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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9606076 | Thibault Damour | Thibault Damour and David Vokrouhlicky | Testing for gravitationally preferred directions using the lunar orbit | 20 pages, Revtex, submitted to Phys Rev D | Phys.Rev.D53:6740-6740,1996 | 10.1103/PhysRevD.53.6740 | IHES/P/95/99 | gr-qc | null | As gravity is a long-range force, it is {\it a priori} conceivable that the
Universe's global matter distribution select a preferred rest frame for local
gravitational physics. At the post-Newtonian approximation, the phenomenology
of preferred-frame effects is described by two parameters, $\alpha_1$ and
$\alpha_2$, the second of which is already very tightly constrained. Confirming
previous suggestions, we show through a detailed Hill-Brown type calculation of
a perturbed lunar orbit that lunar laser ranging data have the potential of
constraining $\alpha_1$ at the $10^{-4}$ level. It is found that certain
retrograde planar orbits exhibit a resonant sensitivity to external
perturbations linked to a fixed direction in space. The lunar orbit being quite
far from such a resonance exhibits no significant enhancement due to solar
tides. Our Hill-Brown analysis is extended to the perturbation linked to a
possible differential acceleration toward the galactic center. It is, however,
argued that there are strong {\it a priori} theoretical constraints on the
conceivable magnitude of such an effect.
| [
{
"created": "Thu, 27 Jun 1996 16:50:16 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Damour",
"Thibault",
""
],
[
"Vokrouhlicky",
"David",
""
]
] | As gravity is a long-range force, it is {\it a priori} conceivable that the Universe's global matter distribution select a preferred rest frame for local gravitational physics. At the post-Newtonian approximation, the phenomenology of preferred-frame effects is described by two parameters, $\alpha_1$ and $\alpha_2$, the second of which is already very tightly constrained. Confirming previous suggestions, we show through a detailed Hill-Brown type calculation of a perturbed lunar orbit that lunar laser ranging data have the potential of constraining $\alpha_1$ at the $10^{-4}$ level. It is found that certain retrograde planar orbits exhibit a resonant sensitivity to external perturbations linked to a fixed direction in space. The lunar orbit being quite far from such a resonance exhibits no significant enhancement due to solar tides. Our Hill-Brown analysis is extended to the perturbation linked to a possible differential acceleration toward the galactic center. It is, however, argued that there are strong {\it a priori} theoretical constraints on the conceivable magnitude of such an effect. |
0704.3595 | Eyo Ita III | Eyo Eyo Ita III | 4-Dimensional General Relativity from the instrinsic spatial geometry of
SO(3) Yang--Mills theory | 16 pages. Background material for revised journal article | Nucl. Phys. B, Vol. 852 (2011) pp.681-695 | 10.1016/j.nuclphysb.2011.07.004 | DAMTP-2007-38 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we derive 4-dimensional General Relativity from three
dimensions, using the intrinsic spatial geometry inherent in Yang--Mills theory
which has been exposed by previous authors as well as as some properties of the
Ashtekar variables. We provide various interesting relations, including the
fact that General Relativity can be written as a Yang--Mills theory where the
antiself-dual Weyl curvature replaces the Yang--Mills coupling constant. We
have generalized the results of some previous authors, covering Einsteins
spaces, to include more general spacetime geometries.
| [
{
"created": "Thu, 26 Apr 2007 17:48:59 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Apr 2007 05:07:12 GMT",
"version": "v2"
},
{
"created": "Wed, 15 Dec 2010 20:53:57 GMT",
"version": "v3"
},
{
"created": "Fri, 18 Mar 2011 06:45:03 GMT",
"version": "v4"
},
{
"created": "Thu, 22 Sep 2011 01:41:48 GMT",
"version": "v5"
}
] | 2012-02-20 | [
[
"Ita",
"Eyo Eyo",
"III"
]
] | In this paper we derive 4-dimensional General Relativity from three dimensions, using the intrinsic spatial geometry inherent in Yang--Mills theory which has been exposed by previous authors as well as as some properties of the Ashtekar variables. We provide various interesting relations, including the fact that General Relativity can be written as a Yang--Mills theory where the antiself-dual Weyl curvature replaces the Yang--Mills coupling constant. We have generalized the results of some previous authors, covering Einsteins spaces, to include more general spacetime geometries. |
2206.14333 | Israel Quiros | Roberto De Arcia, Israel Quiros, Ulises Nucamendi, Tame Gonzalez,
Francisco Antonio Horta-Rangel, Philippe Eenens | Global asymptotic dynamics of the cubic galileon interacting with dark
matter | 22 pages, 6 figures. Version that matches the one published | Phys. Dark Univ. 40 (2023) 101183 | 10.1016/j.dark.2023.101183 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we perform a thorough dynamical systems analysis of the cubic
galileon model non-minimally coupled to the dark matter. Three well-known
classes of interacting models are considered where the energy exchange between
the dark components is a function of the dark matter density and of the dark
energy density: $Q_1=3\alpha H\rho_m$, $Q_2=3\beta\rho_m\dot{\phi}$ and $Q_3=3
\epsilon H \rho_\phi$, respectively. We are able to show the global asymptotic
dynamics of the model for the exponential potential in a homogeneous and
isotropic background. The cosmological implications of the proposed scenarios
are explored and it is found that, in addition to the appearance of new
equilibrium configurations that do not appear neither in the non-interacting
cubic galileon model nor in the interacting quintessence model, there is a
significant impact of the non-minimal coupling through modification of the
stability properties of the critical points. The resulting cosmological
scenario provides a bigbang origin of the cosmic expansion, an early transient
stage of inflationary expansion, as well as matter-scaling late time stable
state of the universe, among other solutions of lesser cosmological interest.
This work extends previous studies of coupled dark energy to a broader class of
gravitational theories.
| [
{
"created": "Wed, 29 Jun 2022 00:06:34 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Mar 2023 16:37:17 GMT",
"version": "v2"
}
] | 2023-03-08 | [
[
"De Arcia",
"Roberto",
""
],
[
"Quiros",
"Israel",
""
],
[
"Nucamendi",
"Ulises",
""
],
[
"Gonzalez",
"Tame",
""
],
[
"Horta-Rangel",
"Francisco Antonio",
""
],
[
"Eenens",
"Philippe",
""
]
] | In this paper we perform a thorough dynamical systems analysis of the cubic galileon model non-minimally coupled to the dark matter. Three well-known classes of interacting models are considered where the energy exchange between the dark components is a function of the dark matter density and of the dark energy density: $Q_1=3\alpha H\rho_m$, $Q_2=3\beta\rho_m\dot{\phi}$ and $Q_3=3 \epsilon H \rho_\phi$, respectively. We are able to show the global asymptotic dynamics of the model for the exponential potential in a homogeneous and isotropic background. The cosmological implications of the proposed scenarios are explored and it is found that, in addition to the appearance of new equilibrium configurations that do not appear neither in the non-interacting cubic galileon model nor in the interacting quintessence model, there is a significant impact of the non-minimal coupling through modification of the stability properties of the critical points. The resulting cosmological scenario provides a bigbang origin of the cosmic expansion, an early transient stage of inflationary expansion, as well as matter-scaling late time stable state of the universe, among other solutions of lesser cosmological interest. This work extends previous studies of coupled dark energy to a broader class of gravitational theories. |
1404.1018 | Gianluca Calcagni | Aurelien Barrau, Martin Bojowald, Gianluca Calcagni, Julien Grain,
Mikhail Kagan | Anomaly-free cosmological perturbations in effective canonical quantum
gravity | 1+52 pages. v2: discussions extended and improved throughout the
text, references added, typos corrected, conclusions unchanged | JCAP05(2015)051 | 10.1088/1475-7516/2015/05/051 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article lays out a complete framework for an effective theory of
cosmological perturbations with corrections from canonical quantum gravity.
Since several examples exist for quantum-gravity effects that change the
structure of space-time, the classical perturbative treatment must be rethought
carefully. The present discussion provides a unified picture of several
previous works, together with new treatments of higher-order perturbations and
the specification of initial states.
| [
{
"created": "Thu, 3 Apr 2014 17:14:46 GMT",
"version": "v1"
},
{
"created": "Tue, 26 May 2015 19:42:27 GMT",
"version": "v2"
}
] | 2015-05-27 | [
[
"Barrau",
"Aurelien",
""
],
[
"Bojowald",
"Martin",
""
],
[
"Calcagni",
"Gianluca",
""
],
[
"Grain",
"Julien",
""
],
[
"Kagan",
"Mikhail",
""
]
] | This article lays out a complete framework for an effective theory of cosmological perturbations with corrections from canonical quantum gravity. Since several examples exist for quantum-gravity effects that change the structure of space-time, the classical perturbative treatment must be rethought carefully. The present discussion provides a unified picture of several previous works, together with new treatments of higher-order perturbations and the specification of initial states. |
gr-qc/0108019 | null | S. Q. Wu and X. Cai | Non-existence of New Quantum Ergosphere Effect of a Vaidya-type Black
Hole | Latex, 9 pages, no figure, submitted to Mod. Phys. Lett. A | Mod.Phys.Lett. A16 (2001) 1549-1558 | 10.1142/S0217732301004789 | null | gr-qc | null | Hawking evaporation of Dirac particles and scalar fields in a Vaidya-type
black hole is investigated by the method of generalized tortoise coordinate
transformation. It is shown that Hawking radiation of Dirac particles does not
exist for $P_1, Q_2$ components but for $P_2, Q_1$ components in any
Vaidya-type black holes. Both the location and the temperature of the event
horizon change with time. The thermal radiation spectrum of Dirac particles is
the same as that of Klein-Gordon particles. We demonstrates that there is no
new quantum ergosphere effect in the thermal radiation of Dirac particles in
any spherically symmetry black holes.
| [
{
"created": "Tue, 7 Aug 2001 01:48:05 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Wu",
"S. Q.",
""
],
[
"Cai",
"X.",
""
]
] | Hawking evaporation of Dirac particles and scalar fields in a Vaidya-type black hole is investigated by the method of generalized tortoise coordinate transformation. It is shown that Hawking radiation of Dirac particles does not exist for $P_1, Q_2$ components but for $P_2, Q_1$ components in any Vaidya-type black holes. Both the location and the temperature of the event horizon change with time. The thermal radiation spectrum of Dirac particles is the same as that of Klein-Gordon particles. We demonstrates that there is no new quantum ergosphere effect in the thermal radiation of Dirac particles in any spherically symmetry black holes. |
2204.02377 | D. Divyajyoti | Abhishek Chattaraj and Tamal RoyChowdhury and Divyajyoti and Chandra
Kant Mishra and Anshu Gupta | High accuracy post-Newtonian and numerical relativity comparisons
involving higher modes for eccentric binary black holes and a dominant mode
eccentric inspiral-merger-ringdown model | null | Phys. Rev. D 106, 124008 - Published 2 December 2022 | 10.1103/PhysRevD.106.124008 | LIGO-P2200106 | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Spherical harmonic modes of gravitational waveforms for inspiraling compact
binaries in eccentric orbits from post-Newtonian (PN) theory accurate to third
post-Newtonian order, and those extracted from numerical relativity (NR)
simulations for binary black holes (BBHs) are compared. We combine results from
the two approaches (PN and NR) to construct time-domain hybrid waveforms that
describe the complete evolution of BBH mergers through inspiral-merger-ringdown
(IMR) stages. These hybrids are then used in constructing a fully analytical
dominant mode ($\ell$=2, $|m|$=2) eccentric IMR model. A simple extension to a
multi-mode model based on this dominant mode model is also presented. Overlaps
with quasi-circular IMR waveform models including the effect of higher modes,
maximized over a time- and phase-shift, hint at the importance (mismatches
$>1\%$) of including eccentricity in gravitational waveforms when analysing
BBHs lighter than $\sim 80 M_{\odot}$, irrespective of the binary's
eccentricity (as it enters the LIGO bands), or mass-ratio. Combined impact of
eccentricity and higher modes seems to become more apparent through smaller
overlaps with increasing inclination angles and mass ratios. Additionally, we
show that the state-of-the-art quasi-circular models including the effect of
higher modes will not be adequate in extracting source properties for signals
with initial eccentricities $e_0$ $\gtrsim0.1$.
| [
{
"created": "Tue, 5 Apr 2022 17:35:51 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Dec 2022 16:24:40 GMT",
"version": "v2"
}
] | 2022-12-07 | [
[
"Chattaraj",
"Abhishek",
""
],
[
"RoyChowdhury",
"Tamal",
""
],
[
"Divyajyoti",
"",
""
],
[
"Mishra",
"Chandra Kant",
""
],
[
"Gupta",
"Anshu",
""
]
] | Spherical harmonic modes of gravitational waveforms for inspiraling compact binaries in eccentric orbits from post-Newtonian (PN) theory accurate to third post-Newtonian order, and those extracted from numerical relativity (NR) simulations for binary black holes (BBHs) are compared. We combine results from the two approaches (PN and NR) to construct time-domain hybrid waveforms that describe the complete evolution of BBH mergers through inspiral-merger-ringdown (IMR) stages. These hybrids are then used in constructing a fully analytical dominant mode ($\ell$=2, $|m|$=2) eccentric IMR model. A simple extension to a multi-mode model based on this dominant mode model is also presented. Overlaps with quasi-circular IMR waveform models including the effect of higher modes, maximized over a time- and phase-shift, hint at the importance (mismatches $>1\%$) of including eccentricity in gravitational waveforms when analysing BBHs lighter than $\sim 80 M_{\odot}$, irrespective of the binary's eccentricity (as it enters the LIGO bands), or mass-ratio. Combined impact of eccentricity and higher modes seems to become more apparent through smaller overlaps with increasing inclination angles and mass ratios. Additionally, we show that the state-of-the-art quasi-circular models including the effect of higher modes will not be adequate in extracting source properties for signals with initial eccentricities $e_0$ $\gtrsim0.1$. |
gr-qc/0612009 | Yu Zhang | Yu Zhang and Y X Gui | Quasinormal modes of gravitational perturbation around a Schwarzschild
black hole surrounded by quintessence | null | Class.Quant.Grav.23:6141-6147,2006 | 10.1088/0264-9381/23/22/004 | null | gr-qc astro-ph | null | In this paper, the quasinormal modes of gravitational perturbation around a
Schwarzschild black hole surrounded by quintessence were evaluated by using the
third-order WKB approximation. Due to the presence of quintessence, the
gravitational wave damps more slowly.
| [
{
"created": "Fri, 1 Dec 2006 12:15:23 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Zhang",
"Yu",
""
],
[
"Gui",
"Y X",
""
]
] | In this paper, the quasinormal modes of gravitational perturbation around a Schwarzschild black hole surrounded by quintessence were evaluated by using the third-order WKB approximation. Due to the presence of quintessence, the gravitational wave damps more slowly. |
2103.12696 | Hao Wei | Hao Wei, Zhong-Xi Yu | Inverse Chameleon Mechanism and Mass Limits for Compact Stars | 18 pages, 1 figure, revtex4; v2: discussions added, JCAP in press;
v3: published version | JCAP 2108 (2021) 011 | 10.1088/1475-7516/2021/08/011 | null | gr-qc astro-ph.HE astro-ph.SR hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As is well known, there are various mass limits for compact stars. For
example, the maximum mass for non-rotating white dwarfs is given by the famous
Chandrasekhar limit about $1.4 M_\odot$ (solar masses). Although the mass limit
for neutron stars is not so clear to date, one of the widely accepted values is
about $2.1 M_\odot\,$. Recently, challenges to these mass limits appeared.
Motivated by the super-Chandrasekhar mass white dwarfs with masses up to $2.4
\sim 2.8 M_\odot\,$, and compact objects (probably neutron stars) in the mass
gap (from $2.5 M_\odot$ or $3 M_\odot$ to $5 M_\odot$) inferred from
gravitational waves detected by LIGO/Virgo in the third observing run (O3), we
reconsider the mass limits for compact stars in the present work. Without
invoking strong magnetic field and/or exotic equation of state (EOS), we try to
increase the mass limits for compact stars in modified gravity theory. In this
work, we propose an inverse chameleon mechanism, and show that the fifth-force
mediated by the scalar field can evade the severe tests on earth, in solar
system and universe, but manifest itself in compact stars such as white dwarfs
and neutron stars. The mass limits for compact stars in the inverse chameleon
mechanism can be easily increased to $3 M_\odot\,$, $5 M_\odot$ or even larger.
We argue that the inverse chameleon mechanism might be constrained by the
observations of exoplanets orbiting compact stars (such as white dwarfs and
neutron stars), and gravitational waves from the last stage of binary compact
star coalescence.
| [
{
"created": "Tue, 23 Mar 2021 17:19:00 GMT",
"version": "v1"
},
{
"created": "Sat, 17 Jul 2021 09:56:00 GMT",
"version": "v2"
},
{
"created": "Tue, 10 Aug 2021 09:58:00 GMT",
"version": "v3"
}
] | 2021-08-11 | [
[
"Wei",
"Hao",
""
],
[
"Yu",
"Zhong-Xi",
""
]
] | As is well known, there are various mass limits for compact stars. For example, the maximum mass for non-rotating white dwarfs is given by the famous Chandrasekhar limit about $1.4 M_\odot$ (solar masses). Although the mass limit for neutron stars is not so clear to date, one of the widely accepted values is about $2.1 M_\odot\,$. Recently, challenges to these mass limits appeared. Motivated by the super-Chandrasekhar mass white dwarfs with masses up to $2.4 \sim 2.8 M_\odot\,$, and compact objects (probably neutron stars) in the mass gap (from $2.5 M_\odot$ or $3 M_\odot$ to $5 M_\odot$) inferred from gravitational waves detected by LIGO/Virgo in the third observing run (O3), we reconsider the mass limits for compact stars in the present work. Without invoking strong magnetic field and/or exotic equation of state (EOS), we try to increase the mass limits for compact stars in modified gravity theory. In this work, we propose an inverse chameleon mechanism, and show that the fifth-force mediated by the scalar field can evade the severe tests on earth, in solar system and universe, but manifest itself in compact stars such as white dwarfs and neutron stars. The mass limits for compact stars in the inverse chameleon mechanism can be easily increased to $3 M_\odot\,$, $5 M_\odot$ or even larger. We argue that the inverse chameleon mechanism might be constrained by the observations of exoplanets orbiting compact stars (such as white dwarfs and neutron stars), and gravitational waves from the last stage of binary compact star coalescence. |
2012.06877 | Tom McClain Ph.D. | Tom McClain | Obstacles to the quantization of general relativity using symplectic
structures | 10 pages. Based on a presentation at the Second Hermann Minkowski
Meeting on the Foundations of Spacetime Physics. Appears in "Spacetime: 1909
- 2019." Reinoud Jan Slagter and Zoltan Keresztes (Editors). Minkowski
Institute Press, 2020 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper I give overviews of the polysymplectic approach to covariant
Hamiltonian field theory and the simplest geometric quantization of classical
particle theories. I then give a synopsis of a recently proposed toy model for
applying this geometric quantization map to polysymplectic field theory. I show
that no special difficulties arise when this toy model is applied to general
relativity. I then sketch the reasons why the standard tools of covariant
Hamiltonian field theory are not up to the challenge of GR, so that the
resulting quantum theory cannot be taken seriously. A few remarks are given
about prospects for future work.
| [
{
"created": "Sat, 12 Dec 2020 17:58:06 GMT",
"version": "v1"
}
] | 2020-12-15 | [
[
"McClain",
"Tom",
""
]
] | In this paper I give overviews of the polysymplectic approach to covariant Hamiltonian field theory and the simplest geometric quantization of classical particle theories. I then give a synopsis of a recently proposed toy model for applying this geometric quantization map to polysymplectic field theory. I show that no special difficulties arise when this toy model is applied to general relativity. I then sketch the reasons why the standard tools of covariant Hamiltonian field theory are not up to the challenge of GR, so that the resulting quantum theory cannot be taken seriously. A few remarks are given about prospects for future work. |
gr-qc/9706029 | Don N. Page | Don N. Page (Canadian Institute for Advanced Research and Theoretical
Physics Institute, University of Alberta, Edmonton, Canada) | Maximal Acceleration Is Nonrotating | 64 pages, no figures, LaTeX, Sections 10 and 11 added with
applications to maximally rotating stellar models of Cook, Shapiro, and
Teukolsky and to the Sun and Solar System with recent data from Pijpers that
the Sun has angular momentum 1.80 x 10^{75} = 0.216 M^2 = 47 hectares = 116
acres (with 0.8% uncertainty) and quadrupole moment (2.18 x 10^{-7})MR^2 =
1.60 x 10^{14} m^3 = 3.7 x 10^{117} (with 3% uncertaity), accepted Feb. 27
for Classical and Quantum Gravity | Class.Quant.Grav. 15 (1998) 1669-1719 | 10.1088/0264-9381/15/6/020 | Alberta-Thy-11-97 | gr-qc | null | In a stationary axisymmetric spacetime, the angular velocity of a stationary
observer that Fermi-Walker transports its acceleration vector is also the
angular velocity that locally extremizes the magnitude of the acceleration of
such an observer, and conversely if the spacetime is also symmetric under
reversing both t and phi together. Thus a congruence of Nonrotating
Acceleration Worldlines (NAW) is equivalent to a Stationary Congruence
Accelerating Locally Extremely (SCALE). These congruences are defined
completely locally, unlike the case of Zero Angular Momentum Observers (ZAMOs),
which requires knowledge around a symmetry axis. The SCALE subcase of a
Stationary Congruence Accelerating Maximally (SCAM) is made up of stationary
worldlines that may be considered to be locally most nearly at rest in a
stationary axisymmetric gravitational field. Formulas for the angular velocity
and other properties of the SCALEs are given explicitly on a generalization of
an equatorial plane, infinitesimally near a symmetry axis, and in a slowly
rotating gravitational field, including the weak-field limit, where the SCAM is
shown to be counter-rotating relative to infinity. These formulas are evaluated
in particular detail for the Kerr-Newman metric. Various other congruences are
also defined, such as a Stationary Congruence Rotating at Minimum (SCRAM), and
Stationary Worldlines Accelerating Radially Maximally (SWARM), both of which
coincide with a SCAM on an equatorial plane of reflection symmetry.
Applications are also made to the gravitational fields of maximally rotating
stars, the Sun, and the Solar System.
| [
{
"created": "Tue, 10 Jun 1997 23:05:02 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Mar 1998 00:26:45 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Page",
"Don N.",
"",
"Canadian Institute for Advanced Research and Theoretical\n Physics Institute, University of Alberta, Edmonton, Canada"
]
] | In a stationary axisymmetric spacetime, the angular velocity of a stationary observer that Fermi-Walker transports its acceleration vector is also the angular velocity that locally extremizes the magnitude of the acceleration of such an observer, and conversely if the spacetime is also symmetric under reversing both t and phi together. Thus a congruence of Nonrotating Acceleration Worldlines (NAW) is equivalent to a Stationary Congruence Accelerating Locally Extremely (SCALE). These congruences are defined completely locally, unlike the case of Zero Angular Momentum Observers (ZAMOs), which requires knowledge around a symmetry axis. The SCALE subcase of a Stationary Congruence Accelerating Maximally (SCAM) is made up of stationary worldlines that may be considered to be locally most nearly at rest in a stationary axisymmetric gravitational field. Formulas for the angular velocity and other properties of the SCALEs are given explicitly on a generalization of an equatorial plane, infinitesimally near a symmetry axis, and in a slowly rotating gravitational field, including the weak-field limit, where the SCAM is shown to be counter-rotating relative to infinity. These formulas are evaluated in particular detail for the Kerr-Newman metric. Various other congruences are also defined, such as a Stationary Congruence Rotating at Minimum (SCRAM), and Stationary Worldlines Accelerating Radially Maximally (SWARM), both of which coincide with a SCAM on an equatorial plane of reflection symmetry. Applications are also made to the gravitational fields of maximally rotating stars, the Sun, and the Solar System. |
1005.3746 | Evan Goetz | E. Goetz and R. L. Savage Jr | Calibration of the LIGO displacement actuators via laser frequency
modulation | 10 pages, 5 figures, submitted to Classical and Quantum Gravity | Class.Quant.Grav.27:215001,2010 | 10.1088/0264-9381/27/21/215001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a frequency modulation technique for calibration of the
displacement actuators of the LIGO 4-km-long interferometric gravitational-wave
detectors. With the interferometer locked in a single-arm configuration, we
modulate the frequency of the laser light, creating an effective length
variation that we calibrate by measuring the amplitude of the frequency
modulation. By simultaneously driving the voice coil actuators that control the
length of the arm cavity, we calibrate the voice coil actuation coefficient
with an estimated 1-sigma uncertainty of less than one percent. This technique
enables a force-free, single-step actuator calibration using a displacement
fiducial that is fundamentally different from those employed in other
calibration methods.
| [
{
"created": "Thu, 20 May 2010 16:03:11 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Jul 2010 22:17:08 GMT",
"version": "v2"
}
] | 2015-03-17 | [
[
"Goetz",
"E.",
""
],
[
"Savage",
"R. L.",
"Jr"
]
] | We present a frequency modulation technique for calibration of the displacement actuators of the LIGO 4-km-long interferometric gravitational-wave detectors. With the interferometer locked in a single-arm configuration, we modulate the frequency of the laser light, creating an effective length variation that we calibrate by measuring the amplitude of the frequency modulation. By simultaneously driving the voice coil actuators that control the length of the arm cavity, we calibrate the voice coil actuation coefficient with an estimated 1-sigma uncertainty of less than one percent. This technique enables a force-free, single-step actuator calibration using a displacement fiducial that is fundamentally different from those employed in other calibration methods. |
2305.04776 | Haroldo Cilas Duarte Lima Junior | Marco A. A. de Paula, Haroldo C. D. Lima Junior, Pedro V. P. Cunha and
Lu\'is C. B. Crispino | Electrically charged regular black holes in nonlinear electrodynamics:
light rings, shadows and gravitational lensing | 16 pages, 13 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Within nonlinear electrodynamics (NED), photons follow null geodesics of an
effective geometry, which is different from the geometry of the spacetime
itself. Over the last years, several works were dedicated to investigate the
motion of photons in the effective geometry of NED-based magnetically charged
regular black hole (RBH) solutions. However, there are few works considering
electrically charged RBHs. We study the light rings, shadows, and gravitational
lensing of the electrically charged RBH solution proposed by Irina Dymnikova
(ID), which is a static and spherically symmetric spacetime with a NED source.
We show that the shadow associated to the effective geometry can be almost 10%
bigger that the one associated to the standard geometry. We also find that the
ID solution may mimic the shadow properties of the Reissner-Nordstr\"om (RN)
BH, for low-to-extreme values of the electric charge. Besides that, by using
the backwards ray-tracing technique, we obtain that ID and RN BH solutions can
have a very similar gravitational lensing, for some values of the correspondent
electric charges. We also show that the motion of photons in the effective
geometry can be interpreted as a non-geodesic curve submitted to a 4-force
term, from the perspective of an observer in the standard geometry.
| [
{
"created": "Mon, 8 May 2023 15:26:20 GMT",
"version": "v1"
}
] | 2023-05-09 | [
[
"de Paula",
"Marco A. A.",
""
],
[
"Junior",
"Haroldo C. D. Lima",
""
],
[
"Cunha",
"Pedro V. P.",
""
],
[
"Crispino",
"Luís C. B.",
""
]
] | Within nonlinear electrodynamics (NED), photons follow null geodesics of an effective geometry, which is different from the geometry of the spacetime itself. Over the last years, several works were dedicated to investigate the motion of photons in the effective geometry of NED-based magnetically charged regular black hole (RBH) solutions. However, there are few works considering electrically charged RBHs. We study the light rings, shadows, and gravitational lensing of the electrically charged RBH solution proposed by Irina Dymnikova (ID), which is a static and spherically symmetric spacetime with a NED source. We show that the shadow associated to the effective geometry can be almost 10% bigger that the one associated to the standard geometry. We also find that the ID solution may mimic the shadow properties of the Reissner-Nordstr\"om (RN) BH, for low-to-extreme values of the electric charge. Besides that, by using the backwards ray-tracing technique, we obtain that ID and RN BH solutions can have a very similar gravitational lensing, for some values of the correspondent electric charges. We also show that the motion of photons in the effective geometry can be interpreted as a non-geodesic curve submitted to a 4-force term, from the perspective of an observer in the standard geometry. |
1110.2007 | Stefanos Aretakis | Stefanos Aretakis | Stability and Instability of Extreme Reissner-Nordstr\"om Black Hole
Spacetimes for Linear Scalar Perturbations I | 37 pages, 11 figures; published version of results contained in the
first part of arXiv:1006.0283, various new results added | Comm. Math. Phys. 307 (2011), 17-63 | 10.1007/s00220-011-1254-5 | null | gr-qc math-ph math.AP math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the problem of stability and instability of extreme
Reissner-Nordstrom spacetimes for linear scalar perturbations. Specifically, we
consider solutions to the linear wave equation on a suitable globally
hyperbolic subset of such a spacetime, arising from regular initial data
prescribed on a Cauchy hypersurface crossing the future event horizon. We
obtain boundedness, decay and non-decay results. Our estimates hold up to and
including the horizon. The fundamental new aspect of this problem is the
degeneracy of the redshift on the event horizon. Several new analytical
features of degenerate horizons are also presented.
| [
{
"created": "Mon, 10 Oct 2011 11:19:04 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Aretakis",
"Stefanos",
""
]
] | We study the problem of stability and instability of extreme Reissner-Nordstrom spacetimes for linear scalar perturbations. Specifically, we consider solutions to the linear wave equation on a suitable globally hyperbolic subset of such a spacetime, arising from regular initial data prescribed on a Cauchy hypersurface crossing the future event horizon. We obtain boundedness, decay and non-decay results. Our estimates hold up to and including the horizon. The fundamental new aspect of this problem is the degeneracy of the redshift on the event horizon. Several new analytical features of degenerate horizons are also presented. |
2405.08303 | Gregory Horndeski Ph.D. | Gregory W. Horndeski | Second-Order Bi-Scalar-Tensor Field Equations in a Space of
Four-Dimensions | 55 pages with no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lagrange scalar densities which are concomitants of two scalar fields, a
pseudo-Riemannian metric tensor, and their derivatives of arbitrary
differential order are investigated in a space of four-dimensions. The most
general second-order Euler-Lagrange tensor densities derivable from such a
Lagrangian are constructed. It is demonstrated that these second-order
Euler-Lagrange tensor densities can be derived from a set of four Lagrangians
which are at most of second-order. These Lagrangians will have a total of six
scalar coefficients, each of which is a concomitant of five variables: the two
scalar fields, and the three inner products of the gradients of the two scalar
fields. Of these six coefficient functions only one is arbitrary, while the
other five must satisfy linear partial differential equations. These
non-arbitrary scalar functions break up into three groups: two groups of two,
and one single function, with different groups appearing in different
Lagrangians. Surprisingly each of these five functions give rise to solutions
to the wave equation in three-dimensional Minkowski space.
| [
{
"created": "Tue, 14 May 2024 03:58:08 GMT",
"version": "v1"
}
] | 2024-05-15 | [
[
"Horndeski",
"Gregory W.",
""
]
] | Lagrange scalar densities which are concomitants of two scalar fields, a pseudo-Riemannian metric tensor, and their derivatives of arbitrary differential order are investigated in a space of four-dimensions. The most general second-order Euler-Lagrange tensor densities derivable from such a Lagrangian are constructed. It is demonstrated that these second-order Euler-Lagrange tensor densities can be derived from a set of four Lagrangians which are at most of second-order. These Lagrangians will have a total of six scalar coefficients, each of which is a concomitant of five variables: the two scalar fields, and the three inner products of the gradients of the two scalar fields. Of these six coefficient functions only one is arbitrary, while the other five must satisfy linear partial differential equations. These non-arbitrary scalar functions break up into three groups: two groups of two, and one single function, with different groups appearing in different Lagrangians. Surprisingly each of these five functions give rise to solutions to the wave equation in three-dimensional Minkowski space. |
2209.03928 | Jo\~ao Marto | K. Sravan Kumar, Jo\~ao Marto | Parity asymmetry of primordial scalar and tensor power spectra | 6 pages, 2 figures. Title changed, figures updated and references
added | null | null | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | Although the cosmic microwave background (CMB) is largely understood to be
homogeneous and isotropic, the CMB power presents anomalies that seem to break
down parity symmetry at large angular scales. We argue that the primordial
scalar and tensor power spectra can be parity asymmetric by considering the
existence of two distinct power spectra in the two parity conjugate regions of
the CMB sky without introducing any additional parameters. We impose a
superselection rule to the vacuum structure for (single field) inflationary
quantum fluctuations based on discrete spacetime transformations
($\mathcal{P}\mathcal{T}$). As a result, we estimate the amplitude of power
asymmetry in the scalar and tensor sectors at different scales of $ 10^{-4}
{\rm Mpc^{-1}}\lesssim k\lesssim 10^{-3}{\rm Mpc^{-1}}$. In particular, we
predict the parity asymmetry for the primordial gravitational waves (PGWs) and
quantify it for different models, like Starobinsky and $\alpha-$attractors
single-field inflation.
| [
{
"created": "Thu, 8 Sep 2022 17:10:09 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Sep 2022 10:55:40 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Jun 2023 17:18:55 GMT",
"version": "v3"
},
{
"created": "Tue, 4 Jun 2024 13:13:20 GMT",
"version": "v4"
}
] | 2024-06-05 | [
[
"Kumar",
"K. Sravan",
""
],
[
"Marto",
"João",
""
]
] | Although the cosmic microwave background (CMB) is largely understood to be homogeneous and isotropic, the CMB power presents anomalies that seem to break down parity symmetry at large angular scales. We argue that the primordial scalar and tensor power spectra can be parity asymmetric by considering the existence of two distinct power spectra in the two parity conjugate regions of the CMB sky without introducing any additional parameters. We impose a superselection rule to the vacuum structure for (single field) inflationary quantum fluctuations based on discrete spacetime transformations ($\mathcal{P}\mathcal{T}$). As a result, we estimate the amplitude of power asymmetry in the scalar and tensor sectors at different scales of $ 10^{-4} {\rm Mpc^{-1}}\lesssim k\lesssim 10^{-3}{\rm Mpc^{-1}}$. In particular, we predict the parity asymmetry for the primordial gravitational waves (PGWs) and quantify it for different models, like Starobinsky and $\alpha-$attractors single-field inflation. |
2312.14041 | Shao-Jiang Wang | Li Hu, Rong-Gen Cai, Shao-Jiang Wang | Distinctive GWBs from eccentric inspiraling SMBH binaries with a DM
spike | v1, 5 pages + references + supplemental material, 6 figures; v2,
references added; v3, discussions extended and references added | null | null | null | gr-qc astro-ph.CO astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent detections of a low-frequency gravitational wave background (GWB) from
various pulsar-timing-array (PTA) observations have renewed the interest in the
inspiraling supermassive black hole binaries (SMBHBs), whose population is
believed to be the most promising candidate of but disfavored by the observed
GWB spectrum naively fitted with purely GW-driven circular binaries. Including
either orbital eccentricity or dark matter (DM) spike can improve the fit to
the current data, but the inclusion of both can further display distinctive
features detectable in future PTA observations. With a typical initial
eccentricity $e_0\sim\mathcal{O}(0.1)$ for the inspiraling SMBHBs, even a
shallow DM spike can easily drive the orbital eccentricity close to unity,
leaving behind a large turnover eccentricity when GWs begin to dominate the
orbital circularization. In particular, the DM spike index $\gamma_\mathrm{sp}$
universally flattens the characteristic strain $h_c\sim
f^{7/6-\gamma_\mathrm{sp}/3}$ in the infrared and produces a novel structure
with an oscillating turnover followed by a flat dip and a bump-like peak at
low, intermediate, and high frequencies, respectively. Future PTA detection of
such characteristics would necessarily provide the smoking gun for the DM spike
and even reveal the nature of DM.
| [
{
"created": "Thu, 21 Dec 2023 17:08:56 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Jan 2024 17:22:23 GMT",
"version": "v2"
},
{
"created": "Thu, 25 Jan 2024 03:32:20 GMT",
"version": "v3"
}
] | 2024-01-26 | [
[
"Hu",
"Li",
""
],
[
"Cai",
"Rong-Gen",
""
],
[
"Wang",
"Shao-Jiang",
""
]
] | Recent detections of a low-frequency gravitational wave background (GWB) from various pulsar-timing-array (PTA) observations have renewed the interest in the inspiraling supermassive black hole binaries (SMBHBs), whose population is believed to be the most promising candidate of but disfavored by the observed GWB spectrum naively fitted with purely GW-driven circular binaries. Including either orbital eccentricity or dark matter (DM) spike can improve the fit to the current data, but the inclusion of both can further display distinctive features detectable in future PTA observations. With a typical initial eccentricity $e_0\sim\mathcal{O}(0.1)$ for the inspiraling SMBHBs, even a shallow DM spike can easily drive the orbital eccentricity close to unity, leaving behind a large turnover eccentricity when GWs begin to dominate the orbital circularization. In particular, the DM spike index $\gamma_\mathrm{sp}$ universally flattens the characteristic strain $h_c\sim f^{7/6-\gamma_\mathrm{sp}/3}$ in the infrared and produces a novel structure with an oscillating turnover followed by a flat dip and a bump-like peak at low, intermediate, and high frequencies, respectively. Future PTA detection of such characteristics would necessarily provide the smoking gun for the DM spike and even reveal the nature of DM. |
2404.09864 | Lorenzo Iorio | Lorenzo Iorio | Measuring a gravitomagentic effect with the triple pulsar PSR J0337+1715 | LaTex2e, 6 pages, no figures, no tables | Universe 2024, 10(5), 206 | 10.3390/universe10050206 | null | gr-qc astro-ph.HE astro-ph.SR physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To the first post--Newtonian order, the orbital angular momentum of the
fast--revolving inner binary of the triple system PSR J0337+1715, made of a
millisecond pulsar and a white dwarf, induces an annular gravitomagnetic field
which displaces the line of apsides of the slower orbit of the other, distant
white dwarf by $-1.2$ milliarcseconds per year. The current accuracy in
determining the periastron of the outer orbit is $63.9$ milliarcseconds after
1.38 years of data collection. By hypothesizing a constant rate of measurement
of the pulsar's times of arrivals over the next 10 years, assumed equal to the
present one, it can be argued that the periastron will be finally known to a
$\simeq 0.15$ milliarcseconds level, while its cumulative gravitomagnetic
retrograde shift will be as large as $-12$ milliarcseconds. The competing
post--Newtonian gravitolectric periastron advance due to the inner binary's
masses, nominally amounting to $74.3$ milliarcseconds per year, can be
presently modelled to an accuracy level as good as $\simeq 0.04$
milliarcseconds per year. The mismodelling in the much larger Newtonian
periastron rate due to the quadrupolar term of the multipolar expansion of the
gravitational potential of a massive ring, whose nominal size for PSR
J0337+1715 is $0.17$ degrees per year, might be reduced down to the $\simeq
0.5$ milliarcseconds per year level over the next 10 years. Thus, a first
measurement of such a novel form of gravitomagnetism, although challenging, may
be somehow feasible in a not too distant future.
| [
{
"created": "Mon, 15 Apr 2024 15:21:12 GMT",
"version": "v1"
}
] | 2024-05-10 | [
[
"Iorio",
"Lorenzo",
""
]
] | To the first post--Newtonian order, the orbital angular momentum of the fast--revolving inner binary of the triple system PSR J0337+1715, made of a millisecond pulsar and a white dwarf, induces an annular gravitomagnetic field which displaces the line of apsides of the slower orbit of the other, distant white dwarf by $-1.2$ milliarcseconds per year. The current accuracy in determining the periastron of the outer orbit is $63.9$ milliarcseconds after 1.38 years of data collection. By hypothesizing a constant rate of measurement of the pulsar's times of arrivals over the next 10 years, assumed equal to the present one, it can be argued that the periastron will be finally known to a $\simeq 0.15$ milliarcseconds level, while its cumulative gravitomagnetic retrograde shift will be as large as $-12$ milliarcseconds. The competing post--Newtonian gravitolectric periastron advance due to the inner binary's masses, nominally amounting to $74.3$ milliarcseconds per year, can be presently modelled to an accuracy level as good as $\simeq 0.04$ milliarcseconds per year. The mismodelling in the much larger Newtonian periastron rate due to the quadrupolar term of the multipolar expansion of the gravitational potential of a massive ring, whose nominal size for PSR J0337+1715 is $0.17$ degrees per year, might be reduced down to the $\simeq 0.5$ milliarcseconds per year level over the next 10 years. Thus, a first measurement of such a novel form of gravitomagnetism, although challenging, may be somehow feasible in a not too distant future. |
2405.08062 | Suvendu Giri | Suvendu Giri, Ulf Danielsson, Luis Lehner, Frans Pretorius | Exploring Black Hole Mimickers: Electromagnetic and Gravitational
Signatures of AdS Black Shells | 18 pages | null | null | UUITP-12/24 | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We study electromagnetic and gravitational properties of AdS black shells
(also referred to as AdS black bubbles) -- a class of quantum gravity motivated
black hole mimickers, that in the classical limit are described as ultra
compact shells of matter. We find that their electromagnetic properties are
remarkably similar to black holes. We then discuss the extent to which these
objects are distinguishable from black holes, both for intrinsic interest
within the black shell model, and as a guide for similar efforts in other
sub-classes of exotic compact objects (ECOs). We study photon rings and lensing
band characteristics, relevant for very large baseline inteferometry (VLBI)
observations, as well as gravitational wave observables -- quasinormal modes in
the eikonal limit and the static tidal Love number for non-spinning shells --
relevant for ongoing and upcoming gravitational wave observations.
| [
{
"created": "Mon, 13 May 2024 18:00:00 GMT",
"version": "v1"
}
] | 2024-05-15 | [
[
"Giri",
"Suvendu",
""
],
[
"Danielsson",
"Ulf",
""
],
[
"Lehner",
"Luis",
""
],
[
"Pretorius",
"Frans",
""
]
] | We study electromagnetic and gravitational properties of AdS black shells (also referred to as AdS black bubbles) -- a class of quantum gravity motivated black hole mimickers, that in the classical limit are described as ultra compact shells of matter. We find that their electromagnetic properties are remarkably similar to black holes. We then discuss the extent to which these objects are distinguishable from black holes, both for intrinsic interest within the black shell model, and as a guide for similar efforts in other sub-classes of exotic compact objects (ECOs). We study photon rings and lensing band characteristics, relevant for very large baseline inteferometry (VLBI) observations, as well as gravitational wave observables -- quasinormal modes in the eikonal limit and the static tidal Love number for non-spinning shells -- relevant for ongoing and upcoming gravitational wave observations. |
1809.03480 | Antonin Coutant | Antonin Coutant, Peter Millington | Quasi-normal modes and fermionic vacuum decay around a Kerr black hole | 25 pages, 2 figures. V2: contains additional minor clarifications,
along with corrections to Fig. 2, and Eqs. (45), (46) and (53), which were
overlooked in the published version. Selected for a CQG+ insight article | Class. Quant. Grav. 36 (2019) 035005 | 10.1088/1361-6382/aaf679 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the instability of the non-rotating fermion vacuum in Kerr
spacetimes. We describe how the co-rotating Fermi sea is formed as a result of
a spontaneous vacuum decay. Most significantly, and drawing upon intuition
gained from analogous electrodynamic processes in supercritical fields, we show
that this decay process is encoded entirely in a subset of quasi-normal fermion
modes.
| [
{
"created": "Mon, 10 Sep 2018 17:51:58 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Jan 2019 10:47:43 GMT",
"version": "v2"
}
] | 2019-01-21 | [
[
"Coutant",
"Antonin",
""
],
[
"Millington",
"Peter",
""
]
] | We analyze the instability of the non-rotating fermion vacuum in Kerr spacetimes. We describe how the co-rotating Fermi sea is formed as a result of a spontaneous vacuum decay. Most significantly, and drawing upon intuition gained from analogous electrodynamic processes in supercritical fields, we show that this decay process is encoded entirely in a subset of quasi-normal fermion modes. |
0706.0179 | Mairi Sakellariadou | William Nelson and Mairi Sakellariadou (King's College, London) | Lattice Refining Loop Quantum Cosmology and Inflation | 12 pages, RevTex Two minor changes to match version to appear in
Physical Review D | Phys.Rev.D76:044015,2007 | 10.1103/PhysRevD.76.044015 | null | gr-qc astro-ph hep-ph hep-th | null | We study the importance of lattice refinement in achieving a successful
inflationary era. We solve, in the continuum limit, the second order difference
equation governing the quantum evolution in loop quantun cosmology, assuming
both a fixed and a dynamically varying lattice in a suitable refinement model.
We thus impose a constraint on the potential of a scalar field, so that the
continuum approximation is not broken. Considering that such a scalar field
could play the role of the inflaton, we obtain a second constraint on the
inflationary potential so that there is consistency with the CMB data on large
angular scales. For a $m^2\phi^2/2$ inflationary model, we combine the two
constraints on the inflaton potential to impose an upper limit on $m$, which is
severely fine-tuned in the case of a fixed lattice. We thus conclude that
lattice refinement is necessary to achieve a natural inflationary model.
| [
{
"created": "Fri, 1 Jun 2007 15:40:37 GMT",
"version": "v1"
},
{
"created": "Sat, 30 Jun 2007 08:59:10 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Nelson",
"William",
"",
"King's College, London"
],
[
"Sakellariadou",
"Mairi",
"",
"King's College, London"
]
] | We study the importance of lattice refinement in achieving a successful inflationary era. We solve, in the continuum limit, the second order difference equation governing the quantum evolution in loop quantun cosmology, assuming both a fixed and a dynamically varying lattice in a suitable refinement model. We thus impose a constraint on the potential of a scalar field, so that the continuum approximation is not broken. Considering that such a scalar field could play the role of the inflaton, we obtain a second constraint on the inflationary potential so that there is consistency with the CMB data on large angular scales. For a $m^2\phi^2/2$ inflationary model, we combine the two constraints on the inflaton potential to impose an upper limit on $m$, which is severely fine-tuned in the case of a fixed lattice. We thus conclude that lattice refinement is necessary to achieve a natural inflationary model. |
1803.01342 | Bruno Carvalho Neves | Bruno Neves | A topological-like gravity model in a four dimensional space-time | Doctoral thesis, in Portuguese | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we consider a model for gravity in 4-dimensional space-time
originally proposed by A. Chamseddine which may be derived by a 5-dimensional
Chern-Simons theory. Its topological origin makes it an interesting candidate
for an easier quantization, e.g., in loop quantization framework. The present
work is dedicated to classical physical consequences and canonical analysis of
the model. Cosmological solutions as well as wave-like solutions were obtained
and compared with the corresponding Einstein's General Relativity with
cosmological constant.
| [
{
"created": "Sun, 4 Mar 2018 11:53:57 GMT",
"version": "v1"
}
] | 2018-03-06 | [
[
"Neves",
"Bruno",
""
]
] | In this work we consider a model for gravity in 4-dimensional space-time originally proposed by A. Chamseddine which may be derived by a 5-dimensional Chern-Simons theory. Its topological origin makes it an interesting candidate for an easier quantization, e.g., in loop quantization framework. The present work is dedicated to classical physical consequences and canonical analysis of the model. Cosmological solutions as well as wave-like solutions were obtained and compared with the corresponding Einstein's General Relativity with cosmological constant. |
gr-qc/0104039 | Bin Zhou | Bin Zhou | Global Structure of Certain Static Spacetimes (I) | Plain LaTeX, 10 pages, no figures | null | null | null | gr-qc | null | In this paper, static spacetimes with a topological structure of R^2 \times N
is studied, where N is an arbitrary manifold. Well known Schwarzschild
spacetime and Reissner-Nordstrom spacetime are special cases. It is shown that
the existence of a constant and positive surface gravity $\kappa$ ensures the
existence of the Killing horizon, with the cross section homeomorphic to N.
| [
{
"created": "Fri, 13 Apr 2001 20:11:04 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Zhou",
"Bin",
""
]
] | In this paper, static spacetimes with a topological structure of R^2 \times N is studied, where N is an arbitrary manifold. Well known Schwarzschild spacetime and Reissner-Nordstrom spacetime are special cases. It is shown that the existence of a constant and positive surface gravity $\kappa$ ensures the existence of the Killing horizon, with the cross section homeomorphic to N. |
2209.09265 | Alex Pandya | Alex Pandya, Elias R. Most, Frans Pretorius | Causal, stable first-order viscous relativistic hydrodynamics with ideal
gas microphysics | 22 pages, 7 figures, updated to match published version (PRD) | null | 10.1103/PhysRevD.106.123036 | null | gr-qc astro-ph.HE nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first numerical analysis of causal, stable first-order
relativistic hydrodynamics with ideal gas microphysics, based in the formalism
developed by Bemfica, Disconzi, Noronha, and Kovtun (BDNK theory). The BDNK
approach provides definitions for the conserved stress-energy tensor and baryon
current, and rigorously proves causality, local well-posedness, strong
hyperbolicity, and linear stability (about equilibrium) for the equations of
motion, subject to a set of coupled nonlinear inequalities involving the
undetermined model coefficients (the choice for which defines the "hydrodynamic
frame"). We present a class of hydrodynamic frames derived from the
relativistic ideal gas "gamma-law" equation of state which satisfy the BDNK
constraints, and explore the properties of the resulting model for a series of
(0+1)D and (1+1)D tests in 4D Minkowski spacetime. These tests include a
comparison of the dissipation mechanisms in Eckart, BDNK, and
Muller-Israel-Stewart theories, as well as investigations of the impact of
hydrodynamic frame on the causality and stability properties of Bjorken flow,
planar shockwave, and heat flow solutions.
| [
{
"created": "Mon, 19 Sep 2022 18:00:05 GMT",
"version": "v1"
},
{
"created": "Sun, 1 Jan 2023 03:57:09 GMT",
"version": "v2"
}
] | 2023-01-03 | [
[
"Pandya",
"Alex",
""
],
[
"Most",
"Elias R.",
""
],
[
"Pretorius",
"Frans",
""
]
] | We present the first numerical analysis of causal, stable first-order relativistic hydrodynamics with ideal gas microphysics, based in the formalism developed by Bemfica, Disconzi, Noronha, and Kovtun (BDNK theory). The BDNK approach provides definitions for the conserved stress-energy tensor and baryon current, and rigorously proves causality, local well-posedness, strong hyperbolicity, and linear stability (about equilibrium) for the equations of motion, subject to a set of coupled nonlinear inequalities involving the undetermined model coefficients (the choice for which defines the "hydrodynamic frame"). We present a class of hydrodynamic frames derived from the relativistic ideal gas "gamma-law" equation of state which satisfy the BDNK constraints, and explore the properties of the resulting model for a series of (0+1)D and (1+1)D tests in 4D Minkowski spacetime. These tests include a comparison of the dissipation mechanisms in Eckart, BDNK, and Muller-Israel-Stewart theories, as well as investigations of the impact of hydrodynamic frame on the causality and stability properties of Bjorken flow, planar shockwave, and heat flow solutions. |
1601.07828 | Seyed Meraj Mousavi Rasouli | S. M. M. Rasouli and Paulo Vargas Moniz | Exact Cosmological Solutions in Modified Brans-Dicke Theory | 23 pages, 8 figures; version accepted for publication in CQG | Classical and Quantum Gravity, Volume 33, 035006, 2016 | 10.1088/0264-9381/33/3/035006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we obtain exact cosmological vacuum solutions for an extended
FLRW homogenous and isotropic Brans-Dicke (BD) universe in five dimensions for
all values of the curvature index. Then, by employing the equations associated
to a modified Brans-Dicke theory (MBDT) [1], we construct the physics on a
four-dimensional hypersurface. We show that the induced matter obeys the
equation of state of a fluid of a barotropic type. We discuss the properties of
such an induced matter for some values of the equation of state parameter and
analyze in detail their corresponding solutions. To illustrate the cosmological
behaviors of the solutions, we contrast our solutions with those present the
standard Brans-Dicke theory. We retrieve that, in MBDT scenario, it is
impossible to find a physically acceptable solution associated to the negative
curvature for both the dust-dominated and radiation-dominated universes.
However, for a spatially flat and closed universes, we argue that our obtained
solutions are more general than those associated to the standard BD theory and,
moreover, they contain a few classes of solutions which have no analog in the
BD cosmology. For those particular cases, we further compare the results with
those extracted in the context of the induced matter theory (IMT) and general
relativity (GR). Furthermore, we discuss in detail the time behaviors of the
cosmological quantities and compare them with recent observational data. We
find a favorable range for the deceleration parameter associated to a
matter-dominated spatially flat universe (for the late times) which is
compatible with recent corresponding observational results.
| [
{
"created": "Thu, 28 Jan 2016 16:49:52 GMT",
"version": "v1"
},
{
"created": "Sun, 3 Jul 2016 14:15:37 GMT",
"version": "v2"
}
] | 2016-07-05 | [
[
"Rasouli",
"S. M. M.",
""
],
[
"Moniz",
"Paulo Vargas",
""
]
] | In this paper, we obtain exact cosmological vacuum solutions for an extended FLRW homogenous and isotropic Brans-Dicke (BD) universe in five dimensions for all values of the curvature index. Then, by employing the equations associated to a modified Brans-Dicke theory (MBDT) [1], we construct the physics on a four-dimensional hypersurface. We show that the induced matter obeys the equation of state of a fluid of a barotropic type. We discuss the properties of such an induced matter for some values of the equation of state parameter and analyze in detail their corresponding solutions. To illustrate the cosmological behaviors of the solutions, we contrast our solutions with those present the standard Brans-Dicke theory. We retrieve that, in MBDT scenario, it is impossible to find a physically acceptable solution associated to the negative curvature for both the dust-dominated and radiation-dominated universes. However, for a spatially flat and closed universes, we argue that our obtained solutions are more general than those associated to the standard BD theory and, moreover, they contain a few classes of solutions which have no analog in the BD cosmology. For those particular cases, we further compare the results with those extracted in the context of the induced matter theory (IMT) and general relativity (GR). Furthermore, we discuss in detail the time behaviors of the cosmological quantities and compare them with recent observational data. We find a favorable range for the deceleration parameter associated to a matter-dominated spatially flat universe (for the late times) which is compatible with recent corresponding observational results. |
gr-qc/0503120 | John Ellis | John Ellis, N.E. Mavromatos, D.V. Nanopoulos | The String Coupling Accelerates the Expansion of the Universe | 7 pages | Gen.Rel.Grav.37:1665-1670,2005; Int.J.Mod.Phys.D14:2327-2334,2005 | 10.1142/S0218271805008042 10.1007/s10714-005-0147-3 | CERN-PH-TH/2005-052 | gr-qc | null | Generic cosmological models in non-critical string theory have a
time-dependent dilaton background at a late epoch. The cosmological
deceleration parameter Q_0 is given by the square of the string coupling,
g_s^2, up to a negative sign. Hence the expansion of the Universe must
accelerate eventually, and the observed value of Q_0 coresponds to g_s^2 ~ 0.6.
In this scenario, the string coupling is asymptotically free at large times,
but its present rate of change is imperceptibly small.
| [
{
"created": "Wed, 30 Mar 2005 17:02:06 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Ellis",
"John",
""
],
[
"Mavromatos",
"N. E.",
""
],
[
"Nanopoulos",
"D. V.",
""
]
] | Generic cosmological models in non-critical string theory have a time-dependent dilaton background at a late epoch. The cosmological deceleration parameter Q_0 is given by the square of the string coupling, g_s^2, up to a negative sign. Hence the expansion of the Universe must accelerate eventually, and the observed value of Q_0 coresponds to g_s^2 ~ 0.6. In this scenario, the string coupling is asymptotically free at large times, but its present rate of change is imperceptibly small. |
1112.1534 | Diego Pavon | Sergio del Campo, Ramon Herrera and Diego Pavon (UAB) | The generalized second law in the emergent universe | 8 pages, 1 figure; to be published in Phys. Letters B | null | 10.1016/j.physletb.2011.12.014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper studies whether the generalized second law of thermodynamics is
fulfilled in the transition from a generic initial Einstein static phase to the
inflationary phase, with constant Hubble rate, and from the end of the latter
to the conventional era of thermal radiation dominated expansion. As it turns
out, the said law is satisfied provided the radiation component does not
largely contribute to the total energy of the static phase.
| [
{
"created": "Wed, 7 Dec 2011 11:58:16 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"del Campo",
"Sergio",
"",
"UAB"
],
[
"Herrera",
"Ramon",
"",
"UAB"
],
[
"Pavon",
"Diego",
"",
"UAB"
]
] | This paper studies whether the generalized second law of thermodynamics is fulfilled in the transition from a generic initial Einstein static phase to the inflationary phase, with constant Hubble rate, and from the end of the latter to the conventional era of thermal radiation dominated expansion. As it turns out, the said law is satisfied provided the radiation component does not largely contribute to the total energy of the static phase. |
2106.06043 | Susanne Schander | S. Schander, T. Thiemann | Backreaction in Cosmology | 41 pages | Front. Astron. Space Sci. 8:692198, 2021 | 10.3389/fspas.2021.692198 | null | gr-qc hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this review, we investigate the question of backreaction in different
approaches to cosmological perturbation theory, and with a special focus on
quantum theoretical aspects. By backreaction, we refer here to the effects of
matter field or cosmological inhomogeneities on the homogeneous dynamical
background degrees of freedom of cosmology. We begin with an overview of
classical cosmological backreaction which is ideally suited for physical
situations in the late time Universe. We then proceed backwards in time,
considering semiclassical approaches such as semiclassical or stochastic
(semiclassical) gravity which take quantum effects of the perturbations into
account. Finally, we review approaches to backreaction in quantum cosmology
that should apply to the very early Universe where classical and semiclassical
approximations break down. The main focus is on a recently proposed
implementation of backreaction in quantum cosmology using a Born-Oppenheimer
inspired method.
| [
{
"created": "Thu, 10 Jun 2021 20:56:31 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Jun 2021 23:10:42 GMT",
"version": "v2"
}
] | 2021-07-29 | [
[
"Schander",
"S.",
""
],
[
"Thiemann",
"T.",
""
]
] | In this review, we investigate the question of backreaction in different approaches to cosmological perturbation theory, and with a special focus on quantum theoretical aspects. By backreaction, we refer here to the effects of matter field or cosmological inhomogeneities on the homogeneous dynamical background degrees of freedom of cosmology. We begin with an overview of classical cosmological backreaction which is ideally suited for physical situations in the late time Universe. We then proceed backwards in time, considering semiclassical approaches such as semiclassical or stochastic (semiclassical) gravity which take quantum effects of the perturbations into account. Finally, we review approaches to backreaction in quantum cosmology that should apply to the very early Universe where classical and semiclassical approximations break down. The main focus is on a recently proposed implementation of backreaction in quantum cosmology using a Born-Oppenheimer inspired method. |
gr-qc/0004060 | Martin Goliath | Alan Coley and Martin Goliath | Closed cosmologies with a perfect fluid and a scalar field | 15 pages, 10 figures | Phys.Rev. D62 (2000) 043526 | 10.1103/PhysRevD.62.043526 | null | gr-qc | null | Closed, spatially homogeneous cosmological models with a perfect fluid and a
scalar field with exponential potential are investigated, using dynamical
systems methods. First, we consider the closed Friedmann-Robertson-Walker
models, discussing the global dynamics in detail. Next, we investigate
Kantowski-Sachs models, for which the future and past attractors are
determined. The global asymptotic behaviour of both the
Friedmann-Robertson-Walker and the Kantowski-Sachs models is that they either
expand from an initial singularity, reach a maximum expansion and thereafter
recollapse to a final singularity (for all values of the potential parameter
kappa), or else they expand forever towards a flat power-law inflationary
solution (when kappa^2<2). As an illustration of the intermediate dynamical
behaviour of the Kantowski-Sachs models, we examine the cases of no barotropic
fluid, and of a massless scalar field in detail. We also briefly discuss
Bianchi type IX models.
| [
{
"created": "Wed, 19 Apr 2000 13:29:13 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Coley",
"Alan",
""
],
[
"Goliath",
"Martin",
""
]
] | Closed, spatially homogeneous cosmological models with a perfect fluid and a scalar field with exponential potential are investigated, using dynamical systems methods. First, we consider the closed Friedmann-Robertson-Walker models, discussing the global dynamics in detail. Next, we investigate Kantowski-Sachs models, for which the future and past attractors are determined. The global asymptotic behaviour of both the Friedmann-Robertson-Walker and the Kantowski-Sachs models is that they either expand from an initial singularity, reach a maximum expansion and thereafter recollapse to a final singularity (for all values of the potential parameter kappa), or else they expand forever towards a flat power-law inflationary solution (when kappa^2<2). As an illustration of the intermediate dynamical behaviour of the Kantowski-Sachs models, we examine the cases of no barotropic fluid, and of a massless scalar field in detail. We also briefly discuss Bianchi type IX models. |
gr-qc/0612173 | Dan Gorbonos | Dan Gorbonos, Gershon Wolansky | A Simplified Mathematical Model for the Formation of Null Singularities
Inside Black Holes II | 25 pages, 10 figures | J.Math.Phys.48:092503,2007 | 10.1063/1.2779949 | null | gr-qc | null | We study a simple system of two hyperbolic semi-linear equations, inspired by
the Einstein equations. The system, which was introduced in gr-qc/0612136, is a
model for singularity formation inside black holes. We show for a particular
case of the equations that the system demonstrates a finite time blowup. The
singularity that is formed is a null singularity. Then we show that in this
particular case the singularity has features that are analogous to known
features of models of black-hole interiors - which describe the inner-horizon
instability. Our simple system may provide insight into the formation of null
singularities inside spinning or charged black holes.
| [
{
"created": "Wed, 27 Dec 2006 21:01:17 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Gorbonos",
"Dan",
""
],
[
"Wolansky",
"Gershon",
""
]
] | We study a simple system of two hyperbolic semi-linear equations, inspired by the Einstein equations. The system, which was introduced in gr-qc/0612136, is a model for singularity formation inside black holes. We show for a particular case of the equations that the system demonstrates a finite time blowup. The singularity that is formed is a null singularity. Then we show that in this particular case the singularity has features that are analogous to known features of models of black-hole interiors - which describe the inner-horizon instability. Our simple system may provide insight into the formation of null singularities inside spinning or charged black holes. |
1604.06378 | Ennio Gozzi | Ennio Gozzi | NEWTON's trajectories versus MOND's trajectories | Improved the abstract, the conclusions and inserted some further new
references | Phys.Lett.B 766 (2017) 112-116 | 10.1016/j.physletb.2017.01.002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | MOND dynamics consists of a modification of the acceleration with respect to
the one provided by Newtonian mechanics. In this paper we investigate whether
it can be derived from a velocity-dependent deformation of the coordinates of
the systems. The conclusion is that it cannot be derived this way because of
the intrinsic non-local character in time of the MOND procedure. This is a
feature pointed out some time ago already by Milgrom himself.
| [
{
"created": "Thu, 21 Apr 2016 16:46:49 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Apr 2016 21:30:04 GMT",
"version": "v2"
},
{
"created": "Thu, 12 May 2016 16:28:16 GMT",
"version": "v3"
},
{
"created": "Wed, 25 May 2016 20:47:25 GMT",
"version": "v4"
},
{
"created": "Mon, 28 Nov 2016 15:04:37 GMT",
"version": "v5"
},
{
"created": "Sun, 25 Dec 2016 17:16:50 GMT",
"version": "v6"
}
] | 2017-02-01 | [
[
"Gozzi",
"Ennio",
""
]
] | MOND dynamics consists of a modification of the acceleration with respect to the one provided by Newtonian mechanics. In this paper we investigate whether it can be derived from a velocity-dependent deformation of the coordinates of the systems. The conclusion is that it cannot be derived this way because of the intrinsic non-local character in time of the MOND procedure. This is a feature pointed out some time ago already by Milgrom himself. |
1006.2448 | Alex Nielsen | Alex B. Nielsen | The spatial relation between the event horizon and trapping horizon | 16 pages, 1 figure | Class.Quant.Grav.27:245016,2010 | 10.1088/0264-9381/27/24/245016 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The relation between event horizons and trapping horizons is investigated in
a number of different situations with emphasis on their role in thermodynamics.
A notion of constant change is introduced that in certain situations allows the
location of the event horizon to be found locally. When the black hole is
accreting matter the difference in area between the two different horizons can
be many orders of magnitude larger than the Planck area. When the black hole is
evaporating the difference is small on the Planck scale. A model is introduced
that shows how trapping horizons can be expected to appear outside the event
horizon before the black hole starts to evaporate. Finally a modified
definition is introduced to invariantly define the location of the trapping
horizon under a conformal transformation. In this case the trapping horizon is
not always a marginally outer trapped surface.
| [
{
"created": "Sat, 12 Jun 2010 09:27:13 GMT",
"version": "v1"
}
] | 2010-12-06 | [
[
"Nielsen",
"Alex B.",
""
]
] | The relation between event horizons and trapping horizons is investigated in a number of different situations with emphasis on their role in thermodynamics. A notion of constant change is introduced that in certain situations allows the location of the event horizon to be found locally. When the black hole is accreting matter the difference in area between the two different horizons can be many orders of magnitude larger than the Planck area. When the black hole is evaporating the difference is small on the Planck scale. A model is introduced that shows how trapping horizons can be expected to appear outside the event horizon before the black hole starts to evaporate. Finally a modified definition is introduced to invariantly define the location of the trapping horizon under a conformal transformation. In this case the trapping horizon is not always a marginally outer trapped surface. |
gr-qc/0503088 | L. C. Garcia de Andrade | L.C. Garcia de Andrade | Relativistic superfluid hydrodynamics | Latex file | null | null | null | gr-qc | null | Relativistic Riemannian superfluid hydrodynamics used in general relativity
to investigate superfluids in pulsars is extended to non-Riemannian background
spacetime endowed with Cartan torsion. From the Gross-Pitaeviskii (GP) it is
shown that in the weak field Cartan torsion approximation, the torsion vector
is orthogonal to the superfluid plane wave velocity. Torsion vector is also
shown to be aligned along the vortex direction in the superfluid. The
background torsion is shown to induce rotation on the fluid as happens with the
acoustic torsion in the analogue non-Riemannian non-relativistic superfluid
models. The torsion part of the current would be connected to the normal part
of the superfluid velocity while the Riemannian part of the velocity would be
connected to the superfluid velocity itself. Magnus effect and the rotation of
the superfluid are analysed. Since the Kalb-Ramond field is easily associated
with torsion our method seems to be equivalent to the vortex-cosmic string
relativistic superfluid method developed by Carter and Langlois to investigate
rotating neutron stars.
| [
{
"created": "Mon, 21 Mar 2005 05:17:07 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Andrade",
"L. C. Garcia",
""
]
] | Relativistic Riemannian superfluid hydrodynamics used in general relativity to investigate superfluids in pulsars is extended to non-Riemannian background spacetime endowed with Cartan torsion. From the Gross-Pitaeviskii (GP) it is shown that in the weak field Cartan torsion approximation, the torsion vector is orthogonal to the superfluid plane wave velocity. Torsion vector is also shown to be aligned along the vortex direction in the superfluid. The background torsion is shown to induce rotation on the fluid as happens with the acoustic torsion in the analogue non-Riemannian non-relativistic superfluid models. The torsion part of the current would be connected to the normal part of the superfluid velocity while the Riemannian part of the velocity would be connected to the superfluid velocity itself. Magnus effect and the rotation of the superfluid are analysed. Since the Kalb-Ramond field is easily associated with torsion our method seems to be equivalent to the vortex-cosmic string relativistic superfluid method developed by Carter and Langlois to investigate rotating neutron stars. |
1304.2482 | Luis Herrera | L. Herrera, J. Ib\'a\~nez and A. Di Prisco | Nature of the vorticity in the G\"{o}del spacetime | Revtex 4, 5 pages. To appear in Phys. Rev. D. Typos corrected and
references updated | Phys. Rev. D87, 087503 (2013) | 10.1103/PhysRevD.87.087503 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The physical meaning of the vorticity of the matter content in G\"{o}del
spacetime is analyzed in some detail. As we shall see, unlike the situation in
general stationnary axially symmetric spacetimes (Lewis--Papapetrou), the
vorticity in G\"{o}del spacetime is not associated to a circular flow of
superenergy on the plane orthogonal to the vorticity vector. This fact might be
at the origin of the strange behaviour of gyroscopes in such spacetime. The
analysis emerging from the tilted version of G\"{o}del spacetime supports
further this point of view. In order to tell apart the two situations (with and
without circular flow of superenergy) we introduce two different definitions of
vorticity, related to the presence (absence) of such a flow.
| [
{
"created": "Tue, 9 Apr 2013 08:07:43 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Apr 2013 09:18:09 GMT",
"version": "v2"
}
] | 2015-06-15 | [
[
"Herrera",
"L.",
""
],
[
"Ibáñez",
"J.",
""
],
[
"Di Prisco",
"A.",
""
]
] | The physical meaning of the vorticity of the matter content in G\"{o}del spacetime is analyzed in some detail. As we shall see, unlike the situation in general stationnary axially symmetric spacetimes (Lewis--Papapetrou), the vorticity in G\"{o}del spacetime is not associated to a circular flow of superenergy on the plane orthogonal to the vorticity vector. This fact might be at the origin of the strange behaviour of gyroscopes in such spacetime. The analysis emerging from the tilted version of G\"{o}del spacetime supports further this point of view. In order to tell apart the two situations (with and without circular flow of superenergy) we introduce two different definitions of vorticity, related to the presence (absence) of such a flow. |
1211.6272 | Alessandro Tronconi | A.Yu. Kamenshchik, A. Tronconi, G. Venturi, S.Yu. Vernov | Reconstruction of Scalar Potentials in Modified Gravity Models | 12 pages, 2 figures, accepted for publication in PRD | Phys.Rev.D87:063503, 2013 | 10.1103/PhysRevD.87.063503 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We employ the superpotential technique for the reconstruction of cosmological
models with a non-minimally coupled scalar field evolving on a spatially flat
Friedmann-Robertson-Walker background. The key point in this method is that the
Hubble parameter is considered as a function of the scalar field and this
allows one to reconstruct the scalar field potential and determine the dynamics
of the field itself, without a priori fixing the Hubble parameter as a function
of time or of the scale factor. The scalar field potentials that lead to de
Sitter or asymptotic de Sitter solutions, and those that reproduce the
cosmological evolution given by Einstein-Hilbert action plus a barotropic
perfect fluid, have been obtained.
| [
{
"created": "Tue, 27 Nov 2012 11:07:41 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Feb 2013 15:14:41 GMT",
"version": "v2"
}
] | 2013-03-08 | [
[
"Kamenshchik",
"A. Yu.",
""
],
[
"Tronconi",
"A.",
""
],
[
"Venturi",
"G.",
""
],
[
"Vernov",
"S. Yu.",
""
]
] | We employ the superpotential technique for the reconstruction of cosmological models with a non-minimally coupled scalar field evolving on a spatially flat Friedmann-Robertson-Walker background. The key point in this method is that the Hubble parameter is considered as a function of the scalar field and this allows one to reconstruct the scalar field potential and determine the dynamics of the field itself, without a priori fixing the Hubble parameter as a function of time or of the scale factor. The scalar field potentials that lead to de Sitter or asymptotic de Sitter solutions, and those that reproduce the cosmological evolution given by Einstein-Hilbert action plus a barotropic perfect fluid, have been obtained. |
0909.0309 | Neda Bostani Dr. | N. Bostani and N. Farhangkhah | Non-Abelian Lovelock-Born-Infeld Topological Black Holes | 15 pages, no figure, references added | IJST (2012) A3: 259-266 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the asymptotically AdS solutions of the Einstein gravity with
hyperbolic horizons in the presence of $So(n(n-1)/2-1, 1)$ Yang-Mills fields
governed by the non-Abelian Born-Infeld lagrangian. We investigate the
properties of these solutions as well as their asymptotic behavior in varies
dimensions. The properties of these kind of solutions are like the
Einstein-Yang-Mills solutions. But the differences seems to appear in the role
of the mass, charge and born-Infeld parameter $\beta$, in the solutions. For
example in Einstein-Yang-Mills theory the solutions with non-negative mass
cannot present an extreme black hole while that of in Einstein-Yang-Mills-Born
Infeld theory can. Also the singularities in higher dimensional
Einstein-Yang-Mills theory for non-negative mass are always spacelike, while
depending on choosing the parameters, we can find timelike singularities in the
similar case of Einstein-Yang-Mills-Born-Infeld theory. We also extend the
solutions of Einstein to the case of Gauss-Bonnet and Lovelock gravity. It is
shown that, these solutions in the limits of $\beta\to0$, and $\beta\to\infty$,
represent pure gravity and gravity coupled with Yang-Mills fields,
respectively.
| [
{
"created": "Wed, 2 Sep 2009 03:06:07 GMT",
"version": "v1"
},
{
"created": "Sat, 24 Oct 2009 02:40:44 GMT",
"version": "v2"
}
] | 2018-03-29 | [
[
"Bostani",
"N.",
""
],
[
"Farhangkhah",
"N.",
""
]
] | We present the asymptotically AdS solutions of the Einstein gravity with hyperbolic horizons in the presence of $So(n(n-1)/2-1, 1)$ Yang-Mills fields governed by the non-Abelian Born-Infeld lagrangian. We investigate the properties of these solutions as well as their asymptotic behavior in varies dimensions. The properties of these kind of solutions are like the Einstein-Yang-Mills solutions. But the differences seems to appear in the role of the mass, charge and born-Infeld parameter $\beta$, in the solutions. For example in Einstein-Yang-Mills theory the solutions with non-negative mass cannot present an extreme black hole while that of in Einstein-Yang-Mills-Born Infeld theory can. Also the singularities in higher dimensional Einstein-Yang-Mills theory for non-negative mass are always spacelike, while depending on choosing the parameters, we can find timelike singularities in the similar case of Einstein-Yang-Mills-Born-Infeld theory. We also extend the solutions of Einstein to the case of Gauss-Bonnet and Lovelock gravity. It is shown that, these solutions in the limits of $\beta\to0$, and $\beta\to\infty$, represent pure gravity and gravity coupled with Yang-Mills fields, respectively. |
1708.04947 | Paul Klinger | Piotr T. Chru\'sciel, Erwann Delay, Paul Klinger | Non-singular spacetimes with a negative cosmological constant: IV.
Stationary black hole solutions with matter fields | 16 pages, journal accepted version | null | 10.1088/1361-6382/aa9e0c | UWThPh-2017-19 | gr-qc hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use an elliptic system of equations with complex coefficients for a set of
complex-valued tensor fields as a tool to construct infinite-dimensional
families of non-singular stationary black holes, real-valued Lorentzian
solutions of the Einstein-Maxwell-dilaton-scalar
fields-Yang-Mills-Higgs-Chern-Simons-$f(R)$ equations with a negative
cosmological constant. The families include an infinite-dimensional family of
solutions with the usual AdS conformal structure at conformal infinity.
| [
{
"created": "Wed, 16 Aug 2017 15:42:49 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Dec 2017 16:47:54 GMT",
"version": "v2"
}
] | 2017-12-13 | [
[
"Chruściel",
"Piotr T.",
""
],
[
"Delay",
"Erwann",
""
],
[
"Klinger",
"Paul",
""
]
] | We use an elliptic system of equations with complex coefficients for a set of complex-valued tensor fields as a tool to construct infinite-dimensional families of non-singular stationary black holes, real-valued Lorentzian solutions of the Einstein-Maxwell-dilaton-scalar fields-Yang-Mills-Higgs-Chern-Simons-$f(R)$ equations with a negative cosmological constant. The families include an infinite-dimensional family of solutions with the usual AdS conformal structure at conformal infinity. |
2308.07360 | Gabriel Le\'on Ph.D. | Gabriel R. Bengochea, Gabriel Leon, Alejandro Perez and Daniel
Sudarsky | A clarification on prevailing misconceptions in unimodular gravity | 26 pages, 2 figures, references updated. Version accepted for
publication | JCAP 11 (2023) 011 | 10.1088/1475-7516/2023/11/011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The traditional presentation of Unimodular Gravity (UG) consists on
indicating that it is an alternative theory of gravity that restricts the
generic diffeomorphism invariance of General Relativity. In particular, as
often encountered in the literature, unlike General Relativity, Unimodular
Gravity is invariant solely under volume-preserving diffeomorphisms. That
characterization of UG has led to some confusion and incorrect statements in
various treatments on the subject. For instance, sometimes it is claimed
(mistakenly) that only spacetime metrics such that $|$det $g_{\mu \nu}| = 1$
can be considered as valid solutions of the theory. Additionally, that same
(incorrect) statement is often invoked to argue that some particular gauges
(e.g. the Newtonian or synchronous gauge) are not allowed when dealing with
cosmological perturbation theory in UG. The present article is devoted to
clarify those and other misconceptions regarding the notion of diffeomorphism
invariance, in general, and its usage in the context of UG, in particular.
| [
{
"created": "Mon, 14 Aug 2023 15:50:20 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Nov 2023 18:47:04 GMT",
"version": "v2"
}
] | 2023-11-08 | [
[
"Bengochea",
"Gabriel R.",
""
],
[
"Leon",
"Gabriel",
""
],
[
"Perez",
"Alejandro",
""
],
[
"Sudarsky",
"Daniel",
""
]
] | The traditional presentation of Unimodular Gravity (UG) consists on indicating that it is an alternative theory of gravity that restricts the generic diffeomorphism invariance of General Relativity. In particular, as often encountered in the literature, unlike General Relativity, Unimodular Gravity is invariant solely under volume-preserving diffeomorphisms. That characterization of UG has led to some confusion and incorrect statements in various treatments on the subject. For instance, sometimes it is claimed (mistakenly) that only spacetime metrics such that $|$det $g_{\mu \nu}| = 1$ can be considered as valid solutions of the theory. Additionally, that same (incorrect) statement is often invoked to argue that some particular gauges (e.g. the Newtonian or synchronous gauge) are not allowed when dealing with cosmological perturbation theory in UG. The present article is devoted to clarify those and other misconceptions regarding the notion of diffeomorphism invariance, in general, and its usage in the context of UG, in particular. |
1911.01307 | Edward Anderson | Edward Anderson | Lie Theory suffices to understand, and Locally Resolve, the Problem of
Time | 4 pages, including 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Lie claw digraph controls Background Independence and thus the Problem of
Time and indeed the Fundamental Nature of Physical Law. This has been
established in the realms of Flat and Differential Geometry with varying
amounts of extra mathematical structure. This Lie claw digraph has Generator
Closure at its centre (Lie brackets), Relationalism at its root (implemented by
Lie derivatives), and, as its leaves, Assignment of Observables (zero
commutants under Lie brackets) and Constructability from Less Structure Assumed
(working if generator Deformation leads to Lie brackets algebraic Rigidity).
This centre is enabled by automorphisms and powered by the Generalized Lie
Algorithm extension of the Dirac Algorithm (itself sufficing for the canonical
subcase, for which generators are constraints). The Problem of Time's facet
ordering problem is resolved.
| [
{
"created": "Mon, 4 Nov 2019 16:15:01 GMT",
"version": "v1"
}
] | 2019-11-05 | [
[
"Anderson",
"Edward",
""
]
] | The Lie claw digraph controls Background Independence and thus the Problem of Time and indeed the Fundamental Nature of Physical Law. This has been established in the realms of Flat and Differential Geometry with varying amounts of extra mathematical structure. This Lie claw digraph has Generator Closure at its centre (Lie brackets), Relationalism at its root (implemented by Lie derivatives), and, as its leaves, Assignment of Observables (zero commutants under Lie brackets) and Constructability from Less Structure Assumed (working if generator Deformation leads to Lie brackets algebraic Rigidity). This centre is enabled by automorphisms and powered by the Generalized Lie Algorithm extension of the Dirac Algorithm (itself sufficing for the canonical subcase, for which generators are constraints). The Problem of Time's facet ordering problem is resolved. |
2312.01277 | Sayak Datta | Sayak Datta | Black holes immersed in dark matter: energy condition and sound speed | null | null | null | null | gr-qc astro-ph.GA astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | In this work, we study the impact of the environment around a black hole in
detail. We introduce non-vanishing radial pressure in a manner analogous to
compact stars. We examine both isotropic and anisotropic fluid configurations
with and without radial pressure respectively. Our focus extends beyond just
dark matter density to the vital role of the energy condition and sound speed
in the spacetime of a black hole immersed in matter. In cases of anisotropic
pressure with vanishing radial pressure, all profiles violate the dominant
energy condition near the BH, and the tangential sound speed exceeds light
speed for all dark matter profiles. In our second approach, without assuming
vanishing radial pressure, we observe similar violations and superluminal sound
speeds. To rectify this, we introduce a hard cutoff for the sound speed,
ensuring it remains subluminal. As a consequence, the energy condition is also
satisfied. However, this results in increased density and pressure near the BH.
This raises questions about the sound speed and its impact on the density
structure, as well as questions about the validity of the model itself. With
the matter distribution, we also compute the metric for different
configurations. It reveals sensitivity to the profile structure. The metric
components point towards the horizon structure.
| [
{
"created": "Sun, 3 Dec 2023 04:30:23 GMT",
"version": "v1"
},
{
"created": "Mon, 6 May 2024 07:44:32 GMT",
"version": "v2"
}
] | 2024-05-07 | [
[
"Datta",
"Sayak",
""
]
] | In this work, we study the impact of the environment around a black hole in detail. We introduce non-vanishing radial pressure in a manner analogous to compact stars. We examine both isotropic and anisotropic fluid configurations with and without radial pressure respectively. Our focus extends beyond just dark matter density to the vital role of the energy condition and sound speed in the spacetime of a black hole immersed in matter. In cases of anisotropic pressure with vanishing radial pressure, all profiles violate the dominant energy condition near the BH, and the tangential sound speed exceeds light speed for all dark matter profiles. In our second approach, without assuming vanishing radial pressure, we observe similar violations and superluminal sound speeds. To rectify this, we introduce a hard cutoff for the sound speed, ensuring it remains subluminal. As a consequence, the energy condition is also satisfied. However, this results in increased density and pressure near the BH. This raises questions about the sound speed and its impact on the density structure, as well as questions about the validity of the model itself. With the matter distribution, we also compute the metric for different configurations. It reveals sensitivity to the profile structure. The metric components point towards the horizon structure. |
2006.09385 | Yen Chin Ong | Brett McInnes, Yen Chin Ong | Event Horizon Wrinklification | 12 pages, 3 figures | null | 10.1088/1361-6382/abce45 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The possible existence of stable black holes with entropies larger than the
corresponding Schwarzschild black hole has been discussed extensively. The
recently proposed "rough" black holes provide a concrete example of this. The
fear is that, in accordance with the Second Law of thermodynamics, the familiar
smooth-skinned black holes might spontaneously "wrinklify" into such an object.
We show that this fear is to some extent justified, in the sense that AdS black
holes with more entropy than the AdS-Schwarzschild black hole of the same mass
do exist.
| [
{
"created": "Tue, 16 Jun 2020 18:00:01 GMT",
"version": "v1"
}
] | 2021-02-03 | [
[
"McInnes",
"Brett",
""
],
[
"Ong",
"Yen Chin",
""
]
] | The possible existence of stable black holes with entropies larger than the corresponding Schwarzschild black hole has been discussed extensively. The recently proposed "rough" black holes provide a concrete example of this. The fear is that, in accordance with the Second Law of thermodynamics, the familiar smooth-skinned black holes might spontaneously "wrinklify" into such an object. We show that this fear is to some extent justified, in the sense that AdS black holes with more entropy than the AdS-Schwarzschild black hole of the same mass do exist. |
1212.1285 | Douglas A. Singleton | H.-J. Schmidt and D. Singleton | Exact radial solution in 2+1 gravity with a real scalar field | 13 pages, minor revisions, updated references, to be published PLB | Phys.Lett.B721:294-298,2013 | 10.1016/j.physletb.2013.03.007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we give some general considerations about circularly symmetric,
static space-times in 2+1 dimensions, focusing first on the surprising (at the
time) existence of the BTZ black hole solution. We show that BTZ black holes
and Schwarzschild black holes in 3+1 dimensions originate from different
definitions of a black hole. There are two by-products of this general
discussion: (i) we give a new and simple derivation of 2+1 dimensional Anti-de
Sitter (AdS) space-time; (ii) we present an exact solution to 2+1 dimensional
gravity coupled to a self-interacting real scalar field. The spatial part of
the metric of this solution is flat but the temporal part behaves
asymptotically like AdS space-time. The scalar field has logarithmic behavior
as one would expect for a massless scalar field in flat space-time. The
solution can be compared to gravitating scalar field solutions in 3+1
dimensions but with certain oddities connected with the 2+1 dimensional
character of the space-time. The solution is unique to 2+1 dimensions; it does
not carry over to 3+1 dimensions.
| [
{
"created": "Thu, 6 Dec 2012 10:58:45 GMT",
"version": "v1"
},
{
"created": "Sat, 9 Mar 2013 14:12:38 GMT",
"version": "v2"
}
] | 2013-04-10 | [
[
"Schmidt",
"H. -J.",
""
],
[
"Singleton",
"D.",
""
]
] | In this paper we give some general considerations about circularly symmetric, static space-times in 2+1 dimensions, focusing first on the surprising (at the time) existence of the BTZ black hole solution. We show that BTZ black holes and Schwarzschild black holes in 3+1 dimensions originate from different definitions of a black hole. There are two by-products of this general discussion: (i) we give a new and simple derivation of 2+1 dimensional Anti-de Sitter (AdS) space-time; (ii) we present an exact solution to 2+1 dimensional gravity coupled to a self-interacting real scalar field. The spatial part of the metric of this solution is flat but the temporal part behaves asymptotically like AdS space-time. The scalar field has logarithmic behavior as one would expect for a massless scalar field in flat space-time. The solution can be compared to gravitating scalar field solutions in 3+1 dimensions but with certain oddities connected with the 2+1 dimensional character of the space-time. The solution is unique to 2+1 dimensions; it does not carry over to 3+1 dimensions. |
gr-qc/9911113 | Zoltan Perjes | Z. Perj\'es | Relativistic perfect fluid models | 10 pages, Presented at the Journees Relativistes 1999, Weimar
(September 12-17) | Annalen Phys. 9 (2000) 368-377 | 10.1002/(SICI)1521-3889(200005)9:3/5<368::AID-ANDP368>3.0.CO;2-Q | null | gr-qc | null | The various schemes for studying rigidly rotating perfect fluids in general
relativity are reviewed. General conclusions one may draw from these are: (i)
There is a need to restrict the scope of the possible ansatze, and (ii) the
angular behaviour is a valuable commodity. This latter observation follows from
a large number of analytic models exhibiting a NUT-like behaviour. A method of
getting around problem (ii) is presented on a simple example. To alleviate
problem (i) for rigidly rotating perfect fluids, approximation schemes based on
a series expansion in the angular velocity are suggested. A pioneering work,
due to Hartle, explores the global properties of matched space-times to
quadratic order in the angular velocity.
As a first example of the applications, it is shown that the rigidly rotating
incompressible fluid cannot be Petrov type D.
| [
{
"created": "Sun, 28 Nov 1999 16:19:47 GMT",
"version": "v1"
}
] | 2017-09-27 | [
[
"Perjés",
"Z.",
""
]
] | The various schemes for studying rigidly rotating perfect fluids in general relativity are reviewed. General conclusions one may draw from these are: (i) There is a need to restrict the scope of the possible ansatze, and (ii) the angular behaviour is a valuable commodity. This latter observation follows from a large number of analytic models exhibiting a NUT-like behaviour. A method of getting around problem (ii) is presented on a simple example. To alleviate problem (i) for rigidly rotating perfect fluids, approximation schemes based on a series expansion in the angular velocity are suggested. A pioneering work, due to Hartle, explores the global properties of matched space-times to quadratic order in the angular velocity. As a first example of the applications, it is shown that the rigidly rotating incompressible fluid cannot be Petrov type D. |
gr-qc/0103092 | Ozay Gurtug | Ozay Gurtug and Mustafa Halilsoy | Null Singularities in Colliding Waves | 6 pages, no figures | null | null | null | gr-qc | null | Colliding Einstein-Maxwell-Scalar fields need not necessarily doomed to
become in a spacelike singularity. Examples are given in which null
singularities emerge as intermediate stages between a spacelike singularity and
a regular horizon.
| [
{
"created": "Mon, 26 Mar 2001 11:30:23 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gurtug",
"Ozay",
""
],
[
"Halilsoy",
"Mustafa",
""
]
] | Colliding Einstein-Maxwell-Scalar fields need not necessarily doomed to become in a spacelike singularity. Examples are given in which null singularities emerge as intermediate stages between a spacelike singularity and a regular horizon. |
gr-qc/0104064 | Slava G. Turyshev | John D. Anderson, Philip A. Laing, Eunice L. Lau, Anthony S. Liu,
Michael Martin Nieto and Slava G. Turyshev | Study of the anomalous acceleration of Pioneer 10 and 11 | Version 4, of 11 Apr. 2002, with errata appended | Phys.Rev.D65:082004,2002 | 10.1103/PhysRevD.65.082004 | LA-UR-00-5654 | gr-qc astro-ph physics.space-ph | null | Our previous analyses of radio Doppler and ranging data from distant
spacecraft in the solar system indicated that an apparent anomalous
acceleration is acting on Pioneer 10 and 11, with a magnitude a_P ~ 8 x 10^{-8}
cm/s^2, directed towards the Sun (anderson,moriond). Much effort has been
expended looking for possible systematic origins of the residuals, but none has
been found. A detailed investigation of effects both external to and internal
to the spacecraft, as well as those due to modeling and computational
techniques, is provided. We also discuss the methods, theoretical models, and
experimental techniques used to detect and study small forces acting on
interplanetary spacecraft. These include the methods of radio Doppler data
collection, data editing, and data reduction.
There is now further data for the Pioneer 10 orbit determination. The
extended Pioneer 10 data set spans 3 January 1987 to 22 July 1998. [For Pioneer
11 the shorter span goes from 5 January 1987 to the time of loss of coherent
data on 1 October 1990.] With these data sets and more detailed studies of all
the systematics, we now give a result, of a_P = (8.74 +/- 1.33) x 10^{-8}
cm/s^2. (Annual/diurnal variations on top of a_P, that leave a_P unchanged, are
also reported and discussed.)
| [
{
"created": "Thu, 19 Apr 2001 22:42:49 GMT",
"version": "v1"
},
{
"created": "Tue, 15 May 2001 20:55:26 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Feb 2002 21:05:21 GMT",
"version": "v3"
},
{
"created": "Thu, 11 Apr 2002 20:28:10 GMT",
"version": "v4"
},
{
"created": "Thu, 10 Mar 2005 23:44:33 GMT",
"version": "v5"
}
] | 2009-09-25 | [
[
"Anderson",
"John D.",
""
],
[
"Laing",
"Philip A.",
""
],
[
"Lau",
"Eunice L.",
""
],
[
"Liu",
"Anthony S.",
""
],
[
"Nieto",
"Michael Martin",
""
],
[
"Turyshev",
"Slava G.",
""
]
] | Our previous analyses of radio Doppler and ranging data from distant spacecraft in the solar system indicated that an apparent anomalous acceleration is acting on Pioneer 10 and 11, with a magnitude a_P ~ 8 x 10^{-8} cm/s^2, directed towards the Sun (anderson,moriond). Much effort has been expended looking for possible systematic origins of the residuals, but none has been found. A detailed investigation of effects both external to and internal to the spacecraft, as well as those due to modeling and computational techniques, is provided. We also discuss the methods, theoretical models, and experimental techniques used to detect and study small forces acting on interplanetary spacecraft. These include the methods of radio Doppler data collection, data editing, and data reduction. There is now further data for the Pioneer 10 orbit determination. The extended Pioneer 10 data set spans 3 January 1987 to 22 July 1998. [For Pioneer 11 the shorter span goes from 5 January 1987 to the time of loss of coherent data on 1 October 1990.] With these data sets and more detailed studies of all the systematics, we now give a result, of a_P = (8.74 +/- 1.33) x 10^{-8} cm/s^2. (Annual/diurnal variations on top of a_P, that leave a_P unchanged, are also reported and discussed.) |
2404.19470 | Valerio Faraoni | Julien Houle and Valerio Faraoni | New phenomenology in the first-order thermodynamics of scalar-tensor
gravity for Bianchi universes | 10 pages, no figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The phase space of Bianchi I universes in vacuum Brans-Dicke gravity is
analyzed in terms of physical variables. The behaviour of the solutions of the
field equations near the fixed points (which are solutions of Einstein gravity)
is compared with basic ideas of the recent first-order thermodynamics of
scalar-tensor gravity, elucidating new phenomenology.
| [
{
"created": "Tue, 30 Apr 2024 11:37:10 GMT",
"version": "v1"
}
] | 2024-05-01 | [
[
"Houle",
"Julien",
""
],
[
"Faraoni",
"Valerio",
""
]
] | The phase space of Bianchi I universes in vacuum Brans-Dicke gravity is analyzed in terms of physical variables. The behaviour of the solutions of the field equations near the fixed points (which are solutions of Einstein gravity) is compared with basic ideas of the recent first-order thermodynamics of scalar-tensor gravity, elucidating new phenomenology. |
0901.0448 | Salvatore Capozziello | S. Capozziello, A. Stabile, A. Troisi | A general solution in the Newtonian limit of f(R)- gravity | 5 pages | Mod.Phys.Lett.A24:659-665,2009 | 10.1142/S0217732309030382 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that any analytic $f(R)$-gravity model, in the metric approach,
presents a weak field limit where the standard Newtonian potential is corrected
by a Yukawa-like term. This general result has never been pointed out but often
derived for some particular theories. This means that only $f(R)=R$ allows to
recover the standard Newton potential while this is not the case for other
relativistic theories of gravity. Some considerations on the physical
consequences of such a general solution are addressed.
| [
{
"created": "Mon, 5 Jan 2009 09:30:16 GMT",
"version": "v1"
}
] | 2009-04-21 | [
[
"Capozziello",
"S.",
""
],
[
"Stabile",
"A.",
""
],
[
"Troisi",
"A.",
""
]
] | We show that any analytic $f(R)$-gravity model, in the metric approach, presents a weak field limit where the standard Newtonian potential is corrected by a Yukawa-like term. This general result has never been pointed out but often derived for some particular theories. This means that only $f(R)=R$ allows to recover the standard Newton potential while this is not the case for other relativistic theories of gravity. Some considerations on the physical consequences of such a general solution are addressed. |
0803.4133 | Patricio S. Letelier | Marcelo Zimbres and Patricio S. Letelier | Multipolar corrections for Lense-Thirring precession | 6 pages, RevTex | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For stationary axially symmetric spacetimes we find a simple expression for
the Lense-Thirring precession in terms of the Ernst potential. This expression
is used to compute, in the weak field approximation, the major non-spherical
contributions to the precession of a gyroscope orbiting the Earth. We reproduce
previously known results and give a new estimation for non-spherical
contributions.
| [
{
"created": "Fri, 28 Mar 2008 14:43:45 GMT",
"version": "v1"
}
] | 2008-03-31 | [
[
"Zimbres",
"Marcelo",
""
],
[
"Letelier",
"Patricio S.",
""
]
] | For stationary axially symmetric spacetimes we find a simple expression for the Lense-Thirring precession in terms of the Ernst potential. This expression is used to compute, in the weak field approximation, the major non-spherical contributions to the precession of a gyroscope orbiting the Earth. We reproduce previously known results and give a new estimation for non-spherical contributions. |
1907.12278 | Nematollah Riazi | A. Farahani and N. Riazi | Dipole and String Solutions of the Kaluza-Klein Theory | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a Kaluza-Klein string solution of five-dimensional spacetime. We
study its physical properties as appearing in (3+1) spacetime. This metric
embraces several different aspects of solutions. The two most notable examples
are the dipole and the boosted dipole solutions. In general, the 4D metric is a
rotating stationary solution with both electric and magnetic fields. The
extension to the Kaluza-Klein dipole soliton solution is briefly discussed.
| [
{
"created": "Mon, 29 Jul 2019 08:50:56 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Jan 2020 07:46:13 GMT",
"version": "v2"
}
] | 2020-01-22 | [
[
"Farahani",
"A.",
""
],
[
"Riazi",
"N.",
""
]
] | We consider a Kaluza-Klein string solution of five-dimensional spacetime. We study its physical properties as appearing in (3+1) spacetime. This metric embraces several different aspects of solutions. The two most notable examples are the dipole and the boosted dipole solutions. In general, the 4D metric is a rotating stationary solution with both electric and magnetic fields. The extension to the Kaluza-Klein dipole soliton solution is briefly discussed. |
gr-qc/0111085 | Luisa T. Buchman | J. M. Bardeen and L. T. Buchman | Numerical Tests of Evolution Systems, Gauge Conditions, and Boundary
Conditions for 1D Colliding Gravitational Plane Waves | 29 pages, 11 figures, submitted to Phys. Rev. D | Phys.Rev. D65 (2002) 064037 | 10.1103/PhysRevD.65.064037 | null | gr-qc | null | We investigate how the accuracy and stability of numerical relativity
simulations of 1D colliding plane waves depends on choices of equation
formulations, gauge conditions, boundary conditions, and numerical methods, all
in the context of a first-order 3+1 approach to the Einstein equations, with
basic variables some combination of first derivatives of the spatial metric and
components of the extrinsic curvature tensor. Hyperbolic schemes, specifically
variations on schemes proposed by Bona and Masso and Anderson and York, are
compared with variations of the Arnowitt-Deser-Misner formulation.
Modifications of the three basic schemes include raising one index in the
metric derivative and extrinsic curvature variables and adding a multiple of
the energy constraint to the extrinsic curvature evolution equations. Redundant
variables in the Bona-Masso formulation may be reset frequently or allowed to
evolve freely. Gauge conditions which simplify the dynamical structure of the
system are imposed during each time step, but the lapse and shift are reset
periodically to control the evolution of the spacetime slicing and the
longitudinal part of the metric. We show that physically correct boundary
conditions, satisfying the energy and momentum constraint equations,
generically require the presence of some ingoing eigenmodes of the
characteristic matrix. Numerical methods are developed for the hyperbolic
systems based on decomposing flux differences into linear combinations of
eigenvectors of the characteristic matrix. These methods are shown to be
second-order accurate, and in practice second-order convergent, for smooth
solutions, even when the eigenvectors and eigenvalues of the characteristic
matrix are spatially varying.
| [
{
"created": "Mon, 26 Nov 2001 20:52:08 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Bardeen",
"J. M.",
""
],
[
"Buchman",
"L. T.",
""
]
] | We investigate how the accuracy and stability of numerical relativity simulations of 1D colliding plane waves depends on choices of equation formulations, gauge conditions, boundary conditions, and numerical methods, all in the context of a first-order 3+1 approach to the Einstein equations, with basic variables some combination of first derivatives of the spatial metric and components of the extrinsic curvature tensor. Hyperbolic schemes, specifically variations on schemes proposed by Bona and Masso and Anderson and York, are compared with variations of the Arnowitt-Deser-Misner formulation. Modifications of the three basic schemes include raising one index in the metric derivative and extrinsic curvature variables and adding a multiple of the energy constraint to the extrinsic curvature evolution equations. Redundant variables in the Bona-Masso formulation may be reset frequently or allowed to evolve freely. Gauge conditions which simplify the dynamical structure of the system are imposed during each time step, but the lapse and shift are reset periodically to control the evolution of the spacetime slicing and the longitudinal part of the metric. We show that physically correct boundary conditions, satisfying the energy and momentum constraint equations, generically require the presence of some ingoing eigenmodes of the characteristic matrix. Numerical methods are developed for the hyperbolic systems based on decomposing flux differences into linear combinations of eigenvectors of the characteristic matrix. These methods are shown to be second-order accurate, and in practice second-order convergent, for smooth solutions, even when the eigenvectors and eigenvalues of the characteristic matrix are spatially varying. |
2404.05957 | Songbai Chen | Zelin Zhang, Songbai Chen, Jiliang Jing | Constraining a disformal Schwarzschild black hole in DHOST theories with
the orbit of the S2 star | 13 pages, 3 figures. To be appeared in EPJC | null | null | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With the observed data of the S2 orbit around the black hole Sgr A$^*$ and
the Markov Chain Monte Carlo method, we make a constraint on parameters of a
disformal Schwarzschild black hole in quadratic degenerate higher-order
scalar-tensor (DHOST) theories. This black hole belongs to a class of
non-stealth solutions and owns an extra disformal parameter described the
deviation from general relativity. Our results show that the best fit value of
the disformal parameter is positive. However, in the range of $1\sigma$, we
also find that general relativity remains to be consistent with the observation
of the S2 orbit.
| [
{
"created": "Tue, 9 Apr 2024 02:32:14 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Aug 2024 00:07:07 GMT",
"version": "v2"
}
] | 2024-08-02 | [
[
"Zhang",
"Zelin",
""
],
[
"Chen",
"Songbai",
""
],
[
"Jing",
"Jiliang",
""
]
] | With the observed data of the S2 orbit around the black hole Sgr A$^*$ and the Markov Chain Monte Carlo method, we make a constraint on parameters of a disformal Schwarzschild black hole in quadratic degenerate higher-order scalar-tensor (DHOST) theories. This black hole belongs to a class of non-stealth solutions and owns an extra disformal parameter described the deviation from general relativity. Our results show that the best fit value of the disformal parameter is positive. However, in the range of $1\sigma$, we also find that general relativity remains to be consistent with the observation of the S2 orbit. |
1103.4758 | Eugen Radu | Burkhard Kleihaus, Jutta Kunz, Eugen Radu and Daniel Senkbeil | Electric charge on the brane? | v2: 21 pages, 4 figures; references added; changes in section 3 | Phys.Rev.D83:104050,2011 | 10.1103/PhysRevD.83.104050 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider black holes localized on the brane in the Randall-Sundrum
infinite braneworld model. These configurations are static and charged with
respect to a spherically symmetric, electric Maxwell field living on the brane.
We start by attempting to construct vacuum black holes, in which case our
conclusions are in agreement with those of Yoshino in JHEP 0901:068, 2009
(arXiv:0812.0465). Although approximate solutions appear to exist for
sufficiently small brane tension, these are likely only numerical artifacts.
The qualitative features of the configurations in the presence of a brane U(1)
electric field are similar to those in the vacuum case. In particular, we find
a systematic unnatural behaviour of the metric functions in the asymptotic
region in the vicinity of the AdS horizon. Our results are most naturally
interpreted as evidence for the nonexistence of static, nonextremal charged
black holes on the brane. In contrast, extremal black holes are more likely to
exist on the brane. We determine their near-horizon form by employing both
analytical and numerical methods. For any bulk dimension d>4, we find good
agreement between the properties of large extremal black holes and the
predictions of general relativity, with calculable subleading corrections.
| [
{
"created": "Thu, 24 Mar 2011 13:02:50 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Mar 2011 23:06:36 GMT",
"version": "v2"
}
] | 2011-06-07 | [
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Radu",
"Eugen",
""
],
[
"Senkbeil",
"Daniel",
""
]
] | We consider black holes localized on the brane in the Randall-Sundrum infinite braneworld model. These configurations are static and charged with respect to a spherically symmetric, electric Maxwell field living on the brane. We start by attempting to construct vacuum black holes, in which case our conclusions are in agreement with those of Yoshino in JHEP 0901:068, 2009 (arXiv:0812.0465). Although approximate solutions appear to exist for sufficiently small brane tension, these are likely only numerical artifacts. The qualitative features of the configurations in the presence of a brane U(1) electric field are similar to those in the vacuum case. In particular, we find a systematic unnatural behaviour of the metric functions in the asymptotic region in the vicinity of the AdS horizon. Our results are most naturally interpreted as evidence for the nonexistence of static, nonextremal charged black holes on the brane. In contrast, extremal black holes are more likely to exist on the brane. We determine their near-horizon form by employing both analytical and numerical methods. For any bulk dimension d>4, we find good agreement between the properties of large extremal black holes and the predictions of general relativity, with calculable subleading corrections. |
1708.03334 | Ofek Birnholtz | Alex B. Nielsen and Ofek Birnholtz | Testing pseudo-complex general relativity with gravitational waves | null | null | 10.1002/asna.201813473 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show how the model of pseudo-complex general relativity can be tested
using gravitational wave signals from coalescing compact objects. The model,
which agrees with Einstein gravity in the weak-field limit, diverges
dramatically in the near-horizon regime, with certain parameter ranges
excluding the existence of black holes. We show that simple limits can be
placed on the model in both the inspiral and ringdown phase of coalescing
compact objects. We discuss further how these bounds relate to current
observational limits. In particular, for minimal scenarios previously
considered in the literature, gravitational wave observations are able to
constrain pseudo-complex general relativity parameters to values that require
the existence of black hole horizons.
| [
{
"created": "Thu, 10 Aug 2017 18:00:18 GMT",
"version": "v1"
}
] | 2018-07-18 | [
[
"Nielsen",
"Alex B.",
""
],
[
"Birnholtz",
"Ofek",
""
]
] | We show how the model of pseudo-complex general relativity can be tested using gravitational wave signals from coalescing compact objects. The model, which agrees with Einstein gravity in the weak-field limit, diverges dramatically in the near-horizon regime, with certain parameter ranges excluding the existence of black holes. We show that simple limits can be placed on the model in both the inspiral and ringdown phase of coalescing compact objects. We discuss further how these bounds relate to current observational limits. In particular, for minimal scenarios previously considered in the literature, gravitational wave observations are able to constrain pseudo-complex general relativity parameters to values that require the existence of black hole horizons. |
1706.02782 | Thiago R.P. Caram\^es | Thiago R. P. Caram\^es, J\'ulio C. Fabris, E. R. Bezerra de Mello and
H. Belich | $f(R)$ global monopole revisited | 16 pages, 1 figure and 1 table. Minor changes to match published
version in EPJC | Eur. Phys. J. C (2017) 77: 496 | 10.1140/epjc/s10052-017-5057-5 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper the $f(R)$ global monopole is reexamined. We provide an exact
solution for the modified field equations in the presence of a global monopole
for regions outside its core, generalizing previous results. Additionally, we
discuss some particular cases obtained from this solution. We consider a setup
consisting of a possible Schwarzschild black hole that absorbs the topological
defect, giving rise to a static black hole endowed with a monopole's charge.
Besides, we demonstrate how the asymptotic behavior of the Higgs field far from
the monopole's core is shaped by a class of spacetime metrics which includes
those ones analyzed here. In order to assess the gravitational properties of
this system, we analyse the geodesic motion of both massive and massless test
particles moving in the vicinity of such configuration. For the material
particles we set the requirements they have to obey in order to experience
stable orbits. On the other hand, for the photons we investigate how their
trajectories are affected by the gravitational field of this black hole.
| [
{
"created": "Thu, 8 Jun 2017 22:20:07 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jul 2017 19:36:14 GMT",
"version": "v2"
}
] | 2017-07-27 | [
[
"Caramês",
"Thiago R. P.",
""
],
[
"Fabris",
"Júlio C.",
""
],
[
"de Mello",
"E. R. Bezerra",
""
],
[
"Belich",
"H.",
""
]
] | In this paper the $f(R)$ global monopole is reexamined. We provide an exact solution for the modified field equations in the presence of a global monopole for regions outside its core, generalizing previous results. Additionally, we discuss some particular cases obtained from this solution. We consider a setup consisting of a possible Schwarzschild black hole that absorbs the topological defect, giving rise to a static black hole endowed with a monopole's charge. Besides, we demonstrate how the asymptotic behavior of the Higgs field far from the monopole's core is shaped by a class of spacetime metrics which includes those ones analyzed here. In order to assess the gravitational properties of this system, we analyse the geodesic motion of both massive and massless test particles moving in the vicinity of such configuration. For the material particles we set the requirements they have to obey in order to experience stable orbits. On the other hand, for the photons we investigate how their trajectories are affected by the gravitational field of this black hole. |
1308.1658 | Genly Le\'on | Carlos R. Fadragas (Havana, Central de Las Villas U.), Genly Leon
(Valparaiso U., Catolica), Emmanuel N. Saridakis (Natl. Tech. U., Athens &
Valparaiso U., Catolica) | Dynamical analysis of anisotropic scalar-field cosmologies for a wide
range of potentials | 48 pages, 5 captioned figures. New sections have been added. Version
published at Class. Quant. Grav | Class. Quantum Grav. 31 (2014) 075018 | 10.1088/0264-9381/31/7/075018 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a detailed dynamical analysis of anisotropic scalar-field
cosmologies, and in particular of the most significant Kantowski-Sachs, Locally
Rotationally Symmetric (LRS) Bianchi I and LRS Bianchi III cases. We follow the
new and powerful method of $f$-devisers, which allows us to perform the whole
analysis for a wide range of potentials. Thus, one can just substitute the
specific potential form in the final results and obtain the corresponding
behavior, without the need of new calculations. We find a very rich behavior,
and amongst others the universe can result in isotropized solutions with
observables in agreement with observations, such as de Sitter,
quintessence-like, or stiff-dark energy solutions. In particular, all
expanding, accelerating, stable attractors are isotropic. Additionally, we
prove that as long as matter obeys the null energy condition, bounce behavior
is impossible. Finally, applying the general results to the well-studied
exponential and power-law potentials, we find that some of the general stable
solutions disappear. This feature may be an indication that such simple
potentials might restrict the dynamics in scalar-field cosmology, opening the
way to the introduction of more complicated ones.
| [
{
"created": "Wed, 7 Aug 2013 19:03:49 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Mar 2014 16:09:35 GMT",
"version": "v2"
}
] | 2014-03-18 | [
[
"Fadragas",
"Carlos R.",
"",
"Havana, Central de Las Villas U."
],
[
"Leon",
"Genly",
"",
"Valparaiso U., Catolica"
],
[
"Saridakis",
"Emmanuel N.",
"",
"Natl. Tech. U., Athens &\n Valparaiso U., Catolica"
]
] | We perform a detailed dynamical analysis of anisotropic scalar-field cosmologies, and in particular of the most significant Kantowski-Sachs, Locally Rotationally Symmetric (LRS) Bianchi I and LRS Bianchi III cases. We follow the new and powerful method of $f$-devisers, which allows us to perform the whole analysis for a wide range of potentials. Thus, one can just substitute the specific potential form in the final results and obtain the corresponding behavior, without the need of new calculations. We find a very rich behavior, and amongst others the universe can result in isotropized solutions with observables in agreement with observations, such as de Sitter, quintessence-like, or stiff-dark energy solutions. In particular, all expanding, accelerating, stable attractors are isotropic. Additionally, we prove that as long as matter obeys the null energy condition, bounce behavior is impossible. Finally, applying the general results to the well-studied exponential and power-law potentials, we find that some of the general stable solutions disappear. This feature may be an indication that such simple potentials might restrict the dynamics in scalar-field cosmology, opening the way to the introduction of more complicated ones. |
1107.0937 | Patrick Meessen | P. Meessen, T. Ort\'in, A. Palomo-Lozano | On supersymmetric Einstein-Weyl spaces | 17 pages, version to be published in JGP | J. Geom. Phys. 62(2012), 301 | 10.1016/j.geomphys.2011.10.017 | FPAUO-11/01; IFT-UAM/CSIC-11-37 | gr-qc hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider weighted parallel spinors in Lorentzian Weyl geometry in
arbitrary dimensions, choosing the weight such that the integrability condition
for the existence of such a spinor, implies the geometry to be Einstein-Weyl.
We then use techniques developed for the classification of supersymmetric
solutions to supergravity theories to characterise those Lorentzian EW
geometries that allow for a weighted parallel spinor, calling the resulting
geometries supersymmetric. The overall result is that they are either
conformally related to ordinary geometries admitting parallel spinors (w.r.t.
the Levi-Civita connection) or are conformally related to certain Kundt
spacetimes. A full characterisation is obtained for the 4 and 6 dimensional
cases.
| [
{
"created": "Tue, 5 Jul 2011 18:37:06 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Jul 2011 17:06:03 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Oct 2011 17:01:46 GMT",
"version": "v3"
}
] | 2011-11-16 | [
[
"Meessen",
"P.",
""
],
[
"Ortín",
"T.",
""
],
[
"Palomo-Lozano",
"A.",
""
]
] | We consider weighted parallel spinors in Lorentzian Weyl geometry in arbitrary dimensions, choosing the weight such that the integrability condition for the existence of such a spinor, implies the geometry to be Einstein-Weyl. We then use techniques developed for the classification of supersymmetric solutions to supergravity theories to characterise those Lorentzian EW geometries that allow for a weighted parallel spinor, calling the resulting geometries supersymmetric. The overall result is that they are either conformally related to ordinary geometries admitting parallel spinors (w.r.t. the Levi-Civita connection) or are conformally related to certain Kundt spacetimes. A full characterisation is obtained for the 4 and 6 dimensional cases. |
1002.4596 | Lorenzo Iorio | Lorenzo Iorio | A-priori "imprinting" of General Relativity itself on some tests of it? | LaTex, 11 pages, no figures, no tables. Accepted in Advances in
Astronomy | Advances in Astronomy Volume 2010 (2010), Article ID 735487 | 10.1155/2010/735487 | null | gr-qc astro-ph.EP hep-ph physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the effect of possible a-priori "imprinting" effects of
general relativity itself on satellite/spaceraft-based tests of it. We deal
with some performed or proposed time-delay ranging experiments in the Sun's
gravitational field. It turns out that the "imprint" of general relativity on
the Astronomical Unit and the solar gravitational constant GM_{\odot}, not
solved for in the so far performed spacecraft-based time-delay tests, induces
an a-priori bias of the order of 10^-6 in typical solar system ranging
experiments aimed to measuring the space curvature PPN parameter gamma. It is
too small by one order of magnitude to be of concern for the performed Cassini
experiment, but it would affect future planned or proposed tests aiming to
reach a 10^-7-10^-9 accuracy in determining gamma.
| [
{
"created": "Wed, 24 Feb 2010 18:03:41 GMT",
"version": "v1"
}
] | 2010-02-25 | [
[
"Iorio",
"Lorenzo",
""
]
] | We investigate the effect of possible a-priori "imprinting" effects of general relativity itself on satellite/spaceraft-based tests of it. We deal with some performed or proposed time-delay ranging experiments in the Sun's gravitational field. It turns out that the "imprint" of general relativity on the Astronomical Unit and the solar gravitational constant GM_{\odot}, not solved for in the so far performed spacecraft-based time-delay tests, induces an a-priori bias of the order of 10^-6 in typical solar system ranging experiments aimed to measuring the space curvature PPN parameter gamma. It is too small by one order of magnitude to be of concern for the performed Cassini experiment, but it would affect future planned or proposed tests aiming to reach a 10^-7-10^-9 accuracy in determining gamma. |
2007.13851 | Andrzej Czarnecki | Anna Czarnecka and Andrzej Czarnecki | Gravitational time dilation, free fall, and matter waves | Added Reference 20, W. K. Wootters, Why Things Fall, Foundations of
Physics 33, 1549 (2003) | American Journal of Physics 89, 634-638 (2021) | 10.1119/10.0003448 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate that a de Broglie wave of a particle in a gravitational field
turns towards the region of a smaller gravitational potential, causing the
particle to fall. This turning is caused by clocks running slower in the
smaller potential. We use the analogy of ocean waves that are slower in
shallower water and turn towards beaches. This approach explains the free fall
qualitatively and quantitatively without postulating motion along geodesics and
with only elementary algebra.
| [
{
"created": "Mon, 27 Jul 2020 20:34:18 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Sep 2022 00:51:03 GMT",
"version": "v2"
}
] | 2022-09-07 | [
[
"Czarnecka",
"Anna",
""
],
[
"Czarnecki",
"Andrzej",
""
]
] | We demonstrate that a de Broglie wave of a particle in a gravitational field turns towards the region of a smaller gravitational potential, causing the particle to fall. This turning is caused by clocks running slower in the smaller potential. We use the analogy of ocean waves that are slower in shallower water and turn towards beaches. This approach explains the free fall qualitatively and quantitatively without postulating motion along geodesics and with only elementary algebra. |
2107.14523 | Shao-Wen Wei | Shao-Wen Wei, Yu-Xiao Liu | The microstructure and Ruppeiner geometry of charged anti-de Sitter
black holes in Gauss-Bonnet gravity: from the critical point to the triple
point | 17 pages, 11 figures, and 1 table | Commun.Theor.Phys. 74, 095402 (2022) | 10.1088/1572-9494/ac65ed | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Ruppeiner geometry has been successfully applied in the study of the black
hole microstructure by combining with the small-large black hole phase
transition, and the potential interactions among the molecular-like constituent
degrees of freedom are uncovered. In this paper, we will extend the study to
the triple point, where three black hole phases coexist acting as a typical
feature of black hole systems quite different from the small-large black hole
phase transition. For the six-dimensional charged Gauss-Bonnet anti-de Sitter
black hole, we thoroughly investigate the swallow tail behaviors of the Gibbs
free energy and the equal area laws. After obtaining the black hole triple
point in a complete parameter space, we exhibit its phase structures both in
the pressure-temperature and temperature-horizon radius diagrams. Quite
different from the liquid-vapor phase transition, a double peak behavior is
present in the temperature-horizon radius phase diagram. Then we construct the
Ruppeiner geometry and calculate the corresponding normalized curvature scalar.
Near the triple point, we observe multiple negatively divergent behaviors.
Positive curvature scalar is observed for the small black hole with high
temperature, which indicates that the repulsive interaction dominates among the
microstructure. Furthermore, we consider the variation of the curvature scalar
along the coexisting intermediate and large black hole curves. Combining with
the observation for different fluids, the result suggests that this black hole
system behaves more like the argon or methane. Our study provides a first and
preliminary step towards understanding black hole microstructure near the
triple point, as well as uncovering the particular properties of the
Gauss-Bonnet gravity.
| [
{
"created": "Fri, 30 Jul 2021 10:10:39 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Feb 2024 09:34:56 GMT",
"version": "v2"
}
] | 2024-02-22 | [
[
"Wei",
"Shao-Wen",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | Ruppeiner geometry has been successfully applied in the study of the black hole microstructure by combining with the small-large black hole phase transition, and the potential interactions among the molecular-like constituent degrees of freedom are uncovered. In this paper, we will extend the study to the triple point, where three black hole phases coexist acting as a typical feature of black hole systems quite different from the small-large black hole phase transition. For the six-dimensional charged Gauss-Bonnet anti-de Sitter black hole, we thoroughly investigate the swallow tail behaviors of the Gibbs free energy and the equal area laws. After obtaining the black hole triple point in a complete parameter space, we exhibit its phase structures both in the pressure-temperature and temperature-horizon radius diagrams. Quite different from the liquid-vapor phase transition, a double peak behavior is present in the temperature-horizon radius phase diagram. Then we construct the Ruppeiner geometry and calculate the corresponding normalized curvature scalar. Near the triple point, we observe multiple negatively divergent behaviors. Positive curvature scalar is observed for the small black hole with high temperature, which indicates that the repulsive interaction dominates among the microstructure. Furthermore, we consider the variation of the curvature scalar along the coexisting intermediate and large black hole curves. Combining with the observation for different fluids, the result suggests that this black hole system behaves more like the argon or methane. Our study provides a first and preliminary step towards understanding black hole microstructure near the triple point, as well as uncovering the particular properties of the Gauss-Bonnet gravity. |
1504.07854 | Saheb Soroushfar | Saheb Soroushfar, Reza Saffari, Jutta Kunz, Claus L\"ammerzahl | Analytical solutions of the geodesic equation in the spacetime of a
black hole in f(R) gravity | 28 pages, 23 figures, Accepted for publication in Physical Review D | Phys. Rev. D 92, 044010 (2015) | 10.1103/PhysRevD.92.044010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the motion of test particles in the spacetime of a black hole in
f(R) gravity. The complete set of analytic solutions of the geodesic equation
in the spacetime of this black hole are presented. The geodesic equations are
solved in terms of Weierstrass elliptic functions and derivatives of Kleinian
sigma functions. The different types of the resulting orbits are characterized
in terms of the conserved energy and angular momentum as well as the
cosmological constant $\Lambda$ and the real constant $\beta$.
| [
{
"created": "Wed, 29 Apr 2015 13:35:06 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Jul 2015 11:35:48 GMT",
"version": "v2"
}
] | 2015-08-19 | [
[
"Soroushfar",
"Saheb",
""
],
[
"Saffari",
"Reza",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Lämmerzahl",
"Claus",
""
]
] | We consider the motion of test particles in the spacetime of a black hole in f(R) gravity. The complete set of analytic solutions of the geodesic equation in the spacetime of this black hole are presented. The geodesic equations are solved in terms of Weierstrass elliptic functions and derivatives of Kleinian sigma functions. The different types of the resulting orbits are characterized in terms of the conserved energy and angular momentum as well as the cosmological constant $\Lambda$ and the real constant $\beta$. |
1605.00456 | Seyed Hossein Hendi Dr. | S. H. Hendi and M. S. Talezadeh | Nonlinearly charged dilatonic black holes and their Brans-Dicke
counterpart: Energy dependent spacetime | 11 pages without figure, typos are fixed. Accepted in Gen. Relativ.
Gravit | General Relativity and Gravitation 49 (2017) 12 | 10.1007/s10714-016-2176-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Regarding the wide applications of dilaton gravity in the presence of
electrodynamics, we introduce a suitable Lagrangian for the coupling of dilaton
with gauge field. There are various Lagrangians which show the coupling between
scalar fields and electrodynamics with correct special situations. In this
paper, taking into account conformal transformation of Brans-Dicke theory with
an electrodynamics Lagrangian, we show that how scalar field should couple with
electrodynamics in dilaton gravity. In other words, in order to introduce a
correct Lagrangian of dilaton gravity, one should check at least two
requirements: compatibility with Brans-Dicke theory and appropriate special
situations. Finally, we apply the mentioned method to obtain analytical
solutions of dilaton-Born-Infeld and Brans-Dicke-Born-Infeld theories with
energy dependent spacetime.
| [
{
"created": "Fri, 29 Apr 2016 10:38:55 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Dec 2016 06:34:11 GMT",
"version": "v2"
}
] | 2016-12-23 | [
[
"Hendi",
"S. H.",
""
],
[
"Talezadeh",
"M. S.",
""
]
] | Regarding the wide applications of dilaton gravity in the presence of electrodynamics, we introduce a suitable Lagrangian for the coupling of dilaton with gauge field. There are various Lagrangians which show the coupling between scalar fields and electrodynamics with correct special situations. In this paper, taking into account conformal transformation of Brans-Dicke theory with an electrodynamics Lagrangian, we show that how scalar field should couple with electrodynamics in dilaton gravity. In other words, in order to introduce a correct Lagrangian of dilaton gravity, one should check at least two requirements: compatibility with Brans-Dicke theory and appropriate special situations. Finally, we apply the mentioned method to obtain analytical solutions of dilaton-Born-Infeld and Brans-Dicke-Born-Infeld theories with energy dependent spacetime. |
2308.01108 | Mehraveh Nikjoo | Mehraveh Nikjoo and Tom Zlosnik | Hamiltonian formulation of gravity as a spontaneously-broken gauge
theory of the Lorentz group | null | null | 10.1088/1361-6382/ad1c84 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | A number of approaches to gravitation have much in common with the gauge
theories of the standard model of particle physics. In this paper, we develop
the Hamiltonian formulation of a class of gravitational theories that may be
regarded as spontaneously-broken gauge theories of the complexified Lorentz
group $SO(1,3)_C$ with the gravitational field described entirely by a gauge
field valued in the Lie algebra of $SO(1,3)_C$ and a `Higgs field' valued in
the group's fundamental representation. The theories have one free parameter
$\beta$ which appears in a similar role to the inverse of the Barbero-Immirzi
parameter of Einstein-Cartan theory. However, contrary to that parameter, it is
shown that the number of degrees of freedom crucially depends on the value of
$\beta$. For non-zero values of $\beta$, it is shown that three complex degrees
of freedom propagate on general backgrounds, and for the specific values
$\beta=\pm i$ an extension to General Relativity is recovered in a
symmetry-broken regime. For the value $\beta=0$, the theory propagates no local
degrees of freedom. A non-zero value of $\beta$ corresponds to the self-dual
and anti-self-dual gauge fields appearing asymmetrically in the action,
therefore in these models, the existence of gravitational degrees of freedom is
tied to chiral asymmetry in the gravitational sector.
| [
{
"created": "Wed, 2 Aug 2023 12:36:28 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Jan 2024 16:50:37 GMT",
"version": "v2"
}
] | 2024-01-11 | [
[
"Nikjoo",
"Mehraveh",
""
],
[
"Zlosnik",
"Tom",
""
]
] | A number of approaches to gravitation have much in common with the gauge theories of the standard model of particle physics. In this paper, we develop the Hamiltonian formulation of a class of gravitational theories that may be regarded as spontaneously-broken gauge theories of the complexified Lorentz group $SO(1,3)_C$ with the gravitational field described entirely by a gauge field valued in the Lie algebra of $SO(1,3)_C$ and a `Higgs field' valued in the group's fundamental representation. The theories have one free parameter $\beta$ which appears in a similar role to the inverse of the Barbero-Immirzi parameter of Einstein-Cartan theory. However, contrary to that parameter, it is shown that the number of degrees of freedom crucially depends on the value of $\beta$. For non-zero values of $\beta$, it is shown that three complex degrees of freedom propagate on general backgrounds, and for the specific values $\beta=\pm i$ an extension to General Relativity is recovered in a symmetry-broken regime. For the value $\beta=0$, the theory propagates no local degrees of freedom. A non-zero value of $\beta$ corresponds to the self-dual and anti-self-dual gauge fields appearing asymmetrically in the action, therefore in these models, the existence of gravitational degrees of freedom is tied to chiral asymmetry in the gravitational sector. |
2407.18165 | Uwe R. Fischer | Satadal Datta, Uwe R. Fischer | Probing Penrose-type singularities in sonic black holes | 7+7 pages, 3+1 figures; version as submitted to journal | null | null | null | gr-qc cond-mat.quant-gas | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Addressing the general question whether Penrose singularities physically
exist inside black holes, we investigate the problem in the context of an
analogue system, a flowing laboratory liquid, for which the governing equations
are at least in principle known to all relevant scales, and in all regions of
the effective spacetime. We suggest to probe the physical phenomena taking
place close to the singularity in the interior of a $2+1$D analogue black hole
arising from a polytropic, inviscid, irrotational, and axisymmetric steady
flow, and propose to this end an experimental setup in a Bose-Einstein
condensate. Our study provides concrete evidence, for a well understood
dynamical system, that the Einstein equations are not necessary for a
singularity to form, demonstrating that Penrose-type spacetime singularities
can potentially also exist in non-Einsteinian theories of gravity. Finally, we
demonstrate how the singularity is physically avoided in our proposed
laboratory setup.
| [
{
"created": "Thu, 25 Jul 2024 16:29:54 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Aug 2024 13:12:52 GMT",
"version": "v2"
}
] | 2024-08-09 | [
[
"Datta",
"Satadal",
""
],
[
"Fischer",
"Uwe R.",
""
]
] | Addressing the general question whether Penrose singularities physically exist inside black holes, we investigate the problem in the context of an analogue system, a flowing laboratory liquid, for which the governing equations are at least in principle known to all relevant scales, and in all regions of the effective spacetime. We suggest to probe the physical phenomena taking place close to the singularity in the interior of a $2+1$D analogue black hole arising from a polytropic, inviscid, irrotational, and axisymmetric steady flow, and propose to this end an experimental setup in a Bose-Einstein condensate. Our study provides concrete evidence, for a well understood dynamical system, that the Einstein equations are not necessary for a singularity to form, demonstrating that Penrose-type spacetime singularities can potentially also exist in non-Einsteinian theories of gravity. Finally, we demonstrate how the singularity is physically avoided in our proposed laboratory setup. |
gr-qc/0010089 | J. Frauendiener | J. Frauendiener and L. B. Szabados | The kernel of the edth operators on higher-genus spacelike two-surfaces | 12 pages | Class.Quant.Grav. 18 (2001) 1003-1014 | 10.1088/0264-9381/18/6/303 | null | gr-qc | null | The dimension of the kernels of the edth and edth-prime operators on closed,
orientable spacelike 2-surfaces with arbitrary genus is calculated, and some of
its mathematical and physical consequences are discussed.
| [
{
"created": "Tue, 24 Oct 2000 19:16:47 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Frauendiener",
"J.",
""
],
[
"Szabados",
"L. B.",
""
]
] | The dimension of the kernels of the edth and edth-prime operators on closed, orientable spacelike 2-surfaces with arbitrary genus is calculated, and some of its mathematical and physical consequences are discussed. |
2210.09357 | Kyriakos Destounis Dr. | Kyriakos Destounis, Arun Kulathingal, Kostas D. Kokkotas and Georgios
O. Papadopoulos | Gravitational-wave imprints of compact and galactic-scale environments
in extreme-mass-ratio binaries | 19 pages, 10 figures, revisions regarding detectability and addition
of new figures and sections, abstract reduced to fit arxiv limits, accepted
for publication in PRD | Phys. Rev. D 107, 084027 (2023) | 10.1103/PhysRevD.107.084027 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Circumambient and galactic-scale environments are intermittently present
around black holes that reside in active galactic nuclei. As supermassive black
holes impart energy on their host galaxy, so the galactic environment affects
the dynamics of solar-mass objects around black holes and the gravitational
waves emitted from non-vacuum asymmetric binaries. Only recently an exact
general-relativistic solution has been found that describes a Schwarzschild
black hole immersed in a dark matter halo of the Hernquist type. We perform an
extensive analysis of generic geodesics delving in such non-vacuum spacetimes
and compare our results with those obtained in Schwarzschild, as well as
calculate their gravitational-wave emission. Our findings indicate that the
radial and polar oscillation frequency ratios descend deeper into the strong
gravity region as the compactness of the halo increases. This translates to a
redshift of non-vacuum geodesics and their resulting waveforms with respect to
the vacuum ones. We calculate the overlap between waveforms resulting from
Schwarzschild and non-vacuum geometries and find that it decreases as the halo
compactness grows, meaning that dark matter environments should be
distinguishable by space-borne detectors. For compact environments, we find
that the apsidal precession is strongly affected due to the gravitational pull
of dark matter; the orbit's axis can rotate in the opposite direction as that
of the orbital motion, leading to a retrograde precession drift that depends on
the halo mass, as opposed to the typical prograde precession transpiring in
galactic-scale environments. Gravitational waves in retrograde-to-prograde
alterations demonstrate transient frequency phenomena around critical
non-precessing turning points, thus they may serve as `smoking guns' for the
presence of compact dark matter environments around supermassive black holes.
| [
{
"created": "Mon, 17 Oct 2022 18:54:39 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Oct 2022 17:39:29 GMT",
"version": "v2"
},
{
"created": "Thu, 30 Mar 2023 16:30:01 GMT",
"version": "v3"
}
] | 2023-04-19 | [
[
"Destounis",
"Kyriakos",
""
],
[
"Kulathingal",
"Arun",
""
],
[
"Kokkotas",
"Kostas D.",
""
],
[
"Papadopoulos",
"Georgios O.",
""
]
] | Circumambient and galactic-scale environments are intermittently present around black holes that reside in active galactic nuclei. As supermassive black holes impart energy on their host galaxy, so the galactic environment affects the dynamics of solar-mass objects around black holes and the gravitational waves emitted from non-vacuum asymmetric binaries. Only recently an exact general-relativistic solution has been found that describes a Schwarzschild black hole immersed in a dark matter halo of the Hernquist type. We perform an extensive analysis of generic geodesics delving in such non-vacuum spacetimes and compare our results with those obtained in Schwarzschild, as well as calculate their gravitational-wave emission. Our findings indicate that the radial and polar oscillation frequency ratios descend deeper into the strong gravity region as the compactness of the halo increases. This translates to a redshift of non-vacuum geodesics and their resulting waveforms with respect to the vacuum ones. We calculate the overlap between waveforms resulting from Schwarzschild and non-vacuum geometries and find that it decreases as the halo compactness grows, meaning that dark matter environments should be distinguishable by space-borne detectors. For compact environments, we find that the apsidal precession is strongly affected due to the gravitational pull of dark matter; the orbit's axis can rotate in the opposite direction as that of the orbital motion, leading to a retrograde precession drift that depends on the halo mass, as opposed to the typical prograde precession transpiring in galactic-scale environments. Gravitational waves in retrograde-to-prograde alterations demonstrate transient frequency phenomena around critical non-precessing turning points, thus they may serve as `smoking guns' for the presence of compact dark matter environments around supermassive black holes. |
1901.02553 | Carlos O. Lousto | James Healy, Carlos O. Lousto, Jacob Lange, Richard O'Shaughnessy,
Yosef Zlochower, Manuela Campanelli | The second RIT binary black hole simulations catalog and its application
to gravitational waves parameter estimation | 23 pages, 10 figures. Major extension of the GW150914 analysis | Phys. Rev. D 100, 024021 (2019) | 10.1103/PhysRevD.100.024021 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The RIT numerical relativity group is releasing the second public catalog of
black-hole-binary waveforms \url{http://ccrg.rit.edu/~RITCatalog}. This release
consists of 320 accurate simulations that include 46 precessing and 274
nonprecessing binary systems with mass ratios $q=m_1/m_2$ in the range $1/6\leq
q\leq1$ and individual spins up to $s/m^2=0.95$. The new catalog contains
search and ordering tools for the waveforms based on initial parameters of the
binary, trajectory information, peak radiation, and final remnant black hole
properties. The final black hole remnant properties provided here can be used
to model the merger of black-hole binaries from its initial configurations. The
waveforms are extrapolated to infinite observer location and can be used to
independently interpret gravitational wave signals from laser interferometric
detectors. As an application of this waveform catalog we reanalyze the signal
of GW150914 implementing parameter estimation techniques that make use of only
numerical waveforms without any reference to information from phenomenological
models.
| [
{
"created": "Tue, 8 Jan 2019 23:16:13 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Jan 2019 14:12:57 GMT",
"version": "v2"
},
{
"created": "Wed, 27 Mar 2019 19:54:14 GMT",
"version": "v3"
}
] | 2019-07-17 | [
[
"Healy",
"James",
""
],
[
"Lousto",
"Carlos O.",
""
],
[
"Lange",
"Jacob",
""
],
[
"O'Shaughnessy",
"Richard",
""
],
[
"Zlochower",
"Yosef",
""
],
[
"Campanelli",
"Manuela",
""
]
] | The RIT numerical relativity group is releasing the second public catalog of black-hole-binary waveforms \url{http://ccrg.rit.edu/~RITCatalog}. This release consists of 320 accurate simulations that include 46 precessing and 274 nonprecessing binary systems with mass ratios $q=m_1/m_2$ in the range $1/6\leq q\leq1$ and individual spins up to $s/m^2=0.95$. The new catalog contains search and ordering tools for the waveforms based on initial parameters of the binary, trajectory information, peak radiation, and final remnant black hole properties. The final black hole remnant properties provided here can be used to model the merger of black-hole binaries from its initial configurations. The waveforms are extrapolated to infinite observer location and can be used to independently interpret gravitational wave signals from laser interferometric detectors. As an application of this waveform catalog we reanalyze the signal of GW150914 implementing parameter estimation techniques that make use of only numerical waveforms without any reference to information from phenomenological models. |
gr-qc/0605019 | Mikolaj Korzynski | Mikolaj Korzynski | Isolated and dynamical horizons from a common perspective | 12 pages, one figure, revtex4. v2: added various references in
introduction and sec. 2, short discussion of applicability to slowly evolving
horizons in sec. 4B. Several minor corrections throughout text | Phys.Rev. D74 (2006) 104029 | 10.1103/PhysRevD.74.104029 | null | gr-qc | null | A framework is developed in which one can write down the constraint equations
on a three--dimensional hypersurface of arbitrary signature. It is then applied
to isolated and dynamical horizons. The derived equations can be used to
extract physicaly relevant quantities describing the horizon irrespective to
whether it is isolated (null) or dynamical at a given instant of time.
Furthermore, small perturbation of isolated horizons are considered, and
finally a family of axially--symmetric exact solution of the constraint
equations on a dynamical horizon is presented.
| [
{
"created": "Tue, 2 May 2006 16:53:49 GMT",
"version": "v1"
},
{
"created": "Sun, 7 May 2006 12:48:51 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Korzynski",
"Mikolaj",
""
]
] | A framework is developed in which one can write down the constraint equations on a three--dimensional hypersurface of arbitrary signature. It is then applied to isolated and dynamical horizons. The derived equations can be used to extract physicaly relevant quantities describing the horizon irrespective to whether it is isolated (null) or dynamical at a given instant of time. Furthermore, small perturbation of isolated horizons are considered, and finally a family of axially--symmetric exact solution of the constraint equations on a dynamical horizon is presented. |
2401.07523 | Puxun Wu | Li-Yang Chen, Hongwei Yu and Puxun Wu | Resonant amplification of curvature perturbations in inflation model
with periodical derivative coupling | 19 pages, 4 figures, refs added | Phys. Lett. B 849 (2024) 138457 | 10.1016/j.physletb.2024.138457 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | In this paper, we introduce a weak, transient and periodical derivative
coupling between the inflaton field and gravity, and find that the square of
the sound speed of the curvature perturbations becomes a periodic function,
which results in that the equation of the curvature perturbations can be
transformed into the form of the Mathieu equation in the sub-horizon limit.
Thus, the parametric resonance will amplify the curvature perturbations so as
to generate a formation of abundant primordial black holes (PBHs). We show that
the generated PBHs can make up most of dark matter. Associated with the
generation of PBHs, the large scalar perturbations will give rise to the scalar
induced gravitational waves which may be detected by future gravitational wave
projects.
| [
{
"created": "Mon, 15 Jan 2024 07:56:24 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Jan 2024 03:00:36 GMT",
"version": "v2"
}
] | 2024-01-30 | [
[
"Chen",
"Li-Yang",
""
],
[
"Yu",
"Hongwei",
""
],
[
"Wu",
"Puxun",
""
]
] | In this paper, we introduce a weak, transient and periodical derivative coupling between the inflaton field and gravity, and find that the square of the sound speed of the curvature perturbations becomes a periodic function, which results in that the equation of the curvature perturbations can be transformed into the form of the Mathieu equation in the sub-horizon limit. Thus, the parametric resonance will amplify the curvature perturbations so as to generate a formation of abundant primordial black holes (PBHs). We show that the generated PBHs can make up most of dark matter. Associated with the generation of PBHs, the large scalar perturbations will give rise to the scalar induced gravitational waves which may be detected by future gravitational wave projects. |
0904.2071 | J\"org Hennig | J\"org Hennig and Marcus Ansorg | The inner Cauchy horizon of axisymmetric and stationary black holes with
surrounding matter in Einstein-Maxwell theory: study in terms of soliton
methods | 21 pages, 1 figure | Annales Henri Poincare 10:1075-1095,2009 | 10.1007/s00023-009-0012-0 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use soliton methods in order to investigate the interior electrovacuum
region of axisymmetric and stationary, electrically charged black holes with
arbitrary surrounding matter in Einstein-Maxwell theory. These methods can be
applied since the Einstein-Maxwell vacuum equations permit the formulation in
terms of the integrability condition of an associated linear matrix problem. We
find that there always exists a regular inner Cauchy horizon inside the black
hole, provided the angular momentum $J$ and charge $Q$ of the black hole do not
vanish simultaneously. Moreover, the soliton methods provide us with an
explicit relation for the metric on the inner Cauchy horizon in terms of that
on the event horizon. In addition, our analysis reveals the remarkable
universal relation $(8\pi J)^2+(4\pi Q^2)^2=A^+ A^-$, where $A^+$ and $A^-$
denote the reas of event and inner Cauchy horizon respectively.
| [
{
"created": "Tue, 14 Apr 2009 08:03:24 GMT",
"version": "v1"
}
] | 2009-11-16 | [
[
"Hennig",
"Jörg",
""
],
[
"Ansorg",
"Marcus",
""
]
] | We use soliton methods in order to investigate the interior electrovacuum region of axisymmetric and stationary, electrically charged black holes with arbitrary surrounding matter in Einstein-Maxwell theory. These methods can be applied since the Einstein-Maxwell vacuum equations permit the formulation in terms of the integrability condition of an associated linear matrix problem. We find that there always exists a regular inner Cauchy horizon inside the black hole, provided the angular momentum $J$ and charge $Q$ of the black hole do not vanish simultaneously. Moreover, the soliton methods provide us with an explicit relation for the metric on the inner Cauchy horizon in terms of that on the event horizon. In addition, our analysis reveals the remarkable universal relation $(8\pi J)^2+(4\pi Q^2)^2=A^+ A^-$, where $A^+$ and $A^-$ denote the reas of event and inner Cauchy horizon respectively. |
2103.15012 | Juan Carlos Degollado | Miguel Alcubierre, Juan Barranco, Argelia Bernal, Juan Carlos
Degollado, Alberto Diez-Tejedor, Miguel Megevand, Dar\'io N\'u\~nez, Olivier
Sarbach | On the linear stability of $\ell$-boson stars with respect to radial
perturbations | 23, pages, 8 figures | null | 10.1088/1361-6382/ac0160 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In previous work we constructed new boson star solutions consisting of a
family of massive complex scalar fields minimally coupled to gravity in which
the individual fields have angular momentum, yet the configuration as a whole
is static and spherically symmetric. In the present article we study the linear
stability of these $\ell$-boson stars with respect to time-dependent, radial
perturbations. The pulsation equations, governing the dynamics of such
perturbations are derived, generalizing previous work initiated by M. Gleiser,
and shown to give rise to a two-channel Schr\"odinger operator. Using standard
tools from the literature, we show that for each fixed value $\ell$ of the
angular momentum number, there exists a family of $\ell$-boson stars which are
linearly stable with respect to radial fluctuations; in this case the
perturbations oscillate in time with given characteristic frequencies which are
computed and compared with the results from a nonlinear numerical simulation.
Further, there is also a family of $\ell$-boson stars which are linearly
unstable. The two families are separated by the configuration with maximum
mass. These results are qualitatively similar to the corresponding stability
results of the standard boson stars with $\ell=0$, and they imply the existence
of new stable configurations that are more massive and compact than usual boson
stars.
| [
{
"created": "Sat, 27 Mar 2021 23:09:06 GMT",
"version": "v1"
}
] | 2021-09-01 | [
[
"Alcubierre",
"Miguel",
""
],
[
"Barranco",
"Juan",
""
],
[
"Bernal",
"Argelia",
""
],
[
"Degollado",
"Juan Carlos",
""
],
[
"Diez-Tejedor",
"Alberto",
""
],
[
"Megevand",
"Miguel",
""
],
[
"Núñez",
"Darío",
""
],
[
"Sarbach",
"Olivier",
""
]
] | In previous work we constructed new boson star solutions consisting of a family of massive complex scalar fields minimally coupled to gravity in which the individual fields have angular momentum, yet the configuration as a whole is static and spherically symmetric. In the present article we study the linear stability of these $\ell$-boson stars with respect to time-dependent, radial perturbations. The pulsation equations, governing the dynamics of such perturbations are derived, generalizing previous work initiated by M. Gleiser, and shown to give rise to a two-channel Schr\"odinger operator. Using standard tools from the literature, we show that for each fixed value $\ell$ of the angular momentum number, there exists a family of $\ell$-boson stars which are linearly stable with respect to radial fluctuations; in this case the perturbations oscillate in time with given characteristic frequencies which are computed and compared with the results from a nonlinear numerical simulation. Further, there is also a family of $\ell$-boson stars which are linearly unstable. The two families are separated by the configuration with maximum mass. These results are qualitatively similar to the corresponding stability results of the standard boson stars with $\ell=0$, and they imply the existence of new stable configurations that are more massive and compact than usual boson stars. |
2202.00786 | Stanley Deser | S.Deser | Why source-free gravity must be quantized | published version | Eur. Phys. J. C (2022) 82:424 | 10.1140/epjc/s10052-022-10375-0 | null | gr-qc hep-th physics.atom-ph | http://creativecommons.org/licenses/by/4.0/ | I show, on the most elementary grounds, its classical ultraviolet
catastrophe, that even source-free General Relativity must be quantized,
despite some eminent opinions to the contrary, an original result involving
some rather tricky subtleties.
| [
{
"created": "Tue, 1 Feb 2022 22:11:37 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Nov 2022 02:04:09 GMT",
"version": "v2"
}
] | 2022-11-23 | [
[
"Deser",
"S.",
""
]
] | I show, on the most elementary grounds, its classical ultraviolet catastrophe, that even source-free General Relativity must be quantized, despite some eminent opinions to the contrary, an original result involving some rather tricky subtleties. |
1401.2587 | L. C. Garcia de Andrade | L. C. Garcia de Andrade (Departamento de fisica teorica UERJ) | Galactic dynamo seeds from non-superconducting spin-polarised strings | arXiv admin note: substantial text overlap with arXiv:gr-qc/0211072 | null | 10.1088/1475-7516/2014/08/023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Earlier Enqvist and Olesen have shown that formation of ferromagnetic planar
walls in vacuum at GUT scales in comoving plasmas may generate a large scale
magnetic field of $B_{now}\simeq{10^{-14}G}$. In this paper we show that
starting from classical Einstein-Cartan-Maxwell strong gravity, a
spin-polarised ferromagnetic cylinder gives rise to a cosmological magnetic
field of the order $B_{now}\simeq{10^{-22}G}$. Vorticity of cylinder is used to
obtain galactic magnetic fields. Magnetic fields up to $B\sim{10^{9}G}$ can be
obtained from the spin density of the cylinder. If matching conditions are used
cosmological magnetic fields of the order of $B\sim{10^{-16}R\frac{Gauss}{cm}}$
where $R$ is the radius of the cosmic strings. For a cosmic string with the
radius of an hydrogen atom the cosmic magnetic field is $B\sim{10^{-32}Gauss}$
which is enough to seed galactic dynamos.
| [
{
"created": "Sun, 12 Jan 2014 03:40:23 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"de Andrade",
"L. C. Garcia",
"",
"Departamento de fisica teorica UERJ"
]
] | Earlier Enqvist and Olesen have shown that formation of ferromagnetic planar walls in vacuum at GUT scales in comoving plasmas may generate a large scale magnetic field of $B_{now}\simeq{10^{-14}G}$. In this paper we show that starting from classical Einstein-Cartan-Maxwell strong gravity, a spin-polarised ferromagnetic cylinder gives rise to a cosmological magnetic field of the order $B_{now}\simeq{10^{-22}G}$. Vorticity of cylinder is used to obtain galactic magnetic fields. Magnetic fields up to $B\sim{10^{9}G}$ can be obtained from the spin density of the cylinder. If matching conditions are used cosmological magnetic fields of the order of $B\sim{10^{-16}R\frac{Gauss}{cm}}$ where $R$ is the radius of the cosmic strings. For a cosmic string with the radius of an hydrogen atom the cosmic magnetic field is $B\sim{10^{-32}Gauss}$ which is enough to seed galactic dynamos. |
1410.0638 | Marcelo Ponce | Marcelo Ponce, Carlos Palenzuela, Enrico Barausse and Luis Lehner | Electromagnetic outflows in a class of scalar-tensor theories: binary
neutron star coalescence | Improved presentation and figures; matches version accepted in PRD | Phys. Rev. D 91, 084038 (2015) | 10.1103/PhysRevD.91.084038 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As we showed in previous work, the dynamics and gravitational emission of
binary neutron star systems in certain scalar-tensor theories can differ
significantly from that expected from General Relativity in the coalescing
stage. In this work we examine whether the characteristics of the
electromagnetic counterparts to these binaries -- driven by magnetosphere
interactions prior to the merger event -- can provide an independent way to
test gravity in the most strongly dynamical stages of binary mergers. We find
that the electromagnetic flux emitted by binaries in these scalar-tensor
theories can show deviations from the GR prediction in particular cases. These
differences are quite subtle, thus requiring delicate measurements to
differentiate between GR and the type of scalar-tensor theories considered in
this work using electromagnetic observations alone. However, if coupled with a
gravitational-wave detection, electromagnetic measurements might provide a way
to increase the confidence with which GR will be confirmed (or ruled out) by
gravitational observations.
| [
{
"created": "Thu, 2 Oct 2014 18:36:02 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Apr 2015 02:49:21 GMT",
"version": "v2"
}
] | 2015-04-22 | [
[
"Ponce",
"Marcelo",
""
],
[
"Palenzuela",
"Carlos",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Lehner",
"Luis",
""
]
] | As we showed in previous work, the dynamics and gravitational emission of binary neutron star systems in certain scalar-tensor theories can differ significantly from that expected from General Relativity in the coalescing stage. In this work we examine whether the characteristics of the electromagnetic counterparts to these binaries -- driven by magnetosphere interactions prior to the merger event -- can provide an independent way to test gravity in the most strongly dynamical stages of binary mergers. We find that the electromagnetic flux emitted by binaries in these scalar-tensor theories can show deviations from the GR prediction in particular cases. These differences are quite subtle, thus requiring delicate measurements to differentiate between GR and the type of scalar-tensor theories considered in this work using electromagnetic observations alone. However, if coupled with a gravitational-wave detection, electromagnetic measurements might provide a way to increase the confidence with which GR will be confirmed (or ruled out) by gravitational observations. |
2003.03903 | Andronikos Paliathanasis | Andronikos Paliathanasis and Genly Leon (Catolica del Norte U.) | Analytic solutions in Einstein-aether scalar field cosmology | 16 pages, 2 figures, to appear in EPJC | null | 10.1140/epjc/s10052-020-7924-8 | null | gr-qc astro-ph.CO math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of Einstein-aether scalar field cosmology we solve the field
equations and determine exact and analytic solutions. In particular, we
consider a model proposed by Kanno and Soda where the aether and the scalar
fields interact through the aether coefficient parameters, which are promoted
to be functions of the scalar field. For this model, we write the field
equations by using the minisuperspace approach and we determine the scalar
field potentials which leads to Liouville--integrable systems. We solve the
field equations for five families of scalar field potentials and, whether it is
feasible, we write down the analytic solutions by using closed-form functions.
| [
{
"created": "Mon, 9 Mar 2020 03:25:24 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Apr 2020 10:37:12 GMT",
"version": "v2"
}
] | 2020-05-20 | [
[
"Paliathanasis",
"Andronikos",
"",
"Catolica del Norte U."
],
[
"Leon",
"Genly",
"",
"Catolica del Norte U."
]
] | In the context of Einstein-aether scalar field cosmology we solve the field equations and determine exact and analytic solutions. In particular, we consider a model proposed by Kanno and Soda where the aether and the scalar fields interact through the aether coefficient parameters, which are promoted to be functions of the scalar field. For this model, we write the field equations by using the minisuperspace approach and we determine the scalar field potentials which leads to Liouville--integrable systems. We solve the field equations for five families of scalar field potentials and, whether it is feasible, we write down the analytic solutions by using closed-form functions. |
1206.0698 | Kostiantyn Ropotenko | K. Ropotenko | Contradictory implications of the nonadditive entropy | 6 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the concept of nonadditive black hole entropy leads to the
contradictory implications in the framework of statistical thermodynamics. In
particular, a black hole with the nonadditive entropy cannot be in thermal
equilibrium with ordinary matter. Moreover, such black holes are mutually
exclusive, i.e. they cannot compose a single system.
| [
{
"created": "Mon, 4 Jun 2012 18:35:04 GMT",
"version": "v1"
}
] | 2012-06-05 | [
[
"Ropotenko",
"K.",
""
]
] | It is shown that the concept of nonadditive black hole entropy leads to the contradictory implications in the framework of statistical thermodynamics. In particular, a black hole with the nonadditive entropy cannot be in thermal equilibrium with ordinary matter. Moreover, such black holes are mutually exclusive, i.e. they cannot compose a single system. |
2105.14123 | Konstantin Osetrin | K.E. Osetrin, I.V. Kirnos, E.K. Osetrin, A.E. Filippov | Wave-like exact models with symmetry of spatial homogeneity in the
quadratic theory of gravity with a scalar field | 24 pages | Symmetry, 2021, 13(7),1173 | 10.3390/sym13071173 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Exact solutions are obtained in the quadratic theory of gravity with a scalar
field for wave-like models of space-time with spatial homogeneity symmetry and
allowing the integration of the equations of motion of test particles in the
Hamilton-Jacobi formalism by the method of separation of variables with
separation of wave variables (Shapovalov spaces of type II). The form of the
scalar field and the scalar field functions included in the Lagrangian of the
theory is found. The obtained exact solutions can describe the primary
gravitational wave disturbances in the Universe (primary gravitational waves).
| [
{
"created": "Fri, 28 May 2021 22:14:59 GMT",
"version": "v1"
}
] | 2022-03-10 | [
[
"Osetrin",
"K. E.",
""
],
[
"Kirnos",
"I. V.",
""
],
[
"Osetrin",
"E. K.",
""
],
[
"Filippov",
"A. E.",
""
]
] | Exact solutions are obtained in the quadratic theory of gravity with a scalar field for wave-like models of space-time with spatial homogeneity symmetry and allowing the integration of the equations of motion of test particles in the Hamilton-Jacobi formalism by the method of separation of variables with separation of wave variables (Shapovalov spaces of type II). The form of the scalar field and the scalar field functions included in the Lagrangian of the theory is found. The obtained exact solutions can describe the primary gravitational wave disturbances in the Universe (primary gravitational waves). |
1205.1253 | Carlos F. Sopuerta | Priscilla Canizares (1,2), Jonathan R. Gair (1), Carlos F. Sopuerta
(2) ((1) IoA, Cambridge, (2) ICE, CSIC-IEEC) | Testing Chern-Simons Modified Gravity with Gravitational-Wave Detections
of Extreme-Mass-Ratio Binaries | RevTeX 4.1. 21 pages, 2 Figures, 7 Tables. Revision to match the
published version | Phys. Rev. D 86, 044010 (2012) [20 pages] | 10.1103/PhysRevD.86.044010 | null | gr-qc astro-ph.CO astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | [abridged] The detection of gravitational waves from extreme-mass-ratio
(EMRI) binaries, comprising a stellar-mass compact object orbiting around a
massive black hole, is one of the main targets for low-frequency
gravitational-wave detectors in space, like the Laser Interferometer Space
Antenna (LISA or eLISA/NGO). The long-duration gravitational-waveforms emitted
by such systems encode the structure of the strong field region of the massive
black hole, in which the inspiral occurs. The detection and analysis of EMRIs
will therefore allow us to study the geometry of massive black holes and
determine whether their nature is as predicted by General Relativity and even
to test whether General Relativity is the correct theory to describe the
dynamics of these systems. To achieve this, EMRI modeling in alternative
theories of gravity is required to describe the generation of gravitational
waves. In this paper, we explore to what extent EMRI observations with LISA or
eLISA/NGO might be able to distinguish between General Relativity and a
particular modification of it, known as Dynamical Chern-Simons Modified
Gravity. Our analysis is based on a parameter estimation study that uses
approximate gravitational waveforms obtained via a radiative-adiabatic method
and is restricted to a five-dimensional subspace of the EMRI configuration
space. This includes a Chern-Simons parameter that controls the strength of
gravitational deviations from General Relativity. We find that, if Dynamical
Chern-Simons Modified Gravity is the correct theory, an observatory like LISA
or even eLISA/NGO should be able to measure the Chern-Simons parameter with
fractional errors below 5%. If General Relativity is the true theory, these
observatories should put bounds on this parameter at the level xi^(1/4) < 10^4
km, which is four orders of magnitude better than current Solar System bounds.
| [
{
"created": "Sun, 6 May 2012 23:21:58 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Aug 2012 21:03:22 GMT",
"version": "v2"
}
] | 2012-08-09 | [
[
"Canizares",
"Priscilla",
"",
"IoA, Cambridge",
"ICE, CSIC-IEEC"
],
[
"Gair",
"Jonathan R.",
"",
"IoA, Cambridge"
],
[
"Sopuerta",
"Carlos F.",
"",
"ICE, CSIC-IEEC"
]
] | [abridged] The detection of gravitational waves from extreme-mass-ratio (EMRI) binaries, comprising a stellar-mass compact object orbiting around a massive black hole, is one of the main targets for low-frequency gravitational-wave detectors in space, like the Laser Interferometer Space Antenna (LISA or eLISA/NGO). The long-duration gravitational-waveforms emitted by such systems encode the structure of the strong field region of the massive black hole, in which the inspiral occurs. The detection and analysis of EMRIs will therefore allow us to study the geometry of massive black holes and determine whether their nature is as predicted by General Relativity and even to test whether General Relativity is the correct theory to describe the dynamics of these systems. To achieve this, EMRI modeling in alternative theories of gravity is required to describe the generation of gravitational waves. In this paper, we explore to what extent EMRI observations with LISA or eLISA/NGO might be able to distinguish between General Relativity and a particular modification of it, known as Dynamical Chern-Simons Modified Gravity. Our analysis is based on a parameter estimation study that uses approximate gravitational waveforms obtained via a radiative-adiabatic method and is restricted to a five-dimensional subspace of the EMRI configuration space. This includes a Chern-Simons parameter that controls the strength of gravitational deviations from General Relativity. We find that, if Dynamical Chern-Simons Modified Gravity is the correct theory, an observatory like LISA or even eLISA/NGO should be able to measure the Chern-Simons parameter with fractional errors below 5%. If General Relativity is the true theory, these observatories should put bounds on this parameter at the level xi^(1/4) < 10^4 km, which is four orders of magnitude better than current Solar System bounds. |
2208.10191 | Lorenzo Iorio | Lorenzo Iorio, Matteo Luca Ruggiero | Effect of some modified models of gravity on the radial velocity of
binary systems | LaTex2e, 19 pages, no tables, no figures. Version matching the one at
press in Universe | Universe 2022, 8(9), 443 | 10.3390/universe8090443 | null | gr-qc astro-ph.EP astro-ph.SR physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For many classes of astronomical and astrophysical binary systems, long
observational records of their radial velocity $V$, which is their directly
observable quantity, are available. For exoplanets close to their parent stars,
they cover several full orbital revolutions, while for wide binaries like,
e.g., the Proxima/$\alpha$ Centauri AB system, only relatively short orbital
arcs are sampled by existing radial velocity measurements. Here, the changes
$\Delta V$ induced on a binary's radial velocity by some long-range modified
models of gravity are analytically calculated. In particular, extra-potentials
proportional to $r^{-N},\,N=2,\,3$ and $r^2$ are considered; the Cosmological
Constant $\Lambda$ belongs to the latter group. Both the net shift per orbit
and the instantaneous one are explicitly calculated for each model. The
Cosmological Constant induces a shift in the radial velocity of the
Proxima/$\alpha$ Centauri AB binary as little as $\left|\Delta V\right|\lesssim
10^{-7}\,\mathrm{m\,s}^{-1}$, while the present-day accuracy in measuring its
radial velocity is $\sigma_V\simeq 30\,\mathrm{m\,s}^{-1}$. The calculational
scheme presented here is quite general, and can be straightforwardly extended
to any other modified gravity.
| [
{
"created": "Mon, 22 Aug 2022 10:25:31 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Aug 2022 13:05:54 GMT",
"version": "v2"
}
] | 2022-08-26 | [
[
"Iorio",
"Lorenzo",
""
],
[
"Ruggiero",
"Matteo Luca",
""
]
] | For many classes of astronomical and astrophysical binary systems, long observational records of their radial velocity $V$, which is their directly observable quantity, are available. For exoplanets close to their parent stars, they cover several full orbital revolutions, while for wide binaries like, e.g., the Proxima/$\alpha$ Centauri AB system, only relatively short orbital arcs are sampled by existing radial velocity measurements. Here, the changes $\Delta V$ induced on a binary's radial velocity by some long-range modified models of gravity are analytically calculated. In particular, extra-potentials proportional to $r^{-N},\,N=2,\,3$ and $r^2$ are considered; the Cosmological Constant $\Lambda$ belongs to the latter group. Both the net shift per orbit and the instantaneous one are explicitly calculated for each model. The Cosmological Constant induces a shift in the radial velocity of the Proxima/$\alpha$ Centauri AB binary as little as $\left|\Delta V\right|\lesssim 10^{-7}\,\mathrm{m\,s}^{-1}$, while the present-day accuracy in measuring its radial velocity is $\sigma_V\simeq 30\,\mathrm{m\,s}^{-1}$. The calculational scheme presented here is quite general, and can be straightforwardly extended to any other modified gravity. |
2205.07893 | Andrea Antonelli | Jonathan R. Gair, Andrea Antonelli and Riccardo Barbieri | A Fisher matrix for gravitational-wave population inference | 14 pages, 4 figures; the results can be reproduced using codes at
https://github.com/aantonelli94/PopFisher. v2: published version, new
sections and appendices added during the peer-review process | null | 10.1093/mnras/stac3560 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive a Fisher matrix for the parameters characterising a population of
gravitational-wave events. This provides a guide to the precision with which
population parameters can be estimated with multiple observations, which
becomes increasingly accurate as the number of events and the signal-to-noise
ratio of the sampled events increases. The formalism takes into account
individual event measurement uncertainties and selection effects, and can be
applied to arbitrary population models. We illustrate the framework with two
examples: an analytical calculation of the Fisher matrix for the mean and
variance of a Gaussian model describing a population affected by selection
effects, and an estimation of the precision with which the slope of a power law
distribution of supermassive black-hole masses can be measured using
extreme-mass-ratio inspiral observations. We compare the Fisher predictions to
results from Monte Carlo analyses, finding very good agreement.
| [
{
"created": "Mon, 16 May 2022 18:00:00 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Dec 2022 11:10:32 GMT",
"version": "v2"
}
] | 2022-12-14 | [
[
"Gair",
"Jonathan R.",
""
],
[
"Antonelli",
"Andrea",
""
],
[
"Barbieri",
"Riccardo",
""
]
] | We derive a Fisher matrix for the parameters characterising a population of gravitational-wave events. This provides a guide to the precision with which population parameters can be estimated with multiple observations, which becomes increasingly accurate as the number of events and the signal-to-noise ratio of the sampled events increases. The formalism takes into account individual event measurement uncertainties and selection effects, and can be applied to arbitrary population models. We illustrate the framework with two examples: an analytical calculation of the Fisher matrix for the mean and variance of a Gaussian model describing a population affected by selection effects, and an estimation of the precision with which the slope of a power law distribution of supermassive black-hole masses can be measured using extreme-mass-ratio inspiral observations. We compare the Fisher predictions to results from Monte Carlo analyses, finding very good agreement. |
1711.06732 | Anshul Saini | Anshul Saini, Dejan Stojkovic | Modified hoop conjecture in expanding spacetimes and primordial black
hole production in FRW universe | null | JCAP05(2018)071 | 10.1088/1475-7516/2018/05/071 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | According to a variant of the hoop conjecture, if we localize two particles
within the Schwarzschild radius corresponding to their center of mass energy,
then a black hole will form. Despite a large body of work on the formation of
primordial black holes, so far this conjecture has not been generalized to
expanding spacetimes. We derive a formula which gives the distance within which
two particles must be localized to give a black hole, and which crucially
depends on the expansion rate of the background space. In the limit of a very
slow expansion, we recover the flat spacetime case. In the opposite limit of
the large expansion rate when the inverse Hubble radius is smaller than the
Schwarzschild radius of a "would be" black hole, the new critical distance
between two particles that can make a black hole becomes equal to the particle
horizon, which is just a requirement that the particles are in a causal
contact. This behavior also nicely illustrates why the Big Bang singularity is
not a black hole. We then use our formula to calculate the number density,
energy density and production rate of black holes produced in collisions of
particles. We find that though black holes might be numerous at high
temperatures, they never dominate over the background radiation below the
Planck temperature.
| [
{
"created": "Fri, 17 Nov 2017 21:36:58 GMT",
"version": "v1"
}
] | 2018-06-01 | [
[
"Saini",
"Anshul",
""
],
[
"Stojkovic",
"Dejan",
""
]
] | According to a variant of the hoop conjecture, if we localize two particles within the Schwarzschild radius corresponding to their center of mass energy, then a black hole will form. Despite a large body of work on the formation of primordial black holes, so far this conjecture has not been generalized to expanding spacetimes. We derive a formula which gives the distance within which two particles must be localized to give a black hole, and which crucially depends on the expansion rate of the background space. In the limit of a very slow expansion, we recover the flat spacetime case. In the opposite limit of the large expansion rate when the inverse Hubble radius is smaller than the Schwarzschild radius of a "would be" black hole, the new critical distance between two particles that can make a black hole becomes equal to the particle horizon, which is just a requirement that the particles are in a causal contact. This behavior also nicely illustrates why the Big Bang singularity is not a black hole. We then use our formula to calculate the number density, energy density and production rate of black holes produced in collisions of particles. We find that though black holes might be numerous at high temperatures, they never dominate over the background radiation below the Planck temperature. |
2109.14319 | Conghua Liu | Conghua Liu, Jin Wang | Path integral and instantons for the process and phase transition rate
of the RNAdS black hole | null | Phys. Rev. D 105. 104024(2022) | 10.1103/PhysRevD.105.104024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new approach to study the dynamical phase transition of RNAdS
black holes on the underlying free energy landscape. By formulating a path
integral framework, we can quantify the kinetic paths representing the history
from the initial state to the end state, which provides us a visualized yet
quantified picture about how the phase transition proceeds. Based on these
paths, we derive the analytical formulas for the time evolution of the
transition probability and provide a physical interpretation of the
contribution to the probability from one "pseudomolecule"
("anti-pseudomolecule"), which is actually the phase transition rate from the
small(large) to the large(small) black hole state. These numerical results show
a good consistency with the underlying free energy landscape topography.
| [
{
"created": "Wed, 29 Sep 2021 10:14:29 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Sep 2021 02:15:50 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Jan 2022 13:07:30 GMT",
"version": "v3"
},
{
"created": "Thu, 20 Jan 2022 04:32:18 GMT",
"version": "v4"
},
{
"created": "Tue, 5 Jul 2022 02:46:46 GMT",
"version": "v5"
}
] | 2022-07-06 | [
[
"Liu",
"Conghua",
""
],
[
"Wang",
"Jin",
""
]
] | We propose a new approach to study the dynamical phase transition of RNAdS black holes on the underlying free energy landscape. By formulating a path integral framework, we can quantify the kinetic paths representing the history from the initial state to the end state, which provides us a visualized yet quantified picture about how the phase transition proceeds. Based on these paths, we derive the analytical formulas for the time evolution of the transition probability and provide a physical interpretation of the contribution to the probability from one "pseudomolecule" ("anti-pseudomolecule"), which is actually the phase transition rate from the small(large) to the large(small) black hole state. These numerical results show a good consistency with the underlying free energy landscape topography. |
gr-qc/0002015 | Luis J. Garay | L. J. Garay, J. R. Anglin, J. I. Cirac, and P. Zoller | Sonic analog of gravitational black holes in Bose-Einstein condensates | RevTeX 3.1, 1 figure, 4 pages | Phys.Rev.Lett.85:4643-4647,2000 | 10.1103/PhysRevLett.85.4643 | null | gr-qc cond-mat quant-ph | null | It is shown that, in dilute-gas Bose-Einstein condensates, there exist both
dynamically stable and unstable configurations which, in the hydrodynamic
limit, exhibit a behavior resembling that of gravitational black holes. The
dynamical instabilities involve creation of quasiparticle pairs in positive and
negative energy states, as in the well-known suggested mechanism for black hole
evaporation. We propose a scheme to generate a stable sonic black hole in a
ring trap.
| [
{
"created": "Thu, 3 Feb 2000 11:53:37 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Dec 2000 10:21:44 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Garay",
"L. J.",
""
],
[
"Anglin",
"J. R.",
""
],
[
"Cirac",
"J. I.",
""
],
[
"Zoller",
"P.",
""
]
] | It is shown that, in dilute-gas Bose-Einstein condensates, there exist both dynamically stable and unstable configurations which, in the hydrodynamic limit, exhibit a behavior resembling that of gravitational black holes. The dynamical instabilities involve creation of quasiparticle pairs in positive and negative energy states, as in the well-known suggested mechanism for black hole evaporation. We propose a scheme to generate a stable sonic black hole in a ring trap. |
2404.17624 | Zhong-Wen Feng | Zhong-Wen Feng, Shi-Yu Li, Xia Zhou, Haximjan Abdusattar | Phase transitions, critical behavior and microstructure of the FRW
universe in the framework of higher order GUP | 12 pages, 8 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we explore the the phase transition, critical behavior and
microstructure of the FRW in the framework of a new higher order generalized
uncertainty principle. Our initial step involves deriving the equation of state
by defining the work density $W$ from GUP-corrected Friedmann equations as the
thermodynamic pressure $P$. Based on the modified equation of state, we conduct
an analysis of the $P-V$ phase transition in the FRW universe. Subsequently, we
obtain the critical exponents and coexistence curves for the small and large
phases of the FRW universe around the critical point. Finally, employing
Ruppeiner geometry, we derive the thermodynamic curvature scalar $R_N$,
investigating its sign-changing curve and spinodal curve. The results reveal
distinctive thermodynamic properties for FRW universes with positive and
negative GUP parameters $\beta$. In the case of $\beta>0$, the phase
transition, critical behavior and microstructure of FRW universe are consistent
with those of Van der Waals fluids. Conversely, for $\beta<0$, the results
resemble those obtained through effective scalar field theory. These findings
underscore the capacity of quantum gravity to induce phase transitions in the
universe, warranting further in-depth exploration.
| [
{
"created": "Fri, 26 Apr 2024 14:47:39 GMT",
"version": "v1"
},
{
"created": "Fri, 3 May 2024 02:31:00 GMT",
"version": "v2"
}
] | 2024-05-06 | [
[
"Feng",
"Zhong-Wen",
""
],
[
"Li",
"Shi-Yu",
""
],
[
"Zhou",
"Xia",
""
],
[
"Abdusattar",
"Haximjan",
""
]
] | In this paper, we explore the the phase transition, critical behavior and microstructure of the FRW in the framework of a new higher order generalized uncertainty principle. Our initial step involves deriving the equation of state by defining the work density $W$ from GUP-corrected Friedmann equations as the thermodynamic pressure $P$. Based on the modified equation of state, we conduct an analysis of the $P-V$ phase transition in the FRW universe. Subsequently, we obtain the critical exponents and coexistence curves for the small and large phases of the FRW universe around the critical point. Finally, employing Ruppeiner geometry, we derive the thermodynamic curvature scalar $R_N$, investigating its sign-changing curve and spinodal curve. The results reveal distinctive thermodynamic properties for FRW universes with positive and negative GUP parameters $\beta$. In the case of $\beta>0$, the phase transition, critical behavior and microstructure of FRW universe are consistent with those of Van der Waals fluids. Conversely, for $\beta<0$, the results resemble those obtained through effective scalar field theory. These findings underscore the capacity of quantum gravity to induce phase transitions in the universe, warranting further in-depth exploration. |
2406.19355 | Jose Beltr\'an Jim\'enez | Antonio G. Bello-Morales, Jose Beltr\'an Jim\'enez, Alejandro
Jim\'enez Cano, Antonio L. Maroto and Tomi S. Koivisto | A class of ghost-free theories in symmetric teleparallel geometry | 11 pages, no figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Theories formulated in the arena of teleparallel geometries are generically
plagued by ghost-like instabilities or other pathologies that are ultimately
caused by the breaking of some symmetries. In this work, we construct a class
of ghost-free theories based on a symmetry under Transverse Diffeomorphisms
that is naturally realised in symmetric teleparallelism. We explicitly show
their equivalence to a family of theories with an extra scalar field plus a
global degree of freedom and how Horndeski theories and healthy couplings to
matter fields can be readily accommodated.
| [
{
"created": "Thu, 27 Jun 2024 17:33:12 GMT",
"version": "v1"
}
] | 2024-06-28 | [
[
"Bello-Morales",
"Antonio G.",
""
],
[
"Jiménez",
"Jose Beltrán",
""
],
[
"Cano",
"Alejandro Jiménez",
""
],
[
"Maroto",
"Antonio L.",
""
],
[
"Koivisto",
"Tomi S.",
""
]
] | Theories formulated in the arena of teleparallel geometries are generically plagued by ghost-like instabilities or other pathologies that are ultimately caused by the breaking of some symmetries. In this work, we construct a class of ghost-free theories based on a symmetry under Transverse Diffeomorphisms that is naturally realised in symmetric teleparallelism. We explicitly show their equivalence to a family of theories with an extra scalar field plus a global degree of freedom and how Horndeski theories and healthy couplings to matter fields can be readily accommodated. |
gr-qc/9408001 | Alan Rendall | Alan D. Rendall | On the Nature of Singularities in Plane Symmetric Scalar Field
Cosmologies | 7 pages, MPA-AR-94-3 | Gen.Rel.Grav.27:213-221,1995 | 10.1007/BF02107959 | null | gr-qc | null | The nature of the initial singularity in spatially compact plane symmetric
scalar field cosmologies is investigated. It is shown that this singularity is
crushing and velocity dominated and that the Kretschmann scalar diverges
uniformly as it is approached. The last fact means in particular that a maximal
globally hyperbolic spacetime in this class cannot be extended towards the past
through a Cauchy horizon. A subclass of these spacetimes is identified for
which the singularity is isotropic.
| [
{
"created": "Mon, 1 Aug 1994 16:30:46 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Rendall",
"Alan D.",
""
]
] | The nature of the initial singularity in spatially compact plane symmetric scalar field cosmologies is investigated. It is shown that this singularity is crushing and velocity dominated and that the Kretschmann scalar diverges uniformly as it is approached. The last fact means in particular that a maximal globally hyperbolic spacetime in this class cannot be extended towards the past through a Cauchy horizon. A subclass of these spacetimes is identified for which the singularity is isotropic. |
0907.1487 | Elizabeth Winstanley | Dominic Hosler and Elizabeth Winstanley | Higher-dimensional solitons and black holes with a non-minimally coupled
scalar field | 17 pages, revtex4, 21 figures, minor changes to match published
version | Phys.Rev.D80:104010,2009 | 10.1103/PhysRevD.80.104010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study higher-dimensional soliton and hairy black hole solutions of the
Einstein equations non-minimally coupled to a scalar field. The scalar field
has no self-interaction potential but a cosmological constant is included.
Non-trivial solutions exist only when the cosmological constant is negative and
the constant governing the coupling of the scalar field to the Ricci scalar
curvature is positive. At least some of these solutions are stable when this
coupling constant is not too large.
| [
{
"created": "Thu, 9 Jul 2009 10:16:37 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Jun 2012 18:25:28 GMT",
"version": "v2"
}
] | 2012-06-12 | [
[
"Hosler",
"Dominic",
""
],
[
"Winstanley",
"Elizabeth",
""
]
] | We study higher-dimensional soliton and hairy black hole solutions of the Einstein equations non-minimally coupled to a scalar field. The scalar field has no self-interaction potential but a cosmological constant is included. Non-trivial solutions exist only when the cosmological constant is negative and the constant governing the coupling of the scalar field to the Ricci scalar curvature is positive. At least some of these solutions are stable when this coupling constant is not too large. |
gr-qc/0412076 | Paola Zizzi | Paola Zizzi | Computability at the Planck scale | 9 pages, misprints corrected, LaTeX version, accepted as contributed
paper at CiE 2005 | null | null | null | gr-qc quant-ph | null | We consider the issue of computability at the most fundamental level of
physical reality: the Planck scale. To this aim, we consider the theoretical
model of a quantum computer on a non commutative space background, which is a
computational model for quantum gravity. In this domain, all computable
functions are the laws of physics in their most primordial form, and non
computable mathematics finds no room in the physical world. Moreover, we show
that a theorem that classically was considered true but non computable, at the
Planck scale becomes computable but non decidable. This fact is due to the
change of logic for observers in a quantum-computing universe: from standard
quantum logic and classical logic, to paraconsistent logic.
| [
{
"created": "Wed, 15 Dec 2004 19:36:39 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Mar 2005 07:15:14 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Zizzi",
"Paola",
""
]
] | We consider the issue of computability at the most fundamental level of physical reality: the Planck scale. To this aim, we consider the theoretical model of a quantum computer on a non commutative space background, which is a computational model for quantum gravity. In this domain, all computable functions are the laws of physics in their most primordial form, and non computable mathematics finds no room in the physical world. Moreover, we show that a theorem that classically was considered true but non computable, at the Planck scale becomes computable but non decidable. This fact is due to the change of logic for observers in a quantum-computing universe: from standard quantum logic and classical logic, to paraconsistent logic. |
1606.00489 | Dheeraj Kumar Mishra | Dheeraj Kumar Mishra, Nitin Chandra, Vinay Vaibhav | Equilibrium properties of blackbody radiation with an ultraviolet energy
cut-off | 26 pages, 9 figures; Published version; Some new calculations added | Annals of Physics 385 605(2017) | 10.1016/j.aop.2017.08.004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study various equilibrium thermodynamic properties of blackbody radiation
(i.e. a photon gas) with an ultraviolet energy cut-off. We find that the energy
density, specific heat etc. follow usual acoustic phonon dynamics as have been
well studied by Debye. Other thermodynamic quantities like pressure, entropy
etc. have also been calculated. The usual Stefan-Boltzmann law gets modified.
We observe that the values of the thermodynamic quantities with the energy
cut-off is lower than the corresponding values in the theory without any such
scale. The phase-space measure is also expected to get modified for an exotic
spacetime appearing at Planck scale, which in turn leads to the modification of
Planck energy density distribution and the Wien's displacement law. We found
that the non-perturbative nature of the thermodynamic quantities in the SR
limit (for both the case with ultravilolet cut-off and the modified measure
case), due to nonanalyticity of the leading term, is a general feature of the
theory accompanied with an ultraviolet energy cut-off. We have also discussed
the possible modification in the case of Big Bang and the Stellar objects and
have suggested a table top experiment for verification in effective low energy
case.
| [
{
"created": "Wed, 1 Jun 2016 22:29:14 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jun 2016 19:25:37 GMT",
"version": "v2"
},
{
"created": "Wed, 13 Sep 2017 02:08:14 GMT",
"version": "v3"
}
] | 2017-09-14 | [
[
"Mishra",
"Dheeraj Kumar",
""
],
[
"Chandra",
"Nitin",
""
],
[
"Vaibhav",
"Vinay",
""
]
] | We study various equilibrium thermodynamic properties of blackbody radiation (i.e. a photon gas) with an ultraviolet energy cut-off. We find that the energy density, specific heat etc. follow usual acoustic phonon dynamics as have been well studied by Debye. Other thermodynamic quantities like pressure, entropy etc. have also been calculated. The usual Stefan-Boltzmann law gets modified. We observe that the values of the thermodynamic quantities with the energy cut-off is lower than the corresponding values in the theory without any such scale. The phase-space measure is also expected to get modified for an exotic spacetime appearing at Planck scale, which in turn leads to the modification of Planck energy density distribution and the Wien's displacement law. We found that the non-perturbative nature of the thermodynamic quantities in the SR limit (for both the case with ultravilolet cut-off and the modified measure case), due to nonanalyticity of the leading term, is a general feature of the theory accompanied with an ultraviolet energy cut-off. We have also discussed the possible modification in the case of Big Bang and the Stellar objects and have suggested a table top experiment for verification in effective low energy case. |
2310.10864 | Cendikiawan Suryaatmadja | Cendikiawan Suryaatmadja, Cemile Senem Arabaci, Matthew P. G. Robbins,
Joshua Foo, Magdalena Zych, Robert B. Mann | Signatures of Rotating Black Holes in Quantum Superposition | null | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new approach for operationally studying the effects of spacetime in quantum
superpositions of semiclassical states has recently been proposed by some of
the authors. This approach was applied to the case of a (2+1)-dimensional
Ba\~nados-Teitelboim-Zanelli (BTZ) black hole in a superposition of masses,
where it was shown that a two-level system interacting with a quantum field
residing in the spacetime exhibits resonant peaks in its response at certain
values of the superposed masses. Here, we extend this analysis to a
mass-superposed rotating BTZ black hole, considering the case where the
two-level system co-rotates with the black hole in a superposition of
trajectories. We find similar resonances in the detector response function at
rational ratios of the superposed outer horizon radii, specifically in the case
where the ratio of the inner and outer horizons is fixed. This suggests a
connection with Bekenstein's seminal conjecture concerning the discrete horizon
spectra of black holes in quantum gravity, generalized to the case of rotating
black holes. Our results suggest that deeper insights into
quantum-gravitational phenomena may be accessible via tools in relativistic
quantum information and curved spacetime quantum field theory.
| [
{
"created": "Mon, 16 Oct 2023 22:24:21 GMT",
"version": "v1"
}
] | 2023-10-18 | [
[
"Suryaatmadja",
"Cendikiawan",
""
],
[
"Arabaci",
"Cemile Senem",
""
],
[
"Robbins",
"Matthew P. G.",
""
],
[
"Foo",
"Joshua",
""
],
[
"Zych",
"Magdalena",
""
],
[
"Mann",
"Robert B.",
""
]
] | A new approach for operationally studying the effects of spacetime in quantum superpositions of semiclassical states has recently been proposed by some of the authors. This approach was applied to the case of a (2+1)-dimensional Ba\~nados-Teitelboim-Zanelli (BTZ) black hole in a superposition of masses, where it was shown that a two-level system interacting with a quantum field residing in the spacetime exhibits resonant peaks in its response at certain values of the superposed masses. Here, we extend this analysis to a mass-superposed rotating BTZ black hole, considering the case where the two-level system co-rotates with the black hole in a superposition of trajectories. We find similar resonances in the detector response function at rational ratios of the superposed outer horizon radii, specifically in the case where the ratio of the inner and outer horizons is fixed. This suggests a connection with Bekenstein's seminal conjecture concerning the discrete horizon spectra of black holes in quantum gravity, generalized to the case of rotating black holes. Our results suggest that deeper insights into quantum-gravitational phenomena may be accessible via tools in relativistic quantum information and curved spacetime quantum field theory. |
0803.0604 | Masakatsu Kenmoku | Maiko Kuwata, Masakatsu Kenmoku and Kazuyasu Shigemoto | Eigenvalue Problem of Scalar Fields in BTZ Black Hole Spacetime | 10 pages, 6 figures | Prog.Theor.Phys.119:939-948,2008 | 10.1143/PTP.119.939 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We studied the eigenvalue problem of scalar fields in the (2+1)-dimensional
BTZ black hole spacetime. The Dirichlet boundary condition at infinity and the
Dirichlet or the Neumann boundary condition at the horizon are imposed.
Eigenvalues for normal modes are characterized by the principal quantum number
$(0<n)$ and the azimuthal quantum number $(-\infty<m< \infty)$. Effects to
eigenvalues of the black hole rotation and of the scalar field mass are studied
explicitly. Relation of the black hole rotation to the super-radiant
instability is discussed.
| [
{
"created": "Wed, 5 Mar 2008 08:05:54 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kuwata",
"Maiko",
""
],
[
"Kenmoku",
"Masakatsu",
""
],
[
"Shigemoto",
"Kazuyasu",
""
]
] | We studied the eigenvalue problem of scalar fields in the (2+1)-dimensional BTZ black hole spacetime. The Dirichlet boundary condition at infinity and the Dirichlet or the Neumann boundary condition at the horizon are imposed. Eigenvalues for normal modes are characterized by the principal quantum number $(0<n)$ and the azimuthal quantum number $(-\infty<m< \infty)$. Effects to eigenvalues of the black hole rotation and of the scalar field mass are studied explicitly. Relation of the black hole rotation to the super-radiant instability is discussed. |
gr-qc/0201063 | Alessandra Buonanno | Alessandra Buonanno and Yanbei Chen | Laser-interferometer gravitational-wave optical-spring detectors | 7 pages, 3 figures; to appear in the Proceedings of 4th Edoardo
Amaldi Conference on Gravitational Waves, Perth, Australia, 8-13 July 2001 | Class.Quant.Grav. 19 (2002) 1569-1574 | 10.1088/0264-9381/19/7/346 | null | gr-qc | null | Using a quantum mechanical approach, we show that in a gravitational-wave
interferometer composed of arm cavities and a signal recycling cavity, e.g.,
the LIGO-II configuration, the radiation-pressure force acting on the mirrors
not only disturbs the motion of the free masses randomly due to quantum
fluctuations, but also and more fundamentally, makes them respond to forces as
though they were connected to an (optical) spring with a specific rigidity.
This oscillatory response gives rise to a much richer dynamics than previously
known, which enhances the possibilities for reshaping the LIGO-II's noise
curves. However, the optical-mechanical system is dynamically unstable and an
appropriate control system must be introduced to quench the instability.
| [
{
"created": "Fri, 18 Jan 2002 17:49:49 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Apr 2002 20:24:47 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Buonanno",
"Alessandra",
""
],
[
"Chen",
"Yanbei",
""
]
] | Using a quantum mechanical approach, we show that in a gravitational-wave interferometer composed of arm cavities and a signal recycling cavity, e.g., the LIGO-II configuration, the radiation-pressure force acting on the mirrors not only disturbs the motion of the free masses randomly due to quantum fluctuations, but also and more fundamentally, makes them respond to forces as though they were connected to an (optical) spring with a specific rigidity. This oscillatory response gives rise to a much richer dynamics than previously known, which enhances the possibilities for reshaping the LIGO-II's noise curves. However, the optical-mechanical system is dynamically unstable and an appropriate control system must be introduced to quench the instability. |
gr-qc/0001061 | Franz Schunck | Eckehard W. Mielke and Franz E. Schunck | Boson Stars: Alternatives to primordial black holes? | 14 pages, uses REVTeX, 1 postscript figure | Nucl.Phys. B564 (2000) 185-203 | 10.1016/S0550-3213(99)00492-7 | null | gr-qc astro-ph | null | The present surge for the astrophysical relevance of boson stars stems from
the speculative possibility that these compact objects could provide a
considerable fraction of the non-baryonic part of dark matter within the halo
of galaxies. For a very light `universal' axion of effective string models,
their total gravitational mass will be in the most likely range of \sim 0.5
M_\odot of MACHOs. According to this framework, gravitational microlensing is
indirectly ``weighing" the axion mass, resulting in \sim 10^{-10} eV/c^2. This
conclusion is not changing much, if we use a dilaton type self-interaction for
the bosons. Moreover, we review their formation, rotation and stability as
likely candidates of astrophysical importance.
| [
{
"created": "Thu, 20 Jan 2000 23:19:32 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Mielke",
"Eckehard W.",
""
],
[
"Schunck",
"Franz E.",
""
]
] | The present surge for the astrophysical relevance of boson stars stems from the speculative possibility that these compact objects could provide a considerable fraction of the non-baryonic part of dark matter within the halo of galaxies. For a very light `universal' axion of effective string models, their total gravitational mass will be in the most likely range of \sim 0.5 M_\odot of MACHOs. According to this framework, gravitational microlensing is indirectly ``weighing" the axion mass, resulting in \sim 10^{-10} eV/c^2. This conclusion is not changing much, if we use a dilaton type self-interaction for the bosons. Moreover, we review their formation, rotation and stability as likely candidates of astrophysical importance. |
1303.0762 | Emanuele Alesci | Emanuele Alesci | A new perspective on early cosmology | 3 pages, contribution to the Proceedings of the 13th Marcel Grossman
Meeting (Stockholm, Sweden, July 1-7 2012) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new perspective on early cosmology based on Loop Quantum
Gravity. We use projected spinnetworks, coherent states and spinfoam
techniques, to implement a quantum reduction of the full Kinematical Hilbert
space of LQG, suitable to describe inhomogeneous cosmological models. Some
preliminary results on the solutions of the Scalar constraint of the reduced
theory are also presented.
| [
{
"created": "Mon, 4 Mar 2013 17:41:50 GMT",
"version": "v1"
}
] | 2013-03-05 | [
[
"Alesci",
"Emanuele",
""
]
] | We present a new perspective on early cosmology based on Loop Quantum Gravity. We use projected spinnetworks, coherent states and spinfoam techniques, to implement a quantum reduction of the full Kinematical Hilbert space of LQG, suitable to describe inhomogeneous cosmological models. Some preliminary results on the solutions of the Scalar constraint of the reduced theory are also presented. |
1008.4835 | Md. Rahman Atiqur | Md. Atiqur Rahman | Longitudinal Wave Propagation in Relativistic Two-fluid Plasmas around
Reissner-Nordstrom Black Hole | 16 pages, 8 figures | Int.J.Theor.Phys.50:698-718,2011 | 10.1007/s10773-010-0600-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The 3+1 spacetime formulation of general relativity is used to investigate
the transverse waves propagating in a plasma influenced by the gravitational
field of Reissner-Nordstrom black hole, as explained in an earlier paper, to
take account of relativistic effects due to the event horizon. Here, a local
approximation is used to investigate the one-dimensional radial propagation of
longitudinal waves. We derive the dispersion relation for these waves and solve
it numerically for the wave number k.
| [
{
"created": "Sat, 28 Aug 2010 05:42:11 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Nov 2010 04:28:53 GMT",
"version": "v2"
}
] | 2011-01-25 | [
[
"Rahman",
"Md. Atiqur",
""
]
] | The 3+1 spacetime formulation of general relativity is used to investigate the transverse waves propagating in a plasma influenced by the gravitational field of Reissner-Nordstrom black hole, as explained in an earlier paper, to take account of relativistic effects due to the event horizon. Here, a local approximation is used to investigate the one-dimensional radial propagation of longitudinal waves. We derive the dispersion relation for these waves and solve it numerically for the wave number k. |
gr-qc/0603100 | Prasanta Mahato | Prasanta Mahato | de Sitter group and Einstein-Hilbert Lagrangian | 14 pages | Phys.Rev.D70:124024,2004 | 10.1103/PhysRevD.70.124024 | null | gr-qc | null | Axial vector torsion in the Einstein-Cartan space $U_{4}$ is considered here.
By picking a particular term from the SO(4,1) Pontryagin density and then
modifying it in a SO(3,1) invariant way, we get a Lagrangian density with
Lagrange multipliers. Then considering torsion and torsion-less connection as
independent fields, it has been found that $\kappa$ and $\lambda$ of
Einstein-Hilbert Lagrangian, appear as integration constants in such a way that
$\kappa$ has been found to be linked with the topological Nieh-Yan density of
$U_{4}$ space.
| [
{
"created": "Sat, 25 Mar 2006 16:58:29 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Mar 2006 16:17:00 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Mahato",
"Prasanta",
""
]
] | Axial vector torsion in the Einstein-Cartan space $U_{4}$ is considered here. By picking a particular term from the SO(4,1) Pontryagin density and then modifying it in a SO(3,1) invariant way, we get a Lagrangian density with Lagrange multipliers. Then considering torsion and torsion-less connection as independent fields, it has been found that $\kappa$ and $\lambda$ of Einstein-Hilbert Lagrangian, appear as integration constants in such a way that $\kappa$ has been found to be linked with the topological Nieh-Yan density of $U_{4}$ space. |
gr-qc/0106004 | Giovanni Amelino-Camelia | Giovanni Amelino-Camelia | Status of Relativity with observer-independent length and velocity
scales | 24 pages, Latex (to appear in proceedings of 37th Karpacz Winter
School) | AIP Conf. Proc.589:137-150,2001 | 10.1063/1.1419321 | null | gr-qc | null | I have recently shown that it is possible to formulate the Relativity
postulates in a way that does not lead to inconsistencies in the case of
space-times whose structure is governed by observer-independent scales of both
velocity and length. Here I give an update on the status of this proposal,
including a brief review of some very recent developments. I also emphasize the
role that one of the kappa-Poincare' Hopf algebras could play in the
realization of a particular example of the new type of postulates. I show that
the new ideas on Relativity require us to extend the set of tools provided by
kappa-Poincare' and to revise our understanding of certain already available
tools, such as the energy-momentum coproduct.
| [
{
"created": "Sun, 3 Jun 2001 13:08:06 GMT",
"version": "v1"
}
] | 2011-09-01 | [
[
"Amelino-Camelia",
"Giovanni",
""
]
] | I have recently shown that it is possible to formulate the Relativity postulates in a way that does not lead to inconsistencies in the case of space-times whose structure is governed by observer-independent scales of both velocity and length. Here I give an update on the status of this proposal, including a brief review of some very recent developments. I also emphasize the role that one of the kappa-Poincare' Hopf algebras could play in the realization of a particular example of the new type of postulates. I show that the new ideas on Relativity require us to extend the set of tools provided by kappa-Poincare' and to revise our understanding of certain already available tools, such as the energy-momentum coproduct. |
2212.06175 | Jaime Redondo-Yuste | Jaime Redondo-Yuste and Luis Lehner | Non-linear black hole dynamics and Carrollian fluids | 27 pages, 11 figures | null | 10.1007/JHEP02(2023)240 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamics of black hole horizons has recently been linked to that of
Carrollian fluids. This results in a dictionary between geometrical quantities
and those of a fluid with unusual properties due its underlying Carrollian
symmetries. In this work we explore this relation in dynamical settings with
the interest of shedding light on either side by relevant observations. In
particular: we discuss how the null surface where the Carrollian fluid evolves
is affected by its behavior; that the fluid's equilibration properties are tied
to teleological considerations; the connection of higher derivative
contributions as both source of energy and dissipation for the fluid and the
non-linear behavior of black holes. This latter point, connects with
discussions of non-linear modes in the relaxation to equilibrium of perturbed
black holes.
| [
{
"created": "Mon, 12 Dec 2022 19:00:05 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jan 2023 17:02:44 GMT",
"version": "v2"
},
{
"created": "Wed, 8 Feb 2023 17:41:23 GMT",
"version": "v3"
}
] | 2023-03-22 | [
[
"Redondo-Yuste",
"Jaime",
""
],
[
"Lehner",
"Luis",
""
]
] | The dynamics of black hole horizons has recently been linked to that of Carrollian fluids. This results in a dictionary between geometrical quantities and those of a fluid with unusual properties due its underlying Carrollian symmetries. In this work we explore this relation in dynamical settings with the interest of shedding light on either side by relevant observations. In particular: we discuss how the null surface where the Carrollian fluid evolves is affected by its behavior; that the fluid's equilibration properties are tied to teleological considerations; the connection of higher derivative contributions as both source of energy and dissipation for the fluid and the non-linear behavior of black holes. This latter point, connects with discussions of non-linear modes in the relaxation to equilibrium of perturbed black holes. |
1711.05034 | Shaoqi Hou | Shaoqi Hou and Yungui Gong | Constraints on Horndeski Theory Using the Observations of Nordtvedt
Effect, Shapiro Time Delay and Binary Pulsars | 17 pages, 1 figure. Correct typos, add new references. Match the
published version | Eur. Phys. J. C 78, 247 (2018) | 10.1140/epjc/s10052-018-5738-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Alternative theories of gravity not only modify the polarization contents of
the gravitational wave, but also affect the motions of the stars and the energy
radiated away via the gravitational radiation. These aspects leave imprints in
the observational data, which enables the test of General Relativity and its
alternatives. In this work, the Nordtvedt effect and the Shapiro time delay are
calculated in order to constrain Horndeski theory using the observations of
lunar laser ranging experiments and Cassini time-delay data. The effective
stress-energy tensor is also obtained using the method of Isaacson.
Gravitational wave radiation of a binary system is calculated, and the change
of the period of a binary system is deduced for the elliptical orbit. These
results can be used to set constraints on Horndeski theory with the
observations of binary systems, such as PSR J1738+0333. Constraints have been
obtained for some subclasses of Horndeski theory, in particular, those
satisfying the gravitational wave speed limits from GW170817 and GRB 170817A.
| [
{
"created": "Tue, 14 Nov 2017 09:59:27 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Nov 2017 02:59:04 GMT",
"version": "v2"
},
{
"created": "Thu, 22 Mar 2018 12:02:08 GMT",
"version": "v3"
}
] | 2018-03-28 | [
[
"Hou",
"Shaoqi",
""
],
[
"Gong",
"Yungui",
""
]
] | Alternative theories of gravity not only modify the polarization contents of the gravitational wave, but also affect the motions of the stars and the energy radiated away via the gravitational radiation. These aspects leave imprints in the observational data, which enables the test of General Relativity and its alternatives. In this work, the Nordtvedt effect and the Shapiro time delay are calculated in order to constrain Horndeski theory using the observations of lunar laser ranging experiments and Cassini time-delay data. The effective stress-energy tensor is also obtained using the method of Isaacson. Gravitational wave radiation of a binary system is calculated, and the change of the period of a binary system is deduced for the elliptical orbit. These results can be used to set constraints on Horndeski theory with the observations of binary systems, such as PSR J1738+0333. Constraints have been obtained for some subclasses of Horndeski theory, in particular, those satisfying the gravitational wave speed limits from GW170817 and GRB 170817A. |
gr-qc/0205116 | Alexander Zhuk | A. Zhuk | Generalized de Sitter solution in multidimensional cosmology with static
internal spaces | LaTeX2e, 8 pages | Astron.Nachr.316:269-274,1995 | 10.1002/asna.2103160502 | null | gr-qc | null | A multidimensional cosmological model with space-time consisting of n (n>1)
Einstein spaces M_i is investigated in the presence of a cosmological constant
Lambda and a homogeneous minimally coupled free scalar field. Generalized de
Sitter solution was found for Lambda > 0 and Ricci-flat external space for the
case of static internal spaces with fine tuning of parameters.
| [
{
"created": "Tue, 28 May 2002 14:12:51 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Zhuk",
"A.",
""
]
] | A multidimensional cosmological model with space-time consisting of n (n>1) Einstein spaces M_i is investigated in the presence of a cosmological constant Lambda and a homogeneous minimally coupled free scalar field. Generalized de Sitter solution was found for Lambda > 0 and Ricci-flat external space for the case of static internal spaces with fine tuning of parameters. |
0801.0527 | Elizabeth Winstanley | Elizabeth Winstanley | Classical Yang-Mills black hole hair in anti-de Sitter space | 41 pages, 14 figures. Based on the lecture given at the 4th Aegean
Summer School | Lect.Notes Phys.769:49-87,2009 | 10.1007/978-3-540-88460-6_2 | null | gr-qc hep-th | null | The properties of hairy black holes in Einstein-Yang-Mills (EYM) theory are
reviewed, focusing on spherically symmetric solutions. In particular, in
asymptotically anti-de Sitter space (adS) stable black hole hair is known to
exist for su(2) EYM. We review recent work in which it is shown that stable
hair also exists in su(N) EYM for arbitrary N, so that there is no upper limit
on how much stable hair a black hole in adS can possess.
| [
{
"created": "Thu, 3 Jan 2008 16:53:26 GMT",
"version": "v1"
}
] | 2009-01-28 | [
[
"Winstanley",
"Elizabeth",
""
]
] | The properties of hairy black holes in Einstein-Yang-Mills (EYM) theory are reviewed, focusing on spherically symmetric solutions. In particular, in asymptotically anti-de Sitter space (adS) stable black hole hair is known to exist for su(2) EYM. We review recent work in which it is shown that stable hair also exists in su(N) EYM for arbitrary N, so that there is no upper limit on how much stable hair a black hole in adS can possess. |
0805.3627 | Branislav Cvetkovi\'c | M. Blagojevi\'c and B. Cvetkovi\'c | Self-dual Maxwell field in 3D gravity with torsion | LATEX, 15 pages, v2: minor corrections | Phys.Rev.D78:044037,2008 | 10.1103/PhysRevD.78.044037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the system of self-dual Maxwell field coupled to 3D gravity with
torsion, with Maxwell field modified by a topological mass term. General
structure of the field equations reveals a new, dynamical role of the classical
central charges, and gives a simple correspondence between self-dual solutions
with torsion and their Riemannian counterparts. We construct two exact
self-dual solutions, corresponding to the sectors with massless and massive
Maxwell field, and calculate their conserved charges.
| [
{
"created": "Fri, 23 May 2008 12:42:17 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Sep 2008 09:53:26 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Blagojević",
"M.",
""
],
[
"Cvetković",
"B.",
""
]
] | We study the system of self-dual Maxwell field coupled to 3D gravity with torsion, with Maxwell field modified by a topological mass term. General structure of the field equations reveals a new, dynamical role of the classical central charges, and gives a simple correspondence between self-dual solutions with torsion and their Riemannian counterparts. We construct two exact self-dual solutions, corresponding to the sectors with massless and massive Maxwell field, and calculate their conserved charges. |
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