it is possible to construct a ground
state that locally satisfies the Hadamard property. In all other cases, we show
that bound state mode solutions exist and, therefore, such construction is not
possible.
| [
{
"created": "Tue, 1 Aug 2017 12:12:37 GMT",
"version": "v1"
}
] | 2017-11-29 | [
[
"Bussola",
"Francesco",
""
],
[
"Dappiaggi",
"Claudio",
""
],
[
"Ferreira",
"Hugo R. C.",
""
],
[
"Khavkine",
"Igor",
""
]
] | We consider a real, massive scalar field in BTZ spacetime, a 2+1-dimensional black hole solution of the Einstein's field equations with a negative cosmological constant. First, we analyze the space of classical solutions in a mode decomposition and we characterize the collection of all admissible boundary conditions of Robin type which can be imposed at infinity. Secondly, we investigate whether, for a given boundary condition, there exists a ground state by constructing explicitly its two-point function. We demonstrate that for a subclass of the boundary conditions it is possible to construct a ground state that locally satisfies the Hadamard property. In all other cases, we show that bound state mode solutions exist and, therefore, such construction is not possible. |
0706.1319 | Luis Lehner | Luis Lehner and Osvaldo M. Moreschi | Dealing with delicate issues in waveforms calculations | null | Phys.Rev.D76:124040,2007 | 10.1103/PhysRevD.76.124040 | null | gr-qc | null | We revisit the calculation of gravitational radiation through the use of Weyl
scalars. We point out several possible problems arising from gauge and tetrad
ambiguities and ways to address them. Our analysis indicates how, relatively
simple corrections can be introduced to remove these ambiguities.
| [
{
"created": "Sat, 9 Jun 2007 16:20:09 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Lehner",
"Luis",
""
],
[
"Moreschi",
"Osvaldo M.",
""
]
] | We revisit the calculation of gravitational radiation through the use of Weyl scalars. We point out several possible problems arising from gauge and tetrad ambiguities and ways to address them. Our analysis indicates how, relatively simple corrections can be introduced to remove these ambiguities. |
1109.0118 | Giacomo Mauro D'Ariano Prof. | Giacomo Mauro D'Ariano and Alessandro Tosini | Emergence of Space-Time from Topologically Homogeneous Causal Networks | This manuscript supersedes arXiv:1008.4805v1. Submitted to Studies in
History and Philosophy of Modern Physics special Issue on Emergent Space-Time | Studies in History and Philosophy of Modern Physics, 44 (2013) | 10.1016/j.shpsb.2013.04.003 | null | gr-qc hep-lat quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the emergence of Minkowski space-time from a causal network.
Differently from previous approaches, we require the network to be
topologically homogeneous, so that the metric is derived from pure
event-counting. Emergence from events has an operational motivation in
requiring that every physical quantity---including space-time---be defined
through precise measurement procedures. Topological homogeneity is a
requirement for having space-time metric emergent from the pure topology of
causal connections, whereas physically homogeneity corresponds to the
universality of the physical law. We analyze in detail the case of 1+1
dimensions. If we consider the causal connections as an exchange of classical
information, we can establish coordinate systems via an Einsteinian protocol,
and this leads to a digital version of the Lorentz transformations. In a
computational analogy, the foliation construction can be regarded as the
synchronization with a global clock of the calls to independent subroutines
(corresponding to the causally independent events) in a parallel distributed
computation. Thus the Lorentz time-dilation emerges as an increased density of
leaves within a single tic-tac of a clock, whereas space-contraction results
from the corresponding decrease of density of events per leaf. The operational
procedure of building up the coordinate system introduces an in-principle
indistinguishability between neighboring events, resulting in a network that is
coarse-grained, the thickness of the event being a function of the observer's
clock.
| [
{
"created": "Thu, 1 Sep 2011 08:01:29 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Jul 2012 14:21:35 GMT",
"version": "v2"
}
] | 2016-01-26 | [
[
"D'Ariano",
"Giacomo Mauro",
""
],
[
"Tosini",
"Alessandro",
""
]
] | We study the emergence of Minkowski space-time from a causal network. Differently from previous approaches, we require the network to be topologically homogeneous, so that the metric is derived from pure event-counting. Emergence from events has an operational motivation in requiring that every physical quantity---including space-time---be defined through precise measurement procedures. Topological homogeneity is a requirement for having space-time metric emergent from the pure topology of causal connections, whereas physically homogeneity corresponds to the universality of the physical law. We analyze in detail the case of 1+1 dimensions. If we consider the causal connections as an exchange of classical information, we can establish coordinate systems via an Einsteinian protocol, and this leads to a digital version of the Lorentz transformations. In a computational analogy, the foliation construction can be regarded as the synchronization with a global clock of the calls to independent subroutines (corresponding to the causally independent events) in a parallel distributed computation. Thus the Lorentz time-dilation emerges as an increased density of leaves within a single tic-tac of a clock, whereas space-contraction results from the corresponding decrease of density of events per leaf. The operational procedure of building up the coordinate system introduces an in-principle indistinguishability between neighboring events, resulting in a network that is coarse-grained, the thickness of the event being a function of the observer's clock. |
gr-qc/0207059 | Sergio De Filippo | Sergio De Filippo, Filippo Maimone | Nonunitary Classically Stable HD Gravity | 6 pages, to appear in Proceedings of the First International
Conference on Quantum Limits to the Second Law, July 29-31, 2002, University
of San Diego, San Diego, CA | AIP Conf.Proc. 643 (2003) 373-378 | null | null | gr-qc | null | Classical instability in fourth order gravity is cured at the expense of
unitarity. The appearance of hidden degrees of freedom replicating those of
ordinary matter allows for ordinary thermodynamic entropy and black hole
entropy to be identified with von Neumann entropy. The emergent picture gives a
substantial agreement with B-H entropy and Hawking temperature.
| [
{
"created": "Tue, 16 Jul 2002 10:05:42 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"De Filippo",
"Sergio",
""
],
[
"Maimone",
"Filippo",
""
]
] | Classical instability in fourth order gravity is cured at the expense of unitarity. The appearance of hidden degrees of freedom replicating those of ordinary matter allows for ordinary thermodynamic entropy and black hole entropy to be identified with von Neumann entropy. The emergent picture gives a substantial agreement with B-H entropy and Hawking temperature. |
1205.6121 | Arindam Lala | Arindam Lala | Critical phenomena in higher curvature charged AdS black holes | LaTex, 29 pages, 14 figures, modified version, accepted for
publication in the Advances in High Energy Physics | Advances in High Energy Physics, Volume 2013, Article ID 918490 | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we have studied the critical phenomena in higher curvature
charged black holes in the anti-de Sitter (AdS) space-time. As an example we
have considered the third order Lovelock-Born-Infeld black holes in AdS
space-time. We have analytically derived the thermodynamic quantities of the
system. Our analysis revealed the onset of a higher order phase transition in
the black hole leading to an infinite discontinuity in the specific heat at
constant charge at the critical points. Our entire analysis is based on the
canonical framework where we have fixed the charge of the black hole. In an
attempt to study the behavior of the thermodynamic quantities near the critical
points we have derived the critical exponents of the system explicitly.
Although the values of the critical points have been determined numerically,
the critical exponents are calculated analytically. Our results fit well with
the thermodynamic scaling laws. The scaling hypothesis is also seen to be
consistent with these scaling laws. We find that all types of AdS black holes,
studied so far, indeed belong to the same universality class. Moreover these
results are consistent with the mean field theory approximation. We have
derived the suggestive values of the other two critical exponents associated
with the correlation function and correlation length on the critical surface.
| [
{
"created": "Mon, 28 May 2012 14:11:44 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Sep 2013 12:25:11 GMT",
"version": "v2"
}
] | 2013-12-20 | [
[
"Lala",
"Arindam",
""
]
] | In this paper we have studied the critical phenomena in higher curvature charged black holes in the anti-de Sitter (AdS) space-time. As an example we have considered the third order Lovelock-Born-Infeld black holes in AdS space-time. We have analytically derived the thermodynamic quantities of the system. Our analysis revealed the onset of a higher order phase transition in the black hole leading to an infinite discontinuity in the specific heat at constant charge at the critical points. Our entire analysis is based on the canonical framework where we have fixed the charge of the black hole. In an attempt to study the behavior of the thermodynamic quantities near the critical points we have derived the critical exponents of the system explicitly. Although the values of the critical points have been determined numerically, the critical exponents are calculated analytically. Our results fit well with the thermodynamic scaling laws. The scaling hypothesis is also seen to be consistent with these scaling laws. We find that all types of AdS black holes, studied so far, indeed belong to the same universality class. Moreover these results are consistent with the mean field theory approximation. We have derived the suggestive values of the other two critical exponents associated with the correlation function and correlation length on the critical surface. |
gr-qc/0402037 | Hironobu Furuhashi | Hironobu Furuhashi, Yasusada Nambu | Instability of Massive Scalar Fields in Kerr-Newman Spacetime | 15 pages, 10 figures. Accepted for publication in Prog.Theor.Phys | Prog.Theor.Phys. 112 (2004) 983-995 | 10.1143/PTP.112.983 | DPNU-03-28 | gr-qc | null | We investigate the instability of charged massive scalar fields in
Kerr-Newman spacetime. Due to the super-radiant effect of the background
geometry, the bound state of the scalar field is unstable, and its amplitude
grows in time. By solving the Klein-Gordon equation of the scalar field as an
eigenvalue problem, we numerically obtain the growth rate of the amplitude of
the scalar field. Although the dependence of the scalar field mass and the
scalar field charge on this growth rate agrees with the result of the analytic
approximation, the maximum value of the growth rate is three times larger than
that of the analytic approximation. We also discuss the effect of the electric
charge on the instability of the scalar field.
| [
{
"created": "Fri, 6 Feb 2004 18:13:18 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Dec 2004 05:32:27 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Furuhashi",
"Hironobu",
""
],
[
"Nambu",
"Yasusada",
""
]
] | We investigate the instability of charged massive scalar fields in Kerr-Newman spacetime. Due to the super-radiant effect of the background geometry, the bound state of the scalar field is unstable, and its amplitude grows in time. By solving the Klein-Gordon equation of the scalar field as an eigenvalue problem, we numerically obtain the growth rate of the amplitude of the scalar field. Although the dependence of the scalar field mass and the scalar field charge on this growth rate agrees with the result of the analytic approximation, the maximum value of the growth rate is three times larger than that of the analytic approximation. We also discuss the effect of the electric charge on the instability of the scalar field. |
2303.07424 | Dhruba Jyoti Gogoi Dr. | Dhruba Jyoti Gogoi, Ali \"Ovg\"un and M. Koussour | Quasinormal Modes of Black holes in $f(Q)$ gravity | 15 pages, 6 figures. Published version | Eur. Phys. J. C 83, 700 (2023) | 10.1140/epjc/s10052-023-11881-5 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this work, we have studied the quasinormal modes of a black hole in a
model of the type $f(Q)=\underset{n}{\sum}a_{n}\left(Q-Q_{0}\right)^{n} $ in
$f(Q)$ gravity by using a recently introduced method known as Bernstein
spectral method and confirmed the validity of the method with the help of well
known Pad\'e averaged higher order WKB approximation method. Here we have
considered scalar perturbation and electromagnetic perturbation in the black
hole spacetime and obtained the corresponding quasinormal modes. We see that
for a non-vanishing nonmetricity scalar $Q_0$, quasinormal frequencies in
scalar perturbation are greater than those in electromagnetic perturbation
scenarios. On the other hand, the damping rate of gravitational waves is higher
for electromagnetic perturbation. To confirm the quasinormal mode behaviour, we
have also investigated the time domain profiles for both types of
perturbations.
| [
{
"created": "Mon, 13 Mar 2023 19:00:41 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Sep 2023 18:05:23 GMT",
"version": "v2"
}
] | 2023-09-06 | [
[
"Gogoi",
"Dhruba Jyoti",
""
],
[
"Övgün",
"Ali",
""
],
[
"Koussour",
"M.",
""
]
] | In this work, we have studied the quasinormal modes of a black hole in a model of the type $f(Q)=\underset{n}{\sum}a_{n}\left(Q-Q_{0}\right)^{n} $ in $f(Q)$ gravity by using a recently introduced method known as Bernstein spectral method and confirmed the validity of the method with the help of well known Pad\'e averaged higher order WKB approximation method. Here we have considered scalar perturbation and electromagnetic perturbation in the black hole spacetime and obtained the corresponding quasinormal modes. We see that for a non-vanishing nonmetricity scalar $Q_0$, quasinormal frequencies in scalar perturbation are greater than those in electromagnetic perturbation scenarios. On the other hand, the damping rate of gravitational waves is higher for electromagnetic perturbation. To confirm the quasinormal mode behaviour, we have also investigated the time domain profiles for both types of perturbations. |
1605.01273 | Thomas M\"adler | Thomas M\"adler and Jeffrey Winicour | The sky pattern of the linearized gravitational memory effect | typos corrected, matches published version | Class. Quantum Grav. 33 (2016) 175006 | 10.1088/0264-9381/33/17/175006 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational memory effect leads to a net displacement in the relative
positions of test particles. This memory is related to the change in the strain
of the gravitational radiation field between infinite past and infinite future
retarded times. There are three known sources of the memory effect: (i) the
loss of energy to future null infinity by massless fields or particles, (ii)
the ejection of massive particles to infinity from a bound system and (iii)
homogeneous, source-free gravitational waves. In the context of linearized
theory, we show that asymptotic conditions controlling these known sources of
the gravitational memory effect rule out any other possible sources with
physically reasonable stress-energy tensors. Except for the source-free
gravitational waves, the two other known sources produce gravitational memory
with E-mode radiation strain, characterized by a certain curl-free sky pattern
of their polarization. Thus our results show that the only known source of
B-mode gravitational memory is of primordial origin, corresponding in the
linearized theory to a homogeneous wave entering from past null infinity.
| [
{
"created": "Wed, 4 May 2016 13:30:57 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Aug 2016 14:40:54 GMT",
"version": "v2"
}
] | 2016-08-03 | [
[
"Mädler",
"Thomas",
""
],
[
"Winicour",
"Jeffrey",
""
]
] | The gravitational memory effect leads to a net displacement in the relative positions of test particles. This memory is related to the change in the strain of the gravitational radiation field between infinite past and infinite future retarded times. There are three known sources of the memory effect: (i) the loss of energy to future null infinity by massless fields or particles, (ii) the ejection of massive particles to infinity from a bound system and (iii) homogeneous, source-free gravitational waves. In the context of linearized theory, we show that asymptotic conditions controlling these known sources of the gravitational memory effect rule out any other possible sources with physically reasonable stress-energy tensors. Except for the source-free gravitational waves, the two other known sources produce gravitational memory with E-mode radiation strain, characterized by a certain curl-free sky pattern of their polarization. Thus our results show that the only known source of B-mode gravitational memory is of primordial origin, corresponding in the linearized theory to a homogeneous wave entering from past null infinity. |
1005.5330 | Laszlo Arpad Gergely | L\'aszl\'o \'Arp\'ad Gergely | Spinning compact binary inspiral II: Conservative angular dynamics | v2: 19 pages, extended, improved, published version | Phys.Rev.D82:104031,2010 | 10.1103/PhysRevD.82.104031 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We establish the evolution equations of the set of independent variables
characterizing the 2PN rigorous conservative dynamics of a spinning compact
binary, with the inclusion of the leading order spin-orbit, spin-spin and mass
quadrupole - mass monopole effects, for generic (noncircular, nonspherical)
orbits. More specifically, we give a closed system of first order ordinary
differential equations for the orbital elements of the osculating ellipse and
for the angles characterizing the spin orientations with respect to the
osculating orbit. We also prove that (i) the relative angle of the spins stays
constant for equal mass black holes, irrespective of their orientation, and
(ii) the special configuration of equal mass black holes with equal, but
antialigned spins, both laying in the plane of motion (leading to the largest
recoil found in numerical simulations) is preserved at 2PN level of accuracy,
with leading order spin-orbit, spin-spin and mass quadrupolar contributions
included.
| [
{
"created": "Fri, 28 May 2010 16:57:09 GMT",
"version": "v1"
},
{
"created": "Sat, 20 Nov 2010 17:05:22 GMT",
"version": "v2"
}
] | 2010-12-09 | [
[
"Gergely",
"László Árpád",
""
]
] | We establish the evolution equations of the set of independent variables characterizing the 2PN rigorous conservative dynamics of a spinning compact binary, with the inclusion of the leading order spin-orbit, spin-spin and mass quadrupole - mass monopole effects, for generic (noncircular, nonspherical) orbits. More specifically, we give a closed system of first order ordinary differential equations for the orbital elements of the osculating ellipse and for the angles characterizing the spin orientations with respect to the osculating orbit. We also prove that (i) the relative angle of the spins stays constant for equal mass black holes, irrespective of their orientation, and (ii) the special configuration of equal mass black holes with equal, but antialigned spins, both laying in the plane of motion (leading to the largest recoil found in numerical simulations) is preserved at 2PN level of accuracy, with leading order spin-orbit, spin-spin and mass quadrupolar contributions included. |
2205.01682 | Jian-Hua He | Yi Qiu, Ke Wang, Jian-hua He | Amplitude modulation in binary gravitational lensing of gravitational
waves | 6 pages, 5 figures | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the detectability of gravitational waves (GWs) lensed by a
system that consists of binary black holes as lenses using time-domain
numerical simulations. The gravitational lensing potential of this system is no
longer static but evolves with time. When GWs from the source pass through the
binary lens, their amplitudes can be modulated, which is similar to the
phenomenon of amplitude modulation (AM) in radio communication. We find that
even the frequency of the binary lens itself is too low to be detected by the
LISA detection band, the sidebands in the spectrum of the lensed GWs due to AM
can still be within the sensitive range of the detection band. Moreover, we
also calculate the relative differences of SNR (mismatch) between the lensed
and unlensed GWs. We find that the {\it mismatch} can be as significant as
9.18%. Since mismatch does not depend on the amplitude of wavefrom, the
differences between the binary lensed and unlensed waveforms are substantial.
This provides a robust way to identify the lensing event for the LISA project
in the future.
| [
{
"created": "Tue, 3 May 2022 14:48:18 GMT",
"version": "v1"
}
] | 2022-05-05 | [
[
"Qiu",
"Yi",
""
],
[
"Wang",
"Ke",
""
],
[
"He",
"Jian-hua",
""
]
] | We investigate the detectability of gravitational waves (GWs) lensed by a system that consists of binary black holes as lenses using time-domain numerical simulations. The gravitational lensing potential of this system is no longer static but evolves with time. When GWs from the source pass through the binary lens, their amplitudes can be modulated, which is similar to the phenomenon of amplitude modulation (AM) in radio communication. We find that even the frequency of the binary lens itself is too low to be detected by the LISA detection band, the sidebands in the spectrum of the lensed GWs due to AM can still be within the sensitive range of the detection band. Moreover, we also calculate the relative differences of SNR (mismatch) between the lensed and unlensed GWs. We find that the {\it mismatch} can be as significant as 9.18%. Since mismatch does not depend on the amplitude of wavefrom, the differences between the binary lensed and unlensed waveforms are substantial. This provides a robust way to identify the lensing event for the LISA project in the future. |
2303.10884 | Mouhssine Koussour | Tee-How Loo, M. Koussour and Avik De | Anisotropic Universe in $f(Q,T)$ gravity, a novel study | AOP accepted version | null | 10.1016/j.aop.2023.169333 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | $f(Q,T)$ theory of gravity is very recently proposed to incorporate within
the action Lagrangian, the trace $T$ of the energy-momentum tensor along with
the non-metricity scalar $Q$. The cosmological application of this theory in a
spatially flat isotropic and homogeneous Universe is well-studied. However, our
Universe is not isotropic since the Planck era and therefore to study a
complete evolution of the Universe we must investigate the $f(Q,T)$ theory in a
model with a small anisotropy. This motivated us to presume a locally
rotationally symmetric (LRS) Bianchi-I spacetime and derive the motion
equations. We analyse the model candidate $f(Q,T)=\alpha Q^{n+1}+\beta T$, and
to constrain the parameter $n$, we employ the statistical Markov chain Monte
Carlo (MCMC) method with the Bayesian approach using two independent
observational datasets, namely, the Hubble datasets, and Type Ia supernovae
(SNe Ia) datasets.
| [
{
"created": "Mon, 20 Mar 2023 06:03:13 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Apr 2023 05:29:37 GMT",
"version": "v2"
}
] | 2023-05-24 | [
[
"Loo",
"Tee-How",
""
],
[
"Koussour",
"M.",
""
],
[
"De",
"Avik",
""
]
] | $f(Q,T)$ theory of gravity is very recently proposed to incorporate within the action Lagrangian, the trace $T$ of the energy-momentum tensor along with the non-metricity scalar $Q$. The cosmological application of this theory in a spatially flat isotropic and homogeneous Universe is well-studied. However, our Universe is not isotropic since the Planck era and therefore to study a complete evolution of the Universe we must investigate the $f(Q,T)$ theory in a model with a small anisotropy. This motivated us to presume a locally rotationally symmetric (LRS) Bianchi-I spacetime and derive the motion equations. We analyse the model candidate $f(Q,T)=\alpha Q^{n+1}+\beta T$, and to constrain the parameter $n$, we employ the statistical Markov chain Monte Carlo (MCMC) method with the Bayesian approach using two independent observational datasets, namely, the Hubble datasets, and Type Ia supernovae (SNe Ia) datasets. |
2107.04830 | Aldo Gamboa | Aldo Gamboa, Carlos Gabarrete, Paola Dom\'inguez-Fern\'andez, Dar\'io
N\'u\~nez, Olivier Sarbach | Accretion of a Vlasov gas on to a black hole from a sphere of finite
radius and the role of angular momentum | 21 pages, 3 figures. Improved version, to appear in Physical Review D | Phys. Rev. D 104, 083001 (2021) | 10.1103/PhysRevD.104.083001 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | The accretion of a spherically symmetric, collisionless kinetic gas cloud on
to a Schwarzschild black hole is analysed. Whereas previous studies have
treated this problem by specifying boundary conditions at infinity, here the
properties of the gas are given at a sphere of finite radius. The corresponding
steady-state solutions are computed using four different models with an
increasing level of sophistication, starting with the purely radial infall of
Newtonian particles and culminating with a fully general relativistic
calculation in which individual particles have angular momentum. The resulting
mass accretion rates are analysed and compared with previous models, including
the standard Bondi model for a hydrodynamic flow. We apply our models to the
supermassive black holes Sgr A* and M87*, and we discuss how their low
luminosity could be partially explained by a kinetic description involving
angular momentum. Furthermore, we get results consistent with previous
model-dependent bounds for the accretion rate imposed by rotation measures of
the polarised light coming from Sgr A* and with estimations of the accretion
rate of M87* from the Event Horizon Telescope collaboration. Our methods and
results could serve as a first approximation for more realistic black hole
accretion models in various astrophysical scenarios in which the accreted
material is expected to be nearly collisionless.
| [
{
"created": "Sat, 10 Jul 2021 12:59:12 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Sep 2021 19:10:44 GMT",
"version": "v2"
}
] | 2021-10-04 | [
[
"Gamboa",
"Aldo",
""
],
[
"Gabarrete",
"Carlos",
""
],
[
"Domínguez-Fernández",
"Paola",
""
],
[
"Núñez",
"Darío",
""
],
[
"Sarbach",
"Olivier",
""
]
] | The accretion of a spherically symmetric, collisionless kinetic gas cloud on to a Schwarzschild black hole is analysed. Whereas previous studies have treated this problem by specifying boundary conditions at infinity, here the properties of the gas are given at a sphere of finite radius. The corresponding steady-state solutions are computed using four different models with an increasing level of sophistication, starting with the purely radial infall of Newtonian particles and culminating with a fully general relativistic calculation in which individual particles have angular momentum. The resulting mass accretion rates are analysed and compared with previous models, including the standard Bondi model for a hydrodynamic flow. We apply our models to the supermassive black holes Sgr A* and M87*, and we discuss how their low luminosity could be partially explained by a kinetic description involving angular momentum. Furthermore, we get results consistent with previous model-dependent bounds for the accretion rate imposed by rotation measures of the polarised light coming from Sgr A* and with estimations of the accretion rate of M87* from the Event Horizon Telescope collaboration. Our methods and results could serve as a first approximation for more realistic black hole accretion models in various astrophysical scenarios in which the accreted material is expected to be nearly collisionless. |
gr-qc/0507014 | Frans Pretorius | Frans Pretorius | Evolution of Binary Black Hole Spacetimes | 4 pages, 3 figures | Phys.Rev.Lett.95:121101,2005 | 10.1103/PhysRevLett.95.121101 | null | gr-qc astro-ph hep-th | null | We describe early success in the evolution of binary black hole spacetimes
with a numerical code based on a generalization of harmonic coordinates.
Indications are that with sufficient resolution this scheme is capable of
evolving binary systems for enough time to extract information about the orbit,
merger and gravitational waves emitted during the event. As an example we show
results from the evolution of a binary composed of two equal mass, non-spinning
black holes, through a single plunge-orbit, merger and ring down. The resultant
black hole is estimated to be a Kerr black hole with angular momentum parameter
a~0.70. At present, lack of resolution far from the binary prevents an accurate
estimate of the energy emitted, though a rough calculation suggests on the
order of 5% of the initial rest mass of the system is radiated as gravitational
waves during the final orbit and ringdown.
| [
{
"created": "Mon, 4 Jul 2005 09:12:46 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Pretorius",
"Frans",
""
]
] | We describe early success in the evolution of binary black hole spacetimes with a numerical code based on a generalization of harmonic coordinates. Indications are that with sufficient resolution this scheme is capable of evolving binary systems for enough time to extract information about the orbit, merger and gravitational waves emitted during the event. As an example we show results from the evolution of a binary composed of two equal mass, non-spinning black holes, through a single plunge-orbit, merger and ring down. The resultant black hole is estimated to be a Kerr black hole with angular momentum parameter a~0.70. At present, lack of resolution far from the binary prevents an accurate estimate of the energy emitted, though a rough calculation suggests on the order of 5% of the initial rest mass of the system is radiated as gravitational waves during the final orbit and ringdown. |
1505.01291 | Alfred Molina | Xavier Ja\'en and Alfred Molina | On the meaning of Painlev\'e--Gullstrand synchronization | null | null | 10.1007/s10714-015-1994-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following on from two recent papers, here we examine the relationship between
Newtonian gravitation and general relativity in more depth. This allows us to
define a scalar potential which is just the proper time of the vector potential
when the latter is interpreted as the geodesic velocity field. The results are
closely related to spacetimes that admit Painlev\'{e}--Gullstrand
synchronization.
| [
{
"created": "Wed, 6 May 2015 09:28:47 GMT",
"version": "v1"
}
] | 2015-12-09 | [
[
"Jaén",
"Xavier",
""
],
[
"Molina",
"Alfred",
""
]
] | Following on from two recent papers, here we examine the relationship between Newtonian gravitation and general relativity in more depth. This allows us to define a scalar potential which is just the proper time of the vector potential when the latter is interpreted as the geodesic velocity field. The results are closely related to spacetimes that admit Painlev\'{e}--Gullstrand synchronization. |
2111.03113 | Ra\'ul Carballo-Rubio | Ra\'ul Carballo-Rubio, Francesco Di Filippo, Stefano Liberati and Matt
Visser | Geodesically complete black holes in Lorentz-violating gravity | 28 pages, 8 figures | null | 10.1007/JHEP02(2022)122 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a systematic study of the geometric structure of non-singular
spacetimes describing black holes in Lorentz-violating gravity. We start with a
review of the definition of trapping horizons, and the associated notions of
trapped and marginally trapped surfaces, and then study their significance in
frameworks with modified dispersion relations. This leads us to introduce the
notion of universally marginally trapped surfaces, as the direct generalization
of marginally trapped surfaces for frameworks with infinite signal velocities
(Ho\v{r}ava-like frameworks), which then allows us to define universal trapping
horizons. We find that trapped surfaces cannot be generalized in the same way,
and discuss in detail why this does not prevent using universal trapping
horizons to define black holes in Ho\v{r}ava-like frameworks. We then explore
the interplay between the kinematical part of Penrose's singularity theorem,
which implies the existence of incomplete null geodesics in the presence of a
focusing point, and the existence of multiple different metrics. This allows us
to present a complete classification of all possible geometries that neither
display incomplete physical trajectories nor curvature singularities. Our main
result is that not all classes that exist in frameworks in which all signal
velocities are realized in Ho\v{r}ava-like frameworks. However, the taxonomy of
geodesically complete black holes in Ho\v rava-like frameworks includes diverse
scenarios such as evaporating regular black holes, regular black holes bouncing
into regular white holes, and hidden wormholes.
| [
{
"created": "Thu, 4 Nov 2021 19:23:14 GMT",
"version": "v1"
}
] | 2022-03-09 | [
[
"Carballo-Rubio",
"Raúl",
""
],
[
"Di Filippo",
"Francesco",
""
],
[
"Liberati",
"Stefano",
""
],
[
"Visser",
"Matt",
""
]
] | We present a systematic study of the geometric structure of non-singular spacetimes describing black holes in Lorentz-violating gravity. We start with a review of the definition of trapping horizons, and the associated notions of trapped and marginally trapped surfaces, and then study their significance in frameworks with modified dispersion relations. This leads us to introduce the notion of universally marginally trapped surfaces, as the direct generalization of marginally trapped surfaces for frameworks with infinite signal velocities (Ho\v{r}ava-like frameworks), which then allows us to define universal trapping horizons. We find that trapped surfaces cannot be generalized in the same way, and discuss in detail why this does not prevent using universal trapping horizons to define black holes in Ho\v{r}ava-like frameworks. We then explore the interplay between the kinematical part of Penrose's singularity theorem, which implies the existence of incomplete null geodesics in the presence of a focusing point, and the existence of multiple different metrics. This allows us to present a complete classification of all possible geometries that neither display incomplete physical trajectories nor curvature singularities. Our main result is that not all classes that exist in frameworks in which all signal velocities are realized in Ho\v{r}ava-like frameworks. However, the taxonomy of geodesically complete black holes in Ho\v rava-like frameworks includes diverse scenarios such as evaporating regular black holes, regular black holes bouncing into regular white holes, and hidden wormholes. |
0710.5493 | Jose M. M. Senovilla | Jos\'e M. M. Senovilla | Report on workshop A1: Exact solutions and their interpretation | 9 pages, no figures. Many typos corrected. Report submitted to the
Proceedings of GR18. To appear in CQG | null | 10.1088/0264-9381/25/11/114014 | null | gr-qc | null | I report on the communications and posters presented on exact solutions and
their interpretation at the GRG18 Conference, Sydney.
| [
{
"created": "Mon, 29 Oct 2007 17:53:00 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Nov 2007 17:44:37 GMT",
"version": "v2"
}
] | 2009-11-13 | [
[
"Senovilla",
"José M. M.",
""
]
] | I report on the communications and posters presented on exact solutions and their interpretation at the GRG18 Conference, Sydney. |
1103.4967 | Claus Kiefer | Claus Kiefer and Manuel Kraemer | Quantum Gravitational Contributions to the CMB Anisotropy Spectrum | 4 pages, v3: sign error in Eq. (5) and its consequences corrected | Phys. Rev. Lett. 108, 021301 (2012) | 10.1103/PhysRevLett.108.021301 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the primordial power spectrum of density fluctuations in the
framework of quantum cosmology. For this purpose we perform a Born-Oppenheimer
approximation to the Wheeler-DeWitt equation for an inflationary universe with
a scalar field. In this way we first recover the scale-invariant power spectrum
that is found as an approximation in the simplest inflationary models. We then
obtain quantum gravitational corrections to this spectrum and discuss whether
they lead to measurable signatures in the CMB anisotropy spectrum. The
non-observation so far of such corrections translates into an upper bound on
the energy scale of inflation.
| [
{
"created": "Fri, 25 Mar 2011 13:48:13 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jul 2011 08:14:34 GMT",
"version": "v2"
},
{
"created": "Tue, 25 Oct 2011 07:30:23 GMT",
"version": "v3"
}
] | 2012-01-17 | [
[
"Kiefer",
"Claus",
""
],
[
"Kraemer",
"Manuel",
""
]
] | We derive the primordial power spectrum of density fluctuations in the framework of quantum cosmology. For this purpose we perform a Born-Oppenheimer approximation to the Wheeler-DeWitt equation for an inflationary universe with a scalar field. In this way we first recover the scale-invariant power spectrum that is found as an approximation in the simplest inflationary models. We then obtain quantum gravitational corrections to this spectrum and discuss whether they lead to measurable signatures in the CMB anisotropy spectrum. The non-observation so far of such corrections translates into an upper bound on the energy scale of inflation. |
gr-qc/0406083 | Francisco Lobo | Francisco S. N. Lobo and Matt Visser | Fundamental limitations on "warp drive" spacetimes | 18 pages, Revtex4. V2: one reference added, some clarifying comments
and discussion, no physics changes, accepted for publication in Classical and
Quantum Gravity | Class.Quant.Grav. 21 (2004) 5871-5892 | 10.1088/0264-9381/21/24/011 | null | gr-qc astro-ph hep-th | null | "Warp drive" spacetimes are useful as "gedanken-experiments" that force us to
confront the foundations of general relativity, and among other things, to
precisely formulate the notion of "superluminal" communication. We verify the
non-perturbative violation of the classical energy conditions of the Alcubierre
and Natario warp drive spacetimes and apply linearized gravity to the
weak-field warp drive, testing the energy conditions to first and second order
of the non-relativistic warp-bubble velocity. We are primarily interested in a
secondary feature of the warp drive that has not previously been remarked upon,
if it could be built, the warp drive would be an example of a "reaction-less
drive". For both the Alcubierre and Natario warp drives we find that the
occurrence of significant energy condition violations is not just a high-speed
effect, but that the violations persist even at arbitrarily low speeds.
An interesting feature of this construction is that it is now meaningful to
place a finite mass spaceship at the center of the warp bubble, and compare the
warp field energy with the mass-energy of the spaceship. There is no hope of
doing this in Alcubierre's original version of the warp-field, since by
definition the point in the center of the warp bubble moves on a geodesic and
is "massless". That is, in Alcubierre's original formalism and in the Natario
formalism the spaceship is always treated as a test particle, while in the
linearized theory we can treat the spaceship as a finite mass object. For both
the Alcubierre and Natario warp drives we find that even at low speeds the net
(negative) energy stored in the warp fields must be a significant fraction of
the mass of the spaceship.
| [
{
"created": "Mon, 21 Jun 2004 11:07:42 GMT",
"version": "v1"
},
{
"created": "Sun, 31 Oct 2004 13:32:19 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Lobo",
"Francisco S. N.",
""
],
[
"Visser",
"Matt",
""
]
] | "Warp drive" spacetimes are useful as "gedanken-experiments" that force us to confront the foundations of general relativity, and among other things, to precisely formulate the notion of "superluminal" communication. We verify the non-perturbative violation of the classical energy conditions of the Alcubierre and Natario warp drive spacetimes and apply linearized gravity to the weak-field warp drive, testing the energy conditions to first and second order of the non-relativistic warp-bubble velocity. We are primarily interested in a secondary feature of the warp drive that has not previously been remarked upon, if it could be built, the warp drive would be an example of a "reaction-less drive". For both the Alcubierre and Natario warp drives we find that the occurrence of significant energy condition violations is not just a high-speed effect, but that the violations persist even at arbitrarily low speeds. An interesting feature of this construction is that it is now meaningful to place a finite mass spaceship at the center of the warp bubble, and compare the warp field energy with the mass-energy of the spaceship. There is no hope of doing this in Alcubierre's original version of the warp-field, since by definition the point in the center of the warp bubble moves on a geodesic and is "massless". That is, in Alcubierre's original formalism and in the Natario formalism the spaceship is always treated as a test particle, while in the linearized theory we can treat the spaceship as a finite mass object. For both the Alcubierre and Natario warp drives we find that even at low speeds the net (negative) energy stored in the warp fields must be a significant fraction of the mass of the spaceship. |
gr-qc/0607058 | Barry Holstein | Barry R. Holstein | Factorization in Graviton Scattering and the "Natural" Value of the
g-factor | 21 pages, 2 figures | null | 10.1103/PhysRevD.74.085002 | null | gr-qc hep-ph hep-th | null | The factorization property of graviton scattering amplitudes is reviewed and
show to be valid only if the "natural" value of the gyromagnetic ratio $g_S=2$
is employed -- independent of spin.
| [
{
"created": "Fri, 14 Jul 2006 15:05:46 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Jul 2006 14:33:18 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Holstein",
"Barry R.",
""
]
] | The factorization property of graviton scattering amplitudes is reviewed and show to be valid only if the "natural" value of the gyromagnetic ratio $g_S=2$ is employed -- independent of spin. |
2311.02065 | Guillem Dom\`enech | Guillem Dom\`enech | Cosmological Gravitational Waves from Isocurvature Fluctuations | Invited review for the AAPPS bulletin | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves induced by large primordial curvature fluctuations may
result in a sizable stochastic gravitational wave background. Interestingly,
curvature fluctuations are gradually generated by initial isocurvature
fluctuations, which in turn induce gravitational waves. Initial isocurvature
fluctuations commonly appear in multi-field models of inflation as well as in
the formation of scattered compact objects in the very early universe, such as
primordial black holes and solitons like oscillons and cosmic strings. Here we
provide a review on isocurvature induced gravitational waves and its
applications to dark matter and the primordial black hole dominated early
universe.
| [
{
"created": "Fri, 3 Nov 2023 17:48:07 GMT",
"version": "v1"
}
] | 2023-11-06 | [
[
"Domènech",
"Guillem",
""
]
] | Gravitational waves induced by large primordial curvature fluctuations may result in a sizable stochastic gravitational wave background. Interestingly, curvature fluctuations are gradually generated by initial isocurvature fluctuations, which in turn induce gravitational waves. Initial isocurvature fluctuations commonly appear in multi-field models of inflation as well as in the formation of scattered compact objects in the very early universe, such as primordial black holes and solitons like oscillons and cosmic strings. Here we provide a review on isocurvature induced gravitational waves and its applications to dark matter and the primordial black hole dominated early universe. |
1204.4744 | Leonid Marochnik | Leonid Marochnik | Dark energy from instantons | 11 two-column pages, 1 figure, V2 is updated pre-publication version.
The title is changed. Section 4 (Birth of Dark Energy) is extended. Misprints
are fixed | Grav. Cosmol. vol.19, No. 3, pp. 178-187, 2013 | 10.1134/S0202289313030067 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that in imaginary time quantum metric fluctuations of empty space
form a self-consistent de Sitter gravitational instanton that can be thought of
as describing tunneling from "nothing" into de Sitter space of real time (no
cosmological constant or scalar fields are needed). For the first time, this
mechanism is activated to give birth to a flat inflationary Universe. For the
second time, it is turned on to complete the cosmological evolution after the
energy density of matter drops below the threshold (the energy density of
instantons). A cosmological expansion with dark energy takes over after the
scale factor exceeds this threshold, which marks the birth of dark energy at a
redshift $1+z\approx 1.3$ and provides a possible solution to the "coincidence
problem". The number of gravitons which tunneled into the Universe must be of
the order of $10^{122}$ to create the observed value of the Hubble constant.
This number has nothing to do with vacuum energy, which is a possible solution
to the "old cosmological constant problem". The emptying Universe should
possibly complete its evolution by tunneling back to "nothing". After that, the
entire scenario is repeated, and it can happen endlessly.
| [
{
"created": "Thu, 19 Apr 2012 18:59:30 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Jun 2013 17:06:13 GMT",
"version": "v2"
}
] | 2015-06-04 | [
[
"Marochnik",
"Leonid",
""
]
] | We show that in imaginary time quantum metric fluctuations of empty space form a self-consistent de Sitter gravitational instanton that can be thought of as describing tunneling from "nothing" into de Sitter space of real time (no cosmological constant or scalar fields are needed). For the first time, this mechanism is activated to give birth to a flat inflationary Universe. For the second time, it is turned on to complete the cosmological evolution after the energy density of matter drops below the threshold (the energy density of instantons). A cosmological expansion with dark energy takes over after the scale factor exceeds this threshold, which marks the birth of dark energy at a redshift $1+z\approx 1.3$ and provides a possible solution to the "coincidence problem". The number of gravitons which tunneled into the Universe must be of the order of $10^{122}$ to create the observed value of the Hubble constant. This number has nothing to do with vacuum energy, which is a possible solution to the "old cosmological constant problem". The emptying Universe should possibly complete its evolution by tunneling back to "nothing". After that, the entire scenario is repeated, and it can happen endlessly. |
2011.07700 | Brett McInnes | Brett McInnes | About Magnetic AdS Black Holes | 21 pages, 7 figures; typos fixed, references added | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There has recently been a strong revival of interest in quasi-extremal
magnetically charged black holes. In the asymptotically flat case, it is
possible to choose the magnetic charge of such an object in such a manner that
the black hole is surrounded by a corona in which electroweak symmetry is
restored on macroscopic scales, a result of very considerable interest. We
argue that holographic duality indicates that the asymptotically AdS analogues
of these black holes have several interesting properties: the dual theory is
only physical if the black hole is required to rotate; in the rotating case,
the magnetic field at the poles does not attain its maximum on the event
horizon, but rather somewhat outside it; the magnetic field at the equator is
not a monotonically decreasing function of the magnetic charge; the electric
fields induced by the rotation, while smaller than their magnetic counterparts,
are by no means negligible; the maximal electric field often occurs neither at
the poles nor at the equator; and so on. Most importantly, in the magnetically
charged case it is possible to avoid the superradiant instability to which
neutral AdS-Kerr black holes are subject; but the need to avoid this
instability imposes upper bounds on the magnetic and electric fields. In some
circumstances, therefore, the corona may not exist in the asymptotically AdS
case.
| [
{
"created": "Mon, 16 Nov 2020 02:57:12 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Nov 2020 03:37:33 GMT",
"version": "v2"
}
] | 2020-12-09 | [
[
"McInnes",
"Brett",
""
]
] | There has recently been a strong revival of interest in quasi-extremal magnetically charged black holes. In the asymptotically flat case, it is possible to choose the magnetic charge of such an object in such a manner that the black hole is surrounded by a corona in which electroweak symmetry is restored on macroscopic scales, a result of very considerable interest. We argue that holographic duality indicates that the asymptotically AdS analogues of these black holes have several interesting properties: the dual theory is only physical if the black hole is required to rotate; in the rotating case, the magnetic field at the poles does not attain its maximum on the event horizon, but rather somewhat outside it; the magnetic field at the equator is not a monotonically decreasing function of the magnetic charge; the electric fields induced by the rotation, while smaller than their magnetic counterparts, are by no means negligible; the maximal electric field often occurs neither at the poles nor at the equator; and so on. Most importantly, in the magnetically charged case it is possible to avoid the superradiant instability to which neutral AdS-Kerr black holes are subject; but the need to avoid this instability imposes upper bounds on the magnetic and electric fields. In some circumstances, therefore, the corona may not exist in the asymptotically AdS case. |
gr-qc/9408038 | Dadhich | Naresh Dadhich, L.K. Patel, K.S. Govinder and P.G.L. Leach | Characterisation of orthogonal perfect fluid cosmological spacetimes | TeX pages 18, IUCAA-27/94 | null | null | null | gr-qc | null | We consider the general orthogonal metric separable in space and time
variables in comoving coordinates. We then characterise perfect fluid models
admitted by such a metric. It turns out that the homogeneous models can only be
either FLRW or Bianchi I while the inhomogeneous ones can only admit $G_2 $
(two mutually as well as hypersurface orthogonal spacelike Killing vectors)
isometry. The latter can possess singularities of various kinds or none. The
non-singular family is however unique and cylindrically symmetric.
| [
{
"created": "Wed, 31 Aug 1994 13:56:29 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Dadhich",
"Naresh",
""
],
[
"Patel",
"L. K.",
""
],
[
"Govinder",
"K. S.",
""
],
[
"Leach",
"P. G. L.",
""
]
] | We consider the general orthogonal metric separable in space and time variables in comoving coordinates. We then characterise perfect fluid models admitted by such a metric. It turns out that the homogeneous models can only be either FLRW or Bianchi I while the inhomogeneous ones can only admit $G_2 $ (two mutually as well as hypersurface orthogonal spacelike Killing vectors) isometry. The latter can possess singularities of various kinds or none. The non-singular family is however unique and cylindrically symmetric. |
gr-qc/9307017 | Ulvi Yurtsever | Ulvi Yurtsever | Algebraic approach to quantum field theory on non-globally-hyperbolic
spacetimes | 21 pages, UCSBTH-92-43 | Class.Quant.Grav.11:999-1012,1994 | 10.1088/0264-9381/11/4/016 | null | gr-qc | null | The mathematical formalism for linear quantum field theory on curved
spacetime depends in an essential way on the assumption of global
hyperbolicity. Physically, what lie at the foundation of any formalism for
quantization in curved spacetime are the canonical commutation relations,
imposed on the field operators evaluated at a global Cauchy surface. In the
algebraic formulation of linear quantum field theory, the canonical commutation
relations are restated in terms of a well-defined symplectic structure on the
space of smooth solutions, and the local field algebra is constructed as the
Weyl algebra associated to this symplectic vector space. When spacetime is not
globally hyperbolic, e.g. when it contains naked singularities or closed
timelike curves, a global Cauchy surface does not exist, and there is no
obvious way to formulate the canonical commutation relations, hence no obvious
way to construct the field algebra. In a paper submitted elsewhere, we report
on a generalization of the algebraic framework for quantum field theory to
arbitrary topological spaces which do not necessarily have a spacetime metric
defined on them at the outset. Taking this generalization as a starting point,
in this paper we give a prescription for constructing the field algebra of a
(massless or massive) Klein-Gordon field on an arbitrary background spacetime.
When spacetime is globally hyperbolic, the theory defined by our construction
coincides with the ordinary Klein-Gordon field theory on a
| [
{
"created": "Wed, 14 Jul 1993 03:11:38 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Yurtsever",
"Ulvi",
""
]
] | The mathematical formalism for linear quantum field theory on curved spacetime depends in an essential way on the assumption of global hyperbolicity. Physically, what lie at the foundation of any formalism for quantization in curved spacetime are the canonical commutation relations, imposed on the field operators evaluated at a global Cauchy surface. In the algebraic formulation of linear quantum field theory, the canonical commutation relations are restated in terms of a well-defined symplectic structure on the space of smooth solutions, and the local field algebra is constructed as the Weyl algebra associated to this symplectic vector space. When spacetime is not globally hyperbolic, e.g. when it contains naked singularities or closed timelike curves, a global Cauchy surface does not exist, and there is no obvious way to formulate the canonical commutation relations, hence no obvious way to construct the field algebra. In a paper submitted elsewhere, we report on a generalization of the algebraic framework for quantum field theory to arbitrary topological spaces which do not necessarily have a spacetime metric defined on them at the outset. Taking this generalization as a starting point, in this paper we give a prescription for constructing the field algebra of a (massless or massive) Klein-Gordon field on an arbitrary background spacetime. When spacetime is globally hyperbolic, the theory defined by our construction coincides with the ordinary Klein-Gordon field theory on a |
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